双选择信道中的时间偏移广义频分复用通信

当信道存在时间-频率双选择性时,严重的子载波间干扰和子符号间干扰将导致广义频分复用(GFDM)系统性能显著下降.为此,该文提出一种时间偏移GFDM系统(TO-GFDM),通过对传统GFDM系统的原型滤波器进行时间偏移,来提高双选择信道下GFDM系统的性能.该文推导了GFDM信号在双选择信道中的平均信干比公式,并提出基于离散导频的联合迭代信道估计与符号检测算法,该算法利用信道估计器与串行干扰消除符号检测器之间的信息交换,逐步减小干扰信号,提高信道估计与符号检测的精度.理论分析与仿真实验结果表明,在双选择信道条件下,时间偏移GFDM比传统的GFDM具有更高的平均信干比和误码率性能;并且,联合迭代信道估计与符号检测算法能有效降低系统误码率.     

水力旋流器内固体颗粒的沉降

水力旋流器内固体颗粒的离心沉降是一种复杂的两相流行为。从分析固液体系的相互作用，分别讨论了颗粒的自由沉降、干涉沉降问题，提出了高浓度下水力旋流器内颗粒之间的几种碰撞模式，阐述了旋流器内颗粒沉降的特殊性及其与使流器工作和旋流器结构间的可能联系，并指出了离心沉降本身有待深入研究的若干问题。     

Study Of The Ozone - Manganese Reaction And The Interactions Of Disulfonate Indigo Carmin/Oxidized Manganese Forms As A Function Of pH

Ozone used in preoxidation for water treatment processes allows the removal of inorganic compounds such as iron and manganese. The reactivity of ozone and manganese has been studied in a wide pH range. However, some difficulties appeared in the determination of the different species because of secondary reactions, the main difficulty being the interaction between indigo (used to determine ozone concentration) and manganese dioxide formed during ozonation.     

Determination of the optical constants of diamond films with a rough growth surface

The determination of the optical constants n and k for polycrystalline diamond films with typical growth surface roughness σ of the order of tens to hundreds of nanometers is both an important and a difficult procedure. A method for determining n, k and σ for rough diamond films is presented here. It is based on theoretical expressions for the optical reflectance R and transmittance T for a free-standing thin film incorporating the effects of surface scattering at one surface. The usefulness and validity of this approach are illustrated using experimental R and T data for diamond films. Simplified expressions for R and T are also presented which are valid when scattering or absorption are sufficiently strong to cause interference effects in the films to be averaged out.

Prime novelty: Simple expressions for n, k and σ are presented which will enable researchers to extract this important information about the optical constants and surface roughness of their CVD diamond films.     

空分气体分析仪器应用中的若干问题

介绍了微量气体分析系统的复杂性 ,分析了分析仪器在应用过程中的各种影响因素和干扰因素 ,具体阐述了分析仪器的校验和验证 ,最后指出合格的分析工程师要不断纳新、提高分析技术     

辐射高温计在热处理生产中的应用

本文介绍了在热处理生产中采用辐射高温计进行非接触测温、控温时，为了获得准确可靠的测量值，应如何正确安装、使用及维护辐射高温计的经验。     

Required protection ratios for co-frequency pal fm tv transmissions

This paper contains the results of a measurement campaign to determine the protection ratio requirements for PAL FM TV satellite transmissions in a form suitable for direct application in satellite planning exercises. The following cases were considered in the study:

• (a) the mutual interference between two co-frequency PAL TV signals frequency modulated using a deviation sensitivity of either 16 MHz/V or 25 MHz/V
• (b) the interference effects created by two independent co-frequency PAL TV carriers interfering with the same victim PAL TV carrier, with all signals frequency modulated using a deviation sensitivity of 25 MHz/V.

Protection ratios were assessed with a wide variety of different conditions assumed for the wanted and interfering signals, such as the target picture quality and the operating carrier to noise ratio. The analysis of the results indicates that the required protection ratio is dependent upon some of the study parameters such as the picture content of the wanted signal. Protection ratio guidelines are derived on the basis of this analysis for co-frequency interference into PAL FM TV signals. The results also confirm that, for planning purposes, multiple interfering signals can be treated by addition on a power basis.     

New insights about interference suppression algorithm based on analog circuits and linear filtering method in ELF communication

In order to improve the communication quality in the extremely-low-frequency communication effectively, a kind of new insight based on analog circuits and linear filtering method for interference suppression is proposed, the latter mainly achieves by the joint diagonalization of the correlation matrices. The proposed algorithm takes place the filter coefficients by a linear combination of eigenvectors, the problem of interference suppression is converted into the solution of constructed coordinates. Besides, three kinds of filters are designed based on the mean square error criterion, the derivation process is given in detail, and several performance evaluation indices are also provided. And the derivation results show that the proposed algorithm can become common filters in speech enhancement when the number of chosen eigenvectors is a certain value. Finally, some experiments are performed in a laboratory environment. And the experimental results show that the proposed algorithm can suppress the interference effectively, and the compromise between the number of interference suppression and the degree of signal distortion can be controlled by changing the number of chosen eigenvectors, the proposed algorithm has potential performance gain.     

净化电磁环境 保障飞行安全

本文从理论和实践两个方面阐明了维护空中电波秩序是保障航空安全的重要前提之一;分析了电磁干扰的特点和影响飞行安全的原因;提出了维护空中电波秩序,消除＂电磁污染＂的几点措施。     

改善直驱式风电系统电磁兼容的随机调制技术

为了解决直驱式永磁风力发电系统中,后级逆变器EMI过大而导致其它设备工作不正常问题,将随机SPWM调制技术应用到该系统,并在基于ATmega128 AVR单片机逆变器平台上进行了实际测试,实验结果证明随机调制技术能减少开关电路引起的EMI,使得系统整体的电磁兼容性得到明显改善,但不会增加控制器的硬件成本.