• 응용통계연구
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• 제22권1호
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• pp.153-161
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• 2009

We consider a logistic model with random effects as the superpopulation for estimating the small area pro-portions. The best linear unbiased predictor under linear mired model is popular in small area estimation. We use this type of estimator under logistic mixed motel for the small area proportions, on which the estimation of mean squared error is also discussed. Two kinds of estimation methods, the parametric bootstrap and the linear approximation will be compared through a Monte Carlo study in the respects of the normality assumption on the random effects distribution and also the magnitude of sample sizes on the approximation.

• Journal of Biosystems Engineering
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• 제21권3호
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• pp.293-305
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• 1996

Effects on the tractor vibrations of tread, wheelbase and axle load distribution were analyzed by using mathematical models of tractor and random road surface. A 4 degrees of freedom tractor model was developed to predict the bounce, pitch and roll motions of tractor. The front axle which is constrained to roll with respect to tractor body was also included in the model. A random road profile was generated and used as an excitation input to the tractor. Output vibrations of the model were predicted and analyzed by a computer simulation method. In general, longer tread tends to reduce rolling and longer wheelbase does bouncing and pitching motions. Tractor vibrations were minimum when the ratio of front to rear axle loads was in the range of 30:70-35:65. Sensitivity analysis showed that rolling and pitching motions most sensitively varied with changes in tread and wheelbase while bouncing motion did with the location of mass center.

• Communications for Statistical Applications and Methods
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• 제21권5호
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• pp.423-433
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• 2014

Test statistics using cumulative sums of residuals have been widely used in various regression models including generalized linear models(GLM). Recently, Pan and Lin (2005) extended this testing procedure to the generalized linear mixed models(GLMM) having random effects, in which we encounter difficulties in computing the marginal likelihood that is expressed as an integral of random effects distribution. The Gaussian quadrature algorithm is commonly used to approximate the marginal likelihood. Many commercial statistical packages provide an option to apply this type of goodness-of-fit test in GLMs but available programs are very rare for GLMMs. We suggest a computational algorithm to implement the testing procedure in GLMMs by a freely accessible R package, and also illustrate through practical examples.

• Asian-Australasian Journal of Animal Sciences
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• 제11권6호
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• pp.642-647
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• 1998

A Poisson error model as a generalized linear mixed model (GLMM) has been suggested for genetic analysis of counted observations. One of the assumptions in this model is the normality for random effects. Since this assumption is not always appropriate, a more flexible model is needed. For count traits, a Poisson hierarchical generalized linear model (HGLM) that does not require the normality for random effects was proposed. In this paper, a Poisson-Gamma HGLM was examined along with corresponding analytical methods. While a difficulty arises with Poisson GLMM in making inferences to the expected values of observations, it can be avoided with the Poisson-Gamma HGLM. A numerical example with simulated embryo yield data is presented.

• Asian-Australasian Journal of Animal Sciences
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• 제24권1호
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• pp.17-27
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• 2011

A selection experiment for reduced residual feed intake (RFI) in Yorkshire pigs consisted of a line selected for lower RFI (LRFI) and a random control line (CTRL). Longitudinal measurements of daily feed intake (DFI) and body weight (BW) from generation 5 of this experiment were used. The objectives of this study were to evaluate the use of random regression (RR) and nonlinear mixed models to predict DFI and BW for individual pigs, accounting for the substantial missing information that characterizes these data, and to evaluate the effect of selection for RFI on BW and DFI curves. Forty RR models with different-order polynomials of age as fixed and random effects, and with homogeneous or heterogeneous residual variance by month of age, were fitted for both DFI and BW. Based on predicted residual sum of squares (PRESS) and residual diagnostics, the quadratic polynomial RR model was identified to be best, but with heterogeneous residual variance for DFI and homogeneous residual variance for BW. Compared to the simple quadratic and linear regression models for individual pigs, these RR models decreased PRESS by 1% and 2% for DFI and by 42% and 36% for BW on boars and gilts, respectively. Given the same number of random effects as the polynomial RR models, i.e., two for BW and one for DFI, the non-linear Gompertz model predicted better than the polynomial RR models but not as good as higher order polynomial RR models. After five generations of selection for reduced RFI, the LRFI line had a lower population curve for DFI and BW than the CTRL line, especially towards the end of the growth period.

• 한국융합학회논문지
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• 제11권6호
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• pp.227-235
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• 2020

본 연구는 주로 의사결정과제를 통해 검증되어왔던 무작위적 리더 선출 방법의 우수성을 실제 수행과제로 확장시켰고, 리더 선출 방법과 집단 효능감의 집단수행에 대한 상호작용효과를 살펴보았다. 2(리더 선출 방법: 공식적/무작위적) × 2(집단 효능감: 저/고) 피험자간 실험설계를 통해 집단수행에 대한 영향을 검증했다. 연구 결과, 리더 선출 방법의 주효과가 유의하여 공식적으로 리더가 선출된 집단보다 리더가 무작위적으로 선출된 집단의 수행이 유의하게 높았다. 또한, 두 변인 간의 상호작용이 유의하였는데, 집단 효능감이 낮을 때는 리더가 공식적으로 선출된 집단과 무작위적으로 선출된 집단 간의 수행차이가 유의하지 않았으나, 집단 효능감이 높을 때는 리더가 공식적으로 선출된 집단보다 무작위적으로 선출된 집단의 수행이 유의하게 높았다. 본 연구의 결과는 높은 집단 효능감이 집단의 수행에 긍정적인 영향을 주기 위해서는 리더가 집단의 사회정체성을 손상시키지 않는 방법(예. 리더와 구성원의 차이점을 부각시키기 보다는 동질성에 대한 지각을 높이는 방식)으로 선출되어야 한다는 점을 제안함으로써 조직과 작업 현장에 기여할 수 있다. 향후에 본 연구를 작업 팀으로 확장하여 연구할 필요성을 논의하였다.

• Earthquakes and Structures
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• 제14권4호
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• pp.313-322
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• 2018

The present study is dedicated to investigate the SH body-as well as Love-waves propagation effects in porous media with uncertain porosity and permeability. A unified formulation of the governing equations for one-dimensional (1-D) wave propagation in anisotropic porous layered media is presented deterministically. The uncertainties around the above two cited parameters are taken into account by random fields with the help of Monte Carlo Simulations (MCS). Random samples of the porosity and the permeability are generated according to the normal and lognormal distribution functions, respectively, with a mean value and a coefficient of variation for each one of the two parameters. After performing several thousands of samples, the mathematical expectation (mean) of the solution of the wave propagation equations in terms of amplification functions for SH waves and in terms of dispersion equation for Love-waves are obtained. The limits of the Love wave velocity in a porous soil layer overlaying a homogeneous half-space are obtained where it is found that random variations of porosity change the zeros of the wave equation. Also, the increase of uncertainties in the porosity (high coefficient of variation) decreases the mean amplification function amplitudes and shifts the fundamental frequencies. However, no effects are observed on both Love wave dispersion and amplification function for random variations of permeability. Lastly, the present approach is applied to a case study in the Adapazari town basin so that to estimate ground motion accelerations lacked in the fast-growing during the main shock of the damaging 1999 Kocaeli earthquake.

• Asian-Australasian Journal of Animal Sciences
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• 제33권9호
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• pp.1387-1399
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• 2020

Objective: The objective of this study was to estimate the genetic parameters and trends for milk, fat, and protein yields in the first three lactations of Thai dairy cattle using a 3-trait,-3-lactation random regression test-day model. Methods: Data included 168,996, 63,388, and 27,145 test-day records from the first, second, and third lactations, respectively. Records were from 19,068 cows calving from 1993 to 2013 in 124 herds. (Co) variance components were estimated by Bayesian methods. Gibbs sampling was used to obtain posterior distributions. The model included herd-year-month of testing, breed group-season of calving-month in tested milk group, linear and quadratic age at calving as fixed effects, and random regression coefficients for additive genetic and permanent environmental effects, which were defined as modified constant, linear, quadratic, cubic and quartic Legendre coefficients. Results: Average daily heritabilities ranged from 0.36 to 0.48 for milk, 0.33 to 0.44 for fat and 0.37 to 0.48 for protein yields; they were higher in the third lactation for all traits. Heritabilities of test-day milk and protein yields for selected days in milk were higher in the middle than at the beginning or end of lactation, whereas those for test-day fat yields were high at the beginning and end of lactation. Genetics correlations (305-d yield) among production yields within lactations (0.44 to 0.69) were higher than those across lactations (0.36 to 0.68). The largest genetic correlation was observed between the first and second lactation. The genetic trends of 305-d milk, fat and protein yields were 230 to 250, 25 to 29, and 30 to 35 kg per year, respectively. Conclusion: A random regression model seems to be a flexible and reliable procedure for the genetic evaluation of production yields. It can be used to perform breeding value estimation for national genetic evaluation in the Thai dairy cattle population.

• 대한전자공학회논문지SD
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• 제37권8호
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• pp.76-85
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• 2000

회절격자 주기의 랜덤 변이가 DFB 레이저의 특성에 미치는 영향을 유효 굴절률 전달 매트릭스 방법을 이용하여 해석하였다. 레이저의 양 거울면은 완전 무반사 처리되었다고 가정하였으며, 회절격자 주기의 변이는 Gaussian 랜덤 변수로 표현하였다. 회절격자 주기의 랜덤 변이는 균일 회절격자 DFB 레이저와 QWS-DFB 레이저 스펙트럼의 대칭성을 깨뜨리고 유효 결합계수를 감소시킨다. 이에 따라 균일 회절격자 DFB 레이저에서는 ${\pm}$1모드 거울면 손실의 평균값이 증가하고 금지 대역폭이 감소하며, QWS-DFB 레이저에서는 단일모드 안정성과 파장 정확도가 저하된다. QWS-DFB 레이저의 거울면 손실 차이는 결합계수에 관계없이 회절격자 주기의 랜덤 변이가 카짐에 따라 감소하고, spatial hole-burning 효과는 정규화된 결합계수가 1.5보다 클 때에는 주는 데 반하여 작을 때에는 커진다.

• 노동경제논집
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• 제27권1호
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• pp.1-25
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• 2004

인적자원이 가장 중요한 경쟁력이 되는 지식정보화 산회에서 숙련의 주기는 짧으며, 노동력의 유동화는 심화되고 있어 자격의 신호기제로서의 역할이 크게 부각되고 있다. 이에 우리나라 자격의 기능을 취득요인, 취업 및 임금효과 측면에서 검토하기 위해 한국노동패널 1~4차년도(1998~2001) 자료를 개인별로 묶어 고정효과 로짓모형, 임의효과모형으로 회귀분석하였다. 추정의 결과 고졸 미만 저학력층의 자격취득 확률이 높게 나타났다. 남자는 실업상태에 있는 경우에 자격취득이 많았고, 여성은 비경제활동의 기타 상태(잠재적 구직상태)에 있는 경우 자격취득이 많았다. 자격의 취업효과는 여성의 경우 1년차, 2년차에 유의하게 나타나나, 남자의 경우는 유의하지 않았다. 취득한 자격의 임금효과는 남녀 공히 유의하지 않았다. 이러한 결과는 현재 우리나라에서 자격취득으로 얻어지는 직업능력이 시장에서 제대로 인정받고 있지 못하는 현실을 반영한다.