Epidemic modelling by ripple-spreading network and genetic algorithm

Mathematical analysis and modelling is central to infectious disease epidemiology. This paper, inspired by the natural ripple-spreading phenomenon, proposes a novel ripple-spreading network model for the study of infectious disease transmission. The new epidemic model naturally has good potential for capturing many spatial and temporal features observed in the outbreak of plagues. In particular, using a stochastic ripple-spreading process simulates the effect of random contacts and movements of individuals on the probability of infection well, which is usually a challenging issue in epidemic modeling. Some ripple-spreading related parameters such as threshold and amplifying factor of nodes are ideal to describe the importance of individuals’ physical fitness and immunity. The new model is rich in parameters to incorporate many real factors such as public health service and policies, and it is highly flexible to modifications. A genetic algorithm is used to tune the parameters of the model by referring to historic data of an epidemic. The well-tuned model can then be used for analyzing and forecasting purposes. The effectiveness of the proposed method is illustrated by simulation results

Space–time prism and accessibility incorporating monetary budget and Mobility-as-a-Service

Recent years in time geography have witnessed a flourishment of space–time prism (STP) modeling extensions for enhancing realism. However, there is little research on the incorporation of monetary budget in STP models to capture personal potential mobility space more realistically. This study considers both time and monetary budget constraints in STP modeling in a multimodal supernetwork integrating mobility-as-a-service and trip chains. We develop an efficient two-stage bi-criterion bidirectional search method to identify Pareto path sets to construct the resulting STP for conducting a flexible activity between two anchor nodes. To demonstrate the effectiveness of the proposed model and solution method, a case study with varying scenarios is conducted to evaluate the impacts of monetary budget on space–time accessibility and equality. The findings show that the ignorance of monetary budget overestimates accessibility and that MaaS, if not well designed, may not improve equality in accessibility as intended.</p