Facile Fabrication of PBS/CNTs Nanocomposite Foam for Electromagnetic Interference Shielding

In order to reduce the pollutants of environment and electromagnetic waves, environment friendly polymer foams with outstanding electromagnetic interference shielding are imminently required. In this paper, a kind of electromagnetic shielding, biodegradable nanocomposite foam was fabricated by blending poly (butylene succinate) (PBS) with carbon nanotubes (CNTs) followed by foaming with supercritical CO₂. The crystallization temperature and melting temperature of PBS/CNTs nanocomposites with 4 wt % of CNTs increased remarkably by 6 °C and 3.1 °C compared with that of pure PBS and a double crystal melting peak of various PBS samples appeared in DSC curves. Increasing the CNT content from 0 to 4 wt % leads to an increase of approximately 3 orders of magnitude in storage modulus and nearly 9 orders of magnitude in enhancement of electrical properties. Furthermore, CNTs endowed PBS nanocomposite foam with adjustable electromagnetic interference (EMI) shielding property, giving a specific EMI shielding effectiveness of 28.5 dB cm³/g. This study provides a promising methodology for preparing biodegradable, lightweight PBS/CNTs foam with outstanding electromagnetic shielding properties.     

Plasmonic Pollen Grain Nanostructures: A Three-Dimensional Surface-Enhanced Raman Scattering (SERS)-Active Substrate

A new route has been developed to design plasmonic pollen grain-like nanostructures (PGNSs) as surface-enhanced Raman scattering (SERS)-active substrate. The nanostructures consisting of silver (Ag) and gold (Au) nanoparticles along with zinc oxide (ZnO) nanoclusters as spacers were found highly SERS-active. The morphology of PGNSs and those obtained in the intermediate stage along with each elemental evolution has been investigated by a high-resolution field emission scanning electron microscopy. The optical band gaps and crystal structure have been identified by UV-vis absorption and X-ray powder diffraction (XRD) measurements, respectively. For PGNSs specimen, three distinct absorption bands related to constituent elements Ag, Au, and ZnO were observed, whereas XRD peaks confirmed the existence of Ag, Au, and ZnO within the composition of PGNSs. SERS-activity of PGNSs was confirmed using Rhodamine 6G (R6G) as Raman-active dyes. Air-cooled solid-state laser kits of 532 nm were used as excitation sources in SERS measurements. SERS enhancement factor was estimated for PGNSs specimen and was found as high as 3.5×10⁶. Finite difference time domain analysis was carried out to correlate the electromagnetic (EM) near-field distributions with the experiment results achieved under this investigation. EM near-field distributions at different planes were extracted for s-, p- and 45° of incident polarizations. EM near-field distributions for such nanostructures as well as current density distributions under different circumstances were demonstrated and plausible scenarios were elucidated given SERS enhancements. Such generic fabrication route as well as correlated investigation is not only indispensable to realize the potential of SERS applications but also unveil the underneath plasmonic characteristics of complex SERS-active nanostructures.     

Generation of a four-qubit cluster state for atoms in a thermal cavity

We propose two schemes for generating a four-atom cluster state in a thermal cavity. With the assistant of a strong classical field the photon-number-dependent parts in the effective Hamiltonian are canceled. Thus the schemes are insensitive to the thermal field. The schemes can also be used to generate the cluster state for the trapped ions in thermal motion.     

Generation of entanglement via atomic coherence in a two-mode three-level cascade atomic system

The generation of continuous variable entanglement via atomic coherence in a two-mode three-level cascade atomic system is discussed according to the entanglement criterion proposed by Duan et al. [Phys. Rev. Lett. 84, 2722 (2000)]. Atomic coherence between the top and bottom levels is induced with two photons of a strong external pump field. It shows that entanglement for the two-mode field in the cavity can be generated under certain conditions. Moreover, by means of the input-output theory, we show that the two-mode entanglement could also be approached at the output.     

二维开口腔体填充多层各向异性介质TM波散射特性分析

应用区域分解法(DDM)结合有限元(FEM)和边界积分法(BIM)分析了填充多层各向异性介质二维开口腔体TM波散射特性.对腔体外区域采用边界积分法进行分析,将腔体内的每层介质作为一个子域用有限元法分析,各子域间通过传输条件进行耦合.作为算例,分别计算了腔体中填充各向同性和各向异性介质时的散射截面,数值结果表明了该方法的有效性.采用这种技术,大大地减少了对计算机内存的需求.     

电磁阻尼器性能参数试验研究

电磁阻尼器性能与多种因素有关,在电磁阻尼器基本性能试验研究基础上,制作了一个电磁阻尼器模型,进行了涡流板厚度参数影响的试验研究:做了3种厚度涡流板在不同频率、不同位移情况下的试验,得到了涡流板厚度对阻尼器性能影响的定性结论。     

基于谱域球谐展开的多层快速多极子算法

介绍了基于谱域球谐函数展开的多层快速多极子算法,通过处理三维金属体的散射问题,验证了算法参数选取的经验公式,并对算法性能做出了理论分析,得出该算法具有内存占用少﹑迭代速度快的优点,数值结果显示了该方法的高效性.     

用于频率域航空电磁数据的二维自动调平

研究了频率域航空电磁数据的自动调平问题.提出了一种基于一维、二维滤波处理的二维自动调平算法.零漂具有随机性且一般变化缓慢,二维滤波处理可从航电数据中求出包含局部异常和零漂的中间结果,一维滤波处理能从中间结果中求出零漂主要成分,二者结合就能从航电数据中除去大部分零漂误差.该算法只需输入简单的处理参数,实际数据处理结果表明它比以往的调平方法计算速度快、调平效果好、人为因素对结果的影响小,可有效除去零漂造成的"窗帘效应",提高视电阻率和平面剖面图质量.二维自动调平算法为频率域航空电磁数据的零漂调平提供了新的处理手段.     

Microwave absorbing properties of Fe3O4–poly(3, 4‐ethylenedioxythiophene) hybrids in low‐frequency band

A facile method is proposed to obtain microwave absorbing materials (MAMs), which possess strong microwave absorption properties in low‐frequency range. By simply mechanical mixing, the obtained Fe₃O₄–poly (3,4‐ethylenedioxythiophene) (PEDOT) hybrids exhibit more excellent microwave absorbing properties than that of Fe₃O₄ or PEDOT individually. The analysis on the microwave absorbing properties of the Fe₃O₄–PEDOT hybrids indicates that the excellent microwave absorbing properties are ascribed to several factors, like the dielectric loss, the interface polarization, eddy current effect, natural ferromagnetic resonance, and the impedance as well as the thickness of the coating. The Fe₃O₄–PEDOT hybrids with appropriate mass ratios of PEDOT to Fe₃O₄ (represented by (PEDOT)/(Fe₃O₄)) show superior microwave absorbing property at low frequency. When the thickness is 4 mm, the reflection loss of the sample reached ?15.8 dB at 3.2 GHz with (PEDOT)/(Fe₃O₄) of 3 and ?31.4 dB at 4.5 GHz with (PEDOT)/(Fe₃O₄) of 2, respectively. The obtained Fe₃O₄–PEDOT MAMs will have a promising application in the practical industry and commerce affairs. Copyright © 2013 John Wiley & Sons, Ltd.     

纳米银对铕配合物荧光性质的影响(英文)

研究了纳米银对稀土铕-吡啶-2,6-二羧酸配合物(Eu(Ⅲ)C7H5NO4,Eu(Ⅲ)DPA)的荧光性质的影响。随着纳米银浓度增加,荧光强度先增强而后逐渐下降。较大粒径的纳米银使Eu(Ⅲ)DPA荧光增强效率较大,且达到最大荧光增强效率所需的纳米银浓度较低。在高浓度Eu(Ⅲ)DPA溶液体系中,纳米银导致荧光猝灭。电偶极子跃迁发射荧光增强效率大于磁偶极子跃迁发射荧光增强效率。分析认为,纳米银对Eu(Ⅲ)DPA荧光性质的影响与表面等离子体共振与激发态荧光中心强烈耦合以及表面等离子体再吸收有关。同时,纳米银对铕配合物的不对称率有影响,其影响因素与局域电磁场增强,折射率以及配位场有关。