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1
Romey, Bernard Timothy. "Modeling Spawning Habitat Potential for Chum (Onchorhynchus keta) and Pink Salmon (O. gorbuscha) in Relation to Landscape Characteristics in Coastal Southeast Alaska." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4252.
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In response to the increasing need for ecosystem services throughout the Southeast Alaska region, decision makers are tasked with balancing the need for natural resources with salmon conservation. However, accurate historical and current information on salmonid population abundance, freshwater distribution, and habitat quality are sparse with limited resolution for large portions of this remote and rugged landscape. Here, I created Intrinsic Potential (IP) models for chum and pink salmon to predict the potential for portions of coastal rivers to provide high-quality spawning habitat. I developed IP models for both species from field redd surveys and synthetic habitat variables derived from 1-m resolution digital elevation models. The surveys were performed at 49 study reaches in five coastal drainage basins on the north end of Chichagof Island, Southeast Alaska. I used a spatially balanced random sampling design that included field surveys for redds during two field seasons with contrasting precipitation patterns and disparate adult salmon escapements. The IP models predict probable spawning habitat for both species based on persistent landform characteristics and hydrologic processes that control the formation and distribution of spawning habitat across the landscape. Selection of persistent reach variables for both species IP models was informed by principal component analysis (PCA), resource selection ratios, random forest modeling, and regression models of field and synthetic variable comparisons. I observed primarily one spawning strategy by chum salmon associated with mainstem channels, and two distinct spawning strategies for pink salmon related to small moderate-gradient channels and tributaries, and lower drainage basin mainstem channels. The relationships suggest that chum and pink salmon primarily selected for unconstrained channel types in large-and small-size channels, with chum salmon being more selective toward the larger mainstem channels, and pink salmon selecting for smaller channels and tributaries. The prediction of chum salmon redd presence within a specific reach for both high and low streamflow regimes was explained by channel gradient, floodplain width, and mean annual flow in order of importance. In general, chum salmon redds were observed in larger unconstrained low-gradient floodplain reaches where accumulation of deposited gravels and adequate flow produce habitat heterogeneity suitable for spawning. Pink salmon redd presence for both survey years was explained by channel gradient, reach elevation, and mean annual flow, in order of importance. Specifically, when flows allowed upstream access, spawning pink salmon utilized smaller moderate-gradient channels where substrate size and flows were better suited to their smaller body size. Remotely sensed persistent fish habitat data is valuable information for helping understand fish population distributions across the landscape. These synthetic metrics enabled the identification and evaluation of persistent landscape features as probable predictors of IP. Validation of LiDAR-derived channel characteristics indicated channel lengths measured from the DEM were 12% longer than field measured channel length, primarily for channels wider than 10 meters. Thus, understanding the limitations of the data is important so that decision makers do not unintentionally set unrealistic objectives. This research highlights the utility of using IP models with high resolution remote sensing to expand known distributions and quality of spawning habitat for these two species in Southeast Alaska coastal streams.
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Jones, Hannah Elizabeth Mary. "Mathematical models for red squirrel conservation." Thesis, Heriot-Watt University, 2017. http://hdl.handle.net/10399/3340.
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In this thesis we develop mathematical models to understand the process of ecological invasion when the invading species also carries a disease that is harmful to the native species. In particular we focus on a key case study system of the invasion of grey squirrels and replacement of red squirrels in the UK, in which the shared disease, squirrelpox, has been suggested as a key driver of the rapid expansion of grey squirrels. Our initial study focused on examining the viability of red squirrels in the stronghold forests of Kidland and Uswayford in Northumberland. These are commercially managed forests that Forestry Commission England manage to improve red squirrel population viability. Through close collaboration with the Forestry Commission, we developed a mathematical model that could test squirrel population viability for a range of felling and replanting strategies. Our findings have been used to direct the forest design plans that will be implemented in these forests. Our second study used spatial, stochastic modelling techniques to model the replacement of red squirrels and subsequent control of grey squirrels on the Isle of Anglesey. Our findings indicated that the replacement of red squirrels by grey squirrels on the island was largely driven by competitive interactions. However, on a local level squirrelpox epidemics could occur and lead to mortality in red squirrel populations. Our model was also fitted to data on the control and eradication of grey squirrels and reintroduction of red squirrels that took place on the Isle of Anglesey between 1998-2013. Our fitted model was then used to examine the best conservation strategies to protect the red squirrels on Anglesey. Our final study compared key findings on the process of disease-mediated invasion in deterministic and stochastic model frameworks. The deterministic frameworks predict that a wave of disease can spread through a native population in advance of a wave of replacement of the invading species. A stochastic representation of this system indicated that this wave of disease in advance of the wave of replacement may not occur if the disease is too virulent to the native species. However, if the disease is supported by the invading species, it will still mediate the invasion at the interface between the native and invading species where local epidemic disease outbreaks can occur. In general this thesis shows that mathematical models are powerful tools for the conservation management of native species under threat from invasion.
3
Ashour, Osama Naim. "Receptivity to free stream acoustic disturbances due to a roughness element on a flat plate." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09052009-040628/.
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Vionnet, Leticia Beatriz, Thomas III Maddock, and David C. Goodrich. "Investigations of stream-aquifer interactions using a coupled surface-water and ground-water flow model." Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1997. http://hdl.handle.net/10150/615700.
Full textAbstract:
A finite element numerical model is developed for the modeling of coupled
surface-water flow and ground-water flow. The mathematical treatment of subsurface
flows follows the confined aquifer theory or the classical Dupuit approximation for
unconfined aquifers whereas surface-water flows are treated with the kinematic wave
approximation for open channel flow. A detailed discussion of the standard approaches to
represent the coupling term is provided. In this work, a mathematical expression similar
to Ohm's law is used to simulate the interacting term between the two major hydrological
components. Contrary to the standard approach, the coupling term is incorporated
through a boundary flux integral that arises naturally in the weak form of the governing
equations rather than through a source term. It is found that in some cases, a branch cut
needs to be introduced along the internal boundary representing the stream in order to
define a simply connected domain, which is an essential requirement in the derivation of
the weak form of the ground-water flow equation. The fast time scale characteristic of
surface-water flows and the slow time scale characteristic of ground-water flows are
clearly established, leading to the definition of three dimensionless parameters, namely, a
Peclet number that inherits the disparity between both time scales, a flow number that
relates the pumping rate and the streamflow, and a Biot number that relates the
conductance at the river-aquifer interface to the aquifer conductance.
The model, implemented in the Bill Williams River Basin, reproduces the observed
streamflow patterns and the ground-water flow patterns. Fairly good results are obtained
using multiple time steps in the simulation process.
5
Vionnet, Leticia Beatriz, and Leticia Beatriz Vionnet. "Investigation of stream-aquifer interactions using a coupled surface water and groundwater flow model." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187414.
Full textAbstract:
A finite element numerical model is developed for the modeling of coupled surface-water flow and ground-water flow. The mathematical treatment of subsurface flows follows the confined aquifer theory or the classical Dupuit approximation for unconfined aquifers whereas surface-water flows are treated with the kinematic wave approximation for open channel flow. A detailed discussion of the standard approaches to represent the coupling term is provided. In this work, a mathematical expression similar to Ohm's law is used to simulate the interacting term between the two major hydrological components. Contrary to the standard approach, the coupling term is incorporated through a boundary flux integral that arises naturally in the weak form of the governing equations rather than through a source term. It is found that in some cases, a branch cut needs to be introduced along the internal boundary representing the stream in order to define a simply connected domain, which is an essential requirement in the derivation of the weak form of the ground-water flow equation. The fast time scale characteristic of surface-water flows and the slow time scale characteristic of ground-water flows are clearly established, leading to the definition of three dimensionless parameters, namely, a Peclet number that inherits the disparity between both time scales, a flow number that relates the pumping rate and the streamflow, and a Biot number that relates the conductance at the river-aquifer interface to the aquifer conductance. The model, implemented in the Bill Williams River Basin, reproduces the observed streamflow patterns and the ground-water flow patterns. Fairly good results are obtained using multiple time steps in the simulation process.
6
Ahn, Taejin 1957. "A procedure for the determination of a flow duration curve at an ungaged basin." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276585.
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The purpose of this study is to develop a method for predicting monthly flow duration curves for ungaged basins that are suitable for estimating average annual flow, and installed capacity and average annual energy generation at potential sites for hydropower development. The procedures were tested by developing monthly rainfall duration curves for five sample watersheds and then developing flow duration curves from the rainfall data. The methods were evaluated by comparing the predicted monthly flow duration curves to daily and monthly flow duration curves based on field data from the selected sites because a plant's potential energy output can be computed directly from a flow duration curve. The methods tested fit duration curves based on field data reasonably well and are suitable for preliminary evaluation of hydropower developments in ungaged basins.
7
Kamwi, Innocent Silibelo. "Fitting extreme value distributions to the Zambezi river flood water levels recorded at Katima Mulilo in Namibia." Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&.
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The aim of this research project was to estimate parameters for the distribution of annual maximum flood levels for the Zambezi River at Katima Mulilo. The estimation of parameters was done by using the maximum likelihood method. The study aimed to explore data of the Zambezi's annual maximum flood heights at Katima Mulilo by means of fitting the Gumbel, Weibull and the generalized extreme value distributions and evaluated their goodness of fit.
8
Putnam, Douglas Alan. "Forecasting for local water management." PDXScholar, 1985. https://pdxscholar.library.pdx.edu/open_access_etds/3540.
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Forecast models are investigated and developed for use in local water management to aid in determining short term water requirements and availability. The forecast models include precipitation occurrence and depth using a Markov chain model, temperature and solar radiation with a multivariate autoregressive model, and streamflow with autoregressive-moving average models. The precipitation, temperature, and solar radiation forecasts are used with a soil moisture model to determine water demands. A state space approach to the Muskingum-Cunge streamflow routing technique is developed. The forecast water demands and streamflow forecasts are used as inputs to this routing model. Forecast model errors and propagation of these errors from one model into the next are investigated.
9
Hofstede, Coen Matthijs. "Ice Stream Dynamics: A Transition between Sheet Flow and Shelf Flow." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/HofstedeCM2008.pdf.
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Imam, Bisher 1960. "Evaluation of disaggregation model in arid land stream flow generation." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277033.
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A Disaggregation model was tested for arid land stream flow generating. The test was performed on data from Black River, near Fort Apache, Arizona. The model was tested in terms of preserving the relevant historical statistics on both monthly and daily levels, the monthly time series were disaggregated to a random observation of their daily components and the daily components were then reaggregated to yield monthly values. A computer model (DSGN) was developed to perform the model implementation. The model was written and executed on the Macintosh plus personal computer Data from two months were studied; the October data represented the low flow season, while the April data represented the high flow season. Twenty five years of data for each month was used. The generated data for the two months was compared with the historical data.
11
Luxhoj, James T. "A dynamic programming approach to the multi-stream replacement problem." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/49829.
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12
Linke, Simon, and n/a. "River conservation planning: accounting for condition, vulnerability and connected systems." University of Canberra. Resource, Environmental & Heritage Sciences, 2006. http://erl.canberra.edu.au./public/adt-AUC20070716.155500.
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Conservation science in rivers is still lagging behind its terrestrial and marine counterparts,
despite increasing threats to freshwater biodiversity and extinction rates being estimated as
five times higher than in terrestrial ecosystems. Internationally, most protected rivers have
been assigned reserve status in the framework of terrestrial conservation plans, neglecting
catchment effects of disturbance. While freshwater conservation tools are mainly index based
(e.g. richness, rarity), modern terrestrial and marine conservation planning methods use
complementarity-based algorithms - proven to be most efficient at protecting a large number
of taxa for the least cost. The few complementarity-based lotic conservation efforts all use
broad river classifications instead of biota as targets, a method heavily disputed in the
literature. They also ignore current condition and future vulnerability.
It was the aim of this thesis to develop a framework for conservation planning that:
a) accounts for the connected nature of rivers
b) is complementarity based and uses biota as targets
c) integrates current status and future vulnerability
I developed two different approaches using macroinvertebrate datasets from Australia,
Canada and the USA. The first new method was a site/based two-tiered approach integrating
condition and conservation value, based on RIVPACS/AUSRIVAS � a modelling technique
that predicts macroinvertebrate composition. The condition stage assesses biodiversity loss by
estimating a site-specific expected assemblage and comparing it to the actual observed
assemblage. Sites with significant biodiversity loss are flagged for restoration, or other
management actions. All other sites progress to the conservation stage, in which an index of
site-specific taxonomic rarity is calculated. This second index (O/E BIODIV) assesses the
number of rare taxa (as defined by <50% probability of occurrence). Using this approach on a dataset near Sydney, NSW, Australia, I was able to identify three regions: 1) an area in need
of restoration; 2) a region of high conservation value and 3) an area that had high
conservation potential if protection and restoration measures could counteract present
disturbance.
However, a second trial run with three datasets from the USA and Canada highlighted
problems with O/E (BIODIV). If common taxa are predicted at lower probabilities of
occurrence (p<50%) because of model error, they enter the index and change O/E (BIODIV).
Therefore, despite an attractive theoretical grounding, the application of O/E (BIODIV) will
be restricted to datasets where strong environmental gradients explain a large quantity of
variation in the data and permit accurate predictions of rare taxa. It also requires extensive
knowledge of regional species pools to ensure that introduced organisms are not counted in
the index.
The second approach was a proper adaptation of terrestrial complementarity algorithms and
an extension to the Irreplaceability-Vulnerability framework by Margules and Pressey (2000).
For this large-scale method, distributions for 400 invertebrate taxa were modeled across 1854
subcatchments in Victoria, Australia using Generalised Additive Models (GAMs). The best
heuristic algorithm to estimate conservation value was determined by calculating the
minimum area needed to cover all 400 taxa. Solutions were restricted to include rules for the
protection of whole catchments upstream of a subcatchment that contained the target taxon. A
summed rarity algorithm proved to be most efficient, beating the second best solution by 100
000 hectares. To protect 90% of the taxa, only 2% of the study area need to be protected. This
increases to 10% of the study area when full representation of the targets is required.
Irreplaceability was calculated by running the heuristic algorithm 1000 times with 90% of the
catchments randomly removed. Two statistics were then estimated: f (the frequency of
selection across 1000 runs) and average c (contribution to conservation targets). Four groups of catchments were identified: a) catchments that have high contributions and are always selected; b) catchments that have high contributions and are not always selected; c)
catchments that are always chosen but do not contribute many taxa; d) catchments that are
rarely chosen and did not contribute many taxa. Summed c, the sum of contributions over
1000 runs was chosen as an indicator of irreplaceability, integrating the frequency of selection
and the number of taxa protected.
Irreplaceability (I) was then linked to condition (C) and vulnerability (V) to create the ICVframework
for river conservation planning. Condition was estimated using a stressor gradient
approach (SGA), in which GIS layers of disturbance were summarised to three principal axes
using principal components analysis (PCA). The main stressor gradient � agriculture �
classified 75% of the study area as disturbed, a value consistent with existing assessments of
river condition. Vulnerability was defined as the likelihood that land use in a catchment
would intensify in the future. Hereby current tenure was compared to land capability. If a
catchment would support a land use that would have a stronger effect on the rivers than its
current tenure, it was classified as vulnerable. 79% of catchments contained more than 50%
vulnerable land.
When integrating the three estimators in the ICV-framework, seven percent of catchments
were identified as highly irreplaceable but in degraded condition. These were flagged for
urgent restoration. Unprotected, but highly irreplaceable and highly vulnerable catchments
that were still in good condition made up 2.5% of the total area. These catchments are prime
candidates for river reserves.
The ICV framework developed here is the first method for systematic conservation planning
in rivers that is complementarity-based, biota-driven but flexible to other conservation targets
and accounts for catchment effects, thus fulfilling all the gaps outlined in the aims.
13
El, Moueddeb Khaled. "Principles of energy and momentum conservation to analyze and model air flow for perforated ventilation ducts." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42024.
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A theoretical model was developed to predict the air distribution pattern and thus to design perforated ventilation ducts equipped with a fan. The analysis of the air distribution pattern of such systems requires accurate measurement procedures. Several experimental methods were tested and compared. Accordingly, the piezometric flush taps and thermo-anemometer were selected to measure respectively the duct air pressure and the outlet air flow.Based on the equations of energy and momentum conservation, a model was formulated to predict the air flow performance of perforated ventilation ducts and to evaluate the outlet discharge angle and the duct regain coefficients without evaluating frictional losses. The basic assumptions of the model were validated by experimentally proving the equivalence of the friction losses expressed in the 2 cited equations. When compared to experimental results measured from four wooden perforated ventilation ducts with aperture ratios of 0.5, 1.0, 1.5, and 2.0, the model predicted the outlet air flow along the full length of perforated duct operated under turbulent flow conditions with a maximum error of 9%. The regain coefficient and the energy correction factor were equal to one, and the value of the discharge coefficient remained constant at 0.65, along the full length of the perforated duct. The outlet air jet discharge angle varied along the entire duct length, and was not influenced by friction losses for turbulent flow.
Assuming a common effective outlet area, the model was extended to match the performance of the fan and the perforated duct and to determine their balance operating point.
14
Lam, King-hang, and 林勁恆. "Techniques for dynamic modelling of BIPV in supporting system design and BEMS." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39558460.
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Choy, Kin-yee, and 蔡建怡. "On modelling using radial basis function networks with structure determined by support vector regression." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B29329619.
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Chan, Shu-ning, and 陳樹寧. "Impact of river training on the hydraulics and sediment transport of Shenzhen River." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43572194.
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Slaughter, Andrew Robert. "Modelling the relationship between flow and water quality in South African rivers." Thesis, Rhodes University, 2011. http://hdl.handle.net/10962/d1006196.
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The National Water Act (Act 36 of 1998) provides for an ecological Reserve as the quantity (flow) and quality of water needed to protect aquatic ecosystems. While there are methods available to quantify the ecological Reserve in terms of flow, methods of linking flow to water quality are lacking. Therefore, the research presented in this thesis investigated various modelling techniques to estimate the effect of flow on water quality. The aims of the research presented in this thesis were: Aim 1: Can the relationship between flow and water quality be accurately represented by simple statistical models? Aim 2: Can relatively simple models accurately represent the relationship between flow and water quality? Aim 3: Can the effect of diffuse sources be omitted from a water quality model and still obtain realistic simulations, and if so under what conditions? Aim 4: Can models that solely use historical monitoring data, accurately represent the relationships between flow and water quality? In Chapter 3, simple Q-C regressions of flow and water quality were investigated using Department of Water Affairs (DWA) historical monitoring data. It was found that while flow versus salinity regressions gave good regression fits in many cases, the Q-C regression approach is limited. A mechanistic/statistical model that attempted to estimate the point and diffuse signatures of nutrients in response to flow was developed in Chapter 4 using DWA historical monitoring data. The model was verified as accurate in certain case studies using observed point loading information. In Chapter 5, statistical models that link land cover information to diffuse nutrient signatures in response to flow using DWA historical data were developed. While the model estimations are uncertain due to a lack of data, they do provide an estimation of the diffuse signature within catchments where there is flow and land cover information available. Chapter 6 investigates the extension of an existing mass-balance salinity model to estimate the effect of saline irrigation return flow on in-stream salinity. The model gave accurate salinity estimates for a low order stream with little or no irrigation within its catchment, and for a permanently flowing river within a catchment used extensively for irrigation. Chapter 7 investigated a modelling method to estimate the reaction coefficients involved in nitrification using only DWA historical monitoring data. Here, the model used flow information to estimate the residence time of nutrients within the studied river reaches. While the model obtained good estimations of nitrification for the data it was applied to, very few DWA data sets were suitable for the model. Chapter 8 investigated the ability of the in-stream model QUAL2K to estimate nutrient concentrations downstream of point and diffuse inputs of nutrients. It was found that the QUAL2K model can give accurate results in cases where point sources dominate the total nutrient inputs into a river. However, the QUAL2K simulations are too uncertain in cases where there are large diffuse source inputs of nutrients as the load of the diffuse inputs is difficult to measure in the field. This research highlights the problem of data scarcity in terms of temporal resolution as well as the range of constituents measured within DWA historical monitoring data for water quality. This thesis in addition argues that the approach of applying a number of models is preferable to applying one model to investigate the research aims, as particular models would be suited to particular circumstances, and the development of new models allowed the research aims of this thesis to be explored more thoroughly. It is also argued that simpler models that simulate a few key processes that explain the variation in observed data, are more suitable for implementing Integrated Water Resource Management (IWRM) than large comprehensive water quality models. From this research, it is clear that simple statistical models are not adequate for modelling the relationship between flow and water quality, however, relatively simple mechanistic models that simulate a limited number of processes and water quality variables, can provide accurate representations of this relationship. Under conditions where diffuse sources are not a major factor within a catchment, models that omit diffuse sources can obtain realistic simulations of the relationship between flow and water quality. Most of the models investigated in this thesis demonstrate that accurate simulations of the relationships between flow and water quality can be obtained using solely historical monitoring data.
18
Watson, Eric Craig. "Use of Distance Weighted Metrics to Investigate Landscape-Stream Temperature Relationships Across Different Temporal Scales." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/3117.
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Stream ecosystems have experienced significant negative impacts from land use, resource exploitation, and urban development. Statistical models allow researchers to explore the relationships between these landscape variables and stream conditions. Weighting the relevant landscape variables based on hydrologically defined distances offers a potential method of increasing the predictive capacity of statistical models. Using observations from three grouped watersheds in the Portland Metro Area (n=66), I have explored the use of three different weighting schemes against the standard method of taking an areal average. These four different model groups were applied to four stream temperature metrics: mean seven-day moving average maximum daily temperature (Mean7dTmax), number of days exceeding 17.8 °C (Tmax7d>17.8), mean daily range in stream temperature (Range_DTR), and the coefficient of variation in maximum daily temperature (CV_Tmax). These metrics were quantified for the 2011 dry season. The strength of these model groups were also examined at a monthly basis for each of the four months within the dry season. The results demonstrate mixed effectiveness of the weighting schemes, dependent on both the stream temperature metric being predicted as well as the time scale under investigation. Models for Mean7dTmax showed no benefit from the inclusion of distance weighted metrics, while models for Range_DTR consistently improved using distance weighted explanatory variables. Trends in the models for 7dTmax>17.8 and CV_Tmax varied based on temporal scale. Additionally, all model groups demonstrated greater explanatory power in early summer months than in late summer months.
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Haltigin, Tim. "Three-dimensional numerical modeling of flow dynamics and investigation of temporal scour hole development around paired stream deflectors in a laboratory flume." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82249.
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A three-dimensional numerical model (PHOENICS) was used to investigate the role of stream deflector angle and length on the flow field in a rectangular laboratory flume. Subsequent bed topography surveys were performed to examine the role of obstruction angle on scour hole development over time. The model was capable of predicting laboratory velocity and turbulent kinetic energy measurements, performing better for flow over a flat stable bed than over a deformed sand bed. A new method of incorporating complex bed topography into a structured Cartesian mesh was developed in the process. Flow field properties such as dynamic pressure, velocity amplification, separation zone length and width, and downwelling extent and magnitude were found to be strongly dependent on deflector geometry. Equilibrium scour hole depths and geometry are also angle-dependent. A predictive equation was produced explaining the rate at which scour holes reach equilibrium, and compared well with existing literature. Finally, a method was developed whereby characteristics of the flow field over a flat, stable bed could be used to predict equilibrium scour hole geometry.
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Mattejat, Peter Paul. "Frequency analysis of low flows: comparison of a physically based approach and hypothetical distribution methods." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/101453.
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Several different approaches are applied in low flow frequency analysis. Each method's theory and application is explained. The methods are (1) physically based recession model dealing with time series, (2) log-Pearson type III and mixed log-Pearson type III using annual minimum series, (3) Double Bounded pdf using annual minimum series, (4) Partial Duration Series applying truncated and censored flows.
Each method has a computer program for application. One day low flow analysis was applied to 15 stations, 10 perennial streams and 5 intermittent streams. The physically based method uses the exponential baseflow recession with duration, initial recession flow, and recharge due to incoming storm as random variables, and shows promise as an alternative to black box methods, and is appealing because it contains the effect of drought length. Log-Pearson is modified to handle zero flows by adding a point mass probability for zero flows. Another approach to zero flows is the Double Bounded probability density function which also includes a point mass probability for zero flows. Maximum likelihood estimation is used to estimate distribution parameters. Partial Duration Series is applied due to drawbacks of using only one low flow per year in annual minimum series. Two approaches were used in Partial Duration Series (i) truncation, and (ii) censorship which represent different low flow populations. The parameters are estimated by maximum likelihood estimation.M.S.
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Valente, Bruno Selim Avian. "Elaboração de um algoritmo de projeto de trocadores de calor para utilização em otimização de redes de trocadores de calor." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266631.
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Orientador: Roger Josef ZempDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: A abordagem tradicional da estimativa da área no procedimento de síntese de redes de trocadores de calor exige a escolha de um conjunto típico de coeficientes de transferência de calor. Uma vez obtida a topologia da rede de trocadores de calor, o projeto detalhado dos trocadores pode exigir a consideração de restrições nas quedas da pressão disponíveis, alterando os valores dos coeficientes de transferência de calor utilizados inicialmente na avaliação da rede e invalidando a otimização econômica da mesma. Com isso tem-se um aumento nos custos de projeto tanto na parte construtiva como na forma de bombas e/ou compressores do processo. Esta dissertação tem como finalidade elaborar uma nova abordagem que possibilite estimar a área de troca térmica a partir de uma relação entre quedas de pressão e coeficientes de transferência de calor no lado do casco e dos tubos. Assim, partindo das quedas de pressão permitidas das correntes pode-se estimar a área e os coeficientes de transferência de calor de um trocador de calor, munido de dados de processo como carga térmica, temperaturas, propriedades físicas e quedas de pressão no lado do casco e dos tubos, e possibilitando uma análise econômica mais correta da rede de trocadores de calor. Os métodos já disponíveis para esta finalidade possuem limitações uma vez que são baseados no método de Kern, que inclui severas simplificações no seu modelo, e o de Bell, que utiliza equações empíricas dependentes de aspectos geométricos. O procedimento de análise de trocadores de calor tipo casco e tubos de Wills & Johnston, utilizado neste trabalho, é uma alternativa bastante viável para este tipo de problema por ser considerado teoricamente mais preciso, baseando-se em equações hidráulicas para o cálculo da queda de pressão no lado do casco considerando os diversos caminhos do fluido no interior do casco
Abstract: In the traditional approach of heat exchanger network synthesis the procedure for area targeting requires de choice of a set of typical heat transfer coefficients. After the heat exchanger network structure has been defined the individual exchangers are design. However, due to pressure drop restrictions the final heat exchanger design might require heat transfer coefficients that are very different from the one originally chosen, leading to increased exchanger area and increased capital cost. This work aims to develop a new that allows the estimate of a correct set of heat transfer coefficients and exchanger area based on available pressure drops. The propose procedure allows for the estimate of heat transfer coefficients and area based on the available pressure drops. Methods already available for this purpose show limitations: the method of Kern includes severe simplifications while the method of Bell uses empirical equations dependent on geometric aspects. The method of Wills & Johnston, used in the present work, is a very feasible alternative for this type of problem as it is based on the pressure drop of the different fluid paths inside the shell side of the exchanger
Mestrado
Sistemas de Processos Quimicos e Informatica
Mestre em Engenharia Química
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Anasis, John George. "A Combined Energy and Geoengineering Optimization Model (CEAGOM) for Climate Policy Analysis." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2620.
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One of the greatest challenges that will face humanity in the 21st century is the issue of climate change brought about by emissions of greenhouse gases. Energy use is one of the primary sources of greenhouse gas emissions. However, it is also one of the most important contributors to improved human welfare over the past two centuries and will continue to be so for years to come. This quandary has led a number of researchers to suggest that geoengineering may be required in order to allow for continued use of fossil fuels while at the same time mitigating the effects of the associated greenhouse gas emissions on the global climate. The goal of this research was to develop a model that would allow decision-makers and policy analysts to assess the optimal mix of energy and geoengineering resources needed to meet global or regional energy demand at the lowest cost while accounting for appropriate emissions, greenhouse gas concentration, or temperature rise constraints. The resulting software model is called the Combined Energy and Geoengineering Optimization Model (CEAGOM). CEAGOM was then used to analyze the recently announced U.S.-China emissions agreement and to assess what the optimal global energy resource mix might be over the course of the 21st century, including the associated potential need for geoengineering. These analyses yielded optimal mixes of energy and geoengineering resources that could be used to inform regional and global energy and climate management strategies.
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Zhou, Xueqing. "Predicting Solute Transport in Natural Streams - A Stochastic Approach." PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/5057.
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The existing theories for predicting longitudinal dispersion in straight open channels have long been recognized as inadequate when applied to natural rivers. These theories tend to grossly underestimate dispersion in real streams since an important mixing mechanism due to nonuniform river cross-section variations is not explicitly taken into account. Recognizing the important role of stream irregularities on solute transport and the analytical difficulties of classical deterministic analysis, we develop a stochastic approach for analyzing solute transport in natural streams. Variations in river width and bed elevation are conveniently represented as one-dimensional random fields, characterized by their autocorrelation functions. Advection and dispersion due to the combined effect of turbulent diffusion and nonuniform flow are described by the stochastic solute transport equation. When boundary variations are small and statistically homogeneous, a stochastic spectral technique is used to obtain closed-form stochastic solutions. In particular, closed-form expressions are obtained for effective mean solute transport velocity and effective dispersion coefficient reflecting mixing due to flow variations both within the river cross-section and in the streamwise direction. The results show that the mean behavior of solute transport in a statistically irregular stream can be described as a gradient dispersion process. The effective mean transport velocity in natural rivers is smaller than that in a corresponding uniform channel, and the effective longitudinal dispersion coefficient in natural rivers can be considerably greater than that of uniform open channels. The discrepancy between uniform channels and natural rivers increases rapidly as the variances of river width and bed elevation increase, especially when the mean flow Froude number is high.
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Hennlock, Magnus. "On strategic incentives and the management of stochastic renewable resources /." Uppsala : Dept. of Economics, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/2005124.pdf.
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Delboni, Roberta Regina 1979. "Dinamica populacional de microrganismos e a conservação de alimentos." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/307208.
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Orientador: Hyun Mo YangDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica
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Resumo: Um grande desafio para a indústria de alimentos é, por um lado, atender a demanda dos consumidores por alimentos minimamente processados, livres de aditivos químicos e submetidos a tramentos térmicos mais brandos, devido ao forte apelo como "alimentos naturais", mas, ao mesmo tempo, garantir a segurança microbiológica destes produtos. Para abordar quantitativamente o controle biológico como técnica de conservação, apresenta-se um modelo matemático da interação entre bactérias lácticas e o patógeno Listeria monocytogenes. A partir deste modelo, estuda-se a possível ação do ácido láctico e da bacteriocina, produzidos pela bactéria láctica, na redução do crescimento da Listeria no alimento. Através do conhecimento bioquímico de regulação da biossíntese de bacteriocina, desenvolve-se outro modelo, com enfoque na bacteriocina nisina. Mostra-se o efeito da nisina na resposta do sistema que regula a expressão de genes necessários para a biossíntese. Expandindo esse modelo, são incluídas equações para descrever também o processo de biossíntese, e avalia-se a resposta do sistema regulatório quando se aumenta a densidade de células da bactéria produtora. Observa-se comportamento típico de histerese. Mostra-se, assim, o funcionamento do mecanismo de "quorum sensing", ou seja, a produção da nisina regulada de maneira dependente da densidade celular, devido a uma transição entre o estado ativado e desativado do sistema regulatório, que correspondem às duas soluções estacionárias assintoticamente estáveis
Abstract: A major challenge for the food industry is the attending of demands of consumers for minimally processed foods, which do not contain chemical preservatives neither were submitted to intensive heat treatments, but at the same time ensuring microbiological safety of these products. To study quantitatively the biological control as a technique of conservation, we developed a mathematical model to describe the interaction between lactic acid bacteria and the pathogen Listeria monocytogenes in the food. The steady states and dynamical trajectories analyses of the model allowed us to study the possible action of the lactic acid and the bacteriocin, produced by lactic acid bacteria, in the reduction of activity of Listeria in the food. Through the knowledge of the bacteriocin biosynthesis biochemical regulation, we developed other model focusing on the production of bacteriocin nisin. We then have shown the effect of nisin on the response of the system which regulates the expression of genes required for biosynthesis. This model was extended to include synthesis of nisin in order to study the dynamic of the regulatory system in a growing bacterial population. Both models demonstrate a typical behavior of hysteresis. Using the last model, we have shown the cell-density-dependent regulation of bacteriocin production, called mechanism of quorum sensing, which is the switch between two stable steady solutions corresponding to non-activated and activated states of the regulatory system
Mestrado
Biomatematica
Mestre em Matemática Aplicada
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Winship, Arliss J. "Estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the North Sea." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/715.
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Dussán-Duque, Beatriz Salomé. "Ecology of the Guiana dolphin (Sotalia guianensis) in the Southern area of the Gulf of Morrosquillo, Colombia : implications for conservation." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/4153.
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Sotalia guianensis is listed as “Data Deficient” by the IUCN and as “Vulnerable” in Colombia. This study aimed to advance understanding of the ecology of this species and its habitats, and to provide information to conservation management in the southern Gulf of Morrosquillo, Colombia. Systematic boat-based surveys were conducted during 395 days in 2002-2006 and 2009-2010, following established routes. Total survey effort was 15,199 km in an area covering ~ 310km². Fine scale habitat use and behavioural modelling, photo-identification and mark-recapture techniques were used to analyze the ecological patterns for this species. The most recent abundance estimate of dolphins using the study area during dry and rainy seasons, varied from 225 (CV = 0.34; 95% CI: 118-426) to 232 (CV = 0.32; 95% CI: 127-246). Annual survival rate is estimated at 0.948 (95% CI = 0.876-0.980). Overall density was 0.74/km². Dolphins were present year-round in the whole study area. Results indicate that they do not use the study area uniformly and that the use of particular zones is related to eco-geographic variables. Dolphins showed a preference for waters greater than 3m in depth with a slightly increased preference for waters about 5m and 15-25m deep. The average group size was nine individuals. Some individuals show long-term high site fidelity to some zones within the study site boundaries. Even though the site fidelity to feeding areas varied individually, all the individuals focused primarily on one specific area. Foraging was among one of the most predominant behaviours observed. The individual movements show that some dolphins use both bay and gulf waters. Dolphins show a range of surface cooperative foraging and feeding strategies. These cooperative behaviours were influenced by zone, group size and prey type. Based on these results an area of special management for the species will be created in Colombia.
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Yang, GuoLu. "Modèle de transport complet en rivière avec granulométrie étendue." Grenoble 1, 1989. http://www.theses.fr/1989GRE10011.
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Les variations des lignes d'eau et du lit des rivieres alluvionnaires dans le cas du transport complet (charriage+suspension) des sediments en granulometrie etendue sont etudiees par un modele mathematique uni-dimensionnel. Dans ce modele le charriage et la suspension sont consideres comme deux phenomenes du transport en tenant compte d'un terme source-puits qui represente l'echange entre eux. Le terme source-puits est formule par un modele d'echanges stochastiques considerant trois etats: suspension, charriage et immobilite, les probabilites des etats sont obtenues par le processus de chaine de markov. Le modele conceptuel d'une "couche melangee" est introduit pour reproduire les phenomenes de pavage et de triage. Le systeme d'equations a resoudre est analyse par la methode des caracteristiques. Une solution numerique decouplee du systeme est presentee. Un nouvel algorithme, assurant le calcul couple du transport par convection-diffusion-reaction, est developpe. Des tests du modele mathematique sont systematiquement effectues afin d'examiner la sensibilite et montrer la precision du modele
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Didoné, Elizeu Jonas. "Modelagem de processos erosivos em uma bacia agrícola: limitações e possibilidades." Universidade Federal de Santa Maria, 2017. http://repositorio.ufsm.br/handle/1/11624.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESThe growing demand for modeling tools able represent erosive processes in catchments, and their connections, requires that mathematical modelling be associated with monitoring. This doctoral thesis sought to contribute to a description of the erosive processes at catchment scale, by combining monitoring and modeling techniques to reduce the impacts of agricultural activities in a large agricultural catchment through scenarios that simulate the impact of different conservation measures. Two studies were carried out in the Conceição River Catchment (800km2), a region characterized by the grain production system in the northwest of Rio Grande do Sul - Brazil. The first study sought to quantify the impact of different conservation measures on erosion and hydrosedimentological dynamics in a no-till agricultural catchment to simulate scenarios using the WATEM SEDEM model. Conservation measures reduced erosion and sediment yield in all scenarios. Crop leveling and terracing were the measures with greater impact in the reduction of the erosive process. The results demonstrate that soil losses due to erosion processes are significant and unsustainable in agricultural catchments in southern Brazil, and that soil erosion is exacerbated by the lack of information provided to the farmers and the use of isolated conservation measures without coordination at the catchment scale. The second study aimed to propose an efficient way to determine the current P factor through modeling, besides proposing conservation measures to better meet current practices. Four areas totaling 25 km2 were selected, representing the various properties present in the site. The efficiency of the current farming was determined by relating the angle between the sowing lines and the terrain level curves. In this study, values of P above 0.8 were obtained in over 60% of the area. This technique proved to be an important tool for determining factor P in a fast and spatialized way with potential for use in large areas, since an efficient determination of the P factor can result in a reduction of the erosion potential. In view of these results it is possible to affirm that conservation measures should not be isolated actions, but rather associated with other practices suitable for each type of land use. The use of mathematical models of erosion can be an important support tool in environmental management decision making and the methodology developed to determine the factor P in GIS can aid mathematical models to better simulate the impacts of conservation practices on erosive processes. Catchment scale modeling should be more widespread in Brazil in order to promote sustainable agricultural practices, reducing the anthropic impact on soil and water degradation. Farmers’ and local communities’ awareness should be raised to reduce soil degradation and sediment transfer to river systems.
A demanda por ferramentas de modelagem, com capacidade de representar os processos erosivos em bacias hidrográficas e suas conexões com os corpos hídricos, exige que o monitoramento esteja associado à modelagem. Este trabalho buscou contribuir para descrição dos processos erosivos em escala de grandes bacias agrícolas, a partir da combinação de técnicas de monitoramento e modelagem para reduzir os impactos das atividades agrícolas de uma grande bacia agrícola por meio de cenários que simulam o impacto de diferentes medidas conservacionistas. Para tanto, dois estudos foram conduzidos na bacia hidrográfica do Rio Conceição (800km2), região característica pelo sistema de produção de grãos no noroeste do Rio Grande do Sul. O primeiro estudo buscou quantificar o impacto de diferentes medidas conservacionistas na erosão e dinâmica hidrosedimentologica em uma bacia agrícola sob plantio direto para simular cenários utilizando o modelo WATEM SEDEM. Todos os cenários com medidas de conservação reduziram erosão e produção de sedimento. A implementação de plantio em nível e terraceamento foram as medidas com maior impacto na redução do processo erosivo. Os resultados demonstram que perdas de solo devido a processos erosivos são significantes e insustentáveis em bacias agrícolas no sul do Brasil e que a erosão é exacerbada pela falta de informação dos produtores e uso isolado de medidas conservacionistas sem que haja um esforço coordenado em escala de bacia. O segundo estudo teve como objetivo propor uma forma eficiente de determinar o atual fator P por meio da modelagem, além de alvitrar medidas conservacionistas para melhor atender as práticas atuais. Dessa maneira, cumpre expor que foram selecionadas quatro áreas totalizando 25 km2, representativa das diversas propriedades presentes no local. A eficiência da semeadura atual foi determinada relacionando o ângulo entre as linhas de semeadura e as curvas de nível do terreno. No segundo estudo, foram obtidos valores de P acima de 0,8 em 60% da área, indicando semeadura em desnível em grande parte das lavouras. Essa técnica mostrou ser uma ferramenta importante para a determinação do fator P de forma rápida e espacializada, com potencial de uso em grandes áreas, pois uma determinação eficaz do fator P pode resultar em redução do potencial de erosão. Diante desses resultados, é possível afirmar que medidas de conservação não devem ser tomadas como ações isoladas, mas sim associadas a outras práticas adequadas para cada tipo de uso do solo. A utilização de modelos matemáticos de erosão pode ser uma importante ferramenta de suporte na tomada de decisões de gestão ambiental e a metodologia desenvolvida para a determinação do fator P em SIG pode auxiliar modelos matemáticos a simular os impactos das práticas conservacionistas sobre os processos erosivos de maneira mais representativa. Sendo assim, a modelagem em escala de bacia deve ser mais difundida no Brasil a fim de promover práticas agrícolas sustentáveis, reduzindo o impacto antrópico na degradação do solo e da água.
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Galdino, Sérgio. "Estimativa da perda de terra sob pastagens cultivadas em solos arenosos da bacia hidrográfica do alto Taquari - MS/MT." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256830.
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Orientadores: Mara de Andrade Marinho, Edson Eiji MatsuraTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola
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Resumo: O assoreamento do rio Taquari constitui grave problema ambiental e socioeconômico do Pantanal Brasileiro e decorre principalmente da erosão acelerada do solo ocupado com pastagens degradadas na parte alta da bacia. Um dos modelos mais utilizado para estimar a perda média anual de solo é a Equação Universal de Perda de Solo (USLE). Novas pesquisas foram realizadas para melhorar as estimativas do modelo, originando a Equação Universal de Perda de Solo Revisada (RUSLE). A principal mudança foi na forma de determinação do fator de uso e manejo do solo (C). Na USLE o fator C é obtido a partir do monitoramento constante da perda de solo em parcelas experimentais durante vários anos, constituindo sério empecilho a sua determinação, principalmente no Brasil. Na RUSLE o fator C para pastagens é estimado mais rapidamente, a partir de levantamentos de parâmetros do solo e da vegetação. O objetivo geral do trabalho foi ajustar os fatores da RUSLE às condições locais da bacia do alto Taquari (BAT) e estimar as taxas de perda de solo por erosão, para posterior estudo de cenários de manejo e identificação das práticas mais protetoras dos solos na bacia. O estudo compreendeu áreas de pastagens cultivadas em solos arenosos da BAT. Os parâmetros necessários para estimativas da razão de perda de solo (SLR) e fator C da RUSLE foram levantados em nove parcelas (pastagens) em duas épocas do ano. Análise da SLR e do fator C identificaram valores de C representativos de pastagem não degradada e com níveis de degradação; baixo/médio e alto. Na espacialização do fator C na BAT utilizou-se o modelo linear de mistura espectral. Para a estimativa das perdas de solo nas áreas de pastagens também foram espacializados os demais fatores da RUSLE. A erosividade das chuvas (Fator R) foi estimada a partir de registros mensais e anuais de precipitação de postos pluviométricos localizados na BAT e entorno. Na estimativa da erodibilidade do solo (Fator K) foram utilizados parâmetros físico-químicos do solo levantados no campo. O fator topográfico (LS da RUSLE) foi obtido empregando algoritmo de contribuição de área a montante e modelo digital de elevação do Banco de Dados Geomorfométricos do Brasil (TOPODATA). O fator de práticas conservacionistas do solo (Fator P) foi considerado unitário na estimativa da perda de solo atual na BAT. Também foram estimadas as perdas de solo para dois cenários futuros de manejo adequado do solo e da pastagem. Resultado evidenciou que os valores do fator C estimados pela RUSLE para pastagens se assemelham àqueles determinados pela USLE. A média da perda de solo nas pastagens da BAT em 2010 foi estimada em 9,638 Mg ha-1 ano-1. O estudo de cenários permitiu uma redução em até 75,97% das taxas de perda de solo por erosão com a implementação de manejo adequado do solo e da pastagem. Conclui-se que a RUSLE apresenta bom potencial de estimativa do fator de uso e cobertura do solo, e que se ajustou bem às condições locais da BAT na estimativa da perda de solo
Abstract: The river siltation Taquari constitutes serious environmental and socioeconomic problem of the Brazilian Pantanal and arises principally from accelerated erosion of land occupied by degraded pastures in the upper basin. One of the models used to estimate the average annual soil loss is the Universal Soil Loss Equation (USLE). New research has been done to improve the model estimates, yielding the Revised Universal Soil Loss Equation (RUSLE). The main change was in the method determines the use and soil management factor (C). With USLE, the C factor is obtained from the constant monitoring of soil loss in plots for several years, constituting serious impediment to their determination, especially in Brazil. With RUSLE, the C factor for pastures is estimated sooner, using surveys of soil parameters and vegetation. The overall goal of this work was to adjust RUSLE factors to upper Taquari basin (UTB) local conditions and to estimate soil loss rates due to erosion, for further management scenarios studies and more protective soil identification practices in the basin. The study included pastures grown on sandy soils of the UTB. The required parameters for soil loss ratio estimates (SLR) and the RUSLE C factor were raised in nine plots (pastures) in two seasons. Further SLR analysis identified C factor values for non-degraded, low, medium and highly degraded pasture levels. C factor spatialization for the UTB used the linear spectral mixture model. To estimate soil loss in grazing areas other RUSLE factors were also spatialized. The rainfall erosivity factor (R) was estimated from records of monthly and annual precipitation of rain gauge stations located in and around the UTB. For soil erodibility (K factor) estimation, physic-chemical soil parameters collected in the area were used. The topographic factor (LS RUSLE) was obtained using algorithm contribution of the upstream area and Brazilian geomorphometric digital elevation model data from TOPODATA. The soil conservation practices factor (P) unit was considered estimating soil loss in the UTB. Two future soil loss scenarios were also estimated. Results showed that the C factor values estimated by RUSLE for pastures resemble those determined by USLE. The average soil loss in the pastures of the UTB in 2010 was estimated at 9.638 Mg ha-1 yr-1. The scenario study allowed for a reduction up to 75.97% in the rates of soil loss due to erosion by implementing proper soil and pasture management. We conclude that the RUSLE estimation shows good potential for land use techniques, which fits well into the UTB local conditions and in the estimation of soil loss
Doutorado
Planejamento e Desenvolvimento Rural Sustentável
Doutor em Engenharia Agrícola
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Aarts, Geert. "Modelling space-use and habitat preference from wildlife telemetry data." Thesis, St Andrews, 2007. http://hdl.handle.net/10023/327.
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Dissart, Jean-Christophe. "The economics of erosion and sustainable practices : the case of the Saint-Esprit watershed." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0006/MQ44158.pdf.
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Rolin, Raphaël. "Contribution à une démarche numérique intégrée pour la préservation des patrimoines bâtis." Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2450/document.
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Au travers de l’ensemble de ces travaux, l’objectif principal consiste à valider la pertinence de la construction et de l’utilisation de modèles 3D géométriques ou paramétriques orientés BIM/hBIM pour des analyses numériques. Il s’agit notamment d’études structurales dans le cas de bâtiments historiques ainsi que la planification potentielle de travaux de restauration, rénovation énergétique et réhabilitation. Des travaux d’exploitation complémentaires des données et des nuages de points, pour la détection, la segmentation et l’extraction d’entités géométriques ont également été intégrés dans les travaux et la méthodologie proposée. Le processus de traitement des données, modélisation géométrique ou paramétrique et leur exploitation, proposé dans ces travaux, contribue à améliorer et mieux comprendre les contraintes et enjeux des différentes configurations et conditions liées aux cas d’études et aux contraintes spécifiques propres aux types de constructions. Les contributions proposées pour les différentes méthodes de modélisation géométriques et paramétriques à partir des nuages de points, sont abordées par la construction de modèles géométriques orientés BIM ou hBIM. De même, les processus de détection d’éléments surfaciques et d’extraction de données à partir de nuages de points mis en place sont présentés. La mise en application de ces méthodes de modélisation est systématiquement illustrée par différents cas d’étude, dont l’ensemble des travaux relatifs ont été effectués dans le cadre de cette thèse. Le but est dès lors de démontrer l’intérêt et la pertinence de ces méthodes numériques en fonction du contexte, des besoins et des études envisagées, par exemple avec la flèche de la cathédrale de Senlis (Oise) et le site de l’Hermitage (Oise). Des analyses numériques de type éléments finis permettent ensuite de valider la pertinence de telles démarchesThroughout this work, the main objective is to validate the relevance of construction and use of geometric or parametric 3D models BIM or hBlM-oriented for numerical analyzes. These include structural studies in the case of historic buildings, as well as planning for restoration work, energy renovation and rehabilitation. Complementary data mining and use of point clouds for the detection, segmentation and extraction of geometric features have also been integrated into the work and proposed methodology. The process of data processing, geometric or parametric modeling and their exploitation, proposed in this work, contributes to improve and understand better the constraints and stakes of the different configurations and conditions related to the case studies and the specific constraints specific to the types of constructions. The contributions proposed for the different geometric and parametric modeling methods from point clouds are addressed by the construction of geometric models BIM or hBlM-oriented. Similarly, the process of surface detection, extraction of data and elements from point clouds are presented. The application of these modeling methods is systematically illustrated by different case studies, all of whose relative work has been carried out within the framework of this thesis. The goal is therefore to demonstrate the interest and relevance of these numerical methods according to the context, needs and studies envisaged, for example with the spire of the Senlis cathedral (Oise) and the Hermitage site (Oise). Numerical analyzes with finite element method are used to validate the relevance of these approaches
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Souza, Grazione de. "Modelagem computacional de escoamentos com duas e três fases em reservatórios petrolíferos heterogêneos." Universidade do Estado do Rio de Janeiro, 2008. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=711.
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Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de JaneiroConsidera-se neste trabalho um modelo matemático para escoamentos com duas e três fases em reservatórios petrolíferos e a modelagem computacional do sistema de equações governantes para a sua solução numérica. Os fluidos são imiscíveis e incompressíveis e as heterogeneidades da rocha reservatório são modeladas estocasticamente. Além disso, é modelado o fenômeno de histerese para a fase óleo via funções de permeabilidades relativas. No caso de escoamentos trifásicos água-óleo-gás a escolha de expressões gerais para as funções de permeabilidades relativas pode levar à perda de hiperbolicidade estrita e, desta maneira, à existência de uma região elíptica ou de pontos umbílicos para o sistema não linear de leis de conservação hiperbólicas que descreve o transporte convectivo das fases fluidas. Como conseqüência, a perda de hiperbolicidade estrita pode levar à existência de choques não clássicos (também chamados de choques transicionais ou choques subcompressivos) nas soluções de escoamentos trifásicos, de difícil simulação numérica. Indica-se um método numérico com passo de tempo fracionário, baseado em uma técnica de decomposição de operadores, para a solução numérica do sistema governante de equações diferenciais parciais que modela o escoamento bifásico água-óleo imiscível em reservatórios de petróleo heterogêneos. Um simulador numérico bifásico água-óleo eficiente desenvolvido pelo grupo de pesquisa no qual o autor está inserido foi modificado com sucesso para incorporar a histerese sob as hipóteses consideradas. Os resultados numéricos obtidos para este caso indicam fortes evidências que o método proposto pode ser estendido para o caso trifásico água-óleo-gás. A técnica de decomposição de operadores em dois níveis permite o uso de passos de tempo distintos para os quatro problemas definidos pelo procedimento de decomposição: convecção, difusão, pressão-velocidade e relaxação para histerese. O problema de transporte convectivo (hiperbólico) das fases fluidas é aproximado por um esquema central de diferenças finitas explícito, conservativo, não oscilatório e de segunda ordem. Este esquema é combinado com elementos finitos mistos, localmente conservativos, para a aproximação dos problemas de transporte difusivo (parabólico) e de pressão-velocidade (elíptico). O operador temporal associado ao problema parabólico de difusão é resolvido fazendo-se uso de uma estratégia implícita de solução (Backward Euler). Uma equação diferencial ordinária é resolvida (analiticamente) para a relaxação relacionada à histerese. Resultados numéricos para o problema bifásico água-óleo em uma dimensão espacial em concordância com resultados semi-analíticos disponíveis na literatura foram reproduzidos e novos resultados em meios heterogêneos, em duas dimensões espaciais, são apresentados e a extensão desta técnica para o caso de problemas trifásicos água-óleo-gás é proposta.
We consider in this work a mathematical model for two- and three-phase flow problems in petroleum reservoirs and the computational modeling of the governing equations for its numerical solution. We consider two- (water-oil) and three-phase (water-gas-oil) incompressible, immiscible flow problems and the reservoir rock is considered to be heterogeneous. In our model, we also take into account the hysteresis effects in the oil relative permeability functions. In the case of three-phase flow, the choice of general expressions for the relative permeability functions may lead to the loss of strict hyperbolicity and, therefore, to the existence of an elliptic region or umbilic points for the system of nonlinear hyperbolic conservation laws describing the convective transport of the fluid phases. As a consequence, the loss of hyperbolicity may lead to the existence of nonclassical shocks (also called transitional shocks or undercompressive shocks) in three-phase flow solutions. We present a new, accurate fractional time-step method based on an operator splitting technique for the numerical solution of a system of partial differential equations modeling two-phase, immiscible water-oil flow problems in heterogeneous petroleum reservoirs. An efficient two-phase water-oil numerical simulator developed by our research group was sucessfuly extended to take into account hysteresis effects under the hypotesis previously annouced. The numerical results obtained by the procedure proposed indicate numerical evidence the method at hand can be extended for the case of related three-phase water-gas-oil flow problems. A two-level operator splitting technique allows for the use of distinct time steps for the four problems defined by the splitting procedure: convection, diffusion, pressure-velocity and relaxation for hysteresis. The convective transport (hyperbolic) of the fluid phases is approximated by a high resolution, nonoscillatory, second-order, conservative central difference scheme in the convection step. This scheme is combined with locally conservative mixed finite elements for the numerical solution of the diffusive transport (parabolic) and the pressure-velocity (elliptic) problems. The time discretization of the parabolic problem is performed by means of the implicit Backward Euler method. An ordinary diferential equation is solved (analytically) for the relaxation related to hysteresis. Two-phase water-oil numerical results in one space dimensional, in which are in a very good agreement with semi-analitycal results available in the literature, were computationaly reproduced and new numerical results in two dimensional heterogeneous media are also presented and the extension of this technique to the case of three-phase water-oil-gas flows problems is proposed.
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Barbosa, Nelson Machado. "Resolução numérica de equações diferenciais parciais hiperbólicas não lineares: um estudo visando a recuperação de petróleo." Universidade do Estado do Rio de Janeiro, 2010. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=1290.
Full textAbstract:
Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de JaneiroO processo de recuperação secundária de petróleo é comumente realizado com a injeção de água no reservatório a fim de manter a pressão necessária para sua extração. Para que o investimento seja viável, os gastos com a extração têm de ser menores do que o retorno financeiro obtido com o petróleo. Para tanto, tornam-se extremamente importantes as simulações dos processos de extração. Neste trabalho são estudados os problemas de Burgers e de Buckley-Leverett visando o escoamento imiscível água-óleo em meios porosos, onde o escoamento é incompressível e os efeitos difusivos (devido à pressão capilar) são desprezados. Com o objetivo de incorporar conhecimento matemático mais avançado, para em seguida utilizá-lo no entendimento do problema estudado, abordou-se com razoável profundidade a teoria das leis de conservação. Foram consideradas soluções fracas que, fisicamente, podem ser interpretadas como ondas de choque ou rarefações, então, para que fossem distinguidas as fisicamente admissíveis, foi utilizado o princípio de entropia, nas suas diversas formas. Inicialmente consideramos alguns exemplos clássicos de métodos numéricos para uma lei de conservação escalar, os quais podem ser vistos como esquemas conservativos de três pontos. Entre eles, o método de Lax-Friedrichs (LF) e o método de Lax-Wendroff (LW). Em seguida, um esquema composto foi testado, o qual inclui na sua formulação os métodos LF e LW (chamado de LWLF-4). Respeitando a condição CFL, foram obtidas soluções numéricas de todos os problemas tratados aqui. Com o objetivo de validar tais soluções, foram utilizadas soluções analíticas oriundas dos problemas de Burgers e Buckley- Leverett. Também foi feita uma comparação com os métodos do tipo TVDs com limitadores de fluxo, obtendo resultado satisfatório. Vale à pena ressaltar que o esquema LWLF-4, pelo que nos consta, nunca foi antes utilizado nas resoluções das equações de Burgers e Buckley- Leverett.
The secondary recovery of petroleum is usually performed with injection of water through an oil reservoir to keep the oil pressure for the exploration. In order to make the exploration profitable, the extraction cost must be less than the financial return, which means that the simulation of the exploration process is extremely relevant. In this work, the Burgers- and- Buckley-Leverett problems are studied seeking a two-phase displacement in porous media. The flow is considered incompressible and capillary effects are ignored. In order to analyze the problem, it was necessary to use the theory of conservation law in a spatial variable. Weak solutions, which can be understood as shock or rarefaction waves, are studied with the entropy condition, so that only the physically correct solutions are considered. Some classical numerical methods, which can be seen as conservative schemes of three points, are studied, among them the Lax-Friedrichs (LF) and Lax-Wendroff (LW) methods. A composite scheme, called LWLF-k, is tested using LF and LW methods, being respected the CFL condition, with satisfactory results. In order to validate the numerical schemes, we consider analytical solutions of the Burgers-and-Buckley-Leverett equations. Was also made a comparison with TVDs methods with flux limiters, obtaining satisfactory results. We emphasize that to the best of our knowledge, the LWLF-4 scheme has never been used to solve the Buckley-Leverett equation.
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Nemeth, Michael W., and University of Lethbridge Faculty of Arts and Science. "Climate change impacts on streamflow in the upper North Saskatchewan River Basin, Alberta." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Geography, c2010, 2010. http://hdl.handle.net/10133/2477.
Full textAbstract:
This research focuses on the estimation of the impacts of climate change on water yield, streamflow extremes, and the streamflow regimes in the Cline River Watershed, and consequently, water availability for hydropower generation in this area. The Cline River Watershed comprises the flow into Lake Abraham, the reservoir for Bighorn Dam, is part of the upper North Saskatchewan River basin (UNSRB).
This objective was achieved by parameterizing the ACRU agro-hydrological modelling system. After parameterization was complete, ACRU output was calibrated and verified against available observed data, including temperature, snow water equivalent, glacier mass balance, potential evapotranspiration, and streamflow data. After ACRU was properly verified, five selected climate change scenarios to estimate impacts of climate change in this area. Overall water yields are projected to increase over time. A large shift in seasonality is likely the biggest impact climate change will have on water resources in the Cline River Watershed.xii, 126 leaves : ill., maps ; 29 cm
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Abreu, Eduardo Cardoso de. "Modelagem e simulação computacional de escoamentos trifásicos em reservatórios de petróleo heterogêneos." Universidade do Estado do Rio de Janeiro, 2007. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=765.
Full textAbstract:
Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorNeste trabalho é apresentado um novo método acurado com passo de tempo fracionário, baseado em uma técnica de decomposição de operadores, para a solução numérica de um sistema governante de equações diferenciais parciais que modela escoamento trifásico água-gás-óleo imiscível em reservatórios de petróleo heterogêneos no qual os efeitos de compressibilidade do gás não foram levados em conta. A técnica de decomposição de operadores em dois níveis permite o uso de passos de tempo distintos para os três problemas definidos pelo procedimento de decomposição: convecção, difusão e pressão-velocidade. Um sistema hiperbólico de leis de conservação que modela o transporte convectivo das fases fluidas é aproximado por um esquema central de diferenças finitas explícito, conservativo, não oscilatório e de segunda ordem. Este esquema é combinado com elementos finitos mistos, localmente conservativos, para a aproximação numérica dos sistemas de equações parabólico e elíptico associados aos problemas de transporte difusivo e de pressão-velocidade, respectivamente. O operador temporal associado ao sistema parabólico é resolvido fazendo-se uso de uma estratégia implícita de solução (Backward Euler). O modelo matemático para escoamento trifásico considerado neste trabalho leva em conta as forças de capilaridade e expressões gerais para as funções de permeabilidade relativa, campos variáveis de porosidade e de permeabilidade e os efeitos da gravidade. A escolha de expressões gerais para as funções de permeabilidade relativa pode levar à perda de hiperbolicidade escrita e, desta maneira, à existência de uma região elíptica ou de pontos umbílicos para o sistema não linear de leis de conservação hiperbólicas que descreve o transporte convectivo das fases fluidas. Como consequência, a perda de hiperbolicidade pode levar à existência de choques não clássicos (também chamados de choques transicionais ou choques subcompressivos) nas soluções de escoamentos trifásicos. O novo procedimento numérico foi usado para investigar a existência e a estabilidade de choques não clássicos, com respeito ao fenômeno de fingering viscoso, em problemas de escoamentos trifásicos bidimensionais em reservatórios heterogêneos, estendendo deste modo resultados disponíveis na literatura para problemas de escoamentos trifásicos unidimensionais. Experimentos numéricos, incluindo o estudo de estratégias de injeção alternada de água e gás (Water-Alternating-Gas (WAG)), indicam que o novo procedimento numérico proposto conduz com eficiência computacional a resultados numéricos com precisão. Perspectivas para trabalhos de pesquisa futuros são também discutidas, tomando como base os desenvolvimentos reportados nesta tese.
We present a new, accurate fractional time-step method based on an operator splitting technique for the numerical solution of a system of partial differential equations modeling three-phase immiscible water-gas-oil flow problems in heterogeneous petroleum reservoirs in which the compressibility effects of the gas was not take into account. A two-level operator splitting technique allows for the use of distinct time steps for the three problems defined by the splitting procedure: convection, diffusion and pressure-velocity. A system of hyperbolic conservation laws modelling the convective transport of the fluid phases is approximated by a high resolution, nonoscillatory, second-order, conservative central difference scheme in the convection step. This scheme is combined with locally conservative mixed finite elements for the numerical solution of the parabolic and elliptic problems associated with the diffusive transport of fluid phases and the pressure-velocity problem, respectively. The time discretization of the parabolic problem is performed by means of the implicit backward Euler method. The mathematical model for the three-phase flow considered in this work takes into account capillary forces and general expressions for the relative permeability functions, variable porosity and permeability fields, and the effect of gravity. The choice of general expressions for the relative permeability functions may lead to the loss of strict hyperbolicity and, therefore, to the existence of an elliptic region of umbilic points for the systems of nonlinear hyperbolic conservation laws describing the convective transport of the fluid phases. As a consequence, the loss of hyperbolicity may lead to the existence of nonclassical shocks (also called transitional shocks or undercompressive shocks) in three-phase flow solutions. The numerical procedure was used in an investigation of the existence and stability of nonclassical shocks with respect to viscous fingering in heterogeneous two-dimensional flows, thereby extending previous results for one-dimensional three-phase flow available in the literature. Numerical experiments, including the study of Water-Alternating-Gas (WAG) injection strategies, indicate that the proposed new numerical procedure leads to computational efficiency and accurate numerical results. Directions for further research are also discussed, based on the developments reported in this thesis.
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Xu, Yi-Long, and 許藝瀧. "Mathematical Model of the Street Light Energy Conservation." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/87969548216453672672.
Full textAbstract:
碩士大葉大學
汽車電子產業研發碩士專班
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In Taiwan, with regard to energy-saving education to reduce carbon, we face a double problem. Taiwan's energy consumption relies on imports of 98.3 percent, this is the limitations of their own resources, together with the now highly dependent on fossil energy, energy easily by outsiders; the other is a global problem, climate change caused by disasters, everyone has the opportunity to be affected. Both to resolve the key to mankind is to control the use of fossil fuels, so that the concentration of atmospheric carbon dioxide rise and slow down the changes caused by global warming, this is the significance of energy conservation to reduce carbon. In this, we will describe the path of the application of mathematical model of energy-saving lamps in the RFID on the theory, we can assume that each receiver are street-lamp, and the assumption that each is a steam locomotive or transmitter, in accordance with, such as RFID can be used as a precise, and things tracking, certification, and re-call to respond to application-specific characteristics, such as to calculate the transmitter and receiver above the exact distance to change the brightness of street lamps the size of the road! By mathematical software MATLAB, we can write out a road suitable for use with the surrounding street people, things, automatically tracking and statistics, and can be found in every street-lamp light the size of the case! Through the application of the case believe that the management of road lighting in the development of a degree of contribution.
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Ngnotchouye, Jean Medard Techoukouegno. "Conservation laws models in networks and multiscale flow optimization." Thesis, 2011. http://hdl.handle.net/10413/7922.
Full textAbstract:
The flow of fluids in a network is of practical importance in gas, oil and water
transport for industrial and domestic use. When the flow dynamics are understood,
one may be interested in the control of the flow formulated as follows: given some
fluid properties at a final time, can one determine the initial flow properties that
lead to the desired flow properties?
In this thesis, we first consider the flow of a multiphase gas, described by the drift flux
model, in a network of pipes and that of water, modeled by the shallow water
equations, in a network of rivers. These two models are systems of partial differential
equations of first order generally referred to as systems of conservation laws. In
particular, our contribution in this regard can be summed up as follows: For the
drift-flux model, we consider the flow in a network of pipes seen mathematically as an
oriented graph. We solve the standard Riemann problem and prove a well posedness
result for the Riemann problem at a junction. This result is obtained using coupling
conditions that describe the dynamics at the intersection of the pipes. Moreover, we
present numerical results for standard pipes junctions. The numerical results and
the analytical results are in agreement. This is an extension for multiphase flows of
some known results for single phase flows. Thereafter, the shallow water equations
are considered as a model for the flow of water in a network of canals. We analyze
coupling conditions at the confluence of rivers, precisely the conservation of mass
and the equality of water height at the intersection, and implement these results for
some classical river confluences. We also consider the case of pooled stepped chutes,
a geometry frequently utilized by dams to spill floodwater. Here we consider an
approach different from the engineering community in the sense that we resolve the
dynamics by solving a Riemann problem at the dam for the shallow water equations
with some suitable coupling conditions.
Secondly, we consider an optimization problem constrained by the Euler equations
with a flow-matching objective function. Differently from the existing approaches
to this problem, we consider a linear approximation of the flow equation
in the form of the microscopic Lattice Boltzmann Equations (LBE). We derive an
adjoint calculus and the optimality conditions from the microscopic LBE. Using
multiscale analysis, we obtain an equivalent macroscopic result at the hydrodynamic
limit. Our numerical results demonstrate the ability of our method to solve
challenging problems in fluid mechanics.Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
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Boyd, Matthew S. "Heat source : stream, river and open channel temperature prediction." Thesis, 1996. http://hdl.handle.net/1957/27036.
Full textAbstract:
Reach defined analysis concentrated on the water temperature change that
occurred in a stream/river segment over the course of one full diurnal cycle. Digital
thermistors, data loggers and computer model development were utilized in reach analysis
to link parameters of the stream system to a specific temperature change. The
methodology employed was relatively simple and fast, and many successive stream
segments were analyzed simultaneously. Reach analysis of stream temperature change
identified the existing components of the stream system that caused increased water
temperature and predicted the effectiveness of managed improvements to the stream
system.
Stream and river temperature regulation has focused on system and basin wide
management. Often, the source of increased water temperature originates in only a part of
the stream system. Reach defined analysis identified the portions of the stream system in
which most water temperature change occurred, offered an explanation for the
temperature response and provided specific information about the alternate strategies that
may ameliorate undesired water temperatures.
The development of the computer model Heat Source included physically based
mathematical descriptions of stream energy and hydrologic processes. An implicit finite
difference numerical method was implemented for simultaneous solution. The
methodology presented in Heat Source is portable and applicable to all streams, rivers and
open channels.Graduation date: 1997
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"Some topics on nonlinear conservation laws." 2007. http://library.cuhk.edu.hk/record=b5893360.
Full textAbstract:
Duan, Ben.Thesis (M.Phil.)--Chinese University of Hong Kong, 2007.
Includes bibliographical references (leaves 61-67).
Abstracts in English and Chinese.
Acknowledgments --- p.2
Abstract --- p.i
Introduction --- p.3
Chapter 1 --- Stability of Shock Waves in Viscous Conservation Laws --- p.10
Chapter 1.1 --- Cauchy Problem for Scalar Viscous Conservation Laws and Viscous Shock Profiles --- p.10
Chapter 1.2 --- Stability of Shock Waves by Energy Method --- p.15
Chapter 1.3 --- L1 Stability of Shock Waves in Scalar Viscous Con- servation Laws --- p.20
Chapter 2 --- Slow Motion of a Viscous Shock --- p.29
Chapter 2.1 --- Propagation of a Viscous Shock in Bounded Domain --- p.29
Chapter 2.1.1 --- Steady Problem --- p.30
Chapter 2.1.2 --- Time-Dependent Problem --- p.34
Chapter 2.1.3 --- Super-Sensitivity of Boundary Conditions --- p.36
Chapter 2.2 --- Propagation of a Stationary Shock in Half Space --- p.39
Chapter 2.2.1 --- Asymptotic Analysis --- p.39
Chapter 2.2.2 --- Pointwise Estimate --- p.40
Chapter 3 --- Viscous Transonic Flow Through a Nozzle --- p.47
Chapter 3.1 --- Nonlinear Stability and Instability of Shock Waves --- p.48
Chapter 3.2 --- Asymptotic Stability and Instability --- p.49
Chapter 3.3 --- Matched Asymptotic Analysis --- p.53
Chapter 4 --- C --- p.60
Bibliography --- p.61
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Cui, Gurong. "Rainfall runoff model improvements incorporating a dynamic wave model and synthetic stream networks." Diss., 1999. http://www.newcastle.edu.au/services/library/adt/public/adt-NNCU20030120.144918/index.html.
Full text
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"Multi-dimensional conservation laws and a transonic shock problem." 2009. http://library.cuhk.edu.hk/record=b5894118.
Full textAbstract:
Weng, Shangkun.Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.
Includes bibliographical references (p. 73-78).
Abstracts in English and Chinese.
Abstract --- p.i
Acknowledgement --- p.iii
Chapter 1 --- Introduction --- p.1
Chapter 2 --- Existence and Uniqueness results of transonic shock solution to full Euler system in a large variable nozzle --- p.11
Chapter 2.1 --- The mathematical description of the transonic shock problem and main results --- p.11
Chapter 2.2 --- The reformulation on problem (2.1.1) with (2.1.5)-(2.1.9) --- p.18
Chapter 2.3 --- An Iteration Scheme --- p.30
Chapter 2.4 --- A priori estimates and proofs of Theorem 2.2.1 and Theorem 2.1.1 --- p.39
Chapter 3 --- A monotonic theorem on the shock position with respect to the exit pressure --- p.50
Chapter 4 --- Discussions and Future work --- p.64
Chapter 5 --- Appendix --- p.66
Chapter 5.1 --- Appendix A: Background solution --- p.66
Chapter 5.2 --- Appendix B: An outline of the proof of Theorem 2.1.2 --- p.67
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"Parameter free document stream classification." Thesis, 2006. http://library.cuhk.edu.hk/record=b6074286.
Full textAbstract:
Extensive experiments are conducted to evaluate the effectiveness PFreeBT and PNLH by using a stream of two-year news stories and three benchmarks. The results showed that the patterns of the bursty features and the bursty topics which are identified by PFreeBT match our expectations, whereas PNLH demonstrates significant improvements over all of the existing heuristics. These favorable results indicated that both PFreeBT and PNLH are highly effective and feasible.For the problem of bursty topics identification, PFreeBT adopts an approach, in which we term it as feature-pivot clustering approach. Given a document stream, PFreeBT first identifies a set of bursty features from there. The identification process is based on computing the probability distributions. According to the patterns of the bursty features and two newly defined concepts (equivalent and map-to), a set of bursty topics can be extracted.
For the problem of constructing a reliable classifier, we formulate it as a partially supervised classification problem. In this classification problem, only a few training examples are labeled as positive (P). All other training examples (U) are remained unlabeled. Here, U is mixed with the negative examples (N) and some other positive examples (P'). Existing techniques that tackle this problem all focus on finding N from U. None of them attempts to extract P' from U. In fact, it is difficult to succeed as the topics in U are diverse and the features in there are sparse. In this dissertation, PNLH is proposed for extracting a high quality of P' and N from U.
In this dissertation, two heuristics, PFreeBT and PNLH, are proposed to tackle the aforementioned problems. PFreeBT aims at identifying the bursty topics in a document stream, whereas PNLH aims at constructing a reliable classifier for a given bursty topic. It is worth noting that both heuristics are parameter free. Users do not need to provide any parameter explicitly. All of the required variables can be computed base on the given document stream automatically.
In this information overwhelming century, information becomes ever more pervasive. A new class of data-intensive application arises where data is modeled best as an open-ended stream. We call such kind of data as data stream. Document stream is a variation of data stream, which consists of a sequence of chronological ordered documents. A fundamental problem of mining document streams is to extract meaningful structure from there, so as to help us to organize the contents systematically. In this dissertation, we focus on such a problem. Specifically, this dissertation studies two problems: to identify the bursty topics in a document stream and to construct a classifiers for the bursty topics. A bursty topic is one of the topics resides in the document stream, such that a large number of documents would be related to it during a bounded time interval.
Fung Pui Cheong Gabriel.
"August 2006."
Adviser: Jeffrey Xu Yu.
Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1720.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references (p. 122-130).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.
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Vortkamp, Irina. "Biological conservation: mathematical models from an ecological and socio-economic systems perspective." Doctoral thesis, 2021. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-202110015459.
Full textAbstract:
Conservation in the EU and all over the world aims at reducing biodiversity loss which has become a great issue in the last decades. However, despite existing efforts, Earth is assumed to face a sixth mass extinction. One major challenge for conservation is to reconcile the targets with conflicting interests, e.g. for food production in intensively used agricultural landscapes. Agriculture is an example of a coupled human-environment
system that is approached in this thesis with the help of mathematical models from two directions.
Firstly, the ecological subsystem is considered to find processes relevant for the effect of habitat connectivity on population abundances. Modelling theory predicts that the species-specific growth parameters (intrinsic growth rate and carrying capacity) indicate whether dispersal has a positive or negative effect on the total population size at
equilibrium (r-K relationship). We use laboratory experiments in combination with a system of ordinary differential equations and deliver the first empirical evidence for a negative effect of dispersal on the population size in line with this theory. The result is of particular relevance for the design of dispersal corridors or stepping stones which are meant to increase connectivity between habitats. These measures might not be effective for biological conservation. A second population model, consisting of two coupled Ricker maps with a mate-finding Allee effect, is analyzed in order to examine the effect of bistability due to the Allee effect in combination with overcompensation in a spatial system. The interplay can cause complex population dynamics including multiple coexisting attractors, long transients and sudden population collapses. Essential extinction teaches us that not only small populations are prone to extinction but chaotic dynamics can drive a population extinct in a short period of time as well. By a comprehensive model analysis, we find that dispersal can prevent essential extinction of a population. In the context of conservation that is: habitat connectivity can promote rescue effects to save a population that exhibits an Allee effect. The two findings of the first part of this thesis have contrasting implications for conservation which shows that universal recommendations regarding habitat connectivity are impossible without knowledge of the specific system. Secondly, a model for the socio-economic subsystem is presented. Agri-environment schemes (AES) are payments that compensate farmers for forgone profits on the condition that they improve the ecological state of the agricultural system. However, classical economic models that describe the cost-effectiveness of AES often do not take the social network of farmers into account. Numerical simulations of the socio-economic model presented in this thesis suggest that social norms can hinder farmers from scheme participation. Moreover, social norms lead to multistability in farmers’ land-use decision behaviour. Informational campaigns potentially decrease the threshold towards more long-term scheme participation and might be a good tool to complement compensation payments if social norms affect land-use decisions. Finally, a coupled human-environment system is analyzed. An integrated economicecological model is studied to investigate the cost-effectiveness of AES if the species of concern exhibits an Allee effect. A numerical model analysis indicates large trade-offs between agricultural production and persistence probability. Moreover, conservation success strongly depends on the initial population size, meaning that conservation is well advised to start before the species is threatened. Spatial aggregation of habitat can promote rescue effects, suggesting land-sparing solutions for conservation. In that case,agglomeration bonuses may serve to increase the effectiveness of AES. Possible causes for population declines are diverse and can be a combination of human influences, e.g. due to habitat degradation and inherent ecosystem properties. That complicates the task of conservation. The models presented in this thesis simplify complex systems in order to extract processes relevant for biological conservation. The analysis of spatial effects and dynamical model complexity, e.g. due to Allee effects or a nonlinear utility function, allows us improve the understanding of coupled human-environment systems.
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Jia, Siwei. "Optimization, conservation and valuation of contingent claims in economic resource management under uncertainty." Thesis, 2004. http://hdl.handle.net/1957/29439.
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Fuller, Trevon Louis. "Area prioritization for optimal conservation planning." 2009. http://hdl.handle.net/2152/18392.
Full textAbstract:
This dissertation develops an optimization framework for conservation planning and illustrates the framework using case studies from Alaska, Balcones Canyonlands National Wildlife Refuge (BCNWR) in central Texas, and Mexico. The common theme of the chapters is the use of optimization models to design conservation areas. Chapter 1 explains how the subsequent chapters are related to one another. Chapter 2 develops a framework for measuring how the cost of establishing conservation areas changes over time. When this method is applied to a data set on Mexican mammals, it is shown that twice as much land would have to be set aside to protect adequate mammal habitat today than would have been required in 1970 due to ongoing deforestation. Chapter 3 presents an optimization model for planning the establishment of conservation areas that incorporates forecasts of species' responses to global warming. The model is applied to analyze endangered birds and the polar bear (Ursus maritimus) on the Arctic coast of Alaska. Chapter 4 discusses the modeling of habitat for two endangered bird species, the Black{capped Vireo (Vireo atricapillus) and the Golden{cheekedWarbler (Dendroica chrysoparia), at BCNWR using a machine{learning algorithm (Maxent). These habitat models serve as part of the input for a one{stage optimization model for acquiring land to expand BCNWR. Chapter 5 uses graph theory to select corridors to establish connectivity between conservation areas in Mexico. The planning method presented in Chapter 5 is implemented in a free software package for corridor design, LQGraph.text
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"Energy conservation methods for wireless sensor networks." Thesis, 2006. http://library.cuhk.edu.hk/record=b6074289.
Full textAbstract:
Based on the above scheme, we propose a number of solutions to reduce the computational complexity and communication cost. To reduce the computational complexity, we propose to aggregate the local data and transit data and route them with a single set of routing variables. To reduce the communication overhead, a different smoothing function is proposed that only requires the information of a set of bottleneck nodes. The optimality conditions are derived and a distributed algorithm is designed accordingly. Simulation results illustrate the effectiveness and efficiency of the proposed solution.Sleeping scheduling is another approach to save energy consumption for sensor networks. The basic idea is to schedule the duty-cycles of sensor nodes such that off-duty sensors are turned off as long as the network functionality can be maintained by working nodes. For applications whereby coordination of sleeping among sensors is not possible or inconvenient, random sleeping is the only option. We present the Asynchronous Random Sleeping (ARS) scheme whereby sensors (i) do not need to synchronize with each other, and (ii) do not need to coordinate their wakeup patterns. The stationary coverage probability and the expected coverage periods for ARS are derived. For surveillance application, we derive in addition the detection probability and detection delay distribution. We find that the expected detection delay of asynchronous random sleeping is smaller than that of the synchronous random sleeping.
This thesis is focused on the design and analysis of energy conservation methods for wireless sensor networks (WSNs). Unlike traditional wireless networks, sensor nodes in WSNs are collaborating towards a common mission. The failure of some sensor nodes may cause significant topological changes and loss of information at the target region. Therefore, network lifetime is the primary objective for designing energy conservation solutions for WSNs.
We address the energy conservation problem from the aspects of maximum lifetime routing, data aggregation and sleeping scheduling. We first propose a data aggregated maximum lifetime routing scheme for wireless sensor networks. We adopt a data aggregation model that decouples the routing of local data and transit data. The objective is to jointly optimize data aggregation and routing so that the network lifetime can be maximized. A recursive smoothing method is adopted to overcome the nondifferentiability of the objective function. We derive the necessary and sufficient conditions for achieving the optimality of the smoothing function and design a distributed gradient algorithm accordingly. We show that the proposed scheme can significantly reduce the data traffic and improve the network lifetime. The distributed algorithm can converge to the optimal value efficiently under all network configurations.
Hua Cunqing.
"June 2006."
Adviser: Tak-Shing Yum.
Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1825.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references (p. 120-131).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.
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Ball, Ian R. (Ian Randall). "Mathematical applications for conservation ecology : the dynamics of tree hollows and the design of nature reserves / Ian R. Ball." 2000. http://hdl.handle.net/2440/19542.
Full textAbstract:
Bibliography: leaves 170-179.vi, 179 leaves : ill. ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Describes a deterministic computer model for simulating forest dynamics which is the applied to a number of different timber harvesting scenarios in the mountain ash (Eucalyptus regnans F.Muell.) forests of Victoria, south-eastern Australia. Also looks at a number of new mathematical problems in the design of nature reserve systems.
Thesis (Ph.D.)--University of Adelaide, Depts. of Applied Mathematics, Environmental Science and Management, 2000?
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Mokgatle, Patrick H. K. "Invariant solutions and conservation laws for soil water redistribution and extraction flow models / Patrick H.K. Mokgatle." Thesis, 2003. http://hdl.handle.net/10394/11297.
Full textAbstract:
In this dissertation we use Lie symmetry analysis to obtain invariant solutions for
certain soil water equations. These solutions are invariant under two-parameter
symmetry groups obtained by the group classification of the governing equation. We
also obtain all nontrivial conservation laws for a class of (2+1) nonlinear evolution
partial differential equations which are related to the soil water equations. It is shown
that nontrivial conservation laws exist for certain classes of equations which admit
point symmetries. We note that one cannot invoke Noether's theorem here as there
is no Lagrangian for these partial differential equations.(M.Sc.) North-West University, Mafikeng Campus, 2003