Accurate measurement of the permittivity and loss tangent of low-loss materials is essential due to their special applications in the field of ultra large scale integrated circuits and microwave devices. In this study, we developed a novel strategy that can accurately detect the permittivity and loss tangent of low-loss materials based on a cylindrical resonant cavity supporting the TE111 mode in X band (8–12 GHz). Based on an electromagnetic field simulation calculation of the cylindrical resonator, permittivity is precisely retrieved by exploring and analyzing the perturbation of the coupling hole and sample size on the cutoff wavenumber. A more precise approach to measuring the loss tangent of samples with various thicknesses has been proposed. The test results of the standard samples verify that this method can accurately measure the dielectric properties of samples that have smaller sizes than the high Q cylindrical cavity method.
Simultaneously implement on building design and evaluation system for green building of Chenjia Town energy management center,whose indexes are simulated.Technology for energy conservation is adopted compatible to local condition.Thus,pre-evaluation on 3-stars green building and build feature are accomplished.
Efficient absorption of solar radiation holds the key to photothermal utilization; however, realizing solar absorber designs with high absorption efficiency remains challenging. Herein, a nickel-based metamaterial selective solar absorber with a nanopillar array structure was proposed to realize nearly perfect optical absorption over a broad spectrum. The average absorbance is up to 96% in the 300–2033 nm wavelength range. Notably, a reasonably detailed analysis of the physical mechanism of the proposed absorber was performed in this paper, attributing the exceptional broadband absorption to the concurrent interaction with surface plasmon resonance, quarter-wavelength resonance, and electric dipole resonance. The absorption efficiency declines significantly when λ > 2.5 μm, with only 20% absorptivity at λ = 6 μm in the radiation-absorbing transition region. This decline is desirable, as it contributes to reducing the emissivity in the mid-infrared range and, therefore, prevents self-radiation. The results demonstrate that the selective absorber possesses the potential to capture solar energy within a broadband, while avoiding undesirable self-radiation, thereby enhancing the integral efficiency of the solar energy conversion system. Moreover, the absorption spectrum shows insensitivity to polarization and angle of incidence. The selective solar absorber proposed here offers excellent performance with a simple structure, showing great promise in the field of photothermal conversion.
In this study, a three-dimensional graphene- and carbon nanotube (CNT)-decorated SiOx composite material (SiOx-Gr-CNT) was synthesized. The dual carbon components were introduced by a simple one-step method of high-energy ball milling. The corresponding SiOx-Gr-CNT composite electrode exhibited superior lithium storage performance because the graphene and CNT components form a flexible network with high conductivity decorating on SiOx. The network is beneficial for the improvement of the conductivity of SiOx particles. The mechanical flexibility of the graphene and CNT components had a negligible volume effect, which could effectively suppress the volume expansion of SiOx and assist to form a durable solid electrolyte interphase film by separating SiOx particles from the electrolyte. Thus, the electrochemical properties of the corresponding SiOx-Gr-CNT composite electrode were effectively enhanced with a large reversible specific capacity of 1015.1 mA h g–1, which was maintained at 1046.6 mA h g–1 after cycling of 100 cycles with a capacity remaining exceeding 100% under a current density of 100 mA g–1. The SiOx-Gr-CNT composite electrode also exhibited outstanding cycling performance under a large current density of 1 A g–1 with more than 800 mA h g–1 reversible specific capacity even after 200 cycles. The method used for the combination of the SiOx-Gr-CNT composite anode material is simple and mass productive and thus is promising for practical application.
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