对索风营水电站坝址区堆积体勘察设计的几点认识

乌江索风营水电站坝址区分布有7个堆积体,其成因有崩塌堆积、蠕变-拉裂-崩解堆积、塌滑堆积及混和堆积等.在勘察过程中采用了地质测绘、钻探、硐探、物探、科研试验等多种勘察方法与手段,在勘察成果基础上对堆积体稳定性进行了分析,并结合对工程的不同影响提出了相应的工程处理措施.     

Direct atomic scale analysis of the distribution of Cu valence states in Cu/γ-Al2O3 catalysts

In this paper, the microstructure of a 1 wt.% Cu/γ-Al₂O₃ catalyst that was reduced in a 4% hydrogen/argon atmosphere at temperatures of 523, 773 and 1073 K, is studied by Z-contrast imaging and electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Results show that the copper species are well dispersed when the catalyst is reduced below 523 K. At 773 K, separated Cu(I) and Cu(0) species are found existing as ring-like and bulk-like particles. This appears to indicate that the copper has not been reduced to its metallic form due to the interaction between the copper oxide and the support. Large spherical particles having core-shell structures with Cu(I) in the shells and Cu(0) in the cores are generated when the catalyst is reduced at 1073 K. The formation of partially oxidized copper species upon reduction at 1073 K is attributed to the metallic copper interaction with the alumina support. This study also demonstrates that high-spatial resolution Z-contrast imaging and EELS performed simultaneously can provide unique information on the morphology and chemistry of metal species in supported metal catalysts.     

机载扫描成象系统的技术发展

叙述了机载扫描成象系统的发展,基本结构,特点及其应用.     

基于蚁群算法的区域覆盖卫星星座优化设计

首先建立了以区域覆盖性能为目标的卫星星座参数优化模型,通过在连续域定义新的蚂蚁分类与转移策略改进了蚁群算法,使算法能够兼顾多目标优化时目标不兼容的情况,给出了基于该算法实现星座参数优化的框架。优化仿真实验验证了该算法的有效性,可为星座方案决策提供有力的支持。     

一种弹载条带式SAR成像方法

弹载条带式SAR信号特点表现为小的距离弯曲量,当分辨率要求不是特别高时,若最大距离弯曲量小于一个距离分辨单元时可忽略不计,而只考虑距离走动量的校正。针对这一特点提出了一种在频域对距离迁移的线性项即距离走动校正的成像方法,并提出了距离误差校正和图像几何校正相结合的方法,使得成像效率更高。仿真成像结果验证了该方法的可行性。     

快速搜寻卫星数字压缩信号

在没有专业仪器，没有明确参照物的条件下，如何快速定位接收天线，搜索到卫星信号，是电视工程技术人员经常遇到的问题，本文就此问题提出了一个新的解决办法，即利用已知卫星的位置来定位其它卫星的位置。     

Preparation of flat-polished specimens for SEM-backscattered electron imaging and X-ray microanalysis—importance of epoxy impregnation

Representative and quantitative microstructural information of cement-based materials can be obtained in the backscattered electron and X-ray modes of the scanning electron microscope (SEM). One prerequisite, of several, is to use flat specimens. Microstructures that are minimally affected by the grinding and polishing necessary to produce the flat surface can be obtained. It is essential to fill the pores of the specimen with epoxy resin prior to grinding and polishing. After hardening, the epoxy stabilizes the microstructure and enables it to withstand the stresses of grinding and polishing without alteration. In the present paper, we describe a preparation technique that we consider to have produced excellent polished specimens. The importance of epoxy impregnation is demonstrated.     

Performance of a turbo‐coded CDMA system in a mobile satellite channel

The bit error rate (BER) performance of a turbo‐coded code‐division multiple‐access (CDMA) system operating in a satellite channel is analysed and simulated. The system performance is compared for various constituent decoders, including maximum a posteriori probability (MAP) and Max‐Log‐MAP algorithms, and the soft‐output Viterbi algorithm. The simulation results indicate that the Max‐Log‐MAP algorithm is the most promising among these three algorithms in overall terms of performance and complexity. It is also shown that, for fixed code rate, the BER performance is improved substantially by increasing the number of iterations in the turbo decoder, or by increasing the interleaver length in the turbo encoder. The results in this paper are of interest in CDMA‐based satellite communications applications. Copyright © 2005 John Wiley & Sons, Ltd.     

基于DVB/MPEG-2的卫星Internet技术

Internet的快速发展，使他已陷入了自身难以克服的困境，这种困境主要来自于骨干网、接入网、服务器三种瓶颈。而卫星通信与Internet的结合能有效地解决目前的这种困境。本文介绍了基于DVB／MPEG-2的卫星Internet原理、结构、应用及其关键技术，并引入了2种现有成熟的Internet接入技术：VSAT接入方式和VSAT与CATV结合接入方式。     

Optical scattering in beef steak to predict tenderness using hyperspectral imaging in the VIS-NIR region

The objective of this research is to develop a non-destructive method for predicting cooked beef tenderness using optical scattering of light on fresh beef muscle tissue. A hyperspectral imaging system (λ = 496–1,036 nm) that consists of a CCD camera and an imaging spectrograph, was used to acquire beef steak images. The hyperspectral image consisted of 120 bands with spectral intervals of 4.54 nm. Sixty-one fresh beef steaks, including 44 strip loin and 17 tenderloin cuts, were collected. After imaging, the steaks were cooked and Warner-Bratzler shear (WBS) force values were collected as tenderness references. The optical scattering profiles were derived from the hyperspectral images and fitted to the modified Lorentzian function. Parameters, such as the peak height, full scattering width at half maximum (FWHM), and the slope around the FWHM were determined at each wavelength. Stepwise regression was used to identify 7 key wavelengths and parameters. The parameters were then used to predict the WBS scores. The model was able to predict WBS scores with an R = 0.67. Optical scattering implemented with hyperspectral imaging shows limited success for predicting current status of tenderness in beef steak.