Reducing Building Conflicts in Map Generalization with an Improved PSO Algorithm

In map generalization, road symbolization and map scale reduction may create spatial conflicts between roads and neighboring buildings. To resolve these conflicts, cartographers often displace the buildings. However, because such displacement sometimes produces secondary spatial conflicts, it is necessary to solve the spatial conflicts iteratively. In this paper, we apply the immune genetic algorithm (IGA) and improved particle swarm optimization (PSO) to building displacement to solve conflicts. The dual-inheritance framework from the cultural algorithm is adopted in the PSO algorithm to optimize the topologic structure of particles. We generate Pareto optimal displacement solutions using the niche Pareto competition mechanism. The results of experiments comparing IGA and the improved PSO show that the improved PSO outperforms IGA; the improved PSO results in fewer graphic conflicts and smaller movements that better satisfy the movement precision requirements

Contextual Building Selection Based on a Genetic Algorithm in Map Generalization

In map generalization, scale reduction and feature symbolization inevitably generate problems of overlapping objects or map congestion. To solve the legibility problem with respect to the generalization of dispersed rural buildings, selection of buildings is necessary and can be transformed into an optimization problem. In this paper, an improved genetic algorithm for building selection is designed to be able to incorporate cartographic constraints related to the building selection problem. Part of the local constraints for building selection is used to constrain the encoding and genetic operation. To satisfy other local constraints, a preparation phase is necessary before building selection, which includes building enlargement, local displacement, conflict detection, and attribute enrichment. The contextual constraints are used to ascertain a fitness function. The experimental results indicate that the algorithm proposed in this article can obtain good results for building selection whilst preserving the spatial distribution characteristics of buildings

The Collaborative Method of Linear Graphic Simplification and Displacement

Linear graphic simplification and displacement operators are usually performed respectively in map generalization. Both of them may give rise to new conflicts with other map features such as surrounding buildings. In this paper, we attempt to coordinate these two operators to avoid repetitious detection of spatial conflicts, thus enhancing the efficiency of data processing. Linear graphic simplification has been taken into account in the process of displacement by transferring the linear graphic simplification into displacement of points on the line, constructing propagation paths between proximal map objects and considering spatial context and map perception rules. At the same time, the spatial characteristics of map objects are maintained as far as possible. Also, the roads and their surrounding buildings as an example are handled by means of this method, and effectiveness and availability of this method is verified

A Combined Approach to Cartographic Displacement for Buildings Based on Skeleton and Improved Elastic Beam Algorithm

<div><p>Scale reduction from source to target maps inevitably leads to conflicts of map symbols in cartography and geographic information systems (GIS). Displacement is one of the most important map generalization operators and it can be used to resolve the problems that arise from conflict among two or more map objects. In this paper, we propose a combined approach based on constraint Delaunay triangulation (CDT) skeleton and improved elastic beam algorithm for automated building displacement. In this approach, map data sets are first partitioned. Then the displacement operation is conducted in each partition as a cyclic and iterative process of conflict detection and resolution. In the iteration, the skeleton of the gap spaces is extracted using CDT. It then serves as an enhanced data model to detect conflicts and construct the proximity graph. Then, the proximity graph is adjusted using local grouping information. Under the action of forces derived from the detected conflicts, the proximity graph is deformed using the improved elastic beam algorithm. In this way, buildings are displaced to find an optimal compromise between related cartographic constraints. To validate this approach, two topographic map data sets (i.e., urban and suburban areas) were tested. The results were reasonable with respect to each constraint when the density of the map was not extremely high. In summary, the improvements include (1) an automated parameter-setting method for elastic beams, (2) explicit enforcement regarding the positional accuracy constraint, added by introducing drag forces, (3) preservation of local building groups through displacement over an adjusted proximity graph, and (4) an iterative strategy that is more likely to resolve the proximity conflicts than the one used in the existing elastic beam algorithm.</p></div

Extraction of the CDT skeleton.

<p>Extracted skeleton graph (left) in a map partition and detailed part (right) of the extracted skeleton graph to illustrate the concepts of skeleton arc, super-arc, and sub-arc.</p

Statistics of displacement magnitude for each data set.

<p>Statistics of displacement magnitude for each data set.</p

Research progress in biodegradable Zn-based materials for orthopedic applications

In recent years, zinc alloys have shown great potential as orthopedic plant materials because of their excellent biocompatibility, osteoinductive and biodegradation activities in vivo. The physiological function, degradation rate and mechanical properties of pure zinc were introduced in this review. Taking the gap between the above indicators and the clinical needs of orthopedics as the clue and the alloy elements as the classification basis, the existing achievements of researchers to improve the properties of zinc-based materials by changing the microstructure of materials and triggering the corresponding strengthening mechanism, and using the physiological synergistic function of added elements were expounded in this paper. The standard formulation, alloy design improvement and the introduction of new technologies such as additive manufacturing in the field of medical zinc based materials were discussed in order to meet the diversified needs of clinical diagnosis and treatment

Data set partitioning.

<p>The data set partitioning method has four major steps: (1) buffering of buildings, (2) merging of buffering polygons, (3) conducting an overlap with street network, and (4) processing a point-in-polygon operation to assign each building to the corresponding partition.</p

Visual result of data set B.

<p>(A) Initial situation (1∶25 000), (B) resultant situation (1∶25 000), and (C) comparing the initial and final states (1∶25 000 enlarged to 1∶12 500).</p

Comparative test results of existing elastic beam algorithm (partition A₃).

<p>(A) <i>E</i> = 50 000, <i>A</i> = 1 and <i>I</i> = 1; (B) <i>E</i> = 200 000, <i>A</i> = 1 and <i>I</i> = 1; and (C) <i>E</i> = 1 000 000, <i>A</i> = 1 and <i>I</i> = 1.</p