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The non-destructive measurement of the radio frequency properties of hard rock borehole coresRutschlin, Marc January 2005 (has links)
Thesis (PhD) -- Stellenbosch University, 2005. / ENGLISH ABSTRACT: The effective use of borehole radar in geophysical exploration requires accurate knowledge of the dielectric
properties of the geological system in which it is employed. The attenuation and propagation velocity
of pulses through rock must be known in order to plan and interpret experimental data. Conventional
destructive methods for the measurement of hard rock cores require the careful preparation of samples.
This firstly necessitates the selection of sampling position and the resulting estimation of rock properties
based on sparse measurements, and secondly results in the loss of material and thus data.
The ready availability of cylindrical borehole core samples invites the use of a nondestructive means
of measuring their properties. A novel design for a flexible guarded capacitor which conforms to a
core's cylindrical surface is presented here. T he proposed device has numerous advantages over previous
methods. No material is lost to sample preparation and a detailed characterisation of the entire core,
including inclusions and transitions between rock types, may be performed.
A detailed methodology for the rapid construction of a robust capacitor is given. Guidelines for its
operation to achieve repeatable and accurate measurements of the complex dielectric constant of samples
of varying homogeneity in the 1- 25 MHz frequency range are presented.
The increased amount of data collected from complete core samples is analysed statistically, and
amongst other things allows the estimation of the rock's homogeneity. Comparisons of the dielectric
properties measured in the laboratory to propagation velocity estimates obtained from crosshole borehole
shoots show that a more homogeneous sample is a better predictor of bulk propagating conditions.
Detailed studies of the dielectric properties of economically important diamondiferous and platiniferous
geological systems show that borehole radar is a feasible tool for the high resolution delineation of ore
bodies and other geological targets. / AFRIKAANSE OPSOMMING: Die effektiewe gebruik van boorgatradar in geofisiese eksplorasie benodig akkurate kennis van die dielektriese
eienskappe van die geologiese sisteme waarin dit gebruik word. Kennis van die verswakking en voortplantingsnelheid
van pulse deur die rots word benodig om eksperimente te beplan en gemete data te
interpret eer. Vir konvensionele destruktiewe meetmetodes van harde rotskerne is noukeurige voorbereiding
van monsters noodsaaklik. Hierdie proses vereis eerstens 'n keuse van meetposisies en die afskatting
van rotseienskappe gebaseer op verspreide metings, en lei tweedens tot die verlies van materiaal en dus
data.
Die beskikbaarheid van silindriese bom·gat kernmonsters maak dit moontlik om die kerneienskappe
op n nie-destruktiewe manier te meet. Die ontwerp van 'n nuwe buigbare afgeskermde kapasitor wat
op 'n silindriese kernoppervlak pas, word hier voorgestel. Die toestel het verskeie voordele bo huidige
metodes. Geen materiaal word gedurende monstervoorbereiding verloor nie, en 'n volledige beskywing
van die eienskappe van die hele kern , met insluitings en oorgange tussen rotstipes, kan verkry word.
'n Gedetaileerde prosedure vir die vinnige konstruksie van 'n robuuste kapasitor word gegee. Die
gebruik van die toestel vir herhaalbare en akkurate metings van die komplekse dielektriese konstante van
verskillend homogene monsters in die 1- 25 MHz frekwensie bereik word beskryf.
Die groter hoeveelheid data wat deur middel van hierdie metode van hele kernmonsters verkry kan
word , word statisties geanaliseer, en laat onder andere 'n skatting van die rots se homogeniteit toe.
Vergelykings van laboratoriumgemete rotseienskappe met veldskattings van voortplant ingsnelhede wys
dat 'n meer homogene monster tot 'n beter afskatting van werklike voortplantingstoestande lei. Studies
van die dielektriese eienskappe van ekonomies belangrike diamanthoudende en platinumryk geologiese
sisteme wys dat boorgatradar geskik is vir hoe resolusie uitkenning van ertsligame en ander geologiese
teikens.
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Snow Interception Measurements using Impulse Radar / Snöinterceptionsmätningar med impulsradarMagnusson, Jan January 2006 (has links)
<p>Interception av snö eller regn på trädkronor är en viktig del av det hydrologiska kretsloppet. Upp till en tredjedel av all snö som faller över skogsområden når aldrig marken på grund av stora avdunstningsförluster av interceptionsförrådet, vilket minskar vårflöden i älvar. Goda prognoser av dessa flöden är viktiga för vattenkraftsindustrin. För att kunna förbättra modeller, i vilka interceptions-avdunstningsprocessen ingår, krävs lämpliga mätmetoder för interceptionförrådet av snö. Syftet med detta arbete var att undersöka om impulsradarutrustning kan användas för att mäta interceptionsförrådet av snö på barrträd. Metoden bygger på att mäta hastigheten och utsläckningen hos en elektromagnetisk impulsvåg, vilken skickas från en sändarantenn genom ett avsnitt skog till en mottagarantenn. Både utsläckningen och hastigheten påverkas av snö och vatten på trädens kronor, och kan med så kallade blandningsformler relateras till mängd vatten. Blandningsformler beskriver de elektromagnetiska egenskaperna hos heterogena material. Laboratorietester visade att interception av flytande vatten på små trädkronor gav upphov till förändringar av impulsvågens hastighet och utsläckning mätbara med radarutrustningen. Uppskattningar av mängden intercepterat vatten från radarmätningarna gav en överskattning jämfört med oberoende referensmätningar, däremot stämde relativa variationer väl överens mellan mätningarna. Tydliga samband mellan impulsvågens utsläckning och mängden intercepterat vatten kunde inte bestämmas från experimenten. Utsläckningsresultaten var svårtolkade och lämpliga blandningsformler hittades inte i litteraturen. Metoden testades även en vecka i fält i norra Sverige. Trots att installationen inte var den bästa visade resultaten ändå god överensstämmelse mellan uppskattade förändringar av interceptionsförrådet från radarmätningarna, och observerade väderförändringar samt oberoende referensmätningar med en trädvågsanordning. Resultaten tyder på att metoden kan ge goda uppskattningar av interceptionsförrådet, då en väl fungerande installation av utrustningen används och efter att vidare kalibreringsförsök genomförts.</p> / <p>Interception of rain or snow in forest canopies is an important component of the hydrological cycle. Up to one third of the total winter precipitation never reaches the ground in forest areas due to evaporation losses of intercepted snow, which reduces spring-time water flow in rivers. Accurate spring flow predictions are important for the hydro-power industry. Appropriate measurement methods of intercepted snow are needed in order to improve models involving the interception evaporation process. The aim of this study was to explore the possibilities of an impulse radar system to measure the snow interception storage on coniferous trees. The method is based on measurements of the velocity and attenuation of an electromagnetic impulse wave, generated in a transmitting antenna and sent through a forest section and detected by a receiving antenna. The attenuation and velocity is affected by ice and water in the canopy air space, and can be related to amounts of water using so-called mixing formulas that describe the average electromagnetic properties of heterogeneous materials. Controlled laboratory measurements on small canopies showed that interception of liquid water was well above the detectable limits of the radar system, with respect to both attenuation and velocity changes. Estimations of the mass of intercepted water based on velocity changes overestimated the reference measurements, but relative variations were well captured. No clear relation could be found between amount of water on canopies and impulse wave attenuation from the experiments. The attenuation results were difficult to interpret, and appropriate mixing formulas were not found in the literature. The method was further tested for one week under field conditions in northern Sweden. In spite of a non-optimal equipment installation results of estimated changes of the interception storage showed a good agreement with observed weather variations and reference measurements using a tree weighing device. The method can have good conditions to give correct estimations of the snow interception storage, using appropriate installation and further calibration measurements.</p>
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Broadband counter-wound helix antenna for land mine detectionShivandas, Dilipkumar 03 1900 (has links)
Approved for public release, distribution is unlimited. / Ground penetrating radars (GPRs), also known as subsurface radars, are used in many applications including detection of land mines and unexploded ordnance (UXO). Despite significant long-term investment in GPRs for mine and UXO detection, it remains true that no GPR system that meets operational requirements has yet been fielded; however, recent advances in several mine detection radars under development have produced significant improvements in detection performance and false-alarm mitigation over what was achievable only a few years ago. This research examines the suitability of modeling helical antennas to achieve a broadband characteristic for GPR implementation. Although the two-arm counter-wound helix provides the required spot illumination, it is expected that more arms may have to be added to reduce the radiation in the back direction and to match the input impedance to the feed line. Microwave Design Studio (MDS) has been used extensively to simulate the broadband characteristics of the helical antenna. An overall design strategy is outlined, together with a more detailed treatment of the ground penetrating radar subsystems and topics that are relevant to effective subsurface radar operation. These include soil characterization, the choice of the frequency of operation, as well as the design and construction of suitable helical antennas. Finally, a new antenna structure called the counter-wound quadrifilar helical antenna (CQHA), which is suitable for subsurface radar applications, is examined. The counter-wound quadrifilar helical antenna has a broad bandwidth and a linear polarization with a controllable plane of polarization from a planar geometry. / Major, Republic of Singapore Air Force
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Mapping the Fresh-Saltwater Transition Zone Across the Beach Environment Using Ground-Penetrating Radar (GPR)Unknown Date (has links)
As sea level rises, saltwater migration can threaten coastal ecosystems and beach-dune environments, which negatively impacts coastal flora. This study uses ground penetrating radar (GPR) to evaluate the spatiotemporal variability of saltwater migration in the near shore at high lateral resolution (i.e. cm) by using daily micro tidal cycles as analogs to infer saltwater migration. Time-lapse GPR profiles were collected at low and high tide capturing phase lags of the tidal flux through different substrates. GPR measurements were collected at two sites in Miami with contrasting lithologies: a) Crandon Park, composed of unconsolidated sand; and b) the Barnacle Historic State Park, composed of the Miami Limestone Formation. Laboratory-scale GPR measurements were collected over samples mimicking field conditions. The results may be helpful to identify regions vulnerable to saltwater migration in the near shore based on lithological variability, and to mitigate negative impacts for flora in beach-dune habitats during sea level rise. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection
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Experimental studies of electromagnetic signals to enhance radio imaging method (RIM)Monaghan, William D. January 2007 (has links)
Thesis (M.S)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xi, 104 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 69-70).
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Autonomous unmanned ground vehicle for non-destructive testing of fiber reinforced polymer bridge decksMercer, Anthony Scott. January 2006 (has links)
Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains x, 100 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 83-86).
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Investigations of rc-loaded bow-tie antennas for impulse ground penetrating radar applicationsSu, Hong 19 September 2006 (has links)
This thesis reports on the investigations of resistive-capacitive (RC) loaded bow-tie antennas with special emphasis on impulse ground penetrating radar applications. Impulse radiation for ground penetrating radar is a challenging research topic because of the unique problem arising from impulse radiation: late-time ringing, which usually masks the important echo signals from the targets. While resistive loading is a common solution for eliminating late-time ringing, use of resistive loading typically sacrifices the radiation efficiency. In this thesis, a resistive-capacitive loading technique is investigated for a circular bow-tie antenna in the attempt to reduce/suppress the late-time ringing as well as to maintain a relatively high radiation efficiency. To implement the system, a microstrip differentiator, which converts a monopulse into a Gaussian-like monocycle to be used as input impulse, is presented. Further, specially designed coplanar waveguide/coplanar strip (CPW/CPS) baluns embedded with Chebyshev transformers of characteristic impedance up to 120 have been constructed and tested. To evaluate the system, instead of using the conventional peak voltage value of the radiated waveform, average radiated energy, average ringing energy, relative radiation efficiency and relative ringing efficiency are utilized and these metrics are easily established using low-cost low-sensitivity probes. Measurement results show that the RC-loading scheme is functioning as expected and the impulse system as a whole is capable of reducing the late-time ringing energy to 50% while maintaining average radiation energy as 83% when compared with capacitive loading cases. / October 2006
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Ground penetrating radar technique to locate coal mining related features: case studies in TexasSave, Neelambari R 12 April 2006 (has links)
The goal of this research project is to identify the efficacy of the ground
penetrating radar (GPR) technique in locating underground coal mine related subsidence
features at Malakoff and Bastrop, Texas. The work at Malakoff has been done in
collaboration with the Railroad Commission of Texas (RRC). RRC has been carrying
out reclamation of abandoned underground coal mines at Malakoff since the early
1990Âs. The history of the specific mining operations (at Malakoff and Bastrop) that
took place in the early 1900Âs has been difficult to ascertain; therefore, the use of a
geophysical techniques like ground penetrating radar to identify hidden voids and
potential subsidence features is vital for future reclamation process. Some of the
underground mine workings at the field site have collapsed over time affecting the
topography by creating sinkholes. GPR data, employing 25 MHz, 50 MHz and 100
MHz frequency antennae, have been collected in common offset patterns and azimuthal
pattern. GPR data indicate the mine tunnels possibly connecting existing sinkholes by
radargram hyperbolae that correspond with mine openings observed visually or during
reclamation. This study also denotes the importance of understanding the variable
physical properties of the stratigraphy, which could lead to false alarms by
misinterpretation of the radar signals. Natural and man-made above-ground structures
cause obstructions in data collection, and hence an optimal design is required for each
survey. RRC successfully ground-truthed the data during its reclamation process. In
turn, the acquired geophysical data helped to guide the reclamation. At Bastrop, GPR
data along with historical documentation led to the conclusion that coal mining did exist
in this region but is not a major concern to the immediate stability and safety of the field
site. It can be concluded from both the studies that the GPR technique identifies
anomalous shafts/tunnels possibly connecting potential failure.
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Hydrogeologic characterization of fractured carbonate aquifers employing ground-penetrating radar /Tsoflias, Georgios Padelis, January 1999 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 91-95). Available also in a digital version from Dissertation Abstracts.
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Distribution of beaver impacted peatlands in the Rocky Mountains2013 December 1900 (has links)
Peatlands provide a variety of ecosystem services including carbon sequestration, nutrient cycling and increased biodiversity, and are thus an important Canadian natural resource. Mountain peatlands, including those in the foothill region of the Canadian Rockies are particularly important due to their proximity to headwater streams which supply the Prairie Provinces with water. Yet, distribution of peatlands in the Canadian Rocky Mountains is unknown. There is also a lack of understanding of the form of these peatlands and the processes influencing them. The purpose of this research is to improve our understanding of Canadian mountain peatlands in terms of their abundance, distribution and subsurface form. Specific objectives are to: determine the distribution of beaver impacted wetlands in the study area; quantify the proportion of these which are peatlands; determine the impact beaver have on one hydrological variable, the area of open water and; describe the stratigraphy of peatlands with beaver at their surface. Beaver impacted wetland distribution was assessed through manual analysis of georeferenced aerial photographs. Combining these data with an existing GIS layer provided the basis of a wetland inventory of the region, allowing wetlands to be separately inventoried by physiographic location (Mountain and Foothills) and jurisdiction (Alberta Parks, Municipal Districts, Improvement Districts and First Nations Reserve). Approximately 75% of wetlands are located in the Foothills and Municipal District areas. Beaver impact is evident in 30% of the 529 wetlands inventoried, with the highest number in protected areas. Area of open water on wetlands, as assessed by manual analysis of aerial photographs, indicated that beaver impacted sites have on average approximately ten times more open surface water area than non- beaver impacted sites. In total, 81 wetlands were ground-truthed of which 77% were peat-forming wetlands or peatlands. Ground penetrating radar surveys and soil coring performed at 9 peatlands with beaver activity at their surface showed structural differences from those peatlands for which ecosystem services are described in the literature in that they are stratigraphically complex. Little is known about the factors affecting how this form develops, and this requires further study. The distribution of peatlands in the study area highlights them as important landscape units, and that in order to best manage them, further research is required into the various influences on their hydrological and ecological function.
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