bluuebunny/crossref_metadata_2025_split huggingface dataset:
Behaviors of Flame and Flow of Swirling Wake During Fuel Jet Oscillation Due to Acoustic Excitations
Authors: Loretero M. E. , Huang R. F. 
Published: May 2011

AbstractThe flame and flow behaviors along with the fuel jet oscillations of non-premixed and axisymmetric swirling wake during acoustic excitations are studied experimentally. Visual observations on the reaction zones are carried out to identify the flame behaviors. Close-up images at the flame base as well as the whole flame images are captured and discussed. Traditional photography techniques are adopted to illustrate the dimensional characteristics of every flame mode. The central jet oscillations are diagnosed by a two component laser Doppler anemometer. Combined images of the flame and flow are gathered using the laser-light sheet assisted Mie scattering method. Results showed that the short and wide flame which was induced during acoustic forcing is principally because of the severe premixing at the tip of the burner tube. Wake recirculation bubble enhanced premixing at low swirl number while it damped the jet oscillation at higher swirl number. Mechanics of mixing at every flame mode during acoustic excitation are reported and discussed.
Variation of Ovalization for Sharp-Notched Circular Tubes Under Cyclic Bending
Authors: Lee K.-L. , Hung C.-Y. , Pan W.-F. 
Published: May 2011

AbstractIn this paper, an experimental investigation on the variation of ovalization for sharp-notched circular tubes subjected to cyclic bending is discussed. The tube bending machine and curvature-ovalization measurement apparatus were used to test the unnotched and sharp-notched 304 stainless steel tubes. For sharp-notched tubes, five different notch depths (0.2, 0.4, 0.6, 0.8 and 1.0mm) were considered in this study. It was found that the experimental curve of the ovalization and the number of cycles could be divided into three stages-an initial, secondary and tertiary stage. An empirical relationship was proposed for simulating the aforementioned curve for the initial and secondary stages in this study. It has been shown that the derived empirical relationship was in good agreement with the experimental data.
Radiological and Mathematical Studies Regarding the Effects of Spinal Fixation on Kinematics and Mechanics at the Parafixed Segments
Authors: Lin S.-C. , Tsai W.-C. , Wu S.-S. , Chen P.-Q. 
Published: May 2011

AbstractSpinal fixation and fusion has been adopted as a common procedure in spinal surgery. However, the degeneration as a result of parafixation may produce clinically significant problems. Previous studies have already shown increased loads, mobility, and intradiscal pressure at the parafixed segments. These may hasten the degeneration and instability of the neighboring segments. However, controversy remains regarding the correlation between surgical fixation and degeneration owing to parafixation. This study tried to elucidate their relationship by analyzing the in vivo roentgenograms of the post-fusion lumbar spine to measure the motion distribution of the fixed and adjacent unfused spinal segments. In addition, a mathematical model was developed to investigate the effects of implant fixation on the kinematics and mechanics at the parafixation segments.The current radiological studies demonstrated that spinal fixation resulted in the redistribution of intersegmental mobility. The loss of flexion mobility at the fixed segments was unequally compensated for by the increased mobility at all adjacent free segments. This mechanical model can predict the redistribution patterns of mobility and stress at the parafixation segments. This redistribution depends on the fixation levels, implant rigidity, and subject predisposition. Additionally, such compensation was more marked in the tri-segmental than in the two-segment fixation, especially among patients who underwent greater spinal load.This study concluded that the increased flexural rigidity at the fixed segment leads to the compensated kinematic and mechanical demands upon the unfixed adjacent segments. Accordingly, the cumulative effects of such increased mobility and loadings on the adjacent segments could be logically postulated to be the principal causes of accelerated degeneration of the adjacent lumbar segments, both upper and lower portions, subsequent to fusion surgery.
All Speed and High-Resolution Scheme Applied to Three-Dimensional Multi-Block Complex Flowfield System
Authors: Hsu Uzu- Kuei , Tai Chang- Hsien , Tsai Chien- Hsiung 
Published: May 2011

ABSTRACTThe improved numerical approach is implemented with preconditioned Navier-Stokes solver on arbitrary three-dimensional (3-D) structured multi-block complex flowfield. With the successful application of time-derivative preconditioning, present hybrid finite volume solver is performed to obtain the steady state solutions in compressible and incompressible flows. This solver which combined the adjective upwind splitting method (AUSM) family of low-diffusion flux-splitting scheme with an optimally smoothing multistage scheme and the time-derivative preconditioning is used to solve both the compressible and incompressible Euler and Navier-Stokes equations. In addition, a smoothing procedure is used to provide a mechanism for controlling the numerical implementation to avoid the instability at stagnation and sonic region. The effects of preconditioning on accuracy and convergence to the steady state of the numerical solutions are presented. There are two validation cases and three complex cases simulated as shown in this study. The numerical results obtained for inviscid and viscous two-dimensional flows over a NACA0012 airfoil at free stream Mach number ranging from 0.1 to 1.0E-7 indicates that efficient computations of flows with very low Mach numbers are now possible, without losing accuracy. And it is effectively to simulate 3-D complex flow phenomenon from compressible flow to incompressible by using the advanced numerical methods.
Gasdynamic-Like Equations for Oblique Shock Waves and Nozzle Flows in Soap Films
Authors: Wen C.-Y. , Lai J.-Y. 
Published: May 2011

ABSTRACTThe governing equations for oblique shock waves and nozzle flows in soap films are formulated based on their very specific property equations. The θ-β-M relation for oblique shock waves and the width-velocity relation for quasi-one-dimensional nozzle flows are presented. The results are similar to those of compressible gases. On short time scales, the analogy of soap films to two-dimensional (2-D) compressible gases with a specific heat ratio of γ = 1.0 that is shown by Wen and Lai [1], Wen, et al. [2] and Chomaz [3] is again demonstrated. The present results supplement the theory of compressible flows in soap films.
Micro-System Displacement and Profile Measurement By an Integrated Photon Tunneling and Confocal Microscope
Authors: Chen Wen-Jong , Lee Chih-Kung , Lu Shui-Shong , Huang Long-Sun , Chu Ta-Shun , Cheng Ying-Chou , Yeh Wu-Fone 
Published: May 2011

ABSTRACTAn integrated optical method for measuring deformation of micro-mechanical systems with better than sub-micron resolutions is detailed. Both a confocal laser scanning microscope and a photon tunneling microscope were integrated into a single microscopy system due to their complimentary capabilities for examining sub-micrometer deformations. A halogen lamp and laser were adopted as the two light sources for the measurements. Since topographic information of samples up to a 15μm by 15μm area can be measured, a three-dimensional displacement field of the sample was extracted by comparing topographies of the same specimen area before and after deformation. The bending and twisting deformation of a micro-mirror driven by the electrostatic force was measured to demonstrate the capability of this newly developed instrument. The experimental data obtained agrees reasonably well with the theoretical results calculated by adopting an analytical solution and a finite element method. The small discrepancy in the result can be traced to the surface roughness effect, which is often non-negligible in micro-systems.
The Stress-Strain Behavior of Densified Mix Design of Concrete
Authors: Chang Ping-Kun 
Published: May 2011

ABSTRACTThis paper investigates the compressive strength and workability of High-Performance Concrete (HPC) which yields a slump at 250 ± 20mm and a slump flow at 650 ± 50mm. From the complete stress-strain curve, it shows the peak strain will be higher while the strength increases. Two kinds of the post failure models can be distinguished. The first type (Type I) is called strain softening and the second type (Type II) is called strain snapping back. Also, it is found that the modulus of elasticityEcdecreases as the volume of cementitious pasteVpincreases. On the other hand, Poisson's ratio ν increases asVpincreases.
Evaluation of Bridge Safety Based on Concrete Nondestructive Test
Authors: Liu Pei-Ling , Sun Pi-Fen 
Published: May 2011

ABSTRACTThis paper develops a framework for the safety assessment of bridges based on the nondestructive test (NDT) results of concrete. The transient elastic wave test is performed to measure the P wave velocity of concrete. The Bayesian approach is adopted to construct the posterior distribution of concrete strength. Then, reliability analysis is carried out to evaluate the safety of the bridge using the modified distribution. The limit-state function is formulated according to the AASHTO specifications. Finally, the reliability index is compared to the target reliability to see if repair or reconstruction is required. A numerical example is presented to illustrate the safety assessment of a solid-slab bridge using the proposed method.
On Approximate Solutions for Two-Dimensional Thermoelastic Problems with a Nearly Circular Hole
Authors: Wang Chung-Hao , Chao Ching-Kong 
Published: May 2011

ABSTRACTThe general approximate solutions for the two-dimensional thermoelastic problems with a nearly circular hole are provided in this study. Based on Stroh formalism and the method of conformal mapping, the boundary perturbation analysis is applied to solve the problems of a hole with arbitrary shape. The radius of the hole considered here is represented as a sum of a reference constant and a perturbation magnitude that is expanded into a Fourier series. In order to illustrate the applicability and efficiency of the present approach, special examples associated with polygonal hole problems are solved explicitly and discussed in detail. Since the general solutions have not been found in the literature, comparison is made with some special cases for which the analytical solutions exist, which shows that our proposed method is effective and general.
A Gurson Yield Function for Anisotropic Porous Sheet Metals and its Applications to Failure Prediction of Aluminum Sheets
Authors: Wang D.-A. , Chien W. Y. , Liao K. C. , Pan J. , Tang S. C. 
Published: May 2011

ABSTRACTAn approximate anisotropic yield function is presented for anisotropic sheet metals containing spherical voids. Hill's quadratic anisotropic yield function is used to describe the anisotropy of the matrix. The proposed yield function is validated using a three-dimensional finite element analysis of a unit cell model under different straining paths. The results of the finite element computations are shown in good agreement with those based on the yield function with three fitting parameters. For demonstration of applicability, the anisotropic Gurson yield function is adopted in a combined necking and shear localization analysis to model the failure of AA6111 aluminum sheets under biaxial stretching conditions.
Stress Wave Propagation for Nonlinear Viscoelastic Polymeric Materials at High Strain Rates
Authors: Wang Li-Lih 
Published: May 2011

ABSTRACTWithout knowing the dynamic constitutive relation of materials under high strain rates, no wave propagation can be correctly analyzed. A Series of experimental and theoretical investigation at high strain rates revealed that the nonlinear viscoelastic behavior of polymers and the related composites are well described by the Zhu-Wang-Tang (ZWT) nonlinear viscoelastic constitutive equation. The impulsive reponse of ZWT materials consists of a rate independent nonlinear elastic response and a high frequency linear viscoelastic response. The dispersion and attenuation of nonlinear viscoelastic waves mainly depend on the effective nonlinearity and the high frequency relaxation time θ2. An “effective influence distance” or “effective influence time” is defined to characterize the wave propagation range where θ2 dominates the impact relaxation process.
A Rigid Elliptic Inclusion in an Elastic Medium With a Slipping Interface
Authors: Wang Yung-Ming 
Published: May 2011

ABSTRACTWhen an elastic medium containing an elliptic inclusion with a sliding interface is subjected to a remote pure shear, it was found that the inclusion behaves like a cavity. Since a circle is a special case of an ellipse, the solution should be applicable to a circular inclusion as well. However, it breaks down when the ellipse degenerates into a circle. This implies that the solution is questionable. In this paper the problem is examined by considering a rigid elliptic inclusion in an elastic medium with sliding interface between them. By taking account of a large rotation of the inclusion instead of a small rotation, we obtain a uniformly valid solution applicable to a circular inclusion as well as to an elliptic inclusion. The solution reveals a remarkable snapping behavior of the inclusion under a critical load. A simple condition for its occurrence is derived.
A Method for the Analysis of Transient Motion of a Kelvin-Voigt Half-Space
Authors: Yeh Chau-Shioung , Liao Wen-I , Teng Tsung-Jen , Shuy Wen-Shinn 
Published: May 2011

ABSTRACTIn this paper, a modified version of method of steepest descent combining with Durbin's method is proposed to study the transient motion in either an elastic or a viscoelastic half-space. The causal condition is satisfied based on the Durbin's method while the wavenumber integral for any range of frequency is evaluated by applying the modified method of steepest descent. The validity and accuracy of the proposed method is tested by studying the transient response generated by a buried dilatational line source in an elastic half-space, for which the exact solution (Garvin's solution) can be obtained. Then the same formalism is extended to Kelvin-Voigt half-space, and the transient surface motions in elastic or viscoelastic half-spaces media are studied and discussed in details.
Studies on Epitrochoid Gear for Cycloid Drives
Authors: Chang Shinn-Liang 
Published: May 2011

ABSTRACTCycloid drives are widely used in the industries because of their excellent characteristics, namely, high gear ratio, smooth transmission, compact size, high efficiency, low noise and long service life. In this paper, a mathematical model of an epitrochoid gear for a cycloid drive with a small tooth number difference has been proposed. Computerized simulation of the generated epitrochoid gear has also been developed. In this paper, the pressure angle, which has an important role in the analysis of cycloid drives as it influences the direction and magnitude of force transmission in gears, is derived based on the theory of differential geometry. The rack cutter profile, which is the fundamental tooth profile of a hob cutter, which in turn is the main manufacturing process of epitrochoid gear, has been obtained based on the theory of gearing. It is anticipated that the results from this paper will be beneficial to the design, analysis and manufacture of cycloid drives.
Oscillatory Flows over a Permeable Wavy Boundary
Authors: Hsiao Shih-Chun , Liu Philip L.-F. 
Published: May 2011

ABSTRACTIn this paper viscous boundary layer flows above and inside a permeable wavy bed are studied. The flow motions are driven by an oscillatory horizontal velocity just outside the Stokes boundary layer above the bed. Analytical and numerical solutions are obtained for both the oscillatory velocity component and the steady streaming inside the permeable bed, the Stokes boundary layer and the outer boundary layer. Two specific situations are examined: (1)Weak oscillatory motions over a wavy bed with finite slope and (2) strong oscillatory motions over a small wavy slope. In both situations, the slip (tangential) velocity and the normal velocity do not vanish on the wavy surface because of the permeability. The magnitude of the bed shear stress decreases as the permeability increases. The permeability can also affect significantly the steady streaming patterns; they could change from having two pairs of recirculating cells above an impervious wavy bed to one pair of recirculating cells above a wavy permeable bed.
A Family of Explicit Dissipative Algorithms for Pseudodynamic Testing
Authors: Chang S.- Y. 
Published: May 2011

AbstractThe α-function method is a family of second-order explicit methods with controlled numerical dissipation. Thus, it is very promising for the pseudodynamic testing of a system where high frequency responses are of no interest. This is because that favorable numerical dissipation can suppress the spurious growth of high frequency responses, which might arise from numerical and/or experimental errors during a test. Furthermore, the implementation of an explicit method for the pseudodynamic testing is much simpler than for an implicit method. The superiority of using this method in performing a pseudodynamic test was verified both analytically and experimentally. In fact, results of error propagation analysis reveal that the spurious growth of high frequency responses can be suppressed and less error propagation is identified when compared to the Newmark explicit method. Actual tests were conducted pseudodynamically to confirm all the analytical results. It is also illustrated that although the high frequency response is insignificant to the total response it may be significantly amplified and propagated and finally destroys the pseudodynamic test results.
Cylindrical Stress Waves in Poroelastic Flat Slabs
Authors: Reddy P. M. , Tajuddin M. 
Published: May 2011

AbstractBiot's poroelastic theory is employed to study stress wave propagation in an infinite slab of arbitrary thickness. The frequency equation is obtained each for pervious and impervious surfaces for a nondissipative medium. Appropriate numerical data is presented in the form of graphs and then results are discussed. Waves in a thin bar and in a semi-infinite slab are discussed as limiting cases.
Enstrophy Cascade and Smagorinsky Model of 2D Turbulent Flows
Authors: Huang Mei-Jiau 
Published: May 2011

ABSTRACTDirect numerical simulations of 2D turbulent flows, freely decaying as well as forced, are performed to examine the mechanism of the enstrophy cascade and serve as a template of developing LES models. The stretching effect on the 2D vorticity gradients is emphasized on the analogy of the stretching effect on 3D vorticity. The enstrophy cascade rate, the Reynolds stresses and the associated eddy viscosity for 2D turbulence are correspondingly derived and investigated. Proposed herein is that the enstrophy cascade rate to be modeled in a large-eddy simulation can be and should be calculated using the only available large-eddy information, especially when the Reynolds number is not very large or when the flow is not stationary.The simulation results suggest all Kolmogorov's, Kraichnan's, and Saffman's similarity spectra. The Kolmogorov's spectrum appears in front of forced wave numbers and creates a subrange of a zero enstrophy cascade rate and a constant energy cascade rate. The Saffman's spectrum is the dissipation spectrum at large wave numbers. Kraichnan's spectrum shows up at intermediate wave numbers when the Reynolds number is sufficiently high. When the Smagorinsky model is employed for a large eddy simulation, its inability of capturing the significant reverse cascade phenomenon as observed in the DNS data becomes a fatal defect. Nonetheless, if only the mean cascade rate is concerned, the required Smagorinsky constant is evaluated using the DNS data and compared with the theoretical prediction of the Kraichnan's spectrum.
The Health Monitoring of Bridges using Artificial Neural Networks
Authors: Liu Pei-Ling , Sun Shyh-Jang 
Published: May 2011

ABSTRACTThis study develops a neural network system to monitor the safety of a bridge structure. A truck of constant mass is driven at constant speed through the target bridge. Then, the maximal and minimal values of the bridge elongations are processed by a monitoring system to evaluate the current condition of the bridge. The monitoring system is composed of parallel backpropagation neural networks. Each neural network monitors a part of the bridge. The neural networks are trained using simulation data. The numerical example shows that the monitoring system is effective in the damage detection of the bridge.
Analysis of Wave Propagation in Infinite Piezoelectric Plates
Authors: Wu C. Y. , Chang J. S. , Wu K. C. 
Published: May 2011

ABSTRACTAn analysis is presented for wave propagation in infinite homogeneous elastic plates of piezoelectric materials. The analysis is an extension to the work by Shuvalov [1] on wave propagation in general anisotropic elastic plates. A real form of dispersion equation is provided for a piezoelectric plate subjected to different boundary conditions on the plate surfaces. Perturbation theory [2] is exploited to obtain long-wavelength low-frequency approximation for physical quantities of wave propagation, including wave amplitude, stress, electric potential, electric displacement and velocity.
Improved similarity scores for comparing motifs
Authors: Tanaka Emi , Bailey Timothy , Grant Charles E. , Noble William Stafford , Keich Uri 
Published: May 2011

Abstract
Motivation: A question that often comes up after applying a motif finder to a set of co-regulated DNA sequences is whether the reported putative motif is similar to any known motif. While several tools have been designed for this task, Habib et al. pointed out that the scores that are commonly used for measuring similarity between motifs do not distinguish between a good alignment of two informative columns (say, all-A) and one of two uninformative columns. This observation explains why tools such as Tomtom occasionally return an alignment of uninformative columns which is clearly spurious. To address this problem, Habib et al. suggested a new score [Bayesian Likelihood 2-Component (BLiC)] which uses a Bayesian information criterion to penalize matches that are also similar to the background distribution.
Results: We show that the BLiC score exhibits other, highly undesirable properties, and we offer instead a general approach to adjust any motif similarity score so as to reduce the number of reported spurious alignments of uninformative columns. We implement our method in Tomtom and show that, without significantly compromising Tomtom's retrieval accuracy or its runtime, we can drastically reduce the number of uninformative alignments.
Availability and Implementation: The modified Tomtom is available as part of the MEME Suite at http://meme.nbcr.net.
Contact: uri@maths.usyd.edu.au; e.tanaka@maths.usyd.edu.au
Supplementary Information: Supplementary data are available at Bioinformatics online.