检索结果-南通市图书馆

Glass-forming Ability and Corrosion Resistance of Zr—Cu—Al—Co Bulk Metallic Glass

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2016年第4期32卷 349-354页

作者： w.zhou w.P.weng J.X.Hou Shagang School of Iron and Steel Soochow University

Investigations were carried out to examine the effects of Co addition on the glass-forming ability （GFA） and corrosion resistance of Zr46Cu46AI8 bulk metallic glass in chloride-containing solution. It is found that the GFA of （Zr46Cu46Al8）100-xCox （x = 0, 1, 2, and 4 at.%） alloys reduces with the increase in Co content and correlates well with the parameters, such as the supercooled liquid region width ATx, the reduced glass transition temperature Trg and γ. The corrosion resistance is however found to be enhanced with the in- crease in Co concentration. The addition of Co causes the enrichment of Zr and Al, but depletes Cu in the surface films, which effectively enhances the corrosion potential and lowers the corrosion current density.

关键词： Bulk metallic glassCo-additionGlass-forming abilityCorrosion resistance

Effects of liquid crystal states on photovoltaic effects of chlorophyll-a

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 1995年第2期13卷 118-123页

作者： HAN, YY zhou, RL YANG, YG zhou, w RUAN, XL SHANDONG TEACHERS UNIV DEPT CHEMSHANDONG 250014PEOPLES R CHINA JINAN STEEL PLANT SCH TECHNOLSHANDONG 250010PEOPLES R CHINA

The photovoltaic effects of chlorophyll-a(chla) and the effects of stearic acid, egg phosphatide and cholesterol on those were investigated by means of measuring the photoinduced potentials of SnO2/chla electrodes. Because of the formation of liquid crystal states, appropriate concentrations of stearic acid and egg phosphatide added in a certain system could increase the photovoltaic effects of chla. Cholesterol always decreased the photovoltaic effects of chla because there was no liquid crystal state formed with it.

关键词： CHLOROPHYLL-A LIQUID CRYSTAL PHOTOVOLTAIC EFFECT

Rheological Behavior of Polymer Melts and Concentrated SolutionsPart V: A New Molecular Theory of Non-linear Viscoelasticity for Polymeric Suspensions

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 1999年第2期15卷 169-177页

作者： Song, MS zhou, w Hu, GX Hu, LJ Beijing Univ Chem Technol Inst Polymer Mat Beijing 100029 Peoples R China Harbin Inst Technol Dept Appl Chem Harbin 150001 Peoples R China

A double-network model is established, which consists of the segments, E and A-constituent chains, the polymeric chains entangled with other ones by multi-entanglement and polymeric chains connected to a great number of destructible particles by multi-adsorption, based on which the E and A-constituent chains can be recreated and released dynamically. The distribution function of the end-to-end vector, the statistical distribution function of conformation for two kinds of chains in the multi-entanglement and multi-adsorption states and their number of polymeric chains are calculated by the combination of statistical mechanics and kinetics. Then the viscoelastic free energies of deformation for two kinds of the networks and suspensions are calculated by Boltzmann's statistical theory. Also, elastic modulus and memory function for two kinds of the network and suspensions are derived. Consequently, a new molecular theory df the non-linear viscoelasticity for polymeric suspensions is proposed, and the constitutive equation and material function with yielding and thinning for the polymeric suspensions in different flow fields are derived from this theory.

关键词： Polymers

Rheological Behaviors of Polymer Melts and Concentrated Solutions Part VI: Comparison of the Material Functions with Yielding and Thinning for Polymeric Suspensions with Their Experimental Values

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 1999年第3期15卷 251-252,523-262页

作者： Song, MS zhou, w Hu, GXX Hu, LJ Beijing Univ Chem Technol Res Inst Polymer Mat Beijing 100029 Peoples R China Harbin Inst Technol Dept Appl Chem Harbin 150001 Peoples R China

The memory function and elastic modulus were introduced into the O-w-F type of constitutive equations with the Cauchy-Green and Finger tensors for simple fluid, and then the concrete constitutive equation and material function for polymeric suspensions in the different flow fields were formulated: 1) Viscosity and first normal-stress difference coefficient in the shear flow field; 2) Tensile viscosity at the uni-axial elongation flow field; and 3) Dynamic viscosity and modulus in the dynamic field. Then the dependence of the material function on the deformation rate and weight fraction of fillers was discussed, and the shear flow curves with four characteristic regions ( I-low shear rate plateau region, II- apparent yielding region, ill-intermediate rate plateau region, and lV-shear thinning region.) were explained theoretically. Finally, it was verified by a number of experimental values for the rheological suspensions and the viscoelastic and mechanical behaviors can be predicted by the molecular theory of non-linear viscoelasticity for polymeric suspension;.

关键词： VISCOSITY LIQUIDS

Laparoscopic wedge resection of synchronous gastric intraepithelial neoplasia and stromal tumor:A case report

在线全文

学校读者我要写书评

暂无评论

world Journal of Gastroenterology 2010年第39期16卷 5005-5008页

作者： Mou YP Xu Xw Xie K zhou w zhou YC Chen K. Department of General Surgery Sir Run Run Shaw Hospital School of Medicine Zhejiang University 3 East Qingchun road Hangzhou 310016 Zhejiang Province China. xuxiaowu77@***

Synchronous occurrence of epithelial neoplasia and gastrointestinal stromal tumor(GIST)in the stomach is *** rare cases have been reported in the *** present here a 60-year-old female case of synchronous occurrence of gastric high-level intraepithelial neoplasia and GIST with the features of 22 similar cases and detailed information reported in the Englishlanguage literature *** the present patient,epithelial neoplasia and GIST were removed en bloc by laparoscopic wedge *** the best of our knowledge,this is the first reported case treated by laparo-scopic wedge resection.

关键词： Laparoscopy Stomach neoplasm Gastrointestinal stromal tumor Gastrectomy Synchronous neoplasm

Dynamic experiment and numerical simulation of frozen soil under confining pressure

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

Acta Mechanica Sinica 2020年第6期36卷 1302-1318,I0004页

作者： w.R.Tang Z.w.Zhu T.T.Fu Z.w.zhou Z.H.Shanggua Applied Mechanics and Structural Safety Key Laboratory of Sichuan Province School of Mechanics and EngineeringSouthwest Jiaotong UniversityChengdu610036China Northwest Institute of Eco-Environment and Resources State Key Laboratory of Frozen Soil EngineeringChinese Academy of SciencesLanzhou730000China

with the development of cold region engineering,it is crucial to study the mechanical properties of frozen *** practice,frozen soil is inevitably subject to impact loading,making the study of frozen soil under impact loading necessary for engineering in cold *** split–Hopkinson pressure bar(SHPB)is an important experimental means for obtaining the dynamic performance of *** this study,an SHPB experiment was conducted on frozen soil under confining *** frozen soil exhibited an evident strain rate effect and temperature effect under confining *** SHPB experiment on frozen soil under confining pressure was simulated numerically using LS-DYNA software and the Holmquist–Johnson–Cook(HJC)material model.A loading simulation with passive confining pressure and active confining pressure was completed by adding an aluminum sleeve and applying a constant *** simulation results obtained using the above methods were in good agreement with the experimental *** strength of the frozen soil under confining pressure was greater than that of the uniaxial impact,and there was an evident confining pressure ***,the confining pressure provided by passive confinement was larger than that provided by active *** passive confining pressure energy absorption efficiency was higher than for the active confining pressure due to the need to absorb more energy under the same damage *** frozen soil exhibited viscoplastic failure characteristics under confining pressure.

关键词： Frozen soil-Dynamic experiment Confining pressure Split-Hopkinson pressure bar Numerical simulation

SUPERPLASTICITY OF A Ni-28.5Al-20.4Fe INTERMETALLIC ALLOY

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

Acta Metallurgica Sinica(English Letters) 2000年第3期13卷 888-892页

作者： zhou, w.L. Guo, J.T. Chen, R.S. zhou, J.Y. Inst of Metal Research Chinese Acad of Sciences Shenyang China

Our previous investigation examined the superplastic behavior of an extruded Ni-28.5Al-20.4Fe alloy. Its tensile properties were determined at temperature from 1123 K to 1323 K and initial strain rates from 1.04×10-2s-1 to 1.04×10-4s-1. A maximum elongation of 233% was obtained at 1123 K and a strain rate of 5.2×10-4s-1. Furthermore, microstructural features, such as decrease in the average grain size after deformation at 850 °C and 980 °C, the presence of many dislocation-free grains adjacent to grains with a high dislocation density, indicate that dynamic recrystallization has occurred as an efficient accommodation mechanism. SEM examination of the fracture sample after superplastic deformation reveals many voids on the fracture surface. By correlating with the result of TEM observation, it is suggested that the superplastic deformation in this alloy should be controlled by a grain boundary sliding-based mechanism accommodated by the movement of dislocation and dynamic recrystallization.

关键词： Activation energy Aluminum alloys Intermetallics Iron alloys Microstructure Recrystallization (metallurgy) Superplasticity Tensile testing

Optimal Selling Time in Stock Market over a Finite Time Horizon

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2012年第3期28卷 557-570页

作者： S.C.P.YAM S.P.YUNG w.zhou The Chinese University of Hong Kong China The University of Hong Kong China

In this paper, we examine the best time to sell a stock at a price being as close as possible to its highest price over a finite time horizon [0, T], where the stock price is modelled by a geometric Brownian motion and the ＇closeness＇ is measured by the relative error of the stock price to its highest price over [0, T]. More precisely, we want to optimize the expression：V^＊=sup 0≤τ≤T E[Vτ/MT],where （Vt）t≥0 is a geometric Drownian motion with constant drift α and constant volatility σ 〉 0, Mt = max Vs 0≤a〈t is the running maximum of the stock price, and the supremum is taken over all possible stopping times 0 ≤ τ≤T adapted to the natural filtration （Ft）t≥0 of the stock price. The above problem has been considered by Shiryacv, Xu and zhou （2008） and Du Toit and Peskir （2009）. In this paper we provide an independent proof that when α=1/ 2 σ^2 , a selling strategy is optimal if and only if it sells the stock either at the terminal time T or at the 1 2 moment when the stock price hits its maximum price so far. Besides, when α 〉1/2σ^2 , selling the stock at the terminal time T is the unique optimal selling strategy. Our approach to the problem is purely probabilistic and has been inspired by relating the notion of dominant stopping pr of a stopping time τ to the optimal stopping strategy arisen in the classical ＂Secretary Problem＂.

关键词： optimal Stopping stock selling buy and hold local time

Indium Composition Dependence of the Size Uniformity of InGaAs Quantum Dots on (311)B GaAs Grown by Molecular Beam Epitaxy

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 1999年第6期15卷 523-526页

作者： Jiang, wH Xu, HZ Xu, B zhou, w Gong, Q Ding, D Liang, JB wang, ZG Chinese Acad Sci Inst Semicond Lab Semicond Mat Sci Beijing 100083 Peoples R China

The deposition of InxGa1-xAs (0.2 less than or equal to x less than or equal to 0.5) on (311)B GaAs surfaces using solid source molecular beam epitaxy (MBE) has been studied. Both AFM and photoluminescence emission showed that homogeneous quantum dots could be formed on (311)B GaAs surface when indium composition was around 0.4. Indium composition had a strong influence on the size uniformity and the lateral alignment of quantum dots. Compared with other surface orientation, (100) and (n11) A/B (n=1,2,3), photoluminescence measurement confirmed that (311)B surface is the most advantageous in fabricating uniform and dense quantum dots.

关键词： Semiconducting gallium arsenide