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Closed-loop expressions for the minimum energy control of a single-input linear digital system are described. They are obtained by two different methods. The optimal inputs are given by state feedback with the bounded variable gains. The gains are independent of the initial state of the system 相似文献
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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
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Melt pool behaviour and the characteristics of the surrounding metal powder during selective laser melting (SLM) are captured using high-speed imaging, and the influence of the substrate temperature and the line building sequence on the formation of the built structure and the generation of spatter particles is experimentally investigated. The results indicate that the substrate temperature has a measurable effect on the formation of droplets and the generation of spatter particles, while the volume specific energy density of the process was the principal factor affecting the built structure. 相似文献
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Hirotsugu Takizawa Naoto HazeKeisuke Okamoto Kyota UhedaTadashi Endo 《Materials Research Bulletin》2002,37(1):113-121
Iron-doped β-rhombohedral boron was synthesized by 28 GHz microwave irradiation on a powder mixture of iron and β-boron. β-Boron strongly absorbs 28 GHz microwaves, and this strong coupling with microwave energy can be used to promote a reaction with iron dopant. The powder mixture was heated to 1800°C within 2 min by microwave irradiation, resulting in the formation of β-rhombohedral boron interstitially doped with iron. The reaction proceeded rapidly without accompanying grain growth. The XRD analysis and the electrical conductivity measurements revealed successful incorporation of iron into two doping sites of β-boron. 相似文献
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A new polymorph of NiSb2 was obtained under high-pressure/temperature condition of 6 GPa and 550–650°C. The crystal structure is orthorhombic with the space group Pbca (No. 61), isostructural with the low-temperature form of NiAs2 (pararammelsbergite). The crystallographic parameters were refined by the Rietveld analysis of the powder X-ray diffraction data (a=0.62866(2) nm, b=0.63643(2) nm, c=1.23670(3) nm, Z=8). The structure can be regarded as an intermediate structure between the marcasite-type and the pyrite-type. The pararammelsbergite-type NiSb2 is a high-pressure form of NiSb2 and the density is slightly higher than that of ambient pressure form with the marcasite-type structure. 相似文献
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Teiichi Kimura Hirotsugu Takizawa Kyota Uheda Tadashi Endo Masahiko Shimada 《Journal of Materials Synthesis and Processing》2001,9(2):57-61
The solid solution of yttrium aluminum garnet-yttrium iron garnet [YAIG, Y3(Al,Fe)5O12] was synthesized from the component oxides by 28 GHz-microwave irradiation. The compositions of the resulting garnets were not the same as the nominal compositions. This difference could be explained by selective coupling of chemical species with microwaves, predictable from the temperature–time profiles of each raw material under microwave irradiation. The diffusion process under microwave irradiation was discussed. 相似文献
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Hirotsugu Takizawa Kyota Uheda Tadashi Endo 《Journal of the American Ceramic Society》2000,83(9):2321-2323
(In0.67 Fe0.33 )2 O3 with the bixbyite structure was synthesized via 28 GHz microwave irradiation, using multimode microwave heating equipment. Indium sesquioxide strongly absorbs 28 GHz microwaves, and this strong coupling with microwave energy can be used to drive a reaction with iron sesquioxide. A mixture of In2 O3 and α-Fe2 O3 powders (In:Fe ratio of 2:1) was irradiated with microwaves at a frequency of 28 GHz. The mixture was heated to 1400°C during the microwave irradiation. The formation of a solid solution was completed within a minute, which indicated a drastic enhancement of the reaction rate. Scanning electron microscopy revealed remarkable grain growth under microwave irradiation. 相似文献