The subject of this diploma thesis is design and static assessment of timber load bearing structure of multipurpose building in Plzeň. It is cupola consited of two radial curved ribs above a triangle ground plan with one oval edge. I got this shape by cutting the cupola vertically on these two triangle edges and that created two walls of the construction. The largest ground plan dimension of load bearing structure is 54,4 meters and the maximum height is +18,0 meters. The design is processed in two various drafts.

This thesis solves design of the pneumobile bodywork designated for robotic manufacturing using curved folding method. The thesis evaluates possibilities of this technology and issue of specific behaviour of CCF geometries. With intention to simplify and speedup the proces of designing, the suggestion of software tool for CCF geometry simulation is proposed. Obtained pieces of knowledge are being used in creating the prototype of designed solution using curved folding.

The objective of this research is to develop a scalable manufacturing process for high-volume production of low-cost graphene materials from lignin. The process includes preparation of catalyst-lignin precursors, pretreatment of precursors, and catalytic graphitization of kraft lignin to graphene materials. A growth concept, “catalytic thermal molecular welding (CTMW)” technique is proposed and validated to produce graphene materials from solid carbon resources. CTMW technique is a single process with two stages, i.e., the carbon-encapsulated metal nanostructures are first prepared. Then in the second stage these core-shell structures are opened by “scissoring molecules”, the cracked carbon shell units are welded and reconstructed to multilayer graphene materials under high temperature with selected “welding reagent gases” like light hydrocarbons (methane, natural gas, etc.) and hydrogen. Multi-layer nano-shell structure-based graphene materials, such as fluffy graphene, graphene chains, multi-layer graphene nanoplatelets, flatten or curved sheet-like graphene can be produced through altering fabrication conditions. The effects of transitional metal catalysts (Ni, Cu, Fe, and Mo) on the yields and structures of multi-layer nano-shell structure-based graphene materials from lignin are compared. The effects of the iron chemical resources (Fe(NO3)3, FeCl2, FeCl3, and Fe2O3 (nano)), iron loading on the yields and structures of multi-layer graphene materials from lignin are also examined. The influences of temperature, heating rate, heating time, metal-lignin precursor particle size, and welding reagent gas types on the yield of multi-layer graphene materials from lignin resources are investigated. Welding temperatures are optimized as1,000°C or above, with heating rates of 10°C or above. Welding gases including, argon (Ar), hydrogen (H2), methane (CH4), natural gas (NG), and mixed of these gases, are used at flow rates from 20 to 300 mL/min. Heating time is controlled between 0 to 5 hours. The effect of precursor particle size on final products is examined between 44 to 426 microns (Delta-m).

Deformation of bridges that are induced by thermal loads can be accommodated by expansion joints and bearings. Integral Abutment Bridges have gained acceptance as a way to mitigate potential damage from thermal movements, eliminating the poor performance and maintenance costs associated with expansion joints and bearings. However, integral abutments significantly change the structural response of the bridges. Several researches including real time field monitoring and finite element analyses have been conducted on straight and skewed integral abutment bridges in order to improve an understanding on field performance of them. Some state transportation agencies have also developed guidelines for the design of straight and skewed integral abutment bridges in recent years. In contrast, very little information is available on the performance of curved integral abutment bridges. A detailed finite element model of Stockbridge Bridge, VT is used to evaluate the behavior of curved integral abutment bridges under self-weight and thermal loading. In addition, a parametric study is carried out to investigate the effects of bridge curvature and abutment backfill soil type. Finally, six additional finite element models are created to compare the responses of jointed (conventional) bridges and integral abutment bridges. Results reported include abutment displacements, rotations, moments in abutment piles, earth pressures and bridge superstructure moments. Suggestions for improvement of analytical modeling and recommendations for design of curved integral abutment bridges are made.

In classical general relativity, the values of elds on spacetime are uniquely determined by their values at an initial time within the domain of dependence of this initial data surface. However, it may occur that the spacetime under consideration extends beyond this domain of dependence, and elds, therefore, are not entirely determined by their initial data. This occurs, for example, in the well-known (maximally) extended Reissner–Nordström or Reissner–Nordström–deSitter (RNdS) spacetimes. The boundary of the region determined by the initial data is called the ‘Cauchy horizon.’ It is located inside the black hole in these spacetimes. The strong cosmic censorship conjecture asserts that the Cauchy horizon does not, in fact, exist in practice because the slightest perturbation (of the metric itself or the matter elds) will become singular there in a sufciently catastrophic way that solutions cannot be extended beyond the Cauchy horizon. Thus, if strong cosmic censorship holds, the Cauchy horizon will be converted into a ‘nal singularity,’ and determinism will hold. Recently, however, it has been found that, classically this is not the case in RNdS spacetimes in a certain range of mass, charge, and cosmological constant. In this paper, we consider a quantum scalar eld in RNdS spacetime and show that quantum theory comes to the rescue of strong cosmic censorship. We nd that for any state that is nonsingular (i.e., Hadamard) within the domain of dependence, the expected stress-tensor blows up with afne parameter, V, along a radial null geodesic transverse to the Cauchy horizon as TVV ∼ C/V 2 with C independent of the state and C 6= 0 generically in RNdS spacetimes. This divergence is stronger than in the classical theory and should be sufcient to convert the Cauchy horizon into a singularity through which the spacetime cannot be extended as a (weak) solution of the semiclassical Einstein equation. This behavior is expected to be quite general, although it is possible to have C = 0 in certain special cases, such as the BTZ black hole

Surface mean pressures, oil flow visualization, and 3-velocity-component laser-Doppler velocimeter measurements are presented for a turbulent boundary layer of momentum thickness Reynolds number, 7300 and thickness delta over two circular based axisymmetric bumps of height H = delta and 2delta and one rectangular based symmetric bump of H = 2delta. LDV data were obtained at one plane x/H ¥ 3.26 for each case. Complex vortical separations occur on the leeside and merge into large stream-wise mean vortices downstream for the 2 axisymmetric cases. The near-wall flow (y+ < 90) is dominated by the wall. For the axisymmetric cases, the vortices in the outer region produce large turbulence levels near the centerline and appear to have low frequency motions that contribute to turbulent diffusion. For the case with a narrower span-wise shape, there are sharper separation lines and lower turbulence intensities in the vortical downstream flow. Fine-spatial-resolution LDV measurements were also obtained on half of the leeside of an axisymmetric bump (H/delta = 2) in a turbulent boundary layer. Three-dimensional (3-D) separations occur on the leeside with one saddle separation on the centerline that is connected by a separation line to one focus separation on each side of the centerline. Downstream of the saddle point the mean backflow converges to the focal separation points in a thin region confined within about 0.15delta from the local bump surface. The mean backflow zone is supplied by the intermittent large eddies as well as by the near surface flow from the side of the bump. The separated flow has a higher turbulent kinetic energy and shows bimodal histograms in local and U and W, which appear to be due to highly unsteady turbulent motions. By the mode-averaged analysis of bimodal histograms, highly unsteady flow structures are estimated and unsteady 3-D separations seem to be occurring over a wide region on the bump leeside. The process of these separations has very complex dynamics having a large intermittent attached and detached flow region which is varying in time. These bimodal features with highly correlated local u and w fluctuating motions are the major source of large Reynolds stresses local u2, w2 and -uw. Because of the variation of the mean flow angle in the separation zones, the turbulent flow from different directions is non-correlated, resulting in lower shearing stresses. Farther from the wall, large stream-wise vortices form from flow around the sides of the bump. / Ph. D.

[pt] Guias de onda são amplamente utilizados na engenharia de telecomunicações para a transmissão de sinais e construção de filtros e outros dispositivos de micro-ondas. Neste trabalho, apresentamos uma formulação baseada na técnica de casamento de modos (MMT) para a análise de descontinuidades em guias de ondas cilíndricos causadas por curvaturas no eixo longitudinal da linha de transmissão. Apresentamos e validamos uma técnica para análise modal de guias de ondas curvos através da aproximação da curvatura por uma sucessão de superfícies oblíquas por meio de suas matrizes de espalhamento generalizadas (GSMs) extraídas do MMT. A presente abordagem é uma alternativa computacionalmente eficiente para modelar curvaturas em guias de ondas cilíndricos quando comparada às técnicas usuais de força bruta numérica (tais como soluções baseadas em elementos, volumes, ou diferenças finitas). Um algoritmo é apresentado para calcular os elementos da matriz GSM para diferentes configurações de junções de guias de onda. A novidade do presente método consiste em considerar a projeção dos campos eletromagnéticos em superfícies oblíquas para a aplicação do MMT. Apresentamos uma série de resultados numéricos que mostram que a técnica apresentada neste estudo pode garantir resultados com boa acurácia e precisão ao realizar a análise do comportamento modal dos campos eletromagnéticos em descontinuidades provocados por curvaturas. / [en] Waveguides are widely used in telecommunications engineering for transmitting signals and manufacturing filters and other devices in the microwave applications. In this work, we present a formulation based on the mode-matching technique (MMT) for the analysis of discontinuities in cylindrical waveguides caused by curvatures in the longitudinal axis of the transmission line. We present and validate a technique for modal analysis of curved waveguides by approximating the curvature in a succession of oblique surfaces by means of their generalized scattering matrices (GSMs) extracted from the MMT. The present approach is a computationally efficient alternative for modeling curvature in cylindrical waveguides when compared to usual numerical brute force techniques (such as element-based, volumebased, or finite difference solutions). An algorithm is presented to compute the GSM matrix elements for different configurations of waveguide junctions. The novelty of the present method consists in considering the projection of electromagnetic fields onto oblique surfaces for the application of MMT. We present a series of numerical results that show that the technique presented in this study can guarantee results with good accuracy and precision when performing the analysis of the modal behavior of electromagnetic fields at discontinuities caused by curvatures.

No description available.

The purpose of this master’s thesis was to investigate if suspension of heavy objectsis possible in the glulam arches at Stockholm Central Station. The main goal was todetermine the arches’ load carrying capacity’s utility ratio, in order to give knowledgeif additional loading can be added.The study included a thorough investigation of available blueprints and calculationreports established during and after the process of design and erection of the arches.In addition, an on-site-inventory was made to confirm and verify the studied material.A method to approximate semi-probabilistic material strength-properties, based onold deterministic material strength properties, was used.When the material had been summarized concluding geometrical attributes, loads, andmaterial properties a calculation model of the arch was developed. The global geometrydescribing the arch’s shape mathematically was established through measures onblueprints and analytical calculations in Mathcad. A finite element method (FEM) wasthen used to calculate reaction- and internal forces and buckling modes taking accountfor 2nd order effects. Once calculation of intrenal forces had been made, the structuralcapacity was checked analytically according to Eurocode’s failure criterion.The results showed that the arches do not fulfill required carrying capacity forEurocode’s symmetric- and non-symmetric distributed snow load. The failurecriterion not fulfilled were simultaneously bending and compression, lateral torsionalbuckling and simultaneously tension perpendicular to grain and shear.It is therefore concluded that suspension of heavy objects is not suitable with thepresent condition of the arch. In order to realize suspension, it is suggested thatreinforcement measures have to be conducted. It is also suggested that shear andiiiflexural carbon fiber reinforced polymer (CFRP) reinforcement would be a suitablemethod of enhancing the strength and stiffness of the arches, without disrupting theiraesthetics and integrity.

Cuttlebone, the endoskeleton of cuttlefish, offers an intriguing biological structural model for designing low-density cellular ceramics with high stiffness and damage tolerance. Cuttlebone is highly porous (porosity ~93%) and lightweight (density less than 20% of seawater), constructed mainly by brittle aragonite (95 wt%), but capable of sustaining hydrostatic water pressures over 20 atmospheres and exhibits energy dissipation capability under compression comparable to many metallic foams (~4.4 kJ/kg). Here we computationally investigate how such a remarkable mechanical efficiency is enabled by the multiscale structure of cuttlebone. Using the common cuttlefish, Sepia Officinalis, as a model system, we first conducted high-resolution synchrotron micro-computed tomography (µ-CT) and quantified the cuttlebone's multiscale geometry, including the 3D asymmetric shape of individual walls, the wall assembly patterns, and the long-range structural gradient of walls across the entire cuttlebone (ca. 40 chambers). The acquired 3D structural information enables systematic finite-element simulations, which further reveal the multiscale mechanical design of cuttlebone: at the wall level, wall asymmetry provides optimized energy dissipation while maintaining high structural stiffness; at the chamber level, variation of walls (number, pattern, and waviness amplitude) contributes to progressive damage; at the entire skeletal level, the gradient of chamber heights tailors the local mechanical anisotropy of the cuttlebone for reduced stress concentration. Our results provide integrated insights into understanding the cuttlebone's multiscale mechanical design and provide useful knowledge for the designs of lightweight cellular ceramics. Upon the prior curvature analysis of the cuttlebone walls, we discovered that the walls were primarily "saddle-shaped". Thus, the characterization of different curvatures, varying between flat, domed, saddled, or cylindrical surfaces, were explored. A mathematical model was utilized to generate multiple walls with different curvature characteristics. We observed the mechanical performance of these walls via finite-element analysis and formulated different techniques for designing effective ceramic structures through incorporation of curvature. / Master of Science / The cuttlefish is a marine species that instead of having an inflatable swim bladder like fish, is a mollusk capable of swimming by utilizing their skeleton, called the cuttlebone. The cuttlefish can freely traverse the waters by controlling the flow of water in and out of their brittle skeletons, changing their buoyancy. For this reason, the cuttlebone must be very porous yet strong to withstand the deep-water pressures, enticing an interest for closer observation of the structure which may be useful in engineering applications involving ceramic structures. In this study, we examined an actual cuttlebone structure to better visualize its features with high-resolution synchrotron micro-computed tomography (µ-CT) and tabulated its mechanical performance through a variety of tests using computational software. The skeletal design of the cuttlebone consists of multiple layered chambers supported by wavy, pillar-like walls. It was revealed that the cuttlebone is remarkable due to its multiscale design: the asymmetric geometry of the walls are designed to tolerate considerable amounts of energy while a stiff construction; at the chamber level, variation of walls (number, pattern, and waviness amplitude) helps avoid complete destruction of the structure in the event of an excessive force; at the entire skeletal level, various of chamber heights reduces inflicted stress in concentrated regions of the cuttlebone. The wavy walls were also observed to retain a saddle-shaped curviness, versus simple flat, domed, or cylindrical shaped walls. This created an incentive to explore the effects of curvature on the structural integrity of brittle ceramic structures. We developed an effective way for generating walls with different curvatures and observed the mechanical performance of each wall by crushing them in computer simulations. It was identified that adding curvature to brittle walls prolonged the failure period significantly. While the cylindrical walls were found to be rather stiff, saddle-shaped walls, although not capable of withstanding as much force as flat or cylindrical walls, has a more progressive failure behavior meanwhile maintaining high energy absorption, hence the saddled walls of the cuttlebone to allow maintenance and self-repair in damaged regions.