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131.
Olson Joanne K. Cox-Petersen Anne M. McComas William F. 《Journal of Science Teacher Education》2001,12(3):155-173
Journal of Science Teacher Education - 相似文献
132.
133.
K. C. Cheung 《Educational Studies in Mathematics》1989,20(1):97-103
This article seeks to examine gender differences across the mathematics curriculum in the various topic areas and mathematical abilities. It is suggested that a profile of these differences, when compared with students at different grade levels or across curricula, would be more fruitful for classroom teachers and curriculum developers. Breakdown and discriminant function statistics reveal that boys performed better than girls in Geometry and excelled in comprehension, and solving routine and non-routine problems. Girls were better at mathematical manipulation problems. 相似文献
134.
Rats were exposed twice in a rotated sequence to a series of six mazes, consisting of hexagonal alleys, balanced for different alley length and structural complexity. Locomotor activity increased with alley length and decreased with structural complexity of the mazes. Locomotion became less stereotyped with increased experience, showing an increasing number of turns, less constant velocity, loss of the initial preference for outward leading alleys and weakening of the forward tendency at reentry from side alleys into hexagonal alleys. In contrast to these qualitative changes of locomotion, the amount of activity remained almost unchanged throughout the experiment. The results suggest that these increases in locomotion complexity depend upon complex interactions between experience and stimulus content of the mazes. 相似文献
135.
The paper describes the design and use of a studio system which arose out of the need to give demonstrations of experimental procedures to practical classes of up to 150 students. Since the requirements could be specified in some detail it was possible to use novel methods of working which turned out to be very efficient and economical. 相似文献
136.
Takashi Sagawa 《浙江大学学报(A卷英文版)》2018,19(1):80-85
Composite materials of Fe/Al2O3, which consist of small particles of iron supported by thermally stable alumina even at 500–700 °C, have been widely used in the water-gas shift reaction for natural gas reforming. Therefore, Fe/Al2O3 is one of the promising candidates for re-transformation of exhausted CO2 into fuels such as alcohols and hydrocarbons. The development of a CO2 reforming system using the composite materials of Fe/Al2O3 through CO2 reduction to CO, dissociation of water into hydrogen, and methanol synthesis has been investigated. It was found that dry and steam (i.e. wet) reforming of CO2 produced almost the same amount of CO. At a temperature above 500 °C, maximal and saturated yields of CO and H2 from CO2 and water were obtained. However, this CO2 reforming system requires higher-pressure conditions from several tens to hundreds standard atmospheric pressure in order to achieve high yield and selectivity for methanol production. In this study we developed the modified CO2 reforming system by the utilization of Ni and/or Cu instead of Fe in order to obtain other types of useful products such as CO, CH4, and carbon, more efficiently and selectively under atmospheric pressure. When Ni or Cu was used, conversion of CO2 was reduced to 76%, while 9% of methane was detected in the case of Ni. On the other hand, though the CO2 conversion reduced half of the Fe, the selectivity of CO from CO2 increased to 95% in the case of Cu. 相似文献
137.
138.
Numerical investigation of cavitating flow behind the cone of a poppet valve in water hydraulic system 总被引:2,自引:0,他引:2
Computational Fluid Dynamics (CFD) simulations of cavitating flow through water hydraulic poppet valves were performed using
advanced RNGk-epsilon turbulence model. The flow was turbulent, incompressible and unsteady, for Reynolds numbers greater than 43000. The
working fluid was water, and the structure of the valve was simplified as a two dimensional axisymmetric geometrical model.
Flow field visualization was numerically achieved. The effects of inlet velocity, outlet pressure, opening size as well as
poppet angle on cavitation intensity in the poppet valve were numerically investigated. Experimental flow visualization was
conducted to capture cavitation images near the orifice in the poppet valve with 30° poppet angle using high speed video camera.
The binary cavitating flow field distribution obtained from digital processing of the original cavitation image showed a good
agreement with the numerical result.
Project supported by the National Natural Science Foundation of China (No. 59835160) and Scientific Research Foundation for
Returned Overseas Chinese Scholars, State Education Ministry of China (No. 50175097) 相似文献
139.
140.
A 3D multi-time scale discrete element method-computational fluid dynamic (DEM-CFD) coupling approach was applied to investigate the filtration of micron-sized particles by different types of fiber arrays. Both the pressure drop and the filtration efficiency were examined to indicate the filtration performance of the fiber arrays. Fibers that were uniformly arrayed in a parallel or staggered manner were compared. Results showed that the staggered array showed a better performance than the parallel array in terms of both pressure drop and filtration efficiency. Further, we compared the performance of different staggered arrays, i.e. a regular case, one densified in the front layers and another densified in the back layers. The front densified array was found to enter the clogging and cake filtration stage in the shortest time, leading to the highest filtration efficiency, but the highest pressure drop. The back densified array still achieved a much higher filtration efficiency, despite a much lower pressure drop comparable to that of the regular array. The results suggest that the two kinds of densified arrays may be suited for different purposes, e.g. baghouse filters or breathing masks. 相似文献