• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.10
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• pp.912-917
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• 2006

In this paper, Trench emitter electrode IGBT structure is proposed and studied numerically using the device simulator, MEDICI. The breakdown voltage, on-state voltage drop, latch up current density and turn-off time of the proposed structure are compared with those of the conventional trench gate IGBT(TIGBT) structures. Enhancement of the breakdown voltage by 19 % is obtained in the proposed structure due to dispersion of electric field at the edge of the bottom trench gate by trench emitter electrode. In addition, the on-state voltage drop and the latch up current density are improved by 25 %, 16 % respectively. However increase of turn-off time in proposed structures are negligible.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.54-61
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• 2004

This paper deals with flow characteristics on the air entrainment and the energy dissipation in nappe flow over the stepped drop structure. Nappe flow occurred at low flow rates and for relatively large step height Dominant flow features include an air pocket, a free-falling nappe impact and a subsequent hydraulic jump on the downstream step. Air entrainment occurred from the step edge, through a free-falling nappe impact and a hydraulic jump. Most energy was dissipated by nappe impact and in the downstream hydraulic jump. It was related with the step height and the overflow depth, but not related with step slope. The stepped drop structure was found to be effcient for water treatment and energy dissipation associated with substantial air entrainment.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1225-1230
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• 2004

In this paper, the pressure drops were investigated according to the sintered porous wick structure in loop heat pipe(LHP) by theoretical analysis. LHP has the wick only in evaporator for the circulation of working fluid, so utilizes porous wick structure which pore diameter is very small for large capillary force. This paper investigates the effects of different parameters on the pressure drops of the LHP such as particle diameter of sintered porous wick, wick porosity, vapor line diameter, thickness of wick and heating capacity. Working fluid is water and the material of sintered porous wick is copper. According to the these different parameters, capillary pressure, pressure drop in wick were analized by theoretical design method of LHP.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.6 s.123
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• pp.484-490
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• 2007

A reciprocating compressor used in domestic refrigerators can be subjected to many different forms of shock. These shocks are usually experienced during transporting the products from a manufacturer to customers. The hermetic structure of this kind of compressor makes it difficult to conduct drop tests for identifying the failure mechanism and their drop behaviors. The drop/impact simulation for a reciprocating compressor has been carried out with the explicit code LS-DYNA and its validation has been experimentally verified. Simulation results are in good agreement with those of drop test. The present method of drop/impact simulation provides an efficient and powerful solution to improve the design quality and reduce the design period.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.3
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• pp.190-193
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• 2010

Various power semiconductor devices have been developed and evolved since 1950s. Among them, IGBT is the most developed power semiconductor device which has high breakdown voltage, high current conduction and suitable switching speed which perform trade-offs between each other. In other words, there are trade-offs between a breakdown voltage and on-state voltage drop, and between on-state voltage drop and turn-off time. In this paper, the new structure is proposed to improve a trade-off between a breakdown voltage and on-state voltage drop. The proposed structure has a trench collector and this trench collector induces an accumulation layer at the bottom of an n-drift region during off-state. And this accumulation layer prevents expansion of depletion layer so that trapezoidal electric field distribution is performed in the n-drift region. As a result of this, breakdown voltage is increased without increasing on-state voltage drop. The electrical characteristics of the proposed IGBT is analyzed and optimized by using representative device simulator, TSUPREM4 and MEDICI. After optimization, the electrical characteristics of the proposed IGBT is compared with NPT IGBT which have the same device thickness. As a result of this, it can be confirmed that the proposed structure increases the breakdown voltage of 800 V than that of the conventional NPT IGBT without increasing the on-state voltage drop.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.22-23
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• 2008

The conventional IGBT has two problems to make the device taking high performance. The one is high on state voltage drop associated with JFET region, the other is low breakdown voltage associated with concentrating the electric field on the junction of between p base and n drift. This paper is about the structure to effectively improve both the lower on state voltage drop and the higher breakdown voltage than the conventional IGBT. For the fabrication of the circular trench IGBT with the circular trench layer, it is necessary to perform the only one wet oxidation step for the circular trench layer. Analysis on both the on state voltage drop and the Breakdown voltage show the improved values compared to the conventional IGBT structure. Because the circular trench layer disperses electric field from p base and n drift junction to circular trench, the breakdown voltage increase. The on state voltage drop decrease due to reduction of JFET region and direction change of current path which pass through reversed layer channel.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1101-1117
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• 2006

In the present article, recent progress of spray-wall interaction research has been reviewed. Studies on the spray-wall interaction phenomena can be categorized mainly into three groups: experiments on single drop impact and spray (multiple-drop) impingement, and development of comprehensive models. The criteria of wall-impingement regimes (i.e., stick, rebound, spread, splash, boiling induced breakup, breakup, and rebound with breakup) and the post-impingement characteristics (mostly for splash and rebound) are the main subjects of the single-drop impingement studies. Experimental studies on spray-wall impingement phenomena cover examination of the outline shape and internal structure of a spray after the wall impact. Various prediction models for the spray-wall impingement phenomena have been developed based on the experiments on the single drop impact and the spray impingement. In the present article, details on the wall-impingement criteria and post-impingement characteristics of single drops, external and internal structures of the spray after the wall impact, and their prediction models are reviewed.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.478-481
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• 1991

This paper discusses the principle and structure of instantaneous voltage drop compensator, which protects damage from instantaneous voltage drop in systems such as computer, variable speed drive, high voltage discharge-lamp, magnet switch. When instantaneous voltage drop occurs, control circuits detect it, then produce output voltage the same as normal condition voltage. Instantaneous voltage drop compensator has condenser bank as energy storage component, so system can be made small, light weight compared with UPS. In normal state, utility source transfers power, and in instantaneous voltage drop state, the energy of condenser bank transfers power through inverter, so high efficiency, compact, and especially low cost system can be manufactured.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.250-254
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• 2011

Main role of landing gear is to absorb the energy which is generated by aircraft lanidng and ground maneuvering. Generally, in order to absorb the impact energy during landing, oleo-pneumatic type shock absorber is used for aircraft landing gear. Oleo-pneumatic type shock absorber has a good energy absorbing efficiency and is light in weight because its structure is relatively simple. For the landing gear development, it is necessary to conduct drop test in order to verify shock absorbing performance. In the drop test, first, gas spring curve verification tests are conducted. Then, limit and reserve energy absorption drop tests are performed based on the STANAG 4671. The drop tests results with performance analysis results are presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.12 s.105
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• pp.1370-1377
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• 2005

The bottom structure of an instrumented capsule is a part which is joined at the receptacle of the flow tube in the reactor in-core. A geometrical change of the bottom structure has an effect on the pressure drop and the vibration of the capsule. The out-pile test to evaluate the structural integrity of the material capsule called 04M-17U was performed by using a single channel and a half core test loop. From the pressure drop test, the optimized diameter of the cone shape's bottom structure which satisfies HANARO's flow requirement (19.6 kg/s) is 71 mm. The maximum displacement of the capsule measured at the half core test loop is lower than 1.0 mm. From the analysis results, it is found that the test hole will not be interfered with near the flow tubes because its displacement due to the cooling water is very small at 0.072 mm. The fundamental frequency of the capsule under water is 9.64 Hz. It is expected that the resonance between the capsule and the fluid flow due to the cooling water in HANARO's in-core will not occur. Also, the new bottom structure of a solid cone shape with 71 mm in diameter will be applicable to the material and special capsules in the future.