bluuebunny/crossref_metadata_2025 huggingface dataset:
Inherent Strain Method and Thermal Elastic-Plastic Analysis of Welding Deformation of a Thin-Wall Beam
Authors: Wang Y.-X. , Zhang P. , Hou Z.-G. , Li C.-Z.
Published: May 2011

The transient thermal process of a thin-wall beam with CO2Gas Metal Arc Welding (GMAW) is analyzed by Finite Element Analysis Method (FEA). The thermal input is simplified as transient section body heat sources and loaded as its actual sequence in the analysis. The transient temperature field obtained can represent the basic characteristics of the real welding process and can be used as the foundation of thermal elastic-plastic analysis. Based on the temperature field, thermal elastic-plastic FEA is performed on the thin-wall beam. The distribution and change of the welding deformation, stress and strain are obtained and compared with the experiment results. Also an improvement can be presented on the inherent strain method. Using the inherent strain method, the welding deformation of the thin-wall beam is calculated. The temperature loading method is developed to load the variable inherent strain value expediently. The loading of inherent strain value on spatial welding line that is unparallel to the global coordinate axis is achieved with the application of element coordinate system. Comparison with the experiment results shows that both the thermal-elastic-plastic analysis and inherent strain analysis method can be used to predict the welding deformation effectively, the results calculated by both the thermal-elastic-plastic analysis and inherent strain analysis are close to the test measure results.
Influences of Microscopic Factors on Macroscopic Strength and Stiffness of Inter-Layered Rocks — Revealed by a Bonded Particle Model
Authors: Jeng F.-S. , Wang T.-T. , Li H. H. , Huang T.-H.
Published: May 2011

Since a conventional petrographic analysis does not allow a systematic and detailed study on how the microscopic factors affect the macroscopic behavior of inter-layered rocks, this research adopted a numerical model, the bonded particle model, to explore the micro-mechanisms associated with the strength and stiffness of inter-layered rocks. The model was first calibrated by comparing the simulations to the actual behavior until they tally with each other. Following, the microscopic factors, including the bond strength, the bond stiffness, type of bonds and friction of particles and type of bond stiffness, are varied to study their influences. As expected, the bond strength and the bond stiffness are found to have a direct and significant influence on the macroscopic uniaxial compressive strength and stiffness, respectively. Furthermore, close observations on the breaking of bonds during the loading process reveal interesting phenomena, including the transition of shear/normal bond breaking, the type of internal fracture and the factors controlling internal failure, etc. These phenomena enlighten the interpretations about the micromechanisms accounting for the macroscopic strength and stiffness of inter-layered rocks.
Simulations of Dam-Break Flows Using Free Surface Capturing Method
Authors: Chang W.-Y. , Lee L.-C. , Lien H.-C. , Lai J.-S.
Published: May 2011

A model adopting the surface capturing method is developed for the simulation of dam-break flows by solving the Navier-Stokes equations of weakly compressible and variable density flows in open channels. Due to the characteristics of weakly compressible flow equations, a compressibility parameter describing the compressibility of fluid is determined to obtain the time-accurate flow fields in both liquid and gas regions simultaneously. Accordingly, the location of free surface can be captured as a discontinuity of the density field for dam-break flow simulations. The numerical algorithm in the proposed method is based on the framework of the finite volume method for discretization in space. To deal with the discontinuity property of fluid density near the free surface, the TVD-MUSCL scheme is adopted to overcome numerical oscillations and dissipation. For discretization in time, the explicit 4-stage Runge-Kutta scheme is employed in the model. Finally, several typical dam-break flow problems in open channel are simulated to demonstrate the validation and applicability of the proposed model.
Strain-Concentration Factor of Circumferentially V-Notched Cylindrical Bars Under Static Tension
Authors: Tlilan H. M. , Al-Shyyab A. S. , Jawarneh A. M. , Ababneh A. K.
Published: May 2011

The FEM is used to study the effects of notch opening angle (β) and notch radius on the new strain-concentration factor (SNCF) for circumferentially V-notched cylindrical bars under static tension. The new SNCF has been defined under the triaxial stress state at the net section. Nevertheless, the conventional SNCF has been defined under uniaxial stress state. The new SNCF () is constant in the elastic deformation. The range where this elastic value remains constant increases with increasing β and increasing notch radius (ρo). The effect of the notch opening angle on the elastic decreases with increasing ρo. Particularly, the elastic of β = 120° is the minimum for all notch radii employed. The new SNCF increases from its elastic value to a peak value and then decreases with plastic deformation for notches with β = 120°. This peak value is the maximum . Nevertheless, for the notches with β < 120° becomes nearly constant or slightly decreasing after the first peak for ρo = 0.5 and 1mm. After that it increases to the maximum SNCF and then slightly decreases for further plastic deformation. The variations in with the ratio of tensile load to that at yielding at the notch root (P/PY) are nearly independent of stress-strain curve up to general yielding.
The Differences in Gait Pattern Between Dancers and Non-Dancers
Authors: Lung C. -W. , Chern J. -S. , Hsieh L. -F. , Yang S. -W.
Published: May 2011

Students in dancing department routinely perform hours of dancing every day. Extreme ankle posture can subject the ankle of the dancers to high stress and can significantly increase the mobility of the ankle. This causes ankle sprain which occurs frequently during daily walking. Measurements of the ground reaction force (GRF) and the center of pressure (CoP) provide useful variables to analyze the walking patterns of dancers, which might help understand the causes of ankle sprain. The aims of this work were (1) to investigate the differences in gait patterns between dancers and non-dancers and (2) to explore the gait characteristics in dancers. Thirteen students in dancing department and twenty age-matched normal healthy subjects were recruited. All subjects were requested to walk along a 10-meter walkway. Results showed that the dancers have greater medial shear force of the GRF, and decreased the CoP velocity during the pre-swing phase, delayed peak-CoP velocity occurrence during the mid-stance, and straighter CoP trajectory through the forefoot at push off. The intense and demanding dancing activities change the walking pattern of dancers, which may lead to higher chance of getting ankle sprain.
Stability Analysis of Symmetric Laminated Composite Plates with Geometric Imperfections Under Longitudinal Temperature Gradient
Authors: Owhadi A. , Samsam Shariat B.
Published: May 2011

Thermal buckling behaviour of rectangular laminated composite plates with initial geometrical imperfections is investigated in this article. The equilibrium, stability, and compatibility equations of an imperfect composite plate are derived using the first order shear deformation plate theory. The plate is assumed to be under longitudinal temperature rise. Resulting equations are used to obtain the thermal buckling load of the composite plate in closed-form solutions. The effect of initial imperfections on buckling loads are discussed.
Improvement of a Microbubble Generator's Performance Via Reliance on Fluid Dynamics Characteristics
Authors: Nouri N. M. , Sarreshtehdari A. , Maghsoudi E.
Published: May 2011

In present research, improvement of a microbubble generator's performance via reliance on fluid dynamics characteristics is studied numerically, and then some experiments are executed. In an elementary cylindrical microbubble generator, water flow enters the device via six diagonal nozzles, and passes a rotational path around a central motionless hub. This flow breaks the big bubbles entering the device by gas injection from air nozzles. The high-intensity turbulence and shear flow in this device is the cause of the air bubble breaking process. These small bubbles can be used to reduce frictional drag on the contact surface of moving solid bodies in water flow. To improve the operation of the apparatus, some suggested geometrical shapes were investigated numerically and were optimized based on the bubbles' effective breaking-up parameters. The experimental results illustrated good performance of the recent apparatus for generating smaller bubbles.
Effects of Slip Boundary Conditions on Rayleigh-Bénard Convection
Authors: Kuo L.-S. , Chen P.-H.
Published: May 2011

This work studied the Rayleigh-Bénard convection under the first-order slip boundary conditions in both hydrodynamic and thermal fields. The variation principle was applied to find the critical Rayleigh number of instability. The exteneded relations of the critical Rayleigh number (Rc) and the wavenumber (ac) under partially slip boundary conditions were derived. The numerical results showed that both Rc and ac are decreasing with increasing the Knudsen number. The dependence of Rc on the Knudsen number (K) shows that when K≤10−3, the boundary can be considered as nonslip, while K≥10, it can be considered as free boundaries. The maximum change rate occurs when the Knudsen number is around 0.1, indicating that the system would be affected significantly in that range.
Acoustic Emission at Wedge Indentation Fracture in Quasi-Brittle Materials
Authors: Chen L. H. , Huang K. C. , Chen Y. C.
Published: May 2011

To improve the safety and automation of mechanical excavation methods used in tunnels, this present report studied the behavior of rock materials indented by a single cutter, based on the theory of indentation fracture mechanics. The development of microcracks during the indentation process and the correlation between microcracks and macrocracks was investigated using the nondestructive technique of acoustic emission. Microseismic activity of the microcracks received by the acoustic emission (AE) technique was used to interpret and represent the initiation and propagation of macrocracks. As the wedge angle increased, the maximum indentation force increased, but the nominal indentation pressure and the destructive indentation depth decreased. On the other hand, the direction of macrocrack propagation did not significantly change with the various wedge angles. Furthermore, the localization occurred earlier and the dimensionless radius of the elasto-plastic interface decreased with increased wedge angle. In addition, the dimensionless radius of the elasto-plastic interface obtained by the experiment was consistent with closed-form analytical solutions.
Characterization of Hygroscopic Swelling and Thermo-Hygro-Mechanical Design on Electronic Package
Authors: Hsu H.-C. , Hsu Y.-T.
Published: May 2011

This paper discusses a successful experimental procedure to determine the hygroscopic swelling property of polymeric materials used in electronic packaging. Saturated moisture concentration and moisture diffusivity were determined by measuring the weight gain during moisture absorption. Hygromechanical properties, such as the coefficientof moisture expansion (CME), were determined through Thermo-Mechanical Analyzer (TMA) and Thermo-Gravimetric Analyzer (TGA) techniques. Fick's law of transient diffusion is solved by using finite element (FE) analysis to evaluate the overall moisture distributions. Both two-dimensional and three-dimensional models based on the FE software ANSYS were developed to predict the thermal-induced strain, hygroscopic swelling deformation, and residual thermohygro-mechanicalstress distributions. Reliability analysis at three JEDEC preconditioning standards 60°C60%RH, 85°C60%RH and 85°C85%RH was carried out. A series of comprehensive parametric studies were conducted in this research.
Laser Surface Hardening Considering Coupled Thermoelasticity
Authors: Sistaninia Me. , Sistaninia Ma. , Moeanodini H.
Published: May 2011

Thermoelastic temperature, displacement and stress in heat transfer during laser surface hardening are solved in both Lagrangian formulation and Eulerian formulation. In the Eulerian formulation, the heat flux is fixed in space and the work-piece is moved through a control volume. In the case of uniform velocity and uniform heat flux distribution, the Eulerian formulation leads to a steady-state problem, while the Lagrangian formulation remains transient. In the Eulerian formulation, the reduction to a steady-state problem increases the computational efficiency. Also, in this study, an analytical solution is developed for an uncoupled transient heat conduction equation in which a plane slab is heated by a laser beam. The thermal results of the numerical models are compared with the results of the analytical model. A comparison of the results shows that numerical solutions in the case of uncoupled problem are in good agreement with the analytical solution.
Mechanical Properties of a Centrally Notched APC-2 Composite Laminate Due to Fatigue Loading at Elevated Temperature (II)
Authors: Jen M.-H. R. , Tseng Y.-C.
Published: May 2011

The temperature versus life (T-N) curves of both centrally notched and unnotched AS-4/PEEK (APC-2) composite laminates due to constant stress amplitude tension-tension (T-T) fatigue loading were investigated systematically. The cross-ply laminate possesses the higher mechanical properties than those of the quasi-isotropic laminate at elevated temperature, and also the mechanical properties of both lay-ups are degraded significantly as the temperature increasing. Combining both effects of notch and temperature at various normalized stresses it is found the cross-ply laminate possesses more resistance to cyclic loading than that of the quasi-isotropic laminate. Additionally, the predictive strain model is in a practical and simple form. Alternatively, the T-N curves, instead of conventionally S-N curves, at variously applied stresses are accomplished for preliminary designs and applications.
Accurate Integration of Nonlinear Systems Using Newmark Explicit Method
Authors: Chang S.-Y.
Published: May 2011

In the step-by-step solution of a linear elastic system, an appropriate time step can be selected based on analytical evaluation resultsHowever, there is no way to select an appropriate time step for accurate integration of a nonlinear system. In this study, numerical properties of the Newmark explicit method are analytically evaluated after introducing the instantaneous degree of nonlinearity. It is found that the upper stability limit is equal to 2 only for a linear elastic system. In general, it reduces for instantaneous stiffness hardening and it is enlarged for instantaneous stiffness softening. Furthermore, the absolute relative period error increases with the increase of instantaneous degree of nonlinearity for a given product of the natural frequency and the time step. The rough guidelines for accurate integration of a nonlinear system are also proposed in this paper based on the analytical evaluation results. Analytical evaluation results and the feasibility of the rough guidelines proposed for accurate integration of a nonlinear system are confirmed with numerical examples.
Molecular Dynamics Simulation of Double-Walled Carbon Nanotube Vibrations: Comparison With Continuum Elastic Theories
Authors: Shayan-Amin S. , Dalir H. , Farshidianfar A.
Published: May 2011

Double-walled carbon nanotubes (DWNTs) are expected to be useful as elements in improving conventional polymer-based fibers and films. An extensive molecular dynamics simulation and continuum analyses are carried out to estimate the influence of matrix stiffness and the intertube radial displacements on free vibration of an individual DWNT. The effects of nanotube length and chirality are also taken into account. The continuum analyses are based on both Euler-Bernoulli and Timoshenko beam theories which considers shear deformation and rotary inertia and for both concentric and non-concentric assumptions considering intertube radial displacements and the related internal degrees of freedom. New intertube resonant frequencies are calculated. Detailed results are demonstrated for the dependence of resonant frequencies on the matrix stiffness. The results indicate that internal radial displacement and surrounding matrix stiffness could substantially affect resonant frequencies especially for longer doublewalled carbon nanotubes of larger innermost radius at higher resonant frequencies, and thus the latter does not keep the otherwise concentric structure at ultrahigh frequencies.
Scattering of Plane Sh-Wave From a Partially Debonded Shallow Cylindrical Elastic Inclusion
Authors: Zhao J.X. , Qi H.
Published: May 2011

The scattering of plane SH-wave from a partially debonded shallow cylindrical elastic inclusion in half space is investigated in this paper by complex function method and expansion method of wave function. The debonding regions are considered as multiple arc-shaped interface cracks with non-contacting faces. Firstly, in the inclusion district, the standing wave function in the elastic inclusion with unknown coefficients which satisfies the boundary condition is constructed and generated into the Fourier series; in the half space, the stress and displacement boundary condition around the elastic inclusion can be modeled as the same as the standing wave function in the elastic inclusion. Then, a set of infinite algebraic equations can be obtained around the same boundary and the solution of problem can be gained. In the end, numerical examples of the surface displacement are provided and discussed. It is found that the interface cracks can raise the surface displacement amplitudes to a certain degree.
Thermal Postbuckling Analysis of 3D Braided Composite Cylindrical Shells
Authors: Li Z.-M. , Yang D.-Q.
Published: May 2011

Thermal postbuckling analysis is presented for 3D braided composite cylindrical shell of finite length subjected to a uniform temperature rise. Based on a micro-macro-mechanical model, a 3D braided composite may be as a cell system and the geometry of each cell is deeply dependent on its position in the cross-section of the cylindrical shell. The material properties of epoxy are expressed as a linear function of temperature. The governing equations are based on Reddy's higher order shear deformation shell theory with a von Kármán-Donnell-type of kinematic nonlinearity and including thermal effects. A singular perturbation technique is employed to determine the buckling temperatures and postbuckling behaviors of 3D braided composite cylindrical shells. The numerical illustrations concern the postbuckling behavior of perfect and imperfect, braided composite cylindrical shells with different values of geometric parameter and of fiber volume fraction. The results show that the shell has lower buckling temperatures and postbuckling equilibrium paths when the temperature-dependent properties are taken into account. The results reveal that the fiber volume fraction, braiding angle and the shell geometric parameter have a significant effect on the thermal buckling and postbuckling behavior of braided composite cylindrical shells.
Derivation of Cyclicp-yCurves From Instrumented Dynamic Lateral Load Tests
Authors: Lin S.-S. , Lai C.-H. , Chen C.-H. , Ueng T.-S.
Published: May 2011

In this paper, an efficient method is proposed to derive cyclicp-ycurves from either push-over or shaking table test results. The Fourier series function, satisfying the boundary conditions of a pile, is used to represent deflection behavior of the pile-soil system at each instant of time during loading interval. In order to obtain soil reaction along the pile shaft, convergence of the series after differentiation is guaranteed by applying the Cesaro sum technique. Results of four push-over tests and two other shaking table test results, conducted at the National Center for Research on Earthquake Engineering in Taiwan, are then used to verify the feasibility of the proposed method.
Evolution Instability and Growth Competition Study on Langmuir Circulation
Authors: Yang R.-Y. , Liu C.-M. , Hwung H.-H. , Kong C.-H.
Published: May 2011

Langmuir circulation that has been disturbed by a perturbed source in a horizontal Couette flow with a vertical density gradient (i.e., the effective Rayleigh numberR) and horizontal Couette flow is investigated. The evolution of instability developing in the presence of a vertical density gradient influenced by the disturbance at various depths and the horizontal Couette flow is considered near the onset of convection under a moderate rate of shear. We use velocity as the basic variable and solve the pressure Poisson equation in terms of the associated Green function. Growth competition between the longitudinal vortices (Lv) and the transverse vortices (Tv), whose axes are respectively in the direction parallel to and perpendicular to the Couette flow, is investigated by the weakly nonlinear analysis of coupled-mode equations. The results show that the Tv mode is characterized in some range of the effective Rayleigh number, and that the stability is dominated by the Lv mode in the system.
Kinematic Study of an Innovative Dynamic Bridging Wrist External Fixator with Arthrodiatasis
Authors: Shih K.-S. , Lin S.-C. , Liu Y.-H. , Chang T.-H. , Hou S.-M. , Lu T.-W.
Published: May 2011

External wrist fixators have been widely used to stabilize distal radial fractures. Ideally an external fixator would create a stable environment for the fracture to heal while allowing proper mobility for the wrist. However, this has been a great challenge to the designers.

The current study aimed to develop a bridging wrist external fixator that is easy for surgeons to create a stable environment for the fracture to heal while allowing proper wrist mobility for rehabilitative purposes. The kinematic geometry of the wrist-fixator system was described using loop equations defined by homogeneous transformation matrices (HTM) of the joints involved, and was evaluated numerically for a set of system parameters that are determined by surgeons during surgery. The results were validated with geometric models and computer simulation. The contributions of individual clinical parameters to the kinematic geometry of the wrist-fixator system were also analyzed using the Taguchi method.

Adequate pin placement and hinge alignment function were found to be critical for the postoperative bridged wrist motion. The results of the current study will be helpful for surgeons to perform fixation using the new wrist fixator and for designers to design new fixators in the future.
Biomechanical Role of the Locomotor System in Controlling Body Center of Mass Motion in Older Adults During Obstructed Gait
Authors: Wang T.-M. , Chen H.-L. , Hsu W.-C. , Liu M.-W. , Lu T.-W.
Published: May 2011

Fifteen young and fifteen older healthy adults walked and crossed obstacles of three different heights while kinematic data and ground reaction forces were acquired to calculate the three-dimensional motion of the centre of mass (COM) and lower limb joint moments. The older group had greater normalized jerk score of the COM. When the leading limb was crossing, the older group kept the COM more posterior and on the trailing stance limb for longer with increased knee extensor crossing moments and thus decreased anterioposterior COM deceleration. When the trailing limb was crossing, the older group decreased vertical COM deceleration through increased hip extensor crossing moments. The older group maintained the same COM motion as the young in the frontal plane with greater hip and knee abductor crossing moments. The older group exhibited significant kinetic changes in their locomotor system with increased muscular demand, leading to a more jerky motion of the body COM. However, these changes helped to maintain the frontal COM motion and to achieve a sagittal COM motion pattern which is thought to be helpful for a safe and successful obstacle-crossing. Failure to meet the kinetic demands in the elderly may increase the risk of falls during obstacle-crossing.
Control of Body's Center of Mass Motion During Level Walking and Obstacle-Crossing in Older Patients with Knee Osteoarthritis
Authors: Hsu W.-C. , Wang T.-M. , Liu M.-W. , Chang C.-F. , Chen H.-L. , Lu T.-W.
Published: May 2011

Knee osteoarthritis (OA) has been reported to affect the performance of ambulation, including unobstructed and obstructed gait. An increased risk of falling in patients with knee OA during obstaclecrossing, as opposed to unobstructed level walking, may be explained by the difference in the control of the body's center of mass (COM) with respect to the center of pressure (COP) while trying to ensure sufficient foot clearance. The purpose of the study was to investigate the dynamic stability in patients with knee OA during level walking and obstacle-crossing. The COM-COP inclination angles and angular velocities, as well as temporal-spatial variables, from eleven patients with bilateral knee OA and eleven normal controls were obtained during level walking and obstacle-crossing using a three-dimensional motion analysis system and forceplates. Demands in the control of the COM relative to the COP were found to be greater during obstacle-crossing in both subject groups. While less stable COM control was found around the end stage of double stance phase during obstacle-crossing when compared to level walking, patients with knee OA successfully acquired strategies in the sagittal plane to maintain close-tonormal stable COM control with normal toe clearances during both level walking and obstacle-crossing. They achieved stable transitions from single limb stance (SLS) to double limb stance (DLS) through a reduced anterior inclination angle and from DLS to SLS through increased anterior angular velocity. It is suggested that assessment of the ability to control dynamic stability in patients with knee OA should consider both the positions and velocities of the COM and COP.
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 two-nodded 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.
Applicability of Reichardt's Hypothesis to the Prediction of Velocity Field of Multiple Parallel Plane Jets
Authors: Nasr A. , Lai J.
Published: May 2011

In this paper the velocity distribution for multiple parallel plane jets based on the superposition of Reichardt's solution for single free jet is derived. The extend of the applicability of Reichardt's hypothesis to prediction of multiple parallel plane jets is examined. Both ventilated and unventilated two parallel plane jets data published in the literature and obtained for this study were used for comparisons with the theoretical results obtained from Reichardt's hypothesis. LDA measurements of mean streamwise velocities and turbulence characteristics of an array of 5 parallel plane jets were also made in order to establish the conditions under which this heuristic approach is valid. Results show that provided the pressure gradient in the lateral direction is small and hence the deflection of the individual jet center line is small, there is a good agreement between experimental results and predictions based on Reichardt's hypothesis for multiple parallel plane jets.
Convective Heat Transfer of the Flow through a Rotating Circular Straight Pipe
Authors: Lei U. , Yang Arthur C. Y.
Published: May 2011

Laminar heat transfer for large ranges of Reynolds numbers, rotational Reynolds numbers, and Prandtl numbers are studied numerically for incompressible fully developed flow in a circular straight pipe, which is rotating constantly about an axis perpendicular to its own axis under the constant wall temperature gradient condition. There exist four types of local Nusselt number distributions associated with the four different flow regimes for different parameters depending on the relative importance of different forces. Correlations of the averaged Nusselt number are also provided. When the Prandtl number is sufficiently large, the temperature distribution in the core is determined essentially by the secondary flow. Scaling analyses are provided for understanding the essential physics of the problem.
Heat Conduction in a Cylindrically Anisotropic Tube of a Functionally Graded Material
Authors: Tarn Jiann-Quo , Wang Yung-Ming
Published: May 2011

A state space approach to heat conduction in a cylindrically anisotropic circular tube of functionally graded materials (FGM) is presented. A power-law type of the radial inhomogeneity for the FGM is considered. By means of eigenfunction expansion and matrix algebra, analytic solutions for transient and steady-state heat conduction in the FGM tube under general thermal boundary conditions are derived.
The Pseudo Dynamic Test of RC Bridge Columns Analyzed Through the Hilbert-Huang Transform
Authors: Li Y.-F. , Chang S.-Y. , Tzeng W.-C. , Huang K.
Published: May 2011

In this paper, the analysis of the responses of the pseudo dynamic test of two rectangular reinforced concrete (RC) bridge columns using the Hilbert-Huang transform (HHT) is introduced. Firstly, two 40%-scaled rectangular RC bridge columns are subjected to the pseudo dynamic test. The input of the pseudo dynamic test is set as the near-fault ground accelerations of the Chi-Chi Earthquake, which happened in 1999 in central Taiwan. After damage occurs to the bridge columns, we use non-shrinkage mortar to repair the columns, and then use 3 layers of CFRP to rehabilitate their plastic zone. The repaired bridge columns are again tested. Then we use the HHT to analyze the responses of the as-built and repaired bridge columns. The merit of applying the HHT to the responses of bridge columns is that it can transfer the displacement-time responses into instantaneous frequency responses, while the spectra are a function of both frequency and time. We can observe from the Hilbert spectra of the bridge columns that, at the instant when the frequency changes, the structural behavior changes from elastic to inelastic. The HHT can therefore be used to obtain the instantaneous natural frequencies of the bridge columns and to understand the relationship between the frequency changes and stiffness condition of the bridge columns.
On the Design of An Innovative Latch Mechanism in SMIFed Wafer Containers
Authors: Pai Wei-Ming , Chen Dar-Zen , Lee Jyh-Jone , Ho Chi-Zer
Published: May 2011

This paper presents the design process for an innovative latch mechanism in a standard mechanical interfaced (SMIFed) wafer container, in which the manufactured integrated circuits are stored. An innovative latch mechanism is proposed and applied to the wafer container, such that the container door can be latched and air-tightly sealed during storage or transportation. The design process is divided into two stages. In the first stage, an output slot-cam is designed in order to generate decoupled fine motions of the output link. The issue is formulated as an optimization problem where the output link dimensions are optimized to minimize the resultant pin forces subject to an adequate transmission angle. In the second stage, the input slot-cam is designed to achieve that kinetic energy of the elastic gasket on the container lid is absorbed at a uniform rate. Finally, a numerical example and computer simulations are given to demonstrate the results of design process. It is believed that this work could aid in enhancing the performance and reliability of the latch mechanism in the SMIF environment.
Depth Measurement of Surface-Breaking Cracks Using Point-Source/Point-Receiver Acoustic Transducer
Authors: Lee Yung-Chun , Kuo Shi Hoa
Published: May 2011

A newly developed point-source/point-receiver (PS/PR) acoustic transducer is used for measuring the depth of surface-breaking cracks. The transducer consists of two miniature conical PZT elements which form a transmitter/receiver pair for generating and detecting surface waves. A tone-burst measurement system operates the PS/PR transducer at a fixed frequency. When a surface-breaking crack is present in between the transmitter and receiver, the change in time-of-flight of surface wave propagation caused by the crack is measured and used to estimate the crack depth. To verify the feasibility of this method, machined slots on a carbon steel sample are tested by the PS/PR transducer for crack depth determination. Good experimental results are obtained. Future applications and improvements on the PS/PR transducer system are addressed.
Fundamentals of a Vector Form Intrinsic Finite Element: Part I. Basic Procedure and A Plane Frame Element
Authors: Ting Edward C. , Shih Chiang , Wang Yeon-Kang
Published: May 2011

In a series of three articles, fundamentals of a vector form intrinsic finite element procedure (VFIFE) are summarized. The procedure is designed to calculate motions of a system of rigid and deformable bodies. The motion may include large rigid body motions and large geometrical changes. Newton's law, or a work principle, for particle is assumed to derive the governing equations of motion. They are obtained by using a set of deformation coordinates for the description of kinematics. A convected material frame approach is proposed to handle very large deformations. Numerical results are calculated by using an explicit algorithm. In the first article, using the plane frame element as an example, basic procedures are described. In the accompanied articles, plane solid elements, convected material frame procedures and numerical results of patch tests are given.
Analytical Solutions of Saint Venant Equations Decomposed in Frequency Domain
Authors: Chung W. H. , Kang Y. L.
Published: May 2011

The Saint Venant equations are often merged into a single equation for being easily solvable. By doing so, the most general form of the single equation is formulated in this study if all terms are preserved. As a result, the generalized model (GM) results and contains several unexpected nonlinear terms that may impose a great limitation on model analyses. In order to identify these redundant terms, this paper discusses the employment of the linearized Saint Venant equations (LSVE) governing subcritical flow in prismatic channels. The LSVE is solved by a new procedure that separates, in the Laplace frequency domain, the governing equation of water depth from that of flow velocity and thus enables us to consider two independent equations rather than two coupled ones. This allows us to obtain analytical solutions in a much easier way. Comparisons of the response functions of LSVE and the linearized generalized model (LGM) show that the two equations provide identical solutions if the redundant terms embedded in LGM are neglected. It then follows that the response function of LGM can be utilized as a replacement for solving the analytical solution of LSVE that is valid for prismatic channels of any shape. Validity of the analytical solution is verified by repeatedly comparing with the corresponding numerical solutions of finite difference method or Crump's algorithm [1], depending on whether the flow domain is finite or semi-infinite. It is clearly demonstrated in this paper that LSVE serves as an excellent substitution for LGM whose variants have been employed for quite a few years.
Thermosolutal Convection in an Inclined Rectangular Enclosure with a Partition
Authors: Wang L. W. , Kung Y. C. , Wu C. Y. , Kang M. F. , Wang S. L.
Published: May 2011

An experimental study of thermosolutal convection in an inclined rectangular enclosure with a partition is presented in this article. Aspect ratio, partition ratio, and inclination angle were kept constant at Ar =0.5, Ap = 0.25 and φ = 30°, respectively. The convective flow is generated by both inclined temperature and concentration gradients under limiting current condition. Both the thermal and solutal buoyancies, which either cooperated or opposed one another, were induced from the copper plates. The temperature gradient was maintained and controlled using two separate constant temperature baths that circulated heated or cooled water through a heat exchanger. We used copper sulphate-sulfuric acid solution as both the working fluid and the electrolyte. An electrochemical method based on a diffusion-controlled electrode reaction was employed to create the concentration gradient. We used the shadowgraph recording technique to visualize and analyze the flow field phenomenon. Thermal Grashof numbers ranging from 8.16 × 105 to 16.32 × 105 and a solutal Grashof number Grm = 4.36 × 106 were investigated. It is demonstrated that the mass transfer rate increases with the increasing thermal Grashof numbers within our experimental ranges. Multilayer structures are found in the cooperating case or the opposing case.
The Constellation Design of Weather Observation Mission for Gravity-Gradient Stabilized Microsatellites
Authors: Lin C.-H. , Hong Z.-C. , Shieh C.-J.
Published: May 2011

This paper focuses on the design of a weather observation constellation consisting of gravity-gradient stabilized satellites for acquiring weather images of Taiwan on an hourly basis. The CCD imaging system is made up of the imaging module, the image-processing module and the sequencing operation controller. The CCD imaging logic is designed to determine the optimal imaging opportunity according to the orbital data. In order to compare with the existing polar systems and the TUUSAT-1 mission, the Walker Constellation method is also employed to calculate the minimum number of satellites required in a constellation. The calculation results show that the 8/8/5 Walker Constellation can satisfactorily meet the coverage requirements. Compared with the design of constellations which are constituted of the existing polar weather satellites and the passive magnetic stabilized satellites respectively, the present constellation design employs a smaller number of satellites to meet the same coverage requirements.
Influence Functions of a Point Force for Kirchhoff Plates with Rigid Inclusions
Authors: Melnikov Y. A.
Published: May 2011

A semi-analytic method is proposed for two problem settings for a Kirchhoff plate containing an absolutely rigid circular inclusion and undergoing a transverse point force. The settings differ by the location (within and out of inclusion) of the force application point. In both cases, the plate's stress-strain state is simulated with a boundary value problem for the biharmonic equation stated over a doubly connected region whose inner contour represents the edge of the inclusion. Boundary conditions imposed on the inner contour bring some parameters which are found via the equations of static equilibrium of the inclusion. A modification of the Kupradze'smethod of functional equationsis proposed for obtaining influence functions of a point force for such plates. Green's functions of the biharmonic equation for appropriately shaped simply connected regions are employed. Numerical differentiation is never required in the computing of stress components and the latter are subsequently found with accuracy level comparable with that attained for the deflection function.
Formulas for Curvature Ductility Design of Doubly Reinforced Concrete Beams
Authors: Chen C. C. , Hsu S. M.
Published: May 2011

With the concrete treated as unconfined, semi-empirical equations for curvature ductility ratios of doubly reinforced beam sections were derived. Based on the resulted semi-empirical equations, design formulas for curvature ductility ratios, which take into account the effect of tension and compression reinforcement ratios and strengths of reinforcement and concrete, are established and calibrated. The proposed design formulas are fairly simple with reasonable accuracy. The proposed design formulas enable the designer to design beam sections for selected ductility ratios, and, consequently, to acquire better control of concrete spalling during major earthquakes. From the aspect of performance based design, the proposed formulas can facilitate beam design for concrete spalling limit state.
Cooling of Micro Spots by Oscillatory Flows
Authors: Chou F. C. , Weng J. G. , Tien C. L.
Published: May 2011

This paper explores a novel design of an encapsulated and integrated device, which employs an oscillatory fluid flow to cool micro spots in micro systems. The oscillatory flow can be induced by two thermal bubbles that form and expand in turn on two micro line heaters at both ends of a sealed fluid channel. Compared with those using outside connecting channels and pumps, this design benefits from its much smaller size. A numerical calculation indicates that the heat transfer enhancement is independent of the Wormersely number, but depends on the Peclet number, Pe, and the cooling capacity of channel walls. The heat transfer rate increases dramatically as Pe increases from 30 to 100.
Theg-Based Jordan Algebra and Lie Algebra Formulations of the Maxwell Equations
Authors: Liu Chein-Shan
Published: May 2011

When it is usually using a bigger algebra system to formulate the Maxwell equations, in this paper we consider a real four-dimensional algebra to express the Maxwell equations without appealing to the imaginary number and higher dimensional algebras. In terms ofg-based Jordan algebra formulation the Lorentz gauge condition is found to be a necessary and sufficient condition to render the second pair of Maxwell equations, while the first pair of Maxwell equations is proved to be an intrinsic algebraic property. Then, we transform theg-based Jordan algebra to a Lie algebra of the dilation proper orthochronous Lorentz group, which gives us an incentive to consider a linear matrix operator of the Lie type, rendering more easy to derive the Maxwell equations and the wave equations. The new formulations fully match the requirements for the classical electrodynamic equations and the Lorentz gauge condition. The mathematical advantage of our formulations is that they are irreducible in the sense that, when compared to the formulations which using other bigger algebras (e.g., biquaternions and Clifford algebras), the number of explicit components and operations is minimal. From this aspect, theg-based Jordan algebra and Lie algebra are the most suitable algebraic systems to implement the Maxwell equations into a more compact form.
Detecting Rebars and Tubes Inside Concrete Slabs Using Continuous Wavelet Transform of Elastic Waves
Authors: Chiang C. H. , Cheng C. C.
Published: May 2011

A typical problem of elastic wave methods, such as the impact echo method, is due to peak detection based solely on amplitude spectrum. Current study aims to improve the feature identification of impact-echo signals obtained from buried objects in concrete slabs. Steel rebar, steel tubes, and PVC tubes embedded in a concrete slab are tested. Numerical simulations are carried out based on models constructed using the finite element method. The received signals, both experimental and simulated, are analyzed using both fast Fourier transform and continuous wavelet transform (CWT). The amplitude spectra can only provide global information and lose some important local effects of frequency components. This can be resolved by continuous wavelet transform for preserving the transient effects in the frequency domain. Localized spectral contents are analyzed and thus better understanding is achieved for the impulse responses due to different objects below the surface of the concrete slab. Features related to steel rebar, PVC and steel tubes are readily identified in the coefficient plot of wavelet coefficients. Multiple reflections and vibration modes related to various characteristics of wave propagation in the concrete slab can now be decomposed into distinctive frequency bands with different time durations. The result of CWT provides more information and is easier to interpret than that of the spectral analysis. The same peak frequency found in the amplitude spectrum is now distinguishable between PVC and steel tubes at a resolution of 0.1kHz or better. Such findings provide a more effective way to pick up true rebar signals using the impact-echo method.
Flexural Characteristics of a Cantilever Plate Subjected to Heating at Fixed End
Authors: Alzaharnah I. T.
Published: May 2011

The flexural characteristic of a cantilever plate, which is heated from a fixed end, is considered and the effects of heat transfer on the plate are examined. The plate is heated with a temperature source while an excitation force is applied at the free end. Size of heat source is varied and temperature dependent properties of the plate are accommodated in the simulations. The finite element method (FEM) is adopted to determine the temperature field in the plate and flexural characteristics due to the applied impulsive load. It is found that the flexural characteristics of the plate change notably with the size of the heat source located at the fixed end of the plate. In this case, increasing the size of the heat source results in the enhancement of the amplitude and time shift in the flexural motion of the plate due to the heating and noheating situations.
Frictionless Contact of a Functionally Graded Half-Space and a rigid Base with an Axially Symmetric Recess
Authors: Barik S. P. , Kanoria M. , Chaudhuri P. K.
Published: May 2011

This paper is concerned with an axially symmetric frictionless contact between an elastically transversely isptropic functionally graded half-space and a rigid base that has a small axisymmetric surface recess. The graded half-space is modeled as a nonhomogeneous medium. We reduce the problem to solving Fredholm integral equations, solve these equations numerically and establish a relationship between the applied pressure and gap radius. The effects of anisotropy and nonhomogeneity parameter of the graded half-space on the normal pressure as well as on the critical pressure have been shown graphically.
Separation of Photoelastic Principal Stresses by Analytical Evaluation and Digital Image Processing
Authors: Chang C.W. , Chen P.H. , Lien H.S.
Published: May 2011

A new method for separation of isochromatic stresses is presented. This method is derived from the series solution of self-equilibrium polynomial stress equations and compatibility equations. The equations are quantified in terms of a stress function as the photoelastic stresses. Those equations are combined with the digital image processing technique and the linear regression curve fitting method to determine the contour equations of isochromictics and isoclinics fields. The solution of those equations provides a relationship between the normal stresses/shear stress and the photoelastic stress (maximum shearing stress). The results are consistent with the results obtained by the finite element method.