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91.
Sn2+-incorporated potassium titanate (K2Ti6O13) nanoribbons were prepared by a facile acid-free ion-exchanged method in a dehydrated methanol solution at room temperature. XRD patterns suggested that K2Ti6O13 (KTO) and Sn2+-incorporated KTO (SKTO) are well crystallized with monoclinic phase structures. The mole ratio of incorporated Sn2+ to K+ in SKTO was estimated to be 2. X-ray photoelectron spectrum showed that the Sn species of SKTO consisted of 90% of Sn2+ and 10% of Sn4+, suggesting that part of Sn2+ was oxidized to Sn4+ in the incorporation process. The band gap of SKTO was 0.7 eV narrower than that of KTO, which was derived from lift of the top of the valence band due to the hybridization of Sn5s and O2p orbitals. The SKTO nanoribbons showed remarkable photocatalytic activities for H2 evolution and rhodamine B degradation under visible light irradiation (λ ≥ 420 nm). The photocatalytic mechanism and durability were studied in detail. The advantage of this acid-free ion-exchange method is ease of ion-exchange of K+ with H+ and maintenance of the integrity of the 1D nanoribbon structures. This method can be applied to preparation of other Sn2+-incorporated compounds with special nanostructures. 相似文献
92.
Na Zhou Takuya Matsumoto Takahiro Hosokawa Tetsuya Suekane 《Flow Measurement and Instrumentation》2010,21(3):262-267
Entrapment of the non-wetting phase in porous media has been observed in a variety of fields such as petroleum engineering, geological storage of carbon dioxide, and remediation of ground water. We investigated gas trapping in porous media from a microscopic point of view. High-resolution, three-dimensional images of pore structure and trapped gas bubbles in Berea sandstones were obtained using a micro-focused X-ray CT scanner. We used vertical and horizontal Berea sandstone cores, 8 mm in diameter and 15 mm long. Based on the three-dimensional image analysis, the statistical distribution of the trapped gas volume was estimated. Trapped bubbles have a pore-network scale size and distribute over several pores. In the case of the vertical core, the porosity fluctuates along the flow direction due to the layered structure. The residual gas saturation also fluctuates with porosity along the flow direction. The higher gas saturation in porous layers at the end of gas injection results in a higher trapped gas saturation compared to dense layers. On the other hand, in dense layers the gas saturation at the end of gas injection is almost the same as residual gas saturation. Therefore, most of the gas injected into the dense layers would be trapped. In the case of the horizontal core, the gas saturation at the irreducible water condition is lower than that for the vertical core, because the injected gas selectively passes through the more permeable layers. However, the residual gas saturation is 29.2% for the horizontal core, which is comparable with that for the vertical core (30.9%). Finally, the effect of capillary number on stability of trapped gas bubbles has been estimated. Trapped gas bubbles are stable against the increased flow rate up to a capillary number of 1.0×10?5. 相似文献
93.
Albert Kochendoerfer Tetsuya Saito Karl Edgar Hagedorn 《Engineering Fracture Mechanics》1972,4(4):665-674
The increase with increasing temperature of KIc, measured with 2CT and 1'CT specimens, from about 103N mm
at 77 K to about 2.103 N mm
at about 170 K is attributed to the increasing proportion of dimple to cleavage fracture as revealed by scanning electron microscope investigation.
The specimens were prestrained to different partial scale yielding states by the same kind of loading, performed at 298 K, as in the later KIctests, performed at 77 K. After pretension KIc = K*Ic is increased by a maximum amount of about half of the value K0Icof nonprestrained specimens, after precompression it is reduced by the same amount if this value is evaluated from the load at which a pop-in occurs. The value KIc = K**Ic for the final fracture lies between K*Ic and K0Ic. These results are interpretated in terms of the residual stress states due to prestraining. 相似文献
94.
Jifei Jia Eishi Tanabe Peng Wang Kouichi Ito Hiroyuki Morioka Ye Wang Tetsuya Shishido Katsuomi Takehira 《Catalysis Letters》2001,76(3-4):183-192
A solid phase crystallization (spc) method was applied for the preparation of SrTiO3-supported Ni catalysts and compared to the impregnation (imp) method. spc-Ni0.2/SrTiO3 has highly dispersed and stable Ni metal particles resulting in higher activity and higher sustainability against coking than imp-Ni0.2/SrTiO3 in the partial oxidation of CH4. Both catalysts were tested for the CH4 pyrolysis in order to elucidate the catalytic nature against coking of spc-Ni0.2/SrTiO3. The amount of carbon and the rate of H2 formation were similar over both catalysts at both 773 and 1073 K. On both catalysts, CH4 continuously decomposed at 773 K, while the rate of CH4 pyrolysis quickly decreased at 1073 K. Fibrous carbons grew up with a Ni metal particle on the tip of the fiber at 773 K, while carbon balls and short carbon fibers with a Ni metal particle encapsulated inside formed and no sufficient growth of the fiber was observed at 1073 K. The carbon species formed at 773 K was hydrogenated completely to CH4 around 873 K, while the hydrogenation of that formed at 1073 K needed higher temperature around 1073 K. However, the carbon species formed on both the catalysts at either 773 or 1073 K was completely oxidized around 773 K. Thus, judging from the anti-coking nature, the behaviors in the CH4 pyrolysis are similar over both catalysts, nonetheless spc-Ni0.2/SrTiO3 was far superior to imp-Ni0.2/SrTiO3 in the CH4 oxidation. It is likely that the high sustainability against coking of spc-Ni0.2/SrTiO3 is not due to its intrinsic nature suppressing the coking but due to its high activity of reforming which can quickly eliminate the carbon formed on the catalyst surface. 相似文献
95.
Modeling of chloride diffusivity coupled with non-linear binding capacity in sound and cracked concrete 总被引:4,自引:0,他引:4
Tetsuya Ishida Prince O'Neill Iqbal Ho Thi Lan Anh 《Cement and Concrete Research》2009,39(10):913-923
The objective of this research is to establish a model that can predict chloride transport phenomena in sound and cracked concrete. The chloride diffusivity is formulated based on computed micro-pore structure, which considers tortuosity and constrictivity of porous network as reduction factors in terms of complex micro-pore structure and electric interaction of chloride ions and pore wall. In the real environment, concrete structures are not always crack-free, therefore chloride transport in cracked concrete is also simulated by section large void spaces in a control volume to represent the crack and by proposing a model of chloride diffusivity through the cracked region The proposed models are implemented into a finite-element computational program DuCOM, which simulates the early-age development process of cementitious materials. The calculated concentration profiles of total chloride ions are verified through a comparison with experiments results. 相似文献
96.
Our recent study on a challenge of new materials for next generation's magnetic recording approaching an ultra high areal recording density beyond 1 Tbit/in.2 is overviewed. We proposed novel methods for fabricating high performance magnetic recording heads and media by making the best use of wet (electro- and electroless-deposition) and dry (sputtering) processes. We believe that these results contribute significantly to the progress in magnetic recording and constitute a breakthrough for materializing an unexplored areal recording density beyond 1 Tbit/in.2. 相似文献
97.
Yoneda E. Kikushima K. Tsuchiya T. Suto K.-I. 《Selected Areas in Communications, IEEE Journal on》1990,8(7):1249-1256
The possibility of an application of Er-doped fiber amplifiers to AM-FDM (frequency division multiplexing) or FM-FDM video distribution networks is discussed. The measured noise and modulation distortion properties of ER-doped fiber amplifiers are good enough to meet even the severe quality standards set for trunk lines. A carrier-to-noise ratio (CNR) of 57 dB for an AM-FDM transmission was measured. A second-order harmonic distortion (HD2) of less than -56 dB was measured by the monotone method (modulation depth m =50%), and a cross modulation distortion (XM) of less than -63 dB was measured by the two-tone method (m =25%×channel). On the basis of these values, composite second-order distortion (CSO) and XM in a 40-channel transmission were estimated as less than -57 dB and -73 dB, respectively. Significant reduction of noise and modulation distortion is made possible by optimizing the length of Er-doped fiber amplifiers and using input- and output-port isolators 相似文献
98.
99.
The effect of heat sealing temperature on the mechanical properties and morphology of OPP/CPP laminate films was investigated. The laminated films were placed in an impulse type heat sealing machine with both CPP sides facing each other. The temperatures investigated ranged from 100 to 250°C. T‐peel and tensile tests in combination with SEM were used to characterize the heat seals. A minimum seal initiation temperature of 120°C was identified for OPP/CPP laminate heat sealing. Peel strength increased sharply from zero at 110°C to maximum at 120°C, after which a gradual decrease was observed. Tensile strength initially increased until 120°C, after which it gradually decreased until 170°C and assumed a constant value beyond that. The initial rise has been associated to cold crystallization, while the reduction between 120°C and 170°C was due to relaxation in molecular orientation. Beyond 170°C, all the orientation in the laminate has been lost so orientation effects are nullified. Morphological studies with SEM revealed that seals were partially formed at lower temperatures, while the laminates were totally fused together at high temperatures, with intermediate temperatures showing properties that lie in between. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 753–760, 2005 相似文献
100.
Hori Tetsuya; Moriyama Hideaki; Kawaguchi Jitsutaro; Hayashi-Iwasaki Yoko; Oshima Tairo; Tanaka Nobuo 《Protein engineering, design & selection : PEDS》2000,13(8):527-533
A temperature-jump (T-jump) time-resolved X-ray crystallographictechnique using the Laue method was developed to detect small,localized structural changes of proteins in crystals exposedto a temperature increase induced by laser irradiation. In achimeric protein between thermophilic and mesophilic 3-isopropylmalatedehydrogenases (2T2M6T), the initial structural change uponT-jump to a denaturing temperature (~90°C) was found tobe localized at a region which includes a ß-turn and aloop located between the two domains of the enzyme. A mutant,2T2M6T-E110P/S111G/S113E, having amino acid replacements inthis ß-turn region with the corresponding residues ofthe thermophilic enzyme, showed greater stability than the originalchimera (increase of Tm by ~10°C) and no T-jump-inducedstructural change in this region was detected by our method.These results indicate that thermal unfolding of the originalchimeric enzyme, 2T2M6T, is triggered in this ß-turn region. 相似文献