bluuebunny/crossref_metadata_2025 huggingface dataset:
Ca2+‐dependent inactivation of Ca2+‐induced Ca2+ release in bullfrog sympathetic neurons
Authors: Akita Tenpei , Kuba Kenji
Published: May 2008

We studied inactivation of Ca2+‐induced Ca2+ release (CICR) via ryanodine receptors (RyRs) in bullfrog sympathetic neurons. The rate of rise in [Ca2+]i due to CICR evoked by a depolarizing pulse decreased markedly within 10–20 ms to a much slower rate despite persistent Ca2+ entry and little depletion of Ca2+ stores. The Ca2+ entry elicited by the subsequent pulse within 50 ms, during which the [Ca2+]i level remained unchanged, did not generate a distinct [Ca2+]i rise. This mode of [Ca2+]i rise was unaffected by a mitochondrial uncoupler, carbonyl cyanide p‐trifluromethoxy‐phenylhydrazone (FCCP, 1 μm). Paired pulses of varying interval and duration revealed that recovery from inactivation became distinct ≥ 50 ms after depolarization and depended on [Ca2+]i. The inactivation was prevented by BAPTA (≥ 100 μm) but not by EGTA (≤ 10 mm), whereas the activation was less affected by BAPTA. When CICR was partially activated, some of the non‐activated RyRs were also inactivated directly. Thus, the inactivation in these neurons is induced by Ca2+ binding to the high‐affinity regulatory sites residing very close to Ca2+ channels and/or RyRs, although the sites for activation are located much closer to those Ca2+ sources. The rate of [Ca2+]i decay after the pulse decreased with increasing pulse duration longer than 10 ms, and this was abolished by BAPTA. Thus, some mechanism counteracting Ca2+ clearance is induced after full inactivation and potentiated during the pulse. Possible models for RyR inactivation were proposed and the roles of inactivation in Ca2+ signalling were discussed.
Design Guidelines for Anisotropic Conductive Adhesive Assemblies in Microelectronics Packaging
Authors: Chin Melida , Hu S. Jack , Barber James R.
Published: May 2008

Multiple parameters are involved in the design of anisotropic conductive adhesive assemblies, and the overlapping influences that they have on the final electrical contact resistance represent a difficult challenge for the designers. The most important parameters include initial bonding force F, number of particles N, the adhesion strength GA, and modulus of elasticity E of the cured resin. It is well known that as the bonding force increases, the contact resistance decreases. However, when the bonding force reaches a certain maximum value, the contact between conductive particle and conductive track is disrupted due to delamination of the cured resin during the elastic recovery. The authors have shown in previous studies that the delamination is caused by high residual stresses and that it largely depends on the adhesion strength of the assembly and on the modulus of elasticity of the cured resin. Additionally, the authors have provided a methodology to quantify the maximum threshold value of the bonding force for different numbers of particles trapped between mating conductive tracks. In this paper, the relationships between contact resistance R and each one of these parameters are systematically investigated to create diagrams that give regions of robust design. Given the number of particles and their size, adhesion strength, and modulus of elasticity of the resin, the required bonding force can be found in order to achieve a desired range in contact resistance.
Merits of Employing Foam Encapsulated Phase Change Materials for Pulsed Power Electronics Cooling Applications
Authors: Lafdi K. , Mesalhy O. , Elgafy A.
Published: May 2008

In the present work, the potential of using foam structures impregnated with phase change materials (PCMs) as heat sinks for cooling of electronic devices has been numerically studied. Different design parameters have been investigated such as foam properties (porosity, pore size, and thermal conductivity), heat sink shape, orientation, and use of internal fins inside the foam-PCM composite. Due to huge difference in thermal properties between the PCM and the solid matrix, two energy equation model has been adopted to solve the energy conservation equations. This model can handle local thermal nonequilibrium condition between the PCM and the solid matrix. The numerical model is based on volume averaging technique, and the finite volume method is used to discretize the heat diffusion equation. The findings show that, for steady heat generation, the shape and orientation of the composite heat sink have significant impact on the system performance. Conversely, in the case of power spike input, use of a PCM with low melting point and high latent heat is more efficient.
Improved Method of CO2 Laser Cutting of Aluminum Nitride
Authors: Molian Raathai , Shrotriya Pranav , Molian Pal
Published: May 2008

The traditional “evaporation∕melt and blow” mechanism of CO2 laser cutting of aluminum nitride (AlN) chip carriers and heat sinks suffers from energy losses due to its high thermal conductivity, formation of dross, decomposition to aluminum, and uncontrolled thermal cracking. In order to overcome these limitations, a thermochemical method that uses a defocused laser beam to melt a thin layer of AlN surface in oxygen environment was utilized. Subsequent solidification of the melt layer generated shrinkage and thermal gradient stresses that, in turn, created a crack along the middle path of laser beam and caused material separation through unstable crack propagation. The benefits associated with thermal stress fracture method over the traditional method are improved cut quality, higher cutting speed, and lower energy losses.
Heat Transfer Measurements and Numerical Simulations in the Cooling of a Circular Cylinder by a Slot Jet of Air
Authors: Gori F. , Petracci I.
Published: May 2008

The present paper reports heat transfer measurements on a circular cylinder, electrically heated, and cooled by a slot jet of air. The diameter of the cylinder is equal to the slot height. Temperature measurements in five positions along the circumference of the circular cylinder, allow the evaluation of the convective heat transfer coefficients or Nusselt numbers at several Reynolds numbers. The Nusselt numbers are compared with the corresponding results in uniform flow around a circular cylinder. The experiments have been performed at several distances from the slot jet exit and different Reynolds numbers. Numerical simulations have been carried out with a commercial code.
Fluid Dynamics Measurements and Flow Visualizations of a Free Slot Jet of Air
Authors: Gori F. , Nino E.
Published: May 2008

The paper reports flow visualizations of a free slot jet of air, obtained with the shadowgraph technique, in the Reynolds number range allowed by the experimental apparatus, i.e. from Re=1,682 to Re=22,107. The Reynolds number is based on the hydraulic diameter of the slot. The shadowgraphs have confirmed the presence of the undisturbed region of flow, which is the zone of the jet flow where velocity and turbulence are about the same as those measured on the slot exit. The undisturbed region of flow is dependent on the Reynolds number. It is higher than three times the slot height, for Re=1,682, and equal to the slot height, for Re=22,107. To confirm the findings of the visualizations, fluid dynamics measurements have been carried out with the hot wire anemometry. The fluid dynamics measurements have confirmed these values with a little over-prediction.
Shape Control of a Flexible Mirror Using an Electron Gun
Authors: Sumali Hartono , Martin Jeffrey W. , Chaplya Pavel , Redmond James M.
Published: May 2008

Mirrors made of PVDF film are being considered for lightweight transportation and deployment in space. An array of electrodes can be used to distribute charges over the PVDF film for active shaping of the mirrors. This paper presents the derivation of a matrix that enables calculation of the shape of the two-dimensional mirror for any given electron distribution. Finite element simulation shows good agreement with a theoretical example. Furthermore, if a desired shape is given, the required voltage distribution can be computed using the singular value decomposition. Experiments were done in a vacuum vessel, where an electron gun was used to actuate a PVDF bimorph to a desired shape. Dynamic shape control is attainable at low frequencies. At higher frequencies, still significantly below structural resonance, actuation lag and parasitic DC offset can be significant problems that require future research to solve.
Design and Analysis of the CMOS Compatible Pressure Sensor Using Flip Chip and Flex Circuit Board Technologies
Authors: Peng Chih-Tang , Lee Chang-Chun , Chiang Kuo-Ning
Published: May 2008

In this study, a silicon base piezoresistive pressure sensor using flip chip and flex circuit packaging technologies is studied, designed and analyzed. A novel designed pressure sensor using flip chip packaging with spacer is employed to substitute the conventional chip on board or SOP packaging technology. Subsequently, a finite element method (FEM) is adopted for the designing of the sensor performance. Thermal and pressure loading is applied on the sensor to study the system sensitivity as well as the thermal and packaging effect. The performance of novel packaging pressure sensor is compared with that of the conventional one to demonstrate the feasibility of this novel design. The findings depict that this novel packaging design can not only maintain well sensor sensitivity but also reduce the thermal and packaging effect of the pressure sensor.
Optimal Weighting Factor for Single-Step Trapezoidal Method
Authors: Zhao Fuzhang
Published: May 2008

A new optimal weighting factor for a single-step trapezoidal method, θ = 0.618, has been developed to solve transient linear and nonlinear heat conduction problems. The numerical results based on the optimal weighting factor developed, through both linear and nonlinear benchmark tests, are compared with other commonly used single-step trapezoidal methods with emphasis on the combination of both accuracy and efficiency in the solution. The optimal weighting factor of single-step method has been proved to be very accurate, stable, and efficient. The relevant features for the single-step trapezoidal methods are also addressed.
Practical Design and Use of Drill Template Jigs in Spacecraft Manufacturing
Authors: Robinson David W.
Published: May 2008

Drill templates are used frequently in the fabrication and assembly of scientific spacecraft at NASA Goddard Space Flight Center (GSFC). They are used to provide precision location of a hole pattern for mating parts and assemblies, from small parts to multi-million dollar space telescopes. Typically these interfaces are one of a kind and crucial to the success of the space mission. Although proper geometric dimensioning and tolerancing for CNC machining can often be relied upon, there are many situations where either it is too difficult to achieve the required tolerances, too difficult to inspect, or too uncertain. Once the decision is made to use a drill template at a critical interface, there are several key design considerations including how to hold the piece to be drilled, how to properly and repeatably align the template to the part, and how to step through the drilling process. In addition to these considerations, there are a remarkable number of tips and techniques used by the people on the shop floor to make the process work well. This paper includes many of these tips gathered from technicians and engineers from around NASA GSFC.
Prediction of the Transport Phenomena in the Micro Capillary Tube of a CPL System
Authors: Park Kyoungwoo , Lee Kwan-Soo
Published: May 2008

A mathematical model is presented to predict the two-phase transport phenomena of the evaporating extended meniscus region in a micro capillary tube which approximates the evaporator of the CPL system. The behavior of a liquid-vapor interface can be estimated by using the augmented Laplace-Young equation. The governing equations for transport fields of liquid and vapor phases can be obtained by adopting the different physical approaches for the meniscus and thin film regions. In this model, the variation of vapor pressure and the disjoining pressure effect are included and the friction force at the liquid-vapor interface is also considered. The results show that the local heat transfer coefficient has an extremely large value in the thin film region. However, the amount of heat transfer rate, of the meniscus region is larger than that of the thin film region. It is also found that the length of the extended meniscus region is affected by the heat flux, the tube radius and the dispersion constant.
Polysilicon Failure Stress and Young’s Modulus Evaluation in MEMS Devices
Authors: Carli Fabio , Cambie Rossana , Vigna Benedetto , Combi Chantal
Published: May 2008

The main object of the paper is the implementation of two different approaches for the estimation of the modulus of elasticity and of the failure strain/stress in micro machined structures manufactured of epitaxial polycrystalline silicon (15 μm thick film). The micro-test-structures are produced using a standard THELMA process becoming an integral part of a MEMS actuator of comb-finger type. The micro-motor is designed to develop electrostatic in plane forces of desired intensity when fed by suitable electric potential difference.
Optimal Capacity Management With Stochastic Market Demand and Imperfect Information
Authors: Asl Farshid Maghami , Ulsoy A. Galip
Published: May 2008

Over-capacity has been a major problem in the world economy over the past decade. Reconfigurable capacity, and optimal capacity management policies, can contribute to increased economic stability. This research introduces a new approach to optimal capacity management for a firm faced with uncertainties and imperfect information of the market demand. It presents an optimal policy for the capacity management problem in a firm facing stochastic market demand, based on Markov decision theory. To make the approach more realistic, it is assumed that the firm has imperfect information of its stochastic market demand, and can only observe its previous sales. Optimal policies are presented as boundaries representing the optimal capacity expansion and reduction levels.
A Comparative Study of Structural Analyses for Flat and Curved Mechanical Heart Valve Prostheses to Enhance Durability
Authors: Kwon Young Joo
Published: May 2008

This paper addresses a comparative study of structural analyses for flat and curved mechanical heart valve prostheses. The same fluid force computed by the fluid mechanics analysis for the blood flow passing through the leaflets of a bileaflet mechanical heart valve prosthesis is used to both flat and curved mechanical heart valve prostheses for comparison. This fluid force is applied to both mechanical heart valve prostheses for the rigid body dynamics analyses to confirm the kinematic and dynamic characteristics of leaflet motions, the structural mechanics analyses for deformed leaflets of both flat and curved mechanical heart valve prostheses are executed to give quite different stress and deflection results even though they have the almost same kinematic and dynamic characteristics.
A Framework for Generating Efficient Simulation Code From Declarative Models
Authors: Larsson Jonas , Krus Petter
Published: May 2008

It is becoming increasingly important to treat models as independent from the tools used to create or compute them; the modelling and simulation tools. Models need to be future proof so that they can be used with any present and future tools. There is also a need to be able to use models in applications the tool developers do not support. The advent of modelling languages meant that models could be defined without any reference to how to compute them. Such models do not put any constraint on what simulation tool to use in the end. These models however need to be adjusted to fit the destination simulation tool and be compiled through a series of complicated steps. Today there exist no tools to perform both the mentioned model fitting and compilation. A framework as well as an implementation has been developed that does most of the work of transforming a model into a computational form that is adapted to a certain destination simulation tool. The framework makes use of a model description in XML that various transformation tools can act upon in a sequence of steps to produce pseudo code. This code is easily translated into the format needed for a specific tool as input or to be used as a standalone application.
Computational Fluid Dynamics Through an Unstructured Lattice Boltzmann Scheme
Authors: Ubertini Stefano
Published: May 2008

Computational fluid dynamics, in its conventional meaning, computes pertinent flow fields in terms of velocity, density, pressure and temperature by numerically solving the Navier-Stokes equations in time and space. At the turn of the 1980s, the Lattice Boltzmann Method (LBM) has been proposed as an alternative approach to solve fluid dynamics problems and due to the refinements and the extensions of the last years, it has been used to successfully compute a number of nontrivial fluid dynamics problems, from incompressible turbulence to multiphase flow and bubble flow simulations. The most severe limitation of the original method is the uniform Cartesian grid on which the LBM must be constructed, that requires the approximation of a curved solid boundary by a series of stair steps. This represents a particularly severe limitation for practical engineering purposes especially when there is a need for high resolutions near the body or the walls. Among the recent advances in lattice Boltzmann research that have lead to substantial enhancement of the capabilities of the method to handle complex geometries, a particularly remarkable option is represented by changing the solution procedure from the original “stream and collide” to a finite volume technique. This paper presents a compact and efficient finite-volume lattice Boltzmann formulation on unstructured grids based on a cell-vertex scheme recently proposed in literature to integrate the differential form of the lattice Boltzmann equation. It is shown that the method tolerates significant grid distortions without showing any appreciable numerical viscosity effects at second order in the mesh size, thus allowing a time-accurate description of transitional flows. Moreover, a new set of boundary conditions to handle flows with open boundaries is presented. The resulting model has been tested against typical flow problems at low and moderate Reynolds numbers.
H∞ Robust Control Design for Hydraulic Front Wheel Drive Speed Control of a Motor Grader
Authors: Robinson William D. , Kelkar Atul G.
Published: May 2008

A dual-mode H∞ robust tracking controller design is presented to regulate the speed of a hydraulic front wheel drive system on a motor grader. The controller design uses a multiplicative unstructured uncertainty model to account for the un-modeled dynamics of the plant and parametric uncertainties such as variations in fluid temperature and air entrainment. The H∞ design is compared to a classical PI controller design, which is the existing industrial practice. It is shown that the H∞ design provides a higher level of stability robustness and better performance guarantees, which make it a viable candidate for motor grader application.
Experimental and Finite Element Analysis of Human Skin Elasticity
Authors: Areias P. M. A. , Jorge R. M. Natal , Barbosa J. T. , Fernades A. A. , Mascarenhas T. , Oliveira M. , Patri´cio B.
Published: May 2008

In this paper, mechanical properties of human skin are inferred from the information of a suction test using a cutometer test. Experiments with a 2 mm probe are carried out and numerical tests using a finite element program developed by the first author are employed for comparison. Regarding the numerical tests, both axisymmetric and complete 3D models of a silicon sheet were employed with the hyperelastic Yeoh constitutive model.
Simulation of a Pollutant Transport in an Atmosphere With Shock Waves
Authors: Martins-Costa Maria Laura , Saldanha da Gama Roge´rio M.
Published: May 2008

In this work a model for transport phenomena in an environment representing the atmosphere containing a pollutant is presented by considering mass and linear momentum conservation for the air-pollutant mixture as well as the mass balance for the pollutant. The resulting mathematical description consists of a nonlinear system of hyperbolic equations that admits discontinuities in addition to smooth or classical solutions. The Riemann problem associated with a class of problems describing the transport of a pollutant in an ideal gas with constant temperature with a discontinuous mass density distribution as initial condition is discussed. Numerical approximations for this nonlinear system in which the problem is solved subjected to a discontinuous initial condition — a jump, originating, in most cases, shock waves — are obtained by employing Glimm’s method and considered in some numerical simulations.
Computational Modeling of Dynamic Cell Adhesion, Deformation, and Rolling Under Blood Flow in a Micro-Channel
Authors: Xu J. , Zhang H.
Published: May 2008

Cell adhesion to postcapillary vascular endothelium in the fluid dynamic environment is an important event in many physiological and pathological processes, e.g. leukocyte emigration is critical for the successful host defense against tissue injury and infection. Since cell-blood interaction is strongly coupled with cell adhesion in the microchannel, we have developed an integrated mathematical model of cell adhesion, deformation, and rolling. Cells are modeled as elastic solids interacting with the flat wall of a micro-channel. The ligand-receptor bonds between the cell and micro-channel wall are simulated as many simple springs. The formation and dissociation rates of bonds are characterized by a reversible kinetic model (Dembo et al., 1988).
Accurate Milling Process Simulation Using ME Z-Map Model
Authors: Lee Han Ul , Cho Dong-Woo
Published: May 2008

In this paper, a milling process simulation system was constructed and ME Z-map (Moving Edge node Z-map) model was developed to elevate the performance of this system. The milling process simulation system computes the cutting configuration and then the cutting forces are predicted using these calculated configurations. In this system, an improved cutting force model which is independent of cutting conditions is used to more precisely predict the cutting forces. In the process, the ME Z-map model was used for more accurate computing of cutting configuration. Due to the edge node, ME Z-map model produces more accurate cutting configuration than the conventional Z-map models even with five to ten times larger grid size, which reduces the computing time dramatically. The superiority of the ME Z-map model was confirmed through comparison with the conventional Z-map.
Static Chaos Microfluid Mixers Using Microblock-Induced Alternating Whirl and Microchannel-Induced Lamination
Authors: Chang Sunghwan , Cho Young-Ho
Published: May 2008

We characterize two types of noble static chaos microfluid mixers for the applications to Micro Total Analysis Systems (μTAS): an AW-type microfluid mixer, having a series of microblocks along a flow channel for generating alternating direction whirl (AW) flows, and an AWL-type microfluid mixer, coupling the AW-type microfluid mixers with divided microchannels for generating lamination flows between the alternating whirl flows. For generating whirling flow in microchannels, we design rotating block geometry in microchannels. For chaos mixing, we suggest alternating-directional whirling flows in microchannels. AW, AWL-type microfluid mixers are made of PDMS (Polydimethylsiloxane). We quantify mixing state using phenolphthalein visualization experiments and measure pressure drop through microfluid mixers.
High-Accuracy Microflow Controllers Using Fluidic Digital-to-Analog Converters
Authors: Yoon Sang-Hee , Cho Young-Ho
Published: May 2008

This paper presents 4-digit digital microflow controllers where fluidic digital-to-analog converters (DACs) achieve an improved linearity with finer flow-rate levels for a given number of digital valves. The fluidic DAC, composed of microchannels with binary-weighted flow resistors, controls flow-rate levels not based on the magnitude of flow resistances, but based on the ratio of the flow resistance. We deign the flow resistance of microchannel using a serial or a parallel connection of an identical fluidic resistor, thus making the controllable flow-rates insensitive to the micromachining errors. Prototype S and P with serial and parallel connections of a unit fluidic resistor and prototype V with the fluidic resistors having different channel width are fabricated using micromachining. At a constant pressure of 2kPa, prototypes S, P and V show the maximum error of 7.5%, 6.2% and 22.5% in the flow-rate range of 0.09μ1/s to 3.33μ1/s, resulting in the differential nonlinearity of 0.28, 0.27 and 0.94, respectively. The prototypes S and P show 70.2% and 71.2% less sensitive to micromachining errors than prototype V, respectively.
Thermal Stress Analysis of Contactless Energy Transfer Micro Module
Authors: Hsu Yung-Yu , Huang Chao-Ta , Chang Chao-Liang , Yao Chih-Min , Lee Ming-Hsiao , Tzeng Kung-Yu
Published: May 2008

The technology of contactless energy transfer is emerging for application in implantable medical device. High transfer efficiency and high quality factor are specific design requirements for micro-inductors which are key component of contactless energy transfer micro-modules. Thermal stress analysis and electrical analysis of an inductor are sequentially performed to elucidate the effect of thermal strain on the electrical properties of a micro-inductor. Three dimensional finite element models of an inductor were generated by the commercial stress analysis software, ANSYS, to calculate the thermal stress and thermal strain. The deformed model of the inductor was then imported to the commercial electrical property analysis software, ANSOFT, to calculate changes of the electrical properties, such as the inductance, the quality factor and the electrical resistance. The investigation shows that the thermal stress is concentrated at the four corners of the inductor with SU8 support, and that the inductor without SU8 support is twisted without substrate warpage. The electrical properties of inductors do not change dramatically under thermal loading caused by a temperature change from −40°C to 125°C.
Integrated Optimization of ACLD Treatment for Shape Control of Flexible Beams Using Multi-Objective Genetic Algorithm
Authors: Hau L. C. , Fung Eric H. K.
Published: May 2008

This paper presents the use of multi-objective genetic algorithm (MOGA) to solve an integrated optimization problem for the shape control of flexible beams with Active Constrained Layer Damping (ACLD) treatment. The design objectives are to minimize the total weight of the system, the input voltage and the steady-state error between the achieved and desired shapes. Design variables include the thickness of the constraining layer and viscoelastic layer, the length and location of the ACLD patches, as well as the control gains. In order to evaluate the effect of different combinations of design variables on the system performance, the finite element method, in conjunction with the Golla-Hughes-McTavish (GHM) method, is employed to model a clamped-free beam with ACLD patches. As a result of the optimization, a Pareto solution is successfully obtained. It is shown that the MOGA is applicable to the present integrated optimization problem, and ACLD treatment is suitable for shape control of flexible structures.
3-Dimensional Hybrid Continuum-Atomistic Simulations for Multiscale Hydrodynamics
Authors: Wijesinghe H. S. , Hornung R. , Garcia A. L. , Hadjiconstantinou N. G.
Published: May 2008

We present an adaptive mesh and algorithmic refinement (AMAR) scheme for modeling multi-scale hydrodynamics. The AMAR approach extends standard conservative adaptive mesh refinement (AMR) algorithms by providing a robust flux-based method for coupling an atomistic fluid representation to a continuum model. The atomistic model is applied locally in regions where the continuum description is invalid or inaccurate, such as near strong flow gradients and at fluid interfaces, or when the continuum grid is refined to the molecular scale. The need for such “hybrid” methods arises from the fact that hydrodynamics modeled by continuum representations are often under-resolved or inaccurate while solutions generated using molecular resolution globally are not feasible. In the implementation described herein, Direct Simulation Monte Carlo (DSMC) provides an atomistic description of the flow and the compressible two-fluid Euler equations serve as our continuum-scale model. The AMR methodology provides local grid refinement while the algorithm refinement feature allows the transition to DSMC where needed. The continuum and atomistic representations are coupled by matching fluxes at the continuum-atomistic interfaces and by proper averaging and interpolation of data between scales. Our AMAR application code is implemented in C++ and is built upon the SAMRAI (Structured Adaptive Mesh Refinement Application Infrastructure) framework developed at Lawrence Livermore National Laboratory. SAMRAI provides the parallel adaptive gridding algorithm and enables the coupling between the continuum and atomistic methods.
Parallel Performance of Lattice Boltzmann and Implicit Finite Difference Approaches to the Approximation of the Two-Dimensional Diffusion Equation
Authors: Velivelli Aditya C. , Bryden Kenneth M.
Published: May 2008

The reduction of computation times is an important aspect of interactive computational fluid dynamics simulations. The lattice Boltzmann method has proved to be an important technique for the numerical solution of partial differential equations because it has nearly ideal scalability on parallel computers for many applications. Utilizing the two-dimensional diffusion equation, Tt=μ(Txx+Tyy), this paper examines the parallel performance for the lattice Boltzmann method and the alternating direction implicit (ADI) method. In this study for 50 time steps the non-cache optimized parallel lattice Boltzmann method was on average two times faster than the parallel ADI method. The cache optimized parallel lattice Boltzmann was on average seven times faster than the parallel ADI method.
Multivariable Control of an Earthmoving Vehicle Powertrain Experimentally Validated in an Emulated Working Cycle
Authors: Zhang Rong , Carter Don E. , Alleyne Andrew G.
Published: May 2008

The operation of an earthmoving vehicle involves the coordination of a multivariable powertrain and the execution of specific tasks in a repetitive fashion. The performance and efficiency depend heavily on human expertise. The purpose of this research is to automate the coordination of a multi-input multi-output (MIMO) nonlinear electro-hydraulic powertrain and to validate the performance and efficiency improvements in a human-machine interaction. Firstly, a robust gain scheduling method is developed to design a powertrain controller and to analyze its robust stability and robust performance. The gain scheduling is based on a Local Controller Network strategy and its satisfactory properties are analytically confirmed using robust control theories. Secondly, the improvement of performance and efficiency are validated through two experiments performed on an Earthmoving Vehicle Powertrain Simulator (EVPS). This testbed is a Hardware-In-the-Loop HIL environment representative of a class of electro-hydraulic systems with multiple loads. The two human-operated experiments include a reference tracking test and a working cycle test. In the second test, three types of loads are modeled for a typical wheel loader and emulated on EVPS for a 180-degree loading cycle. These models include the steering, the drive, and the implement. The load emulation technique ensures that the HIL working cycles are representative of real life cycles. The reference tracking and loading cycle results show the significant improvement in productivity in terms of performance, efficiency, and ease of operation.
Wear Problem in a Linear Hydraulic Actuation System and Solution Using Forced Lubrication
Authors: Sorokin Michael , Egelja Aleksandar
Published: May 2008

The subject of this paper is early hours wear problem of a hydraulic actuator. Material transfer from the actuator housing to the actuator surface was observed after short time of component testing. A general case, where the actuator is tilted in the bore due to side load, is examined. The mechanism of local scuffing (micro-welding) is discussed. The paper describes the theoretical analysis combined with practical experience in solving common wear problems related to poor material pair and lack of lubrication between sliding surfaces. A validated solution is also discussed.
Formulations for the Thermodynamic Properties of Pure Substances
Authors: Adebiyi George A.
Published: May 2008

Complete analysis of thermodynamic systems generally requires knowledge of the property values of substances at different states. Performing such analysis on the computer is facilitated if the equations of state for the substances are available in relatively simple analytic forms. This article presents a procedure for formulation for the thermodynamic properties of pure substances using two primary sets of data, namely the pvT data and the specific heat data such as the constant-pressure specific heat, cp, as a function of pressure and temperature. By developing a correlation of the pvT data in the virial form of equation of state, an appropriate corresponding correlation can be determined for the specific heat of the substance on the basis of the laws of thermodynamics. The resulting equations of state take on remarkably simple analytic forms that give accurate predictions over the range of input data employed.
Design and Fabrication of a Temperature Sensor Based on Thermopile in CMOS Technology
Authors: Voiculescu Ioana , Zaghloul Mona , McGill R. Andrew
Published: May 2008

This paper describes a new geometry for integrated micromachined thermopile structures. Different arrangements for the thermocouples in proximity to the heating element are examined, to optimize the accuracy of the temperature measurement. Several design parameters including thermopile lengths, and the number of thermocouples, are examined. The test chip was designed and fabricated in CMOS technology, including the appropriate opening for post-processing micromachining. The thermopile used was fabricated with polysilicon/aluminum contacts on a silicon oxide/nitride layer provided by the CMOS process. Different microbeam and bridge membrane support structures were designed for the thermopile, in order to investigate the optimal geometry for mechanical stability and to avoid structure buckling.
Oscillatory Heat Transfer at the Heat Exchangers of the Thermoacoustic Refrigeration System
Authors: Nsofor Emmanuel C. , Wang Xudong
Published: May 2008

Thermoacoustic refrigeration systems utilize high intensity sound waves and the interactions with solid boundaries to create temperature gradient, heat pumping and consequent cooling. In this study, a thermoacoustic refrigeration system was designed and constructed. The stack was fabricated from a thermoplastic material to reduce conduction in the direction opposite to heat pumping. The direction of the stack plates perpendicular to the thickness was lined with an aluminum material to increase the heat transfer in this direction. A study on the oscillatory flow heat transfer at the heat exchangers was performed using helium as the working gas. Some important factors that influence the heat transfer coefficient in oscillatory fluid flow and relations to stack fabrication were identified.
Piezoelectric Microbeam Resonators Based on Epitaxial AlxGa1−xAs Films
Authors: Li Lihua , Kumar Parshant , DeVoe Don L.
Published: May 2008

Piezoelectric resonators based on epitaxially-grown Al0.3Ga0.7As have been developed. The resonators are fabricated using a single crystal device structure, with differential doping used to create either piezoelectric or electrode regions. Constitutive layers consist of 0.5μm Si-doped Al0.3Ga0.7As acting as the top electrode layer, 1μm undoped Al0.3Ga0.7As as the piezoelectric layer, and 2μm Si-doped Al0.3Ga0.7As as both the structural and the bottom electrode layer. Resonator fabrication employs a 4 mask process combining inductively coupled plasma reactive-ion etching (ICP RIE) and a highly selective bulk GaAs wet etching process. The frequency response of fabricated beam resonators has been measured using laser Doppler vibrometery (LDV). Both cantilever and doubly-clamped beam resonators have been demonstrated, with fabricated resonators center frequencies showing excellent agreement compared to designed values. The transverse piezoelectric coupling coefficient d31 has also been measured as a function of beam orientation.
Engine Modeling With Inlet and Exhaust Wave Action for Real Time Control
Authors: Wu Yuh-Yih , Chen Bo-Chiuan , Shiao Yaojung , Hsieh Feng-Chi
Published: May 2008

A motorcycle engine model in MATLAB/SIMULINK is introduced in this paper for engine design and control system design. It simulates a 125 cc single cylinder four-stroke spark ignition engine. Sub-models include: inlet/exhaust, combustion, heat transfer, friction, and work done. The method of characteristics is used for calculating the inlet and exhaust flow. Simulated results of bmep, imep, fmep, heat release rate, inlet/exhaust pressure, and cylinder pressure were compared with the experimental data. It was found that satisfactory simulation results were achieved for the proposed model.
Analysis and Design of Thermoelectric Infrared Microsensor
Authors: Liao Ke-Min , Chen Rongshun , Chou Bruce C. S.
Published: May 2008

In this study, a novel thermoelectric infrared microsensor (TIMS) is designed by using commercial CMOS IC processes with subsequent bulk-micromachining process. This microsensor has the advantages of high fill factor, low noise equivalent temperature difference (NETD), and simple fabrication process. The key feature is that thermocouple cantilever beams with low solid thermal conductance have been placed under the membrane of thermoelectric infrared microsensor. In order to improve the performance of the infrared sensor, the basic physical characteristics of this sensor have been analyzed. Finite element analysis is used to simulate the electro-thermo-mechanical behavior of the device and to demonstrate the feasibility of our design. Besides, a method for manufacturing the infrared microsensor is also provided and the performance of the presented design has been examined. The analytical results concluded that lowering down the number of the thermocouples does not affect the responsivity but do reduce the total resistance. Also, the detectivity and responsivity are obviously increased for the proposed TIMS. Finally, the deviation between the theoretical and the simulated results is discussed.
The Control of Aerial Flow by the Magnetizing Force
Authors: Akamatsu Masato , Higano Mitsuo , Takahashi Yoshio , Ozoe Hiroyuki
Published: May 2008

Two-dimensional numerical computations were carried out to clarify the influence of magnetizing force for air in a vertical cylindrical container with the thermal and magnetic field gradients under gravitational and non-gravitational fields. Several axial position of the electric coil was tested for numerical computation. In a vertical cylindrical container with the stagnant conduction and the Benard conditions, the aerial flow was able to be controlled by the magnetizing force under both gravitational and non-gravitational fields. The flow pattern and the heat transfer rate strongly depended on the axial position of the electric coil.
Microfabrication and Laser Diagnosis of Pressure-Swirl Atomizers
Authors: Huang Ker-Jer , Chen Alex C. , Yang Jing-Tang
Published: May 2008

In this work we used deep-molding manufacture of three kinds to fabricate micro pressure-swirl atomizers to promote their performance, and a Phase Doppler Particle Analyzer (PDPA) to measure the characteristic distributions of the spray flow field of these atomizers. The deep-molding techniques were X-ray LIGA process, ICP-LIGA process (inductive coupling plasma etching), and injection molding LIGA process. Parameters of atomizers examined here include configuration of flow channel, diameter of exit orifice, the ratio of diameters of swirl chamber and discharge orifice, and the thickness of atomizer. Experimental results showed that the manufacturing process combining injection molding with electroplating had large yields and that the technique is highly reliable; enable manufacture of an atomizer at small cost and great quality. Moreover, these microatomizers are assembled well with other components and be readily applied. The results of PDPA diagnosis further revealed that the spray features are related with the design parameters of atomizer dimensions.
Clathrate-Hydrate Production From Methane, Xenon, CO2, Helium Gases and Their Mixed Gases
Authors: Nishimoto Hiroyuki , Ota Masahiro , Endou Hajime , Murakami Kazuhiko , Hoshino Daisuke
Published: May 2008

In the present study, the production characteristics of the hydrates from methane, xenon and their mixed gases and the application of a hydrate production technology for the separation of mixed gases such as CO2 and helium gases are discussed. Methane, xenon and CO2 can form hydrates. On the other hand, helium can’t produce the hydrate. Therefore, by using the hydrate production technology, CO2 could be separated from the mixed gases of CO2 and helium as the CO2 hydrate. In the present paper an autoclave experiment apparatus is used for the production of the hydrate.
Fixture Design Methodology for Sheet Metal Assembly Using Computer Simulations
Authors: Dahlstro¨m Stefan , Camelio Jaime A.
Published: May 2008

Sheet metal assembly is a common manufacturing process for several products such as automobiles and airplanes. Since all manufacturing processes are affected by variation, the key characteristics or critical dimensions may not be nominal. This paper presents a new fixture design methodology for early evaluation of sheet metal assemblies. Fixture design has been extensively studied for machining processes. Unfortunately, little investigation has been done for sheet metal assembly processes considering the effect of fixture layout on the assembly dimensional variation. The new fixture design methodology is based on classifying the assemblies into three categories depending on the stiffness of the assembly components: rigid-rigid, compliant-rigid and compliant-compliant assembly. Finite Element Analysis (FEA) and design of computer experiments have been used to derive response models for sheet metal assembly applications. The response models are used to analyze the final assembly sensitivity to fixture, part and tooling variation for different assembly configurations. Based on these results several design guidelines are proposed for fixture design on sheet metal assembly.
Numerical Simulation of the Application of Porous Ceramic Linings in a Gas-Fired Furnace
Authors: Correia Sara A. C. , Ward John , Tucker Robert J. , Rhine Jeff
Published: May 2008

This paper describes the development and application of a mathematical model, which simulates the installation of a porous ceramic section as a replacement for part of the conventional lining in a continuously operated, high temperature, gas-fired furnace for heating steel bars prior to a hot forming process. The overall model iteratively links a sub-model of the flow and heat transfer through the porous section with a zone model of heat transfer in the furnace chamber. The resultant predicted heat fluxes at the top surface of the load are then used in a finite-difference calculation of conduction through the thickness of the bars to predict the temperature distribution within the load and the thermal performance of the furnace. The model is used to investigate the effects of the size and positioning of the porous lining as well as changes in its emissivity. In addition simulations were undertaken for a range of thermal inputs to the furnace. Overall the predictions demonstrate that the replacement of part of the conventional refractory lining by a porous ceramic section can result in enhanced radiative heat transfer to the load and hence significantly improved furnace performance.
Physical Models in Data Center Airflow Simulations
Authors: Rambo Jeffrey D. , Joshi Yogendra K.
Published: May 2008

The trend of increasing functionality of electronics with a reduction in size has caused a rapid increase in the volumetric heat generation of today’s equipment. This problem is compounded by the vertical stacking of such components in tall enclosures, called racks. The organization of these racks into large infrastructure facilities, or data centers, generates enough heat to require a room-level cooling strategy. The total power dissipated in current data centers can be as large as several MW. Since all the heat generated must be removed, a systematic thermal management methodology is required to ensure efficient, reliable and safe operating conditions. The mathematical description of the airflow and heat transfer characteristics involves a range of length scales, all of which are infeasible to approach simultaneously. In this study, a modeling framework for data centers is investigated, with emphasis on the physical models employed in numerical simulations. Computational fluid dynamics (CFD) models are presented to develop a unit cell, or a minimum sized model which is representative of these facilities. A unit cell architecture is a useful design tool for the evaluation of tomorrow’s cooling strategies. A premium on floor space may result in oddly shaped facilities, so a need exists for a common basis of comparison. The flow patterns inside a data center typically fall into the regime of turbulent mixed convection. The choice of turbulence model employed in a Reynolds-averaged Navier-Stokes (RANS) type simulation is examined using a commercial code. Comparisons are made with indoor airflow simulations of office spaces and auditoria because of the similarity of office spaces and auditoria because of the similarity in velocities and length scales. Results shows up to 20% variation in temperature predictions can occur between various commercially-implemented turbulence models.
A New Imaging Method for Arterial Tubes Based on Vibration Measurement
Authors: Zhang Xiaoming , Fatemi Mostafa , Greenleaf James F.
Published: May 2008

A new method for imaging and detecting modal shapes of vessels is introduced. Theory is developed that predicts the measured velocity is proportional to the value of the mode shape at the focal point of the ultrasound beam. Experimental a cylindrical gel phantom of large radius. This model simulates approximately a large artery and the surrounding body. The fundamental frequency was measured 83 Hz for the tube-phantom system. At this frequency the ultrasound transducer was scanned across the vessel plane with velocity measurement at one single point on the vessel and on the phantom by laser. The images obtained show clearly the interior tube and the modal shape of the tube.