Origin Distribution Patterns and Floating Population Modeling:Yiwu City as a Destination

Existing quantitative migration studies are mainly at the inter-region or inter-province level for lacking of detailed geo-referenced migration data.Meanwhile,few of them integrate explorative spatial data analysis and spatial regression model into migration analysis.Based on aggregated registered floating population data from 2005 to 2008,the phenomena that population floating to Yiwu City in Zhejiang Province is analyzed at the provincial and county levels.The spatial layout of Yiwu's pull forces is proved as a V-shaped pattern excluding Sichuan Province based on map visualization method.Using the migration ratio in 2007 as an explanatory variable,two models are compared using ordinary least square,spatial error model and spatial lag model methods for county-level data in Jiangxi and Anhui provinces.The model with migration stock provides an improved fitting over the model without migration stock according to the model fitting results.The floating population flocking into Yiwu City from Jiangxi is determined mostly by migration stock while the determinant factors are migration stock and distance to Yiwu City for Anhui.The distance-decay effect is true for migration flow from Anhui to Yiwu City while the distance rule is not confirmed in Jiangxi with the best fitting model.The correlation between per capita net income of rural labor forces and migration ratio is not significant in Jiangxi and significant but at the 0.1 level only in Anhui.Further analysis shows that the distance,income and man-land ratio are important factors to explain population floating at earlier stage.However,as the dynamic population floating process evolves,the determinant factor would be migration stock.

Spatial distribution visualization of PWM continuous variable-rate spray

Pesticide application is a dynamic spatial distribution process,in which spray liquid should be able to cover the targets with desired thickness and uniformity.Therefore,it is important to study the 2-D and 3-D(dimensional)spray distribution to evaluate spraying quality.The curve-surface generation methods in Excel were used to establish 1-D,2-D,and 3-D graphics of variable-rate spray distribution in order to characterize the space distribution of the variable-rate spray.The 1-D,2-D,and 3-D distribution graphs of Pulse-Width Modulation(PWM)-based continuous variable-rate spray were developed to provide a tool to analyze the distribution characteristics of the spray.The 1-D graph showed that the spray distribution concentrated toward the center of the spray field with the decreased flow-rate.The 2-D graph showed that the spray distribution always spread as the shape of Normal Probability Distribution with the change of the flow-rate.The 3-D graph showed that the spray distribution tended to be uniform when the sprayer travelled forward at the appropriate speed.This study indicated that the visualization method could be directly used for analysis and comparison of different variable-rate spray distributions from different experimental conditions and measuring methods.

Enabling Technologies in the Problem Solving Environment HEDP

Enabling technologies are those technologies preparing input data,analyzing output data and facilitating the whole processes for numerical simulations.This paper outlines current enabling technologies for large-scale multidisciplinary simulations used in the High End Digital Prototyping(HEDP)system,a problem solving environment equipped with capability of mesh generation and large-scale visualization.A problem solving environment is a computer system that provides all the computational facilities necessary to solve a target class of problems.Mesh generation continues to be the pacing technology for a practical numerical analysis,which is essential to yielding an accurate and efficient solution.Large-scale visualization maps the massive data to some kinds of scenes interactively,which can be realized through a tiled display wall system with distributed visualization capability.HEDP is designed for large-scale andmultidisciplinary simulations,and there are four categories of modules involved,namely pre-processing module,computing module,post-processing module,and platform control module.All these modules are coupled through a software bus,which makes the modules integrated seamlessly.Detailed design principles and applications of the HEDP environment are addressed in this paper.