Conditional sea surface statistics and their impact on geophysical sea surface parameters retrieved from SAR altimetry signals

In this study we present an analytical formulation of synthetic-aperture radar (SAR) altimetry signals including narrow banded nonlinear wave fields and conditional statistics between wave elevation displacements, horizontal wave slopes and vertical wave particle velocities. Considering the wave elevation displacements coskewness with respect to horizontal slopes leads to an analytical formulation of the electromagnetic bias within a SAR-mode altimeter stack. This formulation can be either parametrized by the significant wave height (SWH) and mean wave steepness, or in terms of the variance of vertical wave velocities. The effect of conditional vertical wave particle velocity variances with respect to the observed horizontal wave slopes close to nadir incidence angles leads to an effective reduction of the azimuth blurring of SAR-mode stacks. We present here a formulation of this effect by examining JONSWAP ocean wave spectra. In most cases this effect reduces the azimuth blurring by 10% to 30%. Additionally we investigate the effect of a nonlinear wave elevation displacement probability density function (PDF) on estimated geophysical parameters. We were able to show that including an elevation displacement skewness of 0.13 improves significantly the SWH consistency between altimetry and ECMWF Reanalysis v5 ERA5 results.All of these effects are validated with respect to ERA5 model data in the North East Atlantic region and in situ data located in the German Bight and Baltic Sea.The developed model can be used in both SAR and conventional altimetry retrackers.     

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.     

基于粗集的调度Agent知识库建模研究

首先通过相识集、招标集、投标集和中标者的概念，描述了车间调度系统中的调度Agent与资源Agent间任务分配的招投标关系；运用粗集理论，基于任务的属性和资源Agent完全任务的成本、质量、负荷和时间等属性构造决策表；在分析了决策表的特征基础上，生成调度规则集，即调度知识库；最后给出车间调度Agent的调度过程算法。     

多层RAM涂层对任意入射角电磁波的反射特性分析

为了解决结构型吸波材料的分析和设计中所遇到的反射系数计算问题，从电磁场理论出发，导出了电磁波以任意角入射时多层雷达吸波材料（RAM）涂层的反射系数公式，此法简单易行，为结构型吸波材料的计算机辅助分析和设计提供了基础，同时给出了计算曲线的例子，通过实例计算分析了电磁波的入射角，极化状态等对反射特性和隐身效果的影响。     

二硝酰胺铵(ADN)球形化工艺研究

介绍了近年来国外关于二硝酰胺铵（ADN）球形化的工艺方法，重点讨论了中间介质、分散剂、表面活性剂和热稳定剂的作用及其选择方法。     

代理市场细分及营销渠道策略

调查部分国外航空公司,论述了代理人的心理需求、航空公司和代理人之间的关系、代理市场划分等方面的现状。在营销环境和营销策略两方面系统地分析了国外航空公司在华办事处对代理人的市场营销方式和手段。     

从价格学原理看民航国内票价管理体制改革

从价格学原理出发,阐述了市场经济体制下政府在价格管理方面的职能,分析了中国民航国内票价管理体制方面存在的问题以及产生这些问题的原因,介绍了国内票价管理体制改革的基本思路,提出了解决问题的政策和配套措施。     

液压能源管路系统振动主动控制的理论研究

对飞机液压能源管路系统的振动问题进行了探讨.提出一种基于振动主动控制(VAC)技术对飞机液压能源管路系统进行消振的方法,在手段上采用压电/压电致伸技术,以压电陶瓷(PZT)作为作动器,具有驱动力大、响应频率高和体积小等优点;控制方法上采用参数寻优的控制策略,它能始终能根据外界干扰因素的变化来调整控制参数.经过理论分析和仿真验证,证明其具有良好的自适应性和鲁棒性,在变转速和变负载情况下始终能保持最佳的消振效果.     

仿真代理在导弹制导半实物仿真试验系统中的应用

针对独立运行的导弹制导半实物仿真试验系统接入联合试验系统的问题，应用了仿真代理的方法。在对原有系统控制关系进行最小化的改造前提下，通过控制接口的转换，实现了半实物仿真试验系统与其它异类异构系统之间的互联，拓展了半实物仿真试验系统的应用。     

硅烷偶联剂改性Al2 O3p/TDE-85 的力学性能

利用硅烷偶联剂对Al2O3颗粒进行表面改性,制备了Al2O3颗粒增强的TDE-85树脂基复合材料,研究了表面改性对其力学性能的影响,采用差热分析仪测定复合材料的固化反应温度,并计算了固化反应活化能。利用扫描电子显微镜分析了拉伸断口形貌。研究发现,当Al2O3用量为2wt%时,固化反应速度较快,硅烷偶联剂用量为4wt%时,冲击强度为13.2 kJ/m2;拉伸强度为65.2 MPa;弹性模量为2.66 GPa;最大伸长率为3.35%,此时对Al2O3颗粒的表面改性综合效果最好。