The stability analysis of a thin micropolar fluid flowing on a rotating circular disk is investigated numerically. The target is restricted to some neighborhood of critical value in the linear stability analysis. First, a generalized nonlinear kinematic model is derived by the long wave perturbation method. The method of normal mode is applied to the linear stability. After the weakly nonlinear dynamics of a film flow is studied by using the method of multiple scales, the Ginzburg-Landau equation is determined to discuss the necessary condition in terms of the various states of subcritical stability, subcritical instability, supercritical stability, and supercritical explosion for the existence of such flow pattern. The modeling results indicate that the rotation number and the radius of circular disk play the significant roles in destabilizing the flow. Furthermore, the micropolar parameter K serves as the stabilizing factor in the thin film flow.

Analysis of deformation and stress field in a circular elastic cylinder under the extension is presented, with emphasis on the end effect. The problem is formulated on the basis of the state space formalism for axisymmetric deformation of transversely isotropic materials. A rigorous solution that satisfies the prescribed end conditions is determined by using symplectic eigenfunction expansion, thereby, the applicability of the Saint-Venant solution is examined. The results show that the end effect is significant but confined to a local region near the base of the cylinder where the end plane is perfectly bonded or subjected to a concentrated load. As the axial stiffness increases, the end effect on the stress state increases at the loaded end but decreases at the bonded end. The displacement and stress distributions across the section are uniform throughout the length of the cylinder except near the ends.

An elastic Bernoulli–Euler beam model is developed for thermal-mechanical vibration and buckling instability of a single-walled carbon nanotube (SWCNT) conveying fluid and resting on an elastic medium by using the theories of thermal elasticity mechanics and nonlocal elasticity. The differential quadrature method is adopted to obtain the numerical solutions to the model. The effects of temperature change, nonlocal parameter and elastic medium constant on the vibration frequency and buckling instability of SWCNT conveying fluid are investigated. It can be concluded that at low or room temperature, the first natural frequency and critical flow velocity for the SWCNT increase as the temperature change increases, on the contrary, while at high temperature the first natural frequency and critical flow velocity decrease with the increase of the temperature change. The first natural frequency for the SWCNT decreases as the nonlocal parameter increases, both the first natural frequency and critical flow velocity increase with the increase of the elastic medium constant.

Welded structures are vulnerable to fracture due to cracks, especially at the welds. To investigate the safety of T-Shape welded structures used in some construction sites, a method is proposed in this paper to evaluate the crack occurrence probabilities of the structures. Three major factors that affect the crack occurrence are taken into consideration. They are residual stress, diffusible hydrogen content and chemical composition of the weld metal. In the analysis, finite element analysis is performed to find the residual stress distribution of the structures. The uncertainties of diffusible hydrogen content and chemical composition are treated as random variables. The critical cooling time is found and utilized for evaluating the crack occurrence probability of the welded structure. Numerical results indicate that T-shape welded joints lead to higher residual stresses and higher crack occurrence probabilities in comparison with the traditional butt joints. Therefore, more attention should be paid to this kind of welded joints when they are used.

The present paper reveals an analytically computational method for the inverse Cauchy problem of Laplace equation. For the sake of analyticity, and also for the frequent use of rectangular plate in engineering structure, we only consider the analytical solution in a two-dimensional rectangular domain, wherein a missing boundary condition is recovered from a partial measurement of the Neumann data on an accessible boundary. The Fourier series is used to formulate a first-kind Fredholm integral equation for the unknown function of data. Then, we consider a Lavrentiev regularization amended to a second-kind Fredholm integral equation. The termwise separable property of kernel function allows us to obtain a closed-form solution of the regularization type. The uniform convergence and error estimation of the regularization solution are proven. The numerical examples show the effectiveness and robustness of the new method.

In this study a double two-inlet Y-type microchannel with two up-down symmetrical obstacles was applied. This was done because the positions of the obstacles in the flow channel, arranged in an up- down symmetrical fashion, could provide a higher mixing efficiency. As for the optimal layout of obstacles inthe microchannel, the positions of the two up-down symmetrical obstacles were set as the location of obstacle A/D = 0.198, the length of obstacle K/D = 0.453, the horizontal spacing between the two obstacles T/D = 0, and the flow channel width between the two obstacles Y/D = 0.080, This was because it could generate theflow mixing efficiency with 0.984 and at a lower Reynolds number, Re 4.7. These observations willcontribute to the improvement of a Y-type micromixer design.

Considering the SD (strength differential) effect on compressive strength and tensile strength in zirconia ceramic material, a yield criterion with a special parameter is introduced. In addition, by analogy with associated flow rule, the constitutive model of phase transformation ceramic material has been established. Under generalized plane strain condition, the theoretical toughening expressions of mixed-mode I-III stationary cracks and steady-state growing cracks have been developed with the constitutive model. The crack toughening effect has been discussed in detail with the Poisson ratio, parameters k / α (the ratio of nominal yield strength and SD effect factor) and ω (the scale factor of mode I crack and mode III). The integral calculation shows that phase transformation toughening of stationary cracks is negative shielding effect and the toughening effect of the steady-state growing cracks change obviously with the increase of parameter k / α. Comparison between experimental data and theoretical data indicates that the yield criterion is in accord with the actual characteristics of the zirconia ceramic, when the expression of mixed-mode I-III crack is reduced to mode I crack. The results obtained in present paper can provide the useful theoretical reference for the research of phase transformation toughening in ceramic materials.

Variational principle is an important principle in engineering discipline. This principle is suitable for simple problems where an analytical expression can be determined, but there are many practical problems where the classical variational principle is practically impossible to be applied. In this paper, the authors will try to demonstrate that the variational principle can be replaced by the use of modern artificial intelligence based optimization method (harmony search method) which can be applied to much more complicated problems. Two different improved harmony search algorithms are proposed in this paper. The new algorithms differ from the original algorithm in that: (1) The harmonies are rearranged into several pairs and the better pairs are used to develop several new harmonies; (2) Different probabilities are assigned to different harmonies. The robustness of the proposed methods is demonstrated by using three difficult examples, and the sensitivities of the related optimization parameters are investigated through statistical orthogonal analysis.

The study had indicated that the computational performances of the characteristics method with the time-line cubic spline interpolation are related to the endpoint constraint, especially for large Courant number in which the foot of the characteristic trajectory is located near the endpoint. The first derivative endpoint constraint with higher-order central difference approximation provides better simulation results among various endpoint constraints, but it still induces some degree of numerical error. In this study, by locating the foot of the characteristic trajectory away from the endpoint, the temporal reachout technique is proposed to avoid the effect of endpoint constraint on the time-line cubic spline interpolation. Modeling the transport of a Gaussian concentration distribution in a uniform flow with constant diffusion coefficient and the viscous Burgers equation is used to examine the temporal reachout technique. The outcomes show that the temporal reachout technique yields much better simulation results than the first derivative endpoint constraint with higher-order central difference approximation. The effect of endpoint constraint on the time-line cubic spline interpolation can be greatly diminished by the use of the temporal reachout technique.

This paper adopts the finite-volume multi-stage (FMUSTA) scheme to the two-dimensional coupled system combining the shallow water equations and the advection-diffusion equation. For the convection part, the numerical flux is estimated by adopting the FMUSTA scheme, where high order accuracy is achieved by the data reconstruction using the monotonic upstream schemes for conservation laws method. For the diffusion part, the evaluations of first-order derivatives are solved via the method of Jacobian transformation. The hydrostatic reconstruction method is employed for treatment of source terms. The overall accuracy of resulting scheme is second-order both in time and space. In addition, the scheme is non-oscillatory and conserves the pollutant mass during the transport process. For scheme validation, six advection and diffusion transport tests are simulated. The influences of the grid spacing and limiters on the numerical performance are also discussed. Furthermore, the scheme is employed in the simulation of suspended sediment transport in natural-irregular river topography. From the satisfactory agreements between the simulated results and the field measured data, it is demonstrated that the proposed FMUSTA scheme is practically suitable for hydraulic engineering applications.

In this study, the failure behavior of two parallel pinned/bolted composite joints was investigated, experimentally. The laminated composite plates were produced from glass fibers and epoxy matrix. During the tests, various joint geometries and ply orientations were considered to decide the optimum joint geometry and suitable stacking sequence of the laminated composite plates for two parallel pinned/bolted joints. For these reasons, the distance from the free edge of the plate to hole diameter ratio (E/D) was changed from 1 to 5, the distance between two parallel holes to hole diameter ratio (K/D) was selected as 2 and 5, the distance from the lateral edge of the plate to hole diameter ratio (N/D) was taken as 2 and 3. The laminated plates were composed from 8 laminas to stuck onto together with three different orientations as [0°2 / 30°2]s, [0°2 / 45°2]s and [0°2 / 60°2]s. The experiments involved both pinned and bolted joint. Experimental results indicate that failure behaviors of pinned/bolted composite joints are strictly influenced from both orientations of laminated plates and geometrical parameters.

Vehicle energy absorbing components usually have a curved shape to avoid interference with other components like engine, driving system and fuel tank, etc. Crush behaviour of the S-shape square tubes, as a simplified model of front member of a vehicle body, is investigated in the present study. Experimental and numerical investigation into the quasi static crushing of such tubes was performed. Experimental tests were carried out with cross head speed of 5mm/min. Finite element analysis was performed using ABAQUS/Explicit to simulate quasi-static tests conditions. The predicted crushing characteristics such as global deformation mode, plastic folding mode and load-displacement response obtained by numerical approach were found to be in good agreement with the experimental results. The validated numerical model was then used in the parametric study to examine the effect of design parameters such as wall thickness, web width, curve angle and radius of curvature on the energy absorption capability of the S-shape square tubes. It is shown that some interesting relationships can be discovered by the parametric study to be used as useful design approach for improving the performance of the S-shape tubes.

In this technical note, a compound path integral solution (CPIS) method is utilized to calculate the response exceedance probabilities of a nonlinear compliant offshore structure subjected to slow drift wave force excitations. The structure's slow drift response exceedance probabilities have also been calculated by using the original PIS method for comparison purpose. It is found that the efficiency of the CPIS method for predicting the structure's slow drift response exceedance probabilities is higher than that of the original PIS method.

In this study, radiated noise is investigated by experimental and numerical methods for a straight exhaust pipe of diameter 23mm that replaces the original exhaust pipe of a motorcycle of EZ 125cc provided by Kwang Yang Motor Co. In experiment, temperature, pressure and flow speed of the exhausted gas have been measured for different engine speeds ranging from 3000-5000rpm without loading. Sound pressure levels (SPL) at a distance of 0.5m from the exhaust pipe exit for different inclination angles (0° ∼ 90°) were recorded and compared with the result of simulation. In numerical simulation, a high-resolution 5th-order Euler solver was used and conducted on a parallel computation system with a cluster of 4 personal computers with dual processors. It is found that the back-and-forth reflection of expansion waves inside the pipe due to the shock wave diffraction around the pipe exit is the mechanism of radiating sound waves from the exhaust pipe. The numerical result shows the exhausted-gas flow with complicated vortex rings and its associated acoustic field. The acoustic field indicates that there are three sound lobes with different directivities for the engine speed of 4000rpm.

This study assessed the optimal process for the surface smoothing of 3D image models of in vivo human ossicles. A 3D image model of the ossicles was reconstructed from high resolution computed tomography imaging data. Three smoothing methods including constrained smoothing, unconstrained smoothing and smoothsurface will be discussed. The volume of the 3D image model produced by unconstrained smoothing differed substantially from the original model volume prior to smoothing. Constrained smoothing had an uneven effect on the surface of the 3D image models. Using the smoothsurface module, we were able to obtain an optimal surface of the 3D image model of the human ossicles including the malleus, incus and stapes, using 20 iterations and a λ value of 0.6.

In this paper, the basic finite element formulation of a newly developed family of variable thickness, curved, C(0) continuity Mindlin-Reissner model curved beam elements which include shear deformation and rotatory inertia effects is presented. The accuracy, convergence and efficiency of these newly developed curved beam elements are explored through a series of analyses of arch structures and the results are compared with those obtained by other analytical and numerical methods. The comparisons show that the method yields very good results with a relatively small number of elements.

The effect of heat transfer on the axisymmetric flow of MHD micropolar fluid between two radially stretching sheets is described. The governing partial differential equations are reduced into the ordinary differential equations by using transformations. The resulting problems are solved by homotopy analysis method (HAM). Dimensionless velocities and temperature are plotted for the variation of influential parameters. The local skin friction coefficient, local couple stress coefficient and Nusselt number are tabulated with respect to the influence of several physical parameters.

In this work, a method for increasing the storage capability of a solar thermal energy system has been discussed. The system includes two tanks with the flexibility in choosing the best storage medium on the basis of the solar collector's outlet temperature. The results show that using such a hybrid storage system, the storable energy can be increased. Comparing the results with those for simple common storage systems, the extent of improvement was calculated.

For verification of the results, a small pilot system was assembled. The test apparatus operated during 2008-2009 cold months and the parameters were recorded. Comparison of the theoretical and experimental results showed a good agreement.

In this paper, a response integral quantity method is proposed. This technique provides a quantitative characterization of system responses and can assist the role of the traditional stroboscopic technique (Poincaré section method) in observing bifurcations and chaos of the nonlinear oscillators. We numerically analyze and identify the chaos and subharmonic responses in the forced coupled Duffing's oscillators in which we find that chaotic behaviors and high-order subharmonic responses exist. Due to the signal response contamination of system, it is difficult to identify the high-order responses of the subharmonic motion because of the sampling points on Poincaré map being very close to each other. Even the system responses are subject to misjudgments. The simulation results, however, show that the highorder subharmonic and chaotic responses and their bifurcations can be observed effectively.

Stair locomotion is an important but challenging functional activity for people with lower limb pathology. This study aimed to investigate the bilateral changes in force-bearing on lower limbs during stair locomotion in patients with unilateral ACL deficiency. The ground reaction forces (GRF) were collected from three force platforms: One at ground level in front of a 5-step stair and two on the first two steps respectively. Parameters in vertical and anterior-posterior GRF were extracted and compared between the ACL-deficient (ACLD) and control groups. The ACLD group showed significantly slower stepping cadences in both stair ascent and stepping down to the ground (p < 0.05). The vertical GRF in the ACLD group demonstrated smaller peak forces but larger minimum forces between the two peaks than those in the control group during both stair ascent and descent. Significantly reduced anterior propulsive forces and push-off rates in the late stance were also found in both limbs of the ACLD group (p < 0.05). The slower cadences and reduced force-bearing on the affected limb suggested a protective strategy was adopted. However, the anterior loading parameters in the early stance on the unaffected limb demonstrated different adaptations with significantly larger magnitudes during stair ascent but reduced magnitudes during stair descent (p < 0.05). Similar results were also found in the weight- transferring strategies between legs in consecutive steps with a significantly larger percentage of lift-up forces but a smaller percentage of impact forces on the leading unaffected limb. The results of this study indicated a cautious force-bearing strategy and bilateral adaptation were apparent in the patients with unilateral ACL deficiency. This information may provide a safety guideline for the patients and be helpful for a better use of the stair tasks as part of a rehabilitation program.