• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.861-864
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• 2006

In this paper conduction phenomena have been considered for nano structure double gate MOSFET, using the analytical model. The Possion equation is used to obtain the analytical model. The conduction mechanisms to have an influence on current conduction are thermionic emission and tunneling current, and subthreshold swings of this paper is compared with those of two dimensional simulation to verify this model. The deviation of current path and the influence of current path on subthreshold swing have been considered according to the dimensional parameters of double gate MOSFET, i.e. gate length, gateoxide thickness, channel thickness. The optimum channel doping concentration is determined as the deviation of conduction path is considered according to channel doping concentration.

• Journal of Power Electronics
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• v.11 no.3
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• pp.369-374
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• 2011

Usually, a LPF (low pass filter) is used in the feedback loop of a SRF (synchronous reference frame) - PLL (phase locked loop) system because the measured grid voltage contains harmonic distortions and sensor noises. In this paper, it is shown that the cut-off frequency of the LPF should be designed to suppress the harmonic ripples contained in the measured voltage. Also, a new design method for the loop gain of the PI-type controller in the SRF-PLL is proposed with consideration of the dynamics of the LPF. As a result, a better transient response can be obtained with the proposed design method. The LPF frequency and the PI controller gain are designed in coordination according to the steady state and dynamic performance requirements. Furthermore, in the proposed method, the controller gain and the LPF cut-off frequency are changed from their normal value to a transient value when a voltage disturbance is detected. This paper shows the feasibility and usefulness of the proposed methods through the computer simulations and experimental results.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.111-111
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• 2010

최근 전자 소자의 집적기술은 기존의 2차원에서 System on package (SOP) 개념에 기반을 둔 3차원 집적 기술로 발전 되어가고 있다. 소자의 3차원 실장을 실현시키는 과정에서 세라믹의 여러 유용성이 언급되어져 왔지만, 취성이 매우 크다는 등의 단점이 있었다. 이러한 이유로 연성을 가지는 폴리머와 세라믹을 합성한 복합체 기판에 대하여 많은 연구가 되고 있다. 그러나 세라믹 제작을 위해서는 높은 공정온도가 요구되고 있고 이러한 높은 공정상에서의 온도는 3차원 실장에 있어서 문제점이 되고 있다. 이러한 문제점을 극복하기 위하여 상온에서 치밀한 세라믹 후막을 제작할 수 있는 공정인 Aerosol Deposition Method (ADM)방법으로 세라믹-폴리머 후막의 제조를 시도하였다. 일반적으로 ADM은 수백 나노의 출발 파우더를 사용하여 치밀한 세라믹 막을 형성하는데 사용된다. 본 연구에서는 ADM으로 100 nm미만의 나노 세라믹 파우더를 사용하여 다공성의 세라믹 후막을 제조한 후 resin을 함침시키는 방법으로 세라믹-폴리머 후막의 제조를 시도하였다. 그 결과 운송가스, aerosol 농도 등의 공정조건을 변화시켜 다공성의 $Al_2O_3$ 후막을 제조하였고, 이 다공성 후막은 반투명의 특성을 보이며 고충전율로 형성되었다. 이렇게 제조된 나노 다공성 $Al_2O_3$ 후막에 cyanate ester resin을 함침시키는 방법을 사용하여 $Al_2O_3$-cyanate ester 복합체 후막을 제조하였으며, 이의 비유전율 및 품질계수는 각각 1 MHz에서 6.7, 1000으로 우수한 유전특성을 보임이 확인되었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.110-110
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• 2013

진공중을 전파하는 번치된 전자빔은 공간전하 효과로 빔이 퍼지게 된다. 본 연구의 중점 내용은 S-band 고주파 전자 가속기를 개발하는데 있다. 전자 가속기란 전자를 수 MeV의 에너지로 가속시키는 장치이다. 가속기의 중요한 3대 요소는 진공, 전자석, RF이다. 본 연구에서는 가속기에서 중요한 좋은 진공상태에서 좋은 전자석을 사용하여 실험하였다. S-band(2852~2860 MHz) 고주파 전자가속기의 캐비티내 전기장의 효과로 가속되는 번치된 전자빔의 집속 및 스티어링 효과를 얻기 위하여 스티어링 및 솔레노이드 전자석을 제작하여 실험에 사용하였고, 실제 빔을 인출 후 포커싱 및 스티어링 효과를 관찰 할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.109-109
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• 2013

고주파 가속기의 전자선원의 설계 및 제작검증을 위한 hot-firing station을 설계하였다. 본 장치는 전자총의 빔 사이즈, 빔 전류 등을 측정할 수 있는 기기로 전원장치부, 고진공 챔버, 측정장치부 등 크게 세 부분으로 이루어져 있다. 특히 전원장치는 이중에너지 모드를 구현할 수 있도록 에너지의 크기가 다른 두개의 전자총 펄스를 생산해 낼 수 있도록 설계되었다. 고진공 챔버는 고전압 절연체를 이용하여 제작되었으며, 스크롤(건식) 펌프 와 터보 분자펌프를 이용하여 $10^{-7}$ torr 저/고진공 배기를 수행한 뒤, 이온 펌프를 이용하여 $10^{-8}$ torr까지 초고진공 배기를 수행할 수 있도록 설계하였다. 전자총으로 부터 나오는 전자들의 특성을 분석하기 위하여 패러데이 컵과 YAG 스크린을 설치하였다. 패러데이 컵은 전자빔의 인출 파형및 빔 전류를 측정하고, YAG 스크린은 CCD 카메라와 컴퓨터를 이용하여 전자빔의 균일도를 측정하여 정보를 얻도록 한다. 진공 쳄버의 최대 진공배기는 $10^{-9}$ torr이다.

• Korean Journal of Materials Research
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• v.3 no.3
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• pp.276-281
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• 1993

In order to study the sintering kinetics of the ternery system, U-Ce-O, its shrinkage rate with time and temperature at the Ar atmoshpere were measured by using the dilatometer. At the sintering kinetics of U-Ce-O, sintering rate curve revealed bimodal and the first extreme point at bimodal curve was affected by the $UO_2$ the second one was due to the $CeO_2$. The sintering of $(U, Ce)O_2$ was delayed as increasing the $CeO_2$. At the same lOwt. % content, the highest sintering rate was observed at the $(U, Ce)O_2$ sample ball-milled for 4 hours.

• Korean Journal of Materials Research
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• v.7 no.3
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• pp.229-233
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• 1997

Estimation of thermal stability for diglycidy1 ether of bisphenol A(DGEMA)/4, 4'-methylene dianiline (MDA)/pheny1 glycidy1 ether(PGE)-acetamide(AcAm)/carboxy1-terminated acrylonitrile butadiene copolymer (CTBN) system was studied by thermogravimetry(TG) analysis. To get activation energy for thermal degradation, Freeman & Carroll, Kissinger, and Flynn & Wall expressions were used. The activation energy of Freeman & Wall expression was 112.9kj/mol, that of Kissinger expression was 151.5 kj/mol and that of Flynn & Wall was 168.3kj/mol.

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.823-827
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• 1994

The mechanical properties of diglycidyl ether of bisphenol A(DGEBA)/4,4- methylene dianiline(MDA) system with the addition of malononitrile(MN) and hydroquinone(HQ) were investigated. The specimens which were prepared by curing at $150^{\circ}C$ for lhr after curing at $80^{\circ}C$ for 1.5hr were tested. The effects of MN as a chain extender and HQ, a reaction accelerator on the mechanical properties were investigated. With the increase of MN and HQ contents, impact property improved significantly but tensile property decreased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.2
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• pp.238-244
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• 2002

A 5-valve(intake 3-valve) engine has been developed to increase engine performance. These engines have a high power caused by the decrease of inertia mass of an intake valve and the increase of intake effective area. In this study, in-cylinder flow patterns were visualized with laser sheet method and velocity profiles at near intake valves were inspected by using a two-color PIV. In addition, steady flow tests were performed to quantify tumble ratio of flow-fields generated by a tumble control valve(TCV). Experimental results of steady flow test show that the cure of tumble ratio in intake 3-valve engine farmed as a S shape with valve lift changes. This tendency is different from the one in intake 2-valve engine. Using laser sheet method and two color PIV method, we can find that the intake flow through upper valve increases and the velocity gradient also slightly increases as valve lift increases. From this study, the in-cylinder flow characteristics around intake valves were made clearly.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.650-658
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• 1997

Analysis and control of intake charge motion such as swirl and tumble are very important factors in improving the gasoline engine performance. In this paper, single-frame PTV (particle tracking velocimetry) is used to investigate intake tumble patterns in a steady flow test rig of gasoline engine with dual-intake-valve and pent-roof combustion chamber. Intake tumble pattern is quantified in accordance with blockage ratio of TIV (tumble intensifying valve) with single- frame PTv.The view of the instantaneous 2-D velocity field gives a realistic understanding of in-cylinder flow field. Thus it is confirmed that PTV is a effective tool in engine design. In conventional port, two tumble structures appear clearly, and the larger one is observed under the exhaust valve side and the smaller is right below the intake valve side. The larger vorticity is observed in TIV port, thus it is concluded that TIV have an effect on intensified tumble motion in cylinder flow.