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赵胜毅 《电信工程技术与标准化》2019,32(3)
本文简述了电磁场电磁辐射的技术原理,探讨了无线发射设备和天线电磁辐射值的理论计算和实测方法。文中依据相关国内外标准的安全限值,详细分析了多天线不同制式电磁辐射的安全距离问题,给出了针对无线发射设备中电磁辐射防护的一般性建议。 相似文献
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ObjectiveThe global health crisis in the form of COVID-19 has forced people to shift their routine activities into a remote environment with the help of technology. The outbreak of the COVID-19 has caused several organizations to be shut down and forced them to initiate work from home employing technology. Now more than ever, it's important for people and institutions to understand the impact of excessive use of mobile phone technology and electronic gadgets on human health, cognition, and behavior. It is important to understand their perspective and how individuals are coping with this challenge in the wake of the COVID-19 pandemic. The investigation is an effort to answer the research question: whether dependency on technology during lockdown has more effects on human health in comparison to normal times.MethodsThe study included participants from India (n = 122). A questionnaire was framed and the mode of conducting the survey chosen was online to maintain social distancing during the time of the Pandemic. The gathered data was statistically analysed employing RStudio and multiple regression techniques.ResultsThe statistical analysis confirms that lockdown scenarios have led to an increase in the usage of mobile phone technology which has been confirmed by around 90% of participants. Moreover, 95% of the participants perceive an increased risk of developing certain health problems due to excessive usage of mobile phones and technology. It has been evaluated that participants under the age group 15–30 years are highly affected (45.9%) during lockdown due to excessive dependence on technology. And, amongst different professions, participants involved in online teaching-learning are the most affected (42.6%).ConclusionThe findings indicate that dependency on technology during lockdown has more health effects as compared to normal times. So, it is suggested that as more waves of pandemics are being predicted, strategies should be planned to decrease the psychological and physiological effects of the overuse of technology during lockdown due to pandemics. As the lockdown situation unfolds, people and organization functioning styles should be rolled back to the limited dependency on technology. 相似文献
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一种基于电流反馈的分段式PWM控制无刷直流电机转矩波动抑制方法 总被引:1,自引:0,他引:1
无刷直流电机伺服系统具有广泛的应用场合,但转矩波动限制了其在高精度场合的应用。针对非理想反电动势引起的无刷直流电机转矩波动提出了一种基于电流反馈的分段式PWM控制方法。该方法通过线反电动势观测器获得产生目标转矩值的参考电流,以实现对电机转矩的直接控制。同时,针对电机高速与低速运行状态分别采用不同的PWM控制策略来有效消除换相转矩波动,系统具有低转矩波动和高转矩输出的特点。通过在Matlab/Simulink环境下建立系统仿真模型,对该控制方法的转矩直接控制能力进行检验,并对转矩波动进行了对比;搭建实验平台对具有非理想反电动势的无刷直流电机进行了驱动实验。仿真和实验结果表明,该文所提出的控制方法能有效减小转矩波动,提高无刷直流电机伺服系统输出转矩的稳定性和位置控制精确度。 相似文献
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从实际项目出发,介绍了造成助力电机电枢电流波动的几个关键因素,概括了电机参数、MOS管的驱动特性、电机换向以及PWM控制信号对电流产生影响的原因.在结合电路分析的基础上提出如何降低或消除这些影响因子的方法.最后给出了具体的试验结果,验证降低电流波动影响的有效性以及对EPS性能提高的作用. 相似文献
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A. L. Goncharov 《Welding International》2013,27(9):703-709
The results of investigations of the thermoelectric properties of steels of different structural grades and also nickel- and cobalt-based alloys are presented. The temperature dependencies of the absolute thermal electromotive force and the thermal electromotive force coefficient of materials are determined. 相似文献
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