Dissertations / Theses on the topic 'Runoff Measurement Mathematical models'
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1
Sorooshian, Soroosh, and Vijai Kumar Gupta. "Improving the Reliability of Compartmental Models: Case of Conceptual Hydrologic Rainfall-Runoff Models." Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/614011.
2
Hendrickson, Jene Diane, and Soroosh Sorooshian. "CALIBRATION OF RAINFALL-RUNOFF MODELS USING GRADIENT-BASED ALGORITHMS AND ANALYTIC DERIVATIVES." Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/614186.
Abstract:
In the past, derivative-based optimization algorithms have not
frequently been used to calibrate conceptual rainfall -riff (CRR)
models, partially due to difficulties associated with obtaining the
required derivatives. This research applies a recently- developed
technique of analytically computing derivatives of a CRR model to a
complex, widely -used CRR model. The resulting least squares response
surface was found to contain numerous discontinuities in the surface
and derivatives. However, the surface and its derivatives were found
to be everywhere finite, permitting the use of derivative -based
optimization algorithms. Finite difference numeric derivatives were
computed and found to be virtually identical to analytic derivatives.
A comparison was made between gradient (Newton- Raphsoz) and
direct (pattern search) optimization algorithms. The pattern search
algorithm was found to be more robust. The lower robustness of the
Newton-Raphsoi algorithm was thought to be due to discontinuities and a
rough texture of the response surface.
3
Price, Myra Ann. "Seasonal Variation in Runoff Curve Number." Thesis, The University of Arizona, 1998. http://hdl.handle.net/10150/225411.
Abstract:
The seasonal variation in rainfall - runoff response is investigated for about 300 small watersheds throughout the United States. Data from USDA research watersheds were used to define runoff Curve Number for ordered data sets by months. Three major patterns of cyclic variation are found and investigated: 1) distinct and well - defined seasonal variations as typified by forested watersheds in heavy rainfall zones; 2) mildly cyclic variation found typically in meadows and grasslands, and 3) non - cyclic or unidentifiable patterns, including those with insufficient seasonal data. The only pattern that may be present is the well-defined seasonal variation found so far only in forested watersheds. Regional characteristics were found for individual crop types. For the watersheds studied there seemed to be no difference in the variation between crops except for meadow during the summer. Some associated background factors are explored, including long-term and short-term antecedent rainfall.
4
Kapangaziwiri, Evison. "Regional application of the Pitman monthly rainfall-runoff model in Southern Africa incorporating uncertainty." Thesis, Rhodes University, 2011. http://hdl.handle.net/10962/d1006178.
Abstract:
Climate change and a growing demand for freshwater resources due to population increases and socio-economic changes will make water a limiting factor (in terms of both quantity and quality) in development. The need for reliable quantitative estimates of water availability cannot be over-emphasised. However, there is frequently a paucity of the data required for this quantification as many basins, especially in the developing world, are inadequately equipped with monitoring networks. Existing networks are also shrinking due mainly to shortages in human and financial resources. Over the past few decades mathematical models have been used to bridge the data gap by generating datasets for use in management and policy making. In southern Africa, the Pitman monthly rainfall-runoff model has enjoyed relatively popular use as a water resources estimation tool. However, it is acknowledged that models are abstractions of reality and the data used to drive them is imperfect, making the model outputs uncertain. While there is acknowledgement of the limitations of modelled data in the southern African region among water practitioners, there has been little effort to explicitly quantify and account for this uncertainty in water resources estimation tools and explore how it affects the decision making process. Uncertainty manifests itself in three major areas of the modelling chain; the input data used to force the model, the parameter estimation process and the model structural errors. A previous study concluded that the parameter estimation process for the Pitman model contributed more to the global uncertainty of the model than other sources. While the literature abounds with uncertainty estimation techniques, many of these are dependent on observations and are therefore unlikely to be easily applicable to the southern African region where there is an acute shortage of such data. This study focuses on two aspects of making hydrologic predictions in ungauged basins. Firstly, the study advocates the development of an a priori parameter estimation process for the Pitman model and secondly, uses indices of hydrological functional behaviour to condition and reduce predictive uncertainty in both gauged and ungauged basins. In this approach all the basins are treated as ungauged, while the historical records in the gauged basins are used to develop regional indices of expected hydrological behaviour and assess the applicability of these methods. Incorporating uncertainty into the hydrologic estimation tools used in southern Africa entails rethinking the way the uncertain results can be used in further analysis and how they will be interpreted by stakeholders. An uncertainty framework is proposed. The framework is made up of a number of components related to the estimation of the prior distribution of the parameters, used to generate output ensembles which are then assessed and constrained using regionalised indices of basin behavioural responses. This is premised on such indices being based on the best available knowledge covering different regions. This framework is flexible enough to be used with any model structure to ensure consistent and comparable results. While the aim is to eventually apply the uncertainty framework in the southern African region, this study reports on the preliminary work on the development and testing of the framework components based on South African basins. This is necessitated by the variations in the availability and quality of the data across the region. Uncertainty in the parameter estimation process was incorporated by assuming uncertainty in the physical and hydro-meteorological data used to directly quantify the parameter. This uncertainty was represented by the range of variability of these basin characteristics and probability distribution functions were developed to account for this uncertainty and propagate it through the estimation process to generate posterior distributions for the parameters. The results show that the framework has a great deal of potential but can still be improved. In general, the estimated uncertain parameters managed to produce hydrologically realistic model outputs capturing the expected regimes across the different hydro-climatic and geo-physical gradients examined. The regional relationships for the three indices developed and tested in this study were in general agreement with existing knowledge and managed to successfully provide a multi-criteria conditioning of the model output ensembles. The feedback loop included in the framework enabled a systematic re-examination of the estimation procedures for both the parameters and the indices when inconsistencies in the results were identified. This improved results. However, there is need to carefully examine the issues and problems that may arise within other basins outside South Africa and develop guidelines for the use of the framework.iText 1.4.6 (by lowagie.com)
5
Pokhrel, Pranav. "The Study of Temporal and Spatial Variability of Degree Day Factor of Snowmelt in Colorado." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849730/.
Abstract:
Snowmelt is one of the major sources of surface water supply and ground-water recharge in high elevation areas and can also cause flooding in snow dominated watersheds. Direct estimation of daily snowmelt requires daily snow water equivalent (SWE) measurements that are not always available, especially in places without monitoring stations. There are two alternative approaches to modeling snowmelt without using direct measurements of SWE, temperature-based and energy-based models. Due to its simplicity, computational efficiency, and less input data requirement, the temperature-based method is commonly used than the energy-based method. In the temperature-index approach snowmelt is estimated as a linear function of average air temperature, and the slope of the linear function is called the degree-day factor (DDF). Hence, the DDF is an essential parameter for utilizing the temperature-based method to estimate snowmelt. Thereby, to analyze the spatial properties of DDF, 10 years DDF from the entire state of Colorado was calculated for this research. Likewise, to study the temporal properties, DDFs for 27 years from the White Yampa water basin and the Colorado Headwaters water basin were calculated.
As a part of the spatial analysis, the calculated DDFs were correlated with spatial variables (slope, aspect, latitude and elevation) and a spatial correlation graph was created to observe the possibility of predicting DDF. Also a multivariate regression model was prepared using these spatial variables to predict the DDF using spatial variables. Further, the DDFs calculated from Colorado headwaters and the White Yampa water basins were correlated for annual temporal variation, daily variation, variation with peak snow water equivalent and variation with important temporal cycles like accumulation period and melting period of snowmelt. The result obtained from this study showed that the variability of DDF is more dependent upon temporal factors compared to the spatial factors. Also, the results showed that predicting DDF is a difficult process and requires complex methods than simple linear models or multivariate models.
6
Galarraga, Sanchez Remigio Hernan. "Scale effects in determining snowmelt from mountainous basins using a distributed approach for snow water equivalence and radiation, and a point snowmelt model." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/191186.
Abstract:
Rates of snowmelt distributed across Emerald Lake watershed, an alpine basin located in the Sierra Nevada, California, were estimated for water year 1987 using a point snowmelt model applied to regions that were classified based on distributed snow water equivalence and net solar radiation (NSR). A 5-m resolution digital elevation model (DEM) and a 5-m classified digital terrain model of snow water equivalence (SWE) were resampled to coarser resolutions (25-m, 30-m, 50-m, and 100-m) using the nearest neighbor approach. These images were used to define other snowmelt physical parameters and the initial state of the snowpack before melting. Topographic parameters calculated at 50-m and 100-m resolution exhibited significant differences in their histogram distribution as compared to the 5-m DEM. The most important were variations in slope, aspect, sky view factor, and terrain configuration factor, which influenced radiation calculations and the definition of distributed parameters for snowmelt calculations. Elevations, however, did not change significantly from one resolution to the other. The distribution of topographic parameters modeled at 25-m and 30-m, remained almost unchanged. Four, seven and ten classes of snow water equivalence and net solar radiation were combined using a band interleave process to determine the maximum number of combined classes. The point snowmelt model was then applied to these areas, which shared similar SWE and NSR characteristics, to obtain hourly melt rates. Modeled snowmelt rates were compared to the total daily discharge observed at the outlet of Emerald Lake watershed. There was good agreement for resolutions S-, 25-, 30-, and 50-m but not for the 100-m OEM, as modeled net solar radiation was too high and water was released from the basin too early. Model performance using three tests (Nash-Sutcliffe criteria, sum of squares of the deviations and the sum of the absolute differences between observed discharge and computed melting) showed that the 30-m resolution OEM with combined classes of 7 SWE and 7 NSR provided the best snowmelt performance for this distributed approach. Finally, fractional snow cover area at one month intervals were estimated, showing that this approach offers the potential to model spatially distributed snow covered area in alpine regions.
7
Goodrich, David Charles. "Basin Scale and Runoff Model Complexity." Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/614028.
Abstract:
Distributed Rainfall-Runoff models are gaining widespread acceptance; yet, a
fundamental issue that must be addressed by all users of these models is definition
of an acceptable level of watershed discretization (geometric model complexity). The
level of geometric model complexity is a function of basin and climatic scales as well
as the availability of input and verification data. Equilibrium discharge storage is
employed to develop a quantitative methodology to define a level of geometric model
complexity commensurate with a specified level of model performance. Equilibrium
storage ratios are used to define the transition from overland to channel -dominated
flow response. The methodology is tested on four subcatchments in the USDA -ARS
Walnut Gulch Experimental Watershed in Southeastern Arizona. The catchments
cover a range of basins scales of over three orders of magnitude. This enabled a
unique assessment of watershed response behavior as a function of basin scale.
High quality, distributed, rainfall -runoff data was used to verify the model (KINEROSR). Excellent calibration and verification results provided confidence in
subsequent model interpretations regarding watershed response behavior. An
average elementary channel support area of roughly 15% of the total basin area is
shown to provide a watershed discretization level that maintains model performance
for basins ranging in size from 1.5 to 631 hectares. Detailed examination of
infiltration, including the role and impacts of incorporating small scale infiltration
variability in a distribution sense, into KINEROSR, over a range of soils and
climatic scales was also addressed. The impacts of infiltration and channel losses
on runoff response increase with increasing watershed scale as the relative influence
of storms is diminished in a semiarid environment such as Walnut Gulch. In this
semiarid environment, characterized by ephemeral streams, watershed runoff
response does not become more linear with increasing watershed scale but appears
to become more nonlinear.
8
Kapangaziwiri, Evison. "Revised parameter estimation methods for the Pitman monthly rainfall-runoff model." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1006172.
Abstract:
In recent years, increased demands have been placed on hydrologists to find the most effective methods of making predictions of hydrologic variables in ungauged basins. A huge part of the southern African region is ungauged and, in gauged basins, the extent to which observed flows represent natural flows is unknown, given unquantified upstream activities. The need to exploit water resources for social and economic development, considered in the light of water scarcity forecasts for the region, makes the reliable quantification of water resources a priority. Contemporary approaches to the problem of hydrological prediction in ungauged basins in the region have relied heavily on calibration against a limited gauged streamflow database and somewhat subjective parameter regionalizations using areas of assumed hydrological similarity. The reliance of these approaches on limited historical records, often of dubious quality, introduces uncertainty in water resources decisions. Thus, it is necessary to develop methods of estimating model parameters that are less reliant on calibration. This thesis addresses the question of whether physical basin properties and the role they play in runoff generation processes can be used directly in the estimation of parameter values of the Pitman monthly rainfall-runoff model. A physically-based approach to estimating the soil moisture accounting and runoff parameters of a conceptual, monthly time-step rainfall-runoff model is proposed. The study investigates the physical meaning of the model parameters, establishes linkages between parameter values and basin physical properties and develops relationships and equations for estimating the parameters taking into account the spatial and temporal scales used in typical model applications. The estimationmethods are then tested in selected gauged basins in southern Africa and the results of model simulations evaluated against historical observed flows. The results of 71 basins chosen from the southern African region suggest that it is possible to directly estimate hydrologically relevant parameters for the Pitman model from physical basin attributes. For South Africa, the statistical and visual fit of the simulations using the revised parameters were at least as good as the current regional sets, albeit the parameter sets being different. In the other countries where no regionalized parameter sets currently exist, simulations were equally good. The availability, within the southern African region, of the appropriate physical basin data and the disparities in the spatial scales and the levels of detail of the data currently available were identified as potential sources of uncertainty. GIS and remote sensing technologies and a widespread use of this revised approach are expected to facilitate access to these data.
9
Luckemeier, Richard Ewald 1948. "A rainfall-runoff model for an urban watershed in Tucson, Arizona." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277165.
Abstract:
The U.S. Geological Survey and the City of Tucson, Arizona, have been collecting rainfall and runoff data on several watersheds in the Tucson area for several years. Among the purposes of this project is to use the data to test rainfall-runoff models in an effort to find one to successfully simulate flood flows in Tucson. One such model, the Distributed Routing Rainfall-Runoff Model (DR3M), was tested using data collected on Rob Wash in Tucson. It was found DR3M performs about as well as it does in other parts of the United States, although it tends to underestimate flood flows for large storms and overestimate flows for smaller storms. Unique features with regard to the hydrology of urban Tucson require special attention when using DR3M; these features are associated with the nature of dry washes and summer rainfall in Tucson. Experience indicates DR3M is not truly a deterministic model.
10
Koterba, Michael T. "Differential influences of storm and watershed characteristics on runoff from ephemeral streams in southeastern Arizona." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/191126.
Abstract:
Relationships between thunderstorm and watershed variables and runoff from or within semiarid watersheds at Walnut Gulch, Arizona were examined. Variables showing greater sensitivity to basin and storm size were better flow predictors. Stepwise regression with three increasingly nonlinear algebraic models showed mean storm depth was the best simple predictor of runoff. Predictions improved using storm volume, a product of storm depth and areal extent. Initial runoff to streams was best described as a highly nonlinear function of storm and watershed variables. Runoff from a basin was a more linearized function of similar variables. The above differences were ascribed to channel transmission losses, reductions in runoff moving down initially dry channels. For a given basin and small storms, loss to runoff ratios exceeded 10:1 and were highly variable. Ratios were similar and less than 0.5:1 for storms centrally located over a basin and generating sufficient initial runoff to minimize flow variation due to losses. Losses increased disproportionately with basin size. Antecedent rainfall and first summer flows also affected rainfall runoff relationships in a differential manner. Wet conditions enhanced runoff more from larger versus smaller storms. First summer flows were less than expected probably because of higher soil infiltration and channel losses at the onset of summer storms. Overall, as storm size decreased or basin area increased, initial runoff was more often a localized phenomenon and downstream flow more dependent on storm depth, extent, location, and seasonal timing and basin channel losses, but less dependent on antecedent rainfall. Consequently, storm depth accounted for only 60% to 70% of the variation in flows while storm volume, antecedent rainfall, channel losses, and first summer flows explained 80% to 90%. Finally, oversimplifying storm or watershed variables or analytical methods led to errors in assessing their affect on runoff. It was also determined that current arguments supporting a recommendation to delete smaller, frequent annual floods to better fit remaining data to flood frequency curves were oversimplified. Distributed rainfall - runoff models with channel losses and regional storm depth - area - frequency data may be the way to develope flood curves for semiarid basins with short runoff records.
11
Bouraoui, Faycal. "Development of a continuous, physically-based distributed parameter, nonpoint source model." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-10192006-115604/.
12
Mwelwa, Elenestina Mutekenya. "The application of the monthly time step Pitman rainfall-runoff model to the Kafue River basin of Zambia." Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1006171.
Abstract:
This thesis presents a discussion on the study undertaken in the application of the monthly time step Pitman rainfall-runoff model to the Kafue River basin. The study constituted one of the initial steps in the capacity building and expansion of the application of hydrologic models in the southern African region for water resources assessment, one of the core areas of the Southern African FRIEND project (Flow Regimes from International Experimental Network Data). The research process was undertaken in four major stages, each stage working towards achieving the research objectives. The first stage was the preparation of spatial data which included the selection and delineation of sub-catchments and inclusion of spatial features required to run the Pitman model and transferring the spatial data into SPATSIM. The second stage was the preparation of input data, mainly rainfall, streamflow, evaporation, and water abstraction data. This information was then imported into SPATSIM, which was able to assist in the further preparation of data by assessment of the input data quality, linking of observed flows and spatial interpolation of point rainfall data to average catchment rainfall in readiness for running and calibration of the model. The third stage was the running and calibration of the Pitman model. Use was made of both the automatic calibration facility, as well as manual calibration by means of the time series graph display and analysis facility of SPATSIM. Model calibration was used to obtain the best fit and an acceptable correlation between the simulated and the observed flows and to obtain simulation parameter sets for sub-catchments and regions within the Kafue catchment. The fourth stage was the analysis and evaluation of the model results. This included verification of results over different time periods and validation and testing of parameter transfers to other catchments. This stage also included the evaluation of SPATSIM as a tool for applying the model and as a database for the processing and storage of water resources data. The study’s output includes: A comprehensive database of hydrometeorological, physical catchment characteristics, landuse and water abstraction information for the Kafue basin; calibrated Pitman model parameters for the sub-catchments within the Kafue basin; recommendations for future work and data collection programmes for the application of the model. The study has also built capacity by facilitating training and exposure to rainfall-runoff models (specifically the Pitman model) and associated software, SPATSIM. In addition, the dissemination of the results of this study will serve as an effective way of raising awareness on the application of the Pitman model and the use of the SPATSIM software within Zambia and the region. The overall Pitman model results were found to be satisfactory and the calibrated model is able to reproduce the observed spatial and temporal variations in streamflow characteristics in the Kafue River basin.
13
Oogathoo, Shalini. "Runoff simulation in the Canagagigue Creek watershed using the MIKE SHE model." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101157.
Abstract:
The Canagagigue Creek watershed, located in the Grand River Basin, is one of the fastest developing areas in Ontario. The watershed hydrology has changed considerably due to the increased anthropogenic activities, producing frequent floods and droughts as well as water quality problems. MIKE SHE, a watershed-scale model, was used to simulate surface runoff from the Canagagigue Creek watershed. Various management scenarios affecting the surface hydrology were also evaluated. The model was calibrated for four years (1994-95 to 1997-98) and validated for another four years (1990-91 to 19931-94). For the calibration period, the correlation between the observed and simulated daily runoff was satisfactory, as shown by the coefficient of determination value of 0.59. The coefficient of determination was 0.44 for the validation period. The Nash-Sutcliffe coefficients obtained were 59% and 40% for the calibration and validation period, respectively. Use of daily input data together with a simplistic snowmelt routine, was found to affect model performance during the winter/spring period. Henceforth, model performance can be greatly improved by adopting a more comprehensive method for simulating snowmelt and incorporating the frozen soil conditions. Overall, the model was able to simulate surface runoff reasonably well on annual, seasonal, monthly, and daily intervals, representing all the hydrological components adequately.With the various management scenarios simulated, it was found that the deforestation scenario considerably increased the total flow (11%). On the other hand, the high runoff peaks were decreased and low flows were increased considerably in the application of the tile drainage scenario. It was also observed that surface flow increased in wet years and decreased in normal and dry years in the climate change scenario. Though impacts of certain scenarios were almost negligible, their effects were significant when associated with the percentage area under transformation. Hence, it was concluded that the model can be used to simulate various management scenarios to solve hydrologic problems in the Southern Ontario climatic condition.
14
Kwong, Sunny Kai-Sun. "Price-sensitive inequality measurement." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25807.
Abstract:
The existing inequality indexes in the economics literature (including the more sophisticated indexes of Muellbauer (1974) and Jorgenson-Slesnick (1984)), are found to be insensitive to relative price changes or are unjustifiable in terms of social evaluation ethics or both. The present research fills this gap in the literature by proposing a new index, named the Individual Equivalent Income (IEI) index.
A household indirect utility function is hypothesized which incorporates certain attribute parameters in the form of equivalence scales. These attributes are demographic and environmental characteristics
specific to a given household. This indirect utility function gives a number which represents the utility of each member of the household. A particular level of interpersonal comparison of utilities is assumed which gives rise to an exact individual utility indicator named equivalent income. A distribution of these equivalent incomes forms the basis of a price-sensitive relative inequality index.
This index can be implemented in the Canadian context. Preferences
are assumed to be nonhomothetic translog and demand data are derived from cross-section surveys and time-series aggregates. Based on demand data, the translog equivalent income function can be estimated and equivalent incomes imputed to all individuals in society. An Atkinson index of equivalent incomes is then computed to indicate the actual degree of inequality in Canada.
The new IEI index is compared with other indexes based on a common data set. The main findings are: conventional indexes give bad estimates of the true extent of inequality and the IEI index, while providing a more accurate estimate, indicates distributive price impact in a predictable manner, i.e., food price inflation aggravates while transportation price inflation ameliorates the inequality problem.Arts, Faculty of
Vancouver School of Economics
Graduate
15
Michaud, Jene Diane. "Distributed rainfall-runoff modeling of thunderstorm-generated floods a case study in a mid-sized, semi-arid watershed in Arizona /." Diss., The University of Arizona, 1992. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1992_49_sip1_w.pdf&type=application/pdf.
16
Fahy, Benjamin. "Evaluating the Impact and Distribution of Stormwater Green Infrastructure on Watershed Outflow." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/4732.
Abstract:
Green Stormwater Infrastructure (GSI) has become a popular method for flood mitigation as it can prevent runoff from entering streams during heavy precipitation. In this study, a recently developed neighborhood in Gresham, Oregon hosts a comparison of various GSI projects on runoff dynamics. The study site includes dispersed GSI (rain gardens, retention chambers, green streets) and centralized GSI (bioswales, detention ponds, detention pipes). For the 2017-2018 water year, hourly rainfall and observed discharge data is used to calibrate the EPA's Stormwater Management Model to simulate rainfall-runoff dynamics, achieving a Nash-Sutcliffe efficiency of 0.75 and Probability Bias statistic of 3.3%. A synthetic scenario analysis quantifies the impact of the study site GSI and compares dispersed and centralized arrangements. Each test was performed under four precipitation scenarios (of differing intensity and duration) for four metrics: runoff ratio, peak discharge, lag time, and flashiness. Design structure has significant impacts, reducing runoff ratio 10 to 20%, reducing peak discharge 26 to 68%, and reducing flashiness index 56 to 70%. There was a reverse impact on lag time, increasing it to 50 to 80%. Distributed GSI outperform centralized structures for all metrics, reducing runoff ratio 22 to 32%, reducing peak discharge 67 to 69%, increasing lag time 133 to 500%, and reducing flashiness index between 32 and 62%. This research serves as a basis for researchers and stormwater managers to understand potential impact of GSI on reducing runoff and downstream flooding in small urban watersheds with frequent rain.
17
Small, Aaron Brent. "A comparative evaluation of surface runoff models and methods on small developing watersheds in Northern Virginia." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-03302010-020635/.
Abstract:
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993.18 color maps in back pocket. Vita. Abstract. Includes bibliographical references (leaves 137-139). Also available via the Internet.
18
Mendoza, Maria Nimfa F. "Essays in production theory : efficiency measurement and comparative statics." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/30734.
Abstract:
Nonparametric linear programming tests for consistency with the hypotheses of technical efficiency and allocative efficiency for the general case of multiple output-multiple input technologies are developed in Part I. The tests are formulated relative to three kinds of technologies — convex, constant returns to scale and quasiconcave technologies. Violation indices as summary indicators of the distance of an inefficient observation from an efficient allocation are proposed. The consistent development of the violation indices across the technical efficiency and allocative efficiency tests allows us to obtain comparative measures of the degrees of technical inefficiency and pure allocative inefficiency. Constrained optimization tests applicable to cases where the producer is restricted to optimizing with respect to a subset of goods are also proposed. The latter tests yield the revealed preference-type inequalities commonly used as tests for consistency of observed data with profit maximizing or cost minimizing behavior as limiting cases. Computer programs for implementing the different tests and sample results are listed in the appendix.
In part II, an empirical comparison of nonparametric and parametric measures of technical progress for constant returns to scale technologies is performed using the Canadian input-output data for the period 1961-1980. The original data base was aggregated into four sectors and ten goods and the comparison was done for each sector. If we assume optimizing behavior on the part of the producers, we can reinterpret the violation indices yielded by the efficiency tests in part I as indicators of the shift in the production frontier. More precisely, the violation indices can be considered nonparametric chained indices of technical progress. The parametric measures of technical progress were obtained through econometric profit function estimation using the generalized McFadden flexible functional form with a quadratic spline model for technical progress proposed by Diewert and Wales (1989). Under the assumption of constant returns, the index of technical change is defined in terms of the unit scale profit function which gives the per unit return to the normalizing good. The empirical results show that the parametric estimates of technical change display a much smoother behavior which can be attributed to the incorporation of stochastic disturbance terms in the estimation procedure and, more interestingly, track the long term trend in the nonparametric estimates.
Part III builds on the theory of minimum wages in international trade and is a theoretical
essay in the tradition of analyzing the effects of factor market imperfections on resource allocation. The comparative static responses of the endogenous variables — output levels, employment levels of fixed-price factors with elastic supply and flexible prices of domestic resources — to marginal changes in the economy's exogenous variables — output prices, fixed factor prices and endowments of flexibly-priced domestic resources -— are examined. The effect of a change in a fixed factor price on other flexible factor prices can be decomposed Slutsky-like into substitution and scale effects. A symmetry condition between fixed factor prices and flexible factor prices is obtained which clarifies the concepts of "substitutability" and "complementarity" between these two kinds of factors. As an illustration, the model is applied to the case of a devaluation in a two-sector small open economy with rigid wages and capital as specific factors. The empirical implementation of the general model for the Canadian economy is left to more able econometricians but a starting point can be the sectoral analysis performed in Part II.Arts, Faculty of
Vancouver School of Economics
Graduate
19
Enright, Peter 1962. "Simulation of rainfall excess on flat rural watersheds in Quebec." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61952.
20
Li, Yanqiu, and 李艳秋. "Monitoring, analyzing and modeling hydrological processes over a headwater catchment in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43085349.
21
Barchyn, Thomas Edward, and University of Lethbridge Faculty of Arts and Science. "Field-based aeolian sediment transport threshold measurement : sensors, calculation methods, and standards as a strategy for improving inter-study comparison." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Geography, 2010, 2010. http://hdl.handle.net/10133/2616.
Abstract:
Aeolian sediment transport threshold is commonly defined as the minimum wind speed (or shear stress) necessary for wind-driven sediment transport. Threshold is a core parameter in most models of aeolian transport. Recent advances in methodology for field-based measurement of threshold show promise for improving parameterizations; however, investigators have varied in choice of method and sensor. The impacts of modifying measurement system configuration are unknown. To address this, two field tests were performed: (i) comparison of four piezoelectric sediment transport sensors, and (ii) comparison of four calculation methods. Data from both comparisons suggest that threshold measurements are non-negligibly modified by measurement system configuration and are incomparable. A poor understanding of natural sediment transport dynamics suggests that development of calibration methods could be difficult. Development of technical standards was explored to improve commensurability of measurements. Standards could assist future researchers with data syntheses and integration.xi, 108 leaves : ill. ; 29 cm
22
Goodrich, David Charles. "Geometric simplification of a distributed rainfall-runoff model over a range of basin scales." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185051.
Abstract:
Distributed rainfall-runoff models are gaining widespread acceptance; yet, a fundamental issue that must be addressed by all users of these models is definition of an acceptable level of watershed discretization (geometric model complexity). The level of geometric model complexity is a function of basin and climatic scales as well as the availability of input and verification data. Equilibrium discharge storage is employed to develop a quantitative methodology to define a level of geometric model complexity commensurate with a specified level of model performance. Equilibrium storage ratios are used to define the transition from overland to channel-dominated flow response. The methodology is tested on four subcatchments in the USDA-ARS Walnut Gulch Experimental Watershed in southeastern Arizona. The catchments cover a range of basins scales of over three orders of magnitude. This enabled a unique assessment of watershed response behavior as a function of basin scale. High quality, distributed, rainfall-runoff data were used to verify the model (KINEROSR). Excellent calibration and verification results provided confidence in subsequent model interpretations regarding watershed response behavior. An average elementary channel support area of roughly 15% of the total basin area is shown to provide a watershed discretization level that maintains model performance for basins ranging in size from 1.5 to 631 hectares. Detailed examination of infiltration, including the role and impacts of incorporating small-scale infiltration variability in a distribution sense, into KINEROSR, over a range of soils and climatic scales was also addressed. The impacts of infiltration and channel losses on runoff response increase with increasing watershed scale as the relative influence of storms is diminished in a semi-arid environment such as Walnut Gulch. In this semi-arid environment, characterized by ephemeral streams, watershed runoff response does not become more linear with increasing watershed scale but appears to become more nonlinear.
23
Dressler, Kevin Andrew. "Estimating the Spatial Distribution of Snow Water Equivalent and Simulated Snowmelt Runoff Modeling in Headwater Basins of the Semi-arid Southwest." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1063%5F1%5Fm.pdf&type=application/pdf.
24
Mandock, Randal Lee Nicholas. "A multiple beam sodar for the measurement of atmospheric turbulence." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/25869.
25
Lee, Haksu. "Development and performance analysis of a physically based hydrological model incorporating the effects of subgrid heterogeneity." University of Western Australia. School of Environmental Systems Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0129.
Abstract:
[Truncated abstract] The balance equations of mass and momentum, defined at the scale of what has been defined as a Representative Elementary Watershed (REW) has been proposed by Reggiani et al. (1998, 1999). While it has been acknowledged that the REW approach and the associated balance equations can be the basis for the development of a new generation of distributed physically based hydrological models, four building blocks have been identified as necessary to transform the REW approach into, at the very least least, a workable modelling framework beyond the theoretical achievements. These are: 1) the development of reasonable closure relations for the mass exchange fluxes within and between various REW sub-regions that effectively parameterize the effects of sub-REW heterogeneity of climatic and landscape properties, 2) the design of numerical algorithms capable of generating numerical solutions of the REW-scale balance equations composed of a set of coupled ordinary differential and algebraic equations for the number of REWs constituting a study catchment and the sub-regions within the REWs, 3) applications of the resulting numerical model to real catchments to assess its performance in the prediction of any specified hydrological variables, and 4) the assessment of the model reliability through estimation of model predictive uncertainty and parameter uncertainty. This thesis is aimed at making substantial progress in developing each of these building blocks. Chapter 1 presents the background and motivation for the thesis, while Chapter 2 summarizes its main contributions. Chapter 3 presents a description of the closure problem that the REW approach faces, and presents and implements various approaches to develop closure relations needed for the completeness of balance equations of the REW approach. ... In addition, Chapter 4 also shows an initial application of CREW to a small catchment, Susannah Brook in the south-west of Western Australia. Chapter 5 presents the application of CREW to two meso-scale catchments in Australia, namely Collie and Howard Springs, located in contrasting climates. Chapter 6 presents results of the estimation of predictive uncertainty and parameter sensitivity through the application of CREW to two catchments in Australia, namely Susannah Brook and Howard Springs, by using the Generalized Likelihood Uncertainty Estimation (GLUE) methodology. Finally, Chapter 7 presents recommendations for future work for the further advancement of the REW approach. Through these exercises this PhD thesis has successfully transformed the REW-scale coupled balance equations derived by Reggiani et al. (1998, 1999) into a new, well tested numerical model blueprint for the development and implementation of distributed, physically based models applicable at the catchment, or REW scale.
26
McNelis, Robert J. "The measurement and empirical evaluation of quality and productivity for manufacturing processes." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06102009-063228/.
27
Chung, Nga-hang, and 鍾雅行. "Large-eddy simulation of transport of inert and chemically reactive pollutants over 2D idealized street canyons." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47849903.
Abstract:
In view of the worsening air quality in the world, more concerns are focused on the
environment. This thesis uses the technique of CFD and develops the computer model
to investigate the wind and pollutant transport, as well as the chemistry of reactive
pollutants in idealized two-dimensional (2D) street canyons.
Three scientific questions are raised in this thesis. The first task is to find out the po-
sition with the most favorable pollutant removal along the ground level over 2D idealized
street canyon of different building-height-to-street-width (aspect) ratios (ARs). The di-
mensionless parameter, C, represents the pollutant removal performance. In the isolated
roughness regime, the two local maximum C locate at the reattachment point and the
windward corner. In the wake interference regime, C is peaked on the windward side. The
number of vertically aligned recirculations depends on the street depth in the skimming
flow regime. The sizes of the secondary recirculation upstream and downstream deter-
mine how the maximum C shifts from the street centre. After identifying the position of
peaked pollutant removal rate at the ground level, the emission source should be placed
with the highest constant C in order to remove the pollutants upward more quickly to
safeguard the street-level air quality.
After understanding the best pollutant removal in the street canyon of different ARs,
the second task is to find out what AR is the most favorable for the ventilation and
pollutant removal across the roof level. The three parameters, namely friction factor,
air exchange rate (ACH) and pollutant exchange rate (PCH), are introduced to quantify
the pressure difference to sustain the mean flow, the ventilation and pollutant removal,
respectively. The turbulence contributes more than 70% to the total ACH and PCH in
all the three flow regimes. By increasing the atmospheric turbulence in building geometry
as well as the surface roughness, the ventilation and pollutant removal performance can
be improved. The linear relation between the friction factor and ACH demonstrates the
larger resistance that in turn promotes the air exchange over the roof level.
The physical dispersion is studied; however atmospheric pollutants are seldom in-
ert but chemically reactive instead. The last task is to include the three common air
pollutants, NO, NO2 and O3, in the simple NOx ?O3 mechanism in terms of the photo-
stationary state and reaction rates. The Damkohler numbers of NO and O3, DaNO and
DaO3, are parameterized by the concentrations of the sources NO and O3. The normalized
mean and fluctuation NO, NO2 and O3 are separately considered. The integrated pho-
tostationary state (PSS) in the first canyon increases with DaO3 under the same DaNO.
The integrated PSS of the second to the twelveth street canyons are compared with each
case, the monotonic increase in the PSS from the second to twelveth canyon is perceived
in DaNO/DaO3 1, 0.03, 0.02, 0.001 and 0.000333. Further decreases the DaNO/DaO3 to
0.000143, 0.000125, 0.000118, 0.000111 and 0.0001, the PSS is found to be non-linear and
the trough appears in the fourth and fifth canyons.published_or_final_version
Mechanical Engineering
Master
Master of Philosophy
28
Tsuneki, Atsushi. "Essays on the measurement of waste and project evaluation." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27554.
Abstract:
Harberger's methodology for the measurement of deadweight loss is reformulated in a general equilibrium context with adopting the Allais-Debreu-Diewert approach and is applied to various problems with imperfect markets. We also develop second best project evaluation rules for the same class of economies.
Chapter 1 is devoted to the survey of various welfare indicators. We especially discuss the two welfare indicators due to Allais, Debreu, Diewert and Hicks, Boiteux in relation to Bergson-Samuelsonian social welfare function.
We first show that these two measures generate a Pareto inclusive ordering across various social states, but they are rarely welfarist, so that both are unsatisfactory as Bergson-Samuelsonian social welfare functions. We next show that second order approximations to the Allais-Debreu-Diewert measure of waste can be computed from local information observable at the equilibrium, whereas second order approximations to the Hicks-Boiteux measure of welfare or to the Bergson -Samuelsonian social welfare function require information on the marginal utilities of income of households, which is unavailable with ordinal utility theory. Finally, we give a diagrammatic exposition of the two measures and their approximations to give an intuitive insight into the economic implications of the two measures.
Chapter 2 and Chapter 3 study an economy with public goods. In Chapter 2, we compute an approximate deadweight loss measure for the whole economy when the endogenous choice of public goods by the government is nonoptimal and the government revenue is raised by distortionary taxation by extending the Allais-Debreu-Diewert approach discussed in Chapter 1. The resulting measure of waste is related to indirect tax rates, net marginal benefits of public goods, and the derivatives of aggregate demand and supply functions evaluated at an equilibrium. In Chapter 3, cost-benefit rules for the provision
of a public good are derived when there exist tax distortions. We derive the rules as giving sufficient conditions for Pareto improvement, but we also discuss when these rules are necessary conditions for an interior social optimum. When indirect taxes are fully flexible but lump-sum transfers
are restricted, we recommend a rule which generalized the cost-benefit rule due to Atkinson and Stern (1974) to a many-consumer economy. When both indirect taxes and lump-sum transfers are flexible, we suggest a rule which is based on Diamond and Mirrlees' (1971) productive efficiency principle. When only lump-sum transfers are variable, we obtain a version of the Harberger (1971)-Bruce-Harris (1982) cost-benefit rules.
Chapters 4 and 5 study an economy with increasing returns to scale in production and imperfect competition. In Chapter 4, we discuss a methodology for computing an approximate deadweight loss due to imperfect regulation of monopolistic industries by extending the Allais-Debreu-Diewert approach to incorporate the nonconvex technology. With the assumption of the quasi-con-cavity of production functions and fixed number of firms, we can derive an approximate deadweight loss formula which is related to markup rates of firms, and the derivatives of aggregate demand functions, factor supply and demand functions and the derivatives of marginal cost functions. We also discuss various limitations of our approach and the relation between our work and that of Hotelling (1938). In Chapter 5, we consider cost-benefit rules of a large project applicable in the presence of imperfect competition. We show that the index number approach due to Negishi (1962) and Harris (1978) can be extended to handle situations with imperfect competition.Arts, Faculty of
Vancouver School of Economics
Graduate
29
Huth, Anne M. Kramer. "Geochemical and isotopic mixing models : two case studies in a snow-dominated and semi-arid environment." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/191260.
Abstract:
The influence of climate and antecedent moisture conditions on hydrological and biogeochemical fluxes was studied and contrasted in three nested, high-elevation, snowmelt-dominated catchments in the Sierra Nevada, California and one basin-floor, semi-arid catchment in southeastern Arizona. Investigations were completed within a different two-year period at each site, with the second year being climatically different (typically drier) than the first. Spring snowmelt, widespread winter frontal precipitation, and episodic summer rains induce surface water flow in these catchments, though the timing and magnitude of nutrient redistribution among soil and stream compartments varies in each. Surface water flow from spring snowmelt in high-elevation catchments travels through the subsurface or across the surface as direct runoff A more typical process producing surface water flow in semi-arid catchments is flooding during episodic or widespread rainfall. Hydrograph separations at Emerald Lake, Topaz Lake and Marble Fork catchments in Sequoia National Park, California, revealed that the majority of snowmelt flowed through soil before entering the stream in both average and highsnow years. The Emerald Lake watershed had a higher fraction of old water in its outflow in the average accumulation year because of the previous year's high accumulation and longer melt season. A mixing model analysis performed of the upper San Pedro River, Arizona, for wet and dry years showed that summer flood hydrographs were composed mainly of precipitation and surface runoff in both years, though a higher soil-water input occurred in the wetter year and in early season floods in the dry year. Stream and soil water nitrate concentrations were higher during floods in the dry year. Early season floods in the dry year exhibited more variability in stream water nitrate and sulfate, whereas late season flood concentrations reflected a well-mixed system and therefore less variation of these species during flood hydrographs. These data showed that periods of below average precipitation preceding major runoff periods result both in less soil water and solute export during summer floods in basin-floor catchments and less direct snowmelt in high-elevation catchments. Hydrologic and solute export in each catchment, despite their differing geographical locations, responds in similar ways to climate variability.
30
Corless, Robert Malcolm. "Mathematical modelling of the combined effects of vortex-induced vibration and galloping." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26981.
Abstract:
In this thesis a mathematical model for the combined effects of vortex-induced oscillation and galloping of a square section cylinder in cross flow is examined. The model equations are obtained by simply combining Parkinson and Smith's Quasi-Steady Model for galloping with the Hartlen-Currie model for vortex-induced vibration,
which is essentially the same model used by Bouclin in the hydrodynamic case.
The semi-empirical model is solved using three popular approximate analytical
methods, and the methods of solution are evaluated. The solution of the model is compared with recent experimental data.
The methods of solution used are the Method of Van Der Pol, (also called the method of Harmonic Balance), the Method of Multiple Scales, and some results from the Hopf Bifurcation Theory. The Method of Multiple Scales provides the most useful solutions, getting good results even with just the ༠(1) terms, although the next-order terms are necessary for the solution in the resonance regions. The phenomenon of subharmonic resonance, observed in recent experiments, is also observed in the solution of the model equations.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
31
Fonley, Morgan Rae. "Effects of oscillatory forcing on hydrologic systems under extreme conditions: a mathematical modeling approach." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/2075.
Abstract:
At the large watershed scale, we emphasize the effects of flow through a river network on streamflow under dry conditions. An immediate consequence of assuming dry conditions is that evapotranspiration causes flow in the river network to exhibit oscillations. When all links in the river network combine their flow patterns, the oscillations interact in ways that change the timing and amplitude of the streamflow waves at the watershed outlet. The geometric shape of the river network is particularly important, so we develop an analytic solution for streamflow which emphasizes that importance.
Doing hydrology backward is a strategy recently developed by several researchers to deal with uncertainty in measurements of forcing terms applied to hydrologic models. The strategy has also been applied to resolve the assumption of homogeneity on realistic catchments that exhibit many heterogeneous properties. In this work, we demonstrate hydrology in the backward direction applied to two examples: using streamflow at the catchment scale to determine runoff at the hillslope scale and using the hillslope runoff to infer the applied evapotranspiration forcing under the assumption of dry conditions. In order to work across scales, we utilize the analytic solution for streamflow at the outlet of a river network. At the hillslope scale, we develop a soil model to create fluxes consistent with observed soil processes.
32
Sande, Leif Andrew. "Experimental Studies on Infiltration/Soil-Water Movement Processes and Green-AMPT Modeling." Thesis, North Dakota State University, 2011. https://hdl.handle.net/10365/29329.
Abstract:
Experimental studies on infiltration/soil-water movement processes are vital to
better understanding movement of soil-water in the vadose zone. The objective of this
experimental research was to investigate infiltration/soil-water movement processes
utilizing laboratory experiments and computer modeling. Small scale laboratory soil box
infiltration experiments were conducted and utilized for the improved parameterization of
the Green-Ampt (GA) saturated moisture content parameter to produce an effective
moisture content parameter (Be) for utilization in a modified GA model. By incorporating ?e
values into GA modeling, modeling results showed greatly improved wetting front
prediction across different soil conditions. A new soil packing method was proposed for
replicating complex microtopographical surfaces with uniform bulk densities in laboratory
soil box experiments which proved efficient and effective at accomplishing both objectives.
A rainfall simulator and an instantaneous-profile laser scanner were used to simulate
rainfall and quantify surface microtopography for experiments. The results clearly show the
effect of microtopography on infiltration and soil-water movement characteristics. This
offers valuable insight into infiltration/soil-water movement processes as affected by
different soil and surface microtopographic conditions.National Science Foundation (Grant No. EAR-0907588)
33
Liang, Changnian. "A new surface resistance measurement method with ultrahigh sensitivity." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40299.
Abstract:
A superconducting niobium triaxial cavity has been designed and fabricated to study residual surface resistance of planar superconducting materials. Unlike many other structures where the test samples are placed in strong magnetic field positions, the edge of a 25.4 mm or larger diameter sample in the triaxial cavity is located outside the strong field region. Therefore, the edge effects and possible losses between the thin film and the substrate have been minimized in this design, ensuring that the induced RF losses are intrinsic to the test material. The fundamental resonant frequency of the cavity is 1.5 GHz, the same as the working frequency of CEBAF cavities. The cavity has a compact size compared to its TE₀₁₁ counterpart, which makes it more sensitive to the sample's loss.Ph. D.
34
Jahraus, Karen Veronica. "Using the jackknife technique to approximate sampling error for the cruise-based lumber recovery factor." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26419.
Abstract:
Timber cruises in the interior of British Columbia are designed to meet precision requirements for estimating total net merchantable volume. The effect of this single objective design on the precision of other cruise-based estimates is not calculated. One key secondary objective, used in the stumpage appraisal of timber in the interior of the province, is estimation of the lumber recovery factor (LRF). The importance of the LRF in determining stumpage values and the fact that its precision is not presently calculated, prompted this study. Since the LRF is a complicated statistic obtained from a complex sampling design, standard methods of variance calculation cannot be applied. Therefore, the jackknife procedure, a replication technique for approximating variance, was used to determine the sampling error for LRF. In the four cruises examined, the sampling error for LRF ranged from 1.27 fbm/m³ to 15.42 fbm/m³. The variability in the LRF was related to the number of sample trees used in its estimation. The impact of variations in the LRF on the appraised stumpage rate was influenced by the lumber selling price, the profit and risk ratio and the chip value used in the appraisal calculations. In the cruises investigated, the change in the stumpage rate per unit change in the LRF ranged between $0.17/m³ and $0.21/m³. As a result, sampling error in LRF can have a significant impact on assessed stumpage rates. Non-sampling error is also a major error source associated with LRF, but until procedural changes occur, control of sampling error is the only available means of increasing the precision of the LRF estimate. Consequently, it is recommended that the cruise design objectives be modified to include a maximum allowable level of sampling error for the LRF.Forestry, Faculty of
Graduate
35
廖俊豪 and Chun-ho Liu. "Numerical modelling of atmospheric boundary layer with application to air pollutant dispersion." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31239018.
36
Wang, Yuexing, and 王越興. "Sediment nutrient flux for a pulsed organic load: mathematical modeling and experimental verfication." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40987826.
37
So, Shuk-pan Ellen, and 蘇淑彬. "Large eddy simulations of wind flow and pollution dispersion in an urban street canyon." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29332710.
38
Stovold, Matthew R. "Modeling urban stormwater disposal systems for their future management and design." University of Western Australia. School of Environmental Systems Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0111.
Abstract:
[Truncated abstract]This thesis investigates aspects of urban stormwater modeling and uses a small urban catchment (NE38) located in the suburb of Nedlands in Perth, Western Australia to do so. The MUSIC (Model for Urban Stormwater Improvement Conceptualisation) model was used to calibrate catchment NE38 using measured stormwater flows and rainfall data from within the catchment. MUSIC is a conceptual model designed to model stormwater flows within urban environments and uses a rainfall-runoff model adapted to generate results at six minute time steps. Various catchment scenarios, including the use of porous asphalt as an alternative road surface, were applied to the calibrated model to identify effective working stormwater disposal systems that differ from the current system. Calibrating catchment NE38 using the MUSIC model was attempted and this involved matching modeled stormwater flows to stormwater flows measured at the catchment drainage point. This was achieved by measuring runoff contributing areas (roads) together with rainfall data measured from within the catchment and altering the seepage constant parameter for all roadside infiltration sumps. ... The MUSIC model generated future scenario outcomes for alternative stormwater disposal systems that displayed similar or improved levels of performance with respect to the current system. The following scenarios listed in increasing order of effectiveness outline future stormwater disposal systems that may be considered in future urban design. 1. 35% porous asphalt application with no sumps in 2036 2. 35% porous asphalt application with no sumps in 2064 3. 68% porous asphalt application with no sumps in 2036 4. 68% porous asphalt application with no sumps in 2064. Future scenarios using the current stormwater disposal system (with roadside infiltration sumps) with porous asphalt were also run. These scenarios reduced stormwater runoff and contaminant loading on the catchment drainage point however the inclusion of a roadside infiltration sump system may not appeal to urban designers due to the costs involved with this scenario. Climate change will affect the design of future stormwater disposal systems and thus, the design of these systems must consider a rainfall reducing future. Based on the findings of this thesis, current stormwater runoff volumes entering catchment drainage points can be reduced together with contaminant loads in urban environments that incorporate porous asphalt with a stormwater disposal design system that is exclusive of roadside infiltration sumps.
39
Scott, Ryan. "Characterizing Tilt Effects on Wind Plants." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/5035.
Abstract:
Tilting the nacelle of a wind turbine modifies entrainment into the wind plant and impacts total efficiency. Extreme angles can produce flying and crashing wakes where the wake either disrupts entertainment from the undisturbed flow above or is decimated on the ground. The effect of tilt angle on downstream wake behavior was investigated in a series of wind tunnel experiments. Scale model turbines with a hub height and diameter of 12 cm were arranged in a Cartesian array comprised of four rows of three turbines each. Nacelle tilt was varied in the third row from -15° to 15° in chosen 5° increments. Stereo PIV measurements of the instantaneous velocity field were recorded at four locations for each angle. Tilted wakes are described in terms of the average streamwise velocity field, wall-normal velocity field, Reynolds stresses, and mean vertical transport of kinetic energy. Conditional sampling is used to quantify the importance of sweep vs. ejection events and thus downwards vs. upwards momentum transfer. Additionally, wake center displacement and changes in net power are presented and compared to existing models. The results demonstrate large variations in wake velocity and vertical displacement with enhanced vertical energy and momentum transfer for negative tilt angles. Simulation models accurately predict wake deflection while analytic models deviate considerably highlighting the difficulties in describing tilt phenomena. Negative angles successfully produce crashing wakes and improve the availability of kinetic energy thereby improving the power output of the wind plant.
40
Freedland, Graham. "Investigation of Jet Dynamics in Cross-Flow: Quantifying Volcanic Plume Behavior." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/3314.
Abstract:
Volcanic eruption columns inject high concentrations of ash into the atmosphere. Some of this ash is carried downwind forming ash clouds in the atmosphere that are hazardous for private and commercial aviation. Current models rely on inputs such as plume height, duration, eruption rate, and meteorological wind fields. Eruption rate is estimated from plume height using relations that depend on the rate of air entrainment into the plume, which is not well quantified. A wind tunnel experiment has been designed to investigate these models by injecting a vertical air jet into a cross-flow. The ratio of the cross-flow and jet velocities is varied to simulate a weak plume, and flow response is measured using particle image velocimetry. The plumes are characterized and flow data relative to the centerline is examined to measure the growth of weak plumes and the entrainment velocity along its trajectory. It was found that cross-flow recirculates behind the jet and entrainment occurs both up and downstream of the jet. Analysis of the generation of turbulence enhanced results by identifying the transition point to bending plume and the growth of the shear layer in a bending plume. This provides information that can be used to improve models of volcanic ash concentration changes in the atmosphere.
41
Zhou, Jie. "Modeling and measurement of switching converters." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45662.
Abstract:
The methods of modeling and measurement of switching converters are discussed in this thesis. The average model is very simple but is inaccurate when modulation frequencies approach to one-half of the switching frequency. The discrete model can accurately predict the modulation envelope of the output voltage, but it is very complex. The discreteâ average model combines both average and discrete modeling techniques so that it possesses the advantages of both techniques. The experimental results show the deficiency of analog modulation technique for loop gain measurement under certain circumstances. The digital modulator, on the other hand, always provides accurate measurement data. The accuraqy of the discrete-average model is verified by measurement data using the digital modulator.
Master of Science
42
Common, David N. "Development of a system for the measurement of the static bulk modulus of fluids." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17579.
43
Phan, Kenny. "Innovation Measurement: a Decision Framework to Determine Innovativeness of a Company." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1017.
Abstract:
Innovation is one of the most important sources of competitive advantage. It helps a company to fuel the growth of new products and services, sustain incumbents, create new markets, transform industries, and promote the global competitiveness of nations. Because of its importance, companies need to manage innovation. It is very important for a company to be able to measure its innovativeness because one cannot effectively manage without measurement. A good measurement model will help a company to understand its current capability and identify areas that need improvement.
In this research a systematic approach was developed for a company to measure its innovativeness. The measurement of innovativeness is based on output indicators. Output indicators are used because they cannot be manipulated. A hierarchical decision model (HDM) was constructed from output indicators. The hierarchy consisted of three levels: innovativeness index, output indicators and sub-factors.
Experts' opinions were collected and quantified. A new concept developed by Dr. Dundar Kocaoglu and referred to as "desirability functions" was implemented in this research.
Inconsistency of individual experts, disagreement among experts, intraclass correlation coefficients and statistical F-tests were calculated to test the reliability of the experts' judgments. Sensitivity analysis was used to test the sensitivity of the output indicators, which indicated the allowable range of the changes in the output indicators in order to maintain the priority of the sub-factors.
The outcome of this research is a decision model/framework that provides an innovativeness index based on readily measurable company output indicators.
The model was applied to product innovation in the technology-driven semiconductor industry. Five hypothetical companies were developed to simulate the application of the model/framework. The profiles of the hypothetical companies were varied considerably to provide a deeper understanding of the model/framework. Actual data from two major corporations in the semiconductor industry were then used to demonstrate the application of the model.
According to the experts, the top three sub-factors to measure the innovativeness of a company are revenue from new products (28%), market share of new products (21%), and products that are new to the world (20%).
44
Yang, Jing Yi. "An improved algorithm for data filtering based on variation for short term air pollution prediction in Macau." Thesis, University of Macau, 2012. http://umaclib3.umac.mo/record=b2592957.
45
Henson, Susan Kornegay. "The development of a method for determining the best-fit shape for the crotch seam of men's pants." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03142009-040653/.
46
Thornhill, Kenneth L. II. "An investigation of the environment surrounding supercell thunderstorms using wind profiler data." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/26958.
47
Bandeen, Reid Francis 1957. "Simulations of dry well recharge in the Tucson Basin, Arizona." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276654.
Abstract:
The variably saturated flow model Unsat 2 was used for three case study simulations of dry well recharge in the Tucson Basin, Arizona. Dry well design, and rainfall/runoff and vadose zone conditions representative of the locality were assumed in the simulations to address travel time to the regional aquifer, rates and extent of radial flow, and relative degree of solute attenuation by sorption and dilution with regional groundwater. Soil specific surface was used to estimate relative degree of sorption among the three cases. One case of uniform soil composition and two cases of layered soil composition were simulated. Clay content had the greatest influence on specific surface. Hydraulic conductivity had the greatest influence on soil water velocities and degree of radial flow. The presence of layered subsurface conditions that included strata of low hydraulic conductivity enhanced the degree of subsurface solute attenuation by sorption and dilution.
48
Kriel, Dawid Eduard. "Prediction and measurement of the performance of spray cooled heat exchangers." Thesis, Stellenbosch : Stellenbosch University, 1991. http://hdl.handle.net/10019.1/69378.
Abstract:
Thesis (MEng) -- Stellenbosch University, 1991.ENGLISH ABSTRACT: In the present study various mathematical models have been developed for the analysis of spray cooled finnned-tube heat exchangers. These models range from simplified models based on the work by Kreid et al. [78KR1], Nakayama et al. [88NA1] and Erens et al. [90ER1] to a more comprehensive model based on the work by Poppe [84P01]. Computer programs were written to evaluate the performance prediction of these models on spray cooled heat exchangers in the vertical air flow mode. Experimental tests were conducted on a four-row finned-tube heat exchanger in a vertical air /water mist flow to verify the mathematical models and it was found that the performance of this heat exchanger could be predicted within 20 per cent using the accurate model. Significant performance enhancement (up to 3.5 times the dry performance) was found by spraying relatively small amounts of water onto the heat exchanger. The spray water massflow rate was found to have a significant effect on the two phase pressure drop across the heat exchanger. The present study indicated certain important factors which have to be taken into consideration when designing spray cooled heat exchanger units. These include the geometry of the finned-tubes, the temperature difference between the process water and the optimum air and the air /spray water ratio.
AFRIKAANSE OPSOMMING: In die tesis is 'n aantal wiskundige modelle ontwikkel wat gebruik kan word vir die analise van sproei verkoelde vinbuis warmte uitruilers. Die wiskundige modelle wissel van eenvoudige modelle wat gebaseer is op die werk van Kreid et al. [78KR1 ], Nakayama et al. [88NA1] en Erens et al. [90ER1] tot 'n omvattende model wat gebaseer is op die werk van Poppe [84 PO 1]. Rekenaar programme is geskryf om die die modelle se voorspellingsvermoe van die kapasiteit van sproei verkoelde warmte uitruilers te evalueer. 'n Eksperimentele ondersoek is gedoen op 'n warmte uitruiler met vier vinbuis rye in 'n toetsseksie met vertikale lugvloei. Die toets resultate is gebruik vir die evaluasie van die wiskundige modelle en het getoon dat die akkurate model se voorspellings binne 20 per sent van die gemete kapasitiet van die uitruiler val. Die eksperirnentele werk het verder aangetoon dat deur klein hoeveelhede water op die uitruiler te sproei, 'n toename in kapasiteit tot 3.5 keer die droe werkverrigting moontlik is. Die twee-fase drukval oor die uitruiler is sterk bei:nvloed deur die sproei water massavloei. Die analitiese navorsmg wat gedoen is met behulp van die rekenaar programme het aangedui dat daar 'n paar belangrike faktore is wat in ag geneem moet word met die ontwerp van sproei verkoelde warmte uitruilers. Die faktore sluit die vinbuis geometrie, die temperatuur verskil tussen die proses water en lug en optimum lug/sproeiwater massavloei verhouding in.
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Powell, James Eckhardt. "Building a Multivariable Linear Regression Model of On-road Traffic for Creation of High Resolution Emission Inventories." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3415.
Abstract:
Emissions inventories are an important tool, often built by governments, and used to manage emissions. To build an inventory of urban CO2 emissions and other fossil fuel combustion products in the urban atmosphere, an inventory of on-road traffic is required. In particular, a high resolution inventory is necessary to capture the local characteristics of transport emissions. These emissions vary widely due to the local nature of the fleet, fuel, and roads.
Here we show a new model of ADT for the Portland, OR metropolitan region. The backbone is traffic counter recordings made by the Portland Bureau of Transportation at 7,767 sites over 21 years (1986-2006), augmented with PORTAL (The Portland Regional Transportation Archive Listing) freeway traffic count data. We constructed a regression model to fill in traffic network gaps using GIS data such as road class and population density. An EPA-supplied emissions factor was used to estimate transportation CO2 emissions, which is compared to several other estimates for the city's CO2 footprint.
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Shannon, Michael P. "An illicit nuclear material detection system based on photoneutron and photofission interaction." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/17817.