During the last 30 years, China has witnessed rapid economic growth and dramatic urbanization, with about 1.2 x 107 rural people migrating annually into urban areas. Meanwhile, especially since 1995, the rural populat...During the last 30 years, China has witnessed rapid economic growth and dramatic urbanization, with about 1.2 x 107 rural people migrating annually into urban areas. Meanwhile, especially since 1995, the rural population has been declining, which is closely linked to land circulation and the increase in farm size in many villages. Increasing scale of farming operations is often regarded as a key to avoiding the abandonment of farmland and to increasing the income of rural farmers. However, until now, there has been little research on the spatial and temporal variability of farm size at the national level in China. Using data from the national agricultural cen- sus and rural household surveys, this study examines the characteristics of land use circulation and the consequent changes in the area of farmland per household. The results show that： 1） 12.2% of rural households were involved in land circulation at the national level. The highest amounts of land circulation have occurred in those provinces where the farmland per capita is more than 0.2 ha or less than 0.1 ha; 2） over 80% of households operate less than 0.6 ha of farmland; 3） the proportion of mid-sized farms （between 0.2 ha and 0.6 ha per household） has decreased while the smallest and the largest farms have increased. This bears some similarity with the phenomenon known as the ＇disappearing middle＇, referring to the changes in farm size. This study establishes a framework for interpreting the factors affecting the changes in farm size in China, which include two promoting factors （urbanization and agriculture） and four hindering fac- tors （agricultual land system, household registration, stable clan system, and farmland loss）.展开更多
The behavior of matrix converter(MC) drive systems under the condition of MC short-circuit faults is comprehensively investigated. Two isolation strategies using semiconductors and high speed fuses(HSFs) for MC short-...The behavior of matrix converter(MC) drive systems under the condition of MC short-circuit faults is comprehensively investigated. Two isolation strategies using semiconductors and high speed fuses(HSFs) for MC short-circuit faults are examined and their performances are compared. The behavior of MC drive systems during the fuse action time under different operating conditions is explored. The feasibility of fault-tolerant operation during the fuse action time is also studied. The basic selection laws for the HSFs and the requirements for the passive components of the MC drive system from the point view of short-circuit faults are also discussed. Simulation results are used to demonstrate the feasibility of the proposed isolation strategies.展开更多
We present novel vector permutation and branch reduction methods to minimize the number of execution cycles for bit reversal algorithms.The new methods are applied to single instruction multiple data(SIMD) parallel im...We present novel vector permutation and branch reduction methods to minimize the number of execution cycles for bit reversal algorithms.The new methods are applied to single instruction multiple data(SIMD) parallel implementation of complex data floating-point fast Fourier transform(FFT).The number of operational clock cycles can be reduced by an average factor of 3.5 by using our vector permutation methods and by 1.1 by using our branch reduction methods,compared with conventional im-plementations.Experiments on MPC7448(a well-known SIMD reduced instruction set computing processor) demonstrate that our optimal bit-reversal algorithm consistently takes fewer than two cycles per element in complex array operations.展开更多
The changes of numeraire can be used as a very powerful tool in pricing contingent claims in the context of a complete market.By using the method of numeraire changes to evaluate convertible bonds when the value of fi...The changes of numeraire can be used as a very powerful tool in pricing contingent claims in the context of a complete market.By using the method of numeraire changes to evaluate convertible bonds when the value of firm,and those of zero-coupon bonds follow general adapted stochastic processes in this paper,using Ito theorem and Gisanov theorem.A closed-form solution is derived under the stochastic volatility by using fast Fourier transforms.展开更多
基金Under the auspices of National Natural Science Foundation of China(No.4097111241161140352)Ministry of Environmental Protection of the People's Republic of China(No.STSN-09-04)
文摘During the last 30 years, China has witnessed rapid economic growth and dramatic urbanization, with about 1.2 x 107 rural people migrating annually into urban areas. Meanwhile, especially since 1995, the rural population has been declining, which is closely linked to land circulation and the increase in farm size in many villages. Increasing scale of farming operations is often regarded as a key to avoiding the abandonment of farmland and to increasing the income of rural farmers. However, until now, there has been little research on the spatial and temporal variability of farm size at the national level in China. Using data from the national agricultural cen- sus and rural household surveys, this study examines the characteristics of land use circulation and the consequent changes in the area of farmland per household. The results show that： 1） 12.2% of rural households were involved in land circulation at the national level. The highest amounts of land circulation have occurred in those provinces where the farmland per capita is more than 0.2 ha or less than 0.1 ha; 2） over 80% of households operate less than 0.6 ha of farmland; 3） the proportion of mid-sized farms （between 0.2 ha and 0.6 ha per household） has decreased while the smallest and the largest farms have increased. This bears some similarity with the phenomenon known as the ＇disappearing middle＇, referring to the changes in farm size. This study establishes a framework for interpreting the factors affecting the changes in farm size in China, which include two promoting factors （urbanization and agriculture） and four hindering fac- tors （agricultual land system, household registration, stable clan system, and farmland loss）.
基金Project(50807002) supported by the National Natural Science Foundation of ChinaProject(SKLD10KM05) supported by Opening Fund of State Key Laboratory of Power System and Generation EquipmentsProject(201206025007) supported by the National Scholarship Fund,China
文摘The behavior of matrix converter(MC) drive systems under the condition of MC short-circuit faults is comprehensively investigated. Two isolation strategies using semiconductors and high speed fuses(HSFs) for MC short-circuit faults are examined and their performances are compared. The behavior of MC drive systems during the fuse action time under different operating conditions is explored. The feasibility of fault-tolerant operation during the fuse action time is also studied. The basic selection laws for the HSFs and the requirements for the passive components of the MC drive system from the point view of short-circuit faults are also discussed. Simulation results are used to demonstrate the feasibility of the proposed isolation strategies.
文摘We present novel vector permutation and branch reduction methods to minimize the number of execution cycles for bit reversal algorithms.The new methods are applied to single instruction multiple data(SIMD) parallel implementation of complex data floating-point fast Fourier transform(FFT).The number of operational clock cycles can be reduced by an average factor of 3.5 by using our vector permutation methods and by 1.1 by using our branch reduction methods,compared with conventional im-plementations.Experiments on MPC7448(a well-known SIMD reduced instruction set computing processor) demonstrate that our optimal bit-reversal algorithm consistently takes fewer than two cycles per element in complex array operations.
基金supported by the National key scientific instrument and Equipment Development Program of China under Grant No.2012YQ220119Anhui Provincial Natural Science Foundation under Grant No.1308085 MF93+1 种基金the Fundamental Research Foundation for the Central Universities under Grant No.2013HGXJ0223National Natural Science Foundations of China under Grant No.11201108
文摘The changes of numeraire can be used as a very powerful tool in pricing contingent claims in the context of a complete market.By using the method of numeraire changes to evaluate convertible bonds when the value of firm,and those of zero-coupon bonds follow general adapted stochastic processes in this paper,using Ito theorem and Gisanov theorem.A closed-form solution is derived under the stochastic volatility by using fast Fourier transforms.
