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2007

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Articles 1 - 30 of 455

Full-Text Articles in Mechanical Engineering

Fully Dense Aluminum-Rich Aluminum Copper Oxide Powders For Energetic Formulations, Demitrios Stamatis Dec 2007

Fully Dense Aluminum-Rich Aluminum Copper Oxide Powders For Energetic Formulations, Demitrios Stamatis

Theses

The thermite reaction between Al and CuO is well known and highly exothermic. For a conventional thermite mixture comprising mixed metal and oxide powders, this reaction is rate limited by the slow heterogeneous mass transfer at the metal and oxide interface. The relatively low reaction rate and a difficult ignition have restricted practical applications for this reaction. For newly developed, nano-composed thermites, the interface area can be substantially increased resulting in a much higher reaction rate and a new range of possible applications. Nanocomposite Al-CuO materials are produced using a technique referred to as arrested reactive milling. Regular metal and ...


Ignition Of Metal Powder By Electrostatic Discharge Stimulation, Ervin Beloni Dec 2007

Ignition Of Metal Powder By Electrostatic Discharge Stimulation, Ervin Beloni

Theses

Energetic formulations with metal fuel additives are extensively used in propellants, explosives, pyrotechnics, and incendiaries. Currently, replacement of regular metal powders with nanocomposite metal-based materials is being considered. Such nanocomposite reactive materials are capable of very high reaction rates while maintaining the high combustion enthalpies characteristic of metals. However, such novel reactive nano-materials are often highly sensitive to impact, friction, and electrostatic discharge, making them difficult to handle. In particular, their high electrostatic discharge sensitivity (ESD) was reported. While ESD testing is very common and standardized, the mechanisms of powder ignition by electric spark remain unclear. This project is aimed ...


Design Of Gait Rehabilitation System, Andriy Pletenetskyy Dec 2007

Design Of Gait Rehabilitation System, Andriy Pletenetskyy

Theses

This thesis describes the conceptual design of an innovative robotic rehabilitation machine whose purpose is to help in the recovery of people with motor function disabilities. The machine is smaller, simpler and cheaper than current solutions on the market yet it delivers same functionality.

The conceptual development of the gait rehabilitation system also features a human model with average anthropometric dimensions that allows better visualization and understanding of the actual machine operation. The human model is kinematically coupled to the machine and the whole assembly presents a complex mechanism that closely simulates gait training session.

Three-dimensional modeling and analysis techniques ...


Phase Transfer In A Collision Between A Droplet And Solid Spheres, Zheng Shen Dec 2007

Phase Transfer In A Collision Between A Droplet And Solid Spheres, Zheng Shen

Theses

The hydrodynamics of a liquid droplet impinging on a particle is of direct relevance to many engineering applications. The mechanism of heat and mass transfer during the droplet solid collision is essential to the design and operation of many industrial systems. However, very limited systemic research is available to describe the droplet impact on hot solid spheres.

This paper aims to establish a systematic investigation of phase transfer due to the droplet-solid impact, by both experimental and modeling approaches. The targeted phase transfer includes the surface attachment, mass of vaporization, heat transfer to droplet and its partition between vaporization and ...


Incorporating Grain Size Effects In Taylor Crystal Plasticity, Bradley S. Fromm Dec 2007

Incorporating Grain Size Effects In Taylor Crystal Plasticity, Bradley S. Fromm

Theses and Dissertations

A method to incorporate grain size effects into crystal plasticity is presented. The classical Hall-Petch equation inaccurately predicts the macroscopic yield strength for materials with non-equiaxed grains or materials that contain unequal grain size distributions. These deficiencies can be overcome by incorporating both grain size and orientation characteristics into crystal plasticity theory. Homogenization relationships based on a viscoplastic Taylor-like approach are introduced along with a new function, the grain size and orientation distribution function (GSODF). Estimates of the GSODF for high purity α-titanium are recovered through orientation imaging microscopy coupled with the chord length distribution. A comparison between the new ...


Bio-Surfaces And Geometric References For A Standardized Biomechanical Design Methodology For Mass Customization, Kimberly A. Jensen Dec 2007

Bio-Surfaces And Geometric References For A Standardized Biomechanical Design Methodology For Mass Customization, Kimberly A. Jensen

Theses and Dissertations

This dissertation presents a method for the design of customizable products that interface with the human body. The method presented involves first, a consistent method of capturing and representing the human model so that the model can be used with CAx tools and solid modeling techniques. Second, it provides a design methodology based on feature structure planning and assembly modeling that provides a consistent structure to the design process so that it can be reused and parameterized. Third, a strategy for identifying parametric variables that are referenced to the human body is introduced. The core of this method is the ...


Reducing Curvature In Complex Tool Paths By Deviating From Cam-Produced Tool Paths Within A Tolerance Band, George Benjamin Naseath Dec 2007

Reducing Curvature In Complex Tool Paths By Deviating From Cam-Produced Tool Paths Within A Tolerance Band, George Benjamin Naseath

Theses and Dissertations

This thesis develops an algorithm to decrease high-curvature sections in tool paths for complex parts to achieve shorter machining times resulting in higher production rates. In the research sample cases, the algorithm decreased machining times by 1% to 9% for design-induced sections of high curvature and by 16% to 75% for CAM induced ripples using high path tolerances. High-curvature sections in tool paths are caused by complex part geometry, noise, and discontinuities in the model. The curvature is decreased by deviating the tool path within an allowable path tolerance. The feedrate along the tool path is directly related to the ...


Laminar Flow In Mini-Fluidics Channels Assembly And Its Application In Zebra Fish Embryo Research, Radek Glaser Dec 2007

Laminar Flow In Mini-Fluidics Channels Assembly And Its Application In Zebra Fish Embryo Research, Radek Glaser

Radek Glaser

A Mini-Fluidics system was designed to facilitate the muscle growth of the Zebra Fish embryos. This experimental device is made of peristaltic pump, inflow/outflow manifolds, fluid storage tank, series of valves and flexible pipes and the main plate with six mini channels. These closed channels provide pathways for an extremely laminar flow. The Zebra Fish embryos are placed in the channels and exposed to the forces present in the fluid.


College Of Engineering Senior Design Competition Fall 2007, University Of Nevada, Las Vegas Dec 2007

College Of Engineering Senior Design Competition Fall 2007, University Of Nevada, Las Vegas

Senior Projects (COE)

Part of every UNLV engineering student’s academic experience, the senior design project stimulates engineering innovation and entrepreneurship. Each student in their senior year chooses, plans, designs, and prototypes a product in this required element of the curriculum. A capstone to the student’s educational career, the senior design project encourages the student to use everything learned in the engineering program to create a practical, real world solution to an engineering challenge.

The senior design competition helps to focus the senior students in increasing the quality and potential for commercial application for their design projects. Judges from local industry evaluate ...


). Size Dependency Of The Elastic Modulus Of Zno Nanowires: Surface Stress Effect, Guofeng Wang, Xiaodong Li Dec 2007

). Size Dependency Of The Elastic Modulus Of Zno Nanowires: Surface Stress Effect, Guofeng Wang, Xiaodong Li

Faculty Publications

Relation between the elastic modulus and the diameter (D) of ZnOnanowires was elucidated using a model with the calculated ZnOsurface stresses as input. We predict for ZnOnanowires due to surface stress effect: (1) when D>20nm, the elastic modulus would be lower than the bulk modulus and decrease with the decreasing diameter, (2) when 20nm>D>2nm, the nanowires with a longer length and a wurtzite crystal structure could be mechanically unstable, and (3) when D<2nm, the elastic modulus would be higher than that of the bulk value and increase with a decrease in nanowire diameter.


One-Dimensional Radial Flow Turbomachinery Performance Modeling, Robert John Pelton Dec 2007

One-Dimensional Radial Flow Turbomachinery Performance Modeling, Robert John Pelton

Theses and Dissertations

The Two-Element In Series (TEIS) and Two-Zone models have been used successfully for over twenty years to model test data for radial flow compressors and pumps. The models can also be used to predict the performance of new machines provided that the model inputs can be accurately specified. Unfortunately, use of the TEIS and Two-Zone models as a predictive tool has been limited because an accurate and broadly applicable method of predicting the modeling parameters, etaA, etaB, chi and d2p does not exist. Empirical models have been developed to predict the TEIS and Two-Zone modeling parameters based on a large ...


Experimental Verification Of Source Temperature Modulation Via A Thermal Switch In Thermal Energy Harvesting, Robin Mccarty, D. Monaghan, Kevin P. Hallinan, Brian Sanders Dec 2007

Experimental Verification Of Source Temperature Modulation Via A Thermal Switch In Thermal Energy Harvesting, Robin Mccarty, D. Monaghan, Kevin P. Hallinan, Brian Sanders

Mechanical and Aerospace Engineering Faculty Publications

This paper provides a description of research seeking to experimentally verify the effectiveness of a thermal switch used in series with TE devices for waste heat recovery for constant and variable source heat input and for variable source thermal capacitance (mass). Using an experimental set-up comprised serially of a fixed heat source, a variable thermal resistance air gap serving as a thermal switch, a thermoelectric device and a heat sink, the time-averaged power output to power input ratios improved up to 15% and 30% respectively for constant and variable heat input in certain design space conditions. The experimental results, as ...


A Bubble-Powered Micro-Rotor: Conception, Manufacturing, Assembly And Characterization, Jonathan Kao, Xiaolin Wang, John Warren, Jie Xu, Daniel Attinger Dec 2007

A Bubble-Powered Micro-Rotor: Conception, Manufacturing, Assembly And Characterization, Jonathan Kao, Xiaolin Wang, John Warren, Jie Xu, Daniel Attinger

Daniel Attinger

A steady fluid flow, called microstreaming, can be generated in the vicinity of a micro-bubble excited by ultrasound. In this paper, we use this phenomenon to assemble and power a microfabricated rotor at rotation speeds as high as 625 rpm. The extractible power is estimated to be of the order of a few femtowatts. A first series of experiments with uncontrolled rotor shapes is presented, demonstrating the possibility of this novel actuation scheme. A second series of experiments with 65 µm rotors micromanufactured in SU-8 resin is then presented. Variables controlling the rotation speed and rotor stability are investigated, such ...


Investigation Of Vorticity Confinement As A High Reynolds Number Turbulence Model, Nicholas F. Lynn Dec 2007

Investigation Of Vorticity Confinement As A High Reynolds Number Turbulence Model, Nicholas F. Lynn

Doctoral Dissertations

Vorticity Confinement (VC) is a computational technique used to compute fluid flows with thin vortical regions in an accurate and efficient manner. Recent results have shown that it accurately computes the turbulent wake behind blunt bodies at large Reynolds numbers. Physically, these flows are dominated by thin vortices that convect downstream with the flow, which accounts for the important higher-order velocity statistics. These thin vortices are artificially dissipated with traditional methods, whereas VC can accurately compute them.

VC consists of a set of discrete equations with the confinement appearing as a source term in the discretized momentum equations. The term ...


Athermal Resistance To Interface Motion In The Phase-Field Theory Of Microstructure Evolution, Valery I. Levitas, Dong Wook Lee Dec 2007

Athermal Resistance To Interface Motion In The Phase-Field Theory Of Microstructure Evolution, Valery I. Levitas, Dong Wook Lee

Valery I. Levitas

A method of introducing an athermal resistance to interface propagation for the Ginzburg-Landau (GL) approach to the first-order phase transformations (PTs) is developed. It consists of introducing oscillating fields of stresses (due to various defects or a Peierls barrier) or a jump in chemical energy. It removes some essential drawbacks in GL modeling: it arrests experimentally observed microstructures that otherwise converge to a single phase, and it reproduces rate-independent stress hysteresis. A similar approach can be applied for twinning, dislocations, and other PTs (e.g., electric and magnetic).


Virtual Modeling And Verification Of Air-Ride Truck Seat Using Multibody Dynamics For Whole Body Vibration Evaluation, Devdutt Nandkishore Shende Dec 2007

Virtual Modeling And Verification Of Air-Ride Truck Seat Using Multibody Dynamics For Whole Body Vibration Evaluation, Devdutt Nandkishore Shende

Masters Theses

To aid the tuning and optimization of the truck seat design to specific trucks and road profiles during the design phase, this study presents the development and validation of a virtual seat model. This study also assess the utility of the model for whole body vibrations evaluation.

The virtual dynamic seat model was developed in MSC. ADAMS/VIEW. The critical elements like the suspension mechanism, the airspring, dampers and seat cushion were modeled using tested data. To validate the performance of the virtual model, prototype tests were performed using the MTS 6-axis simulator. The modeling process was targeted to achieve ...


Novel Numerical Approaches For The Resolution Of Direct And Inverse Heat Transfer Problems, Gregory Evan Osborne Dec 2007

Novel Numerical Approaches For The Resolution Of Direct And Inverse Heat Transfer Problems, Gregory Evan Osborne

Doctoral Dissertations

This dissertation describes an innovative and robust global time approach which has been developed for the resolution of direct and inverse problems, specifically in the disciplines of radiation and conduction heat transfer.

Direct problems are generally well-posed and readily lend themselves to standard and well-defined mathematical solution techniques. Inverse problems differ in the fact that they tend to be ill-posed in the sense of Hadamard, i.e., small perturbations in the input data can produce large variations and instabilities in the output. The stability problem is exacerbated by the use of discrete experimental data which may be subject to substantial ...


Estimation Of Surface Temperature And Heat Flux Using Embedded Thermocouples, Jeffrey Daniel King Dec 2007

Estimation Of Surface Temperature And Heat Flux Using Embedded Thermocouples, Jeffrey Daniel King

Masters Theses

This thesis investigates several new methods for estimating surface temperature and heat flux based on thermocouples embedded within the interior of a test article. The test apparatus was a Mach 2 axisymmetric rocket nozzle with probes embedded at depths of 1/8” and 1/4” from the inner surface of the nozzle at the throat and exit locations. Three methods for numerically estimating temperature and heat flux at the surface of the nozzle were considered: a one-thermocouple slab-coordinate method, a two-thermocouple slabcoordinate method, and a finite-element analysis (FEA) based on a one-dimensional cylindrical coordinate method. Comparisons between the methods, as ...


Inverse Kinematics Based On Fuzzy Logic And Neural Networks For The Wam-Titan Ii Teleoperation System, Joong-Kyoo Park Dec 2007

Inverse Kinematics Based On Fuzzy Logic And Neural Networks For The Wam-Titan Ii Teleoperation System, Joong-Kyoo Park

Masters Theses

The inverse kinematic problem is crucial for robotics. In this paper, a solution algorithm is presented using artificial intelligence to improve the pseudo-inverse Jacobian calculation for the 7-DOF Whole Arm Manipulator (WAM) and 6-DOF Titan II teleoperation system. An investigation of the inverse kinematics based on fuzzy logic and artificial neural networks for the teleoperation system was undertaken. Various methods such as Adaptive Neural-Fuzzy Inference System (ANFIS), Genetic Algorithms (GA), Multilayer Perceptrons (MLP) Feedforward Networks, Radial Basis Function Networks (RBF) and Generalized Regression Neural Networks (GRNN) were tested and simulated using MATLAB. Each method for identification of the pseudo-inverse problem ...


Analysis Of Electrical Activity Of The Core Muscles Exposed To Whole-Body Vibrations While Driving A Tractor Trailer Using Electromyography Device, Harini Mangavelli Dec 2007

Analysis Of Electrical Activity Of The Core Muscles Exposed To Whole-Body Vibrations While Driving A Tractor Trailer Using Electromyography Device, Harini Mangavelli

Masters Theses

Lower back disorders are observed to be the most significant problem for most of the industrial workers who operate commercial vehicles. A person sitting can have 40% higher load on the lumbar spine than when standing. Human core muscles related to spinal movement respond to rapid potential motions related to external acceleration inputs of vibration in order to control body posture, the increased muscle tension can result in muscle fatigue. The over use of muscles, vibration exposure combined with dehydration of spine and long term seating can lead to lower back pain and axial discomfort to the drivers. Electromyography (EMG ...


Design Of An Active Orthotic Device For Joint Management., Steven Clayton Anderson Dec 2007

Design Of An Active Orthotic Device For Joint Management., Steven Clayton Anderson

Electronic Theses and Dissertations

Existing treatment programs and procedures are incapable of addressing the complications encountered with patients who experience spasticity and hypertonia related joint contractures. Current passive therapy procedures and devices are only capable of managing the extent of joint contractures on patients with chronic and acute onset severe neurological disorders. The project was conceived as a means to develop an active device that is capable of adapting to the state of the joint to mange the extent of contractures and to permit consideration for the prevalence of spastic activity episodes and hypertonia. The project focused on the design of the physical prototype ...


Experimental Study Of Coal Pyrolysis And Gasification In Association With Syngas Combustion, Wei-Hsin Chen Nov 2007

Experimental Study Of Coal Pyrolysis And Gasification In Association With Syngas Combustion, Wei-Hsin Chen

Wei-Hsin Chen

No abstract provided.


Apparatus For Removal Of Minute Particles From A Surface Using Thermophoresis To Prevent Particle Redeposition, Susan Davis Allen Nov 2007

Apparatus For Removal Of Minute Particles From A Surface Using Thermophoresis To Prevent Particle Redeposition, Susan Davis Allen

Mechanical Engineering - Daytona Beach

A method and apparatus for removing minute particles from a surface of a sample are provided that prevent redeposition of the particles onto the surface. By combining thermophoresis with laser assisted particle removal (LAPR), the methods and apparatus remove minute particles (for example, micrometer and nanometer sizes) and assure that they will not redeposit.


High-Speed Three-Dimensional Shape Measurement System Using A Modified Twoplus- One Phase-Shifting Algorithm, Song Zhang, Shing-Tung Yau Nov 2007

High-Speed Three-Dimensional Shape Measurement System Using A Modified Twoplus- One Phase-Shifting Algorithm, Song Zhang, Shing-Tung Yau

Song Zhang

This paper describes a high-resolution, real-time, three-dimensional shape measurement system using the modified two-plus-one phase-shifting algorithm. The data acquisition speed is as high as 60frames∕s with an image resolution of 640×480pixels per frame. Experiments demonstrated that the system was able to acquire the dynamic changing objects such as facial geometric shape changes when the subject is speaking, and the modified two-plus-one phase-shifting algorithm can further alleviate the error due to motion. Applications of this system include manufacturing, online inspection, medical imaging, compute vision, and computer graphics.


Numerical Study Of Fully Developed Laminar And Turbulent Flow Through Microchannels With Longitudinal Microstructures, Kevin B. Jeffs Nov 2007

Numerical Study Of Fully Developed Laminar And Turbulent Flow Through Microchannels With Longitudinal Microstructures, Kevin B. Jeffs

Theses and Dissertations

Due to the increase of application in a number of emerging technologies, a growing amount of research has focused on the reduction of drag in microfluidic transport. A novel approach reported in the recent literature is to fabricate micro-ribs and cavities in the channel wall that are then treated with a hydrophobic coating. Such surfaces have been termed super- or ultrahydrophobic and the contact area between the flowing liquid and the solid wall is greatly reduced. Further, due to the scale of the micropatterned structures, the liquid is unable to wet the cavity and a liquid meniscus is formed between ...


Designing And Manufacturing Microelectronic Packages For High-Power Light-Emitting Diodes, Brian Wright, Jianbiao Pan, Richard Savage Nov 2007

Designing And Manufacturing Microelectronic Packages For High-Power Light-Emitting Diodes, Brian Wright, Jianbiao Pan, Richard Savage

Industrial and Manufacturing Engineering

A new microelectronic package was designed for a high-power light-emitting diode (LED). The objective was to build a package that enables the LED to operate with currents as high as 2 Amps. An innovative thin-film interface has been developed to electrically connect the cathode of the LED die to a 22AWG Cu wire. This thin-film interface is wirebondable and solderable, and consists of three layers: Au, Ni93/V7, and Si. Four 1 mil Au wirebonds, supporting 2A of maximum current, connect the Au thin-film to the LED die cathode. Sn96Ag4 solder is used for connecting the Ni93/V7 thin-film to ...


Undergraduate Research: Experiences From A Three-Year Project, Peter Schuster, Charles Birdsong Nov 2007

Undergraduate Research: Experiences From A Three-Year Project, Peter Schuster, Charles Birdsong

Mechanical Engineering

There are significant benefits of research for the involved undergraduate student. These include exposure to advanced topics, introduction to research methods, and direct interaction with faculty and other students. Faculty and institutions benefit as well by the increased interaction with students – fresh eyes in research projects, more energized research groups, and more engaged alumni. However, there are some challenges in designing a research program to work primarily with undergraduates. These include the students’ lack of exposure to advanced topics, short tenure on the project, and potentially lower commitment to the results. There are a number of ways to address these ...


In-House Development Of Scheduling Decision Support Systems: Case Study For Scheduling Semiconductor Device Test Operations, Tali Freed, K. H. Doerr, T. Chang Nov 2007

In-House Development Of Scheduling Decision Support Systems: Case Study For Scheduling Semiconductor Device Test Operations, Tali Freed, K. H. Doerr, T. Chang

Industrial and Manufacturing Engineering

Most manufacturing processes can benefit from an automated scheduling system. However;: the design of a fast, computerised scheduling system that achieves high-quality results and requires minimal resources is a difficult undertaking. Efficient .. scheduling of a semiconductor device test facility requires an information system that provides good schedules quickly. Semiconductor device testing-is the last stage of the long semiconductor manufacturing process, and therefore. is subjected to customer service pressures. The cost of an off-the-shelf computerised scheduling system may he prohibitive for many companies. In addition, many companies are taken aback by other characteristics of off-the-shelf scheduling systems, such as code confidentiality ...


Fabrication Of Functionally Graded 3a/5a Zeolites By Electrophoretic Deposition, X. Wang, E. A. Olevsky, E. Bruce, M. B. Stern, D. T. Hayhurst Nov 2007

Fabrication Of Functionally Graded 3a/5a Zeolites By Electrophoretic Deposition, X. Wang, E. A. Olevsky, E. Bruce, M. B. Stern, D. T. Hayhurst

Industrial and Manufacturing Engineering

Functionally graded zeolites of molecular sieve type 3A and 5A are deposited by electrophoretic deposition (EPD) from acetone suspension with 8% volume concentration of n-butylamine as particle charging agent. The EPD characteristics of both 3A and 5A suspensions are studied. Functionally graded zeolite 3A/5A deposits are obtained at 200 V DC. Energy dispersive X-ray dispersion (EDX) analysis results confirm the graded structure. The deposited zeolites are also analysed by scanning electron microscopy (SEM). The factors influencing the deposition process are discussed.


Thermal Testing Of Building Insulation Materials, Eoghan Frawley, David Kennedy Nov 2007

Thermal Testing Of Building Insulation Materials, Eoghan Frawley, David Kennedy

Articles

This article explores the testing of building insulation materials and the development of a suitable testing apparatus.