桑荣科技-Sar06500R CDMA VPN路由器

Sar06500R产品结合工业／金融行业以太网发展的要求，广泛应用于远程／现场数据采集、远程监控与控制、家庭网关、视频传输、数字信号处理、网络存储、VPN等多种领域。     

机房监控系统中数据网关服务器的设计

针对机房监控系统中底层设备与上层软件因紧密耦合导致系统维护困难的问题,采用适配器模式和桥接模式设计了底层数据采集接口,实现现场设备、远程监控端、数据网关之间的松散耦合,将DCOM技术作为数据处理的模型,使网关服务器可以提供远程分布式监控服务。实验结果表明,该设计方式实现了底层设备的多型号多协议兼容,降低维护成本,具有较好的可复用性和可扩展性。     

经编机远程监控系统的数据采集与处理

针对现代工业监控的地理位置分散、布线成本高,对数据实时性要求较高的问题,结合3G网络和传统工业监控终端设备,提出了一套经编机监控系统解决方案,通过VPN虚拟专网实现现场设备与中心服务器之间的无线通讯,能够实时远程获取经编机的工况、运行数据以及故障诊断等功能。详细介绍了监控系统软件如何通过3G网络进行数据采集与处理的设计与实现过程。实验结果表明:实时数据采集正常,系统运行状态良好,为现代传统工业实现网络化管理,具有一定的应用推广价值。     

嵌入式Web网关系统的安全研究与设计

为了解决工业智能设备接入Internet时带来的互联网安全问题,根据对电力远程监控系统的安全需求分析和嵌入式网关系统的安全分析,制定了安全措施和安全策略,实现了网关系统的HTTP认证和SSL安全套接字安全机制,采用紧凑安全策略,在保证实时性的前提下,保护工业重要设备不受互联网入侵破坏的威胁,保证了授权数据库的最高安全要求。     

基于Windows Server 2003上启用IPSEC保证数据传输安全的分析

IPSec(IPSecurity Protcol,IP安全协议)是一组开放标准集,它们协同地工作来确保对等设备之间的数据机密性、数据完整性以及数据认证。这些对等实体可能是一对主机或是一对安全网关(路由器、防火墙、VPN集中器等等),或者它们可能在一个主机和一个安全网关之间,就像远程访问VPN这种情况。IPSec能够保护对等实体之间的多个数据流,并且一个单一网关能够支持不同的成对的合作伙伴之间的多条并发安全IPSec隧道。     

基于蓝牙的家居网关数据采集处理系统的设计与实现

介绍了一种基于蓝牙技术的智能家居网关中数据采集处理系统的实现方案,该系统以ARM-Linux嵌入式系统为开发平台;首先讨论了USB蓝牙驱动在ARM9(S3C2410)上的实现和蓝牙协议栈BlueZ的移植;针对家庭环境数据流量较小的特点,采用蓝牙串口操作模式(SPP)建立无线虚拟串口,实现了家庭网关与家居设备之间的无线通信,应用多线程技术实现了家居网关对多个节点设备的实时监控;最后,详细介绍了一种数据包优先级处理算法,实现了对数据包的有效处理,提高了对家居设备监控的效率。     

基于Internet的远程监控系统安全模型研究

讨论了基于Internet的远程监控系统的安全需求.在分析基于IPSec的虚拟专用网(VPN)技术的基础上,给出了基于VPN技术的远程监控系统安全模型,可以实现经Internet对现场工业过程及设备进行远程操作的安全性,方便了使用具有USB接口的电子安全匙的用户漫游.分析表明,该方案既可保证远程操作安全,又可节省网络和通信费用,适用于一般的远程操作监控系统.     

嵌入式网关设计及其在异构系统集成中的应用

为了实现串口与工业以太网之间数据的传输,采用嵌入式Intemet技术,以高性能、低功耗32位RISC结构的ARM9微处理器S3C2410和嵌入式实时操作系统Linux为核心,设计了智能工业以太网网关,并基于ARM-Linux平台,在网关中构建了嵌入式Web服务器.最后,将特定工业监控设备串口通信协议集成到网关中.经测试和实践表明,该网关性能稳定,可以提供Web服务,为数据采集和工业控制系统的异构集成提供了有效的解决途径.     

基于多PLC协同的边缘计算网关测试平台设计

在工业企业数字化转型的大趋势下,边缘计算网关作为数据采集与转发的重要设备,需求快速上升。但目前国内工业企业自动化程度较低,工业互联网标准碎片化问题突出,边缘计算网关需要面对异构设备接入数量不一、工业协议多样、多数据并行采集的工业现场环境。然而,目前缺乏实验室环境下对边缘计算网关异构设备接入能力、工业协议兼容能力及并行数据采集能力快速验证方法的相关研究。设计了一种多PLC协同测试方法实现对工业数据采集现场环境的模拟,采用可视化测试用例开发、多协议融合、多PLC并行管控技术,在实验室条件下实现了对边缘计算网关的多设备、多协议、多数据采集边缘计算能力的快速测试验证。并搭建了一套基于多PLC协同的边缘计算网关测试平台,通过并行数据采集和协议融合等实验,证明该平台能够为工业企业提供快捷有效的边缘计算网关验证,能够极大地降低工业企业试错成本,助力企业数字化转型。     

基于MPC8245的嵌入式VPN的研究与开发

介绍了嵌入式网络应用处理器MPC8245,研究与讨论了基于HHPPC8245-4ETH-R1平台的嵌入式Linux VPN安全网关的开发,对Linux 2.6内核在基于MPC8245的嵌入式系统的移植与嵌入式Linux IPsec VPN安全网关设计进行了深入讨论.     

A Domain Decomposition Preconditioner for p-FEM Discretizations of Two-dimensional Elliptic Problems

In this paper, a uniformly elliptic second order boundary value problem in 2-D discretized by the p-version of the finite element method is considered. An inexact Dirichlet-Dirichlet domain decomposition pre-conditioner for the system of linear algebraic equations is investigated. Two solvers for the problem in the sub-domains, a pre-conditioner for the Schur-complement and an extension operator operating from the edges of the elements into the interior are proposed as ingredients for the inexact DD-pre-conditioner. In the main part of the paper, several numerical experiments on a parallel computer are given.     

Verification of Reduced Convergence Rates

In this short article, we recalculate the numerical example in Kíek and Neittaanmäki (1987) for the Poisson solution u=x(1–x)siny in the unit square S as . By the finite difference method, an error analysis for such a problem is given from our previous study by where h is the meshspacing of the uniform square grids used, and C₁ and C₂ are two positive constants. Let =u–u_h, where u_h is the finite difference solution, and is the discrete H¹ norm. Several techniques are employed to confirm the reduced rate of convergence, and to give the constants, C₁=0.09034 and C₂=0.002275 for a stripe domain. The better performance for arises from the fact that the constant C₁ is much large than C₂, and the h in computation is not small enough.     

Superconvergence of a Mixed Covolume Method for Elliptic Problems

We consider a mixed covolume method for a system of first order partial differential equations resulting from the mixed formulation of a general self-adjoint elliptic problem with a variable full diffusion tensor. The system can be used to model the transport of a contaminant carried by a flow. We use the lowest order Raviart-Thomas mixed finite element space. We show the first order convergence in L ² norm and the superconvergence in certain discrete norms both for the pressure and velocity. Finally some numerical examples illustrating the error behavior of the scheme are provided. Supported by the National Natural Science Foundation of China under grant No. 10071044 and the Research Fund of Doctoral Program of High Education by State Education Ministry of China.     

Efficient Execution of Pure Object-Oriented Programs by Follow-up Compilation

Dynamic type checking and method binding slows pure object-oriented programs such as those written in Smalltalk. Dynamic method lookup is needed to support method overriding and type-method conformance. We have developed a platform independent technique that implements method overriding efficiently for pure object-oriented languages. The technique involves binding non-overridden method calls at compile time. The overridden method calls are also resolved (and bound) statically using simple inferences. Overridden method bindings are corrected dynamically using an Overridden Method Dictionary. Using simulations, we demonstrate that this technique offers 35% –70% reduction in the average method lookup delay over the Berkeley Smalltalk implementation. This technique has very low compile time overhead, memory overhead, does not need specialized hardware and allows shared code pages in concurrent programs. For programs which may be re-used, it is proper to have a follow-up compilation to generate efficient code after the program development is complete. Received November 7, 2001; revised March 27, 2002 Published online: October 24, 2002     

Higher Order Sparse Grid Methods for Elliptic Partial Differential Equations with Variable Coefficients

We present a method for discretizing and solving general elliptic partial differential equations on sparse grids employing higher order finite elements. On the one hand, our approach is charactarized by its simplicity. The calculation of the occurring functionals is composed of basic pointwise or unidirectional algorithms. On the other hand, numerical experiments prove our method to be robust and accurate. Discontinuous coefficients can be treated as well as curvilinearly bounded domains. When applied to adaptively refined sparse grids, our discretization results to be highly efficient, yielding balanced errors on the computational domain.     

The Fourier Finite-element Approximation of the Lamé Equations in Axisymmetric Domains with Edges

This paper is concerned with a priori error estimates and convergence analysis of the Fourier-finite-element solutions of the Neumann problem for the Lamé equations in axisymmetric domains with reentrant edges. The Fourier-FEM combines the approximating Fourier method with respect to the rotational angle using trigonometric polynomials of degree N (N→∞), with the finite element method on the plane meridian domain of with mesh size h (h→0) for approximating the Fourier coefficients. The asymptotic behavior of the solution near reentrant edges is described by singularity functions in non-tensor product form and treated numerically by means of finite element method on locally graded meshes. For the rate of convergence of the combined approximations in is proved to be of the order      

A Refined Finite Element Convergence Theory for Highly Indefinite Helmholtz Problems

It is well known that standard h-version finite element discretisations using lowest order elements for Helmholtz' equation suffer from the following stability condition: ``The mesh width h of the finite element mesh has to satisfy k <sup>2</sup> h≲1', where k denotes the wave number. This condition rules out the reliable numerical solution of Helmholtz equation in three dimensions for large wave numbers k≳50. In our paper, we will present a refined finite element theory for highly indefinite Helmholtz problems where the stability of the discretisation can be checked through an ``almost invariance' condition. As an application, we will consider a one-dimensional finite element space for the Helmholtz equation and apply our theory to prove stability under the weakened condition hk≲1 and optimal convergence estimates. Dedicated to Prof. Dr. Ivo Babuška on the occasion of his 80th birthday.     

<Emphasis Type="Italic">H</Emphasis><Superscript>1</Superscript>-interpolation on quadrilateral and hexahedral meshes with hanging nodes

We propose a Scott-Zhang type finite element interpolation operator of first order for the approximation of H ¹-functions by means of continuous piecewise mapped bilinear or trilinear polynomials. The novelty of the proposed interpolation operator is that it is defined for general non-affine equivalent quadrilateral and hexahedral elements and so-called 1-irregular meshes with hanging nodes. We prove optimal local approximation properties of this interpolation operator for functions in H ¹. As necessary ingredients we provide a definition of a hanging node and a rigorous analysis of the issue of constrained approximation which cover both the two- and three-dimensional case in a unified fashion.      

On the reference mapping for quadrilateral and hexahedral finite elements on multilevel adaptive grids

We study the properties of the reference mapping for quadrilateral and hexahedral finite elements. We consider multilevel adaptive grids with possibly hanging nodes which are typically generated by adaptive refinement starting from a regular coarse grid. It turns out that for such grids the reference mapping behaves – up to a perturbation depending on the mesh size – like an affine mapping. As an application, we prove optimal estimates of the interpolation error for discontinuous mapped -elements on quadrilateral and hexahedral grids.     

A priori and a posteriori error analysis of an augmented mixed finite element method for incompressible fluid flows

In this paper we extend recent results on the a priori and a posteriori error analysis of an augmented mixed finite element method for the linear elasticity problem, to the case of incompressible fluid flows with symmetric stress tensor. Similarly as before, the present approach is based on the introduction of the Galerkin least-squares type terms arising from the constitutive and equilibrium equations, and from the relations defining the pressure in terms of the stress tensor and the rotation in terms of the displacement, all of them multiplied by stabilization parameters. We show that these parameters can be suitably chosen so that the resulting augmented variational formulation is defined by a strongly coercive bilinear form, whence the associated Galerkin scheme becomes well-posed for any choice of finite element subspaces. Next, we present a reliable and efficient residual-based a posteriori error estimator for the augmented mixed finite element scheme. Finally, several numerical results confirming the theoretical properties of this estimator, and illustrating the capability of the corresponding adaptive algorithm to localize the singularities and the large stress regions of the solution, are reported.