Cross-comparative analysis of evacuation behavior after earthquakes using mobile phone data

Despite the importance of predicting evacuation mobility dynamics after large scale disasters for effective first response and disaster relief, our general understanding of evacuation behavior remains limited because of the lack of empirical evidence on the evacuation movement of individuals across multiple disaster instances. Here we investigate the GPS trajectories of a total of more than 1 million anonymized mobile phone users whose positions are tracked for a period of 2 months before and after four of the major earthquakes that occurred in Japan. Through a cross comparative analysis between the four disaster instances, we find that in contrast with the assumed complexity of evacuation decision making mechanisms in crisis situations, the individuals' evacuation probability is strongly dependent on the seismic intensity that they experience. In fact, we show that the evacuation probabilities in all earthquakes collapse into a similar pattern, with a critical threshold at around seismic intensity 5.5. This indicates that despite the diversity in the earthquakes profiles and urban characteristics, evacuation behavior is similarly dependent on seismic intensity. Moreover, we found that probability density functions of the distances that individuals evacuate are not dependent on seismic intensities that individuals experience. These insights from empirical analysis on evacuation from multiple earthquake instances using large scale mobility data contributes to a deeper understanding of how people react to earthquakes, and can potentially assist decision makers to simulate and predict the number of evacuees in urban areas with little computational time and cost, by using population density information and seismic intensity which can be observed instantaneously after the shock

Picosecond Resonance Raman Studies of Solvent Effects on Electron Transfer in Ruthenium-Polypyridine Complexes.

Solvent effects in D\sb3 symmetric ruthenium-polypyridine complexes were studied by using excited state resonance Raman technique. Picosecond laser techniques were used to determine if electron transfer between ligands could be observed in an effort to learn about electron localization in ruthenium-polypyridine complexes. Ru(bpy)\sb3\sp{2+} (bpy is 2,2\sp\prime-bipyridine), Ru(bpym)\sb3\sp{2+} (bpym is 2,2\sp\prime-bipyrimidine), and Ru(Me\sb2-bpy)\sb3\sp{2+} (Me\sb2-bpy is 4,4\sp\prime-dimethyl-2,2\sp\prime-bipyridine) were investigated in viscous glycerol solution at room temperature and -15$x$C. The viscosities of glycerol at these temperatures are 1487cP and 66500cP, respectively. It was found that in all three metal complexes investigated metal-to-ligand-charge-transfer state is already localized on the time scale of less than 30ps in spite of these high viscosity. In addition, it was found that the interligand electron coupling was not strong enough to overcome the vibrational reorganization energy. As a result, delocalization of electron density over all three ligands cannot occur and the solvents do not play a major role in the MLCT state of those metal complexes. The interpretation of the mechanism responsible for producing this result is presented based on quantum mechanical electron transfer theory. In these metal complexes, it is also known that interligand electron transfer takes place in heteroligand substituted complexes. In order to investigate this kind of interligand electron transfer, Ru(bpym)\sb2(bpy)\sp{2+} and Ru(Me\sb2-bpy)\sb2(bpy)\sp{2+} were studied in glycerol and in water at room temperature. It was determined that the former complex has fast interligand electron transfer rate (k\sb{\rm ILET} $\geq$ 2 $\times$ 10\sp{11}) and the latter complex has slow interligand electron transfer rate (k\sb{\rm ILET} $\geq$ 2 $\times$ 10\sp6) in water. By changing the viscosity from 1cP (water at room temperature) to 1487cP (glycerol at room temperature), a solvent dependence of interligand electron transfer was investigated. The result is that in spite of the dramatic change of the viscosity there are no dynamics observed in these metal complexes. These results were interpreted to indicate that interligand electron transfer occurs in the upper electronic states, or singlet metal to ligand charge transfer state

GEO-BLEU: Similarity Measure for Geospatial Sequences

In recent geospatial research, the importance of modeling large-scale human mobility data and predicting trajectories is rising, in parallel with progress in text generation using large-scale corpora in natural language processing. Whereas there are already plenty of feasible approaches applicable to geospatial sequence modeling itself, there seems to be room to improve with regard to evaluation, specifically about measuring the similarity between generated and reference trajectories. In this work, we propose a novel similarity measure, GEO-BLEU, which can be especially useful in the context of geospatial sequence modeling and generation. As the name suggests, this work is based on BLEU, one of the most popular measures used in machine translation research, while introducing spatial proximity to the idea of n-gram. We compare this measure with an established baseline, dynamic time warping, applying it to actual generated geospatial sequences. Using crowdsourced annotated data on the similarity between geospatial sequences collected from over 12,000 cases, we quantitatively and qualitatively show the proposed method's superiority

Three-dimensional simulations of molecular cloud fragmentation regulated by magnetic fields and ambipolar diffusion

We employ the first fully three-dimensional simulation to study the role of magnetic fields and ion-neutral friction in regulating gravitationally-driven fragmentation of molecular clouds. The cores in an initially subcritical cloud develop gradually over an ambipolar diffusion time while the cores in an initially supercritical cloud develop in a dynamical time. The infall speeds on to cores are subsonic in the case of an initially subcritical cloud, while an extended (\ga 0.1 pc) region of supersonic infall exists in the case of an initially supercritical cloud. These results are consistent with previous two-dimensional simulations. We also found that a snapshot of the relation between density (rho) and the strength of the magnetic field (B) at different spatial points of the cloud coincides with the evolutionary track of an individual core. When the density becomes large, both relations tend to B \propto \rho^{0.5}.Comment: 8 pages, 11 figures, accepted for publication in MNRAS, a preprint with fine figures at http://yso.mtk.nao.ac.jp/~kudoh/publist_e.htm