bluuebunny/crossref_metadata_2025 huggingface dataset:
Layerwise Analysis of Thermal Shape Control in Graded Piezoelectric Beams
Authors: Lee H.-J.
Published: May 2008

A layerwise finite element formulation developed for piezoelectric materials is used to investigate the displacement and stress response of a functionally graded piezoelectric bimorph actuator. The formulation is based on the principles of linear thermopiezoelectricity and accounts for the coupled mechanical, electrical, and thermal response of piezoelectric materials. The layerwise laminate theory is implemented into a linear beam element in order to provide a more accurate representation of the transverse and shear effects that are induced by increased inhomogeneities introduced through-the-thickness by using functionally graded materials. The accuracy of the formulation is verified with previously published experimental results for a piezoelectric bimorph actuator. Additional studies are conducted to analyze the impact of electric and thermal loads on the deflections and stresses in a bimorph actuator. Results of the study help demonstrate the capability of the layerwise theory to provide a more complete representation of shear effects that are no longer negligible even in thin piezoelectric beams. In addition, the effects of varying piezoelectric properties through-the-thickness of the beam are shown to provide additional benefits in minimizing the induced deformations and stresses.
Reverse Monte Carlo Method for Transient Radiative Transfer in Participating Media
Authors: Lu Xiaodong , Hsu Pei-Feng
Published: May 2008

The Monte Carlo (MC) method has been widely used to solve radiative transfer problems due to its flexibility and simplicity in simulating the energy transport process in arbitrary geometries with complex boundary conditions. However, the major drawback of the conventional (or forward) Monte Carlo method is the long computational time for converged solution. Reverse or backward Monte Carlo (RMC) is considered as an alternative approach when solutions are only needed at certain locations and time. The reverse algorithm is similar to the conventional method, except that the energy bundle (photons ensemble) is tracked in a time-reversal manner. Its migration is recorded from the detector into the participating medium, rather than from the source to the detector as in the conventional MC. There is no need to keep track of the bundles that do not reach a particular detector. Thus, RMC method takes up much less computation time than the conventional MC method. On the other hand, RMC will generate less information about the transport process as only the information at the specified locations, e.g., detectors, is obtained. In the situation where detailed information of radiative transport across the media is needed the RMC may not be appropriate. RMC algorithm is most suitable for diagnostic applications where inverse analysis is required, e.g., optical imaging and remote sensing. In this study, the development of a reverse Monte Carlo method for transient radiative transfer is presented. The results of non-emitting, absorbing, and anisotropically scattering media subjected to an ultra short light pulse irradiation are compared with the forward Monte Carlo and discrete ordinates methods results.
Cycle-to-Cycle Control of HCCI Engines
Authors: Shaver Gregory M. , Gerdes J. Christian
Published: May 2008

With stated benefits ranging from increased thermal efficiency to significantly reduced NOx emissions, Homogeneous Charge Compression Ignition (HCCI) represents a promising combustion strategy for future engines. When achieved by reinducting exhaust gas with a variable valve actuation (VVA) system, however, HCCI possesses nonlinear cycle-to-cycle coupling through the exhaust gas and lacks an easily identified trigger comparable to spark or fuel injection. This makes closed-loop control decidedly nontrivial. To develop a controller for HCCI, the engine cycle is partitioned into five stages: adiabatic, constant pressure induction of re-inducted product and reactant charge; isentropic compression to the point just prior to combustion initiation; constant volume combustion; isentropic expansion of product gases; isentropic exhaust of product gases. Using this framework, a nonlinear low-order model of HCCI combustion is formulated, where the input is the molar ratio of reinducted products to fresh reactants and the output is the peak in-cylinder pressure. Comparison with experimental in-cylinder pressure data shows that the model, while simple, offers reasonable fidelity. Using the nonlinear model, a linearized model and an accompanying LQR controller are formulated and implemented on a more detailed model presented in previous work. Results from these simulations show that the modeling and control approach is indeed successful at tracking a varying desired work output while maintaining a constant desired combustion phasing.
Pelton Turbine Needle Control Model Development, Validation, and Governor Designs
Authors: Johnson Randell M. , Chow Joe H. , Dillon Michael V.
Published: May 2008

Underspeed needle control of two Pelton turbine hydro units operating in a small power system has caused many incidents of partial system blackouts. Among the causes are conservative governor designs with regard to small signal stability limits, non-minimum phase power characteristics, and long tunnel-penstock traveling wave effects. A needle control model is developed from “water to wires” and validated for hydro-turbine dynamics using turbine test data. Model parameters are tuned with trajectory sensitivity. Proposed governor designs decompose the needle regulation gains into the power and frequency governor loops with a multi-time-scale approach. Elements of speed loop gain scheduling and a new inner-loop pressure stabilization circuit are devised to improve the frequency regulation and to damp the traveling wave effects. Simulation studies show the improvements of the proposed control designs.
Machining Accuracy Due to Tool or Workpiece Vibrations
Authors: Mann Brian P. , Young Keith A. , Schmitz Tony L. , Bartow Matthew J. , Bayly Philip V.
Published: May 2008

This paper presents a newly developed method for predicting dimensional errors caused by vibrations of either the cutting tool or workpiece. In previous literature, this phenomenon has been described as the “surface location error” from process dynamics. Analytical predictions are compared to several milling experiments: 1) a flexible workpiece and rigid tool; and 2) a rigid workpiece and flexible tool. Tool or workpiece vibrations were measured with non-contact sensors during the cutting process. In addition, dimensional errors were directly measured on machined parts. The results from experimental cutting tests show good agreement with theoretical predictions.
Performance Evaluation of the Optimal Control of a Gantry Crane
Authors: Wang Zhonghua , Surgenor Brian
Published: May 2008

For a gantry crane, optimal control of the crane motion requires that the speed of the cart be maximized, and the swing of the hanging payload be minimized. The problem lends itself naturally to optimal linear quadratic (LQ) controllers. This paper examines the performance of four different approaches to the design of an LQ controller, including two optimization approaches as based on: 1) minimal energy of cart and payload and 2) integrated absolute error of payload angle. Both simulation and experimental results are presented. A demonstration is also given as to how the results taken from laboratory scale gantry crane experiments must be treated with caution. Laboratory based studies have generally worked with systems where the moving cart mass is much larger than the suspended payload mass. In the case of industrial scale gantry cranes, the reverse can be true. This has implications with respective to the robustness of the controller. In the case where the cart mass is much greater than the payload mass, the effect of the payload on the cart is correctly neglected. However, there are stability implications if this is not the case. The implications with respect to the tuning of LQ controllers for this application are discussed.
Methods for Target-Setting and Rule Compliance in Automotive Engineering
Authors: Lomangino Paul , Sohn Kyu
Published: May 2008

Automotive design relies heavily upon the use of targets. In addition to providing direction and context for the development of new products, the target-setting process forms links between the subjective and objective characteristics of a product and, when executed properly, can help ensure compliance with regulations and feasibility guidelines. At the start of the target-setting process, business and marketing activities define a desired competitive position for a proposed product using data gathered in the various methods of market analysis. From this desired position, business and marketing develop high-level targets for attributes like performance, comfort, and cargo capacity based upon the current and predicated future qualities of products that are perceived to be potential competitors in the marketplace. These business targets guide the formulation of engineering targets. Engineers interpret the business targets to determine what combination of engineering attributes would best accomplish them. These attributes form the basis of a starting set of engineering targets that must be evaluated against databases of corporate, industry, and governmental regulations as well as rules that indicate the design viability and manufacturability of the product. This paper discusses the source, development, and use of targets in automotive engineering as well as formalisms and methods to describe and handle the target-setting and verification processes. In addition, this paper discusses proposed information technology-based and knowledge-based techniques to strengthen and streamline this critical aspect of the engineering design process.
Integrated Plant, Observer, and Controller Optimization With Application to Combined Passive/Active Automotive Suspensions
Authors: Fathy Hosam K. , Papalambros Panos Y. , Ulsoy A. Galip
Published: May 2008

The plant and control optimization problems are coupled in the sense that solving them sequentially does not guarantee system optimality. This paper extends previous studies of this coupling by relaxing their assumption of full state measurement availability. An original derivation of first-order necessary conditions for plant, observer, controller, and combined optimality furnishes coupling terms quantifying the underlying trilateral coupling. Special scenarios where the problems decouple are pinpointed, and a nested optimization strategy that guarantees system optimization strategy that guarantees system optimality is adopted otherwise. Applying these results to combined passive/active car suspension optimization produces a suspension design outperforming its passive, active, and sequentially optimized passive/active counterparts.
Characterizing the Human Wrist for Improved Haptic Interaction
Authors: Kuchenbecker Katherine J. , Park June Gyu , Niemeyer Gu¨nter
Published: May 2008

Haptic displays provide the user with a sense of touch in both simulation of virtual environments and teleoperation of remote robots. The instantaneous impedance of the user’s hand affects this force interaction, changing the transients experienced during activities such as exploratory tapping. This research characterizes the behavior of the human wrist joint while holding a stylus in a three-fingered grasp. Nonparametric identification methods, evaluating frequency-and time-responses, support a second-order system model. Further analysis shows a positive linear correlation between grip force and wrist impedance for all subjects, though each individual’s trend is unique. These findings suggest that a quick calibration procedure and a realtime grip force measurement could enable a haptic display to predict user response characteristics throughout an interaction. Such knowledge would enable haptic control algorithms to adapt continuously to the user’s instantaneous state for improved performance.
Depolarization of Light by Mono-Dispersed Air Bubbles Coated With Carbonaceous Particles
Authors: Wong Basil T. , Vaillon Rodolphe , Mengu¨c¸ M. Pinar
Published: May 2008

In this paper, the potential use of polarized light for characterization of mono-dispersed air bubbles coated with carbonaceous particles is investigated using a vector Monte Carlo approach. The medium is assumed to be water, loaded with highly-forward scattering ash and coal particles, as well as absorbing and scattering air bubbles coated with a thin carbonaceous (soot) layer. A polarized laser beam is assumed to impinge normally on a cylindrical system at the circumferential surface, and the scattered signals are assumed to be collected within the same plane. The scattering matrix for the entire medium is constructed based on the Fresnel equations. Examination of the absorbing and multiple-scattering results show that if circularly polarized light is used, the bubble size, the bubble separation, as well as the thickness of carbonaceous layer around bubbles can be determined if careful experiments are conducted. It is shown that circularly polarized light is a better choice than the linearly polarized incident radiation for the present diagnosis objectives.
Combustion of Nonane and JP8 Droplets With Additives in Low Convection
Authors: Bae J. H. , Avedisian C. T.
Published: May 2008

The combustion of nonane and JP8 droplets was studied in an environment to promote spherically symmetric droplet flames. Measurements of the droplet, flame and soot ‘shell’ or ‘cloud’ diameters were made to examine how the burning process and sooting dynamics were influenced by three miscible additives: hexanol, tripropylene glycol methyl ether (TPM), and an additive that had been previously developed to improve thermal stability of JP8, called as ‘+100’. The experimental results presented for nonane were used to compare with JP8 for a comparatively simple fuel. The initial droplet diameters ranged from 0.4mm to 0.7mm to allow quantitative measurement of the influence of droplet diameter on the droplet burning process. Spherical symmetry was promoted by carrying out the experiments in microgravity. The burning conditions were room temperature air at atmospheric pressure. Soot formation was found to be massive for JP8 compared to nonane, with thick dark soot clouds that accumulated significant soot as burning progressed. With hexanol and TPM mixed with JP8, soot formation was noticeably reduced. Soot trends in the approximate order of JP8 > JP8+100 > JP8+100 / TPM (90/10, v/v) > JP8+100 / TPM (80/20) > JP8+100 / hexanol (50/50) > nonane are noted for the fixed initial droplet diameter. Significant droplet heating was found for JP8 compared to nonane, due to the higher liquid thermal diffusivity of nonane compared to JP8 and the lower product of density and specific heat of nonane compared to JP8. A distinct influence of initial droplet diameter on the subsequent evolution of droplet diameter after ignition was found for nonane in that larger droplets burned slower than smaller droplets for the range of initial droplet diameters examined. The evolution of soot shell diameter was independent of additive concentrations for JP8 and still distinct from nonane. A new scale variable is presented which collapses the various ‘standoff’ diameters (soot shell and flame) onto a single curve for a given fuel.
Thermal Model of a Thinned-Die Cooling System
Authors: Boiadjieva N. , Koev P.
Published: May 2008

For through-silicon optical probing of microprocessors, the heat generated by devices with power over 100W must be dissipated [1]. To accommodate optical probing, a seemingly elaborate cooling system that controls the microprocessor temperature from 60 to 100° C for device power up to 150W was designed [2]. The system parameters to achieve the desired thermal debug environment were cooling air temperature and air flow. A mathematical model was developed to determine both device temperature and input power. The 3-D heat equation that governs the temperature distribution was simplified to a case of a 1-D rod with one end at the device center and the other at the cooling air intake. Thus the cooling system was reduced to an analytical expression. From experimental data, we computed all coefficients in the model, then ran extensive tests to verify—the accuracy was better than 10% over the entire temperature and power ranges.
Development of Systems Engineering Model for UREX Process
Authors: Royyuru Haritha , Sun Lijian , Chen Yitung , Hsieh Hsuan-Tsung , Clarksean Randy , Pepper Darrell W. , Vandegrift George , Copple Jackie , Laidler James
Published: May 2008

The mission of the Transmutation Research Program (TRP) at University of Nevada, Las Vegas (UNLV) is to establish a national nuclear technology research capability, a nuclear engineering test bed that can carry out effective transmutation and advanced reactor research and development effort. The main task of the Chemical Engineering Division, Argonne National Laboratories (ANL) is to design, model, and demonstrate countercurrent uranium solvent-extraction process. The division has developed MS Excel macros interface, called Argonne Model for Universal Solvent Extraction (AMUSE), to calculate flowsheets for treating high-level liquid waste. The AMUSE code forms all computational basis for flowsheet design and process development. The extraction process, including U, Tc, Pu/Np, Cs/Sr, and Am/Cm separations, is complicate and requires further system optimization for robust performance. A systems engineering model is proposed by the Nevada Center for Advanced Computational Methods (NCACM) at UNLV that provides process optimization through the adjustment on feed compositions, stages, number of sections and flow rates. The NCACM is designing and developing a MS Visual Basic graphical user interface (GUI) that provides multiple-run results and data reporting and presentation. All calculations are made by the interaction with the MS Excel macros, defined in ANL AMUSE codes. An optimization model, developed with the GUI, interconnects with MatLab’s optimization toolbox, commercial software from MathWorks. Due to the nature of the AMUSE code, all the computational results are generated from the existing AMUSE macros. The model also examines measure effects of process deviations, caused by operational upsets or product diversion.
Enhancing DNA Microarray Analysis With Pulsed Source-Sink Flows
Authors: Stremler Mark A. , Haselton F. R.
Published: May 2008

DNA hybridization on microarrays is enhanced with the use of a pulsed source-sink system, a design that is based on the occurrence of chaotic advection. Experimental results demonstrate increased signal levels in faster times, an increase in signal-to-noise ratios, and a decrease in signal variability.
Transient Thermal Evaluation for Integrated Motor Control System With Multiple Dynamic Heat Sources
Authors: Chiriac Victor Adrian , Lee Tien-Yu , Bien David
Published: May 2008

A detailed transient thermal analysis for a single-chip silicon Integrated Motor Control System with multiple dynamic heat sources with various applications in electronics packaging is performed using numerical simulations. The challenge resides in the transient thermal interaction between the various dynamic heat sources, activated simultaneously at different powering profiles. Several operating steps are simulated, and the transient thermal behavior for each source is identified during the process. The peak temperature reached by one of the main motors (powered for 3.6W@15ms) is 68.1°C, ∼14°C lower than its peak temperature with all the other heat sources on, indicating the thermal impact of the surrounding heat sources on the main motor within the first 15 ms. The temperature limits are not exceeded by the system during operation. When the die is powered with uniform 1.6W under steady state conditions, the peak temperature reaches ∼74.8°C (associated junction-to-ambient Rja thermal resistance is ∼31.2°C/W. The replacement of the custom-made board with a standard JEDEC board leads to a drop in the overall junction-to-ambient thermal resistance by almost 20%. An analytical validation for an equivalent simplified transient model is performed. The short-time thermal transient study and the specific set of boundary conditions are a close approximation to the closed form solution of the one-dimensional semi-infinite solid exposed to a uniform heat flux at its free surface. The analytical results are in good agreement with the simulation.
Force Control of Linear Motor Stages for Microassembly
Authors: Gorman Jason J. , Dagalakis Nicholas G.
Published: May 2008

The microassembly of microelectromechanical systems from various micro-components requires the development of many new robotic capabilities. One of these capabilities is force control for handling micro-scale components with force control resolution on the order of micronewtons. In this paper, the force control of linear motor stages is discussed with application to the microassembly of MEMS. Linear motor stages provide an attractive solution for microassembly robots because they have a large working volume and can achieve high-precision positioning. However, the nonlinear friction and force ripple effects inherent in linear stages provide an obstacle to the required level of force control. A model of a single motor stage has been developed including dynamic friction effects. Based on this model, a robust nonlinear force controller has been designed to meet the microassembly requirements. The controller has been tested in simulation to demonstrate its effectiveness.
Design of a Microfabricated Rankine Cycle Steam Turbine for Power Generation
Authors: Fre´chette Luc G. , Lee Changgu , Arslan Selin , Liu Yuan-Chun
Published: May 2008

This paper presents the system-level and component design of a micro steam turbine power plant-on-a-chip which implements the Rankine cycle for micro power generation. The microfabricated device consists of a steam turbine that drives an integrated micropump and generator. Two-phase flow heat exchangers are also integrated on-chip with the rotating components to form a complete micro heat engine unit, converting heat to electricity. The system-level design includes cycle analysis and overall performance predictions, accounting for the expected performance of miniaturized components, thermal and structural integrity of the microsystem, and system-level trade-offs for optimal overall performance. Operating principles and design studies are also presented for the core component, with emphasis on a multistage, planar, radial microturbine and a spiral groove viscous pump. Design consideration for two-phase flow heat exchangers, microbearings, seals and micro-generators are also presented. Expected power levels range from 1–12 W per chip with energy conversion efficiency in the range of 1–11%. This suggests power density of up to 12 kW/kg for this technology, which is an order of magnitude greater than competing technologies, such as thermoelectrics. This study suggests the viability of a micro Rankine power plant-on-a-chip, but also identifies critical engineering challenges that must be met for practical implementation.
Simulation and Analysis for Melt Casting a Metallic Fuel Pin Incorporating Volatile Actinides
Authors: Tan Taide , Clarksean Randy , Chen Yitung , Pepper Darrell , Meyer Mitchell K.
Published: May 2008

The filling and solidification process for melt casting a metallic fuel pin is considered. The problem was analyzed numerically using the commercial finite element software package FIDAP (Fluent, Inc.). Numerical simulations are performed to study process parameters that could impact the solidification of the melt within the mold. A Metallic Fuel Pin mold is a long, thin, straw-like pipe, which has a cylindrical shape. The fluid is a high-temperature melt mixture of Am, Pu, and Zr. which is considered as an incompressible Newtonian fluid. Filling velocities and filling pressures are varied to study what impact these parameters might have on flow and solidification within the melt.
Development of 3D Imaging Unit With Enlarged and Flicker-Free View for Micromanipulation System
Authors: Jiang C. S. , Tso S. K.
Published: May 2008

Micromanipulation systems find increasing applications in many fields. In these systems, operators carry out fine motion directly with the aid of the microscope. In order to free operators from eye-straining operations under the microscope we propose to present the 3D view to a TV or PC screen. Based on stereovision an analog time-division system, a subfield system and a digital field sequential system are synthesized, as described in this paper. The development of these systems is centered on how to eliminate the flicker and how to enhance the resolution of the video images. The experimental results show that the subfield system and the digital field sequential system are effective in addressing the problems associated with the micromanipulation.
Clamping Planning in Workpiece-Fixture Systems
Authors: Xiong Cai-Hua , Xiong You-Lun , Wang Michael Yu
Published: May 2008

This paper presents a general method for the determination of the optimal clamping forces including their magnitude and positions. First, we develop a locally elastic contact model to describe the nonlinear coupling between the contact force and elastic deformation at the individual contact. Further, a set of “compatibility” equations are given so that the elastic deformations among all contacts in the workpiece-fixture system result in a consistent set of rigid-body displacement of the workpiece in its global system. We define the minimum norm of the elastic deformation at contacts as the objective function, then, formulate the problem of determining of the optimal clamping forces as a constrained nonlinear programming problem, which guarantees that the fixturing of the workpiece is passive force closure. The proposed planning method of optimal clamping forces is illustrated with numerical example.
The Unsteady Characteristics of a Laminar Flow and Heat Transfer of a Pair of Confined Impinging Air Jets
Authors: Chiriac Victor Adrian , Rosales Jorge Luis
Published: May 2008

The unsteady laminar flow and heat transfer characteristics for a pair of confined impinging air jets centered in a channel were studied numerically. The time-averaged heat transfer coefficient for a pair of heat sources centered in the channel was determined as well as the oscillating jet frequency for the unsteady cases. The present study continues the authors’ previous investigation [1], which emphasized how the small spacing between the heat sources leads to a reduction in heat transfer when increasing the flow Reynolds (Re) number, particularly in the unsteady regime. It depends on the proximity of the jet inlets, the channel dimensions and the jet Reynolds number. The jet unsteadiness causes the stagnation point locations to sweep back and forth over the impingement region, and the jets “wash” a larger surface area on the target wall. The results indicate that the dual jets become unsteady between a Renumber of 200 and 300. Prior study indicated that in this Re range, a fixed stagnation “bubble” forms on the target wall between the two jets, reducing the local heat transfer and leading to its quasi-independence on flow conditions. In this study, due to the larger space between the heat sources, the “bubble” occurring between the jets is not having a detrimental impact on heat transfer. The oscillating frequency of the flow increases with Re number for the unsteady cases, leading to significant heat transfer enhancement. The time-averaged heat transfer coefficient on the heat sources rises with Re number increase for both steady and unsteady cases. By varying the distance between the heat sources, the “bubble” region does not impact the cooling of the heat sources, as the increase in flow rate leads to increased heat transfer coefficients. Alternative designs and their impact on the heat source thermal performance are further investigated.
Experimental and Modeling Studies of PEM Fuel Cell Performances With Interdigitated Flow Fields
Authors: Wang Lin , Liu Hongtan
Published: May 2008

Systematic experiments with different cell temperatures, humidification temperatures, pressures and reactant gas flow rates have been carried out to study the effects of different parameters on the performance of a PEM fuel cell with interdigitated flow fields. A 3-D fuel cell model was used to simulate the performance of a PEM fuel cell with interdigitated flow fields. The modeling results were compared with experimental data and the comparison shows a good agreement.
hADIABATIC and u’MAX
Authors: Moffat Robert J.
Published: May 2008

In all electronics cooling situations, and many other practical situations, the surface temperature varies in the stream-wise direction. In these cases, defining the heat transfer coefficient using the adiabatic temperature of the surface instead of the mixed mean temperature of the coolant result in significant benefits. The resulting definition is hadiabatic. The theoretical and practical bases for hadiabatic are presented. Examples of its use in electronics cooling are described to show the operational advantages this approach offers. Turbulence strongly affects heat transfer. A simple, turbulence-based correlation is presented that yields an estimate of the heat transfer coefficient good enough for preliminary design estimates and often as accurate as can be relied upon from CFD calculations using present codes.
Next Generation Devices for Electronic Cooling
Authors: Webb Ralph L.
Published: May 2008

Conventional technology to cool desktop computers and servers is that of the “direct heat removal” heat sink, which consists of a heat sink/fan mounted on the CPU. Although this is a very cost effective solution, it is nearing its end of life. This is because future higher power CPUs will require a lower R-value than can be provided by this technology, within current size and fan limits. This paper discusses new technology that uses “indirect heat removal” technology, which involves use of a single or two-phase working fluid to transfer heat from the hot source to an ambient heat sink. This technology will support greater heat rejection than is possible with the “direct heat removal” method. Further, it will allow use of higher performance air-cooled ambient heat sinks than are possible with the “direct heat removal” heat sink. A concern of the indirect heat removal technology is the possibility that it may be orientation sensitive. This paper identifies preferred options and discusses the degree to which they are (or or not) orientation sensitive. It should be possible to attain an R-value of 0.12K/W at the balance point on the fan curve.
Comparative Study of Spine Fixation Technique
Authors: Gao Robert X. , Lee Jonghyun , Cowan Scott , Lee K. Francis
Published: May 2008

Lumbar disc degeneration is an ailment that afflicts a large population. Spinal fusion techniques have been developed to alleviate pain and reestablish spine stability. It has been found that the stress levels within the vertebrae can significantly influence bone healing and resorption. To effectively apply fixation devices, analysis of the interactions between the tissue and inserted devices is needed. This paper presents a biomechanical study using the finite element (FE) method. Specifically, patient-based intact L4-L5 motion segments were constructed through an edge detection algorithm. Intervertebral disc was modeled with composite element. The effect of an anterior lumbar interbody fusion cage with unilaminar (ULFS) and translaminar facet screws (TLFS) was then evaluated. The results were analyzed in the terms of stability and stress distribution.
Analysis of Nonlinear Dynamics for a Rotor-Active Magnetic Bearing System With Time-Varying Stiffness: Part I — Formulation and Local Bifurcations
Authors: Zhang Wei , Zu Jean W.
Published: May 2008

In this two-part paper, we investigate nonlinear dynamics in the rotor-active magnetic bearings (AMB) system with 8-pole legs and the time-varying stiffness. The model of parametrically excited two-degree-of-freedom nonlinear system with the quadratic and cubic nonlinearities is established to explore the periodic and quasiperiodic motions as well as the bifurcations and chaotic dynamics of the system. The method of multiple scales is used to obtain the averaged equations in the case of primary parameter resonance and 1/2 subharmonic resonance. In Part I of the companion paper, numerical approach is applied to the averaged equations to find the periodic, quasiperiodic solutions and local bifurcations. It is found that there exist 2-period, 3-period, 4-period, 5-period, multi-period and quasiperiodic solutions in the rotor-AMB system with 8-pole legs and the time-varying stiffness. The catastrophic phenomena for the amplitude of nonlinear oscillations are first observed in the rotor-AMB system with 8-pole legs and the time-varying stiffness. The procedures of motion from the transient state chaotic motion to the steady state periodic and quasiperiodic motions are also found. The results obtained here show that there exists the ability of autocontrolling transient state chaos to the steady state periodic and quasiperiodic motions in the rotor-AMB system with 8-pole legs and the time-varying stiffness.
Rotating Loosening Mechanism of Nut Connecting Rotary Disc Under Rotating-Bending Force
Authors: Fujioka Yasuo , Sakai Tomotsugu
Published: May 2008

There are fastened structures composed of rotary disc and shaft, which are fastened with bolts and nuts with tapered bearing surfaces. Those are loaded with rotating-bending force. It has been difficult to explain clearly the rotating loosening mechanism of such joint’s nuts by the previously proposed mechanism. In this study, the rotating mechanism of this nut was investigated from theoretical and experimental view points. Finally two types of mechanisms were derived. One is as follows: High pressure contact area is formed by external load oriented in the radial direction of a disc. It gives very small difference of radii between the bearing surface of disc and that of nut. Then, with the revolution of the disc, it makes occurrence of two friction torques in opposite direction, which are Tw and Ts torques on bearing and on threads respectively. When revolving disc, relative rotating direction of nut is dominated by bigger torque of Tw and Ts. If Tw is bigger than Ts, the rotating direction of nut is the same as the disc revolution. If Ts is bigger than Tw, the rotating direction is opposite to disc revolving direction. Taking into consideration this mechanism, some tests were carried out by changing magnitude of the friction coefficients both of bearing surface and of threads surface with greasing and degreasing intentionally. Loosening and tightening rotations were confirmed to occur just as predicted from the above mentioned mechanism. The other is due to the eccentricities caused by dimensional errors around the bolt, the nut and the tapered bearing surface of rotary disc. In this case, the direction of the force transmitted through the high pressure contact area changes from the center of bolt axis. So, the transmitted force can cause the torque which loosens and tightens the nut during one revolution of rotary disc, therefore relative rotation of nut results in small fluctuating of loosening and tightening. Combining two types of mechanisms, repeating small angle of loosening and tightening, nuts are rotated inclined to loosening or tightening direction after many revolutions of disc.
Cryogenic Machining With Brittle Tools and Effects on Tool Life
Authors: Ghosh Ranajit , Zurecki Zbigniew , Frey John H.
Published: May 2008

With the current popularity of finish hard turning, the need for improved productivity and tool life is of significant importance to manufacturers. The present work explores the effects of cryogenic coolants in machining hardened materials, from an industrial perspective, with emphasis on productivity and tool life improvement, environmental effects, as well as reliable performance characteristics for brittle tools. Both alumina ceramic (Al2O3) and polycrystalline cubic boron nitride (PCBN) tools show significant tool life improvement in cryomachining of hard ferrous materials, such as 52100 bearing steel and A2 tool steel. Significant productivity gains have also been observed in cryogenic machining of WC-Co rolls with polycrystalline diamond (PCD) tools. The enhanced performance of cryomachining is attributed to more efficient heat removal from the cutting insert, as well as reduction in thermal softening of the cutting tools at higher temperatures.
An Assessment of Module Cooling Enhancement With Thermoelectric Coolers
Authors: Simons R. E. , Ellsworth M. J. , Chu R. C.
Published: May 2008

The trend towards increasing heat flux at the chip and module level in computers is continuing. This trend coupled with the desire to increase performance by reducing chip operating temperatures presents a further challenge to thermal engineers. This paper will provide an assessment of the potential for module cooling enhancement with thermoelectric coolers. A brief background discussion of thermo-electric cooling is provided citing some of the early history of thermoelectrics as well as more recent developments from the literature. An example analyzing cooling enhancement of a multi-chip module package with a thermoelectric cooler is discussed. The analysis utilizes closed form equations incorporating both thermoelectric cooler parameters and package level thermal resistances to relate allowable module power to chip temperature. Comparisons are made of allowable module power with and without thermoelectric coolers based upon either air or water module level cooling. These results show that conventional thermoelectric coolers are inadequate to meet the requirements. Consideration is then given to improvements in allowable module power that might be obtained through increases in the thermoelectric figure of merit ZT or miniaturization of the thermoelectric elements.
Specifying EB-PVD Process Parameters for Coating of a Second Stage Turbine Blade Using an Experimentally Verified CAD Model of the Process
Authors: Weir William C. S. , Sisson Richard D. , Bose Sudhangshu
Published: May 2008

A model was developed to predict the thickness of the thermal barrier coating (TBC) applied to specific points on a rotating PW4000 second stage turbine blade using electron beam physical vapor deposition (EB-PVD). The theoretical model of coating deposition rates as a function of position in the PVD vapor cloud (Knudsen cosine law) was experimentally verified. The experimental work consisted of a series of four turbine blades coated under various coating conditions. Based on the verified model, a UniGraphics (UG) CAD model of the process was built. A UG User Function (UFunc) was programmed to predict coating thickness for a wide variety of EB-PVD process parameters to populate a database of contoured coating profiles. A software tool was then developed to specify the manufacturing process parameters to fabricate a contoured EB-PVD TBC of partially stabilized zirconia. A coating profile matching routine was included in the software to identify the process parameters closest to the desired coating profile. The focus of this paper is on the experimental methods, the CAD model and the software tool.
Powersplit Hybrid Electric Vehicle Control With Data Dependent Systems Forecasting
Authors: Nesbitt Richard T. , Pandit Sudhakar M. , Muehlfeld Christian M.
Published: May 2008

The focus of this paper is on the implementation of Data Dependent Systems (DDS) forecasting in to the control algorithm of the 2001 Michigan Tech Future Truck. The 2001 MTU Future Truck is a 2000 model year Chevrolet Suburban and utilizes a powersplit transmission, which is similar to the Toyota Prius, for its hybrid conversion. The main source of propulsion comes from a General Motors, all aluminum block, 3.5L V-6. In the Future Truck, the accessory current is not directly measured, so it must be calculated from the measured motor current, generator current and battery current. Accessory current is defined as the current used by all of the high voltage components such as the power steering and AC compressor, except the primary drive motor. In order for the vehicle to be charge sustaining, the generator must produce the same amount of power consumed by the accessories and the drive motor. This calculation will only indicate what the accessory load was at the previous sample time and not what the accessory load will be at the current sample time. When it comes to control of the vehicle, this creates a lag, and the controls will undershoot or overshoot the desired accessory current, which creates inefficiencies due to excessive power flow into and out of the battery pack. In order to better understand the accessory load, Data Dependent Systems (DDS) modeling was done on accessory current data collected from the test vehicle, and an AR(26) model was concluded to be adequate, based on the residual sum of squares (RSS) and unified auto-correlations. The DDS modeling of the accessory current also led to the forecasting of the accessory loads. This helps keep battery use to a minimum by allowing the generator to create the correct amount of power, at that time step, to operate the accessories. Accessory draw from the batteries and generator overshoot going into the batteries is minimized and therefore the overall efficiency of the vehicle goes up. The vehicle was tested on a 50-mile circuit including city and highway driving and elevation changes. The results from the test vehicle showed a power savings of 892 kJ/hour which improved the fuel economy by 3 mpg over stock. The charge sustainability of the vehicle was also achieved which means the range of the vehicle is only limited by the fuel mileage, similar to a conventional vehicle.
Speed and Throttle Position Forecasting on a Parallel Hybrid Electric Vehicle
Authors: Muehlfeld Christian M. , Pandit Sudhakar M.
Published: May 2008

Included in this paper is the forecasting of the speed and throttle position on a thru-the-road parallel hybrid electric vehicle (HEV). This thru-the-road parallel hybrid design is implemented in a 2002 model year Ford Explorer XLT, which is also the Michigan Tech Future Truck. Data Dependent Systems (DDS) forecasting is used in a feedforward control algorithm to improve the fuel economy and to improve the drivability. It provides a one step ahead forecast, thereby allowing the control algorithm to always be a step ahead, utilizing the engine and electric motor in their most efficient ranges. This control algorithm is simulated in PSAT, a hybrid vehicle simulation package, which can estimate the fuel economy and certain performance characteristics of the vehicle. In this paper a fuel economy savings of 2.2% is shown through simulation. Charge sustainability was achieved along with drivability being improved as indicated by the reduction in number of deviations from the speed profile in the driving cycle.
Effects of 3-D Local Unsteadiness on Heat Transfer Prediction in Turbulated Passages
Authors: McDowell Pamela A. , York William D. , Walters D. Keith , Leylek James H.
Published: May 2008

A newly developed unsteady turbulence model was used to predict heat transfer in a turbulated passage typical of turbine airfoil cooling applications. Comparison of fullyconverged computational solutions to experimental measurements reveal that accurate prediction of heat transfer coefficient requires the effects of local small-scale unsteadiness to be captured. Validation was accomplished through comparison of the time- and area-averaged Nusselt number on the passage wall between adjacent ribs with experimental data from the open literature. The straight channel had a square cross-sectional area with multiple rows of staggered and rounded-edge ribs on opposite walls that were orthogonal to the flow. Simulations were run for Reynolds numbers of 5500, 16500, and 25000. Computational solutions were obtained on a multi-block, multi-topology, unstructured, and adaptive grid, using a pressure-correction based, fully-implicit Navier-Stokes solver. The computational results include two-dimensional (2-D) and three-dimensional (3-D) steady and unsteady simulations with viscous sublayers resolved (y+ ≤ 1) on all the walls in every case. Turbulence closure was obtained using a new turbulence model developed in-house for the unsteady simulations, and a realizable k-ε turbulence model was used for the steady simulations. The results obtained from the unsteady simulations show greatly improved agreement with the experimental data, especially at realistically high Reynolds numbers. The key 3-D physics mechanisms responsible for the successful outcome include: (1) shear layer roll-up over the turbulators; (2) recirculation zones both upstream and downstream of the rib faces; and (3) reattachment regions between each rib pair. Results from the unsteady case are superior to those of the steady because they capture the aforementioned mechanisms, and therefore more accurately predict the heat transfer.
Development of a MacroPCM Neck Cooling Collar for Athletes and Runners
Authors: Colvin David P. , Lokody Tom
Published: May 2008

Investigators at Triangle Research and Development Corporation (TRDC) have developed materials and applications for enhanced thermal management using both micro-and macro-encapsulated phase change materials (PCMs) since 1983; including: microPCM coolants, coatings, composites, fibers and PCM apparel. The PECS™ (Personal Environmental Control System) was developed for microclimate body cooling beneath NBC (Nuclear-Biological-Chemical) protective clothing for the US NAVY and USMC (Colvin, 1997 and 2000). Similar cooling apparel using 3–4mm macroPCM COOLBEADS™ were developed for costumed characters at two theme parks as well as potential use by firemen (Colvin, 1998). The results for these programs were reported at the 2000 and 2002 ASME ICEME (Colvin, 2000 and 2002). Civilian apparel has included 3.5 lb and 5 lb vests, a 1.5 lb cowl as well as a 1-lb collar, which suggested the potential for the microclimate cooling of athletes. Extreme heat during outdoor sporting events can be a major problem for athletes. Competitive runners, who often generate 700–900 W/m2, commonly deal with temperatures above 32.2°C (90°F) and a relative humidity greater than 80%. Natural cooling by evaporation and convection are often inadequate for a vigorously exercising athlete. Many athletes fatigue, drop out or have to wrap their chest and shoulders with ices and towels in order to finish the races. Ice and frozen gels, however, are uncomfortable, heavy, and can cause the blood vessels to constrict, thus restricting good blood circulation. Encapsulated PCMs can store 60 J/kg and the air spaces between the particles permit evaporation and convection as well as rapid thermal recharging. Development of an effective cooling collar could potentially permit competitive athletes to combat heat exhaustion and increase the body’s ability to dissipate heat.
Teaching Environmentally Conscious Design and Manufacturing at the Undergraduate Level: A Georgia Tech Perspective
Authors: Bras Bert
Published: May 2008

In this paper, an overview is given of the history and current implementation of an undergraduate Mechanical Engineering course titled “ME 4171 - Environmentally Conscious Design and Manufacturing” at the Georgia Institute of Technology. This course was developed in late 1993 and has been taught every year since as an elective in Mechanical Engineering. The course is designed to give the students an opportunity to learn about environmentally conscious design and manufacture, the growing national and international efforts in reducing the environmental impact of products, and how environmental considerations affect the design’s technical, economical and quality requirements, and vice versa. In this paper, the philosophy behind the course, its objectives and outcomes, and its structure are discussed. The rationale for the course content is given in context of national and international developments in the area. Recommendations for curricular development are also provided.