In the beginning of this study, Molecular dynamics simulation is utilized to investigate the behavior of water molecules confined between two Au plates of (001) planes separated by gaps of 24.48, 16.32, 12.24, 11.22, and 10.20 . The simulation results indicate that the arrangements of the water molecules are dependent on the gap size. An inspection of the variation of the self-diffusion coefficients with the gap size suggests that the difference between the dynamic properties of the water molecules in the z-direction and the x-y plane decreases as the distance between the two Au plates increases. Moreover, we discuss the effects of different lattice structures, (100), (110) and (111)¡Aon the water molecules. The simulation results indicate that the arrangements of the water molecules are dependent on Au plate surface structures. The adsorption of the plate creates flat water layers in the proximity of each plate surface for (100) and (111) cases, but wave-like water layer for Au (110) plate. The absorbed water layer is the most close to plate surface for (110) lattice structure. Moreover, the self-diffusion coefficient in the z-direction for (110) case is the largest, meanwhile, the water molecules have a greater ability to diffuse in the x-y plane for (100) case. Finally¡Athe density distribution, velocity profile, and diffusion coefficients of the water film in a Couette flow are studied. Shear viscosity and its dependence on the shear rate of the water film are also examined in the present research. The diffusion of the whole film increases dramatically as the shear rate greater than a critical value. The shear viscosity decreases as the shear rate increases, especially for the water film with a small thickness, which implies the shear-thinning behavior for viscosity of the nanoconfined film. Moreover, increase in shear viscosity with a decrease in the film thickness can also be found in the present study.

Using equilibrium molecular dynamics simulations, an analysis of the key thermophysical properties critical to heat transfer processes is performed. Replication of thermal conductivity and shear viscosity observations found in experimental investigations were performed using a theoretical nanopthesis-fluid system and a novel colloid-fluid interaction potential to investigate the key nanofluid parameters. Analysis of both the heat current (thermal conductivity) and stress (shear viscosity) autocorrelation functions have suggested that the dominant physical mechanisms for thermal and momentum transport arises from enhancements to the longitudinal and transverse acoustic modes energy transfer brought about by the increased mass ratio of the nanopthesis to the fluid. This conclusion was further supported by analysis of the local density fluctuations surrounding increasing nanopthesis diameters where the longitudinal acoustic mode characteristics for density fluxes were seen to be enhanced by the presence of the heavier platinum nanopthesiss. It is then concluded that the key macroscopic characteristic in obtaining the largest thermal energy transfer enhancement is through the mass of the nanopthesis relative to the base fluid. Also, the small local density effects in the nanofluid are greatly affects the viscosity calculations. These conclusions provide the theoretical framework for many of the experimental results obtained.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23002号 / 理博第4679号 / 新制||理||1671(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 大西 明, 准教授 菅沼 秀夫, 教授 田中 貴浩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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The objective of this research work was to develop a methodology for experimentally estimating the interfacial properties at slag-metal interfaces. From previous experiments carried out in the division, it was decided to use surface active elements like sulfur or oxygen to trace any motion at the interface. For this purpose the following experimental investigations were carried out. Firstly the density of slag was estimated using the Archimedes Principle and the Sessile Drop technique. The density of the slag would give the molten slag height required for the surface active element to travel before reaching the slag-metal interface. Diffusivity measurements were uniquely designed in order to estimate the sulfur diffusion through slag media. It was for the first time that the chemical diffusivity was estimated from the concentration in the metal phase. Experiments carried out validated the models developed earlier. The density and diffusivity value of sulfur in the slag was used to accurately capture the time for sulfur to reach the slag-metal interface. The oscillations were identified by calculating the contact angle variations and the interfacial velocity was estimated from the change in the surface area of the liquid iron drop. The interfacial tension was estimated from the contact angles and the interfacial dilatational modulus was calculated. Based on cold model experiments using water as well as mercury, an equation of the dependence of the interfacial shear viscosity on the interfacial velocity and interfacial tension was established. This paved way for the estimation of the interfacial shear viscosity at the slag-metal interface. The present study is expected to have a strong impact on refining reactions in pyometallurgical industries where slag/metal interfaces play an important role. From a fundamental view point, this provides a deeper insight into interfacial phenomena and presents an experimental technique to quantify the same. / QC 20101130

Conselho Nacional de Desenvolvimento Científico e Tecnológico / When confined in nanometer scale, water presents great variation in their dynamic properties. Here, we carried out molecular dynamics simulations to determine the ratio of the diffusion coefficient and viscosity variation of water confined in carbon nanotubes with different diameters. We have found that both properties are affected by confinement. While the difusion has not monotonic growth with the diameter, the viscosity varies with its fifth root. Furthermore, the viscosity of the contained water is an order of magnitude lower than that of bulk water. By varying the density of water within the pore, we observed that the viscosity is deeply affected, reaching values 300% higher when density is increased by 40%. In addition, we tested the impact of the thermostat selection on viscosity s determination, concluding that the thermostat Langevin has higher values for both the contained water and to the bulk. / Quando confinada em escala nanométrica, a água apresenta grande variação em suas propriedades dinâmicas. Neste trabalho, realizamos simulações de dinâmica molecular para determinar a relação do coeficiente de difusão e da viscosidade da água confinada em nanotubos de carbono com diferentes diâmetros. Encontramos que ambas as propriedades são afetadas pelo confinamento. Enquanto a difusão apresenta crescimento não monotônico com o diâmetro, a viscosidade varia com a sua raíz quinta. Além disso, a viscosidade da água confinada é uma ordem de grandeza menor que a da água bulk. Variando a densidade da água dentro do poro, observamos que a viscosidade é profundamente afetada, chegando a valores 300% maiores ao aumentarmos a densidade em 40%. Além disso, testamos o impacto da seleção do termostato na determinação da viscosidade, chegando à conclusão de que o termostato de Langevin apresenta valores maiores tanto para a água confinada quanto para o bulk.

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Konjac glucomannan (KGM), the main biologically active constituent of konjac flour extracted from corms of Amorphophallus konjac (konjac), can be used to prepare functional foods and may also have potential as a pharmaceutical product to combat obesity. The current study employed three experimental approaches to study the biology and chemistry of konjac, namely (1) glasshouse experiments to study the morphogenesis, growth and productivity of konjac plants, (2) a histological and immunocytochemical investigation of the localisation and developmental regulation of the deposition and metabolism of KGM in developing corm tissues, and (3) a comparative study of methodologies for the extraction and analysis of KGM. The current data demonstrated a morphological and functional separation between the ventral and dorsal regions of corms. The ventral region appeared to function as a source during the initial period of shoot development, while the dorsal region appeared to operate as a sink after the development of mature canopy. Once the corm reached maturity, both an inflorescence and a leaf were produced within a single season. It has also been demonstrated that the age of the ‘mother’ corm is an important factor affecting the quality of offsets produced. An anti-mannan antiserum detected a temporally regulated pattern of mannan epitope production within glucomannan idioblasts in developing corm tissues, with increased expression as the corm approached maturity/dormancy. The current observations also suggest that the mobilization of KGM initiates at the periphery of the corm and proceeds inwards towards the centre of the corm. Compositional analysis showed that the purified konjac flour (PKF) produced using a modified extraction procedure contained 92% glucomannan, with a weight average molecular weight (Mw), polydispersity index (PDI) and degree of acetylation (DA) of 9.5 ± 0.6 x 105 gmol-1, 1.2 and 2.8 wt. %. These data, plus Fourier-transform infrared spectral (FTIR) and zero shear viscosity analyses of the extract (PKF) were all consistent with the literature. Comparison of three existing methodologies for the quantitative analysis of the KGM content, namely 3,5-dinitrosalicylic acid (3,5-DNS), phenol-sulphuric acid and enzymatic colorimetric assays; indicated that the 3,5-DNS colorimetric assay was the most reproducible and accurate method, with a linear correlation coefficient of 0.997 and recoveries between 97% and 103% across three spiking levels of starch. In summary, this study has provided a better understanding of aspects of the biology and cultivation of A. konjac and has also produced methodologies which can be used as the basis for an improved good laboratory practice (GLP) for the commercial extraction and analysis of this multifunctional natural polymer.

No description available.

lthough extensive research work has been carried out on the drag reduction behavior of polymers and surfactants alone, little progress has been made on the synergistic effects of combined polymers and surfactants. A number of studies have demonstrated that certain types of polymers and surfactants interact with each other to form surfactant-polymer complexes. The formation of such complexes can cause changes in the solution properties and may result in better drag reduction characteristics as compared with pure additives. A series of drag-reducing surfactants and polymers were screened for the synergistic studies. The following two widely used polymeric drag reducing agents (DRA) were chosen: a copolymer of acrylamide and sodium acrylate (referred to as PAM) and polyethylene oxide (PEO). Among the different types of surfactants screened, a cationic surfactant octadecyltrimethylammonium chloride (OTAC) and an anionic surfactant Sodium dodecyl sulfate (SDS) were selected for the synergistic study. In the case of the cationic surfactant OTAC, sodium salicylate (NaSal) was used as a counterion. No counterion was used with anionic surfactant SDS. The physical properties such as viscosity, surface tension and electrical conductivity were measured in order to detect any interaction between the polymer and the surfactant. The drag reduction (DR) ability of both pure and mixed additives was investigated in a pipeline flow loop. The effects of different parameters such as additive concentration, type of water (deionized (DI) or tap), temperature, tube diameter, and mechanical degradation were investigated. The addition of OTAC to PAM solution has a significant effect on the properties of the system. The critical micelle concentration (CMC) of the mixed surfactant-polymer system is found to be different from that of the surfactant alone. The anionic PAM chains collapse upon the addition of cationic OTAC and a substantial decrease in the viscosity occurs. The pipeline flow behaviour of PAM/OTAC mixtures is found to be consistent with the bench scale results. The drag reduction ability of PAM is reduced upon the addition of OTAC. At low concentrations of PAM, the effect of OTAC on the drag reduction behavior is more pronounced. The drag reduction behavior of polymer solutions is strongly influenced by the nature of water (de-ionized or tap). The addition of OTAC to PEO solution exhibited a week interaction based on the viscosity and surface tension measurements. However, the pipeline results showed a considerable synergistic effect, that is, the mixed system gave a significantly higher drag reduction (lower friction factors) as compared with the pure additives (pure polymer or pure surfactant). The synergistic effect in the mixed system was stronger at low polymer concentrations and high surfactant concentrations. Also the resistance against mechanical degradation of the additive was improved upon the addition of OTAC to PEO. The mixed PEO/SDS system exhibited a strong interaction between the polymers (PEO) and the surfactant (SDS), Using electrical conductivity and surface tension measurements, the critical aggregation concentration (CAC) and the polymer saturation point (PSP) were determined. As the PEO concentration is increased, the CAC decreases and the PSP increase. The addition of SDS to the PEO solution exhibits a remarkable increase in the relative viscosity compared to the pure PEO solution. This increase is attributed to the changes in the hydrodynamic radius of the polymer coil. The pipeline flow exhibited a considerable increase in DR for the mixed system as compared to the pure PEO solution. The addition of surfactant always improves the extent of DR up to the PSP. Also the mixed PEO/ SDS system shows better resistance against shear degradation of the additive.