Wen Tzai-Hung's Geospatial Research

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WEN Lab's GEOSPATIAL Gallery: 2006-2016

1. Diffusion Patterns

Diffusion is defined in Oxford English Dictionary as “to disperse or be dispersed from a center; to spread widely, disseminate.”
Geographers categorized the structures of spatial diffusion into four types, which can represent the characteristics of the spreading phenomenon. It includes that expansion diffusion is the process which a phenomenon of interest spreading from one place to another; relocation diffusion is the process which the a phenomenon of interest leaving the areas where they originated and moving to another new areas; contagious diffusion is the process which strongly influenced by distance and hierarchical diffusion is the process which a phenomenon of interest spreading through an ordered sequence of classes or places.

Summary: This study proposed an innovative methodology that considers only the spatial-temporal relationships of illness onsets, combining exploratory spatial analysis and network topological indicators, degree centrality and network clustering coefficient, to identify space-time clusters, track possible sources of an epidemic and measure transmission risk of an individual.

Furthering Reading:
1. Two Clustering Diffusion Patterns Identified from the 2001-2003 Dengue Epidemic. American Journal of Tropical Medicine & Hygiene 79(3): 344–352. link
2. Population Movement and Vector-borne Disease Transmission: Differentiating Spatial-temporal Diffusion Patterns of Commuting and Non-commuting Dengue Cases. Annals of the Association of American Geographers 102(5): 1026-1037. link
3. Analyzing the Patterns of Space-Time Distances for Tracking the Diffusion of an Epidemic, In Kwan MP, Richardson D, Wang D and Zhou C (Eds.). Space-Time Integration in Geography and GIScience, Dordrecht: Springer. (ISBN: 978-94-017-9204-2) link

2. Epidemic Dynamics

LINK

Simulating the Spread of Influenza A (H1N1)
in Taiwan under the scenario of Taipei outbreak.

Summary: Our proposed framework, Multilayer Epidemic Dynamics Simulator (MEDSim), has four contact structures: within age group, between age groups, daily commute, and nationwide interaction. We simulated outbreak locations and intervention scenarios for the 2009 swine-origin influenza A (H1N1) epidemic. Our results indicate that lower transmission rates and earlier intervention activation times did not reduce total numbers of infected cases, but did delay peak times.

Furthering Reading:
Integrating Epidemic Dynamics with Daily Commuting Networks: Building a Multilayer Framework to Assess Influenza A (H1N1) Intervention Policies. Simulation: Transactions of The Society for Modeling and Simulation International 87(5): 385-405. link

3. Risk of Exposure to Dengue

Summary: This study clarifies the geographic effects of crowd gathering places on the frequency of dengue vector for assessing the spatial risk of exposure to dengue in Kaohsiung City, Taiwan. Our results indicated that people closer to crowd-gathering places have a higher frequency of contact with Ae. aegypti than with Ae. albopictus larvae. The dengue risk is caused by the human-Aedes aegypti contacts concentrated around city centers, while the risk caused by the human-Aedes albopictus contacts is distributed around the city boundary.

Furthering Reading:
Incorporating the Human-Aedes Mosquito Interactions into Measuring the Spatial Risk of Urban Dengue Fever, Applied Geography 62:256-266. link

4. Dengue Vector Surveillance

Summary: This research evaluated the spatiotemporal distribution of dengue vectors by a human population stratified ovitrap survey. We demonstrated the potential intensity of dengue transmission spatiotemporally in the high epidemic areas. We analyzed the temporal patterns of vector abundances, compared the levels of vector aggregation indoors with outdoors, and assess the vector concentration tendency around residential centers and administration edges form June 2010 to June 2011.

Furthering Reading:
1. A Dengue Vector Surveillance by Human Population-stratified Ovitrap Survey for Aedes (Diptera: Culicidae) Adult and Egg Collections in High Dengue-risk Areas of Taiwan, Journal of Medical Entomology 50(2):261-269. link
2. The Spatio-temporal Characteristics of Potential Dengue Risk Assessed by Aedes aegypti and Aedes albopictus in High-epidemic Areas, Stoch Environ Res Risk Assess 30(8): 2057–2066. link

5. Health Care Utilization

Summary: Employing a GIS-based accessibility approach, this study found that medical resources within-district and distance to cross-district hospitals significantly affected patients’ hospital-seeking behavior. By identifying the non-linear relationship between accessibility to hospitals and patients’ cross-district hospital-seeking, our results showed the importance of incorporating spatial inequality into the planning for the provision and utilization of health care.

Furthering Reading:
1. Profiling the Patient Flow for Seeking Healthcare in Taiwan: using Gravity Modeling to Investigate the Influences of Travel Distance and Healthcare Resources, Taiwan Journal of Public Health 35(2): 136-151. pdf | link
2. Using Geographic Information Systems (GIS) to Identify the Association between Geographic Accessibility and Hospital-seeking Behavior by Hepatocellular Carcinoma Patients in Taiwan. Taiwan Journal of Public Health 28(6): 517-529. pdf

6. Mobility Studies

Summary: We proposed geographically modified PageRank algorithms that incorporate geographic considerations into PageRank algorithms to identify the spatial concentration of human movement in a geospatial network. Our findings indicate the proposed algorithms more effectively capture the spatial locations where people reside than traditional commonly-used network metrics. In comparing location attractiveness and distance decay, we conclude that the concentration of human movement is largely determined by the distance decay. This implies that geographic proximity remains a key factor in human mobility.

Furthering Reading:
1. Incorporation of Spatial Interactions in Location Networks to Identify Critical Geo-Referenced Routes for Assessing Disease Control Measures on a Large-Scale Campus, Int J Environ Res Public Health 12, 4170-4184. link
2. Geographically Modified PageRank Algorithms: Identifying the Spatial Concentration of Human Movement in a Geospatial Network, PLOS ONE 10(10): e0139509. link

7. Urban Congestion

Summary: We proposed an analytical procedure of ranking algorithm, the Flow-based PageRank (FBPR), for investigating the traffic flow concentration, complexity of street network structure and traffic impact areas. Our results indicate that only relying on the topological structure of the street network, this framework could identify the Central Business Districts (CBD), and the areas proximate to the stations of the combination of MRT and train railway systems are prone to traffic congestion. Meanwhile, the delineation of traffic impact areas could be spatially targeted at priorities of traffic improvement for city planners.

Furthering Reading:
1. Understanding the Topological Characteristics and Flow Complexity of Urban Traffic Congestion, PHYSICA A: Statistical Mechanics and Its Applications 473:166-177. link
2. Link Structure Analysis of Urban Street Networks for Delineating Traffic Impact Areas. In Essaaidi and Nemiche (Eds.), Advances in Complex Societal, Environmental and Engineered Systems, Springer Series: Nonlinear Systems and Complexity, Springer. (ISBN 978-3-319-46164-9) link

8. Wireless Geo-sensors for Environmental Sensing

Summary: By deploying wireless sensors on crossroads and main roads, this study established a pilot framework for a wireless sensor network (WSN)-based real-time monitoring system to understand street-level spatial-temporal changes of carbon monoxide (CO) in urban settings. The system consists of two major components. The first component is the deployment of wireless sensors. The other component is a map-based monitoring platform for sensor data visualization and manipulation in time and space. Using intensive real-time street-level monitoring framework, we compared the spatial-temporal patterns of air pollution in different time periods.

Furthering Reading:
Monitoring Street-level Spatial-Temporal Variations of Carbon Monoxide in Urban Settings Using a Wireless Sensor Network (WSN) Framework, Int J Environ Res Public Health 10(12), 6380-6396. link

9. Population Maps

The Census Atlas of Taiwan (1956-2010)

Summary: Taiwan's population structure had changed rapidly after the war. Events such as baby boom during retrocession period and the low birth rate in contemporary era had all dramatically changed the population structure in Taiwan. In order to picture the context of population change in Taiwan, we paid efforts to digitalize the census data released on 1956 and 1966 and publish the Census Atlas of Taiwan (1956-2010). We also established e-Atlas: Taiwan Census Explorer 1956-2010 for publishing interactive maps and charts on the Web.

Furthering Reading:
1. The Census Atlas of Taiwan (1956-2010) , Taipei: NTU Population and Gender Studies Center & Dept. of Geography, 305 pages. (ISBN: 978-986-03-5765-3) link
2. e-Atlas: Taiwan Census Explorer 1956-2010 (Chinese/English) link

10. Natural Resources

Biomass Energy Landscape

Summary: We established a linear complementarity model to simulate the power market equilibrium with cofiring systems in Taiwan. A GIS-based analysis was then used to analyze the geospatial relationships between paddy rice farms and power plants to assess potential biomass for straw-power generation. The above maps illustrate paddy rice straw and the locations of power plants. The results showed spatial distribution of rice straw collection for various cofiring scenarios and CO2 emissions reductions of these power plants.

Furthering Reading:
GIS-based Biomass Resource Utilization for Rice Straw Co-firing in the Taiwanese Power Market, Energy 55:354-360 link

Water Resource Management

Summary: This study proposed a novel spatial scenario-based planning framework, with a database, model base, and scenario-setting modules, to generate flexible spatial planning scenarios for improving irrigation water-demand planning. A prototype of the proposed scenario-based framework is implemented on a geographic information system platform to assist in spatial decision making. Demand planning during a drought period for the Chia-Nan irrigation command area, the largest one in Taiwan, is adopted as a case study to demonstrate the proposed framework for spatial scenario analysis.

Furthering Reading:
Analysis of Spatial Scenarios Aiding Decision-Making for Regional Irrigation Water-Demand Planning, Journal of Irrigation and Drainage Engineering-ASCE 133(5): 455-467. link