用直接估计法预测落叶松枯枝含水率的稳定性和外推误差分析   总被引：1，自引：0，他引：1  

金森  李亮  赵玉晶 《林业科学》2011,47(6)

采用Catchpole等提出的直接估计法分析实验室中3组不同直径(0.5,1.0,1.5cm)的兴安落叶松枯枝的失水过程,通过交叉验证研究所得模型的稳定性,并对模型的外推误差进行分析。结果表明:枯枝的时滞和平衡含水率参数变化很小,结果具有良好的稳定性。同一直径的不同枝条在时滞、平衡含水率参数等方面存在差异。模型外推没有改变残差的正态分布,但外推后的残差增大。非外推残差集中出现在数值较小的区间上,而外推残差在这些区间上出现的概率下降,在非外推残差没有出现的数值较大的区间上出现的概率增加。研究给出枯枝在不同含水率预测值时不同残差出现的条件概率和均值。随含水率预测值的增加,残差有增加的趋势,不仅是平均值,大的残差出现的概率也在增加。据此可对外推模型所预测的含水率进行评判,确定其误差均值和不同残差出现的可能性,以减少据此进行的火险预报和火行为预报中的不确定性。用至少4个枯枝的混合数据在一定程度上可降低外推误差,减少这种不确定性。由于所有材料和实验条件最大程度上减少了材料和环境的差异,上述结果也可被看作用模型外推预测野外可燃物含水率时可能出现的误差的下限。  相似文献   

The effect of aqueous extract of gross and commercial yerba mate (Ilex paraguariensis) on intra-abdominal and epididymal fat and glucose levels in male Wistar rats     

Silva RD  Bueno AL  Gallon CW  Gomes LF  Kaiser S  Pavei C  Ortega GG  Kucharski LC  Jahn MP 《Fitoterapia》2011,82(6):818-826

This study analyzed the plasma lipid profile, glucose levels and fat deposits in male rats treated with aqueous extract of gross yerba mate, commercial yerba mate or water. Yerba mate treatment did not change body weight gain and lipid profile. The consumption of gross yerba mate significantly increased blood glucose (6.6 mmol/L) as compared to the water (4.8 mmol/L) and commercial group (5.2 mmol/L) and decreased epididymal and intra-abdominal deposits (10.1 mg/g and 23.7 mg/g of weight) as compared to the water (15.4 mg/g and 36.9 mg/g of weight) and commercial group (12.5 mg/g and 28 mg/g of weight). The results suggest that gross yerba mate reduces fat more efficiently but produces a greater increase in blood glucose when compared to commercial yerba mate and water groups.  相似文献   

在ERDASIMAGINE中建立邯郸市TM影像土地类型解译标志     

周金艳 《绿色大世界》2011,(6):213-216

为了准确地了解邯郸市的土地利用类型,掌握土地资源的发展动态,在ERDASIMAGINE软件支持下,将Landsat 5号卫星所得的TM4、3、2波段数据组合输出成为标准假彩色影像,对其进行几何校正、重采样、图像裁剪与镶嵌等操作,依据遥感图像特征、地物相关关系、区域特点和全国土地利用分类系统,对处理后所得的邯郸市TM影像建立土地类型解译标志。经过实地验证,其结果判正率比较高,可以满足解译精度的要求,这说明利用遥感技术建立土地利用类型解译标志是可行的。  相似文献   

水准仪的校正以及校正时应注意的事项     

姜久红  刘颖奇  韩金莲 《内蒙古林业调查设计》2011,(4):90-92

文章介绍了在野外作业中对水准仪检查与校正的方法,并且提出在校正时应注意的事项。  相似文献   

不同比例尺DEM提取地面坡度的精度研究——以在黄土丘陵沟壑区的试验为例   总被引：53，自引：8，他引：53  

汤国安  杨勤科  张勇  刘咏梅  刘新华 《水土保持通报》2001,21(1):53-56

以陕北绥德县韭园沟流域为试验样区 ,采用高精度 1∶ 1万 DEM所提取的坡度为准值 ,应用多层面复合分析和比较分析的方法 ,研究该地区 1∶ 5万 DEM提取地面坡度的误差特征与纠正方法。试验结果显示 ,所获得的不同空间尺度下 DEM所提取坡度值的转换图谱 ,可对 1∶ 5万 DEM计算的地面坡度统计值进行有效修正。该成果对于 DEM数据在水土保持领域若干应用标准的制定 ,提供了重要的理论依据与技术路线  相似文献   

Error analysis of worm grinding wheel precise dressing by diamond roller with straight profile     

LIU Feng lin  CHEN Jiu  XU Xiao gang  HE Bing 《保鲜与加工》2011,(12):1-8

In worm grinding wheel dressing with diamond roller, using straight line instead of theoretical curve of roller will result in dressing error. Method of the precise dressing is studied, while the mathematical model is presented. Theoretical curve of diamond roller is calculated based on the space meshing theory and helicoid equation of worm grinding wheel. The fitting error between the theoretical curve and approximate straight line which is obtained by the theoretical curve is calculated. The dressing error on normal section of worm grinding wheel is analyzed. The case study of a kind of worm grinding wheel with single head shows that the dressing error increases with diameter decreasing of worm grinding wheel and diamond roller, while the variation of diamond roller’s diameter makes little contribution. The validity of worm grinding wheel dressing using straight line diamond roller is proved, and the algorithm can be used as guidance in practice.  相似文献   

Reliability model for Subsystems of CNC machine tool with small samples   总被引：1，自引：0，他引：1  

SHEN Gui-xiang  CHEN Bing-kun  ZHANG Ying-zhi  SHAO N  GU Dong-wei  WANG Zhi-qiong 《保鲜与加工》2011,(8):55-59

Many subsystems in CNC machine tool have only a few failures, so they are small samples. In this case, classical reliability modeling method often has large errors. For the failure data of small sample, maximum likelihood estimation method is used to estimate the Weibull distribution model parameters of time between failures of the subsystems. Then, the Weibull distribution model parameters are modified by parameter bias correction method. Finally, the effect of bias correction parametersis tested by the D test and the error area ratio test method. The test results show that the modified models are better.  相似文献   

Enhancing the Simplified Surface Energy Balance (SSEB) approach for estimating landscape ET: Validation with the METRIC model     

G.B. Senay 《Agricultural Water Management》2011,98(4):606-618

Evapotranspiration (ET) can be derived from satellite data using surface energy balance principles. METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) is one of the most widely used models available in the literature to estimate ET from satellite imagery. The Simplified Surface Energy Balance (SSEB) model is much easier and less expensive to implement. The main purpose of this research was to present an enhanced version of the Simplified Surface Energy Balance (SSEB) model and to evaluate its performance using the established METRIC model. In this study, SSEB and METRIC ET fractions were compared using 7 Landsat images acquired for south central Idaho during the 2003 growing season. The enhanced SSEB model compared well with the METRIC model output exhibiting an r² improvement from 0.83 to 0.90 in less complex topography (elevation less than 2000 m) and with an improvement of r² from 0.27 to 0.38 in more complex (mountain) areas with elevation greater than 2000 m. Independent evaluation showed that both models exhibited higher variation in complex topographic regions, although more with SSEB than with METRIC. The higher ET fraction variation in the complex mountainous regions highlighted the difficulty of capturing the radiation and heat transfer physics on steep slopes having variable aspect with the simple index model, and the need to conduct more research. However, the temporal consistency of the results suggests that the SSEB model can be used on a wide range of elevation (more successfully up 2000 m) to detect anomalies in space and time for water resources management and monitoring such as for drought early warning systems in data scarce regions. SSEB has a potential for operational agro-hydrologic applications to estimate ET with inputs of surface temperature, NDVI, DEM and reference ET.  相似文献   

1980～2005年广东农民持久收入与消费的协整分析     

谭莹  许能锐 《仲恺农业技术学院学报》2007,20(4):44-49

文章根据弗里德曼的持久收入理论，应用单位根检验、协整检验以及误差修正模型分析等一系列经济计量方法，对1980～2005年广东农民持久收入与消费支出的关系进行了研究．实证结果表明，广东农民的持久收入与消费支出关系密切；农民的消费支出强烈地依赖于其收入的增加；前期的收入支出节余对当期的消费支出影响很大．  相似文献   

遥感区域大小对森林蓄积估测影响规律的研究   总被引：6，自引：2，他引：6  

李崇贵  赵宪文  蔡体久 《北京林业大学学报》2001,23(4):29-34

该文将 1幅TM遥感图像分别分成 1 4及 1 2幅 ,通过实例分析了 1 4,1 2及整幅TM图像所能达到的几何精校正精度 .然后 ,以样地对应的遥感和GIS信息为影响森林蓄积估测的变量 ,采用最小二乘原理及岭迹分析 ,研究了上述 3种不同面积幅值图像对应林区影响森林蓄积估测的主要变量 .由 3种不同面积遥感区域蓄积估测方程中所含变量的个数、种类及预报精度 ,详细分析了遥感区域大小对蓄积估测的影响规律  相似文献