• Title, Summary, Keyword: Thermal conduction

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Clinical Study of Bell's Palsy with DITI and Nerve Conduction Test(EN0G and EMG) (DITI 및 전기신경전도검사(EN0G 및 EMG)를 이용한 구안와사(Bell's palsy) 환자에 대한 임상적 고찰)

  • Kim, Jin-man;Hong, Chul-hee;Du, In-sun;Hwang, Chung-yeon;Kim, Nam-kwen;Park, Min-chul;Lee, Sang-kwan;Jung, Sang-su;Yoon, Jun-chul
    • The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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    • v.16 no.2
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    • pp.189-211
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    • 2003
  • The clinical data and thermographic imaging were analyzed on the 38 cases of Bell's palsy who were treated admission in the Oriental Medicine Hospital of Wonkwang University from January 2002 to May 2003. 38 patients with Bell's palsy were within one week after the onset of the paralysis, and thermal type in the DITI were hypo or hyper generally. Nerve conduction test(ENOG and EMG) examined in two weeks after onset. We studied interaction effect between thermal type and paralysis grade on admission day. We studied each main effect ; paralysis grade on admission day - nerve conduction test, nerve conduction test - thermal type, thermal type - paralysis grade after 4 weeks, paralysis grade on admission day - paralysis grade after 4 weeks, sasang constitution - nerve conduction test. The following results were obtained that interaction effect between thermal type and paralysis grade on admission day showed no significance, each main effect ; paralysis grade on admission day - nerve conduction test, paralysis grade on admission day - paralysis grade after 4 weeks, showed significance, each main effect ; nerve conduction test - thermal type, thermal type - paralysis grade after 4 weeks, sasang constitution - nerve conduction test, showed no significance.

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Thermal and structural analysis of a cryogenic conduction cooling system for a HTS NMR magnet

  • In, Sehwan;Hong, Yong-Ju;Yeom, Hankil;Ko, Junseok;Kim, Hyobong;Park, Seong-Je
    • Progress in Superconductivity and Cryogenics
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    • v.18 no.1
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    • pp.59-63
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    • 2016
  • The superconducting NMR magnets have used cryogen such as liquid helium for their cooling. The conduction cooling method using cryocoolers, however, makes the cryogenic cooling system for NMR magnets more compact and user-friendly than the cryogen cooling method. This paper describes the thermal and structural analysis of a cryogenic conduction cooling system for a 400 MHz HTS NMR magnet, focusing on the magnet assembly. The highly thermo-conductive cooling plates between HTS double pancake coils are used to transfer the heat generated in coils, namely Joule heating at lap splice joints, to thermal link blocks and finally the cryocooler. The conduction cooling structure of the HTS magnet assembly preliminarily designed is verified by thermal and structural analysis. The orthotropic thermal properties of the HTS coil, thermal contact resistance and radiation heat load are considered in the thermal analysis. The thermal analysis confirms the uniform temperature distribution for the present thermal design of the NMR magnet within 0.2 K. The mechanical stress and the displacement by the electromagnetic force and the thermal contraction are checked to verify structural stability. The structural analysis indicates that the mechanical stress on each component of the magnet is less than its material yield strength and the displacement is acceptable in comparison with the magnet dimension.

CENTRALLY PEAKED X-RAY SNRS : CLOUD EVAPORATION AND THERMAL CONDUCTION (X-선 중심 가광 초신성 잔해 : 성간운 증발과 열전도 모델)

  • CHOE SEUNG-URN;JUNG HYUN-CHUL;PARK BYEONG-GEON
    • Publications of The Korean Astronomical Society
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    • v.14 no.2
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    • pp.69-78
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    • 1999
  • We present the results of one-dimensional numerical simulations of SNR evolution in the in­homogeneous medium considering the effects of the evaporation of the cloud and the thermal conduction. We have included the effects of changing evaporation rate as a function of cloud size and the ambient temperature so that the clouds could be evaporated completely before they reach the center of the SNR. The heat conduction markedly changes the density distribution in the remnant interior. To explain the observed morphologies of the centrally peaked X-ray SNRs(for example W44), the maximal thermal conduction is required. However, this is unlikely due to the magnetic field and the turbulent motion. The effects of the evaporation of the cloud and the thermal conduction described here may explain the class of remnants observed to have centrally peaked X-ray emmision.

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Thermal Performance of a Printed Circuit Heat Exchanger considering Longitudinal Conduction and Channel Deformation (축방향 열전도와 유로 변형을 고려한 인쇄기판형 열교환기 열적 성능)

  • Park, Byung Ha;Sah, Injin;Kim, Eung-seon
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.14 no.1
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    • pp.8-14
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    • 2018
  • Printed circuit heat exchangers (PCHEs) are widely used with an increasing demand for industrial applications. PCHEs are capable of operating at high temperatures and pressure. We consider a PCHE as a candidate intermediate heat exchanger type for a high temperature gas-cooled reactor (HTGR). For conventional application using stainless steels, design and manufacturing of PCHEs are well established. For applications to HTGR, knowledge of longitudinal conduction and deformation of channel is required to estimate design margin. This paper analyzes the effects of longitudinal conduction and deformation of channel on thermal performance using a code internally developed for design and analysis of PCHEs. The code has a capability of two dimensional simulations. Longitudinal conduction is estimated using the code. In HTGR operating condition, about ten percent of design margin is required to compensate thermal performance. The cross-sectional images of PCHE channels are obtained using an optical microscope. The images are processed with computer image process technique. We quantify the deformation of channel with dimensional parameters. It is found that the deformation has negative effect on structural integrity. The deformation enhances thermal performance when the shape of channel is straight in laminar flow regime. It reduces thermal performance in cases of a zigzag channel and turbulent flow regime.

Experimental Study on Manufacturing of Insulation Vacuum Glazing and Measurement of the Thermal Conductance (단열 진공유리의 제작 및 열전달계수 측정에 관한 실험적 연구)

  • Lee Bo-Hwa;Yoon Il-Seob;Kwak Ho-Sang;Song Tae-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.8
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    • pp.772-779
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    • 2006
  • Window is a critical component in the design of energy-efficient buildings. To minimize the heat loss, insulation performance of the glazing has to be improved. Manufacturing of vacuum glazing has been motivated by the possibility of making windows of very good thermal insulation properties for such applications. It is made by maintaining vacuum in the gap between two glass panes. Pillars are placed between them to withstand the atmospheric pressure. Edge covers are applied to reduce conduction through the edge. Accurate measurements have been made of the radiative heat transfer, the pillar conduction and the gas conduction using a guarded hot plate apparatus. Vacuum glazing is found to have low thermal conductance roughly below $1W/m^2K$. Among the heat transfer modes of residual gas conduction, conduction through support pillar and the radiative heat transfer between the glass panes, the last one is the most dominant to the overall thermal conductance. Vacuum glazing using very low emittance AI-coated glass has an overall thermal conductance of about $0.7W/m^2K$.

Effects of Thermal-Carrier Heat Conduction upon the Carrier Transport and the Drain Current Characteristics of Submicron GaAs MESFETs

  • Jyegal, Jang
    • Proceedings of the Korea Society for Industrial Systems Conference
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    • pp.451-462
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    • 1997
  • A 2-dimensional numerical analysis is presented for thermal-electron heat conduction effects upon the electron transport and the drain current-voltage characteristics of submicron GaAs MESFETs, based on the use of a nonstationary hydrodynamic transport model. It is shown that for submicron GaAs MESFETs, electron heat conduction effects are significant on their internal electronic properties and also drain current-voltage characteristics. Due to electron heat conduction effects, the electron energy is greatly one-djmensionalized over the entire device region. Also, the drain current decreases continuously with increasing thermal conductivity in the saturation region of large drain voltages above 1 V. However, the opposite trend is observed in the linear region of small drain voltages below 1 V. Accordingly, for a large thermal conductivity, negative differential resistance drain current characteristics are observed with a pronounced peak of current at the drain voltage of 1 V. On the contrary, for zero thermal conductivity, a Gunn oscillation characteristic is observed at drain voltages above 2 V under a zero gate bias condition.

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Shape Design Sensitivity Analysis of Thermal Conduction Problems using Commercial Software ANSYS (상용 소프트웨어 ANSYS를 이용한 열전도문제의 형상설계 민감도 해석)

  • Choe, Ju-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.3
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    • pp.645-652
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    • 2000
  • A method for shape design sensitivity analysis is proposed utilizing commercial software ANSYS for thermal conduction problems. While the sensitivity formula is derived analytically by introduing adjoint variable concept, sensitivity calculation in practice as well as the primal and adjoint solution of thermal conduction is performed using the ANSYS very easily. Since the formula always takes boundary integral form, sensitivity evaluation in ANSYS requires a little more addition of post-processing routine which involves evaluation of boundary variable from the obtained solution. Though the BEM has been used as a better tool for this purpose, the present study shows it can also be calculated using any kind of analysis code such as ANSYS since the formula is based on analytic nature. Therefore the present study provides a new and efficient way of optimization which was not possible before using commercial software. The usefulness of the method is illustrated via a weight minimization problem of thermal diffuser.

The Property of Frozen Soil Mixed with Shredded Tire and Cement (폐타이어 분말 및 시멘트를 혼합한 동결토의 특성)

  • Kim, Young-Chin;Son, Seung-Mo
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.1487-1493
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    • 2008
  • The frost heaving is related with thermal conduction rate and permeability. If the thermal conduction rate can be controlled, it is effective to prevent from frost heaving. If soil mixed with shredded tire which has relatively lower thermal conduction rate than soil, it helps preventing from frost heaving. However, in this case, the shear strength can get weak. In this study, we compared thermal conduction rate of soil and shredded tire, and test uniaxial compression strength of soil which is mixed with shredded tire and cement in different ratio.

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Thermal Analysis of Electronic Devices in an Onboard Unit Considering Thermal Conduction Environment (열전도 환경을 고려한 전장탑재물의 소자 열 해석)

  • Kim Joon-Yun;Kim Bo-Gwan
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.43 no.5
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    • pp.60-67
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    • 2006
  • Thermal analysis and prediction of electronic components is required to predict and optimize the reliability of onboard electronic unit employed in space vehicles. This paper introduces a methodology on thermal prediction that uses isothermal PCB model, thermal force model, thermal resistance matrix and superposition principle to calculate electronic devices temperatures undergoing thermal conduction environment. An example is Presented including a prediction result by this method and simulation results performed by commercial program.

Comparative Analysis of the Parabolic and Hyperbolic Heat Conduction and the Damped Wave in a Finite Medium (유한한 평판에서 포물선형 및 쌍곡선형 열전도 방정식과 파동 방정식의 비교 해석)

  • Park, S.K.;Lee, Y.H.
    • Journal of Power System Engineering
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    • v.3 no.3
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    • pp.14-21
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    • 1999
  • The wave nature of heat conduction has been developed in situations involving extreme thermal gradients, very short times, or temperatures near absolute zero. Under the excitation of a periodic surface heating in a finite medium, the hyperbolic and parabolic heat conduction equations and the damped wave equations in heat flux are presented for comparative analysis by using the Green's function with the integral transform technique. The Kummer transformation is also utilized to accelerate the rate of convergence of these solutions. On the other hand, the temperature distributions are obtained through integration of the energy conservation law with respect to time. For hyperbolic heat conduction, the heat flux distribution does not exist throughout all the region in a finite medium within the range of very short times(${\xi}<{\eta}_l$). It is shown that due to the thermal relaxation time, the hyperbolic heat conduction equation has thermal wave characteristics as the damped wave equation has wave nature.

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