SeaWiFS资料水色辐射模式验证的研究

从１９９４ 年～１９９７ 年，作者对杭州湾与长江口海区、台湾至吕宋以东海区和渤海海区，进行了多次光谱测量和同步取样试验，将试验所得资料经计算机处理，确定了三种验证区域各种水色要素与遥感光谱值之间的关系，提出适用于我国验证区域各种水色的验证模式。其各水色模式验证偏差均小于２０％ ，并适用于我国海域ＳｅａＷｉＦＳ水色遥感应用。     

土壤冻融对溶解性有机质与菲结合的影响

以沈阳市公园土壤和道路边土壤中的溶解性有机质(DOM)为研究对象,利用荧光淬灭法测定DOM与菲的结合常数(K),考察了冷冻温度、融化温度、冷冻时间和冻融次数对其光谱学特性及其与菲的结合常数(K)的影响,并结合相关性矩阵分析K与其他参数的关系.结果表明:冻融处理条件下,K值与溶解性有机碳含量(DOC)显著负相关(p0.01),与254 nm处的紫外吸光系数(a_(254))和单位浓度DOC的254 nm的紫外吸光值(SUVA)显著正相关(p0.01).城市公园土壤DOM和城市道路边土壤DOM的K值都是3.5×10~4L·kg~(-1),经过冷冻温度、冷冻时间和冻融次数相同的冻融处理后,城市公园土壤DOM的K值始终高于城市道路边土壤DOM,这是由于冻融导致城市土壤DOM的芳香性高于城市道路边土壤DOM,而分子量小于城市道路边土壤DOM.经过冻融作用二者的K值变化范围分别为1.6×10~5～8.4×10~5L·kg~(-1)和1.5×10~5～3.7×10~5L·kg~(-1),冻融作用使二者的K值都增大一个数量级.这一方面会增强固相土壤中多环芳烃的溶出和迁移,另一方面也会降低多环芳烃的生物可利用性.     

Evaluating the blue-light hazard from solid state lighting

Purpose. New light sources including light-emitting diodes (LEDs) have elicited questions about retinal damage, including the blue-light hazard. Some organizations have recommended avoiding using LEDs with correlated color temperatures exceeding 3000?K, since they tend to produce greater short-wavelength energy. This article provides quantitative comparisons among light sources and use cases as they affect the blue-light hazard. Methods. The spectral radiant power characteristics of incandescent, fluorescent, LED and daylight sources were evaluated in terms of blue-light hazard using standard procedures for phakic, aphakic and pseudophakic eyes. Results. Under most use cases, LEDs do not exhibit greater risk for the blue-light hazard than other sources (e.g., incandescent). Because they generally produce little to no ultraviolet energy, LEDs often present less risk to aphakic eyes. Conclusions. LEDs present no special concerns for the blue-light hazard over some other common sources in typical use cases because photophobic responses limit exposure to bright sources. Where photophobic responses might not occur (e.g., eye surgery patients or premature infants) or where individuals suppress these responses (e.g., stage actors), caution is necessary. Evidence remains inconsistent regarding the risk of human retinal damage from long-term exposures to light insufficient to reach acute blue-light hazard thresholds.     

Advanced treatment of municipal wastewater by nanofiltration: Operational optimization and membrane fouling analysis

Municipal sewage from an oxidation ditch was treated for reuse by nanofiltration (NF) in this study. The NF performance was optimized, and its fouling characteristics after different operational durations (i.e., 48 and 169 hr) were analyzed to investigate the applicability of nanofiltration for water reuse. The optimum performance was achieved when transmembrane pressure = 12 bar, pH = 4 and flow rate = 8 L/min using a GE membrane. The permeate water quality could satisfy the requirements of water reclamation for different uses and local standards for water reuse in Beijing. Flux decline in the fouling experiments could be divided into a rapid flux decline and a quasi-steady state. The boundary flux theory was used to predict the evolution of permeate flux. The expected operational duration based on the 169-hr experiment was 392.6 hr which is 175% longer than that of the 48-hr one. High molecular weight (MW) protein-like substances were suggested to be the dominant foulants after an extended period based on the MW distribution and the fluorescence characteristics. The analyses of infrared spectra and extracellular polymeric substances revealed that the roles of both humic- and polysaccharide-like substances were diminished, while that of protein-like substances were strengthened in the contribution of membrane fouling with time prolonged. Inorganic salts were found to have marginally influence on membrane fouling. Additionally, alkali washing was more efficient at removing organic foulants in the long term, and a combination of water flushing and alkali washing was appropriate for NF fouling control in municipal sewage treatment.     

A multiscale hierarchical Markov transition matrix model for generating and analyzing thematic raster maps

A model is described for generating hierarchically scaled spatial pattern as represented in a thematic raster map. The model involves a series of Markov transition matrices, one for each level in the scaling hierarchy. In full generality, the model allows the transition matrices to be different at each level, potentially making available a large number of parameters for landscape characterization. The model is self-similar when the transition matrices are all equal. A method is presented for fitting the model to data that take the form of a single-resolution thematic raster map. Explicit analytic solutions are obtained for the fitted parameters. The fitting method is based on a relationship between the hierarchical transitions in the model and spatial transitions at varying distance scales in the data map, a categorical analogy of the geostatistical variogram.     

Nitrogen to phosphorus ratios of two understory plant species in response to nitrogen and phosphorus addition in tropical forest of southern China北大核心CSCD

The secondary tropical forests in southern China have suffered from frequent human disturbance and increasing high N deposition. In order to explore the nutrient limitation status in secondary tropical forests of South China, this 3-year field experiment of nitrogen (+N) and phosphorus (+P) addition investigated nitrogen (N) and phosphorus (P) concentrations of the aboveground tissue (leaf and branch) of two widely distributed understory native species Clerodendrum cyrtophyllum and Uvaria microcarpa in a secondary tropical forest of South China. The results showed that: 1) the N and P concentrations of the two species were significantly different (P < 0.001); N and P concentrations of different tissues in the same species were different; N&P addition greatly affected N and P concentrations in branch rather than new leaf and older leaf. 2) +N treatment had no significant effect on N or P concentrations of either species, but significantly decreased N:P ratios (P = 0.001), at the level of 9% for C. cyrtophyllum and 50% for U. microcarpa, respectively. 3) +P treatment had no significant effect on tissue N concentrations, but significantly increased plant P concentrations (P < 0.001), at 54% for C. cyrtophyllum and 88% for U. microcarpa, respectively; +P treatment significantly decreased plant N:P ratios (P < 0.001), at 28% and 60%, respectively. 4) The alterations of P concentrations of two species had significantly negative correlations with N:P alterations under +N/+P treatment (P < 0.001), suggesting that the alteration of P concentrations in plant tissue was the major driver for N:P alteration. Our results show that N and P addition would affect tissue N and P concentrations of the two species, with +P treatment having relatively greater effect on nutrient concentrations than +N treatment; the branch is more sensitive than new or older leaf in response to nutrient addition. Therefore, P availability may be the limiting factor for plant growth in the tropical forests.     

A pilot study on the effect of Cu,Zn, and Cd on the spectral curves and chlorophyll of wheat canopy at tiller stage

The aim of this study was to investigate canopy spectral reflectance responses to different levels of heavy metals copper (Cu), zinc (Zn), and cadmium (Cd) induced stress. Random blocks design experiment was conducted to simulate Cu, Zn, and Cd at five concentration levels. Chlorophyll and visible and near infrared canopy reflectance were measured for each treatment 56 days after seeding using chlorophyll meter SPAD-502 and spectroradiometer, respectively. New vegetative indices termed ratio of inclination angles (RIA), MERIS (the medium resolution imaging spectrometer) terrestrial chlorophyll index (MTCI), and normalized difference vegetation index (NDVI) were used to assess the response of canopy spectral reflectance to different heavy metal levels. Significant spectral variability especially in blue, red, and near infrared reflectance was observed for different heavy metal treatments. One-sample test showed significant difference for NDVI, MTCI, and RIA among five-level treatments at the 0.01 level. Correlation analysis demonstrated that the two vegetative indices (RIA and MTCI) were significantly correlated with chlorophyll meter values for Cd, Cu, and Zn treatments. However, NDVI was only significantly correlated with chlorophyll meter values for Cu and Zn treatments. Linear regression analysis also illustrated that RIA and MTCI were potential indices for predicting chlorophyll concentration with significant F test under Cu-, Zn-, and Cd-mediated stress.     

A Special Vegetation Index for the Weed Detection in Sensor Based Precision Agriculture

Many technologies in precision agriculture (PA) require image analysis and image- processing with weed and background differentiations. The detection of weeds on mulched cropland is one important image-processing task for sensor based precision herbicide applications. The article introduces a special vegetation index, the Difference Index with Red Threshold (DIRT), for the weed detection on mulched croplands. Experimental investigations in weed detection on mulched areas point out that the DIRT performs better than the Normalized Difference Vegetation Index (NDVI). The result of the evaluation with four different decision criteria indicate, that the new DIRT gives the highest reliability in weed/background differentiation on mulched areas. While using the same spectral bands (infrared and red) as the NDVI, the new DIRT is more suitable for weed detection than the other vegetation indices and requires only a small amount of additional calculation power. The new vegetation index DIRT was tested on mulched areas during automatic ratings with a special weed camera system. The test results compare the new DIRT and three other decision criteria: the difference between infrared and red intensity (Diff), the soil-adjusted quotient between infrared and red intensity (Quotient) and the NDVI. The decision criteria were compared with the definition of a worse case decision quality parameter Q, suitable for mulched croplands. Although this new index DIRT needs further testing, the index seems to be a good decision criterion for the weed detection on mulched areas and should also be useful for other image processing applications in precision agriculture. The weed detection hardware and the PC program for the weed image processing were developed with funds from the German Federal Ministry of Education and Research (BMBF).     

Uranium isotopes in groundwater from the “Jeffara coastal aquifer” (southeastern Tunisia)

The distributions of ²³⁸U and ²³⁴U in groundwater from the “Jeffara aquifer” were studied by using alpha spectrometric methods. The concentration ranges of ²³⁸U and ²³⁴U/²³⁸U activity ratios were 1.34 ± 0.17 to 3.43 ± 0.38 ppb, and 1.43 ± 0.23 to 1.82 ± 0.27 respectively. Variations in concentrations can be related not only to lithostratigraphic formations but also to different origins of groundwater. U content of Jeffara are found very similar to those of Continental Intercalaire aquifer in both El Hamma and Chenchou regions, indicating that the Continental Intercalaire is the dominant source of the groundwater.     

平稳地震地面运动改进金井清谱的相关函数模型

胡聿贤平稳地震地面运动谱模型是对Kanai-Tajimi模型的一种改进。通过数学推导证明胡聿贤谱是将基岩地震动模拟为过滤白谱过程,经具有某种特性的线性单自由度土层滤波后而形成的,从而在物理上解释了胡聿贤模型的合理性;研究了低频截止频率的作用,推导出胡聿贤模型的相关函数的表达式。本文所得结果可为结构随机地震反应时域分析提供基础。