bluuebunny/crossref_metadata_2025 huggingface dataset:
Prime Silicon and Silicon-on-Insulator (SOI) Wafer Polishing With Magnetorheological Finishing (MRF)
Authors: Tricard Marc , Dumas Paul R. , Golini Don , Mooney James T.
Published: May 2008

The December 2001 [1, 2] edition of the International Technology Roadmap for Semiconductors [3] (ITRS-2001) identifies several challenges for the manufacturing of silicon and silicon-on-insulator (SOI) wafers. For silicon, edge exclusion, site flatness and nanotopography1 requirements will become extremely challenging. For SOI, requirements for the control of the top silicon layer and its associated uniformity are pushing the limits of metrology. Keeping ± 5% tolerances on thicknesses, gradually decreasing from more than 100nm to less than 20nm for partially depleted devices (let alone from 30 to 3nm for fully depleted devices) is exceeding the capabilities of traditional chemo-mechanical-polishing (CMP) processes [5]. This paper will briefly describe magnetorheological finishing (MRF) and its suitability for prime silicon and SOI wafer polishing. Particular emphasis will be placed on MRF’s ability to improve the global flatness and the total thickness variation (TTV) on prime silicon wafers, and to reduce the nominal thickness of the top silicon layer, while improving thickness uniformity on SOI wafers. The paper will also touch upon the process qualification issues associated with the tight requirements of the semiconductor industry.
Parametric Study of Surface Finish in End Milling Using Robust Design Techniques
Authors: Verma Alok K. , Holcomb Steven L. , Blessner Paul , Tilman Dave , Johnston William F.
Published: May 2008

Surface finish in end milling depends upon a number of variables, such as feed rate, cutting speed, tool material, etc. The relative effect of these variables on surface roughness is not understood very well. The Taguchi method is used in end milling process to identify variables having major influence on surface finish. Partial factorial design using L9 orthogonal array is used in the design of experiments. Signal to Noise ratio analysis along with analysis of variance is used to study the effect of these parameters on surface finish. Knowledge about these relationships will help a process planner or a machinist optimize the cutting process with respect to surface finish.
Parameters Associated With Errors in the Nanoindentation at Low Load
Authors: Lee Hong-Lim , Lee Young-Seok , Jeong Seong-Min , Park Sung-Eun , Oh Han-Seog
Published: May 2008

In the nanoindentation at very low load, various parameters give difficulties in estimating mechanical properties. These parameters are the uncertainties of the indenter geometry and limitations including minimum detectable load and surface roughness. The geometrical deviation in the indenter tip shape and surface roughness are key parameters of errors related to measurement of mechanical properties by nanoindentation at very low load. Therefore, in this work, the effect of surface roughness on the indentation hardness was studied for fused silica wafer, fused silica plate and silicon wafer, which have different roughness values one another. To compare the theoretical values with the measured ones, the effect of the indenter tip geometry was studied using the simulation of the finite element analysis (FEA), neglecting other effects, such as indentation size effect (ISE) and surface roughness. As a result, the geometrical deviation in the indenter tip shape was observed to affect the indentation hardness and the contact area at low load. The roughness of specimens is assumed to be related to the scattering of the evaluated indentation hardness.
Failure Properties of Adhesive Joints With Adhesively Filled Columns
Authors: Liu Jiemin , Sawa Toshiyuki
Published: May 2008

Failure properties of bulk adhesive joints with Adhesively Filled Columns (AFCs) subjected to external loads were investigated by experimental method and finite element method (FEM). From the experiment results, it was found that the strengths of the bulk adhesive joints with AFCs increases considerably whether they are subjected to external tensile loads or lateral bending loads. And the joint strenghts increase with increasing of the depths of the blind holes. Failure process of the joints with AFCs was simulated by element birth-death technology developed in FEM. The conclusions obtained from FEM coincide with that obtained from the experiments.
Feedback Control of Brake System on Railway Vehicle Considering Non-Linear Property and Dead Time
Authors: Nankyo Masanobu , Ishihara Tadashi , Inooka Hikaru
Published: May 2008

Increase of deceleration in high-speed and high-density train operation degrades riding comfort and frequently causes wheel skids. This requires an introduction of the control engineering to upgrade the control performance of brake systems on rolling stocks. We are now studying a control method for mechanical brakes that uses friction and pneumatic pressure, including non-linear elements as the basis of brake force. Furthermore, the system itself has certain “dead time”, which is not ignorable and makes controlling difficult. One of our targets is to develop a brake control device that can control deceleration in accordance with a decelerating pattern that optimizes riding comfort and prevents wheel skids. In this paper, a design method of the controller for the deceleration tracking control and the system compensating the dead time are proposed. Finally, the effects of them are confirmed through computer simulations and experimental results.
Modeling of Broaching Process for Improved Tool Design
Authors: Ozturk Ozkan , Budak Erhan
Published: May 2008

High productivity and high quality can be achieved in broaching if the process is applied properly. Roughing, semifinishing and finishing can be performed in one stroke of the tool increasing productivity and reducing set-up time. Furthermore, high quality surface finish can be obtained due to straight motion of the tool. One big disadvantage of broaching is that all process parameters, except cutting speed, are built into broaching tools. Therefore, it is not possible to modify cutting conditions during the process once the tool is manufactured. Improved design of broaching tools needs detailed modeling and analysis of the broaching process. In this paper, tool optimization method and process models are presented. Cutting forces, tooth stresses, part deflections are modeled and analyzed using cutting models and FEA. The results of the analysis are summarized in analytical forms so that they can be used for other applications although turbine disc broaching is considered as the application which is one of the most complex broaching operations. Application of the model for improved and optimized tool design are demonstrated by examples.
A Novel Motion Amplifier Using an Axially Driven Buckling Beam
Authors: Jiang Jie , Mockensturm Eric M.
Published: May 2008

For active materials such as piezoelectric stacks, which produce large force and small displacement, motion amplification mechanisms are often necessary—not simply to trade force for displacement, but to increase the output work transferred through a compliant structure. Here, a new concept for obtaining large rotations from small linear displacements produced by a piezoelectric stack is proposed and analyzed. The concept uses elastic (buckling) and dynamic instabilities of an axially driven buckling beam. The optimal design of the buckling beam end conditions was determined from a static analysis of the system using Euler’s elastica theory. This analysis was verified experimentally. A stack-driven, buckling beam prototype actuator consisting of a pre-compressed PZT stack (140 mm long, 10 mm diameter) and a thin steel beam (60 mm × 12 mm × 0.508 mm) was constructed. The buckling beam served as the motion amplifier, while the PZT stack provided the actuation. The experimental setup, measuring instrumentation and method, the beam preloading condition, and the excitation are fully described in the paper. Frequency responses of the system for three preloading levels and three stack driving amplitudes were obtained. A maximum 16° peak-to-peak rotation was measured when the stack was driven at an amplitude of 325 V and frequency of 39 Hz. The effects of beam preload were also studied.
Parallel Molecular Dynamics Code Validation Through Bulk Silicon Thermal Conductivity Calculations
Authors: Gomes Carlos J. , Madrid Marcela , Amon Cristina H.
Published: May 2008

We have implemented a parallel molecular dynamics algorithm, which incorporates the Stillinger-Weber interatomic potential. The code was parallelized using a ghost cell atomic division approach, ensuring scaling with the number of processors and a significant increase in speed with respect to the serial version. The methodology is validated by computing the thermal conductivity and phonon frequency spectra of bulk silicon single crystals for different domain sizes at 1000K. The predicted thermal conductivities are consistent with the experimental value at that temperature. In addition, the phonon frequency spectra capture the properties expected from the dispersion relations for silicon.
A Complete Study of Equal Channel Angular Extrusion Process: A Promising Method for Production of Nanostructured Materials
Authors: Kaculi Xhemal
Published: May 2008

Equal channel angular extrusion (ECAE) is defined as a deformation process that produces intense and uniform plastic deformation caused by simple shear of the material and it is being investigated as an effective method for forming nanostructured materials. This paper presents a thorough study of the ECAE via finite element. A two dimensional model consisting of a stainless steel billet and the die system was constructed. The effect of the most significant parameters, namely, angle of extrusion, temperature, and friction on the extruded final product was investigated. The stresses, axial strains, shear strains, and principal strains as a function of extrusion time for nine different models, at three different sections (top, bottom and middle of the billet), and eleven equally spaced points per each section are presented. The deformations patterns are different when moving from top to bottom and when moving from center to circumference of the billet. Also all the variables studied, extrusion angle, temperature and friction have a significant effect on the final extruded product.
Constructal Theory and the Optimization of Finned Arrays
Authors: Kraus A. D.
Published: May 2008

Existing expressions for the optimization of individual fins of rectangular profile are reviewed and a new expression that relates the tip admittance to the input admittance is derived. A procedure for finding the optimum longitudinal fin of rectangular profile with tip heat loss is provided and this procedure is illustrated with an example of an array for a forced convection example.
Thermal-Fluid Sciences Laboratory Course
Authors: Fridman Ella , Devarakonda Maruthi
Published: May 2008

At the Department of Engineering Technology at the University of Toledo we are working on introducing laboratory course in thermal-fluid sciences with the elements of controls. The objective is to create a course where the students will learn to see connections between the three branches of the thermal-fluid sciences and will learn to appreciate the integrated nature of modern systems. The proposed laboratory course will be structured around four “equipment centers” represented important areas of applications in the thermal-fluid sciences: 1) Armfield Modules (turbomachinery), 2) Steam Motor and Energy Conversion Set, 3) Modular Air Flow Laboratory, and 4) Experimental Heat Pump and Air Cooler. The students will take the course after they finish courses in Thermodynamics and Fluid Mechanics. The course will give our students an opportunity to observe how the concepts and principles learned in the classroom can be applied in a practical situation. To extend the instructional capability of the equipment and to give the students knowledge of modern instrumentation and control systems we use LabVIEW for computerization and automation of this laboratory. The experiments that have already been developed for the course as well as experiments that have been planned for the future are presented in the paper.
Computation of Ventilation Aerodynamics in Singapore’s Kallang Paya Lebar Expressway Underground Tunnel
Authors: Dayanandan S. , Damodaran M.
Published: May 2008

This work is concerned with the development and application of a computational fluid dynamics based model for predicting all possible ventilation aerodynamic flow, pollution and fire scenarios in an underground road tunnel that is being constructed in Singapore. This work addresses flow modeling for the underground road tunnel ventilation studies, pollution and fire modeling studies and presents the computed results and discussion pertaining to the estimation of pollution levels in the underground road tunnel during a simulated traffic jam and the simulation of vehicular fires in the tunnel and the management and control of a simulated fire in the tunnel by operating flow conditioning and ventilation systems. The model can serve as a tool for enabling the engineers to perform scenario planning for effective design and control of the ventilation inside the tunnel.
A Novel Analysis of the Mechanics of Cochlea, the Inner Ear
Authors: Biswas Amitava
Published: May 2008

The human ear is often regarded as a paragon of mechanical engineering. To understand how the hearing system works, scientists have proposed detailed models of its specific aspects—the transfer of acoustic energy from the atmosphere to the tympanic membrane via the external ear; the coupling of the tympanic membrane to the oval window of the cochlea via ossicles; the resultant fluidic oscillations in the cochlear ducts; the formation of traveling waves in the basilar membrane of the cochlea; the mechanical stimulation of inner hair cells by the basilar membrane; and the consequential transduction of nerve impulses. Scientists have also proposed models to explain the phenomenon of enhancement of the traveling waves in the basilar membrane by synchronized co-contraction in the length of outer hair cells (OHCs). Although it is unrealistic that any OHC would contract in length without expanding in diameter, the models proposed by other analysts have so far incorporated the longitudinal contraction of OHCs only, suggesting that the impact of any diametric expansion of OHCs would be relatively trival. Here we show that the basilar membrane would behave like a Beam-Column system, which may be significantly influenced by the diametric expansion of OHCs.
A Study on the Effect of Inclination on Thermal Behaviors of Natural Convection Inside Thin Electronic Equipment Casing
Authors: Ishizuka Masaru , Kitamura Yoji
Published: May 2008

With rapid increase of the power dissipation density in modern electronic equipment, the cooling design of electronic equipment becomes increasingly important. For widely used forced-convection air-cooled systems, the reliability of and the acoustic noise of the fan present serious concerns as the air velocity is increased to enhance the cooling capacity. Thus, the interest in natural convection air-cooling is growing to take advantages of low noise and energy saving inherent in that cooling mode. One method of promoting the capacity of natural air-cooling is to incline the electronics casing, thereby, induce draft air by what is called the chimney effect. However, the effect of inclination on the thermal behavior and the cooling capacity has not yet been fully understood due to the involvement of many parameters in driving the draft air. This paper presents the results of experimental and numerical studies on the effect of casing inclination on the temperature rise across the casing. The numerical simulation was carried out to find the thermal behavior inside a thin electronic casing. The simulation results are in good agreement with the experimental data. A thermal design guide is obtained regarding how the cooling effect is improved by increasing the inclination angle.
Optimizing Vibration Isolation of Flex Circuits in Hard Disk Drives
Authors: Brake M. , Wickert J. A.
Published: May 2008

Flex circuits are a laminate of polyimide substrate, adhesive, and copper conductors, and they are used to connect the (stationary) electronic components in a hard disk drive to the (rotating) arm that positions the read/write heads above the disk. The transverse and longitudinal vibration of flex circuits couples with motion of the read/write heads and contributes to increased settling time and residual vibration following repositioning of the arm from one data track to another. In this paper, the results of parameter, optimization, and experimental studies are discussed with a view toward increasing the isolation of vibration between the flex circuit to the arm in terms of a metric involving one or several important vibration modes.
Vehicles and Nonlinear Suspensions
Authors: Nakhaie Jazar G. , Mahinfalah M. , Rastgaar Aagaah M. , Fahimi F.
Published: May 2008

An independent suspension for conventional vehicles has been modeled as a nonlinear vibration absorber with a nonlinear third-order ordinary differential equation. In order to obtain conditions that guarantee existence of periodic solutions and stable responses, the Schauder’s fixed-point theorem has been implemented to prove a third-order solution existence theorem for general third-order differential equations. A numerical method has been developed for rapid convergence, and applied for a sample model. The correctness of sufficient conditions and solution algorithm has been shown with appropriate figures.
Design of Applied Reentry Guidance Algorithms for Low Cost Vehicles
Authors: Mahmoudian N. , Rastgaar Aagaah M. , Nakhaie Jazar G. , Mahinfalah M.
Published: May 2008

Simple guidance methods for Reentry Vehicles (RV) with low lift to drag ratio (L/D) during the reentry phase is investigated. Proposed algorithms, based on nominal trajectory method, permit the vehicle to experience the aerodynamic force, which is needed to keep the actual trajectory close to the desired one and increase landing accuracy. Simulation results for a conceptual RV are provided to demonstrate the performance of the trajectory guidance laws under a variety of non-nominal conditions.
Global Chaos in a Periodically Forced, Linear System With a Dead-Zone Restoring Force
Authors: Luo Albert C. J. , Menon Santhosh
Published: May 2008

The Poincare mapping and the corresponding mapping sections for global motions in a linear system possessing a dead-zone restoring force are developed through the switching planes pertaining to the two constraints. The global periodic motions based on the Poincare mapping are determined, and the analysis for the stability and bifurcation of periodic motion is carried out. From the global periodic motions, the global chaos in such a system is investigated numerically. The bifurcation scenario with varying parameters was presented. The mapping structures of periodic and chaotic motions are discussed. The Poincare mapping sections for global chaos are given for illustration. The grazing phenomenon embedded in chaotic motion is observed.
Effect of the Thermostatic Expansion Valve Characteristics on the Stability of a Refrigeration System
Authors: Mulay Veerendra , Agonafer Dereje , Schmidt Roger
Published: May 2008

The combination of increased power dissipation and increased packaging density has led to substantial increases in chip and module heat flux in high-end computers. The challenge has been to limit the rise in chip temperature. In the past virtually all-commercial computers were designed to operate at temperatures above the ambient. However researchers have identified the advantages of operating electronics at low temperatures. The primary purpose of low temperature cooling using vapor compression system are faster switching times of semiconductor devices, increased circuit speed due to lower electrical resistance of interconnecting materials, and a reduction in thermally induced failures of devices and components. Achievable performance improvements range from 1 to 3% for every 10°C lower transistor temperature, depending on the doping characteristics of the chip. The current research focuses on IBM’s mainframe, which uses a conventional refrigeration system to maintain chip temperatures below that of comparable air-cooled systems, but well above cryogenic temperatures. Although performance has been the key driver in the use of this technology, the second major reason for designing a system with low temperature cooling is the improvement achieved in reliability to counteract detrimental effects, which rise as technology is pushed to the extremes. A mathematical model is developed to determine the time constant for expansion valve sensor blub. This time constant varies with variation in thermo-physical properties of sensor element that is bulb size and blub liquid. An experimental bench is built to study the effect of variation of evaporator outlet superheat on system performance. The heat load is varied from no load to full load (1KW) to find out the system response at various loads. Experimental investigation is also done to see how the changes in thermo-physical properties of the liquid in sensor bulb of expansion valve affect the overall system performance. Different types of thermostatic expansion valves are tested to investigate that bulb size; bulb constant and bulb location have significant effect on the behavior of the system. Thermal resistance between the bulb and evaporator return line can considerably affect the system stability and by increasing the thermal resistance, the stability can be further increased.
Surface Finish for a Case of Continuous and Interrupted OD Hard Turning
Authors: Pavel Radu , Sinram Keith , Combs Dana , Pillar Jim , Marinescu Ioan
Published: May 2008

Hard turning is the process to watch in many industries, as it is a perfect candidate for the actual trends toward automation and flexible manufacturing. However, there are still many possible conjunctures created by different geometries or materials of the workpieces versus different types of cutting tools with effect on workpiece surface quality, tool wear, machine tool vibrations, etc. These insufficiently explored combinations make manufacturers hesitate to adopt hard turning as a finishing process. This paper brings new findings concerning the effect of cutting parameters and tool nose radius variations on surface finish as a result of continuous and interrupted hard turning. The considered workpieces are a camshaft made of AISI 1117 steel at 62 HRC for continuous cutting, and a spline shaft made of AISI 1137 steel at 48 HRC for interrupted cutting. Two types of PcBN cutting tools are used for both types of component parts. The investigation highlights the differences between the ideal, geometrically determined, surface roughness Ra and the experimental results, as well as the differences recorded between the continuous and interrupted cutting situations. The factorial experimentation technique was employed taking the resulting surface rughness (Ra) as a response variable. The influence of tool wear was finally considered in the analysis of the predicted values of roughness obtained through characteristic regression equations. A significant difference of roughness evolution versus tool wear was recorded for the continuous and interrupted surfaces. The analysis was completed based on profilometry and light interferometry measurements as well as optical and SEM microscopy observations.
A Hybrid Signal Processing Approach to Sensor Data Analysis
Authors: Yan Ruqiang , Gao Robert X.
Published: May 2008

This paper presents a hybrid signal processing approach combining the wavelet transform and spectral analysis. A new approach to selecting a mother wavelet for decomposition of vibration signals was demonstrated. Subsequently, the bestsuited decomposition scale was selected based on the energy content of the wavelet coefficients. Subsequently, the envelope spectrum of the wavelet coefficients at the best-suited decomposition scale was used to identify the defect and its location. Experimental analysis of signals from a defect-seeded bearing has shown that the developed approach is more efficient than the conventional spectral analysis techniques.
Complex Dynamics of Carbon Nanotube Probe Tips
Authors: Lee Soo Il , Raman Arvind , Howell Stephen W. , Reifenberger Ron , Nguyen Cattien V. , Meyyappan Meyya
Published: May 2008

Carbon nanotube (CNT) tips in tapping mode atomic force microscopy (AFM) enable very high-resolution imaging, measurements, and manipulation at the nanoscale. We present recent results based on experimental analysis that yield new insights into the dynamics of CNT probe tips in tapping mode AFM. Experimental measurements are presented of the static response, the frequency response and dynamic amplitude-distance data of a high-aspect-ratio multi-walled (MW) CNT tip to demonstrate the nonlinear features including tip amplitude saturation preceding the dynamic buckling of the MWCNT. The differences between the nonlinear tapping mode response of CNT tips are compared with previously known results on the nonlinear response of conventional tips. Surface scanning is performed using a MWCNT tip on a SiO2 grating to verify the imaging instabilities associated with MWCNT buckling when used with normal control schemes in the tapping mode. Lastly, the choice of optimal setpoints for tapping mode control using CNT tip are discussed using the experimental results.
Design of a Conformable Rotor Airfoil Using Distributed Piezoelectric Actuation
Authors: Anusonti-Inthra Phuriwat , Gandhi Farhan , Frecker Mary
Published: May 2008

In the present study, a design methodology is developed for determining the optimal distribution of a limited amount of piezoelectric material and optimal skin for a conformable rotor airfoil section. The objective of the design optimization is to generate a conformable airfoil structure that produces significant trailing edge deflection under actuation loads, but minimal airfoil deflection under aerodynamic loads. Energy functions, Mutual Potential Energy (MPE) and Strain Energy (SE), are used as measures of the deflections created by the actuation and aerodynamic loads, respectively. The design objective is achieved by maximizing a multi-criteria objective function that represents a ratio of the MPE to SE. Several design optimization techniques are evaluated including geometry and concurrent geometry-topology optimizations. The results of the study indicate that the optimized conformable airfoil section obtained using the concurrent geometry-topology optimization can produce a significant downward trailing edge deflection, and the airfoil deformation due to the aerodynamic loads alone is small. However, the optimized airfoil design is extremely complex and contains intricate network of actuators, which may be difficult to fabricate. Systematic simplification of the structure is performed to obtain a conformable airfoil design that is simple and may be easy to build. Further parametric optimization is used to find optimal values of the skin axial and bending stiffness for an optimal conformable airfoil design. The airfoil can produce a downward trailing edge deflection equivalent to 3.7° of Effective Flap Angle from the actuation loads, with the peak-to-peak deflection being nearly twice the downward deflection, and the airfoil deformation due to the airload loads is less than 1°. The optimal skin should have less axial stiffness and much more bending stiffness as compared to a conventional skin.
Numerical Investigation of Generalized Correlations for Turbulent Flow Pressure Drop and Heat Transfer Applied in Helically Coiled Tube Systems
Authors: Bowman Anthony J. , Park Hyunjae
Published: May 2008

A numerical analysis using a CFD package (Fluent v5.5) has been employed to investigate the turbulent pressure drop and heat transfer characteristics in the helically coiled tube system. The validity of using the techniques for creating coiled tube geometry and the corresponding volume mesh developed in this work is verified by explicitly comparing the numerically calculated results with those obtained from the experiments and correlations related to the straight and toroidal tubes. The authors’ previous work [5] includes the collection and summary of the general and application-specific published research and correlations. The information describing the pressure drop and heat transfer phenomena related to turbulent forced convection were combined and re-expressed into more generalized correlations using multiple linear regression techniques. In this paper, a numerical research effort using a commercial CFD package has been employed to reassess the actual phenomena with those predicted by the previously developed generalized correlations. The numerically predicted pressure drop and heat transfer coefficients at various Reynolds numbers are about 5–10% lower than those obtained by using existing generalized correlations [5]. For purposes of engineering calculations an error level of 15% or less is appropriate. The level of accuracy of the CFD modeling technique developed in this work is justified to investigate thermal-fluid phenomena in a coiled tube system.
Model Reduction Technique for Improved Multi-Body Vehicle Model Simulation Efficiency
Authors: Soli´s Dari´o , Medina Enrique A.
Published: May 2008

A key challenge in improving computational efficiency of vehicle simulation models is that of accurately assessing how modifications in a model affect its efficiency and reliability. Model development and reduction involves establishing and refining both the structure and the parameters of three mathematical elements: the model of the governing physics, the computational dynamic analyses utilized for evaluating the physical model, and numerical evaluation of vehicle performance characteristics. This paper presents the results of on-going research in model complexity reduction of multi-body vehicle models based on the elimination of certain multi-body model components from a vehicle reference model also defined in this paper. The model reduction problem is addressed here by using the knowledge of how computational efficiency is affected by changes in the topology of the multi-body vehicle model to guide the reduction process. In this approach, no terms are eliminated from the equations of motion or key vehicle degrees of freedom are removed from the model. Numerical examples using a reference multi-body vehicle model and three reduced models are used to demonstrate the model reduction technique.
Heat Transfer and Electrokinetic Flow Analysis in Poly(Dimethylsiloxane) Microfluidic Systems
Authors: Erickson David , Sinton David , Nikolic Vesna , Li Dongqing
Published: May 2008

Electrokinetic pumping is commonly used as a mechanism for species transport in microfluidic systems. Joule heating, caused by current flow through the buffer solution during electroosmotic flow, can lead to significant increases in the system temperature which can be detrimental to electrophoretic separations and temperature sensitive chemical reactions. In this paper, a combined experimental and numerical approach was used to examine Joule heating and heat transfer at a T intersection for PDMS/PDMS and PDMS/Glass hybrid microfluidic systems. In general it was found the PDMS/Glass chips maintained a more uniform and lower buffer temperature than the PDMS/PDMS systems, since the internally generated heat could be transferred more efficiently (due to the higher thermal conductivity of the glass component) from the channel network to the room temperature reservoir. This increase in temperature was shown to significantly increase the current load and the volume flow rate through the PDMS/PDMS system.
Theoretical Investigation Into the Performance of the Positive-Displacement Dispensing Process
Authors: Chen X. B. , Pharoah J. G. , Surgenor B. W.
Published: May 2008

Dispensing has been widely used in industry to control the delivery of fluid materials. Among various dispensing approaches, positive-displacement is recognized as the most promising as its performance is assumed to depend on the mechanical motion of the dispensing apparatus and not on the properties of the fluid dispensed. However, with decreasing volumes dispensed, this assumption is no longer valid as the fluid properties, and in particular the compressibility and flow behavior, can have a significant influence on the performance of the process. This paper presents the development of a model for the positive-displacement dispensing process that accounts for both fluid compressibility and non-Newtonian flow behavior. This model is used to investigate the process performance, with the emphasis on identifying the effects of such factors as the fluid volume in syringe and the needle temperature on the consistency in process performance.
Predictive Pressure Control of a Monopropellant Powered Actuator
Authors: Shields Bobby L. , Barth Eric J. , Goldfarb Michael
Published: May 2008

This work presents a model-based predictive control methodology applicable to systems with discrete input values (on/off) subject to a pure time delay. Specifically, the goal of this work is to develop a controller that will track a desired pressure for a monopropellant-powered pneumatic system with binary on/off input valves. The pneumatic actuator is pressurized by the catalytic decomposition of the liquid monopropellant hydrogen peroxide. The challenge is tracking a proportional output with a binary input, which means the output amplitude is not proportional to the input amplitude, but is proportional in time. This requires the controller to predict the future states for each of the two input candidates, on or off. The error between the predicted future states and the current desired states is calculated for each of the inputs. The control candidate that produces the smallest predicted Lyapunov function value is chosen. This results in the controller tracking a time delayed version of the desired pressure signal. Experimental results of the predictive controller demonstrate the effectiveness of this idea.
A Function-Based Exploration of JPL’s Problem/Failure Reporting Database
Authors: Roberts Rory A. , Tumer Irem Y. , Stone Robert B. , Brown Arthur F.
Published: May 2008

This paper presents the exploration of a failure database derived from a Problem and Failure Reporting (P/FR) database for NASA space missions. The overall goal is to analyze an existing database of problems and anomalies recorded at the Jet Propulsion Laboratory (JPL) for multiple missions, and classify a subset of them into distinct failure modes from a predetermined set of failure modes. Results are presented to describe the failure modes and functional descriptions derived from the PF/R database, using observed in-flight failure reports for six unmanned space missions. The challenges and issues in mining this information are presented, as well as comments on the adequacy of the existing failure mode and function taxonomies to describe the subset of observed failures reported in the PF/R database, and on the utility of such large databases.
An Application of Digital Human Modeling and Ergonomics Analysis in Workplace Design
Authors: Maiteh Bilal
Published: May 2008

In today’s challenging environment, companies gain a competitive advantage by reducing time-to-market of their products. This effort requires an integration of various technologies and effective utilization of simulation tools. As an integral part of any manufacturing environment, operator health and safety is a primary focus of the companies. Digital human modeling and virtual reality tools provide an excellent solution to factor human element early in the design phase and to make proactive choices in workplace and equipment design decisions. In this paper, the process of ergonomics analysis within digital environment is discussed, and an application is summarized. The case study gives details of the integration of digital human modeling, motion capturing, and ergonomics analysis in an automobile part sub-assembly process.
Microcombustors Based on Controllable Solid Fuel Elements
Authors: English Brian E. , DiBiaso Heather H. , Allen Mark G.
Published: May 2008

This paper focuses on the control of solid-fuel burn rate by controlling the solid-fuel chemistry or by controlling heat losses. Laser cutting and lamination have been used to fabricate milli-scale test structures to characterize burn rates of composite solid fuel. The base ingredients for the solid fuels tested were phase-stabilized ammonium nitrate (PSAN), ammonium perchlorate (AP), and sodium azide (SA). These base ingredients were tested alone or mixed with hydroxyl-terminated poly-butadiene (HTPB) plus various accelerants. Several experiments were performed to test the controllability of composite solid fuels. Burn-rate tests at atmospheric pressure consisted of 250 to 500 micron deep square combustion chambers packed with fuel and resistively heated on the top surface until combustion was achieved. Experiments were also performed to increase burn rate through chamber pressurization. Reaction times for a set amount of fuel were observed to increase exponentially as nozzle diameter was decreased. Finally, combustion chamber geometry was altered to control reaction propagation by increasing localized heat losses. A 500 micron thick triangular chamber was fabricated and ignited at the larger end, allowing the reaction to propagate toward the triangle tip. These results indicate that controllable actuation of solid propellants on the microscale for non-thrust, gas generation actuator applications is feasible.
Study of Alternate Surface Finishes for Quad Flat Packs
Authors: Mukadam Muffadal , Meilunas Michael , Srihari K.
Published: May 2008

The purpose of this study is to evaluate three different QFP lead finishes using steam age preconditioning. This evaluation is based on solder joint strength measured by lead pull test. The effects of steam age preconditioning on solder voiding, wetting, fillet formation, and solder joint strength is included. This paper also summarizes the details of the QFP assembly build and process characterization using visual inspection, X-ray, and cross-sectional analysis. Furthermore, microscopic examination of the fracture surfaces following the lead pull tests was performed.
Construct Stability of C2 Replacement Strategies
Authors: Puttlitz Christian M. , Melcher Robert P. , Deviren Vedat , Jeszenszky Dezsoe , Harms Ju¨rgen
Published: May 2008

Reconstruction of C2 after tumor destruction and resection remains a significant challenge. Most constructs utilize a strutgraft with plate or screw fixation. A novel C2 prosthesis combining a titanium mesh cage with bilateral C1 shelves and a T-plate has been used successfully in 18 patients. Supplemental posterior instrumentation includes C0-C3 or C1-C3. Biomechanical comparisons of this C2 prosthesis with traditional fixation options have not been reported. Five fresh-frozen human cadaveric cervical spines (C0-C5) were tested intact. Next, the C2 prosthesis, and strut graft and anterior plate constructs were tested with occiput-C3 and C1-C3 posterior fixation. Pure moment loads (up to 1.5 N-m) were applied in flexion and extension, lateral bending, and axial rotation. C1-C3 motion was evaluated using 3 camera motion analysis. Statistical significance was evaluated using one-way repeated measures ANOVA with Student-Newman-Keuls post hoc pairwise comparisons. All constructs provided a statistically significant decrease in motion in this C2 corpectomy model as compared to the intact condition. There was no significant difference in C1-C3 motion between the 4 constructs, regardless of whether the occiput was included in the fixation. Under these loading conditions, both the C2 prostheisis and strut-graft-plate constructs provided initial C1-C3 stability beyond that of the intact specimen. The occiput does not need to be included in the posterior instrumentation.
Anatomical Reduction Is Not Necessary in Treating Non-Porotic Unstable Intertrochanteric Fracture: A Biomechanical Study of Porcine Model
Authors: Lin Shi-Wei , Wang Jaw-Lin
Published: May 2008

Intertrochanteric fracture occurred more than 200,000 cases each year in the United States, with mortality rate up to 20 percents. Evans classified the intertrochanteric fracture pattern to stable and unstable group. Most of the complications occurred in the unstable group. It is speculated that in the unstable intertrochanteric fracture, the lag screw migrates easily into the porotic femur head and than causing fixation failure. So the treatment of porotic unstable femoral intertrochanteric fracture depends on the bone quality, severity of comminution, anatomical reduction and methods of fixation. An abundant of studies had been focused on how to reinforce the porotic unstable intertrochanteric fracture including osteotomies, cement augmentation, anatomical reduction, and different implant applications. Among the many techniques, the anatomical reduction using cerclage wiring was widely used to enhance the stability of osteoporotic fractured femur. However, in the young adult, the application of cerclage wiring is controversial. The current study compares the mechanical properties of two anatomical reduction techniques of unstable intertrochanteric fracture reconstructed by a compression hip screw. Four porcine femurs of 10 months-old were used to simulate the non-porotic human bone. The specimens were stripped of all soft tissues. Each femur was prepared with four holes for dynamic hip screws following the standard surgical procedure. The anatomical reduction was achieved by a cerclage wiring and without cerclage wiring. The results reveal that in the non-porotic porcine model, there is no statistically difference in stiffness, plate strain and medial bone strain per load. No matter the unstable intertrochanteric fracture is reduced with cerclage wire or not. The non-porotic unstable intertrochanteric fracture anatomical reduction is not necessary if protective weight bearing is obeyed. However, whether the cerclage wiring is necessary or not for the osteoporotic unstable femur fracture needs further study.
How the External Impact Energy Affects the Internal Kinetics of Knee Joint: The Comparison of Porcine and Human Knee Joint
Authors: Wang Jaw-Lin , Chung Cheng-Hsien , Chiang Chung-Kai
Published: May 2008

Degenerative osteoarthritis is recognized as the consequences of mechanical injuries. The abnormal impact force applied to articular cartilage would result in bone fracture or surface fissuring, and would cause the osteoarthritis [1,2]. The relation among the injury and impact energy was well studied. However, how the external energy attenuated to the internal joint is not carefully studied yet. The porcine knee joint was used as a biomechanical model for the simulation of human knee joint during impact loading. The objective of current study was to find the variation of kinetic characteristics between human and porcine knee joint during axial impact loading. Eight fresh-frozen knee joints from 10 month-old swine and seven cadaver human knee joints were used in the experiment. The mechanical responses such as forces and bending moment of knee joint, and the accelerations of femur was quantitatively analyzed. The results showed that the axial force response between human and porcine joints was similar, however, the anteroposterior shear, flexion bening moment and accelerations of these two joints were different.
Modeling and Experimental Study of Flow Forces for Unstable Valve Design
Authors: Yuan Qinghui , Li Perry Y.
Published: May 2008

Single stage electrohydraulic flow control valves are currently not suitable in high flow rate and high frequency applicaitons. This is due to the very significant flow induced forces and the power/force limitation of electromagnetic actuators that directly stokes the spool. An unstable valve has been proposed that can utilize the flow forces to achieve fast responses at high flow rate. In this paper, we model the flow forces, including both steady and transient, of a directional flow control valve for incompressible and viscous fluid. In particular, the viscosity effect and non-orifice flux are investigated. The new models have been verified by CFD analysis to be more accurate than the old models. The paper also presents a systematic experimental study on the flow forces, in particular on the steady flow forces. The estimates according to our new models, revised slightly due to the limitation of the experiment, are consistent with the experimental results. Both the experimental results and the modeling estimation show that, for an unstable valve with negative damping length, both transient and steady flow forces can help to achieve the higher spool agility. The satisfactory modeling and experimental study on the flow forces give us a grounding for the future research of unstable valve design.
The Variation of Gross Force Response of Spinal Motion Segment During Cyclic Loading: A Porcine Biomechanical Model
Authors: Wang Jaw-Lin , Chung Cheng-Hsien , Lai Cheng-Chuan , Chang Chia-Chun
Published: May 2008

The cyclic loading encountered due to exposure to whole body vibration has been implicated as a risk factor for occupational low back disorders (OLBD, Wilder, 1996). The frequent bending and lifting has been identified as a major risk for acute disc prolapse. Wilder (1985) has shown that cyclic loading causes a decline in the stiffness properties of the motion segments and predisposes them to more risk of buckling injury. Numerous studies have also demonstrated that soft tissues subjected to repetitive loading show creep and stress relaxation behavior because of their viscoelastic properties. The cumulative trauma and residual strain in the soft tissues due to repetitive loading may predispose the motion segment to altered load distribution—hence accelerating the process of disc degeneration. Although the association of load and risk of OLBD has been established, the nature of dose-response is less than clear. The current study developed a unique apparatus using an in vitro porcine spine model to quantify the alteration in the load response under cyclic compression loading at different loading conditions. The purpose of current project is to understand the mechanical gross response of the spinal motion segment during repetitive loading. The porcine spine motion segments were used in the study. Two group of loading condition were applied; one is the compression force evenly distributed on the top of vertebrae, and one is compression force at the anterior cortex of vertebrae. Both loading conditions were loaded for 90,000 cycles at 5 Hz. The total loading period is 5 hours. The loading was set at 200 N compression and 50 N tension from peak to peak. The results showed the spine is not stabilized even after 90,000 cycles of loading, and the evenly distributed loading condition obtained higher deformation than the anterior flexed loading condition.
Guided Acoustic Phonon Modes in Layered Anisotropic Nanowires
Authors: Mukdadi Osama M. , Datta Subhendu K. , Dunn Martin L.
Published: May 2008

Acoustic phonons play a critical role in energy transport in nanostructures. The dispersion of acoustic phonons strongly influences thermal conductivity. Recent observations show lower values of thermal conductivity in finite dimensional nanostructures than in the bulk material. In this work, we will present results for guided acoustic phonon modes in (a) a bilayered GaAs-Nb nanowire of rectangular cross section and (b) a trapezoidal Si nanowire. The former has been used for phonon counting in a nanocalorimeter for measuring thermal conductivity and the latter is commonly used in MEMS applications. A semi-analytical finite element (SAFE) analysis technique has been used to investigate the effects of layering, anisotropy, and boundaries on the dispersion of modes of propagation. Many interesting features of group velocities are found that show confinements around the corners, in the low velocity layer, and coupling of the longitudinal and flexural modes. These would strongly influence thermal conductivity and might provide means of nondestrutive evaluation of mechanical properties.