Abstract not available

Doctor of Philosophy / This research aimed to develop new cooling methods to replace, or at least minimise, the use of currently used grinding coolants which are known to be harmful to the environment. The methods used involved the application of a cold air and vegetable oil mist mixture (CAOM), and the use of liquid nitrogen as cooling media. Allied research focused on the development of a segmented grinding wheel equipped with a coolant chamber. The feasibility of a grinding system using CAOM was assessed on the surface grinding of plain carbon steel 1045. It was found that at low material removal rates, ground surfaces were obtained with a quality comparable to that from grinding with a conventional coolant in association with a reduction of grinding forces. There was no significant difference in the subsurface hardness of the components using CAOM, although the latter method showed a stronger dependence of surface residual stresses on the depth of cut due to the limit in cooling capacity of CAOM. The effects of using liquid nitrogen as a cooling medium on the microstructure of quenchable steel were explored. It was found that a martensite layer was induced on the ground surface. The microstructure featured a dispersion of very fine carbides within the martensite lattice, resulting in a remarkable increase in hardness and high compressive residual stresses within the layer. The topography of the ground surfaces indicated that the material was predominantly removed by brittle fracture. Furthermore surface oxidisation was suppressed. In the interest of coolant minimisation, a segmented wheel equipped with a pressurized coolant chamber was developed. A higher quality ground surface was obtained in conjunction with a coolant saving of up to 70%. In addition, the adhesion of ground chips on the wheel surface largely disappeared. Furthermore, surface tensile residual stresses caused by thermal deformation were minimised. The mechanism of coolant disintegration to form mists using this type of wheel system was studied. The Weber theory for Newtonian jet instability was applied to quantitatively determine the contribution of coolant flow rate to mist and ligament modes. A semi-analytical model was then developed to predict the mist flow rate by taking into account both grinding parameters and coolant properties. The model prediction was in agreement with experimental measurements. Based on the principles of fluid motion and the mechanisms of spin-off and splash, analytical models for both conventional and segmented wheels were established to provide a physical understanding of the mechanisms of coolant penetration into the grinding zone. Coolant minimisation was evident using the segmented wheel where the coolant pumping power into the grinding zone increased with wheel speed, but for the conventional wheel it decreased. A quantitative analysis was developed that accounted for the coolant properties and system design characteristics governing the penetration mechanism revealed by the theory established above. In conjunction with the mist formation analysis, the developed model offers a practical guideline for the optimal use of grinding coolants in achieving a balance between the demands of productivity and care for the environment.

The Double-TOP trap is a new type of magnetic trap for neutral atoms, and is suitable for Bose-Einstein condensates (BECs) and evaporatively cooled atoms. It combines features from two other magnetic traps, the Time-averaged Orbiting Potential (TOP) and Ioffe-Pritchard traps, so that a potential barrier can be raised in an otherwise parabolic potential. The cigar-like cloud of atoms (in the single-well configuration) is divided halfway along its length when the barrier is lifted. A theoretical model of the trap is presented. The double-well is characterised by the barrier height and well separation, which are weakly coupled. The accessible parameter space is found by considering experimental limits such as noise, yielding well separations from 230 [mu]m up to several millimetres, and barrier heights from 65 pK to 28 [mu]K (where the energies are scaled by Boltzmann�s constant). Potential experiments for Bose-Einstein condensates in this trap are considered. A Double-TOP trap has been constructed using the 3-coil style of Ioffe-Pritchard trap. Details of the design, construction and current control for these coils are given. Experiments on splitting thermal clouds were carried out, which revealed a tilt in the potential. Two independent BECs were simultaneously created by applying evaporative cooling to a divided thermal cloud. The Double-TOP trap is used to form a linear collider, allowing direct imaging of the interference between the s and d partial waves. By jumping from a double to single-well trap configuration, two ultra-cold clouds are launched towards a collision at the trap bottom. The available collision energies are centred on a d-wave shape resonance so that interference between the s and d partial waves is pronounced. Absorption imaging allows complete scattering information to be collected, and the images show a striking change in the angular distribution of atoms post-collision. The results are compared to a theoretical model, verifying that the technique is a useful new way to study cold collisions.

<p>Rapporten handlar om rörelsehindrades studie- och yrkesval och deras erfarenheter av studie- och yrkesvägledningen under studieåren. Undersökningens syfte är att visa på om respondenterna utsatts för ”cooling down” av sina studie- och yrkesvägledare. Den har genomförts medelst nio intervjuer med unga rörelsehindrade personer. Intervjuerna har analyserats med två kvalitativa analysmetoder, meningskoncentrering och dikotomi. Undersökningens resultat visar att en majoritet av respondenterna blivit utsatta för ”cooling down”- processer av vägledarna enligt följande: 1. Respondenten har haft en egen idé kring studie- och yrkesvalet men utsatts för brist på uppmuntran eller övertalningsförsök att välja andra utbildningar eller utbildningar med lägre krav. 2. Respondenten var i vägledningssituationen osäker på sitt mål och har utsatts för ”lobbying” att välja utbildningar som tycks stereotypa för gruppen till exempel data och kontor eller individuella programmet. Vägledarna fokuserar, i stor utsträckning, inte på individernas möjligheter utan verkar vilja begränsa dem efter de val de själva tycker är lämpliga. Nyckelord: Rörelsehinder, handikapp, cooling down, studie- och yrkesval, studie- och yrkesvägledning</p><p>This report deals with the career choices of the physically impaired their experiences of guidance counselling during their school years. The purpose of this study was to see if the informants had been exposed to ”cooling down” processes by their guidance counsellors. The used method for collecting material was nine qualitative interviews. The result shows that a majority of these informants had been exposed to processes of cooling down by their guidance counsellors as follows: 1. The informant has had his or her own idea of a choice but been exposed to a lack of encouragement or attempts at persuasion of different paths or more simple paths. 2. The informant had no ambition of his or her own and has been exposed to lobbying to choose educational paths that seem stereotype for the group such as office and computers or the individual program. The counsellors seem, to a great extent, to not focus on the abilities for these individuals but seem to have an ambition to limit their choices after what they themselves find is appropriate. Keywords: Physical impairment, disability, cooling down, career choices, guidance counselling</p>

The hot gas temperature in gas turbine engines is far above the permissible metal temperatures. Advanced cooling technologies must be applied to cool the blades, so they can withstand the extreme conditions. Film cooling is widely used in modern high temperature and high pressure blades as an active cooling scheme. In this study, the film cooling effectiveness in different regions of gas turbine blades was investigated with various film hole/slot configurations and mainstream flow conditions. The study consisted of four parts: 1) effect of upstream wake on blade surface film cooling, 2) effect of upstream vortex on platform purge flow cooling, 3) influence of hole shape and angle on leading edge film cooling and 4) slot film cooling on trailing edge. Pressure sensitive paint (PSP) technique was used to get the conduction-free film cooling effectiveness distribution. For the blade surface film cooling, the effectiveness from axial shaped holes and compound angle shaped holes were examined. Results showed that the compound angle shaped holes offer better film effectiveness than the axial shaped holes. The upstream stationary wakes have detrimental effect on film effectiveness in certain wake rod phase positions. For platform purge flow cooling, the stator-rotor gap was simulated by a typical labyrinth-like seal. Delta wings were used to generate vortex and modeled the passage vortex generated by the upstream vanes. Results showed that the upstream vortex reduces the film cooling effectiveness on the platform. For the leading edge film cooling, two film cooling designs, each with four film cooling hole configurations, were investigated. Results showed that the shaped holes provide higher film cooling effectiveness than the cylindrical holes at higher average blowing ratios. In the same range of average blowing ratio, the radial angle holes produce better effectiveness than the compound angle holes. The seven-row design results in much higher effectiveness than the three-row design. For the trailing edge slot cooling, the effect of slot lip thickness on film effectiveness under the two mainstream conditions was investigated. Results showed thinner lips offer higher effectiveness. The film effectiveness on the slots reduces when the incoming mainstream boundary layer thickness decreases.

Rapporten handlar om rörelsehindrades studie- och yrkesval och deras erfarenheter av studie- och yrkesvägledningen under studieåren. Undersökningens syfte är att visa på om respondenterna utsatts för ”cooling down” av sina studie- och yrkesvägledare. Den har genomförts medelst nio intervjuer med unga rörelsehindrade personer. Intervjuerna har analyserats med två kvalitativa analysmetoder, meningskoncentrering och dikotomi. Undersökningens resultat visar att en majoritet av respondenterna blivit utsatta för ”cooling down”- processer av vägledarna enligt följande: 1. Respondenten har haft en egen idé kring studie- och yrkesvalet men utsatts för brist på uppmuntran eller övertalningsförsök att välja andra utbildningar eller utbildningar med lägre krav. 2. Respondenten var i vägledningssituationen osäker på sitt mål och har utsatts för ”lobbying” att välja utbildningar som tycks stereotypa för gruppen till exempel data och kontor eller individuella programmet. Vägledarna fokuserar, i stor utsträckning, inte på individernas möjligheter utan verkar vilja begränsa dem efter de val de själva tycker är lämpliga. Nyckelord: Rörelsehinder, handikapp, cooling down, studie- och yrkesval, studie- och yrkesvägledning This report deals with the career choices of the physically impaired their experiences of guidance counselling during their school years. The purpose of this study was to see if the informants had been exposed to ”cooling down” processes by their guidance counsellors. The used method for collecting material was nine qualitative interviews. The result shows that a majority of these informants had been exposed to processes of cooling down by their guidance counsellors as follows: 1. The informant has had his or her own idea of a choice but been exposed to a lack of encouragement or attempts at persuasion of different paths or more simple paths. 2. The informant had no ambition of his or her own and has been exposed to lobbying to choose educational paths that seem stereotype for the group such as office and computers or the individual program. The counsellors seem, to a great extent, to not focus on the abilities for these individuals but seem to have an ambition to limit their choices after what they themselves find is appropriate. Keywords: Physical impairment, disability, cooling down, career choices, guidance counselling

An experimental activity was performed to observe and study the effects of graphite dispersion and deposition on thermal hydraulic phenomena in a Reactor Cavity Cooling System (RCCS). The small scale RCCS experimental facility (16.5cm x 16.5cm x 30.4cm) used for this activity represents half of the reactor cavity with an electrically heated vessel. Water flowing through five vertical pipes removes the heat produced in the vessel and releases it in the environment by mixing with cold water in a large tank. PIV technique was used to study the velocity field of the air inside the cavity. A set of 52 thermocouples was installed in the facility to monitor the temperature profiles of the vessel and pipes walls and air. 10g of a fine graphite powder (particle size average 2 [mu]m) were injected into the cavity through a spraying nozzle placed at the bottom of the vessel. Temperatures and air velocity field were recorded and compared with the measurements obtained before the graphite dispersion, showing a decrease of the temperature surfaces which was related to an increase in their emissivity. The results contribute to the understanding of the RCCS capability in case of an accident scenario.

In the event of a small break loss of coolant accident (SBLOCA) in a nuclear reactor, cold fluid is injected through the reactor system high pressure injector to compensate for the coolant loss. When this flow rate is less than a critical value, however, the hot fluid in the cold leg penetrates into the vertical injection line in a process called buoyant backflow. Because the resulting penetrations induce thermal stresses in the pipe, the presence of backflow in the injection lines is potentially significant. Since these penetrations could potentially damage the pipe, it was the purpose of this study to evaluate the backflow behavior. To this end, both the critical injection conditions and the subcritical penetration depth were experimentally determined through flow simulation in a 1/5 scale model. In addition, the experimental trends wi-re modeled theoretically. By matching the theoretical results to the experimental data, it was determined that backflow began below a critical Froude number of .65 and increased in depth with the negative logarithm of the injection velocity. The agreement between theory and experiment was excellent. For a certain class of reactor systems, the full scale Froude numbers were then compared to the critical value obtained in the analysis. For the systems involved in this comparison, the full scale Froude numbers were shown to be less than .65 for all practical flow rates. As a consequence, buoyant backflow is expected within the injection lines of these reactors, under safety injection conditions. / Graduation date: 1991

Interstitial laser thermal therapy is a novel local approach to treating prostate cancer. During treatment, thermal ablation may occur on the adjacent rectal wall. The aim of this thesis was therefore twofold: to study the effects of rectal cooling on lesion formation, and secondly, to engineer a computer controlled rectal cooling unit. To study the effects of the coolant temperatures and flow rate, thermal simulations were executed, followed by testing the phenomenon using agar gel phantoms which thermally mimic prostate tissue. Further simulations were run using a treatment planning software, which predicted the required coolant temperatures to protect the outer rectal wall while subsequently determining the shape and size of the resulting coagulated lesion at various laser settings. Results suggest that low coolant temperatures and low flow rates cause maximum cooling rates. Furthermore, the shape and size of the coagulated region is affected by coolant temperatures at specific laser powers and positions within the prostate.

Interstitial laser thermal therapy is a novel local approach to treating prostate cancer. During treatment, thermal ablation may occur on the adjacent rectal wall. The aim of this thesis was therefore twofold: to study the effects of rectal cooling on lesion formation, and secondly, to engineer a computer controlled rectal cooling unit. To study the effects of the coolant temperatures and flow rate, thermal simulations were executed, followed by testing the phenomenon using agar gel phantoms which thermally mimic prostate tissue. Further simulations were run using a treatment planning software, which predicted the required coolant temperatures to protect the outer rectal wall while subsequently determining the shape and size of the resulting coagulated lesion at various laser settings. Results suggest that low coolant temperatures and low flow rates cause maximum cooling rates. Furthermore, the shape and size of the coagulated region is affected by coolant temperatures at specific laser powers and positions within the prostate.