Two approaches to realize a tunable absorber based on patterned graphene metasurface are proposed in this paper. In the first approach, different from available absorption amplitude tunable ...absorbers, the center frequency of the absorber can be tuned by the surface resistance of the graphene in a wide range while maintaining a large absorption coefficient. The second approach, by implying the stack of graphene as the absorbing layer, can introduce a remarkable shift of the center frequency. These two approaches are theoretically illustrated using equivalent circuits and 3-D full wave simulation. Samples that are optically transparent are also fabricated and measured in a rectangular waveguide. A good correlation between simulation and measurement results is obtained.
A patterned graphene-based transparent microwave absorber is proposed in this paper. Graphene is transferred onto polyethylene terephthalate (PET) film, and patterned as μm-level periodic patches, so ...that a capacitive and resistive graphene surface is obtained at microwave band. By placing this graphene/PET film on the top of a glass substrate and applying fluorine-doped tin oxide film as the reflective layer, transparent absorber working at Ku band is realized. The optical transmittance of the fabricated graphene/PET film reaches around 80% in the whole optical light range, while the absorption coefficient reaches 90% at 12.6 GHz. By analyzing the parasitic effects in the rectangular waveguide measurement, a good agreement is obtained among the measurement, three-dimensional full-wave simulation, and the equivalent circuit. Two configurations are further analyzed to enhance the absorption level and the working bandwidth of the absorber. 100% absorption and 3 GHz bandwidth broadening are realized.
A new equivalent dipole model hybrid with artificial neural network (ANN) is proposed in this paper for electromagnetic interference (EMI) estimation. Equivalent dipole method, based on the ...free-space Green's function, is usually used to model unknown EMI sources on printed circuit boards. For high-speed and dense circuits, there may be multi-reflection and/or diffraction between the EMI source and its nearby components. Traditional dipole model usually omits such effects and leads to an inaccurate result in some cases. In our proposed method, the Green's function of dipole is taken as input and the radiated EMI field is taken as the output of ANN. We use the powerful mapping ability of ANN to modify the matrix-vector multiplication between free-space Green's function and dipole moments in the traditional dipole model, so that a new mapping between equivalent dipoles and their radiated fields is established. The near field of the EMI source is obtained by planar scanning, and is used for ANN training. After training, the ANN is used to predict the EMI field at the region of interest. Both numerical example and measurement example are given to show the effectiveness of the proposed ANN method. This paper provides a novel source reconstruction solution for the EMI problems.
Molecular ultralong room‐temperature phosphorescence (RTP), exhibiting multiple stimuli‐responsive characteristics, has garnered considerable attention due to its potential applications in ...light‐emitting devices, sensors, and information safety. This work proposes the utilization of photochemical cascade processes (PCCPs) in molecular crystals to design a stepwise smart RTP switch. By harnessing the sequential dynamics of photo‐burst movement (induced by 2+2 photocycloaddition) and photochromism (induced by photogenerated radicals) in a bismuth (Bi)‐based metal‐organic halide (MOH), a continuous and photo‐responsive ultralong RTP can be achieved. Furthermore, utilizing the same Bi‐based MOH, diverse application demonstrations, such as multi‐mode anti‐counterfeiting and information encryption, can be easily implemented. This work thus not only serves as a proof‐of‐concept for the development of solid‐state PCCPs that integrate photosalient effect and photochromism with light‐chemical‐mechanical energy conversion, but also lays the groundwork for designing new Bi‐based MOHs with dynamically responsive ultralong RTP.
An approach to leveraging photochemical cascade processes (PCCPs) involved photocycloaddition and photogenerated radicals in molecular crystals was proposed, which can be further used to design stepwise smart room‐temperature phosphorescence (RTP) switch. It provides a proof‐of‐concept for developing solid‐state PCCPs integrating light‐chemical‐mechanical energy conversion, paving an effective way to design photo‐controllable ultralong RTP.
In this paper, an electromagnetic probe is proposed for the near-field scanning. Its detection section is made of a miniature loop-wire hybrid structure, which can measure H x , H y , and E z ...simultaneously. It is optimized to achieve a wide working band from 0.1 to 15 GHz. The calibration and measurement error of the probe are discussed in detail. The probe is fabricated as a four-layer printed circuit board (PCB) with the RO4350B dielectric. A near-field scanning system with the manufactured probe is set up to test the near fields above a Z-type microstrip line and an inverted-F antenna. By comparing the measurement and simulation results, the accuracy of the proposed multi-component probe is verified. It greatly improves the near-field scanning efficiency compared to the traditional single-component probe.
This letter presents a deembedding method for the S-parameter extraction of surface-mounted devices (SMDs) with asymmetric fixtures. The proposed method can remove the effects of asymmetric fixtures ...on the SMDs. It extracts the unknown S-parameters of the fixtures and SMD by combining frequency and time domains S-parameters. The accuracy of the proposed method is compared to that of the traditional 2X-thru deembedding method. The advantage of the proposed method is that it can reduce the testing time for asymmetric fixtures. Numerical examples and measurement are carried out for the validation of the proposed deembedding method.
In this letter, a novel low-profile dual-band and dual circularly polarized (CP) microstrip antenna is proposed. The antenna consists of two circular eccentric rings (CECRs) with different sizes. The ...two eccentric rings each work as a single-band circular polarization radiator and are simultaneously excited by an arc-shaped strip. A lumped equivalent circuit model is developed to analyze the operation mechanism of the antenna. In order to simplify the design procedure, empirical formulas are derived based on the physical parameters of the antenna. The proposed structure has been examined by both simulation and experiment, and both results agree very well.
Olivine from mafic–ultramafic intrusions rarely displays growth zoning in major and some minor elements, such as Fe, Mg and Ni, due to fast diffusion of these elements at high temperatures. These ...elements in olivine are thus not useful in deciphering magma chamber processes, such as magma convection, multiple injection and mixing. High-resolution X-ray elemental intensity mapping reveals distinct P zoning patterns of olivine from two mafic–ultramafic intrusions in SW China. Polyhedral olivine grains from lherzolite and dunite of the Abulangdang intrusion show P-rich dendrites similar to those observed in volcanic rocks. Rounded olivine grains from net-textured Fe–Ti oxide ores of the Baima layered intrusion have irregular P-rich patches/bands crosscut and interlocked by P-poor olivine domains. P-rich patches/bands contain 250 to 612 ppm P, much higher than P-poor olivine domains with 123 to 230 ppm P. In electron backscattered diffraction (EBSD) maps, P-rich patches/bands within a single olivine grain have the same crystallographic orientation, indicating that they were remnants of the same crystal. Thus, both P-rich patches/bands and P-poor olivine domains in the same grain show a disequilibrium texture and clearly record two-stage growth. The P-rich patches/bands are likely the remnants of a polyhedral olivine crystal that formed in the first stage, whereas the P-poor olivine domains containing rounded Ti-rich magnetite and Fe-rich melt inclusions may have formed from an Fe-rich ambient melt in the second stage. The complex P zoning of olivine can be attributed to the dissolution of early polyhedral olivine and re-precipitation from the Fe-rich ambient melt. The early polyhedral olivine was in chemical disequilibrium with the ambient melt that may have been developed by silicate liquid immiscibility in a crystal mush. Our study implies that olivine crystals in igneous cumulates with an equilibrium appearance may have experienced disequilibrium growth processes during slow cooling. Therefore, the crystallization sequence of mafic magmas based on textural relationships should be treated with caution.
•P-rich dendrites were found in polyhedral olivine from ultramafic cumulates.•P-rich dendrites of olivine formed by rapid growth far out of equilibrium.•Complex P-zoning patterns were found in rounded olivine from a layered intrusion.•Chemical disequilibrium triggered a two-stage growth of olivine in mafic magmas.
This article presents a novel design of an <inline-formula> <tex-math notation="LaTeX">{E}_{z} </tex-math></inline-formula> probe with a high spatial resolution. The key factors that have significant ...impact on spatial resolution are analyzed, and the optimal design for achieving a high spatial resolution is showcased. By strategically reducing the effective lengths of the probe in <inline-formula> <tex-math notation="LaTeX">{x} </tex-math></inline-formula> or <inline-formula> <tex-math notation="LaTeX">{y} </tex-math></inline-formula>-directions, remarkable spatial resolution is achieved. The proposed probe is cost-effective as it is fabricated on a four-layer printed circuit board (PCB) while exhibits more stable performance. To further improve the spatial resolution and address limitations in PCB fabrication, a blind-hole structure is implemented. Operating in a frequency band of up to 6 GHz, the probe demonstrates outstanding rejection of unwanted fields across a broad spectrum. Simulation and measurement results verify the exceptional performance of the proposed probe.
