• Journal of Power Electronics
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• 제19권1호
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• pp.146-157
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• 2019

The inverter is an essential part of permanent magnet synchronous motor (PMSM) drive systems. The performance of an inverter is greatly influenced by its modulation strategy. Using a proper management of modulation strategies can guarantee high performance from a PMSM under various speed conditions. Switching between modulations is a pivotal technique that determines the performance of a PMSM. Most works on hybrid methods focus on two-level induction motors drive systems. In this paper, in order to improve the performance of PMSMs under various speed conditions, a hybrid method of a pulse width modulation (PWM) control scheme based on a neutral-point-clamped (NPC) three level topology was proposed. This hybrid PWM modulation comprised space vector PWM (SVPWM) and selective harmonic elimination PWM (SHEPWM). Under low speed conditions, the SVPWM is employed to cause the PMSM to start smoothly, and to obtain a rapid response from the control system. Under high speed conditions, the SHEPWM is employed to reduce the switching frequency and to eliminate particular current harmonics. Moreover, the harmonic characteristics of different modulations are analyzed to obtain a smooth transition between the SHEPWM and the SVPWM. Experimental and simulation results indicated the effectiveness of the proposed control method.

• Agribusiness and Information Management
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• 제12권1호
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• pp.18-35
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• 2020

Due to the rise of Information & Communication Technology (ICT) adoption in many fields, it is necessary to diagnose the informatization situations of corporations in agriculture and give suggestions for improvement. For this goal, surveys were designed and conducted to understand the current informatization situations of agriculture corporations in Korea. The survey covers the plan for utilizing information technology, the establishment of infrastructure for information technology, IT application status, and its effect on their performance. The specific focus of our research is to segment the corporations by their type of industries and their level of sales and give differentiated managerial implications for each segment. This is because the type of informatization and information technology assistance they need highly depends on their industry type and sales level. Based on descriptive statistics and regression analyses, tailored managerial and polic.

• 대한토목학회논문집
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• 제34권5호
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• pp.1373-1382
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• 2014

본 연구에서는 하도의 수면곡선을 작성하고 통수능을 평가하기 위해서 하도구간 사이의 배수위 영향 및 유출을 고려할 수 있는 수리거동곡선 모형을 개발하고 이를 낙동강 하도구간에 적용하여 그 적용성을 검토하였다. 본 모형 적용 결과, 수리거동곡선에 의한 수위 모의 결과가 기존 수위관측소 자료와 비교하여 잘 부합하는 것을 알 수 있었으며 널리 이용되고 있는 범용 모형인 HEC-RAS의 모의 결과와도 유사하게 나타나는 것으로 드러났다. 대상구간 내 하나의 수위 관측소를 미계측 지점으로 가정하여 본 모형에 의한 수위예측치를 관측수위와 비교한 결과, 홍수기와 같이 시간에 따른 유량 변화가 크게 나타날 경우 상승기에는 과소 예측을 하고 하강기에는 과대 예측을 하는 것으로 나타났다. 개선책으로서 관측 지점과 예측 지점간의 홍수파 도달시간을 고려했을 경우, 수리거동곡선을 이용한 미계측 지점의 수위 예측 정확도가 크게 향상되는 것으로 나타났다.

• The Journal of Asian Finance, Economics and Business
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• 제8권3호
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• pp.319-329
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• 2021

The study examines the impact of bank-level factors like non-performing assets, capital adequacy, and insolvency risk on bank performance. This study employs a quantitative method with panel data regression. The data was taken from the annual financial statements of state-owned commercial banks and private commercial banks in Indonesia from 2015 to 2019 using a purposive sampling method with a total sample of 470 observations. The result of the study shows that non-performing assets (NPA) have a significant negative impact on bank performance. Capital adequacy has a significant negative impact on bank performance. Insolvency risk for a bank means it cannot repay its depositors because its liabilities are greater than its assets; therefore, it has a significant impact on bank performance. This study is expected to help banks to understand how to manage the risks they face and to maintain their performance. This study uses 'size' and 'age of bank' as control variables and for credit risk and insolvency risk, Z-Score is used.

• 경영과정보연구
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• 제36권3호
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• pp.17-35
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• 2017

본 연구는 기업의 전략적 위치 변화에 성과 피드백, 정당성 그리고 준거집단 성과의 영향을 살펴보고자 한다. 성과 피드백은 목표수준을 기준으로 기업의 성과를 평가한다는 것이다. 선행 연구는 이 이론을 바탕으로 위험감수, 연구개발비 변화 등 여러 기업의 행동을 밝혔다. 여기에서는 성과 피드백에 의한 기업의 전략적 위치 변화와 함께 기업을 둘러싼 환경적 요인인 정당성 그리고 준거집단 성과의 조절효과를 살펴 세 가지 가설을 제시하였다. 북미 원유 및 천연가스 산업을 분석하여 1997년부터 2010년까지 538개 기업을 관찰하여 가설을 검증한 결과 모두 지지되었다. 구체적인 결과는 다음과 같다. 첫째, 기업의 성과가 목표수준보다 낮아짐에 따라, 그 전략적 위치가 산업의 평균에서 더욱 멀어진다. 둘째, 산업의 밀도가 증가함에 따라, 기업의 성과가 목표수준보다 낮아짐에 따라 그 전략적 위치가 산업 평균에서 멀어지는 경향이 약해진다. 셋째, 준거집단의 성과가 하락하면, 기업의 성과가 목표수준보다 낮아짐에 따라 그 전략적 위치가 산업 평균에서 멀어지는 경향이 강해진다. 이 결과를 토대로 기업의 전략적 위치 변화를 이해하기 위한 시사점을 제시하였다.

• 한국시스템다이내믹스연구
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• 제2권1호
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• pp.93-112
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• 2001

Inter-Organizational Cooperation is the most common and important strategy in modern public and privet sectors managerial activities. In this paper the concepts of inter-organizational cooperation means not selfish cooperation as in the game circumstance and theory, but general collaborative action between organizations, they have share same goal. The achievement level of jointed-goal of inter-organization is depended upon the performance of cooperation, which resulted from the conditions and circumstances of cooperation. This paper analyses the effect of inter-organizational cooperation on achievement level of the jointed goal between two organizations with computer simulation model of the system dynamics approach. In the computer simulation model, three factors, goal perception, communication, and control, are considered as a key conditions of cooperation, which impact on the performance of cooperation. Simulation model was constructed with focus on the dynamic interactions between these three factors and the achievement level of jointed-goal. Consequently, the results found in this paper may provide further grounds for reducing the time delay that included in the conditions of cooperation.

• 정보과학회 논문지
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• 제42권8호
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• pp.947-953
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• 2015

PRAM은 바이트 단위의 쓰기와 비휘발성의 특징을 모두 가지고 있으며, DRAM보다 높은 밀 집도가 기대되기 때문에 DRAM을 대체할 수 있을 것으로 예상된다. 이에, PRAM 기반의 버퍼 캐시 교체정책에 대한 연구가 활발하게 진행되고 있다. 그러나 대부분의 기존 연구는 PRAM의 수명 및 느린 쓰기 성능에만 집중함으로써 PRAM의 바이트 단위의 쓰기 성능을 제한적으로 이용한다. 이에, 본 논문에서는 PRAM의 바이트 단위의 쓰기 성능과 스토리지의 성능을 모두 고려한 새로운 버퍼 캐시 교체 정책을 제안 한다. 제안 기법은 바이트 단위의 쓰기 성능을 이용하기 위해 작은 크기의 쓰기 요청이 빈번한 페이지를 PRAM에 유지시키며 DRAM과 PRAM사이의 선택적 페이지 이동을 통해 PRAM의 쓰기 횟수를 감소시킨다. 실험 결과, 제안 기법은 CLOCK 알고리즘에 비해 최고 92%까지 PRAM의 쓰기 횟수를 감소시키고 PRAM 테스트 보드에서 최대 62%까지 수행시간을 향상시키는 것을 확인하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(3)
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• pp.55-58
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• 2001

In this paper, we present the development of a JavaCard for public key crypto algorithms and its performance evaluation. To make a high performance for the public key crypto algorithm such as RSA and ECC on a JavaCard, we have implemented a crypto coprocessor in hardware and ported it to the card operating system and virtual machine environments. The performance of the public key crypto algorithms on the JavaCard shows that our JavaCard is suitable for If card applications which needs high performance and high level of security.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.574-585
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• 2015

This paper aims to improve the performance of conventional direct torque control (DTC) drives proposed by Takahashi by extending the idea for 5-level inverter. Hybrid cascaded H-bridge topology is used to achieve inverter voltage vector composed of 5-level of voltage. Although DTC is very popular for its simplicity but it suffers from some disadvantages like- high torque ripple and uncontrollable switching frequency. To compensate these shortcomings conventional DTC strategy is modified for five levels voltage source inverter (VSI). Multilevel hysteresis controller for both flux and torque is used. Optimal voltage vector selection from precise lookup table utilizing 12 sector, 9 torque level and 4 flux level is proposed to improve DTC performance. These voltage references are produced utilizing a hybrid cascaded H-bridge multilevel inverter, where inverter each phase can be realized using multiple dc source. Fuel cells, car batteries or ultra-capacitor are normally the choice of required dc source. Simulation results shows that the DTC drive performance is considerably improved in terms of lower torque and flux ripple and less THD. These have been experimentally evaluated and compared with the basic DTC developed by Takahashi.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1112-1117
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• 2010

The intelligent safety system for level crossing which employs information and communication technology has been developed in USA and Japan, etc. But, in Korea, the relevant research has not been performed. In this paper, we analyze the cause of railway level crossing accidents and the inherent problem of the existing safety equipments. Based on analyzed results, we design the intelligent safety system which prevent collision between a train and a vehicle. This system displays train approaching information in real-time at roadside warning devices, informs approaching train of the detected obstacle in crossing areas, and is interconnected with traffic signal to empty the crossing area before train comes. Especially, we present the video based obstacle detection algorithm and verify its performance with prototype H/W since the abrupt obstacles in crossing areas are the main cause of level crossing accidents. We identify that the presented scheme detects both pedestrian and vehicle with good performance. Currently, we demonstrate developed railway crossing intelligence system at one crossing of Young-dong-seon line of Korail with Sea Train cockpit.