In micro-grid, the quality problems of grid voltage, i.e. unbalance, harmonic pollution and frequency fluctuation, may occur at the same time. In order to maintain synchronization of grid-connected ...inverter at this particular circumstance, an improved dual second-order generalized integrator (DSOGI) PLL is proposed. The harmonic components of phase and frequency are eliminated by adding closed-loop feedback control of angular frequency. Meanwhile, the precise angular frequency reference is accomplished by means of zero cross detection circuit and relevant soft arithmetic. Moreover, the proposed PLL maintains steady-state precision and dynamic performance in unbalanced, polluted, and frequency fluctuation circumstances at the same time. Simulation results in MATLAB confirm the effectiveness of the proposed method.
This paper introduced the basic principle and main influencing factors of the three-dimensional multipoint stretch forming process and investigated the optimized scheme of the cross section forming ...quality. The main factors affecting the stretch forming process were studied by the orthogonal test through the numerical simulation technique. In the case of a good target shape, the best combination of forming parameters was established by using the range method. The cross-sectional distortion of the formed profile is the smallest when the prestretching amount is 1% of the profile length, the poststretching amount is 0.8% of the profile length, the number of the die heads is 12, and the friction coefficient is 0.15. The optimal combination of forming parameters was verified by the multipoint bending test.
Nowadays, high-performance electromagnetic wave (EMW) absorption materials derived from low-cost biomass materials have attracted widespread attention. Herein, a novel biomass‑carbon with porous ...array structures derived from waste soybean dregs is prepared by a hydrothermal method combined with heat treatment using formaldehyde and KOH as activators. The as-prepared biomass‑carbon with significantly enhanced specific surface area can possess more charge transmission paths, increased multiple reflections and scattering, multiple loss modes, and improved impedance matching, leading to the improvement of EMW absorption performances. The obtained single-component biomass‑carbon without any functional fillers exhibits an effective EMW absorption capability with a wide absorption bandwidth of 4.8 GHz at a thickness of 3.5 mm. This study will provide a valuable approach for the preparation of biomass‑carbon based EMW absorption materials with controllable porous structures by the activation process.
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•High-performance single-component biomass carbon derived from soybean dregs•Unique porous array structures formed through an activation process.•Effective EMW absorption capability with a wide absorption bandwidth of 4.8 GHz.
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•LLE-GC–MS-based metabolomics was used to investigate the VOCs change during koumiss fermentation.•15 differential metabolites between mare’s milk and koumiss were confirmed.•The ...correlation between flavor formation and microbial community was established.•Lactobacillus and Dekkera were the most important flavor-producing microbiota.•The fatty acid synthesis pathway was focused from identified prominent pathways.
Koumiss, naturally fermented mare’s milk, has a unique flavor that is affected by its resident microflora. In this study, we analyzed time-dependent changes in the microbiota and volatile metabolite profiles of koumiss using high-throughput sequencing and liquid–liquid extraction–gas chromatography–mass spectrometry. The dominant microrganisms in mare milk were Enterobacter and Rhodotorula, which were gradually suppressed, then Lactobacillus and Dekkera became the core microorganisms of koumiss. 17 FAA and 52 volatile organic compounds (VOCs) were identified during koumiss fermentation, including 19 odor active compounds and 15 differential metabolites of VOCs, mainly acids and esters, and their anabolism showed significant positive correlations with Lactobacillus and Dekkera. The microbial metabolic network showed that Lactobacillus and Dekkera were identified as the most important flavor-producing microbiota due to their significantly positive correlation with the formation of 33 and 28 flavor metabolites, respectively. These microorganisms produce enzymes that catalyze a series of metabolic pathways that generate VOCs, including carbohydrate metabolism, amino acid metabolism, and fatty acid biosynthesis. Our findings provide new guidance for the screening and application of flavor-producing microorganisms inkoumiss.
Uranium is an important fuel for nuclear power, with 4.5 billion tons of it stored in the oceans, 1,000 times more than on land. Polymer membrane materials are widely used in the marine resources ...fields, due to their convenient collection, good separation and can work continuously. Herein, a poly(amidoxime)-polyacrylonitrile blend membrane (PCP) with high flux, excellent antibacterial properties and uranium adsorption performance has been prepared by using the phase inversion method, and the prepared membrane was used for highly efficient uranium extraction from seawater. In static adsorption experiments, the PCP membrane reached adsorption equilibrium after 48 h, and the adsorption capacity was 303.89 mg/g (C0 =50 mg/L). In dynamic adsorption experiments, it was found that the lower flow rate and higher number of membrane layers were favorable for dynamic adsorption. In addition, the water flux of the PCP membrane was 7.4 times higher than that of the PAN membrane. The adsorption mechanism can be attributed to the chelation between amino and hydroxyl groups in CS, amidoxime group in poly(amidoxime) and uranyl ions. The simple preparation process coupled with the excellent adsorption performance indicated that the PCP membrane would be a promising material for the uranium extraction from seawater.
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•Poly(amidoxime)-polyacrylonitrile membrane has been synthesized by phase inversion method.•Poly(amidoxime) acts as a "surfactant" in the preparation of blended membrane.•The PCP membrane shows high flux, excellent antibacterial and adsorption performance.•Plausible synergistic adsorption mechanism was further discussed.
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•The iron oxide film shows 60 % absorbance for harmful blue light from 400 to 450 nm.•The film exhibits 96 % transmittance for the other visible light.•The hydrophobic-modified film ...has good humid-heat stability.•The film has no distinguishable effect on display quality.•The film can effectively protect human ARPE-19 cells from blue light damage.
With the increasing application of display and lighting devices, the potential injury to human eyes due to blue light has been attracting significant attention. While current anti-blue light films are complex, costly and low stability in humid environments. In this work, anti-blue light films were fabricated using iron oxide as blue light absorbent and polyvinylpyrrolidone as surfactant, under various Fe3+ concentrations and annealing temperatures. Particularly, the films annealed at 300 °C exhibited 60 % absorption rate of blue light in 400–450 nm wavelength range on average and still maintained 96 % transmittance to 500–800 nm visible light. Moreover, the films coated with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS)-modified SiO2 hydrophobic layer showed high hydrophobicity and sequential humid-heat stability. Meanwhile, no obvious changes occurred in transmittance spectra after keeping at 85 °C and 85 % relative humidity for 15 days. With the composite film covered, the color rendering index of the display screen decreased only 0.7 %, while the blue light weighted radiance decreased significantly by 37.1 %. Furthermore, cell experiments with composite films demonstrated that human retinal pigment epithelium cells were effectively protected from blue light injury. Overall, the composite films with high stability exhibited desired anti-blue light function.
The high-order harmonic spectra from laser-ablated tin plasma plumes are investigated experimentally and theoretically at different laser wavelengths. It is found that the harmonic cutoff is extended ...to ∼84 eV and the harmonic yield is greatly improved by decreasing the driving laser wavelength from 800 nm to 400 nm. Appling the Perelomov-Popov-Terent'ev theory with the semiclassical cutoff law and one-dimensional time-dependent Schrödinger equation, the contribution of the Sn
ion to harmonic generation accounts for the cutoff extension at 400 nm. With the qualitative analysis of the phase mismatching effect, we reveal the phase matching caused by the dispersion of free electrons is greatly optimized in the 400 nm driving field relative to the 800 nm driving field. The high-order harmonic generated from laser-ablated tin plasma plumes driven by the short laser wavelength provides a promising way to extend cutoff energy and generate intensely coherent extreme ultraviolet radiation.
An angiotensin-converting enzyme inhibitory (ACEI) peptide with a median inhibitory concentration (IC50) of 1.26 mg/mL was purified from whey proteins resulting from a fermentation using ...Lactobacillus plantarum QS670. The peptide was subsequently derived from an αS1-casein, κ-casein, β-lactoglobulin, or serum albumin fraction. Analysis via liquid chromatography tandem mass spectrometry indicated that it had an amino acid sequence of Gly-Ala (GA). The GA dipeptide was also synthesized using an Fmoc solid-phase method. The GA dipeptide exhibited an IC50 of 1.22 mg/mL and was shown to be stable across both temperature (20 to 60°C) and pH (2 to 12). Digestive enzymes including pepsin, trypsin, and chymotrypsin had negligible effects on activity. The whey exerted hypotensive effects when fed to spontaneously hypertensive rats (SHR), which exhibited a blood pressure drop of 2.33 kPa. A 4-wk gavage treatment resulted in greater decreases of 7.46 kPa. Results of this study indicate that milk fermented using Lb. plantarum QS306 has potential to be used as a functional food to help prevent or reduce hypertension-associated diseases.
Many studies have found that feelings and expressions of gratitude bring profound benefits to people and relationships. We complicate this view of gratitude. We examine two variables known to impact ...people's expectations for relationships: culture (collectivist vs. individualist) and relational distance (close vs. distant), and we find evidence that expressing gratitude conveys that relationship expectations have been exceeded, such that people view it as less desirable to give and receive gratitude for actions that are expected duties of a relationship. In both observational data and real behavior in an experiment, we found that people in a collectivist culture (China) are less likely than those in an individualist culture (America) to express gratitude to close others (Studies 1 and 2). Using hypothetical vignettes, we confirmed this pattern and further found there was no cultural difference for distant others (Study 3). These differences in expressing gratitude reflect differences in underlying feelings of gratitude, as well as differences in expectations of how the target would react to being thanked (Study 4). This cultural difference can be explained by cultural differences in the extent of duties placed on close others (Studies 5 and 6): People in China expect more of their close others. Perhaps as a result, people in China show a weaker preference than Americans for direct expressions of gratitude toward close others, but no difference for distant others (Study 7). Overall, our findings suggest that expressing gratitude may not always be good for close relationships.
Effective evaluation and prediction of aerosol transport deposition in the human respiratory tracts are critical to aerosol drug delivery and evaluation of inhalation products. Establishment of an in ...vitro-in vivo correlation (IVIVC) requires the understanding of flow and aerosol behaviour and underlying mechanisms at the microscopic scale. The achievement of the aim can be facilitated via computational fluid dynamics (CFD) based in silico modelling which treats the aerosol delivery as a two-phase flow. CFD modelling research, in particular coupling with discrete phase model (DPM) and discrete element method (DEM) approaches, has been rapidly developed in the past two decades. This paper reviews the recent development in this area. The paper covers the following aspects: geometric models of the respiratory tract, CFD turbulence models for gas phase and its coupling with DPM/DEM for aerosols, and CFD investigation of the effects of key factors associated with geometric variations, flow and powder characteristics. The review showed that in silico study based on CFD models can effectively evaluate and predict aerosol deposition pattern in human respiratory tracts. The review concludes with recommendations on future research to improve in silico prediction to achieve better IVIVC.
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