Dynamic modelling

  • 文章类型: Journal Article
    背景:自动诊断风险计算器可以改善对有精神病风险的个体的检测。然而,它们依赖于单个时间点评估,并且可以使用动态建模技术进行改进,该技术可以考虑风险随时间的变化。
    方法:我们纳入了n=158,139名患者(n=5,007例事件),这些患者在2008年1月1日至2021年10月8日之间接受了SALMNHS基金会信托的电子健康记录中首次诊断为非器质性和非精神病性精神障碍。根据TRIPOD声明,开发了动态Cox界标模型来估计患精神病的2年风险。动态模型包括在9个地标点提取的24个预测因子(基线,0、6、12、24、30、36、42和48个月):三个人口统计,一个临床,和20种基于自然语言处理(NLP)的症状和物质使用预测因子。将性能与静态Cox回归模型进行比较,所有预测因子仅在基线评估,通过辨别索引(C指数),校准(校准图),以及内部-外部验证中的潜在临床效用(决策曲线)。
    结果:与基线(动态:C指数=0.9;静态:C指数=0.87)到最终界标点(动态:C指数=0.79;静态:C指数=0.76)的静态模型相比,动态模型提高了辨别性能。在较晚的界标点(≥24个月),动态模型的校准(校准斜率=0.97-1.1)也明显优于静态模型。在较晚的地标点(≥24个月),动态的净收益高于静态模型。
    结论:这些发现表明,动态预测模型可以改善二级精神保健中精神病风险个体的检测。
    BACKGROUND: Automatic transdiagnostic risk calculators can improve detection of individuals at risk of psychosis. However, they rely on a single point in time assessment and can be refined with dynamic modelling techniques that account for changes in risk over time.
    METHODS: We included n=158,139 patients (n=5,007 events) receiving a first index diagnosis of a non-organic and non-psychotic mental disorder within Electronic Health Records from the SLaM NHS Foundation Trust between 01/01/2008 and 10/08/2021. A dynamic Cox landmark model was developed to estimate the 2-year risk of developing psychosis according to TRIPOD statement. The dynamic model included 24 predictors extracted at nine landmark points (baseline, 0, 6, 12, 24, 30, 36, 42, and 48 months): three demographic, one clinical, and 20 Natural Language Processing (NLP) based symptom and substance use predictors. Performance was compared to a static Cox regression model with all predictors assessed at baseline only, indexed via discrimination (C-index), calibration (calibration plots), and potential clinical utility (decision curves) in internal-external validation.
    RESULTS: The dynamic model improves discrimination performance compared to the static model at baseline (dynamic: C-index=0.9; static: C-index=0.87) to the final landmark point (dynamic: C-index=0.79; static: C-index=0.76). The dynamic model was also significantly better calibrated (calibration slope=0.97-1.1) than the static model at later landmark points (≥24 months). Net benefit was higher in the dynamic compared to the static model at later landmark points (≥24 months).
    CONCLUSIONS: These findings suggest that dynamic prediction models can improve detection of individuals at risk for psychosis in secondary mental health care.
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  • 文章类型: Journal Article
    提出了描述注塑机动力学和注射过程的一维模型。该模型描述了由双泵电液变速驱动和灌装驱动的注射缸,使用无定形聚合物的注射成型过程的保持和冷却阶段。该模型被建议作为基于模型的压力控制器设计的基础,例如,喷嘴压力。重点是使用材料,构建模型的模具和机器属性,使得在制造硬件或进行实验之前分析和设计动态系统成为可能。提出的模型和开发的控制器与实验结果均显示出良好的一致性。所提出的方法本质上是通用的,可以使设计,机器的分析和评估,仅根据系统的物理特性进行控制器设计的材料和模具动力学。
    A 1D model describing the dynamics of an injection moulding machine and the injection process is presented. The model describes an injection cylinder actuated by a dual-pump electro-hydraulic speed-variable drive and the filling, holding and cooling phases of the injection moulding process utilising amorphous polymers. The model is suggested as the foundation for the design of model-based pressure controllers of, e.g., the nozzle pressure. The focus is on using material, mould and machine properties to construct the model, making it possible to analyse and design the dynamic system prior to manufacturing hardware or conducting experiments. Both the presented model and the developed controller show good agreement with experimental results. The proposed method is general in nature and enables the design, analysis and evaluation of the machine, material and mould dynamics for controller design based solely on the physical properties of the system.
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  • 文章类型: Journal Article
    背景:在肺癌筛查中选择随访测试的时间目标是具有挑战性的。我们的目标是设计动态的,通过低剂量计算机断层扫描检测到的肺结节患者的个性化肺癌筛查方案。
    方法:我们使用来自国家肺部筛查试验的肺结节患者(年龄55-74岁)的数据开发并验证了动态模型。我们在基线(R0)预测了患者特定的风险概况,并在重复的筛选轮(R1和R2)中更新了风险评估结果。我们使用风险截止值来优化早期决策点(3个月)的时间依赖性敏感性和晚期决策点(1年)的时间依赖性特异性。
    结果:在验证中,预测12个月肺癌发病的受试者工作特征曲线下面积在R0和R1-R2分别为0.867(95%置信区间:0.827-0.894)和0.807(0.765-0.948).个性化的模式,与国家综合癌症网络(NCCN)指南和肺-RADS相比,延迟诊断率较低(1.7%vs.1.7%与6.9%)和过度测试(4.9%与5.6%与5.6%)在R0,延迟诊断率较低(0.0%vs.18.2%vs.18.2%)和过度测试(2.6%与8.3%与7.3%)在R2。癌症患者中的早期测试建议使用个性化模式更频繁(与NCCN:29.8%与20.9%,p=0.0065;vs.肺RADS:33.2%vs.22.8%,p=0.0025),尤其是对女性来说,年龄≥65岁的患者,和部分实性或非实性结节。
    结论:与基于规则的协议相比,个性化模式易于实现且更准确。结果突出了个性化方法在实现有效结节管理中的价值。
    BACKGROUND: Selecting the time target for follow-up testing in lung cancer screening is challenging. We aim to devise dynamic, personalized lung cancer screening schema for patients with pulmonary nodules detected through low-dose computed tomography.
    METHODS: We developed and validated dynamic models using data of pulmonary nodule patients (aged 55-74 years) from the National Lung Screening Trial. We predicted patient-specific risk profiles at baseline (R0) and updated the risk evaluation results in repeated screening rounds (R1 and R2). We used risk cutoffs to optimize time-dependent sensitivity at an early decision point (3 months) and time-dependent specificity at a late decision point (1 year).
    RESULTS: In validation, area under receiver operating characteristic curve for predicting 12-month lung cancer onset was 0.867 (95 % confidence interval: 0.827-0.894) and 0.807 (0.765-0.948) at R0 and R1-R2, respectively. The personalized schema, compared with National Comprehensive Cancer Network (NCCN) guideline and Lung-RADS, yielded lower rates of delayed diagnosis (1.7% vs. 1.7% vs. 6.9 %) and over-testing (4.9% vs. 5.6% vs. 5.6 %) at R0, and lower rates of delayed diagnosis (0.0% vs. 18.2% vs. 18.2 %) and over-testing (2.6% vs. 8.3% vs. 7.3 %) at R2. Earlier test recommendation among cancer patients was more frequent using the personalized schema (vs. NCCN: 29.8% vs. 20.9 %, p = 0.0065; vs. Lung-RADS: 33.2% vs. 22.8 %, p = 0.0025), especially for women, patients aged ≥65 years, and part-solid or non-solid nodules.
    CONCLUSIONS: The personalized schema is easy-to-implement and more accurate compared with rule-based protocols. The results highlight value of personalized approaches in realizing efficient nodule management.
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  • 文章类型: Journal Article
    这篇综述强调了为基于生物和高级氧化工艺(AOP)的废水处理系统制定控制策略的重要性。目的是确保废水质量与环境法规保持一致,同时将运营成本降至最低。它强调了理解过程的动态行为在开发有效控制方案中的重要性。解释并列出了污水处理厂(WWTP)中最常见的过程控制策略。强调应根据过程动态行为和控制目标选择适当的控制方案。本研究进一步讨论了与废水处理过程控制相关的挑战,包括开发模型的不足,大多数控制策略对仿真阶段的局限性,对实时数据的迫切需求,以及与实施高级控制器硬件相关的财务和技术复杂性。讨论了实时数据的可用性实现可靠控制的必要性,在过程的合适位置或通过开发和实施软传感器来实现精确的硬件传感器。本研究建议对可用的执行器进行进一步调查,并选择最合适的执行器以在污水处理厂中实现稳健可靠的控制,特别是对于生物和基于AOP的治疗方法。
    This review emphasizes the significance of formulating control strategies for biological and advanced oxidation process (AOP)-based wastewater treatment systems. The aim is to guarantee that the effluent quality continuously aligns with environmental regulations while operating costs are minimized. It highlights the significance of understanding the dynamic behaviour of the process in developing effective control schemes. The most common process control strategies in wastewater treatment plants (WWTPs) are explained and listed. It is emphasized that the proper control scheme should be selected based on the process dynamic behaviour and control goal. This study further discusses the challenges associated with the control of wastewater treatment processes, including inadequacies in developed models, the limitations of most control strategies to the simulation stage, the imperative requirement for real-time data, and the financial and technical intricacies associated with implementing advanced controller hardware. It is discussed that the necessity of the availability of real-time data to achieve reliable control can be achieved by implementing proper, accurate hardware sensors in suitable locations of the process or by developing and implementing soft sensors. This study recommends further investigation on available actuators and the criteria for choosing the most appropriate one to achieve robust and reliable control in WWTPs, especially for biological and AOP-based treatment approaches.
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  • 文章类型: Journal Article
    产出水(PW)是石油和天然气(O&G)现场勘探过程中从油井中流出的最大副产品。PW含有高盐浓度以及其他有机和无机成分;因此,PW必须在处置前进行处理。电凝法(EC)是一种有效去除PW中污染物的方法,已成为许多实验研究的重点,专门用于EC治疗PW的数学模型尚未开发。在这项工作中,一个全面的数学模型已经开发出来,以阐明EC操作参数对PW处理性能的作用,并确定COD(化学需氧量)去除机制。本模型通过估算其速率常数并比较其大小,并研究了EC反应器的多尺度建模,从而考虑并确定了主要的Al-羟基络合物种类及其对合成PW样品中COD去除的贡献。电流密度等工作参数的影响,初始pH值,极间距离,研究并模拟了PW的混合速度和溶液体积对Al混凝剂生产和COD去除的影响。该研究估算了EC工艺去除COD所发生的反应的速率常数,并通过比较它们的大小来确定该过程中涉及的主要反应和促凝剂种类。COD去除的数学模型预测与10mAcm-2,15mAcm-2和20mAcm-2电流密度下的实验数据吻合良好,R2值分别为0.96,0.97和0.92,溶解铝浓度R2值分别为0.96,0.99和0.97。模拟结果再现了在初始pH为6.1、7.3和8.6时的良好拟合,COD去除的R2值分别为0.92、0.96和0.98。数学模型和实验结果表明了占主导地位的Al-羟基配合物的作用,如[公式:见正文],[公式:见正文],[公式:见正文],控制COD去除过程中的[公式:见正文]和[公式:见正文]。在研究中考虑的不同操作条件下,该模型还预测了不同反应器体积下EC反应器的COD去除性能,对于较高的溶液体积和较大的反应器,R2值为0.96。研究中提出的模型和确定的速率常数将为设计提供理论依据,扩大和操作用于油田PW处理的EC反应器。
    Produced water (PW) is the largest by-product that comes out of the oil wells during oil and gas (O&G) field exploration. PW contains high-salt concentration along with other organic and inorganic components; therefore, PW must be treated before disposal. Electrocoagulation (EC) is an effective treatment method to remove pollutants from PW which has been the focus of many experimental studies; however, a mathematical model specifically for PW treatment by EC has not been developed yet. In this work, a comprehensive mathematical model has been developed to elucidate the role of EC operating parameters on the PW treatment performance and determine the mechanism for COD (Chemical Oxygen Demand) removal. The present model considers and identifies the dominant Al-hydroxy complex species and their contribution to the COD removal from synthetic PW samples by estimating their rate constants and comparing their magnitudes and investigates multi-scale modelling of the EC reactor. The influence of working parameters such as current density, initial pH, interelectrode distance, mixing speed and solution volume of PW on Al coagulant production and COD removal was investigated and modelled. The study estimates the rate constants of the reactions taking place for COD removal by EC process and by comparing their magnitudes identifies the dominant reactions and coagulant species involved in the process. The mathematical model prediction of COD removal fits well with the experimental data at 10 mA cm-2, 15 mA cm-2 and 20 mA cm-2 current density with R2 value of 0.96, 0.97 and 0.92, respectively and for dissolved Al concentration R2 value of 0.96, 0.99, and 0.97, respectively. The simulated results reproduced a good fit at initial pH of 6.1, 7.3 and 8.6 with R2 value of 0.92, 0.96 and 0.98, respectively for COD removal. The mathematical model and the experimental results showed the role of dominant Al-hydroxy complex species such as Al OH 2 + , Al OH 2 + , Al OH 3 , Al 2 OH 2 + 4 and Al OH 4 - in controlling the COD removal process. Under different operating conditions considered in the study, the model also predicted the COD removal performance of the EC reactors at different reactor volumes with R2 value of 0.96 for higher solution volume and larger reactor. The model presented and rate constants determined in the study will provide a theoretical basis for designing, scaling up and operating the EC reactor for oil-field PW treatment.
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  • 文章类型: Journal Article
    热处理是一种广泛使用的方法,可确保牛奶的微生物安全性。预测微生物学在定量微生物生长和衰退中起着至关重要的作用。为食品加工操作的设计和优化提供有价值的指导。本研究旨在研究牛奶中单增李斯特菌在等温和动态条件下的热灭活动力学。在等温和非等温条件下,在灭菌和巴氏杀菌的牛奶中进行单核细胞增生李斯特菌的热灭活,有和没有背景微生物群,分别。此外,在肩部效应和温度之间建立了一个二级模型,然后将其集成到动态模型中。结果表明,与在等温温度为60.0、62.5和65℃的灭菌牛奶中生长的细胞相比,在热灭活之前在胰蛋白酶大豆提取物肉汤(TSBYE)中生长的单核细胞具有更高的耐热性。此外,牛奶中背景微生物群的存在显着增强了单核细胞增生李斯特菌的耐热性,正如D值从1.13min增加到2.34min所证明的那样,从0.46分钟到0.53分钟,在60.0、62.5和65°C下从0.25分钟到0.34分钟,分别,无论背景微生物群是否在共同生长后被灭活或与单核细胞增生李斯特菌共灭活。对于非等温失活,基于对数线性肩模型的一步动态模型有效地描述了微生物灭活曲线,并表现出令人满意的模型性能。所开发的模型有助于改进风险评估,使乳制品加工商能够优化热处理并确保微生物安全。
    Thermal processing is a widely used method to ensure the microbiological safety of milk. Predictive microbiology plays a crucial role in quantifying microbial growth and decline, providing valuable guidance on the design and optimization of food processing operations. This study aimed to investigate the thermal inactivation kinetics of Listeria monocytogenes in milk under both isothermal and dynamic conditions. The thermal inactivation of L. monocytogenes was conducted under isothermal and non-isothermal conditions in sterilized and pasteurized milk, with and without background microbiota, respectively. Furthermore, a secondary model was developed between the shoulder effect and temperature, which was then integrated into the dynamic model. The results showed that L. monocytogenes grown in Tryptic Soy Yeast Extract Broth (TSBYE) prior to thermal inactivation exhibited higher heat resistance compared to cells grown in sterilized milk at isothermal temperatures of 60.0, 62.5, and 65℃. Moreover, the presence of background microbiota in milk significantly enhanced the heat resistance of L. monocytogenes, as evidenced by the increased D-values from 1.13 min to 2.34 min, from 0.46 min to 0.53 min, and from 0.25 min to 0.34 min at 60.0, 62.5, and 65 °C, respectively, regardless of whether the background microbiota was inactivated after co-growth or co-inactivated with L. monocytogenes. For non-isothermal inactivation, the one-step dynamic model based on the log-linear with shoulder model effectively described the microbial inactivation curve and exhibited satisfactory model performance. The model developed contributes to improved risk assessment, enabling dairy processors to optimize thermal treatment and ensure microbiological safety.
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  • 文章类型: Journal Article
    本研究的目的是建立一个机制模型来预测高速率活性污泥(HRAS)过程的长期动态性能,包括去除碳(COD),氮(N),和磷(P)。该模型是在活性污泥模型No.1和3(ASM1和ASM3)纳入基本机制,如吸附和储存基质,特定于HRAS系统。遵循逐步方案,使用中试规模的HRAS工厂的动态数据进行校准。灵敏度分析确定了有影响的模型参数,包括最大比生长率(μ),生长产量(YH),存储产量(YSTO),存储速率(kSTO),衰减率(b),和半饱和的易于生物降解的生长基质(KS1)。校准模型实现了超过70%的标准化平均绝对误差(MAE)的混合液体悬浮固体(MLSS)的预测效率,总化学需氧量(TCOD),可溶性COD(SCOD),颗粒COD(XCOD),总氮(TN),氨氮(SNH),总磷(TP),可溶性TP(STP),和微粒TP(XTP)。不确定性分析表明,SCOD被低估了。根据不确定带的动态剖面和观测数据,有可能改善STP中动态行为的估计。观察到的差异可能归因于监测期间废水特性的变化,特别是关于易于生物降解的底物(SS)和可溶性惰性物质(SI)的磷(P)部分,这些参数在模型中不被视为动态变化的参数。
    The objective of this study is to develop a mechanistic model to predict the long-term dynamic performance of High-Rate Activated Sludge (HRAS) process, including the removal of carbon (COD), nitrogen (N), and phosphorus (P). The model was formulated with inspiration from Activated Sludge Models No. 1 and 3 (ASM1 and ASM3) to incorporate essential mechanisms, such as adsorption and storage substrate, specific to HRAS systems. A stepwise protocol was followed for calibration with dynamic data from a pilot-scale HRAS plant. Sensitivity analysis identified influential model parameters, including maximum specific growth rate (μ), growth yield (YH), storage yield (YSTO), storage rate (kSTO), decay rate (b), and half saturation of the readily biodegradable substrate for growth (KS1). The calibrated model achieved prediction efficiencies above the normalized Mean Absolute Error (MAE) of 70 % for mixed liquor suspended solids (MLSS), total chemical oxygen demand (TCOD), soluble COD (SCOD), particulate COD (XCOD), total nitrogen (TN), ammonia nitrogen (SNH), total phosphorus (TP), soluble TP (STP), and particulate TP (XTP). Uncertainty analysis revealed that SCOD was underestimated. Based on the dynamic profiles of uncertainty bands and observed data, there is potential for improving the estimation of dynamic behavior in STP. The observed discrepancies may be attributed to variations in wastewater characteristics during the monitoring period, particularly concerning the phosphorus (P) fractions of the readily biodegradable substrate (SS) and soluble inerts (SI), which were not considered as dynamically changing parameters in the model.
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  • 文章类型: Journal Article
    背景:本文评估了欧盟(EU)的植物健康法规是否对进口产生了影响。采用了动态建模方法,使用面板数据的两步广义矩估计方法,为期8年(2013-2020年)。估计的等式包括贸易量,经济驱动因素,贸易伙伴,和捕获进口要求类别的变量(植物检疫证书,豁免,限制)关于加强生物安全的外部边界措施。
    结果:从分析中我们可以得出结论,进口制度及其最近的变化影响有限,如果有的话,受影响产品的贸易流量。最重要的影响是被归类为高风险工厂的产品,而植物检疫证书要求扩展到新产品似乎对贸易的影响微不足道。
    结论:因此,欧盟外贸易的植物保护制度似乎不会扭曲贸易,同时提供了一个框架来增强欧盟的植物健康。©2023作者。害虫管理科学由JohnWiley&SonsLtd代表化学工业学会出版。
    BACKGROUND: This article assesses whether the European Union\'s (EU\'s) plant health regulations have had an impact on imports. A dynamic modelling approach was applied, using a two-step generalized method of moments estimator for panel data, and covering an 8-year period (2013-2020). The estimated equation includes volumes of trade, economic drivers, the trading partner, and variables capturing categories of import requirements (phytosanitary certificates, exemptions, restrictions) with regards to external border measures for enhanced biosecurity.
    RESULTS: From the analysis we can conclude that the import regime and its recent changes have had a limited impact, if any, on trade flows of the affected products. The most significant impact is found for products classified as high-risk plants, while the extension of the phytosanitary certificate requirement to new products seems to have had negligible effects on trade.
    CONCLUSIONS: Therefore, the plant protection regime for extra-EU trade seems to be not trade distorting while supplying a framework to enhance plant health in the EU. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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  • 文章类型: Journal Article
    雪雪崩是重力过程,其特征是雪团的快速运动,威胁山区居民和破坏山区基础设施。这种现象是复杂的事件,出于这个原因,已经开发了不同的数值模型来再现它们在给定地形上的动力学。在这项研究中,我们专注于二维数值模拟工具RAMMS::AVALANCHE和FLO-2D,旨在比较它们在预测雪崩沉积面积方面的表现。我们还旨在评估FLO-2D模拟模型的使用情况,通常用于水淹或泥浆/泥石流模拟,预测雪雪崩的运动。为此,分析了在博尔扎诺省(IT)发生的两个有据可查的雪崩事件(Knollgraben,PichlerErschbaum雪崩)。通过反分析过程,用两种模型模拟了每个案例研究的沉积区域。模拟结果主要是通过统计指数将模拟沉积面积与观察到的面积进行比较来评估的。随后,最大流动深度,速度和沉积深度也进行了比较模拟结果。结果表明,与FLO-2D模拟相比,RAMMS::AVALANCHE通常更好地再现了观察到的沉积物。FLO-2D在对流变参数进行精心校准后,为干湿雪雪崩提供了合适的结果,因为它们不是雪崩流变学研究中通常考虑的那些。然而,结果表明,FLO-2D可以用来研究雪雪崩的传播,也可以被从业者用来定义危险区域,扩大其应用领域。
    Snow avalanches are gravitational processes characterised by the rapid movement of a snow mass, threatening inhabitants and damaging infrastructure in mountain areas. Such phenomena are complex events, and for this reason, different numerical models have been developed to reproduce their dynamics over a given topography. In this study, we focus on the two-dimensional numerical simulation tools RAMMS::AVALANCHE and FLO-2D, aiming to compare their performance in predicting the deposition area of snow avalanches. We also aim to assess the employment of the FLO-2D simulation model, normally used in water flood or mud/debris flow simulations, in predicting the motion of snow avalanches. For this purpose, two well-documented avalanche events that occurred in the Province of Bolzano (IT) were analyzed (Knollgraben, Pichler Erschbaum avalanches). The deposition area of each case study was simulated with both models through back-analysis processes. The simulation results were evaluated primarily by comparing the simulated deposition area with the observed one through statistical indices. Subsequently, the maximum flow depth, velocity and deposition depth were also compared between the simulation results. The results showed that RAMMS::AVALANCHE generally reproduced the observed deposits better compared to FLO-2D simulation. FLO-2D provided suitable results for wet and dry snow avalanches after a meticulous calibration of the rheological parameters, since they are not those typically considered in avalanche rheology studies. The results showed that FLO-2D can be used to study the propagation of snow avalanches and could also be adopted by practitioners to define hazard areas, expanding its field of application.
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  • 文章类型: Journal Article
    评估髋关节置换设计的弹性的一个重要方面是在导致髋臼衬垫边缘负荷的不利条件下测试其性能。由于接触位置的变化,有限元模型中边缘载荷条件的表示在计算上具有挑战性。需要精细的网格,和系统的动态性质。在这项研究中,在研究髋关节置换装置的边缘负荷时,我们进行了网格和质量缩放敏感性联合研究,以确定显式有限元分析的收敛性和求解时间之间的适当折衷.然后使用优化的模型进行灵敏度测试,研究不同的髋关节模拟器特征(平移夹具的质量和中侧弹簧阻尼)对髋臼衬垫塑性应变的影响。最后,然后,还使用优化模型检查了多个加载循环对塑性应变逐渐累积的影响。开发了一种建模方法,该方法在质量缩放效应和网格细化之间提供了有效的折衷,每个周期的求解时间小于1h。该“推荐网格”模型低估了塑性应变小于10%,与运行时间为190h的“最佳估计”模型相比。因此,从这个模型设置开始将显著减少任何新模型开发时间,同时还允许根据需要灵活地纳入额外的复杂性。发现聚乙烯衬里的塑性应变对模拟器质量和阻尼敏感(使质量或阻尼加倍具有与摆动相位载荷加倍相似的幅度效应),这些理想情况下应该在未来的实验研究中进行描述。大多数塑性应变(99%)在前三个载荷循环中累积。
    An important aspect in evaluating the resilience of hip replacement designs is testing their performance under adverse conditions that cause edge loading of the acetabular liner. The representation of edge loading conditions in finite element models is computationally challenging due to the changing contact locations, need for fine meshes, and dynamic nature of the system. In this study, a combined mesh and mass-scaling sensitivity study was performed to identify an appropriate compromise between convergence and solution time of explicit finite element analysis in investigating edge loading in hip replacement devices. The optimised model was then used to conduct a sensitivity test investigating the effect of different hip simulator features (the mass of the translating fixture and mediolateral spring damping) on the plastic strain in the acetabular liner. Finally, the effect of multiple loading cycles on the progressive accumulation of plastic strain was then also examined using the optimised model. A modelling approach was developed which provides an effective compromise between mass-scaling effects and mesh refinement for a solution time per cycle of less than 1 h. This \'Recommended Mesh\' model underestimated the plastic strains by less than 10%, compared to a \'Best Estimate\' model with a run time of ∼190 h. Starting with this model setup would therefore significantly reduce any new model development time while also allowing the flexibility to incorporate additional complexities as required. The polyethylene liner plastic strain was found to be sensitive to the simulator mass and damping (doubling the mass or damping had a similar magnitude effect to doubling the swing phase load) and these should ideally be described in future experimental studies. The majority of the plastic strain (99%) accumulated within the first three load cycles.
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