Dissertations / Theses: 'Surface free energy'

1

Yildirim, Ismail. "Surface Free Energy Characterization of Powders." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/27525.

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Microcalorimetric measurements and contact angle measurements were conducted to study the surface chemistry of powdered minerals. The contact angle measurements were conducted on both flat and powdered talc samples, and the results were used to determine the surface free energy components using Van Oss-Chaudhury-Good (OCG) equation. It was found that the surface hydrophobicity of talc increases with decreasing particle size. At the same time, both the Lifshitz-van der Waals (gSLW) and the Lewis acid-base (gSAB) components (and, hence, the total surface free energy (gS)) decrease with decreasing particle size. The increase in the surface hydrophobicity and the decrease in surface free energy (gS) can be attributed to preferential breakage of the mineral along the basal plane, resulting in the exposure of more basal plane surfaces to the aqueous phase. Heats of immersion measurements were conducted using a flow microcalorimeter on a number of powdered talc samples. The results were then used to calculate the contact angles using a rigorous thermodynamic relation. The measured heat of immersion values in water and calculated contact angles showed that the surface hydrophobicity of talc samples increase with decreasing particle size, which agrees with the direct contact angle measurements. A relationship between advancing water contact angle qa, and the heat of immersion (-DHi) and surface free energies was established. It was found that the value of -DHi decrease as qa increases. The microcalorimetric and direct contact angle measurements showed that acid-base interactions play a crucial role in the interaction between talc and liquid. Using the Van Oss-Chaudhury-Goodâ s surface free energy components model, various talc powders were characterized in terms of their acidic and basic properties. It was found that the magnitude of the Lewis electron donor, gS-, and the Lewis electron acceptor, gS+, components of surface free energy is directly related to the particle size. The gS- of talc surface increased with decreasing particle size, while the gS+ slightly decreased. It was also found that the Lewis electron-donor component on talc surface is much higher than the Lewis electron-acceptor component, suggesting that the basal surface of talc is basic. The heats of adsorption of butanol on various talc samples from n-heptane solution were also determined using a flow microcalorimeter. The heats of adsorption values were used to estimate % hydrophilicity and hydrophobicity and the areal ratios of the various talc samples. In addition, contact angle and heat of butanol adsorption measurements were conducted on a run-of-mine talc sample that has been ground to two different particle size fractions, i.e., d50=12.5 mm and d50=3.0 mm, respectively. The results were used to estimate the surface free energy components at the basal and edge surfaces of talc. It was found that the total surface free energy (gS) at the basal plane surface of talc is much lower than the total surface free energy at the edge surface. The results suggest also that the basal surface of talc is monopolar basic, while the edge surface is monopolar acidic. The results explain why the basicity of talc surface increases with decreasing particle size as shown in the contact angle and microcalorimetric measurements. Furthermore, the effects of the surface free energies of solids during separation from each other by flotation and selective flocculation were studied. In the present work, a kaolin clay sample from east Georgia was used for the beneficiation tests. First, the crude kaolin was subjected to flotation and selective flocculation experiments to remove discoloring impurities (i.e., anatase (TiO2) and iron oxides) and produce high-brightness clay with GE brightness higher than 90%. The results showed that a clay product with +90% brightness could be obtained with recoveries (or yields) higher than 80% using selective flocculation technique. It was also found that a proper control of surface hydrophobicity of anatase is crucially important for a successful flotation and selective flocculation process. Heats of immersion, heats of adsorption and contact angle measurements were conducted on pure anatase surface to determine the changes in the surface free energies as a function of the surfactant dosage (e.g. hydroxamate) used for the surface treatment. The results showed that the magnitude of the contact angle and, hence, the surface free energy and its components on anatase surface varies significantly with the amount of surfactant used for the surface treatment.
Ph. D.

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2

Zhang, Jinhong. "Surface Forces between Silica Surfaces in CnTACl Solutions and Surface Free Energy Characterization of Talc." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29997.

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In general, the stability of suspension can be studied using two methods. One is to directly measure the forces between two interacting surfaces in media. The other is to study the interfacial surface free energies of the particles in suspension. Direct surface force measurements were conducted between silica surfaces in octadecyltrimetylammonium chloride (C₁₈TACl) solutions using an Atomic Force Microscope (AFM). The results showed that the hydrophobic force existed in both air-saturated and degassed C₁₈TACl solutions. The attraction decreased with NaCl addition, and was the strongest at the point of charge neutralization (p.c.n.) of silica substrate. The force measurement results obtained in C_nTACl solutions showed that the attractions decayed exponentially and became the maximum at the p.c.n.'s. The decay lengths (D) increased with surfactant chain length. The measured forces were fitted to a charged-patch model of Miklavic et al. (1994) with rather large patch sizes. It was also found that the decay length decreased linearly with the effective concentration of the CH2/CH3 groups raised to the power of -1/2. This finding is in line with the model of Eriksson et al. (1989). It suggested that the long-range attractions are hydrophobic forces originating from the changes in water structure across a hydrophobic surface-solution interface. For the TiO₂/water/TiO₂ system, the Hamaker constant was found to be 4±1×10^-20 J. The force curves obtained in the TiO₂/C_nTACl system showed a repulsion-attraction-repulsion transition with increasing surfactant concentration. The long-range attraction observed between TiO₂ surfaces in C_nTACl solutions reached maximum at the p.c.n., and the decay length increased with chain length. In present work, the thin-layer wicking technique was used to determine the surface free energy (γ_s) and its components of talc samples. The results showed that the basal surfaces of talc are weakly basic while the edge surfaces are acidic. The effect of chemicals on the surface free energies of talc was systemically studied. The results showed that CMC (carboxymethyl cellulose sodium salt) and EO/PO (ethylene oxide/propylene oxide) co-polymers made talc surface hydrophilic by increasing the surface free energies, especially γ^LW and γ^-. SOPA (sodium polyacrylate) increased greatly the zeta-potentials instead of the surface free energies.
Ph. D.

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3

Ozcan, Canturk. "Surface Free Energy Evaluation, Plasma Surface Modification And Biocompatibility Studies Of Pmma." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607414/index.pdf.

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PMMA is a widely used biomaterial especially in the fields of orthopedia, orthodontia and ophthalmology. When biocompatibility is considered, modification of the biomaterials&
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surface may be needed to optimize interactions of the biomaterial with the biological environment. After the surface modifications one of the most important changes that occur is the change in the surface free energy (SFE). SFE is an important but an obscure property of the material and evaluation methods with different assumptions exist in the literature. In this study, SFE of pristine and oxygen plasma modified PMMA films were calculated by means of numerous theoretical approaches (Zisman, Saito, Fowkes, Berthelot, Geometric and Harmonic Mean and Acid-Base) using numerous liquids and the results were compared to each other to elucidate the differences of methods. Dispersive, polar, acidic and basic components of the SFE were calculated by the use of different liquid couples and triplets with the application of Geometric and Harmonic mean methods and Acid-Base approach. The effect of SFE and the components of SFE on the cell attachment efficiencies were examined by using fibroblast cells. It was observed that with the treatment of oxygen plasma, cell attachment capability and hydrophilicity of PMMA surfaces were altered depending on the applied power and duration of the plasma.

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Teh, Hee Min. "Hydrodynamic performance of free surface semicircular breakwaters." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7652.

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Different types of breakwaters have been developed in the past for the protection of valuable coastal property, commercial activity and beach morphology. Among these, gravity-type breakwaters are the most common and provide good surface wave attenuation. However, these breakwaters are not always suitable due to their adverse impact on the coastal environment. To alleviate the problem, free surface breakwaters with a variety of caisson designs have been proposed and developed. The main advantages of such breakwaters are low capital cost, freedom from silting and scouring, short construction period, circulation of water beneath the breakwater and exertion of relatively low hydrodynamic forces on the structure as compared to conventional breakwaters. However, complete tranquillity on the lee side is not likely to occur due to wave energy transfer through the permeable parts of the breakwater. The degree of wave attenuation primarily depends on the configuration of the breakwater, the water depth and the incident wave conditions. The hydrodynamic performance of such free surface breakwaters is the subject of this thesis. Semicircular breakwaters mounted on a low-crested rubble mound structure were successfully built for harbour protection in Japan and China. However, the concept of having semicircular structures as free surface breakwaters has not yet been explored by the research community. As a result, this research is initiated with the aim of developing a free surface semicircular breakwater (SCB) that would serve as an anti-reflection barrier and provide reasonably good wave protection to coastal and marine infrastructures. To meet this research goal, a free surface SCB models were constructed and tested in a wave flume under various wave conditions. The experiments were conducted in three stages. For the first stage, the SCB model was initially tested without any perforations on the curved surface (i.e. a solid SCB) for different depths of immersion from the still water level in the wave flume. For the second stage, the front curved wall of the model was subsequently perforated with rectangular openings of different dimensions, producing front wall porosity of 9, 18 and 27%. Following this, two rows of rectangular openings near the crest of the rear curved wall were provided so as to facilitate water infiltration and escape of the run-up waves. For the third stage, additional effort was made to extend the draft of the breakwater by adding a wave screen at the front or/and rear. The screen porosity was 25, 40 and 50%. The hydrodynamic characteristics of the SCB models were investigated in both regular and irregular seas through a series of systematic experimental programme. The water surface elevations were measured at different locations upstream and downstream of the models to determine the coefficients of wave transmission (CT), reflection (CR) and energy dissipation (CL) as well as the wave climate coefficients in front and inside the breakwater chamber. The horizontal wave forces exerted on the SCB models and the wave screen(s) were also measured and subsequently normalised to yield the force coefficients in the analysis. These hydrodynamic coefficients for the respective test cases are presented and discussed in this thesis. The experimental results revealed that even though the solid SCB was a better wave attenuator than the perforated ones, it produced a considerable amount of wave reflection. The perforated SCB with 9% porosity of the front wall (denoted as SCB9) outperformed the other perforated breakwater models; however, it produced high wave transmission when the draft was limited and subjected to longer period waves. Hence, wave screens were added to further enhance the performance of the SCB9. The SCB9 with double screens of 25% porosity was found to provide the highest hydraulic performance. Empirical equations were developed using a multiple regression technique to provide design formulae for wave transmission, wave reflection and horizontal wave forces. The proposed empirical equations showed good agreement with the experimental data. These equations are intended to be of direct use to engineers in predicting the hydrodynamic performance of free surface SCBs. However, sensible engineering judgement must be taken while using these equations as they are based on small scale laboratory tests.

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5

Luangtana-Anan, Manee. "The role of surface free energy in the compaction of powders." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329066.

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6

Lobato, Emilio Marcus de Castro. "Determination of Surface Free Energies and Aspect Ratio of Talc." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/35743.

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Microcalorimetric measurements and contact angle measurements were conducted to assess the surface chemistry of the mineral talc. The contact angles were performed on both flat and powdered samples and the results were used to determine the surface free energy components and parameters (SFEC) using the acid-base theory for solids, according to the van Oss-Chaudhury-Good approach. It was found that the surface hydrophobicity of talc increases with decreasing particle size up to a limit after which hydrophilicity (polarity) increases. The increase in hydrophobicity was attributed to the increase of the delamination of the lamellar talc particles. Delamination is a comminution mechanism that preferentially exposes talc's hydrophobic basal planes, while fracture is another mechanism that breaks the lamellae, rupturing covalent bonds thus exposing more hydrophilic edge surfaces. The decrease in hydrophobicity, beyond a given particle size, could be related to the prevail of fracture over delamination during grinding which generated more hydrophilic edge surfaces.

The flow microcalorymetry combined with thin layer wicking allowed the separate estimation of the SFEC at the basal plane and edge surfaces of talc. The results suggested that the basal surface of talc is monopolar basic, while the edge surface is monopolar acidic, which are in agreement with the crystal structure of the mineral.

The combination of two particle size distribution techniques, which are based on different physical principles, permitted the quantitative determination of the aspect ratio of highly anisometric particles, such as talc. The same trend obtained using flow microcalorimetry was observed for the evolution of the aspect ratio as a function of particle fineness, i.e. the fracture prevails over delamination after achieving a maximum aspect ratio value of about 35. The agreement between two distinct methods was considered rather encouraging.

Master of Science

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7

Doshi, Urmi R. "One-dimensional free energy surface models of protein folding: connecting theory and experiments." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/6875.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.
Thesis research directed by: Biochemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Wang, Feng. "Non-Boltzmann sampling for the accurate calculation of peptide-surface adsorption free energy." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1193079364/.

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Thesis (Ph.D.) -- Clemson University, 2007.
Title from first page of PDF file. Document formatted into pages; contains xvi, 132 p. ; also includes graphics (chiefly col.). Contains additional supplemental file.

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9

Sumner, Loren Bryan Stout. "Energy stability of thermocapillary convection in liquid bridges with a deformed free surface." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/17140.

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Warren, Jonathan Peter. "Quantum evaporation of Â³He from the free surface of â´He." Thesis, University of Exeter, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275902.

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11

Ying, Song. "Energy analysis for a snow-free surface : A technical analysis of the benefits of insulation under the heating pipes." Thesis, Högskolan i Gävle, Energisystem, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-26910.

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Snow-free surfaces is needed for parking place, platform, and playground and even in city center square. With energy prices rising, energy saving is becoming a hot topic. Meanwhile environmental problems are becoming more and more serious, thus, the ways to saving energy is becoming an eye-catcher. So burring heating pipes underground has been a popular way to get ice-free surfaces. Using heating pipes for melting snow is much more efficient and more benefit for the environment comparing with using other methods. In this project, an energy analysis of a football pitch with an area of 5000 m2 is carried out under a series of conditions between insulated and uninsulated construction. All calculations are done with the so-called finite element method (FEM), in the COMSOL. COMSOL is used for simulating and calculating the energy use with outdoor temperatures of -5 ºC and -10 ºC. Top layer materials concrete, grass and stone are also discussed. The ability of XPS and EPS insulation material is compared and noted. The models are divided into two parts, one is with snowfall and the other is without snowfall. The results in the report shows that adding insulation under the heating pipe has significant energy saving potential. The surface with concrete layer has the best insulated ability, which can prevent more heat losses. The EPS insulated construction has a better performance in keeping more heat in the soil.

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Nobrega, Robert P. "Early Folding Biases in the Folding Free-Energy Surface of βα-Repeat Proteins: A Dissertation." eScholarship@UMMS, 2014. https://escholarship.umassmed.edu/gsbs_diss/723.

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Early events in folding can determine if a protein is going to fold, misfold, or aggregate. Understanding these deterministic events is paramount for de novo protein engineering, the enhancement of biopharmaceutical stabilities, and understanding neurodegenerative diseases including amyotrophic lateral sclerosis and Alzheimer's disease. However, the physicochemical and structural biases within high energy states of protein biopolymers are poorly understood. A combined experimental and computational study was conducted on the small β/α-repeat protein CheY to determine the structural basis of its submillisecond misfolding reaction to an off-pathway intermediate. Using permutations, we were able to discriminate between the roles of two proposed mechanisms of folding; a nucleation condensation model, and a hydrophobic collapse model driven by the formation of clusters of isoleucine, leucine, and valine (ILV) residues. We found that by altering the ILV cluster connectivity we could bias the early folding events to either favor on or off-pathway intermediates. Structural biases were also experimentally observed in the unfolded state of a de novo designed synthetic β/α-repeat protein, Di-III_14. Although thermodynamically and kinetically 2-state, Di-III_14 has a well structured unfolded state that is only observable under native-favoring conditions. This unfolded state appears to retain native-like structure, consisting of a hydrophobic 7 core (69% ILV) stabilized by solvent exposed polar groups and long range electrostatic interactions. Together, these results suggest that early folding events are largely deterministic in these two systems. Generally, low contact order ILV clusters favor local compaction and, in specific cases, long range electrostatic interactions may have stabilizing effects in higher energy states.

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Nobrega, Robert P. "Early Folding Biases in the Folding Free-Energy Surface of βα-Repeat Proteins: A Dissertation." eScholarship@UMMS, 2007. http://escholarship.umassmed.edu/gsbs_diss/723.

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Early events in folding can determine if a protein is going to fold, misfold, or aggregate. Understanding these deterministic events is paramount for de novo protein engineering, the enhancement of biopharmaceutical stabilities, and understanding neurodegenerative diseases including amyotrophic lateral sclerosis and Alzheimer's disease. However, the physicochemical and structural biases within high energy states of protein biopolymers are poorly understood. A combined experimental and computational study was conducted on the small β/α-repeat protein CheY to determine the structural basis of its submillisecond misfolding reaction to an off-pathway intermediate. Using permutations, we were able to discriminate between the roles of two proposed mechanisms of folding; a nucleation condensation model, and a hydrophobic collapse model driven by the formation of clusters of isoleucine, leucine, and valine (ILV) residues. We found that by altering the ILV cluster connectivity we could bias the early folding events to either favor on or off-pathway intermediates. Structural biases were also experimentally observed in the unfolded state of a de novo designed synthetic β/α-repeat protein, Di-III_14. Although thermodynamically and kinetically 2-state, Di-III_14 has a well structured unfolded state that is only observable under native-favoring conditions. This unfolded state appears to retain native-like structure, consisting of a hydrophobic 7 core (69% ILV) stabilized by solvent exposed polar groups and long range electrostatic interactions. Together, these results suggest that early folding events are largely deterministic in these two systems. Generally, low contact order ILV clusters favor local compaction and, in specific cases, long range electrostatic interactions may have stabilizing effects in higher energy states.

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Bowlin, Oscar E. "Modeling and simulation of the free electron laser and railgun on an electric Naval surface platform." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Mar%5FBowlin.pdf.

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Topper, Mathew Bernard Robert. "Numerical modelling of flows involving submerged bodies and free surfaces." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5299.

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Kinetic energy extraction devices for ocean and river flows are often located in the vicinity of the fluid free surface. This differs from wind turbines where the atmosphere may be considered to extend to infinity for the purposes of numerical modelling. As most kinetic energy extraction devices are based on lifting surfaces, a numerical model is sought which can model both lifting and free surface flows. One such model is the boundary element method which has been successfully applied to free surface problems and to lifting flows as well as the combined problem. This study seeks to develop a high order boundary element method that is capable of modelling unsteady lifting and free surface flows in three dimensions. Although high order formulations of boundary element methods are common for free surface problems, providing improved accuracy and computational time, their usage for lifting flows is less frequent. This may be due to the hypersingular boundary integral equation (HBIE) which must be solved in order to find the velocity of the vortex wakes behind lifting surfaces. In previous lifting flow studies using high order boundary element methods the wake velocities have been determined at the element centres and then interpolated to the collocation points. Not until the paper of Gray et al. (2004b) has a method been available for the direct solution of the HBIEs at the edges of three dimensional high order elements with C0 continuous interfaces. The solution employs a technique known as the Galerkin boundary element method. This study shows, for the first time, that the Galerkin boundary element method is applicable to the solution of the HBIE on the vortex wake of a lifting body. The application of the technique is then demonstrated as part of the numerical model developed herein. The model is based on the high order boundary element method developed by Xu (1992) for non-linear free surface flows. This formulation is extended to include steady uniform flow throughout the computational domain as well as the presence of lifting and non-lifting bodies. Several verification cases are implemented to test the accuracy of the model.

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Barassa, Jonathan, and Rickard Nordlöf. "Numerical Study on Air Demand of Free Surface Flows in a Discharge Tunnel." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414989.

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Aeration issued through a ventilation shaft is an important measure to prevent cavitation and large gauge pressure in flood discharge tunnels. In order to dimension the ventilation shaft appropriately, itis necessary to have a good understanding of the air-water flow in the tunnel. In this study, the multiphase flow through a discharge tunnel was simulated in the computational fluid dynamics (CFD) software ANSYS Fluent. Since the flow was separated, the simulation setup used the volume of fluid (VOF) multiphase model, that could track the water surface. Furthermore, the so called RNG k-epsilon turbulence model was used. The CFD model was validated with measured data provided from two open channel experiments carried out on a scaled model at Sichuan University. To ensure mesh independence, grid convergence index (GCI)studies were performed for the two validating cases. After the validation, a top wall and a ventilation shaft was added to the CFD model. The flow was then simulated for four different shaft designs and four different water inlet velocities. The air demand and air supply for the various scenarios could thereby be calculated. The results of this study were also compared with previous research on multiphase flow through tunnels with similar design. It was concluded that the air flow downstream in the tunnel converged for the two larger designs. It was also concluded that the air demand in the tunnel was satisfied for the larger ventilation shafts. A smaller study on cavitation was made and the risk was considered non-existent for all the simulated cases.

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Wu, Min. "Adhesion and Surface Energy Profiles of Large-area Atomic Layers of Two-dimensional MoS2 on Rigid Substrates by Facile Methods." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849762/.

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Two-dimensional (2D) transition metal dichalcogenides (TMDs) show great potential for the future electronics, optoelectronics and energy applications. But, the studies unveiling their interactions with the host substrates are sparse and limits their practical use for real device applications. We report the facile nano-scratch method to determine the adhesion energy of the wafer scale MoS2 atomic layers attached to the SiO2/Si and sapphire substrates. The practical adhesion energy of monolayer MoS2 on the SiO2/Si substrate is 7.78 J/m2. The practical adhesion energy was found to be an increasing function of the MoS2 thickness. Unlike SiO2/Si substrates, MoS2 films grown on the sapphire possess higher bonding energy, which is attributed to the defect-free growth and less number of grain boundaries, as well as less stress and strain stored at the interface owing to the similarity of Thermal Expansion Coefficient (TEC) between MoS2 films and sapphire substrate. Furthermore, we calculated the surface free energy of 2D MoS2 by the facile contact angle measurements and Neumann model fitting. A surface free energy ~85.3 mJ/m2 in few layers thick MoS2 manifests the hydrophilic nature of 2D MoS2. The high surface energy of MoS2 helps explain the good bonding strength at MoS2/substrate interface. This simple adhesion energy and surface energy measurement methodology could further apply to other TMDs for their widespread use.

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Maeda, Nobuo, and nobuo@engineering ucsb edu. "Phase Transitions of Long-Chain N-Alkanes at Interfaces." The Australian National University. Research School of Physical Sciences and Engineering, 2001. http://thesis.anu.edu.au./public/adt-ANU20011203.151921.

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An experimental study of phase transitions of long-chain n-alkanes induced by the effect of interfaces is described. ¶ The phase behaviour of long-chain n-alkanes (carbon number 14, 16, 17, 18) adsorbed at isolated mica surfaces and confined between two mica surfaces has been studied in the vicinity of and down to several degrees below the bulk melting points, Tm. Using the Surface Force Apparatus we have measured the thickness of alkane films adsorbed from vapour (0.97 [equal to or greater-than] p/p[subscript o] [equal to or greater-than] 0.997), studied capillary condensation transition, subsequent growth of capillary condensates between two surfaces, and phase transitions in both the adsorbed films and the condensates. By measuring the growth rate of the capillary condensates we have identified a transition in the lateral mobility of molecules in the adsorbed films on isolated mica surfaces. This transition to greater mobility occurs slightly above Tm for n-hexadecane, n-heptadecane and n-octadecane but several degrees below Tm for n-tetradecane, and is accompanied by a change in wetting behaviour and a measurable decrease in adsorbed film thickness for n-heptadecane and n-octadecane. Capillary condensates that form below Tm remain liquid, but may freeze if the degree of confinement is reduced by separation of the mica surfaces. An increase in the area of the liquid-vapour interface relative to that of the liquid-mica interface facilitates freezing in the case of the long-chain alkanes, which show surface freezing at the liquid-vapour interface. ¶ Although thermodynamic properties of the surface freezing transition have been rather well documented, the kinetics involved in formation of such ordered monolayers has so far received very little attention. We studied the surface tension of n-octadecane as a function of temperature in the vicinity of Tm, using the static Wilhelmy plate and the dynamic maximum bubble pressure methods. The two methods give different results on cooling paths, where nucleation of the surface ordered phase is involved, but agree on heating paths, where both methods measure properties of the equilibrium surface phase. On cooling paths, the surface of bubbles may supercool below the equilibrium surface freezing temperature. The onset of surface freezing is marked by a sharp drop in the surface tension. The transition is accompanied by an increased stability of the films resulting in longer bubble lifetimes at the liquid surface, which suggests that the mechanical properties of the surfaces change from liquid-like to solid-like. Our results suggest occurrence of supercooling of the monolayer itself.

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Omidvar, Pourya. "Wave loading on bodies in the free surface using smoothed particle hydrodynamics (SPH)." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/wave-loading-on-bodies-in-the-free-surface-using-smoothed-particle-hydrodynamics-sph(9d744522-6ecf-4496-a784-4ab08292e344).html.

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This thesis investigates wave loading on bodies in the free surface using smoothed particle hydrodynamics (SPH). This includes wave loading on fixed bodies, waves generated by heaving bodies in still water and the heave response of a body in waves, representing a wave energy device. SPH is a flexible Lagrangian technique for CFD simulations, which in principle applies to steep and breaking waves without special treatment allowing us to simulate highly nonlinear and potentially violent flows encountered in a real sea. However few detailed tests have been undertaken even with small amplitude waves.This research uses the open-source SPH code SPHysics. First two forms of SPH formulation, standard SPH with artificial viscosity and SPH-Arbitrary Lagrange Euler (ALE) with a Riemann solver, are used to simulate progressive waves in a 2-D tank. The SPH-ALE formulation with a symplectic time integration scheme and cubic spline kernel is found to model progressive waves with negligible dissipation whereas with the standard SPH formulation waves decay markedly along the tank. We then consider two well-defined test cases in two dimensions: progressive waves interacting with a fixed cylinder and waves generated by a heaving semi-immersed cylinder. To reduce computer time in a simple manner a variable particle mass distribution is tested with fine resolution near the body and coarse resolution further away, while maintaining a uniform kernel size. A mass ratio of 1:4 proved effective but increasing to 1:16 caused particle clumping and instability. For wave loading on a half-submerged cylinder the agreement with the experimental data of Dixon et al. (1979) for the root mean square force is within 2%. For more submerged cases, the results show some discrepancy, but this was also found with other modelling approaches. For the heaving cylinder, SPH results for the far field wave amplitude and vertical force on the cylinder show good agreement with the data of Yu and Ursell (1961). The variable mass distribution leads to a computer run time speedup of nearly 200% in these cases on a single CPU. The results of the vertical force and wave amplitude are shown to be quite sensitive to the value of the slope limiter in the Riemann solver for the 2-D heaving cylinder problem. A heaving 2-D wedge or 3-D cone whose oscillatory vertical motion is prescribed as the elevation of a focused wave group is a precise test case for numerical free-surface schemes. We consider two forms of repulsive boundary condition (Monaghan & Kos, 1999, and Rogers et al., 2008) and particle boundary force (Kajtar and Monaghan, 2009) for the 2-D wedge case, comparing the result with the experimental data of Drake et al. (2009). The repulsive boundary condition was more effective than the particle boundary force method. Variable particle mass with different kernel sizes was then tested for 2-D problems for mass ratios of 1:4, 1:16 and 1:4:16 with satisfactory results without particle clumping and instability. For the 3-D cone case, SPH reproduces the experimental results very closely for the lower frequency tested where there is no separation from the bottom surface of the body but for the higher frequencies the magnitudes of force minima were underestimated. The mass ratios of 1:8 and 1:8:27 in two and three nested regions are tested for the 3-D cone problem where a computer run time speedup of nearly 500% is achieved on 16 processors for the mass ratio of 1:8.Finally, the floating body of a heaving wave energy device known as the Manchester Bobber is modelled in extreme waves without power take-off. The results for a single float are in approximate agreement with the experiment.

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Almeida, Fernando Mattavo de. "Numerical simulation of the flow through an aqxial tidal-current turbine employing an elastic-free-surface approach." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-18092018-074509/.

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Together with the world economic growth is the increasing of energy generation demand. However, the upgrade of world power production capability could affect the environment negatively. Even the clean and renewable sources, such as hydroelectricity and wind powers have socio-economic and environmental disadvantages. For example, the required flooded area for a hydro power plant construction could devastate entire forests, and the installation of a wind farm power plant could affect migratory rotes of birds and generate high levels of noise. Hence, for the balancing of advantages and disadvantages of each power generation source, it is necessary to diversify, which requires investments in new power sources. In this context, the energy generation in the ocean is highlighted. The first point concerning the ocean energy is that there is no need of population removal from the installation area, such as the onshore based methods and the second point is that most of the population is concentrated in coastal areas. Therefore the production occurs near to the demand, decreasing the costs with energy distribution. The two main methodologies for harassing energy from oceans are based on gravity waves and in tides. And since the tidal cycles are governed mainly by the gravitational interaction between oceans, Moon and Sun, they are easily predictable, which increases the reliability of such systems. These works explores methodologies to analyse the power generation from a single axial tidal current turbine through a Steady State RANS methodology. Are discussed the effects of flow directionality, inlet velocity profile and turbulence levels and the results are compared with an experimental scheme. It is proposed an alternative methodology for free surface modelling in the CFD analysis. The usual methodology, VOF, it is based on a homogeneous, biphasic approach which requires an additional mesh refinement and is computationally expensive. This new methodology introduces an elastic wall approach in the free surface region in which the stiffness is calculated to provide the same restoring effect as gravity. In general, the results for open domain matched with the experimental results, validating the numerical model and the confined domain has shown a higher power and thrust coefficients if compared with the open domain, which is in accordance with the actuator disk theory approach. The elastic free surface presented convergence problems related to high Froude numbers and therefore to high deformations. However, a simulation with 10% of the original inlet velocity was performed, achieving reasonable results for both power and thrust coefficients evaluation.
O crescimento econômico mundial e o aumento na demanda pela geração de energia andam juntos. No entanto, uma maior capacidade de produção de energia poderia afetar negativamente o meio ambiente. Mesmo as fontes limpas e renováveis, como a hidrelétrica e a eólica acarretam em impactos socioeconômicos e ambientais. Por exemplo, a construção de uma usina hidrelétrica demanda uma imensa área alagada que pode devastar florestas inteiras e a instalação de uma usina eólica pode afetar a migração de certas espécies de pássaros e produzir altos níveis de barulho. Portanto, para equilibrar as vantagens e desvantagens devidas a cada meio de produção de energia, é necessária a diversificação, que demanda de investimentos em novas fontes. Neste contexto, a geração de energia nos oceanos é destacada. O primeiro ponto a respeito desta fonte é de que não há a necessidade de remoção da população na área de instalação, tal como os métodos de geração dentro do continente. O segundo principal ponto é a respeito da distribuição de energia. A maior parte da população mundial vive em regiões costeiras, diminuindo, portanto, a distância entre a produção e demanda, reduzindo assim, seus custos. As duas principais metodologias para se explorar a energia proveniente dos oceanos são: Energia de Ondas e Energia de Marés. E considerando que os ciclos de mare são governados principalmente pela interação gravitacional entre os oceanos, lua e sol, eles são facilmente previsíveis, o que aumenta a confiabilidade dos sistemas de geração de energia baseados em marés. Este trabalho explora as metodologias para analisar a geração de energia a partir de uma única turbina axial de corrente de maré através de uma metodologia baseada nas equações de Navier-Stokes com a média de Reynolds, analisadas em regime permanente. São discutidos efeitos da direção do escoamento, perfil de velocidades na entrada e nos níveis de turbulência. Os resultados são comparados com experimentos. É proposta uma metodologia alternativa para a modelagem da superfície livre com CFD uma vez que a metodologia atual é baseada em um escoamento bifásico que demanda de um refinamento adicional da malha e é computacionalmente caro. A nova metodologia usa uma parede elástica na região da superfície livre com a rigidez ajustada para se obter o mesmo efeito de restauração que a gravidade. De maneira geral, os resultados para o domínio aberto se aproximaram dos resultados experimentais, validando o modelo numérico e além disso, o modelo considerando confinamento da turbine mostrou maiores valores para os coeficientes de potência e empuxo, estando portanto, de acordo com a teoria do disco atuador. O modelo com a superfície livre elástica apresentou problemas de convergência, relacionados com números de Froude elevados, uma vez que isto se relaciona com maiores deformações na região da superfície livre. Uma simulação com 10% da velocidade original foi realizada, obtendo-se resultados coerentes para ambos coeficientes de potência e empuxo.

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21

Niles, Sean P. "High energy laser applications in a surface combatant : terminal phase theater ballistic missile defense, low atmosphere propagation, and free electron laser gain /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FNiles.pdf.

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22

Bhasin, Amit. "Development of methods to quantify bitumen-aggregate adhesion and loss of adhesion due to water." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5934.

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Moisture induced damage of hot mix asphalt pavements has a significant economic impact in terms of excessive maintenance and rehabilitation costs. The moisture sensitivity of an asphalt mix depends on the combined effects of material properties, mixture design parameters, loading conditions and environmental factors. Traditional methods to assess moisture sensitivity of asphalt mixes rely on mechanical tests that evaluate the mix as a whole. These methods do not measure material properties and their role in moisture sensitivity of the mix independently. This information is very important to select materials resistant to moisture induced damage, or to modify locally available materials to improve their resistance to moisture damage for economic reasons. The objective of this research is to develop experimental and analytical tools to characterize important material properties that influence the moisture sensitivity of asphalt mixes. Quality of adhesion between the aggregate and bitumen binder in wet and dry conditions plays an important role on the moisture sensitivity of the asphalt mix. A part of this research work was to develop the Wilhelmy plate method and the Universal Sorption Device to measure the surface free energy components of the bitumen and aggregate with adequate precision and accuracy, respectively. Surface energy of these materials was used to identify parameters based on thermodynamics that can quantify their interfacial adhesion and propensity to debond in the presence of water. The thermodynamic parameters were shown to correlate well with the moisture sensitivity of asphalt mixes determined from laboratory tests. Specific surface areas of the aggregates were also used to account for the influence of mechanical interlocking at the micro scale. In some mixes, chemical bonding also contributes to the adhesion between bitumen and aggregate. The use of a micro calorimeter was introduced in this research as a versatile and fast tool to quantify the combined effects of physical and chemical adhesion between these materials.

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23

JOSEPH, WAEL. "PHYSICAL CHARACTERIZATION OF VERNIX CASEOSA: IMPLICATIONS FOR BIOLOGICAL FUNCTION." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1022624142.

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24

Lomrén, Erik. "Utvärdering av en sjö- och borrhålsbaserad värmepumpsanläggning i Stockholm." Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-24548.

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Lågtempererade värmekällor som ytvatten och borrhålslager kan i samverkan med en värmepump ses som outnyttjade energikällor. En sjö- och borrhålsbaserad anläggning kan ha en hög total effektivitet om både värme och kylbehov finns och en stor fördel är att frikyla kan användas från sjö och borrhål under delar av året. Kungsbrohuset byggdes 2008 - 2010 med målsättningen att bli världens mest energieffektiva kontorsbyggnad. Mer specifikt var målsättningen att köpt energi skulle vara hälften av boverkets regler. Av den totala bruksarean på 27 000 m2 utgörs ca 19 500 m2 av kontorsyta. Anläggningen värms och kyls huvudsakligen av en värmepump med en värmeeffekt på 350 kW. Vintertid används värmepumpen för både värme och kyla då ett stort kylbehov även finns under uppvärmningssäsongen till serverrum mm. När värmepumpen inte räcker till så används fjärrvärme och fjärrkyla/sjökyla för att täcka behovet. Vid byggnationen installerades en ledning mellan kungsbrohuset och centralstationen för att på centralstationen utnyttja frikyla från sjön samtidigt som kungsbrohuset fick möjligheten att utnyttja värmen i köldbärarreturen. Målet med studien var att utvärdera anläggningen med fokus på tre huvudsakliga frågor. Att undersöka om värmepumpen har högsta möjliga temperatur på förångningssidan vintertid var den första. Den andra frågan var om frikyla från sjön utnyttjades optimalt. Den tredje frågan var att jämföra den projekterade energianvändningen med det verkliga utfallet. Studien utfördes genom besiktningar på plats, insamling av energistatistik samt att studera anläggningen genom driftdator, driftkort, flödesscheman etc. Vintertid så har den egna köldbärarreturen använts nästan uteslutande som värmekälla till värmepumpen då dess temperatur är högre än borrhålslagrets. Utnyttjandet av frikyla från sjön har inte fungerat optimalt då fjärrkyla har använts under vintermånaderna trots att sjöns temperatur är låg. Detta kan åtgärdas genom omprogrammering av villkor för aktivering av frikylan. Jämförelsen mellan projekterad köpt fastighetsenergi på 47 kWh/m2, år med det verkliga utfallet visade att användningen är något högre i verkligheten och hamnade på 55 kWh/m2, år efter att processkylan räknats bort då den inte räknas som fastighetsenergi. Anläggningen är totalt sett väldigt effektiv och har en mycket låg användning av köpt energi. Att kylbehov finns även vintertid gör att värmepumpens effektivitet blir maximal då nyttig energi utnyttjas på båda sidorna.

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25

Popat, Rohit P. "Functionalisation of polyolefins and its effects on surface chemistry and energetics." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/22023.

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The surface functionalisation of polyethylene and polypropylene by industrial and laboratory scale corona treatments and by laboratory flame treatment was studied. The surface sensitive techniques of X-ray photoelectron spectroscopy (XPS), attenuated total reflection infra-red spectroscopy (FTIR-ATR), contact angle measurement and electron microscopy (SEM and TEM) were employed. Corona and flame treatments resulted in incorporation of oxygen only into the surfaces of both polyethylene and polypropylene, resulting in improved surface wettabilities. A variety of oxygen functional groups were introduced by the two treatments. The industrial and laboratory scale treatments of both polymers were found to be similar in terms of the oxygen concentrations incorporated and surface wettabilities achieved. The presence of significant amounts of chain scission products were indicated on corona treated surfaces, while only minimal quantities were indicted on flame treated surfaces. This was attributed to their volatilisation during flame treatment. Introduction of sulfur dioxide into the flame and corona regions during treatment resulted in significant improvements in surface wettability. Incorporation of sulfur and nitrogen resulted from the presence of sulfur dioxide. A possible mechanism involving the formation of sulfonic acid groups and ammonium sulfonate groups was suggested. An oxidation depth model developed for use with variable take-off angle XPS showed that significantly deeper oxidation occurred in the presence of sulfur dioxide. Corona treatment was more effective in improving surface wettabilities than flame treatment, this being attributed to heat induced functional group reorientation during flame . treatment for polyethylene and to differences in surface chemistry resulting from the two treatments in the case of polypropylene. The surface wettability of poly ethylene was more readily improved than the surface wettability of polypropylene after all the treatments investigated. A method for estimating functional group concentrations using chemical derivatisation and contact angle measurement was developed. Functional group estimates for flame treated polyethylene were found to be in good agreement with chemical derivatisation used in conjunction with XPS measurements.

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26

Magens, Ole Mathis. "Mitigating fouling of heat exchangers with fluoropolymer coatings." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/287467.

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Fouling is a chronic problem in many heat transfer systems and results in the need for frequent heat exchanger (HEX) cleaning. In the dairy industry, the associated operating cost and environmental impact are substantial. Antifouling coatings are one mitigation option. In this work, the fouling behaviour of fluoropolymer, polypropylene and stainless steel heat transfer surfaces in processing raw milk and whey protein solution are studied. Methodologies to assess the economics of antifouling coatings are developed and applied. Two experimental apparatuses were designed and constructed to study fouling at surface temperatures around 90 °C. A microfluidic system with a 650 x 2000 µm flow channel enables fouling studies to be carried out by recirculating 2 l of raw milk. The apparatus operates in the laminar flow regime and the capability to probe the local composition of delicate fouling deposit $\textit{in-situ}$ with histological techniques employing confocal laser scanning microscopy. A larger bench-scale apparatus with a 10 x 42 mm flow channel was built to recirculate 17 l of solution in the turbulent flow regime which is more representative of conditions in an industrial plate HEX. Experimental results demonstrate that fluoropolymer coatings can reduce fouling masses from raw milk and whey protein solution by up to 50 %. Surface properties affect the structure and composition of the deposit. At the interface with apolar surfaces raw milk fouling layers are high in protein, whereas a strongly attached mineral-rich layer is present at the interface with steel. Whey protein deposits generated on apolar surfaces are more spongy and have a lower thermal conductivity and/or density than deposits on steel. The attraction of denatured protein towards apolar surfaces and the formation of a calcium phosphate layer on steel at later stages of fouling are explained with arguments based on the interfacial free energy of these materials in water. The financial attractiveness of coatings is considered for HEX subject to linearly and asymptotically increasing fouling resistance and using a spatially resolved fouling model. An explicit solution to the cleaning-scheduling problem is presented for the case of equal heat capacity flow rates in a counter-current HEX. Scenarios where the use of coatings may be attractive or where there is no financial benefit in cleaning a fouled exchanger are identified. Finally, experimental data are used to estimate the economic potential of fluoropolymer coated HEXs in the ultra-high-temperature treatment of milk. In the considered case, the value of a fluoropolymer coating inferred from the reduction in fouling is estimated to be around 2000 US$/m².

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27

Pollard, Travis P. "Local Structure and Interfacial Potentials in Ion Solvation." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491562324303743.

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28

Al-Rawashdeh, Abdalla S. "Performance Assessment of Warm Mix Asphalt (WMA) Pavements in Presence of Water by Using Nano scale Techniques, and Traditional Laboratory Tests." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1342814220.

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29

Sutton, Kirk C. "An investigation of the effect of steam cleaning and aluminum oxide treatment on the wettability and surface free energy of alloys commonly used in dentistry." Thesis, The University of Texas Health Science Center at San Antonio, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10137632.

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Purpose: The purpose of this investigation was to evaluate the effect of aluminum oxide airborne particle abrasion, with and without subsequent steam cleaning on the surface free energy of alloys commonly used in dentistry, in an attempt to produce optimal surfaces for adhesion. Materials and Methods: Twelve samples, with dimensions 13 x 18 x 1 mm, of each: Type IV high noble gold alloy, metal ceramic gold-palladium high noble alloy, chrome-cobalt base metal alloy were cast and divested with glass bead airborne particle abrasion. Twelve samples, with dimensions 13 x 18 x 10 mm, of titanium alloy were milled using an Origin Proteus 5x Milling Machine. Samples were treated with 1) Steam cleaning only, 2) Aluminum oxide airborne particle abrasion and 3) Aluminum oxide airborne particle abrasion with subsequent steam cleaning. Contact angle measurements were recorded immediately after each treatment and at 1 and 12 hours, using a goniometer and the sessile drop method. Surface free energy was calculated using VCA Optima XE software.

Results: Steam cleaning treatment showed no significant changes in surface free energy (dynes/cm), compared to pretreatment values for the alloys investigated except Titanium alloy, which showed a modest increase in surface energy (p < 0.05). Aluminum oxide airborne particle abrasion and aluminum oxide airborne particle abrasion with steam cleaning, resulted in an increase in surface free energy for all alloys investigated when compared to pretreatment and steam clean only values. Steam cleaning following airborne particle abrasion produced significantly lower (p<0.001) surface free energy values compared to airborne particle abrasion alone for high noble gold alloy and metal ceramic gold-palladium high noble alloy. Exposure to ambient air following steam cleaning had minimal or non-enduring effects on surface free energy for all alloys investigated except Titanium alloy, which showed a significant decrease (p<0.001) in surface free energy with time of ambient exposure. Exposure to ambient air following airborne particle abrasion with aluminum oxide resulted in a significant decrease (p<0.001) in surface free energy for high noble gold alloy, metal ceramic gold-palladium high noble alloy and chrome-cobalt base metal alloy, however, Titanium alloy showed no ambient exposure effects. Ambient exposure following aluminum oxide airborne particle abrasion with steam cleaning resulted in a significant decrease (p<0.001) in surface free energy for all alloys investigated.

Conclusions: Within the limitations of this study, it was found that aluminum oxide airborne particle abrasion, with and without subsequent steam cleaning, significantly increased the surface free energy of the dental alloys investigated. Steam cleaning following aluminum oxide airborne particle abrasion significantly reduced the surface free energy gain that the high noble alloys experienced with aluminum oxide airborne particle abrasion alone. And finally, exposure to ambient air following aluminum oxide airborne particle abrasion with and without subsequent steam cleaning resulted in a significant decrease in surface free energy for most alloys investigated.

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30

Alloul, Haytham. "Surfaces moléculaires hétérogènes : un outil vers le control [i.e. contrôle] du mouillage et des morphologies d'auto-assemblage de nano objets." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0353/document.

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La connaissance des interactions interfaciales et l'énergie de surface est nécessaire pour étudier et modéliser les processus qui se déroulent dans le mouillage, l'adhésion ou la diffusion. Tels phénomènes sont rencontrés dans la préparation des suspensions, des émulsions et les peintures. Dans ce contexte, l'énergie de surface représente un paramètre important dans l'étude des propriétés interfaciales solide/liquide où plusieurs applications sont impliquées. Nous avons étudié l'effet de la modification chimique sur l'énergie de surface de deux silices choisies selon deux différentes échelles: l'OX qui présente un substrat nanométrique et les wafers de silicium qui est un substrat millimétrique. Pour la silice OX 50, La modification chimique de la surface a été réalisée avec l'hexadecyltrichlosilane (HTS) à caractère hydrophobe. L'infrarouge en transmission et la quantification de carbone organique ont été efficaces pour estimer les quantités croissantes d'HTS greffées à la surface de la silice. Deux isothermes d'adsorption ont été tracées. Ensuite, la volumétrie d'adsorption continue d'argon et d'azote a été utilisée pour étudier l'évolution de l'hétérogénéité énergétique. Ceci a été achevé en faisant recours à une stratégie d'analyse de volume adsorbée à la monocouche (Vm) d'azote et d'argon. Les résultats obtenus ont servi pour tracer une troisième isotherme d'adsorption. La quantification de l'énergie de surface a été réalisée avec la montée capillaire (technique macroscopique) et la chromatographie gazeuse en phase inverse (CGI) (technique moléculaire). Pour les wafers de silicium, deux types de surfaces ont été élaborées durant cette étude. Le premier hydrophile (traitement Piranha, formations des groupements OH). Cette surface a été obtenue par oxydation de ces wafers (traitement Piranha). La deuxième a été obtenue par le greffage d'HTS (greffons CH3). La quantification de l'énergie de surface a été réalisée avec la mouillabilité (technique macroscopique) et la microscopie à force atomique (AFM) (technique nanoscopique). Enfin, les différentes valeurs d?énergie de surface de la silice vierge OX 50 ont été comparées avec celles de la surface plane hydrophile (OH). Pour les surfaces hydrophobes, on a comparé les valeurs d?énergie de surface de la silice OX 50 modifiée d'une quantité maximale d?HTS avec le wafer de silicium à greffons CH3
The knowledge about interfacial free energy interactions and surface energy is necessary for understanding and modeling many surface and interface processes. The investigation of the surface properties of solids is very important in several applications such as wetting, spreading and adhesion processes. Such processes occur during the preparation of suspensions, emulsions, painting, printing and corrosion protection. Knowledge about surface free energy of solids appears as a very important parameter determining the interfacial properties in solid/liquid and solid/gas interfaces where many implementations are involved. We have studied the effect of the chemical modification on surface energy for two types of silica: Aerosil OX 50 is chosen as a nanometric substrate and the wafers of silicium chosen as micrometric substrate. For silica OX 50, the chemical modification was carried out using the hydrophobic hexadecyltrichlorosilane (HTS). Transmission infrared and the quantification of organic carbon were helpful in the estimation of increasing quantities of HTS grafted to the surface. Two adsorption isotherms were drawn. Then, continuous adsorption isotherm of argon and nitrogen was used to study the evolution of energetic heterogeneity in the course of the chemical reaction. This was achieved by applying an analysis strategy of the monolayer volume (Vm) of adsorbed argon and nitrogen. Results enabled the drawing of a third adsorption isotherm. The quantification of surface energy for various samples was realize using capillary rise (macroscopic technique) and inverse gas chromatography (IGC) (molecular technique). For silicon wafers, two types of surfaces were elaborated in this study. The first hydrophilic (OH grafting), was obtained by oxidation of silicon wafers (Piranha treatment), the second hydrophobic (CH3 grafting), was obtained by grafting HTS molecules to the surface. The quantification of the surface free energy was achieved using the wettability (macroscopic technique) and the atomic force microscopy (AFM) (nanoscopic technique). Finally the different values of surface free energy obtained for native silica are compared to those of hydrophilic (OH) flat surfaces. As for hydrophobic surfaces, the silica OX 50 modified with maximum quantity of HTS is compared to Hydrophobic (CH3) flat surfaces

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Pantoja, Carlos Augusto de Morais Souto 1982. "Influência do etanol na rugosidade, na energia livre de superfície da dentina radicular e no preenchimento de túbulos dentinários = Influence of ethanol on the surface roughness, the surface free energy of the root dentin and filling tubules with AH Plus sealer." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289334.

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Orientadores: José Flávio Affonso de Almeida, Caio Cezar Randi Ferraz
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Este trabalho foi dividido em 2 capítulos, sendo que no capítulo 1 o objetivo foi de avaliar a influência do etanol na rugosidade, na energia livre de superfície da dentina radicular e na interação entre o cimento AH Plus e a superfície dentinária. Foram selecionadas 100 raízes de dentes humanos anteriores superiores e padronizadas com comprimento de 18 mm. As raízes foram cortadas longitudinalmente, obtendo-se 200 amostras dentinárias, divididas aleatoriamente em 4 grupos (n = 50), de acordo com os métodos de secagem: (1) úmido: apenas aplicação de ponta aspiradora, (2) pontas de papel absorvente: ponta aspiradora + pontas de papel absorventes, (3) solução de etanol 70%: etanol 70% (1 minuto) + ponta aspiradora + pontas de papel absorvente, (4) solução de etanol 100%: etanol 100% (1 minuto) + ponta aspiradora + pontas de papel absorvente. As amostras dentinárias foram avaliadas com o auxílio do rugosímetro e goniômetro, dentro dos seguintes parâmetros de avaliação: (1) rugosidade superficial; (2) energia livre de superfície e (3) ângulo de contato formado entre o cimento AH Plus e superfície dentinária. No capítulo 2, o objetivo foi avaliar a influência do etanol no preenchimento dos túbulos dentinários. Foram selecionadas 40 raízes de dentes humanos anteriores superiores, com comprimento radicular padronizado em 18 mm, e divididas aleatoriamente nos mesmos 4 grupos descritos anteriormente. Após a instrumentação, as raízes foram obturadas pela técnica de Schilder, com guta-percha e cimento AH Plus misturado com o marcador fluorescente Rodamina B. Para a visualização em microscopia confocal de varredura a laser foram confeccionadas 4 secções transversais (1 mm de espessura), em cada terço radicular. Foram avaliados os seguintes parâmetros: (1) porcentagem do perímetro da parede do canal coberta com cimento; (2) máxima profundidade de penetração do cimento endodôntico no interior dos túbulos dentinários; (3) porcentagem da área da dentina penetrada pelo cimento e (4) valor da intensidade do marcador fluorescente Rodamina B. Os resultados encontrados foram analisados estatisticamente pelos testes ANOVA / Tukey, com nível de significância de 5%, em ambos os capítulos. No capítulo 1 observou-se que nos grupos em que se utilizou o etanol, quando comparados aos demais, foram encontrados menor rugosidade de superfície da dentina, maior energia livre de superfície e menor ângulo de contato formado entre o cimento AH Plus e a superfície dentinária. Já no capítulo 2, não foi verificada diferença significante entre os grupos, quanto à avaliação da porcentagem do perímetro da parede do canal coberta por cimento. Entretanto, maiores valores de profundidade de penetração e da porcentagem da área da dentina penetrada pelo cimento foram encontrados no Grupo etanol 100%, seguidos pelos Grupos etanol 70%, pontas de papel e úmido. O etanol 100% atingiu resultados significativamente maiores que a concentração 70%, exceto para a intensidade da Rodamina B no terço cervical. Além disso, os resultados do Grupo pontas de papel foram melhores que o Grupo úmido, com exceção da intensidade da Rodamina B no terço apical. Diante da análise dos resultados apresentados nos 2 capítulos, verificou-se que o etanol (70% e 100%) proporcionou melhor molhabilidade do cimento AH Plus na superfície dentinária. Da mesma forma, as soluções de etanol, especialmente na concentração de 100%, favoreceram a penetração do cimento endodôntico no interior dos túbulos dentinários
Abstract: This study was divided into 2 chapters. In chapter 1, the aim was to evaluate the influence of ethanol on dentin roughness, dentin surface free energy and interaction between dentin surface. A hundred roots of human maxillary teeth were selected with length standardized in 18 mm. The roots were split longitudinally yielding 200 dentin samples, which were divided randomly into 4 groups according to the drying method used: (1) wet: vaccum only (2) paper points: vaccum + absorbent paper points, (3) 70% alcohol: 70% alcohol (1min) + vaccum + absorbent paper points and (4) 100% alcohol group: 100% alcohol (1min) + vaccum + absorbent paper points. The specimens were measured with aid of goniometer and rugosimeter within the following evaluation parameters: (1) surface roughness, (2) surface free energy and (3) contact angle formed between AH Plus sealer and dentin surface. In Chapter 2, the aim was to evaluate the influence of ethanol on dentinal tubules filling. Forty roots of human maxillary teeth with length standardized in 18 mm were selected. The roots were randomly divided among the same 4 groups described above. After instrumentation, the roots were filled by Schilder's technique with gutta-percha and AH Plus mixed with rhodamine B fluorescent marker. The roots were cross-sectioned and dentin sections (1 mm thick) were analyzed by confocal laser scanning microscopy. The evaluation parameters were: (1) Percentage of root canal wall coverage, (2) maximum depth of sealer penetration into dentinal tubules, (3) percentage of penetrated area and (4) fluorescent rhodamine B intensity. The results were statistically analyzed by ANOVA and Tukey tests (?=5%). In Chapter 1 the groups in which ethanol was used lower dentin surface roughness, higher surface free energy and lower contact angle formed between AH Plus and dentin surface were found when compared to the control groups. In chapter 2, there was no significant difference between the groups regarding the percentage of root canal wall coverage. Higher values of maximum depth of sealer penetration into dentinal tubules and percentage of penetrated area were found in Group 100% ethanol, followed by 70% ethanol, paper points and wet groups. The results achieved by 100% ethanol were significantly higher than 70% ethanol, except for intensity of rhodamine B in cervical third. Furthermore, the paper points results were better than wet group, except for intensity of rhodamine B in apical third. After analyzing the results presented in the two chapters, it was verified that ethanol solutions (70% and 100%) provide better wettability of AH Plus sealer on dentin surface. Similarly, ethanol solutions, especially at 100% concentration, improve the penetration of the sealer into dentinal tubules
Doutorado
Endodontia
Doutor em Clínica Odontológica

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32

Li, Jingping. "PA12/PBT reactive blending with hydropolysiloxane by carbonyl hydrosilylation reaction : towards new polymer materials." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1306/document.

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Les thermoplastiques contenant du PDMS ont attiré beaucoup d’attention à cause de leur potentiel dans un large spectre d’applications. Lors du mélange du PDMS avec des thermoplastiques, le problème de la compatibilité ne peut être ignoré. Cette dernière engendre de faibles propriétés mécaniques ainsi qu’une surface rugueuse. Par conséquent, le défi principal des mélanges PDMS/thermoplastique est de trouver un moyen efficace et adapté, comme le mélange réactif in situ, pour compatibiliser les différentes phases. Récemment, nous avons trouvé une réaction intéressante entre l’hydrosilane (SiH) et les groupes carbonyles catalysés par le triruthénium dodecacarbonyle [Ru3(CO)12]. Il a le potentiel pour réaliser cette compatibilisation réactive. Dans un premier temps, nous avons étudié le mécanisme de la réaction d’hydrosilylation catalysée par le ruthénium dans le cas du N-méthylpropionamide. Les composés N-silicatés formés qui peuvent jouer par la suite le rôle de compatibilisant lors du mélange réactif. Dans un deuxième temps, cette réaction d’hydrosilylation a été étendue au mélange réactif de PA12 avec du PDMS terminé hydride en conditions de mélange fondu. La réaction a été réalisée rapidement (en 1 minute) en présence de Ru3 (CO) 12 (1wt%). Ensuite, nous avons étudié la microstructure des deux mélanges. En comparaison avec le mélange non réactif, la dispersion du PDMS dans celui réactif était clairement améliorée puisque la taille des domaines. En outre, dans de telles conditions réactives et en présence du catalyste de ruthénium, une réaction d’oxydation du PDMS-SiH est partiellement observée. Ceci inclue par exemple les propriétés de stabilité thermique, de comportement cristallin, d’énergie de surface et de perméabilité et séparation des gaz. Dans un troisième temps, nous nous sommes intéressés à l’application de la réaction d’hydrosilylation catalysée par le ruthénium aux composites PBT/polyméthylhydrosiloxane (PMHS). Cependant, à cause des températures élevées nécessaires à la mise en forme du PBT (220°C), une réaction de réticulation entre le PBT et le PMHS apparait mais également et une auto-réticulation du PMHS. Enfin, ces résultats montrent une application potentielle et initial de ruthénium hydrosilylation catalysées à compatibilisation réactive entre l'hydropolysiloxane et un polyamide ou un polyester
Polydimethylsiloxane (PDMS) containing thermoplastics have attracted much attention due to their potential in wide range of applications. However, when blending PDMS with thermoplastics, the incompatible problem cannot be ignored. It may results in weak mechanical properties and a rough surface. Therefore, the main challenge of PDMS and thermoplastic blend is to find an efficient and convenient way like in situ reactive blending to realize the compatibilization between tthem. Recently, we found an interesting reaction between hydrosilane (SiH) and carbonyl group catalyzed by triruthenium dodecacarbonyl [Ru3(CO)12]. It has potential to realize such reactive compatibilization. Firstly, we investigated the mechanism of ruthenium catalyzed hydrosilylation reaction of N-methylpropionamide, and found that the formed N-silylated compounds which can work as compatibilizers in later reactive blending. Then this hydrosilylation reaction was extended to the reactive blending of PA12 with hydride terminated PDMS under molten processing conditions. The reaction was carried out quickly (in 1 minute) in the presence of Ru3(CO)12 (1wt%). Compared to the unreacted one, the dispersion of PDMS after reaction was obviously improved. Besides, in such reactive conditions, PDMS-SiH oxidation reaction was partially observed. This phenomenon leads to a second PDMS gel based phase. Properties like thermal stability, crystalline behavior, surface energy and gas permeability and separation of such blends were also studied. Secondly, ruthenium catalyzed hydrosilylation was also applied to PBT and polymethylhydrosiloxane (PMHS) which was processed at higher temperature (220°C). The final material includes the crosslinking network formed between PBT and PMHS and a part of PMHS self-crosslinking forming PMHS gel-like phase due to the higher processing temperature of PBT and high reactivity of PMHS. Finally, these results show a potential and initial application of ruthenium catalyzed hydrosilylation to reactive compatibilization between hydride polysiloxane and polyamide or polyester

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33

Li, Jingping. "PA12/PBT reactive blending with hydropolysiloxane by carbonyl hydrosilylation reaction : towards new polymer materials." Electronic Thesis or Diss., Lyon, 2016. http://www.theses.fr/2016LYSE1306.

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Abstract:

Les thermoplastiques contenant du PDMS ont attiré beaucoup d’attention à cause de leur potentiel dans un large spectre d’applications. Lors du mélange du PDMS avec des thermoplastiques, le problème de la compatibilité ne peut être ignoré. Cette dernière engendre de faibles propriétés mécaniques ainsi qu’une surface rugueuse. Par conséquent, le défi principal des mélanges PDMS/thermoplastique est de trouver un moyen efficace et adapté, comme le mélange réactif in situ, pour compatibiliser les différentes phases. Récemment, nous avons trouvé une réaction intéressante entre l’hydrosilane (SiH) et les groupes carbonyles catalysés par le triruthénium dodecacarbonyle [Ru3(CO)12]. Il a le potentiel pour réaliser cette compatibilisation réactive. Dans un premier temps, nous avons étudié le mécanisme de la réaction d’hydrosilylation catalysée par le ruthénium dans le cas du N-méthylpropionamide. Les composés N-silicatés formés qui peuvent jouer par la suite le rôle de compatibilisant lors du mélange réactif. Dans un deuxième temps, cette réaction d’hydrosilylation a été étendue au mélange réactif de PA12 avec du PDMS terminé hydride en conditions de mélange fondu. La réaction a été réalisée rapidement (en 1 minute) en présence de Ru3 (CO) 12 (1wt%). Ensuite, nous avons étudié la microstructure des deux mélanges. En comparaison avec le mélange non réactif, la dispersion du PDMS dans celui réactif était clairement améliorée puisque la taille des domaines. En outre, dans de telles conditions réactives et en présence du catalyste de ruthénium, une réaction d’oxydation du PDMS-SiH est partiellement observée. Ceci inclue par exemple les propriétés de stabilité thermique, de comportement cristallin, d’énergie de surface et de perméabilité et séparation des gaz. Dans un troisième temps, nous nous sommes intéressés à l’application de la réaction d’hydrosilylation catalysée par le ruthénium aux composites PBT/polyméthylhydrosiloxane (PMHS). Cependant, à cause des températures élevées nécessaires à la mise en forme du PBT (220°C), une réaction de réticulation entre le PBT et le PMHS apparait mais également et une auto-réticulation du PMHS. Enfin, ces résultats montrent une application potentielle et initial de ruthénium hydrosilylation catalysées à compatibilisation réactive entre l'hydropolysiloxane et un polyamide ou un polyester
Polydimethylsiloxane (PDMS) containing thermoplastics have attracted much attention due to their potential in wide range of applications. However, when blending PDMS with thermoplastics, the incompatible problem cannot be ignored. It may results in weak mechanical properties and a rough surface. Therefore, the main challenge of PDMS and thermoplastic blend is to find an efficient and convenient way like in situ reactive blending to realize the compatibilization between tthem. Recently, we found an interesting reaction between hydrosilane (SiH) and carbonyl group catalyzed by triruthenium dodecacarbonyl [Ru3(CO)12]. It has potential to realize such reactive compatibilization. Firstly, we investigated the mechanism of ruthenium catalyzed hydrosilylation reaction of N-methylpropionamide, and found that the formed N-silylated compounds which can work as compatibilizers in later reactive blending. Then this hydrosilylation reaction was extended to the reactive blending of PA12 with hydride terminated PDMS under molten processing conditions. The reaction was carried out quickly (in 1 minute) in the presence of Ru3(CO)12 (1wt%). Compared to the unreacted one, the dispersion of PDMS after reaction was obviously improved. Besides, in such reactive conditions, PDMS-SiH oxidation reaction was partially observed. This phenomenon leads to a second PDMS gel based phase. Properties like thermal stability, crystalline behavior, surface energy and gas permeability and separation of such blends were also studied. Secondly, ruthenium catalyzed hydrosilylation was also applied to PBT and polymethylhydrosiloxane (PMHS) which was processed at higher temperature (220°C). The final material includes the crosslinking network formed between PBT and PMHS and a part of PMHS self-crosslinking forming PMHS gel-like phase due to the higher processing temperature of PBT and high reactivity of PMHS. Finally, these results show a potential and initial application of ruthenium catalyzed hydrosilylation to reactive compatibilization between hydride polysiloxane and polyamide or polyester

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34

Li, Zhisong. "Advanced Computational Modeling for Marine Tidal Turbine Farm." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337889611.

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35

Živko, Pavlović. "Karakterizacija površinske strukture neštampajućih elemenata CtP termalne štamparske forme za ofset štampu." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2012. http://dx.doi.org/10.2298/NS20120519PAVLOVIC.

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Disertacija daje pregled novih i relevantnih istraživanja i stavovau naučnoj zajednici na temu štamparskih formi i uticaja procesaštampe na trošenje neštampajućih elemenata. U disertaciji jeukazano na kontinualno praćenje topografskih promenaneštampajućih elemenata štamparskih formi kako bi se kontrolisaoperiod eksploatacije a time i proces reprodukcije. Takođe dajeprilog novim istraživanjima sa analizom velikog brojaeksperimentalnih uzoraka sa dobijenim izmerenim podacima iodgovarajućim korelacijama i predstavlja napredak u shvatanjumehanizma trošenja neštampajućih površina štamparskih formi injihov uticaj na tribološke promene u odnosu na strukturu osnovealuminijuma i sloja aluminijum oksida.
Dissertation gives an overview of the current state, research and theories ofprinting forms and influence of printing process on wearing of non-printingelements within the science community. The dissertation points out the continuousmonitoring of topographic changes of printing form non-printing elements to controlthe exploitation of a period of time and the process of reproduction. This workcontributes to new research with the analysis of large number of experimentalsamples and calculated correlations and represents an advance in thecomprehension of the surface wear mechanism of printing form non-printingelements and their influence on the tribological changes to the structure of thebase layer of aluminium and aluminium oxide.

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36

Bábík, Adam. "Samovolně seskupené vrstvy na bázi křemíku." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2009. http://www.nusl.cz/ntk/nusl-216517.

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Thin film deposition, characterization and properties of self-assembled monolayers based on silicon were studied with emphasis on the SA monolayers deposited from vinyltriethoxysilane and vinyltrichlorsilane. The thesis is aimed at basic properties of the SA monolayer and explanation of its growth. Methods and techniques used for analysis of the monolayer were described as well. Contact angle measurements and an evaluation of the surface free energy are depicted in details. The deposited SA layers were observed with respect to their chemical composition and surface morphology by X-ray photoelectron spectroscopy (XPS), ellipsometry and atomic force microscopy (AFM).

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37

Shariare, Mohammad H. "The rational design of drug crystals to facilitate particle size reduction. Investigation of crystallisation conditions and crystal properties to enable optimised particle processing and comminution." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5395.

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Micronisation of active pharmaceutical ingredients (APIs) to achieve desirable quality attributes for formulation preparation and drug delivery remains a major challenge in the pharmaceutical sciences. It is therefore important that the relationships between crystal structure, the mechanical properties of powders and their subsequent influence on processing behaviour are well understood. The aim of this project was therefore to determine the relative importance of particle attributes including size, crystal quality and morphology on processing behaviour and the characteristics of micronised materials. It was then subsequently intended to link this behaviour back to crystal structure and the nature of molecular packing and intermolecular interactions within the crystal lattice enabling the identification of some generic rules which govern the quality of size reduced powders. In this regard, different sieve fractions of lactose monohydrate and crystal variants of ibuprofen and salbutamol sulphate (size, morphology and crystal quality) were investigated in order to determine those factors with greatest impact on post-micronisation measures of particle quality including particle size, degree of crystallinity and surface energy. The results showed that smaller sized feedstock should typically be used to achieve ultrafine powders with high crystallinity. This finding is attributed to the reduced number of fracture events necessary to reduce the size of the particles leading to decreases in milling residence time. However the frequency of crystal cracks is also important, with these imperfections being implicated in crack propagation and brittle fracture. Ibuprofen crystals with a greater number of cracks showed a greater propensity for comminution. Salbutamol sulphate with a high degree of crystal dislocations however gave highly energetic powders, with reduced degree of crystallinity owing to the role dislocations play in facilitating plastic deformation, minimising fragmentation and extending the residence of particles in the microniser. Throughout these studies, morphology was also shown to be critical, with needle like morphology giving increased propensity for size reduction for both ibuprofen and salbutamol sulphate, which is related to the small crack propagation length of these crystals. This behaviour is also attributed to differences in the relative facet areas for the different morphologies of particles, with associated alternative deformation behaviour and slip direction influencing the size reduction process. Molecular modelling demonstrated a general relationship between low energy slip planes, d-spacing and brittleness for a range of materials, with finer particle size distributions achieved for APIs with low value of highest d-spacings for identified slip planes. The highest d-spacing for any material can be readily determined by PXRD (powder x-ray diffraction) which can potentially be used to rank the milling behaviour of pharmaceutical materials and provides a rapid assessment tool to aid process and formulation design. These studies have shown that a range of crystal properties of feedstock can be controlled in order to provide micronised powders with desirable attributes. These include the size, morphology and the density of defects and dislocations in the crystals of the feedstock. Further studies are however required to identify strategies to ensure inter-batch consistency in these attributes following crystallisation of organic molecules.

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38

Huillca, Palmer Vicente Pulla. "Propriedades superficiais de filmes à base de gelatina." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/74/74132/tde-08042016-093049/.

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O objetivo do presente trabalho foi caracterizar as propriedades superficiais de filmes à base de gelatina. Para o qual foram elaborados filmes de: (i) Gelatina plastificado com glicerol (G) (gelatina: 5 g/100 g SFF; glicerol: 30 g/100 g de gelatina), (ii) Gelatina reforçado com montmorilhonita (G/MMT) (gelatina: 5 g/100 g SFF; glicerol: 30 g/100 g de gelatina; MMT: 5 g/100 g de gelatina) e Gelatina plastificado com citrato de acetiltributila (G/ATB) (gelatina: 5 g/100 g SFF; ATB: 50 g/100 de gelatina; lecitina de soja: 60 g/100 g de ATB; etanol: 20 g/100 g SFF). Os filmes foram produzidos mediante o uso de um aplicador automático de filmes \"Spreading\". Logo, os filmes foram submetidos a testes para determinação da espessura, umidade e propriedades óticas (brilho, cor e opacidade). Também foi caracterizada a microestrutura por microscopia eletrônica de varredura (MEV) e microscopia de força atômica (AFM); às imagens obtidas por MEV foi aplicado um analise de imagem mediante o programa Image J, para obter o valor da dimensão fractal (DF). Depois foram caracterizadas as propriedades superficiais de ângulo de contato (AC), molhabilidade ou coeficiente de espalhamento (Se), e energia livre superficial (ELS) mediante a medida do ângulo de contato pelo método da gota séssil (água: 5 µL e 1-Bromonaftaleno: 3 µL). Para o cálculo da ELS também foi aplicado o método de Owens-Wendt. Estas caracterizações foram feitas em ambos os lados do filme, lado ar e lado placa. A natureza do filme de G/ATB influenciou na umidade e as propriedades óticas, enquanto que os filmes de G e G/MMT apresentaram características similares. Em relação à microestrutura e rugosidade, o filme de G apresentou a superfície mais homogênea e lisa, contrario ao observado no filme de G/MMT, que apresentou a maior rugosidade seguida do filme de G/ATB. Foi observado que houve uma relação entre os valores de rugosidade e DF. De acordo com o valor do AC, os filmes apresentaram um caráter hidrofóbico, pois seus valores foram superiores a 65° (em ambos os lados dos filmes), na seguinte ordem: G/MMT > G > G/ATB; sendo que o Se seguiu a mesma tendência. Cabe mencionar também que não foi encontrada uma correlação significativa entre os valores de AC e rugosidade. Em função dos valores de AC, Se e ELS (especificamente a componente polar), o filme de G/ATB apresentou o menor caráter hidrofóbico, pois apresentou menores valores de AC e maiores valores de Se em comparação com os outros dois filmes. Os valores da componente polar da G/ATB foram os maiores, explicando de melhor maneira o caráter menos hidrofóbico deste filme. Pode-se concluir que os filmes à base de gelatina elaborados no presente trabalho têm propriedades hidrofóbicas (AC>65°), sendo a G/MMT o filme com melhores características hidrofóbicas.
The aim of this study was to characterize the surface properties of gelatin-based films. For which, films were produced as following: gelatin plasticized with glycerol (gelatin: 5 g/100 g SFF; glycerol: 30 g/100 g of gelatin), gelatin reinforced with montmorillonite (gelatin: 5 g/100 g SFF; glycerol: 30 g/100 of gelatin; montmorillonite: 5 g/100 g of gelatin), and gelatin plasticized with acetyltributyl citrate (gelatin: 5 g/100 g SFF; acetyltributyl citrate: 50 g/100 of gelatin, soy lecithin: 60 g/100 g acetyltributyl citrate; ethanol: 20 g/100 g SFF). The films were produced by using an automatic film applicator \"Spreading\". Then, the films were tested for determining thickness, humidity and optical property (gloss, color and opacity). Also the microstructure was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM); in the images obtained by SEM it was applied image analysis using Image J program, to get the value of the fractal dimension (FD). After, the surface properties of contact angle (CA), wettability or spreading coefficient (Cs) and surface free energy (SFE) were characterized by measuring the contact angle by the method of the sessile drop (water: 5 µL, 1-Bromonaphthalene: 3 µL). For the calculation of the ELS, it was also applied the method of Owens-Wendt. These characterizations were made on both sides of the film (air side and plate side). The nature of the G/ATB film influenced the moisture and optical properties, while the films of G and G/MMT showed similar values. With regard to microstructure and roughness, the G film presented a more homogeneous and smooth surface, contrary to that was observed in films of G/MMT, who presented the highest roughness followed by G/ATB film. It was observed that there was a relationship between the roughness values and DF. According to the value of the CA, the three films had a hydrophobic character, because their values were above 65° (on both sides of the film), in the following order: G/MMT > G > G/ATB; the Cs followed the same trend. It should be also mentioned that a significant correlation between the values of CA and the roughness was found. According to the values of CA, Cs and SFE (specifically the polar component), the films of G/ATB had the lowest hydrophobicity, because had lower CA values and higher Cs values, as compared to the other two films. The values of the polar component of the film G/ATB were higher, which explains better the less hydrophobic character of this film. It can be concluded that the gelatin-based films produced in this work have hydrophobic properties (CA>65°), being the film G/MMT which showed better hydrophobic characteristics.

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39

Shariare, Mohammad Hossain. "The rational design of drug crystals to facilitate particle size reduction : investigation of crystallisation conditions and crystal properties to enable optimised particle processing and comminution." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5395.

Full text

Abstract:

Micronisation of active pharmaceutical ingredients (APIs) to achieve desirable quality attributes for formulation preparation and drug delivery remains a major challenge in the pharmaceutical sciences. It is therefore important that the relationships between crystal structure, the mechanical properties of powders and their subsequent influence on processing behaviour are well understood. The aim of this project was therefore to determine the relative importance of particle attributes including size, crystal quality and morphology on processing behaviour and the characteristics of micronised materials. It was then subsequently intended to link this behaviour back to crystal structure and the nature of molecular packing and intermolecular interactions within the crystal lattice enabling the identification of some generic rules which govern the quality of size reduced powders. In this regard, different sieve fractions of lactose monohydrate and crystal variants of ibuprofen and salbutamol sulphate (size, morphology and crystal quality) were investigated in order to determine those factors with greatest impact on post-micronisation measures of particle quality including particle size, degree of crystallinity and surface energy. The results showed that smaller sized feedstock should typically be used to achieve ultrafine powders with high crystallinity. This finding is attributed to the reduced number of fracture events necessary to reduce the size of the particles leading to decreases in milling residence time. However the frequency of crystal cracks is also important, with these imperfections being implicated in crack propagation and brittle fracture. Ibuprofen crystals with a greater number of cracks showed a greater propensity for comminution. Salbutamol sulphate with a high degree of crystal dislocations however gave highly energetic powders, with reduced degree of crystallinity owing to the role dislocations play in facilitating plastic deformation, minimising fragmentation and extending the residence of particles in the microniser. Throughout these studies, morphology was also shown to be critical, with needle like morphology giving increased propensity for size reduction for both ibuprofen and salbutamol sulphate, which is related to the small crack propagation length of these crystals. This behaviour is also attributed to differences in the relative facet areas for the different morphologies of particles, with associated alternative deformation behaviour and slip direction influencing the size reduction process. Molecular modelling demonstrated a general relationship between low energy slip planes, d-spacing and brittleness for a range of materials, with finer particle size distributions achieved for APIs with low value of highest d-spacings for identified slip planes. The highest d-spacing for any material can be readily determined by PXRD (powder x-ray diffraction) which can potentially be used to rank the milling behaviour of pharmaceutical materials and provides a rapid assessment tool to aid process and formulation design. These studies have shown that a range of crystal properties of feedstock can be controlled in order to provide micronised powders with desirable attributes. These include the size, morphology and the density of defects and dislocations in the crystals of the feedstock. Further studies are however required to identify strategies to ensure inter-batch consistency in these attributes following crystallisation of organic molecules.

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Kucserová, Aneta. "Příprava a charakterizace vrstev deponovaných metodou plazmové polymerace na bázi 2-ethyl-2-oxazolinu." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2020. http://www.nusl.cz/ntk/nusl-414168.

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The diploma thesis deals with the deposition of layers of 2-ethyl-2-oxazoline monomer in a dielectric barrier discharge in a nitrogen atmosphere. The theoretical part describes polyoxazolines, dielectric barrier discharge, plasma polymerization and diagnostic methods that describe the characteristics of the prepared layers. The experimental part deals with the deposition of layers and the determination of physicochemical properties. Finally, the results are compared with layers that were made of 2-methyl-2-oxazoline.

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Xin, Bai. "Numerical simulation of a marine current turbine in turbulent flow." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/7900.

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The marine current turbine (MCT) is an exciting proposition for the extraction of renewable tidal and marine current power. However, the numerical prediction of the performance of the MCT is difficult due to its complex geometry, the surrounding turbulent flow and the free surface. The main purpose of this research is to develop a computational tool for the simulation of a MCT in turbulent flow and in this thesis, the author has modified a 3D Large Eddy Simulation (LES) numerical code to simulate a three blade MCT under a variety of operating conditions based on the Immersed Boundary Method (IBM) and the Conservative Level Set Method (CLS). The interaction between the solid structure and surrounding fluid is modelled by the immersed boundary method, which the author modified to handle the complex geometrical conditions. The conservative free surface (CLS) scheme was implemented in the original Cgles code to capture the free surface effect. A series of simulations of turbulent flow in an open channel with different slope conditions were conducted using the modified free surface code. Supercritical flow with Froude number up to 1.94 was simulated and a decrease of the integral constant in the law of the wall has been noticed which matches well with the experimental data. Further simulations of the marine current turbine in turbulent flow have been carried out for different operating conditions and good match with experimental data was observed for all flow conditions. The effect of waves on the performance of the turbine was also investigated and it has been noticed that this existence will increase the power performance of the turbine due to the increase of free stream velocity.

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Moghaddam, Amir. "Dynamics of transformation and fragmentation of composite liquid nano-particles." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/31776/1/Amir_Moghaddam_Thesis.pdf.

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Recent research on particle size distributions and particle concentrations near a busy road cannot be explained by the conventional mechanisms for particle evolution of combustion aerosols. Specifically they appear to be inadequate to explain the experimental observations of particle transformation and the evolution of the total number concentration. This resulted in the development of a new mechanism based on their thermal fragmentation, for the evolution of combustion aerosol nano-particles. A complex and comprehensive pattern of evolution of combustion aerosols, involving particle fragmentation, was then proposed and justified. In that model it was suggested that thermal fragmentation occurs in aggregates of primary particles each of which contains a solid graphite/carbon core surrounded by volatile molecules bonded to the core by strong covalent bonds. Due to the presence of strong covalent bonds between the core and the volatile (frill) molecules, such primary composite particles can be regarded as solid, despite the presence of significant (possibly, dominant) volatile component. Fragmentation occurs when weak van der Waals forces between such primary particles are overcome by their thermal (Brownian) motion. In this work, the accepted concept of thermal fragmentation is advanced to determine whether fragmentation is likely in liquid composite nano-particles. It has been demonstrated that at least at some stages of evolution, combustion aerosols contain a large number of composite liquid particles containing presumably several components such as water, oil, volatile compounds, and minerals. It is possible that such composite liquid particles may also experience thermal fragmentation and thus contribute to, for example, the evolution of the total number concentration as a function of distance from the source. Therefore, the aim of this project is to examine theoretically the possibility of thermal fragmentation of composite liquid nano-particles consisting of immiscible liquid v components. The specific focus is on ternary systems which include two immiscible liquid droplets surrounded by another medium (e.g., air). The analysis shows that three different structures are possible, the complete encapsulation of one liquid by the other, partial encapsulation of the two liquids in a composite particle, and the two droplets separated from each other. The probability of thermal fragmentation of two coagulated liquid droplets is discussed and examined for different volumes of the immiscible fluids in a composite liquid particle and their surface and interfacial tensions through the determination of the Gibbs free energy difference between the coagulated and fragmented states, and comparison of this energy difference with the typical thermal energy kT. The analysis reveals that fragmentation was found to be much more likely for a partially encapsulated particle than a completely encapsulated particle. In particular, it was found that thermal fragmentation was much more likely when the volume ratio of the two liquid droplets that constitute the composite particle are very different. Conversely, when the two liquid droplets are of similar volumes, the probability of thermal fragmentation is small. It is also demonstrated that the Gibbs free energy difference between the coagulated and fragmented states is not the only important factor determining the probability of thermal fragmentation of composite liquid particles. The second essential factor is the actual structure of the composite particle. It is shown that the probability of thermal fragmentation is also strongly dependent on the distance that each of the liquid droplets should travel to reach the fragmented state. In particular, if this distance is larger than the mean free path for the considered droplets in the air, the probability of thermal fragmentation should be negligible. In particular, it follows form here that fragmentation of the composite particle in the state with complete encapsulation is highly unlikely because of the larger distance that the two droplets must travel in order to separate. The analysis of composite liquid particles with the interfacial parameters that are expected in combustion aerosols demonstrates that thermal fragmentation of these vi particles may occur, and this mechanism may play a role in the evolution of combustion aerosols. Conditions for thermal fragmentation to play a significant role (for aerosol particles other than those from motor vehicle exhaust) are determined and examined theoretically. Conditions for spontaneous transformation between the states of composite particles with complete and partial encapsulation are also examined, demonstrating the possibility of such transformation in combustion aerosols. Indeed it was shown that for some typical components found in aerosols that transformation could take place on time scales less than 20 s. The analysis showed that factors that influenced surface and interfacial tension played an important role in this transformation process. It is suggested that such transformation may, for example, result in a delayed evaporation of composite particles with significant water component, leading to observable effects in evolution of combustion aerosols (including possible local humidity maximums near a source, such as a busy road). The obtained results will be important for further development and understanding of aerosol physics and technologies, including combustion aerosols and their evolution near a source.

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Drechsel, Nils Jan Daniel 1980. "Development of a multiscale protocol for the study of energetics of protein dymanics." Doctoral thesis, Universitat Pompeu Fabra, 2013. http://hdl.handle.net/10803/125071.

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Multiscale Molecular Dynamics is a popular trend in the field of computational chemistry and physics. Coarse-grained force-fields have been around for years, and used independently, but used cooperatively with all-atom force-fields combines their advantages and cancels their disadvantages. This seems to be the case, however, only when they are both compatible. In this thesis, a Multiscale Molecular Dynamics Protocol is introduced, based on earlier work by Benjamin Messer, Z. Fan, Arieh Warshel, and in other parts by Christopher Fennel and Ken Dill. The protocol consists of the following tool-set: • A parametrization machinery that created a new coarse-grained force-field named AmberCG. • A multiscale thermodynamic cycle utilized within a free energy perturbation context to cooperatively use the best of coarse-grained and all-atom force-fields. • A collective variable that performs a linearization of the phase space to improve separation of product and reactant states. • A new algorithm to calculate functional quantities on spheres bounded by complicated solvent accessible surface areas - which as a special case calculates the amount of solvent accessible surface area. • A novel algorithm based on simple one dimensional Depth-Buffers, to identify atoms which actively form the boundary of the solvent accessible surface areas. Executing the protocol involves the following steps: 1. Construction of a coarse-grained force-field, based on an all-atom force-field. This involves setting up coarse-grained potentials and optimization of their parameters against selected reference structures and conformations. 2. Parametrization of a solvation model which is compatible to the force-field. 3. Usage of the coarse-grained force-field to sample the conformational space of a reaction. 4. Correction of the coarse-grained results with an all-atom force-field. 5. Analysis of the results using appropriate collective coordinates. 6. Reiteration until accuracies are met. Alternatively, instead of using the methods in the protocol, they can be utilized stand-alone. They simplify calculations, thus provid- ing speed-ups, while at the same time aiming to maintain or improve accuracy. Of course, there is no free lunch, and often the methods will include inaccuracies that exceed an acceptable threshold. However, the multiscale protocol is meant to be seen as an iterative technique, in which deficiency can be detected, and the protocol adjusted to restore balance.
Las simulaciones de dinámica molecular multiescala (Multiscale Molecular Dynamics) son una tendencia al alza en el sector de la Química y la Física computacionales. Los coarse-grained force-fields o campos de fuerza de grano grueso han existido desde hace años, utilizados de forma independiente, y también en cooperación con all-atom force-fields o campos de fuerza de todos los átomos dónde se combinan sus ventajas y cancelan sus desventajas. En este último caso sólo es cierto cuando los dos force-fields son compatibles. En esta tesis, introduzco un protocolo de Multiscale Molecular Dynamics basado en parte a trabajos anteriores de Benjamin Messer, Z. Fan, Arieh Warshel, y también en los de Christopher Fennell y Ken Dill. El protocolo consiste el siguiente conjunto de herramientas: 1. Un método de parametrización con cuál creé un nuevo coarse-grained force-field llamado AmberCG. 2. Un ciclo termodinámico multiescala utilizado en un contexto de perturbación de energía libre para usar cooperativamente el mejor de los coarse-grained force-fields y el de los all-atom force-fields. 3. Una variable colectiva que realiza una liberalización del espacio de fases para mejorar la separación de los estados de productos y reactivo. 4. Un nuevo algoritmo para calcular las cantidades funcionales en esferas limitadas por complicadas superficies accesibles al solvente - que como un caso especial calcula la cantidad de superficie accesible a solvente. 5. Un nuevo algoritmo basado en un buffer de profundidad, para identificar los átomos que forman activamente el límite de las superficies accesibles al solvente. La ejecución del protocolo implica los siguientes pasos: 1. Construcción de un coarse-grained force-field, basado en un all-atom force-field. Esto implica la creación de potenciales coarse-grained y la optimización de sus parámetros contra las estructuras de referencia seleccionados y sus conformaciones. 2. Parametrización de un modelo de solvatación compatible con el force-field. 3. Uso del coarse-grained force-field para muestrear el espacio con formacional de una reacción. 4. La corrección de los resultados coarse-grained con un all-atom force-field. 5. Análisis de los resultados utilizando coordenadas colectivas adecuadas. 6. Repetición hasta alcanzar las precisiones deseadas. Alternativamente, los métodos del protocolo pueden ser utilizados de forma independiente. Esto simplifica los cálculos y procura mantener, si no mejorar, la precisión. Sin embargo, todo tiene un coste y con frecuencia, los métodos incluirán inexactitudes que superarán el umbral aceptable. Aun y así, el protocolo multiescala es una técnica iterativa, en la que la deficiencia puede ser detectada, y el protocolo ajustado para restablecer el equilibrio.

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Vincent, Matthew Ryan. "Crystallization and Melting Studies of Poly(ε-caprolactone) and Poly(ethylene oxide) using Flash™ Differential Scanning Calorimetry and Preparation and Characterization of Poly(δ-valerolactone) Fractions." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/101668.

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The isothermal crystallization and melting temperatures of poly(ε-caprolactone) were correlated using fast differential scanning calorimetry. The melting kinetics was found to be independent of isothermal crystallization temperature and time. The conventional Hoffman-Weeks method could not be used to determine the equilibrium melting temperature because the observed melting temperatures were greater than the crystallization temperatures by a constant, so the Gibbs-Thomson method was used instead, yielding an equilibrium melting temperature of 103.4 ± 2.3°C. A modification was proposed to the non-linear Hoffman-Weeks equation that included a non-linear undercooling dependence for the kinetic fold surface free energy upon crystallization and permitted accurate modeling of the observed melting behavior. The isothermal crystallization rates of four narrow molecular weight poly(ethylene oxide) fractions were characterized using fast differential scanning calorimetry for crystallization temperatures spanning 100°C range with the lower limit approaching the glass transition. A transition from homogeneous to heterogeneous primary nucleation was observed at −5°C. The kinetic analysis suggested that the crystal growth geometry depends strongly on temperature, where rod-like structures begin to appear near the glass transition temperature, highly branched solid sheaves grow throughout the homogeneous primary nucleation temperature range, and spherulites grow in the heterogenous primary nucleation range. Poly(δ-valerolactone) was synthesized using microwave-assisted techniques. Narrow molecular weight fractions were obtained using successive precipitation fractionation. Preliminary isothermal crystallization studies suggest that conventional thermal analysis methods are not adequate to measure the melting temperatures accurately due to reorganization during heating.
Doctor of Philosophy

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Belli, Giacomo. "Thermodynamics and scattering in 2D for 4D theories." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23212/.

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Considering classical open string solutions with a null polygonal contour at the boundary of AdS3, the geometric problem of minimal surfaces related to gluon scattering amplitudes at strong coupling is developed and solved in a set of TBA-like integral equations. Their form resembles that of a TBA system whose free energy yields the dynamic contribution to the area. The corresponding set of functional relations, the so called Y-system, is derived and extensively analyzed in the cases of octagon and decagon together with the set of integral equations. Useful rewrites of the latter establish the connection with a particular class of HSG models and allow us to identify their Y-system (related to a universal TBA) with the one derived in AdS3 when the algebra level k is set to 2. A useful insight that clarifies how to properly reduce to the An series is offered. Thanks to a well defined change of reference frame, whose mathematical structure has been studied in detail, the dynamic part of the remainder function coincides with the extremum of the Yang-Yang functional for the modified TBA equations. Explicit examples have been treated in terms of Y-functions and pseudo-energies, extrapolating useful links with several works concerning null WLs, Hitchin systems and integrable perturbations of CFTs corresponding to Gk-parafermions.

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Khan, Abdullah. "Fundamental investigation to improve the quality of cold mix asphalt." Licentiate thesis, KTH, Bro- och stålbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-191527.

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Cold mix asphalt (CMA) emulsion technology could become an attractive option for the road industry as it offers lower startup and equipment installation costs, energy consumption and environmental impact than traditional alternatives. The adhesion between bitumen and aggregates is influenced by diverse parameters, such as changes in surface free energies of the binder and aggregates or the presence of moisture or dust on the surface of aggregates, mixing temperatures, surface textures (including open porosity), nature of the minerals present and their surface chemical composition, as well as additives in the binder phase. The performance of cold asphalt mixtures is strongly influenced by the wetting of bitumen on surfaces of the aggregates, which is governed by breaking and coalescence processes in bitumen emulsions. Better understanding of these processes is required. Thus, in the work this thesis is based upon, the surface free energies of both minerals/aggregates and binders were characterized using two approaches, based on contact angles and vapor sorption methods. The precise specific surface areas of four kinds of aggregates and seven minerals were determined using an approach based on BET (Brunauer, Emmett and Teller) theory, by measuring the physical adsorption of selected gas vapors on their surfaces and calculating the amount of adsorbed vapors corresponding to monolayer occupancy on the surfaces. Interfacial bond strengths between bitumen and aggregates were calculated based on measured surface free energy components of minerals/aggregates and binders, in both dry and wet conditions. In addition, a new experimental method has been developed to study bitumen coalescence by monitoring the shape relaxation of bitumen droplets in an emulsion environment. Using this method, the coalescence of spherical droplets of different bitumen grades has been correlated with neck growth, densification and changes in surface area during the coalescence process. The test protocol was designed to study the coalescence process in varied environmental conditions provided by a climate-controlled chamber. Presented results show that temperature and other variables influence kinetics of the relaxation process. They also show that the developed test procedure is repeatable and suitable for studying larger-scale coalescence processes. However, possible differences in measured parametric relationships between the bitumen emulsion scale and larger scales require further investigation. There are several different research directions that can be explored for the continuation of the research presented in this thesis. For instance, the rationale of the developed method for analyzing coalescence processes in bitumen emulsions rests on the assumption that the results are applicable to large-scale processes, which requires validation. A linear relationship between the scales is not essential, but it is important to be able to determine the scaling function. Even more importantly, qualitative effects of the investigated parameters require further confirmation. To overcome the laboratory limitations and assist in the determination of appropriate scaling functions further research could focus on the development of a three-dimensional multiphase model to study coalescence processes in more detail, including effects of surfactants, pH and other additives such as mineral fillers and salts. Additionally, better understanding of the breaking process and water-push out could help significantly to optimize CMA mix design. Different methods, both numerical and experimental could be explored for this.
Cold mix asphalt (CMA) eller kall asfaltbetong med hjälp av emulsionsteknik kan vara ett attraktivt alternativ för vägbyggnadsindustrin då det möjliggör lägre uppstart- och investeringskostnader, lägre energiförbrukning och mindre miljöpåverkan än traditionella alternativ. Adhesionen mellan bindemedel och stenpartiklarna påverkas av ett flertal parametrar, så som förändring i fri ytenergi hos både bindemedel och partiklar i närvaro av fukt eller damm på stenytorna, blandningstemperatur, yttextur (inklusive ytporositet), mineralegenskaper och ytornas kemiska sammansättning lika väl som tillsatsmedel i bindemedlen. Beteendet hos kall asfaltbetong är starkt påverkad av vätningsegenskaperna hos bindemedlet när det kommer i kontakt med stenmaterialet och detta i sin tur är beroende på bitumenemulsionens brytegenskaper och förmåga att blandas. Bättre förståelse av dessa processer är av största vikt. I detta arbete är avhandlingen baserad på fri ytenergi hos både mineraler/aggregat och bindemedel, baserat på kontaktvinkel och på ångabsorptionsmetoder. Den exakta specifika ytan hos fyra typer av aggregat och sju mineraler undersöktes med en metod baserad på BET (Brunauer, Emmett och Teller):s teorier genom att mäta den fysiska adsorptionen av utvalda gaser på ytorna och beräkna mängden adsorberad ånga som korresponderade mot ytlagret. Styrkan hos kontaktytornas bindning mellan bindemedlet och stenaggregaten beräknades baserat på mätningar av den fria ytenergin hos bägge ingående komponenterna, dels i torrhet dels i våta omgivningar. Som tillägg har en ny experimentell metod utvecklats för att studera bitumens blandbarhet genom att studera bitumendroppars relaxation i en emulsionsmiljö. Genom att använda denna metod har korelationen mellan sväriska droppar av bitumen undersökts mot förändringen i ytans area under blandningsprocessen. Testprotokollet utformades för att studera blandningsprocessen i varierande miljöer i en klimatkammare. Presenterade resultat visar att temperatur och andra variabler påverkar de kinetiska förhållandena vid relaxationsprocessen. De visar även att den utvecklade testmetoden är repeterbar och passar för studier av storskaliga blandningsprocesser. Det bör dock påpekas att vidare studier krävs för att påvisa skillnaderna mellan bitumenemulsionsskalan och större skalor. Framtida forskning kommer att koncentreras på utveckling av tredimensionella multifasmodeller för att studera blandningsförlopp på en mer detaljerad nivå, inkluderande effekter på ytaktiva ämnen, pH-värden och andra additativ så som mineralfiller och salt. Som tillägg kommer nyttan av nya karaktäriseringsmetoder att utvärderas, så som lågvikelspridning av neutroner eller kombinationer av röntgen, neutronradiologi och datortomografi, för att studera brytmekanismer hos bitumenemulsioner vid kontakt med mineraler och aggregat.

QC 20160901

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Hara, Takayuki. "A calculation of fermi energy in selected materials using doppler broadened positron annihilation spectroscopy." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/20238.

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Kumari, Vandana. "Structure-Based Computer Aided Drug Design and Analysis for Different Disease Targets." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1311612599.

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Galpin, Jean-Marie. "Étude du couplage entre un métal liquide et un champ magnétique alternant à basse fréquence." Grenoble INPG, 1991. http://www.theses.fr/1991INPG0032.

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L'effet d'un champ magnetique alternant a basse frequence sur un metal liquide presentant une surface libre, est etudie a l'aide d'une cuve cylindrique contenant du mercure et placee dans un solenoide alimente par un courant monophase de frequence 1 a 22 hz. Les mouvements internes turbulents, preponderant pour les valeurs de frequence comprises entre 10 et 22 hz, sont, sur de nombreux points, similaires a ceux observes, dans les etudes anterieures, aux plus grandes valeurs de frequence. La principale particularite est la rapide decroissane de la vitesse moyenne typique et du taux de dissipation turbulente. Ce phenomene semble etre correle a la presence de vitesses oscillatoires forcees par la partie pulsatoire des forces de lorentz devient predominante et engendre des mouvements de surface dont la configuration et l'amplitude dependent de l'itensite i et de la frequence f du courant electrique inducteur applique. L'espace des parametres (i, f) peut etre divise en quatre regions correspondant a quatre regimes. Une analyse theorique de la stabilite d'une surface libre soumise a un champ electromagnetique basse frequence montre qu'il apparait un systeme d'ondes concentriques stationnaires forces de frequence 2f et que la croissance des modes azimutaux est gouvernee par un systeme couple d'equations de mathieu. Sous certaines conditions, les ondes azimutales deviennent instables et l'instabilite apparait avec une transition sous-harmonique. La comparaison entre la theorie et l'experience montre que le modele theorique permet une bonne prediction qualitative des phenomenes observes.

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Chen, Chi. "Lanthanide Energy Transfer Donors on Nanoparticles Surfaces : From Fundamental Mechanisms to Multiplexed Biosensing." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS196/document.

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Le multiplexage optique basé sur des nanoparticules offre de nombreux avantages pour la biodétection et l'imagerie à multiparamètres. Toutefois, les modifications apportées à un paramètre entraînent également la modification d’autres paramètres. Par conséquent, la couleur, la durée de vie ou l’intensité ne peuvent pas être utilisées, respectivement, comme paramètre indépendant. Cette thèse peut être divisée en deux aspects. Le premier concerne le développement d'un multiplexage à une seule nanoparticule avec un temps résolu, basé sur le transfert d'énergie par résonance de type Förster (FRET) des complexes de lanthanides aux points quantiques (QD) et ensuite aux colorants fluorescents. Une investigation systématique de toutes les différentes combinaisons avec une large gamme de donneurs et d'accepteurs sur le QD est présentée, et les résultats expérimentaux sont comparés à la modélisation théorique. Le résultat ne contribue pas seulement à une compréhension complète de ces voies de transfert d'énergie compliquée entre multi donneurs / accepteurs sur des nanoparticules, mais offre également la possibilité d'utiliser les modèles pour développer de nouvelles stratégies permettant de préparer le QD avec une couleur, une durée de vie et une intensité réglables de manière indépendante. Le deuxième aspect porte sur le mécanisme de transfert d'énergie du Tb à la nanoparticule d'or (AuNP). Le transfert d'énergie par nanosurface (NSET) s'est révélé être un mécanisme opérationnel pour l'extinction des PL par les AuNP, une information importante pour le développement, la caractérisation et l'application de nanobiocapteurs basés sur l'extinction des PL par les AuNP
Optical multiplexing based on nanoparticles provides many advantages for multiparameter biosensing and imaging. However, the changes in one parameter also lead to changing of other parameters, and thus, color, lifetime, or intensity could not be used as an independent parameter, respectively. This thesis can be divided into two aspects. The first one focuses on developing time-resolved single-nanoparticle multiplexing based on Förster resonance energy transfer (FRET) from lanthanide complexes to quantum dot (QD) to fluorescent dyes. Systematical investigation of all different combinations with a broad range of numbers of donors and acceptors on QD are presented, and the experimental results are compared with theoretical modelling. The result do not only contribute to a full understanding of such complicated multi donor-acceptor energy transfer pathways on nanoparticles but also open the opportunity to use the models for developing new strategies to achieve the QD with independent tunable color, lifetime and intensity. The second aspect focuses on the energy transfer mechanism from Tb to gold nanoparticle (AuNP). Nanosurface energy transfer (NSET) proved to be an operational mechanism in PL quenching by AuNPs, which is important information for the development, characterization, and application of nanobiosensors based on PL quenching by AuNPs

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Dissertations / Theses on the topic 'Surface free energy'

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