The Experts below are selected from a list of 76383 Experts worldwide ranked by ideXlab platform
Eric Delmelle - One of the best experts on this subject based on the ideXlab platform.
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re conceptualizing accessibility to parks in multi modal cities a variable width floating Catchment Area vfca method
Landscape and Urban Planning, 2015Co-Authors: Coline Dony, Eric DelmelleAbstract:Abstract An increasing number of studies have sought to identify disparities or inequalities in the distribution of urban parks and green spaces. Results of these analyses have diverged considerably depending on the method used to assess accessibility. In this article, we revisit an increasingly popular technique, the two-step floating Catchment Area (2SFCA) method, and modify it to better align with the ways in which parks are planned and intended to be used. In this respect, we develop a Variable-width Floating Catchment Area (VFCA) method that models park attractiveness as a function of its size and number of amenities. We further compare accessibility according to four modes of transportation: bicycling, driving, public transit, and walking. A case study on access to public parks in Mecklenburg County, North Carolina, the U.S. is performed. In general, walking access to parks is found to be low throughout the county, access to larger regional parks is greatest for outlying suburban Areas, and center city residents have access to a greater number of park amenities. Study results are compared to those obtained when using the original 2SFCA and indicate important differences in spatial accessibility patterns. Consequently, caution must be adopted when choosing a spatial access model and interpreting the resulting spatial patterns of accessibility. The parameters of the VFCA can easily be set to different values, making it a tool for scenario analyses. This study further improves our understanding regarding accessibility to public parks, which can help develop effective planning strategies.
Lars O. Ericsson - One of the best experts on this subject based on the ideXlab platform.
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Recovery from groundwater extraction in a small Catchment Area with crystalline bedrock and thin soil cover in Sweden.
The Science of the total environment, 2008Co-Authors: Fredrik Mossmark, Hans Hultberg, Lars O. EricssonAbstract:An experiment has been in progress since 1997 in a small Catchment Area (28,000 m(2)) with crystalline bedrock and thin soil cover to study the conceivable impact on groundwater conditions of tunneling and the use of groundwater. The impact on hydrology and hydrochemistry from intensive extraction of groundwater at a depth of 50 m in the bedrock has been studied at Lake Gårdsjön in Sweden. The Catchment Area was first monitored under pristine conditions, followed by four and a half years of extraction and then a recovery phase. The geological conditions result in a low buffer capacity and high sensitivity to acidification. During the period of extraction, the surface runoff decreased by approximately 50% compared to a nearby reference Area. The groundwater extraction caused increased fluctuation in groundwater levels in a wetland, which in turn caused oxidation of reduced sulfur to sulfate. The sulfate concentrations increased almost 100-fold in some instances, causing a lowering of the pH by one unit in shallow groundwater. Since extraction of the groundwater was discontinued, the pH has gradually risen and the sulfate concentrations have decreased. However, the concentration of sulfate in groundwater in the wetland has remained stable at approximately double the pre-experiment levels. Magnesium concentrations were lower after the experiment, caused by exhaustion of the magnesium pool in the wetland through acidification. The extraction of water from the bedrock shortened the retention times and increased the recharge of groundwater in the bedrock. After extraction was terminated, the groundwater levels in the boreholes recovered within a month to levels similar to those before extraction. The hydrochemistry of the bedrock groundwater, which was strongly affected by the hydrochemistry of shallow groundwater during the experiment, has also gradually begun to regain its pre-extraction signature. However, the surface runoff has remained low during the first 2 years of recovery, at about 60% of the volume compared to the unaffected Catchment Area. This could be explained by delayed recovery in resaturation of the shallow rock that was unsaturated during the experiment.
Tara Whippo - One of the best experts on this subject based on the ideXlab platform.
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variable Catchment sizes for the two step floating Catchment Area 2sfca method
Health & Place, 2012Co-Authors: Tara WhippoAbstract:Abstract Government efforts designed to help improve healthcare access rely on accurate measures of accessibility so that resources can be allocated to truly needy Areas. In order to capture the interaction between physicians and populations, various access measures have been utilized, including the popular two-step floating Catchment Area (2SFCA) method. However, despite the many advantages of 2SFCA, the problems associated with using fixed Catchment sizes have not been satisfactorily addressed. We propose a new method to dynamically determine physician and population Catchment sizes by incrementally increasing the Catchment until a base population and a physician-to-population ratio are met. Preliminary application to the ten-county region in northern Illinois has demonstrated that the new method is effective in determining the appropriate Catchment sizes across the urban to suburban/rural continuum and has revealed greater detail in spatial variation of accessibility compared to results using fixed Catchment sizes.
Rogier Lieshout - One of the best experts on this subject based on the ideXlab platform.
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measuring the size of an airport s Catchment Area
Journal of Transport Geography, 2012Co-Authors: Rogier LieshoutAbstract:Although much empirical research exists on the factors that drive passenger airport choice, not much is known about the related topic of airport Catchment Area size. This paper presents a novel methodology to assess the size of airport Catchment Areas and the airport’s market shares therein using a MNL passenger choice model. The methodology is applied to Amsterdam Airport Schiphol. The results show that the size of its Catchment Area differs considerably by destination. Schiphol’s market share within its Catchment Area declined between 2005 and 2011 due to increased competition from airports located to the south and southeast. Airports may use the presented methodology to evaluate the spatial nature of their Catchment Areas to understand passenger airport choice and the competitive forces in their respective hinterland regions. In addition, the methodology shows airports the effects of changes to service level offerings (in terms of frequencies and fares) on their Catchment Area and the market shares therein. Furthermore, the methodology may be of use to policymakers to estimate the competitive position of airports in the OD-markets served and to assess the effects of infrastructure investments on Catchment Area size and airport market shares.
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Measuring the size of an airport’s Catchment Area
Journal of Transport Geography, 2012Co-Authors: Rogier LieshoutAbstract:Although much empirical research exists on the factors that drive passenger airport choice, not much is known about the related topic of airport Catchment Area size. This paper presents a novel methodology to assess the size of airport Catchment Areas and the airport’s market shares therein using a MNL passenger choice model. The methodology is applied to Amsterdam Airport Schiphol. The results show that the size of its Catchment Area differs considerably by destination. Schiphol’s market share within its Catchment Area declined between 2005 and 2011 due to increased competition from airports located to the south and southeast. Airports may use the presented methodology to evaluate the spatial nature of their Catchment Areas to understand passenger airport choice and the competitive forces in their respective hinterland regions. In addition, the methodology shows airports the effects of changes to service level offerings (in terms of frequencies and fares) on their Catchment Area and the market shares therein. Furthermore, the methodology may be of use to policymakers to estimate the competitive position of airports in the OD-markets served and to assess the effects of infrastructure investments on Catchment Area size and airport market shares.
Paul L Delamater - One of the best experts on this subject based on the ideXlab platform.
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spatial accessibility in suboptimally configured health care systems a modified two step floating Catchment Area m2sfca metric
Health & Place, 2013Co-Authors: Paul L DelamaterAbstract:The floating Catchment Area (FCA) family of metrics employ principles from gravity-based models to incorporate supply, demand, and distance in their characterization of the spatial accessibility of health care resources. Unlike traditional gravity models, the FCA metrics provide an output in highly interpretable container-like units (e.g., physicians per person). This work explores two significant issues related to FCA metrics. First, the Three Step Floating Catchment Area is critically examined. Next, the research shows that all FCA metrics contain an underlying assumption that supply locations are optimally configured to meet the needs of the population within the system. Because truly optimal configurations are highly unlikely in real-world health care systems, a modified two-step floating Catchment Area (M2SFCA) metric is offered to address this issue. The M2SFCA is built upon previous FCA metrics, but allows for spatial accessibility to be discounted as a result of the suboptimal configuration of health care facilities within the system. The utility of the new metric is demonstrated through simulated data examples and a case study exploring acute care hospitals in Michigan.