In this thesis, we will examine the properties of subelliptic jets in the Engel group of step 3. Step-2 groups, such as the Heisenberg group, do not provide insight into the general abstract calculations. This thesis then, is the first explicit non-trivial computation of the abstract results.

<p>The main goal for a packaging is to protect the product inside. Typical packaging nowadays is made of layers of paper and barriers consisting of plastics or aluminum foil. A problem with the barrier used today is the environmental thinking. Xylophane® is an environmental friendly and biodegradable alternative to the current barrier material used in packaging. It consists of the natural carbohydrate xylan and additives. Xylophane® is an efficient barrier to oxygen, grease and aroma and can prolong the shelf life of sensitive food.</p><p>The raw material xylan is water soluble and Xylophane® can be coated on paper, board and plastics without using other solvents. A problem with the drying process is the amount of energy needed and the consumption needs to be decreased. Also, the drying capacity of the equipment to be used is often limited and the amount of water to be dried off is critical for the success of the coating process. By increasing the dry content of Xylophane® without increasing the viscosity too much, the drying process can be more effective. In this thesis, studies were made of using a filler as an additive to increase the dry content without destroying the barrier properties.</p><p>With an experimental design, a suitable relationship between the ingredients xylan (X), plasticizer (P) and filler (F) was found. Xylan is the main component and is needed to get a good oxygen barrier. The plasticizer decreases the oxygen barrier properties but is needed to make the material more flexible. The filler is positive for the barrier properties. The chosen composition was X:P = 7:3 and X:F = 1:1. Some extra experiments were made to find a reasonable value of the dry content. Dry contents around 18 % work well with temperatures at and above 45°C, but to manage to perform coating at room temperature the dry content needs to be lower.</p>

<p>A colloid of magnesium hydroxide is used to stabilize droplets of monomers before suspension polymerisation. The characteristics of precipitated magnesium hydroxide changes significantly during the first hours. The viscosity is high and flucctuating at first but decreases and becomes low and stable after a few hours. When the colloid ages the primary particles agglomerate into larger particles which increases in size by time due to, among other things, Oswald ripening and aggregation. This can cause problems with poor reproducibility in the production. Therefore, the purpose of this study was finding a way to age the colloid without an increase in particle size and without changing any other features. Several experiments were made to optimize the precipitation procedure and to find out what parameters that are most important. The results showed that the stirring rate and colloidal concentration have big influence.</p><p>Small amounts of chemicals that modifies the surface of the colloid was added. This made the particle size near constant over time and the colloid was aged for two months without increasing in size or changing other properties. This was confirmed by making microspheres that had the same characteristics as microspheres made with a fresh colloid.</p>

Current commonly use viscosity measurement techniques cannot be used for all types of fluids. For fluids in the under cooled region a new method of measuring the viscosity is required. A process of viscosity measurement, by measuring the speed of droplet coalescence in a microgravity environment, was developed. This paper analyses validation experiments performed on the International Space Station. Four experiments were analyzed. Two of the experiments provided results consistent with the known value for the viscosity. One of the experiments did not provide sufficient data for analysis. The final experiment had possible errors due to the experimental setup. The resulting data from these experiments demonstrated that the method is feasible. However, more experiments are needed to fully verify the process.

Proper selection of drilling fluids plays a major role in determining the efficient completion of any drilling operation. With the increasing number of ultra-deep offshore wells being drilled and ever stringent environmental and safety regulations coming into effect, it becomes necessary to examine and understand the behavior of water based drilling fluids - which are cheaper and less polluting than their oil based counterpart - under extreme temperature and pressure conditions. In most of the existing literature, the testing procedure is simple - increase the temperature of the fluid in steps and record rheological properties at each step. A major drawback of this testing procedure is that it does not represent the continuous temperature change that occurs in a drilling fluid as it is circulated through the well bore. To have a better understanding of fluid behavior under such temperature variation, a continuous test procedure was devised in which the temperature of the drilling fluid was continuously increased to a pre-determined maximum value while monitoring one rheological parameter. The results of such tests may then be used to plan fluid treatment schedules. The experiments were conducted on a Chandler 7600 XHPHT viscometer and they seem to indicate specific temperature ranges above which the properties of the drilling fluid deteriorate. Different fluid compositions and drilling fluids in use in the field were tested and the results are discussed in detail.

A colloid of magnesium hydroxide is used to stabilize droplets of monomers before suspension polymerisation. The characteristics of precipitated magnesium hydroxide changes significantly during the first hours. The viscosity is high and flucctuating at first but decreases and becomes low and stable after a few hours. When the colloid ages the primary particles agglomerate into larger particles which increases in size by time due to, among other things, Oswald ripening and aggregation. This can cause problems with poor reproducibility in the production. Therefore, the purpose of this study was finding a way to age the colloid without an increase in particle size and without changing any other features. Several experiments were made to optimize the precipitation procedure and to find out what parameters that are most important. The results showed that the stirring rate and colloidal concentration have big influence. Small amounts of chemicals that modifies the surface of the colloid was added. This made the particle size near constant over time and the colloid was aged for two months without increasing in size or changing other properties. This was confirmed by making microspheres that had the same characteristics as microspheres made with a fresh colloid.

No description available.

Blood is a dense suspension of flexible red blood cells. In response to a background flow, these cells distribute themselves non-uniformly throughout the vessel. As a result, material properties that are well defined in homogeneous fluids, such as viscosity, are no longer so, and depend upon the flow geometry along with the particle properties. Using a simple model that accounts for the steady-state particle distribution in vessel flow, we derive an expression for the effective viscosity of blood and the suspension flow velocity field in a pressure-driven tube flow. <br /><br /> We derive the steady-state particle distribution from a conservation equation with convective flux arising from particle deformation in the flow. We then relate the particle microstructure to the overall flow through a generalized Newtonian stress-tensor, with the particle volume fraction appearing in the expression for the local viscosity. Comparing with experimental data, we show that the model quantitatively reproduces the observed rheology of blood in tube flow. <br /><br /> We reconsider the problem in an alternate geometry corresponding to the flow between two concentric cylinders. The steady-state particle distribution, suspension velocity field and the measured effective viscosity are all very different from their counterparts in tube flow, casting serious doubt upon the practice of using data from a Couette viscometer to parameterize constitutive models applied to vascular blood flow. <br /><br /> Finally, we calculate the effect of random fluctuations in the particle velocity on the averaged behaviour of the particle conservation equation. Using a smoothing method for linear stochastic differential equations, we derive a correction to the free Einstein-Stokes diffusion coeffcient that is due to the interaction of the particles with their neighbours.

An artificial neural network has been developed for the prediction of the kinematic viscosity of ternary, quaternary, and quinary systems. The systems investigated consisted of the following components: Heptane, Octane, Toluene, Cyclohexane, and Ethylbenzene at atmospheric pressure and temperatures of 293.15, 298.15, 308.15, and 313.15 K. The developed model was based on a three-layer neural network with six neurons in the hidden layer and a back propagation learning algorithm. The neural network was trained with binary systems consisting of 440 data sets and using mole fractions combined with temperature as the input. A comparison of the experimental values and the results predicted from the neural network revealed a satisfactory correlation, with the overall absolute average deviation (AAD) for the ternary, quaternary, and quinary systems of 0.8646%, 1.1298%, and 4.3611%, respectively. The results were further compared to the generalized McAllister model as an alternative empirical model. The neural network produced better results than the generalized McAllister model. The new approach established in this work helps reduce the amount of experimental work required in order to determine most of the parameters needed for other models and illustrates the potential of using a neural network method to estimate the kinematic viscosity of many other mixtures.

Immiscible dispersions of oil and water are encountered in many industries such as food, pharmaceuticals, and petroleum. Phase inversion is a key phenomenon that takes place in such systems whereby the dispersed phase and the continuous phase invert spontaneously. Stabilizers such as surfactants or solid nanoparticles have been used in the past to improve the stability of emulsions. However, the combined effects of surfactants and nanoparticles on phase inversion and stability of oil and water emulsions have not been studied. This study investigates the synergistic effects of silica nanoparticles (of varying hydrophobicities) and non-ionic surfactant on phase inversion of water-in-oil emulsion to oil-in-water emulsion. The effect of oil viscosity on phase inversion phenomenon is also studied. Stabilizers were initially dispersed in the oil phase with the help of a homogenizer. The water concentration of the system was gradually increased while maintaining the mixing. Online conductivity measurements were carried out to obtain the phase inversion point. Experimental results on the effects of pure stabilizers (either silica nanoparticles or surfactant) and mixed stabilizers (combined silica nanoparticles and surfactant) on phase inversion of emulsions are presented. The stability of these emulsions is also investigated. From the results obtained in this study it is clear that catastrophic phase inversion phenomenon and stability of water-in-oil emulsions can be controlled with the help of different stabilizers. In order to extend the critical dispersed phase volume fraction at which phase inversion occurs surfactant type stabilizer was found to be more effective than solid nanoparticles. On the other hand, emulsion stability was mainly dominated by solid nanoparticles. The hybrid of the two stabilizers and its effect on phase inversion and stability are discussed in the thesis.