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Formation of TiN Grid on NiTi by Laser Gas Nitriding for Improving Wear Resistance in hanks' Solution

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Journal of Materials Science & Technology 2016年第5期32卷 459-464页

作者： c.h.Ng O.k.chan h.c.Man Department of Industrial and Systems Engineering The Hong Kong Polytechnic University

Laser gas nitriding （LGN） is a common surface modification method to enhance the wear resistance of titanium （Ti） alloys, which are known to have poor tribological properties. In the present study, a titanium nitride （TIN） grid network was fabricated on the surface of nickel titanium （NiTi） by LGN. The laser processing parameters were selected to achieve nitriding without surface melting and hence to＇maintain a smooth surface finish. The characteristics of the grid-nitrided samples were investigated by scanningelectron microscopy, X-ray diffractometry, optical microscopy, 2-D profilometry, contact angle measurements and nanoindentation. The wear resistance of the nitrided samples was evaluated using reciprocating wear test against ultra-high-molecular-weight polyethylene （UhMWPE） in hanks＇ solution. The results indicate that the wear rates of the grid-nitrided samples and the UhMWPE counter-body in the wear pair are both significantly reduced. The decrease in wear rates can be attributed to the combination of a hard TiN grid and a soft NiTi substrate. In hanks＇ solution, the higher hydrophilicity of the nitrided samples also contributes to the better performance in wear test against hydrophobic UhMWPE.

关键词： Laser Nitriding Surface patterning Titanium alloys Wear

Activation characteristics of candidate structural materials for a near-term Indian fusion reactor and the impact of their impurities on design considerations

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Plasma Science and Technology 2018年第6期20卷 186-193页

作者： h L SWAMI c DANANI A k ShAW Institute for Plasma Research Gandhinagar Gujarat 382428 India homi Bhabha National Institute (hBNI) Anushaktinagar Mumbai 400094 India

Activation analyses play a vital role in nuclear reactor *** analyses,along with nuclear analyses,provide important information for nuclear safety and maintenance *** analyses also help in the selection of materials for a nuclear reactor,by providing the radioactivity and dose rate levels after *** information is important to help define maintenance activity for different parts of the reactor,and to plan decommissioning and radioactive waste disposal *** study of activation analyses of candidate structural materials for near-term fusion reactors or ITER is equally essential,due to the presence of a highenergy neutron environment which makes decisive demands on material *** study comprises two parts; in the first part the activation characteristics,in a fusion radiation environment,of several elements which are widely present in structural materials,are *** reveals that the presence of a few specific elements in a material can diminish its feasibility for use in the nuclear *** second part of the study concentrates on activation analyses of candidate structural materials for near-term fusion reactors and their comparison in fusion radiation *** structural materials selected for this study,***-specific Reduced Activation Ferritic-Martensitic steel（IN-RAFMS）,P91-grade steel,stainless steel 316 LN ITER-grade（SS-316 LN-IG）,stainless steel 316 L and stainless steel 304,are candidates for use in ITER either in vessel components or test blanket *** is also included in this study because of its use for ITER plasma-facing *** study is carried out using the reference parameters of the ITER fusion *** activation characteristics of the materials are assessed considering the irradiation at an ITER equatorial *** presence of elements like Nb,Mo,co and Ta in a structural material enhance the activity level as well as the dose level,which has an

关键词： activation EASY nuclear safety fusion reactor structural materials

System Dynamic Modelling of Patient Flow and Transferral Problem in a Mixed Public-Private healthcare System:A case Study of hong kong SAR

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Journal of Systems Science and Systems Engineering 2020年第5期29卷 590-608页

作者： c.k.M.LEE W.c.TAI kam k.h.NG Department of Industrial and Systems Engineering The Hon g Kong Polytechnic UniversityHung HornHong Kong SARChina School of Mechanical and Aerospace Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore

The current healthcare system in hong kong is experiencing pressure due to constrained resources,with dramatic increases in inpatient services queue lengths,dissatisfaction with the working environment,unacceptable workforce arrangements and high turnover rate of hospital *** maintain the robustness of the healthcare system and a sustainable inpatients flow,the Food and health Bureau launched a public-private partnership programme to utilise the resources of the public and private *** research investigates the potential for extension of the programme and further enhancing the sustainability of the long-term inpatient services under a mixed public-private healthcare policy via system dynamic *** findings show that an increase of human resources in public hospitals does not substantially improve inpatient flow rate ***,the results from the system dynamic approach provide insights into the expansion of the service areas of the programme and suggest increasing the number of referrals to private hospitals.

关键词： System dynamic models scenario analysis inpatient transferral mixed public-private healthcare system

Analysis of electron energy distribution function in a magnetically filtered complex plasma

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chinese Physics B 2013年第4期22卷 324-329页

作者： M k Deka h Bailung N c Adhikary Physical Sciences Division Institute of Advanced Study in Science and Technology Vigyan Path Paschim Boragaon Garchuk Guwahati-781035 Assam India

The electron energy distribution function （EEDF） for a magnetically filtered dusty plasma is studied in a dusty double plasma device where the electron energy can be varied from 0.15 eV to ～ 2.8 eV and plasma density from 10 6 cm-3 to 10 9cm-3 . The characteristics of EEDF for these ranges of plasma parameters are investigated in a pristine plasma as well as in a dusty plasma. The results show that in the presence of dust, there is a drastic modification in EEDF patterns in a plasma with higher electron temperature and density than those in a low temperature and low density plasma produced by the magnetic filter.

关键词： dusty plasma magnetic filter electron energy distribution function

high-cycle Fatigue Life Extension of Glass Fiber/Polymer composites with carbon Nanotubes

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Journal of Wuhan University of Technology(Materials Science) 2009年第2期24卷 167-173页

作者： christopher S Grimmer c k h Dharan Berkeley composites Laboratory University of California 5135 Etcheverry Hall Berkeley CA94720-1740 USA

The present work shows that the addition of small volume fractions of multi-walled carbon nanotubes （cNTs） to the matrix results in a significant increase in the high-cycle fatigue life. It is proposed that carbon nanotubes tend to inhibit the formation of large cracks by nucleating nano-scale damage zones. In addition, the contribution to energy absorption from the fracture of nanotubes bridging across nano-scale cracks and from nanotube pull-out from the matrix are mechanisms that can improve the fatigue life. An energy-based model was proposed to estimate the additional strain energy absorbed in fatigue. The distributed nanotubes in the matrix appear to both distribute damage as well as inhibit damage propagation resulting in an overall improvement in the fatigue strength of glass fiber composites.

关键词： glass fiber composites carbon nanotubes fatigue strain energy

FREE TRANSVERSE VIBRATIONS OF A DOUBLE-WALLED cARBON NANOTUBE:GRADIENT AND INTERNAL INERTIA EFFEcTS

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Acta Mechanica Solida Sinica 2014年第4期27卷 345-352页

作者： k.Y.Xu k.A.Alnefaie N.h.Abu-hamdeh k.h.Almitani E.c.Aifantis Department of Mechanics Shanghai University Department of Mechanical Engineering King Abdulaziz University Jeddah 21589 Saudi Arabia Lab of Mechanics and Materials Polytechnic School Aristotle University Thessaloniki 54124 Greece

This is a modest contribution on higher-order continuum theory for predicting size effects in small-scale objects. It relates to a preceding article of the journal by the same authors（AMSS, 2013, 26： 9-20） which considered the longitudinal dynamical analysis of a gradient elastic fiber but, in addition to an internal length, an internal time parameter is also introduced to model delay/acceleration effects associated with the underlying microstructure. In particular, the free transverse vibration of a double-walled carbon nanotube（DWNT） is studied by employing gradient elasticity with internal inertia. The inner and outer carbon nanotubes are modeled as two individual elastic beams interacting with each other through van der Waals（vdW） forces. General explicit expressions are derived for the natural frequencies and the associated inner-to-outer tube amplitude ratios for the case of simply supported DWNTs. The effects of internal length（or scale）and internal time（or inertia） on the vibration behavior are evaluated. The results indicate that the internal length and time parameters of the adopted strain gradient-internal inertia generalized elasticity model have little influence on the lower order coaxial and noncoaxial vibration modes,but a significant one on the higher order modes.

关键词： carbon nanotubes gradient elasticity internal inertia vibration behavior

DYNAMIc ANALYSIS OF A GRADIENT ELASTIc POLYMERIc FIBER

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Acta Mechanica Solida Sinica 2013年第1期26卷 9-20页

作者： k.Y.Xu k.A.Alnefaie N.h.Abu-hamdeh k.h.Almitani E.c.Aifantis Department of Mechanics Shanghai University Department of Mechanical Engineering King Abdulaziz University Lab of Mechanics and Materials Polytechnic SchoolAristotle University

A dynamic analysis of an elastic gradient-dependent polymeric fiber subjected to a periodic excitation is considered. A nonlinear gradient elasticity constitutive equation with strain- dependent gradient coefficients is first derived and the dispersive wave propagation properties for its linearized counterpart are briefly discussed. For the linearized problem a variational formulation is also developed to obtain related boundary conditions of both classical （standard） and non-classical （gradient） type. Analytical solutions in the form of Fourier series for the fiber＇s displacement and strain fields are provided. The solutions depend on a dimensionless scale parameter （the diameter to length radio d = D/L） and, therefore, size effects are captured.

关键词： gradient elasticity polymeric fibers periodic excitations size effects

cFD Simulation of a hydrogen/Argon Plasma Jet Reactor for coal Pyrolysis

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chemical Research in chinese Universities 2004年第4期20卷 446-451页

作者： chEN h. G. XIE k. c. Taiyuan University of Technology Taiyuan University of Technology Taiyuan 030024 P. R. China City University London EC1V 0HB UKand Taiyuan 030024 P. R. China

A computational Fluid Dynamics(cFD) model was formulated for Dc arc hydrogen/argon plasma jet reactors used in the process of the thermal h_2/Ar plasma pyrolysis of coal to acetylene. In this model, fluid flow, convective heat transfer and conjugate heat conductivity are considered simultaneously. The error caused by estimating the inner-wall temperature of a reactor is avoided. The thermodynamic and transport properties of the hydrogen/argon mixture plasma system, which are usually expressed by a set of discrete data, are fitted into expressions that can be easily implemented in the program. The effects of the turbulence are modeled by two standard k-εequations. The temperature field and velocity field in the plasma jet reactor were calculated by employing SIMPLEST algorithm. The knowledge and insight obtained are useful for the design improvement and scale-up of plasma reactors.

关键词： Plasma Reactor computational fluid dynamics coal pyrolysis

Optimization of cNc cutting parameters using design of experiment(DOE) and desirability function

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Journal of Forestry Research 2018年第5期29卷 1423-1434页

作者： Ender hazir Emine Seda Erdinler kücük hüseyin koc Department of Forest Industrial Engineering Faculty of ForestryIstanbul University

In this study,2~5 （five factors at two-level factorial design） design of experiment was applied to investigate a set of optimal machining parameters to achieve a minimum surface roughness value for Abies *** specimens were prepared using different values of spindle speed,feed rate,depth of cut,tool radius,and cutting *** surface roughness （R_z） values were applied using a *** objectives were to：（1）obtain the effective variables of wood surface roughness;（2） analyze which of these factors had an impact on variability in the cNc machining process;（3） evaluate the optimal cutting values within the range of different cutting levels of machining *** results indicate that the design of experiment（DOE） based on the desirability function approach determined the optimal machining parameters successfully,leading to minimum R_a compared to the observed *** surface roughness values of tangential and radial cutting directions were 3.58 and 3.21 μm,respectively.

关键词： Wood surface roughness Optimization cNc Desirability function Pareto analysis