Search

A three-layered transmitting focusing gradient meta-surface (FGMS) has been proposed, which can achieve broadband gain enhancement from 8.2 GHz to 10 GHz. The element of broadband transmitting FGMS has high transmitting efficiencies that over 0.7 and achieve [0, 2π] phase range with a flat and linear trend in the operating band. The FGMS can transform the spherical waves into plane waves. Three patch antennas working at 8.2 GHz, 9.1 GHz, and 10 GHz respectively are placed the focus of broadband FGMS as the spherical-wave source to build a broadband planar lens antenna system. It achieves a simulation gain of 15.44 dBi which is 7.51dB higher than that of the bare patch antenna at 10 GHz with satisfying SLLs and beamwidths. However, it enhanced the gain of the bare patch antenna in a wide operating band. Finally, the FGMS and the patch antenna are fabricated and measured. The measured results are in good agreement with the simulations.

A novel dual-polarized frequency-selective polarization converter (FSPC) with low-backward scattering is proposed by combining a bandpass frequency-selective surface (FSS) with a polarization converter. The FSPC, comprised of the top polarization conversion layer and the bottom multilayer bandpass FSS, is formed by introducing two polarization converter bands on both sides of the broadband passband. The four-port equivalent circuit model cascading FSS and polarization converter is proposed and investigated. It is numerically demonstrated that a flat 1 dB transmission window can be obtained from 8.5 to 11 GHz with a 25.6% fractional bandwidth (FBW), and the bandwidth of reflection below −10 dB is up to 92% from 5.6 to 15.13 GHz. Moreover, the proposed device can achieve two polarization conversion bands (5.66–6.9 and 12.8–15.2 GHz) with the polarization conversion ratio over 90%. Besides, by arranging the proposed structure in a checkerboard-like distribution, the backward scattering energy can be reduced in a wide frequency band ranging from 4.5 to 16 GHz. Both simulation and experimental results are in good agreement, which demonstrates our design strategy. Compared with the conventional polarization converters, the proposed design presents an extra frequency-selective performance and, hence, can be a great substitute for the frequency-selective rasorber (FSR).

Subretinal injection is a delicate and complex microsurgery. The main surgical difficulties come from the surgeon's hand tremor, dexterous motion, and insufficient visual feedback. In order to begin addressing these challenges, this article presents a robot system for subretinal insertion integrated with intraoperative optical coherence tomography (OCT). The surgical workflow using this system consists of two main parts. The first part is the manual robot control, which aims the target before approaching the retinal surface, while considering the remote center of motion (RCM) constraint. When the injection area has been located precisely, needle is inserted into retina. To ensure surgical safety, needle insertion depth is estimated using OCT images on a continuous basis. A soft RCM control method is designed and integrated for the controller of our hybrid parallel–serial surgical robot. Safety and accuracy performance evaluation with a 15-ms control loop shows that the worst-case RCM deviation error is within 1 mm. Experimental results demonstrated that the proposed system has the ability to improve surgical outcomes by surgeons overcoming their physical limitations in order to enable a better dexterous motion, and furthermore enhancing their visual feedback for a better intraocular perception.

Herein, an integrated multifunctional design for simultaneous perfect absorption and polarization conversion is proposed that worked in the Ku band: the proposed structure consisted of two asymmetric dielectric semi-rings which are supported on a ground plane by two dielectric cylinders with different heights. Simulated results demonstrate that unity absorption and linear cross-polarization conversion can be integrated into one multifunctional structure: absorption and polarization conversion operate at different frequencies. Furthermore, these different functions under the different polarized modes (TE and TM) are integrated into the single structure without adjusting any parameters, while also at a large range of incident angles. The integrated design is more conducive to the miniaturization and multi-functionality of devices and there are also practical applications in other areas.

A dual-polarized frequency-selective rasorber (FSR) with a wide high-transmission passband and two absorption bands is proposed and investigated in this letter. The proposed FSR, is composed of a lossy and a lossless layer, is formed by introducing a broadband transmission window into a wider absorption band. Simple guidelines based on an impedance analysis are proposed, and the wide high-transmission passband is realized by connecting multiple coplanar parallel resonances (MCPRs) in a series, which introduces a large impedance in a wide band for the lossy layer. In this design, the lossy layer and lossless layer consist of a square ring absorber with multiple interdigital resonators and a multilayer broadband frequency selective surface, respectively. The simulation results indicate that the 1 dB transmission window can be obtained from 8.12 to 11 GHz with a 30.4% fractional bandwidth, and the bandwidth of reflection below –10 dB is up to 111% from 4 to 14 GHz. Finally, the proposed structure is fabricated and measured. Both the simulation and experimental results agree well, which suggests that the concept of connecting MCPRs in series can generate a broadband transmission window effectively.

A new family of asymmetrical 1,2-squaraine dyes (1,2-SQs) were designed and synthesized in high yields. The photophysical analysis presented that these 1,2-SQs showed strong red fluorescence in crystal state but weak fluorescence in solution, suggesting their aggregation-induced emission enhancement (AIEE) properties. Single crystals X-ray diffraction revealed that the intense fluorescence in the crystal state can be attributed to the effects of long alkyl chains or large group substituents in the molecules, which efficiently prevented the tight intermolecular contact and reduced π–π interactions. The biocompatibility and cell imaging applications of SQ4 were further investigated. The results demonstrated that SMMC-7721 cell can be clearly imaged by SQ4, which inferred SQ4 had excellent biocompatibility and potential value for bioimaging.

In recent years, with the rapid development and rise of mobile Internet, network security issues have also posed a great threat to people. Botnets are an important problem faced by current network security. DNS protocol-based botnets widely use domain generation algorithm (DGA), which can randomly change the domain name to hide itself, and therefore is very likely to threaten people’s network security. In this paper, we use the domain names of the top 1 million websites in the Alexa global ranking as white samples, and for the DGA sample data, we use the open data of 360netlab as black samples. The character sequence model is used for feature extraction, and the LSTM with Bayesian optimization neural network is used to optimize the hyperparameter combination, which finally makes the accuracy of the model above 97%, and the model has superior performance to compare with the conventional model, which can effectively improve the accuracy of DGA detection and recognition.

A broadband Frequency Selective Rasorber (FSR) with 2.5D FSS structure is proposed. The proposed FSR presents a wideband transmission window between two absorption bands. The FSR consists of a lossless periodic surface and a lossy periodic surface separated by an air layer. The lossy surface is realized by inserting a strip-type Parallel LC (P-LC) of via structure into the center of a dipole loaded with lumped-resistors. The lossless layer is a broadband bandpass frequency selective surface (FSS) consisting of two metal patches surfaces and separated by a thin layer. An equivalent circuit model (ECM) is proposed to analyze operating principle of the FSR. The fractional bandwidth for reflection less than −10 dB is about 70% and a transmission bandwidth with insertion loss of −3 dB is about 22%. The FSR perform stable frequency response from 0 to 30 degrees.

A novel bandpass filter (BPF) based on spoof surface plasmon polaritons (SSPPs) using a compact folded slotline structure is proposed and experimentally demonstrated. The proposed novel SSPPs structure compared with a conventional plasmonic waveguide with slot line SSPPs unit structure at the same size, the considerable advantages in much lower asymptotic frequency with tight field confinement, which enable the proposed filter to be more miniaturization. A high-efficient mode conversion structure is designed to transition from TE-mode to SSPPs-mode by gradient slotline lengths. The low-frequency stop-band can be committed with microstrip to slotline evolution on both sides of the dielectric, while the high-frequency cutoff band is realized by the proposed SSPPs structure. The influence of dispersion relation, electric field distribution, surface current, and structural parameters on the transmission characteristics of the proposed BPF are analyzed by finite difference time domain (FDTD). To validate the design concept, the prototype of the miniaturized SSPPs BPF has been manufactured and measured. The experimental results show high performance of the fabricated sample, in which the working in a range of 0.9 GHz–5.2 GHz with the relative bandwidth is 142%, the insertion loss less than 0.5 dB, the reflection coefficient less than −10 dB, and the group delay is less than one ns. This works provides a mirror for realizing the miniaturization of waveguides, and the application and development of high-confinement SSPPs functional devices in the microwave and THz regimes.

This study explored the adsorption of lead ion from aqueous solution onto biochars produced from date seed biomass. Initial evaluation of nine date seed-derived biochars showed that biochar prepared at 550 °C and heating time of 3 h (DSB550-3) was the best adsorbent for Pb2+ ion removal. Therefore, it was selected for further investigation in batch and column experiments. The effects of contact time, initial Pb2+ concentration, and solution pH were studied. Solution pH showed strong effect on the adsorption ability of DSB550-3 biochar to the lead ion, and the maximum adsorption capacity was found to occur around pH 6.0. The batch maximum adsorption capacity of DSB550-3 biochar was 0.360 mmol g−1. The equilibrium data were adequately fitted to Freundlich and Langmuir isotherms (R 2 = 0.97). The adsorption kinetics were best described by pseudo-second-order model (R 2 = 0.94). The breakthrough curve obtained from the column experiment was best described by the modified dose–response model (R 2 = 0.95). The desorption efficiencies of Pb2+ were 2.1%, 23%, 12%, and 55% for DI water, 0.1 M HCl, 0.1 M CaCl2, and a combination of 0.1 M HCl + 0.1 M CaCl2 eluents, respectively. FTIR analysis and batch experiments results suggested that Pb2+ adsorption mechanism was dominated by complexation with active surface groups, precipitation, and cation exchange. Experimental and model results suggested that date seed-derived biochar has high adsorption capacity for Pb2+ compared to other plant-based biochars reported in other literature.

The photocatalytic reduction of CO2 to organic molecules is one promising approache for both decreasing CO2 concentration in the atmosphere and storing energies. However, most of the photocatalytic reduction of CO2 cannot avoid the utilization of sacrificial agents, which are not atomic economy and restricts the practical application of the photocatalytic reduction of CO2. In this contribution, an atomic economy photocatalytic reduction of CO2 to CH3OH coupling with the oxidation of amine to imine by Cu/TiO2 was reported, which can avoid using the sacrificial agents in the reaction systems. CO2 was reduced to CH3OH by photo-induced electrons; meanwhile benzylamine was selected as the reductant to react with photo-generated holes and converted into imine with high selectivity. The results showed that the maximum conversion of benzylamine to imine is 88.7% with selectivity of 98%, and the highest yield of CH3OH is 961.4 µmol g−1 using ca.0.5 wt% Cu/TiO2 as the catalyst. And also, the reaction mechanism was also investigated by DFT calculation, which would give a detailed explanation for the reaction process. Schematic illustration is that maximum conversion of benzylamine to imine is 88.7% with selectivity of 98%, and the highest yield of CH3OH is 961.4 μmol g−1 using ca.0.5 wt% Cu/TiO2 as the catalyst

Multiblock copolymers of polyether-modified amino silicone softener (ETSO-PEA) were successfully synthesized with epoxy-terminated polysiloxane (ETSO) and polyether amine. The chemical structure of ETSO-PEA was characterized by 1H NMR, FTIR and TGA. Single-factor and orthogonal array design experiments affecting the conversion rate of product were carried out to investigate the optimal reaction conditions. In the first two steps, the data between viscosity/conversion rate and reaction time showed that the two steps were both kinetic first-scale reaction. The application of ETSO-PEA used as softener on cotton fabrics was studied. The results showed that the ETSO-PEA-treated cotton fabrics expressed better hydrophilicity, wettability and whiteness than traditional amino silicone softener-treated samples. The morphology images indicated that the scales and clearance on the surface of the untreated cotton fibers were covered with a smooth film after treating with the silicones solution. Amino silicone softener was fixed onto the cotton fabrics, and the surface was modified with a formation of network structure. Meanwhile, the extent of networking and crosslinking was enhanced a lot, which provided a good soft handle. The polyether segment with less bending on the ETSO-PEA disrupted the continuous arrangement of Si–CH3 groups and limited the movement of polysiloxane segment, giving the cotton fabric a better hydrophilic and slightly rougher surface than ATSO-treated samples. This work provided an optimized and cost-effective method to synthesize high-performance multiblock polyether functional amino silicone softener.

In this paper, three series of heterostructures of 2D transition metal dichalcogenides (including MoS2, MoSe2, MoTe2, WS2, WSe2, and WTe2) sandwiched by graphene (Gr), h-BN, and g-C3N4, which will be referred to as Gr sandwich heterostructures (SHS), h-BN-SHS, and g-C3N4-SHS in the rest of this paper, have been systematically studied firstly by using first-principle calculations. Gr-SHS are found to hold stable structures with an expanded band gap when MoSe2 and WSe2 are used as interlayers, indicating potential applications to Hall switch sensors. With the same type of interlayers, the stable h-BN-SHS shows additionally good response to visible light. In addition to good response to the visible light, effective electron–hole separation is also observed in g-C3N4-SHS. Such properties suggest structures in this sandwich type may be applied in plentiful areas, such as photocatalyst and solar cells. Moreover, the number and density of catalytically active sites in SHS may be dramatically increased. Consequently, we hope our findings could provide guidance for both the design of advanced materials and the corresponding nano-devices.

Electrocatalytic nitrogen reduction under ambient conditions is a promising approach for ammonia synthesis, but it is challenging to develop highly efficient electrocatalysts. In this work, a hybrid of covalent organic framework (COF) and carbon nanotubes (CNTs) are developed for efficient nitrogen electroreduction with a high faradaic efficiency (FE) of 12.7% at 0.0 V versus reversible hydrogen electrode (RHE) and a remarkable production rate of ammonia up to 8.56 [Formula: see text]g h[Formula: see text] mg[Formula: see text] at –0.2 V versus RHE. Experiments and theoretical calculations reveal that Ni centers are active sites for NH3synthesis, while the [Formula: see text]–[Formula: see text] stacking between COF-366-Ni and conductive CNTs scaffold results in the rapid interfacial charge transfer. This investigation provides new insights on the rational design of organic–inorganic porous hybrids for efficient nitrogen conversion and ammonia synthesis at ambient conditions.

Aiming at the inherent unavoidable defects of welded joints, a CTOD (Crack Tip Opening Displacement) test was carried out on the E43 steel weld specimen under the fatigue state. The research results provide experimental and calculation basis for the use of bridge steel. In this paper, a CTOD fatigue pre-crack test study was carried out on the welded joint of E43 steel.

A cationic squaraine-based chemosensor SQM was synthesized and its sensing behaviors towards nucleophiles followed by CO2 gas were described in detail by interpreting the results from UV-Vis, ESI-MS, and 1H NMR spectral analysis. The results indicated that there were two different paths for the bleaching of SQM, depending on whether water existed or not when the nucleophilic addition reaction between SQM and a superbase, such as TBD or DBU, occurred. More interestingly, the bleached SQM in MeCN–H2O (v/v = 90 : 10) could be colorimetrically restored with bubbling CO2 gas, which enabled it to act as a highly sensitive “naked-eye” CO2 gas detector in an aqueous medium. However, when treated in the same way, the SQM bleached in MeCN remained unchanged, unexpectedly. Combining theoretical analysis and experimental tests, a plausible sensing mechanism was proposed to illustrate the bleaching of SQM and the response of the bleached SQM to CO2 gas in an aqueous medium.

The evaluation of bioconcentration, toxicity, and hazard (BTH) of persistent lipophilic organic compounds (LOCs) are generally performed as separate rather than integrated assessments. There are adequate data sets in the literature for chlorobenzenes (CBs) consisting of (a) concentrations in aquatic biota (CB) and water (Cw) in the natural environment, (b) laboratory-derived bioconcentration factors (KB) and field concentration ratios (CR), the field equivalent factor of KB, (c) measured internal lethal concentrations (ILC50) and model estimated ILC50 calculated from KB and lethal concentrations (LC50), and (d) calculated hazard quotients in aquatic biota (HQB) and in water (HQW). However, there have been no integrated studies of those parameter values based on the respective lipid-based parameters (CBL, KBL, CRL, ILC50L, HQBL) performed. This study utilized the lipid-based parameters for CBs; a group of widely occuring, bioaccumulative, and toxic LOCs, and integrated those parameters into a bioconcentration–toxicity–hazard (BTHL) index. The values of the parameters were obtained from selected literature with known lipid contents of the aquatic biota. The results showed that the laboratory derived bioconcentration factors, KBLs, were comparable to the corresponding field based factors, CRLs, and the measured internal lethal concentrations, ILC50L, showed comparable values with the estimated ones. The integrated BTHL index was less than an order of magnitude or moderately acceptable for the assessment of variability, uncertainty, and predictive power of the index. This integrated assessment can be used to support decision making dealing with CBs in specific and LOCs in general, both in regional and global aquatic environments.

In this work, an all-dielectric three-dimensional (3D) dual-band polarization conversion device was proposed, the proposed device was designed by multi-folds arrow structure under the copper background. The proposed device can offer two line-line polarization conversion bands via a single simple structure, the dual-band including a wideband (FBW = 24.58%) and a narrow band (FBW = 4.77%), the polarization conversion rate (PCR) of two bands can reach to over than 95% by adjusting the parameters of the structure.

In this work, a frequency selective rasorber with a wideband transmission and two-sided absorption bands was proposed. The rasorber is consisted of lossy and lossless frequency selective surfaces (FSS). The two cascaded interdigital capacitors and intuctances are served as the lossy FSS. The rasorber can achieve the 90% absorption between 4-7 GHz and 12.8-17 GHz as well as a transmission window between 8.6-10.8 GHz with the insertion loss less than -1 dB.

The miniaturized dual-polarization low-profile frequency selective rasorber (FSR) with interdigital resonator is proposed, which exhibits two absorption bands on either side of the pass band. The lossy layer is a cross-shaped structure that two resistive sheets are loaded on both sides of the interdigital resonator. The lossless layer is a square ring gap structure. The design guideline is proposed to analyze its operating principle with the aid of an equivalent circuit model. The methods of meandering and interdigital resonator are used to achieve miniaturization. The dimension of element is $0.087\lambda_{L}$ and the thickness is $0.084\lambda_{L}$ where $\lambda_{L}$ is the wavelength corresponding to the lowest working frequency. It is shown that an insertion loss of about −0.38dB is obtained at 10.6 GHz under normal incidence. The −3 dB transmission bandwidth is about 17% and the fractional bandwidth for reflection less than −10 dB is about 103%. The FSR show stable incident angles response from 0 to 30 degrees for both TE and TM polarizations.

A broadband transmitting focusing gradient meta-surface (FGMS) has been designed, which is used in application of lens antenna. The element of FGMS is composed of four metallic layers separated by three layers of dielectric, which can achieve high transmitting efficiencies and sufficient phase compensation in the wide operating band. The antennas are placed the focus of FGMS to build a broadband planar lens antenna system. The simulation results show that the lens achieves a gain of 15.6 dBi and achieves 8.44 dB higher than the bare patch antenna at 9.1 GHz. Furthermore, it enhanced the gain of the bare patch antenna from 8.2 GHz to 10 GHz.

The fatigue test of wind turbine blade is an important means to verify the fatigue life of wind turbine blade. This paper analyses the problems existing in the fatigue test of wind turbine blade, focuses on the excitation mode, the relationship between excitation amplitude and vibration frequency and the vibration principle, and puts forward feasible solutions in practical operation.

Iodide and bromide ions in surface and ground waters (typically less than 0.05 mg/L for iodide and 0.5 mg/L for bromide) could react with natural organic matters under oxidative disinfection process and produce toxic disinfectant by-products. Therefore, removal of iodides and bromides in water treatment is desirable for improving drinking water quality. We have synthesized a micro-nano Bi2O3-Bi2S3 composite via a carbogenic sphere-supported synthesis strategy. A hydrothermal processing of sucrose resulted in uniform spherical carbogenic microspheres, which served as an excellent substrate for reaction between Bi(NO3)3 and Na2SO4 in emulsion, forming Bi2O3-Bi2(SO4)3 composites, which was then converted into Bi2O3-Bi2S3 after calcination. Using 8 g/L of this material Bi2O3-Bi2S3, 87.69% of iodide at an initial concentration of 0.05 mg/L was removed after 3 h of contact, and 86.38% of bromide at an initial concentration of 0.5 mg/L was removed after 14 h. Such effective removal efficiency was retained when used in artificial groundwater treatment. Overall, this study developed a new method to produce the Bi2O3-Bi2S3 composite in high yield, and the as-synthesized Bi2O3-Bi2S3 composites exhibited high removal efficiencies toward I− and Br− through adsorption mechanism.

Biochar samples were prepared from date seed biomass using slow pyrolysis at different temperatures (350–550 °C) and heating time (1–3 h). The influence of pyrolysis temperature and heating time on the physiochemical properties of the biochar were studied. Methylene blue (MB) adsorption by the biochar was also studied. Biochar yield decreased with increasing pyrolysis temperature and heating time. Carbon content, ash content and pH of the biochar increased with increasing pyrolysis temperature as well as heating time. FTIR analysis and scanning electron microscopy indicated that the biochars possess various surface functional groups such as carboxylic and phenolic groups. Batch adsorption results showed that the capacity of biochar to remove MB from aqueous solutions correlated positively with pyrolysis temperature and heating time. The highest MB removal capacity was achieved by the biochar prepared at 550 °C and 3 h heating time. The equilibrium results for MB adsorption on the biochar prepared at 550 °C and 3 h was well fitted to Langmuir with maximum adsorption (qmax) of 0.133 mM g−1 (42.57 mg g−1). The results suggest that date seed derived biochar can be a viable option for wastewater treatment.