Efficient Model-Based Estimation of Atmospheric Transmittance and Ocean Wind Vectors From WindSat Data

A new method for estimating the atmospheric transmittance and wind speed over the ocean from WindSat data is derived using a simplified model for the ocean surface reflectivity. The simplified reflectivity model is used to calculate both the surface emissivity and the reflection of downwelling atmospheric radiation. The wind-speed dependence of the surface reflectivity is parameterized using simple rational functions with coefficients determined from the WindSat data. Because the vertically polarized brightness temperature depends primarily on the atmospheric state, it is used to obtain an initial estimate of the atmospheric transmittance at each spatial location. These estimates are then combined with the horizontally polarized brightness temperature to estimate the wind speed at each location. The first wind-speed estimate is used to refine the estimate of the transmittance, and the process is repeated until the estimates converge, resulting in a simultaneous solution for the atmospheric transmittance and the wind speed. The results are illustrated for two WindSat data sets collected on September 12 and 14, 2003. We have also investigated two methods of estimating wind direction using WindSat measurements of the third and fourth Stokes parameters. The first method involves an algebraic solution for the wind direction from simultaneous measurements of the third and fourth Stokes parameters. The second method involves measurements of the third Stokes parameter from two look directions (fore and aft scan angles), made possible by the conical scanning geometry of WindSat. A comparison and evaluation of these methods is made using the same data sets.      

一种基于灰度互相关法的扫描模式下的风场反演算法

该文分析了传统风场反演算法的理论依据、特点和不足,提出一种新的扫描模式下的风场反演算法。该算法考虑两幅相邻扫描周期所成合成孔径雷达图像中海浪波纹的相关特性,应用互相关方法,求解波纹运动矢量,确定风场风向,然后代入地球物理模型求解风速。与传统风场反演算法及浮标实测数据对比可知,该算法提高了风场反演的精确度,且不存在风向模糊问题。机载雷达实测数据的处理结果证明了方法的有效性。     

汇川MD380矢量变频器在冲击式制砂机上的应用

随着国家对铁路、公路、房地产等基础性设施建设步伐的加快,市场对高品质砂石骨料和机制砂的需求旺盛,本文在阐述机制砂生产线的由来、工艺和冲击式制砂机传统驱动方案缺陷等基础上向大家引介汇川MD380矢量变频器Canlink双电机主从驱动控制方案在山西某地区机制砂生产线冲击式制砂机上的成熟应用。     

风力发电中整流器的电压矢量控制系统仿真研究

经针对目前的整流器易受谐波污染和功率因数较低的特点,采用一种实现SVPWM的快速算法,能有效地简化算法,确定电压外环和电流内环PI调节器的基本参数,然后进行适当的调整就可以找到优化的PI参数,减少了实验中选择参数的盲目性。实验仿真结果表明该系统具有很好的抗扰性能。     

浅谈某款商用车车联网技术应用

车联网是伴随着云计算、物联网、传感技术的发展完善而诞生的新兴产业,商用车作为营运车辆,其本身意义是用于运送人员和货物,本文通过对某种商用车车联网技术应用的介绍,来讲述通过将车联网和物流配送有机结合,可以提高运输效率,降低运输环节中因资源整合不合理造成的浪费,最终让车主获取更多的利益,有效降低物流“最后一公里”成本。     

变速恒频双馈风力发电机的矢量控制研究

由于DFIG（双馈发电机）是高阶多变量,强耦合、非线性的机电系统,传统的控制方法无论是在控制精度上还是在动态性能上,远不能达到要求,为了实现DFIG的高性能控制,应采用磁场定向的矢量变换控制技术。借鉴矢量变换技术对于一般交流电机的控制,把矢遁变换控制技术用于对DFIG的控制,通过建立Matlab／Silnulink模型,和仿真征明矢量控制对DFIG良好的控制性。     

A polarimetric survey of radio-frequency interference in C- and X-bands in the continental united states using WindSat radiometry

Transmissions from ground-based systems in C- and X-bands present a significant challenge to the use of these bands for passive microwave remote sensing from aircraft and satellites. Because future missions plan to continue to use these frequencies, it is important to characterize and understand the nature of interference in as much of the candidate spectrum as possible. This paper presents a statistical analysis of interference observed in the continental U.S. using six months of data collected from the C- and X-band channels of the WindSat microwave radiometer. Our findings are consistent with those of previous studies by Li et al. and Njoku et al., which are based on data obtained from the Advanced Microwave Scanning Radiometer-EOS using somewhat similar center frequencies and bandwidths. Results show significant radio-frequency interference (RFI) at C-band, including brightnesses in horizontal and vertical polarizations in excess of 330 K, while X-band RFI is less obvious through direct examination of measured linearly polarized brightnesses. Evidence of lower levels of RFI is provided through use of the spectral and polarization indexes of Li et al., which reveal likely RFI contributions at X-band as well. Further confirmation of X-band RFI is obtained through analysis of the polarimetric channels, which are shown to provide direct evidence of RFI in contrast to the linearly polarized channels. A temporal analysis of the largest C-band RFI sources is also provided in an attempt to further understand their properties.     

Automatic detection and validity of the sea-ice edge: an application of enhanced-resolution QuikScat/SeaWinds data

Sea-ice edge detection is an essential task at the different national ice services to secure navigation in ice-covered seas. Comparison between the Remund and Long ice mask image from enhanced-resolution QuikScat/SeaWinds (QS) products and the analyzed ice edge from high-resolution RADARSAT synthetic aperture radar has shown that the automatically determined QS ice mask underestimates the Arctic ice extent. QS data was statistically analyzed by colocating the data with ice charts around Greenland and with the National Aeronautics and Space Administration Team's Special Sensor Microwave/Imager (SSM/I) ice concentration algorithm over the whole Arctic region. All variables, i.e., the backscatter in vertical and horizontal polarization, the active polarization ratio (APR) and the daily standard deviation, are sensitive to ice types and are strongly correlated with ice concentration when the relationship is expressed in exponential form. Our study showed that the APR is especially suitable for ice-ocean separation, and a threshold of -0.02 was determined. An ice edge algorithm based on this APR threshold was developed using the other variables with conservative season-dependent thresholds to eliminate additional ocean noise. Also, the history of the ice cover is considered in order to detect single ice fields that are separated from the main Arctic pack ice. Validation with RADARSAT 1 and with the Advanced Very High Resolution Radiometer showed that the new algorithm successfully detects very low ice concentrations of about 10% during the entire year. The validity of the detected ice edge for near-real-time issues is also discussed in relation to the ice motion in the Marginal Ice Zone and the integration time necessary to produce the enhanced-resolution images. The new algorithm improves the automatic global ice edge resolution by a factor of two when compared to SSM/I products and could be used in both model initialization and data assimilation.     

Impact of Tweets on Box Office Revenue: Focusing on When Tweets are Written

This study investigates the impact of tweets on box office revenue. Specifically, the study focuses on the times when tweets were written by examining the impact of pre‐ and post‐consumption tweets on box office revenue; an examination that is based on Expectation Confirmation Theory. The study also investigates the impact of intention tweets versus subjective tweets and the impact of negative tweets on box office revenue. Targeting 120 movies released in the US between February and August 2012, this study collected tweet information on a daily basis from two weeks before the opening until the closing and box office revenue information. The results indicate that the disconfirmation that occurs in relation to the total number of pre‐consumption tweets for a movie has a negative impact on box office revenue. This premise suggests that the formation of higher expectations of a movie does not always result in positive results in situations where tweets on perceived movie quality after watching spread rapidly. This study also reveals that intention tweets have stronger effects on box office revenue than subjective tweets.     

多厂商网络环境下连接管理方式的分析与比较

分析比较了多厂商网络环境下连接管理的三种方式:基于TMN的方式,基于TINA的方式和基于移动代理的方式.     

小企业办公和小办公室的一种自动化解决方案

小型企业和小办公室上网需要精打细算，力争以最少的钱办最多的事情。对于他们而言，上网的原则应该是“经济、可靠、易用”，所以，共享Modem上网往往成为小型企业上网的首选。本文介绍利用Modem上网的小型局域网的组网技巧及方法。1选择设备与大企业相比，小型企业没有足够的     

交通监控系统产品比较与设计

通过介绍当前市场上的一些道路监控产品，提出了一种基于三星S3C44b0x的MPEG-4远程视频监控系统。并且对该系统的硬件和软件的设计进行了详细的介绍。实验证明该系统具有实时性好、可扩展性好等优点。     

Capacity Comparison of CDMA and TDMA in Vector Broadcast Channel

1　Introduction　MultipleInputMultipleOutput (MIMO)havereceivedagreatdealofattentionasamethodtoachievelargecapacityandhighreliabilityoverwire lesslink .Accordingtovectorbroadcastchannel,thebasestationanduserinthissystembothhavemulti pleantennas.Costa[1 ] hadpointedoutthatifthein terferencesignalwasindependentoftransmitsignalanditwasknownatthetransmitterthenthechan nelcapacitywiththeinterferenceisthesameasiftheinterferencewasnotexist.　Thoughthepreconditionofcosta sresultisscalarchannel.The…     

自然风对城市自然通风隧道火灾温度场的影响分析

利用火灾模拟软件FDS建立隧道火灾模型,将温度场的模拟数据与实验数据进行对比,验证了模拟的准确性,然后对各种风速风向条件下隧道火灾工况进行模拟,通过对各种条件下的模拟数据的对比分析,得出风速风向因素对火灾时竖井型自然通风隧道内温度场影响规律。     

并行文件系统简介及主流产品对比

对并行文件的主要功能及作用进行了描述,并对各类并行文件系统的技术原理进行了分析;通过对不同产品的元数据管理及锁管理的实现机制的分析,给出了相应技术指标的比较,同时分析不同机制下的优缺点,并结合中国联通BSS系统的特性,给出了各类共享文件系统的适用场景。     

DC—DC 开关功率变换器分析方法的述评

本文对ＤＣ－ＤＣ开关功率变换器分析方法作了一个较全面的述评，着重介绍了拓扑不变的等效电路模型，寄生效应的处理方法，状态空间平均在准谐变换器的应用以及渐近法在变换器中的应用等四个方面，另外，介绍了不稳定分析一些结果。     

风电场对航管二次监视雷达S模式的影响分析

风电场作为一种运动的大型障碍物可能对航管二次监视雷达的性能产生影响。目前航管二次监视雷达正在经历逐步由A/C模式到S模式的转变升级,研究风电场对航管二次监视雷达S模式的影响,对保障民航飞行安全具有重要意义。该文在S模式和A/C模式信号特征对比分析的基础上,分析了S模式询问信号和应答信号可能受到风电场影响的条件,并由此给出了S模式二次雷达附近可能受风电场影响的飞行范围的计算方法,同时给出了其与A/C模式影响范围的定量化比较。该文所提方法及相关结论可以为风电场附近的雷达选址(或新建风电场选址)和飞行程序的设计提供依据。     

风电场对民航监视导航影响的三维可视化评估

新近研究表明风力发电场对民航监视导航设备可能产生显著影响,对其潜在影响的评估对于民航相关设备的选址选型、以及风电场项目的选址与方案确定具有重要的指导意义。论文给出了一种风力发电场电磁影响的三维可视化评估方法。该方法包括风电场限制区评估和风轮机可见性评估两个方面的评估,利用监视导航设备与风轮机相关参数,计算三维风电场限制区边界和设备到风轮机可视线的相关数据,并由这些数据自动生成地理数据标记与可视化语言KML格式的描述文件,将该KML文件载入Google Earth等三维地理信息系统平台,实现三维可视化评估。该方法给出的评估结果结合三维地理信息直观形象,可为进一步的详细评估奠定基础,为相关决策提供有效的依据。      

Impact of Saharan Dust on Ocean Surface Wind Speed Derived by Microwave Satellite Sensors

In the present paper ground truth and remotely sensed datasets were used for the investigation and quantification of the impact of Saharan dust on microwave propagation, the verification of theoretical results, and the validation of wind speeds determined by satellite microwave sensors. The influence of atmospheric dust was verified in two different study areas by investigations of single dust storms, wind statistics, wind speed scatter plots divided by the strength of Saharan dust storms, and wind speed differences in dependence of microwave frequencies and dust component of aerosol optical depth. An increase of the deviations of satellite wind speeds to ground truth wind speeds with higher microwave frequencies, with stronger dust storms, and with higher amount of coarse dust aerosols in coastal regions was obtained. Strong Saharan dust storms in coastal areas caused mean relative errors in the determination of wind speed by satellite microwave sensors of 16.3% at 10.7 GHz and of 20.3% at 37 GHz. The mean relative errors were smaller in the open sea area with 3.7% at 10.7 GHz and with 11.9% at 37 GHz.