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Local meteorology and its effect on electromagnetic wave propagation over the southern coast of the Arabian GulfAlmehrezi, Ali January 2017 (has links)
The propagation of electromagnetic (EM) waves of frequencies above 100MHz is affected by the existence and properties of the atmospheric duct, i.e. a horizontal layer in the lower atmosphere in which radio signals propagate more efficiently. Atmospheric ducts can be found in many parts of the world ocean including the Arabian Gulf. Ambient winds blowing from different directions bring air masses of different properties into the area and hence have a significant impact on the formation and strength of the atmospheric duct. However, little information is available on the long-term and intra-annual variability of wind and its effect on the ducting phenomenon in the Arabian Gulf region. This study addresses this gap by characterising the local meteorology, with a special emphasis on its effect on electromagnetic wave propagation. This study uses a new methodology to measure the persistence of Shamal wind, by considering the number of days associated with the specific wind pattern in addition to commonly used parameters such as the wind speed. In this study, thirty years (1981-2010) of observations and NCEP/NCAR reanalysis data have been analyzed to identify a long-term trend and the intra-annual variability of various wind systems. Results clearly indicate that the Shamal (the northwesterly wind) is the most frequent meteorological feature over the region; therefore it has been investigated in greater detail. The Suhaili (southerly wind) is the second important wind which can occur any time of the year but it is less frequent than the Shamal. The Al-Nashi (cold and dry northeasterly wind) wind occurs only in December, January and February. The analysis shows that the wind strength and the frequency of Shamal days over the region have decreased over the last thirty years. Variations in the occurrence of summer and winter Shamal days were studied in relation to global atmospheric phenomena, and relationships have been established, synoptically and statistically between the frequency of Shamal days and large-scale atmospheric fluctuations. These links include atmospheric fluctuations over the Caspian Sea (a correlation coefficient of 0.66) and Siberia (0.69) in summer and Greenland (0.51) and Western Europe (0.65) in winter. The frequency of winter Shamal days during December, January and February are shown to be statistically related (a correlation coefficient of 0.41) to the North Atlantic Oscillation (NAO) and (0.49) the Arctic Oscillation (AO), as they influence the pathway of the westerly depression over the north Atlantic Ocean during the winter season. It is also shown that the decline in the number of Shamal days is linked to a decrease in the number of westerly depressions. The EM wave propagation has been examined using the Advanced Refraction Effects Prediction System (AREPS) model for different representative air masses. The radiosonde data from Abu Dhabi airport used in AREPS provided evidence of the general influence of each air mass. It was found that atmospheric ducting conditions and characteristics (height, thickness, and type) were variable in the lower part of the atmosphere (surface to 6000m) as a result of changing air masses. The influence of the Shamal conditions develop an elevated duct at approximately 850mb level. The Suhaili increases the thickness of the evaporation duct. In regards to the surface based and elevated duct, Suhaili and Al-Nashi provide standard atmospheric conditions. Land and sea breezes were mostly associated with the surface based duct and sometimes elevated the duct. Atmospheric ducting could extend the range of electromagnetic wave propagation above the usual range. Good knowledge of atmospheric duct characteristics enables the efficient assessment of the range of EM propagation, which is important for a number of practical applications, for example air traffic control and rescue operations. This could include the selection of the appropriate frequency and altitude of the electromagnetic wave device (e.g. radar and/or communication systems) operating with a frequency above 100MHz to be trapped in the duct to cover long distances.
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Predicting the development of weather phenomena that influence aviation at Abu Dhabi International AirportDe Villiers, Michael Pierre 08 February 2010 (has links)
The United Arab Emirates is a new country that has had little time to accumulate a scientific heritage. Meteorologically researched and documented weather material for forecasters is virtually non-existent and that available is fragmented and anecdotal. The thesis tackles this problem by identifying weather phenomena significant to aviation in the Emirates and particularly at Abu Dhabi International Airport (ADIA). Mechanisms responsible for their development are described and applicable forecasting rules and principles are derived. Surface and upper air observation data at ADIA from 1983 to 2002 were analysed to identify the weather phenomena, their associated weather systems and for statistical analyses. When relevant, observation data at Al Ain was also used. Post-processed numerical weather prediction Global Forecast Service Eta model data are used and when and where possible radar and satellite imagery. A secondary aim is to provide information of the general seasonal climate. This was achieved by means of a literature study of the dominating weather systems and the presentation of surface and upper air mean circulation charts. Fog is the most important weather phenomenon and serious disrupter of aviation at ADIA throughout the year. It does not occur during Shamal conditions, but fog can form well inland on the edge of the Empty Quarter at the Liwa Oasis when the Shamal wind becomes light. Contrary to local belief, fog is unlikely to occur on two, or more, consecutive nights. The Shamal can last for several days and disrupt helicopter flights to the oil rigs, while anabatic and katabatic effects often make it gustier and stronger inland at Al Ain than ADIA. While dust storms occur in strong southerly winds off the desert, the Shamal can bring dust from further afield from the north as can the previously unreported Nashi wind. The sea breeze can extend about 150 km inland to Al Ain and the Liwa Oasis. Thunderstorms associated with winter upper air troughs from the west, are the main producers of rain, while occasional thunderstorms off the Hajar Mountains in the east bring some rain in summer. Tropical depressions are a rare event. / Thesis (PhD)--University of Pretoria, 2010. / Geography, Geoinformatics and Meteorology / PhD / Unrestricted
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Haunted Boundaries: Ghost Stories in Isolationist JapanUnknown Date (has links)
One of the most popular forms of literature in Japan is that of “kaidan.,” literally
meaning “strange story,” during the Edo period, but over time “kaidan” has come to
specifically mean stories of “yūrei,” or “Japanese ghosts.” Many Western academic
studies concerning kaidan thus far are concerned with the genre’s shift from religious
didactics to secular entertainment. This is an important evolution to keep in conversation
with this project; However, this study will argue that ghosts work as Edo symbols for
failing boundaries within an isolationist society. Two of the main texts in this project are
translations by Lafcadio Hearn, being “Mimi Nashi Hōichi” and “Jikininki.” The other
two main texts used are translations of “Banchō Sarayashiki” by Zack Davisson. In my
study, I identify breaches of boundaries within social order in these texts using the aid of
Mikhail Bakhtin’s “the grotesque,” Julia Kristeva’s “abject horror,” and Jacques
Derrida’s “hauntology.” / Includes bibliography. / Thesis (M.A.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection
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Hacking for the State? : The Use of Private Persons in Cyber Attacks and State ResponsibilityOlovson, Natali January 2020 (has links)
While there are many examples to turn to regarding the thriving phenomenon of private persons being exploited to launch cyber attacks on behalf of states, this thesis will direct it’s attention onto two special cases. Russia has been accused of being the state actor behind the cyber attacks on Estonia in 2007 and Georgia in 2008. The cases are chosen as Estonia have been recognised as the first coordinated cyber attack on a foreign country, and Georgia being the first case were cyber attacks have been utilised in synchronisation with military action. The purpose of the thesis is to analyse the facts of each case in relation to the International Law Commission’s Draft Articles on Responsibility of States for Internationally Wrongful Acts (DARSIWA). The analysis will work through article 4, article 5, article 8 and article 11. The main question is how Russia may be hold as legally responsible under international law for the private conduct of ’patriotic’ hackers, the Nashi Youth Group and the Russian Business Network. The thesis concludes that while the circumstances of each case highly indicate state-involvement, this cannot be proven under the respective criterias of the articles and Russia does therefore not bear legal responsibility.
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