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2009

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Articles 1 - 30 of 575

Full-Text Articles in Mechanical Engineering

Ultra-Thin Super High Frequency Two-Port Aln Contour-Mode Resonators And Filters, Matteo Rinaldi, Chiara Zuniga, Chengjie Zuo, Gianluca Piazza Feb 2013

Ultra-Thin Super High Frequency Two-Port Aln Contour-Mode Resonators And Filters, Matteo Rinaldi, Chiara Zuniga, Chengjie Zuo, Gianluca Piazza

Matteo Rinaldi

This paper reports on the demonstration of a new class of ultra-thin (250 nm thick) Super High Frequency (SHF) AlN piezoelectric two-port resonators and filters. A thickness field excitation scheme was employed to excite a higher order contour extensional mode of vibration in an AlN nano plate (250 nm thick) above 3 GHz and synthesize a 1.96 GHz narrow-bandwidth channel-select filter. The devices of this work are able to operate over a frequency range from 1.9 to 3.5 GHz and are employed to synthesize the highest frequency MEMS filter based on electrically self-coupled AlN contour-mode resonators. Very ...


Optimal Synthesis Of Planar Adjustable Mechanisms, Chong Peng Dec 2009

Optimal Synthesis Of Planar Adjustable Mechanisms, Chong Peng

Dissertations

Adjustable mechanisms provide degrees of flexibility while retaining desirable features of one degree of freedom close-loop mechanisms, such as simplicity, stability, and high speed capabilities. By adjusting linkage parameters, additional phases of motions can be achieved using the same hardware. However, an adjustment to the mechanism adds only one or two additional design positions and divides desired positions into "phases", each of which contains only a few positions usually insufficient for industrial applications.

In order to extend the design position limitation of adjustable mechanisms, an optimal synthesis method based on link length structural error is developed and applied to kinematic ...


Motion Coordination And Control In The Development Of A Gait Rehabilitation System, Yazan Ahmad Manna Dec 2009

Motion Coordination And Control In The Development Of A Gait Rehabilitation System, Yazan Ahmad Manna

Dissertations

While most take their ability to walk for granted, some are unable to walk due to any number of pathologies, such as traumatic brain injury (TBI), spinal cord injury (SCI), and Parkinson's disease. Decreased activity has been shown to be associated with rapidly deconditioning. Rehabilitation techniques that afford patients the ability to begin reconditioning through walking sooner may ultimately enhance their return to a better quality of life. To assist the functional recovery of such patients, an appropriate afferent input to the spinal cord will help in the therapy of the patient. Manual training is labor intensive, costly, and ...


Method Of Transferring Strained Semiconductor Structure, Michael Nastasi Dec 2009

Method Of Transferring Strained Semiconductor Structure, Michael Nastasi

Mechanical & Materials Engineering Faculty Publications

The transfer of strained semiconductor layers from one substrate to another substrate involves depositing a multilayer structure on a substrate having surface contaminants. An interface that includes the contaminants if formed in between the deposited layer and the substrate. Hydrogen atoms are introduced into the structure and allowed to diffuse to the interface. Afterward, the deposited multilayer structure is bonded to a second substrate and is separated away at the interface, which results in transferring a multilayer structure from one substrate at least one strained semiconductor layer and at least one strain-induced seed layer. The strain-induced seed layer can be ...


Experimental Study On Viscosity And Phase Segregation Of Al–Si Powders In Microsemisolid Powder Forming, Yufeng Wu, Iver E. Anderson, Thomas A. Lograsso, Gap-Yong Kim Dec 2009

Experimental Study On Viscosity And Phase Segregation Of Al–Si Powders In Microsemisolid Powder Forming, Yufeng Wu, Iver E. Anderson, Thomas A. Lograsso, Gap-Yong Kim

Mechanical Engineering Publications

Semisolid powder forming is a promising approach for near-net shape forming of features in macro-/microscale. In this paper, viscosity and phase segregation behavior of Al–Si powders in the semisolid state were studied with back extrusion experiments. The effects of process parameters including shear rate, extrusion ratio, heating time, and precompaction pressure were analyzed using the design of experiments method. The results showed that the effects of shear rate, extrusion, ratio and heating time were statistically significant factors influencing the viscosity. The semisolid state powders showed a shear thinning behavior. Moreover, microstructure analysis of extruded parts indicated severe phase ...


Degeneration Affects The Structural And Tissue Mechanics Of The Intervertebral Disc, Grace D. O'Connell Dec 2009

Degeneration Affects The Structural And Tissue Mechanics Of The Intervertebral Disc, Grace D. O'Connell

Publicly Accessible Penn Dissertations

The intervertebral disc is comprised of mechanically and structurally unique substructures including the annulus fibrosus and the nucleus pulposus, which function together to support and absorb the large complex spinal loads. Disc degeneration causes drastic changes in the composition and may lead to altered mechanics; however, the changes in the internal mechanical function of the nucleus and annulus are not well understood. Moreover, herniation of nucleus pulposus material through the posterior annulus causes low back pain and may alter the mechanical function of the disc. Discectomy, a procedure to relieve the pain by removing the herniated material; however, the effect ...


Configuration Recognition, Communication Fault Tolerance And Self-Reassembly For The Ckbot, Michael G. Park Dec 2009

Configuration Recognition, Communication Fault Tolerance And Self-Reassembly For The Ckbot, Michael G. Park

Publicly Accessible Penn Dissertations

We present and experimentally verify novel methods for increasing the generality of control, autonomy and reliability for modular robotic systems. In particular, we demonstrate configuration recognition, distributed communication fault tolerance, and the organization and control of self-reassembly with the Connector Kinetic roBot (CKBot). The primary contribution of this work is the presentation and experimental verification of these innovative methods that are general and applicable to other modular robotic systems. We describe our CKBot system and compare it to other similar, state-of-the-art modular robotic systems. Our description and comparison highlights various design developments, features, and notable achievements of these systems. We ...


Efficient Rotation Algorithms For Texture Evolution, Mark W. Esty Dec 2009

Efficient Rotation Algorithms For Texture Evolution, Mark W. Esty

Theses and Dissertations

Texture evolution is a vital component of many computational tools that link structure, properties and processes of polycrystalline materials. By definition, this evolution process involves the manipulation, via rotation, of points in orientation space. The computational requirements of the current methods being used to rotate crystalline orientations are a significant limiting factor in the drive to merge the texture information of materials into the engineering design process. The goal of this research is to find and implement a practical rotation algorithm that can significantly decrease the computation time required to rotate macroscopic and microscopic crystallographic textures. Three possible algorithms are ...


Haptic Displayof Realistic Tool Contact Via Dynamically Compensated Control Of A Dedicated Actuator, William Mcmahan, Katherine J. Kuchenbecker Dec 2009

Haptic Displayof Realistic Tool Contact Via Dynamically Compensated Control Of A Dedicated Actuator, William Mcmahan, Katherine J. Kuchenbecker

Departmental Papers (MEAM)

High frequency contact accelerations convey important information that the vast majority of haptic interfaces cannot render. Building on prior work, we present an approach to haptic interface design that uses a dedicated linear voice coil actuator and a dynamic system model to allow the user to feel these signals. This approach was tested through use in a bilateral teleoperation experiment where a user explored three textured surfaces under three different acceleration control architectures: none, constant gain, and dynamic compensation. The controllers that use the dedicated actuator vastly outperform traditional position-position control at conveying realistic contact accelerations. Analysis of root mean ...


Enhance Diamond Coating Adhesion By Oriented Interlayer Microcracking, Habio Guo, Xingcheng Xiao, Yue Qi, Zhi-Hui Xu, Xiaodong Li Dec 2009

Enhance Diamond Coating Adhesion By Oriented Interlayer Microcracking, Habio Guo, Xingcheng Xiao, Yue Qi, Zhi-Hui Xu, Xiaodong Li

Faculty Publications

In this paper, we report a microcrack toughening mechanism for enhancing the adhesion of diamondcoating. The oriented microcracks were formed within the TiC interlayer to dissipate strain energy and accommodate deformation via the crack opening-closing mechanism, thus enhancing the coating/substrate interfacial toughness. The delamination of diamondcoating was effectively prevented when the parallel microcracks were confined within the interlayer and arrested at interfaces of coating/interlayer/substrate. Density functional theory calculations revealed that the highly anisotropicfracture strength of the TiC phase energetically favors crack initiation and propagation along (100) planes only, which are 54.7° away from the interface. These ...


Self-Organized Nanolayers Of Organosilane Molecules, Ocelio V. Lima Dec 2009

Self-Organized Nanolayers Of Organosilane Molecules, Ocelio V. Lima

Engineering Mechanics Dissertations & Theses

There is a high degree of interest in organic thin films for lightweight, low power, rugged and flexible electronics. Conjugated organic molecules with polycyclic rings are being considered a major enabler of such applications. Due to a surface tension mismatch between the organic molecule with the inorganic support (mainly silicon oxides), molecular packing inside these thin films is often disordered, which suppresses the device performance. There are major efforts focused on modifying the bulk properties, for instance, maximizing orbital overlaps in the solid state, little attention was paid to receive long-range ordered thin films. A novel approach to afford conjugated ...


Development Of A Methodology For Numerical Simulation Of A D C Arc Discharge In A Liquid Dielectric, Christopher James Lewis Dec 2009

Development Of A Methodology For Numerical Simulation Of A D C Arc Discharge In A Liquid Dielectric, Christopher James Lewis

Theses and Dissertations

The majority of literature regarding the numerical simulation of arc discharges in gaseous environments has used a plasma physics approach. Virtually all simulations treat the discharge as an idealized gaseous plasma, which can be described by temperature, pressure, and electric field. This approach can work well if the media is a shielding gas such as Argon; however, the approach does not work well for processes such as underwater welding, EDM, and underwater discharges used to generate high purity particles. The reason these discharges do not have many extensive simulation efforts as described in the literature is because they occur in ...


Energy Dissipation Caused By Asphalt Roadway Gouges For Use In Accident Reconstruction, Charles L. Crosby Dec 2009

Energy Dissipation Caused By Asphalt Roadway Gouges For Use In Accident Reconstruction, Charles L. Crosby

Theses and Dissertations

In reconstruction of on-roadway vehicle accidents, roadway surface gouges and the forces and energy attributed to the related vehicle components become important keys to resolving an accurate accident reconstruction. These roadway gouge forces vary depending upon such factors as surface temperature and the velocity and geometry of the gouging mechanism. Accounting for the forces applied to vehicle components and the energy dissipated from such forces can be helpful in accident reconstruction where supporting data exists. This research documents the force necessary to create a given roadway gouge geometry. Controlled pavement gouging tests were performed using roadway surface temperature and gouging ...


Investigation Into Contact Resistance And Damage Of Metal Contacts Used In Rf-Mems Switches, Kevin W. Gilbert Dec 2009

Investigation Into Contact Resistance And Damage Of Metal Contacts Used In Rf-Mems Switches, Kevin W. Gilbert

Theses and Dissertations

This research examines the physical and electrical processes involved in lifecycle failure of Microelectromechanical (MEMS) Radio-Frequency (RF) cantilever beam ohmic contact switches. Failures of these switches generally occur at the contact, but complete details of performance of microcontacts are difficult to measure and have not been previously reported. This study investigated the mechanics of microcontact behavior by designing and constructing a novel experimental setup. Three representative contact materials of varying microstructure (Au, Au5%Ru, Au4%V2O5) were tested and parameters of contact during cycling were measured. The Au4%V2O5, a dispersion strengthened material developed ...


Discrete Film Cooling In A Rocket With Curved Walls, Jonathan F. Mccall Dec 2009

Discrete Film Cooling In A Rocket With Curved Walls, Jonathan F. Mccall

Theses and Dissertations

This study quantified the effects of discrete wall-based film cooling in a rocket with curved walls. Simulations and experiments showed decreasing with wall radius of curvature, holding jet diameter constant, improves net heat flux reduction (NHFR) and adiabatic effectiveness (η) for 90˚ compound injected cylindrical jets, though η is reduced at the highest curvature. NHFR and η improved further with a high favorable stream-wise pressure gradient (K=2.1x10-5) at all tested blowing ratios, but were affected little by a high density ratio (DR=1.76) using carbon dioxide as the coolant. Experiments were run at a Reynolds number ...


Optical Properties Of Semiconducting Boron Carbide For Neutron Detection Applications, Ravi B. Billa Dec 2009

Optical Properties Of Semiconducting Boron Carbide For Neutron Detection Applications, Ravi B. Billa

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

Solid state neutron detection devices based on semiconducting boron carbide have the potential for nearly ideal neutron detection effciency for thermal neutrons. The present work is focused on characterizing optical properties of this semiconducting boron carbide material as a step in further development of the material for neutron detection and other applications.

Semiconducting boron carbide films were grown on silicon substrates using plasma enhanced chemical vapor deposition and their optical properties were characterized using variable angle spectroscopic ellipsometry over a wide spectral range, from mid-infrared to vacuum-ultraviolet wavelengths. The effects of deposition substrate temperature and of post-deposition heat treatments on ...


Multiscale Modeling And Simulation Of Nanocrystalline Zirconium Oxide, Chaojun Wang Dec 2009

Multiscale Modeling And Simulation Of Nanocrystalline Zirconium Oxide, Chaojun Wang

Engineering Mechanics Dissertations & Theses

Nanocrystalline zirconium oxide (ZrO2) nanofibers fabricated with the sol-gel electrospinning process are expected to provide a new class of super-strong yet ultra-flexible materials. To predict their mechanical properties, we have carried out multiscale modeling and analyses. A computational model that combines the Voronoi polycrystal simulation of nanocrystalline structure with the finite element analysis has been developed. It enables the use of the first-principles predictions for the three ZrO2 crystal phases in continuum analysis of the elastic stress and strain fields in the nanofibers under uniaxial-stress tension. Calculations have been performed for each of the three phases and for ...


Multiscale Modeling And Simulation Of Nanocrystalline Zirconium Oxide, Chaojun Wang Dec 2009

Multiscale Modeling And Simulation Of Nanocrystalline Zirconium Oxide, Chaojun Wang

Engineering Mechanics Dissertations & Theses

Nanocrystalline zirconium oxide (ZrO2) nanofibers fabricated with the sol-gel electrospinning process are expected to provide a new class of super-strong yet ultra-flexible materials. To predict their mechanical properties, we have carried out multiscale modeling and analyses. A computational model that combines the Voronoi polycrystal simulation of nanocrystalline structure with the finite element analysis has been developed. It enables the use of the first-principles predictions for the three ZrO2 crystal phases in continuum analysis of the elastic stress and strain fields in the nanofibers under uniaxial-stress tension. Calculations have been performed for each of the three phases and for ...


College Of Engineering Senior Design Competition Fall 2009, University Of Nevada, Las Vegas Dec 2009

College Of Engineering Senior Design Competition Fall 2009, University Of Nevada, Las Vegas

Senior Projects (COE)

Each student in his or her senior year chooses, plans, designs, and prototypes a product in this required element of the curriculum. 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.

A highlight of the year-long senior design project is the senior design competition. This competition, which usually takes place the week before finals each semester, helps focus the senior students on increasing the quality and potential for commercial application for their design projects.

Judges from local industry evaluate the projects on innovation, commercial ...


Study Of Take-Up Velocity In Enhancing Tensile Properties Of Aligned Electrospun Nylon 6 Fibers, Johnny F. Najem Dec 2009

Study Of Take-Up Velocity In Enhancing Tensile Properties Of Aligned Electrospun Nylon 6 Fibers, Johnny F. Najem

Mechanical Engineering Faculty Research

The variation of both the tensile properties and thermal properties of aligned electrospun fibers with the take-up velocity (TUV) of disc collector has not been widely investigated due to the difficulty of handling aligned nanofibers and measuring low loads. In this thesis, 25% of nylon 6 was dissolved in formic acid and then electrospun into fibers and the fibers were aligned using a rotating disc collector. We evaluated the tensile and thermal properties, average fiber diameter, crystallinity, crystalline morphology, molecular and crystalline orientation of aligned electrospun nylon 6 nanofibers as a function of TUV based on a disc collector. It ...


Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam ...


Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam ...


Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam ...


Direct Cooled Ceramic Substrate For Thermal Control Of Automotive Power Electronics, Kirk Townsend Lowe Dec 2009

Direct Cooled Ceramic Substrate For Thermal Control Of Automotive Power Electronics, Kirk Townsend Lowe

Doctoral Dissertations

As electric vehicle technology develops, manufacturers would like to move toward hotter coolants for power electronic components to reduce system level costs. Thus, unique designs of inverter designs were sought to enable operation with 105°C coolant. The proposed solution in this research incorporated flow channels into the ceramic layer of the direct-bonded copper substrate typically found in power electronic packages. The focus of this research details the design and analysis of the direct cooled ceramic substrate from the perspective of its thermal performance and innovative packaging concept.

The research was directed to pursue alumina as the substrate ceramic because ...


Thermodynamically Consistent Large Deformation Constitutive Model For Glassy Polymers, Ashwani Kumar Goel Dec 2009

Thermodynamically Consistent Large Deformation Constitutive Model For Glassy Polymers, Ashwani Kumar Goel

Engineering Mechanics Dissertations & Theses

Polycarbonate(PC), like most glassy polymers when undergoing large deformations exhibits a very complex thermo-mechanical response. We look at PC as a model glassy polymer and examine its response to changes in loading rate, loading direction and temperature. We show that plastic flow in compression is accompanied by a change in the elastic response of PC from isotropic to anisotropic. This provides the necessity to introduce a new modeling method that can capture these changes. A finite deformation plasticity like thermodynamically consistent model is developed to capture this and the observed rate and temperature dependence. For this modeling method, we ...


Computational Investigations Of Characteristic Performance Improvements For Subkilogram Laser Micropropulsion, Richard Joel Thompson Dec 2009

Computational Investigations Of Characteristic Performance Improvements For Subkilogram Laser Micropropulsion, Richard Joel Thompson

Masters Theses

Experimental investigations have evaluated the feasibility of using laser-driven plasma microthrusters for small-thrust, high-specific-impulse space maneuvers, particularly for micro- and nanosatellite missions. Recent work made use of the Mach2 hydromagnetics code for the construction of an adequate computational model of the micro-thruster opera- tion. This thesis expounds on this previous work by extending the computational modeling capabilities, allowing for the determination of plasma plume properties and characteristic performance assessment of the microthruster; this allows for further computational investi- gation of the performance improvements achieved by new design considerations. Two par- ticular design changes are implemented and measured: (i) the simulation ...


Boundary Layer Data System (Blds) Heating System, John Hauge, Drew Hutcheson, Paul Scott Dec 2009

Boundary Layer Data System (Blds) Heating System, John Hauge, Drew Hutcheson, Paul Scott

Mechanical Engineering

The boundary layer data system (BLDS) is the result of a collaborative effort between Dr. Westphal, a researcher and instructor at Cal Poly, and Northrop Grumman. The BLDS is capable of measuring the boundary layer profile and characteristics of flow over aerodynamic surfaces and is intended for high altitude, high speed use. The instruments inside the BLDS malfunction at the low temperatures present when operating in flight at altitudes above 30,000 ft.

To solve this problem, analysis was done on the existing BLDS which determined the heating requirements, around 50 watts, needed to keep the internal temperature within the ...


Two-Material Cylinder Stress Response Software, Katherine Gage, Matt Highstreet, Liz Del Cid Dec 2009

Two-Material Cylinder Stress Response Software, Katherine Gage, Matt Highstreet, Liz Del Cid

Mechanical Engineering

No abstract provided.


Chip Removal Tool Project, Brett Mori, John Cote, Kyle Rowland, Micah Wells Dec 2009

Chip Removal Tool Project, Brett Mori, John Cote, Kyle Rowland, Micah Wells

Mechanical Engineering

The Cal Poly senior project team worked with Helical Products Inc. to develop an automated method for removing swarf and chip buildup from the drill bits of their CNC milling machines. The removal methods in this report were designed for and tested using a Fanuc Robodrill while keeping the potential in mind for their use in other CNC milling machines. After extensive background research, preliminary and prototype design and testing the final chosen design is shown below. The cleaning device is made from flexible sheet metal and placed on a fixture that occupies one of the two pallet locations inside ...


Supermileage Team - Urban Concept Competition Vehicle Chassis Design Report, Andrew Allport, Kevin Braico, Kevin Charles, George Kyi, William Lai Dec 2009

Supermileage Team - Urban Concept Competition Vehicle Chassis Design Report, Andrew Allport, Kevin Braico, Kevin Charles, George Kyi, William Lai

Mechanical Engineering

This research and design project was proposed by the Cal Poly Supermileage team. They have requested for our team to design an Urban Concept car, a new category of vehicles to compete for fuel efficiency in the Shell Eco-marathon in 2010. The primary focus of our team is in the design and construction of a chassis the Supermileage team can use for the 2010 competition in Fontana, CA. This design must meet dimensional and functional requirements set by Shell while being designed to maximize efficiency in the competition.

There were various chassis concepts under consideration that would possibly work for ...