数据流语言中数据频率的自动化处理技术

数据流分析和处理是计算机应用最常见的工作之一,实际系统常常包括不同频率的数据流,而现有的程序语言要求在程序中对数据频率进行显式的处理.旨在提出一种新型的变频数据流处理框架,针对基本的频率运算进行自动化处理.我们基于函数式程序设计语言和依赖类型系统理论,定义了数据流语言FStream,在程序的类型检查过程中对数据流频率进行检查和处理,并给出了离散的Simulink模型到FStream的表示.     

基于FIC法的不可压缩N-S方程稳定分步算法

近年来发展了一种稳定型分步算法,它是在有限增量微积分(Finite Increment Calculus,FIC)求解不可压缩N-S方程理论框架的基础上,引入了对流和压力梯度投影两个附加变量。该方法有效改善了经典分步算法的压力稳定性,同时避免了标准FIC理论框架中存在的空间高阶导数的计算。该文通过采用此方法对各种雷诺数条件下的顶盖驱动方腔流、圆柱绕流和后台阶流进行数值模拟,并将计算结果与前人计算结果及实验结果进行比较,结果表明本文算法计算结果合理可靠。由此可见该算法具有较强的求解不可压缩流动问题的能力以及良好的应用前景。     

A Maximum Principle via Malliavin calculus for combined stochastic control and impulse control of forward‐backward systems

We consider a combined stochastic control and impulse control problem of forward‐backward systems driven by Lévy processes, where both the system coefficients and the objective performance functional are allowed to be random, non‐Markovian; the information available to the controller is partial information. Applying a Malliavin calculus approach, we derive a maximum principle for this control problem, where the adjoint processes are explicitly represented by the parameters and the states of the system. Finally, we give two examples of applications. © 2015 Chinese Automatic Control Society and Wiley Publishing Asia Pty Ltd     

基于模拟退火—遗传算法的非线性密钥序列生成器线性复杂度研究

计算线性等价是研究非线性密钥序列生成器线性复杂度的有效方法。本文先介绍了计算线性等价的模拟退火法,然后使用遗传算法对该算法进行改进,最后使用一组密钥序列生成器对改进后的算法进行性能评估,并将改进后的算法和原算法进行了比较。结果表明改进后的算法能比原算法更有效的找到非线性密钥序列生成器的线性等价。     

In-focus electron microscopy of frozen-hydrated biological samples with a Boersch phase plate

We report the implementation of an electrostatic Einzel lens (Boersch) phase plate in a prototype transmission electron microscope dedicated to aberration-corrected cryo-EM. The combination of phase plate, C_s corrector and Diffraction Magnification Unit (DMU) as a new electron-optical element ensures minimal information loss due to obstruction by the phase plate and enables in-focus phase contrast imaging of large macromolecular assemblies. As no defocussing is necessary and the spherical aberration is corrected, maximal, non-oscillating phase contrast transfer can be achieved up to the information limit of the instrument. A microchip produced by a scalable micro-fabrication process has 10 phase plates, which are positioned in a conjugate, magnified diffraction plane generated by the DMU. Phase plates remained fully functional for weeks or months. The large distance between phase plate and the cryo sample permits the use of an effective anti-contaminator, resulting in ice contamination rates of <0.6 nm/h at the specimen. Maximal in-focus phase contrast was obtained by applying voltages between 80 and 700 mV to the phase plate electrode. The phase plate allows for in-focus imaging of biological objects with a signal-to-noise of 5-10 at a resolution of 2-3 nm, as demonstrated for frozen-hydrated virus particles and purple membrane at liquid-nitrogen temperature.     

A method to determine the local surface profile from reconstructed exit waves

Reconstructed exit waves are useful to quantify unknown structure parameters such as the position and composition of the atom columns at atomic scale. Existing techniques provide a complex wave in a flat plane which is close to the plane where the electrons leave the atom columns. However, due to local deviation in the flatness of the exit surface, there will be an offset between the plane of reconstruction and the actual exit of a specific atom column. Using the channelling theory, it has been shown that this defocus offset can in principle be determined atom column-by-atom column. As such, the surface roughness could be quantified at atomic scale. However, the outcome strongly depends on the initial plane of reconstruction especially in a crystalline structure. If this plane is further away from the true exit, the waves of the atom columns become delocalized and interfere mutually which strongly complicates the interpretation of the exit wave in terms of the local structure. In this paper, we will study the delocalization with defocus using the channelling theory in a more systematic way.     

基于多元索引后继树的时间序列数据流挖掘

本文以地电前兆观测数据流为研究对象,提出了一种新颖的基于多元索引后继树的时间序列数据流挖掘模型。该模型的主要特点是使用一种新颖的位置索引方法,通过一遍扫描创建描述一个序列的所有元素的绝对位置的多元索引后继树,使用索引匹配方法以模式增长的方式生成频繁模式。理论分析与实验表明,该方法简单、高效,具有很好的实用价值。同时,通过对大量持续的地电前兆观测数据流进行分析处理,挖掘隐藏在其中的反映地电参数正常变化规律及趋势的频繁模式,为发现地电前兆异常识别提供依据,从而辅助进行地震预报。     

高性能异构多处理器平台及其应用

在视频编解码领域,随着视频图像分辨率的提高,对处理平台的计算能力、存储、传输带宽的需求急剧增加.为满足高分辨率视频编解码对处理平台的巨大性能需求,本文结合流处理器在媒体处理上的独特优势以及FPGA灵活的可配置性,构建了一个由流处理器和FPGA组成的可配置异构多处理器平台.为了对平台进行性能测试,将MOTION JPEG...     

Efficient parallel implementation of iterative reconstruction algorithms for electron tomography

Electron tomography (ET) combines electron microscopy and the principles of tomographic imaging in order to reconstruct the three-dimensional structure of complex biological specimens at molecular resolution. Weighted back-projection (WBP) has long been the method of choice since the reconstructions are very fast. It is well known that iterative methods produce better images, but at a very costly time penalty. In this work, it is shown that efficient parallel implementations of iterative methods, based primarily on data decomposition, can speed up such methods to an extent that they become viable alternatives to WBP. Precomputation of the coefficient matrix has also turned out to be important to substantially improve the performance regardless of the number of processors used. Matrix precomputation has made it possible to speed up the block-iterative component averaging (BICAV) algorithm, which has been studied before in the context of computerized tomography (CT) and ET, by a factor of more than 3.7. Component-averaged row projections (CARP) is a recently introduced block-parallel algorithm, which was shown to be a robust method for solving sparse systems arising from partial differential equations. It is shown that this algorithm is also suitable for single-axis ET, and is advantageous over BICAV both in terms of runtime and image quality. The experiments were carried out on several datasets of ET of various sizes, using the blob model for representing the reconstructed object.     

Continuous query processing over music streams based on approximate matching mechanisms

It is foreseen that more and more music objects in symbolic format and multimedia objects, such as audio, video, or lyrics, integrated with symbolic music representation (SMR) will be published and broadcasted via the Internet. The SMRs of the flowing songs or multimedia objects will form a music stream. Many interesting applications based on music streams, such as interactive music tutorials, distance music education, and similar theme searching, make the research of content-based retrieval over music streams much important. We consider multiple queries with error tolerances over music streams and address the issue of approximate matching in this environment. We propose a novel approach to continuously process multiple queries over the music streams for finding all the music segments that are similar to the queries. Our approach is based on the concept of n-grams, and two mechanisms are designed to reduce the heavy computation of approximate matching. One mechanism uses the clustering of query n-grams to prune the query n-grams that are irrelevant to the incoming data n-gram. The other mechanism records the data n-gram that matches a query n-gram as a partial answer and incrementally merges the partial answers of the same query. We implement a prototype system for experiments in which songs in the MIDI format are continuously broadcasted, and the user can specify musical segments as queries to monitor the music streams. Experiment results show the effectiveness and efficiency of the proposed approach.