Large Scale multiple input multiple output(MIMO) systems have recently emerged as a promising technology for 5G communications.While they have been shown to offer significant performance benefits in theoretical studie...Large Scale multiple input multiple output(MIMO) systems have recently emerged as a promising technology for 5G communications.While they have been shown to offer significant performance benefits in theoretical studies,the large scale MIMO transmitters will have to be deployed in the limited physical space of today's base stations(BSs).Accordingly,this paper examines effects of deploying increasing numbers of antennas in fixed physical space,by reducing the antenna spacing.We focus on the resulting performance of large-scale MIMO transmitters using low complexity closed form precoding techniques.In particular,we investigate the combined effect of reducing the distance between the antenna elements with increasing the number of elements in a fixed transmitter space.This gives rise to two contradicting phenomena:the reduction of spatial diversity due to reducing the separation between antennas and the increase in transmit diversity by increasing the number of elements.To quantify this tradeoff,we investigate densely deployed uniform antenna arrays modelled by detailed electromagnetic simulation.Our results show the somewhat surprising result that,by reducing the separations between the antennas to significantly less than the transmit wavelength to fit more antennas,the resulting system performance improves.展开更多
Almost the same quantity to net output work of energy has been carried out and wasted by exhaust gas in typical automotive engine. Recovering the energy from exhaust gas and converting to mechanical energy will dramat...Almost the same quantity to net output work of energy has been carried out and wasted by exhaust gas in typical automotive engine. Recovering the energy from exhaust gas and converting to mechanical energy will dramatically increase the heat efficiency and decrease the fuel consumption. With the increasing demand of fuel conservation, exhaust gas energy recovery technologies have been a hot topic. At present, many researches have been focused on heating or cooling the cab, mechanical energy using and thermo-electronic converting. Unfortunately, the complicated transmission of mechanical energy using and the depressed efficiency of thermo-electronic converting restrict their widely applying. In this paper, a kind of exhaust gas energy recovery system of pneumatic driving automotive engine, in which highly compressed air acts as energy storing and converting carrier, has been established. Pneumatic driving motor can produce moderate speed and high torque output, which is compatible for engine using. The feasibility has been certificated by GT-Power simulation and laboratory testes. The technologies about increasing recovery efficiency have been discussed in detail. The results demonstrated that the in parallel exhaust gas energy recovery system, which is similar to the compound turbo-charger structure can recovery 8 to 10 percent of rated power output. At last, a comprehensive system, which includes Rankine cycle based power wheel cycle unit etc., has been introduced.展开更多
基金supported by the Royal Academy of Engineering,UKthe Seventh Framework Programme for Research of the European Commission under grant number HARP-318489
文摘Large Scale multiple input multiple output(MIMO) systems have recently emerged as a promising technology for 5G communications.While they have been shown to offer significant performance benefits in theoretical studies,the large scale MIMO transmitters will have to be deployed in the limited physical space of today's base stations(BSs).Accordingly,this paper examines effects of deploying increasing numbers of antennas in fixed physical space,by reducing the antenna spacing.We focus on the resulting performance of large-scale MIMO transmitters using low complexity closed form precoding techniques.In particular,we investigate the combined effect of reducing the distance between the antenna elements with increasing the number of elements in a fixed transmitter space.This gives rise to two contradicting phenomena:the reduction of spatial diversity due to reducing the separation between antennas and the increase in transmit diversity by increasing the number of elements.To quantify this tradeoff,we investigate densely deployed uniform antenna arrays modelled by detailed electromagnetic simulation.Our results show the somewhat surprising result that,by reducing the separations between the antennas to significantly less than the transmit wavelength to fit more antennas,the resulting system performance improves.
基金National Natural Science Foundation of China ( No. 50976046)
文摘Almost the same quantity to net output work of energy has been carried out and wasted by exhaust gas in typical automotive engine. Recovering the energy from exhaust gas and converting to mechanical energy will dramatically increase the heat efficiency and decrease the fuel consumption. With the increasing demand of fuel conservation, exhaust gas energy recovery technologies have been a hot topic. At present, many researches have been focused on heating or cooling the cab, mechanical energy using and thermo-electronic converting. Unfortunately, the complicated transmission of mechanical energy using and the depressed efficiency of thermo-electronic converting restrict their widely applying. In this paper, a kind of exhaust gas energy recovery system of pneumatic driving automotive engine, in which highly compressed air acts as energy storing and converting carrier, has been established. Pneumatic driving motor can produce moderate speed and high torque output, which is compatible for engine using. The feasibility has been certificated by GT-Power simulation and laboratory testes. The technologies about increasing recovery efficiency have been discussed in detail. The results demonstrated that the in parallel exhaust gas energy recovery system, which is similar to the compound turbo-charger structure can recovery 8 to 10 percent of rated power output. At last, a comprehensive system, which includes Rankine cycle based power wheel cycle unit etc., has been introduced.
