一种宽带吸波的隐身天线罩设计

传统的吸波材料无法使天线同时满足工作带外隐身和工作带内透波的特殊要求。文中结合传统吸波材料的吸波特性和频率选择表面的滤波特性,提出了一种超材料的宽带吸波的隐身天线罩。利用超材料的谐振叠加特性,设计出宽带人工吸波结构。采用阻抗匹配技术进一步提高天线在工作频带内的透过率,并提高天线带外的吸收率。通过调节超材料吸波体的尺寸,构造了一种Ku 频带透波、高于Ku 频段吸波的超材料天线罩,在保证天线带内正常通信前提下,可减小天线带外的雷达散射截面,提高机载天线的隐身性能。     

具有宽带特性的超材料设计与分析*

分别提出具有宽带负磁导率特性的圆盘结构超材料和具有宽带双负特性的互联圆盘结构左手材料。对任意极化的垂直入射波,圆盘结构超材料可在8.71GHz到15.19GHz的频段上产生负的磁导率,而互联圆盘结构左手材料则可在6.04GHz到7.40GHz的频段上产生双负特性。通过有限元仿真、本构参数提取、表面电流分布计算、结构参数扫描等方法,对圆盘结构进行了详细分析。结果表明,该结构通过外加磁场激励起的电流环路构成磁谐振回路,进而获得负磁导率特性。利用无限划分的方法,分析了该结构实现宽带特性的原理,推导了等效的磁谐振频率和品质因数的计算公式,并给出其等效电路结构。通过参数扫描,分析了贴片半径、基板介电常数、损耗特性和入射角大小对负磁导率特性的影响规律。对互联圆盘结构左手材料,在提取其等效本构参数的基础上,着重分析了电响应特性,详细推导了等效电等离子体频率的计算公式。     

一种新型可调谐宽带吸波器的设计

设计了一种新型可调谐且极化不敏感的宽带吸波器。采用了全波仿真方法对该吸波器的吸收率、电场图和表面电流图进行了计算, 并探讨了结构参数z、y 和入射角度啄对吸波器电磁波吸收特性的影响。研究结果表明, 该吸波器在12.17 ~14.19 GHz 频域的吸收率达到90% 以上, 通过激励不同的等离子体谐振区域不但可以改善其吸收特性, 实现吸波器的宽带吸收, 而且还能获得可调谐的吸收频谱。改变结构参数z 和y 可以在拓展吸收带宽的同时使吸收频域发生移动; 且该吸波器具有较好的角度稳定性。     

糖果型电阻膜宽带超材料吸波器的设计

提出了一种糖果型电阻膜宽带超材料吸波器。该吸波器的单元结构采用电阻膜-介质-电阻膜结构,其中顶层电阻膜为糖果型, 介质层由多种材料叠加而成, 介质层材料从顶至底依次为PET、FR-4、PMMA 和PET。CST 软件仿真结果表明本吸波器吸收率的峰值可达100%,吸收率超过99% 的频带宽度约为2.5 GHz, 超过90% 的频段能够完全覆盖X 波段, 部分覆盖Ku 波段,相对带宽为70%。随着电磁波入射角度的变化, 吸收峰所对应的中心频率稳定, 能够实现对相应频段的完美吸波,并且具有宽带吸波特性。     

结构型多尺度超材料吸波体的设计与研究

文中提出了一种结构型多尺度超材料吸波体。微观层面,该吸波体的结构单元采用微米级羰基铁粉 (CIPs)和多壁碳纳米管(MWCNTs),二者可有效提升吸波体的介电损耗及磁损耗特性;宏观层面,吸波体结构单元 顶部为平台型结构,可提升吸波体对电磁波的阻抗匹配特性。仿真结果表明,该超材料吸波体的反射损耗最小值为 -18. 15 dB,吸收率峰值可达0. 98,吸收率超过0. 9 的频带宽度为5. 5 GHz。通过CIPs、MWCNTs 以及吸波体宏观结 构的协同作用,该吸波体可实现高效宽带吸收特性。     

基于电流变液的宽带可调超材料吸波体设计

为将超材料吸波体更好地应用于生产生活中,文中设计了一种基于电流变液的宽带可调超材料吸波体。通过在超材料吸波体中加载电阻器和介电常数电可调的电流变液实现宽带吸收和吸收频带可调。仿真结果表明,吸波体在8.296~15.128 GHz之间的吸收率超过了80%,在11.5~15 GHz之间的吸收率超过了90%,实现了电磁波的宽带吸收。随着电流变液外加电场强度的增加,其吸收频带逐渐往低频发生移动,实现了吸收频带的调控。此外,仿真证实,由于吸波体结构单元具有旋转对称性,其吸收特性具有极化无关性。     

可调谐激光晶体的成分,结构和激光性质

本文分析可调谐激光晶体的激光性质同基质成分和晶体结构的关系。晶体内过渡金属离子的吸收和辐射光谱特性主要由离子的价态、基质格位多面体类型和晶场强度决定。晶场强度受基质成分和结构的强烈影响,如氟化物与氧化物差别大;被置换离子的半径,其它离子等均有影响。本文还讨论离子变价、杂质、格位对称性对激光性能的影响。     

光学透明和双波段吸波超材料的设计与性能

设计和制作了一种基于超材料的光学透明和双波段吸波体,吸波体基本单元由ITO 十字微结构加补丁结构、玻璃及ITO 膜组成。采用时域有限差分法,研究了十字微结构加补丁结构参数对吸波体电磁性能的影响。仿真结果表明,补丁结构的加入,可以实现双波段高效吸收电磁波,材料在8.5 ~11 GHz 和14.5 ~16.5 GHz 频率范围内反射率小于-10 dB。根据仿真结果,制作了透明吸波体样品,测试了材料反射率和透光率,测试反射率结果与仿真结果吻合得较好,且在可见光区及近红外区透光率达到70%以上。     

Black Gold: Broadband,High Absorption of Visible Light for Photochemical Systems

Here, a black Au surface is presented: a material solely composed of Au that is capable of absorbing more than 92% of the incident light over a spectral region ranging from 300 to 600 nm and that can maintain a high absorbance (above 70%) for wavelengths up to 800 nm. The black Au surface is fabricated by a simple and scalable template‐assisted physical vapor deposition technique and possesses the flexibility of adhering to any arbitrary substrate. The high absorbance of Au originates from the close packing of high aspect ratio Au nanotubes possessing a random tapered wall thickness. Fabry–Perot resonances of gap‐plasmon modes between the Au nanotubes are also responsible for the strong suppression of reflectance of black Au as demonstrated by finite element method simulations. Furthermore, the ability of this surface to drive photochemical transformations under visible light illumination is demonstrated. Hence, black Au could provide a new paradigm for the use of highly absorbing metal nanostructures to effectively harvest the entire visible spectrum for photorelated applications such as solar fuel production, photodetection, and photovoltaics.     

3D Printing of Functional Magnetic Materials: From Design to Applications

The research of functional magnetic materials has become a hot topic in the past few years due to their fast, long-range, and precise response in diverse environments. Functional magnetic devices using different magnetic materials and structure designs have been developed and demonstrated good advantages to enable various applications. However, the required magnetic materials and structure designs for diverse functions also increase the fabrication difficulties while developing such devices. 3D printing technology presents a powerful and promising manufacturing approach to rapidly fabricate functional magnetic devices of complex geometries in multiple materials and scales. Here, various 3D printing strategies and the underlying mechanisms of functional magnetic materials for several primary applications are systematically reviewed, including, magnetic anisotropy for property enhancement, magnetic robots, magnetic components in electronics, and magneto-thermal devices. Finally, the current challenges and future perspectives in engineering 3D printed functional magnetic devices are discussed.     

宽带PON系统测试、设备进展和应用展望

宽带正成为国内外运营商战略和业务转型的基础.在国内,宽带已成为拉动固网运营商业务收入增长的主要动力.作为推动宽带业务发展的宽带接入技术正在不断发展和演进,特别是近两年新推出的宽带PON(无源光网络)技术由于带宽高、扩展性好、运维成本低等优点,正成为电信领域的热点.本文就主流宽带PON技术、系统测试、芯片和设备进展进行简要介绍,最后对其应用予以展望.     

Recent Progress on Metal-Based Nanomaterials: Fabrications,Optical Properties,and Applications in Ultrafast Photonics

Nanomaterials have demonstrated excellent mechanical, thermal, optical, and electrical properties in various fields, including 1D carbon nanotubes, as well as 2D materials starting from graphene. Metal-based nanomaterials, mainly divided into metal and metal oxide nanoparticles, also gradually come into the sight of ultrafast photonics applications due to the outstanding optical properties. The optical properties of metal nanoparticles can be enhanced by the interaction between conduction electrons with electric fields that is called surface plasmon resonance. As for metal oxide nanoparticles, optical properties are closely related to bandgap structures. When it comes to transition metal oxides, other phenomena also play important roles in optical absorption such as spin inversion and excitons of iron. Moreover, preparation methods of materials are also crucial for their properties and further applications. Therefore, in this review, commonly used physical and chemical fabrication methods for metal-based nanomaterials are first introduced. Then the optical properties of typical metal and metal oxide nanoparticles are discussed specifically. In addition, the applications of metal-based nanomaterials in ultrafast lasers based on mode-locked and Q-switched techniques are also summarized. Finally, a summary and outlook toward the synthesis, optical properties, and applications in ultrafast photonics of metal-based nanomaterials are presented.     

纳米阵列结构功能材料的制备、性质及应用

综述了用径迹蚀刻膜模板和多孔阳极氧化铝模板等制备纳米阵列结构功能材料的方法,介绍了金属、半导体纳米阵列结构功能材料、碳纳米管阵列结构功能材料及纳米阵列复合材料的性质和应用实例,并探讨了其应用前景。     

多载波传输技术及其在宽带接入网中的应用

多载波传输技术诞生于60年代,理论上具有接近香农极限的性能.分析了以DMT和DWMT为代表的多载波传输技术的特点及关键技术,并全面比较了它们的性能.详细介绍了多载波技术在宽带接入网,如ADSL,DSLIite,VDSL,SDV及HFC等系统中的最新应用,并分析了存在的基本问题.     

PLC校园宽带接入技术与网络管理功能设计

电力线通信（PLC）可以为用户的宽带接入提供一种方便的、节约成本的方案，成为解决“最后一公里”问题的一种可行方法。介绍了电力线校园宽带接入的实现方法，重点阐述了具有校园特色的宽带接入方案和网络管理功能模块，介绍了电力线通信存在的问题和前景。在对电力线通信进行细致研究的基础上，提出了一种可行的宽带接入方案，具有现实意义和应用前景。     

Hydrophobized Hydrogels: Construction Strategies,Properties, and Biomedical Applications

Hydrogels, as 3D networks containing huge amount of water, display similarity to soft tissues, and thus they are of wide interest in tissue engineering. Hydrogels, due to biocompatibility and porous structure, are valuable therapeutic platforms for hydrophilic drugs. Over the last decade, there has been a strong emphasis on the development of hydrogel platforms with the ability to increase the solubility of hydrophobic drugs. However, the pronounced discrepancy between the hydrophilic character of hydrogels and the hydrophobic nature of numerous pharmacologically active compounds is problematic. In recent years, different strategies are applied using special polymer constructs or composite materials exploiting the advanced scientific knowledge in the area of polymer and lipid-based nano- and microcarriers hydrophobization of the hydrogel turns out to be not only valuable in terms of achieving the ability to dissolve poorly soluble drugs in water, but also proves to be crucial in obtaining bioadhesion in wet conditions, but also, unexpected abnormal water swelling behavior, as well as in mechanical properties such as the dissipation mechanism and self-healable hydrogel properties. This review is mainly focused on recent advances in the usage of hydrophobized hydrogels in biomedical applications.     

From Blue to Red: Syntheses,Structures, Electronic and Electroluminescent Properties of Tunable Luminescent N,N Chelate Boron Complexes

A comprehensive study of a series four‐coordinate boron compounds with the general formula of BPh₂(N,N), where N,N are bidentate chelate ligands containing both neutral and negatively charged nitrogen donor atoms has been conducted. The structures of the boron complexes were examined via single‐crystal X‐ray diffraction. The series of molecules display bright luminescence with emission maxima λ_max ranging from blue to red, depending on the nature of the N,N chelate ligand. The electronic effects and their consequences on the luminescent properties of the complexes due to the CH replacement of the chelate ligand by a nitrogen atom, the increase of conjugation, or the change of substituents on the chelate ligand have been examined using electrochemical analysis, UV‐visible, and fluorescence spectroscopic methods, and by molecular orbital calculations (Gaussian 98). Experimental data and MO calculation results established that the emission of this class of compounds is caused by π–π* transitions centered on the chelate ligand. Furthermore, the experimental and theoretical results consistently and conclusively established that electron withdrawing groups on the negatively charged N‐donor portion of the chelate ligand causes a decrease in the highest occupied molecular orbital (HOMO) energy level, thus increasing the energy gap. The CH replacement by a nitrogen atom on the negatively charged portion of the chelate ligand causes a dramatic decrease of the HOMO energy level, and the increase of conjugation in the chelate ligand significantly decreases the energy gap. Blue and red electroluminescent (EL) devices were fabricated successfully using two representative boron compounds from the series. The new boron compounds have been found to be able to function as both emitters and electron transport materials in EL devices.     

Surface Chemistry Routes to Modulate the Photoluminescence of Graphene Quantum Dots: From Fluorescence Mechanism to Up‐Conversion Bioimaging Applications

The bandgap in graphene‐based materials can be tuned from 0 eV to that of benzene by changing size and/or surface chemistry, making it a rising carbon‐based fluorescent material. Here, the surface chemistry of small size graphene (graphene quantum dots, GQDs) is tuned programmably through modification or reduction and green luminescent GQDs are changed to blue luminescent GQDs. Several tools are employed to characterize the composition and morphology of resultants. More importantly, using this system, the luminescence mechanism (the competition between both the defect state emission and intrinsic state emission) is explored in detail. Experiments demonstrate that the chemical structure changes during modification or reduction suppresses non‐radiative recombination of localized electron‐hole pairs and/or enhances the integrity of surface π electron network. Therefore the intrinsic state emission plays a leading role, as opposed to defect state emission in GQDs. The results of time‐resolved measurements are consistent with the suggested PL mechanism. Up‐conversion PL of GQDs is successfully applied in near‐IR excitation for bioimaging.     

Aminoglycoside-Based Biomaterials: From Material Design to Antibacterial and Gene Delivery Applications

Aminoglycosides are a family of naturally isolated or chemically semi-synthesized antibiotics consisting of aminocyclitols with several amino and saccharide units. The unique molecule structures render aminoglycosides promising building blocks with high reactivity to perform various non-covalent and covalent reactions, and they are further employed to rationally fabricate versatile materials, such as hydrogels, amphiphiles, hyperbranched polymers, biointerfaces, and nanoparticles. Despite aminoglycosides are widely used in clinics to treat bacterial infections, almost all the efforts are focused on molecular modifications to reduce their toxicities and overcome antibiotic resistance, while their actions as building blocks to construct biomaterials are scarcely discussed. In this feature article, the current progress on the rational design, emergent properties, and promising biological applications of aminoglycoside-based biomaterials are summarized. It is believed that this paper may provide guidance to develop new biomaterials using natural functional molecules as building blocks, and start a new life of aminoglycosides from the view of materials science.     

Rational Design of Bioactive Hydrogels toward Periodontal Delivery: From Pathophysiology to Therapeutic Applications

Periodontitis is a biofilm-induced, host-mediated inflammatory disease that results in periodontal tissue destruction. The design of functional biomaterials based on disease pathophysiology is essential for enhancing their therapeutic effects in periodontitis treatment. As promising localized drug delivery systems and tissue engineering scaffolds, hydrogels have gained significant interest for controlled and sustained release of bioactive agents in periodontal applications. The rational design of bioactive hydrogels can facilitate bacterial control and modulate destructive host inflammation, thereby preventing the progression of periodontitis. In this review, the pathophysiological mechanisms underlying periodontitis as fundamental principles for the design of functional hydrogel systems are first introduced. In the following part, an overview is systematically provided of the types and functions of the bioactive hydrogel systems loaded with anti-bacterial and anti-inflammatory agents for periodontal delivery. Finally, the remaining challenges and future perspectives of hydrogel delivery systems for periodontal applications are proposed. It is believed that this review will inspire the rational design and development of innovative functional hydrogel biomaterials toward periodontal therapy.