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.     

A bioreactor system for the nitrogen loop in a Controlled Ecological Life Support System.

As space missions become longer in duration, the need to recycle waste into useful compounds rises dramatically. This problem can be addressed by the development of Controlled Ecological Life Support Systems (CELSS) (i.e., Engineered Closed/Controlled Eco-Systems (ECCES)), consisting of human and plant modules. One of the waste streams leaving the human module is urine. In addition to the reclamation of water from urine, recovery of the nitrogen is important because it is an essential nutrient for the plant module. A 3-step biological process for the recycling of nitrogenous waste (urea) is proposed. A packed-bed bioreactor system for this purpose was modeled, and the issues of reaction step segregation, reactor type and volume, support particle size, and pressure drop were addressed. Based on minimization of volume, a bioreactor system consisting of a plug flow immobilized urease reactor, a completely mixed flow immobilized cell reactor to convert ammonia to nitrite, and a plug flow immobilized cell reactor to produce nitrate from nitrite is recommended. It is apparent that this 3-step bioprocess meets the requirements for space applications.     

雷达与ESM相关算法综述

在比较雷达和ＥＳＭ（ＥｌｅｃｔｒｏｎｉｃＳｕｐｐｏｒｔＭｅａｓｕｒｅｍｅｎｔｓ）这两种传感器特点的基础上，分析了雷达与ＥＳＭ相关的特点，介绍了统计方法、模糊方法和优化方法等五种雷达与ＥＳＨ相关算法，并对这些算法进行了评述。     

Electrostatic Noise Spectrum at the Electron Cyclotron Frequency and Electromagnetic Emission in the Inhomogeneous Plasma of the Topside Ionosphere

Measurements of the wave emission of the topside ionosphere made onboard the APEX satellite using the electric component of the wave field in the 0.1–10 MHz frequency band are presented. At middle latitudes a wave intensity decrease was observed in the broad-band spectrum of the electrostatic noise at the electron cyclotron frequency. It is shown that a break in the spectrum of electrostatic modes at the electron cyclotron frequency (the absence of the plasma eigen-frequencies) may be a cause of the observed effect. The increase of the intensity at the electron cyclotron frequency in the ionospheric trough and at latitudes above the trough region as compared to middle latitudes may be explained by the capture by plasma irregularities of the electromagnetic emission of the auroral electron fluxes.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 3, 2005, pp. 201–208.Original Russian Text Copyright © 2005 by Izhovkina, Prutensky, Pulinets, Kiraga, Klos, Rothkael.     

地中式混凝土油罐的数值模拟

对正在开展的战略石油储备,提出用地中预应力混凝土罐进行石油储存.应用结构分析软件ANSYS对巨型混凝土单壁罐和双壁罐进行弹性分析,指出罐壁环向应力几乎全部由温度荷载造成,罐壁温度场和温度应力具有明显时间性,储油初期罐壁温差最大,96?h后罐壁顶部拉应力达到最大;设置中间保温层后,内罐应力减小,外罐应力增大,应对内、外罐连接支墩做特殊设计,以满足罐壁温度变形.     

有限局部环上酉群的Sylow子群

设K=Fq2,其特征为p,q=pα,K有对合自同构:ωa|→aq,G是一个p-群,其阶为p,β群代数R=KG为一局部环。本文给出了R=KG上酉群U2nR的Sylow子群,若charK=p,U2nR的Sylow p-子群同构于某些特殊形式的矩阵生成的子群;若charK=p≠l,U2nR的Sylow l-子群同构于一循环群或半二面体群与若干Zl型循环群的圈积。     

利用非交错对称矩阵构造Cartesian认证码

利用特征为2的有限域上非交错对称矩阵构造了一个Cartesian认证码，并计算出其参数。进而，假定编码规则按照均匀的概率分布所选取，计算出了该码被模仿攻击成功的最大概率只和被替换攻击成功的最大概率Ps。     

Radar Performance with Multipath Using the Complex Angle

The complex angle (CA) method for resolving a low angle target from its multipath signal is evaluated in the presence of system noise. It is shown that standard deviation improvements of around 3-to-1 can be achieved at a 20-dB signal-to-noise power ratio relative to a normal monopulse system without the CA. It is also shown that the CA method is unbiased, giving bias improvements of as much as 100 times relative to normal monopulse. Evaluation of the assumptions in the technique shows very little sensitivity to knowledge of the reflecting surface's conductivity or dielectric constant. However, the method is somewhat sensitive to knowledge of surface roughness.     

1:10人-椅模型上肢的跨-超音速风洞实验

 本文介绍了1:10人椅模型上肢跨-超音速风洞实验的结果。测量了Ma=0.5～2.04和攻角10°～20°范围内上肢的阻力和侧向力。获得了在握扶手和拉中央环两种姿态下手臂的气动力特性。比较了穿衣袖与不穿衣袖两种状态下手臂的气动力数据。实验结果为确定人体上肢对高速气流吹袭的耐久限度和设计防护措施提供了重要的气动力数据。