基于免疫进化算法的投影寻踪聚类在公司债券财务质量评级中的应用

针对公司债券财务质量评级问题,采用投影寻踪聚类(PPC)模型,将多维数据指标转换到低维子空间,并利用免疫进化算法(IEA)优化其投影方向,根据投影函数值的大小评价出样本的优劣,从而做出决策。应用表明,该方法能利用一个综合反映多因素之间复杂关系的特征指标给出客观而直接的评价结果,且根据计算结果还可以分析各个指标对综合评价结果的影响程度,为公司债券财务质量评级提供了一种计算过程简单、直观的新方法。     

Wavelet transform applied to EO-1 hyperspectral data for forest LAI and crown closure mapping

A comparison of the performance of three feature extraction methods was made for mapping forest crown closure (CC) and leaf area index (LAI) with EO-1 Hyperion data. The methods are band selection (SB), principal component analysis (PCA) and wavelet transform (WT). Hyperion data were acquired on October 9, 2001. A total of 38 field measurements of CC and LAI were collected on August 10-11, 2001, at Blodgett Forest Research Station, University of California at Berkeley, USA. The analysis method consists of (1) conducting atmospheric correction with High Accuracy Atmospheric Correction for Hyperspectral Data (HATCH) to retrieve surface reflectance, (2) extracting features with the three methods: SB, PCA and WT, (3) establishing multivariate regression prediction models, (4) predicting and mapping pixel-based CC and LAI values, and (5) validating the CC and LAI mapped results with photo-interpreted CC and LAI values. The experimental results indicate that the energy features extracted by the WT method are the most effective for mapping forest CC and LAI (mapped accuracy (MA) for CC=84.90%, LAI MA=75.39%), followed by the PCA method (CC MA=77.42%, LAI MA=52.36%). The SB method performed the worst (CC MA=57.77%, LAI MA=50.87%).     

Sensitivity of spectral reflectance to variation in live fuel moisture content at leaf and canopy level

Wildland fires burn large areas of the earth's land surface annually, causing significant environmental damage and danger to human health. In order to mitigate the effects, and to better manage the incidence of such fires, fire behaviour models are used to predict, among other things, the likelihood of ignition, the rate of spread, and the intensity and duration of burning. A key input parameter to these models is the amount of water in the vegetation, described as the fuel moisture content (FMC). A number of studies have shown that vegetation indices (VI) calculated from red and NIR reflectances may be used to map spatial and temporal variation in FMC in a range of fire-prone environments, with varying degrees of success. Strong empirical relationships may be established between VI and FMC over grasslands, yet over shrublands and forests, the relationships are weaker. If FMC is to be estimated with greater accuracy and consistency than is currently achieved, it is necessary to fully understand the relative contribution that spatial and temporal variation in the various biophysical and geometrical variables make to reflectance variability at the leaf and canopy level.This paper uses a modelling approach to investigate the sensitivity of reflectance data at leaf and canopy level to variation in the biophysical variables that are used to compute FMC. At the leaf level, the results show that the sensitivity of reflectance to variation in leaf water and dry matter content, used to compute FMC, is greatest in the SWIR and NIR, respectively. Variation in FMC has no effect in the visible wavelengths. At the canopy level, the results show that the sensitivity of reflectance to variation in leaf water and dry matter content is heavily dependent upon the type of model used and the range of variation over which the variables are tested. In the longer wavelengths of the SWIR, the competing influence of variable leaf area index, fractional vegetation cover, and solar zenith angle is shown to be greater than that at the shorter wavelengths of the SWIR and NIR. Empirical relationships between the normalised difference water index (NDWI) and FMC are shown to be weaker than that with canopy water content. However, when the range of the variables under study is more limited, useful empirical relationships between FMC and remotely sensed VI may be established.     

菜地土壤评价中参评因素的选定与分级指标的划分

菜地选片规划应通过土壤详查和评价工作,选出最适地区,才能经济有效、持续发展。土壤评价中参评因素的选定与分级指标的划分是工作的核心。应选取对蔬菜的生长发育和生产力具有重大影响的、稳定性较高的限制因素,并以土壤属性为主,结合环境条件,因地制宜选定。参评因素的分级应尽量采用定量指标,为分等定级提出定量依据,其主要级差应尽量利用有生物学意义的临界指标。在目前全国无统一规定下,试图面向全国选定参评因素及划分为五等六级的分级指标。     

沈阳市建成区树种结构分析

通过对沈阳市建成区城市树木的调查分析发现。沈阳市的各土地利用类型中的树木种类和数量分布不均匀，其中。被调查的2．56块样地中每公顷树种≤5种的样地有113块。占总调查样地的44．14％；每公顷≤lO株的样地共43块．占总样地的16．80％。利用树种多度重要性排序及累积贡献率获得了不同土地类型中的主要树种。多个生物多样性指数表明．公园性质绿地的树种多样性最高．企事业单位用地与居住区用地次之．街道类用地较低。而商业金融用地最低。在此基础上对沈阳市的树种发展提出建议。     

Reduction of Friction by Functionalised Viscosity Index Improvers

A range of functionalised polymethacrylate copolymers have been synthesised with different functionalities, polymer architecture and molecular weight. It is shown that appropriately functionalised block copolymers give enhanced film thickness and greatly reduced friction under low entrainment speed conditions, even with polymer concentration as low as 1% wt. This behaviour almost certainly results from the formation of an adsorbed brush-like film of thickness ca 20 nm on each polar surface. These films provide a highly viscous inlet that promotes fluid entrainment and thus maintains a separating film down to very low entrainment speed. The adsorbed polymer films are also able to maintain separation in stationary contact conditions. Randomly distributed copolymers do not show this type of behaviour. The friction reduction observed is more effective in unidirectional, mixed sliding–rolling than in reciprocating, sliding conditions. However, it is found that functionalised polymers and conventional organic and molybdenum-based friction modifiers can be combined to provide effective friction reduction over the whole range of rubbing conditions.     

The effects of refractive index heterogeneity within kidney tissue on multiphoton fluorescence excitation microscopy

Although multiphoton fluorescence excitation microscopy has improved the depth at which useful fluorescence images can be collected in biological tissues, the reach of multiphoton fluorescence excitation microscopy is nonetheless limited by tissue scattering and spherical aberration. Scattering can be reduced in fixed samples by mounting in a medium whose refractive index closely matches that of the fixed material. Using optical 'clearing', the effects of refractive index heterogeneity on signal attenuation with depth are investigated. Quantitative measurements show that by mounting kidney tissue in a high refractive index medium, less than 50% of signal attenuates in 100 μm of depth.     

应对多馈入直流换相失败的同步调相机布点方法

特高压直流输电网受端交流故障诱发的直流换相失败会造成系统短时大量功率短缺,对系统安全稳定性带来巨大威胁。同步调相机因其强大的动态无功支撑能力,在应对多馈入直流换相失败及加快系统暂态恢复过程方面受到了越来越多的关注。从多馈入直流间相互作用角度出发,分析了调相机应对多馈入直流换相失败的优势,结合多馈入交互作用因子、多馈入有效短路比及相对暂态电压跌落面积指标,逐层确定最佳的动态无功补偿站点,提出一种可运用于工程实际的调相机应对多馈入直流换相失败的布点方法,并在华东电网数据典型运行方式的基础上进行了仿真验证。     

含柔性多状态开关的配电网分区方法

柔性多状态开关是一种新型智能配电装置。结合柔性多状态开关的功能特点,提出了含柔性多状态开关的配电网分区条件。以多层图分割理论框架为基础,提出了由粗化、分区和还原阶段构成的分区方法。在粗化过程中,提出了基于最短电气距离的粗化方法,使用贪婪图生长算法完成初始分区,并在还原阶段提出了基于路径搜索的还原方法。分区方法不仅能够优化配电网的运行指标,还能够提高配电网的可控性和灵活性。通过IEEE 118节点配电网算例对所述分区方法进行了说明和验证,并结合柔性多状态开关的调控对分区效果进行了进一步分析。结果表明,该方法能够改善配电网的日均馈线负载均衡度,并能够和柔性多状态开关的调控相配合,进一步改善配电网每一时刻的馈线负载均衡度和电压分布。     

基于嵌入式系统的光功率监测仪的研制

介绍了一种对通信光缆中多路光纤的光功率进行实时监测的仪器，给出了其设计原理，实现方法及软、硬件结构。为了方便系统的扩展，在结构设计时采用了主从式架构，并在主模块部分应用了嵌入式操作系统。同时系统具有多种报警形式，并具有自动切换光纤的功能。