• 비교교육연구
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• 제28권5호
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• pp.1-19
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• 2018

국제 수학 과학 성취도 추이 연구와 같은 교육평가의 목적은 국가와 같은 집단을 비교하는 것이다. 이와 같이 평가의 단위가 학생보다 상위 수준일 때 집단을 비교하기 위해서는 다층 문항반응이론 기반의 집단 수준 진단평가 모형을 고려할 수 있다. 이 연구에서는 Park과 Bolt(2008)가 제안한 문항특성모형을 수정하여 새로운 다층 문항반응이론 기반의 집단 수준 진단평가 모형을 제안하였다. 이 수정된 모형은 2015년에 실시된 국제 수학 과학 성취도 추이 연구의 8학년 수학 평가 자료에 적용되었다. 그 결과 9개의 인지적 요소에 대한 국가들의 프로파일을 구할 수 있었다. 이 연구 결과는 국가 간 비교 또는 요소 간 상호 비교에 이용될 수 있다. 이와 같이 잔차항을 설명할 수 있도록 수정된 모형은 보다 높은 신뢰도를 지니며 국가 간 비교에 보다 정확한 정보를 제공할 수 있을 것으로 기대된다. 예를 이용하여 연구 결과를 어떻게 해석할 수 있는지 제시하였으며, 연구의 제한점과 후속 연구에 대해서도 논의하였다.

• Journal of Power Electronics
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• 제17권1호
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• pp.136-148
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• 2017

In recent years, voltage source multilevel converters are very popular in medium/high-voltage industrial applications, among which the NPC/H-Bridge converter is a popular solution to the medium/high-voltage drive systems. The conventional finite control set model predictive control (FCS-MPC) strategy is not practical for multilevel converters due to their substantial calculation requirements, especially under high number of voltage levels. To solve this problem, a hierarchical model predictive voltage control (HMPVC) strategy with referring to the implementation of g-h coordinate space vector modulation (SVM) is proposed. By the hierarchical structure of different cost functions, load currents can be controlled well and common mode voltage can be maintained at low values. The proposed strategy could be easily expanded to the systems with high number of voltage levels while the amount of required calculation is significantly reduced and the advantages of the conventional FCS-MPC strategy are reserved. In addition, a HMPVC-based field oriented control scheme is applied to a drive system with the NPC/H-Bridge converter. Both steady-state and transient performances are evaluated by simulations and experiments with a down-scaled NPC/H-Bridge converter prototype under various conditions, which validate the proposed HMPVC strategy.

• Journal of Power Electronics
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• 제17권2호
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• pp.346-357
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• 2017

The Modular Multilevel Converter (MMC) is particularly attractive for medium and high power applications such as High-Voltage Direct Current (HVDC) systems. In order to reach a high voltage, the number of cascaded submodules (SMs) is generally very large. Thus, in the applications with hundreds or even thousands of SMs such as MMC-HVDCs, the sorting algorithm of the conventional voltage balancing strategy is extremely slow. This complicates the controller design and increases the hardware cost tremendously. This paper presents a Two-Way Merge Sort (TWMS) strategy based on the prediction of the capacitor voltages under ideal conditions. It also proposes an innovative Insertion Sort Correction for the TWMS (ISC-TWMS) to solve issues in practical engineering under non-ideal conditions. The proposed sorting methods are combined with the features of the MMC-HVDC control strategy, which significantly accelerates the sorting process and reduces the implementation efforts. In comparison with the commonly used quicksort algorithm, it saves at least two-thirds of the sorting execution time in one arm with 100 SMs, and saves more with a higher number of SMs. A 501-level MMC-HVDC simulation model in PSCAD/EMTDC has been built to verify the validity of the proposed strategies. The fast speed and high efficiency of the algorithms are demonstrated by experiments with a DSP controller (TMS320F28335).

• 대한간호학회지
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• 제45권5호
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• pp.694-703
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• 2015

Purpose: This study was a prospective longitudinal study to identify changes in quality of life in patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT). It was based on Roy's adaptation model. Methods: The questionnaires were administered before HSCT, 30 and 100 days after HSCT. Of the 48 potentially eligible patients, 44 (91.7%) participated in the study and 40 (90.9%) completed the questionnaires at 100 days after HSCT. Multilevel analysis was applied to analyze changes in quality of life. Results: Overall, quality of life showed a decreasing tendency from pre-HSCT to 100 days after HSCT. The adaptation level of participants was compensatory. Type of conditioning was the significant factor influencing quality of life before HSCT (${\beta}_{00}$=79.92, p <.001; ${\beta}_{01}$= - 12.64, p <.001) and the change rate of quality of life (${\beta}_{10}$= - 1.66, p =.020; ${\beta}_{11}$=2.88, p =.014). Symptom severity (${\beta}_{20}$= - 1.81, p =.004), depression (${\beta}_{30}$= - 0.58, p =.001), social dependency (${\beta}_{40}$= - 0.35, p =.165), and loneliness (${\beta}_{50}$= - 0.23, p =.065) had a negative effect on changes in quality of life. Symptom severity and depression were statistically significant factors influencing changes in quality of life. Conclusion: According to the results of this study, the development of nursing intervention is needed to improve quality of life in patients undergoing allogeneic hematopoietic stem cell transplantation in the early immune reconstruction period. The interventions should include programs to enhance coping capacity and programs to help control symptom severity and depression. Also these interventions need to be started from the beginning of HSCT and a multidisciplinary approach would be helpful.

• 아동학회지
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• 제27권3호
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• pp.169-187
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• 2006

A hierarchical linear model(HLM) provides advantages over existing traditional statistical methods (e.g., ordinary least squares regression, repeated measures analysis of variance, etc.) for analyzing multilevel/longitudinal data or diary methods. HLM can gauge a more precise estimation of lower-level effects within higher-level units, as well as describe each individual's growth trajectory across time with improved estimation. This article 1) provides scholars who study children and families with an overview of HLM (i.e., statistical assumptions, advantages/disadvantages, etc.), 2) provides an empirical study to illustrate the application of HLM, and 3) discusses the application of HLM to the study of children and families. In addition, this article provided useful information on available articles and websites to enhance the reader's understanding of HLM.

• 지역연구
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• 제39권4호
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• pp.73-90
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• 2023

기술 진보는 미래의 일자리 구조를 어떻게 변화시키는가? 이 거대한 질문에 답하기 위한 노력의 하나로 이 연구는 로봇의 도입이 미국의 제조업 일자리의 동태에 미친 영향을 탐구한다. 연구는 과업 모형에 기초해 로봇 도입의 효과가 서로 다른 과업 특성을 가진 직종 사이에 차별적으로 작용할 것이라고 전재했다. 이에 기초하여 지역의 로봇 노출도가 과업 특성별로 구분된 직종 군집의 고용 변화에 미치는 영향을 분석하였다. 연구는 2012~2022년 사이 52개 미국 지역 제조업 부문의 관련 직종 307개의 고용 변화 추이를 성장곡선으로 모형화하고, 이를 직종별 고용 통계자료를 활용해 실증하는 방식으로 진행됐다. 분석 결과 손재주 역량을 요구하는 직종 군집에서 일자리 수가 빠르게 감소하는 경향을 확인할 수 있었지만, 지역의 로봇 사용 정도가 이러한 경향을 강화한다는 증거는 확인할 수 없었다. 이는 미국 제조업 부문의 일자리 변화가, 최근 대두된 로봇 기술에 영향을 받는다기보다, 과거부터 이어져 온 탈산업화와 기능적 특화의 경향에 의해 주도되고 있음을 함의한다.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1994년도 춘계공동학술대회논문집; 창원대학교; 08월 09일 Apr. 1994
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• pp.715-725
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• 1994

The objective of this research is to develop a cost model for integrated CAD system. A computerized system realizing this model then is used to aid designers. The first area is to propose a conceptual framework of a multilevel cost model. The methodology of constructing the model is discussed. Then suggestion of an object oriented programming technique for implementing the model is presented. Complicate estimation procedure can be systematically handled by this technique. Interval analysis to deal with the uncertainty of information and decision during design process is used. An experimentation algorithm for calculating the cost distribution is proposed to overcome the shortcoming of interval analysis. Major focus of this research is on net shape manufacturing processes including die casting, injection molding, and metal forming.

• Journal of Preventive Medicine and Public Health
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• 제47권5호
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• pp.258-265
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• 2014

Objectives: To examine whether the nursing practice environment at the hospital-level affects the job satisfaction and turnover intention of hospital nurses. Methods: Among the 11 731 nurses who participated in the Korea Health and Medical Workers' Union's educational program, 5654 responded to our survey. Data from 3096 nurses working in 185 general inpatient wards at 60 hospitals were analyzed using multilevel logistic regression modeling. Results: Having a standardized nursing process (odds ratio [OR], 4.21; p<0.001), adequate nurse staffing (OR, 4.21; p<0.01), and good doctor-nurse relationship (OR, 4.15; p<0.01), which are hospital-level variables based on the Korean General Inpatients Unit Nursing Work Index (KGU-NWI), were significantly related to nurses' job satisfaction. However, no hospital-level variable from the KGU-NWI was significantly related to nurses' turnover intention. Conclusions: Favorable nursing practice environments are associated with job satisfaction among nurses. In particular, having a standardized nursing process, adequate nurse staffing, and good doctor-nurse relationship were found to positively influence nurses' job satisfaction. However, the nursing practice environment was not related to nurses' turnover intention.

• Journal of Preventive Medicine and Public Health
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• 제56권6호
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• pp.504-514
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• 2023

Objectives: This study investigated the relationship between prescribing institutions and medication adherence among patients newly diagnosed with hypertension and diabetes. Methods: This study investigated patients with new prescriptions for hypertension and diabetes in Korea in 2019 with using data collected from general health screenings. A multilevel logistic regression model was applied to explore the relationship between patients' first prescribing institution and their medication adherence, defined as a medication possession ratio (MPR) over 80%. Results: The overall adherence rates were 53.7% and 56.0% among patients with hypertension and diabetes, respectively. The intra-class correlation coefficients were 13.2% for hypertension and 13.8% for diabetes (p<0.001), implying that the first prescribing institution had a significant role in medication adherence. With clinics as the reference group, all other types of hospitals showed an odds ratio (OR) less than 1.00, with the lowest for tertiary hospitals (OR, 0.30 for hypertension; 0.45 for diabetes), and the next lowest in health screening specialized clinics (OR, 0.51 for hypertension; 0.46 for diabetes). Among individual-level variables, female sex, older age, higher insurance premium level, and residing in cities were positively associated with adherence in both the hypertension and diabetes samples. Conclusions: This study showed that the prescribing institution had a significant relationship with medication adherence. When the first prescribing institution was a clinic, newly diagnosed patients were more likely to adhere to their medication. These results highlight the important role played by primary care institutions in managing mild chronic diseases.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2001년도 봄 학술발표논문집 Vol.28 No.1 (A)
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• pp.40-42
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• 2001

본 논문에서는 공유 저장장치 기반 클러스터 시스템의 평균 서비스 시간을 줄이기 위해서 클러스터 시스템의 연선 종류와 부하량에 따라 재구성 시점을 결정하는 적응적 자료 재구성 방식(Adaptive Data Reorganization)을 제안한다. 또한 클러스터 시스템에서 처리해야할 서비스가 없고 서비스 요청도 없을 때 자료 재구성을 수행하는 지연 재구성 방식(Deferred Reorganization)을 채택하였다. 자료 재구성 방식은 전체적인 자료 재구성과 부분적인 자료 재구성으로 나누어 실행된다. 또한 적응적 자료 재구성 방식을 통한 공유 저장장치 기반 클러스터 시스템의 성능 평가를 위해 마르코프 모델(Markov Model)을 사용한다.