• The Korean Journal of Applied Statistics
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• v.33 no.2
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• pp.123-136
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• 2020

It is common to encounter correlated multiple outcomes measured on the same subject in various research fields. In developmental toxicity studies, presence of malformed pups and fetal weight are measured on the pregnant dams exposed to different levels of a toxic substance. Joint analysis of such two outcomes can result in more efficient inferences than separate models for each outcome. Most methods for joint modeling assume a normal distribution as random effects. However, in developmental toxicity studies, the response distributions may change irregularly in location and shape as the level of toxic substance changes, which may not be captured by a normal random effects model. Motivated by applications in developmental toxicity studies, we propose a Bayesian joint model for binary and continuous outcomes. In our model, we incorporate a skewed logit model for the binary outcome to allow the response distributions to have flexibly in both symmetric and asymmetric shapes on the toxic levels. We apply our proposed method to data from a developmental toxicity study of diethylhexyl phthalate.

• Environmental and Resource Economics Review
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• v.24 no.3
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• pp.523-549
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• 2015

This paper investigates an oil refiner's asymmetric behavior in the adjustments of gasoline and diesel prices to changes in his own price and his rivals' prices as well as input costs. An asymmetric error correction model which allows a firm's pricing behavior to the deviation of other firms' prices from their long-run equilibrium level is employed for estimation using weekly data for the period April 2009 to January 2015. Evidence is found that there is a significant degree of asymmetry in the adjustment of wholesale prices to changes in crude oil price. A similar result in regard to the exchange rate is also found by the data. The estimation results for firm's response to changes in other firms' prices indicates that implicit collusion could be more easily exploited in the wholesale petroleum market as results of firms' interaction with each other and anticipation of rivals' pricing behavior. A few refiners show competitive price adjustment in response to the upward deviation of the others' prices from their equilibrium level.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.515-522
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• 1999

Asymmetric polyetherimide membrane were prepared by phase inversion method, and the effects of NaOH concentration and reaction time on the morphology change of the polyetherimide membranes were studied. The morphology of skin layers varied from dense structure to sphere structure with increasing concentration of modification solution. The thickness of dense layer increased with increasing reaction time. However, when either the concentration of modifying solution was very high or the reaction time was very long, the dense layers of the asymmetric membrane were disappeared. From these results, it was found that the surface morphology of the asymmetric polyetherimide membranes depended strongly on the modification conditions such as concentration of modification solution and reaction time. These results might be explained by the hydrolysis reaction of polyetherimide into polyamic acid by the NaOH solution.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2009.05a
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• pp.95-96
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• 2009

행동활성화 및 억제체계의 민감성에 따라 4 개 집단으로 분류하고, 각 집단에 대하여 뇌파를 측정하여 전전두엽의 비대칭성을 평가하였다. 이들 각 집단에 대하여 긍정적 감성을 유발시킬 수 있는 음향(명상음악)과 부정적 감성을 유발시킬 수 있는 음향(소음)을 제시하여 그 반응을 분석한 결과, 명상음악 청취에 대한 주관적 감성평가는 4 개 집단 모두 비슷한 수준의 긍정적 감성을 나타냈지만, 전전두엽의 비대칭성은 행동억제체계가 민감한 집단에 비하여 행동활성화체계가 민감한 집단일수록 좌측 전전두엽이 더 활성화되는 것으로 나타나 Davidson 의 행동활성화 및 행동억제체계의 단일차원을 지지한다. 소음청취에 대한 주관적 평가에서는 4개 집단 모두 비슷한 수준의 부정적 감성을 나타낸 반면에, 전전두엽의 비대칭성은 행동활성화 또는 억제체계의 민감성이 어느 하나라도 높은 3 개 집단 모두에서 우측 전전두엽이 더 활성화 되었지만, 민감성이 모두 낮은 나머지 1 개 집단에서는 좌측 전전두엽이 더 활성화되는 것으로 나타나 Gray의 행동활성화 및 행동억제체계의 독립차원을 지지한다.

• Journal of the Korean Chemical Society
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• v.58 no.2
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• pp.230-233
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• 2014

• Journal of the Korean Ceramic Society
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• v.38 no.1
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• pp.61-67
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• 2001

비대칭 펄스 직류 반응성 스퍼터링을 이용하여 상온에서 Si(100) 기판 위에 AlN 박막을 증착하였다. 100 kHz에서 200 kHz까지 펄스 주파수의 변화 및 70%에서 90%까지 duty cycle의 변화에 따른 아크 발생과 AlN 박막의 결정성 그리고 미세 조직을 관찰하였다. Duty cycle에서 양의 펄스 유지 시간이 증가함에 따라 증착 중에 아크 발생 빈도가 현저히 감소하였고 AlN 박막의 입자 크기와 결정상의 c축 배향성이 증가하였다. 반면에 펄스 주파수 변화에 따른 아크 발생은 일정한 경향을 나타내지 않았지만 전반적으로 많은 아크가 발생했다. 아크 발생 빈도가 늘어남에 따라 c축 배향성이 감소하였다. 양의 펄스 유지 시간과 펄스 주파수가 감소함에 따라 박막의 증착 속도는 증가하였으며 440$\AA$/min의 높은 증착 속도를 나타냈다.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.127-139
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• 2014

Hard-Soft Acid-Base (HSAB) 이론은 일반적인 유기, 무기반응의 반응성을 설명하는데 사용되어 왔다. 밀도범함수이론(DFT)을 기반으로 한 계산을 통하여 반응을 기술하기 위해 필요한 화학 퍼텐셜, global/local hardness/softness와 Fukui 함수 등을 얻을 수 있다. B3LYP 수준 하에서 DFT 양자계산을 이용하여 유기 반응을 분석했을 때 local HSAB 이론의 적용여부와 장단점을 알아보고자 하였다. 1-subtituted 다이엔과 비대칭 친다이엔체를 이용한 딜스-알더 반응의 경우 local HSAB 이론을 적용시켜, 오쏘 이성질체가 주 화합물인 이유를 설명할 수 있었다. 작용기를 변화시켰을 때 나타나는 차이점에서 규칙적인 경향성을 볼 수 없다는 사실을 통해서 전자, 입체 효과로 딜스-알더 반응을 분석할 수 없었던 이유를 이해할 수 있었다. Thiocyanate 음이온의 알킬화 반응의 경우 local HSAB 이론을 적용시켰을 때, 얻은 값을 통해서 반응 지점의 선호도를 예측할 수 없었는데 이는 thiocyanate를 생성하는 반응이 속도론적 지배 하에서 우세하는 반응이기 때문이다.

• 한국전기화학회:학술대회논문집
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• 1999.10a
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• pp.27-27
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• 1999

• Journal of Korea Port Economic Association
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• v.34 no.4
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• pp.181-190
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• 2018

The goal of this study is empirically to investigate the asymmetric relationship between two variables using the dry cargo freight rates and raw material price data from January 2012 to May 2018. First, we estimate the asymmetry of macroeconomic indicators of commodity prices by using a two - step threshold cointegration test. Second, the asymmetric relation test of the trade balance of existing commodity price changes is tested by bypassing to the high frequency dry cargo freight rate index. As a result of the estimation, in contrast to the existing linear analysis, each boundary value for the lower limit and the upper limit has different asymmetry. This implies that the period of fluctuation of the sudden residual that causes irregular rate of return fluctuations does not establish a long term equilibrium relationship between the raw material price and the dry cargo freight rate. Therefore, in order to consider the sudden price change in the analysis, it is necessary to include the band of inaction that controls the irregular volatility, which is consistent with the asymmetry hypothesis.

• The Korean Journal of Applied Statistics
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• v.32 no.5
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• pp.703-720
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• 2019

The influence of temperature on electricity demand is increasing due to extreme weather and climate change, and the climate impacts involves nonlinearity, asymmetry and complexity. Considering changes in government energy policy and the development of the fourth industrial revolution, it is important to assess the climate effect more accurately for stable management of electricity supply and demand. This study aims to analyze the effect of temperature change on electricity demand using the partial linear model. The main results obtained using the time-unit high frequency data for meteorological variables and electricity consumption are as follows. Estimation results show that the relationship between temperature change and electricity demand involves complexity, nonlinearity and asymmetry, which reflects the nonlinear effect of extreme weather. The prediction accuracy of in-sample and out-of-sample electricity forecasting using the partial linear model evidences better predictive accuracy than the conventional model based on the heating and cooling degree days. Diebold-Mariano test confirms significance of the predictive accuracy of the partial linear model.