INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE (ENGLISH)
Year:2004 | Volume:15 | Issue:4|Papers Count:25

In this paper we use the explicit Runge- Kutta method for numerical solution of volterra integral equations of the second kind [1, 2]. We first introduce Pouzet volterra Rungekutta methods (Implicit and explicit forms) PVRK and then study about some extended explicit Bel"tyukov pairs, EBVRK. Each pair uses six stages and consists of an order 3 formula completely embedded in order 4 formula. Theoretical analysis and numerical experiment are provided to support the method. This method is used for solving a system of volterra integral equations and compare with iterative methods. (in [6], [7]).

An iterative nonlinear algorithm is generated for optimal sizing and placement of fixed and switched capacitor banks on radial distribution lines in the presence of linear and nonlinear loads. The HARMFLOW algorithm and the Maximum Sensitivities Selection (MSS) method are used to solve the constrained optimization problem with discrete variables. To limit the burden of calculations and improve convergence, the problem is decomposed into two sub problems. Objective functions include minimum system losses and capacitor cost while IEEE519 power quality limits are used as constraints. Results are presented and analyzed for the 18 bus IEEE distorted system. The advantage of the proposed algorithm compared to the previous work is the consideration of harmonic couplings and reactions of actual nonlinear loads of the distribution system.

This paper addresses a comprehensive model of Life Cycle Cost Analysis (LCCA) with fuzzy methodology. The proposed model enhances the evaluation methods of high voltage substation alternatives. This approach deals with a qualitative model of linguistic parameters which improves the reasoning of the experts in the presence of vague or imprecise data. In contrast with the existing methods of evaluation, the proposed approach enables us to effectiviely implement the cost of qualitative measures. These measures are collected from experts and are transformed to monetary values in a fuzzy expert system model. In order to verify the effectiveness of the proposed model, it is implemented in alternatives evaluation of a High Voltage substation.

In this paper, characterization results via optimality criteria of entropy and maximum entropy for the Pareto family are discussed. Order statistics results related to this family has an important role in statistical inference. We devoted characterization problems in view of the order statistics and entropy linked with the Pareto families in univariate cases. Also, for the above family, results via measures such as kullback Leibler information are derived.

The main advantage of mobile base robotic manipulators is their extended working space. In this paper, a new application is introduced to improve mobile base manipulators dynamic load carrying capacity. The concept of load-works pace is defined as union of places where robot base can be located on them and carries a load on a desired trajectory. By discretizing the load-workspace into some grid points, the base position is considered to be fixed on each grid point. Then, the dynamic effects of load and manipulator are computed separately on joint actuators during the motion on given trajectory. In the next stage, load carrying capacity of manipulator is computed at each base location by considering manipulator joint limit and actuator torque constraints. By applying a sequential procedure, at each step, a smaller subspace of load-workspace is selected such that a global optimum base location for maximum load carrying capacity of manipulator on predefined trajectory is found. Finally, the efficiency of presented algorithm is investigated for different mobile base robotic arms.

The concept of back wave propagation is developed as an inversion method to estimate acoustic parameters of the tissue and material from measurements of the acoustic field for a known source-receiver. A phase-regulated technique is introduced to measure the sensitivity of the back-wave propagation inversion method for estimating weakly sensitive acoustic model parameters. The paper demonstrates theoretically that the sensitivity can be measured by a sensitivity factor using the phase-regulation procedure. The paper also demonstrates that the spatial resolution of back propagated signal energy that is focused at the known source location is increased when sensitivity factor increases. This result leads to the definition of a criterion based on the spatial distribution of the signal energy around the source location. The criterion is formulated based on the spatial variance of the back propagated pressure field in a windows around the known source location. Use of the back wave propagation inversion method is demonstrated for estimating the acoustic model parameters, including type of materials, tissues, water depth, compressional speed of the sediment layer, and mineral density as poro-elastic media.

Analysis and design of enterprises including service enterprises require a proper model for them. Most of the available models are designed for a specific domain. So, different models are designed for various types of purposes in all kind of industries. However, with a reference model as a starting point, some benefits such as reduction in model creation time, enhancement of quality, consistency and interchangeability of enterprise models can be achieved. In this paper a reference model for service enterprises using IDEFO methodology is presented. Since service industry differs from manufacturing industry in procedures and purposes, there is a need for modeling of such enterprises. The presented model is a reference one for service enterprises through each particular service enterprise can customize this model for its own purpose by going further in more detailed levels.

In this paper, a new algorithm to solve a symmetric positive definite linear system of equations is proposed. Then, by exploiting the algorithm a new approach to compute a sparse approximate inverse M of a symmetric positive definite matrix A is presented. The new approach is based on minimizing the Frobenius norm of the residual matrix AM - I and can be decoupled into n subproblems, where n is the dimension of A and I is identity matrix. Hence the computation of the preconditioner can be done in parallel. In this approach the sparsity of the approximate inverse is preserved only by specifying the number of the nonzero elements of each column of M in advance. Some numerical experiments on test matrices from Harwell-Boeing collection are presented to make a comparison with the similar available methods.

It has been shown in recent years that the initiation of crack growth depends significantly on the T-stress for both brittle and ductile mechanisms of fracture. Although several methods have been presented in the papers for determining the T-stress for various specimens, most of the previous studies are based on two-dimensional crack models. The aim in this paper is to calculate the T-stress for double edge crack and internal crack specimens using a three-dimensional model. A set of linear elastic finite element analyses are performed to determine the stress fields around the crack front for each specimen. The T-stress is then computed across different planes through the thickness. The variations of T-stress with different parameters like the Poisson"s ratio, the specimen thickness and the ratio of crack length to specimen width (a/W) are also studied.

Navier-Stokes equations are used to analyze the turbulent flow around an axisymmetric bump numerically. The resulting equations are solved with Runge-Kutta multistage schemes using finite volume method and artificial matrix dissipations. In this work, first the effect of computational grid is considered deeply, then two algebraic and a one-equation turbulence models are implemented for a complicated test case. Further, a new integral procedure is proposed to determine the turbulent boundary layer thickness. It is found that the Baldwin Lomax model combined with the proposed integral method and using an appropriate computational grid domain leads to very accurate predictions in comparison with experiments [1] and other"s numerical results [2,8, 11].

This paper will synopsize the results of a research on a feasible methodology for selection of cases on the process of studies relating to urban design and form from a multidirectional point of view. Before elaborating on the methodology, the paper will investigate other elements that might have an equal influence on the study, i.e. intentions and means. The case studies for the purpose of urban studies should be representative of different historical periods, major cultures and climatic regions. The macro-objective of the research is to recommend a methodology, which could be practical for studies relating to the physical and morphological aspects of the urban form.

This paper describes an algorithm that determines the optimal application and coordination of over current protective devices such as fuses, rec1osers, and sectionalisers in distribution networks. The priority is given to providing all main feeders and the laterals with rec10ser protection, while considering security and selectivity of the protection system. In order to achieve these, first the rec10sers are located, then for protection of the laterals suitable fuses are selected based on coordination with the back-up rec1osers. At this stage also the time settings of reclosers are chosen. If, for a lateral, it is not possible to find a suitable fuse from the available fuse range, then a sectionaliser would be required instead. Based on the proposed algorithm, a software program with graphic interface and user friendly features has been developed to assist coordination of over current protection devices in a distribution network. The software has been tested on an Iranian 20kV network and the results presented show the effectiveness of the algorithm.

A new parameterisation scheme was developed and used to upgrade the continuous ARNO catchments response model to account for and estimate rainfall interception losses independently from transpiration estimates (which in total give evapotranspiration estimates) in order to reflect changes in land cover types on catchment streamflow, i.e. in land-use change studies. The scheme proposed here is considered useful where water balance module of a rainfall-runoff model has to be used in a relatively dense vegetated catchment area. The performance of the approach proposed is studied by using data from an Iranian small representative catchment located in the northern part of the country. The streamflow results in terms of basic statistics in three aggregation levels (i.e. daily, monthly and annual time steps) as well as streamflow assessment criterion (i.e. low flow analysis) for both present and future (altered) land-use are presented and compared with historic values. The results obtained showed the potential capability of the approach that can be employed in land use change studies.