• 대한치과기공학회지
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• 제44권4호
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• pp.126-131
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• 2022

Purpose: The purpose of this study is to evaluate the quality of dental fixed prostheses fabricated by 3DP (three-dimensional printing). Methods: Ten main models were prepared for the study. Ten specimens were printed by 3DP (3DP group). Ten specimens were fabricated by the lost wax technique and casting method to complete the control group (LWC group). The marginal fit was measured for 20 specimens. The measurement of marginal fit was performed using the silicon replica technique. Finally, the marginal fit of 10 specimens from each group was calculated. An independent sample t-test was run to see if the calculated averages for the two groups were mutually significant (α=0.05). Results: According to the experimental results, the mean marginal fit of the 3DP group was 71.9 ㎛, and the LWC group was 55.3 ㎛. The means of the two groups were found to be significantly different (p<0.001) in the results of the independent sample t-test. Conclusion: The marginal fit of fixed dental prostheses produced by 3DP technology was examined with values greater than those fabricated by traditional technology. However, as it appeared to be a value within the range of clinically acceptable range recommended by numerous studies, it was determined that clinical application would be feasible.

• 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.

• Communications for Statistical Applications and Methods
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• 제16권6호
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• pp.971-978
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• 2009

Poisson generalized linear mixed models(GLMMs) have been widely used for the analysis of clustered or correlated count data. For the inference marginal likelihood, which is obtained by integrating out random effects is often used. It gives maximum likelihood(ML) estimator, but the integration is usually intractable. In this paper, we propose how to obtain the ML estimator via Laplace approximation based on hierarchical-likelihood (h-likelihood) approach under the Poisson GLMMs. In particular, the h-likelihood avoids the integration itself and gives a statistically efficient procedure for various random-effect models including GLMMs. The proposed method is illustrated using two practical examples and simulation studies.

• 대한치과기공학회지
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• 제38권3호
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• pp.119-125
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• 2016

Purpose: The purpose of this study is to evaluate the marginal gap of all-ceramic crowns fabricated by CEREC$^{(R)}$ in-office CAD/CAM system. Methods: The mandibular first molar was selected as the abutment for the experiments. Thirty working models were prepared. VITA Mark II(VM) and VITA Enamic(VE), LAVA Ultimate(LU) blocks were milled using CEREC MCXL with CEREC 3D system to construct 10 crowns for each groups. To measure marginal gap, milled restorations were examined under digital microscope with scale under 160x magnifications. The results were statistically analyzed using the one-way ANOVA and Tukey's HSD test(${\alpha}=0.05$). Results: There was no significant difference in the marginal gap regarding to ceramic materials(p>0.05). Conclusion: Single crowns fabricated using CEREC in-office CAD/CAM system provided clinically acceptable marginal gap. This confirmed that the type of ceramic material used does not determine the precision of fit of a prosthesis.

• 대한치과기공학회지
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• 제38권4호
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• pp.305-311
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• 2016

Purpose: The purpose of this study were to analysis of marginal adaptation of metal cores fabricated by selective laser sintering. Methods: Main model was prepared and ten stone models were fabricated. Ten single metal cores were fabricated by selective laser sintering(SLS group) and another ten single metal cores using lost wax technique and casting method were manufactured(CAST group). The marginal adaptation of metal cores were analysis using by the silicone replica technique. Silicone replicas were sectioned two times. The marginal adaptations were measured using by digital microscope. Statistical analyses was performed with independent t-test(${\bullet}{\cdot}=0.05$). Results: Means of marginal adaptations were 90.3 ${\ss}{\uparrow}$ for SLS group and 65.1 ${\ss}{\uparrow}$ for CAST group. Two groups were statistically significant differences (p < 0.05). Conclusion: Marginal adaptation of metal cores fabricated by selective laser sintering were ranged within the clinical recommendation.

• Journal of the Korean Data and Information Science Society
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• 제20권5호
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• pp.895-903
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• 2009

The penalized partial likelihood based on restricted maximum likelihood method has been widely used for the inference of frailty models. However, the standard-error estimate for frailty parameter estimator can be downwardly biased. In this paper we show that such underestimation can be corrected by using hierarchical likelihood. In particular, the hierarchical likelihood gives a statistically efficient procedure for various random-effect models including frailty models. The proposed method is illustrated via a numerical example and simulation study. The simulation results demonstrate that the corrected standard-error estimate largely improves such bias.

• 대한치과보철학회지
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• 제48권4호
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• pp.266-272
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• 2010

연구 목적: 임플란트 경부 역사면의 디자인이 변연골 응력분포에 미치는 영향을 알아보기 위해 유한요소법을 사용하여 비교분석하였다. 연구 재료 및 방법:경부 직경 5.5 mm, 길이 8 mm의 매립형 (submerged type) 고정체 (Dentis Co., Daegu, Korea)를 연구모델로 선정하였다. 임플란트 경부 역사면의 디자인을 높이 (h, 0.4 mm, 1.0 mm)와폭경({5.5 - (3.34 + 2b)} / 2, [b, 0.2 mm, 0.3 mm, 0.4 mm])을 다르게 하여 총 여섯 가지의 실험 임플란트 조합으로 구분하였다. 축대칭 유한요소모델링을 이용하여 임플란트/악골 복합체에 대해 임플란트 장축에 평행한 방향으로 치관 교합면의 중심부에 수직 하중 100 N이 작용할 때 변연골의 최대압축응력을 산출하여 비교 하였다. 결과: 여섯 개의 모든 실험 임플란트 모델에서 변연골의 응력집중이 관찰되지 않았다. 변연골 응력은 임플란트 경부 역사면의 폭과 높이의 차이에 따라 달라지는 것이 관찰되었으며 사면각이 클수록 응력 집중이 증가하는 경향을 보였다. 결론: 임플란트 경부 역사면 디자인의 부여는 변연골 응력 분포 개선에 중요한 역할을 할 수 있을 것으로 여겨진다.

• 농업과학연구
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• 제28권2호
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• pp.132-146
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• 2001

Rice cultivation is not only the main resource of farm income and staple food but also the root of cultural life of Korean people. Korean government has carried out irrigation water development with heavy investment to cope with water shortage in rice fanning as a link of the five years economic development plans. In spite of the continuous accomplishment of irrigation water development, the marginal benefits-costs of irrigation water has not been studied. Owing to the government full support for the operation and maintenance of irrigation facilities, price of irrigation water as a membership fee could not be formed as the municipal and industrial water prices. Accordingly this study is aimed at identifying firstly the marginal benefits-cost of irrigation water, secondly deriving the macro-econometrics models as supply and demand functions of irrigation water and thirdly examining the marginal benefits-cost ratio. The trends of supply and demand prices of irrigation water were estimated annually. Considering the marginal benefits-cost ratio as 1.3, it was identified that additional irrigation water development projects still have an economic feasibility under the present economic situation in Korea.

• 한국경영과학회지
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• 제34권4호
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• pp.123-138
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• 2009

This study examined the first- and second-best pricing by stable dynamics in congested transportation networks. Stable dynamics, suggested by Nesterov and de Palma (2003), is a new model which describes and provides a stable state of congestion in urban transportation networks. The first-best pricing in user equilibrium models introduces user-equilibrium in the system-equilibrium by tolling the difference between the marginal social cost and the marginal private cost on each link. Nevertheless, the second-best pricing, which levies the toll on some, but not all, links, is relevant from the practical point of view. In comparison with the user equilibrium model, the stable dynamic model provides a solution equivalent to system-equilibrium if it is focused on link flows. Therefore the toll interval on each link, which keeps up the system-equilibrium, is more meaningful than the first-best pricing. In addition, the second-best pricing in stable dynamic models is the same as the first-best pricing since the toll interval is separately given by each link. As an effect of congestion pricing in stable dynamic models, we can remove the inefficiency of the network with inefficient Braess links by levying a toll on the Braess link. We present a numerical example applied to the network with 6 nodes and 9 links, including 2 Braess links.

• 한국수자원학회논문집
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• 제45권8호
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• pp.827-837
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• 2012

확률강우량은 수공구조물의 설계에 있어 중요한 역할을 하며 이러한 확률강우량의 산정은 일반적으로 일변량 빈도해석을 수행하고 최적의 확률분포형을 찾아냄으로써 계산된다. 하지만 일변량 빈도해석은 수행 시 지속기간이 제한적이라는 단점이 있으며 이를 보완하기 위해 본 연구에서는 이변량 빈도해석을 수행하였다. 다변량 모형인 copula 모형 중3가지의 분포형을 이용하여 5개 지점의 연최대강우사상에 대해 이 변량 빈도해석을 수행하였으며 확률변수로 강우량과 지속기간을 사용하였다. 주변분포형은 강우량에는 Gumbel (GUM), generalized logistic (GLO) 분포형, 지속기간에는 generalized extreme value (GEV), GUM, GLO 분포형이사용됐으며 copula 모형은Frank, Joe, Gumbel-Hougaard 모형을 이용하였다. 주변분포형의 매개변수는 확률가중모멘트법을 이용하여 추정하였으며, copula 모형의 매개변수는 준모수방법인 의사최우도법을 사용하여 구하였다. 이를 통해 얻어진 확률강우량을 주변분포형과 copula 모형을바꾸어가며 비교하였다. 그 결과, 주변분포형의 종류에 따른 변화에서는 지속기간의 분포형에는 크게 영향을 받지 않는 것으로 나타났다. 강우량의 분포형에 따라서는 조금씩 차이가 났으며 강우량의 분포형이 GUM일 경우, GLO일 때에 비해 재현기간이 증가할수록 확률강우량이 증가하는 경향이 두드러졌다. Copula 모형별로 비교해보았을 때, Joe, Gumbel-Hougaard 모형은 비슷한 경향을 나타내었으며 Frank 모형은 재현기간의 증가에 따른 확률강우량의 증가가 강하게 나타냈다.