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Yang Guo Tyler Stalbaum James Mann Ho Yeung Srinivasan Chandrasekar 《Journal of Manufacturing Processes》2013,15(4):426-431
The application of controlled, low-frequency modulation (~100 Hz) superimposed onto the cutting process in the feed-direction – modulation-assisted machining (MAM) – is shown to be quite effective in reducing the wear of cubic boron nitride (CBN) tools when machining compacted graphite iron (CGI) at high machining speeds (>500 m/min). The tool life is at least 20 times greater than in conventional machining. This significant reduction in wear is a consequence of the multiple effects realized by MAM, including periodic disruption of the tool–workpiece contact, formation of discrete chips, enhanced fluid action and lower cutting temperatures. The propensity for thermochemical wear of CBN, the principal wear mode at high speeds in CGI machining, is thus reduced. The tool wear in MAM is also found to be smaller at the higher cutting speeds (730 m/min) tested. The feed-direction MAM appears feasible for implementation in industrial machining applications involving high speeds. 相似文献
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对华东地区1970年以来5级以上地震的月相效应进行了分析,表明该区地震活动具有明显的月相效应;分别对华东、安徽地区1970年以来4.5级和4级以上地震的月相调制比进行分析研究,认为华东MS5.5级、安徽MS5.5级以上地震活动受月相调制作用显著,分别提出了华东地区MS≥5.5级及安徽地区MS≥5.0级地震发生前月相调制比的定量预测指标,它对这两个区域大震的发生具有中、短期预测意义. 相似文献
3.
Nestmate recognition is a critical element in social insect organization, providing a means to maintain territoriality and
close the colony to parasites and predators. Ants detect the colony chemical label via their antennae and respond to the label
mismatch of an intruder with aggressive behavior. In the fire ant, Solenopsis invicta, worker ability to recognize conspecific nonnestmates decreases if the colony queen is removed, such that they do not recognize
conspecific nonnestmates as different. Here, we tested the hypothesis that the presence of the colony queen influences the
concentration of octopamine, a neuromodulator, in worker ants, which in turn has an effect on nestmate recognition acuity
in workers. We demonstrate that queenless workers exhibit reduced brain octopamine levels and reduced discriminatory acuteness;
however, feeding queenless workers octopamine restored both. Dopamine levels are influenced by honeybee queen pheromones;
however, levels of this biogenic amine were unchanged in our experiments. This is the first demonstration of a link between
the presence of the colony queen, a worker biogenic amine, and conspecific nestmate recognition, a powerful expression of
colony cohesion and territoriality. 相似文献
4.
This study is aimed to clarify whether effect of low-level microwave radiation on human brain differs at different modulation
frequencies. Resting EEG recordings were done on different groups of healthy volunteers. The 450 MHz microwave radiation modulated
at 40 and 70 Hz (15 subjects) and 217 and 1,000 Hz (19 subjects) frequencies was applied. The results of our previous study
at 7, 14 and 21 Hz modulation were included into analysis. Ten cycles of the exposure (1 min off and 1 min on) at each fixed
modulation frequencies were applied. The field power density at the scalp was always 0.16 mW/cm2. Our results showed that microwave exposure increased the EEG energy at EEG frequencies lower or close to the modulation
frequency. No effect was detected at EEG frequencies higher than the modulation frequency. Statistically significant changes
were caused by exposure in the EEG alpha and beta frequency bands; no significant effect was detected in the theta band. Our
results suggest that telecommunication devices with complex spectrum of modulation frequencies like mobile phone can affect
all human EEG frequency bands. 相似文献
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介绍几种提高射流效率、充分利用其能量的方法,其中包括:等能量多次切割,流量(或流速)的脉动调制,有效利用淹没射流的空化段,研制开发优质喷嘴。 相似文献
6.
Anna Suhhova Maie Bachmann Jaanus Lass Deniss Karai Hiie Hinrikus 《The Environmentalist》2009,29(2):210-214
This study is aimed to investigation of the effect of modulated 450 MHz microwave radiation on the EEG inter-hemispheric asymmetry.
Ten cycles of the microwave exposure (1 min off and 1 min on) at fixed modulation frequency were applied on two groups of
healthy volunteers. The first group of 13 subjects was exposed to microwave radiation modulated at 14 Hz and the second group
of 15 subjects at 40 Hz frequency. The peak specific absorption rate (SAR) average over 1 g was 0.303 W/kg. Differences in
SAR between hemispheres were up to 20 dB. Rod antenna was located from the left side of the head. Differences of relative
changes in EEG energy between symmetric channels FP1–FP2, T3–T4, P3–P4 and O1–O2 in exposed and sham conditions were analysed.
The results showed increase in EEG energy from the left side caused by microwave exposure. Statistical analysis done for the
whole group of subjects didn’t reveal significant differences in inter-hemispheres asymmetry between exposed and sham conditions.
However, statistical analysis performed for individual subjects detected significant differences in asymmetry caused by exposure
for 15–35% of individuals. 相似文献
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