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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.
131

Unusual oxidation behavior of light metal hydride by tetrahydrofuran solvent molecules confined in ordered mesoporous carbon

Klose, Markus, Lindemann, Inge, Bonatto Minella, Christian, Pinkert, Katja, Zier, Martin, Giebeler, Lars, Nolis, Pau, Baró, Maria Dolors, Oswald, Steffen, Gutfleisch, Oliver, Ehrenberg, Helmut, Eckert, Jürgen 11 June 2020 (has links)
Confining light metal hydrides in micro- or mesoporous scaffolds is considered to be a promising way to overcome the existing challenges for these materials, e.g. their application in hydrogen storage. Different techniques exist which allow us to homogeneously fill pores of a host matrix with the respective hydride, thus yielding well defined composite materials. For this report, the ordered mesoporous carbon CMK-3 was taken as a support for LiAlH₄ realized by a solution impregnation method to improve the hydrogen desorption behavior of LiAlH₄ by nanoconfinement effects. It is shown that upon heating, LiAlH₄ is unusually oxidized by coordinated tetrahydrofuran solvent molecules. The important result of the herein described work is the finding of a final composite containing nanoscale aluminum oxide inside the pores of the CMK-3 carbon host instead of a metal or alloy. This newly observed unusual oxidation behavior has major implications when applying these compounds for the targeted synthesis of homogeneous metal–carbon composite materials.
132

Flexible in-plane micro-supercapacitors: Progresses and challenges in fabrication and applications

Zhang, Panpan, Wang, Faxing, Yang, Sheng, Wang, Gang, Yu, Minghao, Feng, Xinliang 16 April 2021 (has links)
The great popularity of portable, wearable, and implantable smart electronics has intensively boosted the development of flexible miniaturized power supplies. Owing to the fast charge/discharge capability, high power delivery, long cycling lifetime, easy fabrication and integration, flexible in-plane micro-supercapacitors (FPMSCs) are of significance as the micropower sources for the next-generation flexible on-chip electronics. In this review, we provide a comprehensive overview about FPMSCs and discuss the recent advances in their fabrication and applications. Particular emphasis is put on the emergent device fabrication technologies of FPMSCs, including deposition techniques, coating strategies, etching methods, and printing technologies. Moreover, we highlight the unique applications of FPMSCs in constructing smart responses and self-powered integrated systems in terms of multifunctional operation modes. Finally, the remaining challenges regarding flexibility, performance improvement, smart response, and microdevice integration of FPMSCs are discussed, which will stimulate further research in this thriving field.
133

Vacancy modification of Prussian-blue nano-thin films for high energy-density microsupercapacitors with ultralow RC time constant

He, Yafei, Zhang, Panpan, Wang, Faxing, Wang, Luxin, Su, Yuezeng, Zhang, Fan, Zhuang, Xiaodong, Feng, Xinliang 19 April 2021 (has links)
In-plane micro-supercapacitors (MSCs), as promising power candidates for micro-devices, typically exhibit high power densities, large charge/discharge rates, and long cycling lifetimes. The high areal/volumetric capacitances, high energy/power densities, high rate capability, as well as flexibility are the main scientific pursue in recent years. Among diverse electrode materials for MSCs, coordination polymer frameworks are emerging due to the designable porous structure and tunable functionality. However, the unsatisfied electrochemical performance still hinders their practical applications. In this work, we demonstrate the first time an efficient in-situ growth approach to precisely modify the vacancy of Prussian-blue nano-thin films with pyridine by coordination reaction for high energy-density MSCs. Confirmed by the experimental results and density functional theory calculation, the vacancy modification within Prussian-blue network improved the film-forming property, hydrophilicity, and electrochemical activity of the thin films. The resultant MSCs based on pyridine-modified Prussian-blue exhibited an ultrahigh energy density of up to 12.1 mWh cm⁻³ and an ultra-low time constant (t₀) of 0.038 ms, which are the best values among the state-of-the-art in-plane MSCs. This work provides an attractive solution for structural engineering of promising active materials on molecule level toward high-performance micro-energy devices.
134

NDE applications in microelectronic industries

Meyendorf, N., Oppermann, M., Krueger, P., Roellig, M., Wolter, K. J. 30 August 2019 (has links)
New concepts in assembly technology boost our daily life in an unknown way. High end semiconductor industry today deals with functional structures down to a few nanometers. ITRS roadmap predicts an ongoing decrease of the “DRAM half pitch” over the next decade. Packaging of course is not intended to realize pitches at the nanometer scale, but has to face the challenges of integrating such semiconductor devices with smallest pitch and high pin counts into systems. Advanced techniques of nondestructive evaluation (NDE) with resolutions in volume better than 1 micrometer vixen size are urgently needed for the safety and reliability of electronic systems, especially those that are used in long living applications. The development speed of integrated circuits is still very high and is not expected to decrease in the next future. The integration density of microelectronic devices is increasing, the dimensions become smaller and the number of I/O's is getting higher. The development of new types of packages must be done with respect to reliability issues. Potential damage sources must be identified and finally avoided in the new packages. In power electronics production the condition monitoring receives a lot of interest to avoid electrical shortcuts, dead solder joints and interface crac king. It is also desired to detect and characterize very small defects like transportation phenomenon or Kirkendall voids. For this purpose, imaging technologies with resolutions in the sub-micron range are required.
135

Energieversorgung autarker Sensorsysteme im industriellen Umfeld durch kinetische Energiewandler mit Schwerpunkt auf dem elektrostatischen Wandlerprinzip

Schaufuß, Jörg 12 November 2013 (has links)
In der vorliegenden Arbeit wird die Entwicklung eines kinetischen Energy Harvesters vorgestellt, der auf Grundlage des elektrostatischen Wandlerprinzips aus Vibrationen elektrische Energie generiert. Für die Umsetzung wurde eine Siliziummikrostruktur entworfen, die für Arbeitsfrequenzen unter 100 Hz ausgelegt ist. Die Zahnstruktur der verwendeten Elektroden ermöglicht Spaltabstände im Submikrometerbereich und folglich große Kapazitätsänderungen, die durch die Elektrodengeometrie zusätzlich mit einer höheren Frequenz als die mechanische Bewegung stattfinden. Vergleichsweise große Leistungsausbeuten und geringe Quellimpedanzen sind dadurch erreichbar. Die geometrischen Parameter der Elektroden wurden unter Berücksichtigung der auftretenden Fertigungstoleranzen und Wechselwirkungen zueinander optimiert. Für die Ausnutzung einer ausreichend großen Inertialmasse wurde ein feinwerktechnisch hergestellter Hebelmechanismus an die Mikrostruktur angekoppelt. Über diesen wird zusätzlich ein neuer Ansatz zur Abstimmung der Eigenfrequenz des Harvesters umgesetzt. Experimentelle Untersuchungen zeigten Ausgangsleistungen im einstelligen Mikrowattbereich bei Anregungen im Zehntel m/s²-Bereich. Durch fortschreitende Optimierungen der Fertigungstechnologie sind noch deutliche Leistungssteigerungen um mindestens zwei Größenordnungen möglich. Weiterhin wird ein Energiemanagementsystem vorgestellt, welches die effiziente Übertragung der Energie auf den Verbraucher ermöglicht. / In this work the development of a kinetic energy harvester using the electrostatic conversion principle is presented. The silicon microstructure is designed to work in frequency ranges below 100Hz. Its toothed electrode structure enables gap distances in the sub micrometer range and consequently high changes of capacitance. Additionally, due to the electrode geometry the frequency of the capacitance changes is higher then the frequency of the mechanical movement. Thus high power outputs and low source impedances can be reached. The electrodes geometric parameters were optimized considering manufacturing tolerances and interactions of the parameters. To reach a sufficient inertial mass, a lever mechanism manufactured by precision engineering was connected to the microstructure. This mechanism also allows the implementation of a new method of frequency tuning. In experimental tests power outputs in the single digit microwatt range under excitations of 0.3 m/s² were reached. In accordance of further optimizations of the manufacturing technology significantly higher outputs, by at least two orders of magnitude, are possible,. Furthermore an energy management system is presented, that allows the efficient transfer of the electrical energy to the consumer.
136

Modernisering av mjukvaruarkitektur för äldre mjukvarusystem / Modernization of software architecture for legacy software systems

Saffo, Farah, Saeed, Basma January 2021 (has links)
Flera företag använder sig än idag av mjukvarusystem som är uppbyggda med äldre mjukvaruarkitektur som den monolitiska. Ett av dessa företag är Consid vars personalsystem är uppbyggt med det utdaterade ramverket klassisk ASP och där användargränssnitt samt logik kan direkt kommunicera med varandra. Detta medför begränsningar som uppstår till följd av brister i modularitet på grund av valet av mjukvaruarkitektur, vilket försvårar vidareutveckling och ändringar i ett system. Dessa begränsningar påverkar i sin tur parametrar som prestanda, skalbarhet, säkerhet, robusthet samt integrering med modernare tekniker.  I denna rapport presenteras en litteraturstudie samt en semistrukturerad intervjustudie, i syfte att undersöka vilka mjukvaruarkitekturer som är lämpliga att implementera vid en modernisering av en monolitisk mjukvaruarkitektur. Arbetet diskuterade också vilka utmaningar som kan uppstå vid en sådan modernisering och hur de hanteras på ett effektivt sätt. Ett bedömningsschema med önskvärda parametrar, med avseende på skalbarhet, prestanda, säkerhet och robusthet, togs fram för att underlätta avgörandet vid val av mjukvaruarkitektur. Utifrån detta, beslutades det att en prototyp med en REST-baserad arkitektur skulle implementeras och utvärderas.  Resultatet av prototypen, till följd av re-architecting, visade en ökad modularisering av mjukvaruarkitekturen. I jämförelse mot med det tidigare systemet har den nya prototypen ingen större påverkan på prestanda i form av responstid. Däremot bidrog prototypen till förbättrad skalbarhet när det gäller vidareutvecklingen av systemet, eftersom det förenklar införandet av ny funktionalitet. Prototypen hade också högre säkerhet genom att isolera lager ifrån varandra samt dölja underliggande detaljer i implementationen. Dessutom blev prototypen inte bara mer robust till följd av modulariseringen, men även enklare att utföra integrationstester samt destruktiva tester mot. / Several companies still use software systems that are built with older software architecture such as the monolithic one. One of these companies is Consid, whose personnel system is built with the outdated framework Classic ASP and where the user interface and logic can directly communicate with each other. This entails limitations that arise because of shortcomings in modularity due to the choice of software architecture, which complicates further development and changes in a system. These limitations in turn, affect parameters such as performance, scalability, security, robustness, and integration with modern technologies. In this work, a literature study was conducted as well as a semi-structured interview study in order to investigate which software architectures are suitable to implement when a modernization of a monolithic software architecture, is carried out. The work also discussed the challenges that may arise in a modernization of the software architecture and how they are handled efficiently. An assessment scheme with desirable parameters regarding scalability, performance, security, and robustness, was developed to facilitate the decision in the choice of software architecture. Based on this, it was decided that a prototype with a REST-based architecture would be implemented and evaluated. The result of the prototype, following re-architecting, showed an increased modularization of the software architecture. Compared to the previous system, the new prototype has no major impact on performance in terms of response time. However, the prototype contributed to better scalability in the further development of the system as it simplifies the introduction of new functionality. The prototype also had higher security by isolating layers from each other and hiding the underlying details in the implementation. In addition, the prototype not only became more robust because of the modularization, but also easier to perform destructive tests against.
137

Pěstování microgreens v mateřské škole / Growing Microgreens in Nursery Schools

Kapuciánová, Karolína January 2021 (has links)
The diploma thesis focuses on the topic of cultivating microgreens in nursery school. Microgreens are young plants of various species of vegetable, that are grown in soil and are harvested approximetely after ten days. The simplicity of growing microgreens makes it an appropriate activity for preeschool-age children. Besides rewarding the children with nutricious food, it brings children the oppoturnity to develop key competences and pre- literacies. The theoretical part is an information base for growing microgreens in kindergarten conditions. It describes cultivating plants in kindergarten, it deals with historicaly, legislatively and didactic point of wiew and also describe kinds of microgreens, possibilities of use and cultivation procedures suitable for kindergarten. The aim of the diploma thesis is to present the possibility of growing microgreens in nursery school with preschool children. The empirical part focuses on the design and implementation of a set of activities in which children in kindergarten grow microgreens. In addition to cultivation, other activities are also included, in which children use the topic of microgreens in individual stages of growth. The set of activities aims primarily on reaching environmental education goals and is created using a logical model. It is...
138

Ancient plant cuticle chemistry: preservation and characterization of organic matter as biomarker of past UV-B radiation / Kemin i fossila löv: bevaring och karakterisering av organiskt material som biomarkör för forntida UV-B-strålning

Lopes Cavalcante, Larissa January 2021 (has links)
Biologiska processer hos olika organismer påverkas av ultraviolett-B-strålning (UV-B). Kunskapen om förändringar i UV-B-flödet som nått planetens yta under det geologiska tidsspann sedan flercelligt liv uppstod är dock begränsad. Följaktligen har olika biologiska proxies använts som ett sätt att försöka rekonstruera UV-B-flödet som når jordens yta. Växter reagerar på fluktuationen av UV-B genom att variera produktionen av fenolföreningar såsom parakumarsyra (pCA) och ferulinsyra, och därför kan dessa beståndsdelar användas som UV-B-proxys. UV-B-absorberande föreningar (UAC) finns i växternas yttersta skikt, den så kallade kutikulan men även i pollen och sporer, vilka oftaär välbevarade i det geologiska arkivet. Ändå är användningen av kutikula som UV-B-proxy inte lika undersökt. Därför syftar denna magisteruppsats till att analysera kemiska förändringar i fossila växters från trias – jura-gränsen (c. 200 miljoner år gamla)  och deras potential som UV-B-proxys. Eftersom de fossila löven behövde rengöras från sediment och från förkolnat mesofyll, gjordes också en analys av de kemiska förändringarna som orsakades av de olika rengöringsstegen. Icke-destruktiva tekniker, som mikro-FTIR och konfokalt Raman-mikroskop, användes för analysen. Försöken visade att analysen endast kunde utföras med mikro-FTIR på grund av den höga auto-fluorescensen hos de fossila bladen  vilketförhindrade analys med Raman. Signifikanta förändringar orsakades då Schulzes reagens användes för borttagning av mesofyllet, vilket ledde till nitrering av kutikulan. Ett mindre aggressivt och mer hållbart alternativ till denna process har visat sig vara väteperoxid, vilket orsakade mindre förändringar av den fossila kutikulans kemiska sammansättning. Dessutom upptäcktes indikation på förekomst av UAC endast i Ginkgoites regnellii, vilket indikerar att eventuell nedbrytning av dessa föreningar inträffade under diagenesen av de andra analyserade fossilerna. / Biological processes of different organisms are impacted by ultraviolet-B radiation (UV-B). However, knowledge about alterations in the UV-B flux reaching the planet’s surface during the geological past is limited. Consequently, different biological proxies have been used as an approach to attempt reconstructing the UV-B flux reaching Earth’s surface. Plants respond to the fluctuation of UV-B by varying the production of phenolic compounds such as p-coumaric acid (pCA) and ferulic acid, and therefore these constituents can be used as UV-B proxies. UV-B-absorbing compounds (UACs) can be found in the cuticle, pollen, and spores, which are all well-preserved in the geological record. Nevertheless, the use of cuticles as UV-B proxy is not as explored. Hence, this Master’s thesis aimed to analyse chemical changes in the plant cuticles from the Triassic–Jurassic boundary and their potential as UV-B proxies. Moreover, as the cuticles needed to be cleaned from rocks and isolated from coalified mesophyll, an analysis of the chemical changes caused by the cleaning steps was also done. Non-destructive techniques, as micro-FTIR and confocal Raman microscope, were used for the analysis.  Yet, the analysis could only be conducted with micro-FTIR due to auto-fluorescence of the leaves preventing success with Raman. Main changes during the cleaning steps were caused using Schulze’s reagent, which led to nitration of the cuticles. A less aggressive and more sustainable alternative to this process is shown to be hydrogen peroxide, which caused minor alteration of the fossil cuticle’s chemical composition.  Moreover, indication of the presence of UACs was detected only in Ginkgoites regnellii, indicating that possible degradation of these compounds occurred during diagenesis of the other fossils analysed.
139

Informationssäkerhetsmedvetenhet inom mikro- och småbolag : Medvetenhetsåtgärder hos svenska mikro- och småbolag inom IT-branschen / Information security awareness in micro and small companies.

Vukovic, Alexander, Samet, Özcelik January 2022 (has links)
All organizations, regardless of size, are affected by information security awareness. Information security awareness is an important component, especially for organizations in the IT industry, to be able to respond to new cyber threats but also comply with requirements and regulations for handling customer data. The purpose of the study is to improve awareness-raising measures used by Swedish micro and small companies in the IT industry to increase information security awareness among employees. The study is performed through semi-structured interviews and then analyzed using the Grounded theory-method. The study highlights the awareness measures used in the IT industry and how they are used among companies to make employees aware of information security. In addition, the companies' underlying motives for their choice of awareness measure and their perspective on adapting the measure are examined. The study's conclusions present recommendations that can be used by micro and small companies in the IT industry to improve their awareness-raising measures. The study highlights the importance of adapting training measures, but also that companies should present reality-based scenarios to employees. In addition, it is also emphasized that incentives should be used by information security officers for employees to ensure compliance. / Alla organisationer, oavsett storlek påverkas av informationssäkerhetsmedvetenhet. Medvetenhet om informationssäkerhet är en viktig komponent i synnerhet för organisationer inom IT-branschen för att kunna bemöta nya cyberhot men också efterleva krav och regleringar för hantering av kunddata. Syftet med studien är att förbättra medvetenhetshöjande åtgärder som används av svenska mikro- och småbolag inom IT-branschen för att öka informationssäkerhetsmedvetenheten bland anställda. Studien utförs genom semistrukturerade intervjuer och analyseras sedan med hjälp av Grundad teori-metoden. Studien synliggör vilka medvetenhetsåtgärder som används inom IT-branschen och hur de används bland bolagen för att göra anställda medvetna gällande informationssäkerhet. Dessutom framgår bolagens bakomliggande motiv för deras val av medvetenhetsåtgärd samt deras perspektiv på anpassning av åtgärd. Studiens slutsatser presenterar rekommendationer som kan användas av mikro- och småbolag inom IT-branschen för att förbättra deras medvetenhetshöjande åtgärder. Studien lyfter fram betydelsen av anpassning av utbildningsåtgärder, men även att bolagen bör presentera verklighetsförankrade scenarier till de anställda. Därtill framhävs även att incitament bör användas av informationssäkerhetsansvariga till anställda för att säkerställa efterlevnad.
140

Enhancing Drone Spectra Classification : A Study on Data-Adaptive Pre-processing and Efficient Hardware Deployment

Del Gaizo, Dario January 2023 (has links)
Focusing on the problem of Drone vs. Unknown classification based on radar frequency-amplitude spectra using Deep Learning (DL), especially 1-Dimensional Convolutional Neural Networks (1D-CNNs), this thesis aims at reducing the current gap in the research related to adequate pre-processing techniques for hardware deployment. The primary challenge tackled in this work is determining a pipeline that facilitates industrial deployment while maintaining high classification metrics. After presenting a comprehensive review of existing research on radar signal classification and the application of DL techniques in this domain, the technical background of signal processing is described to provide a practical scenario where the solutions could be implemented. A thorough description of technical constraints, such as Field Programmable Gate Array (FPGA) data type requirements, follows the entire project justifying the necessity of a learning-based pre-processing technique for highly skewed distributions. The results demonstrate that data-adaptive preprocessing eases hardware deployment and maintains high classification metrics, while other techniques contribute to noise and information loss. In conclusion, this thesis contributes to the field of radar frequency-amplitude spectra classification by identifying effective methods to support efficient hardware deployment of 1D-CNNs, without sacrificing performance. This work lays the foundation for future studies in the field of DL for real-world signal processing applications. / Med fokus på problemet med klassificering av drönare kontra okänt baserat på radarfrekvens-amplitudspektra med Deep Learning (DL), särskilt 1-Dimensional Convolutional Neural Networks (1D-CNNs), syftar denna avhandling till att minska det nuvarande gapet i forskningen relaterad till adekvata förbehandlingstekniker för hårdvarudistribution. Den främsta utmaningen i detta arbete är att fastställa en pipeline som underlättar industriell driftsättning samtidigt som höga klassificeringsmått bibehålls. Efter en omfattande genomgång av befintlig forskning om klassificering av radarsignaler och tillämpningen av DL-tekniker inom detta område, beskrivs den tekniska bakgrunden för signalbehandling för att ge ett praktiskt scenario där lösningarna kan implementeras. En grundlig beskrivning av tekniska begränsningar, såsom krav på datatyper för FPGA (Field Programmable Gate Array), följer hela projektet och motiverar nödvändigheten av en inlärningsbaserad förbehandlingsteknik för mycket skeva fördelningar. Resultaten visar att dataanpassad förbehandling underlättar hårdvaruimplementering och bibehåller höga klassificeringsmått, medan andra tekniker bidrar till brus och informationsförlust. Sammanfattningsvis bidrar denna avhandling till området klassificering av radarfrekvens-amplitudspektra genom att identifiera effektiva metoder för att stödja effektiv hårdvarudistribution av 1D-CNN, utan att offra prestanda. Detta arbete lägger grunden för framtida studier inom området DL för verkliga signalbehandlingstillämpningar.

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