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131.
The inequality-constrained least squares (ICLS) problem can be solved by the simplex algorithm of quadratic programming. The ICLS problem may also be reformulated as a Bayesian problem and solved by using the Bayesian principle. This paper proposes using the aggregate constraint method of non-linear programming to solve the ICLS problem by converting many inequality constraints into one equality constraint, which is a basic augmented Lagrangean algorithm for deriving the solution to equality-constrained non-linear programming problems. Since the new approach finds the active constraints, we can derive the approximate algorithm-dependent statistical properties of the solution. As a result, some conclusions about the superiority of the estimator can be approximately made. Two simulated examples are given to show how to compute the approximate statistical properties and to show that the reasonable inequality constraints can improve the results of geodetic network with an ill-conditioned normal matrix. 相似文献
132.
133.
Modern and known-age Pleistocene fluvial sediments were investigated by optical dating of quartz to test the suitability of the approach for dating deposits from the deeply incised Middle Rhine Valley. Samples from modern flood sediments revealed skewed distributions indicating different residual levels of equivalent dose (De) within the different aliquots. Nevertheless, a substantial number of aliquots from the modern deposits reflect De values close to zero. For the Pleistocene samples, optical ages are in general consistent with age control given by the presence of the Laacher See Tephra and radiocarbon dating. However, some samples overestimate the known age by a few thousand years when using the arithmetic mean. This is apparently explained by including aliquots in the determination of mean De where the optical signal was incompletely bleached at deposition. The most difficult issue in this context is identifying a suitable approach that can distinguish between the variability of De due to partial bleaching and microdosimetry. However, even when considering these limitations it appears that optical dating will by a quite suitable method to date Pleistocene sediments from such a complex fluvial environment, especially when focusing on a precision scale beyond a few thousand years. 相似文献
134.
Sediments attributed to flooding events of River Danube concerning the bleaching of the optical stimulated luminescence (OSL) signal were investigated. It is demonstrated that the OSL signal in both quartz and feldspar is not completely but differentially bleached in the sediment grains. Partial bleaching of the samples is clearly indicated by the scatter of equivalent dose determined for several individual single aliquots. It is also shown that residual ages in feldspars are significantly higher than those calculated for quartz. It is furthermore demonstrated that analysing measurement-time dependent equivalent dose estimates is not a suitable method to identify partial bleaching in the investigated sediment grains. However, the transport and deposition process of the investigated samples was probably disturbed by an artificial input of sediment, and this case study may thus not be representative of undisturbed high flood events in the past. 相似文献
135.
Taner Ekici Musa Alpaslan Osman Parlak Abidin Temel 《Chemie der Erde / Geochemistry》2007,67(3):201-212
The study area is located on the middle sector of the Malatya-Ovacık Fault Zone (MOFZ) in the eastern Anatolia. Four basaltic flows from bottom to top, which are tholeiitic in character and intercalated with Pliocene sedimentary rocks, were erupted along this fault zone. Chemical compositions of these flows reveal some differences between the first flow and others in terms of high-field strength elements (HFSEs) (e.g. Ti, Zr, Nb). Limited variations in compositions within the first flow and upper flows suggest a limited fractionation range. Trace-element patterns exhibit that all the flows have similar and OIB-like patterns without positive peak at Pb and a trough at Nb—Ta, indicating minimal or no crustal contribution. Rare-earth element (REE) patterns indicate that the first flow has flat patterns with negative Eu anomaly, whereas the upper flows have variable enrichments in LREE and depletions in HREE. La/SmN, Dy/YbN and Zr/Y ratios exhibit that the degree of partial melting decreases from the first flow to upper flows. Higher values of La/YbN ratio for the upper flows and depletions at Y and Yb on the trace-element patterns suggest the presence of garnet as a residual phase, which imply that the depth of partial melting took place solely in the garnet-stability field. OIB-like trace-element patterns and trace-element ratios (e.g. La/Nb, Ce/Y and Zr/Nb) emphasize that the melts forming the Arguvan basalt were originated from the asthenospheric mantle rather than the lithospheric mantle. 相似文献
136.
137.
In order to predict wind loading on trees (canopy height h) in partially harvested forests, it is necessary to characterize air flow and momentum transfer in progressively more complex
patterns where groups of trees (or aggregates) are retained. In this study, we used large-eddy simulation to explore the effects
of aggregate size, inter-aggregate spacing, and the ratio between the aggregate size and inter-aggregate spacing on air flow
and momentum transfer. Forty-five grid points across an aggregate were needed to achieve an adequate level of turbulence.
Using grid sizes of h/15 throughout was too viscous for the smaller aggregates. Vertical and horizontal flow deflection by the leading aggregates
sheltered some of the downstream aggregates to varying degrees where turbulence increased for subsequent rows. The number
of rows of protected aggregates decreased as aggregate dimensions and the space between aggregates increased. A theoretical
treatment of time-dependent wind is presented for the lead aggregate and a simulation case is presented for the case of a
gust of reduced wind passing through the aggregate pattern. The leading aggregate responded with decreasing moment for decreasing
ambient wind speed as predicted by theory. However, downwind aggregates experienced substantial increases in bending moment.
The overall results of the disruptive aspects of time dependence agrees with arguments regarding the role of irrotational
(potential) flow to this problem. Our treatment of retention pattern design is only a first step and further research suggestions
are presented. 相似文献
138.
数字地图合并的平差原理与方法 总被引:2,自引:0,他引:2
提出了一种基于最小二乘平差的数字地图合并方法,采用平差原理以求得实体调整合并后的空间位置。实验表明,与其他方法相比,该方法具有较高的精度,且较好地保持了原有实体的特征。 相似文献
139.
秩亏自由网平差的一种新解法 总被引:2,自引:1,他引:1
提出秩亏自由网平差的一种新解法,只亲知道误差方程系数阵中t0个线性无关的列向量,就能很快地得到最小二乘最小范数解,实际计算表明,这种新解法是简单有效的。 相似文献
140.
中国地表植被覆盖变化及其与气候因子关系 总被引:74,自引:2,他引:72
本文利用1985-1990年连续69个月的NOAA时间序列数据,进行中国植被覆盖变化的空间,以及时间序列分析,并且结合同期的平均气温,降水数据,进行植被覆盖变化与气候因子相关性分析,该文证实了在中国植被覆盖随时间的推移规律,空间分布规律,以及植被覆盖变化与气温,降水的定量关系。 相似文献