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Zhang S.,Beihang University | Tang Z.,Key Laboratory of Complex Aviation System Simulation | Song X.,Beihang University | Ren Z.,Beihang University | Meng H.,Beihang University
Communications in Computer and Information Science | Year: 2012

A new yet promising technology, Cloud computing, can benefit large-scale simulations by providing on-demand, everywhere simulation services to users. In order to enable multi-task and multi-user simulation tasks with Cloud computing, Cloud Simulation Platform (CSP) is proposed and developed. To promote the running efficiency of HLA systems on CSP, this paper proposes an approach addressing the Virtual Machine task allocation problem, which is divided into two levels of task allocation steps. The first-level uses a heuristic algorithm to optimize the mapping from federates (of HLA system) to virtual machines (of CSP) and aims to achieve load balance on virtual machines in CSP. The second-level dispatches the subtasks of federate to the cores of virtual machines to minimize the makespan (schedule length) of the federate which uses a DAG based list scheduling algorithm: the EST (Earliest-Start-Time) algorithm. Experiments show that the two-level task allocation strategy effectively improves the running efficiency of HLA system on CSP. © 2012 Springer-Verlag.

Zhao G.,Beijing Institute of Technology | Zhang K.,Key Laboratory of Complex Aviation System Simulation | Wang W.,Beijing Institute of Technology | Huang S.,Science and Technology on Information Systems Engineering Laboratory | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

This paper presents a new image enhancement method based on self-adaptive piecewise linear transformation. It is most important to select division points during the processing course of piecewise linear transformation because these division points can decide the quality and efficiency of image enhancement. In this paper, division points are automatically and self-adaptive selected based on the gray grade and histogram feature of images. In order to increase the contrast of the image, it is necessary to extend the object section, maintain the transition section and compress the background section. Our method is easy to use, and the experiment results show that the technique can produce good results on a variety of images. © 2013 SPIE.

Shi D.,Beihang University | Dong C.,Beihang University | Yang X.,Beihang University | Sun Y.,Beihang University | And 2 more authors.
Materials and Design | Year: 2013

Experiments are carried out at elevated temperature to investigate the effect of brazing itself and post-brazing heat treatment on the lifetime of directionally solidified (DS) superalloy. Meanwhile, a new lifetime prediction methodology based on continuum damage mechanics (CDM) is proposed to predict the lifetime of DS superalloy and its brazed joints. After creep and fatigue testing, the fractured specimens are observed by means of Optical Microscope (OM) and Scanning Electron Microscope (SEM) with the Energy Dispersive X-ray Spectrometer (EDXS) to understand their failure mechanisms. The results showed that: (1) under the same test condition, all the brazed joints exhibited a lower creep and fatigue lifetime compared with a typical DS superalloy; (2) the creep and fatigue lifetime of heat treated brazed joint was longer than that of non heat treated one; (3) the developed CDM method can be used to predict the lifetime of all the specimens; (4) all the brazed joints fractured in the brazing seam; and (5) there were many distinctive differences between the failure mechanics of DS superalloy and its brazed joints. © 2012 Elsevier Ltd.

Wang J.,Beihang University | Wang J.,Key Laboratory of Complex Aviation System Simulation | Yang X.,Beihang University
International Journal of Fatigue | Year: 2012

Generally not only the material but also the notch geometry affects the HCF strength. So, when evaluating the fatigue limit of notched Ti-6Al-4V specimens using the conventional theory of critical distance (TCD), a possible critical distance size effect was identified. In this paper, in order to overcome the critical distance size effect, Kt was introduced. And based on an assumption that the product of critical distance and Kt was constant, the TCD was modified to evaluate the HCF strength of notched Ti-6Al-4V specimens. The prediction results fell into an error interval of about ±15% using the modified TCD. © 2011 Elsevier Ltd. All rights reserved.

Wang F.N.,Airborne | Wang S.S.,Key Laboratory of Complex Aviation System Simulation | Che W.F.,Key Laboratory of Complex Aviation System Simulation | Bai Y.,Key Laboratory of Complex Aviation System Simulation
Applied Mechanics and Materials | Year: 2014

An intrusion detection method based on RS-LSSVM is studied in this paper. Firstly, attribute reduction algorithm based on the generalized decision table is proposed to remove the interference features and reduce the dimension of input feature space. Then the classification method based on least square support vector machine (LSSVM) is analyzed. The sample data after dimension reduction is used for LSSVM training, and the LSSVM classification model is obtained, which forms the ability of detecting unknown intrusion. Simulation results show that the proposed method can effectively remove the unnecessary features and improve the performance of network intrusion detection. © (2014) Trans Tech Publications, Switzerland.

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