bluuebunny/crossref_metadata_2025 huggingface dataset:
A Proper Groove Design for Distortion Control of the Multi-Pass Weldment at Pressure Vessel
Authors: Kim Sung-Yun , Shin Sang-Beom , Kim Ha-Geun
Published: May 2008

The purpose of this study is to establish a proper groove design for multi-pass butt weldment with narrow groove of pressure vessel to control welding distortion. To do it, the behavior of angular distortion and longitudinal shrinkage force of the simple butt weldment were evaluated using a finite element analysis and experiment. The effective bending rigidity of the multi pass butt weldment with welding pass was defined as a function of the effective thickness of weld throat. Based on the results, the predictive equations for the welding distortion of the multi-pass both side weldment were established as function of heat input and effective bending/in-plane rigidity of the weldment. Using the equation, a proper ratio of the groove height can be determined to control the distortion for the multipass both side weldment with reference to various groove shape and plate thickness.
Study of the Accelerated Life Test Method for Power Train Components Under Cyclic Loads Using Weibull-IPL (Inverse Power Law) Model
Authors: Lee Geunho , Kim Hyoungeui , Kim Dosik
Published: May 2008

This study was performed to develop the accelerated life test method using Weibull-IPL (Inverse Power Law) model for power train components that are running on cyclic loads. Weibull-IPL model is concerned with determining the assurance life with confidence level and the accelerated life test time. From the relation of weibull distribution factors and confidence limit, the testing times on the no or some number of failure acceptance criteria are determined. The power train components under cyclic loads generally represent wear and fatigue characteristics as a failure mode. IPL based on the cumulative damage theory is applied effectively the mechanical components to reduce the testing time and to achieve the accelerating test conditions. The proposed Weibull-IPL model is an approach to improve the reliability assessment on the statistical distribution and wear out failure mechanism concepts. As the actual application example, accelerated life test method of agricultural tractor transmission was described. Life distribution of agricultural tractor transmission was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 3,000 hours and 90% confidence level for one test sample. According to IPL, because test time can be shorten in case increase test load, test time could be reduced by 482 hours when we put the load 1.1 times of rated load than 0.73 times of rated load that is equivalent load calculated by load spectrum of the agricultural tractor. This time, acceleration factor was 11.7. This Weibull-IPL model can be used to develop accelerated test method of gear reducer, hydraulic hose, bearing and etc.
CFD Solution and Experimental Testing of Buoyancy-Driven Convection Caused by Condensers Immersed in a Water Tank of HPWH
Authors: Gao Zhiming , Mei Viung C. , Chen Fang C.
Published: May 2008

Heat pump water heaters can cut electricity consumption, comparing with the conventional electric resistant water heating tanks by half. A conventional heat pump water heater (HPWH) requires a water circulating pump to sample water temperature every 15 minutes in the tank and to draw water to a condenser-water heat exchanger outside the tank, if water temperature is below the set point. The pump would be on at least once every 15 minutes, 24 hours a day. The novel design presented in this study was to insert the condenser coil through the opening on the top of the water tank. This design eliminated the need of the water circulating pumps, and thus greatly improved the reliability of the HPWH systems. Two types of condenser coil designs were considered; one was a bayonet tube (tube-in-tube) and one was the “U” tube. Previous test data indicated that “U” tube design performed better than the bayonet tube condenser coil, and thus only “U” tube condenser coil was considered in the study. With straight “U” tubes inserted into the tank, it was found that the convective heat transfer was not strong enough to break water temperature stratification in the tank, which resulted in a temperature differential of 16°C (30°F) from top to bottom. However, when the coil was built in “L” shape, the water stratification disappeared. A computational fluid dynamics code, CFD, was used to study the straight and L shaped condenser coils. Results from CFD simulation were compared with the experimental data and found they were close to each other.
A Systems Approach for Analyzing Uncertainties in Misalignment of a Fiber-Optic System
Authors: Radhakrishnan Satish , Subbarayan Ganesh , Nguyen Luu , Mazotti William P.
Published: May 2008

Performance of a fiber-optic system depends on the coupling efficiency and the alignment retention capability. The optoelectronic system experiences performance degradation due to uncertainties in the alignment of the optical fibers with the laser beam. The laser devices are temperature sensitive, generate large heat fluxes, are prone to mechanical stresses induced and require stringent alignment tolerance due to their spot sizes. The performance of an optoelectronic system is also affected by many other factors such as geometric tolerances, uncertainties in the properties of the materials, optical parameters such as Numerical Aperture etc. To analyze such a complex system, we need to understand the dependence and inter-relationships between various elements that together make the complex system. In this paper, we develop systematic, formal procedures for identifying the relationships between the critical system level parameters through system decomposition strategies. A novel technique to include the sensitivity of the variables with respect to the functions to assist in the system decomposition is developed. We apply graph partitioning strategies to decompose the system into different subsystems. We also demonstrate system decomposition technique using a simple to implement simulated annealing algorithm. The results of system decomposition using graph partitioning technique and simulated annealing are also compared.
Motion Planning of a Nonholonomic Multibody System Using Genetic Algorithm
Authors: Ge Xin-Sheng , Chen Li-Qun
Published: May 2008

The motion planning problem of a nonholonomic multibody system is investigated. Nonholonomicity arises in many mechanical systems subject to nonintegrable velocity constraints or nonintegrable conservation laws. When the total angular momentum is zero, the control problem of system can be converted to the motion planning problem for a driftless control system. In this paper, we propose an optimal control approach for nonholonomic motion planning. The genetic algorithm is used to optimize the performance of motion planning to connect the initial and final configurations and to generate a feasible trajectory for a nonholonomic system. The feasible trajectory and its control inputs are searched through a genetic algorithm. The effectiveness of the genetic algorithm is demonstrated by numerical simulation.
Evaluation of a Piezoelectric Energy Extraction Device for Cavity Pressure Sensing in Injection Molding
Authors: Theurer Charles B. , Zhang Li , Kazmer David , Gao Robert X.
Published: May 2008

This paper presents the design, analysis, and validation of a self-energized piezoelectric pressure sensor that extracts energy from the pressure differential of the polymer melt during the injection molding process. To enable a self-energized sensor design, an analytical study has been conducted to establish a quantitative relationship between the polymer melt pressure and the energy that can be extracted through a piezoelectric converter. Temperature and pressure are monitored during an injection molding cycle and the performance of the piezoelectric element is evaluated with respect to a mechanically static, electrically transient model. In addition to corroboration of the proposed model, valuable statistical information about the working temperature in the prototype sensor will prove very useful in the package design of molding cavity sensors. A linear model examining the energy conversion mechanism due to interactions between the mechanical strain and the electric field developed within the piezoelectric device is established. This model is compared to the functional prototype design to evaluate the relevance of the assumptions and accuracy. The presented design enables a new generation of self-energized sensors that can be employed for the condition monitoring of a wide range of high-energy manufacturing processes.
Cooling of a Finned Cylinder by a Jet Flow of Air
Authors: Gori F. , Borgia M. , Doro Altan A.
Published: May 2008

Experimental tests have been carried out to evaluate the heat transfer characteristics on an externally finned cylinder impinged by a jet flow of air. The cylinder is internally heated with an electric system. Thermocouples located inside the cylinder allow to evaluate the wall temperature distribution, in order to calculate the local and average convective heat transfer coefficients.
Pulsating Jets Cooling Circular Cylinders
Authors: Gori F. , Pacchiarotti G. , Petracci I.
Published: May 2008

The paper presents experimental heat transfer results on a circular cylinder cooled by a pulsating slot jet of air. The jet is generated by a new small wind tunnel, designed for flows with low turbulence intensities. The pulsation of the jet is obtained with the introduction of a rotating disk, divided in sectors, between the exit of the slot and the cylinder to be cooled. The disk can rotate at several frequencies. Local and average Nusselt numbers have been measured at several Reynolds numbers and distances from the slot exit. The heat transfer results are dependent on the frequency of the pulsation. The position of the cylinder, which maximizes the heat transfer, is compared to the case of a stationary jet.
Numerical Simulation of the Coupling Between Vortex Shedding and Acoustic Field in a Solid Propellant Engine
Authors: Gori Fabio , Pecorari Riccardo , Mastrapasqua Marco
Published: May 2008

The paper investigates the numerical simulation of vortex shedding in the flow field of solid-propellant rocket motors. This phenomenon, resulting from the strong coupling between shear-layer instability and acoustic waves in the chamber, produces thrust and pressure oscillations. Numerical simulations are performed on the combustion chamber of the Ariane 5 MPS P230 (Solid Rocket Motor) with the commercial code Fluent CFD for conditions corresponding to 89 s of combustion time. The objective of the study is to reproduce the pressure oscillations frequencies and magnitudes, to compare the available experimental data and to capture the vortex shedding phenomena.
Contour Controller Design for Cubic Parallel Machine Tool
Authors: Kim Sungsoo , Lee Seung Hwan , Hong Daehie , Choi Woo Chun , Song Jae-Bok
Published: May 2008

In machining processes, contouring accuracy is usually more important than tracking performance. In order to reduce the contour error, there have been many contour control algorithms for conventional machine tools, which noticeably improve their contouring accuracy. However, the available contour control algorithms cannot be directly applied to the parallel machine tools. The dynamic characteristics of the parallel machine tools are not consistent inside workspace and unsymmetrical disturbances can be imposed on any axis. Due to these, mismatched dynamics cause unwanted contour error. In this paper, we present a contour control algorithm for the cubic parallel machine tool that employs the parallel mechanism for its moving table, which can be also applied to a general parallel manipulator. The contour error estimation method for free-formed curve trajectory is proposed and the relation between the contour error vectors in joint and Cartesian spaces is considered. In order to show the validity of the algorithm, the contour control simulations and experiments are made for various contour trajectories with the cubic parallel machine tool. The results show that the proposed controller reduces the contour error considerably both in joint and Cartesian spaces.
A Flux Vector Splitting Technique for Shallow Water Equations
Authors: Pacheco-Vega Arturo , Pacheco J. Rafael , Rodic´ Tamara
Published: May 2008

We present a flux vector splitting (FVS) for the solution of the shallow water equations with emphasis in their application to film flows for which a hydraulic jump may exist. The governing equations and boundary conditions are transformed from the physical to the computational domain and solved in a rectangular grid. A first-order upwind finite difference scheme is used at the point of the shock while a second-order upwind differentiation is applied elsewhere. Higher-order spatial accuracy is achieved by using a MUSCL approach. Two problems, (a) one-dimensional dam break problem and (b) radial flow with jump, are investigated to show the usefulness and accuracy of the method. Results demonstrate that the method is able to predict accuratelly the hydraulic jump using shallow water theory.
Computational Modeling of Industrial Scale Reactor System Components Using Parallel Processing on a Networked Cluster of Computers
Authors: Lottes Steven A.
Published: May 2008

Industrial scale reactor system components are frequently characterized by a complex geometry that requires a large number of nodes in a computational grid to resolve significant flow features and by reaction and additional complex physics, such as spray vaporization, that greatly increase the number of partial differential equations (PDEs) to solve. On a fast serial workstation, simulations of these systems can take several days, making use of the model for extensive parametric and optimization studies impractical. A parallel multiphase reacting flow code was developed from a family of related serial codes using the industry standard Message-Passing Interface (MPI) and domain decomposition in the primary flow direction. The parallel computational fluid dynamics (CFD) code can now be run on a cluster of networked computers. This capability makes detailed simulation of many industrial reactors feasible without incurring the large increase in cost of moving to simulation on massively parallel computing platforms. The required computers and network are often already present in organizations and idle at night. The parallel CFD code has been applied to studies of transient heat transfer to monolith catalyst substrates and to the design of inlet chambers that evenly distribute a high speed hot air inlet stream over the monolith inlet plane. These studies are part of a program to investigate the feasibility of rapid start fuel reformers. The use of fuel reformers in light duty fuel cell powered vehicles requires a reformer start up time of less than 60 seconds. Parallelization issues and parallel performance are presented with examples of reformer component flow and comparison with experimental data from monolith heat up studies.
Precision Control of Force Produced by Ionic Polymer Metal Composite
Authors: Bhat Nikhil , Kim Wong-Jong
Published: May 2008

In this paper, we present the precision feedback control of the force produced by ionic polymer metal composite (IPMC). The high-precision force generation capability of IPMC at low force level makes it ideal for micro-device applications such as micro-grippers. To design fingers for a micro-gripper using IPMC, the study of the adhesion force is also of critical importance. We measured this adhesion force with an atomic force microscope between a glass micro-sphere of 32.43-μm diameter and an IPMC strip, and it was found to be 144 nN. After the implementation of the feedback controller, the settling time was reduced to 1.5 s from 10 s in open loop, and the overshoot was reduced to 30% from 131.62% in open loop. The current force resolution is one the order of 4 μN at 0.904-μN rms force noise. The crossover frequency of this control system is 1.3 Hz limited by the structural resonance of the polymer strip. We have demonstrated high precision force control capability of IPMC for micro-device applications.
The Design Tradeoffs of Linear Functionally Graded Piezoceramic Actuators
Authors: Alexander Paul W. , Brei Diann
Published: May 2008

It is common practice to reduce the voltage level within piezoelectric actuators by utilizing multiple layers, typically bonded together. Unfortunately, this has a tendency to result in device failure due to delamination. For example, with benders the typical lifetime is 105 to 106 cycles, limiting its use in practical applications. This poses an interesting design tradeoff: the stroke is increased due to sharper gradients between material layers; however, the higher gradients lead to high stress concentrations at those interfaces. One approach to reducing these stresses is to grade the material properties through a monolithic piece of piezoceramic so that no interfaces or bonding elements exist, but this comes at the cost of stroke. This paper explores the design tradeoff inherent to monolithic functionally graded piezoelectrics. An analytical free-displacement model for a monolithic piezoceramic beam with a generic gradient is derived. Key to this is the inclusion of the complex electric field distribution which rises from the non-homogeneous material properties. This model is used along with finite element models to examine the effect of continuous linear and stepwise material gradients on the displacement performance as well as the stress levels. The study shows that using monolithic functionally graded piezocermics can significantly reduce the stresses with only a minor impact on the device stroke.
Cardiovascular Haemodynamic Simulations of Anatomically Accurate Coronaries
Authors: Boutsianis Evangelos , Frauenfelder Thomas , Dave Hitendu , Grunenfelder Jurg , Wildermuth Simon , Zund Gregor , Turina Marko , Poulikakos Dimos , Ventikos Yiannis
Published: May 2008

The present study is devoted to the investigation of the pulsatile blood flow within the first few vessels of the Left Coronary Artery (LCA) vasculature of an anatomically accurate porcine coronary tree. Transient computational fluid dynamics simulations were performed under realistic pulsatile volume inflow boundary conditions. The numerical results have provided a comprehensive collection of information regarding the haemodynamics within the LCA and its major branches, namely the Left Anterior Descending (LAD) and the Left Circumflex (LCX) arteries. The underlying principle of developing computational techniques, which would eventually allow for the realistic simulation of the vascular haemodynamics of patients, lies on the capacity of such tools for predictive diagnostics and non-invasive, hence simulation-based, surgical planning.
The Covenant of NOA: Neighbouring Organ Assistance (NOA) to Soft Tissue Structures
Authors: Arun C. P.
Published: May 2008

Soft tissues hollow structures are capable of collapsing not only under their own power but also able to employ movements of their neighbors to aid their function of propelling content. An intensive study of collapsible hollow structures is a recent development and no general law recognising this convenient coupling of the dynamics of neighboring organs is available in the literature. The literature on whole organ physiology was analysed and examples of neighboring organs providing assistance to soft tissue structures was collected. We offer the title Covenant of NOA to the arrangement that soft tissue structures have with their neighbors. The calf muscle pump and parturition are obvious examples of NOA. From examining videocystometric recordings, we are able to offer, as the latest to a long list of known NOAs, the assistance of the pelvic diaphragm to the urinary bladder that aids the latter in emptying completely. The modeling of soft tissue hollow organs as functioning somewhat in isolation must be considered antediluvian. Very often, soft tissue structures come in pairs to implement NOA: it is time we too hearkened to the Covenant of NOA.
Implementation of Reduced Mechanisms With ISAT Into CFD Simulations of Full-Scale Combustion Systems
Authors: Zhao Wei , Montgomery Christopher J. , Cremer Marc A. , Adams Bradley R. , Eklund Dean R. , Chen J.-Y.
Published: May 2008

The prohibitive CPU cost and memory requirements associated with detailed chemistry prompted the use of reduced mechanisms for turbulent reacting flow simulations. In this study, an In Situ Adaptive Tabulation (ISAT) algorithm, which was originally developed in the context of PDF methods of turbulent combustion, was applied to reduce the cost of the reduced mechanisms. Reduced mechanisms and ISAT have been implemented into VULCAN, a NASA CFD code, to simulate high-speed hydrocarbon combustion. A supersonic diffusion flame case was used to test the efficiency of ISAT. For a 20-specie C2H4 mechanism, the total CPU cost was cut by a factor of 26. ISAT has also been implemented into REI’s proprietary multiphase, turbulent reacting CFD code, GLACIER. It was tested with a 10-specie reduced mechanism to model the selective non-catalytic reduction process for NOx control in a coal fired boiler. CPU savings of approximately 40 percent was observed, which is much lower than that was achieved in VULCAN. The difference in CPU savings was attributed to the different numerical methods used in the two codes. The re-use of Jacobian matrices of the chemical source terms in VULCAN resulted in significant reduction of CPU time.
A Transient Hydrostatic Dynamometer for Single Cylinder Engine Research With Real Time Multi-Cylinder Dynamic Simulation
Authors: Lahti John L. , Andrasko Steven J. , Moskwa John J.
Published: May 2008

A new high-bandwidth transient hydrostatic dynamometer test system has been developed that accurately replicates multi-cylinder engine operation using a single-cylinder research engine. Single-cylinder engines are typically used for research because of their low cost and good cylinder accessibility for instrumentation and optics. This dynamometer maintains these advantages while dramatically improving transient and low speed testing capabilities. The system also incorporates hardware-in-the-loop models for simulation of other components that would typically be present in a vehicle application. These models include: adjoining cylinders and ancillary components in the engine, the transmission, driveline, and vehicle load. Utilizing these models it is possible to replicate actual driving cycles. This high-bandwidth transient dynamometer extends the test capabilities of single-cylinder research far beyond the traditional steady state regime, enabling transient speed single-cylinder engine research while providing single-cylinder engine operation that is comparable to the multi-cylinder engine.
CORBA-Based Task Requirement Driven Design System
Authors: Chen Zhiqiang , Siddique Zahed
Published: May 2008

Today’s design environment has become more distributed and professional. Efficient design management can greatly improve the ability of a company’s competition. To increase efficiency of a design process coordination of Computer-Aided Design and Analysis tools are very important, especially for large complicated systems. In this paper, we introduce the concept of a requirement driven system. Design process usually involves fulfillment of requirements from top-end customer. Adopting requirement driven mechanisms will provide more convenience for design coordination automation and help us find the most resource saving solutions for specific product design. A CORBA framework is discussed to facilitate the implementation of methodologies for requirement driven design coordination. System architecture and modules for the framework are introduced to support a requirement publishing and responding service. Distribution of the tasks is determined by “stigmergy” algorithm, which makes the decision using the performance history of each team and designers. An example of a coffeemaker product design based on the framework, is presented to demonstrate the application of new design system.
Investigation of Customer Needs Frequency vs. Weight in Product Platform Planning
Authors: Kurtadikar Ravindra M. , Stone Robert B.
Published: May 2008

Customer satisfaction is key for survival and success in today’s consumer market. It is crucial that the customer be used to differentiate between different variants of a product, also known as a company’s product portfolio. Numerous examples in industry prove the benefit of a platform strategy in product development. The aim is to capture a wider market share by launching a number of products based on a common platform and to reduce design and development cost by reducing design cycle time. In this paper we explore the possibility of using high level customer needs alone to define the product’s base platform and differentiating modules. The basic idea is to outline platform and differentiating modules during conceptual design stage of product development and thus plan a product family before we consider any architecture. Planning platforms in conceptual design stage reduces additional costs associated with designing, manufacturing and managing resources for each variant separately. We use design tools such as the functional basis and functional modeling in our approach. In this work we seek to validate the technique by first applying it to existing products and comparing the results against known product platforms. In this paper we outline platform and differentiating modules for a bike and shop vacuum. Future work will focus on applying this approach for more products and finally to new products during conceptual design stage.
High Aspect Ratio SU-8 Structures for 3-D Culturing of Neurons
Authors: Choi Yoonsu , Powers Richard , Vernekar Varadraj , Frazier A. Bruno , LaPlaca Michelle C. , Allen Mark G.
Published: May 2008

This paper presents a simplified fabrication method for high aspect ratio micromachined towers for culturing 3-D networks of neurons. The photosensitive epoxy SU-8 was used as both the tower material and the substrate. This material was particularly suitable because of its mechanical stability, biocompatibility, and potential for high aspect ratio fabrication. Fabrication is effectively simplified by a double exposure technique, allowing tower structures and an integral SU-8 substrate to be formed from the same epoxy deposition, thereby addressing column-to-substrate adhesion issues that have traditionally limited the aspect ratios achieved with conventional fabrication techniques. Aspect ratios up to 35:1 have been achieved, and successful cell culturing has been demonstrated.
A Micro-Flow Cytometer Based on Dielectrophoretic Particle Focusing
Authors: Yu Choongho , Shi Li , Vykoukal Jody , Gascoyne Peter R. C.
Published: May 2008

This paper reports an on-chip micro- flow cytometer that focuses cells to the center region of a microchannel by a negative dielectrophoretic force generated by ac fringing fields from microelectrodes. This design eliminates the sheath flow that makes the conventional cytometer sophisticated and difficult to operate. The micro- cytometer has a circular microfluidic channel that is fabricated by isotropic etching of soda lime glass wafers and a subsequent wafer bonding process. Electrode arrays are patterned inside the circular channel to facilitate dielectrophoretic particle focusing. We have demonstrated that the device can focus micro-beads into the center of the channel, and are integrating optical components with the micro- cytometer to realize a handheld device with integrated fluorescence detection, and will test the micro- cytometer for blood cell profiling and tumor cell detection.
A Damage Identification Method Using Vibration Modal Parameters Through Finite Element Discretization
Authors: Zhou Xiaoping , Gupta Abhijit
Published: May 2008

Natural frequencies and mode shapes of a structure will change whenever the structure has any kind of damage. This paper introduces a technique to quantify and locate the damage when the natural frequencies and mode shapes of undamaged and damaged structure are known. Aluminum beams (with and without damage) are used for numerical simulation and experimental verification. To establish the theoretical basis of this method, finite element formulation is used. A set of undetermined equations involving damage indices and natural frequencies and mode shapes of undamaged and damaged structures are obtained. The damage indices are computed using non-negative least squares method. Impact modal testing was conducted with three aluminum beams and damage indices based on experimental data are compared with actual damage cases to establish the effectiveness of this method to identify the damage.
Treatment of Thermophoretic Deposition in Tube Flow for Materials Processing Applications
Authors: Tebbe Patrick A.
Published: May 2008

Material processing techniques based on vapor or particle transport involve a number of interrelated hydrodynamic and thermal effects. For cases with large temperature gradients or small (nano) particles, thermal gradients can induce motion referred to as thermophoresis. Thermophoresis directly impacts material quality and production rates for chemical vapor deposition (CVD) and related processes. A simple yet useful geometry for the study of thermophoretic deposition is axial tube flow. This geometry is particularly useful as it closely represents one process used to produce fiber optic preforms. While considerable research has been conducted on thermophoretic deposition, a global description and understanding of the phenomena is still difficult. This paper will first review the analytical study of thermophoretic deposition. Starting with the simple Graetz problem the development of more complex solutions to the governing Navier-Stokes equations will be detailed from the literature. Next, the creation of a coupled, two code Eulerian approach to solve this problem will be presented. Finally, the results of numerical case studies performed by the author will be discussed. These results will be used to compare and contrast the influence of different factors.
Wafer Level Packaging of RF MEMS for Flip Chip Assembly
Authors: Wei J. , Lok B. K. , Lim P. C. , Nai M. L. , Lu H. J. , Lai F. K. , Wong C. K.
Published: May 2008

In this paper, the development of wafer level packaging of radio frequency (RF) microelectromechanical system (MEMS) is reported. The packaging process consists of wafer bonding, wafer thinning, via etching, plating, under-bump-metallization (UBM) and bumping processes. 6-inch Si and glass wafers are used in the study. RF MEMS devices are fabricated on Si wafers and sandwiched between Si and glass cap wafers. To maintain the pressure balance between the cavities and outside world after bonding process, Si and glass wafers are anodically bonded at a pressure of 2 bar and a bonding temperature of 400 °C. The cavities are hermetically sealed. The glass wafer of the bonded pair is thinned down to 100 μm using mechanical polishing and chemical etching, the good uniformity of the wafer thickness is maintained with etching process. A layer of Cr/Au is sputtered and patterned as the hard mask for glass via etching process. Via holes with undercut closer to the etching depth are formed in HF+HNO3 acid. After stripping the metal mask, a seed layer of TiW/Cu is deposited using sputtering and plating processes. TiW layer is used to enhance the adhesion of metal and glass. With the completion of the re-routing and via metallization processes, benzocyclobutene (BCB) photoresist is used to planarize via holes and opened for UBM process. Finally, the packaged devices can be assembled using flip chip approach.
Biomechanical Modeling of Cervical Tissue: A Quantitative Investigation of Cervical Incompetence
Authors: Febvay Se´bastien , Socrate Simona , House Michael D.
Published: May 2008

We introduce a phenomenological fully three-dimensional constitutive model for the large strain, time dependent mechanical behavior of cervical tissue. The proposed model captures specific aspects of the complex biomechanical response of cervical stroma and is able to account of for the contributions of each constituent and for the cooperative nature of the tissue response. We rely on in vitro mechanical tests to determine representative constitutive parameters for normal (non-pregnant) tissue before it undergoes the maturation process. These parameters are then altered to mimic the effects of the modified biochemical equilibrium associated with a condition of cervical incompetence. The constitutive model is integrated with pelvic anatomy to obtain a finite element model of the cervix in pregnancy. The effects of the altered tissue properties on the ability of the cervix to maintain the pregnancy are investigated.
Virtual Detection of a Radial-Ply Tire’s Three-Dimensional Free Vibration Modes Transmissibility
Authors: Chang Y. P.
Published: May 2008

A full nonlinear finite element P205/70R14 passenger car-radial-ply tire model was developed and run on a 1.7-meter-diameter spinning test drum model at a constant speed of 50 km/h in order to investigate the tire transient response characteristics, i.e. the tire three-dimensional free vibration modes transmissibility in X, Y and Z directions. The tire model was constructed in extreme detail with three-dimensional solid, layered membrane, and beam elements. The reactions forces of the tire axle in longitudinal (X axis), lateral (Y axis) and vertical (Z axis) directions were recorded when the tire rolled over a cleat on the test drum, and then the FFT algorithm was applied to examine the transient response information in the frequency domain. The result showed that this tire has clear peaks of 45, 40, and 84 Hz transmissibility in the longitudinal, lateral and vertical directions. This result was validated against previous studies by analytical, experimental, and FEA model approaches and showed excellent agreement. The parameters adopted in this FEA tire model were also compared with experimental work and the extraordinary agreement was also confirmed. The tire three dimensional free vibration modes transmissibility was successfully detected virtually.
MDT: Micro Deformation Technology
Authors: Kukowski Rob
Published: May 2008

Micro-Deformation Technology (MDT) is a proprietary material deformation process that was originally developed for the production of engineered heat transfer tubing. The patented process employs a fixed tool, which mechanically and plastically deforms the work piece to form finite and repeatable channels. These channels are developed in one continuous pass or multiple passes of the tool and the geometric shape and angle of the tool define the final channeled form. The MDT process can achieve a variety of channles form. The MDT process can achieve a variety of channel depths, channel widths, fin shapes and angularity. It can be applied to rounds, sheet and contoured work pieces. MDT is readily adaptable to conventional machining and milling equipment. The MDT process can be performed on nearly any ductile material. Materials ranging from titanium, stainless steel, silver, aluminum, copper, to the non-metallic materials like Teflon, polyethylene, rubber and PVC have been successfully processed. Most materials can be channeled in excess of 250 channels/inch. The process generates no material fines and lubrication is not required for most applications. MDT is therefore ideal for precious metal conversion and secondary cleaning steps are generally not required. Channeling sheet from opposite sides, MDT is capable of producing fine meshes via the intersection of the angled channel depths. The repeatable and uniform channels produce an extremely uniform pore distribution from a solid body. The unique attributes of MDT make it an enabling technology. By itself or in combination with current processes, it opens capability that previously did not exist. Potential applications include: filters and screens; catalyst substrates; heat transfer; material flow and separation; heat pipes; surface cladding and adhesion; capillary structures; surface preparation; and solid surface lubrication, to name only a few.
Aqua Absorption Turbine Inlet Cooler
Authors: Erickson Donald C. , Kyung Icksoo , Anand G. , Makar E. E.
Published: May 2008

The emerging Distributed Energy Resources (DER) program envisions extensive use of small to midsize turbines for on-site power production. Their output decreases substantially at warm ambient conditions when it is most needed. Therefore inlet air cooling had received much scrutiny as a way to avoid this degradation. This study examines three approaches to inlet air cooling: evaporative cooling; mechanical vapor compression refrigeration; and waste heat powered absorption refrigeration. The benefits and limitations of each process were documented. Ammonia absorption refrigeration is shown to deliver the greatest benefit to continuosly operating turbines at very favorable installed and operating cost. The most economical process identified included an ammonia refrigeration cycle integrated directly into the combustion turbine cycle. This cycle was designed and modeled, and analyzed with ambient temperature conditions for six geographic areas (Boston, Atlanta, Los Angeles, Honolulu, Phoenix, and Chicago). Annual benefits for each area are detailed.
A Neural Fuzzy Approach for Controlling Active Vehicle Suspension Systems
Authors: Abdelhady M. B. A. , Alhasan S. A.
Published: May 2008

In this work, a novel neural fuzzy (NF) control scheme is introduced to design a fully active suspension system. The fuzzy part of the controller handles uncertainties, whereas the neural part learns from past events and tunes the controller to optimize the performance of the suspension system. The two-degree-of-freedom quarter-car model is used to illustrate the control strategy and to evaluate the performance parameters for sinusoidal and random road inputs. A sinusoid road surface description is first used to obtain an initial design of the NF controller. The acceleration of the sprung mass is compared with that of an ideal skyhook model to produce an error signal, e(t); this error signal, as well as Δe(t) are employed as inputs to the controller. Results obtained for this type of road input indicate that the NF active system has significant advantages over the linear quadratic regulator (LQR) active suspension system. In order to get a broader view, more realistic road descriptions and practical control laws were used. The performance parameters were computed when the road surface was presented as a random road input. The control law of the NF active system was modified to achieve a novel non-linear control (NC) strategy. This control law requires only measurement of the body acceleration and the road input displacement, and hence, it can be realized easily in practice when compared with all other control laws, including the LQR one. For a wide range of road surfaces, results show that the performance capability of this novel system is much better than that of the LQR active system. For example, the improvements, under a medium-quality road surface and a 30-m/s vehicle speed, achieved a reduction in the rms values of the ISO weighted body acceleration and the dynamic tyre load by 17% and 20% respectively.
Stochastic Modeling of Chemical Transport Through Human Skin
Authors: Ho Clifford K.
Published: May 2008

A probabilistic, transient, three-phase model of chemical transport through human skin has been developed to assess the relative importance of uncertain parameters and processes during chemical exposure assessments and transdermal drug delivery. Penetration routes through the skin that were modeled include the following: (1) intercellular diffusion through the multiphase stratum corneum; (2) aqueous-phase diffusion through sweat ducts; and (3) oil-phase diffusion through hair follicles. Uncertainty distributions were developed for the model parameters, and a Monte Carlo analysis was performed to simulate probability distributions of mass fluxes through each of the routes for a hypothetical scenario of chemical transport through the skin. At early times (60 seconds), the sweat ducts provided a significant amount of simulated mass flux into the bloodstream. At longer times (1 hour), diffusion through the stratum corneum became important because of its relatively large surface area. Sensitivity analyses using stepwise linear regression were also performed to identify model parameters that were most important to the simulated mass fluxes at different times.
Nonholonomic Motion Planning Using Diffusion of Workspace Density Functions
Authors: Zhou Yu , Chirikjian Gregory S.
Published: May 2008

This paper introduces a trajectory planning algorithm for nonholonomic mobile robots which operate in an environment with obstacles. An important feature of our approach is that the planning domain is the workspace of the mobile robot rather than its configuration space. The basic idea is to imagine the robot being subjected to Brownian motion forcing, and to generate evolving probability density functions (PDF) that describe all attainable positions and orientations of the robot at a given value of time. By planning a path that optimizes the value of this PDF at each instant in time, we generate a feasible trajectory. The PDF of robot pose can be constructed by solving the corresponding Fokker-Planck equation using the Fourier transform for SE(N). A closed-form approximation of the resulting time-dependent PDF is then used to plan a trajectory based on the observation that the evolution of this “workspace density” is a diffusion process. Examples are provided to illustrate the algorithm.
An Experimental and Modeling Study of Electroosmotic Bulk and Near-Wall Flows in Two-Dimensional Micro- and Nanochannels
Authors: Sadr R. , Zheng Z. , Yoda M. , Conlisk A. T.
Published: May 2008

Electrokinetically driven flow of electrolyte solutions through micro- and nanochannels is of interest in microelectromechanical systems (MEMS) and nanotechnology applications. In this work, fully developed and steady electroosmotic flow (EOF) of dilute sodium tetraborate and sodium chloride aqueous solutions in a rectangular channel where the channel hight h is comparable to its width W is examined. EOF is also studied under conditions of electric double layer (EDL) overlap, or λ/h ∼ O(1), where λ is the Debye thickness, for very dilute solutions. The initial experimental data and model results are in very good agreement for dilute sodium tetraborate solutions. The experimental work uses the new nano-particle image velocimetry (nPIV) technique. Evanescent waves from the total internal reflection of light with a wavelength of 488 nm at a refractive index interface is used to illuminate 100 nm neutrally buoyant fluorescent particles in the near-wall region of the flow. The images of these tracer particles over time are processed to obtain the two components of the velocity field parallel to the wall in fully developed EOF of sodium tetraborate at concentrations up to 2 mM in fused quartz rectangular channels with height h up to 10 microns. The spatial resolution of these velocity field data along the dimension normal to the wall is about 100 nm, and the data are obtained within a distance of approximately 100 nm of the wall based upon the 1/e intensity point, or penetration depth. A set of equations modeling EOF in a long channel are solved where h/L << 1, and L is the lengthscale along the flow direction. Unlike most previous models, this work does not use the Debye-Huckel approximation, nor does it assume symmetric boundary conditions. For the case where λ/h << 1, analytical solutions for the velocity, potential and mole fractions are obtained using an asymptotic perturbation approach.
Behavior of Ionic Polymer-Metal Composites Under Subzero Temperature Conditions
Authors: Paquette Jason W. , Kim Kwang J.
Published: May 2008

Actuators that can operate within harsh environments, such as that of cold regions or outer space, could be quite useful. We have found that Ionic Polymer-Metal Composites (IPMCs) provide an attractive solution for cold operation actuators. This is because of their capability for soft actuation with relatively low voltages (1 to 5 V), durability and capability of operating within the subzero regime T < °C. The building block material of IPMCs, which is dependent upon hydration or weak chemical bonding by a solvent (typically water), experiences phase changes within the base material that results in an alteration of the performance of the material in terms of actuator performance. This alteration is to be expected, but the magnitude and degree of deviation from the actuation at normal room temperature are values of interest. An experimental apparatus is consructed in order to have a controlled temperature environment in which to analyze the material. The overall temperature within the reservoir, the temperature on the IPMC surface electrodes, the conductivity of the membrane and the blocking force were all measured and documented. The phase changes inherent at these low temperatures are investigated further by means of Differential Scanning Calorimeter to obtain the phase change temperatures. The electrical conductivity of the material was then used to help explain the phenomena for the overall change in behavior primarily at these phase change temperatures. The results are presented and interpreted to show that there is definite promise for these low temperature polymeric actuators to operate in practical applications. Also, some theoretical consideration is presented.
Two-Color Micro PIV Measurements of Particle and Fluid Motion in AC Electrokinetics
Authors: Wang Dazhi , Meinhart Carl , Sigurdson Marin
Published: May 2008

Two-Color μ-PIV is developed and used to uniquely determine the fluid velocity based on the micron-resolution Particle Image Velocimetry (μ-PIV) technique [1–3]. The fluid velocity field was obtained by measuring the motion of two different sizes particles, 0.7 and 1.0 μm. The different sizes of particles contain different fluorescent dyes, allowing them to be distinguished using fluorescent filter cubes. By comparing the velocity fields from the two different size particles, the underlying fluid motion can be uniquely determined, without a priori knowledge of the electrical properties of the particles, or the electrical field. The test section is formed by two wedge-shaped electrodes sandwiched between two glass wafers. In the presence of nonuniform ac electric fields, the particles experience dielectrophoretic (DEP) forces due to polarization and drag forces due to viscous interaction with the suspending medium, and the fluid motion is induced by the electrothermal effect and/or ac electroosmosis. The micro-PIV measurements are used to determine quantitatively the physical characteristics of the AC electrokinetic effects.