• Title/Summary/Keyword: Transfer Operation

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Development and Implementation of a Skill Transfer System for a Self-Tapping Screw-Tightening Operation

  • Matsumoto, Toshiyuki;Doyo, Daisuke;Shida, Keisuke;Kanazawa, Takashi
    • Industrial Engineering and Management Systems
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    • v.10 no.3
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    • pp.209-220
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    • 2011
  • Self-tapping screws have some operational peculiarities. In spite of their economical advantage that requires no prior tapping operation, a weakness of self-tapping screw-tightening operations is that screws can easily be tightened at a non-right angle, thus resulting in an improper tightening strength. Increases in outsourced workers have reduced labor costs, but the accompanying high worker fluidity means that new workers are more frequently introduced into factories. It is necessary to train new workers for self-tapping screw-tightening operations, which occupies a considerable portion of ordinary assembly works. The purpose of this study is to develop and implement a skill transfer system for the operation. This study (1) proposes a set of characteristic values for evaluating the quality of the operation and develops a device that can measure these values; (2) proposes criteria for evaluating the resultant quality of the tightening; and (3) develops a skill training system for better work performance. Firstly, sets of characteristic values for evaluating the quality of the operation, namely, torque, vertical pressure forces and horizontal vibration forces, are proposed. A device that can measure these values is developed. Secondly, criteria for evaluating the resultant quality of the tightening are identified, involving tightening torque, maximum vertical pressure and timing, vibration area during the processing and tightening period, and work angle. By using such parameters, workers with the proper aptitude can be identified. Thirdly, a skill training system for the operation is developed. It consists of screwdriver operation training and screw-tightening training with feedback information about the results of the operation. Finally, the validity of the training system is experimentally verified using new operators and actual workers.

Study on Heat Transfer Performance Change According to Long-term Operation Using Carbon Nanotube and Graphene Nanofluid (탄소나노튜브 및 그래핀 나노유체 사용시 장기운전에 따른 열전달성능 변화에 대한 연구)

  • Kim, Young-Hun;Kim, Nam-Jin
    • Journal of the Korean Solar Energy Society
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    • v.37 no.1
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    • pp.15-23
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    • 2017
  • Critical heat flux refers to the sudden decrease in boiling heat transfer coefficient between a heated surface and fluid, which occurs when the phase of the fluid near the heated surface changes from liquid to vapor. For this reason, critical heat flux is an important factor for determining the maximum limit and safety of a boiling heat transfer. Recently, it is reported that the nanofluid is used as a working fluid for the critical heat flux enhancement. However, it could be occurred nano-flouling phenomena on the heat transfer surface due to nanoparticles deposition, when the nanofluid is applied in a heat transfer system. In this study, we experimentally carried out the effects of the nano-fouling phenomena in oxidized multi-wall carbon nanotube and oxidized graphene nanofluid systems. It was found that the boiling heat flux decreased by hourly 0.04 and $0.03kW/m^2$, also the boiling heat transfer coefficient decreased by hourly 11.56 and $10.72W/m^2{\cdot}K$, respectively, in the thermal fluid system using oxidized multi-wall carbon nanotube or oxidized graphene nanofluid.

Development of Projectile Transfer System to Prevent Musculoskeletal Problems (근골격계 질환 예방을 위한 포탄 이송장치의 개발)

  • Park, Sung Ho;Lee, Hae Suk
    • Journal of Korean Institute of Industrial Engineers
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    • v.41 no.6
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    • pp.551-558
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    • 2015
  • The purpose of this paper is to investigate the development of mechanical projectile transfer system to prevent musculoskeletal problems in the firing test range. Prior to 2010, the projectile has been transferred from the worktable to the loading device of 155mm K9 fixed-type artillery by manual. Because the amount of firing test has been increased drastically since 2010, two types of mechanical projectile transfer system were developed to prevent musculoskeletal problems. The NIOSH lift equation and the working posture assessment system such as OWAS, RULA and REBA were used to evaluate the appropriacy of working weight and posture by manual transfer of projectile. The configuration and operation procedure of projectile transfer systems which were developed to improve work efficacy and to reduce the burden of manual transferring were described. The improvements were assessed by the number of processes, the tact time and the working posture assessment for operation of this system by comparing to the manual transfer of projectile.

Characteristic Measurement for Ready-Deployed Optical Cable and Simulation for SDH and WDM System Existing Conditions (기포설된 광케이블 특성측정과 이 선로조건에 대한 SDH 및 DWDM 광전송장치 전송특성측정과 시뮬레이션)

  • 이성원;김영범
    • Journal of Applied Reliability
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    • v.1 no.2
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    • pp.121-138
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    • 2001
  • Due to large demand for high speed and great capacity for data transfer, WDM, which uses the wavelength division multiplexing technique, is known as alternative way to satisfy those demand for its flexible network operation and management, easy network expansion with existing networks, and enhancement of efficient data transfer rate. For these reasons, a new high capacity WDM optical communication network plan was established. Therefore, the quality of currently deployed optical cables with 81.6 km in length should be assessed to ensure if high capacity WDM system could be implemented on existing optical cables. Two important characteristic parameters, Transfer Loss and PMD (Polarization Mode Dispersion), were measured to evaluate quality of existing optical cable. Transfer Loss was measured at 0.244 dB per kilometer, which is lower than the design standard value at 0.275 dB/km. The measured PMD value gave at 0.030ps/km, and it, therefore, satisfies the value recommended by ITU-T (International Telecommunication Union-T) of 0.5ps/km. In addition, the transfer characteristic for existing 2.5 Gbps and 10 Gbps system were measured and evaluated, and the results showed that error-free transfer is very much feasible. Computer simulation for DWDM system, which is likely be a future backbone network in Korea, to assess the transfer characteristic using the same condition employed for 2.5 Gbps and 10 Gbps was carried out as well. The simulation verified that a stable network operation and reliable service could be provided.

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Transformer Design Methodology to Improve Transfer Efficiency of Balancing Current in Active Cell Balancing Circuit using Multi-Winding Transformer (다중권선 변압기를 이용한 능동형 셀 밸런싱 회로에서 밸런싱 전류 전달 효율을 높이기 위한 변압기 설계 방안)

  • Lee, Sang-Jung;Kim, Myoung-Ho;Baek, Ju-Won;Jung, Jee-Hoon
    • The Transactions of the Korean Institute of Power Electronics
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    • v.23 no.4
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    • pp.247-255
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    • 2018
  • This paper proposes a transformer design of a direct cell-to-cell active cell balancing circuit with a multi-winding transformer for battery management system (BMS) applications. The coupling coefficient of the multi-winding transformer and the output capacitance of MOSFETs significantly affect the balancing current transfer efficiency of the cell balancing operation. During the operation, the multi-winding transformer stores the energy charged in a specific source cell and subsequently transfers this energy to the target cell. However, the leakage inductance of the multi-winding transformer and the output capacitance of the MOSFET induce an abnormal energy transfer to the non-target cells, thereby degrading the transfer efficiency of the balancing current in each cell balancing operation. The impacts of the balancing current transfer efficiency deterioration are analyzed and a transformer design methodology that considers the coupling coefficient is proposed to enhance the transfer efficiency of the balancing current. The efficiency improvements resulting from the selection of an appropriate coupling coefficient are verified by conducting a simulation and experiment with a 1 W prototype cell balancing circuit.

Seamless Transfer Method of MPPT for Two-stage Photovoltaic PCS (태양광 발전 시스템의 무순단 MPPT 운전 모드 절체 기법)

  • Park, Jong-Hwa;Jo, Jongmin;An, Hyunsung;Cha, Hanju
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.2
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    • pp.233-238
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    • 2018
  • This paper proposes a seamless MPPT operation mode transfer method of photovoltaic system. The photovoltaic system consists of a DC-DC boost converter, a DC-Link, and a 3-level neutral point clamp (NPC) type inverter. The PV voltage fluctuates due to the output characteristics of the solar pane1 depending on the irradiation amount and the temperature. The photovoltaic system requires seamless MPPT mode transfer method that the discontinuity does not occur in order to supply the stable power to system without affecting the fluctuation of the PV voltage. MPPT operation is divided into two modes by the voltage reference. Under the condition that the PV voltage is below 650V, the DC-DC boost converter performs MPPT through duty control based on perturb & observe (P&O) method, and the inverter conducts DC-link voltage and grid current controls in synchronous reference frame. On the other hand, when the PV voltage exceeds above 650V, inverter performs MPPT in accordance with the variation of DC-link voltage control while the converter stops operating. Two MPPT operation modes is smoothly transferred through the proposed method that DC-link voltage or grid current commands are appropriately adjusted from the certain criteria. The feasibility of the MPPT operation mode transfer method is verified using a 10kW solar photovoltaic system, experimental results have good performances that the fluctuation of PV current is reduced to 100%.

Assignment and Operation Sequencing for Remarshalling of a Vertical Yard Block in Automated Container Terminals (자동화 컨테이너 터미널에서 수직형 블록의 이적작업을 위한 할당 및 작업순서)

  • Bae Jong-Wook;Park Young-Man;Kim Kap-Hwan
    • Journal of Navigation and Port Research
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    • v.30 no.6 s.112
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    • pp.457-464
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    • 2006
  • Remarshalling operation is one of the operations considered important in an automated container terminal to perform quickly loading operations and delivery operations. It arranges the containers scattered at a verticla yard block in order to reduce the transfer time and the rehandling time of ATC(Automated Transfer Crane)s. This paper deals with the remarshalling planning problem minimizing the weighted operation time. This problem can be decomposed into 2 subproblems, storage space assignment problem and operation sequencing problem Storage space assignment problem decides to where containers are transported in terms of transportation time cost.. With results of a previous subproblem, operation sequence problem determines the ATC operation sequence, which minimizes the dead-heading of ATC This study formulates each subproblem with mixed integer program and dynamic program. To illustrate the proposed model, we propose an instance to explain the process of remarshalling planning.

Indirect Current Control of Utility Interactive Inverter for Seamless Transfer (연속적인 운전모드의 전환을 위한 계통연계형 인버터의 간접 전류 제어기법)

  • Yu, Tae-Sik;Bae, Young-Sang;Kim, Hyo-Sung;Choi, Se-Wan
    • The Transactions of the Korean Institute of Power Electronics
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    • v.11 no.1
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    • pp.72-78
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    • 2006
  • Distributed generation (DG) systems go to intentional islanding operation to back up private emergency loads when the main grid is out of electric power. Conventional utility interactive inverters normally operated in current control mode in DG system must change their operation mode into voltage control mode to ensure stable voltage source to the emergency loads when intentional islanding operation occurs. During the transfer between current control mode and voltage control mode, serious transient problem may occur on the output terminal voltage of the utility interactive inverter. This paper proposes reasonal inverter topology and its control algorithm for seamless transfer of DG systems in intentional islanding operation. Filter design guide line and data for a LCL filter that is appropriate for the proposed control algorithm are also presented by the authors.

Safety Assessment of LNG Transferring System subjected to gas leakage using FMEA and FTA

  • Lee, Jang-Hyun;Hwang, Seyun;Kim, Sungchan
    • Journal of Advanced Research in Ocean Engineering
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    • v.3 no.3
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    • pp.125-135
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    • 2017
  • The paper considers the practical application of the FMEA(Failure Mode and Effect Analysis) method to assess the operational reliability of the LNG(Liquefied Natural Gas) transfer system, which is a potential problem for the connection between the LNG FPSO and LNG carrier. Hazard Identification (HAZID) and Hazard operability (HAZOP) are applied to identify the risks and hazards during the operation of LNG transfer system. The approach is performed for the FMEA to assess the reliability based on the detection of defects typical to LNG transfer system. FTA and FMEA associated with a probabilistic risk database to the operation scenarios are applied to assess the risk. After providing an outline of the safety assessment procedure for the operational problems of system, safety assessment example is presented, providing details on the fault tree of operational accident, safety assessment, and risk measures.

A Study on Operation Scheme of STS with Emergency Generator for Peak Shedding (첨두부하 저감을 위한 비상발전기 연계형 STS 운영 방안에 관한 연구)

  • Kim, Chang-Hwan;Rhee, Sang-Bong;Kim, Kyu-Ho
    • Proceedings of the KIEE Conference
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    • 2015.07a
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    • pp.155-156
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    • 2015
  • Recently, electricity consumption has rapidly increased along with economic growth. The operating strategy using emergency generator is aimed, to resolve a demand response management. For strategy of peak shedding using emergency generator, it is essential to introduce the fast transfer switching device. One of the most effective solutions is to use a static transfer switch (STS) based on thyristor. However, the characteristic of natural commutated SCR thyristor should anticipate short duration voltage sag. STS system thus requires more than a quarter cycle to successfully complete transfer process. This paper proposes the operation scheme of the STS system using the forced-commutation technique to mitigate instantaneous voltage sag during peak transfer process. Proposed STS system improved turn-off characteristic thus accomplishes the peak load shedding satisfied power quality. Performance of the proposed STS system is evaluated using electromagnetic transient program (EMTP) to confirm the effectiveness.

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