The microstructure evolution and formation mechanism of lighting etched region (LER) during rolling contact fatigue (RCF) in M50 steel were systematically investigated. The results indicate that LER is a kind of microstructure degeneration due to the accumulation of plastic strain. Finite element simulation indicates that under 5 GPa contact pressure, the equivalent stress at the subsurface exceeds the yield strength of M50 steel and thus induces plastic deformation. The dislocation density and fraction of grain boundaries increased in LER and thus the grain size was refined and the micro-hardness increased. The microstructure evolution in LER during RCF was divided into four stages. Stage 1: dislocations and GBs increased significantly while the micro-hardness remained almost unchanged with the increase of RCF cycles; Stage 2: GBs and micro-hardness increased gradually with the increase of RCF cycles; Stage 3: LAGBs evolved to HAGBs and thus the total length of LAGBs decreased and the total length of HAGBs increased. Dislocation density and micro-hardness both increased with the increase of RCF cycles; Stage 4: dislocations and GBs continue to increase with the increase of RCF cycles due to accumulation of plastic deformation, and the micro-hardness also increased.
At present, multiple rendezvous applications, which use only single-transceiver radios to communicate on multiple channels, are widely used in multi-hop ad hoc networks. However, with increasing demands for communication, it is difficult for nodes to obtain an efficiently wireless channel allocation. The root cause is that some matched transceiver-pairs of nodes must exist that cannot correspond with each other; nevertheless, several channels are available in the network in any previous multiple rendezvous approaches. In this paper, a novel distributed algorithm called MCCE is presented to assign snooping channels for nodes by utilising only the status of neighbours within a 2-hop range of the node. Compared with previous ‘similar fair’ approaches, MCCE can improve the performances of MAC protocols in two conditions. If there is no idle-channel in a node’s 2-hop range, then MCCE will direct a best snooping-channel to decrease the potential of channel contention. If there are mass idle-channels in a node’s 2-hop range, then MCCE will direct a snooping-channel to improve the throughput, similar to non-collision channel assignment approaches, which are NP-complete.
We propose an approach of component-based software reliability analysis which includes the benefits of both time domain, and structure based approaches. This approach overcomes the deficiency of existing black box and white box techniques that fall short of addressing repair, and internal system structures simultaneously. Our solution adopts a method of testing data transformation to cover both methods, and is expected to improve reliability prediction. This paradigm starts with consideration of component-based software testing process in view of the assumption of NHPP models. It accounts for software structures by the way of modeling the testing process. According to the testing model it builds the mapping relation from the testing profile to the operational profile of component-based software which enables the testing data transformation to build the reliability dataset required by non-homogeneous Poisson process (NHPP) models. At last an example is evaluated to validate and show the effectiveness of this approach.
Efficient cache management plays a vital role in in-memory data-parallel systems, such as Spark, Tez, Storm and HANA. Recent research, notably research on the Least Reference Count (LRC) and Most Reference Distance (MRD) poli... | Find, read and cite all the research you need on Tech Science Press
Abstract With the growing size and complexity of software applications, research in the area of component software reliability analysis has gained prominence. To ensure analytical tractability, traditional approaches usually ignore fault correction process of component software based on simplifying assumptions of instantaneous and perfect debugging. As a result, the estimates obtained from these models tend to be optimistic. To obtain realistic estimates, it is desirable that the assumptions of instantaneous and perfect debugging be amended. In this paper we discuss fault repair policy according to which debugging to various components may be conducted in integration testing of component software. We then propose a hybrid infinite server queueing model to describe fault correction process with consideration of the possibility of imperfect debugging. Based on fault detection process and repair policy, the model can be resolved to represent component software reliability growth during integration testing. F...
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