• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 32
  • 16
  • 8
  • 5
  • 4
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 80
  • 45
  • 11
  • 10
  • 9
  • 8
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 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.
51

Application of High-Deflection Strain Gauges to Characterize Spinal-Motion Phenotypes Among Patients with CLBP

Baker, Spencer Alan 12 April 2024 (has links) (PDF)
Chronic low back pain (CLBP) is a nonspecific and persistent ailment that entails many physiological, psychological, social, and economic consequences for individuals and societies. Although there is a plethora of treatments available to treat CLBP, each treatment has varying efficacy for different patients, and it is currently unknown how to best link patients to their ideal treatment. However, it is known that biopsychosocial influences associated with CLBP affect the way that we move. It has been hypothesized that identifying phenotypes of spinal motion could facilitate an objective and repeatable method of determining the optimal treatment for each patient. The objective of this research was to develop an array of high deflection strain gauges to monitor spinal motion, and use that information to identify spinal-motion phenotypes. The high deflection strain gauges used in this endeavor exhibit highly nonlinear electrical signal due to their viscoelastic material properties. Two sub-models were developed to account for these nonlinearities: the first characterizes the relationship between quasistatic strain and resistance, and the second accounts for transient electrical phenomena due to the viscoelastic response to dynamic loads. These sub-models are superimposed to predict and interpret the electrical signal under a wide range of applications. The combined model accurately predicts sensor strain with a mean absolute error (MAE) of 1.4% strain and strain rate with an MAE of 0.036 mm/s. Additionally, a multilayered architecture was developed for the strain gauges to provide mechanical support during high strain, cyclic loads. The architecture significantly mitigates sensor creep and viscoplastic deformation, thereby reducing electrical signal drift by 74%. This research also evaluates the effects of CLBP on patient-reported outcomes. An exploratory factor analysis revealed that there are five primary components of well-being: Pain and Physical Limitations, Psychological Distress, Physical Activity, Sleep Deprivation, and Pain Catastrophizing. The presence of CLBP has adverse effects on all these components. It was also observed that different patient reported outcomes are highly correlated with each other, and the presence of CLBP is a significant moderating factor in many of these relationships. Arrays of high-deflection strain gauges were used to collect spinal kinematic data from 274 subjects. Seven phenotypes of spinal motion were identified among study participants. Statistical analyses revealed significant differences in the patient-reported outcomes of subjects who exhibited different phenotypes. This is a promising indication that the phenotypes may also provide important information to clinicians who treat patients suffering from CLBP. Future research will be conducted to develop and identify the optimal treatments for patients according to their phenotypes, which has the potential to reduce medical costs, expedite recovery, and improve the lives of millions of patients worldwide.
52

Questioning Commonplace Ecological Design: a study of waterfront design practices and the ecological well-being of development in the harbor of Oyster, Virginia

Barber, Heather K. 24 March 2006 (has links)
The purpose of this investigation is to examine how landscape architecture can create a different kind of threshold between land and water without controlling the edge between the two entities, but merely guiding the natural process of exchange. The design of Oyster Harbor on the Eastern Shore of Virginia is in contrast to normative development of waterfront sites. The hard edge of common practices of waterfront development stands in tension to the more natural evolving edge of many harbors.When creating a dialogue between land and water, the solution has always been to create a sea wall separating the two entities. It becomes the hard dividing line between a solid surface and liquid life. Is there a way to create a threshold that does not divide? How can landscape architecture create an exchange of qualities with land and water? Does the sea wall become the precedent to all concerns of tide and sea usurping lands edge? The edge between land and water is ever changing, so why not celebrate and personify that edge through creating a natural exchange between water and land. In order to create such an exchange, we must first look at the nature of water and land. Water is a free element that is composed of hydrogen and oxygen. It is inclined to motion, reflection, rise and fall. It holds a unique quality independent of man-induced control. Land is a more solid entity created by layers of stone and elements broken down by water. Land capacity is gauged by water, as in the water table. Throughout history, man has maintained a controlling relationship with land. However this is the opposite with water. Man has an inherent fear of water, the representative of both life and death. Though man tries, he cannot control water, he must work within the bounds set by water. How does one understand the evolutionary relationship of land and water without trying to control the elements that allow the relationship to occur? Through research, it is revealed that land actually usurps water through both a push and pull method of tides and water run off from land. Through time and tide, land builds up and infringes upon the natural edge of land and water. The plains move down, the vegetative roll moves forward, the beach ridges reconfigure, and the tidal flats create a shelf that extends out into the ocean floor.This evolution of land continually cycles on moon and sun paths that dictate the change in light, shade, wind, tides, motion, and human cycles. Whether recognizable or not recognizable, these macro and micro environmental cycles become a dance in the realm of landscape architecture. How does one reveal macro and micro environmental aspects through design with human interaction at the edge between land and water? / Master of Landscape Architecture
53

The Design, Prototyping, and Validation of a New Wearable Sensor System for Monitoring Lumbar Spinal Motion in Daily Activities

Bischoff, Brianna 11 June 2024 (has links) (PDF)
Lower back pain is a widespread problem affecting millions worldwide, because understanding its development and effective treatment remains challenging. Current treatment success is often evaluated using patient-reported outcomes, which tend to be qualitative and subjective in nature, making objective success measurement difficult. Wearable sensors can provide quantitative measurements, thereby helping physicians improve care for countless individuals around the world. These sensors also have the potential to provide longitudinal data on daily motion patterns, aiding in monitoring the progress of treatment plans for lower back pain. In this work it was hypothesized that a new wearable sensor garment that makes use of high-deflection strain gauge technology--called the Z-SPINE System--will be capable of collecting biomechanical information capable of detecting characteristics of motion associated with chronic lower back pain from subjects as compared to skin-adhered wearable sensor systems. The initial prototyping development of the Z-SPINE System focused on optimizing the device's conformity to the skin, as well as the ease of use and comfortability of the design. Preliminary motion capture tests concluded that a waist belt made of an elastic four way stretch material with silicone patches and no ribbing had the highest skin conformity of the garment types tested, and further design decisions were made utilizing this knowledge. A human subject study was conducted with 30 subjects who performed 14 functional movements with both the Z-SPINE System, and the SPINE Sense System--a pre-existing wearable sensor system that utilizes the same high-deflection strain gauge technology and is adhered directly to the back. Multiple features were extracted from the strain sensor datasets for use in machine learning modeling, where the model was trained to distinguish the different movements from each other. The accuracy of the model was assessed using 4 different category number variations--two 4 category, one 7 category, and one 13 category variation. Four different machine learning models were used, with the random forest classifier generally performing the best, yielding prediction accuracies of 85.95% for the SPINE Sense System data, and 71.23% for the Z-SPINE System data in the 4 category tests. As an additional part of the human subject study, the usability of the Z-SPINE System was also assessed. Each participant filled out a system usability scale questionnaire in regards to their opinion and experience with the system after having used it; the average score given by participants was 83.4, with general feedback consisting of positive remarks about the comfort and ease of use of the current design and suggestions for improving the battery placement and fit of the Z-SPINE system. It is concluded that a machine learning model of the data from the Z-SPINE System can identify biomechanical motion with reasonable accuracy as compared to a skin-adhered wearable sensor system when the number of categories is limited. It is also concluded that the system is simple and intuitive to use.
54

Avaliação da deformação média gerada nos intermediários e na região peri-implantar durante as etapas de confecção da prótese parcial fixa parafusada: análise com strain gauges / Evaluation of abutment and simulated bone tissue mean deformation around dental implants, during fabrication stages of screw-retained fixed partial prostheses: strain gauges analysis

Costa, Max Dória 30 May 2011 (has links)
A adaptação passiva e estabilidade têm se tornado os dois pré-requisitos de maior importância na escolha dos materiais e técnicas de confecção em prótese implantossuportada. A proposta deste trabalho foi avaliar, com auxílio dos strain gauges ou extensômetros lineares elétricos, a deformação média ocorrida nos intermediários e na região peri-implantar mediante a instalação da infraestrutura parafusada durante sete etapas de confecção da prótese parcial fixa. Para a investigação, foi utilizado um modelo experimental homogêneo à base de poliuretano com dois implantes hexágono externo paralelos entre si. Sobre os implantes foram acoplados pilares Multi-unit de 5 mm de altura que receberam na sua superfície três strain gauges dispostos de maneira eqüidistante entre si. Também foram colados na superfície superior do bloco experimental quatro strain gauges para cada implante, posicionados nas faces mesial, distal, vestibular e lingual visando medir as tensões nestas áreas. Os testes foram realizados parafusando os corpos de prova sobre os intermediários utilizando-se para isto um dispositivo eletrônico de torque com força máxima de 10 Ncm. As leituras foram realizadas em sete momentos, obtendo os valores médios de deformação no poliuretano e no intermediário respectivamente: 1) cilindros de cobalto-cromo pré-fabricados usinados como grupo controle (36,4µε e 87,5µε), 2) infraestrutura sobrefundida em monobloco com liga de níquel-cobalto-cromo (340,3µε e 131,4µε), 3) em seguida seccionada com espaço livre para solda (43,2µε e 66,6µε), 4) seccionada com espaço para solda preenchida com resina acrílica quimicamente ativada (Duralay) (74µε e 86,8µε), 5) seccionada e soldada (280µε e 146,2µε), 6) soldada com aplicação de cerâmica (288,7µε e 151,1µε) e 7) finalizada com aplicação do glaze, acabamento e polimento (359,9µε e 197,8µε). Estes resultados mostraram um aumento crescente da deformação média tanto nos intermediários como no poliuretano durante todas as etapas de confecção, com excessão da fundição em monobloco que atingiu altos valores, próximos da prótese finalizada. Desta forma, o procedimento de soldagem diminuiu os níveis de derformação, enquanto a aplicação da cobertura cerâmica, glaze, acabamento e polimento, aumentaram as deformações. / Passive fit and stability have become the most important prerequisites during the choice of materials and techniques to implant-supported prostheses. Therefore, the aim of this study was to verify the mean deformation in abutments and simulated bone tissue around dental implants, with the use of strain gages, during framework screw retention, analyzing seven fabrication stages of the fixed partial denture. For this research, an experimental model based on homogeneous polyurethane with two external hexagon implants parallel to each other, provided with 5 mm height multi-unit abutments. For each, abutment surface received three equidistant strain gauges and the experimental block received upper surface four strain gauges, positioned on the mesial, distal, buccal and lingual aspects. The tests were performed screwing the specimens on the abutment using an electronic torque with 10 Ncm maximum force. The readings were made in seven moments, with abutment and polyurethane mean deformation, respectively: 1) control group: cobalt-chromium prefabricated machined cylinder (36,4µε e 87,5µε), 2) framework fabricated by 1-piece method in nickel-cobalt-chromium alloy (340,3µε e 131,4µε), 3) framework sectioned with space for welding (43,2µε e 66,6µε), 4) weld space filled with chemically activated acrylic resin (Duralay) (74µε e 86,8µε), 5) framework sectioned and soldered (280µε e 146,2µε), 6) framework welded and ceramic application (288,7µε e 151,1µε) and 7) framework concluded applying glaze, finishing and polishing (359,9µε e 197,8µε). The results showed the mean strain increase in abutment and polyurethane over fabrication stages, except that framework fabricated by 1-piece method reached high values close to finished prostheses. Thus, the welding procedure decreased strain levels in simulated bone tissue around dental implants, while ceramic and glaze application, finishing and polishing procedures, increased strain.
55

Wafer Level Vacuum Packaging Of Mems Sensors And Resonators

Torunbalci, Mert Mustafa 01 February 2011 (has links) (PDF)
This thesis presents the development of wafer level vacuum packaging processes using Au-Si eutectic and glass frit bonding contributing to the improvement of packaging concepts for a variety of MEMS devices. In the first phase of this research, micromachined resonators and pirani vacuum gauges are designed for the evaluation of the vacuum package performance. These designs are verified using MATLAB and Coventorware finite element modeling tool. Designed resonators and pirani vacuum gauges and previously developed gyroscopes with lateral feedthroughs are fabricated with a newly developed Silicon-On-Glass (SOG) process. In addition to these, a process for the fabrication of similar devices with vertical feedthroughs is initiated for achieving simplified packaging process and lower parasitic capacitances. Cap wafers for both types of devices with lateral and vertical feedthroughs are designed and fabricated. The optimization of Au-Si eutectic bonding is carried out on both planar and non-planar surfaces. The bonding quality is evaluated using the deflection test, which is based on the deflection of a thinned diaphragm due to the pressure difference between inside and outside the package. A 100% yield bonding on planar surfaces is achieved at 390&ordm / C with a v holding time and bond force of 60 min and 1500 N, respectively. On the other hand, bonding on surfaces where 0.15&mu / m feedthrough lines exist can be done at 420&ordm / C with a 100% yield using same holding time and bond force. Furthermore, glass frit bonding on glass wafers with lateral feedthroughs is performed at temperatures between 435-450&ordm / C using different holding periods and bond forces. The yield is varied from %33 to %99.4 depending on the process parameters. The fabricated devices are wafer level vacuum packaged using the optimized glass frit and Au-Si eutectic bonding recipes. The performances of wafer level packages are evaluated using the integrated gyroscopes, resonators, and pirani vacuum gauges. Pressures ranging from 10 mTorr to 60 mTorr and 0.1 Torr to 0.7 Torr are observed in the glass frit packages, satisfying the requirements of various MEMS devices in the literature. It is also optically verified that Au-Si eutectic packages result in vacuum cavities, and further study is needed to quantify the vacuum level with vacuum sensors based on the resonating structures and pirani vacuum gauges.
56

Pressure Sensor Development Using Hard Anodized Aluminum Diaphragm And Thin Film Strain Gauges

Rajendra, A 04 1900 (has links)
The sensor is a device that converts a form of energy concerning which the information is sought, called the measurand, to a form (electrical) in which it can be usefully processed or interpreted. Sensors rely on physical or chemical phenomena and materials where those phenomena appear to be useful. Those phenomena may concern the material itself or its geometry. Hence, the major innovations in sensors come from new materials, new fabrication techniques or both. Normally, thin film sensors are realized by depositing a sensing film on a suitable substrate. There could be many combination of metals and insulating materials being deposited depending upon the application or sensing requirements. In general, sensors for various applications are fabricated using a variety of liquid phase technologies (also called as wet methods) and gas phase technologies (also called as dry methods) of deposition. Hence sensor fabrication technology requires various combination of processing technologies and newer materials. In the present work, an attempt is made to design and fabricate a thin film based pressure sensor using a combination of wet and dry deposition techniques. The diaphragm, used for sensing the pressure is coated with a hard anodic coating (Al2O3) using a wet technology, viz. pulse hard anodizing technique, for electrical insulation requirement. The piezo-resistive strain sensing films were deposited onto this coating by dry method, namely, DC Magnetron sputtering technique.. Chapter 01 gives a brief overview of sensors, their classification, principles of sensing,characteristics, materials used in the fabrication of sensors like conductors and insulators, the components of a sensor. Chapter 02 gives brief information about various techniques of depositions viz., liquid phase technologies (wet methods) and vapour phase technologies (dry methods) used to fabricate the sensors. Also, information regarding the coating property evaluation and coating characterization techniques is included. The chapter 03 presents a detailed account of work carried out to obtain an electrically insulating layer by the development of pulse hard anodizing process for aluminum alloy diaphragm, necessary process optimization and testing. The details related to the development, fabrication and testing of thin film based pressure sensors using aluminum alloy diaphragm with hard anodic coating are presented in Chapter 04. The thin film strain gauges were deposited using DC magnetron sputtering technique. The information about mask design, deposition process parameters, calibration etc is also included. Chapter 05 provides summary of the work carried out and conclusions. The scope of carrying out further work is also outlined.
57

Duality for convex composed programming problems

Vargyas, Emese Tünde 20 December 2004 (has links) (PDF)
The goal of this work is to present a conjugate duality treatment of composed programming as well as to give an overview of some recent developments in both scalar and multiobjective optimization. In order to do this, first we study a single-objective optimization problem, in which the objective function as well as the constraints are given by composed functions. By means of the conjugacy approach based on the perturbation theory, we provide different kinds of dual problems to it and examine the relations between the optimal objective values of the duals. Given some additional assumptions, we verify the equality between the optimal objective values of the duals and strong duality between the primal and the dual problems, respectively. Having proved the strong duality, we derive the optimality conditions for each of these duals. As special cases of the original problem, we study the duality for the classical optimization problem with inequality constraints and the optimization problem without constraints. The second part of this work is devoted to location analysis. Considering first the location model with monotonic gauges, it turns out that the same conjugate duality principle can be used also for solving this kind of problems. Taking in the objective function instead of the monotonic gauges several norms, investigations concerning duality for different location problems are made. We finish our investigations with the study of composed multiobjective optimization problems. In doing like this, first we scalarize this problem and study the scalarized one by using the conjugacy approach developed before. The optimality conditions which we obtain in this case allow us to construct a multiobjective dual problem to the primal one. Additionally the weak and strong duality are proved. In conclusion, some special cases of the composed multiobjective optimization problem are considered. Once the general problem has been treated, particularizing the results, we construct a multiobjective dual for each of them and verify the weak and strong dualities. / In dieser Arbeit wird, anhand der sogenannten konjugierten Dualitätstheorie, ein allgemeines Dualitätsverfahren für die Untersuchung verschiedener Optimierungsaufgaben dargestellt. Um dieses Ziel zu erreichen wird zuerst eine allgemeine Optimierungsaufgabe betrachtet, wobei sowohl die Zielfunktion als auch die Nebenbedingungen zusammengesetzte Funktionen sind. Mit Hilfe der konjugierten Dualitätstheorie, die auf der sogenannten Störungstheorie basiert, werden für die primale Aufgabe drei verschiedene duale Aufgaben konstruiert und weiterhin die Beziehungen zwischen deren optimalen Zielfunktionswerten untersucht. Unter geeigneten Konvexitäts- und Monotonievoraussetzungen wird die Gleichheit dieser optimalen Zielfunktionswerte und zusätzlich die Existenz der starken Dualität zwischen der primalen und den entsprechenden dualen Aufgaben bewiesen. In Zusammenhang mit der starken Dualität werden Optimalitätsbedingungen hergeleitet. Die Ergebnisse werden abgerundet durch die Betrachtung zweier Spezialfälle, nämlich die klassische restringierte bzw. unrestringierte Optimierungsaufgabe, für welche sich die aus der Literatur bekannten Dualitätsergebnisse ergeben. Der zweite Teil der Arbeit ist der Dualität bei Standortproblemen gewidmet. Dazu wird ein sehr allgemeines Standortproblem mit konvexer zusammengesetzter Zielfunktion in Form eines Gauges formuliert, für das die entsprechenden Dualitätsaussagen abgeleitet werden. Als Spezialfälle werden Optimierungsaufgaben mit monotonen Normen betrachtet. Insbesondere lassen sich Dualitätsaussagen und Optimalitätsbedingungen für das klassische Weber und Minmax Standortproblem mit Gauges als Zielfunktion herleiten. Das letzte Kapitel verallgemeinert die Dualitätsaussagen, die im zweiten Kapitel erhalten wurden, auf multikriterielle Optimierungsprobleme. Mit Hilfe geeigneter Skalarisierungen betrachten wir zuerst ein zu der multikriteriellen Optimierungsaufgabe zugeordnetes skalares Problem. Anhand der in diesem Fall erhaltenen Optimalitätsbedingungen formulieren wir das multikriterielle Dualproblem. Weiterhin beweisen wir die schwache und, unter bestimmten Annahmen, die starke Dualität. Durch Spezialisierung der Zielfunktionen bzw. Nebenbedingungen resultieren die klassischen konvexen Mehrzielprobleme mit Ungleichungs- und Mengenrestriktionen. Als weitere Anwendungen werden vektorielle Standortprobleme betrachtet, zu denen wir entsprechende duale Aufgaben formulieren.
58

Avaliação da deformação média gerada nos intermediários e na região peri-implantar durante as etapas de confecção da prótese parcial fixa parafusada: análise com strain gauges / Evaluation of abutment and simulated bone tissue mean deformation around dental implants, during fabrication stages of screw-retained fixed partial prostheses: strain gauges analysis

Max Dória Costa 30 May 2011 (has links)
A adaptação passiva e estabilidade têm se tornado os dois pré-requisitos de maior importância na escolha dos materiais e técnicas de confecção em prótese implantossuportada. A proposta deste trabalho foi avaliar, com auxílio dos strain gauges ou extensômetros lineares elétricos, a deformação média ocorrida nos intermediários e na região peri-implantar mediante a instalação da infraestrutura parafusada durante sete etapas de confecção da prótese parcial fixa. Para a investigação, foi utilizado um modelo experimental homogêneo à base de poliuretano com dois implantes hexágono externo paralelos entre si. Sobre os implantes foram acoplados pilares Multi-unit de 5 mm de altura que receberam na sua superfície três strain gauges dispostos de maneira eqüidistante entre si. Também foram colados na superfície superior do bloco experimental quatro strain gauges para cada implante, posicionados nas faces mesial, distal, vestibular e lingual visando medir as tensões nestas áreas. Os testes foram realizados parafusando os corpos de prova sobre os intermediários utilizando-se para isto um dispositivo eletrônico de torque com força máxima de 10 Ncm. As leituras foram realizadas em sete momentos, obtendo os valores médios de deformação no poliuretano e no intermediário respectivamente: 1) cilindros de cobalto-cromo pré-fabricados usinados como grupo controle (36,4µε e 87,5µε), 2) infraestrutura sobrefundida em monobloco com liga de níquel-cobalto-cromo (340,3µε e 131,4µε), 3) em seguida seccionada com espaço livre para solda (43,2µε e 66,6µε), 4) seccionada com espaço para solda preenchida com resina acrílica quimicamente ativada (Duralay) (74µε e 86,8µε), 5) seccionada e soldada (280µε e 146,2µε), 6) soldada com aplicação de cerâmica (288,7µε e 151,1µε) e 7) finalizada com aplicação do glaze, acabamento e polimento (359,9µε e 197,8µε). Estes resultados mostraram um aumento crescente da deformação média tanto nos intermediários como no poliuretano durante todas as etapas de confecção, com excessão da fundição em monobloco que atingiu altos valores, próximos da prótese finalizada. Desta forma, o procedimento de soldagem diminuiu os níveis de derformação, enquanto a aplicação da cobertura cerâmica, glaze, acabamento e polimento, aumentaram as deformações. / Passive fit and stability have become the most important prerequisites during the choice of materials and techniques to implant-supported prostheses. Therefore, the aim of this study was to verify the mean deformation in abutments and simulated bone tissue around dental implants, with the use of strain gages, during framework screw retention, analyzing seven fabrication stages of the fixed partial denture. For this research, an experimental model based on homogeneous polyurethane with two external hexagon implants parallel to each other, provided with 5 mm height multi-unit abutments. For each, abutment surface received three equidistant strain gauges and the experimental block received upper surface four strain gauges, positioned on the mesial, distal, buccal and lingual aspects. The tests were performed screwing the specimens on the abutment using an electronic torque with 10 Ncm maximum force. The readings were made in seven moments, with abutment and polyurethane mean deformation, respectively: 1) control group: cobalt-chromium prefabricated machined cylinder (36,4µε e 87,5µε), 2) framework fabricated by 1-piece method in nickel-cobalt-chromium alloy (340,3µε e 131,4µε), 3) framework sectioned with space for welding (43,2µε e 66,6µε), 4) weld space filled with chemically activated acrylic resin (Duralay) (74µε e 86,8µε), 5) framework sectioned and soldered (280µε e 146,2µε), 6) framework welded and ceramic application (288,7µε e 151,1µε) and 7) framework concluded applying glaze, finishing and polishing (359,9µε e 197,8µε). The results showed the mean strain increase in abutment and polyurethane over fabrication stages, except that framework fabricated by 1-piece method reached high values close to finished prostheses. Thus, the welding procedure decreased strain levels in simulated bone tissue around dental implants, while ceramic and glaze application, finishing and polishing procedures, increased strain.
59

Fatores de variação das estimativas de precipitação interna em uma floresta secundária

Lima, Raul Sampaio de 05 July 2017 (has links)
Submitted by Bruna Rodrigues (bruna92rodrigues@yahoo.com.br) on 2017-10-04T13:00:24Z No. of bitstreams: 1 DissRSL.pdf: 2218443 bytes, checksum: 6c095cccc15f22c3fe747197514a5b16 (MD5) / Approved for entry into archive by Ronildo Prado (producaointelectual.bco@ufscar.br) on 2017-10-11T11:44:18Z (GMT) No. of bitstreams: 1 DissRSL.pdf: 2218443 bytes, checksum: 6c095cccc15f22c3fe747197514a5b16 (MD5) / Approved for entry into archive by Ronildo Prado (producaointelectual.bco@ufscar.br) on 2017-10-11T11:44:30Z (GMT) No. of bitstreams: 1 DissRSL.pdf: 2218443 bytes, checksum: 6c095cccc15f22c3fe747197514a5b16 (MD5) / Made available in DSpace on 2017-10-11T11:52:44Z (GMT). No. of bitstreams: 1 DissRSL.pdf: 2218443 bytes, checksum: 6c095cccc15f22c3fe747197514a5b16 (MD5) Previous issue date: 2017-07-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Throughfall (TF) is affected by different biotic and meteorological factors that can interact, resulting in high variability in estimates, increasing the uncertainty in hydrological models and the forecast of environmental impacts in watersheds. The knowledge of the relationship between rainfall (RF) and TF is a key factor for the definition of sampling strategies that result within commonly accepted error thresholds. Therefore, the main objective of this study was to analyze sources of TF variability in a secondary forest in SE Brazil, in order to understand the response of TF in function of different environmental drivers and sampling strategies. To attain these objectives, the influences of RF, sampling strategies, and stand structure on TF were analysed. The results indicated significant influence of RF on the response variables [TF volume (TFmm), TF fraction (TF%), and coefficient of variation of TF (CVTF)]. Whereas the linear model showed the best fit for TFmm, nonlinear models presented better fits for TF% and CVTF in response to RF. Regarding the influence of sampling strategies, there were no significant effects on average estimates of TFmm and CVTF. Based on the magnitude of the error, only treatments with 16 fixed gauges and nine roving gauges were able to provide estimates with errors smaller than 10%, both for all rainfall events and for those higher than 10.44 mm (median value). The results suggest that different vegetation structures affect TFmm at different spatial scales. For instance, a significant effect of canopy cover was observed on the point estimates of TFmm. However, no vegetation influences on this variable were observed at the plot scale. Regarding the temporal variability, significant effects were verified at two scales: distance to the nearest trunk at the point scale; and metrics of trees greater than 20 m at the plot scale. Finally, it was verified that combined effects of tree sizes and canopy cover influenced CVTF, indicating that the these variables reflect vegetation complexity. In general, the results suggest that RF is the main source of TF variability in the studied area. Therefore, it is necessary to consider both meteorological factors and characteristics of rainfall events to sample TF with adequate accuracy. Nevertheless, the interactions between biotic and meteorological factors affect their relative influences on TF, highlighting the need for further research in this area. / A precipitação interna (PI) é afetada por diferentes fatores bióticos e meteorológicos que podem interagir entre si, resultando numa elevada variabilidade em suas estimativas, aumentando a incerteza em modelos hidrológicos e na previsão de impactos ambientais em bacias hidrográficas. A compreensão da relação entre a precipitação em aberto (PA) e a PI é importante para a definição de estratégias de amostragem com limiares de erros aceitáveis. Portanto, o objetivo geral deste estudo foi analisar os fatores de variação da PI em uma floresta secundária, localizada no sudeste brasileiro, a fim de compreender o comportamento desse processo em função de diferentes fatores ambientais e de estratégias de amostragem. Para isto, foram analisadas as influências da PA, das estratégias de amostragem e da estrutura da vegetação sobre a PI. Os resultados indicaram influência significativa da PA sobre as variáveis resposta [volume de PI (PImm), fração de PI (PI%) e coeficiente de variação da PI (CVPI)]. Enquanto o modelo linear apresentou o melhor ajuste para PImm, os modelos não lineares tiveram melhores ajustes para PI% e CVPI em função de PA. Quanto à influência das estratégias de amostragem, não houve efeitos significativos sobre as estimativas médias de PImm e CVPI. Com base na magnitude do erro, apenas tratamentos com 16 pluviômetros fixos e nove rotativos foram capazes de fornecer estimativas com erros inferiores a 10%, tanto para o conjunto completo de dados quanto para chuvas superiores a 10,44 mm (valor mediano). Os resultados sugerem que diferentes estruturas da vegetação afetam a PImm em diferentes escalas espaciais. Por exemplo, foi verificado efeito significativo da cobertura do dossel sobre as estimativas pontuais de PImm. No entanto, não foram verificadas influências da vegetação sobre esta variável na escala da parcela. Em relação à variabilidade temporal, verificaram-se efeitos significativos nas duas escalas: da distância para o tronco mais próximo na pontual; e de métricas de árvores maiores que 20 m na escala parcela. Por fim, verificou-se que os efeitos combinados do tamanho das árvores e da cobertura do dossel influenciaram CVPI, indicando que essas variáveis refletem a complexidade da vegetação. Em geral, os resultados sugerem que PA é a principal fonte de variabilidade de PI na área estudada. Portanto, é necessário considera características meteorológicas e dos eventos de chuva para amostrar a PI com precisão adequada. Contudo, as interações entre fatores bióticos e meteorológicos afetam suas influências relativas sobre a PI, destacando a necessidade de mais pesquisas nessa área.
60

Evolution des composantes du niveau marin à partir d'observations de marégraphie effectuées depuis la fin du 18ème siècle en Charente-Maritime / Changes in sea level components from tide gauge data since the end of the 18th century along the Charente-Maritime French Atlantic coast

Gouriou, Thomas 26 March 2012 (has links)
Les estimations de la remontée générale du niveau de la mer, de l’ordre de 17 ± 2 cm sur le siècle dernier, masquent une réalité très variable d’une région à l’autre. Qu’en est-il du littoral charentais ? Des séries temporelles de plus de 40-50 ans sont souvent indispensables pour tirer des tendances fiables à long terme sur les composantes du niveau marin : niveau moyen de la mer, ondes de marée et effets météorologiques. Or, de nombreux lots de mesures marégraphiques du littoral charentais « sommeillaient » dans les centres d’archive français, i.e. : La Rochelle-Vieux port (1775-1892), La Rochelle-La Pallice (1885-auj.), île d’Aix (1824-auj.), fort Enet (1859-1873), fort Boyard(1873-1909) et Cordouan (1812-1994). Les objectifs de nos travaux de recherche étaient multiples : inventorier,sauvegarder et numériser des lots de mesures historiques du niveau marin, puis construire des séries temporelles recomposées à partir de ces lots de mesures hétérogènes, temporellement et spatialement, et enfin les exploiter pour mieux décrire et comprendre l’évolution à long terme du niveau de la mer. La qualité des trois séries construites (LaRochelle : 1775-auj. ; Aix-Enet-Boyard : 1824-auj. ; et Cordouan : 1812-1994) a ensuite été éprouvée en détail afin d’évaluer le niveau de précision de notre reconstruction. A partir de ces séries inédites, nous avons pu étudier l’évolution des composantes du niveau marin. Suite à ces travaux, nous fournissons un inventaire le plus exhaustif possible détaillant les mesures de 25 observatoires de Charente-Maritime, de 1775 à aujourd’hui. Les données des séries temporelles ainsi que des éléments permettant d’apprécier leur qualité seront bientôt disponibles en ligne sur REFMAR (refmar.shom.fr), SONEL (www.sonel.org) et au PSMSL (www.psmsl.org). Nos résultats positifs nous ont permis de reconstruire une série encore plus globale, celle du pertuis d’Antioche, à partir des moyennes mensuelles du niveau marin des séries de La Rochelle et d’Aix-Enet-Boyard. Parmi les résultats marquants obtenus,le niveau moyen de la mer s’est élevé de +1,38 ± 0,08 mm/an dans le pertuis d’Antioche sur la période 1860-2010.Ce résultat est cohérent avec Liverpool (+1,2 ± 0,1 mm/an sur la période 1858-1997 [Woodworth, 1999a]) et avec les récents résultats suggérant que l’élévation du niveau marin sur les côtes atlantiques européennes est moins importante qu’au niveau mondial (+1,7 ± 0,3 mm/an sur la période 1870-2004 [Church & White, 2006]). / Global sea level rise, which is estimated at 17 ± 2 cm over the last century, does not reflect the differences of the sealevel evolution between places across the world. What is the situation along the Charente-Maritime French Atlanticcoast? Time series covering a period of at least 40-50 years are vital to establish reliable long-term trends of sealevel components: mean sea level, tidal constituents and meteorological effects. Many tide gauge data sets of the Charente-Maritime coast have recently been rediscovered in archives: La Rochelle-Vieux port (1775-1892), La Rochelle-La Pallice (1885-today), île d’Aix (1824-today), fort Enet (1859-1873), fort Boyard (1873-1909) and Cordouan (1812-1994). The aims of this thesis were firstly to inventory, to rescue and to digitize historical sea leveldata sets. Secondly, those data sets were put back together in order to construct continuous time series, which have been analysed and led to a better description of long-term sea level changes. In this way, three time series were constructed (La Rochelle: 1775-today; Aix-Enet-Boyard: 1824-today; and Cordouan: 1812-1994) and have been deeply examined to assess the construction validity and quality. From these new time series, we could estimate changes of sea level components. Thanks to this research work, we have been able to provide an inventory as exhaustive as possible, with detailed measurements of twenty five Charente-Maritime’s stations from 1775 to nowadays. All those data will be soon available on REFMAR (refmar.shom.fr), SONEL (www.sonel.org) and PSMSL (www.psmsl.org) websites. From those positive results, we have been able to reconstruct a more global time series (Pertuis d’Antioche) from the monthly mean sea levels of La Rochelle and Aix-Enet-Boyard. Among our results, we can high light that the mean sea level trend on Pertuis d’Antioche is estimated at +1.38 ± 0.08 mm/year, from 1860 to 2010. This result is consistent with Liverpool’s trend (+1.2 ± 0.1 mm/year from 1858 to 1997[Woodworth, 1999a]) and also with recent results suggesting that sea level rise along the European Atlantic coasts isslower than global sea level rise (+1.7 ± 0.3 mm/year from 1870 to 2004 [Church & White, 2006]).

Page generated in 0.0232 seconds