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The Global ETD Search service is a free service for researchers
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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.
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<strong>Organic redox-active materials design for redox flow batteries</strong>Xiaoting Fang (15442055) 30 May 2023 (has links)
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<p>Nowadays, clean and renewable energy sources like wind and solar power have been rapidly growing for the goal of phasing out traditional fossil fuels, achieving carbon neutrality, and realizing sustainable development. Long-duration and large-scale energy storage is needed to address the intermittent nature of these sources. Especially, redox flow battery (RFB) is an attractive energy storage device for large scale applications because of its high scalability, design flexibility, and intrinsic safety. The all vanadium redox flow battery stands for the state-of-the-art system, but the high vanadium cost and limited energy density are among the limiting factors for wide commercialization. Therefore, it is necessary to develop new RFB materials that are cost-effective and highly soluble. Organic redox-active molecules (redoxmers) hold great potential to satisfy these requirements due to structural diversity, tunable chemical and electrochemical properties, and earth-abundant sources. With rational structural design, organic redoxmers can show favorable properties such as high solubility, suitable redox potential, and good chemical stability. However, current efforts are mainly on the development of anolyte redoxmers, e.g. phenazine, anthraquinone and viologen. Only limited types of catholyte candidates have been reported such as ferrocene and TEMPO. The major reason for such slow-paced progress is the limited chemical stability of these catholyte redoxmers. To bridge this critical gap, my efforts are focused mainly on the design and development of promising catholyte redoxmers for both aqueous organic (AORFBs) and non-aqueous organic redox flow batteries (NRFBs).</p>
<p>Phenoxazine functionalized with a hydrophilic tetraalkylammonium group demonstrates good water solubility and suitable redox potential. Cyclic voltammograms (CV) and flow cell testing were used to evaluate the electrochemical properties and battery performance, respectively. Besides, the battery fading mechanism was systematically investigated by CV, liquid chromatography mass spectra (LC-MS) and electron paramagnetic resonance (EPR) spectroscopy. The redoxmer decomposition mechanism analysis will benefit future redoxmer development by guiding the molecular design of more stable structure candidates. </p>
<p>A structural design strategy for the development of novel TMPD-based (tetramethyl-<em>p</em>-phenylenediamine) catholyte redoxmers for NORFBs is presented. Two categories of functional groups, including oligo(ethylene glycol) (EG) either chains and phenyl rings, were incorporated into the TMPD core to improve solubility and stability in non-aqueous electrolytes, respectively. EPR characterization and bulk electrolyte (BE) analysis were carried out to evaluate the redoxmers stability. In addition, DFT studies were conducted to understand the impacts of functional groups on redox potential and chemical stability. The present work demonstrates the feasibility of constructing promising redoxmers from TMPD and provides insights into molecular designing of catholytes to achieve high solubility and excellent stability for non-aqueous redox flow batteries.</p>
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Sdílení plochy při video a audiokonferencích / Desktop sharing through video- and audio-conferencesZukal, Martin January 2010 (has links)
The following diploma thesis is devoted to the desktop sharing description and its opportunities. Existing solutions and their advantages and disadvantages are described at the beginning of the text. The most extensive part deals with the design and the implementation of a new solution for the desktop sharing. The thesis aims at providing a possibility to observe desktop of one computer from another one. For achieving it, two appliactions (a server and a client) have been developed, and they are described in the text with utilization of UML (Unified Modeling Language) diagrams. The RFB (Remote Framebuffer) protocol has been chosen as the means for communication between the applications. A detailed description of this protocol is also included in the text. The developed solution is tested and compared with other similar applications in the final part of the work. After that, some areas needing slight improvements are named to achieve competitiveness of the developed solution with other applications of a similar type.
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Image encoding evaluation in remote desktop systems : A framework for measuring the encoding performance inTigerVNC / Bildkodningsevaluaering i fjärrskrivbordssystemHalim, Adam January 2023 (has links)
Remote desktop solutions have widespread adoption across the world, allowing people to connect to a computer remotely from anywhere in the world. One widely used solution is TigerVNC which uses the RFB protocol for communication between a client and server. TigerVNC supports several encoding types, which use different techniques to compress image data. Currently, there is a lack of a performance evaluation frameworks for VNC software that makes it possible to measure the performance of not only different encoders, but also the performance of the system that chooses which encoding to use for different parts of the image. This thesis presents a framework that was developed to evaluate the performance of TigerVNC server in real-world scenarios. The framework includes a tool that records an X session losslessly and a benchmarking suite that processes a recorded session, providing data regarding execution time and compression ratio. Benchmarks were run using several encoding settings with different recorded sessions representing real-world scenarios. Results show that TigerVNC server has a good tradeoff between compression ratio and execution time. The work done in this thesis lays a foundation on which future research can be done, leading to improvements in the TigerVNC project.
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Aplikace pro prezentaci a modifikaci dat v přenosných zařízeních / Application for Data Presentation and Modification in Mobile DevicesKučera, Pavel January 2009 (has links)
This thesis is aimed to study the possibility of usage of mobile devices in the sphere of automation. One automation company needed to have in hand some PDA-based tool for a remote control of the technological process. There is analysis of ability of contemporary portable devices to run a application software. According to the specified requirements there is designed and implemented the client-server system based on the VNC technology. The server is a Linux-based PC server implemented using Xinetd daemon and the Xvnc. The two standard VNC clients were made. A free software available under the GPL license was modified to implement them. One runs on Windows Mobile operating system and the other one is a Java MIDlet.
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Desenvolvimento e implantação do BDCC - banco de dados comum de credenciamento para controle de acesso pela autoridade aduaneira no porto de Santos. / Development and implementation of BDCC - Common Database Registration for Customs authority access control in port of Santos.Abreu, Vander Serra de 27 May 2015 (has links)
O presente trabalho de pesquisa demonstra o estágio atual de controle, monitoramento e registro da entrada e saída de pessoas e veículos em áreas controladas pela Alfândega da Secretaria da Receita Federal nos Portos Brasileiros, órgão máximo destacado segundo a constituição federal e a Lei 12.815 de 2013 para tal controle. Será apresentado o projeto de desenvolvimento do sistema BDCC Banco de Dados Comum de Credenciamento, sistema implantado pela Associação Brasileira de Terminais e Recintos Alfandegados ABTRA em atendimento à Portaria ALF/STS n.200 da Receita Federal do Porto de Santos que possibilitou um controle único dos acessos, com base nas portarias ALF/STS n. 73 e 200 e aperfeiçoou os processos aproveitando investimentos já realizados pelos Recintos Alfandegados no atendimento ao código internacional de proteção de navios e instalações ISPS CODE com o desenvolvimento dos sistemas SSPP, Supervia, DTe, PSP, SGTC e Portolog. / This research work demonstrates the current state control, monitoring and recording the entry and exit of people and vehicles controlled by the Customs Bureau of Internal Revenue in Brazilian Ports, the highest body highlighted áreas under federal Constitution and Law 12.815 of 2013 for such control highlighting existing systems installed using as case the Port of Santos. Will be presented the project BDCC Banco de Dados Comum de Credenciamento, system implemented by the ABTRA Brazilian Association Of terminals and Customs in compliance with Ordinance ALF/STS n.200 of Federal Revenue Port of Santos that enabled an unified control of the access based on the ALF entrances / STS n. 73 and 200 and optimized the processes leveraging the investments already made by Bonded precincts in meeting the international code of protection of ships and facilities ISPS CODE and the SSPP, DTe, PSP, SGTC and Portolog systems.
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Desenvolvimento e implantação do BDCC - banco de dados comum de credenciamento para controle de acesso pela autoridade aduaneira no porto de Santos. / Development and implementation of BDCC - Common Database Registration for Customs authority access control in port of Santos.Vander Serra de Abreu 27 May 2015 (has links)
O presente trabalho de pesquisa demonstra o estágio atual de controle, monitoramento e registro da entrada e saída de pessoas e veículos em áreas controladas pela Alfândega da Secretaria da Receita Federal nos Portos Brasileiros, órgão máximo destacado segundo a constituição federal e a Lei 12.815 de 2013 para tal controle. Será apresentado o projeto de desenvolvimento do sistema BDCC Banco de Dados Comum de Credenciamento, sistema implantado pela Associação Brasileira de Terminais e Recintos Alfandegados ABTRA em atendimento à Portaria ALF/STS n.200 da Receita Federal do Porto de Santos que possibilitou um controle único dos acessos, com base nas portarias ALF/STS n. 73 e 200 e aperfeiçoou os processos aproveitando investimentos já realizados pelos Recintos Alfandegados no atendimento ao código internacional de proteção de navios e instalações ISPS CODE com o desenvolvimento dos sistemas SSPP, Supervia, DTe, PSP, SGTC e Portolog. / This research work demonstrates the current state control, monitoring and recording the entry and exit of people and vehicles controlled by the Customs Bureau of Internal Revenue in Brazilian Ports, the highest body highlighted áreas under federal Constitution and Law 12.815 of 2013 for such control highlighting existing systems installed using as case the Port of Santos. Will be presented the project BDCC Banco de Dados Comum de Credenciamento, system implemented by the ABTRA Brazilian Association Of terminals and Customs in compliance with Ordinance ALF/STS n.200 of Federal Revenue Port of Santos that enabled an unified control of the access based on the ALF entrances / STS n. 73 and 200 and optimized the processes leveraging the investments already made by Bonded precincts in meeting the international code of protection of ships and facilities ISPS CODE and the SSPP, DTe, PSP, SGTC and Portolog systems.
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ADVANCING PRACTICAL NONAQUEOUS REDOX FLOW BATTERIES: A COMPREHENSIVE STUDY ON ORGANIC REDOX-ACTIVE MATERIALSZhiguang Li (17015934) 25 September 2023 (has links)
<p dir="ltr">As the demand for energy rises and the threat of climate change looms, the need for clean, reliable, and affordable energy solutions like renewable energies has been more crucial. Energy storage systems (ESSs) are indispensable in addressing the intermittent nature of renewable energies and optimizing grid efficiency. Redox flow batteries (RFBs), thanks to their scalability, independent energy and power, swift response time, and minimal environmental impact, are a particularly promising ESS technology for long-duration storage applications. Despite the technological maturity of aqueous RFBs, nonaqueous organic RFBs (NAORFBs) are a prospective solution due to their wider operational voltage, potentially higher energy density, and larger pool of redox-active materials. However, the current state-of-the-art NAORFBs face challenges due to the lack of suitable organic redox-active materials (ORMs).</p><p dir="ltr">Despite the development of new materials, how their variables influence the total system cost of RFBs remains an unsolved challenge. With this regard, we established a techno-economic (TE) model to calculate the capital cost of nonaqueous hybrid RFBs (NAHRFBs). Prior to this work, NAHRFBs, which employs lithium metal as the anode, were regarded as an RFB system with the highest energy density. However, the correlation between their features and the system cost remained unclear, leaving a research gap for new ORMs. In our model, we selected a state-of-the-art NAHRFB system where 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) serves as the catholyte and lithium metal functions as the anode. Thereafter, sensitivity analyses identified several key factors that determine the system cost, including operational current density, area-specific resistance, cell voltage, electrolyte composition, and both the price and equivalent molecular weight of the ORM. To enhance the cost-competitiveness of current NAHRFBs, it is advised to increase the current density by 10 times and modulate the ORM-related characteristics. The virtually optimized condition manifests that the system cost of NAHRFB can meet the long-term cost target set by the U. S. Department of Energy.</p><p dir="ltr">Informed by the TE model, we discovered that elevating the oxidation potential of catholyte ORMs is instrumental in reducing the system cost of RFBs. To explore this possibility, we incorporated fluorine atoms, a potent electron-withdrawing group (EWG), into a dimethoxybenzene (DMB) derivative, yielding a new ORM (ANL-C46) with an oxidation potential enhanced by ~0.41 V. Surprisingly, ANL-C46 demonstrated superior kinetic and electrochemical stability compared to its parent molecule, as indicated by electron paramagnetic resonance (EPR) study and bulk electrolysis. In particular, the cycling performance of ANL-46 during the bulk electrolysis outperformed most reported high-potential (> 1 V vs. Ag/Ag<sup>+</sup>) ORMs. Density functional theory (DFT) calculations reveals that the introduced fluorine substituents suppress the typical side reaction pathways of the DMB series. These findings offer valuable insights into molecular engineering strategies that concurrently improve multiple desired ORM properties.</p><p dir="ltr">The stability of ORMs is critical for ensuring the extended lifetime of RFBs. We conducted a systematic exploration of the conjugation effect, which potentially stabilizes the ORMs by facilitating a more homogeneous distribution of delocalized charges. This was applied to tailor the electrochemical and physical properties of several DMB derivatives with varying aromatic ring counts. As we extended the aromatic core from 1,4-dimethoxybenzene (1,4-DMB) to 1,4-dimethoxynaphthalene (1,4-DMN), we noted a decrease in oxidation potential, enhanced kinetic stability, and an extended cycling life. However, further extending the aromatic core to 2-ethyl-9,10-dimethyanthracene (EDMA) results in rapid dealkylation of the radical cation due to increased strain in the methoxy substituents. Additionally, 1,4-DMN shows cross-reactions between radical cations, likely via disproportionation. This study demonstrates that extending the π-conjugation changes reactivity in multiple ways. Therefore, attempts to lower oxidation potential and improve ORMs stability through π-conjugation should be pursued with caution.</p>
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Dynamic Speed Adaptation for Curves using Machine Learning / Dynamisk hastighetsanpassning för kurvor med maskininlärningNarmack, Kirilll January 2018 (has links)
The vehicles of tomorrow will be more sophisticated, intelligent and safe than the vehicles of today. The future is leaning towards fully autonomous vehicles. This degree project provides a data driven solution for a speed adaptation system that can be used to compute a vehicle speed for curves, suitable for the underlying driving style of the driver, road properties and weather conditions. A speed adaptation system for curves aims to compute a vehicle speed suitable for curves that can be used in Advanced Driver Assistance Systems (ADAS) or in Autonomous Driving (AD) applications. This degree project was carried out at Volvo Car Corporation. Literature in the field of speed adaptation systems and factors affecting the vehicle speed in curves was reviewed. Naturalistic driving data was both collected by driving and extracted from Volvo's data base and further processed. A novel speed adaptation system for curves was invented, implemented and evaluated. This speed adaptation system is able to compute a vehicle speed suitable for the underlying driving style of the driver, road properties and weather conditions. Two different artificial neural networks and two mathematical models were used to compute the desired vehicle speed in curves. These methods were compared and evaluated. / Morgondagens fordon kommer att vara mer sofistikerade, intelligenta och säkra än dagens fordon. Framtiden lutar mot fullständigt autonoma fordon. Detta examensarbete tillhandahåller en datadriven lösning för ett hastighetsanpassningssystem som kan beräkna ett fordons hastighet i kurvor som är lämpligt för förarens körstil, vägens egenskaper och rådande väder. Ett hastighetsanpassningssystem för kurvor har som mål att beräkna en fordonshastighet för kurvor som kan användas i Advanced Driver Assistance Systems (ADAS) eller Autonomous Driving (AD) applikationer. Detta examensarbete utfördes på Volvo Car Corporation. Litteratur kring hastighetsanpassningssystem samt faktorer som påverkar ett fordons hastighet i kurvor studerades. Naturalistisk bilkörningsdata samlades genom att köra bil samt extraherades från Volvos databas och bearbetades. Ett nytt hastighetsanpassningssystem uppfanns, implementerades samt utvärderades. Hastighetsanpassningssystemet visade sig vara kapabelt till att beräkna en lämplig fordonshastighet för förarens körstil under rådande väderförhållanden och vägens egenskaper. Två olika artificiella neuronnätverk samt två matematiska modeller användes för att beräkna fordonets hastighet. Dessa metoder jämfördes och utvärderades.
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