星载激光相干测高计的参量设计

为使星载激光高度计实现高空间分辨力、高距离精度,提出了联合采用调频光纤激光器和相干测距的方法。详细讨论了这种方法的实现方案,并对方案中的激光发射功率、望远镜口径以及脉冲宽度对距离精度及信噪比的影响进行数值模拟。对系统参量进行分析,得到了相关参量的关系和优化的参量。结果表明,当望远镜口径为400 mm时,啁啾调频速率为1 MHz/μs,脉冲时间宽度150~350μs,发射功率10 W左右时,基于相干测距的星载激光高度计可以实现距离精度小于15 cm的技术指标。

新疆阜康地区森林资源与环境的空间分析

研究了新疆阜康地区森林植被资源与环境的特征和其30年来的变化，利用Arcinfo强大的空间分析功能，对资源、DEM模型、景观指数、环境价值和新疆降水量的地统计学规律进行较全面的分析。本文分为五个部分： 1、新疆阜康地区森林资源与环境空间数据库的建立森林资源与环境空间数据库的建立是它们空问分析的基础。利用多期的遥感图象和该区的地形图，建立森林分类图形和属性库（包括森林和环境自变量集）一体化的GIS空间数据库。为了提高TM遥感图象的分类精度，利用ERDAS图象处理软件，对它进行包括主成分、降噪、去条带和自然色彩变换等增强处理，采用监督分类和人工判读相结合的方法进行分类，采用R2V、ERDAS、Arcview、Arcinfo等软件的集成，使得小班面层与某些线层的无缝联接。成功地形成一套适于西部GIS的森林资源与环境空间数据库的技术路径。此外，对新疆阜康北部地区森林资源动态进行初步分析。 2、新疆阜康地区数字高程模型(DEM)及其粗差检测分析为了提高生态建模的精度，模拟和提取该区的地面特征至关重要。在已建立的森林资源与环境空间数据库的支持下，利用Arcinfo和ERDAS，建立了新疆阜康地区的1：5万数字高程模型(DEM)。通过提取地形的海拔、坡度、坡向特征因子，分析森林植被的垂直分布。通过对DEM的粗差检测分析，分析阜康地区的数字高程模型精度。 3、新疆阜康地区景观格局变化分析在1977年、1987年、1999年森林资源与环境空间数据库的支持下，利用景观分析软件编制三个时段的新疆阜康地区植被景观类型图，并分析了近30年来新疆阜康地区景观动态与景观格局变化。结果表明：①在此期间整个研究区的斑块数减少，斑块平均面积扩大，景观中面积在不同景观要素类型之间的分配更加不均衡，景观面积向少数几种类型聚集。说明了在这期间阜康地区的景观类型有向单一化方向发展的趋势;②农耕地分布呈破碎化的趋势，斑块平均面积变小，斑块间离散程度也更高：这些变化说明人为的经济活动在阜康地区的加剧，③天然林面积减少较多，水域的面积却呈现上升的趋势，冰川及永久积雪的面积呈下降趋势， 4、新疆阜康地区森林生态效益的初步分析从广义森林生态效益定义出发，针对12种森林生态效益因变量不完全独立、且各自的自变量集不完全相同，引入具有多对多特征且整体上相容的似乎不相关广义线性模型。通过构造12种森林生态效益的“有效面积系数”和“市场逼近系数”，在森林资源与环境空间数据库的支持下，对新疆阜康地区两期的森林生态效益进行科学的计量。结果表明：新疆阜康地区的森林生态效益货币量1987年是90673.8万元，1999年是84134.4万元，总体上呈下降趋势。 5、利用新疆气象站资料研究年降雨量的空间分布规律利用ArcGIS地统计学模块，在2000年新疆气候信息空间数据库和新疆DEM模型的支持下，做出了新疆地区的年降水量空间分布图。根据新疆气候资料建立趋势而分析模型、模拟了新疆降水量空间分布的趋势值。采用3种算法（距离权重法、普通Kriging法、协同Kriging方法）计算并比较分析了研究区多年的平均降水量的时空变化。利用模拟产生的精度最优的栅格降水空间数据库，建立的多年平均降水资源信息系统，可快速计算研究区内任一地域单元中降水的总量及其空间变化，可以生成高精度的气候要素空间分布图。

针对瞬时故障的控制流容错技术研究

随着微电子器件复杂度的提高，空间辐射对于计算机程序的正确性影响正越来越明显。一般情况下，这些影响并不是永久的，而是瞬时故障。无论是太空中的信息处理系统、嵌入式实时控制系统，还是计算机集群、高性能超级计算机都可能由于错误的输出而导致灾难性的后果。 传统的可靠性系统采用抗辐射部件和冗余的硬件来达到可靠性的要求，但是其价格昂贵，性能落后于今天的商用部件（COTS）。针对COTS在容错能力上存在的不足，软件容错技术可以在不改变硬件结构的情况下，有效的提高计算机系统的可靠性。 瞬时故障在软件层面上主要表现为控制流错误和数据流错误，本文主要针对控制流错误进行容错处理。软件实现的控制流容错技术通过在编译时加入冗余的容错逻辑，在程序执行时进行控制流错误的检测和处理。 如何在保证容错能力的同时，尽量降低冗余逻辑所带来的系统开销，是控制流容错需要解决的主要问题。本文从控制流错误的基本概念，容错单元的选择，签名信息的建立，签名点和检测点的插入位置几个角度对控制流容错进行研究，主要内容有： 1．对常见的控制流容错方法进行了分析比较，对其优点和不足予以说明。 2．对控制流错误进行了分类，以此为基础，提出了基于相关前驱基本块的控制流容错方法（CFCLRB）。 3．提出了一种签名流模型，提出了基于签名流模型的控制流容错方法（CFCSF）。该方法能够对基本块间控制流错误进行检测，具有较低的时间开销、空间开销和较高的错误覆盖率。同时，该方法可以根据容错尺度的要求，灵活的插入和删除签名点与检测点，具有极强的扩展性。该方法还可以应对动态函数指针这种编译时难以确定的控制流情况。 4．基于汇编指令对上述方法予以实现，并实现了国际上常用的控制流容错方法Control Flow Checking by Software Signatures（CFCSS）和Control-flow Error Detection through Assertions（CEDA）做为对比。通过加入冗余的指令逻辑，完成了对原程序的容错功能。 5．基于PIN工具实现了对控制流错误的注入，在相同的实验环境下对CFCLRB ，CFCSF，CFCSS，CEDA进行了对比实验。实验表明, CFCLRB的时间开销为26.9%，空间开销为27.6%，相比不具容错能力的原程序，其错误覆盖率从66.50%提升到97.32%。CFCSF的时间开销为14.7%，空间开销为22.1%，相比不具容错能力的原程序，其错误覆盖率从66.50%提升到96.79%。相比CFCSS，该方法的时间开销从37.2%下降到14.7%，空间开销从31.2%下降到22.1%，错误覆盖率从95.16%提升到96.79%。相比CEDA，该方法的时间开销从26.9%下降到14.7%，空间开销从27.1%下降到22.1%，错误覆盖率仅从97.39%下降到96.79%。 最后，本文对控制流容错的未来研究方向进行了展望。

Effects of Noise and Detection Error in a Dynamic Adaptive Optics System

It is well known that noise and detection error can affect the performances of an adaptive optics (AO) system. Effects of noise and detection error on the phase compensation effectiveness in a dynamic AO system are investigated by means of a pure numerical simulation in this paper. A theoretical model for numerically simulating effects of noise and detection error in a static AO system and a corresponding computer program were presented in a previous article. A numerical simulation of effects of noise and detection error is combined with our previous numeral simulation of a dynamic AO system in this paper and a corresponding computer program has been compiled. Effects of detection error, readout noise and photon noise are included and investigated by a numerical simulation for finding the preferred working conditions and the best performances in a practical dynamic AO system. An approximate model is presented as well. Under many practical conditions such approximate model is a good alternative to the more accurate one. A simple algorithm which can be used for reducing the effect of noise is presented as well. When signal to noise ratio is very low, such method can be used to improve the performances of a dynamic AO system.

Multi-pipe string electromagnetic detection tool and its applications

The MID-K, a new kind of multi-pipe string detection tool is introduced. This tool provides a means of evaluating the condition of in-place pipe string, such as tubing and casino. It is capable of discriminating the defects of the inside and outside, and estimating the thickness of tubing and casing. It is accomplished by means of a low frequency eddy current to detect flaws on the inner surface and a magnetic flux leakage to inspect the full thickness. The measurement principle, the technology and applications are presented in this paper.

A Novel Architecture of Vision Chip for Fast Traffic Lane Detection and FPGA Implementation

This paper presents a novel architecture of vision chip for fast traffic lane detection (FTLD). The architecture consists of a 32*32 SIMD processing element (PE) array processor and a dual-core RISC processor. The PE array processor performs low-level pixel-parallel image processing at high speed and outputs image features for high-level image processing without I/O bottleneck. The dual-core processor carries out high-level image processing. A parallel fast lane detection algorithm for this architecture is developed. The FPGA system with a CMOS image sensor is used to implement the architecture. Experiment results show that the system can perform the fast traffic lane detection at 50fps rate. It is much faster than previous works and has good robustness that can operate in various intensity of light. The novel architecture of vision chip is able to meet the demand of real-time lane departure warning system.

WAVELENGTH POSITIONING ERRORS AND TRUE DETECTION LIMIT IN RELATION TO MULTICOMPONENT ANALYSIS TECHNIQUES FOR THE CORRECTION OF LINE INTERFERENCES IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

The present paper deals with the evaluation of the relative error (DELTA(A)) in estimated analyte concentrations originating from the wavelength positioning error in a sample scan when multicomponent analysis (MCA) techniques are used for correcting line interferences in inductively coupled plasma atomic emission spectrometry. In the theoretical part, a quantitative relation of DELTA(A) with the extent of line overlap, bandwidth and the magnitude of the positioning error is developed under the assumption of Gaussian line profiles. The measurements of eleven samples covering various typical line interferences showed that the calculated DELTA(A) generally agrees well with the experimental one. An expression of the true detection limit associated with MCA techniques was thus formulated. With MCA techniques, the determination of the analyte and interferent concentrations depend on each other while with conventional correction techniques, such as the three-point method, the estimate of interfering signals is independent of the analyte signals. Therefore. a given positioning error results in a larger DELTA(A) and hence a higher true detection limit in the case of MCA techniques than that in the case of conventional correction methods. although the latter could be a reasonable approximation of the former when the peak distance expressed in the effective width of the interfering line is larger than 0.4. In the light of the effect of wavelength positioning errors, MCA techniques have no advantages over conventional correction methods unless the former can bring an essential reduction ot the positioning error.