bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling of the Dynamic Surface Profile in Magnetic Fluid Mirrors
Authors: Iqbal Azhar , Ben Amara Foued
Published: April 2008

Magnetic fluid deformable mirrors (MFDMs) present a simple alternative to the expensive and delicate wavefront correctors currently in use in adaptive optics (AO) systems. Such mirrors are particularly suitable for retinal imaging AO systems. The practical implementation of a retinal imaging AO system incorporating a MFDM requires an effective control system to control the shape of the mirror surface. The real-time control of the mirror surface requires a model of the mirror that can be used to determine the dynamic response of the mirror to a magnetic field applied as the control input. This paper presents such a model that not only determines the dynamic response of the MFDM but also takes into account the unique requirements of the retinal imaging application of the mirrors. The mirror is modeled as a horizontal layer of a magnetic fluid. The dynamic response of the mirror to the applied magnetic field is represented by the deflection of the free surface of the layer. The surface deflection is determined by the modal analysis of the coupled fluid-magnetic system. Considering the requirements of the retinal imaging application, the effects of surface tension and depth of the fluid layer are duly represented in the model. The mirror model is described in a state-space form and can be readily used in the design of a controller to regulate the mirror surface shape.
Coupled Flexural/Torsional Vibrations of a Piezoelectrically-Actuated Vibrating Beam Gyroscope
Authors: Bhadbhade Vikrant , Jalili Nader
Published: April 2008

In this paper, the coupled flexural-torsional vibrations of a cantilever beam with rigid mass attached to its end are studied. The beam base is subjected to a rotational motion, forming a vibrating beam gyroscope undergoing bending-twisting vibrations. The primary (flexural) vibrations are produced in the beam using a piezoelectric patch actuator. Due to the gyroscopic effect, secondary (torsional) vibrations are induced in the beam. First, a detailed mathematical modeling of the system is developed using extended Hamilton's Principle. Partial differential equations of the motion for both bending and torsion vibrations are derived, which are coupled through the gyroscopic terms. Expression for the frequency equation is presented, and the effect of the base rotation on the system natural frequencies is studied. Finally, the system governing equations are solved and simulated using assumed mode model to analyze the relationship between the base rotation and gyroscopic coupling. It is shown that the system natural frequencies are nearly independent of the magnitude of the base rotation for small rotation velocities. Furthermore, the natural frequencies depend on the magnitude as well as dimensions of the end mass. Also, it is shown that the gyroscopic effect increases with increase in base rotation rate and primary excitation amplitude.
A Novel Constant Bias Flow Rate CPAP Mask for OSA Therapy
Treatments
Authors: Zhen Z. F. , Al-Jumaily A. M.
Published: April 2008

Continuous positive airway pressure (CPAP) therapy is considered the most effective treatment for patients with Obstructive Sleep Apnea (OSA) symptom. A CPAP mask is the interface between the patient and the CPAP humidifier, which contains a series of orifice to circulate the air and ensure that the expired carbon dioxide from the patient's breathing is not rebreathed. The flow through those orifices is called bias flow. For the existing CPAP mask, this bias flow rate increases as the CPAP pressure increases. This raised bias flow rate usually causes a bigger pressure swing inside the mask when the patient is breathing, which is unfavorable for OSA therapy due to the much bigger breathing load required. However, a minimum bias flow rate needs to be maintained inside the mask in order to keep carbon dioxide concentration low. Therefore, this paper introduces a novel mask that can produce a relatively constant bias flow rate (CBFR) over a CPAP range of 0-20cm H2O. Dynamic response tests have proved that this CBFR mask can constrict the mask pressure swing by an order of two so as to offer better comfort for OSA patients.
Viscoelastic Material Properties of SU-8 and Carbon-Nanotube-Reinforced SU-8 Materials
Authors: Park Seungbae , Chung Soonwan , Ackler Harold , Makhar Sandeep
Published: April 2008

The viscoelastic material properties of SU-8 and carbon nanotube-reinforced SU-8 composite material are characterized by tensile testing. Dogbone samples of 0.1mm thickness are prepared by micro-fabrication process, which is composed of spin coat, soft bake, expose, and post exposure bake. To fabricate CNT polymer composite, carbon nano-tube of 0.2wt% is mixed with SU-8. To observe the effect of applied strain rate and temperature on Young's modulus and Poisson's ratio, strain rate is varied from 5×10-5 to 2.5×10-4 (/sec) at elevated temperatures in the range of 25 to 200°C. Since the viscoelastic material properties are important in polymer, creep, stress relaxation and dynamic mechanical analyses are performed at elevated temperatures. The viscoelastic material properties of SU-8 and CNT-reinforced SU-8 composite are compared, and the mechanical reliability of these polymers in MEMS applications is discussed.
Mechanical and Thermal Board Level Reliability Comparison Between Electroless Ni Im. Au and Solder on Pad Surface Finishes for Large Flip Chip BGA Packages
Authors: Ramakrishna Gnyaneshwar , Kim Donghyun , Ahamad Mudasir , Gopalakrishnan Lavanya , Hu Mason , Teng Sue , Edwards Bill
Published: April 2008

Large Flip Chip BGA (FCBGA) packages are needed in high pin out applications (>1800), e.g., ASIC's and are typically used in high reliability and robustness applications. Hence understanding the package reliability and robustness becomes one of paramount importance for efficient product design. There are various aspects to the package that need to be understood, to ensure an effective design. The focus of this paper is to understand the BGA reliability of the package with particular reference to comparison of the surface finish, vis-a`-vis, between Electroless Nickel Immersion Gold (ENIG) and Solder On Pad (SOP) on the substrate side of the package, which are the typical solutions for large plastic FC-BGA packages. Tests, which include board level temperature cycling, monotonic bend and shock testing have been conducted to compare the two surface finish options. The results of these tests demonstrate that the mechanical strength of the interface exceeds by a factor of two for the SOP surface finish, while BGA design parameters play a key role in ensuring comparative temperature cycle reliability in comparison with ENIG packages.
Experimental Demonstration and Numerical Simulation of Organic-Aqueous Liquid Extraction Enhanced by Droplet Formation in a Microfluidic Channel
Authors: Mao Xiaole , Yang Sung , Zahn Jeffrey D.
Published: April 2008

Organic-aqueous (phenol) liquid extraction is one of the commonly used DNA purification methods. Effective mass transfer of biological material between the discrete fluid phases is key to achieving efficient extraction when designing microfluidic devices based on this technique. In the microscale regime, mass transfer is often diffusion limited. However, mass transfer can be enhanced through the formation of discrete droplets within a microchannel, which leads to a recirculation flow pattern within the droplet. This recirculation increases the mass transfer rate of material to the organic-aqueous interface. In this study, an experimental and computational examination of sample extraction between the organic and aqueous phases through droplet formation is presented. The experiment is conducted within a converging dual inlet microfluidic channel fabricated in PDMS. By controlling the capillary number of the flow, different flow patterns are created in the channel. The flow patterns are examined using a computational fluid dynamics (CFD) simulation. The CFD model successfully simulates the flow behavior under a variety of flow conditions and provides a closer examination of the internal recirculation pattern within the droplet. The experimental sample extraction utilizes a fluorescent dye localization technique and shows that the droplet flow offers a significant improvement in the speed of sample extraction over diffusional mixing. A preliminary test demonstrates the feasibility of using the droplet formation for fast extraction with biological samples.
Microfabricated Electrode Array Compatible With Optical Imaging of Intrinsic Signals During Somatosensory Stimulation and Cortical Spreading Depression
Authors: Theriot Jeremy J. , Prakash Neal , Toga Arthur W. , Ju Y. Sungtaek
Published: April 2008

Accurate interpretation of functional brain images requires knowledge of the relationship between neurons and their supporting cells and vasculature. Our understanding of this complex and dynamic system would improve if we measure multiple aspects of brain function simultaneously. We have developed a semi-transparent electrode array which allows for concurrent multi-site electrophysiological recording and high-resolution optical imaging of intrinsic signals. The 8-channel electrode array is fabricated on a transparent glass substrate with platinum recording surfaces. We map stimulus-induced field potentials (evoked potentials) and changes in cerebral blood volume in rat somatosensory cortex. We also examine the evolution of these responses during the neuro-pathological state of cortical spreading depression. We have developed a planar multi-electrode array that is fully compatible with Optical imaging of Intrinsic Signals. It provides a sensitive and reliable tool to use in the study of neurovascular coupling in brain activation.
Passive Alignment Structures in Modular, Polymer Microfluidic Devices
Authors: You Byoung Hee , Chen Pin-Chuan , Guy Jason , Datta Proyga , Nikitopoulos Dimitris E. , Soper Steven A. , Murphy Michael C.
Published: April 2008

For connecting polymeric, modular microfluidic devices, precise, passive alignment structures can prevent infinitesimal motions between the devices and minimize misalignment of the devices. The motion and constraint of passive alignment structures were analyzed for the design of assembly features using screw theory. A combination of three v-groove and sphere joints constrained all degrees of freedom of the two mating plates without over-constraint. To validate the designed passive alignment scheme, hot embossing experiments were conducted using a micromilled brass mold insert, containing alignment features. Prototype alignment structures have dimensional variation. The alignment accuracy of the stacked polymeric plates was estimated by the mismatches between alignment marks of two plates. The mismatches ranged from 28 μm to 70 μm.
The RiceWrist: A Distal Upper Extremity Rehabilitation Robot for Stroke Therapy
Authors: O'Malley Marcia K. , Sledd Alan , Gupta Abhishek , Patoglu Volkan , Huegel Joel , Burgar Charles
Published: April 2008

This paper presents the design and kinematics of a four degree-of-freedom upper extremity rehabilitation robot for stroke therapy, to be used in conjunction with the Mirror Image Movement Enabler (MIME) system. The RiceWrist is intended to provide robotic therapy via force-feedback during range-of-motion tasks. The exoskeleton device accommodates forearm supination and pronation, wrist flexion and extension, and radial and ulnar deviation in a compact design with low friction and backlash. Joint range of motion and torque output of the electric-motor driven device is matched to human capabilities. The paper describes the design of the device, along with three control modes that allow for various methods of interaction between the patient and the robotic device. Passive, triggered, and active-constrained modes, such as those developed for MIME, allow for therapist control of therapy protocols based on patient capability and progress. Also presented is the graphical user interface for therapist control of the interactions modes of the RiceWrist, basic experimental protocol, and preliminary experimental results.
Analysis and Experimental Characterization of Statistical Errors in Brownian Microscopy
Authors: Kim Jichul , Ju Y. Sungtaek
Published: April 2008

The Brownian diffusivity is a key parameter characterizing the stochastic motion of particles suspended in a liquid, which in turn reflects the rheological properties and thermodynamic states of the liquid. Fundamental understanding of statistical uncertainty in the Brownian diffusivity is critical since the number of Brownian steps tracked in practical experiments is limited. We develop an approximate analytic expression for statistical errors in the Brownian diffusivity, while accounting for electronic noise and other imperfections in a video microscopy system. The expression is validated using Monte Carlo simulations and microchannel based experiments. The present model allows us to make a priori estimate of overall experimental uncertainty and thereby helps improve the accuracy and reliability of various microrheological and biosensing techniques based on Brownian microscopy
The Construction of a Zero Energy Building in Reunion Island: Presentations of a New Approach to the Design Studies
Authors: Garde Franc¸ois , Bastide A. , Bentaleb D. , Ottenwelter E.
Published: April 2008

This paper presents a zero energy project -ie ZEN applied to a university building in Reunion Island. The construction work will begin in September 2006 and will last one year. The aim is to create a building which uses half the energy of a standard building. The methodology was conceived to meet requirements defined during the thermal design and building systems planning stage. Innovations relating to architectural design, building systems performance and numerical simulation are presented. Solar panels integrated into the roofing provide sufficient electrical energy for the building to produce more energy than it uses.
A Higher Order Synthesis for Harmonic Motion Generating RSSR Mechanisms
Authors: Farhang Kambiz , Ghatti Vinay
Published: April 2008

Consideration of a mechanism for high-speed application inevitably poses certain kinematic design requirements that can be cast as a function generation synthesis problem involving the entire motion cycle of the mechanism. This paper addresses such application of RSSR four bar mechanisms for high-speed application. It employs a perturbational kinematic analysis of the mechanism to obtain approximate equations relating the follower and input angular displacements. The follower angular motion is derived, approximately, as a linear combination of two simple harmonic functions, in terms of the first and second harmonics of the crank angle. Albeit the exact mathematical description relating the input and output links exists it is not conducive to a kinematic design for dynamic performance. In contrast the approximate equations derived in this paper enable function generation of RSSR four bar mechanisms in which the higher harmonics of the input link are minimized. This utility of the approximate equations are demonstrated through several mechanism design examples.
A Matrix WKB Approach to Feedforward and Feedback Control
Authors: Ishihara Abraham K. , Ben-Menahem Shahar
Published: April 2008

We apply a powerful new analytical approximation method, recently developed by the authors, to the design and analysis of feedforward and feedback control systems. This formalism employs a matrix version of the WKB expansion, which is an asymptotic approximation method familiar in quantum mechanics and classical continuum mechanics. Our matrix WKB formalism has proven remarkably useful in approximating and characterizing the long-term dynamics of systems of ODEs (both linear and nonlinear) when there exists a time scale hierarchy. In particular, the linear error dynamics encountered in the analysis and design of controllers for multi-input multi-output systems, is typically formulated as a first-order vector differential equation involving a time-dependent matrix. To illustrate our matrix WKB approach, we consider the feedforward and feedback control of the single link manipulator. The desired trajectory is assumed to vary sinusoidally with time. For sufficiently small expansion parameters, the closed form WKB approximants can be used to determine safe controller parameters. Given a specific time scale hierarchy, we use a theorem reported previously to partition the controller parameter space into three distinct regions in which the system is, respectively: exponentially stable, exponentially unstable, and undecided. The undecided region is a narrow strip about a computable transition hypersurface. This strip can be made progressively narrower by working to a high enough order in the WKB expansion. In the limit of infinitely small expansion parameters, the transition curve tends to the actual stability-instability boundary.
Direct and Inverse Eigenvalue Problems Towards the Design and Identification of Mass-Loaded Micro-Resonators
Authors: Singh Kumar Vikram , Pang Su-Seng
Published: April 2008

The spectral data i.e. eigenvalues (natural frequencies) and eigenvectors (mode-shapes), characterizes the dynamics of the system. Non-destructive vibration testing, involving advanced experimental modal analysis techniques, has a potential to obtain the spectral data of the structures. It is well known that the dynamic characteristics of a structure will change due to the change in its physical properties. In this research, such changes in spectral behavior will be exploited towards the detection of minuscule changes in the mass of microstructures such as cantilever micro-beams, micro-resonators and oscillators, by solving certain direct and inverse eigenvalue problems. Some piecewise uniform micro-cantilever beams are considered here and associated transcendental eigenvalue problems are developed. Examples relevant to the design and identification of such beams are demonstrated through systematic mathematical modeling and effective solution strategy. It is shown that spectral behavior of mass loaded piecewise uniform beams can be obtained accurately and efficiently. Moreover, location and severity of the loaded mass can be identified successfully by using finite number of eigenvalues which may be available from experiments. Such formulations can be useful for, design and optimization of microstructures (micro-cantilever beams, resonators etc.), Bio-MEMS sensor design for the detection of single/multiple microbiological cells, and structural health monitoring.
Application of the Delayed Resonators in Active Suspension Systems of High-Speed Trains
Authors: Pendarathil N. , Younesian D. , Esmailzadeh E.
Published: April 2008

Application of the multiple delayed resonators in suppressing tonal vibration of a coach body is studied in this paper. The excitation arose from the random nature of the rail corrugation is modeled by harmonic and random inputs. Using a standard power spectral density (PSD), the rail surface roughness is generated by application of the Monte Carlo simulation in random space. In order to have a comparison, a tuned mass damper (TMD) system is also designed. The performances of these two controller systems i.e. TMD and DR are investigated for variety of excitations.
Application of Fractional Derivatives for Simulating Diffusion Into Porous Matrix in Mathematical Modeling of the Contaminant Transport in a Confined Fractured Porous Aquifer
Authors: Fomin Sergei , Chugunov Vladimir , Hashida Toshiyuki
Published: April 2008

Solute transport in the fractured porous confined aquifer is modeled by the advection-dispersion equation with fractional time derivative of order γ, which may vary from 0 to 1. Accounting for diffusion in the surrounding rock mass leads to the introduction of an additional fractional time derivative of order 1/2 in the equation for solute transport. The closed-form solutions for concentrations in the aquifer and surrounding rocks are obtained for the arbitrary time-dependent source of contamination located in the inlet of the aquifer. Based on these solutions, different regimes of contamination of the aquifers with different physical properties are modeled and analyzed.
A Model for the Configuration Design of a Tubular Solid Oxide Fuel Cell Stack
Authors: Ciano Chiara , Cali` Michele , Melhus Ole , Verda Vittorio
Published: April 2008

In this paper, a model of a tubular fuel cell is proposed. The model includes thermo-fluid dynamics, chemical reactions and electrochemistry. In order to formulate proper boundary conditions for the cell, a simplified model of the whole stack is proposed. This approach allows one to account for the position of the cell within the stack; this is particularly important for the formulation of the thermal problem. An application to a stack constituted of 24 tubular cells is shown. The temperature distribution, the concentration of species and the polarization curves in each single cell are obtained. The proposed approach is useful for investigating the stack performances and thus examine new configurations.
Novel Magnetic Micro-Tweezers Leveraging on Magnetic Hard-Disk Drive Technology
Authors: Chan M. L. , Jaramillo G. M. , Horsley D. A.
Published: April 2008

We report the implementation of a magnetic tweezer using an inductive write head from a hard-disk drive for applying forces to micro-magnetic particles in a microscopy setup. Forces are generated by magnetic particles in reaction to the localized fields across the inductive head gap. This allow for mechanical manipulation and measurement of particles in fluid. The displacement is measured through image processing and particle tracking algorithm from the video capture data. We demonstrated the magnetic tweezer system with application to 1-2 μm paramagnetic and 4.5 μm ferromagnetic microparticles and measured forces in the range of 0.1–4 pN.
Hybrid Air Foil Bearings With External Pressurization
Authors: Kim Daejong , Park Soonkuk
Published: April 2008

Foil bearings are widely used for oil-free microturbomachinery. One of the critical technical issues related to reliability of the foil bearings is a coating wear on the top foil and rotor during start/stops. Especially for heavily loaded foil bearings, large start torque requires a large drive motor. Bearing cooling is also mandatory for certain applications because the foil bearings can generate significant amount of heat depending on operating conditions. Usually axial flow is used through the space between the top foil and bearing sleeve. In this paper, a hybrid air foil bearing with external pressurization is introduced. A flexible steel tube is attached to the backside of the top foil with orifice holes, and externally pressurized air is directly supplied to the bearing clearance to lift off the rotor before rotor spins. The hybrid operation eliminates the coating wear during start/stop cycles, reduces drag torque during starts, and eliminates axial flow cooling. The hybrid foil gas bearing was constructed using a multiple compression springs to demonstrate a feasibility of the concept. A simple analytical model to calculate top foil deflection under hydrostatic pressurization has been developed. Predictions via orbit simulations indicate the hybrid air foil bearings can have much higher critical speed and onset speed of instability than hydrodynamic counter part. Measured load capacity was slightly higher than hydrodynamic bearing even under smaller amount of air flow. In addition, the hybrid operation was very effective for bearing cooling even if the cooling flow rate was lower than hydrodynamic counterpart. The measured very small drag torque during the start/stop demonstrates the hybrid foil bearing can have near-infinite life time without wear of the bearing and rotor surface. The experimental studies show high potential of the hybrid air foil bearings for various oil-free turbomachinery, especially for heavily loaded high temperature applications.
Use of Contact Angle Hysteresis in Estimating Thin Polymer Film Surface Energy and Wettability
Authors: Bayer I. S. , Megaridis C. M. , Zhang J. , Gamota D.
Published: April 2008

A recent surface energy estimation method [1] interpreting contact angle hysteresis measurements was used to estimate surface energy of various commercially important polymer films including UV radiation cross-linked acrylic based monomer systems. The validity of the method was tested on highly hydrophobic non-polar amorphous fluoro-polymers using a number of polar and low surface tension liquids. Contact angle hysteresis was present on these surfaces even though surface morphology of the solution processed fluoro-polymers is close to ideal. Estimated surface energies using such probe liquids were consistent varying slightly with the probe liquid type. On such highly ordered and non-polar polymer surfaces use of polar and low surface tension liquids results in accurate surface energy estimation. However, use of polar probe liquids commonly employed in surface energy estimation methods, such as, Harmonic mean (HM), Geometric mean (GM) or Lewis Acid-Base method (LWAB) on polar surfaces such as polyester resulted in inconsistent surface energy values. To strengthen this observation, the ASTM surface energy estimation procedure (ASTM D2578 04a) developed for polyethylene and polypropylene surfaces (both non-polar) was employed on a sample polar polyester surface using the ASTM probe liquids. Results showed inconsistent surface energy values supporting the conclusion that care must be exercised during use of polar probe liquids in estimating surface energy on polar polymers with the contact angle hysteresis method. Finally, UV radiation cross-linkable acrylic polymer surface energies were estimated with the hysteresis method. Surface energy results were consistent based on five different probe liquids. It was observed that surface energy of the cross-linked monomer networks decreased slightly with increasing UV curing time.
Control of MEMS Nanopositioners With Nano-Scale Resolution
Authors: Gorman Jason J. , Kim Yong-Sik , Dagalakis Nicholas G.
Published: April 2008

Several approaches for the precision control of micro-scale positioning mechanisms, or MEMS nanopositioners, are presented along with initial experimental results which demonstrate nano-scale positioning resolution. The MEMS nanopositioners discussed in this paper are novel precision mechanisms comprised of a bent-beam thermal actuator and a flexure mechanism for each degree of freedom (DOF). These mechanisms can be used for a host of ultra-precision positioning applications, including nanomanipulation, scanning probe microscopy, high-density data storage and beam steering arrays. Concentrating on a 1 DOF MEMS nanopositioner, empirical static and dynamic models have been derived using characterization data obtained from experiments with optical and laser probe microscopes. Based on these models, three control approaches have been developed: 1) a quasi-static nonlinear open-loop controller, 2) a nonlinear forward compensator, and 3) a nonlinear PI controller. Simulation and initial experimental results are presented, and the benefits of each of these approaches are discussed.
Design and Control of Fast Tool Servo for Boring of Engine Piston Pin Holes
Authors: Wilson Jason T. , Lin Chi-Ying , Tsao Tsu-Chin
Published: April 2008

This paper presents the mechanical and servo control design of a fast tool servo for machining noncircular bores. The rotating boring bar varies the depth of cut dynamically to machine noncircular bores, such as those in engine piston gudgeon pin holes. The piezoelectric actuator driven fast tool servo has 60 micron displacement and about 400 Hz first natural frequency. The design of robust repetitive control of the fast tool servo is discussed and experimental results of cutting tool motion for generating oval bore profiles are presented.
Protective Coatings for Polymer Composites
Authors: Diccar U. V. , Ahmed I. , Vyawahare S. M. , Talia G.
Published: April 2008

Thermal spray coating is being studied as one of the techniques used for coating graphite reinforced polymer composites, which are extensively used in the aviation industry. These coatings are studied for improvement of surface properties such as erosion resistance, UV protection, property retention and electro magnetic shielding. NiAl (63:35) (65%Ni,35%Al) intermetallic, NiAl (95:5) (95%Ni,5%Al), Aluminum and Zinc coating were thermal-spray deposited using different procedures (plasma, flame, electric wire arc) onto composite specimens. Two categories of coating were evaluated: Coatings with bond coating and coatings without bond coating. These coatings were tested for protection against erosion encountered by aircraft components. The microstructures and micro-hardness of these coatings were determined. The bond strength between the substrate and the coating layer was evaluated by means of adhesion tests. The results obtained are discussed, with special attention being paid to the specific characteristics of the different spraying procedures.
A Numerical Study Concerning the Influence of the Grashof Number in the Indirect Ice Storage Tanks Performance
Authors: Stampa Cleyton S. , Nieckele Angela O.
Published: April 2008

The present paper deals with typical chiller-based ice storage tanks. Natural convection of water (Phase Change Material-PCM) near its density maximum leads to a peculiar nature of the flow pattern in the liquid phase of the PCM, giving rise to a multi-cellular regime that affects drastically the heat transfers within the tank. So, this work intends to examine numerically how the flow pattern affects qualitatively the performance of such thermal storage devices. This is done by investigating the influence of the non-dimensional parameter Grashof number during the charging operation step of such devices that corresponds to the ice making process occurring within the storage tank. Besides, the tank is assumed to be vertically positioned, as well as their internal tubes through which the secondary fluid flows. In order to analyze the heat transfer between the PCM and one internal tube during the growth of an ice layer around it, one selected a vertical annulus as the physical model. The inner vertical wall represents one of the tubes packed into a typical storage tank, while the outer vertical wall represents the thickness of formed ice around the tube. Regarding the annulus, the top and bottom walls, as well as the outer vertical wall were considered thermally insulated. The thermal analysis is focused in the heat transfer at the inner wall for different values of Grashof, keeping unchanged all other parameters that govern the natural convection problem with phase change. An overview of the cooling process is analyzed through streamlines and isotherms, for specific instants of the physical process. Further, a heat transfer analysis for the total charging stage is presented.
Hybrid-Electric Powertrain Design Evaluation for Future Tactical Truck Vehicle Systems
Authors: Pisu Pierluigi , Serrao Lorenzo , Cantemir Codrin-Gruie , Rizzoni Giorgio
Published: April 2008

The article presents the results of a large-scale design space exploration for two vehicles part of the Future Tactical Truck System (FTTS) family. A multi-objective optimization tool is presented, that allows designers to make appropriate trade-offs amongst different vehicle characteristics, on the basis of simulations run varying vehicle parameters over a broad range of values. Several powertrain architectures were taken into consideration for the Maneuver Sustainment Vehicle (MSV) and Utility Vehicle (UV). The architecture alternatives include the number of axles in the vehicle (2 or 3), the number of electric motors per axle (1 or 2), the type of internal combustion engine, the type and quantity of devices for energy storage (batteries, electrochemical capacitors or both together). A control strategy for energy management was developed to provide efficiency and performance. The control parameters are tunable and have been included into the design space exploration.
Directional Pumping Performance of an Electrostatic Checkerboard Microvalve
Authors: Kim Hanseup , Astle Aaron A. , Bernal Luis P. , Najafi Khalil , Washabaugh Peter D.
Published: April 2008

This paper reports experimental characterization of directional gas pumping generated by MEMS-fabricated checkerboard-type electrostatic microvalves. It is found that the oscillatory motion of the checkerboard microvalve membrane provides both the pumping and valve functions of a pump, namely: 1) to cause the volume displacement and, thus, compression and transfer of gas, and 2) to direct gas flow in one direction by closing and opening air paths in the proper sequence. Here, we describe the microvalve-only design, and report the pumping performance producing a maximum flow rate of 1.8 sccm and a maximum pressure differential of 3.0 kPa for five microvalves driven simultaneously with a sinusoidal signal of ± 100V amplitude at 5.5 kHz.
Quantifying the Effect of Pressure Oscillations on the Respiratory System: An Engineering Approach
Authors: Reddy P. , Al-Jumaily A. M.
Published: April 2008

The use of respiratory support devices using pressure oscillations has been shown to improve alveolar recruitment in animals and provide clinical benefits over traditional ventilators to infants with respiratory distress syndrome (RDS). The interactions and mechanisms of human lungs with such "bubble oscillation" (BO) devices is unknown. A simple mathematical model of the respiratory system and a BO type device is developed to explore the use of a new assessment parameter to study the effect of the pressure oscillations on lung performance. A mean square spectral density (MSSD) approach is employed in an attempt to observe the contribution of each pressure oscillation frequency on the work rate of unhealthy lungs. Further improvements to the respiratory system model are suggested for more detailed studies into human lung interactions with BO type devices.
Response of Laminar Premixed Flame to Mass Flow Rate and Pressure Fluctuations
Authors: Ray Baidurja , Chakraborty Ishita , Mukhopadhyay Achintya , Ray Subhashis , Sen Swarnendu
Published: April 2008

In this work, we develop an analytical model to describe laminar premixed flame response to an oscillating flow and use this model to predict the relationship between the heat release rate and the instantaneous flow field. Fully developed pulsating flow through a channel is considered. The flow is driven by pressure gradients. To facilitate direct comparison with experiments, the transient velocity profile is obtained in terms of mass flow rate fluctuations. The flame is anchored at the channel wall. The flame is assumed to be a thin surface, separating the reactants and the products. Flame displacement speed is assumed to be constant. The flame displacement is described by a single-valued function of the transverse coordinate. The flame dynamics is represented by a kinematic equation describing the displacement of the surface. The assumption of constant flame speed and fully developed flow allows closed-form solution of the flame response. The temporal variation of the mass flow rate and the flame surface area are compared to determine the gain and phase difference of the flame transfer function, relating the fluctuations in flame surface area to fluctuations in the mass flow rate.
Wrinkling of Thin Membrane Under Thermal Loading
Authors: Gao Jia , Park Seungbae , Pitarresi James , Homentcovschi Dorel
Published: April 2008

There has been an increasing interest in the applications of thin membrane in space application, flexible electronic display, manufacturing of glass displays and growth of film on materials at elevated temperatures. Because of the negligible bending stiffness of thin membranes, membranes are lack of resistance to compressive stress. For the applications at high temperatures, the thermal expansion coefficient mismatch between membrane and substrate materials may generate compressive stress that causes the membrane buckling. The study of thermal buckling of isotropic elastic plate in the context of the large - deflection theory was the subject of a series of papers[1-5]. However, it has been noted that none of these papers has considered the second buckling of the membrane resulting in membrane wrinkling. The presence of wrinkles may significantly change deflection and stress profile of membranes. So, it is important to develop an effective analysis method to investigate the wrinkle formation and evolution in membrane subjected the elevated temperature. This paper presents the experiment work to investigate wrinkle formation and evolution in membranes heated from room temperature up to 170 °C. The specimens consist of polymer and metal membranes with steel and silicon substrate respectively. A wide range of membrane shapes and aspect ratios are considered in this work. An experiment set up is developed to study the deflection profiles of membranes at discrete temperatures. The information gained from this experiment work is used to validate numerical modeling results. The Finite Element Analysis results using nonlinear post-buckling analysis are also included in this paper. The nonlinear post-buckling analysis provides a good understanding of the mechanism of wrinkle generation and evolution as temperature increased. It is shown that the first buckling of membrane significantly reduces bending stiffness thus to create localized buckling modes accounting for the wrinkle generation. The wrinkle pattern is stable until the temperature reaches the next critical value. After this critical temperature, the wrinkle pattern is changed until temperature reaches the next critical value. The new wrinkle pattern is keeping evolved until the final temperature is reached. The finite element analysis results are in good agreement with experimental observations.
An Integral Approach for Predicting Vapour Film Collapse and Growth Around a Hot Sphere in Subcooled Water
Authors: Ghosh Koushik , Mukhopadhyay Achintya , Sen Swarnendu , Sanyal Dipankar
Published: April 2008

The phase-change heat transfer has attracted researchers for its wide range of industrial applications like solidification in liquid containers, cooling of phase change material storage, combustion of spherical droplets and vapour explosion with associated film boiling and film collapse around molten drop in a coolant liquid. Major features of phase-change processes are heat transfer among multiple phases, mass transfer caused by latent heat of phase change and movement of phase interface. In present work a sphericosymmetric numerical model is developed to predict very rapid collapse of a vapour film around a hot melt immersed in a pool of subcooled water. The governing equations for the vapour film and the liquid were transformed into a number of non-linear ordinary differential equations by an integral approach assuming a quadratic temperature profile in both vapour and liquid domain while the melt was modelled as lumped mass. The energy balance across liquid vapour interface was incorporated by an equilibrium phase change model. The contribution of radiation from melt to the interface was considered assuming the vapour film to be non-participating. The non-linear ODE-s was solved by a fourth order Runge-Kutta method. The model was validated against some of the available solutions of liquid-vapour system. The present model shows excellent agreement in predicting growth of a solidification front in a saturated liquid (Stefan problem). The growth of a bubble in a superheated liquid was also validated with the available analytical solution. The results obtained from developed model for film collapse and growth around a hot melt in subcooled liquid were compared with a more accurate numerical model based on Volume of fluid method (VOF). It is found that the present model is able to capture successfully the rapid collapse of film due to condensation with computational time of one order less as compared to VOF based model. The film shows a very fast rebound (~ ms) due to faster condensation around liquid-vapour interface, following which a slower growth of vapour film is observed for different subcooling level.
Thermal Transport in a Microchannel Exhibiting Transverse Ultrahydrophobic Micro-Ribs Maintained at Constant Temperature
Authors: Davies J. , Maynes D. , Webb B. W.
Published: April 2008

There exists considerable incentive for reducing the required pumping power in microscale heat exchanger applications. One approach recently proposed is the use of super ultrahydrophobic channel walls. The influence such walls exert on the overall thermal transport has not been previously addressed and is the focus of this paper. Specifically, this paper presents numerical results exploring the periodically repeating thermal transport in a parallel plate microchannel with ultrahydrophobic walls maintained at constant temperature. The walls considered here exhibit alternating microribs and cavities positioned perpendicular to the flow direction. Results describing the thermally periodically repeating dynamics far from the inlet of the channel have been obtained over a range of flow Reynolds numbers and relative microrib/cavity widths and depths in the laminar flow regime. Previously it has been shown that significant reductions in the overall frictional pressure drop can be achieved relative to the classical smooth channel laminar flow. The present predictions reveal that the overall thermal transport is also reduced as the relative size of the cavity region is increased. The overall Nusselt number behavior is presented and discussed in conjunction with the frictional pressure drop behavior for the parameter range explored. In summary the following conclusions can be made regarding thermal transport for a constant temperature channel exhibiting ultrahydrophobic surfaces: 1) Increases in the shear free fraction (relative cavity length) yields decreases in the Nusselt number 2) increasing the relative rib/cavity module length yields a decrease in the Nusselt number 3) decreases in the Reynolds number result in smaller values of the Nusselt number and 4) the relative cavity depth exhibits negligible influence on the magnitude of the Nusselt number.
Solderability of Indium With Various Oxide Thickness
Authors: Park Seungbae , Kim Jongman , Cho Junghyun , Schoeller Harry
Published: April 2008

The purpose of this paper is to investigate the indium joint strength with known indium oxide thickness. The indium joint strength was assessed by measuring the maximum load of indium solder with the comparison of the wetting angle. The oxide thickness was already grown in different ambient conditions, and provided for the joint strength measurement. The indium joint strength with different oxide thicknesses was tested at a fixed strain rate by tensile loading. This investigation will be very useful to characterize the indium solderability in different environment in terms of the quantitative joint strength.
Control of A Friction Launch Automatic Transmission Using a Range Clutch
Authors: Lee Chunhao J. , Hebbale Kumar , Bai Shushan , Samie Farzad
Published: April 2008

Friction Launch transmissions use a wet multi-plate clutch to replace the torque converter in an automatic transmission. The main benefit of this technology is fuel economy improvement as a result of eliminating the losses in the torque converter. By using one of the range clutches inside the transmission instead of an input clutch in place of the converter, the benefits of this integrated friction launch technology, such as reduction in mass, packaging, and cost, can be enhanced. The availability of new automatic transmissions with higher number of speeds and wider overall ratio spreads makes this technology more viable than ever before. This project focuses on control issues with the friction launch clutch which include developing robust control algorithms for launch and creep, and providing damping to the driveline, when required, and ensuring acceptable vehicle drivability. This paper describes in detail the development of vehicle launch control algorithms. Vehicle test data is presented to show that the control strategy developed in this project significantly reduces the gap between the drivability of a starting clutch vehicle and a torque converter equipped vehicle.
Dynamic Electro-Thermal Simulation of a Tubular Solid Oxide Fuel
Authors: Jiang Wei , Fang Ruixian , Dougal Roger A. , Khan Jamil A.
Published: April 2008

A one-dimensional dynamic model of a tubular Solid Oxide Fuel Cell (SOFC) stack capable of system simulation in the Virtual Test Bed (VTB) computational environment is developed. This model is based on the electrochemical and thermal modeling, accounting for the voltage losses and temperature dynamics. The single cell is discretized by a finite volume method where all the governing equations are solved for each finite volume. The temperature, the current density and the gas concentration distribution along the cell are presented. The dynamic behavior of electrical characteristics and temperature under the variable load is simulated and analyzed. For easy implementation in the VTB platform, the nonlinear governing equations are discretized in Resistive Companion (RC) form. Simulation will be demonstrated at the paper presentation.
Corrosion Effect on Structural Health Monitoring
Authors: Chronister Jessica , Palazotto Anthony
Published: April 2008

A study has been carried out on the effect of a corrosion environment considering sea water as one is attempting to detect the location of an internal damage (notch) within an aluminum beam. The frequency variation is recorded experimentally and the eigenvectors are compared with those of unnotched specimens. A variety of corrosion times are evaluated. The scanning laser vibrometer is the primary tool used in this study to characterize the overall effects. It is possible to determine the extent of the internal notch, and to characterize the corrosion effect on the notch location by examining the change in curvature within the eigenvector. The overall effect on detection of internal damage due to corrosion becomes maximized at a time interval of two weeks. A simple finite element solution helped in initiating the experimental frequency determination.
The Scanning Hot Probe Technique for Seebeck Coefficient Characterization
Authors: Hapenciuc Claudiu L. , Borca-Tasciuc Theodorian
Published: April 2008

Highly efficient solid-state thermoelectric energy conversion requires materials with a large thermoelectric figure of merit Z=σα2/κ where α=thermoelectric power, σ=electrical conductivity, and κ=thermal conductivity [1]. Engineering the electric and thermal transport in nanostructures has emerged as a candidate for factorial enhancements in the thermoelectric figure of merit, as compared with state of the art bulk thermoelectric materials.[2-5] Recent developments in thermoelectric materials are reviewed in Ref [4]. These studies have sparked a flurry of activity to produce nanostructures for thermoelectric applications.
Molecular Dynamics Study of Short-Pulse Laser Melting, Recrystallization, Spallation, and Ablation of Metal Targets
Authors: Zhigilei Leonid V. , Lin Zhibin , Ivanov Dmitriy S.
Published: April 2008

A hybrid computational model combining classical molecular dynamics method for simulation of fast nonequilibrium phase transformations with a continuum description of the laser excitation and subsequent relaxation of the conduction band electrons is developed. The model is applied for a systematic computational investigation of the mechanisms of short pulse laser interaction with bulk metal targets. The material response to laser irradiation is investigated in three regimes corresponding to the melting and resolidification of the surface region of the target, photomechanical spallation of a single or multiple layers/droplets, and ablation driven by the thermodynamic driving forces. The conditions leading to the transitions between the different regimes and the atomic-level characteristics of the involved processes are established.