Switching rate and receiver performance of binary modulations with the selection‐and‐stay combining over independent and correlated Nakagami‐m fading channels

The dual‐branch selection‐and‐stay combining (SSTC) is analyzed for diversity reception on independent and correlated Nakagami‐m fading channels, where the conventional selection combining (SC) is employed only at the switching instance, and the receiver uses the selected branch till its signal‐to‐noise ratio (SNR) estimation is lower than a preset threshold. In this combining scheme, the receiver only needs to continuously estimate the SNR of the single selected branch. For the performance analysis of SSTC, the switching rate and the average bit error rates (BERs) of different binary coherent and non‐coherent modulations are evaluated. Numerical results based on the analysis and simulations are illustrated. According to the analysis and numerical results, the SSTC outperforms the existing switch‐and‐stay combining in the senses of the average BER and switching rate. Copyright © 2011 John Wiley & Sons, Ltd.     

Sub-micrometer particulate air pollution and cardiovascular mortality in Beijing, China

Background

While the link between particulate matter and cardiovascular mortality is well established, it is not fully investigated and understood which properties of the aerosol might be responsible for the health effects, especially in polluted mega-city areas.

Objectives

Our goal was to explore the association between daily cardiovascular mortality and different particle metrics in the sub-micrometer range in Beijing, China.

Methods

We obtained daily counts of cause-specific cardiovascular deaths in the Beijing urban area for the period March 2004 to August 2005. Concurrently, continuous measurements of particle number size distributions were performed. Particle number concentrations (NC) between 0.003 μm and 0.8 μm were converted to particle mass and surface area concentrations assuming spherical particles. Semi-parametric Poisson regression models adjusting for trend, seasonality, day of the week, and meteorology were used to estimate immediate, delayed and cumulative particle effects. Additionally, effect modification by air mass origin was investigated.

Results

We observed associations between daily cardiovascular mortality and particle NC for a 2-days delay. Moreover, nearly all particle metrics showed 2-days delayed associations with ischemic heart disease mortality. The strongest association was found for particle NC in the size range 0.03-0.1 μm (7.1% increase in daily mortality with a 95%-confidence interval of 2.9%-11.5%, per an increase of 6250 particles/cm³). Results for surface and mass concentrations with a lag of two days indicated effect modification by air mass origin, whereas effects of particle NC were not modified.

Conclusions

Results show an elevated risk of cardiovascular mortality in Beijing from short-term exposure to particulate air pollution in the sub-micrometer range. Results also indicate that locally produced smaller particles and regionally transported particles may exhibit different effects in Beijing.     

油田通信动力环境监控系统的应用

机房动力环境对油田通信系统的安全稳定运行至关重要,机房的温湿度、电源设备的运行状况、机房门开启状态等都是事关通信设备能否正常工作的要素。因此,油田通信动力环境监控系统的重要性日益突出。文章介绍了油田通信动力环境监控系统的监控内容、系统组网结构、数据传输方式等。     

一种高可靠性、低功耗单节锂电池保护电路

A single lithium-ion battery protection circuit with high reliability and low power consumption is proposed.The protection circuit has high reliability because the voltage and current of the battery are controlled in a safe range.The protection circuit can immediately activate a protective function when the voltage and current of the battery are beyond the safe range.In order to reduce the circuit’s power consumption,a sleep state control circuit is developed.Additionally,the output frequency of the ring oscillation can be adjusted continuously and precisely by the charging capacitors and the constant-current source.The proposed protection circuit is fabricated in a 0.5 m mixed-signal CMOS process.The measured reference voltage is 1.19 V,the overvoltage is 4.2 V and the undervoltage is 2.2 V.The total power is about 9 W.     

SC型MH-Ni电池的研制

介绍了SC型MH-Ni电池的研制过程。通过正极和负极载体采用新型材料及先进的制作生产工艺，使生产的电池具有放电平台高，荷电保持能力强，高倍率放电性能优良，循环寿命良好的优点，可以满足电动工具的使用要求。     

大电流锂离子电池充电器管理系统SC801及其应用

介绍了Semtech公司最近推出的SC801单节Li 电池恒流/恒压充电器系统的主要性能和特点 ,给出了由SC801组成的用电阻分压器设定输出电压的充电器电路。同时对其预充电、快速充电及充电终止的设定方法进行了说明     

OFDM和SC/FDE在宽带通信中的应用

在宽带无线通信中，传统的单载波时域均衡的方法由于计算的复杂度已很难适应。本文的叙述了的SC／FDE和OFDM系统结构、关键技术和算法，详细的比较了它们在结构和性能上的差异和共同点。最后给出了双模结构的可能性。     

尼龙-6/尼龙-1010共混体系研究 Ⅱ.结晶相分离

结晶相分离是结晶／结晶高聚物共混体系的主要特点，尼龙６／尼龙１０１０共混体系可作为分子链间有较强的相互作用的结晶／结晶高聚物共混体系类型的代表。本文用差示扫描量热法考察其结晶相分离行为的结果表明，无论是从溶液共沉析出，还是从熔体或玻璃体结晶皆为结晶相分离的，且基本符合加和律。从阻隔效应讨论了ｗＰＡ－６＜０．２５时难以结晶的现象。     

CFRPA1010等速降温结晶动力学的研究

将等温Ａｖｒａｍｉ方程推广应用于等速降温的非等温结晶过程，用ＤＳＣ法研究了ＣＦＲＰＡ１０１０的等速降温结晶行为和结晶动力学。结果表明，用此方法得到的动力学参数与文献报导的等温法结果有良好的一致性；ＣＦＲＰＡ１０１０中的ＣＦ使基体的结晶温度明显提高，使结晶峰呈不对称形态，结晶温度范围变窄。其结晶行为和动力学参数ｎ、ｋ、ｔ１／２等结果显示，ＣＦ具有诱导基体结晶作用，影响了ＰＡ１０１０结晶的成核和生长机     

一次枝晶间距模型及在单晶高温合金中的验证(英文)

本文评述了二元系统一次枝晶间距模型的发展及特点,并验证了在多元合金系统中的适用性,结果表明,在 DD8单晶高温合金中,λ_1-G 关系符合二元系统模型,但λ_1-V 关系和二元系统模型有较大的偏离,λ_1为一次枝晶间距,G 为温度梯度,V为凝固速率。在本文凝固条件下,DD8合金的λ_1-G,V关系式为:λ_1=1141.5G~(-0.52)V~(-0.12),其中λ_1单位为μm,G 为 K/mm,V为μm/s。