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M. Kambara K. Miyake K. Murata T. Izumi Y. Shiohara T. Umeda 《Physica C: Superconductivity and its Applications》2000,330(3-4):191-202
Crystal growth of the melt-textured bulk Nd1+xBa2−xCu3O6+d (Nd123) superconducting oxides was investigated by employing isothermal undercooling solidification with hot-seeding in air. From the relationship between growth length and holding time, the Nd123 crystal was found to have almost stopped growing after a certain growth period, while the growth length increased proportionally to the holding time at an early stage of the crystal growth. As a result of quantitative analysis for the Nd123 crystal of which solidification was terminated, the distribution of the Nd/Ba substitution was observed to decrease in the Nd123 single crystal matrix from the seed crystal to the edge of the Nd123 crystals. Also, the substitution content at the edge of the Nd123 crystal, which corresponds to that at the final stage of the crystal growth, was found to be in good agreement with the minimum substitution of the Nd123 solid solution phase in the equilibrium phase diagram at this process temperature. These compositional changes could be explained using the equilibrium phase diagram as associated with the solid solution formation, which is responsible for the non-steady state solidification of the Nd123 crystals even for the isothermal undercooling processing. 相似文献
995.
YU Zu-Rong 《理论物理通讯》2001,(10)
With the help of su(2) algebra technique, a new equivalent form of the fractional Fourier transformation is given. Two examples are illustrated for their physical application in quantum optics.`` 相似文献
996.
997.
Sunkyu Park David K. Johnson Claudia I. Ishizawa Philip A. Parilla Mark F. Davis 《Cellulose (London, England)》2009,16(4):641-647
The crystallinity index of cellulose is an important parameter to establish because of the effect this property has on the
utilization of cellulose as a material and as a feedstock for biofuels production. However, it has been found that the crystallinity
index varies significantly depending on the choice of instrument and data analysis technique applied to the measurement. We
introduce in this study a simple and straightforward method to evaluate the crystallinity index of cellulose. This novel method
was developed using solid state 13C NMR and subtraction of the spectrum of a standard amorphous cellulose. The crystallinity indexes of twelve different celluloses
were measured and the values from this method were compared with the values obtained by other existing methods, including
methods based on X-ray diffraction. An interesting observation was that the hydration of the celluloses increased their crystallinity
indexes by about 5%, suggesting that addition of water increased cellulose order for all the cellulose samples studied. 相似文献
998.
Stephen M. Lipson Ashley J. Cadby Paul A. Lane Diarmuid F. O’Brien Anna Drury Donald D. C. Bradley Werner J. Blau 《Monatshefte für Chemie / Chemical Monthly》2001,132(1):151-158
Summary. We have investigated the effect of film preparation procedures on the photoluminescence efficiency of the luminescent co-polymer
poly-(m-phenylene-co-2,5-dioctoxy-p-phenylenevinylene) (PmPV). The photoluminescence efficiency of PmPV films improved by up to 50% when the solution was degassed by bubbling argon gas through it prior to spin casting in an inert
atmosphere and baking under vacuum. Photoinduced absorption and doping measurements show that this preparation method reduces
polaron photogeneration, which reduces the photoluminescence (PL) yield through exciton quenching and excited state absorption.
It is proposed that this sample preparation method increases interchain separation, reducing the formation of polarons and
non-radiative quenching routes, thus resulting in increased PL efficiency.
Received June 23, 2000. Accepted (revised) August 3, 2000 相似文献
999.
A. Polyakova R. Y. F. Liu D. A. Schiraldi A. Hiltner E. Baer 《Journal of Polymer Science.Polymer Physics》2001,39(16):1889-1899
The oxygen‐barrier properties of amorphous polyethylene terephthalate‐based copolymers with various acid comonomers were examined. The incorporation of increasing amounts of isophthalate, phthalate, or naphthalate gradually reduced the permeability P toward the low values obtained for the corresponding homopolymers. The permeability of poly(ethylene 3,4′‐bibenzoate) homopolymer was only slightly lower than that of polyethylene terephthalate, and the copolymers correspondingly exhibited a very gradual decrease in P as the amount of 3,4′‐bibenzoate (3,4′BB) increased. In contrast, copolymerization with the linear isomer, 4,4′BB, produced a substantial increase in P. Generally, comonomer affected the solubility S less than the diffusivity D, and therefore changes in P reflected primarily changes in D for the polymers studied. The diffusivity and solubility depended on the copolymer composition in accordance with static and dynamic free‐volume concepts of gas permeability in glassy polymers. The solubility S correlated with the amount of free volume as determined by the glass‐transition temperature. Correlation of the diffusivity D with the magnitude of the subambient γ relaxation identified dynamic free volume with thermally activated conformational changes and segmental motions. Correspondence in the activation energy confirmed the relationship. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1889–1899, 2001 相似文献
1000.
物价、利率与收入对居民消费需求影响研究——基于时变参数状态空间模型 总被引:1,自引:0,他引:1
运用时变参数状态空间模型对我国改革开放三十年来物价、利率与收入对农村和城镇居民消费需求影响的动态特征进行了研究。发现物价、收入对农村和城镇居民的消费需求弹性不同,农村消费需求受收入影响较大,而城市居民消费需求受物价影响较大;利率对农村和城镇居民消费需求影响不显著,利率机制目前还不是调解中国消费需求的理想工具。在此基础上给出了相应的政策建议。 相似文献