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131.
土壤水分及土壤-大气界面对麦田水热传输的作用 总被引:13,自引:2,他引:11
文章根据1996年在中国栾城农业生态试验站观测的田间试验资料,分析了土壤水分和土壤-大气界面对麦田水热传输的抑制和加速作用。对于显热和潜热输送,土壤水分起决定作用,土壤水分越小,显热通量越大,潜热通量越小,反之亦然。只在土壤水分较小时界面厚度对显热和潜热输送作用较大。对于土壤热输送,界面厚度起决定作用,界面厚度越大土壤热通量越小。分析还发现60cm深处土壤水势与叶水势和大气水势的相关系数较其它深度处的土壤水势大。0~60cm土层是确定土壤水分运动对界面水热传输影响的一个良好的指示层。 相似文献
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SAR影像与TM影像的几种融合处理方法 总被引:13,自引:2,他引:11
利用彩色空间变换、比值变换及相关系数法分别对SAR影像与TM3 、TM4 、TM5 三波段影像进行融合处理。文章介绍了影像融合中的具体技术问题及其处理方法。因侧视雷达图像一般有明显的孤立噪声,所以,在进行影像融合处理之前,先对SAR影像进行预处理,文中用δ滤波法抑制孤立噪声(光斑) .最后,从视觉效果、熵、平均梯度值以及标准差等4 方面评价了影像融合的质量。 相似文献
134.
为了客观反映跨断层形变资料在地震前出现的异常程度, 减弱场地布设不均匀性造成的影响, 本文基于以往典型震例归纳跨断层异常场地比指标并进行了实例检验。 结果表明: ① 震例统计显示, 异常场地比随震中距增加快速降低, 在青藏块体东北缘5.8级及以上中强地震前, 距震中200 km范围异常场地比约为0.5。 ② 异常场地比等值线高值区对地震震中位置有较好的指示意义, 可以作为中强地震预测的一种定量判定依据, 为区域地震危险性的地点判定提供支持。 ③ 多期异常场地比空间分布特征能够较好地刻画跨断层异常随时间的增强、 减弱或迁移特征, 可为地震紧迫性判定提供一定帮助。 相似文献
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Wave tank tests were carried out to evaluate the total efficiency of a floating OWC Pentagonal Backward Bent Duct Buoy (PBBDB). Two kinds of turbine generators were used in tests. The incident wave power, pneumatic power and electricity were measured. The test results show that the primary efficiency can reach up to 185.98% in regular waves and 85.86% in irregular waves. The total efficiency from wave to wire with Wells turbine-generator set is 33.43% in regular waves and 15.82% in irregular waves. The peak total efficiency of the PBBDB with check valves equipped with the impulse turbine-generator set is 41.68% in regular waves and 27.10% in irregular waves. The efficiency of the turbine-generator set is about 30% in the tests. Obviously, the total efficiency can be further improved with the increasing of turbine efficiency. 相似文献
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Accurate estimation of the ratio of carotenoid (Car) to chlorophyll (Chl) content is crucial to provide valuable insight into diagnoses of plant physiological and phenological status in crop fields. Studies for assessing the ratio of Car to Chl content have been extensively conducted with semi-empirical approaches using spectral indices. However, spectral indices established in previous studies generally relied on site- or species-specific measured data and these indices typically lacked sufficient estimation accuracy for the ratio of Car to Chl content to be used across various species and under different physiological conditions. In this study, we propose a novel combined carotenoid/chlorophyll ratio index (CCRI) in the form of the carotenoid index (CARI) divided by the red-edge chlorophyll index (CIred-edge): The value of the index is illustrated using synthetic data simulated from the leaf radiative transfer model PROSPECT-5 and with extensive measured datasets at both the leaf and canopy level from the ANGERS dataset and winter wheat and maize field experiments. Results show that CCRI was the index with the highest correlation with the ratio of Car to Chl content in PROSPECT-5 simulations (R2 = 0.99, RRMSE = 8.65%) compared to other spectral indices. Calibration and validation results using the ANGERS and winter wheat leaf level data showed that CCRI achieved accurate estimation of the ratio of Car to Chl content (R2 = 0.52, RRMSE = 14.10%). CCRI also showed a good performance (R2 = 0.54, RRMSE = 17.08%) for estimation of the ratio of Car to Chl content in both calibration and validation with the winter wheat and maize canopy spectra measured in field experiments. Further investigation of the effect of the correlation between leaf Chl and Car content on the performance of CCRI indicated that variation of the correlation affected the retrieval accuracy of CCRI, and CCRI might not be very sensitive to changes of the ratio of Car to Chl content with low values (<0.10). 相似文献
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Based on an analysis of the source of errors in marine gravity measurements, an error model, firstly, is constructed mathematically which can characterize the change of systematic errors and with which a new crossover adjustment model is presented in this paper. Then, two methods of compensating the systematic errors are proposed, i.e., the self-calibrating adjustment and the a-posteriori compensation. Some questions involved in solving the adjustment problem, such as the rank deficiency, the choice of error model, the weighting of model parameters and the significance test of compensation efficiency, etc., are discussed in detail. Finally, a practical survey network is used as a case study to test the efficiency and reliability of the two compensation methods. 相似文献
140.