Towards recycling purpose:Converting PET plastic waste back to terephthalic acid using pH-responsive phase transfer catalyst

Converting polyethylene terephthalate(PET)wastes to its monomer and valuable chemicals via ecofriendly chemical method is still a challenge task.Previously,phase transfer catalysts used for alkaline hydrolysis were soluble in reaction media and hardly separated after reaction.Here,we reported several pH-responsive catalysts combined alkyl quaternary ammonium units with heteropolyacid anion for achieving stepwise product/catalyst separation and catalyst recycling.The properties of homogeneous/heterogeneous transfer behavior allow catalyst to be easily separated from reaction media by adjusting of pH value.Among them,[C_(16)H_(33)N(CH_(3))_(3)]_(3)PW_(12)O_(40)(abbreviated as[CTA]_(3)PW)exhibits the highest activity and the most suitable pH responsive values.Such a pH triggered switchable catalytic system not only shows good performance for depolymerization of pure PET,but also some real PET wastes such as coloured trays and PE/PET complex films could be completely degraded into terephthalic acid.Additionally,the reaction kinetics and activation energy of PET alkaline hydrolysis also studied with and without pH-responsive[CTA]_(3)PW.

Controllable Construction of Bifunctional CoxP@N,P-Doped Carbon Electrocatalysts for Rechargeable Zinc–Air Batteries

The exploration of cheap,efficient,and durable bifunctional electrocatalysts for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)is highly desired to push forward the commercialization of rechargeable metal–air batteries.Here,bifunctional ORR/OER electrocatalysts based on CoxP(0<x<2,i.e.,Co_(2)P,Co_(2)P/CoP mixture,and CoP)nanoparticles(NPs)anchored on N,P-doped carbon framework(Co_(x)P@NPC)are developed via one-step carbonization of the mixture of as-synthesized ZIF-67 and melamine–phytic acid supermolecular aggregate(MPSA).The stoichiometric ratio of resultant Co_(x)P NPs can be rationally designed by adjusting the introduced ratio of ZIF-67 to MPSA,enabling their fabrication in a controlled manner.It is found that the as-synthesized Co_(2)P@NPC exhibits the best bifunctional ORR/OER activity among the Co_(x)P@NPC analogues,with a reversible oxygen electrode index(ΔE=E_(j10)−E_(1/2))down to~0.75 V.The constructed Zn–air battery based on Co_(2)P@NPC delivers a peak power density of 157 mW cm^(−2) and an excellent charge-discharge stability with negligible voltage decay for 140 h at 10 mA cm^(−2),superior to those based on Pt/C+RuO_(2) and most Co_(x)P-based electrodes ever reported.

Description of inverse energy cascade in homogeneous isotropic turbulence using an eigenvalue method

A description of inverse energy cascade(from small scale to large scale)in homogeneous isotropic turbulence is introduced by using an eigenvalue method.We show a special isotropic turbulence,in which the initial condition is constructed by reversing the velocity field in space,i.e.,the time-reversed turbulence.It is shown that the product of eigenvalues of the rate-of-strain tensor can quantitatively describe the backward energy transfer process.This description is consistent to the velocity derivative skewness Sk.However,compared with Sk,it is easier to be obtained,and it is expected to be extended to anisotropic turbulence.Furthermore,this description also works for the resolved velocity field,which means that it can be used in engineering turbulent flows.The description presented here is desired to inspire future investigation for the modeling of the backward energy transfer process and lay the foundation for the accurate prediction of complex flows.

Research on the mechanical fault diagnosis method based on sound signal and IEMD-DDCNN

Purpose–The purpose of this paper is to provide a shorter time cost,high-accuracy fault diagnosis method for water pumps.Water pumps are widely used in industrial equipment and their fault diagnosis is gaining increasing attention.Considering the time-consuming empirical mode decomposition(EMD)method and the more efficient classification provided by the convolutional neural network(CNN)method,a novel classification method based on incomplete empirical mode decomposition(IEMD)and dual-input dual-channel convolutional neural network(DDCNN)composite data is proposed and applied to the fault diagnosis of water pumps.Design/methodology/approach–This paper proposes a data preprocessing method using IEMD combined with mel-frequency cepstrum coefficient(MFCC)and a neural network model of DDCNN.First,the sound signal is decomposed by IEMD to get numerous intrinsic mode functions(IMFs)and a residual(RES).Several IMFs and one RES are then extracted by MFCC features.Ultimately,the obtained features are split into two channels(IMFs one channel;RES one channel)and input into DDCNN.Findings–The Sound Dataset for Malfunctioning Industrial Machine Investigation and Inspection(MIMII dataset)is used to verify the practicability of the method.Experimental results show that decomposition into an IMF is optimal when taking into account the real-time and accuracy of the diagnosis.Compared with EMD,51.52% of data preprocessing time,67.25% of network training time and 63.7%of test time are saved and also improve accuracy.Research limitations/implications–This method can achieve higher accuracy in fault diagnosis with a shorter time cost.Therefore,the fault diagnosis of equipment based on the sound signal in the factory has certain feasibility and research importance.Originality/value–This method provides a feasible method for mechanical fault diagnosis based on sound signals in industrial applications.