bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Myoelectric Signals Using System Identification Techniques
Authors: Bingham Jeffrey T. , Schoen Marco P.
Published: April 2008

Human muscle motion is initiated in the central nervous system where a nervous signal travels through the body and the motor neurons excite the muscles to move. These signals, termed myoelectric signals, can be measured on the surface of the skin as an electrical potential. By analyzing these signals it is possible to determine the muscle actions the signals elicit, and thus can be used in manipulating smart prostheses and teleoperation of machinery. Due to the randomness of myoelectric signals, identification of the signals is not complete, therefore the goal of this project is to complete a study of the characterization of one set of hand motions using current system identification methods. The gripping motion of the hand and the corresponding myoelectric signals are measured and the data captured with a personal computer. Using computer software the captured data are processed and finally subjected to several system identification routines. Using this technique it is possible to construct a mathematical model that correlates the myoelectric signals with the matching hand motion.
Dependence of Radiation Effects on System Configuration and Physical Properties in Bridgman Growth of Optical Crystals
Authors: Ma Y. , Zheng L. L.
Published: April 2008

Optical crystals, such as YAG, GGG, sapphire, CaF2, are of high melting temperature. As a result, the radiative heat transfer during the crystal growth process is an important factor to influence the temperature distribution and hence the quality of as-grown crystals. However, the radiation effect is complicated in the optical crystal growth system. It depends on the system geometry and properties, such as the spectral transmittance of the oxide crystals, and the emissivity of the ampoule and the furnace inner wall. In this paper, the analysis of heat transfer coupled with radiation effect has been carried out using one-dimensional thermal resistance network method for optical crystals growth. The results show that radiation plays a significant role in the heat transfer and temperature distribution during growth, and the subsequent quality of the grown crystal. Two-dimensional numerical simulations have also been conducted and the simulation results have been compared with the one-dimensional results. Effects of system configuration and physical properties on crystal quality are also analyzed and discussed.
Modeling and Characterization of the Scratch Drive Actuator
Authors: Bronson Jessica R. , Allen James J. , Wiens Gloria J.
Published: April 2008

This paper presents the characterization of scratch drive actuators (SDAs) built using Sandia National Laboratories (SNL) SUMMiTTM V micromachining process. Experimental data is used to characterize the output step size as a function of input voltage. This data is correlated to an analytical model in an effort to better understand and predict the stepping motion of these devices. The experimental results match well with the predictions from the model. Experimental data shows that the step sizes are on the order of 10 nm, and force estimates show that one SDA is capable of producing forces in excess of 100 μN for each step.
Fabrication and Characterization of Vertical Travel Linear Microactuator
Authors: Toda Risaku , Yang Eui-Hyeok
Published: April 2008

This paper describes design, fabrication and characterization of a proof-of-concept vertical travel linear microactuator designed to provide out-of-plane actuation for high precision positioning applications in space. The microactuator is designed to achieve vertical actuation travel by incorporating compliant beam structures within a SOI (Silicon on Insulator) wafer. Device structure except for the piezoelectric actuator is fabricated on the SOI wafer using Deep Reactive Ion Etch (DRIE) process. Incremental travel distance of the piezoelectric actuator is adjustable at nanometer level by controlling voltage. Bistable beam geometry is employed to minimize initial gaps between electrodes. The footprint of an actuator is approximately 2 mm × 4 mm. Actuation is characterized with LabVIEW-based test bed. Actuation voltage sequence is generated by the LabVIEW controlled power relays. Vertical actuation in the range of 500 nm over 10-cycle was observed using WYKO RST Plus Optical Profiler.
Supersonic Compression Stage Design and Test Results
Authors: Lawlor Shawn P. , Hinkey John B. , Mackin Steven G. , Henderson Scott , Bucher Jonathan , Brown Paul M. , Pudupatty Ram
Published: April 2008

Ramgen Power Systems, Inc. (RPS) is developing a family of high performance supersonic compressors that combine many of the aspects of shock compression systems commonly used in supersonic flight inlet design with turbo-machinery design practices employed in conventional axial and centrifugal compressor design. The result is a high efficiency compressor that is capable of single stage pressure ratios in excess of those available in existing axial or centrifugal compressors. A variety of design configurations for land-based compressors utilizing this system have been explored. A proof-of-concept system has been designed to demonstrate the basic operational characteristics of this family of compressors when operating on air. The test unit was designed to process ~1.43 kg/s and produce a pressure ratio across the supersonic rotor of 2.25:1. The theory of operation of this system will be reviewed along with selected results from initial performance tests.
Effects of Splashing Droplets on Spray Cooling Processes
Authors: Kizito John P. , Vander Wal Randy L. , Tryggvason Gretar
Published: April 2008

The present paper reports ongoing work to develop numerical and modeling tools used to investigate the effects of splashing droplets on spray cooling processes and to determine characteristic non-dimensional parametric dependence for practical fluids and conditions. In particular, we present data that will delineate conditions towards control of the impingement dynamics of droplets upon a heated substrate germane to practical situations.
Analysis of Left Hand Segmental Rotations During Golf Swing
Authors: Teu Koon Kiat , Kim Wangdo , Fuss Franz Konstantin , Tan John
Published: April 2008

This paper presents a different approach of recording and analysing the swing. The method involved utilizing electrogoniometer (biometrics, UK) to obtain the joint angles throughout the motion and by using Dual Euler velocity analysis, the velocity of the measured segment can be estimated. The results are then processed to ascertain individual segmental contribution to the final club head velocity.
Nucleate Boiling Inside the Evaporator of the Planar Loop Heat Pipe
Authors: Suh Junwoo , Shuja Ahmed , Gerner Frank M. , Henderson H. Thurman
Published: April 2008

The Loop Heat Pipe (LHP) under development is a next generation micro heat transfer device that utilizes the latent heat of a working fluid and has excellent transfer capacity compared with that of standard metallic cooling devices. A typical LHP consists of an evaporator, a reservoir (also called the compensation chamber), vapor and liquid lines, a subcooler, and a condenser. As heat is applied to the evaporator, all of the input energy goes into the evaporation of the liquid in the pores of the primary CPS wick or leak to the bottom. The nucleate boiling, which occurs beneath the primary wick in the evaporator, is a very significant phenomena. It affects critical operating issues, such as dry out of the primary wick. Using a clear evaporator machined from Pyrex glass, the nucleation, which occurred in the evaporator, was studied. De-ionized water was utilized as the working fluid.
Molecular Modeling as a Visualization Tool in Design of DNA Crosslinked Polyacrylamide
Authors: Rafaels Karin , Kerrigan John , Langrana Noshir , Lin David
Published: April 2008

Polymers such as polyacrylamide form a diverse class of biomaterials in use today. The experimental research performed by our group has demonstrated how a critical concentration of crosslinking DNA strands can lead to gel formation in the polyacrylamide. The removal or addition of DNA strands can reverse or significantly increase the stiffness and strength of the gel. DNA is a versatile material for the exploration of nanoscale structures because its hybridization chemistry is very specific. DNA crosslinked gels use end-modified DNA oligonucleotides in the gels. The ability to choose the base sequence in the DNA crosslinks offers an opportunity to engineer the nanoscale structure of this material. However, it is extremely difficult to visualize the sequence of events that occurs when DNA is crosslinked with polyacrylamide. Computer modeling is a tool that enables the researchers to study the structural aspects of the newly engineered DNA crosslinkers. In this study, polyacrylamide gel crosslinked with DNA has been assayed with respect to energy and size using AMBER 7.0 software [1]. Since DNA-crosslinked gels are likely to find a range of applications it is important to know how to tailor the gel composition for a particular application. It is also of interest to know what the composition is that would induce the greatest change in stiffness. The molecular models generated in AMBER survey the mechanical properties of the gel as a function of crosslinker density, polyacrylamide density, and crosslinker length. The structure of an equilibrium state is computed using an explicitly solvated model. Visual inspection of the model determines other mechanical properties of the gel and helps predict chemical interactions. A long-term goal of this work is to use computer assisted modeling techniques to guide the experiments, to predict linker stiffness, and to examine other mechanical properties of the DNA crosslinker.
Deformation and Warpage Analysis of Flat and Hemispherical Center-Anchored Deformable Focusing Micromirror With Structure Depositing Metal Layer
Authors: Lin Meng-Ju , Chang Pen-Lun , Tsai Shang-Wei , Lee Yi-Hsiang
Published: April 2008

Deformable focusing micromirror is one of the important optical MEMS devices. The focusing length is determined by the profile of the micromirror surface. The profile of the micromirror is determined by the devices sizes, material properties, and depositing temperature. However, as the deformation is in the unstable regime, warpage will happen. Therefore, the deformation and warpage of two structure types of center-anchored deformable focusing micromirror are discussed. One is flat plate, and the other is semi-spherical shell. Criteria to determine the warpage condition of centered anchored deformable focusing mirrors of flat and hemispherical structure are obtained. The results show, in general, the thinner plate and the thicker metal layer will cause larger deformation. And the results also show that as the ratio of depositing metal and structure layer thickness increasing, the deformation will reach to a limit value due to the saturation of stress gradient. In warpage discussion, by the criteria from theoretical solution, the result shows when the thickness of depositing metal layer increasing, the temperature which induces warpage condition decreases. And the larger thickness of structure plate will cause the warpage temperature increasing nonlinearly. However, in some structure and depositing metal layer sizes, the focusing mirror would not become warpage, even the depositing temperature increases larger than the melting temperature of metal. The effect of outer radii of focusing micromirror on warpage temperature is also discussed. When the outer radii increasing, the depositing temperature causing warpage decreases fast and reaches a limit value. Compared to the theoretical solution, numerical results of finite element have the same tendency.
Optical Properties of InAs/GaAs Quantum Dots Grown by Epitaxy
Authors: Kuo M. K. , Lin T. R. , Liao B. T. , Yu C. H.
Published: April 2008

Strain effects on optical properties of self-assembled InAs/GaAs quantum dots grown by epitaxy are investigated. A new model based on the theory of linear elasticity is developed to analyze three-dimensional induced strain field. The model takes sequence of fabrication process of quantum-dot into account, where the mismatch of lattice constants between wetting layer and substrate is treated as initial strain first for the heterostructure system without capping material. The obtained total strain field is then treated as initial strain again for the whole heterostructure system with capping material. The computed strain from these two-steps analysis is then used as an input for the electronic band structure calculation. The numerical results show that strain field from this new model has significant difference from the usual model where the sequence of fabrication process is omitted. The strain-induced potential is incorporated into the three-dimensional steady state effective mass Schro¨dinger equation with the aid of the Pikus-Bir Hamiltonian and Luttinger-Kohn formalism. Both the strain field and the solutions of the steady state Schro¨dinger equations are found numerically by using of a commercial finite element package. The energy levels as well as the wave functions of both conduction and valence bands of quantum dots are calculated. Finally, energy of interband optical transitions is obtained in numerical experiments.
Study on 3D Temperature Distribution of Milling Insert With Complex Groove
Authors: Tan Guangyu , Liu Guangjun , Li Guanghui , Rong Yiming (Kevin)
Published: April 2008

About 90% energy generated in the milling process is transferred to heat which makes the temperature to increase. The temperature increase has a correlative relationship with the milling mechanism and milling parameters. The severe temperature increase results in the fracture of milling insert during milling process and reduces the life of the tool. Experiments of milling temperature measurement were conducted to study the temperature field in milling. The heating density function on the tool surface was established. The temperature profile and distribution were shown. A parametric model was established to represent the milling insert with 3D complex groove. Based on a finite element analysis, the temperature field on the milling insert was evaluated and the boundary condition was established by using the heating density function. The study provides a reference for the development and optimization of complex grooves of milling inserts.
A Process Model for Laser Surface Treatment of Plasma Sprayed Coatings
Authors: Wu J. , Choi J. , Zhang S. , Hilmas G.
Published: April 2008

Advanced ceramics are not easily fabricated and consolidated by the plasma spray technique because of their extremely high melting temperature. Zirconium diboride (ZrB2) has been successfully plasma sprayed, but the coatings are quite porous. The high levels of porosity are usually a result of unmelted ZrB2 particles that have been incorporated into the coating during deposition. Applying a laser surface treatment to reduce both the porosity and the coating surface roughness, and to improve the coating quality, is of great interest. A laser based surface treatment technique provides a well-controlled heat input, with minimal or no distortion. In this study, a two dimensional mathematical model is developed to investigate the effects of laser power, beam diameter and level of porosity on the coating quality, incorporating melting, solidification, and evaporation phenomena. A continuum model is used to solve Navier-Stokes equations for both solid and liquid phases. Volume-of-Fluid (VOF) is incorporated to track the free surface. The surface force is incorporated as a body force instead of a boundary condition. The porosity level and surface roughness before and after the laser surface treatment are simulated and compared with experimental results.
Comparison of Numerical and Experimental Methods for Predicting the Efficiency of an Automotive Oil Strainer
Authors: Tekam Sydney M. , Demoulin Marc , Daru Virginie
Published: April 2008

The design and set-up of an oil strainer consist in calculating the pressure drop between the outlet and the inlet of the separator and predicting its efficiency (which is defined for each droplet diameter, as the ratio of oil droplets trapped in the strainer above oil droplets entering the strainer). The efficiency spectra of two separators are evaluated with a measurement bench and a comparison is made with numerical simulation. Efficiency is low –down to an average 3% in some cases. Therefore, it is hard to quantify the accuracy of the methods. Additional tests must be performed with a higher volume flow to increase average efficiency. Nevertheless, the accuracy and the relevance of the numerical method employed are far from prior expectation.
Vibrations and Power Flows in a Coupled Beam System
Authors: Li Wen L. , Bonilha Murilo W. , Xiao Jie
Published: April 2008

Vibrations of and power flows between coupled beams have been the subject of many investigations and various techniques have been developed over years. However, most of these techniques are typically proposed for a specific case that involves a particular kind of boundary conditions and/or connections. In this study, a general analytical method is developed for predicting the vibrations of and power flow between two-coupled beams. The coupling between the beams is generically represented by two (translational and rotational) springs of arbitrary stiffnesses. Thus, many rigid and non-rigid connectors of practical interest can be directly taken into account. In addition, because the beams are elastically restrained at each end, the current method can be universally applied to different boundary conditions by simply varying the stiffnesses of the boundary springs. Numerical results are presented to show the excellent accuracy of the proposed approach.
Self-Assembly of Nanovoids in Solids
Authors: Yu Hui-Chia , Lu Wei
Published: April 2008

Experiments show that vacancies in a solid may coalesce into voids and self-organize into a super-lattice. The voids have diameters around 10 nm and spacing of tens of nanometers. This paper develops a thermodynamic model to explain and simulate the remarkable phenomena. We incorporate free energy of mixing, interface energy and elasticity into a continuous phase field model. It is well known that the total interface energy reduces when the voids grow larger. Simulations show that elastic anisotropy may limit the coarsening. Starting from randomly distributed vacancies, the process of coalescence and void lattice formation demonstrates rich dynamics. Long-range elastic interaction and elastic anisotropy are found to play a significant role that determines the self-assembled super-lattice.
Identifying the Shapes of Coupled Vibrations and Deriving Reduced Order Models for Nonlinear Shafts: A Finite Element-Proper Orthogonal Decomposition Approach
Authors: Georgiou I. T. , Bani-Khaled M. A.
Published: April 2008

The spatial structure of the dynamics of a rotating nonlinear shaft is identified by processing its finite element dynamics by the method of Proper Orthogonal Decompositions. The Proper Orthogonal modes furnish characteristic signatures for the rigid body and the whirling modes of a motion. The pattern of energy distribution over the components of a mode reveals the strength of coupling between rigid body rotations and coupled vibrations. These modes are used to derive a two-degree-of freedom reduced model for the whirling motion of the rotating shaft.
An Experimental Study on Subsurface Mechanical Behavior, Residual Stress, and Microstructure Induced by Process Dynamics in Machining
Authors: Warren A. W. , Guo Y. B.
Published: April 2008

Surface integrity of machined components is critical for product performance in service. Process dynamic parameters, such as cutting speed and the changing contact condition between the tool flank face and machined surface, have a significant influence on surface integrity of a machined surface. Due to the very small scale of surface integrity factors on a machined surface, nanoindentation can be used to determine the surface/subsurface mechanical properties. However, the test data may be significantly influenced by machining induced residual stresses, strain hardening, and microstructure changes. The fundamental relationships between residual stress, microstructure, and nanohardness in the machined surface are yet to be understood. Further, it is not clear how to determine residual stress, at least its nature of tensile or compressive, from the nanoindentation data with the presence of complex residual stress state, strain hardening, and microstructure changes. This study focuses on the effects of cutting speed and machining system damping or rigidity (through varying tool flank wear) on subsurface mechanical state and the basic relationships between residual stress, white layer, and nanohardness. A series of nanoindentation tests were conducted to machined samples with distinct surface integrity by hard turning, grinding, and honing. It was found that white layer increases nanohardness and dark layer decreases nanohardness in subsurface, while strain hardening only slightly increases subsurface hardness. The research results indicate that subsurface residual stress can be qualitatively characterized by the load-displacement curve pattern and its parameters such as slope at initial loading, total depth, residual depth, and the ratio of residual depth to total depth. Residual stress would affect a load-displacement curve shape only at onset of yielding. Microstructure changes would make a significant difference on the characteristics of a load-displacement curve, while strain hardening exerts slight influence on the curve characteristics. In addition, the mechanism of residual stress on indentation depth was explained using a Mohr’s circle.
A Higher-Order Poly-Region Boundary Element Method for Steady Thermoviscous Fluid Flows
Authors: Grigoriev M. . M. , Dargush G. F.
Published: April 2008

In this presentation, we re-visit the poly-region boundary element methods (BEM) proposed earlier for the steady Navier-Stokes [1] and Boussinesq [2] flows, and develop a novel higher-order BEM formulation for the thermoviscous fluid flows that involves the definition of the domains of kernel influences due to steady Oseenlets. We introduce region-by-region implementation of the steady-state Oseenlets within the poly-region boundary element fequatramework, and perform integration only over the (parts of) higher-order boundary elements and volume cells that are influenced by the kernels. No integration outside the domains of the kernel influences are needed. Owing to the properties of the convective Oseenlets, the kernel influences are very local and propagate upstream. The localization becomes more prominent as the Reynolds number of the flow increases. This improves the conditioning of the global matrix, which in turn, facilitates an efficient use of the iterative solvers for the sparse matrices [3]. Here, we consider quartic boundary elements and bi-quartic volume cells to ensure a high level resolution in space. Similar to the previous developments [4–6], coefficients of the discrete boundary integral equations are evaluated with the sufficient precision using semi-analytic approach to ensure exceptional accuracy of the boundary element formulation. To demonstrate the attractiveness of the poly-region BEM formulation, we consider a numerical example of the well-known Rayleigh-Benard problem governed by the Boussinesq equations.
Modeling and Analysis of Membrane Humidifiers for Fuel Cell Applications
Authors: Chen Dongmei , Peng Huei
Published: April 2008

Maintaining proper membrane humidity is crucial to ensure optimal operation of a polymer electrolyte membrane fuel cell, which can be achieved by adding a humidifier to the fuel cell system. A membrane-type humidifier system using the fuel cell exhaust gas to humidify the dry inlet air is studied in this paper. We first develop a thermodynamic model, which captures the crucial dynamic variables of the humidifier, including pressure, flow, temperature and relative humidity of air flows. Steady state simulations are then conducted to optimize the humidifier design. Subsequently, dynamic simulations are performed to predict the behavior of the humidifier during typical transient operations for automotive applications. A simple proportional controller was designed to control the humidifier according to the fuel cell stack operating conditions.
Surface Property Directed Microchannel Flows for Enhanced Mixing
Authors: Mautner Tom
Published: April 2008

It is known that rapid mixing in biosensors is required; however, it is necessary to overcome the inherent diffusion limited mixing of laminar flow. The combined effect of wall temperature and surface property distributions presents a new method to manipulate micro channel flow fields. Simulations are used to investigate the combined effects wall temperature distributions and velocity wall boundary conditions to determine if they are beneficial or counter productive in obtaining uniform flow temperature profiles and enhanced binary fluid mixing. In this work, the lattice Boltzmann (LB) method [1–3] has been used to compute the flow, temperature and material transport in both 2D and 3D configurations
Implementation of High Bandwidth Sensor Arrays Using Feedback Mechanisms
Authors: Suranthiran Sugathevan , Jayasuriya Suhada
Published: April 2008

Proposed in this paper is a new method to implement the high operating bandwidth sensor arrays. In certain control applications, it is necessary that a high bandwidth sensor be used to improve the efficiency of feedback. The design of a single sensor with the desired high bandwidth may not be easy and economically feasible. It is shown that the idea of sensor arrays can be utilized to obtain a cost effective and efficient solution to the problem posed. It is discussed that an effective data fusion scheme is necessary in order to implement the proposed sensor array that consists of low bandwidth pass-band sensors with possible overlapping operating regions. Moreover, we point out that obtaining accurate sensor models may not be always easy in practice and this may make the proposed sensor arrays inapplicable for certain applications. To address this issue, a new implementation scheme that utilizes feedback mechanisms to combine multi-sensor data is developed. The proposed framework is validated using simulation examples.
Improved Modeling of Non-Continuum Heat Transfer During Topographical Imaging With a Heated Atomic Force Microscope Cantilever
Authors: Masters Nathan D. , Ye Wenjing , King William P.
Published: April 2008

Thermal Sensing Atomic Force Microscopy (TSAFM) is a promising new technology for topographical imaging and high density data storage that uses the heat transfer between a heated cantilever and the scanned surface as the sensing mechanism. Due to the small operational scan heights (<300 nm), continuum gas phase heat transfer models (as used in previous studies) cannot accurately describe the actual behavior—affecting the accuracy of data interpretation and design of TSAFM systems. In this study two models (Direct Simulation Monte Carlo and a kinetic theory based macro model) are developed to explore the impact of sub-continuum heat conduction on TSAFM operation and to facilitate improved data interpretation and design.
Reconfiguration of a Rolling Sphere: A Problem in Evolute-Involute Geometry
Authors: Das Tuhin , Mukherjee Ranjan
Published: April 2008

The task of complete reconfiguration of a rolling sphere is recast as a problem in planar geometry. Based on our specific choice of coordinate system, two control points are defined that equivalently represent the configuration of the sphere. Under the applied control inputs, the trajectories of these control points are shown to form an evolute-involute pair. The objective of complete reconfiguration is then captured within integral conditions over the path of the control points. A class of solution to the geometric problem is derived and a three step algorithm for complete reconfiguration is proposed. The solution is computationally in-expensive and is confirmed by simulation results.
Design of a Spatial Linkage Haptic Interface
Authors: Steger John Ryan , Chung Ronald M. , Lin Kevin , Kazerooni Homayoon
Published: April 2008

This paper describes the mechanical and electrical design of a compact high fidelity desktop haptic interface that provides three-degree-of-freedom point-force interaction through a handheld pen-like stylus. The complete haptic device combines a spatial linkage, actuation, power amplification, and control electronics in a standalone package with a footprint similar to that of a notebook computer (33cm × 25cm × 10cm). The procedure used to design the statically balanced spatial linkage is explained and both an inexpensive lightweight plastic version and a high stiffness, high strength, aluminum and stainless steel version are presented. The theory and implementation of sinusoidal encoder interpolation and sinusoidal servo-motor commutation used to achieve high-fidelity haptic simulation is covered for two versions of electronic control hardware: custom hardware based on a digital signal processor (DSP) and an off-the-shelf design based on an embedded PC.
High Speed Ring-Based Distributed Networked Control System for Real-Time Multivariable Applications
Authors: Kim Sunghoon , Kazerooni H.
Published: April 2008

A networked control system (NCS) is a control architecture where sensors, actuators and controllers are distributed and interconnected. It is advantageous in terms of interoperability, expandability, installation, volume of wiring, maintenance, and cost-effectiveness. Many distributed network systems of various topologies and network type have been developed, but NCS systems tend to suffer from such issues as nondeterminism, long network delays, large overheads and unfairness. This paper presents the ring-based protocol, called the ExoNet, and its network architecture which are built to achieve better performance as a distributed networked system. A Cypress transceiver CY7C924ADX is applied to the network as a communication unit. The protocol is based on the transceiver and developed to achieve fast communication and allowable latency for controls with high control loop frequency. Compared with other standard network types such as Ethernet, ControlNet or DeviceNet, the network is characterized by its ring-based architecture, simple message and packet formats, one-shot distribution of control data and collection of sensor data, multi-node transmission, echo of a message, and other features. The network also guarantees determinism, collision-free transmission, relatively small overhead, fairness between nodes and flexibility in configuration. Its analysis and comparison with these network types are also provided and its application on the Berkeley Lower-Extremity Exoskeleton (BLEEX) is described.
Theoretical Model of Electric Field Effects on the Enhancement of Critical Heat Flux
Authors: Yajima Takeshi , Yabe Akira , Maki Hiroshi
Published: April 2008

Critical heat flux enhancement by the electrohydrodynamic (EHD) effect has been analyzed quantitatively based on the increased frequency of liquid-vapor interface oscillations around the edge of the bubble. The majority of heat transfer occurs when the liquid film thickness becomes less than 50 μ m, which only occurs once per period. The main mechanism of heat flux enhancement induced by the EHD effect would be a result of an increase in surface tension due to the effect of electric lines of force. By representing the terms of the forces for a change in curvature and the surface tension resulting from the electric lines of force, the equation of the liquid-vapor instability was obtained and analyzed. Experimentally it has been shown that as the applied voltage increased, the periodic time interval of the thickness change was shortened. This effect reduces the potential for dryout of the liquid film by making the minimum thickness time period shorter. By measuring the pressure oscillation on the boiling surface, the change of the thin liquid film thickness and the dynamic shape of bubbles, the relationship among the pressure, the liquid film thickness and the bubble shape was clarified. Consequently, this model successfully explains the relationship between the applied voltage and the enhancement of the critical heat flux.
Biomechanical Role of Trabecula Networks in the Human Proximal Femur Under Static Loading
Authors: Nakatsuchi Hiroki , Watanabe Naoyuki , Nakatsuchi Yukio , Tadano Shigeru , Moriizumi Tetsuji , Mori Shinichiro , Endo Masahiro
Published: April 2008

Finite element models of human femur were constructed from micro structural data measured by a three-dimensional cone beam CT with the resolution of a 0.35mm cube as a voxel size. The results of static analysis on the assumption with one-legged support standing revealed that the tensile stress in the lateral cortex of the femoral neck and the compressive stress in the medical cortex remarkably increased after removing the trabecula networks. The change of stress distribution means that the trabecula networks would make a contribution to dissipating the concentration of tensile and compressive stress in the region of femoral neck. Therefore, the stress concentration even in static condition will increase the fracture risk of femoral neck as osteoporosis advances.
Modular Distributed Models of Structural Dynamics
Authors: Reichenbach Drew , Radcliffe Clark J. , Sticklen Jon
Published: April 2008

Approaches to engineering design and manufacturing such as integrated design and manufacture and just in time fabrication depend on interaction with and among component supply companies that most often use very diverse technologies. Modular Distributed Modeling (MDM) is a distributed, component-based, agent methodology that is realized following a strong black box approach to modeling. An individual Design Agent (DA) is a virtual product capable of encapsulating both descriptive and model based information about the product it represents. Hierarchically recursive agents for sub-systems and/or components are linked via a communications network to form larger integrated model systems. A two dimensional bridge system structural model is used as an example to illustrate the distributed assembly of structural models from components registered as DA’s on a communications network. Modular Distributed Modeling of system dynamics performs dynamic analysis. This paper presents the methodology required to assemble dynamic structural deflection models provided by internet agents representing structural components. The methodology discussed assembles these component models into the structural dynamic model of an assembly. Using MDM method, models of complex assemblies can be built and distributed while hiding the topology and characteristics of their structural subassemblies. The automated, modular, assembly of structural dynamics models will be derived for discrete, multi-degree-of-freedom structural connections. Discrete connections are important to the assembly of components such as truss and shaft structures where the relationship between component displacements involve discrete, matching, degrees of freedom on components to be assembled. Specific examples of discrete assembly of truss bridge component models will be presented. Specific examples for distributed assembly of component models will be presented. Internet connection permitting, real-time, automated assembly of models and deflection analysis will be performed.
Autoresonant Homeostat Concept for Engineering Application of Nonlinear Vibration Modes
Authors: Babitsky V. I. , Sokolov I. J.
Published: April 2008

Analysis of strongly nonlinear systems revealed an existence of nonlinear modes of vibration with spatial and temporal concentration of energy. The modes can be realised, for example, through intensification of the vibration process by condensing the vibration into a sequence of collisions for impulsive action of the tools to the media being treated or can be as a result of some discontinuity (slackening of a contact, arrival of crack etc.) in the structure. The use of the nonlinear modes to develop useful mechanical work leads to necessity of excitation and control of resonance in ill-defined dynamical systems. This is due to the poorly predictable response of the media being treated. Excitation, stabilisation and control of a nonlinear mode at the top intensity in such systems is an engineering challenge and needs a new method of adaptive control for its realisation. Such a control technique was developed with the use of self-exciting mechatronic systems. The excitation of the nonlinear mode in such systems is a result of artificial instability of mechanical system conducted by positive electronic feedback. The instability is controlled by intelligent identification of the mode and active tracing of the optimal relationship between phase shifting and limitation in the feedback circuitry. This method of control is known as autoresonance. Applications of autoresonant control for development of the new machines are described.
Rapid Distortion of Homogeneous Turbulence Between Cylinders
Authors: Emami Babak , Liu Rui , Ting David S.-K. , Checkel M. David
Published: April 2008

The effects of ‘half-full-half’ cylinders on the distortion of a turbulent flow are experimentally investigated. A single hot-wire anemometry unit is used to measure the stream-wise parameters of the flow. The cylinders are 15.2 cm (6 in) in diameter and 76.2 cm (30 in) in height installed in a closed loop wind tunnel with a 76.2 cm by 76.2 cm (30 in by 30 in) cross section. Turbulent flow with a nominal mean velocity of 7.6 m/s was generated by means of a perforated plate situated at the entrance of the wind tunnel. It was found that the mean velocity increases significantly as the flow passes through the contracting passage created by the cylinders, whereas the rms turbulence intensity decreases about 12% but shows an increase of up to 14% very close to the full cylinder. As the flow was distorted, the Kolmogorov length scales were elongated in the stream-wise direction, resulting in a decrease in the rate of turbulence decay which appears as a decrease in energy dissipation rate. The stream-wise integral length scales also increased due to the elongation of eddies in the stream-wise direction. Also, analysis of the turbulence fluctuating velocity in the frequency domain showed a redistribution of stream-wise turbulence kinetic energy from large to small scales during the distortion.
Modeling of Thermal Joint Resistance of Polymer-Metal Rough Interfaces
Authors: Bahrami M. , Yovanovich M. M. , Marotta E. E.
Published: April 2008

A compact analytical model is developed for predicting thermal joint resistance of rough polymer-metal interfaces in a vacuum. The joint resistance includes two components: i) bulk resistance of the polymer and ii) micro, constriction/spreading resistance of the microcontacts at the interface. Performing a deformation analysis, it is shown that the deformation mode of the polymer asperities is plastic. The required input parameters of the model can be measured in the laboratory and/or found in the open literature. It is observed that the thermophysical properties of the polymer control the thermal joint resistance and the metallic body properties have a second order effect on the thermal joint resistance. A non-dimensional parameter, i.e., ratio of microcontacts over bulk thermal resistances, is proposed as a criterion to specify the relative importance of the microcontacts thermal resistance. The present model is compared with more than 140 experimental data points collected for a selected number of polymers and showed good agreement.
Optimization of Absorption in a Porous Media
Authors: Vadnjal Aleksander , Catton Ivan
Published: April 2008

A majority of past investigations focused on solutions to a specific optimization task with a very limited number of spatial parameters to be varied, usually a fixed geometric configuration, that was tuned in their search for a maximum level of acoustic energy absorption. This approach is a “single-scale” approach yielding an optimum for a certain morphology and flow intensity without giving an explanation for why it was achieved. Without an explanation, there is no guidance on how to change the design to improve its performance. For each new morphology, the experiment, whether real or numerical, needs to be performed again. In the acoustics industry there are countless research studies devoted to this problem. Travkin et al. [1] developed a mathematical basis, using volume averaging theory (VAT), see also Whitaker [2], and models for optimization of a heterogeneous, hierarchical scaled media. The treatment of the optimization process can be applied to any specific hierarchical heterostructure with the aim to optimize its performance. In this work, developments of VAT to describe transport phenomena in heterogeneous media are applied to optimization of acoustic energy absorption by a heterogeneous media. The enhancement of acoustic energy absorption is stated mathematically in a way that the lower scale viscous dissipation and the performance of the total device are incorporated for optimization. The VAT equations derived by Vadnjal and Catton [3] are the basis for a model that successfully describes the non-homogeneous nature of the porous media, allowing optimization of a heterogeneous structure for optimum performance.
An H-Adaptive Finite Element Model for Constructing 3-D Wind Fields
Authors: Wang Xiuling , Pepper Darrell W. , Chen Yitung , Hsieh Hsuan-Tsung
Published: April 2008

Calculating wind velocities accurately and efficiently is the key to successfully assessing wind fields over irregular terrain. In the finite element method, decreasing individual element size (increasing the mesh density) and increasing shape function interpolation order are known to improve accuracy. However, computational speed is typically impaired, along with tremendous increases in computational storage. This problem becomes acutely obvious when dealing with atmospheric flows. An h-adaptation scheme, which allows one to start with a coarse mesh that ultimately refines in high gradients regions, can obtain high accuracy at reduced computational time and storage. H-adaptation schemes have been shown to be very effective in compressible flows for capturing shocks [1], but have found limited use in atmospheric wind field simulations [2]. In this paper, an h-adaptive finite element model has been developed that refines and unrefines element regions based upon velocity gradients. An objective analysis technique is applied to generate a mass consistent 3-D flow field utilizing sparse meteorological data. Results obtained from the PSU/NCAR MM5 atmospheric model are used to establish the initial velocity field in lieu of available meteorological tower data. Wind field estimations for the northwest area of Nevada are currently being examined as potential locations for wind turbines.
Force Analysis of the Film in a COF Chip Mounter’s Loader
Authors: Shaw Dein , Lin H. C.
Published: April 2008

In this study, the tension force distributions in the film of COF cartridge are studied. It is noted that if the tension force on the film is too high, the interface between chip and film cracked. If the force is too low, there is no enough friction force to keep the COF in fix position when the cartridge is on the transportation vehicle. The relative motion between the chips of lower layer and the film of upper layer will cause the fatigue of interface of chips and film. It is also important to note that due to the friction the tension force at any section of the film is different. To fine the force distribution, a method to determine the tension force is developed and only effect of axial direction is considered. The assumption makes the film behave like a string. The results show that the forces on the film are different whenever the film passes a chip underneath.
Non-Newtonian Blood Flow in the Right Coronary Artery
Authors: N’Dri Narcisse A. , Giddens Don P.
Published: April 2008

Understanding blood flow in the circulatory system and how it affects intimal thickening is important with respect to atherogenesis and also for the design of vascular treatment devices such as stents and arterial grafts. While the assumption of Newtonian blood flow in large arteries is widely accepted by many investigators, questions remain unanswered for blood flow in the coronaries. In this study we investigate Non-Newtonian blood flow behavior in both the right and the left coronaries. We use a commercial code (FIDAP) to compare the Newtonian model to four Non-Newtonian models (Power law, Casson, Carreau and Quemada models) widely used in the literature. The coronary geometries were reconstructed from MRI images of human subjects. We found a significant difference in time average WSS between the power law and the Newtonian models. Also a difference in time average WSS is observed for the Quemada model. On the other hand, No significant difference is observed for the Newtonian, Casson and Carreau models.
Development of Systems Engineering Model for Spent Fuel Extraction Process
Authors: Sun Lijian , Royyuru Haritha , Hsieh Hsuan-Tsung , Chen Yitung , Vandegrift George , Copple Jackie , Laidler James
Published: April 2008

The mission of the Transmutation Research Program (TRP) at University of Nevada, Las Vegas (UNLV) is to establish a nuclear engineering test bed that can carry out effective transmutation and advanced reactor research and development effort. Chemical Engineering Division, Argonne National Laboratories (ANL) is in charge the design, modeling, and demonstration of countercurrent solvent-extraction process for treating high-level liquid waste, such as U and Tc. The Nevada Center for Advanced Computational Methods (NCACM) at UNLV is developing a systems engineering model that provides process optimization through the automatic adjustment on input parameters, such as feed compositions, stages, flow rates, etc., based on the extraction efficiency of components and concerned output factors. An object-oriented programming (OOP) is considered. Previously designed Microsoft (MS) Excel macro-based program, Argonne Model for Universal Solvent Extraction (AMUSE) code, based on firm understanding of the chemistry and thermodynamics, is the core module for Uranium Extraction process (UREX). Currently AMUSE is the only available module. The Transmutation Research Program System Engineering Model Project (TRPSEMPro) consists of task manager, task integration and solution/monitor modules. A MS SQL server database is implemented for managing large data flow from optimization processing. Task manager coordinates and interacts with other two modules. Task integration module works as a flowsheet constructor that builds task hierarchy, input parameter values and constrains. Task solution/monitor component presents both final and in-progress outputs in tabular and graphical formats. The package also provides a multiple-run process that executes a design matrix without invoking the optimization module. Experimental reports can be generated through database query and formatting.