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Now showing items 1 - 16 of 51

  • System and method for communication resource allocation

    A system and method for communication resource allocation, a resource including a time slot and at least one associated channel, said channel including at least one transmit and/or receive frequency usable during said time slot, in a mobile meshed network including a first set of radio transceivers communicating with one another via radio links, at least one group, comprising a second set of at least one radio transceiver of said first set, said second set including a master transceiver in a master/subordinate relationship with all the radio transceivers of the second set, a central radio transceiver of the network belonging to said first set. Said system is characterized in that it comprises first means for determining said group(s), second means for allocating all or some of said resources through assignment of a resource to a single group which is able to use said resource for one or more communications between radio transceivers of said group; or through allocation of a resource to a single first group which is able to use said resource for communication between radio transceivers of said first group and radio transceivers belonging to one or more neighboring destination groups, if none of the other resources sharing the same time slot with said resource is determined as belonging to one of said destination groups or to a different second group for links to one of said destination groups of the first group, except if the first group and the second group have no transceiver having a common radio neighbor in the destination groups. Finally, said system comprises third means for allocating, for all or some of the groups, all or some of the resources allocated to said group, to one of the radio transceivers in the group.
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  • Enhanced 3D visualization techniques in support of indoor location planning

    Yuhong Zhou   Thi Hong Diep Dao   Jean-Claude Thill   Eric Delmelle  

    Graphical abstract Highlights • Enhanced 3D visualization techniques are proposed for supporting location planning applied to indoor spaces. • We extend traditional 2D visualization techniques to 3D and design novel 3D visualization techniques. • User surveys demonstrate the advantages of 3D visualization solutions in terms of quickness, effectiveness, easiness, and usefulness. Abstract Indoor environments are challenging spaces to handle in location analysis and Geographic Information Science. In this paper, new techniques to visualize solutions of location models used for the optimal indoor placement of emergency devices are proposed in support of location planning decisions. The analysis compares and contrasts extensions of traditional 2D visualization techniques to display diverse aspects of the service coverage of demand nodes by devices in the form of canonical and network-based spider maps, areal and volume coverage. Other innovative approaches are suggested to visualize the spatio-temporal relationship of multiple facilities serving multiple demand nodes across a multi-story building. User surveys suggest that the proposed 3D visualization techniques are preferred to their 2D counterparts in terms of quickness, effectiveness, easiness, and usefulness.
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  • Spatial patterns of landside trade impedance in containerized South American exports

    Kara Carroll Tiller   Jean-Claude Thill  

    Abstract The paper addresses claims implicating higher domestic transportation costs as a significant barrier to Latin America's trade and economic integration - and the region's inadequate transportation infrastructure as the primary cause. The relative “trade space” for U.S.-bound containerized shipments is delineated via reverse spatial interaction modeling. Reconfiguration and reverse calibration of the doubly constrained spatial interaction model is used to derive functional distances between origins and ports of export, as a means of estimating a Trade Impedance Quotient (TIQ) for trade flows at the scale of the continent. Global and local statistics of spatial autocorrelation are then used to analyze the spatial pattern of trade impedance. With this approach, the analysis of containerized flows establishes the existence, extent, location, and spatial distribution of discrepancies in South American landside trade impedance. A large share of trade flows have trade impedance that is disproportionate to distance. Trade impedance at origins is spatially clustered for the total dataset and randomly distributed for commodity segments, and randomly distributed at destinations. Potential focus areas for high trade impedance are identified. Highlights • Delineates existence/extent/spatial distribution of landside trade impedance • Estimates flow Trade Impedance Quotients; depicts clusters at origins/destinations • Utilizes innovative locational verification method for containerized shipment data • Relative space concept employs reverse doubly-constrained spatial interaction model. • Forwards future-focused methodology for transport/various types of flow modeling
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  • Evaluating traffic safety policies for developing countries based on equity considerations

    Pooya Najaf   Mohammad Taghi Isaai   Mohammad Lavasani   Jean-Claude Thill  

    Traffic safety policies are still conventionally ranked on financial and environmental criteria in developing countries, yet the equity concept can be advantageously used as an integral part of the process of traffic safety policy making. Equity in transportation is defined as how appropriately and equally the impacts of transportation are distributed among different types of users. The main contribution of this research is to introduce traffic safety equity in transportation policy making. The authors advocate for a modeling framework that considers traffic safety equity as a focal point. The analytical network process overcomes the drawbacks of data intensive models that are so difficult to implement reliably in developing countries and recognizes the existence of complex interdependencies among traffic safety factors. The approach is demonstrated on the case of Tehran, Iran. In this study, seventeen transportation elements are grouped into four clusters (driver characteristics, roadway characteristics, vehicle characteristics, and traffic control) to evaluate six policies. Public education and information is found to be the most effective policy to increase traffic safety, considering equity. The best equity-conscious policies are independent from physical infrastructures, household income level, and household location. The proposed framework is a sound approach to introduce traffic safety equity in the traffic safety policy making process of developing countries.
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  • Method for dynamically allocating resources in a network of station clusters

    A distributed method for dynamically assigning time-frequency resources in a network comprising several stations is disclosed. The stations are organized in groups (or interfaces) of several stations with each group comprising an allocation table Tsi. Each group exchanges this allocation table by means of a signaling protocol with groups that are defined as being in conflict with it by a constraints graph. The method uses an arbitration function to settle the conflicts and the assignments of allocations between the groups in conflict according to the constraints graph. In performing the method, each interface Ji transmits the allocation table TJi associated with it to the interfaces K indicated as being in conflict in the constraints graph. An interface Ji looks, for each allocation AJi that it has entered in its table TJi, whether the allocation AJi is used in the table received from an interface K that is in conflict. The interface Ji uses the arbitration function to modify the allocation AJi in the table TJi.
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  • Cross-scale Analysis of Spatial Cluster Correspondence

    Jean-Claude Thill   Yongmei Lu  

    A number of phenomena studied in spatial sciences involve two or more locationally- defined point events that are logically or functionally related. Some of the most obvious examples include daily commute that relates the traveler s home location and work place, or the spatial-temporal path followed by human migration. Cluster correspondence analysis examines the local spatial dependence of paired point locations of this sort. It assesses the autocorrelation of a subset of locations when their paired subset of locations form clusters. The evaluation of cluster correspondence is critically related to the spatial resolution (or scale) of the analysis as well as to the definition of neighborhood within which a subset of points or their paired points are examined. This paper expands an exploratory spatial data analysis approach developed by the authors to discuss how the operational neighborhood can be incorporated in the analysis through the definition of the zoning system over the study area. Furthermore, it argues that the scales at which the zones are aggregated into neighborhoods could impact the identified patterns of cluster correspondence. Empirical analyses using pairs of vehicle theft and recovery locations based on different zoning methods and across a series of scales are reported.
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  • Geographical Information Science Research – United Kingdom (GISRUK) 2007

    Jean-Claude Thill  

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  • Geographical Information Science Research – United Kingdom (GISRUK) 2007

    Jean-Claude Thill  

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  • Geographical Information Science Research – United Kingdom (GISRUK) 2007

    Jean-Claude Thill  

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  • Intermodal containerized shipping in foreign trade and regional accessibility advantages

    Jean-Claude Thill   Hyunwoo Lim  

    Intermodalism has become one of the most significant transformations of freight transportation in the United States over the past two decades. The coupling of shipping modes has enabled shippers to more fully realize the respective time and costs advantages of respective modes. The opportunity to take advantage of intermodalism when shipping manufactured goods overseas may provide an essential competitive edge to a company or to an entire region engaged in world commerce. The change in the freight accessibility map of the United States to foreign markets that can be ascribed to intermodal infrastructures and operations has so far not been studied. With the help of a geographic information system, this paper analyzes this transformation in the United States by mapping integral place accessibility measures of five-digit zip code areas with respect to gateways for export of manufactured goods, especially containerized freight. The performance of the intermodal freight network is evaluated by comparing accessibility measures based on the highway network and on the intermodal network, respectively, for all North American container ports, as well as for subgroups of container ports on the Eastern Seaboard, the Western Seaboard, and the Gulf Coast of North America. The paper discusses regional winners and losers in the new national freight transportation system.
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  • Intermodal containerized shipping in foreign trade and regional accessibility advantages

    Jean-Claude Thill   Hyunwoo Lim  

    Intermodalism has become one of the most significant transformations of freight transportation in the United States over the past two decades. The coupling of shipping modes has enabled shippers to more fully realize the respective time and costs advantages of respective modes. The opportunity to take advantage of intermodalism when shipping manufactured goods overseas may provide an essential competitive edge to a company or to an entire region engaged in world commerce. The change in the freight accessibility map of the United States to foreign markets that can be ascribed to intermodal infrastructures and operations has so far not been studied. With the help of a geographic information system, this paper analyzes this transformation in the United States by mapping integral place accessibility measures of five-digit zip code areas with respect to gateways for export of manufactured goods, especially containerized freight. The performance of the intermodal freight network is evaluated by comparing accessibility measures based on the highway network and on the intermodal network, respectively, for all North American container ports, as well as for subgroups of container ports on the Eastern Seaboard, the Western Seaboard, and the Gulf Coast of North America. The paper discusses regional winners and losers in the new national freight transportation system.
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  • Distributed synchronization method and system

    A distributed synchronization method in a communication network is disclosed. A number of stations exchange messages between themselves. A synchronization pattern characteristic of the clock reference of the sender is inserted into each message transmitted by a sender. The clock reference of each station is updated with the clock reference that it receives from another station of the network if, and only if, the received time is leading the clock reference. The update is done by calculating the difference ΔX=T′a−Ta between the time of sending T′a of the message received by a station A and the time of reception Ta of the same message by the station B, and applying a correction 0<ΔY<=ΔX if the received time of sending is leading by a quantity of at least τ (ΔX>τ>0).
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  • Tree Induction of Spatial Choice Behavior

    Jean-Claude Thill   Aaron Wheeler  

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  • Trip making, induced travel demand, and accessibility

    Jean-Claude Thill   Marim Kim  

    Traditional transportation planning practice rests on the premise that the demand for transportation is derived. On the other hand, economic theory advances that enhancement to the transportation system leads to lower travel cost and hence to "induced demand." Such an argument lends support to the view that the rate at which trips are generated is linked to the ease of making trips to potential destinations. Rather conflicting evidence has so far come out of aggregate trip generation modeling applications. This paper revisits this issue with proper characterization of integral accessibility. Poisson regression models of automobile trip generation by trip purpose are estimated on travel survey data in Minneapolis–St. Paul, MN. Alternative measures of accessibility are tested for statistical significance. Conclusions are drawn on the role of accessibility in trip making and on the comparison of integral accessibility measures.
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  • Editorial

    Jean-Claude Thill  

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  • Editorial

    Jean-Claude Thill  

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