Metric Distance Ranking Technique for Fuzzy Critical Path Analysis

In this paper, fuzzy critical path analysis of a project network is carried out. Metric distance ranking technique is used to order fuzzy numbers during the forward and backward pass computations to obtain the earliest start, earliest finish, latest start and latest finish times of the project’s activities. A numerical example is presented with a detailed step by step solution. The results of the numerical example presented are in agreement with published results in literature using other fuzzy ranking technique.© JASEMKeywords: fuzzy, metric distance, critical path method, total floa

Flowshop Scheduling Using a Network Approach

In this paper, a network based formulation of a permutation flow shop problem is presented. Two nuances of flow shop problems with different levels of complexity are solved using different approaches to the linear programming formulation. Key flow shop parameters inclosing makespan of the flow shop problems were obtained without recourse to the traditional approach of using Gantt charts. The linear programming models of the flow shop problems considered were solved using LINGO 7.0. The present technique has been shown to be very effective and efficient.http://dx.doi.org/10.4314/njt.v34i2.1

A Mathematical Model for Predicting Output in an Oilfield in the Niger Delta Area of Nigeria

In this paper, a multiple linear regression model was developed for forecasting crude oil production volume in an oilfield in the Niger Delta area of Nigeria. Data of crude oil production volume and six significant parameters affecting crude oil volume were collected for a two year window. A six variable linear model was developed. The significance of each regression coefficient at   in the six variable model was subjected to further analysis. The regression coefficient screening process resulted in a two variable model for predicting oil field output. The resultant model was found to have greater utility in predicting oil field output as it produced less residual. The present model can be of invaluable use to the oil field manager.http://dx.doi.org/10.4314/njt.v34i4.1

ANALYSIS OF FLOW IN A CONCENTRIC ANNULUS USING FINITE ELEMENT METHOD

This work presents the computational modelling of the velocity distribution of an incompressible fluid flowing in a cylindrical annulus pipe, using the finite element method. The result shows that the velocity distribution increases from the boundaries until midway between the boundaries where it was maximum. Also, the velocity increases as the viscosity decreases. The results obtained were compared with exact second order differential equation solution. The results obtained were highly accurate and converges fast to the exact solution as the number of elements increases. http://dx.doi.org/10.4314/njt.v35i2.1

An Object-Oriented Program for Critical Path Analysis of Project Networks

In this study, program has been developed in Visual Basic.Net platform for critical path analysis of projects. The critical path forward pass as well as the backward pass has been programmed for any complexity of project network. The program is able to output the earliest start, earliest finish, latest start, latest finish, total float, free float and the independent float of the activities in a project network. The program has been tested on a case study has been found to be very accurate. The results demonstrate that using the computer program will be of invaluable help to students and practitioners in the delivery of Critical Path Analysis.Keywords: Object oriented, critical path method, float, projec

A Permutation Encoding Technique Applied to Genetic Algorithm Solution of Resource Constrained Project Scheduling Problem

In this paper, a permutation chromosome encoding scheme is proposed for obtaining solution to resource constrained project scheduling problem. The proposed chromosome coding method is applied to Genetic algorithm procedure and implemented through object oriented programming.  The method is applied to a numerical example with two different stopping criteria. The results obtained are encouraging as they are in agreement with published solutions in literature. The method lends itself easily to programming and can be used to obtain results to large scale problems encountered in practice.http://dx.doi.org/10.4314/njt.v34i1.1

An Investigation into the Decision Makers’s Risk Attitude Index Ranking Technique for Fuzzy Critical Path Analysis

In this paper, the effectiveness of the decision maker’s risk attitude index for fuzzy critical path analysis is considered. The fuzzy CPM algorithm was implemented in Visual Basic .Net and used to obtain the project’s activities times as well as the total float of project activities. Numerical computation reveals that for a benchmark problem, the decision maker’s risk attitude index ranking method produces unrealistic results when the decision maker’s attitude towards risk was neutral. However, a modified problem derived from the benchmark problem produced realistic results. The study shows that the utility of the ranking technique may be limited by the risk index associated with the problem. Therefore users of the technique for ranking fuzzy numbers have to proceed with caution

Numerical Modeling of a Rayleigh Step and Multi Step Slider Bearings using Finite Difference Method

The oil film pressure in a step slider bearing is difficult to obtain because the discontinuous clearance leads to a discontinuous velocity profile. In this paper, the pressure distribution in a step slider bearing is obtained numerically by introducing a virtual clearance to satisfy the continuity of the velocity at the step. The governing equation is discretized using central difference method for each internal node in the flow volume and the resulting system of equations solved using Gauss Seidel scheme with a convergence criterion of 0.0001. The result obtained with the present method is in good agreement with analytical solution for the Rayleigh step slider. The method is also applied to a multi step slider bearing for which no analytical solution exists. The solution converges when the mesh is refined

Analysis of Tube Drawing Process – A Finite Element Approach

In this paper the effect of die semi angle on drawing load in cold tube drawing has been investigated numerically using the finite element method. The equation governing the stress distribution was derived and solved using Galerkin finite element method. An isoparametric formulation for the governing equation was utilized along with C0 cubic isoparametric element. Numerical experimentation showed that the results obtained using the present method is admirable close to the analytical solution and more accurate than finite difference solution. Having established the accuracy of the present solution method, parametric studies were carried out to show the effect of die semi angle on the drawing load for different tube drawing processes. The analysis was carried out using a Visual Basic.Net program developed by the authors. The results are presented in both graphical and tabular forms

Analysis of temperature distribution in a heat conducting fiber with convection losses using finite element method

The temperature distribution in a heat conducting fiber is computed using the Galerkin Finite Element Method in the present study. The weak form of the governing differential equation is obtained and nodal temperatures for linear and quadratic interpolation functions for different mesh densities are calculated for Neumann boundary conditions. The results show that using a mesh of three quadratic elements produces a maximum error of 0.622 compared to 1.1832 for a similar number of linear elements. It is concluded that as the mesh is refined further progressively, the finite element solution approaches the exact solution admirably. The results are displayed inboth graphical and tabular form