祁连山中部树木年轮宽度与气候因子的响应关系及气候重建

研究了祁连山中部不同海拔高度青海云杉的树轮宽度对气候因子的响应,重建了祁连山中部 230 a以来春季3~5月的降水和 170 a以来夏季6~8月的气温序列。结果分析发现,不同高度的云杉树轮生长对春季降水极为敏感,呈现显著正相关;对夏季气温的响应程度,各海拔高度却不相同,夏季气温对上、下限云杉生长有显著影响,但对于森林中部云杉作用并不明显,总体表现为负相关,夏季高温对树木生长不利。气候重建结果发现,祁连山中部的春季230 a以来经历了大幅度长阶段的干湿变化,存在明显的 69 a和 21a周期;170 a以来夏季气温变化频繁,存在明显的2~4a周期。目前,祁连山中部正处于相对干旱和温暖时期,呈现出向暖干方向发展的趋势。     

基于多光谱遥感影像的城市建设用地提取及扩张分析

随着经济的快速发展和城市化水平的提高,城市空间扩展已然成为国内外城市发展研究中的热门问题,城市建成区变化监测是对城市扩展最为直观的分析方式。本文选用了2001、2009年Landsat 4-5/TM以及2016年Landsat 8/OLI 3个时相的多光谱遥感影像,采用OSTU算法结合修正归一化水体指数(MNDWI)、归一化裸露指数(NDBI)和归一化不透水面指数(NDISI),自适应地确定最佳阈值提取地物信息,以分层分类的方法对福州市市辖区建设用地进行提取。根据建成区提取结果,定量研究了城市建成区的扩展速率以及城市重心的移动等,并从人口、经济与规划等方面对福州市的城市扩张进行了分析。     

Soil moisture temporal stability and spatio-temporal variability about a typical subalpine ecosystem in northwestern China

Knowledge of the spatial–temporal variability of soil water content is critical for water management and restoration of vegetation in semi-arid areas. Using the temporal stability method, we investigated soil water relations and spatial–temporal variability of volumetric soil water content (VSWC) in the grassland–shrubland–forest transect at a typical semi-arid subalpine ecosystem in the Qilian Mountains, northwestern China. The VSWC was measured on 48 occasions to a depth of 70 cm at 50 locations along a 240-m transect during the 2016–2017 growing seasons. Results revealed that temporal variability in VSWC in the same soil layer in the three vegetation types and averaged across vegetation types tended to exhibit similar patterns of a decrease with increasing soil depth. Temporal stability in each vegetation type was stronger with an increase in soil depth. However, the results of temporal stability determined with standard deviation of relative difference (SDRD) disagreed with those based on the Spearman's rank correlation coefficient; the forest site had the highest Spearman rank correlation coefficient while the shrubland—the smallest SDRD in the 0–20 cm soil layer. Correlation analyses of VSWCs between two vegetation types indicated that soil water was related among all three vegetation types at the 0–20, and 0–70 cm soil layer, but in the 20–40 and 40–70 cm soil layers, significant correlation (p < .01) occurred only between adjacent vegetation types. In the upper soil layer (0–20 cm), soil water relations were mainly affected by surface runoff. In the lower soil layer (20–40 and 40–70 cm), soil water relations among the three vegetation types were highly complex, and probably resulting from a combination of root distribution and activity, interflow, and the impact of deep soil freeze–thaw dynamics. These results suggest that the factors affecting soil water are complex, and further research should address the relative importance of and interactions among different determining factors.     

Monitoring of water surface temperature of Eurasian large lakes using MODIS land surface temperature product

In this study, data from MODIS land surface temperature product level 3 (MOD11A2) were used to investigate the spatiotemporal variation of Eurasian lakes water surface temperature (LSWT) from 2001 to 2015, and to examine the most influencing factors of that variation. The temperature of most lakes in the dry climate zone and in the equatorial climatic zone varied from 17 to 31°C and from 23 to 27°C, respectively. LSWTs in the warm temperate and cold climatic zones were in the range of 20 to 27°C and −0.6 and 17°C, respectively. The average day time LSWT in the polar climate zone was −0.71°C in the summer. Lakes in high latitude and in the Tibetan Plateau displayed low LSWT, ranging from −11 to 26°C during the night time. Large spatial variations of diurnal temperature difference (DTD) were observed in lakes across Eurasia. However, variations in DTDs were small in lakes located in high latitude and in tropical rainforest regions. The shallow lakes showed a rapid response of LSWT to solar and atmospheric forcing, while in the large and deep lakes, that response was sluggish. Results of this study demonstrated the applicability of remote sensing and MODIS LST products to capture the spatial–temporal variability of LSWT across continental scales, in particular for the vast wilderness areas and protected environment in high latitude regions of the world. The approach can be used in future studies examining processes and factors controlling large scale variability of LSWT.     

Timoshenko beam solution for the response of existing tunnels because of tunneling underneath

An analytical solution for the deflection and internal forces of an existing tunnel because of tunneling underneath is presented. The existing tunnel is modeled as a Timoshenko beam resting on a Winkler foundation, which takes into account the contribution of shear deformation to the total deflection of the existing tunnel. The validity of the analytical solution is verified by a centrifuge test, and the merit of this analytical method is confirmed by comparison with the conventional Euler–Bernoulli beam model. Influential factors on the behavior of the existing tunnel are investigated by consideration of the variations of subgrade modulus, ground loss induced by the new tunnel construction, vertical clearance between the new tunnel and the existing tunnel, and relative existing tunnel–soil stiffness. Results show that the proposed analytical method is a valid and effective method to evaluate shearing‐induced deformation in existing tunnels with large diameters. Results also show that the pattern and the amplitude of the response of the existing tunnel are affected largely by ground loss induced by the new tunnel construction, vertical clearance between the new tunnel and the existing tunnel, and relative existing tunnel–soil stiffness. Copyright © 2015 John Wiley & Sons, Ltd.     

Comparison of column-integrated aerosol optical and physical properties in an urban and suburban site on the North China Plain

The column-integrated optical properties of aerosol in Beijing and Xianghe, two AErosol RObotic NETwork(AERONET)sites situated on the North China Plain(NCP), are investigated based on Cimel sunphotometer measurements from October2004 to June 2012. The outstanding feature found is that the seasonal medians of aerosol optical depth(AOD) at the two stations are in good agreement. The correlation coefficients and the absolute differences between AOD at the two stations are larger than 0.84 and less than 0.05, respectively. Good agreement in AOD at these two sites(one urban and the other suburban; 70 km apart) indicates that aerosol pollution in the Greater Beijing area is regional in nature. However, we find significant differences in the absorption ?Angstr ¨om Exponent(AAE), the real and imaginary part of the refractive index, and thereby the single scattering albedo(SSA), and the difference is seasonally dependent. The feature is found to be more prominent in fall when the fine-mode fraction(FMF) and fine-mode effective radius are significantly different at the two stations,besides the parameters mentioned above. The SSA in Beijing at four wavelengths shows lower values as compared to those in Xianghe, although the difference is not significant in some cases. Significant differences in AAE and fine-mode effective radius indicate that there are differences in aerosol physical and chemical properties in urban and suburban regions on the NCP.     

航空高光谱探测技术在准噶尔盆地东部地区油气调查中的应用

赋存于地下的油气藏(田)一般都存在向地表微渗漏,油气藏上方烃类垂向微渗漏可引起近地表物质的物理与化学性质变化,形成地物反射光谱特征异常,这为航空高光谱技术用于探测烃类微渗漏信息成为可能,成为油气选区调查和寻找油气的有效技术方法。在准东2500 km2范围内开展航空高光谱油气探测技术研究,获取了研究区CASI/SASI/TASI航空高光谱遥感数据,提取了与油气及与油气相关的粘土、碳酸盐、二价铁等信息,通过与已发现的油气藏(田)高光谱油气异常信息的对比研究,在准东地区落实了柳树河子和三台镇2个油气有利区。     

紫外分光光度法测定秋水仙碱中毒血清的临床应用

目的：探讨紫外分光光度法测定秋水仙碱中毒血清,为临床秋水仙碱中毒提供诊疗依据。方法取0．5 mL 血清加提取液（三氯甲烷∶甲醇＝95∶5）4．0 mL。充分震荡萃取,高速离心,取有机层于另一试管中氮气吹干,取0．2 mL 甲醇溶解残渣,混匀,取50 mL 做紫外扫描。结果血清中秋水仙碱最大吸收峰（351±1）nm,浓度在5．0～40μg／mL 范围内呈线性,回归方程Y ＝0．0502X ＋0．0013,其相关系数为0．9995,回收率为83．8％～102．8％,相对标准差为3．3％～4．8％。日内、日间相对标准差分别为3．22％～4．74％和3．45％～4．66％,最低检出浓度为1．0μg／mL。结论该方法操作简便,分析快速,结果准确,为临床诊断秋水仙碱中毒提供了一个简便准确的检测方法。