LTE上行DFT/IDFT的一种设计实现

根据3GPP协议规定,提出一种适于FPGA实现的解决方案。采用分而治之和WFTA的算式分解,最大限度地减少DFT的运算量;采用块浮点动态截取多余位宽,减少系统面积;运用4个双端口RAM读写,使系统能运行在流水线结构;采用对称结构存储每一级的旋转因子,最大化共享因子。     

基于PCA和LDA统一化原理的增强型线性鉴别分析准则

主分量分析(PCA)和线性鉴别分析(LDA)是模式识别领域的使用最为广泛的两种特征抽取方法,而在图像识别中经常采用的是PCA LDA方法来代替单纯的LDA。本文提出一种增强型线性鉴别准则(ELDA),将PCA的优点和LDA的优点充分地融合在一起,不仅解决了PCA过程中使用最小距离方法时识别精度相对低的缺点,而且解决了LDA过程中当类内散布矩阵奇异时投影向量的求解问题,也就是说可以使用该方法来替代PCA LDA的两步骤方法。另外,该方法在识别精度上比PCA和LDA或PCA LDA方法都有较大的提高,通过在ORL、Yale和NUST603人脸库上的实验验证了该算法的有效性。     

An efficient Dijkstra-like labeling method for computing shortest odd/even paths

We show how the problem of determining shortest paths of even or odd length between two specified vertices in a graph G = (V, E) can be reduced to the problem of finding a shortest alternating path with respect to a specific matching in a related graph H. This problem can be solved by a Dijkstra-like labeling procedure of complexity O(|V|²) respectively O(|E|log|V|). Interpreting this procedure appropriately the method can then be applied directly on the given graph G.     

基于粒子群算法的LDA实现方法研究

针对传统线性判别分析方法存在的问题,在研究现有理论成果的基础上,提出一种新的LDA实现方法。该方法首先对原有的Fisher准则进行修正,然后通过迭代搜寻最佳鉴别矢量,最后对获取的鉴别矢量进行比较分析。在标准的JAFFE人脸库上的表情识别和地区综合消费水平的评价中的实验结果表明,此算法不仅具有良好的识别效果而且还可以突破样本维数的限制;与其他LDA算法相比,该算法更具灵活性且更易于实现。     

基于PCA-LDA算法的模拟电路复杂故障在线诊断研究

模拟电路在出现多个元器件同时故障情形时,由于容差多样、耦合关系复杂等因素,难以对其进行准确在线故障诊断。对模拟电路的在线故障诊断过程进行了定量数学描述,提出了幅频特征值获取方法,将PCA方法和LDA方法相结合,构建属性协方差矩阵、类间散度矩阵、类内散度矩阵,对模拟电路的复杂故障样本数据进行降维与分类,采用BP神经网络对样本数据集与故障模式集进行准确匹配。实验结果表明,论文提出的方法对数据分类降维有效、诊断结果正确,样本数据维度由31降到3,故障分类准确率达到100%,较LDA、PCA、KPCA和KPCA-LDA等其它四种方法,本文方法的指标更优。     

An efficient Chebyshev-Tau spectral method for Ginzburg-Landau-Schrödinger equations

We propose an efficient time-splitting Chebyshev-Tau spectral method for the Ginzburg-Landau-Schrödinger equation with zero/nonzero far-field boundary conditions. The key technique that we apply is splitting the Ginzburg-Landau-Schrödinger equation in time into two parts, a nonlinear equation and a linear equation. The nonlinear equation is solved exactly; while the linear equation in one dimension is solved with Chebyshev-Tau spectral discretization in space and Crank-Nicolson method in time. The associated discretized system can be solved very efficiently since they can be decoupled into two systems, one for the odd coefficients, the other for the even coefficients. The associated matrices have a quasi-tridiagonal structure which allows a direction solution to be obtained. The computation cost of the method in one dimension is O(Nlog(N)) compared with that of the non-optimized one, which is O(N²). By applying the alternating direction implicit (ADI) technique, we extend this efficient method to solve the Ginzburg-Landau-Schrödinger equation both in two dimensions and in three dimensions, respectively. Numerical accuracy tests of the method in one dimension, two dimensions and three dimensions are presented. Application of the method to study the semi-classical limits of Ginzburg-Landau-Schrödinger equation in one dimension and the two-dimensional quantized vortex dynamics in the Ginzburg-Landau-Schrödinger equation are also presented.     

Second-order nonlinear optical responses of carboranyl-substituted indole/indoline derivatives: impact of different substituents

Carborane has been the subject of great interest over the last decades due to its high structural, chemical, biological stability and diverse applications. In the present work, carboranyl-substituted indole/indoline compounds and their functionalized derivatives have been systematically investigated by density functional theory (DFT) method with the view of assessing their electronic structures and first hyperpolarizabilities. Significantly, the first hyperpolarizabilities can be obviously enhanced by the introduction of a strong electron-withdrawing group for closed-ring forms, while the strong electron-donating group is beneficial for large first hyperpolarizabilities for open-ring forms. It indicates that the NLO properties of these compounds can be enhanced by controlling their relative substituent groups. Furthermore, the time-dependent DFT calculation illustrates that the enhancement of the first hyperpolarizabilities are found due to the obvious charge transfer (CT) transition, and closed-ring forms have a significant difference on the CT patterns versus open-ring ones. Investigation of the structure–property relationship and substituent effects at the molecular level can benefit for further exploration of carboranyl-substituted indole/indoline derivatives with versatile and fascinating NLO properties.     

带有高效索引的语义Web服务I/O匹配优化方法

目前Web环境中蕴涵着大量的Web服务和Web服务请求,基于语义的Web服务匹配能够提高Web服务发现的准确性,但由于其复杂的语义计算,导致系统响应速度慢。首先,对语义Web服务过程进行了分析,确定大量的语义计算主要集中在输入/输出（I/O）匹配环节;然后,在研究现有I/O匹配算法和分析影响语义相似度的主要因素基础上,给出了一种带有高效索引的语义Web服务I/O匹配优化方法,包括：高效索引的建立和基于哈希二次探测再散列的启发式筛选机制的提出;最后,通过实例证明了该方法切实可行。该方法通过筛除无关Web服务,减少了语义计算量,提高了系统响应速度,进而带来了更好的用户体验。     

ATAT@WIEN2k: An interface for cluster expansion based on the linearized augmented planewave method

We have developed an interface between the all-electron density functional theory code WIEN2k, and the MIT Ab-initio Phase Stability (MAPS) code of the Alloy-Theoretic Automated Toolkit (ATAT). WIEN2k is an implementation of the full-potential linearized augmented planewave method which yields highly accurate total energies and optimized geometries for any given structure. The ATAT package consists of two parts. The first one is the MAPS code, which constructs a cluster expansion (CE) in conjunction with a first-principles code. These results form the basis for the second part, which computes the thermodynamic properties of the alloy. The main task of the CE is to calculate the many-body potentials or effective cluster interactions (ECIs) from the first-principles total energies of different structures or supercells using the structure-inversion technique. By linking MAPS seamlessly with WIEN2k we have created a tool to obtain the ECIs for any lattice type of an alloy. We have chosen fcc Al-Ti and bcc W-Re to evaluate our implementation. Our calculated ECIs exhibit all features of a converged CE and compare well with literature results.     

An efficient GPU-based parallel tabu search algorithm for hardware/software co-design

Hardware/software partitioning is an essential step in hardware/software co-design. For large size problems, it is difficult to consider both solution quality and time. This paper presents an efficient GPU-based parallel tabu search algorithm (GPTS) for HW/SW partitioning. A single GPU kernel of compacting neighborhood is proposed to reduce the amount of GPU global memory accesses theoretically. A kernel fusion strategy is further proposed to reduce the amount of GPU global memory accesses of GPTS. To further minimize the transfer overhead of GPTS between CPU and GPU, an optimized transfer strategy for GPU-based tabu evaluation is proposed, which considers that all the candidates do not satisfy the given constraint. Experiments show that GPTS outperforms state-of-the-art work of tabu search and is competitive with other methods for HW/SW partitioning. The proposed parallelization is significant when considering the ordinary GPU platform.     

Frequency estimation of a sinusoidal signal via a three-point interpolated DFT method with high image component interference rejection capability

This paper proposes a three-point Interpolated Discrete Fourier Transform (IpDFT) method for frequency estimation of a discrete-time sinusoidal signal. It is based on the maximum sidelobe decay (MSD) windows and is highly effective in rejecting the detrimental effect on the estimation accuracy due to the image component of the signal spectrum. This remarkable feature is achieved by using an analytical expression based on a suitable weighting of the three largest DFT spectrum samples. The proposed method provides good results when the effect of the spectral interference due to the image component dominates other estimation error sources. The accuracy of the proposed method and of other state-of-the-art methods such as the multi-point IpDFT methods and the four-parameter sine-fitting (4PSF) algorithm are compared through both computer simulations and experimental results in the case of ideal, noisy, and harmonically distorted sinusoids. A small number of acquired cycles is assumed in order to analyze situations in which the contribution from the image component interference is significant. The performed comparison shows that the proposed method outperforms the considered multi-point IpDFT methods when the Signal-to-Noise Ratio (SNR) is higher than 30 dB and the number of acquired cycles is enough small. The proposed method outperforms also the 4PSF algorithm when the frequency estimation error is dominated by harmonics rather than wideband noise.     

An efficient method for on-line identification of steady state

A novel method for the on-line identification of steady state in noisy processes is developed. The method uses critical values of an F-like statistic, and its computational efficiency and robustness to process noise distribution and non-noise patterns provide advantages over existing methods. The distribution of the statistic is obtained through Monte-Carlo simulations, and analytically derived shifts in the distribution due to process ramp changes and autocorrelations in the process data are shown to cross check with simulations. Application is demonstrated on experimentally measured pH, temperature and pressure data.     

An efficient energy-conserving numerical model for the electron energy distribution function in the presence of electron-electron collisions

An efficient algorithm to calculate the contribution of electron-electron collisions in the Boltzmann equation for free electrons, in the two-term approximation is presented. The electron-electron collision term must be energy-conserving, while, due to non-linearity, commonly used algorithms do not satisfy this requirement. The efficiency of the algorithm make feasible the use of a non-linear iterative solver to conserve electron energy in electron-electron collisions.The performance of the proposed algorithm has been compared with standard numerical schemes obtaining: 1) considerable gain in computational time; 2) the conservation of the total electron energy density in e-e collisions under the required tolerance.     

An efficient adaptive trust-region method for systems of nonlinear equations

We present an adaptive trust-region algorithm to solve systems of nonlinear equations. Using the nonmonotone technique of Grippo, Lampariello and Lucidi, we introduce a new adaptive radius to decrease the total number of iterations and function evaluations. In contrast with the pervious methods, the new adaptive radius ensures that the size of radius is not too large or too small. We show that the sequence generated by the proposed adaptive radius is decreasing, so it prevents the production of too large radius as possible. Furthermore, it is shown that this sequence is reduced slowly, so it prevents the production of the intensely small radius. The global and quadratic convergence of the proposed approach are proved. Preliminary numerical results of our algorithm are also reported which indicate the promising behaviour of the new procedure to solve systems of nonlinear equations.     

DFT studies on armchair (5, 5) SWCNT functionalization. Modification of selected structural and spectroscopic parameters upon two-atom molecule attachment

Density functional theory (DFT) studies on adsorption of several gaseous homo- and hetero-diatomic molecules (AB) including H₂, O₂, N₂, NO and CO on external surface of H-capped pristine armchair (5, 5) single-walled carbon nanotube (SWCNT) were conducted. Structures of C₇₀H₁₀ and the corresponding C₇₀H₁₀–AB adducts were fully optimized at the B3LYP/6-311G* level of theory. Calculated HOMO/LUMO energy gaps (E_g), ¹³C NMR chemical shifts and IR/Raman parameters were analyzed and critically compared with available experimental data. Significant changes of carbon NMR atom chemical shifts (up to −100 ppm) and shielding anisotropies (up to −180 ppm) at sites of addition were observed. Functionalized SWCNTs produced IR and Raman spectra different from the pristine nanotube model. The selective changes in vibrational spectra will help in assigning the topology of functionalization at the nanotube wall.     

An efficient,robust method for processing of partial top-k/bottom-k queries using the RD-Tree in OLAP

Online analytical processing (OLAP) is a widely used technology for facilitating decision support applications. In the paper, we consider partial aggregation queries, especially for partial top-k/bottom-k, which retrieve the top/bottom-k records among the specified cells of the given query. For the efficient processing of partial ranking queries, this paper proposes a set of algorithms using the RD-Tree, which is a data structure previously proposed for partial max/min queries. Through experiments with real data, we show the efficiency, robustness, and low storage overhead of the proposed method.     

An efficient method for fully automatic 3D digitization of unknown objects

Our goal is to develop a complete and automatic scanning strategy with minimum prior information about the object shape. We aim to establish a methodology for the automation of the 3D digitization process. The paper presents a novel approach to determine the Next Best View (NBV) for an efficient reconstruction of highly accurate 3D models. Our method is based on the classification of the acquired surfaces into Well Visible and Barely Visible combined with a best view selection algorithm based on mean shift, which avoids unreachable positions. Our approach is applicable to all kinds of range sensors. To prove the efficiency and the robustness of our method, test objects are first scanned manually by experts in 3D digitization from the VECTEO company. The comparison of results between manual and automatic scanning shows that our method is very efficient and faster than trained experts. The 3D models of the different objects are obtained with a strongly reduced number of acquisitions while moving efficiently the ranging device. The obtained results prove the effectiveness and the versatility of our 3D reconstruction approach for industrial applications.     

基于LIBSVM的融合傅里叶幅值与相位的示功图识别方法

通过示功图来诊断抽油机井工况,是确保油井安全高效生产的一种重要手段。针对现有示功图特征提取只利用其离散傅里叶变换(Discrete Fourier Transform,DFT)的幅度谱而忽略了其相位谱,从而导致识别率较低的问题,提出了一种融合DFT的幅度谱与相位谱的示功图识别方法。首先,将示功图数据组成复数序列,取其DFT的幅度谱与相位谱构造特征向量;其次,对已知故障种类的示功图的特征向量进行训练,构造多分类支持向量机(Support Vector Machines,SVM)分类判别模型;最后,通过LIBSVM分类识别方法对未知类别的示功图进行分类识别,从而诊断抽油井的工况。实测结果表明,与只利用DFT幅度谱的方法相比,该方法能够有效地提高示功图的识别率,能为油井工况的准确分析、诊断与实时优化控制提供技术支撑。