CAREER: State Variables in Granular Materials

颗粒材料在自然和工程系统中无处不在，从沙子到药物再到玉米，由于它们具有固体或液体的能力，因此其行为不可预测。北卡罗来纳州州立大学的这个教师早期职业发展项目旨在通过利用非平衡统计力学的工具在模型系统中进行仔细控制的实验室实验来提高我们对颗粒和其他复杂材料的理解。该项目将测试各种状态变量（如温度变量，压力，空隙空间或有序度）与描述致密颗粒系统的相关性。特别是，它将建立实验，首次直接解决这些变量可以在系统的两个部分之间平衡并在剪切下变化的程度。更好地理解这些变量中的哪些是必要的/足够的，以描述系统的状态将广泛地影响加工工业，岩土工程和地震危险估计，通过提供诊断来测量颗粒系统的状态，在它失败之前。该项目将通过为本科生提供实验室研究机会，以及开发和传播非线性/非平衡系统课程，将研究与本科生教育结合起来。课程和实验室的学生将与北卡罗来纳州立大学的科学之家合作，开发实践推广活动，供当地学校/青年团体使用。技术摘要颗粒材料在自然和工程系统中无处不在，从沙子到药品到玉米，由于存在固体和液体状态，颗粒材料的行为不可预测。北卡罗来纳州州立大学的这个教师早期职业发展项目旨在通过利用非平衡统计力学的工具在模型系统中进行仔细控制的实验室实验来提高我们对颗粒和其他复杂材料的理解。该项目将测试各种状态变量（如"温度“、压力、填充分数、静态接触分数或有序度）与描述致密颗粒系统的相关性。特别是，它将建立的实验，第一次，直接解决的程度，温度类变量（压实/angoricity从爱德华熵和有效温度从波动耗散定理）之间的平衡两个子系统和剪切下的变化。更好地理解这些变量中的哪些是必要的/足够的，以描述系统的状态将广泛地影响加工工业，岩土工程和地震危险估计，通过提供诊断来测量颗粒系统的状态，在它失败之前。该项目将通过为本科生提供实验室研究机会，以及开发和传播非线性/非平衡系统课程，将研究与本科生教育结合起来。从课程和实验室的学生将开发，与北卡罗来纳州的科学之家合作，动手推广活动，与当地学校/青年团体使用。

Nontechnical Abstract Granular materials are ubiquitous in both natural and engineered systems, from sand to pharmaceuticals to corn, and behave unpredictably due to their ability to act like either solids or liquids. This Faculty Early Career Development project at North Carolina State University aims to improve our understanding of granular and other complex materials by utilizing tools from nonequilibrium statistical mechanics to conduct carefully controlled laboratory experiments in model systems. The project will test the relevance of various state variables (such as temperature-like variables, pressure, void space, or degree of ordering) to describing dense granular systems. In particular, it will build experiments which, for the first time, directly address the degree to which these variables can equilibrate between two parts of a system and change under shear. An improved understanding of which of these variables are necessary/sufficient to describe the state of the system will broadly impact processing industries, geotechnical engineering, and earthquake hazard estimation by providing diagnostics to measure the state of a granular system before it fails. The project will integrate research with undergraduate education through providing laboratory research opportunities for undergraduates, as well as developing and disseminating a course on nonlinear/nonequilibrium systems. Students from both the course and the laboratory will develop, in collaboration with NC State's Science House, hands-on outreach activities for use with local school/youth groups.Technical Abstract Granular materials are ubiquitous in both natural and engineered systems, from sand to pharmaceuticals to corn, and behave unpredictably due to the presence of both solid-like and liquid-like states. This Faculty Early Career Development project at North Carolina State University aims to improve our understanding of granular and other complex materials by utilizing tools from nonequilibrium statistical mechanics to conduct carefully controlled laboratory experiments in model systems. The project will test the relevance of various state variables (such as ``temperature'', pressure, packing fraction, fraction of static contacts, or degree of ordering) to describing dense granular systems. In particular, it will build experiments which, for the first time, directly address the degree to which temperature-like variables (compactivity/angoricity from Edwards entropy and effective temperature from the fluctuation-dissipation theorem) equilibrate between two subsystems and change under shear. An improved understanding of which of these variables are necessary/sufficient to describe the state of the system will broadly impact processing industries, geotechnical engineering, and earthquake hazard estimation by providing diagnostics to measure the state of a granular system before it fails. The project will integrate research with undergraduate education through providing laboratory research opportunities for undergraduates, as well as developing and disseminating a course on nonlinear/nonequilibrium systems. Students from both the course and the laboratory will develop, in collaboration with NC State's Science House, hands-on outreach activities for use with local school/youth groups.