• Title/Summary/Keyword: Return system

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Comparison of Return current by the Earth type in the Electrical railway system (전기철도시스템의 접지 유형에 따른 귀선 전류 비교)

  • Lee, Gil-Lo;Kim, Yong-Kyu;Baek, Jong-Hyun;Ryu, Chang-Keun
    • Proceedings of the KIEE Conference
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    • 2005.10b
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    • pp.53-55
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    • 2005
  • In electrical railway system, power supplied to electrical locomotive by catenary is returned to sub-station on track. The current returned to sub-station on track is return current, which is an essential factor for the safety of the wayside electrical equipment and maintenance staff. Therefore, earth system acts an important role to protect wayside electrical equipment and maintenance staff against return current. In general, individual earth system protects partially the electrical railway system, but common earth system does the whole electrical railway system and minimizes the flow of return current. In this paper, we are compared the effect of return current according to earth type by actual measurement in existing electrical railway system. The measurement was conducted at Shinchungju sub~station in high speed trains, and Guro sub-station, which is electrified section in classical line.

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Cooling characteristics of the telecommunication system in a switching room for various air supply and return flow system (교환기실의 급배기방식에 따른 통신 시스템의 냉각 특성)

  • 노홍구;이재헌;고철균
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.5
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    • pp.669-683
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    • 1999
  • Heat dissipation in the domestic switching room has been gradually increased. Therefore, numerical study on the cooling characteristics of the telecommunication system in a switching room for three kinds of the air supply and return flow system was investigated to develop effective flow system. As a result, the cooling performance of the under floor air supply and overhead return flow system was the best.

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Thermal Comfort of the Floor Supply Air Conditioning System for Different Supply-return Locations during Cooling (급배기 위치에 따른 바닥급기 공조시스템의 냉방 열환경)

  • 김요셉;김영일;유호선
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.5
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    • pp.476-485
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    • 2000
  • This study numerically investigates thermal comfort in a space cooled by the floor-supply air conditioning system, in which three different supply-return locations, one floor supply-ceiling return and two floor supply-floor returns, are treated. A complementary experiment is peformed to validate the present numerical analysis, and the prediction agrees favorably with the measured data. In the numerical procedure, a simplified model mimicking the inlet flow through the diffuser is developed for efficient simulations. The calculated results show that the ceiling return type is far better in thermal comfort than the floor return ones within the extent of this study, which seems to be caused by effective vertical penetration of the supply air against natural convection. It is also revealed that the arrangement of port locations in the floor supply-floor return system has insignificant effect on the cooling performance. For selecting a proper system, other characteristics including the heating performance should be accounted for simultaneously with the present estimation.

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A Dynamic Simulation on the Effectiveness of Return Policy in a Capacitated Two-echelon Supply Chain (공급능력제약이 존재하는 2단계 공급체인에서 반품정책의 효과성에 대한 동적 시뮬레이션)

  • Kim, Tae-Hyun;Park, Jeong-Hoon;Jeong, Hyun-Mok
    • Korean System Dynamics Review
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    • v.9 no.2
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    • pp.5-25
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    • 2008
  • This paper analysed the impact of return policy as a coordination mechanism for decentralized supply chain with one capacitated supplier and two competing retailers under random demand distribution. In this study, Shortage gaming also considered to reflect a competing environment of two retailers. System dynamics approach was used to model the baseline two echelon supply chain and return policy on it. Given each of 4 experiment settings being used for 100 simulations with different random seeds, 400 random samples were used in a t-test. The result show that return policy significantly enhance the supply chain profits and fillrates. The analysis suggest that the supply chain performance can be build up by implementing a return policy even though under consideration of a capacitated supplier and competing retailers.

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Analysis of Return Current Effect for AF Non-insulated Track Circuit in ITX Vehicle Operation (ITX 차량 운행에 의한 AF 무절연 궤도회로의 귀선전류 영향 분석)

  • Beak, Jong-Hyen;Kim, Yong-Kyu;Yoon, Yong-Ki;Jang, Dong-Wook;Shin, Dong-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.4
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    • pp.584-590
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    • 2013
  • Depending on the operating characteristics, track circuit is installed for the purpose of control directly or indirectly of the signal device, point switch machine and other security device. These are mainly used for train detection, transmission of information, broken train detection and transmission of return current. Especially, the return current is related to signal system, power system and catenary line, and track circuit systems. It is one of the most important component shall be dealt for the safety of track side staff and for the protection of railway-related electrical system according to electrification. Therefore, an accurate analysis of the return current is needed to prevent the return current unbalance and the system induced disorder and failure due to an over current condition. Also, if the malfunction occurred by the return current harmonics, it can cause problems including train operation interruption. In this paper, we presented measurement and analysis method at return current and it's harmonics by train operation. By the test criteria, we evaluated for safety. Hereafter, it is expected to contribute to the field associated with it.

System Dynamics Approach to Return Policy at Supply Chain (공급체인에서의 반품계약에 대한 시스템다이내믹스 접근)

  • Kim, Tae-Hyun;Park, Jeong-Hoonl;Choi, Dong-Hyun;Kim, In-Hoo
    • Korean System Dynamics Review
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    • v.8 no.1
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    • pp.173-186
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    • 2007
  • This research consists of (1) building (or molding) the Dynamics Simulation Model on Return Policy mainly used in publications, phonographs, and computer industry; which are seen used in supply chain contract known as effective control mechanism under the varied supply chain situations, and (2) analyzing the effects that return rates and seller's contract parameters have in the outcome of the model and (3) observing how the effectiveness of Return Policy changes under such circumstances where the buyer's sales ability and the seller's risk inclination are taken into account. Thus, the main purpose of this research lies in analyzing what exactly are the effects (and or outcome) that sales ability and risk inclination have in Return Policy, and additionally by conducting comprehensive research on Supply Chain Policy Dynamics Simulation Model, we will try to prove that not only the Systems Dynamics approach is highly contributive in supply chain management but also that it will serve as a foothold in future research. As a result of the research, supply chain achievement level turned out to be high when Return Policy is enforced, and the achievement level was even higher when seller's sales ability was taken into consideration along with the Return Policy. On the other hand, the achievement level decreased when the seller had risk aversive tendencies.

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Effect of Supply and Return Locations of a Floor-Supply Cooling System on Thermal Comfort

  • Kim, Young-Il;Kim, Jo-Seph;Yoo, Ho-Seon
    • International Journal of Air-Conditioning and Refrigeration
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    • v.9 no.4
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    • pp.37-46
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    • 2001
  • This study numerically investigates thermal comfort of a space cooled by a floor-supply air-conditioning system, in which three different combinations of supply and return locations, one floor-supply/ceiling-return and two floor-supply/floor-return, are treated. A complementary experiment is performed to validate the present numerical analysis, and the prediction agrees favorably with the measured data. In the numerical procedure, a simplified model mimicking the inlet flow through a diffuser is developed for efficient simulations. The calculated results show that the ceiling-return type is far better in terms of thermal comfort than the floor-return ones within the extent of this study, which seems to be caused by effective vertical penetration of the supply air against natural convection. It is also revealed that the arrangement of port locations in the floor-supply/floor-return system has insignificant effect on the cooling performance. For selecting a proper system, other characteristics including the heating performance should be accounted for simultaneously with the present considerations.

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Development of a synthetic library automation system

  • Lee, Jeong-Hun;Kim, Young-Lyul;Lim, Sung-Jin;Ki, Hwan-Eom;Lee, Jong-Ik;Kim, Jong-Hyun
    • 제어로봇시스템학회:학술대회논문집
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    • 2003.10a
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    • pp.1710-1713
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    • 2003
  • We developed the synthetic library automation system. Developed system is comprised of two main units: an auto sorting system of books and a wireless management system. An auto sorting system is composed of a book return machine, a robot system, and an emergency bookshelf. A book return machine is operated by magnetic removal-revival. A wireless management system is development of RFID, or radio frequency identification, and is composed of a RF module and uninhabited return machine and a loss prevention system. The software for the synthetic library automation system is divided into three groups. We realized the developed automation system, and then get the features.

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A Study of the Reverse Logistics Information Factors for Environmental Conscious Logistics System (환경친화적 물류시스템의 환경물류 정보화 요인 연구)

  • Kim Hyun-Soo
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.27 no.4
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    • pp.59-68
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    • 2004
  • Recently, shifting channel power is forcing supply chain to take back products. As you can imagine returned product has always been a problem for all parties in the supply chain due to the disruption in operations and a headache in processing returned products. Therefore, every member of supply chain should respond to reverse logistics activities particularly for the return handling process. Under such a strong demand of efficient and cost effective reverse logistics activities, particularly for the return handling process, the information system should be implemented and participated in intensively. This study analyzed the reverse logistics information factors for environmental conscious logistics system limited to returns from customers/consumers. The results provide reverse logistics information factors based on the return handling process which can be used as benchmarking for companies seeking implementation of an efficient return handling system.

LPi Engine Combustion and Emission Characteristics Depending on LPG Properties from Various Fuel Supply Types by Using DC Motor Type Fuel Pump (DC모터형 연료펌프를 이용한 연료공급방식별 LPG성상에 따른 LPi엔진 연소 및 배출가스 특성)

  • Kim, Ju-Won;Hwang, In-Goo;Myung, Cha-Lee;Park, Sim-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.12
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    • pp.907-914
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    • 2008
  • This study is mainly focused on the assessment of return, semi return, and returnless fuel supply system for an LPi engine. In order to compare the return type with returnless one with various LPG blends, combustion analysis and cyclic THC emission characteristic were tested at the part load operating condition of the LPi engine. Considering heat balance of each fuel supply systems, pressure and temperature increment of return type showed lower at the fuel rail during idle warm up operation. However, those of returnless type at LPG tank maintained stable and slow increment because the heat transfer from the LPi engine was minimized. Finally, hot restartability of each fuel supply systems were evaluated with the various LPG blends and fuel temperatures. As a result, semi return type has equivalent performance to return type considering combustion and emission characteristic, hot restartability performance for LPi engine.