• 한국측량학회지
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• 제34권1호
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• pp.91-98
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• 2016

지구통계학적인 공간분석의 대표적인 방법인 크리깅(kriging)을 적용하기 위해서는 두 관측점 사이의 거리에 기반한 상관성을 나타내는 공간상관함수의 추정이 우선적으로 이루어져야 한다. 본 연구에서는 다양한 크리깅에 적용할 수 있는 대표적인 상관함수인 semi-variogram, homeogram, covariance function에 대하여 국가지오이드 모델을 기반으로 추정하였다. 경위도 각각 2°의 대상지역 내 통합기준점의 지오이드고를 이용하였으며, 선형모델을 이용하여 공간적인 편향성을 제거하였다. 전체 100개의 샘플 포인트에 대해서 중복되지 않은 두 점 간의 거리를 기준으로 구간을 나누고, 각 함수에 대한 경험적인 값을 계산하였다. 공간상관함수의 경험적인 값은 각각 두 개의 모델에 최소제곱조정 방법으로 피팅한 결과 semi-variogram의 wave 모델 적합도가 가장 높았으며, homeogram과 covariance function은 exponential 모델이 상대적으로 좋은 피팅 결과를 보였다. 본 연구에서 결정한 공간상관함수는 추후 다양한 크리깅 방법을 통해 임의 지점에서의 예측값에 대한 정확도 검증과 이에 대한 평균제곱예측오차(Mean Squared Prediction Error, MSPE)를 계산함으로써 각 함수의 활용성에 대한 추가적인 연구가 수행되어야 한다.

• Journal of electromagnetic engineering and science
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• 제5권4호
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• pp.183-188
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• 2005

A simple microwave backscattering model for vegetation canopies on earth surfaces is developed in this study. A natural earth surface is modeled as a two-layer structure comprising a vegetation layer and a ground layer. This scattering model includes various scattering mechanisms up to the first-order multiple scattering( double-bounce scattering). Radar backscatter from ground surface has been modeled by the polarimetric semi-empirical model (PSEM), while the backscatter from the vegetation layer modeled by the vector radiative transfer model. The vegetation layer is modeled by random distribution of mixed scattering particles, such as leaves, branches and trunks. The number of input parameters has been minimized to simplify the scattering model. The computation results are compared with the experimental measurements, which were obtained by ground-based scatterometers and NASA/JPL air-borne synthetic aperture radar(SAR) system. It was found that the scattering model agrees well with the experimental data, even though the model used only ten input parameters.

• 대한원격탐사학회지
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• 제27권3호
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• pp.303-314
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• 2011

Surface albedo is an important parameter of the surface energy budget, and its accurate quantification is of major interest to the global climate modeling community. Therefore, in this paper, we consider the direct solution of kernel based bidirectional reflectance distribution function (BRDF) models for retrieval of normalized reflectance of high resolution satellite. The BRD effects can be seen in satellite data having a wide swath such as SPOT/VGT (VEGETATION) have sufficient angular sampling, but high resolution satellites are impossible to obtain sufficient angular sampling over a pixel during short period because of their narrow swath scanning when applying semi-empirical model. This gives a difficulty to run BRDF model inferring the reflectance normalization of high resolution satellites. The principal purpose of the study is to estimate normalized reflectance of high resolution satellite (RapidEye) through BRDF components from SPOT/VGT. We use semi-empirical BRDF model to estimated BRDF components from SPOT/VGT and reflectance normalization of RapidEye. This study used SPOT/VGT satellite data acquired in the S1 (daily) data, and within this study is the multispectral sensor RapidEye. Isotropic value such as the normalized reflectance was closely related to the BRDF parameters and the kernels. Also, we show scatter plot of the SPOT/VGT and RapidEye isotropic value relationship. The linear relationship between the two linear regression analysis is performed by using the parameters of SPOTNGT like as isotropic value, geometric value and volumetric scattering value, and the kernel values of RapidEye like as geometric and volumetric scattering kernel Because BRDF parameters are difficult to directly calculate from high resolution satellites, we use to BRDF parameter of SPOT/VGT. Also, we make a decision of weighting for geometric value, volumetric scattering value and error through regression models. As a result, the weighting through linear regression analysis produced good agreement. For all sites, the SPOT/VGT isotropic and RapidEye isotropic values had the high correlation (RMSE, bias), and generally are very consistent.

• Wind and Structures
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• 제17권6호
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• pp.565-587
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• 2013

Obvious vortex induced vibration (VIV) was observed during section model wind tunnel tests for a single main cable suspension bridge. An optimized section configuration was found for mitigating excessive amplitude of vibration which is much larger than the one prescribed by Chinese code. In order to verify the maximum amplitude of VIV for optimized girder, a full bridge aeroelastic model wind tunnel test was carried out. The differences between section and full aeroelastic model testing results were discussed. The maximum amplitude derived from section model tests was first interpreted into prototype with a linear VIV approach by considering partial or imperfect correlation of vortex-induced aerodynamic force along span based on Scanlan's semi-empirical linear model. A good consistency between section model and full bridge model was found only by considering the correlation of vortex-induced force along span.

• 국제지역연구
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• 제12권3호
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• pp.153-169
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• 2008

본 연구는 두 가지 형태의 내생적 성장이론에 대한 실증분석을 실시하는 데 있다. 이 연구목적을 위하여 1981부터 2000년까지 OECD 19개 국가를 대상으로 패널 단위근과 패널 공적분방법을 이용하여 두 이론의 함의에 대하여 실증분석을 시시하였다. 먼저 패널 단위근 실증분석결과를 보면, 총 요소생산성 수준에 대한 세 패널 단위근 검정결과는 비 정상상태를 나타내는 것으로 보이며, 총 요소생산성 증가율에 대한 패널 단위근 검정결과는 정상상태를 나타내는 것으로 나타났다. 둘째, 준 내생적 성장이론에 근거한 Durbin-Hausman 통계량은 공적분 관계가 존재하지 않는다는 귀무가설을 기각하는 것으로 나타났다. 이 분석결과는 총 요소생산성 대비 연구개발비를 사용하거나 연구원수를 사용한 경우에도 동일하게 나타났으나, 패널 공적분 분석결과는 사용변수와 분석통계량에 따라서 서로 상반된 결과를 보였다. 준 내생적성장이론을 뒷받침하는 본 실증분석결과는 연구개발지출과 같은 내생적인 통제변수에 의하여 지속적인 경제성장을 이룩할 수 있다는 이론적 기반을 제공한다. 그러나 지속적인 총 요소생산성증대를 통한 경제성장은 지속적인 연구개발투입량증가만으로 뒷받침 될 수 있으며, 연구개발기여도체감(수확체감)을 극복하기 위한 연구개발투입증가를 더욱 증가시켜야 한다는 이론적 함의를 실증적으로 뒷받침한다고 볼 수 있다.

• 패션비즈니스
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• 제20권6호
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• pp.66-78
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• 2016

Hygroscopic knitted cotton fabric was found to spontaneously absorb water showing a significantly wide concentration gradient in the absorption direction. A semi-empirical diffusion model was introduced to describe how the wicking behavior compared to the classical capillary model (Washburn's equation), which has been widely used in the textiles industry. The capillary sorption curve and the permeability coefficient, which are key variables for the model equations, were measured using an electronic balance. The concentration profile as a function of the wicking distance and the elapsed time was derived, based on the diffusion model. From the concentration profile, the wicking distance detectable by the human eye or a digital camera with the aid of an image-analysis system, could be described realistically as a function of the time. The classical capillary model could be modified by introducing the tortuous correction factor to match the diffusion model. Wicking models and data-processing techniques in the work could provide useful tools for objectively evaluating the textile's wicking performances.

• 산업기술연구
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• 제17권
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• pp.111-118
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• 1997

This thesis is an experimental research of investigating behavior of single pile, subjected to the vertical compression loads, using the centrifuge facility located in the geotechnical engineering laboratory in Kangwon National University. Centrifugal model experiments of model pile were carried out changing diameter of model pile, relative density of sandy ground and the gravitational level applied in the centrifuge. Thus, their effects on the load-settlement behavior and the ultimate bearing capacity of pile were investigated. Experimental results obtained from centrifuge model tests were compared with the theoretical or semi-empirical equations to analyze values of ultimate bearing capacity of model pile. When we compare the ultimate bearing capacity of experimental results with the ultimate bearing capacity of theorical results, the experimental results appear more higher in the De Beer method and Meyerhof. Expecially, Terzaghi method is very same as the experimental results normally.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1834-1846
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• 2020

The SMART (System-integrated Modular Advanced ReacTor) is an integral-type small modular reactor developed by KAERI (Korea Atomic Energy Research Institute). This paper discusses the development of a dynamic equivalent model of the SMART control rod drive mechanism that can be efficiently utilized for complicated analysis during the design of the SMART. A semi-empirical approach is used to develop the equivalent model; that is, the equivalent model is defined analytically and verified empirically. Two types of tests, dynamic characteristics tests and seismic loading tests, are conducted for the development and verification of the dynamic equivalent model, respectively. Acceleration response spectra from the seismic analysis based on the developed equivalent model show good agreement with those from the seismic loading tests.

• Tribology and Lubricants
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• 제24권5호
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• pp.215-220
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• 2008

An internal friction model was developed to model the frictional behavior of automotive Constant Velocity (CV) joints by using the test data from an instrumented CV joint friction apparatus with actual driveshaft assemblies. Experiments were conduced under different realistic operating conditions of oscillatory speeds, CV joint articulation angles, lubrication, and torque. The experimental data were used to develop a physics-based semi-empirical CV joint internal friction coefficient model as a function of different CV Joint operating parameters. It was found that the proposed friction model captures the experimental results well not only the static behavior of friction coefficient, but also the dynamic friction terms, which is the main source of force that causes vehicle vibration problems.

• Journal of Mechanical Science and Technology
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• 제16권8호
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• pp.1144-1153
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• 2002

A hybrid performance prediction method is proposed in the present study. A channel diffuser is divided into four subregions: vaneless space, semi-vaneless space, channel, and channel exit region. One-dimensional compressible core flow and boundary layer calculation of each region with an incidence loss model and empirical correlation of residuary pressure recovery coefficient of a channel predict the performance of diffusers. Three channel diffusers are designed and tested for validating the developed prediction method. The pressure distributions from an impeller exit to the channel diffuser exit are measured and discussed for various operating conditions from choke to nearly surge conditions. The strong non-uniform pressure distribution which is caused by impeller-diffuser interaction is obtained over the vaneless and semi-vaneless spaces. The predicted performance shows good agreement with the measured performance of diffusers at a design condition as well as at off-design conditions.