Building a model-based personalised recommendation approach for tourist attractions from geotagged social media data     

Xiaoyu Sun  Xia Peng  Yiran Chen  Yu Liu 《International Journal of Digital Earth》2019,12(6):661-678

When travelling, people are accustomed to taking and uploading photos on social media websites, which has led to the accumulation of huge numbers of geotagged photos. Combined with multisource information (e.g. weather, transportation, or textual information), these geotagged photos could help us in constructing user preference profiles at a high level of detail. Therefore, using these geotagged photos, we built a personalised recommendation system to provide attraction recommendations that match a user's preferences. Specifically, we retrieved a geotagged photo collection from the public API for Flickr (Flickr.com) and fetched a large amount of other contextual information to rebuild a user's travel history. We then created a model-based recommendation method with a two-stage architecture that consists of candidate generation (the matching process) and candidate ranking. In the matching process, we used a support vector machine model that was modified for multiclass classification to generate the candidate list. In addition, we used a gradient boosting regression tree to score each candidate and rerank the list. Finally, we evaluated our recommendation results with respect to accuracy and ranking ability. Compared with widely used memory-based methods, our proposed method performs significantly better in the cold-start situation and when mining ‘long-tail’ data.  相似文献   

北半球热带中太平洋与印度洋海表温度梯度对夏季西北太平洋热带气旋生成频数变化的影响     

方珂  余锦华 《热带海洋学报》2019,38(5):42-51

基于1951—2018年哈德里中心海温资料、美国气象环境预报中心和美国国家大气研究中心再分析资料和第四代欧洲中心汉堡模式, 针对1994年、2018年等西北太平洋热带气旋(TC)生成异常多的年份, 研究了引起TC增加的海表温度异常(SSTA)模态及其影响机制。结果表明, 北半球热带中太平洋增暖与印度洋变冷是夏季西北太平洋TC生成频数增加的主要原因, 北大西洋负三极型式SSTA促使TC生成的进一步增加。热带中太平洋增暖与印度洋冷却在菲律宾以东激发出西风异常和气旋性环流异常。北大西洋负三极型式SSTA在我国南海、菲律宾至东南沿岸激发出气旋性环流异常。前者在西北太平洋中部, 后者在南海产生有利于TC生成的局地环境。1994年和2018年夏季热带中太平洋出现暖SSTA、印度洋为冷SSTA、北大西洋呈现负三极型式SSTA, 西北太平洋TC生成频数极端增多。近30年来, 当出现热带中太平洋增暖和印度洋冷却时, 北大西洋表现出比1989年以前更强的负三极型式SSTA, 使西北太平洋TC生成频数和北半球热带印度洋-太平洋SSTA梯度的线性相关更显著。  相似文献   

三维复杂地壳结构非线性走时反演   总被引：2，自引：1，他引：1       下载免费PDF全文

俞贵平  徐涛  张明辉  白志明  刘有山  武澄泷  滕吉文 《地球物理学报》2017,60(4):1398-1410

中国大陆中西部乃至全球造山带普遍具有复杂地壳结构.随着矿产资源勘探和深部探测研究的深入,探测造山带及盆山耦合区下方地壳精细结构正逐渐成为当前面临的巨大挑战.人工源深地震测深方法正越来越清晰地揭示出不同构造域地壳速度结构的基本特征,然而传统的层状结构模型参数化方法难以准确描述复杂地质模型,通常情况下多忽略速度结构的精细间断面且采用层边界平滑处理,难以满足地壳精细结构成像的发展要求.针对上述困难,本文采用最近发展的块状结构建模方案构建三维复杂地壳模型,基于逐段迭代射线追踪正演走时计算方法,推导了走时对三角形界面深度以及网格速度的偏导数,开展了非线性共轭梯度走时反演方法研究.发展了利用直达波和反射波等多震相走时数据对界面深度和网格速度的多参数联合反演方法,并引人不同种类震相数据的权系数和不同类型参数偏导数归一化的方法.数值算例表明,基于块状结构的非线性共轭梯度走时反演方法适用于复杂地壳结构模型,在利用人工源走时数据反演复杂地壳精细结构领域具有良好的应用前景.  相似文献   

Evaluation of a probabilistic approach to simulation of alkalinity and electrical conductivity at a river bank filtration site     

A. K. Thakur  V. P. Singh  C. S. P. Ojha 《水文研究》2012,26(22):3362-3368

In river bank filtration, impurities present in the river water travel with the bank filtrate towards the pumping well. During this passage, certain types of impurities, such as turbidity, total coliform, and so forth, may get attenuated; however, it is interesting to note that some of the instant raw river water quality parameters, such as alkalinity and electrical conductivity, increase after the passage of water through the porous medium. This occurs because water, when passing through the soil pores, absorbs many of the solutes that cause an increase in alkalinity and electrical conductivity. Measurements at a river bank filtration site for a year showed that alkalinity of 116–32 mg l^?1 in river water increased to 222.4–159.9 mg l^?1 in the river bank filtered water. Likewise, the electrical conductivity increased from 280–131 μS cm^?1 to 462–409.6 μS cm^?1. This study uses a probabilistic approach for investigating the variation of alkalinity and electrical conductivity of source water that varies with the natural logarithm of the concentration of influent water. The probabilistic approach has the potential of being used in simulating the variation of alkalinity and electrical conductivity in river bank filtrate. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

One‐dimensional consolidation with a threshold gradient: a Stefan problem with rate‐dependent latent heat     

Yang Zhou  Wan‐kui Bu  Meng‐meng Lu 《国际地质力学数值与分析法杂志》2013,37(16):2825-2832

During the process of one‐dimensional consolidation with a threshold gradient, the seepage front moves downward gradually, and the problem is indicated as a Stefan problem. The novel feature in this Stefan problem is a latent heat that varies inversely with the rate of the moving boundary. An exact solution for the external load that increases in proportion to the square root of time is constructed using the similarity transformation technique. Computational examples concerning the effect of different parameters on the motion of the seepage front are presented. The exact solution provides a worthwhile benchmark for verifying the accuracy of numerical and approximate methods. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

有限尺度李雅普诺夫指数与海表温度梯度相关性的初步分析     

曹蕾  张杰  杨俊钢  周超杰  孙伟富  崔伟 《海洋科学进展》2020,38(1):130-139

为了探究海表温度和海面高度之间的瞬时相关性,介绍了一种卫星测高数据的拉格朗日分析指数--有限尺度李雅普诺夫指数(Finite Size Lyapunov Exponent,FSLE),以黑潮延伸体区域的涡旋和南大西洋的亚南极锋为例,通过对观测、模式结果和融合产品结果的分析,探讨了该指数与海表温度梯度(Sea Surface Temperature Gradient,SSTG)之间的相关性。比较FSLE图像和SSTG图像发现,FSLE与SSTG均呈丝状结构,对海洋表层水体结构描述具有一致性,尤其在温度梯度大和地转流强的区域更为一致。二者的一致性要远好于其他常用方式,比如全流速、OW参数涡旋识别方法和Winding-Angle涡旋识别方法。不同区域FSLE与SSTG之间的相关性表现不同,黑潮延伸体区域相关系数存在显著的季节变化,而南大西洋亚南极锋区域季节内变化突出。  相似文献   

预处理共轭梯度法解病态问题及在GPS中的应用     

张同兵  谢建  朱建军 《测绘工程》2010,19(4):60-63

介绍测量数据处理中病态问题的岭估计思想及确定岭参数的方法。引入预处理共轭梯度法求解病态法方程组,说明算法的基本原理和它能有效减弱病态性的原因。用一个GPS差分动态定位的实例,通过与不同岭估计方法的对比分析,验证该方法是一个有效的数值迭代算法。  相似文献   

Rainfall,runoff and shallow groundwater response in a mixed-use,agro-forested watershed of the northeast,USA     

Kaylyn S. Gootman  Jason A. Hubbart 《水文研究》2021,35(8):e14312

Stream and shallow groundwater responses to rainfall are characterized by high spatial variability, but hydrologic response variability across small, agro-forested sub-catchments remains poorly understood. Conceivably, improved understanding in this regard will result in agricultural practices that more effectively limit nutrient runoff, erosion, and pollutant transport. Terrestrial hydrologic response approaches can provide valuable information on stream-aquifer connectivity in these mixed-use watersheds. A study was implemented, including eight stream and co-located shallow groundwater monitoring sites, in a small sub-catchment of the Chesapeake Bay watershed in the Northeast, USA to advance this ongoing need. During the study period, 100 precipitation-receiving days (i.e., 24-hour periods, midnight to midnight) were observed. On average, the groundwater table responded more to precipitation than stream stage (level change of 0.03 vs. 0.01 m and rainfall-normalized level change estimate of 3.81 vs. 3.37). Median stream stage responses, groundwater table responses, and response ratios were significantly different between sub-catchments (n = 8; p < 0.001). Study area average precipitation thresholds for runoff and shallow groundwater flow were 2.8 and 0.6 cm, respectively. Individual sub-catchment thresholds ranged from 0.5 to 2.8 cm for runoff and 0.2 to 1.3 cm for shallow groundwater flow. Normalized response lag times between the stream and shallow groundwater ranged from −0.50 to 3.90 s·cm⁻¹, indicating that stormflow in one stream section was regulated by groundwater flow during the period of study. The observed differences in hydrologic responses to precipitation advance future modelling efforts by providing examples of how terrestrial groundwater response methods can be used to investigate sub-catchment spatial variability in stream-aquifer gradients with co-located shallow groundwater and stream stage data. Additionally, results demonstrate asynchronous stream and shallow groundwater responses on precipitation-receiving days, which may hold important implications for modelling hydrologic and biogeochemical fate and transport processes in small, agro-forested catchments.  相似文献   

Threshold criterion for debris flow initiation in seasonal gullies   总被引：1，自引：0，他引：1  

Yang Wang  Peng Cui  Zhaoyin Wang  Shuangqing Liang 《国际泥沙研究》2017,32(2)

A series of flume experiments were done to investigate the effect of grain composition on the critical gradient and discharge of debris flows initiated in seasonal gullies. The results indicated that the critical gradient and discharge for debris flow initiation decrease initially, and then increase as the mass content of fine particles (<2 mm) increases. As the mass content of fine particles increases, the angle of repose, permeability of widely graded gravel soils, and the incipient motion conditions of the coarse grains in non-uniform sediments decrease at first, and then increase. The mass content of fine particles of all inflection points is the same. The theoretical model based on the combination of hydrodynamic force and shear stress is more applicable to the prediction of the critical gradient for debris flow initiation. The critical discharge model considering the effect of non-homogeneity of the soil and the size of coarse and fine grains provides a more accurate prediction of debris flow initiation than other models based on the mean diameter.  相似文献   

Soil water movement under a bottomland hedgerow during contrasting meteorological conditions     

R. Ghazavi  Z. Thomas  Y. Hamon  Ph. Merot 《水文研究》2011,25(9):1431-1442

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