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Hua Yang Shi-Xiao Wei Han Chen Lang Chen Chak-Tong Au Ting-Liang Xie Shuang-Feng Yin 《American Institute of Chemical Engineers》2022,68(10):e17810
A high-throughput (105.5 g/h) passive four-stage asymmetric oscillating feedback microreactor using chaotic mixing mechanism was developed to prepare aggregated Barium sulfate (BaSO4) particles of high primary nanoparticle size uniformity. Three-dimensional unsteady simulations showed that chaotic mixing could be induced by three unique secondary flows (i.e., vortex, recirculation, and oscillation), and the fluid oscillation mechanism was examined in detail. Simulations and Villermaux–Dushman experiments indicate that almost complete mixing down to molecular level can be achieved and the prepared BaSO4 nanoparticles were with narrow primary particle size distribution (PSD) having geometric standard deviation, σg, less than 1.43 when the total volumetric flow rate Qtotal was larger than 10 ml/min. By selecting Qtotal and reactant concentrations, average primary particle size can be controlled from 23 to 109 nm as determined by microscopy. An average size of 26 nm with narrow primary PSD (σg = 1.22) could be achieved at Qtotal of 160 ml/min. 相似文献
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Mobile Networks and Applications - In order to effectively identify the pattern of personalized adaptive learning in online education and improve the recommendation satisfaction of personalized... 相似文献
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《Ceramics International》2022,48(7):9495-9505
Effects of dopants with different valences on the densification behavior and phase composition of a ZrO2–SiO2 nanocrystalline glass-ceramic (NCGC) during pressureless sintering were investigated in this study. The raw powder of Ca2+, La3+, Ce4+ and Ta5+ ions doped ZrO2–SiO2 (referred to as Ca-ZS, La-ZS, Ce-ZS, Ta-ZS, respectively) and pure ZrO2–SiO2 (PZS) sample were synthesized by sol-gel method, followed by pressureless sintering. Compared with the PZS sample, doping of Ca2+ and La3+ ions significantly promoted the densification of the NCGCs. The “densification promotion” effect was attributed to the formation of oxygen vacancies and the decrease of SiO2 viscosity due to doping of aliovalent cations. The dopants with various valences showed significant effects on the phase compositions of the NCGCs during sintering. Doping of Ca2+ ion accelerated the reaction kinetics between ZrO2 nanocrystallites and amorphous SiO2 to yield ZrSiO4. The La3+ ion acted as destabilizer of t-ZrO2, which resulted in a rapid tetragonal (t) to monoclinic (m) ZrO2 phase transformation during sintering, while in the Ta5+ and Ce4+ ions doped sample, the phase transformation occurred gradually. All the doping ions increased the lattice parameters and the volume of t-ZrO2 unit cell, while the effects of the doping ions on the lattice parameters of m-ZrO2 unit cell were more complex. 相似文献
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《Journal of the European Ceramic Society》2022,42(13):5464-5475
In this paper, a new kinetic model considering both oxidation and volatilization kinetics is established and applied to analyze the oxidation of SiC-B4C-xAl2O3 ceramics and other systems in various oxidation conditions. The effects of diffusion area and volume changes during the oxidation process are considered in this model. The physical meaning of each parameter in this model is explicit and simple. According to this model, the diffusion coefficient of species and the corresponding diffusion activation energy are easily available. The practicability of this model is well verified by the experimental data of SiC-B4C-xAl2O3 and other systems oxidized under different conditions. In addition, the practice shows that the model is applicable not only to the systems where oxidation and volatilization coexist, but also to the system where only oxidation plays a major role. We hope the model proposed in this work can be used in other materials with more complex environments. 相似文献
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Joint photographic experts group (JPEG) can provide good quality with small file size but also eliminate extensively the redundancies of images. Therefore, hiding data into JPEG images in terms of maintaining high visual quality at small file sizes has been a great challenge for researchers. In this paper, an adaptive reversible data hiding method for JPEG images containing multiple two-dimensional (2D) histograms is proposed. Adaptability is mainly reflected in three aspects. The first one is to preferentially select sharper histograms for data embedding after histograms are established by constructing the th () histogram using the th non-zero alternating current (AC) coefficient of all the quantized discrete cosine transform blocks. On the other hand, to fully exploit the strong correlation between coefficients of one histogram, the smoothness of each coefficient is estimated by a block smoothness estimator so that a sharply-distributed 2D-histogram is constructed by combining two coefficients with similar smoothness into a pair. The pair corresponding to low complexity is selected priorly for data embedding, leading to high embedding performance while maintaining low file size. Besides, we design multiple embedding strategies to adaptively select the embedding strategy for each 2D histogram. Experimental results demonstrate that the proposed method can achieve higher rate–distortion performance which maintaining lower file storage space, compared with previous studies. 相似文献
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In this study, microbes were isolated from the rice slurry of a fermented rice cake to obtain lactic acid bacteria and yeast species. These species were identified using microbial physiology and gene sequence analyses. As the growth of the lactic acid bacterial strain R-2b and the yeast J-3a strains were found to be the best, a composite starter comprising these microbes was used for the preparation of fermented rice cakes. Based on single factor and orthogonal experiments, when the proportion of Lactobacillus plantarum, Saccharomyces cerevisiae, and Candida humilis was 1:3:6, the optimal fermentation conditions were addition of sugar and starter amounts of 20% and 6%, respectively, a fermentation temperature of 32 °C, and fermentation time of 8 h. The fermented rice cake with this optimum ratio had the most abundant volatile components and qualified physicochemical and microbial indexes. Additionally, the overall quality was better than that of commercially available products. 相似文献
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Neural Processing Letters - Graph convolutional networks (GCNs), which rely on graph structures to aggregate information of neighbors to output robust node embeddings, have been becoming a popular... 相似文献