Academic literature on the topic 'Cone-valve'

In many hydroelectric projects there is a need to safely dissipate the energy associated with the elevation of the water surface. When the flow is not passing through the turbines, bypass valves are often used. A valve that is commonly used is the fixed-cone valve. Fixed-cone valves, also known as Howell-Bunger valves, are devices often used to safely reduce flow energy at dams with medium to high heads. The valve directs the outflow into a conical hollow jet, which requires a large area for energy dissipation. The flow is controlled by an adjustable sleeve, also known as the gate which surrounds the valve and requires minimal power for operation even for large valves. Depending on the installation, the conical jet may need to be controlled by installing a fixed stationary hood or other structure to contain and direct the conical jet. While the hood reduces the spray, the use of the hood causes the formation of a concentrated hollow jet having a high velocity. To eliminate the hollow jet and dissipate much of the associated energy, the hood can have interior baffles. If the hood is not precisely placed relative to the valve, a phenomenon, known as backsplash, will occur. Backsplash is when a significant amount of water exits the upstream end of the hood. Backsplash is a concern for operators because it can prevent access to the valve during operation and can flood valve vaults. Because the use of fixed-cone valves and baffled-hoods are becoming more popular, the need for guidelines to correctly position the hood relative to the valve will benefit both engineers and contractors. In some hydroelectric sites, submerging the fixed-cone valve is used to control the spray and dissipate energy. Submerging the valve can have can produce violent flow conditions which can cause damage to a structure or heavy erosion. The use of a submerged fixed-cone valve is rarely used, and a submerged valve used with a baffled-hood has never been constructed. The study performed shows that the use of a baffled hood with a fixed-cone valve in submerged conditions performs well. The results may lead the way for more submerged fixed-cone valves in the future.

Calcific aortic valve disease is highly prevalent, especially in the elderly. Currently, the exact mechanism of the calcification process is not completely understood, limiting our ability to prevent or cure the disease. Ex vivo investigations, however, have provided evidence that the aortic valve's biological response is sensitive to mechanical forces, including fluid shear stresses, leading to the hypothesis that adverse fluid shear stress environment play a role in leading to valve calcification. This thesis seeks to investigate this hypothesis. A method for performing experimental measurement of time-varying shear stress on aortic valve leaflets under physiologic flow conditions was first developed, based on the Laser Doppler Velocimetry technique, and was systematically validated. This method was then applied to both the aortic surface and the ventricular surface of a normal tricuspid the aortic valve, and then on a congenital bicuspid aortic valve, using suitable in vitro valve models and an in vitro pulsatile flow loop. It was found that in the tricuspid valve, the peak shear stress on the aortic surface under adult resting condition was approximately 15-19 dyn/cm². Aortic surface shear stresses were elevated during mid- to late-systole, with the development of the sinus vortex, and were low during all other instances. Aortic surface shear stresses were observed to increase with increasing stroke volume and with decreasing heart rate. On the ventricular surface, shear stresses had a systolic peak of approximately 64-71 dyn/cm² under adult resting conditions. During late systole, due to the Womersley effect, shear stresses were observed to reverse in direction to a substantial magnitude for a substantial period of time. Further, it was found that a moderately stenotic bicuspid aortic valve can experience excessive unsteadiness in shear stress experienced by its leaflets, most likely due to the turbulent forward flow resulting from the stenosis, and due to the skewed forward flow. To demonstrate that the measured shear stresses can have an effect on the aortic valve biology, ex vivo experiments were performed in specific to determine the effects of these various shear stress characteristics on the biological response of porcine aortic valve leaflets, using the cone and plate bioreactor. It was found that unsteady shear stress measured in the bicuspid valve resulted in increased calcium accumulation. Further, it was found that low shear stresses and high frequency shear stresses resulted in increased calcium accumulation. Thus, shear stress was found to affect aortic valve pathology, and low and unsteady fluid shear stresses can enhance pathology.

The thesis aims to determine the influence partial or complete submerge of hollow cone valve by outflow on its capacity without space restrictions, by outflow into discharge chamber and by outflow into water tunnel of circular cross section. The valve capacity is for mutual comparability purposes usually characterized by discharge coefficient. Research works have been performed on a spatial hydraulic model of the valve with inlet diameter D = 67 mm and an apex angle of a cone 90°. Values of the discharge coefficient obtained from measurements were statistically analyzed. The dependence of discharge coefficient, expressed by energy head, on submerged level was approximated by an exponential function. Exponent value of this function express the dependance rate of valve capacity on downstream water level. This procedure didn’t demonstrate signifiant dependance downstream water level on hollow cone valve capacity, only on tests at outflow to water tunel showed a low increase in the discharge coefficient partly due to the influence of kinetic energy of the stream flowing out of the tunnel on the energy head and also due to underpressure. Independence of discharge coefficient value on valve head has been prooved for head greather than 232 mm. Also was defined 3 stages of interaction outflow jet from valve and downstream water, some of them may cause on real waterworks structures unfavorable situations (may affect excessive load on valve by pressure pulsations). The presented results allow better evaluation of bottom outlets capacity at higher water levels, when the valves are flooded. Significant effect of sufficient aeration (especially in long water tunnels) on valve capacity was also confirmed. Taking into account on the specifics of hollow jet valves and cone valves, it is possible to generalize some of this resultos on them as well.

Made available in DSpace on 2017-07-10T14:17:04Z (GMT). No. of bitstreams: 1 Mayaha.pdf: 4416602 bytes, checksum: 8b663982eaff70076dc570733618b841 (MD5) Previous issue date: 2013-08-01<br>Bombyx mori multiple nucleopolyedrovirus (BmMNPV) is an entomopathogenic virus of the Baculoviridaefamily, genera Alphabaculovirus, which infects the silkworm (Bombyx Mori) and causes nuclear polyhedrosis disease. This virus is poliorganotrophic and a series of tissues are known as targets; however, literature does not present information in regards to the pylorus, segment of the hindgut, present in the transition with the midgut and responsible for regulating the passage of food towards the ileum. The organ is, thus, of fundamental importance in the ending of the digestive process, affecting the insect s metabolic balance and, the present study sought to analyze its susceptibility and cytopathology in regards to BmMNPV, geographic isolate of Paraná, Brazil. Moreover, due to the complexity of this segment, its general morphology will also be analyzed. In order to do so, hybrid B.mori caterpillars at 5º instar were inoculated experimentally with a viral suspension of BmMNPV. On different day post-inoculation (dpi), from 2º to 9ºdpi, segments of the intestine, containing the pylorus, with its subdivisions (posterior interstitial ring, pyloric cone and pyloric valve), were dissected, following the routine histological processing for paraffin wax blockage and dyes in haematoxylin and eosin, for general morphology analysis, and in modified Azan staining, for cytopathology. Segments also processed to form scanning electronic microscope for analized of morphological details. So the pylorus general morphology the caterpillars of B. mori, was similar to that observed in other insects. The cytopathology showed that the anterior area of the posterior interstitial ring is a secondary target of infection for the BmMNPV, after 5º dpi, and its infectious cycle is similar to that described in literature. In the hypertrophic nucleus one there the formation of viroplasm, place for production of enveloped nucleocapsids or virions, following the formation and development of the polyhedra. Later on, cytolysis occurred, promoting the liberation of polyhedra and the spreading of the disease, mainly in the B. mori creation sheds. The posterior area of the posterior interstitial ring, the pyloric cone and the pyloric valve did not reveal any traces of infection by BmMNPV and, thus, resistance mechanisms involving genetic factors could be acting. The knowledge obtained from this work will contribute in the establishment of the infectious cycle of this important entomopathogenic virus, which may lead to an epizootic that can negatively affect the whole productive chain of silk<br>Bombyx mori multiple nucleopolyedrovirus (BmMNPV) é um vírus entomopatogênico da família Baculoviridae, gênero Alphabaculovirus, que infecta o bicho-da-seda (Bombyx mori) e causa a doença poliedrose nuclear. Este vírus é poliorganotrófico e uma série de tecidos são conhecidos como alvos; contudo, a literatura não apresenta informações sobre o piloro, segmento do intestino posterior, presente na transição com o médio e responsável pela regulação da passagem do alimento em direção ao ileo. O órgão é assim de fundamental importância na finalização do processo digestório, afetando o equilíbrio metabólico do inseto e, o presente estudo objetivou analisar sua susceptibilidade e citopatologia frente ao BmMNPV, isolado geográfico do Paraná, Brasil. Ainda, devido a complexidade deste segmento, também será analisada sua morfologia geral. Para tanto, lagartas híbridas de B. mori no 5° instar foram inoculadas experimentalmente com uma suspensão viral de BmMNPV. Em diferentes dias pós-inoculação (dpi), do 2° ao 9° dpi, segmentos do intestino, contendo o piloro, com suas subdivisões (anel intersticial posterior, cone pilórico e válvula pilórica), foram dissecados, seguindo o processamento histológico de rotina para emblocamento em parafina e colorações em hematoxina e eosina, na análise da morfologia geral, e em Azan modificado, para a citopatologia. Segmentos também foram processados em microscopia eletrônica de varredura para análise de detalhes morfológicos. Assim, a morfologia geral do piloro das lagartas da B. mori foi semelhante à observada em outros insetos. A citopatologia mostrou que a área anterior do anel intersticial posterior é alvo secundário de infecção pelo BmMNPV, a partir do 5° dpi, e seu ciclo infeccioso é semelhante ao descrito em literatura. No núcleo hipertrófico houve a formação do viroplasma, local de produção dos nucleocapsídeos envelopados ou virions, seguindo a formação e o desenvolvimento dos poliedros. Posteriormente, ocorreu a citólise, promovendo a liberação dos poliedros e disseminação da doença, principalmente nos barracões de criação de B. mori. A área posterior do anel intersticial posterior, o cone pilórico e a válvula pilórica não revelaram quaisquer indícios de infecção pelo BmMNPV e, desta forma, mecanismos de resistência envolvendo fatores genéticos poderiam estar atuando. Os conhecimentos obtidos irão contribuir no estabelecimento do ciclo infeccioso deste importante vírus entomopatogênico, cuja conseqüência de uma epizootia pode afetar negativamente toda a cadeia produtiva da seda