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排序方式: 共有491条查询结果,搜索用时 15 毫秒
71.
72.
A magnetically separable photocatalyst TiO(2)/SiO(2)/NiFe(2)O(4) (TSN) nanosphere with egg-like structure was prepared by a unique process that combined a liquid catalytic phase transformation method, reverse micelle technique and chemical precipitation means. The prepared photocatalyst shows high photocatalytic activity for the degradation of methyl orange in water. The magnetic property measurements indicate that the photocatalyst possesses a superparamagnetic nature. It can be separated from water when an external magnetic field is added and redispersed into water solution after the external magnetic field is eliminated. It is one of the promising photocatalysts for wastewater treatment. A transmission electron microscope (TEM) and an x-ray diffractometer (XRD) were used to characterize the structure of the TSN photocatalyst. The results indicate that nickel ferrite core nanoparticles were completely encapsulated into monodisperse silica nanospheres as carrier, and titania nanoparticle aggregates were coated onto the surface of SN nanospheres, forming an imperfect TiO(2) shell for photocatalysis. The SiO(2) layer between the NiFe(2)O(4) core and the TiO(2) shell effectively prevents the injection of charges from TiO(2) particles to NiFe(2)O(4), which gives rise to an increase in photocatalytic activity. Moreover, the recycled TSN exhibits good repeatability of the photocatalytic activity. 相似文献
73.
An improved numerical method for predicting intermetallic layer thickness developed during the formation of solder joints on Cu substrates 总被引:1,自引:0,他引:1
S. Chada W. Laub R. A. Fournelle D. Shangguan 《Journal of Electronic Materials》1999,28(11):1194-1202
An improved numerical method has been developed for calculating the thickness of intermetallic layers formed between Cu substrates
and solders during the soldering process. The improved method takes into account intermetallic dissolution during heating
and intermetallic precipitation during cooling and requires as input (1) the temperature-time profile for the soldering process,
(2) the experimentally determined isothermal growth parameters for the growth of the intermetallic layer into Cu saturated
molten solder, (3) the experimentally determined Nernst-Brunner parameters for the dissolution of Cu into molten solder, (4)
the experimentally determined solubility of Cu in molten solder and (5) assumptions about the thickness of the boundary layer
in the liquid ahead of the growing intermetallic. Calculations show that the improved method predicts intermetallic growth
between Cu substrates and 96.5Sn-3.5Ag solder during reflow soldering better than a previously developed method, which did
not take into account dissolution during heating and precipitation during cooling. Calculations further show that dissolution
has a significant effect on growth, while precipitation does not. 相似文献
74.
0前言电费在供水企业的生产成本中占相当大的比重。各地都有着各自不同的生产条件,除合理选择机泵型号外,积极响应国家的电价政策,提高功率因数,降低电费开支显得尤为重要。用户用电功率因数的高低,对电力系统发、供、 相似文献
75.
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77.
In this study,HEA/AI composite interlayer was used to fabricate Ti/Mg bimetal composites by solidliquid compound casting process.The Al layer was prepared on the surface of TC4 alloy by hot dipping,and the FeCoNiCr HEA layer was prepared by magnetron sputtering onto the Al layer.The influence of the HEA layer thickness and pouring temperature on interface evolution was investigated based on SEM observation and thermodynamic analysis.Results indicate that the sluggish diffusion effect of HEA can ... 相似文献
78.
阻尼多楔带传动系统建模及带滑移控制分析 总被引:1,自引:0,他引:1
考虑多楔带的阻尼特性和带在带轮上的蠕变对带张力的影响,建立了阻尼多楔带传动系统旋转运动模型,给出了带张力和各带轮的旋转角位移的数值计算方法,并引入了滑移因子预测滑移现象的发生.分析研究多楔带阻尼对系统运动特性的影响,及当多楔带传动系统结构参数确定时,张紧器预载荷、安装角对带滑移的影响.建立的阻尼多楔带传动系统旋转运动模型和数值求解方法为带传动系统的研究提供了理论依据,对带滑移控制的分析为带传动系统的设计提供了参考. 相似文献
79.
驾驶员在驾车过程中使用手机会造成驾驶分心,研究驾驶中的补偿行为有助于降低驾驶分心造成的危害。通过模拟驾驶探究驾驶行为和生理指标在是否使用手机、不同路段复杂程度、不同驾驶员类型中的差异,从而使驾驶员注意到驾驶中使用手机的危害并及时采取措施,弥补驾驶分心带来的危害。研究结果表明,使用手机主效应在各项指标中均呈现显著影响(P<0.001),驾驶员类型主效应在阅读短信行为中的踩刹车持续时间上存在显著影响(P<0.01),使用手机与驾驶员类型交互作用在接听电话行为的心率、阅读短信行为中的平均速度、踩刹车持续时间和心率上存在显著影响(P<0.05)。比起接听免提电话,阅读短信时采取补偿行为的幅度更大(P<0.05);驾驶员比学员采取补偿行为的幅度更大(P<0.05)。 相似文献
80.