• Title/Summary/Keyword: junction temperature

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TOWARD AN ACCURATE APPROACH FOR THE PREDICTION OF THE FLOW IN A T-JUNCTION: URANS

  • Merzari, E.;Khakim, A.;Ninokata, H.;Baglietto, E.
    • Nuclear Engineering and Technology
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    • v.41 no.9
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    • pp.1191-1204
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    • 2009
  • In this study, a CFD methodology is employed to address the problem of the prediction of the flow in a T-junction. An Unsteady Reynolds Averaged Navier-Stokes (URANS) approach has been selected for its low computational cost. Moreover, Unsteady Reynolds Navier-Stokes methodologies do not need complex boundary formulations for the inlet and the outlet such as those required when using Large Eddy Simulation (LES) or Direct Numerical Simulation (DNS). The results are compared with experimental data and an LES calculation. In the past, URANS has been tried on T-junctions with mixed results. The biggest limit observed was the underestimation of the oscillatory behavior of the temperature. In the present work, we propose a comprehensive approach able to correctly reproduce the root mean square (RMS) of the temperature directly downstream of the T-junction for cases where buoyancy is not present.

THE DEVELOPMENT OF A LOW NOISE 230 GHZ SIS RECEIVER IN NAGOYA UNIVERSITY

  • XIAO K. C.;OGAWA H.;FUKUI Y.;SUZUKI H.
    • Journal of The Korean Astronomical Society
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    • v.29 no.spc1
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    • pp.413-414
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    • 1996
  • A 230 GHz SIS tunnel junction receiver has been being developed for radio astronomy in Nagoya University. In this heterodyne receiver, we use a $\~$1/3 reduced hight rectangular waveguide SIS mixer with two tuning elements as front end. The mixer block with SIS junction was cooled to 4K with a closed cycle He-gas refrigerator. So far, a double sideband receiver noise temperature lower than l00K in 222-237 GHz is obtained. The receiver exhibits a best DSB noise temperature of 69K at 236 GHz as well as 228 GHz.

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Determination of Penetration Depth of Nb Electrodes in $Nb/A1O_x/Nb$ Josephson Junction by Resistive Method ($Nb/A1O_x/Nb$ 조셉슨 접합에서 저항측정을 이용한 Nb 전극의 침투깊이 측정)

  • 김동호;김규태;박종원;황준석;홍현권
    • Progress in Superconductivity and Cryogenics
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    • v.4 no.1
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    • pp.50-54
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    • 2002
  • Penetration depth of Nb electrodes in $Nb/A1O_x/Nb$ Josephson junctions has been measured by resistive method. For a given applied field, the total flux through the junction is temperature dependent because the penetration depth of Nb electrode varies with temperature. If the total flux equals an integral multiple of the flux quantum at certain temperatures, resistive peaks appear at those temperatures. The penetration depth of Nb can be determined by applying the above condition, The temperature dependence of penetration depth was found to be well described by the two-fluid model.

The Electrical Roperties of TiN/$TiSi_2$ Bilayer Formed by Rapid Thermal Anneal at Submicron Contact (급속열처리에 의한 TiN/$TiSi_2$ 이중구조막을 이용한 submicron contact에서의 전기적 특성)

  • 이철진;성만영;성영권
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.31A no.9
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    • pp.78-88
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    • 1994
  • The electrical properties of TiM/TiSi$_{2}$ bilayer formed by rapid thermal anneal in NH$_{3}$ ambient after the Ti film is deposited on silicon cubstrate are investigated. N$^{+}$ contact resistance slightly increases with increasing annealing temperature with P$^{+}$ contact resistance decreases. The contact resistance of N$^{+}$ contance was less than 24[.OMEGA.] but P$^{+}$ thatn that of N$^{+}$ contact but the leakage current indicates degradation of the contact at high annealing temperature for both N$^{+}$ and contacts. The leakage current of N$^{+}$ Junction was less than 0.06[fA/${\mu}m^{2}$] but P$^{+}$ contact was 0.11-0.15[fA/${\mu}m^{2}$]. The junction breakdown voltage for N$^{+}$ junction remains contant with increasing annealing temperature while P$^{+}$ junction slightly decreases. The Electrical properties of a two step annealing are better than that of one step annealing. The Tin/TiSi$_{2}$ bilayer formed by RTA in NH$_{3}$ ambient reveals good electrical properties to be applicable at ULSI contact.

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Power Loss and Junction Temperature Analysis in the Modular Multilevel Converters for HVDC Transmission Systems

  • Wang, Haitian;Tang, Guangfu;He, Zhiyuan;Cao, Junzheng
    • Journal of Power Electronics
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    • v.15 no.3
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    • pp.685-694
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    • 2015
  • The power loss of the controllable switches in modular multilevel converter (MMC) HVDC transmission systems is an important factor, which can determine the design of the operating junction temperatures. Due to the dc current component, the approximate calculation tool provided by the manufacturer of the switches cannot be used for the losses of the switches in the MMC. Based on the enabled probabilities of each SM in an arm, the current analytical models of the switches can be determined. The average and RMS currents can be obtained from the corresponding current analytical model. Then, the conduction losses can be calculated, and the switching losses of the switches can be estimated according to the upper limit of the switching frequency. Finally, the thermal resistance model of the switches can be utilized, and the junction temperatures can be estimated. A comparison between the calculation and PSCAD simulation results shows that the proposed method is effective for estimating the junction temperatures of the switches in the MMC.

The characterization for the Ti-silicide of $N^+P$ junction by 2 step RTD (2단계 RTD방법에 의한 $N^+P$ 접합 티타늄 실리사이드 특성연구)

  • 최도영;윤석범;오환술
    • Electrical & Electronic Materials
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    • v.8 no.6
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    • pp.737-743
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    • 1995
  • Two step RTD(Rapid Thermal Diffussion) of P into silicon wafer using tungsten halogen lamp was used to fabricated very shallow n$^{+}$p junction. 1st RTD was performed in the temperature range of 800.deg. C for 60 see and the heating rate was in the 50.deg. C/sec. Phosphrous solid source was transfered on the silicon surface. 2nd RTD process was performed in the temperature range 1050.deg. C, 10sec. Using 2 step RTD we can obtain a shallow junction 0.13.mu.m in depth. After RTD, the Ti-silicide process was performed by the two step RTA(Rapid Thermal Annealing) to reduced the electric resistance and to improve the n$^{+}$p junction diode. The titanium thickness was 300.angs.. The condition of lst RTA process was 600.deg. C of 30sec and that of 2nd RTA process was varied in the range 700.deg. C, 750.deg. C, 800.deg. C for 10sec-60sec. After 2 step RTA, sheet resistance was 46.ohm../[]. Ti-silicide n+p junction diode was fabricated and I-V characteristics were measured.red.

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Control of Heat Temperature in Light Emitting Diodes with Thermoelectric Device (열전소자를 이용한 발광다이오드의 발열 온도 제어)

  • Han, S.H.;Kim, Y.J.;Kim, J.H.;Kim, D.J.;Jung, J.Y.;Kim, S.;Cho, G.S.
    • Journal of the Korean Vacuum Society
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    • v.20 no.4
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    • pp.280-287
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    • 2011
  • The heat temperature of a light emitting diode (LED) is investigated with the thermoelectric device (TED). The Peltier effect of the thermoelectric device is used to control the heat radiation and the junction temperature of high-power LEDs. For the typical specific current (350 mA) of high-power (1 W) LEDs, the LED temperature and the p-n junction temperature become $64.5^{\circ}C$ and $79.1^{\circ}C$, respectively. For 0.1~0.2 W driving power of TED, the LED temperature and the junction temperature are reduced to be $54.2^{\circ}C$ and $68.9^{\circ}C$, respectively. As the driving power of the TED increases over 0.2 W, the temperature of LED itself and the junction temperature are increased due to the heat reversed from the heat-sink to LED. As the difference of temperature between LED and the heat-sink is increased, the quantity of reversed heat becomes larger and it results to degrade the cooling capability of TED.

Study of hydrogenated a-SiGe cell for middle cell of Triple junction solar cell (Triple junction 태양전지의 a-SiGe middle cell에 관한 연구)

  • Park, Taejin;Baek, Seungjo;Kim, Beomjoon
    • 한국신재생에너지학회:학술대회논문집
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    • 2010.06a
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    • pp.83.1-83.1
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    • 2010
  • Hydrogenated a-SiGe middle cell for triple junction solar cell was investigated with various process parameters. a-SiGe I-layer was deposited at substrate temperature $245^{\circ}C$ and hydrogen content(R) was up to 26.7. Low optical bandgap(1.45eV) of a-SiGe cell was applied for middle cell although a-SiGe single cell efficiency with low Ge content was higher. And this cell was applied to the middle cell of a glass superstrate type a-Si/a-SiGe/uc-Si triple junction solar cell. The triple junction solar cell was resulted in the initial efficiency of about 9%, area $0.25cm^2$, under global AM 1.5 illumination.

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The Formation of the Shallow Junction by RTD and Characteristic Analysis for $n^+$ -p Diode with Ti-silicide (고속 열 확산에 의한 얕은 접합 형성과 Ti-실리시이드화된 $n^+$ -p 다이오드 특성 분석)

  • 최동영;이성욱;주정규;강명구;윤석범;오환술
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.31A no.8
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    • pp.80-90
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    • 1994
  • The ultra shallow junction was formed by 2-step RTP. Phosphorus solid source(P$_{2}O_{5}$) was transfered on wafer surface during RTG(Rapid Thermal Glass Transfer) of which process condition was 80$0^{\circ}C$ and 60sec. The process temperature and time of the RTD(Rapid Thermal Diffusion) were 950~105$0^{\circ}C$ during 5~15sec respectively sheet resistances were measured as 175~320$\Omega$/m and junction depth and dopth and dopant surface concentration were measured as 0.075~0.18$\mu$m and 5${\times}10^{19}cm^{4}$ respectively. Ti-silicide was formed by 2-step RTA after 300$\AA$ Titanium was deposited. The 1st RTA (2nd RTA) was carried out at the temperature of $600^{\circ}C$(700~80$0^{\circ}C$) for 30 seconds (10~60 seconds) under N$_2$ ambient. Sheet resistances after 2nd RTA were measured as 46~63$\Omega$/D. Si/Ti component ratio was evaulated as 1.6~1.9 from Auger depth profile. Ti-Silicided n-p junction diode (pattern size : 400$\times$400$\mu$m) was fabricated under the RTD(the process was carried out at the temperature of 100$0^{\circ}C$ for 10seconds) and 2nd RTA(theprocess was carried out at the temperature of 750$^{\circ}C$ for 60 seconds). Leakage current was measured 1.8${\times}10^{7}A/mm^{2}$ at 5V reverse voltage. Whent the RTD process condition is at the temperature of 100$0^{\circ}C$ for 10seconds and the 2nd RTA process condition is at the temperature of 75$0^{\circ}C$ for 60 seconds leakage current was 29.15${\times}10^{9}A$(at 5V).

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Influence of Relative Humidity on the Temperature Increase of a Power Converter

  • Xu, Yang;Chen, Hao;Hu, Zhentao;Li, Dong
    • Journal of Power Electronics
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    • v.15 no.3
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    • pp.841-848
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    • 2015
  • As a vital part of renewable energy and electrical traction, power converters are supposed to have high reliability and good performance. However, power semiconductors produce considerable heat when the power converter works, which results in high junction temperatures that lower the reliability and performance of the power semiconductors. Many studies show that ambient humidity has a significant effect on power devices, but the influence of high humidity on junction temperatures has yet to be studied. Therefore, this paper presents a thermal model for power converters in moist air to obtain the junction temperature increase, which is utilized for the power converter used in a Switched Reluctance Motor System. Simulation results show that the law of converter temperature distribution is independent of the relative humidity in the case of fixed ambient temperature, whereas the temperature in the power converter decreases as the ambient relative humidity increases. These simulation results are validated with the experimental results.