A Kriging-based algorithm to optimize production systems approximated by analytical models

Production system optimization still remains a difficult problem even if fast analytical methods are used to estimate their mean performance measures. This paper addresses optimization problems in which the system performance measures are obtained from analytical methods implemented in computer codes that are usually time expensive. A global search algorithm is proposed to solve the addressed optimization problem. A Kriging metamodel is built to approximate the system performance function on the basis of the deterministic output values provided by the analytical model. Then a standard optimization method is applied on the explicit metamodel expression. The main advantages of the proposed method are its generality and ease of use. Indeed, the algorithm can be applied to optimize any production system assessable by an analytical method. Also, the Kriging technique allows contemporarily building the approximation of the unknown function and assessing its quality. Numerical results are satisfactory and prove the applicability of the method to real problems.     

A BASIC computer program for evaluating the effect of sample distribution on the least-squares regression slope estimate

Least-squares regression analysis is widely used in analytical method comparison studies even though model assumptions are typically violated. The advantages favoring the use of the least-squares technique, when applicable, are that its theoretical characteristics are thoroughly developed and the calculations are straightforward and universally known. In order to aid an investigator in determining whether or not the least-squares technique can be acceptably applied in a given method comparison situation, a BASIC computer program is developed that evaluates the bias of the least-squares slope estimate as a function of the precision characteristics of the analytical methods and the proposed sampling distribution for the method comparison experiment.     

Exact and approximate Riemann solvers for compressible two-phase flows

Numerical methods for solving equations of two-phase hydrodynamics, which describe the flow of a dispersed solid and gas mixture are considered. The Godunov method is applied as the main approach to approximate numerical fluxes in solutions of the relevant Riemann problems. The formulations of these problems for the solid and gas phases are given, their exact analytical solution is described, and possible simplified approximate solutions are discussed. The obtained theoretical results are applied to the construction of a discrete model, which results in the generalization of the well-known Godunov-type and Rusanov-type methods to the case of nonequilibrium two-phase media. The numerical results involve the verification of the constructed methods on the analytical solutions of two-phase equations.     

回归实验设计及其在分析测试中的应用

文章介绍了回归实验设计用于寻求分析测试最佳条件的方法。设计了计算机程序,并以锆英石中ZrO_2测定为例,进行了回归实验设计。由计算机直接给出回归方程,预报值和方差分析结果,确定了最佳分析测试条件。分析结果说明,方法是成功的。     

Modeling a nanowire superlattice using the finite difference method in cylindrical polar coordinates

A new procedure for handling periodic boundary conditions within the finite difference method and in cylindrical polar coordinates is presented and applied to modeling a nanowire superlattice. The method is compared for accuracy and efficiency with two other formulations of the same problem: the finite difference method applied to a finite number of unit cells, and the exact solution of the equivalent Kronig-Penney model. The technique is then shown to reproduce a novel physical state, and is applied to an embedded nanowire for which there are no analytical solutions.     

时间-空间混和有限元

分析动力学与分析结构力学在数学理论上是一致的.振动与结构力学问题,其实只是一个符号之差.分析力学方法对两方面可通用.双曲型偏微分方程与椭圆型偏微分方程也是差一个符号.虽然性质不同,但分析上有共同之处.本文提出在有限元分析方面,不用对时间、空间分别离散而是组成混和的时空混和有限元网格.数值结果表明,时空混和有限元是有前途的.     

Application of multistage homotopy-perturbation method in hybrid synchronization of chaotic systems

In this paper, the multistage homotopy-perturbation method (HPM) is applied to realize the synchronization between the Lorenz system and the Chen system using active control. The multistage HPM is only a simple modification of the standard HPM, in which it is treated as an algorithm in a sequence of intervals for finding accurate approximate solutions. The simulation results reveal that the multistage method is an effective tool to give the approximate analytical solutions for chaotic systems.     

The application of homotopy perturbation method for MHD flows of UCM fluids above porous stretching sheets

In this study, by means of homotopy perturbation method (HPM) an approximate analytical solution of the magnetohydrodynamic (MHD) boundary layer flow of an upper-convected Maxwell (UCM) fluid over a porous stretching sheet is obtained. The main feature of the HPM is that it deforms a difficult problem into a set of problems which are easier to solve. HPM produces analytical expressions for the solution of nonlinear differential equations. The obtained analytic solution is in the form of an infinite power series. In this work, the analytical solution obtained by using only two terms from HPM solution. The results reveal that the proposed method is very effective and simple and can be applied to other nonlinear problems. Also it is shown that this method coincides with homotopy analysis method (HAM) for the studied problem.     

Using pattern analysis methods to supplement attention directing analytical procedures

How might the application of analytical procedures be improved given the inherent shortcomings of traditional analytic techniques and the apparent difficulties auditors have in combining all critical cues when evaluating the results of the analytical procedures? This research attempts to improve analytical methods by applying a new technology, Artificial Neural Networks (ANNs), to perform pattern recognition of the investigation signals generated by analytical procedures. ANNs, a type of artificial intelligence technology, are able to recognize patterns in data even when the data is noisy, ambiguous, distorted or variable. Four years of audited financial data from a medium-sized distributor were used to calculate five commonly applied financial ratios. The performance of these ratios, applied independently and in combinations, was evaluated using a presumed lack of actual errors and certain seeded material errors. The ANN method evaluated the information content of the combinations of financial ratios using an entropy cost function derived from information theory. This exploratory study suggests that the use of an ANN to analyze patterns of related fluctuations across numerous financial ratios provides a more reliable indication of the presence of material errors than either traditional analytic procedures or pattern analysis, as well as providing insight to the plausible causes of the error. Preliminary results suggest that the use of pattern analysis methods as a supplement to traditional analytical procedures will offer improved performance in recognizing material misstatements within the financial accounts.     

The precision of 3-D parameters in correspondence-based techniques:the case of uniform translational motion in a rigid environment

A general method of calculating the precision of environmental parameters which differs from conventional methods by finding analytical results, and which does so using only information in the image is discussed. This method called uncertainty-analysis, is applied to the case of first-order-error-based motion algorithms for determining environmental depth by matching corresponding points between two or more frames of a dynamic image sequence. How to calculate the uncertainty of in predicted values for the depth is shown, as well as how to calculate the search region for further instances of the point in subsequent frames, based only on information present in the image. The analysis is applied to a real image sequence with good results     

基于小波能量元和改进双阈值函数的微流控芯片信号去噪方法研究

微流控芯片技术是一种新型的分析检测技术,可广泛应用于生物、化学、医学等领域。为提高微流控芯片信号去噪效果,本文提出了一种基于小波能量元和改进双阈值函数的去噪方法。构建了基于指数和对数函数的小波能量元双阈值函数,继而设计了微流控芯片信号去噪算法。以模拟的微流控芯片信号为研究对象,对比选择db4小波基进行了4层分解去噪仿真实验。仿真结果表明,本文方法优于现有的普通阈值法、空域相关法和能量元浮动阈值法。该方法已应用于自主研发的非接触式微流控芯片便携式分析诊断仪,去噪效果良好,有效提升了设备性能。     

Auxiliary equation method for time-fractional differential equations with conformable derivative

In this paper, the auxiliary equation method is applied to obtain analytical solutions of (2 + 1)-dimensional time-fractional Zoomeron equation and the time-fractional third order modified KdV equation in the sense of the conformable fractional derivative. Given equations are converted to the nonlinear ordinary differential equations of integer order; and then, the resulting equations are solved using a novel analytical method called the auxiliary equation method. As a result, some exact solutions for them are successfully established. The exact solutions obtained by the proposed method indicate that the approach is easy to implement and effective.     

A terrain risk assessment method for military surveillance applications for mobile assets

This study proposes an analytical and flexible terrain risk assessment method for military surveillance applications for mobile assets. Considering the risk as the degree of possibility of insurgent presence, the assessment method offers an efficient evaluation of risk in the surrounding terrain for military combat operating posts or observation posts. The method is designed for unmanned aerial vehicles as the surveillance assets of choice to improve the effectiveness of their use. Starting with the area map and geographical data, the target terrain is first digitized for space representation. Then the data of nine geographical parameters are used to formulate five contributing risk factors. These factors are incorporated in an analytical framework to generate a composite map with risk scores that reveal the potential high-risk spots in the terrain. The proposed method is also applied to a real-life case study of COP Kahler in Afghanistan, which was a target for insurgent attacks in 2008. The results confirm that when evaluated with the developed method, the region that the insurgents used to approach COP Kahler has high concentration of high-risk cells.     

基于正交设计的软件过程度量分析方法

软件过程度量的一项工作是分析、确定影响过程能力的显著因素,并将其结果作为建立过程改进决策的基础,即在软件过程度量中找出影响某一指标的主要因素,针对这些因素对软件过程加以控制和改进.这一过程对建立过程改进的有效决策是至关重要的.将数理统计学中的正交设计方法引入到软件过程度量中,提出了一种基于正交设计的软件过程度量分析方法,量化标识软件过程的主要因素,协助决策者找出需要进行重点监控的关键因素,为过程改进提供了基础.     

脉冲涡流TR探头解析模型的快速求解方法

作为分析脉冲涡流响应的常用工具,解析模型因具有物理意义明确、精度高、计算速度快等优点而得到了广泛关注;近年来,随着脉冲涡流阵列探头的应用,对其阵列单元——即激励和接收线圈非同轴的Transmitter-Receiver阵列单元(以下简称TR探头)的解析分析需求迫切;而当前关于TR探头的解析模型大多数将试件缺陷等效为大面积壁厚减薄缺陷,模型精度较低;为提高TR传感器解析模型的求解精度,将构件缺陷等效为平底盲孔缺陷,建立了含平底盲孔构件脉冲涡流TR探头的解析模型,且提出了一种快速求解该模型解析解的方法:首先,通过分析典型模型解析解的形式,发现其由广义反射系数、线圈系数等乘积组成,且广义反射系数仅与构件结构有关,线圈系数仅与探头有关;然后,参考已有的含平底盲孔构件同轴式探头检测模型和均匀壁厚减薄缺陷的TR探头模型,分别获取广义反射系数和线圈系数解析表达式;最后,将其组合得到含平底盲孔构件脉冲涡流TR探头的解析解;通过和实验数据做比较验证了上述解析解的正确性;所提出的方法可应用到其他脉冲涡流解析模型的快速求解中,降低解析模型的求解难度。     

面向俄文NLP的形态自动分析研究与实现

在俄文自然语言处理中形态分析往往是必不可少的模块,在国内虽有个别理论研究,却还没有可以应用于生产的案例。该文系统归纳了国内外俄文形态自动分析方法,深入剖析了俄罗斯以及欧美等其他国家具有代表意义的俄文形态分析器,并在此基础上提出了多策略融合的俄文形态自动分析方法,测试表明即使将该方法应用于专业领域,也能取得令人较为满意的效果。     

Finite element computation of absorbing boundary conditions for time-harmonic wave problems

This paper proposes a new method, in the frequency domain, to define absorbing boundary conditions for general two-dimensional problems. The main feature of the method is that it can obtain boundary conditions from the discretized equations without much knowledge of the analytical behavior of the solutions and is thus very general. It is based on the computation of waves in periodic structures and needs the dynamic stiffness matrix of only one period in the medium which can be obtained by standard finite element software. Boundary conditions at various orders of accuracy can be obtained in a simple way. This is then applied to study some examples for which analytical or numerical results are available. Good agreements between the present results and analytical solutions allow to check the efficiency and the accuracy of the proposed method.     

Analysis of thin piezoelectric solids by the boundary element method

The piezoelectric boundary integral equation (BIE) formulation is applied to analyze thin piezoelectric solids, such as thin piezoelectric films and coatings, using the boundary element method (BEM). The nearly singular integrals existing in the piezoelectric BIE as applied to thin piezoelectric solids are addressed for the 2-D case. An efficient analytical method to deal with the nearly singular integrals in the piezoelectric BIE is developed to accurately compute these integrals in the piezoelectric BEM, no matter how close the source point is to the element of integration. Promising BEM results with only a small number of elements are obtained for thin films and coatings with the thickness-to-length ratio as small as 10⁻⁶, which is sufficient for modeling many thin piezoelectric films as used in smart materials and micro-electro-mechanical systems.     

Analytic macroelements combined with finite elements: Application in modelling of electromagnetic systems

The paper presents the theoretical development of a conductor macroelement performing analytical solution of the diffusion equation. A numerical model based on the combination of such an element with classical finite elements is exposed. This model provides accurate eddy current calculations in conductors surrounded by saturable iron. The validity of the method is checked in case of a simplified linear example where the analytical solution is known. Moreover this technique is applied to model saturated cage rotors in electric machines.