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New Blast Damage Criterion for Damage Prediction 认领
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作者 Ajay Kumar Jha 《地质资源与工程:英文版》 2020年第2期42-54,共13页
There are several underground mines in India which operate in close proximity to an operating surface mine.Under such scenario,the blast induced stress waves generated due to surface blasting may be a potential source... There are several underground mines in India which operate in close proximity to an operating surface mine.Under such scenario,the blast induced stress waves generated due to surface blasting may be a potential source to cause instability of adjoining underground mine structures.Using seismographs,54 blast induced vibration data were recorded at various locations in the roof,floor and pillars of the underground mine at Hingir Rampur mine of Coal India Limited by synchronizing the timing of surface blasting carried at an adjacent Samleshwari opencast mine.Results of this study show that Artificial Neural Network(ANN)has better prediction potential of peak particle velocity(PPV)and damage to adjacent underground structures due to surface blasting as compared to conventional regression methods.In order to assess and predict the impact of surface blasts on underground workings,Blast Damage Factor(BDF)has been evolved.The study shows that site specific charts can predict the blast damage class at an underground location due to surface blasting for known distances and explosive charge per delay.The severe damage in case study mine site took place when peak particle velocity exceeded 162 mm/s and PPV less than 51 mm/s had no probability of damage to underground structures due to surface blasting. 展开更多
关键词 Blast damage prediction blast damage factor underground damage
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Damage characteristics and catastrophic failure mechanism of coal rock induced by gas adsorption under compression 认领
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作者 Xiaochun Xiao Lei Wang +3 位作者 Jun Xu Xiangfeng Lv Pengfei Guo Yishan Pan 《岩石力学与岩土工程学报:英文版》 SCIE CSCD 2020年第3期587-595,共9页
To reveal the damage characteristics and catastrophic failure mechanism of coal rock caused by gas adsorption,physical tests and theoretical methods are employed.The results show that adsorption swelling can damage co... To reveal the damage characteristics and catastrophic failure mechanism of coal rock caused by gas adsorption,physical tests and theoretical methods are employed.The results show that adsorption swelling can damage coal rock,which can be distinguished by fractal dimension.A fitting relationship between the adsorption damage and fractal dimension is proposed by experimental testing and theoretical analysis.High gas adsorption pressure proves to be the dominant factor that leads to coal failure softening and gas outburst disasters.Three main parameters concerning adsorption damage include the change rate of released energy density,the transition difference in the post-peak acoustic emission(AE)b value and the change rate of cumulative AE energy.Results show that all the three parameters present a step-type decreasing change with the increase in fractal dimension,and the fractal dimension shows a linear relationship within the same failure mode.Finally,a method is proposed to evaluate coal rock disaster transformation,based on the aforementioned three main parameters of adsorption damage. 展开更多
关键词 Damage characteristics Catastrophic failure mechanism Adsorption damage Coal rock
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Localization and Degree of Damage Based on Relative Curvature Difference and Frequency Perturbation 认领
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作者 Mengying Li Ziyan Wu +1 位作者 Haifeng Yang Feng Yue 《固体力学学报:英文版》 SCIE EI CSCD 2020年第2期187-204,共18页
This study proposed a damage identification method compared with the existing ones,based on relative curvature difference and frequency perturbation theory,showing sensitivity to local damage by changes in the curvatu... This study proposed a damage identification method compared with the existing ones,based on relative curvature difference and frequency perturbation theory,showing sensitivity to local damage by changes in the curvature mode and high recognition accuracy of frequencies.Considering the relative curvature difference as a damage index,numerical simulation is used for a simply supported beam under single and multiple damage conditions for different damage degrees.The damage is located according to the curvature mode curves,and the damage degree is qualitatively determined.Based on the perturbation theory,the damage equations are established by the changes between frequencies before and after damage,and the damage localization and degree are verified and determined.Effectiveness of the proposed method for identifying damage at different conditions is numerically investigated.This method potentially promotes the development of damage identification of beam structures. 展开更多
关键词 Damage localization.Damage degree Relative curvature difference Frequency perturbation Beam structures
基于一类非局部宏-微观损伤模型的裂纹模拟 认领
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作者 卢广达 陈建兵 《力学学报》 EI CSCD 北大核心 2020年第3期749-762,共14页
结合近场动力学和统一相场理论的基本思想,最近提出了一类非局部宏-微观损伤模型,为固体裂纹扩展模拟提供了新途径.本文在此基础上改进了微观损伤准则,并给出损伤的λ-l语言以刻画固体破坏过程中位移场的不连续程度.在改进模型中,首先... 结合近场动力学和统一相场理论的基本思想,最近提出了一类非局部宏-微观损伤模型,为固体裂纹扩展模拟提供了新途径.本文在此基础上改进了微观损伤准则,并给出损伤的λ-l语言以刻画固体破坏过程中位移场的不连续程度.在改进模型中,首先根据两物质点(即物质点对)之间的变形量,基于相对临界伸长量的历史最大超越程度,给出表征物质键性能退化的微细观损伤.进而,对影响域内的物质键损伤进行空间局部加权平均,获得宏观拓扑损伤.通过引入能量退化函数,建立基于能量的损伤与宏观拓扑损伤之间的关系,由此将其嵌入连续损伤力学基本框架,形成了问题求解的基本方程.该模型是一类非局部化模型,可采用有限单元法进行离散求解,避免了经典局部损伤力学所面临的网格敏感性问题.文中,进一步将其应用于具有强非线性回弹特性的裂纹扩展模拟问题.实例分析表明,本文方法不仅可以把握裂纹扩展模式,而且能够定量刻画裂纹扩展过程中的载荷-变形关系.最后指出了需要进一步研究的问题. 展开更多
关键词 损伤 宏-微观损伤模型 能量退化因子 裂纹 非局部化
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一种混凝土疲劳损伤模型及其有限元实现 认领
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作者 刘凝瑶 陈明祥 《建筑科学》 CSCD 北大核心 2020年第1期7-12,共6页
混凝土结构在疲劳荷载作用下材料行为会发生变化,损伤的累计对结构产生不利的影响,本文提出了一种简单合适的疲劳损伤模型,并应用ABAQUS有限元软件编写UMAT用户子程序将模型数值化实现,该模型能考虑拉压行为的差异、复杂应力状态和低应... 混凝土结构在疲劳荷载作用下材料行为会发生变化,损伤的累计对结构产生不利的影响,本文提出了一种简单合适的疲劳损伤模型,并应用ABAQUS有限元软件编写UMAT用户子程序将模型数值化实现,该模型能考虑拉压行为的差异、复杂应力状态和低应力水平疲劳荷载作用下的损伤累计。本文合理调整模型中的材料参数,得出:在单轴拉伸和压缩荷载作用下,该模型的应力应变关系曲线与混凝土规范规定的曲线基本一致;在简单疲劳荷载作用下,损伤随疲劳荷载作用次数的增加有明显的两个阶段,刚开始缓慢增长,损伤累计到一定程度时快速增长;随着应力水平的降低,混凝土材料的疲劳寿命明显增长。本文提出的疲劳损伤模型,结合数值模拟方法,对于研究混凝土结构在疲劳荷载作用下,损伤累计和应力重分布特点以及损伤累计对结构的整体受力性能的影响等具有一定的意义。 展开更多
关键词 疲劳 损伤 疲劳损伤模型 有限元 子程序 疲劳寿命 数值模拟 混凝土结构
考虑干湿循环的大理岩统计损伤本构模型 认领
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作者 王辉 王伟 +2 位作者 朱鹏辉 李尧 刘志航 《河南科学》 2020年第6期909-915,共7页
为研究大理岩在干湿循环作用下会产生劣化作用,通过对大理岩在干湿循环作用下的力学特性的变化规律,发现随干湿循环次数的增加,劣化作用会呈现减弱的趋势,最终趋于一个恒定值.通过应用细观方法研究了大理岩微元强度,假设大理岩微元强度... 为研究大理岩在干湿循环作用下会产生劣化作用,通过对大理岩在干湿循环作用下的力学特性的变化规律,发现随干湿循环次数的增加,劣化作用会呈现减弱的趋势,最终趋于一个恒定值.通过应用细观方法研究了大理岩微元强度,假设大理岩微元强度分布服从Weibull分布,然后利用连续损伤理论,认为大理岩损伤劣化规律具备连续性,再由Lemaitre提出的应变等效假说以及基于D-P强度破坏准则度量微元强度提出了大理岩考虑干湿循环效应下的统计损伤本构模型,并应用大理岩干湿循环的单轴压缩实验数据与构建的统计损伤本构模型的应力、应变曲线进行模拟拟合.结果表明,所建立的统计损伤本构模型能够较好地反映考虑干湿循环效应下大理岩弹性阶段的损伤,可见该模型具有一定合理性、有效性. 展开更多
关键词 大理岩 干湿循环 劣化 损伤 统计损伤本构模型 拟合 曲线
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Effects of Selected Pesticidal Plants on Termites Affecting Maize Production in Arusha, Tanzania 认领
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作者 Shaban James Patrick A. Ndakidemi Ernest R. Mbega 《美国植物学期刊(英文)》 2020年第3期510-527,共18页
Investigations under laboratory and field conditions were carried out with purpose of understanding the effects of pesticides of Cupressus lusitanica, Tephrosia vogelii, Eucalpytus dalrympleana, Lantana camara and Aza... Investigations under laboratory and field conditions were carried out with purpose of understanding the effects of pesticides of Cupressus lusitanica, Tephrosia vogelii, Eucalpytus dalrympleana, Lantana camara and Azadirachta indica in the control of termites which affect maize production in Arusha, Tanzania. Termites were collected before and during maize season of 2018 and identified at the Tropical Pesticides Research Institute (TPRI) laboratory. A total of 5279 out of 5307 termite species identified belong to genus Macrotermes, 23 species to genus Odontotermes and 5 species were unknown. The results entailed that the area is rich in species of genus Macrotermes. Moreover, concentrations i.e. 5 g, 10 g and 20 g of each botanical were tested for Macrotermes spp. mortality and repellency ability in the laboratory using a completely randomized design (CRD) with three replicates. The results showed that 98.33% Macrotermes spp. mortality was caused by T. vogelii followed by 93.33% recorded from E. dalrympleana after 24 hours. Besides, C. lusitanica repelled Macrotermes spp. by 97% followed by 95% recorded from T. vogelii and E. dalrympleana each. For field trials, 20 g of each botanical was applied using randomized complete block design (RCBD) with four replicates. The results obtained from field indicated that T. vogelii was more effective to protect maize with an average of 6 maize stands and 3.4 kg of dry total weight of maize grains next to positive control per plot. Also, average of 4 maize stands and 3 kg dry total weight of maize grains were recorded from treatments of E. dalrympleana and C. lusitanica each. Such results highlight the potential of developing bio-termiticides from T. vogelii, C. lusitanica and E. dalrympleana to control Macrotermes spp. 展开更多
关键词 Damage MORTALITY Pesticidal Plants REPELLENCY TERMITES MAIZE
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Resatorvid protects against hypoxic-ischemic brain damage in neonatal rats 认领
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作者 Li-Jun Jiang Zhen-Xing Xu +5 位作者 Ming-Fu Wu Gai-Qin Dong Li-Li Zhang Jun-Yan Gao Chen-Xi Feng Xing Feng 《中国神经再生研究:英文版》 SCIE CAS CSCD 2020年第7期1316-1325,共10页
Secondary brain damage caused by hyperactivation of autophagy and inflammatory responses in neurons plays an important role in hypoxic-ischemic brain damage(HIBD).Although previous studies have implicated Toll-like re... Secondary brain damage caused by hyperactivation of autophagy and inflammatory responses in neurons plays an important role in hypoxic-ischemic brain damage(HIBD).Although previous studies have implicated Toll-like receptor 4(TLR4)and nuclear factor kappa-B(NF-κB)in the neuroinflammatory response elicited by brain injury,the role and mechanisms of the TLR4-mediated autophagy signaling pathway in neonatal HIBD are still unclear.We hypothesized that this pathway can regulate brain damage by modulating neuron autophagy and neuroinflammation in neonatal rats with HIBD.Hence,we established a neonatal HIBD rat model using the Rice-Vannucci method,and injected 0.75,1.5,or 3 mg/kg of the TLR4 inhibitor resatorvid(TAK-242)30 minutes after hypoxic ischemia.Our results indicate that administering TAK-242 to neonatal rats after HIBD could significantly reduce the infarct volume and the extent of cerebral edema,alleviate neuronal damage and neurobehavioral impairment,and decrease the expression levels of TLR4,phospho-NF-κB p65,Beclin-1,microtubule-associated protein l light chain 3,tumor necrosis factor-α,and interleukin-1βin the hippocampus.Thus,TAK-242 appears to exert a neuroprotective effect after HIBD by inhibiting activation of autophagy and the release of inflammatory cytokines via inhibition of the TLR4/NF-κB signaling pathway.This study was approved by the Laboratory Animal Ethics Committee of Affiliated Hospital of Yangzhou University,China(approval No.20180114-15)on January 14,2018. 展开更多
关键词 autophagy hypoxic-ischemic BRAIN DAMAGE neonatal hypoxic-ischemic BRAIN DAMAGE neuroinflammation nuclear factor KAPPA-B resatorvid TAK-242 TOLL-LIKE receptor 4
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Anti-fungal properties of Puroindoline A against Aspergillus glaucus 认领
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作者 Wenjing Yuan Pingping Tian +4 位作者 Ang Lyu Yangyong Lyu Wei Zhang Shan Wei Yuansen Hu 《粮油科技:英文版》 2020年第1期1-8,共8页
Aspergillus glaucus can grow in low moisture grain,and is one of the main fungi responsible for agricultural product losses.Puroindoline A(PINA)is a tryptophan-rich alkaline adiponectin that can effectively inhibit nu... Aspergillus glaucus can grow in low moisture grain,and is one of the main fungi responsible for agricultural product losses.Puroindoline A(PINA)is a tryptophan-rich alkaline adiponectin that can effectively inhibit numerous plant bacteria and fungi.However,the mechanism of PINA against A.glaucus remains unclear.Herein,we found that recombinant PINA(rPINA)could inhibit A.glaucus mycelia growth on salt Czapek dox agar(SCDA)medium and spore germination on Czapek dox(CD)medium.Scanning electron microscopy revealed that incomplete morphological characteristics of both A.glaucus spores and mycelia occurred following rPINA treatment.Laser scanning confocal microscopy(LSCM)showed that rPINA could enter the interior of spores.Flow cytometry and propidium iodide(PI)staining illustrated membranes of spores were severely damaged,especially after treatment with 0.9 mg/mL rPINA for 12 h,and spores with intact membranes were reduced by 30.7%.Additionally,rPINA reduced the mitochondrial membrane potential(MMP)by 5,5′,6,6′-tetrachlorr-1,1′,3,3′-tetraethyl-imidacarbocyanine iodide(JC-1)staining,and caused DNA damage by 4′,6-diamidino-2-phenylindole(DAPI)staining.These results indicated that rPINA may damage cell membranes and DNA structure and reduceMMP,thereby inhibiting the growth of A.glaucus.The antifungal mechanism has been demonstrated in this study,and results show that rPINA has application potential in preventing postharvest loss in the agricultural industry. 展开更多
关键词 PUROINDOLINE A ASPERGILLUS glaucus MEMBRANE INTEGRITY MITOCHONDRIAL MEMBRANE potential DNA damage
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Harvest and Postharvest Factors Affecting Bruise Damage of Fresh Fruits 认领
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作者 Zaharan Hussein Olaniyi AFawole Umezuruike Linus Opara 《园艺学报:英文版》 2020年第1期1-13,共13页
Fresh fruits are susceptible to bruising, a common type of mechanical damage during harvest and at all stages of postharvest handling. In quest of developing and adoption of strategies to reduce bruise damage, it is o... Fresh fruits are susceptible to bruising, a common type of mechanical damage during harvest and at all stages of postharvest handling. In quest of developing and adoption of strategies to reduce bruise damage, it is of utmost importance to understand major factors influencing bruise susceptibility of fresh produce at these stages. This review presents a critical discussion of factors affecting bruising during harvest and postharvest handling of fresh fruits. Excessive compression forces during harvesting by handpicking or machines, and a series of impacts during harvesting, transport and packhouse operations can cause severe bruise damage. The review has further revealed that bruising is dependent on a number of other factors such as produce maturity, ripening, harvest time(during the day or season) and time lapse after harvest. The susceptibility to bruising is partly dependent on how these factors alter the produce physiological and biochemical properties, and the environmental conditions such as temperature, humidity and several other postharvest treatments. Hence, the successful applications of harvesting techniques by use of trained personnel and proper harvesting equipment are essential to reduce both the incidence and severity of bruising.Furthermore, the careful selection of postharvest handling temperature and other treatments can increase resistance of fresh produce to bruise damage. 展开更多
关键词 BRUISE DAMAGE HARVEST POSTHARVEST FRUIT QUALITY
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一种新的岩石非线性损伤蠕变模型 认领
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作者 张亮亮 王晓健 《应用力学学报》 CAS CSCD 北大核心 2020年第1期372-377,I0026共7页
为描述岩石加速蠕变阶段的非线性变形规律,在广义开尔文体基础上串联一个村山体,基于Kachanov损伤率理论,建立了损伤变量D与蠕变时间的函数关系,并根据Lemaitre应变等效原理将村山体中的无损模型参数p用有效模型参数p(1-D)代替,以此来... 为描述岩石加速蠕变阶段的非线性变形规律,在广义开尔文体基础上串联一个村山体,基于Kachanov损伤率理论,建立了损伤变量D与蠕变时间的函数关系,并根据Lemaitre应变等效原理将村山体中的无损模型参数p用有效模型参数p(1-D)代替,以此来表征岩石加速蠕变阶段的非线性,建立了一种新的非线性损伤蠕变模型;根据广义塑性力学理论给出了该模型的三维蠕变方程;采用Levenberg-Marquardt非线性优化最小二乘法对红砂岩和绿片岩常规三轴压缩蠕变试验数据进行拟合,反演得到这两种岩石的蠕变模型参数。拟合结果表明:拟合曲线与试验曲线的拟合相关系数R2分别为0.999和0.992,说明该蠕变模型能较好地反映这两种岩石各阶段的蠕变曲线特征。 展开更多
关键词 岩石力学 加速蠕变 非线性 损伤 本构模型
Anti-perovskite carbides and nitrides A3BX: A new family of damage tolerant ceramics 认领
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作者 Wei Zhang Yuchen Liu +5 位作者 Yanchun Zhou Wai-Yim Ching Qian Li Wenxian Li Jiong Yang Bin Liu 《材料科学技术:英文版》 SCIE EI CAS CSCD 2020年第5期64-71,共8页
Synergy effect of high stiffness and good damage tolerance is always the focus of the development of novel structural materials.Herein,a new strategy on the future damage tolerant material design is proposed to merge ... Synergy effect of high stiffness and good damage tolerance is always the focus of the development of novel structural materials.Herein,a new strategy on the future damage tolerant material design is proposed to merge the strong covalent bonds into the easy shear deformed A3B metallic box.This goal is realized by studying 126 A3BX phases and establishing a database on their mechanical properties through highthroughput first principles calculations.The combination strategies of A3B metallic box and XA3 octahedra show intensive influences on the expected mechanical properties.The family includes 49 quasi-ductile compounds.Among them,four compounds(Ti3AlN,Mn3CuN,Ti3TlN and Ni3SnN)exhibit excellent damage tolerance and the other six compounds(Mn3NiN,Mn3GaC,Mn3GaN,Mn3SnC,Cr3SnN,Co3AlC)show both damage tolerance and high stiffness.Their competitive high temperature properties are demonstrated through the detailed investigation on the typical cases of Co3Al C and Ti3 Tl N.This study leads a novel direction for the design of the future quasi-ductile and high stiffness ceramics. 展开更多
关键词 CERAMICS HIGH-THROUGHPUT calculation A3BX PHASES DAMAGE tolerance
Fatigue Life Prediction for Flange Connecting Bolts of Wind Turbine Tower 认领
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作者 于泽林 孙鹏文 王栋 《上海交通大学学报:英文版》 EI 2020年第4期526-530,共5页
Flange joint part is the weak link of wind turbine tower.In view of the special structure,complex stress and easy failure of the connecting bolt of the wind turbine tower flange,the relationship between the external l... Flange joint part is the weak link of wind turbine tower.In view of the special structure,complex stress and easy failure of the connecting bolt of the wind turbine tower flange,the relationship between the external load of the tower section and the internal stress of the bolt is established by the finite element method,and the time series internal stress of the bolt is calculated by the Schmidt-Neuper algorithm.The S-N curve which is suitable for the connecting bolt material of the tower flange is selected by the GL2010 specification.On the basis of Miner’s fatigue cumulative damage theory and rain flow counting method,the fatigue strength of the whole ring bolt is roughly calculated,and the most dangerous part is determined.The axial symmetry model of screw connection is used for accurately calculating the fatigue cumulative damage of the bolt at the dangerous part.The results show that the fatigue life of the bolts in the most dangerous position can meet the requirements,the engineering algorithm has advantages in determining the dangerous part of the whole ring bolt,and the finite element method has high accuracy in predicting the fatigue life of the bolts in the dangerous part.The proposed method is feasible and effective in predicting the fatigue life of the flange joint bolts of the tower. 展开更多
关键词 fatigue cumulative damage internal stress of bolt engineering algorithm flange connecting bolt wind turbine tower
基于IPSO-BP神经网络的钢丝绳断丝损伤识别模型研究 认领
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作者 钟小勇 刘志辉 《中国安全生产科学技术》 CAS CSCD 北大核心 2020年第4期70-75,共6页
为解决传统钢丝绳断丝损伤识别方法精度低,BP神经网络陷入局部最优等问题,提出改进粒子群算法(IPSO)的BP神经网络识别模型。通过采集钢丝绳断丝损伤信号,提取缺陷信号特征,用峰值、峰峰值、波宽、波形下面积和波动能量5个特征值组成特... 为解决传统钢丝绳断丝损伤识别方法精度低,BP神经网络陷入局部最优等问题,提出改进粒子群算法(IPSO)的BP神经网络识别模型。通过采集钢丝绳断丝损伤信号,提取缺陷信号特征,用峰值、峰峰值、波宽、波形下面积和波动能量5个特征值组成特征向量作为神经网络的输人,断丝数量作为神经网络的输出;利用改进粒子群算法对BP神经网络的初始权值和阈值进行优化;建立基于IPSO-BP算法的神经网络模型,用于钢丝绳断丝的定量识别。结果表明:IPSO-BPS神经网络模型的钢丝绳断丝损伤识别精度、泛化能力均高于传统BP神经网络模型,且改进的粒子群算法迭代寻优速度更快。 展开更多
关键词 钢丝绳 损伤 识别 IPSO-BP神经网络 惯性权重
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Numerical simulations on cutting of frozen soil using HJC Model 认领
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作者 WenQiang Zhang YongHong Niu 《寒旱区科学:英文版》 CSCD 2020年第3期134-143,共10页
Numerical simulation is known as an effective method for mechanical properties during frozen soil excavation.In order to reveal the development of cutting force,effective stress and cutting fragments in frozen silt du... Numerical simulation is known as an effective method for mechanical properties during frozen soil excavation.In order to reveal the development of cutting force,effective stress and cutting fragments in frozen silt during the cutting process,we introduce an explicit finite element program LS-DYNA to establish a two-dimensional numerical model of the frozen soil cut.We also use the Holmquist-Johnson-Cook(HJC)damage constitutive model for simulating the variation of soil mechanical properties according to the strong dependence between the cutting tool and frozen silt during the process with different cutting depths,angles and velocities.Meanwhile,a series of experimental results are acquired of frozen silt cutting to prove the application of the HJC model during simulation of cutting force variations.The result shows that the cutting force and fragment size are strongly influenced by cutting depths and cutting velocities increased,and the maximum effective stress at points where the tool contacts frozen soil during the cutting process.In addition,when the cutting angle is 52°,the cutting force is the smallest,and the cutting angle is optimum.Thus,the prediction of frozen soil mechanical properties on the cutting process by this model is conducive to selecting machinery equipment in the field. 展开更多
关键词 frozen soil cutting numerical simulation HJC damage constitutive model mechanical properties
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The use of Artificial Neural Networks to estimate seismic damage and derive vulnerability functions for traditional masonry 认领
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作者 Tiago Miguel FERREIRA Joao ESTEVAO +1 位作者 Rui MAIO Romeu VICENTE 《结构与土木工程前沿:英文版》 SCIE EI CSCD 2020年第3期609-622,共14页
ABSTRACT This paper discusses the adoption of Artificial Intelligence-based techniques to estimate seismic damage,not with the goal of replacing existing approaches,but as a mean to improve the precision of empirical ... ABSTRACT This paper discusses the adoption of Artificial Intelligence-based techniques to estimate seismic damage,not with the goal of replacing existing approaches,but as a mean to improve the precision of empirical methods.For such,damage data collected in the aftermath of the 1998 Azores earthquake(Portugal)is used to develop a comparative analysis between damage grades obtained resorting to a classic damage formulation and an innovative approach based on Artificial Neural Networks(ANNs).The analysis is carried out on the basis of a vulnerability index computed with a hybrid seismic vulnerability asssment methodology,which is subsequently used as input to both approaches.The results obtained are then compared with real post-earthquake damage observation and critically discussed taking into account the level of adjustment achieved by each approach.Finally,a computer routine that uses the ANN as an approximation function is developed and applied to derive a new vulnerability curve expression.In general terms,the ANN developed in this study allowed to obtain much better approximations than those achieved with the original vulnerability approach,which has revealed to be quite non-conservative.Similarly,the proposed vulnerability curve expression was found to provide a more accurate damage prediction than the traditional analytical expressions. 展开更多
关键词 Artificial Neural Networks seismic vulnerability masonry buildings damage estimation vulnerability curves
单向复合材料横向裂纹黏弹性损伤演化模型 认领
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作者 许飞 李磊 杨胜春 《复合材料学报》 EI CAS CSCD 北大核心 2020年第6期1344-1351,共8页
建立一个考虑基体黏弹性的纤维增强聚合物单向复合材料在产生横向裂纹时的损伤演化模型,有效地预测了单向复合材料横向拉伸行为。假设呈现威布尔分布的缺陷会在变形的驱动下演化为损伤,并以此为基础建立了单向复合材料横向损伤演化模型... 建立一个考虑基体黏弹性的纤维增强聚合物单向复合材料在产生横向裂纹时的损伤演化模型,有效地预测了单向复合材料横向拉伸行为。假设呈现威布尔分布的缺陷会在变形的驱动下演化为损伤,并以此为基础建立了单向复合材料横向损伤演化模型。通过此模型,时间-温度叠加原理(TTSP)得到了更具有物理基础的解释。最后,通过具体例子阐述了此模型的应用,并通过试验对模型预测结果进行了验证。本模型有效地预测了单向复合材料横向拉伸行为。由于单向复合材料横向性能存在脆性,此模型还无法准确预测失效和强度。 展开更多
关键词 损伤 线性黏弹性 一致性准则 横向基体裂纹 威布尔分布 时间-温度叠加原理(TTSP)
近断层地震动斜输入下水电站厂房非线性地震响应研究 认领 被引量:1
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作者 王飞 宋志强 卢韬 《振动与冲击》 EI CSCD 北大核心 2020年第5期63-73,共11页
与远场地震动相比,近断层地震动往往有较大的速度和位移脉冲效应,且由于其发震断层埋深较浅,地震波垂直地表向上入射假定一般不再适用。目前关于水电站厂房抗震研究均未考虑近断层脉冲型地震动斜输入的影响。选取符合某水电站场地条件... 与远场地震动相比,近断层地震动往往有较大的速度和位移脉冲效应,且由于其发震断层埋深较浅,地震波垂直地表向上入射假定一般不再适用。目前关于水电站厂房抗震研究均未考虑近断层脉冲型地震动斜输入的影响。选取符合某水电站场地条件的近断层脉冲型和非脉冲地震动记录各5条,依据波动理论,采用黏弹性动力人工边界法,推导了SV波三维斜入射下的人工边界等效结点力计算公式,并进行了算例验证。建立了水电站厂房三维塑性损伤有限元分析模型,分析了水电站厂房在脉冲型和非脉冲地震动垂直和斜输入条件下的非线性地震响应。结果表明,近断层脉冲型地震动斜输入可以激起厂房结构的高阶振型,引起水电站厂房下部结构较大的损伤、位移、及应力响应,对厂房的破坏作用最强。 展开更多
关键词 近断层脉冲型地震动 斜入射 水电站厂房 非线性分析 损伤
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Strawberry Root Diseases and Control Measures 认领
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作者 Wu Chong Zhang Rong +1 位作者 Han Zhen Zhang Qingtian 《Plant Diseases and Pests(植物病虫害研究:英文版)》 CAS 2020年第1期10-12,共3页
With the development of strawberry protected cultivation industry, continuous cropping of strawberry is becoming more and more com-mon, and soil-borne diseases are increasingly severe. The paper introduces damage symp... With the development of strawberry protected cultivation industry, continuous cropping of strawberry is becoming more and more com-mon, and soil-borne diseases are increasingly severe. The paper introduces damage symptoms, pathogenic bacteria and transmission mode of several main root diseases of strawberry, including Verticillium wilt, Fusarium wilt, root rot and bacterial wilt, and put forward corresponding prevention and control measures. 展开更多
关键词 STRAWBERRY ROOT DISEASES DAMAGE SYMPTOMS PATHOGEN Control measures
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固体发动机推进剂/衬层粘接试件振动损伤分析 认领
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作者 刘磊 李金飞 宋佳明 《指挥控制与仿真》 2020年第3期136-140,共5页
以固体发动机的推进剂/衬层粘接试件为研究对象,设计了单向拉伸试验夹具,开展了三种不同频率的振动加速试验以及单向剪切拉伸试验,应用双因素方差分析法探究了振动时间、振动频率对试件最大剪应力强度的影响规律。结果表明,不同频率下... 以固体发动机的推进剂/衬层粘接试件为研究对象,设计了单向拉伸试验夹具,开展了三种不同频率的振动加速试验以及单向剪切拉伸试验,应用双因素方差分析法探究了振动时间、振动频率对试件最大剪应力强度的影响规律。结果表明,不同频率下的振动试验对推进剂/衬层粘接试件最大剪应力强度的影响无明显区别,且理论振动时间与振动频率之间不存在明显的交互作用;同一频率下,推进剂/衬层粘接试件所能承受的最大剪应力随理论振动时间的增加而减小;从原始未振动状态至理论振动180 d时,三种频率下试件的最大剪应力强度估计边际均值比初始最大剪应力强度分别下降了6.24%、6.15%和6.56%。 展开更多
关键词 粘接试件 振动 损伤
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