Micro-annulus generation under downhole conditions: Insights from three-dimensional staged finite element analysis of cement hardening and wellbore operations

A micro-annulus(MA)is defined as a high permeability zone or gap initiating/occurring at the casingcement and cement-formation interfaces during the wellbore life span.An MA can significantly compromise wellbore integrity by establishing enhanced fluid flow pathways.This study uses a staged finite element approach to simulate wellbore integrity during various loading steps of wellbore operations under downhole conditions.Particular emphasis is placed on the processes of cement poro-elastic property evolution,volume variation,and pore pressure variation as part of the cement hardening step.The resulting state of stress during the life cycle of a typical injection well(i.e.hardening,completion,and injection)is analyzed to assess the onset and evolution of micro-annuli at various interfaces of the composite wellbore system under downhole conditions.The results show that cement shear failure is observed at the casing-cement interface during pressure testing(excessive wellbore pressure);and tensile debonding failure initiates at the cement-formation interface due to cement shrinkage during hardening and injection-related cooling(thermal cycling).Sensitivity analyses considering several parameters show that:(1)the degree of poro-elastic bulk shrinkage has significant implications for both shear and tensile failure initiation e the less the cement shrinks,the less likely the failure initiation is;(2)cement integrity increases with increasing depth;(3)cement pore pressure evolution has significant implications for tensile failure e if cement pore pressure decreases more,higher temperature differences can be sustained before an MA occurs;and(4)cement temperature fluctuations during hardening promote initiation of debonding failure.In summary,the results presented indicate that establishing downhole conditions to quantitatively analyze MA generation is necessary.The results are different compared to laboratory studies without considering/simulating downhole conditions.The knowledge from this study can raise the awareness of predicting and evaluating MA under downhole conditions and can be used to supplement and improve future laboratory experiments.

何为翻译实践——马克思主义实践观视角

从马克思主义实践观来看,翻译实践是翻译实践者通过能动地改造由源文本世界所承载的精神世界,将源系统中的观念转移至目标系统,以改造目标系统中的物质世界的社会性活动。为此,翻译实践可分为原作选择、译作生产和译作接受三个环节,本质上对应于异质观念的选择、转移和接受。翻译实践的每个环节均由主体、客体和中介三要素构成,是翻译实践主体通过实践中介与实践客体互相作用的社会性活动。翻译实践和其他社会实践一样,具有客观现实性、自觉能动性和社会历史性等基本特征。

教师教学交往素养:构成要素、发展阶段与提升路径

教师教学交往素养是从交往视角对教师在教学中所应具备的品格与能力的审视与探讨,包括教学知识素养、师生沟通素养、引导帮扶素养与人际知觉素养四方面。从纵向来看,可划分为注重知识传递的基础阶段、关注学生发展的提升阶段和实现价值引领的高级阶段。为了提升教师教学交往素养,应建立教育性的师生交往制度,在教学交往中将促进学生发展作为核心理念,在教学交往中基于学生立场关怀学生成长,构建尊重—理解—对话的师生交往模式,建构个体教学交往哲学,支撑多维结构的教师教学交往素养。

Remaining Useful Life Prediction of Rolling Element Bearings Based on Different Degradation Stages and Particle Filter

A method is proposed to improve the accuracy of remaining useful life prediction for rolling element bearings,based on a state space model(SSM)with different degradation stages and a particle filter.The model is improved by a method based on the Paris formula and the Foreman formula allowing the establishment of different degradation stages.The remaining useful life of rolling element bearings can be predicted by the adjusted model with inputs of physical data and operating status information.The late operating trend is predicted by the use of the particle filter algorithm.The rolling bearing full life experimental data validate the proposed method.Further,the prediction result is compared with the single SSM and the Gamma model,and the results indicate that the predicted accuracy of the proposed method is higher with better practicability.

一种新型组合式弯曲型金属阻尼器性能研究

为解决U形阻尼器承载能力低、耗能性差的问题,文中提出了由U形金属板与X形金属板组成的一种新型组合式弯曲型金属阻尼器,基于随动强化模型对阻尼器进行静力循环模拟加载,采用ABAQUS软件进行仿真研究,发现组合式金属阻尼器滞回性能和承载能力均有提高,比U形阻尼器承载能力提高了24%,根据材料屈服强度的理论分析,当X形金属板的材料屈服应力大于307.38 MPa时,组合式金属阻尼器可实现双级屈服效果,仿真中选用Q235B钢U形板和Q345B钢X形板,组合式金属阻尼器取得了较好的双阶段屈服效果。

斜拉桥施工阶段π型混凝土梁翼缘板裂缝成因分析与防裂措施研究

为了解斜拉桥施工阶段π型混凝土梁翼缘板斜向裂缝成因并制定合理的防裂措施,以某主跨120 m的π型预应力混凝土梁斜拉桥为背景,针对其悬臂施工阶段主梁翼缘板下表面出现斜向裂缝的现象进行分析。采用ANSYS软件建立该桥施工阶段杆系模型与混凝土梁实体模型,分析梁体自重、斜拉索张拉、预应力张拉、混凝土收缩、混凝土水化热作用下主梁翼缘板下表面应力情况。结果表明:梁体自重及斜拉索张拉作用下,翼缘板下表面未出现拉应力;横向及纵向预应力张拉作用下,翼缘板下表面产生一定的拉应力,但未超过混凝土抗拉强度标准值;混凝土收缩作用下,翼缘板下表面产生极小的拉应力,不会引起裂缝;混凝土养护过程中水化热作用下,翼缘板下表面混凝土与周边混凝土存在一定温差,部分测点第一主应力超过混凝土抗拉强度标准值,是开裂的主要原因。针对混凝土水化热作用影响,提出主肋布置冷却水管与翼缘板下方火炉加热并用的防裂措施,建立热流耦合模型分析防裂效果。结果表明:所采用的措施能够改善主梁养护过程中水化热温度场分布,各测点第一主应力均未超过混凝土抗拉强度标准值。

上颌窦内提升术最佳二期修复时间的有限元分析

背景:牙缺失区由于缺乏功能性加载产生的力学刺激,导致牙槽骨萎缩、骨质丢失,致使牙种植体不能有效埋入。因此种植修复时就需要植入骨粉,弥补牙槽骨高度不足对种植体稳定度的影响。目的:借助有限元分析法从生物力学角度得出种植体二期修复的最佳时间点,为临床缩短种植疗程选择正确二期修复时间点提供了生物力学基础。方法:采集1名女性健康志愿者颅面骨拍摄的锥形束CT,建立正常上颌骨模型、16缺失采用常规种植术(模型B)和16缺失采用上颌窦内提升术(模型A)后的上颌骨三维有限元模型。模型A在黏膜与上颌窦底之间以羟基磷灰石骨粉填充,模型B和正常上颌骨模型无需植骨。设置植骨愈合时间为术后的3-9个月,于术后3-5个月施加200 N的力在邻牙上,6-9个月直接施加在种植体上,模拟二期修复对种植体施加载荷。借助种植体及周围的软硬组织对3种模型进行生物力学分析。结果与结论:①种植体直接加载时,模型A上的应力在103 MPa左右、模型B上的应力在95 MPa左右。植骨后会增加种植体的应力值,而不做植骨则能降低种植体和整个系统的应力。随着骨粉强度的增加,牙槽骨上的应力值随之降低。②当愈合时间到术后6-9个月,在种植体或相应的第1磨牙牙位加载时,正常模型中的应力值最小,模型B次之,模型A最大;植入种植体后的上颌骨的应力大于正常上颌骨。③模型整体松质骨应力水平,在6-9个月模型A的松质骨应力略呈下降趋势,模型B应力水平显著低于正常下颌骨模型。④结论:利用原有的牙槽骨进行修复能提高种植体存活率;植骨后在获得足够的牙槽骨高度的情况下,可在6个月后考虑二期修复。临床应用时可根据患者的骨质、生活习惯、年龄等因素综合判定后,在此基础上适当调整二期修复时间。

混杂B/CFRP层合板拉伸性能及疲劳寿命仿真

为探究混杂玄武岩纤维/碳纤维增强复合材料(B/CFRP)层合板的力学响应和疲劳寿命,采用湿铺层法制作混杂层合板,通过单向拉伸试验方法研究了B/CFRP层合板在不同铺层数量和不同长度下的基本拉伸性能.借助ABAQUS精细化有限元模型,对混杂层合板拉伸过程中响应特征进行模拟研究.结合疲劳理论,分析了B/CFRP层合板的应力-寿命曲线,并基于静载仿真结果,预测了B/CFRP层合板在不同应力幅、应力比下的疲劳寿命.试验结果表明,试件长度对层合板力学性能影响不显著,随着BFRP层数的增加,层合板逐渐出现多级断裂现象.有限元仿真值与试验值较为吻合,B/CFRP层合板疲劳极限强度为0.568倍极限强度.相同应力比情况下,应力上限越大,疲劳寿命越短,且变化幅度较为明显.当应力上限低于0.7倍极限强度时,仿真寿命与理论寿命相差较小.

电动汽车三段式驱动桥桥壳有限元分析

为了实现电动汽车驱动桥桥壳轻量化,对动力总成外壳为铝合金材料的三段式驱动桥桥壳进行有限元分析。首先,对桥壳4种工况进行受力分析,获取桥壳外部载荷;其次,用UG软件建立桥壳几何模型,简化后导入ANSYS Workbench软件建立桥壳有限元模型;最后,对4种工况下的桥壳有限元模型进行约束和施加载荷,求解得桥壳的应力和位移分布规律。结果表明:4种工况下驱动桥桥壳满足强度、刚度要求,为三段式驱动桥桥壳结构设计提供了参考。

叶面喷施硒肥对水稻吸收累积硒及其他矿质元素的影响

为保证硒肥的合理利用及富硒水稻的安全生产,探究水稻植株体内硒及其他矿质元素、重金属含量对外源硒的响应程度。以水稻品种“鄂中五号”和硒肥“中地西能”为试验对象,采用大田随机区组设计,设4个硒肥浓度(0、15、30、60 g/hm^(2))处理,于水稻齐穗期统一喷施,在成熟期检测水稻植株各器官中硒含量、糙米中不同矿质元素含量、叶片中不同重金属元素含量,评价各处理糙米与其他各器官硒元素富集的难易程度。结果表明,水稻糙米各器官中硒含量均随硒营养液喷施浓度的增加而增加,其中,谷壳和叶片对硒肥的响应程度最大,叶面硒肥增加了糙米硒的富集系数、各器官硒的转移系数;叶面硒肥对糙米中不同矿质元素的影响不同,高浓度硒处理降低了氮、锰、铜的含量,但提高了锌、钙、镁、钾、磷元素的含量;高浓度硒处理可有效降低植株叶片中汞、铅、镉、铬含量,低浓度的硒处理降低了砷含量。

广西壮族服饰元素在舞台服装造型中的应用

文章旨在探讨壮族服饰文化元素在舞台服装造型设计中的创新性融合和应用。文章分析了壮族服饰的色彩、图案、材质等元素,并将其巧妙地融入到舞台服装造型设计中,这种融合不仅极大地丰富了舞台服装的文化内涵,同时也展现了壮族服饰所承载的独特民族风格,为舞台表演增添了无与伦比的魅力与艺术感染力,实现了传统与现代的和谐统一。

河流水位对深浅式地铁基坑变形和受力的影响

为了研究河流水位对深浅式地铁基坑工程的影响,运用RS3有限元软件中流固耦合计算模型,探究了河流水位变化对深浅式基坑变形和受力的影响规律。结果表明:地连墙的水平位移和弯矩、坑底隆起位移和格构柱的竖向位移均随河流水位的增加而增加;坑边地表沉降位移和基坑的稳定安全系数随着河流水位的增加而减小。河流水位变化对格构柱的竖向位移影响较小;而河流水位标高为21~22 m范围时,对地连墙的水平位移和弯矩、坑边地表沉降位移、坑底隆起位移和基坑的稳定安全系数有较大的影响;随河流水位的增加,坑边地表沉降位移和坑底隆起位移的影响范围均会向下部和临河侧的土体扩大,临河侧基坑浅部和围护桩底的塑性破坏区域也会增大。

基于三道次数控渐进成形的圆孔翻边研究

针对薄壁件上的圆孔翻边成形问题,研究了基于三道次数控渐进成形技术的圆孔翻边成形方法和工艺流程。研究了面向三道次数控渐进圆孔翻边工艺的各中间道次成形模型建模、成形轨迹生成和支撑设计方法。采用ANSYS软件对基于三道次数控渐进成形技术的圆孔翻边成形过程进行有限元数值模拟,在分析翻边孔厚度、减薄率和轮廓尺寸精度的基础上,给出了提高翻边孔轮廓尺寸精度的方法。

伽马射线探测器冲击减振设计及验证

针对某伽马射线探测器受到振动冲击后敏感器件损坏严重的问题进行减振设计,研究减振器阻尼层尺寸参数对整体固有频率和抗冲击性能的影响,以及薄壁结构基座对抑制振动和冲击传递的影响;进而采取设计减振器、合理选取阻尼层尺寸参数、增加二级阻尼缓冲减振和改进薄壁结构的措施完成减振设计;最后通过仿真和试验验证减振设计的合理性。研究表明:减振器能够降低结构刚度,对冲击产生大幅度衰减作用;阻尼层直径是提高抗冲击性能的主要因素,探测器整体固有频率和冲击响应均随阻尼层直径的增加而减小;薄壁结构基座对激励有放大作用,可以通过调整局部结构降低冲击响应;二级阻尼缓冲减振设计对关键器件有较好的减振功效,尤其是在低频段。该研究可为有结构限制要求的航天器的冲击减振设计提供参考。

矿用防爆柴油机四元组合式尾气后处理系统设计及性能试验

防爆柴油机是矿井辅助运输车辆使用最为广泛的动力源之一,受防爆改造以及井下恶劣环境的影响,导致其尾气污染问题严重,有悖于绿色矿山发展战略。煤矿井下自2020年12月开始实施非道路国III排放标准,但现阶段矿用防爆柴油机尾气净化多采用机内前处理技术,无法满足非道路国IV及更高标准的排放要求。针对防爆柴油机尾气污染严重及净化技术滞后的问题,设计了一种新型四元组合式尾气后处理系统,并通过仿真和台架试验开展了关键部件结构参数优化及尾气污染物净化性能研究。首先,按照煤矿井下防爆要求,超前面向非道路国IV尾气排放标准,设计了一种由氧化催化剂(DOC)、颗粒捕集器(DPF)、选择性催化还原器(SCR)和防爆温控装置(EPTC)组成的防爆柴油机四元组合式尾气后处理系统;采用STAR-CCM+仿真软件对防爆温控装置结构进行传热分析,结果表明:管壁面温度均小于150℃,可满足煤矿安全规程防爆要求。其次,以某型60 kW防爆柴油机为研究对象,基于GT-Power软件分别搭建了DOC、SCR和DPF后处理部件的仿真模型,并对其关键结构参数及净化性能开展正交试验进行优化,确定了尾气后处理系统关键部件的最优结构参数,得到如下规律:污染物的净化效率随DOC和SCR的载体直径、载体长度和通道密度的增大而提高;载体长度和载体直径对DPF捕集效率与DOC和SCR规律一致,而DPF因其特殊的壁流式载体结构,随着通道密度增加,PM颗粒物的捕集效率可始终维持在96%附近。在此基础上,建立了防爆柴油机和后处理系统的耦合模型,开展了防爆柴油机尾气排放污染物净化效率、动力性与经济性仿真试验。最后,研制了四元组合式尾气后处理系统样机并开展台架试验,将试验数据与仿真数据对比分析,结果表明:尾气后处理系统对CO、NO、HC与颗粒物的净化效率分别大于95%、90%、83%以及95%,可满足非道路国IV排放要求;加装尾气后处理系统的防爆柴油机整体输出扭矩平均下降4.83%,整体燃油消耗率平均增加1.19%,对防爆柴油机的动力性与经济性的实际影响较小。

考虑接头变形特性的沉管隧道纵向计算

在沉管隧道纵向计算中,管节接头合理模拟是关键.基于沉管隧道管节接头各组件变形特性分析,建立接头力学模型,将钢端壳以及竖向剪切键锚固区中墙和侧墙组成的刚端头定义为刚臂,而接头GINA止水带与竖向剪切键间橡胶支座则离散为连接两侧刚性板的非线性弹簧,该接头模型可以较好反映相邻管节间竖向剪切与纵向弯曲情况下接头受力特点,将其与沉管隧道管节弹性地基梁模型结合,可分析沉管隧道不同施工阶段管节和接头的内力与变形.最后,以广州某沉管隧道为例,分析了实际荷载工况下沉管隧道纵向受力与变形情况.分析结果表明:隧道整体沉降呈U形分布,从岸上段往江中段沉降逐渐增大;接头最大张开量为0.39 mm,远小于GINA止水带水密性容许张开量;管节与岸上段连接接头受力和变形相比江中段较显著,设计施工时应重点关注;模型计算部分成果与实测结果进行了对比分析,验证了模型的合理性.

Ontogenetic difference of beak elemental concentration and its possible application in migration reconstruction for Ommastrephes bartramii in the North Pacific Ocean

The migration route of oceanic squid provides critical information for us to understand their spatial and temporal variations.Mark-recapture and electronic tags tend to be problematic during processing.Cephalopod hard structures such as the beak,containing abundant ecological information with stable morphology and statolithlike sequences of growth increments,may provide information for studying spatio-temporal distribution.In this study,we developed a method,which is based on elemental concentration of beaks at different ontogenetic stages and sampling locations,to reconstruct the squid migration route.We applied this method to Ommastrephes bartramii in the North Pacific Ocean.Nine trace elements were detected in the rostrum sagittal sections(RSS)of the beak using laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS).For those elements,significant differences were found between the different ontogenetic stages for phosphorus(P),copper(Cu)and zinc(Zn).Sodium(Na),P and Zn were chosen as indicators of sea surface temperature(SST)and a regression model was estimated.The high probability of occurrence in a particular area represented the possible optimal squid location based on a Bayesian model.A reconstructed migration route in this study,combining all the locations at different ontogenetic stages,was consistent with that hypothesized in previous studies.This study demonstrates that the beak can provide useful information for identifying the migration routes of oceanic squid.

An AAS Dependent Method for Quantitative Analysis of Essential Trace Elements from Blood Samples of Pakistani Female Breast Cancer Patients

Breast cancer is the second leading cancer in the world. The long-term exposure of some metallic compounds induces different forms of cancer, including breast cancer. Trace elements are essential metals for the physiological functions of the cell on a molecular level and also contribute in treatment of many diseases. The aim of study was to compare the level of essential trace elements, sodium, potassium, calcium, iron, and zinc in breast cancer patients with normal healthy adult women. Total forty-five patients (age range from 25 - 73 years) were included in this study and divided into three groups according to three different stages of breast cancer including tumor-II, tumor-III and tumor-IV. Blood was collected from all participants after taking history, clinical data and taking consent. However, about fifteen non-cancer healthy women in age range from 26 - 69 years were subjected to this study. The elemental concentrations were determined through atomic absorption spectrophotometer subsequent to microwave-induced acid digestion. The results of Na, K, Zn, Fe, Ca, were observed to decrease in blood samples of breast cancer patients as compared to non-cancer subjects. The results are reliable with other numerous literature reported studies, the efficiency, and deficiency of these trace metals may contribute an important role in the progress of breast cancer.

Three Stages of Zircon Growth in Magmatic Rocks from the Pingtan Complex,Eastern China

Morphological and chemical studies on zircon grains from gabbro and granite of the Pingtan magmatic complex, Fujian Province, eastern China, show that there are three stages of zircon growth. The early stage of zircon growth is characterized by colorlessness, high transparence and birefringence, low and dispersive Ipr and Ipy, weak and homogeneous BSE brightness, lower Hf content and depletion of U, Th and Y; the middle stage is characterized by abruptly increasing lpy, progressively strong and sectoral-zoning BSE brightness, higher Hf content and enrichment of U, Th and Y with Th/U 〉 1; the late stage of growth is characterized by brownish color, poor transparence, low birefringence, highest Ipr and Ipy, middle and oscillatorily-zoning BSE brightness, highest contents of Hf, U and Y with Th/U 〈 1. The stages are considered to be formed in a deep magma chamber, ascent passage and emplacement site, respectively. Due to the more or less long residual time of the magma chamber, the difference in age between the early and late stages of zircon might be great enough to be distinguished, which can be attributed to tectonic constraint for the magnlatism.

水平井分段压裂射孔间距对煤储层压裂缝延伸的影响

水平井分段压裂射孔间距对煤储层渗透性能影响显著,为了探讨不同射孔间距下煤储层压裂缝延伸规律,以鄂尔多斯大宁-吉县矿区为例,采用扩展有限元法模拟射孔间距对压裂缝起裂压力、几何特征和延伸形态的影响。结果表明:当射孔间距较小时,裂缝起裂压力较高,高度与宽度较小,且延伸形态较为复杂,裂缝偏向最小水平主应力方向延伸;随着射孔间距增大,裂缝起裂压力降低,高度与宽度增加,裂缝延伸逐渐回归到最大水平主应力方向;射孔间距达到105 m时,裂缝起裂压力与几何形态基本不再发生变化,所有裂缝不再偏转,压裂效果最佳。现场验证表明,模拟结果与实测数据吻合度较高,各项参数误差仅2%~5%,从而证明所建数值模型的正确性。研究结果可为水平井分段压裂施工设计提供理论依据。