利用影像重定位和遍历检测的遥感影像水印算法     

高光大  任娜  王永志  朱长青 《武汉大学学报(信息科学版)》2012,37(10):1229-1231

针对遥感影像数据,提出了一种基于影像重定位和遍历检测的盲水印算法。实验结果表明,该方法可以有效抵抗压缩、滤波等常见的图像处理攻击,还能有效抵抗裁剪攻击。  相似文献   

改进Faster R-CNN的遥感图像多尺度飞机目标检测     

沙苗苗  李宇  李安 《遥感学报》2022,26(8):1624-1635

为了提高遥感图像中多尺度飞机目标的检测精度,本文提出一种基于改进Faster R-CNN的遥感图像飞机目标检测方法。该方法借助多层级融合结构,将深层次的语义特征与浅层次的细节特征相结合,生成多种尺度的既具有精确的位置信息又具有深层次的语义特征的特征图;再借助Faster R-CNN的多尺度RPN（Region Proposal Network）机制,通过对RPN中候选区域尺度的修正,从而提高遥感图像中多尺度飞机目标的定位精度;最后利用Faster R-CNN的分类回归网络,得到飞机目标检测结果。在高分辨率遥感图像中进行了实验,对3种特征提取网络ZF、VGG-16以及ResNet-50进行改进,改进后的精度分别提高了11.34%、9.87%以及1.66%,并且生成的检测框更加贴合飞机目标。实验结果表明,本文方法适用于遥感图像多尺度飞机目标检测,在提高目标定位精度的同时降低了目标漏检现象。  相似文献   

Simultaneous scaling of soil water retention and unsaturated hydraulic conductivity functions assuming lognormal pore-size distribution     

《Advances in water resources》2001,24(6):677-688

Using simultaneous scaling, soil spatial variability of hydraulic functions can be described from a single set of scaling factors. The conventional scaling approach is based on empirical curve fitting, without paying much attention to the physical significance of the scaling factors. In this study, the concept of simultaneous scaling of the soil water retention and unsaturated hydraulic conductivity functions is applied to a physically based scaling theory. In this approach, it is assumed that soils are characterized by a lognormal pore-size distribution, which leads directly to lognormally distributed scaling factors. To test this concept, a total of 143 undisturbed soil samples were collected from two soil depths (25 and 50 cm), with each depth divided into two subsets based on the median soil capillary pressure head value, as determined from the lognormal pore-size distribution assumption. Moreover, the theory was compared with the conventional simultaneous scaling method. Both the conventional and physically based simultaneous scaling method performed equally well for all four subsets, as determined from the reduction in weighted root mean squared residual (WRMSR) values after scaling. We showed that the theoretical interpretation of the lognormal scaling factor distribution was applicable to simultaneous scaling of soil hydraulic functions.  相似文献   

Geometry and distribution of regional joint sets in a non-homogeneous stress field: case study in the Ebro basin (Spain)     

《Journal of Structural Geology》2001,23(2-3):297-313

Three regional joint sets striking N–S, E–W and WNW–ESE affect the Tertiary rocks of the central Ebro basin. From analysis of their chronological relationships and spatial distribution, it is concluded that they correspond to two different tectonic events. The N–S set (oldest) and the E–W set (younger) are present in the southern and central sectors, while the WNW–ESE joint set predominates in the northern one. The N–S joints propagated in response to joint-normal and fluid loads under an intraplate stress field with S_Hmax oriented near N–S (related to forces caused by the convergence of Africa, Iberia and Europe and rifting at the Valencia trough) during the sedimentary infilling of the basin. These joints are only present in the southern part of the area. The E–W joint set in the southern-central sector records the same fracturing event as the WNW–ESE set does in the northern one. Its orientation was modified by the presence of the older N–S set in the south, which perturbed the regional stress field. The younger WNW–ESE and E–W joint sets are interpreted as unloading joints. These propagated as a consequence of flexural uplift and exhumation related to isostatic rebound at the Pyrenees and the Ebro foreland basin. A numerical approach is used to explain the inhomogeneous distribution of the N–S joint set in terms of their absence being controlled by the depth of the water table at the time of their formation.  相似文献   

Method of auxiliary sources for calculating the magnetic and electric fields induced in a layered Earth     

《Journal of Atmospheric and Solar》2003,65(10):1151-1160

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Neon distribution in South Atlantic and South Pacific waters     

《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(6):721-735

We present and assess the distribution of neon in South Atlantic and South Pacific waters, on the basis of more than 3000 mostly new neon data which were obtained primarily under the hydrographic program of the World Ocean Circulation Experiment (predominantly southern summer to fall cruises). Data precision is better than±0.5%, and the set is internally consistent within±0.3% and partly better, and compatible with reported high-quality neon values. Using suitably averaged data (precision 0.1–0.3%), we find that the total range of neon anomalies relative to a solubility equilibrium with atmospheric neon at the observed potential temperature and salinity (using the solubilities of Weiss, J. Chem. Eng. Data 16 (1971) 235) is approximately 0–4%, and below 2000 m depth, 3–4% only. We consistently observe two types of neon depth profiles, one for the temperate-latitudes ocean, which is characterized by a near-surface maximum and a minimum in Antarctic Intermediate Water, and one for the Southern Ocean that essentially displays a steady increase with depth. The neon distribution reflects the influence of air injected by submerged air bubbles, the areal distribution of atmospheric pressure, seasonal temperature changes in the mixed layer and solar heating below it, and interaction with sea ice and glacial ice, largely in keeping with previous work. However, it appears that interaction with sea ice reduces neon anomalies distinctly less than the literature suggests. The temperate-ocean shallow maxima point to widespread subsurface heating in the course of the summer season by roughly 1 K. Among the major source water masses of the deep waters, the neon anomalies are lowest in Antarctic Intermediate Water (∼1.5%), intermediate in North Atlantic Deep Water (∼3%, confirming previous work) and similarly in Circumpolar Deep Water, and highest in Antarctic Bottom Water (∼3.8%). The anomalies in Southeast Pacific deep waters (>2500 m) are comparatively less (only∼3.3%), as a result of the contribution of Antarctic Intermediate Water. The present study is the first attempt to deal with the oceanic distribution of neon in a systematic fashion. The results can serve to assist assessments of the oceanic distributions of other dissolved gases.  相似文献   

Numerical simulation of non-isothermal multiphase multicomponent processes in porous media.: 1. An efficient solution technique     

《Advances in water resources》2002,25(5):533-550

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Non-reflecting boundary flux function for finite volume shallow-water models     

《Advances in water resources》2002,25(2):195-202

An approach to implement non-reflecting boundary conditions in finite-volume based shallow-water models is presented. Shallow-water models are routinely applied to sections of rivers, estuaries, and coastal zones, introducing computational boundaries where no physical control is present, and necessitating a condition that supplies information to the model while it simultaneously allows disturbances from the interior to pass out unhampered. The approach presented here builds upon the finite-volume convention of constructing a Riemann problem at the interface between cells and then solving it with a flux function. Hence, non-reflecting boundary conditions are achieved using a non-reflecting flux function on cell faces aligned with open boundaries. Numerical tests show that the non-reflecting flux function performs extremely well when waves advance toward the boundary with a small incident angle (approximately less than 45° from the boundary normal direction), while very minor reflections are present when the incident angle is larger. The presence of minor reflections, when the incident angle is large, is consistent with non-reflecting conditions previously implemented in finite-difference based schemes.  相似文献   

Interplanetary phenomena associated with very intense geomagnetic storms     

《Journal of Atmospheric and Solar》2002,64(2):173-181

The dominant interplanetary phenomena that are frequently associated with intense magnetic storms are the interplanetary manifestations of fast coronal mass ejections (CMEs). Two such interplanetary structures, involving an intense and long duration B_s component of the IMF are: the sheath region behind a fast forward interplanetary shock, and the CME ejecta itself. Frequently, these structures lead to the development of intense storms with two-step growth in their main phases.These structures, when combined, lead sometimes to the development of very intense storms, especially when an additional interplanetary shock is found in the sheath plasma of the primary structure accompanying another stream. The second stream can also compress the primary cloud, intensifying the B_s field, and bringing with it an additional B_s structure. Thus, at times very intense storms are associated with three or more B_s structures.Another aspect that can contribute to the development of very intense storms refers to the recent finding that magnetic clouds with very intense core magnetic fields tend to have large velocities, thus implying large amplitude interplanetary electric fields that can drive very intense magnetospheric energization.  相似文献   

Stabilisation scenarios for climate impact assessment     

《Global Environmental Change》2002,12(3):155-165

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