Gas transport and separation with ceramic membranes. Part I: Multilayer diffusion and capillary condensation

Multilayer diffusion and capillary condensation of propylene on supported γ-alumina films greatly improved the permeability and selectivity. Multilayer diffusion, occurring at relative pressures of 0.4 to 0.8 strongly increased the permeability of 6 times the Knudsen permeability, yielding permeabilities of 3.2 × 10−5 mol/m2-sec-Pa. The occurrence of a maximum in the permeability coincides with blocking of the pore by adsorbate (capillary condensation). This point could be predicted, employing adsorption data and the slit shape form of the pore. Separation factors of 27 were obtained with a N2---N3H6 mixture and a supported γ-alumina film, with C3H6 the preferentially permeating component. This very effective separation is due to pore blocking by adsorbate. The separation factor increased to 85 after modification of the system with magnesia by the reservoir method. However, the permeability of propylene decreased by a factor of 20 to 1.6 × 10−6 mol/m2-sec-Pa

Gas transport and separation with ceramic membranes. Part II: Synthesis and separation properties of microporous membranes

Non-supported microporous silica (amorphous) and titania thin films were made by the polymeric gel route. The titania system consisted of particles smaller than 5 nm. Reproducible modification of supported γ-alumina films with silica demands a strict control of every modification step. Silica films of 30–60 nm thickness on top of and presumably partly inside the γ-alumina film were realised. The permeabilities of helium and hydrogen through this film are activated, while the propylene permeability was below the detection limit. Separation factors of a H2---C3H6 mixture are larger than 200 at 200 °C with a flux of the preferentially hydrogen of 1.6 × 10−6 mol/m2-sec-Pa. The pores must be of molecular dimensions to realise this (< 1 nm diameter). Preliminary research shows that changes in the synthesis parameters result in higher activation energies and improved separation properties. The relation between synthesis, resulting microstructure and gas separation properties, however, is not yet fully understood

Gas and surface diffusion in modified γ-alumina systems

The transport of pure gases through a microporous membrane is described. The alumina-based membrane (pores 2.5-4 nm) is suitable for Knudsen diffusion separation. To improve the separation factor, interaction with and mobility on the pore wall of one of the gases of a mixture is necessary. To introduce surface diffusion of oxygen and hydrogen, a γ-alumina membrane was impregnated with silver. If temperature and atmosphere are controlled carefully, finely dispersed silver up to 17% by weight can be introduced. At higher loads and under oxidizing conditions, particle growth occurs. In adsorption experiments, little oxygen adsorption on the silver-modified γ-alumina could be detected. This is due to a decrease in accessible surface area of the silver because of particle growth of silver under oxygen. The mobility of hydrogen on the surface was tested by counterdiffusion experiments, of which the theory is given. Hydrogen shows a considerable mobility on the surface at 293 K. At low pressures the flux ratio of hydrogen to nitrogen improved from 3.8 to 8.8. Magnesia was introduced into the γ-alumina membrane to enhance the adsorption and mobility of CO2. It is known that 30% of the CO2 transport on non-modified γ-alumina is surface diffusion. The highest achievable magnesia load was 2.2% by weight. Introduction of magnesia into the γ-alumina surface gives more strong base sites and fewer weak base sites. This results in stronger bonding of CO2 on the surface, but the amount adsorbed is comparable with the amount of CO2 adsorbed on non-modified γ-alumina. The contribution of surface diffusion to the total transport decreases with the introduction of magnesia, as is shown by counterdiffusion. The more strongly bonded CO2 is less mobile, resulting in a smaller surface flux

Projective Group Representations in Quaternionic Hilbert Space

We extend the discussion of projective group representations in quaternionic Hilbert space which was given in our recent book. The associativity condition for quaternionic projective representations is formulated in terms of unitary operators and then analyzed in terms of their generator structure. The multi--centrality and centrality assumptions are also analyzed in generator terms, and implications of this analysis are discussed.Comment: 16 pages, no figures, plain Te

Third carpal bone sclerosis

The aims of this thesis were to evaluate the DPr-DDiO projection for the assessment of sclerosis and to study the relationships between altered third carpal bone (C3) radiopacity and previous exercise, previous carpal lameness, clinical appearance, and prognosis for future performance. Effects of positioning on radiographic appearance and depth of evaluated C3 were investigated in frozen specimens under beam-cassette angles of 15" to 45". Beam-cassette angles near 40" produced maximal depth of evaluated C3 but grading of sclerosis appeared insensitive to variations in beam-cassette angle in the range 25"-40". A comparison between grading of sclerosis and histomorphometrical bone density estimations in specimens from Standardbred trotters showed a higher bone volume density in subchondral compared to central cancellous bone. Mild sclerosis indicated that the subchondral cancellous bone had reached its maximal density while increasing sclerosis only reflected a further density-increase in central cancellous bone. The association between altered C3 radiopacity and degree of lameness and prognosis for racing was evaluated in a retrospective study of 89 Standardbred trotters diagnosed with traumatic carpitis. No significant relationships between degree of sclerosis and lameness or prognosis for racing within 30 months were found. However, radiolucencies ≥2 mm were found to significantly influence degree of lameness at presentation and time to start but did not affect chances of racing within 30 months. Factors affecting development of increased C3 radiopacity were evaluated in a longitudinal study of 14 Standardbred trotters in professional training, between the mean ages of 20 and 42 months. Carpal lameness was significantly associated with progression of sclerosis although in most cases, sclerosis developed irrespective of carpal lameness. No significant associations were found between grade of sclerosis and previous carpal lameness or between grade of sclerosis and level of performance, classified as training, qualified for racing and actively racing. Sclerosis appears to be of limited value as an indicator of clinical carpal disease or level of performance in Standardbred trotters while radiolucencies are clinically significant findings warranting further research

Evaluation of a health environment training for childcare providers

This qualitative study sought to identify barriers for supporting preschoolers\u27 healthy eating habits and physical activity levels. Almost 800 childcare providers throughout Riverside County were trained on Healthy Habits for Life from July 1, 2009 through December 31, 2009. Centers were for-profit commercial chains, state-funded preschools, or private centers, but they were not affiliated with a school district or a Head Start program. This preschool training is designed to make preschool providers aware of their role in preventing childhood obesity, and to instill good nutrition and physical activity related to the values in young children. This study is a short-term evaluation of the effectiveness of the Healthy Habits for Life training

An OSSE on Mesoscale Model Assimilation of Simulated HIRAD-Observed Hurricane Surface Winds

The hazards of landfalling hurricanes are well known, but progress on improving the intensity forecasts of these deadly storms at landfall has been slow. Many cite a lack of high-resolution data sets taken inside the core of a hurricane, and the lack of reliable measurements in extreme conditions near the surface of hurricanes, as possible reasons why even the most state-of-the-art forecasting models cannot seem to forecast intensity changes better. The Hurricane Imaging Radiometer (HIRAD) is a new airborne microwave remote sensor for observing hurricanes, and is operated and researched by NASA Marshall Space Flight Center in partnership with the NOAA Atlantic Oceanographic and Meteorological Laboratory/Hurricane Research Division, the University of Central Florida, the University of Michigan, and the University of Alabama in Huntsville. This instrument?s purpose is to study the wind field of a hurricane, specifically observing surface wind speeds and rain rates, in what has traditionally been the most difficult areas for other instruments to study; the high wind and heavy rain regions. Dr. T. N. Krishnamurti has studied various data assimilation techniques for hurricane and monsoon rain rates, and this study builds off of results obtained from utilizing his style of physical initializations of rainfall observations, but obtaining reliable observations in heavy rain regions has always presented trouble to our research of high-resolution rainfall forecasting. Reliable data from these regions at such a high resolution and wide swath as HIRAD provides is potentially very valuable to mesoscale forecasting of hurricane intensity. This study shows how the data assimilation technique of Ensemble Kalman Filtering (EnKF) in the Weather Research and Forecasting (WRF) model can be used to incorporate wind, and later rain rate, data into a mesoscale model forecast of hurricane intensity. The study makes use of an Observing System Simulation Experiment (OSSE) with a simulated HIRAD dataset sampled during a hurricane and uses EnKF to forecast the track and intensity prediction of the hurricane. Comparisons to truth and error metrics are used to assess the model?s forecast performance

Death, Poetry, And Dynastic Identity: Reimagining The Gardens At The Taj Mahal

Funerary gardens such as the Taj were spaces in which dynastic identities and literary culture entwined to form a physical landscape. I argue that the experience of the Taj through its gardens is not as singular as prior scholarship has suggested. Instead, a visitor would have experienced a landscape that was evocative not only of Quranic paradise but also of the power of the emperor and the imaginary garden landscapes of love, longing, and separation as created in Persian poetry. In studying the cultural memory of the Mughals and encompassing their patronage of both physical and imaginary gardens, it is evident that viewing the gardens simply through the conventional lens of a paradise garden and its attributes of shade and flowing water makes for an incomplete picture. In this thesis, I argue for a new way to reinterpret the gardens at the Taj Mahal, while considering the ambiguity between secular and religious and physical and imaginary landscapes, in which plantings, perspective, and sensory engagement are paramount. These categories allow dynastic identity, cultural memory, and quranic paradise to interact, making the process of reimagining the gardens more fruitful and experience focused

Gas separation mechanisms in microporous modified γ-al2o3 membranes

The transport of pure gases and of binary gas mixtures through a microporous composite membrane is discussed. The membrane consists of an alumina support with a mean pore diameter of 160 nm and an alumina top (separation) layer with pores of 2-4 nm. The theory of Knudsen diffusion, laminar flow and surface diffusion is used to describe the transport mechanisms. It appears for the composite membrane that Knudsen diffusion occurs in the toplayer and combined Knudsen diffusion/laminar flow in the support at pressure levels lower than 200 kPa. For the inert gas mixture H2/N2 separation factors near 3 could be achieved which is 80% of the theoretical Knudsen separation factor. This value is shown to be the product of the separation factor of the support (1.9) and of the top layer (1.5). The value for the top layer is rather low due to the relatively small pressure drop across this layer. This situation can be improved by using composite membranes consisting of three or more layers resulting in a larger pressure drop across the separation layer. \ud CO2 surface diffusion occurs on the internal surface of the investigated alumina membranes. At 250-300 K and a pressure of 100 kPa the contribution of surface diffusion flow measured by counterdiffusion is of the same order of magnitude as that resulting from gas diffusion. The adsorption energy amounts —25 kJ/mol and the surface coverage is 20% of a monolayer at 293 K and 100 kPa. The calculated surface diffusion coefficient is estimated to be 2-5 x 10-9 m2/sec. Modification of the internal pore surface with MgO increases the amount of adsorbed CO2 by 50-100%. Modifications with finely dispersed silver are performed to achieve O2 surface diffusion