• 조명전기설비학회논문지
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• 제17권6호
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• pp.39-46
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• 2003

본 논문에서는 디지털화 경향에 맞추어 변압기를 보호함과 아울러 감시 및 계측 등의 기능을 갖춘 변압기용 디지털 보호계전기를 개발하기 위한 하드웨어 및 실시간 처리가 가능한 소프트웨어의 구현 방법 등을 제시하였다. 특히 보호계전기의 모든 알고리즘 및 보조 프로그램들이 단일 프로세서에 의해 실시간으로 수행될 수 있도록 DSP의 DMA 제어기를 이용하여 아날로그 입력 데이터를 처리하였다. 아울러 비휘발성 메모리 (EEPROM, flash memory)에 보호계전 알고리즘의 수행에 필요한 각종 설정치, 이벤트 및 고장데이터를 저장하고 UART를 이용하여 데이터를 분석할 수 있도록 하였다. 그리고 시험용 변압기용 디지털 보호계전기를 제작하여 일본 NF 사의 보호계전기 시험기를 이용하여 변압기 보호기능 및 동작특성을 시험하여 그 성능을 입증하였다.

• 한국자동차공학회논문집
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• 제15권2호
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• pp.65-73
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• 2007

The use of an Exhaust Gas Recirculation(EGR) for a diesel engine with variable geometry turbocharger(VGT) has confronted how to obtain the amount of EGR for NOx reduction requirement at wide operating range and less side effect. Through a combined effort of modeling(wave action simulation) and experiment, an investigation into the effect of EGR area ratio and pipe length on EGR characteristics of common rail diesel engine with VGT has been performed. For accurate computation, calibration of constants involved in empirical and semi-empirical correlations has been performed at a specific operating point, before of its use for engine simulation. From the results of this study, it was found that EGR rate is sharply increased with increasing EGR area ratio until area ratio of 0.3. However, the effect of EGR area ratio on EGR rate is negligible beyond this criteria. This study also investigates the effect of EGR pipe length on a EGR amount and pulsating flow characteristics at EGR junction. The results showed that the longer EGR pipe length, the lower EGR amount was achieved due to the flow loss resulting in lower amplitude of pressure wave.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권10호
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• pp.3423-3438
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• 2014

In recent years, wearable sensor devices are reshaping the way people live, work, and play. A wearable sensor device is a computer that is subsumed into the personal space of the user, and is always on, and always accessible. Therefore, among the most salient aspects of a wearable sensor device should be a small form factor, long battery lifetime, and real-time characteristics. Thereby, sophisticated applications of a wearable sensor device use real-time operating systems to guarantee real-time deadlines. The deterministic multi-dimensional task scheduling algorithms are implemented on ARC (Actual Remote Control) with relatively limited hardware resources. ARC is a wearable wristwatch-type remote controller; it can also serve as a universal remote control, for various wearable sensor devices. In the proposed algorithms, there is no limit on the maximum number of task priorities, and the memory requirement can be dramatically reduced. Furthermore, regardless of the number of tasks, the complexity of the time and space of the proposed algorithms is O(1). A valuable contribution of this work is to guarantee real-time deadlines for wearable sensor devices.

• Journal of Power Electronics
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• 제17권5호
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• pp.1256-1267
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• 2017

A fault tolerant structure and its corresponding control strategy for electromagnetic stirring power supplies are proposed in this paper. The topology structure of the electromagnetic stirring power supply contains two-stages. The fore-stage is the PWM rectifier. The back-stage is the fault tolerant inverter, which is a two-phase three-bridge orthogonal inverter circuit while operating normally. When the power switch devices in the inverter are faulty, the structure of the inverter is reconfigured. The two-phase half bridge inverter circuit is constructed with the remaining power switch devices and DC-link capacitors to keep the system operating after cutting the faulty power switch devices from the system. The corresponding control strategy is proposed to let the system work under both normal and fault conditions. The reliability of the system is improved and the requirement of the electromagnetic stirring process is met. Finally, simulation and experimental results verify the feasibility of the proposed fault tolerant structure and corresponding control strategy.

• 한국유체기계학회 논문집
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• 제8권3호
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• pp.16-25
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• 2005

The purpose of this study is localization of safety relief valves for Nuclear Service. The safety relief valve is the important equipment used to protect the pressure vessel, the steam generator and the other pressure facility from overpressure by discharging the operating medium when the pressure of system is reaching the design pressure of the system. We developed design technology used FEM ' CFM about safety relief valve for Nuclear Service according to ASME (or KEPIC) Code and KHNP's Technical Specification. To prove validity of a design technology, actually, we manufactured and inspected and tested the sample products designed according to a developed technology. The capacity qualification test was achieved according to requirement of ASME(or KEPIC) Code by NBBI and the functional qualification test was achieved according to ASME QME-1 for operating condition in technical specification of KHNP by NLI. Therefore we have to achieve the development of safety relief valves for Nuclear Service with our own technologies.

• 산업공학
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• 제18권2호
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• pp.136-147
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• 2005

This paper introduces a simulation study regarding the operation of the Painted Body Storage (PBS) in an automobile factory. In the paint shop of the factory, same colored bodies are grouped together in order to increase the effectiveness of process, for example decrease the loss of cleaning the painting-gun when the color of body changes from one to another. However the production of automobiles in the assembly shop is a typical example of the mixed model assembly production. Therefore PBS locates between the paint shop and the assembly shop for control the input sequence of bodies to the assembly shop, and it enables to meet the smoothing requirement of assembly sequence. There are highly restricted constraints on the assembly sequence in a assembly shop. Those are spacing restriction and smoothing restriction. If such restrictions are violated, conveyor-stop or utility work will be necessary. Thus the major objective of PBS is to control the assembly sequence in a way to meet the two restrictions. In this paper a case study of PBS in an automotive factory is introduced. The storage/retrieval algorithms are suggested and the proposed system is verified using simulation models. Sensitivity analysis for operating factors is also conducted.

• 한국컴퓨터정보학회논문지
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• 제7권3호
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• pp.115-121
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• 2002

본 논문은 ATM망에서의 실시간 서비스 중인 트래픽 추출 시 서비스의 중단, 시간 및 장소 제약 둥의 문제를 해결하기 위한 장치 개발에 대해 연구한 것으로 이 시스템의 특징은 원격으로 제어가 가능하며 서비스 중인 모든 회선에 대해 절단 없이 실시간 트래픽을 추출할 수 있다. 또한, 회선의 상태 감시를 통한 운용의 효율성을 증대할 수 있고, 고가의 측정 장비를 최소화하여 회선 상태 감시 및 유지 보수에 드는 비용의 절감 효과를 창출할 수 있다. 본 논문은 시스템 설계 시 고려된 요구사항, 모듈 구조, 동작 특성 등을 포괄적으로 다루었으며 제어에 필요한 기능 및 명령어들을 포함하고 있다. 이 연구 결과는 KT전화국에 설치하여 동작에 대한 안정성, 신뢰성 등을 시험하였고 그 결과 특별한 문제없이 사용할 수 있음이 검증되었으며 비용 절감 측면의 모듈 구조 개선을 추진하고 있다.

• 전력전자학회논문지
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• 제24권1호
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• pp.40-48
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• 2019

Hybrid electric propulsion systems (H-EPSs) are an intermediate step for integrated full electric propulsion warships. H-EPSs are a dynamic combination of mechanical and electrical propulsion systems to achieve the required mission performances. The system modes could adapt to meet the requirement of the various operation conditions of a warship. This paper presents a configuration and operating modes of H-EPSs considering the operation conditions of a destroyer class warship. The system has three propulsion modes, namely, motoring mode, generating mode [power take off (PTO) mode], and mechanical mode. The PTO mode requires a careful fuel efficiency analysis because the fuel consumption rate of propulsion engines may be low compared with the generator's engines depending on the loading power. Therefore, the calculation of fuel consumption according to the operating modes is performed in this study. Although the economics of the PTO mode depends on system cases, it has an advantage in that it ensures the reliability of electric power in case of blackout or minimum generator operation.

• 한국항해항만학회지
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• 제38권2호
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• pp.135-140
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• 2014

2013년 8월 20일 해사노동협약이 국제적으로 발효되면서 휴식시간의 실제적인 이행 여부를 항만국통제에서 점검하게 되었다. 한일간 셔틀 운항을 하는 선박은 항해시간이 짧고 입항 항구수가 많아 해사노동협약이나 우리나라 선원법에서 정하고 있는 선원휴식시간을 준수하지 못하는 경우가 발생하고 있으며, 이는 선박의 운항에 큰 지장을 초래할 수 있는 사항이 되었다. 이 연구에서는 이러한 선박들에서 휴식시간 규정을 준수할 수 있는 방안을 찾기 위해 항해사들의 당직모델을 여러 가지로 변경하거나 정박당직을 육상직원으로 대체하는 방안 등을 검토하였다. 한일간 셔틀 운항 선박이 휴식시간 규정을 만족하기 위해서는 입항 항구 수의 축소 또는 정박당직의 육상직원 대체와 같은 방안의 복합적인 적용이 필요한 것으로 연구되었다.

• 한국추진공학회지
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• 제9권3호
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• pp.25-37
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• 2005

터보펌프 공급방식 발사체 추진기관은 공급 시작 시점에서부터 종료되는 시점까지 산화제 터보펌프 입구에서의 온도 요구조건을 충족시켜야 한다. 이러한 조건이 만족되지 못할 경우 터보펌프 입구에서 캐비테이션이 발생하여 펌핑(pumping) 성능이 저하되고, 심한 경우 펌프의 손상을 초래할 수 있다. 따라서 극저온 액체산소를 사용하는 액체로켓 추진기관에서는 액체산소의 온도 상승에 대한 적확한 예측이 필수적이다 본 논문에서는 탱크 내의 액체산소 온도상승과 관계된 탱크 내 해석 방법을 체계적으로 제시하였고, 부력동기 경계층 이론을 적용하여 터보펌프 공급방식 로켓 추진기관의 충전, 대기, 선가압, 비행 등의 전 과정을 통하여 탱크에 충전된 액체산소의 온도상승을 예측할 수 있는 모델을 제시 하였다.