Minimum cost wavelength-path routing and wavelength allocation of multiwavelength alloptical transport networks using a genetic-algorithm (GA)/heuristic hybrid approach is described. A cost model is adopted which inco...
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Minimum cost wavelength-path routing and wavelength allocation of multiwavelength alloptical transport networks using a genetic-algorithm (GA)/heuristic hybrid approach is described. A cost model is adopted which incorporates a dependency on link wavelength requirements. The hybrid algorithm developed uses an object-oriented representation of networks, and incorporates four operators: path mutation, single-point crossover, reroute and shift-out. In addition, an operator-probability adaptation mechanism is employed to improve operator productivity. Experimental results from seven fifteen-node test networks, obtained using a tool for optical network optimisation, modelling and design (NOMaD), suggest the GA/heuristic hybrid approach provides superior results compared to three recent wavelength-allocation heuristics, except when the network cost depends most heavily on wavelength requirement.
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 develop...
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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. But 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. In this article, 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.
This research work aims to develop an intelligent constraint-based system that enables designers to consider at the early stages of the design process all activities associated with product's life cycle. One of th...
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This research work aims to develop an intelligent constraint-based system that enables designers to consider at the early stages of the design process all activities associated with product's life cycle. One of the most important aspects of these activities is the evaluation and optimisation of manufacturing processes that require various type of information from the different aspects of product's life cycle. This research article discusses the development of a prototype system for manufacturing process optimisation using a combination of both mathematical methods and constraint-programming techniques. This approach enables designers to evaluate and optimise feasible manufacturing professes in a consistent manner as early as possible during the design process. This helps in avoiding unexpected design iterations that wastage a great amount of time and effort, leading to longer lead-time. The development process has passed through the five major stages: Firstly, an intelligent constraint-based design system for concurrent product and process design has been developed. Secondly, a manufacturing process optimisation module has been constructed. Thirdly, the product features, processes, cost, time and constraints to be used for carrying out various design tasks has been represented in the format of constraints, frames, objects, and rules. Fourthly, the process optimisation and evaluation rules for the selection of feasible processes for complex features, and finally, the information management system that ensures consistency in information exchange and decision making activities have been developed. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.
A node-based data structure is developed for use in either two-dimensional (2-D) or three-dimensional (3-D) finite element method (FEM) problems. This grid uses quadrilateral (2-D) or hexahedral (3-D) elements and is ...
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A node-based data structure is developed for use in either two-dimensional (2-D) or three-dimensional (3-D) finite element method (FEM) problems. This grid uses quadrilateral (2-D) or hexahedral (3-D) elements and is dynamically adaptive according to the 1-irregular requirement for refinement-derefinement. Implemented in C + +,the grid consists of node objects linked with pointers to neighboring node objects. The algorithm used to traverse the grid starts at the first node of the grid and constructs each FEM element by following the links of the nodes. This algorithm uses a stack to maintain the correct order of elements during the grid traversals. Because the elements and their connectivity are not permanently stored, the computer storage requirements for the grid are reduced significantly in 3-D compared with an element-based approach. Although the node-based approach may increase the CPU-time and complexity to access an element, it reduces the complexity and time required to refine and derefine an element. This implementation is applicable to many FEM domains. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
The Common object Request Broker Architecture (CORBA), is a major industrial standard for distributed object-based applications. Today's large-scale CORBA applications have to deal with object crashes, node failur...
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The Common object Request Broker Architecture (CORBA), is a major industrial standard for distributed object-based applications. Today's large-scale CORBA applications have to deal with object crashes, node failures, networks partitioning and unpredictable communication delays. Existing efforts to enhance the CORBA reliability can be roughly categorized into three approaches: integration approach, interception approach and service approach. Each approach has its own merits and prices. In this paper, we propose a service approach solution called object Fault-tolerance Service (OFS). Solutions that adopt the service approach usually specify their service in terms of CORBA IDL interfaces. The implementations of such solutions in general do not modify the ORE infrastructure or IDL language mappings, and thus applications developed with those systems appear to be more portable. OFS differs from other service approach solutions in that OFS does not assume underlying support of reliable group communication. Applications with advance registration can rely on OFS for detection of object and node crashes, and for customized recovery. In this paper, we first present the service specification of OFS. We then give the system architecture of an OFS implementation. This OFS implementation is developed on the Solaris 2.5 platform and with IONA's Orbix 2.0. The performance evaluation of the OFS implementation is also presented. The preliminary experiments indicate that OFS overhead is minimal and client objects experience little response delay when a service object is under OFS surveillance. (C) 1999 Elsevier Science Inc. All rights reserved.
This paper presents selective checkpointing and rollback schemes for MT-GO (multithreaded, object-oriented) programs. There is a need for checkpointing mechanisms that are more sophisticated than the traditional proce...
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This paper presents selective checkpointing and rollback schemes for MT-GO (multithreaded, object-oriented) programs. There is a need for checkpointing mechanisms that are more sophisticated than the traditional process-level checkpointing. The program model, theoretical foundations, and an implementation of the selective checkpointing & rollback schemes are described. The usefulness of the schemes is demonstrated by implementing a higher level fault-tolerance scheme of conversations using them. The performance implications are studied on a prototype internet e-commerce server. The use of the selective schemes in the prototype server showed an appreciable reduction in the loss of work in the presence of faults. Benefits are more pronounced for a larger level of concurrency in the server. The selective scheme usually outperforms the hypothetical zero-cost global scheme in the presence of faults, vis-a-vis completion times. The experiments also show the vast difference between the sizes of selective checkpoints and global checkpoints. The concurrent sessions scheme (based on the concept of relaxed conversations) required 160 checkpoints in less than an hour. Traditionally, such a scheme would be considered outrageous, but the selective schemes still improve performance in the presence of faults. The main contribution of this paper is that it brings forward an OO (object-oriented) approach to checkpointing. Not only does the program model separate program state from process state, but it allows one to identify the state associated with each individual thread of the MT program. The prototype showed that this abstract knowledge about the program state can be made available at runtime in the form of suitable data structures. The availability of this information at runtime fuels the design of selective schemes.
This paper describes the application of an object-oriented Paradigm (OOP) to the implementation of a hyperelastic constitutive e driver. The C++ programming language used in our implementation lends to an efficient an...
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This paper describes the application of an object-oriented Paradigm (OOP) to the implementation of a hyperelastic constitutive e driver. The C++ programming language used in our implementation lends to an efficient and readable program. It will be shown that object-oriented implementation naturally follows from analytical development in isotropic hyperelasticity. Examples of classes developed and results from a number of large deformation hyperelastic numerical test are presented.
Networked computers are finding their way into a broader range of environments, from corporate offices to schools, homes, and shirt pockets. This new computing model fosters the development of distributed software com...
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Networked computers are finding their way into a broader range of environments, from corporate offices to schools, homes, and shirt pockets. This new computing model fosters the development of distributed software components that communicate with one another across the underlying networked infrastructure. A distributed software component can be plugged into distributed applications that may not have existed when it was created. The intention is that many developers will reuse distributed software components to build new systems. An interface definition language usually is used to describe a distributed software component's interface. However, a notable limitation of current IDLs is that they generally only describe the names and type signatures of the component's attributes and operations. Current IDLs don't formally specify the behavior of the software component's operations. To help solve these problems, the authors have developed Biscotti (behavioral specification of distributed software component interfaces), a Java extension that enhances Java remote method invocation interfaces with Eiffel-style preconditions, postconditions, and invariants.
In this paper, we present an object-oriented application framework to support the development of evolving distributed systems. The framework combines concepts of the object-oriented paradigm with those of architectura...
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In this paper, we present an object-oriented application framework to support the development of evolving distributed systems. The framework combines concepts of the object-oriented paradigm with those of architectural design. The result is a framework which supports extensible and reusable configurations of distributed components. The framework addresses the problem of evolution by allowing the addition, replacement and extension of components of a configuration, Evolution is also possible at run time, where a configuration can change dynamically depending on a particular event. The paper outlines the fundamental aspects of our framework and presents a case study, which illustrates its application. (C) 1999 Elsevier Science B.V. All rights reserved.
The majority of problems arising in science and engineering require the solution of a large set of linear algebraic equations such as, in matrix form. Ax = b. This type of equation is usually solved using some form of...
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The majority of problems arising in science and engineering require the solution of a large set of linear algebraic equations such as, in matrix form. Ax = b. This type of equation is usually solved using some form of Gaussian elimination. It is necessary to the finite element users that the nodes and elements are numbered correctly since nearly all computer programs contain linear algebra solution routines. These are usually expressly written to operate efficiently on matrices possessing small bandwidths, profiles or wavefronts (frontwidths). The object-oriented implementation of bandwidth, profile and wavefront reduction is based on an algorithm published by Sloan, which seems to perform consistently better to that of the widely used reverse Cuthill-McKee method and the Gibbs-King method. This article presented for the first time during CST'96 Conference [Gajewski, R.R., Lompies, P., object-oriented implementation of bandwidth, profile and wavefront reduction algorithms, In: Advances in Computational Structures Technology, ed. B.H.V. Topping, Civil Comp Press, 1996, pp. 115-120.] provides a full description of the implemented classes, their hierarchy and implementation. It is also illustrated by examples of practical calculations. (C) 1999 Elsevier Science Ltd and Civil-Comp Ltd. All rights reserved.
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