基于Matlab的幅度调制信号仿真研究

通信系统的仿真是研究通信系统性能的有效手段，很多通信理论比较抽象不易理解，而利用Matlab进行仿真把抽象的东西形象化，便于深刻理解。本文在介绍幅度调制原理的基础上，利用Matlab／Simulink工具箱，对模拟幅度调制系统——常规双边带调幅（AM）、抑制载波双边带调幅（DSB-SC）、单边带调幅（SSB）进行了仿真实现。     

基于ROF系统的FBG滤波特性研究

在ROF系统中为了克服传统双边带调制引起的载波能量衰减，单边带调制方式被提出。作为波长选择性元件，光纤布拉格光栅具有全光纤尺寸、光纤兼容性、插入损耗小、成本低，利用它滤除一个边带实现信号光的单边带传输将有着很好的应用前景。对基于60GHZ的ROF系统，通过对高斯形光信号传输仿真，能实现13dB的边带抑制比。     

无线电振幅调制电路设计

基带信号直接通过天线传送出去的不合理性,决定了用待传输的基带信号去控制高频载波参数电路的必要性。推导分析普通调幅、抑制载波的双边带调幅、单边带调幅的调幅表达式、调制波形、频谱分布。采用多频基带信号作为输入,设计无线电发射机的振幅调制电路。利用示波器观察实验结果,验证调幅电路的可行性。     

24份水稻细胞质雄性不育系异交性能研究

对生产上广泛应用的24份水稻细胞质雄性不育系的异交性能的分析表明:在7个开花性状中,只有开花历时和开花时间与异交结实率呈负相关,而柱头双边外露率、包颈粒率、柱头单边外露率、张颖角度、开花历期都与异交结实率呈正相关。通径分析显示,各个开花性状与异交结实率的直接通径系数由大到小依次为包颈粒率、柱头单边外露率、张颖角度、柱头双边外露率、开花历期、开花时间、开花历时;其中包颈粒率、柱头单边外露率、张颖角度、柱头双边外露率对异交结实率的直接作用都远大于间接作用,这表明这几个性状与异交结实率有很大的相关性;而开花历时的直接通径系数为负值。     

生态控鼠技术研究

正为了研究田间不同形状TBS(围栏+捕鼠器)(单边、双边、四边)捕鼠效果,特安排本试验,为TBS监控技术应用提供科学依据。一、试验地点康保县康保镇剃头庄村,选取鼠密度较高且农艺性状一致的农田。二、试验时间在春播前10天,于5月9日将TBS安装到位,试验调查时间为燕麦播种后至燕麦成熟期间(5月20日—9月2日一个燕麦的生育期)。三、试验处理试验设单边、双边、四边围栏和对照(不设围     

约化模型中含有对手风险的信用违约互换定价

在约化模型中研究了含有对手风险的信用违约互换的定价问题. 通过构建信用违约互换买方、卖方和参考资产之间的衰减传染结构, 借助于测度变换的方法分别导出了含有单边和双边对手风险的信用违约的定价表达式.     

双季杂交水稻株型和产量构成的边际效应

利用江西省双季稻区域试验品种,通过调节栽插密度在田间分别设置四边、双边、单边和无边际效应4种处理的边际类型种植,收获后考察各处理的株叶形态参数和产量构成要素。结果表明两季水稻各品种有效穗数、叶长和穗长均随着边际的减少而呈现下降趋势。近一半早稻品种的株高随着边际的减少而降低,所有早稻品种的叶宽均随着边际的减少略有增加,但晚稻品种的株高和叶宽在不同边际类型中变化差异不大。在早稻大部分品种的双边和单边边际类型中,剑叶角度和叶尖角度均比四边和无边际类型中的角度要小,晚稻在不同边际类型中增减趋势表现不一。穗粒数在早稻季所有品种中均随着边际类型的减少而减少,晚稻只有部分下降。千粒质量在双季稻不同品种和不同边际效应类型中基本保持稳定。综合理论产量,对于穗粒数较多的杂交水稻宜采用本研究中单边边际类型或双边边际类型种植。     

一种新型的海底输油管道检漏技术

针对海底管道发生油溢事故时形成的空气、油膜和海水组合体模型,详细分析了模型的辐射亮温与油膜厚度、有效发射率增量与入射角间、不同频率下辐射亮温与油膜厚度间的关系,认为利用微波遥感技术检测海底管道是否泄漏、泄漏量和污染区域在理论上是可行的。根据此理论设计了机载微波辐射计航测系统,给出了该系统的组成结构和优选方案。     

“一带一路”背景下中国-东盟水果贸易结构与发展机遇分析

中国-东盟水果贸易在双边零关税计划全部实施后增长乏力,而"一带一路"发展战略为双边水果贸易可持续增长带来新的推动力。该文在分析中国-东盟区域水果贸易总量、品种和国别结构的基础上,深入挖掘双边水果贸易增长缓慢、结构集中、抵御风险较弱等问题及原因,从"一带一路"为双边水果贸易带来运输基础设施改善、贸易电子商务发展等机遇方面探讨未来双边水果贸易前景。     

水稻柱头外露性状的遗传分析及QTL定位

将高柱头外露率60B与低柱头外露率辽粳9杂交,以P1、P2、F1和F2为材料,采用主基因+多基因混合遗传模型分析柱头外露性状(开颖单边外露率、开颖双边外露率、开颖总外露率、闭颖单边外露率、闭颖双边外露率、闭颖总外露率)的遗传效应;并以F2群体为材料,采用复合区间作图法对各性状进行了QTL定位。结果表明:柱头外露率的遗传符合E-2、E-1、E-1、E-0、E-1、E-1模型;共检测到控制柱头外露的主效QTLs12个,分别位于第1,2,5,8,9染色体上,其中位于第9染色体上RM257~RM215的位点效应最为显著,其LOD值为12.96,贡献率为32.04%;柱头外露性状的遗传分析结果与QTL定位结果相一致。     

Mineral identification from orbit: initial results from the shuttle multispectral infrared radiometer

A shuttle-borne radiometer containing ten channels in the reflective infrared has demonstrated that direct identification of carbonates and hydroxyl-bearing minerals is possible by remote measurement from Earth orbit.     

Ozone monitoring with an infrared heterodyne radiometer

Measurements of the total burden and of the concentration versus altitude profiles of ozone have been made with a ground-based heterodyne radiometer at Pasadena, California. The measurements were made in the 9.5-micrometer wavelength region, where a strong ozone infrared absorption band exists. The radiometer measured solar absorption at selected wavelengths, with a spectral resolution of 0.001 reciprocal centimeter, equivalent to the half-width of an ozone absorption line at the 10-millibar altitude level. A carbon dioxide laser served as the local oscillator. This technique can be used to gather important data on both tropospheric and stratospheric ozone, which are not readily accessible with other remote-sensing techniques.     

Infrared radiometry experiment on mariner 9

The brightness temperatures at 10 and 20 micrometers measured by the Mariner 9 infrared radiometer differ substantially from those predicted by the radiometer results of Mariners 6 and 7. The results indicate a significant latitude-dependent contribution of the atmospheric dust to the observed thermal emission.     

Astronomy and solar physics: solar irradiance observations

The absolute radiometer on Spacelab 1 was used to obtain solar irradiance observations from space. A number of effects must be taken into account in the data reduction. A provisional value was obtained for the mean solar constant during the observation period (6 to 8 December 1983).     

Quasars revisited: rapid time variations observed via very-long-baseline interferometry

Recent Goldstone-Haystack radio interferometric observations of the quasars 3C 279 and 3C 273 reveal rapid variations in their fine structure. Most notably, the data for 3C 279, interpreted in terms of a symmetric double-source model and the accepted red-shift distance, indicate differential proper motion corresponding to an apparent speed about ten times that of light. A number of possible mechanisms that might give rise to such an apparent speed are considered; although several may be plausible, no definitive choice can be made on the basis of present evidence. More interferometric observations of quasars are clearly needed to clarify their structure and internal kinematics.     

Differentiating stress induced by greenbugs and Russian wheat aphids in wheat using remote sensing

Outbreaks of greenbug and Russian wheat aphid appear in the Great Plains almost every year and have had significant impacts on wheat yields. Early detection of aphid infestation is a critical part of integrated pest management (IPM) for wheat production. A study was done to determine the feasibility of using remote sensing techniques to detect stress in wheat caused by aphid infestation. The purpose of this greenhouse study was to characterize and differentiate stress in wheat due to infestation by greenbugs and Russian Wheat aphids using a hand-held Cropscan radiometer. Reflectance data and derived vegetation indices from the 16 bands of the radiometer were analyzed using SAS PROC MIXED statistical analysis procedure. Results show that it is possible to detect the stress caused by the two aphid species and to discriminate between the two aphid-induced stresses in wheat using remote sensing. Ratio-based vegetation indices (based on 800/450 nm and 950/450 nm) were found useful in differentiating the two stresses in wheat. However, more canopy-level-studies are needed to identify bands and indices that might have potential to differentiate the two stresses on wheat under field conditions.     

基于微波辐射计SSM/I的海面风速反演算法研究及应用

海面风速是海洋环境的重要参数,微波辐射计是卫星监测海面风速的重要手段。通过微波辐射计SSM/I（Special Sensor Microwave/Imager）亮温与浮标实测风速建立的匹配数据集,利用人工神经网络构建海面风速反演模型。比较不同模型的反演效果,得出七通道单参数神经网络模型SANN（Singleparameter Artificial Neural Network ）反演的效果和浮标实测风速较为接近,均方根误差RMSE（Root Mean Square Error）为1.40m/s。因此选择该模型反演全球的月平均风速,并将反演结果与NOAA产品风速比较。结果表明：两者在整体分布和纬度平均上非常接近,均方根误差为1.03m/s。可见,该算法用于海面风速反演还是可行的。     

Seasat visible and infrared radiometer

Visual and infrared images produced by the Seasat visible and infrared radiometer (VIRR) are adequate for the identification of cloud, land, and water features. A statistical comparison of VIRR-derived sea-surface temperatures in a cloud-free region with a National Oceanic and Atmospheric Administration analysis based on various surface measurements taken in the same region showed agreement to +/- 1.7 degrees K root-mean-square.     

Submillimeter heterodyne detection of interstellar carbon monoxide at 434 micrometers

A submillimeter heterodyne radiometer, developed for astronomical applications, uses an optically pumped laser local oscillator and a quasi-optical Schottky diode mixer. The resultant telescope-mounted system, which has a noise temperature less than 4000 K (double sideband) and high frequency and spatial resolution, has been used to detect the J = 6 --> 5 rotational transition of carbon monoxide at 434 micrometers in the Orion molecular cloud. The measurements, when compared with previous millimeter-wave data, indicate that the broad carbon monoxide emission feature is produced by an optically thin gas whose temperature exceeds 180 K.     

基于伪逆学习算法的地基微波辐射计反演算法研究

利用兰州大学半干旱气候与环境观测站(SACOL站)2009-2010年的地基微波辐射计亮温资料和榆中站探空资料,基于伪逆学习算法建立了应用于地基微波辐射计温度、相对湿度和水汽密度反演的神经网络(PIFN),并将反演结果与地基微波辐射计自带反演产品进行了对比,研究了伪逆学习算法在地基微波辐射计气象要素反演算法本地化的应用效果.结果表明:PIFN反演的温度、相对湿度和水汽密度的均方根误差的最大值分别为6.41K,31.21%和1.5g/m3,地基微波辐射计温度、相对湿度和水汽密度产品的均方根误差最大值分别为11.93K,53.18%和3.06g/m3,与微波辐射计自带神经网络反演结果在不同高度层进行比较可以看出PIFN对2～10km、1～7km和0～3km的大气温度、相对湿度和水汽密度廓线的反演均有明显改善,伪逆学习算法能够应用于地基微波辐射计气象要素的反演算法的本地化.