• Nuclear Engineering and Technology
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• 제41권3호
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• pp.307-318
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• 2009

KAERI (Korea Atomic Energy Research Institute) has developed the GAMMA+ code for a thermo-fluid and safety analysis of a VHTR (Very High Temperature Gas-Cooled Reactor). A key safety issue of the VHTR design is to demonstrate its inherent safety features for an automatic reactor power trip and power stabilization during an anticipated transient without scram (ATWS) accident such as a loss of forced cooling by a trip of the helium circulator (LOFC) or a reactivity insertion by a control rod withdrawal (CRW). This paper intends to show the ATWS assessment capability of the GAMMA+ code which can simulate the reactor power response by solving the point-kinetic equations with six-group delayed neutrons, by considering the reactivity changes due to the effects of a core temperature variation, xenon transients, and reactivity insertions. The present benchmark calculations are performed by using the safety demonstration experiments of the 10 MW high temperature gas cooled-test module (HTR-10) in China. The calculation results of the power response transients and the solid core temperature behavior are compared with the experimental data of a LOFC ATWS test and two CRW ATWS tests by using a 1mk-control rod and a 5mk-control rod, respectively. The GAMMA+ code predicts the power response transients very well for the LOFC and CRW ATWS tests in HTR-10.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
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• pp.391-394
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• 2006

This paper presents soft switching zero voltage switching high frequency inverter for rare gas fluorescent lamp using dielectric-barrier discharge phenomenon. The simple high-frequency inverter can completely achieve stable zero voltage soft switching (ZVS) commutation for wide its output power regulation ranges and load variations under its constant high frequency pulse density modulation (PDM) scheme. Its transient and steady state operating principle is originally described and discussed for a constant high-frequency PDM control strategy under a stable ZVS operation commutation, together with its output effective power regulation characteristics-based on the high frequency PDM strategy. The experimental operating performances of this high frequency Inverter are illustrated as compared with computer simulation results and experimental ones. Its light dimming characteristics due to power regulation scheme are evaluated and discussed on the basis of simulation and experimental results. The feasible effectiveness of this high frequency inverter appliance implemented here is proven from the practical point of view.

• Journal of the Optical Society of Korea
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• 제2권2호
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• pp.50-53
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• 1998

We report on the spectroscopic investigation of optical-field ionized plasmas in the soft X-ray spectral region. The experiment was carried out by focusing pulses of the high-power Ti:Sapphire laser with an energy of ~ 40 mJ and time duration of ~30 fs into a gas jet of krypton, xenon, and argon from a pulsed nozzle. Strong soft X-ray emission on lines from ionic stages of $Kr^{7+} , Kr^{8+} , Xe^{7+} , Ar^{7+} , and Ar^{8+}$ is reported. The experimental result was found to be in good agreement with theoretical prediction.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 광주전남지부
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• pp.43-47
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• 2006

In this paper, parameters of electron temperature and density for the mercury-free lighting-source were measured to diagnosis and analyze in Xe based inductively coupled plasma (ICP). As results at several dependences of 20~100mTorr Xenon pressure, the brightness of discharge tube was higher (4,900 $cd/m^2$) than other conditions when Xe pressure was 20mTorr and RF power was 200W. In that case, the electron temperature and density were 3.58eV and $3.56{\times}10^{12}cm^2$, respectively. The key parameters of Xe based ICP depended on Xe pressure more than RF power that could be verified. A high electron temperature and low electron density with a suitable Xe pressure are indispensible parameters for Xe based ICP lighting-source.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.550-552
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• 2008

A small hall thruster with a thrust of about 10 mN and a specific impulse of about 1500 s is being developed with an intent to control or maintain the orbits of small satellites. The total mass, consumed electric power and efficiency of the thruster are approximately 10 kg, 300W and 30%, respectively. The thruster system consists of a hall thruster with a cylindrical cross section, a power processing unit and a Xenon(Xe) gas feed system. Laboratory examination of the thruster performance finds that the thruster meets the design specification.

• Current Optics and Photonics
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• 제4권6호
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• pp.466-471
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• 2020

We analyze the transverse nuclear magnetizations of 129Xe and 131Xe in a vapor cell containing natural Xe, 87Rb, and buffer gases. Th e Xe atoms are polarized th rough spin-exch ange optical pumping (SEOP) with Rb atoms under low-magnetic-field conditions. From the free-induction-decay (FID) signal, we measure the nuclear magnetization of the Xe atoms in the Xe-Rb vapor cell. Furthermore, we measure the dependence of the gyromagnetic ratio on the magnetization of 129Xe and 131Xe by examining the amplitude of the FID signal of each isotope, and we evaluate the relationship between the magnetic field gradient and transverse relaxation rate for both of the 129Xe and 131Xe isotopes.

• 한국전산유체공학회지
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• 제21권2호
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• pp.112-119
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• 2016

NEXTSat-1 is the next-generation small-size artificial satellite system planed by the Satellite Technology Research Center(SatTReC) in Korea Advanced Institute of Science and Technology(KAIST). For the control of attitude and transition of the orbit, the system has adopted a RHM(Resisto-jet Head Module), which has a very simple geometry with a reasonable efficiency. An axisymmetric model is devised with two coil-resistance heaters using xenon(Xe) gas, and the minimum required specific impulse is 60 seconds under the thrust more than 30 milli-Newton. To design the module, seven basic parameters should be decided: the nozzle shape, the power distribution of heater, the pressure drop of filter, the diameter of nozzle throat, the slant length and the angle of nozzle, and the size of reservoir, etc. After quasi one-dimensional analysis, a theoretical value of specific impulse is calculated, and the optima of parameters are found out from the baseline with a series of multi-physical numerical simulations based on the compressible Navier-Stokes equations for gas and the heat conduction energy equation for solid. A commercial code, COMSOL Multiphysics is used for the computation with a FEM (finite element method) based numerical scheme. The final values of design parameters indicate 5.8% better performance than those of baseline design after the verification with all the tuned parameters. The present method should be effective to reduce the time cost of trial and error in the development of RHM, the thruster of NEXTSat-1.

• 대한기계학회논문집B
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• 제40권5호
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• pp.283-288
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• 2016

목표 대상을 치명적이거나 파괴하지 않고 제압할 수 있는 무기를 비살상무기라 하며, 그중 고섬광발생장치는 강한 섬광으로 적의 광학센서를 무력화시키거나 시력을 일시적으로 마비시키는 무기체계이다. 본 연구에서는 고폭화약에 의한 충격파로 인해 발생한 플라즈마를 이용한 폭발형 고섬광발생장치의 형상에 대한 설계 방안을 도출하여 시료를 제작하고 광학센서를 사용한 기초시험을 수행하였다. 또한, 시험결과를 분석하여 설계 변수에 따른 고섬광 효과를 최대화시키는 방안을 도출하고자 한다. 충전가스 종류로 아르곤보다 제논의 경우 2배 가량 광도가 높게 나타났으며, 비활성가스가 광도에 미치는 영향을 알아보기 위한 비교로써 공기보다 제논의 경우 4배 가량 광도가 높게 나타났다. 또한, 화약량이 증가할수록 원주방향으로 전달되는 충격파가 도달할 수 있는 단면적이 증가할수록 광도가 증가함을 알 수 있었으며, 단일기폭보다 이중기폭의 경우 광원이 2배가 되어 광도도 2배됨을 입증하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.161-166
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• 2005

The plasma ion density in AC-PDP has shown to be increased from $5.6{\times}10^{11}cm^{-3}$ to $9.0{\times}10^{11)cm^{-3}$ as the Xe mixture ratio to neon increase from 1 % to 10 %, respectively, at fixed pressure of 400 Torr, by using the micro-Langmuir probe. It is noted that the plasma ion density is density increases as the gas pressure increases in this experiment. The electron temperature decreases from 2.3 to 1.2 eV as the Xe mole fraction increases from 1 % to 10 % at fixed pressure of 400 Torr, which is measured by the micro Langmuir probe and high-speed ICCD camera in this experiment. It is noted that the electron temperature decreases as the gas pressure increases from 150 to 400 Torr in this experiment. It is also observed that the exited Xe atom density and the plasma ion density are in strong correlation sharp between each other in this experiment. It is noted that $5.2{\times}10^{12}cm^{-3}$ in the $1s_5$ metastable state and $1.2{\times}10^{12}cm^{-3}$ in the $1s_4$ resonance state for the PDP cell with gap of 50 um distances under the fixed gas pressure of 400 Torr and Xe content ratio of 10 %.

• 보존과학회지
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• 제31권4호
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• pp.443-455
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• 2015

국내에서 구입 가능한 국내산, 일본산, 중국산 천연안료를 대상으로 단청 재료로서의 안정성을 확인하고자 내광성 및 내공해성 실험을 실시하였다. 본 연구에서는 단청 기법이나 바탕재의 영향을 배제한 채, 안료의 고유한 특성을 확인하고자 하였다. 안료 칠을 위한 교착제로는 천연재료인 아교와 현재 단청 공사 시 널리 사용되는 합성수지를 선택하였으며, 열화 실험용 인공 광원은 제논 아크 램프를, 오염 가스로는 이산화질소 가스를 선정하였다. 안료가 열화 된 정도는 색도를 측정하여 변화 정도를 비교하였다. 내광성 실험 결과, 광물성 안료 중 청색, 녹색계열의 안료와 황토, 백토, 석간주 등 토양성 안료들이 내광성이 양호하게 나타났고, 자황, 웅황, 진사, 연단 등이 좋지 않게 확인됐다. 내공해성 실험 결과, 연단을 제외한 천연안료 대부분의 내공해성이 양호한 것으로 나타났으며, 전반적으로 합성수지로 칠했을 때 보다 아교로 칠 했을 경우 내공해성이 더 양호했다.