The condition of Gas Bubble Trauma in fish was examined in terms of specific symptoms involving bubble development in the circulatory system and buccal cavities of fish. Based on a comparison between the conditions for bubble growth in fish exposed to supersaturated water and mammals exposed to hyperbaric and hypobaric decompression a mathematical model was developed describing environmental water threshold needed to initiate bubble growth in fish. The equation development yielded expressions which related the thresholds in total dissolved gas pressure required to initiate bubble growth in the circulatory system to the partial pressure ratio of dissolved oxygen in the environmental water, oxygen uptake ratio across the gill, the size of nucleation sites in the circulatory system, the surface tension of fish blood and environmental parameters such as water temperature, depth and barometric pressure. In the case of bubble growth in the buccal cavity, environmental water thresholds were related to total gas pressure, nuclei radius, water surface tension, water temperature, depth and barometric pressure. Bubble growth thresholds were examined for a range of the above dependent parameters. / Science, Faculty of / Zoology, Department of / Graduate

Fish exposed to gas supersaturated water often experience a form of stress known as Gas Bubble Trauma (GBT). GBT is an acute condition involving various forms of bubble growth both internal and external to the animal. Theoretical models are developed which establish thresholds for bubble growth. These models apply to: 1. ) Bubble growth in the vascular systems of fish. 2. ) Bubble growth in the environmental water that can occur in the buccal cavity and between gill lamella. 4.) Overinflation of the swimbladder. 3. ) Sub-dermal bubbles that occur on external skin surfaces such as the opercular flaps, between fin rays and in the lining of the mouth. In order to develop the models for general use, it was necessary to establish the effective size of nucleation sites and other physiological parameters contained in the bubble growth threshold equations. This was accomplished through a review of data from the scientific literature and a two phase experimental program. The literature review resulted in the compilation of a database containing over 1000 records of supersaturation data on salmonids. Various filters based on length, species, total gas pressure (TGP), partial pressure of oxygen (PO₂) and other criteria were applied to the database. The filtering operations established the existence of GBT mortality thresholds and identified relationships between other experimental parameters. The results of this analysis suggest that a lower threshold occurs at a water TGP of 1.10 Atms. and a higher threshold occurs at 1.15 to 1.18 Atms. However, it was not established that the apparent mortality thresholds correspond to thresholds for bubble growth predicted by the theoretical models. To make this correlation, a preliminary experimental study examined the physiological response of fish exposed to supersaturated water. It was found that arterial PO₂, hematocrit and blood pressure yield unique responses to bubble growth over specific ranges of water TGP. The results of these experiments also indicate that the lower mortality threshold of the database analyses is associated with a combination of sub-dermal bubble growth in the mouth and extracorporeal bubbles growing between gill lamella. The second phase of experimental study included surveys of blood PO₂, hematocrit and pH along with microscopic studies of intravascular and extracorporeal bubble growth in gills. The results of these experiments confirm the source of mortality for the lower threshold at a water TGP of 1.1 Atms. In addition, the data demonstrate that the upper TGP threshold of 1.15 to 1.18 Atms. of the database analysis corresponds to the threshold for intravascular bubble growth. The results further confirm that, as predicted by the theoretical model, intravascular bubble growth thresholds are dependent on water PO₂ . Combining the results of the database analysis and the experimental studies permitted the effective size of nucleation sites responsible for bubble growth to be back calculated from the theoretical equations. This completed the development of the bubble growth threshold equations. The equations can now be used to predict thresholds for the various forms of bubble growth and mortality that occur in fish exposed to supersaturated water. The experimental results also provide valuable information regarding the physiological response of fish to gas supersaturated water. / Science, Faculty of / Zoology, Department of / Graduate

The thesis presents a defocusing technique to extract bubble depth information. Typically, when a bubble is out of focus in an image, the bubble is ignored by applying a filter or thresholding. However, it is known that a bubble image becomes blurred as the bubble moves away from the focal plane. Then, this technique is applied to determine the bubble distance along the optical path based on the blurriness or intensity gradient information of the bubble. Using the image processing algorithm, images captured in three different experiments are analyzed to develop a correlation between the bubble distance and its intensity gradient. The suggested models to predict the bubble depth are also developed based on the measurement data and evaluated with the measured data. When the intensity gradient of the bubble is lower or when a bubble is located farther from the focal plane, the model can predict the distance more accurately. However, the models show larger absolute and relative error when the bubble is near the focal plane. To improve the prediction in that region, another model should be considered. Also, depth of field analysis is introduced in order to compare three experimental results with different imaging setups. The applicability of the approach is analyzed and evaluated. / Master of Science / Gas and liquid measurements of two-phase flow are very challenging, but it has become more important because of many industrial applications such as chemical, petroleum, and energy industries. Many two-phase flow measurement techniques have been developed and utilized for different flow conditions such as fiber optic probe, multi-sensor conductivity probe, wire-mesh sensor, as x-ray densitometry, particle image velocimetry (PIV), and optical imaging. With the development of the technology, the imaging technique can provide better spatial and temporal resolutions as well as image processing speed has improved greatly. In this study, the imaging and defocusing techniques are combined and used to extract bubble depth information. An image processing algorithm has been developed to process bubble images captured by high speed cameras. By measuring the blurriness or intensity gradient information of the bubble, the bubble distance along the optical path is determined. Based on the measurement data, mathematic models are developed to predict the bubble depth. In addition, depth of field analysis is suggested to compare three experimental results with different imaging setups. The applicability of the approach is analyzed and evaluated.

Wet central heating systems account for a very large portion of energy consumption in the UK and recent figures indicate that its usage in households will be increasing even further. Under such circumstances, it is desirable to use these systems in the most efficient way possible. However, dissolved gases that penetrate into central heating systems are later released as bubbles due to local supersaturated conditions occurring on the primary heat exchanger wall of the boiler. This leads to a two-phase flow throughout the pipework, causing microbubbles to escape to the upper parts of the system and creating cold spots in the radiators, thus, reducing its efficiency. There is an increasing trend in building services to install devices that remove these unwanted gases. Therefore, investigation of two-phase structures throughout different pipe installations will facilitate companies in enhancing their deaerator designs. In this regard, extensive experimental and computational investigations of two-phase flow structures were conducted within this study. Two-phase flow structures were measured by a photographic technique and investigated in means of void fractions, bubble sizes, and velocities. Fluid velocities in the range of 0.5 to 1.1 m/s at typical wet central heating temperature (60 to 80 °C) and pressures (2.2 to 27 bar) were utilized. Results show that that bubble production increases as temperature, boiler heating load, and saturation ratio escalate. On the other hand, it reduces when the pressure and flow rate of the system gets higher. A clear relationship between bubble sizes and system parameters was non-existent, except for the system flow rate (where bubble diameters decrease as the flow rate increases). Moreover, bubbles were evenly distributed during vertical flow when compared to horizontal flow, where bubbles tend to flow at the upper parts of the pipe. Furthermore, it was shown that bubble distributions were highly affected by obstacles like the 90 degree bend, thermocouple or pressure sensors. In addition, it was observed that axial flow development of bubbly flow was a continuous process and void fraction at the upper part of the pipe increased as the flow travelled through horizontal pipeline. Regarding the bubble velocity measurements, it was concluded that, bubble velocity profiles show development along both vertical and horizontal flows and approach to profiles which can be expressed with the power-law. Moreover, coalescence of two bubbles during horizontal flow was captured, emphasizing that the effect of coalescences should not be neglected at low void fractions. It was also found that bubbly flow in central heating systems was in a coalescences dominant regime and maximum bubble diameter observed at most positions were higher than theoretically defined values. Moreover, bubble dissolution effect was not observed at any of the test rig conditions. The reasons were thought to be the variation saturation ratio and axial flow development of two-phase flow, which supress the effect of dissolution and favour coalescence phenomenon. Finally, after evaluating conclusions from the experimental results and computational study regarding the effect of the 90 degree bend on void fraction distributions, it was concluded that the employed physical model and solver settings in ANSYS Fluent 14.5, can be utilized to predict bubble distribution developments throughout the central heating systems’ pipework. Keywords: Central heating systems, two-phase flow, bubbly flow, bubble distributions, bubble sizes, bubble velocities, coalescence, image processing, experimental fluid easurements.

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Gas bubbles that form within water treatment plants can disrupt drinking water treatment processes. Bubbles may form whenever the total dissolved gas pressure exceeds the local solution pressure, a condition termed dissolved gas "supersaturation." This project investigated how bubble formation affects conventional drinking water treatment and examined factors that can reduce these problems. Gas bubbles attached to coagulated floc particles can reduce settling efficiency and create "floating floc." In laboratory experiments, bubbles formed on the surface of the mixing paddle, since this was the location of minimum pressure within the system. The formation and stability of floating floc was dependent on many different factors including the amount and type of dissolved gas supersaturation and surface chemistry of the mixing paddle. The intensity and duration of rapid mixing also controlled the amount of floating floc. Bubbles forming in filter media can block pore spaces and create headloss, a process popularly termed "air binding." During benchscale filtration experiments, bubbles were released upwards from the media in a burping phenomenon, and bubbles could also be pushed downwards by fluid flow. Burping is beneficial since it partly alleviates the bubble induced headloss, but the media disruptions might also decrease filter efficiency (particle capture). Bubble formation within filters can be reduced by increasing the pressure inside the filter via greater submergence (water head above the media), lower hydraulic flow rate, or use of a more porous media. The mode of filter operation (declining or constant flow rate) will also affect the local filter pressure profile. Dissolved gas supersaturation and bubble formation are detected in on-line turbidity devices and particle counters causing spurious measurements. The use of bubble traps usually reduced these problems, but one device worsened turbidity spikes. Flow disturbances may also release bubbles upstream of the on-line turbidimeter, which can cause spikes in turbidity readings. / Ph. D.

Since the introduction of online HTTP-cookies, the technology has been widely discussed, both in terms of its actual function, as well as what it can do to users’ behaviors on the Internet. Cookies are small unique text files found within websites on the Internet that can collect and store personal information in order to enhance the users’ experience, as well as to provide the website with essential information about the user. By a literature review that was conducted on the subject, an unawareness among Internet users of how websites use cookies was found. Most users do not know what kind of information a cookie can store and how their privacy today can be violated. With this in mind, we conducted a internet based survey and a focus group interview to study journalism students and media and communication students knowledge about websites usage of cookies and furthermore, how the students opine the technology. This, since they are expected to have a higher knowledge than the general student about the subject since they are studying to assumably work within branches where they may have important parts regarding ICT in the future. By applying Michel Foucault theory Panopticon, Jürgen Habermas The Public Sphere and Sandra Petronio’s Communication Privacy Management Theory to the result of the study, we could see that there is a general unawareness among the students about what kind of information a cookie can collect. Also, the students express negative opinions regarding this harvesting of information, yet little effort is made to obstruct or deny web sites’ use of cookies.

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The objective of this thesis is to examine the differences in residential property prices across different cities in India. Soaring prices have led to increasingly unaffordable property prices in large metropolitan cities. As a result, there has been academic discourse about the existence of a housing bubble in recent years. In the past, empirical research has focused on national level trends due to a lack of city-level data. I investigate the city-fixed effects on growth in house prices across fifteen different cities. Although different empirical models suggest different conclusions about these effects, point estimates suggest above-normal growth in house prices in Delhi for the period 2009-2013.

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