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This paper illustrates the spatial variations in urban resource and environmental efficiency (REE) amongst 285 cities in China using a Data Envelopment Analysis (DEA) model, and examines the factors that have had the greatest effect on this spatial pattern by regression models. The results gave an average urban REE of 0.6381, and an average pure technical efficiency (PTE) and scale efficiency (SE) of 0.6964 and 0.9225, respectively. The results support the existence of a U-shaped relationship between REE and income level, which means that an increase in urban GDP does not result in an equivalent increase in environmental efficiency. Economic growth affects REE in three ways: scale effects (population scale and urbanization rate); composition effects; and spatial effects. Improvements in urban resource use and environmental efficiency depend upon both technological innovation and effective governance. Policies designed to achieve these improvements should therefore be implemented at all levels of ...

In a wireless mesh network (WMN), gateways act as the bridges between the mesh backbone and the Internet, and significantly affect the performance of the whole network. Hence, how to determine the optimal number and positions of gateways, i.e., gateway deployment, is one of the most important and challenging topics in practical and theoretical research on designing a WMN. Although several approaches have been proposed to address this problem, few of them take load balancing and interference minimization into account. In this paper, we study the Load-balancing and Interference-minimization Gateway Deployment Problem (LIGDP), which aims to achieve four objectives, i.e. minimizing deployment cost, minimizing MR-GW path length, balancing gateway load and minimizing link interference. We formulate it as a multi-objective integer linear program (ILP) issue first, and then propose an efficient gateway deployment approach, called LIGDP Heuristic. The approach joints two heuristic algorithms, i.e., MSC-based location algorithm (MLA) and load-aware and interference-aware association algorithm (LIAA), to determine gateway positions and construct GW-rooted trees. Simulation results not only show that the trade-off between deployment cost and network performance can be achieved by adjusting R-hop, GW throughput and MR throughput constraints, but also demonstrate that, compared with other existing approaches, LIGDP Heuristic performs better on MR-GW path, load balancing and interference minimization without deploying more gateways.