Browsing by Subject "control"

Now showing 1 - 8 of 8
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    Fire Blight of Apples. Revised June 1941.
    (University of Minnesota. Agricultural Extension Service, 1941-06) Sharvelle, E. G.
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    Genetic Methods for Biological Control of Non-Native Fish in the Gila River Basin: Final Report to the U.S. Fish and Wildlife Service
    (University of Minnesota, Institute for Social, Economic and Ecological Sustainability, St. Paul, Minnesota, 2005-09) Kapuscinski, Anne R.; Patronski, Timothy J.
    This report addresses the feasibility of using genetic methods as a new approach for biological control of non-native fish within the Gila River Basin. This feasibility study was sponsored by the Central Arizona Project Funds Transfer Program. The report reviews the status of existing genetic methods including chromosome set manipulations and recombinant DNA techniques; takes a preliminary look at potential ecological and human health risks; outlines policy and regulatory considerations; stresses the need for and presents an approach for multi-stakeholder deliberation; provides general cost and time estimates; and suggests integration of these considerations into a multi-component research and development program.
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    It’s All Under Control: The Conditional Effects of Threat on Political Behavior
    (2018-06) Smith, Brianna
    Past research in political science finds contradictory effects of threat on political behavior. Some researchers find that threatening events of statements increase engagement with politics. Other researchers, meanwhile, find that threat can lead to disengagement. Meanwhile, threat may either increase political opinion polarization or general conservatism, depending on the study. In my dissertation, I identify perceived control over threat as the key factor which predicts which effect threat will have on political behavior. Using both experimental and observational data, I show that preventable (high control) threat increases political engagement, while also increasing political polarization. Inevitable (low control) threat decreases political engagement, while also increasing support for maintaining the status quo (and preventing change). Ultimately, both kinds of threat may have negative consequences for democracy, either by encouraging more fervent political extremism or by dissuading people from getting involved in politics at all.
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    Linear Stability and Sensitivity of a Low-speed Jet in Cross-flow
    (2018-05) Regan, Marc
    The Jet in Cross-flow (JICF) is characterized by a jet of fluid injected transverse to an incoming cross-flow. Complex vortical structures are generated as the cross-flow boundary layer interacts with the jet. The goal of this dissertation is to increase understanding of the stability and sensitivity of the JICF. Achieving this goal will directly benefit the many engineering applications which use the JICF, including gas turbine combustor dilution jets, film cooling, vertical and/or short take-off and landing (V/STOL) aircraft, and thrust vectoring. The JICF is studied . These equations are key components of this research. The JICF is studied using direct numerical simulation of the Navier-Stokes equations, as well as their adjoint, at a Reynolds number of 2000, and two jet-to-cross-flow velocity ratios: R = 2 with an absolutely unstable upstream shear-layer, and R = 4 with a convectively unstable upstream shear-layer. Linear stability analysis of the JICF reveals that the dominant eigenmodes are shear-layer modes whose frequencies match frequencies of the upstream shear-layer observed in simulation (Iyer & Mahesh, 2016) and experiment (Megerian et al., 2007). Asymmetric modes are shown to be more important to the overall dynamics at higher jet-to-cross-flow ratios. Low-frequency modes persist far downstream, and are connected to wake vortices. For R = 4, downstream shear-layer eigenmodes can be more unstable than the upstream shear-layer modes. Adjoint modes show that the upstream shear-layer is most sensitive to perturbations along the upstream side of the jet nozzle exit. Additionally, the lower frequency downstream modes have sensitive regions that extend upstream into the cross-flow boundary layer. Wavemaker results are shown to be consistent with the transition of the upstream shear-layer from absolute to convective instability. Optimal perturbations reveal that for short-time horizons, perturbations that are asymmetric, and grow along the counter-rotating vortex pair, dominate when R = 2. However, as the time horizon increases, growth is focused along the upstream shear-layer. When R = 4, the optimal perturbations for short-time scales are dominated by growth along the downstream shear-layer. For long-time horizons, the optimal perturbations become hybrid modes that grow along the upstream and downstream shear-layers, simultaneously.
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    Magnetic Attitude Control Development and Simulation for a 3U Cube Satellite
    (2020-01) Kukowski, Timothy
    SOCRATES and IMPRESS are two cubesats designed and built by the University of Minnesota's Small Satellite Team. These satellites have similar build and function by seeking to collect information from photons emitted from celestial objects in space. To do so, a cubesat form factor energy spectrometer, Cesium Iodide, Thalium-doped Incident Energy Spectrometer (CITIES), developed at the University of Minnesota is installed onto a 3U cubesat and operates in low-Earth orbit. For CITIES to collect this data, a reliable attitude determination and control system is important to maintain knowledge of the cubesat's position in orbit and keep the detector pointing towards the required celestial object. Based on a lenient attitude pointing requirement and strict energy budget, magnetic control was chosen as the method of actuation. In this thesis, the justification for and theory behind magnetic attitude control are presented. Operating conditions of the cubesats are briefed. Including a description of the types of controllers, how the controllers lie within the state machine architecture, and the concept of operations leading to the commands provided to the attitude controller. Finally, results from a Matlab simulation are presented using a proportional derivative (PD) controller. Results found indicate that given enough time, the magnetic control system stabilizes the cubesat towards its target.
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    Perceptions of Invasive Species and Their Control Among the MN Tourism Industry
    (University of Minnesota Tourism Center, 2014) Schneider, Ingrid E.; Qian, Xinyi
    This project sought baseline information on perceptions of invasive species and theie control among the Minnesota tourism industry. The majority of respondents agreed that both invasive plant & aquatic invasives were harmful to Minnesota’s environment, economy & society. Similarly, the majority of respondents indicated all 7 control methods presented in the questionnaire would be effective to control invasive species.
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    Sparsity-promoting optimal control of power networks
    (2016-12) Wu, Xiaofan
    In this dissertation, we study the problems of structure design and optimal control of consensus and synchronization networks. Our objective is to design controller that utilize limited information exchange between subsystems in large-scale networks. To obtain controllers with low communication requirements, we seek solutions to regularized versions of the H2 optimal control problem. The proposed framework can be leveraged for control design in applications like wide-area control in bulk power systems, frequency regulation in power system/microgrids, synchronization of nonlinear oscillator networks, etc. The structure of the dissertation is organized as follows. In Part I, we focus on the optimal control problems in systems with symmetries and consensus/synchronization networks. They are characterized by structural constraints that arise either from the underlying group structure or the lack of the absolute measurements for a part of the state vector. Our framework solves the regularized versions of the H2 optimal control problems that allow the state-space representations that are used to quantify the system’s performance and sparsity of the controller to be expressed in different sets of coordinates. For systems with symmetric dynamic matrices, the problem of minimizing the H2 or Hinfinity performance of the closed-loop system can be cast as a convex optimization problem. Studying the symmetric component of a general system’s dynamic matrices provides bounds on the H2 and Hinfinity performance of the original system. Part II studies wide-area control of inter-area oscillations in power systems. Our input-output analysis examines power spectral density and variance amplification of stochastically forced systems and offers new insights relative to modal approaches. To improve upon the limitations of conventional wide-area control strategies, we also study the problem of signal selection and optimal design of sparse and block-sparse wide- area controllers. We show how different sparsity-promoting penalty functions can be used to achieve a desired balance between closed-loop performance and communication complexity. In particular, we demonstrate that the addition of certain long-range communication links and careful retuning of the local controllers represent an effective means for improving system performance. In Part III, we apply the sparsity-promoting optimal control framework to two problem encounters in distributed networks. First, we consider the optimal frequency regulation problem in power systems and propose a principled heuristic to identify the structure and gains of the distributed integral control layer. We define the proposed distributed PI-controller and formulate the resulting static output-feedback control problem. Second, we develop a structured optimal-control framework to design coupling gains for synchronization of weakly nonlinear oscillator circuits connected in resistive networks with arbitrary topologies. The structured optimal-control problem allows us to seek a decentralized control strategy that precludes communications between the weakly nonlinear Lienard-type oscillators.
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    Using quantitative and qualitative epidemiological tools for holistic, effective African Swine Fever prevention, early detection, and control
    (2023-03) Schambow, Rachel
    African Swine Fever (ASF) is a viral, hemorrhagic disease of swine that is notifiable to the World Organization for Animal Health. ASF can cause nearly 100% mortality in affected swine herds, and no treatment or vaccine is available. Animal health officials rely on biosecurity, surveillance, and other control measures to manage ASF outbreaks. The United States is free of ASF, but widespread outbreaks in Europe, Asia, and the Dominican Republic have increased concern in the US swine industry. Studies have estimated that an ASF introduction could cost the US over $50 billion USD in losses and control efforts. The objective of this work was to use complementary quantitative and qualitative epidemiological and analytical tools to support the development of holistic ASF prevention and control strategies for the US and globally. Chapter 1 describes the background and important characteristics of ASF and reviews the use of some epidemiological techniques for ASF control. Chapter 2 describes how Strengths, Weaknesses, Opportunities, and Threats analysis was used to characterize stakeholders’ perceptions of ASF control strategies in the Dominican Republic. Chapter 3 demonstrates how quantitative risk analysis was used to characterize the risk of ASF introduction into the US in imported non-animal feed ingredients. In Chapter 4, qualitative participatory methods were used to characterize stakeholder values and needs regarding enhanced passive surveillance for early detection of ASF in the US. Chapter 5 demonstrates the use of Bayesian latent class analysis to estimate the sensitivity and specificity of novel ASF ELISA and qPCR diagnostic tests using field data from Vietnam. The work described in these chapters has demonstrated how both qualitative and quantitative tools can provide important data and socioeconomic context for the development of ASF prevention and control strategies. Future efforts for the US should encompass this holistic strategy to ASF preparedness, from understanding stakeholder values and providing training and support to using analytical and data-driven techniques to enhance biosecurity, surveillance, and outbreak preparedness. Ultimately, global cooperation, collaboration, and transparency will support the international fight against ASF.