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101.
Vincent Forest Loïc Barthe Gaël Guennebaud Mathias Paulin 《Computer Graphics Forum》2009,28(4):1111-1120
Efficiently computing robust soft shadows is a challenging and time consuming task. On the one hand, the quality of image-based shadows is inherently limited by the discrete property of their framework. On the other hand, object-based algorithms do not exhibit such discretization issues but they can only efficiently deal with triangles having a constant transmittance factor. This paper addresses this limitation. We propose a general algorithm for the computation of robust and accurate soft shadows for triangles with a spatially varying transmittance. We then show how this technique can be efficiently included into object-based soft shadow algorithms. This results in unified object-based frameworks for computing robust direct shadows for both standard and perforated triangles in fully animated scenes. 相似文献
102.
Pajot A Barthe L Paulin M Poulin P 《IEEE transactions on visualization and computer graphics》2011,17(8):1108-1121
We present a general method enhancing the robustness of estimators based on multiple importance sampling (MIS) in a numerical integration context. MIS minimizes variance of estimators for a given sampling configuration, but when this configuration is less adapted to the integrand, the resulting estimator suffers from extra variance. We address this issue by introducing the notion of "representativity" of a sampling strategy, and demonstrate how it can be used to increase robustness of estimators, by adapting them to the integrand. We first show how to compute representativities using common rendering informations such as BSDF, photon maps, or caches in order to choose the best sampling strategy for MIS. We then give hints to generalize our method to any integration problem and demonstrate that it can be used successfully to enhance robustness in different common rendering algorithms. 相似文献
103.
Lingfei Zhang José M.F. Ferreira Susana Olhero Loic Courtois Tao Zhang Eric Maire Jens Chr. Rauhe 《Acta Materialia》2012,60(10):4235-4246
Bulk and cellular cordierite ceramics were prepared from a non-stoichiometric powder consisting of corundum, talc (triclinic), α-quartz, K-feldspar, kaolinite, mullite and a small amount of a glass phase. The optimal sintering processing route was evaluated to obtain good mechanical properties. A high flexural strength of 120 MPa and a Young’s modulus of 99 GPa were achieved. The ceramic foams were fabricated by impregnation of polymer preforms with the optimized stock suspension. The mechanical properties of ceramic foams were studied by impulse excitation and compression tests. The Gibson–Ashby model predicted the ceramic foam’s effective modulus and its elastic limit strength well, as measured experimentally. In addition, the actual three-dimensional (3-D) structure obtained from X-ray computed tomography (CT) coupled with the finite element method (FEM) was used to calculate the Young’s modulus and the elasticity limit of the ceramic foam; however, this did not produce aby better agreement between the calculated values and the experimental results. The discrepancy between the Gibson–Ashby model and FEM could probably be attributed to the accuracy and small volume of representative reconstructed 3-D cellular structure. Taking account of the effect of the internal hollow structure on the stress localization in the ceramic struts, the CT–FE modeling provides a good measure of the adaptability and predictability of actual ceramic foam structures for realistic damage modeling. 相似文献
104.
Enabling situated knowledge management for complex instruments by real-time reconstruction of surface coordinate system on a mobile device 总被引:1,自引:1,他引:0
We have developed an approach to implementing a system for managing situated knowledge for complex instruments. Our aim is
to develop a system that guides a user through the steps for operating complex scientific instruments. A user manual is often
inadequate support for a community of users, so direct communication with an expert is often required. One reason for this
is that not all of the author’s expert knowledge was included in the manual, thus limiting the contents to explicit knowledge.
This is a main concern of modern knowledge management practitioners who are attempting to design systems that consider both
explicit and tacit knowledge. The key is to distribute explicit knowledge through interaction with the real world so that
users can develop tacit knowledge as well as acquire explicit knowledge. We describe technical difficulties related to referencing
the real world, which is required for interaction, and describe a novel approach to building a low-cost three-dimensional
pointer for obtaining the required knowledge, which constitutes our preliminary result. 相似文献
105.
We have studied the microstructure dependence of He bubble formation in silicon carbide. Helium accumulation in SiC was performed by 500 keV 3He implantation at room temperature with a fluence of 5 × 1015 cm?2. Depth concentration profiles have been investigated in 6H-SiC single crystals and α-SiC polycrystals by NRA spectrometry. Cross-sectional TEM samples have been imaged to study bubble formation. After annealing at 1300 °C, results clearly demonstrate an influence of grain boundaries on He retention yield in α-SiC polycrystals while helium is totally released from single crystals. Polycrystals also display the formation of intragranular overpressurized bubbles while no bubbles are observed in single crystals. Interpretations are proposed on the basis of the nature of He traps. 相似文献
106.
The behaviour of vacancy like implantation-induced defects created in the track region of 800 keV 3He ions in polycrystalline tungsten was studied by Doppler broadening spectroscopy as a function of annealing temperature. A slow positron beam, coupled with a Doppler broadening spectrometer, was used to measure the low- and high-momentum annihilation fractions, S and W, respectively, as a function of positron energy in tungsten samples implanted at different fluences from 1014 to 5 × 1016 cm−2. The behaviour of the S(E), W(E) and S(W) plots with the annealing temperature clearly indicates that the irradiation-induced vacancy like defects begin to evolve between 523 and 573 K, whatever the implantation fluence. This first temperature stage evolution corresponds to the migration of the monovacancies created during implantation to form larger vacancy like defects of which depth profile is different from the initial radiation-induced defects one. 相似文献
107.
Aurélie Gentils Florence Linez Aurélien Canizarès Patrick Simon Lionel Thomé Marie-France Barthe 《Journal of Materials Science》2011,46(19):6390-6395
This article reports on the influence of the ion energy on the damage induced by Au-ion implantation in silicon carbide single
crystals. 6H-SiC samples were implanted with Au ions at room temperature at two different energies: 4 and 20 MeV. Both Rutherford
Backscattering spectrometry in channelling geometry (RBS/C) and Raman spectroscopy were used to probe the ion implantation-induced
damage. Results show that the accumulated damage increases with the fluence up to the amorphization state. RBS/C data indicate
that 4-MeV implantation induces more damage than 20-MeV implantation at a given fluence. This effect is attributed to nuclear
collisions since the amount of damage is identical at 4 or 20 MeV when the fluence is rescaled in dpa. Surprisingly, Raman
data detect more damage for 20-MeV implantation than for 4-MeV implantation at low fluence (below 1013 cm−2) where point defects are likely formed. 相似文献
108.
L Stefan B Bertrand P Richard P Le Gendre F Denat M Picquet D Monchaud 《Chembiochem : a European journal of chemical biology》2012,13(13):1905-1912
The targeting of higher-order DNA structures has been thoroughly developed with G-quadruplex DNA but not with other structures like branched DNA (also known as DNA junctions). Because these alternative higher-order DNA architectures might be of high biological relevance, we implemented a high-throughput version of the FRET melting assay that enabled us to map the interactions of a candidate with four different DNA structures (duplex- and quadruplex DNA, three- and four-way junctions) in a rapid and reliable manner. We also introduce a novel index, the BONDS (branched and other noncanonical DNA selectivity) index, to conveniently quantify this differential affinity. 相似文献
109.
110.
Lily Deborde Rodolphe Sonnier Loic Dumazert Christophe Lanos Valentin Colson 《乙烯基与添加剂工艺杂志》2023,29(2):259-267
Integrating bio-resources in materials allows to reduce the environmental impact of the building industry. This study deals with fire-retardant treatments, alternative to boric acid and ammonium salts solutions, applied to hemp fibers for thermal insulation application. The aim is to limit the energy, sanitary and environmental impacts of the treatment, while optimizing the technical performances. A laboratory protocol evaluates the flame-retardant effect of the developed treatments. Treated fibers, including commercial treatments, are subjected to characterization tests: direct ignition small flame, thermal analysis (thermogravimetric analysis [TGA], differential thermal analysis [DTA]), pyrolysis-combustion flow calorimeter and cone calorimeter. Some of the methods have been adapted to be applied to fibrous materials. The obtained results orientate the formulation of a treatment and highlight the complementarity of the analysis methods. Coupling the results, the ConeTools's predictive model leads to the estimation of the reaction to fire class according to the Euroclass. Euroclass C appears accessible with a tailored treatment. 相似文献