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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.
1

Belowground Resource Exploitation in Semiarid Plants: A Comparative Study Using Two Tussock Grasses That Differ in Competitive Ability

Eissenstat, David M. 01 May 1986 (has links)
The relative competitive abilities of Agropyron desertorum and Agropyron spicatum were compared using Artemisia tridentata transplants as indicator plants. Although these two tussock grasses have similar shoot growth forms and shoot physiological characteristics, they have substantial differences in their competitive abilities. Artemisia had lower survival, growth, reproduction, and water potential when transplanted into neighborhoods of A. desertorum than in neighborhoods of A. spicatum. Plant attributes associated with the differences in competitive ability were explored. Agropyron desertorum and~ spicatum have remarkably similar potential growth rates at warm soil temperatures. In a prolonged cold soil temperature treatment in the greenhouse, A. desertorum had a 66% greater aboveground relative growth rate than A. spicatum. These differences, however, were not apparent for early spring tiller growth rates in the field. Distinct differences in timing of root growth were found between the two tussock grasses. Aqropyron desertorum exhibited greater root growth during winter and early spring and invaded disturbed soil space more rapidly than A. spicatum, especially if the disturbance occurred soon after the snow had melted. Similarly, A. desertorum proliferated its roots in zones of nutrient enrichment created early in the spring sooner than A. spicatum. No differences in root growth were found between species in zones of nutrient enrichment that were created later in the growing season. Despite differences in early spring root growth, water extraction and radiophosphorus acquisition early in the spring were similar for the two grass species. Later in the spring, A. desertorum extracted more water and radiophosphorus than A. spicatum. Differences in resource extraction between the two species in a specific soil layer occurred weeks before A. spicatum, but not A. desertorurn, had obtained maximum root length. Early root growth probably provides A. desertorum an important head start over A. spicatum in soil exploration each growing season. Differences in resource extraction, however, do not become apparent between the two species of Agropyron until plant demand exceeds soil supply rate to the roots.
2

Simulations of Pre-arcing Times in Diazed Fuses by an Electrothermal Dynamic Model

Andersson Jonsson, Amadeus January 2020 (has links)
The determination of the pre-arcing time of a fuse given a specific current is crucial during the selection process if the fuse is to be effective for the given application. Often the data supplied by the manufacturer is enough to determine this time, however this is not always the case. For this purpose a fuse model of a diazed fuse has been developed in order to simulate the pre-arcing times in the range of 2 ms to 2 s. The model is implemented in MATLAB and simulates the pre-arcing time for a given current together with fuse parameters such as the materials and the geometry of the fuse. The model has been tested experimentally by running specific currents designed to represent a wide variety of currents which a fuse might be subjected to. The tests were done on 10A gG fuses for which the current through the fuse was logged and then used as input to the fuse model, the simulated time and the measured time was then compared. The simulated times are in general faster than the measured pre-arcing times, this is mainly due to the rate of change of thermal conductivity of the sand with respect to temperature being approximated in conjunction with thermal radiation not being taken into consideration. More testing needs to be done to validate the model for different current ratings and fuse-element designs. / Att bestämma smälttiden för en säkring som utsätts för en given ström är viktigt för att kunna avgöra om dess prestanda är tillräcklig för en viss applikation. I de flesta fall är det möjligt att använda tillverkarens data tillsammans med vågformen för att bestämma smälttiden, men det kan även inträffa att detta inte är möjligt. För dessa fall har en modell av en diazed säkring utvecklas för att simulera smälttiden inom 2 ms till 2 s. Modellen har implementerats i MATLAB och beräknar smälltiden för en given ström och parametrar för säkringen. Modellen har testats experimentellt genom att säkringar har utsatts för en mängd olika strömmar som representerar de olika strömmar som säkringen kan utsättas för. Testerna gjordes på 10 A gG säkringar där strömmen genom säkringen loggades för att sedan användas som ingångsvärde till modellen, tiderna för den uppmätta smälttiden och den beräknades smälltiden jämfördes sedan. De simulerade smälttiderna är lägre jämfört med de uppmätta, detta beror dels på att förändringen av värmeledningsförmågan med temperaturökning hos sanden är okänd och är uppskattad från referenser och dels på att värmestrålning inte har ingått i modellen. Mer tester behöver utföras för att validera modellen mot fler strömstyrkor och designer. / Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
3

Hierarchical Temporal Memory Software Agent : In the light of general artificial intelligence criteria

Heyder, Jakob January 2018 (has links)
Artificial general intelligence is not well defined, but attempts such as the recent listof “Ingredients for building machines that think and learn like humans” are a startingpoint for building a system considered as such [1]. Numenta is attempting to lead thenew era of machine intelligence with their research to re-engineer principles of theneocortex. It is to be explored how the ingredients are in line with the design princi-ples of their algorithms. Inspired by Deep Minds commentary about an autonomy-ingredient, this project created a combination of Numentas Hierarchical TemporalMemory theory and Temporal Difference learning to solve simple tasks defined in abrowser environment. An open source software, based on Numentas intelligent com-puting platform NUPIC and Open AIs framework Universe, was developed to allowfurther research of HTM based agents on customized browser tasks. The analysisand evaluation of the results show that the agent is capable of learning simple tasksand there is potential for generalization inherent to sparse representations. However,they also reveal the infancy of the algorithms, not capable of learning dynamic com-plex problems, and that much future research is needed to explore if they can createscalable solutions towards a more general intelligent system.
4

Regional projektfinansiering i Västerbottens kommuner : En inomregional jämförelse / Regional project finance in the municipalities of Västerbotten : intra-re-gional comparison

Burström, Therese January 2021 (has links)
Regional project finance is an important national economic instrument for regional develop-ment in Sweden. Despite that, the research on the subject is limited meaning that there is little knowledge of the instrument’s distribution and consequences. This is problematic regarding the goal of the project funds, which is to contribute to growth throughout the country. The aim of this thesis was therefore partly to investigate how the distribution, and the applications of, regional project funds differ between Swedish municipalities with different geographical characteristics, partly to analyse the reasons for these differences. The study was a qualitative case study of Västerbotten and was divided into two parts. The first part was based on a data material on project funds of Region Västerbotten between 2014-2020 to examine how the project funds were applied for, and distributed, between the region´s municipalities during that period. The second part was mainly based on transcripts from interviews with municipal officials from six municipalities to examine the explanations for those differences. The result shows that there are significant differences between municipalities with different geographical characteristics of Västerbotten which is explained by differences in access to resources and participation in collaborative projects between the municipalities. In conclusion it therefore seems to be some challenges in enabling the whole country to take advantage of these funds.
5

Produkce digitálních obrazových dat a jejich kontrola / Digital Images Production and Quality Control

Vychodil, Bedřich January 2013 (has links)
(EN) This dissertation provides a broad understanding of fundamental terminology and an inside view of the digitization workflow and quality control processes. The main foci are on quality assurance during and outside the digitization processes and identification of the most suitable format for access, long term preservation, rendering and reformatting issues. An analysis of selected digitization centers is also included. An application called DIFFER (Determinator of Image File Format propERties) and subsequently The Image Data Validator - DIFFER has been developed using results from previously conducted research. The application utilizes new methods and technologies to help accelerate the whole processing and quality control. The goal was to develop a quality control application for a select group of relevant still image file formats capable of performing identification, characterization, validation and visual/mathematical comparison integrated into an operational digital preservation framework. This application comes with a well-structured graphic user interface, which helps the end user to understand the relationships between various file format properties, detect visual and non visual errors and simplify decision-making. Additional comprehensive annexes, describing the most crucial still image...

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