检索结果-南通市图书馆

Formation of TiN grid on NiTi by Laser gas Nitriding for Improving Wear Resistance in Hanks' Solution

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

Layered double hydroxide- and graphene-based hierarchical nanocomposites： Synthetic strategies and promising applications in energy conversion and conservation

在线全文

学校读者我要写书评

暂无评论

Nano Research 2016年第12期9卷 3598-3621页

作者： g. Bishwa Bidita Varadwaj Vincent o. Nyamori School of chemistry and Physics University of KwaZulu-Natal Westville Campus Private Bag-X5400 I Durban 4000 South Africa

The persistent need for a sustainable energy economy has led researchers to focus on novel energy conversion and storage technologies, inspiring the discovery of smart material designs such as hierarchical nanocomposites~ These nanocomposites have proven effective in the advancement of energy-based technologies. The synergistic properties of hierarchical nanocomposites composed of two types of two-dimensional layered materials, layered double hydroxides and graphene, have resulted in improved electrochemical as well as photocatalytic performance. Synthetic strategies and their effect on the electrochemical and photocatalytic performance of these nanocomposites as high-performance supercapacitors and water oxidation catalysts are discussed in detail in this review.

关键词： layered double hydroxide graphene nanocomposite supercapacitor water oxidation

Large Eddy Simulation for Plunge Breaker and Sediment Suspension

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

china ocean Engineering 2002年第2期17卷 151-164页

作者：白玉川 c.o.Ng Institute of Sediment on River and coast Engineering Tianjin UniversityTianjin 300072China The State Key Laboratory of Estuarine and coastal Research East China Normal UniversityShanghai 200062China Department of Mechanical Engineering the University of Hong KongHong KongChina

Breaking waves are a powerful agent for generating turbulence that plays an important role in many fluid dynamical processes, particularly in the mixing of materials. Breaking waves can dislodge sediment and throw it into suspension, which will then be carried by wave-induced steady current and tidal flow. In order to investigate sediment suspension by breaking waves, a numerical model based on large-eddy-simulation (LES) is developed. This numerical model can be used to simulate wave breaking and sediment suspension. The model consists of a free-surface model using the surface marker method combined with a two-dimensional model that solves the flow equations. The turbulence and the turbulent diffusion are described by a large-eddy-simulation (LES) method where the large turbulence features are simulated by solving the flow equations, and a subgrid model represents the small-scale turbulence that is not resolved by the flow model , A dynamic eddy viscosity subgrid scale stress model has been used for the present simulation. By applying this model to Stokes' wave breaking problem in the surf zone, we find that the model results agree very well with experimental data. By use of this model to simulation of the breaking process of a periodic wave, it can be found that the model can reproduce the complicated flow phenomena, especially the plunging breaker. It reflects the dynamic structures of roller or vortex in the plunging breaker, and when the wave breaks, many strong vortex structures will be produced in the inner surf zone where the concentration of suspended sediment can thereby become relatively high.

关键词： wave breaking large eddy simualion subgrid-scale model surf zone marker and cell method sediment suspensian

Application of Basin Morphometry Laws in catchments of the south-western quadrangle of south-eastern Nigeria

在线全文

学校读者我要写书评

暂无评论

Frontiers of Earth Science 2013年第3期7卷 361-374页

作者： A.o AISUEBEogUN I.c EZEKWE Department of geography and Environmental Management Niger Delta University Wilberforce Island 560001 Nigeria Department of geography and Environmental Management University of Port Harcourt Port Harcourt 500001 Nigeria

The relationship between process and form has been at the core of research in fluvial geomorphology. Form-process relationships of a natural river basin are strongly influenced by its hydrologic and sedimentologic processes as basin morphometric properties of length, shape, and relief, change in response to various hydrologic stimuli from the environment, but usually in line with well established laws. In the four fiver basins （orashi, otamiri, Sombreiro, New calabar） examined in this study, however, empirical evidence does not conform neatly with theoretical postulates. Remarkable variations are noted in the molphometric properties of the catchments, when compared with established morphometric laws. The most varied in conformity are the orashi and New calabar basins, although the Sombreiro and otamiri catchments also show some level of variation. Prime explanation for the morphometric and topographic non-conformity is caused by the nature of surficial material and the profoundly shallow relief of much of the study area, especially the alluvial flood and deltaic plains to the south and south-west of the study area.

关键词： catchments watershed morphology morpho- metric analysis Nigeria Africa

Entropy, Fisher Information and Variance with Frost-Musulin Potenial

在线全文

学校读者我要写书评

暂无评论

communications in Theoretical Physics 2016年第9期65卷 269-274页

作者： J.o.A.Idiodi c.A.onate Physics Department University of Benin

This study presents the Shannon and Renyi information entropy for both position and momentum space and the Fisher information for the position-dependent mass Schr¨odinger equation with the Frost-Musulin potential. The analysis of the quantum mechanical probability has been obtained via the Fisher information. The variance information of this potential is equally computed. This controls both the chemical properties and physical properties of some of the molecular systems. We have observed the behaviour of the Shannon entropy. Renyi entropy, Fisher information and variance with the quantum number n respectively.

关键词： Fisher information Shannon entropy position-dependent mass

on the Role of Differentiation Parameter in a Bound State Solution of the Klein-gordon Equation

在线全文

学校读者我要写书评

暂无评论

communications in Theoretical Physics 2019年第3期71卷 267-273页

作者： B.c.Lütfüo?lu Department of Physics Faculty of Science Akdeniz University Department of Physics Faculty of Science University of Hradec Králové

Recently, the bound state solutions of a confined Klein-gordon particle under the mixed scalar-vector generalized symmetric Woods-Saxon potential in one spatial dimension have been investigated. The obtained results reveal that in the spin symmetric limit discrete spectrum exists, while in the pseudo-spin symmetric limit it does *** this manuscript, new insights and information are given by employing an analogy of the variational principle. The role of the difference of the magnitudes of the vector and scalar potential energies, namely the differentiation parameter,on the energy spectrum is examined. It is observed that the differentiation parameter determines the measure of the energy spectrum density by modifying the confined particle's mass-energy in addition to narrowing the spectrum interval length.

关键词： Klein-gordon equation generalized symmetric Woods-Saxon potential bound st ate spectrum spin symmetry limit analytic solutions

Multiscale approach to micro/macro fatigue crack growth in 2024-T3 aluminum panel

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2014年第1期57卷 51-58页

作者： SIH g.c. International center for Sustainability Accountability and Eco-Affordability of the Large and Small (ICSAELS) Lehigh UniversityBethlehem PA 18015 USA Key Laboratory of Pressure Systems and Safety Ministry of Education School of Mechanical Engineering East China University of Science and Technology

When two contacting solid surfaces are tightly closed and invisible to the naked eye, the discontinuity is said to be microscopic regardless of whether its length is short or long. By this definition, it is not sufficient to distinguish the difference between a micro- and macro-crack by using the length parameter. Microcracks in high strength metal alloys have been known to be sev- eral centimeters or longer. considered in this work is a dual scale fatigue crack growth model where the main crack can be mi- cro or macro but there prevails an inherent microscopic tip region that is damaged depending on the irregularities of the micro- structure. This region is referred to as the ＂micro-tip＂ and can be simulated by a sharp wedge with different angles in addition to mixed boundary conditions. The combination is sufficient to model microscopic entities in the form of voids, inclusions, precipitations, interfaces, in addition to subgrain imperfections, or cluster of dislocations. This is accomplished by using the method of ＂singularity representation＂ such that closed form asymptotic solutions can be obtained for the development of fa- tigue crack growth rate relations with three parameters. They include：（1） the crack surface tightness o-＊ represented by cro/cr~ = 0.3-0.5 for short cracks in region I, and 0.1-0.2 for long cracks in region II, （2） the micro/macro material properties reflected by the shear modulus ratio/1＂（=,L/micro/]-/macro varying between 2 and 5） and （3） the most sensitive parameter d＊ being the micro-tip characteristic length d＊（=d/do） whose magnitude decreases in the direction of region I ---~II. The existing fatigue crack growth data for 2024-T3 and 7075-T6 aluminum sheets are used to reinterpret the two-parameter da/dN=c（AK）n relation where AK has now been re-derived for a microcrack with surfaces tightly in contact. The contact force will depend on the mean stress ~m or mean stress ratio R as the primary parameter and on the stress amplitude era

关键词： microcrack macrocrack microstructure singularity multiscaling scale shift micro/macro crack growth 7075-T6 and 2024-T3

Estimating complex covariance by observing Two Variables at a Time

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2012年第8期28卷 1507-1520页

作者： c.S.WITHERS S.NADARAJAH o.NΦRKLI R.RAIcH R.g.VAUgHAN Applied Mathematics group Industrial Research LimitedLower HuttNew Zealand School of Mathematics University of ManchesterManchester M13 9PLUK

The estimation of covariance matrices is central in array signal processing systems. This note addresses complex covariance estimation for the situation, where the complex data are available only as independent pairwise sets （observations） corresponding to individual elements of the matrix. The formulation for the empirical estimate and the normal maximum likelihood estimate is developed for the general case of different sample sizes for each observation. The approach allows, for example, the estimate of the p by p covariance matrix of a p-port sensor array from a two-port measurement instrument.

关键词： circular normal complex variance empirical estimate maximum likelihood estimate

From monoscale to multiscale modeling of fatigue crack growth:Stress and energy density factor

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2014年第1期57卷 39-50页

作者： SIH g.c. International center for Sustainability Accountability and Eco-Affordability of the Large and Small (ICSAELS) Lehigh University Bethlehem PA 18015 USA Key Laboratory of Pressure Systems and Safety Ministry of Education School of Mechanical Engineering East China University of Science and Technology

The formalism of the earlier fatigue crack growth models is retained to account for multiscaling of the fatigue process that involves the creation of macrocracks from the accumulation of micro *** effects of at least two scales,say micro to macro,must be accounted *** same data can thus be reinterpreted by the invariancy of the transitional stress intensity factors such that the microcracking and macrocracking data would lie on a straight *** threshold associated with the sigmoid curve *** segmentation is shown to be a necessity for addressing multiscale energy dissipative processes such as fatigue and *** independency and energy release rate are monoscale criteria that can lead to unphysical results,violating the first *** of monoscale failure or fracture criteria to nanomaterials is taking toll at the expense of manufacturing super strength and light materials and structural *** brief view is offered in the spirit of much needed additional research for the reinforcement of materials by creating nanoscale interfaces with sustainable time in *** step by step consideraton at the different scales may offer a better understanding of the test data and their limitations with reference to space and time.

关键词： multiscale fatigue monoscale dualscale stress intensity energy density macro micro nano spatial-temporal crack stability sustaibale time