Power supply for generating frequency-variable resonant magnetic perturbations on the J-TEXT tokamak

To further research the response of the tearing mode(TM) to dynamic resonant magnetic perturbation(DRMP) on the J-TEXT tokamak, a modified series resonant inverter power supply(MSRIPS) with a function of discrete variable frequency is designed for DRMP coils in this study. The MSRIPS is an AC–DC–AC converter, including a phase-controlled rectifier, an LC filter, an insulated gate bipolar transistor(IGBT) full bridge, a matching transformer, three resonant capacitors with different capacitance values, and three corresponding silicon controlled rectifier(SCR) switches. The function of discrete variable frequency is realized by switching over different resonant capacitors with corresponding SCR switches while matching the corresponding driving frequency of the IGBT full bridge. A detailed switching strategy of the SCR switch is put forward to obtain sinusoidal current waveform and realize current waveform smooth transition during frequency conversion. In addition, a resistor and thyristor bleeder is designed to protect the SCR switch from overvoltage. Manufacturing of the MSRIPS is completed, and the MSRIPS equipment can output current with an amplitude of 1.5 kA when its working frequency jumps among different frequencies. Moreover, the current waveform is sinusoidal and can smoothly transition during frequency conversion. Furthermore, the transition time when the current amplitude rises from zero to a steady state is less than 2 ms during frequency conversion. By using the MSRIPS, the expected discrete variable frequency DRMP is generated, and the phenomenon of the TM being locked to the discrete variable frequency DRMP is observed on the J-TEXT tokamak.     

An application of the shortest path algorithm for the identification of weak MHD mode

The identification of magnetohydrodynamic(MHD) modes is a crucial issue in the control of magnetically confined plasmas. This paper proposes a novel method for identifying the evolution of MHD modes from a signal with a low signal-to-noise ratio. The proposed method generates a weighted directed graph from the time-frequency spectrum and calculates the evolution of the mode frequency by solving the shortest path. This method addresses the limitations posed by the lack of data channels and the di...     

M序Walsh变换的快速算法设计

讨论了Walsh函数系的一种序一逆Walsh序（M序），利用矩阵分解法设计了4种M序的快速Walsh变换算法。     

一个带有相似性关系的模糊逻辑

模糊集与模糊逻辑是处理模糊性与不确定性信息的重要数学工具，相似性关系是模糊集的一个基本概念。为了在模糊逻辑中集成相似性关系并考虑其模糊推理，提出了一个带有相似性关系的模糊逻辑，给出了其语法及语义描述，在模糊谓词逻辑情形下，讨论并证明了基于归结与调解方法的模糊推理的有关属性，考虑到许多定理证明器和问题解决系统均是基于否证法，证明了归结与调解方法对模糊谓词演算的反驳完备性定理。     

格子模型的快速序列搜索算法

一种快速序列穷举搜索蛋白质构像空间的算法。该算法利用二分技术将HP序列逐次分解,保存分解过程的中间结果,使搜索算法中所需的计算量大大减少。     

数字图像的自适应公开水印技术

该文提出一种以灰度层图案作水印的自适应公开水印（public watermarking)技术,这种技术在不可感知性和稳健性等方面面临着更大的挑战,而探索图像新的稳定性特征并结合人类视觉系统（HVS）的性质来设计水印算法正是克服这一难题的有效途径。为此,该文分析了一种新的变换域－多小波（multiwavelet)域系数的特征,并将基于单小波域的人眼噪声敏感性模型推广到多小波域,在此基础上,先将灰度层图案水印分解为二值位图平面,然后自适应地将各个位图平嵌入多小波变换域中,实验结果表明,该文方法对多种图像处理具有很好的稳健性。其性能优于文献上的相近方法。     

一种稳健的公开数字图像水印技术

提出一种稳健的公开图像水印技术。随机选取若干象素点及其邻域,通过量化象素与邻域的均值之差来隐藏水印信息。实验表明,该方法简单、高效、安全性能好,且具有较好的不可感知性,对通常的图像处理及JPEG压缩等具有极好的稳健性。     

可扩展的旋转因子表及FFT算法

该文提出了一个用于快速Fourier变换计算的反写码序的旋转因了表，这种旋转因子表具有可扩展性：本质上，这种旋转因子表的分量与变换的点数无关，当点数改变时，这种旋转因子表无须重新计算或者容易扩展；根据这种旋转因子表，该文设计了一个结构规整的基本基4计算2^n点FFT的算法及软件程序，该程序与FFTW软件包进行了对比实验，文中还以蛋白质序列相似性计算为例，对作者的算法与FFTW软件包中的相庆算法进行了对比实验，结果表明，采用该文的算法可节省计算时间约31．7％。     

基于混沌映射和遗传算法的公开数字水印技术

本文提出一种基于混沌映射和遗传算法的鲁棒公开图像水印技术.随机选取若干子块,并在子块中随机选取一个像素点,通过修改该点像素值与子块的均值之间的大小关系来隐藏水印信息.结合混沌映射和遗传算法提高水印的安全性和不可感知性;通过重复嵌入提高水印的鲁棒性.实验结果表明,本文方法具有较好的不可感知性以及对通常的图像处理具有很好的鲁棒性,并且优于同类方法.     

模板匹配的并行算法

模板匹配方法是检测图像边缘的重要方法之一。本文对模板匹配方法的Ｐｒｅｗｉｔｔ算子进行了研究，提出了用该算子检测图像边缘的快速算法，向量及分布式算法，并且在并行虚拟环境ＰＶＭ上实现了分布式计算，加速效果明显。