• 한국전자파학회논문지
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• 제29권7호
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• pp.566-569
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• 2018

철도 전차선 구조에 고주파 전력을 인가할 수 있는 전력선 커플러에 대해 분석하였다. 전차선 구조는 고압의 환경에서 보조전원을 공급하기가 어렵고, 먼 거리까지 전력을 전달하는 방법이 필요하다. 이를 위해 코어를 사용하지 않는 로고스키 코일에 공진을 활용하는 방법을 제안하였다. 조가선, 전차선, 드로퍼로 구성된 간이 전차선 구조를 제작하였고, 여러 사이즈의 커플러를 제작하여 조가선에 연결한 다음 일정 거리만큼 떨어진 두 커플러의 전달 특성을 비교하였다. 가장 성능이 좋은 커플러에 매칭 회로를 적용하여 측정한 결과, 2.5 m 거리에서 53 %의 전달 효율을 나타내었다. 제안하는 방법은 전차선과 같은 특수한 구조물에서 기존의 도선을 활용하여 보조전원을 인가할 수 있음을 보여준다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2913-2917
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• 2007

Turbocharger has been widely used in many passenger cars in application with diesel engines because of high power and fuel efficiency. However, flow-induced noise (whoosh or hissing noise) which is generated within the compressor during its operation at marginal surge line can deteriorate noise characteristics. Hissing noise excitation was associated with the generation of turbulence within the turbocharger compressor and radiated through the transmission path in turbocharger system. In this study, a sharp-edged reactive-type muffler was devised and installed in the transmission path to reduce the hissing noise. Acoustic and fluid dynamic characteristics for the muffler were investigated which is related to the unsteadiness of turbulence and pressure in turbocharger system. A transfer matrix method was used to analyze the transmission loss of the muffler. Simple expansion muffler with extended tube of the reactive type is proposed for the reduction of high frequency component noise. Turbulence computation was carried out by a standard ${\kappa}-{\varepsilon}$ model. An optimal design condition of the muffler was obtained by extensive acoustic and fluid dynamic analysis on the engine dynamometer with anechoic chamber. A significant reduction of the hissing noise was achieved at the optimal design of the muffler as compared with the conventional turbocharger system.

• 대한기계학회논문집B
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• 제33권2호
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• pp.79-84
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• 2009

Turbocharger has been widely used in many passenger cars in application with diesel engines because of high power and fuel efficiency. However, flow-induced noise (whoosh or hissing noise) which is generated within a compressor during its operation at marginal surge line can deteriorate noise characteristics. Hissing noise excitation is associated with the generation of turbulence within the turbocharger compressor and radiated through the transmission path in a turbocharger system. In this study, a expansion muffler with lids is devised and installed in the transmission path to reduce the hissing noise. Acoustic and fluid dynamic characteristics for the muffler are investigated which are related to the unsteadiness of turbulence and pressure in the turbocharger system. A transfer matrix method is used to analyze the transmission loss of the muffler. A simple expansion muffler with lids is proposed for the reduction of high frequency component noise. Turbulence simulation is carried out by a standard k - ${\varepsilon}$ model. An optimal design condition of the muffler is obtained by extensive acoustic and fluid dynamic analysis on the engine dynamometer with anechoic chamber. A significant reduction of the hissing noise is achieved at the optimal design of the muffler as compared with the conventional muffler.

• 한국산학기술학회논문지
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• 제18권12호
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• pp.762-767
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• 2017

본 논문은 전기자동차의 충전부하 이동성에 의한 전력시스템 선로에서의 전송전력에 대한 해석과 개선에 대한 내용을 제시하였다. 전기자동차는 화석연료의 고갈과 환경보호의 중요성이라는 측면에서 사용범위가 크게 늘어나고 있으며, 가까운 미래에 가솔린 연료를 사용하는 운송수단을 대체할 것으로 예상되고 있다. 기존의 예측된 고정 부하량에 기초한 전력시스템에서 전기자동차의 이동성 충전부하는 특정 지역에서 이동성 충전부하의 증가로 인한 전송선로에서의 전송전력 집중과 과부하의 문제를 발생시킨다. 이러한 현상의 해석을 위해 New England 시험계통을 부하특성을 기반으로 4개의 지역으로 분할하여 전기자동차 충전부하의 이동을 고려한 예상 시나리오를 가정하였다. 예상 시나리오에서는 표준이 되는 전기자동차의 충전용량을 고려하여 지역단위의 부하량을 최대 31%까지 증가하면서 선로에서의 전송전력 집중과 과부하 현상을 해석하였다. 이러한 선로에서의 과부하 문제에 대한 해결책으로 TCSC를 과부하가 발생한 선로에 직렬 연결하여 선로의 전송전력을 선로제한값 보다 작은 부하율 100% 이내의 값으로 직접 제어할 수 있도록 하였다. 시뮬레이션 결과로부터 전력시스템에 몇 개의 TCSC를 적용함으로써 전기자동차의 이동성 부하 충전에 의한 선로에서의 전송전력 문제를 효과적으로 그리고 경제적으로 해결할 수 있음을 보였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.579-587
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• 2008

Promotion of the line no.2 in Seoul Metro was changing from the existing signaling facilities for ATS(Automatic Train Stop) vehicles to the up-to-date signaling facilities for ATO(Automatic Train Operation). But, in consequence of conducting a trial run after being equipped with the ATO signaling facilities, the matter related to mix-operation with the existing ATS signaling facilities appeared. The operation of the existing ATS signaling system in combination with the ATO signaling system has made improper working related to frequency recognition of the ATS On-board Computerized Equipment. This obstructs operation of a working ATS vehicle. That is, as barring operation of an ATS vehicle that should proceed, it may make the proceeding ATS vehicle stop suddenly and after all, it will cause safety concerns. In this paper, we designed a wayside track occupancy detector that previously prevents improper working related to frequency recognition of the ATS On-board Computerized Equipment by gripping classification and working processes of operating trains throughout transmission of local signaling information from the existing facilities, which does not need to change or replace the existing signaling facilities. Furthermore, we described general characteristics of the wayside track occupancy detector and modeled the IFC(InterFace Contrivance) device and the logical circuit recognizing signal information. Then, we made an application program of PLC(programmable Logic Computer) based on the stated model. We, in relation to data transfer method, used the frame in TCP/IP transfer mode as the standard, and we demonstrated that ATO transmission frequency is intercepted.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권10호
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• pp.495-499
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• 2004

Characteristics of ohmic Ni/Si/Ni contacts to n-type 4H-SiC are investigated systematically. The ohmic contacts were formed by annealing Ni/Si/Ni sputtered sequentially The annealings were performed at 950℃ using RTP in vacuum ambient and N₂ ambient, respectively. The specific contact resistivity(p/sub c/), sheet resistance(R/sub s/), contact resistance (R/sub c/) transfer length(L/sub T/) were calculated from resistance(R/sub T/) versus contact spacing(d) measurements obtained from TLM(transmission line method) structure. While the resulting measurement values of sample annealed at vacuum ambient were p/sub c/ = 3.8×10/sup -5/Ω㎠, R/sub c/ = 4.9 Ω and R/sub T/ = 9.8 Ω, those of sample annealed at N₂ ambient were p/sub c/ = 2.29×10/sup -4/Ω㎠, R/sub c/ = 12.9 Ω and R/sub T/ = 25.8 Ω. The physical properties of contacts were examined using XRD 3nd AES. The results showed that nickel silicide was formed on SiC and Ni was migrated into SiC. This result indicates that Ni/Si/Ni ohmic contact would be useful in high performance electronic devices.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.96-98
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• 1999

유기전계발광소자(OELD)의 성능 향상을 위한 많은 연구가 진행되고 있지만 아직까지 금속전극과 유기발 광층 사이의 접촉저항(Contact Resistance)에 관한 연구는 거의 보고되지 않고 있다. Ohmic 접합에서 접촉 저항은 효율적이고 신뢰성 있는 소자제작에 있어서 간과되어서는 안될 매우 중요한 부분이다. 본 연구에서는 금속전극과 유기발광충 사이의 접촉저항에 관해서 논의하고자 한다. 본 연구에서 제작된 샘플은 금속전극으로 Ag, 유기발광재료로서 Alq$_3$를 사용하였으며, Alq3의 두께를 100 $\AA$에서 500 $\AA$까지 각각 다르게 하여 서로 다른 두께의 유기발광층을 가지는 샘플을 제작하였다. 금속전극의 매트릭스 구조에 의해 형성된 적선의 크기는 3 mm x 2 mm이며, 제작된 샘플의 접촉비저항은 TLM(Transmission Line Measurement) 방법을 이용하여 구하였다. Planar한 TLM model로부터 새로운 vertical model을 유추하였으며, 이를 근거로 접촉저항 및 transfer length 등을 계산하였다. 상온에서 측정된 전체 저항값은 유기발광층의 두께가 증가함 에 따라 증가하는 경향을 나타냈으며, 이 때 계산된 접촉비저항은 1.49$\times$$10^1$ $\Omega$-$\textrm{cm}^2$ 이다. 접촉저항은 전극 사이의 거리의 증가에 따라 증가하지만, 측정시간의 thermal budget의 영향으로 상대적으로 전체저항이 감 소하였으나, 저항감소분의 포화에 따라서, 거리에 비례하여 다시 저항이 증가하였다.

• 수산해양기술연구
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• 제17권1호
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• pp.29-34
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• 1981

More recently, unsteady flow in small-diameter pipes plays a major role in liquid propellantrocket systems, hydraulic and pneumatic control system, and elsewhere. And it has shown that line dynamics can have a marked effect on the hydraulic system characteristics. In this paper, transfer function of hydraulic lines with an accumulator and an outlet orifice is' developed and compared with experimental data from frequency response tests at various airvolume(V.) and the location of accumulator(ld1t), so that their performance may be correctly and easily predicted and the design of the systems incorporating them improved. The obtained results are as follows: 1. The dynamic response of hydraulic lines may be analyzed more accurately by use of the viscous term(22) in unsteady laminar flow. 2. There was good agreement between the theoretical and experimental results of this investigation, and hydraulic systems with liines included an accumulator can be analyzed more accurately by use of the pressure transfer function given by eq. (16). 3. For the mitigation of surge in hydraulic lines, it is more effective that the location ofaccumulator is close to the pipe outlet side. 4. According to the gas volume of accumulator is increased(the sealing pressure is close tomean line pressure), the damping effect of pressure wave is improved.

• 한국공작기계학회논문집
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• 제11권6호
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• pp.75-82
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• 2002

Design for a quiet operation of fluid power system requires the understanding of noise and vibration characteristics of the system. It's not easy to analyze noise problem in hydraulic cylinder used in typical actuator Because they've got complex fluid dynamics. One of the fundamental problems associated with the hydraulic system is the pulsating flow in pipe lines, which can be tackled by the analysis under simplifying assumptions. The present study focuses on theoretic analysis and experimental study on the dynamics of laminar pulsating flow in a circular pipe. We analyze the propagation characteristics of the pressure pulse within a hydraulic pipe line taking into account the pulsating flow frequency variation. We also measure instantaneous pressure pulses within pipe line to identify the transfer functions. We conduct series of experiments to investigate the propagation characteristics of pressure pulse for various pressure of pulsating flow. The working fluid of the present study is ISO VG46 and the temperature ranges from 20 to $60^{\circ}$ with normal pressure at 4000kPa. The flow rate is measured by using an ultrasonic flow meter. Pressures at fixed upstream and downstream positions are measured concurrently. The electric signals of the pressure sensor are stored and analyzed using a system analyzer(PKE 983 series). The frequency is varied in the range of 10~500Hz. The Reynolds number is kept below 2,000. In the present study, boundary condition was varied by installing a surge tank and an orifice at the end of pipe. Experimental and theoretical results were compared each other under various boundary conditions.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2008년도 한국우주과학회보 제17권2호
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• pp.27.3-28
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• 2008

In this study, we report a new Monte Carlo ray tracing technique for estimating GOCI (Geostationary Ocean Color Instrument) radiative transfer characteristics and imaging performance simultaneously. First, a full scale GOCI optical model was constructed with measured characteristics at the component level and placed in the geostationary orbit. An optical model of approximated GOCI target area centered at the Korean penninsular was then built using the USGS coastal line data and representative land and sea surface reflectivity data. The light rays launched from a simulated sun model travel to the Earth surface, where they are reflected and scattered. Some of the light rays that are headed to the GOCI model in the orbit were selected and traced, as they have entered into the GOCI aperture. As they pass through each GOCI optical part, the ray path and intensity are adjusted according to the measured characteristics for reflection, transmission, refractive index and surface scattering. The ray-traced imaging and radiative transfer performance indicators confirm that the computer generated GOCI optical system with measured characteristics can be used for in-orbit operation simulation following the designed measurement sequence. The computational technique and its implications as a operation support tool are discussed.