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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

Ecological investigation of a new host-parasite relationship : <i>Parelaphostrongylus odocoilei</i> in thinhorn sheep (<i>Ovis dalli</i>)

Jenkins, Emily Joan 20 September 2005 (has links)
Discovery of a new host-parasite relationship, <i>Parelaphostrongylus odocoilei</i> in Dalls sheep (<i>Ovis dalli dalli</i>) in the Canadian North, prompted the first investigation of the geographic distribution, pathogenesis, ecology and epidemiology of this parasite, as well as the related protostrongylid <i>Protostrongylus stilesi</i>, at Subarctic latitudes (60-65ºN). All protostrongylid parasites have an indirect life-cycle, where first-stage larvae are shed in the feces of a mammalian definitive host, penetrate the foot of a gastropod intermediate host, and develop to infective third-stage larvae. <p> Protostrongylid larvae were recovered from over 2000 fecal samples from thinhorn sheep (<i>Ovis dalli</i>) and other hosts for <i>P. odocoilei</i> and <i>P. stilesi</i> across northwestern North America (38-69 ºN). Through novel application of molecular techniques to identify morphologically indistinguishable first-stage larvae, new records for <i>P. odocoilei</i> were established at 20 locations. This provided insight into the historical origins and biogeography of this new host-parasite relationship, and greatly expanded the known geographic range of both protostrongylids. <p> Clinical effects, including a neurological syndrome, were described in five thinhorn sheep experimentally infected with <i>P. odocoilei</i>. Neural and respiratory pathology in these five sheep were compared with over 50 wild Dalls sheep from a population naturally infected with <i>P. odocoilei</i> and <i>P. stilesi</i>. In the end stages, diffuse verminous interstitial pneumonia associated with P. odocoilei led to respiratory failure, and may have acted as a predisposing factor for bacterial pneumonia, which caused sporadic mortalities in this wild population. <p> At Subarctic latitudes, seasonal patterns in host and parasite availability, including larval shedding by Dalls sheep and larval development in experimentally infected gastropods, suggested that lambs become infected with <i>P. odocoilei</i> in a narrow seasonal window in their first fall on winter range. In combination with laboratory experiments, a degree day model for temperature-dependent larval development was developed, validated, and applied to describe and predict the effects of climate warming on protostrongylid parasites of thinhorn sheep in northern North America. In a future of climate warming, the narrow seasonal window for parasite development and transmission would be significantly extended, leading to amplification of populations of <i>P. odocoilei</i> and <i>P. stilesi</i> in endemic regions, and possibly range expansion of <i>P. odocoilei</i>. This may have consequences for the health of thinhorn sheep, as well as other wildlife that are important resources in the Canadian North.
12

Solar thermal heating of a glasshouse using phase change material (PCM) thermal storage techniques

Boampong, James Kwadwo January 2015 (has links)
The Royal Botanic Gardens (RGB) is used as an umbrella name for the institution that runs Kew and Wakehurst Place gardens in Sussex The RBG has a large number of glasshouses at Kew and Wakehurst sites that consume lots of heating energy which is a major concern and the group is looking for an alternative heating system that will be more efficient and sustainable to save energy, cost and reduce CO2 emissions. Glasshouse due to greenhouse effect trap solar energy in the space with the slightest solar gains but the energy trapped in the space most often is vented through the roof wasted to keep the space temperature to the required level. An environmental measurement was carried out in twenty one zones of the glasshouse to establish the temperature and humidity profiles in the zones for at least three weeks. The investigation established that large amount of heat energy is vented to the atmosphere wasted and therefore need a heating system that could absorb and store the waste thermal energy. Phase change material (PCM) thermal energy storage technique was selected to be the best options compared to the others. It has been established that active and passive solar systems could provide enough thermal energy to meet the glasshouse heating requirements. PCM filled heating pipes will be installed to absorb the heat energy trapped in the glasshouse and use it when needed. The research analysis established that 204 MWh of the trapped energy wasted could be saved. The space temperature of the glasshouse could be maintained through melting and freezing of the PCM filled in the heating pipes. The site CHP waste heat could be useful. The research results have shown that nearly zero CO2 emission heating system could be achieved and the project is technically, economically and environmentally viable.
13

Modelování množství sněhové pokrývky v malých povodích / Snow water content modelling in small catchments

Němečková, Klára January 2010 (has links)
Title: Snow water content modelling in small catchments This work deals with modeling of amount of snow cover, snow water equivalent, respectively, on an experimental catchment in the Jizerské hory Mts. Measuring and modelling of the snow cover is an important part of water management practice from the perspective of reservoir operation and flood management. The first part of this thesis describes physical-geographical characteristics of the Jizerské hory Mts.especially from the climatological and hydrological point of view but also other charakteristics and conditions that may affect the dynamic of snow accumulation and melting are described with detailed focus on the experimental catchment of Černá Desná river - Jezdecká. Two modelling approaches were applied to simulate snow water equivalent (SWE) based on observed precipitation and temperature. Beside the well knowen SNOW17 model a simple method based on heat index was developed in this work and its parameters were calibrated based on measured timeseries of daily average air temperature, daily precipitation and observed SWE for winter periods 2001 to 2009. Both methods provided reasonably accurate estimates of SWE over the tested period, however it was found that the results for winters with extreme conditions (very warm or very cold) are less...
14

Zur klimatischen Sensitivität der Massenbilanz der Eiskappe von Devon Island, Nunavut, Kanada

Zahnen, Nikolaus 22 December 2004 (has links)
In dieser Arbeit werden Berechnungen zur klimatischen Sensitivität der Eiskappe von Devon Island (Nunavut, Kanada) durchgeführt, die auf einem mit Wärmesummen arbeitenden Massenbilanzmodell basieren. Wichtigste Datenbasis für die Modellrechnungen sind dabei höhenabhängige Massenbilanzreihen der Devon-Eiskappe sowie tägliche Klimadaten der WMO-Station Resolute Bay. Durch die Bestimmung geeigneter Modellparameter (Temperaturgradienten, Wärmesummenkoeffizienten) ist es möglich, das mittlere Massenbilanzprofil gut zu simulieren. Das auf diese Weise kalibrierte Modell kann dann – als einfache Alternative zu Energiebilanzmodellen – zur Berechnung der Sensitivität der Massenbilanz auf Veränderungen von Temperatur und Niederschlag genutzt werden. Anwendungen des Modells verdeutlichen, dass die Massenbilanz der Devon-Eiskappe stark abhängig von der Entwicklung der Sommertemperaturen und die klimatische Sensitivität im Vergleich mit anderen Eismassen aus feuchteren Klimaten sehr klein ist. Die Einbeziehung der saisonalen Abhängigkeit der Massenbilanz kann schließlich helfen, eine mit Schwierigkeiten verbundene Rekonstruktion der jährlichen Massenbilanz zu verbessern. / In this study, a degree-day approach is used to carry out model simulations to determine the climatic sensitivity of the mass balance of the Devon Island ice cap (Nunavut, Canada). The most important data the model is fed by are a 38 yr long series of specific mass balance data and daily air temperature data from the WMO station Resolute Bay. By determining suitable model parameters (temperature lapse rates, degree-day coefficients) it is possible to simulate the mean mass balance profile convincingly. As a simple alternative to energy balance models, the calibrated degree-day model can then be used to determine the sensitivity of the mass balance to changes in temperature and precipitation. Results show that the mass balance of the Devon Ice Cap is strongly dependent on the summer temperatures and that the overall climatic sensitivity is small compared to those of other ice masses in more humid regions. The reconstruction of the mass balance series is attended with difficulties, but can be improved by including the mass balance''s seasonal sensitivity.
15

The Study of Temporal and Spatial Variability of Degree Day Factor of Snowmelt in Colorado

Pokhrel, Pranav 05 1900 (has links)
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.
16

Biologia de Semiaphis dauci (Fabricius, 1775) e Aulacorthum solani (Kaltenbach, 1843) (Hemiptera: Aphididae) associados à Arracacia xanthorrhiza (Bancroft, 1825) / Semiaphis dauci (Fabricius, 1775) and Aulacorthum solani (Kaltenbach, 1843) (Hemiptera: Aphididae) associated with Arracacia xanthorrhiza (Bancroft, 1825)

Takada, Hélio Minoru 14 September 2011 (has links)
Made available in DSpace on 2016-06-02T19:29:41Z (GMT). No. of bitstreams: 1 4024.pdf: 2377487 bytes, checksum: babf07c158c61273e559c15a8aeab2c3 (MD5) Previous issue date: 2011-09-14 / The aphids are limiting for various crops, and in the case of the horticulture crops, it has been a problem for the cultivation of Arracacia xanthorrhiza (Bancroft, 1825), the arracacha. This plant, of Andean origin, has been well adapted to these climatic conditions of Southeast Brazil and conquered many consumers, currently representing an important food source due to its taste and nutritional value, thus providing a considerable income to small farmers. It is largely cultivated in the South and Southeast regions in Brazil. Although this culture is considered rustic, aphids has been causing great damage to its development. In the present work, the influence of temperature on the development of Semiaphis dauci (Fabricius, 1775) and Aulacorthum solani (Kaltenbach, 1843) was studied. The nymphal development period of S. dauci and A. solani on A. xanthorrhiza was of 23.84 and 33.02 days at 10 °C and 6.7 and 10.04 days at 25 °C, respectively. The minimum thermal threshold of development for the nymphal stage of 4.59 and 4.33 °C, the thermal constant 138.12 and 142.86 degrees-days and the approximate upper limit temperature ranged from 25 to 28 and 27 °C, respectively. The life table parameters indicated that temperatures of 22.5 and 25 °C provided the best thermal conditions for the S. dauci population growth, resulting the highest value of intrinsic rate of natural increase (rm=0.15), the lowest average value of the generation of 10.38 and 8.47 days and the shortest doubling times for the population with 4.74 and 4.55 days, respectively. The observed biological aspects indicate that A. solani has great potential for the population growth and a preference for smaller temperatures than S. dauci, and can be considered a potential pest for A. xanthorrhiza. The infestation of S. dauci in this species also causes severe damage to the plant, nevertheless other factors such as formation of dense colonies, lower mobility, and the action of toxins and viruses may also involved. / Os afídeos são prejudiciais a diversas culturas e no caso das hortícolas, têm representado problemas para a mandioquinha-salsa, Arracacia xanthorrhiza (Bancroft, 1825) a arracacha. Esta planta de origem Andina, adaptou-se bem às condições climáticas do sudeste brasileiro e conquistou consumidores pelas suas qualidades nutricionais e organolépticas. Possibilita uma renda apreciável para o agricultor familiar e é muito cultivada na região Sul e Sudeste do Brasil. A cultura é considerada rústica, entretanto, os afídeos têm provocado prejuízos consideráveis ao seu desenvolvimento. Neste trabalho estudou-se a influência da temperatura no desenvolvimento dos afídeos Semiaphis dauci (Fabricius, 1775) e Aulacorthum solani (Kaltenbach, 1843). O período médio de desenvolvimento ninfal de S. dauci e A. solani associado a A. xanthorrhiza foi de 23,84 e 33,02 dias a 10°C e de 6,70 e 10,04 dias a 25°C, respectivamente. O limiar térmico mínimo de desenvolvimento para o estádio ninfal foi de 4,59 e 4,33°C, a constante térmica de 138,12 e 142,86 graus-dias e o limiar superior situado entre 25 a 28 e 27°C, respectivamente. Os parâmetros da tabela de vida de S. dauci nas temperaturas de 22,5 e 25°C corresponderam ao maior valor da taxa intrínseca de aumento natural (rm=0,15), aos menores valores da duração média da geração de 10,38 e 8,47 dias e período de duplicação da população com 4,74 e 4,55 dias, respectivamente. O desenvolvimento de A. solani teve a 20 e 22,5°C o maior valor da taxa intrínseca de aumento natural (rm=0,22 e 0,23) e os menores tempos para a duplicação da população (TD=3,14 e 3,07 dias), respectivamente. Os aspectos biológicos observados indicam que A. solani apresenta maior potencial de crescimento populacional e preferência por temperaturas menores que S. dauci, e pode ser considerada uma praga em potencial para a mandioquinha-salsa. As infestações de S. dauci na mandioquinha-salsa causam severos danos à planta, no entanto, outros fatores como formação de densas colônias, menor mobilidade, e a ação de toxinas e vírus podem estar também envolvidas.
17

Caracterização da aptidão climática da região da Campanha do Rio Grande do Sul para a viticultura / Characterization of the climatic aptitude of region of the Campanha region of Rio Grande do Sul for the viticulture

Brixner, Gabriel Franke 26 February 2013 (has links)
Made available in DSpace on 2014-08-20T14:33:01Z (GMT). No. of bitstreams: 1 dissertacao_gabriel_franke_brixner.pdf: 2402163 bytes, checksum: 701d885a41fab3e10bd6ac8fd53776cd (MD5) Previous issue date: 2013-02-26 / The climatic characterization of the producing regions with potential for vitiviniculture becomes a demand of modern viticulture. Among the new frontiers of modern viticulture it is highlighted the Campanha region located in Rio Grande do Sul, being driven for presenting soil and climatic conditions favorable for growing grapes vines. This new culture lacks studies of interference of climatic conditions in the development of the plants in the region. The dissertation aims to characterize the suitability of the climate of the region Campaign of Rio Grande do Sul for viticulture. The work was divided into three chapters, the first being a study on the estimation of the evapotranspiration by different methods and its application in the Dryness Index (DI) for the municipalities of Campanha, aiming to identify alternatives methods to the standard one (Penman-Monteith) used in the DI. In the second chapter, it was performed the climatic characterization of the region through the Geoviticulture Multicriteria Climatic Classification System, aiming to identify the thermal and hydric availability of the municipalities of the region under study. In the third chapter, it was held a study of the risk of frost and the duration of phenological subperiods of Cabernet Sauvignon in the Campanha region. In these chapters, we used daily meteorological data, the period from 1961 to 2010, for Alegrete, Bagé, Quaraí, São Gabriel, Santana do Livramento and Uruguaiana as availability of municipalities. It was found that the Thornthwaite, Camargo, Makkink and Blaney-Criddle methods present optimal performance in estimation of the evapotranspiration compared to standard when the using it with DI. It was used the Thornthwaite method for the estimation of the evapotranspiration throughout the Campanha, allowing to analyze a longer period of DI in the region, being this class of the wet type, having hydric availability for cultivation. The index of night cold is of the class of temperate nights in Campanha, however there are variations among municipalities, months and years analyzed. Regarding the heliothermal index, Uruguaiana is of the very hot kind and the other municipalities are of the hot kind, having high thermal availability, combined with climatic conditions that favor the ripening of the grapes with satisfactory condition for winemaking. Regarding the risk of frost, Uruguaiana and São Gabriel in early September have low risk of frost formation at 5% level, while in the other municipalities the last date occurs in early October, characterized as spring frosts. It is also possible to see that Cabernet Sauvignon showed variations in the total number of days in relation to sprouting periods, as well as between municipalities Campaign. / A caracterização climática de regiões produtoras com potencial para a vitivinicultura torna-se uma demanda da viticultura moderna. Dentre as novas fronteiras da viticultura destaca-se a região da Campanha localizada no Rio Grande do Sul, impulsionada por apresentar condições edafoclimáticas favoráveis ao cultivo de videiras viníferas. Trata-se de uma cultura nova que carece de estudos sobre a interferência das condições climáticas no desenvolvimento das plantas na região. A dissertação objetiva caracterizar a aptidão climática da região da Campanha do Rio Grande do Sul para a viticultura. O trabalho foi dividido em três capítulos, sendo o primeiro um estudo sobre a estimativa da evapotranspiração por diferentes métodos e sua aplicação no Índice de Seca (IS) para os municípios da Campanha, objetivando identificar métodos alternativos ao método padrão (Penman-Monteith) empregado no IS. No segundo capítulo, foi realizada a caracterização climática da região por meio do Sistema CCM Geovitícola, visando identificar a disponibilidade térmica e hídrica dos municípios da região. No terceiro capítulo, foi realizado um estudo do risco de geada e duração dos subperíodos fenológicos da Cabernet Sauvignon na região da Campanha. Nestes três capítulos, foram utilizados dados meteorológicos diários, do período de 1961 a 2010, para Alegrete, Bagé, Quaraí, São Gabriel, Santana do Livramento e Uruguaiana, conforme disponibilidade dos municípios. Constatou-se que os métodos Thornthwaite, Camargo, Makkink, Blaney- Criddle apresentam desempenho ótimo, na estimativa da evapotranspiração em relação ao padrão, quando empregado ao IS. Foi utilizado o método de Thornthwaite para estimativa da evapotranspiração em toda Campanha, possibilitando analisar um período maior do IS na região, sendo este da classe do tipo úmido, apresentando disponibilidade hídrica para o cultivo. O índice de frio noturno é da classe de noites temperadas, porém observa-se variações entre os municípios, meses e anos analisados. Quanto ao índice heliotérmico, Uruguaiana é do tipo muito quente e os demais municípios do tipo quente, apresentando elevada disponibilidade térmica, aliada a condições climáticas que propiciam a maturação das uvas com condições satisfatórias para vinificação. Quanto ao risco de geada, Uruguaiana e São Gabriel no início de setembro apresentam baixo risco de formação de geada ao nível de 5%, enquanto que nos demais a última data ocorre no início de outubro, caracterizando-se como geadas primaveris. É também possível constatar que a Cabernet Sauvignon apresentou variações no número total de dias em relação às épocas de brotação, bem como, entre os municípios da Campanha.
18

Life History, Maternal Quality and the Dynamics of Harvested Fish Stocks

Venturelli, Paul Anthony 03 March 2010 (has links)
Knowledge of offspring production (recruitment) is fundamental to understanding and forecasting the dynamics of a population. In this thesis, I focus on two demographic characteristics of fish stocks that are important to recruitment: population density and age structure. First, populations produce more recruits at low density, but quantifying this response has proven difficult. Using data from hundreds of populations of walleye (Sander vitreus), an economically important freshwater fish, I demonstrate that the growing-degree-day metric (a temperature index) is better than age at explaining variation in density-dependent growth and maturity both within and among populations. I then incorporate multi-lake measures of density-dependent life history change into a temperature-based biphasic model of growth and reproduction to predict sustainable rates of mortality for walleye throughout most of their range. Second, the age (or size) structure of a population may also affect recruitment because of positive effects of maternal age on offspring production and survival; however, evidence for these ‘maternal influences’ on recruitment is limited. Using both an analytical model and a meta-analysis of stock-recruitment data from 25 species of exploited marine fish, I show that (i) maximum reproductive rate increased with the mean age of adults in a population, and (ii) the importance of age structure increased with a species’ longevity. I then demonstrate a similar effect of maternal influences on reproductive rate in a detailed study of Lake Erie walleye. By highlighting the importance of fisheries-induced demographic change to recruitment, this thesis provides insight into past and present failures. However, it also demonstrates clearly the benefits of proactive management strategies that (i) identify and respect the limits of exploitation, (ii) protect from exploitation reproductively valuable individuals—principles that apply generally to any freshwater, marine, or terrestrial species that is of recreational, commercial, or conservation value.
19

Life History, Maternal Quality and the Dynamics of Harvested Fish Stocks

Venturelli, Paul Anthony 03 March 2010 (has links)
Knowledge of offspring production (recruitment) is fundamental to understanding and forecasting the dynamics of a population. In this thesis, I focus on two demographic characteristics of fish stocks that are important to recruitment: population density and age structure. First, populations produce more recruits at low density, but quantifying this response has proven difficult. Using data from hundreds of populations of walleye (Sander vitreus), an economically important freshwater fish, I demonstrate that the growing-degree-day metric (a temperature index) is better than age at explaining variation in density-dependent growth and maturity both within and among populations. I then incorporate multi-lake measures of density-dependent life history change into a temperature-based biphasic model of growth and reproduction to predict sustainable rates of mortality for walleye throughout most of their range. Second, the age (or size) structure of a population may also affect recruitment because of positive effects of maternal age on offspring production and survival; however, evidence for these ‘maternal influences’ on recruitment is limited. Using both an analytical model and a meta-analysis of stock-recruitment data from 25 species of exploited marine fish, I show that (i) maximum reproductive rate increased with the mean age of adults in a population, and (ii) the importance of age structure increased with a species’ longevity. I then demonstrate a similar effect of maternal influences on reproductive rate in a detailed study of Lake Erie walleye. By highlighting the importance of fisheries-induced demographic change to recruitment, this thesis provides insight into past and present failures. However, it also demonstrates clearly the benefits of proactive management strategies that (i) identify and respect the limits of exploitation, (ii) protect from exploitation reproductively valuable individuals—principles that apply generally to any freshwater, marine, or terrestrial species that is of recreational, commercial, or conservation value.
20

Stavebně-fyzikální posouzení střešní konstrukce / Building physics assessment of the roof structure

Konopík, Petr January 2017 (has links)
This theses deals with a structural design comparison of heat insulations implementation in flat roofs in light of heat engineering. It also adverts to possible structural design in terms of heat insulations distribution in a flat roof. There are many materials options. I show the possibilities of material solution and also advantages and disadvantages of the single sealing materials at these layers. In the aplication part of this thesis I deal with possible concepts of insulation and solution for a specific roof of an older apartment house in Brno, where I conducted a constructive exploration. There was developed and evaluated a few options of solutions considering the heat insulator used. The following computational programs were used for the evaluations: TEPLO, AREA, CUBE 3D.

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