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- Title
- General Vector Explicit - Impact Time and Angle Control Guidance.
- Creator
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Robinson, Loren, Qu, Zhihua, Behal, Aman, Xu, Yunjun, University of Central Florida
- Abstract / Description
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This thesis proposes and evaluates a new cooperative guidance law called General Vector Explicit -Impact Time and Angle Control Guidance (GENEX-ITACG). The motivation for GENEX-ITACGcame from an explicit trajectory shaping guidance law called General Vector Explicit Guidance(GENEX). GENEX simultaneously achieves design specifications on miss distance and terminalmissile approach angle while also providing a design parameter that adjusts the aggressiveness ofthis approach angle. Encouraged by...
Show moreThis thesis proposes and evaluates a new cooperative guidance law called General Vector Explicit -Impact Time and Angle Control Guidance (GENEX-ITACG). The motivation for GENEX-ITACGcame from an explicit trajectory shaping guidance law called General Vector Explicit Guidance(GENEX). GENEX simultaneously achieves design specifications on miss distance and terminalmissile approach angle while also providing a design parameter that adjusts the aggressiveness ofthis approach angle. Encouraged by the applicability of this user parameter, GENEX-ITACG is anextension that allows a salvo of missiles to cooperatively achieve the same objectives of GENEXagainst a stationary target through the incorporation of a cooperative trajectory shaping guidancelaw called Impact Time and Angle Control Guidance (ITACG).ITACG allows a salvo of missile to simultaneously hit a stationary target at a prescribed impactangle and impact time. This predetermined impact time is what allows each missile involvedin the salvo attack to simultaneously arrived at the target with unique approach angles, whichgreatly increases the probability of success against well defended targets. GENEX-ITACG furtherincreases this probability of kill by allowing each missile to approach the target with a uniqueapproach angle rate through the use of a user design parameter.The incorporation of ITACG into GENEX is accomplished through the use of linear optimal controlby casting the cost function of GENEX into the formulation of ITACG. The feasibility GENEXITACGis demonstrated across three scenarios that demonstrate the ITACG portion of the guidancelaw, the GENEX portion of the guidance law, and finally the entirety of the guidance law. Theresults indicate that GENEX-ITACG is able to successfully guide a salvo of missiles to simultaneouslyhit a stationary target at a predefined terminal impact angle and impact time, while alsoallowing the user to adjust the aggressiveness of approach.
Show less - Date Issued
- 2015
- Identifier
- CFE0005876, ucf:50868
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005876
- Title
- Automated Hybrid Singularity Superposition and Anchored Grid Pattern BEM Algorithm for the Solution of the Inverse Geometric Problem.
- Creator
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Ni, Marcus, Kassab, Alain, Divo, Eduardo, Chopra, Manoj, University of Central Florida
- Abstract / Description
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A method for solving the inverse geometrical problem is presented by reconstructing the unknown subsurface cavity geometry using boundary element methods, a genetic algorithm, and Nelder-Mead non-linear simplex optimization. The heat conduction problem is solved utilizing the boundary element method, which calculates the difference between the measured temperature at the exposed surface and the computed temperature under the current update of the unknown subsurface flaws and cavities. In a...
Show moreA method for solving the inverse geometrical problem is presented by reconstructing the unknown subsurface cavity geometry using boundary element methods, a genetic algorithm, and Nelder-Mead non-linear simplex optimization. The heat conduction problem is solved utilizing the boundary element method, which calculates the difference between the measured temperature at the exposed surface and the computed temperature under the current update of the unknown subsurface flaws and cavities. In a first step, clusters of singularities are utilized to solve the inverse problem and to identify the location of the centroid(s) of the subsurface cavity(ies)/flaw(s). In a second step, the reconstruction of the estimated cavity(ies)/flaw(s) geometry(ies) is accomplished by utilizing an anchored grid pattern upon which cubic spline knots are restricted to move in the search for unknown geometry. Solution of the inverse problem is achieved using a genetic algorithm accelerated with the Nelder-Mead non-linear simplex. To optimize the cubic spline interpolated geometry, the flux (Neumann) boundary conditions are minimized using a least squares functional. The automated algorithm successfully reconstructs single and multiple subsurface cavities within two dimensional mediums. The solver is also shown to accurately predict cavity geometries with random noise in the boundary condition measurements. Subsurface cavities can be difficult to detect based on their location. By applying different boundary conditions to the same geometry, more information is supplied at the boundary, and the subsurface cavity is easily detected despite its low heat signature effect at the boundaries. Extensions to three-dimensional applications are outlined.
Show less - Date Issued
- 2013
- Identifier
- CFE0004900, ucf:49644
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004900
- Title
- DIFFRACTION STUDIES OF DEFORMATION IN SHAPE MEMORY ALLOYS AND SELECTED ENGINEERING COMPONENTS.
- Creator
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RATHOD, CHANDRASEN, Vaidyanathan, Raj, University of Central Florida
- Abstract / Description
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Deformation phenomena in shape memory alloys involve stress-, temperature-induced phase transformations and crystallographic variant conversion or reorientation, equivalent to a twinning operation. In near equiatomic NiTi, Ti rich compositions can exist near room temperature as a monoclinic B19' martensitic phase, which when deformed undergoes twinning resulting in strains as large as 8%. Upon heating, the martensite transforms to a cubic B2 austenitic phase, thereby recovering the strain and...
Show moreDeformation phenomena in shape memory alloys involve stress-, temperature-induced phase transformations and crystallographic variant conversion or reorientation, equivalent to a twinning operation. In near equiatomic NiTi, Ti rich compositions can exist near room temperature as a monoclinic B19' martensitic phase, which when deformed undergoes twinning resulting in strains as large as 8%. Upon heating, the martensite transforms to a cubic B2 austenitic phase, thereby recovering the strain and exhibiting the shape memory effect. Ni rich compositions on the other hand can exist near room temperature in the austenitic phase and undergo a reversible martensitic transformation on application of stress. Associated with this reversible martensitic transformation are macroscopic strains, again as large as 8%, which are also recovered and resulting in superelasticity. This work primarily focuses on neutron diffraction measurements during loading at the Los Alamos Neutron Science Center at Los Alamos National Laboratory. Three phenomena were investigated: First, the phenomena of hysteresis reduction and increase in linearity with increasing plastic deformation in superelastic NiTi. There is usually a hysteresis associated with the forward and reverse transformations in superelastic NiTi which translates to a hysteresis in the stress-strain curve during loading and unloading. This hysteresis is reduced in cold-worked NiTi and the macroscopic stress-strain response is more linear. This work reports on measurements during loading and unloading in plastically deformed (up to 11%) and cycled NiTi. Second, the tension-compression stress-strain asymmetry in martensitic NiTi. This work reports on measurements during tensile and compressive loading of polycrystalline shape-memory martensitic NiTi with no starting texture. Third, a heterogeneous stress-induced phase transformation in superelastic NiTi. Measurements were performed on a NiTi disc specimen loaded laterally in compression and associated with a macroscopically heterogeneous stress state. For the case of superelastic NiTi, the experiments related the macroscopic stress-strain behavior (from an extensometer or an analytical approach) with the texture, phase volume fraction and strain evolution (from neutron diffraction spectra). For the case of shape memory NiTi, the macroscopic connection was made with the texture and strain evolution due to twinning and elastic deformation in martensitic NiTi. In all cases, this work provided for the first time insight into atomic-scale phenomena such as mismatch accommodation and martensite variant selection. The aforementioned technique of neutron diffraction for mechanical characterization was also extended to engineering components and focused mainly on the determination of residual strains. Two samples were investigated and presented in this work; first, a welded INCONEL 718 NASA space shuttle flow liner was studied at 135 K and second, Ti-6Al-4V turbine blade components were investigated for Siemens Westinghouse Power Corporation. Lastly, also reported in this dissertation is a refinement of the methodology established in the author's masters thesis at UCF that used synchrotron x-ray diffraction during loading to study superelastic NiTi. The Los Alamos Neutron Science Center is a national user facility funded by the United States Department of Energy, Office of Basic Energy Sciences, under Contract No. W-7405-ENG-36. The work reported here was made possible by grants to UCF from NASA (NAG3-2751), NSF CAREER (DMR-0239512), Siemens Westinghouse Power Corporation and the Space Research Initiative.
Show less - Date Issued
- 2005
- Identifier
- CFE0000723, ucf:46608
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000723
- Title
- Structure, stability, vibrational, thermodynamic, and catalytic properties of metal nanostructures: size, shape, support, and adsorbate effects.
- Creator
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Behafarid, Farzad, Roldan Cuenya, Beatriz, Chow, Lee, Heinrich, Helge, Kara, Abdelkader, Schoenfeld, Winston, University of Central Florida
- Abstract / Description
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Recent advances in nanoscience and nanotechnology have provided the scientific community with exciting new opportunities to rationally design and fabricate materials at the nanometer scale with drastically different properties as compared to their bulk counterparts. In this dissertation, several challenges have been tackled in aspects related to nanoparticle (NP) synthesis and characterization, allowing us to make homogenous, size- and shape-selected NPs via the use of colloidal chemistry,...
Show moreRecent advances in nanoscience and nanotechnology have provided the scientific community with exciting new opportunities to rationally design and fabricate materials at the nanometer scale with drastically different properties as compared to their bulk counterparts. In this dissertation, several challenges have been tackled in aspects related to nanoparticle (NP) synthesis and characterization, allowing us to make homogenous, size- and shape-selected NPs via the use of colloidal chemistry, and to gain in depth understanding of their distinct physical and chemical properties via the synergistic use of a variety of ex situ, in situ, and operando experimental tools. A variety of phenomena relevant to nanosized materials were investigated, including the role of the NP size and shape in the thermodynamic and electronic properties of NPs, their thermal stability, NP-support interactions, coarsening phenomena, and the evolution of the NP structure and chemical state under different environments and reaction conditions.
Show less - Date Issued
- 2012
- Identifier
- CFE0004779, ucf:49796
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004779
- Title
- Physical-Virtual Patient Simulators: Bringing Tangible Humanity to Simulated Patients.
- Creator
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Daher, Salam, Welch, Gregory, Gonzalez, Laura, Cendan, Juan, Proctor, Michael, University of Central Florida
- Abstract / Description
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In lieu of real patients, healthcare educators frequently use simulated patients. Simulated patients can be realized in physical form, such as mannequins and trained human actors, or virtual form, such as via computer graphics presented on two-dimensional screens or head-mounted displays. Each of these alone has its strengths and weaknesses. I introduce a new class of physical-virtual patient (PVP) simulators that combine strengths of both forms by combining the flexibility and richness of...
Show moreIn lieu of real patients, healthcare educators frequently use simulated patients. Simulated patients can be realized in physical form, such as mannequins and trained human actors, or virtual form, such as via computer graphics presented on two-dimensional screens or head-mounted displays. Each of these alone has its strengths and weaknesses. I introduce a new class of physical-virtual patient (PVP) simulators that combine strengths of both forms by combining the flexibility and richness of virtual patients with tangible characteristics of a human-shaped physical form that can also exhibit a range of multi-sensory cues, including visual cues (e.g., capillary refill and facial expressions), auditory cues (e.g., verbal responses and heart sounds), and tactile cues (e.g., localized temperature and pulse). This novel combination of integrated capabilities can improve patient simulation outcomes. In my Ph.D. work I focus on three primary areas of related research. First, I describe the realization of the technology for PVPs and results from two user-studies to evaluate the importance of dynamic visuals and human-shaped physical form in terms of perception, behavior, cognition, emotions, and learning.Second, I present a general method to numerically evaluate the compatibility of any simulator-scenario pair in terms of importance and fidelity of cues. This method has the potential to make logistical, economic, and educational impacts on the choices of utilizing existing simulators.Finally, I describe a method for increasing human perception of simulated humans by exposing participants to the simulated human taking part in a short, engaging conversation prior to the simulation.
Show less - Date Issued
- 2018
- Identifier
- CFE0007750, ucf:52402
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007750
- Title
- Continuous Oscillation: Vibrational Effects and Acceptable Frequency Ranges of Small Bore Piping in Field Applications.
- Creator
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Kasprzyk, Marie, Kauffman, Jeffrey L., Bai, Yuanli, Gordon, Ali, University of Central Florida
- Abstract / Description
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In turbomachinery, a common failure mode is cracking of welds at the equipment and piping connection point. Each incidence of these cracks causes a forced shutdown to perform repairs that cost millions of dollars. This type of failure is predominately seen in small bore piping, which has a nominal diameter of 2 inches and smaller. This thesis addresses the failure prediction analysis of small bore piping, specifically in turbomachinery applications. Performing failure analysis to predict the...
Show moreIn turbomachinery, a common failure mode is cracking of welds at the equipment and piping connection point. Each incidence of these cracks causes a forced shutdown to perform repairs that cost millions of dollars. This type of failure is predominately seen in small bore piping, which has a nominal diameter of 2 inches and smaller. This thesis addresses the failure prediction analysis of small bore piping, specifically in turbomachinery applications. Performing failure analysis to predict the potential cracking of welds will allow for replacement of the piping during a planned shutdown which in the long term saves money due to costs such as expediting materials, overtime pay, and extended downtime. This analysis uses real-world applications of a chemical plant in Louisiana. The piping analyzed was connected to centrifugal compressors. The data used from these pieces of equipment included the material of construction, the piping schedule, lengths, nominal diameter, and running speeds. Based on research that shows welding the connection point with a full penetration weld greatly increases the life expectancy of the connection, this thesis uses full penetration welds in the analysis. The piping was analyzed using the software ANSYS to perform a finite element analysis, specifically examining the stress due to the induced harmonic forces. It is a common fact that having fewer supports on a vibrating pipe induces greater stresses and strains on the weld connections. Supports installed 12" from the equipment only show one to two ranges of frequencies to avoid compared to the longer piping which has four to five ranges of unacceptable frequencies. Tables are developed to relay acceptable frequencies based on observed stresses of the welds in the model.
Show less - Date Issued
- 2017
- Identifier
- CFE0006749, ucf:51862
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006749
