5,949 research outputs found

    Web 2.0 technologies for learning at Key Stages 3 and 4: summary report

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    The research project on Web 2.0 technologies for learning at Key Stages 3 and 4 was a major initiative funded by Becta to investigate the use and impact of such technologies in and out of school. The purpose of this research was to help shape Becta's own thinking and inform policy-makers, schools and local authorities on the potential benefits of Web 2.0 technologies and how their use can be effectively and safely realised. This document is he summary of the reports published for this project

    Homological dimensions for co-rank one idempotent subalgebras

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    Let kk be an algebraically closed field and AA be a (left and right) Noetherian associative kk-algebra. Assume further that AA is either positively graded or semiperfect (this includes the class of finite dimensional kk-algebras, and kk-algebras that are finitely generated modules over a Noetherian central Henselian ring). Let ee be a primitive idempotent of AA, which we assume is of degree 00 if AA is positively graded. We consider the idempotent subalgebra Γ=(1−e)A(1−e)\Gamma = (1-e)A(1-e) and SeS_e the simple right AA-module Se=eA/eradAS_e = eA/e{\rm rad}A, where radA{\rm rad}A is the Jacobson radical of AA, or the graded Jacobson radical of AA if AA is positively graded. In this paper, we relate the homological dimensions of AA and Γ\Gamma, using the homological properties of SeS_e. First, if SeS_e has no self-extensions of any degree, then the global dimension of AA is finite if and only if that of Γ\Gamma is. On the other hand, if the global dimensions of both AA and Γ\Gamma are finite, then SeS_e cannot have self-extensions of degree greater than one, provided A/radAA/{\rm rad}A is finite dimensional.Comment: 24 page

    Commercial Real Estate Return Distributions: A Review Of Literature And Empirical Evidence

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    This paper review the literature on the distribution of commercial real estate returns. There is growing evidence that the assumption of normality in returns is not safe. Distributions are found to be peaked, fat-tailed and, tentatively, skewed. There is some evidence of compound distributions and non-linearity. Public traded real estate assets (such as property company or REIT shares) behave in a fashion more similar to other common stocks. However, as in equity markets, it would be unwise to assume normality uncritically. Empirical evidence for UK real estate markets is obtained by applying distribution fitting routines to IPD Monthly Index data for the aggregate index and selected sub-sectors. It is clear that normality is rejected in most cases. It is often argued that observed differences in real estate returns are a measurement issue resulting from appraiser behaviour. However, unsmoothing the series does not assist in modelling returns. A large proportion of returns are close to zero. This would be characteristic of a thinly-traded market where new information arrives infrequently. Analysis of quarterly data suggests that, over longer trading periods, return distributions may conform more closely to those found in other asset markets. These results have implications for the formulation and implementation of a multi-asset portfolio allocation strategy.Returns, Distributions, Normality, Asset Class

    Semi-stable subcategories for Euclidean quivers

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    In this paper, we study the semi-stable subcategories of the category of representations of a Euclidean quiver, and the possible intersections of these subcategories. Contrary to the Dynkin case, we find out that the intersection of semi-stable subcategories may not be semi-stable. However, only a finite number of exceptions occur, and we give a description of these subcategories. Moreover, one can attach a simplicial fan in Qn\mathbb{Q}^n to any acyclic quiver QQ, and this simplicial fan allows one to completely determine the canonical presentation of any element in Zn\mathbb{Z}^n. This fan has a nice description in the Dynkin and Euclidean cases: it is described using an arrangement of convex codimension-one subsets of Qn\mathbb{Q}^n, each such subset being indexed by a real Schur root or a set of quasi-simple objects. This fan also characterizes when two different stability conditions give rise to the same semi-stable subcategory.Comment: 39 page

    An experimental investigation of the aerodynamic characteristics of slanted base ogive cylinders using magnetic suspension technology

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    An experimental investigation is reported on slanted base ogive cylinders at zero incidence. The Mach number range is 0.05 to 0.3. All flow disturbances associated with wind tunnel supports are eliminated in this investigation by magnetically suspending the wind tunnel models. The sudden and drastic changes in the lift, pitching moment, and drag for a slight change in base slant angle are reported. Flow visualization with liquid crystals and oil is used to observe base flow patterns, which are responsible for the sudden changes in aerodynamic characteristics. Hysteretic effects in base flow pattern changes are present in this investigation and are reported. The effect of a wire support attachment on the 0 deg slanted base model is studied. Computational drag and transition location results using VSAERO and SANDRAG are presented and compared with experimental results. Base pressure measurements over the slanted bases are made with an onboard pressure transducer using remote data telemetry
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