• Journal of Preventive Medicine and Public Health
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• 제35권1호
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• pp.76-82
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• 2002

Objective : To investigate the relationships of occupational class, educational level and deprivation with mortality in Korea Methods : This study used existing South Korean national data on occupation, educational level, and deprivation and death. Mortality was investigated using registered death data from 1993 to 1997 obtained from the Korean National Statistics Office (NSO) with denominators drawn from the 1995 Census. Statistical analysis consisted of poisson regression modeling and multilevel analysis. Results : The lower occupational class (manual workers) group had a higher mortality rate than the higher occupational class (non-manual workers) group Educational level, and deprivation were both inversely related withand mortality. Occupation was strongly associated with education. Area-based deprivation indicators and individual indices for social class made an independent contribution to the mortality risk. Conclusions : The findings of this study suggests that the relationships of occupational class, educational level and deprivation with mortality appears to be stronger in Korea than in European countries.

• Journal of the Korean Data and Information Science Society
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• 제24권4호
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• pp.931-940
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• 2013

For analysis of clustered survival data, the inferences of parameters in semi-parametric frailty models have been widely studied. It is also important to investigate the potential heterogeneity in event times among clusters (e.g. centers, patients). For purpose of this analysis, the interval estimation of frailty is useful. In this paper we propose a visualizing method to present confidence intervals of individual frailties across clusters using the frailtyHL R-package, which is implemented from h-likelihood methods for frailty models. The proposed method is demonstrated using two practical examples.

• Journal of Power Electronics
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• 제9권4호
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• pp.593-603
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• 2009

This paper proposes and describes the design and operational principles of a three-phase three-level nine switch voltage source inverter. The proposed topology consists of three bi-directional switches inserted between the source and the full-bridge power switches of the classical three-phase inverter. As a result, a three-level output voltage waveform and a significant suppression of load harmonics contents are obtained at the inverter output. The harmonics content of the proposed multilevel inverter can be reduced by half compared with two-level inverters. A Fourier analysis of the output waveform is performed and the design is optimized to obtain the minimum total harmonic distortion. The full-bridge power switches of the classical three-phase inverter operate at the line frequency of 50Hz, while the auxiliary circuit switches operate at twice the line frequency. To validate the proposed topology, both simulation and analysis have been performed. In addition, a prototype has been designed, implemented and tested. Selected simulation and experimental results have been provided.

• Journal of Power Electronics
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• 제16권1호
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• pp.268-276
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• 2016

A hybrid sinusoidal-pulse current (HSPC) charging method for the Li-ion batteries in electric vehicle applications is proposed in this paper. The HSPC charging method is based on the Li-ion battery ac-impedance spectrum analysis, while taking into account the high power requirement and system integration. The proposed HSPC method overcomes the power limitation in the sinusoidal ripple current (SRC) charging method. The charger shares the power devices in the motor inverter for hardware cost saving. Phase shifting in multiple pulse currents is employed to generate a high frequency multilevel charging current. Simulation and experimental results show that the proposed HSPC method improves the charger efficiency related to the hardware and the battery energy transfer efficiency.

• 대한보건연구
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• 제44권4호
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• pp.83-85
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• 2018

As the main aim of infectious disease epidemiology is to prevent a pathogen transmission, traditional epidemiological studies have focused on the evaluation of individual-level risk factors. But group-level factors as well as individual-level are important in understanding and controlling transmission of infectious diseases, especially sex-transmitted infectious diseases. Multi-level analysis (MLA) is known as a powerful analytical tool for investigating both levels simultaneously. While new cases of HIV/AIDS in Korea are increasing annually, it is urgently needed to establish research system for MLA led by Korea Centers for Disease Control & Prevention.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.39-40
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• 2015

As international construction market increases, the importance of risk management in international construction project is emphasized. Unfortunately, current risk management practice does not sufficiently deal with project risks. Although a lot of risk analysis techniques have been introduced, most of them focus on project's external unexpected risks such as country conditions and owner's financial standing. However, because those external risks are difficult to manage and take preemptive action, we need to concentrate on project inherent risks. Based on this premise, this paper proposes a project-oriented risk mining approach which could detect and extract project risk factors automatically before they are materialized. This study presents a methodology regarding how to extract potential risks which exist in owner's project requirements and project tender documents using state of the art data analysis method such as text mining. The project-oriented risk mining approach is expected to effectively reflect project characteristics to the project risk management and could provide construction firms with valuable business intelligence.

• 보건행정학회지
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• 제25권1호
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• pp.31-39
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• 2015

Background: The purpose of this study is comparison of the results between regression and multi-level analysis to find out factors influencing outcome indicators (in-hospital death, length of stay, and medical charges) of stroke patients. Methods: By using patient sample data of Health Insurance Review & Assessment Service, patients admitted with stroke were selected as survey target and 15,864 patients and 762 hospitals were surveyed. Results: For the results of existing regression analysis and multi-level analysis, models were assessed through model suitability index value and as a result, the value of results of multi-level analysis decreased compared to the results of regression, showing it is a better model. Conclusion: Factors influencing in-hospital death of stroke patients were analyzed and as a result, intra-class correlation (ICC) was 13.6%. In factors influencing length of stay, ICC was 11.4%, and medical charges, ICC was 17.7%. It was found that factors influencing the outcome indicators of stroke patients may vary in every hospital. This study could carry out more accurate analysis than existing research findings through analysis of reflecting structure at patient level and hospital level factors and analysis on random effect.

• 컴퓨터교육학회논문지
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• 제20권6호
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• pp.83-94
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• 2017

본 연구의 목적은 3수준 다층모형을 적용하여 초등학생의 컴퓨팅 사고력 및 SW교육태도 영향요인을 분석하는 것이다. 분석결과, 첫째, '가정 내 컴퓨터 유무', 'SW 대회 참가 경험', 'SW교육 만족도', 그리고 'SW에 대한 인식'이 컴퓨팅 사고력 초기값에 정적 영향을, 'SW교육 기간'과 '사전 방과후학교 SW교육 경험'이 컴퓨팅 사고력 변화율에 정적 영향을 주었다. 둘째, 'SW에 대한 인식', 'SW교육 만족도' 그리고 '성별'이 SW교육태도 초기값에 정적 영향을, 'SW교육 기간'이 SW교육태도 변화율에 부적 영향을 주었다. 즉 'SW교육 만족도'와 'SW에 대한 인식'은 사전 컴퓨팅 사고력 및 SW교육태도 모두에 정적 영향을, '가정 내 컴퓨터 유무'와 'SW대회 참가 경험'은 사전 컴퓨팅 사고력에만 정적 영향을, 'SW에 대한 인식'과 'SW교육 만족도'는 사전 SW교육태도에만 정적 영향을 주었다. 또한, 'SW교육 기간'은 컴퓨팅 사고력의 변화율에 가장 큰 정적 영향을 주었으나, SW교육태도의 변화율에는 미약한 부적 영향을 미치는 것으로 나타났다.

• 대한간호학회지
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• 제50권3호
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• pp.333-348
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• 2020

Purpose: The present study investigated the association between nurse staffing and health outcomes among psychiatric inpatients in Korea by assessing National Health Insurance claims data. Methods: The dataset included 70,136 patients aged 19 years who were inpatients in psychiatric wards for at least two days in 2016 and treated for mental and behavioral disorders due to use of alcohol; schizophrenia, schizotypal and delusional disorders; and mood disorders across 453 hospitals. Nurse staffing levels were measured in three ways: registered nurse-to-inpatient ratio, registered nurse-to-adjusted inpatient ratio, and nursing staff-to-adjusted inpatient ratio. Patient outcomes included length of stay, readmission within 30 days, psychiatric emergency treatment, use of injected psycholeptics for chemical restraint, and hypnotics use. Relationships between nurse staffing levels and patient outcomes were analyzed considering both patient and system characteristics using multilevel modeling. Results: Multilevel analyses revealed that more inpatients per registered nurse, adjusted inpatients per registered nurse, and adjusted inpatients per nursing staff were associated with longer lengths of stay as well as a higher risk of readmission. More adjusted inpatients per registered nurse and adjusted inpatients per nursing staff were also associated with increased hypnotics use but a lower risk of psychiatric emergency treatment. Nurse staffing levels were not significantly associated with the use of injected psycholeptics for chemical restraint. Conclusion: Lower nurse staffing levels are associated with negative health outcomes of psychiatric inpatients. Policies for improving nurse staffing toward an optimal level should be enacted to facilitate better outcomes for psychiatric inpatients in Korea.

• Journal of Korean Neurosurgical Society
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• 제52권4호
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• pp.365-371
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• 2012

Objective : To document lumbar lordosis (LL) of the spine and its change during surgeries with the different height but the same angle setting of the anterior cage. Additionally, we attempted to determine if sufficient LL is achieved at different cage heights and to quantify the change in LL during multi-level anterior lumbar interbody fusion (ALIF). Methods : The medical records and radiographs of 42 patients who underwent more than 2 level ALIFs between 2008 and 2009 were retrospectively reviewed. We evaluated 3 parameters seen on lateral whole spine radiographs : LL, pelvic incidence (PI), and sagittal vertical axis (SVA). The mean follow-up time was 28.1 months and the final follow-up radiographs of all patients were reviewed at least 2 years after surgery. Statistical analysis was performed using the paired t-tests. Results : Lumbar lordosis had changed up to 30 degrees immediately and 2 years after surgery (preoperative mean LL, SVA : 22.45 degrees, 112.31 mm; immediate postoperative mean LL, SVA : 54.45 degrees, 37.36 mm; final follow-up mean LL, SVA : 49.56 degrees, 26.95 mm). Our goal of LL is to obtain as much PI as possible, preoperative mean PI value was $55.38{\pm}3.35$. The pre-operative and two year post-surgery follow-up mean of the Japanese Orthopedic Association score were $9.2{\pm}0.6$ and $13.2{\pm}0.6$ (favorable outcome rate : 95%), respectively. In addition, we were able to obtain good clinical outcomes and sagittal balance with a subsidence rate of 22.7%. Conclusion : We were able to achieve sufficient LL, such that it was similar to the PI, utilizing multi-level ALIF with the use of a tall cage with the same angle setting of the cage. We have found out that achieving sufficient lumbar lordosis and sagittal balance require an anterior lumbar cage with high angle and height.