M. L. Kansal

A real coded genetic algorithm for solving integer and mixed integer optimization problems

In this paper, a real coded genetic algorithm named MI-LXPM is proposed for solving integer and mixed integer constrained optimization problems. The proposed algorithm is a suitably modified and extended version of the real coded genetic algorithm, LXPM, of Deep and Thakur [K. Deep, M. Thakur, A new crossover operator for real coded genetic algorithms, Applied Mathematics and Computation 188 (2007) 895-912; K. Deep, M. Thakur, A new mutation operator for real coded genetic algorithms, Applied Mathematics and Computation 193 (2007) 211-230]. The algorithm incorporates a special truncation procedure to handle integer restrictions on decision variables along with a parameter free penalty approach for handling constraints. Performance of the algorithm is tested on a set of twenty test problems selected from different sources in literature, and compared with the performance of an earlier application of genetic algorithm and also with random search based algorithm, RST2ANU, incorporating annealing concept. The proposed MI-LXPM outperforms both the algorithms in most of the cases which are considered.

Reliability analysis of water distribution systems under uncertainty

Abstract In most of the developing countries, the Water Distribution Networks (WDN) are of intermittent type because of the shortage of safe drinking water. Failure of a pipeline(s) in such cases will cause not only the fall in one or more nodal heads but also the poor connectivity of source with various demand nodes of the system. Most of the previous works have used the two-step algorithm based on pathset or cutset approach for connectivity analysis. The computations become more cumbersome when connectivity of all demand nodes taken together with that of supply is carried out. In the present paper, network connectivity based on the concept of Appended Spanning Tree (AST) is suggested to compute global network connectivity which is defined as the probability of the source node being connected with all the demand nodes simultaneously. The concept of AST has distinct advantages as it attacks the problem directly rather than in an indirect way as most of the studies so far have done. Since the water distribution system is a repairable one, a general expression for pipeline avialability using the failure/repair rate is considered. Furthermore, the sensitivity of global reliability estimates due to the likely error in the estimation of failure/repair rates of various pipelines is also studied.

An interactive method using genetic algorithm for multi-objective optimization problems modeled in fuzzy environment

In this paper, an interactive approach based method is proposed for solving multi-objective optimization problems. The proposed method can be used to obtain those Pareto-optimal solutions of the mathematical models of linear as well as nonlinear multi-objective optimization problems modeled in fuzzy or crisp environment which reasonably meet users aspirations. In the proposed method the objectives are treated as fuzzy goals and the satisfaction of constraints is considered at different @a-level sets of the fuzzy parameter used. Product operator is used to aggregate the membership functions of the objectives. To initiate the algorithm, the decision maker has to specify his(er) preferences for the desired values of the objectives in the form of reference levels in the membership space. In each iterative phase, a single objective nonlinear (usually nonconvex) optimization problem has to be solved. It is solved using real coded genetic algorithm, MI-LXPM. Based on its outcomes, the decision maker has the option to modify, if felt necessary, some or all of the reference levels in the membership function space before initiating the next iterative phase. The algorithm is stopped where users aspirations are reasonably met.

An improved algorithm for connectivity analysis of distribution networks

In the present paper, an efficient algorithm for connectivity analysis of moderately sized distribution networks has been suggested. Algorithm is based on generation of all possible minimal system cutsets. The algorithm is efficient as it identifies only the necessary and sufficient conditions of system failure conditions in n-out-of-n type of distribution networks. The proposed algorithm is demonstrated with the help of saturated and unsaturated distribution networks. The computational efficiency of the algorithm is justified by comparing the computational efforts with the previously suggested appended spanning tree (AST) algorithm. The proposed technique has the added advantage as it can be utilized for generation of system inequalities which is useful in reliability estimation of capacitated networks.

Fuzzy fault tree analysis of a power transformer

Power transformer is an essential and integral part of any power system. Failure of power transformer affects the working of entire system. Since failure probability is smaller as compared to success, it is easier to carry out the failure analysis for estimating the success probability. However, past failure information results in short term failure probability which does not provide reliable information about the future behavior of the system. In order to overcome the uncertainty in the analysis, expert fuzzy number based fault tree analysis may be adopted for estimating the failure probability of the transformer. In this study, fuzzy fault tree approach has been described and applied for failure probability estimation of a distribution transformer. The results are compared with Conventional Fault Tree Analysis. Further, the basic failure events are ranked according to Fuzzy Importance Index (FII). This will help the decision maker to prioritize the components for repair and attention so as to improve the reliability of the system.

Computer-Aided Reliability Analysis of Water Distribution Networks

Abstract Frequently, not much attention is paid to the cost optimization and reliability analysis of water distribution systems while designing. Reliability analysis and cost optimization are, however, inter-related. For example, in a branch type network, only one path of supply reaching a demand node may cost less, but at the same time, will have low reliability. In such a case, if any of the pipelines fail, the subsequent demand nodes will not receive any water. However, in a loop-type water distribution network, as the number of paths increases, the cost as well as reliability increase. Although loop-type water distribution networks are provided in urban areas, reliability analysis is generally not resorted to as its computation is uncommon to civil engineers. Reliability engineering concepts are substantially developed and have been used in the field of electrical and communication engineering. The purpose of this paper is to present a simple pathset technique for reliability analysis of demand nodes in water distribution networks. An efficient computer algorithm has been evolved which evaluates the minimal paths in the network and then computes the reliability using the concepts of Boolean algebra and set theory. The sensitivity of reliability with the additional pipeline(s) and demand node(s) for directed and undirected hydraulic networks has also been studied and the suggested methodology is illustrated with the help of examples.

Snow cover area variability assessment in the upper part of the Satluj river basin in India

Abstract In high-altitude areas, snow cover plays a significant role in mountainous hydrology. Satluj, which is a snow-fed river, is a part of the Indus River system in the western Himalayas. Snow cover area (SCA) variability in this river basin affects the spatio-temporal flow availability and avalanche events. Keeping this in mind, the present study focuses on SCA variability and its relationship with various topographical features such as elevation, slope and aspect. The study has been carried out in the upper part of the Satluj River Basin on the basis of MODIS Terra (MOD10A2) data from 2001 to 2014. It has been noticed that the average annual SCA in this part of the Satluj River Basin varies from 44 to 56% with an average of about 48% of the total basin area of 16, 650 km2. Further, snow accumulation and depletion curves have been suggested for assessing the SCA in the study area.

Fuzzy based transformer failure analysis under uncertainty

A typical power system consists of three sub-systems, namely, generation, transmission and distribution. The power transformation from generation to transmission to consumers is carried out through step-up or step-down transformers so as to reduce transmission losses as well as for making the electrical appliances to work. Transformers are also used to control voltage and are equipped with tap changers on one or more windings to change the turn ratio. Therefore, successful operation of a power transformer is an essential requirement for any power system to work which makes it an integral part of the entire system. The present study uses the conventional and expert fuzzy based fault tree analysis and highlights the importance of fuzzy based failure analysis of power transformers which will help the power system managers for paying attention towards maintenance. The expert opinions are utilized using the concept of decision making under uncertainty to carry out the failure analysis. It also ranks the importance of various failures which will fix the priority for maintenance. The suggested methodology has been illustrated with the help of an example which is a case study from India.

Biodiversity and present status of freshwater fishes in Lohit river basin of India

Lohit is a major tributary of the river Brahmaputra in India and is famous for its rich and diverse fish fauna. The river has a difficult terrain, but has high hydropower potential. A large number of storage-based hydropower plants are envisaged on this river in the near-future. This study aims at presenting the existing diverse fish fauna in Lohit river basin. A total of 74 fish species are identified in this river basin and can be classified into seven orders, 20 families, and 52 genera. Further, it has been highlighted that there are seven species which have been categorized as endangered, 12 species are categorized to be vulnerable, three species have been categorized as data-deficient, and the remaining species are in the least concern category. It is expected that the construction of proposed storage-based power plants in this basin will affect the flow and storage characteristics, as well as the temperature of the water, which, in turn, will affect the rich fish fauna. This study emphasizes the need for preparing a comprehensive plan for the adoption of appropriate in situ conservation measures, as well as an awareness program, so as to save the rich and diverse fish fauna of Lohit river basin.

Urban water service quality assessment in Tanzanian towns of Songea and Mbeya

In services, the customer satisfaction and quality of services hold the central place. Although the term ‘quality’ is widely used, but does not represent a clear scientific concept. In public utilities, the quality is conceptualized in terms of gap between the perception and the expectation of the customers and the service provider. Drinking water utilities are one of the most important services, where quality of services has not been paid due attention. Keeping this in mind, the present study attempts to assess the urban water utility service quality in the two towns of Tanzania, namely Songea and Mbeya. The study suggests a methodology to evaluate the customers satisfaction in terms of Customers Satisfaction Index (CSI). A popular SERVQUAL model used in services marketing is applied to these water utilities so as to assess the importance of perceptibility, reliability, responsibility, safety and empathy for the two water utilities. Thereafter, the service quality which is a gap between the perception and expectation is assessed in terms of these parameters and the associated attributes. It has been noticed that the CSI for Songea and Mbeya is of the order of 56.4 and 58.4%, respectively. From the Tanzanian perspective, it can be considered as ‘satisfactory,’ but can be improved by adopting various structural and non-structural measures such as creation of storages, customers awareness, resources management and participation in decision making.