bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary Experiments for Evaluating 3-D Effects on Cracks in Frozen Stress Models
Authors: Smith C. W. , Hansen J. D. , Liu C. T.
Published: May 2008

Information gleaned from applying the frozen stress photoelastic method to cracks emanating from critical locations around the fin tips in models of solid rocket motors is reviewed and assessed together with new experimental results. The studies are the initial part of a program developed to contribute background data for consideration in modifying current motor grain design rationale.
CFD Simulation of Fluid Flow Through Porous Media: Application to Decomposed Gases Flow Through Foam Pattern in Lost Foam Casting
Authors: Bakhtiyarov Sayavur I. , Overfelt Ruel A.
Published: May 2008

Numerical simulation of decomposed gases through foam pattern was conducted using finite element analysis. A new kinetic model is proposed for gaseos phase flow between molten metal and foam material. The computations were performed for a wide range of Reynolds numbers. The results of the simulations are compared with the experiemental data obtained in this study.
Utility of Projection Network for Diagnosis of High Pressure Air Compressor Faults
Authors: Jansuwan C. , Li C. James
Published: May 2008

The utility of a dynamic neural network, i.e., projection network, was established to diagnose the condition of a 4-stage high pressure air compressor. Network structure and parameter initialization and training methods were developed. Using measurements of the compressor’s four stages’ discharge temperatures and pressures collected under different baseline conditons, 3rd stage suction and exhaust value faults, and an unanticipated 3rd stage cylinder pittings as training data, a 99+% of correct classification rate was accomplished with testing data.
Managing a Major Curriculum Reform Effort in a Large Research University
Authors: Schmidt Philip S. , Beaman Joseph J.
Published: May 2008

This paper describes a substantive undergraduate curriculum reform effort being undertaken over a five year period at the University of Texas at Austin, with special consideration to the management issues that are being addressed. The initiative, called Project PROCEED (for Project-Centered Education), grew out of a desire to strengthen our student’s understanding of fundamental engineering theory by continuously tying it to tangible objects and systems, to strengthen our Department’s connections with its industrial stakeholders by actively involving them in the development and delivery of curriculum content, and to provide our students with a broad range of team-based experiences which will better prepare them for growth and leadership in the corporate and professional world. The rationale for PROCEED and key program elements are described. Management issues, such as logistics, promoting faculty and student buy-in, financing, industrial interaction, and program evaluation are discussed.
Functionally Graded Polymeric Composites Having Micro-Tailored Structure Formed by Electric Field
Authors: Kim Geun Hyung , Moeller Daniel K. , Shkel Yuri M.
Published: May 2008

A solid composite having locally micro-tailored structure can be produced by curing liquid polymeric suspensions in an electric field. The redistribution effect of the field-induced forces exceeds the effect of centrifugation, presently employed to manufacture functionally graded materials. Moreover, unlike centrifugational sedimentation, one can electrically rearrange the inclusions in desired targeted areas. The applied electric field can be employed to produce a composite having uniformly oriented structure or only modify the material in selected regions. This technology enables polymeric composites to be locally micro-tailored for given design objectives. We discuss electrical and rheological inteactions in liquid suspensions. Relationships between microstructure and mechanical properties of the obtained functionally graded composites are presented.
Convective Heat Transfer in the Flow of Visco-Elastic Fluid Saturated in a Porous Medium Over a Non-Isothermal Stretching Sheet
Authors: Abel M. Subhas , Prasad K. V. , Ali Mahaboob
Published: May 2008

This paper analyses the steady two-dimensional boundary layer flow of an incompressible visco-elastic fluid saturated in a porous medium over non-isothermal stretching sheet. The presence of Buoyancy force leads to the coupling and non-linearity in the boundary value problem. A numerical shooting technique for two unknown intial conditions with fourth order Runge-Kutta integration scheme is used (Abel et al 2002) to solve the coupled non-linear problem. Results are analysed for different values of non-dimensional physical parameters. One of the important finding is that the effect of Grashof number is to increase the horizontal velocity profile and to decrease the temperature profile in the presence/absence of porous medium.
Shear Dielectric and Rheological Responses of Polymeric Flows
Authors: Peng Yiyan , Shkel Yuri M.
Published: May 2008

A variation of dielectric properties with deformation is typically not seen in viscous liquids. However, the dielectrostriction effect can be observed in viscoelastic liquids such as polymers. The dielectrostriction effect resembles a well-known birefringence phenomenon. While birefringence in liquid polymers is described by the stress-optical rule, the stress-dielectric rule works for dielectrostriction. In this article, experimental evidences of the dielectrostriction effect in liquid polymers are presented for the first time. Dielectric and rheological measurements of liquid silicone elastomers having different degree of cross-linking are conducted at different frequencies and amplitudes of oscillatory shear flow. A stress-dielectric relationship exists between shear dielectrostriction response and storage modulus which is similar to stress-optical rule.
Ionic Liquids as Hyper-Stable Solvents for Ionic Polymer Transducers
Authors: Bennett Matthew D. , Leo Donald J.
Published: May 2008

Nafion™ membranes are known to operate as electromechanical actuators and sensors. The transduction in the material is caused by redistribution of the mobile cations in the material, which is made possible because the material is saturated with a solvent. Typically the solvent used is water, although its use limits the performance of these materials. This is due to the chemical breakdown of the water at relatively low operating voltages and the loss of the water to evaporation when these devices are operated in air, causing a corresponding loss of performance. In the current work, the use of highly stable ionic liquids to replace water is explored. Ionic liquids have the advantage of greater electrochemical stability than water, thus offering the possibility of higher actuation voltages for these materials. Also, ionic liquids are known to be non-volatile and therefore will not leach out of the polymer by evaporation as water will. This paper will present the results of some initial work with ionic liquids and will compare these materials to the same polymers solvated with water.
A Study on Human, Chimpanzee and Canine Lumbar Vertebral Endplates
Authors: Kale Shreedhar P. , Langrana Noshir A. , Lee Casey K. , Kopacz Kenneth J.
Published: May 2008

Vertebral endplates of the lumbosacral spine have various degrees of concavity and/or convexity. Little information is available in the literature on accurate measurement of morphometry of the vertebral endplates of the lumbosacral spine and on biomechanical significance of the curvature. In this study, lumbar vertebral endplate curvatures in anterior-posterior and medial-lateral directions were measured. Human males-females, chimpanzees and canine lumbar endplates were scanned and quantified. Finite Element Analysis (FEA) was performed on endplates and the effects of location of maximum curvature depth on the stress distribution were investigated.
On the Vibration of a Rotor-Shaft System With Viscoelastically Supported Bearings
Authors: Shabaneh N.
Published: May 2008

This paper investigates the dynamic behaviour of a single rotor-shaft system with nonlinear elastic bearings at the ends mounted on viscoelastic suspensions. A Timoshenko shaft model is utilized to incororate the flexibility of the shaft; the rotor is considered to be rigig and located at the mid-span of the shaft. A nonlinear bearing pedestal model is assumed which has a cubic nonlinear spring and linear damping characteristics. The viscoelastic supports of the bearings are modeled as Kelvin-Voigt model. Free vibration analysis is performed on the linear system including the damping of the bearings. Forced vibration analysis is performed on the nonlinear system. Equations of motion are derived for the nonlinear system based on the direct multiple scale method of one-to-one frequency-to-amplitude relationship using third order perturbation expansion. The effects of stiffness and loss coefficients of the viscoelastic supports on the complex natural frequencies are identified for the linear system. The results show that optimum values of the viscoelastic stiffness and loss coefficient can be achieved for a specific rotating shaft system to reduce vibrations and increase the operating regions. In addition, the frequency response of the nonlinear system indicates that a jump phenomenon takes place for high values of the bearing nonlinear elastic coefficient.
Volume Computation of a Levitated Aspherical Droplet From 2-D Image Information
Authors: Dupac Mihai , Bakhtiyarov Sayavur , Overfelt Ruel A.
Published: May 2008

This paper presents an image processing technique in order to predict the volume of levitated aspherical droplet. The technique is of great importance to containerless materials processing. A majority of the electromagnetic levitation techniques utilize two cameras at right angles to observe transversal and frontal view. This allows obtaining two images of the droplet at instant time. In many cases, the portion of the frontal image is missing due to the heating coil. The newly developed technique allows restoration of the missing portion of the image information. The thru image can be reconstructed by combining the recovered shapes. A special computer program is generated to simulate a normalized volume of the droplet.
Tuned Modal Control of a Space-Based Deployable Manipulator
Authors: Zhang Jian , de Silva Clarence W.
Published: May 2008

This paper develops an intelligent hierarchical controller for vibration control of a deployable manipulator. The emphasis is on the tuning of a low-level direct controller using an upper level knowledge-based tuner so as to improve the performance of the manipulator. In the present development, a conventional modal controller is used as the direct controller. First a fuzzy inference system (FIS) is developed for controller tuning. The FIS and the modal controller are integrated into a hierarchical control system for use with the deployable manipulator. An example is presented to illustrate the application of the hierarchical control system for suppressing vibrations caused by initial disturbance of a space-based deployable manipulator system. The simulation results show that the developed system is very effective in suppressing vibrations induced due to an initial disturbance at the tip of a manipulator module. Performance of the modal controller is significantly improved through knowledge-based tuning.
Zero Assignment in Continuous Systems
Authors: Singh Akshay N. , Singh Kumar V. , Ram Yitshak M. , Pang Su-Seng
Published: May 2008

The feedback control gain to absorb the harmonic response at a desired position in continuous vibrating structures may require an infinite product of eigenvalues. Such control gain, for distributed parameter elastic structures, improves monotonically with the increase in model order of their discrete counterparts obtained by the finite difference or finite element methods. However, the estimation of control gain, using such discrete approximations is inaccurate due to dissimilar asymptotoc behavior of eigenvalues of the discrete model and associated distributed parameter system. An alternative formula uses deformation information for determining the control gain, but for non-uniform structures a closed form expression for deformation may not exist. The objective here is to show that a new mathematical model for non-uniform structure, based on piecewise constant approximation, can be successfully used for better approximation of the control gain. For simplicity, the analysis is carried out for a non-uniform vibrating rod in order to validate the above arguments.
Multiscale Modeling of Large Deformation Processes in Polycrystalline Metals
Authors: Maniatty Antoinette , Matous Karel , Lu Jing
Published: May 2008

A mesoscale model for predicting the evolution of the grain structure and the mechanical response of polycrystalline aggregates subject to large deformations, such as arise in bulk metal forming processes, is presented. The gain structures modeled are either experimentally observed or are computer generated and statistically similar to experimentally observed grain structures. In order to capture the inhomogeneous deformations and the resulting grain structure characteristics, a discretized model at the mesoscale is used. This work focuses on Al-Mg-Si alloys. Scale bridging is used to link to the macroscale. Examples involving two-dimensional grain structures and current work on three-dimensional grain structures are presented. The present work provides a framework to model the mesoscopic behavior and interactions between grains during finite strains. The mesoscale is characterized by a statistically representative voluem element (RVE), which contains the grains of a polycrystal. Experimentally observed grain structures are used both as models directly (for two-dimensional cases) and to define statistical characteristics to verify the similarity of computer generated grain structures (for three-dimensional cases). A Monte Carlo method based on the Potts model is used to define three-dimensional grain structures. In order to make the representative grain structure appropriate for scale-bridging, we design them with periodicity. A three-field, updated Lagrangian finite element formulation with a kinematic split of the deformation gradient into volume preserving and volumetric parts is used to create a stable finite element method in the context of nearly incompressible behavior. A fully implicit two-level backward Euler integration scheme is derived for integrating the constitutive equations, and consistent linearization is used in Newton’s method to solve the resulting equations. In addition, the average of the boundary conditions and bulk response must match the macroscopically measured bulk response. To illustrate and verify the proposed model, we analyze examples involving two-dimensional grain structures and compare with results from a Taylor model. Current work on three-dimensional grain structures ara also presented.
Free Vibration Analysis of Rotating Blades With Uniform Tapers
Authors: Wang Gang , Wereley Norman M.
Published: May 2008

The determination of model frequencies and mode shapes of rotating blades, which are either straight or tapered, is usually accomplished via application of conventional assumed displacement finite element or assumed modes methodologies. To ensure accuracy of modal information at low mode num bers, a large number of elements or admissible functions must be utilized in the model. Modal frequencies converge to the exact solutions from above with the increase of number of elements or assumed admissible functions. To apply the resulting large degree-of-freedom model in a dynamic simulation (forced or transient), or to embed such a model in a real-time model-based control problem, can be impractical. As a result, the model order must be reduced via static or dynamic condensation procedures to a practical number of degrees-of-freedom, which is constrained by simulation time, or the control interval in a digital control system. Therefore, a method is proposed, based on a spectral finite element technique, to develop such a low degree-of-freedom dynamic model directly and without resorting to a condensation procedure. The method exploits semi-analytical progressive wave solutions of the governing partial differential equations. We have calculated such results for a number of examples such as a straight beam and beams with uniform taper or compound tapers. Only one single spectral finite element is needed to obtain any modal frequency or mode shape, which is as accurate or better than other approaches reported in the literature for a straight or uniformly tapered beams. The minimum number of such spectral finite element correspond to the number of substructures (i.e., beam sections with different uniform tapers) in a rotating beam in order to capture the complete system dynamic characteristics. The element assembly procedure is accomplished in the same fashion as the conventional finite element approach. Overall, for a rotating blade system, our spectral finite element method provides highly accurate predictions for any modal frequency using a single element or very few elements corresponding to the number of uniform taper changes in the blade system.
Development of a Jet Engine Experiment for the Energy Systems Laboratory
Authors: Pourmovahed A. , Jeruzal C. M. , Brinker K. D.
Published: May 2008

Recently, a jet engine experiment was added to the Energy Systems Laboratory at Kettering University (formerly GMI). The educational objectives of this experiment are: to familiarize the students with the operation of a turbojet engine, the theory behind the thermodynamic processes involved, and the linear momentum equation; to determine theoretical and measured engine thrust and the efficiencies of the compressor, the combustion chamber, and the turbine; to determine the effect of engine speed on thrust-specific fuel consumption (TSFC) and engine emissions; to analyze the combustion process; and to perform a complete energy balance on the jet engine. The apparatus used is a small TTL model SR-30 turbojet engine capable of kerosene and diesel liquid fuel start and operation. Using an automatic data acquisition system, the students operate the engine at 50,000–75,000 rpm and measure various pressures and temperatures as well as fuel flow rate, air flow rate, engine emissions and engine thrust. The data is then used to calculate the TSFC, component efficiencies and the A/F ratio. By using the linear momentum principle, engine thrust is calculated and compared with the measured value. This paper presents the measured test data and analytical results obtained by using the Engineering Equation Solver (EES). Experimental results compare favorably with theoretical predictions.
Analysis of Flexible Fly Fishing Rods and Casting Dynamics
Authors: Wang Gang , Wereley Norman M.
Published: May 2008

In this paper, we studied the fly rod casting dynamics. A nonlinear finite element model was used to analyze the transient response of a fly rod, in which fly rod responses were determined under the simulation of forward casting stroke. The lumped parameter method was used to discretize the fly line system. Finally, we determined the fly line motions during a cast based on the information of fly rod tip responses, which are the initial boundary conditions of the fly line. The fly line loop generation, propagation, and line turn-over were represented numerically. The results were compared to the rigid rod case, in which fly tip path was specified for a given fly rod case, in which fly tip path was specified for a given fly rod butt input. Our numerical results strongly recommended the flexibility (nonlinear) effects of the fly rod must be included in order to capture the actual casting dynamics. The fly rod casting simulation was studied analytically and further experimental validation is needed.
Convective Oxygen Transport Enhancement in Intravenous Membrane Oxygenators
Authors: Escobar Rodrigo A. , Amon Cristina H.
Published: May 2008

Numerical simulations of blood and water flow and oxygen transport in a computational model of an intravenous membrane oxygenator including moving boundaries are presented. The simulations are compared to an analytical transport model which is validated by comparing its result to experimental data reported in the literature. Good agreement is found between numerical, analytical and experimental results.
Recent Improvements of the Algorithm of Mode Isolation
Authors: Ginsberg Jerry H. , Allen Matthew S.
Published: May 2008

The Algorithm of Mode Isolation (AMI) identifies the natural frequencies, modal damping ratios, and mode vectors of a system by proceesing complex frequency response data. It uses an iterative procedure based on the fact that a general frequency response function is a superposition of modal contributions. The iterations focus successively on a singel mode. The mode that is in focus is isolated by subtracting the other modal contributions using prior estimates of their modal properties. This process leads to a self-contained identification of the number of modes that participate in any frequency band, whereas other techniques require a priori guesses. This paper describes modifications intended to improve AMI’s accuracy and reduce its computational effort. These involve the use of a new linear least squares method for identifying the natural frequency and dmaping ratio of a single mode, a linear least squares global fit of the data in order to identify mode vectors. Results are presented for a model of a cantilever beam with suspended spring-mass-dashpot system. This system was used by Drexel, Ginsberg, and Zaki [Journal of Vibration and Acoustics, 2003 (forthcoming)] to assess the prior version’s ability to identify weakly excited modes and modes having close natural frequencies in the presence of high noise levels. Application of the modeified version of AMI to the same system is shown to lead to significantly more accurate damping ratios are mode vectors, with equally good natural frequencies.
Effects of Meniscus Motion on Ejection Performance in Thermal Inkjet Print Heads by 3-D Numerical Simulation and 1-D Lumped Modeling
Authors: Kim Min Soo , Lee Yong Soo , Shin Suho , Lee You-Seop , Shin Seung Joo , Oh Yong Soo
Published: May 2008

Undesired meniscus motion at the nozzle exti can cause detrimental effects on ejection performance of an inkjet print head, resulting in degradation of printing quality at high frequency operation. In this study, visulization of droplet ejection and meniscus motion was performed experimentally, and the results were compared with those of numerical simulations. Effects of design factors on themeniscus motion, such as material properties of ink and geometric dimensions of head structure, were investigated by three-dimensional (3-D) numerical simulations. The result demonstrated that the ejection performance and the following menicus motion might be affected significantly due to changes in the design factors. For simple and fast computation, one-dimensional (1-D) lumped model was constructed, and its results were meaningful for the intuitive understanding of ejection performance and meniscus oscillation. Also, effects of different meniscus conditions on the subsequent ejection were investigated by 3-D numerical computations. The results showed that a stabilizing time, e.g., 70μs, was needed for uniform reproducible ejection. The results of this study will be helpful for development of the inkjet print heads of higher performance.
Effect of Severe Plastic Deformation on the Mechanical Behavior of Ti-6Al-4V
Authors: Karaman Ibrahim , Yapici G. Guven
Published: May 2008

The present work focuses on the microstructural evolution and resulting room temperature mechanical properties of P/M Ti-6Al-4V severely deformed at different temperatures (550°C to 800°C) using Equal Channel Angular Extrusion (ECAE). The bulk materials are extruded through two channels of equal cross section intersecting an angle of 90 degree. Microstructure and mechanical properties of extruded billets are reported through electron microsopy observations and tension, compression and hardness experiments. Results are compared for different extrusion conditions including variations in temperature and processing route. Higher hardness values are obtained after ECAE compared to as-received values. These improvements are correlated with the grain refinement, phase refinement and texture produced during ECAE. The most favorable microstructure in terms of refined grains was two passes at 600°C. The ultimate goal is to develop ECAE thermomechanical-processing maps for the selection of processing schedules to obtain desired end microstructures and improved fatigue life in Ti-Al-V based materials. The investigations revealed that: 1. ECAE shear deformation leads to refinement in β plates and elimination of piror β boundaries. Decreasing extrusion temperature and increasing number of passes decreases α plate size and grain size. Refined α grain size leads to a significant increase in tensile and compressive flow stresses at room temperature. 2. The second extrusion pass at 800°C increased both the yield strength and ductility. This was attributed to the observed α plate refinement. 3. Cavitation at the interface between β strips and α plates at 550°C was thought to be the reason for low ductility and relatively low strain hardening at room temperature. 4. Texture has a pronounced effect on mechanical properties. Tension/compression asymmetry in flow strengths and strain hardening coefficients may be described by the activation of differing slip systems under tension and compression loading because of texture.
Thermal Stress Modeling in Micro- and Opto-Electronics: Review and Extension
Authors: Suhir E.
Published: May 2008

The role and the attributes of, and the challenges in, predictive modeling of thermal stresses, strains and displacements in micro- and opto-electronic packaging are addressed. Merits, shortcomings and interaction of theoretical and experimental approaches are discussed, as well as the role and the interaction of the analytical (“mathematical”) and the numerical (computer-aided, primarily, finite-element) modeling. We briefly review the published work in the field, with an emphasis on the analytical modeling. The review is based, to a great extent, on the author’s work conducted during his eighteen years tenure with Bell Laboratories at Murray Hill, New Jersey. The “extension part” of the article is dedicated to the role that a probabilistic approach might play in understanding and predicting the effects of the variability in materials properties, structural geometry and loading conditions on the thermal stresses, strains and reliability of micro- and opto-electronic assembiles and structures, subjected to thermal loading. The main message of the article is that a viable and reliable micro- or opto-electronic component or device can be successfully created and delivered, as a product, to the market in a timely fashion only provided that predictive modeling, whether analytical or numerical, is widely and effectively employed. Modeling should be conducted in addition and, preferably, prior to the design effort, experimental investigations and accelerated (product development, qualification or life) testing. In this connection, we would like to point out that predictive modeling is also an essential part of the accelerated life testing methodologies and procedures. Another message is that probabilstic approaches could be very helpful in many problems of physical design of micro- and opto-electronic systems subjected to thermal loading.
Stability of a Non-Newtonian Fluid in a Channel With Heat Transfer
Authors: Ozalp Coskun , Pinarbasi Ahmet
Published: May 2008

In this paper the linear stability of plane Poiseuille flow is studied for a non-Newtonian liquid having an exponential viscosity-temperature dependence. Non-Newtonian behavior of the fluid is modeled through Carreau rheological equation. Channels walls are kept at constant but different temperatures. Steady base flow equations and equations describing the evolution of small, two-dimensional disturbances are derived and solved numerically. The stability problem is formulated as an eigenvalue problem for a set of ordinary idfferential equations. Discritization is performed using a pseudospectral technique based on Chebyshev polynomials expanisons. The resulting generalized matrix eigenvalue problem is solved using the QZ algorithm. The results presenting the influence of temperature and shear-rate dependent viscosity on the stability are given in the form of marginal stability curves for a wide range of flow and fluid dimensionless parameters, including channel wall temperature difference ΔT, material time constant λ and power-law index n.
Validation of Analytical Solution for Depth-of-Correlation in Microscopic Particle Image Velocimetry
Authors: Bourdon Christopher J. , Olsen Michael G. , Gorby Allen D.
Published: May 2008

Because the entire flowfield is generally illuminated in microscopic particle image velocimetry (microPIV), determining the depth over which particles will contribute to the measured velocity is more difficult than in traditional, light-sheet PIV. This paper experimentally and computationally measures the influence that volume illumination, optical parameters, and particle size have on the depth of correlation for typical microPIV system. First, it is demonstrated mathematically that the relative contribution to the measured velocity at a given distance from the object plane is proportional to the curvature of the local cross-correlation function at the distance. The depth of correlation is then determined in both the physical experiments and in computational simulations by directly measuring the relative contribution to the correlation function of particles located at a known separation from the object plane. These results are then compared with a previously derived analytical model that predicts the depth of correlation from the basic properties of the imaging sytem and seed particles used for the microPIV measurements. Excellent agreement was obtained between the analytical model and both computational and physical experiments, verifying the accuracy of the previously derived analytical model.
Microstructure and Reliability of Surface Micromachined Polysilicon Used for MEMS
Authors: Buchheit Thomas E. , Bataille Corbett C. , Michael Joseph R. , Boyce Brad L.
Published: May 2008

Surface micromachining (SMM) techniques produce complex microscale polysilicon features on the surface of a silicon wafer using a patterned maultilayer film deposition process. Failure characteristics of SMM polysilicon obtained from testing series of 2 μm and 4 μm wide ligaments fabricated using standard SMM processing techniques, fit a Weibull distribution, suggesting a behavior governed by a distribution of flaws, similar to brittle ceramic materials. However, positive identification of critical flaws that dictate the failure distribution within the ligaments remains unclear. Likely candidates are flaws associated with surface roughness or gain boundary intersections with the polysilicon microstructure. To address the possible connection between microstructure and failure behavior of SMM polysilicon, templates, based on observed polysilicon microstructure were subjected to deformation simulations using polycrystal elasticity modeling. Series of simulations were performed to capture the statistical failure of polysilicon due to local elastically driven stress concentrations between grains with different crystallographic orientations.. Simulated results are presented and discussed in the context of experimental failure data.
Causes of Slip in a Continuously Variable Transmission
Authors: Kim Songho , Peshkin Michael , Colgate J. Edward
Published: May 2008

Rotational CVTs (continuously varible transmissions) constrain the velocities of two rotational joints to a computer-controlled ratio. CVTs traction drive mechanisms that rely on the support of traction forces across rolling contracts. When called upon to transmit loads, CVTs produce a velocity ratio that departs from the ideal transmission ratio. This paper reports on the results of our analysis in pursuit of understanding the mechanics of the rotational CVT. We present the measured velocity ratios in the face of lateral loads at various transmission settings. In addition, wer present our model that closely fits the empirical data.
Numerical Simulation of Enhanced Skin Thermal Signature of Female Breast Tumor Subjected to Forced Convection
Authors: Gupta A. , Hu L. , Gore J. P. , Xu L. X.
Published: May 2008

Early detection is considered to be the best defense against breast cancer and imaging plays a very important role in screening and in the diagnosis of symptomatic women. Infrared thermal imaging of skin temperature changes caused by a malignant tumor in breast is a rapidly developing detection modality with potential for functional detection. Knowledge and control of environmental factors which affect the skin temperature can reduce misinterpretations and false diagnosis associated with infrared imaging. A bio heat transfer based numerical model was utilized to study the energy balance in healthy and malignant breasts subjected to low velocity forced convection in a wind tunnel. Existing estimates of metabolic heating rates and previous measurements of temperature distributions along the radial direction in a region intersecting a known tumor and a comparable region in the healthy breast of the same patient were used to estimate the blood perfusion rates for the tumor. A simplified structural and thermal model was used for representing the changes within and around the tumor. Steady state temperature distributions on the skin surface of the breasts were obtained by numerically solving the conjugate heat transfer problem. Parametric studies on the influences of the airflow on the skin thermal expression of tumors were performed. It was found that the presence of tumor may not be clearly shown due to the irregularity of the skin temperature distribution induced by the flow field. Image processing techniques could be employed to eliminate the effects of the flow field and thermal noise and significantly improve the thermal signature of the tumor on the skin surface.
A Structure of Bistable Electromagnetic Actuated Microvalve Fabricated on a Single Wafer, Implementing the SLA and PDMS Technique
Authors: Bintoro Jemmy Sutanto , Luharuka Rajesh , Wong Edward W. , Hesketh Peter J.
Published: May 2008

This report presents a complete package for bistable electromagnetic actuated microvalve. The function of the valve is to control the fuel delivery system in a fuel cell unit for power generation [1,2]. The microvalves were fabricated on top of a single wafer using 8 masking steps. The fabrication processes have a maximum processing temperature of 300 °C, providing potentially a CMOS compatible process. The valve arrays that compromise of 12 valves per 12 MM × 12 MM chip are built completely by surface micromachining. The chip is assembled into a package with fluidic connection parts. The parts were made from the stereo lithography (SLA) frame that was filled with PDMS. The PDMS also acts as a gasket to seal the microvalve from leaking. The fluidic tests show that the whole valve assembly can stand from leaks up to the pressure of 57.4 kPa.
A Closed Loop Impinging Jet Cooling for Computer Chip
Authors: Bintoro Jemmy Sutanto , Akbarzadeh Aliakbar , Mochizuki Masataka , Nguyen Thang
Published: May 2008

This paper present a new cooling system that adopted triple technologies: Rankine cycle, impingement jet, and mini channel heat exchanger. However the report of his paper will be concentrated in the impinging jet cooling. The established cooling system had capability of removing the maximum heat of 200 W from a single chip with D = 12 mm, which is equivalent to the heat flux of 177 W/cm2. The System maintained the maximum chip-surface temperature of less than 95 °C and the chip temperature variation of less than 2.5 °C. At ambient temperature of 30 °C, the surface temperature of heat exchanger is less than 65 °C.
Passive Alignment of Optical Fiber in a V-Groove With Low Viscosity Epoxy Flow
Authors: Lo Jeffery C. C. , Yung C. S. , Lee S. W. Ricky , Lee Steve H. K. , Wu J. S. , Yuen Matthew M. F.
Published: May 2008

The alignment of optical fibers is very critical in optoelectronic packaging. A slight offset in any direction may severely affect the performance of the photonic device. Recently, passive alignment of optical fibers has attracted substantial attention due to its lower manufacturing cost and faster processing time when compared with active alignment. For conventional passive alignment, the position of each optical fiber is defined by the geometry of a V-groove. The epoxy is dispensed from the top of the V-groove and another cover plate is usually required to press the fiber against the walls of the V-groove. In the present study, a new technique for epoxy dispensing is developed. Instead of being applied from the top of the V-groove, some low viscosity epoxy is dispensed in a “canal” first. The epoxy fills an adjacent “reservoir” and then flows into the V-groove. Subsequently the epoxy flow runs through the gap between the optical fiber and the V-groove walls. It is observed that the flow of epoxy can align the optical fiber by the surface tension. Once the optical fiber is aligned and the epoxy is cured, more epoxy is applied in a glob-top manner to mechanical enhancement. In this paper, the configuration of the V-groove and associated features, the epoxy dispensing process, and the results of alignment are presented in details.
Approximate Optimal Initial Temperature Distribution From a Three Dimensional Model for Processes Requiring Coiling
Authors: Troyani Nando , Ayala Orlando M. , Montano Luis
Published: May 2008

A numerical strategy to determine an estimate to the optimal initial distribution of temperature for industrial processes requiring coiling of bars in hot metal rolling operations based on a three-dimensional mathematical model for the evolution of temperature in a shape changing domain is presented. The corresponding numerical solution is presented as well. The solution integrates a two dimensional geometrically adaptive finite element solution in the coiling plane for a shape changing domain with a finite difference one-dimensional solution in the widthwise direction of the bar using a novel numerical separation of variables strategy. Time is discretized according to a Crank-Nicolson type scheme. The results of a specific numerical study for the coiling of hot steel between the roughing stands and the finishing stands are presented.
Fractal Basin Boundaries and Chaotic Motions in Spring-Pendulum System
Authors: Alasty Aria , Shabani Rasool
Published: May 2008

This study investigates chaotic response in the spring-pendulum system. In this system beside of strange attractors, multiple regular attractors may coexist for some values of system parameters, where it is important to study the global behavior of the system using the basin boundaries of the attractors. Multiple scales method is used to distinguish the regions of stable and unstable attractors. In unstable regions, bifurcation diagram and poincare´ maps are used to study the existence of quasi-periodic and chaotic attractors. Results show that the jumping phenomena may occur when multiple regular attractors exist and for this case fractal basins of attraction are developed using numerical simulations.
Temperature Imaging of Vortex-Flame Interaction by Filtered Rayleigh Scattering
Authors: Kearney Sean P. , Schefer Robert W. , Beresh Steven J. , Grasser Thomas W.
Published: May 2008

This paper describes the application of a filtered-Rayleigh-scattering (FRS) instrument for nonintrusive temperature imaging in a vortex-driven diffusion flame. The FRS technique provides quantitative, spatially correlated temperature data without the flow intrusion or time lag associated with physical probes. Use of a molecular iodine filter relaxes the requirement for clean, particulate-free flowfields and offers the potential for imaging near walls, test section windows and in sooty flames, all of which are preculded in conventional Rayleigh imaging, where background interference from these sources typically overwhelms the weak molecular scattering signal. For combustion applications, FRS allows for full-field temperature imaging without chemical seeding of the flowfield, which makes FRS an attractive alternative to other laser-based imaging methods such as planar laser-induced fluorescencs (PLIF). In this work, the details of our FRS imaging system are presented and temperature measurements from an acoustically forced diffusion flame are provided. The local Rayleigh crosssection is corrected using Raman imaging measurements of the methane fuel molecule, which are then correlated to other major species using a laminar flamelet approach. To our knowledge, this is the first report of joint Raman/FRS imaging for nonpremixed combustion. Measurements are presented from flames driven at 7.5 Hz, where a single vortex stretches the flame, and at 90 Hz, where two consecutive vortices interact to cause a repeatable strain-induced flame-quenching event.
Surface Topology Optimization of Water Tanks Using Genetic Algorithm
Authors: Lawrence Cecil , Szydlowski Wieslaw M.
Published: May 2008

The purpose of this work is to explore the possibility of utilizing Genetic Algorithm in optimizing the surface topology of water tanks. The surface characteristics of a corrugated tank are tested on a small element on its circumference. A mathematical equation to represent most practical corrugated surfaces is developed using the Coons surface with trigonometric series curves. The parameters of this mathematical equation are used to describe the chromosome for different surfaces. A multi-objective fitness function incorporating the performance of a surface and the manufacturing cost associated with that surface is developed, which uses finite element analysis to determine the performance of each surface. Considerable better corrugations, compared to those normally used, were found.
Flat Heat Pipe Cooling Devices for Mobile Computers
Authors: Wang Yaxiong , Peterson G. P.
Published: May 2008

The rapid increases in package density in the high-performance microprocessors utilized in laptop, notebook and other mobile computers has resulted in power-densities that are challenging the existing thermal management technologies. In order to accomodate these challenges within the existing space and volume constraints, a novel, flat, micro heat pipe (MHP) cooling device has been conceptualized, designed, and evaluated analytically. The novel device consists of a flat micro heat pipe heat spreader, fabricated by sintering copper mesh and wires between two thin copper sheets to form a closed chamber. High-efficiency folded fins are then bonded to the condenser to produce a device that is capable of dissipating the high heat loads and reducing the thermal resistance typically present in these packages. Because of its high latent heat and surface tension, water was used as the working fluid. A number of different designs with different CPU mounting positions and fin sets were examined theoretically in an effort to optimize the initial design. The effects of the physical properties of the mesh, wire diameter, and effective thermal conductivity of the capillary structure were then evaluated and optimized. This process resulted in a design optimized on thermal performance, that is an excellent candidate for the thermal management of laptop and/or notebook computers. At a junction temperature of 85 °C, the maximum heat transport capacity and corresponding thermal resistance of an optimized MHP heat sink, 25.4 man wide and 152.4 mm long, were 33 W and 0.80 W/°C, respectively, for an environmental temperature of 45 °C.
Absolute Stability Criteria of Lurie-Type Nonlinear Systems With MIMO Bounded Time-Delays
Authors: Guo Shuli , Yan Shaoze , Wen Shizhu
Published: May 2008

The time delay of Lurie nonlinear system is systems is estimated in which the origin of the nonlinear systems is absolute stability by using a Liapunov-Razumikhn function. Many sufficient conditions are obtained about absolute stability criteria of nonlinear systems. A example is presented to explain the strange time delay phenomena.
Steady Viscoelastic Flow in Channels of Arbitrarily Varying Cross-Section Shape
Authors: Letelier Mario F. , Gaete Rau´l P. , Siginer Dennis A.
Published: May 2008

An analytical method for studying flow in wavy channels is presented. The flow is considered laminar and steady, and the fluid viscoelastic. A shape factor is inserted in expressions for the stream function, thus allowing to model many different cross-section shapes that are the outcome of the chosen shape factor. This work aims at investigating kinematic aspects of the flow that may enhance heat transfer between the channel walls and the fluid.
Cooling Performance of a Narrow Impingement Channel Including the Introduction of Cross Flow Upstream of the First Hole
Authors: Chambers Andrew C. , Gillespie David R. H. , Ireland Peter T. , Dailey Geoffrey M.
Published: May 2008

Impingement channels are often used in turbine blade cooling configurations. This paper examines the heat transfer performance of a typical integrally cast impingement channel. Detailed heat transfer coefficient distributions on all heat transfer surfaces were obtained in a series of low temperature experiments carried out in a large-scale model of a turbine cooling system using liquid crystal techniques. All experiments were performed on a model of a 19-hole, low aspect ratio impingement channel. The effect of flow introduced at the inlet to the channel on the impingement heat transfer within the channel was investigated. A novel test technique has been applied to determine the effect of the initial cross flow on jet penetration. The experiments were performed at an engine representative Reynolds number of 20,000 and examined the effect of additional initial cross flow up to 10% of the total mass flow.
Measurements of the Residual Stresses Due to Cement Polymerization for Cemented Hip Implants
Authors: Nun˜o Natalia , Plamondon Dominic
Published: May 2008

In cemented hip implant, the polymethyl methacrylate (PMMA) also called bone cement is used as grouting material between the implant and the bone. During the operation, the bone cement still in a liquid form is inserted between the femoral component and the bone. During polymerisation of the cement, residual stresses are generated in the bulk cement. The process of cement curing is a complex solidification phenomenon where transient stresses are generated and the residual stresses vary with different boundary conditions during curing (Ahmed et al., 1982). In particular, normal stresses are generated at the implant-PMMA interface resulting in a press-fit problem. The cement does not have a chemical bond with the stem nor the bone, however it fills completely the space between the two and serves to distribute the load being transferred from the stem to the bone. An experiment has been devised to measure directly the residual stresses of the bone cement to reproduce the in-vivo behaviour of the prosthesis. An idealized prosthesis (19-mm diameter) is used. A subminiature load cell (9.5-mm diameter) is inserted inside the stem to measure directly the radial residual stresses of the PMMA on the stem. Bone cement polymerizes between the stem and the synthetic bone (40-mm outside diameter). The tests are conducted at body temperature of 37°C.