Search

In this article, a multifrequency electromagnetic modulator based on the solid-state plasma (SSP) metamaterial is proposed. It can achieve two modulations of electromagnetically induced transparency (EIT) and bandpass/stop filter, to realize speed and switching modulation of electromagnetic waves with specific frequencies. By exciting different SSP resonance units, the metamaterial modulator can obtain two states (states I and II), showing two different transmission spectra. When working as a tunable EIT, the state I appears as double transmission peaks with the delay-bandwidth product (DBP) reaching 0.517 and 0.421, whereas state II has a single peak with DBP up to 0.675. Since there is a one-to-one correspondence between the frequency points of transmission peaks and valleys in the two states, when state I manifests as an EIT, state II can serve as a band stop filter for the transmission peaks of state I. Conversely, when state II acts as an EIT, the state I can serve as its band stop filter to realize the switching modulation of these frequencies. Therefore, such an SSP-based metamaterial modulator can simultaneously meet the modulations of tunable EIT and corresponding bandpass/stop filter, which has great application prospects. [ABSTRACT FROM AUTHOR]

In this article, the design of a frequency reconfigurable broadband THz antenna based on vanadium dioxide (VO2) is investigated. Instead of being fed by the microstrip line directly, a windmill-shaped feeding structure is designed to provide a proximity-coupled feeding method. Many modes with contiguous resonant frequencies can be excited to obtain the wideband performance. The proposed antenna combines gold with metamaterial VO2. Thanks to insulator-metal phase transition characteristic of VO2 at phase transition temperature (68 °C), we can change the length of the resonant branches to realize frequency reconfiguration by changing the external temperature (T). The simulated results illustrate that when T = 50 °C (State I), such an antenna has a bandwidth of 35.2% (7.01–10 THz) with S11 below − 10 dB, and a maximum gain of 6.62 dBic. When T = 80 °C (State II), it has a bandwidth of 21.8% (5.77–7.18 THz) with S11 below − 10 dB, and a maximum gain of 4.49 dBic. Thus, we realize a design of a proximity-coupled antenna with reconfigurable wideband over the THz band. [ABSTRACT FROM AUTHOR]

To get a high sulfur loaded porous carbon/sulfur cathode material with an excellent performance, we investigated four different sulfur loading treatments. The samples were analyzed by the Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) patterns, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). We proved that it is more effective to introduce the sulfur into the pores of porous carbon at 300 °C than at 155 °C. Especially, the porous carbon/sulfur composite heated in a sealed reactor at 300 °C for 8 h presents a fine sulfur load with sulfur content of 78 wt.% and exhibits an excellent electrochemical performance. The discharge capacity is 760, 727, 744, 713, and 575 mAh g of sulfur at a current density of 80, 160, 320, 800, and 1,600 mA g based on the sulfur/carbon composite, respectively. What is more, there is almost no decay at the current density of 800 mA g for 50 cycles and coulombic efficiency remains over 95 %. [ABSTRACT FROM AUTHOR]

The Co-free LiMnNiFeO ( x/ y = 0.5, 1.0, 2.0) materials were synthesized by combustion method. The effects of the preparation condition on the structure, morphology, and electrochemical performance were investigated by X-ray diffractometry, scanning electron microscopy, charge-discharge tests, and cyclic voltammetry (CV). The results indicate that the structure and electrochemical characteristics are sensitive to the preparation condition when a large amount of Fe is included. A pure layered α-NaFeO structure with R-3m space group and the discharge capacities of over 200 mAh g were observed in some as-prepared cathode materials. Particularly, the LiMnNiFeO prepared by mixing an excess amount of lithium and by firing at 600 °C exhibits a second discharge capacity of 264 mAh g in the voltage range of 1.5-4.8 V under current density of 30 mA g at 30 °C and discharge capacity of 223 mAh g at 2.0-4.8 V. Nevertheless, an unpleasant capacity fading was observed and is primarily ascribed to transformation from a rock-layered structure into a spinel one according to CV testing. [ABSTRACT FROM AUTHOR]

Abstract: A novel series of diphenolic chromone derivatives were synthesized and their inhibitory activity on nitric oxide (NO) production and cytotoxicity were evaluated using LPS-activated murine macrophages RAW264.7 assay and MTT method, respectively. Among these compounds, (5,7-dihydroxy-4-oxo-4H-chromen-3-yl) methyl esters (6b, 6c, 6f, 6g, and 6h) showed quite potent inhibitory activities with IC50 values of 2.20, 3.48, 0.35, 0.80, and 0.61μM, respectively. The MTT results showed that all of the active compounds exhibited no cytotoxicity at the effective concentrations. The preliminary mechanism of the most potent compounds (6b, 6c, 6f, 6g, and 6h) was further examined based on the RT-PCR results and the compounds 6f, 6g, and 6h inhibited NO production by suppressing the expression of iNOS mRNA in a dose dependent manner. Furthermore, a computational analysis of physicochemical parameters revealed that the most of the compounds possessed drug-like properties. [Copyright &y& Elsevier]

Abstract: A numerical method is proposed for modeling the distillation process in a randomly packed column. The proposed model is able to predict the axial and radial concentration distributions along the column without introducing the empirical turbulent Schmidt number or the experimentally measured turbulent mass transfer diffusivity. The present model involves the differential mass transfer equation set and the accompanied computational fluid dynamics (CFD) formulation with the conventional k − ε model. For the closure of mass transfer equation, the recently developed two-equation model is adopted, which consists of the equations for expressing the fluctuating concentration variance and its dissipation rate εc [Z.M. Sun, B.T. Liu, X.G. Yuan, C.J. Liu, K.T. Yu, New turbulent model for computational mass transfer and its application to a commercial-scale distillation column, Ind. Eng. Chem. Res. 44 (12) (2005) 4427–4434]. The validity of the proposed model was testified by applying to a commercial scale randomly packed column of 1.22m internal diameter and packed with 50.8mm metal Pall rings in 3.66m bed height for separating cyclohexane/n-heptane mixture under total reflux and 165.5kPa [A. Shariat, J.G. Kunesh, Packing efficiency testing on a commercial scale with good (and not so good) reflux distribution, Ind. Eng. Chem. Res. 34 (4) (1995) 1273–1279]. Satisfactory agreements were found between the model prediction and the published experimental measurement on the axial concentration distributions, the HETP and the turbulent mass transfer diffusivity along the radial and axial directions. [Copyright &y& Elsevier]

Abstract: A series of quinoline derivatives were synthesized and their immunosuppressive activity and cytotoxicity were evaluated with a T-cell functional assay and MTT method, respectively. Most of 5,7-dimethoxyquinolin-4-yl ortho-substituted benzoate derivatives (18, 22, 24, 28, 31 and 37) showed a quite stronger inhibitory activity compared to other analogs. Among the synthesized compounds, 5,7-dimethoxyquinolin-4-yl 2,6-dichlorobenzoate (22) and 5,7-dimethoxyquinolin-4-yl 4-methylbenzenesulfonate (40) exhibited a potent inhibitory activity without significant cytotoxicity at 10μM concentration. The preliminary mechanism of the active compounds 22 and 40 was further clarified based on the fluorescence activated cell sorter (FACS) assay, and the compounds exerted immunosuppressive activity via inhibiting the T cell activation in a dose dependent manner. [Copyright &y& Elsevier]

In this article, a VO2‐based tunable omnidirectional circularly polarized (CP) antenna is designed. The proposed antenna combines copper and metamaterial VO2. By utilizing the characteristics of insulator‐metal phase transition of VO2, we can change the length of the resonant branches to achieve tunable working bandwidth. The proposed antenna is composed of a modified floor loaded with VO2 and copper resonant branches, a top patch with slits, and 14 shorting vias connecting the top path and bottom floor. Different from the traditional electric controlled antennas, antennas based on metamaterial VO2 do not need to design complicated circuit structures and can be easily tailored by the external temperature (T). The simulated results illustrate that when T ≥ 68°C (state I), the proposed antenna has a 10‐dB impedance bandwidth of 15.9% (2.09‐2.45 GHz), and a 3‐dB axial ratio (AR) bandwidth of 23.4% (2.04‐2.58 GHz). When T < 68°C (state II), it has a bandwidth of 6.5% (2.38‐2.54 GHz) with S11 below −10 dB, and a bandwidth of 19.9% (2.39‐2.92 GHz) with AR below 3 dB. [ABSTRACT FROM AUTHOR]

In this article, a tunable wideband omnidirectional circularly polarized (CP) antenna regulated by the gravity field based on the liquid metal Hg is investigated. Under the action of the gravity field, Hg flows in the upper and lower parts by rotating such an antenna, which can constitute dissimilar resonant units to achieve the dynamic regulation of the operating bandwidths. The proposed antenna consists of four tilted glass containers that are filled with Hg in the upper or lower parts, and a feeding structure for power distribution and impedance matching. To verify concept of the design, equivalent prototypes have been fabricated and measured. The measured results are roughly consistent with simulated results within a reasonable error range. The antenna has a 10‐dB impedance bandwidth of 44.3% (2.37‐3.72 GHz), and a 3‐dB axial ratio (AR) bandwidth of 18.9% (2.83‐3.42 GHz) when the proposed antenna is not rotated (state I). When such an antenna is rotated (state II), it has a bandwidth of 40.7% (2.35‐3.55 GHz) with S11 below −10 dB, and a bandwidth of 22.9% (2.40‐3.02 GHz) with AR below 3 dB. Therefore, the operating band of the antenna can be altered between two wide bands. The proposed antenna has the advantages of tunable bandwidth, novel efficient regulation mechanism, and simple structure. [ABSTRACT FROM AUTHOR]

In this paper, a circularly polarized antenna is realized based on the solid-state plasma (SSP), and its working frequency band can be adjusted slightly by simulating the different SSP branches. The proposed antenna is similar to other common coplanar waveguide antennas, but its metal radiation patch and reflective ground are in different planes, which are located at both sides of the dielectric layer. The dielectric layer is made of FR4, and the metal radiation patch and reflective ground are the copper. There are two adjustable branches composed of SSP, which can be excited to tailor its operating frequency. The simulated results show that the proposed antenna can operate at two main communication bands, which are WLAN (2.4–2.4835 GHz) and WiMAX (3.3 GHz), when the different SSP branches are excited. To verify the reliability of the design, two equivalent prototypes have been fabricated and measured. The measured results are probably consistent with simulated results within a reasonable error range. The measured results show that when the left SPP branch is excited (state A), the 10-dB return loss bandwidth is 57.1% (2–3.6 GHz), and the 3-dB axial ratio (AR) bandwidth is 31.1% (1.9–2.6 GHz) containing WLAN. When the right SPP branch is excited (state B), the 10-dB return loss bandwidth is 57.1% (2–3.6 GHz), and the 3-dB AR bandwidth is 31.6% (2.4–3.3 GHz) containing WiMAX. In addition, the better performance of such an antenna can be obtained within a certain angle region. [ABSTRACT FROM AUTHOR]

In this article, a polarization reconfigurable omnidirectional antenna realized by the gravity field tailored is proposed, which is composed of the liquid metal Hg. The antenna is composed of four horizontal glass containers for omnidirectional horizontally polarized (HP) operating state (State I) and four tilted glass containers for omnidirectional circularly polarized (CP) working state (State II). By rotating the antenna, the position of Hg can be changed due to the effect of the gravity field, and different resonant structures can be formed to realize the regulation of polarization states between HP and CP working states. A reflector based on electromagnetic band gap (EBG) structure also is introduced, which can increase the gain and widen axial ratio (AR) bandwidth. The simulated results show that when the antenna is not rotated (State I), the 10‐dB impedance bandwidth is 21.2% (2.83~3.5 GHz). When the antenna is rotated (State II), the 10‐dB impedance bandwidth is 37.7% (2.35~3.44 GHz), and the 3‐dB AR bandwidth is 28.5% (2.35~3.13 GHz). After introducing the reflector, the max gain is increased to 2.1 dBic in State I and 2.2 dBic in State II, respectively. To further characterize the concept of the proposed antenna, a parametric study is carried out using HFSS. [ABSTRACT FROM AUTHOR]

In this article, a dual‐band and wideband omnidirectional circularly polarized (CP) antenna based on the vanadium dioxide (VO2) is investigated. The operating bandwidth of such an antenna can be regulated by altering the outside temperature (T), which is attained by the insulator‐metal transition of VO2. The omnidirectional CP antenna is based on a loop antenna‐dipole model, which is composed of four tilted metal and VO2 resonant units that are loaded around a cuboid and a feeding network for broadening bandwidth. The simulated results show that when T = 50°C (State I), the 10‐dB impedance bandwidth is 45.7% (1.67‐2.66 GHz), and the 3‐dB axial ratio (AR) bandwidth is 40% (1.9‐2.85 GHz). When T = 80°C (State II), the 10‐dB impedance bandwidth is 13.8% (1.62‐1.86 GHz), and the 3‐dB AR bandwidth is 21.8% (1.68‐2.09 GHz). In order to further characterize the concept of the proposed antenna, the related parameters of such an antenna are studied using simulation software HFSS. [ABSTRACT FROM AUTHOR]

In this paper, a solid-state plasma metasurface (SSPM) for linear-to-circular polarization conversion is designed and investigated. The unit cell of such a SSPM consists of three layers from bottom to top, which are the copper coating, the dielectric layer, and the solid-state plasma resonators, respectively. By exciting solid-state plasma resonance units in different regions, we successfully achieved two operating modes (modes I and II). In mode I, the axial ratio band which is less than 3 dB (3 dB AR band) is mainly obtained in 14.34–19.61 GHz (the relative bandwidth is 31.25%). When the proposed SSPM is regulated to mode II, the 3 dB AR band is changed to 8.81–14.34 GHz (the relative bandwidth is 40.90%). The polarization conversion rate, phase difference, AR curves, and surface current diagrams are analyzed to explore the performances of the proposed SSPM. Our design promotes the potential applications of tunable devices. [ABSTRACT FROM AUTHOR]

In this paper, a three-dimensional (3D) linear-to-circular polarization converter (LCPC), innovatively tailored by the gravity field through the fluidity of liquid metal mercury (Hg), is designed and studied. The proposed LCPC is composed of a 3D glass cavity filled with Hg, a copper reflector, a trenched dielectric layer, and a copper patch. Due to the specially designed 3D glass cavity, Hg will flow in different parts of the glass cavity to form different resonant structures by means of rotation under the action of the gravity field. When the proposed LCPC is not rotated (is placed parallel to the xoy plane), the axial ratio band which is less than 3 dB (3-dB AR band) is obtained in the band of 32.42–42.82 GHz (the relative bandwidth is 27.64%). And when such a LCPC is rotated (is placed perpendicular to the xoy plane), the 3-dB AR band shifts to 18.88–32.86 GHz (the relative bandwidth is 54.04%). Besides, the surface current diagrams are investigated to explain the physics mechanism of the proposed LCPC, and relevant parameters are also discussed. In our design, the proposed LCPC has the advantages of wideband, tunable characteristics, and easy adjustment. In addition, it provides an innovative design idea of LCPC to promote potential applications of tunable devices. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a tunable ultra-broadband linear-to-circular polarization converter (LCPC) in terahertz regime containing the graphene is proposed, which are composed of two "I"-shaped gold resonators, a strip-shaped graphene sheet, two dielectric layer and a bottom gold reflector. The proposed LCPC can convert the linearly polarized wave into circularly polarized wave in an ultra-broadband frequency range which can be expanded to the lower frequencies by decreasing the Fermi energy (E f) of the graphene in terahertz region. When E f = 0. 4 eV , 0.6 eV, 0.8 eV and 1.0 eV, the axial ratio band of the proposed LCPC which is less than 3 dB are covered 0.9248 ∼ 2.2880 THz, 0.9408 ∼ 2.2893 THz, 0.9665 ∼ 2.2803 THz, and 0.9746 ∼ 2.2780 THz, whose relative bandwidths are 84.86%, 83.49%, 80.93% and 80.15%, respectively. The maximum 3 dB axial ratio band is located at 0.9248 ∼ 2.2880 THz and its relative bandwidth is 84.86% at the case of E f = 0. 4 eV. The polarization conversion rate curves, reflection phase curves, surface current and electric field diagrams are analyzed to elucidate the physical characteristics of the presented LCPC. In addition, the effect of parameters a , b and c on the axial ratio band are also discussed, respectively. This design offers an effective way to realize the reconfigurable LCPC, and also has enormous potential value in realizing the THz devices. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the characteristics of the extraordinary mode in the 3D magnetized plasma photonic crystals containing the function dielectric with woodpile lattices are investigated in theory. Such photonic crystals are called the function dielectric magnetized plasma photonic crystals (FMPPCs), and only the magneto-optical Voigt effect of the magnetized plasma is considered. The configuration of such a FMPPC is that the function dielectric square columns are embedded into the magnetized plasma. The permittivity of the function dielectric is space-depended. The results which are calculated by the plane wave expansion method illustrate that a narrower photonic band gap can be achieved in the proposed FMPPCs compared with the conventional 3D woodpile PCs, which only contain the plasma or function dielectric. The studies also show that the better performance can be realized by optimizing the parameters of FMPPCs, and give us another alternative way to realize the reconfigurable applications with the 3D FMPPCs. Highlights • The features of extraordinary mode in 3D FMPPCs is investigated. • The formulas of PWE method are derived. • Compared to the PPCs and PCs, the narrower PBG can be obtained. • The PBG can be tuned by I , b , R, ω c and ω p. • The FBRs can be tailored by ω c and ω p. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surfaces (RISs) are of potential use in wireless communication systems due to their ability to perform beam steering, harmonic wave manipulation, and polarization conversion. However, the main challenge in designing RISs is to obtain their electromagnetic (EM) responses, which is time-consuming and computationally prohibitive. In this work, an efficient modeling method is proposed for fast evaluation of the reflection coefficient and far-field patterns of RISs. The proposed method utilizes the microwave network theory to compute the accurate reflection coefficient of RISs elements under the illumination of incident waves from arbitrary directions. Compared to the classical equivalent circuit model, it enables the separate design of meta-atoms and tunable devices at the network level. The proposed method is verified by the full-wave simulation results of two RIS elements and experimental results of a 3-bit RIS. This work forms a fast and feasible route to obtain the responses of RISs, which allows the RISs to find extensive applications in many scenarios. [ABSTRACT FROM AUTHOR]

In this article, a multilayer dielectric antenna with an air layer is used to realize a strain sensor, which can be utilized to measure the pressure. The springs are sandwiched between a parasitic plate and the designed antenna, where an air layer exists. The pressure can be measured by the relationship between the thickness of the air layer and the S‐parameter of the designed antenna. When the springs are deformed within a certain range, the center frequency of the designed antenna (S‐parameter is less than −10 dB) is correlated with the length of deformation, which can be marked by the thickness of the air layer between the parasitic patch and the antenna. The influence of the air layer thickness on the S‐parameter of this antenna is investigated. The results show that the deformation of the springs has an approximate linear relationship with the center frequency of return loss. The design provides a new idea about stress measurement. [ABSTRACT FROM AUTHOR]

In this article, a tailored coplanar waveguide (CPW) circularly polarized (CP) antenna is designed, whose operating band can be adjusted in a large range by the gravity field through rotating the antenna vertically. Due to the fluidity of liquid metal mercury, which is packaged in the antenna's glass containers, when the antenna is rotated, mercury will lead to different metal resonant units in different directions under the influence of gravity. This antenna utilizes CPW whose metal reflective surface and the main radiating patch are on the same side of the dielectric substrate. The dielectric substrate is made of FR4, and the metal radiation patch and the metal reflective ground are made of copper. Two metal branches separated from the main radiation patch are connected to the main radiating patch by a glass container. To verify concept of the design, equivalent prototypes have been fabricated and measured. The measured results are roughly consistent with simulated results within a reasonable error range. The measured results show that when the antenna turns 90° counterclockwise along the x‐axis (state I), the 10‐dB return loss bandwidth is 13.5% (4.54~5.2 GHz), and the 3‐dB axial ratio (AR) bandwidth is 13.8% (4.5~5.17 GHz). When the antenna turns 90°clockwise along the x‐axis (state II), the 10‐dB return loss bandwidth is 23% (3.73~4.7 GHz), and the 3‐dB AR bandwidth is 23% (3.73~4.7 GHz) within the antenna operating range. In the cases of two different working states, the proposed antenna can effectively cover the 5G communication band. [ABSTRACT FROM AUTHOR]

In this article, we proposed a tunable polarization insensitive ultra-broadband absorber (TPIUA) in THz band make use of the plasma metamaterial, which is the solid state plasma. Because the foments of solid state plasma can be controlled by the external voltage, such an absorber can reach tunability. With different resonators being energized, different absorption states can be realized. When all the resonators are at excited state (state 1), the proposed TPIUA can reach an ultra-broadband absorption and the absorption region which is over 90% is from 7.18 THz to 14.29 THz. The corresponding relative bandwidth is 66.2%. If the middle and out resonators are energized (state 2), the proposed absorber can form an absorption region which is 8.42–12.81 THz (the absorptivity is above 90%), and its relative bandwidth is 41.4%. Besides, if all the resonators are nonenergized, the TPIUA can form four absorption frequency points whose absorptivities exceed 90%. And these absorption frequency points are 8.14 THz, 12.12 THz, 14.09 THz and 14.35 THz. Their absorptivities are 98.0%, 98.5%, 95.7% and 93.9%. If the incident angle is not larger than 20°, the absorber can achieve the stable absorption. The surface current distributions of such a TPIUA are shown to expound the physical mechanism. Besides, to analyzing the absorption mechanism of the TPIUA, we also give the electric fields and power loss densities. The reconfigurable device can be realized by tailoring the state of the solid state plasma. [ABSTRACT FROM AUTHOR]