253 research outputs found
Quantifying the overall characteristics of urban mobility considering spatial information
Quantification of the overall characteristics of urban mobility using
coarse-grained methods is crucial for urban management, planning and
sustainable development. Although some recent studies have provided
quantification methods for coarse-grained numerical information regarding urban
mobility, a method that can simultaneously capture numerical and spatial
information remains an outstanding problem. Here, we use mathematical vectors
to depict human mobility, with mobility magnitude representing numerical
information and mobility direction representing spatial information. We then
define anisotropy and centripetality metrics by vector computation to measure
imbalance in direction distribution and orientation toward the city center of
mobility flows, respectively. As a case study, we apply our method to 60
Chinese cities and identify three mobility patterns: strong monocentric, weak
monocentric and polycentric. To better understand mobility pattern, we further
study the allometric scaling of the average commuting distance and the
spatiotemporal variations of the two metrics in different patterns. Finally, we
build a microscopic model to explain the key mechanisms driving the diversity
in anisotropy and centripetality. Our work offers a comprehensive method that
considers both numerical and spatial information to quantify and classify the
overall characteristics of urban mobility, enhancing our understanding of the
structure and evolution of urban mobility systems
Momentum-resolved Raman spectroscopy of non-interacting ultracold Fermi gas
We report the experiment on probing the one-body spectral function in a
trapped non-interacting K Fermi gas by means of the momentum-resolved
Raman spectroscopy The experimental result is in good agreement with the
expected quadratic dispersion in the non-interacting regime. Through the
comparison with the radio-frequency spectrum, we found that the Raman spectrum
shows some new characteristics.Comment: 4 pages, 2 figures, appear in Phys. Rev.
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