Ultra-broadband piezoelectric energy harvesting via bistable multi-hardening and multi-softening

Nonlinear Dynamics - An electromechanical coupled distributed parameter model is derived for a broadband piezoelectric energy harvester with nonlinear magnetic interaction and...     

井筒内杆管柱双层接触有限元分析及应用

构造双层多向接触间隙元描述细长油管柱与内外杆管柱的随机接触摩擦问 题,与空间梁单元相结合,采用变刚度与等刚度交替方式求解,得出抽油杆柱与油管柱以及 油管柱与套管柱的接触状态、接触位置、摩阻力大小以及抽油杆柱与油管柱在任意井深处的 广义内力、应力和变形. 三口井算例表明,抽油杆柱与油管柱的井口悬重误差低 于10{\%}, 能够为抽油杆和油管柱设计和失效分析提供可靠的计算方法和理论依据.     

Oxidative carbonylation of phenol with a Pd-O/CeO2-nanotube catalyst

CeO2 nanotubes (CeO2-NT) were synthesized using carbon nanotubes as template by a liquid phase deposition and hydrothermal method. X-ray diffraction, transmission electron microscopy, and N2 adsorption-desorption were used to characterize the CeO2-NT. The wall of CeO2-NT was composed of small interconnected nanocrystallites ranging from 4 to 9 nm in size. The specific surface area of CeO2-NT was 108.8 m2/g with an outer diameter of 25 nm and length > 300 nm. Supported Pd cata-lyst, Pd-O/CeO2-NT, was prepared using CeO2-NT as the support. Temperature-programmed reduc-tion analysis showed that the surface oxygen on Pd-O/CeO2-NT could be reduced at low tempera-ture, therefore it showed high activity in the reaction. Pd-O/CeO2-NT was used as the catalyst for the oxidative carbonylation of phenol. It has better activity and DPC selectivity than Pd-O/CeO2-P, which was prepared by supporting Pd on zero dimensional CeO2particles. Under the optimized conditions, phenol conversion was 67.7% with 93.3% DPC selectivity with Pd-O/CeO2-NT. However, its catalyt-ic activity decreased when the catalyst was used for the second time. This was attributed to the destruction of the tubular structure of Pd-O/CeO2-NT and Pd leaching during the reaction.     

Nonlinear characterization of the rotor-bearing system with the oil-film and unbalance forces considering the effect of the oil-film temperature

Nonlinear Dynamics - The nonlinear phenomena of the rotor-bearing systems, i.e., the oil whirl, oil whip, quenching and pulling out, due to the oil-film temperature are not yet clear. To...     

Stability and Sensitivity Analysis of Solutions to Weak Vector Variational Inequalities

The paper mainly concerns the study of a parametric weak vector variational inequality. Robinson’s metric regularity and Lipschitzian stability of the solution mapping for the parametric weak vector variational inequality are firstly established. Then sensitivity analysis of the solution mapping for the parametric weak vector variational inequality is discussed. As applications, Lipschitzian continuity and differentiability of the solution mapping are also investigated for a parametric variational inequality.     

Nonlinear characterization of concurrent energy harvesting from galloping and base excitations

An energy harvester is proposed to concurrently harness energy from base and galloping excitations. This harvester consists of a triangular cross-sectional tip mass attached to a multilayered piezoelectric cantilever beam and placed in an incompressible flow and subjected to a harmonic base excitation in the cross-flow direction. A coupled nonlinear-distributed-parameter model is developed representing the dynamics of the transverse degree of freedom and the generated voltage. The galloping force and moment are modeled by using a nonlinear quasi-steady approximation. Under combined loadings and when the excitation frequency is away from the global natural frequency of the harvester, the response of the harvester mainly contains these two harmonic frequencies. Thus, the harvester’s response is generally aperiodic and is either periodic with large period (i.e., period- \(n\) ), or quasi-periodic, or chaotic. To characterize the harvester’s response under a combination of vibratory base excitations and aerodynamic loading, we use modern methods of nonlinear dynamics, such as phase portraits, power spectra, and Poincaré sections. A further analysis is then performed to determine the effects of the wind speed, frequency excitation, base acceleration, and electrical load resistance on the performance of the harvester under separate loadings.     

High performance liquid chromatography analysis of p-aminophenol synthesized by nitrobenzene transfer hydrogenation using formic acid as hydrogen sourceEI北大核心CSCD

Qualitative analysis of the main by-product of 4-hydroxybenzamide in the synthesis of p-aminophenol bynitrobenzene transfer hydrogenation with formic acid as hydrogen source was carried out by electrospray ionization mass spectrometry. The reaction system was quantitatively analyzed by high performance liquid chromatography. The chromatographic conditions were shown as followsShim pack VP-ODS column250 mm× 4.6 mm5 μµmdetection wavelength of 254 nmVmethanolVbuffer solution=114.8 mmol/L sodium dihydrogen phosphate solution1.9 mmol/L dibasic sodium phosphate solutionas the mobile phase and the flow rate of 0.8 mL/min with a column temperature of 35. Nitrobenzenep-aminophenolaniline and formylaniline in the reaction system were quantitatively analyzed by standard curve method with methyl N-phenylcarbamate as internal standard. The correlation coefficientsR2were 0.99930.99950.9998 and 0.9992 for these analytes respectively. The relative standard deviations RSDs were less than 1.0% 0.3% 0.2% and 0.4% respectively. The recoveries were in the ranges of 95.5%-102.6%101.2%-104.8%95.1%-99.8% and 95.7%-101.1%respectively. This method can be used for the simultaneous determination of main and by-products in the transfer hydrogenation of nitrobenzene with formic acid as hydrogen source. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

Nonlinear galloping of internally resonant iced transmission lines considering eccentricity

Based on the curved-beam theory, a nonlinear galloping model considering three displacement (normal, bi-normal and tangential) components and twist is formulated. According to the property of transmission line, one reduced (normal and bi-normal) galloping model, with regard of bending, rotation and eccentricity of cross section, is obtained. Moreover, the initial rotation angle is also introduced in galloping and aerodynamic models. Additionally, based on the reduced model, the bifurcation and stability of the two cases (1:1 resonance and 2:1 resonance) are analyzed. The results turn out that the importance of ice eccentricity needs to be highlighted. Finally, multiple stabilities are found through the analyses of bifurcation and stability and proved by the reduced model and Reduced Amplitude Modulation Equations (RAME) numerically integrated in time history.