Research
Publications
Lu, Y. and X. Chen . 2007. "False alarm of planar K-function for analyzing crime distributed along streets." Social Science Research 36(2): 611-632. Abstract
Chen, X . and F.B. Zhan. 2006. "Mapping the vulnerability to potential toxic substance releases from industrial facilities under emergency situations: A case study of Galveston , Texas." Geographic Information Sciences 12(1): 27-33. Abstract
Chen, X ., J.W. Meaker, and F.B. Zhan. 2006. "Agent-based modeling and analysis of hurricane evacuation procedures for the Florida Keys." Natural Hazards 38(3): 321-338. Abstract
Zhan, F.B., X. Chen , C.E. Noon, and G. Wu. 2005. "A GIS-enabled comparison of fixed and discriminatory pricing strategies for potential switchgrass-to-ethanol conversion facilities in Alabama." Biomass & Bioenergy 28(3): 295-306. Abstract
Publications
Lu, Y. and X. Chen . 2007. "False alarm of planar K-function for analyzing crime distributed along streets." Social Science Research 36(2): 611-632.
Abstract
Many social and economic activities, especially those in urban areas, are subject to location restrictions imposed by existing street networks. To analyze the spatial patterns of these urban activities, the restrictions imposed by the street networks need to be taken into account. K -function is a method commonly used for general point pattern analysis as well as crime pattern study. However, applying the planar K -function to analyze the spatial autocorrelation patterns of urban activities that are typically distributed along streets could result in false alarm problems. Depending on the nature of the urban street networks and the distribution of the urban activities, either positive or negative false alarm might be introduced. Acknowledging that many urban crimes are typically distributed along streets, this paper compares the traditional planar K -function with a network K -function for crime pattern analysis. The patterns of vehicle thefts in San Antonio , Texas are examined as a case study.
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Chen, X . and F.B. Zhan. 2006. "Mapping the vulnerability to potential toxic substance releases from industrial facilities under emergency situations: A case study of Galveston , Texas." Geographic Information Sciences 12(1): 27-33.
Abstract
This research investigates the spatial variations of vulnerability to toxic substance releases under possible emergency outbreaks in Galveston County , Texas . By identifying the potential risk and measuring the extent of possible impact, we provide useful information for the local government and the public to develop more effective evacuation strategies. Assuming that toxic substance releases occur during a worst-case scenario, we determine the vulnerability based on a combination of five factors at the census block level: (1) population density; (2) the percentage of people under 5 years old and above 65; (3) distance between residence and hazardous sites; (4) road network capacity; (5) density of hazardous sites. We employ the Areal Locations of Hazardous Atmospheres (ALOHA) dispersion model to define the impact areas. We calculate an index for each of the five factors. We weigh the indices equally and generate the overall vulnerability index. Results are visualized in a GIS environment.
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Chen, X ., J.W. Meaker, and F.B. Zhan. 2006. "Agent-based modeling and analysis of hurricane evacuation procedures for the Florida Keys." Natural Hazards 38(3): 321-338.
Abstract
The unique geography of the Florida Keys presents both high risk of hurricane landfall and exceptional vulnerability to the e.ects of a hurricane strike. Inadequate hurricane shelters in the Keys make evacuation the only option for most residents, but the sole access road can become impassable well in advance of a major storm. These extraordinary conditions create challenges for emergency managers who must ensure that appropriate emergency plans are in place and to ensure that an orderly exodus can occur without stranding large numbers of people along an evacuation route with inadequate shelter capacity. This study attempts to answer two questions: (1) What is the minimum clearance time needed to evacuate all residents participating in an evacuation of the Florida Keys in advance of a major hurricane for 92,596 people – a population size calculated based on the 2000 US Census population data, census undercounts, and the number of tourists estimated to be in the area? (2) If a hurricane makes landfall in the Keys while the evacuation is in progress, how many residents will need to be accommodated if the evacuation route becomes impassable? The authors conducted agent-based microsimulations to answer the questions. Simulation results suggest that it takes 20 h and 11 min to 20 h and 14 min to evacuate the 92,596 people. This clearance time is less than the Florida state mandated 24-h clearance time limit. If one assumes that people evacuate in a 48-h period and the traffic flow from the Keys would follow that observed in the evacuation from Hurricane Georges, then a total of 460 people may be stranded if the evacuation route becomes impassable 48 h after an evacuation order is issued. If the evacuation route becomes impassable 40 h after an evacuation order is issued, then 14,000 people may be stranded.
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Zhan, F.B., X. Chen , C.E. Noon, and G. Wu. 2005. "A GIS-enabled comparison of fixed and discriminatory pricing strategies for potential switchgrass-to-ethanol conversion facilities in Alabama." Biomass & Bioenergy 28(3): 295-306.
Abstract
Ethanol is produced from organic material and is important as a strategic and cleaner alternative to fossil fuels. The cost of producing ethanol, which ultimately affects its price and demand, depends to a large extent on the delivered cost of raw materials. For a planned ethanol production facility, the cost of raw material is a function of (1) the facility location, (2) the facility size, and (3) the method of procurement. In a previous paper, two of the authors provided a methodology for computing a marginal price ‘‘surface'' to better understand the location decision under several facility size scenarios. The methodology was implemented in a GIS-based decision support system to investigate the economic feasibility of locating a switchgrass-to-ethanol conversion facility in Alabama . In this paper, we use the methodology to construct delivered cost surfaces in order to evaluate two methods of procurement pricing; fixed and discriminatory. In the fixed pricing method of procurement, the facility pays one fixed price per delivered tonne. In the discriminatory pricing method of procurement, the facility pays a source-specific price per tonne before delivery and then pays the cost of delivery transportation. The results from the current study confirm the cost advantage of discriminatory over fixed pricing. However, it was observed that the relative cost advantage showed considerable variation as a function of location and facility size.
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