Impact of rain on wave retrieval from Sentinel-1 synthetic aperture radar images in tropical cyclones

The main objective of our work was to investigate the impact of rain on wave observations from C-band (~5.3 GHz) synthetic aperture radar (SAR) in tropical cyclones. In this study, 10 Sentinel-1 SAR images were available from the Satellite Hurricane Observation Campaign, which were taken under cyclonic conditions during the 2016 hurricane season. The third-generation wave model, known as Simulating WAves Nearshore (SWAN) (version 41.31), was used to simulate the wave fields corresponding to these Sentinel-1 SAR images. In addition, rainfall data from the Tropical Rainfall Measuring Mission satellite passing over the spatial coverage of the Sentinel-1 SAR images were collected. The simulated results were validated against significant wave heights (SWHs) from the Jason-2 altimeter and European Centre for Medium-Range Weather Forecasts data, revealing a root mean square error (RMSE) of ~0.5 m with a 0.25 scatter index. Winds retrieved from the VH-polarized Sentinel-1 SAR images using the Sentinel-1 Extra Wide-swath Mode Wind Speed Retrieval Model after Noise Removal were taken as prior information for wave retrieval. It was discovered that rain did indeed affect the SAR wave retrieval, as evidenced by the 3.21-m RMSE of SWHs between the SAR images and the SWAN model, which was obtained for the ~1000 match-ups with raindrops. The raindrops dampened the wave retrieval when the rain rate was < ~5 mm/hr; however, they enhanced wave retrieval for higher rain rates. It was also found that the portion of the rain-induced ring wave with a wave number > 0.05 rad/m (~125 m wavelength) was clearly observed in the SAR-derived wave spectra.     

液冷头盔致冷效能的医学研究

在45℃高温条件下,应用液冷头盔给10名被试者的头颈部致冷,散热效能较高,可带走安静时30.9％～48.3％的代谢产热。降低身体的热蓄积,减少出汗,减慢心率、直肠温度和皮肤温度的上升速率。对头颈部致冷可降低身体的热紧张度50％～70％,明显改善对温热的舒适感觉。同时表明,致冷液温、流量及液流走向,对致冷效能均有显著影响。为液冷头盔及致冷装置的设计,提供了医学实验依据。     

Further study of the Pencil-MUSIC algorithm

For finding 2-D angles and polarizations of waves arriving at a rectangular array of crossed dipoles, the Pencil-MUSIC method can achieve the near optimum performance with much less computational burden than the MUSIC (multiple signal classification). Following an angle-only ESPRIT (estimation of signal parameters via rotational invariance techniques) method, an angle-only Pencil-MUSIC can be easily formulated which is far more accurate than the former especially in the coherent case. The angle-only Pencil-MUSIC is analyzed and compared with the original Pencil-MUSIC. The new version sacrifices the polarization estimation to achieve about 8 times more efficient computation The accuracy of the new version seems no more than 4 times worse in terms of estimation deviation     

钣金制件表面的相贯线求作方法

本文提出钣金制件表面相贯线求作的新方法。     

图样的知识目标分类与例证性分析

根据教育目标分类学的观点分解课程教学目标，再分别对分解的目标进行例证性分析，能更客观地验证教育目标的实效性和教育过程的可行性。本文通过对图样的知识目标分类与例证性分析，为工程图学教育目标检测做一尝试。     

一种新的六端口测量系统自校准方法

提出了一种新的六端口自校准方法.本方法从六端口相对功率理论出发,导出了六端口系统常数的自校准方程,给出了求解系统常数初值的方法,并利用梯度法对方程组求解,仿真结果表明用一个匹配负载、四个失配负载就可以解出系统常数.     

CBERS-1卫星红外多光谱扫描仪扫描子系统

文章介绍了CBERS -1卫星红外多光谱扫描仪(IRMSS)关键部件扫描子系统研制与应用情况。     

弹道靶红外辐射测量

为深入认识再入物理现象 ,在弹道靶上做了模型头部和近尾流红外辐射测量。发射器为 1 4.5mm口径的二级轻气炮 ,模型为1 0mm的球 ,材料为聚碳酸酯和铝 ,模型发射速度 4～6km/s,使用红外InSb探测器测量波长 3～ 5 .4μm的红外辐射 ,靶室压力 5 .32kPa。实验中使用光电法测量模型速度 ,两站阴影照相进行模型姿态监测和速度核实。实验结果表明 :球模型的红外辐射强度强烈依赖于模型材料和模型飞行速度。对不同材料模型头部和尾流部辐射强度的定性比较说明由于低温材料烧蚀产物的存在 ,极大地增强了头部和近尾流区的辐射强度 ,而且延长了尾流辐射长度