12,346 research outputs found

    Morphological evolution of a 3D CME cloud reconstructed from three viewpoints

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    The propagation properties of coronal mass ejections (CMEs) are crucial to predict its geomagnetic effect. A newly developed three dimensional (3D) mask fitting reconstruction method using coronagraph images from three viewpoints has been described and applied to the CME ejected on August 7, 2010. The CME's 3D localisation, real shape and morphological evolution are presented. Due to its interaction with the ambient solar wind, the morphology of this CME changed significantly in the early phase of evolution. Two hours after its initiation, it was expanding almost self-similarly. CME's 3D localisation is quite helpful to link remote sensing observations to in situ measurements. The investigated CME was propagating to Venus with its flank just touching STEREO B. Its corresponding ICME in the interplanetary space shows a possible signature of a magnetic cloud with a preceding shock in VEX observations, while from STEREO B only a shock is observed. We have calculated three principle axes for the reconstructed 3D CME cloud. The orientation of the major axis is in general consistent with the orientation of a filament (polarity inversion line) observed by SDO/AIA and SDO/HMI. The flux rope axis derived by the MVA analysis from VEX indicates a radial-directed axis orientation. It might be that locally only the leg of the flux rope passed through VEX. The height and speed profiles from the Sun to Venus are obtained. We find that the CME speed possibly had been adjusted to the speed of the ambient solar wind flow after leaving COR2 field of view and before arriving Venus. A southward deflection of the CME from the source region is found from the trajectory of the CME geometric center. We attribute it to the influence of the coronal hole where the fast solar wind emanated from.Comment: ApJ, accepte

    Flow interaction between a streamwise oscillating cylinder and a downstream stationary cylinder

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    In this paper, we present some experimental results about the physical effects of a cylinder’s streamwise oscillation motion on a downstream one in a tandem arrangement. The upstream cylinder undergoes a controlled simple harmonic oscillation at amplitudes A/d = 0.2–0.8, where d is the cylinder diameter, and the frequency ratio of fe/fsfe/fs = 0–3.0, where fefe is the cylinder oscillation frequency and fsfs is the natural frequency of vortex shedding from a single stationary cylinder. Under these conditions, the vortex shedding is locked to the controlled oscillation motion. Flow visualisation using the planar laser-induced fluorescence and qualitative measurements using hot-wire anemometry reveal three distinct flow regimes behind the downstream cylinder. For fe/fs>(fe/fs)cfe/fs>(fe/fs)c , where (fe/fs)c(fe/fs)c is a critical frequency ratio which depends on A/d and Reynolds number Re, a so-called SA-mode occurs. The upstream oscillating cylinder generates binary vortices symmetrically arranged about the centreline, each containing a pair of counter-rotating vortices, and the downstream cylinder sheds vortices alternately at 0.5fe0.5fe . For 0.7–1.

    An empirical analysis of the influence of macroeconomic determinants on World tourism demand

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    This paper considers three econometric models to determine the relationship between macroeconomic variables and tourism demand. Tourism demand is measured by the inbound visitor's population and also by on-the-ground expenditures. Macroeconomic determinants include the exchange rate, the relative domestic prices, and the World GDP per capita. The database is an unbalanced panel of 218 countries over the period 1995-2012. There is evidence that an increase in the World's GDP per capita, a depreciation of the national currency, and a decline of relative domestic prices do help boosting the number of arrivals and the correspondent expenditure level. The World's GDP per capita is more relevant when explaining arrivals, but relative prices become more important when we use expenditures as the proxy for tourism demand. In particular, we cannot reject the hypothesis of a relative prices unitary elasticity of expenditures. Additionally, we have also partitioned our data by income level and by continent. Results are robust in the first partition, but less robust in the second, although the main conclusions still hold.info:eu-repo/semantics/acceptedVersio

    Towards run-time monitoring of web services conformance to business-level agreements

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    Web service behaviour is currently specified in a mixture of ways, often using methods that are only partially complete. These range from static functional specifications, based on interfaces in WSDL and preconditions in RIF, to business process simulations using executable process-based models such as BPEL, to detailed quality of service (QoS) agreements laid down in a service level agreement (SLA). This paper recognises that something similar to a SLA is required at the higher business level to govern the contract between service producers, brokers and consumers. We call this a business level agreement (BLA) and within this framework, seek to unify disparate aspects of functional specification, QoS and run-time verification. We propose that the method for validating a web service with respect to its advertised BLA should be based on run-time service monitoring. This is a position paper towards defining these goals

    Superconducting Pairing Symmetries in Anisotropic Triangular Quantum Antiferromagnets

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    Motivated by the recent discovery of a low temperature spin liquid phase in layered organic compound Îș\kappa-(ET)2_2Cu2_2(CN)3_3 which becomes a superconductor under pressure, we examine the phase transition of Mott insulating and superconducting (SC) states in a Hubbard-Heisenberg model on an anisotropic triangular lattice. We use a renormalized mean field theory to study the Gutzwiller projected BCS wavefucntions. The half filled electron system is a Mott insulator at large on-site repulsion UU, and is a superconductor at a moderate UU. The symmetry of the SC state depends on the anisotropy, and is gapful with dx2−y2+idxyd_{x^2-y^2}+id_{xy} symmetry near the isotropic limit and is gapless with dx2−y2d_{x^2-y^2} symmetry at small anisotropy ratio.Comment: 6 pages, 5 figure

    Where do They Head for University Studies? The University Destinations of Chinese IBDP Graduates: A Study of the International Baccalaureate Diploma Program in China

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    Paper PresentationConference theme: Educational Reform and Social Change: East-West DialogueOver the last decade, the number of IB programs adopted by schools around the world has dramatically increased by almost 400% (IB, 2009; Lee et al., in-press). In recent years China has also evidenced an impressive gain in the number of schools adopting IB programs in general and the DP in particular. Specifically, as of 2011, there were 50 IB schools authorized for the implementation of the DP in China. Of these, 43 schools have been authorized since 2003 (IB, 2012), illustrating the fast growth of IBDP schools in China in recent years. Despite such fast growth (and by implication, popularity) of the IBDP schools in China, empirical studies exploring the impact of Chinese IBDP students’ learning outcomes in terms of their university matriculation to foreign universities seems to be almost nonexistent. With this in mind, the primary goal of this proposal is to document the patterns of university destination of IBDP graduates in China over time. To this end, our analysis centers on the following overarching question: Where have Chinese students who previously graduated from the 50 IB schools been educated? Alongside the focus of the main question, we seek answers to more specific questions: Are there any trends in their university destinations in terms of geographical region or university prestige (by ranking)? Are there any significant differences in students’ enrolment in foreign universities before or after the 50 IB schools’ adoption of the DP (in the case that the 50 IB schools implemented different international programs other than the DP before they adopted the IB)? Does the adoption of the DP contribute to the growth (rate) of DP graduates enrolled in foreign universities? To investigate these questions, we adopt a theoretical framework from research of international student mobility. Specifically, we focus on internal and external forces (Altbach, Reisberg & Rumbley, 2009; Li & Bray, 2007) that influence IB graduates’ international flow in terms of university destination. We employ a sequential explanatory design (Creswell, Plano, Gutmann, & Hanson, 2003). As part of the mixed-methods research project, we plan to collect longitudinal data on DP graduates’ destinations for university study since the adoption of the DP. A series of quantitative analysis (e.g., descriptive trend analysis, pre/post comparison “before and after” the 50 IB schools’ adoption of the DP, and longitudinal analysis using piecewise modeling) will be employed to determine trends and patterns in terms of university matriculation of the 50 schools over time. As first of its kind, this study will evidence the impact of the DP on student preparation for university studies abroad. In addition, the dataset may be employed for broader purposes (e.g., program development or evaluation) within the IB and the community of schools in China or East Asian countries.published_or_final_versio
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