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1.
Yumi Fukuda Ariane Keiko Albessard Iwao Mitsuishi 《Journal of the American Ceramic Society》2019,102(7):4161-4169
The luminescence properties of yellow-emitting Ce3+-doped Sr-containing sialon phosphor Sr(Al,Si)5(O,N)7:Ce3+ were notably improved by the Ce raw material selection. By changing the Ce raw material from oxides to nitrides or chlorides, the emission wavelength shifted to above 560 nm, which is beneficial for higher color rendering index white light-emitting diodes. This result from an increase in the covalency of the host crystal being associated with a decrease in the oxygen content. When Ce chloride was used, both the absorption and internal quantum efficiency increased, resulting in an increase in the external quantum efficiency up to 65%–72%. Inductively coupled plasma mass spectrometry, X-ray diffraction, and electron spin resonance measurements showed that the reason for the absorption increase is an increase in Ce3+ content and suppression of the generation of the second phase, and the reason for the increase in the internal quantum efficiency is a decrease in the host crystal absorption via suppression of anion vacancy generation. It was found that Ce chloride not only suppresses oxygen impurities but also acts as a flux that results in improved crystallinity. 相似文献
2.
Zhishen Wu Yixin Shao Kentaro Iwashita Koji Sakamoto 《Canadian Metallurgical Quarterly》2007,11(3):299-307
Reinforced concrete (RC) beams subject to service loads of 40 or 60% of steel yielding were strengthened using hybrid continuous carbon fiber sheets. The hybrid systems were made of high-strength and high-modulus carbon sheets, and compared with systems using only high-strength carbon. It was found that the use of high-modulus carbon sheets in hybrid systems could increase the yielding load, the flexural stiffness, the postyielding ductility, and reduce the crack opening in concrete. The slope changes on load-deflection curves at steel yielding are not noticeable in hybrid systems. The tensile strains developed in hybrid sheets after the fracture of high-modulus carbon are higher in magnitude and distributed in a larger area, leading to an ultimate carbon fracture with concrete crushing. These unique features are attributed to the high stiffness and low ultimate tensile strain of the high-modulus carbon fibers which stiffen the structures, avoid or delay the fiber-reinforced polymer debonding, and facilitate the deformability during their subsequent breakdown. 相似文献
3.
Solitary DFB laser diodes with 174 kHz beat linewidth are applied to a 10 Gbit/s optical BPSK homodyne detection system for the first time: a sensitivity of -38.9 dBm was achieved. A three-electrode laser forms the local oscillator and is modulated with a partial push-pull scheme to improve its frequency response 相似文献
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The compositions of ester- and amide-linked fatty acids from ceramides of human vernix caseosa were described with emphasis
on the distribution of the branched-chain fatty acid (BCFA). Two novel ceramides were isolated from vernix caseosa in the
course of this study: the acylated type of esterified α-OH-hydroxyacid/sphingosine ceramide (Cer[EAS]) and nonacylated type
of non-OH fatty acid/hydroxysphingosine ceramide (Cer[NH]). Their chemical structures were identified by nuclear magnetic
resonance and chemical procedure. The Cer[EAS] was an acylceramide and consisted of the highest concentrations of ester- and
amide-linked BCFA (62 and 67%, respectively). The iso- or anteiso-branching structures of the aliphatic chains were confirmed
by the mass spectra of their picolinyl or pyrrolidide derivatives. As a whole, amide-linked fatty acids of ceramides 1–7 and
Cer[NH] were normal types of straight-chain fatty acids with or without α- or ω-hydroxylation. The BCFA concentrations of
amide-linked fatty acids in these ceramides (ceramides 1–7 and Cer[NH]) were low and less than 10%. The BCFA thus occurred
exclusively in a novel acylceramide of Cer[EAS] in the vernix caseosa. 相似文献
7.
On fibrous carbon materials, including activated carbon fibers, sorption capacity for heavy oils, less viscous A-grade and more viscous C-grade, was determined. Sorption capacity depended strongly on their bulk density; the correlation was the same as that found previously on exfoliated graphite and carbonized fir fibers. On carbon fiber felts, excellent recycling performance was observed, though sorption capacity was not so high as on exfoliated graphite and carbonized fir fibers. By filtration under suction, about 90% of sorbed A-grade heavy oil could be recovered and no decrease in sorption capacity was detected even after eight cycles. By washing with solvents, n-hexane for A- and C-grade oils and A-grade oil for C-grade oil, almost 100% recovery with no marked reduction in sorption capacity was found for each cycle. For the felts of PAN-based carbon fibers, rather severe operations for oil recovery, centrifugation and squeezing with twisting, could be applied without pronounced decreases in sorption capacity and recovery ratio. 相似文献
8.
Yoshihiro Hirata Kazuyoshi Sakeda Yumi Matsushita Kinji Shimada Yoshimi Ishihara 《Journal of the American Ceramic Society》1989,72(6):995-1002
Submicrometer SiO2 -Al2 O3 powders with compositions of 46.5 to 76.6 wt% Al2 O3 were prepared by hydrolysis of mixed alkoxides. Phase change, mullite composition, and particle size of powders with heating were analyzed by DTA, XRD, IR, BET, and TEM. As-produced amorphous powders partially transformed to mullite and Al-Si spinel at around 980°C. The compositions of mullite produced at 1400° and 1550°C were richer in Al2 O3 than the compositions of stable mullite solid solutions predicted from the phase diagram of the SiO2 -Al2 O3 system. Particle size decreased with increasing Al2 O3 content. The sintered densities depended upon the amount of SiO2 -rich glassy phase formed during sintering and the green density expressed as a function of particle size. 相似文献
9.
Yumi Fukuda Koichi Harada Maki Yonetsu Ariane K. Albessard Yasushi Hattori Kenji Essaki Yasuhiro Goto Tomohiro Suetsuna 《Journal of the American Ceramic Society》2021,104(12):6563-6571
When reaction-bonded silicon nitride containing MgO/Y2O3 additives is sintered at three different temperatures to form sintered reaction-bonded silicon nitride (SRBSN), the thermal conductivity increases with sintering temperature. The β-Si3N4 (silicon nitride) crystals of SRBSN ceramics were synthesized and characterized to investigate the relation between the crystal structure and the lattice oxygen content. The hot-gas extraction measurement result and the crystal structure obtained using Rietveld analysis suggested that the unit cell size of the β-Si3N4 crystal increases with the decrease in the lattice oxygen content. This result is reasonable considering that the lattice oxygen with the smaller covalent radius substitutes nitrogen with the larger one in the β-Si3N4 crystals. The lattice oxygen content decreased with increasing sintering temperature which also correlated with increase in thermal conductivity. Moreover, it is noteworthy from the viewpoint that it may be possible to apply the lattice constant analysis for the nondestructive and simple measurement of the lattice oxygen content that deteriorates the thermal conductivity of the β-Si3N4 ceramics. 相似文献
10.
Takano Masahito Iwashita Yuki Nagumo Kent Oiwa Kosuke Nozawa Akio 《Artificial Life and Robotics》2023,28(2):394-402
Artificial Life and Robotics - The amount of blood under the surface of skin is controlled by the autonomic nervous system and directly influences the facial skin temperature. Classification models... 相似文献