Search

Density Functional Theory (DFT) calculations can determine planar defect energies and slip pathways that are present in ordered intermetallic systems used to strengthen Ni-based superalloys, but analytical models used to evaluate the strengthening effects of these phases often involve significant simplifying assumptions. Instead, Phase Field Dislocation Dynamics (PFDD) is a useful modeling tool that incorporates dislocation interactions with precipitates and slip pathways informed by DFT to determine how precipitate shearing might occur under applied stresses with improved accuracy over previous models. In this work, we apply PFDD to study precipitate shearing in HAYNES® 244®, a high strength Ni-based superalloy strengthened through a novel Ni 2 (Cr, Mo, W) phase that has a low symmetry Body Centered Orthorhombic (BCO) crystal structure which complicates analysis of slip pathways. Through our modeling, we show the formation of and evolution of extended dislocations in the matrix and in the precipitates, the interaction of dislocations with the precipitates, and the formation of planar faults in the precipitate. A key aspect of incorporating the DFT determined slip pathway is the influence of the unstable fault energy and the asymmetry of the energy pathway on the strengthening aspect of the precipitate. The resulting critical strengths are compared to analytical models. The size, orientation, particle distance, and calculated slip pathway for the different variants in this system are all shown to have an important effect on the critical stress to shear these precipitates. [Display omitted] [ABSTRACT FROM AUTHOR]

Understanding Fuel Fragmentation, Relocation and Dispersal (FFRD) phenomena is a major item to predict the behavior of fuel rods in the event of a Pressurized Water Reactor loss-of-coolant hypothetical scenario. In order to introduce an effective medium for fragmented fuel that could be used in fuel performance codes, the heat transfer properties of U O 2 granular beds in He-Kr-Xe gas mixes was studied numerically. The Discrete Element Method was first used to compute the spatial arrangement of fragments only submitted to gravity with a representative granulometric distribution. These generated geometries were then transformed into a 3D grid (voxelized) to perform numerical homogenization and compute their effective properties using a Fast Fourier Transform solver for heat transfer. Different hypotheses were made in the voxelation process about the treatment of gas-solid and solid-solid interfaces, which in turn provided different estimates of the effective properties. Due to limits on the discretization and extended particle size distributions, a two-scale scheme was introduced and numerically tested against direct computations. For several granular beds, computed thermal conductivities were compared to analytical models for granular materials. Some heat transfer properties of fragmented fuel at several burnups were then computed, taking into account approximations for Knudsen and radiation size effects. [ABSTRACT FROM AUTHOR]

• Introduced a novel granular model for analysing rockburst mechanisms. • Validated the true triaxial rockburst model with experimental correlations. • Identified reduction in rockburst strength due to anisotropy angle variations. • Documented diverse micro-crack evolution associated with anisotropic changes. Rockbursts pose significant concerns in underground construction, and understanding their mechanisms is crucial for enhancing safety in tunneling and underground mining operations. This study innovates an inherently anisotropic rock model using the discrete element method to investigate the effect of local strength degradation on rockburst behavior. Unlike the existing rockburst models in which the anisotropy is either not accounted for or simulated by creating transversely weak planes, the inherent anisotropy is achieved in the contacts between rock grains. Following model calibration, the accuracy of the proposed model is demonstrated by simulating the behavior of rock samples subjected to triaxial rockburst tests. The findings highlight the influence of loading conditions on rockburst behavior in inherently anisotropic rocks and compare micro-crack patterns after rockbursts under different triaxial loading stresses and mesoscale failure types. Notably, this study is the first attempt to combine an inherently anisotropic rock model with rockburst analysis, providing new insights into the mesoscale mechanisms underlying rockburst failure. Notably, it reveals a significant variation in rockburst strength, by about a third, when the anisotropy angle shifts from 0 to 90 degrees. The proposed inherently anisotropic rock model offers an alternative for evaluating the impact of grain-scale strength degradation on rockburst behavior. [ABSTRACT FROM AUTHOR]

The progressive collapse of reinforced concrete (RC) beam-column sub-assemblage under catenary action (CA) using the alternate load path method to evaluate structures' robustness has raised much attention in the past decade, both in experimental tests and finite element (FE) simulations. However, a comprehensive multiscale method within concrete to assess structural robustness against progressive collapse, explicitly surrounding concrete matrix under CA, is generally lacking and has not been thoroughly explored in the relevant literature. This study aims to develop an FE macromodel to reliably simulate the progressive collapse resistance of seismic and non-seismic RC beam-column sub-assemblages. The proposed macroscale FE models are extensively validated by experimental results dominated by the CA and excessive deformation of RC beam-column sub-assemblages. Then, the macroscale FE model is further partitioned at the critical region with high-stress concentration to establish a sub-model and elucidate the underlying mesoscopic mechanism to motivate the CA by performing sub-modeling analysis. A 150 mm × 150 mm × 150 mm mesoscale heterogeneous model is established to be composed of aggregates, interfacial transition zone (ITZ), pores, and mortar by 3D voxel and Voronoi-based methods. The numerical predictions of the three macroscale models demonstrate good agreement of the overall deformation and load resistance trends with experimental results at both structural and sectional levels, but an overestimation of the load resistance peak is observed when concrete is crushed. Compared to the macroscale models, the sub-modeling analysis provides a more in-depth understanding of localized phenomena such as cracks and fractures. The 3D mesoscale model is further investigated with different aggregate volume fractions following the Fuller gradation. It is found that aggregates and ITZ (higher porosity, lower elastic modulus, and lower tensile strength compared to the bulk mortar) are more prone to concrete failure mechanisms without considering the role of reinforcement leading to the CA at the mesoscale, maintaining the concrete properties of the three macroscale models. In terms of the material constitutive model, the concrete damage plasticity model, and cohesive elements for mortar and ITZ, respectively, under uniaxial compression and tension behavior, the importance of interface bonding in CA of the surrounding concrete matrix is underlined. Additionally, the established mesoscale modeling method facilitates comprehension of the responses exhibited by macroscale RC sub-assemblies, ultimately shedding light on fracture initiation and propagation mechanisms. • Numerically predict a macroscopic model resistance under catenary action. • Further improve accuracy and dependability of resistance capacity in submodelling. • Unveil the resistance contributions in mesoscale modeling under progressive collapse. [ABSTRACT FROM AUTHOR]

As a subsequent paper for "type-A-choking-oriented unified model for fast fluidization dynamics", the present work aims to provide more systematic mesoscale analyses on clusters. Starting from theoretical derivations on idealized flow patterns of gas and solids around a single falling cluster; the momentum consumption due to particle circulation in clouds and the modification of flows by the constraint of driving force available in the bed were addressed. Complete compensation of the pressure-drop driven percolated gas in clusters by the reversely-penetrating particles was used for the ultimate closure of the model. An important finding of the present work, different from most empirical correlations, but verified by Wei and Zhu's latest experimental data and others, is that the cluster diameter does not vary monotonically with the mean solids holdup of the bed, but has a maximum value in between. Demonstrative calculations show that it is easy for Group A particles to enter the flow regime of high-density fast-fluidization as the circulating solids flux increases continuously, while fast fluidization for Group B particles tends to be stopped at Type C choking in advance. Compared with Group A particles, the clusters for Group B particles are less dense, but the penetration velocities of particles are higher, resulting in much larger dimensionless diameters of clusters. Finally, issues of pseudo-2D fast-bed modeling were discussed, and modeling of fast-beds with uneven flow fields was outlook briefly. [Display omitted] • Idealized flow patterns of gas and solids around single falling cluster were obtained. • Modifications of flow/pressure fields due to particle circulation in cloud were made. • Percolated gas in cluster offset with inversely penetrating particles to close model. • Cluster diameter don't vary monotonically with solids holdup but has maximum in range. • Main differences of fast fluidization of Group-A and Group-B particles were predicted. [ABSTRACT FROM AUTHOR]

We present an intercomparison of a full year of turbulence measurements and simulations at Østerild, a site in northern Denmark with relatively flat terrain and high surface roughness, where a high-quality tall meteorological mast is deployed. Both sonic and cup anemometers are mounted on booms on the mast from 7 up to 244 m, thus covering the range of heights in which modern wind turbines operate. The simulations were performed using the Weather Research and Forecasting model in a multiscale setup, with large-eddy simulations (LESs) nested one-way within mesoscale simulations. The mesoscale domains thus simulated the evolving weather, while the two innermost domains used an LES closure, intending the largest scales of turbulence to be explicitly resolved. For a selected day, we show that the simulated turbulence is accurately resolved within the innermost LES domain, and agrees well with the observations at all vertical levels. For the full year, we show that the innermost domain accurately reproduces mean wind speed, direction, and turbulence levels, whereas the mesoscale simulations have difficulties matching the frequency of occurrence of both low and high turbulence ranges when compared to the observations. The largest differences between the simulated turbulence from the innermost domain and the observations are found under low wind speed conditions close to the surface, particularly during nighttime where the simulated mean wind and turbulence levels are higher and lower, respectively, than the observations, potentially due to the inability of the LES mesh to resolve the very small scales of turbulence and associated momentum transport that those features support. [Display omitted] • We show the ability of an atmospheric model to resolve turbulence for a full year. • The model's simulated turbulence can be used for assessment of site conditions. • The energy content of the model's resolved turbulence is captured by the simulations. • Power density is accurately predicted within large-eddy simulation domains. [ABSTRACT FROM AUTHOR]

• A CA model based on CDRX mechanisms was developed to investigate the substructure evolution of the Ti-10V-2Fe-3Al alloy. • The accuracy of the CA simulation was improved by integrating subgrain formation and rotation models. • The moderate high temperature of 750 ℃ is more conducive to the misorientation increasing and transformation of LAGBs to HAGBs. • A high volume fraction of α -phase with a small grain size could significantly promote the CDRX process. Continuous dynamic recrystallization (CDRX) is the dominant restoration mechanism of near- β titanium alloys during hot deformation. But till now, there is seldom visual modeling of the process which limits its industrial application. Based on CDRX mechanisms characterized by low-angle grain boundaries (LAGBs) formed and partially transformed into high-angle grain boundaries (HAGBs), the present study established a cellular automata (CA) model to investigate the substructure evolution and mechanical response of Ti-10V-2Fe-3Al alloy. Besides, a new set of equations for subgrain rotation considering the effect of the α -phase was integrated into the CA model to improve its applicability in titanium alloy. The model was validated by experimental results and then applied to predict the substructure evolution during hot working. Simulation analysis revealed that, except for high strain rates and temperatures, a high fraction of α / β phase boundaries could also promote the development of CDRX. The proposed CA model provided an effective method for microstructure optimization in hot forging of the Ti-10V-2Fe-3Al alloy. [Display omitted] [ABSTRACT FROM AUTHOR]

The mesoscale model with realistic yarn geometries could improve the accuracy of property prediction of woven composite structures. This paper aims to propose a novel mesoscale modeling method for the woven composite twisted structures. Firstly, the torsional deformation of the yarns in the unit cell model is simulated with high-fidelity using digital element fibers embedded into the matrix solid meshes. Then, the solid geometry model of the twisted composite structures is reconstructed from the digital element deformation model by combining the affine transforms. Finally, the elastic responses of the twisted composite structure under cantilever loading are predicted by assigning the element information of the established mesoscale model to the macroscale model. It is shown that the geometric morphology and predicted mechanical responses of the high-fidelity model are consistent with the experimental results. Furthermore, the effect of twist angles on the stiffness properties of the twisted composite structures is analyzed using the presented numerical method. The proposed digital modeling method could provide a guide for the early design of woven composite structures. [Display omitted] [ABSTRACT FROM AUTHOR]

Experimental information from microscopy, structural biology, and bioinformatics may be integrated to build structural models of entire cells with molecular detail. This integrative modeling is challenging in several ways: the intrinsic complexity of biology results in models with many closely packed and heterogeneous components; the wealth of available experimental data is scattered among multiple resources and must be gathered, reconciled, and curated; and computational infrastructure is only now gaining the capability of modeling and visualizing systems of this complexity. We present recent efforts to address these challenges, both with artistic approaches to depicting the cellular mesoscale, and development and application of methods to build quantitative models. Advances in integration of data and computational infrastructure together are enabling the modeling of large portions of cells, and in some cases, entire cells. Mesoscale models of cellular environments promote research into cellular structure and function by providing thinking tools for hypothesis generation, by providing initial models for simulation and interpretation of experiments, and by providing a new window for the development of drugs. New approaches to visualization and interaction are being developed to address the challenging needs of mesoscale research. [ABSTRACT FROM AUTHOR]

• A mesoscale kMC model is constructed to study the grain size effect of nanoglasses (NGs). • Variable characteristic strain captures the structural variation in terms of a shear band development. • Reduction of elastic constants of STZs simulates the failure behavior akin to the experimental tests. • Inhomogeneous to homogeneous deformation transition occurs as grain size decreases to ∼10 nm. • Deformation mechanism for the deformation transition due to grain size of NGs has been elucidated. Severe shear localization in metallic glasses (MGs) significantly limits their mechanical performance. Nanoglass (NG), composed of heterogeneous glassy domains created by introducing interfaces into MGs at the nanoscale, could be a promising strategy against severe shear localization, as demonstrated by numerous atomistic simulations. This study introduces a novel mesoscale kinetic Monte Carlo (kMC) model with a variable characteristic strain (VCS) to investigate the grain size effect in NGs. This model captures the complex evolution of shear bands during deformation, revealing a surprising transition from inhomogeneous to homogeneous deformation as the NG grain size decreases to approximately 10 nm. This transition is attributed to the impediment of shear band formation by the small grain size, facilitated by softer interfaces guiding early shear transformation zone (STZ) activities across the entire sample. Furthermore, a progressive reduction of elastic constants simulates the failure response observed in experiments. Our model predicts a critical grain size for the transition in agreement with molecular dynamics simulations and experiments, highlighting its potential for designing NGs with enhanced shear resistance. This mesoscale model enables the investigation of NG deformation with microstructural features on an experimentally-relevant spatial-temporal scale. This paves the way for tailoring NG microstructures to achieve enhanced mechanical performance, and opens new avenues for exploring the influence of interfaces in controlling shear localization. [Display omitted] [ABSTRACT FROM AUTHOR]

Fission gases (Xe, Kr) produced during irradiation in nuclear fuel have very low solubility in the matrix, and precipitate into bubbles. These bubbles interact with point defects of the fuel (vacancies, self-interstitials, etc.) causing significant microstructural evolution which may eventually affect the overall performance of the fuel. Spatially resolved models have been developed to predict and model the microstructural changes at the mesoscale. We present a new model, which focuses on the interaction between point defects and xenon gas bubbles in UO 2. This model overcomes the limitation of the existing cluster dynamics models as it can account for spatialization, as well as the limitation of the spatially resolved phase-field models as it can also account for very small defect clusters. Modeling of the phenomena of coalescence of two bubbles in a vacancy supersaturation and the vanishing of a small bubble in the presence of a larger bubble (Ostwald ripening) prove the credibility of the new model. 2-D analysis of the movement and growth of bubbles in a vacancy concentration gradient is presented and it simulates the physical behaviour with good agreement. [ABSTRACT FROM AUTHOR]

• New mesoscale model for the gas phase fluid dynamics in structured packings is presented. • The model represents well the essential gas fluid dynamics in structured packings. • Distribution of velocities, pressures and concentrations in good agreement with CFD results. • Computational cost of the mesoscale model three orders of magnitude lower than CFD. • Experiments and CFD simulations of tracer transport in a single crisscrossing junction. This paper presents a new mesoscale model simulating the gas phase fluid dynamics and concentration distribution in structured packings, used in absorption and distillation columns. The model describes the structured packing as an arrangement of triangular channel sections and is implemented with an own developed mesoscale simulation code (StructuPack). The velocity field is stored at the cell faces and is driven by pressure, inertial and viscous forces. The coupled continuity and momentum equations are solved with the SIMPLE-algorithm, that is usually applied in CFD solvers. The development of the model is based on fundamental investigations with CFD simulations and experiments, described in the first part of the paper. Particularly, the concentration distribution in a representative geometry of structured packings, a single crisscrossing junction of triangular channels, is analysed. As one result of the fundamental investigations the CFD solver could be validated as a predictive tool with respect to concentration distribution for the laminar regime in structured packings. In the second part, the mesoscale model is described in detail and validated with a scenario of tracer distribution in a packing layer. By means of comparison with CFD simulations of the same scenario it was shown that the mesoscale model has the ability to yield good representations of concentration, pressure and velocity profiles in a structured packing. Thereby the mesoscale computational performance was three orders of magnitudes more efficient with respect to CFD. At the advent of high-performance computing this means that models at intermediate scale are a viable tool to simulate scenarios like maldistribution effects in industrial sized structured packings of distillation and absorption columns. [ABSTRACT FROM AUTHOR]

Minor actinide transmutation fuels, of which U-Pu-Zr is one of the most promising, have been the subject of renewed interest for fast reactor applications. Unfortunately, we lack the understanding necessary to make quantitative, mechanistic predictions about the complex phase behaviors exhibited by U-Pu-Zr. This prevents the efficient development and implementation of U-Pu-Zr fuels. Herein, we use state of the art experimental and mesoscale simulation techniques to examine and predict the behavior of U-24Pu-15Zr (weight percent). Experimental and simulated microstructural and phase stability results are compared to one another and to accepted reference data. Experiments revealed a heterogeneous microstructure composed of α Z r , ZrO 2 , δ , β P u , and ζ at room temperature. The unexpectedly high ratio of β P u to ζ is believed to arise from non-equilibrium and surface effects, as both passivation and Pu and Zr segregation were observed in the samples. A modeling technique based on the overall bulk free energy is devised to estimate the extent of a microstructure's departure from equilibrium. Agreement between the datasets is used to justify a set of recommendations for the further study of U-Pu-Zr fuels. These address deficiencies in our fundamental knowledge, fuel fabrication and handling techniques, characterization methods and procedures, modeling capability, and use of coupled experiments and mesoscale simulations. • As-cast U-24Pu-15Zr samples exhibit passivation and surface segregation behaviors. • Surface and near-surface characterizations are obscured by surface effects. • Reference, experimental, and simulated transition temperatures are inconsistent. • Coupled experiments and mesoscale simulations will enhance metallic fuel research. [ABSTRACT FROM AUTHOR]

Abstract Electrochemical energy systems, such as batteries and fuel cells, are being developed for applications ranging from portable devices and electric vehicles to large-scale grid storage. These advanced energy conversion and storage technologies will be a critical aspect of a sustainable energy future and promise to provide cleaner, more efficient energy. Computational modeling at various scales from nanoscale ab initio modeling to macroscale system and controls level modeling, has been a central part of the electrochemical energy research. Much of the complex interactions due to the electrochemistry coupled transport phenomena occur at the interfaces and within the porous electrode microstructures. This is often referred to as the mesoscale and plays a critical role in the operation and efficiency of electrochemical devices. In this critical perspective, we discuss the state-of-the-art, challenges and path forward in mesoscale modeling of electrochemical energy systems and their application to various design and operational issues in solid oxide fuel cells, polymer electrolyte membrane fuel cells, lithium ion batteries and metal-air batteries. Particular focus is given to particle-based methods and fine-scale computational fluid dynamics based direct numerical simulation techniques, along with the challenges and advantages of these methods. Notable results from mesoscale modeling are presented along with discussions of the advantages, disadvantages and challenges facing mesoscale model development. This in-depth perspective is envisioned to serve as a primer to the critical role mesoscale modeling is poised to play in advancing the science and engineering of electrochemical energy systems. [ABSTRACT FROM AUTHOR]

To address the cumbersome nature of mesoscale models for concrete as well as other similar materials, this paper presents an efficient and high-volume fraction mesoscale modeling framework with a novel aggregate surface tracking algorithm as well as an aggregate-cement interface interaction model to replace the interface transition zone (ITZ) in the three-dimensional space. This model could also be used in composite materials such as Fiber-reinforced polymer concrete. In this study, results are compared with the traditional 3 phases concrete models, uniaxial tension and compression models, and triaxial compression models for validation. The results show that the three-dimensional mesoscopic model can capture the detailed process of mesoscopic damage and the macroscopic behavior under different stress states while showing good agreement with the experimental results. It is demonstrated that compared with traditional methods, the new model can save up to 84 % of the preprocessing and computation time and provides a more convenient and efficient scheme for the three-dimensional mesoscopic modeling of concrete alike composite materials with good accuracy. This paper also presents several 3D mesoscale models of Fiber-reinforced polymer concrete. [ABSTRACT FROM AUTHOR]

Predicting a sample size-dependency of the constitutive response of any material system when it is being used in nano- and micro-scale devices, such as NEMS and MEMS, is very crucial for their design process. This also includes the shape memory alloys (SMAs), where predicting a sample size-dependency of the phase transformation process is the key aspect. Many experimental studies with micropillar compression tests showed an increase in critical stress to transformation and an increase in transformation hardening as the sample size decreases below a critical size. In this work, we have employed and extended a recently developed mesoscale framework to model such size effects in SMAs. A plane strain tensile SMA strip of finite width is analyzed within a small deformation framework. The martensitic transformation regions are modeled as Eshelby inclusions in an austenite phase matrix. Circular potential nucleation sites are considered with a square packing for their spatial locations and with nucleation stress assigned to each site from a Gaussian distribution. The combination of the Gaussian distribution of nucleation stress and the size of the nucleation site represents the underlying SMA material microstructure. Our numerical analysis, with varying values of the aspect ratio between the strip width and the nucleation site size, provides a critical value of the aspect ratio characterizing a transitioning length scale between a bulk vs. a sample size-dependent phase transformation behavior. At the transition, the critical stress to phase transformation and the transformation hardening increase drastically as the aspect ratio decreases below its critical value. The limitations of these predictions are discussed with existing literature on experimental observations, and some perspectives to improve the model are stated. • The pseudoelasticity behavior of SMAs is studied using a mesoscale framework. • The heterogeneous distribution of the nucleations provides the transformation hardening. • The behavior is size-dependent for the sample size smaller than a critical size. • The ratio between the sample size and the microstructure size describes the transition. • The critical value of the ratio at the transition is equal to 20. [ABSTRACT FROM AUTHOR]

• This paper verifies the applicability of BSMPM, GIMP, and CPDI in mesoscale simulating the SCJs. • BSMPM based on cubic and quartic splines is most suitable for mesoscale simulating, whose SCJs are in great continuity with little cavity and small surface roughness. • For SCJs material, the strain evolution is hierarchical and the particle trajectories can be classified as a laminar layer, transition layer, and turbulent layer from outer to the axis, consistent with the grain size evolution. Shaped charge (SC) generates a fluid-like high-speed jet (SCJ) undergoing extremely large ductile stretching without fracture. It is a formidable challenge to accurately track and monitor the mesoscale deformation characteristics of materials using fluid simulation algorithms. To address this issue, the Material Point Method (MPM) is introduced as an efficient particle-based method that discretizes the continuum into Lagrangian particles moving through a fixed Eulerian grid. By possessing all material properties, these particles facilitate tracking throughout the deformation process and enable the implementation of history-dependent constitutive models. Regrettably, the utilization of MPM in the study of SCJ formation is restricted. The objective of this study is to assess the capability of 2D-axisymmetric MPMs in modeling SCJ formation and free flight at the mesoscale, thereby providing valuable guidelines for their application in SCJs. The MPMs employed in this study are based on the B-spline (BSMPM) and domain interpolations (generalized and convected particle domain interpolations in MPM). The numerical results indicate that BSMPM with cubic and quartic splines is the most suitable method for calculating SCJs due to its exceptional continuity and alignment with the experimental data. The mesoscale evolution of particles reveals that the material undergoes impact crushing and tensile tearing, transforming into a low-speed slug and a high-speed jet. The equivalent plastic strain (EPS) in SCJs exhibits a radial expansion from the exterior to the axis in a layered manner. Particles in the outer layer with a thickness of approximately 1/2 exhibit a 'laminar' distribution, while particles near the axis exhibit 'turbulent' distribution and undergo severe deformation. The hierarchical progression of EPS and particle motion traces provides insight into the underlying causes of mesoscale experimental phenomena, such as the axial elongation of voids in the SCJ slug and the radial distribution of the material in three concentric circles. [ABSTRACT FROM AUTHOR]

• A mesoscale model was developed for simulating compression testing of crumb rubber mortar. • The effect of randomly distributed rubber particles on the compressive strength of CRM was studied. • The effect of the interface layer on the compressive strength of CRM was investigated. • Rubber content is the controlling factor affecting the reduction of compressive strength of mortar. • Rubber can be considered as pores to analyze their effect on compressive strength. A mesoscale model was developed to study the compressive performance of crumb rubber mortar (CRM). The internal structure of CRM was considered as a three-phase composite consisting of rubber, mortar, and interfacial transition zone (ITZ). The effects of ITZ, rubber aggregate distribution, mortar matrix strength, rubber aggregate shape, and treating rubber as pores on the compressive strength of CRM were studied. The influence of the presence of ITZ on the compressive strength of CRM was lower than 2 % and was negligible. The location of rubber particles has an effect on the strength of CRM. The use of small-sized rubber particles resulted in a more uniform internal structure of the CRM samples and less variation in strength among different samples. Adding rubber reduces the compressive strength of mortar, and the strength reduction rate is mainly affected by the rubber content. Rubber particles can be equivalent to pores to analyze their influence on the compressive strength and failure mode of CRM. The stress concentration that occurs around the position of the rubber particles is a major factor that causes the strength of CRM to decrease. A prediction formula was presented to calculate the compressive strength of CRM, which agreed well with the experimental results. [ABSTRACT FROM AUTHOR]

The aim of the present study is the evaluation of the thermodynamic characteristics of a high impact tornadic event in Skala Lakonia, southern Peloponnese, on September 21, 2015. The study was carried out using the Weather Research and Forecasting (AR-WRF) mesoscale model allowing high spatial resolution for the analysis. For the particular model setup used in this study, different planetary boundary layer (PBL) parameterization schemes were tested. The current study downscales ECMWF reanalysis initial and lateral boundary conditions to 1 km spatial resolution to assess the mixing layer convective available potential energy (MLCAPE – MCAPE hereafter), the reflectivity perceived by radar (dBZ), the storm relative helicity (SRH) and the energy helicity index (EHI) for the different PBL schemes. The validation was conducted using in situ and remote sensing observations of the surrounding area. The results illustrate deep convective activity with MCAPE values indicating a strong instability in the region of interest using both local and non-local closure PBL schemes. The study evaluates the affectability of the PBL physical processes with regard to the thermodynamic variables on the model performance. Finally, Mellor Yamada Janjic local (MYJ) closure PBL scheme is the best PBL scheme for studying this tornado since its simulation results display deep convection activity along with the highest validation scores. [ABSTRACT FROM AUTHOR]

Radiation damage presents a unique challenge for material simulations, with processes ranging from picoseconds to decades in time and nanometers to meters in length. Particularly, the understanding of many processes and fundamental mechanisms at the mesoscale are still lacking. In this paper, the self-evolving kinetic Monte Carlo (SEAKMC) method and its application to study mesoscale defect interaction is presented. SEAKMC is an off-lattice atomistic kinetic Monte Carlo approach which conducts ‘on-the-fly’ saddle point searches (SPS) using selective active volumes. The main components of SEAKMC are examined with focus on the comparative benefits of this method. Future areas of improvement are outlined, including suggestions for general improvements to SPS methods by reducing redundant searching and making predictive initial guesses for point defect migration events. Previous applications of SEAKMC to radiation effects in materials are briefly reviewed. Some potential applications of SEAKMC are given, including discussion of dislocation bias, and the further study of interaction between dislocation loops and point defects, which provide useful insights to understand void swelling, radiation induced segregation, and other important radiation damage processes. [ABSTRACT FROM AUTHOR]

Microstructure-based numerical modeling of ferrite recrystallization in a cold-rolled dual-phase (DP) steel during continuous annealing has been performed by considering the deformation heterogeneity with a coupled simulation method. The plastic deformation inside the two-phase structures is firstly simulated using the crystal plasticity finite element method (CPFEM) at the grain scale with the initial grain structures and crystallographic orientations inputted from EBSD maps based on a digital material representation algorithm. The predicted local stored deformation energy is then incorporated into the cellular automaton model as the driving force for subsequent ferrite recrystallization nucleation and growth. The simulations demonstrate inhomogeneous microstructural behaviors of ferrite recrystallization owing to the microstructural deformation heterogeneity inherited from the deformed multi-phase structures. Reliable predictions regarding the recrystallization kinetics, grain size distribution and microstructure morphology can be made compared with the experimental results. The influence of annealing temperatures and heating rates is also obtained by the simulation approach. [ABSTRACT FROM AUTHOR]

Towards the improvement of the mesoscale modeling for offshore wind application, the real time observational nudging capability of the Weather Research and Forecasting (WRF) model has been implemented aiming for enhanced model performance. Utilizing three different horizontal levels of the offshore meteorological mast, FINO3, in the North Sea, wind speed observations were integrated into the model core. The performance of this modified model was then assessed for three different atmospheric stability conditions. Results from this study, illustrate that for all three stratification cases, there is a significant improvement in model performance when using observational nudging showing a reduction in Root Mean Square Error of up to 27% when compared to the observations from FINO1 platform. This study suggests that observational nudging takes a step towards more accurate simulations in wind resource assessment (WRA). [ABSTRACT FROM AUTHOR]

The links between loading orientation of single crystal Al and the dynamic evolution of defects (dislocations, twins, stacking faults etc.) during spallation are investigated using molecular dynamics (MD) simulations. The microstructural evolution during the shock compression of single crystal Al is observed to be primarily guided by the nucleation and evolution of Shockley partials and twin partials. The shock response and spallation behavior of single crystal Al is observed to be anisotropic and is influenced by the density of various types of dislocations during shock compression and void nucleation at the spall plane. The capability of the “quasi-coarse-grained dynamics” (QCGD) method to reproduce the MD predicted nucleation, interaction and evolution of dislocations during shock compression and spallation of single crystal Al is discussed. The QCGD method retains the relative contribution of different types of dislocations during propagation of shock compression wave, interactions of the wave and spallation of single crystal Al as predicted by MD using a fraction of representative atoms allowing the modeling of of larger sized systems for larger times. [ABSTRACT FROM AUTHOR]

Aircraft icing is one of the most dangerous weather phenomena in aviation security. Therefore, avoiding areas with high probability of icing episodes along arrival and departure routes to airports is strongly recommended. Although such icing is common, forecasting and observation are far from perfect. This paper presents an analysis of an aircraft icing and turbulence event including a commercial flight near the Guadarrama Mountains, during the aircraft approach to the airport. No reference to icing or turbulence was made in the pre-flight meteorological information provided to the pilot, highlighting the need for additional tools to predict such risks. For this reason, the icing episode is simulated by means of the Weather Research and Forecasting (WRF) model and analyzed using images from the Meteosat Second Generation (MSG) satellite, with the aim of providing tools for the detection of icing and turbulence in the airport vicinity. The WRF simulation shows alternating updrafts and downdrafts (> 2 m s − 1 ) on the lee side of the mountain barrier. This is consonant with moderate to strong turbulence experienced by the aircraft on its approach path to the airport and suggests clear air turbulence above the mountain wave cloud top. At the aircraft icing altitude, supercooled liquid water associated with orographic clouds and mountain waves is simulated. Daytime and nighttime MSG images corroborated the simulated mountain waves and associated supercooled liquid water. The results encourage the use of mesoscale models and MSG nowcasting information to minimize aviation risks associated with such meteorological phenomena. [ABSTRACT FROM AUTHOR]

Primitive solar system solids were accreted as highly porous bimodal mixtures of mm-sized chondrules and sub-μm matrix grains. To understand the compaction and lithification of these materials by shock, it is necessary to investigate the process at the mesoscale; i.e., the scale of individual chondrules. Here we document simulations of hypervelocity compaction of primitive materials using the iSALE shock physics model. We compare the numerical methods employed here with shock compaction experiments involving bimodal mixtures of glass beads and silica powder and find good agreement in bulk material response between the experiments and models. The heterogeneous response to shock of bimodal porous mixtures with a composition more appropriate for primitive solids was subsequently investigated: strong temperature dichotomies between the chondrules and matrix were observed (non-porous chondrules remained largely cold, while the porous matrix saw temperature increases of 100’s K). Matrix compaction was heterogeneous, and post-shock porosity was found to be lower on the lee-side of chondrules. The strain in the matrix was shown to be higher near the chondrule rims, in agreement with observations from meteorites. Chondrule flattening in the direction of the shock increases with increasing impact velocity, with flattened chondrules oriented with their semi-minor axis parallel to the shock direction. [ABSTRACT FROM AUTHOR]

The National Weather Service (NWS) considers frequent gusty downslope winds, accompanied by rapid warming and decreased relative humidity, among the most significant weather events affecting southern California coastal areas in the vicinity of Santa Barbara (SB). These extreme conditions, commonly known as “sundowners”, have affected the evolution of all major wildfires that impacted SB in recent years. Sundowners greatly increase fire, aviation and maritime navigation hazards and are thus a priority for regional forecasting. Currently, the NWS employs the Weather Research Forecasting (WRF) model at 2 km resolution to complement forecasts at regional-to-local scales. However, no systematic study has been performed to evaluate the skill of WRF in simulating sundowners. This research presents a case study of an 11-day period in spring 2004 during which sundowner events were observed on multiple nights. We perform sensitivity experiments for WRF using available observations for validation and demonstrate that WRF is skillful in representing the general mesoscale structure of these events, though important shortcomings exist. Furthermore, we discuss the generation and evolution of sundowners during the case study using the best performing configuration, and compare these results to hindcasts for two major SB fires. Unique, but similar, profiles of wind and stability are observed over SB between case studies despite considerable differences in large-scale circulation, indicating that common conditions may exist across all events. These findings aid in understanding the evolution of sundowner events and are potentially valuable for event prediction. [ABSTRACT FROM AUTHOR]

This work investigated the tensile fatigue behaviors of ultra-high performance concrete containing coarse aggregate (UHPC-CA), with an emphasis on exploring the underlying mechanisms induced by CA incorporation. Upon constant-amplitude fatigue tests at four different stress levels, CA incorporation-induced variations in fracture morphology, deformation capacity, and fatigue life of UHPC-CA were analyzed, which were further revealed through multiscale characterization of hydration products, pore structures, and stress state alterations within UHPC matrix. The results showed that despite the considerable enhancement in elastic modulus in comparison with CA-free UHPC, weakened fatigue deformability and accelerated damage evolution are observed for UHPC-CA. As the CA content increased, the performance degradation was continually exacerbated, and it was experimentally evidenced to be highly linear with the loss of bound water and the increase in macropore volume. Compared to CA-free UHPC, the premature fatigue failure of UHPC-CA was primarily attributed to the magnified stress concentration within the matrix. [ABSTRACT FROM AUTHOR]

• Investigating the effect of the maximum aggregate size on the relationship between the FPZ length and the crack extension in concrete. • AE events show an increasing trend of the width of FPZ with increasing aggregate size. • R-curves are aggregate-size dependent. In this paper, an experimental/numerical investigation is proposed to study the effect of maximum aggregate size (D max) on the fracture process zone (FPZ) length variations and the crack extension. Experimentally, three-point bending tests have been realized on plain concrete with different maximum aggregate sizes under crack mouth opening displacement (CMOD) control. The crack growth is monitored using the acoustic emission (AE) technique. The numerical investigation is conducted at a mesoscale level. From the evolution of cohesive tangential stresses along the crack path, the variation of FPZ is explored. The crack extensions are investigated using the equivalent linear elastic fracture mechanics approach (LEFM) to investigate the R-curves. The results show a great influence of the maximum aggregate size both on the FPZ variation and on the global behavior. [ABSTRACT FROM AUTHOR]

• Puck criterion combined with modified Tsai-Wu polynomial criterion is used in numerical simulation of the composites on mesoscale. • The CT three-dimensional reconstruction of the targets which impacted by the ice projectile are carried out. • The generation and distribution of different mode cracks and their influence on the whole structure are analyzed. • This work provides a method to explain the generation mechanism of Barely Visible Impact Damage and judge the overall failure of CFRP. This work studied the barely visible damage caused by hail impact on the aircraft surface's carbon fiber-reinforced polymer (CFRP) plates. The mesoscale model of the composites was established. Puck criterion combined with the modified Tsai-Wu polynomial criterion was used as the criterion of the fiber bundle fracture failure in numerical simulation. According to the computerized tomography three-dimensional reconstruction results and the test results of impact response obtained from previous work, the reliability of numerical simulation was verified. It was shown that different stress states cause different fiber fracture modes. Moreover, the location with the largest crack density was not at the center of the impact area but at the edge where the ice projectile contacted the CFRP plate at the moment of ductile–brittle transition during the impact. Finally, based on the influence mechanism of the fiber bundle's fracture mode on the damage propagation of the internal structure, the damage threshold of composites was determined to be about 4.872 J. This work provides a method to explain the generation mechanism of barely visible impact damage and judge the overall failure of CFRP. [ABSTRACT FROM AUTHOR]

An experimentally validated mesoscale model was developed to simulate the effective thermal conductivity (ETC) of metallic U and U–Zr nuclear fuels. The effects of microstructure, temperature, composition, and interfacial thermal resistance (ITR) were investigated. Companion experiments were conducted to validate the model. The numerical simulations clearly demonstrate that accounting for the interface (Kapitza) thermal resistance and Zr precipitation is necessary to improve the model predictions. The dependence of the effective Kapitza resistance of depleted-U and U-10Zr on temperature was determined. For both materials, the largest difference between the model calculations and the experimental data was about 4.5%, which is within the precision of the experimental measurements. [ABSTRACT FROM AUTHOR]

The mechanics of concrete can be understood comprehensively only if its heterogeneous microstructure is considered in experiments and simulations. We combine mesoscale modeling, in-situ X-ray computed tomography imaging, and in-situ 3D X-ray diffraction measurements for one of the first times to investigate the role of heterogeneities on macroscopic and microscopic responses in concrete. The focus here is on heterogeneities at the micron scale: aggregates, cement paste, interfacial transition zone, high-density phases, and voids. We specifically seek to answer whether all levels of heterogeneities are essential in predicting: (a) elastic macroscopic stress–strain response, (b) microscopic elastic stress–strain concentrations, and (c) representative volume element size for elastic responses. The results demonstrate the significant influence of heterogeneities on local strains in matrix phases and the minimal influence of heterogenities on stresses in individual grains. [ABSTRACT FROM AUTHOR]

• Realize the anisotropic characterization of 2D ice single crystal by peridynamics. • Establish an accurate mesoscale model of 2D polycrystalline columnar ice. • Obtain the minimum grain number of S2 polycrystalline ice to maintain macroscopic isotropy is 225. • Study the mode I fracture characteristics of polycrystalline ice plate. We investigate the numerical modeling method of columnar polycrystalline ice based on peridynamics. A polycrystal with relatively uniform area is established with the Voronoi method to model the mesoscale polycrystalline behavior of S2 columnar ice. The grain orientations are given by the uniform random algorithm, and the characterization of grain anisotropy is realized with a nonspherical influence function. The correctness of the anisotropic characterization method is verified by monitoring the displacement of specific points. A macro homogenization analysis of multiple groups of polycrystalline ice models is conducted by applying periodic boundary conditions, and the equivalent parameters are analyzed comprehensively. Finally, the minimum number of grains required to maintain the isotropy of polycrystalline ice is determined to be 225. The mode I tensile fracture of a polycrystalline ice plate is simulated with the abovementioned numerical method and a critical tensile criterion, and the tensile strength range is obtained. These results closely agree with existing results, indicating that the current method can accurately characterize of polycrystalline materials and enable polycrystals with sufficient grain numbers to stably express isotropy at the macroscale, which is applicable to multiscale research on polycrystalline materials. [ABSTRACT FROM AUTHOR]

Advances in higher resolution experimental techniques have shown that metallic materials can develop fatigue cracks under cyclic loading levels significantly below the yield stress. Indeed, the traditional notion of a fatigue limit can be recast in terms of limits associated with nucleation and arrest of fatigue cracks at the microstructural scale. Although fatigue damage characteristically emerges from irreversible dislocation processes at sub-grain scales, the specific microstructure attributes, environment, and loading conditions can strongly affect the apparent failure mode and surface to subsurface transitions. In this paper we discuss multiple mechanisms that occur during fatigue loading in the high cycle fatigue (HCF) to very high cycle fatigue (VHCF) regimes. We compare these regimes, focusing on strategies to bridge experimental and modeling approaches exercised at multiple length scales and discussing particular challenges to modeling and simulation regarding microstructure-sensitive fatigue driving forces and thresholds. We conclude by discussing some of the challenges in predicting the transition of failure mechanisms at different stress and strain amplitudes. [ABSTRACT FROM AUTHOR]

This work presents a mesoscale model (MSM) simulating the laminar and turbulent gas phase fluid dynamics and concentration mixing in structured packings, used in absorption and distillation columns or static mixers. The MSM aims to provide computationally efficient predictions of the three-dimensional distributions of pressure, velocity and concentration in the structured packing's gas phase. The MSM is successfully calibrated and validated with virtual experiments obtained from DNS (direct numerical simulations) of a single structured packing section featuring concentration mixing under uniform and maldistributed velocity inlet profiles. The packing section scenarios exhibit a variety of physical effects, like backflow, high-velocity fronts and blockage at the packing's borders to the wall, which are all predicted correctly by the MSM. The physical effects have an impact on concentration mixing and velocity smoothing and are particularly interesting for applications of structured packings in dividing-wall columns or static mixers. Finally, the MSM is set up to simulate cylindrical columns with alternately rotated structured packing sections, including wall regions and wipers. MSM simulations of three packed columns of varying diameter are compared against experimental data and correctly predict the pressure drop dependence on the diameter, demonstrating the MSM's potential for scale-up predictions. [Display omitted] • Mesoscale model (MSM) for gas phase flow simulation in structured packing columns. • Calibration and validation of MSM with CFD/DNS of single packing section scenarios. • Scenarios cover a wide range of gas loads from laminar to turbulent regimes. • Scenarios comprise concentration mixing upon uniform and non-uniform inlet velocity. • MSM simulations of columns with wall region predict diameter effect on pressure drop. [ABSTRACT FROM AUTHOR]

Summary Discriminating moisture sources with precision is an important requirement to better understand the processes involved in extreme rainfall episodes. In a previous contribution by Gangoiti et al. (2011b), an innovative technique was presented to assess surface moisture sources contributing to a target precipitation within a Lagrangian framework. The technique was based in transporting parcels of vapor, representing the target precipitation, across a set of nested grids covering a large area at different resolutions. A mesoscale model estimated the meteorological variables to transport and redistribute the vapor back into its original sources, all of them assumed to be at the surface. The sequence of extreme rainfall events, which occurred over central Europe on August 11–13, 2002, was chosen to put the methodology to test. An important innovation has now been introduced. This new advance allows discriminating not only the terrestrial and oceanic sources but also the evaporation from precipitation occurring below the clouds and falling either on land or on the open sea. It is also able to detect with greater precision the relative importance of remote versus local sources, together with the sequence of evaporation of a rainfall event. After its application to the same episode and targets, our results confirm a similar distribution and strength of surface terrestrial and marine sources. Furthermore, the estimated direct evaporation from precipitation columns contributes to the precipitation episode with a significant amount of moisture which averages around 18% of the total sources, with a main fraction evaporated over land and close to the target regions in central Europe. This contribution adds to the surface sources, and it is consistent with the existence of an important mechanism of positive feedback for the inland transport efficiency of moisture and precipitation, operating at the regional level for this type of episodes. Significant regional differences are found in the contribution to different rainfall targets, with a lower fraction of 14% for the southern target (Upper Austria), and 22% for the northern one (Bohemia). [ABSTRACT FROM AUTHOR]

A simple two-dimensional Unit cell (UC) with three different mesoscopic phases may be geometrically modeled as a combination of two concentric circles or squares embedded in a square. In this paper, a two-dimensional three-phase UC with a similar design is developed and utilized for modeling the full deformation and failure response of cement based quasi-brittle cementitious composites under compression. It was identified from the numerical investigation that the three-phase design greatly improved the prediction capability of the UC in suitably capturing the material nonlinearity observed experimentally. [ABSTRACT FROM AUTHOR]

Forecasts of noise pollution from a highway line segment noise source are obtained from a sound propagation model utilizing effective sound speed profiles derived from a Numerical Weather Prediction (NWP) limited area forecast with 1 km horizontal resolution and near-ground vertical resolution finer than 20 m. Methods for temporal along with horizontal and vertical spatial nesting are demonstrated within the NWP model for maintaining forecast feasibility. It is shown that vertical nesting can improve the prediction of finer structures in near-ground temperature and velocity profiles, such as morning temperature inversions and low level jet-like features. Accurate representation of these features is shown to be important for modeling sound refraction phenomena and for enabling accurate noise assessment. Comparisons are made using the parabolic equation model for predictions with profiles derived from NWP simulations and from field experiment observations during mornings on November 7 and 8, 2006 in Phoenix, Arizona. The challenges faced in simulating accurate meteorological profiles at high resolution for sound propagation applications are highlighted and areas for possible improvement are discussed. [ABSTRACT FROM AUTHOR]

In-cloud icing can impose safety concerns and economic challenges for various industries. Icing climate representations proved beneficial for optimal designs and careful planning. The current study investigates in-cloud icing, its related cloud microphysics and introduces a 15-year time period climatology of icing events. The model was initially driven by reanalysis data from North American Regional Reanalysis and downscaled through a two-level nesting of 10 km and 5 km, using a limited-area version of the Global Environment Multiscale Model of the Canadian Meteorological Center. In addition, a hybrid approach is used to reduce time consuming calculations. The simulation realized exclusively on significant icing days, was combined with non-significant icing days as represented by data from NARR. A proof of concept is presented here for a 1000 km area around Gaspé during January for those 15 years. An increase in the number and intensity of icing events has been identified during the last 15 years. From GEM-LAM simulations and within the atmospheric layer between 10 m and 200 m AGL, supercooled liquid water contents indicated a maximum of 0.4 g m − 3 , and 50% of the values are less than 0.05 g m − 3 . All values of median volume diameters (MVD) are approximately capped by 70 μm and the typical values are around 15 μm. Supercooled Large Droplets represent approximately 5%. The vertical profile of icing climatology demonstrates a steady duration of icing events until the level of 60 m. The altitudes of 60 m and 100 m indicate substantial icing intensification toward higher elevations. GEM-LAM demonstrated a substantial improvement in the calculation of in-cloud icing, reducing significantly the challenge posed by complex terrains. [ABSTRACT FROM AUTHOR]

High fidelity mesoscale modeling techniques are of vital importance for exploration of mechanical behaviors and failure mechanisms of concrete. This paper presents an innovative approach in construction of 3D mesoscale models of concrete with ultrahigh volume fraction of randomly distributed irregular-shaped aggregate. The new modeling method combines Voronoi diagram-based method with take-and-place strategy. In this method, a database of irregular-shaped aggregate models is built based on computed tomography (CT) scan of real aggregates. Then the geometric models of concrete are constructed with the coarse aggregates generated by shrinking Voronoi cells and the fine aggregates packed through a modified take-and-place procedure. 3D mesoscale models of 50 mm × 50 mm × 50 mm concrete specimens are created by the proposed method and proven to bear a close resemblance to the real ones. Ultrahigh aggregate volume fraction up to 66.2 vol% is achieved in the model following the Fuller gradation. To demonstrate the reliability of the generated models, the results of finite element analysis for the epoxy polymer concrete under uniaxial compression is compared with the experimental data. The simulation well reproduces the mechanical behaviors of the epoxy polymer concrete. [ABSTRACT FROM AUTHOR]

Abstract: Woven composite materials are receiving particular attention in a wide range of specialized aeronautical applications. Reliable numerical prediction tools based on computational modeling are required to quantitatively characterize the role of the microstructure and damage mechanisms at the mesoscale. In this paper, such a computational strategy is illustrated on a generic SiC/SiC plain weave composite with chemical vapor infiltrated matrix. Matrix and tows damage mechanisms are respectively introduced through the use of an anisotropic damage model, and an homogenized model based on a micromechanical model on the fiber scale. The latter is presented in this paper for the first time. Particular attention is paid to the generation of accurate hexahedral meshes, compatible at the tow–tow and tow–matrix interfaces. The mesh quality is analyzed using an error estimator variable based on the strain energy density. Damage predictions obtained using tetrahedral and hexahedral meshes are compared for basic loading cases, illustrating the need for using high quality meshes in the growing community of woven composites computational modeling. [Copyright &y& Elsevier]

In uranium-zirconium (U-Zr) based metallic fuels, different phases can form at different compositions and temperatures. Typically, lamellar δ-UZr 2 and α-U phases are the dominant microstructures in U-rich U-Zr alloys at temperatures below 880 K. In this work, a finite element method based mesoscale modeling technique is used to calculate the effective thermal conductivities of such heterogeneous microstructures, using the thermal conductivities of two individual phases and their interphase thermal resistance (Kapitza resistance) as input parameters. The Kapitza resistance between δ-UZr 2 and α-U is determined at different temperatures, which shows an approximately T−3 dependence in the temperature range between 300 and 800 K. In addition, the Kapitza resistance exhibits a strong dependence on the aspect ratio of the δ-UZr 2 phase. An analytical model is therefore developed to quantify the effects of both temperature and δ-UZr 2 aspect ratio on the Kapitza resistance. Using this newly developed Kapitza resistance model, the effective thermal conductivities of a number of δ-UZr 2 + α-U heterogeneous microstructures in U-Zr alloys, including non-lamellar microstructures, can be estimated accurately. [ABSTRACT FROM AUTHOR]

Rapid urbanization and industrialization in the eastern seaboard region of China enhance the widespread use of organophosphorus flame retardants (OPFRs). The present study set up a coupled WRF-CMAQ-SMOKE and multi-compartment exchange modeling framework to assess the environmental fate and cycling of OPFRs and their contamination in the Bohai and Yellow Seas' marine food web. The framework predicts meteorological conditions, optimized air emissions, and concentrations of OPFRs in air, seawaters, marine sediment, and the food web. The model was implemented to simulate the temporal and spatial fluctuations of Tris (2-chloroisopropyl) phosphate (TCPP), the most dominant congener of OPFRs in China, in the Bohai and the Yellow Sea ecosystems on a spatial resolution of 10 km. Results revealed the effects of source proximity, atmospheric transport and deposition, and the changes in meteorology on TCPP's temporal-spatial distribution across different areas of coastal waters. The model also captures TCPP levels in commercial fish species in the Bohai Sea. The detailed temporal-spatial characteristics of TCPP with the mesoscale resolution provide useful information and a new tool for the environmental and health consequences of mariculture, urban and industrial emission mitigation in coastal regions for emerging chemicals, and fishery industry development. [Display omitted] • Mesoscale cycling of OPFR across China's marine environment was quantitatively assessed. • Diurnal and monthly variation of OPFR with high spatial resolution are identified. • Source proximity and lipid contents determine OPFR contamination in commercial fish. • The model provides a useful tool to foresee the risk of toxic chemicals in fish. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mesocale methods are being used to investigate techniques for microfluidic sorting and enrichment of biological cells and other particles. [•] Dissipative particle dynamics (DPD) is used to gain a better understanding of the effects that diseases have on the structure and mechanics of red blood cells. [•] Researchers are utilizing mesoscale methods to develop novel techniques for controlled drug delivery. [•] DPD simulations of lipid membranes give insight to function and how specific particles are able to pass through them. [Copyright &y& Elsevier]

Abstract: This paper develops a mesoscale finite element method for realistic modeling of complex cohesive fracture in asphalt mixture with a given gradation. A random aggregate generation and packing algorithm is employed to create 2D and 3D heterogeneous asphalt mixture specimens, and cohesive elements with tension/shear softening laws are inserted into both mastic and aggregate-mastic interfaces to simulate crack initiation and propagation. The nucleation and coalescence of microcracks and propagation of macrocracks in 2D and 3D specimens is realistically modeled in detail with a few important conclusions drawn. The effects of coarse aggregate distributions on performance of asphalt mixture are also evaluated. [Copyright &y& Elsevier]

Abstract: This paper presents general mathematical formulations for simulating electric double layer capacitors (EDLCs) with three-dimensional ordered structures. For the first time, a general set of boundary conditions was derived in order to account for the Stern layer without simulating it in the computational domain. These boundary conditions were valid for planar, cylindrical, and spherical electrode particles or pores. They made possible the simulations of EDLCs with complex geometries while rigorously accounting for both the Stern and diffuse layers. The model also simultaneously accounted not only for 3D electrode morphology but also for finite ion size and field-dependent electrolyte dielectric permittivity. It was used to faithfully simulate the complex structure of an EDLC electrode consisting of ordered bimodal mesoporous carbon featuring both macropores and mesopores. Areal and gravimetric capacitances were predicted based on non-solvated and solvated ion diameters. These two cases set the upper and lower bounds for the predicted capacitances. The capacitances predicted using non-solvated ion diameter were found to be in good agreement with experimental data reported in the literature. All surfaces contributed to the overall capacitance of EDLCs. The gravimetric capacitance of different bimodal carbons increased linearly with increasing specific surface area corresponding to constant areal capacitance. [Copyright &y& Elsevier]