2,220 research outputs found
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
Influence of Helicobacter pylori culture supernatant on the ecological balance of a dual-species oral biofilm
Dental caries is a chronic progressive disease occurring in the tooth hard tissue due to multiple factors, in which bacteria are the initial cause. Both Streptococcus mutans and Streptococcus sanguinis are main members of oral biofilm. Helicobacter pylori may also be detected in dental plaque, playing an important role in the development of dental caries. Objective The aim of this study was to investigate the effect of H. pylori culture supernatant on S. mutans and S. sanguinis dual-species biofilm and to evaluate its potential ability on affecting dental health. Material and methods The effect of H. pylori supernatant on single-species and dual-species biofilm was measured by colony forming units counting and fluorescence in situ hybridization (FISH) assay, respectively. The effect of H. pylori supernatant on S. mutans and S. sanguinis extracellular polysaccharides (EPS) production was measured by both confocal laser scanning microscopy observation and anthrone-sulfuric acid method. The effect of H. pylori supernatant on S. mutans gene expression was measured by quantitative real-time PCR (qRT-PCR) assays. Results H. pylori supernatant could inhibit both S. mutans and S. sanguinis biofilm formation and EPS production. S. sanguinis inhibition rate was significantly higher than that of S. mutans. Finally, S. mutans bacteriocin and acidogenicity related genes expression were affected by H. pylori culture supernatant. Conclusion Our results showed that H. pylori could destroy the balance between S. mutans and S. sanguinis in oral biofilm, creating an advantageous environment for S. mutans, which became the dominant bacteria, promoting the formation and development of dental caries
Nonlinear Weighted Directed Acyclic Graph and A Priori Estimates for Neural Networks
In an attempt to better understand structural benefits and generalization
power of deep neural networks, we firstly present a novel graph theoretical
formulation of neural network models, including fully connected, residual
network (ResNet) and densely connected networks (DenseNet). Secondly, we extend
the error analysis of the population risk for two layer network
\cite{ew2019prioriTwo} and ResNet \cite{e2019prioriRes} to DenseNet, and show
further that for neural networks satisfying certain mild conditions, similar
estimates can be obtained. These estimates are a priori in nature since they
depend sorely on the information prior to the training process, in particular,
the bounds for the estimation errors are independent of the input dimension
Multifractal scaling analyses of the spatial diffusion pattern of COVID-19 pandemic in Chinese mainland
Revealing spatiotemporal evolution regularity in the spatial diffusion of
epidemics is helpful for preventing and controlling the spread of epidemics.
Based on the real-time COVID-19 datasets by prefecture-level cities and date,
this paper is aimed at exploring the multifractal scaling in spatial diffusion
pattern of COVID-19 pandemic and its evolution characteristics in Chinese
mainland. The ArcGIS technology and box-counting method are employed to extract
spatial data and the least square calculation is used to calculate fractal
parameters. The results show multifractal distribution of COVID-19 pandemic in
China. The generalized correlation dimension spectrums are inverse S-shaped
curves, but the fractal dimension values significantly exceeds the Euclidean
dimension of embedding space when moment order q<<0. The local singularity
spectrums are asymmetric unimodal curves, which slant to right. The fractal
dimension growth curves are shown as quasi S-shaped curves. From these
spectrums and growth curves, the main conclusions can be drawn as follows.
First, self-similar patterns developed in the process of Covid-19 pandemic,
which seem be dominated by multi-scaling law. Second, the spatial pattern of
COVID-19 across China can be characterized by global clustering with local
disordered diffusion. Third, the spatial diffusion process of COVID-19 in China
experienced four stages, i.e., initial stage, the rapid diffusion stage, the
hierarchical diffusion stage, and finally the contraction stage. This study
suggests that multifractal theory can be utilized to characterize
spatio-temporal diffusion of COVID-19 pandemic, and the case analyses may be
instructive for further exploring natural laws of spatial diffusion.Comment: 22 pages,6 figures, 4 table
An Extended TODIM Method for Group Decision Making with the Interval Intuitionistic Fuzzy Sets
For a multiple-attribute group decision-making problem with interval intuitionistic fuzzy sets, a method based on extended TODIM is proposed. First, the concepts of interval intuitionistic fuzzy set and its algorithms are defined, and then the entropy method to determine the weights is put forward. Then, based on the Hamming distance and the Euclidean distance of the interval intuitionistic fuzzy set, both of which have been defined, function mapping is given for the attribute. Finally, to solve multiple-attribute group decision-making problems using interval intuitionistic fuzzy sets, a method based on extended TODIM is put forward, and a case that deals with the site selection of airport terminals is given to prove the method
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