Thesis (M. Sc.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 110-115).

La taille de la zone plastique en pointe de fissure dans un matériau est directement liée au facteur d’intensité de contrainte pour une configuration donnée. Cette étude utilise la technique d’indentation avec une très faible charge afin d’étudier la taille de la zone plastique cyclique et monotone au voisinage de la fissure. La zone plastique est caractérisée par la relation entre la dureté, le module réduit, le travail élastique, le travail plastique, l’indice de plasticité et la distance par rapport à la pointe de fissure. Les essais sont menés sur une éprouvette CT pour un alliage d’aluminium 2024T351. Dans une étude complémentaire, le contour des zones plastiques en fond de fissure en mode mixte, le rayon minimum de zone plastique (MPZR) et la direction de la fissure initiale pour l’alliage d’aluminium 2024T351 sur un “Compact Tension spécimen” est déterminé en utilisant le logiciel Matlab. Nous avons calculé la forme, la taille de la zone plastique au fond de fissure, le rayon minimum de la zone plastique par rapport à l’angle de chargement et le facteur d’intensité de contrainte en utilisant le critère de Von Mises. L’étude est effectuée pour les divers angles de chargement. Nous avons constaté que le chargement en mode mixte (13 = 600) est le plus néfaste pour le matériau. / The plastic zone size associated with a propagating crack in a material is directly related to the stress intensity factor for a given configuration. This work utilizes the ultra-low-load indentation techniques to study the cyclic and monotonic plastic zone size at the fatigue crack tip based on the relationship between the hardness, elastic work, plastic work, plasticity index and the distance from the crack tip. The study is conducted essentially on the aluminium alloy 2024T351. In a second part of this work, we study the contour of mixed mode crack-tip plastic zones, the minimum plastic zone radius (MPZR) and the direction of initial crack for the aluminium alloy 2024T351 in a Compact tension specimen by using Matlab software. We have computed the shape, size of plastic zone at crack-tip and the minimum plastic zone radius with respect to the loading angle and stress intensity factor in linear elastic fracture mechanics for plane strain condition according to Von Mises yield criteria, the study is conducted for various loading angle. We found that the mixed mode loading (F36O°) can lead to earlier material fracture earlier than any other biaxial loading.

Les teneurs en pesticides mesurées dans les eaux de drainage agricole peuvent atteindre 10 µg/L voire 395 µg/L. En Lorraine, des Zones Tampons Végétalisées Agricoles (ZTVA) ont été installées en sortie de drains agricoles afin de limiter le transfert de ces eaux de drainage vers la rivière. L’objectif de ce travail était d’évaluer l’influence de l’hydraulique sur l’épuration des pesticides et métabolites en phases dissoute et particulaire des eaux de drainage, en discriminant les processus associés. Pour cela, une approche multi-échelle intégrant des expérimentations au laboratoire en batch et en bacs pilotes ainsi qu’un monitoring pluriannuel de deux ZTVA sur le terrain (un fossé et une mare) a été mise en place. Les expériences de traçages in-situ ont montré que quel que soit le débit, la ZTVA peut être divisée en différentes zones hydrauliques : un chenal principal et des zones isolées, qui se comportent différemment vis-à-vis de l’épuration. Les efficacités d’épuration dans les deux ZTVA varient de (i) -1176% à 96% pour les pesticides dissous, (ii) -20% à 3% pour les métabolites (chloroacétanilides) à l’état dissous, et (iii) -580% à 79% pour les pesticides sous forme particulaire. L’adsorption sur les sédiments permet l’épuration des pesticides à l’état dissous dont le coefficient d’adsorption (Koc) varie de 364 à 1424 L/g (entre 7 et 65% d’épuration), et est favorisé au sein des zones isolées. Cependant, ce processus est réversible et la désorption peut expliquer les efficacités négatives mesurées sur le terrain. Par ailleurs, les pesticides plus hydrophiles (Koc varie de 54 à 401 L/g) et les métabolites (Koc varie de 0 à 0.77 L/g) sont peu épurés (entre -20 et 8% d’épuration). Enfin, les pesticides entrant dans la ZTVA sous forme particulaire sont épurés via la sédimentation des matières en suspension, plus importante dans les zones isolées que le chenal principal. Ce processus est réversible, pouvant conduire à la resuspension des sédiments. Par ailleurs, les débits entrants vont fluctuer au cours de l’année, pouvant entrainer une variation de l’épuration des pesticides. En effet, les études en batch et en bacs pilotes ont permis de souligner l’influence de l’hydrodynamique (débits, etc) sur l’épuration des pesticides à l’état dissous. Ces ZTVA jouent donc un rôle de puits (adsorption, sédimentation) et de source (désorption, resuspension) vis-à-vis de certains pesticides à l’état dissous ou particulaire, en lien avec l’hydrodynamique de la ZTVA / Pesticides amounts measured in agricultural drained water can reach 10 µg/L up to 395 µg/L. In Lorraine, Constructed Wetlands (CW) were set up between drained fields and the river to limit pesticide release. The aim of this study was to evaluate the influence of hydraulic on the mitigation of pesticides and metabolites in both dissolved and particulate phases of drained water, by discriminating associated processes. To do so, a multi-scale approach was performed by integrating both laboratory experiments, such as batch and dynamic conditions in pilots, and a plurennial monitoring of two different ZTVA (ditch and pond). In-situ tracing experiments highlighted that the volume of CW was not homogeneous, independently of the flow rate. CW are divided in two hydraulic zones: a main channel and isolated areas. Moreover, these two zones behave differently regarding pesticides mitigation. Annual mitigation efficiency in both of the CW studied, vary between (i) -1176 % and 96 % for dissolved pesticides, (ii) -20 % and 3 % for dissolved metabolites (chloroacetanilides), and from (iii) -580 % to 79 % for particulate pesticides. Adsorption on sediments allows the mitigation of dissolved pesticides whose adsorption coefficient (Koc) varied from 364 to 1424 L/g (mitigation ranging from 7 to 65 %), and occurred mainly in isolated areas. However, this process is reversible and desorption can explain negative efficiency measured on the field. Additionally, hydrophilic pesticides (Koc between 54 and 401 L/g) and metabolites (Koc between 0 and 0.77 L/g) are few or not mitigated (mitigation ranging from -20 and 8 %). Finally, pesticides entering CW under particulate phase are mitigated through sedimentation of total suspended solids, higher in isolated areas than in main channel. This process is also reversible, leading to sediments resuspension. Otherwise, inlet flow rates vary throughout the year, which could allow a variation of pesticide mitigation. Indeed, batch and pilots studies highlighted the influence of hydrodynamic (flow rate, etc) on mitigation of dissolved pesticides. CW act as a sink (adsorption and sedimentation) and a source (desorption and resuspension) towards specific dissolved or particulate pesticides and related to hydrodynamic of CW

Drivers' mistakes in making immediate decision facing yellow signal interval to stop or go through the intersection is one of main factors contributing to intersection's safety. Incorrect decision might lead to a red light running and a right-angle Collison when passing through the intersection or a rear-end collision when failing to stop safely.Improperly timed traffic signal intervals result in the inability of the drivers to make the right decision and can place them in the dilemma zone. Advance warning systems (AWS) have been used to provide information about the downstream traffic signal change prior to approaching the intersection. On the other hand, advance warning systems increase drivers approach speed according to the literature. However, effect of AWS on dilemma zone has not been studied before. The goal of this thesis is to minimize the number of vehicles caught in dilemma zone by determining more precise boundaries for dilemma zone and to reduce the number of red light violations by predicting the red light runners before arriving to the intersection. Here, dilemma zone boundaries at the presence of AWS has been reexamined with the aid of a large dataset (more than 1870 hours of data for two different intersections). Upper dilemma zone boundaries found to be higher for the intersections with AWS. This is due to vehicles' increasing the speed at the flashing yellow sings to escape the dilemma zone.Moreover, an algorithm for predicting red light runners and distinguishing them from right turners is presented. / Master of Science

published_or_final_version / abstract / Urban Planning and Environmental Management / Master / Master of Philosophy

<p>Bakgrund: Kaliningrad är den mest västliga ryska regionen som ligger mellan två EU-länder. I takt med den höjda levnadsstandarden och på grund av det gynnsamma geografiska läget ökar svenska företagens intresse för regionen. För att öppna upp regionens ekonomi för direkta investeringar från utlandet introducerades Special Economic Zone. Syftet med SEZ-Kaliningrad var att kompensera regionen för det isolerade läget genom tull- och skattelättnader för varor som tillverkas där. SEZ-insatsen i Kaliningrad har attraherat en del direkta investeringar, men resultaten har hittils inte varit speciellt imponerande.</p><p>Syfte: Syftet med denna uppsats är att genomföra en studie av de skandinaviska företagens erfarenheter av SEZ-Kaliningrad. I samband med detta vill författaren även undersöka hur representanter från de lokala myndigheterna, som arbetar med SEZ-frågor, upplever SEZ.</p><p>Teori: Inom uppsatsens teoretiska ramverk diskuteras de viktiga anledningarna för företagens investeringsbeslut och samband mellan statlig politik, marknadens ofullständighet och direkta investeringar i utlandet. Vidare diskuteras begreppen enklav och Special Economic Zone. Avslutningsvis framställs några kriterier för en framgångsrik Special Economic Zone.</p><p>Metod: Uppsatsens undersökning genomfördes med hjälp av den kvantitativa metoden. Svaren på enkät från sex skandinaviska bolag, som är etablerade i Kaliningrad och använder sig av SEZ-villkor, analyserades. Även två representanter från lokala myndigheter, som jobbar med SEZ-frågor, deltog i undersökningen. Resultaten av undersökningen presenterades i löpande text och illustrerades med diagram.</p><p>Analys: Resultatet av den genomförda undersökningen visar att det finns skillnader mellan de lokala myndigheternas uppfattning om hur effektivt Special Economic Zone i Kaliningrad är och de skandinaviska företagens erfarenhet av den. För att öka SEZ-åtgärdernas effektivitet krävs det större intresset från de lokala myndigheternas sida i investerarnas problem. Det krävs även djupare förståelse och högre grad av samarbete mellan parterna för att förbättra den befintliga situationen.</p><p>Nyckelord: Direkta investeringar i utlandet, Special Economic Zone, Kaliningrad</p> / <p>Background: Kaliningrad is the western Russian city situated between two EU countries. Due to the higher living standard and the favourable geographical position the interest from the Swedish companies in the region is growing. In order to open the region’s economy to direct investments, the Special Economic Zone was introduced in the region. The purpose with the SEZ-Kaliningrad was to compensate the region for its isolation with customs and tax reductions on goods manufactured there. The SEZ in Kaliningrad has drawn a number of direct investments, but the results have not been very impressive so far.</p><p>Purpose: The purpose of this thesis is to study the Scandinavian companies’ experience of the SEZ-Kaliningrad. In connection with this the author also wants to study how the representatives from the local authorities, who work with the SEZ matters, experience the SEZ.</p><p>Theory: Within the thesis’ theoretical framework I discuss the important grounds for the companies’ investment decisions and the relation between state policy, the market’s deficiency and the direct investments abroad. Furthermore, enclave and Special Economic Zone concepts are discussed. In conclusion, a number of criteria for a successful Special Economic Zone are presented.</p><p>Method: The survey is carried out with the help of the quantitative methodology. The answers from six Scandinavian companies, which are established in Kaliningrad and implement SEZ conditions, were analyzed. Besides that, two representatives from the local authorities, who work with the SEZ matters, took part in the survey. The results of the survey were presented in the text and illustrated with diagrams.</p><p>Analysis: The results from the survey show that there are differences between the local authorities’ understanding of the efficiency of the Special Economic Zone in Kaliningrad and the Scandinavian companies’ experience of it. To make the SEZ measures more effective a greater interest is needed from the local authorities in the investment companies’ problems. There is even a need of a better understanding and a higher level of cooperation between the parties to improve the present situation.</p><p>Keywords: Foreign Direct Investments, Special Economic Zone, Kaliningrad.</p>

No description available.

The Pampean flat slab subduction in west-central Argentina (latitude 30-33S) and the steeply dipping Northern Costa Rica subduction zone (latitude 9-11N) show significant along-trench variations in both the subducting and overriding plates. This dissertation contains the results of three seismological studies using broadband instruments conducted in these subduction zones, with the aim of understanding the structure of the lithosphere and the correlation between the variability observed in the downgoing and the overriding plates. In the Costa Rica region, by analyzing teleseismic receiver functions we investigate the variability in the hydration state of the subducting Cocos Plate and the nature of three distinct crustal terranes within the overriding Caribbean Plate: the Nicoya and Chorotega terranes that display an oceanic character, and the Mesquito Terrane, which is more compatible with continental crust.In the Pampean region of Argentina, we apply a regional-scale double-difference tomography algorithm to earthquake data recorded by the SIEMBRA (2007-2009) and ESP (2008-2010) broadband seismic networks to obtain high-resolution images of the South America lithosphere. We find that most of the upper mantle has seismic properties consistent with a depleted lherzolite or harzburgite, with two anomalous regions above the flat slab: a higher Vp/Vs ratio anomaly consistent with up to 10% hydration of mantle peridotite and a localized lower Vp/Vs ratio anomaly consistent with orthopyroxene enrichment. In addition, we study the geometry and brittle deformation of the subducting Nazca Plate by determining high-quality earthquake locations, slab contours, and focal mechanisms. Our results suggest that the subduction of the incoming Juan Fernandez Ridge controls the slab geometry and that ridge buoyancy and slab pull are key factors in the deformation of the slab. The spatial distribution of the slab seismicity suggests variability in the hydration state of the subducting Nazca Plate and/or in strain due to slab bending. These observations support the hypothesis that the along-trench variability in bathymetric features and hydration state of the incoming plate has profound effects in the subducting slab geometry and the upper plate structure in both flat and steeply dipping subduction zones.

No description available.

No description available.