Chandra S. Putcha

Probabilistic network analysis for project completion time

Abstract The paper deals with the probabilistic network analysis for project completion time for various networks. As the project completion time depends on the path with the longest total completion time of all the given paths, it is expressed as a function of various activity durations according to known activity precedence relationship in the present study. As all the activity durations are considered probabilistic in nature, the total completion time is also a probabilistic variable and the determination of that requires rigorous mathematical analysis. Rosenblueths two point estimates scheme is used for this non-linear probabilistic analysis problem and the results are compared with Monte Carlo Simulation. Such a study is conducted for two different networks and the results compared very well for both sample problems, both for uniform and normal distribution of the random variables which are the activity durations and the activity precedence relationships in the present study.

A CASE STUDY ON FMEA APPLICATIONS TO SYSTEM RELIABILITY STUDIES

Failure Mode and Effect Analysis (FMEA) has been used quite extensively in aerospace industry for several years to establish hardware criticality. Determination of software reliability is equally important. There are several methods for determining software reliability. One methods for performing software reliability is the software FMEA. This paper discusses the application of principles to FMEA. A typical Tank pressurant is considered as an illustrative example. The tank pressurant system consists of three sets of solenoid valves (each set consists of a pair of valves), three pressure transducers, a vent valve, a heat exchanger and helium cold pressure bottles. Each set of solenoid valves consist of two solenoid valves connected in series. For the system to function properly, certain conditions have to be met. These are discussed in detail later in this paper. Based on the information provided from NASA, it is concluded that FMEA has to be capable of determining the software failure modes, effects and criticality as well as the hardware failure modes effects and criticality which includes the pressure transducers, solenoid valves, vent valve, heat exchanger and helium cold pressure bottles. The paper will discuss both the hardware and software FMEA application in detail.

Development of improved and efficient traffic flow model

Abstract The paper deals with development of efficient and improved traffic flow model to predict the space mean speed, ūs, in terms of the mean free flow speed, uf, and the density, k. The Greenberg model (which is based on fluid-flow analogy concept)satisfies the boundary condition only at jam density, kj. It violates the boundary condition at zero density, k, in the sense that it can only be attained at infinitely high speeds according to Khisty and Lall [1] and Papacostas and Prevedouros [2]. The intent of this research work is specifically to arrive at an improved version of Greenberg model (CSUF model). The CSUF model will be accomplished by expansion of natural log expression in Greenberg expression and considering only linear terms. The correlation coefficient will then be calculated. Existing experimental results will be used to validate the model. These results will then be compared with the results already existing in the literature from the Greenberg model as well as the Underwood and Eddie model.

Time-Dependent Reliability Analysis of Steel Miter Gates

Abstract This article deals mainly with identification of a suitable method for time-dependent reliability and analysis of navigation structures based on a detailed literature review, application of the method to a miter gate, and comparison of results with the existing results in the the literature. The aspect of corrosion is considered in the study. This work is a continuation of the work on rolled steel sections reported by the authors at an international conference in Canada. Detailed computer programs in FORTRAN have been developed as part of this research study. It has been found that the existing results and the results of the present investigation compare very well.

A computer aided technique for shaft design through monte carlo simulation

Abstract The paper predicts the probability of failure of shafts subjected to reverse bending during the process of transfer of power. Since reliability and probability of failure are complementary to each other, the safety levels are calculated in terms of reliability factors. The shafts considered in this study are subjected to tension, compression, bending or torsional loads acting singly or in combination with one another. The static and fatigue strength become important design considerations in cases like these as the shafts are subjected to static stresses, completely reversed stresses and repeated cyclic stresses, all acting at the same time. All this is considered with the input parameters being probabilistic, as in reality, these are supposed to have some variations. Finally, theoretical equations are developed for the output coefficient of variation of shaft diameter as a function of the coefficient of variation of input parameter for various design theories existing in literature. The results are then checked with those obtained by Monte Carlo simulation. Excellent correlation was obtained between the two sets of results.

Total quality engineering, failure analysis and stochastic process evaluation of engineering project alternatives

The interaction of technical ergonomic and product liability concepts within total quality engineering and management frameworks are evaluated. Risk management and insurance industry paradigms are examined as affecting value engineering and decision-making under uncertainty analysis. Joel Barkers Future Edge success paradigms are extended to risk analysis and ergonomics to achieve total quality and robustness. Examination of stochastic evaluation of engineered structures for life-cycle costing used with consideration of project alternatives is emphasized, and is an extension of work done by the authors in the area of legal liability and technical insurance as related to engineering structures. Also considered are factors for safety and risk and project alternatives. Results show that for a complete assessment of project alternatives, concurrent interdisciplinary engineering methods are required.<<ETX>>

Development of a mathematical equation for post-traumatic stress index with and without physician intervention for the general population

Abstract This paper describes the formulation of a post-traumatic stress syndrome index (PTSDI) for the general population based on factors associated with post-traumatic stress syndrome (PTSD). Additionally, the paper estimates the reduction in the PTSDI subsequent to a clinical intervention such as multimodal group therapy. The relationship between the PTSDI and important psychological and social outcomes such as substance abuse, self-medication, divorce, and suicide is evaluated using correlation and regression analyses. The limitations of this study and avenues for future research are discussed in the concluding remarks.

Application of engineering principles to calculate poverty indices

Abstract This paper deals with extension of the previously developed formula by the first author of this paper. This is done in terms of comparing the previously obtained results of poverty index (PI) with 0% below 100 FPL (Federal Poverty Level) and 0% below 125 FPL. The corresponding correlation coefficients between PI and 100% FPL and 125% FPL are also calculated and relevant conclusions are drawn. The results obtained are very useful for researchers as well as to general public.

Financial Analysis of Well-known Disasters Using Utility and Reliability Values

This paper is a significant extension of Putcha (2011), where detailed financial analyses are conducted and reliability levels are calculated for well-known disasters. In this research, three methods, namely deterministic method, utility method, and probabilistic method, are developed to calculate the probability of a disaster associated with the calculation of reliability levels for various well-known disasters. Specifically, the probabilistic method is based on the limit state chosen, functional relationship between various dependent and independent parameters and the uncertainty in the associated parameters. Our analyses are done from the financial point of view based on the concept of utility functions (Ang and Tang, 2007) and previous literature such as Putcha et al. (2008).

Development and Application of a New Optimization Method to Problems in Engineering Design

Abstract This paper introduces a new and uniform method of Linear Programming optimization problems for both standard and non-standard cases. Using this method, all the linear programming (LPP) optimization problems can be solved using slack variables only by a simple transformation. Thus, it eliminates the use of surplus and artificial variables and the need to use the big M method. The efficacy of this method has been shown by few examples which gave same results using the traditional methods.