Collaborative research: Studies of aging and memory in granular materials

耶鲁大学合作研究：颗粒材料的老化和记忆研究。Losert（物理系，IPST和IREAP，马里兰州大学），C.S. O.Hern（耶鲁大学机械工程和物理系）我们寻求对堵塞颗粒材料中的老化和记忆的更深入理解。我们的研究重点是阻塞状态的结构、缓慢演化和初始失效。我们将使用新的3D成像技术的单个颗粒和互补的分子动力学（MD）模拟研究剪切应力下的颗粒材料的颗粒尺度性能的缓慢演变。我们相信，从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堵塞颗粒system.Intellectual优点：很少有研究已经能够分析在颗粒状材料的老化过程中的单个晶粒的安排。这在很大程度上是因为用于定位3D中颗粒位置的非侵入性和非破坏性技术现在才可用。我们将使用几个国家的最先进的技术来研究老化过程中的微观结构：共聚焦显微镜和荧光共振能量转移（FRET）在马里兰州大学和同步辐射X射线显微断层扫描在法国格勒诺布尔的欧洲同步辐射设施。Wolfgang Losert教授（WL）将与教授合作进行实验。雷诺·德兰尼（雷恩）和道格·英格利什（马里兰州）。Corey O.Hern（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配置的稳定性，并探索实验不易获得的参数机制。CO在无热系统的模拟方面拥有丰富的经验，并可获得充足的计算资源。模拟和实验之间的拟议合作将使我们能够在开发颗粒材料老化和历史依赖性的更微观解释方面取得重大而迅速的进展。对堵塞的颗粒物质如何开始流动的基本理解的改进可能会导致这些系统的加工，运输和储存的进步，其中包括大部分工业原材料，食品，和医药产品。具体的进展可能包括：1）即使在长时间储存后，也能防止颗粒介质堆的灾难性故障，2）优化土壤沉降的土木工程程序，3）更好地了解纳米技术应用中的高粘性堵塞纳米颗粒。通过这个项目，我们将培训新的科学家使用几个强大的实验技术，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，向可能不熟悉它们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，例如计算项目是本科生的理想选择，他们具有计算机编程的基本知识，可以开始立即运行现有的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。这两个项目都将积极招募妇女和代表性不足的少数民族参加各自的项目。CO将通过在研究生招生委员会任职来为耶鲁大学工程和应用科学项目提供服务。CO还将指导耶鲁大学少数民族学生科学、技术和研究学者项目的本科生，WL将指导华盛顿地区的少数民族高中和本科生。

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.