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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.
301

Tvorba výpočtového modelu pro deformačně napěťovou analýzu prvků generátoru / Creating a computational model for stress-strain analysis of parts of generator

Sedláček, Radek January 2014 (has links)
This thesis focuses on creating of a computational model for stress-strain analysis of parts of a generator. Computational model is parametric and it allows use of various geometric variants of the shaft and rotor lamination. Parametric computational model in APLD language is compiled in the attached sheet of software MS Excel after entering input values. After solving in software ANSYS 14.5 are results imported into MS Excel sheet for further post processing.
302

Výpočtové modelování srdeční kontrakce / Computational modelling of heart contraction

Vaverka, Jiří January 2016 (has links)
This thesis aims to determine the impact of slowed myocardial conduction velocity and depressed myocyte contractility on the duration of isovolumic contraction time (ICT) of the left ventricle by carrying out simulations using finite element method. A 3D finite element model enabling to simulate both physiological and pathological states of myocardium was created. The model is based on simplified ellipsoidal geometry and accounts for anisotropic behavior of myocardium, its asynchronous contraction and variations in the arrangement of muscle fibers. Slowing of conduction velocity to a half of its physiological value resulted in prolongation of ICT by 27 %; slowing of shortening velocity of myocytes by the same percentage prolonged ICT by 73 %. It is therefore concluded that ICT can be much more prolonged due to depressed contractility than due to conduction slowing. The presented results give an idea of the extent to which ICT can be prolonged due to depressed contractility and conduction slowing and therefore can be useful in identifying the causes of decreased myocardial performance in heart disease.
303

A Computational Study of the Radial Growth of Axons and Neurofilament Kinetics during Postnatal Development

Nowier, Rawan M. 24 May 2022 (has links)
No description available.
304

Computational Intelligent Sensor-rank Consolidation Approach for Industrial Internet of Things (IIoT)

Mekala, M. S., Rizwan, Patan, Khan, Mohammad S. 01 January 2021 (has links)
Continues field monitoring and searching sensor data remains an imminent element emphasizes the influence of the Internet of Things (IoT). Most of the existing systems are concede spatial coordinates or semantic keywords to retrieve the entail data, which are not comprehensive constraints because of sensor cohesion, unique localization haphazardness. To address this issue, we propose deep learning inspired sensor-rank consolidation (DLi-SRC) system that enables 3-set of algorithms. First, sensor cohesion algorithm based on Lyapunov approach to accelerate sensor stability. Second, sensor unique localization algorithm based on rank-inferior measurement index to avoid redundancy data and data loss. Third, a heuristic directive algorithm to improve entail data search efficiency, which returns appropriate ranked sensor results as per searching specifications. We examined thorough simulations to describe the DLi-SRC effectiveness. The outcomes reveal that our approach has significant performance gain, such as search efficiency, service quality, sensor existence rate enhancement by 91%, and sensor energy gain by 49% than benchmark standard approaches.
305

Catalytic Surface Reactions: Monte Carlo Simulations of Systems with Creation, Annihilation and Diffusion of Interacting Reactants

Zvejnieks, Guntars 19 June 2001 (has links)
During the last 30 years considerable attention was paid to open systems far from thermal equilibrium. Under certain conditions these dissipative systems show a qualitatively new behavior on macroscopic length scales, which are known as spatiotemporal structures. These new structures arise as a feature of collective behavior of a many-body systems. One particular example of dissipative systems considered in the present Thesis is the systems with reactant birth and death. Such systems arise, e.g., in description of the population growth or the kinetics of chemical reactions. To describe the systems with a large number of particles, one has to impose some restrictions. So, it is assumed that individual properties of particles are not important, only their interaction and interaction result (reaction) are taken into account. A number of rules, which describe the behavior of particles on the microscopic level, are known as a mathematical model. There exist two methods to analyze properties of a mathematical model. The first is analysis based on the master equation. In general, this method fails to describe the properties of spatiotemporal structures. There are no analytical approximations taking into account the effect of long-range particle correlation, which is important for description of the changes on a macroscopic range. The second approach are Monte Carlo (MC) computer simulations, which actually is alternative to experiments. The MC method takes into account long-range reactant correlations. They arise as a result of microscopical model. MC has disadvantages typical for all numerical methods, e.g., a large simulation time. In the present Thesis the Lotka-type and the A+B->0 models are considered in detail. These reactions are commonly found as one of a component in many chemical reactions. The emphasis is made on understanding the basic properties of these models. Further, several physically important modifications of the Lotka-type and the A+B->0 models are made. Firstly, in Chapter 1. the Lotka-type model is extended to investigate the resonance properties. Secondly, the effect of reactant diffusion and interaction is incorporated into Lotka-type model in Chapter 2. Thirdly, the standard A+B->0 reaction is extended to the case of surface reconstruction in Chapter 3. General conclusion is presented at the end of the Thesis, which is ended by four Appendices.
306

Towards Computational Modeling of Two-dimensional Covalent Organic Frameworks

Raptakis, Antonios 25 January 2022 (has links)
Kovalente organische Frameworks (COFs) haben in den letzten Jahren aufgrund ihrer potenziellen Anwendungen in verschiedenen Bereichen großes Interesse hervorgerufen. Obwohl die Eigenschaften der synthetisierten Materialien empfindlich von den Eigenschaften der entsprechenden organischen Liganden abhängen, ist der Beitrag der einzelnen Bausteine zu den Kristalleigenschaften nicht eindeutig definiert. In dieser Arbeit werden die elektronischen und mechanischen Eigenschaften von einschichtigen zweidimensionalen (2D) COFs untersucht, wobei der Schwerpunkt auf den molekularen Bausteinen liegt. Zunächst wurde die Kristallstruktur als Hooke'sches Federnetzwerk angenommen, und analytische Formeln für 2D-COFs mit quadratischer und hexagonaler Gittertopologie wurden abgeleitet, wobei eine Vorhersage des Kompressionsmoduls aus der Berechnung der Monomer-Federkonstante angestrebt wurde. Alle geschätzten Werte für Moleküle und periodische Strukturen wurden mit der DFTB-Methode (Density Functional based Tight-Binding) berechnet. Benchmarking-Berechnungen mit der Dichtefunktionaltheorie (DFT) wurden eingesetzt, um die Anwendbarkeit der semiempirischen Methode zu überprüfen. In einem zweiten Schritt wurden Methoden vorgeschlagen, um die elektronische Bandstruktur und die elektronischen Eigenschaften von COFs zu verändern, wie z.B. die Änderung von Bindungen oder Linkern, Seitengruppen oder Funktionalisierung und die Erhöhung der Massendichte. Die verschiedenen Methoden ergeben unterschiedliche Eigenschaften der resultierenden Strukturen. Darüber hinaus wurden mehrere Polymere durch periodische Fortsetzung in einer oder zwei Dimensionen auf der Grundlage derselben molekularen Bausteine modelliert. Es wurde ein zweistufiges System auf der Grundlage des Tight-Binding-Ansatzes vorgeschlagen, und dessen Parameter wurden mit Hilfe der Bandoberkante des Valenzbandes und der Bundunterkante des Leitungsbandes abgeschätzt. Ein maschinelles Lernverfahren wurde eingesetzt, um die elektronische Bandlücke auf der Grundlage der gleichen Kernmonomere vorherzusagen. Interessanterweise erbt das 2D-COF die elektronische Lücke von der monomeren Einheit mit der niedrigeren elektronischen Energiedifferenz zwischen besetztem und unbesetztem Band. Schließlich wurde die Protonentautomerisierung in zwei sehr häufig verwendeten Kernmonomeren für 2D-COFs, Porphyrin und Phthalocyanin, und ihren Derivaten untersucht. Die Freie-Energie-Oberfläche wurde mit Quanten-Molekulardynamik-Simulationen durch Kombination von DFTB und Metadynamik berechnet. Durch die Analyse der Potenzialporträts werden die strukturellen Symmetrien des Moleküls in Protonentransferreaktionen widergespiegelt. Ich erwarte, dass die Ergebnisse dieser Arbeit Einsichten für die Synthese von 2D COFs geben werden, welche auf optimierte elektronische Eigenschaften mit hoher struktureller Stabilität abzielt.:ABSTRACT ZUSAMMENFASSUNG 1. INTRODUCTION Motivation Nomenclatures Experimental characterization and computational studies Objectives and outline 2. THEORETICAL AND COMPUTATIONAL BACKGROUND Many-body system Density Functional Theory (DFT) Kohn-Sham auxilary approach and the computational application of DFT Exchange-correlation functional Hybrid functionals Basis-set Pseudo-potentials Tight-binding model Density Functional based Tight-binding model (DFTB) Slater-Koster approach Slater-Koster sets in DFTB Molecular Dynamics and Metadynamics Classical Molecular Dynamics (MD) Quantum Molecular Dynamics (QMD) Metadynamics(MTD) 3. PREDICTING THE BULK MODULUS Conceptualization Equivalent spring constant Two dimensional bulk modulus Computational details COFs with square lattice type Models Molecular Spring constant Single layer 2D COFs COFs with hexagonal lattice type Models Single layer 2D COFs Synopsis 4. ENGINEERING THE ELECTRONIC PROPERTIES Computational details COFs with square lattice type Models Benchmarking of different methods π -conjugated COFs COFs with hexagonal topology Models π -conjugated COFs Synopsis PREDICTING THE ELECTRONIC BAND GAP Conceptualization Models Computational protocol 1D- and 2D-polymer Comparing the cores Predicting the gap Synopsis 6 SIMULATING THE PROTON TAUTOMERIZATION Models Collective variables (CVs) Computational protocol FES portraits and energy barriers Synopsis 7 CONCLUSIONS AND OUTLOOK APPENDIX A APPENDIX B APPENDIX C BIBLIOGRAPHY SCIENTIFIC OUTPUT ACKNOWLEDGEMENTS
307

Investigations Near the Fusion Boundary of Grade 91 Steel Dissimilar Metal Welds with Nickel Based Filler Metals

Kuper, Michael W. January 2018 (has links)
No description available.
308

Locality-Dependent Training and Descriptor Sets for QSAR Modeling

Hobocienski, Bryan Christopher 21 September 2020 (has links)
No description available.
309

[en] BEHAVIOR OF ARCHED STEEL TRUSSES USED IN THE DESIGN AND CONSTRUCTION OF PRESTRESSED STRUCTURES FOR ROOFS / [pt] COMPORTAMENTO DE TRELIÇAS DE AÇO EM FORMA DE ARCO UTILIZADAS NO PROJETO E CONSTRUÇÃO DE ESTRUTURAS PROTENDIDAS DE COBERTURAS

WILLIAM ALFONSO PINEREZ BETTIN 30 June 2020 (has links)
[pt] O efeito da protensão pode ser introduzido sobre estruturas de aço em forma de arco, de tal modo que é adicionado um estado de tensões oposto ao estado proveniente da ação de sucção do vento. Dentro deste escopo, o presente trabalho de pesquisa visa apresentar os resultados obtidos com a modelagem numérica, através do Método dos Elementos Finitos (MEF), sobre o comportamento estrutural de treliças de aço utilizadas no projeto de coberturas protendidas. Para tal, a modelagem numérica é realizada com base em formulações não lineares, com o uso do programa computacional ANSYS, avaliando-se o comportamento estrutural de modelos de treliças de aço em forma de arco até o regime de ruptura. Considerando-se a complexidade do comportamento das treliças em estudo, foram feitas análises com inclusão do efeito da não linearidade física. Com base nos resultados obtidos por meio de uma análise paramétrica, no que tange a comparações entre os valores de resistência das treliças protendidas investigadas, são estabelecidas conclusões e recomendações de projeto. Cabe ressaltar que a economia de material obtida na solução estrutural com base no uso da protensão é resultante do aumento dos níveis de forças de tração nas barras da estrutura, diminuindo-se os de compressão que são menos eficientes. Assim, as soluções estruturais com protensão apresentam diversas vantagens que compensam o seu custo adicional. / [en] Prestressing forces can be introduced on arched steel structures in such a way that a state of tensile stresses is added which to the existing state counteract the state introduced by the wind negative pressures. Within this scope, the present research aims to present the results obtained with the numerical modeling through the Finite Element Method (FEM) on the structural behavior of steel trusses used in the design of prestressed roof structures. For this purpose, the numerical modeling is performed based on non-linear formulations using the ANSYS software in order to evaluate the structural behavior of arched steel trusses modelled up to failure. Considering the complexity of the behavior of the trusses studied, some structural analysis were carried out including the effects of physical nonlinearities. Based on the results obtained through an extensive parametric analysis, with respect to comparisons between the resistance values of the investigated prestressed trusses, conclusions and design recommendations are established. It should be noted that the material savings achieved by the use of prestressing is the resultant from the increase of tensile state of stresses in the bars of the structure, thus reducing the compression stresses, which are less efficient. In this sense, the structural solutions with prestressed trusses have several advantages that compensate for the additional cost of prestressing.
310

Fighting Against Promoter DNA Hyper-Methylation: Protective Histone Modification Profiles of Stress-Resistant Intestinal Stem Cells

Thalheim, Torsten, Hopp, Lydia, Herberg, Maria, Siebert, Susann, Kerner, Christiane, Quaas, Marianne, Schweiger, Michal R., Aust, Gabriela, Galle, Joerg 29 December 2023 (has links)
Aberrant DNA methylation in stem cells is a hallmark of aging and tumor development. Recently, we have suggested that promoter DNA hyper-methylation originates in DNA repair and that even successful DNA repair might confer this kind of epigenetic long-term change. Here, we ask for interrelations between promoter DNA methylation and histone modification changes observed in the intestine weeks after irradiation and/or following Msh2 loss. We focus on H3K4me3 recruitment to the promoter of H3K27me3 target genes. By RNA- and histone ChIP-sequencing, we demonstrate that this recruitment occurs without changes of the average gene transcription and does not involve H3K9me3. Applying a mathematical model of epigenetic regulation of transcription, we show that the recruitment can be explained by stronger DNA binding of H3K4me3 and H3K27me3 histone methyl-transferases as a consequence of lower DNA methylation. This scenario implicates stable transcription despite of H3K4me3 recruitment, in agreement with our RNA-seq data. Following several kinds of stress, including moderate irradiation, stress-sensitive intestinal stem cell (ISCs) are known to become replaced by more resistant populations. Our simulation results suggest that the stress-resistant ISCs are largely protected against promoter hyper-methylation of H3K27me3 target genes.

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