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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.
961

Investigating Sand Dune Location, Orientation and Geomorphometry Through GEOBIA-Based Mapping: A Case Study in Northern Sweden / En undersökning av rumslig förekomst, orientering och morfometri hos fossila sanddyner genom GEOBIA-baserad kartläggning: en fallstudie i norra Sverige

Stammler, Melanie January 2020 (has links)
Climate change has repeatedly been framed as the defining issue of the Anthropocene and with the Arctic changing at unpreceded speed need is high for a profound understanding of the Northern Swedish landscape. Northern Swedish aeolian sand dunes have been impacted by climatic changes throughout time. Their location, orientation and geomorphometry can therefore be used to explore past wind patterns and dune activity. By systematically and spatially mapping the dunes, patterns in location can be illustrated, dune orientations investigated, the dunes’ geomorphometry characterised and sediment sources determined. Based on this knowledge, insight in landscape development along with a better understanding of long-term landscape (in)stability in Northern Sweden can be gained. This M. Sc. thesis sets out to summarize useful concepts to understand the formation of Northern Swedish aeolian sand dunes and to derive its implications for understanding landscape development. Based thereon, it deduces the strong need to systematically and spatially analyse aeolian sand dunes in Northern Sweden. The use of geographic object-based image analysis (GEOBIA) allows for the detection of potential dune locations over a large area and provides defined and reproducible mapping boundaries. Polygons are created by segmenting a residual-relief separated digital elevation model (DEM) as well as slope and curvature data. The multi-resolution segmentation provides best results with a scale parameter of 15 and a homogeneity criterion of 0.1 for the shape criterion, as well as 0.5 for the compactness criterion. A rule-based classification with empirically derived parameters accepts on average 2.5 % of the segmented image objects as potential dune sites. Subsequent expert-decision confirms on average 25 % of the classified image objects as identified dune locations. The rule-based classification provides best results when targeting a smaller area as this allows for less variability within the dune characteristics. The investigation of expert-accepted dune locations confirms a prevalence of parabolic dune forms, reveals the coexistence of simple dunes with large coalesced systems, exemplifies variation in dune orientation and highlights that the majority of dunes are supplied by glaciofluvial deposits. By mapping Northern Swedish aeolian sand dunes and investigating their meaning for landscape development, this thesis furthermore contributes to closing the gap identified for research on Northern Swedish aeolian sand dunes. / Den första associationen till sanddyner är säkert Sahara snarare än norra Sverige. Ändå är dessa fossila sanddyner också mycket relevanta och intressanta att studera. De kan analyseras i samband med det omgivande landskapet och dess orientering. Dessa egenskaper hjälper till att identifiera mönster i landskapsutveckling. Detta och på grund av dynarnas relativt gamla ålder kan slutsatser om landskapets (in)stabilitet på geologiska tidsskalor dras. Detta är mycket användbart eftersom det kan ge insikter om hur klimatet såg ut under tiden som sanddynerna bildades - perioder där människor ännu inte har bevittnat klimatet. Kunskap som till exempel hur klimatet som rådde för länge sedan såg ut kan användas bland annat för att uppskatta hur landskapet kommer förändras i framtiden till följd av klimatförändringar. Trots dessa användbara egenskaper hos sanddynerna har lite forskning gjorts hittills. Det här examensarbet försöker motverka detta kunskapsgap och kartlägger sanddyner i norra Sverige med hjälp av geografisk objektbaserad bildanalys (geographic object-based image analysis, GEOBIA). Det innebär att bildmaterial och digitala höjdmodeller frigjorda från vegetation automatiskt analyseras med hjälp av algoritmer. Fokus här är inte på att analysera enskilda pixlar. Snarare grupperas pixlar med liknande egenskaper så som lutning (slope), krökning (curvature) och spektralegenskaper. Dessa blir sedan grunden för analysen. Möjliga sanddyner upptäcks semi-automatiskt så att deras position och orientering sedan kan analyseras. Den kunskap som erhållits på detta sätt utgör grunden för vidare forskning. Ett annat mål är att bidra till en djupare förståelse kring landskapsutvecklingen i norra Sverige. Det är viktigt att komma ihåg att detta är ett område som särskilt påverkas av klimatförändringar. En ökad kunskap om landskapets tidigare klimatrespons kan därmed bidra till att förutsäga framtiden för denna region. Förutom att öka kunskapen kring sanddyner i norra Sverige hjälper det här mastersarbetet även till att utvidga användningen av GEOBIA inom geomorfologiska studier.
962

Utredning av avloppsprocessers påverkan på recipientens mikrobiologiska status / Investigation of sewage processes impact on the microbiological status of the recipient

Arvidsson, Diana January 2019 (has links)
Ett avloppsvatten innehåller olika föroreningar som påverkar recipientens vattenkvalitet. En förorening somreningsverken inte är optimerade för att reducera är mikroorganismer, som i recipienten påverkar bland annatbadvattenkvalitén. Syftet med examensarbetet var att ta reda på hur utvalda processteg i ett reningsverkpåverkar utgående halter av mikroorganismer, hur utsläppen av mikroorganismer kan övervakas och hur mikroorganismernapåverkar recipientens badvattenkvalitet. Examensarbetet har uppfyllt syftet genom att undersökahur biologiska reningssteg reducerar indikatororganismerna E.coli och intestinala enterokocker jämfört medslutreningsalternativen kontinuerligt sandfilter samt skivfilter. Provtagning genomfördes på två reningsverk ochresultatet analyserades för att besvara frågan. Andra kvalitetsparametrar i avloppsvattnet samt flöde, lufttemperaturoch nederbörd har jämförts med utgående koncentration av indikatororganismerna från reningsverk föratt undersöka om det finns några samband som går att använda för att uppskatta det mikrobiologiska utsläppet.För undersökningen har de statistiska metoderna Kendalls Tau och Partial Least Squares använts. En litteraturstudiepå hur implementering av läkemedelsrening med ozon kan desinficera avloppsvattnet, vilken doseringsom krävs och vad den bör baseras på har genomförts. Efter avloppsutsläpp i en recipient sprids mikroorganismernamed vattnets strömmar och mikroorganismerna dör normalt av med tiden. Denna avdödandeprocesskan beskrivas med en ekvation av första ordningens kinetik. Ekvationens känslighet för variation i variablernasolinstrålning, temperatur, siktdjup och tid har undersökts. Ekvationen har även använts för en fallstudie av avloppsutsläppvid bräddning och hur det påverkar en badplats nedströms. För fallstudien fanns information omflödestid, utspädning och nedbrytningsvariablerna att tillgå. Undersökningen visar att biologisk rening med biobädd reducerar indikatororganismerna effektivast av de undersöktareningsstegen. Sandfiltrets reduktionsförmåga var god men skivfiltret presterade sämre. Från provtagningenframkom också att koncentrationen av E.coli är konsekvent högre och reduceringen sämre än motsvarandeför intestinala enterokocker. Indikatororganismernas koncentration i utgående avloppsvatten är enligtkorrelationsanalysen slumpmässig och inget signifikant och starkt samband fanns till de undersökta parametrarna. På grund av detta är uppskattning av mikrobiologiska utsläpp med hjälp av mätning av andra parametrarinte tillförlitlig. Den genomförda litteraturgranskningen av ozondosering visar att dosen som krävs för desinfektionav avloppsvatten behöver anpassas för varje reningsverk samt att resultat från forskningen går isär omhur doseringen bör optimeras. I recipienten har siktdjupet störst betydelse för nedbrytningen och recipientensegenskaper är viktigare än utsläppets storlek för vattenkvalitén enligt den modell som använts. Fallstudien visadeatt även vid bräddning på reningsverket hinner mikroorganismerna spädas ut och brytas ner tillräckligt föratt badvattenkvalitén inte ska klassas som otjänlig vid närliggande badplats. / Depending on the efficiency of the processes used in a wastewater treatment plant, the recipient receives watercontaining various concentrations of microorganisms. These microorganisms might infect people using therecipient for recreational purposes. The thesis aims to investigate how some process choices affect the concentrationsof microorganisms in sewage and how the concentration can be monitored with the use of other waterquality measurements. Lastly the microbial degradation after discharge in a lake was investigated. Process choiceswere evaluated through sampling before and after two biological treatment steps, one sand filter facilityand one disc filter facility. The obtained results demonstrate that among the investigated alternatives, a biologicalstep using biofilm is the most efficient for removing microorganisms, followed by sand filtration and leastefficient with high variability was disc filtration. The literature review suggests that the use of ozonation forreducing pharmaceutical residues could be efficient in reducing microorganisms, but the required dosage is notuniformly established in previous research. Statistical analysis on water quality measurements with Kendall’sTau and Partial Least Squares did not appear to be a good substitute to use for monitoring and prediction ofbacterial concentrations. The water quality of the recipient, especially the transparency for UV-light, is moreimportant for maintaining good bathing water quality than the outflow concentration of microorganisms in thesewage. In a small case study, it was shown that an official bathing site is not at risk for acute microbiologicalcontamination even when extreme rainfalls causes overflow in the upstream waste water treatment plant.
963

Seafloor ripples created by waves from hurricane Ivan on the west Florida shelf

Bowers, Colleen Marie January 2006 (has links)
Thesis (S.M.)--Joint Program in Applied Ocean Physics and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2006. / Includes bibliographical references (leaves 94-96). / Recent studies have shown that the presence of sand ripples on the seabed improves sonar detection of buried mines at sub-critical angles. Sidescan sonar data of ripples off on the west Florida shelf were collected as part of ONR's Ripples Departmental Research Initiative (DRI) September 26-29th and November 7-9th, 2004. Hurricane Ivan, the strongest storm of the 2004 hurricane season, passed over the experiment site a week before the first data collection. This study focuses on the ripples created by Ivan. Average relict ripple wavelengths left after the storm were found to increase with water depth (50 cm, 62 cm, and 83 cm in 20, 30, and 50 meter water depths) despite the fact that orbital diameter decreases with water depth. Ripple prediction requires information about surface gravity waves and sediment grain size. The most reliable offshore wave field available was created with Wavewatch III by Naval Postgraduate School scientists. These waves were inputted into Delft3D WAVE, incorporating the nearshore wave model SWAN to predict waves at the locations where ripples were measured. Orbital motions at the seabed and grain size were inputted into a time-dependent ripple model with varying dissipation parameters to estimate sand ripples created by Hurricane Ivan. Ripple wavelength was found to be more strongly dependent on grain size than wave dissipation. / by Colleen Marie Bowers. / S.M.
964

Determining the effectiveness of water treatment process barriers for the removal of viruses in drinking water.

Setlhare, Khomotso Charity January 2018 (has links)
M. Tech (Department of Biotechnology, Faculty of Applied and Computer Sciences) Vaal University of Technology. / The presence of enteric viruses in drinking water poses a health risk to consumers. It is therefore very important for drinking water suppliers to provide water that is pathogen free and fit for human consumption. This can be achieved by an effective water treatment system that ensures the safety of water from the treatment plant until the water reaches the consumer. This study assessed the ability of a conventional water treatment system to remove viruses. The system consisted of three unit processes, namely, clarification, sand filtration and disinfection. These processes were simulated on a bench-scale to determine the effectiveness of each one at removing viruses. Clarification was conducted using a Phipps and Bird jar testing system and three different chemical treatments: (i) Polyelectrolyte (SUDFLOC 3835), (ii) a combination of lime and activated silica and (iii) a combination of lime, activated silica and ferric chloride. Sand filtration was simulated using a Phipps and Bird column filtration system. Disinfection was conducted using free chlorine. The findings from this study showed that the removal or inactivation of viruses increased with an increase in the concentration of chemicals added. For clarification, the combination of lime, activated silica and ferric chloride was the most effective treatment for the removal or inactivation of viruses. Sand filtration was found to be ineffective for the removal of viruses. Disinfection was shown to be the most effective process for the removal or inactivation of viruses. While clarification, sand filtration and disinfection did not remove or inactivate viruses equally, the entire treatment chain is still essential. This is because even if a barrier does not directly remove viruses it ensures that subsequent processes can function effectively. Overall the treatment processes should not be considered as discrete barriers but rather an integrated system that must function throughout to avoid a risk to customers.
965

Polyfunkční dům / Multifunctional building

Králík, Martin Unknown Date (has links)
The subject of the diploma thesis is the elaboration of project documentation for the construction of a multifunctional house. The building is located on a building plot of parcel number 2176/15 in the cadastral area of Stará Boleslav. It is located in the northeastern part of the cadastral area. The terrain of the building plot is flat and currently the plot is covered with grass. It is a built-up area in which the development of apartment buildings predominates. The designed multifunctional house is spread over four floors. On the first floor there are three surgeries with a preparation room, facilities for staff and clients and communication areas of the building. The first floor is designed as barrier-free. There are six apartments on the second and third floors. On the fourth floor are designed two apartments and a walking terrace. The underground part consists of technical facilities, storage space and 13 parking spaces.
966

Predicting and Validating Multiple Defects in Metal Casting Processes Using an Integrated Computational Materials Engineering Approach

Lu, Yan 30 September 2019 (has links)
No description available.
967

The Development and Verification of a New Accelerated Polishing Machine

Khasawneh, Mohammad Ali 26 August 2008 (has links)
No description available.
968

Recycling Plastic Materials in Concrete Infrastructure

Abduallah, Ramzi Muftah Ali January 2021 (has links)
No description available.
969

Full-Scale Lateral Load Test of a 3x5 Pile Group in Sand

Walsh, James Matthew 15 July 2005 (has links) (PDF)
Although it is well established that spacing of piles within a pile group influences the lateral load resistance of that group, additional research is needed to better understand trends for large pile groups (greater than three rows) and for groups in sand. A 15-pile group in a 3x5 configuration situated in sand was laterally loaded and data were collected to derive p-multipliers. A single pile separate from the 15-pile group was loaded for comparison. Results were compared to those of a similar test in clays. The load resisted by the single pile was greater than the average load resisted by each pile in the pile group. While the loads resisted by the first row of piles (i.e. the only row deflected away from all other rows of piles) were approximately equal to that resisted by the single pile, following rows resisted increasingly less load up through the fourth row. The fifth row consistently resisted more than the fourth row. The pile group in sand resisted much higher loads than did the pile group in clay. Maximum bending moments appeared largest in first row piles. For all deflection levels, first row moments seemed slightly smaller than those measured in the single pile. Maximum bending moments for the second through fifth rows appeared consistently lower than those of the first row at the same deflection. First row moments achieved in the group in sand appeared larger than those achieved in the group in clay at the same deflections, while bending moments normalized by associated loads appeared nearly equal regardless of soil type. Group effects became more influential at higher deflections, manifest by lower stiffness per pile. The single pile test was modeled using LPILE Plus, version 4.0. Soil parameters in LPILE were adjusted until a good match between measured and computed responses was obtained. This refined soil profile was then used to model the 15-pile group in GROUP, version 4.0. User-defined p-multipliers were selected to match GROUP calculated results with actual measured results. For the first loading cycle, p-multipliers were found to be 1.0, 0.5, 0.35, 0.3, and 0.4 for the first through fifth rows, respectively. For the tenth loading, p-multipliers were found to be 1.0, 0.6, 0.4, 0.37, and 0.4 for the first through fifth rows, respectively. Design curves suggested by Rollins et al. (2005) appear appropriate for Rows 1 and 2 while curves specified by AASHTO (2000) appear appropriate for subsequent rows.
970

Liquefaction Mitigation in Silty Sands Using Stone Columns with Wick Drains

Quimby, Michael James 07 August 2009 (has links) (PDF)
Stone column treatment is commonly used to mitigate liquefaction hazard in sandy soils. Research and experience indicate that this method is effective for clean sands but that it may not be effective for silts and sands with fines contents greater than 15-20%. An alternative to the stone column method involves supplementing stone column treatment with pre-fabricated vertical wick drains installed prior to the stone columns installation. Although this method is used in practice, there has not been a formal academic study of its effectiveness. This thesis evaluates seven different case histories where wick drains were used and one where wick drains were not used, for comparison purposes. The site locations varied as well as the soil properties and treatment plans. CPT testing was done at 3 sites and SPT testing was performed at the other 5 sites. CPT data were correlated to SPT data to facilitate comparisons. One of the case histories includes a unique study in which three different variations of the stone column treatment were applied at the same site, providing a direct comparison of the effectiveness of each method. A 26% area replacement ratio (Ar) with drains was determined to be more effective overall than a 26% Ar without drains and more effective in increasing low initial blow counts than the 34% Ar without drains. The areas with drains were more likely to exceed the minimum project criteria consistently throughout the site. Significant scatter were observed in the results and probable causes for the scatter are noted. Final blow count coefficients of variation ranged from 28% to 77%. Increased fines contents required increased Ar in order to maintain similar average final blow counts. Site improvements were evaluated separately and collectively. Individual site results were compared to clean sand curves developed by Baez (1995). Sites with average fines contents less than 20% which were improved using drains and an 11-15% Ar treatment were comparable to clean sand sites without drains and with 5-10% Ar. To achieve similar improvement at sites with 40-46% fines necessitated drains and Ar values of 23-26%. Design recommendations are provided.

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