• Nuclear Engineering and Technology
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• 제54권2호
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• pp.501-506
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• 2022

Long turn-off time limits high frequency operation of Bipolar Junction Transistors (BJTs). Turn-off time decreases with increases in the recombination rate of minority carriers at switching transients. Fast neutron irradiation on a Si BJT incurs lattice damages owing to the displacement of silicon atoms. The lattice damages increase the recombination rate of injected holes with electrons, and decrease the hole lifetime in the base region of pnp Si BJT. Fast neutrons generated from a beryllium target with 30 MeV protons by an MC-50 cyclotron were irradiated onto pnp Si BJTs in experiment. The experimental results show that the turn-off time, including the storage time and fall time, decreases with increases in fast neutron fluence. Additionally, it is confirmed that the base current increases, and the collector current and base-to-collector current amplification ratio decrease due to fast neutron irradiation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.357-360
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• 2003

In this paper, we designed 4.5kV/1.5kA IGCT devices. GCT thyristor has many superior characteristics compared with GTO thyristor, for examples; snubberless turn-off capability, short storage time, high turn-on capability, small turn-off gate charge and low total power loss of the application system containing device and peripheral parts such as anode reactor and snubber capacitance. In this paper we designed GCT thyristor devices, and analyzed static and dynamic characteristics of GCT thyristor depending on the minority carrier lifetime, n-base thickness and doping concentration of n-base region, respectively. Especially, turn-on and turn-off characteristics are very important characteristics for GCT thyristor devices. So, we considered above characteristic for design and analysis of GCT devices.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.374-377
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• 2003

In this paper, turn on characteristics of (Punch-Through Insulated Gate Bipolar Transistor) PT-IGBT has been studied. Based on the transient power loss, turn on charges first base to collector capacitance. Furthermore we present the charge variation in the base including n+ buffer layer to express the transient turn-on characteristics of the device.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1996년도 창립기념 전력전자학술발표회 논문집
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• pp.63-66
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• 1996

An micro model for the power insulated Gate Bipolar Transistor(IGBT) is developed. The model consistently described the IGBT steady-state current-voltage characteristics and switching transient current and voltage waveform for all loading conditions. The model is based on the equivalent circuit of a MOSFET with supplies the base current to a low-gain, high-level injection, bipolar transistor with its base virtual contact at the collector and of the base. Model results are compared with measured turn-on and turn-off waveform for different drive, load, and feedback circuits.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2003년도 ISIS 2003
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• pp.110-113
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• 2003

Most traffic accidents are caused by drivers' carelessness and lack of information on the surrounding objects. In this paper we proposed a model of human intention recognition through case-base learning and to build up an experiment system. The system can help us recognize object's intention (e.g. turn left, turn right or straight) by using detected data about human's motion, speed of the car and the distance between the car and the intersection. Furthermore, we included an example using case-base learning in this paper to improve the precision of recognition as well as an example to explain the use of the system. PC can be used to predict the driving reaction beforehand and send a warning signal to the driver in time if there is any danger.

• 소성∙가공
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• 제28권3호
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• pp.135-144
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• 2019

Electromagnetic impulse welding (EMIW) is a type of solid state welding using the Lorentz force generated by interaction between the magnetic field of the coil and the current induced in the workpiece. Although many experimental studies have been investigated on the expansion and compression welding of tube using the EMIW process, studies on the EMIW process of lap joint between flat sheets are uncommon. Since the magnetic field enveloped inside the tube can be controlled with ease, the electromagnetic technique has been widely used for tube welding. Conversely, it is difficult to control the magnetic field in the flat sheet welding so as to obtain the required welding velocity. The current study analyzed the effects of coil shape on the impulse velocity for suitable flat one-turn coil for the EMIW of the flat sheets. The finite element (FE) multi-physics simulation involving magnetic and structural field of EMIW were conducted with the commercial software LS-DYNA to evaluate the several shape variables, viz., influence of various widths, thicknesses, gaps and standoff distances of the flat one-turn coil on the impulse velocity. To obtain maximum impulse velocity, the flat one-turn coil was designed based on the FE simulation results. The experiments were performed using an aluminum alloy 1050 sheets of 1.0mm thickness using the designed flat one-turn coil. Through the microscopic interfacial analysis of the welded specimens, the interfacial connectivity was observed to have no defects. In addition, the single lap joint tests were performed to evaluate the welding strength, and a fracture occurred in the base material. As a result, a flat one-turn coil was successfully designed to guarantee welding with bond strength equal to or greater than the base material strength.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.36-38
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• 2001

A basic structure of 2500V-4500V reverse-conducting GCT (RC-GCT) is given in this paper. The punch-through type (PT) is adopted for narrow N-base with high resistivity so that the fast turn-off and low on-state voltage can be achieved. The photo mask design was made upon the both turn-off performance and solution of separation between GCT and integrated freewheeling diode (FWD) part. The turn-on and turn-off characteristics for reserve-conducting gate commutated thyristors (RC-GCTs) were investigated by ISE simulation. Additionally, the local carrier lifetime control by proton irradiation was adopted so as not only to obtain the reduction of turn-off losses of GCT but also to reach a soft reverse recovering characteristics of FWD

• 대한전기학회논문지
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• 제33권4호
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• pp.157-163
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• 1984

The object of this paper is to investigte the gate controlled diode structure for ionic concentration measurement. It includes device fabrication, characterization, device physics and modeling of the gate controlled diode structure. The differences of turn on voltages and surface generation currents in the (100) and (111) silicon crystallographic orientation of the sample device were observed. Therefore the dependence of these two factors of the silicon crystallographic orientation was investigated. It was observed that drifts arose after extended immersion of the sample device in acid or base solutions. The surface generation-recombination velocity of both (100) and (111) increased. The increase in the interfacial traps for both surface, determined by the turn on voltage was directly proportional to the surface generation-recombination velocity increase.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.213-216
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• 2003

Recently a new high power device GCT (Gate Commutated Turn-off) thyristor has been successfully introduced to high power converting application areas. GCT thyristor has a quite different turn-off mechanism to the GTO thyristor. All main current during turn-off operation is commutated to the gate. Therefore, IGCT thyristor has many superior characteristics compared with GTO thyristor; especially, snubberless tum-off capacibility and higher turn-on capacibility. The basic structure of the GeT thyristor is same as that of the GTO thyristor. This makes the blocking voltage higher and controllable on-state current higher. The turn-off characteristic of the GCT thyristor is influenced by the minority carrier lifetime and the performance of the gate drive unit. In this paper, we present turn-off characteristics of the 2.5kV PT(Punch-Through) type GCT as a function of the minority carrier lifetime and variation of the doping profile shape of p-base region.

• Journal of Welding and Joining
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• 제6권2호
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• pp.40-46
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• 1988

The effect of heat input on the content of residual .delta.-ferrite and the hot cracking susceptibility in the austenitic stainless steel overlaid on the carbon steel was studied in the range of heat input from 7.5 to 15.1 KJ/cm. Present study shows that residual .delta.-ferrite content in the overlay is mainly determined by the dilution of the base metal (carbon steel) which is in turn affected by heat input, i.e. the amount of dilution decreases as heat input increase. Accordingly, higher heat input results in a substantial increase in Cr equivalent but a little increase in Ni equivalent due to the less dilution of carbon from base metal. This fact can explain the result obtained in this study, i, e, the higher content of .delta.-ferrite in the weld deposit made with higher heat input. This in turn causes more resistant overlaying weld metal to hot cracking.