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Styrene butadiene (SBR) and natural rubber (NR) can be used as binding matrices to control the release of zinc (Zn) which is a micro-nutrient for plants. The leaching rate of zinc in an aqueous medium depends on the concentration of zinc sulphate loaded in the two types of rubber used, the temperature of the surrounding environment and the pH of the aqueous medium. Water uptake was increased with increasing concentration of ZnSO4. The sustained release of zinc ions from the investigated formulations was prolonged for over five months. The mechanical properties of the vulcanizates were affected as the concentration of zinc sulphate changed. 相似文献
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基于电谐振原理和镜像原理设计了一种周期性接地边耦合SRRs(split ring resonators)结构的新型电谐振人工异向介质,进而将该人工异向介质应用于抑制微带阵列天线元间的互耦.与传统微带阵列天线中的用于抑制互耦的电磁结构相比,该人工电磁结构不仅体积小(厚度仅为0·005λ0),而且能获得优异的阵列单元间互耦抑制性能(抑制度达16·8dB).该研究成果表明人工异向介质在高密度高性能微带天线阵列设计中具有良好的应用潜能. 相似文献
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Reduction in antenna size by using multi-band radiators play a vital role in the miniaturization of present world wireless handheld devices, as dual band behaviour of the antennas result in the integration of more than one communication standard in a single system and thus, saving the installation space required for separate antennas. In this context, this communication presents a shorted-pin dual band metamaterial inspired microstrip patch antenna array. Under the unloaded conditions, the traditional patch antenna array resonates at 5.8 GHz with gain of 9.8 dBi and bandwidth of 540 MHz. However, when each patch of this traditional antenna array is loaded with split ring resonator (SRR) and a metallic via hole is introduced in the patch, the same antenna array produces an additional resonant frequency in IEEE 802.11b/g/n 2.45 GHz Wi-Fi band with bandwidth and gain of 290 MHz and 5.6 dBi, respectively, while the initial resonant frequency (i.e. 5.8 GHz) gets shifted to IEEE 802.11ac 5 GHz Wi-Fi band, providing the gain and bandwidth of 11.4 dBi and 510 MHz, respectively. The proposed antenna array has been fabricated, and the measured results are presented to validate the proposed array. Moreover, the equivalent circuit of the proposed antenna array has been designed and analyzed to validate the simulated, measured and theoretical results. Attainment of dual band characteristics by incorporating the metamaterial with single band traditional patch antenna array makes this structure novel, as this has been achieved without any extra hardware cost, size and loss of structural planarity. Also, both the frequency bands of this proposed metamaterial inspired antenna array possess considerable gain and bandwidth. 相似文献
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提出了一种通过加载开口谐振环隔离板来抑制微带天线阵元之间耦合的方法。首先设计了一款工作频率在6GHz的微带天线阵,然后在其阵列单元间加载单环SRR隔离板结构。该结构在特定频段具有带阻特性,可以有效抑制天线单元间的互耦,增加天线单元间的隔离度。最后利用HFSS软件进行了仿真与优化。仿真结果证明:该结构的引入能使微带天线单元间的互耦因子降低10d B左右,体现了较好的互耦抑制特性。 相似文献
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基于Pendry提出的开口谐振环(SRR)基本理论,结合Falcone建立的SRR互补模型,针对Mohammed构建的哑铃型结构,建立了HFSS模型,完整地仿真了哑铃型互补SRR滤波器主要结构参数对性能的影响,分析了滤波器单元边长、缝隙宽度、缝隙间距、开口宽度、桥接间距和桥接宽度与滤波器中心工作频点、工作带宽和传递系数之间的关系.结果表明,通过调整缝隙宽度和间距能够有效改变滤波器工作频点、带宽和传递系数;增加单元边长,虽可有效降低工作波长,但其带宽和传递系数均会显著恶化;其它参数的改变不会导致滤波器性能发生显著改变.最后,设计了实物样品验证了仿真结果. 相似文献
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In this work, a novel Circularly Polarized (CP) slot antenna is proposed for low RCS and high gain applications. The proposed antenna is designed in two phases. Initially, a metasurface is designed, which is composed of two similar artificial magnetic conductor (AMC) unit cells arranged orthogonally in chessboard-like configuration for broadband RCS reduction. Then, the CP slot antenna is designed by placing dual SRR on the backside of the slot for impedance matching and to achieve circular polarization. Detailed analysis is conducted to investigate the performance of metasurface loaded CP slot antenna. The proposed antenna shows 10 dB RCS reduction over the bandwidth of 41.3% at boresight direction compared to CP slot antenna. The maximum in-band and out-of-band RCS reduction achieved is 24 dB and 20 dB, respectively. The maximum gain of the antenna is also increased by 2.7 dB as a result of parasitic radiation of the metasurface and an improvement in overall performance of the antenna is observed by the employment of metasurface. Measured results of the fabricated prototype are in good agreement with the simulated results. 相似文献
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设计了一种新型宽带准八木天线,该天线采用微带线进行馈电,通过一种新型的巴伦结构实现了微带线到共面带状线的转换。天线有一个辐射振子和两个引向振子,介质板背面的金属地板作为反射器,具有较宽的带宽。为了进一步提高增益,在引向振子前端加载两组开口谐振环单元。改进后天线的-10 dB 阻抗带宽为53.7%(5. 9~10. 2 GHz),增益达到了5. 7~9. 3 dB,相比改进前平均提高了2 dB。对原型天线和改进后天线分别进行了加工测量,测量结果与仿真结果基本吻合。 相似文献
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Dorota A. Pawlak Sebastian Turczynski Marcin Gajc Katarzyna Kolodziejak Ryszard Diduszko Krzysztof Rozniatowski Julita Smalc Irina Vendik 《Advanced functional materials》2010,20(7):1116-1124
Metamaterials offer new unusual electromagnetic properties, which have already been demonstrated, and many postulated new functionalities are yet to be realized. Currently, however, metamaterials are mostly limited by narrow band behavior, high losses, and limitation in making genuinely 3D materials. In order to overcome these problems an overlap between metamaterial concepts and materials science is necessary. Engineered self‐organization is presented as a future approach to metamaterial manufacturing. Using directional solidification of eutectics, the first experimental realization of self‐organized particles with a split‐ring resonator‐like cross section is demonstrated. This unusual morphology/microstructure of the eutectic composite has a fractal character. With the use of TEM and XRD the clear influence of the atomic crystal arrangement on the microstructure geometry is presented. The materials obtained present very high anisotropy and can be obtained in large pieces. Metallodielectric structures can be created by etching and filling the space with metal. The next steps in the development of self‐organized materials exhibiting unusual properties are discussed. 相似文献