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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.
81

Trends and climatic shifts in mesosphere / lower thermosphere planetary waves Collm (52°N, 15°E)

Jacobi, Christoph, Hoffmann, Peter, Kürschner, Dierk 04 April 2017 (has links) (PDF)
Long-period oscillations in the period range between 2-30 days, interpreted as planetary wave (PW) signatures, have been analysed using daily upper mesosphere/lower thermosphere wind measurements near 90 km over Collm (52°N, 15°E) in the time interval 1980-2005. Strong interannual and interdecadal variability of PW are found. Since the 1990s, a tendency for larger zonal amplitudes compared to meridional ones, has been observed, thus long-term trends are visible, which are positive in the zonal component, but negative in the meridional component. The change appears in a stepwise manner, so that a sudden change of the mean is visible rather than a linear trend. The behaviour of the upper middle atmosphere winds is similar to analysed wave changes in the stratosphere, indicating a coupling of the atmospheric layers through planetary waves. / Mit Hilfe von täglichen Windmessungen im Mesopausenbereich bei 90 km werden langperiodische Schwankungen im Zeitbereich von 2-30 Tagen untersucht, die als das Signal planetarer Wellen gelten. Im Zeitraum 1980-2005 werden deutliche Schwankungen von Jahr zu Jahr als auch langfristige Trends gefunden. Einer Zunahme der zonalen Komponente der Schwankungen seit 1990 steht eine Abnahme der meridionalen Komponente gegenüber. Diese Änderung erfolgt in rascher Form, so dass sich die Änderung der Zirkulation im Mesopausenbereich als klimatische Verschiebung, und weniger als Trend darstellt. Das Verhalten der Dynamik im Mesopausenbereich korrespondiert mit möglichen Änderungen klimatischer Parameter in anderen Schichten der Atmosphäre und weist auf eine Kopplung atmosphärischer Schichten untereinander hin.
82

Interannual variability of the quasi two-day wave over Central Europe (52°N, 15°E)

Jacobi, Christoph, Kürschner, Dierk 04 April 2017 (has links) (PDF)
Using the spaced receiver method in the low-frequency (LF) range, lower E-region ionospheric drifts are measured at Collm Observatory, Germany since several decades. These drifts are interpreted as upper mesospheric winds at the reflection height of the used amplitude modulated LF radio waves, the latter being measured since 1983 using travel time differences between the ground wave and the ionospherically reflected sky wave within a small sideband range near 1.8 kHz above and below the carrier frequency. One regular feature of midlatitude upper mesosphere winds is the quasi twoday wave (QTDW), known as a wavenumber 3 or 4 wave in the middle atmosphere, usually occurring as one or more bursts during the summer season at midlatitudes. The OTDW bursts, as measured in LF winds, shows substantial decadal and interannual variability. Comparison with the background winds show that the onset of QDTW bursts is found near maximum values of the vertical wind shear, and maximum QTDW amplitudes are measured, on average, about one week after the maximum wind shear. This supports the theory that the QTDW is forced by instability of the summer mesospheric wind jet. / Am Observatorium Collm werden seit mehreren Jahrzehnten Langwellenwindmessungen in der unteren ionosphärischen E-Schicht durchgeführt. Die zugehörige Reflexionshöhe wird, auf der Basis von Laufzeitdifferenzmessungen zwischen der Raum- und Bodenwelle, seit 1983 ebenfalls registriert. Eines der regelmäßig beobachteten Phänomene ist die quasi 2-Tage-Welle, die als eine planetare Welle der Wellenzahl 3 oder 4 bekannt ist. Diese Welle erscheint in mittleren Breiten in einem oder mehreren Schüben im Sommer. Nach den Messungen am Collm besitzt die Welle eine deutliche Variabilität von Jahr zu Jahr. Vergleiche mit dem zonalen Grundwind zeigen, dass das Auftreten von Maxima der 2-Tage-Welle in vielen Fällen mit erhöhter vertikaler Windscherung in Verbindung steht, so dass im langzeitlichen Mittel maximale Wellenamplituden einige Tage nach dem Auftreten maximaler Windscherung zu finden sind. Dies unterstützt die These, dass die quasi 2-Tage-Welle durch barokline Instabilität des sommerlichen Mesosphärenjets angeregt wird.
83

Untersuchung der Quasi - 2 - Tage Welle im Sommer 2005

Weithäuser, Ina, Stober, Gunter, Fröhlich, Kristina, Jacobi, Christoph 04 April 2017 (has links) (PDF)
Das seit Juli 2004 kontinuierlich arbeitende Meteorradar am Observatorium Collm (53,3°N, 13°E) der Universität Leipzig dient der Messung des horizontalen Windfeldes sowie der Temperatur in der Mesopausenregion. Neben der Betrachtung des jahreszeitlichen Verhaltens von Grund- und Gezeitenwind ist es möglich, die Aktivität planetarer Wellen zu untersuchen. Spezielles Interesse gilt dabei der Quasi-2-Tage Welle im Sommer 2005, da zu dieser Zeit sowohl eine Verschiebung der maximalen Amplituden hin zu kürzeren als auch zu längeren Perioden beobachtbar war. Als mögliche Ursache dafür werden nichtlineare Wechselwirkungen zwischen der Quasi-2-Tage Welle und planetaren Wellen mit größeren Perioden gesehen. Die Untersuchung derartiger Wechselwirkungen erfolgt mit Hilfe der Bispektralanalyse. / Since July 2004 the meteor radar operates continuously at the Observatory (53,3°N, 13°E) of the University of Leipzig. It provides data of the horizontal wind field as well as the temperature of the mesopause region. In addition to the consideration of the seasonal behaviour of prevailing and tidal winds it is possible to examine the activity of planetary waves. Because of the shift of maximum amplitudes of the quasi-2-day wave in summer 2005 to shorter as well as longer periods the event has to be considered more in detail. Possible reasons for the displacements are nonlinear couplings between the quasi-2-day wave and planetary waves with longer periods. The examination of those couplings is performed using bispectral analyses.
84

Doctoral thesis recital (wind conducting)

Hartenberger, Jaclyn 20 July 2012 (has links)
Ouverture fur Harmoniemusik, op. 24 / Felix Mendelssohn-Bartholdy -- Concertino for flute, op. 107 / Cecile Chaminade -- Octet, op. 103 / Ludwig van Beethoven -- Ragtime for eleven instruments / Igor Stravinsky. / text
85

Benchmarking of Optimization Modules for Two Wind Farm Design Software Tools

Yilmaz, Eftun January 2012 (has links)
Optimization of wind farm layout is an expensive and complex task involving several engineering challenges. The layout of any wind farm directly impacts profitability and return of investment. Several software optimization modules in line with wind farm design tools in industry is currently attempting to place the turbines in locations with good wind resources while adhering to the constraints of a defined objective function. Assessment of these software tools needs to be performed clearly for assessing different tools in wind farm layout design process. However, there is still not a clear demonstration of benchmarking and comparison of these software tools even for simple test cases. This work compares two different optimization software namely openWind and WindPRO commercial software tools mutually.
86

Distributed small-scale wind in New Zealand : advantages, barriers and policy support instruments : a thesis submitted to the Victoria University of Wellington in partial fulfilment of the requirements for the degree of Master of Environmental Studies /

Barry, Martin, January 2007 (has links)
Thesis (M.Env.Stud.)--Victoria University of Wellington, 2007. / Includes bibliographical references.
87

Vorhersageverbesserung des Windes im Küstenbereich

Viertel, René, Tetzlaff, Gerd 23 March 2017 (has links) (PDF)
Nachdem der weitere Ausbau der Stromerzeugung aus Windenergie an Land an seine Grenzen stösst, rücken die küstennahen Bereiche der Seegebiete in den Mittelpunkt der Planungen. Aufgrund seiner Komplexität sind die Vorhersagen der relevanten Größen im Zeitbereich bis 48 Stunden in diesen Gebieten oftmals ungenau. Mittels systematischer Vergleiche von Prognosen und Messreihen meteorologischer Größen wurde untersucht, ob sich charakteristische Muster der Abweichung der Windprognose von der Messung in Abhängigkeit meteorologischer Größen und Prognosezeit finden und sich die Abweichungen verringern lassen. / After the further development of the generation of current by wind energy on land areas is pushed to the borders the near-shore areas of the see regions moves into the center of plannings. Because of the complex behavior of such areas the prediction of the required meteorological values often becomes uncertain within the forecast range of 48 hours. Measurements of meteorological values and forecasts were compared systematically. By means of this comparisons it was examined, whether characteristical pattern of the deviation between measurements and forcasts, dependent on other meteorological values and forecast time, can be found. The possibility to reduce this deviations was verified.
88

How to develop onshore wind farm projects in France under the new Grenelle 2 law

BAUDREY, Xavier January 2012 (has links)
With the rising global warming issue and an ever-increasing dependency oil problem, wind power seems to be an alternative source of energy which is clean, non-polluting, and cost effective. The European 20-20-20 goals as well as national targets for the next ten years require a substantial increase in installed renewable capacity in France. Maïa Eolis is a leading French wind project developer and independent renewable energy producer which helps France to meet its new renewable energy targets. Even if the general opinion on wind energy is rather positive, developing a wind power project is a complex process in France because there are many regulations and new environmental constraints due to the Grenelle 2 law. Many administrative and legislative barriers consequently slow down every step of the development process. This includes handling and coordinating the permitting and application process, realizing pre-feasibility studies, and identifying the best suited sites for wind turbines, taking into account obstacles, aesthetics, and other environmental issues, in order to capture as much wind as possible. Ensuring local support is another key element of the success of a project in order to integrate it in the best possible way in its environment.
89

Pandora for Wind Symphony

Walden, Joseph P. 25 August 2015 (has links)
No description available.
90

Technical and economic analysis of US offshore wind power

McDaniel Wyman, Constance Annette 11 June 2014 (has links)
Wind power is the fastest growing sector of electricity generation in the world and the development of offshore wind resources is an increasingly important component of this growth. While more than 1.5GW have been installed in Europe and China, no turbines have been installed in United States waters even though several have been planned. Offshore wind power development in the United States must contend with significant challenges. There are numerous technical considerations including geological issues and undefined environmental conditions that affect the determination of appropriate design loads. Technological advancements are needed, and logistical questions must be addressed. The regulatory structure can be confusing and most permitting frameworks are not well established. Offshore wind projects are capital intensive and concerns exist that the industry will not be able to achieve a suitable economy of scale. Additionally, concerns about offshore wind impacts cross many areas such as the environment, visual and cultural concerns, navigational issues, and competing uses. This research project examines the technical issues of American offshore wind power and models basic project costs to provide an estimate of the total net present value for hypothetical utility-scale offshore wind projects in the United States. Costs have been examined by building a cost model and employing traditional cash flow analysis, regression, design of experiments, and random sampling techniques. / text

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