Waves in complex mesoscopic materials

我的研究计划的目标是发现和了解复杂介观材料中波的显著特性，并基于我们对波散射的知识开发和使用新的超声波技术来探测其结构和动力学。介观材料以中间或介观尺度的内部结构为特征，这些结构支配着它们的宏观性质和性能。它们的重要性在于操纵中观结构的巨大潜力以及它们之间的相互作用，以量身定做和优化材料，以满足社会当前和未来的需求。了解这些材料的波动物理将有助于实现这种潜力，在这些材料中，波在离开介质之前可能会被多次散射，并显示出许多迷人的波现象。例如，从强共振散射(当脉冲在样品中传播得如此之快以至于其速度为负值时)引起的波速的显著变化，到当波变得局部化时在非常强散射的样品中可能发生的波传播的完全抑制。周期结构中的波，被称为光的光子晶体和声音的声子晶体，也表现出不寻常的效应，如负折射和显著的聚焦特性。我们将使用我们实验室开发的创新超声波技术来研究声波和弹性波(声音)的这种波动现象。由于我们探测器的性质，声音与物质相互作用的独特方式，以及使用新的理论模型解释我们的数据的可能性，这些实验很可能在理解介观材料的新的波特性方面取得重大进展，也导致用于材料表征和过程控制的新的超声波光谱仪。我们打算研究的一些介观材料包括声子晶体、多孔材料、泡沫、颗粒和气泡悬浮液，以及充气食品生物材料。

The goals of my research program are to discover and understand the remarkable properties of waves in complex mesoscopic materials, and to develop and use new ultrasonic techniques, based on our knowledge of wave scattering, to probe their structure and dynamics. Mesoscopic materials are characterized by internal structures, at intermediate or mesoscopic length scales, that govern their macroscopic properties and performance. Their importance lies in the enormous potential for manipulating mesostructures and the interactions between them to tailor and optimize materials for society's current and future needs. Realizing this potential will be facilitated by understanding the wave physics of these materials, in which the waves may be scattered many times before leaving the medium and exhibit many fascinating wave phenomena. Examples range from strikingly large variations in wave speeds caused by strong resonant scattering (when a pulse can even appear to travel so quickly through a sample that its velocity is negative) to the complete inhibition of wave propagation that may occur in very strongly scattering samples when waves become localized. Waves in periodic structures, known as photonic crystals for light and phononic crystals for sound, also exhibit unusual effects, such as negative refraction and remarkable focusing properties. We will use innovative ultrasonic techniques, developed in our laboratory, to study such wave phenomena for acoustic and elastic waves (sound). Because of the nature of our detectors, the unique ways in which sound interacts with matter, and the possibility of interpreting our data using new theoretical models, significant advances in understanding the novel wave properties of mesoscopic materials are likely to result from these experiments, leading also to new ultrasonic spectroscopies for materials characterization and process control. Some of the mesoscopic materials that we intend to study include phononic crystals, porous materials, foams, particulate and bubbly suspensions, and aerated food biomaterials.