检索结果-南通市图书馆

Analytical models for the penetration of semi-infinite targets by rigid,deformable and erosive long rods

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2010年第4期26卷 573-583页

作者： he-Ming wen Bin Lan CAS Key Laboratory for Mechanical Behavior and Design of Materials University of Science and Technology of China 230027 Hefei China

A theoretical study is presented herein on the pen- etration of a semi-infinite target by a spherical-headed long rod for Yp 〉 S, where Yp is the penetrator strength and S is the static target resistance. For Yp 〉 S, depending upon initial impact velocity, there exist three types of penetration, namely, penetration by a rigid long rod, penetration by a deforming non-erosive long rod and penetration by an erosive long rod. If the impact velocity of the penetrator is higher than the hydrodynamic velocity （VH）, it will penetrate the target in an erosive mode; if the impact velocity lies between the hydrodynamic velocity （VH） and the rigid body velocity （VR）, it will penetrate the target in a deformable mode; if the impact velocity is less than the rigid body velocity （VR）, it will penetrate the target in a rigid mode. The critical conditions for the transition among these three penetration modes are proposed. It is demonstrated that the present model predictions correlate well with the experimental observations in terms of depth of penetration （DOP） and the critical transition conditions.

关键词： Long rod Semi-infinite target - Penetration Alekseevskii-Tate model Rigid body velocity - Hydrodynamic velocity

A spherical cavity expansion model for penetration of ogival-nosed projectiles into concrete targets with shear-dilatancy

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2011年第6期27卷 1001-1012页

作者： Tao he he-Ming wen Xiao-Jun Guo CAS Key Laboratory for Mechanical Behavior and Design of Materials University of Science and Technology of China 230027 Hefei China

A dynamic spherical cavity-expansion penetration model is suggested herein to predict the penetration and perforation of concrete targets struck normally by ogivalnosed *** dilatancy as well as compressibility of the material in comminuted region are considered in the paper by introducing a dilatant-kinematic relation.A procedure is first presented to compute the radial stress at the cavity surface and then a numerical method is used to calculate the results of penetration and perforation with friction being taken into *** influences of various target parameters such as shear strength,bulk modulus,density,Poisson＇s ratio and tensile strength on the depth of penetration are *** is shown that the model predictions are in good agreement with available experimental *** is also shown that the shear strength plays a dominant role in the target resistance to penetration.

关键词： Spherical cavity expansion Shear dilatancy Ogival-nosed projectile Concrete target Penetration Perforation

Synthesis and Characterization of PEG Polymer Brushes via Cyclopolymerization of 1,2,3-Triazole Tethered Diacrylates

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Physics 2015年第6期28卷 -页

作者： Xiao-ying Zhao he-wen Liu Key Laboratory of Soft Matter Chemistry Chinese Academy of Sciences Department of Polymer Science and Engineering University of Science and Technology of China Hefei 230026 China

Poly(ethylene glycol) (PEG) macromolecular brushes were synthesized directly via reversible addition-fragmentation chain transfer polymerization cyclopolymerization of diacrylate monomers bearing PEG functional groups through the formation of 11-member rings. The diacrylate monomers bearing PEG functional groups are the 1,2,3-triazole-tethered diacrylate macromolecular monomers with di erent PEG lengths synthesized via the so-called “click” chemistry. The bulky hindrance of PEG chains affected the polymerization behavior of the diacrylate macromolecular monomers, and the diacrylate monomers showed strong tendency to cyclopolymerization rather than crosslinking. NMR analysis and gel permeation chromatography profiles proved the high efficiency of cyclopolymerization without side reactions. The aqueous solutions of the obtained PEG macromolecular brushes were fluorescent under UV excitation. The fluorescence depended dramatically on the concentration of brush-like polymers due to the aggregation of cyclopolymer in water, and could be quenched by the addition of DNA.

关键词： Cyclopolymerization Macromolecular brush Fluorescence quenching DNA

The crosstalk between autophagy and apoptosis: where does this lead?

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Protein & Cell 2012年第1期3卷 17-27页

作者： Claire Gordy You-wen he Department of Immunology Duke University Medical CenterDurhamNC 27710USA

Recent advances in the understanding of the molecular processes contributing to autophagy have provided insight into the relationship between autophagy and *** contrast to the concept of“autophagic cell death,”accumulating evidence suggests that autophagy serves a largely cytoprotective role in physiologically relevant *** cytoprotective function of autophagy is mediated in many circumstances by negative modulation of *** signaling,in turn,serves to inhibit *** the mechanisms mediating the complex counter-regulation of apoptosis and autophagy are not yet fully understood,important points of crosstalk include the interactions between Beclin-1 and Bcl-2/Bcl-xL and between FADD and Atg5,caspase-and calpain-mediated cleavage of autophagy-related proteins,and autophagic degradation of *** investigation of these and other means of crosstalk between apoptosis and autophagy is necessary to elucidate the mechanisms controlling the balance between survival and death both under normal conditions and in diseases including cancer.

关键词： autophagy apoptosis Beclin-1 lymphocytes

Impact of Zn(Ⅱ)Ions on Crystallization and Thermal Properties of Poly(lactic acid)

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Physics 2021年第2期34卷 203-209,I0002页

作者： Zan Wang he-wen Liu CAS Key Laboratory of Soft Matter Chemistry Department of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefei 230026China

The issues of low crystallinity and slow crystallization rate of poly(lactic acid)(PLA)have been widely *** this work,we find that doping PLA with Zn(Ⅱ)ions can speed up the process of crystallization of *** kinds of Zn(Ⅱ)salts(ZnCl2,ZnSt and ZnOAc)were tested in comparison with some other ions such as Mg(Ⅱ)and Ca(Ⅱ).The increased crystallinity and crystallization rate of PLA doping with Zn(Ⅱ)are reflected in FT-IR and variable temperature Raman *** crystallinity is further confirmed or measured with differential scanning calorimetry and X-ray *** crystallinity rate of the PLA/ZnSt-0.4 wt%material can reach 22.46% and the crystallinity rate of the PLA/ZnOAc-0.4 wt%material can reach 24.83%,as measured with differential scanning calorimetry.

关键词： Poly(lactic acid) Zn(Ⅱ) Crystallization Thermal performance Differential scanning calorimetry

A three-stage model for the perforation of finite metallic plates by long rods at high velocities

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2019年第3期15卷 409-418页

作者： Yu he Liu-yun Xu he-ming wen Zheng-cao Lu National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid Physics CAEP Mianyang 621900 China CAS Key Laboratory for Mechanical Behavior and Design of Materials University of Science and Technology of China Hefei Anhui 230027 China

A three-stage theoretical model is presented herein to predict the perforation of a thick metallic plate struck normally by a long rod at high velocities. The model is suggested on the basis of the assumption that the perforation of a thick metallic plate by a long rod can be divided into three stages:(1) initial penetration;(2) plug formation and (3) plug slipping and separation. Various analytical equations are derived which can be employed to predict the ballistic limit, residual velocity and residual length of the long rod. It is demonstrated that the present model predictions are in good agreement with available experimental results for the perforation of finite steel targets struck normally by steel as well as tungsten alloy long rods at high velocities. It is also demonstrated that the dynamic maximum shear stress of a plate material has strong effect on plug formation and plug thickness which, in turn, exerts considerable influence on the residual velocities and lengths of a long rod at impact velocities just above the ballistic limit.

关键词： Perforation Long rod Finite metallic plate Ballistic limit Residual velocity Residual length

Interaction of yttrium barrier and calcium-rich phase on production and properties of WC precursor powders and alloys

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第1期42卷 228-236,I0008页

作者： wen he Dunqiang Tan Zhiqiang Yi Zhiqiang Liu School of Materials Science and Engineering Nanchang UniversityNanchang330031China Instrumental Analysis Center of Nanchang Hangkong University Nanchang330063China

In order to reduce or eliminate the adverse effects of calcium impurity,the interaction of Ca and rare earth Y co-doping on the preparation of WC-Co cemented carbides was investigated.X-ray diffraction,scanning electron microscopy and transmission electron microscopy were employed to analyze the phase compositions,particle sizes and morphologies of them,*** results show that the second type of"yttrium barrier effect"is observed and the adverse influence of Ca-rich phase on tungsten powder can be eliminated by *** flexural strength and fracture toughness of YG6-0.01%Ca+0.09%Y alloy are 2199.5 MPa and 11.49 MPa·m^(1/2),showing improvement of 6.5% and 2.7% compared to YG6 alloy,*** evolutions of Ca-rich phase and Y-rich phase at the every alloy preparation stage of WO_(3),W,WC and cemented carbides are ***,the strengthening mechanism of WC-Co cemented carbide with co-addition of Ca and Y is proposed.

关键词： Yttrium barrier effect Ca-rich phase WC-Co cemented Carbide Microstructures Mechanisms Rare earths

Boundary Poisson Structure and Quantization

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2002年第10期38卷 429-432页

作者： ZHAO Liu he wen-Li Institute of Modern Physics Northwest University Xi''an 710069 China Institute of Modern Physics Northwest University Xi''an 710069 China

A new approach for treating boundary Poisson structures based on causality and locality analysis isproposed for a single scalar field with boundary interaction. For the case of linear boundarv condition, it is shown t... 详细信息

关键词： Poisson structure, boundary condition

TECHNOLOGY OF QUANTITATIVE ANALYSIS ON VIBRATORY STRESS RELIEF BASED ON ULTRASONIC TIME-OF-ARRIVAL METHOD

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2005年第3期18卷 461-463页

作者： he wen Ma Zhenyu Wang Xingli College of Mechanical and Energy Engineering Zhejiang University Hangzhou 310027 China

The effect of vibratory stress relief （VSR） is usually evaluated with the indirect method of observing the change of amplitude frequency response characteristics of structures. A new kind of evaluating method of VSR based on the ultrasonic time-of-arrival method （UTM）, which can obtain the residual stress directly through measuring the propagation time of ultrasonic wave in the material, is presented. At first, the principle of the measuring method of residual stress based on UTM is analyzed. Then the measuring system of the method is described, which is in virtue of ultrasonic flaw detector and high-sampling-rate digital oscillograph. And a set of calibration system that contains a piece of standard specimen is also introduced. Experimental results prove the relation between the residual stress and the propagation time of ultrasonic in workpieces. Finally, the measuring and calibration systems are applied in evaluating the effect of VSR. The final test results show that the method is effective.

关键词： Ultrasonic time-of-arrival method Residual stress Measure Vibratory stress relief