A High-Order Kernel-Free Boundary Integral Method for Incompressible Flow Equations in Two Space Dimensions

This paper presents a fourth-order kernel-free boundary integral method for the time-dependent, incompressible Stokes and Navier-Stokes equations defined on irregular bounded domains. By the stream function-vorticity formulation, the incompressible flow equations are interpreted as vorticity evolution equations. Time discretization methods for the evolution equations lead to a modified Helmholtz equation for the vorticity, or alternatively, a modified biharmonic equation for the stream function with two clamped boundary conditions. The resulting fourth-order elliptic boundary value problem is solved by a fourth-order kernel-free boundary integral method, with which integrals in the reformulated boundary integral equation are evaluated by solving corresponding equivalent interface problems, regardless of the exact expression of the involved Green's function. To solve the unsteady Stokes equations, a four-stage composite backward differential formula of the same order accuracy is employed for time integration. For the Navier-Stokes equations, a three-stage third-order semi-implicit Runge-Kutta method is utilized to guarantee the global numerical solution has at least third-order convergence rate. Numerical results for the unsteady Stokes equations and the Navier-Stokes equations are presented to validate efficiency and accuracy of the proposed method.     

Designing Network Encryption Machine Based on Henon Chaotic Key Algorithm

Nowadays, embedded network products are widely used in various technological fields. However, when such products are used, the transmission of network data could not be guaranteed with high security. To address the issue, this paper designed a network encryption machine based on S3C6410 processor and DM9000 Ethernet controller. The hardware circuit of this encryption machine is designed and developed with conciseness and stability. In software design, an improved algorithm of chaotic encryption based on Henon mapping is proposed. The algorithm overcomes the shortcoming in combining Logistic and Tent chaotic sequences. Moreover, the paper demonstrates some comparative experiments about autocorrelation and randomness. The results indicate that the new algorithm based on Henon chaotic sequences has a good performance in safety and is able to meet the requirements of confidential communications.     

数字视频广播数据流的复用

介绍了数字视频广播（ＤＶＢ）标准及其数据流的结构、语法和复用原理,采用面向对象的Ｃ＋ ＋ 语言,结合高速数据采集卡,实现了ＤＶＢ电话点播播放系统,该系统通过串口将用户的点播信息送入计算机,并根据用户的点播申请,将多种形式的ＤＶＢ数据流进行打包、复用和播放．分析结果证明,数据流的复用符合ＤＶＢ标准,可正确播放．     

An advanced multivariate statistical approach to study coastal sediment data

The present paper deals with the application of classical and fuzzy principal components analysis to a large data set from coastal sediment analysis. Altogether 126 sampling sites from the Atlantic Coast of the USA are considered and at each site 16 chemical parameters are measured. It is found that four latent factors are responsible for the data structure (“natural”, “anthropogenic”, “bioorganic”, and “organic anthropogenic”). Additionally, estimating the scatter plots for factor scores revealed the similarity between the sampling sites. Geographical and urban factors are found to contribute to the sediment chemical composition. It is shown that the use of fuzzy PCA helps for better data interpretation especially in case of outliers.     

The proficiency testing programme for trace elements of the CORILA project

Harmonised quality schemes are being implemented in the framework of the thematic area Organization and Dissemination of Data of the Consorzio per la Gestione del Centro di Coordinamento delle Attività di Ricerca Inerenti il Sistema Lagunare di Venezia (Consortium for the Management of the Coordination Centre of Research Activities on the Venice Lagoon System, CORILA). Over the last 2 years, two proficiency tests were completed at the time of writing (while a third one is still in progress) to assess the capabilities of the analytical laboratories involved in the determination of trace elements in environmental inorganic matrices from the Lagoon of Venice.Both interlaboratorial trials were based on the determination of As, Cd, Cr, Cu, Fe, Hg, Pb and Zn in aqueous acidic, matrix-enriched solutions at concentrations within the ranges generally found in marine water and in sediment after chemical digestion, respectively. The proficiency of participants was assessed on the basis of the z score criterion (|z|≤2, acceptable results; 2<|z|<3, questionable results; |z|≥3, unacceptable results). In the two trials, the relevant percentages for the laboratories scoring |z|≤2 and |z|<3 were 61% and 71% and 65% and 77%, respectively. These first two proficiency tests, on the one hand, clearly pointed to the benefits the laboratories had from their participation in these exercises, and on the other hand, provided sound evidence of the need for further trials based on real environmental matrices.     

Chromium available fractions in arousa sediments using a modified microwave BCR protocol based on microwave assisted extraction

In a research of chromium availability, the three-stage sequential extraction procedure, proposed by European Community Bureau of Reference (BCR), has been applied for the metal fractionation in marine sediment samples. The procedure has been modified, evaluating the effect of microwave energy to perform the sequential method. Results achieved a substantial reduction in time in comparison to the traditional shaking technique. The time of the first and the second extractions were reduced to 30 s in both steps using microwave heating and working at 66 W of power. To the third extraction, higher power was necessary so it was chosen to work at 198 W. In the last step investigated, time was reduced to 1 min, being a great improvement respect to the conventional BCR sequential extraction protocol.Chromium determinations in these extracts were carried out by Electrothermal Atomic Absorption Spectrometry (ETAAS). The developed method was applied for chromium determination in marine sediment samples from Ria de Arousa (Galicia, NW of Spain). The values obtained by our laboratory ranged from 0.10 to 1.02 μg g⁻¹ for soluble and reducible fractions, and from 5.5 to 60.0 μg g⁻¹ for the oxidisable fraction. The higher concentrations obtained were the chromium associated with the organic fraction of the marine sediments.     

A uniformly valid asymptotic solution of the Navier-Stokes equations

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A modification of Taylor-Galerkin Finite Element Method and its application

Two basic hypothesises of Taylor-Galerkin Finite Element Method are studied in this paper.One of them which is unreasonable is redefined.The only hypothesis becomes the standpoint of Generalized Finite Element.We use this idea to analysis stream function-vorticity equations with Modified Taylor-Galerkin Finite Element Method,and give the two-step solving method,which makes the solving process more reasonable than ever before.Several computational examples reveal that the results of this new method are satisfied.     

Three-dimensional analysis of the flow in the cyclones

Sincethecycloneisextensivelyusedinindustry,themechanismofitsstreamhasbeeninvestigatedandanalysed.Buttheprocessofthepreviousdiscussionstaysattheleveloftwo-dimensionedmodelanalysis,withtheaddedconsiderationabouttheaxialIysymmetry.lntheseyears,somespecialistshavediscusseditinthelightofthetotalthree-dimensionview.Thispapertriestogivesystematicanddetai]edexp1anationsandtopresentacorrectresultofRef[1].I.GeneralEquationEstablishedFirstweestablishmathematicalexpressionofflowinthecyclone.Wecanimaget…     

两同心旋转球间流动的弱解的存在唯一性

研究了两个同心旋转球间的轴对称不可压缩的粘性流动。该流动广泛应用于大气物理和地球物理等学科中,为了得到流动的流函数－速度形式的Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程的弱解的存在性和唯一性,首先发现了该方程中非线性项之间关系,并引入一个有限维的辅助问题,通过紧性而得到了结论。