Modeling and Visualization of Underground Structures

Based on the solid modeling, transformation operation and Boolean operation techniques widely available in computer-aided design and drafting system, first, this paper proposed a general modeling method for dynamic underground structure simulation. Then, representations of underground structures, ground, and related information in three-dimensional space were investigated. Some suggestions were put forwarded to improve visualization results, including object organization by layers, thematic viewing, level of detail for object representation, and spatial cueing for useful information. Application examples were given to illustrate the visualization effects. Finally, virtual reality technology was employed in the simulation of the underground structures. By positioning objects using real-time information, picking objects, and then accessing their real world working status through the Internet, the realistic results of a virtual system were further discussed. It has also been found that in order to obtain satisfactory visual results using an inexpensive desktop computer, a virtual reality model must be optimized from the perspective of reducing object complexity as well as efficient scene management.     

In Field Soil Characterization: Approach Based on Texture Image Analysis

Building on the development of a tool for in place soil investigation based on the use of endoscopy, this paper presents a method for soil characterization using the images recorded by this tool. Various techniques have been explored including texture analysis which is very attractive because it is based on global image analysis. The use of a third order moment resulting from spectral analysis and its value for soil characterization is presented. The influence of various parameters (particle size distribution, mineralogy, water content, and compaction) on the moment evolution is studied.     

An algorithm for analyzing noisy, in situ images of high-aspect-ratio crystals to monitor particle size distribution

An image analysis algorithm for extracting particle size distribution information from in situ images of suspended, high-aspect-ratio crystals is described. The accuracy of the algorithm is assessed using comparisons with results obtained by manually sizing the imaged crystals. The algorithm can accurately extract crystal size information from in situ images of suspended, high-aspect-ratio crystals for moderate solids concentrations. The algorithm's performance declines somewhat for high solids concentrations and high levels of particle attrition. The speed with which the algorithm analyzes the images is suitable for real-time monitoring and control of particle size distribution mean and variance.     

Measurements of scalar dissipation in a turbulent plume with planar laser-induced fluorescence of acetone

In order to gain a better understanding of the scalar dissipation rate χ in turbulent flows and to test available models for this quantity, high-resolution two-dimensional planar laser-induced fluorescence measurements were undertaken in the mixing field formed by the axisymmetric injection of a fluorescent tracer (acetone) into a confined turbulent co-flow of air, with emphasis on the less explored early region close to the nozzle and on the spatial resolution and level of image denoising necessary for the correct measurement of χ. In the mean, the resulting plumes had Gaussian profiles and axial decay as expected from previous investigations. It was found that, with Kolmogorov lengthscale resolution and careful image processing prior to the calculation of the scalar gradients, the measured χ satisfied global conservation of scalar energy across the plume to within 20%. The estimated mean three-dimensional scalar dissipation rate was used to calculate C_D (twice the timescale ratio) that was found to decrease from values higher than 10 adjacent to the nozzle, to approximately 2 at an axial distance of 2-3 nozzle diameters (corresponding to residence times of 0.1-0.2 turbulent timescales) and retaining this value further downstream. The data can assist the validation of models for 〈χ〉.     

井间层析成像质量影响因素分析

本文利用一些典型数学模型的井间层析成像结果，较为深入地讨论了井间层析成像质量的影响因素，如射线密度，射线有限视角，初至误差，速度差异和射线弯曲等。在此基础上，提出了一些克服上述影响因素的具体建议，这对于井间层析成像以及指导野外施工，都具有重要的意义。     

用低分辨率CCD进行高精度边缘检测的一种新方法——模糊成象法

本文从信息获取的角度出发，提出了一种用低分辨率ＣＣＤ进行高精度边缘检测的新方法，可从根本上突破象元间隙给尺寸测量精度带来的限制，其实质是用光学方法对输入图象进行某种变换（波形展宽），变换的结果使ＣＣＤ探测到更丰富的边缘信息，再用数学方法对其进行反变换（拟合），以恢复被测物体的精确边缘位置信息。     

Development of an atmospheric Cherenkov imaging camera for the CANGAROO-III experiment

A Cherenkov imaging camera for the CANGAROO-III experiment has been developed for observations of gamma-ray-induced air showers at energies from 10¹¹ to 10¹⁴ eV. The camera consists of 427 pixels, arranged in a hexagonal shape at 0.17° intervals, each of which is a -in. diameter photomultiplier module with a Winston-cone-shaped light guide. The camera was designed to have a large dynamic range of signal linearity, a wider field of view, and an improvement in photon-collection efficiency compared with the CANGAROO-II camera. The camera, and a number of the calibration experiments made to test its performance, are described in detail in this paper.     

成像光谱遥感定标模型的分析与评价

通过对目前国际上流行的几种光谱定标模型的分析研究，发现：基于图像结构特征的定标模型具有丢失光谱特征的缺点；基于ＲＴ定标模型对水汽过分敏感；基于ＥＬ的定标模型对地形要求严格；而基于光谱混合理论的定标模型其内部算法仍需改进，等等。由此，在实际工作中，根据实际工作条件和应用要求进行定标模型的取舍是十分重要的     

Energy dissipation and macro instabilities in a stirred square tank investigated using an LE PIV approach and LDA measurements

In this study, the hydrodynamics and turbulence in a square tank stirred with a hydrofoil impeller, a Lightnin A310, is investigated using a large eddy particle image velocimetry (LE PIV) approach. The particle image velocimetry data are used as the large scale part of a large eddy simulation and the small scales are modelled assuming that the turbulent kinetic energy production is limited to the large scale structures, the turbulent energy dissipation is confined to the small scale structures and the transfer of energy takes place in the inertial sub-range. The small scale turbulence was modelled by direct calculation of the turbulent stress tensor using filtered particle image velocimetry data. The spatial distribution of the calculated dissipation rate tensors showed good agreement with previous work.

The macro instabilities of the flow structure were investigated by means of spectral analysis. Low frequency phenomena separated from the mean flow were detected. The cause of these could partly be explained by the circulation time for the tank, which corresponded to the low frequency phenomena found at 0.03N Hz, where N is the rotational speed.     

综合孔径辐射计中二级相关算法的设计与实现

为了解决传统微波遥感辐射计使用FPGA实现多通道数字相关器时资源消耗量过大的问题,本文提出了一种二级相关实现方法.二级相关算法将相关算法分成前后两级,并利用门时钟生成单元使系统保持流型工作状态.前级相关器由基本逻辑资源构成,完成固定短点数的相关处理;多个前级相关器分为一组,分时启动并复用后级长点数相关器.二级相关算法能显著解决微波遥感辐射计中多通道数字相关器资源消耗量巨大的问题,提高数字相关器所容纳的相关通道数,同时优化了FPGA布局布线性能,能提高系统性能并降低成本.