Defining Urban Boundaries by Characteristic Scales

Defining an objective boundary for a city is a difficult problem, which remains to be solved by an effective method. Recent years, new methods for identifying urban boundary have been developed by means of spatial search techniques (e.g. CCA). However, the new algorithms are involved with another problem, that is, how to determine the characteristic radius of spatial search. This paper proposes new approaches to looking for the most advisable spatial searching radius for determining urban boundary. We found that the relationships between the spatial searching radius and the corresponding number of clusters take on an exponential function. In the exponential model, the scale parameter just represents the characteristic length that we can use to define the most objective urban boundary objectively. Two sets of China's cities are employed to test this method, and the results lend support to the judgment that the characteristic parameter can well serve for the spatial searching radius. The research may be revealing for making urban spatial analysis in methodology and implementing identification of urban boundaries in practice.Comment: 26 pages, 5 figures, 7 table

Understanding Fractal Dimension of Urban Form through Spatial Entropy

Spatial patterns and processes of cities can be described with various entropy functions. However, spatial entropy always depends on the scale of measurement, and it is difficult to find a characteristic value for it. In contrast, fractal parameters can be employed to characterize scale-free phenomena. This paper is devoted to exploring the similarities and differences between spatial entropy and fractal dimension in urban description. Drawing an analogy between cities and growing fractals, we illustrate the definitions of fractal dimension based on different entropy concepts. Three representative fractal dimensions in the multifractal dimension set are utilized to make empirical analyses of urban form of two cities. The results show that the entropy values are not determinate, but the fractal dimension value is certain; if the linear size of boxes is small enough (e.g., <1/25), the linear correlation between entropy and fractal dimension is clear. Further empirical analysis indicates that fractal dimension is close to the characteristic values of spatial entropy. This suggests that the physical meaning of fractal dimension can be interpreted by the ideas from entropy and scales and the conclusion is revealing for future spatial analysis of cities. Key words: fractal dimension; entropy; mutlifractals; scaling; urban form; Chinese citiesComment: 26 pages, 7 figures, 8 table

Association between serum albumin concentration change trajectory and risk of hypertension: a cohort study in China

BackgroundWe sought to assess the risk of hypertension based on the trajectory of changes in serum albumin concentrations.MethodsA total of 11,946 nonhypertension adults aged 30–60 years who underwent at least 3 medical examinations between 2009 and 2016 were included in this study. Group-based trajectory models were obtained for 4 category groups, and logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for each category group of serum albumin concentration and the risk of hypertension.ResultsDuring a mean follow-up period of 4.30 years, 1,537 hypertension events occurred in 11,946 subjects without hypertension. A high stable trajectory of serum albumin concentrations (OR, 0.70, 95% CI, 0.51–0.96) was associated with a significantly lower risk of developing hypertension. The results of the sensitivity analysis of the high stable trajectory (OR, 0.64, 95% CI, 0.43–0.96) remained statistically significant. Subjects with normal weight and those ≥45 years of age had a significantly lower risk of hypertension at moderate increase (P = 0.053 or 0.026) and high stable trajectories (P = 0.011 or 0.016). In males and overweight subjects, the risk of hypertension was significantly lower in the high stable trajectory (P = 0.038 or 0.044).ConclusionIn this study, we found that moderate increase in serum albumin concentrations and a high stable trajectory were significantly associated with a reduced risk of hypertension in subjects aged ≥45 years and those with normal weight and that high stable serum albumin concentrations were significantly associated with a reduced risk of hypertension in males and overweight subjects

Influential Factors and Geographical Differences in the Redevelopment Willingness of Urban Villagers: A Case Study of Guangzhou, China

As a crucial part of China’s development strategy, the redevelopment of urban villages and the redevelopment willingness of villagers have attracted considerable scholarly interest. However, the literature to date has neglected the effect of the geographical location of urban villages on the redevelopment willingness of villagers. The purpose of this study is to examine the influential factors of the redevelopment willingness of urban villagers, especially with regard to geographical differences and their effects. Based on prospect theory and 1083 questionnaires administered in 45 selected urban villages in Guangzhou, we use the ordinal logistic regression model to explore the influential factors behind villagers’ redevelopment willingness in inner villages (40 km from the city center). The results show that in inner villages the confirmation of residential land rights can significantly increase redevelopment willingness, but in urban fringe villages the number of stories in dwelling houses significantly decreases the willingness. Further, a high level of villagers’ trust in the government, market enterprises, and the village collective each has a significant positive impact on the redevelopment willingness of villagers in urban fringe villages. However, only trust in the government and market enterprises have significant positive impacts on redevelopment willingness in the inner villages and only trust in the village collective is significant in this regard in suburban villages. The effects of geographical differences imply that China’s redevelopment policy should be applied in a differentiated way based on the geographical locations of urban villages

Beyond-Birthday-Bound Security for 4-round Linear Substitution-Permutation Networks

Recent works of Cogliati et al. (CRYPTO 2018) have initiated provable treatments of Substitution-Permutation Networks (SPNs), one of the most popular approach to construct modern blockciphers. Such theoretical SPN models may employ non-linear diffusion layers, which enables beyond-birthday-bound provable security. Though, for the model of real world blockciphers, i.e., SPN models with linear diffusion layers, existing provable results are capped at birthday security up to 2n/2 adversarial queries, where n is the size of the idealized S-boxes.In this paper, we overcome this birthday barrier and prove that a 4-round SPN with linear diffusion layers and independent round keys is secure up to 22n/3 queries. For this, we identify conditions on the linear layers that are sufficient for such security, which, unsurprisingly, turns out to be slightly stronger than Cogliati et al.’s conditions for birthday security. These provides additional theoretic supports for real world SPN blockciphers

Stochastic Scenarios Generation for Wind Power and Photovoltaic System Based on Generative Moment Matching Network

The penetrations of wind power and photovoltaic system in distribution network are increasing year by year. The randomness and fluctuation of their output powers bring great challenges to the planning and operation of distribution networks. Aimed at the uncertainty of output power of renewable energy, a stochastic scenarios generation method for photovoltaic and wind power based on generative moment matching network (GMMN) is proposed. In this method, the maximum mean discrepancy is adopted as the loss function of the generator, and the auto-encoder is adopted to reduce the dimension of the generated stochastic scenarios, so as to solve the low dimensional manifold problem of the high-dimensional power curves. According to the characteristics of the power curves, the network structure suitable for the stochastic scenarios generation of renewable energy is designed. The effectiveness and adaptability of the proposed method are verified by real data. The simulation results show that the proposed GMMN can not only simulate the shape characteristics, probability distribution characteristics, fluctuation, and spatial-temporal correlation of the photovoltaic and wind power curves, but also has universality. It can be applied to the random field generation tasks for different generation units only by adjusting the structure and parameters of the network.</p

Univariate and multiple linear regression analyses for 23 single nucleotide polymorphisms in 14 genes predisposing to chronic glomerular diseases and IgA nephropathy in Han Chinese

Immunoglobulin A nephropathy (IgAN) is a complex trait regulated by the inter-action among multiple physiologic regulatory systems and probably involving numerous genes, which leads to inconsistent findings in genetic studies. One possibility of failure to replicate some single-locus results is that the underlying genetics of IgAN nephropathy is based on multiple genes with minor effects. To learn the association between 23 single nucleotide polymorphisms (SNPs) in 14 genes predisposing to chronic glomerular diseases and IgAN in Han males, the 23 SNPs genotypes of 21 Han males were detected and analyzed with a BaiO gene chip, and their asso-ciations were analyzed with univariate analysis and multiple linear regression analysis. Analysis showed that CTLA4 rs231726 and CR2 rs1048971 revealed a significant association with IgAN. These findings support the multi-gene nature of the etiology of IgAN and propose a potential gene-gene interactive model for future studies

Changes in soil organic carbon fractions and bacterial community composition under different tillage and organic fertiliser application in a maize−wheat rotation system

The objective of this study was to assess the impact of different tillage and organic fertiliser regimes on soil carbon fractions and bacterial community composition within a maize–wheat cropping system. We conducted a six-year experiment on the Huang-Huai-Hai Plain of China. Six treatments were established: deep tillage (DT), shallow tillage (ST), no-tillage (NT), deep tillage with organic fertiliser (DTF), shallow tillage with organic fertiliser (STF), and no-tillage with organic fertiliser (NTF). Results indicated that during the winter wheat growing season, the highest contents of soil organic carbon (SOC) and easily-oxidised organic carbon (EOC) were in the STF treatment. During the summer maizegrowing season, the DTF treatment had the highest SOC and EOC contents. Compared with the other treatments, the NTF treatment had higher Chao1 and Shannon indices for bacteria; however, the relative abundance of Proteobacteria is highest in all treatments. A redundancy analysis (RDA) revealed that bacterial community composition was correlated with variation of the SOC, DOC, EOC, and microbial biomass carbon (MBC). Our results showed that combining the two components of the SOC fractions and bacterial community composition, STF practice in a maize–wheat rotation was a sustainable approach to optimising soil structure and improving soil quality