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Driving factors and spatiotemporal effects of environmental stress in urban agglomeration: Evidence from the Beijing-Tianjin-Hebei region of China

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Journal of Geographical Sciences 2021年第1期31卷 91-110页

作者： ZHOU Kan YIN Yue LI Hui SHEN Yuming Key Laboratory of Regional Sustainable Development Modeling Institute of Geographic Sciences and Natural Resources ResearchCASBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China College of Resource Environment and Tourism Capital Normal UniversityBeijing 100048China

Environmental stress is used as an indicator of the overall pressure on regional environmental systems caused by the output of various pollutants as a result of human activities. Based on the pollutant emissions and socioeconomic databases of the counties in Beijing–Tianjin–Hebei region, this paper comprehensively calculates the environmental stress index(ESI) for the urban agglomeration using the entropy weight method(EWM) at the county scale and analyzes the spatiotemporal patterns and the differences among the four types of major functional zones(MFZ) for the period 2012–2016. In addition, the socioeconomic driving forces of environmental stress are quantitatively estimated using the geographically weighted regression(GWR) method based on the STIRPAT model framework. The results show that:(1) The level of environmental stress in the Beijing–Tianjin–Hebei region was significantly alleviated during that time period, with a decrease in ESI of 54.68% by 2016. This decrease was most significant in Beijing, Tangshan, Tianjin, Shijiazhuang, and other central urban areas, as well as the Binhai New Area. The level of environmental stress in counties decreased gradually from the central urban areas to the suburban areas, and the high-level stress counties were eliminated by 2016.(2) The spatial spillover effect of environmental stress increased further at the county scale from 2012 to 2016, and spatial locking and path dependence emerged in the cities of Tangshan and Tianjin.(3) Urbanized zones(development-optimized and development-prioritized zones) were the major areas bearing environmental pollution in the Beijing–Tianjin–Hebei region in that time period. The ESI accounted for 65.98% of the whole region, where there was a need to focus on the prevention and control of environmental pollution.(4) The driving factors of environmental stress at the county scale included population size and the level of economic development. In addition, the technical capacity of environmen

关键词： environmental stress spatiotemporal effects driving factors urban agglomeration major functional zones(MFZ) Beijing–Tianjin–Hebei region

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Exploring nonlinear spatiotemporal effects for personalized next point-of-interest recommendation

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Frontiers of Information Technology & Electronic Engineering 2023年第9期24卷 1273-1286页

作者： Xi SUN Zhimin LV Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China

Next point-of-interest(POI)recommendation is an important personalized task in location-based social networks(LBSNs)and aims to recommend the next POI for users in a specific situation with historical check-in ***-of-the-art studies linearly discretize the user’s spatiotemporal information and then use recurrent neural network(RNN)based models for ***,these studies ignore the nonlinear effects of spatiotemporal information on user preferences and spatiotemporal correlations between user trajectories and candidate *** address these limitations,a spatiotemporal trajectory(STT)model is proposed in this *** use the long short-term memory(LSTM)model with an attention mechanism as the basic framework and introduce the user’s spatiotemporal information into the model in *** the process of encoding information,an exponential decay factor is applied to reflect the nonlinear drift of user interest over time and *** addition,we design a spatiotemporal matching module in the process of recalling the target to select the most relevant POI by measuring the relevance between the user’s current trajectory and the candidate *** evaluate the performance of our STT model with four real-world *** results show that our model outperforms existing state-of-the-art methods.

关键词： Point-of-interest recommendation spatiotemporal effects Long short-term memory(LSTM) Attention mechanism

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The Apollon 10 PW laser: experimental and theoretical investigation of the temporal characteristics

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High Power Laser Science and Engineering 2016年第3期4卷 127-133页

作者： D.N.Papadopoulos J.P.Zou C.Le Blanc G.Chriaux P.Georges F.Druon G.Mennerat P.Ramirez L.Martin A.Frneaux A.Beluze N.Lebas P.Monot F.Mathieu P.Audebert Laboratoire pour l'Utilisation des Lasers Intenses CNRSEcole Polytechnique Laboratoire Charles Fabry UMR 8501 Institut d'OptiqueCNRS Univ Paris Sud CEA Iramis SPAM

The objective of the Apollon 10 PW project is the generation of 10 PW peak power pulses of 15 fs at 1 shot min^(-1). In this paper a brief update on the current status of the Apollon project is presented, followed by a more detailed presentation of our experimental and theoretical investigations of the temporal characteristics of the laser. More specifically the design considerations as well as the technological and physical limitations to achieve the intended pulse duration and contrast are discussed.

关键词： high intensity lasers spatiotemporal effects ultrafast lasers

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