近地卫星陨落期地球反照系数估计

为了研究地球反照的可见光对太阳电池阵电流在卫星陨落期间的影响程度,进行阵电流的地球反照系数估计。以运行在300km高度、降交点地方时约10:30AM的某太阳同步轨道近地卫星陨落为例,在讨论卫星轨道半长轴、倾角、光照角、降交点地方时等参数漂移的基础上,重点分析卫星太阳电池阵电流和温度的变化,并对电流进行正弦曲线拟合,进而建立地球反照系数的估计模型,最后用卫星陨落期间的遥测数据进行检验。结果表明,卫星自300km轨道高度向100km轨道高度陨落期间,地球反照系数先由0.21逐渐变大,最大值接近0.40,后又逐渐变小至0.20附近;对估计值的二次曲线拟合结果表明,在轨道高度210~270km这一区间,地球反照对于太阳电池阵的作用最强,对应的地球反照系数极大值约为0.28,作用最强的中心区域可能在250km轨道高度附近。估计结果可应用于在轨航天器长期管理的遥测诊断、能源估计与预测、器件健康状态评估以及可见光载荷应用等方面。     

晴空地表反照率正则化反演算法的POLDEH多角度数据验证

使用偏差原则和正则化方法反演晴空地表双向反射分布函数BRDF、方向-半球反射率DHR 和双半球反射率BHR.利用6S辐射传输模型计算出天空散射光,并以此为权重将DHR和BHR进行线性组合得到地物光谱反照率.最后,通过窄波段反照率向宽波段转换,计算了0.25～2.5μm的短波反照率.使用POLDER-3/PARASOL多...     

New Efficient Albedo Monte Carlo Method for Neutron Streaming Analyses

An efficient albedo Monte Carlo method newly developed has been studied by analyzing two types of experiments on neutron streaming. The method is characterized by employing the energy-angle dependent doubly differential albedos for slab, which can be calculated in a short computer time with a one-dimensional transport theory, such as the Sn method and more efficient invariant imbedding method. This paper describes the features of the present albedo Monte Carlo method, including fundamental formulas. In the analyses of the neutron streaming experiments, the calculated results agreed with the measured data within a factor of 2 for a benchmark experiment at the YAYOI reactor and within a factor of 3 for an SNR sodium duct mock-up experiment.

It is concluded that the present albedo Monte Carlo method is practical and applicable to the reactor shielding analysis concerning radiation streaming.     

Direct and indirect uncertainties in the prediction of tilted irradiance for solar engineering applications

Global radiation measured on fixed-tilt, south-facing planes (40° and vertical) and a 2-axis tracker at NREL’s Solar Radiation Research Lab. in Golden, CO is compared to predictions from ten transposition models, in combination with either optimal or suboptimal input data of horizontal irradiance. Suboptimal inputs are typically used in everyday engineering calculations, for which the necessary data are usually unavailable for the site under scrutiny, and must be estimated in some way. The performance of the transposition models is first evaluated for ideal conditions when optimal data are used. In this specific case, it is found that the Gueymard and Perez models provide the best estimates of global tilted irradiance under clear skies in particular.The performance of four direct/diffuse separation models is also evaluated. Their predictions of direct and diffuse radiation appear biased in most cases, with a model-dependent magnitude. Finally, the performance of the resulting combinations of separation and transposition models is analyzed in a variety of situations. When only global irradiance is known, the accuracy of the tilted irradiance predictions degrades significantly, and is mainly conditioned by the local performance of the direct/diffuse separation method. For the south-facing vertical surface, inaccuracies in the ground reflection calculations becomes another key factor and significantly increase the prediction error. The Reindl transposition algorithm appears to perform best in this case. When using suboptimal input data for the prediction of plane-of-array irradiance on a moderately tilted plane (40°S) or a 2-axis tracking plane, the Hay, Reindl and Skartveit models are less penalized than others and tend to perform better. It is concluded that further research should be conducted to improve the overall process of predicting irradiance on tilted planes in realistic situations where no local high-quality irradiance or albedo measurements are available.     

地表通量对模型参数的不确定性和敏感性分析

基于2007年12月22日~2009年12月31日黑河流域阿柔冻融观测站的气象驱动数据,利用通用陆面模型(Common Land Model,CoLM)模拟的地表通量结果,研究地表通量对模型参数(叶面积指数、地表反照率和植被覆盖度)的不确定性与敏感性。结果表明,叶面积指数、地表反照率和植被覆盖度对地表感热和潜热通量不同组分的影响存在较大的差异。其中,植被层的感热和潜热通量对叶面积指数的敏感性程度较高,敏感系数均达到0.7以上;与潜热通量相比,感热通量对反照率更加敏感,土壤感热、植被感热和总感热通量对反照率的敏感系数分别达到-0.96、-0.97和-0.66,而土壤潜热和总潜热通量对地表反照率的敏感系数仅为0.1左右;植被潜热通量对植被覆盖度的敏感性程度很高,敏感系数范围为0.92~0.96,而土壤感热通量对植被覆盖度最不敏感,敏感系数只有0.18左右。     

城市住区热环境可控影响因素定量分析

以杭州城西52个不同类型住区为例,基于杭州夏季Landsat5 TM 数据和遥感图像解译方法提取了不同住区的地表温度、植被指数和反照率,同时结合目视解译和现场调查,分别计算了不同住区的建筑密度、容积率、平均建筑高度等建设指标.采用线性相关与多元回归分析方法分析城市地表温度与植被指数、地表反照率、容积率、建筑密度等指标之间的定量关系.结果表明：城市热环境与其人为可控影响因素的相关性大小依次为：植被指数>地表反照率>建筑密度>建筑高度>容积率;加强城市住区绿化建设、采用高反照率材料是改善住区热环境的有效手段;适度减少建筑密度和提高容积率可以缓解城市紧凑发展与城市热环境恶化之间的矛盾.     

南京地区不同季节水泥下垫面辐射特征的对比分析

利用2005年夏季与2006年冬季在南京进行的城市边界层外场观测资料,初步分析了水泥下垫面的辐射特性.结果表明:①由于城市上空大气透明度小于郊区,因此太阳总日射辐照度的夏季观测值表现为城区观测值比郊区小约8%;②水泥地表的反照率明显大于草地,而且随着太阳高度角的季节变化,水泥地表反照率也略有差异,夏季平均值为0.34,冬季为0.31;③夏、冬两季水泥下垫面净辐照度白天差异较大,通常约有100W·m-2,但峰值差异较小;在夜间净辐照度均为负值,且夏季观测值略大于冬季观测值,表明夏季夜间净辐照度对地表和大气的冷却作用小于冬季.     

基于机器视觉系统测量有色溶液浓度的方法研究

在化学分析实验中,有色溶液浓度一般采用分光光度法测定。提出一种基于机器视觉系统测定有色溶液浓度的新方法,设计了基于机器视觉系统测定有色溶液浓度的实验装置,结果表明该方法可替代传统的分光光度法,且具有实验装置简单、造价低和功能扩展性强的特点。     

Molecular Mass and Solubility Changes in Pectins during Storage of Satsuma Mandarin Fruits (Citrus unshiu Marc.)

Soluble pectins in satsuma mandarin fruits stored at 5°C were investigated by High Performance Gel Filtration chromatography. Pectins isolated from the flavedo, albedo, membranes and juice sacs were separated into four fractions. The hydrochloric acid soluble pectin fraction in each part was the highest and decreased slightly while the water-soluble pectin increased slightly. The avergae molecular weights of the fractionated soluble pectins in juice sacs were nearly constant but those in flavedo, albedo and membranes decreased as storage time increased. The ratios of higher molecular weight of water soluble and ammonium oxalate-soluble pectins in all the four parts and those of hydrochloric acid soluble pectin in flavedo and membranes decreased as ratios of lower molecular weight fractions increased.     

HJ-1A/B星地表反照率生成算法与检验

提出了适合环境与灾害监测预报小卫星-A、B星(简称HJ-1A/B星)CCD相机的大气订正算法,并基于不同地表特性和大气条件下的辐射传输模拟数据,建立HJ-1A/B星的窄波段向宽波段反照率转换的模型.利用多级灰阶靶标实测数据、敦煌检验场实测数据验证了大气订正算法以及转换模型的可靠性和精度,并将HJ-1A/B星影像数据计算的反照率产品与同时相的MODIS反照率产品进行对比分析.结果表明:文章提出的HJ-1A/B星CCD相机大气订正算法可有效校正大气影响;窄波段向宽波段反照率转换模型反演的反照率精度可靠;基于研究成果生成的HJ-1A/B星地表反照率与MODIS反照率产品一致性较好,满足后续遥感数据定量化模型研究的精度需要.