• 한국시뮬레이션학회논문지
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• 제16권1호
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• pp.1-9
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• 2007

고속 네트워크에서 QoS 라우팅은 수많은 사용자의 요구를 만족하기가 매우 어렵다. 네트워크의 경로설정 알고리즘에서 측도로써 단지 링크지연시간만을 고려한다면 그 경로는 최소지연시간 경로가 될 것이며, 링크비용만을 고려한다면 최소비용경로를 찾을 것이다. 지연시간 한계의 최소비용(Delay Constrained Least Cost; DCLC)문제는 NP-hard 문제로 알려져 있으며, 두 개의 인자 경로비용과 지연시간을 혼합한문제로 생각할 수 있다. 경로설정 시 최소지연시간을 생각하면 그 경로는 상대적으로 높은 비용의 경로이며, 반대로 최소비용만을 생각하면 그 경로는 상대적으로 높은 지연시간을 얻는다. 따라서 DCLC문제를 풀기위해서는 단 하나의 인자만을 고려해서는 안 되며 두 개의 인자를 동시에 고려할 수 있는 새로운 인자를 요구하게 되었다. 따라서 본 논문에서는 DCLC 문제를 풀기위해 경로비용과 지연시간을 동시에 확률적으로 고려한 새로운 인자를 소개한다. 시뮬레이션 결과는 새로운 인자가 DCLC 문제에 적절하다는 것을 보여주었다.

• ETRI Journal
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• 제40권3호
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• pp.330-336
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• 2018

Free-space optical (FSO) systems have attracted much attention from both research and application perspectives owing to their many benefits, such as license-free operation, low-cost, and high data rates. This paper investigates the ergodic capacity of FSO systems, which is an important metric of system performance. The stochastic temporary laser-beam blockage, pointing errors, and atmospheric turbulence are simultaneously considered. The results illustrate that the link blockage causes a decreased ergodic capacity. We show that to maximize the ergodic capacity, there is an optimal value of the laser-beam radius at the waist, which largely depends on pointing errors; however, it is independent of the atmospheric turbulence and the probability of link blockage.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.495-497
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• 1994

Given the constraint of the AC input power factor and the DC-link voltage and current ripple in voltage source inverter, minimizing the size and cost of the DC-link fitter components is very important. This paper presents a procedure for the selection of DC-link filler element values in a three-phase PWM voltage source inverter-fed induction motor drive system, which can not only satisfy the requirements for the system performance but also minimize the filter size.

• 전력전자학회논문지
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• 제18권1호
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• pp.110-116
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• 2013

This paper proposes a current ripple reduction method to improve the control performance of B4 type inverter that is studied for cost-effective drive systems. B4 inverters employ only four switches and they have a center-tapped connection between the split dc-link capacitors and one phase of a three-phase motor or load. In the B4 topology, unbalanced three-phase voltages will be generated due to the dc-link voltage ripple. To solve this problem, this paper presents a voltage distortion compensation method that adjusts the voltage reference with the consideration of dc-link voltage ripple. The validity of the proposed method is verified by simulation and excremental results with an induction machine.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권2호
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• pp.143-149
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• 2017

Purpose: In recent years, weight reduction for improving fuel efficiency of the vehicle and cost reduction have been developed. The structure of suspension link is widely used as a single plate press structure which can reduce process and weight compared to existing pipe welding method. However, it was found that the lifetime of a single plate press structure is determined by initial defects that occurred during initial manufacturing rather than fatigue damage caused by driving. Methods: I research the mechanism of failure phenomenon of the single plate press assist arm of rear wheel. In addition, I investigate durability effect parameters to determine the link lifetime in inserting bush into single plate press process through durability test. Conclusion: I discover significant durability effect parameter in inserting bush into single plate press process. It is expected that the durability can be improved by suggesting a bush inserting process inspection guide for similar suspension link like single plate press structure.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.419-420
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• 2015

In this paper, a low-cost single-phase PWM rectifier with small DC-link capacitors is proposed, where a buck-boost converter with a low power rating is added at the DC link. By controlling the auxiliary circuit so as to absorb the voltage ripple in the DC link, the second-order voltage ripple in DC-link capacitor can be reduced significantly. Therefore, a small film capacitor can be utilized to replace the bulky electrolytic capacitors. The simulation results are shown to verify the validity of the proposed method.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.889-898
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• 2013

The shortest-path searching algorithm must not only find a global solution to the destination, but also solve a turn penalty problem (TPP) in an urban road transportation network (URTN). Although the Dijkstra algorithm (DA) as a representative node-based algorithm secures a global solution to the shortest path search (SPS) in the URTN by visiting all the possible paths to the destination, the DA does not solve the TPP and the slow execution speed problem (SEP) because it must search for the temporary minimum cost node. Potts and Oliver solved the TPP by modifying the visiting unit from a node to the link type of a tree-building algorithm like the DA. The Multi Tree Building Algorithm (MTBA), classified as a representative Link Based Algorithm (LBA), does not extricate the SEP because the MTBA must search many of the origin and destination links as well as the candidate links in order to find the SPS. In this paper, we propose a new Link-Based Single Tree Building Algorithm in order to reduce the SEP of the MTBA by applying the breaking rule to the LBA and also prove its usefulness by comparing the proposed with other algorithms such as the node-based DA and the link-based MTBA for the error rates and execution speeds.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권12호
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• pp.3310-3329
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• 2023

This work designs an eighteen-channel bidirectional Intensity Modulation with Direct Detection (IM/DD) Wavelength Division Multiplexing-Passive Optical Network (WDM-PON) system. The proposed system meets the requirement of the ITU-T 5G fronthaul link suggested design in G-series Recommendations-Supplement 66. The newly designed system, with a 25Gb/s/λ data rate (450Gbps as a system capacity), has been tested and simulated using OptiSystem V.19 software. The system has been evaluated by the BER with respect to variable the optical span and CW laser power. Based on the ITU-T recommendations, the simulation results demonstrate that this system might be used as an F1 and as an Fx 5G fronthaul link for functional split choices starting from options 1 to 7a. These options are required under 25Gbps/λ for each upstream and downstream link direction. Furthermore, the proposed system utilized a bidirectional single-mode optical fiber within short optical spans of up to 10 km. The proposed system is characterized by a low-cost, simple, DSP-free and amplifier-free system with a reasonable system capacity.

• 한국CDE학회논문집
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• 제9권2호
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• pp.148-157
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• 2004

Interactive simulators that simulate mechanical systems are being developed for the purpose of performance evaluation of product design, replacement of physical training, and entertainment game. Use of flight simulator is increasing to reduce risk and cost of physical training, and we need virtual environment which covers large area terrain. We need a method that can reduce development cost and construction time of virtual environment that simulate the real environment. There have been attempts to link GIS or remote sensing field with virtual reality. This paper examines a method that helps to construct virtual environment, and attempts to link geographic information with virtual reality. A construction method of virtual environment based on digital map and satellite image has been studied.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.139-141
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• 2019

Capacitive power transfer has an advantage in the simplicity of the energy link structure. So, the conventional phase -shift full bridge sometime is not always the best choice because of its complexity and high cost. On the other hand, the link capacitance is usually very low and requires high-frequency operation, but, the series resonant converter loses zero-voltage switching feature in the light load condition, which makes the switching loss high especially in CPT system. The paper proposes a new low-cost topology based on asymmetric half-bridge to achieve simplicity as well as wide zero voltage switching range. The design procedure is presented, and circuit operations are analyzed and verified by simulation.