• 제목/요약/키워드: Conduction

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고온 초전도 SMES용 전도냉각시스템 특성시험 (Test of the Conduction Cooling System for HTS SMES)

  • 염한길
    • 한국초전도ㆍ저온공학회논문지
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    • 제10권1호
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    • pp.62-66
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    • 2008
  • The characteristic of the superconducting magnetic energy storage(SMES) system is faster response, longer life time, more economical, and environment friendly than other uninterruptible power supply(UPS) using battery. So, the SMES system can be used to develop methods for improving power quality where a short interruption of power could lead to a long and costly shutdown. Recently, cryogen free SMES has developed using BSCCO(Bismuth Strontium Calcium Copper Oxide) wire. We fabricated and tested the conduction cooling system for the 600 kJ class HTS SMES. The experiment was accomplished for the simulation coils. The simulation coils were made of aluminium, it is equivalent to thermal mass of 600 kJ HTS SMES coil. The coil is cooled with two GM coolers through the copper conduction bar. In this paper, we report that the test results of cool-down and heat loads characteristics of the simulation coils. The developed conduction cooling system adapted to 600 kJ HTS SMES system and cope with the unexpected sudden heat impact, too.

굴패각 배합 석고재료의 열전도 특성 연구 (A Study on Thermal Conduction in Oyster Shell Incorporating Gypsum Objects)

  • 권성현;조대철
    • 청정기술
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    • 제19권2호
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    • pp.90-94
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    • 2013
  • 굴 패각분말을 함유한 석고시험체를 통하여 1차원 열전달 특성을 조사하였다. 굴패각 성분의 함유량이 늘어날수록 기공을 포함한 시험체의 구조적 변형에 근거하여 흡착과 같은 물리화학적 특성이 증가함에 따라 시험체 전체의 열전달 특성도 달라질 것으로 예측되었다. 푸리에(Fourier) 열전도 방정식을 기초로 하여 1차원 슬랩의 열전도 현상을 수치모사한 결과 패각분말의 배합도 및 각 성분재료의 열전달관련 물리적 계수에 따라 상당한 열전도 분포의 변화를 관측할 수 있었으며 이는 모형실험 결과와도 잘 부합하였다.

비정질 Sb-Bi-Te 박막의 전기적 특성에 관한 연구 (A Study on the Electrical Properties of Amorphous Sb-Bi-Te Thin Films)

  • 이준신;이재형
    • 한국전기전자재료학회논문지
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    • 제15권3호
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    • pp.220-226
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    • 2002
  • Amorphous $Sb_{2-x}Bi_xTe_3$ (x = 0.0, 0.5 and 1.0) thin films were prepared by vacuum evaporation. The resistivity of 7he films decreases from 1.4{\times}10^{-2}$ to $8.84{\times}10^{-5}\Omega cm$ and the type of conductivity changes from p to n with the increase of the x value of the films. D.C. conduction studies on these films ate performed at various electric fields in the temperature range of 303-403 K. At low electric fields, two types of conduction mechanisms, i.e. the variable range hopping and the phonon assisted hopping are found to be responsible for the conduction, depending upon the temperature. The activation energy decreases from 0.082 to 0.076 eV in the temperature range of 303-363 K and from 0.47-0.456 eV in the second range of 363-403 K, indicating the shift of the Fermi level towards the conduction band edge and hence the change of the conduction from P to n type with the increase of the Bi concentration. Poole-Frankel emission dominates at high fields. The shape of the potential well of the localized centre is deduced and the mean free path of the charge carriers is also calculated.

비푸리에 열전도 현상에 관한 고찰 (A Study of the Non-Fourier Heat Conduction Phenomena)

  • 최순호;김창복;최현규;윤석훈;김명환;오철
    • 한국마린엔지니어링학회:학술대회논문집
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    • 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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    • pp.37-38
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    • 2005
  • Although the law of classical fourier heat conduction predicts the heat conduction phenomena occurred in most engineering fields with a good accuracy, it is also well-known that the conventional fourier law of a heat conduction has an application limit when the heating and cooling are periodic for a short duration or when the heat conduction is analyzed in the extremely low temperature region. This application limit of classical fourier law results from the fact that it assumed the infinite speed of a heat wave. In this study, we investigated the feasibility of whether the molecular dynamics could be used to calculate the speed of a heat wave through a solid. The calculated sound velocity showed a good agrement with the theoretical prediction qualitatively. From the calculated results, we confirmed that the same methodology can be applied the evaluation of the speed of a heat wave.

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Analytical solution of the Cattaneo - Vernotte equation (non-Fourier heat conduction)

  • Choi, Jae Hyuk;Yoon, Seok-Hun;Park, Seung Gyu;Choi, Soon-Ho
    • Journal of Advanced Marine Engineering and Technology
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    • 제40권5호
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    • pp.389-396
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    • 2016
  • The theory of Fourier heat conduction predicts accurately the temperature profiles of a system in a non-equilibrium steady state. However, in the case of transient states at the nanoscale, its applicability is significantly limited. The limitation of the classical Fourier's theory was overcome by C. Cattaneo and P. Vernotte who developed the theory of non-Fourier heat conduction in 1958. Although this new theory has been used in various thermal science areas, it requires considerable mathematical skills for calculating analytical solutions. The aim of this study was the identification of a newer and a simpler type of solution for the hyperbolic partial differential equations of the non-Fourier heat conduction. This constitutes the first trial in a series of planned studies. By inspecting each term included in the proposed solution, the theoretical feasibility of the solution was achieved. The new analytical solution for the non-Fourier heat conduction is a simple exponential function that is compared to the existing data for justification. Although the proposed solution partially satisfies the Cattaneo-Vernotte equation, it cannot simulate a thermal wave behavior. However, the results of this study indicate that it is possible to obtain the theoretical solution of the Cattaneo-Vernotte equation by improving the form of the proposed solution.

Segmental Sensory Nerve Conduction Study in Vibration Exposed Subjects

  • Kim Mi-Jung;Yoon Cheol-In;Choi Hyun-Ju
    • 대한의생명과학회지
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    • 제11권2호
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    • pp.193-199
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    • 2005
  • The present study was performed to assess peripheral neural involvement by exposure to hand-arm vibration. Segmental sensory nerve conduction in the median and ulnar nerves were measured in shipyard workers exposed to vibration. The subjects were 47 male adults exposed to hand-arm vibration and 7 healthy male controls. The subjects underwent an extensive bilateral neurophysiological examination. Sensory compound nerve action potential (SNAP) of the median and ulnar nerves in palm-finger and wrist-palm segments were measured by antidromic method. And SNAP of the median and ulnar nerves in wrist-proximal finger and wrist-distal finger segments were measured by orthodromic method. Result of sensory nerve conduction study was abnormal in 31 patients $(66\%)$ and normal in 16 patients $(34\%)$ of subjects. The pathological pattern in the hand-arm vibration exposed group was 13 patients $(28\%)$ of carpal tunnel syndrome, 18 patients $(38\%)$ of distal sensory neuropathy, 7 patients $(15\%)$ of multifocal and 1 patient $(2\%)$ of Guyon syndrome. The present study indicates that vibration-induced nerve impairments exist both in the finger-palm and palm-wrist segment of median and ulnar sensory nerves. The results suggest that segmental sensory nerve conduction study would be useful as objective indication of peripheral nerve impairment induced by the hand-arm vibration.

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문턱스며들기 이하 카본블랙 충진 폴리에칠렌기지 복합재료의 전기전도 특성 (Electrical Conduction Property of the Carbon Black-Filled Polyethylene Matrix Composites Below the Percolation Threshold)

  • 신순기
    • 한국재료학회지
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    • 제20권5호
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    • pp.271-277
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    • 2010
  • In this paper two aspects of the percolation and conductivity of carbon black-filled polyethylene matrix composites will be discussed. Firstly, the percolation behavior, the critical exponent of conductivity of these composites, are discussed based on studying the whole change of resistivity, the relationship between frequency and relative permittivity or ac conductivity. There are two transitions of resistivity for carbon black filling. Below the first transition, resistivity shows an ohmic behavior and its value is almost the same as that of the matrix. Between the first and second transition, the change in resistivity is very sharp, and a non-ohmic electric field dependence of current has been observed. Secondly, the electrical conduction property of the carbon black-filled polyethylene matrix composites below the percolation threshold is discussed with the hopping conduction model. This study investigates the electrical conduction property of the composites below the percolation threshold based on the frequency dependence of conductivity in the range of 20 Hz to 1 MHz. There are two components for the observed ac loss current. One is independent of frequency that becomes prevalent in low frequencies just below the percolation threshold and under a high electrical field. The other is proportional to the frequency of the applied ac voltage in high frequencies and its origin is not clear. These results support the conclusion that the electrical conduction mechanism below the percolation threshold is tunneling.

전도냉각형 고온초전도 에너지저장장치의 전기적 특성 (A Study on the Electrical Properties of the Conduction-cooled HTS SMES System)

  • 최재형;곽동순;천현권;김해종;김상현
    • 한국전기전자재료학회논문지
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    • 제20권2호
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    • pp.135-141
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    • 2007
  • The conduction-cooled HTS SMES is operated in cryogenic and high vacuum condition. Thus, Insulation design at cryogenic temperature and high vacuum is a key and an important element that should be established to accomplish miniaturization that is a big advantage of HTS SMES. However, the behaviors of insulators for cryogenic conditions in vacuum are virtually unknown. Therefore, we need active research and development of insulation concerning application of the conduction-cooled HTS SMES. Therefore, in this study, we experimented about insulation characteristic high vacuum and cryogenic similar to driving condition of SMES system. Also, investigated about insulation characteristic of suitable some materials to insulator for conduction-cooled HTS SMES. As this results, we possessed basis data for insulation materials selection and insulation design for development of 600 kJ class conduction-cooled HTS SMES.

Implementation and Experiments of Sparse Matrix Data Structure for Heat Conduction Equations

  • Kim, Jae-Gu;Lee, Ju-Hee;Park, Geun-Duk
    • 한국컴퓨터정보학회논문지
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    • 제20권12호
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    • pp.67-74
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    • 2015
  • The heat conduction equation, a type of a Poisson equation which can be applied in various areas of engineering is calculating its value with the iteration method in general. The equation which had difference discretization of the heat conduction equation is the simultaneous equation, and each line has the characteristic of expressing in sparse matrix of the equivalent number of none-zero elements with neighboring grids. In this paper, we propose a data structure for sparse matrix that can calculate the value faster with less memory use calculate the heat conduction equation. To verify whether the proposed data structure efficiently calculates the value compared to the other sparse matrix representations, we apply the representative iteration method, CG (Conjugate Gradient), and presents experiment results of time consumed to get values, calculation time of each step and relevant time consumption ratio, and memory usage amount. The results of this experiment could be used to estimate main elements of calculating the value of the general heat conduction equation, such as time consumed, the memory usage amount.

A case of acute motor sensory axonal neuropathy presenting reversible conduction block

  • Lee, Dongah;Kim, Hyung Chan;Park, Kang Min;Park, Jinse;Ha, Sam Yeol;Kim, Sung Eun;Lee, Byung In;Kim, Jong Kuk;Yoon, Byeola;Shin, Kyong Jin
    • Annals of Clinical Neurophysiology
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    • 제20권1호
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    • pp.49-52
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    • 2018
  • Reversible conduction block (RCB) was rare in patients with acute motor sensory axonal neuropathy (AMSAN). A-46-year-old man presented with paresthesia, weakness, diplopia, and dysarthria. Nerve conduction study (NCS) exhibited axonal changes with conduction block in motor and sensory nerves. His symptoms were rapidly progressed and recovered. Conduction block was disappeared in the follow-up NCS performed after 2 weeks. The AMSAN case with RCB showed rapid progress and rapid recovery of clinical symptoms as acute motor axonal neuropathy patients with RCB.