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In the past few years, different kinds of structural nonlinearities, such as external magnetic interaction and multistable structures, have been introduced into galloping energy harvesters to enhance energy harvesting efficiency. However, since the galloping-based piezoelectric energy harvester (GPEH) is a self-excited system, the conventional impedance matching method that is widely used in vibration energy harvesters is no longer valid for it. Therefore, the power characteristics of the nonlinear GPEH are still an open question to be solved. To this end, this paper is motivated to derive the approximate analytical solution of a monostable galloping-based piezoelectric energy harvester through the harmonic balance method and impedance matching theory. The analytical maximum power, power limit, and critical electromechanical coupling are studied from the perspective of the influence of structural nonlinearity on the power performance. Firstly, the approximate analytical solutions of output power, power limit, optimal resistance, and critical electromechanical coupling coefficient are derived. The accuracy of the analytical solution is verified by numerical simulation. It is found that the influence of structural nonlinearity on the power characteristics of the nonlinear GPEH is quite different under different wind speeds. After that, the power characteristics of the system under different wind speeds and different coupling conditions are investigated. The results showed that the maximum power of the system can be increased by introducing stiffness nonlinearity under low wind speed and weakly coupled configuration. Even more, the system can be shifted into a strongly coupled system when the nonlinearity is enhanced to a certain level. Reasonable design of stiffness nonlinearity can effectively reduce the critical electromechanical coupling, which indicates that stiffness nonlinearity is a feasible and effective way to improve the power performance of low-speed wind energy harvesting. [ABSTRACT FROM AUTHOR]

Ag–N–C catalyst was synthesized by the calcination process with AgNO3 as precursors, active carbon as support, and melamine as an N source. Series of characterizations showed that Ag was transferred into AgCl during the active phase by HCl, and pyridinic structure in the support was bonded with Ag components. Then, Ag–N–C single atom catalyst (SAC) was obtained by washing Ag–N–C with acid, aberration-correction high-angle-annular-dark-field scanning transmission electron microscopy showed that Ag presented in single atoms form, and Ag coordinated with the nitrogen atom in the support. Ag loss rate for Ag–N–C SAC was only 0.09% after running 10 h in acetylene hydrochlorination process, which was much smaller than Ag–N–C (57%), indicating that the presence of the Ag–N bond could be inhibiting Ag species loss. [ABSTRACT FROM AUTHOR]

Methyl methacrylate/nitrile butadiene rubber/graphene oxide (MMA/NBR/GO) composite materials were prepared by ball‐milling based on the mechano‐chemical principle. The effects of some key process parameters, such as graphene oxide (GO) content, ball‐to‐powder ratio (BPR), and ball‐milling time on textures and structures of MMA/NBR/GO composite materials were studied systematically by Zeta potentials, Raman spectroscopy, Thermogravimetric analysis, Fourier transform infrared spectrometry, and the derivation mechanism was examined. The results indicated composite materials with excellent dispersion stability at GO content of 0.3%, BPR of 3.87, and ball‐milling time of 5 h, the value of sedimentation rate is only 1.0%, the Zeta potential is −41.5 mV, and the mass loss ratio is 40.36%. FT‐IR result shows that the intensity of the characteristic peak all decreases after ball milling, and carboxyl group of GO and hydroxyl group connected to the benzene ring is broken. The graft position is CN and CH2 of NBR, and CH3 of MMA. Under these conditions, the oxygen‐containing functional groups of GO were successfully grafted onto the MMA and NBR. [ABSTRACT FROM AUTHOR]

We report the influence of sp2 content in carbon catalyst on the catalytic activity for acetylene hydrochlorination. Nanodiamonds (NDs) were used as the precursor and calcinated under different temperatures. The resulting ND500, ND700, ND900, and ND1100 catalysts were characterized, and the sp2 content increased with increasing calcination temperature. The specific activities of the catalysts first increased and then decreased with increasing sp2 content. The highest catalytic activity could be obtained in the ND-900 catalyst with a sp2 value of 43.9%. The density functional theory results showed that the adsorption sites for acetylene and hydrogen chloride were located at the interface between sp2 and sp3 configuration. [ABSTRACT FROM AUTHOR]

Background: The purpose of this network meta-analysis (NMA) was to evaluate the efficacy of intravenous opioid μ-receptor analgesics in shortening the duration of mechanical ventilation (MV) in ICU patients., Methods: Randomized controlled trials comparing the efficacy of remifentanil, sufentanil, morphine, and fentanyl on the duration of MV in ICU patients were searched in Embase, Cochrane, Pubmed, and Web of Science electronic databases. The primary outcome was MV duration. The Bayesian random-effects framework was used to evaluate relative efficacy., Results: In total 20 studies were included in this NMA involving 3,442 patients. Remifentanil was not associated with a reduction in the duration of MV compared with fentanyl (mean difference (MD) -0.16; 95% credible interval (CrI): -4.75 ~ 5.63) and morphine (MD 3.84; 95% CrI: -0.29 ~ 10.68). The secondary outcomes showed that, compared with remifentanil, sufentanil can prolong the duration of extubation. No regimen significantly shortened the ICU length of stay and improved the ICU mortality, efficacy, safety, and drug-related adverse events., Conclusion: Among these analgesics, remifentanil did not appear to be associated with a reduction in MV duration. Clinicians should carefully titrate the analgesia of MV patients to prevent a potentially prolonged duration of MV due to excessive or inadequate analgesic therapy., Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, CRD42021232604., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Lu, Qin, Liu, Chen, Dai and Li.)