Learning at large conferences : from the 'sage on the stage' to contemporary models of learning

Peer reviewe

Tax Shift: How to Help the Economy, Improve the Environment, and Get the Tax Man off Our Backs

In the other Washington, there's always talk of scrapping the federal tax code. It's no mystery why. The Internal Revenue Code runs to 7.5 million words and occupies, with regulations, one and one-half feet of shelf space. But complexity is not the worst fault of taxdom. The biggest and least-discussed problem is this: We tax the wrong things. Mostly, we tax things we want more of, such as paychecks and enterprise, not things we want less of, such as pollution and resource depletion. Naturally, we get less money and more messes. Doing the opposite would yield double dividends: cleaner air and flusher bank accounts. "Tax Shift" is a blueprint for a revolt that would get taxes off our backs and onto our side

Failure Investigation of an Intra-Manifold Explosion in a Horizontally-Mounted 870 lbf Reaction Control Thruster

In June 2010, an 870 lbf Space Shuttle Orbiter Reaction Control System Primary Thruster experienced an unintended shutdown during a test being performed at the NASA White Sands Test Facility. Subsequent removal and inspection of the thruster revealed permanent deformation and misalignment of the thruster valve mounting plate. Destructive evaluation determined that after three nominal firing sequences, the thruster had experienced an energetic event within the fuel (monomethylhydrazine) manifold at the start of the fourth firing sequence. The current understanding of the phenomenon of intra-manifold explosions in hypergolic bipropellant thrusters is documented in literature where it is colloquially referred to as a ZOT. The typical ZOT scenario involves operation of a thruster in a gravitational field with environmental pressures above the triple point pressure of the propellants. Post-firing, when the thruster valves are commanded closed, there remains a residual quantity of propellant in both the fuel and oxidizer (nitrogen tetroxide) injector manifolds known as the "dribble volume". In an ambient ground test configuration, these propellant volumes will drain from the injector manifolds but are impeded by the local atmospheric pressure. The evacuation of propellants from the thruster injector manifolds relies on the fluids vapor pressure to expel the liquid. The higher vapor pressure oxidizer will evacuate from the manifold before the lower vapor pressure fuel. The localized cooling resulting from the oxidizer boiling during manifold draining can result in fuel vapor migration and condensation in the oxidizer passage. The liquid fuel will then react with the oxidizer that enters the manifold during the next firing and may produce a localized high pressure reaction or explosion within the confines of the oxidizer injector manifold. The typical ZOT scenario was considered during this failure investigation, but was ultimately ruled out as a cause of the explosion. Converse to the typical ZOT failure mechanism, the failure of this particular thruster was determined to be the result of liquid oxidizer being present within the fuel manifold

Changing lifestyles and consumption patterns in developing countries: A scenario analysis for China and India

China and India are the world's largest developing economies and also two of the most populous countries. China, which now has more than 1.3 billion people, is expected to grow to more than 1.4 billion by 2050, and India with a population of 1 billion will overtake China to be the most populous country with about 1.6 billion population. These two countries are home to 37% of the world's population today. In addition, China and India have achieved notable success in their economic development characterised by a high rate of gross domestic product (GDP) growth in the last two decades. Together the two countries account already for almost a fifth of world GDP. The most direct and significant result of economic growth in India and China is the amazing improvement in quality of life (or at least spending power) for an increasing share of the population. The populations of both the countries have experienced a transition from ‘poverty’ to ‘adequate food and clothing’; today growing parts of the population are getting closer to ‘well to do lifestyles’. These segments of the society are not satisfied any more with enough food and clothes, but are also eager to obtain a quality life of high nutrient food, comfortable living, health care and other quality services. The theme of this paper is to analyse how the major drivers contributed to the environmental consequences in the past, and to take a forward look at the environmental impacts of these driving forces in China and India. The paper identifies population, affluence and technology to be the major driving forces in environmental pollution for these two countries then applies the simple equation of Impact=Population×Affluence×Technology, or I=PAT to evaluate the effects of changes in these drivers on CO2 emissions

Molecular mobility in polymer thin films

Fluorescence recovery after photobleaching was used to measure in-plane dye-probe diffusion coefficients, D, in thin films of monodisperse polystyrene supported on fused quartz substrates. The substrates were prepared with a high density of surface hydroxyl groups which interact favorably with repeat units of the polymer. The effects of temperature and film thickness were investigated, at temperatures above the bulk glass transition of the polymer, T_g, and in the range of film thicknesses from 1-10² times the radius of gyration (R_g) of individual polymer molecules. As the film thickness decreases towards R_g the value of D increases above the bulk values, with significant effects first appearing in films ≃20R_g. In the thinnest films studied, about 4R_g, the values of D lie as much as two orders over bulk values. At the same time, the temperature dependence of D becomes much weaker than in bulk. Analysis by free volume theory indicates that apparent values of both T_g and the thermal expansion coefficient for liquid state, α_L, decrease as the film thickness decreases. The possible effects of surface segregation of the dye probe are discussed

Molecular mobility in polymer thin films

Fluorescence recovery after photobleaching was used to measure in-plane dye-probe diffusion coefficients, D, in thin films of monodisperse polystyrene supported on fused quartz substrates. The substrates were prepared with a high density of surface hydroxyl groups which interact favorably with repeat units of the polymer. The effects of temperature and film thickness were investigated, at temperatures above the bulk glass transition of the polymer, T_g, and in the range of film thicknesses from 1-10² times the radius of gyration (R_g) of individual polymer molecules. As the film thickness decreases towards R_g the value of D increases above the bulk values, with significant effects first appearing in films ≃20R_g. In the thinnest films studied, about 4R_g, the values of D lie as much as two orders over bulk values. At the same time, the temperature dependence of D becomes much weaker than in bulk. Analysis by free volume theory indicates that apparent values of both T_g and the thermal expansion coefficient for liquid state, α_L, decrease as the film thickness decreases. The possible effects of surface segregation of the dye probe are discussed

Reactions at polymer interfaces: A Monte Carlo Simulation

Reactions at a strongly segregated interface of a symmetric binary polymer blend are investigated via Monte Carlo simulations. End functionalized homopolymers of different species interact at the interface instantaneously and irreversibly to form diblock copolymers. The simulations, in the framework of the bond fluctuation model, determine the time dependence of the copolymer production in the initial and intermediate time regime for small reactant concentration $\rho_0 R_g^3=0.163 ... 0.0406$. The results are compared to recent theories and simulation data of a simple reaction diffusion model. For the reactant concentration accessible in the simulation, no linear growth of the copolymer density is found in the initial regime, and a $\sqrt{t}$-law is observed in the intermediate stage.Comment: to appear in Macromolecule