This paper aims to develop a resonant accelerometer for high-sensitivity detection and to investigate the nonlinear vibration of the MEMS resonant accelerometer driven by electrostatic comb fingers. ...First, a nonlinear vibration model of the resonator with comb fingers in a MEMS resonant accelerometer is established. Then, the nonlinear and nonlinear stiffness coefficients are calculated and analyzed with the Galérkin principle. The linear natural frequency, tracking error, and nonlinear frequency offset are obtained by multi-scale method. Finally, to further analyze the nonlinear vibration, a sample-based stochastic model is established, and the uncertainty analysis method is applied. It is concluded from the results that nonlinear vibration can be reduced by reducing the resonant beam length and increasing the resonant beam width and thickness. In addition, the resonant beam length and thickness have more significant effects, while the resonant beam width and the single concentrated mass of comb fingers have little effect, which are verified by experiments. The results of this research have proved that uncertainty analysis is an effective approach in nonlinear vibration analysis and instructional in practical resonant accelerometer design.
Being able to understand pedestrians behavior is essential for urban planning. Despite a burgeoning research effort directed at the design and modelling of effective urban spaces for pedestrians, ...remarkably little is known about how pedestrians actually negotiate urban spaces in severely cold areas. By adopting computer vision technology, this paper reports the results of a video-based observational study aimed at exploring how and to what degree weather and climate affect pedestrian walking speed. The result shows that ice-snow sports, as a source of space attraction, can trigger a sudden change in the walking speed of pedestrians within space at the level of personal willingness. It also shows that the average walking speed at population level, was affected by both apparent temperature and ground conditions. Specifically, the average walking speed is negatively correlated with the instantaneous apparent temperature. The apparent temperature also has a time-lag effect on the average walking speed and the larger the temperature fluctuation, the more significant the time-lag effect. When the ground covered with snow, the average walking speed will decrease by about 0.102 m/s than that of the clean ground. These findings, we hope, should prove useful to any researcher and urban manager interested in and committed to designing more effective pedestrian spaces and in modelling pedestrian behavior at a microscopic level in harsh climate.
•Computer vision technology was used to detect pedestrian behavior.•The average walking speed can be affected by apparent temperature.•The apparent temperature has a time-lag effect on the average walking speed.•Ground covered with snow will slow down the average walking speed.
•Electron beam radiation inhibits the growth and reproduction of R. oryzae.•Electron beam irradiation can damage the cell wall structure of R. oryzae.•Electron beam irradiation can destroy the cell ...membrane integrity of R. oryzae.•Electron beam irradiation can cause oxidative stress in R. oryzae.
Electron beam irradiation is a physical fungicidal technique that has emerged as a potential application in China. However, its antifungal activity and mechanism against Rhizopus oryzae have not been reported. Thus, this study aimed to investigate the antifungal activity and mechanism of electron beam irradiation of R. oryzae. The antifungal activity analysis showed that the D10 value and complete elimination dose of R. oryzae irradiated by electron beam were 1.73 kGy and 8.08 kGy, respectively. Electron beam irradiation has a strong inhibitory effect on the filamentous biomass of R. oryzae. To reveal the antifungal mechanism of electron beam against R. oryzae, this study analyzed the dynamic changes in the cell wall, cell membrane, and oxidative stress induced by different irradiation doses. The results showed that electron beam irradiation destroyed the cell wall structure of R. oryzae, increasing chitinase activity and decreasing chitin content. Cell membrane integrity is disrupted, increasing relative conductivity, decreasing pH values, and decreasing soluble protein content. Electron beam irradiation causes oxidative stress in cells, increasing H2O2 content, decreasing antisuperoxide anion activity, decreasing DPPH free radical scavenging activity, and inhibiting defense enzyme (CAT and SOD) activity. This phenomenon indicates that electron beams can cause structural damage to and metabolic dysfunction of cells and disorders of redox homeostasis, which may be the main cause of growth inhibition and cell death in R. oryzae.
Membrane fouling remains a challenge for membrane bioreactor (MBR) application to wastewater treatment. The hydrophilic/hydrophobic organics present in MBR sludge supernatant form an important part ...of foulant. Their effects on fouling evolution and irreversibility were systematically investigated in this study. The organics, as fractionated into hydrophilic substances (HIS), hydrophobic acids (HOA), hydrophobic bases (HOB), and hydrophobic neutrals (HON), were subjected to fouling experiments using six microfiltration membranes covering the size range of 0.1–0.45µm with varied hydrophobicity. Modeling methods were applied to quantitatively characterize the dynamic fouling process as consisting of the initial pore blocking and subsequent gel layer stages. The results demonstrated the importance of foulant concentration to fouling evolution: the apparent fouling rate on a same membrane followed the order HIS>HOA⪢HOB>HON, whereas the order became HOA>HIS with normalization of concentration to give the intrinsic propensity for fouling evolution (across the initial stage) as well as the specific resistance (for the gel layer stage). Foulant–membrane interactions (i.e. hydrophobic adsorption and size exclusion) and foulant–foulant interaction (polymer–metal–polymer complexation) were identified as key mechanisms for fouling at the initial pore blocking stage and the gel layer stage respectively, with the foulant properties of hydrophobicity, molecular size and carboxylic complexing groups closely involved in the interactions. Additionally, membrane properties were also important factors affecting the fouling behaviors of the hydrophilic/hydrophobic fractions, as suggested by the combined impact of membrane hydrophobicity and pore size on fouling evolution propensity, and the decisive role of membrane hydrophobicity in fouling irreversibility.
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•Fouling behaviors of four organic fractions on six membranes were compared.•Foulant concentration significantly affects the apparent fouling phenomena.•Foulant hydrophobicity and size affect fouling evolution across the initial stage.•Foulant functional groups for metal complexation affects fouling at the gel stage.•Fouling behaviors are jointly affected by foulant and membrane properties.
The use of homogeneous and polluting halides as nucleophilic cocatalysts lowers the economy and benignity of the CO2-epoxide cycloaddition over heterogeneous Lewis-acid catalysts like metal-organic ...frameworks (MOFs). Creating net positive charge at frameworks is a reasonable strategy to heterogenize halide anions within MOFs, but it is still challenging to achieve high halide loading while keeping adequate porosity. In this article, we report a facile approach to ionic MOFs with high halide content and improved catalytic activity. The catalysts were prepared by reacting azide-tagged MIL-101 with alkyne-tagged organic bromide salts. The efficient azide–alkyne click reaction within the mesoporous MOF allows quantitative cationization of the linkers, and the resultant bifunctional ionic MOFs contain one halide ion per metal center to the benefit of the cooperative catalysis. Catalytic studies suggest that the effects of varying the cationic groups and halide anions in the confined ionic space are different from those observed for homogeneous organic halides. The highest catalytic activity was demonstrated for the MOF having the smallest cationic group (quaternized trimethyl ammonium) and the intermediately nucleophilic halide (Br−). The catalyst also outperforms the ionic MOF catalysts reported prior to this work.
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•A series of ionic MOFs were prepared by facile alkyne-azide click reactions.•The MOFs contain one halide per metal to the benefit of cooperative catalysis.•The confined ionic space changes the effects of cationic groups and halide anions.•The optimal catalyst, MIL-101-tz-TMA-Br, outperforms previous ionic MOF catalysts.
Nanoparticle corona phases, especially those surrounding anisotropic particles, are central to determining their catalytic, molecular recognition, and interfacial properties. It remains a ...longstanding challenge to chemically synthesize and control such phases at the nanoparticle surface. In this work, the supramolecular chemistry of rosette nanotubes (RNTs), well‐defined hierarchically self‐assembled nanostructures formed from heteroaromatic bicyclic bases, is used to create molecularly precise and continuous corona phases on single‐walled carbon nanotubes (SWCNTs). These RNT–SWCNT (RS) complexes exhibit the lowest solvent‐exposed surface area (147.8 ± 60 m−1) measured to date due to its regular structure. Through Raman spectroscopy, molecular‐scale control of the free volume is also observed between the two annular structures and the effects of confined water. SWCNT photoluminescence (PL) within the RNT is also modulated considerably as a function of their diameter and chirality, especially for the (11, 1) species, where a PL increase compared to other species can be attributed to their chiral angle and the RNT's inward facing electron densities. In summary, RNT chemistry is extended to the problem of chemically defining both the exterior and interior corona interfaces of an encapsulated particle, thereby opening the door to precision control of core–shell nanoparticle interfaces.
The corona phase of the single‐walled carbon nanotube (SWCNT) is important for their applications oriented engineering. In this study, the self‐assembly of rosette nanotubes (RNTs) around single SWCNTs, is demonstrated creating a molecularly precise wrapping with chirality and diameter selectivity. This system can become an avenue for the precise control of the particle corona.
Abstract In the design and optimisation of marine wireless communication and navigation systems, a thorough investigation of radio wave propagation characteristics under atmospheric ducting ...conditions is essential. The authors aim to enhance the efficiency of radio wave propagation loss prediction in marine atmospheric ducting environments, proposing a prediction model based on Fast Reordered‐Alternate Direction Decomposition (FR‐ADD). By approximating the diffraction term into three independent components, exploiting the commutative properties of the Fourier transform to reduce the spatial dimensions, and incorporating a rapid algorithm for the parabolic equation, the model optimises the stepping process and significantly improves computational efficiency. Simulation experiments demonstrate that, in the long‐distance and complex marine ducting environments, the model not only maintains prediction accuracy but also substantially reduces computational load and prediction time, effectively realising over‐the‐horizon propagation prediction. In the experiment of radio wave propagation characteristics in the Yellow and Bohai Seas, the simulation data from the FR‐ADD model showed significant correlation with actual measurements and simulations from the AREPS software, confirming the method's efficiency and practicality.
A microporous europium metal–organic framework (Eu-MOF), namely, {Eu3(bpydb)3(HCOO)(OH)2(DMF)·3DMF·2H2O}n (1) with asymmetric trinuclear metal clusters extended by 4,4′-(4,4′-bipyridine-2,6-diyl) ...dibenzoic acid has been synthesized via the solvothermal method. PXRD of 1 confirms that it possesses excellent water stability and pH stability. The photo-luminescence properties of 1 exhibit effective recognition of Cr2O72−, MnO4−, and Cr3+ ions and SDBS. Furthermore, a wide linear range, high quenching constant and a low detection limit reveal that 1 can potentially act as a luminescence-based sensor for quantitative and highly sensitive detection of Cr2O72−, MnO4−, and Cr3+ ions as well as SDBS in aqueous solutions. To the best of our knowledge, the detection limit of 1 is the lowest value reported for Ln-MOF-based luminescent sensors to detect Cr2O72− ions (0.5 μM) in aqueous solutions. The use of a rare earth fluorescent probe for detecting MnO4− ions is not common. It is the first time that Ln-MOF as a fluorescence probe is used for detecting SDBS. Moreover, fluorescent-based test papers of 1 have also been prepared, which can be helpful to develop visual detection for Cr2O72−, MnO4−, and Cr3+ ions as well as SDBS in daily applications.
● A novel nonpolar super-aligned carbon nanotube (SACNT) membrane was prepared. ● SACNT membranes achieved smoother and more uniform structures. ● SACNT membranes have inert chemistry and unique ...nonpolar wetting feature. ● SACNT membranes exhibit superior separation and antifouling capabilities. ● SACNT membranes achieved superior oil/water separation efficiency.
Membrane separation technology has made great progress in various practical applications, but the unsatisfactory separation performance of prevailing membrane materials hampers its further sustainable growth. This study proposed a novel nonpolar super-aligned carbon nanotube (SACNT) membrane, which was prepared with a layer-by-layer cross-stacking method. Through controlling the number of stacked SACNT layers, three kinds of SACNT membranes (SACNT_200, SACNT_300, and SACNT_400) were prepared. Systematic characterizations and filtration tests were performed to investigate their physico-chemical properties, surface wetting behavior, and filtration performance. Compared with two commercial membranes (Com_0.22 and Com_0.45), all the SACNT membranes achieved smoother and more uniform structures. Due to the hexagonal graphene structure of CNTs, the surface chemistry of the SACNT membranes is simple and inert, thereby potentially eliminating the covalent-bonding-induced membrane fouling. Besides, the SACNT membranes exhibited a typical nonpolar wetting behavior, with high contact angles for polar liquids (water: ~124.9°–126.5°; formamide: ~80.0°–83.9°) but low contact angles for nonpolar diiodomethane (~18.8°–20.9°). This unique nonpolar feature potentially leads to weak interactions with polar substances. Furthermore, compared with the commercial membranes, the SACNT membranes obtained a significantly higher selectivity while achieving a comparable or higher permeability (depending on the number of stacked layers). Moreover, the SACNT membranes exhibited superior separation performance in various application scenarios, including municipal wastewater treatment (> 2.3 times higher cleaning efficiency), electro-assistant fouling inhibition (or even self-cleaning), and oil/water separation (> 99.2 % of separation efficiency), suggesting promising application prospects in various fields.
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