基于GIS的岷江映秀段泥石流危险性评价

流域地貌是泥石流形成的基础,对泥石流的发育有较大影响。本文基于地貌信息熵理论,利用GIS技术定量分析岷江映秀段小流域地貌发育阶段,以评价岷江映秀段沟谷发生泥石流的危险性。最后利用泥石流沟的实例数据来验证评价结果的准确性,对比结果表明评价结果与实际情况能较好吻合。     

Source diagnostic and weathering indicators of oil spills utilizing bicyclic sesquiterpanes

Bicyclic Sesquiterpanes (BSs) are ubiquitous components of crude oils and ancient sediments. BSs in crude oils and diesel oil were identified and characterized, the effects of moderate weathering on BS distributions were discussed, and a methodology using diagnostic indices of BSs was developed for oil correlation and differentiation. The results showed that crude oils and oil products had different abundances and distributions of BSs and, consequently, resulted in different diagnostic ratios. The selected diagnostic ratio indices of BSs, such as BS4/BS5 (ratio of 4,4,8,9,9-pentamethyl-decahydronaphthalene to 8β (H)-drimane), BS6/BS5 (ratio of 4,4,9,9,10-pentamethyl-decahydronaphthalene to 8β (H)-drimane), BS8/BS9 (ratio of the second peak to the third peak of C 16 sequiterpane), and BS8/BS10 (ratio of C 16 sequiterpane to 8β (H)-homodrimane), still maintained better stabilities (%RSD < 5%) after weathering for 30 d. The longer weathering process (150 d) had some effect on such ratios (5% < %RSD < 10%). The facts of the uniqueness, abundance in petroleum, and chemical stability of BSs enable them to be suitable as an effective diagnostic means for identifying spilled oil with moderate weathering, particularly for lighter refined product samples that are difficult to identify by current techniques.     

南半球10 hPa极地涡旋的多尺度变化特征分析

利用NCEP/NCAR 10 hPa月平均高度场资料, 计算了1948\_2007年南半球10 hPa极地涡旋的强度指数P、 面积指数S和中心位置指数(λc, φc)。用它们分析了南半球10 hPa极地涡旋的季节变化、 年际异常及其可能成因, 分析了10 hPa极地涡旋强度与南极涛动的关系。结果表明： (1) 南半球10 hPa极区12月~1月受反气旋控制, 3~10月受气旋控制, 2月、 11月为环流转换季节。(2) 1(7)月反气旋(气旋)指数P\, S均在1970年代后期发生了显著的跃变; 跃变前反气旋(气旋)由极弱(极强)振荡地增强(减弱)至接近气候均值, 跃变后反气旋由极强振荡趋于气候均值, 气旋在偏弱的状态下振荡。(3) 1月反气旋中心位置存在显著的年代际变化, 而7月气旋中心位置的年际变化明显。(4) 臭氧异常可引起南半球10 hPa 1月极地反气旋年际异常(正相关), 但与7月极地气旋异常无关。(5) 1月、 7月极地涡旋强度指数P与南极涛动指数(AAOI)呈显著的负相关, 可由P来表征AAOI。     

甘肃小铁山隐伏多金属矿床地球化学预测指标

小铁山隐伏多金属矿床是海底火山喷发-沉积建造成因的矿床.赋矿地层、岩性具有较高含量的Cu-Zn-Ba-Ag-Co组合.在矿田和矿床范围内,这些元素形成清晰的原生异常,异常相互交替叠置于矿化地段.在矿体延伸方向上,元素的原生异常分布组合具有轴向分带现象,前缘元素I、Na_2O、Li,与矿体密切相关元素为Cu、Zn,Hg、Au、Pb、Ag、Bi、Sb、As,尾部元素Cd、Mo、Co、Sn.多元素累乘比值[w(Na_2O)×w(Li)]/[w(K_2O)×w(Rb)]从矿上向尾部具有规律的下降,矿体上、下盘的元素组合明显不同,矿体上盘富集亲铁元素,矿体下盘富集亲硫元素.这些指标对评价异常远景和矿化剥蚀程度具有一定的意义.     

Numerical Study on Breaking Criteria for Solitary Waves

Studies of the breaking criteria for solitary waves on a slope are presented in this paper. The boundary element method is used to model the processes of shoaling and breaking of solitary waves on various slopes. Empirical formulae that can be used to characterize the breaking of solitary waves are presented. These include the breaking index, the wave height, the water depth, and the maximum particle velocity at the point of breaking. Comparisons with the results of other researches are given.     

高光谱遥感在农作物长势监测中的应用

该研究是加拿大Saskatchewan Scott农作物轮作系统(ACS)研究的一部分。研究始于1994年,历时18a,评价9个可耕种农作物产量系统的可靠性。由3种处理水平(organic,reduced,high)和3种作物多样性水平(low,diversified annual grains,diversified annual perennials)结合而产生的9个农作物产量系统,被用于监测和评价加拿大牧场不同处理和不同作物种植轮作下可耕种农作物的产量。在2003年生长季共收集了3次叶面积指数和光谱反射率的数据:生长季前期(6月)、生长季旺盛期(7月)、生长季后期(8月)。叶面积指数是由LAI-2000植物冠层分析仪监测的,光谱测量是由覆盖了350-2500 nm波长范围共2215个波段的ADS便携式高光谱仪完成的。结果显示,光学测量可以用于监测农作物生长状况的差异。从生长季的早期到中期,光谱和叶面积指数在不同处理下有显著差异。7月中期是用遥感资料监测农作物长势的最佳季节;红光波段与近红外波段反射率的比值和基于这两个波段构造的归一化植被指数,是检测农作物长势的最佳植被指数。     

城市地下水饮用水水源地安全评价体系研究

随着饮用水质量标准的提高,水源地安全评价指标体系也应随之完善.从水源地安全的内涵出发,构建了包括水量、质量、脆弱性和生态环境4项一级指标、11项二级指标的地下水饮用水水源地安全评价体系,并提出了相应的分析计算方法,从而为新标准实施后地下水源地安全评价提供了科学依据.     

Remote sensing of grassland–shrubland vegetation water content in the shortwave domain

This study compares the ability of spectral approaches operating in the shortwave optical domain to predict absolute and relative vegetation water content (AWC and RWC, respectively) across northern prairie grassland–shrubland. We collected vegetation water content and spectral radiometer data over plots of comparable ground resolution (0.5 m) at seven field sites in the Canadian mixed grass prairie in June 2004. We then aggregated observations to scale these data “up” to an observational scale consistent with that of Landsat-TM satellite imagery (30 m). This allowed us to assess abilities of three spectral approaches to predict AWC and RWC at both observational scales. These approaches were: individual vegetation indices, a combination of spectral bands and a combination of spectral derivatives. Our results showed that (a) the band-combination approach provides the most accurate and precise estimates of AWC and RWC at both 0.5 and 30 m sampling resolutions; (b) the combination of bands providing the greatest predictive abilities are those that emphasize the contrast in reflectance between the NIR and SWIR spectral regions; (c) the band-combination approach predicts AWC with much greater accuracy and precision than RWC and (d) the predictive ability of the band-combination approach decreases only slightly when plot-level data are aggregated to a 30 m sampling resolution. These results are generally consistent with the results of other studies and with theory. While our results suggest that simple spectral methods (e.g. linear band-combinations or indices) are good predictors of AWC over grazed and ungrazed grassland–shrubland landscapes at plot- and Landsat spatial resolutions, they are less encouraging for the estimation of RWC. Despite their good predictive abilities, the temporal and geographical portabilities of the spectral approaches for estimating AWC must be further assessed before they can be considered reliable and robust predictive tools. Thus, the further testing of these techniques over larger geographical extents is required.