Analysis on urban lake change during rapid urbanization using a synergistic approach: A case study of Wuhan,China     

《Physics and Chemistry of the Earth》2015

To grasp the evolution of urban lakes accurately is quite necessary for studying on the mechanism of city ecological development. The study about extraction with different types of water by remote sensing technology has developed for decades. Many water indexes as the main methods are used to extract water information. Each method has advantage and disadvantage in different situation. A synergistic approach in this study can reduce the uncertainty of urban lake extraction by using four methods: NDWI, MNDWI, RNDWI and SPM. The basic idea behind the synergistic approach is to give each pixel a score based upon the agreement among the different products of four water extraction methods. According to the score of each pixel, the synergy map, which has been created by the products of four methods, is decomposed into sixteen sub-synergy maps. We use Bayesian Decision Theory to screen out the sub-synergy maps with low confidence level. The remaining ones are recombined a refined map. The overall accuracy of refined map reaches 96.44%, higher than any one of the four methods. Wuhan, known as the City of Hundred Lakes, is selected as the study area. We use the synergistic method to keep track of twenty lakes in Wuhan City changing from 1990 to 2013. The total area of twenty lakes has reduced from 130.2478 km² to 102.2971 km² during twenty-three years. The area of Shaihu Lake, which is the most serious of all observed lakes, has shrunk by 77.27%. And Nanhu Lake has lost 8.5 km² of its area that is the most among all lakes. We also find 1990–2000 is the high tide of urban lake shrinking. After the year of 2000, the situation of lake shrinking has been controlled gradually.  相似文献   

概率度量空间的一个不动点定理     

张敏先 《成都信息工程学院学报》1987,(2)

1972年以来,由于随机泛函分析理论的发展,国内外不少数学家对概率度量空间的拓扑结构及压缩型不动点定理和迭代序列逼近等问题作过深入的讨论(见引文[1-5]),本文的目的是对文[1.2]的结果作进一步推论。  相似文献   

A note on tidal current rotation     

Noel?CarbajalEmail author 《Ocean Dynamics》2004,54(5):531-536

The rotational form of the vertically averaged equations of motion is applied to derive a formula, linear friction included, which establishes a direct connection between sense of rotation of tidal currents and features of tidal amphidromic systems. Two factors in the formula, called and , influence the sense of rotation of tidal currents; the factor involves the frequency of the tidal signal , the Coriolis parameter f, and the linear friction coefficient r. The sign of the cross-product of the logarithm of sea-surface elevation (), and phase () gradients determines whether the factor favors clockwise or anticlockwise sense of rotation. is a unit vector and is the angle between ln and . The limits ||0, ||0 and 0 lead to a clockwise sense of rotation in the Northern Hemisphere. 0 favors anticlockwise rotation in the Northern Hemisphere. Friction and low frequencies favor an anticlockwise sense of rotation. The theory works well in semi-enclosed regions like the North Sea. Although only linear friction and sea-surface elevation gradients were considered, there are ocean regions where the agreement between theory and observations is also good.Responsible Editor: Hans Burchard  相似文献   

The uses of value     

Daniel Miller   《Geoforum》2008,39(3):1122-1132

This paper proposes a new theory of value based on the observation of how people use this term. In everyday life the word value is commonly used to refer equally to what might be regarded as the incommensurable polarity between value as price, and value as priceless, sometimes portrayed as the contrast between value and values. My theory starts from trying to learn how people manage to use value as a means of bridging this divide. As such it opposes itself to ‘bottom-line’ theories of value. These range from vulgarised forms of Marx’s labour theory of value, to the way management consultants tried to impose a universal belief in shareholder value. An example is provided of how such bottom-line thinking undermined a UK government audit called best-value, and is also found in highly reductionist attempts to impose new-age values in management. By contrast, examples are given of how value is created in the process of bridging the divide between value and values, starting from the work of Zelizer and the case of concubines in 5th century BC Athens. Further examples range from the department store John Lewis to the Swedish social democratic state. Finally the application of this theory is considered in relation to a recent attempts to evaluate the impact of the mobile phone on low-income Jamaicans.  相似文献   

Exploring marine spatial planning education: Challenges in structuring transdisciplinarity     

《Marine Policy》2016

Marine Spatial Planning (MSP) has experienced vigorous growth on the international scale in recent years, and several practices has emerged from different countries. The demand for specific training in the preparation and implementation of marine planning has therefore already shown itself to be quite relevant on a global scale. Educational initiatives related to MSP have to respond to the increased complexity of MSP, which integrates environmental and economic perspectives on marine resources and maritime sectors, considering governance framework as well as maritime affairs and legislation.This paper aims at addressing the educational and training needs for the development of both academic education and professional training in MSP. Learning skills, contents and methods of an ‘ideal’ MSP course are depicted from widely accepted operative guides on MSP and from the EU Framework Directive on MSP (2014/89/EU). They are considered for the analysis of the current educational offer around MSP, performed in a sample of countries that have already undergone a process of implementation of MSP by Law. As result, beside the great variety of courses, it emerges that MSP education seems to be often regarded from an environmental perspective – in continuity with Integrated Coastal Management education – while planning theory and experiences in MSP are the least represented contents. Results are discussed in relation to three major challenges: i) how educational offer reflects on transdisciplinarity, ii) the role of theory in MSP courses, and iii) the enforceability of Plans as major concern in MSP.  相似文献   

New constraints on neutrino masses from cosmology     

Alessandro Melchiorri  Scott Dodelson  Paolo Serra  Ane Slosar 《New Astronomy Reviews》2006,50(11-12):1020

By combining data from cosmic microwave background (CMB) experiments (including the recent WMAP third year results), large scale structure (LSS) and Lyman-α forest observations, we derive upper limits on the sum of neutrino masses of Σm_ν < 0.17 eV at 95% c.l. We then constrain the hypothesis of a fourth, sterile, massive neutrino. For the third massless +1 massive neutrino case we bound the mass of the sterile neutrino to m_s < 0.26 eV at 95% c.l. These results exclude at high significance the sterile neutrino hypothesis as an explanation of the LSND anomaly. We then generalize the analysis to account for active neutrino masses which tightens the limit to m_s < 0.23 eV and the possibility that the sterile abundance is not thermal. In the latter case, the constraints in the (mass, density) plane are non-trivial. For a mass of >1 eV or <0.05 eV the cosmological energy density in sterile neutrinos is always constrained to be ω_ν < 0.003 at 95% c.l. However, for a sterile neutrino mass of 0.25 eV, ω_ν can be as large as 0.01.  相似文献   

Non-circular beam correction to the CMB power spectrum     

Tarun Souradeep  Sanjit Mitra  Anand Sengupta  Subharthi Ray  Rajib Saha   《New Astronomy Reviews》2006,50(11-12):1030

In the era of high precision CMB measurements, systematic effects are beginning to limit the ability to extract subtler cosmological information. The non-circularity of the experimental beam has become progressively important as CMB experiments strive to attain higher angular resolution and sensitivity. The effect of non-circular beam on the power spectrum is important at multipoles larger than the beam-width. For recent experiments with high angular resolution, optimal methods of power spectrum estimation are computationally prohibitive and sub-optimal approaches, such as the Pseudo-C_l method are used. We provide an analytic framework for correcting the power spectrum for the effect of beam non-circularity and non-uniform sky coverage (including incomplete/masked sky maps). The approach is perturbative in the distortion of the beam from non-circularity allowing for rapid computations when the beam is mildly non-circular. We advocate that when the non-circular beams are important, it is computationally advantageous to employ ‘soft’ azimuthally apodized masks whose spherical harmonic transforms die down fast with m.  相似文献   

Detailed insights into the influence of flood-coping appraisals on mitigation behaviour   总被引：1，自引：0，他引：1  

P. Bubeck  W.J.W. Botzen  H. Kreibich  J.C.J.H. Aerts 《Global Environmental Change》2013,23(5):1327-1338

Insights into flood mitigation behaviour are important because of the ongoing shift to risk-based flood management approaches in Europe and worldwide, which envisage a contribution from flood-prone households to risk reduction. The recent literature on factors that influence flood mitigation behaviour indicates that flood-coping appraisal is an important variable to understand and explain flood mitigation behaviour. Coping appraisal originates from Protection Motivation Theory (PMT), and refers to the cognitive process that people undergo when evaluating their own ability to avoid a certain risk. However, the empirical literature on the importance of coping appraisal is still scarce, and, in particular, little is known about the independent influence of the three single components of coping appraisal on precautionary behaviour: namely, response efficacy, self-efficacy, and response cost. This study presents the results of a recent survey among 752 flood-prone households along the river Rhine in order to provide detailed insights into the influence of the components of flood-coping appraisal on four different types of flood mitigation behaviour: structural building measures, adapted building use, the deployment of flood barriers, and the purchase of flood insurance. The results confirm that flood-coping appraisal is an important variable in terms of precautionary behaviour. In particular, both response efficacy and self-efficacy contribute to the models which explain the four different types of flood-mitigation behaviour. Based on these findings, it is concluded that risk communication should focus more strongly on the potential of flood-mitigation measures to effectively reduce or avoid flood damage, as well as on information about how to implement such measures in practice.  相似文献   

砂质碎屑流概念及其在鄂尔多斯盆地延长组深水沉积研究中的应用   总被引：8，自引：1，他引：7  

李相博  付金华  陈启林  刘显阳  刘化清  郭彦如  完颜容  廖建波  魏立花  黄军平 《地球科学进展》2011,26(3):286-294

砂质碎屑流是近年来日益受到重视的一种新的砂体成因类型,其相关理论是对"鲍玛序列"和"浊积扇"等深水沉积理论的部分否定和完善.阐述了砂质碎屑流概念精华与存在问题,指出只有进一步结合我国陆相盆地沉积不断完善该理论,才能提高勘探成功率,从而促进我国石油工业的发展.同时运用砂质碎屑概念,将鄂尔多斯盆地湖盆中心深水区延长组长6段...  相似文献   

译者概念化与语义形成的认知机制研究——兼论翻译过程研究的综合理论方法     

马海燕 《广东海洋大学学报》2011,31(2):64-68

通过融合认知语言学的心理空间和概念整合理论以及语境参数理论,构建一个综合性的理论分析框架,可以对译者在双语转换过程中的动态操作机制进行可证性描述,且多理论融合的研究方法可以拓展译学理论研究的空间。  相似文献