• 보건행정학회지
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• 제32권1호
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• pp.63-72
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• 2022

Background: Depression is a common disease around the world. Many studies are showing that mental health can be improved through physical activity, and daily regular exercise can reduce the negative effects of depression or depressive symptoms. In order to promote individual physical activity, a physical activity-friendly environment must precede. Therefore, this study attempted to confirm whether the number of sports facilities for all affects individual depression. Methods: Among the respondents to the 2018 Community Health Survey, data from 181,086 people excluding missing value were used. Descriptive and chi-square tests were performed to understanding the general characteristics of individual level variables. A multilevel logistic regression was conducted to confirm the effect of individual and regional level variables on depressive symptoms. Results: As a result of confirming the effect of individual characteristics on depressive symptoms, it was confirmed that both socioeconomic and health behavior factors had an effect. Similar results were shown in a model that considered regional level variables, and in the case of the number of sports facilities per population, people who belongs to smaller areas were more likely to have depressive symptoms (odds ratio, 0.98; 95% confidence interval, 0.97-0.99). Conclusion: As a result of the analysis, it was confirmed that both individual level and regional level variables had a significant effect on depressive symptoms. This suggests that not only individual level approaches but also regional level approaches are needed to improve individual depressive symptoms In particular, it may be possible to consider to increase the number of sports facilities in areas where the prevalence of depressive symptoms is high and the number of sports facilities is insufficient.

• 한국전산구조공학회논문집
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• 제36권1호
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• pp.19-26
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• 2023

전산 자원의 발달로 여러 부품들이 결합된 전체 구조물에 대한 해석이 가능해져 해석에 필요한 계산 시간과 데이터의 양이 증가하였다. 이러한 전체 구조물에는 같은 부품이 반복되어 규칙성을 가지는 경우가 많다. 이러한 반복적인 구조물에 균질화 기법을 적용하면 효과적인 해석이 가능하다. 상용 프로그램의 일반적인 균질화 모듈에서 단위 구조는 모든 방향으로 반복된다고 가정한다. 하지만 실제 구조물들은 여러 단위 구조가 복잡하게 반복되는 경우가 많아 기존 균질화 기법을 적용하는데 어려움이 있다. 본 논문에서는 복잡한 반복성을 고려하는 다단계 균질화 기법을 제안한다. 제안된 균질화 기법은 구조물을 여러 영역으로 나누어 균질화를 수행하는 형태로 기존 기법보다 정확한 해석이 가능하다.

• 전기학회논문지
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• 제67권7호
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• pp.846-853
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• 2018

In this paper, an improved model predictive control (MPC) method is proposed, which reduces the amount of calculations caused by the increased number of candidate voltage vectors with the increased voltage level in multi-level inverters. When the conventional MPC method is used for multi-level inverters, all candidate voltage vectors are considered to predict the next-step current value. However, in the case that the sampling time is short, increased voltage level makes it difficult to consider the all candidate voltage vectors. In this paper, the improved MPC method which can get a fast transient response is proposed with a small amount of the computation by adding new candidate voltage vectors that are set to find the optimal vector. As a result, the proposed method shows faster transient response than the method that considers the adjacent vectors and reduces the computational burden compared to the method that considers the whole voltage vector. the performance of the proposed method is verified through simulations and experiments.

• 전기학회논문지
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• 제63권12호
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• pp.1640-1648
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• 2014

This paper proposes a switching frequency reduction method for MMC (Modular Multilevel Converter) utilizing redundancy operation of sub-module, which can offer reduction of voltage harmonics and switching loss. The feasibility of proposed method was verified through computer simulations with PSCAD/EMTDC software. Based on simulation analysis, a hardware scaled-model of 10kVA, DC-1000V MMC was designed and manufactured in the lab. Various experiments were conducted to verify the feasibility of proposed method in the actual hardware system. The hardware scaled-model can be effectively utilized for analyzing the performance of MMC according to the modulation scheme and redundancy operation.

• 산업융합연구
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• 제22권1호
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• pp.1-20
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• 2024

정부지원과 기업 경영성과 간 관계에서 기업 고유의 특성과 공간적 특성의 중요성을 강조하는 많은 논의들이 있지만, 기업 특성과 클러스터 특성이 통합적으로 경영성과에 미치는 영향에 대한 실증연구는 부족한 실정이다. 본 연구는 정부자금지원의 구체적인 투입에 따른 재무적, 비재무적 성과를 실증분석하고, 정부 자금지원과 기업 경영성과 간에 영향을 조절할 것으로 예측되는 기업 특성 및 클러스터 특성을 탐색하여, 개인 및 집단의 2수준 위계적 선형모형(HLM)으로 분석하였다. 데이터는 사업자등록번호 기준으로 기업 및 클러스터 수준으로 재정리하여 최종적으로 기업수 83,395개사 및 클러스터 641개의 패널데이터가 활용되었다. 연구 결과, 정부 자금지원은 기업의 매출액과 특허 모두에 정(+)의 효과를 주는 것으로 나타나, 정부 지원이 시장실패를 보완할 수 있는 유효한 수단이라는 것을 보여준다. 위계적 선형모형으로 분석한 결과, 정부 자금지원과 인적자본역량, 흡수역량, 클러스터 네트워크 밀도와 결합할 경우, 모두 매출액과 유의한 정(+)의 효과가 나타났다. 본 연구는 2수준 위계적 선형모형으로 분석하여, 기업 특성인 인적자본역량과 흡수역량, 클러스터 특성인 클러스터 네트워크 밀도가 조절효과로 정부 자금지원과 기업경영성과를 조절하는 역할을 수행함을 밝혀 이론적, 실무적 시사점을 제공한다.

• ETRI Journal
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• 제31권5호
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• pp.619-621
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• 2009

In this letter, we study the influence of receiver imperfections on bit error rate (BER) degradations in detecting low-density parity-check coded multilevel phase-shift keying signals transmitted over a Rician fading channel. Based on the analytical system model which we previously developed using Monte Carlo simulations, we determine the BER degradations caused by the simultaneous influences of stochastic phase error, quadrature error, in-phase-quadrature mismatch, and the fading severity.

• Journal of electromagnetic engineering and science
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• 제10권3호
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• pp.166-170
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• 2010

To numerically calculate electromagnetic scattering from the electrical-large three-dimensional(3D) objects, the high-frequency approaches have been usually applied, but the accuracy and feasibility of these geometrical and physical optics(GO-PO) approaches, to some extent, are remained to be improved. In this paper, a new framework is developed for calculation of the near-field scattering field of an electrical-large 3D target by using a multilevel fast multipole algorithm(MLFMA) and generation of radar images by using a fast back-projection(FBP) algorithm. The MPI(Message Passing Interface) parallel computing is carried out to multiply the calculation efficiency greatly. Finally, a simple example of perfectly electrical conducting(PEC) patch and a canonical case of Fighting Falcon F-16 are presented.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 추계학술대회 논문집
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• pp.121-122
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• 2014

멀티 레벨 인버터는 높은 출력 전압을 갖으며, 낮은 THD(Total harmonic distortion)를 요구하는 시스템에 적합하다. 그 중 cascaded H-brige 멀티레벨 인버터는 H-bridge 셀별 관리가 쉽고, 레벨 수를 증가시키기 쉽다는 장점 때문에 많이 이용되어 왔다. 본 논문에서는 cascaded H-bridge 인버터의 기존 PI (proportional integral) 제어 기반 PWM (pulse width modulation)기법의 스위칭 패턴과 모델 예측 제어의 스위칭 패턴을 비교하고 모델예측 제어 시 셀 별 스위칭 패턴 균형을 위한 방법을 제안한다.

• Earthquakes and Structures
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• 제15권2호
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• pp.215-225
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• 2018

To reach a better foundation treatment project, an optimized analysis of composite foundation was studied in the field of hydraulic engineering. Its unique characteristics in hydraulic engineering were concluded. And, the overall and detailed analysis of the composite foundation model established was carried out. The index parameters of the vertical reinforced rigid pile composite foundation were formulated. Further, considering the unique role of cushion in hydraulic engineering, its penetration and regularity were analyzed. Then, comparative and optimized analyses of cushion multistage physical dimensions and multistage material characteristics were established. The parameters of the piles distance were optimized and the multilevel scientific and reasonable parameters information was obtained. Based on the information of these parameters, the practical application was verified. It effectively supported the effective application of vertical reinforcement rigid pile composite foundation in hydraulic engineering. The service mechanism of composite foundation was fully analyzed.

• 한국통신학회논문지
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• 제23권4호
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• pp.865-872
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• 1998

This paper proposes a multiuse detection system in a multi-cell M-ary Frequency Shift Keying(MFSK)/frequency hopping(FH)-Code Division Multiple Access(CDMA) environment, in which the channel model is an OR-channel and in the reverse link. We have proposed a multiuse detection system in a single cell. However, this sitye is not adequate to detect multiuser in a multi-cell environment. Therefore, we propose a multiuser detection system based on 3 level OR decision with two threholds. The proposed detection system can delete interference as well as intra-cell interference, receive the weakened desired signal and reject the false alarm. computer simulation shows the performance improvement.