Дисертації з теми "Variable water"
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1
Kamat, Madhusudan Sunil. "Soil moisture change due to variable water table." Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54922.
Повний текст джерелаАнотація:
The thesis numerically models and investigates the effect of a variable water table on the soil moisture content. The modelling is done using COMSOL and Richards' equation. The temporal variation plots can be used to find the capillarity of the soil and its impact on other phenomenon such as vapor intrusion and infiltration.
2
Ropp, David L. "Numerical study of shallow water models with variable topography." Diss., The University of Arizona, 2000. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_2000_165_sip1_w.pdf&type=application/pdf.
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3
Qi, Jiaguo 1959. "Spectral properties of paddy rice with variable water depth." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277119.
Повний текст джерелаАнотація:
An experiment was conducted to determine whether the water depth (above soil) and soil type would have any influence on the multispectral reflectances of paddy rice, and their calculated vegetation index values. The results showed that, when vegetation cover was low (below 600 grams of dry biomass per square meter), the near infrared (NIR) reflectances decreased very little with water depth. The same was true for red reflectances, but to a lesser degree. Overall the changes were not significant at 0.05 level of significance when the water depth was increased from 2.5 centimeters to 10 centimeters. When the vegetation cover became higher most NIR and red reflectances did not show a significant decrease with the increase of the water depth, and sometimes they even increased slightly up to a water depth of 6.4 cm. Nevertheless both rice cover and water depth as well as soils played an important role in the reflectance pattern in red and NIR bands. Some index values increased and some decreased depending on water depth and rice cover. Statistical analysis of the data showed that rice multispectral responses were mainly controlled by vegetation and minimally influenced by soil and water depths.
4
Fritz, Christian. "Surface oscillation in peatlands : how variable and important is it? /." The University of Waikato, 2006. http://hdl.handle.net/10289/2397.
Повний текст джерелаАнотація:
Hydrology, particularly the water table position below the surface, is an mportant control on biogeochemical and ecological processes in peatlands. The position of the water table is a function of total storage changes, drainable porosity and peatland surface oscillation (PSO). Because the absolute level of the peat surface (ASL) oscillates in a peatland, we can assign two different water table positions: the water table depth below the surface (relative water level, RWL) and the water table position above an absolute elevation datum eg. sea level (absolute water level, AWL). A review of 37 studies that report peatland surface oscillation indicate awide range (0.4-55 cm), which is to the same order as (or one order smaller than) water storage changes and RWL fluctuations. PSO can vary substantially across a single peatland and through time. A set of mechanisms (flotation, compression/shrinkage, gas volume changes and freezing) is hypothesised to cause ASL changes. The potential of PSO to reduce RWL fluctuations trended (mean in %) floating peatlands (63) greater than bogs (21), fens (18) greater than disturbed peatlands (10) with respect to peatland types. To investigate the spatiotemporal variability of peatland surface oscillation, AWL and ASL were monitored continuously over a one-year period (one site) and monthly (23 sites) in a warm-temperate peatland that is dominated by Empodisma minus (Restionaceae). A new measurement method was developed by pairing two water level transducers, one attached to a stable benchmark (AWL) and one attached to the peat surface (RWL). From August 2005 until August 2006 the ASL oscillated at one site through a range of 22 cm following AWL fluctuations (in total 47 cm). Consequently, RWL fluctuations were reduced on average to 53% of AWL fluctuations. The strong AWL-ASL relationship was linear for 15 sites with manual measurements. However, eight sites showed significantly higher rates of peatland surface oscillation during the wet season (ie. high AWLs) and thus a non-linear behaviour. Temporary flotation of upper peat layers during the wet season may have caused this non-linear behaviour. On the peatland scale AWL fluctuations (mean 40 cm among sites) were reduced by 30-50% by PSO except for three sites with shallow and dense peat at the peatland margin (7-11%). The reduction of RWL fluctuation was high compared to literature values. The spatial variability of PSO seemed to match well with vegetation patterns rather than peat thickness or bulk density. Sites with large PSO showed high cover of Empodisma minus. Surface level changes exhibited surprisingly hysteretic behaviour subsequent to raised AWLs, when the rise of ASL was delayed. This delay reversed the positive ASL-AWL relationship because the surface slowly rose even though AWL started receding. Hysteresis was more pronounced during the dry season than during the wet season. The observed hysteresis can be sufficiently simulated by a simplistic model incorporating delayed ASL fluctuations. PSO has wide implications for peatland hydrology by reducing RWL fluctuations, which feed back to peat decomposition and plant cover and potentially to (drainable) porosity. Stable RWL also reduce the probability of surface run-off. It is further argued that the gas content of the roots of plants, particularly Empodisma minus, added enough buoyancy to detach the uppermost peat layers resulting in flotation.
5
Killen, Sean Martin. "Propagation of nonlinear water waves over variable depth in cylindrical geometry." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366639.
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6
Wraith, Jon M. "Soil Temperature Influence on Water Use and Yield Under Variable Irrigation." DigitalCommons@USU, 1989. https://digitalcommons.usu.edu/etd/1996.
Повний текст джерелаАнотація:
The need for efficient use of water resources has increased the importance of optimum soil water usage in agricultural systems. Soil temperature has been shown to be important in influencing the early development of many plant species. Many agricultural regions have suboptimal soil temperature regimes for plant growth, and some cultural practices have been shown to reduce near-surface soil temperatures. The seasonal influence of soil temperature on soil water extraction and aboveground and belowground plant growth under variable irrigation was investigated at the USU Greenville Farm in Logan, UT. Soil surface mulches and buried heat cables were used to modify soil temperature. A line-source sprinkler system provided a gradient of water application.
During 1987 yields were mainly influenced by irrigation. During 1988 greater soil temperature differences resulted in significant plant growth and yield responses. Soil water depletion corresponded to soil temperature treatments during the early part of the growing seasons. Depth of maximum soil water depletion was about 20 cm deeper for warm treatments. Water uptake rates of earlier-maturing plants in warm treatments were reduced later in the season, so that cumulative seasonal soil water depletion was similar for all temperature treatments. Although depth of rooting was somewhat greater under high than low irrigation during 1988, low irrigation treatments depleted soil water to greater depth. There was no interactive response of plant growth and yield or of soil water depletion to soil temperature and irrigation treatments.
Modifications were made to a computer simulation model of the soil-plant-atmosphere system in order to more mechanistically simulate plant water uptake and to include influences of soil temperature on seasonal rooting growth and soil water extraction. The model adequately simulated both the pattern and magnitude of soil temperature influences on soil water depletion, and conclusions drawn from model simulations agreed with field observations during 1987 and 1988.
7
Eusuff, M. Muzaffar. "Optimisation of an operating policy for variable speed pumps using genetic algorithms." Title page, contents and abstract only, 1995. http://web4.library.adelaide.edu.au/theses/09ENS/09ense91.pdf.
Повний текст джерелаАнотація:
Undertaken in conjunction with JUMP (Joint Universities Masters Programme in Hydrology and Water Resources). Bibliography: leaves 76-83. Establishes a methodology using genetic algorithms to find the optimum operating policy for variable speed pumps in a water supply network over a period of 24 hours.
8
Panupintu, Wantana. "The propagation of nonlinear water waves over variable depth with shear flow." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246653.
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9
Goswami, Rohit Raj Clement Prabhakar Thangadurai. "Experimental and numerical analysis of variable-density flow and transport scenarios." Auburn, Ala, 2008. http://hdl.handle.net/10415/1430.
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10
Hipkiss, Sarah. "A Camassa-Holm equation for the propagation of water waves over variable depth." Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412646.
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11
Hales, Alwin Livingstone. "A model to determine optimal water management procedures for multi-variable irrigation systems." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259483.
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12
Ip, Kenneth C. W. "Dynamic modular simulation of variable water and air volume flow systems in buildings." Thesis, University of Bristol, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251526.
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13
Svedin, Jeffrey David. "Characterizing the Spatial Variation of Crop Water Productivity for Variable-Rate Irrigation Management." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6878.
Повний текст джерелаАнотація:
Irrigated agriculture is the primary consumer of limited worldwide freshwater resources. Drought, growing world populations, and environmental demands compete with irrigation for freshwater resources"”threatening sustainable global food, fuel, and fiber production. This escalating global crisis demands that agriculture produce more food using less water. Traditional irrigation management has used technology to apply uniform irrigation rates across landscapes"”ignoring natural environmental variation. This provides inherent inefficiencies of over- or under- irrigation within individual fields. Variable-rate irrigation (VRI) is modern technology that employs global positioning systems and geographic information systems to match irrigation to spatially variable crop water demands within a field. Although commercially available, VRI lacks scientifically validated decision support systems to determine spatially and temporally variable crop water demand. The purpose of this research is to explore spatial and temporal variations in crop water demand to inform growers utilizing VRI. This research consists of four seasons of winter wheat (Triticum aestivum L.) production on a commercial farm in Idaho that employs a VRI system. In Chapter 1, the spatial variation of crop water productivity (CWP, the grain produced per unit of water consumed), is characterized for two seasons (2016-2017) and we propose a unique conceptual strategy for VRI management targeted at CWP. Observed CWP ranged from 4.1-21 kg ha-1 mm-1 with distinct spatial variation that, when considered together with grain yield, were shown to be useful for VRI management. During the 2017 growing season, VRI zones conserved 25% of irrigation compared to traditional uniform irrigation management. In the second chapter the spatial variation of soil water holding capacity (SWHC) was measured at 90 sampling points throughout the field. Then, during the 2016-2017 growing seasons, the spatial and temporal variation of soil moisture were modelled to characterize crop stress and its influence on grain yield. Soil within the field showed large spatial variation of SWHC, ranging from 147-369 mm. Under uniform irrigation in 2016, the natural variation of TAW created 21 day variation in the onset of crop stress throughout the field and under VRI in 2017 the onset of crop stress spanned 56 d. Surprisingly the variations in TAW did not statistically influence yield in 2016, and in 2017 the rate of irrigation predicted yield and TAW again did not statistically predict yield. This suggests that other environmental variables should be included when delineating irrigation zones and rates for VRI.
14
Shang, Kun. "GRACE Time-Variable Gravity Field Recovery Using an Improved Energy Balance Formalism." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437393586.
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15
Bang, Gwan-Sik. "Localization of buried objects in water-saturated sand by variable incidence acoustic pulse reflections." Thesis, Washington, D.C. : Dumbarton Oaks Research Library and Collection ; [Cambridge, Mass.] : Distributed by Harvard University Press, 1985. http://hdl.handle.net/10945/21407.
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16
William, Henry Schulz. "Beyond Hydrostatic Pore-Water Pressure - Variable Effects of Groundwater on Landslide Initiation and Mobility." Doctoral thesis, Kyoto University, 2020. http://hdl.handle.net/2433/245815.
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17
Kang, Choongkwan. "Evaluation of economic and water quality effects for variable rate application of nitrogen fertilizer /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9821346.
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18
Nikolaou, Christos. "A multi-objective genetic algorithm optimisation using variable speed pumps in water distribution systems." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6819/.
Повний текст джерелаАнотація:
Due to its practical importance and inherent complexity, the optimisation of distribution networks for supplying drinking water has been the subject of extensive study for the past 30 years. The optimization is governed by sizing the pipes in the water distribution network (WDN) and / or optimises specific parts of the network such as pumps, tanks etc. or try to analyse and optimise the reliability of a WDN.
In this thesis, the author has analysed two different WDNs (Anytown City and Cabrera city networks), trying to solve and optimise a multi-objective optimisation problem (MOOP). The main two objectives in both cases were the minimisation of Energy Cost (€) or Energy consumption (kWh), along with the total Number of pump switches (TNps) during a day. For this purpose, a decision support system generator for Multi-objective optimisation used. Its name is GANetXL and has been developed by the Center of Water System in the University of Exeter. GANetXL, works by calling the EPANET hydraulic solver, each time a hydraulic analysis has been fulfilled. The main algorithm used, was a second-generation algorithm for multi-objective optimisation called NSGA_II that gave us the Pareto fronts of each configuration.
The first experiment that has been carried out was the network of Anytown city. It is a big network with a pump station of four fixed speed parallel pumps that are boosting the water dynamics. The main intervention was to change these pumps to new Variable speed driven pumps (VSDPs), by installing inverters capable to diverse their velocity during the day. Hence, it’s been achieved great Energy and cost savings along with minimisation in the number of pump switches. The results of the research are thoroughly illustrated in chapter 7, with comments and a variety of graphs and different configurations.
The second experiment was about the network of Cabrera city. The smaller WDN had a unique FS pump in the system. The problem was the same as far as the optimisation process was concerned, thus, the minimisation of the energy consumption and in parallel the minimisation of TNps. The same optimisation tool has been used (GANetXL).The main scope was to carry out several and different experiments regarding a vast variety of configurations, using different pump (but this time keeping the FS mode), different tank levels, different pipe diameters and different emitters coefficient. All these different modes came up with a large number of results that were compared in the chapter 8.
Concluding, it should be said that the optimisation of WDNs is a very interested field that has a vast space of options to deal with. This includes a large number of algorithms to choose from, different techniques and configurations to be made and different support system generators. The researcher has to be ready to “roam” between these choices, till a satisfactory result will convince him/her that has reached a good optimisation point.
19
Hernandez, Tatiana X. "Rainfall-Runoff Modeling in Humid Shallow Water Table Environments." Scholar Commons, 2001. https://scholarcommons.usf.edu/etd/1537.
Повний текст джерелаАнотація:
Simulating the processes of rainfall and runoff are at the core of hydrologic modeling. Geomorphologic features, rainfall variability, soil types, and water table depths strongly influence hydrological process in Florida ecosystems. Topographic characteristics of the terrain define the stream paths and landscape. Alteration of these characteristics as a result of urban and/or agricultural developments, for example, can highly influence wetlands and river basin response. There are two predominant landforms in Florida: wetlands, where Variable Saturated Areas form near streams causing saturation excess runoff, and uplands where runoff is mainly generated by infiltration excess. The objective of this work is to analyze the impacts of geomorphologic and hydrologic characteristics on runoff mechanisms in humid environments such as Florida. In general, most research at the hillslope scale use hypothetical values of rainfall, sometimes non-realistic values, and single slope forms to explain the geomorphic and hydrologic process on Variable Saturated Areas. In this thesis, the complexity of hillslope processes on actual Florida topography is assessed by coupling a Digital Elevation Model with a two-dimensional variable saturated-unsaturated flow model called HYDRUS-2D. Actual rainfall records and soil parameters from the Characterization Data for Selected Florida Soils, Soil Survey were used to evaluate hydrologic impacts. A commercial software package, River Tools was used to display and extract topographic information from the Digital Elevation Models.
Results show that when inflitration excess runoff is dominant, infiltration and runoff are very sensitive to time resolution, especially for convective storms. When saturation excess occurs, runoff is not affected by rainfall intensity. However, saturated hydraulic conductivity, depth to the water table, slope and curvature highly influence the extent of Variable Saturated Areas. Results indicate runoff in shallow water table environments is produced mainly by subsurface storm runoff, running below the surface, except in hillslopes with concave curvature and mild slopes. Additionally, concave hillslopes generate more saturation excess runoff than straight and convex hillslopes.
20
Mullen, John A. "Analytical and Experimental Comparison of a Positive Displacement Water Pump Using an Infinitely Variable Transmission." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1492125053378972.
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21
Klingler, Thomas H. (Thomas Henry). "An analysis of adding land cover as a variable to the DRASTIC ground water model." Thesis, North Texas State University, 1993. https://digital.library.unt.edu/ark:/67531/metadc798167/.
Повний текст джерелаАнотація:
This study involved a geographic information systems (GIS) approach to modeling ground water pollution potential in the Southern Edwards Aquifer Region in Texas. The DRASTIC ground water model was analyzed using two methods. First, the effects of adding land cover data to the drastic model were evaluated. In the second approach, the effects of the removal of DRASTIC variables were evaluated. Six, five, and four variable models were generated and analyzed.
22
Woods, Juliette Aimi. "Numerical accuracy of variable-density groundwater flow and solute transport simulations." Title page, contents and abstract only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09phw8941.pdf.
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23
Jang, Wonyong. "Unsteady multiphase flow modeling of IN-SITU air sparging system in a variable saturated subsurface environment." Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-11172005-140745/.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006.Dr. Spyros Pavlostathis, Committee Member ; Dr. Mustafa M. Aral, Committee Chair ; Dr. Turgay Uzer, Committee Member ; Dr. Ching-Hua Huang, Committee Member ; Dr. Sotira Yiacoumi, Committee Member. Vita. Includes bibliographical references.
24
Du, Plessis Gideon Edgar. "A variable water flow strategy for energy savings in large cooling systems / Gideon Edgar du Plessis." Thesis, North-West University, 2013. http://hdl.handle.net/10394/9509.
Повний текст джерелаАнотація:
Large cooling systems consume up to 25% of the total electricity used on deep level mines. These
systems are integrated with the water reticulation system to provide chilled service water and cool
ventilation air. Improving the energy efficiency of these large cooling systems is an important
electrical demand-side management initiative. However, it is critical that the service delivery and
system performance be maintained so as to not adversely affect productivity.
A novel demand-side management strategy, based on variable water flow, was developed to improve
the energy efficiency of large cooling systems like those found on deep mines. The strategy focuses
on matching the cooling system supply to the demand through the use of modern energy efficient
equipment, such as variable speed drives. The strategy involves the modulation of evaporator,
condenser, bulk air cooler and pre-cooling water according to partial load conditions.
A unique central energy management system was developed to integrate the proposed strategies on
large cooling systems. The system features a generic platform and hierarchical network architecture.
Real-time energy management is achieved through monitoring, optimally controlling and reporting
on the developed strategy. The system is robust and versatile and can be applied to various large
cooling systems.
The feasibility of the strategy and energy management system was first investigated through the use
of an adapted and verified simulation model and a techno-economic analysis. The strategy was then
implemented on four large mine cooling systems and its in situ performance was assessed as
experimental validation. The results of the Kusasalethu surface cooling system are discussed in detail
as a primary case study while the results of the Kopanang, South Deep South Shaft and South Deep
Twin Shaft cooling systems are summarised as secondary case studies. The potential to extend the
variable water flow strategy to other industrial cooling systems is assessed through an investigation
on the cooling system of the Saldanha Steel plant. Results indicate that, over a period of three months, average electrical load savings of 606-2 609 kW
(29.3-35.4%) are realised on the four systems with payback periods of 5-17 months. The average
electrical load saving between the sites is 33.3% at an average payback period of 10 months. The
service delivery and performance of the cooling system and its critical subsystems are not adversely
affected. The potential to extend the method to other large cooling systems is also shown. The
developed variable water flow strategy is shown to improve the energy efficiency of large cooling
systems, making a valuable contribution towards a more sustainable future.
This thesis is presented as a detailed discussion of the entire research process. The key results have
also been summarised in a series of five research articles attached as independent annexures. Three
articles have been published in international scientific journals, one has been presented at and
published in the proceedings of an international conference and one is still under review.Thesis (PhD (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013
25
Hasnain, Shahid. "Steady Periodic Water Waves Solutions Using Asymptotic Approach." Thesis, Linköpings universitet, Tillämpad matematik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-69421.
Повний текст джерелаАнотація:
The aim of this work is to study the relation between two invariants of water flow in a channel of finite depth. The first invariant is the height of the water wave and the second one is the flow force. We restrict ourselves to water waves of small amplitude. Using asymptotic technique together with the method of separation of variables, we construct all water waves of small amplitude which are parameterized by a small parameter. Then we demonstrate numerically that the flow force depends monotonically on the height.
26
de, Toro A. Alfredo. "Assessment of field machinery performance in variable weather conditions using discrete event simulation /." Uppsala : Dept. of Biometry and Engineering, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/a462.pdf.
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27
Lee, Raymond M. "Modeling recession flow and tracking the fate and transport of nitrate and water from hillslope to stream." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/98555.
Повний текст джерелаАнотація:
Nitrate (NO⁻3) export can vary widely among forested watersheds with similar nitrogen loading, geology, and vegetation, which suggests the importance of understanding differing internal retention mechanisms. Transport should be studied at the hillslope scale because the hillslope is the smallest unit with spatial and temporal resolution to reflect many relevant NO⁻3 retention and transport (flow-generation) processes, and headwater forested watersheds are largely comprised of sections of hillslopes. I conducted two experiments to elucidate subsurface flow dynamics and NO⁻3 transport and retention mechanisms on a constructed experimental hillslope model.
In the first experiment, I tested whether decadal pedogenetic changes in soil properties in the experimental hillslope used by Hewlett and Hibbert (1963) would lead to changes in recession flow. I repeated (twice) their seminal experiment, whose results led to the development of the Variable Source Area paradigm, by also saturating, covering, and allowing the experimental hillslope to drain until it no longer yielded water. In the historical experiment there was fast drainage for 1.5 d, followed by slow drainage for ~140 d, which led the authors to conclude that recession flow in unsaturated soil could sustain baseflow throughout droughts. This long, slow drainage period was not reproduced in my experiments. Shapes of the drainage curves in my experiments were similar to the historical curve, but slow drainage was truncated, ending after 17 and 12 d, due likely to a leak in the boundary conditions, rather than to pedogenetic changes since the historical experiment. Leakage to bedrock, analogous to the leak in the hillslope model, is a commonly observed phenomenon and this study highlights how that can reduce drainage duration and the contribution of moisture from soils to support baseflow.
In the second experiment, I tested whether movement of NO⁻3, which is considered a mobile ion, would be delayed relative to movement of water through a hillslope. I added concentrated pulses of ¹⁵NO⁻3 and a conservative tracer (²H₂O) on the same experimental hillslope, which was devegetated and irrigated at hydrologic steady state. Retention of the ¹⁵NO⁻3 tracer was high in the soil surface (0–10 cm) layer directly where the tracer was added. The portion of the ¹⁵NO⁻3 tracer that passed through this surface layer was further retained/removed in deeper soil. The reduction in the peaks in δ¹⁵N breakthrough was an order of magnitude larger than in δ₂H breakthrough at the outlet 5 m downslope of the tracer addition. The peaks in δ¹⁵N were also delayed relative to the peaks in δ₂H by 1, 6, 9 and 18.5 d for slope distances of 0, 2, 4, and 5 m, respectively, from tracer addition to the outlet. The excess mass of ¹⁵NO⁻3 recovered at the outlet was less than 3% of the original tracer mass injected. Nitrification and denitrification were estimated to be roughly 1:1 and were large fluxes relative to lateral transport into and out of the riparian zone. This tracer experiment shows that bedrock leakage, coupled with multiple retention/removal mechanisms can significantly delay export of added NO⁻3 with implications of additional NO⁻3 sink strength at the watershed scale.Ph. D.
28
Gallon, Evelina, and Sanna Lindberg. "Where does the stream begin? : Stream initiation under variable wetness conditions in a boreal landscape." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-227045.
Повний текст джерелаАнотація:
The understanding of where the streams begin is an important factor in both hydrology and geomorphology, as well as for land use activities. Despite this, only a few research projects have been done in a snowmelt-dominated boreal landscape. The main objective in this study is to see if one could predict where a stream initiates by knowing possible controlling factors. Data points from stream initiation points in the boreal landscape of Krycklan, situated 50 km Northwest of Umeå, were analyzed. Krycklan is a well-known research area and a lot of research projects have been done here. The landscape is diverse and most of the streams have been modified by human impact. The data points were collected with help of a Global Positioning System (GPS) during three different sampling campaigns; May 2012, May 2013 and August 2013. Maps were made from a Digital Elevation Model (DEM) showing slope, elevation and contributing areas for the stream heads. No clear relationship between the contributing area and slope could be found in this area, although it has been demonstrated in more semi-arid climates. The results show that other factors than the contributing area, elevation and slope seem to have a greater impact for the initiation of streams in a boreal landscape. The results were expected because of the modifications done for the streams.
29
Yang, Teng Teng, and 杨婷婷. "Corals in a variable physical environment : impacts on growth and the [delta]¹¹B pH-proxy." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/209621.
Повний текст джерелаАнотація:
Coral reefs are important to sustain marine ecosystems and provide a reliable resource for studying past climate. Corals are increasingly challenged by changing environments. The marginal corals of Hong Kong provide a natural laboratory to study the combination of environmental conditions controlling coral distribution and growth. Salinity and pH were found to impact corals in studies of coral distribution, extension, and culture. Hong Kong corals have low extension rates (1.2-11.4 mm/yr) and do not colonize in areas of low in salinity and pH. Ten years of instrumental records showed extension related positively to summer salinity and dissolved oxygen. Winter seawater temperature was inversely related to extension, while chlorophyll a showed positive relationship in autumn and winter. Culture results show low salinity negatively impacted coral calcification, photosynthesis, and extension. Corals exhibited reduced growth, paling and bleached. In contrast, coral growth increased under high pCO2, but corals decalcified in dark indicating underlying mechanisms may be altering coral physiology.
The boron isotope (δ11B) proxy in corals is able to reconstruct past seawater pH when the pH of the extracellular calcifying fluid (ECF) is considered. A pH offset (ΔpH) was recorded in reconstructed pHsw due to ion pumping to ensure the ECF is saturated with respect to aragonite. By incorporating carbon isotopes (δ13C) into the δ11B-ΔpH relationship, δ11B can be corrected to remove ECF processes and reconstruct seawater pH. Culture results indicated δ11Baxial from axial tip recorded pH similar to other studies while low salinity impacted δ11Bbasal at the base. The different relationship shown from the same colony within the same cultured conditions suggested vital effects with differing coral metabolisms. δ11Baxial and δ11Bbasal related to extension but insignificantly. The large isotopic offset between δ11Baxial and δ11Bbasal indicated different growth mechanisms could possibly affected boron incorporation. The δ11B variation within a coral colony suggested careful and precise sampling for pH reconstructions is important.published_or_final_version
Earth Sciences
Doctoral
Doctor of Philosophy
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Villarreal, Guerrero Federico. "Enhanced Greenhouse Cooling Strategy with Natural Ventilation and Variable Fogging Rates." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202717.
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High-pressure fog (HPF) systems have advantages for greenhouse cooling compared to traditional systems, such as pad and fan. Such advantages include the potential of improving climate uniformity. Water is distributed throughout the greenhouse space thus reducing water use and energy operation costs, especially if used within naturally ventilated greenhouses. Fog cooling in combination with natural ventilation is difficult to manage, primarily because accurate estimation of air exchange rates is required to determine the precise amount of fog required. This limitation on automated control has been the main reason restricting the widespread commercial use of HPF systems. The goal of this research was to develop and implement a control strategy for a naturally ventilated greenhouse with a variable HPF system. The strategy that was developed included variable rate of fog introduced into the greenhouse, a dynamic control of the air ventilation openings, and it considered the contribution of cooling and humidification from the crop by evapotranspiration. Three evapotranspiration models, including Penman-Monteith, Stanghellini and Takakura, were calibrated and evaluated in terms of prediction accuracy. The Stanghellini model provided the best overall performance for several growing seasons and under two different evaporative cooling systems (i.e. pad and fan and natural ventilation with HPF), and was selected and implemented in the cooling control strategy. The strategy utilized enthalpy and vapor pressure deficit (VPD) of the greenhouse atmosphere for the control parameters. Using a calibrated greenhouse mechanistic climate model, a computer algorithm was created to simulate the capabilities of the proposed. The control strategy that was developed was able to maintain the greenhouse climate closer to the pre-established set points while consuming less water and energy, compared to a constant HPF system based on VPD control. Finally, the strategy was implemented in a single span research greenhouse. A four-day validation study provided good agreement for measured and simulated greenhouse climate values, as well as for water and energy use. Moreover, the strategy was able to maintain VPD around its set point for all the experiments and temperature remained around its set point when outside enthalpy was lower than the enthalpy set point.
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Apostolidou, Ilektra-Georgia. "Variable density shallow flow model for flood simulation." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:71a07d09-0702-40c7-bc40-bcc11de9de3c.
Повний текст джерелаАнотація:
Flood inundation is a major natural hazard that can have very severe socio-economic consequences. This thesis presents an enhanced numerical model for flood simulation. After setting the context by examining recent large-scale flood events, a literature review is provided on shallow flow numerical models. A new version of the hyperbolic horizontal variable density shallow water equations with source terms in balanced form is used, designed for flows over complicated terrains, suitable for wetting and drying fronts and erodible bed problems. Bed morphodynamics are included in the model by solving a conservation of bed mass equation in conjunction with the variable density shallow water equations. The resulting numerical scheme is based on a Godunov-type finite volume HLLC approximate Riemann solver combined with MUSCL-Hancock time integration and a non-linear slope limiter and is shock-capturing. The model can simulate trans-critical, steep-fronted flows, connecting bodies of water at different elevations. The model is validated for constant density shallow flows using idealised benchmark tests, such as unidirectional and circular dam breaks, damped sloshing in a parabolic tank, dam break flow over a triangular obstacle, and dam break flow over three islands. The simulation results are in excellent agreement with available analytical solutions, alternative numerical predictions, and experimental data. The model is also validated for variable density shallow flows, and a parameter study is undertaken to examine the effects of different density ratios of two adjacent liquids and different hydraulic thrust ratios of species and liquid in mixed flows. The results confirm the ability of the model to simulate shallow water-sediment flows that are of horizontally variable density, while being intensely mixed in the vertical direction. Further validation is undertaken for certain erodible bed cases, including deposition and entrainment of dilute suspended sediment in a flat-bottomed tank with intense mixing, and the results compared against semi-analytical solutions derived by the author. To demonstrate the effectiveness of the model in simulating a complicated variable density shallow flow, the validated numerical model is used to simulate a partial dam-breach flow in an erodible channel. The calibrated model predictions are very similar to experimental data from tests carried out at Tsinghua University. It is believed that the present numerical solver could be useful at describing local horizontal density gradients in sediment laden and debris flows that characterise certain extreme flood events, where sediment deposition is important.
32
Haag, Lucas A. "Effects of spatially variable plant available water on optimal corn seeding rate -- field scale and site-specific approaches." Thesis, Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/818.
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Frier, Tracy. "Induced Water Drinking during a Discrete Trial Procedure Using a Variable-Ratio Schedule of Reinforcement with a Canine." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1404586/.
Повний текст джерелаАнотація:
Falk's pivotal 1961 study showed that rats would drink excessive amounts of water when exposed to a time based schedule of reinforcement. Since then, schedule-induced drinking or polydipsia, has been demonstrated with several species and with a variety of different behaviors. Rats, the most commonly used animal, have been shown to drink excessive amounts of water under a variety of different time based schedules of reinforcement; exclusively during a free operant procedure. The current study shows that water drinking can be induced during a discrete trial procedure, and instead of using a time-based schedule of reinforcement, this study used a variable-ratio schedule of reinforcement. The results showed that excessive water drinking was induced under these conditions with a canine.
34
Shah, Nirjhar. "Vadose zone processes affecting water table fluctuations : conceptualization and modeling considerations." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002260.
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Ender, Anna Franziska [Verfasser], and N. [Akademischer Betreuer] Goldscheider. "Evaluation of highly variable water quality as basis for a sustainable water supply in the Dong Van karst region, Northern Vietnam / Anna Franziska Ender ; Betreuer: N. Goldscheider." Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1161008705/34.
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Masek, Caroline Humphrey. "Adapting the SCS method for estimating runoff in shallow water table environments." Scholar Commons, 2002. http://purl.fcla.edu/fcla/etd/SFE0000040.
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Lau, Ken Wan Keung. "The identification of novel marine bacteria, and the construction of single chain fragment variable antibodies for the control of a viral pathogen /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?AMCE%202006%20LAU.
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Brunke, Michael A., Patrick Broxton, Jon Pelletier, David Gochis, Pieter Hazenberg, David M. Lawrence, L. Ruby Leung, Guo-Yue Niu, Peter A. Troch, and Xubin Zeng. "Implementing and Evaluating Variable Soil Thickness in the Community Land Model, Version 4.5 (CLM4.5)." AMER METEOROLOGICAL SOC, 2016. http://hdl.handle.net/10150/612995.
Повний текст джерелаАнотація:
One of the recognized weaknesses of land surface models as used in weather and climate models is the assumption of constant soil thickness because of the lack of global estimates of bedrock depth. Using a 30-arc-s global dataset for the thickness of relatively porous, unconsolidated sediments over bedrock, spatial variation in soil thickness is included here in version 4.5 of the Community Land Model (CLM4.5). The number of soil layers for each grid cell is determined from the average soil depth for each 0.9 degrees latitude x 1.25 degrees longitude grid cell. The greatest changes in the simulation with variable soil thickness are to baseflow, with the annual minimum generally occurring earlier. Smaller changes are seen in latent heat flux and surface runoff primarily as a result of an increase in the annual cycle amplitude. These changes are related to soil moisture changes that are most substantial in locations with shallow bedrock. Total water storage (TWS) anomalies are not strongly affected over most river basins since most basins contain mostly deep soils, but TWS anomalies are substantially different for a river basin with more mountainous terrain. Additionally, the annual cycle in soil temperature is partially affected by including realistic soil thicknesses resulting from changes in the vertical profile of heat capacity and thermal conductivity. However, the largest changes to soil temperature are introduced by the soil moisture changes in the variable soil thickness simulation. This implementation of variable soil thickness represents a step forward in land surface model development.
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Zhang, Fan. "A NEW PARADIGM OF MODELING WATERSHED WATER QUALITY." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2387.
Повний текст джерелаАнотація:
Accurate models to reliably predict sediment and chemical transport in watershed water systems enhance the ability of environmental scientists, engineers and decision makers to analyze the impact of contamination problems and to evaluate the efficacy of alternative remediation techniques and management strategies prior to incurring expense in the field. This dissertation presents the conceptual and mathematical development of a general numerical model simulating (1) sediment and reactive chemical transport in river/stream networks of watershed systems; (2) sediment and reactive chemical transport in overland shallow water of watershed systems; and (3) reactive chemical transport in three-dimensional subsurface systems. Through the decomposition of the system of species transport equations via Gauss-Jordan column reduction of the reaction network, fast reactions and slow reactions are decoupled, which enables robust numerical integrations. Species reactive transport equations are transformed into two sets: nonlinear algebraic equations representing equilibrium reactions and transport equations of kinetic-variables in terms of kinetically controlled reaction rates. As a result, the model uses kinetic-variables instead of biogeochemical species as primary dependent variables, which reduces the number of transport equations and simplifies reaction terms in these equations. For each time step, we first solve the advective-dispersive transport of kinetic-variables. We then solve the reactive chemical system node by node to yield concentrations of all species. In order to obtain accurate, efficient and robust computations, five numerical options are provided to solve the advective-dispersive transport equations; and three coupling strategies are given to deal with the reactive chemistry. Verification examples are compared with analytical solutions to demonstrate the numerical accuracy of the code and to emphasize the need of implementing various numerical options and coupling strategies to deal with different types of problems for different application circumstances. Validation examples are presented to evaluate the ability of the model to replicate behavior observed in real systems. Hypothetical examples with complex reaction networks are employed to demonstrate the design capability of the model to handle field-scale problems involving both kinetic and equilibrium reactions. The deficiency of current practices in the water quality modeling is discussed and potential improvements over current practices using this model are addressed.Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering
40
Belhadji, Lakhdar. "Optimisation du contrôle commande d'un système hydraulique réversible à vitesse variable." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00881633.
Повний текст джерелаАнотація:
Le but de cette thèse est l'optimisation du contrôle commande d'un système hydraulique réversible à vitesse variable. L'approche est d'abord traitée par simulation dynamique pour finir ensuite par validation expérimentale sur maquette physique temps réel hybride basée sur l'émulation (PHIL). La partie simulation concerne la modélisation des différents éléments de la microcentrale hydraulique tel que la turbine, la génératrice et l'interface d'électronique de puissance ainsi que le développement des lois de commande et la synthèse des différents régulateurs. Deux stratégie de contrôle ont été étudié, la première dite commande en vitesse associé à un algorithme MPPT adaptatif développé au cours de la thèse et la deuxième dite en puissance. Le management des contrôles commandes pour assurer la fonction de secours (backup) de la microcentrale hydraulique a été simulé et validé expérimentalement. Et enfin la transition rapide entre les deux modes de fonctionnement d'une petite station de transfert d'énergie par pompage a été proposé et validé par émulation sur la maquette physique.
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Mendes, Melchuna Aline. "Experimental study and modeling of methane hydrates cristallization under flow from emulsions with variable fraction of water and anti-agglomerant." Thesis, Lyon, 2016. http://www.theses.fr/2016EMSE0811/document.
Повний текст джерелаАнотація:
La cristallisation des hydrates pendant la production de pétrole est une source de risques, surtout liés au bouchage des lignes de production dû à l’agglomération des hydrates. Pendant l'extraction de pétrole, l'huile et l'eau circulent dans le pipeline et forment une émulsion instable. La phase eau se combine avec les composants d'hydrocarbures légers et peut former des hydrates. La cristallisation des hydrates a été intensivement étudiée, principalement à faible fraction d’eau. Cependant, lorsque le champ de pétrole devient mature, la fraction d’eau augmente et peut devenir la phase dominante, un système peu étudié concernant à la formation d'hydrates. Plusieurs techniques peuvent être combinées pour éviter ou remédier la formation d'hydrates. Récemment, une nouvelle classe d'additifs a commencé à être étudiée : Inhibiteurs d'Hydrates à Bas Dosage (LDHI), divisés en Inhibiteurs Cinétiques (KHI-LDHI) et anti-agglomérants (AA-LDHI).Ce travail est une étude paramétrique de la formation d'hydrates à partir de l'émulsion, en variant la fraction d’eau, le débit, en absence et en présence d’AA-LDHI. Les expériences ont été réalisées sur la boucle d'écoulement Archimède, qui est en mesure de reproduire les conditions de la mer profonde. L'objectif de cette étude est d'améliorer la compréhension de la formation d'hydrate et de comprendre comment l'additif dispersant évite l'agglomération. Pour ce faire, un modèle comportemental de la cristallisation pour les systèmes sans et avec additif a été développé. Il a également été proposé une technique pour déterminer la phase continue du système et un mécanisme d'action pour l'anti-agglomérant a été suggéréCrystallization of hydrates during oil production is a major source of hazards, mainly related to flow lines plugging after hydrate agglomeration. During the petroleum extraction, oil and water circulate in the flow line, forming an unstable emulsion. The water phase in combination with light hydrocarbon components can form hydrates. The crystallization of hydrates has been extensively studied, mainly at low water content systems. However, as the oil field matures, the water fraction increases and can become the dominant phase, a system less known in what concerns hydrate formation. Actually, several techniques can be combined to avoid or remediate hydrate formation. Recently, a new class of additives called Low Dosage Hydrate Inhibitor (LDHI) started to be studied, they are classified as Kinetic Hydrate Inhibitors (KHI-LDHI) and Anti-Agglomerants (AA-LDHI).This work is a parametric study about hydrate formation from emulsion systems ranging from low to high water content, where different flow rates and the anti-agglomerant presence were investigated. The experiments were performed at the Archimède flow loop, which is able to reproduce deep sea conditions. The goal of this study is enhancing the knowledge in hydrate formation and comprehending how the dispersant additive acts to avoid agglomeration. For this matter, it was developed a crystallization topological model for the systems without and with additive. A technique to determine the system continuous phase and a mechanism of the anti-agglomerant action from the chord length measurements were also proposed
42
Refay, Yahya Ali. "The influence of variable amounts of irrigation water and nitrogen fertilizer and their interaction on the development, growth and nitrogen uptake of grain orghum." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184677.
Повний текст джерелаАнотація:
The influence of variable amounts of irrigation water and nitrogen fertilizer and their interaction on the development, growth, grain yield and nitrogen uptake of grain sorghum were studied under monocrop (May 21 planting) and simulated double crop (July 1 planting) in the 1985 growing season and under monocrop in the 1986 growing season. Six grain sorghum hybrids, three of which had a higher grain yielding ability and the other three with a lower grain in yielding ability, were used in this study conducted at the University of Arizona, Marana Agricultural Center. All six hybrids were grown under two planting dates (May 21, July 1), two levels of irrigation water (dry, wet), and two levels of nitrogen fertilizer (0, 112 kg N/ha) in the 1985 growing season. In the 1986 growing season, two hybrids were grown under three levels of irrigation water (dry, medium, and wet) and three levels of nitrogen fertilizer (0, 84, 168 kg N/ha). Planting on May 21 (monocrop) had more days to 50% bloom, leaf area, heads number, grain yield and total dry weight than the July 1 planting (double crop). However, planting on July 1 produced a longer head exsertion (peduncle length) compared to May 21 planting. Head length, plant height, 500 seed weight, and grain volume-weight were not affected by planting date. Water stress reduced head exsertion, head length, plant height, head number, 500 seed weight, grain yield and total dry matter. However, numbers of days to 50% bloom were increased by dry treatment. Leaf area and grain volume-weight were not significantly affected by water levels. Under the conditions of this study, nitrogen fertilizer rates did not produce an effect on most of the agronomic characteristics of grain sorghum hybrids studied in this experiment. However, increased nitrogen fertilizer rates increased the uptake and nitrogen concentration in all growth stages of hybrids in the 1986 growing season.
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PAN, GUIRONG. "MORPHOLOGY AND PROPERTIES OF ANTI-CORROSION ORGANOSILANE FILMS." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1152291690.
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Xu, Yuelu. "Essays on Water Quality Management for the Chesapeake Bay Watershed." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/96943.
Повний текст джерелаАнотація:
Water quality management for agricultural production is a complicated and interesting problem. Hydrological and economic factors must be considered when designing strategies to reduce nutrient runoff from agricultural activities. This dissertation is composed of three chapters that investigate cost-effective ways to mitigate water pollution from agricultural nonpoint pollution sources and explore farmers' incentives when participating in water quality trading programs.
Chapter 1 investigates landscape targeting of best management practices (BMPs) based on topographic index (TI) to determine how targeting would affect costs of meeting nitrogen (N) loading goals for Mahantango watershed, Pennsylvania. We use the results from two climate models and the mean of the ensemble of seven climate models to estimate expected climate changes and the Soil and Water Assessment Tool-Variable Source Area (SWAT-VSA) model to predict crop yields and N export. Costs of targeting and uniform placement of BMPs across the entire study area (4.23 km2) are compared under historical and future climate scenarios. We find that with a goal of reducing N loadings by 25%, spatial targeting methods could reduce costs by an average of 30% compared with uniform BMP placement under three historical climate scenarios. Cost savings from targeting are 38% under three future climate scenarios. Chapter 2 scales up the study area to the Susquehanna watershed (71,000 km2). We examine the effects of targeting the required reductions in N runoff within counties, across counties, and both within and across counties for the Susquehanna watershed. We set the required N reduction to 35%. Using the uniform strategy to meet the required N reduction as the baseline, results show that costs of achieving a regional 35% N reduction goal can be reduced by 13%, 31% and 36% with cross-county targeting, within-county targeting and within and across county targeting, respectively.
Results from Chapters 1 and 2 suggest that cost effectiveness of government subsidy programs for water quality improvement in agriculture can be increased by targeting them to areas with lower N abatement costs. In addition, targeting benefits are likely to be even larger under climate change.
Chapter 3 investigates the landowner's nutrient credit trading behavior when facing the price uncertainty given the credits are allowed to be banked for future use. A two-step decision model is used in this study. For the first step, we determine the landowner's application level of a BMP on working land in the initial time period. The nutrient credits awarded to the landowner depend on the nutrient reduction level at the edge of field generated by the BMP application. For the second step, we use an intertemporal model to examine the landowner's credit trading behavior with stochastic price fluctuations over time and with transaction costs. The theoretical framework is applied with a numerical simulation incorporated with a hydro-economic model and dynamic programming. Nutrient Management (NM) is selected as the BMP on working land to generate N credits. We find that gains to the landowner from credit banking increase with higher price volatility and with higher price drift, but that gains are larger with price volatility. However, for a landowner holding a small amount of nutrient credits, the gains from credit banking are small due to transaction costs.Doctor of Philosophy
Two considerations are critical for efforts to mitigate nutrient runoff from nonpoint sources: cost effectiveness of strategies to reduce nutrient runoff and landowners' incentives to participate in these programs. This dissertation is composed of three manuscripts, aiming to evaluate the cost effectiveness of government subsidy programs for water quality management in agriculture and investigate the landowner's incentives to participate in water quality trading programs for the Chesapeake Bay watershed. Chapter 1 investigates gains from targeting Best Management Practices (BMPs) under current and future climate conditions based on the soil characteristics relative to uniform BMP application for a small experimental watershed (4.23km2). Chapter 2 scales up the study area to a 71,000 km2 watershed and treats each county within the watershed as a representative farm to explore economic gains from targeting within county and across county based on counties' physical conditions and agricultural patterns. Both Chapters show that cost-effectiveness of government subsidy programs can be improved by spatial targeting BMPs to areas with lower abatement costs. Gains from targeting increase under climate change. In Chapter 3 we shows how a landowner's revenues from nutrient credit selling will be affected if the credits are allowed to be banked for future use when she faces price uncertainty. We find that gains to the landowner from credit banking increase more with higher price volatility than with higher price drift. Gains from banking are largely reduced by transaction costs associated with trading.
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Ghazizadeh, Fard Seyed Mohammad Ali. "An Adaptive Well-Balanced Positivity Preserving Central-Upwind Scheme for the Shallow Water Equations Over Quadtree Grids." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40392.
Повний текст джерелаАнотація:
Shallow water equations are widely used to model water flows in the field of hydrodynamics and civil engineering. They are complex, and except for some simplified cases, no analytical solution exists for them. Therefore, the partial differential equations of the shallow water system have been the subject of various numerical analyses and studies in past decades. In this study, we construct a stable and robust finite volume scheme for the shallow water equations over quadtree grids. Quadtree grids are two-dimensional semi-structured Cartesian grids that have different applications in several fields of engineering, such as computational fluid dynamics. Quadtree grids refine or coarsen where it is required in the computational domain, which gives the advantage of reducing the computational cost in some problems.
Numerical schemes on quadtree grids have different properties. An accurate and robust numerical scheme is able to provide a balance between the flux and source terms, preserve the positivity of the water height and water surface, and is capable of regenerating the grid with respect to different conditions of the problem and computed solution. The proposed scheme uses a piecewise constant approximation and employs a high-order Runge-Kutta method to be able to make the solution high-order in space and time. Hence, in this thesis, we develop an adaptive well-balanced positivity preserving scheme for the shallow water system over quadtree grids utilizing different techniques. We demonstrate the formulations of the proposed scheme over one of the different configurations of quadtree cells. Six numerical benchmark tests confirm the ability of the scheme to accurately solve the problems and to capture small perturbations.
Furthermore, we extend the proposed scheme to the coupled variable density shallow water flows and establish an extended method where we focus on eliminating nonphysical oscillations, as well as well-balanced, positivity preserving, and adaptivity properties of the scheme. Four different numerical benchmark tests show that the proposed extension of the scheme is accurate, stable, and robust.
46
Leow, Aaron S. "Analysis of an aerobic membrane bioreactor with the application of event detection software and variable operational filtration modes." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447070203.
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Costello, Oliver Wood. "Temporal Variations in Spring Water Chemistry and Comparison of Variable Paleozoic Aquifer Discharges in the Ridge and Valley Province of Northwestern Georgia." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/geosciences_theses/18.
Повний текст джерелаАнотація:
The fluctuations in solute concentrations from eight springs in the Ridge and Valley Province in northwestern Georgia were used to determine flow types and to measure each aquifer’s ability to remove contamination. The target springs are located along a northeast trending line in the Ridge and Valley Province of northwest Georgia. This study determined and interpreted the fluctuations in chemistry of each of the sampled spring’s water based upon temporal variations of precipitation in the area and variations in the chemistries measured at each weekly sampling event. Analysis determined that carbonate springs that showed characteristics of diffuse flow, including stable conductance during variable rain events and greater than zero saturation indices increase the potential for the aquifer to filter potential contaminants before the spring discharge. This study attempts to show that by identifying pre-filtered drinking water sources quickly is possible, through field and laboratory analysis.
48
Tesfa, Teklu K. "Distributed Hydrological Modeling Using Soil Depth Estimated from Landscape Variable Derived with Enhanced Terrain Analysis." DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/616.
Повний текст джерелаАнотація:
The spatial patterns of land surface and subsurface characteristics determine the spatial heterogeneity of hydrological processes. Soil depth is one of these characteristics and an important input parameter required by distributed hydrological models that explicitly represent spatial heterogeneity. Soil is related to topography and land cover due to the role played by topography and vegetation in affecting soil-forming processes. The research described in this dissertation addressed the development of statistical models that predict the soil depth pattern over the landscape; derivation of new topographic variables evaluated using both serial and parallel algorithms; and evaluation of the impacts of detailed soil depth representation on simulations of stream flow and soil moisture. The dissertation is comprised of three papers. In paper 1, statistical models were developed to predict soil depth pattern over the watershed based on topographic and land cover variables. Soil depth was surveyed at locations selected to represent the topographic and land cover variation at the Dry Creek Experimental Watershed, near Boise, Idaho. Explanatory variables were derived from a digital elevation model and remote sensing imagery for regression to the field data. Generalized Additive and Random Forests models were developed to predict soil depth over the watershed. The models were able to explain about 50% of the soil depth spatial variation, which is an important improvement over the soil depth extracted from the SSURGO national soil database. In paper 2, definitions of the new topographic variables derived in the effort to model soil depth, and serial and Message Passing Interface parallel implementations of the algorithms for their evaluation are presented. The parallel algorithms enhanced the processing speed of large digital elevation models as compared to the serial recursive algorithms initially developed. In paper 3, the impact of spatially explicit soil depth information on simulations of stream flow and soil moisture as compared to soil depth derived from the SSURGO soil database has been evaluated. The Distributed Hydrology Vegetation Soil Model was applied using automated parameter optimization technique with all input parameters the same except soil depth. Stream flow was less impacted by the detailed soil depth information, while simulation of soil moisture was slightly improved due to the detailed representation of soil depth.
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Sassi, Kamal M. "Optimal scheduling, design, operation and control of reverse osmosis desalination : prediction of RO membrane performance under different design and operating conditions, synthesis of RO networks using MINLP optimization framework involving fouling, boron removal, variable seawater temperature and variable fresh water demand." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5671.
Повний текст джерелаАнотація:
An accurate model for RO process has significant importance in the simulation and optimization proposes. A steady state model of RO process is developed based on solution diffusion theory to describe the permeation through membrane and thin film approach is used to describe the concentration polarization. The model is validated against the operation data reported in the literature. For the sake of clear understanding of the interaction of feed temperature and salinity on the design and operation of RO based desalination systems, simultaneous optimization of design and operation of RO network is investigated based on two-stage RO superstructure via MINLP approach. Different cases with several feed concentrations and seasonal variation of seawater temperature are presented. Also, the possibility of flexible scheduling in terms of the number of membrane modules required in operation in high and low temperature seasons is investigated A simultaneous modelling and optimization method for RO system including boron removal is then presented. A superstructure of the RO network is developed based on double pass RO network (two-stage seawater pass and one-stage brackish water pass). The MINLP problem based on the superstructure is used to find out an optimal RO network which will minimize the total annualized cost while fulfilling a given boron content limit. The effect of pH on boron rejection is investigated at deferent seawater temperatures. The optimal operation policy of RO system is then studied in this work considering variations in freshwater demand and with changing seawater temperature throughout the day. A storage tank is added to the RO layout to provide additional operational flexibility and to ensure the availability of freshwater at all times. Two optimization problems are solved incorporating two seawater temperature profiles, representing summer and winter seasons. The possibility of flexible scheduling of cleaning and maintenance of membrane modules is investigated. Then, the optimal design and operation of RO process is studied in the presence of membrane fouling and including several operational variations such as variable seawater temperature. The cleaning schedule of single stage RO process is formulated as MINLP problem using spiral wound modules. NNs based correlation has been developed based on the actual fouling data which can be used for estimating the permeability decline factors. The correlation based on actual data to predict the annual seawater temperature profile is also incorporated in the model. The proposed optimization procedure identified simultaneously the optimal maintenance schedule of RO network including its design parameters and operating policy. The steady state model of RO process is used to study the sensitivity of different operating and design parameters on the plant performance. A non-linear optimization problem is formulated to minimize specific energy consumption at fixed product flow rate and quality while optimizing the design and operating parameters. Then the MINLP formulation is used to find the optimal designs of RO layout for brackish water desalination. A variable fouling profile along the membrane stages is introduced to see how the network design and operation of the RO system are to be adjusted Finally, a preliminary control strategy for RO process is developed based on PID control algorithm and a first order transfer function (presented in the Appendix).
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Yu, Jing. "A THREE-DIMENSIONAL BAY/ESTUARY MODEL TO SIMULATE WATER QUALITY TRANSPORT." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2434.
Повний текст джерелаАнотація:
This thesis presents the development of a numerical water quality model using a general paradigm of reaction-based approaches. In a reaction-based approach, all conceptualized biogeochemical processes are transformed into a reaction network. Through the decomposition of species governing equations via Gauss-Jordan column reduction of the reaction network, (1) redundant fast reactions and irrelevant kinetic reactions are removed from the system, which alleviates the problem of unnecessary and erroneous formulation and parameterization of these reactions, and (2) fast reactions and slow reactions are decoupled, which enables robust numerical integrations. The system of species transport equations is transformed to reaction-extent transport equations, which is then approximated with two subsets: algebraic equations and kinetic-variables transport equations. As a result, the model alleviates the needs of using simple partitions for fast reactions. With the diagonalization strategy, it makes the inclusion of arbitrary number of fast and kinetic reactions relatively easy, and, more importantly, it enables the formulation and parameterization of kinetic reactions one by one. To demonstrate the general paradigm, QAUL2E was recasted in the mode of a reaction network. The model then was applied to the Loxahatchee estuary to study its response to a hypothetical biogeochemical loading from its surrounding drainage. Preliminary results indicated that the model can simulate four interacting biogeochemical processes: algae kinetics, nitrogen cycle, phosphorus cycle, and dissolved oxygen balance.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering