• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.107.1-107.1
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• 2014

We have developed and commercialize a time-of-flight - medium energy ion scattering spectrometry (TOF-MEIS) system (model MEIS-K120). MEIS-K120 adapted a large solid acceptance angle detector that results in high collection efficiency, minimized ion beam damage while maintaining a similar energy resolution. In addition, TOF analyzer regards neutrals same to ions which removes the ion neutralization problems in absolute quantitative analysis. A TOF-MEIS system achieves $7{\times}10^{-3}$ energy resolution by utilizing a pulsed ion beam with a pulse width 350 ps and a TOF delay-line-detector with a time resolution of about 85 ps. TOF-MEIS spectra were obtained using 100 keV $He^+$ ions with an ion beam diameter of $10{\mu}m$ with ion dose $1{\times}10^{16}$ in ordinary experimental condition. Among TOF-MEIS applications, we report the quantitative compositional profiling of 3~5 nm CdSe/ZnS QDs, As depth profile and substitutional As ratio of As implanted/annealed Si, Ionic Critical Dimension (CD) for FinFET, Direct Recoil (DR) analysis of hydrogen in diamond like carbon (DLC) and InxGayZnzOn on glass substrate.

• 한국압력기기공학회 논문집
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• 제11권2호
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• pp.68-74
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• 2015

Time domain response analysis for vibro-impact nonlinear behavior of multi-span tube with loose supports was performed using commercial FEA code and user subroutine. Support geometry of multi-span tube with a finite gap is realistically modeled by analytical rigid surface. Model of hydrodynamic force is based on the Qusai-steady model which accounts for the inclined angle of relative flow velocity and time delay between flow force and resulting tube motion. During tube vibration from flow loading, impact and friction at the support location is simulated using commercial FEA code with master slave contact algorithm. Analysis results has reasonable agreement with those of references and test experience. Plan of further refinement of analysis model and future test verification is briefly introduced.

• 한국자동차공학회논문집
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• 제22권3호
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• pp.105-113
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• 2014

Spray and combustion process with waste cooking oil (WCO) biodiesel and commercial diesel were analyzed in an optically-accessible single-cylinder compression ignition diesel engine equipped with a high pressure common-rail injection system. Direct imaging method was applied to investigate spray and combustion characteristics. From the mie-scattering results, it was verified that WCO biodiesel had a longer injection delay compared to diesel. Spray tip penetration length of WCO biodiesel was longer and spray angle was narrower than those of diesel due to poor atomization characteristics. In terms of combustion, WCO biodiesel showed later start of combustion, while flame was vanished more rapidly. Analysis of flame luminosity showed that WCO biodiesel combustion had lower intensity and lasted for shorter duration.

• 한국통신학회논문지
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• 제25권1B호
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• pp.175-182
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• 2000

적외선을 이용한 수/발광 다이오드에 집적소자를 혼합한 Hybrid형 단거리 광무선 통신용 원칩모듈을 개발하였다. 발광다이오드는 850nm 의 적외선파장을 30$^{\circ}$지향각을 갖는 AlGaAs계 고속신호용으로서 전파지연이 60 ns 이며, PIN 포토다이오드는 Si계 반도체 수광소자로써 450-1050nm의 파장대에서 수광 흡수율이 양호하고 필터겸용 블록 에포시렌즈를 750nm 파장 저역대를 여과시켰다. 데이터 전송속도는 115.2 kbps이며 IrDA1.0 SIR 표준조건에서 동작이 양호함을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.841-846
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• 2000

The compression wave produced when a high-speed train enters a tunnel propagates along the tunnel ahead of the train. The micro pressure wave related to He compression wave is a special physics Phenomena created by high-speed train-tunnel interfaces. On this work, the method for reducing the micro pressure wave is to delay the gradient of the compression wave by using aerodynamic structures. The objective of this paper is to determine the optimum angle of the slanted portal using the moving model rig. According to the results of the present study, the maximum value of micro pressure wave is reduced by 19.2% fer the $45^{\circ}$ slanted portal installed at the entrance of the tunnel and reduced by 41.9% far the $45^{\circ}$ slanted portals at the entrance and exit of the tunnel. Also it is reduced by 34.6% for the $30^{\circ}$ slanted portals installed at the entrance and exit of the tunnel.

• 한국통신학회논문지
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• 제29권3A호
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• pp.233-239
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• 2004

공간 필터링 시스템은 시ㆍ공간 벡터 채널 특성에 의해 그 성능과 용량이 영향을 밭는다. 본 논문에서는 배열안테나를 이용하여 국내 대도시 환경에서 측정을 수행하고 측정된 데이터를 이용하여 대도시 환경에서의 시ㆍ공간 벡터 채널을 분석하였다. 분석 결과 국내와 같이 높은 건물이 많은 대도시 환경에서는 셀 안에 사용자가 균일하게 분포되어 있더라도 기지국에 수신되는 신호는 도로 방향이나 상가 방향에서 집중되어 수신되었으며, 사용자가 한 방향에서 다른 방향으로 점진적으로 이동할 때 수신되는 신호의 방향은 사용자의 이동에 의해 점진적으로 변하지 않고 한 방향에서 다른 방향으로 급격하게 점프되어 변함을 알 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.1124-1126
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• 1997

The Unified Power Flow Controller(UPFC) with a series inverter and a shunt inverter ia able to control all three line Parameters(voltage, impedance and phase angle) and so UPFC technology has the potential to enhance the implementation and broad application of the FACTS concept with improved Performance. In this Paper, the UPFC is applied in order to improve the power flow oscillation damping. The modal performance measure is minimized in order to determine the optimal parameters of UPFC controller for damping Power flow oscillations. The dynamics of the injected voltage of UPFC is represented as a first order delay element. The UPFC controller used here is of the PIO type and the input signal to the controller is the active power flow through the UPFC. The effect of UPFC application to the Power system are analyzed from the stand point of power system oscillation damping.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1280-1290
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• 2016

This paper presents an advanced estimation method for obtaining the probability density functions of a damage parameter for valve leakage detection in a reciprocating pump. The estimation method is based on a comparison of model data which are simulated by using a mathematical model, and experimental data which are measured on the inside and outside of the reciprocating pump in operation. The mathematical model, which is simplified and extended on the basis of previous models, describes not only the normal state of the pump, but also its abnormal state caused by valve leakage. The pressure in the cylinder is expressed as a function of the crankshaft angle, and an additional volume flow rate due to the valve leakage is quantified by a damage parameter in the mathematical model. The change in the cylinder pressure profiles due to the suction valve leakage is noticeable in the compression and expansion modes of the pump. The damage parameter value over 300 cycles is calculated in two ways, considering advance or delay in the opening and closing angles of the discharge valves. The probability density functions of the damage parameter are compared for diagnosis and prognosis on the basis of the probabilistic features of valve leakage.

• 전기학회논문지
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• 제64권3호
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• pp.445-450
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• 2015

In the moving target problem, the velocity information of the moving target is very important as well as the high accuracy position information. To solve this problem, active researches are being conducted recently with combine the Time Difference of Arrival (TDOA) and Frequency Delay of Arrival(FDOA) measurements. However, since the FDOA measurement is utilizing the Doppler effect due to the relative velocity between the target source and the receiver sensor, it may be difficult to use the FDOA measurement if the moving target speed is not sufficiently fast. In this paper, we propose a method for estimating the position and the velocities of the target by using only the TDOA measurements for the low speed moving target in the indoor environment with sensor network. First, the target position and heading angle are obtained from the estimated positions of two attached transmitters on the target. Then, the target angular and linear velocities are also estimated. In addtion, we apply the Instrumental Variable (IV) technique to compensate the estimation error of the estimated target velocity. In simulation, the performance of the proposed algorithm is verified.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.131-136
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• 2006

Commercial uses of GPS have been growing rapidly with applications for aircraft, ship, and land vehicle navigation as well as for surveying and time keeping. The next generation GPS and Japanese QZS (Quasi Zenith Satellite) will provide three different civil signals. Galileo will also provide several types of civil signals. The availability of the third civil frequency has obvious advantages to instantaneous carrier phase accuracy and ambiguity resolution for centimeter level measurements. This paper discusses the effects of additional new civil signals for the high accuracy positioning in urban areas based on simulation using practical raw data. As for constellation, only GPS and GPS+QZS are considered. For positioning, a short distance baseline is assumed in order to disregard atmosphere effects. In this simulation, mask angle and signal conditions were fixed and ambiguity success rates were compared between different triple frequency combination scenarios. The coefficient of reflection was set randomly from 0.05 to 0.5 and the multipath delay was also set randomly from 5-100 m. Visible satellites and signal strength were determined by raw data collected in Tokyo by car. These simulation results have confirmed that the availability of high accuracy positioning will increase in all scenarios if we use GPS+QZS with triple frequencies.