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141.
本文简要地分析了红外测距仪常数的本质特征及种类,提出了用光束接收受限法测试适合于远距离测量改正的周期误差和加常数以及用正常测试综合求解方法确定适合于近距离测量改正的周期误差、加常数和相位不均匀性综合改正。 相似文献
142.
我国第一个标定航空γ能谱仪的校正模型于1986年10月建成试用,1987年8月通过部级技术鉴定正式启用。本文较为详细地介绍了建造校正模型的依据,模型的设计及制作,模型的主要技术参数和基本特点,并对标定结果进行了评价。 相似文献
143.
We present a method for real-time forecasting of water table depth and soil moisture profiles. The method combines a simple form of data-assimilation with a moving window calibration of a deterministic model describing flow in the unsaturated zone and local as well as regional drainage. The local drainage level is calibrated on-line using a moving window calibration. Assigning more weight to the last available measurements then yields a form of model adaptation that is in between on-line calibration and data-assimilation (i.e. a simplified form of Newtonian nudging). Five-day hydrological forecasts are performed based on 5-day weather forecasts, while on-line observations of phreatic level and soil moisture content are assimilated on a daily basis. Advantages of the proposed method are that it improves the real-time forecasts compared to off-line calibration and ordinary moving window calibration and that it yields physically consistent soil moisture profiles. 相似文献
144.
Steffen Mischke Ulrike Herzschuh Gudrun Massmann Chengjun Zhang 《Journal of Paleolimnology》2007,38(4):509-524
About 145 freshwater to hypersaline lakes of the eastern Tibetan Plateau were investigated to develop a transfer function
for quantitative palaeoenvironmental reconstructions using ostracods. A total of 100 lakes provided sufficient numbers of
ostracod shells. Multivariate statistical techniques were used to analyse the influence of a number of environmental variables
on the distributions of surface sediment ostracod assemblages. Of 23 variables determined for each site, 19 were included
in the statistical analysis. Lake water electrical conductivity (8.2%), Ca% (7.6%) and Fe% (4.8%, ion concentrations as %
of the cations) explained the greatest amounts of variation in the distribution of ostracod taxa among the 100 lakes. Electrical
conductivity optima and tolerances were calculated for abundant taxa. A transfer function, based on weighted averaging partial
least squares regression (WA-PLS), was developed for electrical conductivity (r
2 = 0.71, root-mean-square-error of prediction [RMSEP] = 0.35 [12.4% of gradient length], maximum bias = 0.64 [22.4% of gradient
length], as assessed by leave-one-out cross-validation) based on 96 lakes. Our results show that ostracods provide reliable
estimates of electrical conductivity and can be used for quantitative palaeoenvironmental reconstructions similarly to more
commonly used diatom, chironomid or pollen data. 相似文献
145.
In this contribution we have empirically calibrated the garnet–biotite–muscovite–aluminosilicate–quartz (GBMAQ) barometer using low- to medium–high-pressure, mid-grade metapelites. Application of the barometer suggests that the GBMAQ and GASP barometers show quite similar pressure estimates. Furthermore, metapelites within thermal contact aureole or very limited geographic area show no meaningful pressure diversity determined by the GBMAQ and GASP barometers which is the geological reality. The random error of the GBMAQ barometer is expected to be around ± 0.8 kbar, and this barometer shows no systematic bias with respect to either pressure, or temperature, or AlVI in muscovite, or Fe in biotite, or Fe in garnet. The GBMAQ barometer is thermodynamically consistent with the garnet–biotite geothermometer because they share the same activity models of both garnet and biotite. This barometer is especially useful for assemblages with Ca-poor garnet or Ca-poor plagioclase or plagioclase-absent metapelites. Application of this barometer beyond the calibration ranges, i.e., P–T range and chemical ranges of the minerals, is not encouraged. 相似文献
146.
对一种新型随钻电阻率测井仪器在均质地层中的电磁场分布和接收线圈的响应特性进行分析,并对仪器在真空中的刻度方法进行研究.推导出了圆柱坐标系下径向成层介质中磁流源并矢Green函数的矢量本征函数展开式,从而得到研究该仪器电磁场分布、接收线圈响应、刻度方法所必需的解析计算式.计算发现,钻铤的存在大大提高了仪器的定向探测性能.计算还发现,不同的钻铤尺寸、线圈系到钻铤不同的距离对线圈系在真空中的响应值具有较大影响.钻铤在地层中产生的实部信号可近似认为恒定,而当地层电导率大于001 S/m时,钻铤在地层中产生的虚部信号亦可近似认为恒定.数值计算表明,仪器偏心程度越大,钻铤半径越大,仪器中刻度环电阻所对应的视电导率值越小. 相似文献
147.
148.
运用基于历史资料的模式距平积分订正(ANO)方法,结合欧洲中心的ERA-interim再分析资料和0.1度分辨率的中国地面自动站与CMORPH卫星反演降水资料融合逐时降水产品,对高分辨非静力WRF模式的数值预报结果进行订正试验,检验了ANO方法对灾害性天气、尤其持续性强降水预报的订正改进效果。对1983-2013年7月中旬四川地区数值预报结果订正前后与观测和再分析数据的比较表明,ANO方法不仅在环流场的预报订正试验中有较为显著的效果,对模式降水预报结果也有改进,能够有效提高模式对强降水的预报精度和评分、减小预报偏差,其中对2013年7月8—13日高分辨预报结果的ANO订正试验发现,订正环流场各变量都有改进,其中位势高度距平相关系数ACC平均提高了7.8%,均方根误差RMSE平均降低了55.7%,降水(特别是暴雨以上量级)的ETS评分和TS评分也有不同程度的提高,并得到多年独立样本的高分辨数值预报订正结果的支持。 相似文献
149.
Diatom assemblages and water depth in Lake 239 (Experimental Lakes Area,Ontario): implications for paleoclimatic studies 总被引:3,自引:0,他引:3
Melissa?T. MoosEmail author Kathleen R.?Laird Brian?F.?Cumming 《Journal of Paleolimnology》2005,34(2):217-227
Diatom assemblages in surface sediments were sampled along three transects in Lake 239, from the Experimental Lakes Area (NW Ontario), and analyzed in order to explore the relationship between modern species distributions and water depth. Approximately 170 diatom species were identified in surficial sediments at lake depths from 2 to 30 m. The species composition varied with sample depth but remained highly similar across all three transects. The main patterns of variation in the diatom assemblages across transects, derived from a detrended correspondence analysis (DCA), showed that assemblages were highly correlated (r = 0.97 to 0.98). At depths > 8 m the pattern of predominantly benthic composition changed to a planktonic assemblage dominated by Cyclotella stelligera. This depth currently corresponds to the depth of 1% light penetration as assessed from extinction coefficient measurements. Diatom species diversity increases with the switch to the near-shore benthic taxa in all three transects. Additionally, there is a large decrease in the ratio of chrysophyte scales to diatoms at depths < 8 m. Light transmission data from wet and dry periods over the last 35 years suggests that during dry periods the extent of the littoral zone should change by over 2 m. We suggest that cores along a transect from 8 to 14 m should provide a highly sensitive location for detailed paleoclimatic study. 相似文献