bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Study of Buoyancy-Driven Convection of Molten Gallium Under Magnetic Field
Authors: Zhao Liangju , Zeng Danling , Henry Deniel
Published: April 2008

This paper focuses on the convection of molten gallium contained in an enclosure of aspect ratios 5:1:1.3 subject to horizontal temperature gradient and an external constant magnetic field. Flows without magnetic field are also solved for comparisons by the spectral method. Steady flows and oscillatory flows show different flow structures. The symmetries are strictly maintained for steady flow and the symmetries are broken for oscillatory flow. Near the onset, stable periodical oscillations appear and the symmetries are satisfied between the present state and the state half a period later, which agrees well with the analytical results. The phase characters agree well with the experimental results. Energy analysis shows that the production of fluctuating kinetic energy by shear of mean flow is the main production to the change of the total fluctuating kinetic energy, while viscous effects give the main dissipation term. The dissipation of the fluctuating kinetic energy by magnetic field keeps negative.
On the Area of Equilibrium Thermodynamics Application
Authors: Kaganovich Boris M. , Keiko Alexandre V. , Shamansky Vitalii A. , Shirkalin Igor A.
Published: April 2008

The paper addresses the applicability of equilibrium thermodynamics models and the expediency of their employment for analysis of non-equilibrium systems, first of all, when solving the applied computational problems of large dimensionality. A model of extreme intermediate states (MEIS) is suggested for such an analysis. The methods to include the constraints on chemical kinetics and transfer processes are discussed. These constraints are to be presented in a thermodynamic form, i.e. without time variable. The efficiency of the approach is illustrated with the examples of determining the maximum possible nitrogen oxide concentrations in combustion chambers of gas turbines and modeling the non-stationary flow distribution in multi-loop hydraulic networks.
Reduced-Order Nonlinear Modal Equations of Circular Cylindrical Shells Based on the Finite-Element Method
Authors: Kobayashi Yukinori , Furukawa Tomoaki , Yamada Gen
Published: April 2008

This paper presents a procedure to derive reduced-order nonlinear modal equations of circular cylindrical shells. Modal analysis is applied to the nonlinear finite element equation by using base vectors obtained by the finite element analysis. Reduced-order modal equations are derived by transforming the equations of motion from the physical coordinates to the modal coordinates. Base vectors for the transformation consist of dominant linear eigenmodes and nonlinear displacement vectors derived approximately from the nonlinear finite element equation. Asymmetry of the deformation of the circular cylindrical shell with respect to its neutral surface is taken into consideration to determine the base vectors. Numerical results show good agreement with those presented in other papers.
An Experimental Method for Multi-Variable Analysis of Vehicle Safety Systems and Application to Front Seats and Rear Occupant Interaction in Rear Impacts
Authors: Saczalski Kenneth J. , Kumaresan Sriringham , Sances Anthony , Burton Joseph Lawson , Lewis Paul R.
Published: April 2008

This study presents a combined experimental-analytical method for test efficient, and cost effective, multi-variable analysis of safety system performance related to occupant injury potential analyzed over wide parameter ranges. Experimental techniques such as the “two-level factorial” method, in combination with sled-buck test set-ups (that match vehicle crash characteristics), are applied to demonstrate the technique for front seat performance as it relates to injury potential of the front occupant and rear seated children during rear impacts. The surrogate data from the above test method is combined into a “polynomial response function,” such as HIC, which is developed as a function of the many variables, and allows for analytical “interpolation and extrapolation” at variable combinations not tested. A minimum of 4 test combinations are used to establish the “polynomial injury curves” as functions of two variables (i.e. impact severity and front occupant weight) for a given seat type. Inclusion of a third variable for evaluation of “seat strength effects” can be accomplished with a minimum of 8 test combinations for the factorial method. Both front adult and rear child interactions are studied. Three year-old H-III surrogates are used for the study of rear child passengers. Plots of test generated “polynomial” multi-variable HIC level curves for the front adult and rear child surrogates are presented as functions of impact severity and front occupant weight, for various seat types. Accident case head injury data of rear-seated children is used to verify the experimental-analytical method.
Mechanical Brakes for Electrostatic Actuators
Authors: Grade John D. , Yasumura Kevin Y. , Jerman Hal
Published: April 2008

New DRIE actuator systems have been developed which use a high-force, linear actuator to wrap a flexible brake band around the rigid brake shoe of a large-deflection, rotary actuator. The brake can hold the rotary actuator at any arbitrary location within its full range of travel. A third actuator may be used to engage a pair of locking pins in order to keep the brake motor extended in the event of a power failure. The 100x increase in rotational stiffness after the brake is applied raises the fundamental resonant frequency by more than an order of magnitude, enabling precision optical adjustments over a large tuning range in the presence of external shock and vibration. Consistent braking accuracies of 1 mdeg, or 0.025% of the full-scale deflection, have been demonstrated across the entire rotational range
Novel Carbon Nanotube Reinforced Electro-Active Polymer Sensors for Structural Vibration Control
Authors: Ramaratnam Arun , Jalili Nader
Published: April 2008

Electro-active polymers like poly(vinylidene fluoride) — PVDF and their copolymers, have been emerging as a low cost substitutes for piezoelectric ceramics. Carbon nanotubes with their excellent physical and electronic properties can be used in these electro-active polymers to enhance their actuation and sensing properties. In the work presented here, actuators and sensors have been fabricated using piezoelectric polymers reinforced with carbon nanotubes. Single-walled and multi-walled nanotubes are used to reinforce the piezoelectric polymers. The response of these actuators and sensors are measured and the influence of the fabrication methods on the sensor performance is determined. The use of these materials as actuators and sensors to implement active vibration control is studied. These transducers also serve as additional damping materials added to the structure undergoing vibration due to their viscous damping properties. The change in properties of these piezoelectric polymers with different fabrication conditions and nanotube addition, though provokes doubts about standardization, invokes more research efforts on these new generation transducers.
An Experimental Examination of Seatbelt Webbing Loading Marks on Automobile Plastic D-Rings
Authors: Roberts H. Alex , Martin Mark R. , Canalichio Troy J.
Published: April 2008

This paper documents experimental research determining the belt forces required to create visible and distinct markings on plastic automobile D-rings. The “D-Ring” is the loop through which the shoulder belt feeds before reaching the retractor. In the experimental configuration, ballast is attached to the belt webbing and dropped from a predetermined elevation. By varying the drop height the belt loading characteristics were also changed. Photographs document the resulting loading marks. A Mathematical Dynamic Modeler was used to calculate the Rigid Body Dynamic models to determine occupant belt loads from 5th and 50th percentile Hybrid III anthropomorphic test devices under various crash pulse conditions. These values were correlated to the experimental research. Conclusions are made relating D-ring markings to the delta-V of an automotive accident.
Dynamic Projection Network for Supervised Pattern Classification
Authors: Li C. James , Jansuwan C.
Published: April 2008

This paper describes the development of the utility of a dynamic neural network known as projection network for pattern classification. It first gives the derivation of the projection network, and then describes the network architecture and analyzes properties such as equilibrium points and their stability condition. The procedures for utilizing the projection network for pattern classification problem are established and the benefits are discussed. The proposed classification system is then tested with well-known benchmark data sets, namely the Fisher’s iris data, the heart disease data and the credit screening data and the results are compared to other classifiers including Neural Network Rule Base (NNRB), Genetic Algorithm Rule Base (GARB), Rough Set, and C4.5 decision tree.
Thermoeconomic Simulation of 27 MW Campus Cooling Heating Power (CHP) Plant
Authors: Nayak Sandeep , Radermacher Reinhard
Published: April 2008

This paper describes the modeling of a 27 MW combined cycle cogeneration plant with 10,000 tons of cooling made available as chilled water at the central cooling facility that was designed and is currently operated to provide heating, cooling and electricity to the University of Maryland campus. The topping cycle of the combined cycle cogeneration plant consists of two gas turbines each producing 11 MW of electric power at full load. The energy of the exhaust gases from these gas turbines is then utilized to generate steam in two heat recovery steam generators. The heat recovery steam generators have supplemental duct firing using natural gas to meet the peak steam load. In the bottoming part of the combined cycle, the steam from the heat recovery steam generators is expanded in a backpressure steam turbine to supply steam to the campus at about 963 kPa, generating an additional 5.5 MW of electric power in this process. There is no condenser wherein the campus acts as a sink for the steam. The central cooling facility is designed to supply 10,000 tons of cooling as chilled water out of which 3800 tons is supplied by two steam driven centrifugal chillers, which utilize a part of the steam supplied to the campus and the remaining by the centrifugal electric chillers. The combined cycle cogeneration plant along with the central chilled water-cooling facility is modeled using a commercially available flexible cogeneration software package. The model is built based on the design data available from design manuals of gas turbines, heat recovery steam generators, backpressure steam turbine and centrifugal chillers. Two energy or cost savings opportunities were evaluated using the cogeneration software model. The first is adding inlet air-cooling using either an absorption or electric chiller to increase electrical power output during hot weather. This assessment included estimating kWh savings over a range of ambient temperatures. The second opportunity is using economizers to provide free cooling and reduce the usage of the electric and steam driven chillers. Detailed results of the thermal energy savings as well as the electrical and natural gas cost savings by employing these technologies are discussed in this paper.
Design and Test of 300W, 65K Pulse Tube
Authors: Potratz Seth A. , Nellis Gregory F. , Maddocks James R. , Pfotenhauer John M.
Published: April 2008

This paper describes the design and preliminary experimental results for a large capacity (300W at 65 K) single-stage, Stirling-type pulse-tube. The regenerator, the critical component in the pulse-tube, was optimized via a parametric study accomplished using the REGENv3.2 program. The pulse tube system was subsequently designed using a 1st order model that calculates the pressure-flow characteristics of the system coupled with 2nd order models of the various internal loss mechanisms. An experimental pulse-tube system was fabricated based on this design; the pulse-tube apparatus allows simultaneous, high frequency measurement of instantaneous compressor piston position as well the instantaneous pressures at various locations in the system. In addition, the average temperatures along the regenerator, within the cold heat exchanger gas volume, on the cold heat exchanger surface, and along the pulse-tube are measured. This comprehensive set of measurements will allow a thorough evaluation and verification of the design model over a wide range of operating conditions including compressor stroke, frequency, charge pressure, and load temperature. This paper presents some preliminary experimental progress and compares the measured pressure-flow behavior with the design model predictions.
Large Eddy Simulation of Turbulent Heat Transfer in a Square Duct
Authors: Qin Zhaohui , Pletcher Richard H.
Published: April 2008

Large eddy simulations of turbulent convective heat transfer in a square duct are presented. A finite volume LU decomposition scheme is used to simulate compressible three-dimensional turbulent flow at low Mach numbers in a heated duct. Time derivative preconditioning is used to deal with the low Mach number situation. A localized dynamic subgrid-scale (SGS) model is used to evaluate the unresolved stresses. The calculation domain is divided into two parts. In the first part periodic boundary conditions are used and this provides the fully developed inlet flow for the second part in which the heat transfer conditions are imposed. Characteristic out-flow conditions are applied in the second part. This allows the flow to develop further as it responds to the heating condition. The Reynolds number varied from the order of 1,000 to the order of 10,000. Heated duct cases under constant wall temperature and constant wall heat flux were simulated. Good agreement between the present results with available numerical and experimental data has been obtained.
Compressive Stress Relaxation and Nonlinear Finite Element Analysis of Ethylene/Acrylic Vamac® Terpolymer Elastomer (AEM)
Authors: Fong Rick D. , Sancaktar Erol
Published: April 2008

The main purpose of this paper is to investigate the time dependency of rubber viscoelastic characteristics at various shape factors (SF) and compression percentages (%), namely Compressive Stress Relaxation (CSR) and Retaining Sealing Force (RSF). Results from nonlinear Finite Element Analysis (FEA) were found corresponding with the static CSR data, which could be used for estimating long term CSR effects of particular products with similar SF and compression % and operation environments.
Evaluation of Heat Transfer and Pressure Drop for the Heater-Core in an Automotive Heat Pump System
Authors: Jokar Amir , Eckels Steven J. , Hosni Mohammad H.
Published: April 2008

The heat transfer and pressure drop results for a heater-core of an automotive system are presented and discussed in this article. The heater-core is a type of compact heat exchanger that is used as part of an automobile heating-cooling system for heating the passenger cabin on cold seasons. The automotive heating-cooling system in this study includes a standard refrigeration cycle consists of a condenser, an evaporator, a compressor and an expansion valve using the refrigerant R134a as the working fluid. Furthermore, the system uses two separate secondary fluid loops using a 50% glycol-water mixture to exchange energy with the main refrigeration loop. During the cold weather season, the system is operated in the heat pump mode and one of the fluid loops is used to transfer heat from the condenser to the heater-core for heating the passenger cabin. The heat transfer from the heater-core to the passenger cabin is accomplished using air flow through the heater-core openings in an unmixed and cross-flow fashion. The air-side of the heater-core has a unique louver system that is intended to enhance the air-side heat transfer while the glycol-side has a twisted wire inserts to enhance flow turbulence and heat transfer. Semi-empirical correlations for the heat transfer and pressure drop for both glycol-water mixture and air flows in the heater-core are proposed. The flow of the glycol-water mixture in the heater-core is a single-phase flow within a bundle of parallel circular tubes with the twisted wire inserts. The flow of air through the heater-core is approximated as a flow across a finned-tube compact heat exchanger with continuous plate-fins. A modified Wilson plot technique is applied to determine correlations for heat transfer on both glycol-water mixture and air sides. The frictional pressure drop on the glycol-side is calculated from the total measured pressure drop and adjusted for pressure drops within manifolds and inlet/outlet ports. The results for the heat transfer and pressure drop analyses are finally plotted, discussed and compared with the relevant previous studies. These results show that the heat transfer rate is increased in the glycol-side due to the twisted wire inserts, in comparison with the smooth circular tubes. The air-side heat transfer rate is also enhanced due to the louvers in the air passages, as compared to flat-plate fins in compact heat exchangers.
Sensitivity of Vertebral Compressive Strength to Endplate Loading Distribution
Authors: Buckley Jenni M. , Keaveny Tony M.
Published: April 2008

For a prescribed set of resultant loads, there is uncertainty in vertebral strength due to the unknown nature of the boundary conditions imposed by the disc along the bony endplate. Patient-specific techniques for predicting vertebral strength do not include information regarding the disc-vertebral body interaction since the physical condition of the disc is difficult to diagnose using conventional radiographic techniques, such as CT or MRI. It is unknown whether this omission introduces a large source of error in strength predictions. Thus, quantifying the uncertainty associated with the nature of these boundary conditions is essential for the development of more accurate techniques for in vivo fracture risk prediction.
Design of Experiments Plan With a Capstone Experimentation Course
Authors: Schmaltz Kevin
Published: April 2008

The Mechanical Engineering faculty at Western Kentucky University have developed and implemented a Design of Experiments Plan to assure that graduates of the program have acquired the skills necessary to design and conduct experiments and analyze experimental results. The ME faculty have defined the components of design of experiments, agreed to levels of competence that are expected as a student progresses through the program, and developed assessment tools to quantify student achievement. Instruction is integrated over a dozen courses, and students finally demonstrate the ability to select experimental tools and methods, and apply them to analyze less-defined experimental problems in a senior capstone experimentation class. This class requires student teams to complete three different experiences—mechanical, materials and thermal. The Design of Experiments Plan provides a framework for building upon previous lab work, assessing student progress, and adjusting lab coverage based on prior assessments to assure that graduates of the program are capable experimental practitioners upon graduation.
Investigation of Static Interfacial Fracture in Transparent Glass Fiber Reinforced Polymer Composite Bimaterials Using Photoelasticity
Authors: Ellingsen Marius D. , Khanna Sanjeev K.
Published: April 2008

The effects of static opening mode loading on orthotropic-orthotropic bimaterial interface cracks and isotropic-orthotropic bimaterial interface cracks has been investigated using the experimental technique of transmission photoelasticity. For successful implementation of this experimental technique transparent glass fiber reinforced polyester composite materials were developed, enabling the direct observation and recording of photoelastic fringes in the orthotropic part of the bi-material. Opening mode stress intensity factors have been calculated using the stress field equations for interfacial cracks in the proposed bimaterials in conjunction with an orthotropic stressoptic law.
Control of Mechanical Systems Using a Parameterized Spectral Decomposition Approach
Authors: Sandu Adrian , Sandu Corina , Chan Brendan J. , Ahmadian Mehdi
Published: April 2008

This study investigates a control methodology for dynamic systems based on representing all possible system responses under all possible values of the control variables. The underlying idea is to extend the system along the “control dimension” and explicitly account for the dependence of the system state on control variables. A spectral discretization along the “control dimension” is employed. The optimal control values are chosen to obtain the desired system response. Numerical studies for the control of linear and nonlinear quarter car models riding on various terrain profiles show promising results.
A New Constitutive Model for Predicting Proton Conductivity in Polymer Electrolytes
Authors: Chen Ken S. , Hickner Michael A.
Published: April 2008

A new constitutive model relating proton conductivity to water content in a polymer electrolyte or membrane is presented. Our constitutive model is based on Faraday’s law and the Nernst-Einstein equation; and it depends on the molar volumes of dry membrane and water but otherwise requires no adjustable parameters. We derive our constitutive model in two different ways. Predictions of proton conductivity as a function of membrane water content computed from our constitutive model are compared with that from a representative correlation and other models as well as experimental data from the literature and those obtained in our laboratory using a 4-point probe.
A Thin Film Nitinol Heart Valve
Authors: Stepan Lenka , Levi Daniel , Carman Gregory
Published: April 2008

In order to create a less thrombogenic heart valve with improved longevity, a prosthetic heart valve was developed using thin film nitinol (NiTi). A “butterfly” thin film NiTi valve was constructed using a single, elliptical piece of thin film NiTi and a scaffold made from Teflon tubing and NiTi wire. Flow tests and pressure readings across the valve were performed in vitro in a pulsatile flow loop. Biocorrosion experiments were conducted on untreated and passivated thin film nitinol. To determine the material’s in vivo biocompatibility, thin film nitinol was implanted in a pig using a stent covered with thin film NiTi. Flow rates and pressure tracings across the valve were comparable to those through a commercially available 19 mm Perimount Edwards tissue valve. No signs of corrosion were present on samples of thin film nitinol after immersion in Hank’s solution for 1 month. Finally, organs and tissue samples explanted from the pig 17 days after thin film NiTi implantation appeared without disease, and the thin film nitinol itself was without thrombus formation or endothelialization. Although long term testing will be needed, thin film NiTi may be very well suited for use in artificial heart valves.
Tracking Bearing Spall Severity Through Inverse Modeling
Authors: Li C. James , Shin Hyeongceol
Published: April 2008

The ability to track the severity of a spall in a bearing in operation is desirable for bearing condition monitoring and remaining life estimation. Existing technology estimates spall severity from bearing vibration r.m.s which can be affected by many factors such as operating conditions, and other nearby machine components, and therefore is of little practical use. The proposed method is a model based one and therefore is much more robust. When a spall is present, the impact between rollers and the spall produces a train of impulses which then excite the bearing and its nearby structure. The proposed method identifies a bearing dynamic model from a measured bearing vibration using a system identification method. This bearing dynamic model is then properly inverted to create a stable high fidelity inverse model that recovers the impact impulse behind a measured bearing vibration. Given the vibration of the bearing measured at a different time and therefore a possible different spall size, the inverse model estimates the impulse that excites the bearing vibration. A modeling error compensation scheme then refines the recovered impulse. Subsequently, the spall severity is estimated from the magnitude of impulse by removing the effect of bearing speed. This study also conducted experimental validations to ascertain the effectiveness of the proposed scheme in assessing spall severity.
Active Control of International Space Station Experiment Rack Shelf Simulator Vibrations
Authors: Wang Jingdou , Shepard W. Steve , Williams Keith A. , Gattis Christy B.
Published: April 2008

This research involves the application of methods to actively control the vibrations of an experiment rack shelf. The rack shelf is constructed from a solid rectangular plate restrained along segments of the short sides and is designed to be similar to the experiment rack shelves used in the International Space Station (ISS). Those shelves are subject to vibrations that may adversely affect experiments. Piezoelectric actuators have been proposed as a solution for controlling the rack shelf vibrations. In this work, a two-dimensional asymmetric piezoelectric actuator model is developed first. Then, a Ritz expansion method is employed to derive the Equations of Motion for the active structure with discontinuous boundary conditions. Modal parameters from this analytical solution as well as from experiment modal analysis are used to determine the modal input factors for the piezoelectric actuators. Two control strategies, modal control and collocated output feedback control, are studied with Linear Quadratic Gaussian (LQG) control law. Experimental results show the effectiveness of the proposed control concepts in controlling the first two flexural vibration modes at frequencies below 400 Hz.
Particle Separation in Microfluidic Channels Using Flow Rate Control
Authors: Yang Sung , Zahn Jeffrey D.
Published: April 2008

Microfluidic devices for particle recovery are successfully developed by controlling flow rate ratios of two daughter channels. Devices are prepared by using conventional Polydimethylsiloxane (PDMS) replica molding technique. The flow rate ratios of two daughter channels are controlled by changing the flow resistance through changing the geometry of the downstream channels. The particle recovery studies are conducted using 16 μm-diameter green fluorescent particles and using 8–10 μm-diameter human C8161 melanoma cells. For the fluorescent particles, the particle recovery efficiencies are 87.2%, 95.7%, 100%, and 100% for 2.5:1, 4:1, 6:1, and 8:1 flow rate ratios, respectively. Also, for the human C8161 melanoma cells, the cell recovery efficiencies are 88.7%, 98.9%, 100%, and 100% for 2.5:1, 4:1, 6:1, and 8:1 flow rate ratios, respectively.
A New Unified Approach for Flow Analysis of Magneto-Rheological Fluids
Authors: Kavlicoglu Barkan M. , Gordaninejad Faramarz , Wang Xiaojie , Hitchcock Gregory
Published: April 2008

The focus of this study is to develop a new universal approach for the flow analysis of magneto-rheological (MR) fluids through channels. An experimental study is conducted to investigate the relationship between the pressure loss of a MR fluid as a function of the applied magnetic field strength, volumetric flow rate, and surface roughness without utilizing the assumption of shear yield stress. A relation for nondimensional friction factor is developed in terms of Mason number and dimensionless surface roughness. It is demonstrated that the pressure loss across the MR fluid flow channel is significantly affected by the magnetic field and the surface roughness.
Microprinting of On-Chip Cultures: Patterning of Yeast Cell Microarrays Using Concanavalin-A Adhesion
Authors: Fung Tracy H. , Ball Gregory I. , McQuaide Sarah C. , Chao Shih-Hui , Coleman-Lerner Alejandro , Holl Mark R. , Meldrum Deirdre R.
Published: April 2008

Microprinting has been demonstrated effective in the patterning of surface regions for trapping cells used within microfluidic devices. In this study a polydimethylsiloxane (PDMS) silicone elastomer stamp was microfabricated and used to microstamp concanavalin-A (con-A; protein that binds to yeast) on a glass surface. Yeast cells, Saccharomyces cerevisiae, were brought into contact with patterned con-A producing an array of yeast microscale culture in an ordered array identical to the printed pattern.
Phase-Field Simulation of Solidification With Density Change
Authors: Sun Ying , Beckermann Christoph
Published: April 2008

Phase-field models of solidification with convection often assume the existence of a single (mixture) velocity at any location inside the diffuse interface, and the phase-field, φ, is advected by this mixture velocity. In this paper, the advection of the phase-field is examined for a one-dimensional normal flow to a solidification front induced by a density difference between the solid and liquid. It is found that the results from a phase-field model that assumes a single velocity inside the diffuse interface are generally not in agreement with the sharp interface condition for the kinetic undercooling of the front in the presence of unequal densities, regardless of the interface width. By introducing a two-phase approach, where the solid and liquid are assumed to coexist inside the diffuse interface with different velocities, good agreement with the sharp interface condition is obtained irrespective of the density ratio between the two phases.
Predicting the Mobility of Tracked Robotic Vehicles
Authors: Akcabay Deniz T. , Perkins N. C. , Ma Zheng-Dong
Published: April 2008

Robotic vehicles are an attractive alternative to manned vehicles in hazardous or dangerous off road and urban environments. Present designs of robot vehicles employ wheels or tracks as the running gears and, in general, tracks provide superior mobility on rough or uneven terrain. This paper presents a multibody dynamics model of a tracked robotic vehicle for the purpose of predicting mobility in two different scenarios: 1) steep terrains, and 2) urban terrains in the form of staircases. In both scenarios we study the physical limitations on vehicle mobility imposed by key vehicle design variables and vehicle operating conditions. Example vehicle design variables include the location of the mass center, grouser penetration, and track/terrain friction. Example vehicle operating conditions include climbing under full versus partial track/terrain contact, and climbing on straight versus switch back courses.
Packaging Hand-Held MEMS — MinIMEs (Miniature Integration of MEMS/Electronics)
Authors: Pohl Kenneth R. , Dagel Daryl , Galambos Paul
Published: April 2008

In this paper we present two complete MEMS microsystems, one optical and one microfluidic, with associated packaging, light sources, signal modulation, optics, fluid connections and flow control. These are fully functional hand held devices and as such demonstrate a means of freeing the MEMS device from the laboratory environment and inserting it into the field. This highly integrated packaging concept can be applied to a wide range of surface micromachined MEMS, and probably other non-surface micromachined MEMS devices, which are generally easier to package.
Finite Element Modeling of 3D Turning of Titanium
Authors: Li Rui , Shih Albert J.
Published: April 2008

The finite element modeling and experimental validation of 3D turning of grade two commercially pure titanium are presented. The Third Wave AdvantEdge machining simulation software is applied for the finite element modeling. Machining experiments are conducted. The measured cutting forces and chip thickness are compared to finite element modeling results with good agreement. The effects of cutting speed, a limiting factor for productivity in titanium machining, depth of cut, and tool cutting edge radius on the peak tool temperature are investigated. This study also explores the use of 3D finite element modeling to study the chip curl. Reasonable agreement was observed under turning with small depth of cut. Results of this research help to guide the design of new cutting tool materials and coatings and the studies of chip formation to further advance the productivity of titanium machining.
Continuous Particle Filtration and Concentration by Multigradient Dielectrophoresis
Authors: Fiechtner Gregory J. , Skulan Andrew J. , Barrett Louise M. , Singh Anup K. , Cummings Eric B. , Simmons Blake A.
Published: April 2008

A novel methodology for designing selective particle concentrators in electrokinetic flows is presented. The technique is based on two-level etching of channels to produce ridges along which field gradients are patterned. The field gradients are then used to deflect particles using dielectrophoresis. Using uniform-field designs as a basis, fields in the vicinity of a single ridge are examined both experimentally and numerically. Although isotropic etching causes local deviations from piecewise continuous fields, ridges are found to serve as selective particle deflectors in experiments with both polystyrene beads and Bacillus subtilis. Sequences of parallel ridges are also tested, illustrating the efficacy of corrugated ridge structures for selective particle concentration.
Frequency Dependent Velocity and Vorticity Fields of Electroosmotic Flow in a Closed-End Rectangular Microchannel
Authors: Marcos
Published: April 2008

The frequency dependent electroosmotic flow in a closed-end rectangular microchannel is analyzed in this study. Dynamic AC electroosmotic flow field is obtained analytically by solving the Navier-Stokes equation using the Green’s function formulation in combination with a complex variable approach. With the Debye-Hu¨ckel approximation, the electrical double layer potential distribution in the channel is obtained by analytically solving the linearized two-dimensional Poisson-Boltzmann equation. Additionally, the Onsager’s principle of reciprocity is demonstrated to be valid for AC electroosmotic flow. The effects of frequency-dependent AC electric field on the oscillating electroosmotic flow and the induced backpressure gradient are studied. Furthermore, the expression for the electroosmotic vorticity field is derived, and the characteristic of the vorticity field in AC electroosmotic flow is discussed. Based on the Stokes second problem, the solution of the slip velocity approximation is also presented for comparison with the results obtained from the analytical solution developed in this study.
Performance of Off-Line Polynomial CNC Trajectories Within the Context of HSM
Authors: Lavernhe Sylvain , Duan Xinbin , Tournier Christophe , Lartigue Claire
Published: April 2008

The objective of the article is to present various off-line calculation methods to calculate polynomial tool trajectories, format well adapted to High-Speed Machining. In particular, we are interested in comparing machining performances of various polynomial calculation algorithms such as interpolation, association or inter-approximation with energy minimization. This comparison is achieved using a test part through simulations and machining tests to justify the efficiency of the calculation methods. Measurements of velocity and position during machining highlight differences between the different association methods. Attention is also paid to the visual and geometrical quality of the machined surfaces.
On the Solution of Transcendental Eigenvalue Problem in Transmission Line Bundled Conductors
Authors: Verma Himanshu , Dighe Ashish M. , Hagedorn Peter
Published: April 2008

Overhead electrical transmission lines are always susceptible to aeolian vibrations, caused by light to moderate winds. Spacer dampers are used in bundled transmission lines to keep the conductors at required minimum spacing and to suppress the wind induced vibrations. Mathematical models are necessary for the computation of the conductor vibrations for studying the efficiency of damping measures. The so called energy balance method gives good results for estimating the vortex excited vibrations of overhead electrical transmission lines. In its standard form it requires the knowledge of the eigenfunctions, which are routinely calculated for the single conductor lines. However, the problem becomes more involved in the case of bundled conductors with spacer dampers due to very dense spectrum of the natural frequencies. In the present paper some approaches towards solving the transcendental eigenvalue problem (EVP) for the bundled conductors with spacer dampers are discussed. It is formulated as an algebraic transcendental EVP, which however presents several numerical difficulties. Reasons for these numerical difficulties are discussed in some detail. A new approach, named as “continuous spectrum approach,” provides better engineering solution for the transmission line bundled conductors. The solution of the EVP gives the necessary input data for applying the energy balance.
Multi-Objective Design and Selection of One Single Optimal Solution
Authors: Levi F. , Gobbi M. , Farina M. , Mastinu G.
Published: April 2008

In the paper, the problem of choosing a single final design solution among a large set of Pareto-optimal solutions is addressed. Two methods, the k-optimality approach and the more general k-ε-optimality method will be introduced. These two methods theoretically justify and mathematically define the designer’s tendency to choose solutions which are “in the middle” of the Pareto-optimal set. These two methods have been applied to the solution of a relatively simple engineering problem, i.e. the selection of the stiffness and damping of a passively suspended vehicle in order to get the best compromise between discomfort, road holding and working space. The final design solution, found by means of the k-ε-optimality approach seems consistent with the solution selected by skilled suspensions specialists. Finally the k-optimality method has proved to be very effective also when applied to complex engineering problems. The optimization of the tyre/suspension system of a sports car has been formulated as a design problem with 18 objective functions. A large set of Pareto-optimal solutions have been computed. Again, the k-optimality approach has proved to be a useful tool for the selection of a fully satisfactory final design solution.
A New Test Rig for Measuring the Inertia Properties of Vehicles and Their Subsystems
Authors: Previati Giorgio , Mastinu Giampiero , Gobbi Massimiliano , Piccardi Carlo , Bolzoni Luca , Rinaldi Sergio
Published: April 2008

The aim of the paper is to present the latest issues of a simple and accurate method (and related test-rig) for the measurement of the mass properties of ground vehicles and their subsystems. The method requires 1) to measure the weight and the center of gravity location of the body under investigation, 2) to make the body swing in a rather complex way in the space, 3) to record the swinging motion, 4) to identify the inertia tensor components by means of a proper numerical procedure, based both on a non-linear mathematical model of the system which carries the body and on the recorded data. The carrying system is actually a three or four-bar pendulum. A convenient configuration of the pendulum in order to obtain a good measurement accuracy is derived. A validation of the measuring procedure is presented. The measurement error on the main diagonal components of the inertia tensor is less than 1%. The rig is being used to measure the inertia tensor of a number of road vehicles and engines/gearboxes.
Tensile Deformation and Progressive Failure Behavior of Woven-Fabric GFRP Laminates at Cryogenic Temperatures
Authors: Takano Satoru , Takeda Tomo , Shindo Yasuhide , Narita Fumio
Published: April 2008

This paper focuses on understanding the deformation and progressive failure behavior of glass/epoxy plain weave fabric-reinforced laminates subjected to uniaxial tension load at cryogenic temperatures. Cryogenic tensile tests were conducted on the woven-fabric laminates, and the damage development during loading was characterized by AE (acoustic emission) measurements. A finite element methodology for progressive failure analysis of woven-fabric composite panels was also developed, and applied to simulate “knee” behavior in the stress-strain responses and damage behavior in the tensile test specimens. The effect of strain concentrations due to the fabric architecture on the failure strain of the material was considered by incorporating the SVF (strain variation factor) from meso-scale analysis of a woven-fabric composite unit into the macro-scale analysis of the specimens. A comparison was made between the finite element predictions and the experimental data, and the agreement is good.
Study of the Noise Produced by Trains Coming to a Halt
Authors: Samagaio Anto´nio , Rocha Joana , Godinho Maria
Published: April 2008

The noise resulting from stopping a moving train is often a source of annoyance to both passengers and people who work and sometimes live in the vicinity of railroad stations. The present study attempted to define the characteristics of noise produced by the brakes of trains used in Portugal. The braking process varies widely from train to train and within the same type of train. Therefore, the results of the measurements had to be statistically analyzed. The parameters used to describe noise in this situation were the LAeq, the L10 and the L90 and the corresponding measurements took place both during the daytime and the nighttime period. Data was also obtained as a function of time and in 1/1 octave bands. The results show that there is a direct correlation between the maximum speed of a given train and the corresponding sound pressure level when the train is stopped. It was found that passenger trains that belong to the new, upper class of railroad transportation were the noisiest ones at the time of braking. As to the railroad itself, it was found that long welded rails make a favorable contribution to the decrease of noise levels. It was also found that the nighttime period was less noisy than the daytime period, in particular in terms of LAeq and L10.
In-Situ Fabrication of Composite Piezoelectric Wafer Active Sensors for Structural Health Monitoring
Authors: Giurgiutiu Victor , Lin Bin
Published: April 2008

Structural health monitoring (SHM) is important for reducing maintenance costs while increasing safety and reliability. Traditionally, structural integrity tests required attachment of sensors to the material surface. This is often a burdensome and time-consuming task, especially considering the size and magnitude of the surfaces measured (such as aircraft, bridges, structural supports, etc.). Temporary sensors are a hassle to install; there are some critical applications where they simply cannot accomplish the task required. Piezoelectric wafer active sensors (PWAS) can be permanently attached to the structure and offer a permanent sensor solution. Existing ceramic PWAS, while fairly accurate when attached correctly to the substance, may not provide the long term durability required for SHM. The bonded interface between the PWAS and the structure is often the durability weak link. Better durability may be obtained from a built-in sensor that is incorporated into the material. This paper describes the work on the in-situ fabrication of PWAS using a piezoelectric composite approach. The piezoelectric composite was prepared by mixing small lead zirconate titanate (PZT) particles in an epoxy resin matrix; the mixture was then directly applied onto the surface of a host structure using a designed mask. The curing of the piezo composite was carried out at elevated temperature. After curing, the cured composite was sanded down to the desired thickness. Finally, the piezo composite was poled under a high electric field to activate the piezoelectric effect. The resulting in-situ composite PWAS was utilized as a sensor for dynamic vibration and impact. Characterization of the in-situ composite PWAS on aluminum structure have been recorded and compared with ceramic PWAS before and after polarization. To evaluate the performance of the in-situ composite PWAS, both vibration and impact tests were conducted. In-situ composite PWAS are believed to be a good candidate for reliable low-cost sensor fabrication for SHM.
Confinement Effects on Flow and Combustion Under Fuel Lean Conditions
Authors: Archer S. , Gupta A. K.
Published: April 2008

Three-dimensional (3-D) flowfield data has been obtained using Particle Image Velocimetry (PIV) for varying swirl distributions in the burner. The 3-D data also allows one determine the local swirl number of the resulting flow. Flow characteristics of the resulting flowfield, both without and with combustion, have been examined for the effect of co- and counter-swirl under lean direct injection conditions using unconfined and confined combustor geometry. Experimental results of the effect of swirl and combustion are presented to simulate the flow dynamics of Lean Direct Injection (LDI) configuration gas turbine combustion. The selected configuration is typical because it does not make use a premixing zone and relies totally on the swirl and the injector to accomplish rapid mixing. Specifically, the effect of radial distribution of combustion air and swirl in a burner are examined under non-burning and burning conditions using propane as the fuel. The present study explores single swirler interaction with the use of an experimental double concentric swirl burner that simulates one swirler of a practical gas turbine combustor. Results showed that both swirl and combustion has significant effect on the characteristics of the internal and external recirculation zones. The calculated local swirl number differs significantly form that estimated using geometrical relationship derived from the vane angle only. The effect of combustion for the confined and unconfined geometries was also been found to be different. In the confined geometry combustion decreases the size of the recirculation zone. This is in contrast to that found for the unconfined conditions. Combustion enhances the recirculation zone in the unconfined geometry. Combustion provides greater velocity magnitudes than their counter non-combustion conditions. The counter-swirl combination resulted in smaller and more well defined internal recirculation regions. The results provide the role of swirl and combustion on the mean and turbulence characteristics of flows over a range of swirl and shear conditions between the inner and outer flow of the burner. This data provides important insights on the flow dynamics in addition to providing data for model validation and model development.