• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 75
  • 65
  • 48
  • 21
  • 12
  • 8
  • 4
  • 3
  • 1
  • 1
  • 1
  • Tagged with
  • 262
  • 55
  • 52
  • 49
  • 36
  • 30
  • 29
  • 26
  • 25
  • 23
  • 21
  • 19
  • 19
  • 19
  • 17
  • 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.
21

Personal-portable Cooling Garment Based on Adsorption Vacuum Membrane Evaporative Cooling

Yang, Yifan January 2011 (has links)
A cutting edge man-portable AVMEC cooling garment was demonstrated to be able to provide sufficient cooling for personnel working at mediate activity loads. Studies were first carried out in a well controlled vacuum desiccator at room temperature to elucidate the effects of several key parameters on the performance of an AVEC device, which was similar to AVMEC except that membrane was not involved. Under the best condition, an average cooling capacity of 179 W/M2 was achieved in a period of four hours and cooling continued at a slowly declining rate for another four hours afterward. The temperature of water was maintained at approximately 12.5 oC after the pseudo steady state was established. Then, it was shown that the AVMEC cooling pads were able to provide a cooling capacity of 277.4 W/m2 in a 37 oC ambient environment (incubator). The temperature of the cooling core surface was maintained in a range of 20 – 21.8 oC in the one-hour test period. No power supply was required except for the initialization stage, which took 5 minutes. Furthermore, human subject tests with or without wearing NWBC (Nuclear Warfare Biological and Chemical) suit demonstrated that, a AVMEC garment composed of 12 cooling pads were able to maintain the core body temperature of the subjects below 38.5 oC for up to 90 minutes while the subject was walking on a treadmill at a speed of 2 miles per hour in an environment of 40 oC and 50% RH (relative humidity). These results indicate that the AVMEC garment is a promising man-portable personal cooling technology.
22

Microclimate modelling for agrivoltaic systems

Zainali, Sebastian January 2024 (has links)
Increasing global electricity consumption and population growth have resulted in conflicts between renewable energy sources, such as bioenergy and ground-mounted photovoltaic systems, owing to the limited availability of suitable land caused by competing land uses. This challenge is further compounded by the intertwined relationship between energy and agri-food systems, where approximately 30% of global energy is consumed. In addition, considering that agricultural irrigation accounts for 70% of water use worldwide, its impact on both land and water resources becomes a critical concern. Agrivoltaics offers a potential solution to this land use conflict. However, a knowledge gap remains regarding the impact of integrating these techniques on microclimatic conditions. Addressing this gap is crucial because these conditions directly affect the growth and development of crops, as well as the efficiency of energy yields in photovoltaic panels. Experimental facilities offer valuable insights tailored to specific locations and system designs. Although they provide an in-depth understanding of a particular location, the extrapolation of this information to different locations or alternative systems may be limited. Therefore, the broader applicability of these insights to diverse settings or alternative systems remains unclear. In this thesis, a modelling procedure was developed to evaluate the photosynthetically active radiation reaching crops in typical agrivoltaic configurations across three diverse geographical locations in Europe. This is essential for understanding how solar panel shading affects the incoming photosynthetically active radiation required for crop photosynthesis. Furthermore, computational fluid dynamics were employed to model and assess the microclimate of an experimental agrivoltaic system. The developed model revealed significant variations in photosynthetically active radiation distribution across different agrivoltaic systems and locations, emphasising the need for tailored designs for optimal energy yield and crop productivity. Computational fluid dynamics analysis demonstrated its effectiveness in evaluating microclimatic parameters such as air and soil temperature, wind speed, and solar irradiance within agrivoltaic systems, providing valuable insights for system optimisation. By bridging a knowledge gap, this thesis contributes to the understanding of the modelling and simulation of agrivoltaic system microclimates, thereby facilitating the sustainable coexistence of renewable electricity conversion and agriculture.
23

Examining Microclimatic Vulnerability to Climate Extremes Using High Resolution Remote Sensing and Climatic Tolerances: Methods and Applications

Ednie, Gabrielle 09 December 2022 (has links)
Globally, species are experiencing geographical range shifts as a result of increased frequency and severity of extreme weather events exceeding their realized thermal niche boundaries. Using thermal limit approximations, relative heat indices can predict species extinction-colonization patterns over broad spatial scales. Locally, microclimate refugia can act as buffers against short term thermal extremes and improve species persistence probabilities. Opportunities to explore the role of microclimates in local species extinctions have recently emerged with advances in unmanned aerial vehicle (UAV) and thermal imaging technologies. My first chapter proposed a UAV-based methodology facilitating direct and accurate air temperature measurements at biologically relevant scales for butterfly species. These high-resolution microclimate measurements enabled broad-scale thermal limit approximation model applications to patch-level measurements using a verified thermal positioning index. In my second chapter, I evaluated the applicability of broad-scale models for predictions of local species distributions and abundances. The methodology proposed in Chapter 1 was used to generate patch-specific thermal position indices for butterfly species observed and surveyed in our study patches. Patch-level measurements of thermally tolerable area (overheating index) helped predict aspects of butterfly abundance, presence, and overall species richness, along with other environmental metrics that are relevant for butterfly biology. This thesis explores a frontier of direct UAV-based microclimate measurements and underscores the importance of considering thermal extremes to understand butterfly distribution and abundance, even in protected habitats.
24

Passive Solar Landscape Design: Its Impact on Fossil Fuel Consumption Through Landscape Design

Boelt, Robin Wiatt 09 June 2006 (has links)
Gas, electricity, heating and cooling buildings - comfort — our lives revolve around fossil fuels. Technology and the demands of living in today's society add to our gigantic fossil fuel appetite. With gas prices topping three dollars per gallon, changes must be made. This thesis project presents an analysis of passive solar landscape design (PSLD) principles used to create microclimates within the landscape, and thereby increasing human comfort both indoors and outdoors. The analysis includes case study results of fossil fuel consumption and PSLD implementation. Microclimatic comfort is revealed in the design of a solar park in historic Smithfield, Virginia. Smithfield Solar Park is designed with PSLD principles to be self-sustaining - the Farmer's Market pavilions and educational center generating their own electricity through a solar voltaic system. This system is enhanced by careful siting and selection of trees, shrubs and built structures and use of local materials to reduce transportation distances. Smithfield Solar Park features a Farmer's Market, outdoor movies and Friday Cheers, and will host regional and local festivals and events, enhancing tourism and the economy of Smithfield's Historic District. Landscape architecture stands in prime position to improve landscapes and lessen both our dependency on and consumption of fossil fuels through implementation of PSLD principles. Public education about the benefits of implementing PSLD principles can have local, regional, national and global effects on our fuel consumption. / Master of Landscape Architecture
25

Viability and Accessibility of Urban Heat Island and Lake Microclimate Data over current TMY Weather Data for Accurate Energy Demand Predictions.

Weclawiak, Irena Anna 29 June 2022 (has links)
No description available.
26

Correlates and temporal variation in call phenology of eastern Ontario frogs

KLAUS, SAMANTHA P 14 November 2012 (has links)
Climate change has been predicted to have long-term consequences for North American ecosystems. Amphibians in particular are considered indicators of ecosystem health because of their sensitivity to environmental change – due in part to their semi-permeable skin and aquatic developmental requirements. Amphibians have been experiencing population declines on a global scale, suggested in part to be due to changes in reproductive behaviour and timing. My thesis examines the abiotic correlates of timing of calling in southeastern Ontario anurans, as well as the extent to which the timing of calling events vary within and among species. I focused on eight species of frogs using both a 40-year historical dataset and a 5-year field-collected dataset of environmental variation and anuran activity. From analysis of the historical dataset, Lithobates pipiens was the only species out of eight to emerge significantly earlier, by an estimated 22 days over four decades. Both L. pipiens and Anaraxyus americanus have advanced initiation of calling over a four-decade span significantly earlier by an estimated 37.2 and 19.2 days, respectively, correlating with significant regional increases in spring air temperatures (2.8°C over four decades). Global frog declines or range shifts relate ultimately to changes in reproductive behaviour and timing mediated by shifting climate. From my analysis of the field-collected dataset, I concluded that species varied in the environmental predictors that best predicted this variation may be a consequence of varying reproductive strategies between early spring “explosive” breeders versus late prolonged breeders. There was also significant among-location variation in calling activity for four prolonged breeding species, which may be an effect of significant microclimatic variation between locations surveyed. My study suggests that local temperature increases have affected the timing of emergence and the onset of calling activity in some frogs and that microclimatic differences among breeding habitats may be influencing the timing of breeding in some prolonged breeding species. My research aids future conservation and management strategies for North America’s dwindling amphibian populations by quantifying how abiotic factors influence breeding behaviour on both a fine and extended temporal scale as well as by developing and testing standardized methods for long-term species monitoring. / Thesis (Master, Biology) -- Queen's University, 2012-11-12 23:05:34.12
27

On the impact of 50-years-accumulated land-surface changes upon micrometeorological conditions

Mölders, Nicole 02 December 2016 (has links) (PDF)
The influence of the concurrent land-use changes that took place in East-Germany from the Thirties to Eighties on micrometeorological conditions is examined. These land-use changes lead to a slightly warmer and drier atmospheric boundary layer (ABL). Moreover, they may significantly modify the partitioning of incoming energy between sensible and latent heat as well as partitioning of cloud-microphysical processes between the warm and cold path of precipitation formation. The atmospheric response to concurrent land-use changes deviates from superposition ( of the responses to simple land-use changes) also in areas of nonsignificant changes. / Der Einfluss der akkumulierten Landnutzungsänderungen, die zwischen den 30-er und 80-er Jahren in Ostdeutschland stattfanden, auf das Mikroklima wird untersucht. Diese Landnutzungsänderungen führen zu einer geringfügig wärmeren und trockeneren atmosphärischen Grenzschicht. Die Aufteilung der einfallendenden Energie in Flüsse fühlbarer und latenter Wärme sowie der wolkenmikrophysikalischen Prozesse in den warmen und kalten Pfad der Niederschlagsbildung ändern sich signifikant. Die atmosphärische Response auf die akkumulierten Landnutzungsänderungen weicht auch in Gebieten ohne signifikante Änderungen von der Superposition der Auswirkungen einfacher Landnutzungsänderungen ab.
28

Mechanisms of Native Shrub Encroachment on a Virginia Barrier Island

Thompson, Joseph 01 January 2016 (has links)
Species composition, temperature, soil nutrients, and leaf area index (LAI) were recorded across three encroaching Morella cerifera thicket edges and three free- standing shrubs on Hog Island, Virginia to characterize the effect of shrub thickets on the plant community and microclimate. Electron transport rate (ETR) was taken on shrub leaves to determine if microclimate benefits M. cerifera physiology. Species richness was lowest inside shrub thickets. Soil water content and LAI were higher in shrub thickets compared to grassland. Soil organic matter, N, and C were higher inside shrub thickets. Summer and fall maximum temperatures were more moderate in shrub thickets and at free-standing shrubs. Fall and winter minimum temperatures were higher inside shrub thickets. ETR was higher at the free-standing shrubs compared to the thicket edge. Morella cerifera impacts microclimate characteristics and species composition immediately upon encroachment. Improved shrub physiology was neither supported nor rejected by the research presented here.
29

Topographically driven differences in energy and water constrain climatic control on forest carbon sequestration

Swetnam, Tyson L., Brooks, Paul D., Barnard, Holly R., Harpold, Adrian A., Gallo, Erika L. 04 1900 (has links)
Mountains are vital to ecosystems and human society given their influence on global carbon and water cycles. Yet the extent to which topography regulates montane forest carbon uptake and storage remains poorly understood. To address this knowledge gap, we compared forest aboveground carbon loading to topographic metrics describing energy balance and water availability across three headwater catchments of the Boulder Creek Watershed, Colorado, USA. The catchments range from 1800 to 3500 m above mean sea level with 46-102 cm/yr mean annual precipitation and -1.2 degrees to 12.3 degrees C mean annual temperature. In all three catchments, we found mean forest carbon loading consistently increased from ridges (27 +/- 19 Mg C ha) to valley bottoms (60 +/- 28 Mg C ha). Low topographic positions held up to 185 +/- 76 Mg C ha, more than twice the peak value of upper positions. Toe slopes fostered disproportionately high net carbon uptake relative to other topographic positions. Carbon storage was on average 20-40 Mg C ha greater on north to northeast aspects than on south to southwest aspects, a pattern most pronounced in the highest elevation, coldest and wettest catchment. Both the peak and mean aboveground carbon storage of the three catchments, crossing an 11 degrees C range in temperature and doubling of local precipitation, defied the expectation of an optimal elevation-gradient climatic zone for net primary production. These results have important implications for models of forest sensitivity to climate change, as well as to predicted estimates of continental carbon reservoirs.
30

Ocorrência da Ramulose (Colletotrichum gossypii var. cephalosporioides Costa) sob semeadura convencional e direta relacionada ao microclima, crescimento e desenvolvimento da cultura do algodoeiro / Ramulosis (Colletotrichum gossyppii var. cephalosporioides Costa) over conventional and direct sowing related to microclimate, growth and the development of the cotton-crop

Salvatierra, Daniela Kubiak de 17 April 2008 (has links)
Sistemas com semeadura direta sobre palhada são cada vez mais utilizados na agricultura, e a ramulose do algodoeiro, causada pelo fungo Coletotrichum gossypii var. cephalosporioides Costa, é uma das doenças mais importantes na cultura. Foram realizados durante os anos de 2004/05, 2005/06 e 2006/07 na Escola Superior de Agricultura "Luiz de Queiroz", USP/ESALQ, em Piracicaba, SP, experimentos com a cultura do algodoeiro (Gossypium hirsutum L. var. latifolium Hutch), conduzidos sob preparo do solo convencional com semeadura convencional do algodoeiro, e ausência de preparo do solo com semeadura do algodoeiro sobre palhada de milheto, com o objetivo de avaliar se as modificações microclimáticas causadas pela utilização da palhada de milheto em relação às variáveis temperatura e duração de período de molhamento foliar (DPM) poderiam interferir no desenvolvimento e evolução da ramulose do algodoeiro. Foi utilizado também o Índice de Favorabilidade temperatura-molhamento para a ramulose do algodoeiro, que utiliza os parâmetros temperatura e DPM no seu cálculo para explicar o desenvolvimento da doença entre os dois sistemas de semeadura. Os dados microclimáticos foram medidos por uma plataforma de aquisição de dados na região central da área experimental. Em blocos alternados entre os dois sistemas de semeadura, o patógeno foi inoculado artificialmente nas subparcelas dos blocos, e a doença foi avaliada por escala de notas (1 a 5). As médias de notas de sintomas de ramulose foram submetidas à análise estatística, através de testes não paramétricos. A fim de avaliar se a ausência de preparo poderia interferir no desenvolvimento das plantas, este também foi avaliado. Os resultados permitiram concluir que sob semeadura convencional, houve nos dois primeiros anos maiores médias de massa seca, altura de plantas, IAF, e que no terceiro ano foram constatados maior número de raízes laterais e maior número de plantas com encurvamento da raiz pivotante sob semeadura direta. O aumento da severidade da ramulose foi decorrente de interações muito particulares para cada período, onde muitas variáveis estão envolvidas, ou seja, características intrínsecas ao patógeno, à fase de desenvolvimento da planta e às condições macro e microclimáticas; O IF-tm teve uma boa relação com o aumento da severidade e diferenças na severidade da ramulose entre os dois sistemas de semeadura; Pode ocorrer maior severidade da ramulose para sistemas de produção convencionais em maior proporção do que em sistemas com utilização de palhada em períodos onde os valores de IF-tm são altos, associados à ocorrência de chuvas; Com Índices de Favorabilidade temperatura-molhamento menores que 0,500 não se observau aumento efetivo da severidade da ramulose em quaisquer sistema de semeadura, mesmo havendo outras condições favoráveis; O sistema de semeadura utilizado não influenciou na produtividade da cultura. / Systems with direct seeding over mulching are more often used in agriculture, and the Ramulosis from the cotton plant caused by the fungus Coletotrichum gossypii var. cephalosporioides Costa, one of the most important diseases in cotton crop. During the years of 2004/05, 2005/06; and 2006/07at the University of Agriculture "Luiz De Quieroz", USP/ ESALQ, in Piracicaba, SP, experiments were made with the cotton crop (Gossypium hirsutum L. var latifolium Hutch), under the preparation of conventional tillage with conventional seeding of the cotton crop and the absence of the preparation of the tillage with the seeding of the cotton crop over the mulching of millet (Pennisetum glaucum L.) with the objective to evaluate if the modifications microclimates caused by the use of the mulching of millet in relation to the variables temperatures and the leaf wetness duration, (LWD) could interfere on the development of the ramulosis of the cotton crop. It was also used the Favorability Index for the ramulosis of the cotton crop which uses the temperature parameter and DPM in its calculation to explain the development of the disease between the two systems of seeding. The Weather variables data were measured by a platform of acquisition of data in the central zone of the experimental area. In alternated blocks between both systems of seeding, the pathogen was inoculated artificially and the disease was measured by scales from 1 to 5. The average of ramulosis was submitted to a statistic analysis through not parametric tests with the intent to find out if the absence of the preparation could interfere on the development of the plants, which was also evaluated. The results enable the conclusion that through conventional seeding, on the first two years there was an average of higher dry mass higher height of the plants, IAF, and in the third year it was found a higher number of lateral roots and a higher number of plants with bending on the primary roots over direct seeding. The increase of the severity of the ramulosis happened due to specific interactions for each period where many variables were involved, which means, intrinsic characteristic to the at the stage of the development of the plant and the conditions macro and microclimates. The Favorability Index had a good relation with the increase and the differences within the severity of the ramulosis between both systems of seeding. Higher severity of the ramulosis can occur for conventional systems of production in bigger proportions than in systems that uses the mulching in periods where the value of the IF-tm are high, associated to rain. With indications of Favorability Index lower than 0,500 there is no evidence of the effective increase of the severity of the ramulosis in any system of the seeding. The system of seeding used does not affect in the productivity of the cotton crop.

Page generated in 0.0737 seconds