基于辅助符号的非线性自干扰抵消算法及其简化实现

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。     

机顶盒中SI引擎的分析与设计

在对PSI／SI表进行了详细分析的基础上阐述了如何设计通用、高效、可靠、容错、有可扩展性的处理PSI／SI表SI引擎的相关和关键技术。     

Thermodynamic analysis of spark‐ignition engine using a gas mixture model for the working fluid

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.     

第一代机顶盒的电子节目指南

电子节目指南是由业务商为用户提供的一项重要的服务,它负责电视节目和各种增值业务的导航.讨论了电子节目指南的生成、系统构成及其实现.     

OSI RM网络层基于通信子网的路由选择算法

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。     

数字电视系统中PSI及SI的基础知识及应用

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。     

Experimental study on lean-burn characteristics of an SI engine with hydrogen/gasoline combined injection and EGR

Hydrogen has shown potential for improving the combustion and emission characteristics of the spark ignition (SI) dual-fuel engine. To reduce the additional NO_x 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 α_H2 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 (COV_IMEP) indicate that the addition of hydrogen can effectively extend the EGR limit. Regarding gaseous emissions, NO_x 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 NO_x, 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.     

Effect of the turbulence intensity on knocking tendency in a SI engine with high compression ratio using biogas and blends with natural gas,propane and hydrogen

This research presents the test results carried out in a diesel engine converted to spark ignition (SI) using gaseous fuels, applying a geometry change of the pistons combustion chamber (GCPCC) to increase the turbulence intensity during the combustion process; with similar compression ratio (CR) of the original diesel engine; the increase in turbulence intensity was planned to rise turbulent flame speed of biogas, to compensate its low laminar flame speed. The research present the test to evaluate the effect of increase turbulence intensity on knocking tendency; using fuel blends of biogas with natural gas, propane and hydrogen; for each fuel blend the maximum output power was measured just into the knocking threshold before and after GCPCC; spark timing (ST) was adjusted for optimum generating efficiency at the knocking threshold. Turbulence intensity with GCPCC was estimated using Fluent 13, with 3D Combustion Fluid Dynamics (CFD) numerical simulations; 12 combustion chamber geometries were simulated in motoring conditions; the selected geometry had the greatest simulated turbulent kinetic energy (TKE) and Reynolds number (Re) during combustion. The increased turbulence intensity was measured indirectly through the periods of combustion duration to mass fraction burn 0–5%, 0–50% and 0–90%; for almost all the fuel blends the increased turbulence intensity of the engine, increased the knocking tendency requiring to reduce the maximum output power to keep engine operation just into the knocking threshold. Biogas was the only fuel without power derating by the conditions of higher pressure and higher turbulence during combustion by GCPCC and improve its generating efficiency. Peak pressure, heat release rate, mean effective pressure and exhaust temperature were lower after GCPCC. Tests results indicated that knocking tendency was increased because of the higher turbulent flame speed; fuel blends with high laminar flame speed and low methane number (MN) had higher knocking tendency and lower output power.     

中国先进加工制造工艺与装备技术中的关键科学问题

根据中国国家自然科学基金委员会安排，研讨先进加工制造工艺与装备科学与技术的发展趋势。针对中国先进加工制造和装备学科存在的基础研究不系统、不深入的共性状况，以国家需求为目标，以加强先进制造工艺与装备的理论基础研究和应用基础研究为突破口，提出国家自然科学基金“十一五”(2006～2010)期间先进加工制造工艺和装备领域需要研究的科学问题、研究方向、工程目标，以及应该优先发展的重点方向。 先进加工制造是实现高效率、高精度和低成本制造的技术支撑。先进加工制造的目标是高效化、精密化、智能化、集成化、数字化和洁净化，关键技术包括高速/高效切削加工技术、高速/超高速磨削技术、精密/超精密加工技术、非传统加工及其复合加工技术，以及相关的先进加工制造装备的制造技术。 摘要根据中国国家自然科学基金委员会安排，研讨先进加工制造工艺与装备科学与技术的发展趋势。针对中国先进加工制造和装备学科存在的基础研究不系统、不深入的共性状况，以国家需求为目标，以加强先进制造工艺与装备的理论基础研究和应用基础研究为突破口，提出国家自然科学基金“十一五”(2006～2010)期间先进加工制造工艺和装备领域需要研究的科学问题、研究方向、工程目标，以及应该优先发展的重点方向。 先进加工制造是实现高效率、高精度和低成本制造的技术支撑。先进加工制造的目标是高效化、精密化、智能化、集成化、数字化和洁净化，关键技术包括高速/高效切削加工技术、高速/超高速磨削技术、精密/超精密加工技术、非传统加工及其复合加工技术，以及相关的先进加工制造装备的制造技术。 高速/高效切削加工技术的科学问题包括切削加工时刀具和工件材料相互作用过程刀具摩擦、磨损和破坏机理，工件材料高速切削变形理论与工件表面成形机理，高速切削刀具与机床的动力学分析，高速切削过程的智能监控理论与技术。研究方向包括高速/高效切削机床与刀具，难加工材料的高速/高效切削加工，高速/高效切削表面质量，高速/高效切削加工的动力学与稳定性。工程目标包括超高速切削，机床主轴转速达到1×106r·min-1，铣削铝及其合金的切削速度达到1×104m·min-1；高性能切削，机床主轴功率达到100kW，进给速度达到50m·min-1；采用多坐标驱动，提高机床的柔性和效率。     

阿伏加德罗常数测量与千克重新定义

当千克用固定普朗克常数h的方法定义时,X射线晶体密度法(XRCD)即被用来定义和复现千克,它采用对浓缩²⁸Si原子计数的方法来测量阿伏加德罗常数N_A,已将N_A和h的测量不确定度达到2×10^-8,并反过来确定硅球的质量实现对千克的量值复现。阐述了晶格常数、同位素、浓缩硅、硅球直径及表面氧化层等阿伏加德罗常数测量的关键技术的研究进展。介绍了原子计数法千克定义及其量值复现方法,该方法将为国际单位制改制之后我国质量量值复现提供参考。