Browsing by Subject "College of Science and Engineering"

Now showing 1 - 20 of 204
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    AC Magnetic Susceptibility of a Thin Film of Permalloy
    (2014-10-02) Gray, Isaiah;
    Measurements of noise in magnetic thin lms have variously reported 1=f noise, white noise, and random telegraph noise. The 1=f noise experiments claim magnetic noise by relating the magnetic noise to the susceptibility with use of the uctuation-dissipation theorem. However, neither the linearity of the susceptibility necessary for application of uctuation-dissipation nor the frequency dependence of susceptibility was explored. To investigate more fully the frequency dependence and linearity of the magnetic susceptibility of a magnetic lm, we measured the AC susceptibility of a 100 nm thick lm of permalloy as a function of the magnitude HAC and frequency f of an applied AC magnetic eld over the full hysteresis loop of the lms, i.e., the measurements were performed while slowly varying an applied DC magnetic eld, HDC. The AC frequency range was from 20 Hz to 5 kHz while the AC eld range was between 0.2 G and 1 G. At HDC = 0 the response of the system was measured as a function of HAC at 200 Hz. It was found to be nonlinear but became reasonably close to linear for HAC < 1G - the coercive eld was approximately 15 G. The in-phase and out-of-phase components approximately follow power laws with frequency, with exponents 0.69 and -0.2. The behavior of the out-of-phase component is roughly consistent with previously measured white magnetic noise and a simple harmonic oscillator model, but the in-phase component does not follow the prediction of this model.
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    Accelerating a Simulation of Type-I X-ray Bursts from Accreting Neutron Stars
    (2012-04-18) Mackey, Mark
    The goal of my project was to develop an optimized linear system solver to shorten the runtime of a computer simulation. The simulation was created to study the thermonuclear burning of Type I X-ray Bursts in low-mass X-ray binary star systems (LMXBs). To study these systems, thousands of X-ray bursts need to be simulated. Currently, the simulation can complete around one X-ray burst per day. I worked on accelerating the main bottleneck of the simulation by using very powerful graphics cards (GPUs) instead of the central processing unit (CPU) to perform the necessary calculations. I made steady progress over the summer towards this goal and eventually developed a solution that was four to five times faster than the original code.
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    Accuracy of UAV Pitot-Static System
    (2012-04-18) Carlson, Ryan
    Though they are unnecessary for the structural integrity of the aircraft, an error in the pitot-static system can cause inaccuracies in flight and eventually lead to aircraft failure. Through a series of tests, the University of Minnesota’s UAV pitot-static system error was calculated and graphed. This allows the pressure sensors built into the pitot-static system to be calibrated for error, which prevents harm to the aircraft and operators.
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    AI Implementation in Digital Microfluidics
    (2021) Hein, Henry R
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    Altering Variables in the Half-Reaction for the Synthesis of Selenium Nanoparticles on Supports
    (2019) Wheeler, Samantha; Brockgreitens, John; Ahmed, Snober; Abbas, Abdennour
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    Analysis of Crack Patterns of Active Matters
    (2020) Hong, Sunyoung
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    Analysis of Turbostatic Graphene grown using chemical vapor deposition of Acetylene on Sapphire
    (2011-04-13) Kelly, Priscilla; Rothwell, Sara; Cohen PhD, Philip I
    Growing graphene on sapphire (Al2O3) by chemical vapor deposition (CVD) of acetylene is thought to introduce less strain on the bonds of graphene compared to other CVD methods. This is due to coincidence lattice matching in sapphire's hexagonal structure that appears after annealing. At this stage of my research, we are testing deposition rates of graphene on sapphire which has led to turbostratic, random and disorganized, growth. This poster demonstrates the properties of our turbostratic graphene from data collected by Raman spectroscopy, Scanning Electron Microscopy (SEM), sheet resistance measurements, and optical imaging.
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    Analytic Composition Expansions About Functional Equation Fixed Points
    (2021) Vogt, Cameron;
    Given holomorphic functions satisfying the functional equation φ = σ ◦ φ ◦ τ where τ has an attracting fixed point paired with a repelling fixed point of σ, we prove φ can be expressed as a composition expansion limn→∞ σ ◦ n ◦ ψ ◦ τ ◦ n where ψ approximates φ in some sense. With certain restrictions, φ is the unique function satisfying the functional equation. Conversely, given a functional equation of the specified form, we construct a function which satisfies it. The idea behind the proof is to view the transformation f → σ ◦ f ◦ τ as a contraction mapping on a particular space of holomorphic functions. As a basic example, the functional equation cos z = 2 cos2 (z/2) − 1 generates a composition expansion for cos z.
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    Analytical Analysis of Self-Folded Carbon Nanotube Structures
    (2012-04-18) Sun, Ludong
    Carbon nanotubes (CNT) are allotropes of carbon with a cylindrical nanostructure, which exhibit excellent mechanical properties such as high strength and resilience. They are promising material for many areas. Due to computational limitations of full atomic simulations of CNT systems, one has to use a mesoscopic (coarse-grained) models, that are much more computationally efficient, but still able to capture the important features of the mechanical behavior of CNT systems. The big scope of the project we will research is to see if DEM can be effectively used for modeling CNT systems. Distinct element method (DEM) is a technique currently used for large scale simulations in granular and discontinuous materials such as granular flows, powder mechanics, and rock mechanics. DEM allows the use of particles with complex geometries rather than simply considering point masses and thousands of particles can be considered in a model with a relatively low computational cost. For the UROP I am doing, I did some basic jobs to do the analytical analysis for two configurations (nanoring and nanoracket) to find the critical length when is potential energy reaches the minimum value. The critical length for the nanoring is found to be 2 π √(EI/ η). E is the Young’s modulus of the carbon nanotube; I is the moment inertia for a hollow circular cross section; η is the cohesive energy. For the critical length for the nanoracket, the results varied because the different assumptions of the shape. The most accurate is found to be 12√(EI/ η). The results have been verified using the DEM in PFC3D, which means the DEM to model the carbon nanotube is acceptable.
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    Application of the Dieckmann Condensation to Pyrrole Diesters
    (2012-04-18) Choi, Jua
    The Dieckmann condensation is commonly used in preparation of cyclic indole. The heterocyclic indole can be biologically active against cancer. The application of the Dieckmann condensation in the formation of five-membered pyrrole rings has not been previously reported in literature, making the procedure novel. Using extra equivalents of AlCl3 and Et3N allowed for the successful synthesis of cyclized pyrroles. Whether another choice of Lewis acids may also succeed the reaction remains to be discovered.
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    Assessment of Tissue Damage from Ultrasonic, Pneumatic and Combination Lithotripsy
    (2011-04-13) Cui, Yuqing; Sarkissian, Carl; Mohsenian, Kevin; Monga, Manoj
    Objective: To conduct a comparative evaluation of ultrasonic, pneumatic, and dual ultrasonic lithotripsy to predict the safety of probes on urinary tract tissue. Methods: Lithotriptors (medical device used to breakup kidney stones) tested were the Swiss Lithoclast Ultra (ultrasonic only - US, and ultrasonic-pneumatic combination US+P), and the Gyrus ACMI Cyberwand (dual ultrasonic). Fresh porcine ureters, bladders, and renal pelvis tissues were used for testing. A hands-free set up was used with each probe to vertically apply no pressure, 400 g, or 700 g of pressure for a duration of 3 seconds, 5 seconds or 180 seconds. Repetitive testing of each tissue/pressure/time combination was performed, for a total of 351 trials. Conclusion: All devices afforded a level of safety at tissue durations typical of inadvertent intraoperative contact (3-5 seconds), though the Lithoclast US-only was superior with regard to perforation for all tissue types. Overall, very similar results were observed between the Lithoclast US+P and Cyberwand.
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    Atomic Layer Deposition and Annealing of Co3O4 for Electrocatalytic Oxygen Evolution
    (2022) Nivarty, Tejas;
    In the fight against climate change, renewable energy must be employed to reduce fossil fuel dependence. However, intermittent renewable energy sources like wind and solar require grid energy storage to be feasible at a large scale. Hydrogen shows promise as an energy storage medium, and is also an important chemical feedstock. However, current production of hydrogen is carbon-intensive, and green hydrogen produced by water electrolysis is expensive due to a lack of highly effective, non-precious metal oxygen evolution (OER) electrocatalysts. Co3O4 is one of the most effective metal oxide OER electrocatalysts, but thin films of Co3O4 produced via atomic layer deposition (ALD) have never been explored for OER. Uniform thin films of Co3O4 were successfully produced via ALD using CoCp2 and O3 precursors, and the crystallinity and stoichiometry of these thin films were studied before and after annealing using X-ray photoelectron spectroscopy and X-ray diffraction. The catalytic decomposition of O3 by Co3O4 during ALD was mitigated by using a 200 °C deposition temperature and a 10 s long O3 pulse at 10 torr. 7 nm and 27 nm thick films showed no difference in surface stoichiometry after being deposited by ALD. Annealing under H2 reduced Co3O4 films to CoO, as did annealing under N2 at a high temperature. 27 nm Co3O4 films were found to be much more crystalline than 7 nm Co3O4 films before annealing, and 27 nm films showed improvements in crystallinity after annealing while 7 nm films did not.
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    Automated quantitative analysis of silica nanorod dimensions via watershed segmentation
    (2020) Quan, Michelle C.; Neal, Christopher A.; Calabrese, Michelle A.
    Quantifying the dimensions of silica nanorods often requires manual analysis of their dimensions, but this method is time- consuming and tedious. This work explores the potential for an automated analysis with Matlab to improve the efficiency of this analysis. The program described is a preliminary proof-of-concept version of a nanorod analysis program. Watershed segmentation and minimum-area bounding boxes are viable tools for the automated quantitative analysis of nanorod dimensions, and the automated process saves nearly one minute per particle compared to manual analysis. While the automated process shows promise, the program functions best with minimal nanorod overlap and requires more extensive testing to become feasible for widespread use. Improvements to noise reduction and particle shape prediction will expand the scope of images that can be subject to automatic analysis.
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    Automating the Proofs of Strengthening Lemmas in the Abella Proof Assistant
    (2017) Michaelson, Dawn;
    In logical reasoning, it is often the case that only some of a collection of assumptions are needed to reach a conclusion. A strengthening lemma is an assertion that a given conclusion is independent in this sense of a particular assumption. Strengthening lemmas underlie many useful techniques for simplifying proofs in automated and interactive theorem-provers. For example, they underlie a mechanism called subordination that is useful in determining that expressions of a particular type cannot contain objects of another type and in thereby reducing the number of cases to be considered in proving universally quanti ed statements. This thesis concerns the automation of the proofs of strengthening lemmas in a speci cation logic called the logic of hereditary Harrop formulas (HOHH). The Abella Proof Assistant embeds this logic in a way that allows it to prove properties of both the logic itself and of speci cations written in it. Previous research has articulated a (conservative) algorithm for checking if a claimed strengthening lemma is, in fact, true. We provide here an implementation of this algorithm within the setting of Abella. Moreover, we show how to generate an actual proof of the strengthening lemma in Abella from the information computed by the algorithm; such a proof serves as a more trustworthy certifi cate of the correctness of the lemma than the algorithm itself. The results of this work have been incorporated into the Abella system in the form of a \tactic command" that can be invoked within the interactive theorem-prover and that will result in an elaboration of a proof of the lemma and its incorporation into the collection of proven facts about a given speci cation.
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    Base Line Testing of 10kw GEK Power Pallet
    (2012-04-18) Adams, John
    Background: The Power Pallet is a generator system which uses a gasifier to convert wood chips into a low energy density gas which can be burned in a spark fired Kubota Engine turning a generator. Biomass gasification was widely used in Europe during World War II. Interest in biomass gasification is returning. Objectives: Develop testing method for the Power Pallet System; preform initial testing in order to plan future testing capabilities; test the effectiveness of a butterfly valve in changing reactor oxygen ratio.
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    The Biomechanical Puncture Study of the Fossa Ovalis in Human and Porcine Hearts
    (2011-04-13) Balto, Daniel
    About 1 in every 4 adults here in the U.S. has some sort of congenital heart defect, the majority of these defects is caused by a Patent Fossa Ovalis (PFO). It occurs when the hole between the left and right atria (Foramen Ovale) does not close completely at the moment of birth. The study involved designing and then constructing an apparatus to hold an excised heart in proper anatomical position so that the Fossa Ovalis was accessible from both atria of the heart. Once that was accomplished, a catheter type device was designed and then used to measure the force required to puncture the fossa membrane and the data was recorded. Many different factors were analyzed with this data such as fossa morphology and anatomy. The reason for creating such a device for testing fossa strength was to observe if the fixation of the tissue with formalin would change the properties of the fossa in a variety of human and pig hearts that have been preserved in formalin and used as in vivo equivalents. The data gained will allow me to compare how current PFO’s (heart defects) are fixed and what new surgical procedures or biomedical devices can be created based on the strength of the average Fossa Ovalis of a human.
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    Calibration and Improvement of a Fuel Reformer Vaporization System
    (2017) Vertina, Elizabeth;
    The combustion of fossil fuels in the presence of nitrogen produces Nitrogen Dioxide (NO2) and Nitric Oxide (NO), together referred to as NOx, which are harmful to both human health and the environment. Exhaust gas recirculation (EGR) mixes vaporized fuel with exhaust to increase the heat capacity of the gas, which lowers the combustion temperature and with it, the peak operating temperature of the engine. This reduces NOx emissions and is standard in many engines. EGR can be used in conjunction with reformation, which converts exhaust gas into another source of energy using the hydrogen in the fuel. A testing system was designed, built, and tested to characterize a reformer fueling system. Trials were conducted at various operating pressures to calibrate the micrometer handle metered valve with the fuel mass flow rate. This data will be used to deliver specific amounts of fuel into the reformer depending on desired engine conditions. In addition to the characterization of the valve, the existing vaporizer was redesigned to ensure that the fuel is fully vaporized over the characterized range of mass flow rates. A more powerful 500 Watt vaporizer was designed. In the future, the characterized system will be evaluated in engine tests using a non-oxygenated #2 ultra-low sulfur diesel (ULSD) over a modified type C1 off-road vehicle ISO 8178 eight-point testing cycle.