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The location pattern of different commercial stores in Shichahai, a historic conservation area in Beijing, was investigated from a street centrality perspective. Many previous studies have investigated the relationship between street centrality and land use patterns or commercial activities at interurban or intraurban scales. We considered Shichahai in this study to determine if street centrality applied at the street scale and if the street network was the only factor influencing the selection of store location. First, the nearest neighbor index, nearest neighbor hierarchical spatial cluster (NNHSC), and kernel density estimation (KDE) methods were used to provide baseline spatial distributions of commercial stores. Second, urban network analysis (UNA) tools were used to measure the street centrality indices under two conditions, with and without the weighting of cultural relics calculated by a principal component analysis (PCA). Finally, both store locations and centrality values at nodes were transformed to one unit (raster pixel) for a correlation analysis. The results showed that three of the four store types were clustered and had their own hotspots that were mostly located in the eastern and central parts of city blocks. The most momentous findings were determined from the street centrality indices. Among the three store types with correlation coefficients above 0.5, all centrality indices with landmark weighting, except straightness, had higher correlations, with closeness with landmark weighting having the highest correlation, followed by betweenness with landmark weighting. Therefore, we statistically concluded that street centrality could apply at the street scale and that the street network was not the only factor that influenced store location pattern, with landmarks also playing a significant role. The results provide guidance in determining the selection strategy for stores in a historic conservation area. [ABSTRACT FROM AUTHOR]

Based on the discrete element method (DEM) - continuum mechanics coupling method, a numerical simulation analysis is carried out to model cutting some existing bridge piles that have invaded Beijing Metro Line 12. Firstly, the macroscopic parameters of the reinforced concrete pile and the soil stratum where the shield tunneling machine traversed are calibrated using uniaxial compression and Brazilian test through a series of numerical tests. In this paper, the procedure of building up a DEM-continuum mechanics coupling model is presented, then the model is applied to simulate the process of cutting the pile foundation using the earth pressure balanced (EPB) shield machine. The influences of different advancing parameters on the displacement of the pile bottom, the thrust force, and the torque of the EPB shield machine are investigated. The simulation-calculated results, such as thrust force and torque of the shield machine, are in good agreement with the theoretical method in previous studies and the corresponding monitored data in the field. Finally, a method based on the thrust of a single cutter is proposed to improve the theoretical model so that it can consider the effects of cutting bridge piles. [ABSTRACT FROM AUTHOR]

Abstract: The levels of polybrominated diphenyl ethers (PBDEs) in breast milk from Beijing, China, were studied. The 6 predominant PBDEs congeners (BDE47, BDE99, BDE100, BDE153, BDE154 and BDE183) in 23 pooled breast milk samples from 205 mothers living in Beijing were measured. Mean and median of ΣPBDEs concentrations in all samples were 1.12ngg−1 lipid and 1.07ngg−1 lipid, respectively. The Statistical difference in concentrations was found between urban areas (1.22ngg−1 lipid, n =14) and rural areas (0.97ngg−1 lipid n =9). The sum of BDE47 and BDE153 accounted for more than 70% of ΣPBDEs in most samples. The significant correlation was found between the ΣPBDEs in pooled samples and average of consumption of food of animal origin in the pools in urban area. However, there was no correlation was found between the ΣPBDEs in pooled samples and average of consumption of food of animal origin in the pools in rural area of Beijing. The current study showed that the level of PBDEs in breast milk from Beijing was lower than that from South China and some developed countries such as USA and Sweden. [Copyright &y& Elsevier]