Collaborative research: Studies of aging and memory in granular materials

耶鲁大学：颗粒状材料的老化与记忆研究；Losert（物理系，IPST和IREAP，马里兰大学），C.S.O.Hern,（耶鲁大学机械工程系和物理系）我们在堵塞的颗粒材料中寻求对老化和记忆的更深层次的理解。我们的研究重点是结构、缓慢演化和初始破坏的堵塞状态。我们将使用新颖的单个颗粒三维成像技术和互补分子动力学（MD）模拟来研究剪切应力下颗粒材料粒度性质的缓慢演变。我们相信，这些研究的结果可以用来建立更好的模型屈服和流动的开始在堵塞颗粒系统。智力优势：很少有研究能够分析颗粒材料老化过程中单个晶粒的排列。这在很大程度上是由于在3D中定位颗粒位置的非侵入性和非破坏性技术现在才可用。我们将使用几种最先进的技术来研究老化过程中的微观结构：马里兰大学的共聚焦显微镜和荧光共振能量转移（FRET），以及法国格勒诺布尔欧洲同步辐射设施的同步加速器x射线微断层扫描。沃尔夫冈·洛瑟特教授（香港大学）将与香港大学的雷诺·德兰尼（雷恩）和道格·英格利希（马里兰）。Corey O.Hern教授（CO）将对摩擦颗粒材料的简单模型进行MD模拟，以指导未来的实验，研究实验获得的堵塞构型的稳定性，并探测不容易通过实验获得的参数体系。CO在模拟非热系统方面有丰富的经验，并拥有充足的计算资源。模拟和实验之间的合作将使我们在发展颗粒材料的老化和历史依赖的更微观的解释方面取得重大和迅速的进展。更广泛的影响：提高对堵塞颗粒物质如何开始流动的基本理解可能会导致这些系统的加工、运输和存储方面的进步，其中包括很大一部分工业原料、食品和药品。具体的进展可能包括：1)防止颗粒状介质堆在长时间储存后发生灾难性破坏；2)优化土木工程程序以使土壤沉降；3)更好地理解用于纳米技术应用的高粘性堵塞纳米颗粒。通过这个项目，我们将训练新的科学家使用几种强大的实验技术，如共聚焦显微镜、x射线断层扫描和FRET。我们还将开发演示材料，以非常直观的方式突出颗粒流的复杂和意想不到的特性。这些演示将用于本科课程、实验室开放日和公开讲座，向可能不熟悉颗粒材料的观众展示颗粒材料的迷人特性。我们将强烈鼓励本科生参与拟议的研究，例如，计算项目非常适合本科生，他们具有基本的计算机编程知识，可以立即开始运行现有的MD模拟和分析数据。最后，我们将采取措施减少物理和工程专业学生中存在的种族和性别不平衡。两所学院都将积极招募女性和未被充分代表的少数族裔进入各自的项目。CO将通过在研究生招生委员会任职，为耶鲁大学工程与应用科学项目服务。CO还将指导来自耶鲁大学少数族裔学生的科学、技术和研究学者项目的本科生，WL将指导华盛顿特区少数族裔高中和本科生。

ABSTRACT-0456703-0457431Yale UniversityCollaborative Research: Studies of aging and memory in granular materialsW. Losert (Department of Phyiscs, IPST, and IREAP, University of Maryland),C.S. O.Hern, (Departments of Mechanical Engineering and Physics, Yale University)We seek a deeper understanding of aging and memory in jammed granular materials. Our research focus is on the structure, slow evolution and initial failure of the jammed state. We will use novel 3D imaging techniques of individual grains and complementary molecular dynamics (MD) simulations to study the slow evolution of the grain-scale properties of granular materials under shear stress. We believe that the results from these studies can be used to build better models for yielding and the initiation of flow in jammed granular systems.Intellectual Merit: Few studies have been able to analyze the arrangements of individual grains during the aging process in granular materials. This largely results from the fact that non-invasive and nondestructive techniques for locating the positions of grains in 3D are only now available. We will use several state-of-the-art techniques to study the microstructure during aging: confocal microscopy and fluorescence resonance energy transfer (FRET) at the University of Maryland and synchrotron x-ray microtomography at the European Synchrotron Radiation Facility in Grenoble, France. Prof. Wolfgang Losert (WL) will conduct the experiments in collaboration with Profs. Renaud Delannay (Rennes) and Doug English (Maryland). Prof. Corey O.Hern (CO) will perform MD simulations of simple models of frictional granular materials to guide future experiments, investigate the stability of experimentally obtained jammed configurations, and probe parameter regimes that are not easily accessed by experiments. CO has extensive experience in simulations of athermal systems and access to ample computational resources. The proposed collaboration between simulation and experiment will allow us to make significant and swift progress in developing a more microscopic explanation of aging and history dependence in granular materials.Broader Impact: An improved fundamental understanding of how jammed granular matter starts to flow may lead to advances in the processing, transport, and storage of these systems, which includes a large fraction of industrial raw materials, food, and pharmaceutical products. Specific advances may include 1) prevention of catastrophic failure of heaps of granular media even after prolonged storage, 2) optimized civil engineering procedures for the settling of soil, and 3) a better understanding of highly cohesive jammed nanoparticles for nanotechnology applications. Through this project we will train new scientists to use several powerful experimental techniques such as confocal microscopy, x-ray tomography, and FRET. We will also develop demonstration materials to highlight the complex and unexpected properties of granular flows in very visual ways. These demos will be used in undergraduate courses, lab open houses, and public lectures to demonstrate the fascinating properties of granular materials to audiences that may not be familiar with them. We will strongly encourage undergraduate student involvement in the proposed research, e.g. the computational projects are ideal for undergraduates, who, with a basic knowledge of computer programming can begin immediately running existing MD simulations and analyzing data. Lastly, we will take steps to reduce the racial and gender imbalance that exists among students in physics and engineering. Both PIs will actively recruit women and underrepresented minorities into their respective programs. CO will do so for the Yale Engineering and Applied Science program by serving on the Graduate Admissions Committee. CO will also mentor undergraduate students from the Science, Technology and Research Scholars program for minority students at Yale and WL will mentor minority high school and undergraduate students in the Washington, DC area.