그래프 LASSO에서 모형선택기준의 비교

안형석,박창이 한국데이터정보과학회 2014 한국데이터정보과학회지 Vol.25 No.4

Graphical models can be used as an intuitive tool for modeling a complex stochastic system with a large number of variables related each other because the conditional independence between random variables can be visualized as a network. Graphical least absolute shrinkage and selection operator (LASSO) is considered to be effective in avoiding overfitting in the estimation of Gaussian graphical models for high dimensional data. In this paper, we consider the model selection problem in graphical LASSO. Particularly, we compare various model selection criteria via simulations and analyze a real financial data set. 그래프모형(graphical model)은확률변수들간의조건부독립성(conditional independence)을 시각적인 네트워크형태로 표현할 수 있기 때문에, 정보학 (bioinformatics)이나 사회관계망 (socialnetwork) 등 수많은 변수들이 서로 연결되어 있는 복잡한 확률 시스템에 대한 직관적인 도구로 활용될 수 있다. 그래프 LASSO (graphical least absolute shrinkage and selection operator)는 고차원의 자료에 대한 가우스 그래프 모형 (Gaussian graphical model)의 추정에서 과대적합 (overfitting)을 방지하는데에 효과적인 것으로 알려진 방법이다. 본 논문에서는 그래프 LASSO 추정에서 매우 중요한 문제인 모형선택에 대하여 고려한다. 특히 여러가지 모형선택기준을 모의실험을 통해 비교하며 실제 금융 자료를 분석한다.

Li-Lee 모형에서 준거집단의 선택 문제

안형석,고경표 통계청 2018 통계연구 Vol.23 No.1

The selection of reference group in Li-Lee model is one of the important factors affecting prediction accuracy. There has been no clear criteria for selecting reference group, and discussion has not been done in-depth. In this study, we analysis many cases of selecting reference group based on the root mean square error using the mortality data of countries in Europe. We address the issue of selecting a local category to select the appropriate reference group, and we also consider that consideration of the reference group leads to good predictions. As a result, the prediction accuracy of male mortality rates is improved by expanding the category to the continent of Europe. However, it is confirmed that the prediction accuracy of female mortality rates is improved in the model considering combination the reference group of woman. These results provide evidences for improving the accuracy of prediction when selecting the reference group in the Li-Lee model. Li-Lee 모형에서 준거집단의 선택은 예측의 정확성에 영향을 주는 중요한 요소 중 하나이다. 현재까지 준거집단을 선택하는 명확한 기준이 제시된 바 없으며, 이에 대한 심도 있는 논의 또한 이뤄지지 않았다. 본 연구에서는 유럽대륙 국가들의 사망률 데이터를 이용해 평균 제곱근 오차를 측도로 준거집단 선택이 예측 정확성에 미치는 영향을 분석하였다. 적절한 준거집단을 모색하기 위해 준거집단의 지역적 범주의 확장과 성별 구분을 시도하였다. 분석 결과, 남자는 남녀의 사망률 정보를 모두 고려한 준거집단의 지역 범주를 확장함으로써, 여자는 여자의 사망률만을 고려한 준거집단의 지역 범주를 확장할 때 예측의 정확성이 개선되었다. 이러한 결과는 Li-Lee 모형에서 준거집단을 선택할 때 예측의 정확성을 개선하기 위한 방향과 근거를 제공해 준다.

심장점액종을 완전절제한 환자에서 지연성으로 발생한 다발뇌동맥류

안형석,김건우,박관영,정희재,정동영,김범준,김종성 대한신경과학회 2020 대한신경과학회지 Vol.38 No.4

고해상도혈관벽MRI에서 확인된 교모세포종의 혈관침범에 의한 뇌경색

김건우,안형석,정희재,오현선,김범준 대한신경과학회 2020 대한신경과학회지 Vol.38 No.4

Acute cerebral infarction secondary to glioblastoma is rarely reported, and its mechanism is still controversial. Vascular infiltration of malignant cell, direct mass effect and local procoagulant effect were considered as main pathophysiology. We report a case of glioblastoma-related cerebral infarction documented by high resolution vessel wall magnetic resonance imaging, which reveals concentric enhancement of arterial wall and intraluminal thrombus without direct compression. These findings suggest tumor cell infiltration of intracranial vessels is one of the important mechanisms of glioblastoma-related cerebral infarction.

저체온요법을 사용한 심정지 후 환자에서 정량뇌파분석을 통한 신경계 예후예측

이수현,안형석,김용환,이향운,이정화 대한신경과학회 2020 대한신경과학회지 Vol.38 No.4

Background: Post-cardiac arrest syndrome (PCAS) is one of the critical conditions which can result in a more serious brain injury. Early and accurate prognostication is crucial for deciding the patient’s therapeutic plan and setting the treatment goal. This study aimed to establish the prognostication values of quantitative electroencephalography (QEEG) in PCAS patients. Methods: We recruited 183 PCAS patients treated with therapeutic hypothermia. Electroencephalography (EEG) data within 72 hours after cardiac arrest (CA) and clinical data were collected. QEEG analysis including power spectral density (PSD) and connectivity analysis of default mode network (DMN) with imaginary coherence were performed. Results: There were significantly different patterns of PSD between neurologic good and poor outcome groups; absolute and relative power of the alpha 2 and beta 1 frequency (10-15 Hz) bands were increased in all brain regions of good outcome group. However, the relative power of the delta band and higher frequency bands over fast alpha (beta 3 and gamma bands over 20 Hz) were poor outcome markers. We found out that connectivity of DMN were significantly decreased in the poor outcome group compared with the good outcome group. Conclusions: These findings suggest that QEEG analysis could quantify and automate the interpretation of EEG. Furthermore, they can improve the prognostic values for neurologic outcomes relatively accurately and objectively in PCAS patients treated with hypothermia compared with traditional visual grading.

의료자원 공급, 수요의 성과 효율성에 대한 실증분석

장인수,안형석,Hong Sok(Brian) Kim 한국지역학회 2018 지역연구 Vol.34 No.2

The objective of this study is to observe the efficiency of clinical performance on the supply and demand of medical resources in Korea. For the empirical analysis, we constructed the dataset on age standardized mortality rate, the number of physician, specialist, surgery, medical institution, ratio of general hospitals of 16 provinces in Korea from 2006 to 2013. The panel probability frontier model is employed as an analysis method and considered heteroscedasticity and autocorrelation of the error in panel data. In addition, the demographic and socioeconomic characteristics of the 16 provinces, unemployment rate, elderly population ratio, GRDP per capita, and ratio of hospitals in comparison to the general hospitals are used to find the effect on the technical efficiency of clinical performance on supply and demand of medical resources. The results are as follows. First, for the clinical performance, the supply side of human resources such as doctors and specialists and the demand side factors such as chronic illness clinic per unit population have a significant influence, respectively. Second, the technical efficiency of clinical performance on the supply and demand of medical resources of each input component was 59-70% in terms of clinical efficiency in each region. Third. estimates of technical efficiency of inputs that affect clinical performance showed a slight increase in all regions during the analysis period, but the increase trend decreased slightly. Fourth, the ratio of the elderly population and GRDP per capita have a positive influence on the technical efficiency of clinical performance on the supply and demand of medical resources. The difference of each efficiency by region is due to the regional differences of the input medical resources and the combination of them and the demographic and socioeconomic characteristics of the region. It is understood that the differences in technological efficiency due to the complexity of supply and demand of medical resources, demographic structure and economic difference affecting clinical performance by region are different.

국민연금기금 운용 수익률 제고와 기금관리체계 개선

원종욱,안형석 한국보건사회연구원 2016 보건복지포럼 Vol.234 No.-

현행 국민연금은 보험료수준과 기금 운용 수익률의 연계가 이루어지지 않은 체계를 갖고 있다. 재정목표가 설정되지 않아 재정 목표 달성을 위한 보험료수준과 기금 운용목표수익률이 도출되지 않았고, 기금 소진시점이 재정추계를 통해 도출되었지만 재정추계에서 사용된 기금의 목표수익률은 보험료수준이 감안된 것도 아니며 기금 운용의 전략적 자산배분 등도 고려되지 않았다. 이에 재정목표의 수립, 보험료수준과 기금운용수익률에 대한 사회적 합의가 필요하며, 재정목표가 합의되지 않는 상황에 대비하여 기금 운용부문에서 독자적으로 목표수익률의 도출이 가능해야 한다. 본고는 기금 운용목표수익률을 도출하는 과정에서 시장중립적·전략적 자산배분의 중요성을 기금의 관리체계와 연계시켜 다양한 자료의 비교와 분석을 통해 제시하였다.

국민연금기금 관리 포럼 운영

원종욱,백혜연,안형석 한국보건사회연구원 2016 한국보건사회연구원 연구보고서 Vol.2016 No.-

Effects of caloric restriction on the expression of lipocalin-2 and its receptor in the brown adipose tissue of high-fat diet-fed mice

박경아,김진,안형석,이종율,정은애,최은비,김경은,신현주,이정은,노구섭 대한약리학회 2019 The Korean Journal of Physiology & Pharmacology Vol.23 No.5

Obesity causes inflammation and impairs thermogenic functions in brown adipose tissue (BAT). The adipokine lipocalin 2 (LCN2) has been implicated in inflammation and obesity. Herein, we investigated the protective effects of caloric restriction (CR) on LCN2-mediated inflammation and oxidative stress in the BAT of high-fat diet (HFD)-fed mice. Mice were fed a HFD for 20 weeks and then either continued on the HFD or subjected to CR for the next 12 weeks. CR led to the browning of the white fat-like phenotype in HFD-fed mice. Increased expressions of LCN2 and its receptor in the BAT of HFD-fed mice were significantly attenuated by CR. Additionally, HFD+CR-fed mice had fewer neutrophils and macrophages expressing LCN2 and iron-positive cells than HFD-fed mice. Further, oxidative stress and mitochondrial fission induced by a HFD were also significantly attenuated by CR. Our findings indicate that the protective effects of CR on inflammation and oxidative stress in the BAT of obese mice may be associated with regulation of LCN2.

지방자치단체 재정 여건의 군집 양상과 영향 요인 분석

장인수,우해봉,안형석 한국응용경제학회 2018 응용경제 Vol.20 No.3

본 연구는 우리나라 지방자치단체의 지방재정 여건의 공간적 군집 양상과 함께 이에 영향을 미치는 요인을 분석하였다. 공간계량모형을 적용한 분석결과는 재정자립도와 다른 영향 요인 간 정적(+) 내지는 부적(-) 연관성을 보여주고 있다. 본 연구결과는 낮은 재정자립도를 보이는 지자체를 중심으로 자체적 예산의 확보 및 재정 운영에 대한 규제, 유인적 장치가 실질적으로 구축될 필요성을 시사한다. 추가적으로, 이러한 논의가 낮은 재정자립도의 군집적 양상을 보이는 지역 간 효과적으로 공유되고, 중앙정부의 적극적 관리 및 도움을 바탕으로 실질적으로 수립, 시행될 수 있다면 지역 균형 발전 및 효과적인 지방분권의 토대로 작용할 개연성이 높을 것으로 판단된다. The purpose of this study is to analyze the factors affecting the spatial clustering pattern of local financial condition of local government in Korea. As a result of the spatial analysis, it was found that the relationship between financial independence index and other influence factors is clustered based on spatial dependency. To increase the level of financial independence, regulatory controls and incentives on financial operations need to be substantially established. If the discussion related to these implications is effectively shared between regions with low levels of financial independence and practically established and practiced through the active management and help of the government, it is highly likely that this will act as a foundation for balanced regional development and effective decentralization.