电磁波在正、负折射率媒质形成斐波那契准晶中的传输特性

利用传输矩阵方法研究了光在由正、负折射率介质构成的FC（N）准晶链排列的多层介质膜中传播时的电磁波透射谱性质。结果表明由于负折射率媒质的存在，电磁波透射谱得到了明显的改善，特别是透射谱的禁带宽度明显加宽。     

电磁波在正、负折射率媒质形成斐波那契准晶中的传输特性

利用传输矩阵方法研究了光在由正、负折射率介质构成的FC(N)准晶链排列的多层介质膜中传播时的电磁波透射谱性质。结果表明由于负折射率媒质的存在,电磁波透射谱得到了明显的改善,特别是透射谱的禁带宽度明显加宽。     

有损耗左手材料模型的时域电磁分析

分析了电磁(EM)场在有损耗左手材料(LHM)模型中能量与损耗因子间的关系,推导了有耗LHM模型的时域有限差分法(FDTD)计算公式,数值模拟了EM场在该有耗LHM材料模型中的传播;对比无耗与有耗LHM模型的EM聚焦特性,分析EM场在不同损耗因子LHM材料中的传播.研究表明,数值结果与理论分析得到较好吻合.     

Scattering Characteristics of Dielectric Periodic Structure Composed of Left-handed Materials with Arbitrary Oblique Incidence

Scattering characteristics of monolayer and multilayer dielectric periodic structure composed of left-handed materials (LH-DPS) with plane wave arbitrary oblique incidence are carefully analyzed using a method which combines multimode network theory with the rigorous mode matching method. Our analysis results reveal that the arbitrary oblique incident angles and relative position between different LH-DPS have great effects to the scattering characteristics of LH-DPS which different from the situation of dielectric periodic structure composed of right-handed materials (RH-DPS). The reasons why the reflection characteristics of the LH-DPS are totally different from those of the RH-DPS with arbitrary oblique incidence are also given. The present quantitive investigation provides guidelines for the design of the monolayer and multilayer dielectric frequency selective surfaces for millimeter wave applications.     

新型结构左手材料的仿真设计与实现

左手材料通过其特殊的结构阵列来实现负的介电常数和磁导率,将之应用到天线罩、滤波器和天线等方面,可以较好地改善特性。2种新型左手材料结构被提出,分别是史密斯方形环的简化形式和P型结构,其中P型结构又包含基本形式与改进形式。针对这2种模型,利用仿真软件进行了仿真设计,发现这2种形式可以在4～6 GHz频段实现负的介电常数和磁导率,其中P型结构实现效果更好。     

左手材料理论及其应用

左手材料是一种介电常数和磁导率同时为负值的人工材料,这种材料具有负群速度、负折射率、逆多普勒效应和完美成像等多种奇特的物理性质.叙述了左手材料的概念和基本原理,简单回顾了左手材料研究的发展历程,介绍了左手材料的应用及其发展前景.     

电磁屏蔽材料的新进展

随着电子设备的快速发展,对电磁干扰屏蔽的需求也日益增加,目前已开发研制出一大批新的屏蔽材料.主要针对一些新材料的用途、特性和优点以及电磁干扰屏蔽产品的设计进行了介绍,最后概括出未来电磁屏蔽材料的发展动向.     

左手结构及其在天线微波领域中的应用

左手材料因其具有介电常数和磁导率同时为负值的电磁特性,近年来得到科学界的广泛关注。基于微带线等传输线结构所构成的左手材料与传统右手材料相比传输相移特性亦有不同,因此在天线微波系统中具有很大的应用潜力。文中介绍了这类左手传输结构的基本设计理论和性能特点,并对其在未来天线微波领域中的应用进行了探讨。     

Organic Thermoelectric Materials Composed of Conducting Polymers and Metal Nanoparticles

Organic thermoelectric materials consisting of conducting polymers have received much attention recently because of their advantages such as wide availability of carbon, easy syntheses, easy processing, flexible devices, low cost, and low thermal conductivity. Nevertheless, their thermoelectric performance is still not good enough for practical use. To improve their performance, we present herein new kinds of hybrids of organic conducting polymers and metal nanoparticles (NPs). Since hybridization of polyaniline with poly-(N-vinyl-2-pyrrolidone) (PVP)-protected Au NPs decreased the electrical conductivity of polyaniline films from 150?S?cm^?1 to 50?S?cm^?1, we carried out direct hybridization of polyaniline with Au NPs without PVP in this study. Direct hybridization improved the electrical conductivity to as high as 330?S?cm^?1 at 50°C while keeping the Seebeck coefficient at 15???V?m^?1?K^?2. Poly(3,4-ethylenedioxythiophene) (PEDOT) is another promising conducting polymer. Here, we used hybrid films of PEDOT with Au NPs protected by two kinds of ligands, terthiophenethiol and dodecanethiol (DT), revealing that the hybrid of PEDOT with DT-protected Au NPs showed better thermoelectric performance than pristine PEDOT without Au NPs. Addition of DT-protected Au NPs improved the electrical conductivity of the PEDOT films from 104?S?cm^?1 to 241?S?cm^?1 and the thermoelectric figure of merit from 0.62?×?10^?2 to 1.63?×?10^?2 at 50°C.     

电磁波吸收材料的应用

扼要介绍电磁波吸收材料的形状及其在工程中的应用。     

三种材料构成的超晶格能带结构研究

对由ＧａＡｓ，Ａｌ０．２１Ｇａ０．７９Ａｓ及ＡｌｘＧａ１－ｘＡｓ（ｘ由０．０～０．２１之间变化）三种材料构成的超晶格能带结构进行了研究。结果发现：如果超晶格单胞对其中点不具有对称性，对应自旋向上和向下的能带，此时发生了劈裂．并且由于材料不对称分布引起的劈裂比由于几何尺寸不对称引起的劈裂大。劈裂主要发生在重、轻空穴带相互作用较大的地方。     

电磁屏蔽材料的进展

文章介绍了电磁屏蔽的基本理论，近年来电磁屏蔽材料最新的发展情况，各种新型电磁材料的研究和应用，并对电磁屏蔽材料的研究和应用前景作了展望。     

Omnidirectional Single-negative Gap and in Fibonacci Sequences Composed of Single-negative Materials

The band structures of Fibonacci sequence composed of single-negative materials are studied with a transfer matrix method. A new type of omnidirectional single-negative gaps is found in the Fibonacci sequence. In contrast to the Bragg gaps, such an omnidirectional single-negative gap is insensitive to the incident angles and polarization, and is invariant upon the change of the ratio of the thicknesses of two media. It is found that omnidirectional single-negative gap exists in the other Fibonacci sequence, and it is rather stable and independence of the structure sequence.     

含左手材料的四层平面波导TM模的传输特性

在考虑材料色散的条件下,对含左手材料的四层平面波导的TM振荡模进行了分析。首先利用Maxwell方程组得到了两类TM振荡模的色散方程。基于左手材料实验模型,画出了相关的色散曲线。通过对这些色散曲线的分析,得到了该波导中TM振荡模的色散特性。此外,还计算了该波导中TM振荡模的归一化功率流,发现第一类TM基模的群速和它的归一化功率流方向相反;第一类TM振荡模的归一化功率流恒大于零;而第二类TM振荡模的归一化功率流可以大于零、小于零或等于零。正的归一化功率流则说明能量向前传输;负的归一化功率流则说明能量向后传输;而归一化功率流等于零则说明能量被储存在平面波导中,这为设计新型光开关、光传感器件提供了理论基础。     

任意形状线、面、体组成导体目标的电磁建模

本文用积分方程和矩量法分析具有任意线、面、体组成的理想导体目标的电磁散射和辐射特性.其中统一采用RWG基函数对线、面、体导体上的电流进行展开;对于任意的线-面,面-面连接情况,根据电流连续性条件,给出了通用的设置基函数和未知量的方法;对于辐射问题,给出了设置激励源与计算输入阻抗的方法.最后通过分析导体盒上的单极天线和宽带贴片天线验证了本文方法的可行性和有效性.     

电磁波屏蔽复合材料的研究进展

从电磁波屏蔽的机理出发,介绍导电型、导磁型以及导电导磁型电磁波屏蔽复合材料的发展现状,并展望了电磁波屏蔽材料未来的研究方向。     

Complete Polarization Conversion Characteristics of Dielectric Grating Composed of Left-Handed Materials

The TE/TM polarization conversion characteristics of dielectric grating composed of left-handed materials for the case of plane wave oblique incidence are carefully investigated by a method which combines the multimode network theory with the rigorous mode matching method. It is indicated that complete polarization conversion between TE and TM modes can be realized using left-handed gratings. This can hardly achieve in the conventional right-handed gratings. Comparisons of polarization conversion properties between right-handed gratings and left-handed gratings are given with physical explanations. This unique merit of left-handed periodic structure is of important significance for accurate design of new millimeter wave TE/TM polarization converters.     

A Neuron-Readable Artificial Photoreceptor Composed of Photodeformable Liquid Crystal Polymers and Piezoelectric Materials

Artificial photoreceptors are extensively developed to help the patients with serious eye diseases by converting light into electric signals. However, the existing systems still suffer from poor output signals, restricting signal transduction to cells. Here, a neuron-readable artificial photoreceptor with significant voltage output is constructed by using photodeformable liquid crystal polymers (LCPs) and polyvinylidene fluoride trifluoroethylene (P(VDF-TrFE)). The significant voltage output originates from light-stress-electricity conversion, where the photo-induced stress is attributed to the free volume expansion of the photodeformable LCPs and subsequently converts them into strong electric signals by the P(VDF-TrFE) layer. The photo-induced open-circuit voltage reaches up to 0.79 ± 0.02 V, which is, to the knowledge, 19 times higher than the maximum voltage (0.04 V) that has been reported to date. Hence, such artificial photoreceptor successfully transduces photo-induced electric signals to cells and tissues, communicates with the neurons, and triggers spiking activities in blind retinas. Besides, visual image recognition is demonstrated in a pixelated matrix by analyzing electric signals of each unit. This artificial photoreceptor opens new opportunities for the combination of the photodeformability and piezoelectricity, providing an avenue to develop neuron-readable artificial retinas and implantable sensors.     

电磁屏蔽复合材料的研究现状

电磁屏蔽复合材料是新型电磁辐射防护材料.通过对电磁屏蔽复合材料国内外的研究状况较为全面的综述,指出制备电磁屏蔽复合材料的常用复合方法为填充法,此法工艺相对简单,成型性好;同时对目前屏蔽复合材料研制中存在的问题进行了分析.     

Investigation on a Novel Leaky Wave Antenna with Double Radiation Beam Composed of Left-handed Slab Loaded Hybrid Waveguide using Planar Technology

A novel leaky wave antenna with double radiation beam composed of left-handed slab loaded hybrid waveguide using planar technology is proposed in this paper and its leaky characteristics are investigated with a method that the multimode network theory is combined with mode-matching method. The study of dispersion curves reveals that the proposed antenna structure supports two leaky modes corresponding to the forward and the backward radiations respectively. It demonstrates that the proposed antenna is of desirable property that can radiate both forward and backward directions simultaneously with quite simple and flexible configuration. Extensive numerical results of leaky characteristics with different structural parameters of the antenna are given to provide useful guidelines for the design of the new antenna.