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김용구,Kim, Yong-Ku 대한생물정신의학회 2016 생물정신의학 Vol.23 No.2
Treatment-resistant depression (TRD) is a major public health problem. It is estimated that about 30% of patients with major depressive disorder do not show substantial clinical improvement to somatic or psychosocial treatment. Most of studies for TRD have focused on the subjects already known as TRD. Patients with unipolar depressive episodes that do not respond satisfactorily to numerous sequential treatment regimens were included in the TRD studies. Such post hoc experimental design can be regarded only as consequences of having TRD, rather than as causal risk factors for it. Although informative, data derived from such studies often do not allow a distinction to be made between cause and effect. So, we should shift paradigm toward examining the risk for developing TRD in untreated depressed patients. To deal with this problem, untreated depressed patients should be enrolled in the study to identify biological markers for treatment resistance. The peripheral or central biological markers should be explored before starting treatment. Subsequent systematic administration of treatments with appropriate monitoring in the subjects can determine the risk for developing treatment resistance in untreated individuals. Such information could give a cue to improve the initial diagnosis and provide more effective treatment for TRD.
김용구,Kim, Yong-Ku 대한생물정신의학회 2011 생물정신의학 Vol.18 No.4
Stress, a risk factor of major depression induces cytokine mediated inflammation and decreased neurogenesis. In patients with major depression, significant increases of pro-inflammatory cytokines have been consistently reported. The pro-inflammatory cytokines can stimulate the hypothalamic-pituitary-adrenal (HPA) axis to release glucocorticoids. In the brain, microglia and play a role of immune activation in response to stress. Increased pro-inflammatory cytokine play a role in restricting neurogenesis in the brain. Although neurogenesis may not be essential for the development of depression, it may be required for clinically effective antidepressant treatment. Hence, stimulation of neurogenesis is regarded as a promising strategy for new antidepressant targets. This review introduces changes in neurotransmitter, cytokine and neurogenesis in major depression and explores the possible relationship between pro-inflammatory cytokines and neurogenesis related to stress in major depression.
Stochastic Precipitation Generator with Hidden State Covariates
김용구,이규원 한국기상학회 2017 Asia-Pacific Journal of Atmospheric Sciences Vol.53 No.3
Time series of daily weather such as precipitation, minimum temperature and maximum temperature are commonly required for various fields. Stochastic weather generators constitute one of the techniques to produce synthetic daily weather. The recently introduced approach for stochastic weather generators is based on generalized linear modeling (GLM) with covariates to account for seasonality and teleconnections (e.g., with the El Niño). In general, stochastic weather generators tend to underestimate the observed interannual variance of seasonally aggregated variables. To reduce this overdispersion, we incorporated time series of seasonal dry/wet indicators in the GLM weather generator as covariates. These seasonal time series were local (or global) decodings obtained by a hidden Markov model of seasonal total precipitation and implemented in the weather generator. The proposed method is applied to time series of daily weather from Seoul, Korea and Pergamino, Argentina. This method provides a straightforward translation of the uncertainty of the seasonal forecast to the corresponding conditional daily weather statistics.
A Modified Hybrid Gamma and Generalized Pareto Distribution for Precipitation Data
김용구,Hyeongang Kim,이규원,민기홍 한국기상학회 2019 Asia-Pacific Journal of Atmospheric Sciences Vol.55 No.4
This study introduces a modified hybrid gamma and generalized Pareto distribution. Prior to this, we define a general spliced distribution and its corresponding gamma distribution, which is part of the head, and a generalized Pareto (GP) distribution, which is part of the tail. We then examine the threshold conditions for the modified hybrid gamma and GP distribution and defined probability density function. Also, we derive the negative log-likelihood function of the modified hybrid gamma and GP distribution and estimate approximate maximum likelihood estimates using the differential evolution algorithm for each simulation to minimize it. Moreover, by presenting the mean square error for each sample size, the model is evaluated according to the size of the sample. Finally, we use daily observed summer precipitation for Seoul, Korea, from 1961 to 2011, which includes 4692 data sets.We use 2051 data sets corresponding to wet conditions. As a result, the estimated threshold of the modified hybrid gamma and GP distribution is 0.1455. After deriving Fisher information through the Hessian matrix, we also present the standard error of the maximum likelihood estimator.
중소벤처기업의 조직문화특성이 조직유효성을 매개로 조직성과에 미치는 영향에 관한 연구
김용구,윤미 한국경영공학회 2020 한국경영공학회지 Vol.25 No.2
Purpose This study aims to investigate the relationship between organizational culture characteristics, organizational effectiveness, and management performance in a rapidly changing business environment with trade disputes and the 4th industrial revolution. Methods The study was conducted in the form of a questionnaire and was based on data collected by 445 workers of Korean SMEs. Results The results of this study show that the cohesiveness and rationality of organizational culture characteristics have a positive effect on organizational effectiveness, and that stability and development have a positive effect on management performance. Conclusion In addition, it was found that organizational effectiveness had a positive effect on financial and non-financial performance of management performance, and that organizational effectiveness played a mediating role in the relationship between organizational culture characteristics and management performance.