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Interface defeat studies of long-rod projectile impacting on ceramic targets

Defence Technology（防务技术） 2020年第1期16卷 50-68页

作者： Y.X.Zhai h.Wu q.Fang Amy Engineering University of PLA Nanjing210007China Research Institute of Structural Engineering and Disaster Reduction College of Civil EngineeringTongji UniversityShanghai200092China

The interface defeat phenomenon always occurs when a long-rod projectile impacting on the ceramic target with certain velocity,i.e.,the projectile is forced to flow radially on the surface of ceramic plates for a period of time without significant *** defeat has a direct effect upon the ballistic performance of the armor piercing projectile,which is studied numerically and theoretically at ***,by modeling the projectiles and ceramic targets with the SPh(Smoothed Particle hydrodynamics)particles and Lagrange finite elements,the systematic numerical simulations on interface defeat are performed with the commercial finite element program *** different responses,i.e.,complete interface defeat,dwell and direct penetration,are reproduced in different types of ceramic targets(bare,buffered,radially confined and oblique).Furthermore,by adopting the validated numerical algorithms,constitutive models and the corresponding material parameters,the influences of projectile(material,diameter,nose shape),constitutive models of ceramic(Jh-1 and Jh-2 models),buffer and cover plate(thickness,constraints,material),as well as the prestress acted on the target(radial and hydrostatic) on the interface defeat(transition velocity and dwell time) are syste matically ***,based on the energy conservation approach and taking the strain rate effect of ceramic material into account,a modified model for predicting the upper limit of transition velocity is proposed and *** present work and derived conclusions can provide helpful reference for the design and optimization of both the long-rod projectile and ceramic armor.

关键词： Interface defeat Ceramic Transition velocity Numerical simulation Parametric study

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Fault Identification in Power Network Based on Deep Reinforcement Learning

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CSEE Journal of Power and Energy Systems 2022年第3期8卷 721-731页

作者： Mengshi Li huanming Zhang Tianyao Ji q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou510641China

With the integration of alternative energy and renewables,the issue of stability and resilience of the power network has received considerable *** basic necessity for fault diagnosis and isolation is fault identification and *** conventional intelligent fault identification method needs supervision,manual labelling of characteristics,and requires large amounts of labelled *** enhance the ability of intelligent methods and get rid of the dependence on a large amount of labelled data,a novel fault identification method based on deep reinforcement learning(DRL),which has not received enough attention in the field of fault identification,is investigated in this *** proposed method uses different faults as parameters of the model to expand the scope of fault *** addition,the DRL algorithm can intelligently modify the fault parameters according to the observations obtained from the power network environment,rather than requiring manual and mechanical tuning of *** methodology was tested on the IEEE 14 bus for several scenarios and the performance of the proposed method was compared with that of population-based optimization methods and supervised learning *** obtained results have confirmed the feasibility and effectiveness of the proposed method.

关键词： Artificial intelligence deep q network deep reinforcement learning fault diagnosis fault identification parameter identification power network

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Fault Location in Distribution System Using Convolutional Neural Network Based on Domain Transformation

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CSEE Journal of Power and Energy Systems 2021年第3期7卷 472-484页

作者： Yang Yu Mengshi Li Tianyao Ji q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

Distribution lines are integral parts of the modern power system,which can affect the security and stability of power supply *** effective power system protection scheme should be able to detect all occurring faults as soon as *** are two tasks in fault *** is the fault classification,where high accuracy rates have already ***,this paper focuses on the other task,*** *** by Fourier transform,this paper proposes an online data-driven method,which transforms signals from time domain to image domain through signal-to-image(SIG)algorithm and then process the transformed images with framework based on convolutional neural network(CNN).On the one hand,we can extract more crucial characteristic and information from image *** the other hand,the CNN-based structure is much smaller than *** needs less memory space and would be easier to be transplanted to hardware ***,the proposed algorithm does not require synchronous *** numerical comparison shows that the proposed SIG-CNN fault location model achieves robust and accurate results compared with other data-driven algorithms.

关键词： Convolutional neural network distribution lines domain transformation fault location

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Stochastic Economic Dispatch Considering the Dependence of Multiple Wind Farms Using Multivariate Gaussian Kernel Copula

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CSEE Journal of Power and Energy Systems 2022年第5期8卷 1352-1362页

作者： Yantai Lin Tianyao Ji Yuzi Jiang q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China

Wind farms usually cluster in areas with abundant wind ***,spatial dependence of wind speeds among nearby wind farms should be taken into account when modeling a power system with large-scale wind power *** paper proposes a novel non-parametric copula method,multivariate Gaussian kernel copula(MGKC),to describe the dependence structure of wind speeds among multiple wind *** speed scenarios considering the dependence among different wind farms are sampled from the MGKC by the quasi-Monte Carlo(qMC)method,so as to solve the stochastic economic dispatch(SED)problem,for which an improved meanvariance(MV)model is established,which targets at minimizing the expectation and risk of fuel cost *** this model,confidence interval is applied in the wind speed to obtain more practical dispatch solutions by excluding extreme scenarios,for which the quantile-copula is proposed to construct the confidence interval *** studies are carried out on a modified IEEE 30-bus power system with wind farms integrated in two areas,and the results prove the superiority of the MGKC in formulating the dependence among different wind farms and the superiority of the improved MV model based on quantilecopula in determining a better dispatch solution.

关键词： Multivariate Gaussian kernel copula quasi-Monte Carlo quantile-copula stochastic economic dispatch

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Desertification and Re-Afforestation of the Coastal Land in Changjiang County,hainan Island

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Chinese Journal Of Geochemistry 2001年第4期20卷 374-382页

作者： Bi, h. Liu, q. Institute of Resources/Environment Department of Geography Hainan Teachers' College Haikou 571158 China

Changjiang County is located to the northwest of the tailing range of the Wuzhi Mountains on hainan Island, facing the sea and being against the Mountains. From southeast to northwest, it gradually descends in relief from mountain, hill, tableland, terrace to coastal plain. Its sandy coastal line is measured at 44.85 km in length and its rocky coastal line at 7.15 km along the county. The desertified coastal land covers an area of about 61.15 km2, ex tending from hundreds of meters to 3 km in width, of which the active sand land accounts for 5. 333 km2 and the semi-active sand land, 7. 333 km2. The dunes are developed at the rate of 10 - 30 m per year from the seashore toward the *** Forest Departments of hainan Province and Changjiang County have done a series of sand-control experiments. The chief technological measures are as follows: (1) to stabilize the drift sand first to create an adequate condition for afforestation; (2) to plant the big and strong saplings of Casuarin equisetifolia with nutrient bags in deep pits; and (3) to apply new tech niques in 'dry-season planting' to guarantee the quality of afforestation. The above experi ments were successful. however, there still exist some problems such as quite seriously wilting shoot, lower survival rate of Pandanus tectorius in the vertical lines to the usual wind direc tion, monotonous tree species in afforestation and subsequent poor management. Thus some suggestions are offered in this paper for future extension: ( 1 ) to apply REE fertilizers in the process of afforestation to increase the resistance of the plants; (2) to increase the vertical lines of Pandanus tectorius to the usual wind direction to raise their survival rate in the network of sand stabilization; (3) to enlarge the area of liana planting to enhance the stability of sand; (4)to try to introduce new tree species from other regions, which are of good performance in sand stabilization; (5) to interplant the adaptable economic crops

关键词：海南岛海岸带环境管理荒漠化

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Effects of chemical pressure on diluted magneticsemiconductor(Ba,K)(Zn,Mn)_2As_2

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Chinese Physics B 2019年第5期28卷 288-292页

作者： Y Peng S Yu G q Zhao W M Li J F Zhao L P cao X C Wang q q Liu S J Zhang R Z Yu Z Deng X h Zhu C q Jin College of Materials Science & Engineering Sichuan University Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences School of Physics University of Chinese Academy of Sciences Collaborative Innovation Center of quantum Matter

Chemical pressure induced by iso-valent doping has been widely employed to tune physical properties of materials. In this work, we report effects of chemical pressure by substitution of Sb or P into As on a recently discovered diluted magnetic semiconductor(Ba,K)(Zn,Mn)_2 As_2, which has the record of reliable Curie temperature of 230 K due to independent charge and spin doping. Sb and P are substituted into As-site to produce negative and positive chemical pressures, respectively.X-ray diffraction results demonstrate the successful chemical solution of dopants. Magnetic properties of both K-underdoped and K-optimal-doped samples are effectively tuned by Sb-and P-doping. The hall effect measurements do not show decrease in carrier concentrations upon Sb-and P-doping. Impressively, magnetoresistance is significantly improved from7% to 27% by only 10% P-doping, successfully extending potential application of(Ba,K)(Zn,Mn)_2 As_2.

关键词： chemical pressure (Ba,K)(Zn,Mn)2As2 diluted magnetic semiconductor iso-valent doping

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Mechanical properties of cocoons constructed consecutively by a single silkworm caterpillar,Bombyx mori

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Acta Mechanica Sinica 2008年第2期24卷 151-160页

作者： S.q.huang h.P.Zhao X.q.Feng W.Cui Z.Lin M.q.Xu Department of Engineering Mechanics FML Tsinghua University Beijing 100084 China Department of Sericulture Shandong Agriculture University Tai'an 271018 China Department of Landscape Architecture Human Environment-Biological Polytechnic College. Hengyang 421005 China

Most animals have the ability to adapt, to some extends and in different ways, the variation or disturbance of environment. In our experiments, we forced a silkworm caterpillar to spin two, three or four thin cocoons by taking it out from the cocoon being constructed. The mechanical properties of these cocoons were studied by static tensile tests and dynamic mechanical thermal analysis. Though external disturbances may cause the decrease in the total weight of silk spun by the silkworm, a gradual enhancement was interestingly found in the mechanical properties of these thin cocoons. Scanning electron microscopy observations of the fractured specimens of the cocoons showed that there exist several different energy dissipation mechanisms occurred simultaneously at macro-, meso-, and micro-scales, yielding a superior capacity of cocoons to adsorb the energy of possible attacks from the outside and to protect efficiently its pupa against damage. Through evolution of millions of years, therefore, the silkworm Bombyx mori seems to have gained the ability to adapt external disturbances and to redesign a new cocoon with optimized protective function when its first cocoon has been damaged for some reasons.

关键词： Silk Silkworm cocoon Mechanical property Biomimetics

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ATOMIC STATES AND BRITTLENESS OF hcp Ti_3Al-ORDERED-TYPE ALLOYS

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Acta Metallurgica Sinica(English Letters) 2007年第4期20卷 270-276页

作者： h.J. Peng Y.q. Xie College of Chemistry and Chemical Engineering Central South University Changsha 410083 China College of Materials Science and Engineering Central South University Changsha 410083 China

On the basis of the framework of systematic science of alloys （SSA）, the basic information such as states, volumes, and potential energies of characteristic atoms in hcp Ti-Al system have been determined. The average atomic state of the hcp Ti3Al compound consisting of ψ4^Ti and ψ0^Al atoms is 0.75[Ar] （3dn）^0.573 （3dc）^2.1685 （4sc）^0.972 （4sf）^0.3093 ＋ 0.25[Ne] （3sc）^1.32 （3pc）^1.19 （3sf ＋ 3pf）^0.49. The brittleness of the ordered hcp Ti3Al compound has been discussed considering the fundamental factors, which are atomic states, bond networks, potential energy wave planes, and the ratio xTi/xAl. The existence of more pc and more dc directional electrons in the hcp Ti3Al compound lead to considerable brittleness; From bond networks and potential energy wave planes, the hcp Ti3Al compound has poorer ductility than the pure hcp Ti metal and the pure fcc Al metal; The Al-rich hcp Ti3Al ordered type alloys have poorer ductility than the Ti-rich hcp Ti3Al ordered type alloys.

关键词： Ti3Al alloy atomic state brittleness

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Macroscopic and microscopic mechanical behaviors of climbing tendrils

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Acta Mechanica Sinica 2019年第3期35卷 702-710页

作者： q.Guo J.J.Dong Y.Liu X.h.Xu q.h.qin J.S.Wang Tianjin Key Laboratory of Modern Engineering Mechanics Department of MechanicsTianjin UniversityTianjin 300054China State Key Laboratory of Nonlinear Mechanics (LNM) Institute of MechanicsChinese Academy of ScienceBeijing 100080China Research School of Engineering Australian National UniversityCanberraACT 2601Australia

Tendril-bearing climbing plants must recur to the tendril helices with chiral perversion or dual chirality for climbing and to obtain sun exposure. Despite researchers' prolonged fascination with climbing tendrils since Darwin's time and even earlier, why the soft and slender tendrils can bear heavy loads such as the self-weight of a plant or additional load caused by rain remains elusive. In this paper, we take towel gourd tendrils as an example and investigate the macroscopic and microscopic mechanical behaviors of tendrils through experiments and simulations. Our study indicates that the tendril filament exhibits rubber-like hyperelastic behaviors and can particularly endure large elongation, which is mainly attributed to the superelasticity of the cellulose fibril helix contained in the cell wall. Combination of the tendril helical structure with dual chirality or chiral perversion at a macroscale and a cellulose filament helix at a subcellular level creates superior elasticity for biological species relying on support and climbing. This study provides deep insight into the structure-property relationship of climbing tendrils, and the relationship is useful for the bioinspired design of composite systems with superior elasticity.

关键词： Climbing tendril Mechanical behaviors Structure-property relationship Large elongation

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Experimental Study and Numerical Simulation of the Casting-Forging Complex Near Net Forming of Alternator Claw-pole

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上海交通大学学报 2004年第z2期38卷 79-82页

作者： J.L.Song D.J.hu q.C.Wang h.q.Chen h.G.Guo School of Mechanical and Power Engineering Shanghai Jiaotong University Shanghai200030 China Scool of Materials Science and Engineering Taiyuan Heavy Machinery Institute Taiyuan030024 China School of Mechanical and Power Engineering Shanghai Jiaotong University Shanghai200030 China Scool of Materials Science and Engineering Taiyuan Heavy Machinery Institute Taiyuan030024 China Scool of Materials Science and Engineering Taiyuan Heavy Machinery Institute Taiyuan030024 China Scool of Materials Science and Engineering Taiyuan Heavy Machinery Institute Taiyuan030024 China

As a newly developed precision technology, casting-forging complex near net forming process is utilized to produce complex components with a short lead time, low cost and high precision, thus to accelerate the response speed of the market and enhance the competitive power of products. In this paper, the casting-forging complex near net forming process of alternator claw pole was developed and investigated with a combination of experimental and numerical simulation method. qualified near net workpiece was manufactured, mechanical parameter and relative field information during the forming process was also obtained. While the alternator claw-pole is processed with this technology, the forming force is small, the process is short and the quality of forgings is perfect. Therefore, the complex casting-forging near net forming process of claw-pole is an energy and material saving technology, which will have a vast developing and application prospect in the future.

关键词： alternator claw-pole casting-forging near net forming numerical simulation

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