Mechanism of internal thermal runaway propagation in blade batteries

Blade batteries are extensively used in electric vehicles,but unavoidable thermal runaway is an inherent threat to their safe use.This study experimentally investigated the mechanism underlying thermal runaway propagation within a blade battery by using a nail to trigger thermal runaway and thermocouples to track its propagation inside a cell.The results showed that the internal thermal runaway could propagate for up to 272 s,which is comparable to that of a traditional battery module.The velocity of the thermal runaway propagation fluctuated between 1 and 8 mm s^(-1),depending on both the electrolyte content and high-temperature gas diffusion.In the early stages of thermal runaway,the electrolyte participated in the reaction,which intensified the thermal runaway and accelerated its propagation.As the battery temperature increased,the electrolyte evaporated,which attenuated the acceleration effect.Gas diffusion affected thermal runaway propagation through both heat transfer and mass transfer.The experimental results indicated that gas diffusion accelerated the velocity of thermal runaway propagation by 36.84%.We used a 1D mathematical model and confirmed that convective heat transfer induced by gas diffusion increased the velocity of thermal runaway propagation by 5.46%-17.06%.Finally,the temperature rate curve was analyzed,and a three-stage mechanism for internal thermal runaway propagation was proposed.In Stage I,convective heat transfer from electrolyte evaporation locally increased the temperature to 100℃.In Stage II,solid heat transfer locally increases the temperature to trigger thermal runaway.In StageⅢ,thermal runaway sharply increases the local temperature.The proposed mechanism sheds light on the internal thermal runaway propagation of blade batteries and offers valuable insights into safety considerations for future design.

Multi-Objective Optimization of Aluminum Alloy Electric Bus Frame Connectors for Enhanced Durability

The widespread adoption of aluminumalloy electric buses,known for their energy efficiency and eco-friendliness,faces a challenge due to the aluminum frame’s susceptibility to deformation compared to steel.This issue is further exacerbated by the stringent requirements imposed by the flammability and explosiveness of batteries,necessitating robust frame protection.Our study aims to optimize the connectors of aluminum alloy bus frames,emphasizing durability,energy efficiency,and safety.This research delves into Multi-Objective Coordinated Optimization(MCO)techniques for lightweight design in aluminum alloy bus body connectors.Our goal is to enhance lightweighting,reinforce energy absorption,and improve deformation resistance in connector components.Three typical aluminum alloy connectors were selected and a design optimization platform was built for their MCO using a variety of software and methods.Firstly,through three-point bending experiments and finite element analysis on three types of connector components,we identified optimized design parameters based on deformation patterns.Then,employing Optimal Latin hypercube design(OLHD),parametric modeling,and neural network approximation,we developed high-precision approximate models for the design parameters of each connector component,targeting energy absorption,mass,and logarithmic strain.Lastly,utilizing the Archive-based Micro Genetic Algorithm(AMGA),Multi-Objective Particle Swarm Optimization(MOPSO),and Non-dominated SortingGenetic Algorithm(NSGA2),we explored optimized design solutions for these joint components.Subsequently,we simulated joint assembly buckling during bus rollover crash scenarios to verify and analyze the optimized solutions in three-point bending simulations.Each joint component showcased a remarkable 30%–40%mass reduction while boosting energy absorption.Our design optimization method exhibits high efficiency and costeffectiveness.Leveraging contemporary automation technology,the design optimization platform developed in this study is poised to facilitate intelligent optimization of lightweight metal components in future applications.

Heterogeneous body compositions and all-cause mortality in acute coronary syndrome patients:a ten-year retrospective cohort study

BACKGROUND The association of different body components,including lean mass and body fat,with the risk of death in acute coronary syndrome(ACS)patients are unclear.METHODS We enrolled adults diagnosed with ACS at our center between January 2011 and December 2012 and obtained fol-low-up outcomes via telephone questionnaires.We used restricted cubic splines(RCS)with the Cox proportional hazards model to analyze the associations between body mass index(BMI),predicted lean mass index(LMI),predicted body fat percentage(BF),and the value of LMI/BF with 10-year mortality.We also examined the secondary outcome of death during hospitalization.RESULTS During the maximum 10-year follow-up of 1398 patients,331 deaths(23.6%)occurred,and a U-shaped relationship was found between BMI and death risk(P_(nonlinearity)=0.03).After adjusting for age and history of diabetes,the overweight group(24≤BMI<28 kg/m^(2))had the lowest mortality(HR=0.53,95%CI:0.29-0.99).Predicted LMI and LMI/BF had an inverse linear relationship with a 10-year death risk(P_(nonlinearity)=0.24 and P_(nonlinearity)=0.38,respectively),while an increase in BF was associ-ated with increased mortality(P_(nonlinearity)=0.64).During hospitalization,31 deaths(2.2%)were recorded,and the associations of the indicators with in-hospital mortality were consistent with the long-term outcome analyses.CONCLUSION Our study provides new insight into the“obesity paradox”in ACS patients,highlighting the importance of considering body composition heterogeneity.Predicted LMI and BF may serve as useful tools for assessing nutritional status and predicting the prognosis of ACS,based on their linear associations with all-cause mortality.

Effects of Different Seed Stem Sizes on the Changes of Available Elements in Rhizosphere Soil of Fritillaria thunbergii Miq.

[Objectives]This study was conducted to screen suitable seed stems of Fritillaria thunbergii Miq.from different provenances and to provide a theoretical basis for the high-yielding and high-efficiency cultivation of F.thunbergii Miq.introduced to different places.[Methods]F.thunbergii Miq.from four different provenances including Zhejiang,Nantong and Chongqing were introduced and cultivated in Wanzhou of Chongqing.The contents of available Zn,Fe,Mn,Cu,Mo,N,P,K,Ca and Mg in rhizosphere soil of F.thunbergii Miq.during five growing stages were determined after selecting different stem sizes for field cultivation.[Results]Small stems of Pan an and Ningbo provenances(SSG3,121-160/kg)and middle stems of Nantong and Fengjie provenances(SSG2,81-120/kg)showed higher soil availability.[Conclusions]In the process of introduction and cultivation of F.thunbergii Miq.,high yield and high efficiency can be achieved by selecting smaller seed stems of F.thunbergii Miq.

地方高校应用型人才全过程培养实践教学平台体系探析

培养符合社会和国家需求的人才是高校育人的首要目标。近年来随着国家“新工科”建设项目的实施和“三全育人”理念的倡导,在新形势下如何培养出满足社会和国家发展需求的高素质复合型人才,已成为高校人才培养过程中急需解决的问题。建设人才全过程培养实践教学平台体系不仅可以培养学生的工程实践能力,还可以提高学生的创新思维能力和对理论知识的运用。土木工程类专业具有很强实践性,实践性教学是保证其人才培养质量的重要环节之一。为培养学生的创新实践和应用能力,在人才培养方案制定过程中,将校内实践平台与校外实习基地资源相融合,构架一体化全过程应用型人才培养实践教学平台体系,是地方高校土木工程类专业人才培养的重要途径和方法。通过对所在高校土木工程类专业人才培养实践平台及校外实习基地等现有实践教学资源的调研与分析,从全过程应用型人才培养所需实践平台体系的顶层设计、交叉融合综合实践平台构建、持续稳定校企协同育人机制建立、复合型实践教学团队组建及递进式实践教学体系设立等方面,探讨与分析了应用型人才全过程培养实践平台体系的构建途径和方法,以为地方高校培养应用型人才培养提供参考。

The influence of pressure injury risk on the association between left ventricular ejection fraction and all-cause mortality in patients with acute myocardial infarction 80 years or older

BACKGROUND: We aimed to investigate whether the pressure injury risk mediates the association of left ventricular ejection fraction(LVEF) with all-cause death in patients with acute myocardial infarction(AMI) aged 80 years or older.METHODS: This retrospective cohort study included 677 patients with AMI aged 80 years or older from a tertiary-level hospital. Pressure injury risk was assessed using the Braden scale at admission, and three risk groups(low/minimal, intermediate, high) were defined according to the overall score of six different variables. LVEF was measured during the index hospitalization for AMI. All-cause death after hospital discharge was the primary outcome.RESULTS: Over a median follow-up period of 1,176 d(interquartile range [IQR], 722–1,900 d), 226(33.4%) patients died. Multivariate Cox regression analysis showed that reduced LVEF was associated with an increased risk of all-cause death only in the high-risk group of pressure injury(adjusted hazard ratios [HR]=1.81, 95% confidence interval [CI]: 1.03–3.20;P=0.040), but not in the low/minimal-(adjusted HR=1.29, 95%CI: 0.80–2.11;P=0.299) or intermediate-risk groups(adjusted HR=1.14, 95%CI: 0.65–2.02;P=0.651). Significant interactions were detected between pressure injury risk and LVEF(adjusted P=0.003). The cubic spline with hazard ratio plot revealed a distinct shaped curve relation between LVEF and all-cause death among different pressure injury risk groups.CONCLUSIONS: In older patients with AMI, the risk of pressure injury mediated the association between LVEF and all-cause death. The classification of older patients for both therapy and prognosis assessment appears to be improved by the incorporation of pressure injury risk assessment into AMI care management.

Geometric Accuracy and Energy Absorption Characteristics of 3D Printed Continuous Ramie Fiber Reinforced Thin-Walled Composite Structures

The application of continuous natural fibers as reinforcement in composite thin-walled structures offers a feasible approach to achieve light weight and high strength while remaining environmentally friendly.In addition,additive manufacturing technology provides a favorable process foundation for its realization.In this study,the printability and energy absorption properties of 3D printed continuous fiber reinforced thin-walled structures with different configurations were investigated.The results suggested that a low printing speed and a proper layer thickness would mitigate the printing defects within the structures.The printing geometry accuracy of the structures could be further improved by rounding the sharp corners with appropriate radii.This study successfully fabricated structures with vari-ous configurations characterized by high geometric accuracy through printing parameters optimization and path smoothing.Moreover,the compressive property and energy absorption characteristics of the structures under quasi-static axial compression were evaluated and compared.It was found that all studied thin-walled structures exhibited progressive folding deformation patterns during compression.In particular,energy absorption process was achieved through the combined damage modes of plastic deformation,fiber pullout and delamination.Furthermore,the com-parison results showed that the hexagonal structure exhibited the best energy absorption performance.The study revealed the structure-mechanical property relationship of 3D printed continuous fiber reinforced composite thin-walled structures through the analysis of multiscale failure characteristics and load response,which is valuable for broadening their applications.

Mitigating thermal runaway hazard of high-energy lithium-ion batteries by poison agent

Lithium-ion batteries with high-energy density are extensively commercialized in long-range electric vehicles. However, they are poor in thermal stability and pose fire or explosion, which has attracted the global attention. This study describes a new route to mitigate the battery thermal runaway(TR) hazard by poison agents. First, the self-destructive cell is built using the embedded poison layer. Then, the poisoning mechanism and paths are experimentally investigated at the material, electrode, and cell levels. Finally, the proposed route is verified by TR tests. The results show the TR hazard can be significantly reduced in the self-destructive cell based on a new reaction sequence regulation. Specifically, the maximum temperature of the self-destructive cell is more than 300℃ lower than that of the normal cell during TR. The drop in maximum temperature can reduce total heat release and the probability of TR propagation in the battery system, significantly improving battery safety.

Electrolyte induced synergistic construction of cathode electrolyte interphase and capture of reactive free radicals for safer high energy density lithium-ion battery

As the energy density of battery increases rapidly,lithium-ion batteries(LIBs)are facing serious safety issue with thermal runaway,which largely limits the large-scale applications of high-energy-density LIBs.It is generally agreed that the chemical crosstalk between the cathode and anode leads to thermal runaway of LIBs.Herein,a multifunctional high safety electrolyte is designed with synergistic construction of cathode electrolyte interphase and capture of reactive free radicals to limit the intrinsic pathway of thermal runaway.The cathode electrolyte interphase not only resists the gas attack from the anode but suppresses the parasitic side reactions induced by electrolyte.And the function of free radical capture has the ability of reducing heat release from thermal runaway of battery.The dual strategy improves the intrinsic safety of battery prominently that the triggering temperature of thermal runaway is increased by 24.4℃and the maximum temperature is reduced by 177.7℃.Simultaneously,the thermal runaway propagation in module can be self-quenched.Moreover,the electrolyte design balances the trade-off of electrochemical and safety performance of high-energy batteries.The capacity retention of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)|graphite pouch cell has been significantly increased from 53.85%to 97.05%with higher coulombic efficiency of 99.94%at operating voltage extended up to 4.5 V for 200 cycles.Therefore,this work suggests a feasible strategy to mitigate the safety risk of high-energy-density LIBs without sacrificing electrochemical performances.

γδT细胞在小鼠自身免疫性葡萄膜炎中保护作用的实验研究

目的:γδT细胞在自身免疫性葡萄膜炎(EAU)中的作用尚不完全清楚。以往认为γδT细胞可能是诱导免疫炎症反应的重要启动因素,但体内研究结果:不一。本文拟探讨γδT细胞在EAU的发病中的致病或保护作用。方法:分离纯化小鼠γδT细胞,体外抗原激活后输注于野生型B6小鼠;用GL3抗体注射法清除野生型B6小鼠体内的γδT细胞;或直接使用γδT细胞基因敲除小鼠,IRBP1-20免疫法制作小鼠EAU模型,观察小鼠眼球炎症的临床评分和病理改变,与野生型B6小鼠的EAU模型相比较。结果:1)EAU时γδT细胞数量明显增加;2)早期活化的γδT细胞主要产生和表达IL-17;3)预先输注活化的γδT细胞后,IRBP1-20诱导的EAU眼球炎症明显减轻;4)GL3清除γδT细胞后,EAU眼球炎症明显加重,γδT细胞基因敲除小鼠的EAU眼球炎症明显加重;5)缺乏γδT细胞的小鼠预先输注γδT细胞后,EAU炎症明显减轻。结论:激活的γδT细胞在EAU发病中可能起到控制免疫炎症不致失控的保护作用,这种保护作用可能是通过产生IL-17实现的。

基于Seislet分数阶阈值算法约束的平面波最小二乘逆时偏移

基于平面波编码的平面波最小二乘逆时偏移存在两个问题,即炮数据混叠引入串扰噪音以及平面波道集数目过多又会降低计算效率。针对上述问题,将适用于地震数据的Seislet变换和应用Riemann-Liouville分数阶积分理论的分数阶阈值函数相结合,并将其引入到平面波编码的最小二乘逆时偏移中,实现基于Seislet分数阶阈值算法约束的平面波最小二乘逆时偏移。在实现该方法的基础上,对简单层状模型和复杂模型进行成像测试。结果表明,地震数据在Seislet域中具有较好的稀疏性,且基于Seislet分数阶阈值算法约束的平面波最小二乘逆时偏移能够有效地压制炮数据混叠引起的串扰噪音,同时能够用较少的平面波道集得到与普通方法相同的成像效果,提高了计算效率。

文峪河流域森林群落植物种间联结性

采用方差比率(VR)确定群落总体关联度,基于2×2列联表,以χ^2统计量为基础,以共同出现百分率PC和联结系数AC确定物种间联结性的方法,对文峪河流域主要植物群落的种间关联性进行了研究。结果表明:乔木层种间总体关联性表现出不显著正关联,灌木层、草本层种间总体关联性表现为显著正关联。乔木层中,侧柏-油松、油松-辽东栎种对关联度达到显著水平;灌木层中,胡枝子-照山白种间关系存在显著的正联结性,杭子梢-蒙古荚迷种间关系存在极显著的正联结性,三裂绣线菊-土庄绣线菊种间关系存在极显著的负联结性;草本层中只有堇菜-糙苏1个种对种间关系存在显著的正联结性。其它种对关联度均未达到显著水平。具有相同生态习性的物种间正联结性较强,微生境差异是淡化种间关系的因素之一。

强剪切流动下聚丙烯基复合材料介电性能和结构演变的研究

研究了多壁碳纳米管(MWCNT)、线型低密度聚乙烯(LLDPE)和强剪切流动场对聚丙烯(PP)/MWCNT/LLDPE复合材料的导电性能、结晶性能、力学性能和介电性能的研究。结果表明,PP/MWCNT复合材料随着MWCNT含量的提高,导电性能逐步改善,导电逾渗值约为1.8%,而第二分散相LLDPE的引入使复合材料的导电性能表现出了先降低后升高的现象,并且随着LLDPE含量的增加,MWCNT逐步向LLDPE内部迁移,构成了双连续结构。复合材料经过固态口模拉伸的强剪切流动场之后,随着拉伸速率从10 mm/min增加到300 mm/min的过程中,复合材料的融化温度逐渐向高温方向偏移,表现出了片层厚度增加的现象。复合材料内部分子链取向和纤维结构的形成,能够显著提高复合材料的拉伸强度和介电性能,拉伸强度提高从约50 MPa提高到了约240 MPa,提高了约380%。MWCNT和强剪切流动场的引入也使复合材料的介电常数大幅提升。

基于最佳平方逼近的TTI介质解耦qP波与qSV波逆时偏移

在实际地震资料处理中,若忽略各向异性影响、TTI介质对称轴倾角变化,会造成目标体成像位置偏差,甚至由焦散问题造成振幅不均衡。传统TI介质耦合拟声波方程正演模拟与逆时偏移存在伪横波干扰,且在各向异性参数ε<δ时数值模拟不稳定。为此,借鉴前人经验,首先使用最佳平方逼近(OQA)近似VTI介质精确相速度公式,分别得到较高精度的近似qP波、qSV波相速度公式。然后从近似相速度公式出发,推导了二维TTI介质解耦qP波、qSV波波动方程。为实现高效、稳定的数值模拟,使用有限差分-伪谱混合法求解波动方程。最终,建立了高精度、高效率、稳定的TTI介质正演模拟与逆时偏移成像算法。数值模拟实验表明,所提方法可实现复杂TTI介质偏移成像。

明清民族事务处理和边疆管理的共同追求

明清两朝在处理民族事务和管理边疆时,存在许多共同之处,如建国之初,都面临重建国家意识形态、完成新的儒家化治理体系的任务,都在“大一统”观念的指导下,采取了务实灵活的边疆民族管理政策,积极应对西方殖民者的挑战,为国家的统一和稳定作出了卓越的贡献,促进了边疆地区的大发展和中华各民族的大融合,创造了一批优秀的中华民族传统文化,成为中华各民族共同的精神财富。

集成磁共振成像在轻微型肝性脑病临床应用中的初探

目的探究集成磁共振成像(synthetic magnetic resonance imaging,SyMRI)技术对轻微型肝性脑病(minimal hepatic encephalopathy,MHE)患者脑实质内特定区域弛豫值、质子密度(proton density,PD)值定量检测的价值。材料与方法前瞻性纳入2020年8月至2021年11月在宁夏医科大学总医院感染疾病科经临床诊断为肝硬化的住院患者并根据神经精神量表筛选出MHE患者23名为MHE组。同期招募年龄、性别及受教育程度等相匹配的健康志愿者20名为健康对照(healthy control,HC)组。所有受试者均在3.0 T MRI扫描仪上行SyMRI扫描,选取双侧尾状核、壳核、苍白球、背侧丘脑及额叶白质为感兴趣区(region of interest,ROI),并分别测量T1、T2及PD值。采用组内相关系数(intraclass correlation coefficient,ICC)评价观察者间数据测量的一致性,采用Mann-Whitney U秩和检验对MHE组及HC组T1、T2及PD值进行比较并统计其在两组间的差异及诊断效能。结果两名医师对脑实质各ROI的T1、T2及PD值测量的一致性较好,ICC值分别为0.863、0.822、0.816。除双侧额叶白质外,MHE组较HC组部分亚区T1、T2及PD值降低,差异具有统计学意义(P<0.05)。T1值中双侧壳核、右侧苍白球在MHE组及HC组间差异具有统计学意义;T2值中右侧尾状核、双侧壳核及左侧苍白球在MHE组及HC组间差异具有统计学意义;PD值中右侧壳核在MHE组及HC组间差异具有统计学意义。与HC组相比,MHE组双侧额叶T1值及PD值升高,差异具有统计学意义(P<0.05)。右侧额叶的PD值诊断效能最高,受试者工作特征曲线下面积为0.901。结论SyMRI对MHE患者各脑区弛豫值具有较好的定量能力,其T1、T2及PD值在检出MHE患者中有一定的潜在价值。

平面波优化差分算子弹性波逆时偏移

弹性波逆时偏移基于双程波动方程理论,不受倾角限制,对复杂模型具有较强的适应性,但高额的计算量和内存占用是其用于巨量地震资料处理的主要瓶颈。为此,推导了一种基于平面波优化的等效交错网格弹性波逆时偏移成像方法,通过优化差分系数降低正演波场的频散误差,达到使用低阶优化差分算子替代高阶传统差分算子、降低计算量的目的。在内存需求方面,采用二阶位移弹性波方程,避免了中间变量的出现,且引入了有效边界存储的策略,只利用边界附近区域的部分波场值控制逆时偏移的波场存储方式。模型测试表明:该方法6、10阶空间差分算子逆时偏移结果成像精度分别相当于10、18阶传统方法,有效节约了计算成本;相比于常规弹性波逆时偏移的波场存储方式,有效边界存储在增加部分计算量的前提下,能节约大量内存占用,且使用的差分算子长度越短,内存占用也越少。

合成扩散加权成像评估脑胶质瘤分级的应用研究

目的探讨合成扩散加权成像(synthetic DWI,sDWI)在高低级别胶质瘤评估中的应用价值。材料与方法回顾性分析术前一周行颅脑MRI(GE Signa Architect 3.0 T)检查的脑胶质瘤患者,根据纳入排除标准纳入72例患者病例(低级别胶质瘤30例,高级别胶质瘤42例),两名神经影像诊断医师采用双盲法在sDWI上对图像进行评估勾画病灶感兴趣区,对不同b值对应DWI图像信号强度进行分析并与最终病理结果进行对照。两组间比较使用独立样本t检验,使用logistic回归和受试者工作特征曲线下面积(area under the curve,AUC)分析评估高低级别胶质瘤诊断效能。结果在鉴别高低级别胶质瘤方面,sDWI b值为500、800、1000、1200、1500、1800、2000、2200、2500 s/mm^(2)对应的信号强度值,差异均有统计学意义(P<0.001),b值为2500 s/mm^(2)时鉴别高低级别胶质瘤的诊断效能最高,AUC为0.935,敏感度为98%,特异度为87%。结论sDWI单次扫描可获得0~2500 s/mm^(2)任意b值对应的信号强度值,b值越高对胶质瘤分级的诊断效能越高。

基于Seislet域分数阶阈值去噪算法的地震资料去噪

相较于由图像领域发展的去噪算法,Seislet阈值去噪算法更好适用于地震数据的去噪处理,但在Seislet阈值去噪算法中,常规硬阈值函数在阈值处存在断点,软阈值函数处理得到的系数与原有系数之间存在恒定偏差,且传统阈值确定准则难以适用于Seislet域。为此,将Riemann-Liouville分数阶积分理论应用到阈值函数中,推导出分数阶阈值函数;再根据地震数据在Seislet域低尺度中有效信号分量远多于高尺度中有效信号分量的特点,提出了一种适用于Seislet域的尺度加权阈值;最后将分数阶阈值函数、尺度加权阈值和Seislet稀疏变换相结合,得到Seislet域分数阶阈值去噪算法。人工合成含噪地震记录和实际地震资料测试结果表明:常规硬阈值和软阈值去噪算法虽然能够在一定程度上压制噪声,但压制效果并不明显,且容易损伤与噪声差异较小的有效信号;分数阶阈值去噪算法较好地克服了硬阈值和软阈值去噪算法的缺点,能够有效压制地震资料中的随机噪声,减少了有效信号的损失,提高了地震资料的信噪比。

伪深度域弹性波有限差分数值模拟及逆时偏移

有限差分法地震波场外推通常基于笛卡尔坐标系,当地下介质速度差异很大时,会导致波场的局部过采样现象,增加计算量。为此,将伪深度域的思想引入到弹性波有限差分数值模拟。首先通过坐标转换的链式法则,推导了深度域到伪深度域的坐标映射关系,获得了伪深度域下的弹性波方程(PDD-EWE),在保证精度的前提下,在伪深度域进行波场外推能减少大量内存占用;引入变长度差分算子,即在一定的误差范围内,根据速度的不同设计了不同长度的差分算子。模型测试结果表明,与常规深度域方法相比,伪深度域变长度差分算子弹性波正演模拟和成像算法在保证精度的前提下,既能减少内存占用又能提高计算效率。