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排序方式: 共有1398条查询结果,搜索用时 240 毫秒
931.
932.
Kazumune Katagiri Koichi Kasaba Daisuke Yamakage Satoshi Shimura Naoki Koshizuka 《低温学》2007,47(4):220-224
The mechanical properties of Cu and Cu-alloy (Cu-Zr, Cu-Be and Cu-Cr) sheath in situ PIT-processed MgB2 superconducting wires were studied at room temperature (RT) and 4.2 K. The effects of stress/strain on the critical current (Ic) of the wires have also been studied at 4.2 K and in magnetic fields up to 5 T. Alloying the Cu sheath significantly increased the yield stress of the wires. The 0.5% flow stresses of the Cu-alloy sheath wires were 147-237 MPa, whereas that of Cu was 55 MPa. At RT, the serration in the stress-strain curves corresponding to the multiple cracking was observed around a strain of 0.4% and the curve almost saturated beyond that point. The strain dependence of Ic prior to the critical strain (εirr) was different depending on the magnetic field; being almost constant at 2 T and increased with strain at 5 T. The Ic decreased beyond εirr, which was much larger for Cu-alloy sheath wires as compared with Cu sheath wire. The magnitude of εirr is due to the difference in the thermal compressive strain in the MgB2 core, which was relaxed by yielding in the sheath materials. The transverse compression tests revealed that the Ic of the Cu-alloy sheath wire did not degrade up to about 95 MPa, which is also higher than that of Cu sheath wire. 相似文献
933.
We have performed nitrogen atomic-layer doping into GaAs, AlGaAs, and AlGaAs/GaAs single quantum wells using atomic nitrogen
cracked by a hot tungsten filament. While the atomic-layer-doped GaAs layers show a series of sharp and strong photoluminescence
lines relating to excitons bound to nitrogen atoms at 8K, atomic-layer-doped AlGaAs layers show several broad nitrogen-related
lines. For the atomic-layer-doped single quantum well at the center of the GaAs layer, the quantum well luminescence itself
disappears and a dominant and sharp luminescence is observed at a longer wavelength. It is found that the As pressure during
the atomic-layer doping greatly affects the luminescence characteristics. 相似文献
934.
We studied the effects of buspirone and 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) on duration of immobility in mice in the forced swim test. Buspirone [3-10 mg/kg, intraperitoneally (IP)] potently and dose dependently increased the duration of immobility in mice. In contrast, following a single dose of 8-OH-DPAT (1-3 mg/kg, IP), there was a dose-dependent decrease in the duration of immobility. Pretreatment with the 5-HT synthesis inhibitor p-chlorophenylalanine (200 mg/kg, IP, 3 days before further drug treatment) did not alter the effects of buspirone or 8-OH-DPAT. The increase in the duration of immobility induced by buspirone (3 mg/kg, IP) was blocked by NAN-190 [1-(2-methoxyphenyl)-4-(4-[2-phthalimido]butyl)-piperazine hydrobromide, 1 mg/kg, IP], a postsynaptic 5-HT1A receptor antagonist. However, the effect of 8-OH-DPAT (1 mg/kg, IP) was not blocked by NAN-190 (1 mg/kg, IP). The effect of buspirone (3 mg/kg, IP) was blocked by apomorphine (0.3 mg/kg, IP), a dopamine receptor agonist. Based on the results of this study, it is suggested that the effects of buspirone and of 8-OH-DPAT on immobility in the forced swim test may occur through different mechanisms. 相似文献
935.
Yoshinori Kawase Naoki Omori Masanari Tsujimura 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,61(1):49-55
Mixing time, circulation time and downcomer linear liquid velocity were measured in two sizes of external-loop airlift bioreactors with Newtonian and non-Newtonian fluids. The mixing time increased as a result of an increase of non-Newtonian characteristics. However, the liquid circulation time was affected only slightly by non-Newtonian flow behaviour. A semi-empirical correlation for circulation time in external-loop airlift bioreactors was proposed. The proposed correlation was compared with the present experimental results and those in the literature. Reasonable agreement was obtained between the predicted and experimental values of circulation times. The downcomer liquid velocity was almost independent of the downcomer-to-rise cross-sectional area ratio. The correlation based on the concept of an eddy diffusivity predicted downcomer liquid velocities in Newtonian and non-Newtonian fluids. 相似文献
936.
937.
Information of life is stored in a genome sequence and four nucleotides can be regarded as coding elements and their sequence
as a certain code of life. We study what kinds of code structure the sequences of HIV-1 genes may have. 相似文献
938.
An analytical model is developed to predict the nocturnal thermal performance of a forced-convection type nonselective radiator: its validity is examined by comparison of the predictions with the results of several outdoor experiments. In the experiments, the Reynolds number of a working fluid, which is water in the present study, is varied, while the inlet fluid temperature is kept constant. The presented model predicts time variations in the exit fluid temperature of the radiator accurately. 相似文献
939.
Leptolstatin, a product from Streptomyces sp. SAM1595, is a gap phase-specific inhibitor of the mammalian cell cycle. Physico-chemical properties and spectrometric analyses showed that the structure of leptolstatin is (2Z,6E,8Z,12E,14E,22E)-19,24-dihydro xy-8,10,14,16,18,20,22-heptamethyl-17-oxo-2 , 6,8,12,14,22-tetracosahexaen-5-olide. 相似文献
940.
Naoki Abe 《New Generation Computing》1997,15(1):3-25
In computational learning theory continuous efforts are made to formulate models of machine learning that are more realistic than previously available models. Two of the most popular models that have been recently proposed, Valiant’s PAC learning model and Angluin’s query learning model, can be thought of as refinements of preceding models such as Gold’s classic paradigm of identification in the limit, in which the question ofhow fast the learning can take place is emphasized. A considerable amount of results have been obtained within these two frameworks, resolving the learnability questions of many important classes of functions and languages. These two particular learning models are by no means comprehensive, and many important aspects of learning are not directly addressed in these models. Aiming towards more realistic theories of learning, many new models and extensions of existing learning models that attempt to formalize such aspects have been developed recently. In this paper, we will review some of these new extensions and models in computational learning theory, concentrating in particular on those proposed and studied by researchers at Theory NEC Laboratory RWCP, and their colleagues at other institutions. 相似文献