• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 311
  • 272
  • 78
  • 69
  • 19
  • 14
  • 13
  • 10
  • 8
  • 8
  • 6
  • 6
  • 6
  • 4
  • 4
  • Tagged with
  • 942
  • 107
  • 103
  • 82
  • 64
  • 61
  • 53
  • 52
  • 49
  • 47
  • 41
  • 39
  • 39
  • 38
  • 37
  • 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.
361

Optimalizace návrhu velikosti PV systémů / Optimization proposal of size of PV systems

Vrzal, Martin January 2016 (has links)
The master thesis deals with proposal of size optimization of PV systems. According to results of optimization, alternative solutions of photovoltaic system were proposed for family house. From the perspective of costs efficiency were compared investment costs and savings of implementation of electricity supply directly to private consumption. Particularly for each of the proposed solution, profitability assessment of comparing purchasing costs and returns on investment was performed. Theoretical part of the master thesis consists of introduction into solar radiation principles, structure and functionality of photovoltaic systems, electronics inverters and accumulation of electric energy. The practical part is focused on measuring of electricity consumption in particular family house, calculation of sunlight intensity hitting tested house, making various solutions of photovoltaic power plants placed on the family house in order to evaluate returns on investments. In conclusion are summarized all results of investigated solutions according to economics aspects.
362

Akumulace energie v tlakovém vzduchu / Accumulation of energy in compressed air

Rešiliáno, Tomáš January 2016 (has links)
The thesis deals with the principle and issues associated with operation of the storage power stations, known under the acronym CAES (Compressed Air Energy Storage). Examples of existing and upcoming CAES power stations from commercial sphere are listed and described there. The paper also includes an overview of basic CAES station wiring diagrams and a simplified calculation is performed to compare the efficiency of the chosen diagrams. In the final part of the thesis there is a scheme of so-called adiabatic CAES designed and calculated. For this type of device has been designed suitable wiring and a thermodynamic calculation of the cycle was performed for the purpose of evaluation.
363

Akumulace elektrické energie pro RD / Accumulation of electricity for residences

Blabla, Ondřej January 2016 (has links)
This diploma thesis deals with the accumulation of electrical energy in the scale of small house. The theoretical part describes the various ways of storing power. The practical part is devoted to the design and comparison of electrical energy accumulation for a particular house.
364

Transferencia de masa entre la desembocadura del Río Limarí, Bahía Tongoy y Bahía Barnes. Región de Coquimbo, Chile

Zambra Ramos, Rubén January 2019 (has links)
Este estudio es parte del proyecto FONDECYT N° 1120234 “Geodinámica y tendencia evolutiva del sistema litoral de la mega ensenada de Coquimbo: hacia una prognosis de amenazas naturales para escenarios de cambios ambientales endógenos y exógenos. / Memoria para optar al título de Geógrafo / Se estudia la transferencia de masa entre la desembocadura del río Limarí, bahía Tongoy y bahía Barnes a través de la integración de unidades costeras, identificando las formas de acumulación, las relaciones morfosedimentológicas en los grupos de formas existentes y el transporte de masa en el litoral. Para la identificación de las formas de acumulación en las áreas de estudio, fue necesario realizar una descripción geomorfológica, identificando formas fluviales, fluviomarinas, terrazas marinas y formas eólicas. Para el análisis de las relaciones morfosedimentológicas se hizo necesario realizar análisis granulométrico según los procedimientos de distribución textural y morfoscópico de arenas, además de la mineralogía. Para el transporte de masa litoral se utilizó técnicas cualitativas a través del análisis multitemporal del ambiente de depositación, en un rango temporal de 27 años, analizando imágenes satelitales LandSat de los años 1987,1997, 2004 y 2011. Los resultados alcanzados denotan el fuerte control estructural y la orientación dominantemente oblicua de las bahías como factores que posibilitan la sedimentación de este sistema litoral, operando los principios de efecto de ensenada en éstas. Se considera que la fuente de abastecimiento de las bahías Tongoy y Barnes proviene de la cuenca del río Limarí, pero es necesario también considerar otros medios de transporte de sedimentos que no necesariamente tiene relación con el río ni su zona de descarga. El análisis multitemporal de las imágenes satelitales refleja que la transferencia de masa entre los diferentes sistemas se debe en el período reciente a condiciones que sobrepasen el umbral de transporte de sedimentos, esas condiciones se deben al aumento en la intensidad y torrencialidad de las precipitaciones. Las formas que reflejan cambios en los ambientes de depositación corresponden a flechas litorales y campos dunares las cuales son áreas sensibles a los aportes de sedimentos entre los sistemas. / It is studied that mass transfer between the Limarí river mouth, Tongoy bay and Barnes bay across of the integration of costal units, identifying accumulation forms, morphosedimentological, relations in the groups of existing forms and the mass transport in the coast. For identifying forms of accumulation in the areas of study, it was necessary to make a geomorphological description, identifying fluvial forms, river-marine, marine terraces and aeolian forms. For the analysis of morphosedimentological relations, it became necessary to perform granulometric analysis according to the procedures of textural distribution and sand morphocopic, including the mineralogy. For the transport of littoral mass we used qualitative techniques through the multitemporary analysis the depositional environment, a temporary range of 27 years, analyzing Landsat satellite images of the years 1987, 1997, 2004 and 2011. The results show the strong structural control and oblique orientation dominantly of the bays as factors that enable the sedimentation of the coastal system, operating the effect of cove principles in them. It is considered that the source of supply for Tongoy and Barnes bays comes from Limarí river basin, but it is also necessary to consider other transport means of sediments that does not necessarily have relation to the river or its discharge zone. The multi-temporal analysis of satellite images reflects that the mass transfer between the different systems ocurred in the recent period due to conditions that exceeded the threshold of sediment transport, these conditions are due to increase in the intensity and heavy rainfall. The forms that reflect changes in the deposition environments correspond to coastal arrows and dune fields which are sensitive areas to the contributions of sediments between systems.
365

Stratigraphic and palaeoenvironmental observations in the deposits of a postglacial kettle hole, in the county of Västernorrland

Kourela, Genofeva Eva January 2020 (has links)
The increased human impact on the environment and climate after the retreat of the Last Glacial has strengthened its importance in the region of Västernorrland where Mesolithic sites are evident. This study focuses on a multiproxy analysis, where archaeological and natural science methods are combined to test several techniques in a peat sample. The origin of the peat sample is coming from the formation of a postglacial kettle hole situated near to Mesolithic sites. The aim of this thesis is twofold. Firstly, to estimate the value and the weakness of each method as also the combination of multiple results. Secondly, to reconstruct the palaeoenvironment including the detection of possible indications from past cultures. To begin with, the peat sample was collected from a kettle hole near Lillsjön lake, see (fig. 1) in 2010. The total depth of the peat sample was 80 cm and after its sampling, it was placed in a cold storage room until the spring of 2019, when analysis was conducted. Initially, a theoretical background will be presented as well as information for the area of study in the section of Scientific background. Moreover, a short theory is going to be given for the formation of the landscapes in cold environments as also the validity of beetle fossils with examples from previous case studies. After the theory part, all the methods are specified with results and appropriate diagrams and tables. After the analysis, the discussion will follow by combining all the methods and give potential theories for the reconstruction of the palaeoenvironment. The discussion part is divided into smaller chapters and after the conclusion an appendix is given with fossil photographs that were taken during the identification, see (fig.15,16,17).
366

Can economic freedom promote growth via physical capital accumulation? : A study applying the augmented mean group (AMG) estimator for macro panel data analysis

Gedin, Julia January 2020 (has links)
The efficiency of physical capital accumulation plays a critical role for economic growth. This paper aims at examine if economic freedom promotes economic growth via physical capital accumulation. This is done by estimating a production function by replacing the inputs with institutional indices. The first input is GDP per capital growth rate which serve as a proxy for institutional aspects and the other input are the economic freedom indexes which will serve as proxies for physical capital accumulation. This is done by applying the augmented mean group (AMG) estimator that is designed for dealing with macro panel data analysis, including twenty developing countries where the economies have experienced a rapid growth, and the time period are between 1995 and 2017. The theoretical framework is based on the Solow growth model, institutional theory and marginal efficiency of capital (MEC). The results show that economic freedom promotes economic growth via physical capital accumulation where GDP per capital growth rate served as a proxy for institutional aspects and economic freedom indexes as proxies for physical capital accumulation. The results also show that the AMG estimator is the best fit for macro panel data analysis since it are designed for dealing with heterogeneity.
367

Studium akumulace kademnatých iontů energetickými plodinami / Study of accumulation of cadmium ion by energy crops

Berkyová, Petra January 2012 (has links)
Cadmium is heavy metal toxic for plants and animals and environmental contaminant which must be removed from natural environment. In recent years a new method phytoremediation is getting more attention. This method uses plants called hyperaccumulators for extraction of heavy metals from soils. Hyperaccumulators have, however, after accumulation of heavy metals no other use. Therefore new possibilities are discussed in last few years. Energy plants, in this thesis sorghum and malva, could be used for accumulation of heavy metals from soils and after that these plants could be used as energy source. This thesis wants to find out if sorgum and malva are able to grow in cadmium contaminated environment and if these plants will accumulate cadmium. It also compares different cultivars of sorghum in toxicity tests and compares ability of these cultivars to grow in cadmium contaminated environment and to accumulate this heavy metal. Further it focuses on affection of uptake of kadmium ions by sorhum in presence of glutathione or ethylenediaminetetraacetic acid.
368

Depositional Dynamics in Seagrass Systems of Tampa Bay, FL: Influence of Hydrodynamic Regime and Vegetation Density on Ecosystem Function

Meyers, Alison Cheryl 25 March 2010 (has links)
Many coastal ecosystems around the world are dominated by submerged aquatic vegetation (SAV) habitats. These SAV habitats are known to provide many highly valuable ecosystem services such as habitat for commercial important species and increased water clarity. Water flow is an environmental variable which can have measurable effects on the ecosystem services provided by SAV, but is often not considered in studies assessing these services. This dissertation sought to investigate the links between SAV, primarily seagrasses, and hydrodynamics, paying special attention to the effects on sediments and fauna. Three main areas are discussed: (1) the effects of SAV on flow, (2) the effects of SAV and flow on deposition in SAV beds, and (3) the effects of SAV and flow on faunal communities in SAV beds. Seagrasses and other SAV reduce currents, attenuate waves, and dampen turbulence within their vegetative canopies, which in turn can enhance deposition and reduce the resuspension of sediment, organic matter, and passively settling larvae. The ability of SAV to retard flow may be further enhanced by increases in vegetated structure, such as shoot density, biomass, or canopy height, which can promote increased abundance and diversity of in- and epifauna within SAV beds. Ultimately, it is clear that hydrodynamics is an important factor that shapes SAV communities both physically (e.g. deposition, sediment structure, etc.) and biologically (e.g. faunal community composition, predation pressure, food availability, etc.).
369

Comparison of Transcriptome Changes Associated to Oil Accumulation in Oil Palm Mesocarp and in Oil Seeds

Bourgis, F., Kilaru, Aruna, Cao, X., Legrand, E., Beauvoit, B., Maucourt, M., Deborde, C., Moing, A., Ebongue, G-F., Drira, N., Ohlrogge, J., Arondel, V. 01 January 2012 (has links)
No description available.
370

Influence of a Human Lipodystrophy Gene Homologue on Neutral Lipid Accumulation in Arabidopsis Leaves

James, Christopher Neal 08 1900 (has links)
CGI-58 is the defective gene in the human neutral lipid storage disease called Chanarin-Dorfman syndrome. This disorder causes intracellular lipid droplets to accumulate in nonadipose tissues, such as skin and blood cells. Here, disruption of the homologous CGI-58 gene in Arabidopsis thaliana resulted in the accumulation of neutral lipid droplets in mature leaves. Mass spectroscopy of isolated lipid droplets from cgi-58 loss-of-function mutants showed they contain triacylglycerols with common leaf specific fatty acids. Leaves of mature cgi-58 plants exhibited a marked increase in absolute triacylglycerol levels, more than 10-fold higher than in wild-type plants. Lipid levels in the oil-storing seeds of cgi-58 loss-of-function plants were unchanged, and unlike mutations in beta-oxidation, the cgi-58 seeds germinated and grew normally, requiring no rescue with sucrose. We conclude that the participation of CGI-58 in neutral lipid homeostasis of nonfat-storing tissues is similar, although not identical, between plant and animal species. This unique insight may have implications for designing a new generation of technologies that enhance the neutral lipid content and composition of corp plants.

Page generated in 0.0747 seconds