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Volume 12, Number 4, July 2016 - Editorial - pp 303-304

Vallayil N. A. Naikan

This is the fourth issue of the International Journal of Performability Engineering of the year 2016. This issue of the journal consists of seven technical papers including two short communications and a book review.

The first paper has suggested a bootstrap re-sampling procedure to address the issue of the scarcity of observed data. The authors employed the Gram-Charlier functions and order statistics to approximate the distributions. It is demonstrated how to derive them for a separate repair project and a larger project consisting of a number of concurrently running subprojects. Following this, guidance is provided on how to decide the deadline for completion of the whole work. A simple example is provided.

In the second paper a non-repairable multi-state system with imprecise probabilities and performance rates are taken, representing imprecise probabilities by interval valued probabilities. These intervals are evaluated by computing bound of interval valued ordinary differential equation of the system. For imprecise performance rates random fuzzy variables are introduced. The proposed method is based on hybrid universal generating function and probability intervals to incorporate the uncertainty problem in availability assessment of the system. Finally, availability p-boxes of the system have been evaluated along with a numerical example.

The third paper has shown how knowledge management can be used to achieve quality in finished products and proposed a hybrid spiral model which is integration of spiral model and knowledge management. The authors have proposed a hybrid spiral model to improve software quality using knowledge management which is based on knowledge flow during process. Proposed hybrid spiral model has been illustrated with an example.

In the fourth paper, the data on the wind speed and power generated from a location in the state of Karnataka, India, has been analyzed for the duration of three months. It has been shown that the probability distribution of wind speed conforms closely to Rayleigh distribution. It is demonstrated that, while the wind speed conforms to Rayleigh distribution, the electrical power developed follows a Weibull distribution with two parameters. Besides using graphical methods for estimating the Weibull parameters, Maximum likelihood equations are set up to estimate the parameters. These parameters have been used in estimating / forecasting of wind power using both Weibull algorithm as well as the Monte Carlo Method.

The fifth paper is a review paper on application of simulation for reliability computations. Various simulation methodologies such as Monte Carlo simulation, Discrete event (DE) simulation, Subset simulation, Hybrid subset simulation, Simulated annealing, Stochastic simulation, Digital simulation, and Markov System Dynamics (MSD) simulation are discussed in details. Applications of these techniques in reliability engineering, their advantages and limitations are also presented. The authors have opined that modeling of multi-state devices, degradation and wear out phenomena, state-space approach, point and steady state availability of complex systems can be simplified by simulation techniques. It is also found that the full potential of simulation as a system modeling and analysis approach has not been explored till date in the field of reliability engineering.

The sixth paper (short communication) has proposed a new fault diagnosis method for planetary gearbox based on empirical mode decomposition (EMD) and adaptive multi-scale morphological gradient filter (AMMGF). The proposed method has two dominant strengths: it can be applied to non-linear and non-stationary signal, and it can achieve the goal of de-noising. The framework of the proposed method is introduced first. Experimental data acquired from a planetary gearbox test-rig is then utilized to validate effectiveness of the proposed method. The method is demonstrated to have good performance on both extracting faults characteristic frequency and de-noising.

The seventh paper (short communication) is on the importance measures used in risk-informed applications to characterize the importance of component failures, human errors, common cause failures, etc. In order to decrease the impact of external factors and increase the system survivability, a multilevel protection is applied to its components or subsystems. A multi-state protection survivability importance based on the transitions of protection states is introduced in order to determine which level of protection has the greatest influence on the entire system survivability.

This issue also consists of a book review. The book reviewed is “Energetic Nanomaterials: Synthesis, Characterization, and Application”, Published by Elsevier (2016). This book is edited by Vladimir E. Zarko and Alexander A. Gromov.

I hope that the papers in this issue will be informative to the readers and motivate to do more research in new directions. Suggestions to further improve the journal are most welcome.


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