bluuebunny/crossref_metadata_2025 huggingface dataset:
Post-Release Displacement Uncertainty of Micro-Cantilevers Due to Anchor Over/Under Etching
Authors: Garg Anurag , Small Joshua , Liu Xiaoguang , Scott Sean , Peroulis Dimitrios
Published: August 2009

In this paper we follow an analytical and finite element modeling approach to study the effect of anchor over/under-etch on the post-release tip displacement of MEMS cantilever beams. We show that the last release step is particularly critical in controlling the beam’s post-release displacement, which is of primary importance in a variety of applications. In this paper we isolate the effects of mean stress and imperfect anchor. We assume negligible gradient stress since its effect has been studied in detail in the literature. Beams with perfect anchors and zero under-etch are also presented for comparison. The results emphasize that through careful control of the fabrication parameters and anchor structure, the initial displacement profile and thus performance of micro-cantilevers can be accurately controlled.
A New Multi-DOF Photostrictive Actuator for Dynamic Control of Shells: Modeling and Analysis
Authors: Yue Hong-Hao , Sun Gui-Lan , Deng Zong-Quan , Tzou Horn-Sen
Published: August 2009

Based on the photovoltaic effect and the converse piezoelectric effect, the lanthanum-modified lead zirconate titanate (PLZT) actuator can transform the photonic energy to mechanical strain/stress — the photodeformation effect. This photodeformation process can be further used for non-contact precision actuation and control in various structural, biomedical and electromechanical systems. Although there are a number of design configurations of distributed actuators, e.g., segmentation and shaping, been investigated over the years, this study is to explore a new actuator configuration spatially bonded on the surface of shell structures to broaden the spatial modal controllability. A mathematical model of a new multi-degree-of-freedom (DOF) photostrictive actuator configuration is presented first, followed by the photostrictive/shell coupling equations of a cylindrical shell structure laminated with the newly proposed multi-DOF distributed actuator. Distributed microscopic photostrictive actuation and its contributing components are analyzed in the modal domain. Effects of shell’s curvature and actuator’s size are evaluated. Parametric analyses suggest that the new multi-DOF distributed actuator, indeed, provides better performance and control effect to shell actuation and control. This multi-DOF configuration can be further applied to actuation and control of various shell and non-shell structures.
An Innovative Engineering Curriculum at James Madison University: Transcending Disciplinary Boundaries Through Innovative Problem Based Learning Practices
Authors: Pierrakos Olga , Kander Ronald , Pappas Eric , Prins Robert
Published: August 2009

Global competitiveness, outsourcing, and increased production of overseas engineers are issues that are becoming increasingly relevant in undergraduate engineering education and have prompted a number of calls to protect U.S. global competitiveness. Recent examples of such works include: Educating the Engineer of 2020 [1], Rising Above the Gathering Storm [2], and The World is Flat [3]. All these reports have challenged engineering institutions to increase the production and improve the education of engineering graduates. This is an increasingly important concern because, with the rapid pace of technological change, the future engineer is not only expected to offer technical ingenuity but also adapt to a continuously evolving environment while simultaneously being able to operate outside the narrow limits of one discipline in solving the complex problems of the future.
Analysis of Error Sensitivity of a System for Electrowetting Force Measurement
Authors: Ramadoss Vivek , Crane Nathan
Published: August 2009

Electrowetting systems are commonly studied by measuring contact angle changes with applied voltage. However many applications such as digital droplet manipulation require information about the force applied to a drop to improve performance. This paper analyses a previously demonstrated method of measuring the electrowetting forces to estimate the sensitivity of force measurements to potential errors such as droplet evaporation, variation in volume, and alignment accuracy. The most significant force errors are introduced by uncertainty in droplet volume as by evaporation. However, analysis shows that this can be controlled by lowering the measurement tip to compensate for evaporation. Errors in tangential force due to alignment are shown to be small for alignment errors below 1°.
Aluminum Sand Casting Interfacial Heat Flux Estimation Based on Corrected Temperature Measurements
Authors: Woolley Jonathan W. , Woodbury Keith A.
Published: August 2009

The estimation of the heat flux at the interface between a solidifying metal casting and mold is a frequently investigated topic. Accurate knowledge of the interfacial heat transfer can be used in solidification simulation to reduce the time and cost of the casting design process. A common and well-established approach to estimating the interfacial heat flux is the solution of the inverse heat conduction problem. Temperature measurements from thermocouples imbedded in the sand mold are used as inputs to the inverse solver. It is well-documented that imbedded thermocouples which are subjected to high temperature gradients will yield biased temperature measurements. By accounting for the sensor dynamics with an appropriate model, the measured temperatures can be corrected to mitigate the effect of the bias error in the estimation of the heat flux. In a previous work, experimentally measured temperatures were obtained from aluminum sand castings and the interfacial heat transfer was evaluated. In other works, the temperature measurement error was demonstrated and the kernel method for correcting measured temperatures was demonstrated with a numerical experiment. In this paper, the simulation of the response of a thermocouple with a three-dimensional computational model is used with the kernel method to correct the experimentally measured temperatures. The previous interfacial heat flux estimates are updated by solving the inverse heat conduction problem with the corrected temperatures as the inputs.
Flow Visualization for Pulsatile Vortex Ring Actuators
Authors: Clark Torin K. , Krieg Michael , Mohseni Kamran
Published: August 2009

Formation and evolution of vortex rings produced from pulsatile vortex ring thrusters are studied using flow visualization techniques. A vortex ring thruster consists of a cavity with an orifice at one end and an oscillating plunger at the opposite end which periodically creates a volume change in the cavity forcing a jet emission of fluid through the orifice into the surrounding reservoir. The ratio of the cylindrical jet length to its diameter, known as the stroke ratio, is a primary factor in the vortex ring formation characteristics. Flow visualization is employed in order to measure the translational velocity of the leading vortex ring for the range of stroke ratios of 2.96–5.92. The velocity time history of the vortex rings is studied with the results comparing well with theoretical approximations. Additionally vortex ring dimensions, including semimajor axis, semiminor axis, the ratio of these dimensions, and core to core radius, are considered. Also the volume of the vortex ring atmosphere is studied. The variations of these parameters with respect to stroke ratio, time, and distance from the orifice are investigated.
Spatial Electrostrictive Modal Actuation of Conical Shells
Authors: Tzou H. S. , Chai W. K.
Published: August 2009

Horns, nozzles and load carrying structures of rockets, e.g., inter-stage joint, satellite-rocket joint, solid rocket motor case, etc., are usually made of circular conical shell sections. This study is to investigate distributed electrostrictive actuation and to evaluate spatially distributed microscopic control actions of distributed electrostrictive actuator segments bonded on conical shell surfaces. Mathematical model and open-loop control equations of a generic conical shell are defined first, followed by simplification to a free-free truncated conical shell section with segmented electrostrictive actuators. Natural mode shape functions are defined based on the Donnell-Mushtati-Vlasov approximation; independent modal control equation is derived by the modal expansion. Distributed control actions induced by the electrostrictive actuator segments are evaluated in the modal domain and the total control effect can be divided into four microscopic control actions: the longitudinal/circumferential membrane and bending control actions. Detailed parametric analyses of two mode groups indicate that 1) magnitudes of control actions comply with the quadratic increase with respect to control voltages and 2) the circumferential membrane control action is the most dominating component in the total shell control effect. Also, the spatially distributed modal actuation plots can be used to locate the most effective locations and/or regions of electrostrictive actuators placed on the shell surface.
A Study of Mechanical Engineering Students’ Learning Outcomes During Summer Undergraduate Research Experiences
Authors: Pierrakos Olga
Published: August 2009

Undergraduate research experiences, which are highly promoted and supported by NSF and other agencies, present a great opportunity for our students to learn essential problem solving skills. The National Science Foundation’s Research Experiences for Undergraduates (REU) program is one of the largest initiatives supporting active research participation by undergraduate students in all of the areas of research funded by NSF. The REU program, with more than 600 sites around the world, presently funds over 1000 active awards, totaling over $327 million. From these active REU awards, 384 (38% of the total active awards) are related to engineering (determined by having ‘engineering’ as a keyword in the title and abstract) and account for about $170 million, about half of the total amount of awards to date. In spite of such widespread support and belief in the value of undergraduate research, limited well-grounded research and evaluation studies exist [1]. Most of the existing literature reveals the predominance of program descriptions, explanation of models, and evaluation efforts, rather than studies grounded on research. Only recently have research and evaluation studies focused on assessing the benefits of undergraduate research [1–8]. Some of these benefits are (a) retention for underrepresented groups, (b) increased interest in the discipline, (c) gaining critical thinking skills, (d) increased self-confidence, and (e) clarification of career goals. Moreover, most of these studies on undergraduate research have focused on the sciences, whereas undergraduate research experiences in engineering have been understudied.
Analysis of the Orbits of Electrostatic MEMS Resonators
Authors: Najar F. , Abdel-Rahman E. M. , Nayfeh A. H. , Choura S.
Published: August 2009

We study the dynamic behavior of an electrostatic MEMS resonator using a model that accounts for the system nonlinearities due to mid-plane stretching and electrostatic forcing. The partial-differential-integral equation and associated boundary conditions representing the system dynamics are discretized using the Differential Quadrature Method (DQM) and the Finite Difference Method (FDM) for the space and time derivatives, respectively. The resulting model is analyzed to determine the periodic orbits of the resonator and their stability. Simultaneous resonances are identified for large orbits. Finally, we develop a first-order approximation of the microbeam dynamic response, which reveals an erosion of the basin of attraction of the stable orbits that depends heavily on the amplitude and frequency of the AC excitation. Simulations show that the smoothness of the boundary of the basin of attraction can be lost to be replaced by fractal tongues, which increase the sensitivity of the microbeam response to initial conditions. As a result, the locations of the stable and unstable fixed points are likely to be disturbed.
Balloon/Stent Expansion Dynamics in Stenotic Arteries
Authors: Hyre M. R. , Pulliam R. M.
Published: August 2009

Inflation balloons for stents are typically sized 1–2mm longer than endovascular stents, yet the effects of the degree of balloon overhang are unknown. In this study, a computational model capable of predicting balloon/stent/artery/plaque interactions and their effects on arterial and plaque stresses was developed to assess the effects of length mismatch and plaque classification on stent expansion characteristics and arterial stresses in diseased arteries. A 16-mm long, 1-mm unexpanded diameter, slotted tube stent was modeled and expanded using contact frictional elements by symmetrically-placed, tapered 17-mm and 18-mm balloons within an artery which contained no plaque to evaluate the effects of stent/balloon size mismatch on arterial stresses. The 18-mm balloon was then also used to expand inside an artery lined with plaque. The plaque was crescent shaped and axisymmetric with a maximum stenosis of 40%. In one model the plaque was primarily cellular, while in another model the plaque was calcified. ANSYS was used to perform the FEA. This model takes into account the multilinear elastic balloon expansion, non-linear plastic stent expansion, and the hyper-elastic arterial and plaque deformations. In this study, endflare was defined by stent diameter at proximal end with respect to stent diameter at the midpoint. Results from this study indicate that without plaque repsent, the maximum arterial stress at balloon contact is approximately proportional to the degree of balloon overhang. A 100% increase in balloon overhang results in a 4% increase in maximum endflare and a 39% change in a peak arterial stress. However, at the end of expansion, which is of the most clinical importance, the increase in max endflare is 2% and the increase in maximum arterial stress is 93% at the balloon point of contact and 45% at the point of contact with the far proximal and distal ends of the stent. When comparing the results of calcified and cellular plaque, a maximum endflare of about 55% was observed for both the calcified and cellular plaque cases during expansion. At the end of expansion the increase in max endflare is 10% for the cellular plaque and 40% of the calcified plaque. The peak equivalent stress seen by the artery was about 100% larger in the cellular case than in the calcified plaque case. This was due to much of the stress being contained within the calcified plaque. The peak stress seen by the plaque was 100% larger in the calcified than in the cellular plaque.
Protein Adsorption in a Continuous Flow Microchannel Environment
Authors: Chen Pin-Chuan , Wang Hong , Park Daniel S. , Park Sunggook , Nikitopoulos Dimitris E. , Soper Steven A. , Murphy Michael C.
Published: August 2009

Protein adsorption is a critical issue in microfluidic devices especially for those reactions depending on proteins like the polymerase chain reaction (PCR). Understanding protein absorption phenomena in different geometry microchannels and evaluating the efficiency of dynamic coating, which has been using as a method to prevent protein adsorption, are important tasks. Two different sets of microchannels were designed and fabricated on polymers. Bovine serum albumin (BSA) was used as a model protein for quantification of and monitoring the protein loss in different microchannel geometries. Up to 58% of the BSA was lost after flowing a 2030 mm long microchannel. The BSA adsorption rate changed along the microchannel. Smaller microchannels required a longer time to achieve protein saturation point. Dynamic coating was shown to be a time consuming and inefficient method to prevent protein adsorption in a continuous flow environment.
On the Modeling of a Rectangular Synthetic Jet
Authors: Krishnan Gopi , Mohseni Kamran
Published: August 2009

The flow field of a rectangular synthetic jet is studied in this paper. It is known that synthetic jets exhibit similarities to continuous turbulent jets in that the far field velocity profile of synthetic jets displays self-similar behavior as well. In this paper we systematically model the a rectangular synthetic jet by applying the argument that synthetic jets can be described by the same equations used to describe continuous laminar jets, with the replacement of the kinematic viscosity of laminar flow, with the virtual kinematic viscosity obtained from the experiments on a synthetic jet. The virtual kinematic viscosity is obtained through experimental measurements of the time average velocity profiles using hot wire anemometry. The virtual kinematic viscosity of the synthetic jet under study was found to exceed that of a turbulent jet of equivalent momentum. The inherent periodic excitation of the synthetic is attributed to the increased virtual kinematic viscosity, which results in the faster spreading and increased entrainment observed in experiments. It is observed that the variation in the centerline velocity and jet width with axial distance, for various actuator stroke lengths collapse onto single curves when scaled appropriately.
Time Resolved DPIV in a Transonic Turbine Cascade
Authors: Raben Samuel , Charonko John , Ng Wing F. , Vlachos Pavlos P.
Published: August 2009

This paper presents an extension of existing Proper Orthogonal Decomposition (POD) based methods for gappy data reconstruction to allow its use with experimental data without a priori knowledge of the ‘True’ solution, and applies it time-resolved DPIV data taken in a transonic turbine cascade. The method is based on minimizing the residual of a divergence criterion, in order to determine the optimum number of modes required for reconstruction. This serves as a convergence criterion for termination of Venturi and Karniadakis’s iterative Gappy POD method. Gappy flow fields were created using DNS data from a near wall turbulence simulation. Gappyness levels of 5%, 11%, 20%, 50% and, 80% were created with gap sizes 3×3, 7×7, 11×11, and arbitrary N×M vector spaces. The method is shown to closely predict the optimum required modes for a minimum-error reconstruction, and the errors associated with this convergence criterion are shown to be on or below the error associated basic DPIV velocity uncertainty measurements. Finally, this method is tested on gappy experimental data from a transonic turbine cascade. The resulting reconstructed flow fields demonstrate clearly observable vortical structures and dominant frequencies.
Extreme Elongation of Vesicles Under DC Electric Fields
Authors: Sadik Mohamed M. , Shreiber David I. , Shan Jerry W. , Lin Hao
Published: August 2009

Electrodeformation refers to the deformation of cell or vesicle lipid membranes under the application of an electric field. Such a phenomenon often accompanies electroporation processes, and also can be leveraged to detect pathological changes in cells. Recent studies have suggested that the electrical conductivity difference across the lipid membrane is a dominant factor in determining the characteristics of deformation, and various regimes of deformation were observed. Using a vesicle model system, the current work is the first report of extreme elongation of vesicles of high conductivity ratio under DC electric fields. The results suggest that the osmolarity difference between the encapsulated and bathing solutions may contribute to such abnormal deformation behavior.
Biomolecular Activity Switch: An Application of Metallic Nanoparticle Plasmon Resonance and Femtosecond Pulsed Lasers
Authors: Alper Joshua , Hamad-Schifferli Kimberly
Published: August 2009

With an increased effort within the engineering community to design molecular machines, it has become clear that a specific, external control method is required. Here we propose a simple mechanism for a molecular switch involving conjugating a molecule within the machinery to a gold nanorod. Then actuate that machinery’s active state by affecting a change in the conjugated molecule. We demonstrate the feasibility of the method using a fluorescent probe, and we report on progress we have made toward demonstrating it with a protein.
On the Bio-Mechanical Properties of a Dual-Porous Osteochondral Scaffold
Authors: Sharif Hajar , Shanjani Yaser , Vlasea Mihaela , Toyserkani Ehsan
Published: August 2009

This work is concerned with the finite element modeling of a dual-porous scaffold including both fine and coarse pores. The layer with coarse pores is suitable for bone in vivo ingrowth and the finer pore layer is appropriate for in vitro cartilage culturing. Such scaffolds can be extensively used for repairing of osteochondral defects. The bio-mechanical properties of the proposed scaffold, including apparent stiffness and strain-based capability of the cell ingrowth, are identified using a 3D Finite Element Model. Moreover, to study the effect of the second layer on the strength of the whole scaffold, the stiffness of the dual and single-porous scaffolds was compared. The result of this study shows that the stiffness decreases by adding the second layer to a single-porous scaffold. Additionally, principal strain histograms of the single and the dual-porous scaffolds are compared to assess the effect of added layer on the capability for cell ingrowth stimulation of the whole structure. According to the results, the dual-porous scaffold provides more homogeneous distribution but a smaller amount of micro-strains which may cause different cell-growth behavior.
Experimental Investigations on the Premixed Flames Stabilized on Wire Mesh Materials
Authors: Lee H. S. , Senn Paul L. , Field Kevin M. , Adams Charles W.
Published: August 2009

Experiments were performed to identify the combustion characteristics of the premixed flames stabilized on the Inconel and Kanthal wire woven mesh materials. NOx emissions linearly increased at lower firing rates, followed by a rapid increase at higher firing rates. At the lower firing rates, the prompt NOx mechanism was the major route, and the thermal NOx formation became dominant at the higher firing rates due to an increase in gas temperatures. The CO concentrations generally decreased to reach the minimum and increased again with firing rates. The wire surface temperatures rapidly increased at lower firing rates, suggesting that the heat generated from the combustion process was effectively dissipated from the materials by radiation. The gradual, linear increase in the surface temperatures at higher firing rates supported that the flame was detached from the materials due to excessive heat from combustion. These behaviors of the flame were thought to be responsible for the trends of the CO and NOx formations. The pressure drop in the material was dominated by the mesh size, which determined the velocity of unburned mixture, rather than the material properties. The coefficients of the Forchheimer equation were deduced from the measured pressure drop. The Inconel 24×24 and 26×26 meshes showed the best performance in the materials tested, in terms of the NOx and CO emissions and pressure drop.
Surgically Implanted Energy Harvesting Devices for Renewable Power Sources in Insect Cyborgs
Authors: Reissman Timothy , Garcia Ephrahim
Published: August 2009

This work details the implantation process of an energy harvester platform within a Manduca sexta Hawkmoth for the purpose of creating a cyborg insect. Also included is an evaluation of energy harvesting with respect to present lightweight battery technology and the magnitudes of ambient energy available for the cyborg insect application. Specific emphasis is given to kinetic energy harvester development, with theory and fabrication of the devices detailed.
Experimental Evidence of Density and Mechanical Properties Enhancements of Binary Alloys by Soldification Subject to Vibrations
Authors: Vadasz J. , Meyer J. P. , Govender S. , Andrick M. , Carter W. , Ebrahim H. , Naidoo A. , Ngubane I. , Ogle M.
Published: August 2009

Preliminary evidence of density and mechanical properties enhancement of binary alloys by solidification subject to vibrations is presented. The frequency of vibrations was increased from 0 to 100 Hz by using sound waves as the vibration source. The latter shows that the solidified microstructure, the ultimate tensile strength, and the hardness improve as the frequency increases. The chosen alloy for this study was Pb-Sb 4.4% (lead antimony 4.4%) and was selected because of its low melting temperature. The cast chosen was of a rod shape having a diameter of 10mm and a length 500mm. This choice is consistent with assuming an infinite length and therefore ignoring boundary effects in a planned theoretical follow-up analysis. Also due to the geometry of the mould it can be assumed that the cast was cooled due to conduction alone.
Modeling the Flow of a Liquid Droplet Diffusing Into Various Porous Media for Inkjet Printing Applications
Authors: Suffield Sarah , Jokar Amir
Published: August 2009

Inkjet technology currently relies heavily upon the absorption of ink into porous media. Characterizing the absorption capacity of media as well as the absorption rate can be critical in understanding the entire drying process. Evaluating the absorption performance of a coated medium can particularly be important since the coating may be either semi-absorptive, or in some cases non-absorptive. The absorption performance can also vary among uncoated media. In order to better understand the absorption mechanism, the fluid flow of a water droplet impacting with and diffusing into several porous papers, each with a unique permeability, was analyzed numerically and experimentally in this study. The droplet impact was simulated by computational fluid dynamics techniques for a variety of conditions. The transient computational modeling predicted the shape of the droplet at different time intervals before and after the impact. It also predicted the volume of liquid that had diffused into the porous substrate over time. The results predicted by the computational modeling were then compared to experimental data, which was collected for a real system with the same configuration as in the computational modeling using a high speed digital video camera. The camera captured images of the droplet as it impacted with various coated and uncoated papers. Results showed a relatively good agreement between the computational modeling and experimentation at drop times greater than 0.1 seconds after the impact. A dimensional analysis was also performed on the most effective parameters of the flow process, and a correlation was developed to predict the aspect ratio of the droplet after the impact as a function of the other dimensionless parameters, such as Reynolds and Weber numbers. The results of this study can be useful for drying applications, such as inkjet printing, where absorption of a liquid into a porous medium is critical for the drying process.
A Fast Coupled CFD-Thermal Analysis of a Heavy Duty Diesel Engine Water Cooling System
Authors: Jafarabadi Mazdak , Chamani Hamidreza , Malakizadi Amir , Jazayeri Seyed Ali
Published: August 2009

In recent years, the design of an efficient cooling system together with good thermal efficiency for a new engine is becoming a critical task and therefore the need for an accurate and fast thermo-fluid simulation of engine cooling system is of vital importance. In this study, a detailed CFD and thermal FE simulation of a 12 cylinders V-type medium speed heavy duty diesel engine cooling system has been carried out using ANSYS-CFX commercial code. At first, a global model, for one bank with six cylinders, has been simulated using appropriate mesh density which ensures the accuracy of the results together with reasonable computational time. At this stage, the worst cylinder has been selected based on the wall temperature and the cooling flow rate. Later, using the inlet and outlet boundary conditions extracted from the global model, a series of detailed thermo-fluid analyses have been conducted for the worst cylinder with a finer mesh. The subcooled nucleate boiling heat transfer computation is carried out using the boiling departure lift-off (BDL) model, in which the total heat flux is assumed to be additively composed of a forced convective and a nucleate boiling component. In order to obtain the temperature field for components under consideration, a comprehensive thermal analysis has been preformed coupling with the detailed CFD analyses to reach an accepted value through transferring data between the CFD and FEA software. This method leads to an accurate prediction of the wall temperature and heat flux. It is observed that at hot spots, nucleate boiling occurs for low coolant flow regions specifically around the cylinder head’s exhaust port and liner coolant side wall. Also a considerable increment in the Heat Transfer Coefficient (HTC) has been observed on the superheated regions where the boiling is initiated.
Investigation of Temperature Driven Gas Flows in 4 nm Channels for Applications of Micro-Scale Compressors at Above Atmospheric Pressure
Authors: Han Yen-Lin , Muntz E. P.
Published: August 2009

Based on the rarefied flow phenomenon of thermal creep (or thermal transpiration), the Knudsen Compressor is an unconventional micro/meso-scale compressor or pump. Optimization studies have shown that a Knudsen Compressor operates most efficiently when its membrane’s flow channels are at the transitional flow regime, between continuum and molecular flows; simultaneously it provides a desired mass flow and pressure ratio. At higher pressures (> 1 atm), to maintain membrane channel Knudsen numbers in the transitional regime (Kn ∼ 1), the corresponding membrane channel size needs to be less than about 50 nm. More specifically, at 10 atm, the membrane channel size should be as small as 5 nm to provide the most efficient Knudsen Compressor operation. Prior to this work, there has been no documented experimental investigation of thermal creep measurements through channels less than 5 nm. Phenomena that could be associated with such flows are briefly discussed, and possible selection criteria for thermal creep membranes are included in this study. Apparatus design is discussed. Experimental results are provided for thermal creep flows, within a single stage Knudsen Compressor with 4 nm diameter membrane channels. The maximum pressure increases across the Knudsen Compressor’s thermal creep membrane were measured, over a range of operating pressures from 1 atm to 1.1 atm with Helium or Argon as the working gas. Results showed apparent thermal creep effects across the porous glass membrane, and possibly significant force field effects within the nano-scale channels.
Engine Simulator for ECMs Diagnosis
Authors: Navarrete N. A. , Huertas J. I.
Published: August 2009

Currently, the number of companies that provide diagnosis, repair and maintenance services to the electronic control modules — ECMs of the vehicles is very limited. Even though the demand of the service is still unsatisfied, the possibility of expansion of the existing companies is limited by the need of an engine simulator to semi-automate the ECMs diagnosis process. To fulfill this requirement, the present paper describes the design, implementation and testing of an electronic device that simulates the electrical signals generated by the sensors and transducers commonly installed on engines. The device was programmed to simulate different models of commercial engines and to perform automatically the standard procedures followed to identify the most common failures of the ECMs. This device incorporates systems to guarantee the safety of the information gathered during the diagnosis process and the physical integrity of the ECMs being diagnosed.
Numerical Study on the Performance of a Valveless Micropump
Authors: Dinh Thien X. , Ogami Yoshifumi
Published: August 2009

A valveless micropump based on electromagnetic actuation is numerically described. The pump is formed on one planar layer consisting of two inlet channels, a pump chamber, and an outlet channel whose depths are 0.3mm. The PDMS membrane enclosed on the top of the pump chamber can be periodically actuated by an electromagnetic actuator. So, it generates blowing and suction flows successively along a connecting channel which connects the inlet and outlet channels to the pump chamber. The obtained results show that the flow rate of the pump increases linearly with increasing amplitude of the vibrating plate. The pumping rates on order of 1mL/min were attained. Pump pressure is several 100Pa. The pump also shows that it can work as an efficient micromixer.
Hydrodynamic Characteristics of Crossflow Over MEMS-Based Pillars
Authors: Kos¸ar Ali , Schneider Brandon R. , Peles Yoav
Published: August 2009

Great advancements are currently being made in diverse technological disciplines due to the prodigious advancement in microfluidic systems. Careful design of mass transfer has proven to be essential to the successful realization of numerous microelectromechanical systems, (MEMS) such as heat exchangers for IC chip cooling, micro rockets, micro combustors, micro chemical reactors, micro heat engines, and bioMEMS devices. Micro pin fins pillars are often placed in these systems to enhance chemical reactions, heat transfer, DNA sieving, DNA analysis, and mixing. Since objects in crossflow perturb the flow field and generate excess hydrodynamic drag, the pressure drop required to propel the flow in the systems elevates. It is therefore of prime importance to develop parametric knowledge and correlations of the characteristic pressure drop and friction factor in crossflow over micro scale pin fins under various hydrodynamic conditions.
Models for Component Selection and Thermo-Mechanical Reliability Trade-Offs to Address Component Obsolescence in Military Electronics
Authors: Lall Pradeep , Shirgaokar Aniket , Suhling Jeffrey
Published: August 2009

Product miniaturization trends in microelectronics industry are driving the need for smaller, faster, more reliable, less expensive IC’s. Area array packages have been increasingly targeted for use in harsh environments such as automotive underhood, military and space applications but system-level decision support and part-selection tools and techniques for thermo-mechanical reliability trade-offs while addressing part obsolescence in extreme environments are scarce. The models presented in this paper provide decision guidance for smart selection and substitution to address component obsolescence by perturbing product designs for minimal risk insertion of new packaging technologies. It is conceivable for commercial off the shelf parts to become unavailable during the production-life of a product. Typical Commercial-of-the-Shelf parts are manufactured for a period of two to four years, and IC manufacturing processes are available for five to six years. It is envisioned that the reliability assessment models will enable turn-key evaluation of geometric architecture, material properties, and operating conditions effects on thermo-mechanical reliability. The presented approach enables the evaluation of qualitative parameter interaction effects, which are often ignored in closed-form modeling, have been incorporated in this work. Previously, the feasibility of using multiple linear regression models for reliability prediction has been demonstrated for flex-substrate BGA packages [1, 2], flip-chip packages [3, 4] and ceramic BGA packages [5]. In this paper, principal component regression models (PCR) have been investigated for reliability prediction and part selection of area package architectures under thermo-mechanical loads in conjunction with stepwise regression methods. Package architectures studied include, BGA packages mounted on CU-CORE and NO-CORE printed circuit assemblies in harsh environments. The models have been developed based on thermo-mechanical reliability data acquired on copper-core and no-core assemblies in four different thermal cycling conditions. Solder alloys examined include SnPb and SAC Alloys.
Prognostication and Health Monitoring of Electronics in Implantable Biological Systems
Authors: Lall Pradeep , Gupta Prashant , Kulkarni Manish , Panchagade Dhananjay , Suhling Jeff , Hofmeister James
Published: August 2009

In the present paper auto-regressive and time-frequency based techniques have been investigated to predict and monitor the damage in implantable biological electronics such as pacemakers and defibrillators. The approach focuses is on the pre-failure space and methodologies for quantification of failure in electronic equipment subjected to shock and vibration loads using the dynamic response of the electronic equipment. Presented methodologies are applicable at the system-level for identification of impending failures to trigger repair or replacement significantly prior to failure. Leading indicators of shock-damage have been developed to correlate with the damage initiation and progression in under variety of stresses in electronic systems. The approach is based on monitoring critical solder interconnects, and sensing the change in test-signal characteristics prior to failure, in addition to monitoring the transient strain characteristics optically using digital image correlation and strain gages. Previously, SPR based on wavelet packet energy decomposition and the Mahalanobis distance approach have been studied by the authors for quantification of shock damage in electronic assemblies [Lall 2006]. In this paper, Auto-regressive (AR), wavelet packet energy decomposition, and time-frequency (TFA) techniques have been investigated for system identification, condition monitoring, and fault detection and diagnosis in implantable biological electronic systems. One of the main advantages of the AR technique is that it is primarily a signal based technique. Reduced reliance on system analysis helps avoid errors which otherwise may render the process of fault detection and diagnosis quite complex and dependent on the skills of the analyst. Results of the present study show that the AR and TFA based health monitoring techniques are feasible for fault detection and damage-assessment in electronic units. Explicit finite element models have been developed and various kinds of failure modes have been simulated such as solder ball cracking, package falloff and solder ball failure.
Validation of Hydrodynamic Stability of Supercritical Once-Through Boiler
Authors: Wei Bing , Zhou Dong
Published: August 2009

Operating safety is one of the most important things to supercritical once-through boilers. To study the hydrodynamic characteristics of fluid in water walls of supercritical once-through boilers and to find out the instable factors will be of great significance to boiler operation. In this paper the mathematical models for hydrodynamic characteristics of fluid in water walls are established. With an example of 600MW boiler, by using the calculation program, the hydrodynamic characteristics curves without and with the throttles at the inlets of the water walls at different operating conditions are presented, the fluid flow instability and the reasons are analyzed. The calculation results show that the boiler operates stably and safely at 100% MCR (Maximum Continuous Rating) condition, the hydrodynamic instability exists at low heating loads of 30% MCR. The method of installing the throttles at the inlets of the water wall pipes will increase the parabola characteristics, help to improve the fluid instability to a certain stable extent, but due to the small curve slopes at low mass flowrates, still need to pay more attention to the low heating loads operation. The existence of gravity pressure head is good to the stability of the vertical upward flow.
Micro-CT Analysis of Human Trabecular Tissue From Coxo-Arthritis and Osteoporotic Samples
Authors: Marinozzi Franco , Bini Fabiano , Patane` Federico , Marinozzi Andrea , Bedini Rossella , Pecci Raffaella
Published: August 2009

We performed the analysis of bone samples from four patients during hip replacement surgery. three of them suffered by coxo-arthritis, while the other was affected by osteoporosis. Cubic samples were taken from the sliced femur heads of each donor. After microCT tomographic scanning and subsequent reconstruction with voxels of 11 μm, several morphological parameters were calculated in order to characterize the samples.
Analysis of Electrospinning Nanofibers: Diameter Distribution, Process Dynamics, and Control
Authors: Yan Xuri , Gevelber Michael
Published: August 2009

Electrospinning is a method of producing nanometer scale fibers by accelerating a jet of charged polymer solution in an electric field. In many emerging, high value electrospinning applications, such as the biomedical area, the diameter distribution of electrospun polymeric nanofibers has important implications for the product’s performance and process economics (in terms of yield and production rate). However, the current state-of-the-art electrospinning process results in unpredictable and time varying diameter distributions, both during a run and run-to-run. Thus, this work is focused on developing an appropriate control system to achieve consistent and controllable fiber diameters. Another goal of this work is to develop a better understanding of the relation between process physics and the resulting fiber diameter characteristics. To address these problems, a well instrumented and computer based actuator control system has been developed. The effects of process parameters on fiber diameter are investigated for achieving consistent and repeatable process capability. The fundamental process dynamics are identified and the relation between measurable variables and the resulting fiber diameter distribution is analyzed. This relation provides the basis of developing appropriate control strategies in order to reduce both the process variations from run-to-run and during a run.
Inverse Kinematic and Control Architecture of a Slave Manipulator for MR-Guided Brain Biopsy
Authors: Raoufi C. , Goldenberg A. A. , Kucharczyk W. , Hadian H.
Published: August 2009

In this paper, the inverse kinematic and control paradigm of a novel tele-robotic system for MRI-guided interventions for closed-bore MRI-guided brain biopsy is presented. Other candidate neurosurgical procedures enabled by this system would include thermal ablation, radiofrequency ablation, deep brain stimulators, and targeted drug delivery. The control architecture is also reported. The design paradigm is fundamentally based on a modular design configuration of the slave manipulator that is performing tasks inside MR scanner. The tele-robotic system is a master-slave system. The master manipulator consists of three units including: (i) the navigation module; (ii) the biopsy module; and (iii) the surgical arm. Navigation and biopsy modules were designed to undertake the alignment and advancement of the surgical needle respectively. The biopsy needle is held and advanced by the biopsy module. The biopsy module is attached to the navigation module. All three units are held by a surgical arm. The main challenge in the control of the biopsy needle using the proposed navigation module is to adjust a surgical tool from its initial position and orientation to a final position and orientation. In a typical brain biopsy operation, the desired task is to align the biopsy needle with a target knowing the positions of both the target in the patient’s skull and the entry point on the surface of the skull. In this paper, the mechanical design, control paradigms, and inverse kinematics model of the robot are reported.
Experiment and Computational Analysis of Self-Healing in an Aluminum Alloy
Authors: Martinez Lucci Jose , Amano R. S. , Rohatgi Pradeep , Schultz Benjamin
Published: August 2009

The development of self-healing metals is a novel idea that has not been explored in great detail yet. The concept of self-healing described in this paper consists of incorporating a low temperature melting alloy imbedded within a higher temperature alloy to create a self healing composite (SHC). When the SHC is damaged or cracked, heat may be applied to the affected area whereupon the low melting alloy will melt and flow into the crack healing the damage and sealing the crack. This study consists of theoretical analysis and design of self-healing in aluminum alloy matrix. The experimental and Computational Fluid Dynamics of a self-healing were designed by the authors, the design consists in an aluminum alloy matrix reinforced with microtubes of alumina (Al2O3) that are filled with a low melting point solder alloy. The objective of the study reported here was to find the influence and efficiency of a low melting solder alloy in healing an aluminum matrix. To check this effect a crack was created in the metal surface, piercing the microtube(s) filled with solder, and then the SHC was heated above the melting point of the solder alloy to melt and examine the flow of molten solder alloy into the crack.
Validation and Comparison of Strip Seal Designs for Gas Turbine Engine Nozzle Guide Vanes
Authors: Farahani Arash , Childs Peter
Published: August 2009

Strip seals are commonly used to prevent or limit leakage flows between nozzle guide vanes (NGV) and other gas turbine engine components that are assembled from individual segments. Leakage flow across, for example, a nozzle guide vane platform, leads to increased demands on the gas turbine engine internal flow system and a rise in specific fuel consumption (SFC). Careful attention to the flow characteristics of strip seals is therefore necessary. The very tight tolerances associated with strip seals provides a particular challenge to their characterisation. This paper reports the validation of CFD modelling for the case of a strip seal under very carefully controlled conditions. In addition, experimental comparison of three types of strip seal design, straight, arcuate, and cloth, is presented. These seals are typical of those used by competing manufacturers of gas turbine engines. The results show that the straight seal provides the best flow sealing performance for the controlled configuration tested, although each design has its specific merits for a particular application.
Use of Numerical Modeling to Compare Over-Fire Air Systems on Stoker-Fired Furnaces
Authors: Jorgensen Kris L. , Strempek Joseph R. , Arvan William J. , Schauer Raymond H.
Published: August 2009

The method by which air is introduced to a furnace is an important aspect of the combustion system. With the demands of more stringent regulations affecting modern combustion systems, numerical modeling has become a valuable tool for design and analysis. Numerical modeling has been used to compare a conventional Controlled Combustion Zone (CCZ™) overfire air system design typically used on stoker-fired furnaces to a more advanced design. The new design involves removing the opposed arches and replacing the numerous small overfire air ports with a smaller number of controlled penetration Precision Jet™ ports. Modeling results demonstrate benefits of the advanced design.