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  • Unsteadiness in non-transferred dc arc plasma generators
  • Non-transferred dc arc plasma generators are widely used in materials processing.They are generally considered steadily-operating devises.However,unsteady phenomena do exist in them, and may cause non-ideal effects in processes which require high controllability and reproducibility. These unsteady phenomena can cause parameter fluctuations in the arc and the plasma jet,some of which have been studied in recent years.Several types and mechanisms of these phenomena have been identified.This paper reviews t...
  • Controlled buckling of thin film on elastomeric substrate in large deformation
  • Electronic systems with large stretchability have many applications.A precisely controlled buckling strategy to increase the stretchability has been demonstrated by combining lithographically patterned surface bonding chemistry and a buckling process.The buckled geometry was assumed to have a sinusoidal form,which may result in errors to determine the strains in the film.A theoretical model is presented in this letter to study the mechanics of this type of thin film/substrate system by discarding the ass...
  • Annealing and strain rate effects on the mechanical behavior of ultrafine-grained iron produced by SPD
  • Thermal stability and strain rate sensitivity of ultrafine-grained(UFG)Fe produced by severe plastic deformation(SPD)were investigated.The UFG Fe was processed by equal-channel angular pressing(ECAP)via route Bc.After 6 passes,the grain size of UFG Fe reaches 600 nm, as confirmed by means of electron back scatter diffraction(EBSD).Examination of micro-hardness and grain size of UFG Fe as a function of post-ECAP annealing temperature shows a transition from recovery to recrystallization.The critical trans...
  • A Zener-Stroh crack interacting with an edge dislocation
  • A Zener-Stroh crack interacting with an edge dislocation is studied.The crack faces are assumed to be traction free.The applied ‘generalized loading‘ for crack is the initial displacement jump and the intervention of the edge dislocation.Through decomposing the problem into two subsimple problems,using the superposition principle,its solution is obtained.To demonstrate both the validity of the solution and its potential application,two simple examples related to the crack stress intensity factors are pre...
  • Damage detection based on the propagation of longitudinal guided wave in a bimetal composite pipe
  • This paper investigates the damage detection based on the propagation of guided wave in bimetal composite pipes,which can identify damage locations in both axial and circumferential directions.The feasibility of the method is showed by numerical simulations using FEM code ANSYS. Mode analysis is used to evaluate the guided wave mode and its structure,which can provide the basis of the mode selection in measurements scheme.The guided wave propagation in a damaged pipe is computed by transient analysis.16 ...
  • On edge dislocation in a multilayered laminate
  • We investigate the elastic field induced by an edge dislocation in a multilayered laminated composite composed of(N—2)thin bonded elastic layers sandwiched between two semi-infinite elastic media.A simple closed-form solution is obtained when all the phases have equal shear modulus but different Poisson‘s ratios,and when the dislocation is located in the upper semi-infinite phase.The image force acting on the dislocation due to its interaction with the multilayered structure is also derived. Several spec...
  • Experimental study on the compressive behaviors of CFRP tube-encased concrete columns
  • Nine square concrete columns including 6 CFRP/ECCs and 3 concrete columns are prepared,which have cross-section of 200 mm×200 mm and height of 600 mm.The CFRP tubes with fibers oriented at hoop direction were manufactured to have 3 or 5 layers of CFRP with 10 mm, 20 mm,or 40 mm rounding corner radii at vertical edges.A 100 mm overlap in the direction of fibers was provided to ensure proper bond.Uniaxial compression tests were conducted to investigate the compressive behavior.It is evident that the CFRP t...
  • Longitudinal waves in one dimensional non-uniform waveguides
  • Wave approach is used to analyze the longitudinal wave motion in one dimensional non-uniform waveguides.With assumptions of constant wave velocity and no wave conversion,there exist four types of non-uniform rods and corresponding traveling wave solutions are investigated.The obtained results indicate that the kinetic energy is preserved as a constant and the wave amplitude is inversely proportional to square root of the cross-sectional area of the rod.Under certain condition,there exists a cut-off frequ...
  • Effects of mesh resolution on hypersonic heating prediction
  • Aeroheating prediction is a challenging and critical problem for the design and optimization of hypersonic vehicles.One challenge is that the solution of the Navier-Stokes equations strongly depends on the computational mesh.In this letter,the effect of mesh resolution on heat flux prediction is studied.It is found that mesh-independent solutions can be obtained using fine mesh,whose accuracy is confirmed by results from kinetic particle simulation.It is analyzed that mesh-induced numerical error comes m...
  • Exact analytical solutions for axial flow of a fractional second grade fluid between two coaxial cylinders
  • The velocity field and the adequate shear stress corresponding to the longitudinal flow of a fractional second grade fluid,between two infinite coaxial circular cylinders,are determined by applying the Laplace and finite Hankel transforms.Initially the fluid is at rest,and at time t=0~+, the inner cylinder suddenly begins to translate along the common axis with constant acceleration. The solutions that have been obtained are presented in terms of generalized G functions.Moreover, these solutions satisfy ...
  • Migration-collision scheme of Lattice Boltzmann method for heat conduction problems involving solidification
  • The phase-change problem is solved by the migration-collision scheme of lattice Boltzmann method.After formula derivation,we find that this method can give a rigorous numerical value for the phase-change temperature,which is of crucial importance.One-dimensional solidification in half-space and two-dimensional solidification in a corner are simulated.The phase change temperature and the liquid-solid interface are both obtained,and the results conform to the analytical solution.
  • Theoretical analysis of microscopic oil displacement mechanism by viscoelastic polymer solution
  • The microscopic oil displacement mechanism in viscoelastic polymer flooding is theoretically analyzed with mechanical method.The effects of viscoelasticity of polymer solution on such three kinds of residual oil as in pore throat,in sudden expansion pore path,and in dead end are analyzed.Results show that the critical radius of mobile residual oil for viscoelastic polymer solution is larger than that for viscous polymer solution,which makes the oil that is immobile in viscous polymer flooding displaced u...
  • Time frequency spectrum of atmospheric turbulence and sweeping hypothesis
  • The present study is focused on the structure of time frequency spectrum.A scaling law for Eulerian time frequency spectrum and the corresponding temporal structure function are calculated from the sweeping hypothesis and Kolmogorov‘s similarity law regarding spatial structure function.An experiment is designed to study this scaling law in the atmospheric turbulent boundary layer.The results well support the conclusion derived from relevant theoretical analysis.
  • Dual solutions in mixed convection with variable physical properties
  • Assisting and opposing flows in a mixed convection boundary layer flow over an isothermal vertical plate are studied for the case of variable physical properties and uniform free stream.Fluid viscosity and thermal conductivity are assumed to be linear functions of temperature.Using local similarity the flow and heat transfer quantities are found to be functions of four parameters,i.e. Richardson number,Prandtl number,a viscosity variation parameter and a thermal conductivity variation parameter.Numerical...
  • Dynamic ice loads on conical structures
  • Two series of model tests were performed to observe the dynamic ice loads on conical structures.The variable testing parameters include the water line diameter of the model cone and ice parameters.During small water line diameter tests,two-time breaking is found to be the typical failure of ice on steep conical structure,and also be controlled by other factors,such as ice speed and the cone angle.During big water line diameter tests,the ice sheet failed nonsimultaneously around the cone.Several independe...
  • Numerical simulation of pore-scale flow in chemical flooding process
  • Chemical flooding is one of the effective technologies to increase oil recovery of petroleum reservoirs after water flooding.Above the scale of representative elementary volume(REV), phenomenological modeling and numerical simulations of chemical flooding have been reported in literatures,but the studies alike are rarely conducted at the pore-scale,at which the effects of physicochemical hydrodynamics are hardly resolved either by experimental observations or by traditional continuum-based simulations.In...
  • Algebraic structure and Poisson method for a weakly nonholonomic system
  • The algebraic structure and the Poisson method for a weakly nonholonomic system are studied.The differential equations of motion of the system can be written in a contravariant algebra form and its algebraic structure is discussed.The Poisson theory for the systems which possess Lie algebra structure is generalized to the weakly nonholonomic system.An example is given to illustrate the application of the result.
  • Energy shaping for coordinating internally actuated vehicles
  • This paper considers the stable coordination problem of two vehicles equipping with internal moving mass actuators.The coordinating and stabilizing control are derived by energy shaping. The proposed method is physically motivated and avoids cancelation or domination of nonlinearities.
  • 《力学快报:英文版》封面

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