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   

The potential of contribution of mangrove-derived organic matter in intertidal sediments as a proxy of mangrove development in the northern Beibu Gulf     

Jun Zhang  Xianwei Meng  Peng Xia  Xiangqin Wang  Shan Gao 《海洋学报(英文版)》2020,39(12):21-29

Located between terrestrial and marine ecosystems, mangrove forests are sensitive to changes in climate. The responses of mangrove ecosystems to climate change in the future can be understood by reconstructing past mangrove dynamics using proxies preserved in the intertidal sediments. Considering the complexity of the proxies commonly used, it is necessary to develop a relatively simple, inexpensive proxy. In this study, available chemical tracers (δ13C_org and C:N) of the four cores (YLW02, YLW03, O18, and Q37) from the intertidal zone of the northern Beibu Gulf (NBG) and a three-end-member (mangrove, sea grass, and suspended particulate matter) model was utilized to determine the contribution of mangrove-derived organic matter (CMOM) in carbonate-free sediments. Compared with the summed concentration of mangrove pollen (SCMP), a significant positive correlation between CMOM and SCMP is displayed. The calculated CMOM for an additional 210Pb-dated sediment core from the Yingluo Bay, NBG (YLW01) clearly indicates a mangrove development going through degradation, flourishing, relative degradation, and relative flourishing, which are separately in correspondence with the lowest, highest, lower, and higher air temperature and rainfall in the time intervals of 1890–1918 AD, 1919–1956 AD, 1957–1990 AD, and 1991–2010 AD. This suggests that CMOM preserved in intertidal sediments has a potential to reconstruct historical mangrove development in high resolution, at the very least, along the coasts of the NBG.  相似文献   

边带分离型超导SIS接收机本振耦合噪声研究          下载免费PDF全文

李振强  张旭国  李积斌  左营喜  徐烨  张海龙  金风娟 《天文学报》2020,61(2):18-84

超导SIS (Superconductor-Insulator-Superconductor)接收机因极低的接收机噪声温度成为毫米波和亚毫米波段射电天文观测的首选.本振系统耦合噪声也是接收机噪声的一部分,在多年的天文观测中,发现本振耦合噪声无法完全忽略,对天文观测的灵敏度有一定影响.采用两个不同种类的信号发生器作为本振系统初级信号源,测试了超导SIS接收机的噪声温度,发现信号发生器输出的基底噪声能够耦合到接收机内部,从而增加接收机噪声强度.分析研究了本振系统热噪声和信号发生器基底噪声对接收机噪声的影响.通过在信号发生器输入端加入窄带滤波器滤除其基底噪声,消除了信号发生器基底噪声引入的接收机噪声,降低了接收机的整体噪声,提高了望远镜的灵敏度.  相似文献   

尼日尔三角洲东部深水区构造特征及其形成机理     

赵江  王秋良  卢圣力  付博  杜峰 《大地测量与地球动力学》2019,39(7):691-695

研究尼日尔三角洲东部深水区块发现，整个盆地从陆向洋具有3个大的构造分区：伸展拉张区、过渡区和挤压逆冲区。伸展区以大型同沉积断层伴生大量滚动背斜构造为特征，过渡区发育大量泥底辟构造，挤压区以复杂的逆冲叠瓦构造为主。通过分析形成机理，揭示东部深水转换带上M研究区构造特征，按构造的演化特征将该区构造分为泥底辟型、冲断-泥底辟混合型、逆冲型3种类型，提出研究区内的圈闭主要以构造-岩性圈闭为主，为尼日尔三角洲盆地深水勘探提供新的理论指导。  相似文献   

海水温度对衰亡期浒苔释放生源硫影响的模拟研究   总被引：1，自引：0，他引：1  

韩露  邓雪  李培峰  高先池  刘春颖 《海洋学报》2018,40(10):110-118

为研究浒苔释放生源硫的特征，本文对采集于黄海绿潮中期和末期的浒苔进行了实验室模拟培养，探讨了不同温度对衰亡期浒苔释放生源硫化物的影响。实验结果表明，在10~25℃温度范围内，温度升高能够加速浒苔的衰亡。二甲基硫（DMS）的平均释放速率范围为2.79~150.70 nmol/（L·g·d），二甲基硫基丙酸内盐（DMSP）的平均释放速率范围为2.16~113.26 nmol/（L·g·d）。温度升高能够使DMS和DMSP的释放速率加快，释放量增加，DMS最大平均释放速率在25℃条件下比10℃条件下升高了约60%，培养液中DMS浓度升高了2~3倍。采集于绿潮末期的浒苔培养液中的DMS和DMSP和采集于绿潮中期的浒苔相比，浓度有所增加，采集于浒苔绿潮末期浒苔培养液中DMS的最高平均浓度为418.41 nmol/L，约为中期的4倍；DMSP的最高平均浓度为316.14 nmol/L，是中期的3倍。浒苔绿潮的爆发会对水体中的硫体系循环产生影响，进而影响该海域生态环境。  相似文献   

Galileo广播星历评估及其对定位精度的影响     

韩德强  党亚民  庞辉  薛树强  杨强  张龙平 《大地测量与地球动力学》2018,38(11):1165-1169

分析现阶段伽利略空间信号的精度，并评估伽利略广播星历及其对单点定位的影响。统计30 d健康卫星广播星历，结果表明，FOC和IOV两种类型的广播星历卫星轨道误差优于0.8 m，并且径向误差最小，法向误差次之，切向误差最大；伽利略卫星的钟差误差精度达到1.0 ns；从空间信号测距误差对伽利略卫星进行整体分析，广播星历精度优于1.0 m，FOC与IOV卫星精度相当；用广播星历进行事后单点定位的精度可以达到dm级。  相似文献   

On the dependence of the saturated hydraulic conductivity upon the effective porosity through a power law model at different scales          下载免费PDF全文

Carmine Fallico  Samuele De Bartolo  Massimo Veltri  Gerardo Severino 《水文研究》2016,30(13):2366-2372

We study the scale dependence of the saturated hydraulic conductivity K_s through the effective porosity n_e by means of a newly developed power‐law model (PLM) which allows to use simultaneously measurements at different scales. The model is expressed as product between a single PLM (capturing the impact of the dominating scale) and a characteristic function κ^? accounting for the correction because of the other scale(s). The simple (closed form) expression of the κ^?‐function enables one to easily identify the scales which are relevant for K_s. The proposed model is then applied to a set of real data taken at the experimental site of Montalto Uffugo (Italy), and we show that in this case two (i.e. laboratory and field) scales appear to be the main ones. The implications toward an important application (solute transport) in Hydrology are finally discussed. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Modelling and experimental study of coupled exchange of p,p′‐DDE and colloids in a flume simulated stream–streambed system          下载免费PDF全文

Celina Camarena  Doris Otero  Jianhong Ren 《水文研究》2016,30(1):40-56

Stream–subsurface exchange plays a significant role in the fate and transport of contaminants in streams. It has been modelled explicitly by considering fundamental processes such as hydraulic exchange, colloid filtration, and contaminant interactions with streambed sediments and colloids. The models have been successfully applied to simulate the transport of inorganic metals and nutrients. In this study, laboratory experiments were conducted in a recirculating flume to investigate the exchange of a hydrophobic organic contaminant, p,p′‐dichloro‐diphenyl‐dichloroethane (DDE), between a stream and a quartz sand bed. A previously developed process‐based multiphase exchange model was modified by accounting for the p,p′‐DDE kinetic adsorption to and desorption from the bed sediments/colloids and was applied to interpret the experimental results. Model input parameters were obtained by conducting independent small‐scale batch experiments. Results indicate that the immobilization of p,p′‐DDE in the quartz sand bed can occur under representative natural stream conditions. The observed p,p′‐DDE exchange was successfully simulated by the process‐based model. The model sensitivity analysis results show that the exchange of p,p′‐DDE can be sensitive to either the sediment sorption/desorption parameters or colloidal parameters depending on the experimental conditions tested. For the experimental conditions employed here, the effect of colloids on contaminant transport is expected to be minimal, and the stream–subsurface exchange of p,p′‐DDE is dominated by the interaction of p,p′‐DDE with bed sediment. The work presented here contributes to a better mechanistic understanding of the complex transport process that hydrophobic organic contaminants undergo in natural streams and to the development of reliable, predictive models for the assessment of impacted streams. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

The potential of Pléiades images with high angle of incidence for reconstructing the coastal cliff face in Normandy (France)     

《International Journal of Applied Earth Observation and Geoinformation》2020

To monitor chalk cliff face along the Normandy coast (NW France) which is prone to erosion, we tested the potential of cliff face 3D reconstruction using pairs of images with high angle of incidence at different dates from the agile Pléiades satellites. The verticality aspect of the cliff face brings difficulties in the 3D reconstruction process. Furthermore, the studied area is challenging mainly because the cliff face is north-oriented (shadow). Pléiades images were acquired over several days (multi-date stereoscopic method) with requested incidence angles until 40°. 3D reconstructions of the cliff face were compared using two software: ASP® and ERDAS IMAGINE®. Our results are twofold. Firstly, despite ASP® provides denser point clouds than ERDAS IMAGINE® (an average of 1.60 points/m² from 40° incidence angle stereoscopic pairs on the whole cliff face of Varengeville-sur-Mer against 0.77 points/m² respectively), ERDAS IMAGINE® provides more reliable point clouds than ASP® (precision assessment on the Varengeville-sur-Mer cliff face of 0.31 m ± 2.53 and 0.39 m ± 4.24 respectively), with a better spatial distribution over the cliff face and a better representation of the cliff face shape. Secondly, the quality of 3D reconstructions depends mostly on the amount of noise from raw images and on the shadow intensity on the cliff face (radiometric quality of images).  相似文献   

基于像元二分模型的地表植被覆盖度估算模块化设计与实现     

赵威成  张红华  马福义  叶欣 《北京测绘》2020,(3):285-288

地表植被覆盖度是的一种应用广泛的定量遥感产品,在水文、生态、区域变化等方面都具有重要的意义。像元二分模型是应用最多的一种遥感估算地表覆盖度的方法。目前,用遥感的方法进行地表植被覆盖度估算没有完整、系统的工具,用户只能逐步进行操作,效率低下,鉴于上述情况,本文运用IDL交互式数据语言,基于ENVI二次开发了一个植被覆盖度估算程序,取得了一定的成效,对遥感定量产品的生产、应用具有一定意义。  相似文献