bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of a Piezoelectric Bimorph Harvester with Variable Width
Authors: Hu H. P. , Cui Z. J. , Cao J. G. 
Published: May 2011

AbstractThis article analyzes the performance of a piezoelectric energy harvester in the flexural mode for scavenging ambient vibration energy. The energy harvester consists of a piezoelectric bimorph plate with a variable width. A theoretical study is performed and the computational results show that the output power density increases initially, reaches a maximum, and then decreases monotonically with the increasing width, underscoring the importance for the width design of the scavenging structure. Further analysis indicates that the peak of output power density is determined by both the bimorph deformation amplitude and the efficiency in scavenging-energy. The analysis for this simplified model piezoelectric harvester provides a framework for further development on design guidelines for piezoelectric energy harvesters of optimal performance.
Improved Frequency Responses of Saw Filters with Interdigitated Interdigital Transducers on ZnO/Diamond/Si Layered Structure
Authors: Lin C.-M. , Wu T.-T. , Chen Y.-Y. , Chou T.-T. 
Published: May 2011

AbstractThere are many investigations on surface acoustic wave (SAW) filters with interdigitated interdigital transducers (IIDT) in the last two decades; however, the same is not true for the case of IIDT SAW filters fabricated on layered piezoelectric substrates. Therefore, the aim of this study is to explore the characteristics of the IIDT structures on layered piezoelectric media and further, to improve the frequency response of layered IIDT SAW filters with the unique dispersive properties of a layered piezoelectric structure. A method based on the effective permittivity approach, the coupling of modes (COM) model, and the H-matrix is utilized to analyze the characteristics of IIDT on the ZnO/Diamond/Si layered structure. In this study, it is shown that by optimizing the ratio of input to output IDT pairs, the side-lobe level of frequency responses on the ZnO/Diamond/Si layered structure could be suppressed, similar to that on the half-space substrate. In addition, it is also proved that the notched pass-band could be flattened out by designing the center frequency on the local maximum of the electromechanical coupling coefficient dispersion curve.
Effective Transverse Elastic Properties of Composites Containing Two Types of Continuous Fibers
Authors: Lin P. J. 
Published: May 2011

AbstractBased the previously published model on the two-dimensional micromechanical fiber interaction framework of two-phase composites, effective transverse elastic properties of composites containing two types of randomly located yet unidirectionally aligned circular fibers are studied in this paper. Approximate local solutions for the interaction problem of two randomly located circular fibers of different elastic properties are presented. A fiber-reinforced composite material containing two extreme types of inclusions, voids and rigid fibers, is also investigated. Comparison with Hashin's variational bounds and Mori-Tanaka method, the current approach provides reasonably accurate predictions for three-phase composites. Finally, numerical simulation examples are implemented to demonstrate the capability of the proposed model.
Numerical Study for Centrifugal Model Tests of a Single Pile Foundation Installed in Sandy Deposits
Authors: Lu C. W. 
Published: May 2011

AbstractIt is believed that a dynamic analysis is urgently required to provide a more reliable numerical method for seismic evaluation of a full system, which includes foundation, super structure, and ground in earthquake zones such as Taiwan and Japan. A centrifugal model test of pile foundation is simulated numerically using a three-dimensional finite-element model (3D-FEM) code in this study. In the numerical simulation, parameters of the sandy soils in tij model that are derived from accumulated experiences in static tests are first calibrated by centrifugal vibration tests of sandy ground. Model tests of a single pile foundation installed in grounds of same unit weight of soil as in the static tests are then simulated using the calibrated parameters. The numerical simulation resulted in a good agreement with the corresponding physical model tests. By comparing the computed and the observed results, one can find and confirm that it is necessary to employ an appropriate soil model to reproduce dynamic soil behavior due to major vibration. Representation of pile by beam element in the numerical analysis is applicable when attention is paid on the response acceleration of top of pile foundation, on soils at some distances to the pile foundation, and on bending moment of the pile in a stiffer ground. Equal-displacement boundary condition for two-side boundaries is proven to be efficient. To reduce the computation time, the assumption of a constant damping of viscous matrix is acceptable.
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

AbstractIn 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

ABSTRACTIn 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

ABSTRACTThis 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

ABSTRACTA 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

ABSTRACTAn 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

ABSTRACTUpon 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

AbstractIn 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

AbstractThis 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

ABSTRACTIn 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

ABSTRACTThis 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

ABSTRACTThe 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

AbstractIn 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

AbstractIn 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

ABSTRACTIn 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

ABSTRACTThis 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.