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91.
Shihong Du Xiaonan Wang Chen-Chieh Feng Xiuyuan Zhang 《International journal of geographical information science》2017,31(3):542-568
The exponential growth of natural language text data in social media has contributed a rich data source for geographic information. However, incorporating such data source for GIS analysis faces tremendous challenges as existing GIS data tend to be geometry based while natural language text data tend to rely on natural language spatial relation (NLSR) terms. To alleviate this problem, one critical step is to translate geometric configurations into NLSR terms, but existing methods to date (e.g. mean value or decision tree algorithm) are insufficient to obtain a precise translation. This study addresses this issue by adopting the random forest (RF) algorithm to automatically learn a robust mapping model from a large number of samples and to evaluate the importance of each variable for each NLSR term. Because the semantic similarity of the collected terms reduces the classification accuracy, different grouping schemes of NLSR terms are used, with their influences on classification results being evaluated. The experiment results demonstrate that the learned model can accurately transform geometric configurations into NLSR terms, and that recognizing different groups of terms require different sets of variables. More importantly, the results of variable importance evaluation indicate that the importance of topology types determined by the 9-intersection model is weaker than metric variables in defining NLSR terms, which contrasts to the assertion of ‘topology matters, metric refines’ in existing studies. 相似文献
92.
运用泛函微分方法给出弱随机介质中散射问题的散射幅度Born近似的推广形式。讨论了关于阻尼最小二乘法反演介质参数的各价相关函数的方法,并讨论具有有限支集势函数扰动的逆问题的唯一性,其结果对运用Newton法等数值方法有实际意义。 相似文献
93.
Coupling land use allocation models with raster GIS 总被引:5,自引:0,他引:5
As geographic information systems (GIS) have moved from information storage and retrieval operations towards more decision
support functions, there is a need for more integration of spatial analytical modules that can assist in locational decisions.
This paper presents a methodology for coupling land use allocation models with a raster GIS. For raster systems, the integration
of any decision module has been limited by the size of raster datasets that may contain hundreds of thousands of pixels. Therefore,
decision heuristics have been used rather than exact methods such as mathematical programming models. For the problem of land
use allocation, the special structure of the generalized assignment problem is used here to handle large scale datasets. The
advantage of the mathematical programming approach is the additional information associated with the dual variables and opportunity
costs that can be used in subsequent sensitivity analyses.
Received: 7 April 1998/Accepted: 2 October 1998 相似文献
94.
鱼类形态特征与营养级位置之间关系初探 总被引:2,自引:0,他引:2
以长江中下游洪泛平原湖泊鱼类为例,探讨鱼类功能性形态特征与其营养级位置之间的关系.所用的116种鱼的食性数据来自于226个鱼类群落,总计16267尾鱼.用几何形态测量法的界标分析法提取鱼类形态特征,相对扭曲度法的前2个主成份能较好地区分鱼类的形态差异,它不仅能够生成散点图,而且能客观地反映出鱼类的形态性状.营养级位置采用肠含物定量分析法,合理地假定肠含物的营养级位置,利用食性数据计算出鱼类的营养级位置.采用广义加性模型分析鱼类营养级位置与功能性形态之间的关系.结果表明:只有当鱼类为植食性鱼类和肉食性鱼类才有特化的功能性形态与之相适应,植食性鱼类有较窄的口裂,而对肉食性鱼类而言,不同生活型的鱼类拥有各自特化的形态特征,如伏击型肉食性鱼类体型呈纺锤形,背鳍靠近头部,眼睛较大且靠上,头部面积较大;而追击型肉食性鱼类体型呈流线型,头部较小,背鳍和腹鳍靠近尾部.而杂食性鱼类在本研究中无更多证据证明有特化的外部形态,亟待进一步研究. 相似文献
95.
Z. W. Kundzewicz V. Krysanova R. Dankers Y. Hirabayashi S. Kanae F. F. Hattermann 《水文科学杂志》2017,62(1):1-14
This paper interprets differences in flood hazard projections over Europe and identifies likely sources of discrepancy. Further, it discusses potential implications of these differences for flood risk reduction and adaptation to climate change. The discrepancy in flood hazard projections raises caution, especially among decision makers in charge of water resources management, flood risk reduction, and climate change adaptation at regional to local scales. Because it is naïve to expect availability of trustworthy quantitative projections of future flood hazard, in order to reduce flood risk one should focus attention on mapping of current and future risks and vulnerability hotspots and improve the situation there. Although an intercomparison of flood hazard projections is done in this paper and differences are identified and interpreted, it does not seems possible to recommend which large-scale studies may be considered most credible in particular areas of Europe.
EDITOR D. KoutsoyiannisASSOCIATE EDITOR not assigned 相似文献
96.
Water temperature has a significant influence on aquatic organisms, including stenotherm fish such as salmonids. It is thus of prime importance to build reliable tools to forecast water temperature. This study evaluated a statistical scheme to model average water temperature based on daily average air temperature and average discharge at the Sainte-Marguerite River, Northern Canada. The aim was to test a non-parametric water temperature generalized additive model (GAM) and to compare its performance to three previously developed approaches: the logistic, residuals regression and linear regression models. Due to its flexibility, the GAM was able to capture some of the nonlinear response between water temperature and the two explanatory variables (air temperature and flow). The shape of these effects was determined by the trends shown in the collected data. The four models were evaluated annually using a cross-validation technique. Three comparison criteria were calculated: the root mean square error (RMSE), the bias error and the Nash-Sutcliffe coefficient of efficiency (NSC). The goodness of fit of the four models was also compared graphically. The GAM was the best among the four models (RMSE = 1.44°C, bias = ?0.04 and NSC = 0.94). 相似文献
97.
Hydrologists use the generalized Pareto (GP) distribution in peaks-over-threshold (POT) modelling of extremes. A model with similar uses is the two-parameter kappa (KAP) distribution. KAP has had fewer hydrological applications than GP, but some studies have shown it to merit wider use. The problem of choosing between GP and KAP arises quite often in frequency analyses. This study, by comparing some discrimination methods between these two models, aims to show which method(s) is (are) recommended. Three specific methods are considered: one uses the Anderson-Darling goodness-of-fit (GoF) statistic, another uses the ratio of maximized likelihood (closely related to the Akaike information criterion and the Bayesian information criterion), and the third employs a normality transformation followed by application of the Shapiro-Wilk statistic. We show this last method to be the most recommendable, due to its advantages with sizes typically encountered in hydrology. We apply the simulation results to some flood POT datasets.
EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR E. Volpi 相似文献
98.
采用线性反演法研究了地震动的场地效应,并针对线性反演法的局限性,提出了"传递台站"的方法来扩展其应用.通过传递台站,地震事件不再局限于必须被参考台记录到,台站也不再局限于须与参考台站同时获取到地震记录,改进后可大大增加数据样本,使得结果更趋稳定.同时,对于原来难以参与分析的台站,也可得到其场地反应.研究中,还采用了基于遗传算法的非参考台方法,进一步分析了场地反应和验证所提方法的合理性.将所提方法应用于2013年芦山7.0级地震周边区域,分析了这一地区的强震台站的场地反应和地震波衰减因子Q_s值.研究结果显示,当采用一个和二个传递台站进行分析时,所能利用的地震事件和所能求解场地反应的台站数目逐步增加,随着数据样本的增加,分析结果趋于稳定.研究区域的Q_s值拟合结果为Q_s(f)=334.16f~(0.73).遗传算法结果表明,线性反演法中所选取的参考台站有其自身的场地反应.当利用遗传算法获得的参考场的场地反应去校正线性反演法的结果时,对于多数场地,两者的结果符合得很好,说明了遗传算法的结果可以合理地认为是场地较为真实的反应. 相似文献
99.
针对平面不规则RC框架结构,从构件安全层次出发提出基于传力路径的减震设计方法。首先根据广义结构刚度法的基本原理计算结构中所有构件的重要性系数,再假定消能支撑的截面参数,取每层最重要的构件位置布置支撑,经支撑在最不利地震组合下的轴力验算后确定支撑的最终设计参数和数量,然后考虑远场、近场有脉冲以及近场无脉冲地震动从双向输入对结构响应的影响,对减震前、后结构分别进行动力时程分析。分析结果表明,利用此方法优化布置支撑能为结构中重要构件提供有效保护,且在小、中、大震下消能支撑均能运作良好,使整体结构响应得到很好地控制。 相似文献
100.
针对近海表层沉积物粒度组分空间变异的尺度差异性,提出了基于广义回归神经网络残余kriging的沉积物粒度组分空间预测方法,并以海州湾沉积物粒度数据为基础,分析了其在沉积物粒度组分空间预测和底质类型制图中的应用效果。结果表明,广义回归神经网络残余kriging方法能够获得比普通kriging方法更高的沉积物粒度组分空间预测精度,并且其底质类型的总体空间预测精度达到85%以上,相应的Kappa系数也在0.8以上,显示底质制图的预测类型与样本的实测类型具有较高的一致性。新方法对于开展定量化的沉积物粒度组分空间预测和底质类型制图具有参考价值。 相似文献