Absorptive Function Research Articles

Exploring the physical characteristics of chalcogenide SrZrS3 perovskite: Insights for photovoltaic use

AbstractIn this study, first-principle-based Density functional Theory (DFT) have been utilized to investigate the electronic, optical, mechanical and thermal properties of SrZrS3 for the solar cell application. Semiconducting nature of SrZrS3 was found via the investigation of electronic band structure and density of state (DOS). Electronic band structures reveal direct bandgap semiconductor properties with values 0.57 eV in Perdew-Burke-Ernzerhof functional (PBE) method, and 1.28 eV is in hybrid Functional (HSE06) method for SrZrS3, suggesting specific applications in photovoltaic (PV) cell. Significant constant such as absorption, reflectivity, refractivity, and loss function were also calculated to evaluate the optical properties of SrZrS3. The optical properties highlight the potential of SrZrS3 material for optoelectronic and photovoltaic applications. The Born stability criteria confirmed the mechanical stability of this compound. Furthermore, its minimum thermal conductivity (Kmin = 0.66 Wm−1 K−1) is adequate for maintaining performance without excessive heat buildup, making it suitable for high-efficiency solar cells. Graphical Abstract

Water vapor and soot spatial characteristics retrieve of axisymmetric optically-thin laminar diffusion flame based on visible and near-infrared multi-spectral light field imaging

The comprehension of the distribution of gaseous species and soot particles plays a pivotal role in investigating the combustion process of a flame. A highly effective method to accomplish this is by extracting visible and near-infrared emission information from flames. In this study, we present a novel near-infrared multi-spectral light field imaging model that enables the concurrent extraction of gas and soot property distributions within a flame. A synthetic test of ethylene diffusion flame is assessed using the proposed reconstruction method. The mole fraction of gaseous water, together with the flame temperature and soot volume fraction, are decoupled spectrally using near-infrared and visible wavelengths. The results demonstrate a reliably retrieved temperature range of 1400 K to 2050 K, accurately reconstructing the actual distributions of soot volume fraction and gaseous water mole fraction. Minor influences on the imaging results and property reconstruction are observed due to uncertainties arising from the reconstruction method, absorption function, reconstruction wavelength for H2O mole fraction, and signal-to-noise ratio. This study serves as a theoretical guide for the future development of practical near-infrared multi-spectral light field imaging techniques for rapid and robust flame diagnostic purposes related to soot and gas properties.

Multi-functional flexible PANI-based material for the development of efficient heating sensing equipment: integrating intelligent heating, motion detection, moisture absorption and ultraviolet protection function

With the advancement of technology and the improvement of living standards, multifunctional composite materials are increasingly attracting attention. Conductive polymer polyaniline (PANI), a key component in the fabrication of intelligent composite materials, is widely used in various fields because of its unique properties. When FeCl3 was used as the oxidant, the PANI-based composite material demonstrated a significant increase in maximum saturation temperature from 34.10 °C to 47.43 °C, under a voltage range of 6–12 V. It also exhibited a sensitivity of 1.0960 kPa−1 (greater than 1 kPa−1) at a low pressure of 0.5 kPa, and its response/recovery time is 200 ms for both. Its maximum capillary rise height reached 7.7 cm. Additionally, the PANI-based composite material achieved a UPF value 40+, effectively blocking over 97.5 % of ultraviolet rays. It also absorbed over 90 % of electromagnetic waves within the 0–18 GHz frequency range. The wear resistance has also been significantly improved compared to pure cotton fabrics, with the friction times reaching 1370 before damage when FeCl3 is used as the oxidant for this composite material. The PANI-based composite material developed in this study functions of intelligent heating, motion detection, moisture absorption, and UV protection functions. It holds the potential to develop efficient heating and sensing devices, offering a solution for the design of the next generation of multifunctional flexible composite materials.

1α,25-hydroxyvitamin D3 alleviated rotavirus infection induced ferroptosis in IPEC-J2 cells by regulating the ATF3-SLC7A11-GPX4 axis

Rotavirus (RV) mainly infects mature intestinal epithelial cells and impairs intestinal absorption function, which leads to the death of infected cells and eventually fatal diarrhea. Ferroptosis is a novel regulatory cell death pattern, which can be caused by virus infection. 1α,25-hydroxyvitamin D3 (1,25D3) has an anti-RV infection effect and can regulate ferroptosis. However, whether RV infection can induce ferroptosis, and whether 1,25D3 can inhibit RV infection by regulating ferroptosis has not yet been studied. Present study shows that RV infection or erastin treatment induces IPEC-J2 cell death, which results in mitochondrial shrinkage, decreased mitochondrial membrane potential (MMP) and glutathione (GSH) content, increased MMP, intracellular Fe2+, reactive oxygen species (ROS), and malondialdehyde (MDA) contents. Meanwhile, ferrostatin-1 (Fer-1), liproxstatin-1 (Lip-1), and deferoxamine (DFO) treatment can effectively reverse the increase of intracellular Fe2+, ROS and MDA levels induced by RV infection. Moreover, RV infection increases activating transcription factor 3 (ATF3) mRNA and protein expressions, and inhibited SLC7A11 and glutathione peroxidase 4 (GPX4) expressions, which was partially alleviated by siATF3. 1,25D3 treatment significantly eliminates RV induced ferroptosis via ATF3-SLC7A11-GPX4 axis. Therefore, our results reveals that RV infection induces ferroptosis in IPEC-J2 cell and 1,25D3 alleviates RV induced ferroptosis by regulating the ATF3-SLC7A11-GPX4 axis.

Design Method of Gyroid Lattice Structure Based on the Load Paths Direction and Capacity

The Design of lattice structures with triply periodic minimal surface (TPMS) can improve the specific stiffness, strength, heat dissipation, and energy absorption functions of their physical structures. The load-transferred law in the structure can serve as a crucial basis for the design, including the distribution and anisotropy of the unit cells. In this paper, a design method based on load paths is proposed and a series of Gyroid lattice structures with variable density cells, variable direction cells, and combination of variable density and direction cells, are designed with better mechanical properties. The load paths within a given structure are extracted to explicitly provide the load-transferred law. The capacity of the load paths is then proposed to guide the distribution of the cells, and a mapping relationship with the parameters controlling the porosity is established. The lattice structures with variable density cells are designed. Afterwards, the pointing stress vectors of the load paths is defined as the main load-transferred direction in the local region to guide the direction of the cells. Based on the anisotropic behavior of the Gyroid cells, the direction setting principles are formulated, and the lattice structures with variable direction cells are designed. Furthermore, a model generation method is proposed, and the Gyroid lattice structures that combine variable density and direction cells are implemented. Two models are applied to validate the proposed method, including a two-dimensional three-point bending beam and a three-dimensional supporting beam. The obtained results show that for the same porosity, both the variable density and variable direction designs of Gyroid cells allow to improve the mechanical properties. The variable density design outperforms the variable direction design. In addition, the Gyroid lattice structures combining variable density and direction cells have significantly higher performance, which indicates that the proposed design method can more effectively increase the load-bearing performance.

Integrating morphology, physiology, and computer simulation to reveal the toxicity mechanism of eco-friendly rosin-based pesticides

To mitigate the impact of traditional chemical pesticides on environment, and achieve sustainable crop protection, 24 eco-friendly rosin-based sulfonamide derivatives were synthesized and developed. The in vitro activity assessment showed that compound 4X (Co. 4X) exhibited excellent fungicidal activity against V. mali (EC50 = 1.106 μg/mL), marginally surpassing the positive control carbendazim (EC50 = 1.353 μg/mL). In vivo investigations suggested that Co. 4X exhibited moderate efficacy in mitigating V. mali infection in both apple trees and apples. Physiological assessments revealed that Co. 4X induced severe ultrastructural damage to the mycelium, heightened cell membrane permeability, and inhibited SDH protein activity. Subsequent biosafety evaluations affirmed the environment-friendly of Co. 4X on Zebrafish (LC50(96h) = 25.176 μg/mL). Toxicological research revealed that Co. 4X caused damage to the cells of Zebrafish gills, liver, and intestines, resulting in impaired respiratory, detoxification, digestion, and absorption functions of Zebrafish. In summary, the findings of this study contribute to a deeper understanding of the toxicity mechanisms of novel pesticides, decreasing environmental risks caused by traditional chemical pesticides, and improving the effective management of novel pesticide applications.

Designing micro-3D hierarchical HZCNF@ZS-LDH@MX as advanced electrodes for flexible supercapacitors

The design of electrode materials is the core for enhancing the practicality of supercapacitors. Herein, we report an electrode material with a micro-3D structure, in which the template-shaped ZnS nanorods are fixed on the hollow carbon nanofibers. Subsequently, ZnCo-LDH nanosheets grow on the surface of ZnS nanorods directionally and form a 3D structure. Finally, an MXene layer is coated on the material surface by electrostatic spraying. Experimental analysis shows that due to the construction of a stable polymetallic compound array and a conductive network, the HZCNF@ZS-LDH@MX electrode can maintain rapid charge transfer, thereby significantly improving the kinetics of ion/electron reactions. Taking these advantage, HZCNF@ZS-LDH@MX has a high specific capacitance of 830 F g−1, a specific surface area of 740 m2 g−1, and good cycling stability over 20,000 cycles. In addition, the assembled flexible device reaches an energy density of 65.1 Wh kg−1, which is sufficient to power an LED board. This study proposes an effective strategy for enhancing the ion and charge transport within the hierarchical structure. By making full use of the advantages of two-dimensional materials and designing micro-3D structures, it has opened up new approaches for the development and utilization of supercapacitor electrodes. In addition, according to the special nature of the material, the ability of electromagnetic wave absorbing is further tested. The results showed that the maximum reflection loss is −60 dB, and there is a potential application possibility of dual functions of energy storage and wave absorption.

Ag:MoO3:Yb semi-transparent electrode for top emission organic light-emitting didoes

Silver (Ag) is widely used as a cathode in top-emission organic light-emitting diodes (TEOLEDs) for its high reflectivity and conductivity. However, its high absorption, thickness-dependent transmittance, and high work function require further improvement. While Ag:MoO3 alloy has emerged as an alternative, it still needs further enhancement. In this study, we developed a ternary Ag:MoO3:Yb semi-transparent electrode, improving both the optical and electrical properties of the existing binary system. For example, The 30 nm-thick Ag:MoO3:Yb 4:3:3 film exhibited average transmittance, reflectance, and absorption of 64%, 12%, and 24%, respectively. Additionally, the Ag:MoO3:Yb showed a uniform transmittance spectrum in the visible wavelength range. The photoelectron spectroscopy results showed Ag:MoO3:Yb 4:3:3 film has a low work function of 3.69eV. Despite relatively high sheet resistance around 82~130 Ω/sq, the red phosphorescence TEOLEDs incorporating Ag:MoO3:Yb as cathode showed improved device performances compared to the control device with Ag:MoO3 30% where the current efficiency increased by up to 1.7 times and the power efficiency by up to 2.6 times. Furthermore, the optimized Ag:MoO3:Yb devices with good charge balance resulted in a relatively longer lifetime up to 80% of initial luminance (LT80) of 166hr, which are higher performance than those of the device with Ag:MoO3 30%.

Small intestine structural and functional responses to environmental heavy metal stress in tree sparrow Passer montanus nestlings.

Tree sparrow nestlings predominantly consume protein-rich insect larvae, making them vulnerable to environmental heavy metal contamination through the food web, potentially affecting their growth. Understanding the effects of heavy metals on the structure and function of the small intestine, the principal organ responsible for protein digestion and absorption, is therefore crucial. This study investigated tree sparrow nestlings at three developmental stages (3, 6, and 12days old) in Liujiaxia (LJX), a comparatively unpolluted area, and Baiyin (BY), a heavy metal polluted area, to elucidate the factors and mechanisms by which heavy metals affect nutrient absorption. We compared heavy metal accumulation levels, structural integrity, and protein digestion and absorption functions of the duodenum, jejunum, and ileum. The increase of fluctuating asymmetry and decrease in body condition in tree sparrow nestlings were found to be associated with environmental heavy metal accumulation in the small intestine. Structural impairments of villi and crypts were observed in the duodenum and jejunum of tree sparrow nestlings at 3-, 6-, and 12-day-old in the polluted site BY. Conversely, structures related to the ileum were elevated, and the small intestine of nestlings at all stages exhibited abnormally elevated protein digestibility but diminished absorption of amino acids. However, there was no significant difference in small peptide absorption. These findings indicate that environmental heavy metal pollution impacts the structure of the small intestine in tree sparrow nestlings through the food chain and further affects their digestion and absorption function of proteins.

NIR-driven self-healing PANI/Ag/ basalt scales coatings with robust anticorrosion and microwave absorption properties

Addressing electromagnetic interference and corrosion of electronic devices and communications facilities in the marine environments with high humidity and high salt spray remains a challenge. In this study, polyaniline/silver/basalt scales (PANI/Ag/BS) fillers were prepared to obtain dual functions of microwave absorption (MA) and corrosion resistance, whereas the introduce of PANI not only enabled the fillers to possess the photo-thermal effect, but also improved their compatibility with epoxy resin. The MA performance test proves that the PANI/Ag/BS has a minimum reflection loss (RL) of -30.55 dB at a thickness of 2.08 mm and achieves an effective absorption bandwidth (EAB) value of 5.28 GHz at a thickness of 2.40 mm. Meanwhile, the EIS measurement demonstrates that the coating has exceptional performance during the 240 h immersion, and the low-frequency impedance value (|Z|0.01Hz) is about 2.5 × 108 Ω·cm2. In addition, the photothermal effect of PANI/Ag/BS endows the coating with remarkable photothermal repair capability, which enabled self-healing within 30 s. This work opens another avenue for the development of bifunctional coating with enhanced anti-corrosion and microwave absorption.

Vanadium dioxide and a graphene-based ultra-wideband absorption and polarization conversion switchable terahertz device

A multifunctional terahertz functional device based on vanadium dioxide (VO2) and graphene is proposed, which can realize ultra-wideband absorption and polarization conversion. When the VO2 is in the insulating state, the device can achieve the polarization conversion function to convert the incident wave into the corresponding cross-polarized wave. Polarization conversion ratios (PCRs) can exceed 90% in the 2.1–8 THz frequency range; in the 3–7.5 THz range, the PCR can be more than 95%. When VO2 is in the metallic state and the graphene Fermi energy is 0.9 eV, the device can realize a broadband absorption function. An absorption rate of more than 90% can be achieved over a wide frequency range of 3.3–7.7 THz. In addition, the polarization conversion device can maintain high performance in broadband polarization conversion at incident angles no greater than 40°. The absorber device also exhibits insensitivity to both incident and polarization angles. These advantages which make the proposed multifunctional terahertz functional device have a wide range of applications in the fields of terahertz imaging, sensing, communication, and so on.

Multi-Omics Reveal the Improvements of Nutrient Digestion, Absorption, and Metabolism and Intestinal Function via GABA Supplementation in Weanling Piglets.

The nonprotein amino acid γ-aminobutyric acid (GABA) can enhance intestinal function in piglets; however, the mechanisms involved are not yet fully understood. To explore the effects of GABA and its underlying mechanisms, weanling piglets were randomly assigned to three groups, receiving either a basal diet or a basal diet supplemented with GABA (80 mg/kg or 120 mg/kg). The results demonstrated that dietary GABA improved growth performance and reduced diarrhea incidence (p < 0.05). Additionally, GABA supplementation decreased the serum and intestinal levels of pro-inflammatory cytokines (p < 0.05), and improved intestinal morphology. Multi-omics analyses were employed to explore the alterations caused by GABA supplementation and elucidate the related mechanisms. Microbiota profiling revealed improved beta-diversity and changes in the composition of ileal bacteria and fungi. Amino acid metabolism, lipid metabolism, and digestive processes were primarily enriched in the GABA group according to metabolomics analysis. A transcriptome analysis showed significant enrichment in ion transmembrane transport and nutrition absorption and digestion pathways in the ileum. Furthermore, increased lipase and trypsin activity, along with the elevated expression of tight junction proteins confirmed the beneficial effects of GABA on intestinal nutrient metabolism and barrier function. In conclusion, dietary 80 mg/kg GABA supplementation improved nutrient digestion and absorption and intestinal function in weanling piglets.

Saga of Soggy Sauerkraut

The creation of undesirable (soggy) sauerkraut resulted in the loss of $1,000,000 worth of organic sauerkraut in 2022, which prompted a multistep investigation of the cause and potential solution. The cause of this condition has been previously reported as unique fermentation conditions and the lack of key trace nutrients essential for cabbage (Brassica oleracea var. capitata) cell wall integrity. Because the condition was limited to organic sauerkraut in 2022, this investigation initially focused on differences in fermentation conditions between organic and conventional sauerkraut. No differences in fermentation conditions accounted for the condition; therefore, attention was focused on analyzing the mineral content of cabbage grown for sauerkraut production that pinpointed a deficiency in critical micronutrients such as iron, copper, manganese, boron, and zinc. This deficiency was traced to the use of poultry manure that was contaminated with glyphosate residue from conventionally fed turkeys and chickens that consumed genetically engineered (GE) feed and used as the fertilizer for organic cabbage production. The presence of glyphosate, a potent mineral chelator and antibiotic, was identified as a significant factor that impairs the absorption and physiological function of essential minerals in the shikimate metabolic pathway whereby cell walls and lignin are produced, thus compromising the structural quality of the sauerkraut. After this discovery, the study progressed to evaluate various remediation strategies aimed at eliminating glyphosate from the soil and restoring nutrient uptake. Corn grain and silage were selected as the test crops for this phase. Among the tested remediation solutions were raw sauerkraut juice containing Lactobacillus plantarum, which is reported to degrade glyphosate in the rumen of dairy cows and two patented proprietary microbial mixtures, PB027 and PB027SK, that degrade glyphosate by all three of the known metabolic pathways. These treatments were specifically formulated to degrade residual glyphosate in the soil. The results showed that these interventions could reduce soil glyphosate levels by 80% to 90% within 6 to 7 months to significantly enhance both the yield and quality of corn grain and silage. The increase in corn grain yield from glyphosate degradation on the Shiocton silt loam soil was 907.89 kg·ha−1 (13.5 bushels/acre). The increase in yield on the irrigated Kidder sandy loam soil was quantified at 726.31 kg·ha−1 (10.8 bushels/acre) for corn grain and 6.62 t·ha−1 (2.68 t/acre) for silage, with an additional improvement in silage feed quality beneficial for milk production. The findings underscore the importance of addressing both micronutrient sufficiency and glyphosate residue in soil to ensure the optimal growth of cabbage and the quality of sauerkraut produced. By successfully identifying manure as a subtle source of nutrient immobilization and implementing effective soil remediation techniques, this research highlights a clear path forward for improving crop yield and quality to ultimately enhance the structural integrity and consumer acceptance of sauerkraut. This study has broader applications for the nutritional content and crop yields of many organic crops that use conventional poultry and animal manures that may contain glyphosate in desiccated plant tissues or GE feeding operations.

A comparative study on the physical properties of Ba2XIO6 (X = Li, K) double perovskites alloys

This work concerns the study of the physical properties of Ba2XIO6 (X = Li, K) double perovskites alloys using first principles approach since the density functional theory implemented in Wien2k code. The exchange–correlation potential is treated by WC-GGA and mbJ-GGA. The negative formation enthalpy of both alloys confirms the dynamic stability. Further, the elastic constants reveal that these compounds are mechanically stable and can be synthesized experimentally. The bulk, shear moduli, Young, Poisson’s ratio, anisotropic factor, and Vickers hardness values for these materials are determined using the results of the elastic constants. The Young’s modulus 3D representation showed that the Ba2KIO6 material displays a strong anisotropy compared to Ba2LiIO6. Furthermore, the analysis of electronic band structures and the density of states reveal a semiconducting nature with direct band gaps of 2.340 eV, 4.213 eV 2.350 eV and 4.027 eV for Ba2LiIO6 and Ba2KIO6, respectively, using WC-GGA and TB-mBj-GGA. Moreover, optical functions: absorption, refractive index, reflectivity and loss function are obtained.

Guideline for medical nutritional treatment of adult patients with gastrointestinal dysfunction (2025 edition)

Gastrointestinal dysfunction is a common clinical disease. Due to abnormal gastrointestinal digestive and absorption functions, nutrients, water, and electrolytes cannot be absorbed properly, and therefore, scientific and reasonable nutritional intervention is needed. In order to further standardize medical nutrition treatment of patients with gastrointestinal dysfunction, the Chinese Society of Parenteral and Enteral Nutrition (CSPEN) organized experts and scholars in related fields in China to elaborate on the following topics based on current evidence-based medical evidence: the standard process of medical nutrition treatment for patients with gastrointestinal dysfunction, the time and mode of enteral and parenteral nutrition application, and the nutritional intervention mode for patients with gastrointestinal dysfunction in special disease state. Finally, 29 questions and 58 recommendations were formed to provide reference for the standardized application of medical nutrition therapy for patients with gastrointestinal dysfunction.

Multifunctional Metasurface with PIN Diode Application Featuring Absorption, Polarization Conversion, and Transmission Functions.

The objective of this paper is to explore the potential of integrating three distinct functionalities into a thin, single-layer metasurface. Specifically, the study introduces a metasurface design that combines absorption, polarization conversion, and transmission capabilities. The proposed structure consists of a double square loop disposed on a dielectric substrate, which is covered by a superstrate. In this study, the traditional ground plane was replaced with a periodic array, selectively reflecting frequencies of interest. Then, the absorption and polarization conversion characteristics were achieved by introducing the resonators in the front layer. By introducing asymmetry to the resonators and integrating PIN diodes for control, we demonstrated that the metasurface could efficiently absorb electromagnetic waves (with PIN diodes in the ON state), convert polarization (with PIN diodes in the OFF state), and enable signal transmission in a different frequency range. The numerical results indicated excellent performance in both absorption and polarization conversion. At a frequency of 3.05 GHz, the absorption rate reached 97%, while a polarization conversion rate of 98% was achieved at the resonance frequency of 4.37 GHz. Moreover, the proposed structure exhibited a thickness of λ/30.7 at the absorption peak.

Dietary Prunus armeniaca augments antioxidant-immune-capacity, absorptive function, and growth and upregulates nutrient transporters and immune-regulatory genes of Oreochromis niloticus

Prunus armeniaca (apricot) kernel as a plant by-product, has garnered a lot of attention lately due to its biological and medicinal properties. This study represents a novel attempt to supplement Nile tilapia (Oreochromis niloticus) diets with the P. armeniaca kernels (PK) powder. This approach evaluated its effectiveness on growth, digestive/absorptive capabilities, economic efficiency, physiological/antioxidant status, and immune capacity. Additionally, the expression of nutrient transporters, lipid metabolism, and immune-relevant genes as well as the fish resistance to the Pseudomonas putida challenge were investigated. Fish (n = 160; 21.70 ± 0.22 g body weight) were allotted for a 3-month feeding trial into four treatments (n = 40 fish/treatment) in quadri-replicates (10 fish/replicate). The fish in each treatment were fed on a basal diet fortified with 0, 2, 4, and 8 g of PK/kg diet (PK0, PK2, PK4, and PK8), respectively. The outcomes revealed that all PK-enriched diets boosted growth indices (weight gain, specific growth rate, and protein efficiency ratio), growth hormone level, and intestinal enzyme activity (lipase and amylase). The PK-fortified diets improved intestinal morphometric indices (muscular coat thickness and villus width and length) and declined feed cost/kg gain. This enhancement was in a level-dependent manner with the PK8 treatment presenting the best results (P < 0.05). Up-regulation of the intestinal nutrient transporters-associated genes (solute carrier family 15 member 2, solute carrier family 9 member 3, and sodium-glucose cotransporter 1) was observed in PK-fed treatments. The expression of muscular lipid metabolism-relevant genes was modulated by the dietary PK, where lipid deposition-relevant genes (acetyl-coenzyme A carboxylase beta and sterol regulatory element-binding protein 1) down-regulated, while the lipolysis-relevant gene (carnitine palmitoyltransferase 1) up-regulated. The antioxidant-immune responses (glutathione peroxidase, catalase, total antioxidant capacity, total protein, globulin, serum bactericidal activity, nitric oxide, and complement3) were augmented by dietary PK inclusion with increasing PK dietary levels. Moreover, the expression of splenic immune-related genes (nuclear factor kappa beta, interferon-gamma, and Kelch-like ECH-associated protein1) was up-regulated by PK diets. Post-challenge with P. putida, the fish survival rate in PK8 treatment (87.50 %) was the highest followed by PK4 (81.25 %), and PK2 (75.00 %) treatments compared to PK0 treatment (56.25 %). Overall, it is advised to feed Nile tilapia with the PK-supplemented diets to enhance their growth, immune response, and resistance to P. putida. This provides an outline for the future use of these seed kernels for supporting the aquaculture sector.

A dynamically switchable and tunable metamaterial device based on vanadium dioxide and Dirac semimetal

In this paper, a dual-function metamaterial device based on vanadium dioxide (VO2) and Dirac semimetal (DS) operating in terahertz (THz) frequency range is designed. The reversible phase transition properties of VO2 are exploited to achieve the dynamic switch between the function of broadband absorption and broadband polarization conversion. It is demonstrated that when VO2 is in the metallic state and the Fermi energy level (Ef) of DS is set to 30 meV, the broadband absorption in the operating frequency range of 1.42–3.40 THz can be achieved, and its absorbance exceeds 90 % with a relative bandwidth of 82.16 %. When VO2 is in the insulating state and the Ef of DS is set at 180 meV, the high efficient broadband polarization conversion can be obtained in the operating frequency range of 2.08–4.88 THz and the polarization conversion ratio (PCR) is greater than 90 % with a relative bandwidth of up to 80.46 %. Therefore, the proposed switchable dual-functional THz device can be extensively utilized in absorption, polarization conversion and other potential fields.

Polarization-selective dual-band infrared metamaterial perfect absorber

Abstract Metamaterial absorbers have significant effects and great potential for applications in a variety of important sciences and technologies, including infrared imaging, thermal emitters, electromagnetic shielding, and photodetectors. However, conventional absorbers with a single function are difficult to meet the growing demand of devices, especially for the situations where the absorption and polarization are simultaneously required in infrared detection. If the polarization absorption function is realized by integrating absorption and polarization elements, it will lead to a large overall system size and slow response time. To solve this problem, we propose a dual-band polarization-selective metamaterial perfect absorber, whose maximum absorptions at resonant wavelengths of λ 1 = 2.824 μ m and λ 2 = 7.622 μ m are 99.99% and 99.88%, respectively. The absorber exhibits strong polarization sensitivity, absorbing TM-polarized incident light and reflecting TE-polarized incident light at the two resonant wavelengths. The extinction ratios of the absorber at the two referred resonant wavelengths are 90.9 and 142.7, respectively. The proposed absorber would be beneficial for infrared polarization detection and imaging.

A frequency-independent absorption function surrogate for perfectly matched layer in exterior acoustics

In many engineering applications, the solution of acoustic wave problems in the infinite domain is required over a broad frequency range with densely sampled increments. In order to achieve efficient numerical simulations via a spatial discretization, e.g. finite element method, additional artificial absorbing boundaries are necessary to truncate the computational domain into appropriate bounded sizes. One of the most commonly used non-reflecting techniques to attenuate propagating waves is known as the perfectly matched layer. However, the system matrices arising from the finite element treatment of the Helmholtz equation in the absorbing layers are frequency-dependent, implying that they must be formed and inverted at each frequency of interest. Such a procedure is rather troublesome for frequency sweeps. To address this, a surrogate of perfectly matched layers is proposed, which enables the corresponding system matrices to be independent of the frequency. Moreover, it avoids the use of a relatively large computational domain and relatively thick enclosed layers at low frequencies, thus improving the ability of perfectly matched layers across the entire frequency range. After that, an adaptive projection-based model order reduction scheme is further developed to reduce the computational complexity of exterior acoustic systems. A robust error indicator based on the relative error of two constructed reduced order models is accordingly introduced. The performance of the present solution framework is discussed and compared with other implementation strategies, in the context of multi-frequency solution of two-dimensional test models with single or multiple scatterers.