bluuebunny/crossref_metadata_2025 huggingface dataset:
Integration and Application of a Surface Plasmon Sensor Array On-Chip
Authors: De Leebeeck Angela , Kumar L. Kiran Swaroop , Brolo Alexandre G. , Gordon Reuven , Sinton David
Published: April 2008

A microfluidic device with an embedded surface plasmon resonance (SPR) sensor array was developed. The sensing elements were nanohole arrays, differentiated by periodicity. The device was applied to detection of concentration across a gradient, and the detection of surface binding events. To determine sensitivity and for the gradient-based detection experiments, glucose solutions of known refractive index were employed. Consecutive surface binding events were monitored in the flow-through assembly of a monolayer (cysteamine) with a linker (biotin) and a protein (streptavidin).
Energy Recovery Proposals in an Ammonia/Water System for Power/Refrigeration Cogeneration
Authors: Liu Meng , Zhang Na
Published: April 2008

The authors proposed an ammonia-water cycle for power and refrigeration cogeneration which employs a splitting and absorption unit to adjust the desired solution concentrations. Energy efficiency and exergy efficiency of this cycle are found to be 27.3% and 57.6%, respectively, at the cycle highest heat addition conditions of 450°C /111bar. Nevertheless, a large exergy destruction takes place in the heat transfer and throttling process of this cycle. In this paper, three proposals are investigated to recover the energy of the heat transfer and throttling process. The weak ammonia/water solution is superheated by internal heat recovery, and then its energy is converted into useful outputs by: 1) sending the superheated ammonia-weak stream into the turbine, and the energy is directly converted into the power output: 2) and 3) introducing an ejector to the cycle, the superheated stream is used as the primary stream, the turbine exhaust and the evaporator outlet stream are used as the secondary stream, respectively, the energy is indirectly convert into power or refrigeration output. Simulations show that the three proposals enable the increments of 2.9%, 0.8% and 0.7%, respectively, in the exergy efficiency over the base cycle. Obviously, the first proposal has superiority in term of the thermal performance, while the latter two proposals have some advantages in respect of the operation, maintenance and capital costs.
Nanopore Sensors for Ultra-Fast DNA Analysis
Authors: Kim Min Jun , Wanunu Meni , Soni Gautam , Meller Amit
Published: April 2008

We have developed novel approaches for ultra-fast DNA analysis by measuring of an ionic current blockage and parallel optical readout of DNA translocation through single nanopores and nanopore arrays. Parallelism is achieved by the fabrication of high density solid-state arrays of single nanometer resolution pores and simultaneous optical readout of DNA translocation. Optical readout in arrays circumvents the direct electrical addressing of each pore. We will present new nanofabrication techniques to create nanoscale pores in 50 nm thick silicon nitride membrane using transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) and discuss our progress towards ultra-fast DNA sequencing.
Thermocapillary Convection of Low Prandtl Number Fluid in a Shallow Cylindrical Pool
Authors: Ling Fang , Li You-Rong , Lan Peng , Wu Shuang-Ying , Chen Qing-Hua
Published: April 2008

In order to understand the characteristics of thermocapillary convection, we conducted a series of unsteady three-dimensional numerical simulations of thermocapillary convection of low Prandtl number fluid in a shallow cylindrical pool with an azimuthal nonuniform temperature, an adiabatic solid bottom and free surface. The simulation results indicate that thermocapillary convection is steady three-dimensional flow at the small Marangoni number. But when Marangoni number exceeds some critical value, the flow will undergo a transition to oscillatory three-dimensional flow. The critical conditions for the onset of oscillatory flow are determined. Details of the flow and temperature fields are discussed, and oscillation frequencies are also exhibited.
Contact Mechanics of a Hard Cylinder on a Viscoelastic Layer
Authors: Barrett Steven R. H. , Slocum Alexander H.
Published: April 2008

The rolling/sliding contact of a hard cylinder on a viscoelastic layer is re-examined. The one-dimensional Maxwell model, with the addition of a parallel spring, is used to model the normal stiffness of the viscoelastic layer A solution for the pressure distribution is presented. It is shown that the maximum tractive force that the cylinder can sustain before complete sliding is a function of the sense and magnitude of the rolling velocity. Two regimes of loading are considered - constant cylinder normal force and constant cylinder indentation.
Study of the Influence of Surface Mold Deposits on the Demolding Stage of the Injection Molding Process of Thermoplastics
Authors: Chailly Mikae¨l , Gilbert Vincent , Charmeau Jean-Yves , Bereaux Yves
Published: April 2008

Due to increasing expectings from the market, the aspect of molded parts has to be improved. Some of the defects observed such as scratches on these parts is related to the demolding stage. To limit this, we investigated the influence on demolding forces using various surface deposits on the mold surface, mainly PVD and PACVD deposits : Chromium nitrium (CrN), Titane nitrium (TiN), Diamond like Carbon (DLC), glassy deposit (SiOx), Chromium and polished steel on an cube-shaped insert in an instrumented mold (with force sensors). Injection campaign was led on three polymers which differ in terms of nature : an amorphous polymer (polycarbonate), a semi-crystalline one (polybutylene terephatalate) and one mix of copolymers (styrene acrylonitrile/ acrylonitrile butadiene styrene). We studied the evolution of these forces through the demolding stage. This allowed us to evaluate the work energy necessary to eject the part from the insert, and to correlate those data to shrinkage of the polymer part, adhesion between polymer and mold surface and friction coefficient between those surfaces during the demolding stage. We also measured the influence the surface temperature of the part just before the demolding stage thanks to an infrared camera to investigate the thermal influence of these deposits in the injection process. Our results show an influence of deposits on demolding forces which is strongly dependent on nature of the polymer (of course) but also on its chemical nature. They also have a slight influence on temperature of the part even if they are only a few microns thick. We therefore developped a method to evaluate surface deposits and their impact on demolding forces, in terms of adhesion polymer/treament and friction.
CFD Simulation of Flow Tones From Grazing Flow Past a Deep Cavity
Authors: Bagwell Ted G.
Published: April 2008

Locked-in flow tones due to shear flow over a deep cavity are investigated using Large Eddy Simulation (LES). An isentropic from of the compressible Navier-Stokes equations (pseudo-compressibility) is used to couple the vertical flow over the cavity mouth with the deep cavity resonances (1). Comparisons to published experimental data (2) show that the pseudo-compressible LES formulation is capable of predicting the feedforward excitation of the deep cavity resonator, as well as the feedback process from the resonator to the flow source. By systematically increasing the resonator damping level, it is shown that strong lock-in results in a more organized shear layer than is observed for the locked-out flow state. By comparison, weak interactions (non-locked-in) produce no change in the shear layer characteristics. This supports the 40 dB definition of lock-in defined in the experiment.
A Study of Non-Equilibrium Two-Phase Pressure Drop in Converging Channels Supplied With Atomized Liquid
Authors: Schwarzkopf J. D. , Crowe C. T. , Li B. Q.
Published: April 2008

Two-phase pressure drop measurements are very difficult to make while the fluid is in non-equilibrium condition (i.e. while phase change is occurring). This is further complicated by the fact that supplying the channels with an initial quality comprised of atomized liquid and entrained gas changes the presupposed trends. The purpose of this paper is to present methods of measurement for fluctuating two-phase pressure drop in converging mini-channels with phase change (i.e. in the heat acquisition zone), an initial quality, and varying heat fluxes. The inlet and exit hydraulic diameters of the converging channel are 1.55mm and 1.17mm respectively and the fluid was PF5050. A numerical model was developed to understand the parameters contributing to the trends identified in the data. The numerical model includes the momentum effects of droplets from entrainment and atomization. The model shows good agreement with the experimental data.
Synchronization of Chaotic Systems Using Variable Structure Controllers
Authors: Salarieh Hassan , Alasty Aria
Published: April 2008

In this paper a variable structure system based upon sliding mode control with time varying sliding surface and variable boundary layer is introduced to synchronize two different chaotic systems with uncertain parameters. The method is applied to Lur'e-Genesio chaotic systems, as drive-response systems to investigate the effectiveness and robustness of the controlling method. In addition the simulation is repeated with a conventional sliding mode to compare the performance of the proposed sliding mode technique with a simple sliding mode control. The results show the high quality and improved performance of the method presented in the paper for synchronization of different drive-response chaotic systems.
Flammability Resistance Properties of Epoxy Nanocomposites
Authors: Ibeh Christopher C. , Bubacz Monika , Bietto Stefano
Published: April 2008

Current aerospace and naval applications require blast and flammability resistance characteristics. Materials and formulations with flammability resistance properties are most suitable in these type applications since fire and smoke toxicity are inherently associated with blast situations. In this effort, VAHLUP fabricated epoxy nanocomposites are evaluated and characterized for flammability resistance properties such as effective heat of combustion, ignition time, rate of mass loss, rate of heat release and smoke density. The effects of nanoparticles on the mechanical properties of epoxy nanocomposites are also evaluated. Uncoated polyaramid papers (Kevlar, Nomex with heat release rates of 0.18, 0.175 MJ/m2 respectively) exhibit better flammability resistance properties than resin/nanocomposites coated polyaramid papers. VAHLUP fabricated epoxy nanocomposites exhibit better flammability resistance properties than cast epoxy nanocomposites. Kapton, polyimide film with ignition time of 90 seconds+] give the best overall flammability resistance properties. Mechanical properties of epoxy nanocomposites are enhanced by processing. The preliminary data of the influence of the post-curing protocol tend to suggest the 2.0% nanoclay level as the optimal clay content level with respect to mechanical properties.
Effect of Nitrogen and Oxygen Concentration on NOx Emissions in an Aluminum Furnace
Authors: Golchert Brian , Ridenour Paul , Walker William , Selvarasu Naresh K. , Gu Mingyan , Zhou Chenn Q.
Published: April 2008

For many aluminum melting furnaces, natural gas is mixed with air. The ensuing heat from combustion is then used to melt the solid aluminum and heat the liquid metal. Of increasing concern to the industry are the more stringent regulations in regard to NOx emissions from these plants. The formation of NOx mainly depends on the concentration of nitrogen and the temperature of the gas. One problem that affects this formation that has not been adequately addressed is the variability of the local natural gas supply. Natural gas has molecular nitrogen as a portion of its composition. This percentage ranges from approximately one to seven percent of the total mass fraction. In addition, the aluminum industry is investigating methods to reduce NOx emissions. One method is to replace some of the combustion air with pure oxygen. This reduces the amount of nitrogen coming into the furnace, but also raises the combustion temperature which could promote NOx production. This paper details a systematic computational fluid dynamics study on how the variability of the nitrogen concentration coupled with the partial replacement of air with pure oxygen affects heat transfer and pollutant formation in an aluminum furnace. Trends will be discussed as will the ideal oxygen concentration for a given nitrogen mass fraction.
The Effect of Salinity on In-Situ Generated CO2 Gas: Simulations and Experiments
Authors: Coskun Onur , Grigg Reid , Svec Robert , Bakhtiyarov Sayavur I. , Siginer Dennis
Published: April 2008

Carbon dioxide (CO2) injection has been used as a commercial process for enhanced oil recovery (EOR) since the 1970's. Recently, a new in-situ CO2 gas generation technology has been developed but not well studied. We conducted experiments to observe the dynamics of the system with different temperatures, injection sequences of chemical agents, chemical additives, and behavior of CO2 generation with respect to these varying factors and comparison of the actual CO2 pressure with the calculated values. Experiments on generation of CO2 gas as a result of reactions of gas forming and gas yielding solutions were carried out. It is shown that the injection sequence of the chemicals affects the reaction characteristics, but the total amount of CO2 gas generated does not vary significantly. Regardless of the injected solution (either gas forming or gas yielding) the maximum attainable pressures are less than the calculated pressures as a result of chemical equilibrium in the system; so this difference should be considered while calculating the size of the slug in the field applications. The brine concentration has an impact on CO2 solubility in water and so on CO2 pressure. Because of this impact, brine concentration of formation water should be considered in addition to the brine which is introduced to the system by the reaction.
Self-Sensing of Stresses and Strains Through the Dielectrostriction Effect in Composites
Authors: Lee Ho Young , Shkel Yuri M.
Published: April 2008

Any dielectric material would vary its dielectric properties with deformation. By measuring these variations one could monitor stresses or strains with no mechanical interface with a load-bearing member. This effect, called dielectrostriction, can be formulated as a linear relation between the stress/strain and the dielectric response of a material. A planar capacitor on a rigid substrate is utilized to monitor the dielectrostriction effect. A rosette of such sensors can be located on the surface or embedded in the monitored part. A four-sensor rosette measures principal directions and difference of principal strains. Overall, this sensing technology shows a good potential for Non-Destructive Evaluation (NDE) and structural health monitoring of composite materials. This work provides theoretical background and experimental study of dielectrostriction response in polycarbonate, polyethylene, acrylic, and carbon nanotube composite materials.
Size and Piezoelectric Effects on Optical Properties of Self-Assembled InGaAs/GaAs Quantum Dots
Authors: Kuo M. K. , Lin T. R. , Hong K. B.
Published: April 2008

Size effects on optical properties of self-assembled quantum dots are analyzed based on the theories of linear elasticity and of strain-dependent k-p with the aid of finite element analysis. The quantum dot is made of InGaAs with truncated pyramidal shape on GaAs substrate. The three-dimensional steady-state effective-mass Schro¨dinger equation is adopted to find confined energy levels as well as wave functions both for electrons and holes of the quantum-dot nanostructures. Strain-induced as well as piezoelectric effects are taken into account in the carrier confinement potential of Schro¨dinger equation. The optical transition energies of quantum dots, computed from confined energy levels for electrons and holes, are significantly different for several quantum dots with distinct sizes. It is found that for QDs with the the larger the volume of QD is, the smaller the values of the optical transition energy. Piezoelectric effect, on the other hand, splits the p-like degeneracy for the electron first excited state about 1~7 meV, and leads to anisotropy on the wave function.
In-Situ Failure Identification in Woven Composites Throughout Impact
Authors: Pearson James , Prabhugoud Mohanraj , Zikry Mohammed , Peters Kara
Published: April 2008

In this study, measurements form low-impact velocity experiments including embedded and surface mounted optical fiber Bragg grating (FBG) sensors were used to obtain detailed information pertaining to damage progression in two-dimensional laminate woven composites. The woven composites were subjected to multiple strikes at 2m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces. The FBG sensors were embedded and surface mounted at different critical locations near penetration-induced damaged regions. These FBG sensors were used to obtain initial residual strains and axial and transverse strains that correspond to matrix cracking and delamination. The transmission and reflection spectra were continuously monitored throughout the loading cycles. They were used, in combination with the peak contact forces, to delineate repeatable sensor responses corresponding to material failure. From the FBG spectra, fiber and matrix damage were separated by an analysis based on signal intensity and the behavior of individual Bragg peaks as a function of evolving and repeated impact loads. This provided independent feedback on the integrity of the Bragg gratings which can serve to eliminate errors in the strain data such as due to sensor debonding or fracture. The critical indicators present in the sensor spectra for the mapping of these sensor failure modes are derived.
Fracture Toughness of Space Shuttle Foam
Authors: Ganpatye Atul S. , Kinra Vikram K.
Published: April 2008

Fracture toughness of the rigid, low-density, closed-cell, polyurethane, foam used for insulation on the Space Shuttle External Tank is investigated. Data were obtained by loading double-edge-notched specimens in tension. To account for the anisotropic nature of the foam, two types, of specimens were tested so as to represent fracture properties along two different material directions. Additionally, for each type of specimen, two different notch sizes were tested.
Setting Performance Targets Based on Subsystem Pareto Frontiers in Multilevel Optimization
Authors: Liu Huibin , Hoyle Christopher , Yin Xiaolei , Chen Wei
Published: April 2008

The design of a complex engineering system typically involves tradeoffs among multiple design criteria or disciplinary performance to achieve the optimal design. The design process is usually an iterative procedure with individual discipline sub-systems designed concurrently to meet target values assigned from the system level. One of the most challenging issues is the large number of iterations in this design process, especially when uncertainty is taken into account. To improve the design concurrency while maintaining preferred tradeoffs at the system level, a new method is developed that identifies proper targets based on disciplinary design capability information while optimizing the design goal at the system level. The design capability of a discipline or criterion is represented by the achievable area bounded by its Pareto frontier. Using target values obtained from this method using Pareto information, the number of design iterations can be reduced in both deterministic and probabilistic design scenarios compared to existing approaches, such as Analytical Target Cascading (ATC). To demonstrate applications and benefits of the developed method this approach is applied to the design of a two-bar truss structure.
Steady Shear and Linear Viscoelastic Properties of Melt Mixed and Injection Molded Samples of Polypropylene, Polystyrene, and Polyethylene Nanocomposites With Carbon Black, Vapor Grown Carbon Fibers, and Carbon Nanotubes
Authors: Kujawski Mark P. , Rakesh Leela , Hirschi Stanley , Falhman Brad D. , Finegan Joana C. , Almeida Ekmagage Don N. , Bullard Nicole M. , Hiller Jason , Lalko Michael P. , Miller Jeremy V.
Published: April 2008

Tailoring the rheological properties of polymers is important for practical applications such as the stabilization of polymer emulsions, blends, and foams. Nanomaterial (i.e. Carbon Nanotubes, Carbon Nanofibers, Dendrimers, and Carbon Black) are an excellent way to modify the mechanical, thermal, electrical, and optical properties of materials. This paper presents steady shear and linear viscoelastic oscillation testing of three polymers: Polyethylene (PE); Polypropylene (PP); and Polystyrene (PS). These polymers were studied in bulk form and as composites containing designated volume fractions of nanomaterials over a range of processing temperatures and conditions. The nanomaterials investigated in this study include Carbon Black, Vapor Grown Carbon Nanofibers, Multiwalled Carbon Nanotubes, Single Walled Carbon Nanotubes, and COOH functionalized Single Walled Carbon Nanotubes. The nanocomposite samples used for rheological experimentation were manufactured by melt mixing and injection molding. We will address whether the melt rheological measurements can unequivocally detect the co-continuous composition range in such systems. We will also investigate the melt flow rate through nanomaterial concentration variations, as well as discuss the storage modulus (G'), viscous modulus (G"), and complex viscosity of homogeneous polymer materials versus carbon nanocomposite material at various frequencies.
Distributed Actuation and Shape Control of Ionic Polymer Metal Composites
Authors: Knight Bryce M. , Schoen Marco P. , Perez-Gracia Alba
Published: April 2008

Ionic polymer metal composites (IPMC) present great potential as future actuators and sensors in a variety of fields including aerospace and biomedical engineering. The benefits of using IPMCs are based on the material's large bending deformation capabilities, low power consumption, light weight and compact size. However, before this novel material can be exploited, a better understanding of its electromechanical properties and a higher level of controllability must be obtained. This paper presents the results of experimental research with these goals in mind. The actuation of these electro active polymers is achieved by using geometrically defined actuation points on the polymer's surface. The input voltage is spatially controlled to achieve faster response times as well as increased control of the shape of the polymer's surface. The experimental work is carried out under a constant humidity and uses vision based sensing to detect the various shapes generated by these electro active polymers. The experimental outcomes are compared against a dynamical model. The results demonstrate the ability for increased control of the shape generated by the surface. A good match of the dynamical model to predict the displacement of the polymer at instances in time is found. In addition, the proposed approach improves the response time of an IPMC through the application of distributed voltage sources over the surface of the material.
Design and Characterization of Micropost-Filled Reactor to Minimize Pressure Drop While Maximizing Surface-Area-to-Volume-Ratio
Authors: Yeom J. , Han J.-H. , Bae B. , Shannon M. A. , Masel R. I.
Published: April 2008

Micropost-filled reactors are commonly found in many micro total analysis system applications because of their high surface area for the surrounding volume. Design rules for micropost-filled reactors are presented here to optimize the performance of the micro-preconcentrator, which is a component of a micro gas chromatography system. The dimensionless figure of merit is proposed to be used to minimize the pressure drop while maximizing the surface-area-to-volume-ratio for a given overall channel geometry of the micropost-filled preconcentrator. Two independent models from the literature are used to predict the pressure drop across the micropost-filled channels for low Reynolds number flows. The pressure drop can be expressed solely as a function of a design parameter, β = a/s, a ratio of a radius of each post and a half-spacing between two adjacent posts. Pressure drop measurements are performed to experimentally corroborate the pressure drop model and the optimization using the dimensionless figure of merit. As the number of microposts; for a given β increases in a given channel size, a greater surface-area-to-volume-ratio will occur for a fixed pressure drop. Therefore, increasing the arrays of posts with smaller diameters and spacing will optimize the microreactor for higher surface area for a given flow resistance, at least until Knudsen flow begins to dominate.
Design and Validation of New Exhaust Manifold for 3.8 L Turbocharged-Intercooled Diesel Engine
Authors: Gaikwad Tejsing A.
Published: April 2008

Few Engine Layout and Performance related concerns made way for design and development of new Exhaust Manifold (EM). New EM is designed using 5th degree Polynomial Profile Design (PPD) technology. Existing EM is tested to measure various parameters such as flow pattern, pressure drop across manifold and on skins temperature mappings. Two approaches were studied to validate new EM on the basis of results obtained by CFD and Thermal Analysis as follows, 1. Comparative Method. 2. Experimental Method. The paper aims at presenting the above design and validation approaches for upcoming EM designs.
Undergraduate Renewable Energy Projects to Support Energy Solutions of the Future
Authors: Cooper Heather L.
Published: April 2008

Motivated by energy security requirements and the desire to create a sustainable and safe environment, there is a growing need to transition gradually from fossil fuels toward new and emerging energy sources. The energy solutions of the future will require a significant amount of research and development, as well as increased awareness and acceptance of new and emerging energy technologies. Creating a highly educated workforce who will contribute to overcoming future energy challenges is a key component in bringing about this transition. One method of supporting workforce development in future energy solutions is to incorporate new and emerging energy technology directly into required undergraduate coursework. To this end, renewable energy projects were developed and implemented in a required introductory thermal science course in a mechanical engineering technology curriculum. The goal of the projects was to provide students with a deeper understanding of the need for, the advantages of, and the difficulties associated with renewable energy sources. The open-ended semester-long student projects included (1) research on the history and implementation of a renewable energy source, (2) development of an experimental application of the energy source in an energy conversion process, and (3) an economic analysis of the energy source in an assumed application or case study. This paper presents the design and development of these renewable energy projects, and informal and formal evaluation of the effectiveness of the projects over two years of classroom implementation. In addition, the link between the projects and select accreditation criteria for engineering technology programs is discussed.
Information-Theoretic Sensor Subset Selection: Application to Signal-Based Fault Isolation in Diesel Engines
Authors: Joshi Alok A. , Meckl Peter H. , King Galen B. , Jennings Kristofer
Published: April 2008

In this paper a stepwise information-theoretic feature selector is designed and implemented to reduce the dimension of a data set without losing pertinent information. The effectiveness of the proposed feature selector is demonstrated by selecting features from forty three variables monitored on a set of heavy duty diesel engines and then using this feature space for classification of faults in these engines. Using a cross-validation technique, the effects of various classification methods (linear regression, quadratic discriminants, probabilistic neural networks, and support vector machines) and feature selection methods (regression subset selection, RV-based selection by simulated annealing, and information-theoretic selection) are compared based on the percentage misclassification. The information-theoretic feature selector combined with the probabilistic neural network achieved an average classification accuracy of 90%, which was the best performance of any combination of classifiers and feature selectors under consideration.
Tracking Controller for a Piezoworm™ Stage
Authors: Salisbury Shaun P. , Waechter David F. , Ben Mrad Ridha , Prasad S. Eswar , Blacow Richard G. , Yan Bin
Published: April 2008

In this paper, a closed-loop tracking controller is described that expands the application of the piezoworm stage. A dynamic model of the piezoworm is presented complete with a rule-based friction model to accurately capture the clamp behavior. This dynamic model is used to assess different closed loop controllers for tracking performance. It is determined that a PID controller would offer good performance when the motor is subject to step and sinusoidal signals and state feedback control did not lead to improved performance when compared to the PID performance.
Structural Health Monitoring of Rotordynamic Systems by Wavelet Analysis
Authors: Mani Girindra , Quinn D. Dane , Kasarda Mary E. F.
Published: April 2008

This work describes a foundation of sophisticated diagnostic techniques for the detection of shaft cracks in rotordynamic systems, considering the dynamical behavior of a rotating cracked shaft under the application of external loads. The response is modeled as a modified Jeffcott rotor, while the crack is assumed to induce a time-varying stiffness in the model. The focus of this work is the development of external loading strategies to create damage sensitive measures of vibration response and then analyze that using advanced technologies such as wavelet analysis. This will enable the detection of the crack depth, as represented by the magnitude of the damage-induced time-varying stiffness, from vibration measurements. This entails developing external forcing functions for which features of the vibration response are sensitive to the presence of the damage. The development of such inputs is based on a multiple-scales analysis of the full equations of motion, including the time-varying stiffness. From this, a resonance (called combination resonance) is identified between the operating speed of the shaft, the fundamental frequency of the shaft, and the frequency of the external forcing. When the system is operated at this resonant condition, the translational vibrations of the shaft contain a spectral component near the fundamental shaft frequency that is proportional to the amplitude of the time-varying stiffness. The resonance bandwidth, obtained from this analysis, enables us to build a framework for the development of damage detection techniques for rotating machinery. Continuous Wavelet Transform (CWT) is applied to the vibration response of a rotordynamic system that utilizes harmonic forcing satisfying combination resonance. The variation of wavelet coefficients with respect to the variation of different system parameters is examined. Attention is focused on how the resonant bandwidth affects the variation of wavelet coefficients as crack grows.
Stability Control by Advanced Full-Braking Systems of Motorbike Vehicles
Authors: Hirsch Markus , Alberer Daniel , del Re Luigi
Published: April 2008

The continuously increasing traffic in European urban areas is rapidly stimulating the diffusion of 2-wheeled vehicles in spite of their higher accident risk. This increased risk is due to a large extent to the natural stability limitations of two-wheel vehicles, in particular the loss of the cornering force in curves has a much more dramatic effect as, for instance, in 4-wheel vehicles. This happens for instance during an exaggerated braking action in curves, so that ABS strategy may not simply concentrate on avoiding blocking the wheel but must also avoid overshoots which may lead to a transient, but very dangerous, loss of cornering force. Against this background, this paper proposes a curve safe ABS strategy for motorcycles which is based on three elements: a sensor extension, a tilt angle estimator and a cautious ABS control which takes into account the probable limit and limits the switching operation to a very small region in order to avoid a loss of cornering force. The strategy is developed using a software simulator in Matlab/Simulink tuned on measurements of a KTM Adventure 950 motorcycle.
Differential Mobility Spectrometry Applications in Homeland Security, Clinical Diagnostics and Drug Discovery
Authors: Morgan Joshua , Davis Cristina
Published: April 2008

There is an urgent need for miniaturized sensors that can rapidly, accurately, and specifically detect extremely low concentrations of chemical and biological materials. Such technologies impact many areas including public health, drug development and national defense. Along with other research groups in industry and academia, we are developing new microfabricated sensors based on differential mobility spectrometry - also known as high field asymmetric ion mobility spectrometry. These sensors are suitable for rapid diagnosis of various pulmonary diseases and respiratory pathogens, and they may also be used for explosives and narcotics detection when configured and tuned to detect different chemical signatures. Similarly, we are also applying variations on this technology for the early detection of biological weapons agents. Given the extensive work being performed by many different research groups in many different specialties, there is now a need for a coherent and exhaustive look at the similarities and differences of detection in medical, pharmaceutical, defense and security applications and how these may influence system level designs.
Advanced Thermal Management for Fuel Cell and Automotive Applications
Authors: Muley Arun , Borghese Joseph B. , Myott Robert P. , Kiser Carl , Shah Ramesh K.
Published: April 2008

Thermal management (TM) for fuel cell and advanced automotive applications plays a critical role in overall system performance and is quite complex and challenging. Compact, cost-effective, high performance and lightweight heat exchangers are needed to meet high heat flux removal requirements associated with these systems [1]. Innovative heat transfer enhancement techniques such as, microchannel, metallic foam and advanced platefin surfaces are being considered for development of next generation of heat exchangers that will meet these challenging demands [2-3]. These challenging demands are seen in radiators of fuel cell powered passenger vehicles and for commercial transportation applications. The upcoming 2010 off-highway emissions are also driving the need for much improved performance in charge air coolers and exhaust gas coolers [4]. The overall objective of this study is to present the current state-of-the-art and advances anticipated in the next generation heat exchanger technology.
Characterization of Tissue Scaffolds Fabricated by Rapid Prototyping Techniques Aided by Finite Element Analysis
Authors: Thoreson Andrew R. , Stone James J. , Langner Kurtis L. , Norton Jay , Jang Bor Z.
Published: April 2008

Numerous techniques for fabricating tissue engineering scaffolds have been proposed by researchers covering many disciplines. While literature regarding properties and efficacy of scaffolds having a single set of design parameters is abundant, characterization studies of scaffold structures encompassing a wide range of design parameters are limited. A Precision Extrusion Deposition (PED) system was developed for fabricating poly-ε-caprolactone (PCL) tissue scaffolds having interconnected pores suitable for cartilage regeneration. Scaffold structures fabricated with three-dimensional printing methods are periodic and are readily modeled using Computer Aided Design (CAD) software. Design parameters of periodic scaffold architectures were identified and incorporated into CAD models with design parameters over the practical processing range represented. Solid models were imported into a finite element model simulating compression loading. Model deformation results were used to identify apparent modulus of elasticity of the structure. PCL scaffold specimens with design parameters within the modeled range were fabricated and subjected to compression testing to physically characterize scaffold modulus. Results of physical testing and finite element models were compared to determine effectiveness of the method.
Magnetorheology of Multiwalled Carbon Nanotube Mineral Dispersions
Authors: Yang Zhengtao , Shaito Ali , D'Souza Nandika Anne
Published: April 2008

Multi-walled carbon nanotube (MWCNT) were dispersed in mineral oil and the magnetorheological response was measured. 0.5, 1.5 and 2.53 vol% nanotubes were dispersed in mineral oil. Strain sweep, frequency sweep, magneto sweep and steady shear tests were conducted in various magnetic field strengths. Storage modulus G', loss modulus G", complex viscosity η* and dynamic yield stress τy increased with magnetic field, which was partially attributed to the increasing degree of alignment of nanotubes in stronger magnetic field. G' and G" of MWCNT/mineral oil dispersions scaled with nanotube volume fraction φ by a power-law. The shear thinning behavior of MWCNT/mo dispersions followed the Ostwald-de Waele or power law.
Selection of the Simulation Domain for Turbulent Flow Around an Airfoil
Authors: Roberts Richard A. , Cui Jie
Published: April 2008

The study of flat plate and airfoil wakes is important in the fields of drag reduction, staged axial fans/compressors and acoustics among others. The focus of this research is the influence of the simulation domain and turbulence models on the accuracy of the numerical results when compared to experimental data. The results have shown that the selection of the simulation domain and turbulence model depends highly on the intended application and time requirements. For quick, near-wake averaged quantities, the k-e model is recommended. For studying far wake averaged results, the Reynolds Stress model is superior over the k-e model. While if a time dependant solution is of necessity, LES is the desired option. However, LES does require the airfoil geometry to be included in the domain because it performs poorly when given only inlet velocities, turbulence kinetic energy and eddy dissipation at the trailing edge of the airfoil.
Modeling of Piezoelectric Response in PVDF for Monitoring of Mechanical Bending in Hinges
Authors: Hashmi Salman A. , Jayatissa Ahalapitiya H.
Published: April 2008

Monitoring of bending of hinges is very important to predict the motion of mechanical devices. Piezoelectric based monitoring systems have been utilized to detect the degree of motion and deflection. In order to apply piezoelectric layers on hinges, flexible materials have to be used. Subsequently, polymer materials attracted attention in connection with monitoring of large deflections. In this paper, feasibility of using PolyVinylidine DiFluoride (PVDF) layers to detect bending of a hinge was investigated based on finite element analysis (FEA). A device was designed by placing a PVDF layer on a hinge which can bend 90 degree from the straight position was constructed. Two possibilities of PVDF attachment were investigated: (i) uniformly bonded PVDF along the arms and (ii) attachment of PVDF at the end point of the arms. The effect of bending in different directions on piezoelectric voltage was also evaluated to check the possible noise levels on induced voltages. It was found that PVDF piezoelectric layers can be effectively used in detection of degree of bending and deflection of mechanical components. The voltage generated by PVDF films attached at end points is five times higher than the voltage generated by the uniformly bonded PVDF films indicating that the unbounded PVDF is more sensitive.
A New Experimental Technique to Characterize the Fiber Crush and Fiber Shear Behavior of Composites at Quasi-Static and High Rates of Strain
Authors: Gama Bazle A. , Gillespie John W.
Published: April 2008

A new experimental method is developed to determine the fiber crush strength (SFC) and fiber shear strength (SFS) of composite materials following a punch shear test methodology. The material parameters SFC and SFS are used to model the damage behavior of thick-section composites as described in the LS-Dyna material model MAT_COMPOSITE_DMG_MSC, aka MAT162. The quasi-static experimental methodology is further extended to investigate the rate effect on SFS using a Hopkinson bar direct impact punch shear test method.
Control System Design for Retinal Imaging Adaptive Optics Systems Using Orthonormal Basis Functions
Authors: Ficocelli Maurizio , Ben Amara Foued
Published: April 2008

This paper presents a solution to control system design issues for membrane mirrors used in retinal imaging adaptive optics systems. Such systems allow for the early diagnosis of eye diseases through high resolution imaging of the retina. Optical defects in the eye, known as aberrations, distort the retinal images, hence reducing their resolution. A retinal imaging adaptive optics system makes use of a deformable mirror whose shape is adjusted in real time to cancel the aberration effects. Due to the unknown and time-varying nature of the aberrations in the eye, the main control problem addressed in this paper is the tracking of an unknown and time-varying shape for the membrane mirror. Since the desired shape of the mirror is unknown and time-varying, it is proposed in this paper to design a multivariable controller that is tuned online to converge to the controller needed to achieve regulation. This is done iteratively, by taking advantage of the Q-parameterization of stabilizing controllers, so that the controller will converge to the ideal controller. Most often, finite impulse response (FIR) filters are used to represent the Q-parameter. It is proposed in this paper to represent the Q-parameter using orthonormal infinite impulse response filter basis functions. Such basis functions yield faster convergence rates during parameter estimation, and a Q-parameter representation that is less sensitive to parameter variations from the desired parameters. This is particularly crucial for the proposed application, where small errors in a typical FIR representation for the Q-parameter can lead to significant performance degradation. Simulation results are presented to illustrate the performance of the proposed adaptive controller design approach.
Design of a Ceramic Heat Exchanger for Sulfuric Acid Decomposition
Authors: Wilson Merrill A. , Lewinsohn Charles , Cutts James , Ponyavin Valery
Published: April 2008

It has been proposed that compact ceramic heat exchangers can be used for high temperature, corrosive applications. This paper discusses the design development of a micro-channel heat exchanger for the decomposition of sulfuric acid as part of the hydrogen producing sulfur iodine thermo-chemical cycle. Corrosion studies of candidate materials indicate that ceramic materials have superior corrosion and creep resistance under these high temperature, high acid concentration environments. This compact heat exchanger utilizes micro-channels to enhance the heat transfer while maintaining low pressure drops within the system. Through modular stacking of these micro-channel networks, a "shell and plate" configuration enables the processing of commercial-scale processes. The ceramic materials provide for long-life applications. The design of the micro-channel features captures the enhanced heat transfer characteristics at the micro-scale; the modular assembly permits the integration into macro-scale processes. As a case study, the thermal performance and the economics were investigated to determine the feasibility of this compact heat exchanger for the hydrogen producing sulfur iodine thermo-chemical cycle. The results of this design effort with its associated performance goals and development status will be reported.
A Distributed Sensing System for Vehicles State Estimation
Authors: Bolandhemmat Hamidreza , Clark Christopher M. , Golnaraghi M. F.
Published: April 2008

This paper presents the design of a distributed sensing system that uses an Extended Kalman Filter (EKF) to fuse measurements, so that automotive vehicle states can be estimated for use by a Semi-active Suspension control system. To improve ride comfort and handling quality, relative displacements and velocities of suspension systems are estimated. To control the stability of vehicles, roll, yaw, and pitch must also be determined. The designed (EKF) uses easily accessible measurements such as accelerations and body's angular velocities. These measurements are provided by 8 accelerometers and an Inertial Measurement Unit (IMU). The accelerometers are strategically mounted on the two ends of each individual shock absorber (damper). The IMU was mounted near the vehicle's center of gravity. Computer simulations and experiments were conducted for full vehicle state estimation of a 1993 Toyota Tercel equipped with the above mentioned sensor suite. Results show that except relative displacements, all states of the automobile's semi-active suspension systems can be estimated using this set of sensors. The designed EKF works well despite not knowing accurate information about road inputs, external disturbances and car characteristics such as moments of inertia, mass, and equivalent spring and damping coefficients. Both simulation results and experimental results show the effectiveness of the designed EKF in estimating the required states.