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1
Mui, Tak Sang. "The shearing effect of suction /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202005%20MUI.
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Åslund, Peter. "On Suction Box Dewatering Mechanisms." Doctoral thesis, KTH, Fiber- och polymerteknik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4780.
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In previous studies on suction box dewatering, three mechanisms were identified that determine the dry content of a web, viz. web compression, displacement of water by air and rewetting. In the present work, the relative importance of the three mechanisms was investigated through direct measurement of the web deformation, the dry content changes during and after the suction pulse, the air flow through the fibre network and the saturation of the web after the suction pulse. Suction pressure, suction time and rewetting time were varied. The experiments were done with chemical and mechanical pulp webs of various grammages. It was found that a large web deformation took place during the suction pulse, particularly at its beginning. Compression dewatering was found to be the most dominant dewatering mechanism. Displacement dewatering started after most of the web compression had occurred. Its contribution to the increase in dry content was most pronounced for higher suction pressures, longer suction times and for chemical pulp webs. A surprisingly large expansion of the web was observed immediately after the suction pulse. This expansion was the effect of rewetting. This rewetting strongly reduced the dry content of the web if the web had not been immediately separated from the forming fabric at the end of the suction pulse. Under the conditions studied, the decrease in dry content amounted to the order of 3 to 6 %. Rewetting was smaller for longer suction times and higher suction pressures. A considerable air flow through the web occurred under these conditions. This air flow apparently moved water from the forming fabric into the suction box, thus making less water available for rewetting. Rewetting for mechanical pulp webs was more pronounced and took place faster than for chemical pulps. The use of a membrane on top of the web during suction box dewatering proved to be advantageous for reducing the air flow through the web. However, under the conditions investigated, the dry content could not be improved. Although the web compression was increased when using a membrane, especially at a higher suction pressure, rewetting after the suction pulse had an even larger negative impact on the dry content, which, as a result, was lower.QC 20100924
3
Ulvestad, Anders. "Consolidation Settlement of Suction Caissons." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19504.
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Consolidation settlement analysis is an essential part of the design process for suction caissons. However it is a complex task since soil volume important for settlement analyses is directly affected by the installation process. Consolidation settlements have been found to be the critical design criterion in several subsea developments, adequate and correct analysis is therefore vital. The FEM code PLAXIS has been used to evaluate the reconsolidation process after completed installation of the suction caisson. Emphasize has been placed on studying the shear strength increase with time along the skirt walls. During consolidation dissipation of excess pore pressures result in higher effective stresses. Consequently the modeled undrained shear strength increases. However the increase is small compared to the expected increase in shear strength due to the set-up phenomenon. To account for the deviation an adjusted simulation procedure incorporating incremental increase of friction angle in the interface zones has been suggested. The results were found to be reasonable with respect to final consolidation settlements and development of mobilized shear strength with time.Adequate modeling of the changes in the interface zones adjacent to the caisson walls during consolidation is vital for correct prediction of long term settlements. Modeled undrained shear strength with time have huge impact on the analysis results due to different mobilization of the surrounding soil. Appropriate evaluation of soil structure interaction is essential to assess the reliability of the analysis. Taking into account changes of the soil volume important for settlement analysis is also vital. A simple physical model test has been performed. Due to delays and relatively short test period the results were inconclusive. However the importance of considering short term set-up effects has been underlined by recorded resistance and physical observations in the field.
4
Guan, Yun. "The measurement of soil suction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq23989.pdf.
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Almgren, Birgitta. "Endotracheal Suction a Reopened Problem." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4798.
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Ridley, Andrew Martin. "The measurement of soil moisture suction." Thesis, Imperial College London, 1993. http://hdl.handle.net/10044/1/7933.
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Pinna, Rodney. "Buckling of suction caissons during installation." University of Western Australia. School of Civil Engineering, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0008.
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Suction caissons are a foundation system for offshore structures which offer a number of advantages over traditional piled foundations. In particular, due to the method of installation used, they are well suited for deep-water applications. The suction caisson consists of an open ended cylindrical shell, which is installed below the seabed in a sequence which consists of two loading phases. The caisson is first installed part way under self weight, with the installation being completed by lowering the pressure within the cylinder and thus allowing the ambient water pressure to force the caisson into the ground. This thesis examines a number of structural issues which result from the form of the caisson — essentially a thin walled cylinder — and the interaction of the caisson with the surrounding soil during installation. To do this, variational analysis and nonlinear finite element analysis are employed to examine the buckling and collapse behaviour of these cylinders. In particular, two issues are considered; the influence of the open end, and the interaction between the cylinder and soil on the buckling and collapse loads. First, the behaviour of open ended cylinders is considered, where the boundary condition at the open end is allowed to vary continuously from completely free to pinned, by the use of a variable lateral spring. This lateral spring restraint may be considered to represent the intermediate restraint provided by a ring stiffener which is not fully effective. The effect of various combinations of boundary conditions is accounted for by the use of a multiplier on the lower bound to the buckling load of a cylinder with classical supports. The variable spring at the open end may also be considered to be an initial, simple representation of the effect of soil restraint on the buckling load. More complex representations of the soil restraint are also considered. A nondimensional factor is proposed to account for the influence of this spring on the buckling load. One combination of boundary conditions, where the upper end of the caisson is pinned, and the lower end free (referred to as a PF boundary condition), is found to have buckling and collapse behaviour which is unusual for cylindrical shells. Buckling loads for such shells are much lower than would be found for cylinders with more typical boundary conditions, and of similar dimensions. More unusually however, PF cylinders are shown to have positive postbuckling strength. The behaviour is found to be a result of the large flexibility which results from the low restraint provided by the PF boundary conditions. This is shown by continuously decreasing the flexibility of the cylinder, by increasing the axial restraint at the pinned end. It is shown that this results in a large increase in buckling load, and a return to more usual levels of imperfection sensitivity. In particular, with an intermediate level of axial restraint, buckling loads and imperfection sensitivity are intermediate between those of PF shells with no, and with full, axial restraint. Overall however, collapse loads for PF cylinders with no additional restraint are well below those of cylinders with stiffer boundary conditions, for equal geometries. Eigenvalue buckling of cylinders fully and partially embedded in an elastic material are examined, and two analytical solutions are proposed. One of these is an extension of a method previously proposed by Seide (1962), for core filled cylinders, to pin ended cylinders which have support from both a core and a surrounding material. The second method represents the elastic support as a two parameter foundation. While more approximate than the first method, this method allows for the examination of a wider range of boundary conditions, and of partial embedment. It is found that the buckling load of the shell/soil system decreases as the embedment ratio decreases. Collapse of fully and partially embedded cylinders is also examined, using nonlinear finite element analysis. The influence of plasticity in the soil is also considered. For cylinders with small imperfections, it is found that the collapse load shows a large increase over that of the same cylinder with no soil support. However, as the size of initial geometric imperfections increases, it is found that the collapse load rapidly approaches that of the unsupported cylinder. In particular, in weak soils the gain in strength over the unsupported shell may be minimal. The exception to this is again PF cylinders. As these have relatively low collapse loads, even very weak soils are able to offer an increase in collapse load over the unsupported case. Finally, a summary of these results is provided in the form of guidance for design of such structures.
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Wiklund, Pär-Eric. "Suction dynamics of axial piston pumps /." Stockholm, 1998. http://www.lib.kth.se/abs98/wikl0511.pdf.
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Yang, Shannon X. (Shannon Xuan). "Positive pressure induced channeled suction cups." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83829.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 39-40).
Leaking in water pipe is a critical issue in Middle Eastern countries such as Kuwait where water is scarce. In-pipe robots can be dispatched to discover the network and inspect the inner surface of the pipe. This thesis describes the design and characterization of suction pads for in-pipe robots. The suction cups are made of hyperelastic materials that contain air channels inside. Instead of using conventional suction technique that is prone to leaking and loosing adhesion force, the suction cup is actuated by compressed air or liquid, which deforms the geometry of the cup to achieve suction. In order to verify the geometry changes during actuation, a uniaxial tension test was done on the elastic material used to acquire the material properties and the suction cup designs were then simulated using FEA in ABAQUS. Next, prototypes were designed in SolidWorks and fabricated using soft lithography techniques. To measure the suction force, pressure measurements were taken both inside the prototype channels and underneath the suction cup. Results show that a Positive Pressure Actuated Suction-cup (PPAS) of diameter forty millimeters can achieve suction force up to 68 N. As more air is inserted into PPAS, the suction force also increases. The concept has proved to be a feasible solution for pipe inspection robot.
by Shannon X. Yang.
S.B.
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Buchanan, Donna Lynn 1952. "SUCTION CATHETER PLACEMENT IN THE NEONATE DURING ENDOTRACHEAL SUCTION USING THREE HEAD POSITIONS (BRONCHIAL, CANNULATION, PULMONARY TOILET)." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275533.
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Hubrich, Klaus. "Highly loaded compressor with boundary layer suction /." Lausanne : EPFL, 2005. http://library.epfl.ch/theses/?nr=3237.
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Gottschalk, Malte [Verfasser]. "Zur Beultragfähigkeit von Suction Buckets / Malte Gottschalk." Aachen : Shaker, 2017. http://d-nb.info/1138178322/34.
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Elgabu, Hesham M. "Critical evaluation of some suction measurement techniques." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/49627/.
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Suction is an important stress-state variable of unsaturated soils. The magnitude of suction affects the shear strength, the hydraulic conductivity, and the volume change behaviour of unsaturated soils. The measurement of soil suction is a prerequisite for the characterisation of unsaturated soils. Soil suction can be determined either by adopting direct or indirect measurement techniques. Despite several techniques available currently for measuring and controlling matric and total suctions of soils in the laboratory, several aspects related to various suction measurement techniques, such as the water phase continuity in null- type tests and compatibility of test results from various measuring techniques are yet to be explored in detail. Similarly, studies concerning determination of air-entry values (AEVs) and residual suctions of soils that exhibit volume change during the drying process are limited. Suctions of two soils from Libya (a silty sand and an inorganic clay with intermediate plasticity) were experimentally measured using null- type axis-translation, filter paper, and chilled-mirror dew-point techniques. Axis-translation and vapour equilibrium techniques were used for establishing the drying and wetting suction-water content soil-water characteristic curves (SWCCs) of the soils. Compacted soil specimens were prepared by varying moulding water content, dry density, compaction type, and compaction effort in order to investigate the influence of initial compaction conditions on measured suctions and SWCCs of the soils. The water content-void ratio relationships (shrinkage curves) of the soils from Clod tests were used in conjunction with the drying suction-water content SWCCs to establish the suction-degree of saturation SWCCs that enabled determination of the air-entry values (AEVs) and residual suctions of the soils. Initially saturated slurried specimens of the soils were also considered for comparing with the test results of compacted soil specimens. The test results from the investigation showed that the influence of compaction conditions on SWCCs of the soils was distinct only at a low suction range, whereas their impact was insignificant at higher suctions. The volume change of the soils during the drying process had significant impact on the AEVs and residual suctions. For initially saturated slurried specimens, the AEVs and the residual suctions of the soils determined form the suction-water content SWCCs were found to be distinctly lower than their counterparts determine from the suction-degree of saturation SWCCs. Suctions corresponding to the plastic limits of the soils agreed well with those determined from suction-degree of saturation SWCCs, whereas suctions corresponding the shrinkage limits overestimated the AEVs. An increase in the chamber air pressure soon after the null-type tests were completed clearly indicated that the water phase continuity between the water in the soil specimens, the water in the ceramic disk, and the water in the compartment below the ceramic disk was lacking for all specimens tested. Soil specimens with higher water contents created better continuity in the water phase. At high suction range, the test results from the techniques based on vapour equilibrium (i.e., non contact filter paper, salt solution and chilled-mirror dew-point tests) showed very good compatibility, whereas differences were noted between the test results at low suction range from the techniques that are based on liquid phase equilibrium (i.e., pressure plate and null-type tests).
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Byrne, Byron Walter. "Investigations of suction caissons in dense sand." Thesis, University of Oxford, 2000. http://ora.ox.ac.uk/objects/uuid:64c30b2e-155c-4642-9115-5e2bf5667af5.
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Offshore structures are used in a variety of applications ranging from the traditional oil and gas extraction facilities to emerging renewable energy concepts. These structures must be secured to the seabed in an efficient and cost effective manner. A novel approach is to use shallow inverted buckets as foundations, installed by suction, in place of the more usual piles. These foundations lead to cost savings through reduction in materials and in time required for installation. It is necessary to determine how these foundations perform under typical offshore loading conditions so that design calculations may be developed. This thesis presents experimental data from a comprehensive series of investigations aimed at determining the important mechanisms to consider in the design of these shallow foundations for dense sand. Initially the long term loading behaviour (e.g. wind and current) was investigated by conducting three degree of freedom loading {V:M/2R:H} tests on a foundation embedded in dry sand. The results were interpreted through existing work-hardening plasticity theories. The analysis of the data has suggested a number of improved modelling features. Cyclic and transient tests, representing wave loading, were carried out on a foundation embedded in an oil saturated sand. The novel feature of the cyclic loading was that a 'pseudo-random' load history (based on the 'NewWave' theory) was used to represent realistic loading paths. Of particular interest was the tensile load capacity of the foundation. The results observed suggested that for tensile loading serviceability requirements rather than capacity may govern design. Under combined-load cyclic conditions the results indicated that conventional plasticity theory would not provide a sufficient description of response. A new theory, termed 'continuous hyperplasticity' was used, reproducing the results with impressive accuracy. Surprisingly, under the conditions investigated, loading rate was found to have a negligible effect on response.
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Tessler, Thomaz Martino. "Weather downtime analysis for cutter suction dredgers." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-26012017-092026/.
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The dredging activity is increasing worldwide due to ships that require bigger drafts, and consequently deeper navigation channels. Some dredging projects requires the operation of cutter suction dredgers on open waters, once these are capable of removing compact sediments and rocks while still maintaining a good productivity. These facts motivated the creation of a weather driven downtime prediction software for this type of operation, based on simplified calculations of the main dredging systems of a CSD. The motions caused by waves, and the forces and moments caused on these dredgers by winds, waves and currents were analyzed in order to evaluate the influence of each parameter magnitude and direction on the behavior of the vessel. The main criteria of the dredger influenced by this conditions were determined by a literature review as being the swing winch required power, the interaction between the cutterhead and the soil, and the anchoring system resistance, this that can be both a spud pole system stress or the Christmas tree cable tension. In this research, only the spud pole system bending stress was considered. Three mathematical models were developed to represent those systems. Since the non-linearity of the relation between the reaction forces of the dredger and the soil was not an object of the study, this process is represented by a constant user defined reaction force and a horizontal cutterhead velocity model. The efficiency of these models were tested by applying them on a case study of the dredging of the Açu port on the Brazilian coast by the Taurus II dredger. Simultaneous wind, wave and current data data were used as input to these models by creating a time series scenario of the operation period. The results for both scenarios showed that the operation would be close to impossible due to wave generated dynamic stress on the spud pole.A atividade de dragagem no mundo é cada vez mais significativa em função do aumento dos navios que operam em portos, estes que possuem maior calado e requerem, consequentemente, canais de navegação mais profundos. Alguns projetos de dragagem utilizam dragas de sucção e recalque em mar aberto, dada a capacidade destes equipamentos de remover sedimento compactado e rochas, ainda mantendo uma boa produtividade. Estes fatos motivaram a criação de um programa de previsão de downtime gerado por condições ambientais de dragas de sucção e recalque baseado em modelos matemáticos simplificados. Os movimentos causados por ondas, e as forças e momentos causados na draga por ventos, ondas e correntezas foram analisados de forma a se obter a influência da magnitude e direção de cada um destes parâmetros no comportamento da embarcação. Os principais sistemas da draga influenciados por estas condições foram determinados com base em uma revisão bibliográficas como sendo a potência requerida nos guinchos de varredura, a interação do cortador com o solo e a resistência do sistema de ancoragem, sendo este a tensão de flexão dinâmica na trave do spud ou as tensões de ancoragem pelo sistema de árvore de natal. Três modelos matemáticos foram desenvolvidos para representar estes sistemas. Considerando a não linearidade da interação entre a draga e o solo, este processo foi representado por uma força de reação definida pelo usuário e pela velocidade horizontal do cortador. A eficiência destes modelos foi testada ao aplicá-los em um estudo de caso da dragagem do porto de Açu, na costa brasileira pela draga Taurus II. Valores simultâneos de ondas, ventos e correnteza foram utilizadas como entrada nestes modelos, através da criação de um cenário hipotético de série temporal. Os resultados para ambos os casos demonstraram que a operação seria impossibilitada em função de tensões de flexão dinâmicas no spud maiores que o limite determinado.
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El-Gharbawy, Sherif Lotfy. "The pullout capacity of suction caisson foundations /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Jones, Brendan. "The suction characteristics of power steering pumps." Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299810.
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Westraad, Delme. "Suction induced shear strength of gold mine tailings." Diss., Pretoria : [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-06102005-092115.
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Power, Kenton C. "Suction and compressibility characteristics of an unsaturated till." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/27012.
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Most geotechnical projects involving compacted soils are typically in a state of unsaturated condition. However, compressibility characteristics of such soils are typically estimated extending the principles that are commonly used for saturated soils. The compressibility and settlement characteristics of compacted soils are influenced by several parameters such as the applied loading, water content, compaction energy and soil structure. All the above parameters are in turn influenced by matric suction, which is one of the stress state variables for interpreting the engineering behavior of unsaturated soils. The focus of the research presented in this thesis is to understand the role of matric suction on the compressibility characteristics of a typical glacial till from Indian Head till, Saskatchewan. As a part of this thesis, the current techniques available in the literature for estimating matric suction were reviewed and implemented with varying degrees of success. New and improved techniques are presented for determining the matric suction using both axis-translation and the contact filter paper techniques. Based on the experimental studies undertaken in this research program, an equation is presented for Indian Head till that relates compaction water content to matric suction.
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Supachawarote, Chairat. "Inclined load capacity of suction caisson in clay." University of Western Australia. School of Civil and Resource Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0188.
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This thesis investigates the capacity and failure mode of suction caissons under inclined loading. Parametric finite element analyses have been carried out to investigate the effects of caisson geometry, loading angle, padeye depth (i.e. load attachment point), soil profile and caisson-soil interface condition. Displacement-controlled analyses were carried out to determine the ultimate limit state of the suction caissons under inclined load and the results presented as interaction diagrams in VH load space. VH failure interaction diagrams are presented for both cases where the caisson-soil interface is fully-bonded and where a crack is allowed to form along the side of the caisson. An elliptical equation is fitted to the normalised VH failure interaction diagram to describe the general trend in the case where the caisson-soil interface is fully-bonded. Parametric study reveals that the failure envelope in the fully-bonded case could be scaled down (contracted failure envelope) to represent the holding capacity when a crack is allowed to form. A stronger effect of crack on the capacity was observed in the lightly overconsolidated soil, compared to the normally consolidated soil. The sensitivity of caisson capacity to the changes in load attachment position or loading angle was quantified based on the load-controlled analyses. It was found that, for caisson length to diameter ratios of up to 5, the optimal centreline loading depth (i.e. where the caisson translates with no rotation) is in the range 0.65L to 0.7L in normally consolidated soil, but becomes shallower for the lightly overconsolidated soil profile where the shear strength profile is more uniform. The reduction of holding capacity when the padeye position is shifted from the optimal location was also quantified for normally consolidated and lightly overconsolidated soil profiles at loading angle of 30 [degrees]. Upper bound analyses were carried out to augment the finite element study. Comparison of holding capacity and accompanying failure mechanisms obtained from the finite element and upper bound methods are made. It was found that the upper bound generally overpredicted the inclined load capacity obtained from the finite element analyses especially for the shorter caisson considered in this study. A correction factor is introduced to adjust the upper bound results for the optimal condition. Comparisons of non-optimal capacity were also made and showed that the agreement between the upper bound and finite element analyses are sensitive to the change in the centreline loading depth when the caisson-soil interface is fully bonded, but less so when a crack forms.
21
Svenmarker, Staffan. "Heparin coating and cardiotomy suction in cardiopulmonary bypass." Doctoral thesis, Umeå : Univ, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-134.
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Abbott, Helen Amanda. "Permeability and suction characteristics of compacted unbound aggregates." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278345.
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Lourenço, Sérgio Duarte Nunes. "Suction measurements and water retention in unsaturated soils." Thesis, Durham University, 2008. http://etheses.dur.ac.uk/1331/.
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Techniques for testing unsaturated soils have been investigated by the author where the measurement and control of parameters were undertaken directly. Suction was measured and controlled with a new high suction tensiometer and water content through mass measurements with a balance. These techniques have been used for the determination of soil water retention curves and for the development of a suction . control system using air circulation and water injection. The techniques allow the soil to be subject to the same drying and wetting conditions that occur in nature and avoid the need for elevated air pressures, as are traditionally involved in testing using the axis translation technique. The performance of the new high suction tensiometer was evaluated, followed by its applications to soil testing. The tensiometer performance focused on the factors controlling cavitation, calibration in the negative pressure range and measurement. It was found that isotropic unloading is the most accurate technique for calibration in the negative range and that axis translation techniques can lead to errors. The research confirms high suction tensiometers are easy to use and versatile devices. Techniques were developed to measure and control suction and water content in unconfined and confined samples. Research on the unconfined samples focused on the procedures to obtain the soil water retention curve: discrete (soil dried or wetted in stages) and continuous (soil drying continuously). While both procedures were found not to influence the curves significantly, it is demonstrated that the continuous procedure is sensitive to factors such as the exposed surface area to drying or wetting and so should be used carefully. For confined conditions, wetting, drying, and water content measurement systems were developed. Wetting was based on the injection of water; drying was based on air circulation through a desiccant within a closed loop system. Water content was determined from the. difference between water injected and that adsorbed by the desiccant. This has been applied as part of a· double cell triaxial testing system that allows continuous determination of suction, water content and volume change. A challenge of such a system was imposing an air tight environment. The suitability of environmental scanning electron microscopy to observe unsaturated soils at the particle level was explored. The imaging of micron-sized materials at different relative humidities allowed a series of observations previously undocumented, among them: water menisci were visible, including their shape and interaction with surfaces; the contact angle between the air-water and water-solid interfaces was measurable.
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Kessens, Chad C. "A Self-Sealing Suction Technology for Versatile Grasping." Thesis, University of Maryland, College Park, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10844746.
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This thesis describes the design, development, and evaluation of a novel "self-sealing" suction technology for grasping. As humans desire robots capable of handling an increasingly diverse set of tasks, end effectors that are able to grasp the widest possible range of object shapes and sizes will be needed to achieve the desired versatility. Technologies enabling the exertion of local pulling contact forces (e.g. suction) can be extraordinarily useful toward this end by handling objects that do not have features smaller than the grasper, a challenge for traditional grippers. However, simple operation and cost effectiveness are also highly desirable.
To achieve these goals, we have developed a self-sealing suction technology for grasping. A small valve inside each suction cup nominally seals the suction port to maintain a vacuum within the system. Through the reaction forces of object contact, a lever action passively lifts the valve to engage suction on the object. Any cups not contacting the object remain sealed. In this way, a system with a large number of cups may effectively operate using any subset of its cups, even just one, to grasp an object. All cups may be connected to a central vacuum source without the need for local sensors or powered actuators for operation, forming a simple, compact, cost effective system.
This thesis begins with the detailed design and analysis of the self-sealing suction technology. An extensive evaluation of the technology's robustness and performance demonstrates its features and limits. This includes self-seal quality and leakage, object seal and reseal, cycle performance, and normal and shear force-displacement, among other characterizations. It then describes the development of several devices utilizing the technology. The potential impact of the technology is highlighted through applications of human-controlled, robotic, and aerial grasping and perching. Finally, mathematical tools are developed to analyze potential grasps developed using the technology.
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Van, Sintern Wolff H. "Investigation of suction recirculation in rocket pump inducers." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-08292008-063509/.
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Mahaffey, Ross M. "Review and optimisation of pump suction reducer selection." Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/46255.
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The approach flow to a pump must be undisturbed and free from unequal velocity distributions,
unequal pressure distributions, entrained air or gas bubbles, vortices and excessive pre-swirl. A
reducer fitting is typically used in pump station pipe work to reduce the size of the suction pipe to
match the size of the pump suction end flange. Two types of reducer fittings are commonly
manufactured, namely: Eccentric Reducers and Concentric Reducers. Inlet pipework design
guidelines traditionally prescribe the use of eccentric reducers, with the flat side on top. This
prescription is to allow the transport of air through the fitting. The flow through an eccentric reducer
accelerates along the sloped side as the flow path narrows from below, thereby causing higher
velocities towards this sloped side. These flow conditions are contradictory to the recommended
pump inlet approach flow conditions and pump station failures have been recorded resulting from the
incorrect application of eccentric reducers.
Relationships exist to assess the hydraulic transportation of air through a pipe and these relationships
can be applied to calculate the ability to transport air through a concentric reducer. It is therefore
hypothesised that a correctly designed concentric reducer will not only provide a more uniform
pressure/velocity distribution in comparison to an eccentric reducer, but will allow any free air
to be hydraulically transported through the reducer to the pump.
Computational Fluid Dynamics (CFD) was utilised to assess the resulting velocity distributions
through various concentric and eccentric reducer geometries at various flow rates. Six concentric
reducers and six eccentric reducers were simulated with four inlet velocities. The resulting velocity distributions were recorded with scalar scenes and velocity probes at four positions spaced at a
distance of 1 x the downstream diameter starting at the downstream end of the reducer.
These velocity distributions were then compared to the pump inlet requirements typically used in the
industry. These requirements require the velocity variation along a line drawn through the centre of
the pipe to be less than 10% of the average velocity along that line and the velocity variation along a
circle within the pipe is less than 5% of the average velocity along the circle.
It was found that the eccentric reducers with angles of 15°, 20° and 30° and the concentric reducer
with an angle of 20° do not pass the requirements used in the assessment at all four velocities. From
these results it was highlighted that some of the standard eccentric reducer geometries (including
those specified by AWWA C208) do not pass the inlet requirements. It was then assessed if air can be
hydraulically transported through the concentric reducers utilising available hydraulic air transport
theory. Air can be hydraulically transported through all of the concentric reducers except for the 20°
reducer (the same size that failed the velocity distribution assessment) at 1m/s for the assessed
diameters.
It was therefore shown that a correctly designed concentric reducer (angle less or equal to 15°)
will not only provide a more uniform pressure/velocity distribution in comparison to an
eccentric reducer, but will allow air to be hydraulically transported through the reducer to the
pump.Dissertation (MEng)--University of Pretoria, 2014.
tm2015
Civil Engineering
MEng
Unrestricted
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Leathrum, Travis. "Modular auger design to prevent clogging in suction." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123283.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 47-48).
A mechanical design was conducted for a modular auger system that reduces the risk of clogging in suction piping meant to process sargassum seaweed. The auger supports a slurry pump-based system being designed to address sargassum blooms adversely affecting beaches in the Caribbean. By reducing clogging, the auger will prevent damage to the pump and reductions in productivity. A mathematical model of the auger system was created, then a small-scale physical model was built to test the concept. These tests exposed flaws in the mechanical details of the design, but the viability of the concept was shown, so a full-scale design was completed to be implemented as a backup in an extended field test that will be conducted in the Caribbean during the summer 2019.
by Travis Leathrum.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Lewis, Joshua Mark. "Measuring the effects of cutter suction dredge operating parameters on minor losses due to fixed screens installed at the suction inlet." Thesis, Texas A&M University, 2014. http://hdl.handle.net/10945/44419.
Full textAbstract:
CIVINSOne of the most efficient and versatile types of modern dredges is the cutter suction dredge. Specific regulations mandate the placement of screens over the suction mouth during dredging operations to prevent ordnance, wildlife, and other debris from entering the system; however, these screens change the operational capability of the dredge in the form of an additional minor loss. The goal of this experiment was to determine the effects of different dredge operating parameters – cutter head speed, ladder arm swing speed, flow rate, and screen opening area ratio – on a screen’s calculated minor loss coefficient (or k-value). The Haynes Coastal Engineering Laboratory and Center for Dredging Studies at Texas A&M University houses a model cutter suction dredge that is used to test various parameters associated with hydraulic dredging. Testing consisted of 121 test dredge runs, which included water-only runs and slurry runs, at three flow rates, three swing speeds, three cutter head speeds, and three screen configurations. Minor loss coefficients were calculated for each test run and qualitatively and quantitatively analyzed. The results showed that neither cutter head speed nor swing speed had a significant, direct correlation with the screen’s minor loss in the range of selected parameters; however, they did have an indirect effect on k-value through an increased specific gravity in the slurry. The screen opening area ratio (B) showed a direct correlation with the screen’s k-value and was quantified for water tests and sand tests in the form of an empirical equation which can be applied to both model and prototype cutter suction dredges. The k-values for different screen opening shapes showed an upward or downward shift in the overall k-value curves, indicating the possibility of inherent efficiencies for differently-shaped openings. Qualitative observations of the Haynes Laboratory model dredge included sediment spillage at high cutter head speeds and a sand bulldozer effect at low cutter head speeds. Future testing should focus on a wider range of cutter head speeds and swing speeds to determine if any correlation exists beyond the ranges tested in this experiment. Additional testing of screens with more B- values and different screen opening shapes would increase the resolution and precision of the proposed k-value prediction equations.
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BUTTICE', Vincenzo. "VOLUMETRIC BEHAVIOUR OF SOILS EXPERIENCING WIDE CHANGES IN THE DEGREE OF SATURATION." Doctoral thesis, Università degli Studi di Palermo, 2021. http://hdl.handle.net/10447/499197.
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Kassem, Emad Abdel-Rahman. "Measurements of moisture suction in hot mix asphalt mixes." Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/4259.
Full textAbstract:
The presence of moisture in hot mix asphalt (HMA) causes loss of strength and durability of the mix, which is referred to as moisture damage. This study deals with the development of experimental methods for measuring total suction in HMA, which can be defined as the free energy state of water in HMA mixes. The total suction is related to the ability of moisture to get into the mix under unsaturated conditions; it is also related to the ability of the mix to retain moisture. Soil suction has been studied extensively. However, suction in HMA as a porous material and its relationship to moisture damage have not been studied. The development of a procedure to measure the total suction in HMA mixes is the first objective of this research. The second objective is to relate suction measurements to physical and chemical properties of the mixtures. The objectives were achieved in two phases. In the first phase, the total suction was measured in HMA specimens with different types of aggregates (limestone and granite), and with different air void distributions and aggregate gradations. The results of this phase showed that the drying test using a 60 oC temperature-controlled room is the proper setup for measuring the total suction in HMA using thermocouple psychrometers. The characteristics of suction-moisture content curves were found to be related to the air void distribution in HMA. In the second phase, total suction was measured in sand asphalt specimens. These specimens had different combinations of aggregates and binders with different bond energies and exhibited different field performance in terms of resistance to moisture damage. The suction measurements in sand asphalt specimens were used to calculate the moisture diffusion coefficient. The results revealed that water diffused into sand asphalt specimens that are known to have poor resistance to moisture damage faster than those that are known to have good resistance to moisture damage
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Colmenares, Montanez Julio Estaban. "Suction and volume changes of compacted sand-bentonite mixtures." Thesis, Imperial College London, 2002. http://hdl.handle.net/10044/1/7775.
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Dineen, Kieran. "The influence of soil suction on compressibility and swelling." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/45469.
Full textAbstract:
This thesis presents a study into the influence of suction on the compressibility and swelling characteristics of a broad range of reconstituted clay soils. Soil water relationships are explored, discussing evaporation, shrinkage, swelling and the development of suction. A comprehensive review of suction measurement techniques is detailed, identifying operating principles, performance and limitations of each technique. For the main experimental programme a new, osmotically suction controlled oedometer has been developed. The oedometer utilises the osmotic potential of a large molecular weight salt (polyethylene glycol) across a semi-permeable membrane to control matrix suctions in the sample during testing. Independent continuous measurement of the suction in the sample during testing is made using the Imperial College tensiometer. Four materials have been assessed. Kaolin, London clay, and two expansive soils from Kenya. A series of suction controlled stress path tests were carried out on the four materials. In addition intrinsic and soil moisture characteristics were determined and discussed. Routine soil classification tests, mineralogy and SEM studies were also carried out. The results are presented and discussed, and recommendations for future research made.
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Ghariani, Samia. "Experimental study of wind induced suction on flat roofs." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7540.
Full textAbstract:
A 1:10 scale model building previously tested in the NRCC 9$m \times 9m$ wind tunnel was reproduced with a more exaggerated scale of 1:100 in a smaller wind tunnel and tested. Also tested was a half of the building cut along the line of symmetry and with various heights. The purpose of the testing was (1) to examine the repeatability of the roof pressure patterns with a more exaggerated scaling factors, and (2) to explore the feasibility of using a portion of the building for the testing of structural details against wind action. It was confirmed that the proposed simulation of only a half or even less portion of the building at various scaling factors can be a useful wind tunnel testing method which can reproduce the previously established full building test results as long as the parapet height ratio is kept constant and the wind tunnel blockage ratio is kept minimal.
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Heidarpour, Manouchehr. "Turbulent flow in a porous tube with wall suction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq28345.pdf.
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de, Ruyter Marcus J. M. "Two-dimensional cut plan optimization for cutter suction dredgers." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/79367/.
Full textAbstract:
Optimal cut plans for cutter suction dredgers aim to maximize operational efficiency. Maximizing operational efficiency involves minimization of stoppage time resulting from non-productive dredger movements. To automate a systematic search for optimal twodimensional cut plans for cutter suction dredgers two models with an adaptive simulated annealing-based solution approach were developed. The first model, the dredge cut nesting model, optimizes irregular stock cutting problems where stencils represent dredge cuts and sheets represent dredging areas. Stencils are collections of unit dredge cuts with dimensions related to an effective cutting width which can be achieved with the cutter suction dredger considered. The objectives of the dredge cut nesting model are to maximize sheet coverage and to minimize stencil overlap. Centroids of unit dredge cuts of final nest layouts are extracted and used as grid nodes in the second model. The second model, the dredger routing model, optimizes asymmetric travelling salesperson problems with turning costs. The objectives of the dredger routing model are to minimize total route length and sum of turning angles, and to maximize average link length. A link consists of two or more route edges which are aligned with each other to within specified limits. A significant result of this research is that an engineering application of both models showed that two-dimensional cut plans for cutter suction dredgers can be systematically optimized and that dredger routes with minimum turning costs can be found. However, results also showed that the dredger routing model is not yet sophisticated enough to find cut plans for cutter suction dredgers for which overall project execution time is minimal.
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Wångby, Emil. "Transport of non-spherical particles in pipeflow with suction." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79806.
Full textAbstract:
The interest of how small non-spherical particles transport behaviour when transported in pipe-flow is of large interest in a variety applications. This kind of theory have been used when studying composite manufacturing and how particles behaves in the human lungs. The main focus is to study the statistical deposition rate in a flow-field with and without capillary action and gravity. Two kind of particle shapes are of main interest which are prolate and oblate spheroids. In this study the method of vector projection is used to track particle orientation instead of the more common methods of Euler-angles or quaternions. The method of tracking the particle motion used is Lagrangian tracking method which solves the equations of motion for the particles individually. When studying particles of nano-scale the importance of the phenomenon called Brownian motion arises. The inclusion if the Brownian motion gives rise to the solving of stochastic differential equations for the particle transport. To solve the resulting equations of transport a MATLAB program was developed to using the numerical Euler-Maruyama scheme. Simulations is done with a large amount of particles with a varying particle size and aspect ratio. The deposition results are compared between the different particles shape and sizes. It is seen that the effect of the Brownian motion on particle deposition rate increases with a smaller particle size. It is also concluded that the Brownian motion is the dominating reason for particle deposition. From comparing particle shape and size it is seen to have a major effect of the particles deposition. Including capillary action or gravity the inclusion doesn't affect particles deposition as much.
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Khapko, Taras. "Transition to turbulence in the asymptotic suction boundary layer." Licentiate thesis, KTH, Stabilitet, Transition, Kontroll, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-141344.
Full textAbstract:
The focus of this thesis is on the numerical study of subcritical transition to turbulence in the asymptotic suction boundary layer (ASBL). Applying constant homogeneous suction prevents the spatial growth of the boundary layer, granting access to the asymptotic dynamics. This enables research approaches which are not feasible in the spatially growing case. In a first part, the laminar–turbulent separatrix of the ASBL is investigated numerically by means of an edge-tracking algorithm. The consideration of spanwise-extended domains allows for the robust localisation of the attracting flow structures on this separatrix. The active part of the identified edge states consists of a pair of low- and high-speed streaks, which experience calm phases followed by high energy bursts. During these bursts the structure is destroyed and re-created with a shift in the spanwise direction. Depending on the streamwise extent of the domain, these shifts are either regular in direction and distance, and periodic in time, or irregular in space and erratic in time. In all cases, the same clear regeneration mechanism of streaks and vor- tices is identified, bearing strong similarities with the classical self-sustaining cycle in near-wall turbulence. Bifurcations from periodic to chaotic regimes are studied by varying the streamwise length of the (periodic) domain. The resulting bifurcation diagram contains a number of phenomena, e.g. multistability, intermittency and period doubling, usually investigated in the context of low-dimensional systems. The second part is concerned with spatio–temporal aspects of turbulent ASBL in large domains near the onset of sustained turbulence. Adiabatically decreasing the Reynolds number, starting from a fully turbulent state, we study low-Re turbulence and events leading to laminarisation. Furthermore, a robust quantitative estimate for the lowest Reynolds number at which turbulence is sustained is obtained at Re QC 20140213
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Song, Zhenhe. "Pullout behaviour of suction embedded plate anchors in clay." Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/2173.
Full textAbstract:
In recent years oil and gas mining has moved into increasingly deeper water in search of undeveloped fields. As water depths approach and exceed 3000 m conventional offshore foundation systems become inefficient and ineffective in stabilising platforms and floating production storage units. The trend of supporting structure design in deep water has been to install catenary and taut leg mooring systems. Consequently, many types of anchoring systems are being developed and used in order to withstand large mooring forces. The SEPLA (Suction Embedded Plate Anchor) is ideal for use in this situation. This project has employed advanced numerical techniques and centrifuge testing to study pullout behaviour of plate anchor foundations in different soil profiles and suction caisson installation effect with the aim of generating a robust framework for design. The behaviour of strip and circular plate anchors during vertical pullout in uniform and normally consolidated clays has been studied by means of small strain and large deformation finite element analyses. Both fully bonded (attached), and ‘vented’ (no suction on rear face), anchors have been considered. The current numerical results were compared with existing laboratory test data, finite element results and analytical solutions. This study showed that the ultimate pullout capacity factors (Nc) for deep embedment were 11.6 and 11.7 for smooth and rough strip anchors and 13.1 and 13.7 for smooth and rough circular anchors respectively. When the anchor base was vented, the soil stayed attached to the anchor base for deep embedment, and the pullout capacity was therefore the same as for the attached anchor. The separation depth ratio, Hs/B or Hs/D was found to increase linearly with the normalised strength ratio, su/γ'B or su/γ'D.Numerical simulation has been conducted to assess the bearing capacity for inclined pullout plate anchors. This bearing capacity analysis was performed by embedding the anchors in clay with different initial inclinations and different embedment ratios. Both the attached anchor base and vented base were evaluated. The results showed that the bearing capacities of the inclined plate anchors were associated with the inclination angles and base conditions. The separation depth of the plate anchors can be assessed by a simple equation from vertically pulled out plate anchors. Large deformation finite element analyses of plate anchor keying in clay has been performed. The effects of anchor thickness, anchor padeye eccentricity, anchor-soil interface roughness, soil shear strength, anchor submerged weight and soil disturbance have been studied with anchors in uniform or normally consolidated clays. The numerical results were compared with transparent soil test and existing centrifuge test data. The study showed that the RITSS method works well in simulating the anchor keying process. Anchor padeye eccentricity played an important role in anchor keying. A normalised anchor geometry ratio was used to estimate the loss in embedment during plate anchor’s keying. Both finite element analysis and centrifuge tests have been conducted to study the suction caisson installation effect. In finite element analysis, the soil disturbed zone varied from 3 times the caisson wall thickness to a full area inside a caisson.Centrifuge tests of suction embedded plate anchors were conducted in normally consolidated kaolin clay and transparent uniform soil. It can be concluded that the reduction in anchor capacity due to soil disturbance after suction caisson installation depends on re-consolidation time and soil sensitivity. The soil disturbance also reduced the loss of embedment during the anchor keying process.
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Song, Zhenhe. "Pullout behaviour of suction embedded plate anchors in clay." Curtin University of Technology, Dept. of Civil Engineering, 2008. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=18648.
Full textAbstract:
In recent years oil and gas mining has moved into increasingly deeper water in search of undeveloped fields. As water depths approach and exceed 3000 m conventional offshore foundation systems become inefficient and ineffective in stabilising platforms and floating production storage units. The trend of supporting structure design in deep water has been to install catenary and taut leg mooring systems. Consequently, many types of anchoring systems are being developed and used in order to withstand large mooring forces. The SEPLA (Suction Embedded Plate Anchor) is ideal for use in this situation. This project has employed advanced numerical techniques and centrifuge testing to study pullout behaviour of plate anchor foundations in different soil profiles and suction caisson installation effect with the aim of generating a robust framework for design. The behaviour of strip and circular plate anchors during vertical pullout in uniform and normally consolidated clays has been studied by means of small strain and large deformation finite element analyses. Both fully bonded (attached), and ‘vented’ (no suction on rear face), anchors have been considered. The current numerical results were compared with existing laboratory test data, finite element results and analytical solutions. This study showed that the ultimate pullout capacity factors (Nc) for deep embedment were 11.6 and 11.7 for smooth and rough strip anchors and 13.1 and 13.7 for smooth and rough circular anchors respectively. When the anchor base was vented, the soil stayed attached to the anchor base for deep embedment, and the pullout capacity was therefore the same as for the attached anchor. The separation depth ratio, Hs/B or Hs/D was found to increase linearly with the normalised strength ratio, su/γ'B or su/γ'D.Numerical simulation has been conducted to assess the bearing capacity for inclined pullout plate anchors. This bearing capacity analysis was performed by embedding the anchors in clay with different initial inclinations and different embedment ratios. Both the attached anchor base and vented base were evaluated. The results showed that the bearing capacities of the inclined plate anchors were associated with the inclination angles and base conditions. The separation depth of the plate anchors can be assessed by a simple equation from vertically pulled out plate anchors. Large deformation finite element analyses of plate anchor keying in clay has been performed. The effects of anchor thickness, anchor padeye eccentricity, anchor-soil interface roughness, soil shear strength, anchor submerged weight and soil disturbance have been studied with anchors in uniform or normally consolidated clays. The numerical results were compared with transparent soil test and existing centrifuge test data. The study showed that the RITSS method works well in simulating the anchor keying process. Anchor padeye eccentricity played an important role in anchor keying. A normalised anchor geometry ratio was used to estimate the loss in embedment during plate anchor’s keying. Both finite element analysis and centrifuge tests have been conducted to study the suction caisson installation effect. In finite element analysis, the soil disturbed zone varied from 3 times the caisson wall thickness to a full area inside a caisson.
Centrifuge tests of suction embedded plate anchors were conducted in normally consolidated kaolin clay and transparent uniform soil. It can be concluded that the reduction in anchor capacity due to soil disturbance after suction caisson installation depends on re-consolidation time and soil sensitivity. The soil disturbance also reduced the loss of embedment during the anchor keying process.
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Leivo, T. (Tomi). "Basement membrane zone proteins, epithelial integrins and TGF-β system in reepithelialization, dermatitis herpetiformis and psoriasis:modulation by isotretinoin, betamethasone and calcipotriol." Doctoral thesis, University of Oulu, 2000. http://urn.fi/urn:isbn:951425712X.
Full textAbstract:
Abstract
TGF-βs are cytokines that signal through the receptor
complex of type I and type II receptors. Hemidesmosome (BP180, BP230,
plectin/HD1, α6β4 integrin), anchoring
filaments (laminin 5), and anchoring fibrils (collagen VII) form
a hemidesmosomal adhesion complex that provides stable adherence
of keratinocytes to the epidermal basement membrane. Nidogen, collagen
IV, and laminins are components of the basement membrane, integrins
are cell adhesion molecules, and tenascin-C is a matrix protein.
The expression of TGF-β receptors I and II was studied
in normal epidermis and lesional and non-lesional psoriatic epidermis
by immunohistochemistry. TGF-β1 and TGF-β2 in
suction blister fluid and serum were determined by enzyme-linked
immunoassay. Suction blister fluid and serum samples were obtained
from acne patients before and after oral isotretinoin treatment.
Suction blister fluid samples were also obtained from healthy volunteers
in two age groups from a control site and a betamethasone-pretreated
site. The expression of BP180, BP230, plectin/HD1, α6
integrin, β4 integrin, laminin 5, collagen VII, collagen
IV, nidogen, laminin α3 chain, and laminin β1g1
chains was studied in uninvolved dermatitis herpetiformis skin by
the immunofluorescence technique. The ultrastructure of the hemidesmosomal
inner plaque was studied in uninvolved dermatitis herpetiformis
skin by electron microscopy. The suction blister method was used
to study intact blisters, open wounds (=blister roofs removed
right after blister induction) and calcipotriol-pretreated open
wounds in healthy volunteers. The reepithelialization rate and the
expression of BP180, BP230, plectin/HD1, β4 integrin,
laminin 5, collagen VII, laminin α5 chain, laminin β1
chain, tenascin-C, αvβ5 integrin, β5
integrin, α5 integrin, and α9 integrin during
reepithelialization were studied by haematoxylin and eosin stainings
and the immunofluorescence technique. BP180, BP230, and plectin/HD1
expression were analyzed by body site to exclude regional variation.
In normal epidermis, TGF-β receptors I and II were
detected in the basal epidermis. Diffusion calculations suggest
that circulation is likely to be a major source of TGF-β for
TGF-β receptors in the basal epidermis. Downregulation
of TGF-β receptors I and II was seen in lesional psoriatic epidermis,
suggesting that hyperproliferating lesional epidermis may have lost
TGF-β-mediated growth inhibition. Isotretinoin did not
affect the serum TGF-β1 or TGF-β2 levels, but
caused a 19% local increase in suction blister fluid TGF-β1.
Betamethasone caused a 17% decrease in suction blister
fluid TGF-β1, presumably due to glucocorticoid-induced
vasoconstriction. Modulation of the interstitial fluid TGF-β1
concentration may be one mechanism by which isotretinoin and betamethasone
mediate their effects in skin. Immunoreactivity for BP230 and plectin/HD1
was decreased in the basement membrane zone in uninvolved dermatitis
herpetiformis skin in a significant proportion of the patients,
suggesting distinct molecular changes in BP230 and plectin/HD1.
This may be a factor contributing to blister formation. Reepithelialization
rate was considerably slower in intact blisters than in open wounds
and was not affected by calcipotriol. BP230 and plectin/HD1 appeared
earlier in intact blisters than in open wounds. Reepithelialization
took place on a continuous laminin sheath in intact blisters, but
the laminin sheath in open wounds was partially discontinuous. It
was a novel finding that integrin αvβ5 and integrin β5
antibodies showed divergent distributions in regenerating epidermis.
The present results suggest that, in some bullous diseases, removal
of the blister roof could accelerate blister healing, calcipotriol
treatment does not delay wound epithelialization, a continuous laminin
sheath may inhibit reepithelialization, and the formation of the hemidesmosomal
inner plaque at the leading edge takes place earlier in the more
slowly reepithelializing intact blisters than in open wounds.
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Van, Heerden Jacobus Hendrik Francois. "Direct measurement of pore fluid suction in gold mine tailings." Diss., Pretoria : [s.n.], 2003. http://upetd.up.ac.za/thesis/available/etd-09212005-135324/.
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Chen, Wen. "Uniaxial behaviour of suction caissons in soft deposits in deepwater." University of Western Australia. School of Civil and Resource Engineering, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0136.
Full textAbstract:
Suction caissons are a cost-effective alternative to traditional piles in deep to ultradeep waters. No design rule has been available on the axial capacity of suction caissons as part of the mooring system in soft sediments. In this research, a series of centrifuge tests were performed using instrumented model caissons, to investigate the axial capacity and radial stress changes around caissons during installation, consolidation and vertical pullout in normally consolidated, lightly overconsolidated and sensitive clays. Total pressure transducers instrumented on the caisson wall were calibrated for various conditions. The radial total stress acting on the external wall varied almost linearly during penetration and extraction of the caisson, with smaller gradients observed during post-consolidation pullout. Minimum difference was found in the penetration resistance and the radial total stress for caissons installed by jacking or by suction, suggesting that the mode of soil flow at the caisson tip is similar under these two types of installation. Observed soil heave showed that the soil particles at the caisson tip flow about evenly outside and inside the caisson during suction installation. Comparison was made between measurements and various theoretical predictions, on both the radial stress changes during caisson installation, and the radial effective stress after consolidation. Significant under-predictions on excess pore pressure changes, consolidation times and external shaft friction ratios were found for the NGI Method, based on the assumption that the caisson wall is accommodated entirely by inward motion of the clay during suction installation. Obvious over-predictions by the MTD approach were found in both stress changes and shaft capacity of the caissons. A simple form of cavity expansion method was found to give reasonable estimations of stress changes and post-consolidation external shaft friction. A model for predicting the penetration resistance of suction caissons in clay was evaluated. Upper and lower bound values of external shaft friction ratio during uplift loading after consolidation were derived. Uplift capacity of caissons under sustained loading and cyclic loading were investigated, revealing approximately 15 to 30% reduction of the capacity compared to that under monotonic loading. External shaft friction ratios and reverse end-bearing capacity factors were both found to be significantly lower than those under monotonic loading
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Cotter, Oliver. "Installation of suction caisson foundations for offshore renewable energy structures." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534163.
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Dekker, Marijn Johannes. "The Modelling of Suction Caisson Foundations for Multi-Footed Structures." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27161.
Full textAbstract:
Suction caissons are a type of offshore foundation that allow for fast and noise-free installation and decommissioning of offshore structures. They have been used for 20 years in the oil and gas industry and are also becoming more common in the offshore wind sector as a promising way to cost reduction. SPT is a leading contractor for the installation of both single anchor piles and foundations on multiple caissons. The suction caissons are installed by applying a differential pressure between the inner and outer sides of the caissons, which pushes the caissons into the soil. When a platform is founded on multiple suction caissons, the way the wind and wave loads are transferred through the structure and various caissons into the soil will depend on the stiffness of both the platform and the caissons. The design of the substructure and suction caissons should thus be combined to include the effects of soil-structure interaction. This is currently done by modelling the suction caisson foundations as a set of linear-elastic springs attached to the substructure. These springs are however not able to capture the non-linear behaviour that is often characteristic for soils. A method has been developed to model the suction caisson foundations using non-linear springs. The characteristics of the springs are determined using FEM calculations with a nonlinear soil model in the geotechnical software PLAXIS. The springs are then implemented in a structural model of the substructure and the multiple foundations in the structural software SACS. The resulting loads on and displacements of the suction caisson foundations for a test load case have been compared to results from a complete FE model and a model that uses linear-elastic springs. The comparison has shown that the developed model gives results that match well with the results from the full FE model. The linear-elastic model on the other hand gives results that deviate significantly for high loads.When the stresses in the soil increase the soil will behave softer, leading to an increase of the displacements of the suction caissons for high loads. The substructure will help decrease large differences between the displacements of the suction caissons, resulting in a more even load distribution over the foundations and thus smaller design loads for the suction caissons. This allows for smaller suction caissons and savings of material and costs. The model with nonlinear springs is able to predict this behaviour of the soil and the substructure accurately and can be used to make a more efficient design of suction caisson foundations.
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Reijnen, Duncan P. (Duncan Peter). "Experimental study of boundary layer suction in a transonic compressor." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10754.
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Merchant, Ali A. (Ali Abbas). "Design and analysis of supercritical airfoils with boundary layer suction." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10987.
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Bobke, Alexandra. "Simulations of turbulent boundary layers with suction and pressure gradients." Licentiate thesis, KTH, Linné Flow Center, FLOW, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185275.
Full textAbstract:
The focus of the present licentiate thesis is on the effect of suction and pressure gradients on turbulent boundary-layer flows, which are investigated separately through performing numerical simulations.The first part aims at assessing history and development effects on adverse pressure-gradient (APG) turbulent boundary layers (TBL). A suitable set-up was developed to study near-equilibrium conditions for a boundary layer developingon a flat plate by setting the free-stream velocity at the top of the domain following a power law. The computational box size and the correct definition of the top-boundary condition were systematically tested. Well-resolved large-eddy simulations were performed to keep computational costs low. By varying the free-stream velocity distribution parameters, e.g. power-law exponent and virtual origin, pressure gradients of different strength and development were obtained. The magnitude of the pressure gradient is quantified in terms of the Clauser pressure-gradient parameter β. The effect of the APG is closely related to its streamwise development, hence, TBLs with non-constant and constant β were investigated. The effect was manifested in the mean flow through a much more pronounced wake region and in the Reynolds stresses through the existence of an outer peak. The terms of the turbulent kinetic energy budgets indicate the influence of the APG on the distribution of the transfer mechanism across the boundary layer. Stronger and more energetic structures were identified in boundary layers with relatively stronger pressure gradients in their development history. Due to the difficulty of determining the boundary-layer thickness in flows with strong pressure gradients or over a curvedsurface, a new method based on the diagnostic-plot concept was introduced to obtain a robust estimation of the edge of a turbulent boundary layer. In the second part, large-eddy simulations were performed on temporally developing turbulent asymptotic suction boundary layers (TASBLs). Findings from previous studies about the effect of suction could be confirmed, e.g. the reduction of the fluctuation levels and Reynolds shear stresses. Furthermore, the importance of the size of the computational domain and the time development were investigated. Both parameters were found to have a large impact on the results even on low-order statistics. While the mean velocity profile collapses in the inner layer irrespective of box size and development time, a wake region occurs for too small box sizes or early development time and vanishes once sufficiently large domains and/or integration times are chosen. The asymptotic state is charactersized by surprisingly thick boundary layers even for moderateReynolds numbers Re (based on free-stream velocity and laminar displacement thickness); for instance, Re = 333 gives rise to a friction Reynolds number Reτ = 2000. Similarly, the flow gives rise to very large structures in the outer region. These findings have important ramifications for experiments, since very large facilities are required to reach the asymptotic state even for low Reynolds numbers.QC 20160418
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Stanley, Mary Helen. "Suction Cup Lysimeter Method for Extracting Pine Bark Substrate Solution." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/42244.
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The objective of this study was to determine the effectiveness of suction cup lysimeters (SCL) in extracting substrate solution from pine bark substrates. Lysimeter types tested were 4.8-cm diameter with a ½ or 1-bar air-entry value (AEV) and 2.2-cm diameter also with a ½ or 1-bar AEV. Sufficient volume could be obtained when a vacuum pressure of 30, 40 or 50 cb was applied to lysimeters with a minimum extraction time of five minutes. The 2.2-cm lysimeters were found to be suitable for extracting solution if smaller sample volumes were needed. To determine effect of vacuum pressure and extraction time on volume extracted, the 4.8-cm ½-bar lysimeters were installed in containers with pine bark substrate and Quercus phellos L. (willow oak) trees. Volumes extracted were somewhat erratic and not strongly dependent upon centibars of vacuum or extraction time. Lysimeters immersed in water demonstrated that variability was not due to individual lysimeters, but to the coarse nature of the pine bark substrate. Substrate EC levels were not affected when volume of substrate solution extracted by the SCL's varied from 10 to190 ml.â
To determine the effectiveness of SCL's to monitor nutrient status of container-grown shade trees, two-year-old container-grown willow oak trees were grown in a pine bark substrate and fertilized with 0, 50, 100, 150, 200, 250 or 300 grams Osmocote Plus Northern (15N â 3.9P â 9.8K). Plant height and trunk diameter increased with up to 200 grams of Osmocote per container. There was a good relationship between solution EC and plant growthMaster of Science
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Brucia, Josephine Jacobs. "The effect of suction catheter insertion on head-injured adults." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1060867440.
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Register, Craig H. "A survey of neonatal suction techniques performed by registered nurses." Huntington, WV : [Marshall University Libraries], 2002. http://www.marshall.edu/etd/descript.asp?ref=128.
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