Statistical Physics of Systems of Grains, Fibres and Sheets

* 非技术性摘要 * 松散的颗粒是如何堆积成沙堆的？长长的线是如何排列成有弹性的纤维状物质的？为什么一张薄薄的纸在被压成一个几乎是空的球时会变得坚硬呢？这个个人研究奖支持一个项目，以开发技术，成像的内部结构，以期了解的架构，导致机械性能，定义每一类材料。模型实验室系统将被用来使我们能够了解他们在物理，技术和生物世界中更复杂的同行的行为。 理解这些系统的智力挑战在于，与物质的常规相不同，这些所谓的非平衡系统不仅由它们的当前状态定义，而且由它们所经历的历史定义。来自马萨诸塞大学和该地区其他学院的本科生将领导新项目的探索性工作，而研究生将使用包括一系列现代实验工具在内的技术从事更长期的项目。 所有学生将接触到在日常材料的背景下，在非平衡统计物理学的基本重要性的研究问题。技术摘要 * 这个个人研究奖的重点是理解系统的结构、响应和稳定性，其中组成元素是宏观颗粒、纤维或弹性片。该项目旨在确定指导这种远离平衡系统的相行为、波动、整体响应和结构的一般原则。在这些类中的每一个模型系统的包装和空间配置的实验测定是必不可少的，在物理，技术和生物世界中的同行发展的理解。 这些系统是非热的，它们的结构不仅取决于它们的成分和相互作用，还取决于它们的制备历史。 在纤维和片材的情况下，这些弹性元件的可变形性引起了有趣的几何问题。长期塑性流动和滞后摩擦相互作用的材料挑战加剧了这些问题。 来自马萨诸塞大学和该地区其他学院的本科生将领导新项目的探索性工作，而研究生将使用包括高速视频成像，共聚焦显微镜，光散射，声学和机械响应技术和X射线断层扫描技术在内的技术进行更长期的项目。

****NON-TECHNICAL ABSTRACT****How do loose grains pack into a sand pile? How do long strands arrange into springy, elastic, fibrous matter? How is it that a flimsy piece of paper becomes rigid when crushed into a ball that is mostly empty space? This individual investigator award supports a project to develop techniques for imaging the interior of such structures with a view to understanding the architecture that leads to the mechanical properties that define each of these classes of materials. Model laboratory systems will be used to enable our understanding of the behavior of their more complex counterparts in the physical, technological and biological world. The intellectual challenge in understanding these systems is that unlike conventional phases of matter these so-called nonequilibrium systems are defined not just by their present state but by the history to which they have been subjected. Undergraduates from UMass and other colleges in the area will lead exploratory work on new projects while graduate students will work on more long-term projects using techniques that include a battery of modern experimental tools. All students will be exposed to research questions of fundamental importance in nonequilibrium statistical physics in the context of everyday materials.****TECHNICAL ABSTRACT****The focus of this individual investigator award is the understanding of the structure, response, and stability of systems in which the constituent elements are macroscopic grains, fibres, or elastic sheets. The project seeks to identify general principles governing phase behaviour, fluctuations, bulk response and structure of such far-from-equilibrium systems. An experimental determination of packing and spatial configuration of model systems in each of these classes is indispensable in developing an understanding of their counterparts in the physical, technological and biological world. These systems are nonthermal, and their structure is a consequence of not just their constituents and their interactions but also their history of preparation. In the cases of fibres and sheets, the deformability of these elastic elements raises interesting geometrical issues. These issues are compounded by the material challenges of long-term plastic flow and of hysteretic frictional interactions. Undergraduates from UMass and other colleges in the area will lead exploratory work on new projects while graduate students will work on more long-term projects using techniques that include high-speed video imaging, confocal microscopy, light scattering, acoustic and mechanical response techniques, and x-ray tomography.