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1.
Massimiliano Corsini Elisa Drelie Gelasca Touradj Ebrahimi Mauro Barni 《Multimedia, IEEE Transactions on》2007,9(2):247-256
This paper addresses the problem of assessing distortions produced by watermarking 3D meshes. In particular, a new methodology for subjective evaluation of the quality of 3D objects is proposed and implemented. Two objective metrics derived from measures of surface roughness are then proposed and their efficiency to predict the perceptual impact of 3D watermarking is assessed and compared with the state of the art. Results obtained show good correlations between the proposed objective metrics and subjective assessments by human observers 相似文献
2.
The kinetics of the carbothermal reduction of clay under argon atmosphere has been investigated by the X-ray diffraction method. The clay-carbon (excess) mixture was formed into 2 cm diameter disks of different thicknesses. Experimental data evidences the significant effect of sample thickness on the reaction rate at 1400 °C. Decreasing thickness promotes mullite dissociation and formation of SiC and alumina powders. Mathematical modeling of the reaction system showed the gas diffusion in the Knudsen regime through the pellet to be the rate controlling step. Diffusivity of CO and reacted core tortuosity factor have been calculated. 相似文献
3.
Kazem Tahmasebi Mohammad Maleki Shahraki Touraj Ebadzadeh 《Materials and Manufacturing Processes》2018,33(8):817-821
Coarse-grained ZnO varistors for low-voltage applications were prepared by microwave sintering technique under different soaking times of 5–150?min. For comparison, a low-voltage ZnO varistor was also prepared through a conventional sintering process. Microwave sintering remarkably enhanced the grain growth rate of ZnO varistors. Average grain size of the sample prepared by microwave sintering in 15?min was about 20?µm, which is similar to the grain size of sample prepared conventionally in 150?min time. In addition to grain growth, an increase in microwave sintering time led to precipitation of zinc titanate (Zn2TiO4) on the top surface of samples which sintered for long dwell times. X-ray diffraction and scanning electron microscopy results from different points of the samples declared that precipitation of Zn2TiO4 phase is due to the high rate of bismuth evaporation of Bi-rich liquid from top surface and the reaction between remaining titanium ions on the surface with ZnO. The results showed that increasing sintering time from 5 to 150?min increased the grain size from 14 to 33?µm, consequently, the breakdown field decreased from 90 to 27?V/mm, respectively. These changes led to a switch in the varistor application, from low to very low voltage. 相似文献
4.
Bayesian Network (BN) is a probabilistic graphical model which describes the joint probability distribution over a set of random variables. One of the most important challenges in the field of BNs is to find an optimal network structure based on an available training dataset. Since the problem of searching the optimal BN structure belongs to the class of NP-hard problems, typically greedy algorithms are used to solve it. In this paper a learning automata-based algorithm has been proposed to solve the BNs structure learning problem. There is a learning automaton corresponding with each random variable and at each stage of the proposed algorithm, named BNC-VLA, a set of learning automata is randomly activated and determined the graph edges that must be appeared in that stage. Finally, the constructed network is evaluated using a scoring function. As BNC-VLA algorithm proceeds, the learning process focuses on the BN structure with higher scores. The convergence of this algorithm is theoretically proved; and also some experiments are designed to evaluate the performance of it. Experimental results show that BNC-VLA is capable of finding the optimal structure of BN in an acceptable execution time; and comparing against other search-based methods, it outperforms them. 相似文献
5.
Saeed Hesaraki Touraj Ebadzadeh Shaghayegh Ahmadzadeh-Asl 《Journal of materials science. Materials in medicine》2010,21(7):2141-2149
In this study, bioceramic nanocomposites were synthesized by sintering compacted bodies of hydroxyapatite (HA) mixed with
5 or 15 wt% nanosilicon carbide at 1100 or 1200°C in a reducing atmosphere. Pure hydroxyapatite was also prepared for comparison.
Phase compositions, structural and physical properties of the composites were studied using appropriate techniques. Some in
vitro biological properties of the composites were also investigated by using newrat calvaria osteoblastic cells. X-ray diffraction
analysis indicated that tricalcium phosphate (TCP) comprising negligible α-TCP and considerable β-TCP were formed in composites
during sintering meanwhile hydroxyapatite and silicon carbide (SiC) were also existed in the composition. Based on the results,
that composite made of 5 wt% nanosilicon carbide exhibited higher bending strength, fracture toughness and bulk density than
pure HA and composite with 15 wt% silicon carbide. The scanning electron microscopy coupled with energy dispersive X-ray analysis
revealed that the addition of nanosilicon carbide suppressed the grain growth and yielded a feature of island-type clusters
consisting of blistered calcium phosphate (HA and TCP) and SiC grains. Also, in this study, better proliferation rate and
alkaline phosphatase activity were observed for the osteoblastic cells seeded on top of the composites compared to pure HA.
Overall, the results indicated that the composite of 95 wt% hydroxyapatite and 5 wt% SiC exhibited better mechanical and biological
properties than pure HA and further addition of SiC failed strength and toughness. 相似文献
6.
Microwave-assisted synthesis and sintering of mullite 总被引:2,自引:0,他引:2
Mullitization behaviour of a mixture of clay and alumina as the starting materials was examined by microwave heating of (a) mixed powder and (b) compacted powder samples for different soaking times. X-ray diffraction results showed that in compacted samples mullitization process was completed after 20 min heating with a density of about 87%. Densification and microstructure of samples with different green densities heated in a microwave oven and conventional electric furnace were compared. Results showed that the grain growth of mullite was restricted by microwave heating. 相似文献
7.
The effect of additions of SiC particulates on rheological and sintering behaviour of slip-cast alumina–zircon composites has been investigated. Finely divided alumina, zircon and silicon carbide powders were first processed into slips, using polyacrylite dispersant (0.5 wt.%) to create highly concentrated, stable aqueous suspensions at 40 vol.% loadings, from which test specimens which were then slip cast and dried. They were subsequently sintered in air for 2 h at 1650 °C. Rheological properties of the prepared slips were evaluated and related to the amount of added SiC. After sintering, the resultant porosities, fractional densities, crystallographic phases present, and microstructures were determined. 相似文献
8.
Water samples from a local water treatment plant were analyzed, using gas chromatography Fourier transform ion cyclotron resonance mass spectrometry (GC/FT-ICR MS), to identify potential disinfection byproducts (DBPs). Both liquid-liquid extraction (LLE) and solid-phase microextraction (SPME) techniques were used for sample preparation prior to GC/MS analyses. Based on the averaged mass measurement accuracy (MMA) of better than five parts-per-million (<5 ppm), multiple solvent artifacts were identified. It is shown that solventless SPME can be utilized to reduce potential interferences from solvent stabilizers. Six DBPs were detected and their molecular compositions were assigned at a high level of confidence. At the ppb concentration ranges and in the broadband mass spectral detection mode, internally calibrated mass spectra provided concurrent high resolution (resolving power M/deltaM50% > 30,000 at m/z values -110) and MMA of better than one part-per-million (MMA < 1 ppm). The use of thermochemical data, such as proton affinities, as a complementary tool to enhance analytical resolution is also demonstrated. 相似文献
9.
Farhad Golestani-fardMehdi Mazaheri Masoud AminzareT. Ebadzadeh 《Journal of the European Ceramic Society》2011,31(14):2593-2599
The densification and grain growth of bodies made from a commercial ultrafine alumina powder was investigated. The primary powder was initially subjected to dry (uniaxial cold pressing) and wet shaping (slip casting), followed by conventional (CS)-, two step (TSS)-, and microwave (MS) sintering to explore the effect of each series of treatments on the densification and microstructural evolution of the specimens. It was demonstrated that a uniform microstructure with higher density would be obtained using the wet shaping method. In addition, microwave sintering was found to be more effective into the densification of the specimens and in yielding a finer grain structure. It is believed that the high heating rate and effective particle packing are responsible for the improvements in these properties. On this basis, it was also demonstrated that the fracture toughness of the samples increased significantly through the application of microwave sintering. 相似文献
10.
H. Barzegar Bafrooei E. Taheri Nassaj T. Ebadzadeh C. F. Hu 《Journal of Materials Science: Materials in Electronics》2014,25(4):1620-1626
Sintering behavior, microstructures and microwave dielectric properties of ZnNb2O6 (ZN) ceramics prepared by reaction-sintering method were investigated. The X-ray diffraction patterns of the sintered samples revealed single-phase formation with a columbite structure after 1–5 h sintering at 1,025–1,125 °C. After sintering at 1,125 °C for 5 h, the ZN ceramics with the density of 5.56 g/cm3 (98.9 % of the theoretical density) and good microwave dielectric properties of εr = 23.9, Q × f = 51,000 and τf = ?62 ppm/°C were obtained. The obtained results demonstrated that the reaction-sintering process is a simple and effective method to prepare the ZN ceramics for applications on microwave dielectric resonators. 相似文献