• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.867-872
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• 2002

A high intensity acoustic test facility is constructed at Korea Aerospace Research Institute (KARI) by 2003. The reverberant chamber of the facility has a volume of 1,228 cubic meters and shall provide an acoustic environment of 152 dB over the frequency range of 25 Hz to 10,000 Hz. The facility consists of a large scaled reverberant chamber, acoustic power generation systems, gases nitrogen supply systems, and acoustic control systems. This paper describes how the basic parameters of a chamber and power generation systems are controlled to meet the requirement of the test. The volume of a reverberant chamber is controlled by the size of test objects and the reverberant characteristics of a chamber. The capacity of acoustic power generation systems is determined by the energy absorption of a chamber and the efficiency of acoustic modulators. Simple math is employed to calculate the required power of acoustic modulators. Moreover, the paper explains how the distribution of sound pressure level at low frequency is checked by analytical and numerical methods.

• 한국환경과학회지
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• 제31권1호
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• pp.9-21
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• 2022

Today's cities require deeper understanding of the thermal environment and PM₁₀ as their management becomes more critical. Based on these circumstances, this study investigated the Granger causality between the thermal environment and PM₁₀ of the 25 districts of Seoul, the most populous and urbanized city in Korea. The results of the Granger causality test on the thermal environment and PM₁₀ were classified into 12 types. Except for type 12, the temperature and urban island heat intensity of the other 11 types operated as a Granger-cause to each other in both directions. Temperature operates as a Granger-cause of urban island heat intensity in type 12. The PM₁₀ level and urban pollution island intensity operated as a Granger-cause to each other in all districts. For types 1 and 2, thermal environment operated as a Granger-cause to PM₁₀ in one direction, and type 3-type 12 confirmed that thermal environment and PM₁₀ operated as a Granger-cause in both directions. Findings reveal the intricate causalities between thermal environment and PM₁₀ at the district level and suggest mitigation strategies that are more location based.

• 한국지구과학회지
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• 제40권1호
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• pp.56-67
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• 2019

본 연구에서는 미국 남캘리포니아 지진센터에서 개발한 물리적 지진모델링 기반 광대역 강지진동 모사 플랫폼(버전 16.5)을 활용하여, 규모 6.0, 6.5, 7.0 지진에 대한 진도 감쇠 특성 분석을 수행하였다. 지진 발생 위치는 2016년 규모 5.8 경주 지진 진앙 인근을 가정하였으나 지각 전파 모델의 경우 남캘리포니아 강지진동 모사 플랫폼에서 제공하는 미국의 대표적인 지각 모델 두 개를 사용하였다. 하나는 판 내부를 대표하는 미국 중동부 지역(Central and Eastern United States, CEUS) 모델이고 다른 하나는 판의 경계를 대표하는 미 서부 지역(LA Basin) 모델이다. 버전 16.5 플랫폼에는 5개의 모델링 방법론이 제시되고 있으며 본 연구에서는 Song 모델과 Exsim 모델을 사용하였다. 동일 규모의 지진이라 하더라도 지진발생 환경이 다른 지역(CEUS vs LA Basin)에서는 같은 진앙 거리에서 진도 2 등급에 가까운 차이가 발생할 수 있음을 본 연구를 통해서 발견하였다. 본 연구에서 나타난 지역별 진도 감쇠 특성의 차이를 감안할 때 한반도에서 좀 더 정밀한 지진재해 평가를 위해서는 지역에 적합한 진도 감쇠 특성을 이해하는 것이 중요할 것으로 판단되며 본 연구는 지역 특화된 진도 감쇠 특성을 고려하지 않을 경우 진도 감쇠 분포의 불확실성 정도를 잘 보여준다.

• 한국군사과학기술학회지
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• 제17권3호
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• pp.304-310
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• 2014

Based on atmosphere weather data by balloon in Osan and Gwangju area, if icing condition occurs in weather environment of altitude range where helicopter is operated was analyzed in quantitative way. Yearly icing occurrence frequency for daytime during recent three years was average 102 days in Osan, average 91 days in Gwangju. Icing weather environment to highly affect operation of helicopter varies a little according to analysis methods but icing intensity at MDT level was calculated in all the methods, and 14.5~38 times was suggested in Osan; 2.5~30 times in Gwangju. Icing at MDT level was calculated in common in all the analysis methods through wide periods such as Jan., Feb., Mar., and Nov. in Osan. In Gwangju, icing at MDT level was suggested focusing on Jan. only. Therefore, military helicopter developed in Korea is required to strive obtaining certificate of airworthiness about icing condition at MDT level for implementation of perfect operational mission and safe operation.

• 대한조선학회논문집
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• 제49권3호
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• pp.247-253
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• 2012

Dam-break flows, a type of very shallow gravity-driven flow, are substantially influenced by resistance forces due to viscous friction and turbulence. Assuming turbulent flow, the main focus of this study is to validate the increase of drag forces caused by surface roughness and especially turbulence intensity. A Reynolds Averaged Navier-Stokes(RANS) approach with the standard k-${\varepsilon}$ turbulence model is used for this study, where the free surface motion is captured by using a volume of fluid(VOF) method. Surface roughness effects are considered through the law of the wall modified for roughness, while the initial turbulence intensity which determines the lowest level of turbulence in the flow domain of interest is used for the variation of turbulence intensity. It has been found that the numerical results at higher turbulence intensities show a reasonably good agreement with the physical aspects shown by two different dam-break experiments without and with the impact of water.

• 보건행정학회지
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• 제15권1호
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• pp.30-56
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• 2005

This paper used two threshold approaches to measure the equity in urban households' out-of-pocket payments for health care from 1997 to 2002, which developed by Wagstaff and van Doorslaer. One approach used catastrophic health expenditure, which means that payments exceed a 'pre-specified proportion' of total consumption expenditures or ability to pay and the other used impoverishment that they did not drive households into poverty. Indicies for 'catastrophic expenditure' captured intensity as well as its incidence and also the degree of which catastrophic payments occur disproportionately among poor households. Measure of poverty impact also captured both intensity and incidence. The methods applied with data on out-of-pocket payments from the Urban Household Expenditure Survey Incidence and intensity of catastrophic payments - both in terms of total household consumption as well as ability to pay - increased between 1997 and 2002, and that both incidence and intensity of 'catastrophic expenditure' became less concentrated among the poor, but more concentrated in 2001 than in 1997. The incidence and intensity of the poverty impact of out-of-pocket payments increased between 1997 and 2002. Health security system may not have provided financial protection against catastrophic health expenditure to low-income households, because of high user fee policy not considering income level. The policies alleviating catastrophic health payments among the poor need to be more developed, and two threshold approaches further evaluated on our policy context.

• 음성과학
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• 제10권2호
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• pp.249-258
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• 2003

This study attempted to examine a speaker identification method using difference sum and correlation coefficient determined from a pair of intensity level matrices of band-pass-filtered numeric sounds produced by ten female speakers of similar age and height. Subjects recorded three digit numbers at a quiet room at a sampling rate of 22 kHz on a personal computer. Collected data were band-pass-filtered at five different band ranges. Then, matrices of five intensity levels at 100 proportional time points were obtained. Pearson correlation coefficients and the sum of absolute intensity differences between a pair of given matrices were determined within and across the speakers. Results showed that very high correlation coefficient and small difference sum generally occurred within each speaker but some individual variation was also observed. Thus, the matrix pair with a higher coefficient and a smaller difference sum was averaged to form each individual's model. Comparison among the speakers yielded generally low coefficients and large differences, which suggests successful speaker identification, but among them there were a few cases with very high coefficients and small differences. Future studies will focus on finer band ranges and additional spectral parameters at some peak points of the intensity contour at a low frequency band.

• 대한통합의학회지
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• 제6권2호
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• pp.69-76
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• 2018

Purpose : This study investigated the effects of low-intensity muscle training on neurotransmitters associated with depression and emotion regulation disorders in survivors with stroke who were diagnosed with depression or emotion regulation disorder. Methods : Survivors of chronic stroke diagnosed with depression or emotion regulation disorder (n = ) were included in the study. Concentrations of serotonin, norepinephrine, and epinephrine were measured before and after. Low-intensity muscle training was performed once a day for 50 minutes, 5 times a week for 10 weeks. Result : Levels of serotonin, norepinephrine, and epinephrine improved significantly after intervention (p < .05). Conclusion : These results confirm that low-intensity muscle training has a positive effect on neurotransmitter concentrations in survivors with stroke diagnosed with depression and emotion regulation disorders. Future studies should analyze the changes in neurotransmitters in more detail using various exercise methods and intensities to investigate their effects on depression and emotion regulation disorders.

• 말소리와 음성과학
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• 제2권4호
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• pp.19-28
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• 2010

The purpose of this study was to increase the current understanding of the acoustic characteristics of voices with advancing age. The relationship between age-related changes in body physiology and certain acoustic characteristics of voice was studied in a sample of 80 men representing four chronological age groupings (20-29, 50-59, 60-69, 70-79) who were all of good physical condition. Each subject was asked to phonate the vowel /a/, /i/, and /u/ for as long as possible at comfortable frequency and intensity level and read the sentence. A promising voice analysis program (Multi-Dimensional Voice $Program^{TM}$) was used to measure the fundamental frequency ($f_0$), jitter, shimmer, $f_0$ variation, peak-amplitude variation, smoothed pitch perturbation quotient, smoothed amplitude perturbation quotient, soft phonation index, $f_0$-tremor intensity index, amplitude tremor intensity index, and noise-to-harmonics ratio from the samples.

• Current Optics and Photonics
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• 제6권3호
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• pp.337-343
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• 2022

Microfluidic chips are new devices that can manipulate liquids at the micrometer level, and terahertz (THz) time-domain spectroscopy has good applicability in biochemical detection. The combination of these two technologies can shorten the distance between sample and THz wave, reduce THz wave absorption by water, and more effectively analyze the kinetics of biochemical reactions in aqueous solutions. This study investigates the effects of different external magnetic field intensities on the THz transmission characteristics of deionized water, CuSO₄, CuCl₂, (CH₃COO)₂Cu, Na₂SO₄, NaCl, and CH₃COONa; the THz spectral intensity of the sample solutions decrease with increasing intensity of the applied magnetic field. Analysis shows that the magnetic field leads to a change in the dipole moment of water molecules in water and electrolyte solutions, which enhances not only the hydrogen-bond networking ability of water but also the hydration around ions in electrolyte solutions, increasing the number of hydrogen bonds. Increasing the intensity of this magnetic field further promotes the hydrogen-bond association between water molecules, weakening the THz transmission intensity of the solution.