摘要 :
Cloud computing is a recently developed new technology for complex systems with massive-scale service sharing. Cloud reliability analysis and modeling are not easy tasks because of the complexity and large scale of the system. Due...
展开
Cloud computing is a recently developed new technology for complex systems with massive-scale service sharing. Cloud reliability analysis and modeling are not easy tasks because of the complexity and large scale of the system. Due to the complexity of cloud computing systems, the reliability models for pure software/hardware or conventional networks cannot be simply applied to study the cloud reliability. This paper focuses on reliability evaluation using hybrid methods, which combine MTTF/MTTR and CTMC models. We take into account not only service faults, but also the effect of physical-resource breakdowns. Based on the proposed model, the formal calculation of the system's reliability is given. The effectiveness of the approach is illustrated through an example.
收起
摘要 :
In the reliability assessment of structures, a situation we frequently encounter is that by means of available information some parameters involved can be depicted accurately by their probability distributions and others can only ...
展开
In the reliability assessment of structures, a situation we frequently encounter is that by means of available information some parameters involved can be depicted accurately by their probability distributions and others can only be described by the bounds or ranges of variations. So, it is meaningful to construct a reliability model by which the probabilistic and nonprobabilistic uncertainties can be treated reasonably in an integrated framework. The main purpose of this paper is to establish a strictly mathematical foundation and a unified framework for reliability assessment and reliability based design optimization (RBDO) of structures in the presence of both probabilistic and nonprobabilistic (bounded) hybrid uncertainties. The input uncertain parameters are divided into two different groups and treated respectively as random variables and interval variables, and the traditional probability and convex set models are adopted to describe the probabilistic and bounded uncertainties, respectively. In the reliability measuring system developed in the paper, dimensionless hybrid reliability indices are defined in different situations by adopting a similar method as for the traditional probabilistic reliability method for structures. A computational procedure for performing the RBDO of structures with hybrid uncertainties is presented. Two numerical examples are investigated to demonstrate the effectiveness and feasibility of the presented method.
收起
摘要 :
In paper problem of strength (reliability) determining of electronic elements and circuit on normalised disturbing signal has been formulated in theoretical and practical aspects. The method of strength (reliability) coefficient e...
展开
In paper problem of strength (reliability) determining of electronic elements and circuit on normalised disturbing signal has been formulated in theoretical and practical aspects. The method of strength (reliability) coefficient estimation for chosen system and its components has been proposed. The theoretical considerations were experimentally verified by analysis of the test system (dimmer of halogen lamps) for selected 1.2/50 μs surge levels.
收起
摘要 :
There are differences among sampling data and representation types of uncertain statistical variables, sparse variables and interval variables, which increase the complexity of structure reliability analysis. Therefore, a hybrid f...
展开
There are differences among sampling data and representation types of uncertain statistical variables, sparse variables and interval variables, which increase the complexity of structure reliability analysis. Therefore, a hybrid first order reliability analysis method considering the three types of uncertain variables is demonstrated in this article. First, distribution types and distribution parameters of sparse variables are identified and probabilistically estimated. Secondly, interval variables are transformed into probabilistic types using a uniformity approach. Thirdly, a unified hybrid reliability calculation method considering these uncertain variables simultaneously is demonstrated. The most probable point (MPP) is searched for using the first order reliability method, and then a linear approximation function of performance function is constructed in the neighbourhood of the MPP. Finally, the belief and plausibility measures of the reliability index are efficiently calculated using the theoretical analytical method. Three examples are investigated to demonstrate the effectiveness of the proposed method.
收起
摘要 :
The reliability and efficiency of a Wireless Body Area Network (WBAN) rely on the Media Access Control (MAC) protocol design. This paper proposed an efficient method, namely, the Hybrid MAC (HB-MAC) protocol, to enhance the reliab...
展开
The reliability and efficiency of a Wireless Body Area Network (WBAN) rely on the Media Access Control (MAC) protocol design. This paper proposed an efficient method, namely, the Hybrid MAC (HB-MAC) protocol, to enhance the reliability and maximize the performance of WBAN using a hybrid superframe structure according to IEEE 802.15.6 standard requirements. The HB-MAC consists of a contention access period and a scheduled access period. The proposed protocol is compared to the C-MA C and IEEE 802.15.6 MA C protocols based on the performance metrics of Packet Delivery Ratio (PDR), throughput, energy consumption, and average delay. The simulation results show that the HB-MAC outperforms its competitors as it could achieve up to 95% PDR, 10% enhanced throughput, 20% energy optimization, and 30% improvement in average delay. Therefore, it can be concluded that the HB-MAC protocol is an efficient method for WBAN application.
收起
摘要 :
In this paper, a new reliability analysis method is developed for uncertain structures with mixed uncertainty.In our problem, the uncertain parameters with sufficient information are treated by random distributions, while some one...
展开
In this paper, a new reliability analysis method is developed for uncertain structures with mixed uncertainty.In our problem, the uncertain parameters with sufficient information are treated by random distributions, while some ones with limited information can only be given variation intervals.A complex nesting optimization will be involved when using the existing methods to compute such a hybrid reliability, which will lead to extremely low efficiency or instable convergence performance.In this paper, an equivalent model is firstly created for the hybrid reliability, which is a conventional reliability analysis problem with only random variables.Thus only through computing the reliability of the equivalent model the original hybrid reliability can be easily evaluated.Based on the above equivalent model, an algorithm with high efficiency and robust convergence performance is then constructed for computation of the above hybrid reliability with both random and interval variables.Two numerical examples are provided to demonstrate the effectiveness of the present method.
收起
摘要 :
Using the probabilistic transfer matrix model as the major technology, this paper firstly separated the presentation and quantification of signal relations, and blocked the concurrent signals in fan-out by hybrid coding; secondly ...
展开
Using the probabilistic transfer matrix model as the major technology, this paper firstly separated the presentation and quantification of signal relations, and blocked the concurrent signals in fan-out by hybrid coding; secondly a method to construct the output reliability matrixes and output probability distributions of basic circuit components was proposed based on a virtual method; and then a method to achieve the reliability iterative propagation between the pre-stage and post-stage circuit was designed using a weak equivalence principle. The theoretical analysis and experiment results show that the proposed method can be applied to the reliability evaluation for several-abstract-level circuits that have high calculation precision and linear complexity in time and space. (C) 2016 Elsevier Ltd. All rights reserved.
收起
摘要 :
Besides well-known benefits, commodity cloud storage also raises concerns that include security, reliability, and consistency. We present Hybris key-value store, the first robust hybrid cloud storage system, aiming at addressing t...
展开
Besides well-known benefits, commodity cloud storage also raises concerns that include security, reliability, and consistency. We present Hybris key-value store, the first robust hybrid cloud storage system, aiming at addressing these concerns leveraging both private and public cloud resources. Hybris robustly replicates metadata on trusted private premises (private cloud), separately from data, which are dispersed (using replication or erasure coding) across multiple untrusted public clouds. Hybris maintains metadata stored on private premises at the order of few dozens of bytes per key, avoiding the scalability bottleneck at the private cloud. In turn, the hybrid design allows Hybris to efficiently and robustly tolerate cloud outages but also potential malice in clouds without overhead. Namely, to tolerate up to f malicious clouds, in the common case of the Hybris variant with data replication, writes replicate data across f+1 clouds, whereas reads involve a single cloud. In the worst case, only up to f additional clouds are used. This is considerably better than earlier multi-cloud storage systems that required costly 3f+1 clouds to mask f potentially malicious clouds. Finally, Hybris leverages strong metadata consistency to guarantee to Hybris applications strong data consistency without any modifications to the eventually consistent public clouds. We implemented Hybris in Java and evaluated it using a series of micro and macro-benchmarks. Our results show that Hybris significantly outperforms comparable multi-cloud storage systems and approaches the performance of bare-bone commodity public cloud storage.
收起
摘要 :
A renewable hybrid system combines energy sources for electricity generation and its use is motivated by the call for diversification and decentralization of non-polluting sources and complementarity between renewable resources. T...
展开
A renewable hybrid system combines energy sources for electricity generation and its use is motivated by the call for diversification and decentralization of non-polluting sources and complementarity between renewable resources. This system is more reliable and cost-effective than a system based on a single source and among different combinations of components the most commonly used is solar wind. The operation of these systems depends on factors such as design, optimization, reliability and economic performance. Thus, the main objective of this article is to present the state of the art of renewable hybrid systems worldwide, highlighting its main characteristics. Among the 14 analyzed articles, Homer software is the most used for Hybrid System scaling; for optimization the most commonly used metaheuristic is the PSO. In addition, 36.4% of the articles did not use any type of energy storage, and the remaining used batteries, fuel cells or both technologies. As application, 63.6% of the plants supplied reverse osmosis systems or residential loads; the others supplied the demand for remote rural areas or to charge electric cars.
收起
摘要 :
Traditional probability-based structural reliability analysis method can only consider random uncertaintiesdescribed by random distribution functions, which required sufficient experimental samples. On comparison,interval uncertai...
展开
Traditional probability-based structural reliability analysis method can only consider random uncertaintiesdescribed by random distribution functions, which required sufficient experimental samples. On comparison,interval uncertainties can be more appropriate when lacking information. In realistic situations, severalstructural reliability models considering mixed probabilistic and interval variables are proposed. Besideschoosing reliability model according to the information available of the uncertainties, this paper presents aperspective in structural design that for a specific design, the controllable structural uncertain parametersshould be better described as interval variables while other uncontrollable uncertain parameters such asexternal loads described as random variables if sufficient information is available. The correspondingreliability analysis model is proposed. Further, for simple truss structures, this paper demonstrates that theextreme hybrid reliability index can be attained when the interval variables reach their upper or lower bounds.To solve the hybrid reliability index, a sequential single-loop strategy combined with an intermediate-variablebased response surface and the method of moving asymptotes optimization solver is proposed. Finally,numerical examples are given to demonstrate the applicability of the proposed method and concludingremarks are made.
收起
原文获取