22,812 research outputs found

    Structural response of concrete-filled elliptical steel hollow sections under eccentric compression

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    The purpose of this research is to examine the behaviour of elliptical concrete-filled steel tubular stub columns under a combination of axial force and bending moment. Most of the research carried out to date involving concrete-filled steel sections has focussed on circular and rectangular tubes, with each shape exhibiting distinct behaviour. The degree of concrete confinement provided by the hollow section wall has been studied under pure compression but remains ambiguous for combined compressive and bending loads, with no current design provision for this loading combination. To explore the structural behaviour, laboratory tests were carried out using eight stub columns of two different tube wall thicknesses and applying axial compression under various eccentricities. Moment-rotation relationships were produced for each specimen to establish the influence of cross-section dimension and axis of bending on overall response. Full 3D finite element models were developed, comparing the effect of different material constitutive models, until good agreement was found. Finally, analytical interaction curves were generated assuming plastic behaviour and compared with the experimental and finite element results. Ground work provided from these tests paves the way for the development of future design guidelines on the member level

    What goes on when tertiary students are engaged in an online academic writing course?

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    The learning process is a complex one with many intertwining variables. The learners’ characteristics could be a defining factor and so is prior learning experiences and knowledge, which are the manifests of metacognitive, socio-affective and cognitive systems. A learning task engagement calls for an exertion of personal control and the fulfillment of efficiency expectations. In learning, the learner activates a number of processes such as those that concern attentional, retrieval, metacognitive and rehearsal strategies. McCombs (1988) sums up these complexities in his multimodal model of learning with certain underlying assumptions. Among them is that learning success can be manipulated. In promoting learning, the teacher can promote strategy learning such as self-directed learning. Learners if trained can select and be their own judge as to the efficacy of strategy use for the learning task. Lessard-Closton (1997) identified several basic characteristics to describe language learning strategies: they are learner-generated, they enhance language learning and competence, they may be visible or unseen and they involve the processing of information and the use of memory

    Where Graph Topology Matters: The Robust Subgraph Problem

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    Robustness is a critical measure of the resilience of large networked systems, such as transportation and communication networks. Most prior works focus on the global robustness of a given graph at large, e.g., by measuring its overall vulnerability to external attacks or random failures. In this paper, we turn attention to local robustness and pose a novel problem in the lines of subgraph mining: given a large graph, how can we find its most robust local subgraph (RLS)? We define a robust subgraph as a subset of nodes with high communicability among them, and formulate the RLS-PROBLEM of finding a subgraph of given size with maximum robustness in the host graph. Our formulation is related to the recently proposed general framework for the densest subgraph problem, however differs from it substantially in that besides the number of edges in the subgraph, robustness also concerns with the placement of edges, i.e., the subgraph topology. We show that the RLS-PROBLEM is NP-hard and propose two heuristic algorithms based on top-down and bottom-up search strategies. Further, we present modifications of our algorithms to handle three practical variants of the RLS-PROBLEM. Experiments on synthetic and real-world graphs demonstrate that we find subgraphs with larger robustness than the densest subgraphs even at lower densities, suggesting that the existing approaches are not suitable for the new problem setting.Comment: 13 pages, 10 Figures, 3 Tables, to appear at SDM 2015 (9 pages only

    A Rational Explanation for Boom-and-Bust Price Patterns in Real Estate Markets

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    This paper develops a stylized model to provide a rational explanation for the boom-and-bust price movement pattern that we frequently observe in the real world. Our stylized model indicates that there are three conditions to form a boom-and-bust price pattern in a community: a move-in of high income residents, wide income gap between new and existing residents, and supply process that leads to an inventory buildup. It seems that, based on these three conditions, China is more likely to experience a boom-and-bust price movement pattern than a developed country with a more mature and less vibrant economy.Real Estate Cycles; Boom-and-Bust; Supply Decision; Moving Costs

    Pricing Factors in Real Estate Markets: A Simple Preference Based Approach

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    Conventional wisdom tells us that the price level of properties should be supported by the rent they receive. This paper examines the pricing factors of properties by analyzing how individuals allocate their income to housing consumption and other goods, which in turn become the rent (or implicit rent) to support property values. Our model’s results can explain several puzzling observations in property markets, including why the variance of property appreciation rates is much higher than that of income growth rates in the same area.Preference-based model, pricing factors, property appreciation, property markets

    Supersolid and charge density-wave states from anisotropic interaction in an optical lattice

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    We show anisotropy of the dipole interaction between magnetic atoms or polar molecules can stabilize new quantum phases in an optical lattice. Using a well controlled numerical method based on the tensor network algorithm, we calculate phase diagram of the resultant effective Hamiltonian in a two-dimensional square lattice - an anisotropic Hubbard model of hard-core bosons with attractive interaction in one direction and repulsive interaction in the other direction. Besides the conventional superfluid and the Mott insulator states, we find the striped and the checkerboard charge density wave states and the supersolid phase that interconnect the superfluid and the striped solid states. The transition to the supersolid phase has a mechanism different from the case of the soft-core Bose Hubbard model.Comment: 5 pages, 5 figures
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