Journal of Multiscale Modelling最新文献_第5页

Size Effects on Droplet Displacing Process in Micropores by Multiscale Modeling 微孔中液滴置换过程的多尺度模拟

IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS

Journal of Multiscale Modelling

Pub Date : 2021-08-28 DOI: 10.1142/s1756973721410018

Fanli Liu, Moran Wang

Transport mechanisms of small droplets on walls in micropores become significant for applications in energy, resource and biomedical engineering, however, a suitable numerical tool remains challenging. Macroscopic approach is ideal both in computing cost and simplicity but its applicability is doubted for nanoscale droplet, yet no clear evaluation on when exactly does it become invalid has been made. This work evaluates the applicability of macroscopic approach for the displacing process of droplet in a micropore and investigates relevant size effects, by comparing the simulation results of multiscale modeling and macroscopic method. Three types of size effects affecting the displacement results are identified: Laplace pressure, low interfacial density, and breakdown of macroscopic description. For the system studied, the Laplace pressure dominates for relatively big droplet, then low density region becomes significant for drop diameter smaller than 18 times molecule diameter, and finally macroscopic description gradually fails for drop diameter smaller than 13 times molecule diameter. We further investigate the influences of system scale and fluid type on these size effects and discuss the relative importance of each size effect under different conditions. Results indicate that traditional macroscopic approach may be invalid even when continuum assumption still holds due to other size effects, and corrections for those effects can be made to extend the applicability of macroscopic method.

微孔壁上小液滴的传输机制对能源、资源和生物医学工程的应用具有重要意义，然而，合适的数值工具仍然具有挑战性。宏观方法在计算成本和简单性方面都是理想的，但它对纳米级液滴的适用性受到怀疑，但还没有明确评估它何时失效。本工作通过比较多尺度建模和宏观方法的模拟结果，评估了宏观方法在微孔中液滴位移过程中的适用性，并研究了相关的尺寸效应。确定了影响位移结果的三种类型的尺寸效应：拉普拉斯压力、低界面密度和宏观描述的破坏。对于所研究的系统，拉普拉斯压力在相对较大的液滴中占主导地位，然后对于小于18倍分子直径的液滴直径，低密度区域变得显著，最后对于小于13倍分子直径，宏观描述逐渐失败。我们进一步研究了系统规模和流体类型对这些尺寸效应的影响，并讨论了在不同条件下每种尺寸效应的相对重要性。结果表明，即使由于其他尺寸效应，连续体假设仍然成立，传统的宏观方法也可能是无效的，可以对这些效应进行修正，以扩大宏观方法的适用性。

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引用次数: 0

The Use of Principal Component Analysis for the Prediction of Double Halide Perovskites A2BX6 主成分分析在双卤化物钙钛矿A2BX6预测中的应用

IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS

Journal of Multiscale Modelling

Pub Date : 2021-06-07 DOI: 10.1142/S1756973721500049

Mohamed Boubchir, R. Boubchir, H. Aourag

In this paper, we report a comprehensive and systematic study for predicting the formability of double halide perovskites. Besides the tolerance factor, several complementary criteria for the formation and lattice distortion have been developed and compared with a throughout multivariate technique based on the principal component analysis (PCA) and the partial least square (PLS) methods. Some empirical equations expressing the relationships between the different ionic radii and the electronegativities and the lattice constants of double halide perovskites have been found.

本文对双卤化物钙钛矿的成形性进行了全面系统的预测研究。除了容差因子外，还开发了几种形成和晶格畸变的互补准则，并与基于主成分分析(PCA)和偏最小二乘(PLS)方法的全多元技术进行了比较。建立了双卤化物钙钛矿不同离子半径与电负性和晶格常数关系的经验方程。

引用次数: 1

Modeling the Transmission Dynamics of COVID-19 Pandemic in Caputo Type Fractional Derivative 基于Caputo型分数阶导数的COVID-19大流行传播动力学建模

IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS

Journal of Multiscale Modelling

Pub Date : 2021-06-07 DOI: 10.1142/s1756973721500062

Parvaiz Ahmad Naik, K. M. Owolabi, J. Zu, Mehraj-ud-din Naik

COVID-19 disease, a deadly pandemic ravaging virtually throughout the world today, is undoubtedly a great calamity to human existence. There exists no complete curative medicine or successful vaccines that could be used for the complete control of this deadly pandemic at the moment. Consequently, the study of the trends of this pandemic is critical and of great importance for disease control and risk management. Computation of the basic reproduction number by means of mathematical modeling can be helpful in estimating the potential and severity of an outbreak and providing insightful information which is useful to identify disease intensity and necessary interventions. Considering the enormity of the challenge and the burdens which the spread of this COVID-19 disease placed on healthcare system, the present paper attempts to study the pattern and the trend of spread of this disease and prescribes a mathematical model which governs COVID-19 pandemic using Caputo type derivative. Local stability of the equilibria is also discussed in the paper. Some numerical simulations are given to illustrate the analytical results. The obtained results shows that applied numerical technique is computationally strong for modeling COVID-19 pandemic.

当前，新型冠状病毒病这一几乎在全球范围内肆虐的致命流行病无疑是人类生存的巨大灾难。目前还没有完全治愈的药物或成功的疫苗可用于完全控制这一致命的大流行病。因此，研究这种大流行的趋势至关重要，对疾病控制和风险管理具有重要意义。用数学模型计算基本繁殖数有助于估计爆发的可能性和严重程度，并提供有助于确定疾病强度和必要干预措施的有见地的信息。考虑到COVID-19疾病的传播给卫生保健系统带来的巨大挑战和负担，本文试图研究该疾病的传播模式和趋势，并使用Caputo型导数建立了控制COVID-19大流行的数学模型。文中还讨论了平衡点的局部稳定性。通过数值模拟对分析结果进行了说明。结果表明，应用数值技术模拟COVID-19大流行具有较强的计算能力。

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引用次数: 26

Evaluation of Cyclic Loading Effects on Residual Stress Relaxation in Offshore Wind Welded Structures 循环荷载对海上风力焊接结构残余应力松弛影响的评价

IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS

Journal of Multiscale Modelling

Pub Date : 2021-06-01 DOI: 10.1142/S1756973721500050

G. Statti, A. Mehmanparast, R. Biswal, C. Rizzo

Monopile foundations contain welding residual stresses and are widely used in industry to support offshore wind turbines (OWTs). The monopiles are subjected to hammering loads during installation and cyclic loads during operation, therefore the influence of residual stress redistribution as a result of fatigue cycles must be evaluated in these structures. The existing empirical models to predict the residual stress redistribution in the presence of cyclic loading conditions are strongly dependent on the material, welding process and loading conditions. Hence, there is a need to predict the residual stress redistribution using finite element simulations. In this study numerical analyses have been conducted to predict the initial state of residual stress in a simplified weld geometry and examine the influence of subsequent cyclic loads on the relaxation behavior in residual stress profiles. The results have shown that fatigue cycles have a severe effect on residual stress relaxation with the greatest reduction in residual stress values observed in the first cycle. Moreover, the numerical prediction results have shown that the stress amplitude plays a key role in the extent of residual stress relaxation in welded structures.

单桩基础含有焊接残余应力，广泛应用于海上风力发电机的支撑。单桩在安装过程中承受锤击载荷，在运行过程中承受循环载荷，因此必须对这些结构中疲劳循环引起的残余应力重分布的影响进行评估。现有的预测循环加载条件下残余应力分布的经验模型强烈依赖于材料、焊接工艺和加载条件。因此，有必要利用有限元模拟来预测残余应力的重新分布。在本研究中，进行了数值分析，以预测简化焊缝几何形状中残余应力的初始状态，并研究了后续循环载荷对残余应力曲线松弛行为的影响。结果表明，疲劳循环对残余应力松弛有严重的影响，在第一个循环中观察到的残余应力值降低最大。数值预测结果表明，应力幅值对焊接结构残余应力松弛程度起关键作用。

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引用次数: 2

A High-Temperature Digital Image Correlation Method and its Application on Strain Measurement of Film Cooling Holes 一种高温数字图像相关方法及其在薄膜冷却孔应变测量中的应用

IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS

Journal of Multiscale Modelling

Pub Date : 2021-06-01 DOI: 10.1142/s1756973721500037

Zixu Guo, Ziyuan Song, Dawei Huang, Xiaojun Yan

In this paper, a digital image correlation (DIC) method is developed and applied on film cooling holes in the submillimeter scale in high temperature. Compared with the traditional DIC method, the speckle patterning method and the optical system are improved. In detail, a kind of high temperature-resistant black paint is selected as the basecoat, and the white ZrO2 particles are evenly distributed on the specimen using high-pressure splashing method. Besides, to eliminate the radiation effect of the high-temperature specimen, the blue light source is used to illuminate the specimen, and the optical bandpass filter is placed in front of the camera to allow the blue light passing. In order to verify the DIC method, the strain measurement on a specimen with single skew hole is performed. The relative error in high temperature of the maximum strain between the measurement results and the numerical simulation results given by the finite element method (FEM) is 12%. The strain concentration factor of the single skew hole is measured as 1.83. Finally, the developed method is applied to the strain measurement of the structure with multiple film cooling holes in 870°C. The X-shape strain distribution can be observed at the hole with maximum stress, which suggests that the strain field of multiple holes has coupling effect. In addition, the strain concentration factor of multiple film cooling holes increases to 2.34.

本文提出了一种数字图像相关(DIC)方法，并将其应用于亚毫米尺度的高温薄膜冷却孔。与传统的DIC方法相比，对散斑成像方法和光学系统进行了改进。其中，选择一种耐高温的黑色涂料作为底漆，采用高压溅射法将白色的ZrO2颗粒均匀分布在试样上。此外，为了消除高温试样的辐射影响，采用蓝色光源照射试样，并在摄像机前放置光学带通滤光片，使蓝光通过。为了验证DIC方法的有效性，在单斜孔试件上进行了应变测量。高温下最大应变的测量结果与有限元数值模拟结果的相对误差为12%。单斜孔的应变集中系数为1.83。最后，将该方法应用于多膜冷却孔结构在870℃下的应变测量。在最大应力孔处可以观察到x形应变分布，说明多孔应变场存在耦合效应。此外，多膜冷却孔的应变集中系数增加到2.34。

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引用次数: 0

It sounds like a good handover but can I trust it: the correlation between perceived quality and accuracy? 听起来交接得不错，但我能相信它吗：感知质量与准确性之间的相关性？

Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS

Journal of Multiscale Modelling

Pub Date : 2021-04-28 eCollection Date: 2021-01-01 DOI: 10.15694/mep.2021.000102.1

Malcolm Moore, Suzanne Bain-Donohue, Molly Barry, Phillip Gray

This article was migrated. The article was marked as recommended. Background Safe handover is crucial in healthcare and is taught in undergraduate and pre-vocational training curricula. It is now considered an Entrustable Professional Activity (EPA). Handover assessment tools have been developed but the correlation between the perceived quality of a handover and its accuracy has not been studied. Aims This paper aims to determine the correlation between the perceived quality and the accuracy and safety of handover. Methods This descriptive, quantitative study looked at medical students on long-term rural clinical placements who gave clinical handovers to supervisors. The supervisors scored the handovers using the Clinical Handover Assessment Tool (CHAT) and assessed the accuracy and safety of the handover, after seeing the patient. The correlation between handover scores, accuracy and safety was calculated using Cramer's V coefficient. Results 114 handovers from 25 students were assessed. The correlation coefficient for a global assessment of quality and accuracy was 0.585 and for safety was 0.583, considered large effects (>0.35). This also held using a checklist quality assessment but less strongly: 0.419, 0.363 respectively. Conclusion These findings suggest that handovers that sound 'good' are likely to be accurate: clinicians can 'trust their gut-feeling'. A high quality handover reflects more than the trainee'. clinical reasoning, communication and organisational skills: it suggests that they can provide accurate and safe handover. This supports the use of global assessments of handover as an important part of the multi-source feedback required for summative entrustment decision-making.

本文已迁移。该文章被标记为推荐文章。背景安全交接在医疗保健中至关重要，在本科和职前培训课程中都有教授。现在，它已被视为一项可委托的专业活动 (EPA)。目前已开发出交接班评估工具，但尚未对交接班的感知质量与其准确性之间的相关性进行研究。目的本文旨在确定交接的感知质量与准确性和安全性之间的相关性。方法该描述性定量研究调查了在农村长期临床实习的医学生向导师进行临床交接的情况。导师使用临床交接评估工具（CHAT）对交接班情况进行评分，并在看完病人后对交接班的准确性和安全性进行评估。交接班评分、准确性和安全性之间的相关性采用克莱默 V 系数进行计算。结果对 25 名学生的 114 次交接进行了评估。质量和准确性全面评估的相关系数为 0.585，安全性的相关系数为 0.583，被认为具有较大影响（大于 0.35）。使用核对表进行质量评估时也是如此，但相关性不强：分别为 0.419 和 0.363。结论这些研究结果表明，听起来 "不错 "的交接可能是准确的：临床医生可以 "相信自己的直觉"。高质量的交接不仅反映了受训者的临床推理、沟通和组织技能，还表明他们能够提供准确、安全的交接。这支持将对交接班的全面评估作为终结性委托决策所需的多源反馈的重要组成部分。

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引用次数: 0

Fitness-for-Service Assessment Approach for Ageing Pipeline Section Based on Sparse Historical Data 基于稀疏历史数据的管道段老化适应度评估方法

IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS

Journal of Multiscale Modelling

Pub Date : 2021-03-01 DOI: 10.1142/S1756973721500013

T. Naraghi, M. Najib, A. S. Nobari, K. Nikbin

Fitness-for-service (FFS) assessment is a common evaluation methodology in oil and gas industries to assess the integrity of in-service structures that may contain flaws, metal thinning and pitting damage. However, given the level of unknowns or missing information in the industry deterministic predictions are unacceptable and invariably the lower bound values could also be substantially conservative. The aim of this work is to develop a generic process to ensure, within a level of confidence, the operational safety and integrity of aging gas or oil pipelines sections based on available data. Fitness for service procedure according to “API 579-1/ASME FFS-1” is performed using local metal loss and micro-cracking to predict a range of safe life for the ageing pipeline operated for around 40 years. The mean value predictions of the present assessment indicate that the flaws away from the weld are within an acceptable boundary which implies the pipes would be fit to continue in operation and at least have 10 years remaining life, whilst the flaws near the weld need to be repaired as soon as possible. This is based on the best average values for the NDE and material property results available. However, adopting extreme caution in the analysis will render the pipes obsolete and ready for replacement. Understanding the risks to be taken in such situations becomes an expert system decision based not just on the FFS analysis but on both quantitative historical data, loading history, material degradation due to environment, corrosion rates and metallurgical analysis in addition to qualitative experience collected from other databases and pipes failure data. Beyond such a procedure the safe option would be a full burst pressure testing of the length of pipeline in question to identify possible leaks of old pipes.

适用性（FFS）评估是石油和天然气行业常用的评估方法，用于评估可能存在缺陷、金属减薄和点蚀的在役结构的完整性。然而，考虑到行业中未知或缺失信息的水平，确定性预测是不可接受的，并且下限值也可能是基本保守的。这项工作的目的是根据现有数据，制定一个通用流程，以确保老化天然气或石油管道段在一定程度上的运行安全和完整性。根据“API 579-1/ASME FFS-1”，使用局部金属损失和微裂纹进行维修程序的适用性，以预测运行约40年的老化管道的安全寿命范围。本评估的平均值预测表明，远离焊缝的缺陷在可接受的边界内，这意味着管道可以继续运行，并且至少有10年的剩余寿命，而焊缝附近的缺陷需要尽快修复。这是基于可用的无损检测和材料性能结果的最佳平均值。然而，在分析中采取极端谨慎的做法会使管道过时，随时可以更换。了解在这种情况下要承担的风险成为一个专家系统决策，不仅基于FFS分析，还基于定量历史数据、装载历史、环境导致的材料退化、腐蚀速率和冶金分析，以及从其他数据库和管道故障数据中收集的定性经验。除此之外，安全的选择是对有问题的管道长度进行全面的爆裂压力测试，以确定旧管道可能发生的泄漏。

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引用次数: 0

Crystal Plasticity Finite Element Method for Cyclic Behavior of Single Crystal Nickel-Based Superalloy 单晶镍基高温合金循环行为的晶体塑性有限元法

IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS

Journal of Multiscale Modelling

Pub Date : 2021-03-01 DOI: 10.1142/S1756973721500025

Xiao-yi Qin, G. Han, S. Xia, Weijie Liu, D. Lin

This paper reports the modeling and simulation of cyclic behavior of single crystal nickel-based superalloy by using the crystal plasticity finite element method. Material constitutive model based on the crystal plasticity theory is developed and is implemented in a parallel way as user subroutine modules embedded in the commercial Abaqus[Formula: see text] software. For simplicity in calibration and without loss of generality, the crystal plasticity constitutive relationship used in this work takes the form that only contains a few parameters. The parameters are optimized by using the Powell algorithm. We employ the calibrated constitutive model with the finite element solver on a cuboid and a blade to simulate cyclic and anisotropic properties of single crystal superalloy. Results show that the predicted stress–strain curves are in good agreement with the experimental measurements, and anisotropic results are presented in both elastic and plastic regions.

本文采用晶体塑性有限元法对单晶镍基高温合金的循环行为进行了建模和仿真。建立了基于晶体塑性理论的材料本构模型，并以用户子程序模块的方式并行实现于Abaqus商用软件[公式:见文]。为了便于校准和不丧失一般性，本工作中使用的晶体塑性本构关系采用仅包含几个参数的形式。采用Powell算法对参数进行优化。采用校正后的本构模型和基于长方体和叶片的有限元求解器对单晶高温合金的循环和各向异性性能进行了模拟。结果表明，预测的应力-应变曲线与实验结果吻合较好，且在弹塑性区域均表现出各向异性。

引用次数: 0

Prediction of Reheat Cracking Behavior in a Service Exposed 316H Steam Header 316H蒸汽集箱再热开裂行为预测

IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS

Journal of Multiscale Modelling

Pub Date : 2020-11-20 DOI: 10.1142/s1756973720500092

Haoliang Zhou, A. Mehmanparast, K. Nikbin

Reheat cracking in an ex-service Type 316H stainless steel steam header component has been investigated in this study. The examined steam header was in service for 87,790[Formula: see text]h and the cracks in this component were found in the vicinity of the weld toe. The root cause of this type of failure was due to the welding residual stresses. The welding-induced residual stresses had been present in the header at the early stage of the operation and were released during service. In this paper, a novel technique has been proposed to simulate the residual stress distribution normal to the crack direction by applying remote fixed displacement boundary conditions in an axisymmetric model. This approach can simulate the presence of residual stresses in actual components without the need to develop full weld simulation to quantify them. The predicted residual stress levels and distributions normal to the crack direction have been found in good agreement with the measured residual stresses available in the literature for a similar header. The creep crack growth (CCG) rates have been characterized using the fracture mechanics [Formula: see text] parameter and estimated using predictive models.

本文研究了一种退役316H型不锈钢蒸汽集箱部件的再热开裂问题。被检查的蒸汽集箱使用了87790年[公式:见文本]h，在焊接趾附近发现了该部件的裂纹。这种失效的根本原因是由于焊接残余应力。焊接引起的残余应力在作业初期就存在于封头中，并在使用过程中被释放。本文提出了一种在轴对称模型中应用远程固定位移边界条件来模拟沿裂纹方向的残余应力分布的新方法。这种方法可以模拟实际部件中残余应力的存在，而不需要开发全焊接模拟来量化它们。预测的残余应力水平和分布正态的裂纹方向已被发现很好地一致的测量残余应力可在文献中为一个类似的头。蠕变裂纹扩展(CCG)速率已使用断裂力学参数进行表征，并使用预测模型进行估计。

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引用次数: 2

Computational Homogenization of Heterogeneous Materials by a Novel Hybrid Numerical Scheme 用一种新的混合数值格式计算非均质材料的均匀化

IF 1.5 Q4 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS

Journal of Multiscale Modelling

Pub Date : 2020-11-02 DOI: 10.1142/s1756973720500080

M. Cascio, M. Grifò, A. Milazzo, I. Benedetti

The Virtual Element Method (VEM) is a recent numerical technique capable of dealing with very general polygonal and polyhedral mesh elements, including irregular or non-convex ones. Because of this feature, the VEM ensures noticeable simplification in the data preparation stage of the analysis, especially for problems whose analysis domain features complex geometries, as in the case of computational micro-mechanics problems. The Boundary Element Method (BEM) is a well known, extensively used and effective numerical technique for the solution of several classes of problems in science and engineering. Due to its underlying formulation, the BEM allows reducing the dimensionality of the problem, resulting in substantial simplification of the pre-processing stage and in the reduction of the computational effort, without jeopardizing the solution accuracy. In this contribution, we explore the possibility of a coupling VEM and BEM for computational homogenization of heterogeneous materials with complex microstructures. The test morphologies consist of unit cells with irregularly shaped inclusions, representative e.g., of a fiber-reinforced polymer composite. The BEM is used to model the inclusions, while the VEM is used to model the surrounding matrix material. Benchmark finite element solutions are used to validate the analysis results.

虚元法(VEM)是一种新兴的数值计算技术，能够处理非常普遍的多边形和多面体网格单元，包括不规则或非凸网格单元。由于这一特征，VEM确保了分析数据准备阶段的显著简化，特别是对于分析领域具有复杂几何形状的问题，如计算微力学问题。边界元法(BEM)是一种众所周知的、广泛使用的、有效的数值技术，用于解决科学和工程中的几类问题。由于其基本公式，边界元法允许降低问题的维度，从而大大简化了预处理阶段，减少了计算工作量，而不会损害解决方案的准确性。在这篇贡献中，我们探索了耦合VEM和BEM的可能性，用于具有复杂微观结构的非均质材料的计算均匀化。测试形态包括具有不规则形状内含物的单元胞，例如纤维增强聚合物复合材料的代表性。边界元法用于对夹杂物进行建模，而VEM法用于对周围基体材料进行建模。采用基准有限元解对分析结果进行验证。

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引用次数: 2