基于线性光谱分析的城市旧城改造空间格局遥感研究：以1997～2000年上海中心城区为例

将光谱分解方法应用于城市景观变化及其生态环境效应的研究,对于遥感技术与城市地理的结合具有重要意义．但是,由于城市地表覆盖景观主要以高度复杂的人工材料构成,光谱分解的精度不高是制约该研究方向发展的关键因素．当前国内外将光谱分解应用于城市地理研究主要包括两大方向,一是通过选择植被端元,从而求解出像元尺度上的植被盖度；二是根据人工建筑为代表的高低反照度地物盖度,将低反照度端元中的水面掩膜去除后与高反照度端元相叠加,建立与城市不渗透面的定量模型,从而求解出像元尺度上城市不渗透面盖度．本文的主要贡献是：(i)针对目前线性光谱分解中端元选择的范围过大、在二维空间中选择端元的信息损失较多等问题,对端元的选择方法做了较大改进．首先引入像元纯净指数(PPI),将端元选择范围限定在数量很少的高纯度像元中,端元选择范围减少了95%左右,从而提高了选择准确端元的概率．其次构造了三维特征空间,比传统方法多考虑一个维度,并可以与原始影像、高分辨率航空遥感影像以及PPI结果交互比较,进一步提高选择准确端元的概率．(ii)通过严格的光谱和实地检验,从遥感技术与城市地理相结合的角度,将高低反照度端元与新旧人工建筑表面对应起来,利用不同时相的端元盖度对比分析城市旧城改造格局的时空演变特征．(iii)基于上述改进的混合光谱分析方法,运用1997和2000年的TM和ETM+影像数据,分析了上海市中心城区旧城改造的格局、规模以及模式．结果显示,该阶段是上海市第一轮旧城改造高峰阶段,数量占到总改造面积的近一半,重点区域已经从传统CBD扩展到内环沿线附近；在改造模式上,除了改造为新建筑外,同时伴随着植被恢复与建设,中心城区植被覆盖率也大大提高．

洱海流域不透水面遥感信息提取技术研究

[目的]研究洱海流域不透水面遥感信息提取技术,以期开发水污染形成时空过程动态模拟平台。[方法]采用线性光谱分离技术,实现V-I-S模型求解,从2009年Landsat5的TM数据中对洱海流域进行不透水面遥感信息提取,利用植被、高反照度、低反照度和裸土4种最终光谱端元的线性组合,模拟TM波谱特征,并对其分布范围、空间特征等进行了分析。[结果]中等分辨率影像适合于流域尺度的不透水面提取,其结果可靠、精度较好。[结论]该研究结果为选择洱海非点源污染的调控策略、协调经济发展与环境保护的关系提供了决策依据。

Determination of Melamine by Infrared Spectroscopy Based on Nonlinear Modeling

[Objective] The aim was to develop a nonlinear model of quantitative analysis of melamine content by infrared spectroscopy and provide theoretical basis for the nondestructive detection of melamine. [Method] According to dynamics,mathematical modeling and optimization theory,linear and nonlinear models were respectively set up by taking an absorption peak of 1 550 cm-1 as characteristic absorption peak. [Result] The correlation coefficient of nonlinear model was 0.922 7 and the recovery was 96%,which showed that the nonlinear model was more accurate than linearity model with correlation coefficient of 0.904 9 and recovery of 557%. [Conclusion] It is feasible to determine melamine content by using the nonlinear model quantitatively.

Study on Remote Sensing Information Extraction Technology for the Impervious Surface of Erhai Basin

[Objective] To study the remote sensing information extraction technology for the impervious surface of Erhai basin with the aim to develop dynamic simulation platform for the formation of water pollution. [Method] Linear spectral separation technology was used to achieve Vd-S model solution, extracting remote sensing in- formation of the impervious surface of Erhai basin from the TM data of Landsat5 in 2009. The linear combination of 4 kinds of endmember spectra, namely vegetation, high anti-illumination, low anti-illumination and bare soil, were used to simulate the TM spectral characteristics, and its distribution and spatial characteristics were ana- lyzed. [Result] Middle-resolution image is suitable for the basin-scaled impervious surface extraction with reliable results and satisfactory accuracy. [Conclusion] This study provided basis for deciding the relationship between the regulation strategy on the non-point source pollution of Erhai Lake, coordinated economic development and environmental protection.

On the Non-linear Motion of IGS Station

With the daily SINEX files of the IGS, the time series of IGS stations are obtained using an independently developed software under generalized network adjustment models with coordinate patterns. From the time series, non-linear motions are found. With spectral analysis method, the variation frequency （annual period and semi-annual period） of the site velocity is found. Moreover, the empirical model of the velocity variation of the station has been established by regression analysis method based on the weekly solution coordinate series of the station. With respect to the velocity of the IGS tracking station, it was better to model the variation periodically or to give a velocity periodically using a piece-wise linear function rather than a linear variable to estimate its bias.

Improvement of Urban Impervious Surface Estimation in Shanghai Using Landsat7 ETM+ Data

This paper explores the potential to improve the impervious surface estimation accuracy using a multi-stage approach on the basis of vegetation-impervious surface-soil (V-I-S) model. In the first stage of Spectral Mixture Analysis (SMA) process, pixel purity index, a quantitative index for defining endmember quality, and a 3-dimensional endmember selection method were applied to refining endmembers. In the second stage, instead of obtaining impervious surface fraction by adding high and low albedo fractions directly, a linear regression model was built between impervious surface and high/low albedo using a random sampling method. The urban impervious surface distribution in the urban central area of Shanghai was predicted by the linear regression model. Estimation accuracy of spectral mixture analysis and impervious surface fraction were assessed using root mean square (RMS) and color aerial photography respectively. In comparison with three different research methods, this improved estimation method has a higher overall accuracy than traditional Linear Spectral Mixture Analysis (LSMA) method and the normalized SMA model both in root mean square error (RMSE) and standard error (SE). However, the model has a tendency to overestimate the impervious surface distribution.

Orientation Angle of Molecules at Hexadecane-Water Interface Studied with Total Internal Reflection Second Harmonic Generation

The orientation angle is an important parameter that reflects the structure of molecules at interfaces. In order to obtain this parameter, second order nonlinear spectroscopic techniques including second harmonic generation （SHG） and sum frequency generation-vibrational spec- troscopy （SFG-VS） have been successfully applied through analysis of the nonlinear signal from various polarizations. In some SHG and SFG-VS experiments, total internal reflection （TIR） configuration has been adopted to get enhanced signals. However, the reports on the detailed procedure of the polarization analysis and the calculation of the orientation angle of interracial molecules under TIR configuration are still very few. In this paper, we mea- sured the orientation angles of two molecules at the hexadecane-water interface under TIR and Non-TIR experimental configurations. The results measured from polarization analysis in TIR configuration consist with those obtained from Non-TIR configuration. This work demonstrates the feasibility and accuracy of polarization analysis in the determination of the orientation angle of molecules at the interfaces under TIR-SHG configuration.

Characterization of Rapeseed Oil Using FTIR-ATR Spectroscopy

Fourier transform infrared attenuated total reflectance （FTIR-ATR） spectroscopy was employed to characterize rapeseed oils. The spectral features of rapeseed oils were first investigated. Spectral data was processed using principal component analysis （PCA） and linear discriminant analysis （LDA） to discriminate the oils from three cultivars of rapeseeds. As a result, 100% discrimination accuracy was obtained by LDA. Furthermore, the applicability of FTIR-ATR spectroscopy to characterize the changes of rapeseed oils caused by thermal treatment was studied. The rapeseed oil at 60 ℃ was regularly subjected to spectral measurement, and the spectral changes induced by thermal treatment were analyzed and discussed. This study had demonstrated the good performance of FTIR-ATR spectroscopy in characterizing rapeseed oils.

Remote sensing of spatial patterns of urban renewal using linear spectral mixture analysis： A case of central urban area of Shanghai （1997-2000）

It is very important to integrate remote sensing with urban geography that the spectral mix- ture analysis technique is applied to urban land cover evolvement and its eco-environmental effect. Urban land cover is mainly composed of complicated artifi- cial materials, which is the key factor to limit the de- velopment of the spectral mixture analysis technique. There are two main aspects in which the technique of spectral mixture analysis is applied to urban geog- raphy: one is to calculate vegetation fraction; the other is to build quantitative model of the urban im- pervious surface obtained from the combination be- tween high albedo fraction and low albedo fraction. The technique of spectral mixture analysis is firstly applied to study urban renewal pattern, scale and mode which happened in Shanghai City from 1997 to 2000.

Shaped Pt-Ni nanocrystals with an ultrathin Pt-enriched shell derived from one-pot hydrothermal synthesis as active electrocatalysts for oxygen reduction

Alloy nanocrystals （NCs） of Pt with 3d transition metals, especially Ni, are excellent catalysts for the oxygen reduction reaction （ORR）. In this work, we, for the first time, demonstrated the water phase colloidal synthesis of Pt-M （M = Ni, Co and Fe） alloy NCs with tunable composition and morphology through a facile hydrothermal method. Pt-Ni alloy NCs synthesized with this method presented better ORR activity than commercial Pt/C catalysts. The X-ray energy dispersive spectra （EDS） mapping technique revealed that Pt-enriched shells existed on the as-synthesized Pt-Ni alloy NCs. About two atom thick layered Pt-enriched shells formed on Pts0Nis0 NCs and the thickness of the Pt-enriched shells increased as the Ni content increased. Furthermore, X-ray photoelectron spectroscopy analysis revealed that the oxidation level of the surface Pt atoms on the Pt-Ni alloy NCs decreased compared with monometallic Pt NCs, implying a decrease in the oxophilicity of the surface Pt atoms. Pt-Ni alloy NCs with lower oxophilicity of the surface Pt atoms give higher ORR activity. The most active alloy sample showed 13 times higher specific activity and six times higher mass activity at 0.9 V vs. a reversible hydrogen electrode when compared with commercial Pt/C. Pt-Ni alloy NCs also showed better durability than commercial Pt/C in long term ORR tests.