• Asian-Australasian Journal of Animal Sciences
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• 제19권7호
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• pp.915-921
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• 2006

Various random regression models with different order of Legendre polynomials for permanent environmental and genetic effects were constructed to predict future milk yield of Holstein cows in Korea. A total of 257,908 test-day (TD) milk yield records from a total of 28,135 cows belonging to 1,090 herds were considered for estimating (co)variance of the random covariate coefficients using an expectation-maximization REML algorithm in an animal mixed model. The variances did not change much between the models, having different order of Legendre polynomial, but a decreasing trend was observed with increase in the order of Legendre polynomial in the model. The R-squared value of the model increased and the residual variance reduced with the increase in order of Legendre polynomial in the model. Therefore, a model with $5^{th}$ order of Legendre polynomial was considered for predicting future milk yield. For predicting the future milk yield of cows, 132,771 TD records from 28,135 cows were randomly selected from the above data by way of preceding partial TD record, and then future milk yields were estimated using incomplete records from each cow randomly retained. Results suggested that we could predict the next four months milk yield with an error deviation of 4 kg. The correlation of more than 70% between predicted and observed values was estimated for the next four months milk yield. Even using only 3 TD records of some cows, the average milk yield of Korean Holstein cows would be predicted with high accuracy if compared with observed milk yield. Persistency of each cow was estimated which might be useful for selecting the cows with higher persistency. The results of the present study suggested the use of a $5^{th}$ order Legendre polynomial to predict the future milk yield of each cow.

• 한국초지조사료학회지
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• 제40권3호
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• pp.167-176
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• 2020

The objective of the present study was to determine the best model to describe and quantify the changes in live body weight, height at withers, height at rump, body length and chest girth of Holstein cows raised under Korean feeding conditions for 50 months. The five standard growth models namely polynomial linear regression models, regression of growth variables on the first and second-order of ages in days (model 1) and regression of growth variables on age covariates from first to the third-order (model 2) as well as non-linear models were fitted and evaluated for representing growth pattern of Holstein cows raised in Korean feeding circumstances. Nonlinear models fitted were three exponential growth curve models; Brody, Gompertz, and von Bertalanffy functional models. For this purpose, a total of 22 Holstein cows raised in Korea used in the period from April 2016 to May 2020. Each model fitted to monthly growth curve records of dairy cows by using PROC NLIN procedure in SAS program. On the basis of the results, nonlinear models showed the lower root mean square of error (RMSE) for live body weight, height at withers, height at rump, body length and chest girth (12.22, 1.95, 1.55, 4.04, 2.06) with higher correlation coefficiency (R²) values for live body weight, height at withers, height at rump, body length and chest girth (0.99, 0.99, 0.99, 1.00, 1.00). Overall, the evaluation of the different growth models indicated that the Gompertz model used in the study seemed to be the most appropriate one for standard growth of Holstein cows raised under Korean feeding system.

• Journal of Information Technology Applications and Management
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• 제24권2호
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• pp.71-80
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• 2017

Software reliability is one of the most elementary and important problems in software development In order to find the software failure occurrence, the instantaneous failure rate function in the Poisson process can have a constant, incremental or decreasing tendency independently of the failure time. In this study, we compared the reliability performance of the software reliability model using the parameters of Pareto life distribution with the intensity decreasing pattern and the shape parameter of Erlang life distribution with the intensity increasing and decreasing pattern in the software product testing. In order to identify the software failure environment, the parametric estimation was applied to the maximum likelihood estimation method. Therefore, in this paper, we compare and evaluate software reliability by applying software failure time data. The reliability of the Erlang and Pareto life models is shown to be higher than that of the Pareto lifetime distribution model when the shape parameter is higher and the Erlang model is more reliable when the shape parameter is higher. Through this study, the software design department will be able to help the software design by applying various life distribution and shape parameters, and providing basic knowledge using software failure analysis.

• 한국융합학회논문지
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• 제11권10호
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• pp.225-229
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• 2020

본 연구에서는 총 4가지 Model의 스마트폰들에 대하여 충격을 주었을 때, 각각의 모델들에 대한 변형량과 응력들을 해석하여 그 강도를 서로 비교하였다. 케이스를 장착한 경우의 모델들인 Model B와 Model D는 장착하지 않은 모델들인 Model A와 Model C에 비하여 변형량과 응력이 적은 것을 볼 수 있다. 케이스를 포함한 Model들이 케이스가 없는 Model들보다 질량이 더 많아지게 되어 충격력을 흡수함으로서 변형량과 응력을 감소시킬 수 있다. 또한 질량이 Model C와 Model D가 Model A와 Model B에 비하여 작지만 응력과 변형량이 더 작아짐을 보이고 있다. 스마트폰을 제작시에 무게가 적게 나가면서 충격을 흡수할 수 있도록 하기 위하여 모서리 보호에 특화되어 있는 케이스를 선택하여 설계한다면 스마트폰의 강도를 향상시켜 내구성을 증진할 수 있다고 사료된다. 또한 본 연구가 실제적으로 스마트폰 케이스의 내구성이 있는 효율적인 설계와 스마트 폰의 미적인 융합에 적합하여 보인다.

• 자원ㆍ환경경제연구
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• 제20권3호
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• pp.419-457
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• 2011

본 연구에서는 기후변화 정책 분석의 주요 연구 수단으로 사용되는 CGE 모형의 연산구조를 변화시키는 방법을 통해 모형의 특성을 이해하고자 하였다. 이를 위해 우선 기존의 연구 사례들을 중심으로 CGE 모형으로 대표되는 하향식 모형의 일반적인 특징을 살펴보았고, 나아가 기준 모형인 EPPA 모형에 다른 모형들에서 사용하고 있는 구조를 적용하였을 경우에 나타나는 분석 결과상의 변화를 살펴보고 그 경제적 의미에 대해 논의해 보고자 하였다. 사례연구 결과 장기에 있어서 상향식 및 복합모형의 저감 잠재량이 하향식보다 크게 나오는 일반적인 경향을 추론할 수 있었다. 이는 IPCC 보고서 등의 잠정적인 결론과는 다른 내용으로서 보다 엄밀한 모형 구조분석의 필요성을 제기하였다. EPPA 모형을 대상으로 한 구조분석 결과 온실가스 배출에 직접적인 영향을 미치는 에너지와 관련한 연산구조가 기준 배출량 및 저감률 계산에 가장 큰 영향을 미친다는 사실을 확인할 수 있었다. 이는 에너지와 자본 간의 대체성 및 에너지 복합재 내부의 대체탄력성을 포함한다. 기술묶음 개념의 적용으로 사례연구 결과를 실증적으로 검증할 수 있었으며, 상대적으로 아밍턴재의 대체탄력성 변화는 총합에 있어서는 큰 영향을 주지는 못하는 것으로 나타났다.

• 한국의류학회지
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• 제35권5호
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• pp.561-574
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• 2011

This study investigates the ultimate factor structure of consumer dissatisfaction with the off-line purchase and usage of clothing. It identifies the determinant dimensions of consumer dissatisfaction on clothing purchase and usage and investigates the hierarchical structure of consumer dissatisfaction by assessing and comparing the effectiveness of five alternative factor structure models. A total of 300 women were online-surveyed to assess the level of dissatisfaction based on their dissatisfying experience with clothing purchases and usage in terms of product quality, price, salesperson's attitude, and store environment. The exploratory factor analysis identified the underlying dimensions of dissatisfaction: Handling, Aesthetics, Salesperson, Size, Price, Product Quality, Service, and Environment. By employing a first-order confirmatory factor analysis and higher-order confirmatory factor analysis, consumer dissatisfaction was confirmed to have a hierarchical structure with three second-order constructs Intrinsic instrument is manifested by handling, quality, and size, Intrinsic expression consists of service, salesperson, and environment, and Extrinsic circumstance contains aesthetics and price. On empirically demonstrating the multi-dimensional constructs of consumer dissatisfaction by identifying its hierarchical structure, the study provides the theoretical and practical insights to comprehend consumer purchase and post-purchase behavior. Specifically, it affords an empirical platform to extend the scope of research with condensed concepts of dissatisfaction to researchers. In addition, it also enables marketers to take a broader view of consumer dissatisfaction by providing cues about potential problems and identifying the source of those problems.

• Journal of Preventive Medicine and Public Health
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• 제53권5호
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• pp.371-380
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• 2020

Objectives: This study investigated the effects of socio-demographic factors on the decreasing trend in the sex ratio at birth from 1997 to 2017 in Korea. Methods: Data from 10 349 602 live births registered with Statistics Korea from 1997 to 2017 were analyzed. The secondary sex ratio (SSR), defined as the ratio of male to female live births, during the study period (1997-1999 [phase I], 2000-2002 [phase II], 2003-2005 [phase III], 2006-2008 [phase IV], 2009-2011 [phase V], 2012-2014 [phase VI], and 2015-2017 [phase VII]) was calculated according to selected socio-demographic factors, such as parental age, education, occupation, and birth order. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals for a male birth after adjusting for potential confounders. Results: The SSR gradually decreased from 1.10 (in 1998-2000 and 2002) to 1.05 (in 2013-2016). While a decreasing trend in the SSR was not noted among first births, male-biased sex ratios were prominent among third and higher-order births, for which the highest SSR was 1.46 in 1998. Higher birth order was significantly associated with an excess of male births in phases I-VI (≥third vs. first, OR range, 1.03 to 1.35). Advanced maternal age was significantly associated with an excess of female births in phases II, III, and V (≥40 vs. 20-24 years, OR range, 0.92 to 0.95). Conclusions: This study demonstrated that advanced maternal age and reduction of the artificially-biased SSR among third and higher-order births may partially explain the decreasing trend in the SSR from 1997 to 2017 in Korea.

• 대한수학회논문집
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• 제21권2호
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• pp.375-384
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• 2006

We consider a class of bilinear models with periodic regime switching and find easy-to-check sufficient conditions that ensures the existence of a stationary process obtained from given difference equation. Existence of a higher order moments is examined.

• Wind and Structures
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• 제17권2호
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• pp.135-162
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• 2013

The majority of experiments to characterize the turbulence in the surface layer have been performed in flat, open expanses. In order to characterize the turbulence in built-up terrain, two mobile towers were deployed during Hurricane Ike (2008) in close proximity, but downwind of different terrain conditions: suburban and open. Due to the significant non-stationarity of the data primarily caused by changes in wind direction, empirical mode decomposition was employed to de-trend the signal. Analysis of the data showed that the along-wind mean turbulence intensity of the suburban terrain was 37% higher than that of the open terrain. For the mean vertical turbulence intensity, the increase for the suburban terrain was as high as 74%, which may have important implications in structural engineering. The gust factor of the suburban terrain was also 16% higher than that of the open terrain. Compared to non-hurricane spectral models, the obtained spectra showed significantly higher energy in low frequencies especially for the open terrain.

• 수산경영론집
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• 제25권2호
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• pp.89-102
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• 1994

This paper is to survey the major results of the game-theoretic models and recent research directions of the literature on auctions and competitive biddings. This paper classifies the auctions and competitive biddings into the following four major types:(i) English auction, (ii) Dutch auction, (iii) the first-price sealed-bid auction, (iv) the second-price sealed-bid auction. In order to survey the major ideas related to auctions and competitive biddings, we use two representative theoretical models developed under the game-theoretic framework : (i) the independent private value model are summarized as follows ; (1) The Dutch auction and the first-price auction are strategically equivalent, and so are the English auction and the second-price auction. (2) At the symmetric equilibria, the expected selling price is the same for all four types of auction. Meanwhile, the major results of the general model are as follows ; (1) When bidders are uncertain about their value extimate, the English and second-price auctions are not equivalent, but the dutch and the first-price auctions are still strategically equivalent. (2) The English auction generates the higher expected prices than the second-price auction. Also, when bidders are risk-neutral, the second-price auction generated higher average prices than the Dutch and the first-price auctions.