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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.
21

The Relationships of Streambank Angles and Shapes to Streambank Erosion Rates in the Little River Watershed, TN

Foster, William Ryan 01 August 2010 (has links)
Sediment is a leading cause of water quality impairment throughout the United States. In the Little River watershed in eastern Tennessee, several tributaries have been classified as impaired due primarily to sedimentation. Researchers at The University of Tennessee, in collaboration with a group of local and state organizations, began monitoring Little River tributaries to better understand their sources of pollution. To investigate the rates and processes of streambank erosion, erosion-pin monitoring sites were established on 32 banks in the watershed. This thesis complements the erosion-pin monitoring efforts by determining bank characteristics and examining the relationships of streambank angles and shapes to observed erosion rates. The specific objectives of this study were to: (1) characterize streambank angles, (2) describe the relationships between streambank angles and bank erosion rates, (3) characterize bank shape, and (4) determine if bank shapes at erosion-pin monitoring sites are representative of their immediate stream reaches. Streambank angles were measured at erosion pins. Bank angles averaged approximately 55° and varied significantly between tributaries and individual monitoring sites. Bank angle measurements were compared to erosion-pin exposure using correlation analysis. Data were then sorted into subgroups by pin position, soil texture, and bank shape, and further analyses were conducted. Results indicated streambank erosion was significantly, positively associated with bank angle for angles ≥ 30°. Significant, positive relationships were also found low on banks, where soil texture was clay, and where banks were classified as undercut. Bank profiles were documented to classify the bank shapes of erosion-pin monitoring sites and assess how well the banks at those sites represented the immediate reach. In the Little River watershed, bank profile shapes vary, but nearly three-fourths of all documented bank profiles were steeply sloping or undercut. The majority of monitoring sites (78%) were representative of the immediate stream reach with regard to bank shape. However, other factors, including surrounding land use and soil type, may differ within the immediate reach. Thus, data extrapolation from erosion pins to the reach scale should be done cautiously and take into consideration variability of individual site characteristics.
22

An Investigation of Stratigraphic Evidence for an Abrupt Climatic Event 8200 yr BP in Valle de las Morrenas, Costa Rica

Watson, Brian Thomas 01 May 2011 (has links)
Lago de las Morrenas 4 (9.498056° [degrees] N, 83.486111° [degrees] W, 3466 m elev.) is the lowest lake in a chain of glacial lakes located in the Valle de las Morrenas, a valley facing almost due north from Cerro Chirripó, the highest peak in the Cordillera de Talamanca in Costa Rica. Coarse resolution analyses of pollen, microscopic charcoal, and loss-on-ignition of a ca. 10,000 year sediment record from Lago de las Morrenas 4 was carried out to complement and extend previous research on the environmental history of the Chirripó highlands and to provide context for high-resolution sampling and analysis of early Holocene sediments. The focus of the high-resolution analysis was the period around 8200 cal yr BP, the time of a prominent Holocene climatic event recognized at many northern hemisphere sites between ca. 8000 and 8400 cal yr BP. The high-resolution sampling of sediments encompassing the time period of the 8200 yr BP event revealed a sharp increase in microscopic charcoal indices coincident with a shift from fibrous silty organic sediment to granular peat. These shifts, which occurred ca. 7900 cal yr BP, are interpreted to reflect an interval of drier climate and lower lake level. A decrease in Poaceae pollen percentages and an increase in Alnus pollen from montane forests may reflect reduced pollen production within the páramo at this time. The peak charcoal concentration and influx value at ca. 7800 cal yr BP in the Morrenas 4 record may match a similar peak in the macroscopic charcoal record from nearby Morrenas 1 that occurred ca. 8000 cal yr BP. Both peaks may correspond to the 8200 yr BP event.
23

Geografi på gott och ont : En studie om kriminella och polisens användning av geografiska förutsättningar

Srebrenikovic, Amir January 2009 (has links)
Undersökningen behandlar hur kriminella personer och polisen använder sig av geografiska förutsättningar i sina respektive verksamheter. Hur de först kartlägger objekt i sin omgivning för att sedan välja hur de ska agera. Kriminella personer och polisen undersöks för att visa hur aktörer, på olika sida om lagen, möter liknande geografiska förutsättningar fast upplever dem på olika sätt. Avslutningsvis återges deras inställning till att först kartlägga objekt i sin omgivning innan de agerar. Undersökningen skildrar hur aktörer subjektivt upplever objektiva föremål i sin omgivning på olika sätt, beroende på deras avsikter.  Kriminella personer planerar ett brott genom att först kartlägga sin omgivning. Det leder till att de sedan kan avgöra hur de ska agera på brottsplatsen. De beger sig till brottsplatsen en tid innan brottet ska utföras. På brottsplatsen undersöker de människors dagliga rutiner och hur objekt som exempelvis byggnader är placerade, för att kunna underlätta deras brott.  De kriminella har angett vilken tid på dygnet ett brott är som mest gynnsamt för dem. Om de inte kan utföra ett brott under en särskild tid ökar risken för att gripas. Objekt i en omgivning kan skapa tillfällen och försvåra för kriminella att genomföra brott. Deras erfarenhet bidrar till att hitta tillfällen som lämpar sig för brott i en omgivning. Svårigheter anser de vara andra människor som befinner sig på en brottsplats och väderförhållanden. I polisens arbete kartläggs objekt i omgivningen utförligt, eftersom de inte vill riskera att skada andra poliser, misstänkta eller allmänheten, när de ska agera i arbetet. På en brottsplats försöker de säkra bevismaterial beroende på brottsplatsens förutsättningar. Polisen vill göra ett gripande på säkrast möjliga sätt, i annat fall kan en polisaktion komma att avbrytas. Det kan handla om att gripa en misstänkt under en särskild tid på dygnet. Under ett spaningsarbete ska enskilda poliser själva kartlägga sin omgivning och avgöra hur en förflyttning ska ske. Polisspanare måste ständigt förnya och omvärdera sin omgivning. Både polisen och kriminella anser att de inte kan utföra respektive arbete utan att först ta hänsyn åt de objekt som finns i en omgivning. De resonerar om varandras agerande och uppfattar liknande objekt i omgivningen. Dessa upplever de sedan på olika sätt, till följd av deras avsikter i arbetet.
24

Comparison of Topographic Surveying Techniques in Streams

Bangen, Sara G. 01 May 2013 (has links)
Fine-scale resolution digital elevation models (DEMs) created from data collected using high precision instruments have become ubiquitous in fluvial geomorphology. They permit a diverse range of spatially explicit analyses including hydraulic modeling, habitat modeling and geomorphic change detection. Yet, the intercomparison of survey technologies across a diverse range of wadeable stream habitats has not yet been examined. Additionally, we lack an understanding regarding the precision of DEMs derived from ground-based surveys conducted by different, and inherently subjective, observers. This thesis addresses current knowledge gaps with the objectives i) to intercompare survey techniques for characterizing instream topography, and ii) to characterize observer variability in instream topographic surveys. To address objective i, we used total station (TS), real-time kinematic (rtk) GPS, terrestrial laser scanner (TLS), and infrared airborne laser scanning (ALS) topographic data from six sites of varying complexity in the Lemhi River Basin, Idaho. The accuracy of derived bare earth DEMs was evaluated relative to higher precision TS point data. Significant DEM discrepancies between pairwise techniques were calculated using propagated DEM errors thresholded at a 95% confidence interval. Mean discrepancies between TS and rtkGPS DEMs were relatively low (≤ 0.05 m), yet TS data collection time was up to 2.4 times longer than rtkGPS. ALS DEMs had lower accuracy than TS or rtkGPS DEMs, but ALS aerial coverage and floodplain topographic representation was superior to all other techniques. The TLS bare earth DEM accuracy and precision were lower than other techniques as a result of vegetation returns misinterpreted as ground returns. To address objective ii, we used a case study where seven field crews surveyed the same six sites to quantify the magnitude and effect of observer variability on DEMs interpolated from the survey data. We modeled two geomorphic change scenarios and calculated net erosion and deposition volumes at a 95% confidence interval. We observed several large magnitude elevation discrepancies across crews, however many of these i) tended to be highly localized, ii) were due to systematic errors, iii) did not significantly affect DEM-derived metric precision, and iv) can be corrected post-hoc.
25

"Månen är på semester"- En undersökning om barns föreställningar om jorden, månen och solen / "The moon is on vacation"- A study about childs conceptions about the earth, the moon and the sun

Åhman, Linn January 2003 (has links)
Syftet med denna studie var att undersöka vad elever har för uppfattningar om förhållandena mellan jorden, månen och solen. De områden somhar undersökts har gällt storlek, avstånd och rörelse. Denna studie har också undersökt hur elever uppfattar att månens faser uppkommer. Försök har också gjorts att utröna var deras uppfattningar härrör från. Undersökningen är baserad på 20 intervjuer med elever där deras egna teckningar av de undersökta fenomenen har utgjort grunden. Genom en kvalitativ fenomenografisk analys av intervjuerna har jag kategoriserat elevernas uppfattningar. Resultatet visar att elevernas uppfattningar ofta skiljer sig från den vedertagna vetenskapliga och att deras uppfattningar grundar sig på bilder eller modeller från TV och böcker, där förhållandena mellan objekten aldrig är de riktiga. Även om elever har haft undervisning i skolan så har de kvar sina egna föreställningar. Det visar sig också att det finns ett klart samband mellan elevernas intresse och deras resultat. / The main purpose with this study was to explore students conceptions about the relations between the earth, the sun and the moon. The fields that have been investigated are size, distance and movement. This study has also investigated how students interpret the origin of the phases of the moon. Attempts have been made to find out where the students conceptions originate from. The study is based on 20 interviews with students where their own pictures about the investigated phenomena are the base. By doing a qualitative phenomenographical analysis of these interviews I’ve done categories of the students conceptions. The result shows that students conceptions often differs from the accepted scientific and that their conceptions are a result of pictures and models from TV and books, where the relations between the objects never are the real. Even if the students have had education they still keep on to their own conceptions. It also shows that there are a distinct connection between the students interest and their result.
26

Geovetenskapliga värden i infrastrukturplanering

Sjölund, Elisabeth January 2013 (has links)
Länge har landskapets alla olika processer påverkat och påverkar landskapets utseende och utveckling. Landskapet är i en ständig naturlig förändring, en förändring som är kontinuerlig i tid och rum. Dess strukturer och former är ofta idag avlagringar från istider och processer som skedde för länge sedan och har genom dessa hjälpt människan förstå jordens utveckling. Människan är villkorslöst beroende av landskapet med dess resurser och utnyttjar dem i en allt större utsträckning. Många av resurserna vi utnyttjar har alla sin grund i landskapets geologi. Människans påverkan på landskapet är så pass stor att landskapet med alla dess former och avlagringar hotas om de inte beaktas. För att effektiv kunna anpassa brukande och annan användning av naturens resurser krävs förståelse för landskapets grundstrukturer, geologiska processer och deras resultat. För att i framtiden fortsätta kunna ha kännedom om landskapets bildning och historia och andra samhällsrelevanta faktorer som miljö och vatten är det viktigt att införa de geovetenskapliga värdena i all slags samhällsplanering. När geovetenskapliga värden glöms bort och enbart natur, kultur, friluftslivsvärden etc. sätts i fokus var för sig, förloras helhetssynen. Eftersom de geovetenskapliga värdena är en förutsättning för dessa värden är de ett viktig, idag nästan outnyttjat verktyg för att sammanfoga sektoriella värden till en helhetssyn. I denna studie har en vägplanering valts ut för att illustrera denna brist, där en inventering av studieområdet samt en analys av den valda vägplaneringens rapporter och miljökonsekvensbeskrivningen gjorts. Studien visar att man beaktar värden sektoriellt och oftast objekt för objekt. Helhetssynen på landskapet saknas nästan helt. De geovetenskapliga egenvärdena beaktas inte alls och det verktyg för helhetssyn som geovetenskapen erbjuder används inte alls. / Landscape processes such as erosion and weathering have for very long time shaped and reshaped the landscape. The continuously natural changes of the landscape will never stop. Today its structures and shapes are historical deposits and have helped humans to understand Earth’s history. Humans are unconditionally dependent on Earth’s resources and will continue being so for an unforeseeable future. Human development such as infrastructure alters an unnatural landscape where the natural landscape with all its forms and deposits are threatened to disappear if not protected from exploitation. To continuing understanding Earth’s history in the future and to developing ecological areas, it’s important to introduce the geological values in all types of society planning. When geological values are forgotten or disregarded and ecological values get the majority of attention you loose the bigger picture. Instead a more holistic view is needed that accounts for all natural values. In this study, a path plan has been selected to illustrate this short supply, where an inventory of the study area and an analysis of the selected path plan’s reports and environmental impact assessment have been made. The results from the study indicate that objects are considered object by object and observe the geoscientific values ​​more durable and it’s often unclear how the geological values are affected.
27

Introducing Lantmäteriet’s gravity data in ArcGIS with implementation of customized GIS functions

Ryttberg, Mattias January 2013 (has links)
Gravity is measured and used by Lantmäteriet to calculate a model of the geoid to get accurate reference heights for positioning. Lantmäteriet are continuously measuring new gravity and height data across Sweden to both complement, replace and to add new data points. This is mainly done by measurements in the field at benchmark points. One of the major reasons for continued measurements on e.g. benchmark points is that the measuring always moves forward which makes the measurements more accurate. More accurate data leads to a more accurate calculation of the geoid due to the more accurate gravity values. A more accurate geoid gives the possibility of more precise positioning across Sweden, due to the more precise height values. Lantmäteriet is in the process of updating their entire database of gravity data. They are also measuring at locations where there are none or sparse with measurements. As a stage in the renewing of their database and other systems the Geodesy department wishes to get an introduction to the ArcGIS environment. By customizations of several ArcGIS functions, Lantmäteriet’s work with the extensive data will get easier and perhaps faster. Customized tools will help make e. g. adding and removing data points easier, as well as making cross validation and several other functions only a click of a button away.
28

"Månen är på semester"- En undersökning om barns föreställningar om jorden, månen och solen / "The moon is on vacation"- A study about childs conceptions about the earth, the moon and the sun

Åhman, Linn January 2003 (has links)
<p>Syftet med denna studie var att undersöka vad elever har för uppfattningar om förhållandena mellan jorden, månen och solen. De områden somhar undersökts har gällt storlek, avstånd och rörelse. Denna studie har också undersökt hur elever uppfattar att månens faser uppkommer. Försök har också gjorts att utröna var deras uppfattningar härrör från. Undersökningen är baserad på 20 intervjuer med elever där deras egna teckningar av de undersökta fenomenen har utgjort grunden. Genom en kvalitativ fenomenografisk analys av intervjuerna har jag kategoriserat elevernas uppfattningar. </p><p>Resultatet visar att elevernas uppfattningar ofta skiljer sig från den vedertagna vetenskapliga och att deras uppfattningar grundar sig på bilder eller modeller från TV och böcker, där förhållandena mellan objekten aldrig är de riktiga. Även om elever har haft undervisning i skolan så har de kvar sina egna föreställningar. Det visar sig också att det finns ett klart samband mellan elevernas intresse och deras resultat.</p> / <p>The main purpose with this study was to explore students conceptions about the relations between the earth, the sun and the moon. The fields that have been investigated are size, distance and movement. This study has also investigated how students interpret the origin of the phases of the moon. Attempts have been made to find out where the students conceptions originate from. The study is based on 20 interviews with students where their own pictures about the investigated phenomena are the base. By doing a qualitative phenomenographical analysis of these interviews I’ve done categories of the students conceptions. </p><p>The result shows that students conceptions often differs from the accepted scientific and that their conceptions are a result of pictures and models from TV and books, where the relations between the objects never are the real. Even if the students have had education they still keep on to their own conceptions. It also shows that there are a distinct connection between the students interest and their result. </p>
29

The Relationships of Streambank Angles and Shapes to Streambank Erosion Rates in the Little River Watershed, TN

Foster, William Ryan 01 August 2010 (has links)
Sediment is a leading cause of water quality impairment throughout the United States. In the Little River watershed in eastern Tennessee, several tributaries have been classified as impaired due primarily to sedimentation. Researchers at The University of Tennessee, in collaboration with a group of local and state organizations, began monitoring Little River tributaries to better understand their sources of pollution. To investigate the rates and processes of streambank erosion, erosion-pin monitoring sites were established on 32 banks in the watershed. This thesis complements the erosion-pin monitoring efforts by determining bank characteristics and examining the relationships of streambank angles and shapes to observed erosion rates. The specific objectives of this study were to: (1) characterize streambank angles, (2) describe the relationships between streambank angles and bank erosion rates, (3) characterize bank shape, and (4) determine if bank shapes at erosion-pin monitoring sites are representative of their immediate stream reaches. Streambank angles were measured at erosion pins. Bank angles averaged approximately 55° and varied significantly between tributaries and individual monitoring sites. Bank angle measurements were compared to erosion-pin exposure using correlation analysis. Data were then sorted into subgroups by pin position, soil texture, and bank shape, and further analyses were conducted. Results indicated streambank erosion was significantly, positively associated with bank angle for angles ≥ 30°. Significant, positive relationships were also found low on banks, where soil texture was clay, and where banks were classified as undercut.Bank profiles were documented to classify the bank shapes of erosion-pin monitoring sites and assess how well the banks at those sites represented the immediate reach. In the Little River watershed, bank profile shapes vary, but nearly three-fourths of all documented bank profiles were steeply sloping or undercut. The majority of monitoring sites (78%) were representative of the immediate stream reach with regard to bank shape. However, other factors, including surrounding land use and soil type, may differ within the immediate reach. Thus, data extrapolation from erosion pins to the reach scale should be done cautiously and take into consideration variability of individual site characteristics.
30

Long-Range, Passive Wireless Monitoring Using Energy-Efficient, Electrically-Small Sensor Nodes and Harmonic Radar Interrogator

Nassar, Ibrahim 01 January 2013 (has links)
This dissertation investigates the use of the harmonic radar technique for passive wireless sensing applications. Issues of DC power consumption, high RF activation power, large node size, and short communication range associated with the existing passive wireless sensing technologies are addressed by the development of novel, completely passive, high efficiency, compact 3-D harmonic sensor nodes. The node transceiver employs a passive frequency doubler to return the second harmonic of the interrogation signal, and electrically-small 3-D antennas to achieve the compactness and high efficiency. The developed nodes fit inside a sphere with a diameter < 3 cm and achieve communication range > 60 m using a 43 dBm EIRP interrogator. Effective modulation is demonstrated experimentally using low cost commercial vibration sensors. To address major challenges associated with long-range, embedded, passive wireless sensing including sensor node identification and remote channel calibration, a 3-D dual-channel transceiver is developed. To the best of the author's knowledge, the presented dual-channel transceiver is the first completely passive design with built-in passive remote channel calibration and identification capabilities, and the presented nodes have the best overall performance among previously published designs, in terms of conversion efficiency, communication range, and occupied volume. To reduce the cost and weight and improve the manufacturing process of the proposed nodes, the 3-D digital additive manufacturing and conformal direct printing technologies are employed. The harmonic interrogator antenna design is also an underlying focus of this work. Different interrogator antenna candidates are developed based on different design approaches. The first approach is based on the use of dual-channel antenna array, where one channel is used for transmission and the second channel is used for reception. Two dual-channel harmonic interrogator antennas that consist of 4-element circular patch antenna arrays and 2-element quasi-Yagi dipole antenna arrays are implemented. The second approach employs mechanically reconfigurable antennas to reduce the size and maintain persistent radiation properties over wide frequency bandwidth. Two mechanical reconfiguration methods are developed; the first method is based on the use of Hoberman's planar foldable linkage to vary the operating frequency of planar circular patch antennas and the second mechanical reconfiguration method is based on the use of a rack and pinion mechanism to reconfigure dual-band slot antennas. The third approach employs a single channel multi-octave Vivaldi antenna to provide the capability to interrogate a large number of harmonic tags that are widely spaced in frequency. To improve the antenna radiation performance over a broad frequency range, a new method based on the introduction of a parasitic elliptical patch in the flare aperture is proposed. This method enables gain and bandwidth improvement compared to what has been reported for Vivaldi antennas with a compact size. To provide the interrogator the capability to steer the radiation beam for locating and tracking sensor nodes, a topology to develop a miniature, non-dispersive switchable 4-bit phase shifter is proposed on the basis of composite right/left handed transmission line unit cells.

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