The effectiveness of spectral similarity measures for the analysis of hyperspectral imagery

In geological imaging spectrometry (i.e., hyperspectral remote sensing), surface compositional information (e.g., mineralogy and subsequently chemistry) is obtained by statistical comparison (by means of spectral matching algorithms) of known field- or library spectra to unknown image spectra. Though these algorithms are readily used, little emphasis has been given to comparison of the performance of the various spectral matching algorithms. Four spectral measures are presented: three that calculate the angle (spectral angle measure, SAM), the vector distance (Euclidean distance measure, ED) or the vector cross-correlation (spectral correlation measure, SCM), between a known reference and unknown target spectrum and a fourth measure that measures the discrepancy of probability distributions between two pixel vectors (the spectral information divergence, SID). The performance of these spectral similarity measures is compared using synthetic hyperspectral and real (i.e., Airborne Visible Infrared Imaging Spectrometer, AVIRIS) hyperspectral data of a (artificial or real) hydrothermal alteration system characterised by the minerals alunite, kaolinite, montmorillonite and quartz. Two statistics are used to assess the performance of the spectral similarity measures: the probability of spectral discrimination (PSD) and the power of spectral discrimination (PWSD). The first relates to the ability of the selected set of spectral endmembers to map a target spectrum, whereas the second expresses the capability of a spectral measure to separate two classes relative to a reference class. Analysis of the synthetic data set (i.e., simulated alteration zones with crisp boundaries at 1–2 nm spectral resolution) shows that (1) the SID outperforms the classical empirical spectral matching techniques (SAM, SCM and ED), (2) that SCM (SID, SAM and ED do not) exploits the overall shape of the reflectance curve and hence its outcomes are (positively and negatively) affected by the spectral range selected, (3) SAM and ED give nearly similar results and (4) for the same reason as in (2), the SCM is also more sensitive (again in positive and negative sense) to the spectral noise added. Results from the study of AVIRIS data show that SAM yields more spectral confusion (i.e., class overlap) than SID and SCM. In turn, SID is more effective in mapping the four target minerals than SCM as it clearly outperforms SCM when the target mineral coincides with the mineral phase on the ground.     

超燃冲压发动机性能的准二维计算方法

为了能在双模态超燃冲压发动机流道方案初步论证中提供一种较快速的发动机性能计算方法,在二维N-S方程基础上,引入一维完全燃烧计算方法,提出了预估超燃冲压发动机性能的准二维计算方法。该方法能够计入激波、边界层分离等对发动机性能的影响,可在较短时间计算出整机推力、比冲性能和沿程热力学参数。通过对自由射流发动机计算,验证了此方法。并在此基础上,初步分析了燃料喷注位置和流道构型对发动机性能的影响。      

An evaluation of progress in implementing ecosystem-based management of fisheries in 33 countries

The performance of 33 countries was evaluated for ecosystem-based management (EBM) of fisheries in three fields (principles, criteria and implementation) using quantitative ordination including uncertainty. No country rated overall as ‘good’, only four countries were ‘adequate’, while over half received ‘fail’ grades. A few developing countries performed better than many developed nations. Two case studies test the method. In Indonesia, Raja Ampat and Papua, rated similar to the national evaluation, but better performance might follow successful implementation of a planned EBM initiative. A workshop in Australia rated regional fisheries managed by New South Wales 20% lower for EBM than federally managed fisheries.     

ZD8B与ZD-8地电仪观测精度及性能评价

主要对ZD8B与ZD-8地电仪在观测的精度及稳定性、动态范围、抗干扰能力等方面进行了评价,并对观测数据进行了分析,认为地电仪观测资料可作为地震预报的可靠依据之一。     

A new metric for measuring structure-preserving capability of despeckling of SAR images

In this paper, a new metric called despeckling structure loss (DSL) is proposed for performance assessment of despeckling algorithms with a focus on the preservation of structural features such as edges and textures. The ratio image of a synthetic aperture radar (SAR) image to its despeckled result can clearly indicate the loss of structural features caused by the despeckling process. By taking into account characteristics of the best and worst structure preservation in despeckling, the DSL metric examines the presence of structural features in ratio images by using local correlations between the ratio image and the noise-free reference image at edge points. The DSL is shown to be a monotonic function of structure loss bounded between the best and worst cases, leading an objective and quantitative measure of the structure-preserving capability of despeckling algorithms. Experimental evaluations of the proposed metric have been carried out on simulated SAR images including one generated by SAR raw signal simulator. Despeckled results using five typical algorithms clearly demonstrate the efficiency of the DSL metric. In comparison, the commonly used despeckling metrics including the signal-to-mean-square error ratio, the edge correlation index, the Pratt’s figure of merit, the structural similarity and the equivalent number of looks of ratio images, fail to keep a consistency with the structure loss shown in despeckled results as well as ratio images.     

WiFi室内定位的不同接入点选取策略的性能评估分析

最优无线接入点(access point,AP)子集的选取是进一步改善WiFi室内定位技术的一个难题。本文介绍了现有的AP选取算法并提出了基于奇异检验的AP选取算法,给出了WiFi室内定位的性能评估指标。通过实验评估分析了各AP选取算法的综合性能,结果表明:基于相同原理的AP选取算法,其位置估计误差具有相似性,但不同AP选取算法由于选取原理不同各自具有局限性。在实践应用中,要贴合实际情况,结合各AP选取策略特点,选择合适的AP选取策略。     

基于网格的高性能地理信息系统初探

网格技术不仅可以解决由于WebGIS缺少"集成"和"互操作"所造成异构GIS应用之间的数据共享与互操作问题;而且可以结合高性能计算手段解决GIS扩展应用中的高密集的计算问题。Grid GIS不仅能为应用提供丰富的各类GIS资源,而且为解决分布异构环境下的GIS共享以及互操作提供了可行的解决方案。然而如何利用Grid技术为那些异构GIS应用提供高性能计算服务,成为一个值得探索的问题。为此,本文初步探讨了基于Grid的高性能GIS的体系结构、整体布局等关键技术,同时对如何构建高性能的GIS服务节点提出了相应的解决办法。     

Coagulation Efficiency and Residual Aluminum Content of Polyaluminum Silicate Chloride in Water Treatment

A series of polyaluminum silicate chlorides (PASC), which have different OH^—/Al and Al/Si molar ratios, has been prepared by a copolymerization technique and a composite technique, after which the coagulation efficiency and the residual aluminum content of PASC for water treatment were compared with polyaluminum chloride (PAC) by jar test. The experimental results show that PASC has better coagulation efficiency and lower residual aluminum content than PAC, and the PASC prepared by the copolymerization technique gives a better coagulating effect than that prepared by the composite technique. In addition, the OH^—/Al and Al/Si molar ratios have some effect on the coagulation effect and residual aluminum content of PASC in treated water. With increasing OH^—/Al molar ratio and decreasing Al/Si molar ratio, the residual turbidity and residual aluminum content in treated water diminishes. The pH of the water sample also affects the residual aluminum content of the water and there is a lower residual aluminum content in the neutral pH range.     

CoLM模式在中国温带混交林和亚热带人工针叶林的水热通量模拟性能评估

利用中国陆地生态系统通量观测研究网络(ChinaFLUX)在长白山温带混交林观测站点和千烟洲亚热带人工针叶林观测站点的强化观测资料,考察了一个较为完善的陆面过程模式(Common LandModel,CoLM)在这两种不同植被类型下垫面的模拟性能,特别是其对潜热通量的模拟。模拟结果与强化观测资料的对比表明,CoLM能较好地模拟出实验站点地表能量平衡的基本特征以及潜热通量的日变化和季节变化。其中长白山站和千烟洲站潜热通量日平均的观测值与模拟值的相关系数分别为0.804和0.692,均通过了0.001的显著性水平检验。总体而言,CoLM在长白山站的模拟效果更好一些,模式对不同植被覆盖类型的土壤—植被—大气间水热传输过程的处理可能是造成差别的原因。     

System evaluation of sustainability in the Norwegian cod-fisheries

Overcapacity in the fishing fleets is considered as the most serious threat to sustainable fisheries. More effective fishing vessels and catching gear contribute to increased catch capacity. Increased catch capacity causes environmental problems such as overexploitation and calls for larger quotas. The problem of overcapacity indicates the need for a stronger integration of technological aspects into fisheries management. This article assesses the differences in sustainability between the Norwegian ocean and coastal fishing fleets in the cod fisheries, by using systems engineering methods. Attributes of sustainability in the Norwegian cod fishing fleets are investigated, as well as acceptance criteria and performance indicators. The results show that there are huge differences in the performance between the vessel groups, and that the results of an evaluation of sustainability in the fishing fleets are dependent on which attributes are explored. Thus, the discussion may contribute to a better decision basis and improved sustainability in fisheries management.