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Displacement and mixed finite element formulations of shear localization in materials are presented. The formulations are based on hypoplastic constitutive laws for soils and the mixed enhanced treatment involving displacement, strain and stress rates as independently varied fields. Included in these formulations are the standard displacement method, the three‐field mixed formulation, the enhanced assumed strain method and the mixed enhanced strain method. Several numerical examples demonstrating the capability and performance of the different finite element formulations are presented. The numerical results are compared with available experimental data for Hostun RF sand and numerical results for Karlsruhe sand on biaxial tests. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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V. Cardoso M.C. Espírito Santo M. Paulos M. Pimenta B. Tom 《Astroparticle Physics》2005,22(5-6):399-407
According to recent conjectures on the existence of large extra dimensions in our universe, black holes could be produced during the interaction of Ultra High Energy Cosmic Rays with the atmosphere. However, and so far, the proposed signatures are based on statistical effects, not allowing identification on an event by event basis, and may lead to large uncertainties. In this note, events with a double bang topology, where the production and instantaneous decay of a microscopic black hole (first bang) is followed, at a measurable distance, by the decay of an energetic tau lepton (second bang) are proposed as an almost background free signature. The characteristics of these events and the capability of large cosmic ray experiments to detect them are discussed. 相似文献
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M. Melek 《Astrophysics and Space Science》1995,228(1-2):327-330
The aim of this brief report is to find a lower limit of the Hubble parameter using the COBE's detected fluctuations in the temperature of the CMBR. 相似文献
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Poroelastic two‐phase material modeling: theoretical formulation and embedded finite element method implementation 
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下载免费PDF全文 Nathan Benkemoun Rachel Gelet Emmanuel Roubin Jean‐Baptiste Colliat 《国际地质力学数值与分析法杂志》2015,39(12):1255-1275
This paper presents the formulation of FEMs for the numerical modeling of a poroelastic two‐phase (aggregates/mixture phase) solid. The displacement and pressure fields are decomposed, following the Enhanced Assumed Strain (EAS) method, into a regular part and an enhanced part. This leads to discontinuous strain and pressure gradient fields allowing to capture the jump in mechanical and hydrical properties passing through the interface between the aggregates and the mixture phase. All these enhanced fields are treated in the context of the embedded FEM through a local enhancement of the finite element interpolations as these jumps appear. The local character of these interpolations leads after a static condensation of the enhanced fields to a problem exhibiting the same structure as common poroelastic finite element models but incorporating now the mechanical and hydrical properties of a two‐phase solid. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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The MACFLY Collaboration: P. Colin A. Chukanov V. Grebenyuk D. Naumov P. Ndlec Yu. Nefedov A. Onofre S. Porokhovoi B. Sabirov L. Tkatchev 《Astroparticle Physics》2009,30(6):312-317
For most of the ultra-high-energy cosmic ray (UHECR) experiments and projects (HiRes, AUGER, TA, JEM-EUSO, TUS, …), the detection technique of extensive air showers is based, at least, on the measurement of the air-fluorescence-induced signal. The knowledge of the fluorescence-light yield (FLY) is of paramount importance for the UHECR energy reconstruction. The MACFLY experiment was designed to perform absolute measurements of the air FLY and to study its properties. Here, we report the result of measurement of dry-air FLY induced by 50 GeV electromagnetic showers as a function of the shower age and as a function of the pressure. The experiment was performed at CERN using a SPS-electron-test-beam line. The result shows the air FLY is proportional to the energy deposited in air (Ed). The ratio FLY/Ed and its pressure dependence remain constant independently of shower age, and more generally, independently of the excitation source used (single-electron track or air shower). 相似文献
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Hervé Cabot Christian Meynadier Dorota Sobczyńska Barbara Szabelska Jacek Szabelski Tadeusz Wibig 《Astroparticle Physics》1998,9(4):269-276
We describe the possible measurable difference in the Cherenkov light component of EAS induced by an electromagnetic particle (i.e., e+, e− or γ) and induced by a hadron (i.e., proton or heavier nuclei) in the TeV range. The method can be applied in experiments which use wave front sampling method of EAS Cherenkov light detection (e.g., THEMISTOCLE, ASGAT). 相似文献
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To determine the size of an extensive air shower it is not necessary to have knowledge of the function that describes the fall-off of signal size from the shower core (the lateral distribution function). In this paper an analysis with a simple Monte Carlo model is used to show that an optimum ground parameter can be identified for each individual shower. At this optimal core distance, ropt, the fluctuations in the expected signal, S(ropt), due to a lack of knowledge of the lateral distribution function are minimised. Furthermore it is shown that the optimum ground parameter is determined primarily by the array geometry, with little dependence on the energy or zenith angle of the shower or choice of lateral distribution function. For an array such as the Pierre Auger Southern Observatory, with detectors separated by 1500 m in a triangular configuration, the optimum distance at which to measure this characteristic signal is close to 1000 m. 相似文献
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