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31.
Hitoshi Suto Yasuo Hattori Hiromaru Hirakuchi Naoto Kihara Yasumasa Nakashiki 《Structure and Infrastructure Engineering》2017,13(10):1359-1371
Steel corrosion under atmospheric conditions is a critical issue in the maintenance of structures such as electric transmission towers and bridges during their long-term operation, which are generally located at many places over a wide area. Since a major factor causing corrosion is airborne salt particles coming from the sea, wide-area distributions of the long-term cumulative amount of sea salt deposited on surfaces are needed. Moreover, since the amount of airborne sea salt varies locally with the topography, it is also important to consider the effects of topography. In this paper, a method combining a computational fluid dynamics model and a statistical procedure is proposed to efficiently estimate wide-area distributions of the cumulative amount of airborne sea salt by considering the local topography. The predicted amount of airborne sea salt decreases with increasing distance from the coast and varies with the topography and the offshore wind. A comparison between predicted and observed amounts revealed that: (1) this method appropriately estimates topographical effects on sea-salt transport and enables the estimation of deposited sea salt on structure surfaces, and (2) consideration of the trapping efficiency of sea-salt particles on structure surfaces improves the prediction accuracy. 相似文献
32.
Liquid‐phase sintering of highly Na+ ion conducting Na3Zr2Si2PO12 ceramics using Na3BO3 additive 下载免费PDF全文
Kousuke Noi Kenji Suzuki Naoto Tanibata Akitoshi Hayashi Masahiro Tatsumisago 《Journal of the American Ceramic Society》2018,101(3):1255-1265
Na3Zr2Si2PO12 (NASICON) is a promising material as a solid electrolyte for all‐solid‐state sodium batteries. Nevertheless, one challenge for the application of NASICON in batteries is their high sintering temperature above 1200°C, which can lead to volatilization of light elements and undesirable side reactions with electrode materials at such high temperatures. In this study, liquid‐phase sintering of NASICON with a Na3BO3 (NBO) additive was performed for the first time to lower the NASICON sintering temperature. A dense NASICON‐based ceramic was successfully obtained by sintering at 900°C with 4.8 wt% NBO. This liquid‐phase sintered NASICON ceramic exhibited high total conductivity of ~1 × 10?3 S cm?1 at room temperature and low conduction activation energy of 28 kJ mol?1. Since the room‐temperature conductivity is identical to that of conventional high‐temperature‐sintered NASICON, NBO was demonstrated as a good liquid‐phase sintering additive for NASICON solid electrolyte. In the NASICON with 4.8 wt% NBO ceramic, most of the NASICON grains directly bonded with each other and some submicron sodium borates segregated in particulate form without full penetration to NASICON grain boundaries. This characteristic composite microstructure contributed to the high conductivity of the liquid‐phase sintered NASICON. 相似文献
33.
The oxygen content of silicon nitride with 1 mol% Y2 O3 —Nd2 O3 additive was measured after firing to determine the compositional change during gas-pressure sintering. Oxygen content decreases from 2.5 to 0.94 wt% during firing for 4 h at 1900°C and 10-MPa pressure in N2 . This decrease in oxygen results from the release of SiO gas generated by a thermaldecomposition reaction between Si3 N4 and SiO2 . The resultant sintered silicon nitride material contains less than 1 wt% oxygen. 相似文献
34.
Xin Xu Toshiyuki Nishimura Qing Huang Rong-Jun Xie Naoto Hirosaki Hidehiko Tanaka 《Journal of the American Ceramic Society》2007,90(12):4047-4049
A feasible doping strategy is introduced to synthesize Eu2+ -doped α-Si3 N4 nanowires coated with a thin BN film. The nanowires were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and a fluorescence spectrophotometer. The Eu2+ -doped α-Si3 N4 nanowires emitted strong yellow light, which is related to the 4 f 6 5 d –4 f 7 transition of Eu2+ , upon a broad excitation wavelength range between 250 and 450 nm. The obtained nanowires provided a potential candidate for application in optical nanodevices, as well as in white LEDs. 相似文献
35.
Silicon-doped diamond-like carbon (Si-DLC) films were prepared by dc pulse-plasma chemical vapor deposition (CVD), using a mixture of acetylene (C2H2) and tetramethylsilane (TMS) as the material gas. The pulse voltage was varied from − 2 to − 5 kV, and the TMS flow ratio (TMS/(C2H2 + TMS)) was varied from 0 to 40%. At a pulse voltage of − 2 kV, an increase in TMS flow ratio leads to a decrease in hardness. In contrast, at a pulse voltage of − 5 kV, an increase in TMS flow ratio leads to a slight increase in hardness. The high hydrogen concentration in the films due to an increase in TMS flow ratio promotes the formation of polymeric sp3 C―H bonds, resulting in the fabrication of soft films at a low pulse voltage of − 2 kV. However, an increase in the effect of ion peening on the growth face results in the formation of hard films at a high pulse voltage of − 5 kV. Then, at a pulse voltage of − 5 kV fabricating hard Si-DLC films, an increase in TMS flow ratio leads to an increase in the silicon content in the films, resulting in a decrease in the friction coefficient. Therefore, it is clarified that Si-DLC films fabricated by dc pulse-plasma CVD under a high pulse voltage and high TMS flow ratio exhibit high hardness and a low friction coefficient. Moreover, to investigate the friction coefficient of Si-DLC films fabricated by dc pulse-plasma CVD, films deposited by dc plasma CVD were also evaluated. To obtain the same low friction coefficient, dc pulse-plasma CVD requires less TMS than dc plasma CVD. Hence, it is also clarified that Si-DLC films can be fabricated at a low cost by dc pulse-plasma CVD. 相似文献
36.
Shoji Eita Takahashi Ryuji Isogai Shosei Ito Naoto Kubo Masaki Tsukada Takao Fukuyama Hiroyuki 《Metallurgical and Materials Transactions B》2019,50(5):2454-2458
Metallurgical and Materials Transactions B - Normal spectral emissivity of molten Cu-Fe alloy with different compositions was measured at the wavelength of 807 nm using an electromagnetic... 相似文献
37.
Naoto Koseki 《Journal of Alloys and Compounds》2011,509(3):568-570
A spinel CuIr2S4 exhibits a temperature-induced metal-insulator (M-I) transition at around 226 K. Non-magnetic substitution effect on the M-I transition, TM-I, in Cu(Ir1−xMx)2S4 (M = Sn, Hf) has been studied on the focus of the rather low composition region of x. Magnetic property of Cu(Ir1−xMx)2S4 (M = Sn, Hf) has been examined experimentally. The TM-I decreases with increasing x and the temperature hysteresis becomes unclear within the experimental errors. The step anomaly in the magnetic susceptibility smears out and the TM-I becomes ill defined around x = 0.20 in Cu(Ir1−xSnx)2S4, and x = 0.10 in Cu(Ir1−xHfx)2S4, respectively. These substitutions play an important role in decoupling the spin-dimerization of Ir4+-Ir4+ in CuIr2S4, and lead the destruction of the metal-insulator transition. 相似文献
38.
Naoto Suzuki 《Electrical Engineering in Japan》2010,171(2):23-30
In Kyushu Electric Power's 6.6‐kV distribution system, after a single‐phase ground fault occurred in the circuit of a distribution line, we experienced a phenomenon in which the analogue ground directional relays of the other circuits linked to the same bank were simultaneously tripped. In this paper, focus is placed on the mechanism and possibility of simultaneous tripping of ground directional relays. This mechanism was examined in an experiment carried out using an analogue simulator. The results of the test revealed that such simultaneous tripping was attributable to the neutral instability phenomenon of grounding potential transformers installed in an isolated neutral system. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(2): 23–30, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20919 相似文献
39.
Ferroelectric properties of ultrathin films of Nylon 11 were investigated. The thickness was in the range of 25 to 55 nm. Ferroelectric response was largely affected by thermal annealing and following cooling conditions. Thermal annealing at higher temperature followed by quenching in liquid nitrogen gave larger remanent polarization and smoother surface, whereas cooling down in an ambient atmosphere caused smaller remanent polarization and rough surface. Surface roughness strongly affected the polarization reversal and remanent polarization. Hydrogen bonding in crystal was also significantly related to the polarization reversal and thus remanent polarization. 相似文献
40.
Shin-ichi Morita Yasutaka Hayamizu Akihiko Horibe Naoto Haruki Hideo Inaba 《热科学学报(英文版)》2013,22(2):145-151
Recently, much attention has been paid to investigate the latent heat storage system. Using of ice heat storage system brings an equalization of electric power demand, because it will solved the electric -power-demand-concentration on day-time of summer by the air conditioning. The flowable latent heat storage material, Oil/Water type emulsion, microencapsulated latent heat material-water mixture or ice slurry, etc., is enable to transport the latent heat in a pipe. The flowable latent heat storage material can realize the pipe size reduction and system efficiency improvement. Supercooling phenomenon of the dispersed latent heat storage material in continuous phase brings the obstruction of latent heat storage. The latent heat storage rates of dispersed water drops in W/O (Water/Oil) emulsion are investigated experimentally in this study. The water drops in emulsion has the diameter within 3 ~ 25μm, the averaged water drop diameter is 7.3μm and the standard deviation is 2.9μm. The direct contact heat exchange method is chosen as the phase change rate evaluation of water drops in W/O emulsion. The supercooled temperature and the cooling rate are set as parameters of this study. The evaluation is performed by comparison between the results of this study and the past research. The obtained experimental result is shown that the 35K or more degree from melting point brings 100% latent heat storage rate of W/O emulsion. It was clarified that the supercooling rate of dispersed water particles in emulsion shows the larger value than that of the bulk water. 相似文献