bluuebunny/crossref_metadata_2025 huggingface dataset:
A Priori Motion Profile Control and Dynamic Performance of the Multi-Axis Ride Simulator (MARS) Facility
Authors: Chancey Valeta Carol , Bumgardner Bradley A. , Turner David D. , Breaux-Sims Arlene M. , Flowers George T. , Beale David G.
Published: May 2009

The Multi-Axis Ride Simulator (MARS) facility is a versatile testing facility for the evaluation of vehicle motion effects on personnel and devices. It consists of a 6-DOF Stewart platform driven by a computer-controlled actuation system. An off-line strategy is used to correct the amplifier input and drive the table dynamic response to the desired trajectory. The capabilities and performance limits of the facility are described in detail. The off-line control strategy is also described and its performance evaluated with a series of experimental tests. The results are presented and discussed in detail.
Strength Evaluation and Fatigue Prediction of a Pressurized Thick-Walled Cylinder
Authors: Vakili Omid , Hu Zhong , Delfanian Fereidoon
Published: May 2009

By design, a large caliber gun barrel routinely operates closer to its fatigue envelope than virtually any other device. The lifetime of a gun barrel is limited by bore damage and by fatigue crack growth, which depends crucially upon near-bore thermal damage arising from initial firing, the thermomechanical basis for early cracking and subsequent loss of liner material. The proper understanding and prediction of the strength and fatigue failure of a pressurized thick cylinder is an important prerequisite for any reliable application. In this paper, an analysis of two-dimensional stresses in a thick walled pressurized cylinder using an analytical method followed by fatigue calculation was performed. The effects of wall thickness and internal firing pressure, considering the material properties, on the stress distribution were investigated. This analytical method of stress analysis can be used as a valuable tool for evaluating strength and predicting failure phenomena of a large caliber gun barrel.
Disturbance Observer Based Closed Loop Force Control for Haptic Feedback
Authors: Gupta Abhishek , O’Malley Marcia K. , Patoglu Volkan
Published: May 2009

Most commonly used impedance-type haptic interfaces employ open-loop force control under the assumption of pseudostatic interactions. Advanced force control in such interfaces can increase simulation fidelity through improvement of the transparency of the device, and can further improve robustness. However, closed loop force-feedback is limited both due to the bandwidth limitations of force sensing and the associated cost of force sensors required for its implementation. In this paper, we propose the use of a nonlinear disturbance observer for estimation of contact forces during haptic interactions. This approach circumvents the traditional drawbacks of force sensing while exhibiting the advantages of closed-loop force control in haptic devices. The feedback of contact force information further enables implementation of advanced robot force control techniques such as robust hybrid impedance and admittance control. Simulation and experimental results, utilizing a PHANToM Premium 1.0A haptic interface, are presented to demonstrate the efficacy of the proposed approach.
Optimization of Geometry for Continuous Flow PCR Devices in a Titer Plate-Based PCR Multi-Reactor Platform
Authors: Park D. S. , Chen P.-C. , You B. H. , Kim N. , Park T. , Datta P. , Desta Y. , Soper S. A. , Nikitopoulos D. E. , Murphy M. C.
Published: May 2009

A highly parallel, polymerase chain reaction (PCR) multireactor platform is in high demand to satisfy the high throughput requirements for exploiting the accumulated genetic information from the Human Genome Project. By incorporating continuous flow PCR (CFPCR) devices in a polymer 96-well titer plate format, DNA amplification can be performed with steady-state temperature control and faster reaction speed at lower cost. Prior to the realization of a PCR multi-reactor platform, consisting of a sample delivery chip, a PCR multireactor chip, and a thermal cycler, optimization of the geometry for CFPCR devices in a titer plate-based PCR multi-reactor chip based on manufacturing feasibility is necessary. A prototype PCR multi-reactor chip was designed in a 96-well titer plate format with twelve different CFPCR configurations. High quality metallic, large area mold inserts (LAMIs) were fabricated using an SU-8 based UV-LIGA technique by overplating nickel in SU-8 electroplating templates. Micro molding of polycarbonate (PC) was done using hot embossing, resulting in good replication fidelity over the large surface area. Thermal fusion bonding of the molded PC chips using a custom-made bonding jig yielded acceptable sealing results. The manufacturability investigation throughout the design and the process sequence suggested that the microchannel walls require a minimum width of at least 20 μm and an aspect ratio of 2 for structural rigidity. An optimal CFPCR device for use in a PCR multi-reactor chip can be selected with a series of amplification experiments with the development of a thermal cycler.
Risk Mitigation and Reliability Lessons Learned From Iraq
Authors: Kemper Bart
Published: May 2009

The engineering challenges in developing nations can be significant. This is far more the case in a non-permissive environment. The reliability of infrastructure systems can be compromised not only by direct effects of conflict, but the turnover in personnel and lack of documentation. Risk mitigation, particularly in security matters, can easily but unintentionally be compromised due to materials, construction and fabrication, lack of documentation, and making “reasonable” assumptions based on professional experience in more developed regions. This paper will examine key lessons learned in Iraq.
Three-Dimensional Simulations of Transient Response of PEM Fuel Cells
Authors: Yesilyurt Serhat
Published: May 2009

Transients have utmost importance in the lifetime and performance degradation of PEM fuel cells. Recent studies show that cyclic transients can induce hygro-thermal fatigue. In particular, the amount of water in the membrane varies significantly during transients, and determines the ionic conductivity and the structural properties of the membrane. In this work, we present three-dimensional time-dependent simulations and analysis of the transport in PEM fuel cells. U-sections of anode and cathode serpentine flow channels, anode and cathode gas diffusion layers, and the membrane sandwiched between them are modeled using incompressible Navier-Stokes equations in the gas flow channels, Maxwell-Stefan equations in the channels and gas diffusion layers, advection-diffusion-type equation for water transport in the membrane and Ohm’s law for ionic currents in the membrane and electric currents in gas diffusion electrodes. Transient responses to step changes in load, pressure and the relative humidity of the cathode are obtained from simulations, which are conducted by means of a third party finite-element package, COMSOL.
Process Parameters Optimization in Multilayer Laser Solid Freeform Fabrication Process Using a 3D Transient Numerical Model
Authors: Alimardani Masoud , Toyserkani Ehsan , Paul Christ P.
Published: May 2009

This paper presents a 3D transient numerical approach for thermal and strain/stress modeling of the multilayer laser solid freeform fabrication process, by which correlations between the main process parameters and their effects on the final build-up properties can be studied. This model can be used to optimize the process parameters to increase the controllability of the geometrical and metallurgical variations resulted from the thermal and stress fields. Using this modeling approach, the geometry of the material deposited as well as temperature and thermal stress distributions across the process domain can be predicted based on the process parameters such as powder feed rate, process speed and laser power, assuming the interaction between the laser beam and powder stream is decoupled. The main process parameters affected by a multilayer deposition due to the formation of non-planar surfaces such as powder catchment are also incorporated into the modeling approach. To verify the proposed method, fabrication of a four-layer thin wall of stainless steel AISI 304L on a low carbon steel substrate is modeled with the same process parameters throughout the build-up process. The results show that the temperature and stress slightly increase at the end-points of layers 2, 3, and 4 which cause over deposited materials and micro-crack formations at these regions. The results are then used to discuss optimum process parameters which can be used to have a buildup with better geometrical and physical qualities. The reliability and accuracy of the model are experimentally verified.
A Nonlinear Viscoelastic Modeling of Fiber Metal Laminates
Authors: Sawant Sourabh , Muliana Anastasia
Published: May 2009

A new class of advanced composite materials namely the fibermetal laminates (FMLs) such as ARALL (Aramid Reinforced Aluminum laminate) and GLARE (Glass Reinforced Aluminum laminate) has been developed for primary load bearing components of aircraft fuselage and wings. The FML is composed of alternating layers of fiber reinforced polymer (FRP) and aluminum sheets and shows good fatigue resistance. The metal layers are placed on the top and bottom of the laminate to provide good impact resistance and resistance to extreme environments (moisture, ultraviolet radiation and solvent). Krishnakumar (1994) has provided a survey of extensive works on manufacturing, testing, and modeling of the FMLs. The FMLs exhibit nonlinear viscoelastic and/or plastic behaviors due to the existence of FRP and metal alloy layers. The nonlinearity and time-dependent responses in the FMLs are intensified under high load levels, elevated temperatures, and humid environments. A predictive capability on the overall nonlinear viscoelastic response of the FMLs that recognizes different responses in the FRP and metallic layers becomes necessary. Literature indicates a few advances in this direction by the consideration of the elastic-plastic behavior and the use of classical lamination theory (Chen & Sun, 1989; Hashagen et al., 1995). Pindera et al. (1989) have carried out an experimental investigation of the creep response of ARALL laminates at 121°C. A pronounced viscoelastic behavior is observed in ARALL at stress levels below its proportional limit. Aluminum exhibits a nonlinear viscoelastic behavior while aramid-FRP shows a linear viscoelastic behavior. The classical lamination theory (CLT) was used to model the overall creep response of the laminates.
Gas-Liquid Two-Phase Flow in Hot Embossed Square Microchannels
Authors: Kim Namwon , Evans Estelle T. , Park Daniel S. , Nikitopoulos Dimitris E. , Soper Steven A. , Murphy Michael C.
Published: May 2009

An experimental study was conducted to investigate the characteristics of gas-liquid two-phase flow in 200 μm square microchannels thermoformed in polymer chips. Polymer microfluidic chips were replicated using hot embossing of poly(methyl methacrylate) (PMMA) with micromachined brass mold inserts. The thermoformed microchannels in polymer chips typically had greater surface roughnesses compared to microchannels etched in the silicon substrate. Two more different polymer chips, a direct micromachined PMMA chip and a chip hot embossed with a LIGA nickel mold insert, were fabricated to compare surface characteristics of the sidewalls and bottoms of fabricated microchannels. Deionized water and dry air were injected separately into the chips at superficial velocities of jL = 0.005 – 0.11 m/s for the liquid and jG = 0.003 – 16.67 m/s for the gas. Capillary bubbly, plug, plug-annular, annular, and dry flows were observed in the microchannels. Two-phase flow pattern maps and transitions between flow regimes were determined for fixed values of the homogeneous liquid fraction defined as βL = QL/(QL + QG) where QL and QG are the liquid and gas flow rates, and the liquid Weber number fraction defined as γL = WeL/(WeL + WeG) where WeL and WeG are the liquid and gas Weber number. The surface roughness in submicron range showed minor effect in comparison with the previous work in terms of the gas-liquid two-phase flow patterns and transitions between flow regimes. Dimensionless bubble sizes scaled by the width of observation microchannel were plotted against the homogeneous liquid fraction (βL). A scaling law for the bubble length developed for the previous work with T-junctions was applicable to the present work used the cross junction for generation of segmented flow. With a fixed value of the fitting parameter, scaling law showed a good agreement with the experimental data. Deviation of the scaled bubble length from predicted bubble length line and irregularity of bubble length with a fixed homogeneous liquid fraction increased with higher gas flow rates.
Neighbor Learning Control: Learning Control for Multiple Subsystems
Authors: Menon Manas C. , Asada H. Harry
Published: May 2009

With the rise of smart material actuators, it has become possible to design and build systems with a large number of small actuators. Many of these actuators exhibit a host of nonlinearities including hysteresis. Learning control algorithms can be used to guarantee good convergence of these systems even in the presence of the nonlinearities. However, they have a difficult time dealing with certain classes of noise or disturbances. We present a neighbor learning algorithm to control systems of this type with multiple identical actuators. In addition, we present a neighbor learning algorithm to control these systems for a certain class of non-identical actuators. We prove that in certain situations these algorithms provide improved convergence when compared to traditional iterative learning control techniques. Simulations results are presented that corroborate our expectations from the proofs.
Exploration of the Feasibility of Using Electroosmotic Pumps in Cell Culture
Authors: Glawdel Tomasz , Ren Carolyn
Published: May 2009

A new continuous perfusion cell culture chip is studied that utilizes electroosmotic pumping to control fluid flow. Electroosmotic flow is not typically used for living cells due to the inherently high electric fields that may harm cells. Problems associated with EOF and cells are solved by incorporating electroosmotic pumps (EO pumps) which generate an induced pressure driven flow in regions with cells. Several advantages of EO pumps include pulse free flow, quick flow control and precise movement of minute volumes of fluid. An ion exchange system consisting of photopolymerized salt bridges are used to separate the media from the electrode reservoirs. However, the high salt concentration in cell culture medium creates significant problems for EO pumps such as decreased flow rate due to low zeta potential, increased electrolysis due to high current draw, significant joule heating, bubble formation and polarization. Attempts to solve these problems with the proposed microfluidic chip are discussed. The pumps are characterized to determine the flow rate for applied currents. Preliminary results with rainbow trout gill cells show that pump can be operated for 5hrs without harming the cells. The work presented here discusses the design and development of the system to this point.
Estimation of Plasma Insulin Using Nonlinear Filtering
Authors: Kiriakidis Kiriakos , O’Brien Richard
Published: May 2009

The glucose-insulin dynamics as captured by the standard (Bergman) model are both nonlinear and time-varying. To develop an insulin estimator (or filter), the authors use an aggregate model expansion of the nonlinear dynamics while treating the time-varying component of the model as an exogenous input. The aggregate model allows for the design of a particular nonlinear filter (or observer) that uses a weighted summation of constant feedback gains and admits a straightforward implementation. Furthermore, the aggregate modeling approach enables the stability analysis of the estimation error equation through linear matrix inequalities. The aggregate model insulin filter is compared with an existing insulin filter through numerical simulation.
Experimental Characterization of an EHD Ion-Drag Micropump for Cryogenic Micro-Pumping Applications
Authors: Foroughi P. , Dessiatoun S. , Shooshtari A. , Ohadi M. M.
Published: May 2009

This paper presents a study on the characterization of a planar multi-stage electrohydrodynamic (EHD) ion-drag micropump for pumping of liquid nitrogen. Four designs of the pump — consisting of different emitter configurations (planar and saw-tooth), emitter-collector spacings (20 and 50 microns), and gaps between successive electrode pairs (80, 100 and 200 microns) — were tested at DC voltages ranging from 0 to 2.5 kV. The generated electric currents and static pressure heads were measured to characterize the pumping performance. After collecting and processing the data for the various designs, it was evident that the purity of the liquid plays a vital role in the repeatability of the pumping results. In all cases high-purity liquid nitrogen was used. The complex interaction between the liquid and the electrodes along with the probabilistic nature of the ion-generation process sometimes prohibited achieving the same pumping performance under identical voltage levels, thus purity of the nitrogen used was very important. The highest pressure head (30 Pa at 1700 V) was generated with a (50,100,s) design. The (50,100,s) stands for saw-tooth emitters and planar collectors, 50 μm inter-electrode spacing, and 100 μm electrode-pair spacing.
On the Mechanics of Phonation and Fluid-Structure Interactions in a Three Dimensional Vocal Fold Model
Authors: Khandelwal Somesh , Siegmund Thomas , Frankel Steve H.
Published: May 2009

It is hypothesized that the characteristics of vocal fold self oscillation is dependent on the nonlinearity of the solid structure i.e. the tissue. Studies of fluid structure interaction are conducted for three dimensional larynx models. Simulations were performed using the codes FLUENT and ABAQUS coupled by the code MpCCI. For the air an unsteady, laminar flow model was considered. Visco-hyperelasticity was used to characterize the solid domain representing the tissue structure. The computational model is used to conduct a parametric study on the self-oscillation response of the model with focus on the influence of the non-linearity in the hyperelastic response. Individual computations were compared by documenting the variation of the total energy of the structure. It is demonstrated that dissipation in the flow as well as the non-linearity in the elastic response all interact to stabilize or destabilize the vibration amplitude.
A Discretization Approach to Modeling Capacitive MEMS Filters
Authors: Hammad Bashar K. , Nayfeh Ali H. , Abdel-Rahman Eihab
Published: May 2009

We present a reduced-order model and closed-form expressions describing the response of a micromechanical filter made up of two clamped-clamped microbeam capacitive resonators coupled by a weak microbeam. The model accounts for geometrical and electrical nonlinearities as well as the coupling between them. It is obtained by discretizing the distributed-parameter system using the Galerkin procedure. The basis functions are the linear undamped global mode shapes of the unactuated filter. Closed-form expressions for these mode shapes and the coressponding natural frequencies are obtained by formulating a boundary-value problem (BVP) that is composed of five equations and twenty boundary conditions. This problem is transformed into solving a system of twenty linear homogeneous algebraic equations for twenty constants and the natural frequencies. We predict the deflection and the voltage at which the static pull-in occurs by solving another boundary-value problem (BVP). We also solve an eigenvalue problem (EVP) to determine the two natural frequencies delineating the bandwidth of the actuated filter. Using the method of multiple scales, we determine four first-order nonlinear ODEs describing the amplitudes and phases of the modes. We found a good agreement between the results obtained using our model and the published experimental results. We found that the filter can be tuned to operate linearly for a wide range of input signal strengths by choosing a DC voltage that makes the effective nonlinearities vanish.
Multirate Estimation for the Machining Process Under Multirate Noise
Authors: Lee Cheol W.
Published: May 2009

Asynchronous measurement of process output characterizes a typical machining process in batch production. Various sensors are used for in-process measurement of process variables such as powers, forces, and vibration while the quality of parts and the tool conditions can be measured only by the postprocess inspection in most applications. The multirate scheme is being proposed as an efficient tool for integrating real-time sensor signals with postprocess inspection data for estimating immeasurable variables of the machining process. The machining process is subject to the process noise of varying frequencies including the within-cycle drift, cycle-to-cycle variation, and batch-to-batch variation. A multirate observer for simultaneous state and parameter estimation is built after the propagation of errors along a series of machining cycles is derived. Case studies with the grinding process demonstrate the efficacy of the developed algorithm.
A Portable Power Source Based on MEMS and Carbon Nanotubes
Authors: Hill Frances A. , Havel Timothy F. , Livermore Carol
Published: May 2009

The conceptual design for a portable power source that stores energy in the elastic deformation of carbon nanotubes is presented. The architecture of such a device is comprised of three main system-level components: a CNT-based spring, a generator, and a coupling mechanism between the spring and the generator. A simple model of one possible energy storage device is formulated as a tool to study the feasibility of such a system, the effect of scaling on power output, and the overall efficiency of the system. Energy is stored in a CNT bundle that is stretched in pure axial tension, and an escapement mechanism is used to control the rate of energy release from the system. The stored mechanical energy is converted to electrical energy with a piezoelectric generator. Simulations are run for systems of different size scales, which yield power outputs from 0.4 μW to 4 mW. The efficiency of converting the energy stored in the CNT-based spring to electrical energy approaches 15%. Results of the study show that operating frequency, efficiency, discharge time and power can be acceptable over a range of size scales, leaving some flexibility in the choice of overall size scale, but the high load resistances required to reach high output power favor larger scale systems.
Transient Analysis of a Ceramic High Temperature Heat Exchanger and Chemical Decomposer
Authors: Ponyavin Valery , Mohamed Taha , Trabia Mohamed , Chen Yitung , Hechanova Anthony E.
Published: May 2009

Ceramics are suitable for use in high temperature applications as well as corrosive environment. These characteristics were the reason behind selection silicone carbide for a high temperature heat exchanger and chemical decomposer, which is a part of the Sulphur-Iodine (SI) thermo-chemical cycle. The heat exchanger is expected to operate in the range of 950°C. The proposed design is manufactured using fused ceramic layers that allow creation of micro-channels with dimensions below one millimeter. A proper design of the heat exchanges requires considering possibilities of failure due to stresses under both steady state and transient conditions. Temperature gradients within the heat exchanger ceramic components induce thermal stresses that dominate other stresses. A three-dimensional computational model is developed to investigate the fluid flow, heat transfer and stresses in the decomposer. Temperature distribution in the solid is imported to finite element software and used with pressure loads for stress analysis. The stress results are used to calculate probability of failure based on Weibull failure criteria. Earlier analysis showed that stress results at steady state operating conditions are satisfactory. The focus of this paper is to consider stresses that are induced during transient scenarios. In particular, the cases of startup and shutdown of the heat exchanger are considered. The paper presents an evaluation of the stresses in these two cases.
Constitutive Relations of High Temperature Solders
Authors: Schoeller Harry , Bansal Shubhra , Knobloch Aaron , Shaddock David , Cho Junghyun
Published: May 2009

This study focuses on microelectronic package design for the oil and natural gas drilling of wells with depths in excess of 20,000 ft, where package temperatures can exceed 204°C. At these high temperatures, solder interconnect sites are subject to fatigue and creep failures due to the stress generated by the thermal expansion mismatch between various components in the package. Typically this phenomenon is modeled by finite element analysis (FEA) to predict the number of cycles to failure. To ensure meaningful model results, however, accurate time and temperature-dependent mechanical properties are needed. This study examines five solders suitable for high temperature: 90Pb-10Sn, 95Sn-5Sb, 92.5Pb-5Sn-2.5Ag, 95Pb-5In, and 93Pb-3Sn-2Ag-2In. Uniaxial tension tests of the solder wires are carried out on a MTS servohydraulic machine using wedge grips. To evaluate the time-dependence on deformation, a strain rate study was carried out at 0.5%/sec, 1%/sec, and 5%/sec. Nanoindentation of solder wire is performed and compared to the corresponding solder wires tested through uniaxial tension tests. Dynamic nanoindentation through continuous stiffness measurement is performed on the wires to obtain the indentation data less sensitive to creep of the material, as well as to assess the effect of indentation depth on elastic modulus for each solder. One purpose of nanoindentation testing is to determine its suitability for the mechanical testing of soft solders. Mechanical properties obtained from these tests will be used in future modeling studies to estimate the cyclic fatigue life of these solders under thermal loading.
Design and Fabrication of a Ligase Detection Reaction (LDR) Microchip With an Integrated Passive Micromixer
Authors: Lee Tae Yoon , Nikitopoulos Dimistris E. , Park Daniel S. , Soper Steven A. , Murphy Michael C.
Published: May 2009

The ligase detection reaction (LDR) is a technique that can distinguish low-abundant mutant DNAs from wild-type DNAs. LDR is usually carried out on DNAs amplified using the polymerase chain reaction (PCR). In the realization of modular microfluidic systems, the DNA output of the PCR handed off to the LDR chip needs to be mixed with LDR reagents before continuing the reaction. Polymer, continuous flow ligase detection reaction (CFLDR) devices with integrated passive micromixers, were designed, fabricated and tested. The devices each consisted of: a passive mixer for mixing a PCR sample, a cocktail of primers, and ligase, an enzyme of DNA; an incubator channel (95°C) for preheating the mixture; and a thermal cycling channel for the LDR. The devices were produced by hot embossing polycarbonate (PC) substrates with brass mold inserts manufactured by micro-milling. Experiments using food dyes showed that the appropriate mixture concentrations were delivered to the preheating channel in both the pulling and pushing modes.
Upper Limb Motion Profile During Small to Medium Time-Limited Reaching Tasks in a VR Based Robotic Training Environment
Authors: Xydas Evagoras G. , Louca Loucas S.
Published: May 2009

In the area of rehabilitation robotics, many researchers have investigated the therapeutic effects of forces that are proportional to the difference of the user’s hand trajectory with an optimum trajectory that is usually based on the Minimum Jerk Model (MJM). Forces applied in different studies were based on MJM trajectory variables, e.g., velocity, acceleration, position, etc. Consequently, MJM is a key component for upper limb robotic rehabilitation. However, it is critical to establish the validity of this model in the working environment prior of employing it as a reference control function. This work investigates the validity of the MJM under a haptic-virtual environment. The original ‘real’ tests (with no obstacles) that were employed for validating the MJM in planar motion are duplicated in a virtual environment. Haptic feedback is achieved with the use of a Phantom 1.5 High Force haptic interface. Experiments with healthy users are performed to investigate the validity of the MJM in virtual reality conditions. The experiments demonstrated that the MJM is also valid in virtual environments. Nevertheless it was found that in the virtual world, higher time durations are required for completing the tasks than in the real world. The results of this work will be used in the design of haptic-virtual environments for the rehabilitation of upper limbs of people with neuro-disabilities. Therapeutic forces based on the MJM can be applied given that the Minimum Jerk Model is valid in virtual environments.
Evaluating Pulse Jet Mixing With Non-Newtonian Slurries
Authors: Bamberger Judith Ann , Meyer Perry A. , Bontha Jagan R. , Fort James A. , Nigl Franz , Bates James M. , Enderlin Carl W. , Yokuda Sato T. , Kurath Dean E. , Poloski Adam P. , Smith Harry D. , Smith Gary L. , Gerber Mark A.
Published: May 2009

Pulse jet mixer technology has been selected for implementation in the Hanford Waste Treatment Plant. However, processing non-Newtonian fluids using this technology is not mature. Experiments were conducted at several scales to develop an understanding of the scaling mechanisms that govern this type of mixer performance.
AC Electrokinetics for Assay Enhancement
Authors: Sigurdson M. , Feldman H. , Meinhart C. D.
Published: May 2009

We have developed an AC electrokinetic microstirring technique, and have demonstrated its ability to accelerate diffusion-limited binding in a micro device by nearly an order of magnitude. Binding rates are increased by augmenting diffusive transport with microstirring generated through the application of an AC electric field. Numerical simulations suggest optimized microstirring devices may increase binding by a factor of 20.
Uncertainty Modeling of Residual Stress Development in Polymeric Composites Manufactured With Resin Transfer Molding Process
Authors: Hsiao Kuang-Ting
Published: May 2009

Resin Transfer Molding (RTM) is an advanced process to manufacture high quality thermoset polymeric composites. The quality of the composite depends on the resin infusion stage and the cure stage during the RTM process. The resin curing is a complex exothermic process which involves resin mechanical property evolution, resin volume shrinkage, thermal expansion, heat transfer, and chemical reaction. Since the fibers and resin have many differences in their physical properties, the composite cure stage inevitably introduces the undesired residual stress to the composite parts. As the residual stress could sometimes generate local matrix failure or degrade the performance of the composite, it is important to model and minimize the residual stress. This paper presents a model to predict the residual stress development during the composite cure process. By slightly disturbing the manufacturing parameters such as the mold heating cycle and the cure kinetics of polymer, the variations of residual stress development during the RTM process can be modeled and compared. A parametric uncertainty study of the residual stress development in the polymeric composite manufactured with RTM will be performed and discussed.
The Influence of Different Parameters of Remodeling Rule and Walking Speed on Resultant Density Distribution of the Proximal Femur
Authors: Marzban Ali , Nayeb-Hashemi Hamid , Canavan Paul K.
Published: May 2009

The process of adaptive bone remodeling can be described mathematically and simulated with a self-optimizing finite element method (FEM) model. The aim of this study was to understand the effect of the basic remodeling rule on the bone density distribution of the proximal femur affected by the muscle loadings and the hip joint contact forces during normal gait (walking). The basic remodeling rule, which is an objective function for an optimization process relative to external load, was applied to predict the bone density. The purpose of the process is to obtain a constant value for the strain energy per unit bone mass, by adapting density modeling. The precise solution is dependent on the magnitude and direction of loads, loading rate, initial conditions and the parameters in the remodeling rule. In this study, we applied adaptive bone density remodeling under both static and dynamic loading conditions. In the static case, the forces at different phases in the gait cycle were statically applied as boundary conditions. The density distributions from these loadings were averaged to find the density distribution in the proximal femur. Three different initial densities were considered to investigate the effect of initial conditions. The influence of different parameters and functions on the density distribution and its convergence rate was also investigated. Furthermore, effect of changing of muscle loading and hip joint contact forces on resultant mass and density distribution of proximal femur was studied. In the dynamic approach, the forces of different phases of gait cycle were applied during different gait cycle’s times of 1.27 second (slow speed), 1.11 second (normal speed), 1.01 second (moderately fast speed), and 0.83 second (very fast speed). Although the results of bone density adaptations in both approaches were comparable with an example of an actual bone density distribution of the femoral head, neck and the proximal femoral shaft; the converged density distribution in the static approach was smoother and more realistic. It was shown that by applying more loading conditions through the gait cycle the converged density distribution is smoother. The resultant density distribution was more comparable with actual proximal femur compared to past studies.
Introduction of New Concepts and Problem Solving in Engineering Dynamics
Authors: Abrate Serge
Published: May 2009

A survey of a large number of well-known textbooks for an undergraduate dynamics class showed that often new concepts are introduced without a clear connection to previously discussed material. For example, the concepts of work done by a force, linear momentum, angular momentum, and power are often introduced without a clear direct connection to Newton’s law. Similarly, in rigid body dynamics, important concepts such as the center of mass and the moments of inertia of the body are often introduced with little or no background. This article shows how all the important concepts in dynamics flow directly and logically from Newton’s laws. This is done through simple direct derivations. Connections are made clear by concept maps that help students understand how these different concepts are related. In addition to introducing new concepts and deriving some of the basic equations, a dynamics class should also introduce students to problem solving help them develop a systematic approach. This article describes a five step approach that is recommended for both high context and low context problems. In that context we stress that problem solving is a process that involves the application of known concepts and mathematics.
Tension Observers in Elastic Web Unwinder-Winder Systems
Authors: Gassmann Vincent , Knittel Dominique
Published: May 2009

All thin materials such as textiles, paper, polymers or metals are handled on rollers during their processing inside a plant or from a plant to another. This requires unwinding and winding the web a number of lines. Maintaining web tension in the entire processing line is key for achieving good final product quality. Estimators or observers, developed based on a system model, represent a cost-effective method in order to limit the number of load cells or dancers. After a summary of the fundamental laws used for system modeling, two different approaches to design tension observers are presented and discussed. The first approach is based on a linearized system model using a Kalman filter and the second one is based on the nonlinear model and uses the extended Kalman filter theory. Both approaches are analyzed and discussed with variations in friction torques and nominal set points of the web velocity and tension. The limitation of assuming negligible friction and inertia in the idler rolls are also discussed. Simulation results for different situations with the two approaches are shown and discussed.
Structural Optimization of a Dual-Sensing Module for Temperature and Pressure Measurement in Injection Mold Cavity
Authors: Fan Zhaoyan , Hamid M. Haris , Gao Robert X. , Johnston Stephen , Kazmer David
Published: May 2009

This paper presents the design and optimization of a temperature-pressure sensing module that is structurally integrated into an injection mold. The sensor extracts energy from the polymer melt pressure differential during the injection molding process and uses ultrasonic pulses as the wireless information transmission carrier. The dimension of the piezo ceramic rings that scavenge energy from the mold pressure change is optimized to minimize the volume of the sensor while maintaining the minimum Signal-to-Noise Ratio (SNR) required for reliable signal reception. An analytical expression of the optimal dimension is presented. Based on the optimized design, the sensor module package, together with the injection mold steel and the polymer melt that flows over the sensor into the mold cavity, was modeled using the finite element method. To quantify the behavior of polymer melt and its effect on sensors output, a coupled fluid-structure interaction analysis was performed to examine the mold-melt interface, by using the solution-looping and mesh-morphing techniques. A case study of the sensor design for a 40 mm thick injection mold was investigated by using the presented optimization method and FEA model. Results show that the volume of the piezo stack can be reduced to 0.7 cm3 while meeting the minimum SNR requirement. The minimum insulator thickness of 1 mm is presented by the FEA model to maintain the thermal induced error below 0.5%.
Image-Based Trajectory Estimation for Scanning Tunneling Microscopy
Authors: Clayton G. M. , Devasia S.
Published: May 2009

In this article we present an image-based approach to estimate the probe position trajectory in scanning tunneling microscopes (STMs). STMs are key enabling tools in the experimental investigation and manipulation of nano and sub-nano scale phenomena; however, due to an inability to measure the STM-probe position, typical STMs are limited to low bandwidth operations to ensure positioning accuracy. To overcome sensor deficiencies, thus enabling higher bandwidth STMs, an image-based method which produces discrete samples of the STM-tip trajectory has been developed. In this article we explore how the STM calibration sample and the output affect the reconstructability of the STM trajectory.
Shadow Edge Lithography for Wafer-Scale Nanofabrication
Authors: Bai John Guofeng , Chung Jae-Hyun
Published: May 2009

We propose shadow edge lithography (SEL) as a wafer-scale nanofabrication method. The shadow effect of “line-ofsight” in high-vacuum evaporation is analyzed theoretically to predict the geometric distributions of the fabricated nanoscale gaps. In the experiment, nanoscale gap patterns are created by the shadow of Al edges which are prepatterned using e-beam evaporation and the conventional ultraviolet lithography. Feasibility of the SEL is demonstrated by the fabrication of nanogaps having the width ranging from 15 to 100 nm on 4-inch Si wafers. Furthermore, by using the height differences in the prepatterned Al edges to compensate the geometric distributions of the shadow effect, it is demonstrated that the uniformity tolerance in the nanogap width can be ±1 nm or ±5% across the 4-inch Si wafers at a resolution down to 20 nm. The experimental results agree well with the theoretical prediction considering the virtual source during the e-beam evaporation. Upon the nanogap fabrication, arrays of nanochannels are obtained by reactive ion etching (RIE) using the evaporated Al layers as the etching mask. Our results show that that the evaporated Al layers can be used as the RIE mask to transfer the nanoscale patterns with a high yield and throughput. Thus, the SEL provides a robust method for wafer-scale fabrication especially for sub 50-nm structures.
A Biaxial Shape Memory Alloy Actuated Cell/Tissue Stretching System
Authors: Shan Yingfeng , Dodson Jacob , Abraham Sheena , Speich John E. , Rao Raj , Leang Kam K.
Published: May 2009

In this article, we describe the design of a shape memory alloy-based system to stretch cells cultured on top of a flexible membrane in multi-directions (longitudinal and transverse). Mechanical cues (such as strain and force) can affect the state and behavior of cells, such as, morphology, the differentiation process, and apoptosis. Therefore, a thorough understanding of the effects of mechanical perturbations on cells/tissues will have a deep impact in the biological sciences. The proposed design allows application of anisotropic (multi-axial) strain with high-precision. Certain cells, for example endothelial cells that line the inside of blood vessels, experience multi-axial (circumferential and longitudinal) stresses and strains. A cell stretching device that enables controlled application of biaxial strain will allow for systematic and accurate studies of the effects of externally applied mechanical perturbation throughout the cell, tissue, or organ. A preliminary design is proposed that exploits the strain recovery property of the shape memory alloy (SMA) actuators. We describe the design of the mechanical system and show experimental results to demonstrate stretching of a thin PDMS membrane in the longitudinal and transverse directions. To account for the inherent nonlinearity of the SMA, a feedback controller is implemented to achieve high-precision control of the stretching process. Additionally, the design can be integrated with an atomic force microscope (AFM) for high spatial and temporal resolution studies.
Interactive Video Professor
Authors: Moslehpour Saeid , Smith James , Campana Claudio
Published: May 2009

The goal of this project is to introduce the importance of multimedia instructions in the classroom. By having multimedia instructions, students will be able to have a well rounded and enhanced learning experience. This is demonstrated by use on video accompaniment. The result of this project was to produce videos of each individual subject and highlight the main pints of each topic and detail from a student’s point of view. This is beneficial to the student with learning problems in the classroom setting. These videos are packaged on an easy user interface designed with Camtasia 4.0 menu maker application software and are very user friendly. The videos are designed so that one will see the instructor interact with the Microsoft PowerPoint slideshow presentation and verbalize to the viewing public the important facts of each topic. Digital Electronics with VHDL text book authored by William Kleitz has been the main focus of this technique.
Mobile Robot Design in an Introductory Engineering Course
Authors: Mauer Georg F.
Published: May 2009

The course ‘Introduction to Engineering Design’ is aimed at freshmen students entering Mechanical and Aerospace engineering. The course was restructured from its previous 3-credit lecture format to a 2 credit lecture coupled with a new 1 credit design laboratory. The laboratory project aims at giving the students experience in professional design, engineering practice, and teamwork. While the lecture presents an overview of the engineering profession and its practices, small student teams conduct a structured hands-on design project in the lab. The team assignment is the design, programming, and testing of autonomous mobile ‘Sumo’ robots. Each team develops and builds an autonomous robot, which will compete against the other teams’ robots at the end of the semester. Students find the robot project highly motivating and spend voluntarily several afternoons weekly working in the lab. Student enrollment has increased more than five-fold since course inception six years ago. The course is also being taught regularly to seniors at local high schools through distance education, further broadening the pool of future engineering students. The paper describes the lab course structure, organization, and student learning outcomes.
A Novel Periodic Boundary Condition Treatment in Electrodynamics Wave Interaction With Small Structures
Authors: Fu Kang , Hsu Pei-Feng
Published: May 2009

In the numerical study of the radiative properties of micro- and nano-structure devices, for example, the random roughness surfaces, grating surfaces, periodic photonic devices, the periodic boundary condition are frequently used to simulate device size much larger than the incident wavelength. Existing methods in handling the periodic boundary condition in the solution of the Maxwell’s equations are too limiting. A novel method is developed to efficiently treat such boundary conditions. The concept is not limited to any particular solution method of the Maxwell’s equations. The salient feature is to convert the phase difference between the corresponding boundaries from the time domain to frequency domain using a phasor diagram approach. The resulting electromagnetic field vector component equations at the boundaries are successfully tested in a finite-difference time-domain code at large angle of incidence, up to 80°, on a finite length, flat, and dielectric surface. The computed reflectivity is in good agreement with the analytical value calculated by Fresnel reflectivity.
Experimental and Finite Element Analysis of Stand-Off Layer Damping Treatments for Beams
Authors: Yellin Jessica M. H. , Shen I. Y. , Reinhall Per G.
Published: May 2009

Passive stand-off layer (PSOL) and slotted stand-off layer (SSOL) damping treatments are presently being implemented in many commercial and defense designs. In a PSOL damping treatment, a stand-off or spacer layer is added to a conventional passive constrained layer damping treatment. In an SSOL damping treatment, slots are included in the stand-off layer. A set of experiments using PSOL and SSOL beams in which the geometric properties of the stand-off layer were varied was conducted to analyze the contribution of the stand-off layer to the overall system damping. This set of experiments measured the frequency response functions for a series of beams in which the total slotted area of the stand-off layer was held constant while the number of slots in the stand-off layer was increased for a constant stand-off layer material. Finite element analysis models were developed in ANSYS to compare the predicted frequency response functions with the experimentally measured frequency response functions for the beams treated with PSOL and SSOL damping treatments. In these beams, the bonding layers used to fabricate these treatments were found to have a measurable and significant effect on the frequency response of the structure. The finite element model presented here thus included an epoxy layer between the base beam and the stand-off layer, a contact cement layer between the stand-off layer and the viscoelastic layer, and a method for modeling delamination.