The transition of the global atmospheric circulation in the end of 1970's can clearly be detected in the atmospheric temperature, wind velocity, and so on. Wavelet analysis reveals that the temporal scale of this ...The transition of the global atmospheric circulation in the end of 1970's can clearly be detected in the atmospheric temperature, wind velocity, and so on. Wavelet analysis reveals that the temporal scale of this change is larger than 20 years. Studies in this work indicate that the trend of the transition over the mid-latitude Asia is opposite to that of global average for some variables at the middle troposphere. Another finding of this research is that the African-Asian monsoon circulation is weaker and the trade wind over the tropical eastern Pacific is weaker as well after this transition. Such a signal may be found in the summer precipitation over China as well. Key words Asian monsoon circulation - Weakening - Transition This research was supported by the key project of Chinese Academy of Sciences under Contract KZCX2-203 and the key program of the National Natural Science Foundation of China under Contract 49894170.展开更多
Rock bursts signify extreme behavior in coal mine strata and severely threaten the safety of the lives of miners, as well as the effectiveness and productivity of miners. In our study, an elastic-plastic-brittle model...Rock bursts signify extreme behavior in coal mine strata and severely threaten the safety of the lives of miners, as well as the effectiveness and productivity of miners. In our study, an elastic-plastic-brittle model for the deformation and failure of coal/rock was established through theoretical analyses, laboratory experiments and field testing, simulation and other means, which perfectly predict sudden and delayed rock bursts. Based on electromagnetic emission (EME), acoustic emission (AE) and microseism (MS) effects in the process from deformation until impact rupture of coal-rock combination samples, a multi-parameter identification of premonitory technology was formed, largely depending on these three forms of emission. Thus a system of classification for forecasting rock bursts in space and time was established. We have presented the intensity weakening theory for rock bursts and a strong-soft-strong (3S) structural model for controlling the impact on rock surrounding roadways, with the objective of laying a theoretical foundation and establishing references for parameters for the weakening control of rock bursts. For the purpose of prevention, key technical parameters of directional hydraulic fracturing are revealed. Based on these results, as well as those from deep-hole controlled blasting in coal seams and rock, integrated control techniques were established and anti-impact hydraulic props, suitable for roadways subject to hazards from rockbursts have also been developed. These technologies have been widely used in most coal mines in China, subject to these hazards and have achieved remarkable economic and social benefits.展开更多
In this paper,a new hybrid excited doubly salient stator-permanent-magnet motor is proposed,where both permanent magnets and DC field windings are located in the stator.In theory,the mathematical model and design meth...In this paper,a new hybrid excited doubly salient stator-permanent-magnet motor is proposed,where both permanent magnets and DC field windings are located in the stator.In theory,the mathematical model and design method of the motor are developed.The corresponding output power equation and the relationship between the flux control capability and the extended speed range are deduced in details.By using an efficient "one-step" three-dimensional(3D) finite element method,the electromagnetic performances are analyzed,in which the leakage flux outside the stator circumference and end-effect are taken into account.Based on the operation principle of the motor,the control strategy and scheme are developed and implemented experimentally.Both experimental results and finite element analysis show that the proposed motor not only maintains the advantages of doubly salient permanent magnet motors,but also offers high energy efficiency over a wide speed range,which makes the motor an interesting candidate for electric vehicles.展开更多
基金the key project of Chinese Academy of Sciences under ContractKZCX2-203 and the key program of the National Natural Science Fou
文摘The transition of the global atmospheric circulation in the end of 1970's can clearly be detected in the atmospheric temperature, wind velocity, and so on. Wavelet analysis reveals that the temporal scale of this change is larger than 20 years. Studies in this work indicate that the trend of the transition over the mid-latitude Asia is opposite to that of global average for some variables at the middle troposphere. Another finding of this research is that the African-Asian monsoon circulation is weaker and the trade wind over the tropical eastern Pacific is weaker as well after this transition. Such a signal may be found in the summer precipitation over China as well. Key words Asian monsoon circulation - Weakening - Transition This research was supported by the key project of Chinese Academy of Sciences under Contract KZCX2-203 and the key program of the National Natural Science Foundation of China under Contract 49894170.
基金Project 2010CB226805 supported by the National Natural Science Foundation of Chinaprovided by the National Basic Research Program of China (2010CB226805)+1 种基金the National Eleventh Five-Year Key Science & Technology Project (2006BAK04B02, 2006BAK04B06)the National Natural Science Foundation of China (50474068), are gratefully acknowledged
文摘Rock bursts signify extreme behavior in coal mine strata and severely threaten the safety of the lives of miners, as well as the effectiveness and productivity of miners. In our study, an elastic-plastic-brittle model for the deformation and failure of coal/rock was established through theoretical analyses, laboratory experiments and field testing, simulation and other means, which perfectly predict sudden and delayed rock bursts. Based on electromagnetic emission (EME), acoustic emission (AE) and microseism (MS) effects in the process from deformation until impact rupture of coal-rock combination samples, a multi-parameter identification of premonitory technology was formed, largely depending on these three forms of emission. Thus a system of classification for forecasting rock bursts in space and time was established. We have presented the intensity weakening theory for rock bursts and a strong-soft-strong (3S) structural model for controlling the impact on rock surrounding roadways, with the objective of laying a theoretical foundation and establishing references for parameters for the weakening control of rock bursts. For the purpose of prevention, key technical parameters of directional hydraulic fracturing are revealed. Based on these results, as well as those from deep-hole controlled blasting in coal seams and rock, integrated control techniques were established and anti-impact hydraulic props, suitable for roadways subject to hazards from rockbursts have also been developed. These technologies have been widely used in most coal mines in China, subject to these hazards and have achieved remarkable economic and social benefits.
基金supported by the National Natural Science Foundation of China (Grant Nos.50807022,50337030,50729702)the Foundation of Jiangsu University (Grant No.09JDG031)
文摘In this paper,a new hybrid excited doubly salient stator-permanent-magnet motor is proposed,where both permanent magnets and DC field windings are located in the stator.In theory,the mathematical model and design method of the motor are developed.The corresponding output power equation and the relationship between the flux control capability and the extended speed range are deduced in details.By using an efficient "one-step" three-dimensional(3D) finite element method,the electromagnetic performances are analyzed,in which the leakage flux outside the stator circumference and end-effect are taken into account.Based on the operation principle of the motor,the control strategy and scheme are developed and implemented experimentally.Both experimental results and finite element analysis show that the proposed motor not only maintains the advantages of doubly salient permanent magnet motors,but also offers high energy efficiency over a wide speed range,which makes the motor an interesting candidate for electric vehicles.
