Origin of the Scaling Law in Human Mobility: Hierarchical Organization of Traffic Systems

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)].Comment: 6 figures, 4 page

Anomalous magnetohydrodynamics with temperature-dependent electric conductivity and application to the global polarization

We have derived the solutions of the relativistic anomalous magnetohydrodynamics with longitudinal Bjorken boost invariance and transverse electromagnetic fields in the presence of temperature or energy density dependent electric conductivity. We consider the equations of states in a high temperature limit or in a high chiral chemical potential limit. We obtain both perturbative analytic solutions up to the order of \hbar and numerical solutions in our configurations of initial electromagnetic fields and Bjorken flow velocity. Our results show that the temperature or energy density dependent electric conductivity plays an important role to the decaying of the energy density and electromagnetic fields. We also implement our results to the splitting of global polarization for \Lambda and \bar{\Lambda} hyperons induced by the magnetic fields. Our results for the splitting of global polarization disagree with the experimental data in low energy collisions, which implies that the contribution from gradient of chemical potential may dominate in the low energy collisions

From alleviating extreme poverty to the construction of an international NGO : changes observed in individuals and communities involved

This paper is with two purposes, one, to inform the general public about how the serving of the extremely poor can lead to a global non-government organization aiming at combating poverty; two, to let the participants on the day of the seminar enter the workshop format in which they discuss about issues related to what most people living in developed nations like Taiwan would not be able to really imagine. The paper will begin by telling the story of Knight Club, the service works it has done in different nations in Asia, particularly in Myanmar and how it ended up in Kenya where they found the desert-like land caused by global warming has influenced the livelihood of the millions. Confronted by such huge tasks ahead while experiencing trials and failures, Community Up International was born, with the participants, locals involved and researched in this paper, coming from different nationalities who build up the bond in between each other and weave an inspiring story that beats the normal idea People need to be very rich in order to do good. On the contrary, the paper, alongside with the workshop, will tell a single story that echoes in the mind of all involved: With some willpower, everyone can make a difference, even when the person is merely a travellers or a person who seems to have nothing to offer, for a warm gesture and friendly interaction can be life-changing