Community dynamics generates complex epidemiology through self-induced amplification and suppression

The development of quantitative models of outbreaks is key to their eventual control, from human and computer viruses through to social (and antisocial) activities. Standard epidemiological models can reproduce many general features of outbreaks. Unfortunately, the large temporal fluctuations which often dominate real-world data are thought to require more complicated, system-specific models involving super-spreaders, specific social network topologies and rewirings, and birth-death processes. However we show here that these large fluctuations have a generic explanation in terms of underlying community dynamics. Communities increasing (or decreasing) in size, act as instantaneous amplifiers (or suppressors) yielding a complex temporal evolution whose features vary dramatically according to the relative timescales of the community dynamics. We uncover, and provide an analytic theory for, a novel epidemiological phase transition driven by the population's response to an outbreak. An imminent epidemic will be suppressed if individual communities start to break up more frequently or join together less frequently, but will be amplified if the reverse is true

A New Measurement Method of Relative Volume Wear Ratio Based on Discharge Debris Composition Analysis in Micro-EDM

In microelectrical discharge machining (micro-EDM) milling process, due to the unavoidability of electrode wear, selection of electrode with high electrical erosion resistance and accurate electrode compensation is entitled to be conducted to ensure high precision and high quality. The RVWR is used as criterion for electrode wear characteristics and is fundamental to achieve accurate electrode compensation; however, it is hardly measured accurately with conventional methods. In this paper, firstly, the error of RVWR measured by conventional measurement method is analyzed. Thereafter, for accurately measuring RVWR, a new measurement method is proposed based on electrical debris composition analysis. The RVWR of widely used tungsten, molybdenum, and copper electrode in machining different materials is measured, respectively, and the optimum electrode is selected based on the measuring results. Finally, microgrooves on different materials are machined with tungsten electrode, and the experiment results show that the microstructures have good bottom surface profiles, which indicates that the proposed method is effective to precisely measure the RVWR and guarantee accurate electrode compensation in micro-EDM process

Non-Analytic Magnetic Response and Intrinsic Ferromagnetic Clusters in a Dirac Spin Liquid Candidate

Finding distinct signatures of a quantum spin liquid (QSL) is an ongoing quest in condensed matter physics, invariably complicated by the presence of disorder in real materials. In this regard the 2D Kagome system YCu$_3$(OH)$_6$[(Cl$_x$Br$_{(1-x)}$)$_{3-y}$(OH)$_y$] (YCOB-Cl), where the vast mismatch in size of Y and Cu avoids subsitutional disorder, otherwise present in kagome materials, has emerged as a favorable candidate. In crystals of this system, with $x<$ 0.4 and no long range order, we report an unusual field dependent magnetization $M(B)$, where $M/B$ changes linearly with $|B|$, the absolute value of the field, in contrast to the expected quadratic behavior. Model calculations with a distribution of ferromagnetic (FM) clusters faithfully capture observed features suggesting such clusters to be intrinsic to real QSL materials. YCOB-Cl has a field enhanced $T^2$ heat capacity as expected for a Dirac QSL but lacks a linear $T$ behavior in the spin susceptibility. By demonstrating that FM clusters dominate the contribution to the susceptibility but not the heat capacity, our work paves the way towards reconciling the apparent inconsistency with a Dirac QSL.Comment: 6 pages and 4 figure

NMR evidence of spinon localization in kagome antiferromagnet YCu3_3(OH)6_6Br2_2[Br1−x_{1-x}(OH)x_x]

We performed nuclear magnetic resonance studies on a kagome antiferromagnet YCu$_3$(OH)$_6$Br$_2$[Br$_{1-x}$(OH)$_{x}$]. No significant NMR spectral broadening is found in the Br center peak from 1 K down to 0.05 K, indicating absence of static antiferromagnetic ordering. In contrast to signatures of dominant 2D kagome antiferromagnetic fluctuations at temperature above 30 K, both the Knight shift $K_{\rm{n}}$ and the spin-lattice relaxation rate $1/T_{1}$ increase when the sample is cooled from 30 K to 8 K, which can be attributed to the scattering of spin excitations by strong non-magnetic impurities. Unusually, a hump is observed in $K_{\rm{n}}$ and $1/T_{2}$ close to 2 K (far below the exchange energy), which indicates the existence of excitations with a large density of states close to zero energy. These phenomena are reproduced by a mean-field simulation of Heisenberg model with bond-dependent exchange interactions, where the sign fluctuations in the spinon kinetic terms caused by impurities result in localization of spinons and an almost flat band close to the Fermi energy.Comment: 9 pages, 7 figures. The supplementary materials can be obtained upon reques

Human group formation in online guilds and offline gangs driven by common team dynamic

Quantifying human group dynamics represents a unique challenge. Unlike animals and other biological systems, humans form groups in both real (offline) and virtual (online) spaces -- from potentially dangerous street gangs populated mostly by disaffected male youths, through to the massive global guilds in online role-playing games for which membership currently exceeds tens of millions of people from all possible backgrounds, age-groups and genders. We have compiled and analyzed data for these two seemingly unrelated offline and online human activities, and have uncovered an unexpected quantitative link between them. Although their overall dynamics differ visibly, we find that a common team-based model can accurately reproduce the quantitative features of each simply by adjusting the average tolerance level and attribute range for each population. By contrast, we find no evidence to support a version of the model based on like-seeking-like (i.e. kinship or `homophily')

二項分類法のための粒子群最適化に基づくパラメータ推定とその応用

早大学位記番号:新7059早稲田大