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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.
151

Évolution des mouvements verticaux néogènes de la chaîne du Rif (Nord-Maroc) : apports d’une analyse structurale et thermochronologique / Neogene vertical movements evolution in the Rif chain (North-Morocco) : insights from structural and thermochronological analysis

Romagny, Adrien 17 December 2014 (has links)
La chaîne du Rif (Nord du Maroc) constitue, avec les Cordillères des Bétiques (Sud de l’Espagne), la terminaison occidentale de la ceinture alpine. C’est un secteur clé pour la compréhension des mouvements verticaux associés aux processus orogéniques. Jusqu’à présent, aucune étude n’a permis de contraindre les mouvements verticaux postérieurs au Miocène inférieur, malgré la présence de dépôts marins pliocènes surélevés. L’objectif de ce travail est d’apporter des arguments permettant de discuter des mécanismes géochronologiques et cinématiques impliqués dans les mouvements verticaux de la marge du Rif depuis le Néogène. Une comparaison des déplacements identifiés dans les zones internes, a pu être effectuée, avec ceux estimés dans le domaine des flyschs (Sud de l’accident de Jebha), grâce aux données AHe. Les corrélations entre mouvements verticaux et évolution du champ de déformation mettent en évidence le lien existant entre les périodes de mouvements verticaux majeurs et les phases d’extension radiale. 1-Les derniers stades d’exhumation des unités métamorphiques, depuis près de 12-10 km de profondeur, résultent d’un stade d’extension radiale affectant ces formations. Le domaine de collapse s’étend depuis le faciès Schiste Vert jusqu’au domaine fragile durant l’Aquitano-Burdigalien. Les mouvements extensifs sont limités aux parties superficielles de l’orogène tandis que les parties plus profondes et situées en avant-chaîne sont en compression. 2-Une période de surrection lente associée à de l’extension radiale, affecte l’intégralité des zones internes, au moins depuis le Pliocène inférieur. La zone des flyschs se surélève à plus grande vitesse. / The Rif chain (Northern Morocco) belongs, with the Betic Cordillera (Southern Spain), to the westernmost part of the Alpine belt. This sector is one of the main targets for the comprehension of vertical movements linked to orogenic processes. Despite the numerous investigations lead on the Pliocene uplifted deposits in the Rif Chain, the timing and amplitude of the vertical motions subsequent to the period of cooling have never been constrained. This work aims to discuss the geodynamical processes involved in the vertical motion of the Rif margin since the Neogene. A comparison between the vertical movements determined in the internal zones and estimated in the flyschs domain (South of Jebha fault), has been realized on the basis of AHe data. Correlations reported between the vertical movements and the evolution of the stress field highlighted the linkage between the main stages of vertical motion and extension period with a radial pattern. 1-The latest exhumation stages of the deep-seated metamorphic rocks, from 12-10 km of depth, were triggered by the radial extension of these units. The collapse extended from the low grade metamorphism (Greenschists facies) to the brittle strata during the Aquitano-Burdigalian times. This extension is expressed in the superficial units, whereas deepest parts and sectors at the front of the Rif chain underwent a compression. 2-A second uplift stage proceeds at a very slow raising pace and is associated to radial extension in throughout the internal zones since the Lower Pliocene. Le flyschs sector was uplifted faster since the Late Miocene.
152

Reinforcement Schemes for Cold-Formed Steel Joists Having Web Openings

Acharya, Sandesh Raj 08 1900 (has links)
The use of cold-formed steel (CFS) structures has become increasingly popular in different fields of building technology. For example, small housing systems using cold-formed steel for wall structures, framing systems and roof structures, including trusses and shielding materials, have been developed during recent years. The reasons behind the growing popularity of these products include their ease of fabrication, high strength/weight ratio and suitability for a wide range of applications. These advantages can result in more cost-effective designs, as compared with hot-rolled steel, especially in short-span applications. It has been common practice in cold-formed steel construction to cut openings in the web of beams for the passage of service ducts and piping. The provision of such openings reduces the story heights and consequently can result in saving of considerable amount of construction materials. On the other hand, the presence of a large web opening causes localized redistribution of stress around the opening region. The large opening causes loss of strength and changes the buckling characteristics of an entire member. It also affects the flexural stiffness, resulting in poor performance of member under serviceability. It is common practice to reinforce the opening of hot-rolled steel members, but proper reinforcement schemes for CFS perforated members has not been established yet. Various reinforcement schemes for cold-formed steel sections were investigated during this study. Two types of reinforcement schemes (for flexural zones and shear zones) were developed. Fifty-four flexural tests and 33 shear tests were conducted. Two types of sections (lipped channel joists with h/t ratio 180 and 118) were tested in flexure and one type of section (lipped channel joists with h/t ratio 180) was tested in shear. The study also included a finite element based numerical investigation, consisting of parametric studies on the size (web depth and thickness) of joists, size and shape of web openings, reinforcement and associated fastening schemes. It was observed that a 75 percent of opening in the web of CFS channel joist causes up to 25 percent reduction in flexural strength and up to 60 percent reduction in shear strength. Such reduced flexural and shear strengths were re-captured by providing proper reinforcement schemes. The flexural reinforcement schemes recommended by the current AISI Standard were found to be ineffective for the sections having low w /t ratios. Bridging channel reinforcement scheme was also considered in this study. Bridging channel reinforcement scheme was capable of restoring the flexural strength of cold formed steel joist having w /t ratios 118 and 180. Similarly, the reinforcement schemes recommended in AISI Standard were not adequate to restore the shear strength of joist sections. A newly developed Virendeel type reinforcement system was capable of restoring the original shear strength of a cold-formed steel joist section. / Thesis / Doctor of Philosophy (PhD)
153

Talus, Solifluction And Raised Marine Deposits At Cape Ricketts, S.W. Devon Island, N.W.T.

Cox, R. L. 20 April 1969 (has links)
No Abstract / Thesis / Bachelor of Arts (BA)
154

Identification des zones de contrainte de drainage aux opérations forestières à l'aide des données lidar

Drolet, Emilie 03 February 2021 (has links)
Sur la très vaste majorité des forêts publiques du Québec, notamment en forêt boréale, les principales données disponibles permettant de décrire les milieux humides sont celles provenant de l’inventaire forestier du quatrième décennal. Ces données manquent toutefois de précision, ce qui occasionne de nombreuses difficultés dans la planification et la récolte forestière. La cartographie à haute résolution, rendue possible grâce à l’acquisition de données lidar, devrait néanmoins permettre de pallier à cette problématique. Ce mémoire permet l’évaluation de la capacité d’outils cartographiques d’identification des zones humides potentielles à détecter les zones de contraintes de drainage aux opérations forestières (ZC) identifiées sur le terrain. Le « Topographic Wetness Index » (TWI), le« SAGA Wetness Index » (SAGAWI) et le « Depth-to-Water » (DTW) ont été produits à partir d’un modèle numérique de terrain (MNT) d’une résolution de 1 m dérivé du traitement des données lidar aéroporté. Des données de validation ont été prises sur le terrain dans les régions de la Capitale-Nationale et de l’Outaouais. La comparaison des indices a été réalisée à l’aide de statistiques zonales produites, d’arbres de classification et de matrices de confusion en lien avec les données de validation prises sur le terrain. Les résultats montrent que le SAGAWI est plus performant que le TWI pour l’identification des ZC. Il semble également plus efficace que le DTW : avec un seuil calibré pour l’ensemble des secteurs à l’étude, la précision globale du SAGAWI a été évaluée à 89%, alors que celle du DTW a été évaluée à 59%. On s’attend à ce que l’utilisation du SAGAWI puisse efficacement identifier des zones humides où les contraintes aux opérations forestières mécanisées sont potentiellement fortes, permettant ainsi de réduire les coûts environnementaux et économiques liés au l’altération du sol, favorisant une meilleure gestion intégrée des ressources.
155

In the Zone: the Effects of Soil Pipes and Dunes on Hyporheic and Riparian Zone Hydraulics and Biogeochemistry

Lotts, William Seth 10 June 2022 (has links)
Streams and rivers are a vital part of our ecosystem. They are imperiled by human ecological activities such as urbanization, industrialization, and agriculture which discharge excess nitrate and other pollutants into our waterways. Here, this dissertation seeks to understand the physical and biogeochemical processes which attenuate pollutants in stream corridors. The focus is hyporheic zones which form the interface between surface water and groundwater below and adjacent to stream channels, and riparian zones which form the interface between channels and adjacent uplands, both of which can attenuate pollutants. In this context, soil-pipes can dominate subsurface hydraulics. This research first employed MODFLOW and MT3D-USGS to model transient hyporheic hydraulics and nitrate transport in a length of riparian/riverbank soil to probe the effects of soil pipes on hydraulics and denitrification due to peak flow events in the channel. Findings showed that inserting just one soil pipe 1.5 m in length caused a ~75% increase in both hyporheic exchange and denitrification. A rough upscaling showed soil pipes could remove up to ~3% of nitrate along a 1-km reach. Next, the ability of soil pipes to bypass the often championed ability of riparian buffers to remove nitrate migrating from uplands to the channel was evaluated. This effort also employed MODFLOW and MT3D-USGS to simulated hydraulics and nitrate removal along a length of riparian soil. Findings showed that soil pipes increased flow of nitrate to the banks by five orders of magnitude in some cases. We posited a non-dimension parameter which governs when nitrate bypass is significant. In addition to soil pipes, dune bedforms can also enhance hyporheic exchange, primarily in the stream/riverbed. Again employing MODFLOW but now pairing with the transport code SEAM3D to simulate microbially-mediated aerobic metabolism of dissolved organic carbon and dissolved oxygen, the combined effects of dune translation and microbial growth and death were explored. Major findings include that neglecting microbial growth can lead to inaccurate modeling of biogeochemistry, and that aerobic metabolism increased with celerity. The results herein bolster knowledge of natural pollutant attenuation in stream and river corridors, and have implications for pollutant mitigation strategy and stream credit allocation. / Doctor of Philosophy / Streams are a vital part of our ecosystem. They are imperiled by human ecological activities such as urbanization, industrialization, and agriculture which discharge nitrate and other pollutants into our waterways. Here, this dissertation seeks to understand the physical and biological processes which attenuate pollutants. The hyporheic zone is the interface between surface water and groundwater below the bed and adjacent to stream banks, and can attenuate pollutants. Transient peak flow events such as a storm or snow melt raise the stream water levels, causing the water pressure in the stream channel to temporarily outweigh the water pressure in the soil pore spaces adjacent to the stream channel. This drives water into the banks subjecting it to pollutant attenuation processes. Soil pipes (long cylindrical void spaces created by decayed plant roots) are prevalent along stream banks, and they dominate subsurface hydraulics. This dissertation implemented a numerical study on a chunk of riparian soil to probe the effects of soil pipes on hydraulics and denitrification. Findings showed that inserting just one – 1.5 m soil pipe caused a ~75% increase in both water flow volume into the bank and nitrate removal. Riparian buffers are the vegetated strips adjacent to stream channels and have long been championed as stalwarts of pollutant removal. Soil pipes undermine this by acting as a bypass mechanism. A numerical study was again performed on a chunk of riparian soil to quantify the effects soil pipes on riparian bypass of nitrate. Findings showed that soil pipes increased flow of nitrate to the banks by five orders of magnitude in some cases. This means that a buffer enhancement strip with fine roots that prevent the formation of soil pipes should be installed along riparian buffers. In addition to soil pipes, dune bedforms can increase flowrate of water into the hyporheic zone. This dissertation modeled the combined effects of dune translation and microbial growth and death. Major findings include that neglecting microbial growth can lead to inaccurate modeling of biogeochemistry, and that biodegradation increases with increased dune velocity. The results herein bolster knowledge on natural pollutant attenuation in streams, and have implications in terms of pollutant mitigation strategy and stream credit allocation.
156

Development of a Guide to Lake and Reservoir Zone Determination

Saji, Niffy 15 April 2008 (has links)
Reservoirs are generally created by damming rivers. The upper reaches of any reservoir is generally narrow and winding like the parent river. This is the riverine zone of the reservoir. The reservoir is deepest and widest near the dam. Here, lake-like conditions exist and the water is quiescent. This is the lacustrine zone. The transitional zone separates the lacustrine and riverine zone. It has intermediate characteristics. There are many characteristics, both physical and chemical, that differentiate between these three zones. Based on the differences in characteristics between the three zones, a method has been developed to successfully divide any reservoir into three zones. The method developed was applied to Lake Manassas and the Occoquan Reservoir located in the Occoquan watershed in Virginia. Both are man-made impoundments. Analysis of data, based on the method developed, was successfully in dividing both reservoirs into the three zones. This method may therefore be successfully applied to obtain zonation in reservoirs. / Master of Science
157

A Stakeholder-Based Planning Framework For The Gherkin Agricultural Export Zone In Karnataka

Kumar, B J Ashwini 02 1900 (has links)
In 2001, the Government of India announced a program for the establishment of Agricultural Export Zones (AEZ). This is the first national program in India to adopt a regional approach to promoting exports of agricultural products, with the combined action of the central and state governments. The gherkin AEZ, covering eight districts of Karnataka, was notified in November 2001. Gherkin is an export-oriented vegetable that is being produced and exported from Karnataka since the late 1980s. Exploration of data on gherkin exports and cultivation costs, for the period 2001-06, revealed the following trends, namely, the share of value of total exports from the gherkin AEZ in India’s gherkin exports has declined from 81% to about 54%; overall (bulk + bottled) gherkin export quantities and value from the AEZ have grown with an annual rate of 18% and 21% respectively; unit price of AEZ bulk gherkins in 200506 is about 4% higher than its unit price in 2001-02 while the unit price of AEZ bottled gherkins is lower by about 9%; and the cost of gherkin cultivation has increased by about 27%. The aim of this research is to apply a stakeholder-based planning framework for enhancing the performance of the Gherkin AEZ in Karnataka. To meet the research aim, the following objectives were defined: 1.Forecasting the primary performance indicators of the gherkin AEZ, in the medium term, given the current policy environment 2.Conducting stakeholder analysis, identifying system structures that influence the gherkin AEZ’s performance and the interventions preferred by stakeholders to enhance gherkin AEZ performance 3.Exploring probable impacts of the identified interventions on gherkin AEZ’s competitiveness 4.Developing policy suggestions and a planning framework for enhancing the performance of the Gherkin AEZ Towards meeting the research objectives, the following approach has been used. One, data has been collected on AEZ performance indicators. Evolution of those variables, given the prevailing policy environment, is forecast using the Seasonal Auto Regressive Integrated Moving Average (SARIMA) methodology. Second, System elements of the gherkin AEZ are identified and organized as a system dynamics model. Stakeholder analysis of the Gherkin AEZ has been done to identify stakeholder groups. Preferred interventions for improvement of AEZ performance are collected from most stakeholders, and the impact of key interventions on system elements is qualitatively assessed. Considering the large number of system elements and the interrelationships between them, a multiple criteria decision making technique, the analytic network process, is used to describe the decision making environment and prioritize the system elements (factors and subfactors influencing AEZ performance, stakeholder objectives and interventions). Third, the probable impact of preferred interventions on competitiveness of gherkin cultivation in the AEZ is assessed using the Policy Analysis Matrix. Fourth, the analysis and learnings are integrated to suggest policy interventions and develop a planning framework for improved performance of the gherkin AEZ. The 3-year SARIMA models, to forecast the AEZ’s performance indicators, indicate a continued growth in the quantities of gherkin exports from the AEZ with a higher rate of growth in exports of bottled gherkins. The forecast also indicate a continued fall in the unit prices of both bottled and bulk gherkins. Stakeholder analysis and System dynamic models indicate the presence of several stakeholders with multiple objectives, multiple factors which influenced AEZ performance, and several preferred interventions. In this multiple criteria decision making environment, the system elements along with dependencies shown in the system dynamics model, the interventions collected from stakeholders (alternatives), and stakeholder objectives derived from stakeholder analysis, are organized to develop an Analytic Network Process (ANP) model. The cluster priorities from the ANP model indicate that global trade conditions are the most important determinant of AEZ performance. The limit matrix indicates that the element of tastes and preferences of world consumers obtains the highest priority followed by price of other countries’ gherkins, and sanitary and phytosanitary conditions as applicable to Gherkins. The probable impacts of the identified interventions on competitiveness of gherkin cultivation in the AEZ are assessed by applying the policy analysis matrix (PAM). Synthesis of sectoral performance data and factors, results of the system dynamics, ANP and PAM analysis resulted in the development of the planning framework for the gherkin AEZ. Overall, the results and analyses demonstrate that the AEZ program should focus on increasing demand, enhancing prices of AEZ gherkins and reducing cultivation costs. Towards achieving this, recommended policy interventions have been prioritized and participating stakeholders identified. This work represents an application of the multiple criteria methodology of the ANP to agricultural regional planning. The system dynamic methodology has been integrated with ANP to identify the important elements in the gherkin AEZ. This thesis on agricultural exports planning has collected and used micro data (price, product form and grade data) to identify and analyze sectoral issues.
158

Empirical modeling of windthrow occurrence in streamside buffer strips /

Drake, Timothy P. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 78-85). Also available on the World Wide Web.
159

The impact of illegal fishing on South Africa's economy / Leenke Schraader

Schraader, Leenke January 2013 (has links)
This study focuses specifically on the laws and regulations relating to commercial fishing within the Exclusive Economic Zone of South Africa and the impact of illegal fishing (IUU). The goal is to determine how overfishing can be stopped or minimised and ultimately for South Africa to harvest the illegally caught fish in such a way that it becomes part of the South African economy and generates revenue. The study will analyse the international legal instruments applicable and their impact on the development of the South African maritime laws. An in depth look at the relevant South African maritime laws will be vital as to determine if these laws are adequate to protect the fish resources from illegal exploitation and official mismanagement. To see if South Africa’s maritime laws are lacking with other countries a comparison must be done, particularly with a country like Australia that has one of the highest success rates when it comes to combating IUU fishing. It will be found that the international legal instruments and agreements on the use of the sea have afforded rights and powers to coastal states to protect their sea zones, but it will remains the responsibility of each coastal state to determine how it will use these rights and powers to protect its own sea zones. Further it will be shown that South Africa has the necessary legislative measures in place to protect its fish resources, but the problem lies with the implementation of those measures Australia does not only rely on its legislation to stop IUU fishing, but it also uses external methods, that South Africa will have to consider. / LLM (Import and export Law), North-West University, Potchefstroom Campus, 2014
160

The impact of illegal fishing on South Africa's economy / Leenke Schraader

Schraader, Leenke January 2013 (has links)
This study focuses specifically on the laws and regulations relating to commercial fishing within the Exclusive Economic Zone of South Africa and the impact of illegal fishing (IUU). The goal is to determine how overfishing can be stopped or minimised and ultimately for South Africa to harvest the illegally caught fish in such a way that it becomes part of the South African economy and generates revenue. The study will analyse the international legal instruments applicable and their impact on the development of the South African maritime laws. An in depth look at the relevant South African maritime laws will be vital as to determine if these laws are adequate to protect the fish resources from illegal exploitation and official mismanagement. To see if South Africa’s maritime laws are lacking with other countries a comparison must be done, particularly with a country like Australia that has one of the highest success rates when it comes to combating IUU fishing. It will be found that the international legal instruments and agreements on the use of the sea have afforded rights and powers to coastal states to protect their sea zones, but it will remains the responsibility of each coastal state to determine how it will use these rights and powers to protect its own sea zones. Further it will be shown that South Africa has the necessary legislative measures in place to protect its fish resources, but the problem lies with the implementation of those measures Australia does not only rely on its legislation to stop IUU fishing, but it also uses external methods, that South Africa will have to consider. / LLM (Import and export Law), North-West University, Potchefstroom Campus, 2014

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