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Monte Carlo simulations of hard-sphere (HS) crystal grown on a square patterned wall under gravity have been performed. While previous simulations were performed with step-wise controlled gravity, in the present simulations constant gravity has been applied from the first. In the case in which a flat wall is used as the bottom wall, if a large gravity is suddenly applied, the system does polycrystallize. On the other hand, in the present simulations, despite the sudden application of gravity, the system has not polycrystallize. Crystalline nucleation on the square pattern and successive crystal growth upward are suggested to overcome the homogeneous nucleation inside and result in. Defect disappearance, which has been essentially the same as that for the case with step-wise controlled gravity, has also observed for the present case. The characteristic of the square patterned bottom wall simulation with a large horizontal system size has been existence of triangular defects suggesting stacking tetrahedra.

The purpose of this paper is to present an image based method for estimating the 3D motion of rigid particles from high‐speed video footage (HSV). The computed motion can be used as either a means to generate quantitative feedback for a process or to validate the accuracy of discrete element method (DEM) simulation models.

Experiments consist of a diamond impacting an angled plate and video is captured at 4,000 frames per second. Simple image analysis is used to track the particle in each frame and to extract its 2D silhouette boundary. Using an approximate 3D model of the particle generated from a multi‐camera setup, a pose estimation scheme based on silhouette consistency is used in conjunction with a rigid body model to compute the 3D motion.

Under reasonable conditions, the method can reliably estimate the linear and angular motion of the particle to within 1 per cent of their true values.

As an example application, we demonstrate how the method can be used to validate DEM simulations of simple impact experiments captured with HSV, providing valuable insight towards further development. In particular, we investigate the effects of shape representation through sphere‐clumping and the applicability of different contact models.

The novelty of our method is its ability to accurately compute the motion associated with a real world interaction, such as an impact, which provides numerical ground truth at an individual particle level. While similar schemes have been attempted with ideal particles (e.g. spheres), the resulting models do not naturally extend to realistic particle shapes. Since our method can track real particles, real‐world processes can be better quantified.

After reviewing a previous work on the disappearance of a stacking fault in the hard-sphere (HS) system confined between the top and bottom flat walls under gravity, we present results of a Monte Carlo (MC) simulation of HSs confined between the top flat wall and the bottom square patterned wall under gravity. In MC simulations of HSs between flat walls we observed disappearance of an intrinsic stacking fault through the glide of the Shockley partial dislocation in fcc (001) stacking forced by the stress from a small simulation box. The artifact that the driving force for the fcc (001) growth was the stress from the simulation box has been circumvented; the stress realizing the fcc (001) stacking has been replaced by that from square pattern on the bottom wall. Defect disappearance has also been observed for the square patterned bottom wall case.

The permeate flux in microfiltration (MF) declines sharply with time due to membrane fouling, which seriously restricts its use in industrial applications. The purpose of this paper is to investigate particles deposition in MF processes, and propose a three-dimensional numerical model that focuses on particle-fluid flow and considers both permeable boundary conditions and cake deposition.

The two-ways coupling model was solved using Euler-Lagrange methods in which the suspended particle was traced by a hard sphere model and the fluid was simulated using large eddy model.

The numerical results predicted based on this model demonstrated the permeate flux increased as trans-membrane pressure and inlet velocity increased but decreased with an increase in feed concentration.

Good agreement was observed between the values obtained with the model and experimental values from the literature. The error is less than 20 per cent both permeate flux and cake thickness. In addition, a precise visualisation of cake morphology with filtration time was provided.

These analyses allowed for an estimation of the three-dimensional motion of suspended particles in turbulent flow. It saves manpower and financial resources for experiment, which possess important theoretical and industrial significance.

The purpose of this paper is to investigate the evolution of the permeability of spherical packing during cold compaction by pore-scale modeling.

The discrete element method (DEM) is used to generate spherical packing structure under different compressive pressures and the Lattice Boltzmann method (LBM) is adopted to calculate the permeability of each spherical assembly.

It is found that the decrease of the porosity is the main reason of the reduction in permeability in the initial compression stage, but its influence becomes insufficient in the late compression stages. Besides, two empirical formulas are obtained, which describe the relation between the permeability and the equivalent mean diameter and the variation of normalized permeability with compressive pressure, respectively.

In this study, the authors study the spherical particles and ignore the non-spherical effects. Besides, the classical contact model, the linear-spring-damping model, is used in DEM, so the plastic deformation cannot be considered.

The DEM and the LBM are well combined to study the compaction effects on permeability of spherical packing. Two simple expressions of the spherical packing structure with uniform diameter distribution are given for the first time.

This article discusses themes emerging from two independent research projects. In order to understand how women negotiate and transgress time frames, we critically explore and make visible the strategies used by two very different groups, who are placed in different locales and time orderings. The first group are women in later life and in prison and the second group, women students in higher education. It is by inserting the words of women into debates on time, agency and space that we are able to make visible the strategies that women harness in order to do, make and reclaim time. Within this article we discuss the different research strategies employed by the authors. First, we look at conceptualisations of time and gender. Then we discuss how these respectively inform our research. Azrini Wahidin discusses the role and meaning of time in relation to how female elders in prison come to understand and simultaneously negotiate coercive time use in prison and the passing of time on the outside. She focuses on how the strictures of disciplinary time and the lack of choice create innovative ways of negotiating and resisting the disciplining of institution time in prison. Dot Moss discusses the everyday practice and experience of women students, who, in contrast, have relative freedom to time‐structure their day. She focuses on the ways in which space and time to study are both socially and personally constructed out of other’s time and time for other things (Davies 1990). Common themes arising in relation to the analysis of gender and time are then discussed.

The purpose of this paper is to fundamentally develop a mathematical model for predicting the particle size distribution (PSD) in fluidized beds because their hydrodynamics depend on the PSD and its evolution during operation. To predict the gradual PSD change in a fluidized bed by using the population balance method (PBM), the kinetic parameter for agglomerate formation should be known and this parameter, in this work, is determined by the results of computational fluid dynamic–discrete element method (CFD-DEM) simulation.

Momentum and energy conservation equations and soft-sphere DEM are used to simulate the agglomeration phenomenon at high temperature in a two-dimensional air-polyethylene fluidized bed in bubbling regime. The Navier–Stokes equations for motion of gas are solved by the SIMPLE algorithm. Newton’s second law of motion is applied to describe the motion of individual particles. Collision between particles is detected by the no-binary search algorithm.

A correlation is proposed for estimating the kinetic parameter for agglomerate formation based on collision frequency, collision efficiency and inlet gas temperature. Based on the corrected kinetic parameter, the PBM is able to predict the PSD evolution in the fluidized bed in a fairly good agreement with the results of the CFD-DEM.

The results of the agglomeration process cannot be compared quantitatively with experimental results. Because three-dimensional fluidized bed mostly contains millions of particles and simulating them takes a long computing time in DEM. As far as temperature is a dominant parameter in the agglomeration process, effects of inlet gas temperature are examined on the kinetic parameter. On the other hand, wider and deeper insights in which the effect of other parameters, such as velocity and so on will be studied, is one of the goals in the authors’ next works to compensate for the shortcomings in this work.

This study helps to understand the effect of the inlet gas temperature during the agglomeration process on the kinetic parameter and provides fundamental information in dealing with kinetic parameter to attain PSD in fluidized bed by the PBM.

The paper aims to discuss design, fabrication, testing and simulation of a novel tactile probe used for measuring the stiffness of biological soft tissues/materials with a view to medical and surgical applications.

Both finite element modeling and experimental approach were used in this research. The novel tactile probe capable of recording force-deformation feedback is accompanied with the tactile-status-display which is a custom-designed user-friendly interface. This system can evaluate the stiffness in each part of force-deformation status.

The new system named novel tactile probe was fabricated, and the results on artificial materials (with different stiffnesses) and the sheep kidney (containing a hard object) were reported. Recording different stiffnesses, detecting hard object embedded in soft tissue and predicting the exact location of it are the main results that have been extracted through the diagrams obtained by the novel tactile probe system.

The designed and fabricated system can be modified and miniaturized to be used during different minimally invasive surgeries in the future.

The most distinguishing feature of this novel tactile probe is its applicability during different laparoscopic surgeries, so the in vivo data can be obtained.

For the first time, a tactile probe has been designed and tested in the form of laparoscopic instrument which upgrades the efficiency of available laparoscopic instruments. Also, the novel tactile probe can be used in both in vivo and in vitro experimental setups for measuring the stiffness of sensed objects.

Polyurea is an elastomeric two-phase co-polymer consisting of nanometer-sized discrete hard (i.e. high glass transition temperature) domains distributed randomly within a soft (i.e. low glass transition temperature) matrix. A number of experimental investigations reported in the open literature clearly demonstrated that the use of polyurea external coatings and/or internal linings can significantly increase blast survivability and ballistic penetration resistance of target structures, such as vehicles, buildings and field/laboratory test-plates. When designing blast/ballistic-threat survivable polyurea-coated structures, advanced computational methods and tools are being increasingly utilized. A critical aspect of this computational approach is the availability of physically based, high-fidelity polyurea material models. The paper aims to discuss these issues.

In the present work, an attempt is made to develop a material model for polyurea which will include the effects of soft-matrix chain-segment molecular weight and the extent and morphology of hard-domain nano-segregation. Since these aspects of polyurea microstructure can be controlled through the selection of polyurea chemistry and synthesis conditions, and the present material model enables the prediction of polyurea blast-mitigation capacity and ballistic resistance, the model offers the potential for the “material-by-design” approach.

The model is validated by comparing its predictions with the corresponding experimental data.

The work clearly demonstrated that, in order to maximize shock-mitigation effects offered by polyurea, chemistry and processing/synthesis route of this material should be optimized.