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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.
1

Stabilisering av flotte avsedd för muddring av fibersediment längs Sveriges östkust / Stabilization of raft intended for dredging of fibrous sediments along the Swedish east coast.

Ljungberg, Erik January 2022 (has links)
Sverige har en stor miljöskuld i form av fiberbankar fulla med miljöfarliga restprodukter från den pappers- och massaindustri som har definierat stora delar av svensk industri. Stora delar av östkusten samt flertalet sjöar fortsätter påverkas av dessa fiberbankar som kontinuerligt släpper ut miljögifter allt eftersom de eroderas av vågor eller då det organiska materialet bryts ned. Att minska dessa utsläpp av miljögifter är ett måste. Ett alternativ för att ta vara på de gamla restprodukterna är att muddra bort det varsamt för att sedan processera det på land. En sugenhet har tagits fram i ett tidigare examensarbete som minimerar spridning av sedimenten vid muddring. Syftet med detta projekt är att konstruera en flotte som möjliggör användandet av den tidigare framtagna sugenheten utan att onödig upprörning och spridning av sediment riskeras. En potentiell källa till upprörning är då sugenheten kommer i svängning pga. okontrollerade rörelser på flotten som uppstår via vågpåverkan. En litteraturstudie över olika stabiliseringsmetoder gjordes och därefter togs ett flertal koncept fram som sedan utvärderades mot kravspecifikationen. Det koncept som sedan vidareutvecklades var en flotte som baseras på SWATH teknik samt med så kallade ”Heave plates”, horisontella plattor under vattnet som skapar ett hydrodynamiskt motstånd Flotten som tagits fram baserar sig på uppdragsgivarens, Teknikmarknad, tidigare flotte för muddring av organiska sediment. En uppskattning av konceptets kostnad gjordes sedan genom skapandet av en komponentlista där för konceptet nödvändiga delar listades tillsammans med pris. Det framtagna konceptet är autonomt, relativt billigt, kräver minimalt med underhåll och minimerar risken för spridning av miljöfarliga ämnen vid muddring. / Sweden has a large environmental debt in form of underwater fibre deposits, full of leftover chemicals from the pulp and paper industries that has defines large parts of early Swedish industry. Large parts of the east coast and several lakes continues to be affected by these deposits that continuously release environmentally hazardous materials when the deposits are eroded by waves or the organic material breaks down. To slow down these emissions is a must. One alternative is to carefully dredge the material away with purpose-built equipment to later process it on land. In an earlier thesis, a dredgehead was developed that minimize the spreading of material during dredging. The purpose of this project is to develop a barge that enables the use of the earlier developed dredgehead without increasing the risk of spreading of sediment. A potential cause of spreading is if the dredgehead would start swinging due to uncontrolled motions of the barge caused by waves. A literature study was conducted to find different stabilizing methods and several concepts where developed. The different concepts were evaluated based on the requirement specification. The superior concept was a SWATH based design with added Heave plates to increase the hydrodynamic resistance. The barge is based on a previous barge developed by the stakeholder, Techmarket, for low flow dredging of organic sediment. An estimate of the concept added cost was done through a component list where the necessary parts were listed together with the price. The proposed concept is autonomous, demands minimal maintenance and minimizes the risk of spreading of hazardous materials while dredging.
2

Key aspects of the structural design of small SWATH ships

Loscombe, Peter Robin January 1989 (has links)
No description available.
3

Improving the Capabilities of Swath Bathymetry Sidescan Using Transmit Beamforming and Pulse Coding

Butowski, Marek 30 April 2014 (has links)
Swath bathymetry sidescan (SBS) sonar and the angle-of-arrival processing that underlies these systems has the capability to produce much higher resolution three dimensional imagery and bathymetry than traditional beamformed approaches. However, the performance of these high resolution systems is limited by signal-to-noise ratio (SNR) and they are also susceptible to multipath interference. This thesis explores two methods for increasing SNR and mitigating multipath interference for SBS systems. The first, binary coded pulse transmission and pulse compression is shown to increase the SNR and in turn provide reduced angle variance in SBS systems. The second, transmit beamforming, and more specifically steering and shading, is shown to increase both acoustic power in the water and directivity of the transmitted acoustic radiation. The transmit beamforming benefits are achieved by making use of the 8-element linear angle-of-arrival array typical in SBS sonars, but previously not utilized for transmit. Both simulations and real world SBS experiments are devised and conducted and it is shown that in practice pulse compression increases the SNR, and that transmit beamforming increases backscatter intensity and reduces the intensity of interfering multipaths. The improvement in achievable SNR and the reduction in multipath interference provided by the contributions in this thesis further strengthens the importance of SBS systems and angle-of-arrival based processing, as an alternative to beamforming, in underwater three dimensional imaging and mapping. / Graduate / 2015-04-15 / 0544 / 0547 / mark.butowski@gmail.com
4

Improving the Capabilities of Swath Bathymetry Sidescan Using Transmit Beamforming and Pulse Coding

Butowski, Marek 30 April 2014 (has links)
Swath bathymetry sidescan (SBS) sonar and the angle-of-arrival processing that underlies these systems has the capability to produce much higher resolution three dimensional imagery and bathymetry than traditional beamformed approaches. However, the performance of these high resolution systems is limited by signal-to-noise ratio (SNR) and they are also susceptible to multipath interference. This thesis explores two methods for increasing SNR and mitigating multipath interference for SBS systems. The first, binary coded pulse transmission and pulse compression is shown to increase the SNR and in turn provide reduced angle variance in SBS systems. The second, transmit beamforming, and more specifically steering and shading, is shown to increase both acoustic power in the water and directivity of the transmitted acoustic radiation. The transmit beamforming benefits are achieved by making use of the 8-element linear angle-of-arrival array typical in SBS sonars, but previously not utilized for transmit. Both simulations and real world SBS experiments are devised and conducted and it is shown that in practice pulse compression increases the SNR, and that transmit beamforming increases backscatter intensity and reduces the intensity of interfering multipaths. The improvement in achievable SNR and the reduction in multipath interference provided by the contributions in this thesis further strengthens the importance of SBS systems and angle-of-arrival based processing, as an alternative to beamforming, in underwater three dimensional imaging and mapping. / Graduate / 0544 / 0547 / mark.butowski@gmail.com
5

Redimensionamento de distribuidor pendular para grandes vazões de calcário / Pendulum spreader resizing for large limestone flow rate

Duarte, Cássio da Costa 19 February 2019 (has links)
Aproximadamente 70% do solos com potencial agrícola no Brasil são classificados como solos ácidos, e para sua correção realiza-se, normalmente, a aplicação do calcário em pó. Apesar de ser o insumo sólido mais consumido no país, nota-se uma baixa qualidade em suas aplicações além da inexistência de equipamentos dedicados à sua aplicação e de esforços em pesquisa e desenvolvimento de novos conceitos de máquinas nesse sentido. Atualmente a maior parte das aplicações a lanço de granulados (fertilizantes) e pós (corretivos) são realizadas através de distribuídores centrífugos. Provavelmente essa tenha sido a razão para os fabricantes optaram por investir mais nessas máquinas, estagnando assim a evolução dos distribuidores de princípio pendular, os quais realizam as aplicações através do movimento oscilatório horizontal de um tubo. Diante desse cenário, buscou-se adaptar e redimensionar um distribuidor de princípo pendular dedicados à fertilizantes para aplicação de grandes vazões de calcário em pó. Fabricou-se um protótipo com mecanismo dosador volumétrico e acionamento do pêndulo via motor elétrico conectado a um inversor de frequência. Utilizou-se pêndulos de policloreto de vinila (PVC) com diferentes comprimentos com e sem rampa em suas extremidades. Os ensaios foram realizados em sete diferentes frequências, e mensurou-se a largura máxima de lançamento das partículas. Notou-se que tanto o incremento da frequência e do comprimento do pêndulo, assim como a utilização de uma rampa na extremidade foram, na maioria dos casos, capazes de produzir um aumento na distância de lançamento da partícula. Este estudo demonstrou a capacidade do protótipo em realizar aplicações de calcário em pó em faixa com uma vazão superior (até 6,5 kg s-1) às convencionais (1,5 kg s-1) com coeficientes de variação inferiores a 3,14 %. Além disso, mostou-se que é possivel variar a largura da faixa de aplicação de 1,89 m até 5,69 m com a mudança do comprimento do pêndulo, frequência e utilização da rampa. / Approximately 70% of the soils with agricutural potential in Brazil are classified as acid, and, for their neutralization the application of lime powder is usually carried out. Despite of being the most used solid agricultural input in the country, it can be noticed a low quality in its application, besides the lack of equipament dedicated exclusively to its application and of efforts in research and development of new concepts of machines in that sense. Currently, most of the granulated and powder application carried out through centrifugal spreaders. Probably this was the reason why manufactures opted to invest more in these kind of spreader, stagnating the evolution of pendulum spreaders, which realize the distribution through the horizontal oscillatory moviment of a tube (spout). In this context, it was intended to adapt and resize a pendular spreader dedicated to fertilizers for application of large flows of lime powder. A prototype with volumetric measure mechanism and eletric motor drive, connected to a frequency inverter, was developed. Polyvinyl chloride (PVC) pendulums with different lengths were used, with and without a ramp at their ends.. The tests were perfomed at seven different frequencies, and the higher widht distance was measured. It was noted that the increase in frequency and length of the tube, as well as the addition of a ramp at the border were, in most cases, able to increase the flight distance of the particles. This study demonstrated the ability of the prototype to spread limestone with a higher flow rate (up to 6.5 kg s-1) than the conventional ones (1.5 kg s-1) with coefficient of variation lower than 3.14%. Furthermore, it has been shown that is possible to vary the width of the application range form 1.89 m to 5.69 m by modifying the length of the tube, frequency and use of the ramp.
6

Sentinel-1 Wide Swath Interferometry: Processing Techniques and Applications

Yuxiao Qin (5930171) 03 January 2019 (has links)
<div>The Sentinel-1 (S1) mission is a part of the European Space Agency (ESA) Copernicus program. In 2014 and 2016, the mission launched the twin Synthetic Aperture Radar (SAR) satellites, Sentinel-1A (S1A) and Sentinel-1B (S1B). The S1 mission has started a new era for earth observations missions with its higher spatial resolution, shorter revisit days, more precise control of satellites orbits and the unprecedented free-to-public distribution policy. More importantly, S1 adopts a new wide swath mode, the TOPS mode as it default acquisition mode. The TOPS mode scans several different subswaths for gaining a larger coverage. Because the S1 mission is aimed at earth observation missions, for example, earthquakes, oods, ice sheets flow, etc., thus it is desired to have large monitoring areas. Although TOPS is still a relatively new idea, the high quality data and wide application scopes from S1 has earned tremendous attention in the SAR community.</div><div><br></div><div><div>The signal properties of wide swath mode such as TOPS are different from the more conventional stripmap mode, and it requires special techniques for successfully processing such data in the sense of interferometry. For the purpose of doing Interferometric SAR (InSAR), the coregistration step is of most critical because it requires a 1/1000 accuracy. In addition, processing wide swath mode requires special steps such as bursts stitching, deramping and reramping, and so on. Compared with stripmap, the processing techniques of wide swath mode are less developed. Much exploitations are still needed for how to design a generic and robust wide swath interferometric</div><div>processing chain.</div></div><div><br></div><div><div>Driven by the application needs of S1 wide swath interferometric processing, this research studies the key methodologies, explores and implements new processing chain, designs a generic wide swath processing </div><div>flow that would utilize the existing stripmap processing platform, as well as carries out preliminary applications. For studying key methods, this study carries out a quantitative analysis between two different coregistration methods, namely the cross-correlation approach and the geometrical</div><div>approach. The advantages and disadvantages for each method are given by the author, and it is proposed to choose the suitable method based on one's study area. For the implementation of the new processing chain, the author proposes a user-friendly stripmap-like processing </div><div>ow with all the wide swath related process done behind the scene. This approach allows people with basic knowledge in InSAR and very few knowledge in wide swath mode to be able to process and get interferometric products. For designing the generic process flow, the author applied TOPS's work flow to the other wide swath mode, ScanSAR mode and demonstrated the feasibility of processing two different wide swath mode with the same processing chain.</div><div>For preliminary applications, the author shows a large number of interferometric data throughout the research and presents a case study with multi temporal time series analysis using a stack of S1 dataset.</div></div><div><br></div><div><div>This research is application oriented, which means the study serves for real-world applications. Up to now, the processing chain and methodologies implemented in this</div><div>research has been shared by many research groups around the world and has seen a number of promising outcomes. The recognition from others is also an affrmation to the value of this research.</div></div>
7

Enhancing the mass spectrometric analysis of ubiquitin-like modifications

Chicooree, Navin January 2014 (has links)
Mamalian protein ubiquitination and SUMOylation are reversible post translational modifications, which are involved in a multitude of important complex regulatory processes within the cell. Current mass spectrometry approaches that involve bottom-up proteomics to comprehensively analyse these modifications, have proved to be problematic. In this work, analytical approaches are carried out to improve and enhance the comprehensive analysis of these modifications. Tryptic proteolysis of ubiquitinated proteins results in the generation of isopeptides bearing adi-glycine (GG) remnant. Current mass spectrometry approaches used to identify these isopeptides are predominantly reliant on detecting the signature mass shift of the GG remnant (114.043 Da). The lack of sequence information from the GG remnant post MS/MS acquisition results in database search algorithms falsely identifiying these isopeptides. Reductive methylation chemistry was employed to derivatize these isopeptides. Upon collision induced dissociation of the isopeptides two robust ions were released from the iso-N-terminus of the GG remnant ; i) an a1’ ion at m/z 62.09, corresponding to the G of the remnant and ii) a b2’ ion at m/z 147.11, corresponding to the full GG remnant. Post-acquisition data extraction of these unique diagnostic ions demonstrated enhanced selectivity towards identifying these isopeptides. Tryptic proteolysis of SUMOylated proteins results in the generation of isopeptides bearing a substantial iso-C-terminal SUMO remnant. The CRA(K) (Consecutive Residue Addition tolysines (K)) approach combined independant use of proteolytic enzymes and unbiased consecutive residue addition of amino acids pertaining to these iso-C-terminal SUMOremnants, on all lysine residues. This approach enabled the identification of analytically useful novel wildtype isopeptides derived from the proteolysis of SUMO(1/2/3)ylated proteins, bearing GG, TGG and QTGG remnants. The analytically useful isopeptides derived from proteolysis of SUMO(2/3)ylated proteins lacked robust diagnostic information from their iso-C-terminal bearing TGG and QTGG remnants. Reductive methylation chemistry was utilised to derivatize these isopeptides and enabled diagnostic a’ and b’ ions to be released from their iso-N-termini; i) a1’ (m/z 133.13),b2’ (m/z 262.17) and b4’ (m/z 376.22) ions, corresponding to the QTGG remnant and ii) (m/z106.10), b2’ (m/z 191.14) and b3’ (m/z 248.14) ions, corresponding to the TGG remnant. Post-acquisition data extraction of these unique diagnostic ions, enabled comprehensive structural elucidation of these isopeptides and enhanced selectivity towards identification.
8

Application of Quantitative Phosphoproteomics to the Study of Cnidarian-Dinoflagellate Symbiosis

Simona, Fabia 03 1900 (has links)
Corals are cnidarian animals that build the founding structures of tropical reefs, which survival depends upon the obligate symbiotic association to photosynthetic dinoflagellate algae in the family Symbiodiniaceae. As corals are facing increasing environmental and anthropogenic stress, understanding the molecular principles governing this unique symbiotic association is crucial to predict their adaptive potential. Due to logistic, costly, and experimental difficulties of working with corals, we use the sea anemone Aiptasia (sensu Exaiptasia pallida) as a tractable model organism for the molecular study of cnidarian-algal symbiosis. A major advantage of Aiptasia is that it establishes a facultative symbiotic association with Symbiodiniaceae algae, that is, this anemone can be maintained in an aposymbiotic (symbiont-free) state, allowing for comparison of symbiotic and ‘control’ aposymbiotic processes. The main aim of this dissertation was to investigate the signaling pathways involved in the regulation of this symbiotic interaction, and in particular, phosphorylation-mediated protein signaling. Phosphorylation is indeed a major post-translational modification that mediates signal transduction within and across cells. To investigate if protein phosphorylation regulates the complex intercellular signaling that occurs between symbiotic partners, a mass spectrometry-based phosphoproteomic approach was employed. Given the novelty of this application in the field of coral reef biology, the first research chapter details the development and optimization of a protocol that allows quantification of protein phosphorylation in the sea anemone Aiptasia. This chapter includes mass spectrometric analysis in 1) data-dependent acquisition (or shotgun proteomics) for the generation of a so-called assay (spectral) library, a reference dataset that servers for 2) accurate and reproducible label-free quantification of protein phosphorylation in data-independent acquisition (DIA/SWATH-MS). In the second research chapter, the developed protocol was employed to generate a phosphopeptide assay (spectral) library for aposymbiotic and symbiotic Aiptasia, which would allow further quantification of protein phosphorylation across symbiotic conditions. We consistently quantified more than 3,000 phosphopeptides, totaling more than 1,600 phosphoproteins, across biological replicates and symbiotic conditions. Characteristic phosphoproteomic profile distinguished the two symbiotic groups and differential phosphorylation targeted biological processes that have not been previously described in the context of cnidarian-algal symbiosis, namely the phospholipase D signaling pathway and protein processing in the endoplasmic reticulum. We suggest that changes in the phosphorylation status of these signaling pathways may have a potentially relevant role in the control of an established cnidarian-algal association.
9

Multi-Fidelity Structural Modeling For Set Based Design of Advanced Marine Vehicles

Raj, Oliver Neal 22 May 2018 (has links)
This thesis demonstrates that a parametrically-modifiable Advanced Marine Vehicle Structural (AMVS) module (that can be integrated into a larger framework of marine vehicle analysis modules) enables stakeholders, as a group, to complete structurally feasible ship designs using the Set-Based Design (SBD) method. The SBD method allows stakeholders to identify and explore multiple solutions to stakeholder requirements and only eliminating the infeasible poorer solutions after all solutions are completely explored. SBD offers the and advantage over traditional design methods such as Waterfall and Spiral because traditional methods do not adequately explore the design space to determine if they are eliminating more optimal solutions in terms of cost, risk and performance. The fundamental focus for this thesis was on the development of a parametrically modifiable AMVS module using a low-fidelity structural analysis method implemented using a numerical 2D Finite Element Analysis (FEA) applied to the HY2-SWATH. To verify the AMVS module accuracy, a high-fidelity structural analysis was implemented in MAESTRO to analyze the reference marine vehicle model and provide a comparison baseline. To explore the design space, the AMVS module is written to be parametrically modified through input variables, effectively generating a new vessel structure when an input is changed. AMVS module is used to analyze an advanced marine vessel in its two operating modes: displacement and foil-borne. AMVS demonstrates the capability to explore the design space and evaluate the structural feasibility of the advance marine vehicle designs through consideration of the material, stiffener/girder dimensions, stiffener/girder arrangement, and machinery/equipment weights onboard. / Master of Science / In designing large marine products, it is necessary to follow a structured process to ensure the final product adequately meets the needs of a stakeholder’s requirements through engineering verification and validation analyses steps. This thesis demonstrates that the Advanced Marine Vehicle Structure (AMVS) module can be used by marine engineering professionals, in a group, to quickly analyze many structural variations of an advanced marine vehicle without freezing or locking in on an early and potentially suboptimal design. AMVS is intended to be integrated and to work in conjunction with other marine vehicle modules that, together, shipbuilder engineers can use to analyze all major design aspects of the marine vehicle in the total ship design process. Together the modules are implemented as a Set-Based Design (SBD) process to explore multiple total advance marine vehicle solutions to the stakeholder’s requirements and to eliminate the infeasible and worse solutions later during analysis.
10

Applications of CryoSat-2 swath radar altimetry over Icelandic ice caps and Patagonian ice fields

Foresta, Luca Umberto January 2018 (has links)
Satellite altimetry has been traditionally used in the past few decades to measure elevation of land ice, quantify changes in ice topography and infer the mass balance of large and remote areas such as the Greenland and Antarctic ice sheets. Radar altimetry is particularly well suited to this task due to its all-weather year-round capability of observing the ice surface. However, monitoring of ice caps and ice fields - bodies of ice with areas typically smaller than ~ 10,000 km2 - has proven more challenging. The large footprint of a conventional radar altimeter and coarse ground track coverage are less suited to observing comparatively small regions with complex topography. Since 2010, the European Space Agency’s CryoSat-2 satellite has been collecting ice elevation measurements over ice caps and ice fields with its novel radar altimeter. CryoSat-2’s smaller inter-track spacing provides higher density of observations compared to previous satellite altimeters. Additionally, it generates more accurate measurements because (i) the footprint size is reduced in the along-track direction by means of synthetic aperture radar processing and (ii) interferometry allows to precisely locate the the across-track angle of arrival of a reflection from the surface. Furthermore, the interferometric capabilities of CryoSat-2 allow for the processing of the delayed surface reflections after the first echo. When applied over a sloping surface, this procedure generates a swath of elevations a few km wide compared to the conventional approach returning a single elevation. In this thesis, swath processing of CryoSat-2 interferometric data is exploited to generate topographic data over ice caps and ice fields. The dense elevation field is then used to compute maps of elevation change rates at sub-kilometer resolution with the aim of quantifying ice volume change and mass balance. A number of algorithms have been developed in this work, partly or entirely, to form a complete processing chain from generating the elevation field to calculating volume and mass change. These algorithms are discussed in detail before presenting the results obtained in two selected regions: Iceland and Patagonia. Over Icelandic ice caps, the high-resolution mapping reveals complex surface elevation changes, related to climate, ice dynamics and sub-glacial, geothermal and magmatic processes. The mass balance of each of the six largest ice caps (90% of Iceland’s permanent ice cover) is calculated independently for the first time using spaceborne radar altimetry data. Between October 2010 and September 2015 Icelandic ice caps have lost a total of 5.8± 0.7 Gt a ̄1, contributing 0.016± 0.002 mm a ̄1 to eustatic sea level rise. This estimate indicates that over this period the mass balance was 40% less negative than the preceding 15 years, a fact which partly reflects the anomalous positive balance year across the Vatnaj ̈okull ice cap (~ 70% of the glaciated area) in 2014/15. Furthermore, it is demonstrated how swath processing of CryoSat-2 interferometric data allows the monitoring of glaciological processes at the catchment scale. Comparison of the geodetic estimates of mass balance against those based on in situ data shows good agreement. The thesis then investigates surface elevation change on the Northern and Southern Patagonian Ice Fields to quantify their mass balance. This area is characterized by some of the fastest flowing glaciers in the world, displaying complex interactions with the proglacial environments (including marine fjords and freshwater lakes) they often drain into. Field observations are sparse due to the inaccessibility of these ice fields and even remotely sensed data are limited, often tied to comparisons to the topography in 2000 as measured by the Shuttle Radar Topography Mission. Despite gaps in the spatial coverage, in particular due to the complex topography, CryoSat-2 swath radar altimetry provides insight into the patterns of change on the ice fields in the most recent period (2011 to 2017) and allows to independently calculate the mass balance of glaciers or catchments as small as 300 km2. The northern part of the Southern Patagonian ice field displays the strongest losses due to a combination between ice dynamics and warming temperatures. In contrast Pio XI, the largest glacier on this ice field and in South America, is advancing and gaining mass. Between April 2011 and march 2017, the two ice fields combined have lost an average of 21.29± 1.98 Gt a ̄1 (equivalent to 0.059± 0.005 mm a ̄1 eustatic sea level rise), 24% and 42% more negative when compared to the periods 2000-2012/14 and 1975-2000. In particular the Northern Patagonian ice field, responsible for one third of the mass loss, is losing mass 70% faster compared to the first decade of the 21st century. These results confirm the overall strong mass loss of the Patagonian ice fields, second only to glaciers and ice caps in Alaska and the Canadian Arctic, and higher than High Mountain Asia, which all extend over areas ~ 5-8 times larger (excluding glaciers at the periphery of the Greenland and Antarctic ice sheets).

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