bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid, Traditional, and Virtual: Prototypes in the Undergraduate Curriculum
Authors: Lenoir Joel
Published: April 2008

The Mechanical Engineering (ME) faculty at Western Kentucky University (WKU) has developed a curricular plan to balance the strengths and weaknesses of three types of design prototyping: rapid, traditional, and virtual. Rapid prototyping refers to any of the modern 3D printing tools, such as Fused Deposition Modeling. Traditional prototyping has been defined as primarily machined parts, ranging from simple fabricated parts to CNC machined components. Virtual prototyping is used to describe designs that exist only in the digital domain as parts and assemblies in a 3D drawing program. Over the entire four years of the WKU ME curriculum, students work on a range of projects that allow them to utilize all three types of prototypes. The ME Freshman Experience allows students to blend the study of design methodologies with basic instruction in machine tools. Each student designs, builds, and tests their own air-powered steam engine. Sophomore Design finds the students working not only on a virtual design project, but also a more extended design-build-test project focused on experimentation. Junior design blends an externally sponsored virtual design along with the ASME Regional Student Competition (RSC). As with the RSC, Capstone Design in the senior year allows students to use a balance of all three types of prototyping as they judge appropriate and/or requested by their external sponsor. Design projects utilizing rapid and traditional prototyping resources require a large commitment by faculty and staff for support. A balance between time, resources, and level of student effort must be maintained, but careful planning can lead to improved student design performance. Virtual prototyping can appear to be easier to manage, but student expertise in creating fidelity between digital drawings and the desired physical parts varies widely. The deficiencies can show up when creating assemblies, but students can often mask the errors. The most important aspect of all these prototyping activities is the need for continual interaction between students, faculty, and staff. Students do not usually possess an innate project management ability, but experience has shown that strong project management skills are necessary for successful prototyping activities. All persons involved in the efforts must understand the prototyping facilities available, the time and resources necessary to utilize them effectively, and the reasonable expectations of the course effort. Students can gain understanding through repeated course exposure, but faculty must present a consistent voice with respect to the technologies available.
Experimental Study of the Vascular Dynamics of a Saccular Basilar Aneurysm
Authors: Tsai William W. , Savas O¨mer , Maitland Duncan , Ortega Jason , Small Ward , Wilson Thomas S. , Saloner David
Published: April 2008

A majority of patients who suffer hemorrhaging as a result of a ruptured cerebral aneurysm experience reduced quality of life, long term brain damage, or death. Improved understanding of the flow patterns in cerebral aneurysms will lead to better techniques for their detection and treatment. Experiments are conducted in a generic flow phantom to characterize the basic behavior of blood flow in basilar saccular aneurysms. The test setup models a saccular aneurysm that forms at the bifurcation of the basilar artery into the Circle of Willis. Three input flow conditions are tested: a physiological flow waveform obtained from Kato (2002) [1] and two steady flow conditions corresponding to the peak and mean flow rates of the physiological flow waveform. Steady cases are examined to study the effect of increasing Reynolds number on the flow and the pulsatile case to quantify unsteady effects. The results reveal highly three dimensional flow patterns within the aneurysm. Velocity and vorticity fluctuations are extracted to investigate the nature of the unsteady flows. Wall shear stress is estimated around the aneurysm dome to examine its role in wall weakening and failure.
A Fuel Cell Project for Advanced Thermodynamics Courses
Authors: Blekhman David
Published: April 2008

Secondary thermodynamics courses study advanced energy cycles. They have also started to include some introduction to fuel cell operation. Seemingly difficult, the fuel cell concepts can naturally be drawn from the topics of chemical equilibrium, which are also introduced in these courses for chemical reactions and combustion. The Nernst equation, a cornerstone of fuel cell operation, is based on a change of the Gibbs energy in a non-equilibrium fuel cell reaction. The resulting terms in the Nernst equation include the concentrations of the reactants, which dynamically change as the fuel and oxidizer deplete in the reaction while flowing through the cell. This becomes particularly interesting in high temperature fuel cells that incorporate fuel reforming and fuel utilization into a single system. The introduced fuel cell project proposes to combine the chemical equilibrium and non-equilibrium concepts simultaneously coexisting in a high temperature fuel cell. Relatively low operational temperatures allow for a simplified chemical equilibrium analysis of the fuel flowing in the fuel cell while superimposing it on the fuel cell reaction and fuel/oxidizer utilization. The variety of fuel and oxidizer mixtures, operating temperatures and pressures allows for creating a large number of individualized assignments. Students will benefit from a project that reinforces their understanding of fuel cell performance while increasing their comfort with chemical equilibrium concepts.
A Bubble-Powered Micro-Rotor: Manufacturing, Assembly and Characterization
Authors: Kao Jonathan , Warren John , Xu Jie , Attinger Daniel
Published: April 2008

This paper demonstrates experimentally the feasibility of a novel micro-rotor actuation concept. We demonstrate how a fluid flow, created by the interactions between a bubble and acoustic waves, can be exploited to assemble and power a micro-rotor at a speed as high as 625 rpm. The 65μm microrotor is manufactured in SU-8 using photolithography, all inspired by a biological structure: the winged seed of the maple tree. Variables controlling the rotation speed are investigated, such as the bubble diameter, the acoustic excitation amplitude and frequency, as well as the rotor geometry. The extractible power is estimated to be in the femtowatt range. Finally, steps are outlined to develop this micro-rotor into a MEMS-based motor delivering tunable, rotary power at the microscale.
Chemotherapy Drug Encapsulated Poly(Lactic-Co-Glycolic Acid) Nanoparticles
Authors: Jayasuriya A. Champa , Darr Anthony , Ebraheim Nabil A.
Published: April 2008

In order to exhibit pharmacological activity at the bone cancer site, high-dose chemotherapy drugs need to be used. This often causes toxicity and unfavorable systemic adverse effects leading to significant problems to the patient. Since nanoparticles are in subcellular size, they can effectively entered to the cell membrane that could result in higher cellular uptake. In this study, we report preparation and characterization of poly(lactic-co-glycolic acid) - PLGA nanoparticles, which encapsulated with chemotherapy drug cisplatin.
The Use of Ionic Liquids in Refrigeration
Authors: Sen Mihir , Paolucci Samuel
Published: April 2008

Ionic liquids are salts, usually with organic cations and inorganic anions, that are liquid at room temperature. There are a wide variety of ionic liquids that can be synthesized with different properties for different applications. They are generally non-volatile, non-toxic, and non-flammable with high heat capacity, high density, high thermal and chemical stability. We propose its use as an absorbent in an absorption refrigeration cycle. The refrigerant in this case would be a gas such as carbon dioxide. The present work deals with the desirable properties of ionic liquids for this application. For example, the absorbent must have a high solubility, and the heat and mass transfer coefficients of the absorbent-refrigerant solution must be large. The viscosity of the mixture, on the other hand, should not be so large as to make its pumping difficult.
Wear Behavior of Carbon Steels
Authors: Akbar Ahmed A. , Shuaeib Farag M. , Younis Aimen M.
Published: April 2008

The present work is concerned with study the wear behavior of 1020, 1060, and 1095 steels under different wear conditions, rotating contact speeds (500,850, and 1200 rpm) and normal contact loads (50,100,150 and 200 N) using pin on wheel wear testing machine. The prepared specimens were normalized to make sure that all types of steels are in the same structure. Wear testing results were recorded by measuring weight loss at different contact times (10, 20, 30, 60 and 90 min). The aim of this paper was to study the effect of normal loads and rotating speeds and their interactions on wear behavior of steels under various continuous sliding contact times. The presented relations between the volume loss and working conditions showed that low carbon steel had wear loss higher than other carbon content. In addition, results for all types showed that lower rotating speed had higher effect than other speeds and high normal load had higher effect than other loads. The highest volume loss was observed at high normal load and low rotating speed. And the relation between wear coefficient and working conditions was also observed that wear coefficient decreases as both normal load and rotating speed increase.
Prediction of Ductile Damage in Sheet Metal Blanking Process Including the Thermo-Mechanical Coupling
Authors: Rafasnjani Ahmed , Abbasion Saeed , Farshidianfar Anoushiravan , Irani Nilgoon
Published: April 2008

In this paper a methodology is proposed to predict ductile damage in metal forming process by using a coupled thermomechanical finite element method. The simulation contains the influence of thermal effects on material properties. The interaction between the damage evolution and the temperature distribution caused by heat generation due large strains has been correctly described by the proposed model. The results obtained with simulation of sheet metal blanking process show the importance of the strong coupling between thermal effects, plasticity, and ductile damage effect at large plastic strain with contact/friction. This model can be used for the prediction of the temperature field in some dynamic metal forming or machining processes.
Enhanced Thermal-Hydraulic Performance of a Wavy-Plate-Fin Compact Heat Exchanger: Effect of Corrugation Severity
Authors: Muley Arun , Borghese Joseph B. , White Steve L. , Manglik Raj M.
Published: April 2008

Enhanced forced-convective heat transfer behavior of air flows (Pr ~ 0.7) in a compact heat exchanger with three-dimensional, sinusoidal-wavy-plate fins is investigated both experimentally and computationally. Plate-fins with three different corrugation aspect ratio γ = (2A/L) = 0.0667, 0.1333, and 0.2667 are explored. Experimental j and f measurements are presented for flow rates in the range 500 < Re < 5000. Computational results, based on control-volume techniques, are obtained for periodically-fully-developed flows with 10 ≤ Re ≤ 1000. The numerically simulated local temperature and flow field map shows the complex influence of corrugation aspect-ratio γ, and the concomitant j and f predictions are in good agreement with experimental measurements. Both j and f increase with γ to reflect the relatively stronger flow recirculation in the wall-trough regions, and spatially more frequent periodic boundary-layer disruptions upstream of the corrugation peaks that enhance heat transfer in plate-fin channels. The relative enhancement, as measured by the Area Goodness Factor (j/f), however is found to be highest with γ = 0.0667.
Design Parameter Sensitivity for a Mountain Bike Rear Shock
Authors: Redfield Robin C.
Published: April 2008

As the sport of mountain biking matures, equipment continually evolves to afford better biking performance, enjoyment, and safety. In the arena of suspension systems, mountain bikes have moved from rigid suspensions with large, knobby tires to front fork suspensions, and finally full suspensions. Suspensions have gone from elastomeric compliance to air and coil springs with adjustable travel. Damping has progressed from fixed to adjustable rebound, compression, and lockout. The current trend is to add force or frequency dependent damping to minimize response of a suspension from pedal input. A bond graph model of a mountain bike rear shock is developed incorporating adjustable rebound and low-speed compression, high-speed compression, and rider controlled, compression damping initiation. An air shock with a nitrogen charge is modeled with velocity across the shock as input. The dynamic equations that come from the bond graph are simulated to predict key forces, pressures, and flow-rates. Experimental response (forces, displacements, and velocities) of the modeled shock is acquired subject to periodic velocity inputs. The experimental response is used to tune the design parameters of the model and for validation. A sensitivity analysis is then undertaken to determine how significant key design parameters are to the performance of the shock. Once validated, the model is used to better understand the physics and performance of the mountain bike shock and to relate performance to the requirements of expert mountain bikers.
Optimal Estimation of Blood Insulin From Blood Glucose
Authors: Kiriakidis Kiriakos , O'Brien Richard
Published: April 2008

Plasma insulin estimation from plasma glucose has been proposed in order to avoid hyperinsulinemia in the control of diabetes. This paper presents an estimator with error feedback based on measured and predicted plasma glucose designed to tolerate measurement noise as well as discretization error by means of the H∞ criterion. The proposed estimator is tested and evaluated using synthetic patient data.
Effects of the Electric Field Configuration's Variation Due to Micro-Cantilever Beam's Curvature on Pull-In Phenomenon
Authors: Oskouei Seyed Babak Ghaemi , Ahmadian Mohammad Taghi
Published: April 2008

Micro-electromechanical systems (MEMS) have wide application in the development of sensors for the detection of magnitudes in almost any domain [1]. Resonant mode operation of micro and nano-scale oscillators have gained wide interest for applications including filters, amplifiers, non-linear mixers, atomic scale imaging, biological and chemical sensors. The device that we propose is an electrically actuated microcantilever beam. More precisely, in our design the microcantilever constitutes the movable plate of a micro-capacitor and its displacement is controlled by the voltage applied across the plates. Review of literature shows that the electric field pattern between the beam and the substrate has always been assumed to be straight parallel lines normal to the substrate. In reality the electric field must be normal both to the substrate and the beam. Considering this phenomenon, the force exerted on the beam should always be normal to its surface and as the beam's curvature increases, the direction of the force also deviates proportionally.
Midstream Modulation of Nanotechnology in an Academic Research Laboratory
Authors: Fisher E. , Mahajan R. L.
Published: April 2008

No clear implementation methods exist for US legislation on integrating societal considerations into nanotechnology research and development. An empirical study was thus undertaken to investigate the possibility and utility of "sociotechnical integration" during nanoscale engineering research in an academic setting. For twelve weeks, an "embedded humanist" interacted with three graduate engineering researchers to identify and assess opportunities for influencing research decisions in accordance with societal concerns. The study focused not on the nature of societal concerns, but on the nature of engineering decisions, and on the potential capacity of researchers to perform integration by "modulating" their decisions. Engineering research decisions were found to be subject to societal influences, and researchers were found to become aware of the possibility of modulating their decisions accordingly. The interactions were not found to hamper research and were found to add value to research. No attempt was made to alter research decisions, only to stimulate awareness of the possibility of doing so. Still, one researcher did alter several decisions as a result of the study. Midstream modulation represents a promising approach for implementing US nanotechnology policy.
A Numerical Analysis of Growing Water Droplet inside an Air Supply Channel of a PEM Fuel Cell
Authors: Mukherjee A. , Kandlikar S. G.
Published: April 2008

The present study is performed to analyze the growth and departure of a water droplet inside a minichannel with air flowing through it. The minichannel is of 1 mm square cross section with a water droplet growing at the top wall and air coming in through the channel inlet. This is a typical situation encountered in the gas flow passages of a PEM fuel cell. The excess water generated in the membrane due to the fuel cell reaction diffuses through the gas diffusion media and enters the gas supply minichannel passages where it gets entrained in the flow. The excess water needs to be removed quickly to prevent flooding of the membrane and gas flow passages which stops the fuel cell operation. The complete Navier-Stokes equations along with continuity equation are solved using the SIMPLER method. The liquid vapor interface is captured using the level set technique. The droplet grows due to flow of water at its base and at the same time is dragged due to the air flowing over it. The droplet growth and its departure are studied for different values water flow rate, incoming air flow rate and contact angle. The droplet departure is found to be hindered by excessive water flow rate and increase in surface wettability.
Incorporation of Flow Pattern Phenomena Into the Study of Advanced Micro Cooling Modules
Authors: Keska Jerry K. , Simon William E.
Published: April 2008

The need for high-performance thermal protection and fluid management techniques for systems ranging from cryogenic reactant storage devices to primary structures and propulsion systems exposed to extreme high temperatures, and other space systems such as cooling or environmental control for advanced space suits and integrated electronic circuits, requires an effective cooling system to accommodate the compact nature and high heat fluxes associated with these applications. A two-phase forced-convection, phase-transition system can accommodate such requirements through the use of the concept of Advanced Micro Cooling Modules (AMCMs), which are essentially compact two-phase heat exchangers constructed of microchannels and designed to remove large amounts of heat rapidly from critical systems by incorporating phase transition. Realizing the significance of research in this area, this paper presents the results of experimental research on two-phase flow in microchannels with verification and identification of data using concomitant measurement systems, where based on the experimental research conducted on air-water mixture flows in the entire range of concentration and flow patterns in a horizontal square microchannel, a mathematical model based on in situ parameters is developed and presented, which describes pressure losses in two-phase flow incorporating flow pattern phenomena. Validation of the model is accomplished. A hypothetical model for the two-phase heat transfer coefficient is also presented, which incorporates the flow patterns through the use of a flow pattern coefficient.
Conditional Statistics for Passive-Scalar Mixing in Confined Turbulent Shear Flows
Authors: Feng Hua , Olsen Michael G. , Fox Rodney O. , Hill James C.
Published: April 2008

A combined particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) system was employed to investigate turbulent mixing in a confined rectangular jet. The Reynolds number based on bulk velocity and hydraulic diameter was 50,000. The Schmidt number for the passive scalar was 1,250. Velocities conditioned on the scalar were evaluated. Since the joint PDF was not jointly Gaussian in this flow, the conditional mean velocity agreed with a linear model only when the mixture fraction is close to the local mean mixture fraction. A gradient PDF model for the conditional velocity was also tested against the experimental data. The model predicted the crossstream conditional velocity very well, but gave poor predictions for the streamwise conditional velocity. Finally, the scalar fluctuations conditioned on velocity were presented and analyzed against a linear model.
Mechanical Characterization of Zinc Oxide Nanowires
Authors: Desai A. V. , Haque M. A.
Published: April 2008

Semiconductor nanowires like zinc oxide nanowires are potential materials for future nanoscale sensors and actuators. Due to their unique length scale, they are expected to have length-scale dependent mechanical properties. In this paper, we report experimental investigations on the mechanical properties of zinc oxide nanowires. We have designed a MEMS test-bed for mechanical characterization of nanowires and use a microscale version of pick-and-place as a generic specimen preparation and manipulation technique. We performed experiments on zinc oxide nanowires inside a scanning electron microscope (SEM) and estimated the Young's modulus to be approximately 21 GPa and the fracture strain to vary from 5 % to 15 %.
Electro-Fluidic Packaging for CMOS Based Laboratory-on-Chips
Authors: Ghafar-Zadeh Ebrahim , Sawan Mohamad , Therriault Daniel
Published: April 2008

Direct-write fabrication process (DWFP) is a robotic deposition technique used to produce planar or three-dimensional (3D) microscale structures. These structures consist of paste-like filaments which are extruded through a micronozzle and deposited on a substrate [1]. These filaments are encapsulated inside an epoxy resin and then melted and removed by applying a moderate temperature for the creation of microfluidic components (e.g., microchannels, reservoirs). Following our previous reports [2–3] on the fabrication of microchannels by DWFP and high precision CMOS capacitive sensors [4], we present in this paper a microfluidic packaging procedure to realize microchannel and fluidic connections on top of CMOS chip. The compatibility of this fluidic packaging procedure with conventional electrical packaging techniques (e.g. wire bonding) is an important advantage of DWFP for CMOS based Laboratory-On-Chip applications. The fabrication challenges are discussed in the experimental section.
Vision-Based Kinematic Synthesis of Hand Motion
Authors: Duraisamy Karthikeyan , Perez-Gracia Alba , Schoen Marco P.
Published: April 2008

The purpose of this work is to develop a human hand model that will work in conjunction with the myoelectric signals from the arm muscles, for those people who have lost their upper extremity. Though there are many prostheses available on the market with variable cost and functional accuracy, it is hard to find a prosthesis that mimics the complete functionality of the human hand, due to the complex hand motion, the complex dynamics of the myoelectric signals, and the difficulty involved in the acquisition of these signals, which complicates the implementation. In order to overcome some of these problems, the proposed hand model mimics most of the hand movements and it is used together with a kinematic synthesis process to identify the motion of the hand, obtained from visual data. In this paper, the human hand is modeled as a collection of five serial chains. For each movement performed by the joints in the finger/wrist, revolute joints are considered in different configurations, which yield movements similar to those of the human hand. The forward kinematics in matrix form is formulated using Denavit-Hartenberg parameters and expressed using Clifford Algebra exponentials. Kinematic synthesis is used to adjust the dimensions of the proposed model to the hand of the subject, and to identify the angles at each joint for a given hand motion. In the kinematic synthesis process, the forward kinematics equations of the hand are solved for both the angles of the joints and the dimensions of the hand. The synthesis equations obtained from the kinematic synthesis process are solved using a Levenberg-Marquardt nonlinear least-squares algorithm. The experimental setup for the real-time motion capturing consists of three camerasand is to be used in future work to relate the joint motion to the myoelectric signals acquired from the subject's arm.
Lumped Element Modeling of Piezoelectric Cantilever Beams for Vibrational Energy Reclamation
Authors: Kasyap Anurag , Phipps Alex , Sheplak Mark , Ngo Khai , Nishida Toshikazu , Cattafesta Louis N.
Published: April 2008

In this paper, an accurate physical model of a piezoelectric cantilever beam that is suitable for multi domain simulations of the transducer for energy harvesting is presented. In a composite piezoelectric cantilever beam with a proof mass that is subjected to a base acceleration, a strain is developed in the structure that produces a voltage due to the piezoelectric effect. Subsequently, the piezoelectric composite is connected to an energy reclamation circuit that uses a flyback converter topology, to maximize power transfer via an impedance match with the structure. Hence, an accurate model of the device is required to characterize its overall electromechanical behavior, to theoretically predict the power generation, and to optimize the device and power converter circuit. The Lumped Element Model (LEM) thus developed was validated within 10% experimentally on meso-scale piezoelectric cantilever composite beams.
Unsteady Velocity Field Measurements of Outlet Flow in an Automotive Supercharger
Authors: Mahendra Pranay , Olsen Michael G.
Published: April 2008

Recently the automotive industry has been using superchargers to boost the power generated by the engine, but the noise generated by these superchargers is of great concern. The noise generated during the working of the supercharger is primarily a fluid mechanics phenomenon. Particle Image Velocimetry (PIV) was used to study air flow characteristics of a positive displacement supercharger with an emphasis on gaining insights into strategies for noise reduction. PIV was used to measure the instantaneous and ensemble-averaged velocity fields of the flow at the outlet of the supercharger as a function of blade position, allowing for visualization of the flow as it leave the blades. The preliminary results show that the flow exits the supercharger as a high speed jet at the end closer to the pulley end, and the flow varies with the change in blade position.
Vibration Isolation Control for Hydraulic Hybrid Vehicles
Authors: Nguyen The M. , Elahinia Mohammad M.
Published: April 2008

In recent decades, many types of hybrid vehicles have been developed to compensate for the limited sources of oil and gas production. Gasoline-electric hybrid technology shows a significant improvement in fuel efficiency for small and medium-sized passenger vehicles. However, that hybrid type is not economically beneficial for larger vehicles due to large, harmful and expensive battery packs. Hydraulic hybrid technology has been found effective for heavy duty vehicle because of its high power density. Other advantages of hydraulic hybrid are the lower cost and environmental friendliness over the electric batteries. The potential achievement in fuel efficiency has been proved in several studies and experiments by different schools, institutes and laboratories. The only problems preventing this hydraulic hybrid technology going to the market are noise and vibration involving with the hydraulic system. This study focuses on using magnetorheological (MR) technology to reduce the noise and vibration transmissibility from the hydraulic system to the vehicle body. MR technology has been well-known with automotive applications such as engine mounts, vehicle's main suspension system. In order to study the nature of the problem, structure of a hydraulic hybrid vehicle in series design is analyzed. The operational characteristics of the powertrain are carefully studied, and the vibration data is formulated. This research shows that not only MR elements play an important role in vibration suppression, but also the geometrical configurations of the mounting systems affect the efficiency in noise and vibration isolation. To this end, simulation results are also used to determine the most effective control method for the MR mounts.
Experimental Investigation of Switching Oxygen Sensor Behavior Due to Exhaust Gas Effects
Authors: Vosz Adam , Midlam-Mohler Shawn , Guezennec Yann , Yurkovich Steve
Published: April 2008

Switching type exhaust gas oxygen sensors are critical to the performance of air-to-fuel ratio control in stoichiometric SI engines. Controlling the air-to-fuel ratio around stoichiometry is necessary for adequate three-way catalyst performance to meet government emissions regulations. However, the feedback signal from the sensor does not always truly depict the actual chemical mixture present in the exhaust gasses, which intrinsically affects the catalyst performance. A sensor may not provide correct air-to-fuel ratio feedback due to certain species in the exhaust gas which affect the equivalence ratio that the sensor switches from the high to low voltage or vice versa. This work attempts to characterize the impact of gas on fresh and aged sensors and builds upon earlier work in the field by using real engine exhaust rather simulated exhaust gas. In these experiments, the air-to-fuel ratio of a stoichiometric gasoline engine is incrementally increased from a lean to rich mixture to elicit the full switching response of the oxygen sensor. Additional sensor output curves are generated in the presence of external additive gases such as hydrogen, carbon monoxide, propane, and gasoline vapor. An automotive emissions analyzer and a hydrogen analyzer detect the concentrations of the exhaust gases and the chemical equivalence ratio is calculated using a carbon balance. This equivalence ratio creates a reference to examine the accuracy of the switch point of the sensor to actual stoichiometry. Using these data sets, it is possible to determine observe the effect of various gas species on the air to fuel ratio at which the sensor switches. The sensitivity of the different sensors to gas concentrations are quantified and presented, which form an elementary model to predict the sensor switch point in the presence of these gas species. Primary findings indicate that the impact of species on the sensor switch point is linearly related to the concentration of the species; sensor type and sensor age have an effect on a sensor's sensitivity to species; and different hydrocarbon species affect sensors differently. The findings support the simulated exhaust gas results reported in the literature in that the degree of interference of a species is related to the diffusion rate of the species with respect to oxygen through the sensor. The results also point toward the importance of the species of hydrocarbons in the engine exhaust, which are uncontrolled and can vary with engine operating conditions. This feature is critical to the application of this knowledge to automotive control.
Elastomer-Based Micromechanical Energy Storage System
Authors: Bergbreiter Sarah , Pister Kristofer S. J.
Published: April 2008

An elastomer-based energy storage system for MEMS has been designed, built, and tested. Micro rubber bands have been fabricated from silicone using two different methods, laser-cut and molded, and assembled into silicon microstructures fabricated in a two-mask silicon-on-insulator (SOI) process. Using silicon hooks and force gauges designed in this process, these micro rubber bands have been characterized as to their energy storage potential and efficiency by stretching them with a probe tip. These tests showed recovered energy efficiencies up to 92% at strains over 200% with a maximum stored energy over 19 μJ. In addition, a fully integrated micromechanical energy storage system to both store and release energy has been demonstrated using an electrostatic inchworm motor to stretch the elastomer band and release it. Using the inchworm motor, an estimated 4.9 nJ of energy was stored in the elastomer spring and quickly released.
Beating the Thermal Conductivity of Air Using Packed Nanoparticle Bed
Authors: Prasher Ravi
Published: April 2008

Thermal conductivity of packed bed of nanoparticles is calculated in this paper. Results show that effective thermal conductivity of nanoparticle bed can be very low. Thermal conductivity of the nanoparticle bed can be smaller than the thermal conductivity of air. Thermal conductivity depends on pressure, surface energy of the nanoparticle, and phonon mean free path.
Modeling and Simulation of a Surface Micromachined Knudsen Pump
Authors: Gupta Naveen K. , Gianchandani Yogesh B.
Published: April 2008

This paper presents a simulation model for a silicon micromachined Knudsen pump that combines analytical and numerical methods. It involves numerical modeling of the thermal response, followed by an analytical estimate of the pumping using Kennard's model. The loss of performance resulting from gas diffusion though walls of the pump is specifically addressed. The results are subsequently validated against the previously reported experimental measurements of a single-stage Knudsen pump. This device, which has a total footprint of less than 1500 × 2000 μm2, has multiple narrow channels connecting two cavities, one of which is heated. This cavity is further connected through a wide channel to a third cavity, which remains at ambient. The simulation model for this device predicts a vacuum pressure of 0.47 atm. at an input power of 97.6 mW, which deviates less than 20% from the experimentally observed data. Finally, the paper extends the concept of single stage pumping to a multi-stage pump. While Kennard's model is used for modeling the first stage, the simulation for subsequent stages, which are characterized by a relatively high Knudsen number, uses an empirically corrected
Simulation of Low Speed Gas Flow Over Backward Facing Step in Microchannels
Authors: Kursun Umit , Kapat Jayanta S.
Published: April 2008

Proper design of thermal management solutions for future nano-scale electronics or photonics will require knowledge of flow and transport through micron-scale ducts. As in the macro-scale conventional counterparts, such micron-scale flow systems would require robust simulation tools for early-stage design iterations. This paper concentrates on such a flow process, namely pressure-driven gas flow over a backward facing step in a microchannel. A well-known particle-based method, Direct Simulation Monte Carlo (DSMC) is used as the simulation tool. Separating the macroscopic velocity from the molecular velocity through the use of the Information Preservation (IP) method eliminates the high-level of statistical noise as typical in DSMC calculations of low-speed flows. The non-isothermal IP method is further modified to incorporate the pressure boundary conditions, which are expected to be more prevalent in design of thermal management systems. The applicability of the method in solving a real flow situation is verified using the backward facing step flow in a micro geometry. The flow and heat transfer mechanisms at different pressures in Knudsen transient regime are investigated. The range of parameters for this investigation are: Re from 0.03 to 0.64, Ma from 0.013 to 0.083, and Kn from 0.24 to 4.81, all based on maximum values.
Eight-Axle Railcar Carbody Roll Performance: Center of Gravity and Track Wavelength Effects
Authors: Shust William , Wilson Nicholas , Gurule Stan
Published: April 2008

Heavy-duty railcars carry greater than typical payloads by employing additional wheelsets to lessen wheel/rail contact stresses. Rather than the common 4-axle designs, these cars may have up to 16 axles supporting one deck. Traditionally, these car types have not performed as well as desired. As a response, designers have created depressed center body styles to lower the overall center-of-gravity (CG) height. Such designs lead to more complexity and expense. In this investigation, a heavy-duty 8-axle flatcar has been modeled, both with a flat carbody and a depressed body style. Simulations of harmonic roll perturbations were performed using various CG heights, track perturbation wavelengths and operating speeds. Results include comparisons of design versus performance trade-offs.
The Influence of Muscle Loadings on the Density Distribution of the Proximal Femur
Authors: Marzban Ali , Warner Grant M. , Canavan Paul K. , Nayeb-Hashemi Hamid , Ajdari Amin
Published: April 2008

This paper presents an efficient method for simulating the bone remodeling procedure. This method is based on the trajectorial architecture theory of optimization and employs a truss-like model for bone. The truss was subjected to external loads including 5 point loads simulating the hip joint contact forces and 3 muscular forces at the attachment sites of the muscles to the bone. The strain in the links was calculated and the links with high strains were identified. The initial truss is modified by introducing new links wherever the strain exceeds a prescribed value; each link undergoing a high strain is replaced by several new links by adding new nodes around it using the Delaunay method. Introduction of these new links to the truss, which is conducted according to a weighted arithmetic mean formula, strengthens the structure and reduces the strain within the respective zone. This procedure was repeated for several steps. Convergence was achieved when there were no critical links remaining. This method was used to study the 2D shape of proximal femur in the frontal plane and provided results that are consistent with CT data. The proposed method exhibited capability similar to more complicated conventional nonlinear algorithms, however, with a much higher convergence rate and lower computation costs.
Compressive Superplastic Behavior of 6Al-4V Titanium Caused by an Applied DC Current
Authors: Kronenberger Thomas J. , Warner Matthew K. , Roth John T.
Published: April 2008

Recent research has shown that the flow stress necessary to deform certain metallic materials can be decreased when an electrical current is present in the material while undergoing deformation. As part of this testing, it was found that, under higher current densities, the various metals began to exhibit strain weakening and superplastic behavior (i.e., the stress either remained constant or decreased as the strain increased). During typical compression testing, it is expected that the stress will continually increase as the strain increases. This is due to the increase in the cross-sectional area of the test specimen as well as the frictional effects that are present between the specimen and the fixture throughout the test. Since this strain weakening and subsequent superplastic behavior is opposite of what typically occurs during normal low temperature compression tests, it introduces a new electrical current-related phenomenon. This paper contains a detailed investigation of superplastic behavior using experimental results, focusing on 6A1-4V Titanium in particular. To examine this phenomenon, compression tests are run at different current densities. Some tests are conducted with the electricity present the entire time, while other tests are conducted with the electricity turned off at various points within the superplastic region. Still other tests have a pulsed electrical current present. It will be shown that the superplastic behavior allows significant increases in total deformation to be achieved using extremely low forces.
Experimental Studies on Galling Onset in OCTG Connections: A Review
Authors: Ekwaro-Osire S. , Karpat F.
Published: April 2008

With today's high prices for natural gas and oil, the demand for oil and country tubular goods (OCTG), with superior performance properties, is very high. Failures in OCTG can be attributed to numerous sources, for example, makeup torque, corrosion, and galling. Thread galling is the most common mode of failure. This failure often leads to leakage, corrosion of the material, and loss of mechanical integrity. The failure of OCTG eventually amounts to excessive operational costs for the gas and oil industry. The have been numerous approaches taken to improve the galling resistance of OCTG connections. The advocacy of these approaches is often achieved through experimental studies using galling testers. In this paper, it is proposed to classify the galling testers in seven distinct groups. There is a need to design and use effective galling testers to understand and improve the performance of OCTG connections. Thus, the objective of this paper was to present a concise review of literature related to the galling testers that may have applications to OCTG.
Adaptive Robust Control for a Class of Non-Minimum Phase Nonlinear System
Authors: Xie Bo , Yao Bin
Published: April 2008

The paper presents the state feedback adaptive robust control approach to track the reference input for a class of nonminimum phase nonlinear systems. The key for this approach is to combine the adaptive robust control design techniques and the inputto-state property to deal with a class of non-minimum phase nonlinear systems with unknown parameter and unstructural uncertainties. The control design will guarantee that the tracking error dynamics is stabilized with bounded internal states and the closed-loop system is robust to the unstructural uncertainties.
Characterization Studies on the SOFC Anode Material Using RSM Technique
Authors: Rajaram Gukan , Xu Zhigang , Desai Salil , Pai Devdas M. , Sankar Jag
Published: April 2008

The characteristics of the Ni/YSZ anode material for the solid oxide fuel cells (SOFCs) were investigated in order to study the relation between the porosity and the conductivity of the cell. Response Surface Methodology (RSM) was used for the study. The anode material was prepared with NiO and YSZ along with the graphite as pore former. The experiments were performed based on a central composite design matrix, which yielded nine sets of experiments. Porosity and conductivity measurements were performed on the sintered and reduced anode material. Using the measured values as output variables, statistical analysis was performed. The results indicated that the porosity increases by reducing the sintering temperature values, while the conductivity values were on the reverse scale. The conductivity values increase with increasing temperature. Using RSM technique, a ideal point was found in order to obtain a desired porosity volume and conductivity value.
Numerical Simulation of a Small Bubble Impinging Onto an Inclined Wall
Authors: Podvin Be´renge`re , Moraga Francisco , Attinger Daniel
Published: April 2008

This paper presents a numerical modeling of the collision between a small bubble -of a few hundred microns, initially moving at terminal velocity, and an inclined wall, with relevance to drag reduction schemes. The theoretical model uses the lubrication theory to describe the film drainage as the bubble approaches the wall, and compute the force exerted by the wall as the integral of the excess pressure due to the bubble deformation. The model is solved using finite differences. The trajectory of the bubble is then determined using equations of classical mechanics. This study is an extension of previous work by Moraga, Cancelos and Lahey, [Multiphase Science and Technology, 18,(2),2006] where the simulation and comparison with experiments was carried out for a horizontal wall. In the present study where the wall is inclined, the bubble trajectory is no longer onedimensional and axisymmetry around the vertical axis is lost, allowing for more complex behavior. The influence of various parameters (Reynolds number, Weber number) is examined. Numerical results are compared with the experimental data from Tsao and Koch [Physics Fluids 9, 44, 1997]
A New Passive Controller for a Hydraulic Human Power Amplifier
Authors: Li Perry Y.
Published: April 2008

A new, intrinsically passive controller for hydraulic human power amplifier is presented. The hydraulic human power amplifier is a tool that amplifies (or attenuates) the force that the human exerts on it. The control objective is to cause the system to behave like a passive mechanical tool when interacting with the human and with the work environment with a specified power scaling factor. Although a previous Proportional-integral with velocity feedforward force controller [1] works well in the constrained space, it lacks robustness or performance during freemotion because of the sensitivity to the implementation of velocity feedforward term. The difficulty in implementing the velocity feedforward term also prevents the controller from being intrinsically passive. The new controller recasts the human power amplifier problem into one of velocity coordination by generating a fictitious reference mechanical system. Force amplification become a natural consequence of velocity coordination. This enables the controller to be intrinsically passive and to achieve good performance both in free motion and constrained motion. These properties have been experimentally validated.
Correcting Measurement Nonlinearity in Dynamic Nanoindentation
Authors: Mann Brian P. , Liu Jian , Hazra Siddharth
Published: April 2008

This paper investigates methods of improving measurement interpretations in dynamic nanoindentation. In particular, a shift in the system's primary resonance is observed experimentally and investigated through modeling and numerical studies. The result of these investigations is that different sources of nonlinearity, namely, nonlinearities from the tip-sample contact force and the indenter's capacitive transducer, compete to alter the system's primary and secondary resonances. Furthermore, this study implies that the accurate characterization of a material surface requires the implementation of higher fidelity models that include nonlinear expressions, as opposed to linearized versions, for the tip-sample contact force and transducer electrostatic force.
A New Micromechanics Model for Predicting Thermal Properties of Heterogeneous Materials
Authors: Yu Wenbin , Tang Tian
Published: April 2008

A new micromechanics model, namely, the variational asymptotic method for unit cell homogenization (VAMUCH), is extended to predict thermal properties of heterogeneous anisotropic materials. In comparison to existing micromechanics models, VAMUCH is unique in the following three aspects: (1) it invokes only essential assumptions within the concept of micromechanics and achieves the same accuracy as mathematical homogenization theories; (2) it calculates the complete set of properties simultaneously without applying any loads; and (3) the dimensionality of the problem is determined by the dimension of the unit cell and the complete set of material properties can be obtained for one-dimensional unit cells. The present theory is implemented in the computer program VAMUCH, a recently developed, versatile engineering code for homogenization of heterogeneous materials. Several examples will be used to demonstrate the application and accuracy of the theory and the code of VAMUCH.