This study investigates the steady state dynamic interactions between a vehicle and guideway of a high-speed ground transportation system based on magnetically levitated (Maglev) vehicles. The guideway is assumed to be made up of identical simply supported beams with single spans and rigid supports. The vehicle is considered two-dimensional, with numerous degrees of freedom representing the passenger cabin and primary and secondary suspensions of the vehicle with lumped masses, linear springs and dampings. The Bernoulli-Euler beam equation is utilized to model the characteristics of a flexible guideway, and the guideway synthesis is based on a modal analysis method. The dynamic behaviors of both vehicle and guideway are then simulated to investigate how the locations of the passenger cabin mass of center and asymmetric suspension characteristics of the vehicle suspensions influence high speed vehicle-guideway interaction. Finally, simulation results are compared. Results of this study provide basic design guidelines for Maglev vehicle-guideway systems.

The no-moving-part valve (NMPV) pump design has been proven to be a better micro pump design for its easier fabrication, cost-effective and no destroying flow particle. Previous literatures often used a diffuser design with a divergent angle for NMPV studies. Different from previous studies, we apply a convergent-divergent (C-D) nozzle with convergent half angle θ1 and divergent half angle θ2 for NMPV design in this study. By using the dipole value (Dip) of current C-D nozzle type NMPV as an objective function in “Design of Experiments” (DOE) and “Response Surface Modeling” (RSM) optimization methods, C-D nozzle type NMPV with convergent half angles near θ1 = 46° ∼ 54° and divergent half angles θ2 = 113° ∼ 116° has a maximum peak region for Dip value. It is found that the optimal design with the convergent half angle of θ1 = 60° and the divergent half angle of θ2 = 110°. The operational Reynolds numbers raging from 20 to 30 are suggested for the optimal design and operation condition for the current C-D nozzle type NMPV. It is also verified that the C-D nozzle type NMPV pump design has a better performance than the typical diffuser type NMPV pump design. These findings would be useful to the design and operation for C-D nozzle type NMPV micropump.

A locking free formulation of 4-node bilinear shell element and its application to shell structures is demonstrated. The Enhanced Assumed Strain (EAS) method based on three-field variational principle of Hu-Washizu is used in the formulation. Transverse shear locking and membrane locking are circumvented by means of enhancing the displacement-dependent strain field with extra assumed strain field. Several benchmark shell problems are analyzed.

Thermal postbuckling analysis is presented for 3D braided composite cylindrical shell of finite length subjected to a uniform temperature rise. Based on a micro-macro-mechanical model, a 3D braided composite may be as a cell system and the geometry of each cell is deeply dependent on its position in the cross-section of the cylindrical shell. The material properties of epoxy are expressed as a linear function of temperature. The governing equations are based on Reddy's higher order shear deformation shell theory with a von Kármán-Donnell-type of kinematic nonlinearity and including thermal effects. A singular perturbation technique is employed to determine the buckling temperatures and postbuckling behaviors of 3D braided composite cylindrical shells. The numerical illustrations concern the postbuckling behavior of perfect and imperfect, braided composite cylindrical shells with different values of geometric parameter and of fiber volume fraction. The results show that the shell has lower buckling temperatures and postbuckling equilibrium paths when the temperature-dependent properties are taken into account. The results reveal that the fiber volume fraction, braiding angle and the shell geometric parameter have a significant effect on the thermal buckling and postbuckling behavior of braided composite cylindrical shells.

The formulation of one Timoshenko curved beam on which a pair of piezoelectric segments bonded is presented. The analytical-transfer matrix method is adopted to study structural responses of the surface-mounted actuation curved beam induced by an external force at the tip of the beam and by an applied voltage on the actuator. The effects of length, location and thickness of the piezoelectric pair on the structural responses of the entire curved beam are investigated.

With applying Computational Fluid Dynamics (CFD) techniques, hydrodynamics of a twodimensional non-reactive gas-solid fluidized bed reactor was investigated. A multi fluid Eulerian model incorporating the kinetic theory for solid particles was applied to simulate the unsteady state behavior of this reactor and momentum exchange coefficients were calculated by using the Syamlal-O'Brien drag functions. A suitable numerical method that employed finite volume method applied to discritize the equations. Simulation results also indicated that small bubbles were produced at the bottom of the bed. These bubbles collided with each other as they moved upwards forming larger bubbles. Also, solid particles diameter and superficial gas velocity effect on hydrodynamics were studied. Simulation results were compared with the experimental data in order to validate the CFD model. Pressure drops and bed expansion ratio as well as the qualitative Gas-Solid flow patterns predicted by the simulations were in good agreement with experimental measurements at superficial gas velocities higher than the minimum fluidization velocity. Furthermore, this comparison showed that the model can predict hydrodynamicsbehavior of gas solid fluidized bed reasonably well.

The turbulent flow in a channel with periodic porous ribs on one wall is numerically studied. The numerical model utilizes the Reynolds averaged Navier-Stokes (RANS) equations with a k−ε turbulent model for turbulence closure. Computational results show good agreements with experimental data in flows over a porous rib. The parameter effects, including the pitch ratio PR (1 ∼ 9) and porosity γ (0.4 ∼ 0.6), on flow fields are further examined in detail. Systematic variations of streamline, streamwise and vertical velocities, and turbulent kinetic energy are clearly identified. As to the PR effect, the interaction between outer flow and flow within the cavity is promoted by arranging ribs due to the penetration of the outer flow. Increasing porosity can reduce the downward outer flow by strong flows passing through the porous ribs. The numerical calculations suggest that the flow characteristics for porous ribs are not only a function of the rib geometry, i.e. pitch ratio, but also the porous property, i.e. porosity.

In this paper, an efficient method is proposed to derive cyclic p-y curves from either push-over or shaking table test results. The Fourier series function, satisfying the boundary conditions of a pile, is used to represent deflection behavior of the pile-soil system at each instant of time during loading interval. In order to obtain soil reaction along the pile shaft, convergence of the series after differentiation is guaranteed by applying the Cesaro sum technique. Results of four push-over tests and two other shaking table test results, conducted at the National Center for Research on Earthquake Engineering in Taiwan, are then used to verify the feasibility of the proposed method.

In this paper, a methodology with workable procedures was proposed and successfully transferred the hysteresis loops of BGA solder joint specimen held by loading-directionally aligned grip system under oblique displacement controlled cyclic tests, into hysteresis loops of “representative” solder ball itself under proportional straining and constant strain rate cyclic tests. Under the elastic unloading during cyclic test, value of elastic modulus of bulk solder specimens and the linear behavior of grip system were used. Following the study of Endochronic cyclic viscoplasticity, the kernel function ρ(Z) = ρ0 exp (−KZ)/Zα was found to be independent of the oblique angle (Φ) of straining paths. However, the steady cyclic behavior of material function f(ξ) ≡ f0 in the definition of intrinsic time Z contained two functions: (1) is the effective inelastic strain amplitude, and (2) f(Φ) Φ(rad) between Φ = 0 (uniaxial) and Φ = π/2 (shear). With (ρ0, α, K) = (4MPa, 0.84, 46) and f0 = [0.24(π/2−Φ)2 − 0.018(π2−Φ) + 1.2] , the endochronic theory predicted experimental hysteresis loops of BGA Sn/3.5Ag/0.75Cu solder joint specimens and Φ = 0°, 27°, 45°, 63°, 90° quite well.

Results of ρ(Z) under f0 = 1 were found under independent study based on cyclic tests of bulk specimens under constant uniaxially strain amplitude and various constant strain rates. The values of (ρ0, α, K) = (7.3MPa, 0.84, 30) with f0 = 1.0 were all independent of strain rates. Comparisons of results of both types of specimens revealed that the values of (α, K) were almost the same but (1) ρ0 was smaller for micro-size solder ball, (2) is a material function of Sn/3.5Ag/0.75Cu itself (3) f(Φ) is not a material function, rather it is a special feature to reflect the effects of detail design of solder joint specimen and its connecting methods to the substrates

Langmuir circulation that has been disturbed by a perturbed source in a horizontal Couette flow with a vertical density gradient (i.e., the effective Rayleigh number R) and horizontal Couette flow is investigated. The evolution of instability developing in the presence of a vertical density gradient influenced by the disturbance at various depths and the horizontal Couette flow is considered near the onset of convection under a moderate rate of shear. We use velocity as the basic variable and solve the pressure Poisson equation in terms of the associated Green function. Growth competition between the longitudinal vortices (Lv) and the transverse vortices (Tv), whose axes are respectively in the direction parallel to and perpendicular to the Couette flow, is investigated by the weakly nonlinear analysis of coupled-mode equations. The results show that the Tv mode is characterized in some range of the effective Rayleigh number, and that the stability is dominated by the Lv mode in the system.

The flame and flow behaviors along with the fuel jet oscillations of non-premixed and axisymmetric swirling wake during acoustic excitations are studied experimentally. Visual observations on the reaction zones are carried out to identify the flame behaviors. Close-up images at the flame base as well as the whole flame images are captured and discussed. Traditional photography techniques are adopted to illustrate the dimensional characteristics of every flame mode. The central jet oscillations are diagnosed by a two component laser Doppler anemometer. Combined images of the flame and flow are gathered using the laser-light sheet assisted Mie scattering method. Results showed that the short and wide flame which was induced during acoustic forcing is principally because of the severe premixing at the tip of the burner tube. Wake recirculation bubble enhanced premixing at low swirl number while it damped the jet oscillation at higher swirl number. Mechanics of mixing at every flame mode during acoustic excitation are reported and discussed.

A theoretical approach for an optical lens tip on a single-mode fiber end to improve power coupling from laser diode is presented in this work. The lens shape considered here is an ellipsoid. Based on scalar diffraction and Gaussian mode shapes for the laser and fiber fields, a theoretical model is developed to predict the coupling performance of this microlens. Theoretically, both a high coupling efficiency up to 77% and a large alignment tolerance for 10% off-peak are achieved. The proposed method facilitates mass production to achieve a high-yield and high-coupling efficiency that is suitable to be used in the commercial fiber transmission industry.

In the conceptual design phase of a turbocharger, where emphasis is mainly on parametric studies, before manufacturing and tests, a generalized and robust model that implies over a wide range properly, is unavoidable. The critical inputs such as compressor maps are not available during the conceptual design phase. Hence, generalized compressor models use alternate methods that work without any supplementary tests and can operate on wide range. One of the common and applicable modeling methods in design process is the ‘Dimensionless Modeling’ using the constant coefficient scaling (CCS). This method almost can predict the compressor characteristics at design point. However, at off design conditions, error goes up as mass flow and speed parameters increase. Therefore, the results are not reliable at these points. In this paper, a variable coefficient scaling (VCS) method is described. Then, a centrifugal compressor is modeled using the VCS method. To evaluate the model and compare it with the experimental results, some supplementary experiments are performed. Experimental studies are carried out on the compressor of a S2B model of the Schwitzer turbocharger in the turbocharger Lab., at Sharif University of Technology. The comparison between the experimental results and those obtained by the VCS method indicates a good agreement. It also suggests that the present model can be used as an effective design tool for all operating conditions.

This study develops an intelligent non-dominated sorting genetic algorithm (GA), called INSGA herein, which includes a non-dominated sorting, crowded distance sorting, binary tournament selection, intelligent crossover and non-uniform mutation operators, for solving multi-objective optimization problems (MOOPs). This work adopts Goldberg's notion of non-dominated sorting and Deb's crowded distance sorting in the proposed MOGA to achieve solutions with good diversity-preservation and uniform spread on the approximated Pareto front. In addition, the chromosomes of offspring are generated based on an intelligent crossover operator using a fractional factorial design to select good genes from parents intelligently and achieve the goals of fast convergence and high numerical accuracy. To further improve the fine turning capabilities of the presented MOGA, a non-uniform mutation operator is also applied. A typical mutation approach is to create a random number and then add it to corresponding original value. Performance evaluation of the INSGA is examined by applying it to a variety of unconstrained and constrained multi-objective optimization functions. Moreover, two engineering design problems, which include a two-bar truss design and a welded beam design, are studied by the proposed INSGA. Results include the estimated Pareto-optimal front of non-dominated solutions.

The present theoretical study investigates turbulent film boiling on an elliptical tube with steam heating surface inside. The flow direction of the heating steam is opposite to the vapor film of the outer tube. Thus, the surface temperature is expressed by cosine function. The effect of temperature amplitude, eccentricity, nonlinear viscosity, nonlinear thermal conductivity, radiation and eddy diffusivity are all included in the present analysis. And the paper also discusses the vapor thickness, local Nusselt number and mean Nusselt number. The result shows, first, under the free convection turbulent film boiling with temperature variation, the bigger the temperature amplitude value is, the better the heat transfer efficiency is. Next, the increase of the eccentricity values will bring out the increase of the Nusselt number. Finally, a comparison between the results of the present study and those reported in a previous theoretical data is provided.

An improved method of space-time conservation element and solution element (CE/SE) is developed to solve the equations of conservation laws in fluid dynamics. The present method substantially differs in both concept and methodology from the traditional CE/SE method. In this paper the improved second-order CE/SE method is presented in a hexahedral grid. Furthermore, the present CE/SE method was successfully applied to solve the interaction problem of shock waves and detonation. Several numerical examples were also given. Numerical results have compared with the results of experiments and other computational methods. The compared results have shown a good agreement. The improved CE/SE method has higher accuracy and becomes a more prospective scheme.

A coupled structural and fluid flow analysis was performed to assess the hydroelastic behavior of a composite marine propeller. The finite element method and lifting surface theory were applied in the structural and fluid analyses, respectively. A coupled equation derived from the Bernoulli equation and the hydrostatic pressure in terms of the blade deflection and strength of the vortex was solved by Newton-Raphson procedure. A MAU 3–60 propeller was analyzed with different stacking sequences of composite layup. The hydroelastic behaviors of the propeller with balanced and unbalanced stacking sequences were investigated and discussed. The unbalanced Stacking sequences were shown to influence the performance of the composite propeller, especially in the region in which the advanced coefficient is low.

This study discusses the components' geometry and its effect on the capability of heat transmission and pressure drop because of its evident influence on the performance of micro capillary pumped loop (MCPL). On analyzing the dimensional effect on heat transmission and pressure gradient of MCPL device, some results were yielded and addressed as follows: The vapor line was the most important factor among the components of MCPL in heat transmission and pressure drop. Furthermore, the depth of vapor line was the main parameter because of its drastic effect. In addition, at depth of vapor line, hv, ranging from 20 μm to 150 μm, the amount of heat transferred for system will increase, but decrease the pressure drop. However, for hv larger than 150 μm, the heat transfer and pressure drop both will reach a limit. A new family of geometrical dimensions of MCPL possessing an excellent heat flux of 178 W/cm2 would be obtained. These findings will be useful in designing a better MCPL.

For improving the performance of a miniature loudspeaker, engineers have been pursuing a goal of lowering its first damped frequency to have a broad and smooth region of its sound-pressure-level response. This article applies the approach of electro-mechano-acoustical analogy to study the first damped frequency of a miniature loudspeaker used for cellular phones. Using the analogy approach, the authors derive an explicit formulation for the sound-pressure-level of a typical miniature loudspeaker of dynamic type. The veracity of the derived formulation is verified by comparing with the experimental result recorded by B and K apparatus. The derived formulation is further simplified by neglecting factors that are either irrelevant or insignificant for the first damped frequency. Through basic algebraic and calculus operations, this article also presents an explicit form of the first damped frequency. This work has laid the platform for engineers to tailor the design in pursuit of improving the performance of miniature loudspeakers.

The formulation of a beam on which a pair of piezoelectric segments bonded is presented. The method of transfer matrix is adopted to study the structural responses of the surface-mounted actuation beam induced by an external force on the beam and by a voltage on the actuator. Furthermore, the modal frequencies and the corresponding mode shape functions of the beam also are obtained by the method. The orthogonality of any two distinct sets of mode shape functions of the beam is shown. The method of modal analysis is presented to study the forced vibration of the beam due to a concentrated transient force. The effects of length, location and thickness of the piezoelectric pairs on the structural responses and the modal frequencies of the beam are investigated.