• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.131-131
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• 2009

Silicon Carbide (SiC) is a material with a wide bandgap (3.26eV), a high critical electric field (~2.3MV/cm), a and a high bulk electron mobility ($\sim900cm^2/Vs$). These electronic properties allow high breakdown voltage, high-speed switching capability, and high temperature operation compared to Si devices. Although various SiC DMOSFET structures have been reported so far for optimizing performances, the effect of channel dimension on the switching performance of SiC DMOSFETs has not been extensively examined. This paper studies different channel dimensons ($L_{CH}$ : $0.5{\mu}m$, $1\;{\mu}m$, $1.5\;{\mu}m$) and their effect on the the device transient characteristics. The key design parameters for SiC DMOSFETs have been optimized and a physics-based two-dimensional (2-D) mixed device and circuit simulator by Silvaco Inc. has been used to understand the relationship. with the switching characteristics. To investigate transient characteristic of the device, mixed-mode simulation has been performed, where the solution of the basic transport equations for the 2-D device structures is directly embedded into the solution procedure for the circuit equations. We observe an increase in the turn-on and turn-off time with increasing the channel length. The switching time in 4H-SiC DMOSFETs have been found to be seriously affected by the various intrinsic parasitic components, such as gate-source capacitance and channel resistance. The intrinsic parasitic components relate to the delay time required for the carrier transit from source to drain. Therefore, improvement of switching speed in 4H-SiC DMOSFETs is essential to reduce the gate-source capacitance and channel resistance.

• 수산해양기술연구
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• 제35권4호
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• pp.343-352
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• 1999

Because stow net being used in now is doing throwing net and hauling net through a ship's side, the work is very complicated and the fishing boat needs many seamen and it could cause a loss of lives and ship in stormy weather. We are now using small mesh size 36~500mm and it even catches young fish, so we call it the fishing gear of resource reduction type.Therefore we must make manpower reduction in automatic operation, safe operation of throwing net and hauling net in the stern and the stern-typed stow net of resource management using large mesh. And we performed three-typed model tests to examine the fishing gear. The obtained results are as follows;1. The fishing gear being used in the ship's side type stow net has inappropriate standard and arrangement of the net, resistance increase of the fishing gear and frequent breakdown of the net.2. To supplement the fault of A-typed stow net, we schemed fishing gear developed as both B-type(12-seamed net) and C-types(8-seamed net) of the stern-typed stow net. 3. In model tests, C-typed model net(mesh size 40~1,600mm) was proved good fishing gear because the resistance in accordance with the flowing speed was comparatively small and it's mouth area was broad. 4. A-typed stow net had the spreading device attached to side panel of the net, but the stern-typed stow net had the spreading device consisted of 4 lines far behind about 6m from side panel of the net mouth. In the flowing speed 2knot, the spreading condition of fishing gear was proved batter than the former.

• 대한기계학회논문집A
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• 제38권8호
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• pp.911-916
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• 2014

레저보트산업은 미래형 고부가가치 산업으로 최근 국내에서는 한국형 고속레저낚시보트에 대한 연구가 수행되었다. 본 논문에서는 고속레저낚시보트의 대량생산을 위한 기초연구로서 제품구성모델 기반의 건조공수 추정 연구를 수행하였다. 이를 위해 레저보트의 건조공정을 분석하고 범용 작업분류체계를 적용하였으며, 업체 설문조사를 통해 계층분석법 기반의 레저보트 건조공수 비례계수를 도출하였다. 또한 실적선의 공수를 기반으로 비례계수를 이용한 개발선 후보들의 정량적인 공수추정을 수행하였으며, 그 결과 실적선 공수 대비 17% 감소된 쌍동형 개발선을 최종 선정할 수 있었다. 이는 개발된 레저보트의 설계가 실제 건조단계에서 가격경쟁력을 갖출 수 있는 양산가능수준의 제품임을 의미한다.

• 한국재료학회지
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• 제25권3호
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• pp.138-143
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• 2015

Aluminum nitride, a compound semiconductor, has a Wurtzite structure; good material properties such as high thermal conductivity, great electric conductivity, high dielectric breakdown strength, a wide energy band gap (6.2eV), a fast elastic wave speed; and excellent in thermal and chemical stability. Furthermore, the thermal expansion coefficient of the aluminum nitride is similar to those of Si and GaAs. Due to these characteristics, aluminum nitride can be applied to electric packaging components, dielectric materials, SAW (surface acoustic wave) devices, and photoelectric devices. In this study, we surveyed the crystallization and preferred orientation of AlN thin films with an X-ray diffractometer. To fabricate the AlN thin film, we used the magnetron sputtering method with $N_2$, NH3 and Ar. According to an increase in the partial pressures of $N_2$ and $NH_3$, Al was nitrified and deposited onto a substrate in a molecular form. When AlN was fabricated with $N_2$, it showed a c-axis orientation and tended toward a high orientation with an increase in the temperature. On the other hand, when AlN was fabricated with $NH_3$, it showed a-axis orientation. This result is coincident with the proposed mechanism. We fabricated AlN thin films with an a-axis orientation by controlling the sputtering electric power, $NH_3$ pressure, deposition speed, and substrate temperature. According to the proposed mechanism, we also fabricated AlN thin films which demonstrated high a-axis and c-axis orientations.

• 한국분무공학회지
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• 제27권2호
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• pp.84-93
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• 2022

To implement carbon-neutrality in transportation sectors until 2050, hydrogen is considered a promising fuel for internal combustion engines because hydrogen does not contain carbon itself. Although hydrogen does not emit CO₂ emission from its combustion process, the low energy density in a volume unit hinders the adoption of hydrogen. Therefore, the understanding of hydrogen jet behavior and measurement of equivalence ratio must be conducted to completely implement the high-pressure hydrogen direct injection. The main objective of this research is feasibility test of hydrogen local equivalence ratio measurement by laser-induced breakdown spectroscopy (LIBs). To visualize the macroscopic structure of hydrogen jet, high-speed schlieren imaging was conducted. Moreover, LIBs has been adopted to validate the feasibility of hydrogen local equivalence ratio measurement. The hydrogen injection pressure was varied from 4 MPa to 8 MPa and injected in a constant volume chamber where the ambient pressure was 0.5 MPa. The increased injection pressure extends the vertical penetration of hydrogen jet. Due to the higher momentum supply when the injection pressure is high, the hydrogen has easily diffused in all directions. As the laser trigger timing has delayed, the low hydrogen atomic emission was detected due to the longer mixture formation time. Based on equivalence ratio measurement results, LIBs could be applied as a methodology for hydrogen local equivalence ratio measurement.

• 전기학회논문지
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• 제67권4호
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• pp.569-577
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• 2018

In this paper, with the aid of information which is included within data, preprocessing algorithm-based black plastic classifier is designed. The slope and area of spectrum obtained by using laser induced breakdown spectroscopy(LIBS) are analyzed for each material and its ensuing information is applied as the input data of the proposed classifier. The slope is represented by the rate of change of wavelength and intensity. Also, the area is calculated by the wavelength of the spectrum peak where the material property of chemical elements such as carbon and hydrogen appears. Using informations such as slope and area, input data of the proposed classifier is constructed. In the preprocessing part of the classifier, Principal Component Analysis(PCA) and fuzzy transform are used for dimensional reduction from high dimensional input variables to low dimensional input variables. Characteristic analysis of the materials as well as the processing speed of the classifier is improved. In the condition part, FCM clustering is applied and linear function is used as connection weight in the conclusion part. By means of Particle Swarm Optimization(PSO), parameters such as the number of clusters, fuzzification coefficient and the number of input variables are optimized. To demonstrate the superiority of classification performance, classification rate is compared by using WEKA 3.8 data mining software which contains various classifiers such as Naivebayes, SVM and Multilayer perceptron.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1783-1786
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• 2016

The paper investigates the insulation properties of the supercritical $CO_2$ ($SCCO_2$) fluid as an insulating medium for electrical apparatuses. The insulating material is crucial for electrical apparatuses and $SF_6$ gas has been widely used for high power electrical apparatuses. There have been many research efforts to develop substituents for $SF_6$ gas because of high global warming potential. We obtained above 350 kV/mm insulation strength with 12.0 MPa $SCCO_2$. The positive and negative IEC standard pulses are applied between two 10 mm diameter spherical electrodes. The insulation strength of $SCCO_2$ is at least 2.5 times higher than that of $CO_2$ gas at 6.0MPa. The insulation strength of $SCCO_2$ fluid is about 10 times higher than that of $SF_6$ at 0.5MPa which is the ordinary operating pressure of electrical switchgears. Using the result, we expect that the time for switching and dielectric recovery could be reduced using $SCCO_2$ fluid as an insulating medium.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.115-115
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• 2009

Current sensing in power semiconductors involves sensing of over-current in order to protect the device from harsh conditions. This technique is one of the most important functions in stabilizing power semiconductor device modules. The Power MOSFET is very efficient method with low power consumption, fast sensing speed and accuracy. In this paper, we have analyzed the characteristics of proposed sense FET and optimized its electrical characteristics to apply conventional 40 V power MOSFET by numerical and simulation analysis. The proposed sense FET has the n-drift doping concentration $1.5\times10^{14}\;cm^{-3}$, size of $600\;{\mu}m^2$ with $4.5\;{\Omega}$, and off-state leakage current below $50\;{\mu}A$. We offer the layout of the proposed Power MOSFET to process actually. The offerd design and optimization methods are meaningful, which the methods can be applied to the power devices having various breakdown voltages for protection.

• 한국컴퓨터산업학회논문지
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• 제7권5호
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• pp.487-494
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• 2006

초고속 통신망과 인터넷정보가전기기의 개발로 인해 사이버 아파트를 중심으로 홈네트워크 환경을 빠르게 갖추게 되었다. 홈 네트워크 환경은 가정내의 수많은 가전기기들이 네트워크로 연결되어 윤택한 가정 내의 환경을 제공해 준다. 그러므로, 최근 네트워크로 연결된 인터넷 정보가전의 등장으로 인하여 해킹, 오동작 및 고장과 홈 오토메이션에서의 방범, 화재, 침입 등을 통합 관리하는 서비스 요구가 증대되고 있다. 본 논문에서는 홈 네트워크 정보가전기기 환경에서의 통합위기관리 서비스 모델을 설계 제안한다. 즉, 정보가전 위기관리 서비스를 분류하고 XML로 위기관리 메시지를 정의한다. 위기상황이 발생된 메시지는 무선단말기인 PDA나 휴대폰 또는 관련기관에 통보되어 처리된다.

• 한국전기전자재료학회논문지
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• 제23권6호
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• pp.436-439
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• 2010

SiC power device possesses attractive features, such as high breakdown voltage, high-speed switching capability, and high temperature operation. In general, device design has a significant effect on the switching characteristics. In this work, we report the effect of the interface states ($Q_f$) on the transient characteristics of SiC DMOSFETs. The key design parameters for SiC DMOSFETs have been optimized by using a physics-based two-dimensional (2-D) mixed device and circuit simulator by Silvaco Inc. When the $SiO_2$/SiC interface charge decreases, power losses and switching time also decrease, primarily due to the lowered channel mobilities. High density interface states can result in increased carrier trapping, or more recombination centers or scattering sites. Therefore, the quality of $SiO_2$/SiC interfaces has a important effect on both the static and transient properties of SiC MOSFET devices.