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Acta Mechanica Sinica 2017年第5期33卷 855-867页

作者： G.Q.zhou y.zhou X.y.Shi State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and Technology School of Mechanics and Civil Engineering China University of Mining and Technology JiangSu Collaborative Innovation Center for Building Energy Saving and Construct Technology

One-dimensional non-Darcy flow in a semi-infinite porous media is investigated. We indicate that the non-Darcy relation which is usually determined from experimental results can always be described by a piecewise linear function, and the problem can be equivalently transformed to a multiphase implicit Stefan problem. The novel feature of this Stefan problem is that the phases of the porous media are divided by hydraulic gradients, not the excess pore water pressures. Using the similarity transformation technique, an exact solution for the situation that the external load increases in proportion to the square root of time is developed. The study on the existence and uniqueness of the solution leads to the requirement of a group of inequalities. A similar Stefan problem considering constant surface seepage velocity is also investigated, and the solution, which we indicate to be uniquely existent under all conditions, is established. Meanwhile, the relation between our Stefan problem and the traditional multiphase Stefan problem is demonstrated. In the end, computational examples of the solution are presented and discussed. The solution provides a useful benchmark for verifying the accuracy of general approximate algorithms of Stefan problems, and it is also attractive in the context of inverse problem analysis.

关键词： Moving boundary problem Stefan problem Analytical solution Non-Darcy flow Soil consolidation

Five-year long-term outcomes of laparoscopic surgery for colon cancer

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World Journal of Gastroenterology 2010年第39期16卷 4992-4997页

作者： Bai HL Chen B zhou y Wu XT. Department of Gastrointestinal Surgery West China Hospital Sichuan University 37 Guo Xue Rd Chengdu 610041 Sichuan Province China. wxt1@***

AIM:To perform a meta-analysis to answer whether long-term recurrence rates after laparoscopic-assisted surgery are comparable to those reported after open ***:A comprehensive literature search of the MEDLINE database,EMBASE database,and the Cochrane Central Register of Controlled Trials for the years 1991-2010 was *** randomized clinical trials(RCTs)were eligible if they included patients with colon cancer treated by laparoscopic surgery vs open surgery and followed for more than five ***:Three studies involving 2147 patients reported long-term outcomes based on five-year data and were included in the *** overall mortality was similar in the two groups(24.9%,268/1075 in the laparoscopic group and 26.4%,283/1072 in open group).No significant differences between laparoscopic and open surgery were found in overall mortality during the follow-up period of these studies[OR(fixed) 0.92,95%confidence intervals(95%CI):0.76-1.12,P=0.41].No significant difference in the development of overall recurrence was found in colon cancer patients,when comparing laparoscopic and open surgery [2147 pts,19.3%vs 20.0%;OR(fixed)0.96,95% CI:0.78-1.19,P=0.71].CONCLUSION:This meta-analysis suggests that laparoscopic surgery was as efficacious and safe as open surgery for colon cancer,based on the five-year data of these included RCTs.

关键词： Colon cancer Laparoscopic surgery Open surgery Randomized clinical trials Meta-analysis

INFLUENCE OF FIBER COATING ON TENSILE BEHAVIOR OF UNIDIRECTIONAL C/Mg COMPOSITES

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Acta Metallurgica Sinica(English Letters) 1997年第5期10卷 398-402页

作者： Zhang, K. Wang, y.Q. zhou, B.L. zhou, y.H. Li, H.L. Inst of Metal Research Chinese Acad of Sciences Shenyang China

The mechanical properties and deformation mechanisms of unidirectional carbon fiber reinforced magnesium composites under tensile loading are studied. Two different materials are used as fiber coatings: a single silica and a gradient C/SiC/SiO[sb 2]. The results show that, under the same preparation conditions, composite with the former coating is broken in a non-cumulative mode and its failure stress is rather low. Conversely, the latter coating demonstrates much better efficiency and the corresponding composite is broken in a cumulative mode.

关键词： Metallic matrix composites Carbon fibers Tensile strength Elastic moduli Coatings Silica Deformation Crack propagation Crack initiation Fracture Stresses Strain

Dual Topological Features of Weyl Semimetallic Phases in Tetradymite BiSbTe_(3)

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Chinese Physics Letters 2021年第7期38卷 69-73页

作者： Z.Z.zhou H.J.Liu G.y.Wang R.Wang X.y.zhou Center for Quantum Materials and Devices College of PhysicsChongqing UniversityChongqing 401331China Key Laboratory of Artificial Micro-and Nano-Structures of Ministry of Education and School of Physics and TechnologyWuhan UniversityWuhan 430072China Chongqing Institute of Green and Intelligent Technology Chinese Academy of ScienceChongqing 400714China

Based on first-principles calculations and symmetry arguments,we reveal that the non-centrosymmetric ternary tetradymite BiSbTe_(3) possesses exotic dual topological features of Weyl semimetallic phases with Z_(2) index(1:000).The results show that the helical Dirac-type surface states protected by the time-reversal symmetry are present in the vicinity of the Brillouin zone center,which is consistent with the experimental ***,we show that four pairs of Weyl points reside exactly at the Fermi level,which are guaranteed to be located on high-symmetry planes due to mirror *** helical surface states and the projected Weyl nodes are well separated in the momentum space,facilitating their observations in *** work not only uncovers a unique quantum phenomenon with dual topological features in the tetradymite family but also paves a fascinating avenue for exploring the coexistence of multi-topological states with wide applications.

关键词： metallic symmetry topological

ON THE DyNAMIC CHARACTERISTICS OF MOULD-FILLING UNDER COUNTERGRAVITy

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Acta Metallurgica Sinica(English Letters) 1997年第5期10卷 409-414页

作者： Zeng, J.M. Gu, H. zhou, y.H. Guangxi Univ Nanning China

In this paper, the mathematical models for mould-filling under countergravity are derived on the basis of the principle of momentum. Dynamic processes of mould-filling are observed on a perspex model by means of high speed photography. The results indicate that the mould-filling under countergravity can be described by the second order nonlinear differential equations characterized by damping oscillations. The velocity oscillations amplify as the pressuring speed increases if the pressure differential functions are of the same type. On the other hand, if the functions are of different type, then the velocity oscillations depend upon whether the functions progressively increase or decrease. Velocity oscillations can be diminished dramatically by increasing the local damping within the gating system.

关键词： casting mould-filling dynamics

A Comparative in vitro Study on Biomedical Zr-2.5X(X=Nb,Sn) Alloys

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Journal of Materials Science & Technology 2014年第4期30卷 299-306页

作者： F.y.zhou K.J.Qiu D.Bian y.F.Zheng J.P.Lin Centre for Biomedical Materials and Engineering Harbin Engineering University Department of Materials Science and Engineering College of EngineeringPeking University State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

Nb and Sn are major alloying elements in Zr alloys. In this study, the microstructure, mechanical properties, corrosion behavior, cytocompatibility and magnetic resonance imaging （MRI） compatibility of Zr-2.5X （X = Nb, Sn） alloys for biomedical application are comparatively investigated. It is found that Zr-2.5Nb alloy has a duplex structure of ~ and ~ phase and Zr-2.5Sn alloy is composed of α phase. Both separate addition of Nb and Sn can strengthen Zr but Nb is more effective in strengthening Zr than Sn. The studied Zr-2.5X （X = Nb, Sn） alloys show improved corrosion resistance compared to pure Zr as indicted by the decreased corrosion current density. The alloying addition of Nb enhances the pitting resistance of Zr, whereas the addition of Sn decreases the pitting resistance of Zr. The extracts of Zr-2.5X alloys produce no significant deleterious effect on fibroblast cells （L-929） and osteoblast-Iike cells （MG 63）, indicating good in vitro cytocompatibility. The Zr-2.5X （X = Nb, Sn） alloys show decreased magnetic susceptibility compared to pure Zr and their magnetic susceptibility is far lower than that of pure Ti and Ti-6AI-4V alloy. Based on these facts, Zr-2.5Nb alloy is more suitable for implant material than Zr-2.5Sn alloy. Sn is not suitable as individual alloying addition for Zr because Sn addition decreases the pitting resistance in physiological solution.

关键词： Zr alloys Mechanical properties Corrosion resistance Cytocompatibility Magnetic susceptibility

SUPERPLASTICITy OF A Ni-28.5Al-20.4Fe INTERMETALLIC ALLOy

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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

A dissolution-diffusion sliding model for soft rock grains with hydro-mechanical effect

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第3期10卷 457-467页

作者： Z.Liu C.y.zhou B.T.Li y.Q.Lu X.yang Guangdong Engineering Research Center for Major Infrastructure Safety School of Civil Engineering Sun Yat-sen University

The deformation and failure of soft rock affected by hydro-mechanical（HM） effect are one of the most concerns in geotechnical engineering, which are basically attributed to the grain sliding of soft rock. This study tried to develop a dissolution-diffusion sliding model for the typical red bed soft rock in South China. Based on hydration film, mineral dissolution and diffusion theory, and geochemical thermodynamics, a dissolution-diffusion sliding model with the HM effect was established to account for the sliding rate. Combined with the digital image processing technology, the relationship between the grain size of soft rock and the amplitude of sliding surface was presented. An equation for the strain rate of soft rocks under steady state was also derived. The reliability of the dissolution-diffusion sliding model was verified by triaxial creep tests on the soft rock with the HM coupling effect and by the relationship between the inversion average disjoining pressure and the average thickness of the hydration film. The results showed that the sliding rate of the soft rock grains was affected significantly by the waviness of sliding surface, the shear stress, and the average thickness of hydration film. The average grain size is essential for controlling the steady-state creep rate of soft rock. This study provides a new idea for investigating the deformation and failure of soft rock with the HM effect.

关键词： Soft rock Hydro-mechanical (HM) effect Mineral dissolution-diffusion Grain sliding model

Linking discrete particle simulation to continuum process modelling for granular matter: Theory and application

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Particuology 2011年第4期9卷 342-357页

作者： H.P. Zhu Z.y. zhou Q.F. Hou A.B. yu School of Engineering University of Western Sydney Locked Bag 1797 Penrith NSW 2751 Australia Laboratory for Simulation and Mo-delling of Particulate Systems School of Materials Science and Engineering The University of New South Wales Sydney NSW 2052 Australia

Two approaches are widely used to describe particle systems： the continuum approach at macroscopic scale and the discrete approach at particle scale. Each has its own advantages and disadvantages in the modelling of particle systems. It is of paramount significance to develop a theory to overcome the disadvantages of the two approaches. Averaging method to link the discrete to continuum approach is a potential technique to develop such a theory. This paper introduces an averaging method, including the theory and its application to the particle flow in a hopper and the particle-fluid flow in an ironmaking blast furnace.

关键词： Particle flow Gas-solid flow Discrete approach Averaging method Hopper flow Blast furnace

WIDE-BAND LASER CLADDING: WEAR AND CORROSION RESISTANCE OF A Ni-BASED ALLOy

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Acta Metallurgica Sinica(English Letters) 1997年第5期10卷 445-452页

作者： Pan, Q.y. Huang, W.D. Li, y.M. Lin, X. zhou, y.H. yang, X.C. Northwestern Polytechnical Univ Xi'an China

A novel wide-band laser cladding system, with high rate of cladding, has been developed in the present work. The system mainly consisted of a 5kW CO2 laser, an automatic powder feeder and a wide-band scanning rotative polygon mirror which can produce a linear or rectangular focused laser beam. Using this system, a Ni-Cr-Si-B alloy powder was cladded on the surface of type 321 austenitic stainless steel in order to improve its wear and corrosion resistance. The pitting corrosion, high temperature oxidation and wear tests were conducted in order to evaluate the properties of the laser cladded layer. The results demonstrated that the cladded layer can significantly improve the adhesive wear and pitting corrosion resistance of the substrate. Moreover, the cladded layer exhibited good oxidation resistance, which is almost the same as that of GMR-235D Ni-based superalloy.

关键词： Boron Chromium alloys Cladding (coating) Laser applications Nickel alloys Silicon alloys Wear resistance