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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.
261

Geomorphic evolution and coastal hazards along the Iranian coast of Makran / Évolution géomorphologique et risques côtiers le long des rivages du Makran (Iran)

Shah-Hosseini, Majid 21 March 2014 (has links)
Cette thèse a deux objectifs principaux: (i) la reconstruction de l'évolution des plaines côtières autour des baies de Chabahar et de Pozm et (ii) L'évaluation des risques côtiers (tsunamis et tempêtes extrêmes) par l'étude des dépôts de haute énergie. Vastes plaines côtières et paleo-rivages protégées par des terrasses marines soulevées sont présents autour des baies de Chabahar et Pozm. Nous avons mise en évidence des changements du niveau marin relatif le long de quatre profils. L'architecture interne des paleo-rivages a été imagée en utilisant le géoradar (GPR). Des analyses sédimentologiques et stratigraphiques des séquences côtières ont été examinées par carottages et tranchées. Les paleo-rivages sont datées entre 4800 et 270 ans BP à des distances respectives de 5 km et de 670 m du rivage actuel. La position spatiale des paléo-rivages montre une chute du niveau relatif de la mer de 15 m au cours des 4800 derniers années. Nous insistons aussi sur le rôle de contrôle des structures géologiques. Les dépôts d'événements (tsunami et tempêtes) ont été étudiés en contexte de côte meuble par Les sédiments sableux et coquilliers d'origine marine, et sur les côtes rocheuses par les dépôt des blocs déplacés. Nous avons appliqué des modèles hydrologiques pour évaluer et comparer la hauteur des vagues et la distance d'inondation. Nos résultats montrent qu'aucun événement de tempête, connu ou potentiel, n'est capable de transporter les blocs observés. Des vagues de tsunamis de l'ordre de 4 m de hauteur sont suffisantes pour transporter les blocs. La côte de Makran a enregistré des indices de paléo-tsunamis probablement générés par de grands séismes dans la zone de subduction. / In this thesis we have two main goals: (i) to reconstruct the Holocene coastal evolution and relative sea-level changes using strandplains around the Chabahar and Pozm bays; and (ii) to evaluate coastal hazards (tsunami and extreme storms) along the Iranian coast of Makran using high-energy deposits. Since the mid-Holocene, the shoreline rimming the bays of Chabahar and Pozm has prograded ~5 km and formed extensive strandplains. We documented relative sea-level changes along four coast-normal profiles. Internal architecture of strandplain imaged using Ground Penetrating Radar (GPR). The sedimentology and stratigraphy of the coastal sequence were studied by coring and trenching. The highest paleo-coastline is located about 5 km inland and stands approximately 15 m above present sea level. Paleo-shorelines date back between 4800 and 270 years BP at respective distances of 5 km to 670 m from the active shoreline. The spatial position of the palaeo-coastlines demonstrates a fall in local sea level of around 15 m during the last ~4800 years. Event deposits attesting to high-energy waves have been studied in low-lying coast by study of Over-washed sandy and shelly marine sediment and on the rocky shore by study of displaced boulder deposits. We applied hydrologic models to estimate the height and inundation distance of exceptional waves. Our results demonstrate that no known or probable storm is capable of detaching and transporting the boulders. Tsunami waves 4 m in height are enough to transport the boulders. We conclude the Makran coast has archived evidence of palaeo-tsunami events generated in the Makran subduction zone.
262

Mapping of Massive Ground Ice Using Ground Penetrating Radar Data in Taylor Valley, McMurdo Dry Valleys of Antarctica / Kartläggning av massiv markis med hjälpav markradar i Taylor Valley, Antarktis

Drake, Alexandra January 2015 (has links)
The distribution of massive ground ice in the ground in Taylor Valley of the McMurdo Dry Valleys, Antarctica, is quite unknown, and could provide answers to questions such as where the ice comes from, if it has been affected and removed by proglacial lakes and how landscapes underlain by massive ground ice responds to climate change. It could also be a source for atmospheric information in the past and hence a key in climate research. The main goal with this project was therefore to map the distribution of massive ground ice mainly in Taylor Valley, but also in the adjacent Salmon Valley and Wright Valley, using ground penetrating radar to see how the distribution varied and if there was any spatial patterns. The technical computing programme MATLAB was used for editing of the raw radar data, merging of GPR profiles and digitalization of reflectors for possible massive ground ice and several compilations of different files. The data obtained from MATLAB was imported and interpreted using the geographic information system ArcGIS. A series of histograms showing the distribution of massive ground ice depending on the parameters elevation, slope and aspect were made by using the spreadsheet application Microsoft Excel. The results showed that the distribution of massive ground ice was more common at elevations up to 200 m, at the mouth of the valleys and also more frequent in Taylor Valley than in Wright Valley. There was a slightly higher amount of massive ground ice at northeast-east aspects, probably due to different incoming solar radiation. The lack of, or not that prominent, differences for slope and aspect can be due to lack of data, a not enough detailed digital elevation model or that it have existed for a too short period of time to display big differences caused by effects from these parameters. The higher frequency of massive ground ice in Taylor Valley can be due to a thicker sediment cover when compared with the situation in Wright Valley. The distribution of massive ground ice at different slopes seems to follow the distribution of radar measurements, whereas the origin of the massive ground ice and sediment cover can be responsible for the distribution across different elevations. The reason why massive ground ice still occurs despite the existence of Glacial Lake Washburn that previously occupied Taylor Valley could be that the glacial lake did not remain for a sufficiently long time to melt all the massive ice. Massive ground ice is very common in a zone that is believed to be very susceptible for future warming, which means that changes that already have been observed in areas rich in massive ground ice can continue to happen and changes in other areas with massive ice can be enabled. The ice can thus play a major role in the development of the landscape in the McMurdo Dry Valleys depending on the amount of warming. / Markis kan hittas i mark som har temperaturer under 0°C under åtminstone 2 år i följd och därav klassas som permafrost, skillnaden mellan markis och permafrost är däremot att permafrost inte behöver vara just is utan kan enbart vara kall mark. För att markis ska klassas som massiv is så ska andelen is i marken vara minst 250 % jämfört med vikten på torr jord. Utbredningen av sådan massiv is i Taylor Valley i McMurdos torrdalar på Antarktis är inte helt känd, och kunskapen om att veta vart den finns (om den finns) skulle kunna ge svar på frågor som vart den kommer ifrån, om den har påverkats och smält bort av isuppdämda sjöar och hur landskap som är grundade av massiv markis påverkas av klimatförändringar. Isen skulle även kunna vara en informationskälla för tidigare atmosfäriska förhållanden. Huvudsyftet med detta arbete var därför att kartlägga utbredningen av massiv is främst i Taylor Valley, men även i de närliggande dalarna Salmon Valley och Wright Valley, och undersöka hur utbredningen varierar beroende på olika landskapsegenskaper som påverkar dess förekomst. Datorprogrammet och programspråket MATLAB användes för att editera rådatat från radar-mätningarna i området, samt för att sammanföra och digitalisera horisonter för möjlig massiv markis i radarfigurerna och för ett antal sammanställningar av olika filer. Data erhållet från MATLAB importerades till det geografiska informationssystemet ArcGIS där det kunde visualiseras i kartor och tolkas. Ett antal histogram skapades i kalkylprogrammet Microsoft Excel för att visa frekvensen av massiv markis vid olika höjder, sluttningsvinklar och olika väderstrecksriktningar. Resultaten visade att det var mer vanligt med massiv is höjder upp till 200 m, vid mynningarna av dalarna samt i Taylor Valley jämfört med Wright Valley. Det var en aning mer vanligt med massiv markis vid nordöst-östliga sluttningsriktningar, vilket antagligen beror på olika mängder inkommande solstrålning till de olika riktningarna. Avsaknaden av, eller inte så märkbara, skillnader för olika sluttningsvinklar och riktningar kan bero på att mängden data var för liten, att höjdkartan inte var tillräckligt detaljerad eller att isen inte har funnits tillräckligt länge för att bli påverkad av dessa parametrar. Anledningen till att det finns mer massiv markis i Taylor Valley än i Wright Valley kan vara att det skyddande sedimenttäcket är tunnare i Wright Valley än i Taylor Valley. Frekvensen av massiv markis vid olika sluttningsvinklar verkar bero på det totala antalet mätningar gjorda, fler mätningar leder till en högre frekvens av markis, medan dess ursprung samt det antagna tunnare sedimenttäcket på högre höjder kan vara anledningen till de olika frekvenserna av massiv markis vid olika höjder. Anledningen till varför det fortfarande finns massiv markis trots existensen av den isuppdämda sjön Washburn som tidigare fanns i Taylor Valley, och att isen således inte helt har smält bort på grund av sjön, kan vara att den fanns under en för kort tid så att de långsamma termodynamiska processerna som skulle orsaka smältningen inte hann agera tillräckligt länge för att smälta all is. Den massiva markisen är vanlig i en zon som tros vara väldigt mottaglig för framtida uppvärmning, vilket betyder att landskapsförändringar som redan har observerats i områden med mycket massiv markis kan fortsätta att ske samtidigt som andra områden med massiv markis kan börja förändras. Isen kan därför spela en stor roll i landskapsutvecklingen i McMurdos torrdalar beroende på hur mycket varmare det blir i området.
263

Stavební průzkum a diagnostika železobetonové konstrukce / Survey and Diagnostics of Reinforced Concrete Structure

Bernard, Lukáš January 2020 (has links)
This diploma thesis deals with construction and technological survey of the reinforced concrete structure. The first part of the diploma thesis deals with the properties of the reinforced concrete and with the building survey methods applied in the second part of the thesis. The second part of the diploma thesis focuses on diagnostics of existing structure. More specifically, the hardness of the concrete is tested using a Schmidt hammer and then it is further specified by testing the cores. The reinforcement in the reinforced concrete is also tested using electromagnetic indicator, ground-penetrating radar, and chopped probes. Lastly, a static assessment of the selected girder and column is conducted.
264

Stavební průzkum a diagnostika konstrukce / Survey and Diagnostics of Building Construction

Řezáč, David January 2021 (has links)
The diploma thesis deals with the construction and technical survey of a reinforced concrete structure. The theoretical part describes the tested properties of concrete and the methodology of their tests used in the practical part. The practical part is devoted to the diagnosis of the existing structure, which was determined the strength of concrete using core holes, concrete adhesion by tear tests, and reinforcement of reinforced concrete elements of the structure determined by ground-penetrating radar, electromagnetic indicators and additional chopped probes.
265

GRAIN SIZE ANALYSIS OF A PRECURSOR TO A FLYING SPIT IN THE WESTERN MAUMEE BASIN IN NW OHIO, AND COMPARISON TO THE PRESQUE ISLE FLYING SPIT

Smith, Courtney B. 24 August 2021 (has links)
No description available.
266

Stavební průzkum a diagnostika konstrukce / Survey and Diagnostics of Building Construction

Resl, Jaroslav January 2016 (has links)
The thesis is focused on the overview of the diagnostic methods for engineering surveys reinforced concrete constructions. The practical part explains engineering surveys of industrial building, evaluation of concrete strength on existing building and results from search reinforcements on individual elements. Next part is focused on load testing precast floor slab removed from construction and evaluation load capacity. The last part include structural design of elected parts (precast floor slab and beam).
267

Možnosti ERT a GPR pro analýzu polygonálních kryogenních struktur / Using ERT and GPR in polygonal patterned ground analysis

Široký, Jakub January 2014 (has links)
Polygonal cryogenic structures cannot be investigated with conventional methods as they could be harmed during measurement. A real3D GPR and ERT non-destructive surveys were used to examine and prove applicability for topsoil covered ice-wedge pseudomorphs and coarse-grained sorted polygons (patterned ground). A list of processing tools and algorithm suitable for such environments was created and tested. The benefits of 3D measurements are illustrated on horizontal slices and pseudo3D visualisation of 3D Cube. Basic morphometry characteristics of both forms were collected. Abilities of geophysical imaging for advanced shape characterisations are discussed, too. The low-frequency measurements gave better results at both sites. Pseudomorphs, 2 wide and up to 6,5 long, were found penetrating depth bigger than 3,5 . Sorted polygons, 2,5 wide in diameter, were depicted locked by stony ring of width around 1 . Sorting depth extends up to 0,54 depth for sure, perhaps more.
268

Non-Destructive Evaluation of the Condition of Subsurface Drainage in Pavement Using Ground Penetrating RADAR (GPR)

Hao Bai (5929478) 14 December 2020 (has links)
<div>Pavement drainage systems are one of the key drivers of pavement function and longevity, and effective drain maintenance can significantly extend a pavement's service life. Maintenance of these drains, however, is often hampered by the challenge of locating the drains. Ground Penetrating Radar (GPR) typically offers a rapid and effective method to detect these underground targets. However, typical detection schema that rely upon the observation of the hyperbolic return from a GPR scan of a buried conduit still tend to miss many of the older drains beneath pavements as they may be partially or fully filled with sediment and/or may be fabricated from clay or other earthen materials, yielding a return signal that is convolved with significant background noise. </div><div><br></div><div>To manage this challenge, this work puts forward an improved background noise and clutter reduction method to enhance the target signals in what amounts to a constructed environment that tends to have more consistent subsurface properties than one might encounter in a general setting. Within this technique, two major algorithms are employed. Algorithm 1 is the core of this method, and plays the role of reducing background noise and clutter. Algorithm 2 is supplementary, and helps eliminate anomalous discontinuous returns generated by the equipment itself, which could otherwise lead to false detection indications in the output of Algorithm 1. Instead of traditional 2-D GPR images, the result of the proposed algorithms is a 1-D plot along the survey line, highlighting a set of “points of interest” that could indicate buried drain locations identified at any given GPR operating frequency. Subsurface exploration using two different operating frequencies, 900 MHz and 400 MHz herein, is then employed to further enhance detection confidence. Points of interest are ultimately coded to define the confidence of the detection. Comparing the final result of proposed algorithms with the original GPR images, the improved algorithm is demonstrated to provide significantly improved detection results, and could potentially be applied to similar problems in other contexts.</div><div><br></div><div>Besides the background reduction methods, a group of simulations performed using GPRMAX2D software are examined to explore the influence of road cross-section designs on sub-pavement drainage conduit GPR signatures, and evaluate the effectiveness of alternate GPR antennae configurations in locating these buried conduits in different ground conditions. Two different models were explored to simulate conduit detection. In addition, different pipe and soil conditions were modeled, such as pipe size, pipe material, soil moisture level, and soil type. Four different quantitative measurements are used to analyze GPR performance based on different key factors. The four measurements are 1) signal to background ratio (SBR) in dB; 2) signal to receiver noise ratio (SNR) in dB; 3) signal energy in Volts; and 4) average signal band power in Watts.</div><div><br></div><div>The water and clay content of subsurface soil can significantly influence the detection results obtained from ground penetrating radar (GPR). Due to the variation of the material properties underground, the center frequency of transmitted GPR signals shifts to a lower range as wave attenuation increases. Examination of wave propagation in the subsurface employing an attenuation filter based on a linear system model shows that received GPR signals will be shifted to lower frequencies than those originally transmitted. The amount of the shift is controlled by a wave attenuation factor, which is determined by the dielectric constant, electric conductivity, and magnetic susceptibility of the transmitted medium. This work introduces a receiver-transmitter-receiver dual-frequency configuration for GPR that employs two operational frequencies for a given test - one higher and one slightly lower - to take advantage of this phenomenon to improve subpavement drain detection results. In this configuration, the original signal is transmitted from the higher frequency transmitter. After traveling through underground materials, the signal is received by two receivers with different frequencies. One of the receivers has the same higher center frequency as the transmitter, and the other receiver has a lower center frequency. This configuration can be expressed as Rx(low-frequency)-Tx(high-frequency)-Rx(high-frequency) and was applied in both laboratory experiments and field tests. Results are analyzed in the frequency domain to evaluate and compare the properties of the signal obtained by both receivers. The laboratory experiment used the configuration of Rx(400MHz)-Tx(900MHz)-Rx(900MHz). The field tests, in addition to the configuration used in the lab tests, employed another configuration of Rx(270MHz)-Tx(400MHz)-Rx(400MHz) to obtain more information about this phenomenon. Both lab and field test results illustrate the frequency-shift phenomenon described by theoretical calculations. Based on the power spectrum for each signal, the lower frequency antenna typically received more energy (higher density values) at its peak frequency than the higher frequency antenna.</div>
269

A Geophysical Study of Subsurface Paleokarst Features and Voids at Ohio Caverns, Champaign County, Ohio

Scaggs, Laura M. 09 June 2014 (has links)
No description available.
270

AI-Assisted Optimization Framework for Advanced EM Problems

Rosatti, Pietro 02 July 2024 (has links)
This thesis concerns the study, development and analysis of innovative artificial intelligence (AI)-driven optimization techniques within the System-by-Design (SbD) framework aimed at efficiently addressing the computational complexity inherent in advanced electromagnetic (EM) problems. By leveraging the available a-priori information as well as the proper integration of machine learning (ML) techniques with intelligent exploration strategies, the SbD paradigm enables the effective and reliable solution of the EM problem at hand, with user-defined performance and in a reasonable amount of time. The flexibility of the AI-driven SbD framework is demonstrated in practice with the implementation of two solution strategies to address the fully non-linear inverse scattering problem (ISP) for the detection and imaging of buried objects in ground penetrating radar (GPR)-based applications, and to address the design and optimization of mm-wave automotive radars that comply multiple challenging and contrasting requirements. A comprehensive set of numerical experiments is reported to demonstrate the efficacy and computational efficiency of the SbD-based optimization techniques in solving complex EM problems.

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