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1.
The resolution of a nonlinear parametric adjustment model is addressed through an isomorphic geometrical setup with tensor
structure and notation, represented by a u-dimensional “model surface” embedded in a flat n-dimensional “observational space”.
Then observations correspond to the observational-space coordinates of the pointQ, theu initial parameters correspond to the model-surface coordinates of the “initial” pointP, and theu adjusted parameters correspond to the model-surface coordinates of the “least-squares” point
. The least-squares criterion results in a minimum-distance property implying that the vector
Q must be orthogonal to the model surface. The geometrical setup leads to the solution of modified normal equations, characterized
by a positive-definite matrix. The latter contains second-order and, optionally, thirdorder partial derivatives of the observables
with respect to the parameters. This approach significantly shortens the convergence process as compared to the standard (linearized)
method. 相似文献
2.
The electronic structure of the three polymorphs of Al2SiO5, andalusite, sillimanite, and kyanite, is studied by linearized-augmented-plane-wave (LAPW) calculations using the WIEN code.
Total energy calculations verify, in agreement with recent pseudopotential calculations, that andalusite is the most stable
phase, followed by sillimanite and kyanite.We determine the electronic charge density distribution and find strong polarizations
on all oxygen ions. We identify different polarizations due to Al or Si neighbors which depend on their respective distances
to the oxygen atom. The chemical bonding is not purely ionic in nature but has important covalent contributions. Electric
field gradients (EFGs) at all sites are calculated and agree well (within 10%) with available experimental data on Al. We
identify the origin of the EFGs and demonstrate its relation to the nearest-neighbor coordination and the resulting anisotropy
of the electronic charge distribution.
Received: 22 March 2000 / Accepted: 3 August 2000 相似文献
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The approach presented is directed toward a specific adaptation of the least‐squares collocation with noise, yielding smooth predictions of geophysical quantities. The smoothing corresponds here to a truncated gravity field equivalent to an (n’, n') spherical‐harmonic expansion. This is reflected in the truncation, at the degree n‘, of the pertinent covariance and cross‐covariance functions in most (but not all) instances. The smooth predictions of geophysical quantities, made in an equilateral grid corresponding to the truncation degree n‘, serve in constructing contour maps after having been densified for the needs of a contour routine. Such a densification is carried out efficiently via errorless collocation with the degree truncation n‘ throughout. Consistent with this procedure, “residuals” at observation points (i.e., discrepancies between the contour map and the data) are computed using the same algorithm. The complete collocation approach is utilized for a 2° resolution of the earth's gravity field with emphasis on the oceanic geoid, based on the residuals from a global spherical‐harmonic adjustment of SEASAT altimetry. The presented results include contour maps of geoid undulations and gravity anomalies. They are compared to the results of a point‐mass adjustment, another technique based on the spherical‐harmonic adjustment. The agreement between these two techniques is found to be excellent. 相似文献
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对北京首都机场高速公路旁采集的土壤柱状T01剖面的磁学参数和金属元素分析,探讨了研究区内现代交通导致的土壤磁学性质的变化及其对环境污染的响应.结果表明,磁参数(χ,ARM和SIRM)与重金属含量呈同步垂向变化趋势.来源于交通运输排放的污染物是土壤剖面上部(0～8 cm)磁性和金属含量增强的主要原因,8cm以下,土壤基本未受到污染,磁性矿物和重金属含量较低,磁性颗粒变化稳定,基本代表了该地区土壤的自然背景.尽管土壤岩石磁学分析表明剖面上下部受污染和未受污染样品的磁载体均是粒度较粗的多畴磁铁矿,但是结合磁参数比值曲线,说明底部样品的磁颗粒的粒度较顶部偏细.磁性矿物的含量变化没有影响磁颗粒的粒度特征.指标聚类等相关分析表明,土壤磁参数(χ,ARM和SIRM)与重金属元素(Pb,Zn和Cu)含量显著相关;结合模糊聚类分析,磁参数可用于追踪、识别交通污染物质在土壤剖面中的富集、迁移状态,揭示不同深度土壤的污染程度. 相似文献
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Mingjie Shen Shouyun Hu Uli. Blaha Haitao Yan Wolfgang. R?sler Ewin. Appel Viktor. Hoffmann 《Frontiers of Earth Science》2008,2(4):400-407
An expressway-side soil profile 22 cm long was sampled from the grassland of the expressway linking Beijing and the Capital
International Airport. Magnetic measurements, geochemical and multivariate statistic analyses were performed on the soil samples.
The results reveal that the soil profile can be divided into two parts with significant difference in magnetic proxies and
heavy metal concentration. The uppermost soil horizon (0–8 cm) represents the pollution-rich layer with higher concentration
of ferrimagnetic phases and metallic elements. The values of xare very high with an average of 141.60 × 10−8 m3·kg−1 in the layer. We explain that the anthropogenic dust input from traffic is the predominant cause for strong signals of magnetic
phases and heavy metals. Below the profile depth of 8 cm, there is minor pollution in the soil with lower concentration of
magnetic minerals and heavy metals compared to the natural background values. χ remains quite stable and relatively low with
an average of 49.44 × 10−8 m3·kg−1. S-ratio also generally decreases with depth, and it changes from 0.93 in the 0–8 cm layer to 0.87 below the depth of 8 cm.
It indicates that the soil samples are overwhelmingly predominated by ferrimagnetic minerals in the upper part soil, while
the contribution of imperfect antiferromagnetic components is stronger in the lower part. Rock magnetic experiments show MD
magnetite as the main magnetic carrier both in the upper and lower parts. Themagnetic grain size in the upper part is, however,
a bit coarser than that in the lower part. Cluster analysis shows a positive correlation between magnetic properties (χ, ARM,
SIRM) and heavy metal pollutants of Pb, Zn, Cu. Fuzzy C-means cluster analysis can clearly help divide the soil profile into
two different layers and distinguish their characteristics. It can be concluded that these magnetic concentration-related
parameters can be used as proxies for pollution investigation in a fast, sensitive, low-cost and highly efficient approach
to screening heavy metal pollution.
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Translated from Quaternary Sciences, 2007, 27(6): 1113-1120 [译自:第四纪研究] 相似文献
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Georges Blaha 《Journal of Geodesy》1982,56(3):209-219
The main goal of this paper is to show that the solution obtained by adjusting a free network via the inner adjustment constraint
method is the minimum norm solution. The latter is a special case of the class of “minimum trace” solutions, where the trace
of the variance-covariance matrix for the adjusted parameters is a minimum. The derivations are carried out in terms of pseudo-inverses,
the various other forms of generalized inverses having been left out of consideration. 相似文献
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G. Blaha 《Journal of Geodesy》1978,52(1):19-23
A simple formula is presented giving the value of γ−γ
r
to better than 0.001 mgal associated with an arbitrary reference ellipsoid, where γ is the normal gravity and γ
r
is its radial component. Further simplifications of this formula are possible, depending on the desired accuracy. Since in
the actual field g−gr equals γ−γ
r
to a good approximation, this formula makes it possible to work in terms of gr rather than in terms of the measured quantity g. Such a choice is attractive mainly because the spherical harmonic expansion
of gr is very simple. 相似文献