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41.
Yuta Fujita Akihiro Ametani Keisuke Nakamura Koichi Yamabuki 《Electrical Engineering in Japan》2014,188(1):36-45
This paper investigates the mutual grounding impedance between vertical grounding electrodes based on field measurements and FDTD simulations. In the case of vertical electrodes, the mutual impedance between the electrodes is almost completely independent of the electrode length, and thus the induced voltage is nearly constant as the electrode length becomes longer. This characteristic is different from that of an overhead conductor, where the electromagnetic‐induced voltage is proportional to the conductor length. The greater the separation distance between the electrodes, the smaller the induced voltage, as in the case of an overhead conductor. The propagation speed increases as the separation increases. It is found that the speed is not necessarily proportional to the inverse of the relative permittivity of the earth. 相似文献
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Satoshi Semboshi Shigeo Sato Mikio Ishikuro Kazuaki Wagatsuma Akihiro Iwase Takayuki Takasugi 《Metallurgical and Materials Transactions A》2014,45(8):3401-3411
We investigated the precipitation processes in Cu-4 mol pct Ti alloy specimens aged at 723 K (450 °C), by means of X-ray diffraction and chemical analyses of the precipitates extracted from the parent alloy specimens. Aging-induced precipitate particles of a spinodally decomposed disorder, α′; those of a metastable order, β′-Cu4Ti; and those of a stable order, β-Cu4Ti, were continuously formed in the aged specimens. The extraction of the precipitate particles from the aged specimens by submergence in a nitric solution allowed for not only the structural analyses of the constituent precipitate phases but also the quantitative evaluation of their chemical compositions and volume fractions. Early during the aging process, the supersaturated Cu solid solution decomposes spinodally in a continuous manner, and an unstable disorder, α′, appears. Then, fine needle-shaped β′-Cu4Ti particles, which have a Ti content of approximately 37.5 mol pct, form in the Cu matrix. During prolonged aging, coarse cellular components composed of the terminal Cu solid solution and stable β-Cu4Ti particles which have a Ti content of 20.5 mol pct nucleate and grow, primarily in the grain boundaries, at the expense of the metastable β′-Cu4Ti particles. The volume fraction of the β′-Cu4Ti particles in the alloy reaches a maximum of approximately 1.7 pct after aging for 24 hours, while that of the β-Cu4Ti particles increases steadily to more than 18 pct after 480 hours. The volume fraction of the fine β′-Cu4Ti particles in the alloy specimens remained constant throughout the age-hardening, indicating that the hardening is primarily owing to the fine dispersion of the β′-Cu4Ti particles and not because of the large volume fraction of coarse β-Cu4Ti particles. 相似文献
44.
Effects of Atmospheric Composition on the Molecular Structure of Synthesized Silicon Oxycarbides 下载免费PDF全文
Masaki Narisawa Fuji Funabiki Akihiro Iwase Fumihiro Wakai Hideo Hosono 《Journal of the American Ceramic Society》2015,98(10):3373-3380
The dependence of silicon oxycarbides' chemical composition and molecular structure on their reaction conditions was tested by varying the atmosphere under which pyrolysis was performed. To obtain the silicon oxycarbides, densely cross‐linked silicone resin particles with an averaged diameter of 2 μm were pyrolyzed in various atmospheres of H2, Ar, and CO2, in the temperature range 700°C–1100°C. The residual mass of resin after pyrolysis was almost constant at 700°C, although their apparent colors varied distinctly. The sample obtained from the H2 atmosphere was white, whereas that obtained from the CO2 atmosphere was dark brown. Fourier‐transform infrared (FT‐IR) spectra of the residues suggested that the Si–O–Si network evolution was accelerated in the CO2 atmosphere. Beyond 800°C, the chemical compositions of the compounds obtained from a H2 atmosphere increasingly approached near‐stoichiometric SiO2–xSiC composition with increasing the pyrolysis temperature. Compounds from a CO2 atmosphere approached a composition of SiO2–xC with no free SiC as the pyrolysis temperature increased. In the products from an Ar atmosphere, SiO2–xSiC–yC compositions were typically obtained. The observed effects of the pyrolysis atmosphere on the resulting chemical compositions were analyzed in terms of thermodynamic calculations. Electron spin resonance (ESR) spectra revealed broad and intense signals from products obtained from either Ar or CO2. Estimating from the signal intensity, the residual spin concentrations were in the range 1018–1019 g?1. Meanwhile, the spectra from the samples obtained in H2 showed weak and sharp signals with estimated spin concentrations ranging from 1016–1017 g?1. This signal attenuation may have been due to the hydrogen capping of dangling bond formed during pyrolysis. 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.
Inside Cover: Biosynthetic Gene Cluster for Surugamide A Encompasses an Unrelated Decapeptide,Surugamide F (ChemBioChem 18/2016) 下载免费PDF全文
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Poly(p‐phenylene sulfide) (PPS) nanofibers are prepared by irradiating a PPS fiber with a carbon dioxide (CO2) laser while drawing it at supersonic speeds. A supersonic jet is generated by blowing air into a vacuum chamber through the fiber injection orifice. Nanofibers obtained at a laser power of 30 W and chamber pressure of 10 kPa exhibit an average diameter of 600 nm and a draw ratio of 110,000. Scanning electron microscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction analyses are employed to investigate the relationships among the chamber pressure, fiber morphology, and crystallization behavior. The nanofibers exhibit two melting temperatures (Tm): approximately 280°C and 320°C. The endothermic peak at Tm = 280°C is ascribable to lamellar crystals and that at Tm = 320°C to the highly complete crystals, since the polymer molecular chain is highly oriented. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40922. 相似文献
49.
Akon Higuchi Qing-Dong Ling S. Suresh Kumar Yung Chang Ta-Chun Kao Murugan A. Munusamy Abdullah A. Alarfaj Shih-Tien Hsu Akihiro Umezawa 《Progress in Polymer Science》2014
The physical and chemical characteristics of biomaterial surface and hydrogels can be altered by external stimuli, such as light irradiation, temperature changes, pH shifts, shear stress forces, electrical forces, and the addition of small chemical molecules. Such external stimulus-responsive biomaterials represent promising candidates that have been developed for the culture and differentiation of embryonic stem (ES) cells, induced pluripotent stem (iPS) cells, and adult stem cells. Biomaterials that are designed to respond in a reversible manner to specific external signals can be formed on micropatterned or non-micropatterned surface, in hydrogels, or on microcarriers. Stem cells and the cells differentiated from them into specific tissue lineages can be cultured and/or differentiated on dishes with immobilized external stimulus-responsive polymers. Cells can be detached from these dishes without using an enzymatic digestion method or a mechanical method when the appropriate external stimulus is generated on the surface. This review discusses the polymers and polymeric designs employed to produce surface and hydrogels for stem cell culture, differentiation, and/or cell detachment using various external stimuli. 相似文献
50.
Sang Jun Yoon Jae Goo Lee Hideo Tajima Akihiro Yamasaki Fumio Kiyono Tetsuya Nakazato Hiroaki Tao 《Journal of Industrial and Engineering Chemistry》2010,16(3):350-354
Extractions of five kinds of lanthanide metal ions by bis(2-ethylhexyl)phosphoric acid (DEHPA) with [1-Cn-3-methylimidazolium][PF6](Cn = C2, C4) or [1-butyl-4-methylpyridinium][PF6] were carried out under various DEHPA and HNO3 concentrations from 0 to 1 M and under different temperature conditions from 298 to 333 K. These results were compared with those using the conventional organic solvent, hexane, in terms of their distribution coefficient values. Under all of the conditions in this study, the ionic liquid system shows more than three times greater extractability for lanthanide compared to when hexane was used. The distribution coefficient of lanthanide ions decreased as the length of the alkyl chain increased from the ethyl to the butyl. In addition, the imidazolium cation generally shows a higher distribution coefficient compared to the pyridinium cation in an ionic liquid. The concentration ratio of lanthanides and DEHPA resulted in an extraction affinity transition for lanthanides. Also evaluated in this study were issues related to the selectivity associated with the lanthanide mixture and the dependency of the ionic radius during lanthanide extraction. 相似文献