• 한국항공우주학회지
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• 제46권9호
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• pp.712-722
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• 2018

본 논문에서는 곤충 모방 날갯짓 비행체의 가장 중요한 설계 변수 중 하나인 날개에 대한 파라메트릭 연구에 대해 서술하였다. 추력, 피칭모멘트, 소비전력, 추력 대 전력비의 비교 및 분석을 통해 날개 형상에 대한 실험적 연구를 진행하였다. 힘과 모멘트는 2축 밸런스를 이용하여 측정되었으며 날갯짓 주파수는 홀센서를 이용하여 측정되었다. 날개 형태는 겹 날개 형태를 채택하였으며 이를 통해 Clap and fling 효과를 구현하였다. 기준 날개 형상으로 잠자리의 날개를 선정하였고, 이를 기준으로 가로세로비 및 면적에 대한 실험을 진행하였다. 결과적으로, 가로세로비와 면적이 증가할수록 추력, 피칭모멘트, 소비전력이 증가하는 것을 확인하였다. 또한, 일정 수준 이상의 가로세로비 혹은 면적을 가지는 날개를 메커니즘에 적용하였을 때 메커니즘이 정상적으로 구동되지 않는 것을 확인하였다. 최종적으로 날개 형상 선정은 필요한 최소추력을 만족시키는 날개 중에서 추력 대 전력비를 비교함으로써 이루어졌다. 하지만 추력선과 무게중심의 불일치로 인한 모멘트의 발생으로 안정성을 확보할 수 없었다. 이에 안정성을 확보하기 위해 상단과 하단에 댐퍼를 부착한 실내 비행 시험을 통해 날개의 파라메트릭 연구 결과에 대한 간접적인 성능 검증을 수행하였다.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2002년도 춘계 학술발표회 논문집
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• pp.73-78
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• 2002

In this paper we develop a method for constructing a Bayesian HPD (highest probability density) interval of a ratio of two multivariate normal generalized variances. The method gives a way of comparing two multivariate populations in terms of their dispersion or spread, because the generalized variance is a scalar measure of the overall multivariate scatter. Fully parametric frequentist approaches for the interval is intractable and thus a Bayesian HPD(highest probability densith) interval is pursued using a variant of weighted Monte Carlo (WMC) sampling based approach introduced by Chen and Shao(1999). Necessary theory involved in the method and computation is provided.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.389-392
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• 2000

Electronics and Telecommunications Research Institute (ETRI) developed the Ka-band satellite communications payload. This system is able to provide a high data rate communication service with a bandwidth of 200 MHz, a wideband digital flunking services up to 155 Mbps and asymmetrical internet multimedia service. The system employs the common receive/transmit antenna and the 2-for-1 redundant scheme for the LNA-Downconverters. The different types of high power amplification, TWTA for one chain and SSPA for the other chain, are used lot the variety of experimental options. For the reliable test of the payload, EGSE was also developed. The parametric RF tests were carried out in order to measure the performance of Ka-band communication subsystem, in most case the results of RF performance test complied the payload requirement.

• 천문학회보
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• 제40권2호
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• pp.29.1-29.1
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• 2015

We study the environmental dependence of the mass-size relation for the most massive early type galaxies (M > $10^{10.7}M_{\odot}$) in the redshift range 0.10~0.15. As a measure of the environment, galaxy number densities are measured by the $10^{th}$ nearest galaxies within 6500km/s from galaxies with spectroscopic redshifts. The sizes of galaxies are measured by non-parametric method. We find that galaxies more massive than $10^{11.1}M_{\odot}$ show the environmental dependence in the mass-size relation. The galaxies with M > $10^{11.1}M_{\odot}$ located in the densest, cluster like environment have larger sizes and extended surface brightness profiles than their counterparts located in a low dense environment. We also find that the environmental dependence of the mass-size relation is more significant for the brightest cluster galaxies (BCGs) than non-BCGs. Our result can be explained with a hierarchical growth of the most massive galaxies through dissipation-less merger in dense environment.

• Journal of the Korean Data and Information Science Society
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• 제8권2호
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• pp.153-161
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• 1997

본 연구에서는 우리나라 6대 생명보험회사의 모든 남자의 개인보험 계약자를 대상으로 조사한 1988년부터 1992년까지 25,000,000건의 자료를 가중이동평균모형을 이용한 보간법과 곰페 르츠모형을 이용한 보외법을 적용하여 경험생명표를 작성하였다. 적합성 및 평활성 기준에서 가중이동평균모형의 차분수와 항수, 곰페르츠모형의 모수 및 두 모형이 접촉하는 접점의 연령을 산출하였다. 특히 연립방정식을 이용하여 곰페르츠 모형의 모수를 폐쇄형으로 추정하는 방법을 제안하였다.

• 소음진동
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• 제4권3호
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• pp.365-375
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• 1994

Periodic longitudinal vibrations of a video and audio tape and the like used for transducing pictures and sounds may be induced by self-excited vibrations which are caused by frictions against the heads and guides, and their eccentricity, noncircularity or irregularity. It is important to analyze the longitudinal vibration of a tape because it causes distortions of a reproduced signal. It is difficult to measure directly the longitudinal vibration. In this paper a method estimating longitudinal vibration using impulse responses in the transverse direction is presented. And, the parameters boundary domain where the transverse and longitudinal vibration can be decoupled is introduced. In the domain where the both vibrations are decoupled, analytic methods using frequency characteristics and transient responses of the transverse vibration, respectively, are presented. The time domain method predicted more exactly the instantaneous phase of the longitudinal vibration than frequency domain method did.

• Journal of the Korean Statistical Society
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• 제21권2호
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• pp.93-110
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• 1992

A model selection approach is used to find out whether the mean and the variance of a unique sample are different from the pre-specified values. Normal distribution is selected as an approximating model. Kullback-Leibler discrepancy comes out as a natural measure of discrepancy between the operating model and the approximating model. Several estimates of selection criterion are computed including AIC, TIC, and a coupleof bootstrap estimator of the selection criterion are considered according to the way of resampling. It is shown that a closed form expression is available for the parametric bootstrap estimated cirterion. A Monte Carlo study is provided to give a formal comparison when the operating family itself is normally distributed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.845-850
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• 2003

The scattered light pattern from a machined surface generally contains much information concerning the surface roughness. The light pattern can be acquired by optical system and analyzed by statistical method. This kind of surface roughness measurement system can be easily adopted on the machine measurement. But the fully assembled system is too complex to implement on small systems using micro-controller. This study proposes the idea of reducing the number of optical components by removing screen and examines image processing of a light pattern to minimize the negative result of incomplete optical system. And the Gaussian blur filtering is concluded to be the best method of proposed measurement system. Furthermore light intensity variation of image pattern can be treated as a signal, therefore FIR filtering gives the similar result of Gaussian blur effect.

• 대한산업공학회지
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• 제37권4호
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• pp.350-357
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• 2011

In the recent, it is gradually important for airport to consider environmental aspects as sustainable development is emerged. ICAO, FAA and individual countries has tried to reduce airport noise and pollution. Thus, the effort is needed to incorporate environmental factor into productivity indicator of airport. Our paper use DEA method with the non-parametric directional output distance function(DDF) to assess productivity of 14 airports in Korea during 2008~2010. In addition to three inputs, two conventional outputs, two undesirable outputs have been considered : noise and air pollution. Results are compared from models that do not include undesirable outputs. Inclusion in the analysis of the undesirable effects of airport operations leads to greater and closer airport's efficiency scores.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.104-109
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• 2008

Distribution of welding residual stresses are mainly characterized by degrees and frequencies of thermal loads applied to materials. However, other effects as component size and clamping condition can also affect stress distributions to a certain extent thus careful manipulation of these parameters based on clear understanding of how they affect residual stresses distributions and why can be additional measure to mitigate residual stresses. This paper discusses aforementioned issues for the case of safety and relief nozzle in nuclear power plant through finite element analysis.