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Search Results: 1 - 10 of 33413 matches for " FENG Huijun "
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Optimal ratios of the piston speeds for a finite speed endoreversible Carnot heat engine cycle
Feng, Huijun;Chen, Lingen;Sun, Fengrui;
Revista mexicana de física , 2010,
Abstract: the performance of an endoreversible carnot heat engine cycle is analyzed and optimized using the theory of finite time thermodynamics based on agrawal and menon'si model of finite speed of the piston on the four branches and curzon and ahlborn'sii model of finite rate of heat transfer. the finite speeds of the piston on the four branches are further assumed to be different, which is unlike the model of constant-speed of the piston on the four branches. the analytical formula between power and efficiency of the cycle is derived for a fixed cycle period. there exist optimal ratios of the finite piston speeds on the four branches. the effects of the temperature ratio of the heat reservoirs on the dimensionless power versus efficiency of the cycle and isothermal expansion ratio are obtained by numerical examples.
Heating load, COP, exergy loss rate, exergy output rate and ecological optimizations for a class of generalized irreversible universal heat pump cycles
Chen, Lingen;Feng, Huijun;Sun, Fengrui;
Revista mexicana de física , 2010,
Abstract: the optimal performance of a class of generalized irreversible universal steady flow heat pump cycle model, which consists of two heat-absorbing branches, two heat-releasing branches and two irreversible adiabatic branches with the losses of heat-resistance, heat leakage and internal irreversibility is analyzed by using finite time thermodynamics. the analytical formulae about heating load, coefficient of performance (cop), exergy loss rate, exergy output rate and ecological function of the universal heat pump cycle are derived. moreover, performance comparisons among maximum cop condition, a given exergy output rate condition and maximum ecological function condition are carried out by using numerical examples. it is shown that the ecological function objective is an excellent candidate objective with the ideal of an ecological and long-term goal. the effects of heat leakage and internal irreversibility on the cycle performance are discussed. the universal cycle model gives a unified description of seven heat pump cycles, and the results obtained include the performance characteristics of brayton, otto, diesel, atkinson, dual, miller and carnot heat pump cycles with the losses of heat-resistance, heat leakage and internal irreversibility.
Interannual variability of Mascarene high and Australian high and their influences on summer rainfall over East Asia
Feng Xue,Huijun Wang,Jinhai He
Chinese Science Bulletin , 2003, DOI: 10.1007/BF03183258
Abstract: Based on the reanalysis data from NCEP/NCAR and other observational data, interannual variability of Mascarene high (MH) and Australian high (AH) from 1970 to 1999 is examined. It is shown that interannual variability of MH is dominated by the Antarctic oscillation (AAO), when the circumpolar low in the high southern latitudes deepens, the intensity of MH will be intensified. On the other hand, AH is correlated by AAO as well as El Ni o and South Oscillation (ENSO), the intensity of AH will be intensified when El Ni o occurs. Both correlation analysis and case study demonstrate that summer rainfall over East Asia is closely related to MH and AH. When MH intensifies from boreal spring to summer (i.e. from austral autumn to winter), there is more rainfall over regions from the Yangtze River valley to Japan, in contrast, less rainfall is found over southern China and western Pacific to the east of Taiwan, and most of regions in mid-latitudes of East Asia. Compared with MH, the effect of AH on summer rainfall in East Asia is limited to localized regions, there is more rainfall over southern China with the intensification of AH. The results in this study show that AAO is a strong signal on interannual timescale, which plays an important role in summer rainfall over East Asia. This discovery is of real importance to revealing the physical mechanism of interannual variability of East Asian summer monsoon and prediction of summer precipitation in China.
Finite time exergoeconomic performance optimization for an irreversible universal steady flow variable-temperature heat reservoir heat pump cycle model
Huijun Feng, Lingen Chen, Fengrui Sun
International Journal of Energy and Environment , 2010,
Abstract: An irreversible universal steady flow heat pump cycle model with variable-temperature heat reservoirs and the losses of heat-resistance and internal irreversibility is established by using the theory of finite time thermodynamics. The universal heat pump cycle model consists of two heat-absorbing branches, two heat-releasing branches and two adiabatic branches. Expressions of heating load, coefficient of performance (COP) and profit rate of the universal heat pump cycle model are derived, respectively. By means of numerical calculations, heat conductance distributions between hot- and cold-side heat exchangers are optimized by taking the maximum profit rate as objective. There exist an optimal heat conductance distribution and an optimal thermal capacity rate matching between the working fluid and heat reservoirs which lead to a double maximum profit rate. The effects of internal irreversibility, total heat exchanger inventory, thermal capacity rate of the working fluid and heat capacity ratio of the heat reservoirs on the optimal finite time exergoeconomic performance of the cycle are discussed in detail. The results obtained herein include the optimal finite time exergoeconomic performances of endoreversible and irreversible, constant- and variable-temperature heat reservoir Brayton, Otto, Diesel, Atkinson, Dual, Miller and Carnot heat pump cycles.
Optimal ratios of the piston speeds for a finite speed endoreversible Carnot heat engine cycle
Huijun Feng,Lingen Chen,Fengrui Sun
Revista mexicana de física , 2010,
Abstract: Se analiza y optimiza el funcionamiento cíclico de un motor endoreversible de Carnot, utilizando la teoría termodinámica de tiempo finito basada en el modelo de Agrawal y Menon i de velocidad finita del pistón en los cuatro cilindros, y en el modelo de rapidez finita de transporte de calor de Curzon y Ahlborn ii. También se supone que las velocidades del pistón en los cuatro cilindros son diferentes. Se deduce la fórmula analítica de la potencia y la eficiencia para un período del ciclo. Resultan cocientes óptimos para las velocidades finitas del pistón en los cuatro cilindros. Se obtienen, mediante ejemplos numéricos, los efectos del cociente de temperatura de los focos térmicos sobre la potencia versus la eficiencia del ciclo y el coeficiente de dilatación isotérmica.
Heating load, COP, exergy loss rate, exergy output rate and ecological optimizations for a class of generalized irreversible universal heat pump cycles
Lingen Chen,Huijun Feng,Fengrui Sun
Revista mexicana de física , 2010,
Abstract: Se analiza el funcionamiento óptimo de una clase de modelo universal irreversible generalizado del ciclo de una bomba térmica de flujo constante, que consiste en dos ramas de absorción térmica, dos ramas de liberación de calor y dos ramas adiabáticas irreversibles con pérdidas de resistencia al calor, de salida del calor y de irrevocabilidad interna, usando la termodinámica de tiempos finitos. Se obtienen las fórmulas analíticas de la carga de calor, del coeficiente del funcionamiento (CF), del índice de pérdida de exergía, del índice de salida de exergía, así como de la función ecológica del ciclo universal de la bomba de calor. Por otra parte, se compara el funcionamiento de la condición máxima del CF dada una condición de razón de salida de exergía con la condición del máximo de la función ecológica usando ejemplos numéricos. Se demuestra que el objetivo de la función ecológica es un excelente de candidato para el ideal de una meta ecológica y de largo plazo. Se discuten los efectos del escape de calor y de la irreversibilidad interna sobre el funcionamiento del ciclo. El modelo universal del ciclo da una descripción unificada de siete ciclos de la bomba de calor, y los resultados obtenidos incluyen las características de funcionamiento de los ciclos de Brayton, de Otto, Diesel, Atkinson, Dual, Miller y Carnot para bombas térmicas con pérdidas de la resistencia al calor, del escape de calor y de irreversibilidad interna.
The Spring Monsoon in South China and Its Relationship to Large-Scale Circulation Features
中国华南春季季风及其与大尺度环流特征的关系

Wang Huijun,Xue Feng,Zhou Guangqing,
Wang Huijun
,Xue Feng,Zhou Guangqing

大气科学进展 , 2002,
Abstract: In this paper, the authors define the spring monsoon in South China, and study the climatology and the interannual variation through analysis of the precipitation and the related atmospheric circulation, as revealed by the NCEP/NCAR reanalysis data. The results indicate that the spring monsoon season in South China occurs climatologically in April and May, which is supported by both seasonal and interannual variation of the atmospheric circulation and precipitation. The related atmospheric circulation is different from that during the East Asian summer or winter monsoon season. The interannual variation of the spring monsoon rainfall in South China relates primarily to the anomalous circulation over the North Pacific, which is linked with the westerly jet over North Asia and with the polar vortex. It is also connected with sea surface temperature anomalies in the Pacific. Changes in the Asian tropical atmospheric circulation has little influence on the spring monsoon in South China according to this research.
Responses of Reactive Oxygen Scavenging Enzymes, Proline and Malondialdehyde to Water Deficits among Six Secondary Successional Seral Species in Loess Plateau
Feng Du, Huijun Shi, Xingchang Zhang, Xuexuan Xu
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0098872
Abstract: Drought can impact local vegetation dynamics in a long term. In order to predict the possible successional pathway of local community under drought, the responses of some drought resistance indices of six successional seral species in the semi-arid Loss Hilly Region of China were illustrated and compared on three levels of soil water deficits along three growing months (7, 8 and 9). The results showed that: 1) the six species had significant differences in SOD, POD activities and MDA content. The rank correlations between SOD, POD activities and the successional niche positions of the six species were positive, and the correlation between MDA content and the niche positions was negative; 2) activities of SOD, CAT and POD, and content of proline and MDA had significant differences among the three months; 3) there existed significant interactions of SOD, CAT, POD activities and MDA content between months and species. With an exception, no interaction of proline was found. Proline in leaves had a general decline in reproductive month; 4) SOD, CAT, POD activities and proline content had negative correlations with MDA content. Among which, the correlation between SOD activity and MDA content was significant. The results implied that, in arid or semiarid region, the species at later successional stage tend to have strong drought resistance than those at early stage. Anti-drought indices can partially interpret the pathway of community succession in the drought impacted area. SOD activity is more distinct and important on the scope of protecting membrane damage through the scavenging of ROS on exposure to drought.
Nonequilibrium Glass Transition in Mixtures of Active-Passive Particles
Huai Ding,Mengkai Feng,Huijun Jiang,Zhonghuai Hou
Physics , 2015,
Abstract: We develop a mode coupling theory(MCT) to study the nonequilibrium glass transition behavior of a mono-disperse mixture of active-passive hard-sphere particles. The MCT equations clearly demonstrate that the glass transition is shifted to higher values of total volume fraction when doping a passive system with active particles. Interestingly, we find that the glass transition point may show a non-monotonic dependence on the effective diffusivity of the active component, indicating a nontrivial type of activity induced reentrance behavior. Analysis based on the nonergodic parameters suggest that the glassy state at small activity is due to the caging effect, while that at high activity could result from activity induced dynamic clustering.
The African Climate as Predicted by the IAP Grid-Point Nine-Layer Atmospheric General Circulation Model (IAP-9L-AGCM)
Chineke Theo Chidiezie,Bi Xunqiang,Wang Huijun,Xue Feng,
Chineke Theo Chidiezie
,Bi Xunqiang,Wang Huijun,Xue Feng

大气科学进展 , 1997,
Abstract: A brief introduction is given of the Grid-point 9-layer Atmospheric General Circulation Model (AGCM) de-veloped at the Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences. The results of the 1980-1989 Atmospheric Model Inter-Comparison Program (AMIP) run were compared with observed European Centre for Medium-Range weather Forecasts (ECMWF) temperature data for the same period. The statistical analysis, and Grids Analysis and Display System (GrADS) results have shown that the model holds a great promise in predicting the African climate with considerable accuracy, within and across the seasons. This is a great hope for climate re-search in Africa which is data-sparse region.
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