Aeroelastic aspects of unmanned aerial vehicles (UAVs) is analyzed by treatment of a typical section containing geometrical nonlinearities. Equations of motion are derived and numerical integration of these equations subject to quasi-steady aerodynamic forcing is performed. Model properties are tailored to a high-altitude long-endurance unmanned aircraft. Harmonic balance approximation is employed based on the steady-state oscillatory response of the aerodynamic forcing. Comparisons are made between time integration results and harmonic balance approximation. Close agreement between forcing and displacement oscillatory frequencies is found. Amplitude agreement is off by a considerable margin. Additionally, stochastic forcing effects are examined. Turbulent flow velocities generated from the von Karman spectrum are applied to the same nonlinear structural model. Similar qualitative behavior is found between quasi-steady and stochastic forcing models illustrating the importance of considering the non-steady nature of atmospheric turbulence when operating near critical flutter velocity.

The study intended to investigate the phylogeography of mid-altitude species, Japalura brevipes, which is the endemic to Taiwan. I used mitochondrial cytochrome b sequences and morphological characters to investigate the phylogeography. The molecular results showed that there are 16 haplotypes. The length of partial cytochrome b sequences is 617 bp including 84 informative sites, and the mean genetic distance is 5.4%. In phylogenetic analyses, three major clades were found in the phylogenetic trees. Moreover, these clades (north, central-north and south) corresponded to the geographic distribution. Analysis of population genetic structure revealed significant differentiation among populations, and most of the haplotypes were restricted to the locally. The morphological analyses showed that there is no difference between sexes at 18 characters, with the exception of the axilla-groin length and dorsal-crest scales. The Principal Component Analysis and Canonical Discriminate Analysis using 16 morphological characters showed the different results. Principal Component Analysis failed to separate populations. However, Canonical Discriminate Analysis could discriminate the populations of Guanwu, Nanheng, Sihyuantkou and Wuling Farm from others. Phylogeography of J. brevipes belonged to category 1 defined by Avise (2000). I infer refuge effect and dispersal ability hypotheses to explain the genetic structure of J. brevipes.

Flight simulators are widely used by the military, civil and commercial aviation. Visual cues are an essential part of helicopter flight. The required cues for hover are especially large due to closeness to the ground and small movements. In this thesis, density and height parameters of the 3D (Three Dimensional) objects in the scene are analyzed to find their effect on hovering and low altitude flight. An experiment is conducted using a PC-based flight simulator with three LCD monitors and flight control set. Ten professional military pilots participated in the experiment. v Results revealed that object density and object height are effective on the horizontal and vertical hovering performance. There is a peak point after which increasing the density does not improve the performance. In low altitude flight, altitude control is positively affected by smaller object height. However, pilots prefer the scenes composed of the high and mixture objects while hovering and flying at low altitude. Distance estimation is affected by the interaction of the object density and height.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2009. / Härtill 4 uppsatser.

No description available.

The auroral density cavity constitutes the boundary between the cold, dense ionospheric plasma and the hot, tenuous plasma sheet plasma. The auroral density cavity is characterized by low electron density and particle populations modified by parallel electric fields. Inside the cavity the electron densities can be as much as a factor 100-1000 lower than same altitude outside the cavity.The Cluster mission's wide range of instruments, long lifetime and ability to make multi-spacecraft observations has been very successful. Over its 15 year lifespan, the Cluster satellites have gathered data on auroral density cavities over a large altitude range and throughout an entire solar cycle, providing a vast data material.The extent of the density cavity and acceleration region is large compared to the typical altitude coverage of a satellite crossing the cavity. This makes it difficult to produce a comprehensive altitude/density profile from a single crossing. In order to facilitate comparisons between data from different events, we introduce a new reference frame, pseudo altitude. Pseudo altitude describes the satellites' position relative to the acceleration region, as opposed to relative to the Earth. This pseudo altitude is constructed by dividing the parallel potential drop below the satellite with the total parallel potential drop. A pseudo altitude of 0 corresponds to the bottom of the acceleration region and a pseudo altitude of 1 to the top of the acceleration region. As expected, the pseudo altitude increases with altitude. The electron density exhibits an anti-correlation with the pseudo altitude, the density becomes lower close to the upper edge of the acceleration region. The upper edge of the acceleration region is located between a geocentric altitude of 4.375 and 5.625 RE. Above the upper edge of the acceleration region, the electron density continues to decrease for the entire range of the study, 3.0-6.5 RE. This is much further than the geocentric altitude range of 2-3 RE which is suggested by previous models. We can conclude that the auroral density cavity is not confined by the auroral acceleration region, as suggested by previous models, and may extend all the way to the plasma sheet. / <p>QC 20151102</p>

This study aims to investigate the stable isotopic characteristics of meteoric and ground waters, and to obtain spring flow rates in the Coronet Peak Skifield, Queenstown. Spring flows were gathered during the winters of 2008 and 2009, whilst water samples were collected from precipitation, springs, reservoirs and groundwater during July, August and September 2009. The spring flows were examined and the water samples were analysed for δD and δ¹⁸O values using the CF-IRMS at the University of Canterbury. A database has been gathered from all natural water sources to give a local meteoric water line (LMWL) for the area that fits clearly with the global meteoric water line. The LMWL has an R2 value of 0.97 and the equation is δD = 8 δ¹⁸O +10. An understanding of evaporation as it occurs in the water storage reservoirs of the mountain has also been obtained, giving rise to a local evaporation line. The stable isotope ratios of hydrogen and oxygen within precipitation have been used extensively to characterise the hydrogeology with emphasis on altitude effects, storm duration and variations in storm track trajectories. Of these three phenomena, it is the trajectory of the storm track that is best shown to affect the composition of precipitation in this area. The air masses advancing on the study area from the north being more depleted in their isotopic signatures, with approximate δD and δ¹⁸O values of –130‰ and -16‰. The air masses approaching from a southerly direction are more positive in comparison, having approximate δD and δ¹⁸O values of –65‰ and -9‰. The altitude effect in precipitation on the Skifield has led to an altitude gradient being found: for every 100-metre increase in elevation, δ¹⁸O decreases by 0.71‰. However there were some inconsistencies. The influence on precipitation from storm duration is also inconsistent in this area. The R2 values range from 0.14 to 0.99, but this method does not take into account the position of the individual samples. Some samples did not plot in the expected order that is governed by a decrease in stable isotopic ratios with storm duration. The stable isotopic compositions within meteoric waters can be used as tracers of water sources. The isotope date of the springs also infers an altitude effect. The springs gave an altitude gradient of a decrease –0.43‰ with each 100-metre increase in elevation. This indicates that precipitation is the main influence on the stable isotopic composition of the springs in this area. However, data shows differences between the current precipitation and the groundwater compositions, indicating that present precipitation is not flowing from the springs, past precipitation is. The stable isotopic compositions of the springs have also been correlated with groundwater isotope data and suggest the sources of the springs are groundwater dominated. Although some springs compositions indicate an influence by current precipitation. This is shown by a negative stable isotopic trend in the precipitation sampled in August, corresponding with a relatively negative stable isotopic composition in some springs during this time period. Monitoring of spring flows on Coronet Peak have led to an average winter flow rate being established of 26.5 litres per second. Spring flow rates range from 0.25 – 6 litres per second. This monitoring has indicated the springs of the greatest yield that are not already being utilised on the Skifield. It is these springs that should be further investigated as to whether they would provide a sustainable source of water on the mountain. This locally derived water would then be utilised for the purposes of artificial snowmaking and other activities and amenities that are currently operated by NZ Ski on Coronet Peak.

Use of an inflatable/rigidizable wing is explored for Mars airplane designs. The BIG BLUE (Baseline Inflatable-wing Glider Balloon Launched Unmanned airplane Experiment) project was developed at the University of Kentucky, with an objective to demonstrate feasibility of this technology with a flight-test of an high-altitude glider with inflatable/rigidizable wings. The focus of this thesis research was to design and analyze the wing for this project. The wings are stowed in the fuselage, inflate during ascent, and rigidize with exposure to UV light. The design of wings was evaluated by using aerodynamic and finite element software and wind tunnel testing. The profile is chosen based upon aerodynamic results and consideration of manufacturability of the inflatable wing structures. Flow over prototypes of inflatable/rigidizable and ideal shaped wings were also examined in the wind tunnel. Flow visualization, lift and drag measurements, and wake survey testing methods were performed. Results from the wind tunnel testing are presented along with suggestions in improving the inflatable/rigidizable wings aerodynamic efficiency and use on a low Reynolds number platform. In addition, high altitude wing deployment tests and low altitude flight tests of the inflatable/rigidizable wing were conducted.

Den här studien är en uppföljning av föryngringsresultatet efter maskinell sådd av contorta ( Pinus contorta Dougl. var. latifolia Engelm.) i Härjedalen. Efter tre växtsäsonger uppgick det totala antalet såddplantor till 3 700 per ha och antalet huvudplantor uppgick till 1 800 per ha. Andelen nollytor uppgick till 2 %. Det var ingen skillnad i föryngringsresultat mellan låg och hög altitud. Generellt gav maskinell sådd av contorta ett tillfredsställande föryngringsresultat. På mindre bördig mark var såväl det totala antalet såddplantor som antalet huvudplantor högre än på bördigare mark. / Mechanical regeneration by seeding of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) in the province of Härjedalen in Sweden was studied. After three growing seasons the total number of seedlings were 3 700 per ha and the number of main seedlings were 1 800 per ha. 2% of the sample plots had no plants within 3 m. No difference could be found between objects on high and low altitudes. In general mechanical seeding gave satisfactory regeneration. On low fertile soils the total number of seedlings as well as the future main seedlings was higher than on more fertile soils.

One of the key points to reduce the world dependence on fossil fuels and the emissions of greenhouse gases is the use of renewable energy sources. Recent studies showed that wind energy is a significant source of renewable energy which is capable to meet the global energy demands. However, such energy cannot be harvested by today’s technology, based on wind towers, which has nearly reached its economical and technological limits. The major part of the atmospheric wind is inaccessible to the conventional wind turbines and wind at higher altitude is the major source of potential energy which has not been fully exploited yet. The thesis paper has presented a study aimed to devise a new class of wind generator based on extracting energy from high altitude wind.A brief theoretical study is presented to evaluate the potential of an innovative high altitude wind power technology which exploits a tethered airfoil to extract energy from wind at higher altitude. Among the various concepts proposed over last few decades, a kite power system with a single kite is selected for the design purpose.The designed ground station is an improvisation over existing prototypes with an energy reservoir for having a continuous power output. A flywheel is used as the energy storage system which stores the extra energy during traction phases and supplies it during recovery phases and thus giving a continuous power generation regardless of the kite’s motion and keeping the rotor speed in a permissible range defined by the design constraints. Manufacturability of the structure, availability of the components, safety and maintenance criteria have been taken into account while building the ground station CAD model.A dynamic simulation model is developed to investigate the power transmission system of the kite power unit which reflects the torque, speed and power behaviour of the modelled ground station driveline. The functionality of the designed model for the selected concept is tested with several numerical and graphical examples.