湖泊藻类水体浮游植物色素遥感反演模型

2009年10月15～16日,在巢湖蓝藻暴发期间进行实际采样和数据分析,通过Gons和Simis算法对浮游植物色素吸收及其浓度遥感反演进行了研究.结果表明,Gons和Simis算法可以用于蓝藻水华未覆盖水体的遥感反演,而在水华覆盖水体表面时算法失效;在未覆盖水体时,Gons算法(RMSE=0.04 m-1)相对于Simis算法(RMSE=0.13 m-1)可以更好地反演浮游植物色素吸收;Simis算法可以用于巢湖藻蓝素反演,但模型参数需要重新率定.总体来说,Gons和Simis算法在巢湖取得了较好的结果,有助于浮游植物色素遥感反演后续工作的进行.     

基于哨兵3A-OLCI影像的内陆湖泊藻蓝蛋白浓度反演算法研究

蓝藻是内陆富营养水体水华发生的主要优势藻种, 而藻蓝蛋白 (Phycocyanin, PC) 是蓝藻的标志性色素, 因此利用遥感估算水体中藻蓝蛋白浓度从而对蓝藻水华预警具有重要意义。利用太湖、滇池、洪泽湖的实测数据, 构建藻蓝蛋白随机森林遥感估算模型, 并将模型应用到哨兵3A-OLCI影像。通过对随机森林的输入自变量进行重要性分析, 发现第7波段 (620 nm) 、第8波段 (665 nm) 和第9波段 (675 nm) 三个波段对藻蓝蛋白反演的影响程度最大。同时, 反演结果表明, 随机森林反演的藻蓝蛋白浓度平均绝对百分比误差 (MAPE) 为34. 86%, 均方根误差 (RMSE) 为38. 67μg/L, 与Simis等半分析算法和齐琳的PCI (Phycocyanin Index) 指数模型相比, 平均绝对百分比误差 (MAPE) 分别提高了85. 06%和15. 65%, 均方根误差分别提高了26. 08μg/L和19. 86μg/L。利用地面实测数据对同步卫星影像大气校正进行精度评价, 发现MUMM (The Management Uint Mathematical Model) 算法可以用于OLCI影像的大气校正, 尤其在560779 nm处共8个波段的MAPE低于30%, 光谱曲线与实测光谱曲线形状保持一致。结果表明所构建的基于哨兵3A-OLCI影像的藻蓝蛋白随机森林反演模型, 可以成功的应用于我国的内陆富营养化湖泊, 为我国内陆湖泊藻蓝蛋白浓度的遥感反演提供一个新的算法。     

富营养化水体颗粒有机碳浓度的遥感估算及动态变化特征

基于2011年5次太湖水体现场测量数据,分析富营养化水体颗粒有机碳(POC)对遥感反射比的影响,构建了POC含量的遥感定量估算模型,并结合MERIS遥感影像资料,揭示了太湖水体POC浓度的时空变化特征.结果表明,太湖水体中的POC对560~709 nm波段范围内的遥感反射比影响显著;基于海洋水环境特征构建的POC浓度遥感估算模型不适于太湖水体;通过分析富营养化水体的光学特性以及POC对遥感反射比的影响,发现MERIS传感器红(620 nm)、近红外(709 nm)波段遥感反射比的比值与POC浓度具有较好的相关关系(R2=0.75,n=132,RMSE=33.27%,P0.05),适于太湖水体POC浓度的遥感估算.     

悬浮颗粒物和叶绿素普适性生物光学反演模型

基于太湖、巢湖、滇池和三峡水库水体组分生物光学特性, 根据辐射传输模型和神经网络优化算法建立悬浮颗粒物和叶绿素浓度优化生物光学反演模型.利用野外实测数据对优化生物光学算法进行检验, 结果表明, 该优化生物光学反演模型在一定程度上可以减少测量噪音对反演精度的影响.反演结果表明, 受悬浮颗粒物和叶绿素生物光学特性时空差异影响, 该优化生物光学反演模型在太湖、巢湖、滇池和山峡反演精度具有一定的差异, 但总体上能够较为准确地反演悬浮颗粒物和叶绿素浓度.其中悬浮颗粒物反演精度(平均绝对误差: MAPE, 均方根误差: RMSE)分别能够达到23%和15.13mg/L(样本数N=228), 叶绿素反演精度(MAPE和RMSE)分别能够达到26%和17.68μg/L(样本数N=228).     

湖泊水体高光谱遥感反演总磷的地统计算法设计

高光谱遥感应用于内陆湖泊水质监测具有较好的发展前景,但由于内陆湖泊水体光学环境的时空多变性,如何高效利用水体高光谱特征信息,降低数据冗余度,发展高精度的水质参数反演模型具有重要的意义。针对上述问题,以巢湖为例,将遗传算法和地统计学相结合,利用环境一号(HJ-1A)卫星HSI高光谱遥感数据,建立了基于协同克里格遗传算法的湖泊水质总磷浓度高光谱遥感反演模型。实验结果显示,与传统遗传算法比较,协同克里格遗传算法模拟的ME、RMSE分别提高了128.2%、53%。经总磷实测值和反演值比对,建模和检验的相关系数R2分别为0.85、0.77。反演结果表明:协同克里格遗传算法通过利用克里格插值对传统遗传算法目标函数优化改进,使其具备克里格最佳局部估计能力,能够有效提高反演的精度。     

浑浊II类水体叶绿素a浓度遥感反演(II):MERIS遥感数据的应用

基于2004～2010年太湖4次野外观测数据,结合MERIS遥感资料,评价两波段、三波段、改进三波段和四波段4个模型在浑浊II类水体叶绿素a浓度估算的精度,并利用太湖(13个有效样点)以及巢湖(21个有效样点)进行模型验证.结果表明,改进三波段模型反演叶绿素a浓度较高,更适于浑浊II类水体叶绿素a浓度的遥感反演,决定系数R2在0.34~0.94之间变化,RMSE变化范围为: 3.17~8.70 μg/L.分季节率定改进三波段模型参数,并建立太湖水体春、夏、秋、冬季的模型输入参数查找表,最终将改进三波段模型应用于MERIS遥感影像(8、9、10波段),获取太湖水体叶绿素a浓度的空间分布和年内、年际变化.     

悬浮泥沙浓度分布方差与尺度修正——八邻域算法

在归纳总结悬浮泥沙反演模型尺度效应研究现状的基础上,提出了基于八邻域窗口估算像元泥沙浓度分布方差算法,并利用该算法的计算结果,推导与计算了线性模型、对数模型和指数模型的尺度修正方法.结合太湖Landsat/TM影像数据和同步实测泥沙浓度数据及光谱数据的分析表明:悬浮泥沙浓度定量模型的尺度效应误差与模型密切相关.对于像太湖这样的复杂Ⅱ类水体,尺度效应可以导致反射率的相对误差达到16%.     

浑浊Ⅱ类水体叶绿素a浓度遥感反演(Ⅰ):模型的选择

受高浓度悬浮物的影响,浑浊Ⅱ类水体叶绿素a浓度高精度定量反演一直是研究难点之一.利用2004年到2010年太湖4次实测光谱数据和水质参数,分别建立了两波段、三波段、改进三波段及四波段的叶绿素a估算模型;选择最优模型,利用巢湖2009年的实测数据进行独立验证.结果表明,四波段模型最适合高浑浊水体,线性相关性较好,决定系数...     

基于半分析模型的新庙泡叶绿素a浓度反演研究

叶绿素a(Chl-a)含量是反映水体水质的重要参数之一,利用遥感技术监测其浓度具有众多优势.本研究利用2004年5-9月的吉林省新庙泡实测高光谱数据和实验室分析数据,建立了基于三波段的Chl-a浓度反演模型.该模型基于水体叶绿素a、悬浮物、溶解有机物、纯水的生物光学特性分析,优化组合了3个特征波长.结果表明用该方法建立的模型具有一定的物理基础,反演精度较高,其决定系数和均方根误差分别为0.8758、4.98μg·L-1,适合于内陆水体Chi-a含量的定量提取.     

利用Hyperion星载高光谱传感器监测太湖水质的研究

通过分析Hyperion星载高光谱传感器的数据特征和水质参数监测精度,确定并详细讨论了波段比值、差值和NDVI算法与叶绿素、悬浮物浓度的相关性差异和敏感波段分布,建立并验证了水质参数高光谱遥感反演模型,初步评价了太湖水体富营养化状况.利用模拟环境小卫星的波段设置和反射率光谱,对比分析了Hyperion和环境小卫星高光谱监测太湖水质参数的反演精度,展示了星载高光谱监测内陆水体水质的应用潜力,有力地促进了我国环境小卫星高光谱数据在水体生态遥感监测中的预研工作.     

藻类垂向分布对内陆湖泊叶绿素a反演算法影响的模拟研究

利用高斯模型模拟不同的藻类垂向分布结构,研究其对于典型叶绿素a反演算法波段比值法的影响.结果显示,藻类垂向分布不均一性导致了叶绿素a浓度反演结果与藻类生物量间不存在一一对应的关系;藻类分布集中于水面以及水下0.5 m水深时会严重干扰波段比值反演算法的准确性,说明当水体表面存在藻华现象时,将导致反演算法失效;若排除此类情况,波段比值法与水体表层0.25 m处叶绿素a浓度、0~0.25 m、0~0.5 m水深范围内平均叶绿素a浓度值之间具有独立于藻类生物量以及藻类垂向分布的相关性;内陆湖泊叶绿素a反演算法与藻类垂向分布模型相结合,是获取藻类生物量的必要条件.     

基于VIIRS数据洪泽湖悬浮物浓度估算算法研究

基于2012~2015年洪泽湖4次星地同步试验数据,建立了较高精度的水体悬浮物浓度单波段(671 nm)模型(R~2=0.74,RMSE=8.58 mg/L),并进行了验证(R~2=0.72,RMSE=11.98 mg/L);然后,将该算法成功应用到了2012~2015年464景VIIRS无云影像上.结果表明,洪泽湖悬浮物浓度呈现春夏低、秋冬高的季节特征和东、中部高,西、北部低的空间分布特征;在年际变化尺度上,悬浮物浓度年均值呈现较小的减少趋势.总体来说,VIIRS在浑浊水体悬浮物浓度上表现了较好的探测能力,在湖泊水色遥感领域具有较大潜力.     

On Next Generation CDMA Technologies: The REAL Approach for Perfect Orthogonal Code Generation

All currently available code-division multiple-access (CDMA) technologies used in second-generation and third-generation mobile cellular systems are interference limited and can be appropriately called first-generation CDMA, whereas next-generation CDMA should provide a nearly interference-free performance. This paper addresses the issues on spreading code generation that is suitable for next-generation CDMA systems. The real environment adaptation linearization (REAL) approach is proposed to generate perfectly orthogonal complementary (POC) codes characterized by multiple access interference (MAI)-free and multipath interference (MI)-free operation. The REAL approach takes into account almost all major impairing factors in real applications, such as multipath propagation, asynchronous transmission, random data signs, and burst traffic, such that a CDMA system using them can offer an interference-resist operation. Two important conclusions are drawn in this paper: First, implementation of an interference-free CDMA will not be possible unless using complementary codes, such as the POC codes. Second, to enable interference-free CDMA, the flock size of the signature codes should preferably be equal to the set size of the codes. A fast algorithm to generate supercomplementary codes (a subset of POC codes) is also presented, and their ideal orthogonality is explicitly proven.      

Using a rapid communication approach to improve a POC Chlamydia test

Chlamydia trachomatis is a common sexually transmitted infection in young women. Available point-of-care (POC) diagnostic tests perform poorly, but development of new devices can be costly and time consuming. We explored the feasibility (user friendliness) and test characteristics (sensitivity and specificity) of a new prototype device to detect Chlamydia in adolescent women by using small numbers of subjects and rapid communication with the manufacturer. We compared cervical POC test results to the gold standard (cervical nucleic acid amplification testing). We also assessed the accuracy of the POC test on self-collected vaginal swabs by comparing results to cervical nucleic acid amplification test and to the cervical POC test. We frequently reviewed user experience and test results with the manufacturer. The results showed the feasibility and accuracy of the device. Feasibility--initial device malfunctions were identified and corrected. This device would be easy to use in a nonclinical setting, as it is self-contained and the color change for some specimens was dramatic and immediate. Accuracy--initial prototypes demonstrated low sensitivities (38%) for vaginal and cervical swabs. After feedback, the company developed new prototypes with improved sensitivity (80%). However, the increased sensitivity was accompanied by a high percentage of indeterminate results and false positives that lowered specificity.     

Porous Organic Cage Induced Spontaneous Restructuring of Buried Interface Toward High-Performance Perovskite Photovoltaic

In perovskite solar cells (PSCs), the buried interface containing high concentrations of defects is critical for efficient charge extraction toward high-performance device. Herein, porous organic cage (POC) is introduced between tin dioxide and perovskite to spontaneously reconstitute the buried interface. Through the chemical linkage formed by polydentate chelation of POC with SnO₂ and perovskite, the buried interface achieves greatly reduced defect density and enhanced carrier extraction. More importantly, it is found that iodide ions in aged devices to migrate down to the electron transport layer and even invade the ITO electrode, changing the work function of ITO. This detrimental effect can be well resolved by POC since the host-guest interaction of POC can effectively suppress the iodide ions trying to migrate downward. As a result, the PSC fabricated by POC-restructured strategy yields a superior PCE of 24.13%. Moreover, the unencapsulated PSCs exhibit conspicuous improved long-term stability and retain 93% of its initial efficiency after 5000 h in ambient condition.     

Hybrid Paper–Plastic Microchip for Flexible and High‐Performance Point‐of‐Care Diagnostics

A low‐cost and easy‐to‐fabricate microchip remains a key challenge for the development of true point‐of‐care (POC) diagnostics. Cellulose paper and plastic are thin, light, flexible, and abundant raw materials, which make them excellent substrates for mass production of POC devices. Herein, a hybrid paper–plastic microchip (PPMC) is developed, which can be used for both single and multiplexed detection of different targets, providing flexibility in the design and fabrication of the microchip. The developed PPMC with printed electronics is evaluated for sensitive and reliable detection of a broad range of targets, such as liver and colon cancer protein biomarkers, intact Zika virus, and human papillomavirus nucleic acid amplicons. The presented approach allows a highly specific detection of the tested targets with detection limits as low as 10² ng mL^?1 for protein biomarkers, 10³ particle per milliliter for virus particles, and 10² copies per microliter for a target nucleic acid. This approach can potentially be considered for the development of inexpensive and stable POC microchip diagnostics and is suitable for the detection of a wide range of microbial infections and cancer biomarkers.     

Graphene Enabled Low-Noise Surface Chemistry for Multiplexed Sepsis Biomarker Detection in Whole Blood

Affinity-based electrochemical (EC) sensors offer a potentially valuable approach for point-of-care (POC) diagnostics applications, and for the detection of diseases, such as sepsis, that require simultaneous detection of multiple biomarkers, but their development has been hampered due to biological fouling and EC noise. Here, an EC sensor platform that enables detection of multiple sepsis biomarkers simultaneously by incorporating a nanocomposite coating composed of crosslinked bovine serum albumin containing a network of reduced graphene oxide nanoparticles that prevents biofouling while maintaining electroconductivity is described. Using nanocomposite coated planar gold electrodes, a sensitive procalcitonin (PCT) sensor is constructed and validated in undiluted serum, which produced an excellent correlation with a conventional ELISA (adjusted r²  = 0.95) using clinical samples. A single multiplexed platform containing sensors for three different sepsis biomarkers—PCT, C-reactive protein, and pathogen-associated molecular patterns—is also developed, which exhibits specific responses within the clinically significant range without any cross-reactivity. This platform enables sensitive simultaneous EC detection of multiple analytes in human whole blood, and it can be applied to detect any target analyte with an appropriate antibody pair. Thus, this nanocomposite-enabled EC sensor platform may offer a potentially valuable tool for development of a wide range of clinical POC diagnostics.     

基于改进证据理论的多时相微波遥感图像融合及在城区地表变化检测中的应用

该文发展证据理论融合算法,采用不同时相的微波遥感图像检测复杂城市区域地表的变化信息。首先通过综合考虑证据本身的确信度和证据对辨别框架中子集的平均支持度进行证据间的加权合成,改进证据理论对证据的合成,提高其可靠性;然后提取不同时相图像间的散射幅度的对比度和概率密度分布函数在皮尔逊图中的欧式距离,两种特征参数代表了像元级和区域级不同空间尺度下微波遥感图像中关于地表变化的信息;最后将改进的证据理论用于两特征之间的融合处理,得到地表的变化信息。为了实验和验证该文的方法,选择上海市陆家嘴地区不同时相的微波遥感图像,进行地表的变化检测,得到较好的结果。