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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.
221

Leitwertkontrolle einzelner elektrisch kontaktierter Moleküle

Sendler, Torsten 02 October 2015 (has links)
Die molekulare Elektronik setzt sich zum Ziel, passive und aktive Bausteine in integrierten Schaltkreisen auf molekularer Ebene zu realisieren. Dabei ist entscheidend, dass sich der elektrische Leitwert der molekularen Bauelemente hinreichend regulieren lässt. Um zu belegen, dass dies möglich ist, wird in dieser Dissertation die gezielte Leitwertkontrolle einzelner über Nanoelektroden kontaktierter Moleküle nachgewiesen. Die erzielten Ergebnisse ergänzen dabei nahtlos aktuellste Studien. Zum einen werden kontaktierte molekulare Schalter durch Bestrahlung mit Licht einer bestimmten Wellenlänge in-situ von einem nicht-leitenden in einen leitenden Zustand geschaltet, wobei der Einfluss unterschiedlicher Seitengruppen für eine zusätzliche Modifikation des Leitwerts sorgt. Ausschlaggebend ist hierbei die elektronische Anbindung des Moleküls an die Elektroden. Zum anderen werden Molekül-Metall-Komplexe durch die Einbindung eines Übergangsmetallions von einem isolierenden in einen leitenden Zustand versetzt. In diesem Fall lässt sich der leitende Zustand durch die Wahl des Ions innerhalb einer Größenordnung variieren, was eine völlig neue Möglichkeit der Leitwertkontrolle in molekularen Bausteinen darstellt. Das Ion bestimmt dabei sowohl die mechanische Stabilität als auch die elektronische Struktur des Moleküls. Für die Kontaktierung einzelner Moleküle kommt die Technik des mechanisch kontrollierten Bruchkontakts zum Einsatz. So lassen sich feine Goldnanoelektroden herstellen, an die Moleküle anbinden. Um eine präzise Analyse durchzuführen, werden über zwei unabhängige Messstrategien Informationen über das elektrische Transportverhalten sowie über die elektronische Struktur der Moleküle erworben. In dieser Arbeit sind echte Neuentwicklungen auf dem Gebiet der molekularen Elektronik gelungen, die einen wesentlichen Beitrag für die Umsetzung integrierter molekularer Schaltkreise leisten.
222

Entwicklung und Gestaltung variabler Bedienelemente für ein Bedien- und Anzeigesystem im Fahrzeug

Sendler, Jochen 31 March 2008 (has links)
Angesichts der steigenden Anzahl von Funktionen in Fahrzeugen, insbesondere im Pkw, sind neue Bedien- und Anzeigesysteme notwendig, die eine optimale Bedienbarkeit der Funktionen sicherstellen und die Ablenkung des Fahrers von der Fahraufgabe minimieren. Im Rahmen dieser Arbeit wird dazu der Einsatz variabler Bedienelemente verfolgt, die sich der aktuellen Bedienaufgabe optimal anpassen. Ziel dieser Arbeit ist es insbesondere, Vorgehensweisen und Gestaltungsempfehlungen für variable Beschriftung von Tasten und zentrale Bedienelemente mit variabler Formcodierung für abgesetzte Bedien- und Anzeigesysteme zu erarbeiten. Unter Zuhilfenahme arbeitswissenschaftlicher Methoden wird dafür zunächst die Gestaltung variabler Beschriftung von Tasten untersucht und Empfehlungen für deren Gestaltung abgeleitet. Des Weiteren wird die Entwicklung eines zentralen Bedienelements mit variabler Formcodierung beschrieben. Dazu wird, aufbauend auf bekannten Entwicklungs- und Auswahlverfahren für Bedienelemente, eine Vorgehensweise zur Entwicklung variabler Bedienelemente vorgeschlagen. Das entwickelte variable zentrale Bedienelement wird darüber hinaus hinsichtlich seiner Bedienbarkeit und Ablenkungswirkung bewertet. Aus den Versuchsergebnissen konnten Gestaltungsempfehlungen abgeleitet werden, wie durch ein variables zentrales Bedienelement die Bedienbarkeit von abgesetzten Bedien- und Anzeigesystemen verbessert und die Ablenkungswirkung reduziert werden kann. Die Ergebnisse dieser Arbeit leisten einen Beitrag zur Entwicklung zukünftiger abgesetzter Bedien- und Anzeigesysteme und geben insbesondere Entwicklern und Gestaltern eine Hilfestellung beim Einsatz variabler Bedienelemente.
223

Entirely soft dielectric elastomer robots

Henke, E.-F. Markus, Wilson, Katherine E., Anderson, Iain A. 06 September 2019 (has links)
Multifunctional Dielectric Elastomer (DE) devices are well established as actuators, sensors and energy harvesters. Since the invention of the Dielectric Elastomer Switch (DES), a piezoresistive electrode that can directly switch charge on and off, it has become possible to expand the wide functionality of DE structures even more. We show the application of fully soft DE subcomponents in biomimetic robotic structures. It is now possible to couple arrays of actuator/switch units together so that they switch charge between themselves on and off. One can then build DE devices that operate as self-controlled oscillators. With an oscillator one can produce a periodic signal that controls a soft DE robot { a DE device with its own DE nervous system. DESs were fabricated using a special electrode mixture, and imprinting technology at an exact pre-strain. We have demonstrated six orders of magnitude change in conductivity within the DES over 50% strain. The control signal can either be a mechanical deformation from another DE or an electrical input to a connected dielectric elastomer actuator (DEA). We have demonstrated a variety of fully soft multifunctional subcomponents that enable the design of autonomous soft robots without conventional electronics. The combination of digital logic structures for basic signal processing, data storage in dielectric elastomer ip-ops and digital and analogue clocks with adjustable frequencies, made of dielectric elastomer oscillators (DEOs), enables fully soft, self-controlled and electronics-free robotic structures. DE robotic structures to date include stiff frames to maintain necessary pre-strains enabling sufficient actuation of DEAs. Here we present a design and production technology for a first robotic structure consisting only of soft silicones and carbon black.
224

Building a real data warehouse for market research

Lehner, Wolfgang, Albrecht, J., Teschke, M., Kirsche, T. 08 April 2022 (has links)
This paper reflects the results of the evaluation phase of building a data production system for the retail research division of the GfK, Europe's largest market research company. The application specific requirements like end-user needs or data volume are very different from data warehouses discussed in the literature, making it a real data warehouse. In a case study, these requirements are compared with state-of-the-art solutions offered by leading software vendors. Each of the common architectures (MOLAP, ROLAP, HOLAP) was represented by a product. The result of this comparison is that all systems have to be massively tailored to GfK's needs, especially to cope with meta data management or the maintenance of aggregations.
225

Building a real data warehouse for market research

Lehner, Wolfgang, Albrecht, J., Teschke, M., Kirsche, T. 19 May 2022 (has links)
This paper reflects the results of the evaluation phase of building a data production system for the retail research division of the GfK, Europe's largest market research company. The application specific requirements like end-user needs or data volume are very different from data warehouses discussed in the literature, making it a real data warehouse. In a case study, these requirements are compared with state-of-the-art solutions offered by leading software vendors. Each of the common architectures (MOLAP, ROLAP, HOLAP) was represented by a product. The result of this comparison is that all systems have to be massively tailored to GfK's needs, especially to cope with meta data management or the maintenance of aggregations.
226

Exploiter la coopérativité d'assemblages supramoléculaires d'ADN pour contrôler la plage dynamique d'interrupteurs moléculaires

Lauzon, Dominic 04 1900 (has links)
L’autoassemblage de diverses biomolécules pour former des complexes moléculaires est à la base de la machinerie cellulaire et des processus biologiques qui s’y rattachent. Il est typiquement considéré qu’un assemblage de plusieurs protéines offre des avantages régulatifs comparativement à une structure protéique similaire construite avec une ou un nombre inférieur de composantes. Ces assemblages offrent, par exemple, la possibilité de contrôler l’activité d’un complexe grâce à la dépendance directe de l’assemblage sur la concentration de ces composantes. De plus, la coopérativité d’interaction entre ces diverses composantes ouvre la voie vers l’obtention de nouveaux mécanismes de régulation. Toutefois, les avantages et les inconvénients directement reliés au nombre de composantes impliquées dans un assemblage ne sont pas totalement bien compris puisque les protéines ont évolué et ont divergé suivant des millions d’années d’évolution. L’objectif principal de cette thèse est d’abord de créer un modèle moléculaire simplifié permettant de mieux comprendre les avantages coopératifs des autoassemblages biologiques pour ensuite s’en inspirer afin de mettre au point de nouveaux mécanismes moléculaires permettant d’optimiser la plage dynamique d’interrupteurs moléculaires autoassemblés. En même temps, il sera possible de mettre en lumière certains avantages évolutifs qui ont poussé les protéines à acquérir plus de composantes moléculaires. Tout d’abord, la création d’assemblages moléculaires fut effectuée en fragmentant une structure unimoléculaire en plusieurs fragments qui pourront, grâce à leurs interactions, reformer la structure originale. Grâce à une nanostructure simple d’ADN, c.-à-d. une jonction à trois branches, il fut possible d’étudier directement l’impact du nombre de composantes sur la fonctionnalité et la régulation d’assemblages multimériques. Il fut observé, malgré l’association plus lente d’un assemblage de trois composantes, que ce même assemblage s’associe de manière plus coopérative tout en permettant la création de nouveaux mécanismes de régulation (p. ex. plage dynamique étendue, auto-inhibition et minuterie moléculaire). Ce système simplifié d’ADN a donc permis de conclure que la fragmentation d’une nanostructure en plusieurs composantes est une méthode simple permettant d’optimiser un nanosystème artificiel ou naturel. Ensuite, une autre méthode de création d’assemblages moléculaires fut étudiée. Celle-ci consiste à fusionner des domaines interagissant par le biais d’un espaceur. Dans une telle stratégie, l’espaceur est appelé à jouer un rôle important dans les propriétés de l’assemblage. Ainsi, en utilisant le même modèle d’ADN à trois composantes, il fut en effet observé que les propriétés de l’espaceur (p. ex. sa longueur, sa composition ou sa nature chimique) affectent grandement les propriétés d’assemblage d’un système à trois composantes (p. ex. sa stabilité, son niveau de coopérativité ou sa plage dynamique d’assemblage). En effectuant une étude thermodynamique approfondie sur divers assemblages trimériques d’ADN, il fut découvert qu’un espaceur optimal stabilise l’association des diverses composantes en créant une structure plus compacte où les espaceurs se cachent au coeur de la jonction. Il fut aussi démontré qu’en optimisant l’espaceur, il est possible de programmer précisément la plage dynamique d’un assemblage moléculaire à trois composantes. Finalement, ces découvertes sur les avantages d’un assemblage à trois composantes ont permis la création d’une nouvelle stratégie afin d’optimiser la plage dynamique d’interrupteurs moléculaires. À l’inverse des activateurs allostériques classiques qui altèrent la force d’interaction d’un ligand, c.-à-d. le KD, en modifiant la conformation de l’interrupteur, un activateur multivalent permet de programmer précisément la plage dynamique de l’interrupteur en exploitant une nouvelle surface d’interaction grâce à la formation d’un assemblage à trois composantes. Cette nouvelle stratégie d’optimisation des interrupteurs moléculaires fut validée grâce à une tige-boucle d’ADN servant comme balise moléculaire. Cette preuve de concept permet de démontrer la viabilité des assemblages moléculaires pour conceptualiser de nouvelles nanotechnologies avec une plage dynamique optimisée. Il est donc possible d’imaginer que les assemblages moléculaires auront un impact immédiat dans divers domaines de la nanotechnologie comme en diagnostic médical, en délivrance contrôlée de médicaments ou en imagerie moléculaire. / The self-assembly of various biomolecules to form molecular complexes is at the basis of the cellular machinery and their related biological processes. It is typically thought that an assembly of several proteins provides regulatory advantages compared to a similar protein built with one or fewer molecular components. These molecular assemblies offer, for example, the possibility to control their activity through the direct dependency of the assembly on the concentration of its components. Moreover, the cooperativity of interaction between their multiple components opens the door to acquiring novel regulation mechanisms. However, the advantages and disadvantages directly related to the number of components involved in an assembly are not totally understood since proteins have evolved and diverged over millions of years of evolution. The main objective of this thesis is to first create a simplified molecular model that will enable to better understand the cooperative advantages of biological self-assemblies. Then, inspired by these new understandings, novel molecular mechanisms will be developed to enable the optimization of the dynamic range of self-assembled molecular switches. Meanwhile, it will be possible to highlight some advantages that have pushed proteins to acquire more molecular components. The creation of molecular assemblies was demonstrated by fragmenting a nanostructure into multiple fragments which, through their intermolecular interactions, reassemble into the original structure. Using a simple DNA-based nanostructure, i.e., a three-way junction, it was possible to directly study the impact of the number of components on the functionality and regulation of multimeric assemblies. It was found that despite the slower assembly rate of a three-component assembly, this same assembly undergoes a more cooperative assembly enabling the creation of new regulatory mechanisms (e.g., extended dynamic range, self-inhibition and molecular timers). This simplified DNA-based system has therefore made it possible to conclude that fragmenting a nanostructure into multiple components is a simple method to optimize an artificial or a natural nanosystem. Next, another method to create molecular assemblies was studied. This method consists in fusing interacting domains through a linker. In this strategy, the linker will play an important role in dictating the properties of the assembly. Therefore, by using the same three-component DNA-based model, it has been observed that the chemical properties of the linker (e.g., its length, its composition, or its chemical nature) considerably affect the assembly properties of a three-component system (e.g., its stability, its level of cooperativity, or its dynamic range). Through an exhaustive thermodynamic study on various trimeric DNA-based assemblies, it was determined that the optimal linker stabilizes the association of all components by creating a more compact assembly where the linkers are buried within the core of the junction. It was also demonstrated that the optimization of the linkers allows to precisely program the dynamic range of the assembly. Finally, these discoveries on the advantages of a three-component assembly have enabled the creation of a new design strategy to optimize the dynamic range of molecular switches. In contrast to the classic allosteric activator which alters the affinity of a ligand (i.e., the KD) by changing the conformation of the switch, a multivalent activator enables to precisely program the dynamic range of a switch by exploiting a new interacting interface through the formation of a three-component assembly. This new strategy to optimize molecular switches was validated using a DNA-based molecular beacon. This proof of concept demonstrates the viability of molecular assemblies to design novel nanotechnologies with optimized dynamic range. It is possible to imagine that these molecular assemblies could have a direct impact on multiple fields of nanotechnology including medical diagnostics, controlled drug delivery and molecular imaging.
227

Synthesis and conformational study of trans-2-aminocyclohexanol-based pH-triggered molecular switches and their application in gene delivery

Zheng, Yu 01 January 2013 (has links) (PDF)
Trans-2-Aminocyclohexanol (TACH) is a promising model for pH-triggerable molecular switches with a variety of potential applications. In particular, such a switch, when incorporated into cationic liposomes, provides a novel design of the pH-sensitive helper lipids for gene delivery. Protonation of TACH molecules results in a strong intramolecular hydrogen bond between the amino and its neighboring hydroxyl groups, which triggers a conformational flip, and forces changes of the relative position of other substituents on the ring. In this work, a library of TACH-lipids has been designed and built based on structural modifications of both hydrophilic headgroups and hydrophobic tails, and their conformational behavior has been studied by 1 H NMR. NMR-titration has been done to quantitatively monitor the conformational switch for TACH derivatives. It was discovered that conformational behavior of TACH-lipids is independent from the length or shape of their hydrophobic tails. Therefore, a simplified model was suggested based on TACH with diethyl groups instead of hydrocarbon tails. Conformational study of these models has demonstrated that the position of equilibrium shift A [special characters omitted] BH + can be effectively changed by altering structure of NR 2 R 3 group. Furthermore, the pH-induced conformational flip occurs in a certain pH range that mostly depends on the basicity of group NR 2 R 3 , allowing a broad tuning of the pH-sensitivity of TACH-based conformational switches in a wide range of acidity. The hydrophilic OH group was also modified to influence the conformational equilibrium. External stimuli including addition of acid, change of solvent and of the solution ionic strength also showed impact on conformation equilibrium to different extents. To explore the potential to serve as pH-sensitive helper lipids in gene delivery, a variety of TACH-lipids were incorporated into lipoplexes together with the cationic lipid DOTAP to mediate DNA transfection in Bl6F1 and HeLa cancer cell lines. The lipoplex comprising TACH-lipid 3o (R 1 = C 19 H 37 ; R 2 R 3 = CF 3 CH 2 NH) exhibited one to two orders of magnitude better transfection efficiency than the one with the conventional helper lipid DOPE while only inducing slight higher cytotoxicity. Thus, the lipid can be suggested as a novel helper lipid for efficient gene transfection with low cytotoxicity.
228

<b>Leveraging Advanced Large Language Models To Optimize Network Device Configuration</b>

Mark Bogdanov (18429435) 24 April 2024 (has links)
<p dir="ltr">Recent advancements in large language models such as ChatGPT and AU Large allow for the effective integration and application of LLMs into network devices such as switches and routers in terms of the ability to play a role in configuration and management. The given devices are an essential part of every network infrastructure, and the nature of physical networking topologies is complex, which leads to the need to ensure optimal network efficiency and security via meticulous and precise configurations.</p><p dir="ltr">The research explores the potential of an AI-driven interface that utilizes AU Large to streamline, enhance, and automate the configuration process of network devices while ensuring that the security of the whole process is guaranteed by running the entire system on-premise. Three core areas are of primary concern in the given study: the effectiveness of integrating the AU Large into network management systems, the impact on efficiency, accuracy, and error rates in network configurations, and the scalability and adaptability to more complex requirements and growing network environments.</p><p dir="ltr">The key performance metrics evaluated are the error rate in the generated configurations, scalability by looking at the performance as more network devices are added, and the ability to generate incredibly complex configurations accurately. The high-level results of the critical performance metrics show an evident correlation between increased device count and increased prompt complexity with a degradation in the performance of the AU Large model from Mistral AI.</p><p dir="ltr">This research has significant potential to alter preset network management practices by applying AI to make network configuration more efficient, reduce the scope for human error, and create an adaptable tool for diverse and complex networking environments. This research contributes to both AI and network management fields by highlighting a path toward the “future of network management.”</p>
229

Towards No-Penalty Control Hazard Handling in RISC architecture microcontrollers

LINKNATH SURYA BALASUBRAMANIAN (8781929) 03 September 2024 (has links)
<p dir="ltr">Achieving higher throughput is one of the most important requirements of a modern microcontroller. It is therefore not affordable for it to waste a considerable number of clock cycles in branch mispredictions. This paper proposes a hardware mechanism that makes microcontrollers forgo branch predictors, thereby removing branch mispredictions. The scope of this work is limited to low cost microcontroller cores that are applied in embedded systems. The proposed technique is implemented as five different modules which work together to forward required operands, resolve branches without prediction, and calculate the next instruction's address in the first stage of an in-order five stage pipelined micro-architecture. Since the address of successive instruction to a control transfer instruction is calculated in the first stage of pipeline, branch prediction is no longer necessary, thereby eliminating the clock cycle penalties occurred when using a branch predictor. The designed architecture was able to successfully calculate the address of next correct instruction and fetch it without any wastage of clock cycles except in cases where control transfer instructions are in true dependence with their immediate previous instructions. Further, we synthesized the proposed design with 7nm FinFET process and compared its latency with other designs to make sure that the microcontroller's operating frequency is not degraded by using this design. The critical path latency of instruction fetch stage integrated with the proposed architecture is 307 ps excluding the instruction cache access time.</p>
230

Advances in the stochastic and deterministic analysis of multistable biochemical networks

Petrides, Andreas January 2018 (has links)
This dissertation is concerned with the potential multistability of protein concentrations in the cell that can arise in biochemical networks. That is, situations where one, or a family of, proteins may sit at one of two or more different steady state concentrations in otherwise identical cells, and in spite of them being in the same environment. Models of multisite protein phosphorylation have shown that this mechanism is able to exhibit unlimited multistability. Nevertheless, these models have not considered enzyme docking, the binding of the enzymes to one or more substrate docking sites, which are separate from the motif that is chemically modified. Enzyme docking is, however, increasingly being recognised as a method to achieve specificity in protein phosphorylation and dephosphorylation cycles. Most models in the literature for these systems are deterministic i.e. based on Ordinary Differential Equations, despite the fact that these are accurate only in the limit of large molecule numbers. For small molecule numbers, a discrete probabilistic, stochastic, approach is more suitable. However, when compared to the tools available in the deterministic framework, the tools available for stochastic analysis offer inadequate visualisation and intuition. We firstly try to bridge that gap, by developing three tools: a) a discrete `nullclines' construct applicable to stochastic systems - an analogue to the ODE nullcines, b) a stochastic tool based on a Weakly Chained Diagonally Dominant M-matrix formulation of the Chemical Master Equation and c) an algorithm that is able to construct non-reversible Markov chains with desired stationary probability distributions. We subsequently prove that, for multisite protein phosphorylation and similar models, in the deterministic domain, enzyme docking and the consequent substrate enzyme-sequestration must inevitably limit the extent of multistability, ultimately to one steady state. In contrast, bimodality can be obtained in the stochastic domain even in situations where bistability is not possible for large molecule numbers. We finally extend our results to cases where we have an autophosphorylating kinase, as for example is the case with $Ca^{2+}$/calmodulin-dependent protein kinase II (CaMKII), a key enzyme in synaptic plasticity.

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