CAREER: State Variables in Granular Materials

非技术性的颗粒材料在天然和工程系统中普遍存在，从沙子到制药再到玉米，它们的行为不可预测，因为它们的行为像固体或液体一样。北卡罗来纳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(如类似温度的变量、压力、空隙空间或有序度)与描述稠密颗粒系统的相关性。特别是，它将建立实验，第一次直接解决这些变量在系统的两个部分之间的平衡程度，以及在剪切下的变化。更好地了解这些变量中的哪些是描述系统状态所必需的/足够的，将通过提供诊断来测量颗粒系统在故障之前的状态，从而广泛影响加工工业、岩土工程和地震危险估计。该项目将通过为本科生提供实验室研究机会，以及开发和传播一门关于非线性/非平衡系统的课程，将研究与本科教育相结合。本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，开展实践推广活动，供当地学校/青年团体使用。技术摘要颗粒材料普遍存在于从沙子到制药再到玉米的自然和工程系统中，由于固体和液体状态的存在，颗粒材料的行为不可预测。北卡罗来纳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、堆积分数、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，它将建立实验，首次直接解决类温度变量(爱德华兹熵的紧凑度/变形度和涨落耗散定理的有效温度)在两个子系统之间平衡和在剪切下变化的程度。更好地了解这些变量中的哪些是描述系统状态所必需的/足够的，将通过提供诊断来测量颗粒系统在故障之前的状态，从而广泛影响加工工业、岩土工程和地震危险估计。该项目将通过为本科生提供实验室研究机会，以及开发和传播一门关于非线性/非平衡系统的课程，将研究与本科教育相结合。该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，开展实践推广活动，供当地学校/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.