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Effective Thermal Conductivity for 3D Five-Directional Braided Composites Based on Microstructural Analysis

Transactions of Nanjing University of Aeronautics and Astronautics 2019年第1期36卷 128-138页

作者： ZHAO Xiao MAO Junkui jiang hua Key Laboratory of Aerospace Power System College of Energy and Power EngineeringNanjing University of Aeronautics and Astronautics Cummins(China) Investment Co. Ltd. Commercial Aircraft Corporation of China Ltd.

A method for predicting effective thermal conductivities(ETCs) of three-dimensional five-directional(3D5D) braided composites is presented. The effective thermal conductivity prediction method contains a digital image processing technology. Multiple scanning electron microscopy(SEM)images of composites are analyzed to obtain actual microstructural features. These actual microstructural features of 3D5D braided composites are introduced into representative volume element(RVE) modeling. Apart from applying actual microstructural features,compression effects between yarns are considered in the modeling of RVE,making the RVE more realistic. Therefore,the ETC prediction method establishes a representative unit cell model that better reflects the true microstructural characteristics of the 3D5D braided composites. The ETCs are predicted with the finite element method. Then thermal conductivity measurements are carried out for a 3D5D braided composite *** comparing the predicted ETC with the measured thermal conductivity, the whole process of the ETC prediction method is proved to be effective and accurate,where a relative error of only 2.9 % is ***,the effects of microstructural features are investigated,indicating that increasing interior braiding angles and fiber fill factor can lead to higher transverse ETCs. Longitudinal ETCs decrease with increasing interior braiding angles,but increase with increasing fiber fill factor. Finally,the influence of variations of microstructure parameters observed in digital image processing are investigated. To explore the influence of variations in microstructural features on variations in predicted ETCs,the actual probability distributions of microstructural features obtained from the 3D5D braided composite sample are introduced into the ETC investigation. The results show that,compared with the interior braiding angle,variations in the fiber fill factor exhibit more significant effects on variations in ETCs.

关键词： effective thermal conductivity digital image processing variation 3D five-directional braided composites

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Analysis of the M~[X] /G/1 Queues with Second Multi-optional Service and Unreliable Server

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Acta Mathematicae Applicatae Sinica 2010年第3期26卷 353-368页

作者： Jin-ting Wang jiang-hua Li Department of Mathematics Beijing Jiaotong University Beijing 100044 China Commanding and Engineering Institute of Chemical Defence Beijing 102205 China

A bulk-arrival single server queueing system with second multi-optional service and unreliable server is studied in this paper. Customers arrive in batches according to a homogeneous Poisson process, all customers demand the first ＂essential＂ service, whereas only some of them demand the second ＂multi-optional＂ service. The first service time and the second service all have general distribution and they are independent. We assume that the server has a service-phase dependent, exponentially distributed life time as well as a servicephase dependent, generally distributed repair time. Using a supplementary variable method, we obtain the transient and the steady-state solutions for both queueing and reliability measures of interest.

关键词： Bulk-arrival queue first essential service second optional service reliability

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Lattice-based certificateless encryption scheme

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Frontiers of Computer Science 2014年第5期8卷 828-836页

作者： Mingming jiang Yupu HU Hao LEI Baocang WANG Qiqi lai State Key Laboratory of Integrated Service Networks Xidian University Xi'an 710071 China Security and Privacy Lab CRDU Huawei Technologies Co. LTD. Beijing 100095 China

Certificateless public key cryptography （CL- PKC） can solve the problems of certificate management in a public key infrastructure （PKI） and of key escrows in identity-based public key cryptography （ID-PKC）. In CL- PKC, the key generation center （KGC） does not know the private keys of all users, and their public keys need not be cer- tificated by certification authority （CA）. At present, however, most certificateless encryption schemes are based on large in- teger factorization and discrete logarithms that are not secure in a quantum environment and the computation complexity is high. To solve these problems, we propose a new certificate- less encryption scheme based on lattices, more precisely, us- ing the hardness of the learning with errors （LWE） problem. Compared with schemes based on large integer factoriza- tion and discrete logarithms, the most operations are matrix- vector multiplication and inner products in our scheme, our approach has lower computation complexity. Our scheme can be proven to be indistinguishability chosen ciphertext attacks （IND-CPA） secure in the random oracle model.

关键词： lattice-based cryptography LWE identity-based encryption (IBE) post-quantum cryptography certifi-cateless encryption

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Computational analysis of fluid-structure interaction in case of fish swimming in the vortex street

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Journal of Hydrodynamics 2021年第4期33卷 747-762页

作者： Lang Yan Xing-hua Chang Nian-hua Wang Run-yu Tian lai-ping Zhang Wei Liu College of Aerospace Science and Engineering National University of Defense TechnologyChangsha410073China Unmanned Systems Research Center National Innovation Institute of Defense TechnologyBeijing100071China China Aerodynamics Research and Development Center State Key Laboratory of AerodynamicsMianyang621000China Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development CenterMianyang621000China

The fluid-structure interaction (FSI) in case of fish swimming in the vortex street is investigated by numerical simulations. The vortex street is generated by a D-section cylinder. A 2-D fish model is placed on the downstream centerline of the bluff cylinder at a distance of 4 diameters away from the center of the cylinder. To simulate the fish body undulation and movement, the moving mesh is generated by a coupling approach based on the radial basis function and the overset grid technology. The Navier-Stokes equation in the arbitrary Lagrangian-Eulerian form is solved by coupling with the kinematics equation. Three cases are investigated: in a stationary position without deformation, a passive locomotion without deformation, and an active deformation based on the Kármán gait model. The results indicate that the fish body is acted by an alternating force and moment when it is located in the centerline of the vortex street. Furthermore, the fish could extract sufficient kinetic energy to overcome the drag under suitable conditions even when it keeps rigid and out of the suction zone. When the fish body undulates based on the Kármán gait model, the interaction is evidently shown between the fish body and the vortices. The theoretical analysis demonstrates that the lateral force and the moment acting on the fish body vary in a cosine formula, with the lateral translation and the body rotation as a result. This study focuses on the behavior of the fish body in the bluff cylinder wake and reproduces some phenomena observed in the experiments. Besides, the Kármán gait model is also theoretically analyzed, for the further exploration of the FSI mechanism in case of fish swimming.

关键词： Computational analysis fluid-structure interaction(FSI) Kármán gait vortex street passive locomotion fish swimming

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Construction of a key-dependent message secure symmetric encryption scheme in the ideal cipher model

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Frontiers of Computer Science 2014年第3期8卷 469-477页

作者： Qiqi lai Yuan CHEN Yupu HU Baocang WANG Mingming jiang State Key Laboratory of Integrated Service Networks Xidian University Xi'an 710071 China

Key-dependent message （KDM） security is an important security issue that has attracted much research in recent years. In this paper, we present a new construction of the symmetric encryption scheme in the the ideal cipher model （ICM）; we prove that our scheme is KDM secure against active attacks with respect to arbitrary polynomialtime challenge functions. Our main idea is to introduce a universal hash function （UHF） h as a random value for each encrypfion, and then use s = h（sk） as the key of the ideal cipher F, where sk is the private key of our symmetric encryption scheme. Although many other schemes that are secure against KDM attacks have already been proposed, in both the ideal standard models, the much more significance of our paper is the simplicity in which we implement KDM security against active attacks.

关键词： symmetric encryption key-dependent message,challenge function universal hash function ideal cipher model

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Collective stochastic resonance behaviors of two coupled harmonic oscillators driven by dichotomous fluctuating frequency

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Chinese Physics B 2021年第6期30卷 176-187页

作者： Lei jiang Li lai Tao Yu Maokang Luo College of Mathematics Sichuan UniversityChengdu 610064China College of Aeronautics and Astronautics Sichuan UniversityChengdu 610064China

The collective behaviors of two coupled harmonic oscillators with dichotomous fluctuating frequency are investigated,including stability, synchronization, and stochastic resonance(SR). First, the synchronization condition of the system is obtained. When this condition is satisfied, the mean-field behavior is consistent with any single particle behavior in the system. On this basis, the stability condition and the exact steady-state solution of the system are derived. Comparative analysis shows that, the stability condition is stronger than the synchronization condition, that is to say, when the stability condition is satisfied, the system is both synchronous and stable. Simulation analysis indicates that increasing the coupling strength will reduce the synchronization time. In weak coupling region, there is an optimal coupling strength that maximizes the output amplitude gain(OAG), thus the coupling-induced SR behavior occurs. In strong coupling region, the two particles are bounded as a whole, so that the coupling effect gradually disappears.

关键词： coupled harmonic oscillators dichotomous fluctuating frequency synchronization stability stochastic resonance

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Experimental Study on a New Dual-Layer Granular Bed Filter for Removing Particulates

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Journal of China University of Mining and Technology 2007年第2期17卷 201-204页

作者： YANG Guo-hua ZHOU jiang-hua Maritime College Ningbo University Ningbo Zhejiang 315211 China

A new dual-layer granular bed filter for hot gas cleanup was invented and studied experimentally. Fine sand,0.5-1 mm grain size and about 1350 kg/m3 bulk density,was used as the lower layer of the filter. Expanded perlite par-ticles,2-5 mm grain size and about 70 kg/m3 bulk density,was used for the upper layer of the filter in this study. It was confirmed that the sizes and densities of these two media matched well; the binary media remained in complete segre-gation during regeneration by fluidization. Test results show that the filtration of the expanded perlite particle layer was characterized as "deep bed filtration." Filtration of the fine sand layer was "surface cake filtration." The expanded per-lite particle layer contributed about 90% to the bed dust capacity,but only about 20% to the total bed pressure drop,which increased the bed dust capacity ten fold compared to a single-layer bed of the same sand and the same total bed pressure drop. The dust cake on the surface of the fine sand layer raised the collection efficiencies to over 99.99%.

关键词： filtration granular bed filter particulate

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Targeting the P2X7 receptor in microglial cells to prevent brain inflammation

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Neural Regeneration Research 2020年第7期15卷 1245-1246页

作者： Lin-hua jiang Sébastien Roger School of Biomedical Sciences Faculty of Biological SciencesUniversity of LeedsSino-UK Joint Laboratory of Brain Function and Injury and Department of Physiology and NeurobiologyXinxiang Medical UniversityXinxiangHenan ProvinceChina EA4245 TransplantationImmunology and InflammationFaculty of MedicineUniversity of ToursToursFrance

Microglial cells are the key innate immune cells in the brain and they are crucial in maintaining brain parenchyma *** physiological conditions,microglial cells assume a ramified morphology with a small cell body and an extensive network of fine processes,which secrete neurotrophic factors and patrol the surroundings in search for pathogens and eliminate cellular debris via *** cells express a repertoire of pattern recognition receptors(PRRs)that enable them to detect diverse danger-associated molecular patterns(DAMPs)released from damaged cells or cells under stress,or pathogen-associated molecular patterns generated by pathogens during infection.

关键词： IL ATP APP Targeting the P2X7 receptor in microglial cells to prevent brain inflammation

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Influences of aerodynamic loads on hunting stability of high-speed railway vehicles and parameter studies

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Acta Mechanica Sinica 2014年第6期30卷 889-900页

作者： Xiao-Hui Zeng Han Wu jiang lai Hong-Zhi Sheng Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences

The influences of steady aerodynamic loads on hunting stability of high-speed railway vehicles were investigated in this study.A mechanism is suggested to explain the change of hunting behavior due to actions of aerodynamic loads：the aerodynamic loads can change the position of vehicle system（consequently the contact relations）,the wheel/rail normal contact forces,the gravitational restoring forces/moments and the creep forces/moments.A mathematical model for hunting stability incorporating such influences was developed.A computer program capable of incorporating the effects of aerodynamic loads based on the model was written,and the critical speeds were calculated using this *** dependences of linear and nonlinear critical speeds on suspension parameters considering aerodynamic loads were analyzed by using the orthogonal test method,the results were also compared with the situations without aerodynamic *** is shown that the most dominant factors a ff ecting linear and nonlinear critical speeds are different whether the aerodynamic loads considered or *** damping of yaw damper is the most dominant influencing factor for linear critical speeds,while the damping of lateral damper is most dominant for nonlinear *** the influences of aerodynamic loads are considered,the linear critical speeds decrease with the rise of cross wind velocity,whereas it is not the case for the nonlinear critical *** variation trends of critical speeds with suspension parameters can be significantly changed by aerodynamic *** actions of aerodynamic loads and suspension parameters also a ff ect the critical *** effects of such joint action are more obvious for nonlinear critical speeds.

关键词： Hunting stability Linear critical speed Nonlinear critical speed Aerodynamic loads Suspension parameters Orthogonal experimental design

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Effective spin dephasing mechanism in confined two-dimensional topological insulators

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Science China(Physics,Mechanics & Astronomy) 2016年第7期59卷 70-75页

作者： JunJie Qi HaiWen Liu hua jiang XinCheng Xie Institute of Physics Chinese Academy of Sciences Beijing 100190 China Center for Advanced Quantum Studies Department of Physics Beijing Normal University Beijing 100875 China College of Physics optoelectronics and Energy Soochow University Suzhou 215006 China International Center for Quantum Materials and School of Physics Peking University Beijing 100871 China Collaborative Innovation Center of Quantum Matter Beijing 100871 China

A Kramers pair of helical edge states in quantum spin Hall effect （QSHE） is robust against normal dephasing but not robust to spin dephasing. In our work, we provide an effective spin dephasing mechanism in the puddles of two-dimensional （2D） QSHE, which is simulated as quantum dots modeled by 2D massive Dirac Hamiltouian. We demonstrate that the spin dephasing effect can originate from the combination of the Rashba spin-orbit coupling and electron-phonon interaction, which gives rise to inelastic backscattering in edge states within the topological insulator quantum dots, although the time-reversal symmetry is preserved throughout. Finally, we discuss the tunneling between extended helical edge states and local edge states in the QSH quantum dots, which leads to backscattering in the extended edge states. These results can explain the more robust edge transport in InAs/GaSb QSH systems.

关键词： quantum spin Hall effect bound helical states spin dephasing Rashba spin-orbit coupling electron-phonon interaction

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