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排序方式: 共有1649条查询结果,搜索用时 15 毫秒
41.
The interface area between the bubble and emulsion phases in a fluidized catalyst bed is one of the important parameters used to analyze and design the fluidized bed reactor. We used a fast‐scanning X‐ray CT system to observe the bubble shape and structure. We then obtained the transient 2‐dimensional cross sectional gas‐phase distribution in a fluidized catalyst bed. Using image‐processing techniques, pseudo 3‐dimensional images of the bubbles were reconstructed. The bubble structure was studied based on the 3‐dimensional images and the previously obtained results in a 2‐dimensional fluidized bed. It was found that the bubble shape was not spherical but complicated, and that the bubbles ascending in a fluidized catalyst bed consisted of some smaller bubbles. 相似文献
42.
Effects of Annealing on Dielectric Loss and Microstructure of Aluminum Nitride Ceramics 总被引:1,自引:0,他引:1
Shoichi Kume Masaki Yasuoka Naoki Omura Koji Watari 《Journal of the American Ceramic Society》2005,88(11):3229-3231
The effect of annealing on tan δ and microstructures of aluminum nitride (AlN) ceramics were explored. Yttria was added as a sintering additive to AlN powders, and the powders were pressureless-sintered at 1900°C for 2 h in a nitrogen flow atmosphere. In succession to sintering, AlN samples were annealed at 720, 970 and 1210°C for 2 and 4 h. Very low tan δ values between 2.6 and 6.0 × 10−4 at 28 GHz were obtained when the AlN samples were annealed for 4 h at all the annealing temperatures. 相似文献
43.
Yu-Ping Zeng Jian-Feng Yang Naoki Kondo Tatsuki Ohji Hideki Kita Shuzo Kanzaki 《Journal of the American Ceramic Society》2005,88(6):1622-1624
The fracture energies of the tape-cast silicon nitride with and without 3 wt% rod-like β-Si3 N4 seed addition were investigated by a chevron-notched-beam technique. The material was doped with Lu2 O3 –SiO2 as sintering additives for giving rigid grain boundaries and good heat resistance. The seeded and tape-cast silicon nitride has anisotropic microstructure, where the fibrous grains grown from seeds were preferentially aligned parallel to the casting direction. When a stress was applied parallel to the fibrous grain alignment direction, the strength measured at 1500°C was 738 MPa, which was almost the same as room temperature strength 739 MPa. The fracture energy of the tape-cast Si3 N4 without seed addition was 109 and 454 J/m2 at room temperature and 1500°C, respectively. On the contrary, the fracture energy of the seeded and tape-cast Si3 N4 was 301 and 781 J/m2 at room temperature and 1500°C, respectively, when a stress was applied parallel to the fibrous gain alignment. The large fracture energies were attributable primarily to the unidirectional alignment fibrous Si3 N4 grains. 相似文献
44.
Influence of the introduction of flexible alkyl chains on the thermal behavior and mechanical properties of mesogenic epoxy thermosets 下载免费PDF全文
A mesogenic epoxy resin (DGETAM) was cured with a series of curing agents having different lengths of long alkyl chain (nBAB, n = 4, 8, 12). Properties of the curings were compared with those of the DGEBA cured with the same curing agents revealing the achievement of a balance between certain levels of thermal properties and excellent mechanical properties. Moreover, some curing systems were prepared with twin mesogenic type epoxy resins (DGEnMA, n = 4, 6, 8, 10, 12) having different lengths of alkyl chain as a flexible spacer and the same curing agents (n′BABs). Combinations of the same concentrations of chemical structures in the basic units of the network structure were applied, and the thermal and mechanical properties of their curing systems were investigated. The fracture energy of each system increased considerably with the increase of the alkyl chain length that adjoins the two mesogenic groups in the epoxy resins. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44244. 相似文献
45.
Akihiro Shimamura Manabu Fukushima Mikinori Hotta Tatsuki Ohji Naoki Kondo 《Journal of the American Ceramic Society》2016,99(2):440-444
A novel fabrication route to make macroporous silicon carbide (SiC) has been proposed in this study. The route is composed of the following two steps: the fabrication of porous α‐SiC/novolac‐type phenolic composite using hexamethylenetetramine (HMT) as a curing/blowing agent for the novolac monomer and a conventional reaction‐bonded (RB) sintering of the composite. The α‐SiC/novolac‐type phenolic composite was carbonized at 800°C for 2 h in N2 gas and then reacted with the molten silicon at 1450°C for 30 min under vacuum, resulting in the macroporous RB‐SiC with an open porosity of 48% and relatively large pore size of ~110 μm. The compressive strength of the macroporous RB‐SiC was 113 MPa, which is relatively high compared to those reported for macroporous SiC of equivalent porosities and pore sizes. 相似文献
46.
Naoki Yasumaru Kenzo MiyazakiJunsuke Kiuchi Eisuke Sentoku 《Diamond and Related Materials》2011,20(4):542-545
This paper reports macro and micro frictional properties of DLC, TiN, CrN films and GC substrate of which surfaces are nanostructured with femtosecond (fs) laser pulses. The friction coefficient μ of the nanostructured surface was measured at a usual load with a ball-on-disk friction test machine. The results have shown that carbon materials of DLC and GC provide lower values of μ than TiN and CrN, and μ of DLC and TiN measured with a hardened steel ball decreases with an increase of the laser pulse energy. On the other hand, μ of nanostructured surfaces of thin films monotonously increases with an increase in laser pulse energy, which was measured with a micro-scratch test at an ultralight load of 1.5 mN utilizing a diamond tip. The friction coefficient of the GC substrate irradiated at a low fluence around the ablation threshold has shown a lower value than that of the non-irradiated surface. 相似文献
47.
Takayama H Takahashi S Moriya T Osada H Iwabuchi Y Kanoh N 《Chembiochem : a European journal of chemical biology》2011,12(18):2748-2752
Seeing below the surface: A small-molecule droplet array platform on an NADH-immobilized solid surface and a biotinylated acetophenone derivative were developed to identify the substrate candidates for soluble P450 enzymes of interest. This methodology is thought to be easily applicable to other class I P450 systems, including those that use NADPH as cofactor. 相似文献
48.
Chiral diporphyrin nanotweezers 1 consisting of two chiral porphyrins with N-substituted 3,6-carbazolylene in between have been studied for the separation of single-walled carbon nanotubes (SWNTs). As compared to the analogous nanotweezers 2 without an N-substitutent, nanotweezers 1 with the N-octylcarbazolylene spacer exhibit much higher extraction ability and better selectivity for SWNTs. A narrower diameter range of SWNTs, from 0.88 to 0.92 nm, was selectively extracted with nanotweezers 1. In addition, only (7,6)-SWNTs of 0.90 nm diameter were optically enriched through extraction with 1, while SWNTs extracted with 2 showed lower optical purity of (7,6)-SWNTs. These enhanced extraction and discrimination abilities of 1 can be attributed to the formation of a more stable SWNT complex of 1 than of 2 in methanol. 相似文献
49.
50.
Koganesawa Nozomi; Aizawa Tomoyasu; Masaki Kazuo; Matsuura Atsushi; Nimori Taisuke; Bando Hisanori; Kawano Keiichi; Nitta Katsutoshi 《Protein engineering, design & selection : PEDS》2001,14(9):705-710
Expression systems of human and silkworm lysozymes were constructedusing the methylotrophic yeast Pichia pastoris as a host. Theleader sequence and its prepro peptide of 相似文献