基于Voronoi建模和Cohesive单元的PBX细观力学模型

针对PBX的细观力学模型存在模型结构与真实PBX细观形貌不符、破坏行为描述不全面(仅考虑界面脱粘)、研究对象单一(大多针对PBX-9501)等问题,建立了基于Voronoi建模和Cohesive单元的PBX细观力学模型。首先,基于光学显微镜下的细观结构图,采用Voronoi方法构建了更贴近实际形貌的PBX炸药细观模型;然后,采用内聚力有限元方法在炸药晶体内部、黏结剂内部及炸药颗粒/黏结剂界面处都引入了Cohesive单元,以在二维尺度上实现任意路径破坏行为的模拟;最后,针对某HMX基-F2311黏结剂炸药和某HMX基-F2313黏结剂炸药标定了模型参数,模拟了这两种炸药的准静态拉伸行为。结果表明,两种炸药数值模拟的拉伸变形曲线、破坏应力、破坏应变都与试验数据吻合良好,表明该模型不仅适用于不同PBX炸药材料(线弹性PBX、非线性PBX)的变形行为描述,还可以分析PBX炸药在拉伸破坏过程中的细观机理,刻画不同PBX炸药的裂纹萌生、扩展和贯穿的过程。

Finite Element Simulations of the Localized Failure and Fracture Propagation in Cohesive Materials with Friction

Strain localization frequently occurs in cohesive materials with friction(e.g.,composites,soils,rocks)and is widely recognized as a fundamental cause of progressive structural failure.Nonetheless,achieving high-fidelity simulation for this issue,particularly concerning strong discontinuities and tension-compression-shear behaviors within localized zones,remains significantly constrained.In response,this study introduces an integrated algorithmwithin the finite element framework,merging a coupled cohesive zone model(CZM)with the nonlinear augmented finite elementmethod(N-AFEM).The coupledCZMcomprehensively describes tension-compression and compressionshear failure behaviors in cohesive,frictional materials,while the N-AFEM allows nonlinear coupled intraelement discontinuities without necessitating extra nodes or nodal DoFs.Following CZM validation using existing experimental data,this integrated algorithm was utilized to analyze soil slope failure mechanisms involving a specific tensile strength and to assess the impact of mechanical parameters(e.g.,tensile strength,weighting factor,modulus)in soils.

Investigation of FRP and SFRC Technologies for Efficient Tunnel Reinforcement Using the Cohesive Zone Model

Amid urbanization and the continuous expansion of transportation networks,the necessity for tunnel construction and maintenance has become paramount.Addressing this need requires the investigation of efficient,economical,and robust tunnel reinforcement techniques.This paper explores fiber reinforced polymer(FRP)and steel fiber reinforced concrete(SFRC)technologies,which have emerged as viable solutions for enhancing tunnel structures.FRP is celebrated for its lightweight and high-strength attributes,effectively augmenting load-bearing capacity and seismic resistance,while SFRC’s notable crack resistance and longevity potentially enhance the performance of tunnel segments.Nonetheless,current research predominantly focuses on experimental analysis,lacking comprehensive theoretical models.To bridge this gap,the cohesive zone model(CZM),which utilizes cohesive elements to characterize the potential fracture surfaces of concrete/SFRC,the rebar-concrete interface,and the FRP-concrete interface,was employed.A modeling approach was subsequently proposed to construct a tunnel segment model reinforced with either SFRC or FRP.Moreover,the corresponding mixed-mode constitutive models,considering interfacial friction,were integrated into the proposed model.Experimental validation and numerical simulations corroborated the accuracy of the proposed model.Additionally,this study examined the reinforcement design of tunnel segments.Through a numerical evaluation,the effectiveness of innovative reinforcement schemes,such as substituting concrete with SFRC and externally bonding FRP sheets,was assessed utilizing a case study from the Fuzhou Metro Shield Tunnel Construction Project.

Extended finite element-based cohesive zone method for modeling simultaneous hydraulic fracture height growth in layered reservoirs

In this study,a fully coupled hydromechanical model within the extended finite element method(XFEM)-based cohesive zone method(CZM)is employed to investigate the simultaneous height growth behavior of multi-cluster hydraulic fractures in layered porous reservoirs with modulus contrast.The coupled hydromechanical model is first verified against an analytical solution and a laboratory experiment.Then,the fracture geometry(e.g.height,aperture,and area)and fluid pressure evolutions of multiple hydraulic fractures placed in a porous reservoir interbedded with alternating stiff and soft layers are investigated using the model.The stress and pore pressure distributions within the layered reservoir during fluid injection are also presented.The simulation results reveal that stress umbrellas are easily to form among multiple hydraulic fractures’tips when propagating in soft layers,which impedes the simultaneous height growth.It is also observed that the impediment effect of soft layer is much more significant in the fractures suppressed by the preferential growth of adjoining fractures.After that,the combined effect of in situ stress ratio and fracturing spacing on the multi-fracture height growth is presented,and the results elucidate the influence of in situ stress ratio on the height growth behavior depending on the fracture spacing.Finally,it is found that the inclusion of soft layers changes the aperture distribution of outmost and interior hydraulic fractures.The results obtained from this study may provide some insights on the understanding of hydraulic fracture height containment observed in filed.

基于cohesive单元海域天然气水合物储层水力压裂模拟

天然气水合物作为一种高效清洁能源,广泛分布于我国南海海域的沉积地层中。我国先后于2017年和2020年成功开展了2次试开采,但由于海域天然气水合物特殊的赋存条件,单井水合物试采仍然面临着开采范围小、高产稳产时间短等问题。为了提高水合物的开采范围,基于cohesive单元进行了水合物储层二维水力压裂数值模型研究,比较了100 m×100 m和20 m×20 m两种模型的裂缝半长和宽度,得出了当注入压力为25 MPa时,压裂裂缝半长均为6 m,最大宽度分别为5.8、5.5 mm,构建尺寸较大的模型得出的实验结果更加准确。并且研究了裂缝宽度随注入时间的变化规律,随着注入压力和注入量的不断增加,初期裂缝宽度急速变大,后续在地应力和注入流体压力的共同作用下裂缝出现“阶梯式”的扩展规律。该研究在页岩气和煤层气等非常规能源储层水力压裂模型分析中得到了成功运用,为海域天然气水合物储层水力压裂提供一定的理论指导。

Numerical simulation of the mechanical behavior of superconducting tape in conductor on round core cable using the cohesive zone model

Cables composed of rare-earth barium copper oxide(REBCO)tapes have been extensively used in various superconducting devices.In recent years,conductor on round core(CORC)cable has drawn the attention of researchers with its outstanding current-carrying capacity and mechanical properties.The REBCO tapes are wound spirally on the surface of CORC cable.Under extreme loadings,the REBCO tapes with layered composite structures are vulnerable,which can lead to degradation of critical current and even quenching of superconducting devices.In this paper,we simulate the deformation of CORC cable under external loads,and analyze the damage inside the tape with the cohesive zone model(CZM).Firstly,the fabrication and cabling of CORC are simulated,and the stresses and strains generated in the tape are extracted as the initial condition of the next step.Then,the tension and bending loads are applied to CORC cable,and the damage distribution inside the tape is presented.In addition,the effects of some parameters on the damage are discussed during the bending simulations.

(α,γ)-Anti-Multi-Fuzzy Subgroups and Some of Its Properties

Recently,fuzzy multi-sets have come to the forefront of scientists’interest and have been used in algebraic structures such asmulti-groups,multirings,anti-fuzzy multigroup and(α,γ)-anti-fuzzy subgroups.In this paper,we first summarize the knowledge about the algebraic structure of fuzzy multi-sets such as(α,γ)-anti-multi-fuzzy subgroups.In a way,the notion of anti-fuzzy multigroup is an application of anti-fuzzy multi sets to the theory of group.The concept of anti-fuzzy multigroup is a complement of an algebraic structure of a fuzzy multi set that generalizes both the theories of classical group and fuzzy group.The aim of this paper is to highlight the connection between fuzzy multi-sets and algebraic structures from an anti-fuzzification point of view.Therefore,in this paper,we define(α,γ)-antimulti-fuzzy subgroups,(α,γ)-anti-multi-fuzzy normal subgroups,(α,γ)-antimulti-fuzzy homomorphism on(α,γ)-anti-multi-fuzzy subgroups and these been explicated some algebraic structures.Then,we introduce the concept(α,γ)-anti-multi-fuzzy subgroups and(α,γ)-anti-multi-fuzzy normal subgroups and of their properties.This new concept of homomorphism as a bridge among set theory,fuzzy set theory,anti-fuzzy multi sets theory and group theory and also shows the effect of anti-fuzzy multi sets on a group structure.Certain results that discuss the(α,γ)cuts of anti-fuzzy multigroup are explored.

Virtual strain loading method for low temperature cohesive failure of asphalt binder

Cohesive failure is one of the primary reasons for low-temperature cracking in asphalt pavements.Understanding the micro-level mechanism is crucial for comprehending cohesive failure behavior.However,previous literature has not fully reported on this aspect.Moreover,there has been insufficient attention given to the correlation between macroscopic and microscopic failures.To address these issues,this study employed molecular dynamics simulation to investigate the low-temperature tensile behavior of asphalt binder.By applying virtual strain,the separation work during asphalt binder tensile failure was calculated.Additionally,a correlation between macroscopic and microscopic tensile behaviors was established.Specifically,a quadrilateral asphalt binder model was generated based on SARA fractions.By applying various combinations of virtual strain loading,the separation work at tensile failure was determined.Furthermore,the impact of strain loading combinations on separation work was analyzed.Normalization was employed to establish the correlation between macroscopic and microscopic tensile behaviors.The results indicated that thermodynamic and classical mechanical indicators validated the reliability of the tetragonal asphalt binder model.The strain loading combination consists of strain rate and loading number.All strain loading combinations exhibited the similar tensile failure characteristic.The critical separation strain was hardly influenced by strain loading combination.However,increasing strain rate significantly enhanced both the maximum traction stress and separation work of the asphalt binder.An increment in the loading number led to a decrease in separation work.The virtual strain combination of 0.5%-80 provided a more accurate representation of the actual asphalt's tensile behavior trend.

基于网络群组特征的生态管理分区--以武汉市为例

生态管理分区是维持区域生态安全、实现城市生态差异化治理的重要手段。然而现有分区方法侧重生态功能属性,较少考虑生态斑块之间联系强度差异,忽视了斑块的群组结构。以武汉市为例构建生态网络,从生态系统结构和功能的视角,结合斑块空间组织和斑块联系强弱,运用凝聚子群方法,提取联系紧密的生态组分,将网络划分为异质性群组,基于网络群组特征和生态景观辐射范围进行分区覆盖分析,并进行分区评价。结果表明:(1)86条生态廊道连接研究区34处生态斑块,进一步形成8个生态群组;(2)多数群组内部连通性较好,北部群组之间联系较强,南部群组之间联系相对较弱;(3)依据群组结构功能特征,形成6大网络群组分区,通过与武汉市经济发展规划分区对比,两者具有较高的一致性;(4)城市外围的分区网络稳定性较好,中部稳定性较差,识别分区内13个重要斑块和16条重要廊道,作为重点发展保护对象;(5)综合分区特征将6大分区确立为生态屏障区、生态控制区、生态改善区、生态修复区、生态开发区以及生态保育区,并提出生态发展差异化保护措施。研究将生态功能属性和空间结构属性进行有机关联并制定分区策略,为区域生态管理分区、生态保护规划提供新视角。

智能算法的亚群优化策略综述

群智能算法的优化是提升群智能算法性能的一个主要途径,随着群智能算法越来越广泛地运用到各类模型优化、生产调度、路径规划等问题中,对智能算法性能的要求也越来越高。亚群策略作为一种优化群智能算法的重要手段,能够灵活地平衡算法的全局勘探能力和局部开发能力,已经成为群智能算法的研究热点之一。为了促进亚群优化策略的发展和应用,对动态亚群策略、基于主从范式的亚群策略和基于网络结构的亚群策略进行了详细调查,阐述了各类亚群策略的结构特点、改进方式和应用场景。最后,总结了亚群策略目前存在的问题以及未来的研究趋势和发展方向。

植物油微胶囊沥青混合料的微观力学性能及自愈合机制

为了研究植物油微胶囊沥青混合料的微观力学性能及自愈合机制,利用分子动力学方法基于12分子沥青模型构建沥青微裂缝模型,采用植物油提取物油酸、亚油酸以及石油基再生剂乙基四氢化萘作为芯材,探究三种芯材释放后沥青微裂缝的自愈合进程,计算沥青分子的自扩散系数并分析不同芯材的作用机制,同时构建沥青-集料模型,采用粘聚能、粘附能、粘附强度等指标分析融入不同芯材后沥青-集料界面的微观力学性能。结果表明:芯材的释放加速了沥青分子的自扩散,提高了微裂缝的自愈合能力,且微裂缝自愈合能力随温度的升高而增强;与芯材融合后老化沥青的粘聚能和粘附能分别提高了37.2%和36.8%以上,并且老化沥青-集料界面的粘附强度增加;与石油基再生剂相比,植物油能更好地促进微裂缝的愈合。通过分子动力学技术可以更深入地探查微胶囊沥青路面的自愈合机制,从而为微胶囊芯材的设计与选择提供可行的方法。

政策衔接:政策有效性的一种实现机制

政策衔接作为公共政策实践中的常见现象,是不同政策间相互连接和协调的政策过程,旨在确保关联政策的连贯性、互补性和协同性,呈现结果与行动相统一、共性与个性相融合的特征。在现实场景中,由于社会问题的复杂性与多元性,公共政策常常面临一定程度的分立与冲突,导致政策执行者往往面临工具不统一、目标不一致等难题。为了提升政策制定和执行效能,在多重任务导向下,政策衔接成为政策有效性的一种实现机制。首先,在政策衔接功能上,关联政策的目标弥合有助于提升政策执行方向的明确性、工具组合使用有助于提升政策执行手段的合理性、资源整合有助于提升政策执行资源的匹配度。其次,在政策衔接过程上,通过政策转译实现与上级政策的衔接,延展政策的情境适用性;通过政策协同实现与同层级政策的衔接,提高政策的系统整合性;新政策通过政策接续实现与旧政策的衔接,增强政策更迭的稳定性。最后,在政策衔接的结构保障上,为消除治理结构中的不利干扰,采取赋能正向行动的可行性建构,提升政策主体的主观能动性,以及政策的合意性与稳定性;借助程序与结果的合法性建构,确保政策衔接过程符合制度规范和社会规范、衔接结果获得内部认同和社会认同,避免政策制定者的偏离行为破坏政策有效性。总之,政策衔接的三种样态及其相互交叠,有助于缓和科层体制与有效治理的张力、缓和专业治理与整体治理的张力、缝补路径依赖与制度创新的裂隙,共同回应国家治理现代化进程中的空间与时间命题,提升国家治理效能。

纳米材料杨氏模量的尺度依赖性

【目的】纳米材料杨氏模量与其对应的大块材料的杨氏模量完全不同,并且具有明显的尺度依赖性,然而纳米材料杨氏模量随尺度的变化却是多样且复杂的。一些金属纳米材料杨氏模量随着尺度减小而增大,并高于块体杨氏模量值;而一些半导体纳米材料的杨氏模量却随尺度的减小而降低,且低于块体杨氏模量值。这种相反的变化趋势的原因却并不清楚。【方法】基于纳米热力学理论,以纳米材料结合能为基础,从原子势函数与材料杨氏模量的内在关系出发,引入反映材料原子键本质的参数,详细推导了纳米材料杨氏模量定量解析过程,阐述了金属、非金属等纳米材料杨氏模量值和其随尺度的变化规律;揭示了纳米材料表面模量、内部模量对体系杨氏模量的贡献,并利用材料参数阐明纳米材料杨氏模量与尺度、原子键的物理关系。【结果】所构建的理论解析模型对零维纳米颗粒、一维纳米线和二维纳米薄膜的杨氏模量都进行了成功的预测。

基于Roe-Siegmund循环内聚力模型焊趾疲劳裂纹萌生仿真

为建立焊趾疲劳裂纹萌生行为仿真方法,基于Roe-Siegmund循环内聚力模型对ABAQUS进行二次开发,形成用于反映疲劳累积损伤的VUMAT子程序,依据文献方法及试验数据获取Q345焊接区域材料的内聚力参数,通过Voronoi图法和内聚力单元法生成具有疲劳累积损伤特性和晶粒特征的微观模型,并与宏观对接焊缝模型合并,进行多尺度疲劳裂纹萌生仿真模拟,获得裂纹萌生路径、临界循环次数及晶粒力学响应特征.结果表明,此方法能够自发地选择符合实际情况的裂纹萌生位置以及短裂纹扩展路径,完成对焊接区域材料微观断裂过程的模拟,不同仿真组获取的临界循环次数存在于一定的分布范围内,模型中的累积内聚力长度需通过试验数据进行拟合.

党建引领:铸牢中华民族共同体意识的实现路径

基于中华民族共同体、中华民族共同体意识、铸牢中华民族共同体意识三个概念之间“社会存在-社会意识-转化过程”的关系分析,各民族认同凝聚是铸牢中华民族共同体意识的关键环节。党建引领则在具备权力、组织、制度、意识形态、法律、规范等凝聚工具的基础上,成为各民族认同凝聚的有效方式。基于所具备的各民族认同凝聚功能,党建引领铸牢中华民族共同体意识的主要实现路径如下:首先,以党建引领巩固民族政治共识性基础、塑造民族现代性政治认同,在强化中华民族共同政治凝聚中,铸牢各民族的政治归属意识;其次,以党建引领扩充民族关系网络纽带、实现民族社会信任增蓄,在培育中华民族共享社会资本中,铸牢各民族的社会互助意识;再次,以党建引领拓展民族公共文化空间、打造民族政治文化符号、供给民族核心价值观念,在构筑中华民族共有精神家园中,铸牢各民族的精神共通意识;最后,以党建引领代表各民族共同性利益、调节具体性利益,在协调中华民族共生利益关系中,铸牢各民族的利益联结意识。

3D打印混凝土界面力学行为及其对材料弹性常数影响的数值分析

应用复合材料细观力学分析理论,提出了基于界面模型的3D打印混凝土(3DPC)各向异性数值模拟方法,定量揭示了层、条界面力学行为及其对3DPC各向异性弹性常数的影响规律。采用界面单元和连续体单元相结合,模拟界面滑移开裂行为与基体的力学性能,设计单轴压缩、劈拉、十字交叉拉伸和斜剪试验确定模型所需参数及相应取值范围。结果表明:界面拉伸和剪切张力-位移曲线均呈双线性特征,条间界面强度总体高于层间;界面剪切行为在两个剪切主方向上无显著差异;条间和层间弹性模量对整体弹性模量具有线性影响,对整体泊松比具有指数函数影响,条间和层间界面剪切模量对整体剪切模量具有综合影响。

基于内聚力模型的汽轮机末级叶片涂层裂纹扩展数值模拟

为探究汽轮机末级叶片基体与涂层结合强度和分析涂层裂纹萌生及扩展规律,基于双线性内聚力模型理论,建立了基体-涂层界面裂纹扩展计算力学模型,采用有限元仿真方法模拟了汽轮机末级叶片熔覆涂层脱落情况。结果表明,涂层和基体材料参数会影响涂层脱落时的裂纹扩展规律和力学响应;适当增大基体材料弹性模量和减小涂层材料弹性模量能延缓水蚀过程中涂层的失效时间;增大涂层和基体材料弹性模量,能提高涂层与基体结合界面在裂纹扩展中所能承受的最大应力,进而提升涂层与基体结合界面的耐冲击能力。

ABO基因第7外显子c.539G>C突变致A_(2)B亚型结果分析

目的:探讨ABO基因第7外显子c.539G>C突变致A_(2)B亚型结果分析。方法:采用试管凝集法检测ABO血型,采用Sanger测序法进行基因测序及序列分析。结果:4例先证者红细胞为A弱B表型,根据血清学特征定义为A_(2)B血型,先证者1、3、4血清中无抗-A_(1)抗体;先证者2血清中存在抗-A_(1)抗体;4例血型基因型为ABO^(*)A2.08/ABO^(*)B.01,测序结果与A102基因序列比对,A208在c.467C>T和c.539G>C位发生突变,导致多肽链P156L和R180P替换。结论:α-1,3-N-乙酰半乳糖胺转移酶基因c.539G>C突变产生A208表型。

微生物分解硅酸盐矿物增黏对砂土强度的影响

砂土因其无黏聚力而易导致地震液化和渗流侵蚀等工程病害问题,微生物矿化与分解技术的发展为提高砂土黏聚力提供了新的可能。利用胶质芽孢杆菌能够分解硅酸盐矿物的特性,采取人工营养液激励加速含钾长石、黑云母等硅酸盐矿物砂土的生物风化,分析经微生物处理前后砂土的强度参数、黏粒含量、矿物组分和粒间微结构的变化规律。结果表明:胶质芽孢杆菌处理后的砂土中黏粒含量增加了1.6%;黏聚力与处理时长呈线性正相关,120 d内有效黏聚力增加了23 kPa,有效内摩擦角则有轻微的减小;砂土中的钾长石、黑云母等硅酸盐矿物均产生了不同程度的分解破坏,X射线衍射谱图显示,微生物处理120 d后砂土中出现了新的高岭石衍射峰,表明胶质芽孢杆菌分解了黑云母和钾长石等硅酸盐矿物,产生次生黏土矿物高岭石,使砂土中黏粒含量增加。微生物分解硅酸盐矿物产生黏土矿物和胞外聚合物是砂土黏聚力提升的主要原因。营养物激励下矿物分解菌对硅酸盐矿物的风化作用对于改善砂土抗液化和抗渗流性能具有潜在的价值。

参杞强精颗粒对慢性疲劳综合征脾肾阳虚证大鼠免疫调节作用研究

目的:探讨参杞强精颗粒对慢性疲劳综合征(CFS)脾肾阳虚证模型大鼠的影响以及免疫调节作用。方法:将50只无特定病原体(SPF)级健康雄性斯泼累格·多雷(SD)大鼠随机分为正常对照组,模型对照组,参杞强精颗粒高剂量组、中剂量组、低剂量组,采用游泳力竭实验造成大鼠体力疲劳,慢性束缚应激造成大鼠心理疲劳,同时给予番泻叶煎煮液灌胃造成脾肾阳虚证候,构建CFS脾肾阳虚证大鼠模型,造模成功后分别按照各组剂量灌胃,连续给药21 d后,测定各组大鼠的胸腺和脾脏指数,酶联免疫吸附试验(ELISA)检测血清免疫球蛋白G(IgG)、免疫球蛋白M(IgM)、免疫球蛋白A(IgA)浓度以及细胞因子白细胞介素2(IL-2)、白细胞介素6(IL-6)和γ干扰素(IFN-γ)含量,MTT法检测脾脏T、B淋巴细胞增殖能力,流式细胞法检测各组大鼠外周血T淋巴细胞亚群分布情况。结果:行为学结果显示,模型大鼠的体质量增长缓慢,精神萎靡,摄食水量减少,活动减少,便质稀软,力竭游泳时间减少,悬尾静止时间增加。药物干预后,与模型组比较,各给药组大鼠精神状态、体质量、摄食水量均显著改善,力竭游泳时间增加、悬尾静止时间减少(P<0.01或P<0.05);参杞强精颗粒各剂量组能显著提升大鼠胸腺和脾脏指数,提高IgG、Ig M、IgA浓度和IL-2、IL-6、IFN-γ的含量,显著提高脾脏T、B淋巴细胞增殖能力,也能提高CD3+、CD4+T淋巴细胞百分率和CD4+/CD8+T比值,降低CD8+T淋巴细胞百分率,差异有统计学意义(P<0.01或P<0.05)。结论:参杞强精颗粒能显著改善慢性疲劳综合征脾肾阳虚证大鼠免疫功能,缓解疲劳症状,且具有很好的免疫调节作用。