bluuebunny/crossref_metadata_2025 huggingface dataset:
Slip Flow Analyses of a Capacitive Pressure-Based Micro Flow Sensor
Authors: Jang Jaesung , Wereley Steven T.
Published: May 2008

We present gas flow measurements and slip flow analyses considering velocity slip at the wall in a capacitive pressure-based micro flow sensor. The sensor consists of a pair of capacitors for measuring pressure difference between the inlet and outlet and absolute pressure at the outlet, inlet/outlet reservoirs, and the main microchannel. The main microchannel is 128.0μm wide, 4.64μm deep, and 5680μm long, where the outlet Knudsen number is 0.0137. The sensor was fabricated using wet etching, ultrasonic drilling, Deep Reactive Ion Etching (RIE) and anodic bonding. The capacitance change of the sensor and the mass flow rate of nitrogen were measured as the inlet to outlet pressure ration increased up to 1.24. With the increasing pressure difference, the capacitance change of the differential pressure sensor increases. The TMAC for the channel whose sides are made of silicon dioxide and Pyrex #7740 glass was extracted for nitrogen. The friction factor was also measured and compared with a previous simulation result.
Design Optimization of a Novel, Large-Displacement, Multi-Axis, Silicon/Polymer Hybrid Actuator for Micro Optics
Authors: Tung Yi-Chung , Kim Jeong-Gil , Kurabayashi Katsuo
Published: May 2008

This paper investigates a novel silicon/polymer hybrid MEMS actuator and reports on its design optimization. The actuator, incorporating a three-dimensional poly(dimethylsiloxane) (PDMS) flexural microstructure, is designed to generate multi-axis displacement of motion. This work develops a four-bar linkage model for parametric design of the actuator and validates it using finite element analysis (FEA). The optimization of the device geometry is performed using Genetic Algorithm (GA) such that the resulting out-of-plane displacement can achieve a maximum value under several design constrains due to fabrication and operation limitations. The out-of-plane displacement of the optimized actuator structure is calculated to be as large as 60 μm at 50 V input actuation voltage. Due to its unique mechanical and optical material properties, the PDMS microstructure allows the proposed device to achieve actuation performances suitable for a wide variety of micro-optics applications, including micro optical scanners, dynamic-focus micro lens holders, and mechanically flexible optical gratings.
Microfabricated PDMS Check Valves
Authors: Yang Bozhi , Lopez George C. , Lin Qiao , Rosenbloom Alan J.
Published: May 2008

This paper presents two types of novel micro check valves that are based on PDMS. The valves consist of a thin flap and a flow restriction block inside a microchannel. The flap is perpendicular to the flow and lies near the block, which forms a restricted fluid path inside the channel. The valves are fabricated entirely from PDMS through replica molding techniques and can be readily integrated in PDMS-based complex microfluidic systems. Testing results show that for a reverse flow, the 2D valve has a saturated leakage rate at higher pressures, leading to an interesting “fluid diode” phenomenon, while the 3D valve has zero leakage at higher pressures.
Principle and Experimental Study of a MEMS Explosive Particle Detector
Authors: Zhang Yan , Mei Tao , Kong Deyi , Zhang Chengmei , Tao Yongchun , Hu Shengjun
Published: May 2008

A new explosive particle detection with MEMS is presented in this paper, which utilize the properties of explosive particles. The principle of the detector is described firstly: every explosive has unique melting and evaporation point, when single explosive particle on the sensor surface melts and absorbs heat from it, the temperature change of the sensor will occurs. Unlike other indirect detecting method, a step heating method was proposed to control the working state of the sensor. The method had the advantages of easy implementation, active controlling and high selectivity: Firstly, the voltage will make the temperature of the sensor a little lower than the melting point of explosive, and the fusion of the explosive will not occur yet; With the voltage begin to increase again, the temperature of the sensor will also increase up to the melting point and produce a respond graph called base graph. The same voltage pulse was sent through the sensor before and after putting the explosive particles on the sensor surface. Absorption of heat from it during melting and evaporation causes its temperature changing and the shift on the respond graph is different from the former. Furthermore, experiments have been performed to confirm the feasibility to measure the temperature directly, and the graph is presented to show the difference between the changing with TNT sample existing or not, the resistance changing is apparent in graph when the temperature increase close to the melting point of TNT.
Natural Convection in Two-Dimensional Horizontal Channel With Heat Sources
Authors: Dias Tito , Milanez Luiz Fernando
Published: May 2008

Laminar natural convection in a two-dimensional horizontal channel is very important in laptop design, since optimizing the utilization of the cooler saves energy from the battery. In this work, this configuration has been numerically studied. Three cases were studied according to the position of the heat sources in the lower wall, upper wall and both. The computational domain consisted of two adiabatic walls where the heat sources were positioned, and two open boundaries, where the manometric pressure and normal gradient of velocity were zero. Ambient temperature was prescribed for the entering fluid and zero normal gradient for the exiting fluid. Fluid properties were assumed constant except for the density change with temperature on the buoyancy term. The influence of the modified Rayleigh number, position of the heat sources and heat flux ratio between the sources were analyzed for Prandtl number of 0.7. The maximum temperature excess on the heat source is lower for the case with two heat sources and Ra = 104. This preliminary study showed the existence of a minimum value of the excess temperature for the studies aspect ratio (0.1).
Study on the Transient Characteristics of the Sensor Tube of a Thermal Mass Flow Meter
Authors: Kim Dong Kwon , Han Il Young , Kim Sung Jin
Published: May 2008

Thermal mass flow meters (TMFMs) are most widely used for measuring mass flow rates in the semiconductor industry. A TMFM should have a short response time in order to measure the time-varying flow rate rapidly and accurately. Therefore, it is important to study transient heat transfer phenomena in the senor tube of a TMFM. Many models have been presented by previous investigators. But most of them focused on steady heat transfer phenomena, so it is impossible to analyze transient heat transfer phenomena in the sensor tube using previous models. Furthermore, it is impossible to predict the response time using results from previous research works. In the present work, a simple numerical model for transient heat transfer phenomena of the sensor tube of a TMFM is presented. The proposed model treats the fluid region and the tube region separately. Numerical solutions for the tube and fluid temperatures in a transient state are obtained using the proposed model and compared with experimental results to validate the proposed model. Based on numerical solutions, heat transfer mechanism in a transient state in the sensor tube is explained. A correlation for predicting the response time of a sensor tube is also presented. The functional form of the correlation is obtained using the scale analysis and coefficients appearing in the correlation are obtained by the proposed numerical model. The correlation is verified by experimental results. Using the proposed correlation, physical meaning and characteristics of the response time of the sensor tube are presented.
The Next Generation of Gage Restraint Measurement Systems
Authors: Bloom Jeffrey A. , Carr Gary A. , Seyrlehner Georg
Published: May 2008

This paper presents a new generation Gage Restraint Measurement System (GRMS) being developed by ENSCO, Inc. and Plasser American for delivery to the Federal Railroad Administration, Office of Research and Development. GRMS technology was developed in the early 1980’s as a performance-based method to evaluate ties and fasteners. The technology has been adopted by many railroads, and commercial versions of the GRMS are being utilized daily throughout the country. A shortcoming of the current commercial system is that the unique split-axle system can derail when operating through switches and other track hardware. Since the split-axle is a main running axle, a derailment can have significant consequences. The new GRMS is designed as a fifth axle that is deployed from the frame of a track geometry vehicle instead of using one of the vehicle’s running axles. This results in a more flexible and safer GRMS design. This paper discusses the details of the new design and its advantages.
Identification of a Mean Value Model of a Modern Diesel Engine for Control Design
Authors: Hopka Michael , Upadhyay Devesh , Guezennec Yann , Rizzoni Giorgio
Published: May 2008

The modern diesel engine with its multiple subsystem interactions is a very complex plant. Especially fascinating are the interactions of the VGT and EGR control actions in their cumulative effect on the overall air loop dynamics. To circumvent the problem of manpower intensive engine mapping for determining the best operating control map, a generic mean value model of a diesel engine, based on physical principles and empirical definitions where necessary, was developed. In this paper we present the identification of this model with respect to a Fiat 2.4L JTD 166. It will be shown that there is an essential set of parameters that must be identified in order to model processes that are too complicated for physics based modeling. The parameter set is utilized in simplified empirical relationships to model complex engine phenomena such as combustion and orifice flow through the EGR and VGT, facilitating model portability. Results from matching these empirical relationships to the engine of interest and model predictions of air loop system response to EGR and VGT control inputs show good agreement with actual engine performance and are presented in this paper.
Inverse Solution of a Heat Conduction Problem Using Evolutionary Data Segregation Techniques
Authors: Johnson Peter E. , Bryden Kenneth M. , Ashlock Daniel A.
Published: May 2008

Engineering problems are typically solved by direct solution. For the direct solution of engineering problems the boundary conditions and physical properties of the domain are given, and the dependent variable is calculated throughout the domain. In contrast to this, for inverse engineering problems the dependent variable is known at select locations in the domain, and the material properties and/or the boundary conditions need to be determined. This paper will present a novel technique for the inverse solution of a heat transfer engineering design problem in which the temperature profile and materials are known, but the placement of these materials and the heat flux on the boundaries are unknown. This technique uses evolutionary optimization in the form of the Adaptive Modeling by Evolving Blocks Algorithm (AMoEBA) to determine the material configurations. The material configurations, geometry, and properties are defined by evolving binary trees. The evolved domains are solved directly and then compared with the known temperature profile. Fitness of the new designs is determined by the least squared error between the proposed and the known profile. When this fitness reaches a defined level, the material placement scheme of the real system is found, and boundary conditions matching the problem definition are identified.
Evolutionary Optimization Using Graph Based Evolutionary Algorithms
Authors: Corns Steven M. , Bryden Kenneth M. , Ashlock Daniel A.
Published: May 2008

Graph based evolutionary algorithms (GBEAs) are a novel evolutionary optimization technique that utilize population graphing to impose a topology or geography on the evolving solution set. In many cases in nature, the ability of a particular member of a population to mate and reproduce is limited. The factors creating these limits vary widely and include geographical distance, mating rituals, and others. The effect of these factors is to limit the mating pool, reducing the rate of spread of genetic characteristics, and increased diversity within the population. GBEAs mimic these factors resulting in increased diversity within the solution population. When properly tuned to the problem and the size of the population set, GBEAs can result in improved convergence times and a more diverse number of viable solutions. This paper examines the impact of the fitness landscape, population size, and choice of graph on the evolutionary process. In general, it was found that there was an optimal population size and graph combination for each problem. This optimal graph/population was problem dependent.
Sequential Electrolytic Bubble-Based Micro-Pump Dosing System
Authors: Lewandowski Melanie , Ateya Daniel A. , Shah Ashish A. , Hua Susan Z.
Published: May 2008

An electrolytic bubble actuated micropump has been fabricated and characterized for dosing application. The micropump consists of a series of bubbles formed directly inside a microfluidic channel, and the volume displacement characteristics of inflating/deflating electrolytic bubbles are utilized to move the liquid along the channel. Prototype chips with five sequential bubbles were built using standard photolithography techniques. The pump performance was characterized as a function of the voltage required to generate electrolytic bubbles of varying size (3.5–4.5 V), pulse-width (50–300 ms), time interval between pulses (50–300 ms), and backpressure; each parameter being varied independently. It was found that the size of the bubble, and hence the quantity of liquid displaced, increases with voltage. Also, the pump rate increases with a reduction in pulse-width and the time interval between pulses. The optimum pump rate of 24 nl/min, corresponding to a flow velocity of 640 μm/s, was obtained for the current channel size of 25×25μm in cross-section. The pump performed successfully against backpressures up to 107 kPa.
NIOSH AutoROPS 3rd Generation Static Testing and Human Interaction Element
Authors: McKenzie E. A. , Etherton J. R. , Harris J. R. , Cantis D. M. , Lutz T. J.
Published: May 2008

To address the need for rollover protective structures (ROPS) on farm tractors that are easily adapted to low overhead clearance situations, the Division of Safety Research (DSR), National Institute for Occupational Safety and Health (NIOSH), developed an automatically deploying, telescoping ROPS (AutoROPS). The NIOSH AutoROPS at the present is in the third generation design and static testing phase, and the first phase of human subject (human operator) testing and manufacturing. The static testing is based on the SAE J2194 standard for testing ROPS for agricultural tractor use. The nature of the NIOSH AutoROPS is to be in a retracted position until an overturn is determined to be imminent. It is during the deployment time period that potential safety hazards exist that are not present in a traditional fixed ROPS and not addressed in the standards. Human interaction is a key ingredient in refining the design to be both functional and desirable while considering possible hazards. Feedback from farmers who have operated a tractor with the NIOSH AutoROPS installed and in the ready state will enhance the design and acceptability. NIOSH’s goal is to reduce the number of fatal agricultural overturns by increasing the percentage of tractors with ROPS and seatbelts which operate in low clearance environments. This design has met laboratory static testing criteria of the SAE J2194 standard for ROPS on agricultural tractors. Field evaluation of the AutoROPS use by poultry farmers (N=32) in eastern West Virginia showed favorable results and a preference for wanting to purchase and use the NIOSH AutoROPS compared with a currently available manually foldable ROPS. This paper discusses the overall performance of the NIOSH AutoROPS as subjected to the SAE J2194 standard and human interaction/feedback of operating an agricultural tractor with this added safety device.
Design and Performance Verification of Variable Dampers Using MR Fluid
Authors: Shiraishi Toshihiko , Sakuma Tomoya , Morishita Shin
Published: May 2008

Two typical types of MR damper were proposed, where the orifice for MR fluid was designed to place between the piston and the cylinder in one type, and to place on the piston in the other type. In the former design, MR fluid was expected to be subjected to shear flow in the orifice, and subjected to Poiseuille flow in the latter design. The damping force of MR dampers was experimentally measured under various conditions of piston speed, piston amplitude and applied electric current to the magnetic coil. The experimental results showed that the maximum damping force were almost the same in both types of damper under the same conditions, except for case under very little amplitude. It was also shown that typical characteristics of MR damper depended on the clearance of orifice and air volume in MR dampers, and the optimal design for the dynamic range of damping force existed in relation to the clearance of orifice. The experimental result of the damping force of these dampers showed good agreement with the analytical result.
Measurement of the Air Pressure for a Rotary Vane Compressor
Authors: Huang Yuan Mao , Yang Sheng An
Published: May 2008

This study introduces an experimental method that can measure air pressures in the vane segments when a sliding-vane rotary compressor performs suction and compression phases in stable or unstable rotational speeds. When the air pressures of these two phases can be measured, the intake effect of the compressor’s inlet and the seal effect of the vane segments can be evaluated, respectively. Because a frequency converter provides unstable rotational speeds when it controls rotational speeds of a motor with a compressor, an encoder mounted on the output shaft of the motor was applied to record the angular location of the compressor rotor. Two strain gauge type pressure transducers were inserted into the cover plate of the compressor to measure air pressures in the vane segments. Comparing the signals of the encoder with pressure transducers, the air pressures in completions of suction and compression phases could be determined in stable or unstable rotational speeds. The air pressures when the compressor performed suction and compression phases were 99.5 kPa and 153 kPa, respectively, in 1400 rpm. The air pressure when the compressor performed suction phase decreased with the rotational speed faster than 800 rpm. The size or shape of the inlet port of the compressor should be enlarged or modified to provide the suction air pressure without dropping too much. The designed air pressure when the compressor performed compression phase was 244 kPa in 140 rpm, the manufacture precision of the compressor should be increased to decrease leakage.
Analysis of Slip in a Continuously Variable Transmission
Authors: Bonsen B. , Klaassen T. W. G. L. , van de Meerakker K. G. O. , Steinbuch M. , Veenhuizen P. A.
Published: May 2008

High clamping force levels reduce the efficiency of the Continuously Variable Transmission (CVT). However, high clamping force level are necessary to prevent slip between the belt and the pulleys. If a small amount of slip is allowed, the clamping force level can be reduced. To achieve this, slip in a CVT is investigated. From measurements on an experimental setup, Traction curve data and efficiency measurements are derived. A model describing slip in a CVT is verified using measurements with a belt with increased play. It is found that small amounts of slip can be controlled in a stable way on the setup. The traction curve was mostly dependent on the CVT ratio. Efficiency is found to be highest for 1 to 2% slip depending on the ratio. The model is in reasonable agreement with the measurements.
Uncoupling the Conjugate Heat Transfer Problem in a Horizontal Plate Under the Influence of a Laminar Flow
Authors: Va´squez Ricardo S. , Bula Antonio J.
Published: May 2008

The conjugate heat transfer process of cooling a horizontal plate in steady state condition is studied. The model considers both solid and fluid regions in Cartesian coordinates. The problem was solved analytically, considering the fluid flowing in a laminar condition and hydrodynamically developed before any interaction with the heated body. The height of the fluid considered was enough to allow the generation of a thermal boundary layer without any restriction. The conservation of mass, momentum and energy equations were considered to turn the problem into a non dimensional form. The heated body presented a constant heat flux at the bottom side, and convective heat transfer at the top side in contact with the fluid. The other two boundary conditions are adiabatic. The energy equation was considered in the solid to turn it into a non dimensional form. The interface temperature was obtained from a regression using the Chebyshev polynomial approximation. As the problem deals with the cooling of a electronics components, the solution presents the mathematical solution of the energy equation for the solid, including the isothermal lines. The non dimensional form allows a thorough analysis of the problem, considering the influence of the different parameters in the conjugate heat transfer problem. The solution is compared with numerical solution of different problems, and the parameters considered are Reynolds number, plate thickness, Prandtl number, and solid thermal conductivity. The results obtained present isothermal lines, local Nusselt number, and average Nusselt number.
Finite Time Lyapunov Exponent for Micro Chaotic Mixer Design
Authors: Niu Xi-Ze , Tabeling Patrick , Lee Yi-Kuen
Published: May 2008

In this paper, the Finite Time Lyapunov Exponent (FTLE) approach is used to analyze and optimize chaotic mixing in an active microchannel and a static mixer. The characteristics of FTLE related to chaotic mixing are discussed. By comparing the similarity of Poincare´ mapping and FTLE contour, it is shown that FTLE can be used to evaluate the chaotic mixing of liquid in the micromixer qualitatively and quantitatively. The minimum channel length needed for full mixing in the mixers can be estimated by the mean FTLE. The results are consistent with CFD simulations directly solving the Navier-Stokes equations coupled with the diffusion equation. More than 3 orders of CPU time can be saved by using FTLE compared with the classical infinite time Lyapunov exponent approach. Moreover, the FTLE is used to optimize the design and operation of the chaotic micromixers to improve the mixing efficiency for the first time.
Simultaneous Electrical and Thermal Modeling of a Contact-Type RF MEMS Switch
Authors: Jensen Brian , Wang Zhongde , Saitou Kazuhiro , Volakis John L. , Kurabayashi Katsuo
Published: May 2008

Improving the power handling capability of direct contact RF MEMS switches requires a knowledge of conditions at the contact. This paper models the temperature rise in a direct contact RF MEMS switch, including the effects of electrical and thermal contact resistance. The maximum temperature in the beam is found to depend strongly on the power dissipation at the contact, with almost no contribution from dissipation due to currents in the rest of the switch. Moreover, the maximum temperature is found to exceed the limit for metal softening for a significant range of values of thermal and electrical contact resistance. Since local contact asperity temperature can be hundreds of degrees higher than the bulk material temperature modeled here, these results underscore the importance of understanding and controlling thermal and electrical contact resistance in the switch.
On the Entropic Heating of Microfluidics for PCR Applications
Authors: Walsh E. J. , Walsh P. A. , Grimes R. , Davies M. R. D.
Published: May 2008

Polymerized Chain Reaction (PCR) technology has for a number of years been used as a tool for a range of applications in genetic research. Indeed, in the world of genetics PCR is considered to be one of the most important discoveries of the last century. This work is focused upon understanding and utilizing the thermodynamics of the fluid flow through microsystems, with the aim of developing an efficient thermocycler for PCR applications. The novel approach of utilizing the entropy generation rate in a couette type flow to provide entropic heating to the bio-fluid is addressed. The advantages of such a PCR device include, the removal of external heaters, an even distribution of heating through the bio-fluid, possibility of enhanced mixing, fast cycle times and the requirement for small sample sizes. These parameters are key requirements for an efficient PCR on the microscale. It is also demonstrated that this concept is not possible on the macro scale due to the ratio of heat generation relatively to fluid volume, however on the micro scale it is demonstrated to be theoretically plausible.
The Debonding of Viscoelastic Fiber Composites in Antiplane Shear
Authors: Levy Alan J. , Xie Mayue
Published: May 2008

In this paper, we first review previous work on the antiplane shear of an elastic fiber composite containing fibermatrix interfaces that suffer nonlinear slip. We extend the theory to account for viscoelastic matrix response treating the solitary fiber problem and effective composite response along the way. The elastic and viscoelastic constitutive relations developed are used to analyze the pure torsion of a circular cylinder containing unidirectional fibers aligned parallel to the cylinder axis. The existence and character of singular surfaces, i.e., surfaces that separate regions of fully slipped material from a minimally slipped core are analyzed as well.
AC Electrokinetics for Microfluidic Immunosensors
Authors: Sigurdson M. , Meinhart C. , Wang D. , Liu X. , Feng J. J. , Krishnamoorthy S. , Sundaram S.
Published: May 2008

A technique is proposed to enhance microfluidic immuno-sensors, specifically, sensors in which a ligand immobilized within a microchannel binds analyte flowing through the channel for the purpose of detection of that analyte. These sensors can be limited in both response time and sensitivity by the diffusion of analyte to the sensing surface. The sensitivity and response of these heterogeneous immunoassays may be improved by using AC electrokinetically-driven microscale fluid motion to enhance antigen motion towards immobilized ligands. Specifically, electrothermal effects can produce swirling flow patterns that carry sample past the binding surface. Numerical simulations of antigen in a microchannel flow subjected to the electrothermal effect suggest that 14 V rms applied to electrodes strategically placed opposite a narrow binding region can increase binding in the first few minutes by a factor of five. Optimization of the electrode geometry and placement can render this technique useful for a large variety of microfluidic sensors.
Turbulent Natural Convection in Horizontal Composite Cavities
Authors: Braga Edimilson J. , de Lemos Marcelo J. S.
Published: May 2008

Turbulent natural convection in a two-dimensional horizontal composite square cavity, isothermally heated at the left side and cooled from the opposing surface, is numerically analyzed using the finite volume method. The composite square cavity is formed by three distinct regions, namely, clear, porous and solid region. Accordingly, the development of a numerical tool able to treat all these regions as one computational domain is of advantage for engineering design of thermal systems. Governing equations are written in terms of primitive variables and are recast into a general form. It was found that the fluid begins to permeate the porous medium for values of Ra greater than 106. Nusselt number values show that for the range of Ra analyzed there are no significant variation between the laminar and turbulent model solution..
Robust Control of Oscillations in Agricultural Tractors
Authors: Andersen Torben Ole , Hansen Michael Ryygaard , Conrad Finn
Published: May 2008

This paper relates to analyses and control of the oscillations occurring in many off road vehicles, which are designed without any suspension. Without suspension, the tire is the only elastic element acting between the vehicle and the ground but the suspension and damping properties of the tires cannot meet the demands for fast, safe and comfortable road transportation. In this paper the above-mentioned phenomenon is investigated with special focus on agricultural tractors. A control strategy is developed to make the implement counteract the movement of the tractor and thereby reducing the pitching oscillation. The control strategy is based on a linear plant model with constant or slowly varying parameters. Using a frequency-response approach the disturbance rejection is made effective over a significant portion of the system bandwidth. To improve robustness with respect to bounded disturbances (from the road) natural frequencies for the vehicle and implement is identified and the controller parameters tuned adaptively based on an optimization formulation.
Sound Attenuation in Heterogeneous Porous Media Due to Viscous Effects
Authors: Vadnjal A. , Catton I.
Published: May 2008

Volume averaging theory (VAT) is used to develop acoustic governing equations and consistent closure for one dimensional wave propagation in a heterogeneous porous media. These equations are based on continuum mechanics and scaled to delineate the parameters governing wave propagation in the media. The parameters can be evaluated for different media and be the basis for calculation of the performance of a given porous media. Comparison with experimental data are made and the comparison is very good. More general closure parameters will require experimental measurement to give appropriate models of non-homogeneous, media.
Oxygen Fluorescence as a Means for Temperature and Pressure Measurement
Authors: Semenic Tadej , Blake Ben , Messana Matthew , Catton Ivan
Published: May 2008

The application of interest in this work is the measurement of air temperature and pressure using broadband laser-induced fluorescence (LIF). Because of the cost, bulkiness, and operating complications of ArF lasers, a xenon flashlamp is used instead of LIF. The oxygen is excited by photons in the 185–200nm range. Large wavelength windows (100nm and 65nm) are used to reduce the fluctuations in the total measured fluorescence. A correlation between temperature and fluorescence ratio is developed with an error in fluorescence ratio of approximately ±1.3%, resulting in an error in temperature of ±1.35° C for temperatures from 25–50° C.
On the Optimum Synthesis of Six-Bar Linkages Using Differential Evolution and the Geometric Centroid of Precision Positions Technique
Authors: Koladiya D. , Shiakolas P. S. , Kebrle J.
Published: May 2008

This paper presents the development of a methodology for the synthesis of six-bar dwell mechanisms combining Differential Evolution, an evolutionary optimization scheme, and the Geometric Centroid of Precision Positions technique for defining the initial bounds of the design variables. Two penalty functions are employed one for constraint violation and one for relative accuracy. The results of the initial application of this methodology were also used as “good initial guesses” for improving the desired accuracy level. The developed methodology is applied to the synthesis of six-bar linkages for dwell and dual-dwell mechanisms with prescribed timing and transmission angle constraints. The six-bar mechanism is synthesized using two different approaches: four-bar and extension to six-bar, direct six-bar. Results demonstrating the successful application of the developed methodology and the three approaches are presented.
Failure Analysis of Stepladders Manufactured From Extruded Aluminum
Authors: Snyder G. A. , Glancey J. L. , Vinson J. R. , Cintavey D. M.
Published: May 2008

Despite advances in materials and manufacturing techniques for extruded aluminum and fiberglass reinforced composite structures, accidents involving ladders cause an estimated 300 deaths and 130,000 injuries annually. Although the origins of accidents are rarely known, the causes are usually attributed to the actions of the user and not the failure of the structure. To better understand the material and structural characteristics of common, commercially available aluminum stepladders, and the potential role they play in accidents, a structural analysis was performed on several typical designs. Stress analysis of common structural geometries revealed that the potential modes of failure are complex, and might often be the result of a combination of compression, bending, and torsion in the front side rails. In addition, some loading scenarios suggest failure can result from elastic buckling in either the front or rear side rails. Measurements to quantify variations in the material and geometric properties of the ladder components revealed that significant variations can exist and are attributable to several different aspects of the manufacturing process. In some instances, actual rail strength and section properties did not meet the specifications of the ladder manufacturer. Overall, the susceptibility of these structures to failure under certain loading scenarios, coupled with the inherent variations associated with extrusion manufacturing, indicate that aluminum stepladders, especially Type II and Type III, are not adequately designed for strength, and that current designs do not demonstrate a factor of safety sufficient to meet the standards required by the ladder industry.
A High-Density Flexible Connector Array for Multi-Substrate Packages
Authors: Ucok Asli B. , Giachino Joseph M. , Najafi Khalil
Published: May 2008

This paper presents the design and fabrication challenges of a high-density flexible connector array for use in compact and multi-substrate packages containing circuits, sensors, and actuators in a re-workable and modular approach. The package is designed as a cube with highly flexible connectors providing electrical and fluidic connections between these substrates. The cables are integrated in the inside walls of the cube and make pressure contacts to the pads on stacked substrates. The cables should be designed to be flexible, be capable of being manipulated so that individual dice can be inserted to populate the cube. Several material candidates have been considered, including polymers such as Parylene, and metal such as gold. Preliminary designs have been carried out to understand the mechanical limits. Fabrication processes have been also considered and cables of different materials have been fabricated to identify fabrication complexities and challenges. Parylene is the first material of choice since it is easy to deposit in thin layers, is quite flexible, and provides sufficient mechanical strength and chemical inertness for many applications.
Fluorescence Image Reconstruction for Optical Tomography Based on Transient Radiation Transfer Equation
Authors: Quan Haiyong , Guo Zhixiong
Published: May 2008

Image reconstruction is a bottleneck problem that impedes real time application of optical tomography technology. In this paper, we propose a novel fluorescence optical tomography method with a fast yet accurate algorithm for 3D image reconstruction. This imaging method is demonstrated using radiation transfer modeling based design. First the transport of ultrafast laser radiation governed by radiation transfer equation in participating media is simulated. Then the transient fluorescence field is obtained by solving the same radiation transfer equation in which the quantum yield of fluorescence is added to correlate the absorbed laser radiation with fluorescence emission intensity. Finally, 3D images are reconstructed using the temporal signals of fluorescence at detectors around the boundary of targeted tissues. We use the early time of fluorescence flight and the maximum fluorescence intensity to directly reconstruct the 3D images. Two new concepts, i.e., the photon migration statistic property and the solid geometric correlation property, are introduced for signal and image processing, respectively. The image reconstruction in this new method is very fast and does not require any inverse optimization. The accurate and efficient image and location of a 2.4×2.4×2.4mm3 tumor embedded at two different locations inside a 20×20×20mm3 rectangular tissue are demonstrated.
Micro Fluidic Platform for Manipulation of Micro- and Nanoscale Particles
Authors: Kadaksham J. , Batton J. , Singh P. , Aubry N.
Published: May 2008

In this paper, we study the manipulation and immobilization of micro- and nano-sized particles, such as living cells, suspended in a liquid. Our technique focuses on dielectrophoresis, that is, the use of spatially nonuniform electric field, while not damaging the manipulated particles or cells. The small size of the particles considered here requires the use of micro-electro-mechanical device (MEMS). We first simulate the suspended system by means of our new computational fluid dynamics (CFD) tool based on the distributed Lagrange Multiplier method (DLM), which takes into account not only fluid-particle but also particle-particle interactions. Results for both positive and negative dielectrophoresis are presented. We also show the existence of various regimes for the particle structures depending on the relative magnitude of the dielectrophoretic force and the electrostatic particle-particle interactions. We then design, fabricate and test a MEMS platform containing several microdevices.
Design, Fabrication and Thermal Characterization of a MEMS Device for Control of Nerve Cell Growth
Authors: Jain Ankur , Ness Kevin , McConnell Angie , Jiang Linan , Goodson Kenneth
Published: May 2008

There has been significant work on use of MEMS for biomedical applications in the past few years. This work presents a microheater device for use in experiments to study the effect of temperature on nerve cell growth. The device consists of a thin membrane with embedded heater and temperature sensors. Nerve cells could be immobilized on the membrane surface and their growth behavior could be studied by applying different heating powers, the goal being the actuation and control of cell growth using temperature. This work presents the design and fabrication of the microheater device being used in these cell growth experiments. Experimental data and finite element modeling are used to characterize the thermal response of the device. This yields a low value of the membrane thermal conductivity which indicates the amorphous nature of the thin film.
Dimensionless Sensitivity Methods to Identify Vehicle Cornering Stiffness From Yaw Rate Measurements
Authors: Brennan Sean N.
Published: May 2008

A simplified method of identifying a dynamic model is presented that utilizes explicit and implicit coupling between Bode parameter sensitivities. This focus of this work is the identification, in real-time, of the Cornering Stiffness parameter. This parameter governs the tire-road interaction within the simplified bicycle model description of vehicle chassis dynamics at highway speeds. This novel sensitivity coupling method, discovered earlier as sensitivity invariance in circuit network analysis, explicitly limits the possible parameter gradients of the system model to a very small subspace. By constraining the parameter identification or adaptation to solely this possible subspace, a simplified and efficient parameter identification can be obtained at a reduced computational and modelling cost. Both simulation and experimental implementation on a research vehicle under changing road conditions are presented.
The Shell and Tube Heat Exchanger Efficiency and Its Relation to Effectiveness
Authors: Fakheri Ahmad
Published: May 2008

The heat exchanger efficiency is defined as the ratio of the actual heat transfer in a heat exchanger to the optimum heat transfer rate. The optimum heat transfer rate, qopt, is given by the product of UA and the Arithmetic Mean Temperature Difference, which is the difference between the average temperatures of hot and cold fluids. The actual rate of heat transfer in a heat exchanger is always less than this optimum value, which takes place in a balanced counter flow heat exchanger. It is shown that for parallel flow, counter flow, and shell and tube heat exchanger the efficiency is only a function of a single nondimensional parameter called Fin Analogy Number. Remarkably, the functional dependence of the efficiency of these heat exchangers on this parameter is identical to that of a constant area fin with an insulated tip. Also a general algebraic expression as well as a generalized chart is presented for the determination of the efficiency of shell and tube heat exchangers with any number of shells and even number of tube passes per shell, when the Number of Transfer Units (NTU) and the capacity ratio are known. Although this general expression is a function of the number of shells and another nondimensional group, it turns out to be almost independent of the number of shells over a wide range of practical interest. The same general expression is also applicable to parallel and counter flow heat exchangers.
A Case Study in Computer-Aided Process Planning and System Design for Automotive Powertrain Machining
Authors: Wang Wencai , Yip-Hoi Derek , Huang Zhengdong
Published: May 2008

Process planning and system design for automotive powertrain machining represent a large investment in engineering upon which decisions are made for equipment acquisitions that typically falls in the range of hundreds of millions of dollars. The use of Computer-Aided Process Planning (CAPP) and system design (CASD) applications in the early stages of a new engine program can greatly increase the reliability and quality of the solutions upon which these decisions are made. They can also reduce the engineering time and the time to evaluate proposals from system integrators. This leads to shorter product launch windows giving manufacturers a competitive edge. This paper reports upon a case study conducted to evaluate the state of the art in of CAPP and CASD technology based on a typical configuration of commercial and evolving software applications. The results show maturity of the technology in most of the core technologies. Challenges exist in integrating these solutions into a manufacturer’s working environment.
Fatigue Behavior of Electronically Conductive Adhesive Joints
Authors: Gomatam Rajesh R. , Sancaktar Erol
Published: May 2008

This paper describes a novel fatigue-life prediction methodology aimed at providing the design engineer an easy fatigue life predictive tool using experimental data, for both cumulative fatigue damage, as well as constant loading fatigue conditions. This encompasses an integrated approach to joint testing, analysis, and modeling. Utilizing the proposed methodologies, we aim to predict the changes in fatigue life of the adhesive, based on the whole spectrum of test variables including temperature, humidity, stress ratio, preconditioning (variable stress ratios), and frequency. This modeling approach is expected to give the design engineer an initial assessment tool for the effects of detrimental fatigue conditions, eventually leading to a much improved fatigue life, improved fail-safe capability, and reduced manufacturing costs.
Effects of Surface Roughness and Turbulence Intensity on the Aerodynamics Losses Produced by a Suction Surface of a Simulated Turbine Airfoil
Authors: Zhang Qiang , Lee Sang Woo , Ligrani Philip M.
Published: May 2008

The effects of surface roughness on the aerodynamic performance of turbine airfoils are investigated with different inlet turbulence intensity levels of 0.9 percent, 5.5 percent and 16.2 percent using the University of Utah Transonic Wind Tunnel. Three symmetric airfoils, each with the same shape and exterior dimensions, are employed with different rough surfaces created to match the roughness which exists on operating turbine vanes and blades subject to extended operating times and significant surface particulate deposition. The non-uniform, irregular, three-dimensional roughness is characterized using the equivalent sand grain roughness size. Mach numbers along the airfoil range from 0.4 to 0.7. Chord Reynolds numbers based on inlet and exit flow conditions are 0.54×106 and 1.02×106, respectively. The contributions of varying surface roughness and turbulence intensity level to aerodynamic losses, Mach number profiles, normalized kinetic energy profiles, and Integrated Aerodynamics Losses (IAL) are quantified. Results show that effects of changing the surface roughness condition on IAL values are substantial, whereas the effects of different inlet turbulence intensity levels are generally relatively small. Relative to smooth airfoils, these variations are due to: (i) augmentations of mixing and turbulent transport in the boundary layers which develop along the roughened airfoils, (ii) thicker boundary layers at the trailing edges of roughened airfoils, (iii) separation of flow streamlines at airfoil trailing edges, and (iv) increased turbulent diffusion in the transverse direction within the wakes of roughened airfoils as they advect downstream.
Modeling of an Automotive Planetary Gear Set Based on Karnopp Model for Clutch Friction
Authors: Deur Josˇko , Asgari Jahan , Hrovat Davor
Published: May 2008

Planetary gear sets of automotive automatic transmissions include several hydraulic and one-way clutches. Clutch friction is traditionally described by the generalized, Stribeck, speed-dependent static function approximated by a steep straight line in the zero-speed region (so-called classical friction model). Another approach based on the Karnopp clutch friction model is proposed in this paper. Simulation results for park/reverse engagement and 1–2 upshift shows that the proposed gear set modeling method compared to the classical friction modelbased method yields significant improvement with respect to simulation time, as well as accuracy.
The Effects of Process-Induced Residual Stress on Rolling Contact Stress of Hard Machined Components
Authors: Guo Y. B. , Barkey Mark E. , Yen David W.
Published: May 2008

Compared with grinding, hard turning is a competitive manufacturing process that in many cases has substantial benefits. The most significant difference between hard turning and grinding is that hard turning may induce a relatively deep compressive residual stress. However, the interactions among the residual stress profile, applied load, and surface material, and their effects on component life in rolling contact are poorly understood. Further, contact stresses and strains are difficult to measure using the current experimental techniques due to the small-scale of the phenomena. A new simulation model of rolling contact has been developed to account for a process-induced residual stress profile. It has shown that distinct residual stress patterns hardly affect neither the magnitudes nor the locations of peak stresses and strains below the surface. However, they have a significant influence on surface deformations. The slope and depth of a compressive residual stress profile are key factors for rolling contact fatigue damage, which was substantiated by the available experimental data. Equivalent plastic strain could be a parameter to characterize the relative fatigue damage. The magnitudes of process-induced residual stress are reduced in rolling contact. The predicted residual stress pattern and magnitude agree with the test data in general. In addition, rolling contact is more sensitive to normal load and residual stress pattern than tangential load.