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Dai Y.,Nanjing University of Aeronautics and Astronautics | Dai Y.,Beijing Institute of Nearspace Vehicles Systems Engineering | Li N.,Nanjing University of Aeronautics and Astronautics | Yang L.,Nanjing University of Traditional Chinese Medicine
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2013

In view of the complex product development project characteristics, a project work decomposition model was presented herein, which integrated PBS, OBS and WBS together. By the definition of PBS model, OBS model and WBS model, the analysis of model mapping and model workflow, establishment of complex product responsibility assignment matrix (PRM) from PBS-OBS model mapping, generation of project work breakdown structure (PWBS) from PRM-WBS model mapping, the project WBS for complex product development were constructed in standardization and formalization. Finally, the application process of the proposed model was illustrated with a case of launch vehicle. This proves the method effectiveness and maneuverability.

Cui M.,Dalian University of Technology | Yang K.,Dalian University of Technology | Xu X.-L.,Beijing Institute of Nearspace Vehicles Systems Engineering | Wang S.-D.,Dalian University of Technology | Gao X.-W.,Dalian University of Technology
International Journal of Heat and Mass Transfer | Year: 2016

Despite numerous studies of Levenberg-Marquardt (LM) algorithms for solving inverse heat conduction problems, sensitivity coefficients are mainly evaluated by numerical differentiation methods. However, sensitivity coefficients are difficult to be precisely calculated by numerical differentiation methods, if multi-dimensions, transient states and nonlinearities are involved. To the best knowledge of the authors, there has not been a general method for accurately calculating sensitivity coefficients for a LM algorithm, except numerical differentiation methods. In this study, a modified LM algorithm is presented by introducing the complex-variable-differentiation method for sensitivity analysis, and multi-parameters of boundary heat flux are simultaneously recovered by solving transient nonlinear inverse heat conduction problems. The results show that the modified LM algorithm has the advantages of the conventional LM algorithm, that are effective, accurate and robust for simultaneous estimation of multi-parameters of boundary heat flux. Meanwhile, the efficiency and the convergence stability of the modified LM algorithm are improved, which are attributed to accurate evaluation of sensitivity coefficients, compared with the conventional LM algorithm. © 2016 Elsevier Ltd. All rights reserved.

Ma K.,China Aerospace Science and Technology Corporation | Jin J.,China Aerospace Science and Technology Corporation | Li W.,Beijing Institute of Nearspace Vehicles Systems Engineering | Zhang P.,Northwest Regional Air Traffic Management Bureau of CAAC
Proceedings of the International Conference on Anti-Counterfeiting, Security and Identification, ASID | Year: 2016

In this paper, a two-staged decoding strategy which can be used for the Weighted Bit Flipping (WBF) based decoding algorithm for LDPC codes is presented. At the two stages, a parallel WBF and bit-flipping (BF) algorithms are adopted separately. Correspondingly, by the study of the iterative decoding process of the PWBF algorithm, a simple function is introduced to dynamically implement the switch of two decoding stages. The proposed algorithm can noticeably lower the error floor of PWBF algorithm with a modest increase in computation complexity and hardware cost. The validation of the proposed algorithm is verified by simulation. © 2015 IEEE.

Zhang Y.,China Aerodynamics Research And Development Center | Lei J.,Beijing Institute of Nearspace Vehicles Systems Engineering | Mao M.,China Aerodynamics Research And Development Center | Chen J.,China Aerodynamics Research And Development Center
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2015

Based on CARDC hypersonic numerical simulation platform Chant-2.0, applications of γ-Reθ model to hypersonic boundary layer transition are investigated preliminarily. The transition onset and length are predicted by solving two transport equations for turbulence intermittency factor and momentum thickness Reynolds number. Firstly, γ-Reθ transition model using local correlation functions is calibrated through four cases of low speed flat flows, and in the process freestream turbulence intensities have a wide range from low level natural transition to high level bypass transition. Then, taking account of flow properties of hypersonic boundary layer, the pressure gradient function used in the transition model's Reθt correlation is properly modified for high Mach number flows. Finally, by adopting the new model functions, hypersonic boundary layer transitions of flat and sharp cone are calculated and compared with referrence data. The simulation results indicate that the specially calibrated correlations for hypersonic platform software can accurately predict the onset and length of transition region in low speed cases, and high Mach number correction shows good performance in hypersonic simulations. ©, 2015, Editorial Board of ACTA AERODYNAMICA SINICA. All right reserved.

Xu C.,Nanjing University of Aeronautics and Astronautics | Xu C.,Beijing Institute of Nearspace Vehicles Systems Engineering | Wang X.,Nanjing University of Aeronautics and Astronautics
Transactions of Nanjing University of Aeronautics and Astronautics | Year: 2012

Impact dynamics of flexible solids is important in engineering practice. Obtaining its dynamic response is a challenging task and usually achieved by numerical methods. The objectives of the study are twofold. Firstly, the discrete singular convolution (DSC) is used for the first time to analyze the impact dynamics. Secondly, the efficiency of various numerical methods for dynamic analysis is explored via an example of a flexible rod hit by a rigid ball. Three numerical methods, including the conventional finite element (FE) method, the DSC algorithm, and the spectral finite element (SFE) method, and one proposed modeling strategy, the improved spectral finite element (ISFE) method, are involved. Numerical results are compared with the known analytical solutions to show their efficiency. It is demonstrated that the proposed ISFE modeling strategy with a proper length of conventional FE yields the most accurate contact stress among the four investigated models. It is also found that the DSC algorithm is an alternative method for collision problems.

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