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A DIREcT SEARcH FRAME-BASED cONjUGATE GRADIENTS METHOD

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journal of computational Mathematics 2004年第4期22卷 489-500页

作者： I.D.coope c.j.Price DepartmentofMathematicsandStatistics UniversityofCanterburyPrivateBag4800ChristchurchNewZealand

A derivative-free frame-based conjugate gradients algorithm is presented. convergence is shown for c^1 functions, and this is verified in numerical trials. The algorithm is tested on a variety of low dimensional problems, some of which are ill-conditioned, and is also tested on problems of high dimension. Numerical results show that the algorithm is effective on both classes of problems. The results are compared with those from a discrete quasiNewton method, showing that the conjugate gradients algorithm is competitive. The algorithm exhibits the conjugate gradients speed-up on problems for which the Hessian at the solution has repeated or clustered eigenvalues. The algorithm is easily parallelizable.

关键词： conjugate gradients Derivative-free Frame-based methods Numerical results

Flow of a biomagnetic viscoelastic fluid:application to estimation of blood flow in arteries during electromagnetic hyperthermia,a therapeutic procedure for cancer treatment

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Applied Mathematics and Mechanics(English Edition) 2010年第11期31卷 1405-1420页

作者： j.c.MISRA A.SINHA G.c.SHIT Department of Information Technology Siksha O Anusandhan University School of Medical Science and Technology Indian Institute of Technology Department of Mathematics Jadavpur University

The paper deals with the theoretical investigation of a fundamental problem of biomaguetic fluid flow through a porous medium subject to a magnetic field by using the principles of biomagnetic fluid dynamics （BFD）. The study pertains to a situation where magnetization of the fluid varies with temperature. The fluid is considered to be non-Newtonian, whose flow is governed by the equation of a second-grade viscoelastic fluid. The walls of the channel are assumed to be stretchable, where the surface velocity is proportional to the longitudinal distance from the origin of coordinates. The problem is first reduced to solving a system of coupled nonlinear differential equations involving seven parameters. considering blood as a biomagnetic fluid and using the present analysis, an attempt is made to compute some parameters of the blood flow by developing a suitable numerical method and by devising an appropriate finite difference scheme. The computational results are presented in graphical form, and thereby some theoretical predictions are made with respect to the hemodynamical flow of the blood in a hyperthermal state under the action of a magnetic field. The results clearly indicate that the presence of a magnetic dipole bears the potential so as to affect the characteristics of the blood flow in arteries to a significant extent during the therapeutic procedure of electromagnetic hyperthermia. The study will attract the attention of clinicians, to whom the results would be useful in the treatment of cancer patients by the method of electromagnetic hyperthermia.

关键词： biomagnetic fluid blood stretching walls porous medium electromagnetic hyperthermia

New Nanocomposite Materials by Incorporation of Nanocrystalline TiO_2 Particles into Polyaniline conductive Films

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journal of Materials Science & Technology 2014年第5期30卷 449-454页

作者： F.j.Feliciano O.c.Monteiro Department of chemistry and Biochemistry and cQB Faculty of SciencesUniversity of LisbonCampo Grande1749-016 LisbonPortugal

This work is focused on the combination of two building-blocks, nanocrystalline TiO2 particles and polyaniline conductive films （PAni）. The preparation of new nanostructured composite materials, displaying electron- and proton-conductive properties, to be used for the fabrication of new and superior energy storage devices was envisaged. The semiconducting TiO2 nanoparticles were obtained by means of a hydrothermal route. The PAni films were prepared on glassy carbon electrodes by electrochemical polymerization, under potential dynamic conditions. After characterization by X-ray diffraction, transmission electron microscopy or scanning electron microscopy and electrochemical techniques, the nanocrystalline particles were immobilized in the polymer matrix. The incorporation of the TiO2 was achieved using two distinct approaches： during the polymer growth or by deposition over previously prepared PAni films. The results demonstrate that the PAni morphology depends on the experimental conditions used during the polymer growth. After TiO2 immobilization, the best electrochemical response was obtained for the nanocomposite structure produced through the TiO2 incorporation after the PAni film synthesis. The modified electrodes were structurally and morphologically characterized and their electro-catalytic activity towards the hydrogen evolution reaction was analyzed. A new electrochemical performance related with the oxidation of molecular hydrogen entrapped in the PAni-TiO2 matrix was observed for the modified electrode after TiO2 incorporation. This behavior can be directly associated with the synergetic combination of the TiO2 and PAni, and is dependent on the amount of the semiconductor.

关键词： PolyaniHne (PAni) Nanosized TiO2 Nanocomposites Hydrogen trapping

An analytical model for electrode-ceramic interaction in multilayer piezoelectric actuators

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Acta Mechanica Sinica 2007年第2期23卷 199-208页

作者： B.L.Wang j.c.Han center for composite Materials Harbin Institute of TechnologyHarbin 150001China

The present paper develops an analytical model for multi-electrodes in multi-layered piezoelectric actuators, in which the electrodes are vertical to and terminated at the edges of the medium and electroelastic field concentrations ahead of the electrodes in the multilayer piezoelectric actuators are examined. By considering a representative unit in realistic multilayers, the problem is formulated in terms of electric potential between the electrode tips and results in a system of singular integral equations in which the electric potential is taken as unknown function. Effects are investigated of electrode spacing and piezoelectric coupling on the singular electroelastic fields at the electrode tips, and closed-form expressions are given for the electromechanical field near the electrode tips. Exact solution for un-coupled dielectrics is provided, where no piezoelectric coupling is present.

关键词： Actuators . Piezoelectric materials . Electrodes. Multilayer. Fracture mechanics

Hot cracking in AZ31 and AZ61 Magnesium Alloy

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journal of Materials Science & Technology 2011年第7期27卷 633-640页

作者： c.j. Huang c.M. cheng c.P. chou F.H. chen Department of Mechanical Engineering National Chiao Tung University Hsinchu 300 Taiwan China Department of Industrial Education National Taiwan Normal University Taipei 106 Taiwan China

This paper examined the impact of the number of thermal cycles and augmented strain on hot cracking in AZ31 and AZ61 magnesium alloy. Statistical analyses were performed. Following observation using a scanning electron microscope （SEM）, an energy dispersive spectrometer （EDS） was used for component analysis. Results showed that Al content in magnesium alloy has an effect on hot cracking susceptibility. In addition, the nonequilibrium solidification process produced segregation in Al content, causing higher liquid Mg-alloy rich Al content at grain boundaries, and resulting into liquefied grain boundaries of partially melted zone （PMZ）. In summary, under multiple thermal cycles AZ61 produced serious liquation cracking. AZ61 has higher （6 wt%） Al content and produced much liquefied Mg17Al12 at grain boundaries under multiple thermal cycles. The liquefied Mg17Al12 were pulled apart and hot cracks formed at weld metal HAZ due to the augmented strain. Since AZ31 had half the Al content of AZ61, its hot-cracking susceptibility was lower than AZ61. In addition, AZ61 showed longer total crack length （TcL） in one thermal cycle compared to that in three thermal cycles. This phenomenon was possibly due to high-temperature gasification of Al during the welding process, which resulted in lower overall Al content. consequently, shorter hot cracks exhibited in three thermal cycles. It was found the Al content of AZ31 and AZ61 can be used to assess the hot-cracking susceptibility.

关键词： Varestraint test Thermal cycles Hot-cracking susceptibility Gas tungsten arc welding (GTAW) AZ31 AZ61

Numerical analysis of straight and curved underground pipeline performance after rehabilitation by cured-in-place method

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Underground Space 2020年第1期5卷 30-42页

作者： K.j.Shou c.c.Huang Department of civil Engineering Chung Hsing University250Kuo Kuang RoadTaichungTaiwanRepublic of China Department of Civil EngineeringChung Hsing University250Kuo Kuang RoadTaichungTaiwanRepublic of China

Underground pipelines are prone to damage by corrosion in Taiwan due to the humid climate and the aging and overuse of ***-dig technologies are necessary,as the cities in Taiwan are highly *** methods,including the cured-in-place pipe(cIPP)method,provide an alternative to the new no-dig installation methods,which are comparatively more *** this study,the numerical analysis software ABAQUS was used to simulate straight-line and curved underground pipelines damaged by *** calibration by small-scale physical modeling in the laboratory,numerical models were applied to the analysis of the mechanical behavior of straight-line and curved underground *** analyze the performance of the cIPP rehabilitation method,different scenarios for straight-line and curved pipelines were *** included before-and after-rehabilitation,different internal pressures and surface loading conditions,and different liner deformabilities and pipe-liner interface *** results suggest that the cIPP method can reinforce damaged pipes by reducing stress concentration and differential displacement near the corrosion ***,proper liner thickness,liner material properties,and pipe-liner interface strength are essential for well-designed cIPP rehabilitation.

关键词： Straight-line pipeline curved pipeline No-Dig Rehabilitation cured-in-place-pipe Soil-pipe interaction

Reactive wetting behaviors of Sn/cu systems: A molecular dynamics study

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Nano-Micro Letters 2010年第2期2卷 60-67页

作者： j.Y.Hsieh j.L.chen c.chen H.c.Lin S.S.Yang c.c.Hwang Department of Mechanical Engineering Ming Hsin University of Science and Technology Institute of Precision Mechatronic Engineering Ming Hsin University of Science and Technology Department of Mechanical Engineering Wu Feng Institute of Technology Department of Information Management Meiho Institute of Technology Department of Engineering Science National Cheng Kung University

Influences of temperature and Sn-cu droplet's composition on reactive wettings of cu(100), cu(110), and cu(111) surfaces were analyzed, by using molecular dynamics(MD) calculations. As a result, the spreading on cu(110)(cu(100)) has the fastest(slowest) wetting kinetics. A higher temperature or a diluter cu content in the Sn-cu alloy droplet results in a higher wettability. Moreover, this work has addressed a theory for positioning the interface separating the liquidus and solidus alloys in the spreading film to confirm the hypothesis that the reactive wetting will come to the end when the interface saturates with the temperature-dependent solidus weight fraction of cu.

关键词： Wetting Surface alloying Molecular dynamics Droplet

Alternative techniques for forecasting mineral commodity prices

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International journal of Mining Science and Technology 2018年第2期28卷 309-322页

作者： c.A.Tapia cortez S.Saydam j.coulton c.Sammut School of Mining Engineering UNSW Sydney UNSW Business School UNSW Sydney School of computer Science and Engineering UNSW Sydney

Forecasting mineral commodity(Mc) prices has been an important and difficult task traditionally addressed by econometric, stochastic-Gaussian and time series techniques. None of these techniques has proved suitable to represent the dynamic behavior and time related nature of Mc markets. chaos theory(cT) and machine learning(ML) techniques are able to represent the temporal relationships of variables and their evolution has been used separately to better understand and represent Mc markets. cT can determine a system's dynamics in the form of time delay and embedding dimension. However, this information has often been solely used to describe the system's behavior and not for *** to traditional techniques, ML has better performance for forecasting Mc prices, due to its capacity for finding patterns governing the system's dynamics. However, the rational nature of economic problems increases concerns regarding the use of hidden patterns for forecasting. Therefore, it is uncertain if variables selected and hidden patterns found by ML can represent the economic *** their refined features for representing system dynamics, the separate use of either cT or ML does not provide the expected realistic accuracy. By itself, neither cT nor ML are able to identify the main variables affecting systems, recognize the relation and influence of variables though time, and discover hidden patterns governing systems evolution simultaneously. This paper discusses the necessity to adapt and combine cT and ML to obtain a more realistic representation of Mc market behavior to forecast long-term price trends.

关键词： Price forecasting Mineral commodity Market dynamics chaos theory Machine learning

SOME NEW cLASSES OF ALMOST PERIODIc FUNcTIONS

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chinese Annals of Mathematics,Series B 1989年第2期10卷 200-213页

作者： c.j.F.UPTON University of Melbourne Parkville Victoria 3052 Australia

In this paper classes of almost periodic functions are formed whlch lie between those established by W. Stepanoff and by H. Burkill.

关键词： cLASSES everywhere adding proof whenever 妇功 false apply Lebesgue 即夕