The increased demand for broadband communications has led to the rapid development of the conventional terrestrial and satellite wireless communications systems. One of the main challenges to next generation wireless systems is to deliver high-capacity and cost-efficient solutions to cope with an increasing usage of broadband services and applications. In the recent years, an emerging competitive system has attracted the attention for providing wireless broadband communications and other services based on quasi-stationary aerial platforms operating in the stratosphere known by high altitude platforms (HAPs), and located 17-22 km above the earth surface. This solution has been described by the International Telecommunication Union (ITU) as "a new and long anticipated technology that can revolutionize the telecommunication industry''. The HAP systems provide important advantages such as low cost, high elevation angles, low propagation delay, easy and incremental deployment, flexibility in operation, broad coverage, broadcast and broadband capability, ability to move around in emergency situations, etc. Therefore, they have been proposed by ITU for the provision of fixed, mobile services and applications, e.g. the third generation (3G) services licensed by ITU and backbone link for terrestrial networks in remote areas. This thesis explores and investigates the wireless communication and techno-economic performance of terrestrial systems and HAPs. An overview of research and development on aerial platforms worldwide is given. Coexistence performance and techniques of heterogeneous systems to provide broadband wireless communications based on Worldwide Interoperability Microwave Access (WiMAX) are investigated. A heterogeneous scenario is developed to examine the coexistence performance of heterogeneous systems. The capacity and deployment aspects of HAPs are analyzed, and further compared with terrestrial Universal Mobile Telecommunications Systems (UMTS) through techno-economic studies including a proposed partnership based business model for HAPs. Performance of wireless sensor network applications via HAPs is also investigated, and shows the high potential of HAPs for large-area and long-endurance surveillance and emergency applications. The thesis shows that communications from the aerial platforms provide the best features of both terrestrial and satellite systems. HAPs can effectively coexist in a heterogeneous radio environment, and are competitive solutions in urban and suburban scenarios in terms of capacity, coverage and business perspective. This makes HAP a viable competitor and complement to conventional terrestrial infrastructures and satellite systems.


I have indicated here some features of a kind of entity which I have called a cultural identity system, and I have focused on a variety of this general type—the persistent system. In general terms it is best described as a system of beliefs and sentiments concerning historical events. I suggest using the term "a people" for the human beings who, at any given time, hold beliefs of this kind. These are phenomena with which we have been long familiar, but they have not been systematically studied by any but a few investigators. I have emphasized that a persistent system is a cumulative cultural phenomenon, an open-ended system that defines a course of action for the people believing in it. Such peoples are able to maintain continuity in their experience and their conception of themselves in a wide variety of sociocultural environments. I hold that certain kinds of identifiable conditions give rise to this type of cultural system. These may best be summarized as an oppositional process involving the interactions of individuals in the environment of a state or a similar large-scale organization. The oppositional process frequently produces intense collective consciousness and a high degree of internal solidarity. This is accompanied by a motivation for individuals to continue the kind of experience that is "stored" in the identity system in symbolic form. The persistent identity system is more stable as a cultural structure than are large-scale political organizations. When large-scale states disintegrate, they often appear to decompose into cultural systems of the persistent type. Large-scale organizations also give rise to the kind of environment that can result in the formation of new persistent systems. It is possible that, while being formed, states depend for their impetus on the accumulated energy of persistent peoples. A proposition for consideration is that states tend to dissipate the energy of peoples after transforming that energy into state-level integrations, and then regularly break down in the absence of mechanisms for maintaining human motivations in the large-scale organizations that they generate.


Abstract. In July 2013 very strong boreal fire plumes were observed at the northern rim of the Alps by lidar and ceilometer measurements of aerosol, ozone and water vapour for about 3 weeks. In addition, some of the lower-tropospheric components of these layers were analysed at the Global Atmosphere Watch laboratory at the Schneefernerhaus high-altitude research station (2650 m a.s.l., located a few hundred metres south-west of the Zugspitze summit). The high amount of particles confirms our hypothesis that fires in the Arctic regions of North America lead to much stronger signatures in the central European atmosphere than the multitude of fires in the USA. This has been ascribed to the prevailing anticyclonic advection pattern during favourable periods and subsidence, in contrast to warm-conveyor-belt export, rainout and dilution frequently found for lower latitudes. A high number of the pronounced aerosol structures were positively correlated with elevated ozone. Chemical ozone formation in boreal fire plumes is known to be rather limited. Indeed, these air masses could be attributed to stratospheric air intrusions descending from remote high-latitude regions, obviously picking up the aerosol on their way across Canada. In one case, subsidence from the stratosphere over Siberia over as many as 15–20 days without increase in humidity was observed although a significant amount of Canadian smoke was trapped. These coherent air streams lead to rather straight and rapid transport of the particles to Europe.


Retrospective research accessing the Electronic Health Record (EHR) of the University of Pittsburgh School of Dental Medicine [axiUm database and software, Exan Group, Las Vegas, Nevada]. The research compared the success (survival) of narrow-platform dental implants (3.0-3.6mm) vs. wider-platform dental implants (3.7-6mm) in the posterior maxilla and mandible (molars and premolars), and, using axiUm measuring tools, evaluated marginal bone loss in each tooth/implant investigated. Datapoints from standard oral radiographs (periapical x-rays) existing in the Electronic Health Record were measured and recorded. Analysis of the data from the Electronic Health Record shows that both narrow and wider-diameter implants will present statistically significant marginal bone loss post-placement and restoration, averaging 0.7mm initial bone loss for the narrow diameter implants and 0.5mm initial bone loss for the wider-diameter implants. These results, from analysis of this existing University of Pittsburgh Electronic Health Record data, may not reflect the success rate anticipated clinically, nor that expected from anecdotal experience.


The movement of luminance-defined targets can be easily extracted by elementary motion detectors (EMDs) of the correlation type which often are referred to as Reichardt-detectors. In contrast to such 'primary motion', in 'secondary motion' the moving target is defined by more complex features, like changes in texture, flicker, or local contrast. Such stimulus attributes have to be extracted from the retinal intensity distribution by some nonlinear preprocessing, before they are fed into motion detectors. An intriguing case is the perception of the movement of the motion signal, as is present in theta motion, where an object moves in a different direction than the texture on its surface. A two-layer model of hierarchically organised EMDs has been postulated to account for such motion extraction. Other than for the first layer, the computational nature of the mechanism underlying motion processing in the second layer so far is a matter of speculation, and is therefore characterized here by means of computer simulations and psychophysical experiments. Random dot kinematograms were generated in which sinusoidally modulated vertical dot motion defined gratings, and coherence thresholds were measured for the direction discrimination of a horizontally travelling modulation function. This was done for a variety of spatial frequencies and speeds of the modulation sinusoid. Thresholds turn out to be lowest not for a particular speed, but for a fixed temporal frequency of the modulation function (about 1 cycle per second), when various combinations of fine and coarse, and fast and slow secondary gratings are tested. This result favours a correlation-type mechanism over a gradient-type scheme which should lead to a speed-optimum independent of spatial frequency.