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Mechanical Engineering

2014

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Full-Text Articles in Nanoscience and Nanotechnology

Two-Dimensional Scalar Differential Equations For Transversely Varying Thickness Modes In Piezoelectric Plates And Applications In Acoustic Wave Resonator Sensors, Huijing He Dec 2014

Two-Dimensional Scalar Differential Equations For Transversely Varying Thickness Modes In Piezoelectric Plates And Applications In Acoustic Wave Resonator Sensors, Huijing He

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

Generalizations are made for three types of well-known and widely used twodimensional scalar differential equations in the literature describing transversely varying thickness modes in piezoelectric plate resonators. They are for singly-rotated quartz plates, doubly-rotated quartz plates, and plates of crystals of class 6mm with the c-axis along the plate thickness, respectively. The purpose of the generalizations is to include the effects of surface mechanical loads such as mass layers or fluids for resonator -based acoustic wave sensor applications. Surface acoustic impedance is introduced to take into account various surface loads in a general manner for time-harmonic motions. Both unelectroded and ...


Wear Resistant Polydopamine/Ptfe Nanoparticle Composite Coating For Dry Lubrication Applications, Samuel George Beckford Dec 2014

Wear Resistant Polydopamine/Ptfe Nanoparticle Composite Coating For Dry Lubrication Applications, Samuel George Beckford

Theses and Dissertations

This dissertation presents an investigation into the effect of nanoparticle fillers and a polydopamine adhesive primer on the tribological performance of thin PTFE films. The principal objective of this investigation was to reduce wear in PTFE films, an issue which precludes the use of PTFE films in tribological applications requiring high durability. The friction and wear of the composite films were evaluated using a ball-on-flat configuration in linear reciprocating motion. It was found that the use of a polydopamine adhesive primer reduces the wear of PTFE films more than 600 times. X-ray photoelectron spectroscopy (XPS) results show that a tenacious ...


Highly Transparent, Self-Cleaning, And Antireflective Nanoparticle Coatings, Corey Seth Thompson Dec 2014

Highly Transparent, Self-Cleaning, And Antireflective Nanoparticle Coatings, Corey Seth Thompson

Theses and Dissertations

Current solar panel technologies require a sheet of glass to serve as both mechanical support and to protect the cells from the environment. The reflection from the glass sheet can reflect up to 8% of the incident light, reducing the power output of the panel. Antireflective coatings can be used to allow more light to enter the panel to be converted into usable electricity. However, no solid thin film materials exhibit a low enough index of refraction to serve as antireflective coatings for common solar glass. The main goal of this research was to investigate the self-cleaning, antifogging, and antireflective ...


Nanogap Device: Fabrication And Applications, Jun Hyun Han Oct 2014

Nanogap Device: Fabrication And Applications, Jun Hyun Han

Dissertations (2009 -)

A nanogap device as a platform for nanoscale electronic devices is presented. Integrated nanostructures on the platform have been used to functionalize the nanogap for biosensor and molecular electronics. Nanogap devices have great potential as a tool for investigating physical phenomena at the nanoscale in nanotechnology. In this dissertation, a laterally self-aligned nanogap device is presented and its feasibility is demonstrated with a nano ZnO dot light emitting diode (LED) and the growth of a metallic sharp tip forming a subnanometer gap suitable for single molecule attachment.

For realizing a nanoscale device, a resolution of patterning is critical, and many ...


Thermal Convection Of Non-Fourier Fluids, Rahim Mohammadhasani Khorasany Sep 2014

Thermal Convection Of Non-Fourier Fluids, Rahim Mohammadhasani Khorasany

Electronic Thesis and Dissertation Repository

The natural convection of non-Fourier fluids of the dual-phase-lagging (DPL) type is examined. These fluids possess a relaxation time and a retardation time, reflecting the delay in the response of the heat flux and the temperature gradient with respect to one another. DPL fluids span a wide range of applications, including low-temperature liquids, fluids subjected to fast heat transfer processes, and nanofluids (NFs), for which both the relaxation and retardation times are expressed in terms of nanoparticle concentration and solution properties. Both stationary and oscillatory convection become equally probable as the relaxation time increases. A nonlinear spectral approach is also ...


Nonlinear Vibration Analysis Of Nonlocal Nanowires, Hassan Askari Aug 2014

Nonlinear Vibration Analysis Of Nonlocal Nanowires, Hassan Askari


No abstract provided.


Structural, Electronic And Catalytic Properties Of Graphene-Supported Platinum Nanoclusters, Ioanna Fampiou Aug 2014

Structural, Electronic And Catalytic Properties Of Graphene-Supported Platinum Nanoclusters, Ioanna Fampiou

Doctoral Dissertations

Carbon materials are predominantly used as catalytic supports due to their high surface area, excellent electrical conductivity, resistance to corrosion and structural stability. Graphene, a 2D monolayer of graphite, with its excellent thermal, electronic and mechanical features, has been considered a promising support material for next generation metal-graphene nanocatalysts. The main focus of this dissertation is to investigate the properties of such metal-graphene nanocomposites using computational methods, and to develop a comprehensive understanding of the experimentally observed enhanced catalytic activity of graphene-supported Platinum (Pt) clusters.

In particular, we seek to understand the role of graphene supports on the ground-state morphology ...


Granular Matter: Microstructural Evolution And Mechanical Response, Aashish Ghimire, Ishan Srivastava, Timothy S. Fisher Aug 2014

Granular Matter: Microstructural Evolution And Mechanical Response, Aashish Ghimire, Ishan Srivastava, Timothy S. Fisher

The Summer Undergraduate Research Fellowship (SURF) Symposium

Heterogeneous (nano) composites, manufactured by the densification of variously sized grains, represent an important and ubiquitous class of technologically relevant materials. Typical grain sizes in such materials range from macroscopic to a few nanometers. The morphology exhibited by such disordered materials is complex and intricately connected with its thermal and electrical transport properties. It is important to quantify the geometric features of these materials and simulate the fabrication process. Additionally, granular materials exhibit complex structural and mechanical properties that crucially govern their reliability during industrial use. In this work, we simulate the densification of soft deformable grains from a low-density ...


Thermal Properties Of Soft Nanomaterials: Thermal Measurement Design, Yu Han, Meng Pan, Amy Marconnet, Collier Miers Aug 2014

Thermal Properties Of Soft Nanomaterials: Thermal Measurement Design, Yu Han, Meng Pan, Amy Marconnet, Collier Miers

The Summer Undergraduate Research Fellowship (SURF) Symposium

Soft materials like hydrogels have multiple tunable material properties because of their unique structures. Due to the ability to respond to stimuli like temperature or chemical environment, they have numerous applications in different fields like delivering drugs inside the human body and other medical uses. Details of the thermal transport mechanisms, as well as the overall thermal properties, are critical for a variety of applications. Multi-property measurements elucidate the underlying transport mechanisms in the soft materials. This research demonstrates a new methodology of measuring thermal properties of soft materials. This work uses the 3w method [1,2] for measuring the ...


Thermal Properties Of Soft Nanomaterials: Materials Synthesis And Fabrication, Meng Pan, Collier Miers, Amy Marconnet, Yu Han Aug 2014

Thermal Properties Of Soft Nanomaterials: Materials Synthesis And Fabrication, Meng Pan, Collier Miers, Amy Marconnet, Yu Han

The Summer Undergraduate Research Fellowship (SURF) Symposium

The properties of soft nanomaterials are hard to measure exactly due to their mechanical properties and unstable shape. In particular, hydrogels are a class of cross-linked polymers that can absorb large quantities of water changing their shape under the influence of various conditions such as humidity, temperature, and pH. This research addresses the fabrication of a material that has a significant contrast in properties under different conditions (e.g. temperature, wetting, and pH) and determine the physical mechanisms of heat transfer in this nanomaterial. The hydrogels are made using a several cycles of a freeze-thaw method. The method requires soluble ...


Atomistic Simulation And Virtual Diffraction Characterization Of Alumina Interfaces: Evaluating Structure And Stability For Predictive Physical Vapor Deposition Models, Shawn Patrick Coleman Aug 2014

Atomistic Simulation And Virtual Diffraction Characterization Of Alumina Interfaces: Evaluating Structure And Stability For Predictive Physical Vapor Deposition Models, Shawn Patrick Coleman

Theses and Dissertations

The objectives of this work are to investigate the structure and energetic stability of different alumina (Al2O3) phases using atomistic simulation and virtual diffraction characterization. To meet these objectives, this research performs molecular statics and molecular dynamics simulations employing the reactive force-field (ReaxFF) potential to model bulk, interface, and surface structures in the θ-, γ-, κ-, and α-Al2O3 system. Simulations throughout this study are characterized using a new virtual diffraction algorithm, developed and implemented for this work, that creates both selected area electron diffraction (SAED) and x-ray diffraction (XRD) line profiles without assuming prior ...


Optical Direct-Write Nanolithography Based On Self-Assembled Resist, Meghana Akella Jul 2014

Optical Direct-Write Nanolithography Based On Self-Assembled Resist, Meghana Akella

Open Access Theses

Holographic display is being developed for next generation mobile phones. However, manufacturing of miniature gratings for the holographic projectors cost a few thousand dollars today, not making the concept practical for commercial purposes. In this thesis, we discuss the feasibility of self-assembled nanoparticles to manufacture holographic gratings cost-effectively and at the nanoscale. Using our approach, the gratings can be manufactured at the scale of 20nm and the cost per chip is expected to cost a few dollars.^ In this thesis, a hydrophobic SAM was used to modify the surface of silicon. Direct-write UV laser lithography was used for photothermal patterning ...


Electrical Detection Of Cellular Penetration During Microinjection With Carbon Nanopipettes, Sean E. Anderson, Haim H. Bau Apr 2014

Electrical Detection Of Cellular Penetration During Microinjection With Carbon Nanopipettes, Sean E. Anderson, Haim H. Bau

Departmental Papers (MEAM)

The carbon nanopipette (CNP) is comprised of a pulled-glass pipette terminating with a nanoscale (tens to hundreds of nm) diameter carbon pipe. The entire inner glass surface of the CNP is coated with a carbon film, providing an electrically conductive path from the carbon tip to the distal, macroscopic end of the pipette. The CNP can double as a nanoelectrode, enabling electrical measurements through its carbon lining, and as a nanoinjector, facilitating reagent injection through its hollow bore. With the aid of a lock-in amplifier, we measured, in real time and with millisecond resolution, variations in impedance as the CNP ...


Particle Deposition On Superhydrophobic Surfaces By Sessile Droplet Evaporation, Mercy G. Dicuangco Apr 2014

Particle Deposition On Superhydrophobic Surfaces By Sessile Droplet Evaporation, Mercy G. Dicuangco

Open Access Theses

Prediction and active control of the spatial distribution of particulate deposits obtained from sessile droplet evaporation is essential in ink-jet printing, nanostructure assembly, biotechnology, and other applications that require localized deposits. In recent years, sessile droplet evaporation on bio-inspired superhydrophobic surfaces has become an attractive method for depositing materials on a site-specific, localized region, but is less explored compared to evaporative deposition on hydrophilic surfaces. It is therefore of interest to understand particle deposition during droplet evaporation on superhydrophobic surfaces to enable accurate prediction and tunable control of localized deposits on such surfaces. The purpose of the present work is ...


Electrochemical And Metal-Phase Processes Accompanying Hydrogen Absorption In Aluminum During Aqueous Corrosion, Kurt R. Hebert, Ömer Ö. Çapraz, Pranav Shrotriya, Guiping Zhang Mar 2014

Electrochemical And Metal-Phase Processes Accompanying Hydrogen Absorption In Aluminum During Aqueous Corrosion, Kurt R. Hebert, Ömer Ö. Çapraz, Pranav Shrotriya, Guiping Zhang

Ömer Özgür Çapraz

Alkaline corrosion of aluminum results in large supersaturations of hydrogen, and formation of hydride and subsurface voids.1-4 Aluminum itself is not susceptible to stress corrosion cracking (SCC), but hydrogen and hydride effects are significant for SCC mechanisms on Al and Mg alloys. Chu found evidence that corrosion-induced tensile stress in several alloys additively combines with external tensile stress to promote SCC, and attributed the former to lattice contraction associated with vacancies injected during corrosion.5 Evidence for vacancy injection on Al was found from X-ray diffraction and in situ curvature measurements on Al thin films undergoing corrosion.1,6 ...


Passive Biaxial Mechanical Properties And In Vivo Axial Pre-Stretch Of The Diseased Human Femoropopliteal And Tibial Arteries, Alexey Kamenskiy, Iraklis I. Pipinos, Yuris A. Dzenis, Clay Lomneth, Syed A. Jaffar Kazmi, Nicholas Y. Phillips, Jason N. Mactaggart Mar 2014

Passive Biaxial Mechanical Properties And In Vivo Axial Pre-Stretch Of The Diseased Human Femoropopliteal And Tibial Arteries, Alexey Kamenskiy, Iraklis I. Pipinos, Yuris A. Dzenis, Clay Lomneth, Syed A. Jaffar Kazmi, Nicholas Y. Phillips, Jason N. Mactaggart

Mechanical & Materials Engineering Faculty Publications

Surgical and interventional therapies for atherosclerotic lesions of the infrainguinal arteries are notorious for high rates of failure. Frequently, this leads to expensive reinterventions, return of disabling symptoms, or limb loss. Interaction between the artery and repair material likely plays an important role in reconstruction failure, but data describing the mechanical properties and functional characteristics of human femoropopliteal and tibial arteries are currently not available. Diseased superficial femoral (SFA, n=10), popliteal (PA, n=8), and tibial arteries (TA, n=3) from 10 patients with critical limb ischemia were tested to determine passive mechanical properties using planar biaxial extension. All ...


Obtaining A Relationship Between Process Parameters And Fracture Characteristics For Hybrid Co2 Laser∕Waterjet Machining Of Ceramics, Dinesh Kalyanasundaram, Pranav Shrotriya, Palaniappa A. Molian Feb 2014

Obtaining A Relationship Between Process Parameters And Fracture Characteristics For Hybrid Co2 Laser∕Waterjet Machining Of Ceramics, Dinesh Kalyanasundaram, Pranav Shrotriya, Palaniappa A. Molian

Pranav Shrotriya

A combined experimental and analytical approach is undertaken to identify the relationship between process parameters and fracture behavior in the cutting of a 1mm thick alumina samples by a hybrid CO2 laser∕waterjet (LWJ) manufacturing process. In LWJ machining, a 200W power laser was used for local heating followed by waterjet quenching of the sample surface leading to thermal shock fracture in the heated zone. Experimental results indicate three characteristic fracture responses: scribing, controlled separation, and uncontrolled fracture. A Green’s function based approach is used to develop an analytical solution for temperatures and stress fields generated in the workpiece ...


Electrospinning Applications Air Filtration And Superhydrophobic Materials, Negar Ghochaghi, Adetoun Taiwo Jan 2014

Electrospinning Applications Air Filtration And Superhydrophobic Materials, Negar Ghochaghi, Adetoun Taiwo

Graduate Research Posters

Electrospinning is a widely applicable technique that generates non-woven fibers in the micro and nano range. In this project two of its applications are highlighted namely filtration media and enhancement of wettability. The first project demonstrates that electrospinning can be used to produce new fiber filtration media with controlled microstructure. The bimodal and unimodal orthogonal and random filters were made and characterized against their filtration efficiency and pressure drop. Figure of Merit (FOM) was also calculated and discussed. It is shown that the FOM increases when the electrospun fibers are arranged into alternating layers of aligned course and fine fibers ...


Enhancing Phase-Change Heat Transfer With Copper Nanowire-Structured Surfaces, Qian Li Jan 2014

Enhancing Phase-Change Heat Transfer With Copper Nanowire-Structured Surfaces, Qian Li

Mechanical Engineering Graduate Theses & Dissertations

As energy consumption drastically increases in the electronics and energy conversion systems, heat dissipation becomes increasingly important for device reliability and system efficiency. Phase change heat transfer, which takes advantage of the latent heat during the phase change process, is the most promising method to efficiently remove high heat fluxes. Nano structures, which provide extended surface areas and enhanced hydrophilicity or hydrophobicity have been widely used in phase change heat transfer enhancement. Copper nanowires are one of the most promising nano structures due to ease of fabrication, controllable structure dimensions, and high thermal conductivity. In this study, the heat transfer ...


Nanowire Arrays And 3d Porous Conducting Networks For Li-Ion Battery Electrodes, Miao Tian Jan 2014

Nanowire Arrays And 3d Porous Conducting Networks For Li-Ion Battery Electrodes, Miao Tian

Mechanical Engineering Graduate Theses & Dissertations

There have been growing interests in developing high-capacity, high-power, and long-cycle-life lithium-ion (Li-ion) batteries due to the increasing power requirements of portable electronics and electrical vehicles. Various efforts have been made to utilize nano-structured electrodes since they can improve the performance of Li-ion batteries compared to bulk materials in many ways: fast electrode reaction due to the large surface area, efficient volume-change accommodation due to the small size, and fast Li-ion transport along the nanoscale gaps. Among various nanostructures, nanowire arrays present an excellent candidate for high performance lithium-ion battery electrodes, which have attracted intensive research over the past few ...


Advancing Microscope And Probe Design For Near-Field Scanning Microwave Microscopy, Joel C. Weber Jan 2014

Advancing Microscope And Probe Design For Near-Field Scanning Microwave Microscopy, Joel C. Weber

Mechanical Engineering Graduate Theses & Dissertations

In this thesis, we address the design and application of a microscope and probes for near-field scanning microwave microscopy. We provide an introduction to the development of microwave microscopy and its contributions to material metrology. In particular, we focus on its application to the study of photovoltaics. We then expand beyond these studies to the fabrication of nanowire-based probes for microwave microscopy. These probes provide avenues for advancing an array of scanning probe techniques, including continued measurements on photovoltaics with improved resolution.

To begin, we present a near-field scanning microwave microscope that has been configured for imaging photovoltaic samples. Our ...


Fabrication Of Magnetic Two-Dimensional And Three-Dimensional Microstructures For Microfluidics And Microrobotics Applications, Hui Li Jan 2014

Fabrication Of Magnetic Two-Dimensional And Three-Dimensional Microstructures For Microfluidics And Microrobotics Applications, Hui Li

Theses and Dissertations--Mechanical Engineering

Micro-electro-mechanical systems (MEMS) technology has had an increasing impact on industry and our society. A wide range of MEMS devices are used in every aspects of our life, from microaccelerators and microgyroscopes to microscale drug-delivery systems. The increasing complexity of microsystems demands diverse microfabrication methods and actuation strategies to realize. Currently, it is challenging for existing microfabrication methods—particularly 3D microfabrication methods—to integrate multiple materials into the same component. This is a particular challenge for some applications, such as microrobotics and microfluidics, where integration of magnetically-responsive materials would be beneficial, because it enables contact-free actuation. In addition, most existing ...


Altered Mechanobiology Of Schlemm’S Canal Endothelial Cells In Glaucoma, Darryl R. Overby, Enhua H. Zhou, Rocio Vargas-Pinto, Ryan M. Pedrigi, Rudolf Fuchshofer, Sietse T. Braakman, Ritika Gupta, Kristin M. Perkumas, Joesph M. Sherwood, Amir Vahabikashi, Quynh Dang, Jae Hun Kim, C. Ross Ethier, W. Daniel Stamer, Jeffrey J. Fredberg, Mark Johnson Jan 2014

Altered Mechanobiology Of Schlemm’S Canal Endothelial Cells In Glaucoma, Darryl R. Overby, Enhua H. Zhou, Rocio Vargas-Pinto, Ryan M. Pedrigi, Rudolf Fuchshofer, Sietse T. Braakman, Ritika Gupta, Kristin M. Perkumas, Joesph M. Sherwood, Amir Vahabikashi, Quynh Dang, Jae Hun Kim, C. Ross Ethier, W. Daniel Stamer, Jeffrey J. Fredberg, Mark Johnson

Mechanical & Materials Engineering Faculty Publications

Increased flow resistance is responsible for the elevated intraocular pressure characteristic of glaucoma, but the cause of this resistance increase is not known. We tested the hypothesis that altered biomechanical behavior of Schlemm’s canal (SC) cells contributes to this dysfunction. We used atomic force microscopy, optical magnetic twisting cytometry, and a unique cell perfusion apparatus to examine cultured endothelial cells isolated from the inner wall of SC of healthy and glaucomatous human eyes. Here we establish the existence of a reduced tendency for pore formation in the glaucomatous SC cell—likely accounting for increased outflow resistance—that positively correlates ...


Thermal Conductivity Of Alumina And Silica Nanofluids, Julian Bernal Castellanos Jan 2014

Thermal Conductivity Of Alumina And Silica Nanofluids, Julian Bernal Castellanos

All Theses, Dissertations, and Other Capstone Projects

This thesis studies the effects of the base fluid, particle type/size, and volumetric concentration on the thermal conductivity of Alumina and Silica nanofluids. The effects of base fluid were observed by preparing samples using ethylene glycol (EG), water, and mixtures of EG/water as the base fluid and Al2O3 (10 nm) nanoparticles. The particles type/size and volumetric concentration effects were tested by preparing samples of nanofluids using Al2O3 (10nm), Al2O3 (150nm), SiO2 (15 nm), and SiO2 (80 nm) nanoparticles and ionized water as base fluid at different volumetric concentrations. All samples were mixed using a sonicator for 30 ...


Quality And Safety Of Minimally Invasive Surgery: Past, Present, And Future, Bernadette Mccrory, Chad A. Lagrange, M. S. Hallbeck Jan 2014

Quality And Safety Of Minimally Invasive Surgery: Past, Present, And Future, Bernadette Mccrory, Chad A. Lagrange, M. S. Hallbeck

Mechanical & Materials Engineering Faculty Publications

Adverse events because of medical errors are a leading cause of death in the United States (US) exceeding the mortality rates of motor vehicle accidents, breast cancer, and AIDS. Improvements can and should be made to reduce the rates of preventable surgical errors because they account for nearly half of all adverse events within hospitals. Although minimally invasive surgery (MIS) has proven patient benefits such as reduced postoperative pain and hospital stay, its operative environment imposes substantial physical and cognitive strain on the surgeon increasing the risk of error. To mitigate errors and protect patients, a multidisciplinary approach is needed ...


Polymer Aggregation Correlated Transition From Schottky-Junction To Bulk Heterojunction Organic Solar Cells, Bin Yang, Zhengguo Xiao, Jinsong Huang Jan 2014

Polymer Aggregation Correlated Transition From Schottky-Junction To Bulk Heterojunction Organic Solar Cells, Bin Yang, Zhengguo Xiao, Jinsong Huang

Mechanical & Materials Engineering Faculty Publications

The fullerene-based organic Schottky-junction solar cells have recently attracted intensive research interest because of their unique electrical performance, such as significant photocurrent generation from excitons created in fullerenes and large open-circuit voltage (VOC) output induced by high Schottky-barrier height between the anode and the fullerene acceptor. This manuscript reports another remarkably appealing advantage that the fullerene-based Schottky-junction solar cells are more stable than the bulk heterojunction counterparts. The better stability is likely due to mitigative polymer photo-oxidation and/or little morphological change of active film in the aged Schottky-junction devices. The transition from Schottky-junction to bulk heterojunction appears at ...


Qualifying Composition Dependent P And N Self-Doping In Ch3Nh3Pbi3, Qi Wang, Yuchuan Shao, Haipeng Xie, Lu Lyu, Xiaoliang Liu, Yongli Gao, Jinsong Huang Jan 2014

Qualifying Composition Dependent P And N Self-Doping In Ch3Nh3Pbi3, Qi Wang, Yuchuan Shao, Haipeng Xie, Lu Lyu, Xiaoliang Liu, Yongli Gao, Jinsong Huang

Mechanical & Materials Engineering Faculty Publications

We report the observation of self-doping in perovskite. CH3NH3PbI3 was found to be either n- or p-doped by changing the ratio of methylammonium halide (MAI) and lead iodine (PbI2) which are the two precursors for perovskite formation. MAI-rich and PbI2-rich perovskite films are p and n self-doped, respectively. Thermal annealing can convert the p-type perovskite to n-type by removing MAI. The carrier concentration varied as much as six orders of magnitude. A clear correlation between doping level and device performance was also observed.


Arising Applications Of Ferroelectric Materials In Photovoltaic Devices, Yongbo Yuan, Zhengguo Xiao, Bin Yang, Jinsong Huang Jan 2014

Arising Applications Of Ferroelectric Materials In Photovoltaic Devices, Yongbo Yuan, Zhengguo Xiao, Bin Yang, Jinsong Huang

Mechanical & Materials Engineering Faculty Publications

The ferroelectric-photovoltaic (FE-PV) device, in which a homogeneous ferroelectric material is used as a light absorbing layer, has been investigated during the past several decades with numerous ferroelectric oxides. The FE-PV effect is distinctly different from the typical photovoltaic (PV) effect in semiconductor p–n junctions in that the polarization electric field is the driving force for the photocurrent in FE-PV devices. In addition, the anomalous photovoltaic effect, in which the voltage output along the polarization direction can be significantly larger than the bandgap of the ferroelectric materials, has been frequently observed in FE-PV devices. However, a big challenge faced ...


Dynamic Fracture Analysis Of Polycarbonate By The Optical Method Of Caustics, Guiyun Gao, Zheng Li, Mehrdad Negahban Jan 2014

Dynamic Fracture Analysis Of Polycarbonate By The Optical Method Of Caustics, Guiyun Gao, Zheng Li, Mehrdad Negahban

Mechanical & Materials Engineering Faculty Publications

Glassy polycarbonate (PC) is a widely used engineering material in industries, since it has high strength and toughness as well as good transparency. However, these advantages of PC can be suppressed by physical aging, especially its dynamic fracture toughness. In addition, the material properties of PC can be changed dramatically after large plastic compressive deformation, and it can show obvious orthotropic behavior. Here, the combined effect of aging and plastic compressive deformation on dynamic facture of PC was investigated by the optical method of caustics. The dynamic reflective method of caustics for orthotropic materials was developed here to study the ...


Measurement Of Hydrodynamic Force Generation By Swimming Dolphins Using Bubble Dpiv, Frank E. Fish, Paul Legac, Terrie M. Williams, Timothy Wei Jan 2014

Measurement Of Hydrodynamic Force Generation By Swimming Dolphins Using Bubble Dpiv, Frank E. Fish, Paul Legac, Terrie M. Williams, Timothy Wei

Mechanical & Materials Engineering Faculty Publications

Attempts to measure the propulsive forces produced by swimming dolphins have been limited. Previous uses of computational hydrodynamic models and gliding experiments have provided estimates of thrust production by dolphins, but these were indirect tests that relied on various assumptions. The thrust produced by two actively swimming bottlenose dolphins (Tursiops truncatus) was directly measured using digital particle image velocimetry (DPIV). For dolphins swimming in a large outdoor pool, the DPIV method used illuminated microbubbles that were generated in a narrow sheet from a finely porous hose and a compressed air source. The movement of the bubbles was tracked with a ...