FAST IMPLEMENTATION OF CONVOLUTION BACKPROJECTION ALGORITHM IN SPOTLIGHT SAR

A fast implementation of the convolution backprojection（CBP）algorithm in spotlight synthetic aperture radar（SAR）is presented based on the fast Fourier transform（FFT）.Traditionally,the computation of the ＇backprojection＇ process is expensive,since resampling in the process is implemented by using the interpolation operation.By analyzing the relative location relationship among different pixels,the algorithm realizes the ＇backprojection＇ using a series of FFTs instead of the interpolation operation.The point target simulation validates that the new algorithm accelerates the CBP algorithm,and the computational rate increases about 85%.

A fast implementation for computing spatial impulse response of ultrasonic transducers

The spatial impulse response（SIR） method is often used as the ＇gold standard5 in simulation of transient acoustic wave fields due to its high accuracy in the linear domain.However, a high sampling frequency is often required in order to achieve the high accuracy. As a result, a large amount of data has to be processed. In this paper a fast approach for computing spatial impulse response is proposed to reduce the computation burden. The proposed approach is developed by employing the relationship of SIRs at observed points and SIRs of the projection points on the transducer surface. Two critical parameters used in the proposed approach, the calculation sampling frequency and the interpolation sampling frequency, are then analyzed.Results show that for a 2.25 MHz rectangular transducer with the size of 5 mm×10 mm,a calculation sampling frequency of 1000 MHz and an interpolation sampling frequency of500 MHz can achieve superior performance while improving the computation efficiency 18 times than the direct solving.

Implementation of Villagers Autonomy on Fast Lane——In commemoration of the fifth anniversary of the promulgation and implementation of the Organic Law of the Villagers Committees

It is already five years since the 10-year-old experimental law on the organization of villagers committees adopted in November 1987 by the Standing Committee of the National People’s Congress was made permanent, ending an intense political debate about how much independence villagers committees should be given to manage village affairs and to what extent villagers should be allowed to choose their leaders. It is five years in which the implementation of villagers autonomy as defined by the law proceeded the fastest and the achievements were the most fruitful. Local laws Over the past five years, all places

A trinomial type of σ-LFSR oriented toward software implementation

In this paper, we introduce a new type of feedback shift register based on words, called G-linear feedback shift register （σ-LFSR） which can make full use of the instructions of modern CPUs so that we can find good σ-LFSR with simple structure and fast software implementation. After analysis, we find a class of simple σ-LFSR with maximal period and give an algorithm of searching for those σ-LFSRs. As a result, we provide a new optional fast component in the design of modern wordbased stream ciphers.

A superlinear convergence scheme for nonlinear fractional differential equations and its fast implement

In this paper,we first construct an efficient scheme for nonlinear Caputo fractional differential equations with the initial value and the fractional degree 0<α<1.Then,the unconditional stability and the superlinear convergence with the order 1+αof the proposed scheme are strictly proved and discussed.Due to the nonlocal property of fractional operators,the new scheme is time-consuming for long-time simulations.Thus,a fast implement of the proposed scheme is presented based on the sum-of-exponentials(SOE)approximation for the kernel tα−1 on the interval[h,T]in the Riemann-Liouville integral,where h is the stepsize.Some numerical experiments are provided to support the theoretical results of the new scheme and demonstrate the computational performance of its fast implement.