Monitoring stress levels on rice with heavy metal pollution from hyperspectral reflectance data using wavelet-fractal analysis

Remote sensing allows monitoring heavy metal pollution in crops for agricultural production and food security. This paper presents an approach to wavelet-fractal analysis for exploring a set of sensitive spectral parameters to monitor the heavy metal pollution levels in rice crops from hyperspectral reflectance data. Hyperspectral and biochemical data were collected from three study farms in Changchun, Jilin Province, China. Our study explored the fractal dimension of reflectance with wavelet transform (FDWT) that demonstrated a better performance than other existing methods. Our results obtained in this study show that the red edge position (REP) was the most sensitive indicator for monitoring the heavy metal pollution levels in rice crops among common indices. As compared with REP, the FDWT is more sensitive to biochemical composition, namely with respect to chlorophyll concentrations, N, Cu and Cd. The established linear models showed a correlation coefficient (R²) above 0.70, model efficiency (ME) above 0.65 and a root mean square error (RMSE) below 3.5. Minimum FDWT values occurred in rice with Level II pollution followed by Level I pollution, and finally the safe level. This study suggests that wavelet transform is well suited as a spectral analysis method to eliminate noise and amplify the stress information from heavy metals. The wavelet transform in conjunction with fractal analysis is promising for detecting heavy metal-induced stress in rice crops.     

Delineation of arsenic-contaminated zones in Bengal Delta, India: a geographic information system and fractal approach

Groundwater extracted from shallow aquifers in the Bengal Delta is contaminated with arsenic. The fluviodeltaic process that creates aquifers, ironically, extends its role to also contaminating them with arsenic. The arsenic distribution maps show a spatial association of arsenic-contaminated wells with palaeo/cut-off/abandoned channels. Weight-on-evidences analysis indicates that the zones of contamination occur around palaeo-channels within a corridor of 500–700 m that contains most of the contaminated wells. These corridors are interpreted to be the zone of channel shifting. Contaminated wells represent point fractal geometry that can be separated into isolated points and clusters. Clusters occur within the zone of channel shifting as obtained by weight-on-evidences analysis. Isolated points occur within floodplain or back swamp areas. Clusters and isolated point fractals are interpreted to reflect the process of arsenic release into groundwater. The migration of biomass within the permeable sandy domain of channel deposits is proposed to be the predominant process in generating clusters. The isolated points represent restricted biomass spreading in less permeable clay-silt dominated floodplains.     

喀斯特洼地的分形特性研究*

以贵州高原中部普定马官地区和云南高原边缘西畴峰丛-洼地区为试验区,研究和探讨了喀斯特洼地发育过程中的分形特性。     

应用CT技术研究瘦煤在不同温度下孔隙变化特征

应用µCT225kvFCB型高精度(µm级)CT试验分析系统,对直径1 mm的瘦煤从18 ℃到600 ℃高温下的热破裂过程进行了显微CT观测和分析.发现了瘦煤的热破裂规律:300 ℃煤样中大量小的孔隙贯通成大的孔隙团,因此瘦煤的热破裂阈值在300 ℃附近,从常温到300 ℃煤样的孔隙率增加了0.5倍左右.研究了煤样在100~600 ℃范围内热破裂孔隙分布的分形规律,研究发现:从100 ℃到600 ℃,煤样的分形维数D随温度升高呈现先减小、后增加的趋势.孔隙的演化规律:由初始较规则的小孔隙变形,过渡到大量较规则、小孔隙贯通成不规则的大的孔隙团,之后孔隙团缩合减小趋于规则.分布初值的对数随温度升高呈现先降低后增加的趋势;从18 ℃到600 ℃孔隙数量的演化规律为先减小后增加.     

地震活动性的层次模型及推导的地震活动经验公式和分维性质

文章从一个简单的地震活动层次模型出发，推导地震活动性中几个经验公式以及地震活动的时、空和震源大小分维性质。研究结果表明：（１）震级和频度关系式即Ｇｕｔｅｎｂｅｒｇ－Ｒｉｃｈｔｅｒ公式中的比例系数ｂ值等于震级和平均震中距关系式中的比例系数ｂ１的２倍，并且ｂ值也等于震级和平均时间间隔关系式中的比例系数ｂ２。（２）平均震中距分维值为２，平均时间间隔分维值为１，震源大小分布的分维值的２ｂ。     

Evaluation of the uncertainty in estimation of metal resources of skarn tin in Southern China

This study is concerned with the problem of how many undiscovered mineral deposits can be expected to occur in the vicinity of any known deposit, especially if the deposit is nearly mined out. Skarn tin deposits in southern China were chosen to demonstrate that fractal modeling can be a useful tool to characterize the spatial–temporal distribution of mineral deposits, and to quantify their grades and tonnages. The results show that the spatial–temporal distribution of skarn tin deposits as well as their grades and tonnages satisfy fractal statistic, and suggest that 14 skarn tin deposits could be found around a known skarn tin deposit within a radius of 80 km. Monte Carlo simulation was used to combine the number of deposits and the frequency distributions of grade and tonnage and to capture the uncertainty in estimation of metal resources. At the 90%, 50% and 10% confidence levels, tin metal resources amount to 6 ton, 200 ton, and 1.0 × 10⁴ ton around a known tin deposit within a radius of 80, respectively.     

On estimating the earthquake-induced changes in hydrogeological properties of the Choshuishi Alluvial Fan, Taiwan

The hydrological response of the Choshuishi alluvial fan to the 1999 Chi-Chi earthquake shows that the earthquake did impact the aquifer. The possible earthquake-induced changes in hydrogeological properties were investigated in this study. First, contour maps of the hydrologic anomaly, seismic factors, and vertical ground-surface displacement were compared qualitatively. Bulls eye patterns were found on the contour maps of hydraulic conductivity, coseismic groundwater-level change and vertical ground-surface displacement but did not occur with other seismic factors. The more permeable zones of the aquifer were found to coincide with the locations of greater vertical ground-surface displacement and coseismic groundwater-level change in the 1999 Chi-Chi earthquake. This indicates that the change of the hydrogeologic properties of Choshuishi alluvial fan due to the 1999 Chi-Chi earthquake may have mainly occurred in the highly permeable zones. Fractal, cross semivariogram and cross correlogram analyses were performed to quantitatively measure the persistency, variability and similarity, respectively, of spatial hydrologic response, seismic factors and hydraulic conductivity. The groundwater-level change, earthquake intensity, and vertical ground-surface displacement were found to show antipersistent tendencies while other factors showed the opposite. Higher correlations were found between hydraulic conductivity and groundwater-level change in aquifers 2–1 and 2–2, and between hydraulic conductivity and vertical ground-surface displacement in aquifer 3. Changes in porosities and hydraulic conductivity were evaluated in the main aquifers of the Choshuishi alluvial fan based on the data of hydrologic anomaly and the vertical ground-surface displacement. While both approaches show that the 1999 Chi-Chi earthquake has impacted the Choshuishi alluvial fan by reducing its porosity and hydraulic conductivity, these changes were not significant relative to natural variation in hydraulic conductivity.This revised version was published in May 2005 with correction to the rubric.     

Multifractal Analysis of Earthquakes in the Southeastern Iran-Bam Region

Earthquakes in Iran and neighbouring regions are closely connected to their position within the geologically active Alpine-Himalayan belt. Modern tectonic activity is forced by the convergent movements between two plates: The Arabian plate, including Saudi Arabia, the Persian Gulf and the Zagros Ranges of Iran, and the Eurasian plate. The intensive seismic activity in this region is recorded with shallow focal depth and magnitude rising as high as M_w = 7.8. The study region can be attributed to a highly complex geodynamic process and therefore is well suited for multifractal seismicity analysis. Multifractal analysis of earthquakes (m_b ≥ 3) occurring during 1973 – 2006 led to the detection of a clustering pattern in the narrow time span prior to all the large earthquakes: M_w = 7.8 on 16.9.1978; M_w = 6.8 on 26.12.2003; M_w = 7.7 on 10.5.97. Based on the spatio-temporal clustering pattern of events, the potential for future large events can be assessed. Spatio-temporal clustering of events apparently indicates a highly stressed region, an asperity or weak zone from which the rupture propagation eventually nucleates, causing large earthquakes. This clustering pattern analysis done on a well-constrained catalogue for most of the fault systems of known seismicity may eventually aid in the preparedness and earthquake disaster mitigation.     

基于TM影像的闽江口湿地信息提取及其动态变化研究

以分形理论为基础,借助GIS和RS技术,利用1986年和2002年两期TM遥感影像,提取获得了这两期闽江河口湿地资源的空间信息,根据分形理论中分形维数和稳定性指数的物理意义,揭示了闽江河口湿地资源动态变化情况.研究表明,1986～2002年间,闽江河口区有大量湿地转变为非湿地,总体上看,各湿地类型斑块的形状较为复杂,稳定性差,并且未来有加快演变的趋势.福州市在实施"东扩南进"的城市发展战略过程中对湿地资源的直接占用,是导致闽江口湿地减少,稳定性差的主要原因.今后在闽江南、北港的开发过程中,需要在积极发展经济的同时,加强湿地生态保护.     

西北地区城市规模分形结构的研究

本文利用分形理论和相空间概念，从理论的角度演绎推导出城市规模分形结构的一般模式，并以此为基础，结合西北地区自然，经济，社会状况，对五省萄城市规模分形结构进行初步分析，为深入研究其城市体系，制定城市，区域发展战略提供一定的参考。