Language：English   Publishing type：Research paper (scientific journal)  

This study aimed to discover an easy and precise prediction model for the acoustic properties of nanofiber nonwoven fabrics. For this purpose, a prediction model focusing on the two dominant parameters in the Limp frame model-bulk density and flow resistivity-was suggested. The propagation constant and characteristic impedance was generated from the effective density and effective volume modulus generated by the predictive model and treated as a one-dimensional transfer matrix. The sound absorption coefficient was then estimated using the transfer matrix approach. The trend of the normal Incident sound absorption coefficient measured and the sound absorption coefficient obtained from the predictive model were consistent. Thus, it is suggested that the predictive model for the proposed nanofiber nonwoven composite sheet is valid.

DOI： 10.3390/nano12173050

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Zero-mass metamaterials comprise an orifice and a thin film. The resonance between the film and the air mass of the orifice hole is caused by sound waves, which significantly decreases the transmission loss at a specific frequency. The study novelly incorporates acoustic metamaterials in the delay tube of an interference silencer. In this case, it is determined that an interference silencer and a "side-branch silencer with two different branch pipe lengths" can be realized in a single silencer. At certain frequencies, the acoustic mass of the acoustic metamaterial approaches zero, which results in an interference silencer with the full length of the delay tube applied. At other frequencies, the acoustic metamaterial acts as a rigid wall with high transmission loss, thereby reflecting sound waves at the zero-mass metamaterial location. In this case, it is a side-branch silencer with two different tube lengths, corresponding to the tube lengths from the entrance and exit of the delay tube to the zero-mass metamaterial, respectively. The incorporation of zero-mass metamaterial into an interference-type silencer can introduce the silencing effect of a side-branch silencer with two different branch tube lengths without increasing the volume of the interference-type silencer. Theoretical values were obtained using the transfer matrix. Consequently, the theoretical and experimental values were close, enabling us to predict the transmission loss of the proposed silencer.

DOI： 10.3390/ma15155140

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Language：English   Publishing type：Research paper (scientific journal)  

The purpose of this study was to improve the accuracy of the theoretical analysis of sound absorption mechanisms when a back air space is used in nonwoven fabrics. In the case of a nonwoven sheet with a back air space, it can be shown that there is a difference between the experimental results and theoretical analysis results obtained using the Miki model when the area of the nonwoven sheet is large. Therefore, in this study, the accuracy of the theoretical values was improved using the plate vibration model in conjunction with the Miki model. The experimental results showed that when the vibration of the nonwoven sheet was suppressed, the sound absorption coefficient was higher than that of the vibration-prone nonwoven sheet alone. The sound absorption coefficient at the peak frequency was increased by >0.2, especially for 3501BD. Using the support frame, the sound absorption coefficient at the peak frequencies of 3A01A and 3701B was increased to 0.99. In the theoretical analysis of a large-area, vibration-prone nonwoven fabric, in which the vibration of the nonwoven fabric was taken into account, the theoretical values were in agreement with the experimental values, and the accuracy of the theoretical values was improved. Comparing the theoretical values for nonwoven fabrics without high ventilation resistance, the sound absorption coefficient was greater when vibration was not considered. Therefore, it was suggested that the vibration of the nonwoven fabric hinders sound absorption.

DOI： 10.3390/ma15113840

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In general, the acoustic effective length of the open end of an air column is longer than its geometric length. Here, the effective increment of the geometric length of an air column is called the open-end correction length, which is an acoustically crucial issue. The purpose of this study is to experimentally clarify the open-end correction length for a slit shape with a narrow clearance. For this reason, the sound absorption coefficient was measured using a sample in which the neck of the Helmholtz resonator was shaped as a slit with a narrow clearance. Next, the open-end correction length (i.e., mass end correction length and resistive end correction length) was calculated backward by comparing the experimental and theoretical sound absorption curves. The resistive end correction increased as the slit width became narrower within the range of 0.5 mm or less for both the center slit and the slit near the wall, indicating a significant discrepancy between the theoretical equation and the estimated value. For the mass end correction, in the case the center slit, the estimated value is close to the theoretical value of in the slit width range from 0.3 mm to 1.0 mm. The results of this study may be useful in eliminating discrepancies in correction values for open-end correction in slits with narrow clearance.

DOI： 10.3397/1/377011

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We performed a theoretical analysis on collection of equilateral triangular holes with consideration for sound wave attenuation within the tube and then calculated the sound-absorption coefficient and transmission loss. We then compared these results with experimental values. In the experiment, we measured the sound-absorption coefficient and transmission loss of a test sample using impedance measurement tubes with two and four microphones. We estimated the sound-absorption coefficient and transmission loss because of the dimensions of a collection of equilateral triangular holes through theoretical analysis and then compared these results with experimental values. In the present analysis, the propagation constant and characteristic impedance were introduced into a one-dimensional transfer matrix. Considering the effects of sound wave attenuation in the tubule from three-dimensional analysis, we derived the propagation constant and characteristic impedance. Values for the sound-absorption coefficient and transmission loss obtained through the analysis of holes as triangles rather than as circles gave calculation results closer to the experimental values. This is because this method more suitably simulates the effects of the boundary layer that occupies the space within the hole. The results show that the sound absorption coefficient and transmission loss of triangular honeycombs can be estimated with sufficient accuracy using only geometric dimensions and physical properties.

DOI： 10.3397/1/377013

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In this study, the sound-absorption coefficients of a pin-holder structure consisting of a group of cylinders were estimated and compared with the experimental values for the case where sound waves are incident in the direction perpendicular to the cylinder's axis. To estimate the sound-absorption coefficient, the gap in the pin-holder structure is divided into elements and approximated as being between two parallel planes, taking the exact shape of the divided elements into account. The characteristic impedance and propagation constant of the approximated clearances were calculated and treated as a one-dimensional transfer matrix. The transfer matrices for each element were used to calculate the sound-absorption coefficient. The calculated theoretical values were compared with the experimental ones. In the experiment, the samples were fabricated using a 3D printer, and the sound-absorption coefficient was measured using a two-microphone impedance-measurement tube. Although the experimental and theoretical values differed, they showed similar trends. We also found that the prediction error in the practical sound-absorption coefficient could be reduced by adjusting the diameter of the pins used in the calculation.

DOI： 10.3397/1/377012

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A structure that possesses a continuous pore space packed with a granular material exhibits acoustic characteristics based on the principle similar to that of a porous material. Such a structure is used in low-noise pavement and ballast track. Therefore, predicting the sound absorption characteristics of a clearance generated in a granular material from the particle diameter and the physical property of gas is useful for engineering. This article deals with two packing models, namely, the simple cubic lattice model and the hexagonal lattice model, to measure the sound absorption coefficient of the structure packed with a granular material whose particle diameter is a few mm. Furthermore, a simple and accurate theoretical analysis that uses a one-dimensional transfer matrix method, which does not require numerous parameters, was performed. Comparing experimental values, when the particle diameter of the granular material was 4 mm, the percentage of the boundary layer in the clearance was moderately larger than when the diameter was 8 mm; therefore, the effect of viscosity on it was larger, and its sound absorption coefficient peak was higher. Moreover, compared with the simple cubic lattice, the hexagonal lattice had a higher percentage of boundary layer in the clearance because of its smaller volume of pore space. Then, the influence of friction due to the viscosity on it was higher, and its sound absorption coefficient peak was higher. In addition, the theoretical values obtained by the proposed analysis method typically matched the experiment values.

DOI： 10.3397/1/376937

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In this study, a theoretical analysis of the acoustic characteristics of a pin holder structure was conducted. In addition, the sound absorption coefficient, entering its clearance through the geometrical dimension of the clearance or the physical property of air, was calculated. The analysis model approximates the aperture of a pin holder structure as the clearance between two parallel surfaces. Thus, the propagation constant and characteristic impedance were obtained and treated as a one-dimensional transfer matrix. Subsequently, the sound absorption coefficient was calculated using the transfer matrix method and was compared with the experimental results. In the experiment, a two-microphone impedance tube was used to measure the sound absorption coefficient of the test samples. We attempted to perform a simple yet accurate estimation using these procedures. The theoretical analysis values exhibited a similar tendency to that of the experimental values.

DOI： 10.3397/1/376911

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This article focuses on the theoretical analysis and experiment of a small plate vibration sound-absorbing device with a clearance and without surrounding restriction. Generally, a plate vibration sound-absorbing device absorbs sound in a frequency range lower than that of porous material, which is used as a sound-absorbing material, and its sound absorption coefficient is small. Furthermore, note that the plate is fixed at the periphery in a conventional plate vibration sound-absorbing device. Hence, when the plate is small, vibration barely occurs and effective sound-absorbing effect is not obtained. Given that the plate vibration sound-absorbing device has a restriction wherein a particular size of plate is required, it is primarily utilized for indoor finishing considering the architectural acoustics, and finding applications for small-sized machines has been challenging. Theoretical values in this work are calculated assuming that the clearance and back air layer for the small plate vibration sound-absorbing device constitute a Helmholtz resonator. Furthermore, experiments were conducted to perform comparisons against the theoretical value. The theoretical analysis was conducted by connecting the clearance and back air layer in parallel with the plate portion in the electrical equivalent circuit. By performing the experiments using various parameters, the sound absorption characteristics of the proposed plate vibration sound-absorbing device were determined. If the clearance is smaller than the boundary layer thickness, then the conventional resistive end correction cannot be applied.

DOI： 10.3397/1/37693

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：The Institute of Noise Control Engineering of the USA, Inc.  

In this study, we conducted theoretical analyses and experiments related to the acoustic characteristics of the situation where sound waves are incident upon the side surfaces of a group of cylinders forming a pin-holder structure. The sound-absorption coefficient, entering its clearance between cylinders through the geometrical dimension of the clearance or the physical property of gas, was calculated. In the analytical model, the gap part of the pin-holder structure was divided into elements and approximated as a gap surrounded by two parallel planes. The characteristic impedance and propagation constant of the approximate gap were obtained and treated as one-dimensional transfer matrices
the sound-absorption coefficient was then calculated using the transfer-matrix method. The calculated value was compared to that obtained in an experiment with a sample prepared using a 3D printer
the sound-absorption coefficient was measured using a 2-microphone impedance-measuring tube. We attempted to make a simple yet accurate estimation of sound-absorption coefficient using these procedures. Our theoretical values displayed a similar tendency to that obtained by experiment.

DOI： 10.3397/IN2021-2497

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In this study, the sound absorption characteristics of lightweight powders with a particle size on the order of tens of micrometers have been investigated. Herein, to theoretically determine the sound absorption coefficient of a fine lightweight powder in the longitudinal vibration mode, it was assumed that the powder was continuum and could be treated as a multiple degree-of-freedom damping vibration system. In addition, the acoustic impedance was calculated by assuming proportional viscous damping to determine the sound absorption coefficient. Finally, the theoretical and experimental values were compared. With the presented theoretical analysis, values close to the experimental results were obtained. Among the three calculated values based on proportional viscous damping, i.e., Rayleigh damping, rigidity proportional damping, and mass proportional damping, the results for Rayleigh damping were the closest to the experimental values.

DOI： 10.1121/1.5126951

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The sound absorption coefficient of thin tubes with a honeycomb-corrugated structure was estimated via theoretical analysis assuming the dimensions of the tube and the known physical properties of air. This analysis yields a propagation constant and characteristic impedance, which can be modeled as a one-dimensional transfer matrix. The sound absorption coefficient is then calculated by the transfer-matrix method and the results of comparison with the experiments are reported. The corrugated clearance was divided into elements for which approximations that assumed the clearance between two planes and took into account the perimeter and cross-sectional area of each element were considered. The theoretical value of the sound absorption coefficient obtained using this method was shown to be in good agreement with the experimental results. The experimental value of the sound absorption coefficient was larger than the theoretical value in the previous method in the analysis wherein each divided element was approximated by the distance between two planes taking into account the thickness and cross-sectional area of the clearance.

DOI： 10.1121/1.5089427

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DOI： 10.7567/1347-4065/aaec10

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The present study focuses on a silencer built within the thick portion of a door edge and reports on the results of evaluating silencers by determining sound transmission loss via theoretical analysis and experiments on three types of silencers. The theoretical analysis involved determining the calculated values of sound transmission loss obtained using the transfer matrix method. The change in cross-sectional shape was analyzed by elemental division of the transfer matrix. Using the above, simulations were performed with respect to the optimum shape of the silencer. These theoretical analyses were then compared with the measurement results. Furthermore, the study includes the results of an experiment that attempted to restrain the dip in sound transmission loss by adding a non-woven fabric to the opening of the silencer. In a side branch silencer with an increasing shape wherein the longitudinal cross-section is a linear or an exponential function, the peak of the transmission loss was shifted to the lower frequency side when compared with that in the case of a rectangular side branch silencer. Furthermore, in comparisons between the two, the sound attenuation peak frequency was lower in the case of the exponential shape. The resonance of the side branch was suppressed by adding a non-woven fabric to the opening of the side branch silencer. As a result, the peak and dip of sound attenuation were alleviated, and the sound attenuation characteristics could be adjusted.

DOI： 10.1121/1.5082301

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Acoustical Society of America  

Closely packed nested structure circular tubes form three types of clearances: circular clearances, concentric clearances, and longitudinal clearances. The cross-sectional shape of rice straw, including three types of clearances?circular clearances, concentric clearances, and clearances formed by three closely packed cylinders?is similar to that of the samples of the present study. Herein, the propagation constant and characteristic impedance of the circular, concentric, and longitudinal clearances surrounded by three cylindrical surfaces are treated as a transfer matrix. Then, by connecting these transfer matrices in parallel, a transfer matrix integrating these clearances is determined, and the sound absorption coefficient is calculated. Test samples that have three types of clearances are also created, and measure their sound absorption coefficients. The contributions of the concentric and circular clearances are significant because of the dimensions of the used tubes. The results of the calculations that took eccentricity into account revealed no significant impact on the sound absorption coefficient in wide-frequency range. The results of the calculations that took flexure int

DOI： 10.1121/1.5063348

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Other Link： https://asa.scitation.org/doi/abs/10.1121/1.5063348

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

While standard laser range finders use modulation signals, such as sharp pulses, the method we devised employs laser diode's frequency noise, and a frequency discriminator, to produce the intensity noise signal, which we use to generate fast physical random numbers. Observed through a frequency discriminator, beams traveling along two different paths share intensity noise patterns, i.e., the same fast physical random numbers, but with a time lag. We compared the two, and calculated their cross-correlation. By sweeping their time lags, we confirmed the length of the two optical paths, up to 50m.

DOI： 10.1117/12.2288086

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

While optical laser range finders use random signals to determine distance, a laser diode's fast frequency noise can perform the task. Moreover, this signal can be applied to physical-random number generation. This research describes a method, whereby laser diode's frequency noise characteristics generate a large number of physical-random numbers and determine the distance to a target [1] [2]. We tested the random number generating- and distance- measuring capabilities of two types of lasers
a Fabry-Perot-LD and VCSEL: (Vertical Cavity Surface Emitting Laser). With the Fabry-Perot etalon functioning as frequency discriminator, we investigated the physical-random numbers' characteristics from both Fabry-Perot-LD's and the VCSEL's characteristic's points of view. We verified the generated binary number's randomness, using NIST FIPS140-2 test, and noted the Random Number Generation (RNG) speed of a FP-LD was 48 Gbit/s, and that of a VCSEL was 159 Gbit/s. When the generation speed of the physical-random number is high, we can increase the sampling rate of our range finders and improve resolution.

DOI： 10.1117/12.2324692

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

While standard laser range finders use modulation signals, such as sharp pulses and periodic signals, to generate fast physical random numbers, our method does away with the modulator, and instead, utilizes laser diodes' frequency noise and a frequency discriminator, to produce the intensity noise signals that generate fast physical random numbers. Observed through a frequency discriminator, beams having the same intensity noise patterns travel along two different paths, but with a time lag. We measured and calculated their cross-correlation, confirming the degree of difference in their optical paths, up to a distance of 50 m. We improved range resolution by taking advantage of the polynomial approximation of the coefficients around the peak of the correlation waveform.

DOI： 10.1117/12.2324829

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

An inordinate amount of time, effort (and paper) has been spent trying to find a way to stabilize laser-diode frequencies, but our research team has been working on the premise, that frequency instability can, in fact, have its up-sides. In the present work, we focus on a method that uses laser diodes' own noise to generate physical random numbers. Introducing a frequency discriminator as a reference, we control and stabilize the difference between the frequency reference and the laser frequency, thereby generating random numbers at a suitable point.

DOI： 10.1117/12.2288035

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

Not so long ago, pseudo random numbers generated by numerical formulae were considered to be adequate for encrypting important data-files, because of the time needed to decode them. With today's ultra high-speed processors, however, this is no longer true. So, in order to thwart ever-more advanced attempts to breach our system's protections, cryptologists have devised a method that is considered to be virtually impossible to decode, and uses what is a limitless number of physical random numbers. This research describes a method, whereby laser diode's frequency noise generate a large quantities of physical random numbers. Using two types of photo detectors (APD and PIN-PD), we tested the abilities of two types of lasers (FP-LD and VCSEL) to generate random numbers. In all instances, an etalon served as frequency discriminator, the examination pass rates were determined using NIST FIPS140-2 test at each bit, and the Random Number Generation (RNG) speed was noted.

DOI： 10.1117/12.2288160

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：FRONTIERS MEDIA SA  

Light-gated ion channels and transporters have been applied to a broad array of excitable cells including neurons, cardiac myocytes, skeletal muscle cells and pancreatic b -cells in an organism to clarify their physiological and pathological roles. Nonetheless, among nonexcitable cells, only glial cells have been studied in vivo by this approach. Here, by optogenetic stimulation of a different nonexcitable cell type in the cochlea of the inner ear, we induce and control hearing loss. To our knowledge, deafness animal models using optogenetics have not yet been established. Analysis of transgenic mice expressing channelrhodopsin-2 (ChR2) induced by an oligodendrocyte-specific promoter identified this channel in nonglial cells-melanocytes-of an epithelial-like tissue in the cochlea. The membrane potential of these cells underlies a highly positive potential in a K C -rich extracellular solution, endolymph; this electrical property is essential for hearing. Illumination of the cochlea to activate ChR2 and depolarize the melanocytes significantly impaired hearing within a few minutes, accompanied by a reduction in the endolymphatic potential. After cessation of the illumination, the hearing thresholds and potential returned to baseline during several minutes. These responses were replicable multiple times. ChR2 was also expressed in cochlear glial cells surrounding the neuronal components, but slight neural activation caused by the optical stimulation was unlikely to be involved in the hearing impairment. The acuteonset, reversible and repeatable phenotype, which is inaccessible to conventional gene-targeting and pharmacological approaches, seems to at least partially resemble the symptom in a population of patients with sensorineural hearing loss. Taken together, this mouse line may not only broaden applications of optogenetics but also contribute to the progress of translational research on deafness.

DOI： 10.3389/fnmol.2017.00300

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Language：Japanese   Publisher：日本機械学会  

<p>In this article, we examined several longitudinal-sectional sizes of a silencer whose volume was limited by the thickness and aperture ratio of the ventilation door. We report the results of improvement in the sound attenuation properties of these shapes. As an evaluation method for the silencer, we measured transmission losses using an impedance measurement tube and calculated them on the basis of a theoretical analysis. The following results were obtained from the evaluation of the silencer using the measurement and calculation results and from the verification of the improved shape of a silencer and silencer array. For a side branch tube silencer with a 1/3 aperture ratio, assuming that it is installed into the ventilation door, we observed a side branch tube with an linear expanded longitudinal-sectional shape by improving the shape using the theoretical analysis of transmission losses. In addition, as a result of the experiment with a sample on the basis of the theoretical analysis, both the experimental and the theoretical analysis were in good agreement. Furthermore, the expanded shape of the longitudinal-section of the side branch tube decreased the frequency of the sound attenuation peak. It was found that a silencer with a combination of four of these silencers can be arrayed side-by-side in a ventilation door; this results in a flat transmission loss of more than 5 dB over a broad band.</p>

DOI： 10.1299/transjsme.16-00575

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

An optical range finder system that relies on laser diodes' frequency noise, instead of intensity or frequency modulations, and its improvement in resolution are reported. The distance to the target is measured by calculating the cross-correlation of two signals reflected from the target and reference mirrors. These two signals are converted from the laser diodes' frequency noise signals by frequency/intensity converters, such as a Fabry-Perot etalon. We obtained the distance to the target by checking time lags between the target and reference beams at the highest correlation coefficient. We also measured the change in the correlation coefficient around the peak sampling point by adjusting the reference-path length, achieving a resolving power of +/- 3 mm. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.

DOI： 10.1117/1.OE.56.6.064101

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Language：Japanese   Publisher：日本機械学会  

In this paper, we report the use of sound-absorbing materials, specifically sound-absorbing structures of bundled rice straws, that are oblique arranged incident to the sound waves. In addition, we investigated the normal and oblique incident sound-absorption coefficients of sound-absorbing structures made of bundled rice straws in free space. In this study, we placed sound-absorbing structures made of bundled rice straws at an angle against the direction of the thickness in order to elongate the rice-straw element without increasing the apparent thickness. We then experimentally investigated the increase in sound absorption in the low-frequency range. The following conclusions were drawn. For test samples in which rice straws were arranged both in a normal direction and in an oblique manner, the value of the normal incident sound-absorption coefficient in free space was close to the results obtained using acoustic tubes. For test samples with rice straws arranged both in the normal direction and in the oblique manner, the sound-absorption peak of the oblique incident sound-absorption coefficient in free space was shifted to the high-frequency side compared with that of the normal

DOI： 10.1299/transjsme.16-00344

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Other Link： https://www.jstage.jst.go.jp/article/transjsme/83/845/83_16-00344/_article/-char/ja/

Language：English   Publisher：Japanese Society for Engineering Education  

In 1996, when the Faculty of Engineering of Niigata University, Niigata Japan first set up its international student exchange program with Otto-von-Guericke-University, in Magdeburg, Germany, few students showed an interest in studying abroad. Twenty years later, the students' attitudes have changed. The number of students who express a desire to study abroad and have experienced the international conference has increased markedly. In this article, two directions of opportunities for students to start studying abroad are presented; one is short-term summer school program as a subject of general education to remove the students' barriers to go abroad, and the other is research-oriented students' exchange program.

DOI： 10.20549/jseeen.2017.0_31

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Language：English   Publishing type：Research paper (scientific journal)  

A stable microwave source using frequency stabilized diode lasers was developed. The Doppler-free spectra of Rb atoms produced by saturated absorption spectroscopy were used to obtain highly-sensitive control signals and lock the frequency of diode lasers to it. The beat frequencies between two independently stabilized diode lasers were 1.2 GHz and 2.9 GHz. The fluctuations in beat frequencies were 40 kHz and 400 kHz respectively in the best stability.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Co-application of acoustoelasticity and optical interferometry to residual stress analysis is discussed. The underlying idea is to combine the advantages of both methods. Acoustoelasticity is capable of evaluating a residual stress absolutely but it is a single point measurement. Optical interferometry is able to measure deformation yielding two-dimensional, full-field data, but it is not suitable for absolute evaluation of residual stresses. By theoretically relating the deformation data to residual stresses, and calibrating it with absolute residual stress evaluated at a reference point, it is possible to measure residual stresses quantitatively, nondestructively and two-dimensionally. The feasibility of the idea has been tested with a butt-jointed dissimilar plate specimen. A steel plate 18.5 mm wide, 50 mm long and 3.37 mm thick is braze-jointed to a cemented carbide plate of the same dimension along the 18.5 mm-side. Acoustoelasticity evaluates the elastic modulus at reference points via acoustic velocity measurement. A tensile load is applied to the specimen at a constant pulling rate in a stress range substantially lower than the yield stress. Optical interferometry measures the resulting acceleration field. Based on the theory of harmonic oscillation, the acceleration field is correlated to compressive and tensile residual stresses qualitatively. The acoustic and optical results show reasonable agreement in the compressive and tensile residual stresses, indicating the feasibility of the idea.

DOI： 10.3390/ma9020112

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Other Link： http://www.mdpi.com/1996-1944/9/2/112

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

In this study, we theoretically and experimentally explore the acoustic leak of an entire acoustic system as well as the various gap occurring between a gasket and flange. We conducted the first-ever fundamental research related to sound transmission loss through a narrow gap between a gasket and flange. In the experiments, we constructed pipeline elements, including the gap and the leakage path, in the impedance measurement tube. In the theoretical analysis, we replaced the fluid path, including the gap, with acoustic elements that comprise an electrical equivalent circuit. We then conducted the analysis using the transfer matrix method. To calculate the attenuation of sound waves propagating through the gap, we considered friction in association with viscosity, primarily in the boundary layers of the inner wall, to derive the characteristic impedance and propagation constant. The trends between the calculated and the actual experimental values for transmission loss in the entire acoustic system coincided enough with regard to a large gap size range between 0.01 and 0.2 mm. Furthermore, the transmission loss linearly increased with the decreasing logarithm of gap for the calculated regions. Furthermore, the theoretical analysis and experimental results show agreement for incline gap conditions between the gasket and flange. The maximum gap also greatly affects the acoustic transmission loss for the inclined gaps. This was confirmed both by the experimental and the calculated values. We consider that these results provide fundamental acoustic knowledge specific to the narrow gap between the gasket and flange in an acoustic system.

DOI： 10.1299/jamdsm.2016jamdsm0067

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

This study estimates the sound-absorption coefficient and transmission loss for the dimensions of clearances among the close-packed cylinders by theoretical analysis and compares these estimates with experimental values. In the analysis, we performed an elemental breakdown of the clearance configuration, and then approached each element as the clearance between two planes. Considering the effects of sound wave attenuation in each element of clearance, we found the propagation constant and characteristic acoustic impedance using three-dimensional analysis. By connecting these elements in parallel, we treated them as a one-dimensional transfer matrix. We then calculated the sound-absorption coefficient and transmission loss through the transfer matrix method. No sound-absorption coefficient could be obtained with calculations that did not account for attenuation. In addition, calculations that approached the clearance as an equivalent circle and a triangle did not match experimental values well. On the other hand, calculations using the method that accounted for clearance shape, that is the method used in this study, closely matched experimental values. Estimations of transmission loss expressed all clearances by connecting their transfer matrices in parallel. In calculations, these estimations did not account for attenuation, and the falling curve for transmission loss greatly diverged from experimental values. In the three calculations that accounted for attenuation, the falling segment of transmission loss showed frequency characteristics that were close to experimental values. Calculations through the methods that accounted for clearance shapes and that analyzed clearance as an equivalent triangle also had peak transmission loss values that closely matched experimental values.

DOI： 10.1299/jamdsm.2015jamdsm0065

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Other Link： https://www.jstage.jst.go.jp/article/jamdsm/9/5/9_2015jamdsm0065/_pdf

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER-VERLAG BERLIN  

This paper reports a natural ventilation silencer for an animal cage having considerable sound insertion loss. Many veterinary hospitals face a serious problem that hospitalized animals are stressed from the barks of other dogs in the hospital. To address this problem, a solution that barely affects caged dogs' health is required. We attempted to use a silencer with sound insertion loss by attaching it to an opening side of the cage. We constructed the tested prototype silencers by using the resonance of a rectangular room and a nonwoven fabric. We measured the acoustic characteristics of the silencers that were attached to the real scale model of the animal cage. We also measured their insertion loss by considering the estimated frequency characteristics of the dogs' barking sound. The result shows that proposed silencers have more than 10 dB insertion loss; therefore, they can maintain respiratory environment of a caged dogs along with good visibility.

DOI： 10.1007/978-3-319-06986-9_16

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER-VERLAG BERLIN  

This paper reports a natural ventilation silencer for an animal cage having considerable sound insertion loss. Many veterinary hospitals face a serious problem that hospitalized animals are stressed from the barks of other dogs in the hospital. To address this problem, a solution that barely affects caged dogs' health is required. We attempted to use a silencer with sound insertion loss by attaching it to an opening side of the cage. We constructed the tested prototype silencers by using the resonance of a rectangular room and a nonwoven fabric. We measured the acoustic characteristics of the silencers that were attached to the real scale model of the animal cage. We also measured their insertion loss by considering the estimated frequency characteristics of the dogs' barking sound. The result shows that proposed silencers have more than 10 dB insertion loss; therefore, they can maintain respiratory environment of a caged dogs along with good visibility.

DOI： 10.1007/978-3-319-06986-9_16

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

This study focuses on acoustic silencers on indoor-use doors positioned in an array. In this paper, we discuss our studies of side branch silencers which are built in the ventilation door. By designing and fabricating a special attachment, we were able to attach silencers to the measurement tube that had larger cross sections than the impedance measurement tube. Using this attachment, we measured acoustic transmission losses for each of six different prototype silencers. By adding orifice silencer effects, we obtained transmission losses across a wide frequency range. However, attenuation decreased in frequency ranges below the attenuation peak of the side branch tubes. A wedge-shaped longitudinal cross section for the side branch tubes can double the length of the silencer and develop lower-frequency attenuation effects, while maintaining the same volume. This wedge-shaped side branch tube is suitable for a long silencer placed side by side in an array formation We performed theoretical analyses of acoustic transmission losses of silencers using the transfer matrix method based on a one-dimensional wave equation. We performed element decomposition on the transfer matrix for silencers with side branch tubes with a wedge-shaped longitudinal cross section. We obtained calculated results that were sufficiently valid compared to our experimental measurements.

DOI： 10.1299/jamdsm.2015jamdsm0028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

In this paper, we propose a louver with a simple structure and a high aperture ratio. A louver element with a sound attenuating structure composed of layered two flat rectangular tubes, each of which is wedge-shaped with thickness decreasing toward the closed end, was constructed and experimentally and theoretically analyzed. Samples having more basic structures were also constructed and compared. In the theoretical analysis, the sound attenuation characteristics of a louver element were clarified considering sound attenuation in the clearance between two planes, as is typically observed in the flat rectangular tubes furnished in the louver element. To consider the sound attenuation due to the viscosity of the air in the rectangular tube, the propagation constant and characteristic acoustic impedance were derived using the Navier-Stokes equations, etc. Further, the sound transmission loss was calculated by the transfer matrix method. The tendency of the theoretical values in consideration of the attenuation of sound wave roughly agreed with the experimental values. Note that the attenuation of sound wave is evident in a thin or wedge-shaped tube and has to be considered in the theoretical analysis. The number of flat rectangular tubes was doubled without increasing the thickness of a louver element. The structure is useful as a louver slat because sound attenuation is achieved in a wide frequency range while maintaining a high aperture ratio.

DOI： 10.1299/jamdsm.2015jamdsm0039

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

There are engineering benefits if we can predict the acoustic properties such as the sound absorption coefficient of a sound incident on the clearance of such an annular cross-section based on the geometric dimensions of the tubes and the physical properties of the gas. However, a successful theory for the sound absorption coefficient of narrow tubes of the abovementioned shapes has not yet been presented, and the comparison between experimental and theoretical values has not been made. Further, the propagation constant and characteristic impedance in the clearance in a double cylinder have not yet been derived in the cylindrical coordinate system or by other methods. Therefore, in this paper, the propagation constant and characteristic impedance were derived by approximating clearance of an annular cross-section with clearance between two parallel planes. And the sound absorption coefficient was calculated, then compared with experimental results. The theoretical values, according to this method, agreed well with the experimental values, and practically sufficient accuracy was obtained. It was experimentally confirmed that the eccentricity of a round bar in a circular hole does not appreciably influence the sound absorption coefficient. Even when this calculation method is applied to a circular hole, the results agree with the theoretical and experimental values for the circular hole. Therefore, this method is effective even if the diameter of the internal cylinder is considerably smaller than that of the external cylinder.

DOI： 10.1299/jamdsm.2015jamdsm0040

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

We conducted a study related to sound absorbing materials created by folding thin material in the shape of a Japanese folding fan. In order to conduct a calculation of the shape of a clearance in the folding fan-shaped test sample, we performed an approximation of element decomposition in both the incidence direction of the sound wave and the lateral direction. In a theoretical analysis, we considered sound wave attenuation due to boundary layer friction in the clearance between two surfaces. We compared experimental and calculated values for the sound absorption coefficient. Trends in both matched closely. Errors in the calculated values for large clearances could be attributed mainly to irregularity in the size of the clearances. Frequency shift of the calculated values for small clearances were due to errors in estimating the sound attenuation. Sound absorbing structures shaped like a folding fan possess sound absorption characteristics are similar to the wedge-shaped sound absorbing structures shown in previous reports. This was also shown in calculated values based on theoretical analysis. In cases with an appropriate back air space, sound absorption peak frequencies decreased relative to cases without a back air space, and sound absorption characteristics were superior across a wide frequency range.

DOI： 10.1299/jamdsm.2015jamdsm0062

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Language：Japanese   Publisher：Japan society of Mechanical Engineers  

To quantitatively predict leakage rates through gasket/flange interface, it is important to observe contact conditions at seal surfaces because the leakage path consists of the non-contact portions between the flange and gasket surfaces. The contact surfaces of the flanges were finished by lathe turning. In this study, we observed real contact area on gasket surfaces using a laser microscope with a wide field of view. The observations indicated that the leakage paths on the gasket surfaces were in the radial direction perpendicular to a lathe-turned groove and the circumferential direction along the groove. As the closing loads increased, the leakage paths in the radial direction disappeared and only the leakage path in the circumferential direction remained. The critical contact pressure where the leakage paths in the radial direction disappear was determined from the observation of the contact surface of the gasket. Over the critical contact pressure, the leakage rates obtained from the experiments showed good agreement with the calculated values under the assumption of laminar flow along the turned groove. Under the critical contact pressure, the recalculated values considered t

DOI： 10.1299/transjsme.2014dsm0173

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Science Publishing Group  

This paper reports a natural ventilation silencer for an animal cage having considerable sound insertion loss. Many veterinary hospitals face a serious problem that hospitalized animals are stressed from the barks of other dogs in the hospital. To address this problem, a solution that barely affects caged dogs’ health is required. First, we estimated aperture ratio of the silencer device which was considered by physiological sustainability of dog. Next, we attempted to use a silencer with sound insertion loss by attaching it to an opening side of the cage. We constructed the tested prototype silencers by using the resonance of a rectangular room and a nonwoven fabric. We measured the acoustic characteristics of the silencers that were attached to the real scale model of the animal cage. We also measured their insertion loss by considering the estimated frequency characteristics of the dogs’ barking sound. The result shows that proposed silencers have more than 10 dB insertion loss; therefore, they can maintain respiratory environment of a caged dogs along with good visibility.

DOI： 10.11648/j.ijmea.20140201.14

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

We investigated the sound absorption coefficient within a sound-absorbing structure made of layered clearances between two planes. We discussed the experimental results from the existing literature and conducted a theoretical analysis on several different sound-absorbing structures that take into account the viscosity of the boundary layer at the clearances. First, we examined the case of thin sheets placed in parallel. Then, we examined the case where the size of the clearance continuously changed perpendicular to the direction of incidence of the sound waves. Subsequently, we examined the case where the clearance continuously decreased in the direction of incidence of the sound waves. In latter two cases, the transfer matrix used in the calculations was divided into elements perpendicular or coincident to the direction of incidence of the sound waves and the size of the clearance for each element was changed in a stepwise fashion. We then calculated the sound absorption coefficients for various structures and dimensions and observed that the calculated and experimental data agreed well. On the basis of the calculation simulation, the differences between the calculated and experimental absorption coefficient data were attributed mainly to the changes in the flexure of the sheet materials. The proposed calculation methods will be useful in determining the absorption coefficient of such shapes, and in the design of sound-absorbing materials that use such shapes.

DOI： 10.1299/jamdsm.2014jamdsm0036

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

This paper discusses a noise reduction structure with a thin Helmholtz resonator array integrated in louver elements. Using theoretical analysis, we derived the propagation constant and characteristic acoustic impedance with consideration for sound wave attenuation in the clearance between two planes for a thin cavity within the louver. The experiments with variation in three conditions were also performed: number of necks, internal thickness of the cavity, and number of partitions. Another experiment was conducted to verify that sound reduction characteristics change depending on the number of holes. The results closely matched with those calculated with consideration for attenuation, demonstrating the validity of the theoretical analysis. With respect to changes in the internal thickness of the cavity, experimental results showed that attenuation increased for clearances of 2 mm, causing significant differences in the sound reduction characteristics. At clearances of 8 mm, there was almost no attenuation in the clearance. Louvers with thin internal dimensions, in which holes diameter equal to the internal thickness of the cavity had been formed, created a larger effect than those with normal open end correction length. This resulted in a reduction in sound reduction frequency. Additionally, when cavities seen from the neck are created on the end face of the louver element as acoustic tubes, the properties of the acoustic tubes are added to the properties of the air spring. This achieved a significant reduction in the sound reduction peak frequency without increasing the volume of the cavity.

DOI： 10.1299/jamdsm.2014jamdsm0022

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASME  

To quantitatively predict the leakage rates of static metal seals, it is important to observe the real contact area at seal surfaces because the leakage path consists of the noncontact portions between the flange and gasket surfaces. In a previous study, we observed the real contact situation using a thin polymer film 1 mu m in thickness. In the present study, we observed the real contact area on gasket surfaces using a laser microscope with a wide field of view. With this method, observation time over the whole gasket surface could be greatly reduced compared with conventional methods. The observations indicated that the leakage paths on the gasket surfaces were in the radial direction perpendicular to a lathe-turned groove and the circumferential direction along the groove. As the closing loads increased, the leakage paths in the radial direction disappeared and only the leakage path in the circumferential direction remained. When the closing loads increased further, the widths of the leakage paths at both the inside and outside on the gasket surface became narrower. The critical contact pressure where the leakage paths in the radial direction disappear was determined from the observation of the contact surface of the gasket. The leakage rates obtained from the experiments showed good agreement with the calculated values under the assumption of laminar flow along the turned groove over the critical contact pressure.

DOI： 10.1115/1.4024781

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

We describe a method of generating physical random numbers by means of a diode laser that has an extremely wide-band frequency-noise profile. Fluctuations in the laser frequency affect the intensity of the light transmitted through the optical frequency discriminator, detected thereafter as random fluctuations. This allows us to simultaneously generate 8 random bit streams, due to the parallel processing of 8-digit binary numbers sampled by an 8-bit analog-to-digital converter. Finally, we generated physical random numbers at a rate of 3 Gbit/s, by combining one data stream with another stream that is delayed by 2 ms, by exclusive-OR. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. [DOI: 10.1117/1.OE.52.1.014302]

DOI： 10.1117/1.OE.52.1.014302

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

Narrow hole bundle structures, whether or not designed for use as sound-absorbing materials and silencers, are frequently observed in catalysts and honeycomb constructions. Being able to make an accurate estimation of the sound-absorption coefficient and transmission loss with respect to such narrow hole bundle structures by using just their dimensions is important. Therefore, in this study, the authors attempted to develop a theoretical estimation method and verified its effectiveness by comparing the results with those of experiments that were performed using two-microphone and four-microphone impedance tubes. Primarily, a propagation constant and the characteristic impedance of sound propagation in a cylindrical narrow tube, which is based on a two-dimensional cylindrical coordinate system analysis including attenuation, was used to perform calculations for precision estimation. Next, an accurate propagation constant and characteristic impedance based on a two-dimensional analysis were converted and introduced to one-dimensional axial coordinate system analysis based on a transfer matrix. The developed method proved to be capable of making an accurate estimation by a simple process using a one-dimensional transfer matrix that is generally used for designing silencers. © 2013 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaic.79.4164

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Sound transmission loss is relatively small in thin louver boards with a high aperture ratio. This study investigated louver elements with a sound attenuating function. Using narrow tubes, an array silencer was built into composite louver boards and a high aperture ratio was maintained. Several constructions for such louvers were prototyped, measured, and analyzed theoretically. Sound transmission loss was measured using four-microphone impedance tube. Then, sound transmission loss was calculated by a transfer matrix based on one-dimensional axial coordinate system analysis. The attenuation of sound in tubes should be calculated because a thin louver board must comprise narrow tubes. Therefore, an accurate propagation constant and a characteristic impedance based on two-dimensional analysis were introduced to enable theoretical analysis. The calculation results, including attenuation, and the experimental results had good coincidence. Moreover, the theoretical analysis confirmed that the silencer worked effectively and could be applied to silencer designs. © 2013 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaic.79.2817

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

In this paper fundamental sound absorption characteristics of expanded polystyrene beads with several geometries are reported when they are packed in some thick layers with and without back air space. The normal incidence sound absorption coefficients, which were obtained by the experiments using two-microphone impedance tube, were evaluated comparing to theoretical estimations. Experimental data were also compared to the similar conditions but hard material particles like glass beads whose acoustic property was investigated by Sakamoto et. al. in a preceding study. Then following results were obtained; packed layer with expanded polystyrene beads has almost equal sound absorption coefficient to the similar layer with hard and solid material: numerical estimation of sound absorption coefficient is valid enough except for the case having large back air space: lowering peak frequency of sound absorption coefficient is available by overfilling and compressing particles. The authors also consider that applying soft, light, and low cost material to the sound absorbing structures is very meaningful. Because human damage caused by falling of wall and ceiling panel of buildings is avoidable particularly under an earthquake attack.

DOI： 10.1299/jamdsm.7.677

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

Sound transmission loss is relatively small in thin louver boards with a high aperture ratio. This study investigated louver elements with a sound attenuating function. Using narrow tubes, an array silencer was built into composite louver boards and a high aperture ratio was maintained. Several constructions for such louvers were prototyped, measured, and analyzed theoretically. Sound transmission loss was measured using four-microphone impedance tube. Then, sound transmission loss was calculated by a transfer matrix based on one-dimensional axial coordinate system analysis. The attenuation of sound in tubes should be calculated because a thin louver board must comprise narrow tubes. Therefore, an accurate propagation constant and a characteristic impedance based on two-dimensional analysis were introduced to enable theoretical analysis. The calculation results, including attenuation, and the experimental results had good coincidence. Moreover, the theoretical analysis confirmed that the silencer worked effectively and could be applied to silencer designs.

DOI： 10.1299/jamdsm.7.690

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Other Link： https://www.jstage.jst.go.jp/article/jamdsm/7/4/7_690/_pdf

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan society of Mechanical Engineers  

This study deals with the attenuation characteristics of a double orifice silencer on ventilation holes. In this study, we inserted a tubular sheet of nonwoven fabric between the two orifices to improve the dip characteristics of the silencer. Then, we measured the sound transmission loss of the silencer with a four-microphone impedance tube. Simple double orifice silencers can be analyzed in one-dimension, but the acoustical analysis of the nonwoven fabric sheet is much difficult. In addition, in one- dimensional analysis, we must deal with the acoustical model with regard to the radial direction transparency of sound through the nonwoven fabric sheet. The sound transmission loss of the double orifice silencer, which bridged the nonwoven fabric sheet, was calculated via one-dimensional analysis. In addition, in this analysis, the acoustical constants of the nonwoven fabric sheets measured by the "two-cavity method" were installed in an equivalent circuit. It was observed that the analysis and the experimental results were in similar trend. © 2013 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaic.79.3474

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

A large portion of patients of larynx cancer tekes total laryngectomy and loses their original voice consequently. Some ways to obtain substitute voice for total laryngectomees have been presented, however, each of them cannot conquer inconveniences, tone quality, extremely low tone, monotonousness etc. We invented very simple, small enough to be built in TE (tracheaesophageal) shunt valve but functional substitute voice that is driven by patient's own expiration and its tone pitch can be controlled by expiratory pressure simultaneously. The new device has an outward-striking membrane as an oscillating valve and a set of piston-cylinder mechanism, which controls oscillator's tension and alters pitch of sound. As results of performance experiments applied to the prototype model made as twice scale as an actual dimension, the device produces the lowest sound frequency of 205 Hz and pitch range of 374 cent being approximately proportional to driving air pressure between 0.8 and 2.2 kPa. It is said that normal pitch of female voice is around 210 Hz, thus we consider the possibility of the device as a new substitute voice was shown that contributes to improvement of total laryngectomees' QOL particularly to female patients.

DOI： 10.1299/jamdsm.7.777

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

In this study, the sound-absorption coefficients of the sound-absorbing structure using bundle of narrow clearances between a number of thin plates were measured for various formations and size. It is found by the experiment that, when the clearance between thin plates is reduced, the peak sound absorption value is increased and the frequency decreases. This phenomenon is related to velocity boundary layer thickness. Therefore, its occurrence is limited to clearances of 70 microns or more. When the clearances decrease in depth, the absorption coefficient is high compared with the case where clearances remain constant. This decrease also tends to improve the dip in the frequency characteristic curve of the absorption coefficient. However, when the clearances change to lateral direction continuously, this dip is not improved. When the amounts of materials constituting thin plates are identical, sound absorption performance of a folding-fan-type sound-absorbing structure is equivalent to a wedge-shaped sound-absorbing structure © 2013 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaic.79.4141

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

In this paper, several diameter of solid glass spherical grain was dealt. Each diameter grain has the each characteristic impedance and the complex wave constant. At first, the characteristic impedance and the complex wave constant for each grain diameters were measured. Then, the normal incidence absorption coefficient of each grain diameters for arbitrary layer thickness can be calculated. Likewise, the normal incidence absorption coefficient for multilayer with different grain diameters and arbitrary thicknesses can be calculated. This calculation process is comparatively lengthy, so the experiments for real multilayer and the calculations were compared. Result of the calculations coincided to the experiments. Consequently, calculation result of normal incidence absorption coefficient for multilayer with different grain diameters is useful.

DOI： 10.1299/jee.7.12

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Other Link： https://www.jstage.jst.go.jp/browse/jee/7/1/_contents

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

This paper describes sound quality changes caused by a sound aerodynamic failure in a micro-axial fan when applying acoustic diagnostic methods at a cooling fan motor assembly line. The aerodynamic failure sound was focused to a rotational fan blade tone and a blade passing noise with a change in the fan blade run-out. Experimentally obtained results clarified the correlation between the sound quality metrics (Sharpness, Roughness, Fluctuation strength, Tone-to-noise ratio) and the blade run-out. Furthermore, an acoustic diagnosis technique for fan blade run-out is proposed using an adaptive spectrum enhancer. This proposed acoustic diagnosis technique is used for an adaptive feedback algorithm using an internal model control architecture to extract an abnormal periodic signal including aerodynamic sound generated by a rotating micro-axial fan. The experimentally obtained results show that the blade passing sound signal with the blade run-out change was improved by about 10 dB using this adaptive feedback algorithm.

DOI： 10.1299/jee.7.1

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 日本機械学会  

A large portion of patients of larynx cancer tekes total laryngectomy and loses their original voice consequently. Some ways to obtain substitute voice for total laryngectomees have been presented, however, each of them cannot conquer inconveniences, tone quality, extremely low tone, monotonousness etc. We invented very simple, small enough to be built in TE (tracheaesophageal) shunt valve but functional substitute voice that is driven by patient's own expiration and its tone pitch can be controlled by expiratory pressure simultaneously. The new device has an outward-striking membrane as an oscillating valve and a set of piston-cylinder mechanism, which controls oscillator's tension and alters pitch of sound. As results of performance experiments applied to the prototype model made as twice scale as an actual dimension, the device produces the lowest sound frequency of 205 Hz and pitch range of 374 cent being approximately proportional to driving air pressure between 0.8 and 2.2 kPa. It is said that normal pitch of female voice is around 210 Hz, thus we consider the possibility of the device as a new substitute voice was shown that contributes to improvement of total laryngectomees' QOL particularly to female patients. © 2012 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaic.78.3053

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

In this paper, the problem in the CO2 infrared laser medical operation device that propagates the laser in the hollow optical fiber was dealt. There is risk of the accident of damaging by a fire when leak is opened in the hollow optical fiber, and the laser light is discharged outside. This study is the detecting method for the leak on hollow optical fiber by using the sound. A basic experiment concerning this method and comparison result between the theoretical analysis and the experiment are reported. The leakage of the narrow tube with large attenuation can be detected. The experiment was corresponding to the tendency to the theoretical analysis for the presence of the leakage and the change in the hole diameter. This method is inexpensive than the method of adding the optical device, it makes small hand peace, and doesn't ruin handling that is the advantage of the hollow optical fiber.

DOI： 10.1299/kikaic.77.2096

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

The porous material with continuous pore is useful for the sound absorbing material. In this research work, rice straw, rice husks, and buckwheat husks were dealt as a porous sound absorbing material that applied the biomass. About rice straw, geometrical condition of that was reproduced in the narrow tube of the simple structure, and the effect of absorbing sound of the tubule in the composite structure was verified. In the experiment, for the various thickness and the back air space were tested by using two microphone impedance tube, and the normal incidence sound absorption coefficient was measured. Moreover, the absorption coefficient was calculated from the acoustical constant obtained from the result of a measurement in a specific condition. And, these calculation values were compared with experiment values. As a result, it was shown to be able to estimate the absorption coefficient of the condition of the unmeasurement. As for rice straw, rice husks, and buckwheat husks, it has been understood it has a useful characteristic of absorbing sound. It leads to the fixation of the carbon, and even if the incineration processing is done, it is a carbon neutral.

DOI： 10.1299/jee.6.352

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

In this paper fundamental sound absorption characteristics of expanded polystyrene beads with several geometries are reported when they are packed in some thick layers with and without back air space. The normal incidence sound absorption coefficients, which were obtained by the experiments using two-microphone impedance tube, were evaluated comparing to theoretical estimations. Experimental data were also compared to the similar conditions but hard material particles like glass beads whose acoustic property was investigated by Sakamoto et. al. in a preceding study. Then following results were obtained
packed layer with expanded polystyrene beads has almost equal sound absorption coefficient to the similar layer with hard and solid material : numerical estimation of sound absorption coefficient is valid enough except for the case having large back air space : lowering peak frequency of sound absorption coefficient is available by overfilling and compressing particles. The authors also consider that applying soft, light, and low cost material to the sound absorbing structures is very meaningful. Because human damage caused by falling of wall and ceiling panel of buildings is avoidable particularly under an earthquake attack.

DOI： 10.1299/kikaic.76.2545

Scopus

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

The porous material with continuous pore is useful for the sound absorbing material. In this research work, rice straw, rice husks, and buckwheat husks were dealt as a porous sound absorbing material that applied the biomass. About rice straw, geometrical condition of that was reproduced in the narrow tube of the simple structure, and the effect of absorbing sound of the tubule in the composite structure was verified. In the experiment, for the various thickness and the back air space were tested by using two microphone impedance tube, and the normal incidence sound absorption coefficient was measured. Moreover, the absorption coefficient was calculated from the acoustical constant obtained from the result of a measurement in a specific condition. And, these calculation values were compared with experiment values. As a result, it was shown to be able to estimate the absorption coefficient of the condition of the unmeasurement. As for rice straw, rice husks, and buckwheat husks, it has been understood it has a useful characteristic of absorbing sound. It leads to the fixation of the carbon, and even if the incineration processing is done, it is a carbon neutral.

DOI： 10.1299/kikaic.75.3223

Scopus

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

In this paper, variation of airborne sound absorption coefficient for granular material with small quantity water is dealt. The granular matter under the test is solid glass spherical grain as diameter 1 mm. The relationship between water content by volume and absorption coefficient for each thickness of layer is measured by experiments. And tortuosity as one of the Biot's parameters is also measured by ultrasonic. It was proved that peak frequency of absorption coefficient decreases as increasing of water content. The reason is that reduced virtual sound velocity makes effect of larger sample thickness. Result of this study is useful for expecting absorption coefficient of wet or liquid bonded granular matter.

DOI： 10.1299/kikaic.75.2515

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

This paper describes a sound quality change caused by a failure aerodynamic sound in a micro axial fan in order to apply an acoustic diagnosis at cooling fan motor assembly line. The failure aerodynamic sound is focused to a rotational fan blade tone and blade passing noise with fan blade run-out change. In this experimental result, a correlation between the sound quality metrics (Sharpness, Roughness, Fluctuation strength, Tone to-noise ratio) and the blade run-out is cleared. In addition, an acoustic diagnosis technique for a fan blade run-out is proposed using an adaptive spectrum enhancer. This proposed acoustic diagnosis technique is used to adaptive feedback algorithm using internal model control architecture to extract a periodic abnormal signal including aerodynamic noise generated by rotating a micro axial fan. As the experimental results, the blade passing sound signal with the blade run-out change was improved about 10 dB by using this adaptive feedback algorithm.

DOI： 10.1299/kikaic.75.1194

Scopus

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Language：Japanese   Publisher：一般社団法人 日本機械学会  

In this paper, several diameter of solid glass spherical grain was dealt. Each diameter grain has the each characteristic impedance and the complex wave constant. At first, the characteristic impedance and the complex wave constant for each grain diameters were measured. Then, the normal incidence absorption coefficient of each grain diameters for arbitrary layer thickness can be calculated. Likewise, the normal incidence absorption coefficient for multilayer with different grain diameters and arbitrary thicknesses can be calculated. This calculation process is comparatively lengthy, so the experiments for real multilayer and the calculations were compared. Result of the calculations coincided to the experiments. Consequently, calculation result of normal incidence absorption coefficient for multilayer with different grain diameters is useful.

DOI： 10.1299/kikaic.74.2240

CiNii Article

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

The attenuation characteristics of a slit resonator that combined the adaptive feedback ANC system at a ventilation aperture of the package for leakage noise is investigated. The discrete tones radiated from an AC axial flow fan are controlled by DSP using Filtered-X Least Mean Square algorithm. The attenuation is found at the range of: 3<i>dB</i>-14<i>dB</i> with circular slit resonator, 2<i>dB</i>-15<i>dB</i> with elliptic slit resonator. Results of measurement show that the proposed system can achieve TNR(Tone to Noise Ratio) and PR(Prominence Ratio) under threshold effectively.

DOI： 10.1299/jee.2.470

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Other Link： http://orcid.org/0000-0002-5745-1668

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本機械学会  

The attenuation characteristics of a slit resonator that combined the adaptive feedback ANC system at a ventilation aperture of the package for leakage noise is investigated. The discrete tones radiated from an AC axial flow fan are controlled by DSP using Filtered-X Least Meane Square algorithm. The attenuation is found at the range of : 3dB-14dB with circular slit resonator, 2dB-15dB with elliptic slit resonator. Results of measurement show that the proposed system can achieve TNR (Tone to Noise Ratio) and PR (Prominence Ratio) under threshold effectively.

DOI： 10.1299/kikaic.71.327

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本機械学会  

This paper deals with the development of a new method for measurement of the height for granular material in a cylinder. For monitoring of automated filling processes of cartridges in a series production a new measurement method was developed which allows to detect rapidly incorrect products and to improve the process capability by the use of this method. The aim of this research work is to measure the level of granular material in a cartridge without contacting the material. The material is the mixture of the solid particles and air. The material is assumed as the porous media from the viewpoint of acoustics. As that, the inside of the cartridge, which is filled with granular material, is the acoustic system including porous media. The measuring method used the relationship between amount of granular meterial in the cartridge and the characteristics of the transfer function of the acoustic system is developed. The acoustic characteristic of the granular material, which is used for the theoretical analysis was also measured.

DOI： 10.1299/kikaic.70.679

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本機械学会  

This paper deals with the development of a new method for determination of powder form materials in plastic bag by sound. It is useful to determine the kind of powder form materials in the opaque plastic bag without open or contact. This detector utilizes the variation of the amplitude of the frequency response within entire acoustic system. The incident impedance of powder form materials varies with the diameter of particles and so on. For contactless determination, small distance gap between face of detector and plastic bag is adopted. Characteristic acoustic impedance and complex wave number are measured by the transfer function method. These measured parameters of powder form materials are introduced into theoretical analysis. The trends of the experiments and theory show good coincidence.

DOI： 10.1299/kikaic.69.42

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本機械学会  

This paper describes insulation characteristics of slit resonator that a single channel ANC system for silencing leakage noise at ventilation aperture of package. The circular slit resonator composed of thin air layer that is radial expansion with very short axial length was set up package wall. The circular thin air layer is driven by one to four speakers that are controlled using Filtered-X-LMS algorithm to minimize sound power at error microphone. The experimental results show that the noise reduction region spreads to the high frequency side, as the slit depth decreases. The noise reduction quantity increases, as the slit width widens. Visualization of SPL and phase on the circular slit resonator indicate that the noise reduction mechanism is the interference of control sound and noise.

DOI： 10.1299/kikaic.68.3122

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本機械学会  

This paper deals with the development of a new method for detecting the number of cloth without contact. It is necessary to detect one or plural number of sheets to avoid mishandling. This detecting sensor utilizes the variation of the phase of the transfer function within entire acoustic system. The incident impedance of sheets varies with the number of sheets. Characteristic acoustic impedance and complex wave number define peculiar and most fundamental characteristics of the material. It is useful for the detection of the number of cloth to know characteristic impedance of cloth. So that, we tried to measure characteristic impedance and wave number. The measured impedance of sheets by the transfer function method was introduced into theoretical analysis. The results of the experiments and theoretical analysis show fairly good coincidence

DOI： 10.1299/kikaic.67.1276

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmehs.2000.37.147

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DOI： 10.1299/kikaic.64.986

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人日本機械学会  

In this paper, we discuss the development of a new noncontact method for determining cylinder configurations using sound phase delay, In order to improve the accuracy of the measurements, the effect of the cavity in which the cylinder is placed has been studied. When the cylinder is placed near a side wall of the cavity, the phase delay angle increases, particularly for cylinders with odd periodic deflection. Thus, by varying the gap between the cylinder and the side wall, it is possible to determine the cylinder configuration even if the deflections are small. We propose a new method, in which the influence of noise is avoided by measuring the noise interference using a pair of microphones in the cavity.

DOI： 10.1299/kikaic.63.1989

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Recently, noncontact method for measuring cylinder configurations are required in industry. This paper reports the development of a new method for measuring cylinder configurations, using sound signal without contacting the contour surface. This method is based on the fact that the phases of sound waves scattered by a cylinder are delayed according to the diameter of the cylinder. Experiments were performed for various cylinder configurations formed by single and plural periodical deflection, using a loudspeaker, microphone and FFT-analyzer. It was found that the phase delays of sound waves were periodically changed according to the revolution of the cylinder, and the period between the phase delay and cylinder deflection was in good agreement. In addition, the angle of phase delay was linearly proportional to the magnitude of deflection.

DOI： 10.1299/kikaic.62.4250

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Other Link： http://www.jstage.jst.go.jp/article/kikaic1979/62/603/62_603_4250/_pdf

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DOI： 10.1299/kikaic.62.949

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1299/kikaic.61.1516

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS SANSHIN HOKUSEI BLDG  

This paper deals with a newly developed underwater displacement sensor utilizing the acoustic resonant frequency of water in a submerged pipe. Both ends of the pipe are closed. A speaker to generate sound is fixed on the end of the pipe with the reflector at the other end. A piezoelectric ceramic is used as a speaker. Sweeping signal is radiated from the speaker to the water column in the pipe. The sound pressure takes the largest value at the resonant frequency. The displacement of the reflector which is inserted from the other end of the pipe by the plunger, corresponds to the length of the water column. The displacement of the reflector has good correspondence to the resonant frequency of the water column. It is found from the experiment that it is possible to measure accurately underwater displacement using this sensor.

DOI： 10.1299/jsmec1993.38.42

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DOI： 10.1299/kikaic.60.994

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper deals with the development of a new detecting method of a number of sheets without contact. For example, in a cash dispenser paper sheets are transferred one by one and counted synchronously. So it is necessary to detect one or a plural number of sheets to avoid mistransferring. Hitherto, the contact measuring method has been used for detecting the transference of sheets. This noncontact sensor utilizes the variations of frequency response of the whole acoustic system of the sensor with sheets which are set near the sensor. The impedance of sheets varies with its number. The number of sheets has shown good correspondence with the resonant frequency and frequency response of the acoustic system. An electrical analogy is adopted for theoretical analysis of the acoustic system. The results of the calculation and experiments coincide significantly. It is possible to detect the number of sheets within a very short time period by means of variations of the frequency response.

DOI： 10.1299/kikaic.59.819

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Other Link： http://hdl.handle.net/10191/5797

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper deals with a newly developed underwater displacement sensor utilizing the acoustic resonant frequency of water in a submerged pipe. Both ends of the pipe are closed. A speaker to generate sound is fixed on the end of the pipe with a reflector at the other end. Piezoelectric ceramic is used as a speaker. A sweep signal is radiated from the speaker to the water column in the pipe. The sound pressure takes the largest value at the resonant frequency. The displacement of the reflector which is inserted from another end of the pipe by a plunger, corresponds to the length of the water column. The displacement of the reflector has good correspondence to the resonant frequency of the water column. It is found from the experiment that it is possible to accurately measure underwater displacement, using this sensor.

DOI： 10.1299/kikaic.59.587

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Other Link： http://hdl.handle.net/10191/5909

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DOI： 10.1299/kikaic.58.3259

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS SANSHIN HOKUSEI BLDG  

A new method of measuring displacement by means of variations of sound frequency and length of an air column in a stopped resonant pipe has been investigated. In this study, a speaker was used as the sound-generating source instead of the air jet, which was used for the feedback excitation mechanism on the edge instrument. This paper deals with a new kind of displacement sensor using an electric feedback circuit. A sweep signal is radiated from the speaker through the small hole which is opened on one end of the closed resonant pipe, toward the inside of the air column. The sound pressure takes the largest value at the resonant frequency. The displacement of the plunger which is inserted from the other end of the pipe corresponds to the length of the air column. Thus, the displacement of the plunger corresponds well to the resonant frequency of the air column. The phase-locked loop device is adopted for stability of the resonance and frequency.

DOI： 10.1299/jsmec1988.35.9

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Language：Japanese   Publisher：日本機械学会  

A new displacement measuring method using variations in sound frequency and length of an air column in a closed resonant pipe has been investigated. This noncontact displacement sensor is oscillated by the feedback loop, which is composed of a speaker, microphone and phase-locked loop. The sound pressure takes the largest value at the resonant frequency. The displacement of the measuring object corresponds to the impedance of one end of the air column. Thus the displacement of the measuring object has good correspondence to the resonant frequency of the acoustic system. The original resonant point is measured by transfer function from the FFT analyzer. An electrical analogy is adopted for theoretical analysis of the acoustic system. The results of the calculation and experiments coincide significantly.

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Language：Japanese   Publisher：the Japan society of Mechanical Engineers  

This research paper presents a new method of measuring the length of a pipe by using sound frequency. A sweep signal is radiated from the speaker toward the inside of the pipe. The sound pressure at the resonant frequency of the air column in the pipe indicates the largest value. The length of the pipe to be measured corresponds well to the resonant frequency. The phase. locked loop device is adopted to obtain the stabilities of resonation and frequency. A frequency counter with a reciprocal mode is adopted for higher resolution within a shorter time period because of low frequency.

DOI： 10.1299/kikaic.57.2217

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Other Link： http://hdl.handle.net/10191/5793

Language：Japanese   Publisher：the Japan society of Mechanical Engineers  

A new measuring method of displacement by means of variations of sound frequency and length of an air column in a closed resonant pipe has been investigated. This displacement sensor is oscillated by the feedback loop which is composed of a speaker, microphone and phase-locked loop instead of an air jet for the feedback excitation mechanism on the edge instrument. The sound pressure takes the largest value at the resonant frequency. The displacement of the plunger corresponds to the length of the air column. Thus the displacement of the plunger has good correspondence to the resonant frequency of the air column. However the oscillating frequency shifts from the original resonant frequency at the end of the range due to the use of the filter and simple circuit. Thus, the original resonant point is measured by transfer function from the FFT analyzer. An electrical analogy is adopted for theoretical analysis of the acoustic system. The results of the calculations and experiments coincide significantly.

DOI： 10.1299/kikaic.57.780

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Other Link： http://hdl.handle.net/10191/5791

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A new measuring method of displacement by means of variations of sound frequency and length of air column in a closed resonant pipe has been investigated. In this paper, a speaker is used as a sound generating source in stead of air jet for the feedback excitation mechanism on the edge instrument. This paper deals with a new kind of displacement sensor using a electric feedback circuit. A sweep signal is radiated from the speaker through the small hole at one end of the closed resonant pipe toward inside of the air column. The sound pressure takes the largest value at the resonant frequency. The displacement of the plunger which is inserted from other end of the pipe, corresponds to the length of the air column. So, the displacement of the plunger makes good correspondence to the resonant frequency of the air column. The phase locked loop devise is adopted for stability of the resonation and frequency.

DOI： 10.1299/kikaic.56.2562

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Other Link： http://hdl.handle.net/10191/5789

Language：Japanese   Publisher：the Japan society of Mechanical Engineers  

A new measuring method of displacement by means of variations of sound frequency and length of the air column in a closed resonant pipe has been investigated. This paper deals with the theoretical analysis of this device as a small and closed edge instrument (for example, a dog training whistle or a closed organ pipe). The electrical analogous circuit of a closed edge instrument was introduced for theoretical analysis. In the calculation, the velocity distribution of blown air on the mouth of the instrument was adopted. The results of the calculation of theoretical equations and experiments coincide significantly.

DOI： 10.1299/kikaic.56.435

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Other Link： http://hdl.handle.net/10191/5781

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS SANSHIN HOKUSEI BLDG  

DOI： 10.1299/jsmec1988.31.727

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This paper deals with the development and analysis of a new measuring method of displacement and position by means of the variations of the sound frequency and the air column in a resonant pipe. Sound generates when compressed air is blown onto an open-ended face of a small pipe. The sound frequency varies with the length of the air column in the resonant pipe. By applying this phenomena, a new, accurate and simple measuring method for the displacement and position is examined and developed. The displacement corresponds to the length of the air column and the variation of the sound frequency shows a good relationship with the displacement. The resonant frequency of the pipe can be shown by a simple equation; however, the resonant frequency does not coincide with the sounding frequency of the pipe. The difference of these two frequencies could be introduced in this paper as an active end correction of the pipe.

DOI： 10.1299/kikaic.54.651

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Other Link： http://hdl.handle.net/10191/5775

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© INTER-NOISE 2018 - 47th International Congress and Exposition on Noise Control Engineering: Impact of Noise Control Engineering. All rights reserved. It was reported the use of sound-absorbing materials, specifically sound-absorbing structures of bundled rice straws, that are oblique arranged incident to the sound waves. In addition, we investigated the normal and oblique incident sound-absorption coefficients of sound-absorbing structures made of bundled rice straws in free space. In this study, we placed sound-absorbing structures made of bundled rice straws at an angle against the direction of the thickness in order to elongate the rice-straw element without increasing the apparent thickness. We then experimentally investigated the increase in sound absorption in the low-frequency range. For test samples with rice straws arranged both in the normal direction and in the oblique manner, the sound-absorption peak of the oblique incident sound-absorption coefficient in free space was shifted to the high-frequency side compared with that of the normal incident sound-absorption coefficient and the sound-absorption curve became flat in the high-frequency range. We demonstrated that the use of an oblique arrangement of rice straws inside acoustic tubes and in free space can improve the sound absorption in low-frequency range without increasing the apparent thickness of the material.

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An inordinate amount of time, effort (and paper) has been spent trying to find a way to stabilize laser-diode frequencies, but our research team has been working on the premise, that frequency instability can, in fact, have its up-sides. In the present work, we focus on a method that uses laser diodes' own noise to generate physical random numbers. Introducing a frequency discriminator as a reference, we control and stabilize the difference between the frequency reference and the laser frequency, thereby generating random numbers at a suitable point.

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Event date： 2018

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Not so long ago, pseudo random numbers generated by numerical formulae were considered to be adequate for encrypting important data-files, because of the time needed to decode them. With today's ultra high-speed processors, however, this is no longer true. So, in order to thwart ever-more advanced attempts to breach our system's protections, cryptologists have devised a method that is considered to be virtually impossible to decode, and uses what is a limitless number of physical random numbers. This research describes a method, whereby laser diode's frequency noise generate a large quantities of physical random numbers. Using two types of photo detectors (APD and PIN-PD), we tested the abilities of two types of lasers (FP-LD and VCSEL) to generate random numbers. In all instances, an etalon served as frequency discriminator, the examination pass rates were determined using NIST FIPS140-2 test at each bit, and the Random Number Generation (RNG) speed was noted.

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While standard laser range finders use modulation signals, such as sharp pulses, the method we devised employs laser diode's frequency noise, and a frequency discriminator, to produce the intensity noise signal, which we use to generate fast physical random numbers. Observed through a frequency discriminator, beams traveling along two different paths share intensity noise patterns, i.e., the same fast physical random numbers, but with a time lag. We compared the two, and calculated their cross-correlation. By sweeping their time lags, we confirmed the length of the two optical paths, up to 50m.

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In 1996, when the Faculty of Engineering of Niigata University, Niigata Japan first set up its international student exchange program with Otto-von-Guericke-University, in Magdeburg, Germany, few students showed an interest in studying abroad. Twenty years later, the students' attitudes have changed. The number of students who express a desire to study abroad and have experienced the international conference has increased markedly. In this article, two directions of opportunities for students to start studying abroad are presented; one is short-term summer school program as a subject of general education to remove the students' barriers to go abroad, and the other is research-oriented students' exchange program.

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Semiconductor laser range-finder systems use so-called "time-of-flight" methods that require us to modulate semiconductor lasers' intensity and frequency, and detect those of reflected lights, in order to compare optical paths to the reference and the target. But, accurate measurement requires both high-speed modulation and detection systems. By taking advantage of semiconductor lasers' broad-spectrum frequency noise, which has a range of up to a few GHz, and converting it to intensity noise, we were able to generate a set of high-speed physical random numbers that we used to precisely measure the distance. We tuned the semiconductor lasers' oscillation frequencies loosely to the Rb absorption line and converted their frequency noise to intensity noise, in the light transmitted. Observed through a frequency discriminator, beams traveling along two different paths will always share intensity noise patterns, but there is a time lag. We calculate the cross-correlation of the two signals by sweeping their time lags. The one with the highest degree of correlation was that corresponding to the difference in the length of the two optical paths. Through our experiments, we confirmed that the system was accurate up to a distance of 50 m, at a resolution of 0.03 m, when the sampling rate was adjusted to 0.2 ns.

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Event date： 2014.8

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Because of their low cost, light weight, low power consumption and durability, semiconductor lasers are ideal, for use as optical range finder light-sources. Their oscillation-frequency fluctuations generate the physical random numbers, which are used to measure distances. While normal range finders use modulation signals, such as sharp pulses, the method we devised employs semiconductor lasers&#039; frequency noise, and a frequency to intensity converter, such as the rubidium absorption profile, to produce physical random numbers. This allowed us to construct an optical range finder that requires no additional modulation of the semiconductor laser, - has a range of up to 50 meters, and resolution of 0.06 meters. We also consider the resolving power of this method without changing its sampling rate.

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Event date： 2014.8

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The encryption technique is necessary for the internet community. The encryption using the pseudo-random numbers is considered safe because it takes a lot of time to decode it. However, since high speed processing computers are emerging in these days, it may not safe anymore. On the other hand, quantum cryptographic communications which are theoretically impossible to decode have been advanced and need a large number of physical random numbers. This paper describes a method, whereby semiconductor laser diodes&#039; frequency noise-signatures generate a series of physical random numbers. As a result, we generated random number bit strings at 40Gb/s in a VCSEL and at 50Gb/s in a FPLD.

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Event date： 2014.8

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Because of their low cost, light weight, low power consumption and durability, semiconductor lasers are ideal, for use as optical range finder light-sources. Their oscillation-frequency fluctuations generate the physical random numbers, which are used to measure distances. While normal range finders use modulation signals, such as sharp pulses, the method we devised employs semiconductor lasers&#039; frequency noise, and a frequency to intensity converter, such as the rubidium absorption profile, to produce physical random numbers. This allowed us to construct an optical range finder that requires no additional modulation of the semiconductor laser, - has a range of up to 50 meters, and resolution of 0.06 meters. We also consider the resolving power of this method without changing its sampling rate.

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Event date： 2013.8

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The light output from a semiconductor laser has high speed noise in both intensity and frequency region. We generate physical random numbers from frequency noise which will be converted into intensity frequency noise by using a frequency discriminator. In this report, we compared two random numbers, one is generated from the free-running laser and the other is generated from the narrower-oscillation-width laser.

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Event date： 2013.8

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A semiconductor laser&#039;s frequency fluctuates owing to the refractive index fluctuations caused by the spontaneous emission in a laser cavity. In this study, a new application of semiconductor laser&#039;s frequency noise characteristics is discussed. We propose a new laser rangefinder using the semiconductor laser&#039;s frequency noise. This method calculates the correlation between the divided laser beams and determines the optical distance without any modulation, and its accuracy are expected unchanged even in a long distance measurement. We measured the distance from 0 to 35m using the proposed method.

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Event date： 2013.8

Language：Japanese  

The light output from a semiconductor laser has high speed noise in both intensity and frequency region. We generate physical random numbers from frequency noise which will be converted into intensity frequency noise by using a frequency discriminator. In this report, we compared two random numbers, one is generated from the free-running laser and the other is generated from the narrower-oscillation-width laser.

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Event date： 2013.8

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Recently, cryptographic is important to protect information. Now, the pseudo-random number is used for cryptographic. But, it will be deciphered easily because of the computer development in the near future. Physical random number attracts attention because it is difficult to be deciphered when the physical random number is used in coding system. On the other hand, it is difficult to create it fast. Therefore, many fast physical-random number generation methods, which use the wide intensity noise characteristic of a diode laser, have been reported. We demonstrated a fast physical random number generation using the laser diode&#039;s frequency noise characteristic.

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Event date： 2013.8

Language：Japanese  

A semiconductor laser&#039;s frequency fluctuates owing to the refractive index fluctuations caused by the spontaneous emission in a laser cavity. In this study, a new application of semiconductor laser&#039;s frequency noise characteristics is discussed. We propose a new laser rangefinder using the semiconductor laser&#039;s frequency noise. This method calculates the correlation between the divided laser beams and determines the optical distance without any modulation, and its accuracy are expected unchanged even in a long distance measurement. We measured the distance from 0 to 35m using the proposed method.

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Event date： 2013.8

Language：Japanese  

Recently, cryptographic is important to protect information. Now, the pseudo-random number is used for cryptographic. But, it will be deciphered easily because of the computer development in the near future. Physical random number attracts attention because it is difficult to be deciphered when the physical random number is used in coding system. On the other hand, it is difficult to create it fast. Therefore, many fast physical-random number generation methods, which use the wide intensity noise characteristic of a diode laser, have been reported. We demonstrated a fast physical random number generation using the laser diode&#039;s frequency noise characteristic.

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Event date： 2013.8

Language：Japanese  

A semiconductor laser&#039;s frequency fluctuates owing to the refractive index fluctuations caused by the spontaneous emission in a laser cavity. In this study, a new application of semiconductor laser&#039;s frequency noise characteristics is discussed. We propose a new laser rangefinder using the semiconductor laser&#039;s frequency noise. This method calculates the correlation between the divided laser beams and determines the optical distance without any modulation, and its accuracy are expected unchanged even in a long distance measurement. We measured the distance from 0 to 35m using the proposed method.

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Event date： 2013.8

Language：Japanese  

The light output from a semiconductor laser has high speed noise in both intensity and frequency region. We generate physical random numbers from frequency noise which will be converted into intensity frequency noise by using a frequency discriminator. In this report, we compared two random numbers, one is generated from the free-running laser and the other is generated from the narrower-oscillation-width laser.

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Event date： 2013.8

Language：Japanese  

The light output from a semiconductor laser has high speed noise in both intensity and frequency region. We generate physical random numbers from frequency noise which will be converted into intensity frequency noise by using a frequency discriminator. In this report, we compared two random numbers, one is generated from the free-running laser and the other is generated from the narrower-oscillation-width laser.

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Event date： 2013.8

Language：Japanese  

Recently, cryptographic is important to protect information. Now, the pseudo-random number is used for cryptographic. But, it will be deciphered easily because of the computer development in the near future. Physical random number attracts attention because it is difficult to be deciphered when the physical random number is used in coding system. On the other hand, it is difficult to create it fast. Therefore, many fast physical-random number generation methods, which use the wide intensity noise characteristic of a diode laser, have been reported. We demonstrated a fast physical random number generation using the laser diode&#039;s frequency noise characteristic.

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Event date： 2013.8

Language：Japanese  

A semiconductor laser&#039;s frequency fluctuates owing to the refractive index fluctuations caused by the spontaneous emission in a laser cavity. In this study, a new application of semiconductor laser&#039;s frequency noise characteristics is discussed. We propose a new laser rangefinder using the semiconductor laser&#039;s frequency noise. This method calculates the correlation between the divided laser beams and determines the optical distance without any modulation, and its accuracy are expected unchanged even in a long distance measurement. We measured the distance from 0 to 35m using the proposed method.

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Event date： 2013.8

Language：Japanese  

Recently, cryptographic is important to protect information. Now, the pseudo-random number is used for cryptographic. But, it will be deciphered easily because of the computer development in the near future. Physical random number attracts attention because it is difficult to be deciphered when the physical random number is used in coding system. On the other hand, it is difficult to create it fast. Therefore, many fast physical-random number generation methods, which use the wide intensity noise characteristic of a diode laser, have been reported. We demonstrated a fast physical random number generation using the laser diode&#039;s frequency noise characteristic.

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Event date： 2013.8

Language：Japanese  

Recently, cryptographic is important to protect information. Now, the pseudo-random number is used for cryptographic. But, it will be deciphered easily because of the computer development in the near future. Physical random number attracts attention because it is difficult to be deciphered when the physical random number is used in coding system. On the other hand, it is difficult to create it fast. Therefore, many fast physical-random number generation methods, which use the wide intensity noise characteristic of a diode laser, have been reported. We demonstrated a fast physical random number generation using the laser diode&#039;s frequency noise characteristic.

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Event date： 2013.8

Language：Japanese  

The light output from a semiconductor laser has high speed noise in both intensity and frequency region. We generate physical random numbers from frequency noise which will be converted into intensity frequency noise by using a frequency discriminator. In this report, we compared two random numbers, one is generated from the free-running laser and the other is generated from the narrower-oscillation-width laser.

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Event date： 2013.8

Language：Japanese  

A semiconductor laser&#039;s frequency fluctuates owing to the refractive index fluctuations caused by the spontaneous emission in a laser cavity. In this study, a new application of semiconductor laser&#039;s frequency noise characteristics is discussed. We propose a new laser rangefinder using the semiconductor laser&#039;s frequency noise. This method calculates the correlation between the divided laser beams and determines the optical distance without any modulation, and its accuracy are expected unchanged even in a long distance measurement. We measured the distance from 0 to 35m using the proposed method.

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Event date： 2013.8

Language：Japanese  

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Event date： 2013.8

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Event date： 2013.8

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Event date： 2013.5

Language：Japanese  

We have been constructed a physical random number generator which utilizes laser diode&#039;s frequency noise characteristics. A linewidth of a laser diode indicates the range in which its oscillation frequency fluctuates. In this study, we generate random numbers using a laser diode which operates in a free-running condition and in an external cavity diode laser system which have a narrow linewidth. We used the &quot;FIPS140-2&quot; test as a statistical test suitable for the evaluation of random numbers and compared the random numbers which are generated in our two laser systems so that we consider the influence of linewidth of laser diodes.

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Event date： 2013.5

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Event date： 2013.3

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Event date： 2013.3

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Event date： 2013.3

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Event date： 2013

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Event date： 2013

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Event date： 2013

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The Japanese Student Services Organization (JASSO) has started its "Short-Stay and Short-Visit scholarship programs (SS-SV programs)" in the academic year 2011. The Faculty of Engineering, Niigata University, has obtained these scholarships for both German and Japanese students in 2011 and 2012. The objective of these "SS-SV programs" is to support students to visit a foreign country and stay there for less than three months. Because of our past experience of the "Two-week Summer School", which has been developed within the cooperation between Otto-von-Guericke-University Magdeburg, Germany and Niigata University, Japan since 1996, we experienced that a short term stay in a foreign country works as an initiator for the students' interest and will to study further in foreign countries. The authors believe that this type of short-term exchanges has actually proved to be very effective to encourage the students in engineering fields to start international activities.

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Event date： 2013

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Event date： 2013

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Event date： 2013

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Event date： 2013

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Event date： 2013

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Event date： 2013

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Event date： 2012.12

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Event date： 2012.12

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Event date： 2012.8

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Event date： 2012.8

Language：Japanese  

The pseudo-random number is normally used for large-scale simulation and encryption of communication. On the other hand, the physical-random number is recently expected to be used in these fields because it has no calculable periodicity and so makes the safer cipher. Therefore, many fast physical-random number generations, which use the wide intensity noise characteristic of a diode laser, have been reported. Because the diode laser has very fast frequency noise, we propose the method using it here.

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Event date： 2012.8

Language：Japanese  

The pseudo-random number is normally used for large-scale simulation and encryption of communication. On the other hand, the physical-random number is recently expected to be used in these fields because it has no calculable periodicity and so makes the safer cipher. Therefore, many fast physical-random number generations, which use the wide intensity noise characteristic of a diode laser, have been reported. Because the diode laser has very fast frequency noise, we propose the method using it here.

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Event date： 2012.8

Language：Japanese  

The frequency of a semiconductor laser fluctuates around its center optical frequency, owing to a refractive index variation resulting from carrier density fluctuations. By using the frequency discriminator, the frequency noise is converted into the intensity noise, then the amplitude is converted into binary numbers and produce the physical random number from it. But it may degrade its random number characteristic when its center oscillation frequency varies. Here we measure the examination pass rate of the generated binary numbers through this test.

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Event date： 2012.8

Language：Japanese  

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Event date： 2012.8

Language：Japanese  

The frequency of a semiconductor laser fluctuates around its center optical frequency, owing to a refractive index variation resulting from carrier density fluctuations. By using the frequency discriminator, the frequency noise is converted into the intensity noise, then the amplitude is converted into binary numbers and produce the physical random number from it. But it may degrade its random number characteristic when its center oscillation frequency varies. Here we measure the examination pass rate of the generated binary numbers through this test.

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Event date： 2012.8

Language：Japanese  

The pseudo-random number is normally used for large-scale simulation and encryption of communication. On the other hand, the physical-random number is recently expected to be used in these fields because it has no calculable periodicity and so makes the safer cipher. Therefore, many fast physical-random number generations, which use the wide intensity noise characteristic of a diode laser, have been reported. Because the diode laser has very fast frequency noise, we propose the method using it here.

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Event date： 2012.8

Language：Japanese  

The frequency of a semiconductor laser fluctuates around its center optical frequency, owing to a refractive index variation resulting from carrier density fluctuations. By using the frequency discriminator, the frequency noise is converted into the intensity noise, then the amplitude is converted into binary numbers and produce the physical random number from it. But it may degrade its random number characteristic when its center oscillation frequency varies. Here we measure the examination pass rate of the generated binary numbers through this test.

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Event date： 2012.8

Language：Japanese  

The pseudo-random number is normally used for large-scale simulation and encryption of communication. On the other hand, the physical-random number is recently expected to be used in these fields because it has no calculable periodicity and so makes the safer cipher. Therefore, many fast physical-random number generations, which use the wide intensity noise characteristic of a diode laser, have been reported. Because the diode laser has very fast frequency noise, we propose the method using it here.

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Event date： 2012.8

Language：Japanese  

The frequency of a semiconductor laser fluctuates around its center optical frequency, owing to a refractive index variation resulting from carrier density fluctuations. By using the frequency discriminator, the frequency noise is converted into the intensity noise, then the amplitude is converted into binary numbers and produce the physical random number from it. But it may degrade its random number characteristic when its center oscillation frequency varies. Here we measure the examination pass rate of the generated binary numbers through this test.

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Event date： 2012.8

Language：Japanese  

The pseudo-random number is normally used for large-scale simulation and encryption of communication. On the other hand, the physical-random number is recently expected to be used in these fields because it has no calculable periodicity and so makes the safer cipher. Therefore, many fast physical-random number generations, which use the wide intensity noise characteristic of a diode laser, have been reported. Because the diode laser has very fast frequency noise, we propose the method using it here.

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Event date： 2012.8

Language：Japanese  

The frequency of a semiconductor laser fluctuates around its center optical frequency, owing to a refractive index variation resulting from carrier density fluctuations. By using the frequency discriminator, the frequency noise is converted into the intensity noise, then the amplitude is converted into binary numbers and produce the physical random number from it. But it may degrade its random number characteristic when its center oscillation frequency varies. Here we measure the examination pass rate of the generated binary numbers through this test.

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Event date： 2012.8

Language：Japanese  

The pseudo-random number is normally used for large-scale simulation and encryption of communication. On the other hand, the physical-random number is recently expected to be used in these fields because it has no calculable periodicity and so makes the safer cipher. Therefore, many fast physical-random number generations, which use the wide intensity noise characteristic of a diode laser, have been reported. Because the diode laser has very fast frequency noise, we propose the method using it here.

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Event date： 2012.3

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Event date： 2012.3

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Event date： 2012.3

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Event date： 2012.3

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Event date： 2012.3

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Event date： 2012.3

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Event date： 2012.3

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Event date： 2012

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Event date： 2012

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Event date： 2012

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Event date： 2012

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Event date： 2012

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Event date： 2012

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Event date： 2011.3

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Event date： 2011.3

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Event date： 2011.1

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Event date： 2011

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Event date： 2011

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Event date： 2010.10

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Event date： 2010.10

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Event date： 2010.3

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Event date： 2010.3

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Event date： 2010.3

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Event date： 2010.3

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Event date： 2010.3

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Event date： 2010.3

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Event date： 2010.2

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Event date： 2010

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Event date： 2010

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Event date： 2010

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Event date： 2010

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Event date： 2010

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Event date： 2010

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Event date： 2010

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Event date： 2010

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Event date： 2010

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The purpose of this study is about noise reduction by Active Noise Control (ANC) at the opening with a louver which attached Piezoelectric Card Speaker. In a house and an apartment not only machinery, louvers are used at large opening aimed for air conditioning and ventilation. Leakage of a sound from the opening set louver becomes a problem. In this experimental study, proposed ANC system is independent parallel control system using two single channel ANC systems. One of them, secondary noise source is set at each bane down side of louver. The other one is set slit of enclosure opening. The experimental results show that noise reduction is obtained from 5dB to 25dB in sound field on this proposed ANC system.

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Event date： 2010

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Event date： 2009.10

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Event date： 2009.8

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Event date： 2009.8

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Event date： 2009.8

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Event date： 2009.3

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Event date： 2009.3

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Event date： 2009.3

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Event date： 2009.3

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Event date： 2009.3

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Event date： 2009

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Event date： 2009

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Event date： 2009

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Event date： 2009

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Event date： 2009

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Event date： 2009

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Sirocco fan having a big static pressure is used for ventilation of the bathroom or cooling of the projector. This paper described the reduction of an air born sound radiated from the sirocco fan when put an absorption sheet on the casing inside. And an airflow-static pressure characteristics and noise reduction was clarified when change the kind and the thickness of absorption sheet. An air born sound was reduced to occur by putting absorption sheet on the casing inside, but it became clear that maximum airflow decreased with it.

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Event date： 2009

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Event date： 2009

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Event date： 2009

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Event date： 2008.9

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Event date： 2008.9

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Event date： 2008.5

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Event date： 2008

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Event date： 2008

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Event date： 2008

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Event date： 2008

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Event date： 2008

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Event date： 2007.3

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Event date： 2007

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Event date： 2007

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Event date： 2007

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Event date： 2006.12

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Event date： 2006.12

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Event date： 2006.3

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Event date： 2006.3

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Event date： 2006.3

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Event date： 2006.3

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Event date： 2006

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Event date： 2006

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Event date： 2006

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Event date： 2006

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Event date： 2006

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Event date： 2006

Language：Japanese  

The purpose of this study is about noise reduction by Active Noise Control at the opening with a louver which installed Piezoelectric Vibrator. From the viewpoint of improvement of appearance and privacy, louvers are used at large opening aimed for air conditioning and ventilation. In late years, in a house and an apartment, a leak of a sound from the opening which installed a louver becomes a problem. The experimental results show that noise reduction is obtained from 5dB to 30dB at control point by ANC system.

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Event date： 2005.3

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Event date： 2005

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Event date： 2005

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This paper describes an acoustic diagnosis for a failure aerodynamic sound in a micro DC fan motor assembly line. The failure sound is caused by assembly accuracy of which an eccentricity of fan casing, a yawing of fan blade, etc. Proposed acoustic diagnosis technique is used to Adaptive Line Enhancer (ALE) to extract a periodic abnormal signal including aerodynamic noise generated by rotating a micro DC fan motor. Then, this research performed improvement in a S/N ratio in sound diagnosis of a micro DC fan using adaptive line enhancer. Consequently, the noise signal is not correlative in time decreased by about 10dB, the typical periodic signal with high correlation was acquired as an output signal, and it was cleared that this periodic signal could be used for unusual diagnosis.

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Event date： 2005

Language：Japanese  

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Event date： 2003.9

Language：Japanese  

The attenuation characteristics of a slit resonator that has the adaptive feedback ANC system for leakage noise at a ventilation aperture of the package is investigated. The discrete tones that are radiate from an AC axial fan are controlled by DSP using Filtered-X LMS algorithm. The attenuation level at each discrete tone in using the circular slit resonator is between 4dB and 14dB. Also, the attenuation level between 6dB and 15dB is observed in the ellipse slit resonator. The proposed system, which consists of a slit resonator with control speakers and the adaptive feedback ANC, enable us to reduce discrete tones effectively.

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Event date： 2003.6

Language：Japanese  

This paper deals with the development of a new method for Measurement of powder level in the cylinder. For monitoring of automated filling processes of cartridges in a series production a new measurement method was developed which allows to detect rapidly incorrect products and to improve the process capability by the use of this method. The aim of this research work is to measure the level of powder in a cartridge without contacting the powder. The powder is a mixture of solid particles and air, and therefore porous media from the viewpoint of acoustics. As above, the inside of the cartridge, which is filled with powder, is an acoustic system including porous media. The here developed measuring method use the relationship between amount of powder in the cartridge and the characteristics of the transfer function of the acoustic system. The acoustic characteristic of the powder, which is used for the theoretical analysis and FEM was also measured.

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Event date： 2003.6

Language：Japanese  

This paper describes noise attenuation characteristics of a slit resonator that has adaptive feedback NANC system for silencing leakage noise at ventilation aperature. The slit resonator contains a thin air layer that extends radially over a very short axial length. In order to calculate the noise attenuation, computer simulations use the actual data such as fan noise and the transfer function from the canceling source to the error microphone. The effectiveness of the slit resonator that has adaptive feedback ANC system is clarified by computer simulations.

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