• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 64
  • 58
  • 25
  • 9
  • 4
  • 3
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 196
  • 140
  • 58
  • 47
  • 44
  • 39
  • 34
  • 33
  • 30
  • 29
  • 26
  • 25
  • 22
  • 19
  • 18
  • 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.
41

AVALIAÇÃO DE VAZÕES MÁXIMAS ESTIMADAS A PARTIR DOS MODELOS HEC-HMS E SWMM ESTUDO DE CASO PARA O NÚCLEO URBANO E REGIÃO PERIURBANA DE MUNIZ FREIRE

SOUZA, T. C. T. 04 August 2017 (has links)
Made available in DSpace on 2018-08-01T23:59:24Z (GMT). No. of bitstreams: 1 tese_11471_Dissertação - Tainah de Souza CD.pdf: 4931542 bytes, checksum: fab9c37691c8c2445e4f9540b0310b3e (MD5) Previous issue date: 2017-08-04 / A determinação da vazão de projeto constitui etapa fundamental para o adequado dimensionamento de obras de drenagem ou para possibilitar a adequada tomada de decisão sobre medidas não estruturais relacionadas com a drenagem pluvial. Em regiões que não dispõem de dados fluviométricos recorre-se, usualmente, à utilização dos modelos do tipo chuva-vazão para determinação indireta da vazão de projeto. Função da diversidade de modelos disponíveis, cabe ao modelador a escolha do modelo mais adequado às singularidades da área avaliada, permitindo a produção de resultados que se apresentem mais próximos da realidade. Neste estudo foi realizada a análise comparativa dos modelos Storm Water Management Model (SWMM) e Hydrologic Engineering Center - Hydrologic Modeling System (HEC-HMS) quando da estimativa de vazões máximas associadas ao núcleo urbano e regiões periurbanas do município de Muniz Freire (ES). A estimativa do escoamento superficial foi realizada através do método Hidrograma Unitário e as perdas de infiltração pelo método SCS Curve Number. A equação de chuvas intensas foi apropriada através do método de Chow-Gumbel e a chuva de projeto pelo método dos blocos alternados. Os modelos apresentaram relevantes diferenças nos valores de vazão de pico e volume de escoamento superficial. Para períodos de retorno entre 2 e 5 anos, os valores de vazão de pico e volumes de escoamento superficial estimados pelo SWMM apresentaram-se superiores aos obtidos pelo HEC-HMS para todas as bacias avaliadas, invertendo-se esta tendência com o aumento do período de retorno. As simulações associadas aos períodos de recorrência de 10 e 20 anos, usualmente utilizados em estudos e projetos de drenagem urbana, foram as que se apresentaram mais próximas, com as menores diferenças relativas para as variáveis hidrológicas avaliadas.
42

Eletrólitos sólidos poliméricos à base de polissacarídeos: síntese e caracterização. / Solid polymer electrolytes based on polysacharide: synthesis and characterization.

Anelise Maria Regiani 10 November 2000 (has links)
A síntese e a caracterização de um novo tipo de eletrólito sólido polimérico são descritas neste trabalho. Os materiais preparados consistiram de filmes de hidroxietil celulose ou hidroxipropil celulose entrecruzadas com diisocianatos de poli(óxido de etileno) e poli(óxido de propileno) ou enxertadas com monoisocianato de poli(óxido de propileno). Todos estes isocianatos foram sintetizados a partir das respectivas aminas comerciais. Filmes de hidroxietil celulose entrecruzada com hexametileno diisocianato ou enxertados com fenil isocianato também foram estudados. Como técnicas de caracterização foram utilizadas espectroscopia no infravermelho, no ultravioleta e de ressonância magnética nuclear, análises térmicas e difração de raios-X. Os filmes dopados com LiClO4 foram caracterizados utilizando-se as mesmas técnicas e a condutividade foi determinada através do método de impedância complexa. Os resultados foram da ordem de 10-5 Scm-1 a 60oC. Este valor permitiu concluir que as cadeias de derivado de celulose parecem não influenciar no fenômeno de condução; aparentemente este encontra-se mais relacionado ao tipo de isocianato utilizado na formação do filme. Os resultados de condutividade e de mobilidade de cadeia polimérica indicam que os sistemas aqui estudados podem ser aplicados como eletrólitos sólidos poliméricos. Os filmes com isocianatos comerciais, no entanto não apresentaram resultado de condução interessante. / The synthesis and characterization of new types of solid polymer electrolytes based on hydroxyethyl and hydroxypropyl cellulose grafted with different polyethers were investigated. The synthesis is based on the reaction between the cellulose derivative and mono and difunctional isocyanates prepared from amines of polyethylene oxide and polypropylene oxide. It were also synthesized films of hydroxyethyl cellulose grafted with hexamethylene diisocyanate and phenylisocyanate. These materials were characterized through techniques of infrared, ultraviolet and nuclear magnetic ressonance spectroscopies, thermal analysis and X-ray diffraction. The films of polysaccharide and polyether that contained LiClO4 showed conductivity values of the order of 10-5 Scm-1 at 60oC. The value of this parameter seems to be independent of the cellulose derivative parameters and it is better related to the type of isocyanate grafted on the polysaccharide chain. The conductivity and chain mobility results show that the systems studied here can be applied as solid polymer electrolytes. The materials synthesized using commercial isocyanates as grafting reactant did not show interesting conductivity response.
43

Assessing the ability of HEC-HMS rainfall-runoff model to simulate stream flow across Sweden

Alavimoghaddam, Mohammadreza January 2017 (has links)
Computer modeling is the powerful tool for simulating nature’s behavior; however, still more efforts are need for reaching perfect simulation with computer models (especially in the hydrological field of study). In this Master’s thesis, the accuracy of the HEC-HMS computer model for long term rainfall-runoff simulation was evaluated across Sweden. Five different catchments from north to south of Sweden were selected and then simulation have done for 34 years of available data. Simulation was conducted using daily, monthly and yearly time scale resolutions. Results from the north to the south of Sweden were completely different. Simulated runoff and observed runoff in northern catchments followed the same pattern over different time scales but in the southern part of Sweden the results had different patterns in space and time. The best results with HEC-HMS were found in the northern catchments with steep main river slopes. In the southern catchments the model could not predict runoff in any realistic manner at any time and space scale. In total the HEC-HMS model cannot simulate the rainfall runoff for long periods of simulation across Sweden. This is especially true in southern parts of the country dominate with low elevation catchments. However, with regards to its ability for event-based simulation HEC-HMS could be a suitable tool to simulate flood event discharges that are needed for road or other hydraulic structures designs. But, this would require significant amounts of calibration and model development.
44

Distributed storage modeling in Soap Creek for flood control and agricultural practices

Wunsch, Matthew John 01 May 2013 (has links)
In 1988, the counties of Appanoose, Davis, Monroe, and Wapello created the Soap Creek Watershed Board. This group put in place a plan to fund and construct 154 farm ponds in an effort to provide water for agriculture practices as well as provide flood protection for the residents inside the Soap Creek watershed. Through collaborative efforts and funding from federal, state, and local sources, to date 132 ponds have been constructed. Currently there is no stream monitoring in place in the watershed to observe stream conditions. This leads to no stored data on the benefits of the projects in the basin and the reduced flood impacts. With funding from the Iowa Watershed Projects (IWP) through the IIHR - Hydroscience & Engineering lab, a lumped parameter surface water model was created to show the benefits of the constructed projects. Using detailed LiDAR data, a Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) model was created. This model used arcHydro and ARC-GeoHMS, tools in ARCgis. Detailed LiDAR, SURGGO soil data, and land cover data was used to create the model parameters. Several design and historical storms were modeled to quantify the benefits in peak flow reductions and in amounts of water stored behind the projects.
45

Flood Capacity Improvement of San Jose Creek Channel Using HEC-RAS

Mowinckel, Erland Kragh 01 June 2011 (has links)
The Santa Ynez Mountains of Santa Barbara County, California, have seen many major storm events during the past century. San Jose Creek, which runs out of these mountains, through the town of Goleta, and into the Pacific Ocean, has experienced several intense flood events as a result. The lower portion of the creek was diverted in 1960 to alleviate flooding through Old Town Goleta. However, flooding still occurred in the storms of 1995 and 1998. This study incorporates a hydraulic analysis component of a project aimed at re-designing this diverted portion of the channel. It presents an analysis of modifications to this reach in order to improve its capacity and reduce flooding during a 100-year event. As one of the most prominent software for hydraulic modeling for steady and unsteady state open channel flow, HEC-RAS is used to analyze multiple variations in channel geometry and combinations of lining materials. Of these modifications, the best configuration is suggested.
46

Vyhodnocení povodňové situace na vybrané části toku / Analysis of flood situation on selected part of river

Štěpánová, Markéta January 2017 (has links)
The thesis deals with an evaluation of flood situation at the area of the river Svitava in Brno throughout three different flows Q5, Q20 a Q100 and that proposes a possible solution for flood protection. Current state of the river stream is evaluated through hydraulic calculation combining 1D and 2D numerical modelling of flow rate with the use of HEC-RAS software.
47

Assessment of nutrient loading in lake Ringsjön from the catchment of Hörbyån Creek in Southern Sweden.

Singh, Durgesh Kumar January 2013 (has links)
Lake Ringsjön, located in south of Sweden, has been subject of eutrophication since 1950s and received several restoration efforts. Latest restoration effort, “Project Ringsjön”, was proposed in 2003 to improve lake condition against eutrophication by reducing nutrient concentration. This study was done to assess the nutrient loading into the lake from the catchment of Hörbyån Creek, which is discharging into the lake from southeast. Study addresses the nutrient loading conditions from Hörbyån Creek before and after the implementation of “Project Ringsjön” in 1998 and 2010 respectively. Thus a water quality analysis was performed to observe the changes in total nitrogen and total phosphorus concentration in Hörbyån Creek between these years. Effort was also made to investigate nutrients contribution of different watersheds in the catchment. This study also addresses the effect of seasonal variability and land use on nutrient loading. In order to achieve objectives, annual and monthly water quality modelling was performed on the river. HEC-RAS software was used to simulate water quality variables loading from catchment into the lake, such as nitrates, nitrite, ammonium, organic nitrogen, inorganic phosphorus and orthophosphate. Results indicated increase in average annual total nitrogen concentration from 4.18 mg/l to 4.56 mg/l and reduction in average annual total phosphorus concentration from 0.165 mg/l to 0.083 mg/l in the water discharging into the lake from catchment. The watershed occupying mostly agriculture area was observed to have maximum nutrients contribution, which might be due to high fertilizer leakage. It was also observed that maximum nutrient loading was taking place in November and March; probably due to high runoff generated from precipitation and snow melting that carried additional nutrients to the water bodies. Results also indicated that the studied catchment area was contributing high nutrient concentration for eutrophication in both years; however, there was small decrease in total phosphorus concentration in 2010 compare to 1998.
48

Hydraulic modelling at Finsjö Övre hydropower plant : Study for evaluation of a fishway's attractiveness / Hydraulisk modellering vid Finsjö Övre vattenkraftverk : Studie för utvärdering av en fiskvägs attraktivitet

Blomström, Eddie January 2022 (has links)
In connection with the government’s approval on the proposed national plan (NAP) in 2019, it has become highly topical to find solutions problems regarding fish migration in Swedish watercourses. At Finsjö Övre hydropower plant in Emån, a new type of fishway is planned to be installed and evaluated starting at the end of 2022. The fishway is a double Archimedes screw turbine that has never been assessed in a Nordic country. The energy company Fortum is operating the power plant. Fortum’s main purpose with the installation is to evaluate the double-screw turbine to gain knowledge about how it performs in Nordic conditions and with Swedish fish species. The evaluation of the fishway will focus on why fish choose to use it or not. It will then be advantageous to have knowledge of velocities in the area below the fishway since fish´s choice of route is affected by that.   The goal of this project was to investigate flow velocities below the intended fishway through hydraulic simulations. Then by the results produce a basis that can be helpful in future evaluations of the fishway’s function for upstream fish migration. In addition to this, to also link the results to previous studies on upstream fish migration to be able to detect shortcomings. In that case to give suggestions for improvement measures.   Field measurements were conducted to collect data on the environment at the hydropower plant. The environment was then recreated in the simulation software HEC-RAS and the planned fishway was added to the model. Three different flow scenarios were assessed and information on flow velocities was obtained.   The simulations showed that the velocity distribution below the fishway probably is suitable for most fish species due to both fast and calm water near the fishway’s opening. No obvious shortcomings emerged. However, the volume flow rate from the fishway is low and is below the recommended guide values. Upstream fish migration will probably work best at low volume flow rates in the river since the velocity of the attraction flow then is relatively high compared to the currents from the hydropower plant. The higher flows from the hydropower plant and the spillway, the less attractive the flow from the fishway becomes. / I samband med att regeringen fattade beslut den nationella planen (NAP) år 2019 har det blivit högaktuellt att hitta lösningar på problematiken kring fiskvandring i svenska vattendrag. Vid Finsjö Övre vattenkraftverk i Emån är en ny sorts fiskväg planerad att installeras och utvärderas med början i slutet av 2022. Fiskvägen är en dubbel Arkimedesskruv som aldrig tidigare har testats i ett nordiskt land. Energiföretaget Fortum, som ansvarar för driften av kraftverket, har som huvudsyfte med installationen att utvärdera skruven för att få kunskap om hur den presterar i nordiska förhållanden och med svenska fiskarter. Vid utvärdering av fiskvägen är det fördelaktigt att ha kunskap om hydrauliska förhållanden i området nedanför fiskvägen, då det bland annat ska undersökas varför fiskar väljer att använda den eller inte.   Målet med detta projekt var att genom hydrauliska simuleringar undersöka flödeshastigheter nedanför den tilltänkta fiskvägen. På så vis sedan ta fram ett underlag som ska kunna användas vid framtida utvärderingar av fiskvägens funktion gällande uppströmsvandring. Utöver detta att också koppla resultaten till tidigare studier kring fiskvandring för att kunna upptäcka eventuella brister och i så fall ge förslag på förbättringsåtgärder.   Fältmätningar genomfördes för att samla in data om miljön vid vattenkraftverket. Därefter återskapades miljön i simuleringsprogrammet HEC-RAS och den planerade fiskvägen adderades till modellen. Tre olika flödesscenarior testades och information om flödeshastigheter erhölls.   Simuleringarna visade att hastighetsfördelningen nedanför fiskvägen troligtvis lämpar sig för flertalet fiskarter på grund av både snabbt och lugnt vatten i nära anslutning till fiskvägens öppning. Inga uppenbara brister visade sig. Dock är flödeshastigheten från fiskvägen låg och ligger under rekommenderade riktvärden. Troligtvis kommer uppströmsvandring fungera bäst vid låga volymflöden i ån eftersom hastigheten på lockvattnet då är relativt hög. För ju högre flöden från kraftverket och spillfåran, desto mindre attraktivt blir flödet från fiskvägen.
49

Increased Functionality of Floodplain Mapping Automation: Utah Inundation Mapping System (UTIMS)

Stevens, Brian K. 01 May 2010 (has links)
Flood plain mapping has become an increasingly important part of flood plain management. Flood plain mapping employs mapping software and hydraulic calculation packages to efficiently map flood plains. Modelers often utilize automation software to develop the complex geometries required to reduce the time to develop hydraulic models. The Utah Inundation Mapping System (UTIMS) is designed to reduce the time required to develop complex geometries for use in flood plain mapping studies. The automated geometries developed by UTIMS include: flood specific river centerlines, bank lines, flow path lines, cross sections and areal averaged n-value polygons. UTIMS thus facilitates developing automated input to US Army Corps of Engineer's HEC-RAS software. Results from HEC-RAS can be imported back to UTIMS for display and mapping. The user can also specify convergence criteria for water surface profile at selected locations along the river and thus run UTIMS and HEC-RAS iteratively till the convergence criterion is met. UTIMS develops a new flood specific geometry file for each iteration, enabling an accurate modeling of flood-plain. Utilizing this robust and easy to operate software within the GIS environment modelers can significantly reduce the time required to develop accurate flood plain maps. The time thus saved in developing the geometries allows modelers to spend more time doing the actual modeling and analyzing results. The time thus saved can also result in faster turn around and potential cost cutting in flood-plain modeling work. In this paper the authors describe UTIMS capabilities, compare them with other available software, and demonstrate the UTIMS flood plain automation process using a case study.
50

Modeling Flood Reduction Scenarios for a Small Coastal Community

Perez, Evan J. 01 March 2013 (has links) (PDF)
The Arroyo Grande Creek Watershed, an approximately 170 mi2 watershed located on the central coast of California, drains to the Pacific Ocean via the Arroyo Grande Creek that passes through several coastal cities including the community of Oceano. At the mouth of the Creek is the Arroyo Grande Lagoon, which is connected to another lagoon known as the Oceano Lagoon, by a tidal flap-gate whose hydraulics is a function of water levels in the two lagoons. Historically the Oceano Lagoon has played a part in floods that have occurred in the community of Oceano. The most recent flooding occurred in 2010 when a storm with about a10-yr frequency caused flooding that led to an estimated property damage of about two million dollars. This study was conducted to understand hydrology of the Arroyo Grande watershed that also feeds Lopez Lake, a reservoir that provides water for drinking, agriculture, and environmental flows; to characterize hydraulics of the Oceano Lagoon; and to explore scenarios for flood mitigation. Objectives of the study are to provide a better understanding of the causes of the historical floodings; map the extent of floodings for various storm events including 10 year, 50 year, and 100 year under current conditions; and examine potential solutions to reduce future floodings. Surface water hydrology of the Arroyo Grande Creek Watershed was studied using HEC-HMS to quantify runoff specifically into the Oceano Lagoon. HEC-HMS was calibrated using known streamflow to improve the accuracy of the model. The HEC-HMS model was developed using spatial data that was organized in ArcMAP. Data such as elevation, land use, soil type, and impervious surface were processed using HEC-GeoHMS and exported to HEC-HMS. Mitigation measures were simulated in HEC-HMS by adjusting parameters such as the outlet configuration and the increased volume in Oceano Lagoon. Each mitigation measure delivered varying effectiveness. Results show that while the peak flow and volume in the lagoon can be reduced, larger design storms will continue to inundate the area unless drastic steps are taken. The findings could assist local flood control agencies by evaluating the risks of continuing to use the existing drainage system, and identifying opportunities available to reduce those risks.

Page generated in 0.048 seconds