Blown films of high molecular weight high density polyethylene (HMW-HDPE) were produced from two resins of differing molecular weight (MW) and molecular weight distribution (MWD) using a high stalk bubble configuration. The processing conditions were varied such that three film gauges, each fabricated at three frost line heights (FLH), were produced. Crystalline orientation and tear resistance properties of the films were measured. Under appropriate conditions, the formation of two populations of lamellar stacks with their surface normals orthogonal to one another were observed. Increasing the FLH increased the amount of transverse direction (TD) stacked lamellae. This finding was related to bubble shape and relaxation behavior. Balanced in plane crystalline orientation was noted to give the best dart impact performance. Interestingly, for the lower Mw resin in the study, this could be achieved by down gauging. In a second project, structure-property-processing relationships were investigated in a series of high density polyethylene (HDPE) blown films. The use of metallocene and chromium oxide based resins allowed the effects of MW and MWD on orientation behavior to be studied. All films possessed Keller-Machin low stress morphologies oriented along the film MD. Under identical processing conditions, the narrower MWD resins produced films with greater orientation than the broader MWD resins of equivalent weight average MW. Greater processing stresses and shorter quench times were noted to produce higher levels of orientation. Moisture vapor transmission rate (MVTR) performance of these films was also measured. Orientation effects were seen to influence MVTR as permeation behavior did not scale directly with the crystalline content in the films. Additional studies investigated the relationship between comonomer content and the thermal and structural properties of novel poly(acrylonitrile-co-methyl acrylate) materials. Five polymers were studied with methyl acrylate (MA) content varying between 0 and 15 mol%. The MA decreased both the glass transition and melting temperatures. Melting point depression was sufficient in the two highest MA content copolymers to allow for complete melting prior to the onset of thermal degradation using modest heating rates (20 ºC/min). Insight into the heterogeneous structure of poly(acrylonitrile) homopolymer was gained through both conventional and modulated differential scanning calorimetry. / Ph. D.

En raison de leurs propriétés : légèreté, isolation thermique et acoustique, résistance aux chocs. . . , les mousses de polymères sont omniprésentes dans notre société. Ce travail, portant sur les mousses de polyuréthane, a deux objectifs : remplacer les agents d’expansion physiques (CFC, HFC) par le dioxyde de carbone issu de la réaction isocyanate-eau & fixer le catalyseur au sein du réseau polyuréthane. Pour cela, les cinétiques des réactions de formation du réseau de polyuréthane et de libération du dioxyde de carbone sont étudiées séparément. La cinétique de polymérisation est étudiée par spectroscopie IRFT et par rhéométrie. Nous considérons les polyuréthanes linéaires et réticulés. L’effet de la nature du catalyseur et de sa concentration ainsi que celui de la température sur la cinétique de polymérisation a été étudié. L’intérêt du butanediol pour le contrôle de la structure du polyuréthane formé a été démontré. La triéthanolamine possédant des fonctions amines jouant le rôle de catalyseur et des fonctions hydroxyles permettant la réticulation est testée. Nous montrons que les paramètres suivants : température, masses du diisocyanate, nature et concentration en catalyseur, n’ont qu’une influence relativement limitée sur la cinétique de libération du dioxyde de carbone. Enfin, des mousses sont réalisées à partir d’une formulation industrielle et différents agents d’expansion physiques et chimique. Nous montrons qu’il est possible de remplacer ces agents par de l’eau. / Because of their properties (low density, insulation, impact resistance. . . ), polymer foams are widely used. This work focused on polyurethane foams aims at : replacing physical blowing agents (CFCs, HFCs) by the carbon dioxide formed by the reaction of isocyanate and water & trapping a catalyst in the polyurethane network. The formation of water-blown polyurethane foams involves two reactions. The polymerization (or gelling) reaction which creates the polyurethane network. And the blowing reaction which generates carbon dioxide. A proper balance is required between the two reaction rates to obtain a foam with atisfactory properties. The kinetics of each reaction considered separately was studied. Thus, on one hand IRFT and rheology were used to study the kinetic of the polyurethane formation. Both linear and crosslinked polyurethane were studied. We showed the interest of using utanediol to control the structure of the linear polyurethane. The effect of temperature and nature and concentration of catalyst on the kinetics of polymersation was showed. Moreover, triethanolamine which contains amine groups ( catalyst) and hydroxyl groups (crosslinkingagent) was tested. One the other hand, an appartus was made to study the kinetic of the blowing reaction. We show that the following parameters : temperature, weight of the diisocyanate, nature and concentration of catalyst, have a relatively limited influence on the kinetics of release of carbon dioxide. A study of polyurethane foams based on a commercial fomulation showed that it is possible to replace the physical blowing agents by water.

Results from Cal Poly's recent wind tunnel test, during the Winter of 2011-2012, in the 40- by 80-foot test section at the National Full-Scale Aerodynamics Complex (NFAC) at NASA Ames Research Center are presented. AMELIA, the Advanced Model for Extreme Lift and Improved Aeroacoustics, is the first full-span, cruise efficient, short take-off and landing (CESTOL) model incorporating leading- and trailing-edge blowing wing circulation control and over-the-wing mounted turbine propulsion simulators (TPS) to date. Testing of the 10 foot span model proved successful and was the result of a 5 year NASA Fundamental Aeronautics Program Research Announcement. The test generated extensive low-speed experimental aerodynamic and acoustic measurements. All of the results associated with Cal Poly's effort will be available in an open-source validation database with the goal of advancing the state-of-the-art in prediction capabilities for modeling aircraft with next generation technologies, focusing on NASA's N+2 generation goals. The model's modular design allowed for testing of 4 major configurations. Results from all configurations are presented. Out of a total of 292 data runs, 14 repeat run configurations were obtained. Overall repeatability of test data are good. Factors contributing to non-repeatability in the test data were assessed and showed high pressure air line temperature to be a primary factor. Test data shows drastic improvements in performance are obtained when incorporating leading edge blowing: wing stall can be delayed to more than 25 degrees angle-of-attack at lift coefficients exceeding six. Without the introduction of leading edge blowing to increase boundary layer momentum and maintain flow attachment around the leading edge, STOL performance suffers. Similar runs for isolated trailing edge blowing show a reduction in maximum lift coefficient to three with stall occurring at zero angle-of-attack. Testing at two engine pylon heights allowed for the highly coupled propulsion and flow control system to be characterized.

Aeolian sand transport models, widely employed by coastal scientists and managers, assume temporal and spatial homogeneity within the saltation field. This research questions that assumption by demonstrating that the saltation field is event-driven, therefore indicating that the saltation field is not temporally steady. The findings from this research may explain a portion of the conclusions from previous studies that indicated inequalities between model-estimated and field-measured aeolian sand transport. The relationship between unsteadiness in a turbulent wind field and pulses in a sand transport field was investigated on a beach near Shoalhaven Heads, New South Wales, Australia. Microphone-based saltation sensors, “miniphones,” and thermal anemometers (both instruments constructed exclusively for this field experiment) were co-located (0.02 m separation on center) and deployed between 0.01 and 0.0225 m above the bed, and sampled at 6000 Hz. Average grain size at the field site was 0.30 mm. Five runs totaling 2050 seconds of wind and saltation data were analyzed. The continuous wavelet transform, using the Morlet wavelet base, was the principle method for analyzing the wind and saltation records. The cross continuous wavelet transform was used to analyze the wind and saltation time series concurrently. Wind, saltation, and cross events were discerned by selecting wavelet power coefficients between wavelet scales of 0.4 and 3.0 seconds and with coefficients exceeding the 95% confidence interval. Average event spacing was 6.10, 6.50, and 6.73 seconds for the wind, saltation, and cross events, respectively. The average event spacing measured in this research was compared to the empirical-based model presented by Rao, Narashimha, and Narayanan (1971). The correspondence between the model and this research strongly suggests that bursting-type coherent structures were present. The durations of average wind, saltation, and cross events were 1.87, 2.10, and 1.73 seconds, respectively. Integral time scales, calculated using normalized auto correlation and power spectral density analysis, were approximately two seconds for the wind and saltation systems. The temporal coincidence of the integral time scale estimations and the event durations for the wind and saltation system strongly suggests that wind events are driving sand transport events.

Made available in DSpace on 2014-06-11T19:27:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-06-06Bitstream added on 2014-06-13T19:35:10Z : No. of bitstreams: 1 felipe_lm_me_jabo.pdf: 356871 bytes, checksum: 16d6d5f606db8c2a71fd32fc4c6570dc (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A deterioração “blown pack” é caracterizada por abundante produção de gás, induzindo a completa distensão da embalagem durante o processo de estocagem sob refrigeração. Quando a embalagem é aberta, há um odor desagradável, levemente fecal. O gás presente na embalagem é composto por dióxido de carbono e hidrogênio e por vários tipos butíricos do metabolismo fermentativo. O objetivo deste experimento foi determinar possíveis causadores deste tipo de deterioração, quantificando as populações de bactérias da família Enterobacteriaceae, e caracterizando-as nos principais gêneros e espécies encontradas, o número de bactérias ácido-lácticas, a freqüência de Clostridium estertheticum e do Clostridium gasigenes, em carnes próprias para o consumo e em carnes que apresentaram a deterioração “blown pack”. Para contagem e identificação dos membros da família Enterobacteriaceae e contagem de bactérias ácido-lácticas utilizou-se de técnicas microbiológicas clássicas. Já para pesquisa do C. estertheticum e C. gasigenes fez-se uso de técnicas de biologia molecular. Os microrganismos da família Enterobacteriaceae e bactérias ácido-láticas estavam presentes em populações elevadas e em maior número nas carnes com deterioração “blown pack”. A espécie mais freqüentemente encontrada foi a Hafnia alvei. As amostras com deterioração “blown pack’ apresentaram maior positividade para o C. estertethicum que amostras não deterioradas. Não houve diferença estatística de positividade para a presença do C. gasigenes entre amostras com deterioração “blown pack” e carnes não deterioradas. A principal forma de controle desta deterioração é a prevenção da contaminação da carne por material fecal. / The blown pack spoilage is characterised by abundant gas production, leading to complete gross distention pack during refrigerated storage. When the packaging is opened, there is an unpleasant smell, lightly fecal. The gas present in the package is composed of carbon dioxide and hydrogen and also of several butyric types of metabolism fermentation. The purpose of this experiment was to determine possible causes of this spoilage type, quantifying the populations of bacteria of the family Enterobacteriaceae, and characterizing them in the major genera and species found, the number of lactic acid bacteria, the frequency of Clostridium estertheticum and Clostridium gasigenes in meat proper for consumption and meat which showed the blown pack spoilage. In order to enumerate and identify the members of the Enterobacteriaceae family, and to enumerate the lactic acid bacteria the procedure was classical microbiological techniques. However to search the C. estertheticum and C. gasigenes the procedure was molecular biology techniques. The microorganisms of the family Enterobacteriaceae and lactic acid bacteria were present in large populations and in greater numbers in meat with blown pack spoilage. The species which were found more often was the Hafnia alvei. Samples of blown pack“ spoilage had greater positive features for C. estertethicum than samples not damaged. There was no statistical difference of positive features for the presence of C. gasigenes between samples of blown pack spoilage and not damaged meat. The main way to control this spoilage is the prevention of contamination of meat by fecal material.

This research programme explores, theoretically and experimentally, a new liftsystem for Vertical/Short Take-off and Landing (V/STOL) Aircraft. It is based upon an annular wing wrapped around a centrifugal flow generator, potentially creating a vehicle with no external moving parts, reduced vehicle aerodynamic losses compared to previous V/STOL technologies and substantially eliminating induced drag. It is shown that such a wing works best with a thick aerofoil section, and appears to offer greatest potential at a micro-aerial vehicle scale with regard to fundamental performance parameter “lift to weight ratio”. Certain efficiency losses are encountered mainly occurring from annular flow expansion and problems with achieving acceptable blower slot heights. Experimental methods are described along with results, and a comparison shows that the experimental values remain below theoretical values, partly due to flow asymmetry but possibly also other factors. Symmetrical blowing, as initially hypothesised, was found to be impracticable; this suggested use of pure upper surface blowing with Coanda effect. The modified approach was further explored and proved viable. The ultimate goal of this work was to develop an understanding and the facility to integrate the annular-wing into a vehicle to achieve controlled powered flight. To serve the purpose, issues encountered on current and past V/STOL aircraft are being investigated to set a path for further research/development and to validate/justify the design of future V/STOL aircraft. Also, presented is a feasibility study where different physical scales and propulsion systems are considered, and a turbofan has shown to achieve the best performance in terms of Range and Endurance. This privilege allows one to accurately study the V/STOL technologies around.

The aim of this thesis work is to increase the knowledge of phenomena taking place during the initial stage in a top blown converter. The work has been done in a few steps resulting in four different supplements. Water model experiments have been carried out using particle image velocimetry (PIV) technology. The system investigated was a fundamental top blown converter where an air jet was set to impinge on a water surface. The flow field of the combined blown case, where an air jet was introduced through a bottom nozzle, was also captured by the PIV. The work clearly showed that the flow field caused by an impinging top blown jet alone could not match that of the bottom blown case. The main re-circulation loop (or vortex) was investigated with respect to position and it was found that an increased flow rate pushes the center of the re-circulation loop downwards into the bath. However, for the top-blown case there is a point when the flow rate is too large to cause a distinguishable re-circulation loop since the jet becomes more plunging (i.e. penetrates deep into the bath) than impinging, with large surface agitation and splashing as a result.A numerical model with the same dimensions as the experimental system was then created. Three different turbulence models from the same family were tested: standard-, realizable- and a modified-(slight modification of one of the coefficients in order to produce less spreading of the air jet) k-ε turbulence model. It could be shown that for the family of k-ε turbulence models the difference in penetration depth was small and that the values corresponded well to literature data. However, when it comes to the position of the re-circulation loop it was shown that the realizable k-ε model produced better results when comparing the results to the experimental data produced from the PIV measurements, mentioned earlier.It was then shown how the computational fluid dynamics (CFD) model could be coupled to thermodynamics databases in order to solve for both reactions and transport in the system. Instead of an air-water system, a gas-steel-slag system was created using the knowledge obtained in the previous simulation step described above. Reactions between gas-steel, gas-slag, steel-slag and gas-steel-slag were considered. Extrapolation of data from a few seconds of simulation was used for comparison to experimental data from the literature and showed reasonable agreement. The overall conclusion was that it is possible to make a coupling of the Thermo-Calc databases and a CFD software to make dynamic simulations of metallurgical processes such as a top-blown converter.A parametric study was then undertaken where two different steel grades were tested; one with high initial carbon content (3.85 mass-%) and one with lower carbon content (0.5 mass-%). The initial silicon content was held constant at 0.84 mass-%. Different initial temperatures were tested and also some variation in initial dissolved oxygen content was tried. It was found that the rate of decarburization/desiliconization was influenced by the temperature and carbon concentration in the melt, where a high temperature as well as a high carbon concentration favors decarburization over desiliconization. It was also seen that the region affected by a lower concentration of alloys (or impurities) was quite small close to the axis where the impinging jet hits the bath. Add the oscillating nature of the cavity and it was realized that sampling from this region during an experiment might be quite difficult. / QC 20100720

<p>This thesis work aimed at increasing the knowledge regarding phenomena occurring when gas is injected using a top-blown lance on to a bath. All results are based on physical modeling studies carried out both using low and high gas flow rates and nozzle diameters ranging from 0.8 mm to 3.0 mm. At the low gas flow rates, the penetration depth in the bath was studied. The experiments focused on studying the effect of nozzle diameter, lance height and gas flow rate on the penetration depth. It was found that the penetration depth increases with decreasing nozzle diameter, decreasing lance height and with increasing gas flow rate. The results were also compared with previous work. More specifically, it was studied how the previous published empirical relationships fitted the current experimental data. It was found that the relationships of Banks [1], Davenport [2], Chatterjee [3] and Qian [4] agreed well with the experimental data of this investigation for nozzle diameters of 2.0 mm and 3.0 mm. However, for smaller nozzle diameters there were considerable deviations. Therefore, a new correlation heuristically derived from energy conservation consideration was suggested and showed better agreement for small nozzle diameters.</p><p>The experiments carried out at higher gas flow rates focused on the study of swirl motion. The effects of nozzle diameter, lance height, gas flow rate and aspect ratio on the swirl motion were investigated. The amplitude and period of the swirl as well as the starting time and the damping time of the swirl were determined. The amplitude was found to increase with an increased nozzle diameter and gas flow rate, while the period had a constant value of about 0.5 s for all nozzle diameters, gas flow rates and lance heights. The starting time for the swirl motion was found to decrease with an increased gas flow, while the damping time was found to be independent of gas flow rate, nozzle diameter, lance height and ratio of depth to diameter.</p>

No description available.

The objectives of this study were to determine the microbial ecology of “blown-pack” fresh beef obtained from a federally inspected facility and to use biopreservation to prevent spoilage of vacuum packaged chilled beef. Organic acids and alcohols in the purge obtained from the “blown” beef packages were detected using HPLC. PCR analysis indicated that Clostridium spp. were present in the purge of the commercial sample. Biochemical tests, RFLP and 16S rDNA sequencing were used to identify organisms isolated from the meat. Out of 66 isolated strains, 26 isolates were strict anaerobes and RFLP indicated that all were clonal isolates. Based on sequence analysis, the isolate was identified as Clostridium putrefaciens. The isolate caused “blown-pack” spoilage and produced butyric and propionic acids when inoculated onto fresh meat and Carnobacterium maltaromaticum UAL307 prevented the production gas and obvious signs of spoilage. / Food Science and Technology