bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Neural Network and Genetic Algorithm to the Optimum Design of Perforated Tube Mufflers
Authors: Chiu M.-C. , Chang Y.-C.
Published: May 2011

Research on new techniques of perforated silencers has been well addressed. However, the research work on shape optimization for a volume-constrained silencer within a constrained machine room is rare. Therefore, the optimum design of mufflers becomes an essential issue. In this paper, to simplify the optimum process, a simplified mathematical model of the muffler is constructed with a neural network using a series of input design data (muffle dimensions) and output data (theoretical sound transmission loss) obtained by a theoretical mathematical model (TMM). To assess the optimal mufflers, the neural network model (NNM) is used as an objective function in conjunction with a genetic algorithm (GA). Moreover, the numerical cases of sound elimination with respect to pure tones (500, 1000, 2000Hz) are exemplified and discussed.

Before the GA operation can be carried out, the accuracy of the TMM is checked by Crocker's experimental data. In addition, both the TMM and NNM are compared. It is found that the TMM and the experimental data are in agreement. Moreover, the TMM and NNM confirm.

The results reveal that the maximum value of the sound transmission loss (STL) can be optimally obtained at the desired frequencies. Consequently, it is obvious that the optimum algorithm proposed in this study can provide an efficient way to develop optimal silencers.
An Innovative Technique for Simultaneous Measurement of Three-Dimensional Kinematics and Induced Flow of a Swimming Fish
Authors: Ting S.-C. , Yang J.-T.
Published: May 2011

In this work, we introduced an innovative technique that enables simultaneous measurement of the 3D kinematics and 2D–3 Components fluid velocities of the induced flow of a swimming fish, which greatly advanced the experimental technique for research in fish biomechanics. This technique was theoretically based on the combined use of new reconstruction formulas of position and the calibration polynomials of stereo-DPIV, employing only two cameras in the imaging system. Both kinematic and hydrodynamic characteristics of a fish executing three-dimensional and complicated locomotion are readily and accurately revealed. Measuring simultaneously 3D kinematics and hydrodynamics is significantly important for an accurate investigation of fish biomechanics because fish motions are three-dimensional. We demonstrate results of 3D kinematics and fluid velocity fields measured in the wake of a maneuvering pectoral fin of a fish, which proves the effectiveness and usefulness of this technique. The application of this technique is extendable to biomechanics research concerning locomotion of both swimming and flying animals.
Investigation of Dynamic Responses for Piezoceramic Plates in Resonance by Using Fiber Bragg Grating
Authors: Chuang K.-C. , Ma C.-C. , Liang C.-Y.
Published: May 2011

A fiber Bragg grating (FBG) sensor system which can simultaneously measure the point-wise, out-of-plane and in-plane dynamic displacements is proposed. A demodulation system based on the fiber Bragg grating filter is used. The steady-state responses of particle motions of a piezoceramic plate measured by the FBG out-of-plane and in-plane displacement sensors are simultaneously compared with those obtained by a laser Doppler vibrometer (LDV) and a surface-mounted FBG strain sensor, respectively. The integration of the FBG displacement sensor with a dynamic signal analyzer (FBG-DSA) forms a measurement system which has the ability to acquire the frequency response of a piezoceramic plate. An LDV-DSA system and an impedance analyzer are used to compare the results obtained from the dynamic signal analyzer combined with the out-of-plane FBG sensor (OFBG-DSA) and the in-plane FBG sensor (IFBG-DSA), respectively. The experimental results of the impulse excitation as well as the random excitation of the piezoceramic plate are also presented. To explain the experimental results, an optical full-field measurement technique called amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and FEM numerical calculations are also used to provide full-field vibration mode shapes of the piezoceramic plate. These results indicate that the proposed displacement sensor system has the multiplexing capability to measure the dynamic displacements up to 45kHz.
Reliability-Based Code Calibration for Axial Ultimate Bearing Capacities of Single Bored Piles in Taipei Basin
Authors: Ching J. Y. , Lin H.-D. , Yen M.-T.
Published: May 2011

In Taipei, many pile proof load tests were not conducted to failures but only to a multiple (e.g., 2) of the design load. This leads a difficulty of incomplete information: For these test results, the ultimate bearing capacities of the test piles are unknown. This paper addresses the issue of calibrating resistance factors of piles for the axial ultimate bearing capacities based on the incomplete information from these tests. A simplified probabilistic method is proposed to resolve this issue. A local pile test database of Taipei is presented, and the analysis results show that the inclusion of the incomplete pile load test data helps in calibrating the resistance factors. Moreover, it is found that the calibrated resistance factors for the axial ultimate bearing capacities are consistent to the safety factors that are adopted in the current Taiwan design code. This paper also addresses another important issue for the pile design in Taipei: the end bearing capacity in the sandstone layer is very uncertain. A maximum likelihood method is taken to identify the best estimate for this end bearing capacity. The conclusion of this paper may be useful for reliability-based designs for the axial ultimate bearing capacities of single bored piles in the Taipei region.
A Finite Element Study of the Effect of Contact Forces Between an Implant-Retained Crown and its Adjacent Teeth on Bone Stresses
Authors: Chaichanasiri E. , Nanakorn P. , Tharanon W. , Vander Sloten J.
Published: May 2011

Most of finite element (FE) models used to study single tooth dental implants consider only an isolated implant. It is of course more realistic to model also the adjacent teeth of the implant. However, including the adjacent teeth significantly increases the complexity of the model and necessitates the complex contact analysis. The main difference between the FE models with and without the adjacent teeth is that the model without the adjacent teeth cannot capture the effect of the contact forces that are transferred between the implant-retained crown and the adjacent teeth. In this study, the hypothesis that the contact forces are not important is verified by the FE contact analysis. Realistic 3D FE models of a mandible and a single tooth implant with and without adjacent teeth are constructed and analyzed. It is found from the results that the difference between the maximum bone stresses of the two models is very small when various loading directions are considered. The obtained results, therefore, indicate that the effect of contact forces between a dental implant and its adjacent teeth is not significant. Consequently, the adjacent teeth can be excluded from FE models if various loading directions are considered.
A Three-Dimensional Aggregate Generation and Packing Algorithm for Modeling Asphalt Mixture with Graded Aggregates
Authors: Xu R. , Yang X.H. , Yin A.Y. , Yang S.F. , Ye Y.
Published: May 2011

A three-dimensional aggregate generation and packing algorithm applicable for modeling asphalt mixture with high content of graded aggregates is presented in this paper. In the algorithm, arbitrary-shaped polyhedra are used to model aggregates, so that the effect of aggregate shape on the mechanical performance of asphalt mixture can be considered. The algorithm consists of two steps: Aggregate generation and packing. Polyhedra are created by extending triangular fundaments and treated as visualized aggregates after passing through convex control and sharpness judgment. After that, graded aggregates are taken out from the aggregate base and randomly packed in a given cylindrical or cubical region one by one equiprobably. Overlapping between nearby aggregates is avoided by the help of Boolean partition operation in ANSYS. Finally, some asphalt mixture samples with a given gradation are modeled as examples, and their effective elastic properties and creep behaviors under uniaxial compression are simulated.
Magnetic Fields Generated by a Mechanical Singularity in a Magnetized Anisotropic Half Plane
Authors: Yeh C.-S. , Ren C.-W.
Published: May 2011

The induced magnetic fields generated by a line mechanical singularity in a magnetized anisotropic half plane are considered in this paper. The linear theory for a soft ferromagnetic elastic with multidomain structure, which has been developed by Pao and Yeh [1] is adopted to investigate this problem. By applying the Fourier transform technique, the exact solutions for the generated magnetic inductions due to various mechanical singularities such as single force, a dipole, single couple and dislocation are obtained in a closed form. The distributions of the generated inductions on the surface are shown graphically.
Adaptive Trajectory Control and Dynamic Friction Compensation for a Flexible-Link Robot
Authors: Erfanian Vahid , Kabganian Mansour
Published: May 2011

Friction compensation techniques are studied for control of a flexible-link robot based on the LuGre friction model. To overcome the problem of uncertain parameters in the friction model, adaptive control schemes are used for two different types of parametric uncertainties. A novel dual-observer technique is proposed to estimate the internal state inside the friction model. A distributed-parameter dynamic model is used for the flexible arm to design the controllers. The Lyapunov stability theorem is used to guarantee the global asymptotic stability of the controllers. The performance of position tracking and link vibration attenuation is verified through experimental results. The results also confirm the effectiveness of the proposed friction compensation schemes.
Visualization of Flow Phenomena for Confined Circular Jet Impingement
Authors: Hsieh Shou-Shing , Huang Jung-Tai , Tsai Huang-Hsiu
Published: May 2011

Flow visualization was made for water to broaden our fundamental understanding of the physical process of the confined circular jet impingement. Transition (with laminar wall jet) and turbulent regimes are identified. A correlation of boundary layer thickness was developed in terms of relevant parameters.
Measurements of Fractal Properties of Premixed Turbulent Flames and Their Relation to Turbulent Burning Velocities
Authors: Yang S. I. , Shy S. S.
Published: May 2011

The fractal properties of premixed transient flames propagating downwards through a near-isotropic turbulent flow field in a fan-stirred cruciform burner were investigated. The long vertical section of the cruciform burner was used to provide a downward propagating premixed flame at 1 atm. The large horizontal vessel equipped with a pair of counter-rotating fans and perforated plates at each end was used to generate near-isotropic turbulence. Turbulent flame front images were obtained using high-speed laser sheet imaging for both methane-air and propane-air mixtures. The nondimensional turbulent intensity (u′/SL), Reynolds number based on the integral length scale, and turbulent Karlovitz number were varied from 1 to 10, from 698 to 6032, and from 0.05 to 1.43, respectively. Hundreds of runs for each experimental condition were carried out to obtain sufficient images of these turbulent transient flame fronts just in the central uniform region. These images were then processed to extract fractal dimension, inner and outer cutoffs using both the circle and the caliper methods. It was found that the mean fractal dimension is only 2.18, nearly independent of u′/SL, in support of recent Bunsen-flame results found by Gülder and his co-workers. This contradicts the findings of many previous studies in which the fractal dimension may approach asymptotically to a value of 2.33 when u′/SL > 3. The inner (εi) and outer (ε0) cutoffs are found to be nearly constant for all flames studied, where ε0 is an order of magnitude greater than εi and it is smaller than the integral length scale of unreacted turbulence. Finally, the present fractal characteristics cannot predict turbulent burning velocities correctly when the available fractal closure model was used, indicating a limit of the fractal analysis on prediction of turbulent burning velocities.
Inversion of Residual Stress
Authors: Kuo M. K. , Lee H. T.
Published: May 2011

A technique for inverting residual stress based on a theory of acoustoelasticity is presented. A general incremental constitutive relation is first derived for a pre-stressed material subjected to an additional infinitesimal elastic deformation. The theory is then employed on using ultrasonic means to evaluate residual stresses of residually stressed materials. The residual stresses are assumed to be homogeneous in materials as usual. The only major assumption in this formulation is that the additional deformations caused by ultrasonic evaluating process are infinitesimal and elastic. No assumption on the origin of residual stresses is needed, nor the assumption on the possible existence of “natural state” of the materials. Successful inversion of residual stresses are demonstrated through a preliminary numerical experiment.
Gas Evolution in Rotating Electrochemical Cells Under Reduced and Normal Gravity Conditions
Authors: Weng Fang-Bor , Su Ay , Kamotani Yasuhiro , Ostrach Simon
Published: May 2011

Electrochemical experiments in microgravity are essential for the optimum design of advanced life support systems and power storage systems in space. In the absence of gravity, the evolved gas bubbles will clog the electrode and slow the reaction. Here, a rotating cell concept is introduced as a plan for improving mass transfer and bubble removal in a microgravity environment. A primary experimental study of bubble behavior in rotating water electrolysis cells has been done in reduced gravity through KC-135 parabolic flight. The results show that the cell resistance decreases with increasing rotation rate. Without rotation, the bubbles stick on the electrode surface during reduced gravity period, thus, the cell efficiency degrades. Mass transfer enhanced by bubble generation is investigated in ground-based work at high rotation rate of test cells, so that gravitational effects are minimized.
Refining Strategy of the Supersonic Turbulent Flow Over a Backward-Facing Step
Authors: Yang Shih-Ying
Published: May 2011

A modified error indicator is developed to study the supersonic turbulent flow over a backward-facing step. In the Cartesian coordinate system, the unsteady Navier-Stokes equations with a low-Reynolds-number k−ε turbulence model are solved. The modified error indicator, in which the unified magnitude of substantial derivative of pressure and unified magnitude of substantial derivative of weighted vorticity magnitude are incorporated, is applied to treat the mesh refining. To assess the present approach, the transonic turbulent flow around an NACA 0012 airfoil is performed. Based on the comparison with the experimental data, the accuracy of the present approach is confirmed. According to the high-resolutional result on the adaptive mesh, the structure of backstep corner vortex, expansion wave and oblique shock wave is distinctly captured.
Nonlinear Finite Element 2D Analysis for RC Beams Strengthened by Epoxy Bonded Steel Plates
Authors: Lin Wen-Shan , Kao Chen-Chang
Published: May 2011

This paper presents the nonlinear finite element modeling of the global behavior for RC beam strengthened by externally epoxy bonded steel plates up to failure. In addition to the consideration of nonlinear behavior and cracking of concrete, the model involves interface element to capture not only the shear and normal stress concentration at the plate curtailment, but also the separation due to the exceeded peak shear and normal stress. The internal steel bar using truss element and the external steel plate using deformation theory of plastic have been confirmed by compare finite element solution with plastic theory. The proposed finite element solutions result in close correlation with experimental data available for RC beams strengthened by epoxy bonded steel plates with different thickness.
Measurement of Acoustoelastic Effect of Surface Wave with an Improved Acoustic Transducer
Authors: Lee Yung-Chun , Kuo Shi Hoa
Published: May 2011

A new acoustic transducer and measurement method have been developed for precise measurements of surface wave velocity. This technique is used to investigate the acoustoelastic effect of surface waves in polymethylmethacrylate (PMMA). The transducer utilizes two miniature conical PZT elements for surface wave transmitter and receiver, and hence can be viewed as a point-source/point-receiver (PS/PR) surface wave transducer. Surface waves are excited and detected with the PZT elements and the surface wave velocity can be accurately determined over a small measurement area. Improvement has been made so that the transducer can be used for both conductive and non-conductive materials. The transducer is then applied to measure the acoustoelastic effect of surface wave in a PMMA specimen. The acoustoelastic coefficients are experimental determined.
Deformation Kinetics of Steady Creep in Sn/Pb Solder Alloys With Applications
Authors: Lee C. F. , Chang M. K. , Chung W. K.
Published: May 2011

In this paper, a constitutive equation of steady creep rates:

is derived based on a liaison of the theory of irreversible thermodynamics of continuous media with internal state variables (ISV); and the deformation kinetics. In steady creep, only one ISV is used, whose evolution equation is derived by the concepts of deformation kinetics, in which micromotions are generated by a group of atoms climbing over a tilted potential barrier of the highest height ε0.

Applications of the constitutive equation in the cases of some Sn/Pb solder alloys-63Sn/37Pb, 60Sn/40Pb and 97.5Pb/2.5Sn under shear creep tests; and 98Pb/2Sn under tensile creep tests, show that the theoretical results can describe the experimental data quite well. These results pave the way for future research in the comparisons of creep resistance among solders with various Sn/Pb compositions and in the generalization of three-dimensional constitutive equation.
Fundamentals of a Vector Form Intrinsic Finite Element: Part II. Plane Solid Elements
Authors: Ting Edward C. , Shih Chiang , Wang Yeon-Kang
Published: May 2011

In the second article of the series, the vector form intrinsic finite element is extended to formulate plane solid elements, a three-node triangular element and a four-node isoparametric element. Also, conceptual differences of the intrinsic element and traditional element based on variational formulation are discussed.
Fundamentals of a Vector Form Intrinsic Finite Element: Part III. Convected Material Frame and Examples
Authors: Shih Chiang , Wang Yeon-Kang , Ting Edward C.
Published: May 2011

In the third article of the series, a convected material frame is used to develop an incremental analysis procedure to calculate motions with large deformation and large displacement. Five numerical examples are given. The first three illustrate some numerical problems in explicit finite element that are resolved in the present approach. The other two demonstrate the stability and convergence of the method.
Analytical Solutions for Crack Tip Plastic Zone Shape Using the Von Mises and Tresca Yield Criteria: Effects of Crack Mode and Stress Condition
Authors: Jing P. H. , Khraishi T.
Published: May 2011

Analytical closed-form solutions for the crack tip plastic zone shape have been derived for a semi-infinite crack in an isotropic elastic-perfectly plastic solid under both plane stress and plane strain conditions. Two yield criteria have been applied: the Von Mises and Tresca yield criteria. The solutions have been developed for crack modes I and III (mode II has been published previously). The results, which favorably compare to a limited number of existing experimental and analytical findings, indicate that the Tresca zone is larger in size than the Von Mises zone. Moreover, an interesting observation is that both zones are generally much larger than the ones predicted by classical Irwin and Dugdale-Barenblatt solutions.
Theoretical Prediction of Fiber Coupling for Ellipsoidal Microlens
Authors: Chao C.-K. , Hu J.-Y. , Hung S.-Y. , Yang H. H.
Published: May 2011

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.
Dynamic Analysis and Critical Speed of Pressurized Rotating Composite Laminated Conical Shells Using Generalized Differential Quadrature Method
Authors: Ghayour M. , Ziaei Rad S. , Talebitooti R. , Talebitooti M.
Published: May 2011

Free vibration analysis of rotating composite laminated conical shells with different boundary conditions using the generalized differential quadrature method (GDQM), is investigated. Equations of motion are derived based on Love's first approximation theory by taking the effects of initial hoop tension and the centrifugal and Coriolis acceleration due to rotation and initial uniform pressure load into account. Then, the equations of motion as well as the boundary condition equations are transformed into a set of algebraic equation applying the GDQM. The results are obtained for the frequency characteristics of different orthotropic parameters, rotating velocities, cone angles and boundary conditions. The presented results are compared with those available in the literature and good agreements are achieved.
Response of a Maglev Vehicle Moving on a Two-Span Flexible Guideway
Authors: Yau J. D.
Published: May 2011

This paper is intended to present a preliminary framework for dynamic interaction analysis of a maglev (magnetically levitated) vehicle running on a two-span guideway using a comprehensive iterative approach. A maglev vehicle with electrodynamic suspension (EDS) system is simplified as a two degrees-of-freedom (2-DOF) maglev oscillator tuned by a PID (Proportional-Integral-Derivative) controller. The guideway is modeled as a two-span continuous beam with uniform section. Two sets of equations of motion are written, with the first set for the guideway and the second set for the maglev oscillator traveling on the guideway through a motion-dependent magnetic force. To achieve the stable levitation gap for a maglev vehicle moving on a flexible guideway, Ziegler-Nicholas (Z-N) tuning rules are used to determine the tuning parameters of the PID controller. Numerical simulations demonstrate that the levitation gap affects the dynamic response of the maglev vehicle while little influence on the guideway response since the inertial force of the moving maglev vehicle is much lower than its static load.
Analysis of the Concentric Distraction and Distraction Loss of the Bridged Elbow by a Dynamic Fixator
Authors: Shih K.-S. , Lee W.-S. , Tseng C.-S. , Lu T.-W. , Hou S.-M. , Lin S.-C.
Published: May 2011

The mechanisms of concentric distraction and distraction loss within the elbow-fixator-pin construct remains unclear. Furthermore, the literature reports are inconsistent regarding the correct distraction distance between the articulating surfaces of a bridged elbow. This study investigated the mechanism of the distraction loss in terms of the relevant fixator design and elbow angle. Four elbow joints flexed at 90°, 120°, 150°, and 180° were developed in this study. The contribution of each humeral and ulnar distractor to the concentric distraction at the elbow center was evaluated by the finite-element method. The distraction loss within the elbow-fixator-pin construct was studied along the specific load-transferring paths on both elbow sides. Among four elbow models, both concentric and eccentric distractions simultaneously occur at the elbow center. The distraction loss always exists in the joint distraction of the bridged elbow. Comparatively, the 120° elbow model showed the more effectively concentric distraction. For the 180° elbow model, the distraction loss was the highest. This distraction loss was mainly attributed to the lateral deflection of the fixing pins and the vectorial transformation of the distracted length of the distractors. The lateral deflection of the fixing pins is a function of the stiffness of both pins and periarticular tissues. The spatial relationship of the elbow anatomy, elbow angle, and fixator frame plays a significant role in the vectorial transformation of the effective distraction between the elbow articulating surfaces.
Effects of Stacking Sequence on Nonlinear Hydroelastic Behavior of Composite Propeller Blade
Authors: Lin H. J. , Lai W. M. , Kuo Y. M.
Published: May 2011

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.
Magnetoelectroelastic Interaction between a Generalized Screw Dislocation and Multiple Circular Inclusions
Authors: Shen M. H. , Chen F.M. , Hung S. Y. , Chen S.N.
Published: May 2011

In this paper, the interaction of a generalized screw dislocation with multiple circular inclusions perfectly bonded to an unbounded matrix under remote magnetoelectromechanical loadings is dealt with. The analytical solutions of electric field, magnetic field and displacement field either in the inclusions or the matrix are obtained by use of the complex variable method. The image force acting on the magnetoelectric screw dislocation is calculated by using the generalized Peach-Koehler formula. Finally, the influence of material combinations on the image force is examined for several practical examples. The obtained solutions can be used as Green's functions for the analysis of the corresponding magnetoelectric crack problem.
A Finite Element Model for Composite Beams with Piezoelectric Layers using A Sinus Model
Authors: Beheshti-Aval S. B. , Lezgy-Nazargah M.
Published: May 2011

In this study, finite element modeling of composite beams with distributed piezoelectric sensors and actuators which is based upon a coupled electromechanical model has been considered. For modeling of mechanical displacement through the thickness, a sinus model that satisfies continuity conditions of transverse shear stresses and the boundary conditions on the upper and lower surfaces of the beam has been employed. In the presented model, the number of unknowns is not dependent on the number of layers. The variation of electric potential in each piezoelectric layer has been modeled using layer-wise theory. By applying the virtual work principle (VWP), a formulation has been developed for a twonodded Hermitian-2(n + 1) layer-wise nodded element for a n-layered beam. The VWP leads to a derivation that could include dynamic analysis. However, in this study only static problems have been considered. Comparison of results obtained from this formulation with available works in the literature, demonstrates efficiency of proposed model in analysis of laminated beams under mechanical and electrical loadings.
Elastic Constants of Composite Materials by an Inverse Determination Method Based on A Hybrid Genetic Algorithm
Authors: Hwang S.-F. , Wu J.-C. , Barkanovs Evgeny , Belevicius Rimantas
Published: May 2011

A numerical method combining finite element analysis and a hybrid genetic algorithm is proposed to inversely determine the elastic constants from the vibration testing data. As verified from composite material specimens, the repeatability and accuracy of the proposed inverse determination method are confirmed, and it also proves that the concept of effective elastic constants is workable. Moreover, three different sets of assumptions to reduce the five independent elastic constants to four do not make clear difference on the obtained results by the proposed method. In addition, to obtain robust values of the five elastic constants for a transversely isotropic material, it is recommended to use the out-of-plane Poisson's ratio instead of the out-of-plane shear modulus as the fifth one.
Identification of Adhesive Bond in A Multi-Layered Structure Via Sound Insulation Characterestics
Authors: Malakooti S. , Mohammadi N. , Mahjoob M. J. , Mohammadi K.
Published: May 2011

In this paper, adhesive bonds in multi-layered plates are identified based on experimental values of their sound insulation characteristics. An exact model based on two-dimensional elasticity theory is formulated. The problem is a time harmonic plane acoustic progressive wave interaction with an isotropic multi-layered infinite elastic plate with interlaminar bonding imperfections. The T-matrix solution technique, which involves a system global transfer matrix, is formed as the product of individual transfer matrices. This is accomplished by applying continuity of the displacement and stress components at the interfaces of neighboring layers along with the relevant boundary conditions at the left and right interfaces of the plate with the surrounding acoustic fluid (air). The resulting equations are then solved for the unknown plane wave reflection and transmission coefficients. The experimental values of sound transmission loss (TL) are measured by a modified B&K impedance tube. Results are presented for a double-layered (lead-steel) plate while the layers are bonded together with metal glue. The normal and transverse adhesive spring constants of the metal glue are then identified in an inverse manner. The agreement of experiments with the analytical TL values predicted for a new triple-layered plate (based on the identified bond properties) confirms the validity of the method.
Simulation of Entrainment Mass Transfer in Annular Two-Phase Flow Using the Physical Concept
Authors: Baniamerian Z. , Aghanajafi C.
Published: May 2011

Most of two-phase heat transfer analysis involve estimation of dry-out phenomenon in order to find whether it takes place and if so, at what location in the tube it will happen. Dry-out phenomenon considerably reduces heat transfer rate and it should be avoided as far as possible. Entrainment highly affects dry-out occurrence chance and location. Therefore a great attention should be paid on simulation of entrainment in order to have a good estimation of heat transfer and to safely design thermal systems.Although there are many models available for simulation of entrainment phenomenon, few are instrumentally employed in heat and fluid flow analyses, since most of those are empirical and limitedly can be applied due to the restricted conditions of experiments. There also are few theoretical approaches in the literature for simulating entrainment phenomenon by applying the physical potential of entrainment but some of those have a considerable deviation from the available empirical models. In the present study a conceptual approach is employed to simulate entrainment. In this regard the most important potential of this phenomenon, known as interfacial waves, are studied and modeled to find how they will lead to entrainment and how much the amount of entrainment is in vertical annular two-phase flows. An entrainment correlation is proposed at the end and will be compared with the available empirical ones for the verification objectives.
Revisit of Two Classical Elasticity Problems by using the Null-Field Boundary Integral Equations
Authors: Chen J. T. , Lee Y. T. , Chou K. H.
Published: May 2011

In this paper, the two classical elasticity problems, Lamé problem and stress concentration factor, are revisited by using the null-field boundary integral equation (BIE). The null-field boundary integral formulation is utilized in conjunction with degenerate kernels and Fourier series. To fully utilize the circular geometry, the fundamental solutions and the boundary densities are expanded by using degenerate kernels and Fourier series, respectively. In the two classical problems of elasticity, the null-field BIE is employed to derive the exact solutions. The Kelvin solution is first separated to degenerate kernel in this paper. After employing the null-field BIE, not only the stress but also the displacement field are obtained at the same time. In a similar way, Lamé problem is solved without any difficulty.
Generation of Harmonics by Non-Breaking Water Waves Over Permeable Submerged Breakwaters
Authors: Ting Chao-Lung , Lin Ming-Chung
Published: May 2011

This work examines the interesting phenomenon of the generation of harmonics by non-breaking waves over permeable submerged obstacles. Nine model geometries, each with six different porosities, from 0.421 to 0.912, were considered to examine the effects of model width, porosity, and submergence depth on harmonic generation. The results revealed coupled effects on harmonic generation. A modified Ursell number was proposed to analyze experimental data. Almost no harmonic generation occurs at a modified Ursell number of less than five and/or a model width to wavelength ratio of over 1.6. After harmonics have been generated, wave profiles become dimpled, and the energy of the fundamental mode is transferred to higher-frequency components. Furthermore, the higher harmonics become more pronounced as the models widen, the depth of submergence becomes shallower, and model porosity declines.
Coefficients of Time and Length Scales of Turbulent Eddies
Authors: Chang Keh-Chin , Jeng Shih-Shiang
Published: May 2011

The turbulence time and length scales representing the energy containing eddies are by Tt= CtTk/ε and ℓt= Ctℓk32/ε, respectively, while the Kolmogorov time and length scales representing the energy dissipative eddies are expressed by Tk= CkT(ν/ε)1/2and ℓk= Ckℓ(ν3/ε)1/4, respectively. The available DNS data for fully developed channel flows with and without wall injection / suction are used to determine the coefficients. It is found that, with the typical values of CtT= Ctℓ= 1 which are usually adopted in the turbulence study, ckT= 2 and Ckℓ= 3. However, this set of coefficients lead to underprediction of the thickness of viscous sublayer. By relaxing the usual assumption of CtT= Ctℓ= 1, a new set of coefficients: CtT= Ctℓ= 0.8, CkT= 4, and Ckℓ= 9 is suggested. Thecalculated with this set of coefficients becomes more physically reasonable.
Qualitative Properties of Frequencies and Modes of Beams Modeled by Discrete Systems
Authors: Wang D. J. , Chou C. S. , Wang Q. S.
Published: May 2011

In this paper, a discrete system model and its equation of motion for beams with arbitrary supports at two ends are established. These supports include elastic, rigid and free supports in translation and rotation directions. Based on theory of oscillatory matrices, a series of qualitative properties of frequencies and modes of this system are derived. The basic properties include: non-zero frequencies are distinct; the ith displacement mode has i - 1 nodes; nodes of ith mode and (i + 1)th mode interlace.

Some additional important qualitative properties owned by rotation modes and strain modes are given as well.
Inverse-Ray Imaging of 2D Layered Structures from Seismic Reflection Data
Authors: Wang Tan K. , Tan S. C.
Published: May 2011

Shooting angle of an inverse ray for imaging 2D multi-layered structures from reflected travel-times is derived in a closed form. By considering the normal incidence of two neighboring rays reflected at interfaces when sources are at the same locations as receivers, the traveling distance and direction of two inverse-rays are determined successively from the lowermost layer to the uppermost layer. This approach is similar to and also confirmed with the Huygens' principle that the equal travel-time along a wave front (perpendicular to the rays) is conserved. The closed-form solution of the inverse rays is further applied to image a complex structure of a ramp-flat fault with eleven layers. The results demonstrate that the inverse-ray imaging from travel-time picks of all layers is superior to that picked by a layer-stripping approach.
Fundamental Singularities in a Two-Fluid Stokes Flow with a Plane Interface
Authors: Yu H. Y.
Published: May 2011

A modified image method is presented for obtaining the solutions of the fundamental singularities in the neighborhood of a plane interface between two semi-infinite, immiscible, and incompressible viscous fluids. The fundamental singularities considered are the stokeslet, rotlet, stresslet, stokes-doublet, source, and source-doublet. The Galerkin vector function representation introduced reduces the complexity of the expressions for the solutions. Moreover, the physical meaning of each solution is clearly identified by these new expressions.
Application of Spline Collocation Method in Analysis of Beam and Continuous Beam
Authors: Wu Lai-Yun , Chen Yang-Tzung
Published: May 2011

In this paper, spline collocation method (SCM) is successfully extended to solve the generalized problems of beam structures. The spline functions in SCM are re-formulated by finite difference method in a systematical way that is easily understood by engineers. The manipulation of SCM is further simplified by the introduction of quintic table so that the matrix-vector governing equation can be easily formulated to solve the weighting coefficients. SCM is first examined by the problems of a generalized single-span beam undergoing various types of loadings and boundary conditions, and it is then extended to the problems of continuous beam with multiple spans. By comparing with available analytical results, differential quadrature method (DQM), if any, excellent accuracy in deflection is achieved.
Finite Element Model Verification for the Use of Piezoelectric Sensor in Structural Modal Analysis
Authors: Wang B.-T. , Chen P.-H. , Chen R.-L.
Published: May 2011

This paper presents the theoretical modal analysis for the use of PVDF sensor in structural modal testing via finite element analysis (FEA). A series of rectangular PVDF films are adhered on the surface of cantilever beam as sensors, while the point impact force is applied as the actuator for experimental modal analysis (EMA). Natural frequencies and mode shapes determined from both FEA and EMA are validated. In FEA, the beam structure is modeled by 3D solid elements, and the PVDF films are modeled by 3D coupled field piezoelectric elements. Both modal analysis and harmonic response analysis are performed to obtain the structural modal parameters and frequency response functions, respectively. Results show that both FEA and EMA results agree well. In particular, the PVDF sensor mode shapes, proportional to the slope difference between the two edges of PVDF film, are numerically and experimentally validated by FEA and EMA, respectively. Therefore, the simulation of PVDF films for vibration analysis in FEA can be verified and easily extended to other complex structures that may contain piezoelectric materials.
Topological Flow Structures of Annular Swirling Jets
Authors: Tsai Feng Chin , Huang Rong Fung
Published: May 2011

The effects of blockage and swirl on the macro flow structures of the annular jet past a circular disc are experimentally studied through the time-averaged streamline patterns. In the blockage-effect regime, the flows present multiple modes, single bubble, dual rings, vortex breakdown, and triple rings, in different regimes of blockage ratio and swirl number. The topological models of the flow structures are proposed and discussed according to the measured flow fields to manifest the complex flow structures. The single bubble is a closed recirculation bubble with a stagnation point on the central axis. The dual-ring flow is an open-top recirculsation zone, in which a pair of counter-rotating vortex rings exists in the near wake. The fluids in the dual rings are expelled downstream through a central jet-like swirling flow. A vortex breakdown may occur in the central jet-like swirling flow if the exit swirl number exceeds critical values. When the vortex breakdown interacts with the dual rings, a complex triple-ring flow structure forms. Axial distributions of the local swirl number are presented and discussed. The local swirl number increases with the increase of the exit swirl number and attains the maximum in the dual-ring mode. At large exit swirl numbers where the vortex breakdown occurs, the local swirl number decreases drastically to a low value.
Simulation of Flow Induced Vibrations of Tube Bundle in Cross Flow
Authors: Lin Tsun-Kuo , Yu Ming-Huei
Published: May 2011

The flow-induced vibration of tubes in a rotated triangular array subject to cross flow is simulated numerically. In the study, the flow field around the tube bundle is computed by solving the continuity and Navier-Stokes equations with assumption of constant fluid properties, and the kε-model for turbulent Reynolds stress. With the flow field known, the fluid forces on the tube surfaces can be calculated, and then the displacement of each tube due to the fluid force can be evaluated. Iteration is needed to obtain the dynamic response of the tube structure in the fluid flow. The parameters in the study are inlet velocity of the cross flow and properties of the tube bundle including natural frequency, damping factor, and mass. Based on the tube response, the critical flow conditions of tube vibration are determined for varying mass damping. Once tube vibrations occur, it is shown that the vibrations of the tubes in the second and fourth tube rows are significant as compared to other tubes. The orbits of the tube vibration look like an ellipse with major axis in the cross-stream direction, implying large lift force on the tubes. The dominant frequency in the spectrum of lift coefficients of the tubes is the same as the natural frequency, and the corresponding amplitude is increased with increasing the inlet velocity. The calculated data predicted for the critical reduced velocity agrees well with the data by Kassera and Strohmeier [17].
Rheological Characteristics for Thin Film Elastohydrodynamic Lubrication
Authors: Chu H.-M. , Lee R. T. , Hu S. Y. , Chang Y.-P.
Published: May 2011

This paper uses three lubrication models to explore the differential phenomenon in the status of thin film lubrication (TFL). According to the viscous adsorption theory, the modified Reynolds equation for thin film elastohydrodynamic lubrication (TFEHL) is derived. In this theory, the film thickness between lubricated surfaces is simplified as three fixed layers across the film, and the viscosity and density of the lubricant vary with pressure in each layer. Under certain conditions, such as a rough or concentrated contact of a nominally flat surface, films may be of nanometer scale. The thin film elastohydrodynamic lubrication (EHL) analysis is performed on a surface forces (SF) model which includes van der waals and solvation forces. The results show that the proposed TFEHL model can reasonably calculate the film thickness and the average relative viscosity under thin film EHL. The adsorption layer thickness and the viscosity influence significantly the lubrication characteristics of the contact conjunction. The differences in pressure distribution and film shape between surface forces model and classical EHL model were obvious, especially in the Hertzian contact area. The solvation force has the greatest influence on pressure distribution.
Experimental Study on Direct Displacement-Based Seismic Design of RC Columns
Authors: Lin Y.-Y. , Chang K.-C. , Wang Y.-L.
Published: May 2011

For performance-based seismic engineering of buildings, the direct displacement-based seismic design method is different from the coefficient method used in FEMA-273 and the capacity spectrum method adopted in ATC-40. The method not only is a linear static procedure but also is applied to the design of new constructions. This paper concerns with experimental studies on the accuracy of the direct displacement-based design procedure. Experimental results of three reinforced concrete (RC) columns designed by the displacement procedure are presented and discussed through pseudo-dynamic tests and cyclic loading tests. From the tests, it is shown that the stiffness degrading factor of RC columns plays a key role. The direct displacement-based seismic design method can reliably capture the maximum displacement demand of the test RC columns if the stiffness degrading factor adopted in the displacement design method for RC material is adequate.
Rebound of Antarctic ozone
Authors: Salby Murry , Titova Evgenia , Deschamps Lilia
Published: May 2011

Restrictions on CFCs have led to a gradual decline of Equivalent Effective Stratospheric Chlorine (EESC). A rebound of Antarctic ozone, however, has remained elusive, masked by large interannual changes that dominate its current evolution. A positive response of ozone is not expected to emerge for at least 1–2 decades, possibly not for half a century. We show that interannual changes of the Antarctic ozone hole are accounted for almost perfectly by changes in dynamical forcing of the stratosphere. The close relationship enables dynamically‐induced changes of ozone to be removed, unmasking the climate signal associated with CFCs. The component independent of dynamically‐induced changes exhibits a clear upward trend over the last decade ‐ the first signature of a rebound in Antarctic ozone. It enables ozone to be tracked relative to CFCs and other changes of climate.
Stress drop variations of induced earthquakes at the Basel geothermal site
Authors: Goertz‐Allmann Bettina P. , Goertz Alex , Wiemer Stefan
Published: May 2011

We determine stress drops from P‐wave spectra of about 1000 earthquakes induced by hydraulic stimulation in crystalline rock for a deep heat mining project in Basel, Switzerland. We observe an increase in stress drop by about a factor of five with radial distance from 10 m to 300 m, which suggests that stress drop correlates with pore pressure perturbations due to the injection. We test this hypothesis by calculating the injection‐related pore pressure perturbation based on a simple linear pore pressure diffusion model and find a good correlation of the expected pore pressure perturbation with the estimated stress drops.