bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Study on the Thawing of Frozen Biological Tissue Induced by Laser Irradiation
Authors: Zhou Jianhua , Liu Dengying
Published: June 2008

Because of its strong scattering effect in biological tissue, laser light (especially at near-infrared wavelength) can heat a comparatively large volume of tissue. This volume heating, coupled with other advantages (e.g. lasers can deliver high intensity light to small well-defined areas under precise control), makes the laser an excellent heat source. It can thus be used to achieve the thawing of frozen biological tissue. This may have great potentials in medicine (e.g. rewarming of cryopreserved biological tissue) and food industry.
A New Bio-Heat Transfer Model and Its Application for Concealed Perspiration
Authors: Zhu G. M. , Liu W. , Zeng T. , Yang K.
Published: June 2008

A human being’s limb can be modeled in terms of three physiological layers from inside to outside in the radial direction: the bone, the muscle and the skin as shown in Fig. 1. The skin layer could be regarded as a kind of porous tissue at macro-scale, though it is not a perfect porous material. This is because the skin layer has all the important physical characteristics of a porous medium: the solid matrix, skin tissue covering all the objective space; and the voids/pores formed by sweat glands that are interconnected. This allows one to use the model for an unsaturated porous medium to describe the flow and heat transfer of sweat in the skin layer.
The Design Environment for MEMS
Authors: Bart Stephen F.
Published: June 2008

Microsystems Technology (MST) or Microelectromechanical Systems (MEMS) by their nature as sensors and actuators are inherently coupled systems that are sensitive to their environment. Therefore, simulating and understanding these influences on the MEMS device’s performance is critical to a successful design. Such simulations require a complex design environment that allows model construction, detailed physical simulation, reduced-order system simulation, and verification. Since these devices almost always interact with IC circuitry, the system level models must, in general, be intergratible with well-established VLSI circuit simulation environments. Also, MEMS are particularly sensitive to package interactions and thus the ability to simulate coupled package interactions are required. In addition to these technical requirements, a MEMS CAD environment must meet several market requirements in order to grow and evolve. This paper examines these requirements and the current state of CAD for MEMS.
Flow Induced Vibration of Tube-Bundles: Numerical Experiment Approach
Authors: Kaplounov Saveliy M. , Frolov Konstantin V. , Valles Natali G.
Published: June 2008

Development of effective analysis of the complex excitation mechanism with special attention to the complicated interaction of vortex shedding and fluid-elastic excitation is the most important problem in designing of different heat exchangers for prevention intensive vibration and construction damage of tube-bundles at present. Common approach proposed in this report is based on the use of Modernized Discrete Vortex Method (MMDV) and corresponding theoretical investigations of hydroelastic instability worked out by authors. MMDV makes it possible to define the working regime parameters, to reproduce in details the main resonance peak (common smooth curve) of tube system and to clear up the transition of the system in the zone of stability loss with further definition of stability region borders.
Adaptive Time-Discontinuous Galerkin Methods for Acoustic Scattering in Unbounded Domains
Authors: Thompson Lonny L. , He Dantong
Published: June 2008

Comprehensive adaptive procedures with efficient solution algorithms for the time-discontinuous Galerkin space-time finite element method (DGFEM) including high-order accurate nonreflecting boundary conditions (NRBC) for unbounded wave problems are developed. Sparse multi-level iterative schemes are developed to solve the resulting system equations for the interior hyperbolic equations coupled with the first-order equations associated with auxiliary functions in the NRBC. The iterative strategy requires only a f ew iterations per time step to resolve the solution to high accuracy. Further cost savings are obtained by diagonalizing the mass and boundary damping matrices. In this case the algebraic structure decouples the diagonal block matrices giving rise to an unconditionally stable explicit iterative method. An h-adaptive space-time strategy is employed based on the superconvergent patch recovery (SPR) technique, together with a temporal error estimate arising from the discontinuous jump between time steps. For accurate data transfer (projection) between meshes, we develop a new superconvergent interpolation (SI) method. Numerical studies of transient scattering demonstrate the accuracy, reliability and efficiency gained from the adaptive strategy.
The Customer-Foundry Relationship in MEMS Manufacturing
Authors: Foster John S. , Heaton Monteith G.
Published: June 2008

MEMS industry has seen mixed success over the last decade or so. Today, there are only a limited number of MEMS products available on the market, notably airbag accelerometers, desktop inkjet print heads and pressure sensors for automotive and biomedical applications. Despite major infusion of funds in other applications, such as optical telecommunications, RF, and biomedical/microfluidics, these efforts have failed to produce working MEMS in high volumes. The net result is that MEMS have not yet lived up to their anticipated promise.
Self-Excited Vibration of Cross-Shaped Tube Bundle in Cross Flow
Authors: Inada Fumio , Nishihara Takashi , Yasuo Akira , Morita Ryo , Sakashita Akihiro , Mizutani Jun
Published: June 2008

Cross-shaped tube bundle is proposed for a lower plenum structure in a next generation LWR. Vibration response of cross-shaped tube bundle in cross flow has been measured in water tunnel tests. First, small-scale test was conducted. Tests were conducted with 3×3 flexible tubes as well as single flexible tube in rigid tube bundle. The flexible tubes could vibrate in lift, drag, and torsional direction. The effect of arrangements of tube bundle and the natural frequency ratio of bending and torsional vibrations were considered. Second, a large-scale test was conducted for only one case to check the effect of Reynolds number, in which Reynolds number was 10 times larger than that of small-scale test. In all the cases, large amplitude vibration could appear when the flow velocity became larger than a critical value, and a self-excited vibration was found to occur. The nondimensional critical gap velocity of the large-scale test agreed well with that of the small-scale test, which suggested that the effect of Reynolds number was not so large. A design guideline to prevent self-excited vibration was proposed for cross-shaped tube bundle.
Turbulence-Induced Fluid Dynamic Forces Acting on Cross-Shaped Tube Bundle in Cross Flow
Authors: Nishihara Takashi , Inada Fumio , Yasuo Akira , Morita Ryo , Sakashita Akihiro , Mizutani Jun
Published: June 2008

A cross-shaped tube bundle with dense arrangement may be designed for a lower plenum structure in a next generation LWR, though the characteristics of flow-induced vibration of this type of tube bundle remain virtually unknown. In this study, turbulence-induced fluid dynamic forces acting on a cross-shaped tube bundle with a dense arrangement subject to cross flow were measured by water tunnel tests with two types of scale models. One is a small-scale model to measure local fluid dynamic forces and their correlation length in the lift and drag direction. The other is a large-scale model to investigate the effect of the Reynolds number on fluid dynamic forces in the lift, drag and torsional directions. Free oscillation tests with another small-scale model were also conducted to measure vibration amplitude by random excitation force. In conclusion, the following results were obtained. Vortex-induced vibration cannot arise in the cross-shaped tube bundle, since a typical peak corresponding to periodic vortex shedding was not observed in power spectral density for fluid excitation force. Power spectral densities of fluid dynamic forces in the drag, lift and torsional directions have mutually similar properties and they are hardly dependent on the Reynolds number. The experimental results were compiled into dimensionless correlation equations composed of the power spectral density for the local fluid excitation force and its correlation length. They are useful for evaluating the random vibration amplitude. The estimated amplitudes of turbulence-induced vibration by the correlation equation coincide with those of the experimental results obtained by the free-oscillation tests.
Parametric Studies of the Turbulence Response of Heat Exchanger Tubes in Loose Supports
Authors: Hassan M. A. , Weaver D. S. , Dokainish M. A.
Published: June 2008

This paper reports the results of the numerical simulation of a loosely-supported heat exchanger tube excited by turbulence. The effect of support clearance, support geometry, and flow orientation are investigated. The finite element method is utilized to model the vibrations and impact dynamics. Three different friction models are examined to account for the tube/support friction forces. Issues regarding the efficiency and accuracy of the different techniques are discussed. Tube response and tube/support interaction parameters, such as the impact force, the contact ratio, and most importantly, the integrated product of the contact force and the sliding distance (work rate), are presented. The study indicates that some flow orientations and support geometries provide favourable support conditions for higher tube sliding motion against its support and therefore, potentially greater wear rates under service conditions.
Abdominal Aortic Aneurysm Wall Stresses After Endovascular Repair
Authors: Di Martino Elena S. , Makaroun Michel S. , Vorp David A.
Published: June 2008

The early benefits of an endovascular approach to abdominal aortic aneurysm (AAA) treatment has been reported by many authors [1,2]. One of the major advantages is that endovascular repair of AAA (EVAR) as opposed to traditional open surgery, is not a major abdominal surgery. EVAR has been shown to be associated with a death rate comparable to that of surgical repair [3]. In short term follow-up, EVAR is associated with fewer complications and a more rapid recovery [2]. On the contrary very limited data is available on long term follow-up of EVAR patients. Graft-related secondary interventions affect a consistent percentage of the treated cases. The EUROSTAR study [4] recently reported 13% of reintervention in 15.4 months. Our surgical unit reported 20.6% across 48 months in a recent review of 242 cases [3]. The frequence and type of reintervention, whose principal cause is endoleak or perigraft flow, requires careful consideration.
Stochastic Simulation for Crash and Other Performance Improvements: How to Balance Value and Cost
Authors: Kamarajan Jawahar , Forrest Marlon
Published: June 2008

Stochastic simulation is the technique of including the uncertainties into a numeric model. The value of stochastic simulation has been emphasized in literature through different applications in product development process. These applications include simulation of several product performance attributes including crashworthiness, safety, durability and comfort. The comparative cost of running stochastic simulation is usually an order higher than traditional deterministic analysis. However, if properly applied, the value obtained through this technology far exceeds than that through deterministic methods. The higher cost implies that the value has to be clearly defined, measured and balanced against the additional investment. The objective of this paper is to outline a framework for setting up guidelines for stochastic simulation as applied to product development process. Discussions are made on how the model complexity and model accuracy strongly influence the value obtained from stochastic simulation.
Simulations of Synaptic Transmission Using Lattice Boltzmann Methods
Authors: Mahmoudi Mehrak , Zamankhan Piroz , Polashenski William
Published: June 2008

The nervous system remains one of the least understood biological structures due in large part to the enormous complexity of this organ. A theoretical model for the transfer of nerve impulses would be valuable for the analysis of various phenomena in the nervous system, which are difficult to study by experiments. The central nervous system is composed of more than 100 billion neurons, through which information is transmitted via nerve impulses. Nerve impulses are not immediately apparent since each impulse may be blocked during transmission, changed from a single impulse into repetitive impulse, or integrated with impulses from other neurons to form highly intricate patterns. In the human central nervous system, a neuron secretes a chemical substance called a neurotransmitter at the synapse, and this transmitter in turn acts on another neuron to cause excitation, inhibition, or some other modification of its sensitivity.
Effects of Loading Conditions and Types of Motion on PWR Fuel Rod Cladding Wear
Authors: Joulin T. P. , Gue´rout F. M. , Lina A. , Moinereau D.
Published: June 2008

The objective of this study was to investigate the effects of types of motion and loading conditions on the wear of Pressurized Water Reactor (PWR) fuel rod cladding made of Zircaloy-4 in contact with a grid support cell. Fretting-wear tests, for various combinations of motion and preload, were conducted at 310°C and 11.7 MPa using primary circuit water chemistry. Wear coefficients, derived from three-dimensional profilometry, were used to assess the severity of the wear process. The types of motion and the loading conditions were found to have a significant interdependent effect on fuel rod wear coefficients. Scanning Electron Microscope (SEM) examinations were performed on the worn fuel rod cladding specimens to identify wear mechanisms.
An Evaluation of Two Methods for Producing Intermetallic Microchannels
Authors: Paul Brian K. , Hasan Hadi , Dewey Tyler , Alman David , Wilson Richard D.
Published: June 2008

Microtechnology-based Energy and Chemical Systems (MECS) offer opportunities for portable power generation, distributed heat pumps, hydrogen separation for automotive fuel cells, on-site waste remediation and point-of-use chemical synthesis. In order to realize many of these applications, it is recognized that new techniques must be developed for producing microchannels within refractory materials. Material requirements include high-temperature resistance, chemical inertness and low-cost microfabrication. Advances in multilayer ceramics have allowed the microlamination of microreactor structures from ceramic tape. The tapes are formed in the green state and subsequently bonded through a sintering process. Problems include sagging, porosity, and volumetric shrinkage which can lead to dimensional instability. Intermetallics are another class of refractory materials which may hold some promise for high-temperature microchannel development. In this paper, several proposed methods of forming microchannel arrays in aluminide intermetallics are evaluated. These methods have the advantage of eliminating volumetric shrinkage due to binder removal. Results show that some NiAl systems may be suitable for microchannel designs. Issues to be addressed include cost, volumetric shrinkage due to phase changes or other creep-related phenomena incurred during phase changes.
Reduced Order Modeling of Limit Cycle Oscillation for Aeroelasticity Systems
Authors: Beran Philip S. , Lucia David J. , Pettit Chris L.
Published: June 2008

Limit-cycle oscillations of a nonlinear panel in supersonic flow are computed using a reduced-order aeroelastic model. Panel dynamics are governed by the large-deflection, nonlinear, von Ka´rma´n equation as expressed in low-order form through a Galerkin approximation. The aerodynamics are described by the Euler equations, which are reduced in order using proper orthogonal decomposition. The coupled system of equations is implicitly time integrated with second-order temporal accuracy to predict limit-cycle oscillation (LCO) amplitude, and linearly analyzed to predict LCO onset. The fluid is synchronized with the structure in time through subiteration, using only 18 degrees of freedom to describe the aeroelastic system. The Jacobian employed in the fully implicit analysis is of equivalently low rank, enabling rapid analysis. Using the reduced order model, LCO onset is predicted directly at a computational cost of approximately 400 time steps with a high accuracy verified by full-order analysis.
Aeroelastic Modeling of Active Twist Rotorblades Using Particle-Wake Aerodynamics and Non-Linear Beam Structural Dynamics
Authors: Opoku Daniel G. , Nitzsche Fred , Cheng Tao , Cesnik Carlos E. S.
Published: June 2008

An overview of the initial development of SMARTROTOR — a code for active aeroelastic aeroacoustic analysis of rotorcraft — is presented. SMARTROTOR interfaces a particle-wake panel method code with an active non-linear mixed variational intrinsic beam element code. In addition, a Ffowcs Williams-Hawkings equation-based acoustic component was developed for SMARTROTOR. The theory behind each component is reviewed. The method for aeroelastic coupling of the aerodynamic and structural components is presented. Sample acoustic results are presented for a model scale rotor. Sample aeroelastic results are presented for the NASA/ARMY/MIT Active Twist Rotor in hover. Future plans for SMARTROTOR, including acoustic and vibration studies, are discussed.
A Process Management System for Collaborative Manufacturing
Authors: Chung Moon Jung , Kwon Patrick , Pentland Brian , Kim Sangchul
Published: June 2008

A new approach to enacting processes “on the fly” by the participants is proposed for collaborative manufacturing. This approach allows the selection and planning of processes at a higher level as mutiple participants around the world can theoretically engage in planning the processes. Reconfigurable manufacturing system in such scenario means the selection of an appropriate sequence of processes, the process planning of the selected processes and the assignment of appropriate resources to carry out the processes. To achieve that, it requires a new method of representing, sharing and executing process information. In addition, the representation of organizations providing the services and their resources is the prerequisite to the problems we intend to resolve. Thus, rather than applying it to develop a new process planning, this paper proposes this system to connect, share, and reconfigure the network of manufacturing and design companies who are collaborating for a common project. Our system called MIDAS provides functionalities for the representation of processes including alternatives, the planning of resources and the execution of process. Moreover, MIDAS uses XML to encode the process grammar, constraints and other business, design and manufacturing logic, facilitating scalability required for large-scale collaboration.
A Numerical Modelling of Stator-Rotor Interaction in a Turbine Stage With Oscillating Blades
Authors: Gnesin V. I. , Kolodyazhnaya L. V. , Rzadkowski R.
Published: June 2008

In real flows nonstationary phenomena connected with the circumferential non-uniformity of the main flow and those caused by oscillations of blades are observed only jointly. An understanding of the physics of the mutual interaction between gas flow and oscillating blades, and the development of predictive capabilities is essential for improved overall efficiency, durability and reliability. In the study presented the algorithm proposed involves the coupled solution of 3D unsteady flow through a turbine stage and dynamic problem for rotor blades motion by action of aerodynamic forces without separating of outer and inner flow fluctuations. The partially integrated method involves the solution of the fluid and structural equations separately, but information is exchanged at each time step, so that solution from one domain is used as boundary condition for the other domain. 3D transonic gas flow through the mutually moving stator and rotor blades with periodicity on the whole annulus is described by the unsteady Euler conservation equations, which are integrated using the explicit monotonous finite-volume difference scheme of Godunov-Kolgan. The structure analysis uses the modal approach and 3D finite element model of a blade. The blade moving is assumed to be constituted as a linear combination of the first natural modes of blade oscillations with the modal coefficients depending on time. There has been performed the calculation for the last stage of the steam turbine. The numerical results for unsteady aerodynamic forces due to stator-rotor interaction are compared with results obtained with taking into account the blades oscillations. It has investigated the mutual influence of both outer flow nonuniformity and blades oscillations. It has shown that amplitude-frequency spectrum of blade oscillations contains the high frequency harmonics, corresponding to rotor moving past one stator blade pitch, and low frequency harmonics caused by blade oscillations and flow nonuniformity downstream from the blade row. Moreover, the spectrum involves the harmonics which are not multiple to the rotation frequency.
Analysis of Fluid-Structure Interaction of an Elastic Blade in Cascade
Authors: Leung R. C. K. , Lau Y. L. , Si R. M. C.
Published: June 2008

A time-marching numerical model for the analysis of fluid-structure interaction caused by oncoming alternating vortices has been developed by Jadic et al. (1998). Its applicability to analyzing realistic fluid–structure interaction problems has successfully been established in a recent experimental work of a flat plate in a circular cylinder wake (Lau et al. 2002). Using the model, So et al. (1999) have predicted that, under the excitation of oncoming Karman vortex street (KVS) vortices, an elastic airfoil/blade in inviscid uniform flow exhibits two types of fluid–structure resonance, namely aerodynamic and structural resonance. Aerodynamic resonance is of pure aerodynamic origin and occurs with rigid airfoil/blade excited at normalized frequency parameter c/d = 0.5, 1.5, 2.5 etc., where c is the blade chord and d is the streamwise separation between two neighboring vortices. For an elastic airfoil/blade, as a result of coupled fluid–structure interaction, structural resonance occurs at a normalized frequency close to the natural frequency in vacuo of the airfoil/blade. The occurrence of fluid-structure resonance has also been shown critical in noise generation process (Leung & So 2001). The present study extends the scope of the analysis to fluid–structure interactions occurring in axial–flow turbomachine cascade. When the flow is passing through the rotor, it generates wakes containing KVS vortices behind the rotor blades. The convecting wake will induce perturbations on the downstream stator blades at a wake passing frequency (Rao 1991). Such wake–blade interaction is important in determining the fatigue life of the blades and noise generation of the cascade. The cascade analysis starts with modeling the two-dimensional turbine stator by five high–loading blades evenly separated by s in inviscid uniform flow. Oncoming KVS vortices are released upstream to represent the passing wake originating from the rotor, and are allowed to pass through the stator blades. The blade pitch to blade chord ratio s/c and normalized frequency parameter c/d are important parameters of the problems. Fluid–structure interactions are fully resolved by the same numerical technique (Jadic et al. 1998, So et al. 1999). The combined effects of s/c and c/d on the aerodynamic and structural responses of the central blade are studied and discussed.
Vortex-Induced Vibration of a Three-Body Launch Vehicle During Ascent
Authors: Dotson Kirk W. , Engblom William A.
Published: June 2008

Launch vehicles composed of three bodies can experience the shedding of vortices due to strong crossflow acceleration towards the center body, or core. Upon formation, the vortices obstruct the freestream flow, which diverts the local angle of attack towards the opposite side of the core, and a new pair of vortices are formed. This alternate vortex-pair shedding can induce significant pitch structural responses during transonic flight. Computational fluid dynamics (CFD) simulations have been used to illustrate the phenomenon and to generate forcing functions for structural dynamic analyses. Structural responses from these analyses are in good agreement with flight responses. This success suggests that CFD can be used for preflight predictions of the phenomenon. It also indicates that CFD can be used to supplement wind tunnel data when the test instrumentation does not adequately resolve the alternate vortex-pair shedding.
Effect of Aerodynamic Loads on Dynamic Stability of Slender Launch Vehicle Subjected to an End Rocket Thrust
Authors: Ohshima Tsukasa , Sugiyama Yoshihiko
Published: June 2008

This paper deals with dynamic stability of a slender launch vehicle subjected to aerodynamic loads and an end rocket thrust. The flight vehicle is simplified into a uniform free-free beam subjected to an end follower thrust. Two types of aerodynamic loads are assumed in the stability analysis. Firstly, it is assumed that two concentrated aerodynamic loads act on the flight body at its nose and tail. Secondly, to take account of effect of unsteady flow due to motion of a flexible flight body, aerodynamic load is estimated by the slender body approximation. Extended Hamilton’s principle is applied to the considered beam for deriving the equation of motion. Application of FEM yields standard eigen-value problem. Dynamic stability of the beam is determined by the sign of the real part of the complex eigen-values. If aerodynamic loads are concentrated loads that act on the flight body at its nose and tail, the flutter thrust decreases by about 10% in comparison with the flutter thrust of free-free beam subjected only to an end follower thrust. If aerodynamic loads are distributed along the longitudinal axis of the flight body, the flutter thrust decreases by about 70% in comparison with the flutter thrust of free-free beam under an end follower thrust. It is found that the flutter thrust is reduced considerably if the aerodynamic loads are taken into account in addition to an end rocket thrust in the stability analysis of slender rocket vehicle.
Experiments on the Active Control of Multiple Wave Types in Fluid Filled Piping Systems
Authors: Kiyar M. Baris , Johnson M. E. , Fuller C. R.
Published: June 2008

This paper presents active control approaches for the control of structure borne and fluid borne waves in piping installations. At low frequencies the vibration in a fluid filled pipe travels dominantly as a fluid wave, bending waves, a shear wave and a compressive wave in the shell. Although one shell wave may be responsible for the majority of the vibration transmission into supporting structures it is still necessary to control all the waves since discontinuities in the system re-couple all of the wave types. A closed circuit fluid filled piping system, driven by a pump, is used as a test rig. A multi-channel filtered X-LMS feedforward active control system is used to drive a number of electromagnetic actuators attached to the pipe. Reference signal are taken from sensors on the pump and on the pipe. Error signals are taken from accelerometers and pressure sensors on the pipe. Using a set of vibration and pressure sensors both the power flow and amplitudes of the wave types are determined before and after control and the results from various combinations of actuator and sensor locations are presented. It is shown that structural actuators can be used to control all of the wave types.
An Active Flow Distortion Control System for Serpentine Inlets
Authors: Anderson Jason M. , Burdisso Ricardo , Ng Wing
Published: June 2008

An active flow control system for reducing distortion in serpentine inlets was developed using non-intrusive microphones as feedback sensors. While the serpentine inlet can provide large benefits to an air vehicle by reducing its overall size and therefore weight, it unfortunately delivers a non-uniform (spatially-distorted) flow to the compressor due to the formation of a secondary flow created by separation of the turbulent boundary layer in the aggressive turn. An active means of controlling distortion has been developed using an array of micro air jet vortex generators. It was hypothesized that microphones in the vicinity of the distorted flow would record higher amplitudes pressure fluctuations compared to those microphones in the vicinity of the undistorted flow. Experiments showed that the difference between the microphone readings in these two flow regimes was correlated to the distortion level. This difference in microphone signals was then used as feedback in a PID control system that regulated spatial distortion levels during steady flight conditions, as well as sudden ramps in aircraft speed.
Multibranch and Period Tripling Flutter
Authors: Bendiksen O. O.
Published: June 2008

This paper discusses two nonlinear phenomena of relevance in transonic flutter analysis and testing: (1) The possible appearance of more than one flutter mode (branch) in the aeroelastic response, for certain transonic Mach numbers at high mass ratios; and, (2) the possibility of bifurcations to subharmonic flutter at low mass ratios. In the first instance, the superposition principle breaks down and flutter may not necessarily occur when the first aeroelastic eigenvalue crosses into the right half-plane. In the second instance, the nonlinearities open up a new route to flutter, whereby the reduced frequency of the critical aeroelastic mode is lowered into the unstable range through a period-tripling bifurcation. Neither behavior can be understood within the framework of classical linear aeroelasticity.
How Microimaging Technology Is Transforming the Field of Skeletal Genetics
Authors: Turner Charles H.
Published: June 2008

Microcomputed tomography (microCT) is emerging as the technique of choice for skeletal genetics research. The goal of these studies is to identify genes that modulate bone strength and skeletal biomechanics. Many studies use animal models, namely rats and mice. To fully characterize the skeletal phenotype, one must determine the size, shape, and microstructure of the bones preferably in three dimensions. In what follows are three examples of how μCT has been used to illuminate genetic effects on bone structure.
Current Waveform Optimization for Low Noise Permanent Magnet Motors
Authors: Jiao Guandong , Rahn Christopher D.
Published: June 2008

During torque production, the varying magnetic fields inside an electric motor excite vibration that radiates acoustic noise. In consumer applications, this noise can influence the perceived product quality. Noises from propulsion and auxiliary electric motors on naval vessels create an acoustic signature that increases detectability. The dominant noise occurs at twice the electrical frequency (2E). For permanent magnet (PM) machines, the attraction between the rotor permanent magnets and the stator iron causes a radial force that varies sinusoidally around the stator. The stator coil currents generate a rotating magnetic field that produces rotor torque. This paper develops a new commutation strategy for PM machines that uses higher stator currents to minimize 2E noise by reducing radial force ripple without sacrificing torque. An analytical model is developed that predicts rotor torque and radial force ripple as functions of the stator currents. Based on this model, the phase currents are optimally commutated to maintain constant torque production and reduce force ripple. The optimal commutation is numerically investigated on a small PM motor using ANSYS FEA. The ANSYS results show a 30% reduction in force ripple at no load.
Limit Cycle Stability Reversal via Singular Perturbation and Wing-Flap Flutter
Authors: Dessi Daniele , Mastroddi Franco
Published: June 2008

A three degrees of freedom aeroelastic typical section with control surface is theoretically modeled including nonlinear springs and augmented states for linear unsteady aerodynamic description. The system response is determined by time marching of the governing equations by using a standard Runge-Kutta algorithm in conjunction with a ‘shooting method’ to find out stable and unstable limit cycles along with stability reversal in the neighborhood of the Hopf bifurcation. Furthermore, the equations of motion are analyzed by a singular perturbation technique, specifically, by using a normal form method. Approximate analytical expressions for amplitudes and frequencies of limit cycles are obtained and the terms which are responsible of the nonlinear system behavior are identified.
Digital Holographic PIV for 3D Flow Measurement
Authors: Pan Gang , Meng Hui
Published: June 2008

We have developed a simple digital holographic PIV system for 3D measurement of turbulent and multiphase flow. This system records in-line holograms of tracer particles directly on a digital camera and reconstructs the 3D particle field numerically. Using a novel complex amplitude-based method, we are able to overcome the depth of focus problem and the speckle noise problem associated with the low resolution of digital sensors and the in-line holographic setup. In this paper we will give detailed description of our system, and present the preliminary result of the benchmark experiment using a water jet.
A Study of Aerodynamics Around Rotating Blades in a Lawnmower Deck
Authors: Hagen P. A. , Chon W. , Amano R. S.
Published: June 2008

The objective of this study is to investigate the flow behavior within a triple-blade lawnmower deck. The test section was constructed for velocity measurement with an open bottom and side-discharge. Velocity measurements were collected at several different tangential and axial sections inside the deck. The flow behaviors are observed using Laser Doppler Velocimetry (LDV) and a high-speed video camera capturing 2000 frames per second. Several different visualization techniques have been attempted: particle feeding, water vapor injection, tuft method, and others. To further enhance the experimental accuracy, fresh sod was fed into the system simulating normal cutting conditions. Along with the extensive velocity analysis, strain and static pressure were also examined at various surface locations along the blade using linear strain gages, piezoresistive pressure transducers, and Finite Element Analysis (FEA) methods. Validation of the above analyses was performed using Computational Fluid Dynamics (CFD) investigation. It has been observed that the deck and blade configurations share equal significance in the resultant flow profiles.
Finite Element Analysis of a Proposed New Express Car Wheel Design
Authors: Gagarin Gregory , Lonsdale Cameron , Pilch James , Dedmon Steven
Published: June 2008

This paper describes the engineering development work associated with a new wheel design intended for use under a proposed new, 256,000 pounds gross rail load (GRL) express car to be run at speeds up to 110 mph. Initial project assumptions are reviewed, and the new car’s proposed combination disc/tread braking system is described. Several assumed braking scenarios, based upon different thermal loading scenarios including a grade braking sequence to be experienced by the proposed new car in service, were used to determine the braking (thermal) load inputs for the finite element analysis (FEA) work. Wheel stress and temperature results from the various FEA computer simulations are reviewed and discussed in the context of wheel suitability and safety. Recommendations for future work are also discussed.
Computer Controlled Braking System for Amtrak High Speed Trainsets
Authors: Hesser Kenneth R. , Gagarin Gregory A.
Published: June 2008

The new Amtrak High Speed Trainsets used in ACELA Express service on the Northeast Corridor are equipped with an advanced microprocessor controlled braking system with full pneumatic control back-up protection. The system is designed to provide high reliability, to prioritize high levels of electric braking from power cars on each end of the trainset and to fully blend electric braking effort with the pneumatic friction braking effort of the entire trainset. This type of control which optimizes power conservation through regenerative braking and decreases wear and thermal stress on friction brake components is similar to that used on the German Railways ICE trainsets but is totally new and unique to North American inter-city rail vehicles. This paper will describe the system, special components and performance of this equipment.
Train-to-Train Impact Test: Analysis of Structural Measurements
Authors: Tyrell David , Severson Kristine , Perlman A. Benjamin , Rancatore Robert
Published: June 2008

This paper describes the results of the train-to-train impact test conducted at the Transportation Technology Center in Pueblo, Colorado on January 31, 2002. In this test, a cab car-led train, initially moving at 30 mph, collided with a standing locomotive-led train. The initially moving train included a cab car, three coach cars, and a trailing locomotive, while the initially standing train included a locomotive and two open-top hopper cars. The hopper cars were ballasted with earth such that the two trains weighed the same, approximately 635 kips each. The cars were instrumented with strain gauges, accelerometers, and string potentiometers, to measure the deformation of critical structural elements, the longitudinal, vertical, and lateral car body accelerations, and the displacements of the truck suspensions. The test included test dummies in the operator’s seat of the impacted locomotive, in forward-facing conventional commuter passenger seats in the cab car and first coach car, and in intercity passenger seats modified with lap and shoulder belts in the first coach car. During the train-to-train test, the cab car overrode the locomotive; the underframe of the cab car sustained approximately 22 feet of crush and the first three coupled connections sawtooth buckled. The short hood of the locomotive remained essentially intact, while there was approximately 12 inches of crush of the windshield center post. There was nearly no damage to the other equipment used in the test. The measured response of the trains compare closely with predictions made with simulation models.
On the Application of Magneto-Rheological Fluid Technology for Improving Rail Vehicle Dynamics
Authors: Ahmadian Mehdi
Published: June 2008

The primary purpose of this paper is to review the fundamentals, concepts, and merits of new technologies that hold a promise for helping the railroad industry in its missions. The author hopes that this paper will be the first of a series of papers that will be devoted to reviewing new technologies that are on the horizon and can benefit the rail industry, in a manner similar to the current papers that report on the progress of different aspects of transit and passenger cars, locomotives, and freight cars. The fundamental difference between this paper and current papers is that it will be devoted to new technologies that are in a more distant horizon (10–15 years), as opposed to the more immediate future developments that are covered in current papers. The first technology that will be highlighted is the magneto-rheological (MR) technology that has received a tremendous amount of attention in the past five years in the transportation industry, in particular for automotive applications. This paper will provide an overview of MR technology and its common applications, and provide some fruits for thoughts on how MR technology can be used in the rail industry.
Nonlinear Tapping-Tip Dynamics in Atomic Force Microscopy
Authors: Lee Soo Il , Raman Arvind , Hu Shuiqing , Howell Stephen W. , Reifenberger Ron
Published: June 2008

Tapping or intermittent contact atomic force microscopy (AFM) is widely used scanning probe techniques for high resolution imaging, manipulation and nanolithography. The presence of van der Waals forces and nanoscale impacts render highly nonlinear the dynamics of the AFM microcantilever while it operates in the tapping mode. A comprehensive nonlinear analysis of the nonlinear dynamics of AFM microcantilevers tapping on a nanostructure using the theoretical and computational tools of modern nonlinear dynamics has not yet been presented. Also, a rational connection between certain features of the tip-sample interaction potential and the nonlinear response has not been established satisfactorily. To address this problem, we have combined both experimental and nonlinear computational analysis of the tapping response of a microcantilever as a function of the excitation frequency. We show that this approach enables a comprehensive understanding of the nonlinear dynamic behavior observed in AFM experiments.
Development of Multi-Layered Composite PZT Thin Films for Active Sliders in Hard Disk Drives
Authors: Tagawa Norio , Kitamura Ken-ichi , Mori Atsunobu
Published: June 2008

This paper describes the development of novel PZT thin films for active sliders in hard disk drives. So far, it is common that single-layered thin films are used as micro-actuators for conventional PZT thin films such as sol-gel or sputtered thin films. In this study, however, the novel composite PZT thin films are developed. The feature is that sol-gel PZT thin film is deposited on sputtered PZT thin film fabricated on Pt/Ti bottom electrode. These multilayered composite PZT thin films are found to have the higher (111) preferred orientation as well as better P-E hysteresis loop characteristics than not only sol-gel PZT thin films but also sputtered PZT thin films. Furthermore, the piezoelectric strain constant d31 for the novel PZT thin films is identified to be 189 × 10−12m/V. This value is 2.0 times higher than that for conventional PZT thin films and it is found that the novel PZT thin films have good piezoelectric properties.
Three Dimensional PDMA Assembly: Design, Process, and Applications
Authors: Liu C. , Chen J. , Zou J. , Fan Z.
Published: June 2008

This paper discusses a recent three-dimensional assembly process called the Plastic Deformation Magnetic Assembly (PDMA) method. The PDMA method allows three dimensional micromechanical structures to be realized efficiently using surface micromachining and wafer-scale, post-sacrificial-release assembly. We will discuss the principle of the PDMA method, along with the design methodology. The PDMA process has been used for a number of applications, including vertical micro RF inductors, micromachined hot wire anemometers, artificial lateral line sensors, and two dimensional neuron probes. The process for these applications will be discussed to illustrate the usefulness of the PDMA process.
Thermal, Electrical, and Thermoelectric Measurements by Scanning Probe Microscopy
Authors: Miner Andrew C. , Chapp Michael , Li Deyu , Majumdar Arun
Published: June 2008

This work brings together aspects of scanning thermal microscopy (SThM) and scanning spreading resistance microscopy (SRM) into a single tool for thermoelectric measurement. The measurement tool presented here allows simultaneous electrical and thermal measurement of samples using a probe tip of radius on the order of 50 nm. Thermal and mechanical design allow topographic resolution on the order of 4Å while minimizing detrimental heat flow from the probe to sample. This tool integrates sensors allowing for heat flux measurement and control, enabling a variety of thermal, electrical and thermoelectric measurements. Preliminary thermal and electrical measurements of bismuth telluride nanowire arrays demonstrate the capabilities of this scanning probe design.
Characterization of the Crystallization and Grain Growth of Amorphous, Silicon Rich, Low Stress Silicon Nitride
Authors: Olson James M.
Published: June 2008

Stoichiometric silicon nitride (Si3N4) serves a variety of functions in semiconductor manufacturing. The intrinsic component of the residual stress of a sub-set of this material, so-called low stress nitride (LSN), is a function of the excess Si present in the lattice. In microscopic electro-mechanical systems (MEMS), this material is used as an etch-stop, insulating material and foundation layer for a variety of complicated structures. Under a variety of processing conditions, localized regions of LSN are susceptible to crystallization. In some cases, the crystallization event may form a region of low electrical resistance leading to electrical shorts in MEMs devices and other problems. The crystallization event is explained by a reduction in thermodynamic free energy brought about by the presence of a potential energy barrier lowering catalyst. Catalysts are shown to include but are not limited to inhomogeneities in the distribution of dopant species and seed particles located at the free-surface or interface between the LSN and a capping layer. Following crystallization, the growth front propagates by precipitation of excess Si ahead of the growing crystalline region. As in all grain growth/crystallization events, the event is driven by time and temperature.
Design and Characterization of a MEMS Piezoresistive Cochlear-Like Acoustic Sensor
Authors: White Robert D. , Grosh Karl
Published: June 2008

The mammalian cochlea achieves excellent acoustic transduction though the use of mechanical signal processing. The device presented in this paper mimics the structure of the cochlea with a micromachined array of nearly 3000 0.34 μm thick silicon beams suspended between two wafer-high ducts. Piezoresistive strain gauges are incorporated into the beams to produce 38 channels of realtime frequency information. Device mechanical and electrical models are presented. Initial mechanical measurements in air demonstrate good agreement with predicted frequency sensitive and response amplitude. Device sensitivity in air is tentatively measured to be 30 mm/s of beam center velocity response per Pascal of input pressure, corresponding to a predicted piezoresistor sensitivity of 7000 ppm/Pa. This gives an expected achievable resolution of 250 μParms in a 100 kHz band in air. Note that this differs from the intended operating mode of the transducer, which is in fluid over a 20 kHz band.
Design and Analysis of an Electro-Thermally Driven Long-Stretch Micro Drive With Cascaded Structure
Authors: Hsu Chen-Peng , Tai Wen-Chuan , Hsu Wensyang
Published: June 2008

A single micro actuator usually can provide only limited output force and displacement. Therefore, proper integration of several basic actuators into an arrayed structure becomes an attractive way to magnify the output. Here an electro-thermally driven large-stretch micro drive (LSMD) with cascaded compliant structure and compact size (about 2000μm ×500μm) is designed and analyzed. Two kinds of materials, polysilicon and electroplated nickel, are used in finite element simulations. From simulations, several design parameters are found to have significant influence on the output displacements. The simulated output displacements can achieve over 100μm and 200μm for polysilicon-made and nickel-made LSMDs respectively. Larger out-stretching displacements are feasible by proper choice of design parameters. Preliminary fabrication and testing results of nickel-made LSMDs are also presented.