bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cooling of Micro Spots by Oscillatory Flows
Authors: Chou F. C. , Weng J. G. , Tien C. L. 
Published: May 2011

AbstractThis 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

AbstractWhen 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

AbstractA 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

AbstractThe 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

AbstractThis 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

AbstractA 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.
Development of Time Dependent Stress-Strain Simulation of Clay
Authors: Ou C.-Y. , Liu C.-C. , Chin C.-K. 
Published: May 2011

AbstractThe objective of this study is to derive a time dependent effective based constitutive law on the basis of framework of the Modified Cam-Clay model. This model takes into account the anisotropic characteristics and creep behavior, based on the theory of viscoplasticity. The model sets the initial yield surface symmetric to theKoline for modeling the initialKocondition. A method is then developed to compute the gyration and expansion of the loading surface to simulate the anisotropic behavior due to the principal stress gyration after shear. The creep or time dependent behavior is considered in the model by adopting Kutter and Sathialingam's model, which was derived from Taylor's secondary consolidation theory and Bjerrum's delayed compression model. Compared with the Modified Cam-Clay model, the model requires five additional parameters to describe the soil behavior. All of the additional parameters can be obtained through conventional soil tests or parametric studies. The model is evaluated through a series of simulation of undrained shear tests and undrained creep tests.
Anticipation of Stability Limits for Two Degree-of-Freedom Interrupted Milling
Authors: Imani B. M. , Sadeghi M. H. , Kazemi M. 
Published: May 2011

AbstractMilling is becoming an increasingly universal machining operation for producing parts used in aerospace, automotive, and life science engineering industries. The characteristics common to such parts are a high level of complexity and structural flexibility, both of which usually necessitate using low radial immersion milling operations. Low radial immersion milling operations involve interrupted cutting which induces chatter vibration under certain cutting conditions. The stability behavior of low immersion helical end milling processes is investigated in this paper. Time Finite Element Analysis (TFEA) is suggested for an approximate solution for delayed differential equations encountered during interrupted milling. An improved TFEA is proposed which includes the effects of helix angle variations on cutting force, cutting time and specific cutting force coefficients for a 2 DOF vibratory system. To verify the proposed method, experimental tests have been conducted which prove that the improved TFEA method accurately predicts the stability behavior of low immersion milling.
Stability and Chaotic Vibrations of a Fluid-Conveying Pipe with Additional Combined Constraints
Authors: Wang L. , Ni Q. , Huang Y. Y. 
Published: May 2011

AbstractThe stability and possible chaotic vibrations of a fluid-conveying pipe with additional combined constraints are investigated. The pipe, restrained by motion constraints somewhere along the length of the pipe, is modeled by a beam clamped at the left end and supported by a special device (a rotational elastic constraint plus a Q-apparatus) at the right end. The motion constraints are modeled by both cubic and trilinear models. Based on the Differential Quadrature Method (DQM), the nonlinear dynamical equations of motion for the system are formulated, and then solved via a numerical iterative technique. Calculations of bifurcation diagrams, phase portraits, time responses and Poincare maps of the oscillations establish the existence of chaotic vibrations. The route to chaos is shown to be via period-doubling bifurcations. It is found that the effect of spring constant of the rotational elastic constraint on the dynamics is significant. Moreover, the critical fluid velocity at the Hopf bifurcation point for the cubic model is higher than that for the trilinear model.
Characteristics of Hydraulic Shock Waves in an Inclined Chute Contraction - Experiments
Authors: Jan C.-D. , Chang C.-J. , Lai J.-S. , Guo W.-D. 
Published: May 2011

AbstractThis paper presents the experimental results of the characteristics of hydraulic shock waves in an inclined chute contraction with consideration of the effects of sidewall deflection angle φ, bottom inclination angle θ and approach Froude number Fr0. Seventeen runs of laboratory experiments were conducted in the range of 27.45° ≤φ ≤ 40.17°, 6.22° ≤ θ ≤ 25.38° and 1.04 ≤ Fr0 ≤ 3.51. Based on the experimental data, three empirical dimensionless relations for the shock angle, maximum shockwave height, and corresponding position of maximum shockwave were obtained by regression analyses, respectively. These empirical relations would be useful for hydraulic engineers in designing chute contraction structures.
Semi-Active Fuzzy Control of MR Damper on Structures by Genetic Algorithm
Authors: Huang Z.-S. , Wu C. , Hsu D.-S. 
Published: May 2011

AbstractThe magnetorheological (MR) damper is a new device proposed for structural protection. It is filled with MR fluid that can be changed, when exposed to a magnetic field, regularly from free flowing liquid, linear viscous one to semi-solid. A phenomenological model based on the Bouc-Wen hysteresis model is adopted to predict both the force-displacement behavior and the complex nonlinear force-velocity response. The theory of fuzzy control is adopted here to determine the command voltage of MR dampers, but the applying of fuzzy control rules has always to deal with the classic problem of optimization. And due to the structural responses of analysis results, it can be confirmed that the reducing effects have an obviously improvement after an optimization by genetic algorithm.
Numerical Calculation of Turbulent Channel Flow with Porous Ribs
Authors: Chan H. C. , Zhang Yaoxin , Leu J. M. , Chen Y.-S. 
Published: May 2011

AbstractThe turbulent flow in a channel with periodic porous ribs on one wall is numerically studied. The numerical model utilizes the Reynolds averaged Navier-Stokes (RANS) equations with a k−ε turbulent model for turbulence closure. Computational results show good agreements with experimental data in flows over a porous rib. The parameter effects, including the pitch ratio PR (1 ∼ 9) and porosity γ (0.4 ∼ 0.6), on flow fields are further examined in detail. Systematic variations of streamline, streamwise and vertical velocities, and turbulent kinetic energy are clearly identified. As to the PR effect, the interaction between outer flow and flow within the cavity is promoted by arranging ribs due to the penetration of the outer flow. Increasing porosity can reduce the downward outer flow by strong flows passing through the porous ribs. The numerical calculations suggest that the flow characteristics for porous ribs are not only a function of the rib geometry, i.e. pitch ratio, but also the porous property, i.e. porosity.
A New Analytical Model of a Centrifugal Compressor and Validation by Experiments
Authors: Pourfarzaneh H. , Hajilouy-Benisi A. , Farshchi M. 
Published: May 2011

AbstractIn the conceptual design phase of a turbocharger, where emphasis is mainly on parametric studies, before manufacturing and tests, a generalized and robust model that implies over a wide range properly, is unavoidable. The critical inputs such as compressor maps are not available during the conceptual design phase. Hence, generalized compressor models use alternate methods that work without any supplementary tests and can operate on wide range. One of the common and applicable modeling methods in design process is the ‘Dimensionless Modeling’ using the constant coefficient scaling (CCS). This method almost can predict the compressor characteristics at design point. However, at off design conditions, error goes up as mass flow and speed parameters increase. Therefore, the results are not reliable at these points. In this paper, a variable coefficient scaling (VCS) method is described. Then, a centrifugal compressor is modeled using the VCS method. To evaluate the model and compare it with the experimental results, some supplementary experiments are performed. Experimental studies are carried out on the compressor of a S2B model of the Schwitzer turbocharger in the turbocharger Lab., at Sharif University of Technology. The comparison between the experimental results and those obtained by the VCS method indicates a good agreement. It also suggests that the present model can be used as an effective design tool for all operating conditions.
Free Vibration of Rectangular Plate with Delamination
Authors: Shiau L.-C. , Zeng J.-Y. 
Published: May 2011

AbstractIn this paper, the effect of delamination on free vibration of a simply supported rectangular homogeneous plate with through-width delamination was investigated by the finite strip method. A constrained model was used and a finite strip with bending and in-plane stiffness was derived for the free vibration analysis. The effects of delamination length, delamination location in the thickness-wise and spanwise directions, and aspect ratio of the plate on the natural frequencies of the plate were presented. Results show that the delamination has considerable effect on the natural frequencies of the plate. The aspect ratio of the plate is also having significant effect on the natural frequency of the plate, especially on the mode 2 frequency of the plate.
Effect of Vapor Superheating on Mixed-Convection Film Condensation Along an Isothermal Vertical Cylinder
Authors: Chang T.-B. 
Published: May 2011

AbstractThis paper presents an analytical investigation into the effect of vapor superheating on the mixed-convection of a condensate layer flowing along the outside surface of an isothermal vertical cylinder. The governing system of partial differential equations is transformed into a dimensionless form using the nonsimilar transformation method. In investigating the heat transfer characteristics within the condensate layer and vapor phase, the analysis takes account of both the inertia effects and the convection effects within the condensate layer and the shear resistance at the liquid-vapor interface. The numerical results reveal that vapor superheating has a negligible effect on the temperature profile and local Nusselt number within the condensate layer. Moreover, it is found that a higher forced-flow intensity increases the temperature gradient in the vapor phase, but has a marginal effect on the temperature profile in the condensate layer. Finally, it is shown that the velocity at the liquid-vapor interface increases as the intensity of the forced-flow increases or as the ratio of the condensate layer viscosity to the vapor phase viscosity reduces.
The Effect of Kinematic Oscillations on Harmonic Wheel Flange Wear of Rail Vehicles
Authors: Ali Rezvani Mohammad , Asadi Lari Ali 
Published: May 2011

AbstractA number of factors affect rail vehicle steel wheels. Kinematic oscillations uncovered by Klingel, is amongst the parameters affecting dynamic behaviour of the wheelset. Normal and tangential forces are also included within the wheel/rail interface. Geometry and material properties of the contacting bodies are within these parameters. Altogether, these inputs to the rail/wheel system can result in plastic deformation and wear. The authors of this paper make their attempts to introduce a noble study including a harmonic wear pattern in circumference of the flange region when contacting the rail gauge corner. Theoretical aspects of this harmonic pattern are then developed and presented.
Analysis of a Pot-Like Ultrasonic Sensor with an Anisotropic Beam Pattern
Authors: Cheng C.-C. , Lin C.-Y. , Ho J.-H. , Chen C.-S. , Shieh J. , Wu W.-J. , Wu K.-C. , Lee C.-K. 
Published: May 2011

AbstractWe investigated the design parameters of a compact pot-like ultrasonic sensor which possesses a highly anisotropic beam pattern. As the sensor size is small due to its application constraint, the parameters are thus highly coupled to one another. We analyzed the respective effects of the parameters in the case where there is a vertical beam width reduction. The parameters investigated include resonant frequency, vibrating plate width-expanded angle, and ratio of thickness discontinuity of the vibrating plate. Numerical models developed by combining finite-element analysis and spatial Fourier transforms were adopted to predict the far-field radiating beam pattern of the various design configurations. The displacement distribution of the vibrating plate was measured using a microscopic laser Doppler vibrometer and the far-field pressure beam patterns were measured using a standard microphone in a semianechoic environment. The three configurations we used to validate the simulation model resulted in an H-V ratio of 2.67, 2.68 and 3.13, respectively which all agreed well with the numerical calculations. We found that by increasing the operating resonant frequency from 40kHz to 58kHz, the vertical far-field beam width of an ultrasonic sensor can be reduced by 31.62%. We found that the vertical beam width can be significantly reduced when the ratio of the thickness discontinuity of the vibrating plate decreases from 1 to 0.4 and is incorporated with its optimal width-expanded angle of the vibrating plate. It appears that an ultrasonic sensor with this type of anisotropic beam pattern can be ideally adopted for today's automotive applications.
Micro-Droplets Atomizer Using PZT Ring Actuator
Authors: Huang Y.-L. , Chang S.-H. 
Published: May 2011

AbstractThis paper presents the ultrasonic atomizer composed of the lead zirconate titanate (PZT) ring actuator and the Ni nozzle plate with numerous minute nozzles. The atomizer operates at its resonant frequency in out-of-plane vibration. De-ionized (DI) water is fed by the open trough to the porous sponge that is in contact with one face of the nozzle plate and it is ejected through nozzles. Micro-droplets are formed at the opposite face of the nozzle plate. The resonance frequencies of the PZT ring are investigated and compared in theoretical analysis, three-dimensional (3-D) finite-element models (FEM) numerical simulation, and experimental measurement. The performance of the atomizer is examined. This ring shape design of ultrasonic atomizer demonstrates advantage of high atomization rate (64.3ml/min) and high atomization efficiency (l,007ml/h/W) at low power consumption (8.244W).
Rectangular-Plate Turbulator Effects on Heat Transfer and Near-Wall Flow Characteristics in Fan Flows
Authors: Chen T.Y. , Chen Y.H. 
Published: May 2011

ABSTRACTHeat transfer and near-wall flow characteristics in an inherently swirling fan flow, containing rectangular-plate turbulators with 45° and 90° angles of attack, were experimentally investigated. The heat transfer characteristics for uniform flows with the turbulators were also investigated for comparison. Eight heated aluminum plates, installed along a bottom duct-wall, were used as the heat transfer surfaces, which allows the studies of heat transfer variations along the duct and the studies of the relations between the local fluid flows and heat transfer variations. Three-component mean and fluctuating velocities were measured using a laser Doppler velocimetry to obtain the near-wall flow parameters, including the axial mean velocity, axial vorticity and turbulent kinetic energy. The temperatures on the eight heat transfer surfaces were measured using thermocouples to obtain the Stanton number distributions. Results suggest that the rectangular-plate turbulators in fan flows may cause the increases in the near-wall flow parameters and, consequently, augment the heat transfer, especially around the flow reattachment regions. Also, the rectangular-plate turbulator effect on heat transfer augmentation in fan flows may be as attractive as that in uniform flows at the investigated X/H ranges.
Development and Characterization of Jet-Injected Vee-Gutter
Authors: Chang Kuo T. , Huang Rong F. 
Published: May 2011

ABSTRACTThe vee-gutter, which was conventionally used in a combustor for flame holding, was re-designed by employing the unsteady Coanda effect to inject fluids periodically into near wake of the vee-gutter. Fluidic targets were developed to induce self-sustained transverse oscillation of slit-jet. The self-sustained oscillating jet was conducted through passages and injected into the near wake of the vee-gutter. The behaviors and frequency characteristics of the slit-jet in the oscillation cavity and the turbulence properties in the wake were studied experimentally in a wind-tunnel by using the smoke-wire flow visualization technique and the hot-wire anemometer. The oscillation frequencies of the presently developed jet-injection vee-gutter were about 25 to 40 times higher than that of the conventionally used fluidic flowmeter. By estimating the Lagrangian integral time scale and employing the Taylor's frozen flow hypothesis, the integral length scales of turbulence fluctuations were calculated. The results showed that the integral length scales of turbulences of the jet-injected vee-gutter were significantly smaller than their counter parts of the conventional vee-gutter, which indicated the effects of vortex stretching induced by the periodic jet injection. The modifications of turbulence properties were presented and discussed.