ON THE MECHANISM OF TURBULENT COHERENT STRUCTURE (III)──A STATISTICAL AND DYNAMICALMODEL OF COHERENT STRUCTURE AND ITSHEAT TRANSFER MECHANISM

I.IntroductionItisaveryinlportulltdiscoveryofcoherentstrLICturcinshetlrturbulellt11owsbyexperimentinthelate1950s,whichleadsustoseekthenaturall,ropertiesofturbulcllcefromthenewideaandilladifferentway.ThestudyofthecoherclltstrLlcttlrcisofgreatimportallcetounderstandthegeneration,developmentanddecayof'tLlrbulellce,allditlsoconstructsInorerealisticturbulencemodeltheory.Meanwhile,itwillbeor11elpIYomengineerillgpoint,suchaslllassandheattrallslbr,dl'agI.eductiolland11oisecontrolproblems.Soinlnlel…     

ON THE MECHANISM OF TURBULENT COHERENT STRUCTURE（II）──A PHYSICAL MODEL OF COHERENT STRUCTURE FOR THE ROUGH BOUNDARY LAYER

（刘宇陆）（蔡树棠）ＯＮＴＨＥＭＥＣＨＡＮＩＳＭＯＦＴＵＲＢＵＬＥＮＴＣＯＨＥＲＥＮＴＳＴＲＵＣＴＵＲＥ（ＩＩ）──ＡＰＨＹＳＩＣＡＬＭＯＤＥＬＯＦＣＯＨＥＲＥＮＴＳＴＲＵＣＴＵＲＥＦＯＲＴＨＥＲＯＵＧＨＢＯＵＮＤＡＲＹＬＡＹＥＲ￥ＬｉｕＹｕｌｕ；Ｃ...     

ON THE MECHANISM OF TURBULENT COHERENT STRUCTURE(II)──A PHYSICAL MODEL OF COHERENT STRUCTURE FOR THE ROUGH BOUNDARY LAYER

In this paper, the differences of turbulent coherent structure between the smooth and rough boundary layers are analysed. Based on the discussing the transient properties from the smooth wall to the rough wall, the physical model of coherent structure for the rough boundary layer are established. The width of slowly-moving turbulent spot and the bursting time are obtained, which are in agreement with experimental results.The project supported by the National Nature Science Foundation of China     

TURBULENT COHERENT STRUCTURE AND DYNAMIC SYSTEM

The main difficulties in the study of turbulence via dynamic system lie in how to relatecontinuum systems of infinite dimension with dynamic system in low dimension space andhow to depict its special structure.In this paper,we’ll give a comprehensive review onvarious methods to describe complex systems in low dimension space and new approaches tothe resolution of turbulence problems.     

ON THE MECHANISM OF TURBULENT COHERENT STRUCTURE (I)──THE PYSICAL MODEL OF THE COHERENT STRUCTUREFOR THE SMOOTH BOUNDARY LAYER

In this paper, based on the discussion of properties of the turbulent coherent structure for smooth boundary layer, a physical model has been established. The width of slowly-moving streak line and bursting time of coherent structure expressed by momentum thickness Reynolds number of boundary layer have been obtained, which are in agreement with the experimental data^[3,4,5,7] Project supported by the National Natural Science Foundation of China     

MECHANISM AND CATASTROPHE THEORY ANALYSIS OF CIRCULAR TUNNEL ROCKBURST

Mechanism of circular tunnel rockburst is that, when the carrying capacity of the centralized zone of plastic deformation in limiting state reduces, the comparatively intact part in rock mass unloads by way of elasticity; rockburst occurs immediately when the elastic energy released by the comparatively intact part exceeds the energy dissipated by plastic deformation. The equivalent strain was taken as a state variable to establish a catastrophe model of tunnel rockburst, and the computation expression of the earthquake energy released by tunnel rockburst was given. The analysis shows that, the conditions of rockburst occurrence are relative to rock's ratio of elastic modulus to descendent modulus and crack growth degree of rocks; to rock mass with specific rockburst tendency, there exists a corresponding critical depth of softened zone, and rockburst occurs when the depth of softened zone reaches.     

SYNTHESIS AND CHARACTERIZATION OF NANO METALS WITH CORE-SHELL STRUCTURE

Using AUcore-Ptshell as an example, the synthesis and characterization of nano metals with core-shell structure is demonstrated in a systematic study on the amount-dependent morphology change in a series of Au-Pt bimetallic nanoparticles synthesized using chemical reduction. While the amount of Au precursor is kept constant throughout the whole series of compounds to obtain a fixed Au core size (-7.5 nm), the Au/Pt ratio is varied from 1/1 to 1/4 in order to synthesize Pt shell layers of different thickness. We observed a remarkable shift of surface plasmon band to around 410 nm. With the aid of high resolution transmission electron microscope (HRTEM) and energy-dispersive spectrometer (EDS), the composition of the shell layer is found to be a Pt-enriched Au-Pt alloy. As the amount of Pt increases, string-like Pt clusters form on the surface of the nanoparticles. The average diameter of these Pt clusters is about 2 nm. This special structure may possess unique catalytic properties.     

THE DESIGN AND ANALYSIS OF VIBRATION STRUCTURE OF VERTICAL DYNAMIC BALANCING MACHINE

I. INTRODUCTION The shape of some ?ying objects (called workpieces) is similar to that of shafts. These ?ying objectsoften have a large size. Their dispersion e?ect a?ects the ?ying control and the precision in hitting atarget. The dispersion e?ect is the statistical deviation when ?ying objects depart from their preconcerted?ying orbits. As the unevenness of mass distribution is the major cause of the dispersion e?ect, thedouble-plane vertical dynamic balancing technique for ?ying ob…     

STUDY ON TENSILE FAILURE MECHANISM AND HYBRID EFFECT OF INTRAPLY HYBRID COMPOSITES

The random critical-core model is adapted to investigate the tensile failure mech-anism and hybrid effect of unidirectionally arrayed hybrid composites with alternating low andhigh elongation fibers.By utilizing the model in conjunction with the results of the stress con-centration analysis in which the interfacial damage between fiber and matrix is considered,amicroscopic statistical analysis of both the first failure and ultimate failure of hybrids is per-formed.The variations of the first failure strain,the ultimate failure strain and the hybrid effectas the interfacial shear strength are obtained quantitatively.The concept of the hybrid effect forstrains has been clarified.The present results are compared with available experiment data anda reasonable agreement is found between the analytical predictions and the experimental results.     

ON THE STRUCTURE OF CONTINUA AND THE MATHEMATICAL PROPERTIES OF ALGEBRAIC ELASTODYNAMIC OF A TRICLINIC STRUCTURAL SYSTEM

This paper is neither laudatory nor derogatory but it simply contrasts with what mightbe called elastostatic(or static topology),a proposition of the famous six equations.Theextension strains and the shearing strainsfor all i,j,k=1,2,3.which were derived by A.L.Cauchy,are linearly expressed in terms of nine partialderivatives of the displacement function(u_i,u_j,u_k)(?)u(x~i,x~j,x~k)and it is impossiblefor the inverse proposition to sep up a system of the above six equations in expressing thenine components of matrix((?)(u_i,u_j,u_k)/(?)(x~i,x~j,x~k)).This is due to the fact that ourgeometrical representations of deformation at a given point are as yet incomplete .On theother hand,in more geometrical language this theorem is not true to any triangle,exceptorthogonal,for“squared length”in space.The purpose of this paper is to describe some mathematic laws of algebraicelastodynamics and the relationships between the above-mentioned important questions.     

UNIFORM NORMAL STRUCTURE AND SOLUTIONS OF REICH’S OPEN QUESTION

The open question raised by Reich is studied in a Banach space with uniform normal structure, whose norm is uniformly Gateaux differentiable. Under more suitable assumptions imposed on an asymptotically nonexpansive mapping, an affirmative answer to Reich＇ s open question is given. The results presented extend and improve Zhang Shisheng＇ s recent ones in the following aspects ： （i） Zhang＇ s stronger condition that the sequence of iterative parameters converges to zero is removed; （ii） Zhang＇ s stronger assumption that the asymptotically nonexpansive mapping has a fixed point is removed; （iii） Zhang＇ s stronger condition that the sequence generated by the Banach Contraction Principle is strongly convergent is also removed. Moreover, these also extend and improve the corresponding ones obtained previously by several authors including Reich, Shioji, Takahashi,Ueda and Wittmann.     

UNIFORM NORMAL STRUCTURE AND SOLUTIONS OF REICH’S OPEN QUESTION

IntroductionThroughout this paper we assume thatEis a real Banach space,E*is the dual space ofE,Dis a nonempty subset ofEandJ:E→2E*is the normalized duality mapping defined byJ(x)={f∈E*:〈x,f〉=‖x‖.‖f‖,‖f‖=‖x‖},x∈E,(1)where〈.,.〉denotes the ge     

THE METHOD OF MIXED BOUNDARY CONDITION FOR A KION OF LINEAR AND NONLINEAR COMPOSITE STRUCTURE

This paper deals with the axisymmetrical deformation of shallow shells in largedeflection,which are in conjunction with linear elastic structures at the boundary.A methodof mixed boundary condition for this problem is introduced.then the problem of a compositestructure is transformed into a problem of a single structure and the integral equations aregiven.The perturbation method is used to obtain the solutions and an example of compositestructure consisting of a shallow spherical and a cylindrical shell is presented.     

ELASTO-PLASTIC COUPLED ANALYSIS OF BURIED STRUCTURE AND SOIL MEDIUM BY PERTURBATIONAL SEMI-ANALYTIC METHOD

I.IntroductionMoreandmoreelasto-plasticanalysesareusedinCivilEngineering.TheMohr-Coulombyieldconditionisoftenappliedtorockandsoilmediumtostudythesituationofdestruction.Theperturbationalmethodwasfirstusedinthestudyofcelestialmechanics,thenithasbeenusedinsolidmechanicstocarryoutthegeometricallyandphysicallynonlinearanalysis[']'12].Forlarge?scalcproblems,thegeneralnumericalmethodsmaynotbeapttothiscomplexcalculation,butsemi-analyticalmethodscandoitwell.Touseanalyticalfunctionsinoneortwodirectio…     

SYMPLECTIC STRUCTURE OF POISSON SYSTEM

When the Poisson matrix of Poisson system is non-constant, classical symplectic methods, such as symplectic Runge-Kutta method, generating function method, cannot preserve the Poisson structure. The non-constant Poisson structure was transformed into the symplectic structure by the nonlinear transform.Arbitrary order symplectic method was applied to the transformed Poisson system. The Euler equation of the free rigid body problem was transformed into the symplectic structure and computed by the midpoint scheme. Numerical results show the effectiveness of the nonlinear transform.     

STATIC ANALYSIS OF CABLE STRUCTURE

Based on the nonlinear geometric relation between strain and displacement for flexible cable, the equilibrium equation under self-weight and influence of temperature was established and an analytical solution of displacement and tension distribution defined in Eulerian coordinate system was accurately obtained. The nonlinear algebraic equations caused by cable structure were solved directly using the modified Powell hybrid algorithm with high precision routine DNEQNE of Fortran. For example, a cable structure consisting of three cables jointly supported by a vertical spring and all the other ends fixed was calculated and compared with various methods by other scholars.     

TOPOLOGY OPTIMIZATION OF TRUSS STRUCTURE WITH FUNDAMENTAL FREQUENCY AND FREQUENCY DOMAIN DYNAMIC RESPONSE CONSTRAINTS

In this paper, adaptive genetic algorithm (AGA) is applied to topology optimization of truss structure with frequency domain excitations. The optimization constraints include fundamental frequency, displacement responses under force excitations and acceleration responses under foundation acceleration excitations. The roulette wheel selection operator, adaptive crossover and mutation operators are used as genetic operators. Some heuristic strategies are put forward to direct the deletion of the extra bars and nodes on truss structures. Three examples demonstrate that the proposed method can yield the optimum structure form and the lightest weight of the given ground structure while satisfying dynamic response constraints.     

AN ANALYTICAL METHOD FOR SOLVING INTERNAL FORCES AND DEFORMATIONS OF BAR-SYSTEM STRUCTURE IN SPACE

In this paper.based on the idea of finite element method the initial parametric methodin bending problem of a beam is extended to analyse the bar-system structure by employingDiracδfunction and Heaviside step function.Then a new method for analysing the internalforces and deformations of bar-system structure in space is suggested by improving themixed method in statically indeterminate structure.The inferred process and obtained answer will be more succinct and accurate when theproblem of internal forces and deformations of bar-system structure is analysed by usingthe new method providea in this paper.     

THE INFLUENCE OF SHRINKAGE AND MOISTURE DIFFUSION ON IDEALIZED TOOTH STRUCTURE INVOLVING DEBONDING DAMAGE

This study highlights the joint effect of early polymerization shrinkage and longtermmoisture diffusion on the behavior of the restoration-tooth structure. The interphase debonding between particle and polymer resin in dental composite is taken into account by introducing the damage variable. The idealized model is designed and constructed for representing the restorationtooth structure, which consists of enamel, dentin, composite and interphase, each considered as homogenous material. The simulation is carried out using the general-purpose finite element software package, ABAQUS incorporated with a user subroutine for definition of damaged material behavior. The influence of Young‘s moduli of composite and interphase on stress and displacement is discussed. The compensating effect of water sorption on the polymerization shrinkage is examined with and without involving damage evolution. A comparison is made between the influence of hyper-, equi- and hypo-water sorption. Interfacial failure in the specific regions as well as cuspal movement has been predicated. The damage evolving in dental composite reduces the rigidity of composite, thus in turn reducing consequent stress and increasing consequent displacement. The development of stresses at the restoration-tooth interface can have a detrimental effect on the longevity of a restoration.     

FINITE ELEMENT SYSTEM OF ELASTIC STRUCTURE

The article deals with the problems of controllability.obser-vability and stabilizability of an elastic-structural systemtreated by the finite element method. The results obtained hereagree with that obtained in distributed parameter-system model,nevertheless,they are more convenient than those in carrying outthe computation with a computer, at the same time the method ap-pears much easier than the conventional one. In section one, thesystem’s controllability and observability are studied and someconditions which are easier to be justified by computer are givenIn section two,the problem of stabilizing an elastic object bythe use of linear feedback is fully discussed. As the attainedresults there show that, so far as an elastic-structural systemis concerned,it is possible to assign arbitrary frequencies ofvibration only by the use of displacement feedback. however, itis impossible to stabilize the system while the system is com-pletely controllable. while the velocity feedback can stabilizethe system, b