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Vasant Natarajan 《Resonance》2013,18(1):39-50
We discuss the absorber theory of radiation as put forward by Wheeler and Feynman. We show that it gives a better understanding of the photon compared to the usual quantum electrodynamics (QED) picture. 相似文献
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Vasant Natarajan 《Resonance》2001,6(8):44-59
We trace the evolution of standards for weights and measures from olden days to their modern scientific definitions. Even in the era of modern science, standards till recently used to be defined by artifacts. It is only in the last few decades that we have gone over to definitions based on fundamental constants of nature. This has made the standards universally reproducible. The present standards for time, length, and electrical units are all based on physical constants. The mass standard, represented by the prototype kilogram, is the only remaining artifact, but there are promising proposals to replace that in the near future. 相似文献
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A general theory is developed for extended bandwidth operation of actively compensated finite gain amplifiers. Designs for three new circuits are given which implement the theory. These circuits employ only operational amplifiers and resistors and their gains depend only on their resistor ratios. Thus they are suitable for IC fabrication. Further in IC technology, the characteristics of the operational amplifiers as well as the resistor ratios track closely with each other with reference to temperature and aging. Thus the extended bandwidth operation of the amplifiers will be available over a wide temperature range as well as under varying aging conditions. Their characteristics can be tuned easily by trimming only two resistors. Applications of the new amplifiers have been considered in RC active filters as well as in inductance simulation schemes. Experimental results are given which closely agree with theoretical predictions. The results also indicate that substantial improvement in the usable bandwidth of the circuits employing the new amplifiers may be expected over those using the conventional design of finite gain amplifiers. 相似文献