Free-standing structures that do not require any holder or substrate show high levels of flexibility and stretchability and hence are well-suited for THz applications. In this work, a free-standing ...three-dimensional metallic woven mesh is experimentally and numerically investigated at terahertz frequencies. Such mesh fabricated by weaving techniques exhibits sharp Fano-like resonances, which has not been found in previous studies. Investigation results indicate that the high Q resonances originate from the bending effect in bent wires, which can be termed as Wood’s anomalies. The resonance field longitudinally covers the input and output end faces of the woven mesh, thereby obtaining a large field volume. These properties in this kind of meshes are well suited for wave manipulation and biomolecular sensing in the terahertz regime.
•We examined the land use/land cover changes（LUCC) during 2000–2020.•The multi-scenario land-use spatial patterns were optimized and simulated with Markov-PLUS and MOP-PLUS.•We assessed the ecosystem ...service value (ESV) with a spatially modified ESV assessment model.•Identify drivers that determine ESV spatial stratified heterogeneity with geographic detectors.•LULC conversion of 1% would result in average changes of 0.43% in ESV, and the responses of ecosystem services to LUCC were not very marked.
High-intensity human activities have changed land use/land cover (LULC) patterns in the Huangshui River Basin (HRB), which has brought significant challenges to ecosystems sustainable development. Discerning ecosystem service dynamic characteristics and responses under different land use/cover change (LUCC) scenarios are necessary to increase the public willingness to pay for the ecosystem and guide the decision-making process. We examined LULC spatiotemporal dynamics in the HRB from 2000 to 2020 and coupled Markov-chain, multi-objective programming (MOP), and patch-generating land use simulation (PLUS) models to optimize and simulate LULC spatial pattern for five scenarios: natural development scenario (NDs), city expansion scenario (CEs), ecological protection scenario (EPs), economic development scenario (EDs), ecological and economic balance scenario (EEBs). Given regional differences, a spatially modified ecosystem service value (ESV) assessment model was proposed to evaluate ESV. Factors driving ESV spatial stratified heterogeneity were identified using geographic detectors. Ecosystem service value sensitivity in response to LUCC was discriminated against using the elasticity model. The study area was dominated by 56.86–60.40 % grassland and 33.11–36.27 % cropland. Grassland and cropland area decreased by 579.75 km2 and 423.87 km2 over the period 2000–2020, while the other areas such as forestland, water area, construction land, and barren land increased by 289.81 km2, 140.77 km2, 489.10 km2, and 83.96 km2, respectively. Land conversion mainly occurred among grassland, cropland, and construction land. Total ESV was 39,665 million yuan in 2020, an increase of 2.25 % compared to 2000. Total ESV of NDs, EPs, EDs, and EEBs increased by 0.34 %, 1.04 %, 2.01 %, and 7.78 %, respectively compared to 2020, while that of CEs decreased by 0.17 %. ESV sensitivity coefficient response to LUCC was 0.43 during 2010–2020, indicating that LULC conversion of 1 % would result in average changes of 0.43 % in ESV. Ecosystem services response to LUCC was not very marked in the HRB. Elevation was the dominant driver of LULC and ESV stratified spatial heterogeneity in the HRB. The effects of elevation on LUCC and ESV should receive more attention in management. Multi-objective optimization and multi-scenario analysis effectively guided land-use planning and decision-making involved in ecosystem uncertainty, complexity, and interaction. The EPs and EEBs may be more suitable for future HRB development.
The accident of nuclear power plant might release the uranium fission product Cs-137, which is harmful to the human environment. The isotope of Cs-137 may enter the water and the radioactive waste ...water will pollute the environment. In order to reduce the radioactive wastewater with Cs-137 released from nuclear power plant and store the radioactive waste more efficiently, novel titanate nanotubes (TNTs) were prepared by hydrothermal method to adsorb the isotope of Cs-137 from radioactive liquid. The flow column cold test and hot test are used to verify the adsorption capacity in this study. It was proven in the tests that TNTs feature good adsorption performance for Cs, that was, 1 gram of TNTs could adsorb 99% of Cs-137 or more from 10 L radioactive wastewater whose initial concentration of Cs-137 is 135 Bq/mL.
To accurately predict coal burst hazards and estimate the failure of coal pillars in underground coal mining systems, it is of great significance to understand the mechanical behavior of coal-rock ...bimaterial composite structures. This paper presents experimental and numerical investigations on the response of rock-coal, coal-rock, and rock-coal-rock bimaterial composite structures under triaxial compression. The triaxial compression experiments are conducted under confining pressures in the range of 0–20 MPa. The resulting inside fracture networks are detected using X-ray-based computed tomography (CT). The experimentally observed data indicate that the mechanical parameters of the rock-coal-rock composites are superior to those of the rock-coal and coal-rock combinations. After compression failure, the coal-rock combination specimens are analyzed via X-ray CT. The results display that the failure of the coal-rock composite bodies primarily takes place within the coal. Further, the bursting proneness is reduced by increasing confining pressure. Subsequently, the corresponding numerical simulations of the experiments are carried out by using the particle flow code. The numerical results reveal that coal is vulnerable with regard to energy storage and accumulation.
One composite plasmonic slab with a broad bandgap (40%) is experimentally and numerically demonstrated in the terahertz (THz) region. The composite slab consists of double-layer metallic gratings and ...a dielectric film, which supports two resonant modes. Electric field vectors and charge distributions proved that the low-frequency resonant mode originates from the symmetric plasmonic mode, while the high-frequency resonant mode is induced by the hybrid mode of plasmonic and dielectric modes. Compared with the double-layer metallic grating, the inserted dielectric film significantly enhances the transmission of the transverse magnetic (TM) waves and induces Fano resonances. The near-field coupling between metal gratings and dielectric film can be manipulated by changing the thickness and the refractive index of dielectric films. We further demonstrated that the plasmonic bandgap can be manipulated by tuning the grating width. These results suggest that this composite plasmonic slab is promising in terahertz integrated components development such as a filter, polarizer, or sensor.
Studying the influence of microstructure on the damage and cracking process of rocks is of great practical engineering importance for evaluating the mechanical properties of surrounding rocks in ...complex geological engineering environments. To incorporate rock microstructures into numerical models, two main methods, i.e. computer generation methods (e.g. molecular dynamics, MD) and image reconstruction methods (e.g. digital image processing, DIP), are frequently adopted. However, the strengths and weaknesses, the differences and applicability regarding the two major methods have not been systematically discussed and analyzed in simulating the damage and cracking in heterogeneous rocks. In this study, the MD model was firstly optimized based on the previous work, and the “Realistic grain size based microstructure model generation program” was developed by the observed mineral grain sizes from microscopic images. The DIP model was developed by directly using digital images of rock materials via the image reconstruction methods. On this basis, the damage and cracking process of rocks was investigated and compared with the above two models using a technique based on the Fast Fourier transforms (FFT). To this end, a series of macro and micro experiments were conducted to obtain the basic mechanical properties of the Dingziwan Granite (DG) and several examples are generated by the MD and DIP model with calibrated macro and micro parameters by the laboratory data. The two models combined with the FFT method are applied to predict the macro and micro mechanical behavior of the DG under different confining pressures and their differences and applicability are quantitatively analyzed and compared. The results indicate that, in general, the two models are both capable of predicting the macro and micro mechanical behaviors of the heterogeneous rocks, but each has its own strength. The improved MD model can efficiently study the influence of the rock heterogeneity on its macroscopic behavior, while the DIP model can highly reproduce the microcracking process such as intragranular, transgranular and grain boundary cracking.
•Developed the “Realistic grain size based microstructure model generation program”.•Quantitative comparison of improved MD and DIP models.•The improved MD model is suitable for studying the overall mechanical behavior of rocks.•The DIP model can highly reproduce the brittle-ductile failure pattern transition of rocks.
A laser-fabricated metallic resonator based on a double-slit array (DSA) is numerically and experimentally demonstrated at terahertz frequencies. Such free-standing resonators achieve a sharp ...resonance with high quality (
Q
) factor, arising from a distortion of symmetry-protected bound states in the continuum (BIC). By breaking the structural symmetry of DSAs, the BIC with infinite
Q
-factor can be transformed into quasi-BICs, and the
Q
-factors decrease gradually as the asymmetry parameter increases. We analyzed the influence of the imperfection in experimental samples such as the round edge and the trapezoid shape on the transmission properties of DSAs. Different from the DSAs composed of ideal perfect electrical conductors, copper DSAs show lower
Q
-factor because of the Ohmic loss. The effect of metal thickness on the quasi-BICs for DSAs is also investigated. Results exhibit that thinner resonators can achieve sharper quasi-BICs. These findings suggest that such metallic resonators with high
Q
-factors have great potential for practical applications in electromagnetic wave filtering and biomolecular sensing.
•The AR characteristic of 1-D moth-eye structures has been successfully controlled by adjusting the effective refractive index distribution of micro tapers for THz waves, which is achieved by ...employing femtosecond laser processing.•The THz-TDS measured and FDTD simulated results showed good agreement for all the samples, which can induce the power reflectance nearly to 0.•The stair profile displayed the most stable reflectance distribution of nearly 0 maintained in the 0.5–1.0-THz range, as well as lower total power reflectance for a broadband THz region from 0.1–1.0 THz.
The present study focuses on controlling the antireflective (AR) characteristics of one-dimensional moth eye structures on a high-resistivity silicon substrate by adjusting the profile (i.e., refractive index distribution) of its micro-tapers using femtosecond laser processing. Moth eye structures that comprise periodically arranged tapers with varying sizes and profiles (triangle, parabola, stair, and triangle–stair) were fabricated using femtosecond laser ablation via a fine adjustment of the processing pattern. The AR characteristics of these samples were experimentally evaluated by a standard terahertz (THz) time-domain spectroscopy and modeled by employing the method of Finite-difference time-domain (FDTD). The measurement data agreed well with the simulation results, and the power reflectance of these structures was induced from approximately 30% (bare silicon substrate) to a very low value (less than 5%) for a broad THz band. Furthermore, the profiled structures showed a varying power reflectance distribution with respect to the frequency in the THz region, especially for the low reflection one (<5%) approximately from 0.5 to 1.0 THz. Three samples with different aspect ratios (approximately 1–3) but having the similar refractive index distribution were also fabricated by using an industrial high-power femtosecond laser (40 W) to demonstrate the relationship between the AR characteristics and the aspect ratio of the moth-eye structures, as well as the processing efficiency. The structures displayed a very good AR performance for a broadband THz region. Besides the broad AR band and low reflectance, this adjustability for the profile of laser-fabricated tapers could improve the flexibility of anti-reflection for THz devices, such as THz wave emitters, receivers, and filters, and the antireflective frequencies less than 1 THz suggest that this technology can be used in the next generation of mobile communication.
To report a novel tigecycline resistance gene, tet(X6), and its variants in four bacterial species isolated from chickens and pigs in China.
WGS was conducted to identify the suspected resistance ...genes in the tigecycline-resistant Myroides phaeus 18QD1AZ29W. Functional cloning, homology modelling and molecular docking were performed to compare the function with other Tet(X) variants. Retrospective screening for tet(X6) was conducted for 80 isolates in our WGS data collection, and all genomic environments of tet(X6)-positive isolates were analysed.
The tigecycline-resistant M. phaeus 18QD1AZ29W isolated from a pig farm in Shandong in 2018 was positive for tet(X2) and a novel tet(X) gene, designated tet(X6). Tet(X6) could increase the MICs of all tested tetracyclines/glycylcyclines for Escherichia coli only 2- to 4-fold, which was possibly due to a lower tetracycline binding capacity of Tet(X6) compared with that of other Tet(X) variants. Retrospective screening showed that seven other isolates (7/80, 8.8%), comprising four Proteus spp. and three Acinetobacter spp. from chickens and pigs in Shandong and Guangdong, were positive for three different variants of tet(X6). The analysis of the genomic environment revealed that two tet(X6)-positive isolates from M. phaeus and Proteus cibarius, respectively, contained ISCR2, which may play a role in tet(X6) transmission.
This study identified a novel type of tigecycline resistance gene, tet(X6), in Myroides, Acinetobacter and Proteus from chickens and swine. Tet(X6) conferred lower tetracycline/glycylcycline MICs than other Tet(X) variants, and ISCR2 may play a role in the transmission of tet(X6).
This paper proposes a novel magnetic field sensor based on a microfiber coupler (MFC) combined with a magnetic fluid (MF) in a Sagnac loop formed from a polarization maintaining fiber (PMF). Thanks ...to the small (~2.6 μm) waist diameter of the MFC, the resulting interference is strongly influenced by the presence of the MF and this leads to the desirable high sensitivity of the structure to the applied magnetic field. The maximum magnetic field sensitivities of -100 pm/mT and -488 pm/mT have been experimentally demonstrated with the PMF lengths of 75 cm and 20 cm respectively in the range of magnetic field strengths from 0 to 200 mT. The dependence of the magnetic field orientation on the performance of the proposed sensor was also examined. The proposed magnetic field sensor is advantageous for applications requiring higher sensitivity over a wide magnetic field range.
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