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261.
Alexei V. Soloviev Mikhail N. Shapiro John I. Garver Ekaterina A. Shcherbinina Igor R. Kravchenko-Berezhnoy 《Island Arc》2002,11(1):79-90
Abstract The Lesnaya Group is part of a thick, poorly dated turbidite assemblage that sits in the footwall of a regionally extensive collision zone in which the Cretaceous–Paleocene Olutorsky island arc terrane was obducted onto continental margin basin strata. Nannoplankton from 18 samples from the upper part of the Lesnaya Group yield Paleocene through Middle Eocene assemblages. Detrital zircons from nine sandstone samples have a young population of fission-track ages that range from 43.7 ± 3.4 to 55.5 ± 3.5 Ma (uppermost Paleocene to Middle Eocene). The deformed footwall rocks of the Lesnaya Group and the overlying thrusts of the Olutorsky arc terrane, are unconformably overlain by neoautochthonous deposits which are Lutetian (lower Middle Eocene) and younger. Together, these new data indicate that thrusting, which is inferred to have been driven by collision of the Cretaceous–Paleocene island arc with north-eastern Asia, took place in the mid-Lutetian, at about 45 Ma. 相似文献
262.
Time-dependent effects of heat advection and topography on cooling histories during erosion 总被引:9,自引:0,他引:9
Both erosion and surface topography cause a time-dependent variation in isotherm geometry that can result in significant errors in estimating natural exhumation rates from geochronologic data. Analytical solutions and two-dimensional numerical modelling are used to investigate the magnitude of these inaccuracies for conditions appropriate to many rapidly exhumed mountain chains of rugged relief. It is readily demonstrated that uplift of the topographic surface has a negligible effect on the cooling history of an exhumed rock sample and cannot be quantified by current geochronologic methods. The topography itself perturbs the isotherms to a depth that depends on both the vertical and horizontal scale of the surface relief. Estimations employing different isotopic systems in the same sample with higher closure temperatures (> 200°C) are not generally influenced by topography. However, direct conversion of cooling rates to exhumation rates assuming a simple constant linear geotherm markedly underestimates peak rates, due to variation of the geothermal gradient in time and space and to the time lag between exhumation and cooling. Estimations based on the altitude variation in apatite fission-track ages are less prone to such inaccuracies in geothermal gradient but are affected by near-surface time-dependent variation in isotherm depth due to advection and topography. In tectonically active mountain belts, high exhumation rates are coupled with rugged topography, and exhumation rates may be markedly overestimated, by factors of 2 or more. Even at lower exhumation rates on the order of 1 mm/a, the shape of the cooling curve is modified by advection and topography. A convex-concave shape to the cooling curve does not necessarily imply a change of exhumation rate; it may also be attained by a more complicated geothermal gradient induced by topographic relief. Very fast cooling below 100°C, often interpreted as reflecting faster exhumation, can be more simply explained by the lateral cooling effect of topographic relief, with samples exhumed in valleys displaying a different near-surface cooling history to those on ridge crests. 相似文献
263.
The iron ores of the Gushan mine occur in the contact zone of a Mesozoic diorite intrusion and are composed primarily of hematite microcrystallites and chalcedony,The hematite microcrystallites have undergone post-mineralization recrystallization and coarsening with resultant formation of lath-shaped hematite porphyroblasts.Microscopic investigation reveals that recrystallization and coarsening of the hematite ores of the Gushan mine took place without the formation of new nuclei,due to the coalescence of the microcrystallites.The whole process could have begun with the mutual approach of the microcrystallites,followed by grain rotation to realize paralleism and ending by the welding of these grains to form optically homogeneous porphyroblastic hematite. 相似文献
264.
提出的串行Cauchy机引导的影像镶嵌方法,基于灰度特征,综合人机交互优势,可操作性强,精度高,最大误差不超过0.5像素,可满足高精度影像处理需要。 相似文献
265.
In this paper, we set out to study the ensemble forecast for tropical cyclones. The case study is based on the Conditional Nonlinear Optimal Perturbation related to Parameter (CNOP-P) method and the WRF model to improve the prediction accuracy for track and intensity, and two different typhoons are selected as cases for analysis. We first select perturbed parameters in the YSU and WSM6 schemes, and then solve CNOP-Ps with simulated annealing algorithm for single parameters as well as the combination of multiple parameters. Finally, perturbations are imposed on default parameter values to generate the ensemble members. The whole proposed procedures are referred to as the Perturbed Parameter Ensemble (PPE). We also conduct two experiments, which are control forecast and ensemble forecast, termed Ctrl and perturbed-physics ensemble (PPhyE) respectively, to demonstrate the performance for contrast. In the article, we compare the effects of three experiments on tropical cyclones in aspects of track and intensity, respectively. For track, the prediction errors of PPE are smaller. The ensemble mean of PPE filters the unpredictable situation and retains the reasonably predictable components of the ensemble members. As for intensity, ensemble mean values of the central minimum sea-level pressure and the central maximum wind speed are closer to CMA data during most of the simulation time. The predicted values of the PPE ensemble members included the intensity of CMA data when the typhoon made landfall. The PPE also shows uncertainty in the forecast. Moreover, we also analyze the track and intensity from physical variable fields of PPE. Experiment results show PPE outperforms the other two benchmarks in track and intensity prediction. 相似文献
266.
267.
Adaptive hybrid global inversion algorithm 总被引:2,自引:0,他引:2
Most geophysical inversions can be regarded as multiparameter, nonlinear, and multiminimum discontinuous optimization problems.
An adaptive hybrid global inversion algorithm based on simulated annealing, downhill simplex method, uniform design, and adaptive
annealing rule is formulated. Numeral test and model computation show that this algorithm has very fast speed and high efficiency
in searching for global minimum.
Project sponsored by the National Natural Science Foundation of China (Grant No. 49474232) and Special Foundation under the
auspices of president of Chinese Academy of Sciences. 相似文献
268.
269.
改进模拟退火法在估计河流水质参数中的应用 总被引:3,自引:0,他引:3
将模拟退火法应用于求解分析河流水团示踪试验数据,确定河流水质参数的函数优化问题。针对标准SA算法收敛速度缓慢的弱点,采取了增加附加约束条件、设置内阈值提前降温和增加记忆功能等综合措施对算法进行了改进。算例表明,综合改进措施能够明显地提高算法收敛速度,并可以得到满意的参数计算结果。计算结果也表明,内循环次数不会对外循环次数产生明显的影响。由于算法对目标函数没有附加要求,而且算法的收敛性与待估参数的初值无关,因此,改进SA算法在分析河流水质试验数据、确定水质参数方面.将会具有非常广的应用范围。 相似文献
270.