青藏高压东侧偏北大风对梅雨暴雨影响的合成分析

利用常规观测资料对1991～1996年江淮地区梅雨大暴雨期的高、低层流场进行合成诊断分析,结果表明,梅雨期暴雨时,在对流层上部,由于青藏高原向东扩、在高压东侧出现偏北大风轴,由此构成的高空辐射区随着高压的东移而东移,它常常位于低空急流前端的上空、形成上层东北风,下层西南风的特殊耦合关系。     

高频地波雷达的东海试验

“高频地波雷达海洋环境监测技术”是由武汉大学主持的国家“863”计划海洋领域的重大课题,本课题组研制了两套高频地波雷达OSMAR2000,并于1999年底,在浙江省舟山市朱家尖和宁波市象山分别建立了两个雷达实验站,进行了一年的现场自检试验和与传统海洋测量仪器的对比验证试验.试验结果表明,雷达探测海流和海风的距离达到200km,探测浪高的距离达到120km,系统整体性能达到国外同类雷达20世纪90年代后期先进水平.     

Radiological safety assessment inside ancient Egyptian tombs in Saqqara

Many archaeological sites in Egypt are unique worldwide, such as ancient tombs and pyramids, because they document fundamental developments in human civilization that took place several thousands of years ago. For this reason, these sites are visited by numerous visitors every year. The present work is devoted to provide a pre-operational radiological baseline needed to quantify occupational radiation exposure at the famous Saqqara region in Cairo, Egypt. A hyperpure Ge detector has been used in the γ-ray spectrometric analysis while the ²²²Rn concentration was measured using a portable radon monitor RTM 1688-2, SARAD. The mean specific activities of ²²⁶Ra, ²³²Th and ⁴⁰K in the samples collected from the interior walls of the Saqqara tombs were determined and found to show average values of 16, 8.5 and 45 Bq kg^?1, respectively. The concentration of radon was measured inside the tombs Serapeum, South tomb and the Zoser Pyramid (fifth level) and an associated average working level of 0.83 WL was obtained. In order to avoid the health hazards associated with the exposure to radon during the long period of work inside these tombs, proposed solutions are introduced.     

自然循环加热段内对流传热特性的实验研究

本文以常压去离子水为工质,对自然循环工况下上升加热段内单相水的对流传热特性进行了实验研究。实验结果表明,自然循环工况下上升加热段内工质的物性变化及由浮升力引起的自由流动对对流传热特性有重要影响。通过分析,提出了计算自然循环工况下上升加热段内单相水的对流换热系数的经验关系式。     

相干多普勒测风激光雷达

 鉴于多普勒测风激光雷达在航空航天、遥感遥测、气象观测等军事及民用领域中的广泛应用,结合相干探测工作原理,介绍了国外几种典型波段相干多普勒测风激光雷达系统,重点分析了激光发射机/接收机、空间扫描、数据处理等关键技术,并对相干多普勒激光雷达的广阔应用前景进行了展望。指出国内相干多普勒测风激光雷达研究已取得的一些重要进展。     

Variation of the Payne Effect in Natural Rubber Reinforced by Graft-Modified Carbon Black

Carbon black (CB) was modified by liquid grafting and used for natural rubber (NR) reinforcement. Payne effects during NR reinforcement by the graft-modified carbon black (GCB) were analyzed in this paper. The results showed a proportional relationship between filler content and the Payne effect. Rubber compounds with GCB presented weaker Payne effects than their non-modified counterparts. Qualitative analysis of the correlation between filler network structure and filler content was conducted according to the relationship between bound rubber of a rubber compound and shear modulus. The impact of the storage period on the Payne effect was further studied, and the results demonstrated that the longer the storage period of the rubber compound, the stronger the Payne effect tended to be. The mechanisms by which the Payne effects were manifested differed according to the content of the filler in the rubber.     

模拟大气风场及其数据处理技术的研究

热层大气风速的测量可以采用干涉法来进行,由于光源（气辉辐射谱线）的强度很弱,故干涉法对测量系统要求很高。利用半导体激光器（LD）的调制特性和法布里-帕罗干涉仪(FPI)的高光谱分辨能力设计了一种用简单设备进行大气风场模拟与测量的方法。改变LD的驱动电流使其输出激光频率改变,从而模拟气辉辐射的多普勒频移,通过分析FPI获得的干涉图可检测出该频移,进而得到等效风速。模拟风速的相对误差不超过6.5%,最小模拟风速为20.01m/s,且测量结果与LD的线性调制特性很相符。使用该方法可以有效地对多普勒风速测量原理、数据处理方法、系统性能以及测量误差进行分析和评估。     

Accuracy analysis and stabilization design of the Fabry–Perot frequency discriminator in double-edge wind lidars

The measurement error of a double-edge wind lidar caused by a disturbed Fabry–Perot interferometer (FPI) is analyzed. Several error sources such as air pressure variations, temperature changes, and mechanical vibrations are considered in the measurement-error model. The simulation results show that a double-edge wind lidar is so sensitive to environmental variations that the measurement error reaches ±60 m/s if the FPI is not stabilized. In order to compensate the external disturbance acting on the FPI, a nonlinear proportional–integral–derivative (PID) control scheme is designed based on the transmission measurement of the calibration channel. An arc tangent function is used to improve the feedback gain of the usual PID control design. The results show that with the new controller the measurement accuracy of the wind lidar can be improved 4–5 times in comparison with the usual control design, and the range of the measurement error is only ±3 m/s.