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1.
Understanding diverse characteristics of human mobility provides profound knowledge of urban dynamics and complexity. Human movements are recorded in a variety of data sources and each describes unique mobility characteristics. Revealing similarity and difference in mobility data sources facilitates grasping comprehensive human mobility patterns. This study introduces a new method to measure similarities on two origin–destination (OD) matrices by spatially extending an image‐assessment tool, the structural similarity index (SSIM). The new measurement, spatially weighted SSIM (SpSSIM), utilizes weight matrices to overcome the SSIM sensitivity issue due to the ordering of OD pairs by explicitly defining spatial adjacency. To evaluate SpSSIM, we compared performances between SSIM and SpSSIM with resampling the orders of OD pairs and conducted bootstrapping to test the statistical significance of SpSSIM. As a case study, we compared OD matrices generated from three data sources in San Diego County, CA: U.S. Census‐based Longitudinal Employer–Household Dynamics Origin–Destination employment statistics, Twitter, and Instagram. The case study demonstrated that SpSSIM was able to capture similarities of mobility patterns between datasets that varied by distance. Some regions showed local dissimilarity while the global index indicated they were similar. The results enhance the understanding of complex mobility patterns from various datasets, including social media. 相似文献
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主要探讨水稻田休耕期间蓄水对休耕后土壤肥力之影响。选择两块水稻田区,在水稻收割后,将田区翻耕一次。一田区以人工连续灌溉,蓄存水量于田区;另一田区则为天然蓄水。在每一田区四边及中央处,以10cm为一层采取土样,取至60cm。再将每一层土样气干后,通过0.42mm筛网土样混合,分析田区同一层在不同时段与不同深度下之pH值、电导度值、有机质、全氮、有效磷、钙离子、镁离子、钾离子及钠离子之变化。试验结果显示:休耕后水稻根系腐化,造成土壤有机质以及有效磷显著的增加。蓄水后天然蓄水田区有机质和有效磷分别增加51%及88%,连续蓄水田区分别增加13%和69%。而天然蓄水田区镁、钾、钠分别降低35%、24%和47%,连续蓄水田区分别降低29%、14%及41%。 相似文献
3.
Yuanzhi Zhang Hongtao Duan Hongyan Xi Zhaojun Huang JinYeu Tsou Tingchen Jiang 《大气与海洋》2018,56(4):277-288
AbstractAquatic plants and lake bottoms in optically shallow waters (OSWs) wield great influence on reflectance spectra, resulting in the inapplicability of most existing bio-optical models for water colour remote sensing in lakes. Based on radiative transfer theory and measured spectra from a campaign for Lake Taihu in October 2008, absorption and backscattering coefficients were used to simulate the remote-sensing reflectance, which are considered to be reliable if matched to their measured counterparts. Several cases of measured spectra at different depths, Secchi disk depth transparency, and aquatic plant height and coverage were analyzed thoroughly for spectral properties. The contribution of aquatic plants was evaluated and compared with the measured and simulated remote-sensing reflectance values. This is helpful for removing the influence of aquatic plants and lake bottoms from the spectra and for constructing an improved chlorophyll a retrieval model for OSWs, such as that for Lake Taihu, China. 相似文献
4.
Ick-Hoi Kim Chen-Chieh Feng Yi-Chen Wang Brian H. Spitzberg Ming-Hsiang Tsou 《The Professional geographer》2017,69(4):629-643
The 2015 Middle East respiratory syndrome (MERS) outbreak in South Korea gave rise to chaos caused by psychological anxiety, and it has been assumed that people shared rumors about hospital lists through social media. Sharing rumors is a common form of public perception and risk communication among individuals during an outbreak. Social media analysis offers an important window into the spatiotemporal patterns of public perception and risk communication about disease outbreaks. Such processes of socially mediated risk communication are a process of meme diffusion. This article aims to investigate the role of social media meme diffusion and its spatiotemporal patterns in public perception and risk communication. To do so, we applied analytical methods including the daily number of tweets for metropolitan cities and geovisualization with the weighted mean centers. The spatiotemporal patterns shown by Twitter users' interests in specific places, triggered by real space events, demonstrate the spatial interactions among places in public perception and risk communication. Public perception and risk communication about places are relevant to both social networks and spatial proximity to where Twitter users live and are interpreted in reference to both Zipf's law and Tobler's law. 相似文献
5.
Lanxue Dang Zhuo Chen Ming-Hsiang Tsou 《International journal of geographical information science》2019,33(8):1545-1568
This article reports the findings from simulating the spatial diffusion processes of memes over social media networks by using the approach of agent-based modeling. Different from other studies, this article examines how space and distance affect the diffusion of memes. Simulations were carried out to emulate and to allow assessment of the different levels of efficiency that memes spread spatially and temporally. Analyzed network structures include random networks and preferential attachment networks. Simulated spatial processes for meme diffusion include independent cascade models and linear threshold models. Both simulated and real-world social networks were used in the analysis. Findings indicate that the numbers of information sources and opinion leaders affect the processes of meme diffusion. In addition, geography is still important in the processes of spatial diffusion of memes over social media networks. 相似文献
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Traditional GISystems are no longer appropriate for modern distributed, heterogeneous network environments due to their closed architecture, and their lack of interoperability, reusability, and flexibility. Distributed GIServices can provide broader capabilities and functions for data management, browsing, and exchange. This paper introduces a dynamic architecture for distributing GIServices. The term dynamic indicates that the architecture is constructed temporarily by connecting or migrating geodata objects and GIS components across a network. The intention of the paper is to overview components and protocols necessary for a workable implementation of dynamically linked GIServices. The paper introduces a metadata scheme for both geodata objects and software components, and proposes an implementation framework based on existing languages, computing architectures and web services. In the framework, GIS nodes form the basic processing unit. All GIServices can be accomplished through collaboration between GIS nodes. The design of the presented framework emphasizes scalability, reusability, and dynamic integration. Current distributed computing environments cannot fully support dynamic architectures for technical and other reasons. Throughout the discussion, we distinguish what currently can be implemented from what cannot. We summarize costs and benefits of adopting a dynamic GIServices paradigm in a final section. 相似文献
7.
E. Grün Z. Sternovsky M. Horanyi V. Hoxie S. Robertson J. Xi S. Auer M. Landgraf F. Postberg M.C. Price R. Srama N.A. Starkey J.K. Hillier I.A. Franchi P. Tsou A. Westphal Z. Gainsforth 《Planetary and Space Science》2012,60(1):261-273
The Stardust mission returned two types of unprecedented extraterrestrial samples: the first samples of material from a known solar system body beyond the moon, the comet 81P/Wild2, and the first samples of contemporary interstellar dust. Both sets of samples were captured in aerogel and aluminum foil collectors and returned to Earth in January 2006. While the analysis of particles from comet Wild 2 yielded exciting new results, the search for and analysis of collected interstellar particles is more demanding and is ongoing.Novel dust instrumentation will tremendously improve future dust collection in interplanetary space: an Active Cosmic Dust Collector is a combination of an in-situ dust trajectory sensor (DTS) together with a dust collector consisting of aerogel and/or other collector materials, e.g. such as those used by the Stardust mission. Dust particles’ trajectories are determined by the measurement of induced electrical signals when charged particles fly through a position sensitive electrode system. The recorded waveforms enable the reconstruction of the velocity vector with high precision.The DTS described here was subject to performance tests at the Heidelberg dust accelerator at the same time as the recording of impact signals from potential collector materials. The tests with dust particles in the speed range from 3 to 40 km/s demonstrate that trajectories can be measured with accuracies of ～1° in direction and ～1% in speed. The sensitivity of the DTS electronics is of the order of 10?16 C and thus the trajectory of cosmic dust particles as small as 0.4 μm size can be measured. The impact position on the collector can be determined with better than 1 mm precision, which will ease immensely the task of locating sub-micron-sized particles on the collector. Statistically significant numbers of trajectories of interplanetary and interstellar dust particles can thus be collected in interplanetary space and their compositions correlated with their trajectories. 相似文献
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Coupling fluvial processes and landslide distribution toward geomorphological hazard assessment: a case study in a transient landscape in Japan 总被引：1，自引：0，他引：1
Ching-Ying Tsou Masahiro Chigira Yuki Matsushi Narumi Hiraishi Noriyuki Arai 《Landslides》2017,14(6):1901-1914
This study quantified the relationship among deep-seated gravitational slope deformations (DGSDs), landslides, and river rejuvenation in the upper reaches of the Kumano River in the Kii Mountains of Japan, an area of frequent bedrock landslides. River profiles and hillslope landforms were examined, and high-resolution digital elevation models (DEMs) were used to identify DGSDs and landslides. Many of the deep-seated landslides were associated with rainstorms in 1889 and 2011. Landslide volumes were related to landslide areas on the basis of 52 deep-seated landslides that failed during the 2011 rainfall, providing basic data for landscape denudation and sediment yield. River rejuvenation occurred stepwise, incising moderate relief paleosurfaces and forming two series of knickpoints and V-shaped inner gorges that are up to 400-m deep. More than 65% of DGSDs and 75% of the landslides were located in association with the incised inner gorges along the peripheries of the paleosurfaces or were entirely contained within the inner gorges. DGSDs and landslides associated with the incised inner valley slopes tended to be larger than those developed within the paleosurfaces and may be long-term transient hillslope responses to river incision. Hillslope undercutting caused by rejuvenated river incision may play an important role in long-term slope stability and distribution of mass movements, and could serve as an indicator of landslide hazard. 相似文献
9.
In Florida, issues related to alterations of estuarine salinity caused by freshwater withdrawal have recently gained increasing attention. We examined nekton community structure in the Suwannee River estuary (1997–2000) and investigated the relationship between environmental factors and the abundance of fisheries resources. We compared nekton community structure and environmental factors seasonally and annually using multidimensional scaling (MDS) ordination and cluster analysis and observed a strong seasonal pattern. This pattern was consistent among years and closely paralleled those for temperature and river discharge. Representative species for cold seasons includedLeiostomus xanthurus andLagodon rhomboides, and those for warm seasons includedMembras martinica andAnchoa hepsetus. Species that contributed most to the dissimilarity in community structures between wet and dry seasons were abundant and generally preferred lower salinity (e.g.,L. xanthurus, Eucinostomus spp., andMenidia spp.). A period of low freshwater inflow during the latter portion of our study coincided with both decreases and increases in the abundances of some dominant and some economically important species. We have established a baseline which will assist in measuring the effects of long-term changes in freshwater input on the nekton communities of the Suwannee River estuary, but our ability to predict these effects is still limited. 相似文献
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