• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.777-780
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• 2003

In this paper, an improved full wave mode ZVT-PWM DC-DC Converter is presented to maximize the regeneration ratio of resonant energy by only putting an additional diode in series with auxiliary switch. The operation of auxiliary switch in a half wave mode makes possible the soft switching condition of all switches. Furthermore, the increase of the regeneration ratio to resonant energy results in low conduction losses and minimum voltage and current stresses. The operation principles of the proposed converters are analyzed using the PWM boost converter topology as an example. Theoretically analysis and experimental results verify the validity of the boost converter topology with the proposed full wave mode ZVT-PWM converters

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.95-98
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• 2003

A ZVT PWM Boost Converter is proposed to reduce current stresses and conduction losses of main switch in a conventional circuit. By attaching resonant inductor Lr1 in parallel with capacitor Cr, the resonant circulating current is diverted to the additional component and then the main switch is subjected to minimum current stresses same as those in their PWM counterparts. Moreover, the operation of the auxiliary switch in a half wave mode to prevent reverse resonant energy from freewheeling can be able to lessen the conduction losses. The operation principles of the proposed converters are analyzed using the PWM boost converter topology as an example. Theoretically analysis and experimental results verify the validity of the boost converter topology with the proposed circuit.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2840-2851
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• 2022

Electric boilers (EBs) are the backup steam source for the auxiliary steam system of high-temperature gas-cooled reactor nuclear power plants. When the plant is in normal operations, the EB is always in hot standby status. However, the current hot standby operation strategy has problems of slow response, high power consumption, and long operation time. To solve these problems, this study focuses on the optimization of hot standby operations for the EB system. First, mathematical models of an electrode immersion EB and its accompanying deaerator were established. Then, a control simulation platform of the EB system was developed in MATLAB/Simulink implementing the established mathematical models and corresponding control systems. Finally, two optimization strategies for the EB hot standby operation were proposed, followed by dynamic simulations of the EB system transient from hot standby to normal operations. The results indicate that the proposed optimization strategies can significantly speed up the transient response of the EB system from hot standby to normal operations and reduce the power consumption in hot standby operations, improving the dynamic performance and economy of the system.

• 한국정밀공학회지
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• 제29권4호
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• pp.386-394
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• 2012

Recent trends in the flexible manufacturing systems are morphing cell control for the shop-wide production operation system and providing the integrated operation and execution system together with vendor-specific FMC/FMS platform. In these requirements, the shop-floor level operation system plays a role of coordinating the control activity of each cell, and has to provide flexibility for the complexity of mixed operations of various cells. This paper suggests a system architecture for the mixed environments of multi-cells and job shop, its corresponding enabling technologies based on comparative studies with other related studies and commercialized systems. This approach includes a process definition model considering the integration with upper BOM-BOP and external service modules, and reconfigurable device-level interface which provides dynamic interconnections with machine tools and cell controllers. The function modules and their implementation results are also described to provide the feasibility of the proposed approaches as the flexible shop-floor operation system for the multi-cell environments.

• International Journal of Advanced Culture Technology
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• 제12권1호
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• pp.293-298
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• 2024

The purpose of an internal control system is to prevent the occurrence of errors and fraud in the process of producing accounting information, thereby providing investors with reliable information. For the effective operation of an internal control system, it is necessary to secure a sufficient number of personnel and experienced staff. This study focuses on the personnel directly involved in producing accounting information, examining whether companies that invest in their internal control staff experience a mitigation in the phenomenon of valuation errors. The analysis revealed that the size and experience months of the personnel responsible for internal control have a significant negative relationship with valuation errors. This result implies that by securing sufficient personnel for the smooth operation of the internal control system and placing experienced staff within the system, investors can effectively make judgments about the intrinsic value based on quality accounting information, thereby reducing valuation errors.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2300-2305
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• 2011

A Train control system is intended to assure train operation safety and to improve train operation efficiency. To perform these missions, the Train Control System consists of train safety space control part, train route control part and train operation management part. Train control technology changed from track circuit based to wireless based. And Wireless based train control technologies were developed by some railway signaling companies in Korea. To commercialize these control technologies, the development project is carried now. This project did analyze system requirements, and made the system development specification. Now this project finished system functions allocation, which will be performed by some subsystem. This paper describes roles of each function and the allocation of these functions to each subsystem.

• International Journal of Automotive Technology
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• 제5권3호
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• pp.201-208
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• 2004

Response characteristics of the CVT system for a parallel hybrid electric vehicle (HEV) are investigated. From the experiment, CVT ratio control algorithm for the optimal engine operation is obtained. To investigate the effect of the CVT system dynamic characteristics on the HEV performance, a hardware in the loop simulation (HILS) is performed. In the HILS, hardwares of the CVT belt-pulley and hydraulic control valves are used. It is found that the engine performance by the open loop CVT ratio control shows some deviation from the OOL in spite of the RCVs open loop control ability. To improve the engine performance, a closed loop control of the CVT ratio is proposed with variable control gains depending on the shift direction and the CVT speed ratio range by considering the nonlinear characteristics of the RCV and CVT belt-pulley dynamics. The HILS results show that the engine performance is improved by the closed loop control showing the operation trajectory close to the OOL.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.159-160
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• 2007

Two analog predsitorters (PDs) using the mixing operation are proposed to compensate for the memory effects of the power amplifier and then significantly cancel IM3 components with the independent control of IM3 terms. In the first PD, IM3 terms are generated by using mixing operation of low frequency terms. In the second PD, the double mixing operation of the fundamental components is used. For a two-tone signal with 20-MHz tone spacing, the notable IM3 suppression is achieved over a whole output power range.

• Journal of Computing Science and Engineering
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• 제8권1호
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• pp.1-10
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• 2014

The Bacterial Foraging Optimization Algorithm is a swarm intelligence optimization algorithm. This paper first analyzes the chemotaxis, as well as elimination and dispersal operation, based on the basic Bacterial Foraging Optimization Algorithm. The elimination and dispersal operation makes a bacterium which has found or nearly found an optimal position escape away from that position, which greatly affects the convergence speed of the algorithm. In order to avoid this escape, the sphere of action of the elimination and dispersal operation can be altered in accordance with the generations of evolution. Secondly, we put forward an algorithm of an adaptive adjustment of step length we called improved bacterial foraging optimization (IBFO) after making a detailed analysis of the impacts of the step length on the efficiency and accuracy of the algorithm, based on chemotaxis operation. The classic test functions show that the convergence speed and accuracy of the IBFO algorithm is much better than the original algorithm.

• Journal of Platform Technology
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• 제9권3호
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• pp.78-83
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• 2021

4차 산업혁명 기술의 융합으로 신산업 드론에 대한 연구가 증가하고 있다. 특히, 정부 정책적으로 4차 산업혁명의 대응책을 D.N.A 플랫폼으로 지정함에 따라, 해당 플랫폼을 차용한 다양한 시나리오 기반의 연구주제들이 부각되고 있다. 한편, 산업용, 연구용 드론은 관제 운항을 통한 시나리오 기반의 임무를 수행하기 때문에 시분할로 이루어진 공간적 특성을 갖추게 된다. 이에 따라서, 관제 드론 운항 시에는 기존의 보안성을 향상시키기 위한 방법을 다차원적으로 응용할 필요성이 나타났다. 이에 따라 본 연구에서는 보안성을 향상시키기 위한 시나리오 기반의 드론 플랫폼에 대한 연구를 수행하였다. 그 결과 지상 관제시스템, 드론, 드론 데이터 서버의 3분류로 공간을 분류하고 시나리오 기반의 보안기술 적용방안에 대하여 설계하였다.