bluuebunny/crossref_metadata_2025 huggingface dataset:
Utilizing UAV Payload Design by Undergraduate Researchers for Educational and Research Development
Authors: Semke William H. , Schultz Richard R. , Dvorak David , Trandem Samuel , Berseth Brian , Lendway Matthew
Published: May 2009

An undergraduate team consisting of mechanical and electrical engineering students at the University of North Dakota developed an electro-optical and un-cooled thermal infrared digital imaging remote sensing payload for an Unmanned Aerial Vehicle (UAV). The first iteration of the payload design began in the fall of 2005 and the inaugural flight tests took place at Camp Ripley, Minnesota, a National Guard facility, in the fall of 2006 with a corporate partner. The second iteration design with increased performance in object tracking and data processing is expected to fly in the summer of 2007. Payload development for integration into a UAV is a process that is not currently well defined by industrial practices or regulated by government. These processes are a significant part of the research being conducted in order to define the “best practices.” The emerging field of UAVs generates tremendous interest and serves to attract quality students into the research. As with many emerging technologies there are many new exciting developments, however, the fundamentals taught in core courses are still critical to the process and serve as the basis of the system. In this manner, the program stimulates innovative design while maintaining a solid connection to undergraduate courses and illustrates the importance of advanced courses. The payload development was guided by off-the-shelf components and software using a systems engineering methodology throughout the project. Many of the design and payload flight constraints were based on external factors, such as difficulties with access to airspace, weather-related delays, and ITAR restrictions on hardware. Overall, the research project continues to be a tremendous experiential learning activity for mechanical and electrical engineering students, as well as for the faculty members. The process has been extremely successful in enhancing the expertise in systems engineering and design in the students and developing the UAV payload design knowledge base and necessary infrastructure at the university.
Performance Analysis of Solid Oxide Fuel Cell Stack: Part 1 — Model Description and Validation
Authors: Verda Vittorio , Cali` Michele
Published: May 2009

In this paper a detailed model for the simulation of a tubular solid oxide fuel cell stack is presented. The model solves heat transfer, current transfer and fluid flow in the stack. The effect of mass transfer is accounted by means of the information provided by a CFD model of a single cell. The approach used to build the model allows one to simulate large stacks, predicting the temperature, current and mass flow rate profiles. The model has been applied to the CHP100 manufactured by Siemens. The results obtained by the stack model are compared with some of the available measurements.
Performance Analysis of Solid Oxide Fuel Cell Stack: Part 2 — Radiation Heat Transfer
Authors: Verda Vittorio , Borchiellini Romano
Published: May 2009

Radiation plays an important role in the temperature distribution of high temperature fuel cells and thus on their performance. In this paper, a detailed description of a possible approach for modeling radiation heat transfer in the tubular solid oxide fuel cell stack is provided. Each solid surface is divided into small surfaces, each characterized by a single temperature value. Surfaces are considered as grey bodies. Fuel is considered as a participating medium (grey): it is divided into volumes, each characterized by a temperature value. Radiation between surface and surface, surface and gas, gas and gas is expressed through quantities called the direct exchange areas. Diagrams showing the direct exchange areas for the geometries involved in the CHP100 stack model are presented. In addition, a procedure to obtain these quantities for any geometry is explained.
Fabrication of a Novel 3D Porous Micromixer Using Selective Ultrasonic Foaming
Authors: Wang Hai , Li Wei
Published: May 2009

Mixing on the micro scale has been considered as one of the most challenging tasks in microfluidic related chemical and biological applications. With a trend for polymeric microfluidic systems, a simple yet efficient passive micromixer is highly preferred [1–2].
Modeling Bubble Growth in Micro-Channel Cooling Systems
Authors: Nickerson Joshua L. , Cerza Martin , Garcia Sonia M. F.
Published: May 2009

The solution of the heat conduction equation in the liquid layer beneath a moving bubble’s base and the resulting local heat transfer coefficient are presented. An analytical model was constructed using separation of variables to solve the heat conduction equation for the thermal profile in the liquid film beneath the base of a bubble moving through a microchannel at a given velocity. Differentiating the resulting liquid thermal profile and applying the standard definition for the local heat transfer coefficient resulted in a solution for local heat transfer coefficient as a function of bubble length. Analysis included varying pertinent parameters such as film thickness beneath the bubble base, wall heat flux, and superheated temperature in the microchannel. Water and FC-72 were analyzed as prospective coolant fluids. Analytical data revealed that as the superheated temperature in the microchannel increases, local heat transfer coefficients increase and arrive at a higher steady-state value. Increasing wall heat flux achieved the same result, while increasing film thickness resulted in lower heat transfer coefficients. The model indicated that water had superior performance as a coolant, provided the dielectric fluid (FC-72) is not mandated.
Design and Simulation of an Off-Line Internal Navigation System for Pipeline Inspection Applications
Authors: Durali Mohammad , Nabi Ali , Fazeli Amir
Published: May 2009

The aim of this paper is to design an inertial navigation system (INS) for use in a geometry pipe inspection gauge, capable of measuring pipeline movements and producing the line’s 3D map with a reasonable accuracy. A suitable reference path was generated as a design platform. Solving the navigation equations and compensating for the errors, by using extended Kalman filter (EKF) approach, the INS path was generated and its position errors in all three directions were considered. Divergence problems due to far apart GPS position observations, was overcome by defining suitable threshold for the variances of the estimated errors.
An Experiment in Design and Materials: Undergraduate Students Designing Test Machines
Authors: Ridgely John R.
Published: May 2009

An exercise has been developed for an undergraduate design laboratory. In the exercise, students design, build, and test load cells, then build computer interfaced tensile testing machines in which the load cells are integrated. Data is acquired through the use of a simple, low-cost bridge amplifier and digital counter circuit which was developed for this exercise. The circuit design and software are released as an open source project to encourage widespread use and participation by the academic community. The tensile test machine exercise has been tested on a group of 45 junior-level mechanical engineering students, with significant success in students demonstrating an understanding of the principles taught. The open source interface is being adopted by other courses and student projects at the host University; use at other institutions is encouraged.
Warpage Measurement Using Projection Moire´ System and Two Automatic Image Segmentation Algorithms
Authors: Tan Wei , Ume I. Charles
Published: May 2009

Out-of-plane displacement (warpage) has been a major reliability concern for board-level electronic packaging. Printed wiring board (PWB) and component warpage results from CTE mismatch among the materials that make up the PWB assembly (PWBA). Warpage occurring during surface-mount assembly reflow processes and normal operations may lead to serious reliability problems. In this paper, a projection moire´ warpage measurement system and two types of automatic image segmentation algorithms were presented. In order to use the projection moire´ technique to separately determine the warpage of a PWB and assembled electronic packages in a PWBA, two image segmentation algorithms based on mask image models and active contour models (snakes) were developed. They were used to detect package locations in a PWBA displacement image generated by the projection moire´ system. The performances of the mask image and snake approaches based on their resolutions, processing rates, and measurement efficiencies were evaluated in this research. Real-time composite Hermite surface models were constructed to estimate the PWB warpage values underneath the electronic packages. The above automatic image segmentation algorithms were integrated with the projection moire´ system to accurately evaluate the warpage of PWBs and assembled chip packages individually.
The Fluid Mechanics of Membrane Filtration
Authors: Hale Jack S. , Harris Alison , Li Qilin , Houchens Brent C.
Published: May 2009

Reverse osmosis and nanofiltration membranes remove colloids, macromolecules, salts, bacteria and even some viruses from water. In crossflow filtration, contaminated water is driven parallel to the membrane, and clean permeate passes through. A large pressure gradient exists across the membrane, with permeate flow rates two to three orders of magnitude smaller than that of the crossflow. Membrane filtration is hindered by two mechanisms, concentration polarization and caking. During filtration, the concentration of rejected particles increases near the membrane surface, forming a concentration polarization layer. Both diffusive and convective transport drive particles back into the bulk flow. However, the increase of the apparent viscosity in the concentration polarization layer hinders diffusion of particles back into the bulk and results in a small reduction in permeate flux. Depending on the number and type of particles present in the contaminated water, the concentration polarization will either reach a quasi-steady state or particles will begin to deposit onto the membrane. In the later case, a cake layer eventually forms on the membrane, significantly reducing the permeate flux. Contradictive theories suggest that the cake layer is either a porous solid or a very viscous (yield stress) fluid. New and refined models that shed light on these theories are presented.
Process Model for the Production of Syngas via High Temperature Co-Electrolysis
Authors: McKellar M. G. , O’Brien J. E. , Stoots C. M. , Hawkes G. L.
Published: May 2009

A process model has been developed to evaluate the potential performance of a large-scale high-temperature co-electrolysis plant for the production of syngas from steam and carbon dioxide. The co-electrolysis process allows for direct electrochemical reduction of the steam-carbon dioxide gas mixture, yielding hydrogen and carbon monoxide, or syngas. The process model has been developed using the Honeywell UniSim systems analysis code. Using this code, a detailed process flow sheet has been defined that includes all the components that would be present in an actual plant such as pumps, compressors, heat exchangers, turbines, and the electrolyzer. Since the electrolyzer is not a standard UniSim component, a custom one-dimensional co-electrolysis model was developed for incorporation into the overall UniSim process flow sheet. The one dimensional co-electrolysis model assumes local chemical equilibrium among the four process-gas species via the gas shift reaction. The electrolyzer model allows for the determination of co-electrolysis outlet temperature, composition (anode and cathode sides); mean Nernst potential, operating voltage and electrolyzer power based on specified inlet gas flow rates, heat loss or gain, current density, and cell area-specific resistance. The one-dimensional electrolyzer model was validated by comparison with results obtained from a fully three dimensional computational fluid dynamics model developed using FLUENT, and by comparison to experimental data. This paper provides representative results obtained from the UniSim flow sheet model for a 300 MW co-electrolysis plant, coupled to a high-temperature gas-cooled nuclear reactor. The co-electrolysis process, coupled to a nuclear reactor, provides a means of recycling carbon dioxide back into a useful liquid fuel. If the carbon dioxide source is based on biomass, the entire process would be climate neutral.
Organized Iterative Learning Control for Trajectory Tracking
Authors: Fine Benjamin , Tomizuka Masayoshi
Published: May 2009

In trajectory tracking applications where a single trajectory is followed many times, Iterative Learning Control (ILC) is used to improve tracking performance by compensating for controller lag and disturbances that are repetitive across iterations. These tracking errors are not necessarily found throughout the iteration and may even be sufficiently learned after only a few iterations. Influenced by segmented and multirate control, this paper presents a new ILC algorithm which reduces how often the ILC input signal is updated as learning progresses. Portions of the signal where sufficient learning has occurred are divided and approximated as constant based on where the magnitude of the input is small and is slowly changing. Organized ILC is compared to the p-type ILC formulation and is shown to perform just as well as the full cycle learning. During sections of constant velocity, the organized ILC quickly compensates for the error as does the p-type ILC. In portions where tolerances are satisfied, the organized ILC begins partitioning and approximating the input signal and is shown to significantly reduce the number of times the input signal is updated. Measurement noise is also introduced and the RMS of the error signal for each iteration is compared. The organized ILC is shown to handle measurement noise significantly better than p-type ILC.
Mobile Agent-Based Computational Steering for Distributed Simulation
Authors: Chou Yu-Cheng , Ko David , Cheng Harry H. , Davis Roger L. , Chen Bo
Published: May 2009

Two challenging problems in the area of scientific computation are long computation time and large-scale, distributed, and diverse data sets. As the scale of science and engineering applications rapidly expands, these two problems become more manifest than ever. This paper presents the concept of Mobile Agent-based Computational Steering (MACS) for distributed simulation. The MACS allows users to apply new or modified algorithms to a running application by altering certain sections of the program code without the need of stopping the execution and recompiling the program code. The concept has been validated through an application for dynamic CFD data post processing. The validation results show that the MACS has a great potential to enhance productivity and data manageability of large-scale distributed computational systems.
2D Analytical Model Investigating the Effect of Structural Heat Recirculation on the Temperature Profiles in a Parallel Plate Reactor With a Premixed Laminar Flame
Authors: Veeraragavan Ananthanarayanan , Cadou Christopher P.
Published: May 2009

A two-dimensional model for heat transfer in reacting channel flow is developed along with an analytical solution that relates the temperature field in the channel to the flow Pe number. The solution is derived from first principles by modeling the flame as a volumetric heat source and by applying “jump conditions” across the flame. The model explores the role of heat recirculation via the channel’s walls by accounting for the thermal coupling between the wall and the gas. The uniqueness of the model lies in that it is developed by simultaneously solving the two dimensional temperature fields in both the wall and structure analytically. The solution is obtained using separation of variables in the streamwise (x) and the transverse (y) direction. Thermal coupling between the wall and gas is achieved by requiring that the temperature and heat flux match at the interface. The outer wall boundary can be either adiabatic or have a convective heat loss based on Newton’s law of cooling. The resulting solution is a Fourier series (for both wall and gas temperature fields) which depends on the flow Pe and the outer wall boundary condition. This simple model and the resulting analytical solution provide an extremely computationally efficient tool for exploring the effects of varying channel height and gas velocity on the temperature distribution associated with reacting (combusting) flow a channel. Understanding these tradeoffs is important for developing miniaturized, combustion-based power sources.
Decentralized Exergy/Entropy Thermodynamic Control for Collective Robotic Systems
Authors: Robinett Rush D. , Wilson David G.
Published: May 2009

This paper develops a distributed decentralized control law for collective robotic systems. The control laws are developed based on exergy/entropy thermodynamic concepts and information theory. The source field is characterized through second-order accuracy. The proposed feedback control law stability for both the collective and individual robots are demonstrated by selecting a general Hamiltonian based solution developed as Fisher Information Equivalency as the vector Lyapunov function. Stability boundaries and system performance are then determined with Lyapunov’s direct method. A robot collective plume tracing numerical simulation example demonstrates this decentralized exergy/entropy collective control architecture.
Finite Element Analysis for Demolding Process in Thermal Imprint Lithography
Authors: Song Zhichao , Lee Jaejong , Park Sunggook
Published: May 2009

In thermal imprint lithography, most of the imprint failures occur during demolding, a process to separate the mold insert from the substrate after conformal molding. The success of demolding is determined by the stress generated in the resist with respect to the yield stress of the resist. In this paper we simulated the demolding process in thermal imprint lithography using the finite element method to study the stress distribution and deformation in poly(methyl methacrylate) (PMMA) resist during demolding. During demolding, the stress concentrates both at the transition corner zone between the residual layer and the replicated pattern, and close to the contact region with the moving stamp. As demolding proceeds, the highest local stress for both locations shows two maximums, indicating that a structural failure may occur not only when demolding starts, but also immediately before demolding ends. The structural failure at the second maximum becomes dominant as the angular offset from the ideal normal demolding to the substrate surface increases or for the structures located far away from the symmetric centerline. In addition, we will discuss the influence of other process and geometry parameters, including demolding rate and stamp aspect ratio.
Modeling and Characterization of a Chemomechanical Actuator Based on Protein Transporters
Authors: Sundaresan Vishnu Baba , Leo Donald J.
Published: May 2009

Plants and animal cells are naturally occurring actuators that exhibit force and motion driven by fluid transport through the cell membrane. The protein transporters embedded in the cell membrane serve as the selective gateway for ion and fluid transport. The actuator presented in this work generates force and deformation from mass transport through an artificial membrane with protein transporters extracted from plant cell membranes. The artificial membrane is formed from purified 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-Phosphoethanolamine (POPE) lipids and supported on a porous substrate. The protein transporter used in the actuator membrane is a proton-sucrose cotransporter, SUT4, extracted from yeast cells that genetically modified to grow the cotransporter in their cell membranes. The SUT4 transporter conducts proton and sucrose from the side of the membrane with higher concentration and carries water molecules across the membrane. It is observed from transport characterization experiments that fluid flux through the membrane varies with the applied sucrose concentration and hence is chosen as the control stimulus in the actuator. A modified four-state facilitated diffusion model is applied to the transport characterization data to compute the two characteristic parameters for fluid transport, saturation concentration and translocation rate, through the membrane. The flux rate through the membrane is observed to increase with the concentration till a particular value and saturates at a higher concentration. The concentration at which the flux rate through the membrane saturates is referred to as the saturation concentration. The saturation concentration for the actuator is experimentally found to be 6±0.6mM sucrose on the side with lower pH. The corresponding maximum translocation rate is found to be 9.6±1.2 nl/μ.cm2.min. The maximum steady state deformation produced by the actuator is observed at 30 mM sucrose that corresponds to a force of 0.89 mN.
Model Development and Validation of the Semi-Active Roll Control (SARC) System
Authors: Sardar Hemant M. , Barron Richard , Green Steve J.
Published: May 2009

This paper presents some of the work done to model the dynamics of TRW’s semi-active roll control (SARC) actuator. The SARC system is designed to reduce vehicle body roll in a turn and to allow for improved ride and handling while driving straight ahead. The SARC system consists of a hydraulic actuator, vehicle state sensors and an electronic control unit (ECU). The vehicle state sensors and ECU are optional in that existing ESC/VSC elements could be used to control the actuator with the proper control algorithms. The actuator is a compact hydraulic unit consisting of a linear actuator, pressurized reservoir, and associated valves. It mounts between one end of the sway bar and the vehicle suspension, and essentially works to engage or disengage the sway bar. The model was developed to understand and predict the dynamic behavior of the actuator for simulated vehicle inputs. The model was developed in Matlab/Simulink and was validated against experimental test rig data. Model parameters were determined from experimental data and basic engineering principles. This included modeling the dynamics of the seal frictions and the multi-stage control valve. Different vehicle inputs were simulated and the behavior of the actuator under various load regimes was matched to experimental test-rig data. The results show that this model is a reasonably accurate representation of the dynamics of the physical system allowing for usage in controller development and synthesis, and integrating in to vehicle models for integrated software-in-loop (SIL) and hardware-in-loop (HIL) development.
Computation of Turbulent Free Convection in Oblique Porous Enclosures Using a Macroscopic Two-Equation Model
Authors: de Lemos Marcelo J. S. , Braga Edimilson J.
Published: May 2009

This paper presents computations for turbulent natural convection within an inclined cavity filled with a fluid saturated permeable medium. The finite volume method in a generalized coordinate system is applied. The inclined walls are maintained at constant but different temperatures, while the horizontal walls are kept insulated. Governing equations are written in terms of primitive variables and are recast into a general form. Flow and heat transfer characteristics are investigated for a wide range of values of Rayleigh number and inclined angles. The turbulent model used is the macroscopic k-eps model with a wall function. In this work, the turbulence model is first switched off and the laminar branch of the solution is found. Subsequently, the turbulence model is included so that the solution merges to the laminar branch for a reducing Ram. This convergence of results as Ram decreases can be seen as an estimate of the well known laminarization phenomenon. Present solutions are compared with published results and the influence of the inclination angle on Racr is analyzed. For Ram greater than around 104, both laminar and turbulent flow solutions deviate, indicating that such critical value for Ram was reached.
Laser Thermal Processing of Nanowires
Authors: Misra Nipun , Pan Yaoling , Grigoropoulos Costas P.
Published: May 2009

Semiconductor nanowires offer an alternative bottom-up route for nanoscale electronics and photonics application. The possibility of combining nanowires with cheap flexible substrates in the form of nanowire thin-films or composite materials composed of nanowires has opened up a new paradigm for inorganic semiconductor based technologies on flexible substrates. Recently, thin film transistors have been fabricated on plastic substrates based on this technique. This paper discusses laser thermal processing of nanowires as an alternative to conventional thermal processing. Ultra-short pulsed lasers allow for localized energy deposition into nanowires and can therefore enable thermal processing of nanowires on sensitive substrates such as plastics. Laser-based annealing of ion-implanted silicon nanowires is investigated for application in high performance flexible electronics. The efficacy of laser processing is examined through studies of the effect of number of pulses and incident fluence levels on conductance of the nanowires. Finally, numerical predictions of the absorption in the nanowires are presented.
Passive Wireless Sensing of Temperature Using RF Technology
Authors: Zhang Miaogeng , Gonzalez-Argueta Luis , Sundararajan V.
Published: May 2009

Sensor networks are emerging as an attractive technology for deployment in monitoring applications due to their flexibility, small size, ease of installation, low cost and low power characteristics. Since the wireless nodes use batteries as energy sources, their operating lives are limited by the life of the batteries. Replacing batteries periodically in a sensor network can be a burden as the nodes may be dispersed over a wide area. Moreover the battery increases the size of the sensor nodes and offsets one of the primary advantages of such networks. This study proposes a design for wireless sensing of temperature based on passive RF-technology. The experimental setup includes: 1) signal generator 2) sensor tag 3) receiver. The carrier signal is produced by function generator. The sensor tag consists of a voltage divider circuit combined with loop antennas. The sensor tag filters the carrier signal and transmits back a modulated signal of the same frequency. The variable resistor acting as a thermistor is connected as a voltage divider. The change in amplitude of the output signal is relative to the temperature change. Experimental results show that the passive RF design can be effective way for wireless temperature monitoring. The results can be generalized to any sensor that converts the measured signal into a change of resistance.
Power/Efficiency Optimization of a Sorption Cooler Under Quantified Design Uncertainty
Authors: Lloyd George M. , Kim K. J.
Published: May 2009

While the design paradigm in engineering of searching for the optimum system has proven fruitful (and given a good model relatively straightforward, in principle), the desired end result of engineering development is rarely a model (even the optimum one), but a system. In this regard it has frequently been observed (generally with some disappointment) that what one can specify is not always what one gets. It is frequently the case that realized systems, no matter how carefully constructed according to specifications derived from verified and validated models, frequently depart from the designed-for behaviour, due to parametric incertitude. Given this not uncommon circumstance, a somewhat more useful question one might seek to answer during an optimization process is “what is the best system under the constraints which I can reasonably hope to build?” Design optimization under incertitude approaches based on intrusive modifications to the deterministic model, such as stochastic finite elements and chaos expansions, are tedious to apply, computationally expensive, and fraught with convergence issues. The simplest nonintrusive approach—direct Monte Carlo sampling— is far too slow to efficiently sample the joint response distribution of complex thermophysics transient models. The purpose of this paper is to address this topic by incorporating design uncertainty itself as a constraint during the optimization of a sorption cooler. In our method a Markov Chain Monte Carlo sampler is used as the means to develop a suitable ensemble from a practical set of computational results which circumscribe the power/efficiency characteristics of a cooler as a function of several dimensionless stochastic optimization parameters. The ensemble is used to estimate the covariance structure of the design uncertainty, which is then projected into the best low rank subspace where tests of hypothesis under the dominant generalized parameters can be formulated; growth in fluctuations of the generalized parameters along optimization trajectories becomes clearly evident and quantifiable. The method results in a classical power/efficiency diagram, with the addition of quantified design uncertainty. The utility of these diagrams is that they enable rapid-prototyping efforts to target the best cooler design that is most likely to function as expected.
Real-Time Parameter ID Using Polynomial Chaos Expansions
Authors: Southward Steve C.
Published: May 2009

A novel real-time parameter identification algorithm has been developed that exploits polynomial chaos expansion (PCE) representations of uncertain parameters. Dynamic system models inevitably contain parameters whose values are rarely known with absolute certainty. In many cases, such parameters are either not measurable, or they are slowly time varying. In some cases, the dynamic system model is inadequate and parameter values are simply chosen to provide a “best fit” representation. For the method proposed here, we assume apriori knowledge of the probability distributions associated with the uncertain parameters. Within the PCE framework, the uncertain parameter distribution is explicitly propagated through the dynamic system equations using a Galerkin projection onto an orthogonal polynomial basis. The probabilistic PCE model is then collapsed to a deterministic model where an adaptive algorithm is designed to effectively reduce the uncertainty. For illustration, this algorithm is numerically demonstrated using a simple first order dynamic system with only a single uncertain parameter.
A Modified Fractional Derivative Approach to Model Hysteresis
Authors: Rabius Sunny M. Mohammed , Kapania Rakesh K. , Moffitt Ronald D. , Mishra Amitabh , Goulbourne Nakhiah
Published: May 2009

This paper describes the development of a fractional calculus approach to model the hysteretic behavior shown by the variation of resistance with strain in nano-composites (like MetalRubberOˆ). Experiments have been carried out on MetalRubberOˆ to study the strain-resistance variation of this material under strains varying in a triangular manner. Combined fractional derivative and integer order integral model and fractional integral model (with two sub-models) have been developed to model this behavior. Effieiency of these models has been discussed by comparison of their results with the experimental result.
Representative Results for Condensation Measurements at Hydraulic Diameters ∼ 100 Microns
Authors: Agarwal Akhil , Garimella Srinivas
Published: May 2009

Condensation pressure drops and heat transfer coefficients are measured in small quality increments in channels with 100 < Dh < 200 microns. The channels are fabricated on a copper substrate by electroforming copper onto a mask patterned by X-ray lithography, and sealed by diffusion bonding. Subcooled liquid is electrically heated to the desired quality, followed by condensation in the test section. Downstream of the test section, another electric heater is used to heat the refrigerant to a superheated state. Energy balances on the pre- and post heaters establish the refrigerant inlet and outlet states at the test section. Water at a high flow rate serves as the test section coolant to ensure that the condensation side presents the governing thermal resistance. Heat transfer coefficients are measured for 200 < G < 800 kg/m2-s for 0 < x < 1 at several different saturation temperatures. Conjugate heat transfer analyses are conducted in conjunction with local pressure drop profiles to obtain accurate driving temperature differences and heat transfer coefficients. The effects of quality, mass flux, and saturation temperature on condensation pressure drops and heat transfer coefficients are illustrated through these experiments.
Aligned Carbon Nanotube Polymer Composites
Authors: Liu Yayong , Das Narayan C. , Wang Howard , Zhang Guangneng , Cho Junghyun , Hong Kunlun , Eres Gyula , Uhrig David
Published: May 2009

Carbon nanotube (CNT) polymer nanocomposites are promising new materials with a unique combination of mechanical and transport properties. As physical properties such as mechanical behavior, dielectric relaxation, thermal and electrical conductivities depend strongly on morphological structures of composites, we illustrate in this study the structure/property relationship in vertically aligned CNT (VACNT)/polymer nanocomposites. We have prepared VACNT/polystyrene composites and characterized their morphologies and properties. We have reported previously the continuous variation of alignment order along the height of CNT, which remain unaltered upon forming composites as revealed by small angle neutron scattering (SANS). Nanoindentation shows that both the elastic modulus and hardness vary along the CNT growth direction due to the varying tube density, alignment order and entanglement.
CFD Computation of Fan Interaction Noise
Authors: Grace Sheryl M. , Sondak Douglas L. , Dorney Daniel J. , Logue Michaela
Published: May 2009

In this study, a 3-D, unsteady, Reynolds-averaged Navier-Stokes (RANS) CFD code coupled to an acoustic calculation is used to predict the contribution of the exit guide vanes to tonal fan noise downstream. The configuration investigated is that corresponding to the NASA Source Diagnostic Test (SDT) 22-in fan rig. One configuration from the SDT matrix is considered here: the approach condition, and outlet guide vane count designed for cut-off of the blade passage frequency. In this chosen configuration, there are 22 rotor blades and 54 stator blades. The stators are located 2.5 tip chords downstream of the rotor trailing edge. The RANS computations are used to obtain the spectra of the unsteady surface pressure on the exit guide vanes. The surface pressure at the blade passage frequency and its second harmonic are then integrated together with the Green’s function for an annular duct to obtain the pressure at locations in the duct. Comparison of the computed sound power level at the exhaust plane with experiment show good agreement at the cut-on circumferential mode. The results from this investigation validate the use of the CFD code along with the acoustic model for downstream fan noise predictions. This validation enables future investigations such as the effect of duct variation on the exhaust tonal power level and the validity of using this method for predicting broadband noise levels.
Undergraduate Research: Experiences From a Three-Year Project
Authors: Schuster Peter , Birdsong Charles
Published: May 2009

Undergraduates receive many benefits from participation in research activities, including exposure to advanced topics, introduction to research methods, and direct interaction with faculty and other students. Faculty and institutions benefit as well — fresh eyes in research projects, more energized research groups, and more engaged alumni. However, there are some challenges in designing a research program to work primarily with undergraduates. These include the students’ lack of exposure to advanced topics, short tenure on the project, and potentially lower commitment to the results. There are a number of ways to address these concerns, however. Short student tenure and limited student experience may be offset by breaking up a long-term project into manageable short-term chunks, identifying specific deliverables for each student, and implementing a rigorous data reporting and storage system. Student motivation may be enhanced by linking performance to grades or to an external competition. This paper presents results of using these and other techniques in a multi-disciplinary vehicle sensing research project involving sixteen undergraduates over a three-year period. Although individual student time on the project ranged from only three to twelve months, all students were able to contribute to the project. Student activities were grouped into individual and small group tasks, each with specific goals and timetables. Rigorous electronic documentation and data storage techniques were employed to enable new students to come up-to-speed quickly. A mix of course credits, supplemental pay, and an intercollegiate competition were used to maintain student motivation. Project successes include high student satisfaction, conference papers, a demonstration pre-crash sensing system, and participation in an international student competition.
Novel Particle Shift Filtering Method for Simultaneous Two Phase Separation in Time Resolved Stereo PIV Measurements
Authors: Cheng Y. , Torregrosa M. M. , Diez F. J.
Published: May 2009

This paper describes a novel particle shift filtering method to study jets laden with particles by separating the 3D velocity field of the two phases. Multiphase jets laden with particles appear in many engineering and environmental processes. Typical examples are sprays containing liquid fuel drops in combustion processes, air jets laden with coal particles in a power plant, and the dispersion of harmful substances like soot and pollutants from steady exhaust flows or waste waters, among others. Distribution and mixing of particles/drops in these processes determine the efficiency of the engineering systems concerned but studies of particle-laden turbulent flows suggest that particle distribution is not uniform but preferential. In order to understand the mechanism of particle dispersion, the dispersed phase (particles/drops) needs to be separated from the ambient flow (tracer particles). A new technique is proposed that builds on previous work done by Kiger & Pan (2000) and Khalitov & Longmire (2002). The later work used a discrimination algorithm for two-phase 2D PIV where the tracer particles are differentiated from the dispersed phase based on size and brightness intensity. The present work expands on that technique and introduces a 3D velocity discrimination algorithm of two-phase flows for time resolved stereo PIV.
Information-Theoretic Sensor Motion Control for Distributed Estimation
Authors: Ryan Allison D. , Durrant-Whyte Hugh , Hedrick J. Karl
Published: May 2009

Estimate uncertainty is a clear metric for sensing problems, but is not traditionally used for optimal control of mobile sensors because it is difficult to model how it is affected by sensor motion. This work develops a multiple-step receding horizon cost for sensor motion control based on minimization of expected entropy of the estimate distribution. The structure of the cost function is analyzed and used to upper bound the degree of coupling between sensors. The contribution is a multiple step prediction of the estimate entropy incorporating probabilistic sensor and target motion models and a decomposition for its decentralized calculation. Multiple-step receding horizon control has the potential to provide better performance than single-step optimization in the cases of delayed payoff or sensor motion constraints, and has not generally been implemented for non-Gaussian models. An example is developed based on a team of unmanned air vehicles carrying vision sensors, and initial simulation results confirm the accuracy of the predictive cost calculation.
Annealing Procedures and Their Effects on PZT/Nanoparticle Thin Films via a Modified Sol-Gel Process
Authors: Easter Clayton , O’Neal Chad B.
Published: May 2009

The development of lead zirconate titanate (PZT) films can be a fairly troublesome process when trying to obtain a viable thick crack-free film. Traditional methods for film fabrication via a pure sol-gel solution provide the best results, but still can have many problems. This paper maps out the specific spin-coating and annealing steps used in order to achieve a PZT film with minimal-to-no cracking and/or delamination. A seed layer of PbTiO3 (PT) was used in order to create nucleation sites for the subsequent PZT layers, virtually eliminating any delamination. All layers, including the PT base layer, were spin-coated at 3000 rpm onto a 100-mm silicon wafer (previously sputtered with Ti and Pt for adhesive and conductive purposes, respectively) and soft-baked at 150 °C for 10 min. Initial annealing procedures produced severe cracking, a result of the relatively high cooling rates through the Curie temperature (∼350 °C). The annealing process was refined, for individual layers, to 550°C for 120 s, with a cooling rate of 0.042 °/s between 400 and 300 °C. Final annealing was conducted at 600 °C for 30 min, with a cooling rate of 0.028 °/s between 400 and 300 °C. The resulting PZT layer was virtually crack-free. Platinum was sputtered again subsequent to PZT deposition in order to pole the piezoelectric material. A PZT/nanoparticle powder mixture was also investigated as the piezoelectric layer. PZT nanoparticles were suspended in the sol-gel precursor solution and then spin-coated also at 3000 rpm onto a 100-mm wafer and soft-baked at 150 °C for 10 min. The relatively slow cooling rate was extended between 500 and 100 °C in order to prevent any cracking that might occur along grain boundaries between the individual PZT nanoparticles. The resulting film was crack-free, however displaying areas of agglomerated nanoparticles.
A Fully Lagrangian Numerical Method for Calculating the Dynamics of Oscillating Micro and Nanoscale Objects Immersed in Fluid
Authors: Hashemi Nastaran , Paul Mark , Alcazar Javier , Radovitzky Raul
Published: May 2009

Many micro and nano-technologies rely upon the complicated motion of objects immersed in a viscous fluid. It is often the case that for such problems analytical theory is not available to quantitatively describe and predict the device dynamics. In addition, the numerical simulation of such devices involves moving boundaries and use of the standard Eulerian computational approaches are often difficult to implement. In order to address this problem we use and validate a fully Lagrangian finite element approach that treats the moving boundaries in a natural manner. We validate the method for use in calculating the dynamics of oscillating objects in a viscous fluid. Specifically, the dynamics of a micron-scale cylinder oscillating in water are studied numerically. The fluid dynamics generated by an infinitely long cylinder are a good approximation for the flow field around an oscillating cantilever. The numerical results agree well with analytical theory. It is anticipated that further development of the fully Lagrangian numerical approach for fluid-solid interaction problems will be useful in the development of micro and nano-technologies.
Study of Design Parameters in Hydrogen Microsensors Integrated With Metal Semiconductor Nanoparticles
Authors: Zhang P. , Deshpande S. , Medelius P. J. , Seal S. , Cho H. J.
Published: May 2009

We investigated the effect of electrode design parameters on the performance of hydrogen microsensors. The sensors with varying electrode parameters were fabricated integrating micromachined interdigitated electrodes with indium oxide (In2O3) doped polycrystalline tin dioxide (SnO2) nanoparticles and tested in a controlled gas environment. It was observed that the sensitivity was closely related to the gap between, and a ratio of the gap to the width in interdigitated electrodes (IDE).
Internet Based Lab Framework Development for Distance Learning in Robotics and Mechatronics Education
Authors: Chiou Richard , Kwon Yongjin
Published: May 2009

A number of Internet-based educational tools have been developed to support mechanical education with Internet-based technologies. However, many of these tools have limitations as mostly just visual assistant tools for understanding engineering lectures. This paper describes lab framework development integrated with Internet-based robotics and mechatronics for mechanical education. The development efforts include advanced course and laboratory activities integrated with sensor networks and Internet-based technologies. The instructional materials for Internet-based robotics and automation education utilize Robotics and Mechatronics lab as the experiments of choice. The new Internet-based techniques allow the remotely situated students to program, control, and monitor the mechanical operations through the Internet. The architecture of the Internet-based lab focusing on remote data acquisition and measurement, as well as industrial control and automation applications, is illustrated. Implementation of a remote robotic vision feedback control lab is also described.
The Evolution of Microstructure Due to Heat Treatment on Highly Porous Copper/Silver Systems
Authors: Murtha Brian A. , Kulkarni Anil K. , Singh Jogender
Published: May 2009

The sintering phenomenon is examined in highly porous materials by first cold pressing powdered copper and silver and separately heat treating them in an un-pressurized furnace. The initial microstructure prior to heat treatment as compared to that after heat treatment showed similar characteristics regardless of the material or powder geometry. However, after heat treatment, there are significantly different microstructures among samples. The microstructures depend on the maximum furnace temperature, the particle geometry, material composition, and the particle surface area. While the microstructures change significantly, there is no change in porosity between pre- and post-heat treated samples.
Fabrication of Free-Standing Polymer Membranes via Imprint Lithography and Selective Immobilization of Lipid Vesicles at Micropores in the Membrane
Authors: Roychowdhury Anish , Choi Junseo , Yi Alum , Xu Feng , Park Sunggook
Published: May 2009

This study presents fabrication of free-standing, perforated membranes in polymer with the pore diameter down to 500 nm via novel imprint lithography and use of the membrane to selectively immobilize lipid vesicles at the micropores in the membrane. For the fabrication, a combination of imprint lithography and a sacrificial layer technique was employed in order to get a clean, fully released, and mechanically stable membrane with perforated pores. Si molds with microscale pillar structures fabricated via photolithography were used to define patterns in SU-8 resist layer which was spin-coated on lift-off resist (LOR) used as a sacrificial layer. This was followed by a UV curing process to achieve enough mechanical strength in the SU-8 layer to be fee-standing. Release of the SU-8 layer from the LOR sacrificial layer by lift-off results in the free-standing, perforated membranes with pore diameter down to sub-micrometer range. Prior to the application of lipid vesicles, the SU-8 membrane surface was treated with poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) which prevents non-specific adsorption of the lipid vesicles on the membrane surface. As a result, lipid vesicles were found to selectively adsorb at the pore sites in the membrane, as observed with an evanescence fluorescence microscope. This result indicates that the perforated polymer membranes with micro- and nanoscale pores have potential as a platform for fundamental study of biological systems.