• 한국소음진동공학회논문집
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• 제22권4호
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• pp.318-327
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• 2012

The operating sound radiated from a laser printer includes tonal noise components caused by the rotating mechanical parts such as gear, shaft, motor, fan, etc. The negative effects of the tonal noise components need to be considered in the process of developing a sound quality index for the quantitative evaluation of the emotional satisfaction in terms of psycho-acoustics. However, in a previous paper, it was confirmed that the Aures tonality did not have enough correlation with the results of jury evaluation. The sound quality index based on loudness, articulation index, fluctuation strength has a little problem in considering the effects of rotating mechanical parts on the sound quality. In this paper, to solve the tonality evaluation problem, the calculation algorithm of Aures tonality was investigated in detail to find the cause of decreasing the correlation. The new tonality evaluation model was proposed by modifying and optimizing the masking effect, loudness ratio, and shape of weighting curve based on the basic algorithm of Aures tonality, and applied to two kinds of operating sound groups in order to verify the usefulness of proposed model. As a result, it is confirmed that the proposed tonality evaluation model has enough correlation and usefulness for expressing the tonalness in the operating sounds of laser printers. In the following paper, this results will be used to model the sound quality index as the input data by using the classification algorithm.

• 한국의류산업학회지
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• 제15권4호
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• pp.620-629
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• 2013

This study examines the rustling sound characteristics of electrospun nanofiber web laminates according to layer structures. This study assesses mechanical properties and frictional sounds (such as SPL); in addition, Zwicker's psychoacoustic parameters (such as Loudness (Z), Sharpness (Z), Roughness (Z), and Fluctuation strength (Z)) were calculated using the Sound Quality Program (ver.3.2, B&K, Denmark). The result determined how to control these characteristics and minimize rustling sounds. A total of 3 specimens' frictional sound (generated at 0.63 m/s) was recorded using a Simulator for Frictional Sound of Fabrics (Korea Patent No. 10-2008-0105524) and SPLs were analyzed with a Fast Fourier Transformation (FFT). The mechanical properties of fabrics were measured with a KES-FB system. The SPL value of the sound spectrum showed 6.84~58.47dB at 0~17,500Hz. The SPL value was 61.2dB for the 2-layer PU nanofiber web laminates layered on densely woven PET(C1) and was the highest at 65.1dB for the 3-layer PU nanofiber web laminates (C3). Based on SPSS 18.0, it was shown that there is a correlation between mechanical properties and psychoacoustic characteristics. Tensile properties (LT), weight (T), and bending properties (2HB) showed a high correlation with psychoacoustic characteristics. Tensile linearity (LT) with Loudness (Z) showed a negative correlation coefficient; however, weight (T) with Sharpness (Z) and Roughness (Z), and bending hysteresis (2HB) with Roughness (Z) indicated positive correlation coefficients, respectively.

• 한국지반공학회지:지반
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• 제3권1호
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• pp.7-24
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• 1987

울산만 북서측 임해지역체 발달된 연약해성점토를 개양하기 위하려 선행대중과 Wick Drain공법의 병용공법이 적용되었다. 상기 공법의 적용에 따른 연약해성점토의 거동 및 강침특성을 요명하여, 안전하고 신속하게 시공을 실시하기 위하여 현장계측에 의한 공학적인 시공관리를 실시하였다. 본 고는 연약해성점토를 개량하기 위하여 적용한 선행하중과 Wick Drain공법의 설계, 시공 및 안전관리방법을 수록하고 있다.

• 한국소음진동공학회논문집
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• 제23권12호
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• pp.1035-1044
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• 2013

면내 하중을 지지하는 면재와 면외 하중을 지지하는 심재로 구성되는 샌드위치 패널 구조물은 높은 비강도와 비강성을 가지므로 경량화가 요구되는 대형 구조물에 자주 이용된다. 그러나, 이러한 구조물은 필연적으로 높은 하중에 대하여 유연성의 증가를 일으키게 되므로, 이에 대한 구조 안전성 분석이 이루어져야 한다. 이에 대해 실제 풍하중은 거스트 영향 등을 비롯한 비선형성을 가지는 요소들이 고려되어야 하며, 구조물의 안전성 분석을 위하여 입력 하중에 대해 보다 실제 물리현상에 근접하게 모사되어야 한다. 이에 이 연구에서는 유체-구조 연성해석 기법을 이용하여 대형 등격자-보강 패널 구조물에 대한 구조 안전성 분석이 수행되었다. 입력하중인 풍하중에 대하여 보다 실제적 모사를 위해 불규칙 변동 속도성분인 거스트 영향이 고려된 랜덤분포 풍하중에 대한 유동장을 생성하여 압력-변위 사상을 통하여 연성해석이 수행되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.348-353
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• 2012

This paper presents the HRTF based experimental approach to figure out why the human auditory perception on the interior noise source including the directional tonal components does not well match with the dominant features extracted from recorded acoustic signals in terms of psycho-acoustics. Since the general objective evaluation models for tonalness among various sound attributes are a function of width, frequency, excessive level of tonal components respectively, the directional tonal components cannot be properly evaluated without considering the effects of head-related transfer function on the binaural auditory perception. Thus, the directivity of source is additionally considered to prevent the erroneous conclusions from the same sound source in the process of source identification. The signal synthesis technique is used to solve a little difficulty in measuring all of desired acoustic signals for jury evaluation. The sound attributes of synthetic acoustics signals are analyzed to roughly predict the results of jury evaluation in advance by using sound quality factors such as loudness, sharpness, roughness, fluctuation strength and tonality. The jury evaluation is carefully conducted based on the recommended guideline suggested by N. Ottoet al. Each sound is respectively evaluated by selecting a value between -2 and 2 in intervals of 0.2 point. Through above procedure, based on the results of jury evaluation, it is confirmed that serious problems can be caused in the process of analyzing the dominant sound attributes in terms of psycho-acoustics according to the type of a microphone and a playback system.

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.536-545
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• 2016

Household refrigerator radiates noise of which the pattern is dependent on the operating condition of its parts, such as compressor, flow fans, etc. Thus the refrigerator noise has a variety of frequency characteristics. Therefore, it is required to consider the noise characteristics for evaluating the noise quality and eventually developing the sound quality index of the refrigerator noise. In this study, five units of household refrigerator were selected to measure their noises that were used to generate sound sources for jury test of the study. The measured noises of five refrigerators were divided into ten kinds of sound source by considering operating condition and frequency characteristics. Additionally, the ten sources were each edited to have the same SPL of 30 dBA. Totally twenty kinds of sound sources (10-original SPL, 10-edited SPL 30 dBA) were evaluated by twenty-two subjects, and compared with their sound quality metrics. It was found that only the loudness of the metrics was meaningfully correlated with the subjective evaluation. The rests, sharpness, roughness and fluctuation strength, were not related. The conclusion of this study is that a new sophisticated index is necessary to be developed to qualitatively evaluate the household refrigerator noise.

• 수산해양기술연구
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• 제40권4호
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• pp.282-294
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• 2004

아르헨티나 짧은지느러미오징어는 1993년에 99,000톤에서 1994년 56,600톤으로 감소하고 1996년에는 78,600톤에서 1997년 130,300톤으로 다시 증가하였다. 어획량의 급감 및 급증한 1993~1994년과 1996~1997년의 성어기인 3~5월의 풍도 원인을 구명하기 위하여 아르헨티나 짧은지느러미오징어의 수온 변동에 따른 풍도 변화를 분석하였다. 호황을 보였던 해인 1993년과 1997년은 성어기에 주로 50$^{\circ}$~51$^{\circ}$S간 해역에서 주어장이 형성되었고, 불황을 보였던 1994년과 1996년에는 50$^{\circ}$S이북에서 성어기 어장이 형성되었으며 포클랜드 어장의 평균수온은 3월 10~11$^{\circ}$C, 4~5월은 9$^{\circ}$C로 평균 등온선이 형성되는 위치에 따라 어황이 변동하는 것으로 나타났다. 아르헨티나 짧은지느러미오징어의 높은 단위노력 당어획량(kg/line) 및 어획량은 어장이 포클랜드 해류의 영향을 받지 않은 1993년 및 1997년은 호황을 보였고, 북상하는 포클랜드 해류의 영향을 받은 1994년 및 1996년에는 급격히 감소되어 불황을 보였다.

• Tribology and Lubricants
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• 제33권1호
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• pp.15-22
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• 2017

Because the running speed of vehicles is increasing and a shorter braking distance is required, high heat-resistant brake pads are needed to satisfy the requirements of customers and car makers. In the near future, hazardous materials such as Cu, Cr, Zn, and Sb will be restricted from use in friction materials. Ceramic composites reinforced by carbon fibers are good candidates for eco-friendly friction materials. In this study, we develop ceramic composite friction materials. The friction materials are composed of carbon fibers, Si, SiC, graphite, and phenol resin and are prepared by hot forming and heat treatment at high temperatures. The density, void ratio, and compressive strength are $1.59-1.66g/cm^3$, 16.6-20, and 70-90 MPa, respectively. Friction and wear tests are performed using a pin-on-plate-type reciprocating friction tester at 25, 100, and $200^{\circ}C$. The counterpart material is a CrMoV steel extracted from a KTX brake disc. Friction coefficient, wear amount, and wear mechanism are measured and examined. We determine that the friction coefficients depend on the temperature and the fluctuation of the friction coefficients is larger at higher temperatures. The amount of wear increases with the surface temperatures of the specimens. The tribological properties of the developed composites are similar to those of a Cu-based sintered friction material. Through this study, it is confirmed that ceramic composite materials can be used as friction materials.

• 한국재료학회지
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• 제2권2호
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• pp.119-125
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• 1992

수평자장을 건 Czochralski(HMCZ) 방법으로 자장강도(B)와 도가니 회전속도(C)가 실리콘 단결정의 산소편석에 미치는 영향에 대하여 연구하였다. B=2, 3, 4kG와 C=4-15rpm에서 <100> 방향으로 성장시킨 57mm 직경의 단결정들 내의 산소분포는 대체로 축을 따라서 불균일하였고 톱니모양을 나타내었다. 종래의 CZ 방법과 비교할 때, 이러한 산소분포의 불균일성은 위 강도의 수평자장이 결정성장계면으로의 산소전달에 불안정한 요소로 작용했음을 나타낸다고 볼 수 있다. 반면에 C의 증가는 산소분포의 불균일성의 약화와 산소농도의 전반적인 증가를 유도하였다. 이 결과를 토대로 B=2kG에서 27-36ppma인 산소분포를 가진 단결정이 프로그램된 C에 의해서 얻어졌다. 소자제조공정을 모의한 열처리 과정에서 HMCZ 실리콘의 산소석출은 종래의 CZ 실리콘의 산소석출에 비해서 상대적으로 불균일하였고, as-grown 상태에서의 고르지 못한 HMCZ 실리콘의 산소분포가 주요 원인임이 밝혀졌다.

• 한국통신학회논문지
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• 제37권6C호
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• pp.462-468
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• 2012

본 논문은 SDR(software-defined radio)기반 무선 통신장비를 위한 디지털 AGC(Automatic Gain Control) 알고리즘에 대한 것이다. 수신신호는 무선 채널 구간에서 발생하는 경로 감쇄 및 수신단 front-end 동작에 의해 시간에 따라 변하는데, 신뢰성 있는 신호 복호를 위해서는 빠르고 정확한 AGC 기술이 적용되어야 한다. 또한, 하나의 수신기에서 다양한 웨이브폼을 수신하는 SDR 통신장비를 위해서는 적응적인 AGC 기술이 필요하다. 본 논문에서 다양한 웨이브폼에 대해 적용하기 위한 2단계로 구성된 적응적 구조를 제안한다. 제안한 적응적 구조는 수신신호 크기에 따라 이득값(gain) 선택 단계를 선택, 변경함으로써 빠르고 안정적인 이득값 조절을 가능하게 한다. 컴퓨터 모의실험을 통하여 제안하는 방식의 수렴속도 및 안정화 정도를 검증하고, 기존 방식과 비교하여 빠른 수렴 속도를 보임을 확인한다.