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1
Fugate, David C. "Estuarine suspended aggregate dynamics and characteristics." W&M ScholarWorks, 2002. http://www.vims.edu/physical/projects/CHSD/publications/reports/F2002%5FPHD.pdf.
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Chanyotha, Seree 1956. "Some river characteristics dependent on sediment transport." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/191975.
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The characteristics and behavior of rivers depend on numerous factors which are highly variable and complex. Sediment characteritics and sediment-transport capacity of rivers are important factors that influence river characteristics. Significant amounts of ground-water inflowing to or outflowing from a river reach affect flow characteristics of that reach, which in turn alter the capability of the reach for transporting sediment and result in changed river characteristics. In addition, inflow from a tributary carrying a sediment load with the same concentration as the main stream increases the capability to transport the sediment load of the downstream reach of the confluence. A simplified mathematical model of a generalized river reach was developed to investigate how ground-water recharge and inflow to the stream and tributary inflow affect and alter river characteristics.
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Wang, Zhanxian. "Improved representation of cross-shore sediment transport characteristics /." Licensed for access by UF students, faculty, and staff (and others in a UF library), 2004. http://wwwlib.umi.com/cr/ufl/fullcit?p3135226.
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He, Lilin. "Structure and transport characteristics of highly rigid ionomers." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1219851912/.
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Fung, Ka Man. "Injection characteristics of transport layers in PIN OLED." HKBU Institutional Repository, 2012. https://repository.hkbu.edu.hk/etd_ra/1448.
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Bendiksen, Bård A., Espen H. Blokkdal, and Eddy W. Hansen. "Unconsolidated material characteristics obtained by PFGNMR using (two) different probe molecules." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183710.
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Mahgoub, Abdelmagid. "Characteristics and mechanics of subaqueous debris flows /." Internet access available to MUN users only, 1998. http://collections.mun.ca/u?/theses,36691.
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Maldonado, Miguel. "Fabrication of mesoscopic semiconductor devices and their transport characteristics." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15006.
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Khoshtaghaza, Mohammad Hadi. "Hydrothermal characteristics and quality of alfalfa cubes during transport." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq23947.pdf.
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Uhlman, Kristine. "Arsenic in Arizona Ground Water -- Source and Transport Characteristics." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008. http://hdl.handle.net/10150/146413.
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4 pp.Following on the U.S. Environmental Protection Agency's "Arsenic Rule" decision to require public water systems to lower the allowable arsenic content in drinking water from 50 parts per billion (ppb) to 10 ppb by January 23, 2006, private well owners across the state have realized the importance of testing their own water supply for arsenic. Under Arizona law, it is the sole responsibility of the private well owner to determine the quality (potability) of their private well water. This article discusses the geologic prevelance of arsenic across the state, and options available to the well owner to address this water quality concern. Expected to be the first in a 3-part series on ground water quality issues common in Arizona.
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Ikeler, David S. "Transport in a nanostructure with quasiperiodically varying potential characteristics." Virtual Press, 1997. http://liblink.bsu.edu/uhtbin/catkey/1061879.
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Multiple longitudinal potential barriers affect electron transport in a nanostructure. In addition to a symmetric, aperiodic quantum wire with five potential barriers, a quantum wire containing thirteen potential barriers was modeled based on a quasiperiodic sequence known as the Fibonacci sequence. Conductance of the wires and transmission coefficients of the corresponding one-dimensional systems were calculated and analyzed in this work.Conductance calculations were performed using a FORTRAN computer program, tbgf, which performs the tight-binding, recursive Green's function method. Also Program Tran Coeffwas developed in order to calculate one-dimensional transmission coefficients using the method known as wavefunction matching. This method matches electronic wavefunctions in neighboring regions to determine the one-dimensional transmission coefficients at the electron energy normalized to the barrier strengths. The program uses the data file generated by Program Data Input.Department of Physics and Astronomy
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Karlis, Alexandros K., Fotios K. Diakonos, Christoph Petri, and Peter Schmelcher. "Fermi acceleration induces self-organized critical characteristics to the driven Lorentz channel." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183123.
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De, Santis Silvia, Giulia Di Pietro, Mauro Rebuzzi, and Silvia Capuani. "High field MR microimaging investigation gives more insights on spongy bone characteristics." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186404.
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Spongy-bone is a porous system characterized by a solid trabecular network immersed in bonemarrow and characterized by a different relative percentage of water and fats. In our previous paper, we demonstrated using calf bone samples, that water is more prevalent in the boundary zone while fats are rearranged primarily in the central zone of each pore. Moreover we showed that water internal gradient (Gi) magnitude from the samples was directly proportional to their trabecular bone density. Using a 9.4T MR micro-imaging system, here we evaluated T2, T2*, apparent diffusion coefficient (ADC) and Gi parameters from in vitro calf samples in spatially resolved modality, for both water and fat components. Moreover, relative percentages of water and fats were quantified from spectra. T2, T2* and ADC values are higher in fat than in water component. Moreover, the differential effects of fat and water diffusion result in different T2 and Gi behaviours. Our results suggest that differently from fat parameters, water T2*, ADC and Gi, may be reliable markers to assess not only trabecular bone density but, more generally, the status of spongy bone.
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Nichols, Samantha Laura, and 黎焯霖. "Sustainable transport in Hong Kong : reshuffling the transport hierarchy based on geographical and trip characteristics variations." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2015. http://hdl.handle.net/10722/212625.
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With the increased concern as to sustainable development in recent years, there is a need to develop a sustainable transport system as urban transportation plays an important role in cities. Transportation is an important part of daily life as it is related to mobility; and enhanced mobility will contribute to economic development and improve the quality of life. However, the most commonly used transport modes (i.e. motorised transportation) have contributed to heavy air and noise pollution, degrading our environment and affecting people’s quality of life. With this unsustainable urban transport system, there is an urgent need to apply the principles of sustainable development to the development of the transport system.
The aim of this study is to revisit the general transport hierarchy, examine how the hierarchy varies according to geographical and trip characteristics, and propose new sustainable transport hierarchies that take local contexts, availability of existing infrastructures, travel distance, and income level into consideration. In this study, Hong Kong is chosen as the focus of the study despite the fact that government has already identified the heavy rail system as the backbone of Hong Kong’s transport system, and 90% of all travel trips in Hong Kong are carried out on public transport, yet there is much room for improvements, for example the high roadside air pollution, the public transport are not fully utilised, non-motorised transport modes are not widely used, and the public transport fares are on the high side. The Travel Characteristics Survey 2001 will be used for examining trip characteristic variations in Hong Kong.
The findings suggest that the general transport hierarchies in Hong Kong do not match with the theoretically most sustainable transport hierarchy. Furthermore, the findings suggest that travel distance and income level have an effect on people’s choice of transport modes. The results give a better understanding of the overall sustainability of Hong Kong’s transport system and its local variations so that supportive policy can be formulated to further promote sustainable transportation based on the local characteristics, such as the availability of infrastructure, and the socio-economic and travel characteristics of residents in different districts.published_or_final_version
Geography
Master
Master of Philosophy
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Shimada, Takashi, Toshiki Sugai, Yutaka Ohno, Shigeru Kishimoto, Takashi Mizutani, Hiromichi Yoshida, Toshiya Okazaki, and Hisanori Shinohara. "Double-wall carbon nanotube field-effect transistors: Ambipolar transport characteristics." American Institute of Physics, 2004. http://hdl.handle.net/2237/7006.
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Khodary, Reda Hassan. "Influence of track shoe design on its performance characteristics." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389954.
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Phillips, John Mansell. "The effective particle size characteristics of fluvial suspended sediment." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296287.
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Bendiksen, Bård A., Espen H. Blokkdal, and Eddy W. Hansen. "Unconsolidated material characteristics obtained by PFGNMR using (two) different probe molecules." Diffusion fundamentals 20 (2013) 83, S. 1-2, 2013. https://ul.qucosa.de/id/qucosa%3A13670.
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Lavallee, Katherine. "Suspended Cohesive Particle Characteristics in the Connecticut River Estuary." Thesis, Boston College, 2017. http://hdl.handle.net/2345/bc-ir:107936.
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Thesis advisor: Gail C. KinekeTo determine the role of cohesive suspended particle characteristics on sediment transport patterns in an energetic estuary floc size, density, and settling velocity were investigated in the Connecticut River estuary over three years spanning varying fluvial discharge regimes. Concurrent measurements of in-situ floc size, flow, bed stress, salinity and suspended-sediment concentration (SSC) were used to identify primary influences on floc size variability. Water discharge ranged from 202 to 910 m³/s between the three sampling campaigns, and the timing of major sediment discharge events preceding measurement periods from 23 to 162 days. Two distinct particle populations were observed under high and low sediment discharge regimes. With abundant fluvial sediment input, flocculation occurred resulting in large, loosely-packed flocs dominating the suspended signal (median sizes of 194-209 µm; median excess densities of 13-17 kg/m³). Following an extended period of low sediment discharge, small, dense aggregates resuspended from the bed were observed throughout the water column (median size of 171 µm and excess density of 60 kg/m³). The timing of and partial decoupling of water and sediment discharge led to inter-annual patterns of cohesive particle characteristics controlled by fresh sediment supply. The large, light flocs with lower settling velocities characteristic of high sediment supply regimes likely bypass the estuary. Smaller compact aggregates dominated the low-sediment discharge regimes. However, the similar disaggregated size distribution of the two regimes suggests the same fine source material is reintroduced to the estuary with the intrusion of the salt wedge, which extends farther up-estuary during low discharge regimes and ultimately supplies the off-channel bays and coves
Thesis (MS) — Boston College, 2017
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Earth and Environmental Sciences
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El, Rashidy Rawia Ahmed Hassan. "The resilience of road transport networks : redundancy, vulnerability and mobility characteristics." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/7782/.
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This thesis is concerned with the development of a composite resilience index for road transport networks. The index employs three characteristics, namely redundancy, vulnerability and mobility, measuring resilience at network junction, link and origin-destination levels, respectively. Various techniques have been adopted to quantify each characteristic and the composite resilience index as summarised below. The redundancy indicator for road transport network junctions is based on the entropy concept, due to its ability to measure the system configuration in addition to being able to model the inherent uncertainty in road transport network conditions. Various system parameters based on different combinations of link flow, relative link spare capacity and relative link speed were examined. The developed redundancy indicator covers the static aspect of redundancy, i.e. alternative paths, and the dynamic feature of redundancy reflected by the availability of spare capacity under different network loading and service level. The vulnerability indicator for road transport network links is developed by combining vulnerability attributes (e.g. link capacity, flow, length, free flow and traffic congestion density) with different weights using a new methodology based on fuzzy logic and exhaustive search optimisation techniques. Furthermore, the network vulnerability indicators are calculated using two different aggregations: an aggregated vulnerability indicator based on physical characteristics and the other based on operational characteristics. The mobility indicator for road transport networks is formulated from two mobility attributes reflecting the physical connectivity and level of service. The combination of the two mobility attributes into a single mobility indicator is achieved by a fuzzy logic approach. Finally, the interdependence of the proposed characteristics is explored and the composite resilience index is estimated from the aggregation of the three characteristics indicators using two different approaches, namely equal weighting and principal component analysis methods. Moreover, the impact of real-time travel information on the proposed resilience characteristics and the composite resilience index has been investigated. The application of the proposed methodology on a synthetic road transport network of Delft city (Netherlands) and other real life case studies shows that the developed indicators for the three characteristics and the composite resilience index responded well to traffic load change and supply variations. The developed composite resilience index will be of use in various ways; first, helping decision makers in understanding the dynamic nature of resilience under different disruptive events, highlighting weaknesses in the network and future planning to mitigate the impact of disruptive events. Furthermore, each developed indicator for the three characteristics considered can be used as a tool to assess the effectiveness of different management policies or technologies to improve the overall network performance or the daily operation of road transport networks.
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Karlis, Alexandros K., Fotios K. Diakonos, Christoph Petri, and Peter Schmelcher. "Fermi acceleration induces self-organized critical characteristics to the driven Lorentz channel." Diffusion fundamentals 20 (2013) 52, S. 1-2, 2013. https://ul.qucosa.de/id/qucosa%3A13625.
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De, Santis Silvia, Giulia Di Pietro, Mauro Rebuzzi, and Silvia Capuani. "High field MR microimaging investigation gives more insights on spongy bone characteristics." Diffusion fundamentals 14 (2010) 6, S. 1-4, 2010. https://ul.qucosa.de/id/qucosa%3A13855.
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Spongy-bone is a porous system characterized by a solid trabecular network immersed in bonemarrow and characterized by a different relative percentage of water and fats. In our previous paper, we demonstrated using calf bone samples, that water is more prevalent in the boundary zone while fats are rearranged primarily in the central zone of each pore. Moreover we showed that water internal gradient (Gi) magnitude from the samples was directly proportional to their trabecular bone density. Using a 9.4T MR micro-imaging system, here we evaluated T2, T2*, apparent diffusion coefficient (ADC) and Gi parameters from in vitro calf samples in spatially resolved modality, for both water and fat components. Moreover, relative percentages of water and fats were quantified from spectra. T2, T2* and ADC values are higher in fat than in water component. Moreover, the differential effects of fat and water diffusion result in different T2 and Gi behaviours. Our results suggest that differently from fat parameters, water T2*, ADC and Gi, may be reliable markers to assess not only trabecular bone density but, more generally, the status of spongy bone.
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Tyack, J. N. "The effect of catchment characteristics on sewage settling velocity grading." Thesis, Aston University, 1995. http://publications.aston.ac.uk/14146/.
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A procedure has been developed which measures the settling velocity distribution of particles within a complete sewage sample. The development of the test method included observations of particle and liquid interaction using both synthetic media and sewage. Comparison studies with two other currently used settling velocity test procedures was undertaken. The method is suitable for use with either DWF or storm sewage. Information relating to the catchment characteristics of 35 No. wastewater treatment works was collected from the privatised water companies in England and Wales. 29 No. of these sites were used in an experimental programme to determine the settling velocity grading of 33 No. sewage samples. The collected data were analysed in an attempt to relate the settling velocity distribution to the characteristics of the contributing catchment. Statistical analysis of the catchment data and the measured settling velocity distributions was undertaken. A curve fitting exercise using an S-shaped curve which had the same physical characteristics as the settling velocity distributions was performed. None of these analyses found evidence that the settling velocity distribution of sewage had a significant relationship with the chosen catchment characteristics. The regression equations produced from the statistical analysis cannot be used to assist in the design of separation devices. However, a grading curve envelope was produced, the limits of which were clearly defined for the measured data set. There was no evidence of a relationship between settling velocity grading and the characteristics of the contributing catchment, particularly the catchment area. The present empirical approach to settling tank design cannot be improved upon at present by considering the variation in catchment parameters. This study has provided a basis for future research into the settling velocity measurement and should be of benefit to future workers within this field.
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Carvalho, Simoes Francisco Manuel de. "Fish and mammalian glut4 traffic characteristics: an evolutionary perspective on the importance of glut4 protein motifs for trafficking." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/662890.
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Glucose transporters (GLUTs) are extremely important for glucose metabolism. Glucose transporters uptake glucose from blood stream into the cells where it can be metabolized. Among the glucose transporters family, GLUT4, which is solely expressed in muscle and adipose tissues, displays a unique feature as it can change its cellular distribution within minutes in response to insulin to regulate glucose uptake. Therefore, the study of GLUT4 cellular trafficking is fundamental to understand its functioning and to deepen our knowledge on glucose homeostasis.
In this work, we utilized a GLUT4 fish variant, brown trout GLUT4, to study GLUT4 trafficking and the role of GLUT4 protein motifs in this process, in 3T3-L1 adipocytes. We observed that, in comparison to mammalian GLUT4 (RatGLUT4), brown trout GLUT4 (BtGLUT4) had a much weaker translocation to the plasma membrane in response to insulin which was in part due to a slower cellular trafficking (exocytosis and endocytosis) and to a poor targeting to the GLUT4 storage vesicles responsible for “holding” GLUT4 inside the cell in the absence of insulin; these vesicles represent the main pool of insulin-responsive GLUT4. In this thesis we also studied the most common GLUT4 endocytic routes. We analyzed the contribution of the clathrin-mediated and the cholesterol-dependent endocytic pathways for RatGLUT4 and BtGLUT4 internalization. We observed that whilst RatGLUT4 internalizes through both the clathrin-mediated and the cholesterol-dependent pathways, BtGLUT4 only utilizes the former. It has been suggested that in adipocytes, the main cholesterol-dependent internalization pathway is the caveolar route. The internalization through this pathway is mediated by plasma membrane structures called caveolae. The formation of these structures is dependent on the caveolin-1 protein. To analyze the role of caveolae in GLUT4 internalization we blocked its formation by knocking down caveolin-1 and observed an increase of RatGLUT4 and BtGLUT4 internalization; however, both GLUT4 isoforms showed less internalization through the clathrin-mediated and cholesterol-dependent pathways in the absence of cavolin-1. Therefore, we suggest that in 3T3-L1 adipocytes caveolin-1 knockdown induces internalization of GLUT4 through alternative pathways.
GLUT4 trafficking is regulated by cellular machinery that interacts with GLUT4 protein motifs. To analyze the role of the mammalian N-terminal FQQI8 and C-terminal TELEY502 motifs in GLUT4 trafficking we mutated the corresponding motifs in BtGLUT4 (FQHL8 and TELDY495, respectively) and observed that mutations in the C-terminal had little effect on BtGLUT4 trafficking whereas mutations on the N-terminal (especially FQQL8 mutant) improved BtGLUT4 intracellular retention in the absence of insulin. Furthermore, we verified that FQQL8 mutation increased BtGLUT4 retention in a syntaxin-6-rich compartment, possibly the trans-Golgi network. In addition to studying BtGLUT4 mutants we also analyzed the trafficking of a chimera consisting of a RatGLUT4 backbone with the large cytoplasmic loop of BtGLUT4 (L-GLUT4). We observed that L-GLUT4 possessed higher plasma membrane levels in the absence of insulin and as a result a weaker translocation. Moreover, we observed that this was caused, at least in part, by a reduction in the endocytosis of L-GLUT4 in the absence of insulin. We also analyzed the contribution of the clathrin-mediated and cholesterol-dependent pathways for L-GLUT4 internalization and observed that the loop substitution (L-GLUT4) reduced RatGLUT4 internalization through the cholesterol-dependent route. Moreover, in the absence of insulin and in caveolin-1, L-GLUT4 internalization did not increase as much as that of RatGLUT4. The internalization of L-GLUT4 in the absence of caveolin-1 and insulin occurred through a clathrin-mediated pathway, similarly to BtGLUT4, but it also internalized through a cholesterol-dependent pathway, unlike RatGLUT4 and BtGLUT4.
In summary, in this thesis we have contributed to increase the knowledge on GLUT4 trafficking and on the roles of the FQQI8 motif and large cytoplasmic loop in this process, in 3T3-L1 adipocytes.El transportador de glucosa GLUT4 tiene la capacidad de, en respuesta a insulina, cambiar su localización celular y de esta forma regular el transporte de glucosa. En este trabajo, hemos utilizado una variante de GLUT4 de trucha (BtGLUT4) para estudiar el trafico de GLUT4, así como sus dominios proteicos involucrados en este proceso, en adipocitos 3T3-L1. Hemos observado que en comparación con el GLUT4 de mamíferos (RatGLUT4), el BtGLUT4 tenia una menor capacidad de translocación a la membrana plasmática en respuesta a insulina y que esto se debía a una trafico celular mas lento (exocitosis y endocitosis) y a una peor retención en las vesículas responsables por retener el transportador dentro de la célula en ausencia de insulina. En este trabajo hemos observado que RatGLUT4 ha internalizado por la vía de endocitosis mediada por clatrina y por la vía dependiente de colesterol, mientras que BtGLUT4 solo ha utilizado la primera. Además, hemos inhibido la internalización caveolar, mediante bajada de la expresión de caveolina-1, y hemos observado un aumento de la internalización de RatGLUT4 y BtGLUT4. Con el objetivo de estudiar el papel del dominio FQQI8 (extremo -N) de mamífero en el trafico de GLUT4, hemos mutado la secuencia correspondiente en BtGLUT4 (FQHL8) y hemos observado que mutaciones en este dominio han mejorado la retención intracelular de BtGLUT4 en ausencia de insulina. También hemos estudiado el trafico de una quimera que consiste en la secuencia de RatGLUT4 con el lazo citoplasmático largo de BtGLUT4 (L-GLUT4). Hemos observado que la sustitución del lazo ha aumentado los niveles de RatGLUT4 en superficie en ausencia de insulina y que esto era debido, por lo menos en parte, a una menor endocitosis en ausencia de la hormona. También hemos observado que la sustitución del lazo de RatGLUT4 ha reducido su internalización a través de la vía dependiente de colesterol en ausencia de insulina. Además, en ausencia de caveolina-1 y insulina, la internalización de L-GLUT4 ha aumentado menos que la de RatGLUT4 y ha ocurrido a través de las vías mediada por clatrina y dependiente de colesterol.
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Müller, Nora [Verfasser]. "Stochastic Transport Equations: Method of Characteristics versus Scaling Transform Approach / Nora Müller." Bielefeld : Universitätsbibliothek Bielefeld, 2019. http://d-nb.info/1197798102/34.
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Armstrong, Ian. "A study of the transport characteristics of mammalian retinal pigment epithelium (RPE)." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276870.
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Pöllänen, Roy. "Nuclear fuel particles in the environment : characteristics, atmospheric transport and skin doses." Helsinki : University of Helsinki, 2002. http://ethesis.helsinki.fi/julkaisut/mat/fysik/vk/pollanen/.
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Watson, Sally Jane. "Solute transport and hydrodynamic characteristics in the Chalk aquifer at Tilmanstone, Kent." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1445180/.
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Research on the hydrodynamic characteristics of the Chalk aquifer is described in relation to the timescales and spatial extent of solute transport, focussing on the Tilmanstone - Eastry valley in east Kent. Groundwater contamination occurred there over a 70-year period as a result of coalfield brine infiltrating from surface lagoons. The resulting contamination is used as a large-scale, long-term conservative solute transport experiment, within which a series of geological and hydrogeological observations, and tracer tests, are used to investigate the transport properties of the Chalk. The objective is to consider appropriate methodologies for application to groundwater contamination investigations in the Chalk and characterisation of Chalk groundwater bodies in the context of the requirements of the EU Water Framework Directive. The geology and hydrogeology of the Tilmanstone area are reassessed in the light of recent work on Chalk lithostratigraphy, using available hydrological data and employing a regional groundwater flow model, coupled with a solute transport model utilising a first order mass transfer coefficient dual porosity approach. Field tests are analysed in terms of aquifer properties pertinent to solute transport at a scale of metres to tens of metres. Vertical profiles of hydraulic conductivity, groundwater velocity, fracture aperture and effective porosity are developed. A profile of chloride concentration in porewater is interpreted in the light of this work to develop a hydrostratigraphy for the area. A 1-D dual porosity model employing Fickian diffusive exchange is used to compute chloride concentration of fracture water and matrix porewater over time. This provides predictions for comparison with observations and the results of the mass transfer coefficient approach in the 3-D regional model. The combined results from the 1-D and 3-D models are used to direct development of a conceptual model of contaminant transport in the Chalk. Emphasis is placed on the effects of diffusive exchange between porewater and fracture water and the effects of the solute exchange approach adopted at different times in the plume history. Results are used to judge the applicability of methods for investigating contaminated groundwater and characterising groundwater bodies in the dual porosity Chalk aquifer.
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Ali, Aamer. "Evaluation of membrane characteristics and thermal polarization in membrane distillation." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30359/document.
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Le présent travail de thèse met l'accent sur divers aspects de la distillation membranaire dans l'objectif de concevoir des procédés de dessalement proches du " zéro effluent liquide ". De manière générale, deux sujets sont discutés en détail: (i) la corrélation entre les caractéristiques de la membrane et les performances du procédé de distillation membranaire (ii) la compréhension et le contrôle de la polarisation thermique en DM. L'analyse de l'état de l'art en distillation membranaire porte notamment sur les progrès dans le développement des membranes, dans la compréhension des phénomènes de transport, les récents développements dans la conception des modules et le colmatage. Des phénomènes annexes et les applications innovantes sont également discutés dans la partie introductive de la thèse. L'effet des conditions de fabrication et de la composition des collodions sur les caractéristiques des membranes et la corrélation entre ces dernières et leurs performances a été discuté dans la section suivante. Il est établi que la morphologie de la membrane joue un rôle crucial dans ses performances pour des applications sur des fluides réels. En outre, on met en évidence que l'impact de la morphologie de la membrane est différente selon que la procédé fonctionne avec une phase liquide froide du côté distillat (Direct Contact Membrane Distillation - DCMD)) ou avec un courant d'air sec ou le vide (Air Gap ou Vacuum Membrane Distillation). Dans une deuxième partie, les aspects théoriques et expérimentaux de la polarisation thermique en distillation membranaire (DCMD) ont également été étudiés. Les phénomènes de polarisation thermique sur une membrane plane ont été étudiés en utilisant une cellule spécialement conçue. L'effet des conditions de fonctionnement et de la concentration de la solution sur la polarisation thermique a été étudié expérimentalement. Nous avons observé que l'augmentation de concentration de la solution favorise la polarisation thermique à cause d'une détérioration de l'hydrodynamique résultante à la surface de la membrane. Certaines techniques actives et passives pour réduire la polarisation thermique et le colmatage en distillation membranaire ont également été examinées dans l'étude cette étude. Nous avons montré que la polarisation thermique peut être considérablement réduite en générant des écoulements secondaires dans le fluide circulant à l'intérieur du canal d'alimentation, donc à l'intérieur de la fibre creuse si c'est cette configuration qui est retenue. Dans la présente étude, l'induction d'un écoulement secondaire a été réalisée en utilisant les fibres torsadées en hélice et une configuration ondulée. En raison de l'amélioration du niveau de polarisation thermique du côté de l'alimentation et du distillat, les géométries de fibres ondulées fournissent des flux et des taux de rendement supérieurs à ceux des autres configurations. La mise en œuvre d'un écoulement pulsé et intermittent pour contrôler la polarisation en distillation membranaire a également été examinée. Notre étude permet de conclure que ces types d'écoulements ont un impact positif sur les taux de rendement et le facteur d'amélioration volumique (gain en flux ramené par rapport à l'augmentation du volume de l'équipement) sans compromis sur le taux de remplissage des carters de fibres creusesThe current PhD work emphasizes on various aspects of membrane distillation for approaching zero liquid discharge in seawater desalination. In broader sense, two themes have been discussed in detail: (i) correlation between membrane features and their performance in MD (ii) understanding and control of thermal polarization in MD. Introduction and state-of-the-art studies of MD including progress in membrane development, understanding the transport phenomenon, recent developments in module fabrication, fouling and related phenomenon and innovative applications have been discussed in introductory part of the thesis. The effect of operating conditions and dope compositions on membrane characteristics and correlation between membrane features and their performance has been discussed in subsequent section. It has been established that membrane morphology plays a crucial role in performance of the membrane for real applications. Furthermore, it has been demonstrated that the effect of membrane morphology is different for direct contact and vacuum configurations. Theoretical and experimental aspects of thermal polarization in direct contact membrane distillation have also been investigated. Thermal polarization phenomenon in a flat sheet membrane has been studied by using a specifically designed cell. The effect of operating conditions and solution concentration on thermal polarization has been explored experimentally. It has been observed that increased solution concentration favors the thermal polarization due to resulting poor hydrodynamic at the membrane surface and increase in diffusion resistance to the water vapors migrating from bulk feed phase to the membrane surface. Some active and passive techniques to decrease thermal polarization and possible fouling in membrane distillation have also been discussed in the current study. Thermal polarization can be greatly reduced by inducing secondary flows in the fluid flowing inside the fiber. The induction of secondary flows in the current study has been realized by using the fibers twisted in helical and wavy configurations. Due to improvement of thermal polarization coefficient on up and downstream, the undulating fiber geometries provide high flux and superior performance ratio. Application of intermittent and pulsatile flow to control thermal polarization in MD has also been discussed. It has been inferred that these flows have positive impact on performance ratio and volume based enhancement factors without compromising on packing density of the system. The application of MD for treatment of produced water has also been studied
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Ankers, Claire. "An investigation of the influence of catchment characteristics and source material on suspended sediment properties." Thesis, University of Exeter, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275897.
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Müller, Roland H., and Doreen Hoffmann. "Uptake of the herbicide 2,4-dichlorophenoxyacetate (2,4-D) by Delftia acidovorans MC1 - complex kinetic characteristics in dependence of pH and growth substrate." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194980.
Full textAbstract:
The uptake of the herbicide 2,4-dichlorophenoxyacetate (2,4-D) by the bacterial strain Delftia acidovorans MC1 was studied using 14C-labeled compound. Implication of active transport was suggested due to the effect of carbonylcyanide m-chlorophenylhydrazone (CCCP) as an uncoupler of the proton motive force, the presence of which reduced the uptake rate by up to 90%. Kinetic characteristics revealed a complex pattern that was strongly affected by the external pH. With 2,4-D-grown cells, the uptake characteristics followed a hyperbolic shape at pH 6.8 showing an intermediary plateau at ca. 20-100 μM 2,4-D. In contrast, the kinetics at pH 7.5 and 8.5 revealed a sigmoidal pattern. The maximum rate was obtained at around 400 μM 2,4-D, and amounted to 15-20 nmol/min*mg protein. Higher substrate concentrations led to inhibition. With cells grown on (RS)-2-(2,4-dichlorophenoxy)propionate [(RS)-2,4-DP], the uptake rate increased to about 65 nmol/min*mg protein which hints at substrate-dependent induction of specific carrier(s). With 2,4-D-grown cells, such a high rate was obtained only after cloning and expression of the tfdK gene, which encodes a specific transporter for 2,4-D. The uptake pattern of 2,4-D changed with mutant strains of MC1 that were phenotypically deficient of cleavage activity to ether bond in phenoxyalkanoate herbicides. Apparently, genes coding for proteins in uptake function were in addition deleted. With strains that lacked (R)-2,4-DP cleavage, the plateau disappeared and the kinetics followed a more continuous pattern. Strains that lacked (S)-2,4-DP cleavage showed faint 2,4-D uptake at all. The present picture hints at three proteins that are involved in 2,4-D uptake by active transport. With degradation-negative mutants of strain MC1, the influx of 2,4-D proceeded at a low rate. It was linearly dependent on the 2,4-D concentration correspond-ding to a micro-molar rate constant of 1.08*10-5 min-1 mg protein-1. The latter hints at 2,4-D influx into the cell by diffusion via cytoplasmic membrane at a low rate.
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Chen, Rong. "Coupled electrochemical and heat/mass transport characteristics in passive direct methanol fuel cells /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?MECH%202007%20CHEN.
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Bennett, Paul. "Evaluation of the solute transport characteristics of surcharged manholes using a RANS solution." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/3098/.
Full textAbstract:
Urban drainage networks contain a large number of structures; the most common of which is a manhole. Previous studies investigating solute transport through manholes identified a threshold level of surcharge at which the hydraulic conditions in the manholes sharply altered. At high levels of surcharge, a dead zone formed above the main jet, potentially retaining solute for later discharge. This phenomenon could have significant impacts on the results obtained from 1D urban drainage network models which only consider pure advection. Previous research (including other CFD based studies) concentrated on steady flow conditions through these structures which are not thought to be representative of the dynamic flow conditions experienced in practice. During large storm events, the capacity of combined sewer networks may be exceeded. This leads to the discharge of untreated sewage to receiving watercourses. Discharges such as these are governed by legislation and, therefore, an understanding of pollutant transfer through urban drainage networks is required. Using existing laboratory and Computational Fluid Dynamics (CFD) data, this study produced a primary and secondary validated methodology for meshing and modelling manholes using CFD. This was then extended to free-surface multiphase modelling allowing for more realistic unsteady conditions to be considered. This included an in-depth comparison of suitable turbulence models and solute-modelling options. It was found that, whilst it was possible to model multiphase free-surface flow within such a structure, it was unnecessarily computationally expensive as temporal changes in the flow field are rapid when compared with a practical time-step for use with 1D models. The validated modelling methodology was then used to recreate the original study that identified the hydraulic threshold. This included a selection of manholes with a range of inlet to manhole diameter ratios. However, this was extended further to include manholes with a ratio less than five (commonly found in UK sewer systems). It was shown that the hydraulic threshold broke down below this limit, removing the need for this to be modelled in 1D systems.
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Mao, Ningtao. "Effect of fabric structure on the liquid transport characteristics of nonwoven wound dressings." Thesis, University of Leeds, 2000. http://etheses.whiterose.ac.uk/3171/.
Full textAbstract:
Nonwoven materials are widely used in medical and hygiene applications, and may demonstrate significant anisotropic characteristics in liquid transport. This study investigates the anisotropic liquid transport in such structures, and establishes a relationship between the structure and anisotropic properties of liquid transport. A comprehensive literature review is concerned with previous work on liquid transport in general with particular reference to its importance in the function of wound dressings. Preliminary experiments using commercial nonwoven wound dressing fabrics demonstrated the anisotropic nature of liquid absorption. After a review of existing steady state and dynamic methods of measuring the liquid transport in fabrics, a novel computer-integrated instrument is described that measures the in-plane liquid transmission in up to eight different directions. Needle-punched and hydroentangled fabrics with different structural parameters (fibre type, fibre diameter, fabric porosity and fibre orientation) were produced and characterised. The anisotropic liquid transport properties of these fabrics were tested using the new instrument. Unique theoretical models were established to predict the specific directional permeability of nonwoven fabrics based on the main fabric structural parameters (fibre diameter, fabric porosity and fibre orientation distribution).
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Fischer, Sandra. "Sensitivity of sediment transport on river characteristics in the large, braided Brahmaputra River." Thesis, Stockholms universitet, Institutionen för naturgeografi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-118443.
Full textAbstract:
Erosional issues in the Brahmaputra River in the eastern Himalayas pose increasing pressure on the nearby societies and ecosystems. With a proceeding climate change and increasing anthropogenic disturbance, predictive models are needed to evaluate the effect on sediment transport. Especially in braided rivers, like the Brahmaputra, sediment transport processes imply high demands on numerical models. The objective is therefore to assess the sensitivity of sediment transport on changed river characteristics in the Brahmaputra River, in order to qualitatively evaluate future possible dynamics. Through the one-dimensional steady state model, HEC-RAS 4.1, the braided river was simplified into a single straight channel to enable an extensive reach (700 km) to be modelled. Since little comparative data were at hand, a literature review gathered independent estimates of each parameter. Their natural variability was applied in the sensitivity analysis, and the model produced a suspended sediment load representing approximately 35% of observed data. The sensitivity analysis showed that the channel bathymetry form had a large impact on the model results, whereas the amount of lateral inflow (both surface and subsurface waters) to the main channel flow had a very small impact. Overall, the suspended sediment load were interpreted to be increasing from a future climate change, while further river regulation could counteract such elevation. Further studies are required concerning the river bathymetry in large scale modelling and to address transport of finer cohesive sediments. This methodology proposes a novel approach on how to analyze sediment transport at a large scale that could be used as a tool to interpret future possible changes and ultimately contribute to a better understanding of sediment transport modelling in the area.
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Lee, Heejae. "Analysis of Current-Voltage Hysteresis and Ageing Characteristics for CH3NH3PbI3-xClxBased Perovskite Thin Film Solar Cells." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX009/document.
Full textAbstract:
Les perovskites organiques-inorganiques en halogénures de plomb sont des matériaux très prometteurs pour la prochaine génération de cellules solaires avec des avantages intrinsèques tels que leur faible coût de fabrication (grande disponibilité des matériaux de base et leur mise en œuvre à basse température) et leur bon rendement de conversion photovoltaïque. Cependant, les cellules solaires pérovskites sont encore instables et montrent des effets d'hystérésis courant-tension délétères. Dans cette thèse, des résultats de l’analyse physique de couches minces de pérovskite à base de CH3NH3PbI3-xClx et de cellules solaires ont été présentés. Les caractéristiques de transport électrique et les processus de vieillissement ont été étudiés avec différentes approches.Dans une première étape, la synthèse du matériau pérovskite a été optimisée en contrôlant les conditions de dépôt des films en une seule étape telles que la vitesse de rotation (6000 rpm) de la tournette et la température de recuit des films (80 °C). Dans un second temps, des cellules solaires perovskites à base de CH3NH3PbI3-xClx ont été fabriquées en utilisant la structure planaire inversée et caractérisées optiquement et électriquement.Grace à l’utilisation de la spectroscopie optique à décharge luminescente (GDOES), un déplacement des ions halogénures a été observé expérimentalement et de façon directe sous l’application d’une tension électrique. Une longueur de diffusion ionique de 140 nm et un rapport de 65% d'ions mobiles ont été déduits. Il est montré que l'hystérésis courant-tension dans l'obscurité est fortement affectée par la migration des ions halogénures provoquant un écrantage substantiel du champ électrique appliqué. Nous avons donc trouvé sous obscurité un décalage de la tension à courant nul jusque 0,25 V et un courant de fuite jusque 0,1 mA / cm2 en fonction des conditions de mesure. Grâce aux courbes courant-tension en fonction de la température, nous avons déterminé la température de transition de la conductivité ions/électrons à 260K et analysé les résultats expérimentaux en utilisant l'équation de Nernst- Einstein donnant une énergie d'activation de 0.253 eV pour les ions mobiles.Enfin, le processus de vieillissement de la cellule solaire a été étudié avec des mesures optiques et électriques. Nous avons déduit que le processus de vieillissement apparaît d'abord à la surface des cristaux de pérovskite ainsi qu’aux joints de grains. Les mesures GDOES nous indiquent que les caractéristiques électriques des cellules pérovskites sont perdues par une corrosion progressive de l'électrode supérieure en argent causée par la diffusion des ions ioduresOrganic-inorganic lead halide perovskites are very promising materials for the next generation of solar cells with intrinsic advantages such as a low-cost material due to the availability of source materials and low-temperature solution processing as well as a high power conversion efficiency of the sunlight. However, perovskite solar cells are still unstable and show deleterious current-voltage hysteresis effects. Inthis thesis, analyses of CH3NH3PbI3-xClx based perovskite thin films and solar cells are presented. The electrical transport characteristics and the ageing processes are investigated using different approaches.The synthesis of the halide perovskite materials is optimized in a first step by controlling the deposition conditions such as annealing temperature (80°C) and spinning rate (6000 rpm) in the one step-spin-casted process. CH3NH3PbI3-xClx based perovskite solar cells are then fabricated in the inverted planar structure and characterized optically and electrically in a second step.Direct experimental evidence of the motion of the halide ions under an applied voltage has been observed using glow discharge optical emission spectroscopy (GDOES). Ionic diffusion length of 140 nm and ratio of mobile iodide ions of 65 % have been deduced. It is shown that the current-voltage hysteresis in the dark is strongly affected by the halide migration which causes a substantial screening of the applied electric field. Thus we have found a shift of voltage at zero current (< 0.25 V) and a leakage current (< 0.1 mA/cm2) in the dark versus measurement condition. Through the current-voltage curves as a function of temperature we have identified the freezing temperature of the mobile iodides at 260K. Using the Nernst-Einstein equation we have deduced a value of 0.253 eV for the activation energy of the mobile ions.Finally, the ageing process of the solar cell has been investigated with optical and electrical measurements. We deduced that the ageing process appear at first at the perovskite grain surface and boundaries. The electrical characteristics are degraded through a deterioration of the silver top-electrode due to the diffusion of iodides toward the silver as shown by GDOES analysis
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Bello, Kelani. "Modeling multiphase solid transport velocity in long subsea tiebacks : numerical and experimental methods." Thesis, Robert Gordon University, 2013. http://hdl.handle.net/10059/3138.
Full textAbstract:
Transportation of unprocessed multiphase reservoir fluids from deep/ultra deep offshore through a long subsea tieback/pipeline is inevitable. This form of transportation is complex and requires accurate knowledge of critical transport velocity, flow pattern changes, phase velocity, pressure drop, particle drag & lift forces, sand/liquid/gas holdup, flow rate requirement and tieback sizing etc at the early design phase and during operation for process optimisation. This research investigated sand transport characteristics in multiphase, water‐oil‐gas‐sand flows in horizontal, inclined and vertical pipes. Two critical factors that influence the solid particle transport in the case of multiphase flow in pipes were identified; these are the transient phenomena of flow patterns and the characteristic drag & lift coefficients ( D C , L C ). Therefore, the equations for velocity profile were developed for key flow patterns such as dispersed bubble flow, stratified flow, slug flow and annular flow using a combination of analytical equations and numerical simulation tool (CFD). The existing correlations for D C & L C were modified with data acquired from multiphase experiment in order to account for different flow patterns. Minimum Transport Velocity (MTV) models for suspension and rolling were developed by combining the numerically developed particle velocity profile models with semi‐empirical models for solid particle transport. The models took into account the critical parameters that influence particle transport in pipe flow such as flow patterns and particle drag & lift coefficients, thus eliminate inaccuracies currently experienced with similar models in public domain. The predictions of the proposed MTV models for suspension and rolling in dispersed bubble, slug flow and annular flow show maximum average error margin of 12% when compared with experimental data. The improved models were validated using previously reported experimental data and were shown to have better predictions when compared with existing models in public domain. These models have the potential to solve the problems of pipe and equipment sizing, the risk of sand deposition and bed formation, elimination of costs of sand unloading, downtime and generally improve sand management strategies.
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Kovach, Bob. "TEMPORAL ALIGNMENT OF TELEMETRY STREAMS WITH DIVERSE DELAY CHARACTERISTICS." International Foundation for Telemetering, 2003. http://hdl.handle.net/10150/605597.
Full textAbstract:
International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, NevadaIn many test ranges, it is often required to acquire a number of telemetry streams and to process the data simultaneously. Frequently, the streams have different delay characteristics, requiring temporal alignment before the processing step. It is desired to have the capability to align these streams so that the events in each stream are coincident in time. Terawave Communications has developed technology to perform temporal alignment for a number of streams automatically. Additionally, the algorithm performs the delay compensation independent of the source data rate of each stream. Terawave will present the algorithm and share the results of their testing in a test installation.
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Smith, David A. "Effect of particle shape on grain size, hydraulic, and transport characteristics of calcareous sand." Thesis, University of Hawaii at Manoa, 2003. http://proquest.umi.com/pqdweb?index=0&did=764803691&SrchMode=1&sid=2&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1233275673&clientId=23440.
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Charest, Abigail J. "Investigation of Physical Characteristics Impacting Fate and Transport of Viral Surrogates in Water Systems." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-dissertations/54.
Full textAbstract:
A multi-scale approach was used to investigate the occurrence and physical characteristics of viral surrogates in water systems. This approach resulted in a methodology to quantify the dynamics and physical parameters of viral surrogates, including bacteriophages and nanoparticles. Physical parameters impacting the occurrence and survival of viruses can be incorporated into models that predict the levels of viral contamination in specific types of water. Multiple full-scale water systems (U.S., Italy and Australia) were tested including surface water, drinking water, stormwater and wastewater systems. Water quality parameters assessed included viral markers (TTV, polyomavirus, microviridae and adenovirus), bacteriophages (MS2 and ΦX-174), and coliforms (total coliforms and E. coli). In this study, the lack of correlations between adenovirus and that of bacterial indicators suggests that these bacterial indicators are not suitable as indicators of viral contamination. In the wastewater samples, microviridae were correlated to the adenovirus, polyomavirus, and TTV. While TTV may have some qualities which are consistent with an indicator such as physical similarity to enteric viruses and occurrence in populations worldwide, the use of TTV as an indicator may be limited as a result of the detection occurrence. The limitations of TTV may impede further analysis and other makers such as coliphages, and microviridae may be easier to study in the near future. Batch scale adsorption tests were conducted. Protein-coated latex nanospheres were used to model bacteriophages (MS2 and ΦX-174) and includes a comparison of the zeta potentials in lab water, and two artificial groundwaters with monovalent and divalent electrolytes. This research shows that protein-coated particles have higher average log10 removals than uncoated particles. Although, the method of fluorescently labeling nanoparticles may not provide consistent data at the nanoscale. The results show both that research on viruses at any scale can be difficult and that new methodologies are needed to analyze virus characteristics in water systems. A new dynamic light scattering methodology, area recorded generalized optical scattering (ARGOS) method, was developed for observing the dynamics of nanoparticles, including bacteriophages MS2 and ΦX-174. This method should be further utilized to predict virus fate and transport in environmental systems and through treatment processes. While the concentration of MS2 is higher than ΦX-174 as demonstrated by relative total intensity, the RMSD shows that the dynamics are greater and have more variation in ΦX-174 than MS2 and this may be a result of the hydrophobic nature of ΦX-174. Relationships such as these should be further explored, and may reflect relationships such as particle bonds or hydrophobicity.
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Gunow, Geoffrey Alexander. "Full core 3D neutron transport simulation using the method of characteristics with linear sources." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119030.
Full textAbstract:
Thesis: Ph. D. in Computational Nuclear Science and Engineering, Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 269-274).
The development of high fidelity multi-group neutron transport-based simulation tools for full core Light Water Reactor (LWR) analysis has been a long-standing goal of the reactor physics community. While direct transport simulations have previously been far too computationally expensive, advances in computer hardware have allowed large scale simulations to become feasible. Therefore, many have focused on developing full core neutron transport solvers that do not incorporate the approximations and assumptions of traditional nodal diffusion solvers. Due to the computational expense of direct full core 3D deterministic neutron transport methods, many have focused on 2D/1D methods which solve 3D problems as a coupled system of radial and axial transport problems. However, the coupling of radial and axial problems also introduces approximations. Instead, the work in this thesis focuses on explicitly solving the 3D deterministic neutron transport equations with the Method of Characteristics (MOC). MOC has been widely used for 2D lattice physics calculations due to its ability to accurately and efficiently simulate reactor physics problems with explicit geometric detail. The work in this thesis strives to overcome the significant computational cost of solving the 3D MOC equations by implementing efficient track generation, axially extruded ray tracing, Coarse Mesh Finite Difference (CMFD) acceleration, linear track-based source approximations, and scalable domain decomposition. Transport-corrected cross-sections are used to account for anisotropic without needing to store angular-dependent sources. Additionally, significant attention has been given to complications that arise in full core simulations with transport-corrected cross-sections. The convergence behavior of transport methods is analyzed, leading to a new strategy for stabilizing the source iteration scheme for neutron transport simulations. The methods are incorporated into the OpenMOC reactor physics code and simulation results are presented for the full core BEAVRS LWR benchmark. Parameter refinement studies and comparisons with reference OpenMC Monte Carlo solutions show that converged full core 3D MOC simulations are feasible on modern supercomputers for the first time.
by Geoffrey Alexander Gunow.
Ph. D. in Computational Nuclear Science and Engineering
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Ho, Hao-Che. "Investigation of unsteady and non-uniform flow and sediment transport characteristics at culvert sites." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/814.
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The present study is an integral part of a broader study focused on the design and implementation of self-cleaning culverts, i.e., configurations that prevent the formation of sediment deposits after culvert construction or cleaning. Sediment deposition at culverts is influenced by many factors, including the size and characteristics of material of which the channel is composed, the hydraulic characteristics generated under different hydrologic events, the culvert geometry design, channel transition design, and the vegetation around the channel. The multitude of combinations produced by this set of variables makes the investigation of practical situations challenging.
In addition to the above considerations, the field observations, and the laboratory and numerical experiments have revealed additional complexities of the flow and sediment transport through culverts that further increase the dimensions of the investigation. The flow complexities investigated in this study entail: flow non-uniformity in the areas of transition to and from the culvert, flow unsteadiness due to the flood wave propagation, and the complex correlation between the flow and sediment hydrographs produced during storm events. To date, the literature contains no systematic studies on sediment transport through multi-box culverts. Similarly, there is limited knowledge about the non-uniform, unsteady sediment transport in channels of variable geometry. Furthermore, there are few readily useable numerical models that can reliably simulate flow and sediment transport in such complex situations.
Given the current state of knowledge, the main goal of the present study is to investigate the above flow complexities in order to provide the needed insights for optimizing the culvert design. The research was phased so that field observations were conducted first to understand the culvert behavior in Iowa landscape. Modeling through complementary hydraulic model and numerical experiments was subsequently carried out to gain the practical knowledge for the development of the self-cleaning culvert designs.
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Ng, Karen Karpui. "Malpighian tubules of A. dorsalis mosquito larvae : general characteristics and mechanism of magnesium transport." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24873.
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Malpighian tubules of A. dorsalis mosquito larvae, studied in vitro, actively transported magnesium at high rates against concentration gradients as large as 16-fold and transepithelial potential gradients of approximately -l5mV. Fluid secretion rates, determined over 90 minute periods, in the presence and absence of cAMP, indicated that A. dorsalis tubules were viable and had secretion rates of the same magnitude as those reported for A. taeniorhynchus tubules. Having characterized the in vitro preparation of Malpighian tubules, the main hypothesis that Mg²⁺ transport is driven predominately by counter transport with Na⁺ was tested. This hypothesis was not supported by kinetic, Na-substitution, or inhibitor studies. Kinetic and Bumetanide studies suggest backflux of K drives J mg;
however, this was not consistently found in other studies.Science, Faculty of
Zoology, Department of
Graduate
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Kim, Young-chul. "Characteristics of plasma turbulence in the Mega Amp Spherical Tokamak." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:23eea01f-e910-418c-993e-06b3b85d5d43.
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Turbulence is a major factor limiting the achievement of better tokamak performance as it enhances the transport of particles, momentum and heat which hinders the foremost objective of tokamaks. Hence, understanding and possibly being able to control turbulence in tokamaks is of paramount importance, not to mention our intellectual curiosity of it. We take the first step by making measurements of turbulence using the 2D ($8$ radial $imes$ $4$ poloidal channels) beam emission spectroscopy (BES) system on the Mega Amp Spherical Tokamak (MAST). Measured raw data are statistically processed, generating spatio-temporal correlation functions to obtain the physical characteristics of the turbulence such as spatial and temporal correlation lengths as well as its motion. The reliability of statistical techniques employed in this work is examined by generating and utilizing synthetic 2D BES data. The apparent poloidal velocity of fluctuating density patterns is estimated using the cross-correlation time delay method. The experimental results indicate that the poloidal motion of fluctuating density patterns in the lab frame arises because the patterns are advected by the strong toroidal plasma flows while the patterns are aligned with the background magnetic fields which are not parallel to the flows. Furthermore, various time scales associated with the turbulence are calculated using statistically estimated spatial correlation lengths and correlation times of turbulence. We find that turbulence correlation time, the drift time associated with ion temperature or density gradients, the ion streaming time along the magnetic field line and the magnetic drift time are comparable and possibly scale together suggesting that the turbulence, determined by the local equilibrium, is critically balanced. Finally, we argue that we have produced a critical manifold in the experimentally obtained local equilibrium parameter space separating dominant turbulent transport from a non-turbulent or weakly turbulent state. It shows that the inverse ion-temperature-gradient scale length is correlated inversely with $q/arepsilon$ (safety factor/inverse aspect ratio) and positively with the plasma rotational shear. Practically, this means that we can attain the stiffer ion-temperature-gradient, thus hotter plasma core, without increasing the rotational shear.
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Cooke, Sean. "Investigating the relationships between land use characteristics, public transport network features and financial viability at a corridor scale." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22716.
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The successful integration of public transport and land development planning is likely to be central in determining how effectively the cities in the 'global south' manage the mounting pressures from rapid urbanization, population growth and rising income inequality. While a number of Sub-Saharan African cities, particularly in South Africa, have commenced large scale public transport reform, little research has been undertaken to date on appropriate public transport-land use integration in these contexts. As a result, both of the initial phases of BRT corridor implementation, in Cape Town and Johannesburg, have been found to be financially unsustainable in their current urban forms. The major decisions regarding the design of land use environments and public transport networks, in the context of rapidly developing cities, still occur without due consideration for each other. The aim of this study is to investigate the relationships between land use characteristics, network features and viable public transport services in the South African context and at a corridor scale. The study utilises a public transport corridor operating cost model that was created to simulate the effects of variation in four land use characteristics (population density, density distribution, land use mix and destination accessibility) and two public transport network features (mode technology and service configuration) on the financial viability of services. The corridor operating cost model consists of cascading land use, transport and costing sub-models for which the output of one supplies the input of the next. Gross population density was found to have the weakest causal relationship with financial viability. Density distribution was shown to have a very significant effect on the average passenger trip length, and financial viability as a result. When the majority of the population is articulated adjacent to the public transport trunk corridors, at a higher density, far fewer inefficient feeder services are required. Additionally, the chosen non-motorised transport mode for those accessing the trunk service directly had a considerable effect as the higher speed of bicycles increases the catchment area within which a feeder service is usually not required. Bicycle-based density articulation was able to halve the total cost of the public transport network in one of the cases, relative to the conventional pedestrian-based variety. Land use mix had a strong connection to public transport financial viability, through substantial effects on peak passenger volume. The final land use characteristic, destination accessibility, was represented by distance to the Central Business District (CBD), as well as dictating the length of the transport corridor. It was found to have a substantial influence on financial viability and affordability, especially in the context of a distance-based fare system. Passenger volume is the key determinant of mode technology choice and is influenced by population density, as well as the other three land use characteristics to a lesser degree. Low population densities intuitively favour smaller vehicles, while high densities or economies of scale promote the use of suburban rail and other capital intensive modes. Long public transport corridors with unsupportive land use environments favour larger vehicles, such as the BRT and non-BRT articulated bus modes. Fewer of these large vehicles are required to meet the demand and they can efficiently operate over longer distances than their smaller competitors. Whereas, short corridors and supportive land use environments favour the space priority that the conventional and articulated BRT modes possess. The higher speed that the segregated lanes allow the vehicles to reach over the shorter route distance also decreases vehicle requirements due to the higher rate of trips per hour per vehicle. The trunk-feeder and direct service configurations reacted similarly to the changes in land use characteristics, when the optimum modes are chosen to minimise costs. The results of the study suggest that a detailed land use development plan is necessary for each major public transport corridor, with unique targets for population density, density articulation and land use mix. It also demonstrated that, in the South African context, to achieve a high public transport modal split and sustainable public transport service requires high population densities, high articulation, mixed land uses, small corridor catchment areas and minimal feeder services.
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Perea-Estrada, Hugo. "Development, Verification, and Evaluation of a Solute Transport Model in Surface Irrigation." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1322%5F1%5Fm.pdf&type=application/pdf.
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Pandya, Tara M. "Long Characteristic Method in Space and Time for Transport Problems." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7484.
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Discretization and solving of the transport equation has been an area of great
research where many methods have been developed. Under the deterministic transport
methods, the method of characteristics, MOC, is one such discretization and solution
method that has been applied to large-scale problems. Although these MOC,
specifically long characteristics, LC, have been thoroughly applied to discretize and
solve transport problems in the spatial domain, there is a need for an equally adequate
time-dependent discretization. A method has been developed that uses LC discretization
of the time and space variables in solving the transport equation. This space-time long
characteristic, STLC, method is a discrete ordinates method that applies LC
discretization in space and time and employs a least-squares approximation of sources
such as the scattering source in each cell. This method encounters the same problems
that previous spatial LC methods have dealt with concerning achieving all of the
following: particle conservation, exact solution along a ray, and smooth variation in
reaction rate for specific problems. However, quantities that preserve conservation in
each cell can also be produced with this method and compared to the non-conservative results from this method to determine the extent to which this STLC method addresses
the previous problems.
Results from several test problems show that this STLC method produces
conservative and non-conservative solutions that are very similar for most cases and the
difference between them vanishes as track spacing is refined. These quantities are also
compared to the results produced from a traditional linear discontinuous spatial
discretization with finite difference time discretization. It is found that this STLC
method is more accurate for streaming-dominate and scattering-dominate test problems.
Also, the solution from this STLC method approaches the steady-state diffusion limit
solution from a traditional LD method. Through asymptotic analysis and test problems,
this STLC method produces a time-dependent diffusion solution in the thick diffusive
limit that is accurate to O(E) and is similar to a continuous linear FEM discretization
method in space with time differencing. Application of this method in parallel looks
promising, mostly due to the ray independence along which the solution is computed in
this method.
48
Chanyotha, Seree. "Some river characteristics dependent on sediment transport." 1988. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1988_161_sip1_w.pdf&type=application/pdf.
Full text
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Lu, Meng-I., and 呂孟奕. "Transport Characteristics of InSe Field-Effect-Transistors." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/4d68v7.
Full textAbstract:
碩士國立清華大學
電子工程研究所
107
In the presence of short channel effect along with device scaling down, the use of 2D materials may be a possible solution. Indium selenide(InSe), which belongs to III-VI group layered semiconductors, is a promising material with small electron effective mass and large tunable bandgap. Instability like black phosphorus making InSe devices easy to be affected by water and O_2 molecules. In this thesis, surface treatment by 90 torr, pure oxygen environment was made to form a protective oxide layer. By comparing transport characteristics of devices with different oxidation time, we find that 6-hours-oxidation device had the best performance. Next, we measured current hysterysis and I-T curves of devices to confirm different oxide quality. Furthermore, we find that using e-beam lithography to scale down channel length may largely degrade device performance. Finally, in order to improve device performance by photo-assisted charge transfer, we deposited PbS quantum dot on InSe devices. The result showed that chemicals used in ligand exchange process will damage InSe channel, therefore the improvement of transport characteristics can not be seen.
50
Lee, Su-Yun, and 李素昀. "Electrically controlled transport characteristics in nanoparticle compacts." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/947e37.
Full textAbstract:
碩士國立中央大學
物理研究所
94
The nanoparticle compacts were fabricated by evenly mixing 2.4 nm Ag and 4.8 nm core/shell Cu/Cu2O nanoparticles with selective mass ratios. The nanocompacts of x/100-x mass ratio for Ag/(Cu/Cu2O) was donated as (Ag)x(Cu/Cu2O)100-x. Its relative mass density with respect to the bulk material would be used to denote the compacting density (CD). An (Au)100-68% nanocompact was also be fabricated by 2.2 nm Au nanoparticles. The resistivities of the nanocompacts were measured by the standard four-probe setup, operated in the constant current or constant voltage mode. The resistivities of nanocompacts may be described by tunneling transport. For nanocompacts consist of ultra small nanoparticles, the resistivities growing indicate that tunneling barrier potentials increase as the temperature was raised. In addition, the resistivities were also found to be very sensitive to the bias voltage.