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.     

深亚微米SoC中的电源/地网络设计

随着芯片集成度的不断提高,其上所消耗的功率也在不断增加,因此,电源/地网络设计的可靠性与有效性就成为了SoC设计中一个关键性的问题.以往的设计中,通常都是由设计师根据经验进行电源/地网络的设计,因而可能导致设计效率的降低,延长了芯片的上市时间.针对这个问题,本文首先介绍了IR压降和电迁移现象的产生原因及其影响因素.其次,提出了一种方法,在芯片物理设计的初始阶段,就对其电源/地网络进行可靠的估算,并在估算的基础上进行电源/地网络的设计,从而在设计的早期确保了电源分配的可靠性,提高了设计效率.最后,本文通过一个DSP＆CPU芯片的设计实例,介绍了该方法的使用,并获得了良好的效果.     

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。     

Special Report on Electrical Standards: New Internationally Adopted Reference Standards of Voltage and Resistance

This report provides the background for and summarizes the main results of the 18th meeting of the Consultative Committee on Electricity (CCE) of the International Committee of Weights and Measures (CIPM) held in September 1988. Also included are the most important implications of these results. The principal recommendations originating from the meeting, which were subsequently adopted by the CIPM, establish new international reference standards of voltage and resistance based on the Josephson effect and the quantum Hall effect, respectively. The new standards, which are to come into effect starting January 1, 1990, will result in improved uniformity of electrical measurements worldwide and their consistency with the International System of Units or SI. To implement the CIPM recommendations in the U.S. requires that, on January 1, 1990, the value of the U.S. representation of the volt be increased by about 9.26 parts per million (ppm) and the value of the U.S. representation of the ohm be increased by about 1.69 ppm. The resulting increases in the U.S. representations of the ampere and watt will be about 7.57 ppm and 16.84 ppm, respectively. The CCE also recommended a particular method, affirmed by the CIPM, of reporting calibration results obtained with the new reference standards that is to be used by all national standards laboratories.     

基于SI4432的可燃气体报警仪设计

基于射频芯片SI4432设计的可燃气体无线报警仪,具有结构简单、响应快速和扩大报警范围等优点.该报警器采用C8051F020单片机,其集成了12位A/D转换器能够精确的进行数据的采集,通过射频芯片SI4432能够快速准确的发送报警信号.给出了软硬件的设计方法,经实验测试:该系统性能稳定,能够快速准确的发送报警信号,具有很高的实用价值.     

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。     

数字电视清流备份系统建设

对现有数字电视前端系统进行深入分析,提出地市级前端数字电视应急备份系统设计思路,此方案简化了备份系统硬件构成,降低了系统投资成本,实现了本地信源的有效备份,主要介绍系统建设原则、基本原理及其方案流程.     

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.     

Experimental based comparative exergy analysis of a multi-cylinder spark ignition engine fuelled with different gaseous (CNG,HCNG, and hydrogen) fuels

The experimental investigation was carried out on a multi-cylinder spark ignition (SI) engine fuelled with compressed natural gas (CNG), hydrogen blended CNG (HCNG) and hydrogen with varying load at 1500 rpm in order to perform comparative exergy analysis. The exergy analysis indicates that work exergy, heat transfer exergy and exhaust exergy were the highest with hydrogen at all loads due to its high flame temperature, low quenching distance, and high flame speed. The engine's exergy efficiency was the highest with hydrogen (34.23%), and it was about 24.23% and 24.08% with CNG and HCNG respectively at high load (20.25 kW). This indicates a higher potential of hydrogen to convert chemical energy input of fuel into heat and then power output. The exergy destruction was observed minimum with hydrogen at all loads, and it was drastically reduced at high loads. The combustion irreversibility which was calculated using species present during combustion, was the main contributor to exergy destruction, and it decreased with hydrogen. The minimum combustion irreversibility was 11.75% with hydrogen, followed by HCNG and CNG with 16.46% and 18.88% respectively at high load. The high quality of heat due to high in-cylinder temperature and low entropy generation during combustion caused by less number of chemical species in hydrogen combustion are the main reasons for lower combustion irreversibility with hydrogen.