Decentralising a service-oriented architecture

Service-oriented computing is becoming an increasingly popular paradigm for modelling and building distributed systems in open and heterogeneous environments. However, proposed service-oriented architectures are typically based on centralised components, such as service registries or service brokers, that introduce reliability, management, and performance issues. This paper describes an approach to fully decentralise a service-oriented architecture using a self-organising peer-to-peer network maintained by service providers and consumers. The design is based on a gradient peer-to-peer topology, which allows the system to replicate a service registry using a limited number of the most stable and best performing peers. The paper evaluates the proposed approach through extensive simulation experiments and shows that the decentralised registry and the underlying peer-to-peer infrastructure scale to a large number of peers and can successfully manage high peer churn rates.     

构件化ColdFire系列MCUs通用GPIO驱动设计

嵌入式底层构件是建立在硬件构件的基础上,根据硬件构件的实际功能和接口,实现与之对应的硬件模块的驱动分解。GPIO是嵌入式系统的通用构件并且作为底层内部构件被其他底层外设构件所调用。本文以飞思卡尔ColdFire系列为例,根据软件工程构件化设计,提出GPIO构件化设计方法并且给出应用实例,说明嵌入式底层内部构件的可复用性与可移植性。     

GUARDS: a generic upgradable architecture for real-time dependablesystems

The development and validation of fault-tolerant computers for critical real-time applications are currently both costly and time consuming. Often, the underlying technology is out-of-date by the time the computers are ready for deployment. Obsolescence can become a chronic problem when the systems in which they are embedded have lifetimes of several decades. This paper gives an overview of the work carried out in a project that is tackling the issues of cost and rapid obsolescence by defining a generic fault-tolerant computer architecture based essentially on commercial off-the-shelf (COTS) components (both processor hardware boards and real-time operating systems). The architecture uses a limited number of specific, but generic, hardware and software components to implement an architecture that can be configured along three dimensions: redundant channels, redundant lanes, and integrity levels. The two dimensions of physical redundancy allow the definition of a wide variety of instances with different fault tolerance strategies. The integrity level dimension allows application components of different levels of criticality to coexist in the same instance. The paper describes the main concepts of the architecture, the supporting environments for development and validation, and the prototypes currently being implemented     

Computing offsets of trimmed NURBS surfaces

Offsetting of trimmed NURBS surfaces is one of the widely used functionalities in the design and manufacture simulations of composite laminates. This paper presents an approach for the offsetting of a trimmed NURBS surface. The approach has been developed mainly to meet the stringent accuracy requirements in the simulation of composite laminate design and manufacturing processes. However, the approach is applicable for the offset of a general trimmed NURBS surface. Though the method is based on known techniques in literature, the practical approach and the treatment of the subject presented is unique and has not been reported earlier. The basic approach consists of offsetting the underlying surface, offsetting of all the trimming loops and the creation of offset trimmed surface using the offset surface and the offset trimming loops. This is a unified offset approach for trimmed surfaces where in the offset of underlying surface and the offset of trimming loops are obtained using the same approach. The approach has better error control and results in less number of control points. Further the approach can be extended to obtain offsets of a general B-Rep. The approach has been used in the creation of offset surfaces of various aircraft components.     

Improving acoustic vehicle classification by information fusion

We present an information fusion approach for ground vehicle classification based on the emitted acoustic signal. Many acoustic factors can contribute to the classification accuracy of working ground vehicles. Classification relying on a single feature set may lose some useful information if its underlying sound production model is not comprehensive. To improve classification accuracy, we consider an information fusion diagram, in which various aspects of an acoustic signature are taken into account and emphasized separately by two different feature extraction methods. The first set of features aims to represent internal sound production, and a number of harmonic components are extracted to characterize the factors related to the vehicle’s resonance. The second set of features is extracted based on a computationally effective discriminatory analysis, and a group of key frequency components are selected by mutual information, accounting for the sound production from the vehicle’s exterior parts. In correspondence with this structure, we further put forward a modified Bayesian fusion algorithm, which takes advantage of matching each specific feature set with its favored classifier. To assess the proposed approach, experiments are carried out based on a data set containing acoustic signals from different types of vehicles. Results indicate that the fusion approach can effectively increase classification accuracy compared to that achieved using each individual features set alone. The Bayesian-based decision level fusion is found to be improved than a feature level fusion approach.     

Spatially nested sampling schemes for spatial variance components: Scope for their optimization

Efficient designs for nested sampling are needed in many areas of science. In the geosciences they are used to discover the important spatial scales on which properties vary. However, while the practical advantages and disadvantages of various nested designs have been discussed, no attempt has been made to optimize nested sampling schemes. This paper shows how an optimal nested sampling design can be found by a method of numerical combinatorial optimization: simulated annealing. The sample design is optimized over a space of possible designs for a fixed sample size and predetermined levels (spatial scales). The objective function for optimization is based on the expected covariance matrix for errors in the estimates of variance components, and so depends on what those components are. By simulation it was shown that optimized sampling schemes can detect scale-dependent variance components with common requirements for statistical power on smaller total sample sizes than are required with commonly used spatially nested sample designs such as the balanced design. Although the optimized design depends on the underlying covariance structure, sampling designs can be identified that perform better than the commonly used ones over a wide range of conditions.     

基于服务访问代理的组件集成技术研究

在企业应用集成的发展进程中,组件扮演着十分重要的角色。组件类型的多样性使得不同类型组件的集成工作面临很大的困难,如何对不同的组件在合理规划的基础上进行统一管理,一直以来都是软件设计师们研究的热点。通过分析不同类型组件的特征,提出了将远程组件本地化的思想,并基于此思想设计了服务访问代理以及一个基于元数据的组件容器,在设计过程中运用了多种设计模式,以使其更加高效。     

基于组件程序的模型及动态唤醒

软件重用致力于根据已存组件的构造软件,在应用重用技术进行设计时,所需考虑的一个重要问题是如何唤醒底层子组件的服务,本文首先给出了基于组件设计的模型,然后给出了一种动态唤醍的策略,这种唤醒方式通过动态说明匹配和考察组件的运行时特性来确定目标线件,并较之静肪唤醒提供了更多的的灵活性和扩展性。     

Multi-phase field topology optimization of polycrystalline microstructure for maximizing heat conductivity

The present study proposes multi-scale topology optimization for polycrystalline microstructures applying a multi-phase field method. The objective function is to maximize the heat compliance of macrostructure and the equality constraint is the material volume of constituents in an alloy consisting of two components with different heat conductivity. Two-scale steady-state heat conduction problem based on a homogenization method is conducted. The Allen-Cahn non-conserved time evolution equation with the additional volume constraint scheme is employed as the optimization strategy for updating the crystal configuration. In the time evolution equation, sensitivities of objective function with respect to phase-field variables are considered to relate topology optimization to the multi-phase field method. It is verified from a series of numerical examples that the proposed method has great potential for the development of material design underlying polycrystalline structure.     

MOG user interface builder: a mechanism for integrating application and user interface

Tools which provide graphical editing techniques for the design of user interface presentations are increasingly commonplace. Such tools vary widely in the mechanisms used to define user interfaces and while some are general purpose, others are targeted at particular application domains. Designers faced with varying requirements must choose one tool and live with its shortcomings, purchase a number of different tools, or implement their own. The paper describes an approach to facilitating the latter by providing a library of augmented user interface components called MOG objects which embody both end-user and editing semantics. User interface design tools based on this approach need only provide mechanisms for composing MOG objects into user interfaces and the addition of any other, higher-level functionality. MOG-based user interfaces retain an in-built editing capability and are inherently tailorable.     

Recovery of sensor embedded washing machines using a multi-kanban controlled disassembly line

Product recovery involves the recovery of materials and components from returned or end-of-life products. Disassembly, an element of product recovery, is the systematic separation of an assembly into its components, subassemblies or other groupings. Stricter environmental regulations together with dramatic decrease in natural resources and landfills have increased the importance of disassembly as all product recovery options require some level of disassembly. Due to changes made during the lifetime of a product by customers or service personnel, the number and the version of components prior to disassembly is unknown. Customers may also discriminate between and demand different versions of components. The existence of non-functional components further adds to the uncertainty associated with disassembly yield. Sensors implanted into products during their production can address this uncertainty by providing information on the number, condition and version of components prior to disassembly. In this study, we evaluate the impact of sensor embedded products (SEPs) on the various performance measures of a washing machine (WM) disassembly line controlled by a multi-kanban system, which takes into consideration the highly stochastic behavior of the line while managing material and kanban flows. First, separate design of experiments studies based on orthogonal arrays are performed for conventional products and SEPs. In order to observe the response of each experiment, detailed discrete event simulation (DES) models for both types of products are developed considering the precedence relationships among the components of a WM. Then, pair-wise t-tests are conducted to compare the two cases based on different performance measures. According to the results, SEPs provide significant reductions in all costs (viz., backorder, holding, disassembly, disposal, testing and transportation) while increasing revenue and profit.     

Global stabilization and disturbance suppression of a class of nonlinear systems with uncertain internal model

This paper deals with global stabilization and disturbance suppression of a class of nonlinear systems using output feedback. The disturbances generated from a unknown linear exosystem are completely compensated. The order of the exosystem is assumed known and the eigenvalues are distinct. No other assumptions are needed in the control design. This means that the proposed control design is able to completely compensate the disturbances without knowing their amplitudes, frequencies and phases, as long as the number of different frequency components in the disturbances is known. A new formulation of state estimation is introduced to ensure the global stabilization and complete disturbance suppression. Adaptive control technique is used to design an adaptive internal model based on a recently introduced formulation of unknown exosystems and the parameters in the adaptive internal model converge to the actual values, from which the unknown disturbance frequencies can be calculated. In the proposed control design, a number of control coefficients are made adaptive so that the result is global with respect to unknown frequencies in the disturbances.     

Quantum behaved Particle Swarm Optimization (QPSO) for multi-objective design optimization of composite structures

We present a new, generic method/model for multi-objective design optimization of laminated composite components using a novel multi-objective optimization algorithm developed on the basis of the Quantum behaved Particle Swarm Optimization (QPSO) paradigm. QPSO is a co-variant of the popular Particle Swarm Optimization (PSO) and has been developed and implemented successfully for the multi-objective design optimization of composites. The problem is formulated with multiple objectives of minimizing weight and the total cost of the composite component to achieve a specified strength. The primary optimization variables are – the number of layers, its stacking sequence (the orientation of the layers) and thickness of each layer. The classical lamination theory is utilized to determine the stresses in the component and the design is evaluated based on three failure criteria; Failure Mechanism based Failure criteria, Maximum stress failure criteria and the Tsai–Wu Failure criteria. The optimization method is validated for a number of different loading configurations – uniaxial, biaxial and bending loads. The design optimization has been carried for both variable stacking sequences as well as fixed standard stacking schemes and a comparative study of the different design configurations evolved has been presented. Also, the performance of QPSO is compared with the conventional PSO.     

A geometric approach to cluster validity for normal mixtures

 We study indices for choosing the correct number of components in a mixture of normal distributions. Previous studies have been confined to indices based wholly on probabilistic models. Viewing mixture decomposition as probabilistic clustering (where the emphasis is on partitioning for geometric substructure) as opposed to parametric estimation enables us to introduce both fuzzy and crisp measures of cluster validity for this problem. We presume the underlying samples to be unlabeled, and use the expectation-maximization (EM) algorithm to find clusters in the data. We test 16 probabilistic, 3 fuzzy and 4 crisp indices on 12 data sets that are samples from bivariate normal mixtures having either 3 or 6 components. Over three run averages based on different initializations of EM, 10 of the 23 indices tested for choosing the right number of mixture components were correct in at least 9 of the 12 trials. Among these were the fuzzy index of Xie-Beni, the crisp Davies-Bouldin index, and two crisp indices that are recent generalizations of Dunn’s index. Received: 29 July 1997/Accepted: 1 September 1997     

Application integration: Constructing composite applications from interactive components

Creating new applications by integrating user interface and application components is a relatively new idea which is currently of wide interest. A significant part of this problem is clearly defining the separation between user interface and application components. This paper proposes a new design methodology based on the concept of an abstract data view (ADV), a structuring method which cleanly defines this separation. A number of examples of composite interactive documents, ones which could contain several different user interfaces with entities such as text, calculations, drawings and possibly even multi-media presentations, illustrate the ADV concept. These examples lead naturally to the introduction of the concept of hole, a user interface area in a composite interactive document which is managed by an external program, and uses ADVs. Prototypes of a number of systems supporting ADVs and holes are currently running in our laboratory.     

Identifying the components

Most, if not all, databases are mixtures of samples from different distributions. Transactional data is no exception. For the prototypical example, supermarket basket analysis, one also expects a mixture of different buying patterns. Households of retired people buy different collections of items than households with young children. Models that take such underlying distributions into account are in general superior to those that do not. In this paper we introduce two MDL-based algorithms that follow orthogonal approaches to identify the components in a transaction database. The first follows a model-based approach, while the second is data-driven. Both are parameter-free: the number of components and the components themselves are chosen such that the combined complexity of data and models is minimised. Further, neither prior knowledge on the distributions nor a distance metric on the data is required. Experiments with both methods show that highly characteristic components are identified.     

基于测距的无线传感器网络定位系统

主要研究了无线传感器网络(WSN)的定位算法,结合N-hop Multilateration定位算法,针对CrossBox公司的无线传感器网络节点开发了一个小型定位系统,在实现过程中结合TinyOS系统提供的底层组件对原算法进行了一些改进,最后实物实验表明所设计的定位系统的可行性。     

Design and simulation based validation of the control architecture of a stacker crane based on an innovative wire-driven robot

Automated Storage/Retrieval Systems (AS/RS) have an important role in the improvement of the performance of automated manufacturing systems, warehouses and distribution centers. Existing AS/R systems are usually based on Cartesian Storage/Retrieval Manipulators (SRM). Such systems have reached their maximum performance due to the limitations of their underlying mechanical design and associated control architecture. Going beyond the limits of existing systems requires structural innovation and breakthrough solutions to enhance their design and performance. In this study, we introduce the design and simulation based evaluation of a stacker crane based on an innovative wire-driven SRM. We describe the basic components and provide an overview of the mechanical design of the system. We design the high-level control architecture that allows handling mini-load operations. We develop the equations that determine the single and dual command cycle times for the wire-driven SRM in case of random and class-based storage policies. We validate the suggested control architecture using a simulation software specifically developed for this purpose. We benchmark the wire-driven SRM against an equivalent Cartesian SRM. Results show that the new wire-driven SRM design and control architecture are more competitive than Cartesian SRM in terms of travel cycle times, and more suitable for buildings growing in height.     

Design patterns in object-oriented frameworks

Developing interactive software systems with complex user interfaces has become increasingly common. Given this trend, it is important that new technology be based on flexible architectures that do not require developers to understand all the complexities inherent in a system. Object-oriented frameworks provide an important enabling technology for reusing both the architecture and the functionality of software components. Frameworks typically have a steep learning curve since the user must understand the abstract design of the underlying framework as well as the object collaboration rules or contracts-which are often not apparent in the framework interface-prior to using the framework. The author describes her experience with developing an object-oriented framework for speech recognition applications that use IBM's ViaVoice speech recognition technology. Design patterns help to effectively communicate the internal framework design and reduce dependence on the documentation     

Mutual information theory for adaptive mixture models

Many pattern recognition systems need to estimate an underlying probability density function (pdf). Mixture models are commonly used for this purpose in which an underlying pdf is estimated by a finite mixing of distributions. The basic computational element of a density mixture model is a component with a nonlinear mapping function, which takes part in mixing. Selecting an optimal set of components for mixture models is important to ensure an efficient and accurate estimate of an underlying pdf. Previous work has commonly estimated an underlying pdf based on the information contained in patterns. In this paper, mutual information theory is employed to measure whether two components are statistically dependent. If a component has small mutual information, it is statistically independent of the other components. Hence, that component makes a significant contribution to the system pdf and should not be removed. However, if a particular component has large mutual information, it is unlikely to be statistically independent of the other components and may be removed without significant damage to the estimated pdf. Continuing to remove components with large and positive mutual information will give a density mixture model with an optimal structure, which is very close to the true pdf