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A Framework For Studying Meshfree Geometry And A Method For Explicit Boundary Determination, Joseph Bradley Alford

USF Tampa Graduate Theses and Dissertations

Patient-specific biomechanical analysis is an important tool used to understand the complex processes that occur in the body due to physical stimulation. Patient-specific models are generated by processing medical images; once an object from the image is identified via segmentation, a point cloud representation of the object is extracted. Generating an analysis suitable representation from the point cloud has traditionally required generating a finite element mesh, which often requires a well defined surface to accomplish. Point clouds lack a well defined geometry, meaning that the surface definition is incomplete at best. Point clouds that have been generated from images have …

Experimental And Computational Study On Fracture Mechanics Of Multilayered Structures, Hai Thanh Tran

USF Tampa Graduate Theses and Dissertations

Many devices in electronics are in the form of multilayered structures. These structures can fail catastrophically if they contain defects or cracks. Enhancing their fracture properties is therefore critical to improve the reliability of the systems. The interface-dominated fracture mechanics of multilayered structure was studied using experiments and finite element (FE) modeling by considering two examples: thin films on polymer substrates in flexible electronics and Cu leadframe/epoxy molding compound (EMC) in micro-electronics packaging.

In the first example, aluminum-manganese (Al-Mn) thin films with Mn concentration up to 20.5 at.% were deposited on polyimide (PI) substrates. A variety of phases, including supersaturated …

Sputtering Power Effects On Growth And Mechanical Properties Of Cr2alc Max Phase Coatings, Muhammad Naveed, Aleksei Obrosov, Andrzej Zak, Wlodzimierz Dudzinski, Alex A. Volinsky, Sabine Weiß

Mechanical Engineering Faculty Publications

Coating growth and mechanical properties of nanolamellar Cr₂AlC coatings at various sputtering power were investigated in the present study. Cr₂AlC coating was deposited on the IN 718 superalloy and (100) Si wafers by DC magnetron sputtering at different sputtering powers. The structure and properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanoindentation. It was found that coatings had columnar structure with nanocrystalline substructure. Deposition rate increased with the sputtering power. XRD results showed the presence of the Cr₂AlC MAX phase, intermetallic AlCr₂ and Cr_{7 …}

Molybdenum Disulfide-Conducting Polymer Composite Structures For Electrochemical Biosensor Applications, Hongxiang Jia

USF Tampa Graduate Theses and Dissertations

Lactic acid is widely existing in human bodies, animals and microorganisms. Recently, using biosensor to detect the concentration of lactic acid and diagnose disease have attracted great research and development interests. Nanocomposites is one of the best material used for biosensor because their wonderful conductivity, optical and electrochemical properties. In the study, MoS₂ and polypyrrole (PPY) are used for the composite material electrode. To determine whether lactate oxidase (LOD) was helpful for the biosensor’s detective properties, both PPY-MoS₂ film with LOD and PPY-MoS₂ film without LOD are being tested. The fourier transform infrared spectroscopy (FTIR) and Raman …

Simulation And Verification Of Fluid Jet Polishing, Senmiao Hu

USF Tampa Graduate Theses and Dissertations

Fluid jet polishing (FJP) is a new advanced polishing technology that finds applications in many industries, especially in the optics industry. With the broad application of various surfaces in optics, the sub-micrometric scale and the nanometric surface roughness accuracy are major challenges. Fluid jet polishing is a technology developed from abrasive water jet machining. This technology is a water jet cutting technology, which uses high-pressure flow to cut/remove materials.

In this thesis, the working principle, and simulations, as well as verification of fluid jet polishing are thoroughly investigated. The verification of fluid jet polishing in this thesis includes velocity distribution …

Effect Of Void Fraction On Transverse Shear Modulus Of Advanced Unidirectional Composites, Jui-He Tai

USF Tampa Graduate Theses and Dissertations

In composite materials, transverse shear modulus is a critical moduli parameter for designing complex composite structures. For dependable mathematical modeling of mechanical behavior of composite materials, an accurate estimate of the moduli parameters is critically important as opposed to estimates of strength parameters where underestimation may lead to a non-optimal design but still would give one a safe one.

Although there are mechanical and empirical models available to find transverse shear modulus, they are based on many assumptions. In this work, the model is based on a three-dimensional elastic finite element analysis with multiple cells. To find the shear modulus, …

Application And Analysis Of Asymmetrical Hot And Cold Stimuli, Ahmad Manasrah

USF Tampa Graduate Theses and Dissertations

The human body has a unique mechanism for perceiving surrounding temperatures. When an object is in contact with the skin, we do not feel its temperature. Instead, we feel the temperature change that is caused on our skin by that object. The faster the heat is transferred, the more intense the thermal sensation is. In this dissertation, a new dynamic thermal display method, where different rates of warm and cold are applied on the skin to generate a unique sensation, is presented. The new method can be related in a wide range of applications including thermal haptics and virtual reality. …

The Development Of A Prosthetic Training Software For Upper Limb Amputees, Tyler Kayne Sullins

USF Tampa Graduate Theses and Dissertations

The purpose of this study was to develop an intuitive software that aids in the field of prosthetic training and rehabilitation by creating an individualized visualization of joint angles. This software is titled “the prosthetic training software (PTS) for individualized joint angle representation”, and it enables the individualized portrayal of predicted or pre-recorded joint angles. The PTS is an intuitive program for clinicians and prosthesis users that produces an animation of a virtual avatar reflecting the user’s segment lengths and amputation for rehabilitation and training purposes.

The PTS consists of a graphical user interface (GUI) and a 3D visualization of …

Waterproofing Shape-Changing Mechanisms Using Origami Engineering; Also A Mechanical Property Evaluation Approach For Rapid Prototyping, Andrew Jason Katz

USF Tampa Graduate Theses and Dissertations

My work has been focused on compliant mechanisms, origami engineering, and rapid prototyping. Two of the projects that I worked on were focused on compliant mechanisms and origami engineering. The similar goal of both of those projects was to create an origami membrane whose kinematics mimic that of an existing mechanism. The first project created an origami membrane to mimic the kinematics of a planar shape-changing mechanism. This mechanism was a square shaped unit-cell which could shear, compress, and expand in its own plane. In addition to waterproofing the mechanism, the first project also sought to optimize the dimensions of …

Droplet-Based Mechanical Actuator Utilizing Electrowetting Effect, Qi Ni

USF Tampa Graduate Theses and Dissertations

The goal of this work is to quantify the key design parameters such as the load capacity, actuation force, positioning repeatability, and reliability for droplet-based electrowetting actuators. Due to the fact that surface tension dominates gravity at both the mesoscale and microscale, droplet-based actuators can provide adequate force in manipulation tasks at those scales. Electrowetting, which uses an electric field to modulate the apparent surface tension of the liquid-ambient, provides a method to actuate droplets, which in turn transports the object carried by the droplet.

Most previous electrowetting actuation efforts have concentrated on manipulating droplets in a closed two-plate configuration. …

Eigenstress Model For Electrochemistry Of Solid Surfaces, Hongxin Ma, Xilin Xiong, Panpan Gao, Xi Li, Yu Yan, Alex A. Volinsky, Yanjing Su

Mechanical Engineering Faculty Publications

Thermodynamic analysis and molecular dynamics simulations were conducted to systematically study the size-dependent electrochemical response of solids. By combining the generalized Young-Laplace equation with the popular Butler-Volmer formulation, the direct influence of surface stress on solid film electrochemical reactions was isolated. A series of thermodynamic formulas were developed to describe the size-dependent electrochemical properties of the solid surface. These formulas include intrinsic surface elastic parameters, such as surface eigenstress and surface elastic modulus. Metallic films of Au, Pt, Ni, Cu and Fe were studied as examples. The anodic current density of the metal film increased, while the equilibrium potential decreased …

Dynamic Recrystallization Behavior And Processing Map Of The Cu–Cr–Zr–Nd Alloy, Yi Zhang, Huili Sun, Alex A. Volinsky, Baohong Tian, Kexing Song, Zhe Chai, Ping Liu, Yong Liu

Mechanical Engineering Faculty Publications

Hot deformation behavior of the Cu–Cr–Zr–Nd alloy was studied by hot compressive tests in the temperature range of 650–950 °C and the strain rate range of 0.001–10 s⁻¹ using Gleeble-1500D thermo-mechanical simulator. The results showed that the flow stress is strongly dependent on the deformation temperature and the strain rate. With the increase of temperature or the decrease of strain rate, the flow stress significantly decreases. Hot activation energy of the alloy is about 404.84 kJ/mol and the constitutive equation of the alloy based on the hyperbolic-sine equation was established. Based on the dynamic material model, the processing map …

Al/Ti Nanostructured Multilayers: From Mechanical, Tribological, To Corrosion Properties, Sina Izadi

USF Tampa Graduate Theses and Dissertations

Nanostructured metallic multilayers (NMMs) are well-known for their high strength in smaller bilayer thicknesses. Six Al/Ti (NMM) with different individual layer thickness were tested for their mechanical hardness using a nanoindentation tool. Individual layer thicknesses were chosen carefully to cover the whole confined layer slip (CLS) model. Nano-hardness had a reverse relation with the square root of individual layer thickness and reached a steady state at ~ 5 nm bilayer thickness. Decreasing the layer bilayer thickness from ~ 104 nm to ~ 5 nm, improved the mechanical hardness up to ~ 101%. Residual stresses were measured using grazing incident X-ray …

Optimization And Characterization Of Integrated Microfluidic Surface Acoustic Wave Sensors And Transducers, Tao Wang

USF Tampa Graduate Theses and Dissertations

Surface acoustic waves (SAWs) have a large number of applications and the majority of them are in the sensor and actuator fields targeted to satisfy market needs. Recently, researchers have focused on optimizing and improving device functions, sensitivity, power consumption, etc. However, SAW actuators and sensors still cannot replace their conventional counterparts in some mechanical and biomedical areas, such as actuators for liquid pumping under microfluidic channels and sensors for real-time cell culture monitoring. The two objectives of this dissertation are to explore the potential of piezoelectric materials and surface acoustic waves for research on actuators and sensors in the …

Hydrogen Effects On X80 Steel Mechanical Properties Measured By Tensile And Impact Testing, Xuan Li

USF Tampa Graduate Theses and Dissertations

The effect of hydrogen charging current density and tensile strain rate on the mechanical properties of X80 pipeline steel were investigated by slow strain rate test (SSRT), Charpy impact test, and scanning electron microscopy (SEM) in this thesis. The results show that both the ultimate tensile strength and elongation to failure of X80 steel were deteriorated significantly after charging with hydrogen. With a strain rate of 5 x 10^-5 s^-1, the relative tensile strength and plasticity loss of X80 steel had no significant change within the range of assumed hydrogen partial pressures at room temperature. At room …

Modified Yttrium Hydroxide/Mc Nylon Nanocomposites And Scaling Effects In Multilayer Polyethylene Films, Jia Chen

USF Tampa Graduate Theses and Dissertations

In this thesis, monomer casting (MC) nylon was synthesized. MC nylon could replace nonferrous metals in certain applications, including gears, wheels, and other moving parts. However, compared with metals, MC nylon products have poor strength and stiffness, and crack easily, especially at low temperatures. In addition, the dimensional stability of MC nylon is poor, especially in the large casting nylon products, causing significant internal stresses due to shrinkage. Thus, MC nylon cracks easily when cast and molded. The yttrium hydroxide particles were modified by stearic acid and dispersed in the caprolactam. The polymerization time was short due to fast anionic …

On Event-Triggered Adaptive Architectures For Decentralized And Distributed Control Of Large-Scale Modular Systems, Ali Albattat, Benjamin C. Gruenwald, Tansel Yucelen

Mechanical Engineering Faculty Publications

The last decade has witnessed an increased interest in physical systems controlled over wireless networks (networked control systems). These systems allow the computation of control signals via processors that are not attached to the physical systems, and the feedback loops are closed over wireless networks. The contribution of this paper is to design and analyze event-triggered decentralized and distributed adaptive control architectures for uncertain networked large-scale modular systems; that is, systems consist of physically-interconnected modules controlled over wireless networks. Specifically, the proposed adaptive architectures guarantee overall system stability while reducing wireless network utilization and achieving a given system performance in …

Functional Performance Differences Between The Genium And C-Leg Prosthetic Knees And Intact Knees, Michael J. Highsmith, Jason T. Kahle, Rebecca M. Miro, M. E. Cress, Derek J. Lura, William S. Quillen, Stephanie Carey, Rajiv V. Dubey, Larry J. Mengelkoch

Mechanical Engineering Faculty Publications

Microprocessor prosthetic knees (MPKs) have advanced technologically, offering new features to decrease impairment and activity limitations for persons with transfemoral amputation (TFA). The Genium knee is functionally untested, and functional differences between it and intact knees are unknown. This study sought to determine whether Genium use improves functional performance compared with the C-Leg. A randomized experimental crossover design was used, with a cross-section of five nonamputee controls for comparison to nor­mal. Twenty community-ambulating persons with TFA were trained and tested for accommodation with study components. All subjects (n = 25) were assessed using the Continuous-Scale Physical Functional Performance-10 (CS-PFP10) …

Microfocusing At The Pg1 Beamline At Flash, S. Dziarzhytski, N. Gerasimova, Rene Goderich, T. Mey, M. Rübhausen, F. Siewert, H. Weigelt, G. Brenner

Mechanical Engineering Faculty Publications

The Kirkpatrick-Baez (KB) refocusing mirror system installed at the PG1 branch of the plane-grating monochromator beamline at the soft X-ray/XUV free-electron laser in Hamburg (FLASH) is designed to provide tight aberration-free focusing down to 4 µm × 6 µm full width at half-maximum (FWHM) on the sample. Such a focal spot size is mandatory to achieve ultimate resolution and to guarantee best performance of the vacuum-ultraviolet (VUV) off-axis parabolic double-monochromator Raman spectrometer permanently installed at the PG1 beamline as an experimental end-station. The vertical beam size on the sample of the Raman spectrometer, which operates without entrance slit, defines and …

User Involvement In The Partner Program Of The Educational Social Network, Ilya V. Osipov, Alex A. Volinsky, Anna Y. Praskikova

Mechanical Engineering Faculty Publications

The paper describes experiments to attract active online system users to the partner program. The objective is to grow the number of users by involving existing system users in viral mechanics. Several examples of user motivation are given, along with the specific interface implementations and viral mechanics. Viral K-factor was used as the metrics for the resulting system growth assessment. Specific examples show both positive and negative outcomes. Growth of the target system parameters is discussed.