It widely is assumed that property markets can be predicted and to be able to make forecasts, concerning future housing prices, a number of different indicators are used. But if it possible to know the future today, why do we still experience bubbles in housing markets? To answer this question the reliability of four of the most commonly used indicators were tested for the time period between 2000 and 2010. To evaluate the indicators predicting power the development in, Germany, Sweden, Spain and the UK was studied. Germany and Sweden did not experience a correction during the most recent financial crises, while Spain and the UK did. If the evaluated indicators would be good predictors of future developments, it should have been possible to see differences in the attained values prior to the crises and it should have been easy to forecast that prices would fall in the UK and Spain and that they would be fairly stable in Germany and continue to increase in Sweden. The results from this study do not support the statement, that property prices can be forecasted, but, on the contrary, indicates that the investigated indicators have very limited predictive power in forecasting future price developments in housing markets. The result also show that variable rate mortgages can be expected to play a smoothing effect on property prices during economic cycles.

It widely is assumed that property markets can be predicted and to be able to make forecasts, concerning future housing prices, a number of different indicators are used. But if it possible to know the future today, why do we still experience bubbles in housing markets? To answer this question the reliability of four of the most commonly used indicators were tested for the time period between 2000 and 2010. To evaluate the indicators predicting power the development in, Germany, Sweden, Spain and the UK was studied. Germany and Sweden did not experience a correction during the most recent financial crises, while Spain and the UK did. If the evaluated indicators would be good predictors of future developments, it should have been possible to see differences in the attained values prior to the crises and it should have been easy to forecast that prices would fall in the UK and Spain and that they would be fairly stable in Germany and continue to increase in Sweden. The results from this study do not support the statement, that property prices can be forecasted, but, on the contrary, indicates that the investigated indicators have very limited predictive power in forecasting future price developments in housing markets. The result also show that variable rate mortgages can be expected to play a smoothing effect on property prices during economic cycles.

Neutron irradiated copper-boron alloys are employed to study the mutual interaction between metallic crystalline lattices and inert gases. Inert gases precipitate to form gas bubbles and their growth induces dilation of the matrix. This dilation, technically designated as swelling, affects the structural integrity of nuclear fuels during their service. The estimated enthalpy of solution of helium in copper is 5.5 eV/atom. As a Consequence, its solubility in the copper matrix is extremely poor and it cannot enter a copper based matrix via any thermo-chemical route. Hence, recourse to a nuclear reaction is taken to impregnate copper with helium. Helium is produced in situ through neutron irradiation in copper-boron alloys as a result of (n, alpha) nuclear reaction between boron atoms and neutrons. The characteristic feature of the growth of helium gas bubbles driven by isothermal annealing of the metallic matrix is that their rate of growth is highly sensitive to the distance of the bubbles from the external surface of the specimen. The growth of gas bubbles as a function of time and temperature is modulated by the flow of vacancies from the free surface of the specimen. A theory for the surface induced growth of helium gas bubbles in the neutron irradiated copper-boron alloys is presented here.

The rates of dissolution of heavy crude oil in liquid solvents and rates of desorption of solvents from oil have been measured. The crude oil used is a non-volatile heavy oil of 4253 mPa.s viscosity at room temperature. The solvents used are hexane, heptane and toluene. When the oil (black) is contacted with a solvent (transparent) an interface is seen which moves with time and takes a very long time to become fuzzy. The rate of movementof the front is measured. The dissolution experiments give very consistent results, but there are two parameters involved, Do, the diffusivity at infinite dilution and alpha which determines the concentration dependence. As a result it is necessary to do desorption experiments to be able to calculate both constants from the rate of movement of the front data. However, desorption experiments could not be performed under conditions of low concentrations suitable for the present case because of the very viscous nature of the oil. As a result, although the desorption experiments also showed good results, they could not be used to obtain good values of the parameters. When Stokes-Einstein equation was used to calculate Do, excellent results were obtained with alpha ~ 10 for the dissolution experiments and good deal smaller for the desorption experiments. That result is used to conclude that the above form for concentration dependent diffusivity is correct and concentration dependence is very high at low solvent concentrations explaining the sharp interfaces during dissolution.Other evidences have also been offered.

<div>Mixing of stratified fluids due to motion of bubble swarms can happen through two major mechanisms. The first is the capture and transport of heavier liquid into the lighter layers by the bubble wake. The second is the mixing due to turbulent dispersion. Stratification also affects bubble dynamics in various ways, namely by reducing the horizontal and vertical bubble fluctuations and extent, altering the drag experienced by rising bubbles, and changing the wake dynamics. The objective of this study is to understand these explained phenomena by decoupling their effects from each other and studying them individually. CFD offers powerful capabilities to achieve the decoupling and perform in-depth analysis of the fluid flow. </div><div><br></div><div>Firstly, the study of mixing induced in stratified fluids by bubbly flow in a Hele-Shaw Cell will be performed. Simulations are run for a range of void fractions and Froude numbers. The confinement prevents turbulence production, and mixing occurs primarily due to transport of colder liquid into the hotter layers by the bubble wake. Bubbles move in a zigzag motion attributed to the periodic vortex shedding in their wake. We report the formation of horizontal clusters and establish a direct correlation between the size of clusters and the rise velocity of the bubbles. We report an increase in the buoyancy flux across the isopycnals as the void fraction increases. The fraction of energy production due to the buoyancy flux increases with the strength of stratification, giving rise to a higher mixing efficiency. At the same time, cross isopycnal diffusion is higher at weaker stratification strengths.</div><div><br></div><div>Subsequently, direct numerical simulations of up to 146 bubbles rising in unbounded stratified fluids are performed. Both the bubble dynamics and destratification effects caused by the bubble motion are analyzed. The importance of bubble deformability and bubble Reynolds numbers on the induced background mixing are studied by varying the $E\ddot{o}tv\ddot{o}s$ number in the range 1.55 to 4.95 and Reynolds number in the range 25 to 200. Highly deformable, high Reynolds number bubbles undergo path instabilities and give rise to higher levels of mixing. Liquid and bubble velocity fluctuations and pseudo-turbulence caused by the bubble motion in the unconfined setting are examined and are seen to play an important role in mixing statistics. An increase in turbulent kinetic energy (TKE) levels with void fraction is noted. TKE levels are seen to decrease slightly as the stratification strength is increased, indicating increasing stability and resistance to destratification. Regardless of the stratification strength, a kinetic energy spectrum slope value between $-3 \sim -3.25$ is reported depending on Reynolds number. The dependence of mixing parameters on the void-fraction of bubbles and stratification strength of the liquid is also presented. </div><div><br></div><div>Next, the study of buoyancy driven motion of a single air bubble in stratified liquid is undertaken. A range of parameters including Froude number, Reynolds number and Bond number are explored. The Reynolds and Bond numbers will be maintained at values where the bubble motion and wake can be assumed to be axisymmetric. Wake dynamics and drift-volumes associated with the bubble rising in the stratified fluid are analyzed. The presence of secondary and tertiary vortices, which are alternating in direction, in the wake of the bubble due to the negative buoyant force experienced by the isopycnals is reported. The isopycnals oscillate before coming back to their stable state and the frequency of oscillations increases with stratification strength. The dependence of drag coefficient, determined by an unsteady force balance, and steady state bubble velocities, on the above mentioned parameters are studied. Analysis of bubble rise in partial stratification reveals the differences between homogeneous and stratified mediums.</div><div><br></div><div>Since most stratified bubbly flows occur near the free surface, an attempt is made at modeling the bubble rise up-to the free surface and subsequent bubble bursting. A brief study of in-line bubble coalescence is also attempted and potential future work for bubbly flows with topological changes is discussed.</div>

When a sphere or a stream of water hits the surface of a pool of water and enters a crater or air cavity often forms. This topic has been studied, both formally and informally, for a long time. This dissertation investigates four areas of water impact that are still poorly understood using high-speed photography. First, it examines a stream of droplets impacting on a pool of water, similar to a faucet drizzling into a full bucket. For these types of impacts we predict the depth, diameter, velocity, and shape of the cavities that the droplet stream forms. Second, it examines what occurs when a sphere impacts a pool of soapy water, such as a bubble bath or kitchen sink. The minimum velocity for a cavity to form decreases when soap is present. If the water has bubbles on the surface, the sphere will always form a cavity. Third, it examines how different coatings on a sphere (car wax, etc.) affect whether the sphere forms a cavity, and it shows how the coating affect the shape of that cavity. Fourth, when objects impact a water surface they experience a large force, which many people have noticed when participating in cliff jumping, high diving, and belly flop competitions. We show that the force of impact can be reduced by 75% simply by allowing a mass of water to impact in front of the object.

Capillary flows continue to be important in numerous spacecraft systems where the effective magnitude of the gravity vector is approximately one millionth that of normal Earth gravity. Due to the free fall state of orbiting spacecraft, the effects of capillarity on the fluid systems onboard can dominate the fluid behavior over large length scales. In this research three investigations are pursued where the unique interplay between surface tension forces, wetting characteristics, and system geometry control the fluid behavior, whether in large systems aboard spacecraft, or micro-scale systems on Earth. First, efforts in support of two International Space Station (ISS) experiments are reported. A description of the development of a new NASA ground station at Portland State University is provided along with descriptions of astronaut training activities for the proper operation of four handheld experiments currently in orbit as part of the second iteration of the Capillary Flow Experiments (CFE-2). Concerning the latter, seven more vessels are expected to be launched to the ISS shortly. Analysis of the data alongside numerical simulations shows excellent agreement with theory, and a new intuitive method of viewing critical wetting angles and fluid bulk shift phenomena is offered. Secondly, during the CFE-2 space experiments, unplanned peripheral observations revealed that, on occasion, rapidly compressed air bubbles migrate along paths with vector components common to the residual acceleration onboard the ISS. Unexpectedly however, the migration velocities could be shown to be up to three orders of magnitude greater than the appropriate Stokes flow limit! Likely mechanisms are explored analytically and experimentally while citing prior theoretical works that may have anticipated such phenomena. Once properly understood, compressed bubble migration may be used as an elegant method for phase separation in spacecraft systems or microgravity-based materials manufacturing. Lastly, the stability of drops on surfaces is important in a variety of natural and industrial processes. So called 'wall-edge-vertex bound drops' (a.k.a. drops on blade tips or drops on leaf tips which they resemble) are explored using a numerical approach which applies the Surface Evolver algorithm through implementation of a new file layer and a multi-parameter sweep function. As part of a recently open sourced SE-FIT software, thousands of critical drop configurations are efficiently computed as functions of contact angle, blade edge vertex half-angle, and g-orientation. With the support of other graduate students, simple experiments are performed to benchmark the computations which are then correlated for ease of application. It is shown that sessile, pendant, and wall-edge bound drops are only limiting cases of the more generalized blade-bound drops, and that a ubiquitous 'dry leaf tip' is observed for a range of the critical geometric and wetting parameters.

The indebtedness of Swedish households has more than doubled in the last ten decades despite the implementation of a mortgage ceiling and stricter amortization requirements. This study takes form to investigate how it is possible that debt related to housing is rising while new regulations against it has been set and how housing prices continues to increase when lending is supposed to be harder.This analysis estimates whether there are indications of an existing price bubble in the housing market of Stockholm. It is done by testing fundamental economic factors to the price index of housing in Stockholm, to see if they support the price development. If the analysis shows that housing prices cannot be predicted by the fundamental economic factors, it is possible that the price is a self-running series1 which could be an indicator of a price bubble. If fundamental factors that are being used as control variables seem to follow the same trend as the price development of the housing market, the speculation of price bubble will be rejected.

The scarce internet access in Ethiopia puts heavy weight on traditional media and people to spread news and information. By testing if the marketing strategy Word of Mouth is applicable on informative content, rather than just brands and products, this thesis explore the motivation to spread news as well as how it is received by a non-internet using group. As with brands, a common trigger for WOM was the subject being brought up in a discussion, both offline and online. Conditions that increased WOM in marketing such as being sociable and feeling a responsibility also increased WOM for more political content. The study also found that there is a low trust for internet as a source, but a high trust for the word of many. If the message was heard multiple times it was more believable, even though a primary source was lacking. In general both internet users and non-internet users were actively spreading information with the reason that it needed to be spread, something that was concluded as a collectivist action where information is spread quickly through social ties. Non-internet users were considered to be extra fragile and exposed to fake news due to the unequal distribution of information and technology. Since trust was based on the message of many, echo chambers and confirmation bias is discussed, as well as how Ethiopia might tackle the segregation of technology in the country in order to decrease inequality in the future. / Den svaga tillgången till internetuppkoppling i Etiopien lägger ett stort ansvar på traditionell media, och människor, för att sprida nyheter och information till landets stora befolkning. Genom att testa om marknadsföringsstrategin Word of Mouth också är applicerbar på informativa budskap undersöker denna uppsats motivationen bakom att sprida nyheter, samt hur denna mottas av en grupp som inte använder internet. Liksom med varumärken var en vanlig trigger för WOM med informativ kontext att ämnet nämndes i en pågående diskussion, både online och offline. Förutsättningar som stärkte WOM vid marknadsföring, såsom att vara social och känna ett samhällsansvar ökade också WOM för nyheter. Studien fann också att det var låg tillit för internet som källa, men att det fanns stor tilltro till information som upprepades av olika personer. Ett budskap som hördes från flera olika var mer trovärdigt, oavsett vilken den primära källan var eller om den saknades helt. Generellt spred både internetanvändare och icke-användarna information av anledningen att det behövdes spridas och höras av alla invånare, vilket tolkades som en kollektivistisk handling där nyheter snabbt spreds i sociala nätverk. De som inte använder internet ansågs vara extra exponerade för fake news på grund av den ojämställda distributionen av information och tillgången till teknologi. Då tillit var baserat på upprepning från många diskuterar uppsatsen även echo chambers och confirmation bias, samt hur Etiopien i framtiden kan tackla den tekniska segregationen.

Bacteria in biofilms adhere well to surfaces and are quite difficult to remove. Oral plaque is one example of a biofilm. Many researchers have studied ways to remove plaque and bacteria from surfaces. It has been found that the passage of a bubble across a surface to which bacteria has adhered can remove the bacteria from the surface. Biofilms of Streptococcus mutans were grown on glass coverslips as a simple model for oral plaque. The coverslips were mounted in a Plexiglas chamber filled with artificial saliva. A bubble stream was directed at the mounted biofilm. The velocity, gas fraction, median bubble diameter, and impingement angle were all varied to determine the effect of each parameter on removal and which parameter was the most significant. To investigate the influence of sound on removal, a Ling oscillator was attached to the chamber, and was used simultaneously with and without a bubble stream. The acoustic intensity and the frequency were varied to determine if there was any effect on biofilm removal. Biofilm removal was also video taped. The results of these experiments confirmed that biofilms are removed by a stream of bubbles. Removal of biofilm is a function of stream velocity, gas fraction, and median bubble diameter, but not of impingement angle. The results of the acoustic experiments show that sound does not affect the removal of biofilm under the conditions used in these experiments. Mathematical models relating the removal of biofilm as a function of time were also developed from the data obtained from the video recording of the experiments. Additional tests using acoustic waves to remove biofilm should be performed to determine if more intense sound can remove biofilm. The intensity of the sound used in these experiments was low and the time of exposure was only 5 sec. Additional tests that more closely simulate the conditions of the mouth during brushing, like adding a surfactant, would also provide more insight as to whether bubbles in a clinical setting would remove biofilm.