Micro-macro Model Research Articles

Micro-macro modeling of polymeric fluids and shear-induced microscopic behaviors with bond-breaking

Micro-macro modeling of polymeric fluids and shear-induced microscopic behaviors with bond-breaking

Micro-macro modeling of tensile behavior of a friction stir welded hybrid joint of AlSi10Mg parts produced by powder bed fusion and casting

Additive manufacturing (AM) has gained considerable interest due to its ability to produce lightweight parts with hierarchical microstructures. However, the current constraints on the build chamber size in powder-bed fusion type AM processes limit its industrial application. A hybrid welded joint, consisting of an AM-processed and a conventionally manufactured part, can be employed to produce larger components. Due to the varying processing conditions, these hybrid welded joints contain a wide range of microstructural heterogeneities, which influences the mechanical properties of the joint. Using a numerical model to predict the mechanical behavior of welded joints by considering the microstructural variations is essential for the safe and reliable implementation of hybrid welded joints. This study aims to predict the local tensile behavior of each region of a hybrid friction-stir welded joint of AlSi10Mg produced by laser-based powder bed fusion and casting using a microstructure-sensitive model as well as the global tensile behavior by considering the properties of each region using a joint macroscopic model. The results from this modeling approach agree well with the experimental results. Therefore, this method can predict the mechanical behavior of hybrid welded joints and can establish the structure–property relationship in each weld region.

An improved micro–macro model of multicomponent reactive transport for multimineral systems

The multiscale coupled reactive transport model has attracted increasing attention in recent years because it can reveal the different characteristics of the spatial structure evolution of porous media. A micro–macro model of multiscale coupled reaction transport has been derived from detailed pore-scale models by using the upscaling technique based on homogenization method. Because of its clear upscaling theory, it has been widely used. However, the current micro–macro model still has obvious defects in dealing with the geochemical reaction process in multimineral systems. To solve this problem, we coupled the model with existing geochemical models that have been widely verified so that the model has the ability to deal with multimineral reactions under complex hydrochemical conditions. The newly developed coupling model and the current model are used to simulate the same problem, which proves the superiority of the new model for geochemical reaction prediction. We extend the new model to a two-dimensional scanning electron microscope image, where a challenging medium geometry setup is handled well during simulation. At the same time, the new model also accurately captures the abrupt changes in macroscopic effective parameters caused by the change in geometric topological structure. Finally, we use the principle of mass conservation to quantify numerical errors caused by geometric evolution, ensuring the accuracy and validity of simulation results, which verifies the numerical scheme of the model to a certain extent.

A micro-macro-economic modelling approach to major welfare system reforms: The case of a Universal Basic Income for Scotland

This paper develops – and applies – a micro-macroeconomic modeling approach for assessing major welfare system reforms. With a growing interest in the value of bold welfare reforms in the light of persistent and widening inequalities, we demonstrate the value of a comprehensive analysis of both the (micro) impact upon the distribution of household incomes and wider (macro) impacts upon national income, unemployment and government spending. By combining microsimulation with CGE modeling, we argue that our findings demonstrate the importance of any major social welfare or broad fiscal reform being the subject of a micro-macro modeling approach. We illustrate this through an application to the introduction of a universal basic income in Scotland.

Estimation of traffic energy consumption based on macro-micro modelling with sparse data from Connected and Automated Vehicles

Traffic energy consumption estimation is significant for the sustainable transportation. However, it is difficult to directly employ macro traffic flow data to accurately estimate the traffic energy consumption due to many traffic energy consumption models need second-by-second vehicle trajectory. To solve this problem, this paper proposes a traffic energy consumption model based on the macro-micro data, which the macro data derived from the fixed-location sensors and sparse micro data derived from the Connected and Automated Vehicles (CAVs). The completed vehicle trajectories are constructed by the nonparametric kernel smoothing algorithm and variational theory. To test the performance of the proposed method, the Next Generation Simulation micro (NGSIM) dataset and Caltrans Performance Measurement System macro dataset obtained from the same road and time are used. The results indicate that the proposed method not only can reflect the characteristics of traffic kinematic waves caused by traffic congestion, but also minimize the errors generated by the macro-micro transformation. In addition, it can significantly improve the accuracy of energy consumption estimation.

Managerial values and corporate social responsibility practices: multilevel and multistakeholder analysis

PurposeThis study aims to posit that managerial value would be one of the responsible factors for the difference in corporate social responsibility practice among businesses. It then empirically tested the effect of managerial value, with the moderation of organizational culture, on corporate social responsibility practice.Design/methodology/approachThe authors have devised a “moderated micro-macro model” type of multilevel model, wherein managerial value took the micro (individual level) predictor variable role, stakeholder-based corporate social responsibility practice the macro (organizational level) outcome variable role and organizational culture the macro level moderating variable role. Because they need the attention of inquiry, large manufacturing firms in the Amhara region of Ethiopia, with a sample size of 53, constituted the organizational level units. The recent performance of the firms against corporate social responsibility practice and organizational culture have been judged by 473 randomly chosen employees. Managerial value has been rated by randomly picked managers, numbered 253. Analytically, Croon and van Veldhoven’s multilevel analytical package and Mplus software suited the designed model.FindingsThe study has revealed that managerial value, indeed, is a potential positive driver of CSR practice, the two managerial value dimensions demonstrated differential effects on corporate social responsibility practice and only one of the organizational culture dimensions, hierarchical culture, played a moderation role in managerial value – corporate social responsibility practice link.Originality/valueThe model and this empirical test have not been previously verified.

Global strong solutions and large time behavior to a micro-macro model for compressible polymeric fluids near equilibrium

In this paper, we mainly study the global strong solutions to a micro-macro model for compressible polymeric fluids with small initial data and their long-time decay rates of all order spatial derivatives. This model is a coupling of isentropic compressible Navier-Stokes equations with a nonlinear Fokker-Planck equation. We first present that the micro-macro model admits a unique global strong solution provided the initial data are close to equilibrium state for d≥2. Moreover, for d≥3, we show a new critical Fourier estimation that allows us to derive the long-time decay rates of the L2 norm for all order spatial derivatives.

Implications of COVID-19 and mitigation measures on gender and the Zimbabwean economy

This paper provides a macro-micro modeling analysis of the ex-ante effects of COVID-19 mitigation and recovery policies on macroeconomic and distributional effects, particularly on female and male workers, income distribution, and poverty in Zimbabwe. With an emphasis on modeling gender-disaggregated labor markets and COVID-19 policy responses, the paper presents and combines the most recent data on poverty, gender, and the economy at the national level. The study finds that i) without any government mitigation measures, the gross domestic product will remain below business-as-usual levels; ii) poorer women are hardest hit because they are employed in sectors that are exposed and vulnerable to COVID-19 response measures; and iii) mitigation measures to counteract the negative effects of increases in poverty are effective only in the short term, and additional measures to sustain poverty reduction for the long term to sustain the poverty reductions are required. These results highlight the short-term versus long-term dilemma the government faces when contemplating responses to COVID-19.

A Multi-Scale Study on Deformation and Failure Process of Metallic Structures in Extreme Environment.

It is a macro-micro model study for defect initiation, growth and crack propagation of metallic truss structure under high engine temperature and pressure conditions during the reentry atmosphere. Till now, the multi-scale simulation methods for these processes are still unclear. We explore the deformation and failure processes from macroscale to nanoscale using the Gas-Kinetic Unified Algorithm (GKUA) and all-atomic, molecular dynamic (MD) simulation method. The behaviors of the dislocations, defect evolution and crack propagation until failure for Aluminum-Magnesium (Al-Mg) alloy are considered with the different temperature background and strain fields. The results of distributions of temperature and strain field in the aerodynamic environment obtained by molecular dynamics simulations are in good agreement with those obtained from the macroscopic Boltzmann method. Compared to the tensile loading, the alloy structure is more sensitive to compression loading. The polycrystalline Al-Mg alloy has higher yield strength with a larger grain size. It is due to the translation of plastic deformation mode from grain boundary (GB) sliding to dislocation slip and the accumulation of dislocation line. Our findings have paved a new way to analyze and predict the metallic structural failure by micro-scale analysis under the aerodynamic thermal extreme environment of the reentry spacecraft on service expiration.

Integrated macro-micro modelling for individual vehicle trajectory reconstruction using fixed and mobile sensor data

Vehicle trajectories can provide a clear picture of the traffic flow that plays a pivotal role in traffic management and control. Two types of traffic sensors, i.e., fixed and mobile sensors, are widely adopted to collect road traffic information. However, fully-sampled vehicle trajectories are far from obtainable through those sensors due to their fixed-location measurements or low penetration rates. To overcome these issues, this study proposes an integrated macro–micro framework to reconstruct individual vehicle trajectories on freeways under a multi-source data environment, in which fixed-location sensor data that collect positions and velocities of vehicles in a certain place and a small fraction of probe vehicle (PV) data that yield continuous trajectories are available. The framework consists of three modules. First, at the macro level, we apply shockwave theory and fundamental diagram to expand the partially detected information to the whole space–time diagram, and then establish a velocity baseline for evaluation of the trajectory fusion thereafter. Second, at the micro level, we develop two trajectory estimation algorithms based on extended car-following models to generate individual trajectories between any two consecutive PVs, in which two candidate trajectories will be generated for each non-probe vehicle. Third, we tailor a trajectory fusion algorithm to integrate the macro- and micro-level models, and apply dynamic programming to solve the optimal trajectories as per the established velocity baseline. The proposed framework is finally tested with NGSIM and HighD datasets. The results show that our integrated method attains a notable improvement in accuracies and smoothness of reconstructed trajectories compared to the non-integrated and the classical Variational Theory-based methods respectively.

Nations ranking in scientific competition: Countries get what they paid for

How to explain the success of China or South Korea in the global scientific (academic research) competition over the past two decades? So far, the literature answers by assuming new comparative advantages (in terms of learning or training) for East Asian countries and/or deficient research organization in Western economies. We develop an original micro-macro model based on the aggregation of individual knowledge production functions. Our model predicts the existence of a stable macro power law, relating the world share of countries' scientific production (publications and citations) to their world share of public investment in scientific research. We test and support this prediction, using bibliometric cross-country longitudinal data for OECD and non-OECD countries, over the 1996–2015 period. This analysis shows that East Asian countries’ impressive catch-up is due, to the first order, to sustained investment efforts in scientific research – efforts that are greater than those undertaken in traditional scientific countries.

Micro-macro modelling of thermal evolution during solidification of binary equiaxed alloys with experimental validation

A micro-macro model based on deterministic continuum mechanics and the modified source term method has been used to study the solidification problems involving binary Al-4.0 wt% Cu eutectic system. The model is further tested with other equiaxed eutectic binary aluminium alloys that include Al-3.0 wt% Si, Al-6.0 wt% Mg and Al-3.0 wt% Zn. All the heat transfer regimes including convection and radiation at the open top surface of the mould are considered. The nucleation steps are accounted for by considering continuous nucleation and growth kinetics. Information such as undercooling, nucleation rate, recalescence, growth rate, solid fraction, cooling curve, grain size and volumetric grain density which directly link to mechanical properties of cast components are accurately predicted. The model result is validated against the experimental data obtained from the current study and others published in the literature. From the results predicted in the current work, it is observed that the model gives the actual cooling history instead of a rough estimation of cooling curves as obtained from previous models. Among the aluminium-based alloys analysed, the Al–Cu alloy has the fastest nucleation and solidification rates. The predicted volumetric grain density suggests that magnesium has a more grain refinement effect on the aluminium matrix than copper, zinc and silicon. The model results are in agreement with the physical metallurgy of alloy theory and can be used by alloy manufacturers to improve the mechanical properties of alloy castings.

Global existence of classical solutions for a reactive polymeric fluid near equilibrium

In this paper, we study a new micro-macro model for a reactive polymeric fluid, which is derived recently in [Y. Wang, T.-F. Zhang, and C. Liu, \emph{J. Non-Newton. Fluid Mech.} 293 (2021), 104559, 13 pp], by using the energetic variational approach. The model couples the breaking/reforming reaction scheme of the microscopic polymers with other mechanical effects in usual viscoelastic complex fluids. We establish the global existence of classical solutions near the global equilibrium, in which the treatment on the chemo-mechanical coupling effect is the most crucial part. In particular, a weighted Poincar\'e inequality with a mean value is employed to overcome the difficulty that arises from the non-conservative number density distribution of each species.

In a team forgiveness climate, the influence of paradoxical thinking of leaders on the team voice behavior: Mediated by team cooperation.

In order to clarify the influence of the paradoxical thinking of leaders on team voice behavior, a moderating mediation model was constructed to explore the mediating role of team cooperation and the moderating effect of team forgiveness climate based on the social exchange theory. Based on the "leader-employee" matching data of 477 employees from 101 teams, SPSS (Statistic Package for Social Science) and AMOS (a macro-micro model of Scotland) were used to analyze the three-stage data linear regression. The research conclusions indicate that: (1) The paradoxical thinking of leaders positively affects team voice behavior; (2) Team cooperation plays a completely mediating role in the relationship between the paradoxical thinking of leaders and team voice behavior; (3) The team forgiveness climate positively moderates the relationship between the paradoxical thinking of leaders and team cooperation, which means that their positive relationship is stronger in a higher forgiveness climate; (4) The team forgiveness climate moderates the mediating role of team cooperation between the paradoxical thinking of leaders and team voice behavior. Compared with a lower forgiveness climate, this moderating mediating effect is significant at a higher forgiveness level. This study clarifies the connection of the paradoxical thinking of leaders to the team voice behavior through team cooperation and has practical insights into how a team forgiveness climate promotes the team voice behavior.

Efficiency of Micro-Macro Models for Reactive Two-Mineral Systems

In this paper, we introduce a pore-scale model for reactive flow and transport in evolving porous media exhibiting two competing mineral phases. By formal two-scale asymptotic expansion in a level-set framework an effective micro-macro model is derived. As such, our approach comprises flow and transport equations on the macroscopic scale including effective hydrodynamic parameters calculated from representative unit cells. Conversely, the macroscopic solutes' concentrations alter the unit cells' geometrical structure by triggering dissolution or precipitation processes. The numerical implementation of such micro-macro models poses several challenges, especially in terms of geometry representation and computational complexity. In this research, the Voronoi implicit interface method is applied to characterize and evolve the two-mineral structure and first-order convergence is obtained in a test case where analytical solutions are available. Furthermore, we present a sophisticated overall solution strategy for the introduced fully coupled nonlinear micro-macro problem and conduct numerical simulations. In doing so, the significant performance enhancements arising from machine learning techniques are evaluated. To this end, a convolutional neural network is trained on (realistic) unit cell geometries for permeability prediction and deployed in a micro-macro simulation. The outcome is compared to the respective results obtained by classical methods in terms of predictive power and computational effort.

A Micro-Macro Model of Foreign Direct Investment: Knowledge-Based Gravity Forces, Self-selection and Third-Country Effects

A Micro-Macro Model of Foreign Direct Investment: Knowledge-Based Gravity Forces, Self-selection and Third-Country Effects

Qualitative Research and Aging in Context: Implications to Social Study in China

This article begins with a review of methods that gerontologists use in social and behavioral research. The value and focus of qualitative research are highlighted with their epistemological roots. Qualitative approaches and their uses are summarized in terms of “interpretive” and “critical” social sciences that draw the insights of sociological paradigms. With a further review of qualitative research on aging and gerontological studies in China, the article focuses on an integrated micro-macro model by illuminating the ideas of clinical sociology and the general public policy framework of an “economic state in transition.” Implications to social policy study (particularly on aging in China) are discussed.

Impact of COVID-19 on Saudi Arabia's economy: evidence from macro-micro modelling

Purpose Even with the Saudi Arabian Government's discretionary measures to mitigate the spread of the coronavirus disease 2019 (COVID-19), the economic sectors were not spared from the damage. Thus, the paper aims to use a computable general equilibrium (CGE) model to evaluate the impact of COVID-19 on the Kingdom of Saudi Arabia's (KSA) economy, with a special focus on small and medium enterprises (SMEs) and production. These influence the level of poverty. Design/methodology/approach The paper adopted the social accounting matrix (SAM) for Saudi Arabia built in 2021 by Imtithal Althumairi from Saudi Arabia's 2017 SAM. The model represents a snapshot of the economy and different flows that exist within the tasks and institutions. Two simulations (mild and severe) were conducted because of the focus on the distributional outcomes. Findings Decrease in job creation and economic growth were significant evidence from the study's findings. Findings show that more families hit below the poverty line because the negative impacts of the pandemic have shifted the income allocation curve. Findings show that the weakest of the poor are mitigated by government social grants during the pandemic. Research limitations/implications The paper is restricted to the relevant literature relating to the impact of COVID-19 on Saudi Arabia's economy and evaluated using the SAM model. Moreover, the COVID-19 is still an ongoing scenario; thus, the model should be updated as data utilised for the operationalisation are made available. Practical implications The information from the suggested model can be suitable to measure the degree of the harm, and thus, the likely extent of the desirable policy feedback. Also, the model can be updated, as data are made available and formulated policies based on the updated data implemented by the policymakers. Originality/value Apart from the recovery planning of SMEs during the pandemic, the paper intends to stir up Saudi Arabia's policymakers through the macro-micro model to recovery planning and resilience of the economy with emphasis on mitigating unemployment.

Micro-macro modelling of laminated composite rectangular reservoir

This article has a multidisciplinary character. It combines the scientific field of micro-macro modelling of reinforced polymer composite laminates applied in the seismic response area of a rectangular composite tank filled with liquid. The calculation of the seismic response of the laminate composite rectangular tank is carried out at three levels. Within the micro-level, the material characteristics are calculated using a fictitious periodic microstructure model. A classical theory of laminates is used to obtain effective material characteristics by using a representative laminate volume element at the meso-level. At the macro level, a seismic response of a laminate composite rectangular tank filled with liquid is solved for the region of Slovakia.

Mechanism of Crack Initiation and Propagation of Re-Entrant Auxetic Honeycombs Under Thermal Shock

Abstract Thermal shock multiple cracking behaviors of re-entrant auxetic honeycombs with a negative Poisson’s ratio are investigated, and the crack initiation and propagation behavior are discussed. An effective macro continuum model is developed to detect the effects of cracking density and microstructures of auxetic honeycombs on the thermal stress and intensity. The microscale tensile stresses in the struts ahead of the crack as functions of the corresponding thermal stress intensity factor (SIF) at the macroscale are evaluated by employing a macro–micro model. Then, a lower-bound method is proposed to assess the critical thermal load of auxetic honeycombs by combining the macro-micro model and the macro continuum model. A significant increase in both transient thermal stress and intensity as the growing cell-wall angle is demonstrated. Results for the maximum thermal SIF as well as the maximum tensile stress in the middle of cracks are calculated as functions of crack density and length. With the identical SIF, the microscale tensile stresses ahead of the crack in honeycombs with smaller cell-wall angles are greater than that in mediums with larger angles due to the more significant crack tip opening displacement. Critical thermal load prediction reveals that the honeycombs with smaller cell-wall angles generally possess more excellent thermal shock resistance. Also, the varying failure modes of different auxetic honeycomb strips under specific thermal load are predicted. The corresponding mechanisms of crack initiation and propagation are revealed.