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71.
72.
The dispersion relations and impedance expressions for both two-dimensional (2-D)/μ-negative and e-negative transmission line metamaterials, which may be paired to form a virtual image of the object, are presented. Under the conjugate matched condition, the voltage distri-butions inside and outside such paired slabs are derived for a plane-wave excitation. Green's functions corresponding to the voltages by a y directed elementary current source excitation are utilized to computed voltage phase and mag-nitude in all regions. The 2-D plots show that the voltage waves, the propagating waves and the evanescent waves, can pass through the conjugate matched slabs and so sub-wavelength virtual imaging has been achieved. 相似文献
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74.
A water-resistant adhesive for plywood panels for engineered wood floors was developed using thermal–chemically treated wheat flour (WF), polyvinyl alcohol (PVA), and polymeric diphenylmethane diisocyanate (p-MDI) as the cross-linker. The thermal–chemical treatment was performed at 100°C in the presence of sulfuric acid or sodium dodecyl sulfate (SDS). Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and scanning electron microscopy were used to investigate the chemical structure, crystalline degree, and morphology change, respectively, of the thermal–chemically treated WF. The boiling water-insoluble content and acetaldehyde values of the thermal–chemically treated WF were also evaluated and compared with those of the controls—native WF and thermally treated WF alone. The bond property evaluation showed that the water resistance of the thermal-SDS-treated WF (T-SDS-WF)-based adhesive was significantly improved, which is mainly attributed to the formation of a three-dimensional crosslinking network resulting from self-crosslinking of the wheat protein, the Maillard reaction between the wheat starch and wheat protein, and the increased crosslinking between T-SDS-WF and p-MDI. Overall, the developed WF-based adhesive is a promising bio-based candidate in the production of plywood for engineered wood floors. 相似文献
75.
Neural Computing and Applications - Vehicle positioning and vehicle identification of natural scene images are an important part of intelligent transportation systems and unmanned driving research.... 相似文献
76.
With the rapid development of 5G NR(New Radio),the explosive increment of traffic amount is calling the utilization of unlicensed band.3GPP has proposed LAA(Licensed Assisted Access)to use LTE in unlicensed band and pointed out that NR-U(NR-Unlicensed)can reuse most designs of it.However,the existing channel access mechanism of LAA is conservative under the coexistence scenario of NR-U,which leads to the waste of time resource.To address the problem this paper proposes a hybrid channel access mechanism to take advantage of the LBT(Listen-Before-Talk)mechanism of LAA when channel is quite busy and transmit directly with reduced power when it is relatively idle.The channel busy degree is judged by a series of periodically updated adaptive thresholds.System-level simulation verifies that under the coexistence scenario of NR-U the proposed mechanism can achieve higher UPT(User Perceived Throughput)and lower delay than other channel access mechanisms. 相似文献
77.
基于晴空辐射模型和太阳光线入射角模型,从集热器集热面接收太阳辐射量的角度,对4种跟踪类型的槽式集热器进行理论计算。通过对比分析得知:采用双轴跟踪槽式集热器接收的太阳辐射量最多,其次为地轴跟踪槽式集热器。综合考虑跟踪系统的稳定性、复杂程度和成本问题,夏季供冷建议优先选用东西跟踪槽式集热器,冬季供热应选用南北跟踪槽式集热器,供冷和供热两用时,优先考虑选用东西跟踪槽式集热器。 相似文献
78.
随着网络威胁的暴露范围越来越广,开发新的工具来改进网络防御是一个重大挑战。网络防御中最重要的问题是人员技能培训,网络靶场就是用于此目的。它提供用于训练和对抗比赛的虚拟环境。本文用VDSL语言定义了一个定制的网络环境,并实现了一个框架,允许将网络靶场场景转换为Prism模型。这样就可以进行训练和赛事结果的定量分析并可以对这个框架进行持续优化。 相似文献
79.
Soybean‐Oil‐Based Thermosetting Resins with Methacrylated Vanillyl Alcohol as Bio‐Based,Low‐Viscosity Comonomer 下载免费PDF全文
Yuehong Zhang Vijay Kumar Thakur Yuzhan Li Thomas F Garrison Zhenhua Gao Jiyou Gu Michael R. Kessler 《大分子材料与工程》2018,303(1)
A novel, bio‐based, aromatic monomer (methacrylated vanillyl alcohol, MVA) is synthesized using vanillyl alcohol and methacrylic anhydride in the absence of solvents. The resulting MVA is used as a sustainable comonomer to replace styrene in a maleinated acrylated epoxidized soybean‐oil (MAESO) resin to produce novel thermosets via free radical polymerization. The influence of MVA loading on the viscosity, gelation time, curing extent, thermomechanical properties, and tensile properties of the MAESO–MVA thermoset is investigated. The synthesized MVA exhibits very low volatility, which is beneficial for the development of construction material with low or zero emission. The viscosity of the MAESO–MVA system can be tailored to meet the commercial requirements. Increasing the MVA content accelerates the crosslinking reaction rate and improves thermal and mechanical properties of the MAESO–MVA system. The glass transition temperature increases with increasing MVA content. Soxhlet extraction experiments show that more than 90% of the components are incorporated into the crosslinking network. Overall, the developed MVA monomer shows promising properties to be used as an effective, green comonomer to replace styrene. 相似文献
80.
运用目前流行的ANSYS/LS-DYNA非线性有限元程序,针对苍山陨石撞击事件,选择对称罚函数法,研究分析撞击作用区域岩体力学参数的变化是如何影响陨石撞击形变场的形成、发展和演化,并得到弹性模量等几个典型参数与撞击形变场的关系曲线。 相似文献