CALCULATION OF CONVECTIVE FLOW ON THE PERSONAL COMPUTER USING A MODIFIED FINITE-ELEMENT METHOD

A modified finite-element method is used to simulate convective flow of an incompressible fluid in two dimensions. The time-dependent governing equations are solved explicitly using equal-order basis functions for the unknown variables, mass lumping, and one-paint quadrature. Petrov-Galerkin weighting is applied to the advection terms. Global assembly and storage of the coefficient matrices are replaced by local assembly. Although spatial accuracy is O(h²) for simply shaped elements, results are accurate for steady-state conditions. The method is cost effective and easy to implement. Problems requiring several thousand nodes can be run on a personal computer     

Real time stochastic scheduling in broadcast systems with decentralized data storage

Data broadcasting is an efficient method to disseminate information to a large group of requesters with common interests. Performing such broadcasts typically involve the determination of a broadcast schedule intended to maximize the quality of service provided by the broadcast system. Earlier studies have proposed solutions to this problem in the form of heuristics and local search techniques designed to achieve minimal deadline misses or maximal utility. An often ignored factor in these studies is the possibility of the data items being not available locally, but rather have to be fetched from data servers distributed over a network, thereby inducing a certain level of stochasticity in the actual time required to serve a data item. This stochasticity is introduced on behalf of the data servers which themselves undergo a dynamic management of serving data requests. In this paper we revisit the problem of real time data broadcasting under such a scenario. We investigate the efficiency of heuristics that embed the stochastic nature of the problem in their design and compare their performance with those proposed for non-stochastic broadcast scheduling. Further, we extend our analysis to understand the various factors in the problem structure that influence these heuristics, and are often exploited by a better performing one.     

Open-loop discretization methods for control systems design

In this paper, a unified theory is presented which addresses essential aspects of the open-loop discretization procedure. Initially, factors which affect the generation and propagation of discretization errors are identified by analytical, heuristic and experimental arguments. Following this, a discretization algorithm is presented which takes these factors into account. The fundamental idea of the discretization method is the replacement of the analogue integrators of the prototype continuous-time system by discrete-time approximations. This is done in such a way as to optimize a given cost function with respect to a given input. Unlike many discretization schemes presented in the literature, the procedure developed attempts to first determine the magnitude of the expected discretization errors, and then discretize with an appropriate complexity, giving the designer control over the order of the discrete-time system. This appears to be an effective means of designing filters with low complexity which still retain essential properties of the prototype system. An emphasis of this work is to view the discretization process from a control theory and engineering perspective. This results in a number of new perspectives relating to the discretization process.     

Authorisation Requirements on a Budget

Engineering information system deployment is squeezed by a shrinking commitment to requirements definition and an expanding need to determine the security requirements of such systems. This paper examines the causes and effects of this squeeze. Commitment is shrinking because of past requirements experiences, misunderstood trends in system development and requirements fatigue, while needs are expanding because of recent emphasis on Internet access to data, online transactions and workflow, which greatly increase the severity of the authorisation problem. Some approaches to quantifying and addressing this problem are introduced. Correspondence and offprint requests to: D. Raymond, 305 Bushview Crescent, Waterloo, Ontario, Canada N2V 2A6. Email: darrell.raymond@sympatico.ca     

Virtual organizational learning in open source software development projects

We studied virtual organizational learning in open source software (OSS) development projects. Specifically, our research focused on learning effects of OSS projects and the factors that affect the learning process. The number and percentage of resolved bugs and bug resolution time of 118 SourceForge.net OSS projects were used to measure the learning effects. Projects were characterized by project type, number and experience of developers, number of bugs, and bug resolution time. Our results provided evidence of virtual organizational learning in OSS development projects and support for several factors as determinants of performance. Team size was a significant predictor, with mid-sized project teams functioning best. Teams of three to seven developers exhibited the highest efficiency over time and teams of eight to 15 produced the lowest mean time for bug resolution. Increasing the percentage of bugs assigned to specific developers or boosting developer participation in other OSS projects also improved performance. Furthermore, project type introduced variability in project team performance.     

Integrated Civil Engineering Curriculum: Five-Year Review

An integrated curriculum, which draws material from different areas to teach students about design and problem-solving, offers civil engineering educators an option for accommodating new topics without increasing the number of courses. Freshman engineering and the senior capstone course are two examples of integrated courses, and the writers present a 5-year perspective on an approach that extends the concept of integration to six additional courses, comprised of an 8-course, integrated civil engineering core curriculum. Drawing on their combined experiences with the courses and assessment in a review by the Accreditation Board for Engineering and Technology, the writers conclude that the curriculum offers a useful vehicle by which to add material to the 4-year program without increasing the number of credit hours, and offers flexible courses to meet goals of professional groups. The paper describes lessons learned, challenges that remain, and current approaches to improvement.