Narrow Results

Recently, individual-based models originally used for biological purposes revealed interesting insights into processes of the competition of languages. Within this new field of population dynamics a model considering sexual populations with aging is presented. The agents are situated on a lattice and each one speaks one of two languages or both. The stability and quantitative structure of an interface between two regions, initially speaking different languages, is studied. We find that individuals speaking both languages do not prefer any of these regions and have a different age structure than individuals speaking only one language.

The understanding of language competition helps us to predict extinction and survival of languages spoken by minorities. A simple agent-based model of a sexual population, based on the Penna model, is built in order to find out under which circumstances one language dominates other ones. This model considers that only young people learn foreign languages. The simulations show a first order phase transition of the ratio between the number of speakers of different languages with the mutation rate as control parameter.

Numerical unsteady approach based on Galerkin method with the inclusion of adaptive mesh was executed in this paper to simulate the freezing of water within a container. The domain has two triangular and trapezoidal cold surfaces and two adiabatic walls. The governing equations show the domination of conduction and transient source term has been involved. Galerkin method for modeling was applied and good accommodation has been reported based on comparison with previous data. Adding nano-powders makes the amount of heat to be released with stronger conduction and freezing time decreases about 26.76% when $m=8.6$. Augmenting the fraction of powders can make the rate of process increase. For the greatest fraction of powders, an augmenting shape factor can enhance the speed of process about 6.95%.

Anti-icing is a crucial concern for solid surfaces in numerous industrial domains and has garnered significant attention in recent years. Traditional anti-icing methods for solid surfaces often require a substantial input of energy. In this study, we provide a brief overview of the potential applications of anti-icing and recent advancements in the field. Then, we present a novel anti-icing method, the design of superhydrophobic anti-icing surfaces based on droplet dynamics. Additionally, we delve into several related topics that could benefit future research in the area, such as the design of solid surfaces with various bio-inspired properties, among others.

Membrane-type acoustic metamaterials have a favorable noise suppression effect. Hence, a membrane-type acoustic metamaterial plate (MAML) with an X-shaped pendulum arm and cylindrical mass blocks (CMB) was proposed in this paper. The theoretical model based on spring–mass systems and numerical simulation models of the membrane-type acoustic metamaterial cell (MAMC) were established under fixed and periodic boundary conditions to reveal the noise attenuation mechanism quantitatively, and the necessity of the CMB is discussed. Based on the results, it can be observed that the normal displacement of the membrane is nearly zero when the noise frequency is at the peak of the sound transmission loss (STL) curve. However, when the frequency is at the valley of the STL curve, the displacement is nonzero and fluctuates significantly. Meanwhile, by comparing the STL curves with and without the CMB, it was found that the MAMC performance is improved effectively by the CMB at low frequencies. The effective mass density of MAMC was found to be negative. To verify the accuracy of numerical calculations, an impedance tube experiment was conducted. Finally, orthogonal experiments were designed to describe the effects of the structural parameters a, l, and t on the effective bandwidth $\mathrm{\Omega }$, peak frequency $\mathrm{\Phi }$, and comprehensive index $\xi$ and to obtain the optimal structural parameter combinations for different indexes. This work further contributes to applying and developing the membrane-type acoustic metamaterial.

Employing a coupled model for vehicle–track interaction, this paper presented the dynamic analysis of railway track system in the presence of weld irregularities with different geometric profiles in two parallel rails. A 3D model of a standard railway wagon running on a ballasted track system is used to examine the vibrations of the system under track irregularities. Four samples of measured rail profiles at rail welds are considered as the source of dynamic excitations, in which the profiles of parallel rails are unequal. Hence, the individual profiles of left/right rails are imported into the numerical model, taking into account the nonuniform conditions of rail welds in both sides of the railway track. The dynamic responses of the track system caused by irregularities at welds are studied by performing the time-domain vibration analysis. The time histories of the nodal responses under various weld scenarios (measured in an actual railway track site) are recorded. Finally, the peak responses of dynamic forces along the track are determined for left/right rails. The results of dynamic simulations in various weld scenarios are compared and the values of dynamic amplification factors (DAFs) are evaluated. Such findings provide an estimation for the levels of dynamic forces occurring under impact loading conditions of nonuniform rail welds in left/right rails.

In this paper, a comprehensive comparative study on several existing vehicle–bridge interaction (VBI) models is presented with the aim to provide a useful reference to the selection of vehicle and bridge models when conducting the VBI simulation. A simply-supported slab-on-girder highway bridge and the AASHTO HS20-44 vehicle are adopted in the numerical analysis. The bridge is modeled as an Euler–Bernoulli beam, grillage, plate-and-beam system and solid-element system, respectively, while the vehicle is modeled as a moving-force, moving-mass and spring-damper-mass (SDM) system, respectively. Other factors, including the road roughness and the contact condition between the vehicle tire and bridge, are also considered. The effects of different VBI models on the bridge responses are studied and the results from different models are compared in terms of their accuracy, efficiency and suitability. The results show that the accuracy of different types of bridge responses calculated varies with the number of bridge vibration modes used in the simulation. It is also found that the type of element used in the bridge model and the vehicle tire model both have a larger impact on the bridge acceleration than bridge deflection.

A 3D finite-element model for the dynamic analysis of soil–pile–slab is presented, with the soil–pile–mattress–slab interaction included in studying the dynamic behavior of the rigid–pile–reinforced soils. The soil, piles, and mattress are represented as continuum solids, and the slab is represented by structural plate elements. Quiet boundaries are placed at the boundaries of the model to avoid wave reflection. The formulation is based on the sub-structure method. Different geometric configurations are studied in terms of dynamic impedance. The numerical results are presented to show the influence of the mattress stiffness and the pile–soil contact conditions on the dynamic response of the foundation system. The horizontal and vertical impedances of the pile foundations are presented with the results compared with those available in previous studies.

This paper presents an investigation on the seismic behavior of steel moment frames with mechanical hinge beam-to-column connections. The connection uses a mechanical hinge to carry shear force and a pair of buckling-restrained steel plates bolted to the beam flange to transfer bending moment. The moment-rotation behavior of the connection was theoretically studied. A nonlinear numerical model for steel moment frames under strong earthquakes was developed and validated using a shaking table test of an 18-story steel moment frame at the E-Defense facility. Then, nonlinear static and time-history analyses were conducted to compare the seismic behavior of a conventional steel moment frame and three innovative steel frames equipped mechanical hinge connections in terms of roof displacement, base shear, inter-story drift ratio, and plastic hinge rotation.

It was found that polyurea coating could improve the integrity and the corresponding durability of the structural components. However, the strengthening effect of polyurea coatings for structures built with emerging ultra-high-performance concrete (UHPC) is still unknown due to the lack of studies. Therefore, this paper investigated the effect of the polyurea coating on the lateral impact resistance of UHPC columns through a combined numerical and experimental study. A total of five specimens were fabricated, including two UHPC columns and three UHPC columns with polyurea coating. To better characterize the structural response under dynamic loading, impact cases with different drop weight impact heights and axial force ratios were employed. The results showed that the UHPC column with polyurea coating exhibited superior lateral impact resistance compared to the UHPC column. The presence of the axial force increased the lateral impact stiffness and further reduced the deflection of the specimen. In contrast, the polyurea coating improved the specimen’s ductility and mitigated the peak impact force, thereby maintaining the specimen’s integrity without sudden shear failure. A three-dimensional finite element (FE) model of polyurea-coated UHPC columns under impact loading was then established and confirmed the experimental results. With the validated FE model, an intensive parametric study was conducted to investigate the effects of polyurea thickness, axial force ratio and impact energy on the lateral impact resistance of the UHPC column. The presence of the polyurea coating could significantly improve the lateral impact resistance of the specimen, thereby preventing the shear failure of the UHPC column, and thus, the effective thickness of the polyurea layer for the UHPC column was determined to be 2–6mm. The outcome of this research demonstrates the great merits of polyurea coating in improving the ductility and integrity of the UHPC column under lateral impact loading.

In this paper, we investigate the behavior of biological tissues (skin) coupled to a substrate (sensor) based on a numerical model taking into account the relationship between strain/stress components at the interface. Based on this study, we understand and quantify the most appropriate biomechanical factors in order to optimize sensor/biological tissue interface conditions. A micromechanical description based on a mathematical formulation has been developed to evaluate the biomechanical behavior provided by a 2D viscoelastic model of Kelvin–Voigt. The results show a spatio-temporal law of tissue motion highlighting the need for an optimized interface for reliable data transmission in the case of connected device in a dynamic movement or in the manufacturing of intelligent and reactive prosthesis device.

The speed and the versatility of today's computers open up new opportunities to simulate complex biological systems. Here we review a computational approach recently proposed by us to model large tumor cell populations and spheroids, and we put forward general considerations that apply to any fine-grained numerical model of tumors. We discuss ways to bypass computational limitations and discuss our incremental approach, where each step is validated by experimental observations on a quantitative basis. We present a few results on the growth of tumor cells in closed and open environments and of tumor spheroids. This study suggests new ways to explore the initial growth phase of solid tumors and to optimize antitumor treatments.

Abrasive waterjet is widely used for mass-cutting during coal mining or other mining process. Such a cutting process involves complex fluid–solid coupling, which require an effective method capable of simulating the large deformation and spalling of materials. This paper uses method of smoothed particle hydrodynamics (SPH) to establish a model to simulate the cutting process of coal seams by abrasive waterjets. In our SPH model, both fluid and solid are discretized with SPH particles. These particles are different in physical properties representing waterjet, abrasive particles and target materials. The waterjet is treated as viscous fluid and the coal (as a target material) is modeled as a brittle solid material. All these SPH particles of various medium are governed by the Navier–Stokes (NS) equations. Our established SPH model is then applied to study the efficiency of coal cutting using different waterjet formations. The results show that the cutting efficiency of the abrasive waterjet is higher than that of the standard waterjet. Our SPH model is capable of reveal the detailed interactions of the micro waterjet abrasive particles with the particles on the surface of coal. It enables the study on the mechanisms of coal seam breaking and cutting processes. It provides an effective computational tool for improving the efficiency of coal mining and of the development of new techniques for coal mining.

A three dimensional baroclinic numerical model which consists of hydrodynamic, transport and turbulence model components, has been applied to two test cases, including: the wind induced flow in a laboratory basin and tidal flow in a model rectangular harbor. The agreement between the physical and numerical model results is highly encouraging. Model has been implemented to Ölüdeniz Lagoon located at the Mediterranean coast of Turkey to simulate tidal and wind driven currents. M2 tide is the dominant tidal constituent for the area. There exist some field measurements performed on water salinity, water temperature and current pattern in Ölüdeniz Lagoon. Even though measurements provide only some preliminary data for the site, favorable results have been obtained from the application of the model to a real coastal water body.

A one-dimensional parametric model for undertow and longshore current velocities assuming a triangular velocity distribution in a surface roller was developed. This model as well as a parametric model with the assumption of a uniform velocity distribution in a roller was compared with field data obtained on barred beaches at Hasaki in Japan and at Duck in the USA. The comparisons showed that the present model predicted the velocity fields at the two sites reasonably well, and the prediction accuracy of the present model is slightly better than that of the other model. However, the present model underpredicted the undertow velocities on the trough regions, and overestimated the longshore current velocities near the shorelines.

The morphology of a bleb and its changes are critical to the amoeboid migration of a cell. By releasing bonds between the membrane and the cortex of a cell, the formation of a bleb can be observed experimentally, but the mechanism that affects the size and shape of a bleb during amoeboid migration requires further study. In this study, by adapting the governing equations and discrete equations of the two-dimensional fluid–solid coupling model recommended by Strychalski and Guy [2013 “A computational model of bleb formation,” Mathematical Medicine and Biology30(2), 115–130], we overcome the defect that the bleb by traditional means is always too small compared with experimental results, and simulate the behaviors of cell blebs successfully. The effects of various parameters such as the number of broken bonds, the viscosity coefficient of the cortex, and the cell’s membrane modulus on the size and the shape of the bleb are investigated. Numerical results show that the model effectively simulates the formation and evolution of a bleb, thus, the contributions of several factors to bleb shape and size are successfully derived.

Cantilever walls are frequently and necessarily built not only in earthquake prone regions but also on different foundation subsoils with various physical and mechanical characteristics. The response of these structures is a complicated soil-structure interaction (SSI) problem, in which the relative stiffness between the soil and structure is of critical importance. In addition to different soil conditions and earthquake motions, the wall configurations have an important role in the cantilever retaining wall design. Thus, the major objective of this work is to investigate the effects of various configurations on seismic response of the cantilever retaining walls considering SSI. Accordingly, the seismic response of the interaction systems is revealed using the 3D finite element models (FEM) in time domain, assuming linearly elastic behavior for the wall, and elastoplastic behavior for backfill and foundation soil. Viscous absorbent boundaries are employed to both simulate radiation scenario and avoid undesirable wave reflections generated by soil lateral boundaries. Backfill-wall interfaces are modeled using the unidirectional interface elements with nonlinear force-deflection abilities. The interaction systems are analyzed considering three different cantilever wall configurations (inverted T-type, L-type, and the wall with a base key), four different ground motion records, and four different subsoil systems. Nonlinear seismic analyses are carried out to visit how considering the variation of these parameters influences the wall behavior. The results from parametric studies show that the wall configuration, SSI effects and ground motions are remarkably influential on seismic responses of the cantilever walls such as the stresses and horizontal displacements.

A dispersion model for the estimation of crosswind integrated concentrations in the surface-based inversion is proposed. The generalized forms of eddy diffusivity with spatial dependence in both horizontal and vertical directions and vertical height-dependent wind speed are considered. In view of the computational limitation associated with numerical models for Dirac-delta function, the source term is expressed as a limiting case of normal distribution. The accuracy of the employed numerical scheme to solve the resulting partial differential equation with appropriate physically relevant boundary conditions is checked with those obtained from the respective analytical solutions available in literature for the particular forms of eddy diffusivity and wind speed. Concentrations computed from the proposed model are found close to those obtained from analytical models. The concentrations obtained from the proposed model are evaluated for the generalized functional forms of eddy diffusivity (Degrazia and Moraes, 1992; Degrazia et al., 2001) and diabatic logarithmic profile as well as power-law profile of wind speed with the observations from Hanford (Doran et al., 1984) and Copenhagen (Gryning and Lyck, 1984) diffusion experiments in stable and unstable conditions, respectively. Majority of the cases i.e., 64% and 96% are predicted in factor of two to observations in both stable and unstable conditions, respectively.

The restrictions imposed by Montreal Protocol for use of CFCs fluids and Kyoto Protocol to HCFCs have motivated researchers and the industry to seek new alternatives. Within this context, R410A has emerged as one of the most likely replacement of R22. The purpose of this work is to develop a numerical model of an air cooler to simulate its behavior operating under dynamic conditions loaded with R22 or R410A refrigerant. The model divides the air cooler in volumes control in which mass, energy, and momentum balance equations are applied and solved. Theoretical data obtained by model simulations repeated tendencies observed in experimental data taken from literature. Model simulations have also shown that for a step change in the inlet refrigerant mass flow, the superheating response of air cooler is almost the same when it is working with R22 or R410A refrigerant.

Foundations can be subjected to dynamic or seismic loads depending on their applications and the site being constructed in. The researchers concentrated their works on investigating the reasons of the significant damage of piles during seismic excitation. Based on the findings of laboratory experiments and other numerical analyses, such failures were referred to as the kinematic impact of the earthquake on piles since they were associated with discontinuities in the subsoil because of sudden changes in soil stiffness. The current work investigates the seismic response of closed-end (CE) pipe pile using three-dimensional finite element analysis, including the impact of the scaling-up model, acceleration-time history of the ground motion, and ground conditions. The numerical model is developed using a variety of scaling rules and the outputs of the available laboratory tests. The current results showed that the saturated sand models have larger pile deformation factors than dry sand models. Pile frictional resistance was evaluated numerically, and the entire findings were evaluated against the earlier work. Mainly, the frictional resistance around the pile shaft was lower than that at the pile tip, and the frictional resistance factor on the soil surface of dry soil models was larger than that of saturated soil models. Owing to the acceleration amplifications, the pile and soil suffered cycles of compression and tension stresses. A hysteresis loop is broader and flatter on the x-axis as the shear strain increases serve to identify the shear stress–strain plane behavior. The main outputs of the scaled models were normalized to provide a deep insight of model to prototype scaling effects.