Browsing by Subject "efficiency"

Now showing 1 - 5 of 5
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    An Assessment of the Safety and Efficiency of Log Trucks with Increased Weight Limits on Interstate Highways in Minnesota and Wisconsin
    (University of Minnesota, 2023) Carson, Michael T.; Blinn, Charles R.; Timothy, J. O'Hara
    Design standards for the Interstate Highway System in the US are generally higher than those on other roads within most states, making it the safest road system in the US. Federal law prevents states from enforcing vehicle weight limits on interstate highways that deviate from established Federal weight limits or state-specific grandfathered weight limits or exceptions. While state gross vehicle weight (GVW) limits for trucks that haul logs exceed federal interstate highway limits in all major timber-producing states that don’t have grandfathered limits, state-legal weight log trucks are not allowed to travel fully loaded on the interstate Trucks hauling logs at legal state limits must travel on state, county, township and local roads. On these routes trucks pass through towns/cities, school zones and encounter on-coming traffic and intersections. All these encounters increase the risk of an accident. This study compared the relative importance of the transport of raw forest products by trucks to the top five non-timber commodities and the fatality rates of log trucks to other heavy trucks in the lower 48 states, compared available national road damage cost estimates for interstate and non-interstate roads and assessed the impact of relaxing interstate weight limits on hauling distance, travel time, safety, pavement damage and CO2 emissions for hauling timber along three travel corridors in Wisconsin and Minnesota. Logs are an important commodity in many states but generally represent a minor percentage of the tonnage of commodities hauled by trucks. On a per load basis, log trucks have a lower fatality rate than other heavy trucks in 83% of the lower 48 states, including in those states that have higher GVW allowances on the interstate due to grandfathering. Due to the higher design standards, pavement damage costs are lowest on interstate highways as compared to other road types. Allowing state-legal, loaded log trucks access to federal interstate highways would improve the overall safety and efficiency of timber transportation while reducing pavement damage costs and CO2 emissions along the three travel corridors. The safety benefits generally exceeded the efficiency gains. Overall, study findings suggest that allowing state-legal, loaded log trucks to operate on interstate highways would improve the safety and efficiency of timber transportation in Wisconsin and Minnesota.
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    Configuration and Performance of Hydraulic Transformer Power Distribution Systems
    (2016-09) Gagnon, Pieter
    Hydraulic transformers implemented in a common pressure rail architecture have been suggested as a means to efficiently distribute hydraulic power to a system of actuators. This thesis explores the role that the configuration of the system plays in the operating region and efficiency performance of the power distribution system. The primary tool used in this thesis is a dynamic loss model of a hydraulic transformer. Full mathematical documentation and experimental parameter tuning are described. Six configurations for distributing power with a hydraulic transformer are presented, and it is shown that each configuration has a unique operating region and efficiency trend. The hydraulic circuit is given for a port switching transformer that utilizes valves to switch between configurations during operation, and experimental tests demonstrate successful switching on a prototype machine. The maximum displacements of the two rotating groups within a set of hydraulic transformers distributing power to linear actuators driving the hip, knee, and ankle joints of a humanoid robot are optimized to maximize efficiency over a walking gait duty cycle. The resulting size ratios of the groups vary from a 1:1 ratio to a 1:2.4 ratio for the three duty cycles investigated. A comparison of the hydraulic transformer architecture against a throttling valve architecture for the humanoid robot indicates that the transformer system can achieve a distribution efficiency of 47.6%, which is a 31.9% increase over the throttling architecture distribution efficiency of 16.0%. The transformer system consumes 142 J to drive a single step of the walking gait, which is a decrease of 281 J from the 422 J required by the throttling architecture. This thesis thoroughly captures the efficiency performance and operating region of hydraulic transformers, and demonstrates how system configurations can improve the performance of the system beyond what has been generally considered in previous literature. These factors can then be weighed along with complexity, size, control performance, production cost, and other such metrics to enable a decision as to whether transformers are an appropriate power distribution architecture for a given application.
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    Hydrogen Fuel Cell Cold Operation
    (2019-09) Bell, Christina
    The purpose of this project is to model the operation of a proton exchange membrane (PEM) fuel cell during operation in weather as cold as -40 °C. The fuel cell must be kept above the freezing point of water, and it is hypothesized this can be done by utilizing the heat produced in the system. The system is being designed to provide off-grid power for operation of various scientific sensors requiring power output of 20 W at a potential of 12 V. A fuel cell combines hydrogen and oxygen to form water, heat, and electricity. Process steps include generating hydrogen from the alcoholysis and/or hydrolysis of sodium borohydride, creating electricity from the fuel cell to charge a battery, and preheating feed air to provide oxygen to the fuel cell. The project explores 1) modeling of the reaction kinetics for hydrogen production, 2) modeling the efficiency and kinetics of the catalytic reaction between the generated hydrogen and oxygen from air within the fuel cell, and 3) modeling heat flow within the system to preheat the incoming air and maintain good fuel cell temperature. The reaction kinetics show sufficient hydrogen production to keep the fuel cell running as specified. The modeled efficiency gives an average efficiency just above 50% for the conversion of chemical potential energy to usable power. The heat flow, assumed to be 1-dimensional, shows sufficient heat transfer to keep the area around the fuel cell above the freezing point of water as modeled.
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    Replicable Associations between Conscientiousness and Efficiency of the Salience/Ventral Attention Network
    (2022-05) Sassenberg, Tyler
    Previous research in the field of personality neuroscience has identified associations of conscientiousness and related constructs like impulsivity and self-control with structural and functional properties of particular regions in the prefrontal cortex (PFC) and insula. Network-based conceptions of brain function suggest that these regions probably belong to a single large network, labeled the salience/ventral attention network (SVAN). The current study tested associations between conscientiousness and resting-state functional connectivity in this network using two community samples (N = 244 and 239) and data from the Human Connectome Project (N = 1000). Individualized parcellation was used to improve the accuracy of functional localization and to facilitate replication. Functional connectivity was measured using an index of network efficiency, a graph theoretical measure describing the capacity for parallel information transfer within a network. Efficiency of a set of parcels in the SVAN was significantly associated with conscientiousness in all samples. Findings are consistent with a theory of conscientiousness as a function of variation in neural networks underlying effective prioritization of goals.
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    Waste to Energy Prime Mover Efficiencies for Commercially Available Technology
    (2020-03-27) Lasode, Aduramo; Northrop, William; lasod002@umn.edu; Lasode, Aduramo; University of Minnesota Thomas E Murphy Engine Lab
    The data provides a collected set of information on electric power rating and efficiency for commercially available prime movers in waste to energy applications. The five main technologies in focus are: steam turbines, gas turbines, microturbines, reciprocating internal combustion engines, and fuel cells (specifically solid oxide). The technology data points collected are systems that can use fuel with components from biogas (methane, hydrogen, etc) generated during anaerobic waste treatment. The data set provides a commercial preview of each technology that could guide potential use in different ranges based on desired electric output (and required power input).