538 research outputs found

    Elastoplastic Model of Sand under Complex Loading

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    The unified hardening model for overconsolidated clay is extended to the cyclic model considering the stress–strain relationship for sands by adopting the rotational hardening rule. The equations for the normal consolidated line and critical state line are revised in the e-lnp space to describe the breakage behavior of gravel sands under high pressures. The power function is used to define the above equations.Принцип унифицированной модели уплотнения для переуплотненной глины использован при построении циклической модели песка, которая учитывает зависимость напряжение–деформация и закон ротационного уплотнения. Поведение крупнозернистого песка при дроблении под действием высокого давления описывают уравнения для линии нормального уплотнения и линии критического состояния в e-lnp пространстве. В уравнениях использована степенная функция

    Phi Meson Production in Heavy-Ion Collisions at SIS Energies

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    Phi meson production in heavy-ion collisions at SIS/GSI energies (2\sim 2 GeV/nucleon) is studied in the relativistic transport model. We include contributions from baryon-baryon, pion-baryon, and kaon-antikaon collisions. The cross sections for the first two processes are obtained in an one-boson-exchange model, while that for the last process is taken to be of Breit-Wigner form through the phi meson resonance. The dominant contribution to phi meson production in heavy ion collisions at these energies is found to come from secondary pion-nucleon collisions. Effects due to medium modifications of kaon masses are also studied and are found to reduce the phi meson yield by about a factor of two, mainly because of increased phi decay width as a result of dropping kaon-antikaon masses. In this case, the ϕ/K\phi/K^- ratio is about 4%, which is a factor of 2-3 below preliminary experimental data from the FOPI collaboration at GSI. Including also the reduction of phi meson mass in medium increases this ratio to about 8%, which is then in reasonable agreement with the data.Comment: 46 pages, including 21 postscript figure

    The Kuiper Belt and Other Debris Disks

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    We discuss the current knowledge of the Solar system, focusing on bodies in the outer regions, on the information they provide concerning Solar system formation, and on the possible relationships that may exist between our system and the debris disks of other stars. Beyond the domains of the Terrestrial and giant planets, the comets in the Kuiper belt and the Oort cloud preserve some of our most pristine materials. The Kuiper belt, in particular, is a collisional dust source and a scientific bridge to the dusty "debris disks" observed around many nearby main-sequence stars. Study of the Solar system provides a level of detail that we cannot discern in the distant disks while observations of the disks may help to set the Solar system in proper context.Comment: 50 pages, 25 Figures. To appear in conference proceedings book "Astrophysics in the Next Decade

    Seeing phi meson through the dilepton spectra in heavy-ion collisions

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    Dilepton spectra from the decay of phi mesons produced in heavy-ion collisions at SIS/GSI energies (2\sim 2 GeV/nucleon) are studied in the relativistic transport model. We include phi mesons produced from baryon-baryon, pion-baryon, and kaon-antikaon collisions. The cross sections for the first two processes are obtained from an one-boson-exchange model, while that for the last process is taken to be the Breit-Wigner form through the phi meson resonance. For dileptons with invariant mass near the phi meson peak, we also include contributions from neutron-proton bremsstrahlung, pion-pion annihilation, and the decay of rho and omega mesons produced in baryon-baryon and meson-baryon collisions. Effects due to medium modifications of the kaon and vector (rho, omega and phi) meson properties are investigated. We find that the kaon medium effects lead to a broadening of the dilepton spectrum as a result of the increase of phi meson decay width. Furthermore, the dropping of phi meson mass in nuclear medium leads to a shoulder structure in the dilepton spectrum besides the main peak at the bare phi meson mass. The experimental measurement of the dilepton spectra from heavy-ion collisions is expected to provide useful information about the phi meson properties in dense matter.Comment: RevTeX, 18 pages, including 13 postscript figures, submitted to Nuclear Physics

    Measurements of ψ(2S)\psi(2S) decays into Vector- Tensor final states

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    Decays of the ψ(2S)\psi(2S) into vector plus tensor meson final states have been studied with 14 million ψ(2S)\psi(2S) events collected with the BESII detector. Branching fractions of \psi(2S) \rt \omega f_{2}(1270), ρa2(1320)\rho a_2(1320), K(892)0Kˉ2(1430)0+c.c.K^*(892)^0\bar{K}^*_2(1430)^0+c.c. and ϕf2(1525)\phi f_2^{\prime}(1525) are determined. They improve upon previous BESI results and confirm the violation of the "12%" rule for ψ(2S)\psi(2S) decays to VT channels with higher precision.Comment: 7 pages, 7 figures and 2 table

    Manifesto of computational social science

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    The increasing integration of technology into our lives has created unprecedented volumes of data on society's everyday behaviour. Such data opens up exciting new opportunities to work towards a quantitative understanding of our complex social systems, within the realms of a new discipline known as Computational Social Science. Against a background of financial crises, riots and international epidemics, the urgent need for a greater comprehension of the complexity of our interconnected global society and an ability to apply such insights in policy decisions is clear. This manifesto outlines the objectives of this new scientific direction, considering the challenges involved in it, and the extensive impact on science, technology and society that the success of this endeavour is likely to bring about.The publication of this work was partially supported by the European Union’s Seventh Framework Programme (FP7/2007–2013) under grant agreement No. 284709, a Coordination and Support Action in the Information and Communication Technologies activity area (‘FuturICT’ FET Flagship Pilot Project). We are grateful to the anonymous reviewers for the insightful comments.Publicad
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