bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-Assembled Nano Wires
Authors: Saif Taher , Alaca B. Erdem , Sehitoglu Huseyin
Published: June 2008

We present a novel technique to fabricate self assembled nano wires on substrates, or channels of nano dimensions on thin films. The width of the wires or channels can be 50 nm and below, but their lengths can be 100s of micro meters. The technique is as follows: a substrate is coated by a film which is then strained either by applying load on the film-substrate system or by residual stress of the film itself. If the stress on the film exceeds that of its fracture stress, the film cracks with nano-dimensional opening to the substrate. The pattern of the cracks on the film depends on the type of stress (uniaxial or biaxial), strength of the interface between the substrate and the film, and the fracture strength of the film. Thus, the crack pattern can be controlled by tuning such parameters. The self assembled network of cracks can be used as nano channels, or the cracks can be filled by a metal that bonds with the substrate, which, after removal of the cracked film, gives a network of nano wires. We present the results of our initial experiments which have resulted Nickel wires on Si substrate. The wires are 300nm wide and millimeters long.
Body Heat Stress Measurements With MacroPCM Cooling Apparel
Authors: Colvin David P.
Published: June 2008

Heat stress is a major problem for people who work or fight in hot environments while dressed in insulated or protective apparel. Such is the case for military personnel who must wear nuclear/biological/chemical (NBC) protective clothing or HAZMAT personnel as well as civilian personnel such as industrial workers, firemen, and costumed characters in amusement or theme parks. Responding to a request in 1991 by the NAVY to develop simple and lightweight cooling garments for use beneath NBC (nuclear/biological/chemical) protective clothing, the investigators at Triangle Research and Development Corporation (TRDC) have developed PECS (Personal Environmental Control System) and COOLTECH apparel, that utilizes 3–4mm diameter macro-encapsulated phase change materials or MacroPCMs to provide 1–2 hours of comfort and relief from heat stress, while permitting the garment’s thermal recharging without refrigeration or freezers.
Estimation of the Acoustic Scattering Matrix for a Centrifugal Pump
Authors: Bardeleben M. J. R. , Weaver D. S.
Published: June 2008

This paper presents the results of a theoretical and experimental investigation into the acoustic scattering matrix for a centrifugal pump. Background is provided which examines past research into acoustic two-port models, illustrating the benefits and laying the groundwork for the current incarnation of the scattering matrix. The results reveal that the traditional form of the transmission matrix is not adequate for predicting the parameters of the scattering matrix and a new form is suggested. With a simple modification, the predicted values successfully capture the trend in the experimental data. The presented research is still ongoing, looking to improve the model by including the compliance of the pump housing and inertial effects at the pump ports.
Aeroacoustical Coupling and Its Structural Effects on a PWR Steam Line: Part 2 — Vibroacoustical Analysis of Pipe Shell Deformations
Authors: Caillaud Se´bastien , Lambert Christophe , Devos Jean-Paul , Lafon Philippe
Published: June 2008

A pure tone phenomenon has been observed at 460 Hz in a PWR steam line. The acoustical energy has been identified to be generated in an open gate valve. The objective here is to understand the way of energy transfer from the fluid to the main pipe using two fully coupled methods. The first method consists in a modal analysis of the line using a fluid-structure finite elements model. The second one is based on the analysis of dispersion diagrams derived from the local equations of cylindrical shells filled with fluid. The way of energy transfer in transverse acoustical waves induced combined flexion-ovalisation deformations of the pipe is highlighted using both methods. The dispersion diagrams allow a fast and accurate analysis. The modal analysis using a finite elements model may complete the first one with quantitative data.
Wavelet Analysis of Sound Signal in Fluid-Filled Viscoelastic Pipes
Authors: Prek Matjaz
Published: June 2008

In viscoelastic pipes, where the material properties depends on a complex bulk modulus as well as on a complex shear modulus, the sound field within the fluid is affected. Therefore, the dispersion of flexural waves occurs in the pipe, while the speed of flexural waves decreases due to the coupled fluid mass. Coupling between the pipe wall and the fluid also decreases the sound speed in the fluid. Likewise, the speed of sound in fluid is frequency-dependent, just as the group velocity of bending waves depends on the frequency. Wavelet transform of non-stationary sound signal was used to identify the frequency-dependent fluid sound speed. A time-frequency map, constructed by plotting the wavelet coefficient against the translation and scale parameters, shows an alteration in the low frequency waves. The so called fluid mode and pipe mode resonant frequencies are also clearly evident. Lastly, the impact of different pipe wall material properties is also shown. Results suggests that the wavelet transform gives in general more information from measured results.
Acoustic Vibration in a Stack Induced by Pipe Bends
Authors: Eisinger F. L. , Sullivan R. E. , Feenstra P. , Weaver D. S.
Published: June 2008

Acoustic vibration in two stack liners located inside a stack downstream of two induced draft fans occurred at high loads. Measurements confirmed that an acoustic wave developed in the fundamental diametral mode of the cylindrical stack liners. It manifested itself as a pure tone traveling through the stack to surrounding residential areas. It was suspected that turbulent flow in the pipe bends upstream of the stack and downstream of the fans was the source of the excitation. Laboratory scale model tests confirmed that the bends indeed acted as the source. Two guide vane configurations placed inside the bends were tested experimentally. The tests showed that properly placed guide vanes would reduce the acoustic levels in the stack. The paper gives a description and evaluation of the problem.
A Demonstration of EFAB™ as a Fundamental Shift in the Way Microdevices Are Manufactured
Authors: Evans John D. , Bang Christopher
Published: June 2008

The authors introduce the EFAB™ manufacturing process originally invented at the University of Southern California and currently being commercialized by MEMGen Corporation. They discuss its significant recent evolution as an alternative to conventional microdevice manufacturing technologies, suggest a range of geometries and applications that are enabled by this process, and develop the case that EFAB represents a fundamental shift in the way the microdevices are manufactured.
Design and Fabrication of an Annular High Frequency Resonator
Authors: Lee Ki Bang , Ryder Steve , Lee Chih-Chen , Lin Liwei
Published: June 2008

We present a new high frequency resonator using a high order mode shape of an annular structure. The basic concept of an annular high frequency resonator (AHFR) is presented and the AHFR is fabricated by using a standard surface micromachining technology. Using theoretical analysis, the resonant frequency of the AHFR was expressed in a simple form. On this basis, a theoretical formula for the AHFR has been developed in terms of the structure’s geometry and material properties. The outer diameters of the 3.5 μm-thick polysilicon AHFR with resonant frequencies of 100MHz, 500MHz and 1GHz are 192 μm, 96 μm and 61 μm, respectively. This results in areas sufficient large to readily sense the filtered signal. Fundamental characteristics of the mode shape and resonant frequency of the AHFR have been discussed.
A Novel Embedded Root Method to Construct Thick Metal Microstructures Using SU-8 in UV-LIGA Process
Authors: Ho Chien-Hung , Chin Kan-Ping
Published: June 2008

To upgrade the electrostatic force, movable devices in micro-electro-mechanical systems may require three-dimensional microstructures with large capacitive areas and vertical sidewalls with several hundred micrometers in height. The photoresist, NANO™ XP SU–8, can be implemented in the fabrication of high-aspect-ratio microstructures in low-cost MEMS production. In this study, using SU-8 as an electroplating mold, an improved method for consolidating the adhesion of the plated microstructures to the substrate is utilized. By constructing an embedded root as the substructure, this novel technique can greatly increase the thickness of the metal components, and simultaneously, the hard-to-strip crosslinked SU-8 may be removed completely. The fabrication of stators and bearing post for an electrostatic micro motor is used here to demonstrate the effectiveness of the proposed method, where the structural height and the minimum gap of the stators are 300 μm and 50 μm, respectively. For comparison, some fabricated results of typical approaches by a heated remover to strip the cured SU-8 mold are also shown in this paper.
A Simple Process for Lateral Single Crystal Silicon Nanowires
Authors: Milanovic´ Veljko , Doherty Lance
Published: June 2008

In a single-mask standard photolithography based process and a single etch step, lateral silicon nanowires are fabricated according to arbitrary layout and over a range of diameters and lengths. Nanowires with diameters from ∼20 nm and with lengths ranging from 2 μm to 100 μm were fabricated in direct contact with two silicon probing pads for measurement. These nanowires are electrically isolated in the silicon-on-insulator wafer device layer, and suspended over the substrate, thereby increasing thermal and electrical isolation. Because they are formed from single crystal silicon, minimal defects are expected. The addition of a polysilicon deposition and patterning further enhances the process by allowing coaxial silicon nanostructures.
Aeroacoustic Model Testing of the Vaned Intake of a Centrifugal Compressor
Authors: Manfrida G. , Fiaschi D. , Giachi M.
Published: June 2008

A model of the vaned intake of a centrifugal compressor was instrumented and tested for the investigation of aero-acoustic excitation modes for specific flow conditions, in order to check the possibility of damage to the Inlet Guide Vanes (IGV). The tests demonstrate that several acoustic modes occur for such complex geometries, and that their frequencies and amplitudes should be verified in order to avoid the excitation of forced vibration of the blades.
Effects of Flexible Walls on Radiated Sound From a Turbulent Boundary Layer
Authors: Zheng Z. Charlie
Published: June 2008

In this paper, radiated sound from low Mach number turbulent boundary layers is studied using Lighthill’s analogy. The focus is to investigate the behavior of wall pressure fluctuations on a flexible wall boundary. Comparisons are made between the results from rigid and flexible walls. At low frequencies, the flexible wall results have shown much higher levels of power spectra. At high frequencies, the spectra of the flexible wall sound radiation and those of the rigid wall sound radiation merge. These trends are in agreement with other experimental and theoretical results in literature. This theoretical study of the two-dimensional turbulent boundary layer can clarify the effects of a flexible wall on radiated sound in low Mach number flows.
Nondestructive Methods for the Damage Assessment of Cylindrically Curved Composite Laminates Subjected to Low-Velocity Impact
Authors: Kwon Oh-Yang , Jun Jung-Kyu , Dzenis Yuris A.
Published: June 2008

Curved composite laminates appeared to be more vulnerable than flat ones to rapid transverse loading. Damage induced by low-velocity impact on the cylindrically curved composite laminates has been experimentally investigated. Graphite/epoxy shells with the radius of curvatures of 150 mm showed quite different impact response and damage behavior from that of flat laminate. Under the same impact energy level, the maximum contact force varied with the radius of curvatures, which is directly related to the impact damage. Delamination was distributed rather evenly at each interface along the thickness direction of curved laminates on the contrary to the case of flat laminates, where delamination is typically concentrated at the interfaces away from the impact point. Due to the presence of curvature, the acoustic microscopy could not be directly applied to the layer-by-layer assessment of delamination damage. As an alternative, the penetrant-enhanced X-radiography (PEXR) was introduced and the results from PEXR were compared with those from destructive examination of the cross-section by scanning electron microscopy.
Non-Contact Laser Ultrasonic Inspection for Cryogenically Introduced Interlayer Defects in Epoxy-Based Composites
Authors: Vedantham Vikram , Thummalapalli Anirudh , Yang Baozhong , Suh C. Steve
Published: June 2008

Traditional transducer-based techniques for Non-Destructive Evaluation (NDE) are limited by fixed frequency-bandwidth for generation and sensing, and thus provide unsatisfactory resolution for certain types of material defects. Thermo-Acousto-Photonic NDE (TAP-NDE) is a proven alternative that is non-invasive and non-contact, and suited for real-time applications. This paper focuses on employing TAP-NDE to examine the presence of microcracks and fissures in multi-layered composites. Tests were performed on layered composite panels of specific epoxyresin composition and constant thickness to identify localized delaminations formed by subjecting the specimen to cryogenic cycling. Interrogation of the undamaged specimen using laser-generated broadband surface waves revealed a standard reference knowledge base, as seen in the instantaneous frequency-time domain. Tests were repeated after each specimen was subjected to a set number of cycles of liquid nitrogen cycling, which caused damages at the micron scale in the bulk material. Analyses showed changes in the time of wave arrival and absence of prominent high frequency components. Wave velocity and dispersion characteristics of the cycled specimen were altered. Thus, the specimen, on cryogenic cycling, was found to undergo a decrease in stiffness, which is speculatively the result of micro-voids, fissures or delaminations between layers. Hence, when combining with the basic notion of instantaneous frequency, TAP-NDE acts as an effective broadband generation and sensing technique, demonstrating feasibility and greater versatility for inspecting layered composites as against contemporary narrowband techniques.
Noncontact Evaluation of Defects in Thin Plate With Multimodes Lamb’s Waves and Wavelet Transform
Authors: Murase Morimasa , Kawashima Koichiro
Published: June 2008

Multimode’s Lamb waves in aluminum plates with various defects were excited by a Q-switched Nd:YAG laser. The Lamb waves past through the defects were received a laser interferometer. The received signals of the Lamb waves are processed by the wavelet transformation. The wavelet transformation is generally shown on the time-frequency domain. By dividing a propagation distance by the time, the group velocities are identified. In this way, group velocity dispersion maps of multimode’s Lamb waves are constructed with the received temporal signals. By changing the shape of the mother wavelet, Gabor function, we can identify the dispersion curves of the higher mode Lamb waves. The group velocity dispersion maps of a intact specimen agree well on theoretical dispersion curves of S0, A0, S1, A1, S2, A2, and A3 modes. The difference between the dispersion maps of the intact specimen and that with defects clearly visualizes the existence of defects. This non-contact method is effective for inspecting various defects in thin plate structures.
Building Artificial Nerves for Structures
Authors: Pammi SriLaxmi , Brown Courtney , Datta Saurabh , Kirikera Goutham R. , Schulz Mark J. , Kaul Payal , He Peng , Shi Donglu , Boerio F. James , Sundaresan Mannur J.
Published: June 2008

Building artificial nerves for smart structures and for structural health monitoring is discussed. Structural Health Monitoring refers to using in-situ sensors to monitor the strains and strain waves and from these interpret the health of a structure in real-time. This will allow a structure to be operated at its maximum performance and efficiency while minimizing fatigue and other damage. To achieve this capability on a large structure, artificial nerves are used to mimic the biological nervous system. Two design concepts for nerve fibers are considered; piezoceramic active fibers and carbon nanotube conductive fibers. The piezoceramic fibers are self-powered and can sense acoustic emissions and dynamic strains due to damage. The carbon nanotube fibers change conductance when strained and can sense high strain due to damage. The processes being developed to fabricate the two types of nerves are discussed and some initial experimental results are presented.
Quantitative Determination of the Stability of Implant-Bone Interface Using Resonance Frequency Analysis
Authors: Delgado Daniel , Fuentes Arturo A. , Jones Robert , Lumsdaine Arnold
Published: June 2008

It is important to have a quantitative method to establish a standard way to measure stability and osseointegration of implants. Among other benefits, these measurements would provide information leading to the prediction of healing time around the implant and the monitoring of the health of the implant’s interface. The dental industry has been looking for non-destructive methods to measure implant integration within the bone. In previous studies, resonance frequency analysis revealed a clear relationship between resonance frequency measurements and stiffness of the implant interface and the effective length of the implant. These studies have examined only one mode of vibration or have suffered from measurement difficulties. Furthermore, no study has evaluated the damping properties of the interface and surrounding tissues. This paper describes the development of an instrument capable of capturing and measuring information to characterize the process of dental implant osseointergration. The parameters needed to measure stability and osseointegration of implants are the stiffness of the implant components (which are a function of their geometry and material composition) and the stiffness and damping properties of the implant-bone interface and surrounding tissues. The instrument developed provides valuable information about the stiffness and damping properties of the implant-bone interface obtained through resonance frequency analysis with torsional, longitudinal and transverse vibration. Experimental, analytical, and finite element analysis results are presented.
Investigation of Field Amplified Sample Stacking With Particle Image Velocimetry
Authors: Devasenathipathy Shankar , Bharadwaj Rajiv , Santiago Juan G.
Published: June 2008

This paper presents an experimental investigation of field amplified sample stacking (FASS) with micron resolution particle image velocimetry (μPIV). The preliminary experiments reported in this work show particle velocity fields in electrokinetic flow in a glass microchannel with a single buffer-buffer interface. The buffer-to-buffer conductivity ratio is 10. Stacking of latex microspheres (i.e., increases in their number density) in the presence of a background electroosmotic flow is demonstrated. The generation of an internal pressure gradient is quantified using μPIV. This work is part of an ongoing study of the spatial and temporal development of the velocity and concentration profiles of FASS systems.
Electrokinetic Flow Instability in High Concentration Gradient Microflows
Authors: Chen Chuan-Hua , Santiago Juan G.
Published: June 2008

This paper documents the scalar imaging of an electrokinetic flow instability that is directly relevant to microfluidic systems that aim to handle and analyze heterogeneous sample streams. The instability occurs in simple T-junctions where two streams of different ionic concentration flow into a common channel. Using neutral dye visualizations, general qualitative behavior of the instability is documented including the formation of a wave in the stream/stream material line that originates at the junction of the two channels and propagates downstream. Several quantitative properties of this phenomenon are measured including wave speed and the extent of the perturbation boundary. This work is part of an ongoing project to identify the physics of this instability and determine the regime of stability, with an ultimate goal of developing methods to either enhance or suppress the instability.
Active Control of the Profile Drag of Two-Dimensional Cylinders
Authors: Nigim Hani H. , Koyama Hide S. , Shiino Kohta
Published: June 2008

The control of profile drag on a circular cylinder was studied experimentally at Reynolds numbers, ranging from 160 to 400, using an acoustic active control system. The investigation has been carried by, quantitatively, hot-wire to measure the mean and fluctuating velocities and, qualitatively, by using smoke-wire flow visualization technique to examine the formation of the flow field down-stream of the cylinder. The present active control method is able to influence the rate of entrainment from main flow into the wake flow. When the Reynolds number is relatively small, it is the size of the cylinder and the induced sound field velocity as well as Reynolds number which are the significant parameters in determining the controlling reverse and optimum phase lag angels. The reported control strategy is able to alter the profile drag of a two-dimensional circular cylinder. At optimum lag angle and low Reynolds number the profile drag was reduced by 9%.
Material Handling Expansion for a Package Routing Hub
Authors: Warber Michael , Standridge Charles R.
Published: June 2008

Ground-based delivery companies often rely on a network of terminals and hubs to move packages throughout the country. Most of the hubs are located in major cities with hundreds of terminals located in smaller cities. A conveyor system is used to unload, sort and transport packages throughout the hub. Due to the enormous size of hub facilities, some containing 8 miles of conveyor, each is built in phases. Each phase typically adds a copy of the original and ties into the existing conveyor system. The same core processes typically are found in each hub with some site-specific variations: the unload area, primary sorter, and secondary sorter. This paper discusses an analysis of a typical hub expansion to determine if equipment and resources are being used efficiently and to identify possibilities for reducing the cost of capital equipment. Simulation is the primary tool used to carry out the analysis.
Simulation of MEMS Piezoelectric Micropump for Biomedical Applications
Authors: Moussa Walied A. , Gonza´lez Ulises F.
Published: June 2008

In this study, we demonstrate the usefulness of Finite Element Analysis (FEA) and simulation techniques in the design of MEMS micropumps. Such pumps provide for the handling of milliliter-scaled fluid volumes desired in many lab-on-a-chip chemical and biomedical applications. This work is focused on a micropump driven by the piezoelectric effect, which in turn invokes the dominant resonance behavior. Because the design of the device is the emphasis of this study, the model was originated in CAD and includes the fme-scale geometric details commonly encountered in a wide variety of micropumps. The model considered in this study is a rectangular micropump with a piezoelectrically actuated diaphragm on its top and two valves on its bottom. The mechanical efficiency of the pump hinges on using resonance to generate sufficient motion of the diaphragm. Mechanical Event Simulation (MES) commercial software from ALGOR was utilized to simulate this motion, and thus provide a method for optimizing the design. The results show that consideration needs to be given to the voltage-driving frequency because of its effect on the pump performance and the stress levels within it.
Intermittent Hydrostatic Pressurization Modulates Gene Expression in Human Dermal Fibroblasts Seeded in Three-Dimensional Polymer Scaffolds
Authors: Nicoll Steven B. , Mauck Robert L. , Tsay Rick C. , Hung Clark T. , Ateshian Gerard A.
Published: June 2008

Mechanical stimuli are known to regulate the morphology and differentiated function of connective tissue cells. In particular, hydrostatic pressure has been reported to alter cytoskeletal organization in osteoblast-like cells (1) and chondrocytes (2), and to modulate metabolic activity in both chondrocytes (3–5) and intervertebral disc cells (6). The cellular response to continuous hydrostatic pressure is generally catabolic (3) while intermittent hydrostatic pressure at frequencies ranging from 0.25–1.0 Hz (3–5) is anabolic, giving rise to increased expression and biosynthesis of extracellular matrix (ECM) components. Previously, human dermal fibroblasts in monolayer culture were shown to respond to hydrostatic pressure by increasing heat shock protein expression levels (7). In this study, we characterize the effects of intermittent hydrostatic pressure on gene expression in human dermal fibroblasts seeded in three-dimensional polymer scaffolds.
Experiences in Modeling, Simulation, and Optimization of Chemical Industry Supply Chains
Authors: Standridge Charles R. , Heltne David R.
Published: June 2008

We have developed and applied simulation as well as combined simulation – optimization models to represent process industry plant logistics and supply chain operations. The simulation model represents plant production, inventory, and shipping operations as well as inter-plant shipments. When a combined simulation-optimization approach is used, the simulation periodically invokes a classical production planning optimization model to set production and shipping levels. These levels are retrieved by and used in the simulation model. Process industry supply chain operations include stochastic elements such as customer demands whose expected values may vary in time as well as transportation lead times. The complexity of individual plant operations and logistics must be considered. Simulation provides the methods needed to integrate these elements in a single model. Periodically during a simulation run, production planning decisions that require optimization models may be made. Simulation experimental results are used to determine service levels to end customers as well as to set rail fleet sizes, inventory capacities, and capital equipment requirements for logistics as well as to assess alternative shipping schedules.
A Metric-Based Approach to 2D Tool-Path Optimization for High-Speed Machining
Authors: Wang Hongcheng , Stori James A.
Published: June 2008

Conventional tool-path generation strategies are readily available to generate geometrically feasible trajectories. Such approaches seldom take into consideration physical process concerns or dynamic system limitations. In the present work, an approach for improving a geometrically feasible tool-path trajectory based on quantifiable process metrics is developed. Two specific measures of toolpath quality are incorporated into the iterative improvement algorithm: instantaneous path curvature and instantaneous cutter engagement. These metrics are motivated by a desire to minimize acceleration requirements and maintain a stable steady-state cutting process during high-speed machining. The algorithm has been implemented for two-dimensional contiguous end-milling operations with flat end-mills, and case studies are presented to illustrate the approach.
Active Control Methods of Flow-Induced-Vibrations: Near-Wall-Turbulent-Pressure-Fluctuation Measurements
Authors: Kudashev Efim B. , Yoblonik Leonid R.
Published: June 2008

Near-wall pressure fluctuations in turbulent flows are of considerable interest in many engineering applications. We shall concentrate on a number of specific questions related to the resolution of components of wall pressure spectra. Our emphasis shall be on outstanding problems of experiment and theory and their relationship to one another. A study on pressure fluctuations transducer’s interaction with wall vibration resulting from near-wall turbulent flows has been performed. Piezoelectric pressure transducer generates the signal also on vibration influence. Algorithm of assign of turbulent surface pressure in conditions of flow-induced-vibration is suggested. An active method of vibration control has been developed.
Packaging Dissimilar Materials for Microfluidic Applications
Authors: Galambos Paul , Okandan Murat , Pohl Kenneth R. , Benavides Gilbert L. , Jenkins Mark W. , Bennett Dawn J. , Stay Mathew S.
Published: June 2008

In this paper we address the problem of assembling several different microfluidic devices, often made from different materials, into a hybrid packaged system. The focus will be on integration of silicon microfluidic die into larger hybrid systems. Details of three different approaches are presented: 1) a plastic flow manifold with tape die attach, 2) multiple capillary die insertion utilizing PDMS (Polydimethylsiloxane – silicone adhesive) for sealing and structural support, and 3) die attachment to a glass flow manifold utilizing anodic bonding. The unique tools required for each of these three techniques will be described. Sealed microfluidic connections (>10 ATM pressure) between silicon microfluidic chips (die) and flow manifolds are demonstrated.
Microchannel Flow Measurement Using Micro Particle Image Velocimetry
Authors: Lee Sang-Youp , Wereley Steven T. , Gui Lichuan , Qu Weilin , Mudawar Issam
Published: June 2008

Since microfabrication techniques are typically planar processes, microchannel flows typically have significant predevelopment due to the upstream reservoir having the same height as the microchannel. The main concerns of the current study are categorized into finding the effects of typical microchannel geometry on the velocity entrance length in the laminar flow regime and providing the turbulence transitional Reynolds number range using the details of the velocity profile rather than global measurements of pressure drop. A rectangular micro-channel of aspect ratio ∼2.65 and the hydraulic diameter 380μm was used in this study. Micro particle image velocimetry measurement was performed to measure the velocity profiles. The entrance length is reduced about 45% and the transitional velocity profile is measured at Re=2900. The velocity profiles do not show deviation from the fully developed laminar flow profiles up to Re=2100. Related to the flow transition, the close resemblance between the correlation function peak broadening and the turbulence intensity is observed.
The Effects of Shear Stress on Endothelial Cells at Hypothermic Temperatures
Authors: Slater John H. , Jain Shailendra , Coger Robin N. , Lee Charles Y.
Published: June 2008

Hypothermic machine perfusion preservation (MPP) has proven to be a successful technique for hypothermic kidney storage, however this technology has not successfully been applied to the liver. Recent research has indicated that the endothelial cells lining the liver sinusoids display rounding phenomena during MPP that is not fully understood. In order to gain a better understanding of endothelial cell shear stress response and the factors that induce rounding, a temperature-controlled micro-shear chamber has been designed and fabricated. The micro-shear chamber has been used to apply shear stresses, corresponding to those imposed during MPP, to rat liver primary endothelial cell cultures in order to form an understanding of how these stresses affect endothelial cell morphology. The chamber allows for the application of shear stresses ranging from 0.2 ± .01 dynes/cm2 to 2.3 ± 0.3 dynes/cm2, corresponding to what occurs during MPP.] Twenty-four hour in vitro experiments with shear stresses ranging from 0 to 1.49 dynes/cm2 at 4 °C were conducted in order to replicate in vivo conditions of the liver during hypothermic MPP. It has been demonstrated that endothelial cell rounding increases with increasing shear and can be prevented by utilizing low flow rates.
To Slip or Not to Slip: Water Flows in Hydrophilic and Hydrophobic Microchannels
Authors: Choi Chang-Hwan , Westin K. Johan A. , Breuer Kenneth S.
Published: June 2008

The slip effects of water flow in hydrophilic and hydrophobic microchannels of 1 and 2 μm depth are examined experimentally. Fabrication processes for silicon/Pyrex microchannels were chosen to ensure good control of the channel height and to obtain atomically smooth surfaces. Hydrophilic surfaces were prepared with an RCA-1 cleaning, while hydrophobic surfaces were created by coating the channel surface with the self-assembled monolayer of octadecyltrichorosilane (OTS). The flow rates of pure DI water at various applied pressure differences for each surface condition were measured using a high precision flow metering system and it was observed that the flow rates in hydrophobic channels is larger than in the same hydrophilic channel. The increase of the flow rate can be explained by assuming a slip velocity at the wall. The slip effects become more pronounced as the channel height decreases and the wall shear rate increases. The slip length was found to vary as approximately the square root of the shear rate and had values of approximately 40 nm in the hydrophobic channels and 15 nm in the hydrophilic channels at a shear rate of 105 s−1.
Model for Acoustic Microscopy Inspection of Microelectronics Packages With Thin Layers
Authors: Canumalla Sridhar
Published: June 2008

A broadband model is proposed to describe the nature of ultrasonic pulses in multilayered systems with a sub-wavelength thickness layer. This model, which is targeted towards acoustic microscopy of microelectronic devices, can incorporate measured ultrasonic properties of electronic materials and predict the complete ultrasonic pulse-train for all the interfaces in an electronic device. The model is robust, and incorporates material and geometric variables commonly encountered in microelectronics applications. Results are presented to illustrate how delaminations and cracks with foreign material or moisture ingress can appear to be well-bonded and why acoustic images of interfaces with thin layers can sometimes give erroneous indications of the bond state.
Chaotic Electroosmotic Flow
Authors: Qian Shizhi , Bau Haim H.
Published: June 2008

Two dimensional, time-independent and time-dependent electroosmotic flows driven by a uniform electric field in rectangular cavities with uniform and non-uniform zeta potential distributions along the cavities’ walls are investigated theoretically. The time-independent flow fields are computed with the aid of Fourier series. The series’ convergence is accelerated so that highly accurate solutions are obtained with just a few (<10) terms in the series. The analytic solution is used to compute flow patterns for various distributions of the zeta potential along the cavities’ boundaries. It is demonstrated that by time-wise periodic modulation of the zeta potentials, one can induce chaotic advection in the cavities. Such chaotic flows may be used to stir and mix fluids in microfluidic devices.
Prediction of Interfacial Positions in Steady Converging Microchannel Flows at Low Reynolds Numbers
Authors: Harris T. R. , Hitt D. L. , Macken N.
Published: June 2008

Previous work has shown that interfaces formed in steady, converging microchannel flows tend to be planar in nature under a wide variety of MEMS-relevant conditions. Assuming a planar interface, we have developed analytical models to predict the interfacial location in the outlet branch. The analytical results show good agreement with 3-D computational cases and experimental measurements. Application of this analytical, planar interface method represents a significant degrease in computational effort when compared to using CFD to determine interfacial positions.
DEM Simulation of the Granular Compaction Process
Authors: Sheng Yong , Lawrence C. J. , Briscoe B. J.
Published: June 2008

In this paper, the discrete element method is employed to simulate the powder compaction process and to produce the detailed results of micro mechanical response in particle scale. The DEM program is capable to calculate the contact between particles considering of surface adhesion, The statistical average properties of the compacts are then obtained from the sum of the particle movements and contacts. The calculated results show that the variation of the particle properties such as contact friction and elastic-plastic contact criteria can significantly affect the bulk response of the assembly. The connection between micro properties of particles and macroscopic continuum description of the behaviour of granular media is then discussed.
Interpretation of Mechanical Testing Measurements for Pastes
Authors: Basterfield Robert A. , Lawrence Chris J. , Adams Michael J.
Published: June 2008

Pastes occur as intermediates or final product forms in many industrially important manufacturing sectors. The use of computer simulation techniques, such as the finite element method, is becoming more common in the design of paste processing operations. A major problem in the application of this approach is the development of sufficiently representative materials models. It has been established that pastes may be described as elasto-viscoplastic materials with the plastic flow being governed by the Herschel-Bulkley relationship. This paper describes the development of analytical and numerical models that can be used as a basis for deriving the material parameters from experimental data obtained using extrusion, compression and bending procedures. Measurements have also been carried out on a model paste and the derived material parameters are compared with published data for the same paste. The merits of the three experimental methods are compared on this basis.
Methology for Engineering Cost and Lead-Time Estimation in Metal Casting Applications
Authors: Tomovic Mileta M.
Published: June 2008

Accurate cost and lead-time estimation are very important issues during product design stage as well as for procurement process. The initial cost estimate can have profound effect on the project success or its failure. Inaccurate initial cost estimation can lead to financial losses that can have severe consequences on the project and company. Hence it is important to have accurate and easily accessible method for accurate cost and lead-time estimation. There are several estimation methods with focus on different manufacturing processes. These methods are based on general process description, and their process models and associated empirical data have limited accuracy. Also, most of them are not readily accessible to the engineers or procurement personnel. This paper presents application of one the more accurate estimation methods developed by the Air Force for metalcasting cost estimation. The method has been deployed on the Internet and can be easily accessed.
Future of Engineering Technology Education
Authors: Rennels Kenneth E.
Published: June 2008

Engineering technology education in the United States can trace its history back to the Wickenden and Spahr study of 1931, which identified the place of engineering technology education in the technical spectrum [1]. By 1945, the Engineering Council for Professional Development developed the first accreditation procedures for two-year engineering technology programs and by 1946, the first program was accredited. On this timeline the Purdue University engineering technology programs at Indianapolis can trace their history back to 1946 [2]. Over the last 70 years, engineering technology education in the United States has distinguished itself by a history of evolution, development and continuous improvement. Engineering technology education faces significant challenges during the next several years. These challenges are driven by the rapid evolution of computer technology and changing expectations of the educational process by the stakeholders. Stakeholders include not only students and faculty but also various groups in both the public and private sectors including industry, professional organizations, funding agencies, state government and the university system. Two specific challenges facing engineering technology educators are ‘basic faculty credentials’ and changing expectations for ‘creative activities’. These two challenges can be delineated by the following questions: • Will a doctorate degree be necessary for engineering technology faculty in the future for promotion and tenure in the university environment? • Will applied research or pedagogical research be ‘good enough’ for tenure? This paper addresses these two issues using a study of current engineering technology faculty hiring practices as a basis. Ultimately, critical future discussions must occur as engineering technology education continues to evolve and move into the future.
Predicting Surface Roughness in End Milling Using an Innovative Technique From EC (Evolutionary Computation)
Authors: El-Mounayri Hazim , Dugla Zakir , Deng Haiyan
Published: June 2008

A new technique from EC (Evolutionary Computation), PSO (Particle Swarm Optimization), is implemented to model the end milling process and predict the resulting surface roughness. Data collected from cutting experiments is used for model calibration and validation. The inputs to the model consist of Feed, Speed and Depth of cut while the output from the model is surface roughness. The model is validated through a comparison of the experimental values with their predicted counterparts. A good agreement is found. The proved technique opens the door for a new, simple and efficient approach that could be applied to the calibration of other empirical models of machining.
Tribological Aspects of Workpiece/Fixture Contact in Machining Processes
Authors: Deiab Ibrahim M. , Elbestawi Mohamed A.
Published: June 2008

This work presents an experimental investigation of the effect of different factors including normal load, workpiece surface roughness, and fixture roughness, on the coefficient of friction along the workpiece/fixture contact for machining processes. A full factorial design of experiment was used. Randomization, blocking, and averaging schemes were utilized to reduce the experimental error and variability. The data was statistically analyzed and explanations for the observed trends were given. This investigation is part of an ongoing research project to develop an integrated modular dynamic model of the milling process including the effect of fixture dynamic.
Hybrid Spindle Current Regulation System With Tool Wear Detection Algorithm
Authors: Lee Taik M. , Yang Min Y.
Published: June 2008

In this paper, a hybrid adaptive control algorithm that controls feedrate to regulate spindle current and detects tool wear is proposed. For this purpose, variation of steady state spindle current, time constant, and time delay were examined through experiments based on step end milling under various cutting conditions. The developed hybrid adaptive control algorithm is composed of adjustable proportional feedback control (adjustable P control), fine control, entry feedrate control, and tool wear detection algorithm. Adjustable P control carries out large scale control, fine control carries out detailed control, entry feedrate control reduces the peak current produced when a tool makes contact with a workpiece, and tool wear detection algorithm perceives tool wear and breakage qualitatively. The adjustable P control algorithm was verified through comparisons between calculated P gains and experimentally obtained P gains. The hybrid adaptive control algorithm was applied to various cutting conditions and it showed global stability as well as excellent applicability behavior.
Cross-Linked Microchannels for VLSI Hotspot Cooling
Authors: Jiang Linan , Koo Jae-Mo , Wang Evelyn , Bari Abdullahel , Cho Eun Seok , Ong Wendy , Prasher Ravi S. , Maveety Jim , Kim Min Soo , Kenny Thomas W. , Santiago Juan G. , Goodson Kenneth E.
Published: June 2008

Thermal management for the future generations of electronics faces challenges including total heat dissipations exceeding 100 W and local hotspots resulting from non-uniform heating. This work develops microchannel heat sinks with cross-linked channels to achieve a better chip temperature uniformity under non-uniform heating conditions. Stream-wise microchannels with a hydraulic diameter of 420 μm are subjected to pressure driven water flow. Channel cross-links with a hydraulic diameter of 150 μm, under non-uniform heating conditions, allow fluid lateral transport between the stream-wise channels in the region receiving the largest heat flux and those on the rest of the chip. As a result, a better chip temperature uniformity is achieved by utilizing the local pressure difference and capillary effect. Experimental results with a localized heating condition demonstrate an improvement of approximately 10% in the ratio of temperature of the heater to that of the rest of the chip. Analysis suggests that greater improvement can be achieved through optimization of the dimensions of the cross-links with respect to those of the stream-wise channels and through tailoring more cross-links within the hotspot region.
The Effects of Drive-In Process Parameters on the Residual Stress Profile of the Boron-Doped Silicon Layer
Authors: Jeong Ok Chan , Yang Sang Sik
Published: June 2008

The paper represents the effects of the drive-in process parameters on the residual stress profile of the p+ silicon film quantitatively. Since the residual stress profile is not uniform along the direction normal to the surface, the residual stress is assumed to be a polynomial function of the depth. All of the coefficients of the polynomial are determined from the deflections of cantilevers and the displacement of a rotating beam structure, which are measured with a surface profiler meter and a microscope. As the drive-in temperature or the drive-in time increases, the boron concentration decreases and the magnitude of the average residual tensile stress decreases. Also, near the surface of the p+ film the residual tensile stress is transformed into the residual compressive stress and its magnitude increases. The correlation coefficients between the residual stress profiles and the simulated boron concentration are calculated. As the drive-in time and temperature increase, all correlation coefficients become close to 1, and the boron concentration profiles after the drive-in process are similar to the stress profiles. Also, the lattice contractions of test wafers are measured by HRXRD (High Resolution X-Ray Diffractometry).
Flip Chip Process Development and Relaibility Evaluation With Lead-Free Solder Alloy
Authors: Yunus Mohammad , Venkateswaran Muthiah , Borgesen Peter
Published: June 2008

Usually, flipchip technology is based on either high-Pb or eutectic Sn/Pb solder forming the connections between the semiconductor chip and the carrier substrate. However decay of the 210Pb constituent, via 210Bi and 210Po, to 206Pb involves the emission of energetic alpha particles which have a tendency to cause soft errors in nearby active elements on the chip. Also, impending legislations in Europe and Japan on the elimination of Pb from electronic products have prompted the investigation of alternative solder alloys. This paper outlines an initial development effort focussed on the Sn/Ag/Cu (95.8/3.5/0.7) alloy. The study involved the development of a flip chip assembly process followed by a reliability evaluation comparing the fatigue resistance of the Sn/Ag/Cu alloy to that of eutectic Sn/Pb solder. The test vehicle used was a 225μm bump pitch, 11mm square die mounted on a ceramic substrate.