bluuebunny/crossref_metadata_2025 huggingface dataset:
Rimming Flow of Non-Newtonian Fluids
Authors: Fomin Sergei , Hashida Toshiyuki
Published: April 2008

The present study is related to the rimming flow of non-Newtonian fluid on the inner surface of a horizontal rotating cylinder. Using a scale analysis, the main characteristic scales and non-dimensional parameters, which describe the principal features of the process, are found. Exploiting the fact that one of the parameters is very small, an approximate asymptotic mathematical model of the process is developed and justified. For a wide range of fluids, a general constitutive law can be presented by a single function relating shear stress and shear rate that corresponds to a generalized Newtonian model. For this case, the run-off condition for rimming flow is derived. Provided the run-off condition is satisfied, the existence of a steady-state solution is proved. Within the bounds stipulated by this condition, film thickness admits a continuous solution, which corresponds to subcritical and critical flow regimes. It is proved that for the critical regime solution has a corner on the rising wall of the cylinder. In the supercritical flow regime, a discontinuous solution is possible and a hydraulic jump may occur. It is shown that straightforward leading order steady-state theory can work well to study the shock location and height. For the particular case of a power-law model, the analytical solution of steady-state equation for the fluid film thickness is found in explicit form. More complex theological models, which show linear Newtonian behavior at low shear rates with transition to power-law at moderate shear rates, are also considered. In particular, numerical computations were carried out for Ellis model. For this model, some analytical asymptotic solutions have been also obtained in explicit form and compared with the results of numerical computations. Based on these solutions, the optimal values of parameters, which should be used in the Ellis equation for correct simulation of coating flows, are determined; the criteria that guarantee the steady-state continuous solutions are defined; the size and location of the stationary hydraulic jumps, which form when the flow is in the supercritical state, are obtained for the different flow parameters.
Network-Conscious Damage Tracing Method for Beam Structures Based on Measurements Acquired by Distributed MEMS Gyroscopes
Authors: Masuda Arata , Sone Akira
Published: April 2008

The aim of this conceptual paper is to develop a damage tracing method to detect and track the evolution of structural damages in aerospace structures, in particular, large beam structures, considering the applicability in a decentralized computing environment of wireless sensor networks. We first present a modal flexibility-based damage indices that have simple and intuitive physical interpretation. Since the damage indices are computed using angular mode shapes of the lowest several modes, vibratory gyroscopes are adopted as the sensing device in this approach. The damage evaluation algorithm is then modified to a decentralized form, which is to be implemented as the local computation of mode separation at each sensor unit and the global computation of the damage index at the central monitoring station. Some illustrative experiments simulating both stationary damages and sudden damages are conducted to show that the proposed method is capable to indicate the location of the damages and the time when they occur.
Analytical Models for Economic Demanufacturing Inventory Management
Authors: Gunter Kenneth L. , Sutherland John W.
Published: April 2008

For value recovery activities to be successful in the U.S., the components recovered through demanufacturing operations must be sold at a profit. One of the most important challenges faced by demanufacturing facilities is the management of inventory, which can significantly impact company profitability. In order to achieve profitability, demanufacturers require tools to effectively manage recovered component inventories and scrap/recyclate. In this paper, analytical models are developed to predict the optimal selling quantity and selling period for recovered parts and scrap/recyclate in a demanufacturing system. In addition, total system profit is examined, including break-even conditions.
Subcooled Flow Boiling Critical Heat Flux in Short Vertical Tube: Influence of Inner Surface Roughness
Authors: Hata Koichi , Shiotsu Masahiro , Noda Nobuaki
Published: April 2008

The subcooled flow boiling CHF and the heat transfer characteristics for the flow velocities (u=4.0 to 13.3 m/s), the inlet subcoolings (ΔTsub,in=137.49 to 153.87 K), the inlet pressure (Pin=740.67 to 975.78 kPa) and the dissolved oxygen concentration (O=8.63 to 0.0288 ppm) are systematically measured by the experimental water loop installed the pressurizer. The SUS304 tubes of d=3 mm and L=66.5 mm (L/d=22.17) with the inner surfaces of smooth and mirror finished are mainly used in this work. Heat transfer characteristics and CHF data are compared with those for the rough finished inner surface (RF) previously obtained and the CHFs are compared with the values calculated by the CHF correlations against outlet and inlet subcoolings based on the experimental data for the rough finished inner surface under the N2 gas pressure. The influence of inner surface roughness on the heat transfer characteristics and the CHFs for wide range of dissolved gas concentration are investigated in detail.
Transient, Three-Dimensional Numerical Model of a Laser Cutting Process With Phase Change Consideration
Authors: Gutie´rrez Gustavo , Araya Juan Guillermo
Published: April 2008

Phase change problems are encountered in several manufacturing and material processing applications. Such problems are computationally challenging because it is necessary to solve a non-linear heat conduction equation and take into considerations the conditions needed to produce material ablation, varying continuously the heat source position, thermo physical properties and physical shape of the domain. This research presents a numerical simulation of the temperature field and the removed material resulting from the impingement of a moving laser beam on a ceramic surface. A finite volume approach has been developed to predict the temperature field including phase changes generated during the process. The model considers heat losses by convection and radiation due to the high temperatures involved and uses a coordinate system affixed to the workpiece; therefore no quasi-steady conditions are assumed, as in the majority of previous works. Numerical predictions were compared with former three-dimensional numerical models considering a semi-infinite solid and from experimental data found in the literature. This study gives insight into the interactions between the laser beam and a silicon nitride workpiece during the cutting.
Micromachining in Exotic Materials
Authors: Rother Burkhard K.
Published: April 2008

More and more exotic materials are being used in micro technology, which require specific machining technologies. First the process requires the right type of machines with accuracies of ±0.001 mm. These machines and the spindles used should be free of vibrations. Hence special materials, such as polymer concrete are used to absorb possible vibrations to the greatest extent. In-process controls maintain high accuracies in unmanned operations. Cutting tools as small as 30 micron (0.02286 inches) in diameter may require spindle speeds of up to 160 000 rpm/min. These small tools cannot easily be seen by the human eye but still have to be monitored during operation. A laser beam of 30 micron in diameter is measuring small tools to the accuracy of ±1 micron.
Inverse Kinematics and Geometric Relations of an Intelligent Modified Stewart Platform for Thrust Vector Control
Authors: Ghasemi Nejhad Mehrdad N.
Published: April 2008

Adaptive or intelligent structures which have the capability for sensing and responding to their environment promise a novel approach to satisfying the stringent performance requirements of future space missions. This research effort focuses on the development of an intelligent thruster mount structure with precision positioning and active vibration suppression capability for use in a space satellite. The intelligent thruster mount would utilize piezoelectric stacks and patches for precision positioning and vibration suppression to provide fine-tuning of position tolerance for thruster alignment and low transmissibility of vibration to the satellite structure. This vibration, if not suppressed, renders sensitive optical or measurement equipment non-operational until the disturbance has dissipated. This intelligent system approach would greatly enhance mission performance by fine tuning attitude control, potentially eliminating the non-operational period as well as minimizing fuel consumption utilized for position correction. The configuration of the intelligent thruster mount system is that of a modified Stewart platform. Precision positioning of this structure is achieved using active composite strut members that use piezoelectric stack actuators and extend or contract to tilt the top device-plate where the thruster is mounted. The geometric relationship between the Stewart platform and the modified Stewart platform is described, and an inverse kinematics analysis of the modified Stewart platform has been developed and is used to determine the required axial displacement of the active struts for the desired angular tilt of the top device-plate. The active struts can participate in precision positioning as well as vibration suppression of the top device-plate where the thruster, i.e., the source of the unwanted vibrations and misalignment, is mounted. The proposed Thrust Vector Control (TVC) intelligent platform offers a promising method for achieving fine tuning of positioning tolerances of a thruster as well as minimizing the effects of the disturbances generated during thruster firing in spacecraft such as a satellite.
Finite Element Analysis of Self-Piercing Riveting Process
Authors: Sui Bo , Du Dong , Chang Baohua
Published: April 2008

A nonlinear finite element model is built to study the self-piercing riveting process. In this model, the elasto-plastic properties of sheets and rivet, i.e., the dependency of flow stress on effective strain is considered. The adaptive meshing technology is used for the separation of sheet material. The piercing operation on two 2 m m-thick 5754-O aluminum sheets is simulated, and the results obtained are in agreement with the published experimental results. Using this method, residual stress and strain are calculated under different die tip heights and rivet strengths, to obtain insights into the local mechanical behavior of the joints and the effect of process variables. It is found that the hoop residual stress is the main stress that affects the mechanical properties of joint. Higher riveting pressure is needed for higher die tip and higher rivet strength. Both the die tip height and river strength can affect the joint shape and residual stress.
Electromechanical Model of an Active Polymer Thin Circular Disk
Authors: Buechler Miles A. , Leo Donald J.
Published: April 2008

Ionic polymers exhibit an electromechanical response similar to a piezoelectric bender. It has been shown that material properties similar to piezoelectric properties can be used to effectively model ionic polymer devices. One proposed ionic polymer device is a circular disk fabricated from the ionic polymer material for shape and vibration control can be accomplished through electrical boundary conditions applied to the ionic polymer rather than by adding external actuators. This paper extends the formulae for natural frequencies and mode shapes of a thin disk to include quasi-piezoelectric properties and electrical boundary conditions. An electromechanical model for ionic polymers using equivalent circuit representation has been previously developed. Three materials properties, which are compatible with accepted piezoelectric actuator and transducer relationships were derived and experimentally verified. The equivalent Young’s modulus, dielectric permittivity, and the strain coefficient were found to be frequency dependant over the range 0.1 Hz to 500 Hz. In this paper the variational energy method is applied to develop a two-dimensional model of a thin electro-active polymer disk. The variational model relies on an extension of the electromechanical material properties derived for ionomeric materials. An example of a disk with simply supported geometric boundary conditions is presented and operational deflection shapes are simulated for electrical excitation between 0.1 and 500 Hz. The model predicts that the frequency dependence of the material properties will produce modal responses with both real and imaginary components, indicating the existence of travelling waves in the disk. Voltage to deflection transfer functions are also developed for several geometric boundary conditions using this model and then compared to experimental results. The model correctly predicts damped resonant frequencies as a result of the viscoelastic properties. It also accurately predicts low frequency phase lag and resonant frequencies of the electromechanical response.
Mobile Agent and Semantic Web Based Frameworks for the Realization of Virtual Manufacturing Enterprises
Authors: Cecil J. , Gobinath N.
Published: April 2008

In a virtual Manufacturing Enterprise (VME), the manufacturing and software resources are geographically distributed and communicate electronically using mediums such as the Internet. In such a context, there is a need to explore the design of distributive computing frameworks for the realization of VMEs. In this paper, 2 frameworks are discussed which are based on a mobile agent paradigm and the notion of a ‘semantic web’ respectively. In this paper, the first segment explores the design of such a mobile agent framework to support process planning and manufacturing activities; in the second segment of this paper, the creation of preliminary software modules as part of a ‘mini’ semantic web is described; the use of such a ‘semantic web’ based framework provides a new dimensionality of ‘meaning’, thereby enabling better cooperation and interaction between machines and humans.
Teaching Bioheat Transfer Based on “How People Learn” Methodology
Authors: Diller Kenneth R. , Roselli Robert J. , Martin H. Taylor
Published: April 2008

This paper presents the organizational structure for teaching the bioheat transfer component of a biotransport course based on the How People Learn (HPL) pedagogical model. The presentation to students consists of a series of design challenges in a sequence that directs learning through the major components of bioheat transfer knowledge taxonomy. Students encounter various taxonomic subjects in either a primary learning context or in a secondary application in which adaptive expertise is developed. The primary and secondary intersections between the challenge and taxonomy vectors are displayed in a matrix format.
An Optimisation Approach Applied to Design the Hydraulic Power Supply for a Forklift Truck
Authors: Pedersen Henrik C. , Andersen Torben O. , Hansen Michael R. , Lindholdt Per N.
Published: April 2008

This paper describes the first part of a method that may be used in the design of the most energy efficient hydraulic open-circuit systems, when also considering the operational aspects of the system given in the design specifications. The method builds on a numerically based multi-level optimisation approach, and is in the current paper exemplified through the design of the hydraulic power supply for a forklift truck. The paper first describes the prerequisites for the method and then explains the different steps in the approach to design the hydraulic system. Finally the results of the optimisation example for the forklift truck are presented along with a discussion of the method.
Active Vibration Control of Periodic Rotating Shafts
Authors: Toso M. , Baz A. , Pines D.
Published: April 2008

The propagation of transverse waves in periodic rotating shafts is controlled actively by using piezoelectric inserts which are placed periodically along these shafts. The control strategies aim at tuning the unique filtering characteristis of the periodic shafts in such manner that prevent the propagation of the waves within specific frequency bands called “stop bands.” The spectral characteristics of these “stop bands” are controlled in response to the shaft vibration. A finite element model is developed for this class of actively controlled periodic shafts which is then used to generate the “transfer matrix” for the unit cell of these shafts. The eigenvalues of the resulting transfer matrix are utilized to predict the characteristics of the stop and the pass bands of the rotating shaft as function of the shaft geometry, rotation speed, and control gains of the active inserts. The obtained characteristics are validated experimentally using shafts driven via gearbox assembly which subject the shafts to broadband excitations. The obtained results are also compared with the characteristics of passive shafts with stepped periodic geometries. Such a comparison aims at demonstrating the effectiveness of the active periodic shafts in redistributing the energy spectrum by confining the propagation to specific frequency bands. Particular emphasis is placed on studying the effect of the active control strategies on the vibration damping characteristics of the shafts. The proposed class of active periodic shafts can be useful in numerous critical applications such as the drive shafts of helicopters where transmitted vibrations can have detrimental effect on the performance of the tail rotor. Other applications are only limited by our imagination.
Robust Control of Dual-Stage Cable Suspended Robots With Input Constraints for Cargo Handling
Authors: Oh So-Ryeok , Mankala Kalyan , Agrawal Sunil K. , Albus James S.
Published: April 2008

Skin to skin transfer of cargo is a very challenging task. In a typical skin-to-skin transfer operation, the end-effector and the target are located on different ships and hence subjected to disturbances, which are not in phase. Hence, this transfer operation can be unstable unless the sea condition is properly accounted for. The cable robot should be designed for a versatile motion to track the target. NIST has proposed a dual-stage cable robot, each with six-degrees-of-freedom for this purpose. In this paper, the robust controller of the dual-stage cable robot with positive input constraints is developed which can assure robust tracking of the target in the presence of the disturbance due to the pitch, roll, and yaw motion of a ship, as well as a translation motion. Also, Pointwise optimization techniques are incorporated in order to generate feasible desired trajectories, which satisfy the input constraints. Simulations show the feasiblity of the proposed control method for the control of a dual-stage cable robot.
Heat Dissipation in GaN Power Semiconductor Devices
Authors: Christensen Adam , Graham Samuel
Published: April 2008

In this work, a numerical study is presented of the impact of growth substrates on thermal dissipation in GaN devices. Substrates included in this study are sapphire, SiC, GaN, ZnO, and LiGaO2. Based on a model high power HFET device with the rear side held at a fixed temperature, the maximum junction temperature in the devices were calculated using finite element analysis and compared. Both interface resistance and the effects of dislocations in the GaN layer were accounted for. Results show that state of the art devices dissipating 10 W/mm of power must be fabricated on high thermal conductivity substrates like GaN or SiC when rear side heat dissipation is utilized. In contrast, an analysis of high heat flux removal convective cooling was investigated for the application of front side heat dissipation. These results show that junction temperatures below 150°C are readily obtainable using this method and are substrate independent. The implications of the substrate independent cooling scheme are discussed.
Hands-On Experimentation in the Fluid Mechanics Classroom as Homework With eFluids.com
Authors: Dwyer Elisabeth , Gogineni Sivaram , Smits Alexander , Adrian Ron , Tavoularis Stavros , Rogers Chris
Published: April 2008

In an introductory fluid mechanics course, it is important for students to realize that the mathematical models they are deriving in class sometimes model the real world well and sometimes not so well. One way to demonstrate this is to have the students model a simple experiment and compare the results of the model to those of the experiment. This exercise teaches the importance of the model assumptions and the applicability of the model. It would be even more effective if the experiments were simple enough so that students could do them at home as a homework assignment, rather than restricting their experience to a “canned” two hour lab course. At eFluids.com, we are building a library of such experiments in an effort to build a community of educators that moves beyond the traditional mathematical exercises for homework. Here, we describe a number of these experiments and how they can be used in classes. We also present some methods of using the eFluids.com Gallery of Images in the classroom to give students the opportunity to see “Fluids in Action.” Finally, we introduce the eFluids Olympiad section where faculty can post effective and “interesting” homework problems.
A Generalized Madymo Modeling Approach With Both Frontal Occupants in a Range of Impact Situations
Authors: Shea Rex T.
Published: April 2008

A generalized MADYMO model that includes both the driver and passenger was developed to simulate the occupant responses under different restraint conditions in various impact situations. Traditionally in safety simulations the occupant was given the inverse of the vehicle acceleration and the vehicle compartment remains stationary. This approach works for frontal impacts where the longitudinal motion of the occupants dominates the kinematics. For an offset or angled impact, where the vehicle experiences a general three-dimensional motion, this approach loses its advantage. A prescribed motion approach is used instead, where the vehicle was given a prescribed three-dimensional motion, and the occupant’s responses are recorded similar to an actual crash. Driver and passenger models are generally being developed separately for each impact situation. This creates a maintenance and updating problem, because a single design change could require modifying a family of models. In this study a master model was developed using the prescribed motion approach, and both the driver and the passenger were incorporated into the model. This has the advantage of streamlining the restraint system development process, and avoiding tedious maintenance at the same time. A single model can be used for a range of impact situations, and all occupant responses can be generated. The model can be used to simulate frontal impacts at different speeds, angled impacts, and offset deformable barrier tests. A pair of angled impacts and an NCAP test were used as examples to demonstrate the versatility of the model and correlations to barrier tests were discussed.
Feasible Set Points With Positive Tensions for a Cable Suspended Robot With a Lyapunov Controller
Authors: Oh So-Ryeok , Agrawal Sunil K.
Published: April 2008

This paper considers characterization of the admissible workspace of set-points for a cable-suspended robot with positive input constraints. The main steps are: find the range of system states in terms of set-points using the system’s error dynamics, use the constraint inequalities in a manner such that positive input constraints are satisfied. The feasible workspace obtained by the proposed method is compared with the workspace given by iterative simulations. Finally, the effectiveness of the method is illustrated by laboratory experiments on a six-degree-of-freedom cable-suspended robot.
Management Model for the Product Concept Phase in the Early Stages of Product Innovation Process
Authors: Jamali Nadia , Meier Markus
Published: April 2008

The product concept phase of the product innovation process is a creative and interdisciplinary activity that transforms a market opportunity and technological innovation into successful products. It is a set of activity based processes in a product-oriented enterprise, and is essential to the economics success of such organization. Well-designed processes reduce development time, create better products, generate profit, and increase market share. In contrast, poorly-designed processes can harm both product lines and the companies that manufacture them. Determining important methods in the product concept phase and determining their relationship with organizational capability are crucial to the sustainable success in product development. Studying their relationship would give us insights into the product development dynamics. This paper will focus on the development of an engineering management model for the product conceptual phase of the product Innovation process. The (PCP) begins with the scope of the project having been formalized by either a request for proposal from an external entity or an internally generated mission statement. This document will specify a particular market opportunity and lay out the broad constraints of the project. Basically it will specify which direction to go, and will generally specify a precise destination or a particular way to get there. During the product concept phase, customer needs are identified, multiple product concepts are generated based on these needs, and a single product concept is selected for further development after a thorough evaluation has been accomplished. A well thought-out product concept will consist of a description of the form, function, and features of the product as well as a set of specifications, an analysis of competitive products, and an economic justification for the project. The aim of this paper to determine the most effective methods, tools and techniques to design a theoretical product concept phase (PCP) model, which consists of four activity elements or modules. The model highlights the iterative series of activities that may take anywhere from a few seconds in the minds of individuals to many months or years for defining a breakthrough concept. The product concept phase (PCP) model will be created during the problem definition activity very early in the product development process. The PCP module will be organized in a way that requires participation by virtually all the major product development functions within the organization such as marketing, technology, product design and manufacturing. It also involves interactions with stakeholders such as customers, suppliers that are outside of the organization. The interface of the PCP module to other product innovation process phases will be achieved through the design of an IT - Platform; that includes all the needs and requirements for and form other phases.
Miniature Joule–Thomson (JT) Cryocoolers for Propellant Management
Authors: Notardonato W. , Haddad G. , Krishna-Murty K. V. , Zhu J. , Kapat J. S. , Chow L. C.
Published: April 2008

Boil-off of cryogenic propellants is an issue of concern in any space mission. There could be boil-off of liquid propellants in the cryogenic storage tank, transfer line or in the space vehicle external tank itself due to heat leak. The current insulation technology uses a multilayered thermal protective coating of 304 Stainless Steel and Welded Invar, which allows the propellant to withstand the extreme internal and external temperature variations generated during pre-launch, launch, and flight operations, which does not provide for zero boil-off (ZBO). Usage of a cryocooler to prevent propellant boil-off would potentially reduce the launch costs. Owing to its attractive features like simplicity, compactness and rapid cool-down characteristics, an innovative concept of using Joule-Thomson (JT) cryocoolers for prechilling, densification and ZBO applications of cryogenic propellants is focused upon. The liquid oxygen propellant transfer line at NASA Kennedy Space Center is considered for demonstration of the above concept. Various thermodynamic cycle parameters are optimized for the cryocooler to make the demonstration possible. Cycle optimization is done also taking into account the feasibility to develop some crucial components for the JT cryocooler like a micro channel heat recuperator and cold heads. Current state of developments in the heat exchanger is briefly described. Some advantages of using miniaturized cryocoolers in launch vehicle operations are also discussed.
Extending Design for Disassembly Index to Consider End of Life-Cycle Use
Authors: Howsmon Steven , Vinay Amatiganahally Shivashankar , Reddy Ravula Sumeer , Siddique Zahed
Published: April 2008

The idea of “green” engineering has recently been recognized as having a profound impact in the manufacturing industry. The need for environmentally friendly products continues to increase, and that starts in the design phase. Design for Disassembly stems from the need to recycle. After a product has completed its useful life, it needs to be disassembled then recycled, remanufactured or scrapped. Since disassembly can have a major impact on a company’s bottom line, and a product’s shelf life, a tool for proper evaluation of a product for its disassembly efficiency is essential. Most of the existing Design for Disassembly tools usually focus only on disassembly operations and does not consider the end of life use of the components. In this paper we present a Design for Disassembly index that integrates Reuse, Remanufacture, and Recycle associated with disassembly. The modified disassemblability index combines relevant issues related to disassembly and recycling of products, such as fastening method, cleaning, hazards, ease of reuse, ease of reconditioning, ease of reassembly and ease of disassembly. Specific scales for each of these criteria and a simple spreadsheet based tool are also presented in the paper. The modified disassembly index and the tool are demonstrated by applying it on a printer.
Wall Stresses Before and After Endovascular Repair of Abdominal Aortic Aneurysms
Authors: Di Martino Elena S. , Bohra Ajay , Scotti Christine , Finol Ender , Vorp David A.
Published: April 2008

Endovascular aneurysm repair (EVAR) technique is a minimally invasive procedure approach to abdominal aortic aneurysm (AAA) repair. Following EVAR, isolated aortic tissue starts remodeling after the new blood path is established. The commercially available endovascular grafts (EVG) have been found to be prone to Type I endoleak, which is re-pressurization of the degenerated AAA sac following a breach in the seal mechanism of the EVG or migration due to failure of the mechanism holding the graft in place (Chuter, 2002) These inadequacies of EVGs might be attributed to the effect of non-optimal design of graft anchoring system. In the present study, we utilized pre-operative and post-operative computer tomography (CT) data with previously derived material properties to construct three-dimensional finite element (FE) models for AAA before and after the EVAR procedure. We studied the nature of stresses acting on the aorta before and after EVAR. In particular we investigated the physical forces acting on the EVG and how they are transferred to the aortic wall at graft anchoring sites.
Optimal Placement of Piezoelectric Transducers for Passive Vibration Control of Geometrically Non-Linear Structures
Authors: Venna Suresh V. , Lin Y. J.
Published: April 2008

In this paper, an attempt is made to determine optimal location of piezoelectric transducers for passive vibration control of geometrically complicated structures and shells with non-linear curvatures. Industry-standard aircraft leading edge structure is considered for the analysis and experimental verification. Finite element model of the leading edge structure consisting of a thin layer of piezoelectric elements on the inner surface of the leading edge covering the whole surface is built and appropriate boundary conditions are applied. All the piezoelectric properties are incorporated into the elements. Modal piezoelectric analysis is performed to investigate the electric potential developed in the piezoelectric elements in the first bending and torsion modes. Location of the piezoelectric elements yielding highest amount of electric potential is identified as the best location for vibration absorption. Based on the analysis results, six piezoelectric vibration absorbers are determined to be used for performing the passive vibration control of the two modes. Results of the analysis are verified with an experimental testing of the aluminum leading edge with piezoelectric vibration absorbers firmly attached to it. A good agreement is found between the analytical and experimental results. Further, two resistive shunt circuits are designed for the passive damping of the first bending and torsion modes in which the electric potential developed would be dissipated as heat to obtain passive vibration compensation. Experimental verification of the passive damping is performed at these two modes with appropriate shunt circuits affixed to the piezoelectric vibration absorbers. Amplitude reduction around 30% and 25% and Q-factor reduction up to 15% and 10% are obtained in the bending and torsion modes, respectively. In addition, some amount of damping is observed at higher modes as well.
Pore Fluid Effects on Shear Modulus for Sandstones With Soft Anisotropy
Authors: Berryman James G.
Published: April 2008

A general analysis of poroelasticity for vertical transverse isotropy (VTI) shows that four eigenvectors are pure shear modes with no coupling to the pore-fluid mechanics. The remaining two eigenvectors are linear combinations of pure compression and uniaxial shear, both of which are coupled to the fluid mechanics. After reducing the problem to a 2 × 2 system, the analysis shows in a relatively elementary fashion how a poroelastic system with isotropic solid elastic frame, but with anisotropy introduced through the poroelastic coefficients, interacts with the mechanics of the pore fluid and produces shear dependence on fluid properties in the overall mechanical system. The analysis shows, for example, that this effect is always present (though sometimes small in magnitude) in the systems studied, and can be quite large (up to a definite maximum increase of 20 per cent) in some rocks — including Spirit River sandstone and Schuler-Cotton Valley sandstone.
Membrane Integrity as a Therapeutic Target in Neural Cell Injury
Authors: Barbee Kenneth A. , Serbest Gulyeter , Horwitz Joel
Published: April 2008

The importance of cell membrane integrity for normal cell function and indeed survival is well established, yet the role of membrane disruption in cellular pathology is seldom considered except as a prelude to, or indication of, cell death. However, evidence from diverse fields strongly implicates membrane disruption as a key precipitating event in the pathological responses to various stimuli. Dynamic mechanical loading of neural cells produces an acute disruption of the plasma membrane as indicated by a rapid and transient release of LDH from the cytoplasm of injured cells. In this report, we show that this cellular level injury is not immediately fatal, but rather gives rise to a cascade of signaling events that lead to cell death in the long term. In our model, over 50% of the cells were dead at 24 hours post injury, the majority of which were apoptotic as assessed by the TUNEL assay using flow cytometry. Though many of the signaling pathways involved in this response to injury have been studied, the link between the initial membrane damage and the subsequent signaling is poorly understood. We report for the first time that treating injured neurons with an agent that promotes resealing of membrane pores can rescue the cells from both necrotic cell death and apoptosis at 24 hours post injury. Treatment with the nonionic surfactant, poloxamer 188 (P188), at 15 minutes post injury restored cell viability at 24 hours to control values. The role of the pro-apoptosis MAP kinase, p38, in cell death following injury was investigated using Western blot analysis. Activation of p38 was increased over 2-fold at 15 minutes post injury. P188 treatment at 10 minutes inhibited p38 activation. However, treatment with a specific inhibitor of p38 activation produced only a partial reduction in apoptosis and had no effect on necrotic cell death. These data suggest multiple signaling pathways are involved in the long term response of neurons to mechanical injury. Furthermore, the putative mechanism of action of P188 to promote membrane resealing suggests that the acute membrane damage due to trauma is a critical precipitating event lying upstream of the many signaling cascades that contribute to the subsequent pathology.
Induction of Microdamage Through Application of Acoustic Energy to Cortical Bone
Authors: Tami Andrea E. , Knothe Tate Melissa L. , Streem Jamie R. , Comisford Ryan S. , O’Leary Jared M. , Streem Stevan B. , Knothe Ulf
Published: April 2008

Extracorporeal shock waves (ESW) are used routinely to break up kidney stones. Recently ESW has been implemented in the orthopaedic arena to treat heel spurs, although the mechanism underlying this therapeutic effect is not known. Acoustic energy has been shown to increase transport in bone. Furthermore, naturally occurring microdamage in bone has been implicated as a trigger for the onset of remodeling. We hypothesize that controlled application of ESW to bone tissue increases transport and stimulates bone turnover through production of low-level microdamage. The goal of this study was to identify the bandwidth and the application regime of acoustic energy to produce such damage. Transverse sections of sheep metacarpi (1 cm) were subjected to acoustic loading regimes of varying shock wave number and intensity. Thereafter, the blocks were bulk-stained with procion dye, embedded in PMMA, and sectioned into 100 mm slices for confocal microscopy and analysis. The blocks loaded with the highest energy regimes showed marked diffuse microdamage and microcracks, usually at sites of discontinuity along the periosteal edge. These results provide a first step in testing our hypothesis and ultimately may provide a basis for the exploitation of ESW to prevent osteopenia and/or osteoporosis.
Design and Fabrication of a UV-LIGA Compliant Micrograsper for Ophthalmic Surgery
Authors: Yang Ming , Culkar Kristin M. , Powell Katherine , Frecker Mary I. , Zahn Jeffrey D.
Published: April 2008

A miniaturized grasping tool was designed and fabricated for use in ophthalmic procedures. The grasping travel range was optimized to have a 2–4 mm jaw spacing in the open position which is a requirement for ophthalmic surgery. Design optimization approaches were utilized to design a grasper which can tolerate large displacements without fracture. The device was fabricated using the UV-LIGA technique using SU-8 photoresist as a molding template. After the device was fabricated it was integrated with a 20-gauge cylindrical package which guides the device’s movement. The packaging tube is used to manipulate the device. In the device’s natural position the jaws remain open. As the device is pulled through the tube, the tube’s wall forces the jaws closed for a grasping motion. The pull-off force of the micrograpser during grasping motion was measured and the value is comparable value to that of a commercial micrograpser developed by Alcon Manufacturing Ltd. using traditional fabrication techniques. A microcutter was also developed by substituting the grasping jaws of the micrograsper with sharp blades. Ex vivo tests were further conducted in order to evaluate the performance of the miniaturized instruments for manipulating and cutting objects similar to those encountered during an ophthalmic procedure.
Tensile Load Deformation Behaviour of Woven Fabrics
Authors: Ramgulam Rajcoomar , Potluri Prasad
Published: April 2008

This paper is concerned with the mechanics of woven fabrics under tensile loading. The yarns are treated as elastica. The yarns bent into shape for both warp and weft are assumed to be elastic, homogenous, and weightless. During deformation the yarns are subjected to bending, extension and transverse compression. The initial geometry of the yarns in the fabric, under no external loading, is first obtained using a force-equilibrium method based on Love’s ordinary approximate theory, a generalisation of the Bernoulli-Euler theory of elastic rods. A non-linear boundary-value problem with a system of five differential equations has been formulated and solved. Application of load will further change the shape of the bent yarns due to bending and stretching. For a yarn with given initial geometry, as obtained by the force-equilibrium method, the solution of the deformed configuration is obtained from the solution of two nonlinear differential equations using appropriate boundary conditions. The formulation of the latter problem is based on the energy method. The sum of the energy terms due to bending, stretching together with the potential energy due to the applied load provides an expression for the total energy of the system. The variation of the total energy in terms of the variations of two parameters is then obtained, using the techniques from calculus of variations. One parameter described the deviation of the bent yarn from a straight line while the other is the length as measured along the yarn axis. This leads to a set of differential equations that fully describe the deformed yarns. The models, initially developed for plain weave, are being currently extended to non-plain weaves and 3D woven fabrics.
Dynamic Modeling of α in the Isotropic Lagrangian Averaged Navier-Stokes-α Equations
Authors: Zhao Hongwu , Mohseni Kamran , Marsden Jerrold E.
Published: April 2008

A dynamic procedure for the Lagrangian Averaged Navier-Stokes-α (LANS-α) equations is developed where the variation in the parameter α in the direction of anisotropy is determined in a self-consistent way from data contained in the simulation itself. In order to derive this model, the incompressible Navier-Stokes equations are Helmholtz-filtered at the grid and a test filter levels. A Germano type identity is derived by comparing the filtered subgrid scale stress terms with those given in the LANS-α equations. Assuming constant α in homogenous directions of the flow and averaging in these directions, results in a nonlinear equation for the parameter α, which determines the variation of α in the non-homogeneous directions or in time. Consequently, the parameter α is calculated during the simulation instead of a pre-defined value. As an initial test, the dynamic LANS-α model is used to compute isotropic homogenous forced and decaying turbulence, where α is constant over the computational domain, but is allowed to vary in time. The resulting simulations are compared with direct numerical simulations and with the LANS-α simulations using fixed value of α. As expected, α is found to change rapidly during the first eddy turn-over time during the simulations. It is also observed that by using the dynamic LANS-α procedure a more accurate simulation of the isotropic homogeneous turbulence is achieved. The energy spectra and the total kinetic energy decay are captured more accurately as compared with the LANS-α simulations using a fixed α. The current results suggest some promising applications of this dynamic LANS-α model, such as to a spatially varying turbulent flow, which we hope to undertake in future research.
Irreversibility Approach for Sustainability Analysis of a Netshape Manufacturing System
Authors: Sankara Jayasankar , Sekulic Dusan P.
Published: April 2008

The approach advocated in this work implements energy/exergy analysis and indirectly an irreversibility evaluation to a continuous manufacturing process involving discrete netshape production of compact heat exchangers through a complex controlled atmosphere brazing (CAB) process. To the best knowledge of the authors, this investigation constitutes the first effort in merging a thorough study of materials processing phenomena and an exergy/irreversibility approach for sustainability analysis in manufacturing. The system under consideration involves fifteen cells of a continuous ramp-up heating, melting, reactive flow, isothermal dwell, and rapid quench solidification processing sequence during a controlled atmosphere brazing of aluminum compact heat exchangers. Detailed mass, energy, and exergy balances were performed. The irreversibility sources were identified and the quality of energy utilization at different processing steps determined.
Sequential and Near-Simultaneous Multi-Body Collisions
Authors: Quinn D. Dane , Bairavarasu Kalyan
Published: April 2008

This work considers a three mass collision model with finite-time, compliant contacts. If the masses are initially separated by a sufficient distance, the collision sequence is sequential, that is, comprised of a sequence of pairwise impacts. The final velocities of each mass are then independent of the specific initial spacing. In contrast, if the initial spacing between the masses is sufficiently small there exists an interval during which the three masses interact simultaneously. In this instance the final velocity state also depends on the initial configuration of the system. Given an assumed impact duration and coefficient of restitution for a pairwise collision, a two-dimensional map is derived to describe those initial conditions that lead to pairwise sequences. Finally, for a specific nonlinear compliance model the variation in the final velocities is characterized in terms of the initial configuration and velocity state of the system.
Manipulation of Bio-Particles by Electrokinetics
Authors: Chu Kuang Han , Liu Cheng-Hsien
Published: April 2008

We propose and develop a new bio-particles manipulation device that has the similar size order as targeted bio-objects and is a non-contact approach to bio-objects using AC electrokinetics. We use micro pyramid array made by MEMS KOH anisotropic etch in our design. Simulation results using CFD-ACE+ and ANSYS show extremely high electric field around micro pyramids for our concept proof. Experimental results successfully demonstrate the feature of micro-object manipulation for our device. In this paper, we will present the design, fabrication, modeling, simulation, and testing results of our manipulation device using electrokinetic force.
Integrating Model Validation and Uncertainty Analysis Into an Undergraduate Engineering Laboratory
Authors: Steele W. G. , Schneider J. A.
Published: April 2008

In undergraduate engineering education, a commonly used teaching method for an experimental methods course would be to compare an engineering calculation with an experimental result. A fundamental question for the students is “Do the theoretical model predictions and the experimental data agree?” Sometimes uncertainty is assigned to the experimental data, but to answer the comparison question with validity, the uncertainty of the theoretical calculations must also be considered. In this paper, the concept and methodology of using experimental data and uncertainty analysis for the validation of theoretical predictions is described in the context of the application to an undergraduate engineering laboratory course at Mississippi State University (MSU).