广州城市水上休闲交通意象空间探讨

通过对广州城市水上休闲交通意象的调查,分析了广州城市水上休闲交通意象要素的基本特点及城市水上休闲交通意象空间特征.认为广州城市水上休闲交通意象空间未能形成一个完整的结构体系,意象空间存在相互不连续的区域,城市新的发展中尚未形成向心性较强的标志点,并未有一个比较认同的"公众形象".     

Limnological and sedimentary processes at Sawtooth Lake,Canadian High Arctic,and their influence on varve formation

This paper synthesizes data collected to document the modern limnological and sedimentary processes in South Sawtooth Lake located on northern Ellesmere Island, Nunavut, Canada. Field observations show that the finely laminated sediments deposited in the distal basin are formed by the settling of overflows and interflows, and in rare occasions, by non-erosive hyperconcentrated density flows. Thin-sections of these sediments allowed for the classification of the sedimentary fabrics into six facies, each representing different limnological processes. The sediments in this distal basin are considered to be continuous and annually laminated (varved) based on radioisotope analyses, and both limnological and sedimentological evidence.     

A data-mapping approach to 3-D wavefield redatuming

In case of a complex overburden, the seismic data can be greatly improved by applying a full wavefield redatuming procedure. In practice, the application of the redatuming process to 3-D data acquired by conventional acquisition designs is non-trivial. Because of the large amount of data involved in the 3-D redatuming process and because of the sparseness of these data, it is impossible to apply conventional wave equation datuming directly.
We present a data mapping approach to redatuming (DMR), which follows the concept of Kirchhoff data mapping. A simplified background medium where no ray bending occurs is assumed for the medium below the datum in order to map an input data set referenced to the acquisition surface to an output data set referenced to the new datum level. The DMR method can be interpreted as a simplified version of the Kirchhoff summation redatuming (KSR) method, where one of the 2-D integrals over the acquisition coordinates can be solved analytically. Consequently, in this approach fewer traces are involved in the computation of one time sample (a 2-D integral is computed instead of a 4-D integral), which makes it particularly attractive for the application to 3-D data sets.
In this paper the theory underlying data mapping redatuming is discussed and the proposed approach is tested on fully sampled 2-D and 3-D synthetic data from models with both simple and complex velocity distributions in the subsurface.
The tests clearly show that the objective of producing results that are comparable to the conventional KSR has been achieved. The redatumed traces are dynamically and kinematically correct. Furthermore, these results confirm that the dependency of the new approach on the assumed medium below the datum level is, indeed, weak because the assumption of a velocity medium where no ray bending occurs is already sufficient to produce correct results.     

Variations of horizontal and vertical velocities over two-dimensional transverse dunes: A wind tunnel simulation of the effect of windward slope

The changes in wind velocity induced by dune topography have an important significance in dune dynamics. In this paper, the horizontal and vertical velocities over six transverse dune models were measured non-intrusively by means of Particle Image Velocimetry in a wind tunnel. The windward slope angle and the free-stream wind velocity both affected the horizontal and vertical velocity components. On the windward side, the acceleration of horizontal velocity depended mainly on the windward slope angle and the height above the dune surface, but was also affected by the free-stream wind velocity. The speed-up ratio increased with increasing slope angle but decreased with increasing height. The ascending vertical velocities also increased with increasing slope angle and free-stream wind velocity. The maximum values moved upper along the dune when the windward angle became steeper. In the leeward sides, the horizontal velocity decreased and reversed because of airflow separation; the maximum reverse velocity in the separation cell was about 17% of the free-stream wind velocity. Behind the dune crest, the airflow moves downwards, and its maximum downward velocity is found near the flow reattachment point. Finally, we discussed the significance of these velocity variations for sediment transport and dune dynamics.     

我国利用遥感数据提取土地利用现状信息的技术进展

结合作用所参加的研究工作,探讨了我国近年来利用遥感数据获取土地利用现状信息的技术方法的阶段性发展规律,并对其发展趋势做出了预测。     

影像匹配中金字塔数据结构比较与快速算法

分析了多种金字塔数据结构的生成方法 ,比较了不同方法在影像匹配中的优劣 ,并提出了一种影像金字塔生成的快速算法。     

城市灾害现场图像传输系统的技术选择——以厦门市为例

以厦门市为例,介绍了灾害应急指挥通讯系统在实施灾害救援时依据无线电传输特性所作的技术选择。主要可归纳为：①现场图像至现场应急指挥车间的微波模拟传输。选择穿透能力较强的频道,实测无阻挡时可传输8km,有阻挡情况下穿透3、4堵墙壁;②现场指挥车至城市应急指挥中心间的甚高频数字化传输。在经过城市实际电磁空间噪音场扫描后选定适宜的频道窗口,以实现10km左右的传输要求：③现场应急指挥车在有条件的场地也可接驳宽带电话网实现与城市应急指挥中心的图像传送。     

面向真正射影像处理的对象定义及其语义关联

真正射影像作为新一代数字影像产品,其应用需求日益广泛。随着高分辨率倾斜影像的日益可得,逐像素处理的真正射影像生产方法局限性越来越突出。为此,针对面向对象的真正射影像处理,本文提出了物方对象和像方对象的概念,并描述了两类对象间的语义关联关系,并用实例分析了其特殊价值。     

Estimation of geological dip and curvature from time‐migrated zero‐offset reflections in heterogeneous anisotropic media

Starting from a given time‐migrated zero‐offset data volume and time‐migration velocity, recent literature has shown that it is possible to simultaneously trace image rays in depth and reconstruct the depth‐velocity model along them. This, in turn, allows image‐ray migration, namely to map time‐migrated reflections into depth by tracing the image ray until half of the reflection time is consumed. As known since the 1980s, image‐ray migration can be made more complete if, besides reflection time, also estimates of its first and second derivatives with respect to the time‐migration datum coordinates are available. Such information provides, in addition to the location and dip of the reflectors in depth, also an estimation of their curvature. The expressions explicitly relate geological dip and curvature to first and second derivatives of reflection time with respect to time‐migration datum coordinates. Such quantitative relationships can provide useful constraints for improved construction of reflectors at depth in the presence of uncertainty. Furthermore, the results of image‐ray migration can be used to verify and improve time‐migration algorithms and can therefore be considered complementary to those of normal‐ray migration. So far, image‐ray migration algorithms have been restricted to layered models with isotropic smooth velocities within the layers. Using the methodology of surface‐to‐surface paraxial matrices, we obtain a natural extension to smooth or layered anisotropic media.     

NOAA卫星图像云点检测的三维统计图集合判别

在应用NOAA-AVHRR图像对地球资源环境进行监测的研究中,云点检测是一项基本工作。本文以实例分析云的图像特征,选取特征指标建立像元分布三维统计图,直接在统计图上观察云点集群分布阈值,并以此作为云点集合判别的条件,以实现自动检测。此法灵敏度高,稳定性好,且直观方便。