光纤／无线系统误码率的模型与性能改进

定量分析了光纤无线通信系统中误码率底限(EF,error floor)现象的成因和改善途径,得出可将EF改善1个量级的结论,对光纤无线电系统的性能提高有重要的参考作用。     

Optical Diffraction in Close Proximity to Plane Apertures. I. Boundary-Value Solutions for Circular Apertures and Slits

In this paper the classical Rayleigh-Sommerfeld and Kirchhoff boundary-value diffraction integrals are solved in closed form for circular apertures and slits illuminated by normally incident plane waves. The mathematical expressions obtained involve no simplifying approximations and are free of singularities, except in the aperture plane itself. Their use for numerical computations was straightforward and provided new insight into the nature of diffraction in the near zone where the Fresnel approximation does not apply. The Rayleigh-Sommerfeld integrals were found to be very similar to each other, so that polarization effects appear to be negligibly small. On the other hand, they differ substantially at sub-wavelength differences from the aperture plane and do not correctly describe the diffracted field as an analytical continuation of the incident geometrical field.     

The assessment of actual wind power availability in ireland

Data on actual wind energy availability in Ireland are sparse. This is because (a) relatively little data on wind speeds have been collected in Ireland at sites of interest for wind exploitation, and (b) such data need in any case to be integrated with the characteristics of actual windmills which respond more efficiently to certain wind speed than to others. This paper describes a methodology for performing such an integration, and offers tables of specific output for windmills of different characteristics located at different sites in Ireland. the variations in this specific output are discussed.     

Thermal conductivity of oxygen in the critical region

The thermal conductivity of oxygen has been measured in a broad region around the critical point by means of Rayleigh light scattering. Measurements were made on two isochores and on the saturation boundary. The results are compared with current methods of predicting the anomalous thermal conductivity in the critical region.     

空时分组编码CDMA系统的性能分析

空时分组编码 ( STBC)可有效的应用于无线系统中 ,提高系统的容量。 STBC采用最大似然译码算法 ,译码过程中需要信道信息。本文利用导频辅助的方式获得信道信息 ,分析了Rayleigh信道下随着移动台速度的变化 STBC- CDMA系统的误码率性能     

数字信号处理技术应用于路轨探伤

提出了一种路轨探伤的新方法。它的特点在于（１）以波束脉冲直通方式代替了常规的波束脉冲回波方式；（２）利用雷利波的色散特性计算与它相互作用的裂痕深度；（３）使用信号处理技术，对所传送的雷利波进行ＦＦＴ和频谱分析，从而直接计算裂痕深度。处理方法简单快速，可提高实时处理的速度和可靠性。最后还介绍了探伤装置的组成结构和处理流程。     

Application of metal single crystal wedges to high frequency rayleigh wave propagation

Techniques for propagating Rayleigh waves with frequencies varying from <1 to 270 MHz were developed for the purpose of nondestructive evaluation of composition or defect gradients near the surface of nonpiezoelectric solids. The surface waves with frequencies greater than 15 MHz were obtained from a novel technique using single crystal wedges, whereas the low frequency waves were produced by a previously used high voltage impulse. Measurements of Rayleigh wave velocities on single crystals of Ge and Al were performed as a test of accuracy and precision and are compared with calculated values.     

改进的Summer算法及其在Turbo译码中的应用

由于Summer信噪比算法采用的信道模型为AWGN信道,他对衰落信道并不适用。通过在接收信号中增加了衰落因子,提出了一种能够应用于Nakagami衰落信道的改进Summer信噪比估计算法。仿真表明,运用改进的算法获得的信道信噪比信息非常接近实际的信噪比信息,同时,改进的Summer在线估计器使得Turbo译码性能得到明显的改善,而且不影响Turbo译码过程的总复杂度。     

混凝土大坝裂缝光纤监测关键性基本问题的协同研究

灵敏性与复用能力是基于瑞利散射的混凝土坝裂缝光纤监测两个最为关键、且相互约束、不可分割的基本参量。基于单裂缝混凝土模型试验，对大坝裂缝光纤监测中采用的光纤传感技术的灵敏性和复用能力进行了定量化协同研究，得到了传感光纤在大坝安全监控缝宽控制范围内、对应于同一光信号衰减规律的灵敏性和复用能力与裂缝宽度关系曲线，为光纤传感在我国大型水电工程裂缝监测中的进一步研究和应用提供了基本参照。