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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.
251

The hydrology of debris-covered glaciers

Fyffe, Catriona Louise January 2012 (has links)
Studies of glacier-hydrology have focused on clean Alpine glaciers, and recently ice sheet outlet glaciers, but there are few studies on debris-covered glaciers. It is known debris affects ablation rates, and that debris-covered glaciers evolve differently to their debris-free counterparts, but how the debris influences the hydrology is poorly understood. This thesis aims to understand the influence of the debris on the hydrological system and water balance of Miage Glacier, Western Italian Alps. The supraglacial hydrology was studied by modelling ablation using a distributed energy balance melt model, and measuring supraglacial stream discharges; the structure and evolution of the englacial and subglacial network was investigated using dye tracing and water chemistry monitoring; and the proglacial runoff was examined through detailed hydrograph analysis. Glacier velocity measurements were used to investigate the debris’ influence on the glacier dynamics. High ablation rates occurred on clean ice and beneath thin debris on the upper glacier, resulting in large supraglacial streams which led into an efficient drainage system. Glacier velocities had a greater magnitude and variability close to the upper glacier moulins. Thick debris on the lower glacier reduced ablation, and consequently the discharge of supraglacial streams and efficiency of the hydrological network. Despite locally inefficient subglacial drainage, glacier velocities on the lower glacier remained subdued, partly because the debris attenuated water inputs. This attenuation reduced the occurrence of high amplitude diurnal cycles in the proglacial runoff and confined them to particularly warm weather. Lag times from peak air temperature to peak runoff were long relative to comparable debris-free glaciers. Evaporation of rainfall from debris-surfaces was high, and dependant on the debris permeability, suggesting this is an important water balance component. Under climate warming, it is predicted the ablation of Miage Glacier will increase, but this may be negated given an increase in debris cover.
252

Provenance-based computing

Carata, Lucian January 2019 (has links)
Relying on computing systems that become increasingly complex is difficult: with many factors potentially affecting the result of a computation or its properties, understanding where problems appear and fixing them is a challenging proposition. Typically, the process of finding solutions is driven by trial and error or by experience-based insights. In this dissertation, I examine the idea of using provenance metadata (the set of elements that have contributed to the existence of a piece of data, together with their relationships) instead. I show that considering provenance a primitive of computation enables the exploration of system behaviour, targeting both retrospective analysis (root cause analysis, performance tuning) and hypothetical scenarios (what-if questions). In this context, provenance can be used as part of feedback loops, with a double purpose: building software that is able to adapt for meeting certain quality and performance targets (semi-automated tuning) and enabling human operators to exert high-level runtime control with limited previous knowledge of a system's internal architecture. My contributions towards this goal are threefold: providing low-level mechanisms for meaningful provenance collection considering OS-level resource multiplexing, proving that such provenance data can be used in inferences about application behaviour and generalising this to a set of primitives necessary for fine-grained provenance disclosure in a wider context. To derive such primitives in a bottom-up manner, I first present Resourceful, a framework that enables capturing OS-level measurements in the context of application activities. It is the contextualisation that allows tying the measurements to provenance in a meaningful way, and I look at a number of use-cases in understanding application performance. This also provides a good setup for evaluating the impact and overheads of fine-grained provenance collection. I then show that the collected data enables new ways of understanding performance variation by attributing it to specific components within a system. The resulting set of tools, Soroban, gives developers and operation engineers a principled way of examining the impact of various configuration, OS and virtualization parameters on application behaviour. Finally, I consider how this supports the idea that provenance should be disclosed at application level and discuss why such disclosure is necessary for enabling the use of collected metadata efficiently and at a granularity which is meaningful in relation to application semantics.
253

A Comparison between Vector Algorithm and CRSS Algorithms for Indoor Localization using Received Signal Strength

Obeidat, Huthaifa A.N., Dama, Yousef A.S., Abd-Alhameed, Raed A., Hu, Yim Fun, Qahwaji, Rami S.R., Noras, James M., Jones, Steven M.R. 03 1900 (has links)
no / A comparison is presented between two indoor localization algorithms using received signal strength, namely the vector algorithm and the Comparative Received Signal Strength (CRSS) algorithm. Signal values were obtained using ray tracing software and processed with MATLAB to ascertain the effects on localization accuracy of radio map resolution, number of access points and operating frequency. The vector algorithm outperforms the CRSS algorithm, which suffers from ambiguity, although that can be reduced by using more access points and a higher operating frequency. Ambiguity is worsened by the addition of more reference points. The vector algorithm performance is enhanced by adding more access points and reference points while it degrades with increasing frequency provided that the statistical mean of error increased to about 60 cm for most studied cases. / Unable to contact publisher. Contact webform only works for members - no email addresses. Raed said he would try and get contact details - email 14th March 2016 / The full text is unavailable. The publisher is unable to be contacted.
254

Etude des propriétés optiques et radiatives des cirrus par télédetection active : apport des observations polarisées

Noel, Vincent 09 October 2002 (has links) (PDF)
Les nuages sont une incertitude majeure pour l'étude du climat. Parmi eux, les cirrus en sont des modulateurs essentiels, par leur effet de serre élevé et leur effet d'albedo. Cependant, leur haute altitude et leur composition atypique compliquent leur étude. Les nombreuses campagnes de mesure des vingt dernières années ont montré la complexité de leur composition et la forte variabilité de leurs propriétés microphysiques : taille, forme et orientation des cristaux qui les composent. Ce manque de connaissance entraîne de graves lacunes dans leur modélisation, et une incohérence certaine dans les résultats des simulations climatiques à grande échelle. Les avantages des instruments de télédétection pourraient conduire à de nouvelles méthodes d'étude des cristaux dans les cirrus. Cette thèse analyse l'apport potentiel de mesures spatiales pour caractériser les nuages de glace, en prévision de l'Aqua-Train, une formation de satellites pour l'étude de l'atmosphère. La diffusion lumineuse dans les cristaux a été modélisée en prenant en compte leurs multiples propriétés, menant à plusieurs techniques de restitution de la microphysique des cirrus par des mesures de l'état de polarisation de la lumière par télédétection active et passive. Ces techniques ont été appliquées à des données sol pour évaluer leur pertinence, et leur application potentielle à des mesures spatiales envisagée. Combinées dans un cadre théorique homogène, elles ont conduit à la restitution cohérente des propriétés des cristaux dans les cirrus : orientation spatiale et angle maximum de déviation à partir de mesures polarisées (lidar à balayage, radiomètre) ; facteur de forme par observations lidar polarisées ; taille par synergie multi-instruments (lidar, radiomètre IR). La restitution de ces paramètres à l échelle globale conduira à une meilleure compréhension des propriétés radiatives des cirrus, et à une meilleure interprétation de leur importance dans le contexte du bilan radiatif terrestre.
255

Efficiency of LTTng as a Kernel and Userspace Tracer on Multicore Environment

Guha Anjoy, Romik, Chakraborty, Soumya Kanti January 2010 (has links)
<p><em>With the advent of huge multicore processors, complex hardware, intermingled networks and huge disk storage capabilities the programs that are used in the system and the code which is written to control them are increasingly getting large and often much complicated. There is increase in need of a framework which tracks issues, debugs the program, helps to analyze the reason behind degradation of system and program performance. Another big concern for deploying such a framework in complex systems is to the footprint of the framework upon the setup. LTTng project aims to provide such an effective tracing and debugging toolset for Linux systems. Our work is to measure the effectiveness of LTTng in a Multicore Environment and evaluate its affect on the system and program performance. We incorporate Control and Data Flow analysis of the system and the binaries of LTTng to reach for a conclusion.</em></p>
256

Effectiveness of Tracing in a Multicore Environment

Sivakumar, Narendran, Sundar Rajan, Sriram January 2010 (has links)
<p>Debugging in real time is imperative for telecommunication networks with their ever increasing size and complexity. In event of an error or an unexpected occurrence of event, debugging the complex systems that controls these networks becomes an insurmountable task. With the help of tracing, it is possible to capture the snapshot of a system at any given point of time. Tracing, in essence, captures the state of the system along with the programs currently running on the system. LTTng is one such tool developed to perform tracing in both kernel space and user space of an application. In this thesis, we evaluate the effectiveness of LTTng and its impact on the performance on the applications traced by it. As part of this thesis we have formulated a comprehensive load matrix to simulate varying load demands in a telecommunication network. We have also devised a detailed experimental methodology which encompasses a collection of test suites used to determine the efficiency of various LTTng trace primitives. We were also able to prove that, in our experiments, LTTng’s kernel tracing is more efficient than User Space Tracing and LTTng’s User Space Tracing has a performance impact of around three to five percent.</p>
257

Image Chunking: Defining Spatial Building Blocks for Scene Analysis

Mahoney, James V. 01 August 1987 (has links)
Rapid judgments about the properties and spatial relations of objects are the crux of visually guided interaction with the world. Vision begins, however, with essentially pointwise representations of the scene, such as arrays of pixels or small edge fragments. For adequate time-performance in recognition, manipulation, navigation, and reasoning, the processes that extract meaningful entities from the pointwise representations must exploit parallelism. This report develops a framework for the fast extraction of scene entities, based on a simple, local model of parallel computation.sAn image chunk is a subset of an image that can act as a unit in the course of spatial analysis. A parallel preprocessing stage constructs a variety of simple chunks uniformly over the visual array. On the basis of these chunks, subsequent serial processes locate relevant scene components and assemble detailed descriptions of them rapidly. This thesis defines image chunks that facilitate the most potentially time-consuming operations of spatial analysis---boundary tracing, area coloring, and the selection of locations at which to apply detailed analysis. Fast parallel processes for computing these chunks from images, and chunk-based formulations of indexing, tracing, and coloring, are presented. These processes have been simulated and evaluated on the lisp machine and the connection machine.
258

Norm consolidation in the European Union: : The EU14 - Austria crisis in 2000

Ulfgard, Rebecka January 2005 (has links)
In late January 2000, the EU14 initiated a protest co-ordinated by the Portuguese EU Presidency against the coalition between Wolfgang Schüssel’s ÖVP and Jörg Haider’s right-wing extremist/populist FPÖ, accused of violating EU fundamental values expressed in Article 6(1) TEU. When the government took office on 4 February diplomatic ‘sanctions’ were launched. During spring, the EU14’s wider interpretations of the sanctions, clumsy handling of Austrian countermeasures and deficient strategy on dismantling the protest contributed to crisis escalation. The solution was the appointment of so-called ‘wise men’ to evaluate the political nature of the FPÖ and the effects of the EU14’s ‘diplomatic whipping’ on government policies. Shortly after the Wise Men Report was published the EU14 lifted the ‘sanctions’ unconditionally, but insistent question marks remained. At the informal European Council meeting in Biarritz 13-14 October, the EU14 and the Austrian government agreed on amendments to the trigger mechanisms for the ‘sanctions article’, Article 7 TEU, incorporated in the Nice Treaty from December 2000. This study argues that the EU14’s interests and preferences concerning Article 6(1) TEU, coupled with a consensus-reflex and imagined and ‘real’ time pressure manifested in groupthink and ‘tele groupthink’, a concept including telephone diplomacy, affected the norm during its ‘journey’ through five stages: warning, implementation, crisis escalation, crisis de-escalation, and consequences. A central claim is that both self-interested behaviour and ideational/normative motives guided the EU14, but in a ‘more or less’ way. Mutually complementary arguments from both the rationalist and constructivist paradigms prove compelling in investigating this particularly complex and multi-faceted case. This study concludes that the EU14-Austria crisis resulted not in a rupture in the integration process, but in consolidation of EU fundamental values expressed in Article 6(1) TEU. Thanks to mixed experiences with the EU14’s ‘diplomatic whipping’ of the FPÖ-ÖVP government, the Union took another step towards tighter monitoring of Member States’ compliance with its constituent values. This step was reflected in amendments to Article 7 TEU. The EU14-Austria crisis, as here presented, illustrates the claim that Union-wide crises can have a positive effect on its normative foundation.
259

Neural Crosstalk Between Sympathetic Nervous System and Sensory Circuits to Brown Adipose Tissue

Liu, Yang 08 April 2013 (has links)
Brown adipose tissue (BAT) is a critical organ for non-shivering thermogenesis, which is under control of both sympathetic and sensory neural innervation. We utilized both a retrograde sympathetic nerve tract tracer pseudorabies virus and an anterograde sensory tract tracer the H129 strain of herpes simplex virus-1 to locate individual neurons across the neuroaxis that are part of the SNS outflow from brain to interscapular BAT and are part of the sensory input to the brain. We found specific neuronal phenotype of the double-infected neurons distributed from the hindbrain to the forebrain with highest densities in several discrete brain regions: the paraventricular hypothalamus (PVH), lateral hypothalamus (LHA), parabrachial nucleus (PB) and raphe pallidus (RPa). The neuroanatomical reality of the SNS-sensory feedback loops suggests coordinated control of BAT thermogenesis at several sites and indicates plasticity of SNS-sensory crosstalk.
260

A Security Analysis of Some Physical Content Distribution Systems

Jiayuan, Sui January 2008 (has links)
Content distribution systems are essentially content protection systems that protect premium multimedia content from being illegally distributed. Physical content distribution systems form a subset of content distribution systems with which the content is distributed via physical media such as CDs, Blu-ray discs, etc. This thesis studies physical content distribution systems. Specifically, we concentrate our study on the design and analysis of three key components of the system: broadcast encryption for stateless receivers, mutual authentication with key agreement, and traitor tracing. The context in which we study these components is the Advanced Access Content System (AACS). We identify weaknesses present in AACS, and we also propose improvements to make the original system more secure, flexible and efficient.

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