Emergent Phenomena in the Macroworld: Jamming and Flow of Particulate Systems

宏观世界中的新兴现象：颗粒系统的干扰和流动

• 批准号: 1409093
• 负责人: Bulbul Chakraborty
• 金额: $ 32.89万
• 依托单位: Brandeis University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1409093&HistoricalAwards=false
• 关键词: Emergent; Phenomena; Macroworld; Jamming; Flow

NONTECHNICAL SUMMARYThis award supports theoretical research and educational activities focused on emergence in the macroworld. Diversity in the natural world emerges from the collective behaviors of large numbers of interacting objects. The origin of collectively organized structures at atomic and molecular scales is the competition between energy and entropy, with thermal motion providing the mechanism for organization by allowing particles to explore the space of configurations. This well-established paradigm of temperature-assisted emergent behavior breaks down for collections of macroscopic objects ranging from grains of sand to asteroids. Sand dunes are created by shearing forces, and asteroid belts self-assemble under gravity. Even in this granular world, however, there are structures that resemble gases, liquids and solids. But without the regularizing influence of thermal motion, the changes can be abrupt and often catastrophic. Avalanches and earthquakes are examples of such catastrophic failures. The overarching goal of this research project is to establish the unifying principles of emergence in systems where friction and dissipation are important, thermal motion is absent and the dynamics is dominated by large, rare fluctuations. To achieve this, the grand challenge is to construct a predictive theoretical framework analogous to thermodynamics and statistical mechanics. This research will impact the understanding of a broad range of materials, which do not necessarily belong to the macro world, but whose structures and collective properties are shaped by internal and external stresses, and not by temperature. These include active materials such as assemblies of biopolymers and motors, and carbon nanotube suspensions.In terms of broader impacts, sand is the quintessential playground of children and an ideal platform to awaken their scientific curiosity. The education part of this project builds on the idea to create hands-on-activities for Elementary School children. Sparking interest in Physics and Materials Science in children at this age has the potential to sustain excitement in these subjects through the Middle and High School years, a time when many minorities and women lose interest in science. The activities will be showcased at the Acton Discovery Museum in Massachusetts, which is participating in a program called "Portal to the Public". The museum-related activities will be designed at Brandeis with the help of graduate students and postdoctoral associates. This training of early-career scientist in conducting informal science education will enhance the broader impact of the scientific community as a whole.TECHNICAL SUMMARYThis award supports theoretical research and educational activities with focus on the collective properties and emergent behavior of athermal systems. The PI's group will study materials that epitomize non-thermal matter, which stay in a single configuration unless driven externally. Examples of such systems include granular materials, and dense, non-Brownian suspensions. At the atomic and molecular levels, thermal motion allows the system to organize into structures that are determined by a competition between energy and entropy. This well-established paradigm of temperature-assisted emergent behavior breaks down, however, for collections of macroscopic objects ranging from grains of sand to asteroids. In this world of macroscopic objects, mechanical forces are all important and the ambient temperature is completely ineffective at exploring phase space. Without the regularizing influence of thermal fluctuations, failures are often catastrophic, and there are no established relations between fluctuations and response. Using a judicious combination of modeling and data analysis, the PI's group will address fundamental questions such as (i) what characteristics can be used to distinguish fluids from solids in the macroworld where thermal fluctuations are irrelevant, (ii) are there universal features of transitions between these phases, (iii) the nature of large scale fluctuations such as failures and flow of solids. These explorations are intended to establish a theoretical framework, analogous to that of equilibrium statistical mechanics, which can predict the collective behavior of athermal systems.This research would impact our understanding of a broad range of materials including those that do not belong to the macro world, but where internal and external stresses, not temperature, shape structures and collective properties. These could include active materials such as assemblies of microtubules and motors, tissues undergoing morphogenesis or wound healing.

非技术摘要这一奖项支持理论研究和教育活动，该奖项的重点是宏伟世界中的出现。 自然世界中的多样性来自大量相互作用对象的集体行为。在原子和分子尺度上集体组织结构的起源是能量和熵之间的竞争，热运动通过允许颗粒探索构型的空间来提供组织机制。这种良好的温度辅助紧急行为范式分解了宏观物体的收集，从沙子到小行星。沙丘是由剪切力和小行星带在重力下自组装而产生的。然而，即使在这个颗粒状的世界中，也有类似于气体，液体和固体的结构。但是，如果没有热运动的正则影响，这些变化可能会突然且经常发生灾难性。雪崩和地震是这种灾难性失败的例子。该研究项目的总体目标是在摩擦和耗散很重要的系统中建立统一的出现原则，没有热运动，并且动态由较大的罕见波动主导。为了实现这一目标，巨大的挑战是构建类似于热力学和统计力学的预测理论框架。这项研究将影响对不一定属于宏观世界的广泛材料的理解，而其结构和集体特性是由内部和外部压力而不是温度塑造的。这些包括活跃的材料，例如生物聚合物和电动机的组装以及碳纳米管悬架。在更广泛的影响方面，沙是儿童的典型游乐场，也是唤醒其科学好奇心的理想平台。 该项目的教育部分是基于为小学生创造动手活性的想法。在这个年龄段的儿童中对物理和材料科学的兴趣有可能在中学和高中时期对这些学科的兴奋，这是许多少数群体和妇女对科学失去兴趣的时期。这些活动将在马萨诸塞州的Acton Discovery博物馆展示，该博物馆正在参加一个名为“ Portal to the Pliepal”的计划。博物馆相关的活动将在研究生和博士后员工的帮助下在Brandeis设计。对早期职业科学家进行非正式科学教育的培训将增强整个科学界的更广泛的影响。技术摘要这一奖项支持理论研究和教育活动，重点是集体属性和Athermal Systems的新兴行为。 PI的小组将研究表现出非热物质的材料，除非外部驱动，否则该材料保持单一配置。 此类系统的例子包括颗粒状材料和致密的非棕色悬浮液。在原子和分子水平上，热运动使系统可以组织成由能量和熵之间的竞争决定的结构。然而，这种良好的温度辅助出现行为范式崩溃了，但是，宏观物体的收集范围从沙子的谷物到小行星。 在这个宏观物体的世界中，机械力都很重要，环境温度在探索相空间时完全无效。 没有热波动的正规影响，失败通常是灾难性的，并且波动与反应之间没有建立的关系。 PI的组将使用明智的建模和数据分析结合，将解决诸如（i）可以使用哪些特征将流体与巨大波动无关的固体区分开来，（ii）是否存在这些阶段之间过渡的普遍特征，这些阶段（（iii）（iii）固体的性质（例如，固体范围）的性质，例如流量和流动。 这些探索旨在建立一个理论框架，类似于均衡统计力学的框架，该框架可以预测雅典系统的集体行为。这项研究将影响我们对包括宏观世界的广泛材料的理解，而内部和外部压力，而不是内部和外部压力，不是温度，形状结构和集体属性。这些可能包括活跃的材料，例如微管和电动机的组件，经历形态发生或伤口愈合的组织。