晶体中隐含的半群结构

序列性和莫比吾思反演已应用到物理中各类逆问题,诸如黑体辐射逆问题、比热逆问题和各类费米体系逆问题.文章要介绍这种方法对提取体材料中原子相互作用势的结合能逆问题的应用,以及对提取界面两侧原子间相互作用势的界面粘结能逆问题的应用.这些方法的关键是要发现对象体系中的半群结构.     

A Pseudo-Stokes Mesh Motion Algorithm

This work presents a moving mesh methodology based on the solution of a pseudo flow problem. The mesh motion is modeled as a pseudo Stokes problem solved by an explicit finite element projection method. The mesh quality requirements are satisfied by employing a null divergent velocity condition. This methodology is applied to triangular unstructured meshes and compared to well known approaches such as the ones based on diffusion and pseudo structural problems. One of the test cases is an airfoil with a fully meshed domain. A specific rotation velocity is imposed as the airfoil boundary condition. The other test is a set of two cylinders that move toward each other. A mesh quality criterion is employed to identify critically distorted elements and to evaluate the performance of each mesh motion approach. The results obtained for each test case show that the pseudo-flow methodology produces satisfactory meshes during the moving process.     

Assessing lateral period of building frames incorporating soil-flexibility

Flexibility of soil medium below foundation decreases the overall stiffness of the building frames resulting in a subsequent increase in the natural periods of the system. It is well established that the seismic lateral response may considerably alter due to the change in lateral natural periods. Hence in the present study, an attempt has been made to observe the effect of soil–structure interaction on the change in lateral natural periods of building frames resting on isolated and grid foundations. Variation of a number of factors such as (a) different soil conditions, (b) number of stories, (c) number of bays, (d) the ratio of flexural stiffness of columns to that of beams and (e) frequency of the ground excitation is considered. For such analysis, buildings are modelled by four alternate approaches, namely, (1) bare frame with fixed supports, (2) bare frame with supports accounting for soil-flexibility, (3) frame with brick in-fill having fixed supports and (4) frame with brick in-fill having supports accounting for soil-flexibility. For each category, two cases, viz., one without tie beams, and the other with tie beams at plinth level are considered. The soil-flexibility for various types of soil and foundation based on their properties, e.g., shear modulus, the Poisson ratio of the soil, and shape and size of the footings are computed by methodology prescribed in well-accepted literature. Modelling the system so rigorously, a comparative study of variations of lateral natural periods of various building frames due to variation in different influencing factors are made and interpreted physically. The study shows that the presented variation curves for dynamic characteristics may be used for reasonably accurate assessment of the effect of soil–structure interaction on any building frame with the help of simple linear interpolation. These curves are also useful for incorporating the effect of soil-flexibility in calculating base shear through a simple methodology and may prove useful in the design offices for its simplicity and accuracy.     

Cheminformatics analysis and learning in a data pipelining environment

Summary Workflow technology is being increasingly applied in discovery information to organize and analyze data. SciTegic's Pipeline Pilot is a chemically intelligent implementation of a workflow technology known as data pipelining. It allows scientists to construct and execute workflows using components that encapsulate many cheminformatics based algorithms. In this paper we review SciTegic's methodology for molecular fingerprints, molecular similarity, molecular clustering, maximal common subgraph search and Bayesian learning. Case studies are described showing the application of these methods to the analysis of discovery data such as chemical series and high throughput screening results. The paper demonstrates that the methods are well suited to a wide variety of tasks such as building and applying predictive models of screening data, identifying molecules for lead optimization and the organization of molecules into families with structural commonality.     

基于FPGA的嵌入式双核系统设计

随着测试信息处理领域对嵌入式高性能处理需求的快速增长,基于FPGA构建的嵌入式单核系统逐渐暴露出功耗高、并行性差等性能上的不足,针对此问题,提出了基于Xilinx Virtex-5系列FPGA构建嵌入式双核系统的设计方法,搭建了嵌入式双核系统的整体架构,解决了系统中双核之间的数据交互、双核同步以及双核系统配置文件的存储和自动加载等关键问题。最后,通过Virtex-5 ML510开发平台上的实验,验证了设计方法的合理性和正确性,同时,有效的设计方法可以为其它基于FPGA的嵌入式双核系统设计提供可靠参考。     

Control volume finite element method for radiation

In this paper a new methodology is presented by the authors for the numerical treatment of radiative heat transfer in emitting, absorbing and scattering media. This methodology is based on the utilisation of Control Volume Finite Element Method (CVFEM) and the use, for the first time, of matrix formulation of the discretized Radiative Transfer Equation (RTE). The advantages of the proposed methodology is to avoid problems that confronted when previous techniques are used to predict radiative heat transfer, essentially, in complex geometries and when there is scattering and/or non-black boundaries surfaces. Besides, the new formulation of the discretized RTE presented in this paper makes it possible to solve the algebraic system by direct or iterative numerical methods. The theoretical background of CVFEM and matrix formulation is presented in the text. The proposed technique is applied to different test problems, and the results compared favourably against other published works. Moreover this paper discusses in detail the effects of some radiative parameters, such as optical thickness and walls emissivities on the spatial evolution of the radiant heat flux. The numerical simulation of radiative heat transfer for different cases using the algorithm proposed in this work has shown that the developed computer procedure needs an accurate CPU time and is exempt of any numerical oscillations.     

Bronsted acid-catalyzed rapid enol-ether formation of 2-hydroxyindole-3-carboxaldehydes

A one-step Bronsted acid-catalyzed synthetic methodology leading to 3-(alkoxymethylene)indolin-2-ones was developed starting from easily accessible 2-hydroxyindole-3-carboxaldehydes. The procedure simply involves a treatment of differently substituted 2-hydroxyindole-3-carboxaldehydes with various alcohols (primary/secondary/tertiary/allyl/propargyl/benzyl) in the presence of a catalytic amount of Bronsted acids such as $p$ -toluenesulfonic acid and trifluroacetic acid. A series of 19 indolin-2-one-based enol-ethers were synthesized in excellent yields, which implies the general character of our methodology. The enol-ethers produced could be used as a useful building block for the synthesis of indole-based heterocycles.     

Bilinear modal representations for reduced-order modeling of localized piecewise-linear oscillators

A novel reduced-order modeling method for vibration problems of elastic structures with localized piecewise-linearity is proposed. The focus is placed upon solving nonlinear forced response problems of elastic media with contact nonlinearity, such as cracked structures and delaminated plates. The modeling framework is based on observations of the proper orthogonal modes computed from nonlinear forced responses and their approximation by a truncated set of linear normal modes with special boundary conditions. First, it is shown that a set of proper orthogonal modes can form a good basis for constructing a reduced-order model that can well capture the nonlinear normal modes. Next, it is shown that the subspace spanned by the set of dominant proper orthogonal modes can be well approximated by a slightly larger set of linear normal modes with special boundary conditions. These linear modes are referred to as bi-linear modes, and are selected by an elaborate methodology which utilizes certain similarities between the bi-linear modes and approximations for the dominant proper orthogonal modes. These approximations are obtained using interpolated proper orthogonal modes of smaller dimensional models. The proposed method is compared with traditional reduced-order modeling methods such as component mode synthesis, and its advantages are discussed. Forced response analyses of cracked structures and delaminated plates are provided for demonstrating the accuracy and efficiency of the proposed methodology.     

红外图像处理在墙体空鼓检测上的应用研究

提出了一种基于红外图像的建筑物墙体空鼓检测方法,不但可以远距离、无损地对建筑物空鼓等缺陷进行定性检测,还能对建筑物热工缺陷进行定量分析;采用一种红外图像处理方法来消除墙体温度分布中梯度干扰的影响;通过自适应地调整参数对红外图像进行图像增强处理,有效地排除了环境干扰;通过基于空鼓缺陷边缘轮廓的连通域计算,可直接得到空鼓面积的大小数据;建筑物缺陷现场检测实验结果表明,提出的检测方法既能快速定位出建筑物空鼓等缺陷位置又能以78.3%的精度检测出空鼓面积大小,具有较高的工程应用性。     

Communities of minima in local optima networks of combinatorial spaces

In this work, we present a new methodology to study the structure of the configuration spaces of hard combinatorial problems. It consists in building the network that has as nodes the locally optimal configurations and as edges the weighted oriented transitions between their basins of attraction. We apply the approach to the detection of communities in the optima networks produced by two different classes of instances of a hard combinatorial optimization problem: the quadratic assignment problem (QAP). We provide evidence indicating that the two problem instance classes give rise to very different configuration spaces. For the so-called real-like class, the networks possess a clear modular structure, while the optima networks belonging to the class of random uniform instances are less well partitionable into clusters. This is convincingly supported by using several statistical tests. Finally, we briefly discuss the consequences of the findings for heuristically searching the corresponding problem spaces.     

A grid redistribution method for singular problems

Many physical phenomena develop singular, or nearly singular behavior in localized regions, e.g. boundary layers or blowup solutions. Using uniform grids for such problems becomes computationally prohibitive as the solution approaches singularity. Ren and Wang developed a semi-static adaptive grid method [W. Ren, X.P. Wang, An iterative grid redistribution method for singular problems in multiple dimensions, J. Comput. Phys. 159 (2000) 246–273] for the solution of these problems, known as the iterative grid redistribution (IGR) method. In this study we develop a theoretical basis for semi-static adaptive grid method for singular problems. Based on this theory, we obtain the key result of this study – a methodology for designing robust weight functionals which ensures grid resolution in the singular region, as well as control of the maximal grid spacing in the outer region. Using this methodology, we introduce a semi-static adaptive grid method, which does not involve an iterative procedure for grid redistribution, as in the IGR method. We demonstrate the efficacy of this method with numerical examples of solutions which localize by more than nine orders of magnitude.     

Disturbing,but not surprising: Did Gödel surprise Einstein with a rotating universe and time travel?

The question is raised as to the kind of methodology required to deal with foundational issues. A comparative study of the methodologies of Gödel and Einstein reveals some similar traits which reflect a concern with foundational problems. It is claimed that the interest in foundational problems stipulates a certain methodology, namely, the methodology of limiting cases.In honor of Professor Max Jammer on the occasion of his 80th birthday.This paper was completed while I was a DAAD (Deutscher Akademischer Austauschdienst) fellow at the Zentrum Philosophie und Wissenschaftstheorie, Universität Konstanz, Germany. I gratefully acknowledge the generous assistance of the DAAD. Special thanks are due to Martin Carrier, Olivier Darrigol, and Gereon Wolters.     

A spectral FC solver for the compressible Navier–Stokes equations in general domains I: Explicit time-stepping

We present a Fourier continuation (FC) algorithm for the solution of the fully nonlinear compressible Navier–Stokes equations in general spatial domains. The new scheme is based on the recently introduced accelerated FC method, which enables use of highly accurate Fourier expansions as the main building block of general-domain PDE solvers. Previous FC-based PDE solvers are restricted to linear scalar equations with constant coefficients. The FC methodology presented in this text thus constitutes a significant generalization of the previous FC schemes, as it yields general-domain FC solvers for nonlinear systems of PDEs. While not restricted to periodic boundary conditions and therefore applicable to general boundary value problems on arbitrary domains, the proposed algorithm inherits many of the highly desirable properties arising from rapidly convergent Fourier expansions, including high-order convergence, essentially spectrally accurate dispersion relations, and much milder CFL constraints than those imposed by polynomial-based spectral methods—since, for example, the spectral radius of the FC first derivative grows linearly with the number of spatial discretization points. We demonstrate the accuracy and optimal parallel efficiency of the algorithm in a variety of scientific and engineering contexts relevant to fluid-dynamics and nonlinear acoustics.     

Electrospray self-assembly: An emerging jet-based route for directly forming nanoscaled structures

Electrosprays, a unique physical phenomenon has in the past decade or so been investigated for several applications spanning the physical and life sciences. Recently, these electrified jets were established for directly forming self-assembled structures with a range of non-conducting nanomaterials [Physica E 33 (2006) 398]. The current work demonstrates the ability to directly form functionalised building blocks in the nano-range with conducting nanoparticulates. In the remit of these investigations, we also studied whether particulate loading in suspension has an affect on the forming of these nanoscaled self-assemblies. Thus, these results have widespread promising implications for patterning a wide range of surface topographies either as near-annular islands—or track-like structures. Hence, such nano-assemblies formed by means of this top-down approach could be explored as a bottom-up methodology for encouraging cell migration to those architectures for forming cell patterns to nano-electronics, which are a few examples, respectively.     

A scalable framework for the solution of stochastic inverse problems using a sparse grid collocation approach

Experimental evidence suggests that the dynamics of many physical phenomena are significantly affected by the underlying uncertainties associated with variations in properties and fluctuations in operating conditions. Recent developments in stochastic analysis have opened the possibility of realistic modeling of such systems in the presence of multiple sources of uncertainties. These advances raise the possibility of solving the corresponding stochastic inverse problem: the problem of designing/estimating the evolution of a system in the presence of multiple sources of uncertainty given limited information.A scalable, parallel methodology for stochastic inverse/design problems is developed in this article. The representation of the underlying uncertainties and the resultant stochastic dependant variables is performed using a sparse grid collocation methodology. A novel stochastic sensitivity method is introduced based on multiple solutions to deterministic sensitivity problems. The stochastic inverse/design problem is transformed to a deterministic optimization problem in a larger-dimensional space that is subsequently solved using deterministic optimization algorithms. The design framework relies entirely on deterministic direct and sensitivity analysis of the continuum systems, thereby significantly enhancing the range of applicability of the framework for the design in the presence of uncertainty of many other systems usually analyzed with legacy codes. Various illustrative examples with multiple sources of uncertainty including inverse heat conduction problems in random heterogeneous media are provided to showcase the developed framework.     

A databank of sound insulation measurements

An acoustic databank of sound insulation measurements is being compiled at the University of Liverpool. In this paper we discuss the necessity for, and advantages of, such a databank. The formation of the entries in the bank has been discussed and then classified under established concepts. The coding and the purpose of the parameters selected for the compilation of the databank is explained, and the uses intended for the databank given.The databank is expected to benefit the building industry as a whole, as well as research workers engaged in related problems.