网络交通流是以前主要吃饭的家伙，但是最近好几年没有怎么碰过了。

凑巧昨天同时完成了两篇交通流的论文，也是自己花了大力气完全写了论文的，感觉好像回到了两三年前，那个时候王文旭和严钢前锋，我和殷传洋后腰，狠搞了一段时间交通流。这两篇虽然工作水平不怎么了不起，但都还是蛮有趣的论文，因为现在交通流的研究对我来说已经是支流中的支流（套用严钢的一句话：我们已经封刀了！），再完完整整写交通流的论文可能也很少了，所以贴出来和大家共享一下。

1. Optimal transport on supply-demand networks  (0908.1184)

    Yuhan Chen, Binghong Wang, Lichao Zhao, Changsong Zhou, Tao Zhou

Previously, transport networks are usually treated as homogeneous
networks, that is, every node has the same function, simultaneously
providing and requiring resources. However, some real networks, such
as power grid and supply chain networks, show a far different
scenario in which the nodes are classified into two categories: the
supply nodes provide some kinds of services, while the demand nodes
require them. In this paper, we propose a general transport model
for those supply-demand networks, associated with a criterion to
quantify their transport capacities. In a supply-demand network with
heterogenous degree distribution, its transport capacity strongly
depends on the locations of supply nodes. We therefore design a
simulated annealing algorithm to find the optimal configuration of
supply nodes, which remarkably enhances the transport capacity, and
outperforms the degree target algorithm, the betweenness target
algorithm, and the greedy method. This work provides a start point
for systematically analyzing and optimizing transport dynamics on
supply-demand networks.

[PDF]

2. Origin of the Scaling Law in Human Mobility: Hierarchical Organization of Traffic Systems (0908.1221)

    Xiaopu Han, Qiang Hao, Binghong Wang, Tao Zhou

Uncovering the mechanism leading to the scaling law in human
trajectories is of fundamental importance in understanding many
spatiotemporal phenomena. We propose a hierarchical geographical
model to mimic the real traffic system, upon which a random walker
will generate a power-law travel displacement distribution with
exponent -2. When considering the inhomogeneities of cities'
locations and attractions, this model reproduces a power-law
displacement distribution with an exponential cutoff, as well as a
scaling behavior in the probability density of having traveled a
certain distance at a certain time. Our results agree very well with
the empirical observations reported in [D. Brockmann et al.,
Nature 439, 462 (2006)].