Investigation on step overcharge to self-heating behavior and mechanism analysis of lithium ion batteries

To obtain intrinsic overcharge boundary and investigate overcharge mechanism,here we propose an innovative method,the step overcharge test,to reduce the thermal crossover and distinguish the overcharge thermal behavior,including 5%state of charge(SOC)with small current overcharge and resting until the temperature equilibrium under adiabatic conditions.The intrinsic thermal response and the self-excitation behaviour are analysed through temperature and voltage changes during the step overcharge period.Experimental results show that the deintercalated state of the cathode is highly correlated to self-heating parasitic reactions.Before reaching the upper limit of Negative/Positive(N/P)ratio,the temperature changes little,the heat generation is significantly induced by the reversible heat(endothermic)and ohmic heat,which could balance each other.Following that the lithium metal is gradually deposited on the surface of the anode and reacts with electrolyte upon overcharge,inducing selfheating side reaction.However,this spontaneous thermal reaction could be“self-extinguished”.When the lithium in cathode is completely deintercalated,the boundary point of overcharge is about 4.7 V(~148%SOC,>40℃),and from this point,the self-heating behaviour could be continuously triggered until thermal runaway(TR)without additional overcharge.The whole static and spontaneous process lasts for 115 h and the side reaction heat is beyond 320,000 J.The continuous self-excitation behavior inside the battery is attributed to the interaction between the highly oxidized cathode and the solvent,which leads to the dissolution of metal ions.The dissolved metal ions destroy the SEI(solid electrolyte interphase)film on the surface of the deposited Li of anode,which induces the thermal reaction between lithium metal and the solvent.The interaction between cathode,the deposited Li of anode,and solvent promotes the temperature of the battery to rise slowly.When the temperature of the battery reaches more than 60℃,the reaction between lithium metal and solvent is accelerated.After the temperature rises rapidly to the melting point of the separator,it triggers the thermal runaway of the battery due to the short circuit of the battery.

原位聚合法制备聚苯乙烯/Laponite纳米复合乳液及其性能表征

首先通过甲基丙烯酸二甲氨基乙酯与溴乙烷反应制得N,N,N,N-二甲基乙基甲基丙烯酰氧乙基溴化铵,利用该季铵盐对纳米片层材料Laponite进行化学改性来提高Laponite与苯乙烯(St)的相容性,然后以辛基苯酚聚氧乙烯(10)醚(OP-10)为助乳化剂通过原位Pickering乳液聚合制备了PSt/Laponite复合乳液。利用透射电镜、扫描电镜、X射线衍射、差示扫描量热分析、热重分析等测试手段探究了乳化体系、改性程度等对复合乳液的制备及性能的影响。最后,将PSt/Laponite复合乳液与苯丙乳液(PSB)共混后成膜,考察了PSt/Laponite复合乳液用量及Laponite改性程度对复合乳胶膜力学性能和透水汽性的影响。结果表明,OP-10与Laponite复配有助于获得稳定的PSt/Laponite复合乳液,Laponite的改性程度对复合微球的大小及形貌有重要影响,Laponite的引入亦使复合体系的Tg和热稳定性有所改善;将5%PSt/Laponite组分引入PSB体系所得乳胶膜拉伸强度(Rm)由8.3MPa提升至14.8MPa,同时其透水汽性较加入同比例不改性PSt/Laponite复合乳液所得乳胶膜提升了19%。

Effects of square micro-pillar array porosity on the liquid motion of near surface layer

The influence rules of square micro-pillar array porosity on the liquid motion characteristics of the near-surface layer are investigated by quartz crystal microbalance(QCM).QCM is a powerful and promising technique in studying the interfacial behavior,which exhibits great advantages in investigating the effects of surface microstructure,roughness,and array.In our experiments,three different arrays with the same height of about 280 nm and center distance of 200μm,but different diameters of about 78μm,139μm,and 179μm are investigated.The results indicate that when the surface array has a large porosity,its influence on the liquid motion of the near surface layer is slight,thus resulting in a small increase of half-bandwidth variation due to the additional friction energy dissipation.When the surface array has a small porosity,the array tends to make the liquid film trapped in the array oscillating with the substrate,then there may be a layer of liquid film behaving like rigid film,and it also will make the liquid motion near the array layer more complicated.Thus for the#3 surface with a small porosity,both the absolute values of frequency shift|Δf3|and half-bandwidth variationΔΓ3 increase obviously.The experimental results show good consistence with the theoretical model of Daikhin and Urbakh.This study sheds light on understanding the influence mechanism of surface array porosity on the liquid motion of near-surface layer.

基于正交实验的赤苍藤组培快繁体系建立

以赤苍藤(Erythropalum scandens)带芽点的半木质化枝条为材料建立赤苍藤组培快繁体系,研究外植体灭菌条件,通过正交实验,设计不同植物生长调节剂组合对赤苍藤愈伤组织诱导、愈伤组织分化、生根壮苗及移栽驯化的影响。结果表明,赤苍藤外植体消毒最佳方法是以体积浓度为75%乙醇浸泡60秒后,再以质量浓度为0.1%HgCl_2消毒10分钟,成功率为48.89%;叶片愈伤组织诱导的最佳培养基为MS+0.5 mg·L^(-1) 6-BA+1.0 mg·L^(-1) 2,4-D+1.0 mg·L^(-1) IBA,培养30天,诱导率达71.11%,且绿色紧密;茎段诱导愈伤组织的最佳培养基为MS+1.0 mg·L^(-1) 6-BA+0.5 mg·L^(-1) 2,4-D+1.0 mg·L^(-1) IBA,培养30天,诱导率为70.00%,且绿色紧密;诱导愈伤组织增殖以及分化的最佳培养基为MS+2.0mg·L^(-1) 6-BA+0.5mg·L^(-1)TDZ+1.0 mg·L^(-1) IBA,芽分化率达98.89%,增殖系数为3.33;生根最佳培养基为MS+1.5 mg·L^(-1) 6-BA+0.5 mg·L^(-1) IBA,生根率为100%,平均生根数为2.2条;生根苗在小颗粒泥炭土中成活率达88.89%。该研究建立了赤苍藤组培快繁体系,为赤苍藤优质种苗生产奠定了良好基础。

Education Platform of Congenital Heart Disease Based on Mixed Reality Technology

Recently the Mixed Reality (MR) technology has a rapid development and strong application prospect in various fields. This technology has been successfully applied in clinical work by means of surgical navigation and puncture positioning. However, there is few reports about MR technology’s applications in China. Therefore, based on the MR technology, a medical education platform was designed for related professions through the reconstruction of 3D heart model. Because of the various types of congenital heart diseases and the comprehensive medical knowledge system involved, it will start from congenital heart disease and expand to other organs later. The teaching mode was enriched and basic and clinical teaching materials were provided. And students’ interests were motivated and learning efficiency was strengthened. An equal communication mechanism between teachers and students was constructed. Experimental results show that both teachers and students benefit from this proposed platform.

An object detection method for bayberry trees based on an improved YOLO algorithm

To quickly detect and count the number of bayberry trees,this paper improves the YOLO-v4 model and proposes an optimal YOLO-v4 method for detecting bayberry trees based on UAV images.We used the Leaky_ReLU activation function to accelerate the model extraction speed and used the DIoU NMS to retain the most accurate prediction boxes.In order to increase the recall rate of the object detection and construct the optimal YOLO-v4 model,the K-Means clustering method was embedded into DIoU NMS.We trained the model using UAV images of bayberry trees,it was determined that the optimal YOLO-v4 model threshold was 0.25,which had the best extraction effect.The optimal YOLO-v4 model had a detection accuracy of up to 97.78%and a recall rate of up to 98.16%on the dataset.The optimal YOLO-v4 model was compared with YOLO-v4,YOLO-v4 tiny,the YOLO-v3 model,and the Faster R-CNN model.With guaranteed accuracy,the recall rate was higher,up to 97.45%,and the detection of bayberry trees was better in different contexts.The result shows that the optimal YOLO-v4 model can accurately achieve the rapid detection and statistics of the number of bayberry trees in large-area orchards.

A correlation analysis method for analyzing tribological states using acoustic emission, frictional coefficient, and contact resistance signals

A multi-physical signal correlation analysis method is proposed to identify the different tribological properties of materials.The acoustic emission(AE),contact resistance,and frictional force behaviors during dry sliding between four metals,45#carbon steel,YG12 carbide,2A12 aluminum alloy,and H62 brass,have been studied.Both positive and negative correlations between the root mean square of the amplified AE(AE RMS)signal and the frictional coefficient have been found in the experiments.In addition,the AE RMS signal and the contact resistance changed with changing sliding speed and normal load in different ways.The different correlation behaviors have been attributed to diverse tribological states under different experimental conditions due to different material characteristics.The correlation analysis provides a new method of quantitatively identifying the tribological states and the AE sources during frictional interaction.The observed anomalous correlations between the AE signal and frictional coefficient should be properly considered according to the different material properties during industrial friction condition monitoring using AE technology.

Reviving chloroquine for anti-SARS-CoV-2 treatment with cucurbit[7]uril-based supramolecular formulation

The wide-spreading SARS-CoV-2 virus has put the world into boiling water for more than a year,however pharmacological therapies to act effectively against coronavirus disease 2019(COVID-19)remain elusive.Chloroquine(CQ),an antimalarial drug,was found to exhibit promising antiviral activity in vitro and in vivo at a high dosage,thus CQ was approved by the FDA for the emergency use authorization(EUA)in the fight against COVID-19 in the US,but later was revoked the EUA status due to the severe clinical toxicity.Herein,we show that supramolecular formulation of CQ by a macrocyclic host,curcurbit[7]uril(CB[7]),reduced its non-specific toxicity and improved its antiviral activity against coronavirus,working in synergy with CB[7].CB[7]was found to form 1:1 host-guest complexes with CQ,with a binding constant of$104 L/mol.The CQ-CB[7]formulation decreased the cytotoxicity of CQ against Vero E6 and L-02 cell lines.In particular,the cytotoxicity of CQ(60 mmol/L)against both Vero E6 cell line and L-02 cell lines was completely inhibited in the presence of 300 mmol/L and 600 mmol/L CB[7],respectively.Furthermore,the CB[7]alone showed astonishing antiviral activity in SARS-CoV-2 infected Vero E6 cells and mouse hepatitis virus strain A59(MHV-A59)infected N2 A cells,and synergistically improved the antiviral activity of CQ-CB[7],suggesting that CB[7]-based CQ formulation has a great potential as a safe and effective antiviral agent against SARS-CoV-2 and other coronavirus.

Winter wheat leaf area index inversion by the genetic algorithms neural network model based on SAR data

The leaf area index(LAI)is an important agroecological physiological parameter affecting vegetation growth.To apply the genetic algorithms neural network model(GANNM)to the remote sensing inversion of winter wheat LAI throughout the growth cycle and based on GaoFen-3 Synthetic aperture radar(GF-3 SAR)images and GaoFen-1 Wide Field of View(GF-1 WFV)images,the Xiangfu District in the east of Kaifeng City,Henan Province,was selected as the testing region.Winter wheat LAI data from five growth stages were combined,and optical and microwave polarization decomposition vegetation index models were used.The backscattering coefficient was extracted by modified water cloud model(MWCM),and the LAI was obtained by MWCM inversion as input factors to construct GANNM to invert LAI.The root mean square error(RMSE)and determination coefficient(R2)were used as evaluation indicators of the model.The fitting accuracy of winter wheat LAI in five growth stages by GANNM inversion was better than that of the BP neural network model;the R2 was higher than 0.8,and RMSE was lower than 0.3,indicating that the model could accurately invert the growth status of winter wheat in five growth stages.

Cucurbit[7]uril as a Broad-Spectrum Antiviral Agent against Diverse RNA Viruses

The emergence and re-emergence of RNA virus outbreaks highlight the urgent need for the development of broadspectrum antivirals.Polyamines are positively-charged small molecules required for the infectivity of a wide range of RNA viruses,therefore may become good antiviral targets.Cucurbit[7]uril(CB[7]),a synthetic macrocyclic molecule,which can bind with amine-based organic compounds with high affinity,has been shown to regulate bioactive molecules through competitive binding.In this study,we tested the antiviral activity of CB[7]against diverse RNA viruses,including a panel of enteroviruses(i.e.human enterovirus A71,coxsackievirus A16,coxsackievirus B3,and echovirus 11),some flaviviruses(i.e.dengue virus and Zika virus),and an alphavirus representative Semliki forest virus.CB[7]can inhibit virus replications in a variety of cell lines,and its mechanism of action is through the competitive binding with polyamines.Our findings not only for the first time provide evidence that CB[7]can be a promising broad-spectrum antiviral agent,but more importantly,offer a novel therapeutic strategy to fight against RNA viruses by supramolecular sequestration of polyamines.