针对城市环境中,现有路由算法在选择路由时未能考虑网络的全局信息、历史信息等问题,提出了一种适合于城市环境的车载自组织网络路由算法(a Routing Protocol for Urban Vehicular ad hoc networks,RPUV),该算法通过考虑路由中每个路段...针对城市环境中,现有路由算法在选择路由时未能考虑网络的全局信息、历史信息等问题,提出了一种适合于城市环境的车载自组织网络路由算法(a Routing Protocol for Urban Vehicular ad hoc networks,RPUV),该算法通过考虑路由中每个路段的实时信息、路段的历史信息,保证路由的实时性和稳定性;同时,通过选择下一个十字路口时考虑网络的全局信息,保证了路由的可靠性。与现有路由算法相比,RPUV算法具有实时性和可靠性的特点,通过仿真表明了RPUV在数据包投递率和传输时延上具有更大的优越性。展开更多
The accurate measurement on the compressibility and thermal expansion coefficients of density standard liquid at 2329kg/m3（DSL-2329） plays an important role in the quality control for silicon single crystal manufact...The accurate measurement on the compressibility and thermal expansion coefficients of density standard liquid at 2329kg/m3（DSL-2329） plays an important role in the quality control for silicon single crystal manufacturing. A new method is developed based on hydrostatic suspension principle in order to determine the two coefficients with high measurement accuracy. Two silicon single crystal samples with known density are immersed into a sealed vessel full of DSL-2329. The density of liquid is adjusted with varying liquid temperature and static pressure, so that the hydrostatic suspension of two silicon single crystal samples is achieved. The compression and thermal expansion coefficients are then calculated by using the data of temperature and static pressure at the suspension state. One silicon single crystal sample can be suspended at different state, as long as the liquid temperature and static pressure function linearly according to a certain mathematical relationship. A hydrostatic suspension experimental system is devised with the maximal temperature control error ±50 μK; Silicon single crystal samples can be suspended by adapting the pressure following the PID method. By using the method based on hydrostatic suspension principle, the two key coefficients can be measured at the same time, and measurement precision can be improved due to avoiding the influence of liquid surface tension. This method was further validated experimentally, where the mixture of 1, 2, 3-tribromopropane and 1,2-dibromoethane is used as DSL-2329. The compressibility and thermal expansion coefficients were measured, as 8.5′10–4 K–1 and 5.4′10–10 Pa–1, respectively.展开更多
The accuracy of solid density primary standard is decided mainly by the accuracy of the diameter measurement of silicon sphere. With traditional five-interferogram algorithm to unwrap phase for di- ameter measurement,...The accuracy of solid density primary standard is decided mainly by the accuracy of the diameter measurement of silicon sphere. With traditional five-interferogram algorithm to unwrap phase for di- ameter measurement, the phase steps should be equal to π/2 exactly, but this is almost impossible to achieve in nanometer positioning technique. In order to overcome this defect, we have derived an im- proved five-interferogram algorithm, which not only keeps the high accuracy of traditional five-inter- ferogram algorithm, but also does not require absolute equal step to unwrap phase. Instead, the im- proved five-interferogram algorithm only needs measuring phase shifting. Based on the improved al- gorithm, we have developed a novel interferometer with special etalon, and the cavity length of this etalon can be changed by pressure from vertical direction to realize phase shifting. The accuracy of this interferometer is better than 3 nm and can be improved in future research.展开更多
文摘针对城市环境中,现有路由算法在选择路由时未能考虑网络的全局信息、历史信息等问题,提出了一种适合于城市环境的车载自组织网络路由算法(a Routing Protocol for Urban Vehicular ad hoc networks,RPUV),该算法通过考虑路由中每个路段的实时信息、路段的历史信息,保证路由的实时性和稳定性;同时,通过选择下一个十字路口时考虑网络的全局信息,保证了路由的可靠性。与现有路由算法相比,RPUV算法具有实时性和可靠性的特点,通过仿真表明了RPUV在数据包投递率和传输时延上具有更大的优越性。
基金Supported by National Natural Science Foundation of China(Grant No.51105347)National Key Technology R&D Program of Ministry of Science and Technology of China(Grant No.2011BAI02B03)
文摘The accurate measurement on the compressibility and thermal expansion coefficients of density standard liquid at 2329kg/m3（DSL-2329） plays an important role in the quality control for silicon single crystal manufacturing. A new method is developed based on hydrostatic suspension principle in order to determine the two coefficients with high measurement accuracy. Two silicon single crystal samples with known density are immersed into a sealed vessel full of DSL-2329. The density of liquid is adjusted with varying liquid temperature and static pressure, so that the hydrostatic suspension of two silicon single crystal samples is achieved. The compression and thermal expansion coefficients are then calculated by using the data of temperature and static pressure at the suspension state. One silicon single crystal sample can be suspended at different state, as long as the liquid temperature and static pressure function linearly according to a certain mathematical relationship. A hydrostatic suspension experimental system is devised with the maximal temperature control error ±50 μK; Silicon single crystal samples can be suspended by adapting the pressure following the PID method. By using the method based on hydrostatic suspension principle, the two key coefficients can be measured at the same time, and measurement precision can be improved due to avoiding the influence of liquid surface tension. This method was further validated experimentally, where the mixture of 1, 2, 3-tribromopropane and 1,2-dibromoethane is used as DSL-2329. The compressibility and thermal expansion coefficients were measured, as 8.5′10–4 K–1 and 5.4′10–10 Pa–1, respectively.
文摘The accuracy of solid density primary standard is decided mainly by the accuracy of the diameter measurement of silicon sphere. With traditional five-interferogram algorithm to unwrap phase for di- ameter measurement, the phase steps should be equal to π/2 exactly, but this is almost impossible to achieve in nanometer positioning technique. In order to overcome this defect, we have derived an im- proved five-interferogram algorithm, which not only keeps the high accuracy of traditional five-inter- ferogram algorithm, but also does not require absolute equal step to unwrap phase. Instead, the im- proved five-interferogram algorithm only needs measuring phase shifting. Based on the improved al- gorithm, we have developed a novel interferometer with special etalon, and the cavity length of this etalon can be changed by pressure from vertical direction to realize phase shifting. The accuracy of this interferometer is better than 3 nm and can be improved in future research.
