• 제목/요약/키워드: joule heating

검색결과 154건 처리시간 0.03초

소스 및 드레인 전극 재료에 따른 비정질 InGaZnO 박막 트랜지스터의 소자 열화 (Hot carrier induced device degradation in amorphous InGaZnO thin film transistors with source and drain electrode materials)

  • 이기훈;강태곤;이규연;박종태
    • 한국정보통신학회논문지
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    • 제21권1호
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    • pp.82-89
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    • 2017
  • 본 연구에서는 소스 및 드레인 전극 재료에 따른 소자 열화를 분석하기 위해 Ni, Al, 및 ITO를 소스 및 드레인 전극 재료로 사용하여 InGaZnO 박막 트랜지스터를 제작하였다. 전극 재료에 따른 소자의 전기적 특성을 분석한 결과 Ni 소자가 이동도, 문턱전압 이하 스윙, 구동전류 대 누설전류 비율이 가장 우수하였다. 소스 및 드레인 전극 재료에 따른 소자 열화 측정결과 Al 소자의 열화가 가장 심한 것을 알 수 있었다. InGaZnO 박막 트랜지스터의 소자 열화 메카니즘을 분석하기 위하여 채널 폭과 스트레스 드레인 전압을 다르게 하여 문턱전압 변화를 측정하였다. 그 결과 채널 폭이 넓을수록 또 스트레스 드레인 전압이 높을수록 소자 열화가 많이 되었다. 측정결과로부터 InGaZnO 박막 트랜지스터의 소자 열화는 큰 채널 전계와 주울 열의 결합 작용으로 발생함을 알 수 있었다.

자외선 가속열화에 의한 실리콘 고무의 트래킹 특성 변화에 관한 연구 (A Study on the Tracking Characteristics of Silicone Rubber Degraded by Accelerated UV Exposure)

  • 김숙철;이준호;황보승;이동영;한민구
    • 대한전기학회논문지:전기물성ㆍ응용부문C
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    • 제49권5호
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    • pp.302-309
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    • 2000
  • The tracking characteristics of silicone rubber degraded by accelerated outdoor exposure employing a weather-o-meter were investigated. The tracking test was performed according to ICE Publ.587 method but the concentration of conductive solution was two times higher than IEC standard in order to accelerate the tracking failure. The number of large effective scintillation and the current of high voltage circuit were measured simultaneously. It was shown that the number of effective scintillation had valuable information of the tracking degradation state of silicone rubber, while the average current between electrodes could not provide information enough for diagnosis. Based upon the experimental results, it could be said that the key factor accelerating tracking failure was not Joule heating by current but pyrolysis by burning of silicone rubber, and that reduction of contact angle was due to chain scission which resulted in the free radicals of low molecules.

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지상지자기변화기록을 이용한 우주천기연구 (SPACE WEATHER RESEARCH BASED ON GROUND GEOMAGNETIC DISTURBANCE DATA)

  • 안병호
    • 천문학논총
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    • 제15권spc2호
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    • pp.1-13
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    • 2000
  • Through the coupling between the near-earth space environment and the polar ionosphere via geomagnetic field lines, the variations occurred in the magnetosphere are transferred to the polar region. According to recent studies, however, the polar ionosphere reacts not only passively to such variations, but also plays active roles in modifying the near-earth space environment. So the study of the polar ionosphere in terms of geomagnetic disturbance becomes one of the major elements in space weather research. Although it is an indirect method, ground magnetic disturbance data can be used in estimating the ionospheric current distribution. By employing a realistic ionospheric conductivity model, it is further possible to obtain the distributions of electric potential, field-aligned current, Joule heating rate and energy injection rate associated with precipitating auroral particles and their energy spectra in a global scale with a high time resolution. Considering that the ground magnetic disturbances are recorded simultaneously over the entire polar region wherever magnetic station is located, we are able to separate temporal disturbances from spatial ones. On the other hand, satellite measurements are indispensible in the space weather research, since they provide us with in situ measurements. Unfortunately it is not easy to separate temporal variations from spatial ones specifically measured by a single satellite. To demonstrate the usefulness of ground magnetic disturbance data in space weather research, various ionospheric quantities are calculated through the KRM method, one of the magneto gram inversion methods. In particular, we attempt to show how these quantities depend on the ionospheric conductivity model employed.

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Parametric Study of AC Current Lead for the Termination of HTS Power Cable

  • Kim, D.L;Kim, S.H.;S. Cho;H.S. Yang;Kim, D.H.;H.S. Ryoo;K.C. Seong
    • 한국초전도ㆍ저온공학회논문지
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    • 제5권1호
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    • pp.107-110
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    • 2003
  • High Temperature Superconductor (HTS) transmission cable can carry more than 2 to 5 times higher electricity and also obtain substantially lower transmission losses than conventional cables. Liquid nitrogen is to be used to cool the HTS power cable and its cost is much cheaper than the liquid helium used for the cooling of metal superconducting wire. In Korea the HTS power cable development project has been ongoing since July, 2001 with the basic specifications of 22.9kV, 50MVA and told dielectric type as the first 3-year stage. The cryogenic system of the HTS cable is composed of HTS cable cryostat termination and refrigeration system. Termination of HTS cable is a connecting part between copper electrical cable at room temperature and HTS cable at liquid nitrogen temperature. In order to design the termination cryostat, it is required that the conduction heat leak and Joule heating on the current lead be reduced, the cryostat be insulated electrically and good vacuum insulation be maintained during long time operation. Heat loads calculations on the copper current lead have been performed by analytical and numerical method and the feasibility study fer the other candidate materials has also been executed.

펄스파워를 이용한 실린더형 전극간 금속 플라즈마 생성현상의 전산유동해석 (COMPUTATIONAL MODELING AND SIMULATION OF METAL PLASMA GENERATION BETWEEN CYLINDRICAL ELECTRODES USING PULSED POWER)

  • 김경진;곽호상;박중윤
    • 한국전산유체공학회지
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    • 제19권4호
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    • pp.68-74
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    • 2014
  • This computational study features the transient compressible and inviscid flow analysis on a metallic plasma discharge from the opposing composite electrodes which is subjected to pulsed electric power. The computations have been performed using the flux corrected transport algorithm on the axisymmetric two-dimensional domain of electrode gap and outer space along with the calculation of plasma compositions and thermophysical properties such as plasma electrical conductivity. The mass ablation from aluminum electrode surfaces are modeled with radiative flux from plasma column experiencing intense Joule heating. The computational results shows the highly ionized and highly under-expanded supersonic plasma discharge with strong shock structure of Mach disk and blast wave propagation, which is very similar to muzzle blast or axial plasma jet flows. Also, the geometrical effects of composite electrodes are investigated to compare the amount of mass ablation and penetration depth of plasma discharge.

초고압 단로기 접점의 단락전류 통전성능 평가기술 개발 (Development of Evaluating Technology for the Capability of Carrying Short-Circuit Current at Electrical Contacts in EHV Disconnecting Switches)

  • 오연호;송기동;정진교
    • 전기학회논문지
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    • 제57권1호
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    • pp.46-51
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    • 2008
  • Extra-high voltage(EHV) disconnecting switch(DS) consists of the electrical contacts and mechanical parts which actuate the contacts. When the short-circuit condition occurs, a large amount of current flows through the electrical contact in disconnecting switches and this causes considerable temperature rise due to Joule heating. If the temperature rise is higher than the melting point of contact material, the DS contact becomes melting and cannot be usable anymore. For this reason, the analysis for capability of carrying short-circuit current in DS contacts must be performed at a design stage. Here, we proposed a numerical technique for evaluating the capability of carrying short-circuit current at electrical contacts in EHV DS. In this numerical approach, the mechanical and thermal analyses were simulated to check the capability of carrying short-circuit current. First, the applied pressure at contact parts was analyzed considering the mechanical properties, and then contact resistance was calculated by an empirical equation. Finally, thermal analysis was performed with resistance variation at electrical contacts. To verify these numerical results, the distributions of temperature in DS were experimentally measured and compared with each other. The results from experiments were agreed well with those from the proposed numerical simulations.

PCAS공정에 의한 고융점 소결체 열전달 해석 및 특성분석 (Thermal Characteristic Simulation and Property Evaluation of High Melting Point Materials by Pulsed Current Activated Sintering Process)

  • 남효은;장준호;박현국;오익현
    • 센서학회지
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    • 제26권3호
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    • pp.214-222
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    • 2017
  • In this study, the effects of internal heat treatment associated sintering temperatures were simulated by the Finite Element Method (FEM). The sintering mechanism of pulsed current activated sintering process (PCAS) is still unclear because of some unexplainable heat transfer phenomena in coupled multi-physical fields, as well as the difficulty in measuring the interior temperatures of metal powder. We have carried out simulation study to find out thermal distributions between graphite mold and Ruthenium powder prior to PCAS process. For PCAS process, heating rate was maintained at $100^{\circ}C/min$ the simulation indicates that the sintering temperature range was between $1000^{\circ}C$ to $1300^{\circ}C$ under 60 MPa. The heat transfer inside the Ruthenium sintered-body sample was modelled through the whole process in order to predict the minimum interior temperature. Thermal simulation shows that the interior temperature gradient decreased by graphite punch length and calculation results well agreed with the PCAS field test results.

Silver nanowire-containing wearable thermogenic smart textiles with washing stability

  • Dhanawansha, Kosala B.;Senadeera, Rohan;Gunathilake, Samodha S.;Dassanayake, Buddhika S.
    • Advances in nano research
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    • 제9권2호
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    • pp.123-131
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    • 2020
  • Conventional fabrics that have modified in to conductive fabrics using conductive nanomaterials have novel applications in different fields. These of fabrics can be used as heat generators with the help of the Joule heating mechanism, which is applicable in thermal therapy and to maintain the warmth in cold weather conditions in a wearable manner. A modified fabric can also be used as a sensor for body temperature measurements using the variation of resistance with respect to the body temperature deviations. In this study, polyol synthesized silver nanowires (Ag NWs) are incorporated to commercially available cotton fabrics by using drop casting method to modify the fabric as a thermogenic temperature sensor. The variation of sheet resistance of the fabrics with respect to the incorporated mass of Ag NWs was measured by four probe technique while the bulk resistance variation with respect to the temperature was measured using a standard ohm meter. Heat generation profiles of the fabrics were investigated using thermo graphic camera. Electrically conductive fabrics, fabricated by incorporating 30 mg of Ag NWs in 25 ㎠ area of cotton fabric can be heated up to a maximum steady state temperature of 45℃, using a commercially available 9 V battery.

Parameter Design and Analysis for Aluminum Resistance Spot Welding

  • Cho, Yong-Joon;Li, Wei;Hu, S. Jack
    • Journal of Welding and Joining
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    • 제20권2호
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    • pp.102-108
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    • 2002
  • Resistance spot welding of aluminum alloys is based upon Joule heating of the components by passing a large current in a short duration. Since aluminum alloys have the potential to replace steels fur automobile body assemblies, it is important to study the process robustness of aluminum spot welding process. In order to evaluate the effects of process parameters on the weld quality, major process variables and abnormal process conditions were selected and analyzed. A newly developed two-stage, sliding-level experiment was adopted fur effective parameter design and analysis. Suitable ranges of welding current and button diameters were obtained through the experiment. The effects of the factors and their levels on the variation of acceptable welding current were considered in terms of main effects. From the results, it is concluded that any abnormal process condition decreases the suitable current range in the weld lobe curve. Pareto analysis of variance was also introduced to estimate the significant factors on the signal-to-noise (S/N) ratio. Among the six factors studied, fit-up condition is found to be the most significant factor influencing the SM ratio. Using a Pareto diagram, the optimal condition is determined and the SM ratio is significantly improved using the optimal condition.

발전기 냉각용 On-Site 수소 생산 시스템 적용연구 (Application Study of An On-site Hydrogen Production System for Power Generator Cooling)

  • 문전수;이재근;박필양;박경일
    • 한국수소및신에너지학회논문집
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    • 제20권5호
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    • pp.410-415
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    • 2009
  • A hydrogen cooling method is used in a power generator for removing the unnecessary heat due to the windage loss of a rotor and the joule heat of a stator. A MEA (Membrane Electrolyte Assembly) hydrogen generator has been developed and applied as a hydrogen supplying system for the cooling of a 350MW power generator. As a field application result, the average potential of eleven cells and the voltage efficiency were measured 2.26V/cell and 65.4% (Higher Heating Value) respectively at the hydrogen pressure of 6 Bar, the hydrogen flow rate of 9.1L/min, and the current of 150A.