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Steven, Adelina. "Risk Assessment of Dropped Cylindrical Objects in Offshore Operations." ScholarWorks@UNO, 2018. https://scholarworks.uno.edu/td/2495.
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Dropped object are defined as any object that fall under its own weight from a previously static position or fell due to an applied force from equipment or a moving object. It is among the top ten causes of injuries and fatality in oil and gas industry. To solve this problem, several in-house tools and guidelines is developed over time to assess the risk of dropped objects on the sub-sea structures. This thesis focuses on compiling and comparing those methods in hope to improve the recommended practices available in the market. A simple modification is done on the in-house tools to better predict the landing point distribution of the dropped cylindrical objects on the seabed by imposing the random three-dimensional rotation around the water depth axis. This tool is then used to compare the result of annual hit frequency using the recommended practice and further compared with the available experimental data.
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Ranne, Katriina. "Heavenly drops." Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-90863.
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Iba Ndiaye Diadji, a Senegalese professor of aesthetics, sees water as intrinsic to African ontology. He also argues that water is the most important substance to inspire African artists. (Diadji 2003: 273–275.) Water certainly has a significant role in Swahili poetry, written traditionally by people living on the coast of the Indian Ocean. Swahili poems have used aquatic imagery in expressing different ideas and sensations, in different contexts and times. Water imagery can be found in hundreds of years old Islamic hymns as well as in political poetry written during the colonial German East Africa. This article discusses water imagery in traditional Islamic Swahili poetry.
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German, Guy. "Yield-stress drops." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/3792.
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The behaviour of viscoplastic drops during formation and detachment from a capillary nozzle, free-fall, impact on a solid substrate and subsequent spreading are investigated experimentally by high-speed imaging. Drop dynamic behaviour is an integral component of many contemporary industrial processes ranging from fuelinjection systems in combustion engines to spray coating, agrochemical and pharmaceutical delivery, fire extinguishment and ink-jet printing. Yield-stress fluids are commonly used nowadays in products ranging from mayonnaise to hair-gel. It is hoped that through understanding the dynamics of viscoplastic fluids, additional spray applications can be developed that will help to advance and optimise industrial processes. Viscoplastic fluids exhibit shear-thinning behaviour when the applied stress exceeds a certain threshold value, called the yield-stress. Below this threshold however, the fluid behaves like an elastic solid. By comparing the behaviour of viscoplastic drops with both Newtonian and shear-thinning fluids, yield-stress is shown to be capable of altering detachment behaviour, drop shape during free-fall, impact morphology and the final sessile shape of drops after spreading. For drops attached to the end of a capillary tube, growth continues until a maximum supportable tensile stress is reached in the drop neck. After this critical point, drops become unstable and detach. The critical break-up behaviour of low yield-stress drops is found to be similar to those of Newtonian and shear-thinning fluids. Above a threshold value however, characterised in terms of the ratio between yield-stress magnitude and capillary pressure, yield-stress forces exceed surface tension forces and the maximum tensile stress achievable in the drop neck at critical stability is governed by the extensional yield-stress, established using the von Mises criterion. This threshold value can also be used to characterise equilibrium drop shapes during free-fall. Whereas Newtonian, shear-thinning and low yield-stress fluids form near spherical equilibrium drop shapes, fluids above a threshold value become increasingly more prolate as the yield-stress increases. Upon impact, viscoplastic drops can exhibit central peaks at the end of inertial spreading. The influence of yield-stress magnitude on impact behaviour is qualitatively established by measuring the size of these peaks. Peaks indicate that deformation during impact is localized and within a threshold radius, shear stresses will not be large enough to overcome the yield-stress, therefore fluid within this region will not deform from the drop shape prior to impact. After impact, spreading will be dependent on the surface energy. Again, the ratio of the yield-stress magnitude to the capillary pressure can be used to characterise the final sessile drop shape. Whilst the equilibrium contact angle of Newtonian, shear-thinning and low yield-stress drops is independent of the yield-stress magnitude, above a threshold value, contact angles vary as a function of yield-stress magnitude. Whilst the research presented in this thesis highlights how fluid yield-stress can influence drop dynamics, some results are only qualitative. To establish more quantitative results, computational fluid dynamics methods should be used to examine viscoplastic drop dynamics. This research should focus primarily on impact behaviour, an aspect that has not received much attention previously. Modelling shear-thinning and viscoplastic fluid behaviour can be achieved by incorporating the relevant rheological models into the flow equations and examining impact morphology using a volume of fluid method. Numerical results can then be directly compared with the experimental results. Useful further experimentation could examine the relaxation behaviour of diamagnetically levitated viscoplastic drops. The results from this work could provide further insight into what rheological model best describes viscoplastic behaviour for shear-stresses below the yield-point.
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Döbel, Björn. "Request tracking in DROPS." Master's thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-26214.
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Runtime analysis of applications can help to gain insight into control flow of applications as well as detect performance issues. This work presents efficient means for integrating runtime monitoring facilities into the DROPS operating system and uses these to analyse performance and behavior of L4-based applications such as L4Linux.
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Barnum, Peter. "Light and Water Drops." Research Showcase @ CMU, 2011. http://repository.cmu.edu/dissertations/182.
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Water drops are present throughout our daily lives. Microscopic droplets create fog and mist, and large drops fall as rain. Because of their shape and refractive properties, water drops exhibit a wide variety of visual effects. If not directly illuminated by a light source, they are difficult to see. But if they are directly illuminated, they can become the brightest objects in the environment.
This thesis has two main components. First, we will show how to create two-and three-dimensional displays using water drops and a projector. Water drops act as tiny spherical lenses, refracting light into a wide angle. To a person viewing an illuminated drop, it will appear that the drop is the same color as the incident light ray. Using a valve assembly, we will fill a volume with non-occluding water drops. At any instant in time, no ray from the projector will intersect with two drops. Using a camera, we will detect the drops locations, then illuminate them with the projector. The final result is a programmable, dynamic, and three-dimensional display.
Second, we will show how to reduce the effect of water drops in videos via spatio-temporal frequency analysis, and in real life, by using a projector to illuminate everything except the drops. To remove rain (and snow) from videos, we will use a streak model in frequency space to find the frequencies corresponding to rain and snow in the video. These frequencies can then be suppressed to reduce the effect of rain and snow. We will also suppress the visual effect of water drops by selectively “missing” them by not illuminating them with a projector. In light rain, this can be performed by tracking individual drops. This kind of drop-avoiding light source could be used for many nighttime applications, such as car headlights.
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Carnasciali, Maria-Isabel. "Kinetic friction of nonwetting drops." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22650.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Neitzel, G. Paul; Committee Member: Allen, Mark G.; Committee Member: Degertekin, F. Levent; Committee Member: Schatz, Michael; Committee Member: Smith, Marc K.
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Munro, James. "Coalescence of bubbles and drops." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288543.
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When two fluid drops come close enough together to touch, surface tension quickly pulls the drops together into one larger drop. This is an example of a singular fluid flow, as the topology of the interface changes at the moment of contact. Similarly, when a pair of bubbles touch, the surface topology changes and a singular flow begins. Since the stress from surface tension depends on the surface curvature, these singularities are often characterised by divergent fluid velocities. Experimental observation or numerical simulation of these flows is therefore difficult due to the high velocities and small lengthscales. In this thesis, I will find multi-scale theoretical solutions for the singular flows during the initial stages of the coalescence of bubbles and drops, solving for the velocity field in the fluid and the rate of coalescence. Each solution has several lengthscales, and on each lengthscale, we must solve some form of the Navier--Stokes equations. I will employ a variety of analytical and numerical techniques to solve for the flow on each scale. These asymptotic solutions are valid at early times; future numerical simulations of the subsequent flow could be initialised with these solutions, rather than the actual singularity. In the course of solving for these singular flows, I will also describe the solution for the motion of a stretched fluid edge, the retraction of a narrow fluid wedge, the capillary flow around a parabola, and the effect of a time-dependent force on a fluid half-space. These fundamental flows have applications outside of coalescence, which I will outline throughout the thesis.
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Enuguri, Venkata Kotaiah Shiva Teja, and Sri Harsha Karra. "Colliding Drops in Spray Dryers." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-17386.
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Spray drying is a process, which produces powders from the fluid state. This type of process is mostly used in the industrial sector. In this process, a liquid slurry is atomized, forming droplets, which are dried with hot air. During spray drying these droplets will interact and upon impact can show different types of interactions; droplet-droplet collisions as well as interactions with partially or completely dried particles, leading to agglomeration. The result of collision gives properties of the dried powder. The focus of the thesis is to investigate the droplet-droplet collision outcomes of WPC 80 (Whey Protein Concentrate 80) and Lactose. Then the effects of the absolute droplet diameter and the droplet diameter ratios are to be determined. Existing experimental setup and Image Processing Tool of MATLAB is used to study the collision outcome. The outcomes are shown in a regime map. The present results are compared with different products result and literature study. It is observed that there is an effect on collision outcome for different droplet size ratios and no effect for absolute droplet diameter.
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Mishra, Neeraj Kumar Ratner Albert. "Effect of chamber pressure on liquid drop impacts on a stationary smooth and dry surface." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/408.
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Mudeme, Sipho. "Drop formation and rupture in shearing during processing of highly concentrated emulsions." Thesis, [S.l. : s.n.], 2009. http://dk.cput.ac.za/cgi/viewcontent.cgi?article=1062&context=td_cput.
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Baughman, Kyle. "Deposition of Bacteria from Sessile Drops." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/194109.
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This dissertation reports on the discovery of a new method of patterning bacteria (Pseudomonas aeruginosa PAO1) on a surface using a drying sessile drop. This work identifies bacterial suspension age and the length of time mica is exposed to the laboratory atmosphere as the key parameters which impact the behavior of the sessile drop and the resulting residue. Possible origins of mica aging and bacterial suspension aging are discussed in light of the literature and the experimental conditions. The residue area and the fraction of the residue area on which substantial bacteria and salt deposits remained after the drying of the drop (fill-in fraction) were measured via analysis of optical micrographs. In general, smaller residues are more filled in. For fresh bacterial suspensions, and short mica exposure times, the residue covers the largest area and is characterized by rings formed during discrete depinning events as the solvent evaporates. As the exposure time increases and the mica surface slowly picks up contaminants from the atmosphere, the drop residue shrinks in size and bacteria are deposited in a regular cellular film in the interior of the drop residue. The fraction of the interior area covered by the cellular film is well correlated with the mica exposure time. For sufficiently aged bacterial suspensions, residues are small and more filled-in than residues formed from fresh suspensions on similarly aged mica. In addition, the interior deposition pattern transitions from a cellular film characteristic of fresh suspensions to a cracked carpet pattern for aged suspensions. Suspension aging related changes in the residues are attributed to accumulation of organic materials such as DNA, RNA, proteins, and other bacterial components in the suspension. The suspension aging process is also observed to be at least partially dependent on ventilation of the suspension during aging.
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Urban, April. "Drops of Light in the Dark." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5715.
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The short stories in this collection focus on young individuals', especially women's, experience and development as they navigate personal relationships and search for a place in the world. Both longer stories and flash fiction are included, and stories are told in past and present tense, and from first, second, and third person point of view. However, the narration of all of these stories stays close to the characters' points of view, inhabiting their visceral experience. These stories take place in a variety of settings, including a beachside motel, college campuses, bars, and offices. All of these characters, though, struggle with questions of identity, intimacy, and purpose. These conflicts are revealed through the characters' interactions with others and reactions to their environments, especially focusing on the small details of ordinary events and settings. By depicting these characters' encounters with the everyday, their sense of self and experiences are shown, and thus the particularities of women's relationships with their selves, their bodies, and their relationships are represented. In addition to this collection of short stories, the Writing Life Essay in this thesis discusses my development as a writer, my aims, and the writers, such as Dylan Landis, Joy Williams, and Mary Gaitskill, who have influenced my work. A Reading List of influential works, including fiction, non-fiction, and poetry, follows.M.F.A.
Masters
English
Arts and Humanities
Creative Writing
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Fowler, R. F. "Computer simulation of microscopic liquid drops." Thesis, University of Kent, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371212.
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Segura-Sanchez, Mararita. "Collisions in a stream of drops." Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364298.
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Lanauze, Javier A. "Transient Electrohydrodynamics of Low–Conductivity Drops." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/841.
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Saenz, Pedro Javier. "Evaporation of liquid layers and drops." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/9980.
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This thesis focuses on investigating the stability, dynamics and physical mechanisms of thermocapillary flows undergoing phase change by means of direct numerical simulations and experiments. The novelty of the general approach developed in this work lies in the fact that the problems under consideration are addressed with novel fully-coupled transient two-phase flow models in 3D. Traditional simplifications are avoided by accounting for deformable interfaces and by addressing advection-diffusion mechanisms not only in the liquid but also in the gas. This strategy enables a realistic investigation of the interface energy and mass transfer at a local scale for the first time. Thorough validations of the models against theory and experiments are presented. The thesis encompasses three situations in detail: liquid layers in saturated environments, liquid layers in unsaturated environments and evaporation of liquid droplets. Firstly, a model grounded in the volume-of-fluid method is developed to study the stability of laterally-heated liquid layers under saturated environments. In this configuration, the planar layer is naturally vulnerable to the formation of an oscillatory regime characterized by a myriad of thermal wave-like patterns propagating along the gas-liquid interface, i.e. hydrothermal waves. The nonlinear growth of the instabilities is discussed extensively along with the final bulk flow for both the liquid and gas phases. Previously unknown interface deformations, i.e. physical waves, induced by, and enslaved to, the hydrothermal waves are reported. The mechanism of heat transfer across the interface is found to contradict previous single-phase studies since the travelling nature of the hydrothermal waves leads to maximum heat fluxes not at the points of extreme temperatures but somewhere in between. The model for saturated environments is extended in a second stage to assess the effect of phase change in the hydrothermal waves for the first time. New numerical results reveal that evaporation affects the thermocapillary instabilities in two ways: the latent energy required during the process tends to inhibit the hydrothermal waves while the accompanying level reduction enhances the physical waves by minimizing the role of gravity. Interestingly, the hydrothermal-wave-induced convective patterns in the gas decouple the interface vapour concentration with that in the bulk of the gas leading to the formation of high (low) concentrations of vapour at a certain distance above interface cold (hot) spots. At the interface the behavior is the opposite. The phase-change mechanism for stable layers is also discussed. The Marangoni effect plays a major role in the vapour distribution and local evaporation flux and can lead to the inversion of phase-change process, i.e. the thermocapillary flow can result into local condensation in an otherwise evaporating liquid layer. The third problem discussed in this thesis concerns with the analysis of evaporating sessile droplets by means of both experiments and 3D numerical modeling. An experimental apparatus is designed to study the evaporation process of water droplets on superheated substrates in controlled nitrogen environments. The droplets are simultaneously recorded with a CCD camera from the side and with an infrared camera from top. It is found that the contact line initially remains pinned for at least 70% of the time, period after which its behaviour changes to that of the stick-slip mode and the drop dries undergoing contact line jumps. For lower temperatures an intermediate stage has been observed wherein the drop evaporates according to a combined mode. The experimental work is complemented with numerical simulations. A new model implementing the diffuse-interface method has been developed to solve the more complex problems of this configuration, especially those associated with the intricate contact-line dynamics. Further insights into the two-phase flow dynamics have been provided as well as into the initial transient stage, in which the Marangoni effect has been found to play a major role in the droplet heating. For the first time, a fully-coupled two-phase direct numerical simulations of sessile drops with a moving contact line has been performed. The last part of this work has been devoted to the investigation of three-dimensional phenomena on drops with irregular contact area. Non-sphericity leads to complex three-dimensional drop shapes with intricate contract angle distributions along the triple line. The evaporation rate is found to be affected by 3D features as well as the bulk flow, which become completely non-axisymmetric. To the best of our knowledge, this work is the first time that three-dimensional two-phase direct numerical simulations of evaporating sessile drops have been undertaken.
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Watts, Frank. "The effect of electrical potential on drop formation : a basis for an automated interfacial tensionmeter." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/10122.
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Souccar, Adham. "Heat transfer and mass transfer with heat generation in drops at high peclet number /." Connect to Online Resource-OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1177603981.
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Dissertation (Ph.D.)--University of Toledo, 2007.Typescript. "Submitted as partial fulfillment of the requirements for The Doctor of Philosophy degree in Engineering." Bibliography: leaves 65-74.
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Donnelly, Keith. "Three Deadly Drops: A Donald Youngblood Mystery." Digital Commons @ East Tennessee State University, 2012. http://amzn.com/089587587X.
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"In the fourth Donald Youngblood mystery more than a year has passed since Don closed the file on the Three Devils case. His personal life is trending upward, his business is booming, and no one has come to him with a case likely to get him killed.
All of that changes when Jessica Crane walks into Don's office, asking him to look into the apparent heart-attack death of her husband. Don is convinced that Mrs. Crane's request is just the delusion of a grieving widow. As he goes through the motions of his investigations, he uncovers a mysterious note and a 20-year-old photograph of a group of soldiers known as the Southside Seven. Don soon thinks the grieving widow might be on to something.
The Silver Star, a soldier with a stress problem, an Army Ranger black ops mission gone wrong, a mysterious assassin, and a missing vial are all pieces to the puzzle that Don races to fit together before anyone else dies.
In the desert of New Mexico, the bayou country of Louisiana, the mean streets of Memphis, and small towns in South Carolina and Kentucky, a haunting mystery unfolds as Donald Youngblood uncovers a startling secret from Desert Storm that haunted the seven men who shared it."--AMAZONhttps://dc.etsu.edu/alumni_books/1003/thumbnail.jpg
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GUTIERREZ, JOSE ANGEL FLORIAN. "FLOW OF OIL DROPS THROUGH MICRO CAPILLARIES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2013. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23869@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
PROGRAMA DE EXCELENCIA ACADEMICA
Estudos recentes mostram que a injeção de emulsões óleo-água pode levar a uma melhor varredura do reservatório e reduzir consideravelmente a saturação residual de óleo em processos de recuperação avançada. Estes efeitos estão diretamente ligados ao comportamento do escoamento de gotas de óleos suspensas em água através das gargantas de poros. Desta forma, a otimização do processo de injeção e da formulação da emulsão com o objetivo de aumentar o volume de óleo recuperado requer por um melhor entendimento do escoamento na escala de poros. Este trabalho apresenta um estudo do escoamento de gotas de óleos suspensa em água através de micro canais de seção reta constante e através de uma garganta, que são usados como modelos do espaço poroso. O campo de velocidade da fase contínua e a velocidade da gota de óleo foi determinado através da técnica de velocimetria por imagem de partículas em escala micrométrica (Micro-PIV) para diferentes tamanhos de gotas e geometria do capilar e garganta. Os resultados obtidos mostram a variação do padrão do escoamento devido a presença da gotas de óleo e fornecem importantes informações de como gotas de óleo mudam a mobilidade do fluido injetado quando o mesmo escoa através de poros com gargantas menores do que tamanho das gotas.
Recent studies show that oil-water emulsion injection may lead to a better reservoir sweep and reduce residual oil saturation in enhanced oil recovery processes. These effects are directly linked to the flow behavior of oil drops suspended in water through the pore throats of a porous material. Therefore, the optimization of the injection process and of the emulsion properties with the goal to increase the volume of oil displaced requires a better understanding of the emulsion flow in the pore scale. This work presents an analysis of the flow of oil drops suspended in water through micro channels with constant cross-section area and with a throat, that are used as a model for the pore scale. The velocity field of the continuous phase and the drop velocity are obtained using the micro particle image velocimetry techniques (Micro-PIV) for different drop sizes and micro channel geometries. The results show the changes in the flow pattern due to the presence of oil drops and yield important information on how oil drops reduce the mobility of the injected liquid when it flows through pore throats smaller than the drop size.
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Tsamopoulos, John Abraham. "Nonlinear dynamics of simple and compound drops." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/119604.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 176-186.
by John Abraham Tsamopoulos.
Ph.D.
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Al-Faize, Mustafa M. "Mass transfer characteristics of large oscillating drops." Thesis, Aston University, 1986. http://publications.aston.ac.uk/10193/.
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Yakhoub, Hamat Abderrahmane. "Effect of high shearing on rheological/structural properties of highly concentrated w/o emulsions /." Thesis, [S.l. : s.n.], 2009. http://dk.cput.ac.za/cgi/viewcontent.cgi?article=1064&context=td_cput.
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Kimble, Paul. "Measuring the Momentum of Throughfall Drops and Raindrops." TopSCHOLAR®, 1996. http://digitalcommons.wku.edu/theses/806.
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The methods previously used to determine the momentum and kinetic energy of throughfall drops in the field do not account for the drop's shape at impact or for the variations of the drop's velocity caused by chaotic air currents. The drop's shape at impact is critical because it influences the drop's measurable momentum, kinetic energy, impact force, and the amount of soil that can be displaced by the falling water drop. Since the momentum and kinetic energy of raindrops and throughfall drops are used as indices of soil particle displacement the most accurate momentum and kinetic energydata would be required to produce the most accurate estimate of soil particle displacement. The purpose of this project was to develop and utilize a simple digital electronic instrument which could be used in the field to directly measure the momentum of throughfall drops and raindrops. The instrument consisted of a voltage amplifier, voltage comparator, reference voltage, digital counting circuit and a digital display. The instrument was activated by an impact sensor constructed from an 8.0 ohm, 5.0 inch diameter audio speaker. A falling water drop's momentum was quantified as the amount of time (milliseconds) that the speaker's amplified voltage exceeded the reference voltage. The instrument displayed the drop's momentum as a function of time which was recorded and later converted into units of momentum (g*m/s) by an empirically determined calibration curve. The instrument was utilized in Benton County, Tennessee by measuring raindrop momenta during a single storm event and the throughfall drops produced by commercially planted loblolly pine trees and indigenous deciduous trees. The substitution of the loblolly pine for the deciduous trees represents a human induced change of the vegetation which could have an impact on the drainage basin's erosional characteristics. The purpose of the investigation was to determine if there were any differences between the sample means. The sample having the highest mean momentum would have the greatest potential to dislocate soil particles and cause subsequent soil erosion. The analysis of the sample data revealed that both of the throughfall drop momentum sample means (evergreen: 0.602 g*m/s, deciduous: 0.355 g*m/s) were greater than the raindrop momentum sample mean, 0.02 8 g*m/s. The differences between the sample means suggested that the throughfall drops have a greater potential to displace soil particles and cause subsequent soil erosion than the raindrops that produced the throughfall drops. Also, the evergreen throughfall drop momentum sample had the highest mean of the three samples, indicating that the evergreen throughfall drops had the greatest potential to displace soil particles. The nonparametric Wilcoxon rank sum test was used to determine if the samples' respective population means were equal. The results of the Wilcoxon test indicated that both of the throughfall drop momentum population means were greater than the raindrop momentum population mean, thus reaffirming the results of the sample data analysis. However, the test indicated that the throughfall drop momentum population means were equal, suggesting that the evergreen and deciduous throughfall drops have equal potential to dislocate soil particles and cause subsequent soil erosion.
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Hagesæther, Lars. "Coalescence and Break-Up of Drops and Bubbles." Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2148.
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Fluid particle break-up and coalescence are important phenomena in a number of industrial processes.
A Lagrangian momentum balance model for the collision process between two fluid particles has been developed and tested favorably against experimental data. It is based on an earlier model developed in our department. Oscillations were introduced and the volume balances that are solved avoid earlier approximations. Film drainage was also implemented into the model based on a literature review given. It is believed this approach will lead to a more fundamental modeling of the coalescence process.
An improved break-up model has been developed. It is an extension of earlier work at the department and it introduces an additional criterion for break-up. This criterion gives a lower limit for the daughter fragment sizes in binary break-up, thus also limiting the break-up of smaller fluid particles, and is a more consistent model than the earlier one.
Two break-up models, original model by Luo (1993) and improved model, and a coalescence model have been implemented in a population balance as algebraic sink and source terms. This population balance is in turn included in an in-house CFD-code. The models have been tested against experimental data from a bubble column in our laboratory, and the improved break-up model compares favorably with the experimentally obtained accumulated mass distribution. Too few bubbles are predicted in the lower population classes, but it is shown that this may as well be a result of the coalescence model used as the improved break-up model.
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Aryafar, Hamarz. "Coalescence of liquid drops at liquid-liquid interfaces." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1666392591&sid=9&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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AZEVEDO, BRUNO NIECKELE. "FLOW OF TWO DROPS THROUGH A STRAIGHT MICROCAPILLARY." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23533@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Emulsões podem ser usadas como agentes de controle de mobilidade em métodos de recuperação avançada de óleo de forma a conseguir um varrido mais eficiente do reservatório. A aplicação de tal técnica requer um entendimento completo de como as emulsões escoam em um material poroso. O comportamento macroscópico do escoamento deve ser determinado baseado no escoamento na escala de poros, em que as emulsões não podem ser tratadas como líquidos não Newtonianos monofásicos, uma vez que os diâmetros das gotas são da mesma ordem de magnitude das gargantas de poros. Experimentos realizados por Cobos et al.(1) sobre o escoamento de emulsões através de micro-capilares com garganta, que serviu como modelo para a geometria de uma garganta de poro conectando dois poros adjacentes, mostrou o efeito da fase dispersa na queda de pressão para diferentes condições de escoamento e características das emulsõs. De forma a ampliar a faixa de número de capilaridade e tamanhos de gota explorados nos experimentos, determinar o efeito da tensão interfacial, razão de viscosidades, geometria do capilar e determinar características do escoamento com mais de uma gota, é estudado o escoamento de gotas suspensas em uma fase contínua escoando através de um micro-capilar. A evolução da interface das gotas é determinada pelo método de level-set, que é acoplado a solução das equações de Navier Stokes, baseada no método de elementos finitos. Foi investigado o efeito da distância inicial entre duas gotas, assim como o efeito da tensão interfacial na velocidade de cada uma das gotas. Os resultados obtidos fornecem uma descrição mais detalhada do escoamento de emulsões em gargantas de poros.
Emulsions can be used as mobility control agent in enhanced oil recovery methods in order to achieve a more efficient sweep of the reservoir. The application of such technique requires full understanding of how emulsions flow in a porous material. The macroscopic flow behavior can be determined based on the pore scale flow, at which emulsions cannot be treated as a single phase non Newtonian liquid, since the drop diameters are in the same order of magnitude of the pore throats. Experiments by Cobos et al.(1) of flow of emulsions through constricted micro capillaries, wich served as a model to the geometry of a pore throat connecting two adjacent pore bodies, have shown the effect of the dispersed phase on the pressure drop for different flow conditions and emulsions characteristics. In order to widen the range of capillary number and drop size explored in the experiments and to determine the effect of interfacial tension, viscosity ratio, capillary geometry and determine the characteristics of the flow with more the one drop, we study the flow of a drops suspended in a continuous phase flowing through a constricted micro capillary. The evolution of the drop interface is determined by the level set method which is incorporated to a fully coupled implicit Navier Stokes solver based finite element method. We investigate the effect of an initial distance between the two drops, as well as the effects of the interfacial tension on the drops speed. The results provide a more detailed description of the flow of emulsions through pore throats.
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Liu, Yuanyuan. "Inkjet printed drops and three-dimensional ceramic structures." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/inkjet-printed-drops-and-threedimensional-ceramic-structures(36785d3d-cca6-4903-8e5b-043fd2198e0f).html.
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Inkjet printing is a versatile manufacturing method with applications beyond its traditional application in graphics and text printing, particularly in structural and functional materials. This thesis aims to enhance the understanding of DOD inkjet printing processes by investigating the behaviour of solvent mixtures and nanoparticle suspensions to identify the key parameters affecting drop ejection, drying and stacking processes. Drop ejection and flight were investigated with two modes of inkjet printheads, using a range of fluids formulated from solvent mixtures and characterised by the dimensionless Z number. The printable range was found to be 1.17 smaller or equal to Z smaller or equal to 36.76 for a 10 pl (21.5 micro metre diameter) shear-mode Dimatix printhead. However, with an 80 micro metre diameter squeeze-mode MicroFab printhead, the range was found to be narrower with 4.02 smaller or equal to Z smaller or equal to 16.2. However, both printheads were found to show a printable range of Weber number with 0.4 <We <20. Weber number is determined by the drop velocity and hence the actuating pulse. When designing inks for future printing work, not only the fluid properties, but also the pulse voltages need to be considered. The drop stacking and solidification processes of drops containing nano ZrO2 particles were investigated to enhance the understanding of drop drying and drop/drop interactions. In-situ synchrotron X-ray radiography provides a promising method to track the time-evolved solid segregation within printed drops during drying. Both the initial contact angle and substrate temperature during printing strongly influence the drying process and the final dried deposit shape. The drops were first pinned and then there was a slight sliding of the three-phase contact line. Drops were deformed by the stacking of overprinted drops when printed on Kapton tapes and silicon wafer surfaces, but not on glass slides due to the small contact angle of water on glass slides. Crack-like defects were found at the edge of the final dried stacking structures. The coffee stain effects within a single inkjet printed droplet and the 3D structures before and after sintering were investigated to find out the influence of ink properties, printing parameters and substrate temperature on inkjet printed structures. It was found coffee staining was more obvious at high substrate temperatures. When adding 25 vol% ethylene glycol (EG) or 5 wt% polyethylene glycol (PEG), the coffee stain effect is reduced or eliminated under room temperature drying. X-ray tomography has been demonstrated as a valuable tool for the characterization of 3D printed objects and defects that form during their manufacture. Defects were characterised as microvoids or large-scale crack-like defects. The majority of the microvoids revealed are associated with mechanisms and processes within a single drop, e.g. segregation during dryings such as the formation of coffee stains or coffee rings. The size or distribution of microvoids can be controlled by changing the ink formulation, with higher PEG content inks showing lower concentrations of microvoids.
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Betton, Eleanor Susanne. "Impact and coalescence of ink-jet printed drops." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610068.
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Andrew, Matthew. "Impact of drops upon surfaces with complex morphology." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:6ffaf1d5-7591-497d-b60c-369f7b45b317.
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Drop impacts are ubiquitous in nature forming a vital pathway for the transport of liquids, primarily water, and any dissolved substances. The axisymmetric impact of drops has been heavily studied but less work has been done on droplet impacts in which axial symmetry is broken. To analyse such impacts we used a two phase lattice Boltzmann code capable of simulating high density differences. We studied the impact of droplets on cylindrical surfaces, with radius of curvature similar to that of the drop. We found that the symmetry breaking nature of these surfaces leads to droplets bouncing faster and in elongated shapes. The origin of this effect is a positive feedback mechanism through which the momentum asymmetry resulting from the impact grows during retraction. We next looked at how varying the size of the cylinder affected this phenomenon. We found that smaller cylinders increased the contact time reduction, as long as they were still bigger than the droplet, but that below this limit the drop contacted the flat surface and entered a new regime. The work was expanded to look at other types of bouncing asymmetry, using a simple, exactly solvable Lagrangian model. We found that contact time reduction can result from an asymmetric droplet shape, an initially asymmetric velocity or if the surface has an asymmetric drag. A study of the impact of liquid drops containing embedded air bubbles was also undertaken. This was found to lead to jet formation from the bottom of the bubble. We showed how the jet velocity depended on the physical parameters of the drop and impact. In particular the jet formation was very sensitive to the position of the air bubble inside the drop.
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Soto, Dan. "Non-wetting drops : from impacts to self-propulsion." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066627/document.
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Nous étudions à travers plusieurs expériences la dynamique spéciale engendrée par des objets non mouillants. Un liquide en état Leidenfrost est autopropulsé lorsqu’on le pose sur un substrat texturé avec des rainures formant un motif à chevrons: les textures canalisent l'écoulement de vapeur dans une direction bien définie de sorte que ces aéroglisseurs liquides sont entraînés par la vapeur sous-jacente. Ces objets déformables subissent très peu de friction sur une surface plane. Toutefois, sur des substrats crénelés, les impacts sur les textures créent une friction spéciale qui est également étudiée. Nous étendons ce scénario d'entraînement visqueux dans d'autres situations où le liquide est remplacé par une plaque solide. Pour permettre la lévitation, on le place sur un substrat poreux à travers lequel de l'air est soufflé. Une fois de plus, l’écoulement est rectifié par des textures permettant l’entraînement d’une lamelle de verre dans un mouvement de translation ou même de rotation. Si nous augmentons la profondeur des textures, le confinement est perdu et on observe un mouvement dans la direction opposée dû à l'effet fusée. Nous nous intéressons également à une situation de non mouillage particulièrement simple: la goutte en chute libre. Nous abordons le problème de l’issue de cette chute: l'impact. Nous étudions d'abord l'impact d'une goutte sur un tamis. Dans cette situation, le liquide passe à travers les trous ou est arrêté par les sections bouchées. Nous nous concentrons ensuite à la force d’impact subie par le substrat. Nous la mesurons et la calculons en fonction des caractéristiques du liquide, de l’impact, et de la nature du substratWe investigate through several experiments the special dynamics generated by non-wetting objects.On a substrate textured with grooves forming a herringbone pattern, a Leidenfrost levitating liquid is propelled: the textures channel the vapor flow in a well-defined direction so that the slider above is driven by vapor viscosity. These deformable objects undergo very little friction on flat surfaces. However, on crenelated substrates, impacts on the texture sides greatly enhance dissipation. We extend this entrainment scenario to other situations where the liquid (and its deformable nature) is not involved anymore. A solid plate can levitate over a porous substrate through which air is blown. Again, escaping flow can be rectified by the textures and entrain the plate, leading to translation movement or even to rotation. If we create deeper channels (hence losing flow confinement), we observe motion in the opposite direction due to “rocket effect” (conservation of momentum). We are also interested in an extreme non-wetting situation: the falling drop. Indeed, all along the fall, the drop only experiences air drag friction, easily reaching high speeds. We tackle the problem of the dramatic issue of this fall: the impact. We first study the impact of a drop on a sieve. In this situation intermediate between a solid wall and no obstacle at all, mass either passes through the holes or gets stopped by the closings. We then focus on the impact force experienced by the substrates and characterize the force as a function of the drop and impact properties, but also of the nature of the solid on which impact takes place
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David, Samuel. "Investigation of the Wetting Behaviour of Evaporating Drops." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/12174.
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Sujith, R. I. "Behavior of droplets in axial acoustic fields." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/12487.
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Vukasinovic, Bojan. "Vibration-induced droplet atomization." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17237.
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Bose, Feler. "Hydrodynamics of dispersed liquid droplets in synthetic fibrous slurries." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/18238.
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Blancher, Roman Adrien. "Numerical simulations of high speed droplet collision." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/19127.
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Siddique, Pasley Rehana. "The physical and chemical reclamation and recycling of elements from black aluminium furnace residues." Thesis, Brunel University, 2003. http://bura.brunel.ac.uk/handle/2438/7272.
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Dross is the inevitable waste product generated by the world-wide primary and secondary aluminium industries. Around 3.5 million tonnes of white dross and 0.85 million tonnes of black dross are produced per year. Drosses are classified depending on metal content. White dross contains 40% and black dross contains 10% of aluminium. About half of the white dross is currently landfilled along with almost all of the black dross, and the annual cost to the UK industry of landfilling this waste is about £90 million per year. There is no commercially viable method of recovering the aluminium, which is potentially recyclable from these drosses, and no current conventional process has the custom-built capability to avoid their disposal to landfill. The practice of landfilling aluminium dross has raised problems for both industry and environment, because of potential leaching of heavy metals into groundwater from the landfill. The black dross has been physically and chemically characterised. The results show that the dross contains mostly metallic aluminium, aluminium nitride, alumina, sodium chloride, potassium chloride and silica with almost 50% of the dross being a mixture of sodium chloride and potassium chloride. A counter current leaching process has been developed to recycle the salts back to the secondary furnace. The environmental impact of black dross has been investigated using simulated landfill conditions. Leachability studies were carried out using water, and other leach media to model the following conditions: humic acid-containing systems, acid rain (pH 2.5), and acetic acid solutions (pH 5). Up to 60% of the dross was leached out in all media with the production of the saline solution providing the major impact. Only small amounts of aluminium were leached out under all these condition. No leachability behaviour was detected once the black dross was washed. So landfilling washed black dross can minimise both environmental and economical problems. Black dross residue, after washing with water, is enriched with alumina. Added value chemicals (of >95% purity) including aluminium hydroxide, alumina, aluminium chloride, aluminium nitrate, aluminium sulphate and aluminium carboxylates have been prepared using the washed black dross. Preliminary calculations have shown that the technology developed to recycle black dross to added-value chemicals is economically viable. A methodology has been developed which enables low grade alumnium waste, black dross, to be treated, commercially viable chemicals to be prepared, reagent use to be minimised through recycle and the diversion of millions of tonnes of furnace residue from landfill.
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Ai, Xin. "The instability analysis and direct numerical simulation of turbulent flows in electromagnetically levitated droplets." Online access for everyone, 2004. http://www.dissertations.wsu.edu/dissertations/Spring2004/x%5Fai%5F051404.pdf.
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Seth, Julie Janine Ravnanger. "Electrohydrodynamic Structuring of Colloidal Particles on Leaky Dielectric Drops." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23482.
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This Master's thesis shows experimentally how colloidal particles in leakydielectric liquid drops are actively structured by applying a DC electric eld.Colloidal particles in small droplets with a diameter of 100 m show similarstructuring to what has previously been observed on bigger drops (1 mm),showing ribbon formation, spinning domains and pupil eects. It is shownhow electrohydrodynamic assembly of colloidal particles on a drop surfacedepends on the electric eld strength, and how this enables fast assembly ofthe particles. The particles used in the experiments are clay particles, layereddouble hydroxides and insulating beads. The layered double hydroxides showsimilar structuring to the clay particles. The results suggest that active con-trol of colloidal particles on leaky-dielectric drops by an electric eld can leadto new ways of producing Janus shells and other 'smart armoured' droplets.
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Andersson, Sofia. "Study of Dross in Ductile Cast Iron Main Shafts." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-37148.
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The study of dross in ductile cast iron main shafts was performed at Global Castings Guldsmedshyttan AB and presented in this master thesis. The purpose of the study was to obtain answers to why dross defects were present in some of the foundry's casted main shafts, with the main problem located at the flange of the shaft. The chemical composition of the dross formations and which steps in the casting process that increased the dross formation were of interest. The study only included dross in main shafts manufactured at Global Castings Guldsmedshyttan AB. Dross particles form when elements such as Mg, Ca, Si and Mn react with O. These elements, which are highly reactive to O, are used in ductile cast irons to achieve the spheroidal graphite nodules that regulate the cast materials ductile properties. If a higher amount of dross particles has formed, the particles will start to cluster, resulting in a growing dross formation. Dross formations works as surface crack initiation points and reduces the castings fatigue strength and ductility. During the study it was seen that the cause of dross formations is a combination of many parameters increasing the melts exposure to O resulting in dross defects. The dross formations could be connected to worn out ladles, low melt temperatures, incorrect additions of Mg treatment, lack of an extra slag removal station and finally turbulence as the melt were poured into the mould. At Global Castings Guldsmedshyttan AB a greater part of the main shafts containing dross defects were a result of worn out ladles and low melt temperatures. The types of dross found in the main shaft material were mainly Mg, Ca, Si and Al which had reacted with O. S bonded with Mg and Ca was also detected in the dross formations. It was shown that the dross particles could be derived from charge material, Mg treatment and inoculation. To avoid dross defects the first step would be to set up an extra slag station, shorten the interval of maintenance of the ladles and to better adjust the melt temperature to the condition of the specific ladle. To minimize dross due to excess Mg a better controlled process would be recommended with an increased number of monitored manufacturing parameters.Studien av dross i axlar tillverkade av segjärn gjordes hos Global Castings Guldsmedshyttan AB och presenteras i denna examensrapport. Syftet med studien var att hitta anledningar till varför drossdefekter bildas i flänsen på vissa av gjuteriets tillverkade axlar. Drossens kemiska komposition likväl de steg i tillverkningsprocessen som inverkade på drossbildning var av intresse. Studien inkluderade endast drossdefekter i axlar tillverkade av Global Castings Guldsmedshyttan AB. Drosspartiklas bildas när till exempel Mg, Ca, Si och Mg reagerar med O. Dessa ämnen, vilka är väldigt reaktiva med syre, används vid framställning av segjärn för att de sfäriska grafitnodulerna som starkt reglerar materialets duktila egenskaper ska bildas. Ett större antal drosspartiklar i en smälta leder till kluster av dross vilka växer i takt med att nya partiklar bildas. Dross fungerar som sprickinitieringspunkter i gjutgodsytor och reducerar godsets utmattningshållfasthet och duktilitet. Under studien kunde det ses att dross bildas på grund av en kombination av parametrar som ökar smältans exponering av syre vilket resulterar i drossdefekter. Drossdefekter kunde kopplas till slitna skänkar, låga smälttemperaturer, felaktig mängd magnesiumbehandling, brist på en extra slaggstation och slutligen turbulens när smätan hälls i formen. Hos Global Castings Guldsmedshyttan AB är en stor del av axlarna med drossdefekter ett resultat av framför allt slitna skänkar och låga smälttemperaturer. Vid analys sågs det att ett antal olika typer av drosspartiklar kan bildas i det duktila gjutjärn som används till axlarna; främst Mg, Ca, Si och Al som reagerat med O. Mg och Ca som bundit med S kunde också hittas i vissa av de studerade drossformationerna. Det kunde visas att den kemiska kompositionen i drosspartiklarna var härrörande från grundmaterialet, magnesiumbehandlingen och ympmedlet. Ett första steg Global Castings Guldsmedshyttan AB skulle kunna ta för att undvika drossdefekter är att ha en extra slaggstation, införa tätare underhåll av skänkarna och bättre anpassa smälttemperaturen till skicket på den specifika skänken. För att minimera dross som bildats på grund av ett överskott av Mg skulle en mer kontrollerad process rekommenderas med ett ökat antal bevakade tillverkningsparametrar.
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Kazmierski, Bethany Kate. "The drying of inkjet printed drops on patterned substrates." Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12604/.
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Inkjet printing provides a promising method for the fabrication of OLED displays but currently, inkjet printed displays are not commercially viable. This thesis focuses on understanding the drying processes that occur once drops have been delivered to the patterned substrates necessary for OLED devices. To this end, internal flows in drops evaporating within wells were investigated and the changing drop profiles during drying were imaged. A method was suggested for successful fabrication of OLED devices. Particle tracking was carried out on both pure solvents and binary solvent mixtures within square wells. Due to the large particle size in comparison to the depth of fluid these experiments were not very informative, though they did confirm evaporation was faster at the contact line than in the centre of the drops. Evaporation was also slightly faster in the corners of the wells relative to the straight edges. Studies on pure solvents identified the influence of evaporation rate on profile development in drying drops. Two main drying regimes were identified and the main influence on drop profile development was found to be the evaporation rate of the solvent. Slow drying drops gave U-shaped profiles and fast drying drops gave W-shaped profiles. The influence of thermal effects on drop profiles was also considered. Thermal Marangoni flows were found to have a profound influence on profile development, with drops giving M-shaped profiles. Thermal effects could not always be reliably reproduced and it was concluded that further experimentation in this area was necessary. The lack of repeatability in the results was assumed to be due to the sensitivity of the drop profile to its initial behaviour. Binary solvent mixtures were also found to have an impact on profile progression during drying. Solutal Marangoni flows gave M-shaped profiles in the case where the more volatile solvent had a lower surface tension and enhanced drainage from the corners of the wells towards the centre in the case where the more volatile solvent had a higher surface tension. The thesis then moved on to investigate the effect of active materials on drop profiles. The active materials used were found to increase the surface tension of the solvents, giving M-shaped profiles when dissolved in single solvents. In some slow drying solvents, diffusion of the material evened out concentration gradients during drying and U-shaped profiles were seen. When solvent mixtures which had shown flows in opposition to those caused by active materials were used to print the actives, the profile development showed enhanced drainage from the corners of the wells suggesting solvent driven Marangoni flows were dominant over active material driven Marangoni flows. Crystallisation of the active material in this case showed re-circulatory flows were present with the active materials following the flows. This suggested particle tracking should be possible in these systems. A proposed method for obtaining flat deposits from printed drops was then presented, along with some initial results towards that goal. The initial results were promising but more investigation is needed in this area.
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Dai, Chen. "Development of Aluminum Dross-based Material for Engineering Application." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/16.
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Aluminum dross is a by-product of Aluminum production. At present, dross is processed in rotary kilns to recover the Al, and the resultant salt cake is sent to landfills; although it is sealed to prevent from leaching, the potential for leaching exists and could harm the environment as the salt cake contains fluorides and other salts. Furthermore, much energy is consumed to recover the Al from the dross; this is energy that can be saved if the dross could be diverted and utilized as an engineering material. The objective of this work is to eliminate waste and instead utilize the waste in a natural cycle (closed loop) by using it as an engineered material. Three avenues were investigated to utilize the dross: (i) refractory materials; (ii) aluminum composites; (iii) high temperature additive for de-sulphurizing steel. We have found that the use of dross waste to manufacture refractory material has much merit. Mechanical property evaluations revealed the possibility for dross waste to be utilized as filler in concrete, resulting in a 40% higher flexural strength and a 15% higher compressive strength compared to pure cement. These results will be presented and discussed.
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Axelsson, Josefine, and Helena Möller. "Weekly drops : studie av konceptet Pronto Moda inom Ellos." Thesis, Högskolan i Borås, Institutionen Handels- och IT-högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-18602.
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De senaste åren har konkurrensen inom textilbranschen ökat avsevärt. Produkter på modemarknaden är fler. Den förändrade efterfrågan ifrån kunder innebär att kunden kräver nyheter oftare och det har lett till snabba trendväxlingar. Ledtider måste kortas om modeföretag ska vara beredda på de snabba trendväxlingarna. De korta ledtiderna ställer krav på effektivitet och flexibilitet i företagens processer. Det gäller för modeföretag att hitta en effektiv inköpsstrategi och styrning av supply chain. Men det räcker dock inte, vi menar att grunden till effektivitet i företagens processer är att alla i företaget vet vart de är på väg, att alla arbetar mot samma vision och mål. Ellos är ett distanshandelsföretag, som konkurrerar i modebranschen. Att vara ett distanshandelsföretag innebär långa ledtider då även en katalog ska tryckas. Ellos startade för ett år sedan ett nytt koncept som de kallar Pronto Moda. Pronto Moda ska konkurrera med återförsäljare som ligger trendmässigt i framkant och produkterna ska endast säljas på Ellos hemsida. Pronto Moda ställer andra krav på distanshandelsföretaget Ellos. Syftet med uppsatsen är att identifiera och ge förslag på förbättringsområden för Pronto Moda för att konceptet ska bli mer konkurrenskraftigt. För att få en klar bild av hur Pronto Modas organisation ser ut idag har sex personliga djupintervjuer utförts på Ellos med personal inom områdena, sortiment, Internetkollektioner, logistik, export/import samt inköp. I arbetet med uppsatsen har vi haft ett hermeneutiskt synsätt som innebär att våra subjektiva uppfattningar påverkar tolkandet. Forskningsansatsen är abduktiv, alltså pendlas mellan teori och empiri. Det empiriska materialet har analyserats efter fördjupade teoretiska studier Teorin appliceras i analysen på empirin. Avslutningsvis presenteras, utifrån analysen, diskussion och slutsats.Sex områden, inom Pronto Moda, som behöver ses över har identifieras. Områdena är, vision & affärsidé, intern marknadsföring, tvärfunktionella team, supply chain, inköpsprocessen samt produktutveckling. Även hur Pronto Moda bör förbättra områdena för att bli mer konkurrenskraftiga ges förslag på. Vi anser bland annat att, vision och affärsidé bör fastställas för Pronto Moda och kommuniceras ut i organisationen. Vi menar också att inköpsavdelningen bör integreras mer i Pronto Modas inköpsprocess och så vidare.Uppsatsnivå: C
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Gallo, Tommaso <1981>. "Theoretical studies of microfluidics: "walking" drops and "melting" snowflakes." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3875/.
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The present PhD thesis summarizes two examples of research in microfluidics.
Both times water was the subject of interest, once in the liquid state (droplets adsorbed on chemically functionalized surfaces), the other time in the solid state (ice snowflakes and their fractal behaviour). The first problem deals with a slipping nano-droplet of water adsorbed on a surface with photo-switchable wettability characteristics. Main focus was on identifying the underlying driving forces and mechanical principles at the molecular level of detail. Molecular Dynamics simulation was employed as investigative tool owing to its record of successfully describing the microscopic behaviour of liquids at interfaces. To reproduce the specialized surface on which a water droplet can effectively “walk”, a new implicit surface potential was developed.
Applying this new method the experimentally observed droplet slippage
could be reproduced successfully. Next the movement of the droplet was analyzed at various conditions emphasizing on the behaviour of the water molecules in contact with the surface. The main objective was to identify driving forces and molecular mechanisms underlying the slippage process. The second part of this thesis is concerned with theoretical studies of snowflake melting. In the present work snowflakes are represented by filled von Koch-like fractals of mesoscopic beads. A new algorithm has been developed from scratch to simulate the thermal collapse of fractal structures based on Monte Carlo and Random Walk Simulations (MCRWS). The developed method was applied and compared to Molecular Dynamics simulations regarding the melting of ice snowflake crystals and new parameters were derived from this comparison. Bigger snow-fractals were then studied looking at the time evolution at different temperatures again making use of the developed MCRWS method. This was accompanied by an in-depth analysis of fractal properties (border length and gyration radius) in order to shed light on the dynamics of the melting process.
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Arora, Srishti. "Drops, beads and filaments of gels under extreme deformations." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS018/document.
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Nous étudions le comportement de gels, transitoires auto-assemblés et réticulés permanents, soumis à des contraintes mécaniques extrêmes. D'une part, nous étudions la déformation biaxiale de nappes libres produites par impact d'une goutte liquide (Newtonienne ou viscoélastique) ou d’une perle de gel polymère sur des surfaces solides dans des conditions de dissipation minimale, obtenues soit avec une petite cible solide, soit avec une surface répulsive. Lors de l'impact, la goutte ou perle est transformée en une nappe mince qui s’étend et se rétracte sous l’action de forces de rappel élastiques. Pour les fluides viscoélastiques avec un temps de relaxation plus petit que la durée de vie typique de la nappe, la dynamique de la nappe viscoélastique est similaire à d’un liquide visqueux Newtonien de même viscosité. L’expansion maximale de la nappe diminue avec la viscosité et est modélisée quantitativement en utilisant un bilan énergétique entre l'inertie, la tension superficielle et la dissipation du cisaillement visqueux sur la cible solide, qui peut être prise en compte en mesurant une vitesse effective de la nappe à temps court, en sortie de cible. Nous montrons en outre que la dissipation visqueuse peut être sensiblement éliminée en utilisant une surface solide sur la base d'un effet de Leidenfrost inverse. Les expériences effectuées à l'aide de perles élastiques de modules élastiques variables, de gouttes liquides de tensions superficielles variables et de gouttes viscoélastiques révèlent un comportement universel pour l’expansion maximale de la nappe avec la vitesse d'impact, avec une dynamique analogue à celle d'un système ressort-masse conventionnel. Nous montrons en outre que, pour les gouttes qui impactent une petite cible solide, une description similaire peut être utilisée une fois que la dissipation visqueuse est prise en compte en remplaçant la vitesse d'impact par la vitesse effective. Un autre comportement fascinant des fluides viscoélastiques est l’expansion hétérogène de la nappe associée à l’apparition de fissures, révélant la nature élastique du fluide viscoélastique. D’autre part, nous étudions la déformation uniaxiale et la facture de filaments de doubles réseaux transitoires en couplant rhéométrie extensionnelle et imagerie rapide des filaments étirés. Nous établissons un diagramme d'état qui délimite le régime de du filament, lorsqu'il est étiré à un taux supérieur à l'inverse du temps de relaxation du plus lent des deux réseaux. Nous démontrons quantitativement que les processus de dissipation ne sont pas pertinents dans nos conditions expérimentales et que, suivant la densité des nœuds dans les réseaux, la rupture se produit dans le régime élastique linéaire, ou non linéaire précédé d'une augmentation considérable de la viscosité extensionnelle. L'analyse des profils d'ouverture des fissures indique, pour des réseaux faiblement connectés, des écarts par rapport à une forme parabolique en pointe de fissure, caractéristique d’une fracture fragile en régime linéaire. Nous montrons une corrélation directe entre l'amplitude de la déviation de la forme parabolique et le caractère non linéaire de la déformation élastiqueWe investigate the behavior of transient self-assembled and permanently crosslinked gels subjected to extreme mechanical stresses. On the one hand, we study the dynamics of freely expanding sheets produced by impacting a (Newtonian or viscoelastic) liquid drop or a bead of polymeric gel on solid surfaces in minimal dissipation conditions, achieved using either a small solid target or a repellent surface. Upon impact, the drop or bead is transformed into a thin sheet that expands and retracts due to elasticity. For viscoelastic fluids with a relaxation time smaller than the typical lifetime of the sheet, the dynamics of the viscoelastic sheet is similar to that of Newtonian liquids with equal viscosity. The maximal expansion of the sheet decreases with the viscosity and is quantitatively modeled using an energy balance between inertia, surface tension and viscous shear dissipation on the solid target that can be accounted by measuring an effective velocity of the expanding sheet at short time scale. We further show that the shear dissipation can be substantially eliminated by performing impact experiments on a solid surface based on an inverse Leidenfrost effect. Experiments performed using elastic beads of various elastic moduli, viscoelastic or liquid drops of various surface tensions reveal a universal scaling behavior of the maximum expansion with the impact velocity, with a dynamics that mimics that of a conventional spring-mass system. We furthermore show that, for drops impacting a solid target, a similar scaling holds once the viscous dissipation is accounted by replacing the impact velocity with the effective velocity. Another fascinating behavior of viscoelastic fluids is a heterogeneous expansion of the sheet with the occurrence of cracks, revealing the elastic nature of the viscoelastic fluid. On the other hand, we study the uniaxial deformation and the fracture of reversible double transient networks by coupling extensional rheology to fast imaging. We provide a state diagram that delineates the regime of fracture without necking of the filament, when it is stretched at a rate larger than the inverse of the slowest relaxation time of the networks. We quantitatively demonstrate that dissipation processes are not relevant in our experimental conditions and that, depending on the density of nodes in the networks, fracture occurs in the linear elastic regime, or in a non-linear elastic regime preceded by a considerable strain hardening. In addition, analysis of the crack opening profiles indicates, for weakly connected networks, deviations from a parabolic shape close to the crack tip, which is expected for the linear elasticity of a brittle fracture. We demonstrate a direct correlation between the amplitude of the deviation from the parabolic shape and the amount of non-linear elasticity
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Bandekar, Ashish. "Electrowet Coalescence Of Water Drops In Water-ULSD Dispersion." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1490898933759055.
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Bou-Zeid, Wassim. "Wettability and evaporation of sessile drops of biological fluids." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4348/document.
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Le processus d'étalement et d'évaporation d'une goutte de suspensions de particules sur une surface solide est très intéressant permettant la formation de motifs. Une étude expérimentale à été effectuée avec du sang total humain et avec des fluides purs dans une chambre sous atmosphère contrôlée en humidité relative. Pour des angles de contact faible, le processus d'étalement/évaporation peut être divisé en deux régimes. Un premier régime rapide gouverné par un équilibre entre les forces visqueuses et les forces capillaires et un deuxième régime plus lent dominé par la cinétique d'évaporation. Nous montrons que les bio-colloïdes jouent un rôle significatif sur la dynamique de la ligne de contact. La vitesse moyenne de la ligne de contact suit la même dynamique d'étalement que le modèle de Tanner, où le temps d'étalement et les paramètres géométriques de la goutte sont fonctions de l'humidité. Dans cette étude, nous montrons que l'humidité relative influence les paramètres géométriques de la goutte et par conséquent le motif a la fin du processus d'évaporation. Un modèle purement diffusif pur a été obtenu dont le diamètre de mouillage et l'angle de contact sont fonction de l'humidité. Pour l'analyse morphologique des motifs de craquelures, une méthode de segmentation manuelle a été utilisée comme une méthode de référence pour la validation de la méthode de segmentation automatique développée dans "iBlood". Par cette méthode, nous montrons que la cinétique d'évaporation influence la distribution structurelle et morphologique des cellules de forme trapézoïdale, et par conséquent, l'espacement des fractures moyenne finaleSpreading/evaporation process of droplets over solid surfaces is a fundamental process and a wide research field because of number of applications in printing, micro-electronics, DNA analysis and even in biomedical. This experimental work aims to investigate the effect of relative humidity on the contact line dynamics, on the evaporation dynamics and on the final pattern of a drop of whole human blood. The spreading of a pure fluid model that has the same physical properties as human blood was studied and compared to the blood. We showed that bio-colloids play significant effect on the dynamics of contact line and the pinning effect of the drop. For low contact angles, we showed that the spreading/evaporation process could be divided into two regimes. A fast first regime determined by a balance between viscous forces and capillary forces and a second slower regime dominated by the evaporation rate. Physical mechanisms that are responsible for the spreading enhancement are proposed and discussed. The average velocity of the contact line was found to follow the same behaviour as Tanner's model, where the spreading dynamics and geometrical parameters of the droplet are function of relative humidity. The experimental measurements are in a good agreement with the purely diffusive model where the equilibrium wetting radius and contact angle are function of relative humidity. For the morphological analysis of crack patterns, a manual segmentation method was used as a reference for the validation of the automatic developed segmentation method. We showed that the evaporation rate influences structural distribution of plaques in the corona region and hence, the mean crack spacing
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Liao, Liang. "Diamagnetic levitation of liquid-grain systems and liquid drops." Thesis, University of Nottingham, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.716466.
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This thesis describes the use of diamagnetic levitation for experimental studies of fluid and granular dynamics in a pseudo-weightless environment. A superconducting solenoid magnet was used to generate a large 18 T inhomogeneous magnetic field in order to levitate liquid water, organic liquids and bismuth particles diamagnetically, and glass particles using the magneto-Archimedes effect. We first present an experimental study of the behaviour of a pair of magnetically suspended spheres in an oscillating liquid. The spheres have a density greater than that of the liquid in which they are immersed, so that vibration of the liquid results in relative motion of the spheres through the liquid, generating streaming flows. Under vibration, the spheres attract one another. Spontaneous orbiting of the spheres was observed above a critical vibration amplitude. Experimental and numerical studies of the flow reveal the origin of the fluid dynamical instability. The collapse of experimental and numerical data onto a single curve shows that the fluid dynamical instability occurs at a critical value of the streaming Reynolds number. In addition we compared our experimental measurements of the relative amplitude of spheres through the vibrated liquid with existing numerical models. This thesis also describes an experimental study of the equilibrium shapes and stability of a freely levitated, spinning and electrically-charged liquid droplet. Beginning with a spherical droplet at rest, we observed the equatorial diameter of the droplet expand with increasing angular momentum, until it evolved into a triaxial shape at the theoretically predicted angular momentum. With increasing angular momentum, the droplet fissioned into two droplets of equal volume. With increasing charge, the critical angular momentum to reach the two-lobed bifurcation point and to fission the droplet was lowered. Our experimental data confirms the theoretically predicted critical charge density (Rayleigh limit) required to fission a non-rotating droplet. In addition, our experiments show that fission becomes asymmetric above a critical charge density.
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Eow, John Son. "Electrostatic enhancement of coalescence of water drops in oil." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/842815/.
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Dispersed water drops in oils can cause detrimental effects. For example in refining and cracking of crude oil, poisoning of catalysts and equipment corrosion can be major problems due to the presence of water. Therefore there is a need to develop more efficient and cost-effective separators. The work in this thesis covers an investigation of the underlying electrostatic phenomena (i.e. drop-drop and drop-interface coalescence and drop deformation and break-up) leading to the development of compact electrocoalescer-separators. Using novel two-dimensional electrode systems, it is shown here that coalescence readily occurs when the electric field is applied in the same direction as the line joining the centres of the two drops, in line with the previous theoretical prediction of the maximum attractive force induced in this way. An adaptive Finite Element Method, incorporating automatic error and mesh generator programmes, has been used to quantify the electric-induced forces of charged spheres in an insulating medium, for short distances that are much smaller than the drop radius, where analytical solutions are no longer reliable. Moreover, drop-drop attraction can also occur when the angle is 125.3° from the electric field direction. Previous work suggests that pulsed d.c. fields are effective for low-aqueous-content systems, and this has been further investigated here. The applied electric field and pulse frequency can be optimised to achieve the highest coalescence rate. High electric fields (> 3.5 kV/cm) are shown to deform and break up aqueous drops when the electric field-induced stresses overcome the interfacial tension. A critical electrostatic Weber number, corresponding to the onset of drop break-up, has been evaluated to be about 0.49 for several aqueous-oil systems. For the separation of dispersed aqueous drops from an oil phase, it is advantageous to incorporate an aqueous layer to induce drop-interface coalescence. A suitably applied electric field is shown to give efficient drop-interface coalescence. The above investigations have led to the design and development of two compact electrocoalescer-separators. The first separator combines the effects of electrocoalescence and gravitational settling. The second separator, which utilises the electrocoalescence and centrifugal effects, can handle larger throughputs with reasonable separation efficiency. Both devices significantly enhance the separation and are good examples of how the fundamental understanding gained in this studies can be applied to realistic practical situations.
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Avila-Segura, Francisco E. Sabersky Rolf H. "The creeping motion of immiscible drops through a converging/diverging tube : I. Non-Newtonian effects of viscoelastic drops. II. Effects of constant pressure gradient condition for the flow. III. Motion of drops through a parallel channel /." Diss., Pasadena, Calif. : California Institute of Technology, 1988. http://resolver.caltech.edu/CaltechETD:etd-10312007-093206.
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