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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.
1

Rotordynamics/discharge water-hammer coupling via seals in pump rotordynamics

Zhang, Kaikai 30 September 2004 (has links)
A new closed-loop frequency-domain model is developed to incorporate the water hammer effect with pump rotordynamics, in order to investigate the sub-synchronous instability problem observed in a field pump. Seal flow-rate perturbations due to eccentricity are calculated from Soulas and San Andres's seal code. A complete transfer function matrix between rotor motion and reaction force due to pressure perturbation is developed in detail. Stability analysis with transfer-function'add-in' modules is conducted in XLTRC2. Seal clearances and the reaction force angle are found to be important in shifting natural frequencies and damping. The sub-synchronous instability observed in field is duplicated successfully with double-clearance seals.
2

Rotordynamics/discharge water-hammer coupling via seals in pump rotordynamics

Zhang, Kaikai 30 September 2004 (has links)
A new closed-loop frequency-domain model is developed to incorporate the water hammer effect with pump rotordynamics, in order to investigate the sub-synchronous instability problem observed in a field pump. Seal flow-rate perturbations due to eccentricity are calculated from Soulas and San Andres's seal code. A complete transfer function matrix between rotor motion and reaction force due to pressure perturbation is developed in detail. Stability analysis with transfer-function'add-in' modules is conducted in XLTRC2. Seal clearances and the reaction force angle are found to be important in shifting natural frequencies and damping. The sub-synchronous instability observed in field is duplicated successfully with double-clearance seals.
3

Vyhodnocení vztahu teploty vody a vydatnosti pramene v oblasti Klatovska / Evaluation of spring discharge/temperature relation in Klatovsko region

HAVEL, Zdeněk January 2012 (has links)
This work focuses on the evaluation of dependence between the spring discharge fluctuations and water temperature, both during the year and extreme rainfall-runoff events, on spring equipped with a V-notch weir with a continuous monitoring of spring water temperature and water level above the weir. Data were gathered on descending fissure spring of Tocnicky stream, located in the southwestern part of the Planicky ridge natural park in Klatovsko region. More data and stand characteristics (air temperature, soil temperature profile, soil moisture) were measured for better evaluation of the dependence, both at the spring location and in the infiltration area on the western slope of local highest peak Rovná. The formation of runoff on the slope above measured spring is likely to be subject to a combination of shallow circulation with a component of preferential flow during extreme rainfall-runoff events and deeper circulation, which is not yet well known and understood.
4

SÍNTESE DE NANOTUBOS DE CARBONO EM MEIO AQUOSO

Kaufmann Junior, Claudir Gabriel 05 June 2012 (has links)
Submitted by MARCIA ROVADOSCHI (marciar@unifra.br) on 2018-08-16T17:25:35Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ClaudirGabrielKaufmannJunior.pdf: 4418925 bytes, checksum: 687c661d424523cd9edfde7f671305ad (MD5) / Made available in DSpace on 2018-08-16T17:25:35Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ClaudirGabrielKaufmannJunior.pdf: 4418925 bytes, checksum: 687c661d424523cd9edfde7f671305ad (MD5) Previous issue date: 2012-06-05 / The nanotechnology has been focused of many studies and become scientifically and technologically revolutionary. It can be found in many products on the market. The nanoscale is defined as a billionth of a meter (10-9m). The manipulation in this scale has provided a series of studies in the health, computing, physics, chemistry, materials and others fields. In the context of manipulation of nanostructures, this paper proposes an alternative produtcion of NTC on arc discharge method, which dispense the use of sealed cameras and working with water as an insulator environment. The project was divided in two main stages: the software development and the production of NTC. A control system via software to manage the approach speed of the electrode (cathode) and the speed of rotation of electrode (anode) was developed in the first stage. In the second stage, tests were performed with different parameters for the production of NTC: source type (direct current and alternating current), type of catalyst, solubilized iron in the water and iron doped in the anode electrode, and also two types of graphite called A and B (higher purity). The material produced was characterized by the Raman Spectroscopy and Scanning Electron Microscopy techniques. Carbon nanotubes were produced when the graphite with higher purity was used, independently of the type of catalyst and the source used. In addition to the CNT was possible to observe with graphite B the production of several carbon nanostructures as nanosphere, nanorods, nanohoneycombs and nanoflowers of grapheme. However the graphite A (low purity) produced microspheres and nanospheres. / A nanotecnologia vem sendo o foco de diversas pesquisas tornado-se uma verdadeira revolução na ciência e tecnologia, já se pode encontrá-la em diversos produtos no mercado. A nanoescala é definida como a bilionésima parte do metro (10-9m). A manipulação nesta ordem de grandeza despertou uma serie de estudos nas áreas de saúde, computação, física, química, materiais, entre outras. Dentro do contexto de manipulação de nanoestruturas o presente trabalho propõe um método alternativo de produção de nanotubos de carbono por arco elétrico, o qual dispensa a utilização de câmeras seladas, trabalhando com água como meio isolante. O Trabalho foi divido em duas etapas principais: o desenvolvimento do software e a produção de NTC. Na primeira etapa foi desenvolvido um sistema de controle via software para gerenciar a velocidade de aproximação do eletrodo (cátodo) e a velocidade de giro do eletrodo (ânodo). Na segunda etapa realizaram-se testes com diferentes parâmetros para produção de NTC: tipo de fonte (corrente continua e alternada), tipo de catalisador: ferro solubilizado em água e ferro dopado no eletrodo ânodo, além de dois tipos de grafite, denominadas A e B (grafite B com maior pureza). O material produzido foi caracterizado pelas técnicas de Espectroscopia Raman e por Microscopia Eletrônica de Varredura. Nanotubos de carbono foram produzidos quando se utilizou grafite B de alta pureza, independendo do tipo de catalisador e da fonte utilizada. Alem dos NTC foi possível observar com a grafite B a produção de diversas nanoestruturas de carbono como nanoesferas, nanorods (nanovaras), nanofavos de mel e nanoflores de grafeno. Já para a grafite A, com baixa pureza, produziu apenas microesferas e nanoesferas.
5

The impact of point source pollution on an urban river, the River Medlock, Greater Manchester

Medupin, Cecilia January 2017 (has links)
The River Medlock is a small (22km) urbanised river, and is one of the five main tributaries which forms part of the River Irwell Catchment in Greater Manchester, UK. The river has a legacy of pollution from the 18th century and continues to be affected by anthropogenic factors including point source pollution from waste water treatment works (WwTWs) and combined sewer overflows (CSOs). In order to investigate the impact of CSOs and the WwTWs on the river hydrology, water quality and ecology of the lower largely urbanised reach, data sets were obtained from the Environment Agency and from direct sampling of the river. Load estimations from continuous discharge records from the river's gauging station plus estimates of sub-catchment area indicate the lower sites, classified as a "highly modified water body" and downstream of treatment works had had a higher load of discharge and phosphate-P linked to point sources and episodic discharges. Short term, continuous monitoring revealed that CSOs were active during high velocity, but increased concentrations of nutrients post high velocity indicate WwTW effects and possibly diffuse sources. This project reveals that the WwTW are a major source of phosphate-P and that the impact of CSOs on the river quality is short-lived and depends on the degree of precipitation. Other parameters indicate good water quality although the benthic macroinvertebrate community is degraded as a result of episodic increases in the quantity of water destabilising the river bed. Therefore, pollution from the CSOs, the WwTW and rapid changes in discharge are the reasons for the river's failure to conform to EU's requirements of the Water Framework Directive.
6

Lactuca sativa L. : Evaluation écotoxicologique de rejets industriels complexes et de solutions synthétiques / Lactuca sativa L. : Industrial discharge waters and synthetic solutions ecotoxicological assement bioindicator

Priac, Anne 27 November 2014 (has links)
Ce travail de thèse a concerné l’évaluation des impacts écotoxicologiques de rejetsindustriels complexes issus de la filière du traitement de surface et de solutionssynthétiques mono- et polycontaminées sur la laitue Lactuca sativa L. Il est ainsimontré que les résultats des tests écotoxicologiques de germination des semences delaitue reflètent la variabilité de la composition chimique des rejets et de leuramélioration après traitement d’abattement de la charge métallique et/ou organique.Ces tests ont également permis de classer selon leur toxicité croissante certains ETM(Fe, Cr, Co, Cu, B, Al, F, Ni, Cd, Ag, Zn, Sn) et quelques molécules organiques (4NP,NAP, DBP, NP9). En revanche, quelle que soit la qualité chimique du rejet testé, lestaux de germination des semences et les élongations des plantules (principalement leslongueurs racinaires) dépendent de la variété de laitue choisie pour le test. Cetteobservation s’applique aussi aux solutions synthétiques métalliques monocontaminées.Ainsi, pour un même rejet, la Batavia dorée de printemps apparait plus résistante auxpolluants que la Kinemontepas et la Grosse Blonde Paresseuse, et que l’Appia (CE50estimées respectivement à ~99, 59, 43 et 25 %). Ces différences intraspécifiquess’observent également pour la composition interne et les tendances d’enrichissement encertains nutriments et ETM, malgré la présence de Cd dans le péricarpe de semences“vierges”. / This thesis has explored the surface treatment DW and mono- and polycontaminatedsynthetic solution ecotoxicological impact assessment on lettuce Lactuca sativa L.Ecotoxicological seed germination bioassays reflect the DW chemical variability, theirchemical improvement after metallic and/or organic abatement, and also permit toclassify MTE (Fe, Cr, Co, Cu, B, Al, F, Ni, Cd, Ag, Zn, Sn) and POP (4NP, NAP,DBP, NP9) according to their increasing ecotoxicity. However, whatever the DWchemical quality, seeds germination rates and plantlets elongations (mainly rootelongations) depend on lettuce variety’s choice. It is also true for monometallicsolutions. Thus for the same DW sample, the Batavia dorée de printemps varietyappears to be more resistant to pollutant than the Kinemontepas and the GrosseBlonde Paresseuse varieties, and than the Appia variety (estimated EC50 respectively99, 59, 43 and 25 %). Despite the presence of Cd in virgin pericarp seeds, intraspecificdifferences occured as well when analyzing the inner plantlet compositions and thenutrients and MTE uptake patterns.
7

Uncertainties in Digital-Computer Modeling of Ground-Water Basins

Gates, Joseph S., | Kisiel, Chester C. 23 April 1971 (has links)
From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / Much future computer modeling of the responses of groundwater to water development stresses may be poorly done if the errors and limitations of digital models are not fully appreciated by groundwater hydrologists. Two digital models were constructed of the Tucson basin, one with 1,890 nodes of 1/4 square mile area each and one with 509 nodes of 1 square mile each. The starting point for the digital model was the 2-dimensional, linear, parabolic, time-and space-invariant differential equation of incompressible flow through porous media. An explicit finite-difference equivalent was determined, and a set of 1,890 equations were put in implicit form and solved on a computer in less than 20 seconds at a cost of 2.00 dollars. The errors associated with the model are discussed. In deciding what new data collected in the Tucson basin would give the most improvement in the digital model, a statistical decision theory approach was utilized in which expected opportunity loss and expected worth of sample were calculated for 5 variables. The data was computed using about 110 seconds of computer time, costing about 13.00 dollars. This technique has the advantage of including basin dynamics in estimating worth of additional data by means of using the digital model to compute all values of predicted and 'true' water levels included in the loss function.
8

Management of Artificial Recharge Wells for Groundwater Quality Control

Wilson, L. G. 23 April 1971 (has links)
From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / Recharge wells may be used in various problems relating to chemical water quality because of the phenomenon of in-aquifer mixing. This paper reviews specific recharge well-mixing techniques of possible utility in underground mixing operations for nitrate control. Illustrative data from field studies at a recharge site near Tucson, Arizona are presented. Both single- and 2-well types of mixing were investigated. In single-well operations, effluent recharge and pumping of the subsequent mixture occur at the same well. Differences in chlorine ion levels were used to distinguish between recharge effluent and native groundwater. Undiluted effluent was discharged in single-well operations until a pumped volume ratio of about 0.4 was attained. Dilution increased steadily with increased pumping and the relative concentration versus pumped volume curve was s-shaped. Seven-day pauses after effluent recharge resulted in immediate pumping of almost completely diluted water, probably because groundwater movement swept the effluent beyond the pumping unit during the pause. With 2-well pumping, the chlorine breakthrough curve reached a constant level at about 13 days and was close to that of the pause-type, single-well regime.

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