Hybrid acoustic metamaterial as super absorber for broadband low-frequency sound

A hybrid acoustic metamaterial is proposed as a new class of sound absorber, which exhibits superior broadband low-frequency sound absorption as well as excellent mechanical stiffness/strength. Based on the honeycomb-corrugation hybrid core (H-C hybrid core), we introduce perforations on both top facesheet and corrugation, forming perforated honeycomb-corrugation hybrid (PHCH) to gain super broadband low-frequency sound absorption. Applying the theory of micro-perforated panel (MPP), we establish a theoretical method to calculate the sound absorption coefficient of this new kind of metamaterial. Perfect sound absorption is found at just a few hundreds hertz with two-octave 0.5 absorption bandwidth. To verify this model, a finite element model is developed to calculate the absorption coefficient and analyze the viscous-thermal energy dissipation. It is found that viscous energy dissipation at perforation regions dominates the total energy consumed. This new kind of acoustic metamaterials show promising engineering applications, which can serve as multiple functional materials with extraordinary low-frequency sound absorption, excellent stiffness/strength and impact energy absorption

Two-dimensional Mo decorated borophenes: high critical temperature, large magnetic anisotropy, and stacking-dependent magnetism

Two-dimensional magnetic materials with high critical temperature, large magnetic anisotropy energy and intrinsic magnetism hold great promise for advancements in spintronics. However, synergizing these attributes within a single material remains challenging. Through the application of swarm-intelligence-based structure searching along with first-principles calculations, we identify two Mo decorated borophene variants, denoted as MoB _4 and MoB _6 , are such candidates with high thermal and dynamical stabilities. MoB _4 and MoB _6 are characterized as either ferromagnetic or antiferromagnetic metals. Notably, both MoB _4 and MoB _6 display sizable magnetic anisotropy energy—924 and 932 μ eV per Mo atom, respectively—surpassing that of the widely studied CrI _3 monolayer, which measures 685 μ eV per Cr atom. Monte Carlo simulation suggests the Curie temperature of MoB _4 sheet is 390 K, which is above room temperature. Our examination uncovers that bilayer Mo _x B _y formations exhibit layer-specific van der Waals interactions, contrasting with bilayer borophenes produced experimentally, which display robust interlayer chemical bonding. We determine that the stacking order profoundly influence both the magnetic anisotropy energy and critical temperatures of the material. Specifically, the magnetic anisotropy energy for both structures doubles in their bilayer configurations, with AB-stacked MoB _4 and AC-stacked MoB _6 demonstrating critical temperatures of 550 K and 320 K, respectively. The exceptional electronic and magnetic characteristics of the Mo _x B _y monolayers position them as favorable candidates for future spintronic devices

Parametric study on air brayton cycle as an exhaust energy recovery method

Exhaust energy recovery is one of the ways to improve engine’s fuel utilization. Parametric study of Air Brayton Cycle (ABC) as an exhaust energy recovery was done to see its feasibility. Parameters such as the mass flow rate, heat exchanger effectiveness, compressor and turbine efficiencies and heat exchanger pressure drop were analyzed to see their effects. It was found that the ABC can extract up to 3-4 kW of energy from the exhaust of a 5.9 liter diesel engine. This translates to about 3-4% of Brake Specific Fuel Consumption (BSFC) improvement. Careful integration of the main components is crucial to the success of the ABC as an exhaust energy recovery

Zero-Dimensional Interstitial Electron-Induced Spin–Orbit Coupling Dirac States in Sandwich Electride

The development of inorganic electrides offers new possibilities for studying topological states due to the nonnuclear-binding properties displayed by interstitial electrons. Herein, a sandwich electride 2[CaCl]+:2e− is designed, featuring a tetragonal lattice structure, including two atomic lattice layers and one interstitial electron layer. The interstitial electrons form nonsymmorphic-symmetry-protected Dirac points (DPs) at the X and M points, which are robust against the spin–orbit coupling effect. DPs exhibit an approximately elliptical shape, characterized by a relatively high anisotropy, resulting from the interplay between the electron and atomic layers. In addition, 2[CaCl]+:2e− possesses a lower work function (WF) (3.43 eV), endowing it with robust electron-supplying characteristics. Due to the low WF and interstitial electrons, 2[CaCl]+:2e− loaded Ru shows outstanding catalytic performance for N2 cleavage. A potential research platform for exploring the formation of topological states and promoting nitrogen cracking in electrides is provided

Graphene oxide based molecularly imprinted polymers with double recognition abilities : The combination of covalent boronic acid and traditional non-covalent monomers

In this work, graphene oxide (GO) based molecularly imprinted polymers with double recognition abilities (DR-MIPs) were prepared and considered as adsorbent for the specific recognition and capture of luteolin (LTL). To exhibit the tightest binding hosts for LTL, the double recognition abilities were achieved by adopting 4-vinylphenyl boronic acid (BA) and methacrylic acid (MAA) to be the covalent and non covalent imprinted monomers, respectively. Then, their functional groups and shape of imprinted sites endowed DR-MIPs with a specific affinity for cis-diol-containing structure, hydroxyl and carbonyl groups of LTL. The results of batch mode experiments indicated kinetic equilibrium time and binding capacity of DR-MIPs were 30 min and 56.27 mg g(-1) at 298 K, respectively. The Langmuir isotherm and pseudo second-order kinetic models were the main adsorption mechanisms for DR-MIPs, and the fast adsorption and large binding amount were resulted from the two-dimensional (2D) structure of GO and enough imprinted sites with double recognition abilities. DR-MIPs also showed excellent recognition ability, and the estimated relative selectivity coefficients (k') for structural analog quercetin (QRT), hydroquinone (HDQ) and p-nitrophenol (P-NP) were 13.73, 18.62 and 19.95, respectively. In addition, DR-MIPs possessed outstanding reusability and enhanced purification property for 85% raw LTL. The purified LTL products achieved approximately 93.47%, and they exhibited the obvious antibacterial performance

Investigation of the Effect of the Degree of Processing of Radix Rehmanniae Preparata (Shu Dihuang) on Shu Dihuangtan Carbonization Preparation Technology

Carbonization of Radix Rehmanniae Preparata (Shu Dihuangtan) via stir-frying could increase its homeostasis maintaining and antidiarrheal effects. To ensure these pharmacological functions, the quality of the raw material (processed Rehmanniae Radix) must be well controlled. Therefore, we analyzed the effects of different degrees of processing and adjuvants on processed Rehmanniae Radix (Shu Dihuang) by High Performance Liquid Chromatography (HPLC) chromatographic fingerprints, thermal gravimetric analysis and Fourier transform infrared spectroscopy (FTIR). Based on the results from HPLC fingerprints combined with similarity analysis (SA) and hierarchical cluster analysis (HCA) the optimum processing method for Shu Dihuang was five cycles of steaming and polishing, which follows the ancient processing theory. The intensity of thermal weight loss rate peaked near 210.33 ± 4.32 °C or 211.33 ± 2.62 °C, which was an important indicator for the degree of processing of Shu Dihuang. A temperature near 290.89 ± 2.51 °C was the upper limit for carbonizing Shu Dihuangtan. FTIR spectroscopy analysis showed that the overall chemical composition of Shu Dihuangtan was affected by both the degree of processing and adjuvant, which are very important for its quality

Intercomparison of NO3 under Humid Conditions with Open-Path and Extractive IBBCEAS in an Atmospheric Reaction Chamber

We report an open-path incoherent broadband cavity-enhanced absorption spectroscopy (OP-IBBCEAS) technique for in situ simultaneous optical monitoring of NO2, NO3, and H2O in a reaction chamber. The measurement precision values (1σ) are 2.9 ppbv and 2.9 pptv for NO2 and NO3 in 2 s, respectively, and the measurement uncertainties are 6% for NO2 and 14% for NO3. Intercomparison of measured concentrations of NO2 and NO3 by open-path and extractive IBBCEAS was carried out in the SAES-ARC reaction chamber during the reaction of NO2 with O3. The measurement accuracy of OP-IBBCEAS is verified by an NO2 intercomparison and the NO3 transmission efficiency of the extractive IBBCEAS is determined by comparison against the in situ NO3 measurement. The relationship between H2O absorption cross section and its mixing ratio at 295 K and 1 atm was analysed. Due to the spectral resolution of IBBCEAS system, the strong and narrow absorption lines of H2O are unresolved and exhibit non-Beer–Lambert Law behaviour. Therefore, a correction method is used to obtain the effective absorption cross section for fitting the H2O structure. An inappropriate H2O absorption cross section can cause an overestimation of NO3 concentration of about 28% in a humid atmosphere (H2O = 1.8%). This spectroscopic correction provides an approach to obtain accurate NO3 concentrations for open-path optical configurations, for example in chamber experiments or field campaigns. The measurement precision values are improved by a factor of 3 to 4 after applying Kalam filtering, achieving sub-ppbv (0.8 ppbv) and sub-pptv (0.9 pptv) performance in 2 s for NO2 and NO3, respectively

Intercomparison of NO₃ under Humid Conditions with Open-Path and Extractive IBBCEAS in an Atmospheric Reaction Chamber

We report an open-path incoherent broadband cavity-enhanced absorption spectroscopy (OP-IBBCEAS) technique for in situ simultaneous optical monitoring of NO2, NO3, and H2O in a reaction chamber. The measurement precision values (1σ) are 2.9 ppbv and 2.9 pptv for NO2 and NO3 in 2 s, respectively, and the measurement uncertainties are 6% for NO2 and 14% for NO3. Intercomparison of measured concentrations of NO2 and NO3 by open-path and extractive IBBCEAS was carried out in the SAES-ARC reaction chamber during the reaction of NO2 with O3. The measurement accuracy of OP-IBBCEAS is verified by an NO2 intercomparison and the NO3 transmission efficiency of the extractive IBBCEAS is determined by comparison against the in situ NO3 measurement. The relationship between H2O absorption cross section and its mixing ratio at 295 K and 1 atm was analysed. Due to the spectral resolution of IBBCEAS system, the strong and narrow absorption lines of H2O are unresolved and exhibit non-Beer–Lambert Law behaviour. Therefore, a correction method is used to obtain the effective absorption cross section for fitting the H2O structure. An inappropriate H2O absorption cross section can cause an overestimation of NO3 concentration of about 28% in a humid atmosphere (H2O = 1.8%). This spectroscopic correction provides an approach to obtain accurate NO3 concentrations for open-path optical configurations, for example in chamber experiments or field campaigns. The measurement precision values are improved by a factor of 3 to 4 after applying Kalam filtering, achieving sub-ppbv (0.8 ppbv) and sub-pptv (0.9 pptv) performance in 2 s for NO2 and NO3, respectively

Potential Roles of Large Language Models in the Production of Systematic Reviews and Meta-Analyses

Large language models (LLMs) such as ChatGPT have become widely applied in the field of medical research. In the process of conducting systematic reviews, similar tools can be used to expedite various steps, including defining clinical questions, performing the literature search, document screening, information extraction, and language refinement, thereby conserving resources and enhancing efficiency. However, when using LLMs, attention should be paid to transparent reporting, distinguishing between genuine and false content, and avoiding academic misconduct. In this viewpoint, we highlight the potential roles of LLMs in the creation of systematic reviews and meta-analyses, elucidating their advantages, limitations, and future research directions, aiming to provide insights and guidance for authors planning systematic reviews and meta-analyses