• Title/Summary/Keyword: temperature variations

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Electron Tunneling Characteristics of PtSi-nSi Junctions according to Temperature Variations (온도변화에 따른 백금 실리사이드-엔 실리콘 접합의 전자 터널링 특성)

  • 장창덕;이정석;이광우;이용재
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1998.06a
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    • pp.87-91
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    • 1998
  • In this paper, We analyzed the current-voltage characteristics with n-type silicon substrates concentration and temperature variations (Room temperature, 50$^{\circ}C$, 75$^{\circ}C$) in platinum silicide and silicon junction. The electrical parameters of measurement are turn-on voltage, saturation current, ideality factor, barrier height, dynamic resistance in forward bias and reverse breakdown voltage according to variations of junction concentration of substrates and measurement temperature variations. As a result, the forward turn-on voltage, reverse breakdown voltage, barrier height and dynamic resistance were decreased but saturation currents and ideality factor were increased by substrates increased concentration variations in platinum silicide and n-silicon junction. In increased measurement temperature (RT, 50$^{\circ}C$, 75$^{\circ}C$), the extracted electrical parameter values of characteristics were rises by increased temperature variations according to the forward and reverse bias.

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The Effect of the Oceanic Condition on Variations of the Catches of Alaska Pollack in the East Sea (the Japan Sea)

  • HONG Chul-hoon;CHO Kyu-Dae
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.30 no.6
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    • pp.997-1004
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    • 1997
  • The effect of the oceanic condition on variations of the catches of Alaska pollack (Theragra chalcogramma) in the East Sea (the Japan Sea) is examined using monthly catches data of this fish and temperature data during 1972 to 1991. Since 1973 the catches of Alaska pollack have gradually increased, showing a peak in 1981, and then rapidly decreased after 1986. A significant negative correlation was found between variations of the catches and the temperature at 50 m depth offshore Mukho. In 1981, the year of the highest catches in the study period, the water mass in the Eastern Korean Coastal Sea of the East Sea was extremely cold, while the year of poor catch, 1979, was much warmer than the annual mean temperature. The results show that the temperature variations around the Eastern Korean Coastal Sea play an important role in the variations of the catches of Alaska pollack, implying that the effect of the Tsushima Warm Current is also very important.

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Temperature Variations in the Mixed Layer with the Passage of Typhoons Using One-Dimensional Numerical Model (1차원 모델상에서 태풍통과시의 혼합층 수온 변화)

  • Hong, Chul-Hoon;Masuda, Akira
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.51 no.1
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    • pp.107-112
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    • 2018
  • One-dimensional numerical model is implemented to investigate temperature variations in the mixed layer depth (MLD) with the passage of typhoons. In the model, we assume a non-divergent, infinite ocean and consider wind effects only, excluding isostatic effects (inverse barometric effects) and upwelling with vertical movement of the water column. Numerical experiments investigate the effects of typhoon tracks on temperature variations, including their dependence on vertical resolutions in the MLD and these results are compared with those in a three-dimensional primitive equation model (POM). The model reproduces features of the observed temperature variations in the MLD fairly well, and implies that wind effects, rather than isostatic effects, play a predominant role in temporal and spatial temperature variations in the MLD. After the passage of typhoons, however, the model does not reproduce well the temperature variations observed in the MLD, because a limitation of the model is its inability to reproduce events such as cyclonic eddy formation (Hong et al., 2011; Masuda and Hong, 2011). The model also shows well the so called 'rightward bias' (Price, 1981) of sea surface cooling which is the most predominant in the right hand side of typhoon's track.

Measurement of Surface Heat Transfer Using Exponential Temperature Variations (지수형 온도변화를 이용한 표면 열전달의 측정)

  • Park, Byung Kyu;Hong, Taek;Park, Sang Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.9
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    • pp.1121-1128
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    • 1999
  • A single blow, transient testing method for determining the heat transfer characteristics of heat exchanger surfaces are presented. The exponential inlet temperature variations were made using screen mesh with small time constant and frontal velocities of the test section. The system is used to investigate the usefulness of a model with exponential inlet temperature variations. A data reduction program is developed to calculate the temporally and spatially averaged heat transfer coefficient using the measured disturbance and response of the fluid temperature. The results are compared with the existing theoretical and experimental data for parallel plate stacks. It was recommended to take an average for the time greater than the 99% of the final temperature had reached in order to obtain fairly good results.

Estimating groundwater recharge from time series measurements of subsurface temperature

  • Koo, Min-Ho;Kim, Yongje
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2003.09a
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    • pp.213-216
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    • 2003
  • Efforts for better understanding of the interaction between groundwater recharge and thermal regime of the subsurface medium is gaining momentum for its diverse applications in water resources. A numerical model is developed to simulate temperature variations of the subsurface under time varying groundwater recharge. The model utilizes MacCormack scheme for finite difference approximation of the partial differential equation describing the conductive and advective heat transport. For the estimation of recharge rate, optimization of the model is realized by searching for the unknown parameters which minimize the root-mean-square error between simulated and measured temperatures. Simulation results for 22-year time series data of temperature measurements reveal that the proposed model can accurately simulate subsurface temperature variations resulting from the redistribution of the heat due to the movement of water and it can also estimate temporal variations of recharge. Seasonal variations of recharge and a linear relationship between precipitation and recharge are clearly reflected in the simulated results.

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A study on the development of constant temperature hot wire type air flow meter for automobiles (자동차용 정온도 열선식 공기유량계의 개발에 관한 연구)

  • 조성권;유정열;고상근;김동성
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.12
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    • pp.2407-2414
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    • 1992
  • Constant temperature hot wire air flow meter for automobiles requires temperature compensation system because hot wire output signal is sensitive to ambient temperature variations as well as fluid velocity. The objectives of the present study are to design an air flow meter circuit which is capable of compensating the hot wire output signal for ambient temperature variations and to investigate the mechanism of such temperature compensation. This circuit is composed of platinum hot wire, platinum resistor, two variable resistors, a constant resistor and a DC-amplifier. In particular, by simply replacing a constant resistor in one of the bridge arms of the conventional circuit with platinum resistor and a variable resistor for the purpose of temperature compensation, the deviation of output signal with respect to ambient temperature variations between 27deg. C 70deg. C could be reduced to less than 2.5% for mass flow rate and to less than 5% for velocity respectively. The mechanism of temperature compensation against ambient temperature variations was explained by means of measuring the heat transfer coefficient with hot wire temperature variations and analyzing and analyzing conventional empirical equations qualitatively.

Parameter Analysis of Platinum Silicide Rectifier Junctions acceding to measurement Temperature Variations (측정 온도 변화에 따른 백금실리사이드 정류성 접합의 파라미터 분석)

  • 장창덕;이용재
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 1998.05a
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    • pp.405-408
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    • 1998
  • In this paper, We analyzed the current-voltage characteristics with n-type silicon substrates concentration and temperature variations (Room temperature, 5$0^{\circ}C$, 75$^{\circ}C$) in platinum silicide and silicon junction. Measurement electrical parameters are forward turn-on voltage, reverse breakdown voltage, barrier height, saturation current, ideality factor, dynamic resistance acceding to junction concentration of substrates and temperature variations. As a result, the forward turn-on voltage, reverse breakdown voltage, barrier height and dynamic resistance were decreased but saturation current and ideality factor were increased by substrates concentration variations. Reverse breakdown voltage and dynamic resistance were increased by temperature variations.

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SEASONAL AND SUBINERTIAL VARIATIONS IN THE SOYA WARM CURRENT REVEALED BY HF OCEAN RADARS, COASTAL TIDE GAUGES, AND A BOTTOM-MOUNTED ADCP

  • Ebuchi, Naoto;Fukamachi, Yasushi;Ohshima, Kay I.;Wakatsuchi, Masaaki
    • Proceedings of the KSRS Conference
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    • 2008.10a
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    • pp.340-343
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    • 2008
  • The Soya Warm Current (SWC) is a coastal boundary current, which flows along the coast of Hokkaido in the Sea of Okhotsk. Seasonal and subinertial variations in the SWC are investigated using data obtained by high-frequency (HF) ocean radars, coastal tide gauges, and a bottom-mounted acoustic Doppler current profiler (ADCP). The HF radars clearly capture the seasonal variations in the surface current fields of the SWC. The velocity of the SWC reaches its maximum, approximately 1 m/s, in the summer, and becomes weaker in the winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 50 km. The almost same seasonal cycle was repeated in the period from August 2003 to March 2007. In addition to the annual variation, the SWC exhibits subinertial variations with a period from 10-15 days. The surface transport by the SWC shows a significant correlation with the sea level difference between the Sea of Japan and Sea of Okhotsk for both of the seasonal and subinertial variations, indicating that the SWC is driven by the sea level difference between the two seas. Generation mechanism of the subinertial variation is discussed using wind data from the European Centre for Medium-range Weather Forecasts (ECMWF) analyses. The subinertial variations in the SWC are significantly correlated with the meridional wind component over the region. The subinertial variations in the sea level difference and surface current delay from the meridional wind variations for one or two days. Continental shelf waves triggered by the meridional wind on the east coast of Sakhalin and west coast of Hokkaido are considered to be a possible generation mechanism for the subinertial variations in the SWC.

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Damage Detection in Bridges Using Modal Flexibility Matrices Under Temperature Variation (상시 온도변화 효과를 고려한 모드 유연도행렬 기반의 교량의 손상탐색기법)

  • Koo, Ki-Young;Lee, Jong-Jae;Yun, Chung-Bang
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2007.04a
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    • pp.651-656
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    • 2007
  • Changes in measured structural responses induced by a damage could be significantly smaller than those by environmental effects such as temperature and temperature gradients. It is highly desirable to develop a methodology to distinguish the changes due to the structural damage from those by the environmental variations. In this study, a novel method to extract the damage-induced deflection under temperature variations is presented using the outlier analysis on the deflections obtained using the modal flexibility matrices. The main idea is that temperature change in a bridge would produce global increase or decrease in deflections over the whole bridge while structural damages may cause local variations in deflections near the damage locations. Hence, the correlation between the deflection measurements may show high abnormality near the damage locations. A series of laboratory tests were carried out on a bridge model with a steel box-girder for 14 days. It has been found that the damage existence assessment and localization can carried out for a case with relatively small damage under the temperature variations

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Electrical Performance Characteristics of 200W PEM-Type Fuel Cells with Variations on Mass Flow Rate and Stack Temperature (공급유량 및 스택온도의 변이에 따른 200W급 PEM형 연료전지의 전기적 성능특성)

  • Hong, Kyung-Jin;Park, Se-Joon;Choi, Yong-Sung;Lee, Kyung-Sup
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.58 no.4
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    • pp.563-567
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    • 2009
  • The polymer electrolyte membrane fuel cell(PEMFC) with the advantages of low-operating temperature, high current density, low cost and volume, fast start-up ability, and suitability for discontinuous operation becomes the most reasonable and attractive power system for transportation vehicle and micro-grid power plant in a household. 200W PEM-type FCs system was integrated by this study, then the electrical characteristics and diagnosis of the fuel cell were analyzed with variations on mass flow rate and stack temperature. The ranges of the variations are 1~8L/min on $H_2$ volume and $20{\sim}70^{\circ}C$ on stack temperature.