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921.
High-Temperature Toughness and Tensile Strength of Whisker-Reinforced Silicon Nitride 总被引:2,自引:0,他引:2
Tatsuki Ohji Yasuhiro Goto Akihiko Tsuge 《Journal of the American Ceramic Society》1991,74(4):739-745
The R -curve behavior of hot-pressed silicon nitride reinforced with silicon carbide whiskers is investigated from room temperature to 1300°C using the chevron-notch bend test. The bridging stress, estimated from increment of fracture resistance in the rising R -curve, is discussed in relation to tensile strength measured with various displacement rates at 1300°C. The reinforcing whiskers provide most of the tensile strength in the creep-deformation range at 1300°C. The whiskers appear to bear a great deal of the applied tensile stress during slow crack growth. 相似文献
922.
923.
In this paper, a new design scheme of multiloop predictive self‐tuning PID controllers is proposed for multivariable systems. The proposed scheme firstly uses a static pre‐compensator as an approximately decoupling device, in order to roughly reduced the interaction terms of the controlled object. The static matrix pre‐compensator is adjusted by an on‐line estimator. Furthermore, by regarding the approximately decoupled system as a series of single‐input single‐output subsystems, a single‐input single‐output PID controller is designed for each subsystem. The PID parameters are calculated on‐line based on the relationship between the PID control and the generalized predictive control laws. The proposed scheme is numerically evaluated on a simulation example. 相似文献
924.
925.
In this paper we consider a 2-out-of-n:F system composed of repairable primary and degradation units. Two stochastic models are proposed depending upon the policies of the repair discipline. We derive the availability, the expected number of visits to system failure per unit time and the MTBF by applying an extended Markov renewal process for each model. We finally show the numerical examples and investigate the impacts of introducing degradation units on the reliability measures obtained above. 相似文献
926.
The photosensitive characteristics of organometallic films composed of silver and anthraquinone derivatives (AQDs) were investigated. AQDs with electron-attracting substituents form charge transfer complexes in which an electron is transferred from the silver to the AQD. Film complexes were fabricated both by vacuum deposition and using an electrochemical process. The photosensitive properties were investigated using argon laser light irradiation. The complexes decomposed to form silver colloids and AQDs after irradiation. The decomposition mechanism is discussed. 相似文献
927.
Nabeshi H Yoshikawa T Arimori A Yoshida T Tochigi S Hirai T Akase T Nagano K Abe Y Kamada H Tsunoda S Itoh N Yoshioka Y Tsutsumi Y 《Nanoscale research letters》2011,6(1):93
Surface properties are often hypothesized to be important factors in the development of safer forms of nanomaterials (NMs). However, the results obtained from studying the cellular responses to NMs are often contradictory. Hence, the aim of this study was to investigate the relationship between the surface properties of silica nanoparticles and their cytotoxicity against a murine macrophage cell line (RAW264.7). The surface of the silica nanoparticles was either unmodified (nSP70) or modified with amine (nSP70-N) or carboxyl groups (nSP70-C). First, the properties of the silica nanoparticles were characterized. RAW264.7 cells were then exposed to nSP70, nSP70-N, or nSP70-C, and any cytotoxic effects were monitored by analyzing DNA synthesis. The results of this study show that nSP70-N and nSP70-C have a smaller effect on DNA synthesis activity by comparison to unmodified nSP70. Analysis of the intracellular localization of the silica nanoparticles revealed that nSP70 had penetrated into the nucleus, whereas nSP70-N and nSP70-C showed no nuclear localization. These results suggest that intracellular localization is a critical factor underlying the cytotoxicity of these silica nanoparticles. Thus, the surface properties of silica nanoparticles play an important role in determining their safety. Our results suggest that optimization of the surface characteristics of silica nanoparticles will contribute to the development of safer forms of NMs. 相似文献
928.
Yasuhiro Tachibana Hitomi Y. Akiyama Susumu Kuwabata 《Solar Energy Materials & Solar Cells》2007,91(2-3):201-206
Optical simulation has been employed, for the first time, for rigorous evaluation of transmittance into the TiO2 nanocrystalline film, entering from the fluorine-doped SnO2 (F-SnO2) coated glass side, in dye sensitized solar cells. The refractive index of the TiO2 film with various porosities was determined theoretically, and was in agreement with the data obtained by ellipsometric measurements. The simulation clearly indicates that the transmittance into the TiO2 film is 85–90% at 450–800 nm, on adjusting the porosity to 0.5–0.75. In contrast, transmittances experimentally determined for the TiO2 film deposited on F-SnO2 exhibits 70–83% at 450–800 nm, under-estimating the transmittance by about 10% compared to the simulated results. The simulation method was further substantiated by observing the high IPCE value (85% at 530 nm) for the solar cell using the same TiO2 film sensitized by ruthenium dye. 相似文献
929.
Susmita Saha Ruma Mandal Saswati Barman Dheeraj Kumar Bivas Rana Yasuhiro Fukuma Satoshi Sugimoto YoshiChika Otani Anjan Barman 《Advanced functional materials》2013,23(19):2378-2386
Tunable magnonic properties are demonstrated in two‐dimensional magnonic crystals in the form of artificial ferromagnetic nanodot lattices with variable lattice symmetry. An all‐optical time‐domain excitation and detection of the collective precessional dynamics is performed in the strongly magnetostatically coupled Ni80Fe20 (Py) circular dot lattices arranged in different lattice symmetry such as square, rectangular, hexagonal, honeycomb, and octagonal symmetry. As the symmetry changes from square to octagonal through rectangular, hexagonal and honeycomb, a significant variation in the spin wave spectra is observed. The single uniform collective mode in the square lattice splits in two distinct modes in the rectangular lattice and in three distinct modes in the hexagonal and octagonal lattices. However, in the honeycomb lattice a broad band of modes are observed. Micromagnetic simulations qualitatively reproduce the experimentally observed modes, and the simulated mode profiles reveal collective modes with different spatial distributions with the variation in the lattice symmetry determined by the magnetostatic field profiles. For the hexagonal lattice, the most intense peak shows a six‐fold anisotropy with the variation in the azimuthal angle of the external bias magnetic field. Analysis shows that this is due to the angular variation of the dynamical component of magnetization for this mode, which is directly influenced by the variation of the magnetostatic field on the elements in the hexagonal lattice. The observations are important for tunable and anisotropic propagation of spin waves in magnonic crystal based devices. 相似文献
930.
Elias H. Penilla Yasuhiro Kodera Javier E. Garay 《Advanced functional materials》2013,23(48):6036-6043
Alumina (Al2O3) is one of the most versatile ceramics, utilized in an amazing range of structural and optical applications. In fact, chromium‐doped single crystal Al2O3 was the basis for the first laser. Today, most photoluminescent (PL) materials rely on rare earth (RE) rather than transition‐metal dopants because RE doping produces greater efficiencies and lower lasing thresholds. RE‐doped alumina could provide an extremely versatile PL ceramic, opening the door for a host of new applications and devices. However, producing a transparent RE:Al2O3 suitable for PL applications is a major challenge due to the very low equilibrium solubility of RE (~10?3%) in Al2O3 in addition to alumina's optical anisotropy. A method is presented here to successfully incorporate Tb3+ ions up to a concentration of 0.5 at% into a dense alumina matrix, achieving a transparent light‐emitting ceramic. Sub‐micrometer alumina and nanometric RE oxide powders are simultaneously densified and reacted using current‐activated, pressure‐assisted densification (CAPAD), often called spark plasma sintering (SPS). These doped ceramics have a high transmission (~75% at 800 nm) and display PL peaks centered at 485 nm and 543 nm, characteristic of Tb3+ emission. Additionally, the luminescent lifetimes are long and compare favorably with lifetimes of other laser ceramics. The high transparencies and PL properties of these ceramics have exciting prospects for high energy laser technology. 相似文献