This is the second issue of the International Journal of Performability Engineering of the year 2016 and the first issue under the editorship of the two new Co-Editors-in-Chief, namely, Dr. Dianxiang Xu, Professor & Graduate Coordinator of the Department of Computer Science at Boise State University, USA (e-mail: ijpe.xu@gmail.com) and Dr. Vallayil N. A. Naikan, - Professor and Head of the Reliability Engineering Centre at IIT Kharagpur, India (e-mail: naikanijpe@gmail.com). The scope of the journal, procedure for paper submission, the review process and the editorial policy remain unchanged. We are in the process of implementing an on-line paper management system for the journal. Once this is fully operational, it will be informed through the journal and also on the website of the journal. Till that time, authors are encouraged to submit their full research papers, case studies, review papers, short communications, book reviews, and other information such as details on conferences within the scope of the journal to any one of the Co-Editors-in-Chief by e-mail. The authors are also encouraged to submit the list of four referees with their current affiliation and contact details to accelerate the process of blind review of their paper. The new editorial board acknowledges the hard work and the invaluable contribution of the founder and long term editor of the journal Professor Krishna B. Misra. We also thank the editorial board members, the authors, paper reviewers and the readers of the journal for their enthusiasm, encouragement, support, and patience without which the journal could not have achieved its present status. We also expect that the journal will achieve more and more milestones in the years to come with the active participation and support of all concerned.

This issue of the journal consists of eight technical papers and a short communication.

The first paper shows that the lean manufacturing principles in conjunction with the simulation can be applied in processes of providing public services and contribute positively to the identification of process improvements. The paper also presents a case study from Brazil.

The second paper presents the effects of implementing turbulence device on the effectiveness of catalytic converter which represents the reduction in pollution rate through vehicles by minimizing the harmful emissions.

The third paper proposes a method for incorporation of acceleration in zero-failure testing cases. The paper, with a numerical example, proposes an optimum time censored zero-failure ALT plan under triangular cyclic-stress loading for Burr type XII distribution by minimizing the variance of the reliability function at used condition such that zero failures occur with reliability at high confidence level.

The fourth paper proposes an optimum test plan and statistical inference of 3-step step-stress accelerated life tests (SSALT) under progressive Type-I censoring.

The fifth paper reviews the investigations on the effects of heat treatment on the microstructure, quality of casting and mechanical properties of Al-7Si-0.3Mg (LM25) alloy.

The sixth paper highlights the optimization of Orbital Tungsten Inert Gas (OTIG) welding process parameters by Design of Experiment (DOE) using Taguchi method for stainless steel tubes used in propulsion feed system in satellites.

The seventh paper discusses the limitations of the existing research and proposes application of Lean Six Sigma to the medium consumption reduction in order to reduce the medium consumption of dense-medium coal separation, trace back the root causes and key factors of high medium consumption, and provide an efficient solution.

The eighth paper proposes a Memetic Algorithm to obtain a solution to the problem of preventive maintenance planning for a multi-component machine.

This issue of the journal also has a short communication. This paper presents a theoretical modeling approach to evaluate the performance metric that captures both service time of virtual machines (VM) and parse time of the cloud controller (CC) to ensure high fidelity.(text goes here - replace this text)

Through the application of simulation and lean manufacturing principles, this paper aims to highlight the features and operation of a system of providing public services in Brazil, which brings together, in one single place, a call to various services of a public nature, thus presenting a proposal for improvements of the services offered, specifically the process of renewal of driver's license. The results obtained in this study showed that the process of renewal of driver's licenses currently offered by Poupatempo system is a process which has already implemented improvements since its structure, but there are still opportunities to be applied to make it more efficient. The study showed that the lean manufacturing principles in conjunction with the simulation can be applied without any restrictions in processes of providing public services and contribute positively to the identification of process improvements.

This paper presents the effects of implementing turbulence device on the effectiveness of catalytic converter which represents the reduction in pollution rate through vehicles by minimizing the harmful emissions. This effectiveness basically deals with the rate of redox reactions of exhaust gases with the catalysts present inside the catalytic converter such as palladium (Pd), platinum (Pt) and rhodium (Rh). Chief purpose of the turbulence is to increase the catalytic reactions in the catalytic converter for cleaner emissions. Devices used are designed in such a manner that they don?t cause any backpressure on the combustion system that might affect the engine performance. By creating turbulence just before the catalytic converter, it creates high degree of randomness in the exhaust gases particles and due to this random movement they face larger contact area with the catalysts inside the catalytic converter and thus improves the effectiveness of the catalytic converter by increasing the rate of redox reactions. Different sets of readings has been recorded by noting down the pre and post position temperatures of the catalytic converter at different engine speeds and analyzed to obtain the best out of the designed turbulence devices.

In industry, zero-failure testing is used to demonstrate that a product achieves the required reliability at a high confidence level. Since modern day products are highly reliable; lasting for several years, therefore zero-failure testing performed under accelerated environmental condition helps in achieving this goal quickly. A zero-failure accelerated testing is characterized by the sample size, test time and test stresses. Various ALT models under constant, step-stress, progressive stress and their various combinations have been designed in the literature. However, none of these models has been used in zero failure testing. This paper incorporates acceleration in zero-failure testing. Optimum time censored zero-failure ALT plan has been formulated under triangular cyclic-stress loading for Burr type XII distribution. The optimum plan is devised by minimizing the variance of the reliability function at used condition such that zero failures occur with reliability at high confidence level. The method developed has been explained using a numerical example and sensitivity analysis carried out.

In this paper, the optimum test plan and statistical inference of 3-step step-stress accelerated life tests (SSALT) under progressive Type-I censoring is studied. It is assumed that the lifetime of a test unit follow a Weibull distribution with mean lifetime of a unit is a log-quadratic function of stress level. The maximum likelihood and Bayesian method are used to obtain the point and interval estimates of the model parameters under progressive Type-I censoring. The Bayes estimates are obtained using Markov Chain Monte Carlo (MCMC) simulation based on Gibbs sampling. The optimum 3-step SSALT plan under progressive Type-I censoring is developed by minimizing asymptotic variance of the maximum likelihood estimators of log of mean life at the design stress. Finally, the numerical study is presented to illustrate the proposed study.

This paper investigates a study on the effects of heat treatment on the microstructure, quality of casting and mechanical properties of Al-7Si-0.3Mg (LM25) alloy. The large reputation of Al-7Si-0.3Mg (LM25) alloy in automobile industry stems from its light weight (density of about 2.68 g/cc), high strength to weight ratio, excellent casting characteristics, high corrosion resistance, low coefficient of thermal expansion, good thermal & electrical conductivity and good mechanical properties including high machinability and workability. The microstructure of this alloy depends strongly on its composition and solidification rate. The slow-cooling rates encountered in sand castings lead to acicular silicon phase. The silicon phase in the form of large plates with sharp sides and edges act as internal stress risers in the microstructure and provide easy paths for fracture leading to inferior mechanical properties. The applications of this alloy demand several techniques and research methodologies to modify the microstructure and there by improve mechanical properties. Alloying, chemical modification, mould vibration during solidification and heat treatment were found to be effective in modifying the microstructure. In this view, this article presents the information?s about the influences of all such techniques which modify the microstructure and increase the quality of casting and mechanical properties.

This paper highlights the optimization of Orbital Tungsten Inert Gas (OTIG) welding process parameters by Design of Experiment (DOE) using Taguchi method forwelding of stainless steel of 6mm diameter and 0.7 mm thickness for satellite propulsion feed system. This proposed methodology identifies the optimum parameters for welding and brings out the significance of the individual parameter, combination of any of the two parameters (interaction effect) using Taguchi method by linear model analysis of Signal to Noise (SN) ratio and means verses input parameters. Detailed experiments were carried out and optimum parameters are arrived. Further these are tested by different methods to evaluate the strength required for intended application. This ensures sound and reliable weld joint. The optimum levels of these parameters thus developed are being followed and no call for any rework is reported thereafter. By varying the input parameters (current, RPM, gap between electrode and the job), the weld penetration level or weld quality has been studied in several 6mm diameter tube specimens andthe significance were studied and discussed in the test results.The Factorial Factor design is followed for minimum of 27 (three parameters and three levels=3×3=27) samples for this experiment. By further fine tuning the experiment, the optimized values achieved are current 18.35 Amps, electrode rotation 10 rpm and gap between electrode and job 0.8 mm. The weld specimen quality was verified in accordance with the user's quality standards and found satisfactory. This approach is easy to develop and easy to use that assures the best combination of parameters required for Orbital TIG welding which yield strong and defect free weld joint for Satellite application.

In order to reduce the medium consumption of dense-medium coal separation, trace back the root causes and key factors of high medium consumption, and provide an efficient solution, the limitation of the existing research is examined and the application of Lean Six Sigma to the medium consumption reduction is studied. By defining the waste and defection in the control of medium consumption and analyzing the inapplicability of the existing model, a lean sigma based method with detailed implementation procedures is proposed. The proposed method was implemented to reduce medium consumption of dense-medium coal separation in a coal mining industry, and the medium consumption is reduced from 2.17kg/t to 0.59kg/t. The application of the proposed method demonstrates that the new method can facilitate identifying and analyzing the root causes and key factors of medium consumption. In addition, the proposed approach and the outcomes from the case study establish a theoretical foundation for generic coal preparation applications in which medium consumptions are of major concerns in terms of cost saving and efficiency improvement.

Failure of a machine in a manufacturing industry leads to disruption of operations that severely impacts the enterprise in terms of revenue and customer satisfaction. The most prevalent strategy to mitigate the chance of machine failure is to perform preventive maintenance. Optimizing the preventive maintenance schedule is important to minimize operations cost and machine downtime. Further, for a multi-component machine, the knowledge of which components to perform preventive maintenance on can be crucial for such optimization. A stochastic simulation model can be used to evaluate all possible candidates and find the optimum preventive maintenance schedule. However, this involves infeasible computational time owing to the combinatorial nature of the problem. A Memetic Algorithm is proposed as a heuristic in the present work to address this challenge. Accuracy of obtained solutions and run-time is compared with brute-force search method and genetic algorithm for the same system. The Memetic Algorithm is found to yield better results as it can explore the search space more efficiently.

In realistic scenarios of cloud computing, performance of a cloud service is indeed a random variable due to random resource failures. To make more precise evaluation, the random change of performance caused by resource failures and subsequent recovery should be captured. In this paper, we consider a cloud system that has a hierarchical failure recovery mechanism consisting of three typical kinds of repair. A theoretical modeling approach is presented to evaluate the performance metric that captures both service time of virtual machines (VM) and parse time of the cloud controller (CC) to ensure high fidelity. Numerical examples are illustrated.