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921.
Zhichao Huang Junfeng Yao Zichun Zhong Yang Liu Xiaohu Guo 《Computer Graphics Forum》2014,33(7):239-248
Sparse localized decomposition is a useful technique to extract meaningful deformation components out of a training set of mesh data. However, existing methods cannot capture large rotational motion in the given mesh dataset. In this paper we present a new decomposition technique based on deformation gradients. Given a mesh dataset, the deformation gradient field is extracted, and decomposed into two groups: rotation field and stretching field, through polar decomposition. These two groups of deformation information are further processed through the sparse localized decomposition into the desired components. These sparse localized components can be linearly combined to form a meaningful deformation gradient field, and can be used to reconstruct the mesh through a least squares optimization step. Our experiments show that the proposed method addresses the rotation problem associated with traditional deformation decomposition techniques, making it suitable to handle not only stretched deformations, but also articulated motions that involve large rotations. 相似文献
922.
Jiuxin Jiang Bo Zhu Peiling Wang Weiwu Chen Dongsheng Yan Hanrui Zhuang Yibing Cheng 《Journal of the American Ceramic Society》2005,88(4):950-953
The Pr α-sialon powders prepared by self-propagating high-temperature synthesis (SHS), consisting of 55 wt% Pr α-sialon and 45 wt% of β-sialon (abbreviated as α' and β'), were hot-pressed at 1800°C for 1 h. The results showed that Pr α' phase would transfer to β' with the appearance of JEM phase (Pr(Si6− z Al z )(N10− z O z )) after sintering, thus resulting in the increase of β' phase to 86 wt%. The addition of Y2 O3 into SHS-ed Pr α' powders as the starting materials restrains the transformation of α' to β' and prevents the formation of JEM phase as well. The nucleation mechanism of Pr α' grain during hot-pressing was investigated in terms of transmission electron microscope and energy-dispersive spectrometer analysis. Two nucleation modes of Pr α' grains were found, i.e., nucleating on the undissolved Pr α' grains and on the nuclei of (Pr, Y) α' grains precipitated from liquid phase. 相似文献
923.
在全球变化等多种因素的影响下,许多流域的泥沙问题严重,泥沙管理的重要性日益突出。通过对联合国教科文组织国际泥沙计划所开展的案例研究进行综述,认识到自然地理特征、社会经济条件、水利工程建设对流域产沙、输沙和水资源利用有重要影响。土壤侵蚀加速、水库淤积、下游输沙量减少和生态平衡破坏是目前全球各大流域面临的主要问题。综合各项案例,研究泥沙管理技术,提出流域综合泥沙管理的策略,包括水库淤积管理、推移质泥沙管理、土地管理和水土保持等技术手段,以及法律、行政和组织措施。 相似文献
924.
925.
926.
927.
林产化学加工学科的现况与发展前景 总被引:2,自引:0,他引:2
本文了介绍了并论述了林产化学加工学科所含的五个专业方向,木材化学加工工程,树木提取物化学工程,林产生物化工,木材保护与改性,林产化工装备与控制的研究内容,工业现状,存在问题与发展前景。 相似文献
928.
合成丁酸异戊酯的新方法 总被引:3,自引:0,他引:3
采用超强酸代替浓硫酸作催化剂,对丁酸异戊酯合成反应进行了研究,讨论了影响收率的多种因素,在最佳条件下,酯化反应时间短,催化剂可以重复使用,丁酸异戊酯收率达到98%。 相似文献
929.
Wu -Hsun Cheng 《Catalysis Letters》1996,38(1-2):135-141
Selectivities in methanol oxidation over silica supported molybdenum oxide catalysts were investigated in relation with the phase distribution. The supported catalysts were prepared by impregnation with ammonium heptamolybdate. In addition to crystalline MoO3, Mo containing cluster species of 1–2 nm size were observed by STEM even from a used catalyst with 13% catalyst loading. The percentage of Mo present as crystalline MoO3 increases with the catalyst loading. An ESCA study indicates that part of surface Mo in the supported catalysts is reduced to Mo5+. The dimethyl ether selectivity increases with the catalyst loading and its formation occurs over the crystalline MoO3 phase. The Selectivities to CO and methyl formate are greatly enhanced because of the presence of support, and are relatively independent of the catalyst loading and phase distribution. The dependence and independence of the Selectivities of different byproducts on the loading make the silica supported catalysts with high catalyst loadings less selective for the partial oxidation of methanol to formaldehyde. 相似文献
930.
Hong-Wen Wang Chien-Hung Kuo Hsiu-Chu Lin I.-Ting Kuo Chi-Feng Cheng 《Journal of the American Ceramic Society》2006,89(11):3388-3392
Rapid formation of active, mesoporous, and crystalline TiO2 photocatalysts via a novel microwave hydrothermal process is presented. Crystalline anatase mesoporous nanopowders 100–300 nm in size with worm hole-like pore sizes of 3–5 nm were prepared by a modified sol–gel of titanium tetra-isopropoxide, accelerated by a microwave hydrothermal process. The organic surfactant, tetradecylamine, which is used as a self-assembly micelle in the sol–gel and microwave hydrothermal process, enables to harvest crystallized mesoporous anatase nanoparticles with a high-surface area. Mesoporous worm hole-like and crystalline powders with surface areas of 243–622 m2 /g are obtained. X-ray diffraction, N2 -adsorption isotherms (Barrett–Joyner–Halenda and Brunauer–Emmet–Teller method), scanning electron microscope, and transmission electron microscope are used to identify the characteristics and morphologies of the powders. It is shown that crystallization by calcination at 400°C/3 h inevitably reduced the surface area, while the microwave hydrothermal process demonstrated a rapid formation of crystalline mesoporous TiO2 nanopowders with a high-surface area and excellent photocatalytic effects. 相似文献