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Deflagration and detonation induced by shock wave focusing at different Mach numbers

Chinese Journal of Aeronautics 2024年第2期37卷 249-258页

作者： Zezhong YANG jun CHENG bo ZHANG School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai 200240China

Shock wave focusing is an effective way to create a hot spot or a high-pressure and hightemperature region at a certain place,showing its unique usage in detonation initiation,which is beneficial for the development of detonation-based *** flame propagation behavior after the autoignition induced by shock wave focusing is crucial to the formation and self-sustaining of the detonation *** this study,wedge reflectors with two different angles(60°and 90°)and a planar reflector are employed,and the Mach number of incident shock waves ranging from 2.0 to 2.8 is utilized to trigger different flame propagation *** pressure transducers and the high-speed schlieren imaging system are both employed to investigate the shock-shock collision and ignition *** results reveal a total of four flame propagation modes:deflagration,DDT(Deflagration-to-Detonation Transition),unsteady detonation,and direct *** detonation wave formed in the DDT and unsteady detonation mode is only approximately 75%-85%of the Chapman-Jouguet(C-J)speed;meanwhile,the directly induced detonation wave speed is close to the C-J *** waves,which are strong evidence for the existence of detonation waves,are discovered in *** usage of wedge reflectors significantly reduces the initial pressure difference ratio needed for direct detonation *** also provide a practical method for differentiating between detonation and deflagration modes,which involves contrasting the speed of the reflected shock wave with the speed of the theoretically nonreactive reflected shock *** findings should serve as a reference for the detonation initiation technique in advanced detonation propulsion engines.

关键词： Deflagration Detonation Hydrogen Ignition Shock wave focusing

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Analysis and Design of Surgical Instrument Localization Algorithm

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Computer Modeling in Engineering & Sciences 2023年第10期137卷 669-685页

作者： Siyu lu jun Yang bo Yang Zhengtong Yin Mingzhe Liu Lirong Yin Wenfeng Zheng School of Automation University of Electronic Science and Technology of ChinaChengdu610054China College of Resource and Environment Engineering Guizhou UniversityGuiyang550025China School of Data Science and Artificial Intelligence Wenzhou University of TechnologyWenzhou325000China Department of Geography and Anthropology Louisiana State UniversityBaton Rouge70803USA

With the help of surgical navigation system,doctors can operate on patients more intuitively and *** positioning accuracy and real-time performance of surgical instruments are very important to the whole *** this paper,we analyze and design the detection algorithm of surgical instrument location mark,and estimate the posture of surgical *** addition,we optimized the pose by ***,the algorithm of location mark detection proposed in this paper and the posture analysis data of surgical instruments are verified and analyzed through *** final result shows a high accuracy.

关键词： Surgical navigation system surgical instruments positioning positioning mark detection algorithm matching algorithm posture analysis

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Data envelopment analysis procedure with two non-homogeneous DMU groups

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Journal of Systems Engineering and Electronics 2018年第4期29卷 780-788页

作者： CHEN Ye WU Liangpeng lu bo College of Economics and Management Nanjing University of Aeronautics and Astronautics

The classic data envelopment analysis（DEA） model is used to evaluate decision-making units＇（DMUs） efficiency under the assumption that all DMUs are evaluated with the same criteria setting. Recently, new researches begin to focus on the efficiency analysis of non-homogeneous DMU arose by real practices such as the evaluation of departments in a university, where departments argue for the adoption of different criteria based on their disciplinary characteristics. A DEA procedure is proposed in this paper to address the efficiency analysis of two non-homogeneous DMU groups. Firstly, an analytical framework is established to compromise diversified input and output（IO） criteria from two nonhomogenous groups. Then, a criteria fusion operation is designed to obtain different DEA analysis strategies. Meanwhile, Friedman test is introduced to analyze the consistency of all efficiency results produced by different strategies. Next, ordered weighted averaging（OWA） operators are applied to integrate different information to reach final conclusions. Finally, a numerical example is used to illustrate the proposed method. The result indicates that the proposed method relaxes the restriction of the classical DEA model,and can provide more analytical flexibility to address different decision analysis scenarios arose from practical applications.

关键词： data envelopment analysis (DEA) non-homogeneousdecision-making unit (DMU) criteria fusion Friedman test ordered weighted averaging (OWA) operator

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A novel method for importance measure analysis in the presence of epistemic and aleatory uncertainties

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Chinese Journal of Aeronautics 2014年第3期27卷 568-576页

作者： Ren bo lu Zhenzhou Zhou Changcong School of Aeronautics Northwestern Polytechnical University

For structural systems with both epistemic and aleatory uncertainties, research on quantifying the contribution of the epistemic and aleatory uncertainties to the failure probability of the systems is conducted. Based on the method of separating epistemic and aleatory uncertainties in a variable, the core idea of the research is firstly to establish a novel deterministic transition model for auxiliary variables, distribution parameters, random variables, failure probability, then to propose the improved importance sampling （IS） to solve the transition model. Furthermore, the distribution parameters and auxiliary variables are sampled simultaneously and independently;therefore, the inefficient sampling procedure with an＇＇inner-loop＇＇ for epistemic uncertainty and an＇＇outer-loop＇＇ for aleatory uncertainty in traditional methods is avoided. Since the proposed method combines the fast convergence of the proper estimates and searches failure samples in the interesting regions with high efficiency, the proposed method is more efficient than traditional methods for the variance-based failure probability sensitivity measures in the presence of epistemic and aleatory uncertainties. Two numerical examples and one engineering example are introduced for demonstrating the efficiency and precision of the proposed method for structural systems with both epistemic and aleatory uncertainties.

关键词： Aleatory uncertainty Epistemic uncertaintyImportance sampling Sensitivity analysis Uncertainty system

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Inverse Heat Conduction Estimation of Inner Wall Temperature Fluctuations under Turbulent Penetration

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Journal of Thermal Science 2017年第2期26卷 160-165页

作者： GUO Zhouchao lu Tao LIU bo School of Mechanical and Electrical Engineering Beijing University of Chemical TechnologyBeijing100029China Science and Technology on Space Physics Laboratory Beijing100076China

Turbulent penetration can occur when hot and cold fluids mix in a horizontal T-junction pipe at nuclear plants. Caused by the unstable turbulent penetration, temperature fluctuations with large amplitude and high frequency can lead to time-varying wall thermal stress and even thermal fatigue on the inner wall. Numerous cases, however, exist where inner wall temperatures cannot be measured and only outer wall temperature measurements are feasible. Therefore, it is one of the popular research areas in nuclear science and engineering to estimate temperature fluctuations on the inner wall from measurements of outer wall temperatures without damaging the structure of the pipe. In this study, both the one-dimensional(1D) and the two-dimensional(2D) inverse heat conduction problem(IHCP) were solved to estimate the temperature fluctuations on the inner wall. First, numerical models of both the 1D and the 2D direct heat conduction problem(DHCP) were structured in MATLAB, based on the finite difference method with an implicit scheme. Second, both the 1D IHCP and the 2D IHCP were solved by the steepest descent method(SDM), and the DHCP results of temperatures on the outer wall were used to estimate the temperature fluctuations on the inner wall. Third, we compared the temperature fluctuations on the inner wall estimated by the 1D IHCP with those estimated by the 2D IHCP in four cases:(1) when the maximum disturbance of temperature of fluid inside the pipe was 3℃,(2) when the maximum disturbance of temperature of fluid inside the pipe was 30℃,(3) when the maximum disturbance of temperature of fluid inside the pipe was 160℃, and(4) when the fluid temperatures inside the pipe were random from 50℃ to 210℃.

关键词： IHCP SDM Temperature fluctuations Turbulent penetration

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Charmless Hadronic Decays B→VV in the Topcolor－Assisted Technicolor Model

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Communications in Theoretical Physics 2003年第1X期40卷 77-84页

作者： XIAOZhen-jun GUOLi-bo DepartmentofPhysics NanjingNormalUniversityNanjing210097China

Based, on the effective Hamiltonian with the generalized factorization approach, we calculate the branching ratios and CP asymmetries of B→VV decays in the Topcolor-assisted Technicolor (TC2) model. Within the considered parameter space we find that: (a) for the pengunin-domdnated B→K^+φ and K^0φ decays, the new physics enhancements to the branching ratios are around 40%; (b) the measured branching branching ratios of B→K^+φ and K^φ decays prefer the range of 3bout half of the Belle's measurement; and (d) for most B→VV decays, the new physics corrections on their CP asymmetries are generally small or moderate in magnittude and insensitive to the variation of m* and Nc^eff.

关键词： B介子介子衰退分支比不对称 QCD 强相互作用

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Lithium Diffusion and Stress in a Polycrystalline Film Electrode

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Acta Mechanica Solida Sinica 2018年第3期31卷 290-309页

作者： YanFei Zhao bo lu junqian Zhang Department of Civil Engineering Shanghai University Materials Genome Institute Shanghai University and Shanghai Materials Genome Institute Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai University Department of Mechanics Shanghai University

In the present work, the two-dimensional analytical solution for Li diffusion in grains and grain boundaries of a polycrystalline film electrode is established with consideration of Li-segregation at the grain boundary. The stress field induced by the inhomogeneity of Li con- centration, called chemical stress here for brevity, is analyzed via the finite element simulation. The effects of the grain boundary including its size, its diffusion coefficient as well as the segrega- tion phenomenon on the solute concentration and the chemical stress are examined. It shows that grain boundaries can assist fast diffusion and significantly affect the stress profile in the whole film. It proves that tailoring the grain boundary size or other grain boundary-related parameters may provide an alternative strategy for improving the overall diffusivity and mechanical stability of battery electrodes.

关键词： Polycrystalline film Two-dimensional diffusion Grain boundary Segregation Chemical stress

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Convergence analysis of the corrected Uzawa algorithm for symmetric saddle point problems

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Applied Mathematics(A Journal of Chinese Universities) 2014年第1期29卷 29-35页

作者： lu jun-feng Hangzhou Institute of Commerce Zhejiang Gongshang University

For the large sparse saddle point problems, Pan and Li recently proposed in [H. K. Pan, W. Li, Math. Numer. Sinica, 2009, 31（3）： 231-242] a corrected Uzawa algorithm based on a nonlinear Uzawa algorithm with two nonlinear approximate inverses, and gave the detailed convergence analysis. In this paper, we focus on the convergence analysis of this corrected Uzawa algorithm, some inaccuracies in [H. K. Pan, W. Li, Math. Numer. Sinica, 2009, 31（3）： 231-242] are pointed out, and a corrected convergence theorem is presented. A special case of this modified Uzawa algorithm is also discussed.

关键词： Saddle point problem Uzawa algorithm convergence analysis

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Preparation and Properties of Organically Modified Sepiolite/High-performance Epoxy Nanocomposites

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Chinese Journal of Aeronautics 2006年第B12期19卷 41-46页

作者： lu Hai-jun Aerospace Institute of Special Materials and Technology Beifing 100074 China

Fibrous organic sepiolites （OSEP） and novel epoxy/OSEP nanocomposites were prepared, and different methods were investigated to produce an intercalated/exfoliated structure of OSEP. Experimental results show that the modifier molecules can be easily adsorbed by the sepiolite, but the layer space （d001 of the sepiolite, linked by means of covalent bond, remains unchanged. A proper method to solve this problem appears to exert large shearing force on the original sepiolite followed by its organic modification （OSEP2）. The morphology observation shows that there are formed an even dispersion of nano-sized OSEP2 fibers in epoxy resin and a structure intercalated by epoxy molecules, which lead to significantly improved mechanical properties. Impact strength of the epoxy/OSEP2 nanocomposite increases from 32.1 kJ/m^2 to 44.4 kJ/m^2, 38.3% higher than that of pristine matrix with 3 wt% OSEP2 content. It is also noted that the flexural strength of the OSEP/epoxy composites has risen by about 3% higher than that of the pure epoxy resin.

关键词： sepiolite intercalation/exfoliation epoxy nanocomposites

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Tests and Simulation Analysis on Fracture Performance of Concrete

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Journal of Wuhan University of Technology(Materials Science) 2013年第3期28卷 527-534页

作者：胡少伟 lu jun Nanjing Hydraulic Research Institute

To obtain the fracture parameters of concrete, fracture tests were conducted with three-point bending beam method aiming at 30 concrete beams with different sizes and different intensity. The concrete specimen with prefabricated crack to determine the fracture parameters of concrete were conducted and the fracture performance of the specimen was analyzed. The test results show that, initial fracture toughness is unrelated to the size of specimens; while unstable fracture toughness is related to the size of specimens. As for specimens of bastard size, when concrete intensity is relatively low, unstable fracture toughness increases along with the increase of intensity; when concrete intensity is relatively high, unstable fracture toughness will decrease; when concrete intensity increases continuously, unstable fracture toughness will further increase somewhat. As for specimens of standard size, unstable fracture toughness will increase along with the increase of intensity. Aiming at concrete beam specimens, we conducted two-dimensional non-linear finite element analysis, obtained the stress intensity factor, and carried out contrastive analysis with the experimental results.

关键词： concrete beam fracture performance fracture toughness acoustic emission mode damage variable

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