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排序方式: 共有439条查询结果,搜索用时 18 毫秒
101.
Ramiro Varela Arias Camino Rodríguez Vela Jorge Puente Peinador Cesar Alonso González 《International journal of parallel programming》2000,28(3):275-319
We present a new model for parallel evaluation of logic programs. This model can exploit the main sources of parallelism that the language of logic expresses: Independent AND parallelism and OR parallelism, together with a secondary source emerging as a consequence of the Independent AND Parallelism: the producer/consumer parallelism. The efficiency is derived from the use of ordered structures for managing the information generated throughout the search process. The model is suitable for evaluating programs with a high degree of non-determinism because it never generates two processes for solving the same subgoal and hence it can exploit the same real parallelism generating a lower number of processes than other models. As an application example, we consider the Job Shop Scheduling problem. We report experimental results showing that logic programs can be designed that exhibit parallelism, and that the use of heuristic information translates into speedup in obtaining answers. 相似文献
102.
SnO2 samples were prepared as ultrafine powder by a chemical synthesis method and deposited on the surface of commercial float glass substrates. The glass surface was impregnated with these powders under high gas pressure (1.6-1.8 MPa) and heating to below the glass transition temperature in a designed pressurized chamber, forming SnO2 films on glass surface. Phases were analyzed by X-ray diffraction and the results confirmed the SnO2 powders as a single-phase tetragonal structure. Analysis of the chemical composition of glass substrates before and after powder impregnation revealed an ion exchange process caused by the substitution of sodium ions by tin ions on the glass surface. Differences in the surface morphology of SnO2 films on glass surface were related to the morphology of synthesized powders for deposition and impregnation. The mechanism of SnO2 films on glass surface was based on mass transfer between the glass substrates and SnO2 powders as a function of the treatment temperature. 相似文献
103.
Sophie Salasca Bruno Cantone André Grosman Basilio Esposito Fabio Moro Daniele Morocco Rosaria Villari Maurizio Angelone Esther Rincon Carlos Hidalgo Daniel Nagy Gabor Kocsis Paulo Varela Gabor Porempovics Guillaume Perrollaz Kunal Patel Yuri Krivchenkov Michael Walsh 《Fusion Engineering and Design》2013,88(6-8):602-606
Diagnostics in ITER are mandatory to characterize the parameters of plasma and study its interactions with plasma-facing components. Diagnostics components in the vicinity of the plasma are supported by metallic structures called port plugs. At the tokamak mid-plane, these components are installed in port plugs through intermediate structures called drawers. Apart from hosting the diagnostics, the port plugs act as shielding against neutrons and gammas, in order to limit the nuclear loads in crucial components (such as diagnostics and superconducting coils) as well as the dose levels in the controlled zones of the tokamak. The radiation shielding function of the port plugs is ensured through an optimized mixture of heavy metallic materials and water, forming shielding blocks surrounding the diagnostics and called Diagnostic Shield Modules (DSMs). These DSMs constitute the rear part of the drawers (the front part being composed of the Diagnostic First Wall). This paper presents the main results of a study performed in Europe on the integration of a particular diagnostics port plug, the Equatorial Port Plug 1 (EPP1). The paper first provides the results of the EPP1 diagnostics integration analysis. In a second step it focuses on the design of the EPP1 DSMs and summarizes the major results of a thorough set of analyses aiming at studying the DSMs behaviour under different loads, suggesting recommendations to improve their current design. 相似文献
104.
A wide band measurement campaign has been carried out in the DVB-T frequency band. The coherence bandwidth has been measured and its variation with the antennas separation is studied. Also, the relation between the coherence bandwidth and the RMS delay spread is investigated 相似文献
105.
G.F. Teixeira M.A. ZagheteG. Gasparotto M.G.S. CostaJ.W.M. Espinosa E. LongoJ.A. Varela 《Journal of Alloys and Compounds》2012,512(1):124-127
Micro-cube-shaped lead zirconate titanate was synthesized using the microwave-assisted hydrothermal method. Photoluminescence and field emission scanning electron microscopy were used for monitoring the formation of mesocrystals. Based on these results, a growth mechanism was then proposed which involved nanoparticle aggregation, nanoplate self-assembly on specific architecture and the final formation of mesoscopic micro-cube-shaped lead zirconate titanate. 相似文献
106.
Merenbloom SI Koeniger SL Valentine SJ Plasencia MD Clemmer DE 《Analytical chemistry》2006,78(8):2802-2809
Multidimensional ion mobility spectrometry (IMS-IMS and IMS-IMS-IMS) techniques have been combined with mass spectrometry (MS) and investigated as a means of generating and separating peptide and protein fragment ions. When fragments are generated inside a drift tube and then dispersed by IMS prior to MS analysis, it is possible to observe many features that are not apparent from MS analysis alone. The approach is demonstrated by examining fragmentation patterns arising from electrospray ion distributions of insulin chain B and ubiquitin. The multidimensional IMS approach makes it possible to select individual components for collisional activation and to disperse fragments based on differences in mobility prior to MS analysis. Such an approach makes it possible to observe many features not apparent by MS analysis alone. 相似文献
107.
Giraldi TR Ribeiro C Escote MT Conti TG Chiquito AJ Leite ER Longo E Varela JA 《Journal of nanoscience and nanotechnology》2006,6(12):3849-3853
The technological interest in transparent conductive oxide films (TCOs) has motivated several works in processing techniques, in order to obtain adequate routes to application. In this way, this work describes a new route to obtain antimony-doped tin oxide (ATO) films, based in colloidal dispersions of oxide nanocrystals. The nanoparticles were obtained by a hydrolisis method, using SnCl2 and SbCl3 in ethanolic solutions. The residual halides were removed by dyalisis, obtaining a limpid and transparent colloidal suspension. By this, the method offers the advantage of producing ultrathin films without organic contaminants. This route was employed to produce films with 5, 10, 14, and 18 mol% Sb doping, with thickness ranging from 40 to 70 nm. The physical characterization of the samples showed a uniform layer deposition, resulting in good packing density and high transmittance. A preliminar electrical study confirmed the low electrical resistivity even in the ultrathin films, in such level similar of reported data. The method described is similar in some aspects to layer-by-layer (LbL) techniques, allowing fine control of thickness and interesting properties for ultrathin films, however, with low cost when compared to similar routes. 相似文献
108.
In this study, the effect of bismuth content on the crystal structure, morphology and electric properties of barium bismuth niobate (BaBi2Nb2O9) thin films was explored with the aid of X-ray diffraction (XRD), scanning electron microcopy (SEM), atomic force microscopy (AFM) and dielectric properties. BaBi2Nb2O9 (BBN) thin films have been successfully prepared by the polymeric precursor methods and deposited by spin coating on Pt/Ti/SiO2/Si (1 0 0) substrates. The phase formation, the grain size and morphology of the thin films were influenced by the addition of bismuth in excess. It was observed that the formation of single phase BBN for films was prepared with excess of bismuth up to 2 wt%. The films prepared with excess of the bismuth showed higher grain size and better dielectric properties. The 2 wt% bismuth excess BBN thin film exhibited dielectric constant of about 335 with a loss of 0.049 at a frequency of 100 kHz at room temperature. 相似文献
109.
L.H. Oliveira A.P. de Moura T.M. Mazzo M.A. Ramírez L.S. Cavalcante S.G. Antonio W. Avansi V.R. Mastelaro E. Longo J.A. Varela 《Materials Chemistry and Physics》2012
In this paper, calcium copper titanate (Ca1−xCux)TiO3 microcrystals with (x = 0, 0.01 and 0.02) were synthesized by the microwave–hydrothermal method at 140 °C for 30 min. These crystals were analyzed by X-ray diffraction (XRD), Rietveld refinement, X-ray absorption near-edge structure spectroscopy (XANES), micro-Raman spectroscopy, field emission scanning electron microscopy (FE-SEM). Its optical properties were investigated by ultraviolet–visible (UV–vis) absorption and photoluminescence (PL) measurements. XRD patterns, Rietveld refinement and micro-Raman spectroscopy indicated that these crystals present a perovskite-type orthorhombic structure. The Rietveld refinement data, micro-Raman and XANES spectra suggested that the substitution of Ca by Cu in A-site promoted a displacement of Ti atoms to off-center symmetric, which leads distortions on the cuboctahedral [CaO12] clusters neighboring and consequently promotes a strain into the CaTiO3 lattice. FE-SEM images showed that these cube-like microcrystals have an irregular shape due to Ostwald-ripening and self-assembly of plates and cubes in growth process. The defects and distortions into lattice at medium- and short-range on the [CaO12]/[TiO6] clusters promotes the structural order–disorder responsible by the intense PL properties of these microcrystals. The microcrystals are promising candidates for future applications in optical devices. 相似文献
110.
R. S. Nasar M. Cerqueira E. Longo E. R. Leite A. J. Varela A. Beltrán J. Andrés 《Journal of Materials Science》1999,34(15):3659-3667
An experimental and theoretical study of the ferroelectric and piezoelectric behavior of PZT doped with barium is presented. Ab initio perturbed ion calculations was carried out. The properties, such as remnant polarization, coercive field and the coupling factor of the PZT at constant sintering temperature was compared with the Zr4+/Ti4+ ions dislocation energy and the lattice interaction energy. An agreement between the experimental and theoretical results, with a decrease of the interaction energy and an inversion of the energy stability from tetragonal to rhombohedral phase was observed. 相似文献