La nano-structuration de matériaux semiconducteurs à grand gap à base de GaN fait l'objet d'un très grand intérêt de par son potentiel pour l'élaboration de composants optoélectroniques innovants émettant dans la gamme spectrale de l’ultraviolet. Le contrôle de la croissance à l'échelle nanométrique doit être ainsi démontré. L'épitaxie sélective ou SAG (Selective Area Growth) étendue au domaine nanométrique (NSAG pour NanoSAG) est un excellent choix pour l'élaboration de nanostructures de semiconducteur. Cette technique consiste en la croissance localisée du matériau sur un substrat partiellement recouvert d'un masque en diélectrique. La NSAG permet l'élaboration d'hétéro-structures en fort désaccord de maille grâce aux mécanismes singuliers de relaxation des contraintes à l'intérieur des nanostructures qui réduisent considérablement la densité de dislocations créées. La première partie de la thèse porte sur la mise en œuvre de l'épitaxie sélective du GaN sur pseudo-substrat de GaN à l'échelle micrométrique puis nanométrique par la technique d'épitaxie en phase vapeur aux organométalliques. Dans un deuxième temps, la NSAG est utilisée pour l'épitaxie de nanostructures de GaN sur substrats de SiC-6H et pseudo-substrat d'AlN. L'influence des conditions de croissance et des motifs définis dans le masque sur la forme des nanostructures est étudiée par la microscopie électronique à balayage et la microscopie à force atomique. Finallement la microscopie électronique en transmission et la nano-diffraction des rayons X par rayonnement synchrotron sont utilisées pour l'analyse structurale approfondie des nanostructures / GaN based wide bandgap semiconductor materials nanostructures have a tremendous potential of applications for innovative optoelectronic devices emitting in the UV region (190-340nm). Thus, the feasibility of the nanoscale growth must be demonstrated. Selective Area Growth (SAG) extended to the nanoscale (NSAG for NanoSAG) is an excellent approach for growing semiconductor nanostructures. This technique is based on localized growth of the material on substrates partially covered by dielectric masks. NSAG technique allows the growth of highly mismatched materials because the density of dislocation is reduced thanks to singular stress relief mechanisms that occur at nanoscale. The first part of the work consists in the implementation of the GaN selective epitaxy on GaN template substrate at the micrometer and nanometer scales by Metal Organic Vapor Phase Epitaxy. In a second time, the NSAG technique is used for the growth of GaN nanostructures on SiC-6H substrate and AlN template substrate. The influence of the growth conditions and the mask pattern on the nanostructures shape is demonstrated using Scattering Electronic Microscopy and Atomic Force Microscopy. Fine structural analysis of the nanostructures is finally investigated using advanced characterization tools such as Transmission Electron Microscopy and X-rays nano-diffraction by synchrotron radiation

This master's thesis describes Grand Central Dispatch technology. It is technology for parallel computing and task processing. It also describes history and techniques of parallel computing. As an example stand simple HTTP server with 4 methods of request parallel processing. Server is connected to AVG antivirus software and check each request for viruses.

The aim of this work will be to analyze the final phase of the Cold War. The 1980s was an extraordinary period for anyone interested in the history of the Cold War. Not only did the Cold War end or bring their final stages, but even before the 1980s, with a similarly almost unprecedented limitation of tensions between the two major players in the East-West conflict, the US and the Soviet Union. In my diploma thesis I will analyze the basic premises of the "triumphalistic" and "revisionist" schools of the Cold War. Diploma thesis from the concept of "national security approach". The conclusion of the work is that Ronal Reagan has had an impact on the end of the study wars and thus does not apply the conclusions of the "revisionist" school. However, there are no conclusions that apply only to cases where only diplomatic and compromise measures are involved.

No description available.

The main purpose of this essay is to examine the effect of budget transparency on petty and grand corruption. To highlight the differences between the two measurements of corruption, and their relationship with budget transparency, the study will also make a comparison to a broader measurement of corruption. The research question for this essay is: Does budget transparency affect grand and petty corruption differently? Regression analysis is used to examine the relationship between budget transparency and corruption. The regressions are based on cross-section data from close to a hundred countries from all regions of the world. It is widely recognised that corruption is a difficult concept to measure. However, the study does find some interesting results. The initial bivariate regressions indicate that budget transparency is associated with lower levels of both petty and grand corruption, these are however not statistically significant. When controlling for democracy the coefficient for budget transparency is statistically significant for grand corruption, but not for petty corruption. The results also indicate that budget transparency generally has a stronger negative effect on grand corruption compared to petty corruption.

Gully erosion has been damaging archaeological sites in Grand Canyon during the last several decades, and there is a need to protect these features through mitigation, monitoring, and better geomorphic understanding. The purpose of this study was to assess the effectiveness of erosion-control structures , determine the accuracy and utility of aerial photogrammetry for monitoring gullies , and understand the geomorphology of the erosion . We performed total-station surveys and other data collection during February and October , 2002, at nine study sites in eastern and western Grand Canyon. Erosion-control structures are more prone to be damaged by flow when they are placed in reaches of very high local gradient. Treatments are generally successful in slowing erosion or causing deposition of sediment, but damaged erosion-control structures were shown to be less effective than intact structures, and actually increase local erosion in cases. Aerial photogrammetry was performed on four eroding archaeological sites in western Grand Canyon in March and October 2002 in order to assess the accuracy and change-detection utility of this tool. Accuracy was assessed on several different levels by comparing photogrammetry data to ground-survey data, and mean absolute vertical error ranged from 6-10 cm. Error of manual photogrammetry digital terrain models (DTMs) increased with topographic ruggedness and decreased with greater photogrammetric point density. Mean error reached a minimum of 5 cm for March and 6.5 cm for October when the ratio of point density to topographic ruggedness was ~40. Ground surveys and repeat photography indicated that two study gullies eroded or aggraded during the study period by 10-20 cm, but these changes were mostly undetected in the photogrammetry DTMs. Repeat ground surveys showed that gullies erode most at knickpoints and in steep reaches , and that new knickpoints tend to form in relatively steep reaches of a given channel. An area-slope erosion threshold was identified for the study sites and applied in a GIS-based model at four sites to show areas that exceed the threshold and are sensitive to gully erosion . Overall results show an upcatchment control of gully erosion and suggest that baselevel changes due to Glen Canyon Dam operation are subordinate controls.

Tectonics and drainage evolution are controlling overall landscape incision in eastern Grand Canyon. Superimposed on downcutting are dynamic responses of hillslopes, tributary streams, and the Colorado River to glacial-interglacial climate cycles. Five tributary stream fill terraces have been identified, and luminescence dating indicates aggradation was occurring 50- 34 ka {S3), 12-7 ka (S2), and 5-3.5 ka (S1). Seven Colorado River fill terraces have been identified, and luminescence and U-series dating indicate deposition was occurring 343-322 ka (M5), 151-118 ka (M4), and 71-64 ka (M3). Aggradation by the Colorado River in eastern Grand Canyon begins during glacial advances and continues into the subsequent climate reversals. It appears to be driven by increases in sediment yield associated with glacial advances in headwater areas and glacial conditions elsewhere in the Colorado River drainage basin. Local catchments have buffered responses to climate change, with stream aggradation being driven by changes in sediment yield and hydrology of hillslopes. Tributary stream aggradation during full-glacial conditions (S3) is caused by a decrease in precipitation intensity and an increase in bedrock weathering. Aggradation during glacial-interglacial transitions (S2) and interglacial conditions (S1) is the result of increased erosion of older surficial deposits and decreases in vegetation cover. In the context of the current working model for the response of drylands to climate change, eastern Grand Canyon is distinct in that significant tributary stream aggradation occurs during full-glacial climate conditions and throughout the tributary drainage networks. This suggests that landscape response to climate change in semiarid environments may be slightly different than in arid settings. Bedrock incision by the Colorado River has been occurring at a rate of 0.13 mm/yr over middle-late Quaternary time. The technique used to make this calculation involves comparing snapshots of the river at analogous positions within its aggradation-incision cycles. The most accurate calculation results from tracing the elevation of the valley bottom through time. This method requires robust age control, but is advantageous because true bedrock incision is calculated and possible error associated with the use of short time intervals and thick fill deposits is eliminated.

No description available.

No description available.

No description available.