Current Issue : January - March Volume : 2016 Issue Number : 1 Articles : 6 Articles
In recent times, spare parts inventory systems have been extensively researched, but most inventory models were not fully adequate\ndue to the stochastic nature of inventory environment. This paper proposes an approach that supports decision making process\nin planning and controlling of spare parts in aircraft maintenance systems. Reliability characteristics of aircraft consumable parts\nwere analyzed in order to substantiate this approach.Moreover, the proposed reliability model was used to evaluate characteristics\nof subassemblies and/or assemblies these parts belong to. Finally, an innovative approach for determining the total amount of parts\nrequired in inventory and underage costs, based on observing the total unit time as a stochastic process, is presented herein....
The methyl esters synthesis from babassu oil and methanol using potassium methoxide (KOCH3) as catalyst has been developed and optimized by application of the Factorial Design of Experiments and Response Surface Methodology. The different variables affecting the alkaline methanolysis of babassu oil were studied. Temperature reaction was found to have the most significant influence on conversion. According to this study and from an economical point of view, the best conditions for overall process are catalyst concentration of 0.95% and an operation temperature of 45�°C working with 6:1 methanol/oil molar ratio. With these conditions the maximum conversion obtained was 99.85%. The biodiesel produced from babassu oil has a high percentage of saturated fatty acids, 91%, mainly composed of lauric (51.8%) and myristic (22.2%) fatty acids making it particularly stable towards oxidation and resulting in good low temperature properties. The babassu oil methyl esters (BOME) could be converted in a highly promising substitute for conventional fuel possibly due to the good cold flow properties, high oxidative stability displayed and matching the European Biodiesel Standard EN 14214. These properties could make babassu oil methyl esters of a great interest....
Speech signals in enclosed environments are often distorted by reverberation and noise. In speech communication\nsystems with several randomly distributed microphones, involving a dynamic speaker and unknown source location,\nit is of great interest to monitor the perceived quality at each microphone and select the signal with the best quality.\nMost of existing approaches for quality estimation require prior information or a clean reference signal, which is\nunfortunately seldom available. In this paper, a practical non-intrusive method for quality assessment of reverberated\nspeech signals is proposed. Using a statistical model of the reverberation process, we examine the energies as\nmeasured by unidirectional elements in a microphone array. By measuring the power ratio, we obtain a measure for\nthe amount of reverberation in the received acoustic signals. This measure is then utilized to derive a blind estimation\nof the direct-to-reverberation energy ratio in the room. The proposed approach attains a simple, reliable, and robust\nquality measure, shown here through persuasive simulation results....
Since the censored characteristics are unmonitored effectively in the manufacturing process, the produced product tends to have an\nunexpected high infant failure rate.Thus, this paper analyzes the associated relationship between product reliability and censored\nquality characteristics in manufacturing process firstly, and the dynamic and universal control demands for censored characteristics\nare presented. In view that traditional CEV-based control charts are usually confined to some specific types when dealing with\ncensored characteristics, which greatly restrict the wide application of censored control charts in the high-quality manufacturing\nprocess, the convergent CEV technique based on the principle of asymptotic reduction is proposed to be better applied in the\nanalysis of censored characteristics. And novel design procedures and simple but practical performance indicator in the form of\nthe most dangerous alarm distance for censored characteristics of Weibull distribution are put forward. Finally, the validity of\nthe proposed method is verified by a case study of monitoring a censored characteristic relative to lifetime of some aeronautical\nbearings, and the result proves that the sensitivity of the proposed control chart increased 79.96% compared to traditional CEV\nchart and is proved to be applicable to monitoring mixed censored characteristics affecting product reliability in manufacturing\nprocess....
At present, many cloud services are managed by using open source software,\nsuch as OpenStack and Eucalyptus, because of the unification management of data, cost\nreduction, quick delivery and work savings. The operation phase of cloud computing has\na unique feature, such as the provisioning processes, the network-based operation and the\ndiversity of data, because the operation phase of cloud computing changes depending on\nmany external factors. We propose a jump diffusion model with two-dimensional Wiener\nprocesses in order to consider the interesting aspects of the network traffic and big data\non cloud computing. In particular, we assess the stability of cloud software by using\nthe sample paths obtained from the jump diffusion model with two-dimensional Wiener\nprocesses. Moreover, we discuss the optimal maintenance problem based on the proposed\njump diffusion model. Furthermore, we analyze actual data to show numerical examples of\ndependability optimization based on the software maintenance cost considering big data on\ncloud computing....
The construction industry needs to move towards more relational procurement procedures to\nreduce extensive losses of value and avoid conflicts and disputes. Despite this, the actual\nconceptualization and assessment of relationships during conflict and dispute incidents seem to\nbe neglected. Via a review of literature, relationship quality is suggested as a systematic\nframework for construction projects. General system theory is applied and a framework\nconsistent of four layers respectively labelled as triggering, antecedent, moderation and outcome\nis suggested. Two different case studies are undertaken to represent the systematic framework;\nwhich verifies that changes in contracting circumstances and built environment culture can affect\nthe identified layers.\nThrough system reliability theories a fault tree is derived to represent a systematic framework of\nrelationship quality. The combinations of components, causes, and events for two case studies\nare mapped out through fault tree. By analysing the fault tree the combination of events that lead\nto relationship deterioration may be identified. Consequently the progression of simple events\ninto failure is formulized and probabilities allocated. Accordingly the importance and the\ncontribution of these events to failure become accessible. The ability to have such indications\nabout relationship quality may help increase performance as well as sustainable procurement....
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