• Journal of the Korean Data and Information Science Society
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• 제23권2호
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• pp.385-392
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• 2012

Logistic regression is a well known binary classification method in the field of statistical learning. Mixed-effect regression models are widely used for the analysis of correlated data such as those found in longitudinal studies. We consider kernel extensions with semiparametric fixed effects and parametric random effects for the logistic regression. The estimation is performed through the penalized likelihood method based on kernel trick, and our focus is on the efficient computation and the effective hyperparameter selection. For the selection of optimal hyperparameters, cross-validation techniques are employed. Numerical results are then presented to indicate the performance of the proposed procedure.

• Communications for Statistical Applications and Methods
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• 제23권5호
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• pp.433-444
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• 2016

When we observe binary responses in a cluster (such as rat lab-subjects), they are usually correlated to each other. In clustered binomial counts, the independence assumption is violated and we encounter an extra-variation. In the presence of extra-variation, the ordinary statistical analyses of binomial data are inappropriate to apply. In testing the homogeneity of proportions between several treatment groups, the classical Pearson chi-squared test has a severe flaw in the control of Type I error rates. We focus on modifying the chi-squared statistic by incorporating variance inflation factors. We suggest a method to adjust data in terms of dispersion estimate based on a quasi-likelihood model. We explain the testing procedure via an illustrative example as well as compare the performance of a modified chi-squared test with competitive statistics through a Monte Carlo study.

• 한국군사과학기술학회지
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• 제14권4호
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• pp.648-654
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• 2011

We can model marine uplink channel environment as time-correlated rician fading channel that has direct path and time varying reflected path. In this channel, error performance of uncoded system can be seriously degraded by multipath inteference. In this paper, we propose Concatenated Zigzag(CZZ) coded binary FSK signaling with noncoherent detection to improve error performance of uplink data in marine environment. CZZ code is a kind of channel coding scheme that is fast decodable as well as fast encodable. We have confirmed error performance of uplink data in marine environment can be improved dramatically through applying CZZ code.

• 응용통계연구
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• 제33권2호
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• pp.123-136
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• 2020

하나의 개체에서 여러가지 측정치가 동시에 관찰되는 경우는 다양한 연구 분야에서 흔히 나타난다. 발달 독성학 연구에서는 특정 독성 물질의 각기 다른 수준에 노출된 임신한 어미 쥐에 대해 기형인 태아의 존재와 태아의 무게가 동시에 측정된다. 이런 두 변수를 결합하여 모형화하는 것은 각기 독립적인 두 모형으로 분석하는 것보다 더 효율적인 결과를 낸다고 알려져 있다. 대부분의 결합 모형은 정규분포를 랜덤효과로 가정하여 분석한다. 그러나 발달 독성학 연구에서처럼 반응변수들의 분포가 독성 물질이 변함에 따라 불규칙하게 변하는 경우 정규분포의 가정으로는 그 특징을 잡아낼 수 없게 된다. 본 논문에서는 이진수 자료와 연속형 자료에 대해 비대칭 로짓 모형을 사용한 베이지안 결합모형을 제시한다. 본 모형은 비대칭 로짓 모형을 사용함으로써 반응변수의 분포의 형태가 독성 물질의 수준에 따라 대칭/비대칭의 형태를 자유롭게 띨 수 있는 장점을 가지고 있다. 모형의 적합성을 살펴보기 위해 발달 독성학 연구에서 독성 물질 DEHP에 적용하여 그 결과를 확인해본다.

• Korean Chemical Engineering Research
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• 제55권4호
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• pp.520-529
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• 2017

Viscosity data were measured at 298.15 K and 308.15 K for formamide + 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol or 2-methyl-2-propanol mixtures. For an equimolar mixture, deviation in viscosity follows the sequence: 2-methyl-2-propanol >2-methyl-1-propanol>1-butanol>2-propanol>1-propanol. The viscosity data were further analyzed in terms of graph theory. Free energy of activation was also calculated from experimental viscosity data along with previously reported excess volume data. The deviation in viscosity and free energy of activation were fitted to Redlich-Kister polynomial equation. The viscosity data were also correlated by correlations like Grunberg-Nissan, Tamura-Kurata, HindMcLaughlin-Ubbelohde, and Katti-Chaudhari relation. Various adjustable parameters, $G_{12}$, $T_{12}$, $H_{12}$, and $W_{vis}/RT$, of various correlations were used to predict viscosity deviation of binary mixtures. Positive value of $G_{12}$ indicates strong interaction in the studied systems. Grunberg-Nissan relation has lowest deviation among the four correlations for formamide + 1-propanol or 2-propanol mixtures; and for mixtures of formamide with 1-butanol or 2-methyl-1-propanol, TamuraKurata has lowest deviation. Grunberg-Nissan gives lowest deviation for formamide + 2-methyl-2-propanol mixtures.

• 한국안전학회지
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• 제29권6호
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• pp.76-80
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• 2014

The flash point is one of the most important physical properties used to determine the fire hazard of flammable liquid mixture and defined as the lowest temperature at which a liquid produces sufficient vapor to form a combustible mixture with air. The main purpose of this paper is to measure and predict the flash point of binary flammable miscible mixtures. The flash points for n-hexanol+n-butyric acid and n-butanol+propionic acid, were measured by using Seta-flash closed cup method. The experimentally derived data were correlated with the binary interaction parameters of the van Laar and NRTL equations through the optimization method. The flash points estimated by these correlations were compared with those calculated by the method based on Raoult's law. The optimization method were found to be better than the method based on the Raoult's law.

• 한국가스학회지
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• 제18권5호
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• pp.60-65
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• 2014

가연성 액체 혼합물의 화재 위험성을 특징짓는 주된 물리적 성질은 인화점이다. 본 연구는 이성분계 가연성 혼합물의 인화점을 측정하고 예측하고자 한다. Seta flash 밀폐식 장치를 이용하여 n-propanol+propionic acid 계의 인화점을 측정하였다. van Laar 식과 NRTL 식을 이용한 최적화 기법을 통해 인화점을 예측하였다. 이 계산치와 라울의 법칙에 의한 계산치를 비교하였다. 그 결과, 최적화 기법에 의한 계산치가 라울의 법칙에 의한 계산치 보다 측정값에 보다 근사하였다.

• Korean Chemical Engineering Research
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• 제54권2호
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• pp.206-212
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• 2016

Experimental data are reported on the phase equilibrium of propoxylated neopentyl glycol diacrylate in supercritical carbon dioxide. Phase equilibria data were measured in static method at a temperature of (313.2, 333.2, 353.2, 373.2 and 393.2) K and at pressures up to 27.82 MPa. At a constant pressure, the solubility of propoxylated neopentyl glycol diacrylate for the (carbon dioxide + propoxylated neopentyl glycol diacrylate) system increases as temperature increases. The (carbon dioxide + propoxylated neopentyl glycol diacrylate) system exhibits type-I phase behavior. The experimental result for the (carbon dioxide + propoxylated neopentyl glycol diacrylate) system is correlated with Peng-Robinson equation of state using mixing rule. The critical property of propoxylated neopentyl glycol diacrylate is predicted with Joback and Lyderson method.

• Korean Chemical Engineering Research
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• 제57권6호
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• pp.826-831
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• 2019

Experimental data of phase equilibrium is reported for caprolactone acrylate in supercritical carbon dioxide. Bubble-point data was measured by synthetic method at temperatures ranging from (313.2 to 393.2) K and pressures up to 55.93 MPa. In this research, the solubility of carbon dioxide for the (carbon dioxide + caprolactone acrylate) system decreases as temperature increases at a constant pressure. The (carbon dioxide + caprolactone acrylate) system exhibits type-I phase behavior. The experimental result for the (carbon dioxide + caprolactone acrylate) system was correlated with Peng-Robinson equation of state using mixing rule. The critical property of caprolactone acrylate was predicted with the Joback and Lyderson method.

• 응용통계연구
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• 제21권1호
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• pp.35-51
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• 2008

제 3상 임상시험에서 치료효과가 여러 반응변수(endpoints)로 측정될 때, 이들 반응 변수가 대둥하게 중요하여 주요 반응변수(primary endpoint)를 선택할 수 없는 상황이 발생할 수 있다. O'Brion (1984)은 이들 반응변수 모두를 종합하여 치료효과에 대한 단축검정(one-tailed testing) 통계량으로서 반응변수가 연속형(continuous) 자료로 측정되었을 때 Ordinary Least Square(OLS)와 Generalized Least Square(GLS) 검정 통계량을 제시하였다. Pocock 등 (1987)은 여러 형태, 즉 연속형, 이산형(binary), 생존(survival) 자료의 반응변수를 함께 분석할 수 있음을 언급하고 있으나 실제로 이와 같이 여러 형태의 반응변수 병합에 대한 문제점을 설명하거나 구체적으로 모의 실험으로서 이러한 경우의 OLS와 GLS통계량의 효율성을 알아보지는 않았다. 본 논문에서는 특히 여러 형태의 반응변수를 종합하여 치료효과에 대한 결론을 내리는데 P값의 병합 통계량을 제안하며, 이때 각 반응변수의 치료효과에 대한 검정 결과인 P값은 서로 상관성이 존재하는 P값이다. OLS 및 GLS 검정 통계량보다 장점을 지닌 P값의 병합방법 중, 방법 F와 G는 제 1종 오류가 유의수준보다 커서 검정의 결론이 잘못 내려질 수 있는 경우가 있고 방법 B는 제 1종의 오류가 잘 통계되고 또한 효율성이 높은 것으로 나타났다.