The non-hydrostatic mesoscale model MM5V3 is used to simulate the wind andtemperature fields of the atmospheric boundary layer over Beijing area in summer with the meshresolution of 1 km. The simulation results show t...The non-hydrostatic mesoscale model MM5V3 is used to simulate the wind andtemperature fields of the atmospheric boundary layer over Beijing area in summer with the meshresolution of 1 km. The simulation results show that the numerical model can successfully simulatethe urban heat island effect and the wind and temperature fields which are affected by thecomplicated topography and urban heat island. The results show that: (1) the west area (from Haidianto Fengtai Districts) is always the high temperature center of Beijing, where the surfacetemperature is about 6 K higher than the other suburbs; and (2) due to the unique topography thewind of Beijing area during the daytime is southern anabatic wind and at the night is northernkatabatic wind. The results comparing well with the data from surface observation stations validatethe accuracy of the simulation.展开更多
Self‐regulating high‐temperature superconducting(HTS)flux pumps enable direct current injection into a closed‐loop superconducting coil without any electrical contact.In this work,the process of charging a coil by ...Self‐regulating high‐temperature superconducting(HTS)flux pumps enable direct current injection into a closed‐loop superconducting coil without any electrical contact.In this work,the process of charging a coil by a self‐regulating HTS flux pump is examined in detail by numerical modeling.The proposed model combines an H‐formulation finite element method(FEM)model with an electrical circuit,enabling a comprehensive evaluation of the overall performance of self‐regulating HTS flux pumps while accurately capturing local effects.The results indicate that the proposed model can capture all the critical features of a self‐regulating HTS flux pump,including superconducting properties and the impact of the secondary resistance.When the numerical results are compared to the experimental data,the presented model is found to be acceptable both qualitatively and quantitatively.Based on this model,we have demonstrated how the addition of a milliohm range,normal‐conducting secondary resistance in series with the charging loop can improve the charging process.In addition,its impact on the charging performance is revealed,including the maximum achievable current,charging speed,and the generated losses.The modeling approach employed in this study can be generalized to the optimization and design of various types of flux pumps,potentially expediting their practical application.展开更多
We report the circuit simulations and experiments of millimeter-wave radiation from a high temperature superconducting(HTS) bicrystal Josephson junction(BJJ) array. To study the effects of junction characteristic para...We report the circuit simulations and experiments of millimeter-wave radiation from a high temperature superconducting(HTS) bicrystal Josephson junction(BJJ) array. To study the effects of junction characteristic parameters on radiation properties, new radiation circuit models are proposed in this paper. The series resistively and capacitively shunted junction(RCSJ) models are packaged into a Josephson junction array(JJA) model in the simulation. The current-voltage characteristics(IVCs) curve and radiation peaks are simulated and analyzed by circuit models, which are also observed from the experiment at liquid nitrogen temperature. The experimental radiation linewidth and power are in good agreement with simulated results. The presented circuit models clearly demonstrate that the inconsistency of the JJA will cause a broad linewidth and a low detected power. The junction radiation properties are also investigated at the optimal situation by circuit simulation. The results further confirm that the consistent JJA characteristic parameters can successfully narrow the radiation linewidth and increase the power of junction radiation.展开更多
A sub-circuit SPICE model of a MOSFET for low temperature operation is presented.Two resistors are introduced for the freeze-out effect,and the explicit behavioral models are developed for them.The model can be used i...A sub-circuit SPICE model of a MOSFET for low temperature operation is presented.Two resistors are introduced for the freeze-out effect,and the explicit behavioral models are developed for them.The model can be used in a wide temperature range covering both cryogenic temperature and regular temperatures.展开更多
为了建立基于生理的黄瓜生长可视化生长模型,该研究根据黄瓜地上部分对温度和有效光合辐射的响应,建立了以光温因子—辐热积(product of thermal effectiveness and PAR,TEP)为尺度的黄瓜地上部分模型,并用独立的试验数据进行了检验。...为了建立基于生理的黄瓜生长可视化生长模型,该研究根据黄瓜地上部分对温度和有效光合辐射的响应,建立了以光温因子—辐热积(product of thermal effectiveness and PAR,TEP)为尺度的黄瓜地上部分模型,并用独立的试验数据进行了检验。模型对黄瓜叶片形态特性、叶柄长度和直径以及节间高度和直径的模拟值和实测值的符合度较好,对黄瓜主茎高度的模拟值与实测值之间有一定的差异,模型对黄瓜叶片形态特性的模拟值与实测值之间的决定系数分别为0.92、0.91、0.95,回归标准误差分别为8.5,6.9,2.8 mm;模型对叶柄长度和直径的决定系数分别为为0.89,0.93,回归标准误差分别为5.6,0.3 mm;模型对节间长度和节间直径以及主径高度的决定系数分别为0.87,0.91,0.75,回归标准误差分别为4.5、0.8、120 mm;模型对果长和果径的决定系数分别为0.85和0.92,回归标准误差分别为8.2和2.4 mm。该研究建立的辐热积模型能较准确地预测黄瓜地上部分的生长情况,可为黄瓜生长可视化系统的开发提供理论参考。展开更多
基金Project supported by the National Natural Science Foundation of China and Hong Kong under Grant Nos. 40275004,4001161948.
文摘The non-hydrostatic mesoscale model MM5V3 is used to simulate the wind andtemperature fields of the atmospheric boundary layer over Beijing area in summer with the meshresolution of 1 km. The simulation results show that the numerical model can successfully simulatethe urban heat island effect and the wind and temperature fields which are affected by thecomplicated topography and urban heat island. The results show that: (1) the west area (from Haidianto Fengtai Districts) is always the high temperature center of Beijing, where the surfacetemperature is about 6 K higher than the other suburbs; and (2) due to the unique topography thewind of Beijing area during the daytime is southern anabatic wind and at the night is northernkatabatic wind. The results comparing well with the data from surface observation stations validatethe accuracy of the simulation.
文摘Self‐regulating high‐temperature superconducting(HTS)flux pumps enable direct current injection into a closed‐loop superconducting coil without any electrical contact.In this work,the process of charging a coil by a self‐regulating HTS flux pump is examined in detail by numerical modeling.The proposed model combines an H‐formulation finite element method(FEM)model with an electrical circuit,enabling a comprehensive evaluation of the overall performance of self‐regulating HTS flux pumps while accurately capturing local effects.The results indicate that the proposed model can capture all the critical features of a self‐regulating HTS flux pump,including superconducting properties and the impact of the secondary resistance.When the numerical results are compared to the experimental data,the presented model is found to be acceptable both qualitatively and quantitatively.Based on this model,we have demonstrated how the addition of a milliohm range,normal‐conducting secondary resistance in series with the charging loop can improve the charging process.In addition,its impact on the charging performance is revealed,including the maximum achievable current,charging speed,and the generated losses.The modeling approach employed in this study can be generalized to the optimization and design of various types of flux pumps,potentially expediting their practical application.
基金Project supported by the National Natural Science Foundation of China(Grant No.51002081)the Fundamental Research Funds for the Central Universities,China+1 种基金the China Manned Space Advance Research Program,China(Grant No.030201)the Research Program of Application Foundation and Advanced Technology of Tianjin,China(Grant No.15JCQNJC01300)
文摘We report the circuit simulations and experiments of millimeter-wave radiation from a high temperature superconducting(HTS) bicrystal Josephson junction(BJJ) array. To study the effects of junction characteristic parameters on radiation properties, new radiation circuit models are proposed in this paper. The series resistively and capacitively shunted junction(RCSJ) models are packaged into a Josephson junction array(JJA) model in the simulation. The current-voltage characteristics(IVCs) curve and radiation peaks are simulated and analyzed by circuit models, which are also observed from the experiment at liquid nitrogen temperature. The experimental radiation linewidth and power are in good agreement with simulated results. The presented circuit models clearly demonstrate that the inconsistency of the JJA will cause a broad linewidth and a low detected power. The junction radiation properties are also investigated at the optimal situation by circuit simulation. The results further confirm that the consistent JJA characteristic parameters can successfully narrow the radiation linewidth and increase the power of junction radiation.
基金Project supported by the Natural Science Foundation of Jiangsu Province,China(NoBK2008287)the Advanced Research of National Natural Science Foundation of Southeast University,China(NoXJ2008312)
文摘A sub-circuit SPICE model of a MOSFET for low temperature operation is presented.Two resistors are introduced for the freeze-out effect,and the explicit behavioral models are developed for them.The model can be used in a wide temperature range covering both cryogenic temperature and regular temperatures.
文摘为了建立基于生理的黄瓜生长可视化生长模型,该研究根据黄瓜地上部分对温度和有效光合辐射的响应,建立了以光温因子—辐热积(product of thermal effectiveness and PAR,TEP)为尺度的黄瓜地上部分模型,并用独立的试验数据进行了检验。模型对黄瓜叶片形态特性、叶柄长度和直径以及节间高度和直径的模拟值和实测值的符合度较好,对黄瓜主茎高度的模拟值与实测值之间有一定的差异,模型对黄瓜叶片形态特性的模拟值与实测值之间的决定系数分别为0.92、0.91、0.95,回归标准误差分别为8.5,6.9,2.8 mm;模型对叶柄长度和直径的决定系数分别为为0.89,0.93,回归标准误差分别为5.6,0.3 mm;模型对节间长度和节间直径以及主径高度的决定系数分别为0.87,0.91,0.75,回归标准误差分别为4.5、0.8、120 mm;模型对果长和果径的决定系数分别为0.85和0.92,回归标准误差分别为8.2和2.4 mm。该研究建立的辐热积模型能较准确地预测黄瓜地上部分的生长情况,可为黄瓜生长可视化系统的开发提供理论参考。
