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排序方式: 共有1091条查询结果,搜索用时 31 毫秒
11.
12.
Starting from an effective action for the order parameter field, we derive a coupled set of generalized hydrodynamic equations
for a Bose condensate in an optical lattice at finite temperatures. Using the linearized hydrodynamic equations, we study
the microscopic mechanism of the Landau instability due to the collisional damping process between the condensate and noncondensate
atoms. It is shown that the Landau criterion for the stability of a superfluid in a uniform system is modified due to the
presence of the periodic optical lattice potential. 相似文献
13.
A continuous Si-Ti-C-O fibre with 12 wt% oxygen content, which is lower than the usual 18 wt% found in the normal fibres, was synthesized by using polytitanocarbosilane which has fewer Si-Si bonds than the usual precursor polymer. The density, tensile strength, tensile modulus and thermal conductivity were found to be 2.37 g cm–3, 3.4±0.3 GPa, 190±10 GPa and 1.40 W m–1 K–1, respectively. Amongst these properties, the tensile modulus was improved by 20 GPa and the thermal conductivity had a higher value in comparison with that of the ordinary Si-Ti-C-O fibre with 18 wt% oxygen content. The Si-Ti-C-O fibre with a 12 wt% oxygen content has a better heat resistance above 1400 °C in an argon atmosphere and 1300 °C in air, than the usual fibre. About 60 and 40% of its tensile strength at room temperature were retained in air at respectively, 1500 and 1600 °C. This improved ceramic fibre is considered to be useful as a reinforcing material for advanced composites such as high-temperature ceramic matrix composites and metal matrix composites. 相似文献
14.
We developed a noble technique for the fine-particle handling in plasmas. In this method a pair of point electrodes are introduced in the plasma, to which positive pulses are applied alternatively. When the pulse repetition period is shorter than the particle response time, the particles feel only time-averaged force because of their large mass. Spatial profile of the equivalent potential of the time-averaged force varies from a circle to an ellipse with an increase in the local discharge at the electrodes. The particles are eventually transported toward a middle point between two point-electrodes, being almost independent of their initial positions. This method is quite effective for converging fine particles in the plasma. 相似文献
15.
K Horino H Nishiura T Ohsako Y Shibuya T Hiraoka N Kitamura T Yamamoto 《Canadian Metallurgical Quarterly》1998,78(5):603-617
HL-60 cells derived from a human promyelocytic leukemia underwent apoptosis by heat treatment. When the heat-treated HL-60 cells were injected into guinea pig skin, monocyte/macrophage infiltration was observed 24 or 36 hours later, and the apoptotic cells were phagocytically cleared by 48 hours after their injection. The infiltration and clearance patterns were quite different from those observed in injection of necrotic or boil-fixed HL-60 cells. The apoptotic cells released a monocyte chemotactic factor in vitro 24 hours after the heat treatment. The chemotactic factor generated was identified as the cross-linked homodimer of S19 ribosomal protein by its immunologic and physicochemical properties. A serine protease that inactivates the monocyte chemotactic factor was also released from the apoptotic cells 30 hours after the heat treatment. A super infusion of this protease into the skin where the apoptotic cells had been injected diminished the number of infiltrated monocytes. The present results indicate an important role of the S19 ribosomal protein dimer in the phagocytic clearance of apoptotic cells. 相似文献
16.
Yusuke Soraji Kazuo Furuta Taro Kanno Hisae Aoyama Satoru Inoue Daisuke Karikawa Makoto Takahashi 《Cognition, Technology & Work》2012,14(2):93-105
Since controller teams are in charge of en-route air traffic control, team cooperation is a key issue for good control performance. We conducted ethnographic field observation at the Tokyo Area Control Center and then analyzed the obtained data to develop a cognitive model of team cooperation in en-route air traffic control. We segmented conversational records, behavioral records, and so on by control unit, and then clarified relations between the segments and identified expert knowledge and judgment behind them. Cognitive processes of controller teams were reconstructed based on a concept of distributed cognition. The analysis revealed that the mutual belief model is applicable to team cooperation processes, the role assignment of tasks within a controller team is implicit and that control plans are implemented smoothly once team situation awareness has been established. A cognitive model of controllers?? team cooperation has been constructed based on these findings. 相似文献
17.
In Situ Observation of Phase Separation of a Barium Borate Melt in a Stable Immiscibility Region under Microgravity 总被引:1,自引:0,他引:1
Satoru Inoue Akio Makishima Hiroyuki Inoue Kohei Soga Tomoya Konishi Tomoyoshi Asano Yuu Ishii Masato Koyama 《Journal of the American Ceramic Society》1997,80(9):2413-2417
The precipitation of droplets was directly observed on a BaO–B2 O3 melt in a drop shaft experiment. This is the first time that precipitation of droplets has been observed in a 4.5 s drop test. The melt film of 4BaOz96B2 O3 (mol%) held on a platinum wire loop was heated above the critical tem-perature to produce uniformity and was cooled down to the phase separation temperature range. Phase separation of the melt was observed directly with a video camera. The IR image of the melt was simultaneously detected with a CCD array and was converted into a two-dimensional thermograph. 相似文献
18.
A fractal approach is adopted to describe the dynamic behavior of a circulating fluidized bed. Two times series, differential pressure fluctuations along the riser height and solids momentum fluctuations along the radial direction, are measured and analyzed in terms of fractal dimensions. The influences of operating conditions and axial/radial positions on the fractal dimension are discussed. Attempts are also made to interpret the flow structure in the bed in terms of the fractal dimension. It is found that fractal analysis can provide a useful tool for understanding the characteristics of gas-solids flow in circulating fluidized beds. 相似文献
19.
Masahiro Tajima Miki Niwa Yasushi Fujii Yutaka Koinuma Reiji Aizawa Satoshi Kushiyama Satoru Kobayashi Koichi Mizuno Hideo Ohuˆchi 《Applied catalysis. B, Environmental》1997,12(4):1418
The decomposition of chlorofluorocarbons (CFCs) in the presence of water was examined over a variety of solid acid catalysts. The TiO2ZrO2 catalyst was found to have the highest activity and longest life among the catalysts examined. The activity of the TiO2ZrO2 catalysts depended upon the content of TiO2. At the contents of TiO2 from 58 to 90 mole%, the TiO2ZrO2 catalysts exhibited high activity, and these catalysts were proven to contain TiZrO4 crystal. From the study of the XRD peak intensity of the TiZrO4 crystal, it was highest on the TZ-58 which contained 58 mole% of TiO2, and decreased with increasing the content of TiO2. Furthermore, the conversion of CFC113 measured at 673 K was highest at TZ-58, and decreased gradually with increasing TiO2 content. Therefore, the TiZrO4 crystal influences the activity of decomposition of CFC113. However, the TiO2ZrO2 catalyst was gradually deactivated during the reaction due to the elimination of titanium atoms. A good relationship was found between the activity on TiO2ZrO2 catalyst and bond energy of CCl in the compounds of chlorofluorocarbons and hydrochlorocarbons, suggesting that the rate controlling step was the cleavage of CCl bond. 相似文献
20.
Controlling the familywise error rate in functional neuroimaging: a comparative review 总被引:1,自引:0,他引:1
Functional neuroimaging data embodies a massive multiple testing problem, where 100,000 correlated test statistics must be assessed. The familywise error rate, the chance of any false positives is the standard measure of Type I errors in multiple testing. In this paper we review and evaluate three approaches to thresholding images of test statistics: Bonferroni, random field and the permutation test. Owing to recent developments, improved Bonferroni procedures, such as Hochberg's methods, are now applicable to dependent data. Continuous random field methods use the smoothness of the image to adapt to the severity of the multiple testing problem. Also, increased computing power has made both permutation and bootstrap methods applicable to functional neuroimaging. We evaluate these approaches on t images using simulations and a collection of real datasets. We find that Bonferroni-related tests offer little improvement over Bonferroni, while the permutation method offers substantial improvement over the random field method for low smoothness and low degrees of freedom. We also show the limitations of trying to find an equivalent number of independent tests for an image of correlated test statistics. 相似文献