• 소성∙가공
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• 제14권9호통권81호
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• pp.756-763
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• 2005

The applicability and productivity of hydroforming process can be increased by combining pre- and post-forming processes such as the bending, piercing and embedding process. For the fabrication of automotive parts, the hollow bodies with connecting nuts are widely used to connect parts together. Hollow body with connecting nuts has been conventionally fabricated by welding nuts or screwing in autobody screws. It requires multiple steps and devices fur the welding and/or screwing Therefore in this study, hydro-embedding process that combines the hydraulic embedding of connecting element(nut) with hydroforming process is investigated. Studies on the hydro-embedding technology have been performed to optimize the shape of the connecting element by analyzing the deformed mode of the embedded tube The effects of the shape of the screw tip, screw thread and shape of thread on the connection force between the tube and the connecting element have been investigated to optimize the shape of connecting element. Finite element analysis has also been performed to provide deformation behaviors of the tube surrounding a hole produced by hydro-embedding.

• Structural Monitoring and Maintenance
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• 제4권3호
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• pp.237-253
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• 2017

Among various structural health monitoring technologies, impedance-based damage detection has been recognized as a promising tool for diagnosing critical members of civil structures. Since the piezoelectric transducers used in the impedance-based technique should be bonded to the surface of the structure using bonding layers (e.g., epoxy layer), it is hard to maintain the as-built condition of the bonding layers and to reconfigure the devices if needed. This study presents an experimental investigation by using magnetically attached PZT-interface for the impedance-based damage detection in bolted girder connections. Firstly, the principle of the impedance-based damage detection via the PZT-interface device is outlined. Secondly, a PZT-interface attachment method in which permanent magnets are used to replace the conventional bonding layers is proposed. Finally, the use of the magnetic attraction for the PZT-interface is experimentally evaluated via detecting the bolt-loosening events in a bolted girder connection. Also, the sensitivity of impedance signatures obtained from the PZT-interface is analyzed with regard to the interface's material.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.78-81
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• 2011

Generally, vehicle is insulated from the earth by rubber tire which is intrinsically the insulation material. The electrical ground of vehicle was floated in the sense of electric potential over the electric power sources. First of all, the floated electrical ground of vehicle should be equipotentially connected with the (-) line of electrical equipment. Bimodal tram has the different kinds of electric system. They must be kept insulated to each other electrically. When there is some unbalanced event or connection between them, it will invoke some errors or breakdown to electrical devices including sensors and actuators. This paper has investigated the floating ground effect of bimodal tram built with composite body and shown the effect according to the unbalanced ground of vehicle and the connection between different electric systems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.268-270
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• 2004

There are various researches on MPEG techniques. MPEG technique is used to digital TV(DTV) and internet image communication. Connection method between server and client is usually using wire. Applications may be expanded, if wireless technology is used between server and client system. In this paper, Bluetooth is used for connection method between server and client. Bluetooth offers fast and reliable transmissions of both voice and data over the globally available 2.4GHz ISM (Industrial, Scientific and Medical) band. One of the major application purposes of Bluetooth is the cable replacement for mobile and peripheral devices. Bluetooth has the advantage of small size, low power and low cost. It has the disadvantage of limited bandwidth and limited range. In order to transfer effectively image Information between server and client using Bluetooth, we apply MPEG-2 and MPEG-4 image compression techniques and the results are compared with each other.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.90-92
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• 2005

In this paper, we design a digital protection IED(Intelligent Electric Device) for a distributed power system in connection with power grid. The device can measure various elements for protection and communicate with another devices through network. The protection IED is composed of specific function modules: signal process module which converts analog signal from PT and CT handle algorithm to digital one; communication module for connection with another IEDs; input/output module for user-interfaces; main control module for control the whole modules. A general purpose DSP board with TMS320C2812 is used in the IED. Experiments with the power system simulator DOBLE have been made to verily the proposed hardware system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.507-509
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• 1989

In multiple current source inverter, generally, transformer connection method and direct connection method in output side have been used. But these methods have faults such as the increment of the number of inverter and the need of the transformer for changing phase in order to get above 12 phase. In this system, we obtained the output currents of 24 phase by adding 2taps in 12 phase inverter. Therefore, this system has such characteristics as the miniaturization of devices and the simplicity of control signal by controlling two inverters and two SCRs for changing taps.

• 조명전기설비학회논문지
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• 제26권7호
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• pp.92-98
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• 2012

It is made compulsory to install SPD for the purpose of protecting electric and electronic devices when an abnormal voltage such as lightning occurs to power line using power frequency of 60Hz. Recently, the high speed communication technology utilizing power line is receiving attention again as a communication technology for smart grid. The SPD influences the performances of power line communication when using SPD and power line communication system together. In order to improve the performance of power line communication, a proposed scheme for series connection of gas discharge tube to ZnO varistor was presented. This paper measured the impacts of series connection of GDT to SPD using ZnO varistor on the limit voltage of Class III SPD. This paper also presented the DC operating voltage of GDT which satisfies the limit voltage of power line communication system and SPD simultaneously.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.195-197
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• 1998

The large scale industry needs high voltage converters. Therefore series connection of power semiconductor devices is necessary. It is important to prevent a device induced the overvoltage above ratings by proper voltage balancing in the field of IGBT series connection. In addition, the overvoltage induced by a stray inductance has to be limited in the high power circuit. This paper proposes a new gate control scheme which can balance the voltage properly and limit the overshoot by control the slope of collector voltage under series connected IGBT turn-off transient. The propose gate control scheme limits the overvoltage by sensing the collector voltage and controlling the gate signal actively. The new series connected IGBT gate driver is made and its validity is verified by the experimental results for series connected IGBT circuit.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.137-138
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• 2019

태양광 접속반은 태양전지에서 발생된 전압을 인버터에 연결해주는 장치이다. 태양광 접속반에는 인버터에서 태양전지로 흐르는 역전압을 차단하기 위해 다이오드가 사용된다. 이 다이오드의 발열이 태양광 접속반 화재의 주 원인이다. 본 논문에서는 IoT 기기들을 사용하여 다이오드의 발열상태를 감시하고 화재를 예방하는 방법을 제안한다.

• 한국표면공학회지
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• 제55권5호
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• pp.299-307
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• 2022

Gold plating is used as a coating of connector in printed circuit boards, ceramic integrated circuit packages, semiconductor devices and so on, because the film has excellent electric conductivity, solderability and chemical properties such as durability to acid and other chemicals. In most cases, internal connection between device and package and external terminals for connecting packaging and printed circuit board are electroless Ni-P plating followed by immersion Au plating (ENIG) to ensure connection reliability. The deposition behavior and film properties of electroless Au plating are affected by P content, grain size and mixed impurity components in the electroless Ni-P alloy film used as the underlayer plating. In this study, the correlation between electroless nickel plating used as a underlayer layer and cyanide-free electroless Au plating using thiomalic acid as a complexing agent and aminoethanethiol as a reducing agent was investigated.