• 한국음향학회지
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• 제34권4호
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• pp.288-294
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• 2015

광섬유 사냑 간섭계는 음향 및 진동과 같은 물리적 변화량을 탐지하는 센서로 잘 개발되어 있다. 본 논문에서는 변압기유가 채워진 원통형 캐비티에 음압이 발생되었을 때 한 개의 루프내에 설치된 광섬유 배열 센서를 이용하여 음향을 탐지하였다. 서로 다른 외부 음향 주파수 $f_1$과 $f_2$를 피에조 재료를 이용하여 발생시키고 주파수는 5 kHz에서 90 kHz까지로 선정하였다. 실험 결과 광섬유 센서는 하모닉 성분인 $f_1$, $f_2$, $2f_1$, $2f_2$, ${\mid}f_1-f_2{\mid}$, ${\mid}f_1+f_2{\mid}$의 주파수를 탐지하였다. 제안된 광섬유 센서 배열은 변압기 내의 부분 방전으로 인한 음압과 진동과 같은 물리량을 모니터링 하는데 적용할 수 있을 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제89권5호
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• pp.437-452
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• 2024

Functionally graded materials (FGMs) have gained substantial attention from researchers due to their exceptional strength and thermal resistance. Their utilization in the aviation and automobile industries has significantly improved the efficiency of various structural components. Moreover, stiffened panels find wide applications in aerospace and automobile structures and these panels are frequently exposed to extreme environments. It is from this perspective that our research is focused on analysing the vibroacoustic response of stiffened functionally graded panels subjected to external dynamic excitations in a thermal environment. In the present research work, a finite element model is developed to conduct the dynamic analysis of functionally graded stiffened panels using the first-order shear deformation theory. Subsequently, a boundary element based model is also developed and coupled with the finite element model to investigate the sound radiation behaviour of those panels in a thermal environment. The material properties of FG stiffened panels are considered as temperature dependent, while the thermal environment is assumed to be acting as linearly varying through the panel's thickness. The present investigation aim to compare the vibroacoustic responses of different panels due to stiffener orientations, material compositions, power law indices and plate thicknesses at various temperatures. The research findings highlight the significant impact of addition of stiffeners, its orientation and material compositions on the sound radiation characteristics of these panels under thermal environments. The present numerical model can easily be employed for analysing the sound radiation behaviour of other types of flat or curved stiffened panels having arbitrary geometry and boundary conditions.

• 대한치과교정학회지
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• 제48권6호
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• pp.377-383
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• 2018

Objective: This study was performed to investigate the effects of external tooth bleaching with flouridation on the appearance of white spot lesions (WSLs) in vitro. Methods: In total, 125 bracket-bonded bovine incisor enamel blocks with artificial WSLs were randomly divided into a control group and four treatment groups (home bleaching, home bleaching + fluoridation, in-office bleaching, and in-office bleaching + fluoridation). A spectroradiometer (SR) and digital images (DIs) were used to evaluate colorimetric parameters (Commission Internationale l'Eclairage $L^*a^*b^*$) for all specimens. Color measurements were obtained before WSL formation (T1), after WSL formation (T2), and after completion of the external tooth bleaching treatment (T3). Results: The SRbased color change after bleaching was significantly greater in the treatment groups than in the control group (p < 0.05). SR-based lightness ($L^*$) and redgreen ($a^*$) values were significantly higher at T2 than at T1 (p < 0.001), with no significant changes in yellow-blue ($b^*$) values. At T3, SR-based $L^*$ values had increased while $a^*$ and $b^*$ values had decreased in the treatment groups (p < 0.001). The DI-based color difference between the sound enamel and WSL areas (DE*DI) increased significantly from T1 to T2 in all groups (p < 0.001) and significantly decreased from T2 to T3 in the treatment groups (p < 0.001). No significant differences in ${\Delta}E^*DI$ at T3 were shown between the four treatment groups (p > 0.05). Conclusions: The findings of this study suggested that external tooth bleaching with fluoridation can alleviate the conspicuity of WSLs.

• 한국음향학회지
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• 제29권7호
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• pp.448-457
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• 2010

단면의 형상이 길이방향으로 일정한 무한길이 도파관 구조물 (waveguide structures)에 대한 진동 및 파동전파 특성은 도파관유한요소법 (waveguide finite element method, WFEM)을 이용해 효과적으로 해석할 수 있다. 도파관유한요소법은 2차원 단면만을 FE 모델링하여 해석하므로 모델의 크기가 작고 연산시간이 짧다는 장점이 있다. 도파관 구조물이 외부 유체와 연성된 경우, 원통형 실린더 또는 파이프와 같이 단면의 형상이 단순한 경우에는 이론적 해석을 수행할 수 있다. 반면 복잡한 형상의 단면을 가진 도파관구조물이 유체와 연성된 경우에는 수치해석 방법이 요구된다. 외부 유체와 연성된 도파관 구조물은 외부 유체와 도파관유한요소 (WFE)를 연성시켜 해석하는 수치해석 방법을 고려할 수 있다. 본 논문에서는 외부 유체 모델링에 경계요소 (Boundary Element)를 도입하고 이를 도파관유한요소와 연성시킨 WFE/BE 방법을 소개한다. 이 방법의 적용 예로써 단순형상의 파이프에 대해 외부 유체의 유/무에 따른 분산선도와 가진점 모빌리티 (point mobility)를 구하고 이를 이론해석 결과와 비교하였다. 또한 WFE/BE 방법을 이용해 파이프에서 외부 유체로 방사되는 음향파워를 구하고 접수 유/무에 따른 영향을 살펴보았다.

• Journal of Biosystems Engineering
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• 제22권3호
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• pp.295-302
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• 1997

An ultimate purpose of this study was to develop an automatic system for brown rice quality inspection using image processing technique. In this study emphasis was put on developing an algorithm for discriminating the brown rice kernels depending on their external quality with a color image processing system equipped with an adaptor magnifying the input image and optical fiber for oblique lightening. Primarily, geometical and optical features of images were analyzed with paddy and the various brown rice kernel samples such as a sound, cracked, peen-transparent, green-opaque, colored, white-opaque and brokens. Secondary, geometrical and optical parameters significant for identifying each rice kernels were screened by a statistical analysis(STEPWISE and DISCRIM procedure, SAS wer. 6) and an algorithm fur on- line discrimination of the rice kernels in static state were developed, and finally its performance was evaluated. The results are summarized as follows. 1) It was ascertained that the cracked kernels can be detected when e incident angle of the oblique light is less than 2$0^{\circ}C$ but detectivity was significantly affected by the angle between the direction of the oblique light and the longitudinal axis of the rice kernel and also by the location of the embryo with respect to the oblique light. 2) The most significant Parameters which can discriminate brown rice kernels are area, length and R, B and r values among the several geometrical and optical parameters. 3) Discrimination accuracies of the algorithm were ranged from 90% to 96% for a sound, cracked, colored, broken and unhulled, about 81 % for green-transparent and white-opaque and 75 % for green-opaque, respectively.

• 복식
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• 제45권
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• pp.147-160
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• 1999

The purposes of this study were to classify the university women according to their life styles and to analyze the cosmetic consumption behavior of classified groups. The results of this study may suggest cosmetics production and sales plan to manufactures and distributers and to provide cosmetic consumption guides for the university women. For empirical study a questionnaire developed by researchers was distributed to 456 of university women in Chonbuk province from Aug. 26 to Sep. 17 1998. Frequencies and percentages were claculated. And factor analysis cluster analysis and $\chi$2-test were used. The results were as follows: 1. University women were clustered into 5 types of sound and self pursuit type realistic and fashion pursuit type external and liberal type delightful and enjoying type and passive and stagnate type according to their life styles. 2. Sound and self pursuit type was characterized by the faithfulness to school and home life and economical lining. They got cosmetics information through direct experiences by use of samples put on full make-ups to protect their skin and selected refill cosmetic products to save money. 3. Realistic and fashion pursuit type were sensitive to fashion and had a strong desire for material achievement. They put on full make-ups exchange unsatisfactory cosmetics at the store where they bought and had a lot of imported cosmetics experiences. 4. External and liberal type showed little concern with saving and had progressive thinking. They bought cosmetics at the department store got informations from market-oriented information sources. perferred shopping at department stores considerred price most important when selecting cosmetics exchanged unsatisfactory cosmetics at the store they bought when they were not satisfied with the flavor or skin troule. 5. Delightful and enjoying type showed the least faithfulness to their home and school life. They put on partial make-ups for the correction of facial defects or etiquette. 6. Passive and stagnate type enjoyed home life but were passive in real life and open-mindness They got cosmetics information from marketer-oriented information sources bought cosmetics at discount stores considered price most important when selecting cosmetics put on basic or at least mke-ups to protect their skin had the least experience in the imported cosmetics and refill products.

• 센서학회지
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• 제23권3호
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• pp.178-184
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• 2014

Key components of implantable hearing aids are consist of an acoustic sensor that collect external sound by suppressing the body noise, a signal processor module for compensation algorithm of hearing loss, and a output transducer which has tiny size but have high efficiency, respectively. In the partial implantable hearing aids, technologies of transducer and signal processor are so matured that can be applied not too much difficulty. However, due to the difficulties in implantable acoustic sensor technology, such as minimization of masticatory sound and damage of sensor's membrane from external impact, practical use of fully implantable hearing aids have not successful so far. In this paper, we have proposed a novel implantable acoustic sensor which has trans-tympanic structure, and is verified that the proposed method can be very useful for fully implantable hearing aids by cadaveric experiments.

• International journal of advanced smart convergence
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• 제10권4호
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• pp.241-255
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• 2021

The human auricle is the first part to receive sound from the outside. In this part, the frequency range of human recognizable form is divided and organized. In this study, we propose modeling by applying a single sound source to the surface of the human auricle. This means that when the sound pressure of a low frequency (low frequency) sound enters the pinna, the impedance felt at the tip of a part of the non-linear surface of the pinna is mainly due to the tensile force at the end of the part of the non-linear surface of the pinna. By expressing the situation of moving at a very small speed, the characteristic impedance of the pinna was confirmed to be negative infinity, and it was also confirmed that the speed at the tip of a part of the non-linear surface of the pinna was 0 in the anti-resonance state. It was found that the wave propagation phenomenon that determines the characteristics of the filter is determined by how large the wavelength, kL, is compared to the length of the tip of a part of the non-straight surface of the pinna. Humans first receive sounds from outside through their ears. The auricle is non-linear and has a curved shape, and it is known that it analyzes frequencies while receiving external sounds. The human ear has an audible frequency range of 20Hz - 20,000Hz. Through the study, we applied the characteristics of the notch filter to hypothesize that the human audible frequency range is separated from the auricle, and applied filter theory to analyze it, and as a result, meaningful results were obtained. The curved part and the inner part of the auricle function as a trumpet, collecting sounds, and at the same time amplifying the weak sound of a specific band. The point was found and the shape of the envelope detected in the auricle was found. Selectivity for selecting sounds coming from the outside is the formula of the pinna that implements the function of Q. The function of distinguishing human-recognizable sound from the pinna from low to high through frequency analysis is performed in the pinna, and the 2-3kHz area, where human hearing threshold is the most sensitive, is also the acoustic impedance of the most recessed area of the pinna. It can be seen that starting from.

• 한국주거학회논문집
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• 제11권4호
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• pp.85-96
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• 2000

The purpose of this study was to evaluated noise environment of the low-rise multi-family house in Athens, Georgia. The results of this study can be applied to the prevention of noise when planning multi-family houses, roads and cities in Korea. The subjects of this study were the place of 1m, 10m, 50m, 100m from 4-lane road ofT apartment and 233 residents lived in the low-rise multi-family houses in Athens. The results of this study were as follows. 1. The average noise level at 1m, 10m, 50m and 100m was 55.5dB, 46.7dB, 43.0dB, 43.0dB and 41.2dB respectively from 4-lane road of T apartment. From the view of the standard in this study, the physical noise was good. 2. The results of the residents subjective response on the noise were as follows. The external noise residents felt - that was a noise by operating machines, and traffic noise - ware as 2.57 on average. The noise by the daily activities, the noise of nature are a little as 2.38 on average. They were disturbed a little by the external noise. They felt the solid born sounds(average 2.49) more than airbone sound(average 2.23) by the internal noise. They are suffered worse from noise in summer and they worse from 8-12 oclock due to external noise and 16-20 oclock due to internal noise. Comparing the noise environment of Korean with that of American, I found a meaningful difference of nature and the noise of daily activities of external noise and all internal noise.

• 한국융합학회논문지
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• 제10권4호
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• pp.107-113
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• 2019

1인가구의 가장 높은 비율을 차지하는 연령층은 60대 이상의 노인이다. 그들의 상당수가 경제적으로 어려운 상황에 처해있어 낙후된 주거공간에 거주한다. 노인의 주거공간의 창문은 존재하지 않거나 창문으로써의 역할을 제대로 하지 못하는 경우가 많다. 그들은 우울증, 고독사 등 사회적 문제에 취약한 상태로 노출되어 있다. 그래서 비상상황에 대한 대처능력이 현저히 떨어진다. 본 논문은 낙후된 주거공간에 거주하는 1인가구 중 60대 이상 노인을 대상으로 하는 외부 환경 정보 반영 대화형 창문 인터페이스를 제안한다. 본 콘텐츠는 별도의 공간과 비용이 요구되지 않는 보급형 TV 혹은 PC 모니터를 활용한다. 노인이 사용하는데 어려움이 없는 직관적인 터치센싱을 통해 손을 인식하면 현재 외부 환경을 반영하는 날씨 영상, 온도 정보를 제공한다. 보다 중요한 노인의 비상상황에 대비하여 알림소리, SMS전송 서비스를 제공한다. 본 콘텐츠를 통해 사용자는 정서적 안정을 느낄 수 있고 비상상황에 빠르게 대처할 수 있다.