bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermodynamic Formulation of Endochronic Cyclic Viscoplasticity With Damage- Application to Eutectic Sn/Pb Solder Alloy
Authors: Lee C. F. , Chen Y. C.
Published: May 2011

In this paper, an endochronic theory of cyclic viscoplasticy with damage is established based on the irreversible thermodynamics of continuous media with internal state variables containing an isotropic damage parameter. The constitutive equations derived have the same mathematical form as those of convectional endochronic theory without damage, except the effective stress with damage is used. This result coincides with the Lemaitre's statements of stain equivalence principle.

Using the experimental cyclic stress-strain curves of 63Sn/37Pb solder bars, corrected from the uniaxially constant displacement amplitude cyclic tests under MTS Tytron microtester, the computational results of cyclic stess-strain curves with several degrees of damage can reproduce the experimental data quite well. Based on compressive buckling appeared in the vicinity of the compressive end parts of the hysteresis loop, the critical values of damage are determined between 0.3 and 0.4.

The evolution equation of damage proposed in terms of the intrinsic damage time scale and its results in the modified Coffin-Manson LCF law can be extended in the future research for a statistical theory of life distribution under low cycle fatigue tests.
Shape Optimization of One-Chamber Cross-Flow Mufflers by GA Optimization
Authors: Chang Y.-C. , Chiu M.-C.
Published: May 2011

In order to reduce the venting noise within a confined room, the development of a high performance muffler within certain space constraints is imperative. Therefore, the main purpose of this paper is to develop an optimally shaped one-chamber cross-flow perforated muffler that will dramatically increase the acoustical performance within a limited space.

On the basis of plane wave theory, a four-pole system matrix for evaluating acoustical performance is derived by using a decoupled numerical method. Moreover, in order to search for a global optimum, a genetic algorithm (GA) with tournament selection in elitism and uniform crossover/mutation (analogous to a genes' evolutionary process) has been used for the mufflers' optimization. To assure the GAs' correctness, the STLs' maximization of one-chamber cross-flow perforated mufflers with respect to three targeted frequencies (200, 400, and 800Hz) is exemplified. Furthermore, a numerical case for dealing with an octave band noise emitted from an air compressor using one-chamber cross-flow mufflers has been introduced and fully discussed. To achieve a better optimization with the GA, various GA parameter sets were used. Before the GA operation is carried out, the mathematical models of cross-flow perforated mufflers are verified by comparing the numerical result and experimental data with those obtained by Sullivan and Wu respectively.

Consequently, the results reveal that the acoustical performance for a cross-flow perforated muffler is excellent. Moreover, they reveal that the optimization approach proposed in this study is easy, economical, and quite effective.
Active Piezoelectric Dynamic Absorbers on Vibration and Noise Reductions of the Fuselage
Authors: Huang Y.-M. , Tseng H.-C.
Published: May 2011

This research focuses on the analysis of vibration and noise control of a fuselage. A closed cylindrical shell is chosen as the theoretical model of the fuselage of an aircraft. The noise resulted from propellers is the main source of excitation to the fuselage vibration. The vibration can further induce interior noise within the fuselage. For attenuating the vibration of the fuselage and its accompanying interior noise, several pairs of piezoelectric sheets are attached to the shell. Each piezoelectric pair connected to an appropriate electric circuit can serve as a dynamic absorber. For a better performance, feedback control algorithms are introduced to form active absorbers. The dynamic responses of the composite cylindrical shell and the corresponding interior sound fields are analytically formulated. Numerical results are presented. The active absorbers are proven to yield good effects on vibration and noise reductions. Some parameter studies are also given in this manuscript.
A Theory for Elastic Potential Energy Change and Applied Stresses Accompanying Phase Transformation
Authors: Pan Huang Hsing
Published: May 2011

A theory is proposed to derive the resultant elastic potential energy change in the systems accompanying phase transformation for a finite concentration of inclusions. Based on the thermodynamic equilibrium, this elastic potential energy due to the interaction of ellipsoidal inclusions is employed to evaluate the critically applied stress that induces phase transformation. It is shown that the material system with the disc inclusions is easier to get the stress-induced transformation than that with other shapes. The inclusions with 3-D random orientation are the most effective one to have toughness increments. The height of the transformation zone strongly depends on the volume concentration and the shape of the inclusions. As compared with the experimental data, the theory is in an acceptable range of accuracy.
Parametric Identification of Frame Structures Using Transient Strains
Authors: Liu Pei-Ling , Chen Cheng-Chieh
Published: May 2011

An inverse method for identifying the element rigidities of frame structures is developed in this paper. The primary input of this method is the longitudinal strains of the frame elements measured in transient tests. The spectral element method is employed to formulate the equilibrium equation of the frame in the frequency domain. The equilibrium equation is rewritten in terms of the strains of the frame elements. The identification problem is then formulated as an optimization program in which the error norm of the equilibrium equation is minimized. The proposed method is applicable to total structure identification as well as substructure identification. The issue of identifiability is addressed in this study. A numerical example is presented to illustrate the proposed method. The influence of noise is investigated through the example.
The Modified Gait Patterns During Stepping on Slippery Floor
Authors: Chou You-Li , You Jia-Yuan , Lin Chii-Jeng , Su Fong-Chin , Chou Pei-Hsi
Published: May 2011

Upon encountering a wet or contaminated floor, people often modify their gait and posture to prevent themselves from slipping. This study was conducted to investigate the modification of gait patterns in healthy young adults as they approached and stepped on a slippery floor. Ten females and twelve males were instructed to walk at two different pacer speeds, 90 and 120steps/min, guided by a metronome, on a walkway with two forceplates placed at the center. During the step immediately prior to stepping on a forceplate with or without slippery disturbance, temporo-spatial parameters, selected kinematic parameters, and foot-floor reaction forces were evaluated in each cadence. The results showed that modifications of gait patterns for slip perturbation included shorter step length, increases of flexion angles of hip and knee joints,increases of plantarflexion angles of ankle joint with flattened foot, and decreases of the forward and backward groundreaction forces. However, it was found that such modifications for slip perturbation did not seem to efficiently prevent people from falling.
The Porous Effect on the Bottom Instability Under Partially Standing Waves
Authors: Hsiao Shih-Chun , Liu Philip L.-F.
Published: May 2011

In this paper, we extended Blondeaux [1], Liu, et al. [2] and Mei and Yu's [3] theories to study the porous effect on instability of rippled bed under the partially standing surface waves. Comparisons are made with both Blondeaux and Mei & Yu's theoretical predictions and experimental data performed by many other authors. We found that based on the linear instability analysis and the parameter regimes we explored the percolation effect can change the threshold conditions by 10 ∼ 20 percent and the seepage force is negligible up to O(∈). Furthermore, the steady streamings with or without porous effect show the considerable difference in intensities at the same locations and it might change the sediment transport rate especially the suspended load.
An Asymptotic Solution for Non-Linear Behavior of Imperfect Shallow Spherical Shells
Authors: Nie G.H. , Yao J.C.
Published: May 2011

This paper deals with non-linear behavior of an elastically restrained shallow spherical shell with imperfections and subjected to uniform normal load by the asymptotic iteration method. An asymptotic relation between the external load and central transverse displacement (deflection) of the structure incorporating the effects of the characteristic geometrical parameter, imperfection factor and edge-restraint coefficients is formulated. The corresponding solutions resulting from the use of the second and third iteration processes are compared with each other and available data. The numerical calculations show that the second iteration is adequate for the non-linear analysis of the structure. The effects of geometrical imperfections and boundary constraint coefficients on buckling of the structures are presented graphically.
Optimization of Piezoelectric Transformers Using Genetic Algorithm
Authors: Yang Y.-J. , Kang C.-Y. , Lee C.-K.
Published: May 2011

In this paper, we present the optimization works of two disk-type piezoelectric transformers (PTs), the single-output PT and the dual-output PT, by using the elite Genetic Algorithm (GA) and the finite-element solver, NTUPZE. The goal of optimization is to maximize the efficiency under the constraint that the voltage gain is greater than 50 for igniting CCFL. The design parameters are the radii of the outputelectrode sections and the electrode areas, as well as the dimensions of the device structure. With different electrical loading impedances, the voltage gain and the efficiency were computed using the NTUPZE. The results were also validated with measured data. The optimization process is parallelized by the MPI library and a PC cluster for improving the computation efficiency. The characteristics of the optimal designs with different loads are also calculated. The optimized voltage gain and the efficiency for the PT with single output electrode are about 53 and 91.9%, respectively. Also, the voltage gains and the efficiency of PT with dual output electrodes are above 57 and 91%, respectively.
Evaporation of Non-Newtonian Fluid in Porous Medium Under Mixed Convection
Authors: Shih M.-H. , Luo W.-J. , Yu K.-C.
Published: May 2011

This study investigates the problem of non-Newtonian liquid evaporation from an impermeable vertical plate in a porous medium under mixed convection conditions. The analysis examines the effects of non-Darcian flow phenomena on the evaporation process and investigates the heat and mass transfer characteristics under a range of flow conditions in the aiding and opposing flow types. The parameters of interest include Rak,non, Pex,non, Pr and Sc. The data required for the calculations include a fixed wall temperature of Tw = 45°C, a free flow temperature of T∞ = 20°C and an air free flow rate of u∞ = 4m/sec and the corresponding humidity of 50% flows over fixed temperature and moist wall.

The results indicate that an increasing buoyancy force enhances the mixing effect and therefore improves the rate of heat transfer, the latent heat flux is the primary mode of heat transfer in evaporation processes and the velocity gradient at the wall increases with an increasing buoyancy effect. Furthermore, the evaporation rate increases with a reducing flow index and an increasing buoyancy effect.
The Fission Process of N-Waves Over a Mild Slope
Authors: Lin Y.-H. , Hwung H.-H.
Published: May 2011

The aim of this paper is to investigate the mechanism of the fission process and the flow field of N-waves in the near-shore region. From the elaborate experimental analysis, a subsequence of a second soliton released during shoaling reigon is identified to realize the further evolution of N-waves over a sloping beach, in comparison with the non-fission case. The fission index is indicated by a dimensionless factor A0/d0, which is used to describe the nonlinearity as well. It is known that the reflecting wave and the breaking effect could easily initiate another soliton, especially for strong nonlinear case. A series of experiments were conducted in a super wave flume (300m × 5m × 5.2m) at Tainan Hydraulics Laboratory (THL), National Cheng Kung University (NCKU). The entire evolution of the leading and second solitons and the generation mechanism for the third soliton would be discussed in this paper.
The Vibration Reduction Analysis of a Rotating Mechanism Deck System
Authors: Wang Y.-R. , Chen T.-H.
Published: May 2011

In this paper, an optimized position of a mass-spring-damper vibration absorber is proposed for a rotating mechanism device (such as optical disk drive or rotary-wing and deck coupled system). A nonlinear 3-D theoretical model for a deck is established by Lagrange's equation. A 2-bladed rotor and deck (foundation) coupled aeroelastic system with vibration reduction device is presented and studied as well. The analytical solution is obtained by the Multiple-scales method for the case of no vibration absorber. The numerical results in time and frequency domain and with/no absorber are acquired. This research provides a theoretical background for the preliminary vibration reduction design for industries. It is found that the existing disk drives vibration can be reduced by simply adding the absorber at the end corner isolator of the deck, but without changing the main configurations. This will not only save costs but also increase testing efficiency, achieving the most cost-effective vibration reduction result.
Comparison of Combustion Models in Cleanroom Fire
Authors: Huang Y.-L. , Shiu H.-R. , Chang S.-H. , Wu W.-F. , Chen S.-L.
Published: May 2011

In this paper, the cleanroom fire simulation in a semi-conductor factory is investigated by using the commercial computational fluid dynamics (CFD) code. We using three different combustion models in the fire simulation. The combustion models including the volume heat source (VHS) model, the eddy break-up (EBU) model and the presumed probability density function (prePDF) model are considered to predict the cleanroom fire. The turbulence models coupled with different combustion models, while the radiation model is coupled with the turbulent combustion processes. Additionally, the discrete transfer radiation method (DTRM) is used in the global radiation heat exchange. For the fire simulation, the different combustion models are evaluated for their performance and compared with the experimental data from the literature to verify. Thus, these numerical simulations can be adopted as a useful tool to design and optimize the smoke control strategy in cleanroom fire.
Two-Dimensional Incompressible Flows by Velocity-Vorticity Formulation and Finite Element Method
Authors: Lo Der-Chang , Young Der-Liang
Published: May 2011

In this study, the motion of incompressible viscous fluid in a two-dimensional domain is solved by the finite element method using the velocity-vorticity formulation. To demonstrate the model feasibility, first of all the steady Stokes flow in a square cavity are computed. The results of square cavity flow are comparable with the numerical solutions of Burggraff (1966, FDM) [1]. Then the unsteady Navier-Stokes flow are computed and compared with other models [1∼4]. The results reveal that finite element analysis is a very powerful approach in the realm of computational fluid mechanics.
Design and Characterization of Valveless Impedance Pumps
Authors: Wen C.-Y. , Chang H.-T.
Published: May 2011

This study designs, fabricates and characterizes three valveless impedance pumps, namely a symmetrical pump with a circular cross-section, an asymmetrical pump with a circular cross-section, and an asymmetrical pump with a rectangular cross-section. The pressure head and flow rate characteristics of the three pumps are investigated as a function of the compression location, the compression frequency and the compression amplitude. The experimental results show that the flow is reversible in every case. Moreover, the pressure head is found to be significantly dependent on the actuating frequency, the compression location and the compression amplitude. However, no pressure head is produced when the pinching effect is applied at the center of channel configuration for the symmetrical pump. In the symmetrical pump, a maximum pressure head of 590mm is obtained at a frequency of 26Hz, and results in a flow rate of 0.581/min in the positive direction (i.e. from the left-hand reservoir of the pump to the righthand reservoir). Meanwhile, in the asymmetrical pumps with circular and rectangular cross-sections, respectively, maximum pressure heads of −620mm and −570mm are developed at frequencies of 36Hz and 32Hz, respectively. The corresponding flow rates are determined to be 0.641/min and 0.531/min, respectively. In both cases, the fluid moves in the negative direction (i.e. from the right-hand reservoir of the pump to the left-hand reservoir). Overall, the valveless impedance pumps developed in this study generate a high pumping rate, are easily fabricated and have no moving mechanical valves. As a result, they are eminently suitable for pumping applications in such diverse systems as biomedical devices, fuel cells, PC cooling systems, and so forth.
A Modified Non-Dominated Sorting Genetic Algorithm with Fractional Factorial Design for Multi-Objective Optimization Problems
Authors: Liu J.-L. , Lee T.-F.
Published: May 2011

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.
Computational Modeling of Microchannel Flows on Laboratory Compact Disk (LABCD)
Authors: Lin C.-M. , Lin T.-C. , Tan C.-M. , Tsai T.-H.
Published: May 2011

This paper models and analyzes flows in linear and curved microchannels on a rotating Laboratory Compact Disk (LabCD). The effects of centrifugal force are introduced into the governing equations of the microchannel flow to promote the fluidic velocity in the microchannel. The microchannel types on the LabCD must be designed following a process of mathematical identification. A flow model which takes into account the combined effects of viscosity, capillary forces, pressure difference and rotation is developed. A reduction-order technique is applied to obtain linear and nonlinear governing equations for flows in straight and curviform microchannels, respectively. The analytical solutions for the flow in the tubular microchannel are obtained using the Laplace transform method, while the numerical solutions for the curviform microchannel or microchannel with a varying cross-section are obtained using a piecewise linear method. The results show that the analyzed models are easily presented by a mathematical expression for the case of a tubular microchannel and simulated using a numerical program for the case of special microchannels. The modeling presented in this paper enables the performance of LabCD devices to be significantly enhanced by providing insights into the fluid flow behavior in microchannels of varying configurations under different rotational velocities.
The Dynamics of Balance Control During Slipping
Authors: Chou You-Li , You Jia-Yuan , Lin Chii-Jeng , Su Fong-Chin , Chou Pei-Hsi
Published: May 2011

This study investigates experimentally the velocity of the center of mass with respect to the base of support while subjects step on slippery flooring. The moments of the joints of both legs are also investigated to gain further insights into the source of any correlation found in reacting to slippery perturbation. Twenty-two healthy subjects dressed with safety harness walked first without and then with slippery perturbation, guided by a metronome at 120 steps/min and 90 steps/min cadence. Data were collected from a motion analysis system and force plates. Subjects falling had distinguishably slower velocity of center of mass with respect to the lead stance foot compared to the subjects maintaining balance at contralateral toe off. Larger knee flexion moment and ankle plantar flexion moment in the perturbed leg were found among subjects regaining balance. Faster velocity of center of mass with respect to base of support is noteworthy in subjects regaining balance from slippery perturbation. The response of lower extremities, especially about the thigh and leg in the lead stance limb, were important to improve the velocity of the center of mass with respect to base of support.
A Novel Method for Determining Poisson's Ratio of Thin Film Materials Using Ultra-Wide Micromachined Bilayer Cantilevers
Authors: Hou Max Ti-Kuang , Chen Rongshun
Published: May 2011

Narrow micromachined bilayer cantilevers, which are broadly used to determine different thin film material properties, have rarely been used to characterize the Poisson's ratio. It is difficult to be determined from the tip deflection, and thus the Poisson's ratio, of the narrow bilayer cantilever. In this paper, the tip deflections of ultra-wide micromachined bilayer cantilevers carry the needed information for finding the Poisson's ratio of thin-film materials. The measurement process and its corresponding model, based on the plate theory, is introduced and tested. The Poisson's ratio of the thin film is determined by comparing the tip deflections of the bilayer cantilever before and after the deposition of the upper layer. Because the fabrication processes are widely used in surface micromachining, the method can be easily implemented.
Collinear Crack Problem in Antiplane Elasticity for a Strip of Functionally Graded Materials
Authors: Chen Y. Z.
Published: May 2011

In this paper, elastic analysis for a collinear crack problem in antiplane elasticity of functionally graded materials (FGMs) is present. An elementary solution is obtained, which represents the traction applied at a point “x” on the real axis caused by a point dislocation placed at a point “t” on the same real axis. The Fourier transform method is used to derive the elementary solution. After using the obtained elementary solution, the singular integral equation is formulated for the collinear crack problem. Furthermore, from the solution of the singular integral equation the stress intensity factor at the crack tip can be evaluated immediately. In the solution of stress intensity factor, influence caused by the materials property “α” is addressed. Finally, numerical solutions are presented.
Velocity Distribution of Non-Darcy Flow in a Porous Medium
Authors: Leu J. M. , Chan H. C. , Tu Lih-Fu , Jia Yafei , Wang S. Y.
Published: May 2011

This study theoretically and experimentally investigates the velocity distributions of the interface boundary layer region in a porous medium. By combining a quadratic non-Darcy law and a practical eddy viscosity model, an analytical solution is derived and presented. Three additional parameters, i.e., the depth of the interface boundary layer region, the slip velocity, and proportionality constant, are contained in the analytical solution. The measured experimental data show the depth of the interface boundary layer region only depends on the characteristics of the porous medium rather than the relative flow depth, bed slop, or Reynolds number. The values of the slip velocity are found to increase with increasing relative mean clear fluid velocities. The proportionality constant plays an important role in modeling the penetration of turbulence and the associated momentum transfer. The measured experimental velocity distribution is used to evaluate the accuracy of the analytical predicted profile. The analytical results obtained in this study are in agreement with the measured experimental results.
An Analytical Approach for the Green's Functions of Biharmonic Problems with Circular and Annular Domains
Authors: Chen J. T. , Liao H. Z. , Lee W. M.
Published: May 2011

In this paper, an analytical approach for deriving the Green's function of circular and annular plate was presented. Null-field integral equations were employed to solve the plate problems while kernel functions were expanded to degenerate kernels. The unknown boundary data of the displacement, slope, normal moment and effective shear force were expressed in terms of Fourier series. It was noticed that all the improper integrals were avoided when the degenerate kernels were used. After determining the unknown Fourier coefficients, the displacement, slope, normal moment and effective shear force of the plate could be obtained by using the boundary integral equations. The present approach was seen as an “analytical” approach for a series solution. Finally, several analytical solutions were obtained. To see the validity of the present method, FEM solutions using ABAQUS were compared well with our analytical solutions. The displacement, radial moment and shear variations of radial and angular positions were presented.
The Magnetoelastic Problem for a Soft Ferromatnetic Elastic Half-Plane with a Crack and a Constant Magneic Induction
Authors: Yeh C.-S. , Ren C.-W.
Published: May 2011

The stress state of a magnetized elastic half-plane with a uniformly pressurized crack parallel to the free surface subjected to a uniform magnetic induction Bo is considered. The linear theory for a soft ferromagnetic elastic solid with muti-domain structure, which has been developed by Pao and Yeh [1] is adopted to investigate this problem. A numerical method is developed to determine the magnetoelastic stress intensity factor. The effect of the magnetic field and the boundary conditions on the magnetoelasitc stress intensity factor are shown graphically and numerically.
General Interface Conditions in Surface Elasticity of Nanoscaled Solids in General Curvilinear Coordinates
Authors: Weng C.-N. , Chen T. Y.
Published: May 2011

We consider an arbitrarily curved three-dimensional thin interphase with surface stresses between two anisotropic solids. Letting the interphase be infinitely thin and assuming that the kinematic constraints between the two anisotropic solids remain intact during the deformation, we derive the interface jump conditions along the interface. These conditions are derived analytically in general non-orthogonal curvilinear coordinates in the setting of linear elasticity and steady state conduction. The proof is made directly from a force balance consideration of a small element of the curved interface. Simplified results are also deduced for oblique coordinate systems in which the coordinate axes are straight lines that are not perpendicular to each other. When the axes are orthonormal, we prove that our results agree with the previous known Young-Laplace conditions in solids.
Dynamic Interactions of a High-Speed Vehicle and a Distributed Discretely Supported Guideway
Authors: Hu C.-Y. , Chen K.-C. , Chen J.-S.
Published: May 2011

This study investigates the dynamic interactions between a vehicle and guideway of a high-speed ground transportation system based on 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 to a two-dimensional vehicle model with primary and secondary suspensions. Three kinds of loading modes acting at each beam of guideway are first developed according to the locations of suspensions of vehicle. Coupled equations of motion of both vehicle and guideway in various loading modes are derived and solved by using numerical integration method. The simulations have been performed to investigate the parameters of vehicle/guideway system which may affect the steady-state responses of the vehicle and guideway.
Optimal Design and Operation on Convergent-Divergent Nozzle Type No-Moving-Part Valves (NMPV) in Microchannel
Authors: Leu T.-S. , Wang C.-T. , Sun J.-M.
Published: May 2011

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.
Unsteady Analysis of the Flow Rectification Performance of Conical Microdiffuser Valves for Valveless Micropump Applications
Authors: Wang Y.-C. , Lin S.-H. , Jang D.
Published: May 2011

A numerical analysis of the unsteady flows in conical microdiffusers appropriate for valveless micropump applications is performed. The rectification efficiency of the diffuser valve is calculated directly as a function of geometric and operational parameters, including diffuser angle, diffuser slenderness, sizes of actuation chamber and inlet/outlet port, actuation frequency, and amplitude of actuation pressure. The computational results show that the diffuser with diverging angle of 10° and slenderness of 7.5 has the best rectification performance. For large actuation pressure amplitude, the optimal rectification efficiency and its corresponding Roshko number are relatively high. At the optimal Roshko number, the flow impedance is found to be dominated by fluid inertia. Sizes of the pump chamber and inlet/outlet port are shown to have a prominent effect on valve performance. Small actuation chamber or small inlet/outlet port can significantly deteriorate the valving performance of the diffuser.
Atomistic Analysis of Nano-Scale Crystal Plasticity in Thin Metal Films
Authors: Shen Y.-L. , Leger R. W.
Published: May 2011

Numerical simulations based on molecular statics are carried out to study nano-scale plastic deformation behavior in thin metal films. Particular attention is devoted to correlating the overall mechanical response and the underlying crystal defect mechanisms during mechanical loading. The simulations are within the two-dimensional framework involving pair molecular interactions in singlecrystal materials. Special modeling features are utilized for studying the formation of dislocations, interface characteristics, and defect interactions. Specific problems investigated in this work include: plastic deformation and tensile fracture in a free-standing film, interface-constrained plasticity in substrate-bonded films, and homogeneous nucleation of dislocations during nanoindentation.
Heat and Mass Transfer in an Inclined Semi-Annular Enclosure
Authors: Wang L.W. , Kung Y.C. , Lai S.D.
Published: May 2011

An experimental investigation of heat transfer carried out for a semiannular enclosure. Inner and outer walls of the enclosure were kept at different but constant temperatures. The semiannular enclosure was filled with a CuSO4 - H2SO4 - H2O solution. An electrochemical method has been used for the mass transfer. The purpose of this study is to investigate flows resulting from buoyancy due to a combination of both temperature and concentration gradients in the enclosure. The flow structure in the enclosure was visualized by the shadowgraph technique. Flow visualization photograph showed interesting multi-cell flow structures in the enclosure for the cooperating and opposing thermal and solutal buoyancy. An optical technique is based on the idea that the intensity of the light beam absorbed by the copper sulphate solution is proportional to the solution concentration when the light beam passes through the solution. For each flow regime the mass transfer coefficient across the enclosure was also measured. The ranges of the dimensionless parameters studied in the experimental were Ar = 0.23, k = 2.5, Sc = 1700∼2300, Pr = 6.5 ∼ 7.3, Grt = 104 ∼ 106, N = −15.44 ∼ 6.16, θ = 45°∼90°.
On Invariants of Anisotropic Elasticity Constants
Authors: Wang Min-Zhong , Zhao Bao-Sheng
Published: May 2011

With the aid of a six-dimensional special eigenvectorq, T.C.T.Ting finds five new invariants of anisotropic elasticity constants. The purpose of this paper is to consider some character of the eigenvectorq. It is pointed that the six-dimensional special eigenvectorqis unique, if it is independent of the coordinate transformation, and the general form of a three-rank orthogonal matrix is given if it has a three-dimensional special eigenvector likeq. In addition, the concept of the special eigenvectorqis extended and 20 invariants of anisotropic elasticity constants are obtained under rotation about x3-axis.
On the Energy Release Rate of Elliptical Cracks in Anisotropic Elastic Media
Authors: Xue Yibin , Qu Jianmin
Published: May 2011

This brief note discusses some issues related to the calculation of energy release rate for elliptical cracks in anisotropic solids. By using the Stroh formalism, analytical expressions of the energy release rate are obtained for elliptical cracks in an unbounded anisotropic solid. Because of material anisotropy and geometric asymmetry of the crack, the local energy release rate varies along the crack front. The average energy release rate can be obtained by integrating the local energy release rate over the entire crack front. On the other hand, the total work done by the crack-surface traction on the entire crack opening displacement can be easily evaluated once the crack opening displacement is known. It is shown that the average energy release rate is equal to the rate of change per unit crack area increment of the work done by the external load on the crack opening displacement.
Green's Function for the Damped Wave Equation on a Finite Interval Subject to Two Robin Boundary Conditions
Authors: Yen David H. Y.
Published: May 2011

The Green's function for the damped wave equation on a finite interval subject to two Robin boundary conditions is studied. The problem for a semi-infinite interval with one Robin boundary is considered first by the Laplace transform method to establish the reflection principle at a Robin boundary. It is seen that the reflected wave generated by an exiting wave at a Robin boundary is a convolution involving the exiting wave and some kernel function. This generalizes the well known classical results for reflections at Dirichlet and Neumann boundaries. The reflection principle at a Robin boundary is then used for the finite interval case by considering multiple reflections and this leads to an infinite sequence of waves. In order to justify the results obtained here we also study the finite interval case by the Laplace transform method. The Laplace transform of the Green's function is expanded, for large values of the transform parameter, into an infinite series of negative exponentials and then inverted term by term. Agreement is reached between these two approaches.
Design and Simulation of Continuous Dielectrophoretic Flow Sorters
Authors: Leu T.-S. , Chen H.-Y. , Hsiao F-B.
Published: May 2011

This paper was an attempt to investigate, through numerical simulation, the designs of DEP flow sorters when applied with different ratios of the electrodes to generate different electrical fields, and to explore the sorting capability of the flow sorters, defined as the degree of particle deflection, under different operation of parameters.

In order to obtain the maximal DEP negative particle deflection, which was believed as an indicator of greater sorting capability, we have investigated different non-uniform electrical fields produced by combinations of electrodes with different length of two poles, ranging from 1:2 up to 1:9. The finding of numerical simulation indicated that the length ratio 1:3 of the electrode poles produced the electrical fields that maximized the particle deflection.

Moreover, different parameters of applied voltage, flow rate, particle diameters, and distance between two electrical poles were designed to investigate their effects on particle deflection of flow sorters. The numerical simulation of the study showed that the DEP flow sorter was demonstrated as a linear system with respect to the applied voltage and particle diameter. In this study, we tried to operationally define flow rate as the time duration while the flow passed the electrical fields, and thus investigated how particle deflect with the different time given. We found that the particle deflected more when the flow was allowed with longer time to pass the electrical fields. The study also showed that the distance the particles deflect from the centerline is in inverse proportion to the square distance between the two electrical poles.
Dependence of the Smagorinsky-Lilly's Constant on Inertia, Wind Stress, and Bed Roughness for Large Eddy Simulations
Authors: Chung W.-H.
Published: May 2011

Equations governing large eddy simulations are usually closed by incorporating with the Smagorinsky-Lilly's turbulence model of eddy viscosity. The model contains a so-called filtering length and a Smagorinsky-Lilly “constant” that changes among different researchers. The variation range of the constant is wide and its value is usually determined in a sense of “guessing”. Since the constant is closely related to the magnitude of eddy viscosity, hence to our numerical solutions eventually, setting a more precise and determinate procedure for prescribing the constant seems to be worthy it. The constant,CSL, is first estimated in use of the properties of fluid flow within the inertia subrange. Then, along with a general derivation, the explicit closed-form expression for the constant is presented for steady uniform flows. It is found that, with the analogy between the filtering technique and Reynolds average,CSLmay not necessarily be constant but proportional to the Manning n and water depth. Other than the determination ofCSL, the vertical flow velocity profile in an infinitely long wide rectangular channel without spiral flow motion is obtained through the use of the Smagorinsky-Lilly's turbulence closure model. It is shown analytically that the velocity profile in unsteady open channel flow can be expressed as a function of an integration functionJn(z)that accounts for wind stress and inertia terms. With the velocity profile, effects of inertia terms, wind stress, and channel bed roughness onCSLare deeply explored in response to the dependence ofCSLonJn(z).
An Investigation of the Diffusion Errors in Diffusion Vortex Methods
Authors: Huang M.-J. , Chen Y.-Y.
Published: May 2011

To model the viscous effect, the core area of particles in Leonard's core spreading vortex method must grow linearly in time, which however results in growing convective errors and consequently causes the failure of a correct convergence of the method to the Navier-Stokes equations. The so-called diffusion vortex method was proposed and claimed to have smaller core-area growth rates because part of the viscous effect is modeled into the movement of particles. The growth rates however are non-uniform and an additional diffusion error arises due to the nonzero divergence of the diffusion velocity. The goal of this work is to analyze the associated errors of several existing versions of the diffusion vortex method and compare them with that of Leonard's. Simulations of two axisymmetric flows are performed to measure the involved diffusion errors and consequently distinguish these diffusion vortex methods. The results show that the circulation conservation is important, besides a small core-area growth rate, in obtaining a good accuracy. Under the consideration of both efficiency and accuracy, the diffusion vortex method in which each vortex particle conserves its own circulation on its core area alone is recommended.
Study of Static Fracture Propagation by Element-Free Galerkin Method With Singular Weight Function at Crack Tip
Authors: Shen K.-J. , Sheng J. P. , Wang C.-Y.
Published: May 2011

Element-free Galerkin method (EFGM) based on moving least-square curve fitting concept is presented and applied to elastic fracture problems. Because no element connectivity data are needed, EFGM is very convenient and effective numerical method for crack growth analysis. This paper is intended as an investigation of crack trajectory for different notch locations under three-point bending test. The initial crack growth angles obtained by element-free Galerkin method in comparison with those obtained by lab test reveal that both results are very close. However, numerical results also show that the location of an original notch can stronger affect the variation of crack path for different increment. The stress intensity factors (SIF) of cracks under three-point bending test with different increment are also investigated by EFGM.
Hyperresolution global land surface modeling: Meeting a grand challenge for monitoring Earth's terrestrial water
Authors: Wood Eric F. , Roundy Joshua K. , Troy Tara J. , van Beek L. P. H. , Bierkens Marc F. P. , Blyth Eleanor , de Roo Ad , Döll Petra , Ek Mike , Famiglietti James , Gochis David , van de Giesen Nick , Houser Paul , Jaffé Peter R. , Kollet Stefan , Lehner Bernhard , Lettenmaier Dennis P. , Peters‐Lidard Christa , Sivapalan Murugesu , Sheffield Justin , Wade Andrew , Whitehead Paul
Published: May 2011

Monitoring Earth's terrestrial water conditions is critically important to many hydrological applications such as global food production; assessing water resources sustainability; and flood, drought, and climate change prediction. These needs have motivated the development of pilot monitoring and prediction systems for terrestrial hydrologic and vegetative states, but to date only at the rather coarse spatial resolutions (∼10–100 km) over continental to global domains. Adequately addressing critical water cycle science questions and applications requires systems that are implemented globally at much higher resolutions, on the order of 1 km, resolutions referred to as hyperresolution in the context of global land surface models. This opinion paper sets forth the needs and benefits for a system that would monitor and predict the Earth's terrestrial water, energy, and biogeochemical cycles. We discuss six major challenges in developing a system: improved representation of surface‐subsurface interactions due to fine‐scale topography and vegetation; improved representation of land‐atmospheric interactions and resulting spatial information on soil moisture and evapotranspiration; inclusion of water quality as part of the biogeochemical cycle; representation of human impacts from water management; utilizing massively parallel computer systems and recent computational advances in solving hyperresolution models that will have up to 109 unknowns; and developing the required in situ and remote sensing global data sets. We deem the development of a global hyperresolution model for monitoring the terrestrial water, energy, and biogeochemical cycles a “grand challenge” to the community, and we call upon the international hydrologic community and the hydrological science support infrastructure to endorse the effort.
Reducing Obesity Stigma: The Effectiveness of Cognitive Dissonance and Social Consensus Interventions
Authors: Ciao Anna C. , Latner Janet D.
Published: May 2011

Obese individuals experience pervasive stigmatization. Interventions attempting to reduce obesity stigma by targeting its origins have yielded mixed results. This randomized, controlled study examined the effectiveness of two interventions to reduce obesity stigma: cognitive dissonance and social consensus. Participants were college undergraduate students (N = 64, 78% women, mean age = 21.2 years, mean BMI = 23.1 kg/m2) of diverse ethnicities. Obesity stigma (assessed with the Antifat Attitudes Test (AFAT)) was assessed at baseline (Visit 1) and 1 week later, immediately following the intervention (Visit 2). Participants were randomly assigned to one of three intervention groups where they received standardized written feedback on their obesity stigma levels. Cognitive dissonance participants (N = 21) were told that their AFAT scores were discrepant from their values (high core values of kindness and equality and high stigma), social consensus participants (N = 22) were told their scores were discrepant from their peers' scores (stigma much higher than their peers), and control participants (N = 21) were told their scores were consistent with both their peers' scores and their own values. Following the intervention, omnibus analyses revealed significant group differences on the AFAT Physical/Romantic Unattractiveness subscale (PRU; F (2, 59) = 4.43, P < 0.05). Planned contrasts revealed that cognitive dissonance group means were significantly lower than control means for AFAT total, AFAT PRU subscale, and AFAT social/character disparagement subscale (all P < 0.05). No significant differences were found between social consensus and controls. Results from this study suggest that cognitive dissonance interventions may be a successful way to reduce obesity stigma, particularly by changing attitudes about the appearance and attractiveness of obese individuals.