Spectral pattern recognition in under-sampled functions     

Robert F. Shurtz 《Mathematical Geology》1988,20(6):731-751

Fourier optics and an optical bench model are used to construct an ensemble of candidate functions representing variational patterns in an undersampled two dimensional functiong(x,y). The known sample functions(x,y) is the product ofg(x,y) and a set of unit impulses on the sample point patternp(x,y) which, from the optical point of view, is an aperture imposing strict mathematical limits on what the sample can tell aboutg(x,y). The laws of optics enforce much needed—and often lacking—conceptual discipline in reconstructing candidate variational patterns ing(x,y). The Fourier transform (FT) ofs(x,y) is the convolution of the FT's ofg(x,y) andp(x,y). If the convolution shows aliasing or confounding of frequencies undersampling is surely present and all reconstructions are indeterminate. Then information from outsides(x,y) is required and it is easily expressed in frequency terms so that the principles of optical filtering and image reconstruction can be applied. In the application described and pictured the FT ofs(x,y) was filtered to eliminate unlikely or uninteresting high frequency amplitude maxima. A menu of the 100 strongest remaining terms was taken as indicating the principle variational patterns ing(x,y). Subsets of 10 terms from the menu were chosen using stepwise regression. By so restricting the subset size both the variance and the span of their inverse transforms were made consistent with those of the data. The amplitudes of the patterns being overdetermined, it was possible to estimate the phases also. The inverse transforms of 9 patterns so selected are regarded as ensembles of reconstructions, that is as stochastic process models, from which estimates of the mean and other moments can be calculated.This paper was presented at Emerging Concepts, MGUS-87 Conference, Redwood City, California, 13–15 April 1987.  相似文献   

中国名山名水写景地图集的设计编制特色     

王利军 《地球信息科学学报》2000,2(3):72-74

本文论述中国名山名水写景地图集的编制选题、内容、设计特点,重点讨论用中国山水绘画形式配合景点象形符号表现山岳形态景观,运用图、文、表融合展示方法,编制旅游地图集的尝试。这种图文并茂有机协调的旅游地图集,可以满足不同旅游者多方面、多层次的需求。  相似文献   

Sensitivity of goodness-of-fit statistics to rainfall data rounding off     

Roberto Deidda  Michelangelo Puliga 《Physics and Chemistry of the Earth》2006,31(18):1240-1251

An analysis based on the L-moments theory suggests of adopting the generalized Pareto distribution to interpret daily rainfall depths recorded by the rain-gauge network of the Hydrological Survey of the Sardinia Region. Nevertheless, a big problem, not yet completely resolved, arises in the estimation of a left-censoring threshold able to assure a good fitting of rainfall data with the generalized Pareto distribution. In order to detect an optimal threshold, keeping the largest possible number of data, we chose to apply a “failure-to-reject” method based on goodness-of-fit tests, as it was proposed by Choulakian and Stephens [Choulakian, V., Stephens, M.A., 2001. Goodness-of-fit tests for the generalized Pareto distribution. Technometrics 43, 478-484]. Unfortunately, the application of the test, using percentage points provided by Choulakian and Stephens (2001), did not succeed in detecting a useful threshold value in most analyzed time series. A deeper analysis revealed that these failures are mainly due to the presence of large quantities of rounding off values among sample data, affecting the distribution of goodness-of-fit statistics and leading to significant departures from percentage points expected for continuous random variables. A procedure based on Monte Carlo simulations is thus proposed to overcome these problems.  相似文献   

水泥土添加剂室内配比试验的模糊正交分析     

李志斌  叶观宝  徐超 《水文地质工程地质》2005,32(4):117-119

利用模糊正交试验,对水泥土添加剂室内配比试验结果进行分析。以无侧限抗压强度和试样成本为考核指标,得出水泥土试样在2 8d和90d时水泥掺入比、添加剂掺入比和水灰比的最佳组合,为实际工程提供有价值的参考。  相似文献   

近红外反射光谱学在岩石矿物研究中的应用Ⅲ．快速测定地质样品中二氧化碳   总被引：1，自引：1，他引：1  

龙梅  裴世桥 《岩矿测试》2005,24(1):26-30

使用一组不同岩石矿物性质的25个地质样品,研究了地质样品中二氧化碳含量和近红外漫反射光谱的关系。利用多重散射光校正、标准正常变量转换及导数光谱等化学计量统计学方法,预处理了漫反射光谱数据,获得了偏最小二乘法(PLS)回归的多变量校正方法,建立了应用近红外(NIR)反射光谱学方法无损快速测定各种地质样品中二氧化碳模型。从光谱特性方面解释了大多数进入多变量校正模型的波长与碳酸盐矿物的CO2-3基团光谱吸收有关。NIR估算结果表明,应用二氧化碳校正模型来定量分析地质样品中二氧化碳的方法是可行的。  相似文献   

氢化物发生-原子荧光光谱法测定地球化学样品中痕量铋   总被引：4，自引：0，他引：4  

于兆水  李淑娟张勤 《岩矿测试》2005,24(3):217-220

样品经王水溶解后,加入KMnO4溶液氧化,草酸除去过量KMnO4后的体系,直接用氢化物发生原子荧光光谱法测定地质样品中痕量Bi。方法使Au、Pd、As、Sb、Se、Te等元素的允许量大为提高,减少了不同测定体系中共存元素对Bi测定的干扰。方法的检出限(6s)为0.042μg/g,精密度(RSD,n=12)为1.88%~5.57%。经国家一级地质标准物质验证,测定值与标准值吻合。  相似文献   

Biases of submerged bulk and freeze‐core samples     

Andr Zimmermann  Moise Coulombe‐Pontbriand  Michel Lapointe 《地球表面变化过程与地形》2005,30(11):1405-1417

Freeze‐coring and bulk sampling are routine methods used to sample subsurface spawning gravel under shallow water. Both methods have limitations. Freeze‐coring is not believed to representatively sample coarse grain sizes and the sample volumes are relatively small. Conversely, when bulk sampling, even within an enclosure, some fine sediment is suspended and washed away from the sample. This paper assesses the biases in sampling performance between the two methods and determines whether the loss of fines that occurs when bulk sampling could be predicted and thus corrected for. At six riffles the spawning substrate was sampled under approximately 50 cm of water with a bulk sample and three adjacent freeze‐cores. For each riffle, data from the two samples were combined using the method of Fripp and Diplas (1993) and the resultant composite sample was compared with the original freeze‐core and bulk samples to assess the relative precision and biases of the two techniques. On average, the D₅₀ of the bulk samples was 4 mm larger and a one‐third loss of the <2 mm fraction occurred compared with the composite samples. In contrast, freeze‐core samples contain on average 32% more sediment >16 mm compared with composite samples. Based on six samples, taken from six riffles, the amount of sediment finer than 0·5 mm lost using our bulk sampling technique with an enclosure appears to be predictable and correctable. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

长江口沉积物全量硼的测定初探   总被引：1，自引：0，他引：1  

姚荷孙  陈中原  李绿芊  韦桃源  赵怡文 《上海国土资源》2002,(2):17-21

利用ICP－AES测试方法准确测定长江口水下沉积物中的全量硼，对三种不同的样品消化方法进行了初步探索，我们认为HF－HCIO4－HNO3-H3PO4消化方法是可靠的理想的样品消化方法。  相似文献   

对数字化绘图软件TOPMAP数据采集与存储方式的改进     

马真安  熊才胜  李勇 《四川测绘》2002,25(2):79-81

本文就数字化成图的数据采集与存储方式进行了探讨 ,并对TOPMAP测图软件数据采集方式进行了改进 ,使其更有利于野外作业  相似文献   

用原子荧光法同时测定砷、锑、铋、汞   总被引：8，自引：0，他引：8  

卢青  张争京  李红霞 《黄金地质》2002,8(1):75-77

试样经王水分解 ,在HCl (1+ 9)介质中 ,用硫脲 抗坏血酸将 5价As、Sb还原为 3价 ,再用KBH4 还原为氢化物。在HCl (1+ 4 )介质中 ,与KBH4 作用生成AsH3、SbH3、BiH3和Hg ,以特制空心阴极灯为光源 ,用双道无色散原子荧光仪测定As、Sb、Bi、Hg的荧光强度 ,各元素的检出限分别为As 5 9× 10 - 10 ,Sb 5 0× 10 - 10 ,Bi 6 9× 10 - 10 ,Hg 2 9× 10 - 1  相似文献