An experimental investigation was performed to study the influence of the bubble size on an effervescent atomization. Experiments were conducted in horizontal facility with a 25.4mm diameter feeding pipe using water and air as the working fluids that were sprayed through an effervescent nozzle. Water flow rates from 113 to 189 kg/min and air to liquid mass ratios from 1% to 4% were selected. High speed photographs, of the bubbles in the feeding conduit and of the resulting droplets on the spray, were taken to use the particle projected areas to estimate their sizes. A monotonic positive correlation was found between the bubble size and the droplet size, in a fairly narrow range of feed flow void fractions. A bubble size sensitivity parameter was defined. Knowledge of the droplet behaviour provides data to enhance the design and operating conditions of the atomization process and a means to control droplet size.

An experimental investigation was performed to study the influence of the bubble size on an effervescent atomization. Experiments were conducted in horizontal facility with a 25.4mm diameter feeding pipe using water and air as the working fluids that were sprayed through an effervescent nozzle. Water flow rates from 113 to 189 kg/min and air to liquid mass ratios from 1% to 4% were selected. High speed photographs, of the bubbles in the feeding conduit and of the resulting droplets on the spray, were taken to use the particle projected areas to estimate their sizes. A monotonic positive correlation was found between the bubble size and the droplet size, in a fairly narrow range of feed flow void fractions. A bubble size sensitivity parameter was defined. Knowledge of the droplet behaviour provides data to enhance the design and operating conditions of the atomization process and a means to control droplet size.

A static electrochemical discharge machining (ECDM) tester, where the tungsten needle is used as the cathode and the platinum as the anode and the glass as the specimen, and the depth of electrode is set to be 1mm in the aqueous electrolyte of 30wt% KOH at the test time of 10s, is employed to investigate the influence of geometry and size of the electrode, supply voltage and gap on the characteristic of electrochemical discharge machining. According to the current/voltage measurements combined with the photographs of the bubble layer on the cathode and the behavior of discharge under different geometry and size of the electrode during the ECDM process, three regimes have been identified as: (I): non-machining. (II): glow discharge. (III): spark discharge. From the observation on the surface of machined glass specimen by using SEM, the experimental result show that damage of the glass increases with the increase of supply voltage.

The web is getting more and more characterized by personalization. Big socialnetworks like Facebook as well as the leading search engine Google increasingly usepersonalization algorithms to tailor the information that they present to users. All inorder to make the information more relevant and engaging for the end consumer. Howdoes this personalization affect journalists who increasingly search the web as a partof their journalistic research? In this essay we have looked at the effects thatpersonalization has on the journalists of tomorrow by conducting a survey amongstudents of journalism. We have also done a study of literature and theories to try anddetermine what consequences personalization will have on the internet in the future.We make an in depth study of the search engine Google as this is one of the mainsources of information for journalists and we have tried to tie this to theories of filter-bubbles and gatekeeping. We find that the question is in need of further studies toreally determine the threat that we face but conclude that information onpersonalization should be far more evident when it occurs.

Unwanted gas bubbles are a challenge for microfluidic-based systems, as adherence to channel networks can disrupt fluid delivery. This is especially true for devices with biological applications, as the presence of a single bubble creates thin fluid films with extremely high shear stresses, which can damage biological samples. Current strategies to remove bubbles require complicated fabrication or off-chip components. This thesis describes an on-chip microfluidic strategy utilizing permeation for in-plane trapping and removal of occasional gas bubbles. The trap was demonstrated with nitrogen bubbles, which were consistently removed at a rate of 0.14 µL/min for a single trap, and shown to have long-term operation capability by removing approximately 4,000 bubbles during one day without failure. The trap was integrated with a microfluidic system for the study of small blood vessels. Experiments were complemented with analytical and numerical models to characterize the bubble removal process.

Unwanted gas bubbles are a challenge for microfluidic-based systems, as adherence to channel networks can disrupt fluid delivery. This is especially true for devices with biological applications, as the presence of a single bubble creates thin fluid films with extremely high shear stresses, which can damage biological samples. Current strategies to remove bubbles require complicated fabrication or off-chip components. This thesis describes an on-chip microfluidic strategy utilizing permeation for in-plane trapping and removal of occasional gas bubbles. The trap was demonstrated with nitrogen bubbles, which were consistently removed at a rate of 0.14 µL/min for a single trap, and shown to have long-term operation capability by removing approximately 4,000 bubbles during one day without failure. The trap was integrated with a microfluidic system for the study of small blood vessels. Experiments were complemented with analytical and numerical models to characterize the bubble removal process.

The use of reduced oxygen-packaging techniques has resulted in anaerobic bacteria emerging as a problem for the brewing industry over the last twenty-five years. The genus Pectinatus, consisting of the species<i>P. cerevisiiphilus</i> and<i> P. frisingensis</i>, is a concern for producers of unpasteurized beer. As a result, there is an ongoing need to both understand this genus and develop rapid detection methodologies to combat its presence in the brewery. The objectives of this study were to sequence and characterize the flagellin genes from both Pectinatus species and evaluate the genes and proteins from a taxonomic and detection-suitability standpoint. <p>A combination of micro-protein sequencing, polymerase chain reaction (PCR) and Bubble-PCR was used to completely sequence one flagellin gene from each Pectinatus species. This knowledge was then utilized to sequence the flagellin gene from four additional Pectinatus isolates, two from each species. To confirm the identity of the flagellin genes, one flagellin gene from each species was cloned, expressed and detected with Pectinatus-specific antibodies. A discrepancy between of the predicted protein size and the actual protein size led to tests for glycosylation, a post-translational modification. Taxonomic analyses, based on the flagellin genes, were conducted at both the superkingdom and genus levels. Finally, genus- and species-specific PCR primer sets were designed and tested for the specific detection of Pectinatus in the brewery. <p>Cloning and expression data confirmed the identity of the sequenced genes as Pectinatus flagellin genes. Glycosylation was positively confirmed to be a post-translational modification for five of the six strains tested. Phylogenetic analysis revealed that both of the Pectinatus species grouped with the phylum Firmicutes (low G+C, Gram-positive bacteria) and that there was more diversity at the species level within the <i>P. frisingensis</i> flagellin gene than the <i>P. cerevisiiphilus</i> flagellin gene. As a final point, the detection of most Pectinatus isolates was achieved with the preliminary PCR primer sets designed, however, some non-Pectinatus beer spoilage organisms, primarily wort spoilage organisms, were also detected. Both the basic science and the applied results generated from this study will aid the brewing industry in its ongoing battle to control Pectinatus contamination.

Bubble and cavitation effects phenomena can be encountered in two-phase gas-liquid systems in industry. In certain industries, particularly high-risk systems such as a nuclear reactor/plant, the detection of bubble dynamics, and the monitoring and measurement of their characteristics are necessary in controlling temperature. While in the petro-chemical engineering industry, such as oil transportation pipelines, the detection and monitoring of bubbles/cavitation phenomena are necessary to minimise surface erosion in fluid carrying components or downstream facilities. The high sensitivity of Acoustic Emission (AE) technology is feasible for the detection and monitoring of bubble phenomena in a two phase gas-liquid system and is practical for application within the industry. Underwater measurement of bubble oscillations has been widely studied using hydrophones and employing acoustic techniques in the audible range. However, the application of Acoustic Emission (AE) technology to monitor bubble size has hitherto not been attempted. This thesis presents an experimental investigation aimed at exploring AEs from gas bubble formation, motion and destruction. AE in this particular investigation covers the frequency range of between 100 kHz to 1000 kHz. The AE waveform analysis showed that the AE parameter from single bubble inception and burst events, i.e. AE amplitude, AE duration and AE energy, increased with the increase of bubble size and liquid viscosity. This finding significantly extends the potential use of AE technology for detecting the presence of bubbles in two-phase flow. It is concluded that bubble activity can be detected and monitored by AE technology both intrusively and non-intrusively. Furthermore, the bubble size can be determined by measurement of the AE and this forms the significant contribution of this thesis.

This thesis is based on observations of the physical properties of wheat flour dough using ultrasonic measurements. Three frequency ranges were used in the study, low frequencies (near 40 kHz), intermediate frequencies (1 to 5 MHz, where bubble resonance effects are apparent), and high frequencies (near 20 MHz). Doughs mixed under different head space air pressures, from vacuum to atmospheric pressure, as well as under nitrogen, were studied at low frequency to investigate their relaxation behavior. Subsamples from ambient dough and vacuum dough displayed differences in the dependence of velocity and attenuation on time after compression, but no post mixing relaxation effect was apparent. A critical headspace pressure of approximately 0.16 atmospheres determined whether vacuum-like or ambient-like relaxation was observed. A peak in attenuation and changes in ultrasonic velocity were observed around the bubble resonance frequency, and these ultrasonic parameters changed substantially as a function of time. A bubble resonance model was used to interpret the results around the bubble resonance frequency, and bubble size distributions were estimated for ambient and vacuum dough from the ultrasonic data. For the high frequency range, a molecular relaxation model was used to interpret the results. Different fast relaxation times were observed for ambient dough (5 ns) and vacuum dough (1 ns). This relaxation time may be associated with conformational rearrangements in glutenin inside the dough matrix. These experiments have enabled dough relaxation to be probed over a very wide range of time scales (from ns to hours), and will lead to a better understanding of the role of dough matrix and gas cell effects on the physical properties of wheat flour doughs. / October 2007

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