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101.
Influences of forest on MODIS snow cover mapping and snow variations in the Amur River basin in Northeast Asia during 2000–2014
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Xianwei Wang Yuan Zhu Yaning Chen Hailing Zheng Henan Liu Huabing Huang Kai Liu Lin Liu 《水文研究》2017,31(18):3225-3241
The study applies the improved cloud‐free moderate resolution imaging spectral radiometer daily snow cover product (MODMYD_MC) to investigate the snow cover variations from snow hydrologic year (HY) HY2000 to HY2013 in the Amur River basin (ARB), Northeast Asia. The fractions of forest cover were 38%, 63%, and 47% in 2009 in China (the southern ARB), Russia (the northern ARB), and ARB, respectively. Validation results show that MODMYD_MC has a snow agreement of 88% against in situ snow depth (SD) observations (SD ≥ 4 cm). The agreement is about 10% lower at the forested stations than at the nonforested stations. Snow cover durations (SCDs) from MODMYD_MC are 20 days shorter than ground observations (SD ≥ 1 cm) at the forested stations, whereas they are just 8 days shorter than ground observations (SD ≥ 1 cm) at the nonforested stations. Annual mean SCDs from MODMYD_MC in the forested areas are 21 days shorter than those in the nearby farmland in the Sanjiang Plain. This indicates forest has a complex influence on the snow accumulation and melting processes and even on optical satellite snow cover mapping. Meanwhile, SCD and mean snow cover are negatively correlated with air temperature in ARB, especially in the snow melting season, when mean air temperature in March and April can explain 86% and 74% of the mean snow cover variations in China ARB and Russia ARB, respectively. From 1961 to 2015, the annual mean air temperature presented an increased trend by 0.33 °C/decade in both China ARB and Russia ARB, whereas it had a decrease trend from HY2000 to HY2013. The decrease of air temperature led to an increase of snow cover, which is different from the global decrease trend of snow cover variations. SCD and snow cover had larger increase rates in China ARB than in Russia ARB, and they were larger in the forested areas than in the nearby farmland in the Sanjiang Plain. 相似文献
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103.
本文分析了引发Jmax灯亮的三种原因。即X线管电流检测回路R33电位计故障;KV参数值产生回路V24管击穿故障,以及灯丝初级加热回路V2管软击穿故障,所以导致的高压发生器低电流保护,Jmax灯亮,不同的是前二项原因使曝光开始即刻Jmax灯亮。 相似文献
104.
本文对建筑结构抗震设计时程法所需的输入地震波提出一种基于规范反应谱的、与设防烈度、场地条件、设计近震或远震、结构自振特性有关的选择原则和方法。按远、近震和四类场地标定了反应谱、延性谱和积累损伤谱。通过对六幢不同高度的剪切和弯曲型结构模型的弹塑性分析,表明离差很小。建议在进行结构时程法分析时,按地震加速度反应谱特定的分布规律选择4条加速度记录作为输入计算。两个实际的例子表明按上述方法计算的结果与按底部剪力法计算的结果基本相符。 相似文献
105.
在收集河南省及邻省地磁台的核旋绝对观测资料基础上,应用最小二乘法原理进行线性空间相关分析和精度检验。结果表明,三类地磁台核旋观测资料精度较高,F总强度不仅精度高且稳定性好。尤其是郑州-信阳台间各项精度指标均名列前茅,显示出内在质量的优越性。 相似文献
106.
本文分析了腹部平片,静脉肾盂造影,B 超及CT 对肾脏疾病的诊断价值。CT 的组织分辨力为普通X 线的十倍,并能提供二维图象,对肾囊肿,结石等疾病可作出定性及定量诊断。静脉肾盂造影有禁忌症限制。B 超受到肠道积气及脂肪影响。4cm 以上肿块行B 超导引穿刺,而深部小于4cm 病灶应行CT 导引下穿刺。 相似文献
107.
盆地分析与油藏描述代表了当代石油地质科学研究的发展方向,它们以高度综合性和定量化为显著标志,大大推进了油气勘探与开发。作者连续几年对三春集等地区先后作了盆地构造岩相分析和精细油藏描述,通过前者建立了该区构造岩相模式,指出了油气富集规律,指导了勘探布置;通过后者建立了油藏地质模型,具体地提出了精细勘探和改善开发效果的建议。最后指出盆地构造相分析法和油藏描述技术应大力推广。 相似文献
108.
109.
LAN Kai YAN Taining. Drilling Engineering Technology Institute Zhongyuan Petroleum Exploration Bureau Puyang Henan China . Engineering Faculty China University of Geosciences Wuhan China 《东北亚地学研究》2009,(3):174-178
Drilling fluid is a common flushing medium used in pile foundation, geological drilling and petroleum drilling. Study on ultrasonic propagation properties in drilling fluid is of vital importance, not only for developing equipments to non-contact measuring concrete casting level for bored pile, but also for developing equip- ments considering drilling fluid as signal channel. The existence of clay particles makes the ultrasonic propagation and attenuation in drilling fluid much different from pure water. In order to know the relation among ultrasound frequency, slun-y density and depth, a series of laboratory experiments about ultrasound propagation in water-based bentonite slurry were finished. Wavelet method was adopted to process the gained original waves of ultrasonic propagation in slurry, so we knew the velocity and attenuation coefficient of ultrasound propagated in different drilling fluids with different density. The first group experiments shows that with density of drilling fluid increase, ultrasonic velocity will decrease but attenuation coefficient will increase if ultrasonic frequency keep constant. The second group experiments shows that the power of ultrasound will intensify in small bore hole, the attenuation coefficient is much smaller than theoretical value. 相似文献
110.
Geochemistry and Modes of Occurrence of Hazardous Trace Elements in the No. 11 Coal Seam, Antaibao Surface Mine, Shanxi Province 总被引:1,自引:0,他引:1
SONG Dangyu QIN Yong WANG Wenfeng ZHANG Junying ZHENG Chuguang 《《地质学报》英文版》2007,81(1):135-140
Concentrations of seventeen hazardous trace elements including As, Pb, Hg, Se, Cd, Cr, Co, Mo, Mn, Ni, U, V, Th, Be, Sb, Br and Zn in the No.ll coal seam, Antaibao surface mine, Shanxi Province were determined using Instrumental Neutron Activation Analysis (INAA), Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), Cold-Vapor Atomic Absorption Spectrometry (CV-AAS) and Graphite Furnace Atomic Absorption Spectrometry (GF-AAS). Comparisons with average concentrations of trace elements in Chinese coal show that the concentrations of Hg and Cd in the No. 11 coal seam, Antaibao surface mine are much higher. They may be harmful to the environment in the process of utilization. The variations of the trace elements contents and pyritic suffur in vertical section indicated that: (a) the concentrations of As, Pb, Mn, and pyritic sulfur decrease from roof to floor; (b) the concentrations of Cr, Zn and Mo are higher in roof, floor and lower in coal seam; (c) the concentration of Br, Sb, and Hg are higher in coal seam and lower in roof and floor; (d) the concentrations of Mo, V, Th and AI vary consistently with the ash yield. Cluster analysis of trace elements, pyritic sulfur, ash yield and major elements, such as AI, Fe, P, Ca shows that: (a) pyritic sulfur, Fe, As, Mn, Ni, Be are closely associated and reflect the influence of pyrite; (b) Mo, Se, Pb, Cr, Th, Co, Ca and A! are related to clay mineral, which is the main source of ash; (c) U, Zn, V, Na, P maybe controlled by phosphate or halite; (d) Hg, Br, Sb and Cd may be mainly organic-associated elements which fall outside the three main groups. The concentration distribution characteristics of trace elements in coal seam and the cluster analysis of major and trace elements showed that the contents of trace elements in the No. 11 coal seam, Antaibao surface mine, are mainly controlled by detrital input and migration from roof and floor. 相似文献