A monolithic microwave integrated circuit （MMIC） power amplifier （PA） is proposed. It adopts a new on-chip bias circuit, which not only avoids the instability of the direct current bias caused by the change in the...A monolithic microwave integrated circuit （MMIC） power amplifier （PA） is proposed. It adopts a new on-chip bias circuit, which not only avoids the instability of the direct current bias caused by the change in the power supply and temperature, but also compensates deviations caused by the increase in input power. The bias circuit is a current-mirror configuration, and the feedback circuit helps to maintain bias voltage at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit. A shunt capacitor at the base node of the active bias transistor enhances the linearity of the PA. The chip is fabricated in an InGaP/GaAs heterojunction bipolar transistor （HBT） process. Measured results exhibit a 26. 6-dBm output compression point, 33.6% power-added efficiency （PAE） and - 40.2 dBc adjacent channel power ratio （ACPR） for wide-band code division multiple access （W-CDMA） applications.展开更多
With the large-signal model extracted from the InGaP/GaAs HBT with three fingers,a three-stage,class AB power amplifier at ISM band is designed.Through the optimization of the traditional bias network,the gain compres...With the large-signal model extracted from the InGaP/GaAs HBT with three fingers,a three-stage,class AB power amplifier at ISM band is designed.Through the optimization of the traditional bias network,the gain compression at the low input power level is eliminated successfully.At 3.5V of supply voltage of the power amplifier after optimization exhibits 30dBm of maximum linear output power,43.4% of power added efficiency 109.7mA of a quite low quiescent bias current ,29.1dB of the corresponding gain,and -100dBc of the adjacent channel power rejection (ACPR) at the output power of 30dBm.展开更多
In the process of tobacco production, the moisture content of tobacco leaves directly affects the quality of tobacco leaf. Since the water content in the leaf is low, it needs to process with the conditioning treatmen...In the process of tobacco production, the moisture content of tobacco leaves directly affects the quality of tobacco leaf. Since the water content in the leaf is low, it needs to process with the conditioning treatment for a short time beforetobacco grading, so as to improve the tobacco moisture content and reduce breakage, as well as ensure the quality and yield of tobacco, ahd meet the requirements of the follow-up process of tobacco. Therefore, a comprehensive overview was given to the pre-conditioning method for tobacco leaf, and the current application status of tobacco leaf pre-conditioning equipment in China was explored.展开更多
Much has been written and researched about transformational change and the exogenous events that result in radical institutional transformation （Di Maggio ＆ Powell, 1983; Hannan＆ Freeman, 1989; Fligstein, 1996; Zor...Much has been written and researched about transformational change and the exogenous events that result in radical institutional transformation （Di Maggio ＆ Powell, 1983; Hannan＆ Freeman, 1989; Fligstein, 1996; Zorn, Dobbin, ＆ Kwok, 2006）. Accounts are provided of external agents disturbing the existing stasis of the institution and transforming the institution into something else that reflect a new paradigm or set of interests. Often, what is neglected in these accounts is what fractures exist in the original institution that would make them vulnerable and allow penetration by exogenous influences. Mahoney and Thelen （20 l 0） went beyond a general model of change that described the collapse of one set of institutional norms to be replaced by another. The model of change they propose takes into account both exogenous as well as endogenous factors as being the source of institutional change. They went on to state a view that transformation change as being a result of abrupt, wholesale breakdown needs to be rethought to include incremental, endogenous shifts in thinking that can often result in fundamental transformations.展开更多
Considering the flexibility and controllability of heat exchanger networks (HENs), bypasses are widely used for effective control of process stream target temperatures. However, the optimal location for the bypass is ...Considering the flexibility and controllability of heat exchanger networks (HENs), bypasses are widely used for effective control of process stream target temperatures. However, the optimal location for the bypass is generally difficult to design with the trade-off between controllability and capital investments. In this paper, based on the steady-state model of heat exchanger networks the optimal bypass location was firstly selected by iteratively calculating the non-square Relative Gain Array (ns-RGA). To simplify the calculation process, rules of bypass selection were also proposed. In order to evaluate this method, then, the structural controllability of heat exchanger networks was analyzed. With both the consideration of the controllability and capital investments, the bypasses locations were finally selected. A case study on the HEN in Crude Distillation Unit was presented in which the ns-RGA and structural controllability were used to select bypasses and also to evaluate the results.展开更多
In the evolution of economic growth drivers, technology gaps are a key variable that determines the efficiency of resource allocation. Analysis of an optimal resource allocation path based on an extended endogenous gr...In the evolution of economic growth drivers, technology gaps are a key variable that determines the efficiency of resource allocation. Analysis of an optimal resource allocation path based on an extended endogenous growth model reveals that economic growth drivers evolve from productive investment to R＆D investment and a shift from imitation to innovation. Empirical analysis based on China＇s provincial-level panel data suggests that the effect of productive investment and R＆D investment, as well as innovation and imitation, on economic growth and technological progress varies greatly among regions of disparate technology levels. As a late-starting country, China should properly allocate resources between productive investment and R＆D investment, and between imitational investment and innovative investment while advancing the transformation of economic growth patterns on a differentiated basis in light of regional technology disparities.展开更多
We report where and how ions are accelerated in the proximity of earthward propagating dipolarization fronts （DFs） in the magnetotail during a magnetospheric substorm on February 15, 2008. Two DFs were observed by m...We report where and how ions are accelerated in the proximity of earthward propagating dipolarization fronts （DFs） in the magnetotail during a magnetospheric substorm on February 15, 2008. Two DFs were observed by multiple THEMIS space- craft in the near-Earth magnetotail （-10 Re）. We studied the ion dynamics associated with these DFs by comparing observed results with large scale kinetic （LSK） simulation results. The LSK simulation reproduced the sudden ion energy flux enhance- ment concurrent with the arrival of the DF at the satellite locations. We found that ions can be accelerated to more than 100 keV energy at the DF. These ions were initially non-adiabatically accelerated near magnetic reconnection site and then still non-adiabatically accelerated at the DF structure.展开更多
基金The National High Technology Research and Development Program of China(863 Program)(No.2009AA01Z260)
文摘A monolithic microwave integrated circuit （MMIC） power amplifier （PA） is proposed. It adopts a new on-chip bias circuit, which not only avoids the instability of the direct current bias caused by the change in the power supply and temperature, but also compensates deviations caused by the increase in input power. The bias circuit is a current-mirror configuration, and the feedback circuit helps to maintain bias voltage at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit. A shunt capacitor at the base node of the active bias transistor enhances the linearity of the PA. The chip is fabricated in an InGaP/GaAs heterojunction bipolar transistor （HBT） process. Measured results exhibit a 26. 6-dBm output compression point, 33.6% power-added efficiency （PAE） and - 40.2 dBc adjacent channel power ratio （ACPR） for wide-band code division multiple access （W-CDMA） applications.
文摘With the large-signal model extracted from the InGaP/GaAs HBT with three fingers,a three-stage,class AB power amplifier at ISM band is designed.Through the optimization of the traditional bias network,the gain compression at the low input power level is eliminated successfully.At 3.5V of supply voltage of the power amplifier after optimization exhibits 30dBm of maximum linear output power,43.4% of power added efficiency 109.7mA of a quite low quiescent bias current ,29.1dB of the corresponding gain,and -100dBc of the adjacent channel power rejection (ACPR) at the output power of 30dBm.
基金Supported by the Project of Zhengzhou Tobacco Company of Henan Province(201415)~~
文摘In the process of tobacco production, the moisture content of tobacco leaves directly affects the quality of tobacco leaf. Since the water content in the leaf is low, it needs to process with the conditioning treatment for a short time beforetobacco grading, so as to improve the tobacco moisture content and reduce breakage, as well as ensure the quality and yield of tobacco, ahd meet the requirements of the follow-up process of tobacco. Therefore, a comprehensive overview was given to the pre-conditioning method for tobacco leaf, and the current application status of tobacco leaf pre-conditioning equipment in China was explored.
文摘Much has been written and researched about transformational change and the exogenous events that result in radical institutional transformation （Di Maggio ＆ Powell, 1983; Hannan＆ Freeman, 1989; Fligstein, 1996; Zorn, Dobbin, ＆ Kwok, 2006）. Accounts are provided of external agents disturbing the existing stasis of the institution and transforming the institution into something else that reflect a new paradigm or set of interests. Often, what is neglected in these accounts is what fractures exist in the original institution that would make them vulnerable and allow penetration by exogenous influences. Mahoney and Thelen （20 l 0） went beyond a general model of change that described the collapse of one set of institutional norms to be replaced by another. The model of change they propose takes into account both exogenous as well as endogenous factors as being the source of institutional change. They went on to state a view that transformation change as being a result of abrupt, wholesale breakdown needs to be rethought to include incremental, endogenous shifts in thinking that can often result in fundamental transformations.
基金Supported by the National Natural Science Foundation of China （21006127）, the National Basic Research Program of China （2012CB720500） and the Science Foundation of China University of Petroleum, Beijing （YJRC-2011-11）.
文摘Considering the flexibility and controllability of heat exchanger networks (HENs), bypasses are widely used for effective control of process stream target temperatures. However, the optimal location for the bypass is generally difficult to design with the trade-off between controllability and capital investments. In this paper, based on the steady-state model of heat exchanger networks the optimal bypass location was firstly selected by iteratively calculating the non-square Relative Gain Array (ns-RGA). To simplify the calculation process, rules of bypass selection were also proposed. In order to evaluate this method, then, the structural controllability of heat exchanger networks was analyzed. With both the consideration of the controllability and capital investments, the bypasses locations were finally selected. A case study on the HEN in Crude Distillation Unit was presented in which the ns-RGA and structural controllability were used to select bypasses and also to evaluate the results.
文摘In the evolution of economic growth drivers, technology gaps are a key variable that determines the efficiency of resource allocation. Analysis of an optimal resource allocation path based on an extended endogenous growth model reveals that economic growth drivers evolve from productive investment to R＆D investment and a shift from imitation to innovation. Empirical analysis based on China＇s provincial-level panel data suggests that the effect of productive investment and R＆D investment, as well as innovation and imitation, on economic growth and technological progress varies greatly among regions of disparate technology levels. As a late-starting country, China should properly allocate resources between productive investment and R＆D investment, and between imitational investment and innovative investment while advancing the transformation of economic growth patterns on a differentiated basis in light of regional technology disparities.
基金supported by National Natural Science Foundation of China(Grant Nos.41174147,41274170,41331070)China Postdoctoral Science Foundation Funded Project,and the Fundamental Research Fund for theCentral Universities(Grant No.2042014kf0017)
文摘We report where and how ions are accelerated in the proximity of earthward propagating dipolarization fronts （DFs） in the magnetotail during a magnetospheric substorm on February 15, 2008. Two DFs were observed by multiple THEMIS space- craft in the near-Earth magnetotail （-10 Re）. We studied the ion dynamics associated with these DFs by comparing observed results with large scale kinetic （LSK） simulation results. The LSK simulation reproduced the sudden ion energy flux enhance- ment concurrent with the arrival of the DF at the satellite locations. We found that ions can be accelerated to more than 100 keV energy at the DF. These ions were initially non-adiabatically accelerated near magnetic reconnection site and then still non-adiabatically accelerated at the DF structure.
