Wind tunnel flow generation section

A flow generation section for a wind tunnel test facility is described which provides a uniform flow for the wind tunnel test section over a range of different flow velocities. The throat of the flow generation section includes a pair of opposed boundary walls which are porous to the flowing medium in order to provide an increase of velocity by expansion. A plenum chamber is associated with the exterior side of each of such porous walls to separate the same from ambient pressure. A suction manifold is connected by suction lines with each one of the chambers. Valves are positioned in each of the lines to enable the suction manifold to be independently varied

Advanced porous transonic wind-tunnel nozzles

Advances in the design and control of the porous bleed flow distribution along the nozzle walls solves the problem of nonuniform flow at off-design conditions. This is accomplished in a two dimensional nozzle with porous parallel sidewalls backed with a single plenum chamber and employing a sliding compartment wall or backed with multiple plenum chambers within which the pressure can be controlled

Nuclear recoil energy scale in liquid xenon with application to the direct detection of dark matter

We show for the first time that the quenching of electronic excitation from nuclear recoils in liquid xenon is well-described by Lindhard theory, if the nuclear recoil energy is reconstructed using the combined (scintillation and ionization) energy scale proposed by Shutt {\it et al.}. We argue for the adoption of this perspective in favor of the existing preference for reconstructing nuclear recoil energy solely from primary scintillation. We show that signal partitioning into scintillation and ionization is well-described by the Thomas-Imel box model. We discuss the implications for liquid xenon detectors aimed at the direct detection of dark matter

Jet engine air intake system

An axisymmetric air intake system for a jet aircraft engine comprising a fixed cowl extending outwardly from the face of the engine, a centerbody coaxially disposed within the cowl, and an actuator for axially displacing the centerbody within the cowl was developed. The cowl and centerbody define a main airflow passageway therebetween, the configuration of which is changed by displacement of the centerbody. The centerbody includes a forwardly-located closeable air inlet which communicates with a centerbody auxiliary airflow passageway to provide auxiliary airflow to the engine. In one embodiment, a system for opening and closing the centerbody air inlet is provided by a dual-member centerbody, the forward member of which may be displaced axially with respect to the aft member

Aircraft engine nozzle

A variable area exit nozzle arrangement for an aircraft engine was a substantially reduced length and weight which comprises a number of longitudinally movable radial vanes and a number of fixed radial vanes. The movable radial vanes are alternately disposed with respect to the fixed radial vanes. A means is provided for displacing the movable vanes along the longitudinal axis of the engine relative to the fixed radial vanes which extend across the main exhaust flow of the engine

Statistical mechanics of a Feshbach coupled Bose-Fermi gas in an optical lattice

We consider an atomic Fermi gas confined in a uniform optical lattice potential, where the atoms can pair into molecules via a magnetic field controlled narrow Feshbach resonance. The phase diagram of the resulting atom-molecule mixture in chemical and thermal equilibrium is determined numerically in the absence of interactions under the constraint of particle conservation. In the limiting cases of vanishing or large lattice depth we derive simple analytical results for important thermodynamic quantities. One such quantity is the dissociation energy, defined as the detuning of the molecular energy spectrum with respect to the atomic one for which half of the atoms have been converted into dimers. Importantly we find that the dissociation energy has a non-monotonic dependence on lattice depth.Comment: 9 pages, 5 figure

Improvisation and teacher expertise: implications for the professional development of outstanding teachers

This paper reports on the findings of a PhD research project into the improvisatory nature of teacher expertise. The data is taken from a series of comparative case studies of seven experienced teachers working in secondary schools in the South West of England and who have been identified as being expert within their school setting. Constant comparative methods of analysis have been used to draw out themes from the data. This has contributed to a grounded theory that identifies the nature of teacher expertise. The findings that arise from the data are that teacher’s expertise is best expressed as continually evolving practice, a process as opposed to an end state that reflects a prototype model. Teacher expertise is seen as fundamentally improvisatory through being socially constructed and that this has a positive impact on the quality of teaching. A grounded theoretical model of teacher expertise casts new light on how we understand advanced professional practice and this paper explores the implications of this contribution to knowledge for school leaders, teachers, researchers and those with responsibility for the initial training and the continuing professional development of teachers

Discovery and Assessment of New Target Sites for Anti-HIV Therapies

Human immunodeficiency virus (HIV) infects cells by endocytosis and takes over parts of the cell’s reaction pathways in order to reproduce itself and spread the infection. One such pathway taken over by HIV becomes the inflammatory pathway which uses Nuclear Factor κB (NF-κB) as the principal transcription factor. Therefore, knocking out the NF-κB pathway would prevent HIV from reproducing itself. In this report, our goal is to produce a simple model for this pathway with which we can identify potential targets for anti-HIV therapies and test out various hypotheses. We present a very simple model with four coupled first-order ODEs and see what happens if we treat IκK concentration as a parameter that can be controlled (by some unspecified means). In Section 3, we augment this model to account for activation and deactivation of IκK, which is controlled (again, by some unspecified means) by TNF

The Asymmetric Effect of the Business Cycle on the Realtion between Stock Market Returns and their Volatility

We examine the relation between US stock market returns and the US business cycle for the period 1960 - 2003 using a new methodology that allows us to estimate a time-varying equity premium. We identify two channels in the transmission mechanism. One is through the mean of stock returns via the equity risk premium, and the other is through the volatility of returns. We provide support for previous findings based on simple correlation analysis that the relation is asymmetric with downturns in the business cycle having a greater negative impact on stock returns than the positive effect of upturns. We also obtain a new result, that demand and supply shocks affect stock returns differently. Our model of the relation between returns and their volatility encompasses CAPM, consumption CAPM and Merton's (1973) inter-temporal CAPM. It is implemented using a multi-variate GARCH-in-mean model with an asymmetric time-varying conditional heteroskedasticity and correlation structure.Equity returns, risk premium, asymmetry

An Asset Market Integration Test Based on Observable Macroeconomic Stochastic Discount Factors

There are a number of tests and measures of the degree of integration in the literature. An example is the idea that integrated markets should provide rates of return that are highly correlated with one another and that a measure of correlation provides an appropriate test. This particular idea is clearly false; for substantial periods of time we don't ever see stocks traded on the same market moving together. Specific models of what prices risk in individual markets could provide the basis of a test of integration. However, as has been widely shown, any differences between these pricing models will be subject to arbitrage by informed traders and so cannot form the basis for a test. In this paper we exploit the absence of arbitrage possibilities and the operation of the 'Law of One Price' in stochastic discount factor (SDF) theory to construct a test of integration based on a common approach to pricing assets in all markets, not only for stocks. The SDF approach that we adopt says that one SDF should price all assets as the model is not market or asset-specific.Unlike much of the literature, we adopt a direct parametric approach which takes estimates of an identical SDF from two asset markets and asks whether the price of risk associated with this SDF is the same for the two assets as SDF theory says it should. Another distinctive feature of our approach is that we employ observable macroeconomic factors. This allows us to estimate and compare the estimated risk premia in the markets concerned, with and without the integration restriction being applied. The paper uses this methodology to test market integration between the UK equity and FOREX markets. Our test rejects market integration for the consumption-based capital asset pricing model (CCAPM) and two variable SDF models based on consumption growth and inflation and on output and money growth. As equity and FOREX returns have a similar degree of variability, the finding that the risk premium in the FOREX market is generally much more variable than that in the equity market may contribute to the the test outcome.