• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.660-663
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• 2011

우주방사선이나 과도펄스(Transient Radiation) 형태의 감마 방사선이 반도체에 조사되면 소자 내부에서 짧은 시간에 다량의 전하가 생성된다. 이 전하들과 증폭된 과전류는 소자의 고장(Upset, Latchup)과 오동작을 유발시키게 되고 나아가 전자부품이 소진(Burnout)되는 직접적인 원인이 된다. 본 연구에서는 이러한 핵폭 방출 과도방사선에 대한 전자부품/장비의 내방사선관련 기초연구로 군전자부품의 감마-과도방사선에 대한 피해분석 시험을 수행하고 나아가 과도방사선 방호기술 체계구축의 필요성에 대해 논하였다. 과도펄스 방사선시험은 군용으로 분류된 반도체 칩을 대상으로 포항 전자빔가속기를 사용하였다. 핵폭발 방출 과도방사선을 모사하기 위해 감마선 변환장치를 MCNP 설계를 통해 제작하고 단일모드의 마이크로초 단위 감마펄스 방사선을 방출시켜 시험대상 칩을 부착한 시험보드에 조사하는 과정으로 실험을 진행하였다. 온라인 고속 측정장치를 통한 전자소자의 과도방사선시험에서 다양한 피해현상을 측정할 수 있었고, 열상카메라 촬영을 통하여 과열상태를 관측함으로써 피해현상의 검증과 더불어 소진현상으로의 전개 가능성을 확인하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.10 s.253
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• pp.950-956
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• 2006

A mathematical heat transfer model for the prediction of heat flux on the slab surface and temperature distribution in the slab has been developed by considering the thermal radiation in the furnace and transient conduction governing equations in the slab, respectively. The furnace is modeled as radiating medium with spatially varying temperature and constant absorption coefficient. The slab is moved with constant speed through non-firing, charging, preheating, heating, and soaking zones in the furnace. Radiative heat flux which is calculated from the radiative heat exchange within the furnace modeled using the FVM by considering the effect of furnace wall, slab, and combustion gases is applied as the boundary condition of the transient conduction equation of the slab. Heat transfer characteristics and temperature behavior of the slab is investigated by changing such parameters as absorption coefficient and emissivity of the slab. Comparison with the experimental work shows that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.116-121
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• 2004

Simulation of proton irradiation in space is undertaken with a cyclotron accelerator. The cyclotron is capable of accelerating protons up to 200MeV with nominal fluxes near $10^6-10^8\;protons/cm^2/s$. Accelerated protons are irradiated onto a MPC860 for space application. Both the transient and cumulative responses of the device are found due to the proton irradiation. The primary transient response of the device is modification of the stored data in the circuit, whereas intermittent functional interrupts are also found. The cumulative response of the device is the increase of current consumption by the device.

• Journal of computational fluids engineering
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• v.19 no.4
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• pp.45-51
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• 2014

We develop a numerical method for solving the radiation hydrodynamic equations in one-dimensional spherical coordinates. The present method is validated through simulations of shock tube, thermal radiative diffusion and point explosion problems. The transient growth of the fireball is investigated by varying explosion yields. The present study clearly captures well-known breakaway phenomena related to the shock separation between pressure waves and thermal shock front. The fireball radius at the breakaway point is roughly increased by the yield to power of 0.4.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2582-2589
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• 1993

Transient heat transfer characteristics of cooling of a spherical body were investigated in the radiatively active spherical medium. Initially the spherical body and the medium were maintained at their constant temperatures. Then heat transfer begins from spherical body t medium. The heat transfer mode inside the spherical body is just conduction. But heat is transferred by both conduction and radiation inside the medium. All thermodynamic properties were held constant in time. Spherical symmetry is assumed. DOM was adopted to solve RTE. The effect of characteries-tic optical thickness, conduction to radiation parameters, and solid surface emissivity has been studied.

• The Journal of the Acoustical Society of Korea
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• v.2 no.1
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• pp.48-58
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• 1983

The transient sound radiation from the impact between a steel ball and a thick plate is analyzed theoretically and compared with experiment results. The derivation process itself is difficult to analyze sound radiation characteristics theoretically for a thick plate with some resonances but may be investigated from measured data. During mechanical impacts, arbitrary driving point importance for an elastic system enables to predict by using mechanical importance method. In order to obtain approximate solution for an impact model testing, the surface Helmholtz integral formulation based on the integral expression for pressure in the field in terms of surface pressure and normal velocity is used as a basis. A simple expression is developed for an impulsive response function, which is time dependent velocity potential and pressure for an impact may then be computed by a convolution of exciting force. In estimating of elastic-acoustical correlation problems, mechanical inertance, overall transfer function and radiation resistance obtained by signal processing techniques are used. The usefulness is confirmed by applying these methods prediction of arbitray driving pint inertance, radiated sound pressure and exciting force.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.381-384
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• 2005

The purpose of this study is to develop a prediction model for evaluating heavy-weight floor impact sounds in a test building. Three rooms in the test building (slab thickness In and 240mm), which consist of frame concrete structures were tested and modeled. First, the SPL distribution in the receiving room was analyzed by measuring SPL at 90 positions using a bang machine. Then, a vibration model using finite element method is proposed considering the material properties and boundary conditions. In addition, the result of transient analysis was compared with field measurements using a standard heavy-weight impact source. Through a vibro-acoustic simulation program, an acoustic model evaluating the building elements (reflected wall, nor, window and door) was proposed. Finally, validation of the prediction model was conducted by vibro-acoustic analysis with field measurements of noise radiation characteristics in receiving rooms.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2353-2364
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• 1995

The ignition phenomena of a solid fuel plate of polymethyl-methacrylate(PMMA), which is vertically positioned and exposed to a thermal radiation source, is numerically studied here. A two-dimensional transient model includes such various aspects as thermal decomposition of PMMA, gas phase radiation absorption, gas phase chemical reaction and air entrainment by natural convection. Whereas the previous studies considers the problem approximately in a one-dimensional form by neglecting the natural convection, the present model takes account of the two-dimensional effect of radiation and air entrainment. The inert heating of the solid fuel is also taken into consideration. Radiative heat transfer is incorporated by th Discrete Ordinates Method(DOM) with the absorption coefficient evaluated using gas species concentration. The thermal history of the solid fuel plate shows a good agreement compared with experimental results. Despite of induced natural convective flow that induces heat loss from the fuel surface, the locally absorbed radiant energy, which is converted to the internal energy, is found to play an important role in the onset of gas phase ignition. The ignition is considered to occur when the rate of variation of gas phase reaction rate reaches its maximum value. Once the ignition takes place, the flame propagates downward.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.3
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• pp.540-544
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• 2017

In this study, we analyzed the effects of TID(Total Ionizing Dese) and TREE(Transient Radiation Effects on Electronics) on nMOSFET and pMOSFET fabricated by 0.18um CMOS process. The size of nMOSFET and pMOSFET is 100um/1um(W/L). The TID test was conducted up to 1 Mrad(Si) with a gamma-ray(Co-60). During the TID test, the nMOSFET generated leakage current proportional to the applied dose, but that of the pMOSFET was remained in a steady state. The TREE test was conducted at TEST LINAC in Pohang Accelerator Laboratory with a maximum dose-rate of $3.16{\times}10^8rad(si)/s$. In that test nMOESFET generated a large amount of photocurrent at a maximum of $3.16{\times}10^8rad(si)/s$. Whereas, pMOSFETs showed high TREE immunity with a little amount of photocurrent at the same dose rate. Based on the results of this experiment, we will progress the research of the radiation hardening for CMOS unit devices.

• Journal of Microbiology and Biotechnology
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• v.23 no.12
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• pp.1785-1790
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• 2013

The synthetic machinery of ATF4 (activating transcription factor 4) is activated in response to various stress conditions involved in nutrient restriction, endoplasmic reticulum homeostasis, and oxidation. Stress-induced inhibition of proteasome activity triggers the unfolded protein response and endoplasmic reticulum stress, where ATF4 is crucial for consequent biological events. In the current study, we showed that the $NAD^+$-dependent deacetylase, SIRT1, suppresses ATF4 synthesis during proteasome inhibition. SIRT1 depletion via transfection of specific siRNA into HeLa cells resulted in a significant increase in ATF4 protein, which was observed specifically in the presence of the proteasome inhibitor MG132. Consistent with SIRT1 depletion data, transient transfection of cells with SIRT1-overexpressing plasmid induced a decrease in the ATF4 protein level in the presence of MG132. Interestingly, however, ATF4 mRNA was not affected by SIRT1, even in the presence of MG132, indicating that SIRT1-induced suppression of ATF4 synthesis occurs under post-transcriptional control. Accordingly, we propose that SIRT1 serves as a negative regulator of ATF4 protein synthesis at the post-transcriptional level, which is observed during stress conditions, such as proteasome inhibition.