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Research on the Comprehensive Demodulation of Gear Tooth Crack Early Fault
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作者 CUI Lingli DING Fang GAO Lixin ZHANG Jianyu (College of Mechanical Engineering and Applied Electronics Technology,Beijing University of Technology,Advanced Manufacturing Technology,The Key Laboratory of Beijing Municipality,Beijing 100022,China 《武汉理工大学学报》 CAS CSCD 北大核心 2006年第S2期596-599,共4页
The component of gear vibration signal is very complex,when a localized tooth defect such as a tooth crack is pre- sent,the engagement of the cracked tooth will induce an impulsive change with comparatively low energy... The component of gear vibration signal is very complex,when a localized tooth defect such as a tooth crack is pre- sent,the engagement of the cracked tooth will induce an impulsive change with comparatively low energy to the gear mesh signal and the background noise.This paper presents a new comprehensive demodulation method which combined with amplitude envelop demodulation and phase demodulation to extract gear crack early fault.A mathematical model of gear vibration signal contain crack fault is put forward.Simulation results based on this model show that the new comprehensive demodulation method is more effective in finding fault and judging fault level then conventional single amplitude demodulation at present. 展开更多
关键词 DEMODULATION gear TOOTH crack early FAULT amplitude MODULATION phase MODULATION
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Thermal and Stress Analysis of Early Age Concrete for Spread Footing
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作者 丁红岩 张磊 +1 位作者 张浦阳 朱奇 《Transactions of Tianjin University》 EI CAS 2015年第6期477-483,共7页
The early age performance of spread footing, especially the growth of cracks, is deeply influenced by the heat of hydration of cement. In this paper, 3D finite element method(FEM)models are set up to analyze the tempe... The early age performance of spread footing, especially the growth of cracks, is deeply influenced by the heat of hydration of cement. In this paper, 3D finite element method(FEM)models are set up to analyze the temperature distribution and thermal stresses of the spread footing during the first seven days after concrete placement. The mechanical properties of early age concrete are calculated, which are further used in the FEM models. The possibilities of crack growth are estimated by the method of crack index. The crack indexes of quite a number of points are very close to the allowable limit of 1.0 during the last three days. It is also indicated that the influence of foundation ring on the thermal stresses of concrete can be neglected. 展开更多
关键词 mass concrete heat of hydration early age concrete thermal crack crack index
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Fatigue crack initiation and early propagation behavior of 2A97 Al-Li alloy 被引量:6
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作者 钟警 钟申 +2 位作者 郑子樵 张海锋 罗先甫 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第2期303-309,共7页
The fatigue crack initiation and early propagation behavior of 2A97 Al-Li alloy was studied. The smooth specimens were fatigued at room temperature under constant maximum stress control when stress ratio (R) is 0.1 ... The fatigue crack initiation and early propagation behavior of 2A97 Al-Li alloy was studied. The smooth specimens were fatigued at room temperature under constant maximum stress control when stress ratio (R) is 0.1 and frequency (f) is 40 Hz. Microstructure observations were examined by optical microscopy, transmission electron microscopy, scanning electron microscopy and electron back scattered diffusion, in order to investigate the relationship between microstructure and fatigue crack initiation and early propagation behavior of 2A97 alloy. The results show that the fatigue cracks are predominantly initiated at inclusions and coarsen secondary phases on the surface of 2A97 alloy. The fatigue crack early propagation behavior of 2A97 alloy is predominantly influenced by the interactions between grain structure and dislocations or persistent slip bands (PSBs). When the misorientation of two neighbouring grains is close to the orientations of the favorable slip plane within these two grains, high-angle grain boundary severely hinders the PSBs passing through, and thus leads to crack bifurcation and deflection. 展开更多
关键词 2A97 Al-Li alloy fatigue crack initiation fatigue crack early propagation
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Development of Maintenance Management Strategy Based on Reliability Centered Maintenance for Marginal Oilfield Production Facilities
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作者 Olawale D. Adenuga Ogheneruona E. Diemuodeke Ayoade O. Kuye 《Engineering(科研)》 CAS 2023年第3期143-162,共20页
The present work adopted Reliability Centered Maintenance (RCM) methodology to evaluate marginal oilfield Early Production Facility (EPF) system to properly understand its functional failures and to develop an efficie... The present work adopted Reliability Centered Maintenance (RCM) methodology to evaluate marginal oilfield Early Production Facility (EPF) system to properly understand its functional failures and to develop an efficient maintenance strategy for the system. The outcome of the RCM conducted for a typical EPF within the Niger Delta zone of Nigeria provides an indication of equipment whose failure can significantly affect operations at the production facility. These include the steam generation unit and the wellhead choke assembly, using a risk-based failure Criticality Analysis. Failure Mode and Effect Analysis (FMEA) was conducted for the identified critical equipment on a component basis. Each component of the equipment was analyzed to identify the failure modes, causes and the effect of the failure. The outcome of the FMEA analysis aided the development of a robust maintenance management strategy, which is based on an optimized mix of corrective, preventive and condition-based monitoring maintenance for the marginal oilfield EPF. 展开更多
关键词 Criticality Analysis Corrective maintenance Condition-Based maintenance early Production Facility Preventive maintenance Risk Priority Number
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Assessment of early-age cracking of high-performance concrete in restrained ring specimens 被引量:2
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作者 Quang-phu NGUYEN Lin-hua JIANG Qiao ZHU 《Water Science and Engineering》 EI CAS 2010年第1期113-120,共8页
High-performance concrete (HPC) is stronger and more durable than conventional concrete. However, shrinkage and shrinkage cracking are common phenomena in HPC, especially early-age cracking. This study assessed earl... High-performance concrete (HPC) is stronger and more durable than conventional concrete. However, shrinkage and shrinkage cracking are common phenomena in HPC, especially early-age cracking. This study assessed early-age cracking of HPC for two mixtures using restrained ring tests. The two mixtures were produced with water/binder mass ratio (mw/mB) of 0.22 and 0.40, respectively. The results show that, with greater steel thickness, the higher degree of restraint resulted in a higher interface pressure and earlier cracking. With steel thickness of 6 mm, 19 mm, and 30 mm, the age of cracking were, respectively, 12 days, 8 days, and 5.4 days with the mw/mB = 0.22 mixture; and 22.5 days, 12.6 days, and 7.1 days with the mw/mB= 0.40 mixture. Cases of the same steel thickness show that the ring specimens with a thicker concrete wall crack later. With the mw/mB = 0.22 mixture, concrete walls with thicknesses of 37.5 mm, 75 mm, and 112.5 mm cracked at 3.4 days, 8.0 days, and 9.8 days, respectively; with the mw/mB = 0.40 mixture, the ages of cracking were 7.1 days, 12.6 days, and 16.0 days, respectively. 展开更多
关键词 high-performance concrete SHRINKAGE early-age cracking restrained ring test
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Cracking Tendency of Restrained Concrete at Early Ages
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作者 BA Hengjing SU Anshuang GAO Xiaojian TAO Qi 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2008年第2期263-267,共5页
A modified testing system characterized by full automation, steady operation and high accuracy of strain and stress measurements was developed to determine the cracking tendency of high strength concrete (HSC) in re... A modified testing system characterized by full automation, steady operation and high accuracy of strain and stress measurements was developed to determine the cracking tendency of high strength concrete (HSC) in restrained condition at early ages. The shrinkage stress and the tensile creep behavior of HSC at early ages were investigated. The influence of W/C ratio and curing conditions on the early-age shrinkage stress and tensile creep was evaluated. It was found that the lower W/C ratio and drying curing condition resulted in higher shrinkage stress, stress induced tensile creep and greater cracking tendency. 展开更多
关键词 cracking tendency shrinkage stress tensile creep CONCRETE early ages
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Influence of Early Life Stress on Alcohol and Crack Dependents
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作者 Elton Brás Camargo Júnior Maria Neyrian de Fátima Fernandes +3 位作者 Larissa Bessani Hidalgo Gimenez Jaqueline Rodrigues Stefanini Ana Carolina Guidorizzi Zanetti Edilaine Cristina da Silva Gherardi-Donato 《Open Journal of Nursing》 2020年第5期490-512,共23页
Background: Early life stress is a significant public health problem associated with increased rates of psychiatric disorders, especially those related to drug abuse. Objective: To identify the prevalence of early lif... Background: Early life stress is a significant public health problem associated with increased rates of psychiatric disorders, especially those related to drug abuse. Objective: To identify the prevalence of early life stress in drug users, to compare the intensity of trauma in alcohol and crack users, and to relate the power of injury to the severity of drug dependence. Method: Cross-sectional analytical study with a sample of 105 alcohol and crack users treated by an outpatient service. The instruments for data collection were sociodemographic data questionnaire, the Mini-International Neuropsychiatric Interview, and the Severity of Dependence Scale. The categorical variables association was analyzed using the Chi-squared test, considering p Results: High prevalence of early stress and severity of dependence were identified, with higher rates among crack users. The early stress revealed in the Alcohol group high rates of emotional (88.7%) and physical (94.3%) neglect and in the Crack group significant frequency of physical (61.5%) emotional abuse (51.9%), sexual (46.2%), and emotional (78.8%) and physical (90.4%) neglect. Crack users are 2.6 times more likely to have been emotionally abused, and 2.1 times more likely to have been sexually abused during childhood when compared to the alcohol group. Conclusion: Early stress was prevalent with significant intensity in drug users, and evaluation of this problem is essential for a better understanding of these disorders. 展开更多
关键词 CHILDHOOD Trauma ADVERSE CHILDHOOD Experiences Child ABUSE early Life Stress Substance ABUSE crack ALCOHOL
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GEAR CRACK EARLY DIAGNOSIS USING BISPECTRUM DIAGONAL SLICE 被引量:4
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作者 Li WeihuaZhang GuicaiShi TielinYang ShuziSchool of Mechanical Scienceand Engineering,Huazhong University of Scienceand Technology,Wuhan 430074, China 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2003年第2期193-196,共4页
A study of bispectral analysis in gearbox condition monitoring is presented.The theory of bispectrum and quadratic phase coupling (QPC) is first introduced, and then equationsfor computing bispectrum slices are obtain... A study of bispectral analysis in gearbox condition monitoring is presented.The theory of bispectrum and quadratic phase coupling (QPC) is first introduced, and then equationsfor computing bispectrum slices are obtained. To meet the needs of online monitoring, a simplifiedmethod of computing bispectrum diagonal slice is adopted. Industrial gearbox vibration signalsmeasured from normal and tooth cracked conditions are analyzed using the above method. Experimentsresults indicate that bispectrum can effectively suppress the additive Gaussian noise andchracterize the QPC phenomenon. It is also shown that the 1-D bispectrum diagonal slice can capturethe non-Gaussian and nonlinear feature of gearbox vibration when crack occurred, hence, this methodcan be employed to gearbox real time monitoring and early diagnosis. 展开更多
关键词 condition monitoring gear crack early diagnosis quadratic phase coupling bispectrum diagonal slice
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Optimal Risk-Based Maintenance Planning of Ship Hull Structure
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作者 Mohammad Reza Zareei Mehdi Iranmanesh 《Journal of Marine Science and Application》 CSCD 2018年第4期603-624,共22页
Various structures such as marine structures age over time. In order to always maintain safety conditions, maintenance processes including inspection and repair should be implemented on them. Corrosion and fatigue cra... Various structures such as marine structures age over time. In order to always maintain safety conditions, maintenance processes including inspection and repair should be implemented on them. Corrosion and fatigue cracks are two main factors that reduce the ultimate strength of the ship's hull girder over time and thus increase the probability and risk of failure. At the time of inspection,the structural conditions must be checked so that, if necessary, the required repairs can be done on it. The main objective of this paper is to provide optimized maintenance plans of the ship structure based on probabilistic concepts with regard to corrosion and fatigue cracks. Maintenance activities increase the operational costs of ships; therefore, it is advisable to inspect and repair in the optimal times. Optimal maintenance planning of the ship structure can be conducted by formulating and solving a multi-objective optimization problem. The use of risk as a structural performance indicator has become more common in recent years. The objective functions of the optimization problem include minimizing the structure's lifecycle maintenance costs, including inspection and repair costs, and also minimizing the maximum risk of structural failure during the ship's life. In the following,to achieve better responses, reliability index has been added to the problem as the third objective function. The multi-objective optimization problem is solved using genetic algorithms. The proposed risk-based approach is applied to the hull structure of a tanker ship. 展开更多
关键词 SHIP HULL GIRDER Optimummaintenance planning LIFECYCLE cost RISK Failure CONSEQUENCE Inspection Repair Corrosion Fatigue cracks
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基于综合性能试验的混凝土早期开裂行为研究 被引量:1
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作者 王骞 郑忠良 +3 位作者 尤博 张兆彪 李宇翔 曹明莉 《大连理工大学学报》 CAS CSCD 北大核心 2024年第1期82-89,共8页
为提高混凝土的早期抗裂性能,突破单因素改善其早期稳定性,进行了多因素补偿混凝土各性能缺陷方面的研究.基于调控混凝土配合比开展了胶凝材料水化热、混凝土早期收缩试验和大板加速开裂试验.通过相关收缩机理分析了不同混凝土拌和物的... 为提高混凝土的早期抗裂性能,突破单因素改善其早期稳定性,进行了多因素补偿混凝土各性能缺陷方面的研究.基于调控混凝土配合比开展了胶凝材料水化热、混凝土早期收缩试验和大板加速开裂试验.通过相关收缩机理分析了不同混凝土拌和物的开裂行为;运用双参数Weibull分布分析试验结果,得出了混凝土大板裂缝经时开裂规律.试验结果表明:采用高效稳定型聚羧酸减水剂可以增加浆体的和易性,结合66.7%矿物掺合料(粉煤灰和矿渣粉与水泥质量比)、较好级配碎石和0.29的水胶比有利于延长混凝土的初裂时间和控制裂缝宽度,即提高混凝土的早期抗裂性能.同时,该调控手段也可以降低浆体的水化热,提高混凝土的抗压强度.此外,混凝土裂缝宽度的经时变化规律很好地服从双参数Weibull分布. 展开更多
关键词 水化热 开裂行为 抗裂性能 早期收缩 矿物掺合料
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基于声发射技术的早龄期混凝土断裂性能 被引量:1
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作者 范向前 葛菲 《建筑材料学报》 EI CAS CSCD 北大核心 2024年第2期153-160,共8页
为探究早龄期混凝土的断裂性能,针对5种养护龄期(3、7、14、21、28 d)的混凝土试件,开展20根含预制裂缝的三点弯曲梁断裂试验,得到其荷载-裂缝口张开位移(P-CMOD)曲线.基于该曲线,计算得到早龄期混凝土的断裂韧度(起裂韧度和失稳韧度)... 为探究早龄期混凝土的断裂性能,针对5种养护龄期(3、7、14、21、28 d)的混凝土试件,开展20根含预制裂缝的三点弯曲梁断裂试验,得到其荷载-裂缝口张开位移(P-CMOD)曲线.基于该曲线,计算得到早龄期混凝土的断裂韧度(起裂韧度和失稳韧度)和断裂能.采用声发射(AE)技术,通过振铃计数和累计振铃计数与时间的关系曲线,探讨养护龄期对早龄期混凝土试件损伤断裂过程的影响;通过计算上升角(RA)和平均频率(AF),分析了早龄期混凝土的破坏模式.结果表明:早龄期混凝土的断裂韧度和断裂能均随着养护龄期的增加而增大,抗开裂能力提高,延性变差.当养护龄期由3 d增至14 d时,混凝土的断裂韧度和断裂能增速较快;当养护龄期由14 d增至28 d时,混凝土的断裂韧度和断裂能增速变缓.振铃计数和累计振铃计数均能较好地反映早龄期混凝土的损伤破坏过程,其中累计振铃计数的增速随着养护龄期的增加而减小.混凝土的剪切裂缝占总裂缝的比例随着养护龄期的增加而增加. 展开更多
关键词 早龄期混凝土 裂缝 断裂韧度 断裂能 声发射
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聚丙烯纤维磷石膏胶结体早期力学强度特性及增韧机理研究
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作者 张卫中 周凯 +3 位作者 孔德华 吴倩倩 康钦容 潘登 《金属矿山》 CAS 北大核心 2024年第2期97-103,共7页
在传统水泥基复合材料的研究领域,纤维增强了材料的强度、韧性、延展性和抗裂性。为了提高磷石膏胶结体的早期强度,掺入聚丙烯纤维作为增强剂,开展了掺纤维磷石膏胶结体制备试验以及单轴抗压强度试验,分析了纤维对磷石膏胶结体破坏规律... 在传统水泥基复合材料的研究领域,纤维增强了材料的强度、韧性、延展性和抗裂性。为了提高磷石膏胶结体的早期强度,掺入聚丙烯纤维作为增强剂,开展了掺纤维磷石膏胶结体制备试验以及单轴抗压强度试验,分析了纤维对磷石膏胶结体破坏规律的影响,并通过SEM探究了纤维对磷石膏胶结体的增韧机理。研究结果表明:随纤维掺量增加磷石膏胶结体单轴抗压强度呈先增加后降低的趋势,且纤维最优掺量为1%;掺入纤维的磷石膏胶结体能延缓峰值抗压强度达到时间且破坏时的峰值应力更大,未掺入纤维的磷石膏胶结体在荷载超过应力峰值后快速失稳,掺入聚丙烯纤维的磷石膏胶结体则呈缓慢降低趋势;随着纤维的掺入,磷石膏胶结体的裂纹数量逐渐减少,且裂而不断,磷石膏胶结体的延性变形明显;微观下聚丙烯纤维表面附着有絮团状水化产物,且在磷石膏胶结体固结过程中相互缠结形成稳定的网状结构。研究成果可为磷石膏基复合材料在固废胶结充填现场的应用提供一定参考。 展开更多
关键词 聚丙烯纤维 磷石膏胶结体 早期力学特性 裂纹演化
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桥上CRTSⅠ型双块式无砟轨道早期开裂行为研究 被引量:2
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作者 张凯 元强 +3 位作者 李秋义 黄庭杰 左胜浩 黄志斌 《铁道学报》 EI CAS CSCD 北大核心 2024年第3期41-49,共9页
以桥上CRTSⅠ型双块式无砟轨道为研究对象,基于混凝土早期性能发展基本理论,利用Ansys建立三维温度场与应力场分析模型,考虑养护方法、拆模龄期、拆模温度与钢筋直径等参数影响,对双块式无砟轨道早期开裂行为进行数值模拟。结果表明:无... 以桥上CRTSⅠ型双块式无砟轨道为研究对象,基于混凝土早期性能发展基本理论,利用Ansys建立三维温度场与应力场分析模型,考虑养护方法、拆模龄期、拆模温度与钢筋直径等参数影响,对双块式无砟轨道早期开裂行为进行数值模拟。结果表明:无砟道床不同位置处混凝土主拉应力整体呈循环上升趋势;拆模前后混凝土应力时程曲线波动程度差异较大,拆模后4 h内道床混凝土主拉应力时程曲线出现明显增长。合理选用养护方式可有效降低道床板早期开裂风险;伴随着拆模龄期的延长与拆模温度的升高,拆模后无砟道床4 h内温度改变量与道床混凝土开裂风险均呈降低趋势;相同配筋率下,减小钢筋直径可降低桥上CRTSⅠ型双块式无砟轨道早期开裂风险。 展开更多
关键词 桥上双块式无砟轨道 早期温度场 早期开裂 数值模拟
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混凝土早龄期收缩开裂细观力学机理研究 被引量:1
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作者 张翔 田正宏 +3 位作者 张闻起 沈雷 徐磊 张礼彬 《水电能源科学》 北大核心 2024年第2期57-61,共5页
缓减混凝土早龄期收缩开裂是提升混凝土结构耐久性和防水性能的关键环节,对此研究了基于细观力学的混凝土早龄期收缩开裂机理。采用随机骨料模型对混凝土内粗骨料、砂浆和界面过渡区(ITZ)进行参数化建模生成混凝土细观结构,建立混凝土... 缓减混凝土早龄期收缩开裂是提升混凝土结构耐久性和防水性能的关键环节,对此研究了基于细观力学的混凝土早龄期收缩开裂机理。采用随机骨料模型对混凝土内粗骨料、砂浆和界面过渡区(ITZ)进行参数化建模生成混凝土细观结构,建立混凝土细观数值模型,针对现行试验规范,确定模拟所需力学参数并验证计算方法。结果表明,混凝土早龄期的收缩应变随时间的变化趋势受粗骨料随机分布的影响不大,不同分布形式下的混凝土24 h收缩应变值最大相对误差为7%;平板混凝土试件早龄期的收缩裂缝沿着裂缝诱导器尖端区域的ITZ单元发展,不同粗骨料分布形式下的裂缝面积最大相对误差为9.5%。 展开更多
关键词 混凝土 早龄期 收缩开裂 细观力学机理
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基于注意力机制的YOLOv5路面裂缝检测与识别 被引量:1
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作者 周双喜 杨丹 +2 位作者 潘远 丁建新 丁杨 《华东交通大学学报》 2024年第2期56-63,共8页
【目的】针对传统路面裂缝检测实时性差、准确率低的问题。【方法】利用深度学习网络在目标检测方面的优势,提出一种改进的YOLOv5算法,称为YOLOv5s-attention,以实现路面裂缝自动化检测与识别。首先,对采集到的裂缝图片用LabelImg标注... 【目的】针对传统路面裂缝检测实时性差、准确率低的问题。【方法】利用深度学习网络在目标检测方面的优势,提出一种改进的YOLOv5算法,称为YOLOv5s-attention,以实现路面裂缝自动化检测与识别。首先,对采集到的裂缝图片用LabelImg标注软件进行手工标记,然后通过改进YOLOv5网络训练得到网络模型参数。最后,利用所建立的模型对裂缝进行验证和预测。除此之外,采用综合评价指标(F1-measure,F_(1))和平均精度均值(mean average precision,mAP)这两个指标来比较原YO-LOv5s、YOLOv5s-attention模型在路面裂缝上检测与识别的性能。【结果】经YOLOv5s与YOLOv5s-attention比较发现,YO-LOv5s-attention检测准确率(Precision)提高1.0%,F1提高0.9%,mAP提高了1.8%。【结论】由此可知,该网络在实现道路裂缝自动化识别上具有一定的现实意义。 展开更多
关键词 道路养护 路面裂缝 目标检测 YOLO 注意力机制 图像处理
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混杂纤维对混凝土抗裂性能的影响研究 被引量:1
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作者 林斌 刘延军 +3 位作者 成凯 王伟 花培舒 喻林 《新型建筑材料》 2024年第3期141-145,共5页
为探究混杂纤维对混凝土抗裂性能影响,利用超高分子质量聚乙烯(UHMWPE)纤维弹模大、韧性好的优势来阻碍混凝土内部裂缝的扩展和宏观裂缝的形成,利用钢纤维抗拉、抗弯、抗剪性能好的优势来提高混凝土抗裂性能。测试了2种纤维掺量以及单... 为探究混杂纤维对混凝土抗裂性能影响,利用超高分子质量聚乙烯(UHMWPE)纤维弹模大、韧性好的优势来阻碍混凝土内部裂缝的扩展和宏观裂缝的形成,利用钢纤维抗拉、抗弯、抗剪性能好的优势来提高混凝土抗裂性能。测试了2种纤维掺量以及单掺、复掺方式下混凝土的干燥收缩率及早期抗裂性能。结果表明:UHMWPE纤维与钢纤维复掺时,混凝土干燥收缩性能最优的纤维掺量为0.2%,且钢纤维占比为75%时,28 d开裂收缩率较基准组降低了60.7%,总体降低率低于单掺纤维混凝土;复掺和单掺纤维对混凝土抗裂性能均有明显提升,复掺时效果最优,几乎没有裂缝产生。 展开更多
关键词 钢纤维 UHMWPE纤维 干燥收缩性能 混凝土 早期抗裂性能
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基于透析基本数据、超声和常规血生化构建维持性血液透析患者容量超负荷的早期预警模型及临床效用分析
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作者 曾财花 陶玲玲 +2 位作者 程静 黄琴 樊梅荣 《临床肾脏病杂志》 2024年第8期651-659,共9页
目的基于透析基本数据、超声和常规血生化构建维持性血液透析(maintenance hemodialysis,MHD)容量超负荷的早期预警模型及临床效用。方法回顾性纳入2023年1月至2023年12月在南昌大学第一附属医院肾内血透中心接受MHD患者603例,按照2:1... 目的基于透析基本数据、超声和常规血生化构建维持性血液透析(maintenance hemodialysis,MHD)容量超负荷的早期预警模型及临床效用。方法回顾性纳入2023年1月至2023年12月在南昌大学第一附属医院肾内血透中心接受MHD患者603例,按照2:1比例分为建模集(n=402)、验证集(n=201)。收集患者临床资料,单因素、LASSO-Logistic回归分析建模集中MHD容量超负荷的影响因素,并构建风险预测列线图模型,采用一致性指数、校准曲线、受试者工作特征曲线(receiver operating characteristic curve,ROC)、决策曲线对该预测模型进行内外部验证。结果建模集中超负荷组血清白蛋白、尿素清除指数(urea clearanceindex,Kt/V)、残余肾功能(residual renal function,RRF)、左室射血分数低于正常组,N末端脑钠肽前体(N-terminal pro-brain natriuretic peptide,NT-proBNP),肺超声显示B线,右房内径高于正常组(P<0.05);LASSO结果显示,血清白蛋白、Kt/V、RRF、左室射血分数、NT-proBNP、超声肺B线、右房内径是MHD容量超负荷的前期的特征变量。Logistic回归结果显示,Kt/V、血清白蛋白、RRF、左室射血分数是MHD容量超负荷情况的保护因素,NT-proBNP,肺超声显示B线,右房内径是MHD容量超负荷情况的危险因素(P<0.05);根据Logistic回归影响因素构建患者容量超负荷的风险预测列线图模型,在建模集和验证集中一致性指数分别为0.860、0.814,校准曲线显示该模型在建模集和验证集中预测MHD容量超负荷发生率与实际发生率基本一致,ROC曲线显示该模型在建模集和验证集中预测的曲线下面积分别为0.917(95%CI:0.886~0.948)、0.916(95%CI:0.869~0.962),决策曲线显示,当建模集高风险阈值在0~0.7时、验证集高风险阈值在0~0.7时该模型具有较好的临床净收益。结论MHD患者容量超负荷发生受众多因素影响,如血清白蛋白、Kt/V、RRF、左室射血分数、NT-proBNP,肺超声显示B线,右房内径,根据患者发生容量超负荷相关因素构建的早期预警模型具有良好预测能力和临床获益度。 展开更多
关键词 血液透析 超声 常规血生化 MHD 容量超负荷 预警模型 临床效用
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抗裂高性能混凝土的制备与性能研究 被引量:1
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作者 王国军 岳伟杰 储洪强 《广州建筑》 2024年第2期75-79,共5页
混凝土的开裂问题一直是工程上一道亟待解决的难题。为改善混凝土工作性能,降低水化放热量,增强其抗裂性能,本文通过试验,对不同粉煤灰掺量的混凝土的各项性能进行对比研究,包括力学性能、热学性能和长期性能,比较分析不同粉煤灰掺量下... 混凝土的开裂问题一直是工程上一道亟待解决的难题。为改善混凝土工作性能,降低水化放热量,增强其抗裂性能,本文通过试验,对不同粉煤灰掺量的混凝土的各项性能进行对比研究,包括力学性能、热学性能和长期性能,比较分析不同粉煤灰掺量下混凝土的各项性能差异。结果表明,随粉煤灰掺量增加,混凝土呈现出强度前期降低后期迅速增长的趋势,当粉煤灰掺量达到50%时,与未掺粉煤灰的试件相比,其7 d抗压强度降低了40.3%,60 d强度较7 d强度增长了53.9%;粉煤灰的加入明显地降低了胶凝体系的放热速率,粉煤灰掺量为50%的胶凝材料7 d水化放热量为171 J/g,较纯水泥的放热量降低了40.3%;在水胶比固定的情况下,粉煤灰的掺入可以降低混凝土的收缩率,粉煤灰掺量为30%时对混凝土的减缩效果最好。 展开更多
关键词 粉煤灰 抗裂混凝土 力学性能 水化热 干燥收缩 早期平板抗裂
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明挖法超长节段现浇混凝土隧道早期开裂机制现场试验研究
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作者 肖碧宏 蒋礼 +4 位作者 梁振宇 刘唐进 郝小虎 傅金阳 王树英 《隧道建设(中英文)》 CSCD 北大核心 2024年第10期1982-1992,共11页
为研究超长节段明挖隧道混凝土早期开裂机制,依托实际工程,根据隧道前期已浇筑节段开裂情况调查结果,在隧道侧墙和顶板结构的中心线处埋置温度、湿度、应变传感器,对混凝土早龄期的温度、湿度、应变进行连续监测,并结合温度应力理论和... 为研究超长节段明挖隧道混凝土早期开裂机制,依托实际工程,根据隧道前期已浇筑节段开裂情况调查结果,在隧道侧墙和顶板结构的中心线处埋置温度、湿度、应变传感器,对混凝土早龄期的温度、湿度、应变进行连续监测,并结合温度应力理论和现场裂缝调查对隧道混凝土早期开裂机制进行分析。分析结果表明:1)隧道侧墙和顶板结构浇筑后产生的水化热温升可达40℃以上,隧道顶板结构应变的变化趋势主要与温度相关。2)结构温度下降引起的收缩变形在受到下部旧混凝土的约束作用后产生的拉应力是引起开裂的主要原因;长度方向上的应变差、里表温差产生的不均匀收缩和湿度下降产生的干燥收缩会进一步加大开裂风险。3)结构中心与外表面的最大温差高出与内表面的最大温差12℃以上,因而结构外表面更容易出现开裂。4)在连续式的外约束作用下,浇筑段中部开裂的可能性更大。5)结构表面与内部的裂缝会逐渐沿裂缝走向扩展导致风险较低的区域也出现开裂。 展开更多
关键词 明挖法隧道 现浇混凝土 早期开裂 现场试验 温度场 相对湿度 应变
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基于图神经网络的路面病害态势预测方法
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作者 马泽超 刘小明 +3 位作者 夏汗青 王伟强 王久增 申海涛 《浙江大学学报(工学版)》 EI CAS CSCD 北大核心 2024年第12期2596-2608,共13页
针对路面病害生成和恶化的预测问题,提出应用图卷积神经网络的路面病害态势预测方法.通过聚类算法建立拓扑网络,选取目标病害在演化过程中的主要影响因素;为了增强图神经网络对病害信息的表达能力,采用图拓扑增强的方法,从静态和动态方... 针对路面病害生成和恶化的预测问题,提出应用图卷积神经网络的路面病害态势预测方法.通过聚类算法建立拓扑网络,选取目标病害在演化过程中的主要影响因素;为了增强图神经网络对病害信息的表达能力,采用图拓扑增强的方法,从静态和动态方面分别构造与病害信息相关的视图;采用图神经网络(GNN)架构增强的方法,在视图维度上应用注意力机制调整不同视图的影响力,并在时间维度上应用Transformer和GRU模块,增强模型在长时间序列中对病害状态的预测性能.设计模型的内部调整测试,经消融试验、多样本测试和超参数对照组的验证,证明所提模型的适用性和稳定性.针对大型稀疏的路面病害数据集,此模型的平均绝对误差均值收敛在4.0以内,综合性能优于传统预测算法. 展开更多
关键词 公路养护 路面病害 图神经网络 时间序列预测 裂缝
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