Recently a large amount of interest has developed around separating out impurities of small size; pertinent examples are found within fuel and solvent processing. For such applications a leading candidate process is nanofiltration. This thesis focuses on SRNF (solvent resistant nanofiltration) composite membranes consisting of a dense polymer active layer bonded to a stronger, but ultimately more porous, support layer. The composite membranes that have been produced during the course of this work consist of a PDMS (polymdimethylsiloxane) active layer bonded to a commercially available support layer of PAN (polyacrylonitrile). To create the membrane a monomer was spread over the support layer and then polymerised to form the matrix which was responsible for separation. Commercially, either heat or radiation is often applied to cause polymerisation, however the membranes in the current work have been formed by the used of a homogeneous catalyst. This thesis investigates the transport and separation dynamics of the produced membranes for a series of fuel simulants composed of organometallics and poly-nuclear aromatic solutes dissolved in aromatic and alkane solvents. Membrane composition and the extent of polymer swelling were found to be the two key factors which had the greatest influence on solvent flux and solute rejection. By increasing catalyst concentration it was found that the dual effects of increased rejection and reduced flux occurred, with the converse also being true. The effective pore size of the membrane could also be controlled by varying the catalyst amount during manufacture as this directly affected the limit of crosslinking which formed. Polymer swelling was the most pronounced using solvents with a solubility parameter close to that of the polymer. The membrane transport mechanism was most accurately forecast by the solution diffusion model for flux predictions and the convection diffusion model for rejection predictions, however all the models tried were in close agreement. This was postulated to be due to the swelled polymer matrix which allows for both convective and diffusive transport to occur.

In this thesis we have shown that a seemingly complicated mathematical structure can exhibit 'tame behaviour'. The structure we have dealt with is a field (a space in which there are addition and multiplication which satisfy natural properties) together with a dense subset (a subset which has spread in all parts of the this set, as Q does in R) and a discrete subset (a subset comprised of single points which keep certain distances from one another). This tameness is essentially with regards to not being trapped with the 'Godel phenomeonon' as the Peano arithmetic does.

Densification of the urban structure is a hot topic in urban development, but densification is almost absent as a strategy in rural settlements. This project studies densification in a rural settlement in a Nordic context by using the "dense and low-rise" design strategy and the concept of linear cities. Is linearity the key to rural densification? The concepts are tested on the small town of Kimito in south-western Finland.

Cette thèse présente les résultats issus de l’investigation de la réponse optique de la transition D2 du Rubidium 87 en fonction de la densité de l’ensemble atomique. Afin de sonder cette transition nous utilisons un faisceau laser proche de la résonance (780nm) sur un échantillon de Rubidium ultra-froid (100µK). Nous observons ainsi la transmission en fonction de la longueur d’onde pour des densités allant de 10^12 atomes/cm^3 à 10^14 atomes/cm^3. Lorsque la densité augmente, on s’attend à ce que les interactions dipôle-dipôle jouent un rôle de plus en plus important du fait de la proximité des éléments diffusants. Quantitativement, les dipôles induits par le faisceau sonde commencent à jouer un rôle important lorsque la densité n atteint n*(lambda/2Pi)^3 = 1, une densité que nous atteignons dans notre système.Deux études systématiques seront présentées. La première montre les résultats obtenus pour un système à 12 niveaux, la deuxième pour un système à 2 niveaux obtenu par polarisation de l’ensemble atomique. Les résultats issus de ces études sont ensuite comparés aux théories existantes. La première approche est microscopique et décrit les interactions des dipôles couplés, la deuxième approche, macroscopique, est donnée par l’équation de Clausius-Mosotti.Les propriétés de propagation d’impulsions à travers ce système sont étudiées et révèlent en particulier un avancement fractionnel de l’impulsion et un indice de groupe inégalés. / This thesis investigates the response of the D2 transition of Rubidium 87 for various densities.To probe this transition we illuminate an ultra cold (100µK) sample of Rubidium 87 with close toresonance of lambda = 780 nm laser light.We observe the transmitted light while scanning the frequency over the atomic resonance. Such a spectrum is taken for peak densities ranging from 10^12 atoms/cm^3 to 10^14 atoms/cm^3. As matter gets denser and denser dipoie-dipole interaction start playing a role due to the close proximity of neighbouring scatteres. These interactions are caused by the probe light induced dipoles and start being important when the density reaches n*(lambda/2Pi)^3 = 1, which for us is the case at the upper end of the explored density range.We start off measuring these transmission data for degenerate 12-level Rubidium 87 and afterwardsfor Rubidium 87, which we first spin polarize and then by lifting the degeneracy generate an artifical2-level system. These results are systematically compared to the two available theories.A microscopic one, which is described by coupled dipoles and a macroscopic one the so calledClausius-Mosotti equation. None of the ab initio theories can explain the results obtained during this thesis.The rigerous comparison of the various acquired datasets shows that the data in itself is consistentand relative changes going from a 12-level system to a 2-level system are understood.Additionally we also investigate the pulse propagation behaviour through such a systemrevealing stunning values for the fractional pulse advancement and the group index.

No description available.

The computational constitutive Modified Cam Clay Model (MCCM) was developed at Cambridge to study the behavior of clays and has been proven to be effective. In this study, this model is extended to the case of dense sands to analyze the accuracy of the stress-strain behavior. This analysis is based on triaxial test data applied to remolded and compacted sand samples under drained conditions. The laboratory triaxial tests were performed by the Florida Department of Transportation to research the permeability effect in sandy soils compacted up to 95% of maximum unit weight at the optimum moisture content. Each soil sample was tested using different stress paths. In addition, these data were also used to obtain the soil parameters. These soil parameters are used as input data for the Modified Cam Clay Model. Moreover, a computer program in MATLAB was developed based on the MCCM constitutive theory and application in order to predict the stress-strain response for overconsolidated soils under drained condition. Based on observations of the qualitative behavior of these soils, a modification is proposed in this thesis to the original constitutive model to improve the predicted stress-strain behavior. The results of the computer program are typically presented in the deviatoric stress versus shear strain and the stress path plane (deviatoric stress versus mean effective stress). These are the principal plots used for the behavior prediction of soil specimens. Furthermore, the results of the computer program were compared to the laboratory triaxial test data. In general, it is may be concluded that, MCCM with some modification, is applicable to dense sands.

Effective space utilization is an important consideration in logistics systems and is especially important in dense storage environments. Dense storage systems provide high-space utilization; however, because not all items are immediately accessible, storage and retrieval operations often require shifting of other stored items in order to access the desired item, which results in item location uncertainty when asset tracking is insufficient. Given an initial certainty in item location, we use Markovian principles to quantify the growth of uncertainty as a function of retrieval requests and discover that the steady state probability distribution for any communicating class of storage locations approaches uniform. Using this result, an expected search time model is developed and applied to the systems analyzed. We also develop metrics that quantify and characterize uncertainty in item location to aid in understanding the nature of that uncertainty. By incorporating uncertainty into our logistics model and conducting numerical experiments, we gain valuable insights into the uncertainty problem such as the benefit of multiple item copies in reducing expected search time and the varied response to different retrieval policies in otherwise identical systems.

A near-net-shape process for the production of mullite matrix ceramic composites below 1300 °C has been achieved by reaction bonding AI2O3, silicon, mullite seeds and a eutectic of A12O3-SiO2-mixed rare earth oxide. The roles of the transient liquid phase from the eutectic and the mullite seeds are examined. The approximate eutectic composition was estimated from the A12O3-SiO2-Y2O3 phase diagram as 22 wt % AI2O3/46 wt% S102/3 2 wt% Y2O3. The fusion temperature of the mixed-rare-earth-based eutectic composition was lower (1175 °C vs. those of pure, rare earth oxides based eutectic composition; Pr6On/A12O3/SiO2: 1224 °C, EU2O3/AI2O3/S1O2: 1259 °C and Y2O3/Al2O3/SiO2: 1345 °C). The densification characteristics of the reaction-bonded mullite (RBM) mixture were investigated. Density increased with eutectic, and decreased with mullite seed contents. Oxidation and volume expansions due to Si and mullite formation are examined by thermogravimetric analysis (TGA) and dilatometric measurement. TThe measured weight gain and maximum volume expansion were lower than theoretical values due to preoxidation of the Si powder. Dilatometric curves indicated sintering shrinkage is compensated by the oxidation-induced volume-expansion. AI2O3 + SiO2 mixtures of the mullite composition exhibited shrinkage exclusively. X-ray diffraction of the RBM sinters display major mullite peaks and minor residual a-A12O3. Mullite develops with low residual AI2O3 when 7.5 wt% mixed-rare-earth-oxide eutectic and 5 wt% mullite seeds are incorporated into the mix. The final sinter is > 90 % theoretical density, > 90 % mullite, and suffers 2.2 % sintering shrinkage. Transmission-electron-microscopy (TEM) and Energy dispersive X-ray spectra (EDX) were employed to follow mullite evolution. Model samples were utilised to study diffusion-, and reaction-, rates. The highest reaction rates at the lowest temperature occur when the eutectic penetrates an AI2O3/S1 layer. Bimodal pellets with and without eutectic (or with and without mullite seeds) directly illustrate their roles. Mullite seeds promote mullite formation, but the transient liquid accelerates Si oxidation, mullite formation and densification. / Thesis / Master of Engineering (ME)

No description available.

Neutron stars are stellar objects of extreme properties. The dense core enables usto study nuclear matter beyond saturation density. The exact composition of matterat such densities is not yet established, but the thermodynamic states of the matteris theoreticized by the Equation of State (EOS). The EOS cannot be derived analyt-ically and is dependent on constraints from neutron stars and nuclear experiments inlaboratories on earth. Recent advances in astrophysical experiments have probed newconstraints on the EOS by studying properties such as mass, radius and tidal deformabil-ity of neutron stars. Especially the possibility to detect gravitational waves from mergingbinary systems by the LIGO/VIRGO collaboration and the mass-radius measurementsby NICER have contributed a great deal. Constraints from terrestrial experiments havebeen derived by studying matter at supra saturation density in Heavy Ion Collisions andby determining the neutron skin thickness. In this work, an overview of neutron stars,dense matter and the EOS is presented. Further, results of studies aiming to determineand constrain the EOS are reviewed. Even though there is consensus about some neutronstar properties among different research groups, there are still major uncertainties as allresult depend on a relatively small set of observational data. Therefore, the EOS can stillbe considered to be far from precise and the knowledge of the true neutron star matterremains undisclosed.