Engineering Commons^™

The Characterization, Assessment, And Shear Strength Of Turfgrass Soil In North American Thoroughbred Racing, Peter Schmitt

Theses and Dissertations--Biosystems and Agricultural Engineering

Minimizing catastrophic injuries to racehorses, which also protects the riders, is critical for the future of the Thoroughbred racing industry. While the causes of catastrophic injuries are multifactorial, the condition of the racing surface is one of only a few factors that affects all horses in competition. Horse racing surfaces must retain enough shear strength to support the hoof of a Thoroughbred at a gallop. Turfgrass racing surfaces also require healthy turf to reinforce the footing while also achieving a high infiltration rate to allow races to run on the turf soon after or even during rain. This research is …

Mimicking The Namib Desert Beetle With Hydrophilic And Hydrophobic Surfaces, Tyler Bracewell

Williams Honors College, Honors Research Projects

The Namib Desert beetle, Stenocara gracilipes, condenses fog that rolls in off the west coast of Namibia to provide itself with the water it needs for the day. By lifting its abdomen into the air to collect the water vapor, it condenses on hydrophilic bumps that are about 500μm in diameter and are spaced apart about 500-1500μm. Once the water reaches a critical size, the droplet rolls off the hydrophilic bump and onto the flat hydrophobic surface of the elytra. Since the beetle is angled with its abdomen in the air, the water rolls down to its mouth. A …

Wetting Transition On 3d-Printed Surfaces, Isabelle Moryan

Williams Honors College, Honors Research Projects

Taking the previous research conducted, this project aims to further the study and research of the wettability of surfaces. Surface features and types are important factors to their wettability. The geometric properties of a surface can make it more hydrophobic and hydrophilic. Extreme cases of hydrophobic and hydrophilic surfaces lead to water repulsion or water absorption, even under extreme conditions. The goal of this project is to gain further insight on how fabricated 3D-printed featured surfaces and examine the wetting transition on these surfaces. In particular, cylindrical pillars will be studied with varied pillar spacing, height and diameter. In addition, …

Development And Characterization Of Nb₃N/Al₂0₃ Superconducting Multilayers For Particle Accelerators, Chris Sundahl, Junki Makita, Paul B. Welander, Yi-Feng Su, Fumitake Kametani, Lin Xie, Huimin Zhang, Lian Li, Alex Gurevich, Chang-Beom Eom

Physics Faculty Publications

Superconducting radio-frequency (SRF) resonator cavities provide extremely high quality factors > 10¹⁰ at 1-2 GHz and 2 K in large linear accelerators of high-energy particles. The maximum accelerating field of SRF cavities is limited by penetration of vortices into the superconductor. Present state-of-the-art Nb cavities can withstand up to 50 MV/m accelerating gradients and magnetic fields of 200-240 mT which destroy the low-dissipative Meissner state. Achieving higher accelerating gradients requires superconductors with higher thermodynamic critical fields, of which Nb₃Sn has emerged as a leading material for the next generation accelerators. To overcome the problem of low vortex penetration …

Pool Boiling Heat Transfer To Cuo-H2o Nanofluid On Finned Surfaces, Zhixiong Li, M Sarafraz, Arash Mazinani, Tasawar Hayat, Hamed Alsulami, Marjan Goodarzi

Faculty of Engineering and Information Sciences - Papers: Part B

© 2020 Elsevier Ltd In the present research, the general aim is to understand further the potential effect of the surface shape and geometrical specification of rectangular parallel fins developed on the surface on the heat transfer coefficient, bubble formation, and fouling of the nanoparticles. To achieve this, the boiling thermal performance of the copper oxide nano-suspension (NS) was quantified on the modified surfaces with different geometrical specifications, including the width and height of the fins and space between fins. Results showed that the designed fins reduce the rate of the fouling of the nanoparticles on the boiling surface such …

Anomalous Stranski-Krastanov Growth Of (111)-Oriented Quantum Dots With Tunable Wetting Layer Thickness, Christopher F. Schuck, Simon K. Roy, Trent Garrett, Paul J. Simmonds

Materials Science and Engineering Faculty Publications and Presentations

Driven by tensile strain, GaAs quantum dots (QDs) self-assemble on In_0.52Al_0.48As(111)A surfaces lattice-matched to InP substrates. In this study, we show that the tensile-strained self-assembly process for these GaAs(111)A QDs unexpectedly deviates from the well-known Stranski-Krastanov (SK) growth mode. Traditionally, QDs formed via the SK growth mode form on top of a flat wetting layer (WL) whose thickness is fixed. The inability to tune WL thickness has inhibited researchers’ attempts to fully control QD-WL interactions in these hybrid 0D-2D quantum systems. In contrast, using microscopy, spectroscopy, and computational modeling, we demonstrate that for GaAs(111)A QDs, we …

Investigation Of Photo-Responsive Titania Surfaces, Evan Hyden, Matthew J. Beck

Commonwealth Computational Summit

Titania (TiO₂) is an oxide commonly used for photocatalysis. This proclivity to form free radicals when exposed to light has also prompted interest in applying porous TiO₂ as a reactive/responsive membrane. Surfaces of both main polymorphs of TiO₂ (especially rutile {110} and anatase {101}) have been shown to be stable and photo-active.

Polyacrylic acid (PAA) is a molecule of interest as changes in pH can cause the molecule to contract or expand, due to changes in the charge distribution relating to the carboxyl group. Due to TiO₂’s ability to generate photocarriers, we hypothesize that …

Analytical Solution Of Microbes Interacting With Surfaces, Junyuan Li, Arezoo M. Ardekani

The Summer Undergraduate Research Fellowship (SURF) Symposium

Nowadays, there is a rising interest in studying the behavior of microbes and their interactions with flow and surfaces. In order to explore the velocity field, pressure and forces around the microbes, the solution of Stokes equations, which is called a Stokeslet, is used. This solution represents a singular velocity field due to a concentrated external force acting on fluid at a single point. This singularity could cause the expression of velocity not integrable. We use the Regularized Stokeslet Method and Method of Images to deal with this problem. The expression of force is replaced by a radially symmetric function, …

Contraction Of Convex Surfaces By Nonsmooth Functions Of Curvature, Ben H. Andrews, James A. Mccoy

Faculty of Engineering and Information Sciences - Papers: Part A

We consider the motion of convex surfaces with normal speed given by arbitrary strictly monotone, homogeneous degree one functions of the principal curvatures (with no further smoothness assumptions). We prove that such processes deform arbitrary uniformly convex initial surfaces to points in finite time, with spherical limiting shape. This result was known previously only for smooth speeds. The crucial new ingredient in the argument, used to prove convergence of the rescaled surfaces to a sphere without requiring smoothness of the speed, is a surprising hidden divergence form structure in the evolution of certain curvature quantities.

Finite Time Singularities For The Locally Constrained Willmore Flow Of Surfaces, James A. Mccoy, Glen Wheeler

Faculty of Engineering and Information Sciences - Papers: Part A

In this paper we study the steepest descent L²-gradient flow of the functional W_λ1,λ2, which is the the sum of the Willmore energy, λ1-weighted surface area, and λ2-weighted enclosed volume, for surfaces immersed in R³. This coincides with the Helfrich functional with zero `spontaneous curvature'. Our first results are a concentration-compactness alternative and interior estimates for the flow. For initial data with small energy, we prove preservation of embeddedness, and by directly estimating the Euler-Lagrange operator from below in L² we obtain that the maximal time of existence is finite. Combining this result …

Chemical Nature Of Alkaline Polyphosphate Boundary Film At Heated Rubbing Surfaces, Shanhong Wan, Anh Kiet Tieu, Qiang Zhu, Hongtao Zhu, Shaogang Cui, David R. G Mitchell, Charlie Kong, Bruce Cowie, John A. Denman, Rong Liu

Faculty of Engineering and Information Sciences - Papers: Part A

Alkaline polyphosphate has been demonstrated to be able to reduce significant wear and friction of sliding interfaces under heavy loads (>1 GPa) and elevated temperature (800°C and above) conditions, e.g. hot metal manufacturing. The chemical composition and fine structure of polyphosphate lubricating film is not well understood as well as the role of alkaline elements within the reaction film at hot rubbing surface. This work makes use of the coupling surface analytical techniques on the alkaline polyphosphate tribofilm, XANES, TOF-SIMS and FIB/TEM. The data show the composition in gradient distribution and trilaminar structure of tribofilm: a shorter chain phosphate …

Fatigue Of Swollen Elastomers

Faculty of Engineering University of Malaya

The compatibility of the properties of elastomer with conventional diesel fuel has made it favourable in many engineering applications. However, due to global energy insecurity issues, there is an urgent need to find alternative renewable sources of energy as replacements to conventional diesel. In this respect, biodiesel appears to be a promising candidate. Hence, research into the compatibility and fatigue characteristics of elastomers exposed to biodiesel becomes essential. The present paper introduces the first attempt to investigate the effect of different solvents on the fatigue of swollen elastomers. The filled nitrile rubbers are immersed in the palm biodiesel and conventional …

Gap Phenomena For A Class Of Fourth-Order Geometric Differential Operators On Surfaces With Boundary, Glen Wheeler

Faculty of Engineering and Information Sciences - Papers: Part A

In this paper we establish a gap phenomenon for immersed surfaces with arbitrary codimension, topology and boundaries that satisfy one of a family of systems of fourth-order anisotropic geometric partial differential equations. Examples include Willmore surfaces, stationary solitons for the surface diffusion flow, and biharmonic immersed surfaces in the sense of Chen. On the boundary we enforce either umbilic or flat boundary conditions: that the tracefree second fundamental form and its derivative or the full second fundamental form and its derivative vanish. For the umbilic boundary condition we prove that any surface with small L2-norm of the tracefree second fundamental …

Thin Film Lubrication Of Hexadecane Confined By Iron And Iron Oxide Surfaces: A Crucial Role Of Surface Structure, Thi Dinh Ta, A Kiet Tieu, Hongtao Zhu, Buyung Kosasih

Faculty of Engineering and Information Sciences - Papers: Part A

A comparative analysis of thin film lubrication of hexadecane between different iron and its oxide surfaces has been carried out using classical molecular dynamic simulation. An ab initio force-field, COMPASS, was applied for n-hexadecane using explicit atom model. An effective potential derived from density functional theory calculation was utilized for the interfacial interaction between hexadecane and the tribo-surfaces. A quantitative surface parameterization was introduced to investigate the influence of surface properties on the structure, rheological properties, and tribological performance of the lubricant. The results show that although the wall-fluid attraction of hexadecane on pure iron surfaces is significantly stronger than …

Convexity Estimates For Surfaces Moving By Curvature Functions, Ben Andrews, Mat Langford, James A. Mccoy

Faculty of Engineering and Information Sciences - Papers: Part A

We consider the evolution of compact surfaces by fully nonlinear, parabolic curvature ows for which the normal speed is given by a smooth, degree one homogeneous function of the principal curvatures of the evolving surface. Under no further restrictions on the speed function, we prove that initial surfaces on which the speed is positive become weakly convex at a singularity of the flow. This generalises the corresponding result [26] of Huisken and Sinestrari for the mean curvature ow to the largest possible class of degree one homogeneous surface flows.

Conductive Surfaces With Dynamic Switching In Response To Temperature And Salt, Alissa Hackett, Jenny Malmström, Paul J. Molino, Julien Gautrot, Hongrui Zhang, Michael J. Higgins, Gordon G. Wallace, David E. Williams, Jadranka Travas-Sejdic

Australian Institute for Innovative Materials - Papers

This work demonstrates polymer brushes grafted from conductive polymer films which display dynamic surface switching dependent on salt, temperature and electrode potential. The electroactivity presented by the conductive polymer and the responsiveness of the grafted brushes leads to an interface with multiple control parameters. Here, we demonstrate this concept by grafting of uncharged brushes of poly(ethylene glycol)methyl ether methacrylates from conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT), and observe a temperature- and salt-induced switch of brush conformation, and their effect on the electrochemistry of the material. The switching conditions can be tailored by copolymerizing monomers with different numbers of ethylene glycol units. In …

Spectroscopic Investigation Of The Chemical And Electronic Properties Of Chalcogenide Materials For Thin-Film Optoelectronic Devices, Kimberly Horsley

UNLV Theses, Dissertations, Professional Papers, and Capstones

Chalcogen-based materials are at the forefront of technologies for sustainable energy production. This progress has come only from decades of research, and further investigation is needed to continue improvement of these materials.

For this dissertation, a number of chalcogenide systems were studied, which have applications in optoelectronic devices, such as LEDs and Photovoltaics. The systems studied include Cu(In,Ga)Se2 (CIGSe) and CuInSe2 (CISe) thin-film absorbers, CdTe-based photovoltaic structures, and CdTe-ZnO nanocomposite materials. For each project, a sample set was prepared through collaboration with outside institutions, and a suite of spectroscopy techniques was employed to answer specific questions about the system. These …

Transparent Conducting Oxides: A Δ-Doped Superlattice Approach, Valentino R. Cooper, Sung S. Ambrose Seo, Suyoun Lee, Jun Sung Kim, Woo Seok Choi, Satoshi Okamoto, Ho Nyung Lee

Physics and Astronomy Faculty Publications

Metallic states appearing at interfaces between dissimilar insulating oxides exhibit intriguing phenomena such as superconductivity and magnetism. Despite tremendous progress in understanding their origins, very little is known about how to control the conduction pathways and the distribution of charge carriers. Using optical spectroscopic measurements and density-functional theory (DFT) simulations, we examine the effect of SrTiO3 (STO) spacer layer thickness on the optical transparency and carrier distribution in La δ-doped STO superlattices. We experimentally observe that these metallic superlattices remain highly transparent to visible light; a direct consequence of the appropriately large gap between the O 2p and Ti 3d …

Effects Of Playing Surface And Shoe Type Of Acl Tears In Soccer Players, Melissa Mansfield

Honors Theses

Anterior Cruciate Ligament injuries have become more common in athletes over the past decade which is believed to result from playing on more artificial turf surfaces. This study tested the playing surface theory by building upon a previous study conducted with Albany Medical Center which tested surface samples using an axial-torsion load frame located at Union College. The motion that causes most ACL noncontact injuries is replicated by the load frame which pushes and rotates a shoe against the playing surface and measures the torque it experiences. The foot position, normal load, degree of rotation and rate of rotation were …

Surface Properties And Interaction Forces Of Biopolymer-Doped Conductive Polypyrrole Surfaces By Atomic Force Microscopy, Jani M. Pelto, Suvi P. Haimi, Aliisa S. Siljander, Susanna S. Miettinen, Kirsi M. Tappura, Michael J. Higgins, Gordon G. Wallace

Gordon Wallace

Surface properties and electrical charges are critical factors elucidating cell interactions on biomaterial surfaces. The surface potential distribution and the nanoscopic and microscopic surface elasticity of organic polypyrrole-hyaluronic acid (PPy-HA) were studied by atomic force microscopy (AFM) in a fluid environment in order to explain the observed enhancement in the attachment of human adipose stem cells on positively charged PPy-HA films. The electrostatic force between the AFM tip and a charged PPy-HA surface, the tip-sample adhesion force, and elastic moduli were estimated from the AFM force curves, and the data were fitted to electrostatic double-layer and elastic contact models. The …

Cation Exchange At Semiconducting Oxide Surfaces: Origin Of Light-Induced Performance Increases In Porphyrin Dye-Sensitized Solar Cells, Matthew J. Griffith, Kenji Sunahara, Akihiro Furube, Attila J. Mozer, David L. Officer, Pawel Wagner, Gordon G. Wallace, Shogo Mori

Gordon Wallace

The origin of simultaneous improvements in the short-circuit current density (Jsc) and open-circuit voltage (Voc) of porphyrin dye-sensitized TiO2 solar cells following white light illumination was studied by systematic variation of several different device parameters. Reduction of the dye surface loading resulted in greater relative performance enhancements, suggesting open space at the TiO2 surface expedites the process. Variation of the electrolyte composition and subsequent analysis of the conduction band potential shifts suggested that a light-induced replacement of surface-adsorbed lithium (Li+) ions with dimethylpropylimidazolium (DMPIm+) ions was responsible for an increased electron lifetime by decreasing the recombination with the redox mediator. …

Fabrication Of Robust Superconducting Granular Aluminium/Palladium Bilayer Microbolometers With Sub-Nanosecond Response, Thomas E. Wilson

Thomas E. Wilson

We provide a convenient recipe for fabricating reliable superconducting microbolometers as acoustic phonon detectors with sub-nanosecond response, using imagereversal optical lithography and dc-magnetron sputtering, and our recipe requires no chemical or plasma etching. Our approach solves the traditional problem for granular aluminium bolometers of unreliable (i.e., non-Ohmic) electrical contacts by sequentially sputtering the granular aluminium film and then a palladium capping layer. We use dc calibration data, the method of Danilchenko et al. [1], and direct nanosecond-pulsed photoexcitation to obtain the microbolometer’s characteristic current, thermal conductance, characteristic relaxation time, and heat capacity. We also demonstrate the use of the deconvolution …

Frequency Selective Surfaces For Extreme Applications, Jay Houston Barton

Open Access Theses & Dissertations

It is known that for high-power microwaves and other extreme environments, the use of resonant metallic elements in frequency selective surfaces can be problematic. The solution developed within this Dissertation to solve these problems was to use guided-mode resonance phenomenon to create all-dielectric frequency selective surfaces that could survive these extreme environments.

To fully understand how these devices work, three different computational electromagnetic methods are formulated and implemented. The formulation of these methods start with the differential form of Maxwellâ??s equation and are derived all the way down to the final simulation state. This is done sequentially and all the …

Three-Dimensional Measurement Of Object Surfaces With Complex Shape And Color Distribution Based On Projection Of Color Fringe Patterns, Ke Chen, Jiangtao Xi, Yanguang Yu, Sheng Tong, Qinghua Guo

Faculty of Engineering and Information Sciences - Papers: Part A

A challenging issue associated with three-dimensional (3D) fringe patterns profilometry (FPP) is the unwrapping of phase maps resulting from color object surfaces. This paper proposes a new colorprojection-based 3D FPP, making use of the three primary color channels [i.e., red, green, and blue (RGB)] associated with digital projectors. One channel (e.g., red) is used for projecting sinusoidal fringes required by phase shift profilometry (PSP); the other two channels are employed for generating binary stripe patterns. In order to achieve reliable phase unwrapping, each fringe of the sinusoidal patterns is identified by a unique binary sequence. These sequences are then encoded …

Unstable Willmore Surfaces Of Revolution Subject To Natural Boundary Conditions, Anna Dall'acqua, Klaus Deckelnick, Glen Wheeler

Faculty of Engineering and Information Sciences - Papers: Part A

In the class of surfaces with fixed boundary, critical points of the Willmore functional are naturally found to be those solutions of the Euler-Lagrange equation where the mean curvature on the boundary vanishes. We consider the case of symmetric surfaces of revolution in the setting where there are two families of stable solutions given by the catenoids. In this paper we demonstrate the existence of a third family of solutions which are unstable critical points of the Willmore functional, and which spatially lie between the upper and lower families of catenoids. Our method does not require any kind of smallness …

Tuning Of The Transverse Magneto-Optical Kerr Effect In Magneto-Plasmonic Crystals, Martin Pohl, L. E. Kreilkamp, Vladimir I. Belotelov, Ilya A. Akimov, A N. Kalish, N E. Khokhlov, V J. Yallapragada, A V. Gopal, Mohammad Nur-E-Alam, Mikhail Vasiliev, D R. Yakovlev, Kamal Alameh, A K. Zvezdin, M Bayer

Research outputs 2013

The spectral properties of the transverse magneto-optical Kerr effect (TMOKE) in periodic metal–dielectric hybrid structures are studied, in particular with respect to the achievable magnitude. It is shown that the TMOKE is sensitive to the magneto-optical activity of the bismuth-substituted rare-earth iron garnet, which is used as a dielectric material in the investigated structures. For samples with larger Bi substitution level and, consequently, larger gyration constant, the magnitude of the TMOKE increases and reaches 13% in the case of a Bi1.8Lu1.2Fe3.6Al1.4O12 magnetic film. Further, it is demonstrated that the TMOKE vanishes at the high-symmetry points of the Brillouin zone (at …

Autonomous Thin Spray-On Liner Application In Irregular Tunnel And Mine Roadway Surfaces, M P. Tibbs, O K. Tyler, S Van Duin, E Baafi

Faculty of Engineering and Information Sciences - Papers: Part A

An autonomous spray application system for a structural Thin Spray-on Liner (TSL) is targeting productivity and safety on underground coal continuous miners by replacing steel mesh, and has broader applications as surface support and confinement in metalliferous mines and civil tunnelling. Polymer chemistry, coating formulation, geotechnical assessment and the autonomous application system are being developed within an integrated package as part of a continuous miner automation project. The polymer-based TSL system, dubbed "ToughSkin", has significant benefits over conventional steel mesh, including; more automatable by spray application, complete skin confinement, active skin reinforcement as a fast-curing composite with substrate, and effective …

Surface Properties And Interaction Forces Of Biopolymer-Doped Conductive Polypyrrole Surfaces By Atomic Force Microscopy, Jani M. Pelto, Suvi P. Haimi, Aliisa S. Siljander, Susanna S. Miettinen, Kirsi M. Tappura, Michael J. Higgins, Gordon G. Wallace

Australian Institute for Innovative Materials - Papers

Surface properties and electrical charges are critical factors elucidating cell interactions on biomaterial surfaces. The surface potential distribution and the nanoscopic and microscopic surface elasticity of organic polypyrrole-hyaluronic acid (PPy-HA) were studied by atomic force microscopy (AFM) in a fluid environment in order to explain the observed enhancement in the attachment of human adipose stem cells on positively charged PPy-HA films. The electrostatic force between the AFM tip and a charged PPy-HA surface, the tip-sample adhesion force, and elastic moduli were estimated from the AFM force curves, and the data were fitted to electrostatic double-layer and elastic contact models. The …

Cation Exchange At Semiconducting Oxide Surfaces: Origin Of Light-Induced Performance Increases In Porphyrin Dye-Sensitized Solar Cells, Matthew J. Griffith, Kenji Sunahara, Akihiro Furube, Attila J. Mozer, David L. Officer, Pawel Wagner, Gordon G. Wallace, Shogo Mori

Australian Institute for Innovative Materials - Papers

The origin of simultaneous improvements in the short-circuit current density (Jsc) and open-circuit voltage (Voc) of porphyrin dye-sensitized TiO2 solar cells following white light illumination was studied by systematic variation of several different device parameters. Reduction of the dye surface loading resulted in greater relative performance enhancements, suggesting open space at the TiO2 surface expedites the process. Variation of the electrolyte composition and subsequent analysis of the conduction band potential shifts suggested that a light-induced replacement of surface-adsorbed lithium (Li+) ions with dimethylpropylimidazolium (DMPIm+) ions was responsible for an increased electron lifetime by decreasing the recombination with the redox mediator. …

A Classification Theorem For Helfrich Surfaces, James Mccoy, Glen Wheeler

Faculty of Engineering and Information Sciences - Papers: Part A

In this paper we study the functional W , which is the the sum of the Willmore energy, weighted surface area, and weighted volume, for surfaces immersed in R^3. This coincides with the Helfrich functional with zero `spontaneous curvature'. Our main result is a complete classification of all smooth immersed critical points of the functional with nonnegative surface area weight and small L^2 norm of tracefree curvature. In particular we prove the non-existence of critical points of the functional for which the surface area and enclosed volume are positively weighted.