左手材料的研究进展与应用前景

左手材料是一种介电常数ε和磁导率μ同时为负的人工复合材料,具有许多反常的物理性质,是材料、电磁、光学等领域的热门研究方向.在结合国内外研究现状的基础上综述了左手材料的理论、结构特征、制备工艺、性能测试等,最后探讨了左手材料的发展趋势、应用前景和亟需解决的问题,以期获得对左手材料更为深刻和全面的理解.     

左手材料的研究进展

左手材料是一种介电常数ε和磁导率μ同时为负值的电磁材料.介绍了左手材料的基本原理,阐述了微波段、红外和可见光波段左手材料的实现方式,展望了左手材料的应用前景.     

微波左手材料及其应用前景

左手材料是一种介电常数ε和磁导率μ同时为负的人工周期结构材料,在其中传播电磁波的群速度与相速度方向相反,从而呈现出许多奇异特性.本文介绍了左手材料的基本概念、实现原理,综述了其在理论与实验研究方面取得的最新进展、研究热点、缺陷效应及实现负折射的其它途径.最后对左手材料的应用前景进行了展望.     

左手材料设计与制备的研究进展

左手材料是一种介电常数ε和磁导率μ同时为负值的超材料,具有许多非常奇异的电磁学性质.阐述了左手材料的基本概念和性质,介绍了能够同时实现负介电常数和负磁导率的Ω形、S形和树枝等单一结构,综述了利用机械加工法和化学制备法制备的高频段负磁导率材料,以及基于耦合作用的电磁波垂直入射条件下左手材料的设计与制备方法,阐述了超材料负磁导率或左手行为的验证方法,最后展望了左手材料的应用前景.     

左手材料设计的研究进展

阐述了左手材料的基本概念和性质,介绍了目前几种常见金属基元左手材料的结构、基本原理及特点,综述了左手材料近年来的研究动态及发展前景,指出左手材料要得到应用必须向低损耗和宽带宽方向发展。     

YIG/SRR结构的磁可调太赫兹左手材料

利用钇铁石榴石(YIG)在外加磁场作用下,等效磁导率为负值和电谐振环结构可以实现负介电常数的性质,组合设计出了一种新型磁可调左手材料.通过理论分析与计算表明,该结构在太赫兹频段范围内实现了左手通带,且左手通带可以随着外加磁场的增大而产生蓝移,达到了磁可调的目的.该结构具有通带性能良好、损耗低、制作方便等优点,在未来太赫兹波功能器件设计中具有广泛的应用前景.     

左手材料的光学特性及其应用

左手材料是一种人工制备的具有亚观结构的材料，因为其独特的电磁学特性，在很多方面都具有潜在的应用价值。本文简要介绍了左手材料在完美透镜、一维光子晶体、薄板波导等方面的研究进展，对其理论研究和实验结果进行了评述，并探讨了其发展前景。     

基于双Y型金属条的二维左手材料设计

以经典的周期性排列金属细棒和开口谐振环结构左手材料为基础,提出了一种以氧化铝陶瓷片为介质板,平行金属片和细金属条附于其表面的双Y型二维左手材料结构。利用三维电磁仿真软件进行电磁仿真,通过Kramers-Kronig关系改进NRW算法计算等效参数。结果表明,该结构单元在9.3～17.3 GHz范围内均有左手通性带出现,相比于同类二维左手材料展现出更优秀的宽频带特性以及各向同性,具有更强的实用性和易拓展性。该研究对于未来二维左手材料的发展具有参考价值。     

"超材料(metamaterials)":设计思想、材料体系与应用

"超材料(metamaterial)"指的是一些具有天然材料所不具备的超常物理性质的人工复合结构或复合材料.从本质上讲,metamaterial更是一种新颖的材料设计思想,这一思想是通过在材料的关键物理尺度上的结构有序设计来突破某些表观自然规律的限制.从而获得超常的材料功能.迄今发展出的"超材料"包括"左手材料"、光子晶体、"超磁性材料"等.本文就这一领域近年来的发展动向及其在信息技术上的潜在应用做简单的介绍.     

左手材料薄板波导中的传导模

推导了左手材料薄板波导中传导模的色散方程,分析了波导中存在传导模与波导材料和包敷材料参数取值范围之间的关系.数值算例证实了这些关系.     

Elastic instabilities,microstructure transformations,and pattern formations in soft materials

Large deformations of soft materials can give rise to the development of various elastic instabilities. The phenomenon is associated with a sudden and dramatic change in structure morphologies. The underlying mechanism is crucial for the formation of complex morphologies in biology. Moreover, the concept of instability-induced pattern transformations is promising for designing novel materials with switchable functions and properties. In this paper, we review the state of the art in elastic instability phenomena in soft materials. We start by considering the classical buckling in beam-based structure lattice designs. Then, we discuss the instability-induced microstructure transformations in soft porous materials, and heterogeneous multiphase and fiber composites. Next, the mechanisms – often involving the post-buckling consideration – leading to the wrinkling and folding, creasing, fringe, and fingering are discussed.     

Atomic origami

Here we summarize recent experimental work in the field of atomic origami: the folding of 3D structures from sheets that are just atoms thick. We highlight current techniques for folding at the microscale and provide scaling arguments as to why some approaches work better than others at small sizes. Finally, we point out that for folding structures made from 2D materials, miniaturization can extend another three orders of magnitude: current state of the art devices are microns in size while, as a platform, atomic membranes should be foldable down to the nanoscale. The ability to scale folding structures over a wide range in size could open diverse applications, from microscopic robots to new interfaces with biology.     

Analysis of guided modes in metamaterial photonic crystals

The characteristics of surface waves in left handed-metamaterials (LHMs) and monodimensional photonic crystal are investigated. An analytical expression of dispersion relations is derived. It is theoretically demonstrated that surface modes exist. The calculated results show that the localised magnetic field at the superstrate-LHM interface decays as the propagation distance increases. Also, it is found that transmission spectrum of the proposed structure exhibits band gaps at certain frequency range. By calculating the group velocity and the transmission bands, the regions of negative refraction are found.     

Numerical investigation of Cherenkov radiations emitted by an electron beam bunch in isotropic double-negative metamaterials

The electron-beam-induced Cherenkov radiations in isotropic double-negative metamaterials (DNMs) are numerically investigated in this paper. The frequency-dependent permittivity and permeability functions are approximated by the Drude-Lorentz model. This model is implemented by the finite-difference time-domain (FDTD) and the auxiliary difference equation (ADE) methods. The interaction between electromagnetic fields and electrons is simulated by the particle-in-cell (PIC) method. The fundamental physics of the direct and the reversed Cherenkov radiations from an electron beam bunch in a typical sandwich structure is well presented. The numerical results show that the use of an electron beam bunch rather than an ultra short laser pulse to excite DNMs raises questions and novel opportunities regarding the selectivity with which Cherenkov radiations with different components and frequencies can be excited.     

曲轴维修与再制造现状与展望

曲轴作为关键重要的传动零件,被广泛应用于汽车、煤矿、船舰、化工、石化等领域,其质量的好坏直接关系着工作系统的性能。列举分析了曲轴类零件的典型失效形式及其主要原因,归纳总结了曲轴修复和再制造常用技术手段,包括镀层技术、焊层技术、激光熔覆技术、热喷涂技术以及热喷涂层的重熔技术,并重点介绍了高速电弧喷涂技术在曲轴再制造方面的优势及应用现状。总结了目前曲轴维修与再制造存在的主要问题,并对曲轴再制造的发展方向进行了展望。     

废旧家用电器的机械破碎与分选技术

简要分析了废旧家用电器的材料组成、联结方式，以及发达国家废旧家用电器处理技术现状，详细阐述了废旧家用电器的机械破碎和机械分选技术，介绍了国内外废旧家用电器成套处理设备的研究开发进展，并提出了适合我国国情的废旧家用电器处理的工艺技术路线。