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91.
Lattice and grain-boundary interdiffusion coefficients were calculated from the concentration distributions determined for Zr-Hf interdiffusion in polycrystalline 16Y2O3·84(Zr1–x
Hf
x
)O2 withx=0.020 and 0.100. The lattice interdiffusion coefficients were described byD=0.031 exp [–391 (kJ mol–1)/RT] cm2 sec–1 and the grain-boundary diffusion parameters byD=1.5×10–6exp [–309(kJ mol–1)/RT] cm3 sec–1 in the temperature range 1584–2116° C. Comparison of the results with those for the systems CaO-(Zr+Hf)O2 and MgO-(Zr+Hf)O2 indicated that the Zr self-diffusion coefficient was insensitive to the dopants in the fluorite-cubic ZrO2 solid solutions. 相似文献
92.
The effect of intercritical heat treatments on the tensile properties of iron-based P/M steels was investigated. For this purpose, atomized iron powder (Ancorsteel 1000) was admixed with 0.3 wt.% graphite powder. Tensile test specimens were cold pressed at 700 MPa and sintered at 1120 °C for 30 min under pure argon gas atmosphere. After sintering, ∼20% pearlite volume fraction in a ferrite matrix was obtained. To produce coarse ferrite + martensite microstructures, the sintered specimens were intercritically annealed at 724 and 760 °C and quenched in water. To obtain fine ferrite + martensite microstructures, the sintered specimens were first austenitized at 890 °C and water-quenched to produce a fully martensitic structure. These specimens were then intercritically annealed at 724 and 760 °C and re-quenched. After the intercritical annealing at 724 and 760 °C and quenching, martensite volume fractions were ∼ 18% and 43%, respectively, in both the coarse- and fine-grained specimens. Although the intercritically annealed specimens exhibited higher yield and tensile strength than the as-sintered specimens, their elongation values were lower. Specimens with a fine ferrite + martensite microstructure showed high yield and tensile strength and ductility in comparison to specimens with a coarse ferrite + martensite microstructure. The strength values of specimens increased with increasing martensite volume fraction. 相似文献
93.
M. Aoyama J. Temuujin M. Senna T. Masuko C. Ando H. Kishi 《Journal of Electroceramics》2006,17(1):61-64
Z-type hexaferrites (Ba3(1 − x)Sr3x
Co2Fe24O41with x = 0–0.5, Z-hex) were prepared in a nearly phase pure state by a two-step calcination with an intermediate wet milling. The
first calcination of the starting mixture comprising oxides or hydroxides at temperatures below 1100∘C brought about a mixture of layer-structured M and Y-type hexaferrite phases, together with a spinel phase of Co ferrite.
Z-hex was fully crystallized after the second calcination up to 1230∘C. Wet milling between the two calcination steps was decisive for the phase purity. Emphasis was laid on the quantitative
analyses of Z-hex, together with the evaluation of anisotropic growth of the crystallites. Sr addition stabilizes Z-hex, while
decreases degree of anisotropy simultaneously. 相似文献
94.
Nobuyoshi Koshino Masayuki Harada Yasuji Morita Toshiaki Kiikuchi Yasuhisa Ikeda 《Progress in Nuclear Energy》2005,47(1-4):406-413
We have developed a simple reprocessing process for spent FBR fuels using N-cyclohexyl-2-pyrrolidone (NCP) which has selective precipitation ability for UO22+ ions. It was confirmed that NCP has sufficient precipitation ability for UO22+ ions, decontamination capability (separation of UO22+ from simulated fission products), and resistance to γ-ray radiation in nitric acid solutions. These findings indicate that NCP is applicable to our reprocessing process. We have also evaluated performances of other precipitants such as N-n-propyl-2-pyrrolidone (NProP), N-n-butyl-2-pyrrolidone (NBP), and N-n-butyl-2-pyridone (NBPyr). It was found that higher decontamination factors (DFs) are obtained by using NProP and NBP. This can be interpreted that the hydrophobicity of NProP and NBP is lower than that of NCP. Furthermore, we have obtained an experimental result that the resistance of NBPyr to γ-ray radiation is superior to that of NCP. 相似文献
95.
We present analytical and experimental results on fluxgate magnetometers that make use of a readout technique based on residence times. This approach allows for enhancing sensitivity to weak target signals in particular when the reduction of the sensor dimensions are considered. Our approach, exploiting the inherent nonlinear character of the bistable core dynamics, is based on the time domain characterization of the transitions between the two saturation states of the hysteresis loop that is inherent in the ferromagnetic core dynamics. This readout technique can be implemented with bias signals having lower amplitude and frequency than those used in conventional fluxgate processing schemes, thus reducing the device power requirements. The efficacy of this strategy is shown through an analytical approach and via experimental results which suggests guidelines for optimal device design and realization. The experiments have been carried out on a miniaturized laboratory fluxgate prototype; this device shows numerous desirable characteristics, including very good sensitivity and resolution, as well as ease of operation and a very low cost. 相似文献
96.
Tu Bao Ho Trong Dung Nguyen Hiroshi Shimodaira Masayuki Kimura 《Applied Intelligence》2003,19(1-2):125-141
The process of knowledge discovery in databases consists of several steps that are iterative and interactive. In each application, to go through this process the user has to exploit different algorithms and their settings that usually yield multiple models. Model selection, that is, the selection of appropriate models or algorithms to achieve such models, requires meta-knowledge of algorithm/model and model performance metrics. Therefore, model selection is usually a difficult task for the user. We believe that simplifying the process of model selection for the user is crucial to the success of real-life knowledge discovery activities. As opposed to most related work that aims to automate model selection, in our view model selection is a semiautomatic process, requiring an effective collaboration between the user and the discovery system. For such a collaboration, our solution is to give the user the ability to try various alternatives and to compare competing models quantitatively by performance metrics, and qualitatively by effective visualization. This paper presents our research on model selection and visualization in the development of a knowledge discovery system called D2MS. The paper addresses the motivation of model selection in knowledge discovery and related work, gives an overview of D2MS, and describes its solution to model selection and visualization. It then presents the usefulness of D2MS model selection in two case studies of discovering medical knowledge in hospital data—on meningitis and stomach cancer—using three data mining methods of decision trees, conceptual clustering, and rule induction. 相似文献
97.
Toshikazu Fujino Katsumi Iwamoto Kentaro Tanaka Masayuki Shima 《Tribology International》2007,40(10-12):1638
In recent years, the techniques improving sliding performances have progressed by using coated films possessing superior tribological properties, to reduce the failures of the mechanical elements. Those techniques are often used under severe conditions such as elastohydrodynamic lubrication (EHL). In this paper, numerical three-dimensional analysis of the maximum shear stress applied into the coated film and substrate under a single EHL operating condition was performed with a range of coated film thickness and elastic properties. The strength of coated film as one of those techniques was evaluated numerically, resulting in an optimum design of coated film. As a result, coated films with a larger value of thickness and a smaller modulus of elasticity than that of substrate are preferable. 相似文献
98.
Masayuki Nogami Akihiko Koiwai Takamasa Nonaka 《Journal of the American Ceramic Society》2016,99(4):1248-1254
Glasses doped with well‐controlled Eu3+ and Eu2+ ions have attracted considerable interest due to the possibility of tuning the wavelength range of the emitted light from violet to red by using their 5D0→7Fj and 5d–4f electron transitions. Glasses were prepared to dope Eu3+ ions in a Na2O–Al2O3–SiO2 system, and the changes in the valence state of Eu3+ ions and the glass structure surrounding the Eu atoms during heating under H2 atmosphere were investigated using fluorescence spectroscopy, X‐ray absorption fine‐structure spectroscopy, and 27Al magic‐angle spinning solid‐state nuclear magnetic resonance spectroscopy. The reduction behavior of Eu3+ ions was dependent on the Al/Na molar ratio of the glass. For Al/Na < 1, the Al3+ ions formed the AlO4 network structure accompanied by the Na+ ions as charge compensators; the Eu3+ ions occupied the interstitial positions in the SiO4 network structure and were not reduced even under heating in H2 gas. On the other hand, in the glasses containing Al2O3 with the Al/Na ratio exceeding unity, the Eu3+ ions commenced to be coordinated by the AlO4 units in addition to the SiO4 network structure. When heated in H2 gas, H2 gas molecules reacted with the AlO4 units surrounding Eu3+ ions to form AlO6 units terminated with OH bonds, and reduced Eu3+ ions to Eu2+ via the extracted electrons. 相似文献
99.
100.