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71.
72.
提出了基于GTM900C和SI4421构建的二级通信网络路灯控制系统设计方法,通过设计出合理的通信协议,实现路灯照明的智能控制。详细介绍了二级通信网络路灯智能控制系统的总体设计,网关及路灯控制节点的硬件设计及整个通信系统间的通信协议的设计。通过GPRS网络及自组建的局域网络,该系统可靠地实现了路灯的智能控制,定时开关,状态获取,以及路灯控制节点的故障自报警等功能。 相似文献
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同频同时全双工是第5代(5G)通信关键技术之一,数字自干扰抵消算法是其重要研究方向。针对非线性数字自干扰抵消算法中,失真系数估计受到自干扰信道估计误差的影响这一问题,该文提出一种基于辅助符号的非线性自干扰抵消算法,通过对辅助符号做自干扰抵消,将信道估计符号的失真误差映射到其抵消结果中并提取出来,从中估计失真系数。接着针对算法开销问题提出一种简化实现方案。仿真结果显示,接收自干扰信号为-5 dBm时,算法可将自干扰非线性失真分量抵消至约-100 dBm,且性能随接收自干扰功率降低而提高。 相似文献
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This paper presents thermodynamic analysis of spark‐ignition engine. A theoretical model of Otto cycle, with a working fluid consisting of various gas mixtures, has been implemented. It is compared to those which use air as the working fluid with variable temperature specific heats. A wide range of engine parameters were studied, such as equivalence ratio, engine speed, maximum and outlet temperatures, brake mean effective pressure, gas pressure, and cycle thermal efficiency. For example, for the air model, the maximum temperature, brake mean effective pressure (BMEP), and efficiency were about 3000 K, 15 bar, and 32%, respectively, at 5000 rpm and 1.2 equivalence ratio. On the other hand, by using the gas mixture model under the same conditions, the maximum temperature, BMEP, and efficiency were about 2500 K, 13.7 bar, and 29%. However, for the air model, at lower engine speeds of 2000 rpm and equivalence ratio of 0.8, the maximum temperature, BMEP, and efficiency were about 2000 K, 8.7 bar, and 28%, respectively. Also, by using the gas mixture model under these conditions, the maximum temperature, BMEP, and efficiency were about 1900 K, 8.4 bar, and 27%, i.e. with insignificant differences. Therefore, it is more realistic to use gas mixture in cycle analysis instead of merely assuming air to be the working fluid, especially at high engine speeds. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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本文论述了OSI RM网络层基于通信子网的路由选择算法的若干问题,包括算法的设计原则、原理、实现方法以及关于算法完善性的讨论。 相似文献
79.
数字电视系统中PSI及SI的基础知识及应用 总被引:1,自引:0,他引:1
PSI与SI都是数字电视系统的重要信息。PSI是MPEG标准规定的用于提供给解码器所需解码参数的信息。SI是由DVB标准定义的重要信息。其作为PSI的补充,不仅用于提供接收解码器解码所需解码参数的信息,还提供了如频道名称等等其他有用的信息。本文首先介绍了PSI及SI的基础知识,并结合实际情况进行阐述。深圳有线电视台所使用的PSI及SI设备,结合实际,说明这些表格是如何产生并如何应用于数字电视系统的。 相似文献
80.
《International Journal of Hydrogen Energy》2019,44(26):13988-13998
Hydrogen has shown potential for improving the combustion and emission characteristics of the spark ignition (SI) dual-fuel engine. To reduce the additional NOx emissions caused by hydrogen direct injection, in this research, the cooperative control of the addition of hydrogen with exhaust gas recirculation (EGR) in the hydrogen/gasoline combined injection engine was investigated. The results indicate that both the addition of hydrogen and the use of EGR can increase the brake mean effective pressure (BMEP). As the αH2 value increases from 0% to 25%, the maximum BMEP increases by 9%, 12.70%, 16.50%, 11.30%, and 8.20%, respectively, compared with the value without EGR at λ = 1.2. The CA0-10 tends to increase with increases in the EGR rate. However, the effect of EGR in increasing the CA0-10 can be offset by the addition of 15% hydrogen at λ = 1.2. Measurements of the coefficient of variation of the indicated mean effective pressure (COVIMEP) indicate that the addition of hydrogen can effectively extend the EGR limit. Regarding gaseous emissions, NOx emissions, after the introduction of EGR and the addition of hydrogen, are lower than those of pure gasoline without EGR. An 18% EGR rate yields a significant reduction in NOx, reaching maximum decreases of about 82.7%, 77.8%, and 60% compared to values without EGR at λ = 1.0, 1.2, and 1.4, respectively. As the EGR rate increases, the hydrocarbon (HC) emissions continuously increase, whereas a blend of 5% hydrogen can significantly reduce the HC emissions at high EGR rates at λ = 1.4. Finally, according to combustion and emissions, the coupling of a 25% addition of hydrogen with 30% EGR at λ = 1.2, and the coupling of a 20% addition of hydrogen with an 18% EGR rate at λ = 1.4 yield the best results. 相似文献