一种混沌扩频序列的产生方法及其优选算法

提出一种基于组合映射模型产生混沌扩频序列的方法. 根据扩频序列的特性要求和多址干扰性能指标,给出了一种混沌扩频序列的优选算法;将得到的优选序列应用于直扩码分多址系统,在不同信道条件下进行仿真,并与优选的Logistic混沌扩频序列进行性能比较,结果表明本方法产生的混沌扩频序列具有和Logistic混沌扩频序列相近的良好性能,而且保密性更好. 关键词： 码分多址 优选算法 多径信道 误码率     

An NLMS algorithm with optimized preparatory step-size parameters for SQUID-based MCG data processing

We present a new least-mean-square algorithm of adaptive filtering to improve the signal to noise ratio for magnetocardiography data collected with high-temperature SQUID-based magnetometers. By frequently adjusting the adaptive parameter $\alpha $ to systematic optimum values in the course of the programmed procedure, the convergence is accelerated with a highest speed and the minimum steady-state error is obtained simultaneously. This algorithm may be applied to eliminate other non-steady relevant noises as well.     

Real-time construction of optimized predictors from data streams

A new approach to the construction and optimization of local models is proposed in the context of data streams, that is, unlimited sources of data where the utilization of all observations is impractical. Real-time revision of the learning set allows selective coverage of regions in state space which contribute most to reconstructing the underlying dynamical system.     

An algorithm for generating Goldstone and Bloch-Brandow diagrams

An algorithm for the automatic generation of Goldstone and Bloch-Brandow diagrams, needed for diagrammatic perturbation expansions, is described (the Bloch-Brandow diagrams are required for degenerate perturbations). Diagrams are produced in sets, each set consisting of members related by exchanges about interaction lines. Only distinct connected diagrams are generated. Applications are described.     

Reducing spatial data using an optimized regressive discrete Fourier series

With the development of optical measurement techniques it is possible to obtain vast amounts of data. In vibrometry applications in particular operational deflection shapes are often obtained with very high spatial resolution. Fortunately, many techniques exist to reduce (approximate) the measurement data. One of the most common techniques for evaluating optical measurement data is by means of a Fourier analysis. However, this technique suffers from what is known as leakage when a non-integer number of periods is considered. This gives rise to non-negligible errors, which will obviously hamper the accuracy of the synthesized shape. Another technique such as a discrete cosine transform, used in the widely spread -jpeg standard does not suffer these anomalies but can still prove erroneous at times. One of the more recent approaches is via a so-called regressive discrete Fourier series (introduced by Arruda) which suffers one disadvantage. The problem statement is nonlinear in the parameters and needs a priori information about the deflection shape. This can be resolved by using the optimized regressive discrete fourier series (ORDFS), introduced in this article, which uses a nonlinear least squares approach. In this article the method will be applied in particular to the reduction of data for laser vibrometer measurements performed on an inorganic phosphate cement (IPC) beam (1D), as well as on a car door (2D). The proposed technique will also be validated on simulations to illustrate the properties concerning compression ratio and synthesized mode shape error. The introduced method will be bench marked for compression ratio and synthesized deflection shape error with all prior mentioned techniques.     

一种复杂网络路由策略的普适优化算法

现有的复杂网络路由策略很多,改进算法也不断涌现,但是目前还没有一个统一的标准来衡量算法是否达到网络最佳传输效果.针对这一问题,本文提出一种适用于现有路由策略的普适优化算法.首先通过理论分析指出制约网络传输能力的关键因素是最大介数中心度,因而"最大介数中心度是否已经最低"成为评判路由策略是否最优的标准.在此基础上,采用"惩罚选择法"避开网络中介数中心度值比较大的节点,使网络介数中心度值分布更均匀,均衡网络中各个节点的传输负载.仿真结果显示,该优化算法针对现有路由策略均能降低最大介数中心度值,大幅度提高网络的传输能力.     

Algorithms for generating surrogate data for sparsely quantized time series

The method of surrogate data is frequently used for a statistical examination of nonlinear properties underlying original data. If surrogate data sets are generated by a null hypothesis that the data are derived by a linear process, a rejection of the hypothesis means that the original data have more complex properties. However, we found that if an algorithm for generating surrogate data, for example, amplitude adjusted Fourier transformed, is applied to sparsely quantized data, there are large discrepancies between their power spectrum and that of the original data in lower frequency regions. We performed some simulations to confirm that these errors often lead to false rejections.In this paper, in order to prevent such drawbacks, we advance an extended hypothesis, and propose two improved algorithms for generating surrogate data that reduce the discrepancies of the power spectra. We also confirm the validity of the two improved algorithms with numerical simulations by showing that the extended null hypothesis can be rejected if the time series is produced from chaotic dynamical systems. Finally, we applied these algorithms for analyzing financial tick data as a real example; then we showed that the extended null hypothesis cannot be rejected because the nonlinear statistics or nonlinear prediction errors exhibited are the same as those of the original financial tick time series.     

一种公共网络攻击数据挖掘智能算法研究

公共网络的开放性和自组织特性导致网络容易受到病毒干扰和入侵攻击,对攻击数据的准确高效挖掘能确保网络安全。传统方法采用时频指向性波束特征聚类方法实现攻击数据挖掘,在信噪比较低时攻击数据准确挖掘概率较低。提出一种基于自适应滤波检测和时频特征提取的公共网络攻击数据挖掘智能算法。首先进行公共网络攻击数据的信号拟合和时间序列分析,对含噪的攻击数据拟合信号进行自适应滤波检测,提高信号纯度,对滤波输出数据进行时频特征提取,实现攻击数据的准确挖掘。仿真结果表明,采用该算法进行网络攻击数据挖掘,对攻击数据特征的准确检测性能较高,对干扰的抑制性能较强,能有效实现网络安全防御。     

A fast onboard star-extraction algorithm optimized for the SVOM Visible Telescope

The Space multi-band Variable Object Monitor (SVOM) is a proposed Chinese astronomical satellite, dedicated to the detection, localization and measurement of gamma-ray bursts (GRBs) on a cosmological scale. An efficient algorithm is developed for the purpose of onboard star extraction from the CCD images obtained with the Visible Telescope (VT) onboard the SVOM. The CCD pixel coordinates of the reference stars will be used to refine the astronomical position of the satellite, which will facilitate triggering rapid ground-based follow-up observations of the GRBs. In this algorithm, the image is divided into a number of grid cells and the “global” pixel-value maximum within each cell is taken as the first-guess position of a “bright” star. The correct center position of a star is then computed using a simple iterative method. Applying two additional strategies, i.e., scanning the image only by even (or odd) lines or in a black-white chess board mode, we propose to further reduce the time to extract the stars. To examine the efficiency of the above algorithms, we applied them to the experimental images obtained with a ground-based telescope. We find that the accuracy of the astronomical positioning achieved by our method is comparable to that derived by using the conventional star-extraction method, while the former needs about 25 times less CPU time than the latter. This will significantly improve the performance of the SVOM VT mission.     

V-cluster algorithm: A new algorithm for clustering molecules based upon numeric data

Summary Clustering molecules based on numeric data such as, gene-expression data, physiochemical properties, or theoretical data is very important in drug discovery and other life sciences. Most approaches use hierarchical clustering algorithms, non-hierarchical algorithms (for examples, K-mean and K-nearest neighbor), and other similar methods (for examples, the Self-Organization Mapping (SOM) and the Support Vector Machine (SVM)). These approaches are non-robust (results are not consistent) and, computationally expensive. This paper will report a new, non-hierarchical algorithm called the V-Cluster (V stands for vector) Algorithm. This algorithm produces rational, robust results while reducing computing complexity. Similarity measurement and data normalization rules are also discussed along with case studies. When molecules are represented in a set of numeric vectors, the V-Cluster Algorithm clusters the molecules in three steps: (1) ranking the vectors based upon their overall intensity levels, (2) computing cluster centers based upon neighboring density, and (3) assigning molecules to their nearest cluster center. The program is written in C/C++ language, and runs on Window95/NT and UNIX platforms. With the V-Cluster program, the user can quickly complete the clustering process and, easily examine the results by use of thumbnail graphs, superimposed intensity curves of vectors, and spreadsheets. Multi-functional query tools have also been implemented.     

Reduced scattering-matrix algorithm for high-density plasmonic structures

We describe a method to compute S-matrix interface terms using a selection of eigenmodes. When solving the modal equation, the computation of left and right eigenvectors leads to rectangular eigenmodes matrices. Expressions of S-matrix interface terms are then expressed so as to allow for a significant reduction of the computation cost. The reduction is even further decreased in the case of the B-spline modal method, which deals with sparse matrices. Its convergence is illustrated on a high-density plasmonic structure and compared to a full modal method.     

Three-dimensional weight-accumulation algorithm for generating multiple excitation spots in fast optical stimulation

We report here an algorithm for calculating a hologram to be employed in a high-access speed microscope for observing sensory-driven synaptic activity across all inputs to single living neurons in an intact cerebral cortex. The system is based on holographic multi-beam generation using a two-dimensional phase-only spatial light modulator to excite multiple locations in three dimensions with a single hologram. The hologram was calculated with a three-dimensional weighted iterative Fourier transform method using the Ewald sphere restriction to increase the calculation speed. Our algorithm achieved good uniformity of three dimensionally generated excitation spots; the standard deviation of the spot intensities was reduced by a factor of two compared with a conventional algorithm.     

Hyperfine aperiodic optical superlattice optimized by iterative domino algorithm for phase-matching engineering

We proposed and experimentally demonstrated the iterative domino algorithm to optimize optical superlattice with >10(5) unit blocks to achieve arbitrary target phase-matching power spectrum. This scheme can achieve unprecedented overall conversion efficiency and spectral fidelity with extremely high computation efficiency.     

Non-minimum phase reconstruction from amplitude data in fiber Bragg gratings using an adaptive simulated annealing algorithm

Adaptive simulated annealing algorithm used for phase reconstruction in fiber Bragg grating (FBG) is presented. Theory and numerical simulations show that the non-minimum phase of the FBG can be reconstructed by using this method.     

Helical structures from an isotropic homopolymer model

We present Monte Carlo simulation results for square-well homopolymers at a series of bond lengths. Although the model contains only isotropic pairwise interactions, under appropriate conditions this system shows spontaneous chiral symmetry breaking, where the chain exists in either a left- or a right-handed helical structure. We investigate how this behavior depends upon the ratio between bond length and monomer radius.     

An optimized line by line code for plume signature calculations—I: model and data

An optimized line-by-line fortran code for the calculation of aircraft infrared plume signature has been developed an implemented. In this model, the absorption coefficient is separated into two components. The first, which varies quickly with wavenumber, results from the addition of nearby individual line contributions with Voigt line-shapes. The second term, which accounts for both line-wings and collision-induced absorption processes, has a simple dependence on pressure and varies slowly with wavelength. It is pre-calculated and tabulated versus wavenumber and temperature and its treatment involves very small CPU times. For an efficient calculation of the contributions of nearby lines, where most of the computational effort lies, a number of procedures have been developed. The first is a quick evaluation of the Voigt line shape through interpolations within tabulated values. The second is the use of multiple frequency grids of increasing steps on which the various parts of the lines are projected successively starting from line center. The third optimization is a sort of the lines accounted for in the calculations which rejects those of negligible contribution. Finally, more CPU time can be saved by using a proper cut-off distance in the line wings and/or stopping the calculations in spectral regions that are optically very thick. One of the characteristics of our approach, when compared to previous ones, is that all approximations made to quicken calculations lead to errors that are controlled through precision criteria which are chosen by the user.     

Bowl-shaped structures from acylphloroglucinols: an ab initio and DFT study

ABSTRACT

Molecular structures containing bowl-shaped cavities are interesting for purposes such as hosting metal ions or a variety of molecules, including drug molecules. This study considers bowl-shaped structures formed from phloroglucinol (1,3,5-trihydroxybenzene) or acylphloroglucinols (its derivatives containing a COR group) and containing 3 or 4 identical monomeric units. The monomeric units are linked in the same way as in naturally occurring trimeric and tetrameric acylphloroglucinols, i.e. by a methylene bridge and two intermonomer hydrogen bonds. The representativeness of the structures considered is pursued by selecting different R chains. Two conformers were identified for each structure, differing by the orientation of the OH in para to the COR group. Calculations were performed at the HF/6-31G(d,p) and DFT/B3LYP/6-31+G(d,p) levels with fully relaxed geometry, and were complemented by single point MP2/HF/6-31G(d,p) calculations. Corresponding open structures were also calculated for comparison sake. The results indicate the presence of steric stress in trimeric bowl-shaped structures, whereas the geometry of tetrameric bowl-shaped structures is close to one of the local-minima geometries of corresponding open structures and appears free of steric stress.