bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance Charateristics of Advanced Gas Turbine Cogeneration Power Plants
Authors: Boyce Meherwan P.
Published: April 2008

The performance analysis of the new generation of Gas Turbines in combined cycle operation is complex and presents new problems, which have to be addressed. The new units operate at very high turbine firing temperatures. Thus variation in this firing temperature significantly affects the performance and life of the components in the hot section of the turbine. The compressor pressure ratio is high which leads to a very narrow operation margin, thus making the turbine very susceptible to compressor fouling. The turbines are also very sensitive to backpressure exerted on them by the heat recovery steam generators. The pressure drop through the air filter also results in major deterioration of the performance of the turbine. The performance of the combined cycle is also dependent on the steam turbine performance. The steam turbine is dependent on the pressure, temperature, and flow generated in the heat recovery steam generator, which in turn is dependent on the turbine firing temperature, and the air mass flow through the gas turbine. It is obvious that the entire system is very intertwined and that deterioration of one component will lead to off-design operation of other components, which in most cases leads to overall drop in cycle efficiency. Thus, determining component performance and efficiency is the key to determining overall cycle efficiency. Thermodynamic modeling of the plant with individual component analysis is not only extremely important in optimizing the overall performance of the plant but in also determining life cycle considerations.
Photovoltaic Power Plant Experience at Tucson Electric Power
Authors: Moore Larry , Post Hal , Mysak Terry
Published: April 2008

Tucson Electric Power Company (TEP) currently has nearly 5.0 MWdc of utility-scale grid-connected photovoltaic (PV) systems that have been installed in its service territory since 2000. Most of this installed PV capacity is in support of the Arizona Corporation Commission Environmental Portfolio Standard (EPS) goal that encourages TEP to generate 1.1% of its energy generation through renewable resources by 2007, with 60% of that amount from photovoltaics. The EPS program provides for multi-year, pay-as-you-go development of renewable energy, with kWhac energy production as a key program measurement. A total of 26 crystalline silicon collector systems, each rated at 135 kWdc, have been installed at the Springerville, AZ generating plant by TEP making this one of the largest PV plants in the world. These systems were installed in a standardized, cookie-cutter approach whereby each uses the same array field design, mounting hardware, electrical interconnection, and inverter unit. This approach has allowed TEP to achieve a total installed system cost of $5.40/Wdc and a TEP-calculated levelized energy cost of $0.10/kWhac for PV electrical generation. During this time, much has been learned regarding performance, cost, maintenance, installation and design. This paper presents an assessment of these topics and a perspective associated with this PV experience.
Optimization of Component Sizes in Parallel Hybrid Electric Vehicles via Genetic Algorithms
Authors: Montazeri-Gh Morteza , Poursamad Amir
Published: April 2008

This paper describes the optimization of the parallel hybrid electric vehicle (HEV) component sizing using a genetic algorithm approach. The optimization process is performed over three different driving cycles including the European ECE-EUDC, American FTP and TEH-CAR cycles in order to investigate the influence of the driving pattern on the optimal HEV component sizes. Hybrid Electric Vehicles are considered as a solution to the world’s need for cleaner and more fuel-efficient vehicles. HEVs use a combination of an internal combustion engine and an electric motor to propel the vehicle. Proper execution of a successful HEV design requires optimal sizing of its key mechanical and electrical components. In this paper, genetic algorithm is used as the optimization approach to find the best size of internal combustion engine, electric motor and energy storage system. The objective is minimization of fuel consumption and emissions while vehicle performances, like acceleration and gradeability are defined as constraints. These constraints are handled using penalty functions. Simulation results reveal that the HEV optimal component sizing is independent from the driving pattern. However, the amount of fuel use and emissions are extremely dependent on the driving cycles. In addition, the results show, while the performance constraints are within the standard criteria, the reduction in fuel consumption and emissions are achieved.
Numerical Modeling of Pressure Drop and Pump Design for High Power Density Microchannel Heat Sinks With Boiling
Authors: Na Yun Whan , Chung J. N. , Forster Fred
Published: April 2008

A physical and mathematical model has been developed to predict the two-phase flow and heat transfer in a microchannel with boiling. Based on the above physical model, a total of seven unknowns with corresponding equations resulted. The liquid film thickness, the vapor pressure and the axial heat flow rate have been solved using a fourth-order Runge-Kutta method. The liquid pressure, the vapor and liquid temperatures have been solved using the finite difference method with first order accuracy. The interfacial temperature and pressure have been solved using the root finding method for every mesh point in the axial direction. In addition to the sample calculations that were used to calibrate the model, computations based on the current model were performed to generate results for comparison with Carey’s macro-scale model (Carey, 1992) and with the experimental data of Jiang et al. (2002) where three different mass flow rates of the working fluid were used in the experiment. The comparisons of pressure drops were made for 25 W, 38 W and 58 W of heating with mass flow rates of 2 ml/min, 5 ml/min and 9ml/min, respectively. In general, Carey’s model underpredicted the experimental data by Jiang et al. (2002), especially at the lower flow rates. The calculated results from the current model matched closely with those of Jiang et al. (2002). The main reason for the poor performance of Carey’s model is that it was developed for the macrosystems, where the surface tension and the Marangoni effects are not important.
Edge Finishing and Delamination Effects Induced During Abrasive Waterjet Machining on the Compression Strength of a Graphite/Epoxy Composite
Authors: Ramulu M. , Colligan K.
Published: April 2008

In this study the machined edges produced by abrasive waterjet (AWJ), were characterized by compression testing to assess the influence of edge finishing and delamination on the strength of graphite/epoxy laminates. The AWJ machined edges indicated that the surface finish of the machined edges was closely related to the feed rate and abrasive flow rate. Abrasive waterjet trimming of graphite/epoxy laminates is prone to producing exit ply delaminations, and these delaminations may have abrasive particles embedded in them, which tend to hold the delaminated surfaces apart. It was found that the abrasive waterjet process induced edge surface finish does not significantly reduce the strength of the laminate, however, the delaminations that that were induced in edge finishing do result in significant reductions in strength.
Electrorheological Fluid Hysteresis
Authors: Kim Young Dae , De Kee Daniel
Published: April 2008

Electrorheological (ER) fluids are suspensions of polarizable particles dispersed in insulating liquids. They exhibit a rapid and reversible transition from a liquid-like to a solid-like state upon the application of an electric field. The observed shear stress - shear rate hysteresis makes the precise control of the ER mechanical devices very difficult. Hysteresis behavior of TiO2 ER fluids were observed by varying particle concentration, electric field strength, maximum shear rate, and the time of hysteresis loop. In the absence of an electric field, the stress level of the up curve exceeds that of the down curve. The presence of an electric field, reverses this trend. The extent of hysteresis becomes more significant with increasing electric field strength, particle concentration, and maximum shear rate. Hysteresis behavior of TiO2 ER fluids seems to arise mainly due to the change of the particle structure during shearing. To describe the complex rheological behavior of ER fluids, a kinetic theory is presented. Model predictions show qualitative agreement with the experimental hysteresis data.
A Room Temperature Hydrogen Sensor With High Sensitivity and Selectivity Using Nanocrystalline Semiconductor Particles
Authors: Zhang Peng , Shukla Satyajit , Ludwig Larry , Cho Hyoung J. , Seal Sudipta
Published: April 2008

Micro hydrogen sensor with interdigitated electrodes and indium doped nanopolycrystalline SnO2 particles was fabricated and tested. Giant sensitivity as high as 105 with good repeatability and recovery was observed. The sensor showed an excellant selectivity of hydrogen (H2) sensing over helium (He).
A Semantic Web Service and Simulation Framework to Intelligent Distributed Manufacturing
Authors: Son Young-Jun , Kulvatunyou Boonserm , Cho Hyunbo , Feng Shaw
Published: April 2008

To cope with today’s fluctuating markets, a virtual enterprise (VE) concept can be employed to achieve the cooperation among independently operating enterprises. The success of VE depends on reliable interoperation among trading partners. This paper describes a framework based on semantic web of manufacturing and simulation services to enable business and engineering collaborations between VE partners, particularly a design house and manufacturing suppliers. To this end, we first give an overview of distributed manufacturing in the web service framework, including detailed activity and information flow diagrams. Second, we propose an ontological definition of resource models and process-capability models using an ontology definition language. Third, we propose a method based on stochastic discrete-event simulation, whose model is automatically generated from the resource and process models, to evaluate highly nonlinear process plans. Finally, we present a prototype system to demonstrate an interoperable collaboration using semantic webs.
Life Cycle Analysis of Energy Efficient Measures in a Tropical Housing Design
Authors: Duell Michael G. , Martin Lorien A.
Published: April 2008

Energy conservation has become an issue of global significance, which is a focus reflected in the Australian housing industry’s renewed emphasis on energy-efficient design. The Australian Building Codes Board (ABCB) has proposed to increase the stringency of the Building Code of Australia (BCA) to ensure the industry adopts energy efficient measures, including the enhancement of thermal performance and greater recognition of thermal mass in energy rating schemes. However, this proposal’s potential to effect energy savings in tropical housing is yet to be assessed. In order to determine its relative merits under tropical conditions, a standardised house design used in the Tiwi Islands of the Northern Territory (NT) was subjected to life cycle analysis, including analysis of embodied energy, the efficiency of energy saving measures and the resulting active energy consumption. This standardised house, like others in the NT, is designed for retrofitting within 10 years, which reduces the time available for savings in operational energy to exceed energy invested in installing these measures. Housing lifespan would, therefore, significantly impact upon potential benefits resulting from changes to the BCA. In addition, the spatial distances between population settlements in the NT greatly increases embodied energy values. It was found that adopting the proposed measures would result in an increase in energy efficiency through a reduction in the need for refrigerative air conditioner use, and that the embodied energy payback period would fall within the lifespan of the house. Therefore, for this specific tropical design, the BCA’s proposed measures for saving energy were found to be beneficial.
Variation Simulation of Fixtured Assembly Processes for Compliant Structures Using Piecewise-Linear Analysis
Authors: Stewart Michael L. , Chase Kenneth W.
Published: April 2008

While variation analysis methods for compliant assemblies are becoming established, there is still much to be done to model the effects of multi-step, fixtured assembly processes statistically. A new method is introduced for statistically analyzing compliant part assembly processes using fixtures. This method yields both a mean and a variant solution, which can characterize an entire population of assemblies. The method, called Piecewise-Linear Elastic Analysis, or PLEA, is developed for predicting the residual stress, deformation and springback variation resulting from fixtured assembly processes. A comprehensive, step-by-step analysis map is presented for introducing dimensional and surface variations into a finite element model, simulating assembly operations, and calculating the error in the final assembly. PLEA is validated on a simple, laboratory assembly and a more complex, production assembly. Significant modeling issues are resolved as well as the comparison of the analytical to physical results.
Second Order Sliding Mode Neural Network-Based Visual Servoing of Robot Hands With Fast Manipulation, Including Transition
Authors: Garci´a-Rodri´guez Rodolfo , Parra-Vega V. , Rui´z-Sa´nchez Francisco
Published: April 2008

Strictly speaking, transition tasks such as those executed by robot hands involve free, impact, and constrained motion regimes, with changing dynamics. Impulsive, unilateral constraints arises in the impact regime, which makes very difficult to design a control system. Moreover, algebraic constraints arise in the constrained regime. The trivial approach would be to avoid impact, and to commute consistently ODE- and DAE-based controller, or to impose virtual constraints to model as a DAE system all regimes. In any case, it is required to know exactly the commuting time. In this paper, a very simple control scheme is proposed based on avoiding impact regime, through zero transition velocity from free to constrained motion, therefore impulsive dynamics does not appear. This is possible because we guarantee exactly the time to commute with a novel well-posed finite time convergence scheme, to produce convergence toward any desired trajectory at any given arbitrarily time and for any initial condition. In this way, ODE and DAE dynamics/controllers commute stably. Inertial and gravitational forces are compensated by a recurrent neural network driven by image-based position and force tracking errors, with a decentralized structure for each robot. The network is tuned on line with a second order force-position sliding modes to finally guarantee exponential tracking.
Microstructures and Failure Mechanisms of Spot Friction Welds in Lap-Shear Specimens of Aluminum 6061-T6 Sheets
Authors: Wang Dung-An , Lee Sheng-Chiang , Hsieh Kang-Yuan
Published: April 2008

Microstructures and failure mechanisms of spot friction welds in aluminum 6061-T6 lap-shear specimens are investigated based on experimental observations. Different processing parameters were used to join the aluminum sheets. Optical micrographs of the cross sections of spot friction welds in lap-shear specimens before and after failure are examined. These spot friction welds show the failure mode of nugget pullout under lap-shear loading conditions. The experimental observations suggest that under lap-shear loading conditions, the failure is initiated near the stir zone in the middle part of the nugget and the failure propagates along the circumference of the nugget to final fracture.
The Value of Enterprise Data Integration and Trending Analysis Results for an Effective Equipment Reliability Program
Authors: Niemkiewicz Evan , Walejeski Walter
Published: April 2008

In the power industry, many companies are trying to improve Equipment Reliability by focusing on Performance Monitoring and the application of diagnostic technologies. Software tools are focused on performing detailed technical analysis and trending of diagnostic parameters. The diagnostic data is often stored in archival databases that can track this data for many years. However, the analysis results generated by engineering and maintenance personnel are often stored outside the diagnostic tools in various databases, spreadsheets, and word documents. This valuable information is then difficult to track, trend, and then recall when a similar event occurs in the future. The paper will focus on developed and implemented web-based tools that facilitate tracking, trending, and sharing these analysis results across sites and enterprises. This paper further discusses implementation details and demonstrates the value of incorporating this information seamlessly into existing as well as developing condition monitoring programs.
Experimental and Numerical Studies of Natural Insulation Materials
Authors: Rahbar S. , Khan M. M. , Satish M. , Ma F. , Islam M. R.
Published: April 2008

To find 100% natural, unrefined materials in place of synthetic materials for insulation industry, laboratory experiment and numerical modeling have been carried out. The materials studied include human hair, tree leaves, cotton and sawdust. The experiments have been done in a cylindrical vessel with a hollow center. Time history of temperature at the inside surface has been recorded in the laboratory. Accordingly, thermal diffusivity for the four different materials has been obtained. It is found that cotton has the maximum value of thermal diffusivity, with leaves ranking the second, and sawdust following as the third. On the assumption that the natural material is uniform and isotropic, in which heat transfer takes the form of conduction, the numerical modeling procedure has been developed. It is based on the differential energy equation in cylindrical coordinates. Numerically, the finite difference approach has been used. The results include thermal diffusivities for the four natural materials and the temperature distribution in both time and space. The numerical results agree well with experiment.
Heat Transfer Enhancement by EHD-Induced Oscillatory Flows
Authors: Lai F. C. , Mathew J.
Published: April 2008

Prior numerical solutions of electrohydrodynamic (EHD) gas flows in a horizontal channel with a positive-corona discharged wire have revealed the existence of steady-periodic flows. It is speculated that heat transfer by forced convection may be greatly enhanced by taking advantage of this oscillatory flow phenomenon induced by electric field. To verify this speculation, computations have been performed for flows with Reynolds numbers varying from 0 to 4800 and the dimensionless EHD number (which signifies the effect of electric field) ranging from 0.06 to ∞. The results show that heat transfer enhancement increases with the applied voltage. For a given electric field, oscillation in the flow and temperature fields occurs at small Reynolds numbers. Due to the presence of oscillatory secondary flows, there is a significant enhancement in heat transfer.
EHD-Enhanced Forced Convection by Oscillatory Gas Flow in Horizontal Channels
Authors: Lai F. C. , Tay K. K.
Published: April 2008

Prior studies of enhanced forced convection by electrohydrodynamics (EHD) in a horizontal channel have revealed the existence of oscillatory flows. These oscillatory flows are the product from the interaction between the primary flow and electric body force. It has also been shown that heat transfer can be significantly enhanced when operating in this oscillatory flow mode. Thus, it is speculated that heat transfer may be further enhanced by exciting the primary flow in a frequency similar to those observed for the oscillatory flows (i.e., the so-called resonant effect). To verify this speculation, computations have been performed for primary flows with a frequency that is either a fraction or multiple of the natural frequency observed in the original oscillatory flows. The results show that an inlet flow excited at the natural frequencies produces the best heat transfer enhancement in the single-cell regime, and the enhancement increases with the Reynolds number. However, the results show an opposite trend in the multiple-cells regime.
Radiative Properties of Pattered Wafers With Linewidth Below 100 nm
Authors: Chen Y.-B. , Zhang Z. M. , Timans P. J.
Published: April 2008

Temperature nonuniformity is a critical problem in rapid thermal processing (RTP) of wafers because it leads to uneven diffusion of implanted dopants and introduces thermal stress that can produce defects. One cause of the problem is nonuniform absorption of thermal radiation, especially in patterned wafers, where the optical properties vary across the surface of the wafer. Recent developments in RTP have lead to the use of millisecond-duration heating cycles, where light with very high power density is used to heat the surface of the wafer. Pattern effects are especially important here, because there is very little time for thermal diffusion to even out temperature distributions during the heating cycle. There have been very few studies on the radiative properties of patterned wafers, especially for the structures expected to be used on advanced semiconductor devices. The feature size is already below 100 nm and is comparable or smaller than the wavelengths of radiation (200–1000 nm) emitted by the flash-lamps typically used for millisecond processing. Hence, this work is devoted to a parametric numerical study of the radiative properties of patterned wafers with the smallest dimension down to 30 nm. The effects of wavelength, wave polarization, and angle of incidence on selected periodically patterned wafers are presented. The methods include the rigorous coupled wave analysis (RCWA) and the effective medium approach (EMA). RCWA is used to obtain exact solutions of Maxwell’s equations, and EMA is used to approximate the periodic structures as a planar multilayer structure with an effective dielectric function. This study provides an assessment of the applicability of EMA for simulations of radiative properties of patterned wafers.
Thermoelectric Nondestructive Characterization of Subsurface Inclusions
Authors: Carreon Hector
Published: April 2008

A comparison between published analytical results with experimental ones of the magnetic field produced by thermoelectric currents of subsurface semi-spherical pure tin inclusions embedded in a copper bar under the influence of an external heating (+45°C) and cooling (+10°C) into the specimen is presented. The measurements were taken from a 12.7 mm-thick copper bar with several subsurface semi-spherical pure tin inclusion diameters at different lift-off distances. The experimental magnetic flux density measurements show a good agreement with analytical ones as a function of the lift-off distances with the different inclusion diameters with the exception of the intrinsic material background magnetic signal that affected deeply the detectability of subtle imperfections in noncontacting thermoelectric measurements. The main sources of such adverse background signals in thermoelectric NDE are the intrinsic variations of the material properties of the specimen to be inspected.
A Visualization Study of Heterogeneous Condensation on Nano-Particles in a Fully Saturated Microchannel
Authors: Son Sang Young
Published: April 2008

The high heat transfer rate and compactness of micro/minichannel mutiphase flow system associated with phase change phenomena have been increasingly attractive in thermal management and microfluidic sensor development for applications which demand requirements such as small, light, and efficient systems. In this paper, quarts square microchannels with a hydraulic diameter of 1000 μm and a length of 20 mm are used for the path of fully saturated forced convection air flow with nano-particles (Θ ~ 100 nm). The outside of microchannel wall is cooled by natural convection of room air. Two distinctive heterogeneous condensation modes are observed as of droplet condensation on the channel wall and nano-particle nucleate condensation in the core air stream. At the exit of microchannel, liquid droplets with an order of micrometer diameter are observed by microscopic visualization using Nd:YAG (532 nm) Laser sheet illumination. The droplet growth visualization data show a influence of gas mixture mass flux, local vapor concentration, and wall surface condition either on wall droplet condensation and nucleate condensation droplet.
Nonlinear Vibrations of Rectangular Plates With Different Boundary Conditions: Theory and Experiments
Authors: Amabili M. , Augenti C.
Published: April 2008

Large-amplitude vibrations of rectangular plates subjected to harmonic excitation are investigated. The von Ka´rma´n nonlinear strain-displacement relationships are used to describe the geometric nonlinearity. A specific boundary condition, with restrained normal displacement at the plate edges and fully free in-plane displacements, not previously considered, has been introduced as a consequence that it is very close to the experimental boundary condition. Results for this boundary condition are compared to nonlinear results previously obtained for: (i) simply supported plates with immovable edges; (ii) simply supported plates with movable edges, and (iii) fully clamped plates. The nonlinear equations of motion are studied by using a code based on arclength continuation method. A thin rectangular stainless-steel plate has been inserted in a metal frame; this constraint is approximated with good accuracy by the newly introduced boundary condition. The plate inserted into the frame has been measured with a 3D laser system in order to reconstruct the actual geometry and identify geometric imperfections (out-of-planarity). The plate has been experimentally tested in laboratory for both the first and second vibration modes for several excitation magnitudes in order to characterize the nonlinearity of the plate with imperfections. Numerical results are able to follow experimental results with good accuracy for both vibration modes and for different excitation levels once the geometric imperfection is introduced in the model. Effects of geometric imperfections on the trend of nonlinearity and on natural frequencies are shown; convergence of the solution with the number of generalized coordinates is numerically verified.
Experimental Study of Single-Phase Heat Transfer in Circular Milli-Channels for Cooling of Micro Components
Authors: Ramos Antonio , Bula Antonio J. , Cely Maria
Published: April 2008

The increase of processing speed in applications such as servers, laptops and workstations requires heat-sinking technologies with higher levels of power dissipation than the current methods. For this reason, this paper presents an experimental study of heat transfer in water-cooled milli - channel heat sinks. The experimental process consists of fabrication and testing of rectangular plates with multiple parallel channels oriented in the flow direction. Variations in the number of channels, channel diameter, and volumetric flow were considered in order to study the conjugate heat transfer phenomena. Overall heat transfer coefficients in single-phase flow regimes are presented and analyzed.
Study of Liquid Injection on Pressure Drop of Refrigerant Mixtures Inside Enhanced Surface Tubing
Authors: Sami S. M. , Comeau J.
Published: April 2008

Two phase flow pressure drop characteristics observed under liquid injection during boiling of refrigerant mixtures R-404A, R407C and R507 as well as R-410A are presented in this paper. Experiments showed that liquid injection tends to decrease the pressure drop during boiling which will have positive impact in increasing the boiling heat transfer rate, heat flux and system efficiency. However, condensation data demonstrated that liquid injection increases the pressure drop. In addition, the data also reveals that the refrigerant under investigation exhibit the same behaviour at higher Reynolds numbers or mass flow rates.
Numerical Simulation of Steam Reforming of Methanol in Micro-Channel Reactor
Authors: Cui Wenzhi , Li Longjian , Jen Tien-Chien , Chen Qinghua , Liao Quan
Published: April 2008

On-board hydrogen generation from hydrocarbon fuels, such as methanol, natural gas, gasoline and diesel, etc., will be technically feasible in the near future for fuel cell powered vehicles. Among all the fuel processing methods, steam reforming is considered as the most widely used method of hydrogen reforming for the lower reactive temperature, pressure and higher hydrogen ratio in reformate. A laminate micro-channel catalytic reactor was designed for the purpose of hydrogen generation from hydrocarbons. The depth of the reaction channel is 0.5 mm, and the length and width are 50 mm and 40 mm, respectively. The same geometry is designed for the heating channels. A metal sheet is placed between reacting and heating channels to separate them. Piling up alternately the two channels is to buildup the laminate microchannel reactor. Numerical simulation has been conducted in one reactive unit, i.e., one reacting channel and one heating channel. The reactant is the solution of methanol and water mixing with a certain ratio. And the reaction heat is provided by hot air flow with a temperature of 600K. A 2D steady model of the reforming reactive processes was developed and solved numerically. The ratio of water and methanol is set to be at 1.3. The conversion rate of methanol was nearly 100% at the outlet of reactor, while the volume ratio of hydrogen is 51.4% with the selectivity of CO2 reaches 49.2%. Detail results showed that the 50 mm long reacting channel could be divided into four different regimes along with the reacting course. In the first regime (0-5mm), methanol in the reactants is almost completely converted and CO is mainly generated in the third one (15-20mm), while reactions in the other two regimes are indiscoverable. The reasons leading to such phenomena are clarified in this paper.
Osteoblast Adhesion on Tissue Engineering Scaffolds Made by Bio-Manufacturing Techniques
Authors: Dutta Roy T. , Stone J. J. , Sun W. , Cho E. H. , Lockett S. J. , Wang F. W. , Henderson L.
Published: April 2008

Scientific exploration into understanding and developing relationships between three-dimensional (3D) scaffolds prepared by rapid prototyping (RP) and cellular response has focused primarily on end results targeting osteoblast proliferation and differentiation. Here at the National Institute of Standards and Technology (NIST), we take a systems approach to developing relationships between material properties and quantitative biological responses. This study in particular focuses on the screening of parameters controlled by RP techniques and their ability to trigger signalling events leading to cell adhesion. This pioneering research in our group also characterizes the in vitro cell-material interactions of 2D films and 3D scaffolds. From there, one can postulate on contributory factors leading to cell migration, proliferation, and differentiation. In summary, we believe that the quantitative information from this fundamental investigation will enhance our knowledge of the interactions between cells and 3D material interfaces with respect to formation of focal adhesions. This work consists of two sections — the application of imaging techniques for 3D characterization of properties and culturing of osteoblasts for size and shape determination. This includes quantifying the number of focal adhesion sites. We are using 3D RP polycaprolactone (PCL) scaffolds as this surrogate model in which to compare 2D to 3D material performance and cell interactions. Using RP bio-manufacturing techniques to fabricate tissue engineering scaffolds allows for control of pore size, strut size, and layer thickness, therefore providing adjustable parameters to study which can potentially influence, or even dynamically modulate, cellular adhesion. Imaging results after culturing for 24 h showed differences in cell morphology and spreading relative to the different structures. The focal adhesion response also varied, indicating an apparent loss of organization in 3D scaffolds compared to 2D surfaces. See Results and Discussion for details.
Temporal Species Concentrations in a Water Model of a Blast Furnace Hearth
Authors: Roldan David , Yan Fang , Zhou C. Q. , Tripathi Mayanlk , Laurendeau Normand , Lucht Robert
Published: April 2008

The overall purpose of this paper is to predict species evolution in a water-model hearth using a comprehensive three-dimensional computational fluid dynamics (CFD) code and to validate the code with experimental data. The water model is built to simulate the flow patterns in a blast furnace hearth. The water model is a 1/50th scale of Ispat Inlands’s BF#7. The data focus on time-dependent concentration profiles in a three-dimensional water model. The concentration is determined by using a fluorescence laser dye called rhodamine 590 chloride. The effects of flow rate and different geometries on species concentration evolution are studied.
Development of High Performance Mg/SiC Composites Containing Nano-Size SiC Using Microwave Assisted Rapid Sintering
Authors: Wong W. L. E. , Gupta M.
Published: April 2008

Magnesium composites containing nano-size silicon carbide (SiC) particulates were synthesized using powder metallurgy technique coupled with a novel microwave assisted rapid sintering. The sintered specimens were hot extruded and characterized in terms of microstructural, physical and mechanical properties. Microstructural characterization revealed minimal porosity and the presence of a continuous network of nano-size SiC particulates decorating the particle boundaries of the metal matrix. Thermal mechanical analysis revealed a marginal reduction in the average coefficient of thermal expansion (CTE) values of the matrix with the addition of nano-size SiC reinforcement. Mechanical characterization revealed that the addition of nano-size SiC particulates lead to an increase in microhardness, 0.2% yield strength (YS), ultimate tensile strength (UTS) and ductility of the matrix. Particular emphasis was placed to correlate the effects of nano-size SiC reinforcement on the microstructural, physical and mechanical properties of monolithic magnesium.
Low Cost Metal Mini-Cap Process for Suspended MEMS Device Packaging
Authors: Chung Wei , Wang Leonardo , Fang W.
Published: April 2008

A new wafer capping process is investigated in this study. The objective of this study is to come out a simple and low cost wafer capping process to make the capped MEMS device wafers “transparent” to traditional IC assembly processes. The carrier wafers with metal mini-caps are bonded on the MEMS device wafers through solder bonding, and the mini-caps are then transferred and left on the MEMS device wafer through a selective etching of the carrier wafers. The metal mini-cap capped device wafers are virtually of the same thickness as original ones; in addition, the transferred metal mini-caps provide a mechanical protection to the MEMS devices during the consequent assembly processes such as wafer dicing, die bonding, molding, etc. With an additional design of 2nd level interconnection on the mini-cap carrier wafer, the transferred MEMS device wafers can be singulated and become a wafer level package with compliant leads.
Magnetic Bearing Control Using Interval Type-2 Fuzzy Logic
Authors: Simon Andra´s , Flowers George T.
Published: April 2008

Magnetic bearings are an exciting and innovative technology that has seen considerable advances in recent years. Being unstable by nature, these systems require active control. Most often linear techniques are used very successfully. On the other hand, there are applications where linear methods have limited effectiveness. Fuzzy logic control performs very well in nonlinear control situations where the plant parameters are either partially or mostly unidentified. Its effectiveness for nonlinear systems also offers advantages to magnetic bearing systems. Type-2 fuzzy logic systems represent significant advances over traditional fuzzy logic systems in general. These fuzzy logic systems are capable to deal with uncertainties which can be found in almost every practical system. Uncertainties stem from several sources; noise present in the position input signals, the location and shape of fuzzy sets and the fuzzy rule-base describing the operation of the fuzzy controller, among others. Since a mathe-matical model of the controlled plant is often only a conveniently close approximation of the real process at hand, a major challenge lies in the application of the control methods to real plants. Type-2 fuzzy logic and fuzzy logic systems in general tackle the control problem at hand using human reasoning based on rules and expert knowledge of the plant described by human expressions. The current work consist of model development, controller design, simulation and experimental validation. The basic simulation model consist of a horizontal shaft supported by a radial magnetic bearing. The magnetic bearing is modeled as a nonlinear element. The controller designs are implemented and tested using a bench-top rotor rig equipped with a radial magnetic bearing. Some representative results are presented and discussed.
Requirements for the Manufacturing of Scaffold Biomaterial With Features at Multiple Scales
Authors: Sebastine I. M. , Williams D. J.
Published: April 2008

Tissue engineering aims to restore the complex function of diseased tissue using cells and scaffold materials. Tissue engineering scaffolds are three-dimensional (3D) structures that assist in the tissue engineering process by providing a site for cells to attach, proliferate, differentiate and secrete an extra-cellular matrix, eventually leading cells to form a neo-tissue of predetermined, three-dimensional shape and size. For a scaffold to function effectively, it must possess the optimum structural parameters conducive to the cellular activities that lead to tissue formation; these include cell penetration and migration into the scaffold, cell attachment onto the scaffold substrate, cell spreading and proliferation and cell orientation. In vivo, cells are organized in functional tissue units that repeat on the order of 100 μm. Fine scaffold features have been shown to provide control over attachment, migration and differentiation of cells. In order to design such 3D featured constructs effectively understanding the biological response of cells across length scales from nanometer to millimeter range is crucial. Scaffold biomaterials may need to be tailored at three different length scales: nanostructure (<1μm), microstructure (<20–100μm), and macrostructure (>100μm) to produce biocompatible and biofunctional scaffolds that closely resemble the extracellular matrix (ECM) of the natural tissue environment and promote cell adhesion, attachment, spreading, orientation, rate of movement, and activation. Identification of suitable fabrication techniques for manufacturing scaffolds with the required features at multiple scales is a significant challenge. This review highlights the effect and importance of the features of scaffolds that can influence the behaviour of cells/tissue at different length scales in vitro to increase our understanding of the requirements for the manufacture of functional 3D tissue constructs.
On the Safety of Name Badge Lanyards
Authors: Brickman Dennis B.
Published: April 2008

A tragic accident occurred when a seven year old child was struck in the eye with a metal barb tip on an elastic lanyard which released from a plastic name badge worn around the child’s neck. The safety hierarchy would suggest that attempting to eliminate the elastic lanyard impact danger through design is the first priority. Non-elastic lanyards and safety breakaway lanyards are explored as design alternatives for accident prevention.
Analysis of Solid-Liquid Phase Change Under Pulsed Heating
Authors: Krishnan Shankar , Murthy Jayathi Y. , Garimella Suresh V.
Published: April 2008

Solid/liquid phase change occurring in a rectangular container with and without metal foams subjected to periodic pulsed heating is investigated. Natural convection in the melt is considered. Volume-averaged mass and momentum equations are employed, with the Brinkman-Forchheimer extension to Darcy’s law to model the porous-medium resistance. A local thermal non-equilibrium model, assuming equilibrium melting at the pore scale, is employed for energy transport through the metal foams and the interstitial phase change material (PCM). Separate volume-averaged energy equations for the foam and the PCM are written and are closed using a heat transfer coefficient. The enthalpy method is employed to account for phase change. The governing equations for the PCM without foam are derived from the porous medium equations. The governing equations are solved implicitly using a finite volume method on a fixed grid. The coupled effect of pulse width and natural convection in the melt is found to have a profound effect on the overall melting behavior. The influence of pulse width, Stefan number, Rayleigh number and interstitial Nusselt number on the temporal evolution of the melt front location and the melting rate for both the cases with and without metal foams is investigated.
Strain-Based Flexure Assessment for the Printed Circuit Board Assembly Environment
Authors: Ralph W. Carter , Joyce Frank W.
Published: April 2008

Mechanical damage to due to over-flexure is an increasing concern in the printed circuit board assembly environment. This damage can result in part rejection during manufacturing, or may combine with other failure mechanisms to result in field returns. Therefore, flexure control during circuit board assembly is a vital part of overall product quality. A metric has been developed for component-specific strain-based flexure limits using a spherical bend mode and a novel strain metric, along with a detailed method for strain gage measurement in the assembly environment. This paper presents a review of the trends that have contributed to the increased risk of damage, as well as the development of the diagonal strain metric and the use of the spherical bend mode. These methods have been successfully employed to identify excessive flexure and reduce risks to function and reliability. Two case studies that demonstrate the application and effectiveness of the procedures are presented.
Inexpensive Heat Transfer Equipment to Demonstrate the Effect of Extended Surfaces on the Convection Heat Transfer Rate
Authors: Mapa Lash B.
Published: April 2008

Extended surfaces are used specifically to increase heat transfer rate between a solid and an adjacent fluid. The rate of heat transfer is from the solid surface to the fluid is governed by the Newton’s law of cooling. A simple inexpensive apparatus to demonstrate the effect of the length of the extended surface and the effect of different materials on the heat transfer rate was developed with the assistance of senior students enrolled in a senior project. Using this apparatus student was able to determine the temperature gradient and calculate the heat losses to the surroundings assuming infinitely long extended surface or negligible heat loss from the tip of the extended surface. Experiments were performed on three different materials, aluminum, copper and stainless steel by maintaining the base of the fin at a constant temperature and taking temperature measurements at regular intervals along the length of the extended surface. The apparatus was developed to be portable and used in a class room environment to enhance the understanding of heat transfer principles during a lecture rather than in a laboratory situation. The visual communication is much more powerful in many learning situations; the spoken word may be redundant. The feedback from the students was overwhelmingly positive. The paper describes the apparatus, method of construction and experimental results in a graphical form with discussion questions and answers
Comparative Analysis of Different Thermal Conductivity Models for Nanofluids in a Square Enclosure Under Natural Convection Conditions
Authors: Anand Sushant , Arora R. C.
Published: April 2008

Previous investigations have revealed that addition of nanoparticles dispersed in conventional fluids such as water or ethylene glycol result in a new class of coolant which has anomalously high thermal conductivity under stagnation conditions. Few theoretical models have been proposed to resolve this abnormal behavior of nanofluids. This study focuses on the comparative study of some of these models namely, Wasp’s model, Choi’s modified Maxwell model, Bruggeman model and Xue’s model for complex nanoparticles. Flow in a cavity has been considered with insulated horizontal walls and vertical walls at different uniform temperatures under Boussinesq’s approximation. Results obtained are presented in form of plots of streamlines, isotherms and Nusselt number. Steady state solutions have been obtained for natural convection in a square cavity partially filled with copper-water. Parameters considered are Grashof number (103 to 105) and particle concentration (φ = 0%–20%). The results validate the stand that nanofluids are better coolants under dynamic conditions than conventional fluids. The flow properties have been found to be dependent upon the choice of thermal conductivity models chosen. The flow patterns predicted by various models have been found to be in close agreement with each other; however substantial variance has been found to exist in Nusselt numbers predicted by these models.
Quasi-Steady Herschel-Bulkley Analysis of Magnetorheological Dampers With Preyield Viscosity
Authors: Hong Sung-Ryong , John Shaju , Wereley Norman M.
Published: April 2008

A magnetorheological (MR) fluid, modeled as a Bingham-plastic material, is characterized by a field dependent yield stress, and a (nearly constant) postyield plastic viscosity. Based on viscometric measurements, such a Bingham-plastic model is an idealization to physical magnetorheological behavior, albeit a useful one. A better approximation involves modifying both the preyield and postyield constitutive behavior as follows: (1) assume a high viscosity preyield behavior over a low shear rate range below the yield stress, and (2) assume a power law fluid (i.e., variable viscosity) above the yield stress that accounts for the shear thinning behavior exhibited by MR fluids above the yield stress. Such an idealization to the MR fluid’s constitutive behavior is called a viscous-power law model, or a Herschel-Bulkley model with preyield viscosity. This study develops analytical quasi-steady analysis for such a constitutive MR fluid behavior applied to a flow mode MR damper. Closed form solutions for the fluid velocity, as well as key performance metrics such as damping capacity and dynamic range (ratio of field on to field off force). Also, specializations to existing models such as the Herschel-Bulkley, the Biviscous, and the Bingham-plastic models, are shown to be easily captured by this model when physical constraints (idealizations) are placed on the rheological behavior of the MR fluid.