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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.
501

Měření posunů a přetvoření střešní konstrukce sportovní haly / Deformation Measurement of the Roof Structure of a Sport Hall

Klinčík, Radoslav January 2021 (has links)
Diploma thesis describes the measurement and evaluation of displacements and deformations of the wooden roof structure of the aquapark hall in Brno – Kohoutovice. Part of the work is devoted to the preparation and testing of used devices and tools. The main part of the work consists of performing one stage of measurement using the polar method and the laser scanning method. The polar method measurement is compared with the results of the polar method of the previous stage. The next part of the work deals with the comparison of the polar method and the laser scanning method measured in the last stage. The results achieved are interpreted in the final part of the work.
502

Vliv přísad redukujících smrštění na reologické vlastnosti vysokopevnostního betonu / The effect of the shrinkage reducing additives on rheological properties of high-strength concrete

Červenka, Jiří January 2013 (has links)
Master’s thesis examines the effect of the shrinkage reducing additives on rheological properties of high-strength concrete. The first part is focused on high-strength concrete in terms of their composition and properties. The second part contains a detailed analysis of the cementitious composites shrinkage problems. Total shrinkage is divided into individual elementary shrinkages. For each of them there is a detailed description of causes and factors that affect their sizes. The next part describes the basic additives used to reduce the shrinkage of cementitious composites. The experimental part is focused on verifying the effectiveness of the shrinkage reducing additives during preparation of high-strength concrete. Usage of shrinkage drains for relative strain measurement enables to determine the process of shrinkage immediately after placing the concrete in the form and to obtain the overall curve of the hight-strength concrete volume changes during its setting and hardening. At the end of the thesis, there are overall analysis and summary of the results of the performed experiments.
503

Dynamická analýza konstrukce zatížená seismickým zatížením / Dynamic analysis of structure loaded seismic loads

Šulerová, Zdeňka January 2014 (has links)
This thesis deals with the calculation of response of reinforced concrete construction on the effect of seismic tension. Time and spectral analysis were made. They are mentioned as possible ways of calculation in EN 1998 - 1:2004 norm. Final figures of global deformations and stress on selected beam from the time and spectral analysis were firstly compared for the horizontal components of seismic stress affecting only in one direction. Subsequently comparison of time progress to combination of these effects mentioned in relevant norm was made. In the conclusion the results of used analysis are appraised.
504

Optimalizace konstrukce saní CNC horizontálních vyvrtávacích strojů / Optimizing design of the slide CNC horizontal boring machines

Valenta, Tomáš January 2016 (has links)
This master's thesis deals with proposals for solutions to increase the stiffness of the slide for CNC horizontal boring standing in order to optimize the design of the slide. Selected problem was solved by sensitivity analysis using desegin of experiment in conditions of linear regression analysis. Data for the sensitivity analysis were obtained by using computational modeling using finite element method. The solution provides a view of the degree of influence on the deformation of the examined elements of the slide. Based on these results were selected elements with the greatest influence and created three ideological designs for improvement. Of these designs, was chose an optimal variant by PATTERN method acoording on the technical, economic and technical-economic aspect. This work offers a new look for the innovating the design to increase rigidity.
505

Elektronski sistem za merenje deformacija pri savijanju pomoću polimernog optičkog vlakna sa osetljivom zonom / Electronic system for measurement of deformations under bending by usingpolymer optical fiber with sensitive zone

Stupar Dragan 21 April 2016 (has links)
<p>U ovoj doktorskoj disertaciji je razvijen elektronski senzorski sistem za merenje deformacija pri savijanju pomoću polimernog optičkog vlakna sa osetljivom zonom. Opisana je metoda izrade fiber-optičkog senzora zakrivljenosti pomoću polimernog optičkog vlakna. Izvršena je simulacija ponašanja senzora i urađena je karakterizacija senzora. Ispitana je mogućnost primene elektronskog senzorskog sistema za detekciju savijanja i loma građevinskih struktura. Pomoću istog senzora je realizovan fiber-optički goniometar za merenje ugla savijanja ljudskog kolena koji karakterišu linearni odziv u opsegu uglova od -45&deg; do 25&deg;, rezolucija od 1&deg; i osetljivost od 20 mV/&deg;. U tezi je takođe data metoda eliminacije grešaka koje mogu nastati usled savijanja delova vlakna koji vode do i od osetljive zone.</p> / <p>In this thesis, an electronic system for measurement of bend-induced<br />deformations by using polymer optical fiber with sensitive zone is developed.<br />A method for fabrication of the fiber-optic curvature sensor by using polymer<br />optical fiber is described. The simulation and characterization of the sensor<br />behavior have been conducted. The possibility of application of the proposed<br />electronic system in structural health monitoring for bending and crack<br />detection of civil engineering structures is investigated. Also, a fiber-optic<br />goniometer for human joint movement monitoring characterized by a linear<br />response in the range from -45&deg; to 25&deg;, resolution of 1&deg;, and the sensitivity of<br />20 mV/&deg; is implemented. A method for the elimination of errors which may be<br />caused due to bending of lead-in and lead-out sections of the fiber (leading<br />to and from the sensitive zone) is also described.</p>
506

On Partial Regularities and Monomial Preorders

Nguyen, Thi Van Anh 28 June 2018 (has links)
My PhD-project has two main research directions. The first direction is on partial regularities which we define as refinements of the Castelnuovo-Mumford regularity. Main results are: relationship of partial regularities and related invariants, like the a-invariants or the Castelnuovo-Mumford regularity of the syzygy modules; algebraic properties of partial regularities via a filter-regular sequence or a short exact sequence; generalizing a well-known result for the Castelnuovo-Mumford regularity to the case of partial regularities of stable and squarefree stable monomial ideals; finally extending an upper bound proven by Caviglia-Sbarra to partial regularities. The second direction of my project is to develop a theory on monomial preorders. Many interesting statements from the classical theory of monomial orders generalize to monomial preorders. Main results are: a characterization of monomial preorders by real matrices, which extends a result of Robbiano on monomial orders; secondly, leading term ideals with respect to monomial preorders can be studied via flat deformations of the given ideal; finally, comparing invariants of the given ideal and the leading term ideal with respect to a monomial preorder.
507

Spolehlivost zemních hrází ohrožených filtračními deformacemi / Reliability analysis of embankment dams endangered by filtration deformations

Čejda, Marek January 2016 (has links)
Subject of the dissertation is a probability analysis on creation of embankment subsoil filtration deformations. Out of the broad topic of filtration deformations, the dissertation is focused at initiation of the process. At this phase, the overlying layers downstream of levee get uplifted, and eventually get breached. The process of downstream subsoil failure probability estimation is formulated using mathematical and statistical modelling. Within the scope of parametrical study the suggested method is applied onto a test environment. Results of the probability estimation are compared with results obtained using Limit state design method. The results of stochastic modelling can be used for improvement of Limit state design method precision.
508

Beobachterkonzepte und Darstellungsformen der nichtlinearen Kontinuumsmechanik

Ihlemann, Jörn 28 July 2007 (has links)
Im Rahmen der geometrisch und physikalisch nichtlinearen Kontinuumsmechanik werden Beobachterkonzepte und Darstellungsformen tensorieller Größen diskutiert und zum Teil neu eingeführt, die insbesondere die Modellierung und FEM-Implementierung komplizierter Modelle für inelastisches Materialverhalten bei großen Deformationen wirkungsvoll unterstützen. / Observer concepts and several kinds of representations of tensorial quantities are discussed and partly introduced within the framework of geometrically und physically nonlinear continuum mechanics. They are intended to support the modelling of complicated inelastic materials undergoing large deformations.
509

Beobachterkonzepte und Darstellungsformen der nichtlinearen Kontinuumsmechanik: Observer concepts and tensorial representations within the framework of nonlinear mechanics

Ihlemann, Jörn 28 July 2007 (has links)
Im Rahmen der geometrisch und physikalisch nichtlinearen Kontinuumsmechanik werden Beobachterkonzepte und Darstellungsformen tensorieller Größen diskutiert und zum Teil neu eingeführt, die insbesondere die Modellierung und FEM-Implementierung komplizierter Modelle für inelastisches Materialverhalten bei großen Deformationen wirkungsvoll unterstützen. / Observer concepts and several kinds of representations of tensorial quantities are discussed and partly introduced within the framework of geometrically und physically nonlinear continuum mechanics. They are intended to support the modelling of complicated inelastic materials undergoing large deformations.
510

Using molecular dynamics to quantify biaxial membrane damage in a multiscale modeling framework for traumatic brain injury

Murphy, Michael Anthony 11 August 2017 (has links)
The current study investigates the effect of strain state, strain rate, and membrane planar area on phospholipid bilayer mechanoporation and failure. Using molecular dynamics, a 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) bilayer was deformed biaxially to represent injury-induced neuronal membrane mechanoporation and failure. For all studies, water forming a bridge through both phospholipid bilayer leaflets was used as a failure metric. To examine the effect of strain state, 72 phospholipid structures were subjected to equibiaxial, 2:1 non-equibiaxial, 4:1 non-equibiaxial, strip biaxial, and uniaxial tensile deformations at the von Mises strain rate of 5.45 × 108 s-1. The stress magnitude, failure strain, headgroup clustering, and damage behavior were strain state dependent. The strain state order of detrimentality in descending order was equibiaxial, 2:1 non-equibiaxial, 4:1 non-equibiaxial, strip biaxial, and uniaxial with failure von Mises strains of 0.46, 0.47, 0.53, 0.77, and 1.67, respectively. Additionally, pore nucleation, growth, and failure were used to create a Membrane Failure Limit Diagram (MFLD) to demonstrate safe and unsafe membrane deformation regions. This MFLD allowed representative equations to be derived to predict membrane failure from in-plane strains. To examine the effect of strain rate, the equibiaxial and strip biaxial strain states were repeated at multiple strain rates. Additionally, a 144 phospholipid structure, which was twice the size of the 72 phospholipid structure in the x dimension, was subjected to strip biaxial tensile deformations to examine planar area effect. The applied strain rates, planar area, and cross-sectional area had no effect on the von Mises strains at which pores greater than 0.1 nm2 were detected (0.509 plus/minus 7.8%) or the von Mises strain at failure (0.68 plus/minus 4.8%). Additionally, changes in bilayer planar and cross-sectional areas did not affect the stress response. However, a strain rate increase from 1.4 × 108 to 6.8 × 108 s-1 resulted in a yield stress increase of 44.1 MPa and a yield strain increase of 0.17. Additionally, a stress and mechanoporation behavioral transition was determined to occur at a strain rate of ~1.4 × 108 s-1. These results provide the basis to implement a more accurate mechano-physiological internal state variable continuum model that captures lower-length scale damage.

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