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71.
72.
阐述了高压电器可靠性研究的意义,探讨了高压电器自身可靠性的特点,总结了国内外在高压电器可靠性研究方面的经验和成果,在此基础上提出了对我国高压电器可靠性研究的一些看法. 相似文献
73.
根据汽油机喷油器结焦积碳形成机理,建立了一套有效的汽油清净分散剂的评定装置———电控喷射模拟试验装置。该装置通过对喷油器强化加热,控制喷油器的喷油时间间隔,从而强化了喷油器结焦积碳的形成条件,缩短了试验时间。为验证该装置的有效性,选用几种在实验室发动机台架上清净性效果较好的添加剂对其进行了试验验证。同时,通过控制喷油器的加热状况,以模拟汽车试验15/45喷油器环境温度。试验表明,该模拟试验装置对各种添加剂分辨效果明显,重复性好,试验可靠。通过对该模拟试验装置评定结果与试验室台架试验的评定结果的比较可知,两者评定结果趋势一致。 相似文献
74.
The shear properties of thin films of star and linear polyisoprene (PIP) melts under high pressure were investigated as a function of sliding velocity (shear rate) using the surface forces apparatus. The results were contrasted with their bulk rheological properties; effects of thickness constraint on the shear behavior were discussed. The melts of PIP in bulk exhibit Newtonian-like constant viscosity at least at low shear rates (frequencies), which suggests that individual molecules flow with lateral sliding motion. However, thin films of PIP melts show tribological features involving apparent shear-thinning behavior, indicative of the correlated motions in confined geometries. The shear-property change from bulk rheological behavior to thin-film tribological behavior along with the thickness decrease reflects the physical states and their transitions in the systems; the thickness constraint induces glasslike transitions. Effects of molecular weights and molecular architecture (star-branched or linear) on the shear properties are also discussed. 相似文献
75.
绝对码编码器中一种新型的编码方法 总被引:13,自引:1,他引:13
提出了码盘式传感器码盘的一种全新的码制——单道码绝对码编码法,即绝对码简码。它是一种单道码编码法,图形简单,制作方便,容易提高精度,将对绝对码编码器的小型化,集成化和绝对式磁编码器的研制提供一种新的思路。 相似文献
76.
Comparison of friction measurements using the atomic force microscope and the surface forces apparatus: the issue of scale 总被引:1,自引:0,他引:1
Results are presented of lateral force measurements using the atomic force microscope (AFM) and the surface forces apparatus (SFA). Two different probes are used in the AFM measurements; a sharp silicon nitride tip (radius R20 nm) and a glass ball (R15 m). The lateral force is measured between the (silicon nitride or glass) probe and a mica surface which has been coated by a thin lubricant film. In the SFA, a thin lubricant film separates two molecularly smooth mica surfaces (R1 cm) which are slid relative to each other. Perfluoropolyether (PFPE) and polydimethylsiloxane (PDMS) were used as the lubricant films. In the SFA where the contact diameter is largest, the PFPE film shows much lower friction than PDMS. As the size of the probe decreases, the difference in the measured friction decreases. For sharp AFM tips, no clear distinction between the tribological properties of the films can be made. Hence, the measured coefficient of friction varies according to the length scale probed, at least for small dimensions. 相似文献
77.
The friction of three chemically distinct esters was measured in order to determine how molecular architecture influences friction. The friction coefficients of mica surfaces separated by a thin film (<2 nm) of -chlorodecyl benzoate, -chlorodecyl pentafluoro benzoate, and -chlorodecyl perfluoro hexanoate were measured to be 0.15±0.015, 0.13±0.012, and 0.12±0.02, respectively. The friction coefficients for the esters are lower than the previously measured friction coefficients of simple hydrocarbon liquids such as n-tetradecane (=0.8), but are comparable to the friction coefficients of surfactant monolayer coated surfaces (=0.001–0.2). The results suggest that the ester molecules adsorb onto the mica surface with the (phenyl or hexyl) carbonyl next to the surface and the hydrocarbon tail pointing away from the surface. Hence, the friction is controlled by the packing density and properties of the hydrocarbon tail. Changes in the chemistry and structure of the carboxylic acid portion of the ester only give rise to small changes in the friction coefficient. 相似文献
78.
79.
提出PX型正压防爆电气控制柜的设计与调试,可供从事本专业人员设计调试PX型正压防爆控制柜借鉴与参考。 相似文献
80.
In this paper, extremely low frequency (ELF) magnetic fields (MFs) were measured during the temperature-rise test of various electrotechnical equipment. The number of workers subjected to magnetic fields from the temperature-rise test is small; however, the exposure can be significant as the testing currents can be in the order of hundreds amperes. The resultant magnetic field during testing can exceed the ICNIRP limits for occupational exposure. The magnetic field exposure was recorded and statistical measures were extracted for three electrotechnical apparatus. It was found that the Time-Weighted Average exposure per unit current can reach 0.0598 μT/A. Additionally, in order to mitigate the exposure, a rule of thumb regarding safety distances has been proposed. It is shown that the use of this rule of thumb can reduce the magnetic field exposure. 相似文献