Spatial distribution of soil heavy metal pollution estimated by different interpolation methods: Accuracy and uncertainty analysis

Mapping the spatial distribution of contaminants in soils is the basis of pollution evaluation and risk control. Interpolation methods are extensively applied in the mapping processes to estimate the heavy metal concentrations at unsampled sites. The performances of interpolation methods (inverse distance weighting, local polynomial, ordinary kriging and radial basis functions) were assessed and compared using the root mean square error for cross validation. The results indicated that all interpolation methods provided a high prediction accuracy of the mean concentration of soil heavy metals. However, the classic method based on percentages of polluted samples, gave a pollution area 23.54-41.92% larger than that estimated by interpolation methods. The difference in contaminated area estimation among the four methods reached 6.14%. According to the interpolation results, the spatial uncertainty of polluted areas was mainly located in three types of region: (a) the local maxima concentration region surrounded by low concentration (clean) sites, (b) the local minima concentration region surrounded with highly polluted samples; and (c) the boundaries of the contaminated areas. (C) 2010 Elsevier Ltd. All rights reserved.

Comparison for DNA primary sequence

In this article, two schemes are suggested based on three exons of beta-globin gene belonging to 10 species for comparison of DNA primary sequences. At first, the positions of four nucleic acid bases were extracted, and then based on the information, as the numerical characterization of DNA sequences, the sequence invariants were derived. Sequences comparisons of 10 species selected in this work by using these invariants were performed. The results, especially with scheme 2, are quite satisfactory.

On highly discriminating molecular topological index

A highly discriminating molecular topological index, EAID, is proposed based on the extended adjacency matrix. A systematic search for degeneracy was performed for 3 807 434 alkane trees, 202 558 complex cyclic or polycyclic graphs, and 430 472 structures containing heteroatoms. No counterexamples (two or more nonisomorphic structures with the same EAID number) were found. This is a hitherto unheard of power of discrimination. Thus EAID might be possibly used as supplementary reference for CAS Registry Numbers for structure documentation.

A new topological index for the Changchun institute of applied chemistry C-13 NMR information system

A method to assign a single number representation for each atom (node) in a molecular graph, Atomic IDentification (AID) number, is proposed based on the counts of weighted paths terminated on that atom. Then, a new topological index, Molecular IDentification (MID) number is developed from AID. The MID is tested systematically, over half a million of structures are examined, and MID shows high discrimination for various structural isomers. Thus it can be used for documentation in the Changchun Institute of Chemistry C-13 NMR information system.

ESTIMATION OF THE ONE-PHASE STRUCTURE SEMINVARIANTS IN THE SINGLE ISOMORPHOUS REPLACEMENT CASE - AN APPLICATION OF HAUPTMANS DISTRIBUTION

A method for estimating the one-phase structure seminvariants (OPSSs) having values of 0 or pi has been proposed on the basis of the probabilistic theory of the three-phase structure invariants for a pair of isomorphous structures [Hauptman (1982). Acta Cryst. A38, 289-294]. The test calculations using error-free diffraction data of protein cytochrome c(550) and its PtCl42- derivative show that reliable estimates of a number of the OPSSs can be obtained. The reliability of the estimation increases with the increase of the differences between diffraction intensities of the native protein and its heavy-atom derivative. A means to estimate the parameters of the distribution from the diffraction ratio is suggested.

PROBABILISTIC ESTIMATION OF THE STRUCTURE SEMINVARIANTS IN THE MONOCLINIC AND ORTHORHOMBIC SYSTEMS WHEN ANOMALOUS SCATTERERS ARE PRESENT

The estimate formulas for the two-phase structure seminvariants (TPSSs) in the presence of anomalous scattering are obtained from the estimate of the two-phase structure invariants [Hauptman (1982). Acta Cryst. A38, 632-641; Giacovazzo (1983). Acta Cryst.

A NEW SCHEME FOR ASSIGNMENT OF A CANONICAL CONNECTION TABLE

A new algorithm for deriving canonical numbering of atoms in a molecular graph has been developed. Some graph invariants, such as node properties, degree (connectivity), topological path, the smallest node ring index, etc., are encoded together to partit

THERMODYNAMICS OF AMINO-ACID DISSOCIATION IN MIXED-SOLVENTS .3. GLYCINE IN AQUEOUS GLUCOSE SOLUTIONS FROM 5-DEGREES-C TO 45-DEGREES-C

The first thermodynamic dissociation constants of glycine in 5, 15 mass % glucose + water mixed solvents at five temperatures from 5 to 45-degrees-C have been determined from precise emf measurements of a cell without liquid junction using hydrogen and Ag-AgCl electrodes and a new method of polynomial approximation proposed on the basis of Pitzer's electrolytic solution theory in our previous paper. The results obtained from both methods agree within experimental error. The standard free energy of transfer for HCl from water to aqueous mixed solvent have been calculated and the results are discussed.

THE DETERMINATION OF STANDARD ELECTROMOTIVE FORCE OF CELL Cu vertical bar CuSO4 vertical bar Hg2SO4-Hg AT DIFFERENT TEMPERATURES

The emfs of Cu|CuSO_4|Hg_2SO_4-Hg were determined at 5 temperature points from 278.15K to 313.15K. Based on the Pitzer' s Equation a polynomial approximation for the determination of standard emf, E_m, was proposed. The values of E_m obtained by author's method agree with values of E_m obtained by the extended Debye-Huckel equation within experimental errors. Compared with the extrapolation result of extended Debye-Huckel equation, the uncertainty by the selecting of parameter of ion size was avoided.By the...

Quantitatively distinguishing sediments from the Yangtze River and the Yellow River using delta Eu-N-I REEs pound plot

Sediment samples were collected from the lower channel of the Yangtze River and the Yellow River and the contents of rare earth elements (REEs) were measured. In addition, some historical REEs data were collected from published literatures. Based on the delta Eu-N-I REEs pound plot, a clear boundary was found between the sediments from the two rivers. The boundary can be described as an orthogonal polynomial equation by ordinary linear regression with sediments from the Yangtze River located above the curve and sediments from the Yellow River located below the curve. To validate this method, the REEs contents of sediments collected from the estuaries of the Yangtze River and the Yellow River were measured. In addition, the REEs data of sediment Core 255 from the Yangtze River and Core YA01 from the Yellow River were collected. Results show that the samples from the Yangtze River estuary and Core 255 almost are above the curve and most samples from the Yellow River estuary and Core YA01 are below the curve in the delta Eu-N-I REEs pound plot. The plot and the regression equation can be used to distinguish sediments from the Yangtze River and the Yellow River intuitively and quantitatively, and to trace the sediment provenance of the eastern seas of China. The difference between the sediments from two rivers in the delta Eu-N-I REEs pound plot is caused by different mineral compositions and regional climate patterns of the source areas. The relationship between delta Eu-N and I REEs pound is changed little during the transport from the source area to the river, and from river to the sea. Thus the original information on mineral compositions and climate of the source area was preserved.

一种基于多项式的图像离焦建模方法研究

本文针对显微视觉的图像恢复与3D 重建问题,从显微光学成像的离焦机理和基于点扩散函数的图像模糊化描述出发,通过模糊测度算子分析序列显微图像的离焦分布规律,提出了一种用于构建较为精准离焦模型的方法。该模型采用混合参数多项式结构,与传统高斯模型相比,可以更接近真实离焦过程,这为较为精确的光学显微图像恢复和3D 重构提供了新的技术途径。

Theoretical and experimental research on time-optimal trajectory planning and control of industrial robots

提出了一种用于工业机器人时间最优轨迹规划及轨迹控制的新方法，它可以确保在关节位移、速度、加速度以及二阶加速度边界值的约束下，机器人手部沿笛卡尔空间中规定路径运动的时间阳短。在这种方法中，所规划的关节轨迹都采用二次多项式加余弦函数的形式，不仅可以保证各关节运动的位移、速度 、加速度连续而且还可以保证各关节运动的二阶加速度连续。采用这种方法，既可以提高机器人的工作效率又可以延长机器人的工作寿命以PUMA560机器人为对象进行了计算机仿真和机器人实验，结果表明这种方法是正确的有效的。它为工业机器人在非线性运动学约束条件下的时间最优轨迹规划及控制问题提供了一种较好的解决方案。

并联机床平面约束机构误差分析与建模

针对五轴数控机床平面约束机构进行了误差分析 ,指出了并联机床平面约束机构误差主要影响因素为机构的制造误差和安装误差·前者与由其引起的约束机构顶边中点沿x方向的位移成非线性关系 ,而后者则成线性关系·提出了一种依据测量数据反演非线性误差模型的建模方法 ,给出了五轴并联机床约束机构实测信息与模型输出间的多项式误差模型·比较仿真结果与测量结果可知 ,基于上述方法建立的误差模型精确 ,进而利用该模型对机床进行实时精度补偿 ,可使机床x方向定位精度大为提高

基于Stewart平台六维力传感器的分区静态标定方法

基于Stewart平台的六维力传感器具有结构紧凑、刚度大、量程宽等特点,它在工业机器人、空间站对接等领域具有广泛的应用前景。好的标定方法是正确使用传感器的基础。由于基于Stewart平台的六维力传感器是一个复杂的非线性系统,所以采用常规的线性标定方法必将带来较大的标定误差从而影响其使用性能。标定的实质是,由测量值空间到理论值空间的映射函数的确定过程。由函数逼近理论可知,当只在已知点集上给出函数值时,可用多项式或分段多项式等较简单函数逼近待定函数。基于上述思想,本文将整个测量空间划分为若干连续的子测量空间,再对每个子空间进行线性标定,从而提高了整个测量系统的标定精度。实验分析结果表明了该标定方法有效。

一种新型四自由度并联机器人运动学正问题的求解

对一种新型四自由度并联机器人运动学正问题进行了研究，利用３个变量构造 出求解正问题的３个约束方程，然后运用符号计算和析配消元法推导出了只含有一 个变元的３２次多项式方程，并且应用计算机软件系统Ｍａｔｈｅｍａｔｉｃａ进行了求正问 题实解的数值验证。