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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
411

EVALUATIONS ON ENZYMATIC EPOXIDATION, EFFICIENCY AND DECAY

Elena A Robles Molina (9751112) 14 December 2020 (has links)
<p>The potential use of enzymes in industrial synthesis of epoxidized soybean oil has been limited through the high cost of the enzyme catalyst, in this work we evaluate the effectiveness of chemo enzymatic epoxidation of high oleic soybean oil (HOSBO) using lipase B from <i>Candida antarctica </i>(CALB) on immobilization support Immobead 150 and H<sub>2</sub>O<sub>2 </sub>in a solvent-free system. Additionally, we evaluated the production decay rates for hydrolytic activity and epoxide product formation over consecutive batches to determine half-life of the enzyme catalyst. </p> <p> Batch epoxidation of HOSBO using CALB on 4wt% loading shows yields higher than 90% after 12 hrs. of reaction, and with a correlation to the consumption of double bonds suggesting that the reaction is selective and limiting side product reactions. Non-selective hydrolysis of oil was not found beyond the initial hydrolysis degree of raw HOSBO. Evaluations of decay given by epoxide product formation and released free fatty acids shows a half-life of the enzyme catalyst on these activities is of 22 ad 25 hrs. respectively. Finally, we evaluated the physical parameters influencing this decay, and found that H<sub>2</sub>O<sub>2</sub> presence is the most important parameter of enzyme inactivation with no significant effect from its slowed addition. We propose a new reactor configuration for the analysis of the specific steps on epoxide formation through peracid intermediates. </p>
412

Energiemanagement Strategien für elektrische Energiebordnetze in Kraftfahrzeugen

Büchner, Stefan 10 July 2008 (has links)
Die elektrische Energieform gewinnt im Kraftfahrzeug wegen ihrer Nutzungsvielfalt und sehr guten Steuerbarkeit für die Realisierung neuartiger Funktionen zunehmend an Bedeutung. Voraussetzung für ihren Einsatz ist eine zuverlässige und effiziente Bereitstellung durch das Kfz-Energiebordnetz. Dafür ist ein intelligentes Energiemanagement erforderlich, welches mit geeigneten Strategien die Leistungsflüsse im Energiesystem koordiniert. In dieser Arbeit werden die beiden Entwurfsziele der Zuverlässigkeit und der Effizienz bei der Entwicklung von elektrischen Energiemanagement-Strategien systematisch betrachtet. Es erfolgt eine Beschreibung und Zuordnung der einzelnen Ziele und Maßnahmen anhand der Energieflüsse und Wirkungsketten. Ein Schwerpunkt bildet dabei die Beherrschung von Lastwechseln im Bordnetz. Für Aussagen hinsichtlich einer effizienten Erzeugung elektrischer Energie erfolgt eine Untersuchung der Energiewandlungskette anhand analytischer Methoden und mit Hilfe einer simulationsgestützten Optimierung. Ein weiterer Fokus der Arbeit liegt in der Betrachtung zur Anwendung ökonomischer Modelle für eine Energiekoordination. Es werden die theoretischen Grundlagen der Mikroökonomie zusammengestellt und mögliche Funktionsstrukturen eines einseitigen und zweiseitigen Allokationsmechanismus verglichen und bewertet. Abschließend zeigen experimentelle Untersuchungen an einem Bordnetzprüfstand zum Lastwechselverhalten und die Integration eines Energiemanagement-Systems den praktischen Bezug zum realen System.
413

DIGITAL HYDRAULICS IN ELECTRIC HYBRID VEHICLES TO IMPROVE EFFICIENCY AND BATTERY USE

Jorge Leon Quiroga (9192758) 31 July 2020 (has links)
The transportation sector consumes around 70% of all petroleum in the US. In recent years, there have been improvements in the efficiency of the vehicles, and hybrid techniques that have been used to improve efficiency for conventional combustion vehicles. Hydraulic systems have been used as an alternative to conventional electric regenerative systems with good results. It has been proven that hydraulic systems can improve energy consumption in conventional combustion vehicles and in refuse collection vehicles. The control strategy has a large impact on the performance of the system and studies have shown the control strategy selection should be optimized and selected based on application. The performance of a hydraulic accumulator was compared with the performance of a set of ultracapacitors with the same energy storage capacity. The energy efficiency for the ultracapacitor was around 79% and the energy efficiency of the hydraulic accumulator was 87.7%. The power/mass ratio in the set of ultracapacitors was 2.21 kW/kg and 2.69 kW/kg in the hydraulic accumulator. The cost/power ratio is 217 US$/kW in the ultracapacitors and 75 US$/kW in the hydraulic accumulator. Based on these results, the hydraulic accumulator was selected as the energy storage device for the system. A testbench was designed, modeled, implemented to test the energy storage system in different conditions of operation. The experimental results of the testbench show how system can be actively controlled for different operating conditions. The operating conditions in the system can be adjusted by changing the number of rheostats connected to the electric generator. Different variables in the system were measured such as the angular shaft speed in the hydraulic pump, the torque and speed in the hydraulic motor, the pressure in the system, the flow rate, and the current and voltage in the electric generator. The control algorithm was successfully implemented, the results for the pressure in the system and the angular speed in the electric generator show how the control system can follow a desired reference value. Two different controllers were implemented: one controller for the pressure in the system, and one controller for the speed.
414

Investigation of energy management topologies for forming presses with electro hydrostatic drivetrains

Reidl, Tim, Weber, Jürgen, Ihlenfeldt, Steffen 25 June 2020 (has links)
Recent Power On Demand approaches, realized by using speed and/or displacement variable pump units, led to a significant increase of energy efficiency on hydraulic forming presses. In this paper we follow up on this development by laying the focus on the energy management and storage design of such machinery. With a derived fluidtronical model, we compare five different topologies that supply and manage the power flow for a forming press with die cushion. Our evaluation criteria are: energy consumption, minimization of the infeed power, and qualitative costs. For a representative forming cycle, the losses occurring on each of the drivetrain components and the power electronics accessory are derived in detail. We expect that this research will lead to deeper investigation of more intelligent energy management systems that use multiple storages in an optimal way and further learn and adapt during operation.
415

Distributed Optimization Algorithms for Inter-regional Coordination of Electricity Markets

Veronica R Bosquezfoti (10653461) 07 May 2021 (has links)
<p>In the US, seven regional transmission organizations (RTOs) operate wholesale electricity markets within three largely independent transmission systems, the largest of which includes five RTO regions and many vertically integrated utilities.</p> <p>RTOs operate a day-ahead and a real-time market. In the day-ahead market, generation and demand-side resources are optimally scheduled based on bids and offers for the next day. Those schedules are adjusted according to actual operating conditions in the real-time market. Both markets involve a unit commitment calculation, a mixed integer program that determines which generators will be online, and an economic dispatch calculation, an optimization determines the output of each online generator for every interval and calculates locational marginal prices (LMPs).</p> <p>The use of LMPs for the management of congestion in RTO transmission systems has brought efficiency and transparency to the operation of electric power systems and provides price signals that highlight the need for investment in transmission and generation. Through this work, we aim to extend these efficiency and transparency gains to the coordination across RTOs. Existing market-based inter-regional coordination schemes are limited to incremental changes in real-time markets. </p> <p>We propose a multi-regional unit-commitment that enables coordination in the day-ahead timeframe by applying a distributed approach to approximate a system-wide optimal commitment and dispatch while allowing each region to largely maintain their own rules, model only internal transmission up to the boundary, and keep sensitive financial information confidential. A heuristic algorithm based on an extension of the alternating directions method of multipliers (ADMM) for the mixed integer program is applied to the unit commitment. </p> The proposed coordinated solution was simulated and compared to the ideal single-market scenario and to a representation of the current uncoordinated solution, achieving at least 58% of the maximum potential savings, which, in terms of the annual cost of electric generation in the US, could add up to nearly $7 billion per year. In addition to the coordinated day-ahead solution, we develop a distributed solution for financial transmission rights (FTR) auctions with minimal information sharing across RTOs that constitutes the first known work to provide a viable option for market participants to seamlessly hedge price variability exposure on cross-border transactions.
416

Development of a Reduced Computational Model to Replicate Inlet Distortion in an APU-Style Inlet of a Centrifugal Compressor

Evan Henry Bond (12455190) 25 April 2022 (has links)
<p>The purpose of this research was to determine what components of a complex centrifugal  compression system inlet needed to be modelled to accurately predict the swirl and total pressure  distortions at the compressor face. Two computational models were developed. A full-fidelity case  where all the inlet geometry was modelled and a reduced model where a small portion of the inlet  was considered. Both the numerical cases were compared with experimental data from a research  compressor rig developed by Honeywell Aerospace. The test apparatus was designed with a  modular inlet system to develop swirl distortion patterns. The modular inlet system utilized  transposable baffles within the radial-to-axial section of the inlet and blockage plates of varying  sizes and geometries at the inlet to this section.  Discerning the dominant inlet component that dictates distortion behavior at the compressor  face would allow the reduced modelling of inlet components for compression systems and would  allow coupling with more tortuous systems. Furthermore, it would reduce the design iteration and  simulation time of the inlet systems. Several investigations utilizing a reduced model only  considering a radial-to-axial inlet are available in literature, but no comprehensive justification has  been presented as to the impact this has on the distortion behavior.   Experimental surveys of flow conditions just upstream of the inducer of the centrifugal  compressor were conducted at several operating conditions. The highest and lowest mass flow  rates of these operating points were simulated using ANSYS CFX 2020R1 for both the  computational models. Multiple inlet configurations were simulated to test the robustness of the  reduced model in comparison to the full fidelity. The numerical simulations highlighted  shortcomings of the instrumentation used to characterize the experimental flow field at the inducer,  particularly with respect to total pressure distortion. Furthermore, transient pressure data were  measured in experiment and indicated unsteady fluctuations in the inlet that would not be captured  by steady computational fluid dynamic simulations. These data matched locations of disagreement  with swirl distortion behavior at high mass flow rates. This suggested that transient vortex  movement occured at the aerodynamic interface plane in certain configurations.   The total pressure distortion metrics between the two models were remarkably comparable.  Furthermore, the simplified model accurately predicted the mixing losses associated with the  blockage plates at the inlet to the radial-to-axial inlet using a simple inlet extension. Swirl  18  distortion was dictated by the radial-to-axial inlet. The reduced model data trends were comparable  with experiment for both the baffle and blocker plate configurations. The swirl intensities for all  configurations were comparable between the two models. The reduced model swirl directivity  trends matched those of experiment. The most notable deviations between the full-fidelity model  and the reduced model were observed with swirl directivity numerics. </p>
417

Rooftop PV Impacts on Fossil Fuel Electricity Generation and CO2 Emissions in the Pacific Northwest

Weiland, Daniel Albert 27 August 2013 (has links)
This thesis estimates the impacts of rooftop photovoltaic (PV) capacity on electricity generation and CO2 emissions in America's Pacific Northwest. The region's demand for electricity is increasing at the same time that it is attempting to reduce its greenhouse gas emissions. The electricity generated by rooftop PV capacity is expected to displace electricity from fossil fueled electricity generators and reduce CO2 emissions, but when and how much? And how can this region maximize and focus the impacts of additional rooftop PV capacity on CO2 emissions? To answer these questions, an hourly urban rooftop PV generation profile for 2009 was created from estimates of regional rooftop PV capacity and solar resource data. That profile was compared with the region's hourly fossil fuel generation profile for 2009 to determine how much urban rooftop PV generation reduced annual fossil fuel electricity generation and CO2 emissions. Those reductions were then projected for a range of additional multiples of rooftop PV capacity. The conclusions indicate that additional rooftop PV capacity in the region primarily displaces electricity from natural gas generators, and shows that the timing of rooftop PV generation corresponds with the use of fossil fuel generators. Each additional Wp/ capita of rooftop PV capacity reduces CO2 emissions by 9,600 to 7,300 tons/ year. The final discussion proposes some methods to maximize and focus rooftop PV impacts on CO2 emissions, and also suggests some questions for further research.
418

Design, Fabrication, and Testing of an EMR Based Orbital Debris Impact Testing Platform

Maniglia, Jeffrey J, Jr. 01 June 2013 (has links) (PDF)
This paper describes the changes made from Cal Poly’s initial railgun system, the Mk. 1 railgun, to the Mk. 1.1 system, as well as the design, fabrication, and testing of a newer and larger Mk. 2 railgun system. The Mk. 1.1 system is developed as a more efficient alteration of the original Mk. 1 system, but is found to be defective due to hardware deficiencies and failure, as well as unforeseen efficiency losses. A Mk. 2 system is developed and built around donated hardware from the Naval Postgraduate School. The Mk. 2 system strove to implement an efficient, augmented, electromagnetic railgun and projectile system capable of firing an approximate 1g aluminum projectile to speeds exceeding 2 km/s. A novel three part projectile is proposed to mitigate rail and projectile degradation. Projectile and sabot system kinematic equations are derived and the projectile is designed and tested along with Mk. 2 barrel. A numerical electromechanical model is developed to predict the performance of the Mk. 2 system and projectile assembly, and predicts a final velocity for the fabricated system exceeding 3.5 km/s and an efficiency as high as 24%. Testing of the Mk. 2 system showed catastrophic failure of the projectile during initial acceleration, resulting in very short acceleration times and distance, low velocity projectiles, and low efficiencies. During further testing of various projectile configurations, the barrel structure failed due to a large internal arc. Future work for the Mk. 2 system is discussed, a revised external barrel structure suggested, and a solid, more conventional solid chevron projectile design suggested.
419

Performance Enhancement and Characterization of an Electromagnetic Railgun

Gilles, Paul M 01 December 2019 (has links) (PDF)
Collision with orbital debris poses a serious threat to spacecraft and astronauts. Hypervelocity impacts resulting from collisions mean that objects with a mass less than 1g can cause mission-ending damage to spacecraft. A means of shielding spacecraft against collisions is necessary. A means of testing candidate shielding methods for their efficacy in mitigating hypervelocity impacts is therefore also necessary. Cal Poly’s Electromagnetic Railgun was designed with the goal of creating a laboratory system capable of simulating hypervelocity (≥ 3 km/s) impacts. Due to several factors, the system was not previously capable of high-velocity (≥ 1 km/s) tests. A deficient projectile design is revised, and a new design is tested. The new projectile design is demonstrated to enable far greater performance than the previous design, with a muzzle velocity ≥ 1 km/sbeing verified during testing, and an energy conversion efficiency of 2.7%. A method of improving contact and controlling wear at the projectile/rail interface using silver plating and conductive silver paste is validated. A mechanism explaining the problem of internal arcing within the railgun barrel is proposed, and design recommendations are made to eliminate arcing on the basis of the work done during testing. The primary structural members are found to be deficient for their application and a failure analysis of a failed member, loading analysis of the railgun barrel, and design of new structures is undertaken and presented.
420

Adaptive traction, Power and Torque Control strategies and optimization in an all-electric powertrain

Hidara, Aymane 08 December 2023 (has links) (PDF)
Electric and hybrid-electric vehicles lean heavily on intricate control algorithms to provide smooth, reliable, and secure operations under any driving conditions. Three distinct supervisory control strategies have been developed, each aiming to improve reliability and vehicle performance of a dual-motor electric vehicle equipped with an all-wheel-drive, fully electric powertrain. These algorithms are adept at dynamically modulating and constraining the torque provided to the wheels, leveraging two autonomous permanent magnet electric drive units. This study utilizes a vehicle model jointly provided by MathWorks and General Motors in partnership with industry sponsors. The these strategies were implemented in the model and enhanced the performance, vehicle range, energy consumption, regenerated energy using specific EDUs provided by sponsors. Adhering to a systematic engineering iterative method, the emphasis was heavily placed on simulation and modeling during the development and validation of these strategies. Simulations ensured robust testing before field implementation, emphasizing software modeling's vital role.

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