bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Displacement and Frequency of Oscillating Flow on Heat Transfer in a Porous Channel
Authors: Jin L. W. , Leong K. C.
Published: April 2008

The development in modern electronics has resulted in rapid increases in power densities for electronic packages. Traditional cooling methods are not capable of removing such high heat fluxes. It is imperative to find new methods to cool high-speed electronic components. One of these methods is to implement a channel filled with a high conductivity porous medium. Many investigations have been conducted on the heat transfer of a channel filled with porous media. However, steady flow through a porous channel still yield a higher temperature difference along the flow direction. It is conceivable that oscillating flow through a porous channel will produce a more uniform temperature distribution due to the two thermal entrance regions of oscillating flow. Some researchers have investigated forced convective heat transfer in porous channels in oscillating flow with different kinds of porous media. Their results showed that the operating temperatures of electronic components can be reduced significantly when an oscillatory flow device is employed. However, research into the two critical factors of displacement and frequency for oscillating flow in a porous channel is very sparse. This paper presents the experimental results of an investigation into the effects of varying flow displacement and frequency on heat transfer enhancement in a porous channel subject to oscillating flow. A comparison was made between the heat transfer performance of oscillating flow through a plate channel without a porous medium and a channel filled with sintered metal foam. The maximum displacements of oscillating flow were varied from 52 to 68 mm and frequencies of oscillation ranged from 1 to 10 Hz. The characteristics of pressure drop, the effects of the dimensionless amplitude of displacement and dimensionless frequency of oscillating flow on heat transfer in porous channel were analyzed. The results revealed that heat transfer in oscillating flow is significantly enhanced by employing porous media in a plate channel. The cycle-averaged local Nusselt number increases with both kinetic Reynolds number Reω and the dimensionless amplitude of flow displacement A0. Based on the experimental data, a correlation equation of the length-averaged Nusselt number with the dimensionless parameters of Reω and A0 is obtained for a porous channel with L/Dh = 3. This correlation equation will be useful to determine heat transfer rates in oscillating flow through a porous channel for applications in electronics cooling.
Control of Temperature Uniformity During the Manufacture of Stable Thin-Film Photovoltaic Devices
Authors: Malhotra Chetan P. , Mahajan Roop L. , Sampath W. S. , Barth Kurt L. , Enzenroth Robert A.
Published: April 2008

The production of stable thin-film photovoltaic devices requires tight control of temperature uniformity of the glass substrates during the vacuum deposition process. As a first step towards developing an optimized control system for maintaining thermal uniformity as the substrates traverse multiple stations during the deposition process, a finite element thermal model of a single deposition station has been developed. The model couples cavity radiation processes with conduction within the graphite sources and the substrate itself. The effect of adjustable parameters such as radiation shielding, addition of a radiation spreader and varying power distribution among the radiation lamps has been studied. It is concluded that while radiation shielding substantially improves the uniformity, it cannot bring the temperature variation down to the very low levels necessary for producing stable devices. Addition of a radiation spreader improves the uniformity. Seeking and applying the optimum power distribution among the radiation lamps results in more incremental gain in uniformity but a change in lamp configuration is required for attaining the desired uniformity levels.
Effect of Dynamic Deformational Loading on the Transport of Dextran Molecules Into Agarose Gels
Authors: Chahine Nadeen O. , Lima Eric G. , Hung Clark T. , Ateshian Gerard A.
Published: April 2008

The poor intrinsic healing capacity of articular cartilage has led to a number of attempts to engineer a replacement tissue [1]. One of these approaches, termed functional tissue engineering, suggests that the application of mechanical preconditioning, mimicking the in vivo loading environment, may enhance the development of material properties in these constructs [2,3]. Using this approach, our previous studies have demonstrated that dynamic loading (DL) increases the mechanical properties of chondrocyte-seeded agarose hydrogels relative to free swelling (FS) controls [4–6]. One mechanism by which the increase in mechanical properties occurs is hypothesized to be due to enhanced transport of nutrients and/or growth factors under dynamic loading [7]. The goal of the current study is to determine the effect of dynamic loading on the transport of neutral dextran molecules into agarose gels. Dextran, a neutral and generally inert solute commonly used in diffusion and transport studies, is used in its fluorophore-conjugated form thus making it possible to track the solute and quantify its content inside a hydrogel. We hypothesize that the uptake of dextran molecules into the agarose gels will be significantly enhanced under the influence of physiological dynamic deformation loading. Two varying molecular weights of dextran, 3 kDa and 70 kDa, were chosen in this study to ascertain a wide range of transport behaviors, and to interpret the experimental results in the context of a recently developed mixture theory model for the transport of neutral solutes in a neutrally charged gel, such as agarose [8].
CFD Analysis of the Acoustic and Mean Flow Performance of Simple Expansion Chamber Mufflers
Authors: Middelberg J. M. , Barber T. J. , Leong S. S. , Byrne K. P. , Leonardi E.
Published: April 2008

The acoustic and mean flow performance of different configurations of simple expansion chamber mufflers has been considered. The different configurations include extended inlet/outlet pipes and baffles inside the expansion section of the muffler. Both the acoustic and mean flow performance has been evaluated for each muffler. The acoustic CFD model of the muffler uses an axisymmetric grid with no mean flow and a single period sinusoid of suitable amplitude and duration imposed at the inlet boundary. The time history of the acoustic pressure and particle velocity are recorded at two points, one in the inlet pipe and the other in the outlet pipe. These time histories are Fourier transformed and the transmission loss of the muffler is calculated. The mean flow model of the muffler uses the same geometry, but has a finer mesh and has a suitable inlet velocity applied at the inlet boundary and the pressure drop across the muffler is found. The acoustic performance is compared with published experimental results.
A Numerical Study of the Effect of Flow Plate Geometry on the Pressure Distribution and Channel-to-Channel Flow Cross-Over in a PEM Fuel Cell Using a Serpentine Flow Channel System
Authors: Oosthuizen P. H. , Sun L. , McAuley K. B.
Published: April 2008

It is common in a PEM fuel cell to have the air flow through serpentine channels with a rectangular cross-sectional shape in a flow plate. There is a porous diffusion layer adjacent to this flow plate. Flow cross-over of air through the porous diffusion layer from one part of the channel to another can occur, as a result of the pressure differences between different parts of the channel, and it causes the flow rate through the channel to vary with distance along the channel and also has an influence on the pressure distribution along the channel. These changes in the pressure distribution as a result of cross-over can effect the fuel cell performance. In the present study the conditions under which cross-over occurs and the effects of the cross-over on the pressure distribution and local channel flow rates have been examined by numerically solving for the flow through the plate-porous layer assembly. Two flow channel arrangements have been considered: (i) a single serpentine channel flow system with different land widths between the channel sections (ii) a two-channel parallel serpentine flow system. A single phase flow has been considered. The governing equations have been written in dimensionless form using the channel width as the length scale and the mean velocity in the channel as the velocity scale. The resultant set of dimensionless equations has been numerically solved using a commercial finite element code, FIDAP. The solution was obtained by simultaneously numerically solving the dimensionless governing equations for the flow in the channels and for the flow through the porous gas diffusion layer. The numerical calculations were obtained using a commercial finite element code, FIDAP.
Micro Thin Film Sensor Embedding in Metals by Ultrasonic Welding for Production of Miniature Smart Tooling
Authors: Cheng Xudong , Schwieso Patrick , Choi Hongseok , Datta Arindom , Li Xiaochun
Published: April 2008

This work is to study micro thin film sensor embedding in metals for the production of miniature smart tooling. This technique promises to significantly improve the safety and reliability for manufacturing processes and reduce operation costs. One key concern of the current research is to investigate if sensor functionality can be maintained during and after embedding in metals by use of ultrasonic welding (USW), which could be hostile to micro thin film thermocouples (TFTCs) embedded near the welding interface. The welding workpieces, consisting of a nickel strip with embedded micro sensors and a copper thin sheet, were welded by USW process. Experimental results showed that TFTCs survived the ultrasonic welding process. The embedded TCFCs were also capable of measuring temperature in-situ near the weld interface during the embedding process.
High Speed Particles Separation Using Ultrasound for Lab-on-Chip Application
Authors: Li Holden , Vitikkate Vipin , Kenny Thomas
Published: April 2008

Engineers have long envisioned that a handheld portable blood diagnosis device would be able to give an accurate measurement of chemical content based on a very small sample in the shortest time possible. One of the immediate applications of such device is the Point Of Care (POC) diagnosis system, whereby a single drop of human blood would determine his health status. However, a major technical challenge lies in the ability to separate different particles, which in the case of human blood, is to separate red and white blood cells and plasma in a quick, cheap, reliable device with low power consumption (less than 100mW). In this paper, we present some preliminary results from our tests of ultrasound standing waves as a potential separation mechanism for blood cells. Micro Particle Image Velocimetry (PIV) technique is the studies.
Estimation of SI Engine Load Torque: Adaptive Kalman Filter vs. Luenberger Estimator
Authors: Deur Josˇko , Pavkovic´ Danijel , Hrovat Davor
Published: April 2008

The SI engine load torque is key information for many engine and power train control systems. Since the torque is not measured in production vehicles, it needs to be estimated on-line. The paper presents design and analysis of second-order and third-order Luenberger load torque estimators. With the aim to reduce the estimator noise sensitivity without deteriorating its transient performance, an adaptive Kalman filter is proposed and compared with the Luenberger estimator. The adaptation mechanism is based on a load torque change detection algorithm. The estimators are examined by computer simulations and experiments.
High-Pressure Hydraulic Stimulation of Geothermal Reservoir
Authors: Fomin Sergi , Hashida Toshiyuki , Chugunov Vladimir
Published: April 2008

Hydraulic stimulation is performed by high-pressure fluid injection, which permanently increases the permeability of a volume of rock, typically transforming it from the microdarcy into the millidarcy range. After a period of stimulation, fluid injection and recovery boreholes are introduced into the stimulated rock volume, and heat is extracted by water circulation. In the present study a simplified mathematical model of non-steady-state hydraulic stimulation is proposed and analyzed. Fluid flow is assumed to be radial, injected flow rate constant; and fluid density, rock porosity, and permeability depend on fluid pressure. The conventional boundary of the growing stimulated rock volume is introduced as a surface where the porosity and permeability of the stimulated rock exhibit a sharp decline and remain constant within the undisturbed area. The problem is solved analytically by a modified method of integral correlations. As a result, approximate close-form solutions for pressure distributions in the stimulated and non-stimulated (undisturbed) areas are obtained, and an equation for the moving boundary of the stimulated volume is derived. The correctness of the approximate solution is validated by comparison to an exact self-similar solution of the problem obtained for the particular case when the well’s radius is assumed to be equal to zero.
Heatlane Technology for High Heat Flux Chip Cooling
Authors: Katoh Takahiro , Vogel Marlin , Xu Guoping , Novotny Shlomo
Published: April 2008

This paper proposes a new solution for high heat flux chip cooling. The authors attempted to apply Heatlane technology for a heat sink of high-end server chip cooling. This unique technology, which is also called oscillating or pulsating heat pipe, showed very high thermal performance, and the experimental results were compared with conventional copper base heat sink in this paper. The experimental and analysis results showed that the Heatlane technology transferred heat very effectively and highly improved the fin efficiency. And the Heatlane heat sink also showed very small gravity effect and high reliability under vibrating conditions. Those experimental results were also shown in this paper. From this study, the authors has convinced that the Heatlane technology for a heat sink can be a strong candidate to solve a thermal issue of high heat flux chip cooling, especially for high-end server applications.
Modelling Tow Compression in Textile Preforms During Composites Processing
Authors: Potluri P. , Thammandra V. S. , Ramgulam R. B.
Published: April 2008

Fiber assemblies, in the form of woven, braided, nonwoven or knitted structures, are used as reinforcements in composites. These textile structures are subjected to in-plane membrane stresses such as tensile and shear, and out-of-plane stresses such as bending and transverse compression. Amongst various modes of deformation, transverse compaction behaviour is the least understood mode; however this mode is very important for composites processing using vacuum forming, resin transfer moulding, thermoforming and hot compaction methods. The present paper reports a computational approach to predicting the load-deformation behaviour of textile structures under compressive loading. During the compression of a random fiber assembly, fibers are subjected to kinematic displacements, bending and finally transverse compression of individual fibres. In the case of interlaced architectures, such as woven and braided structures, it is convenient to deal with deformations at meso-scale involving yarns or tows, and deal with inter-fiber friction and fibre compression at yarn/tow level. It can be seen from the load deformation graphs that the initial part is dominated by bending energy and the final part by compression energy. A combined yarn bending and compression model was in good agreement with the experimental curve during the entire load-deformation cycle. On the other hand, an elastica-based bending model predicts well during the initial part while tow compression model predicts well during the final part. Inter-fiber friction was initially ignored — this is being introduced in the refined model for both the dry and wet states.
Design and Analysis of Direct Liquid Multi-Jet Impingement Schemes for Electronics Applications
Authors: Iyengar Madhusudan , Ellsworth Michael
Published: April 2008

The meteoric rise in cooling requirements of commercial computer products mandates the development of extremely aggressive thermal management techniques. Direct liquid jet impingement cooling is one such method, especially if water is the coolant. While the use of water would require advanced chip packaging, it is necessary to investigate, design, and optimize systems using direct water cooling, to meet the cooling needs of the future. The thermal performance of two direct liquid jet impingement configurations, are characterized and studied, via CFD (Computational Fluid Dynamics) models constructed using a commercial numerical solver. The hydraulic performance is analytically estimated using a basic loss coefficient based model. In the first scheme, the coolant is collected at the periphery of the chip, while the second design incorporated fluid return for each jet within the vicinity of the jet itself. A square 10×10×0.75 mm3 chip, dissipating 400W, and cooled by water at 32°C, is considered as the representative example for the analysis. The effect on thermal performance of jet density, in the range of 1–36 jets/cm2, for both schemes, is investigated, for several feasible flow parameters, i.e. inlet jet velocity and volumetric flow rate. The peripheral return configuration was found to outperform the parallel return for all of the cases investigated. Barring one case, the peripheral return data from this study, for the effective heat transfer coefficient, compared with Martin’s correlation to within 17% (average) with a standard deviation of 8%. The convective thermal resistance was found to constitute an important part of the total junction-to-ambient thermal resistance.
Sensitivity Analysis of the Rating Scales and Worth Calculation Schemes Used in QFD Matrices
Authors: Takai Shun , Ishii Kosuke
Published: April 2008

Quality Function Deployment (QFD) is matrix method that identifies relative worth of product requirements from the customer requirements and their importance. Understanding the relative worth enables engineers to evaluate the potential of design concepts to achieve important requirements. In a QFD matrix called “House of Quality” or QFD I, engineers assess correlations between product requirements and customer requirements using a linear (e.g., 1–3–5) or an exponential (e.g., 1–3–9) rating scale. The exponential scale assigns product requirements that have large correlations with customer requirements a higher ratings of 9 instead of 5, and therefore, gives them larger relative worth. This paper studies how the choice of linear 1–3–5 and exponential 1–3–9 rating scales changes the relative worth of product requirements. To avoid being restricted to any specific pattern of a QFD matrix, this paper uses simulations and analytic approaches to obtain distributions of changes of relative worth, and to calculate the upper bounds of these changes. Finally, in an illustrative example, the authors integrate QFD and concept evaluation activities and provide a case in which the choice of rating scale in a QFD I matrix changes the optimal concept.
IR Thermograph Inspection on Adhesion Integrity
Authors: Omar Mohammed , Hassan Mohammed , Saito Kozo , Alloo Ritchard
Published: April 2008

The infrared thermography offers a flexible, non-contact and non-destructive tool for investigating the adhesion integrity in different applications. The IR thermography technique has been demonstrated to have wide applications to testing and quality assurance in automobile manufacturing processes. This paper addresses the capability of IR thermography in evaluating the adhesion integrity for two cases which occurred during automobile assembly processes. They are the coated surfaces adhesion integrity inspection and the adhesion strength in welded composite polymer plastic joints. Analytical models for the above two cases will be discussed in comparison to the corresponding thermographs. IR thermography technique can be used with one of or combination of the following mechanisms: the transmitted, the pulsed reflected signals. This paper discusses what type of processing scheme can be best applied to each of these signals.
A Hybrid CFD-Mathematical Model for Simulation of a MEMS Loop Heat Pipe
Authors: Ghajar M. , Darabi J. , Crews N.
Published: April 2008

A Hybrid CFD-Mathematical (HyCoM) model was developed to predict the performance of a Micro Loop Heat Pipe (MLHP) as a function of input heat rate. A micro loop heat pipe is a passive two-phase heat transport device, consisting of microevaporator, microcondenser, micro-compensation chamber (CC), and liquid and vapor lines. A CFD model was incorporated into a loop solver code to identify heat leak to the CC. Two-phase pressure drop in the condenser was calculated by several two phase correlations and results were compared [2]. Capillary tube correlations [3] were used for pressure drop calculations in fluid lines. Effects of working fluid and change in geometry were studied. For a heat transport distance of 10 mm, the base model MLHP was 50mm long, 16mm wide and 1mm thick. In the base model, widths of the grooves, liquid and vapor lines, evaporator, and condenser were 55μm, 200μm, 750μm, 2mm, and 4mm respectively.
Direct Simulation of Electrorheological Suspensions
Authors: Singh Pushpendra , Aubry Nadine
Published: April 2008

A numerical scheme based on the distributed Lagrange multiplier method (DLM) is used to study the motion of particles of a dielectric suspensions subjected to uniform and nonuniform electric fields. The Maxwell stress tensor method is used for computing electrostatic forces. In the point dipole approximation the total electrostatic force acting on a particle can be divided into two distinct contributions, one due to dielectrophoresis and the second due to particle-particle interactions. The former is zero when the applied electric field is uniform and the latter depends on the distance between the particles. In the Maxwell stress tensor approach these two contribution appear together. Simulations show that as expected the error in the point dipole approximation decreases, as the distance between the particles increases.
Shell Elements Performance in Crashworthiness Analysis
Authors: Wu Shen Rong , Saha Nripen , Chen Ping
Published: April 2008

Crashworthiness analysis, a type of large deformation transient dynamics, has been an important and active area of researches and engineering applications. Several shell elements have been implemented in the finite element software for crashworthiness analysis. Among them, the 4-node quadrilateral Belytschko-Tsay element, using lower order integration technique is most commonly employed, due to its efficiency, robustness and overall accuracy. However, the lower order integration brings in some uncertainty. This paper is to conduct an engineering evaluation on performance of various shell elements, including Belytschko-Tsay, Belytschko-Leviathan (QPH), Bathe-Dvorkin, discrete Kirchhoff triangular elements, available in the commercial explicit finite element software. The study uses several linear and nonlinear benchmark examples and high-speed impact examples, to investigate the performance of these elements. Results of engineering interest and efficiency of computation are reported. Also, the behavior of finite element convergence, observed from the results by a sequence of refined meshes is investigated.
FEM Simulation Supported KEE in High Strength Steel Car Body Design
Authors: Sandberg Stefan , Kalhori Vahid , Larsson Tobias C.
Published: April 2008

With an increasing number of and also more complex demands on today’s automobiles the need for fast and accurate simulations to support the Engineering Design (ED) process is getting more important. The demands that are put on the automotive designs are often contradictory i.e. weight against stiffness, and no one optimal set of solutions can be found, rather a trade-off situation. At Volvo Cars Corporation, known all over the world for their safety policy, the advancement to more high strength materials is causing new problems for the engineers. As widely known, a steel material that has been exposed to plastic deformation will suffer hardening in those areas. The work in this paper, exemplified in a deployed demonstrator, show that it is possible to combine forming and crashworthiness simulations in an automated way to make advanced simulation accessible to more people in the product development process. The Knowledge Enabled Engineering (KEE) demonstrator combines forming and crashworthiness simulations for dealing with the constant trade-off in ED.
An Expert Framework Aide for Determining Optimal Design Models
Authors: Lin Y. J. , Chandra Santanu
Published: April 2008

This paper presents the development of a CAD-based expert framework aide for the decision making on choosing optimal design methods. The proposed framework is based on a comparative study of gradient enhanced meta-models using response surface modeling (RSM) and Kriging techniques, the two most promising meta-modeling techniques studied extensively in design optimization schemes for approximating complex systems. However, current and past research shows that the performance of these methods mandates significant improvements due to the fact that a large number of sample points are needed from within the design space for a considerable accurate model. This makes the designers face a dilemma between accuracy and computational cost. To overcome this so called curse of dimensionality problem, a proper framework with which the models can be validated and its reliability can be evaluated is proposed and established in this research work. Our approach is aimed at forming a GUI-based software framework (utilizing DACE) in MATLAB® that will aid the designers to decide which Meta-model would be most suitable for a certain modeling for design. It will help designers to plan the design of experiments and train the models using the gradient information available at low cost and consequently, validate the model with existing data, as well as produce error analysis graphs and performance criterion charts of all the models for a final decision making. A comparative study of performance of the gradient enhanced RSM and gradient enhanced Kriging models are conducted for six different test equations of various degrees of non-linearity using this proposed framework. A Pro/Engineer® model of a bracket is taken as a test case for the verification of the efficiency and effectiveness of the proposed expert framework as a decision-making tool for designers of engineering products. All the tested Metamodels performed satisfactorily within the specified error margins.
Cryoinjury Enhancement of Breast Cancer Cells by Use of a Molecular Adjuvant (TNF-alpha)
Authors: Han Bumsoo , Egberg Matthew D. , Haung Pung-Pung , Swanlund David J. , Bischof John C.
Published: April 2008

Cryoinjury of human breast cancer cells (MCF7) in engineered tissue equivalents and the enhancement of the cryoinjury by use of a molecular adjuvant (tumor necrosis factor alpha, TNF-α) was studied. Tissue equivalents (TEs) were constructed by seeding MCF7 cells in collagen solutions at the concentration of 100,000 cells/ml. After cultured in vitro for 2 days, the TEs were exposed with 100ng/ml TNF-α and cultured for 24 hours, and then underwent a single freeze-thaw cycle by a cryosurgery simulator. With the concentration and duration of TNF-α treatment studied, no apoptotic or necrotic cell death was observed by the administration of TNF-α only. After a freeze/thaw, MCF7 cells within the frozen region of the TEs were significantly injured immediately (i.e. ≤ 20% survival), but gradually repopulated and reached approximately 80% survival in Day3 without TNF-α pre-treatment. MCF7 with TNF-α pre-treatment showed the slight enhancement of immediate injury in the frozen region (i.e. ≤ 10% survival), and the repopulation was significantly inhibited so the viability remained below 40% even in Day 3. These results imply that TNF-α can be a potent adjuvant for cryosurgery.
Development of Crash Energy Management Designs for Existing Passenger Rail Vehicles
Authors: Martinez Eloy , Tyrell David , Perlman Benjamin
Published: April 2008

As part of the passenger equipment crashworthiness research, sponsored by the Federal Railroad Administration and supported by the Volpe Center, passenger coach and cab cars have been tested in inline collision conditions. The purpose of these tests was to establish baseline levels of crashworthiness performance for the conventional equipment and demonstrate the minimum achievable levels of enhancement using performance based alternatives. The alternative strategy pursued is the application of the crash energy management design philosophy. The goal is to provide a survivable volume where no intrusion occurs so that passengers can safely ride out the collision or derailment. In addition, lateral buckling and override modes of deformation are prevented from occurring. This behavior is contrasted with that observed from both full scale tests recently conducted and historical accidents where both lateral buckling and/or override occurs for conventionally designed equipment. A prototype crash energy management coach car design has been developed and successfully tested in two full-scale tests. The design showed significant improvements over the conventional equipment similarly tested. The prototype design had to meet several key requirements including: it had to fit within the same operational volume of a conventional car, it had to be retrofitted onto a previously used car, and it had to be able to absorb a prescribed amount of energy within a maximum allowable crush distance. To achieve the last requirement, the shape of the force crush characteristic had to have tiered force plateaus over prescribed crush distances to allow for crush to be passed back from one crush zone to another. The distribution of crush along the consist length allows for significantly higher controlled energy absorption which results in higher safe closing speeds.
Electrokinetically-Induced Flow Over a Nano-Hole Array Sensor
Authors: De Leebeeck Angela , Sinton David , Brolo Alexandre G. , Arctander Erin , Gordon Reuven , Kavanagh K. L.
Published: April 2008

A microfluidic device with an embedded surface-plasmon resonance (SPR) sensor was developed. The detector allows real-time monitoring of chemical processes on-chip. Microfabrication of a poly(dimethylsiloxane) chip incorporating a gold-on-glass nano-hole array (SPR sensor) was developed. This was the first time a SPR sensor operating in transmission mode was built in an on-chip format. Electrokinetic transport phenomena in a microchannel over the gold-on-glass plate was modeled using Computational Fluid Dynamics. The modeling results indicated that the flow over the gold-on-glass plate was pressure driven since there was no variation in electrical potential over the conductor (gold). The flow was electrokinetically driven where an electric field was present. The exchange of solutions in the nano-holes was also modeled and it was found that this process took less than a second. This permeation time is expected to scale with the diffusion coefficient. Lastly, preliminary optical measurements were performed to demonstrate the efficiency of the array of nano-holes as on-chip SPR sensors.
Capstone Thermal System Design Project Using Engineering Equation Solver (EES)
Authors: Pascual Christopher C.
Published: April 2008

The capstone thermal system design course at California Polytechnic State University in San Luis Obispo has been modified to reinforce fundamental concepts in introductory fluid mechanics, heat transfer, and thermodynamics through a quarter-long design project. Through the use of Engineering Equation Solver (EES), the computational effort of thermal design is reduced; because EES has built-in thermophysical properties for most common solids, liquids, and gasses. As a result, the students can focus on design iterations and not on interpolation of property tables. At the end of the quarter, the students present their design to panelists who evaluate their design based on expected cost. In the past three years, the students have designed a hydronic snow-melting system, a ground source heat pump system for a small office building, a radiant heating system for a greenhouse, and a refrigeration system for an ice rink.
Three-Dimensional Laminar Flow for Localized Cellular Stimulation
Authors: Yang Jui-Ming , LeDuc Philip R.
Published: April 2008

Stimulation of living mammalian cells is primarily accomplished by the delivery of chemical agents to single cells or cell populations. Due to the fast response time of diffusion for these agents over the small size scale of individual cells, localized stimulation is limited. Currently, there are alternate techniques that can produce localized gradients of chemical stimulants over single cells, but they lack the ability for long time scale events that are requisite for many cellular processes because of this diffusion limitation. We have developed a device that is able to create chemical agent separation in three dimensions along distinct boundaries that can be applied to cells. As many techniques are two-dimensionally constrained, this provides us with a more physiologically relevant system for investigating cellular signal transduction and can allow basal to apical activation separations. To accomplish this, multiple flow paths were introduced to manipulate spatiotemporally distinct regions inside a single capillary channel. Solutions that flow laminarly inside these fluidic channels deliver predefined chemicals to specific locations without turbulent mixing. Separation using this system under laminar flows created not only side by side domains in this capillary but also vertical as well. This device has multiple potential applications both in cell and molecular biology as well as in fluid dynamics and fabrication processes.
Product Development via Industry-University Joint R&D Ventures: What Makes a “Win-Win” Partnership?
Authors: Nye T. J.
Published: April 2008

There are substantial benefits for both industry and universities from performing joint R&D projects. Given the significant potential benefits, both tangible and intangible, the level of such activity, however, seems surprisingly low. One reason hypothesized for this discrepancy is that the potential partners are motivated towards opposite goals: industry wishes to limit publication of research results due to fears of loss of competitive advantage in their markets as competitors obtain the benefits of the research at no cost, while academia is motivated to maximize publication. Intuitively, this would seem to be a fundamental difference between the potential partners. This paper studies this issue through the use of insights gained by a new analytic model of the profitability of such collaborations. First amongst these is that given the typical speed of product innovation and the typical publishing delay found in archival journals, little or no competitive advantage is expected to be lost by the industrial partner by allowing unrestricted publication freedom to the university partner. A second interesting insight occurs in the situation where a firm’s competitor forms the collaboration with the university partner. In general, if it is profitable for one industry partner to join the collaboration, the most beneficial decision for other firms in that market is to also join the collaboration.
Thermal Conductivity of Single-Wall Carbon Nanotubes
Authors: Zhong Hongliang , Lukes Jennifer R.
Published: April 2008

Despite the significant amount of research on single-wall carbon nanotubes, their thermal conductivity has not been well established. To date only one experimental thermal conductivity measurement has been reported for these molecules around room temperature, with large uncertainty in the thermal conductivity values. Existing theoretical predictions based on molecular dynamics simulation range from several hundred to 6600 W/m-K. In an attempt to clarify the order-of magnitude discrepancy in the literature, this paper utilizes molecular dynamics simulation to systematically examine the thermal conductivity of several (10, 10) single-wall carbon nanotubes as a function of length, temperature, boundary conditions and molecular dynamics simulation methodology. The present results indicate that thermal conductivity ranges from about 30–300 W/m-K depending on the various simulation conditions. The results are unconverged and keep increasing at the longest tube length, 40 nm. Agreement with the majority of literature data is achieved for the tube lengths treated here. Discrepancies in thermal conductivity magnitude with experimental data are primarily attributed to length effects, although simulation methodology, stress, and intermolecular potential may also play a role. Quantum correction of the calculated results reveals thermal conductivity temperature dependence in qualitative agreement with experimental data.
Biomechanical Response of a Functional Spine Unit Under Various Loading Conditions: A Viscoelastic Finite Element Approach
Authors: Esat Volkan , Acar Memis
Published: April 2008

Biomechanical and epidemiologic studies state that recreational activity and industrial work, embodying static work postures, physically heavy tasks, frequent bending, and twisting motions, lifting and sudden loading incidents are highly related to low back pain disorders. In order to provide a comprehensive understanding of the low back pain under severe and traumatic static and dynamic loading conditions, the finite element (FE) technique is widely used as a computational method to model, simulate and analyse the behaviour of the spinal segments in the lumbar spine, which are much more difficult with in vitro and in vivo experimental studies. Intervertebral discs, having many other functions, support a huge extent of the compressive loadings the trunk is subjected to. The results of the FE analyses can be employed to understand the injury mechanisms occurring in and about the intervertebral discs, providing stress and strain distributions, and to aid the therapists in selecting the type of treatment for low back pain, and in developing guidelines for industrial safety.
Control Strategies for Distributed Real-Time Control With Time Delays and Packets Losses
Authors: Ji Kun , Ambike Ajit , Kim Won-Jong
Published: April 2008

Investigation on using network for distributed systems is an important topic in the motion control industry. This paper presents solutions to time-delay and packet-loss problems encountered in distributed real-time operation of an open-loop unstable magnetic levitation (maglev) test bed via an Ethernet. A novel model predictive control strategy with optimal controller design is developed to overcome the adverse influences of time delays and packet losses. By using the prediction of system states and the event-driven and time-driven smart actuator simultaneously, the plant receives the current control signal in every sampling interval even at the presence of time delays and packet losses. Thus we can compensate the time-delay and packet-loss in a uniform way. The simulation and experimental results demonstrated the feasibility and effectiveness of this control algorithm for NCSs with long stochastic time delays and successive packet losses.
Product Design Support: Exploring a Design Repository System
Authors: Bohm Matt R. , Stone Robert B.
Published: April 2008

This paper reports on a knowledge rich design repository system. Current design tools and methodologies are reviewed and used to identify necessary design knowledge to populate a design repository. Building on previous research, an operational design repository is reviewed. The design repository system demonstrated includes a single point of entry application for product information, a relational database for archiving design knowledge and web-based tools. Web services are used to support design knowledge retrieval through search, browse and real-time design tool generation. From the repository interface, design tools such as bills of materials and design structure and function component matrices are generated. The output design tools are tested in real world design applications and validated. The result is a useful tool — applicable to several phases of product design.
A Homogenization-Based Laminated Plate Theory
Authors: Guiamatsia Irene , Hansen Jorn S.
Published: April 2008

A new approach to plate theory is presented which yields a straight-forward yet extremely accurate plate model. The approach yields precise and complete three-dimensional stress and strain states with minimal computational effort. This development is based on the assumption that the plate response characteristics can be represented in terms of far-field stress and strain solutions corresponding to constant, linear, quadratic, , nth degree bending states; such solutions, referred to as Fundamental State Solutions (FS), can be determined uniquely and are independent of boundary conditions. Defining the problem variables as through-thickness moments eliminates difficulties in classical plate theories associated with discontinuous or non-differentiable solution fields and is therefore an enormous advantage. Also, post-processing is based on the FS and yields a completely internally consistent approximation. In order to illustrate the capabilities of this approach, comparisons are made to three-dimensional finite element analyses performed with the commercial code ASAS. The results show an excellent agreement between the new plate theory and the finite element calculations for all stress and strain components. In particular, the transverse shear stresses and strains, and the transverse normal stress and strain are obtained extremely accurately. A few millimeters in from the plate edge, the results of the theory and 3D model coalesce. Complete results show that the through-thickness distribution of all stress and strain components is accurately captured with the new theory; the expected parabolic distribution for transverse shear components in the isotropic case, and the discontinuous strains/continuous stresses for the sandwich plate.
Assessment of Hex-Dominant Mesh Efficacy for Nonlinear Finite Element Method Structural Analyses
Authors: Shoykhet Nissan , Di Martino Elena S. , Vorp David A. , Shimada Kenji
Published: April 2008

The objective of this study is to compare different types of meshes for the solution of static structural problems under large deformation conditions, using nonlinear materials. The three types of mesh used in this study are a structured hexahedral mesh, an unstructured tetrahedral mesh, and a hex-dominant mesh generated automatically by the bubble packing algorithm, [1]. The two geometries tested were a hypothetical, partially symmetric model of an Abdominal Aortic Aneurysm (AAA), and a three dimensional representation of an in vivo AAA reconstructed from CT scan images (Fig 1). In order to evaluate the accuracy of the finite element approximation the mean square (or L2) norm of the error was estimated.
Tumor Imaging Through Temporal Log-Slope Difference Mapping of Transient Radiation Signals
Authors: Guo Zhixiong , Wan Siew Kan , August David A. , Dunn Stanley M. , Semmlow John L.
Published: April 2008

A novel optical approach is proposed for cancerous tumor detection using transient radiation signals. In this method, target tissue is illuminated by near-infrared ultrashort laser pulses from various surface source points, and backscattered time-resolved light signals are collected at the same surface points. By analyzing the log-slopes of decaying signals over all points on the source-detection grid, a log-slope distribution on the surface is obtained. After administration of absorption contrast agents, the presence of cancerous tumors increases the decaying steepness of the transient signals. The mapping of log-slope difference between native tissue and absorption-enhanced cancerous tissue indicates the location and projection of tumors on the detection surface. In this paper, we examine this method through the detection of a small tumor in a model tissue phantom via computer simulation. The model has a spherical tumor of 6 mm in diameter embedded at the tissue center. Monte Carlo methods were employed to simulate the light transport and signal measurement. It is shown that the tumor in the tissue model can be accurately projected onto the detection surface by the proposed log-slope difference mapping method. The image processing is very fast and does not require any inverse optimization in image reconstruction.
Performance of Micro/Meso-Scale Thermal Transpiration Pumps at Low Pressures
Authors: Han Y. L. , Young M. , Muntz E. P.
Published: April 2008

The Knudsen Compressor is a solid-state micro/meso-scale gas roughing pump based on the rarefied gas phenomena of thermal transpiration. Knudsen Compressors operate by imposing a temperature gradient across a high porosity, low thermal conductivity transpiration membrane, typically a silicon aerogel membrane. Previous optimization studies have concluded that significant reductions of both energy consumption and device volume per unit throughput and pressure difference for a given pressure ratio can be achieved when each stage of the cascade operates with a Knudsen number based on the mean pore radius of approximately one. Perforated aerogels (using the same bulk aerogel material, but with machined arrays of properly sized parallel capillaries) are appealing candidate low-pressure transpiration membranes and are the focus of this investigation. Conventional drilling techniques using micro drills have successfully demonstrated perforated aerogel with pore diameters ranging from 200μm to 500μm. This range of pore sizes corresponds to efficient Knudsen Compressor operation between roughly 500mTorr and 200 mTorr. The performance of a low pressure Knudsen Compressor is clearly affected by rarefaction phenomena including “reverse” thermal transpiration and possible thermally induced internal flow circulation at low pressures due to the relatively large Knudsen number in the connector section.
Autonomy Measures for Robots
Authors: Huang Hui-Min , Messina Elena , Wade Robert , English Ralph , Novak Brian , Albus James
Published: April 2008

Robots are becoming increasingly autonomous. Yet, there are no commonly accepted terms and measures of how “autonomous” a robot is. An ad hoc working group has been formed to address these deficiencies, focusing on the unmanned vehicles domain. This group is defining terminology relevant to unmanned systems and is devising metrics for autonomy levels of these systems. Autonomy definitions and measures must encompass many dimensions and serve many audiences. An Army general making decisions about deployment of unmanned scout vehicles may want to only know a value on a scale from 1 to 10, whereas test engineers need to know specifics about the types of environments and missions that the vehicles are expected to deal with. Any system will have to communicate with humans, hence this is an important dimension in evaluating autonomy. The autonomy levels for unmanned systems (ALFUS) group is therefore developing metrics based on three principal dimensions: task complexity, environmental difficulty, and human interaction. This paper reports on the current state of the ALFUS metric for evaluating robots.