Nonlinear wave-wave interactions and wedge waves

A tetrad mechanism for exciting long waves, for example edge waves, is described based on nonlinear resonant wave-wave interactions. In this mechanism, resonant interactions pass energy to an edge wave,from the three participating gravity waves. The estimated action flux into the edge wave can be orders of magnitude greater than the transfer fluxes derived from other competing mechanisms, such as triad interactions. Moreover, the numerical results show that the actual transfer rates into the edge wave from the three participating gravity waves are two- to three- orders of magnitude greater than bottom friction.     

大型贯通测量中加测陀螺定向边的位置选取分析

大型贯通测量中常常使用加测陀螺边来提高贯通测量精度,但目前对于陀螺定向边的位置选取并无明确规范和要求。本文主要探讨了不同位置的陀螺定向边选取对贯通测量精度的影响。实验结果表明,井下选取的陀螺定向边与测定仪器常数的地面已知边之间距离过大对于贯通测量精度影响较大,在井下选取陀螺定向边位置时,应与测定仪器常数的地面已知边距离保持在3 000 m以内为优。     

Multiscale segmentation of well logs

Examination of well logs leads to the observation that they exhibit characteristic behavior over a wide range of scales, differing from a foot to hundreds of feet. This behavior is not accounted for in conventional segmentation methods. The segmentation method that is proposed here aims to solve this problem. It is based on a multiscale representation of the well log. This is a representation of the well log at different levels of smoothness. The behavior of edges, which are associated with extrema of the first derivative, across scales is of great importance in the segmentation. Analysis of this behavior leads to a multiscale segmentation of the well log, in which a fine-scale segment is a part of one coarse scale segment only. In this way the geologist is able to analyze the log at different scales simultaneously. An extension of this approach is not to preserve all fine-scale information but to zoom in only on parts of the log where it is considered to be of interest.     

Geomagnetic Models and Edge Recognition of Hydrothermal Sulfide Deposits at Mid-ocean Ridges

Near-bottom magnetic prospecting is considered to be an efficient method for investigating inactive hydrothermal areas and the study of the spatial structure of hydrothermal systems. Furthermore, geophysical forward modeling is widely used to simulate the anomalous characteristics of geological bodies. To understand the magnetic and magnetic structure features of hydrothermal sulfide deposits at mid-ocean ridges, we built 3D forward models for both mafic- and ultramafic-hosted hydrothermal sulfide deposits to simulate the near-bottom magnetic field. Our modeling results showed a low amplitude magnetic anomaly above the mafic-hosted hydrothermal sulfide deposits, and a high amplitude magnetic anomaly above the ultramafic-hosted deposits. These features allow us to identify and classify the host rocks of hydrothermal sulfide deposits. Moreover, we can recognize the edge of the magnetic anomalies using the intensity of the spatial differential vector method, considering variables such as the width of the alteration zone, the height of the observation platform, and the magnetic inclination and declination. Therefore, we propose the intensity of the spatial differential vector method as an effective approach to define the boundaries of hydrothermal sulfide deposits.     

Integrating volunteered smartphone data with multispectral remote sensing to estimate forest fuels

Volunteered data sources are readily available due to advances in electronic communications technology. For example, smartphones provide tools to collect ground-based observations over broad areas from a diverse set of data collectors, including people with, and without, extensive training. In this study, volunteers used a smartphone application to collect ground-based observations. Forest structural components were then estimated over a broader area using high spatial resolution RapidEye remote sensing imagery (5 spectral bands 440–850 nm, 5 m spatial resolution) and a digital elevation model following a three nearest neighbor approach (K-NN). Participants with professional forestry experience on average chose high-priority fuel load locations near buildings, while nonprofessional participants chose a broader range of conditions over a larger extent. When used together, the professional and nonprofessional observations provided a more complete assessment of forest conditions. A generalized framework is presented that utilizes K-NN imputation tools for estimating the distribution of forest fuels using remote sensing and topography variables, ensuring spatial representation, checking attribute accuracy, and evaluating predictor variables. Frameworks to integrate volunteered data from smartphone platforms with remote sensing may contribute toward more complete Earth observation for Digital Earth.     

交通地理信息中基于梯度方向的车道线提取

针对所摄路面影像,本文提出了基于梯度方向的车道线提取方法。车道线上边缘点的梯度方向大体与本车道线垂直,据此我们可以将车道线上的边缘点从所有边缘点中分离出来,再将这些点拟合,得到车道线。实验结果表明,本文方法具有很好的鲁棒性,对复杂路面的车道线提取效果较好。     

2.5维电子地图渲染成图接边方法探讨

2.5维电子地图与二维、三维矢量地图有着明显区别,其分批渲染成果是栅格数据,最后成果也是图像的形式,所以在地图接边的方式上比矢量图接边的方法要复杂得多。本文探讨了一种方法,使用虚拟相机确定2.5维电子地图俯瞰视角,制作批量渲染成图的接边参考框架,最后分批渲染景观模型与框架进行图像叠合。这种方法在项目实践中初见成效,能最大限度地缩小接边误差,不足之处是人工干预部分较多,必然导致误差累积,有待改进。     

基于HOT影像优化的遥感影像去雾算法

针对BSHTI和IBSHTI两种算法对卫星影像云雾校正后,地表的色调和纹理等细节缺失严重的问题,提出OIBSHTI算法对IBSHTI算法得出的雾厚度图像进行地表信息削减。通过填洼算法去除暗色区域,并引入纹理和边缘信息等进行优化处理,在彻底去除云雾的同时保留地表的色调和纹理,特别是蓝色或红色建筑物房顶的校正效果较为明显。     

基于二阶局部纹理熵的边缘检测方法

针对传统的边缘检测方法将灰度变化较为平缓的区域误判为边缘的问题,提出了基于二阶局部纹理熵的边缘检测方法。利用了二阶局部纹理熵能表示局部区域灰度变化大小的性质,并采用灰度错位压缩法消除灰度值压缩造成的条纹现象。实验表明,本文提出的方法能有效地检测出各类边缘,解决了上述的误判问题;通过不同大小窗口的边缘检测效果比较,建议在采用基于二阶局部纹理熵的边缘检测方法时将窗口设置为3×3。     

Continental slope sea level and flow variability induced by lateral movements of the Gulf Stream in the Middle Atlantic Bight

As described by [Csanady, G.T., Hamilton, P., 1988. Circulation of slope water. Continental Shelf Research 8, 565–624], the flow regime over the slope of the southern Middle Atlantic Bight (MAB) includes a current reversal in which southwestward flow over the upper and middle slope becomes entrained in the northeastward current adjacent to the Gulf Stream. In this paper we use satellite-derived data to quantify how lateral motions of the Gulf Stream impact this current system. In our analysis, the Gulf Stream’s thermal front is delineated using a two-year time series of sea surface temperature derived from NOAA/AVHRR satellite data. Lateral motions of the Gulf Stream are represented in terms of temporal variations of the area, east of 73°W, between the Gulf Stream thermal front and the shelf edge. Variations of slope water flow within this area are represented by anomalies of geostrophic velocity as derived from the time series of the sea level anomaly determined from TOPEX/POSEIDON satellite altimeter data. A strong statistical relationship is found between Gulf Stream displacements and parabathic flow over the continental slope. It is such that the southwestward flow over the slope is accelerated when the Gulf Stream is relatively far from the shelf edge, and is decelerated (and perhaps even reversed) when the Gulf Stream is close to the shelf edge. This relationship between Gulf Stream displacements and parabathic flow is also observed in numerical simulations produced by the Miami Isopycnic Coordinate Model. In qualitative terms, it is consistent with the notion that when the Gulf Stream is closer to the 200-m isobath, it is capable of entraining a larger fraction of shelf water masses. Alternatively, when the Gulf Stream is far from the shelf-break, more water is advected into the MAB slope region from the northeast. Analysis of the diabathic flow indicates that much of the cross-slope transport by which the southwestward flow entering the study region is transferred to the northeastward flow exiting the region occurs in a narrow band roughly centered at 36.75°N, order 150 km north of Cape Hatteras. This transport, and thus the cyclonic circulation of the southern MAB, strengthens when the Gulf Stream is relatively close to the shelf edge, and weakens when the Gulf Stream is far from the shelf edge.