In order to meet the demand of increasing population with fast depleting resources of the world and looking to the alarming rate of degradation of Earth’s environment, emphasis has now shifted to the concern for developing environment friendly products, systems and services [1-5]. The urgency of this requirement arose from the consideration that we are consuming resources at a much faster rate while generating tremendous waste at the same time, leading to environmental pollution at a very fast rate, which may even threaten the existence of humanity on the Earth. We have already wasted considerable amount of Earth’s resources and spoiled its pristine environment. Realizing the importance of the subject, the Editor in 1996 initiated steps to popularize the concept of performability engineering by emphasizing the importance of clean production [1] so that we conserve resources and use minimum resources and optimize the production process while minimizing waste and environmental pollution. We also need to dematerialize the production process and make use of recycling, reuse and remanufacturing and use minimum energy and maximize the performance in terms of quality, reliability and safety.

This journal (IJPE), in fact, was started a decade back with the objective of invigorating the process of designing systems, products and services that are sustainable. Although much progress has been attained but still much is desired to be achieved in this direction. The main difficulty still remains and that is how to define and assess what should be called as a sustainable system, product or service. There is not much available in the literature which tells a designer what attributes be used to systematically and analytically obtain a sustainable design or for comparing different sustainable designs. Please see also a book review on page 517 of this issue.

Obviously, a sustainable product, system or service should be created using minimum material (or what is termed as the process of dematerialization) so that we consume less and less resources (since the world population is increasing and there should be enough resources left for the future generations to share them). A sustainable product, system or service should also consume lesser and lesser energy during its manufacture, operation, and disposal or over its entire life time.

A sustainable product, system or service in addition to above requirements, should be safe and reliable and should create minimum wastages of any kind during its manufacture or operation. Only then we can call a product, system or service sustainable.

We also know that we cannot achieve these attributes unless we can assess the effectiveness of the above measures for achieving sustainability. Sustainability, otherwise, would remain an abstract concept. We also know that we already have sufficient tools to measure and assess various attributes of a sustainable product, system or service as detailed out above in part but we do not have a way to integrate them to come to a single figure of merit that may represent the sustainability of a product, system or service. The concept of performability as introduced in the inaugural Editorial of this journal was put forward based on the composite attribute of dependability and sustainability. As of today, dependability can be measured and assessed but we do not have any convincing measure to assess the attribute of sustainability. We need to find that/ later on the question of integrating the attributes of performance of a product, system or service over its entire life cycle.

We have specialists or experts working on a part of the problem of performance of a product, system or service (for example, technical performance can be specified in terms of dependability which in turn is a composite attribute and can be derived from other attributes) but none seems to know how we can integrate dependability with sustainability entailing all considerations to achieve a single figure of merit for the purpose of comparing performance, numerically. If we achieve this feat, then only we would be able to specify performability of a product, system or service, numerically and design it in a product, system or service, or even compare the performability of different products quantitatively. Till then, it will remain an abstract subject. We have a large amount of literature available on sustainability but can we say that such and such product is sustainable and has such and such a figure for sustainability. The answer is in negative.

I would like to invite the attention of researchers world over to overcome this shortcoming in the state of the art. IJPE would welcome any contribution that moves the state-of-art to next higher level of achievement towards this goal.

Lastly, I would like to draw the attention of our readers to the update provided on the next page (p.406) of this issue which speaks volumes about this journal’s achievements over a decade since it was launched in July 2005. I thank the contributors to this journal who kept me busy and well-informed on the subject. I also like to thank reviewers who helped us in the task of selecting good papers and for maintaining high standards of the journal over this period.

Machine availability and reliability are two of the most essential concerns for a gas turbine power plant system. A good maintenance program that increases power plant availability while reducing the losses due to unplanned shutdowns should be instituted. A Risk Based Maintenance (RBM) methodology is developed in this paper. It calculates the future risk of failure of a gas turbine power plant system so that the maintenance can be planned just before occurrence of failure. To calculate the risk, first a General Log Linear Lognormal (GLL- Lognormal) model, which tells about damage growth of the machine, is developed. Bayesian approach is then used to update the model parameters (i.e., GLL- Lognormal parameters) on the basis of new inspection data (i.e., crack length) and calculate the updated risk. It is recommended that risk should be continuously updated with the age of the unit to increase the effectiveness of RBM policy. The novelty in this work is that the failure probability is directly dependent on observed crack length instead of time to failures. The whole analysis is illustrated with cap effusion plate inspection data of actual gas turbine system. It is found that the proposed risk based approach gives more accurate results than a normal fleet level model.

This paper works on the evaluation of performability for information systems by adopting the stochastic-flow network model. To construct an information system as an information network, each arc (delivery medium) has two parameters, the bandwidth and the lead time. Consider maintenance budget and time limitation, we evaluate the performability such that a given amount of data can be delivered from the source to the sink. The contributions of this paper are twofold: (i) an algorithm integrated branch-and-bound elevating method is proposed to generate all lowest bandwidth vectors satisfying demand, maintenance budget, and time limitation. The performability is computed in terms of such vectors accordingly; (ii) the proposed algorithm is applied to a real case of Taiwan Academic Network to show the applicability and efficiency.

The paper attempts to model the imperfect repair with the concept of arithmetic reduction of age (ARA) and also sequentially incorporates the effect of imperfect corrective and preventive maintenance. Four virtual age processes are devised to describe the various after repair restoration patterns as well as different restoration degrees for both CM and PM. The GRP maximum likelihood estimators (MLE) are derived and then used for parameter estimation. The expected number of failures for the proposed approaches are estimated using Monte Carlo simulation. Two different repair effectiveness indices for CM and PM are estimated for all the four approaches to provide a better insight of the maintenance processes. The residual life is predicted using residual mean time to failure based on virtual age at each repair point. The paper concludes with comparative analysis to get adequate insights into the goodness of fit for the proposed models.

This paper deals with the design of Optimal Step-Stress Partially Accelerated Degradation Test (PADT) using Wiener Process for modelling degradation paths. In partial step-stress loading, the unit is tested at usual stress for some time and then stress is accelerated. This helps in preventing over-stressing the test specimens. Failure occurs when the performance characteristic crosses the critical value the first time. The first passage time follows Inverse Gaussian Distribution. The optimal plan consists in determining the optimal test duration, and number of inspections at each intermediate stress level by minimizing asymptotic variance of MLE of quantile of the lifetime distribution at use condition subject to the constraint that total testing or experimental cost does not exceed a pre-specified budget.

The reliability and maintainability analysis of an automated robotic system was carried out. Descriptive statistics of failure and repair data, and the best fit of them were carried out. Furthermore, the reliability, maintainability, failure rate, and repair rate models of the robotic system were calculated. The models could prove to be a useful tool both to assess the current conditions and to predict the reliability for upgrading the operations management policies of the robotic system. It was pointed out that (a) the operating time of the robotic system was 88.22% and the remaining 11.78% of the total operating time was under repair, and (b) the failure times follow the lognormal distribution whereas the repair times comply with the loglogistic distribution. The analysis could prove to be a useful tool for manufactures of robotic systems that could improve the design and operation of the systems that they manufacture and operate.

An enclosed human occupancy chamber is commonly known as hyperbaric chamber system (HCS). The medical treatment to divers suffering from decompression sickness is administered inside a hyperbaric chamber. The hazards inherent inside the chamber include sudden loss of pressure, fire and rapid loss of life-supporting gases. Fire can be catastrophic inside the oxygen-enriched confined space of a hyperbaric chamber. The fire protection system (FPS), a hazard barrier against fire is designed to respond to the true demand of the initiating event (fire incidence) which can happen at any time. The paper is devoted to the risk assessment of fire incidence inside a hyperbaric chamber and gives a methodology for risk assessment for incident of fire using fault tree and event tree analyses. The mean proportion of time the system is not functioning upon demand is a measure of safety for the fire protection system, which is estimated using the mean fractional dead time (FDT). The minimum mean time between hazards (MTBH) of a life-safety system, indicates the minimum performance level of hazard barriers designed to provide protection against hazards, can be considered as design matric for risk analysis. The MTBF of FPS is calculated and its usefulness is discussed.

Trace elements in drinking water can influence the longevity of human beings. Drinking water samples from a longevity county Xiayi and a nearby non-longevity county Yucheng were collected and tested the element concentrations. Support vector machine (SVM), as a pattern recognition technique for small sample size classification problem, was applied to analyze the difference of element concentrations in the drinking water from both counties. Further the SVM is used to select the elements with the most discrepancy. The study revealed large discrepancies in element concentrations in drinking water from these two counties. Barium, Ca, F, Mg, Mn, Si and Sr in drinking water from Xiayi is higher than that from Yucheng, whereas the Fe, K, Pb, Cu, Co, Cr, Ni in drinking water from Xiayi is lower. The significance of difference is Cr> Mn> Co> Fe. The high Mn, Ca and low Cr, Cd, Co, Fe contents in drinking water from Xiayi are conductive to local longevity.

Gait identification task becomes difficult due to the change of appearance by different cofactors (e.g., shoe, surface, carrying, view, and clothing). Some parts of gait are affected by cofactors and other parts remains unaffected. Most of the gait identification systems consider only most effective parts thereby omitting less effective parts. However some significant features for gait identification resides in less effective parts and are important for more accurate recognition.In this paper, adaptive fusion of part based gait identification is proposed. The proposed gait identification adaptively fuses the best informative less effective part with the most effective parts. The best informative less effective part is selected by using Multi objective adaptive PSO to the varying threshold value. These parts are fused using adaptive fusion method and from these fused parts, the variance ratio is estimated and recognition is done based on variance threshold value. The variance threshold value is calculated based on Particle Swarm optimization (PSO) which dynamically calculates the threshold value for varying parts. Experimental result of proposed system achieves better result when compared with recognition using EnDFT.

Practically, it is impossible to substitute internal combustion engine which has become an integral part of the transportation and agriculture sectors. The fossil fuel resources are limited and depleting at very fast. Therefore, in future our energy system will have to be renewable and sustainable, efficient and cost effective, convenient and safe. In order to cope with the environmental concerned there have been many studies and trials on various types of automobile engines. As indicated by recent studies hydrogen fuelled vehicles appeared to be more eco-friendly and available in abundance. However the problems associated with hydrogen fuelled engine are pre-ignition, backfiring, rapid rate of pressure rise and knocking which need to be overcome so that hydrogen fuelled driven engine could be further develop and commercialize. This review paper is basically deliberating the various problems associated with the use of hydrogen driven engines in automobile sectors and suggestions to make this technology commercially viable.

The initial route discovery or the final node to node association is an important metric to determine the performance of any routing protocol. While not remarking on the efficiency of the existing routing protocols, we develop a method to construct an initial backbone structure that can be used for communications. Specific to application domains in a wireless sensor network, the quality of service parameters varies. Our approach is based on a backbone structure that takes care of the robustness of the followed routes by employing a hybrid algorithm ‘Quasi-MST’. Also, it guarantees the communication reliability by maintaining an alternate parent list in case of node failures due to energy depletion. We try to analyze the effect of varying ranges and sink positions on the reliability of the network when subject to node failures. We also put forward a more robust mechanism to counter for route failures.

In the expression corresponding to the Shannon’s entropy of the Student-t distribution the gamma and digamma integral functions appear. We propose a simple analytical approximation for its entropy function for all degrees of freedom which assures the continuity between normal and Cauchy distributions. A possible application is to define a normal distribution “equivalent” of the Student-t, usable for any degrees of freedom (integral or fractional) larger than 7.