Department Personnel

Xuwei Chen

    Xuwei Chen

       chen@niu.edu

 

Publications, Grants, Presentations, and Book Reviews

 

 

Publications:

Chen, X. and R. Greene. 2012. Spatial-Temporal Dynamics of China’s Changing Urban Hierarchy (1950–2005) Urban Studies Research vol. 2012, Article ID 162965, 13 pages, 2012. doi:10.1155/2012/162965. Abstract

Chen, X.  Agent-based micro-simulation of staged evacuations. International Journal of Advanced Intelligence Paradigms, 4(1): 22-35. Abstract

VanLandegan, L. and X. Chen. 2011. Microsimulation of large-scale evacuations utilizing Metrorail transit. Applied Geography, 32: 787-797. Abstract

Greene, R. and X. Chen. 2011. Geo-visualizing China’s Changing Urban Hierarchy 1985 to 2005. Proceedings of the 19th International Conference on GeoInformatics, Shanghai, China. June 24-26, 2011. ISBN: 978-1-61284-849-5. Abstract

Chen, X. 2011. Agent-Based Modeling of Emergency Evacuation in a Spatially-Aware and Time-Aware Environment. Proceedings of the 25th International Cartographic Conference. Paris, France. July 3-8, 2011. ISBN: 978-1-907075-05-6. Abstract

Chen, X. and F.B. Zhan. 2010. A spatial and temporal analysis of commute pattern changes in Central Texas. Annals of GIS 16(4): 255-267. Abstract

Zhan, FB; Chen, X. 2008. Agent-based modeling and evacuation planning.  In Daniel Z. Sui (Eds.), Geospatial Technologies and Homeland Security: Research Frontiers and Future Challenges (pp. 189-208). Springer: Netherlands. Abstract

Zhan, F.B. and X. Chen. 2008.  Intercity commute patterns in Central Texas.  In: Liu, Lin; Li, Xia; Liu, Kai; Zhang, Xinchang; Wang, Xinhao (Eds.), Geoinformatics 2008 and Joint Conference on GIS and Built Environment: The Built Environment and Its Dynamics. In Proceedings of the SPIE-The International Society for Optical Engineering, 7144(2): 71442N.1-71442N.8.

Chen, X. 2008. Microsimulation of evacuation strategies of Galveston Island. The Professional Geographer 60(2): 160-173. Abstract

Chen, X. and F.B. Zhan. 2008. Agent-based modeling and simulation of urban evacuation: Relative effectiveness of simultaneous and staged evacuation strategies. Journal of the Operational Research Society 59: 25-33. Abstract

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:

Chen, X. and R. Greene. 2012. Spatial-Temporal Dynamics of China’s Changing Urban Hierarchy (1950–2005) Urban Studies Research vol. 2012, Article ID 162965, 13 pages, 2012. doi:10.1155/2012/162965.

Abstract
This paper examines the dynamic spatial and temporal patterns of China’s urban hierarchy from 1950 to 2005. We limit the study to mainland China’s 137 urban agglomerations of 750,000 or more population as of 2005. The paper improves upon a classic approach to measuring shifting ranks within an urban hierarchy by applying advanced spatial analysis techniques. We use a Getis-Ord Gi, a space-time Moran scatter plot, and dynamic LISA paths to examine the regional difference and change for these urban agglomerations. Our study revealed a north-south divide in the changing urban hierarchy of China after 1990. The analysis demonstrated that the spatial and temporal shift of urban dominance in China was closely associated with policy and economic factors. The paper concludes with a discussion of the differences across the six different time periods of change from 1950 to 2005.
Top  


Chen, X.  Agent-based micro-simulation of staged evacuations. International Journal of Advanced Intelligence Paradigms, 4(1): 22-35. 

Abstract
One of the most critical issues for an evacuation is to design an effective evacuation strategy that could lead to the reduction of the total evacuation time. Previous studies demonstrated the advantage of certain staged evacuation strategies over the simultaneous evacuation strategy. This study aims to identify an effective yet feasible evacuation zoning structure for staged evacuation strategies of Galveston Island. The proposed zoning structure attempts to reduce the traffic pressure at the beginning of the IH-45 bridge, the only exit to the mainland. This study employs VISSIM, an agent-based microsimulation software package, to simulate the evacuation process. The sensitivity of the total evacuation time to time intervals between notifications of the staged evacuation is examined. The findings suggest that when an appropriate interval is selected, the staged evacuation using the proposed zoning structure is more effective than a simultaneous evacuation. A longer span between notifications could reduce the evacuation time of the last vehicle, but does not necessarily lead to the reduction of the total evacuation time.
Top  


VanLandegan, L. and X. Chen. 2011. Microsimulation of large-scale evacuations utilizing Metrorail transit. Applied Geography, 32: 787-797.

Abstract
Public transit plays an important role in emergency evacuations, particularly for areas where public transit serves as a major commute mode for commuters. Microsimulation techniques provide great flexibility in assessing different scenarios in emergency situations. Combining GIS-based network analysis with microsimulation techniques, this study developed a framework to simulate emergency evacuations using rail transit. Applying the framework to a hypothetical attack on the Pentagon, this study investigated the performance of the Washington Metropolitan Area Transit Authority’s Metrorail for large-scale evacuations. A network-based analysis was performed to estimate the number of riders in association with each metro line and station. Using VISSIM, a multi-mode micro-simulation software package, this study integrated a pedestrian model with a Metrorail transit model to evaluate the performance of the Metrorail in the hypothetical evacuations. The simulation results suggested that if the potential of Metrorail transit is effectively utilized, it could be very useful resource during a large-scale evacuation. This study demonstrated the great potential and flexibility of microsimulation techniques for evaluating complex evacuation scenarios and strategies. The framework and approach used in this study can be applied to analyze other similar situations and help develop effective evacuation plans.
Top  


Greene, R. and X. Chen. 2011. Geo-visualizing China’s Changing Urban Hierarchy 1985 to 2005. Proceedings of the 19th International Conference on GeoInformatics, Shanghai, China. June 24-26, 2011. ISBN: 978-1-61284-849-5.

Abstract
In a prior study, a rank mobility index (RMI) was applied to China's 137 urban agglomerations and mapped using a graduated symbol map to show dramatic changes in China's urban hierarchy from 1985 to 2005. This paper improves the visualization of those rank changes by applying advanced spatial analysis techniques. We use a Moran's scatter plot and a Getis-Ord Gi to examine the regional difference and change for these urban agglomerations ranks. We then use a weighted Voronoi diagram (WVD) approach to produce polygons whose size reflects the magnitude of the RMI. The paper concludes with a discussion of the strengths and weaknesses of the various geo-visualization approaches.
Top  

 


 

Chen, X. 2011. Agent-Based Modeling of Emergency Evacuation in a Spatially-Aware and Time-Aware Environment. Proceedings of the 25th International Cartographic Conference. Paris, France. July 3-8, 2011. ISBN: 978-1-907075-05-6.

Abstract
Agent-based modeling (ABM) has advantages in capturing emerging behavior resulting from interactions between individuals in a complex system and has been applied in many fields. However, in current GIS environments, applying agent-based modeling to geospatial simulations is rudimentary. From the other side of the equation, most agent-based software packages typically do not provide good support for representing complex geospatial environments. Furthermore, dealing with time-varying data is still an emerging research area in GIScience. In an emergency evacuation, the environment often changes. How to communicate time-varying information from the environment with intelligent and adaptive agents effectively remains as a challenge. This study aims to address two critical issues in coupling agent-based modeling with a dynamic geographic environment: implementing spatial awareness of agents in geographic space and integrating the dynamics of the environment and its impacts on the behavior of agents. Spatial awareness refers to the capability of agents to detect the properties of their environment and adapt their behaviors to changes in that environment. Time-aware GIS, in this study, refers to a geographic information system that can present and update the dynamics of the geographic space or the environment of the agents. The conceptual framework of the system is comprised of four components: mobile agents, behavioral rules, activity space of the agents, and geographic space. A prototype of spatially-aware and time-aware agent-based model within a dynamic environment is built based upon an open source ABM toolkit – Netlogo. The agents – evacuating vehicles, are individual intelligent decision-makers that can detect changes in their activity space and environment. Their movements are constrained by the behavioral rules, the activity space, and the geographic space. The properties of the activity space are defined by the transportation network under study, including attributes of links and nodes, origins and destinations of the agents. The behavioral rules define how agents react in interactions with other agents and their environment. The geographic space, either dynamic or static, offer an environment with all the relevant information required to accurately represent the emergency evacuation scenarios. The prototype model is applied to a simulated emergency evacuation scenario. It provides a microscope test bed for simulating real world emergency evacuation scenarios and helps evaluate emergency evacuation plans and strategies.
Top

 


 

Chen, X. and F.B. Zhan. 2010. A spatial and temporal analysis of commute pattern changes in Central Texas. Annals of GIS 16(4): 255-267.

Abstract
The Austin-San Antonio Corridor, which encompasses the Austin metropolitan area and the San Antonio metropolitan area, has experienced significant increase of commute traffic since 1990. Research suggested that the level of traffic congestion increased dramatically in the past two decades. An analysis of the trend of the commute patterns would help better understand the underlying causes of traffic congestion and provide policy implications for urban planning and traffic management. This study used the U. S. Census Transportation Planning Package (CTPP) 1990 and 2000 data at the TAZ level to examine journey-to-work trends in Central Texas. This study developed a set of GIS-based methods to analyze the spatial and temporal change of commute patterns and commute flows from 1990 to 2000 in the study area. The analyses revealed places that experienced significant increasing commute needs and identified major travel corridors in the study area. The findings, therefore, provide necessary information for public transportation providers and other stakeholders to improve the coordination of rural to urban public transportation services.
Top


 

Zhan, FB; Chen, X. 2008. Agent-based modeling and evacuation planning.  In Daniel Z. Sui (Eds.), Geospatial Technologies and Homeland Security: Research Frontiers and Future Challenges (pp. 189-208). Springer: Netherlands.

Abstract
In evacuation planning, it is advantageous for community leaders to have a thorough understanding of the human and geophysical characteristics of a community, be able to anticipate possible outcomes of different response and evacuation strategies under different situations, inform the general public, and develop a set of evacuation plans accordingly. In order to achieve this goal, evacuation managers in a community can use computer modeling techniques to simulate different ‘what-if’ scenarios, use the results from these simulations to inform the public, and generate different evacuation plans under different circumstances. The complexity associated with evacuation planning in an urban environment requires a computer modeling framework that can incorporate a number of factors into the modeling process. These factors include the nature of the disaster in question, the anticipated human behavioral patterns in the evacuation process, the unique geography and transportation infrastructure in a given area, the population distribution in the area, the population dynamics over different time periods, and the special needs of different population groups, to name a few. Agent-Based Modeling (ABM) provides a general approach that can be used to account for these factors in the modeling and simulation process. In this chapter, the authors provide an overview of agent-based modeling and simulation, illustrate how agent-based modeling and simulation were used in estimating the evacuation time for the Florida Keys, and report some preliminary results in planning a hypothetical route for evacuating the elderly from a nursing home on Galveston Island, Texas, based on network dynamics during an evacuation.
Top


 

Chen, X. 2008. Microsimulation of evacuation strategies of Galveston Island. The Professional Geographer 60(2): 160-173.

Abstract
This article investigates the effectiveness of simultaneous and staged evacuation strategies for hurricane evacuations of Galveston Island using agent-based microsimulation techniques. In the simultaneous strategy the entire population is informed to evacuate simultaneously, whereas in a staged evacuation strategy, people are informed to evacuate in a sequence. The results suggest that (1) the most efficient staged evacuation strategy can help reduce the evacuation time for Galveston Island by approximately one hour, (2) previous studies might have underestimated the evacuation time of Galveston, and (3) an evacuation under the rapid response assumption does not necessarily lead to an effective evacuation.
Top


 

Chen, X. and F.B. Zhan. 2008. Agent-based modeling and simulation of urban evacuation: Relative effectiveness of simultaneous and staged evacuation strategies. Journal of the Operational Research Society 59: 25-33.

Abstract
This study investigates the effectiveness of simultaneous and staged evacuation strategies using agent-based simulation. In the simultaneous strategy, all residents are informed to evacuate simultaneously, whereas in the staged evacuation strategy, residents in different zones are organized to evacuate in an order based on different sequences of the zones within the affected area. This study uses an agent-based technique to model traffic flows at the level of individual vehicles and investigates the collective behaviours of evacuating vehicles. We conducted simulations using a microscopic simulation system called Paramics on three types of road network structures under different population densities. The three types of road network structures include a grid road structure, a ring road structure, and a real road structure from the City of San Marcos, Texas. Default rules in Paramics were used for trip generation, destination choice, and route choice. Simulation results indicate that (1) there is no evacuation strategy that can be considered as the best strategy across different road network structures, and the performance of the strategies depends on both road network structure and population density; (2) if the population density in the affected area is high and the underlying road network structure is a grid structure, then a staged evacuation strategy that alternates non-adjacent zones in the affected area is effective in reducing the overall evacuation time.
Top


 

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.
Top


 

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.
Top


 

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.
Top


 

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.
Top


 

Grants

Development of Theme-based Course Material using Geovisualization Techniques for GEO 202 World Regional Geography. 2011 Instructional Research and Improvement Grant

GIS Analysis of Travel Patterns in Chicagoland. Undergraduate Research Apprenticeship Program, 2011 (URAP)

Mapping the Current State of Environmental Issues: Enrichment Activities for World Regional Geography Honor Mini-Sections. 2010 With Sarah Blue (Unfunded)
Top


 

Presentations

Chen, X. 2011. A Dasymetric Mapping Approach to Geovisualizing Chicago's Job Centers. West Lake Division Annual Meeting of the Association of American Geographers. Chicago, IL, September 9-11, 2011.

Chen, X. 2011. Agent-Based Modeling of Emergency Evacuation in a Spatially-Aware and Time-Aware Environment. 25th International Cartographic Conference. Paris, France. July 3-8, 2011

Greene, R. and X. Chen. 2011. Geo-visualizing China’s Changing Urban Hierarchy 1985 to 2005. The 19th International Conference on GeoInformatics, Shanghai, China. June 24-26, 2011.

Chen, X. 2011. Coupling Spatially-Aware and Time-Aware Models in Simulating Emergency Evacuations. Annual Meeting of the Association of American Geographers. Seattle, April.

Chen, X. 2010. Emergency evacuation simulation on a dynamic network using spatially aware agent-based model. West Lake Division Annual Meeting of the Association of American Geographers. Macomb, IL October 21-23.

VanLandegen, Luke, and Chen, X. 2010. Microsimulation of large-scale evacuations utilizing metro transit. Annual Meeting of the Association of American Geographers. Washington DC, April.

Chen, X. 2010. Activity-based modeling and microsimulation of emergency evacuations. Annual Meeting of the Association of American Geographers. Washington DC, April.

Chen, X. 2010. Modeling and simulation of staged evacuations. National Evacuation Conference. New Orleans, LA, February.

Chen, X. 2009. Agent-based modeling and simulation of emergency evacuations. AAG 2009 West Lakes Division Annual Meeting. Minneapolis, MN, October.

Chen, X. 2009. Modeling and simulation of staged evacuations: A case study of hurricane evacuations of Galveston Island. Annual Meeting of the Association of American Geographers. Las Vegas, NV, March.

Zhan, FB and X. Chen.  2008. Intercity commute patterns in Central Texas. Geoinformatics 2008 and Joint Conference on GIS and Built Environment: The Built Environment and Its Dynamics. Guangzhou, China, June.

Chen, X., 2008: Journey-to-work trends in Central Texas. Annual Meeting of the Association of American Geographers. Boston, MA, April.
Collins, B., FB, Zhan, and X. Chen. 2008. Evacuation microsimulation of diurnal population distributions. Annual Meeting of the Association of American Geographers. Boston, MA, April.

Chen, X. 2007. Microsimulation of evacuation strategies of Galveston Island. Annual Meeting of the Association of American Geographers. San Francisco, CA, April.

Chen, X and FB Zhan. 2006. Commute patterns in Central Texas. Annual Meeting of the  Association of American Geographers. Chicago, IL, March.

Zhan, FB and X. Chen. 2006. Agent-based modeling and evacuation planning. 2006 Texas A&M University Symposium on “Geospatial Technologies and Homeland Security”. College Station, TX, November.
Top


 

Book Reviews

Chen, X.  2008. Book Review: Critical Infrastructure: Reliability and Vulnerability, edited by A. T. Murray and T. H. Grubesic: Springer, 2007, 311pp. ISBN 978-3-540-68055-0. Growth and Change 39(4).
Top