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排序方式: 共有648条查询结果,搜索用时 15 毫秒
1.
JIAHong-bo CHENBao-xue ZHOUJian-zhong ZHAODe-xir LUHong-liang YUANYi-fang ISOMamoru 《半导体光子学与技术》2004,10(1):21-27
Based on the measurement of dispersion characteristic and birefractive index of the fluorinated polyimide film,a statistical optimum design method is proposed and used to realize the design of 32-and 36-wavelengths optical waveguide wavelength-interleave coupler (i,e.,interleaver) with the optimization of polarization fluctuation and wavelength interval of 0.8nm at 1550nm. The largest cross coupling ratios of the two interleavers are respectively less than 1.8% and 3.5%, while the least through coupling ratios are respectively greater than 98. 2% and 96. 5%. The output differences due to polarization fluctuation are less than 1.7% and 3.2% 相似文献
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3.
Rong-Jun Xie Mamoru Mitomo Kyota Uheda Fang-Fang Xu Yoshio Akimune 《Journal of the American Ceramic Society》2002,85(5):1229-1234
Rare-earth-doped oxynitride or nitride compounds have been reported to be luminescent and may then serve as new phosphors with good thermal and chemical stabilities. In this work, we report the photoluminescence (PL) spectra of europium-, terbium-, and praseodymium-doped Ca-α-SiAlON ceramics. The highly dense ceramics were prepared by hot pressing at 1750°C for 1 h under 20 MPa in a nitrogen atmosphere. Europium-doped Ca-α-SiAlON displayed a single broad emission band peaking at λ= 550–590 nm depending on the europium concentration. The emission bands in the spectra of europium-doped Ca-α-SiAlONs were assigned to the allowed transition of Eu2+ from the lowest crystal field component of 4 f 6 5 d to 8 S7/2 (4 f 7 ) ground-state level. The emission spectra of terbium- and praseodymium-doped Ca-α-SiAlON ceramics both consisted of several sharp lines, which were attributed to the 5 D4 →7 F j ( j = 3, 4, 5, 6) transitions of Tb3+ and 3 P0 →3 H j ( j = 3, 4, 5) transitions of Pr3+ , respectively. In particular, the terbium-doped α-SiAlON ceramics showed a strong green emission among these phosphors. 相似文献
4.
Phase-separated domains prepared in the two-phase region were dissolved at a temperature in the single-phase region, and their dissolution dynamics was studied by using the time-resolved light scattering (TRLS) technique and a scanning electron microscope (SEM). The time tps of preparation of domains was chosen to be long enough for phase separation to proceed into the late stage. The scattered light intensity at small wavenumbers increased before it attenuated. As tps increased, the increase at smaller wavenumbers became more significant and the peak intensity decreased only slightly with dissolution time. The characteristic wavenumber qm evaluated from TRLS and SEM followed the power-law relation qmt−0.3. 相似文献
5.
Relatively uniform polymeric microspheres, the coefficients of variation being close to 10%, were obtained by the BPO-initiated suspension polymerization of styrenic monomers. Unlike the conventional stirred-tank system, a particular microporous glass membrane (SPG) provided uniform monomer droplets continuously when monomer was allowed to permeate through the micropores. The monomer droplets were suspended in an aqueous solution containing the stabilizing agents, transferred to a stirred vessel, and polymerized. Up to 10μm spheres, of a far narrower size distribution than those obtained by conventional microsuspension polymerization spheres, were obtained. The initial droplet size and distribution were retained with the successful suppression of secondary particle nucleation by the addition of hydroquinone in the aueous phase. Crosslinked polystyrene spheres were also synthesized in the presence of various low-molecular-weight diluents. While a good solvent, toluene, was not so effective; poor solvents, n-heptane and n-heptane, easily yielded the microporous structure, the specific surface area being as high as 160 m2/g. © 1994 John Wiley & Sons, Inc. 相似文献
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Yutaka Kokai Akira Fukuhara Ken'Ichi Morita Tatsunori Kanke Mamoru Kata Tatsuo Hayashi Toru Takenuki 《Electrical Engineering in Japan》1992,112(6):59-74
Electric power systems are expanding in size and complexity, and the requirement for the energy management system (EMS) is becoming more important. In this computer control system, a single control computer is used mainly as the primary computer and its software is very complicated because of its hugh number of small, quick tasks to obtain high response speed. Therefore, much effort is needed to develop and modify the programs, and the responsiveness of this centralized architecture varies greatly when many faults occur in the power system. This paper describes a new distributed architecture for the EMS. Distributed processors execute the functions cooperatively with periodic access to the common bulletin board database in which information about the power system exist. This architecture facilitates the software development and maintenance, and it also enhances the performance by the parallel processing of the distributed functions. 相似文献
8.
Guo-Dong Zhan Yuichi Ikuhara Mamoru Mitomo Rong-Jun Xie Taketo Sakuma Amiya K. Mukherjee 《Journal of the American Ceramic Society》2002,85(2):430-436
The microstructures of fine-grained β-SiC materials with α-SiC seeds annealed either with or without uniaxial pressure at 1900°C for 4 h in an argon atmosphere were investigated using analytical electron microscopy and high-resolution electron microscopy (HREM). An applied annealing pressure can greatly retard phase transformation and grain growth. The material annealed with pressure consisted of fine grains with β-SiC as a major phase. In contrast, the microstructure in the material annealed without pressure consisted of elongated grains with half α-SiC. Energy-dispersive X-ray analysis showed no differences in the amount of segregation of aluminum and oxygen atoms at grain boundaries, but did show a significant difference in the segregation of yttrium atoms at grain boundaries along SiC grains for the two materials. The increased segregation of yttrium ions at grain boundaries caused by the applied pressure might be the reason for the retarded phase transformation and grain growth. HREM showed a thin secondary phase of 1 nm at the grain boundary interface for both materials. The development of a composite grain consisting of a mixture of β/α polytypes during annealing was a feature common to both materials. The possible mechanisms for grain growth and phase transformation are discussed. 相似文献
9.
Nylon-6,6 — a typical polyamide — was annealed in the swollen state in glycerol to promote the partial melting of the polymer crystal. The recrystallization or lamellar thickening of nylon-6,6 crystal following partial melting was easily induced by this annealing, and the lamellar thickness of the crystal increased stepwise by monomer unit length with increasing annealing temperature or annealing time. In addition, another distinct layer-thickening mechanism was observed which led to approximately doubling (and frequently quadrupling) the straight stem length of the lamellar crystal for all samples annealed under adequate conditions. New melting endotherms corresponding to these layer thicknesses (range of long spacings 140–180Å) were obtained by differential scanning calorimetry (d.s.c.) at temperatures ranging from 270° to 282°C. The mechanism of lamellar thickening is discussed with reference to the experimental results. 相似文献
10.
The sintering behaviour of -Si3N4 powder was investigated in 980 kPa (10 atm) nitrogen at 1800–2000 °C. It is shown that -Si3N4 has a higher sinterability than the finer -Si3N4. The solution of small grains and reprecipitation on large grains occurred during sintering at >1600 °C. The rate-determining step in the liquid-phase sintering is believed to be the diffusion of material through the liquid phase at grain boundaries. There was no abnormal grain growth during gas pressure sintering of -Si3N4. The microstructures of gas pressure sintered materials from -Si3N4 were more uniform than those from -Si3N4. The densification mechanism of -Si3N4 is discussed in relation to that of -Si3N4. 相似文献