共查询到20条相似文献，搜索用时 31 毫秒
1.
《Urban geography》2013,34(5):543-566
This study offers new perspectives on the impact of global and local interactions on cities today. We look at two opposing ways of integrating global processes with the local functioning of cities. The first mode relates to a city representing unique local significance that is recognized and valued on the global scale. This globality is not economic but it affects the global interactions of individuals, institutions, and businesses in these cities. We term this type of city a global locality. The second mode is a city that serves as a local cultural and economic gateway to its region. Whether located higher or lower on the World Cities roster, at the local and regional scale it serves as both business center and cultural hub. We term this type of city a local globality. In this article, we discuss both city types using Tel Aviv-Jaffa and Jerusalem as examples. 相似文献
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Downstream variation of hydraulic geometry in rivers, characterized by fine textured banks and low width to depth ratios (7–25), is investigated in Victoria, Australia, with the aim of developing predictive models of channel geometry for large-scale spatial modeling applications. A one-dimensional hydraulic model is used to determine the mean bank-full geometry and discharge (Qbf) for 93 sites which are investigated in relation to discharge of fixed average recurrence interval (ARI). The median bank-full ARI is estimated at 0.8 years with 75% of sites between 0.5 and 2.5 years. Exponents in the downstream hydraulic geometry relations for width, depth and velocity are respectively 0.43, 0.40 and 0.18 (Q = Qbf) and 0.44, 0.38 and 0.03 (Q = Q2, i.e., 2-year ARI), falling near the mode of global values. Q2 and slope explain 66% of variance in Qbf, while Q2 explains 73% and 69% of the variance in width and depth relations, respectively: Q2 provides a reliable substitute for Qbf in spatial modeling applications. Spatial variation in hydraulic geometry relations within and between river basins remains largely unexplained. The W/D ratio characteristically decreases with increasing distance along the lower reaches of most rivers and this has contributed to the lower than expected value for the width exponent. 相似文献
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Somayeh Dodge Patrick Laube Robert Weibel 《International journal of geographical information science》2013,27(9):1563-1588
This article describes a novel approach for finding similar trajectories, using trajectory segmentation based on movement parameters (MPs) such as speed, acceleration, or direction. First, a segmentation technique is applied to decompose trajectories into a set of segments with homogeneous characteristics with respect to a particular MP. Each segment is assigned to a movement parameter class (MPC), representing the behavior of the MP. Accordingly, the segmentation procedure transforms a trajectory to a sequence of class labels, that is, a symbolic representation. A modified version of edit distance called normalized weighted edit distance (NWED) is introduced as a similarity measure between different sequences. As an application, we demonstrate how the method can be employed to cluster trajectories. The performance of the approach is assessed in two case studies using real movement datasets from two different application domains, namely, North Atlantic Hurricane trajectories and GPS tracks of couriers in London. Three different experiments have been conducted that respond to different facets of the proposed techniques and that compare our NWED measure to a related method. 相似文献
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John R. Underhill 《Basin Research》1991,3(2):79-98
A new interpretation of a comprehensive seismic- and well-database has resulted in the subdivision of the Mesozoic into four, basin-wide, seismo-stratigraphic depositional megasequences in the Inner Moray Firth (IMF) basin. Regional mapping of the megasequences has led to the construction of a new model for Mesozoic-Recent basin development in the IMF. It now appears that extensional tectonics was the main control on the basin's evolution during the Mesozoic. Structural geometries suggest that both the Triassic (Tr) and Rhaetian-mid Oxfordian (Jl) megasequences were controlled by regional broad-based subsidence associated with local extensional fault activity prior to the onset of renewed rifting in the IMF. In contrast, the late Oxfordian-Ryazanian (Berriasian; J2) megasequence developed in response to active extension characterised by half-graben development. Subsequent Early Cretaceous (Kl) deposition appears to have occurred during a further period of broad regional (thermal) subsidence. It is evident that strike-slip movement on the Great Glen Fault played a negligible role in Mesozoic basin development and it appears only to have had a local control on structural styles during its reactivation in the Tertiary as it accommodated regional uplift and basin inversion. Further subdivision of the J2 megasequence was possible using biostratigraphically-controlled seismic reflector terminations and led to the definition of five regional seismo-stratigraphic sequences (J2.1–2.5). Their geometric, thickness and sedimentary facies variations imply that the onlap-defined sequence boundaries within the late Oxfordian-Ryazanian (Berriasian; J2) megasequence were caused by syn-sedimentary extensional tectonism in a fully marine domain, rather than by fluctuations in global sea-level in a basin that was relatively quiescent tectonically. The new interpretation has particular significance in view of the fact that the Late Jurassic of the IMF was used by Exxon workers to construct part of their chart demonstrating relative changes of coastal onlap and global eustatic sea levels. As they considered that data from the area showed ‘no evidence that tectonics caused the unconformities’, the new interpretation casts doubt on the global applicability of the Late Jurassic section of Exxon's original sea-level chart. Furthermore, the study demonstrates that reflector terminations within both tectonically active and/or fully marine sequences should be treated with extreme caution and not be used to define either periods of apparent low-stand or coastal onlap. Indeed, their appearance may sometimes only represent relatively local, auto- and allo-cyclic sedimentary processes such as submarine fan avulsion or channel switching, unrelated to changes in sea-level. Finally, the work shows that care must be taken in the selection of seismic lines used to establish and illustrate the nature of depositional sequences and their geometries if pitfalls are to be avoided. 相似文献
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Maximilian Konzack Thomas McKetterick Tim Ophelders Maike Buchin Luca Giuggioli Jed Long 《International journal of geographical information science》2017,31(2):320-345
The analysis of interaction between movement trajectories is of interest for various domains when movement of multiple objects is concerned. Interaction often includes a delayed response, making it difficult to detect interaction with current methods that compare movement at specific time intervals. We propose analyses and visualizations, on a local and global scale, of delayed movement responses, where an action is followed by a reaction over time, on trajectories recorded simultaneously. We developed a novel approach to compute the global delay in subquadratic time using a fast Fourier transform (FFT). Central to our local analysis of delays is the computation of a matching between the trajectories in a so-called delay space. It encodes the similarities between all pairs of points of the trajectories. In the visualization, the edges of the matching are bundled into patches, such that shape and color of a patch help to encode changes in an interaction pattern. To evaluate our approach experimentally, we have implemented it as a prototype visual analytics tool and have applied the tool on three bidimensional data sets. For this we used various measures to compute the delay space, including the directional distance, a new similarity measure, which captures more complex interactions by combining directional and spatial characteristics. We compare matchings of various methods computing similarity between trajectories. We also compare various procedures to compute the matching in the delay space, specifically the Fréchet distance, dynamic time warping (DTW), and edit distance (ED). Finally, we demonstrate how to validate the consistency of pairwise matchings by computing matchings between more than two trajectories. 相似文献
7.
Jianan Shen Tao Cheng 《International journal of geographical information science》2016,30(9):1785-1805
ABSTRACTDatasets collecting the ever-changing position of moving individuals are usually big and possess high spatial and temporal resolution to reveal activity patterns of individuals in greater detail. Information about human mobility, such as ‘when, where and why people travel’, is contained in these datasets and is necessary for urban planning and public policy making. Nevertheless, how to segregate the users into groups with different movement and behaviours and generalise the patterns of groups are still challenging. To address this, this article develops a theoretical framework for uncovering space-time activity patterns from individual’s movement trajectory data and segregating users into subgroups according to these patterns. In this framework, individuals’ activities are modelled as their visits to spatio-temporal region of interests (ST-ROIs) by incorporating both the time and places the activities take place. An individual’s behaviour is defined as his/her profile of time allocation on the ST-ROIs she/he visited. A hierarchical approach is adopted to segregate individuals into subgroups based upon the similarity of these individuals’ profiles. The proposed framework is tested in the analysis of the behaviours of London foot patrol police officers based on their GPS trajectories provided by the Metropolitan Police. 相似文献
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分布式水文模型全局敏感性高效分析方法研究(英文) 总被引：4，自引：0，他引：4
Sensitivity analysis of hydrological model is the key for model uncertainty quantification. However, how to effectively validate model and identify the dominant parameters for distributed hydrological models is a bottle-neck to achieve parameters optimization. For this reason, a new approach was proposed in this paper, in which the support vector machine was used to construct the response surface at first. Then it integrates the SVM-based response surface with the Sobol’ method, i.e. the RSMSobol’ method, to quantify the parameter sensitivities. In this work, the distributed time-variant gain model (DTVGM) was applied to the Huaihe River Basin, which was used as a case to verify its validity and feasibility. We selected three objective functions (i.e. water balance coefficient WB, Nash-Sutcliffe efficiency coefficient NS, and correlation coefficient RC) to assess the model performance as the output responses for sensitivity analysis. The results show that the parameters g1 and g2 are most important for all the objective functions, and they are almost the same to that of the classical approach. Furthermore, the RSMSobol method can not only achieve the quantification of the sensitivity, and also reduce the computational cost, with good accuracy compared to the classical approach. And this approach will be effective and reliable in the global sensitivity analysis for a complex modelling system. 相似文献
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ABSTRACT There is continued interest in how the rate of relative sea‐level rise [A ( > 0)] and the rate of sediment supply [S] function during the growth and evolution of deltaic shorelines. The theory of shoreline autoretreat, recently corroborated in flume experiments, claims that (1) A( > 0) and S can never be in equilibrium, and (2) shoreline or shelf‐edge progradation inevitably turns to retrogradation, when relative sea level is rising even modestly and even if A/S = const (> 0). Autoretreat arises because the area of the clinoform surface of the delta (or shelf edge) per kilometer of shoreline must increase as the relative sea level rises, and the delta (or shelf edge) progrades into deeper water. A finite sediment supply rate is thus liable to become inadequate to sustain progradation. The problem increases further as a rising sea level also greatly increases the delta‐plain volume that needs to be filled, further limiting the progradation of the system. The fundamental trajectory of shoreline migration is thus one characterized by a concave‐landward shape, even under the steady forcing of the basin. The magnitudes of A (> 0) and S, or A/S do not determine whether the landward turnaround of the shoreline is realized or not, but affect merely the length and height of the fundamental trajectory curve. Thus, any attempt to detect and interpret temporal changes in A and S from the observed stratigraphic record of shoreline trajectory needs first to take full account of the inbuilt autoretreat mechanism. We develop here a simple, semi‐quantitative method of reconstructing the basin conditions (A and S) from the stratigraphic record of prograding deltaic shorelines (or prograding shelf‐margin clinoforms) on the basis of the theory of shoreline autoretreat. The deterministic nature of the autoretreat theory is advantageous in managing this latter issue, because any expected or unexpected change emerges as some discrepancy from a trajectory that was predicted for the initial conditions. The autoretreat theory also provides a convenient graphical method of dealing with the uncertainty of the field data, and with evaluating the accuracy of any reconstruction. Our methodology has been developed to deal with the behaviour of deltaic shorelines, but is basically applicable to any clinoform system, the development of which is affected by relative sea level. The suggested method is applied to an Early Eocene (Ypresian) regressive shoreline succession in the Central Tertiary Basin on Spitsbergen. The studied regressive wedge developed as a delta‐driven, progradational shelf‐margin system under a regime of overall (i.e. long‐term) rise of relative sea level, but also suffered short‐term sea‐level falls associated with valley incisions on the coastal plain and shelf. On the assumption that S was constant or was steadily decreasing, the analysis of field data obtained from three sites within the basin suggests that the initial water depth in the basin was around 0.45 km, and that the overall relative sea‐level rise (c. 0.80 km) happened largely during an early time period and was followed by a longer period of much lower rate of rise. This pattern of relative sea‐level rise is consistent with the Palaeogene tectonic subsidence trend of the basin which was determined independently through a geohistory analysis. The uncertainty of the field data does not negate our reconstruction. The combined effects of autoretreat and A/S changes on a deltaic shoreline trajectory are confirmed through the development of an autoretreat‐based methodology. Conventional sequence stratigraphic models that assume a possible equilibrium condition between A and S are both conceptually misleading and insufficient to analyse basin conditions quantitatively. Sequence stratigraphic analyses of shorelines need to incorporate the autoretreat concept. 相似文献
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The polar snowpack (and sea-ice) plays a major role in affecting overlying boundary layer chemistry and has only recently come to light. Furthermore, the understanding of this system and its importance is steadily growing. Investigations done thus far, nonetheless, examined the subsets of the polar environment as an uncoupled system. Analogous to some materials, the surface of snow/ice exhibits thin liquid layers (e.g., the quasi-liquid layer (QLL) and brine layer (BL)). This paper gives an overview of thin liquid films and illustrations of their function in Earth science. The impact of such films in polar science (i.e., polar snowpack photochemistry) is discussed within the context of how field data has been elucidated through laboratory data and modeling techniques. Specifically, what laboratory and modeling investigations have revealed about the effect of thin liquid layers on constraining field observations and, more importantly, the physicochemical mechanisms that govern the behavior of trace gases within the snowpack (and sea-ice) and how they are released from the polar snowpack. Current and future impacts of these findings are discussed, along with putative implications of the effect of thin liquid films in planetary science. 相似文献
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Elham Naghizade Jeffrey Chan Martin Tomko 《International journal of geographical information science》2020,34(10):2004-2029
ABSTRACT The ubiquity of personal sensing devices has enabled the collection of large, diverse, and fine-grained spatio-temporal datasets. These datasets facilitate numerous applications from traffic monitoring and management to location-based services. Recently, there has been an increasing interest in profiling individuals' movements for personalized services based on fine-grained trajectory data. Most approaches identify the most representative paths of a user by analyzing coarse location information, e.g., frequently visited places. However, even for trips that share the same origin and destination, individuals exhibit a variety of behaviors (e.g., a school drop detour, a brief stop at a supermarket). The ability to characterize and compare the variability of individuals' fine-grained movement behavior can greatly support location-based services and smart spatial sampling strategies. We propose a TRip DIversity Measure --TRIM – that quantifies the regularity of users' path choice between an origin and destination. TRIM effectively captures the extent of the diversity of the paths that are taken between a given origin and destination pair, and identifies users with distinct movement patterns, while facilitating the comparison of the movement behavior variations between users. Our experiments using synthetic and real datasets and across geographies show the effectiveness of our method. 相似文献
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Fang Qiancheng Nguyen Hoang Bui Xuan-Nam Tran Quang-Hieu 《Natural Resources Research》2020,29(2):593-607
In the present work, blast-induced air overpressure is estimated by an innovative intelligence system based on the cubist algorithm (CA) and genetic algorithm (GA) with high accuracy, called GA–CA model. Herein, CA initialization model was developed first and the hyper-parameters of the CA model were selected randomly. Subsequently, the GA procedure was applied to perform a global search for the optimized values of the hyper-factors of the CA model. Root-mean-square error (RMSE) is utilized as a compatibility function to determine the optimal CA model with the lowest RMSE. Gaussian process (GP), conditional inference tree (CIT), principal component analysis (PCA), hybrid neural fuzzy inference system (HYFIS) and k-nearest neighbor (k-NN) models are also developed as the benchmark models in order to compare and analyze the quality of the proposed GA–CA algorithm; 164 blasting works were investigated at a quarry mine of Vietnam for this aim. The results revealed that GA significantly improved the performance of the CA model. Based on the statistical indices used for model assessment, the proposed GA–CA model was confirmed as the most superior model as compared to the other models (i.e., GP, CIT, HYFIS, PCA, k-NN). It can be applied as a robust soft computing tool for estimating blast-induced air overpressure.
相似文献15.
G. WADGE 《International journal of geographical information science》2013,27(2):143-152
Abstract The component of gravitational acceleration parallel to the slope of the local surface partly determines the state of slope stability and the kinematics of flow under gravity on that slope. Geographical information systems based on digital elevation models offer the potential to be able to map this variable and permit the modelling of a variety of stability criteria and surface processes including landslides, rock avalanches, pyroclastic flows and lava flows. Three types of models and the basic map operations required to run them are discussed. The models are as follows: (i) sites of potential shallow slope failure (e.g. landslides), (ii) maps of flow deposition based on energy balance calculations (e.g. rock avalanches) and (iii) finite difference, initial value type simulations of dynamic flow (e.g. lava flows). The potential value of these models to hazard assessment is great but their application in specific cases must be assessed with reference to the accuracy of the digital elevation model used. 相似文献
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Mineral resource classification plays an important role in the downstream activities of a mining project. Spatial modeling of the grade variability in a deposit directly impacts the evaluation of recovery functions, such as the tonnage, metal quantity and mean grade above cutoffs. The use of geostatistical simulations for this purpose is becoming popular among practitioners because they produce statistical parameters of the sample dataset in cases of global distribution (e.g., histograms) and local distribution (e.g., variograms). Conditional simulations can also be assessed to quantify the uncertainty within the blocks. In this sense, mineral resource classification based on obtained realizations leads to the likely computation of reliable recovery functions, showing the worst and best scenarios. However, applying the proper geostatistical (co)-simulation algorithms is critical in the case of modeling variables with strong cross-correlation structures. In this context, enhanced approaches such as projection pursuit multivariate transforms (PPMTs) are highly desirable. In this paper, the mineral resources in an iron ore deposit are computed and categorized employing the PPMT method, and then, the outputs are compared with conventional (co)-simulation methods for the reproduction of statistical parameters and for the calculation of tonnage at different levels of cutoff grades. The results show that the PPMT outperforms conventional (co)-simulation approaches not only in terms of local and global cross-correlation reproductions between two underlying grades (Fe and Al2O3) in this iron deposit but also in terms of mineral resource categories according to the Joint Ore Reserves Committee standard.
相似文献17.
Mousaab Zakhrouf Hamid Bouchelkia Madani Stamboul Sungwon Kim Salim Heddam 《自然地理学》2018,39(6):506-522
The complexity of hydrological processes and lack of data for modeling require the use of specific tools for non-linear natural phenomenon. In this paper, an effort has been made to develop a conjunction model – wavelet transformation, data-driven models, and genetic algorithm (GA) – for forecasting the daily flow of a river in northern Algeria using the time series of runoff. This catchment has a semi-arid climate and strong variability in runoff. The original time series was decomposed into multi-frequency time series by wavelet transform algorithm and used as inputs to artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) models. Several factors must be optimized to determine the best model structures. Wavelet-based data-driven models using a GA are designed to optimize model structure. The performances of wavelet-based data-driven models (i.e. WANFIS and WANN) were superior to those of conventional models. WANFIS (RMSE = 12.15 m3/s, EC = 87.32%, R = .934) and WANN (RMSE = 15.73 m3/s, EC = 78.83%, R = .888) models improved the performances of ANFIS (RMSE = 23.13 m3/s, EC = 54.11%, R = .748) and ANN (RMSE = 22.43 m3/s, EC = 56.90%, R = .755) during the test period. 相似文献
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ABSTRACTThe density-based spatial clustering of applications with noise (DBSCAN) method is often used to identify individual activity clusters (i.e., zones) using digital footprints captured from social networks. However, DBSCAN is sensitive to the two parameters, eps and minpts. This paper introduces an improved density-based clustering algorithm, Multi-Scaled DBSCAN (M-DBSCAN), to mitigate the detection uncertainty of clusters produced by DBSCAN at different scales of density and cluster size. M-DBSCAN iteratively calibrates suitable local eps and minpts values instead of using one global parameter setting as DBSCAN for detecting clusters of varying densities, and proves to be effective for detecting potential activity zones. Besides, M-DBSCAN can significantly reduce the noise ratio by identifying all points capturing the activities performed in each zone. Using the historic geo-tagged tweets of users in Washington, D.C. and in Madison, Wisconsin, the results reveal that: 1) M-DBSCAN can capture dispersed clusters with low density of points, and therefore detecting more activity zones for each user; 2) A value of 40 m or higher should be used for eps to reduce the possibility of collapsing distinctive activity zones; and 3) A value between 200 and 300 m is recommended for eps while using DBSCAN for detecting activity zones. 相似文献
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Rebecca W. Loraamm 《International journal of geographical information science》2020,34(8):1607-1627
ABSTRACT Animal movement is a dynamic spatio-temporal process. While trajectory data reflect the instantaneous animal position in space and time, other factors influence movement decisions between these observed positions. While some methods incorporate environmental (habitat) context into their understanding of the animal movement process, it is often captured in terms of simple parameters or weights influencing model results; primary behavioral data are not used directly to inform these models. Here, a new space-time constrained agent-based model is introduced, capable of producing ordered, behaviorally informed animal potential paths between observed space-time anchors. Potential paths generated by this approach incorporate both observed animal behavior and classical space-time constraints, and are used to construct associated visit probability distributions. Additionally, the notion of a behavioral space-time path is introduced, a variant of the space-time path based on the results of behaviorally aware animal movement simulation. The results of this approach demonstrate a means to better understand the varied movement opportunities within space-time prisms from an animal behavior perspective. From a spatial ecology perspective, not only is the environmental context considered, but the animal’s choice of transition and movement magnitude between contexts is modeled. This approach provides insight into the complex sequence of behaviorally informed actions driving animal movement decision-making. 相似文献
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Lucas May Petry Camila Leite Da Silva Andrea Esuli Chiara Renso Vania Bogorny 《International journal of geographical information science》2020,34(7):1428-1450
ABSTRACT The increasing popularity of Location-Based Social Networks (LBSNs) and the semantic enrichment of mobility data in several contexts in the last years has led to the generation of large volumes of trajectory data. In contrast to GPS-based trajectories, LBSN and context-aware trajectories are more complex data, having several semantic textual dimensions besides space and time, which may reveal interesting mobility patterns. For instance, people may visit different places or perform different activities depending on the weather conditions. These new semantically rich data, known as multiple-aspect trajectories, pose new challenges in trajectory classification, which is the problem that we address in this paper. Existing methods for trajectory classification cannot deal with the complexity of heterogeneous data dimensions or the sequential aspect that characterizes movement. In this paper we propose MARC, an approach based on attribute embedding and Recurrent Neural Networks (RNNs) for classifying multiple-aspect trajectories, that tackles all trajectory properties: space, time, semantics, and sequence. We highlight that MARC exhibits good performance especially when trajectories are described by several textual/categorical attributes. Experiments performed over four publicly available datasets considering the Trajectory-User Linking (TUL) problem show that MARC outperformed all competitors, with respect to accuracy, precision, recall, and F1-score. 相似文献