测量重力加速度的一种新方法

提出了一种测量重力加速度的新方法,结合CCD杨氏模量实验仪给出了重力加速度和杨氏模量的物理关系式,从测量结果可知,所测重力加速度与标准值相比其相对误差甚小,说明该实验方案确实可行,具有一定的应用价值。     

PARALLEL QUASI-CHEBYSHEV ACCELERATION TO NONOVERLAPPING MULTISPLITTING ITERATIVE METHODS BASED ON OPTIMIZATION

In this paper, we present a parallel quasi-Chebyshev acceleration applied to the nonover- lapping multisplitting iterative method for the linear systems when the coefficient matrix is either an H-matrix or a symmetric positive definite matrix. First, m parallel iterations are implemented in m different processors. Second, based on l1-norm or l2-norm, the m opti- mization models are parallelly treated in m different processors. The convergence theories are established for the parallel quasi-Chebyshev accelerated method. Finally, the numeri- cal examples show that the parallel quasi-Chebyshev technique can significantly accelerate the nonoverlapping multisplitting iterative method.     

采用双层靶提高激光薄膜相互作用中加速质子的产额

 在激光等离子体相互作用实验中测量到的加速质子,来源于薄膜靶表面的碳氢沾染物。为了提供稳定充足的质子源,设计一种新的复合靶,在2.5 μm塑料溅射200 nm 金薄层形成双层靶,并在中等强度激光功率密度下开展研究,采用磁谱仪和CR-39探测器测量得到其能谱,结果表明：双层靶结构能够有效地增加质子的产额,并可能改善加速质子束的单能性。     

基于埃特金加速的改进Landweber迭代正则化方法

为克服Landweber迭代正则化方法在求解大规模不适定问题时收敛速度慢的不足,将埃特金加速技巧与不动点迭代相结合,构建了能快速收敛的改进Landweber迭代正则化方法.数值实验结果表明:改进的迭代正则化方法在稳定求解不适定问题时,能够快速地收敛至问题的最优解,较Landweber迭代正则化方法大大提高了收敛速度.     

Velocity bunching in travelling wave accelerator with low acceleration gradient

We present the analytical and simulated results of our study of the influence of the acceleration gradient in the velocity bunching process, which is a bunch compression scheme that uses a travelling wave accelerating structure as a compressor. Our study shows that the bunch compression application with low acceleration gradient is more tolerant to phase jitter and more successful in obtaining a compressed electron beam with symmetrical longitudinal distribution and low energy spread. We also present a transverse emittance compensation scheme to compensate the emittance growth caused by the increase of the space charge force in the compressing process, which is easy to adjust for different compression factors.     

守恒型扩散方程非线性离散格式的性质分析和快速求解

对于守恒型扩散方程,研究其二阶时间精度非线性全隐有限差分离散格式的性质,证明了其解的存在唯一性.研究了二阶时间精度的Picard-Newton迭代格式,证明了迭代解对原问题真解的二阶时间和空间收敛性,以及对非线性离散解的二次收敛速度,实现了非线性问题的快速求解.本文中方法也适用于一阶时间精度格式的分析,并可推广至对流扩散问题.数值实验验证了二阶时间精度Picard-Newton迭代格式的高精度和高效率.     

飞秒激光中高能质子的产生与加速的研究

为了探索飞秒激光与固体靶相互作用中高能质子的产生和加速机制,在超短超强激光装置“SILEX-I”上进行了飞秒激光与平面固体薄膜Cu靶的相互作用中高能质子空间分布、能谱和产额的实验研究。实验采用固体核径迹探测器CR39和Thomson离子谱仪相结合的方式,在固体靶背表面法线方向测量了质子空间分布、能谱和产额。实验结果表明：质子沿着靶背法线方向发射,质子空间分布呈圆环状,存在一定的立体角;质子在一定能量处出现截断;截断能量的大小与靶厚度有关。经分析,高能离子的产生和加速是多种作用机制共同作用的结果,其中静电场中的TNSA加速机制则占主导地位。     

基于多传感器融合的摔倒检测算法的研究

针对传统摔倒检测算法中误报和漏报率高的不足,提出一种基于多传感器融合的摔倒检测算法。该算法分别以人体的加速度和姿态角值为判定依据。首先,采用三轴加速度传感器和电子罗盘对上述两种数据进行采集,并通过无线模块发送至PC机。之后对采集数据进行分析和处理,进而根据阈值进行异常姿态检测。最终,综合加速度和姿态角的分析结果给出准确的检测结论。实验结果表明,该算法检测的准确率达99.2%、与传统检测算法相比具有更强的稳定性与可靠性。     

Convergence analysis of Anderson‐type acceleration of Richardson's iteration

We consider Anderson extrapolation to accelerate the (stationary) Richardson iterative method for sparse linear systems. Using an Anderson mixing at periodic intervals, we assess how this benefits convergence to a prescribed accuracy. The method, named alternating Anderson–Richardson, has appealing properties for high‐performance computing, such as the potential to reduce communication and storage in comparison to more conventional linear solvers. We establish sufficient conditions for convergence, and we evaluate the performance of this technique in combination with various preconditioners through numerical examples. Furthermore, we propose an augmented version of this technique.     

A Facile Synthesis of 3H-Benzo[1,2]Dithiole-3-Thiones and Their Condensation with Active Methylene Compounds

Abstract

3H-Benzo[1,2]-dithiole-3-thiones were prepared from potassium sulfide and 2-halobenzaldehydes in moderate-to-good yields, and a plausible mechanism for this catalyst-free intramolecular heteroannulation reaction has been proposed. The Knoevenagel condensation reactions of 3H-benzo[1,2]dithiole-3-thiones with active methylene compounds such as ethyl 2-cyanoacetate and diethyl malonate, and the three-component one-pot reactions of potassium sulfide, 2-halobenzaldehydes, and ethyl 2-cyanoacetate, affording the corresponding products, have been developed.

GRAPHICAL ABSTRACT