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1.
GeoPDEs (http://geopdes.sourceforge.net) is a suite of free software tools for applications on Isogeometric Analysis (IGA). Its main focus is on providing a common framework for the implementation of the many IGA methods for the discretization of partial differential equations currently studied, mainly based on B-Splines and Non-Uniform Rational B-Splines (NURBS), while being flexible enough to allow users to implement new and more general methods with a relatively small effort. This paper presents the philosophy at the basis of the design of GeoPDEs and its relation to a quite comprehensive, abstract definition of IGA. 相似文献
2.
On the Assumed Natural Strain method to alleviate locking in solid-shell NURBS-based finite elements
J. F. Caseiro R. A. F. Valente A. Reali J. Kiendl F. Auricchio R. J. Alves de Sousa 《Computational Mechanics》2014,53(6):1341-1353
In isogeometric analysis (IGA), the functions used to describe the CAD geometry (such as NURBS) are also employed, in an isoparametric fashion, for the approximation of the unknown fields, leading to an exact geometry representation. Since the introduction of IGA, it has been shown that the high regularity properties of the employed functions lead in many cases to superior accuracy per degree of freedom with respect to standard FEM. However, as in Lagrangian elements, NURBS-based formulations can be negatively affected by the appearance of non-physical phenomena that “lock” the solution when constrained problems are considered. In order to alleviate such locking behaviors, the Assumed Natural Strain (ANS) method proposed for Lagrangian formulations is extended to NURBS-based elements in the present work, within the context of solid-shell formulations. The performance of the proposed methodology is assessed by means of a set of numerical examples. The results allow to conclude that the employment of the ANS method to quadratic NURBS-based elements successfully alleviates non-physical phenomena such as shear and membrane locking, significantly improving the element performance. 相似文献
3.
Agnesi A. Carra L. Pirzio F. Reali G. Tomaselli A. Scarpa D. Vacchi C. 《Quantum Electronics, IEEE Journal of》2006,42(8):772-776
An optimized diode-laser side-pumped grazing-incidence Nd:YVO/sub 4/ amplifier was used to increase the power of a 50-mW 150-MHz continuous-wave (CW)-pumped mode-locked oscillator up to 6.1 W in single pass, with 22% optical-to-optical efficiency, or up to 8.4 W in double pass, with 30% efficiency. Both beam quality (M/sup 2/<1.4 from TEM/sub 00/ seed pulses) and pulse duration (7.5 ps from 6.9 ps) were preserved. Single- or double-pass small-signal gain greater than 40 dB was achieved. These experimental results have been corroborated by a numerical model analysis of the amplifier. 相似文献
4.
V. Bidoli M. Casolino G. Furano L. Narici A. Morselli M. P. De Pascale P. Picozza E. Reali R. Sparvoli W. G. Sannita A. M. Gal''per N. R. Vavilov M. G. Korotkov A. V. Popov Yu. V. Ozerov A. M. Khodarovich S. V. Avdeev W. Bonvicini A. Vacchi N. Zampa G. Mazzenga M. Ricci P. Spillantini G. Castellini M. Boezio P. Carlson C. Fuglesang 《Instruments and Experimental Techniques》2001,44(5):623-625
An algorithm for reconstructing the characteristics (charge, mass, and energy) of cosmic-radiation nuclei with 20- to 200-MeV/nucleon energies is described. The detector is a telescope of three two-coordinate planes with two 1-mm-thick iron filters inserted between them. Each plane is composed of two strip silicon detectors with 3.6-mm-wide orthogonally oriented strips, an effective area of 6 × 6 cm2, and a thickness of 380 m. The algorithm for reconstructing the nuclei characteristics is based on the analysis of how the specific ionization losses change as the nuclei pass through the filter material. The results of the Monte Carlo simulation are presented for the energy dependence of the telescope acceptance and the energy deposited in the detectors by different nuclei in view of the detector calibration on the nuclear beams of the accelerator. The mass resolution of the telescope is 30, 12, and 5% for He, N, and Al nuclei, respectively. The energy resolution, which is 20%, is much the same for all nuclei. 相似文献
5.
The goal of this letter is to present a model to compute a quality-of-service (QoS) index to characterize IP services. Then, we show how such a score may be used in a clear and flexible way for defining advanced usage-based tariff criteria to charge QoS guaranteed network services to address the dynamics of the expected future telecommunications scenario. 相似文献
6.
Agnesi A. Dell'Acqua S. Piccinini E. Reali G. Piccinno G. 《Quantum Electronics, IEEE Journal of》1998,34(8):1480-1484
Powerful CW diode-pumped Nd:YAG and Nd:YVO4 lasers Q-switched by Cr:YAG saturable absorbers demonstrate efficient (30%-60%) harmonic and parametric conversion, generating hundreds of milliwatts from ultraviolet to mid-infrared 相似文献
7.
This study concerns a refrigerator-heat-pump desalination scheme (RHPDS), which allows energy-efficient recovery of fresh water and salt from the sea. In this scheme, a salt-water chamber is continuously refilled with sea water via atmospheric pressure. Sea water is evaporated into a vacuum chamber and the water vapor is condensed on top of a fresh-water chamber. A refrigerator-heat-pump circuit maintains the two water chambers at suitably different operating temperatures and allows efficient recovery of the latent heat of condensation. The scheme is analyzed with special consideration to potential exploitation of renewable energy sources such as solar and wind energy. 相似文献
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10.
The report presents an innovative solar barometric distillation technology for seawater desalting (SW-SBD) which has several attractive features such as: (1) efficient vacuum solar collectors of simple construction; (2) a barometric layout for quasi-steady operation at subatmospheric pressure; (3) a demister system of simple mechanical construction; and (4) an electronic control system regulating plant productivity parameters on available solar radiation flux. The proposed seawater desalting technology consists of single-effect distillation with water vapor produced and heated at subatmospheric pressure in a solar collector loop; the basic layout, operational features, and energy efficiency are presented and analysed in detail. Subsequent reports will provide technico-economical data from prototype desalting plants in view of industrial implementation. A promising specific electric energy consumption,∼2 kWm3 offresh water produced, was found by estimating pumping power requirements of major SW-SBD plant pumps. A sizable reduction in produced water cost with respect to an existing solar seawater desalting plant in Abu Dhabi is expected on the basis of a preliminary economic evaluation for a ∼100 m3/d plant prototype. 相似文献