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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Solar cycle variation of stratospheric ozone: Multiple regression analysis of long-term satellite data sets and comparisons with models

Soukharev, B. E., Hood, L. L. 31 October 2006 (has links)
Previous multiple regression analyses of the solar cycle variation of stratospheric ozone are improved by (1) analyzing three independent satellite ozone data sets with lengths extending up to 25 years and (2) comparing column ozone measurements with ozone profile data during the 1992–2003 period when no major volcanic eruptions occurred. Results show that the vertical structure of the tropical ozone solar cycle response has been consistently characterized by statistically significant positive responses in the upper and lower stratosphere and by statistically insignificant responses in the middle stratosphere (∼28–38 km altitude). This vertical structure differs from that predicted by most models. The similar vertical structure in the tropics obtained for separate time intervals (with minimum response invariably near 10 hPa) is difficult to explain by random interference from the QBO and volcanic eruptions in the statistical analysis. The observed increase in tropical total column ozone approaching the cycle 23 maximum during the late 1990s occurred primarily in the lower stratosphere below the 30 hPa level. A mainly dynamical origin for the solar cycle total ozone variation at low latitudes is therefore likely. The amplitude of the solar cycle ozone variation in the tropical upper stratosphere derived here is somewhat reduced in comparison to earlier results. Additional data are needed to determine whether this upper stratospheric response is or is not larger than model estimates.
12

Variabilidade genética para o teor de óleo entre progênies autofecundadas de mamona (Ricinus cummunis L.) da cultivar guarani

Myczkowski, Mirina Luiza [UNESP] January 2003 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:22:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2003Bitstream added on 2014-06-13T19:27:26Z : No. of bitstreams: 1 myczkowski_ml_me_botfca.pdf: 94102 bytes, checksum: acf2ae8422a1d023a113297ec3036a90 (MD5) / O presente trabalho teve como objetivo avaliar a variabilidade genética para teor de óleo entre progênies autofecundadas da cultivar de mamona Guarani. O material utilizado foi constituído de 135 progênies obtidas de plantas individuais, por meio de autofecundações artificiais, divididas em três experimentos e parcelas com 10m2. As avaliações foram realizadas em duas localidades, em Araçatuba - SP e em São Manuel - SP, na Fazenda Experimental São Manuel, da Faculdade de Ciências Agronômicas – UNESP/Botucatu. Foi avaliado o teor de óleo obtido por meio do método químico Soxhlet. Para cada localidade foram realizadas análises estatísticas segundo o delineamento de blocos ao acaso e também uma análise conjunta para os dois locais. Foram determinados os parâmetros genéticos, variância genética e coeficiente de herdabilidade. Os quadrados médios da interação de progênies por locais avaliadas na análise conjunta foram significativos a 5% de probabilidade pelo teste F em todos os experimentos, o que define a existência de comportamento diferencial de progênies em relação aos locais quanto ao teor de óleo. Os quadrados médios da análise de variância entre progênies dentro de locais apresentaram significância a 5% de probabilidade pelo teste F em todos os experimentos de Araçatuba, mostrando a existência de diferenças genéticas entre progênies, já nos experimentos de São Manuel os quadrados médios não foram significativos indicando assim ausência ou baixa variabilidade genética para teor de óleo. A média de teor de óleo, em São Manuel foi 43,22%, variando de 34,87% a 49,24%. Em Araçatuba, a média foi 43,59%, variando de 30,24% a 53,60%. A variância genética e o coeficiente de herdabilidade foram, respectivamente 0.32 e 0,10 para São Manuel e 4,87 e 0,44 para Araçatuba. Estes valores mostram a possibilidade de sucesso na seleção para teor de óleo nas condições de Araçatuba. / The purpose of the research was to evaluate the genetic variability for oil content among lines of castor bean, cv. Guarani. Using artificial self- fertilizations, 135 lines were obtained from individual plants and tested in two locations in the state of São Paulo : Araçatuba and São Manuel, utilizing randomized block design with three replications and plots with 10m2. Oil content was determined by the Soxhlet chemical method. Individual and joint analysis of variance were made to estimate genetic parameters. The mean squares of the line x location interaction were significant by the F test with 5% of probability, that demonstrated the existence of differential behavior of lines due locations for oil content. The mean squares of the variance analysis among lines were significant by the F test with 5% of probability in Araçatuba, showing the existence of genetic differences among lines. However, in São Manuel, the mean squares were not significant, showing absence or low genetic variability for oil content. Average of line oil content, in São Manuel was 43.22% (from 34.87% to 49.24%). In Araçatuba the oil content mean was 43.59% (from 30.24% to 53.6%). Genetic variance and heritability coefficients were respectively 0.32 and 0.10 for São Manuel and 4.87 and 0.44 for Araçatuba. Those values show the possibility to improve the oil content by selection in Araçatuba conditions.
13

Managing the effect of infiltration variability on the performance of surface irrigation

Gillies, Malcolm H. January 2008 (has links)
[Abstract]: Infiltration variability is a major issue during the design phase and management for all types of irrigation systems. Infiltration is of particular significance for furrow irrigation and other forms of surface irrigation as the soil intake rate at any given position not only determines the depth applied but also governs the distribution of water to other locations in the field. Despite this, existing measurement and evaluationprocedures generally assume homogeneous soil infiltration rates across the field to simplify data collection and computational requirements. This study was conducted to(a) determine whether spatial and temporal variations in soil infiltration characteristics have a significant impact on the performance of surface irrigation and (b) identify more appropriate management strategies that account for this variability and substantially improve irrigation performance.The soil infiltration rate is typically expressed as an empirical function of opportunity time. The infiltration function parameters cannot be directly measured but are commonly estimated from field hydraulic measurements using an appropriate simulation model. The volume balance model as used in the inverse solution for infiltration (e.g. Two Point Method) was modified to enable runoff data collected during the inflow period to be used in the estimation of the infiltration parameters. The resulting model, IPARM also accommodates the full (variable) inflowhydrograph rather than relying on a constant inflow assumption. Inclusion of runoff data in the inverse solution improved the accuracy of the infiltration curve during the runoff phase and hence offered the greatest benefit where the irrigation time exceededthe completion of advance. Analysis of field data collected from multiple furrows at a single site indicated that accounting for the variable inflow in IPARM both reduced the variability (e.g. reduction in the coefficient of variance (CV) of cumulative infiltrated depths of 18.6% and 11.5% at opportunity times of 100 and 500 minutes,respectively) and standardised the shape of the estimated infiltration curves. Hence, a significant proportion of the apparent variability in soil infiltration rates was shown to be a consequence of the constant inflow assumption. Sensitivity analysis indicatedthat IPARM is highly sensitive to the runoff measurements but is not influenced by the relative numbers of advance and runoff data points. Validation of IPARM estimated infiltration parameters using the full hydrodynamic model SIRMOD showed that the inclusion of runoff data in the inverse procedure did not compromise the ability to predict the measured advance trajectory but significantly improved the fit to the measured runoff volumes (average decrease in absolute error of simulated runoff volumes of 84%). Whereas the use of runoff data enabled SIRMOD to estimate runoff volumes, accounting for variable inflow improved the fit of the predicted runoff rates to the shape of the measured outflow hydrograph.Field data collected from several sites across the Darling Downs, Queensland has shown that the infiltration rates vary significantly (e.g. by up to 65% at 500 minutes),both spatially between furrows and temporally over the season. For the sites studied, the spatial variance in infiltration was surpassed by the seasonal variance (e.g. average CV of infiltration of 33.1% compared to 12.5%) but no consistent trends were identified. It was found that the lognormal distribution provided the best fit for thevariance in the infiltration curves which was in turn strongly related to the statistical distribution of the infiltration term of the volume balance. From this research, a procedure was developed to predict the infiltration parameters using a single advancepoint and any number of “known” infiltration curves from the same field.The IrriProb model was developed to extend the process of simulation from a single furrow scale to the whole field scale. IrriProb performs the full hydrodynamicsimulation for multiple independent furrows which are combined to form a spatial representation of the water application. Each furrow can have a unique infiltrationrate, inflow rate (Q), time to cut off (TCO) and soil moisture deficit. Validation of IrriProb using multiple sets of field data demonstrated that the single furrowsimulations failed to predict the true whole field irrigation performance (e.g. furrow distribution uniformity (DU) between 72.2% and 86.2% compared to the whole field DU of 64.8%).An optimisation routine was developed within IrriProb to maximise irrigation performance through identification of optimal values of Q and TCO. The optimisation objective function is comprised of a Boolean combination of customisable performance criteria. The user selects the appropriate performance terms and the optimal management is determined through a graphical overlay of the complyingranges of Q and TCO. Hence, the objective function of IrriProb retains the importance of each individual performance term, an advantage over those based on numerical combinations of weighted terms. Simulation of the whole field application under practical ranges of Q and TCO demonstrated the complex interactions between theperformance indices (e.g. the trade off between requirement efficiency (RE) and application efficiency (AE)). In cases of low infiltration variability it was possible to optimise the whole field performance using a single value of Q and TCO. However, under increased infiltration variability it was more appropriate to manage the field using two or more different management strategies. Irrigation optimisation based onmeasurements from a single furrow or the average infiltration curve, cannot identify the optimal combination of Q and TCO for the whole field. Simulation of field management based on the optimisation strategy obtained from single furrow measurements results in lower whole field performance than estimated from simulation of the single furrow data (e.g. field RE, AE and distribution uniformity of the root zone up to 26%, 18% and 66% lower than predicted). Field trials were used to demonstrate the ability to estimate whole field infiltration variability, evaluate whole field irrigation performance and optimise whole field irrigation management while taking into account the influence of spatial variability.
14

Variability in Extended and Alternating Extinction

Neshausen, Leanne January 2008 (has links)
Hens were trained to peck a square stimulus on a touch-sensitive screen under an FR5 reinforcement schedule for a maximum of 30 reinforcers (taking approximately 10 minutes). Then hens experienced extinction sessions of 40 minutes duration. For a total of six conditions, reinforcement and extinction conditions were alternated. Each condition consisted of between approximately 7 and 10 sessions. Results show that structures developed during conditioning remain in extinction, at least for the duration of previous reinforcement sessions. After approximately 10 minutes, behaviour becomes more variable. There was also an absence of any 'extinction burst'. Extended extinction conditions, and alternating extinction conditions with reinforcement conditions had little effect on the variability of behaviour, but did influence the rate of responding. Responding persisted a little longer before gradually declining across sessions in the first extinction condition. In extinction conditions 2 and 3 responding tended to occur more as 'peaks'; short periods of increased responding with periods of non-responding between peaks.
15

Essays in the study and modelling of exchange rate volatility

Sucarrat, Genaro 28 September 2006 (has links)
The thesis is a contribution to the literature on the study and modelling of exchange rate variability, and contains seven chapters. Chapter 1 motivates the study by providing a historical context about its importance, sketches the main themes of the thesis, and gives an overview of the Norwegian economy since the empirical studies are on the Norwegian krone against the Euro exchange rate. Chapter 2 makes a distinction between period and within-period exchange rate variability, a distinction which is of special interest when studying variability across different exchange rate regimes. Also, the exponential model of variability (EMOV) is put forward as a particularly convenient framework for explanatory exchange rate variability modelling. Chapter 3 makes full fuse of these ideas in studying the impact of market activity on exchange rate variability in the case of Norway. The main findings of this study are that the impact of short-term change in market activity, as measured by relative week-to-week changes in quoting frequency, is positive and statistically significant for both definitions of variability, and that the impact is relatively stable across three different exchange rate regimes. Also, our results do not suggest that the persistence in variability can be explained by persistence in the level of quoting. Chapter 4 undertakes an out-of-sample forecast evaluation of general to specific (GETS) modelling of exchange rate volatility, and our results suggest GETS-derived models are particularly useful in conditional forecasting. Chapter 5 studies the relation between exchange rate variability, market activity and heterogeneity using a measure of spot NOK/EUR transaction volume from banks within Norway's regulatory borders. Our results do not support the hypothesis that short-term Norwegian market activity has an impact on variability. However, we do find some support of the hypothesis that large and small banks have an opposite impact through their long-term activity. Chapter 6 proposes a solution to a shortcoming in the first stage of David F. Hendry's reduction theory by interpreting the underlying outcome space as a set of possible worlds made up of indeterministic and historically inherited particulars. Finally, chapter 7 concludes and provides suggestions for further research.
16

Interannual variability of summer precipitation in Texas and its implication to summer drought

Myoung, Boksoon 15 May 2009 (has links)
Since Texas normally receives most of its precipitation in the warm season, precipitation deficits in summertime may bring serious agricultural and hydrological disasters. While the underlying physical processes of summer precipitation deficit and drought are unclear, they can be understood in terms of convective instability. This research is designed to investigate how convective instability influences monthly mean precipitation in Texas in the summertime and to examine the modulation of convective instability and precipitation by upper-level circulations, soil moisture, vertical motion, and low-tropospheric warm air transport using NCEP/NCAR reanalysis data. Statistical approaches including correlation analysis, multiple linear regression analysis and back trajectory analysis were used to reveal the underlying dynamics of their linkage and causality. The results show that warming at 700 mb and surface dryness result in excessive convective inhibition (CIN), leading to precipitation deficits on a monthly time-scale. Temperature at 700 mb (Tlt) and surface dewpoint have little correlation suggesting different processes contribute to warming at 700 mb and surface dryness, respectively. Correlation analysis among the surface variables emphasizes the role of soil moisture on the dewpoint and thermodynamics at the surface. Back trajectory analysis indicates that a significant contributor to warming at 700 mb is the inversion caused by warm air transport from the Rocky Mountains and the Mexican Plateau where the surface potential temperature is greater than 307.5K rather than by subsidence. It was found that downward motion and warm air transport are enhanced in Texas when upper-level anticyclonic circulation develops in the southern US. Upper-level anticyclonic circulations in the southern US strongly affect Texas summertime precipitation by modulating the principal processes as follows. They increase CIN not only by enhancing warm air transport from the high terrain but also by suppressing occurrence of disturbances. The resulting reduced precipitation and dry soil significantly modulate surface conditions, which elevates CIN and decreases precipitation. The aforementioned chain-reaction of upper-level anticyclone influences can be understood in the context of CIN.
17

Essays in the study and modelling of exchange rate volatility

Sucarrat, Genaro 28 September 2006 (has links)
The thesis is a contribution to the literature on the study and modelling of exchange rate variability, and contains seven chapters. Chapter 1 motivates the study by providing a historical context about its importance, sketches the main themes of the thesis, and gives an overview of the Norwegian economy since the empirical studies are on the Norwegian krone against the Euro exchange rate. Chapter 2 makes a distinction between period and within-period exchange rate variability, a distinction which is of special interest when studying variability across different exchange rate regimes. Also, the exponential model of variability (EMOV) is put forward as a particularly convenient framework for explanatory exchange rate variability modelling. Chapter 3 makes full fuse of these ideas in studying the impact of market activity on exchange rate variability in the case of Norway. The main findings of this study are that the impact of short-term change in market activity, as measured by relative week-to-week changes in quoting frequency, is positive and statistically significant for both definitions of variability, and that the impact is relatively stable across three different exchange rate regimes. Also, our results do not suggest that the persistence in variability can be explained by persistence in the level of quoting. Chapter 4 undertakes an out-of-sample forecast evaluation of general to specific (GETS) modelling of exchange rate volatility, and our results suggest GETS-derived models are particularly useful in conditional forecasting. Chapter 5 studies the relation between exchange rate variability, market activity and heterogeneity using a measure of spot NOK/EUR transaction volume from banks within Norway's regulatory borders. Our results do not support the hypothesis that short-term Norwegian market activity has an impact on variability. However, we do find some support of the hypothesis that large and small banks have an opposite impact through their long-term activity. Chapter 6 proposes a solution to a shortcoming in the first stage of David F. Hendry's reduction theory by interpreting the underlying outcome space as a set of possible worlds made up of indeterministic and historically inherited particulars. Finally, chapter 7 concludes and provides suggestions for further research.
18

Variability in software architecture : views and beyond

Galster, Matthias, Weyns, Danny, Avgeriou, Paris, Becker, Martin January 2013 (has links)
Variability (the ability of a software system or software artifact to be adapted for use in a specific context) is reflected in and facilitated through the software architecture. The Second International Workshop on Variability in Software Architecture (VARSA) was held in conjunction with the Joint 10th Working IEEE/IFIP Conference on Software Architecture & 6th European Conference on Software Architecture 2012 in Helsinki, Finland. The workshop aimed at exploring current and emerging methods, languages, notations, technologies and tools to model, implement, and manage variability in the software architecture. It featured one industrial talk, five research paper presentations, and three working group discussions. Working groups discussed topics that emerged during the workshop. This report summarizes the themes of the workshop and presents the results of the working group discussions.
19

Ceramic variability of Shang society at Huanbei in Anyang, China

Fong, Denise Catalina 11 1900 (has links)
The study of ceramic variability in Chinese archaeology is conventionally understood in the context of temporal and regional differences, where emphasis is placed on explaining variability in terms of identifying regional styles and long-term changes. In this thesis, I examine ceramic variability of Shang pottery between two contiguous daily-use contexts at Huanbei, a Middle Shang period (1400-1250 BCE) site located in the Central Plains of China. Based on the analysis of pottery sherds collected from daily-use contexts at Hanwangdu (HWD) and Huyuanzhuang (HYZ), I argue that ceramics collected within a single-site context can be highly varied and distinct due to differences in use-context. Assemblage differences and ceramic variation are evaluated according to rim sherd attributes including vessel shape, rim and lip shape, dimensional properties, and surface treatment styles. Possible interpretive models for explaining observed patterns of variability are presented. Results of this study suggest that siginificant variability in pottery vessel design can be observed in the samples examined from the Huanbei site. Consumers from the HWD (a palace context) consumed a greater variety of pottery vessel types but with a more limited range of shapes and decorative styles. In contrast, consumers from HYZ (a non-palatial context) consumed a limited range of pottery vessel types but with a greater variability in the range of shapes and decoration. The observed patterns of variation reinforce current assumptions regarding the contextual differences between HWD and HYZ, and also provide new insight into the differential pottery consumption patterns by different social classes at Huanbei. Results of this study indicate the potential value of studying intra-site ceramic variation in Chinese archaeology and its importance in creating new knowledge on the material consumption behavior of different social classes.
20

Interannual variability of summer precipitation in Texas and its implication to summer drought

Myoung, Boksoon 15 May 2009 (has links)
Since Texas normally receives most of its precipitation in the warm season, precipitation deficits in summertime may bring serious agricultural and hydrological disasters. While the underlying physical processes of summer precipitation deficit and drought are unclear, they can be understood in terms of convective instability. This research is designed to investigate how convective instability influences monthly mean precipitation in Texas in the summertime and to examine the modulation of convective instability and precipitation by upper-level circulations, soil moisture, vertical motion, and low-tropospheric warm air transport using NCEP/NCAR reanalysis data. Statistical approaches including correlation analysis, multiple linear regression analysis and back trajectory analysis were used to reveal the underlying dynamics of their linkage and causality. The results show that warming at 700 mb and surface dryness result in excessive convective inhibition (CIN), leading to precipitation deficits on a monthly time-scale. Temperature at 700 mb (Tlt) and surface dewpoint have little correlation suggesting different processes contribute to warming at 700 mb and surface dryness, respectively. Correlation analysis among the surface variables emphasizes the role of soil moisture on the dewpoint and thermodynamics at the surface. Back trajectory analysis indicates that a significant contributor to warming at 700 mb is the inversion caused by warm air transport from the Rocky Mountains and the Mexican Plateau where the surface potential temperature is greater than 307.5K rather than by subsidence. It was found that downward motion and warm air transport are enhanced in Texas when upper-level anticyclonic circulation develops in the southern US. Upper-level anticyclonic circulations in the southern US strongly affect Texas summertime precipitation by modulating the principal processes as follows. They increase CIN not only by enhancing warm air transport from the high terrain but also by suppressing occurrence of disturbances. The resulting reduced precipitation and dry soil significantly modulate surface conditions, which elevates CIN and decreases precipitation. The aforementioned chain-reaction of upper-level anticyclone influences can be understood in the context of CIN.

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