bluuebunny/crossref_metadata_2025 huggingface dataset:
Cubane-forming cyclic dienes that exhibit orthogonal reactivities in the solid state
Authors: Li Changan , Sinnwell Michael A. , Swenson Dale C. , MacGillivray Leonard R.
Published: June 2021

Cubane-like cages are constructed quantitatively in the solid state using either a cocrystal or single-component pure solid.
The design of dihalogenated TPE monoboronate complexes as mechanofluorochromic crystals
Authors: García-González Ma. Carmen , Navarro-Huerta Armando , Rodríguez-Muñoz Fanny Chantal , Vera-Alvízar Estefanía Guadalupe , Vera Ramírez Marco A. , Rodríguez-Hernández Joelis , Rodríguez Mario , Rodríguez-Molina Braulio
Published: June 2021

Mechanofluorochromic crystals based on tetraphenylethylene and boronates reversibly change their emission upon grinding, setting the path to develop bistable switches in the future.
Trinuclear molybdenum clusters with sulfide bridges as potential anionic receptors via chalcogen bonding
Authors: Novikov Alexander S. , Gushchin Artem L.
Published: June 2021

Trinuclear Mo3S7 cluster complexes with sulfide bridges as potential anionic receptors due to chalcogen bonding.
Solid-state behaviors of imines: colossal biaxial positive thermal expansion, motion capability, and phase transitions
Authors: Juneja Navkiran , Zahid Ethan , Unruh Daniel K. , Hutchins Kristin M.
Published: June 2021

The torsional flexibility of imines affects solid-state packing and properties. Behaviors including colossal thermal expansion, pedal motion, and phase transitions in imine-containing solids are described.
Unravelling the structures of sodiated β-cyclodextrin and its fragments
Authors: Rabus Jordan M. , Pellegrinelli Robert P. , Khodr Ali Hassan Abi , Bythell Benjamin J. , Rizzo Thomas R. , Carrascosa Eduardo
Published: June 2021

Experiment and theory unravel the structure and formation mechanism of β-cyclodextrin fragment ions.
Single-atom cobalt-fused biomolecule-derived nitrogen-doped carbon nanosheets for selective oxidation reactions
Authors: Xia Miao , Huang Haitao , Zhang Xuefei , Wei Qiao-Hua , Xie Zailai
Published: June 2021

Single-atom cobalt-fused biomolecule-derived nitrogen-doped carbons were fabricated for selective oxidation reactions with high performance.
Main interactions of dopamine and risperidone with the dopamine D2 receptor
Authors: Martínez Ana , García-Gutiérrez Ponciano , Zubillaga Rafael A. , Garza Jorge , Vargas Rubicelia
Published: June 2021

A comparison between dopamine and risperidone shows that weak non-covalent interactions are relevant in understanding the antipsychotic drug mechanism.
New bifunctional ionic liquid-based plant systemic acquired resistance (SAR) inducers with an improved environmental hazard profile
Authors: Markiewicz Marta , Lewandowski Piotr , Spychalski Maciej , Kukawka Rafal , Feder-Kubis Joanna , Beil Stephan , Smiglak Marcin , Stolte Stefan
Published: June 2021

SAR inducers with minimized environmental hazards and high biological activity are a step towards more sustainable agricultural practice.
Extractivein situproduct removal for the application of naturally producedl-alanine as an amine donor in enzymatic metaraminol production
Authors: Mack Kevin , Doeker Moritz , Grabowski Laura , Jupke Andreas , Rother Dörte
Published: June 2021

The efficiency of the enzymatic metaraminol production with the amine donorl-alanine was increased two-fold by applying extractivein situproduct removal.
Screening anti-metastasis drugs by cell adhesion-induced color change in a biochip
Authors: Chou Shih-En , Lee Kuang-Li , Wei Pei-Kuen , Cheng Ji-Yen
Published: June 2021

Cell adhesion process monitored on a commercial scanner for screening/repurposing drugs with anti-metastasis capability.
3D micromixer for nanoliposome synthesis: a promising advance in high mass productivity
Authors: Firmino Priscilla C. O. S. , Vianna Sávio S. V. , da Costa Ohanna M. M. M. , Malfatti-Gasperini Antônio A. , Gobbi Angelo L. , Lima Renato S. , de la Torre Lucimara G.
Published: June 2021

Synthesis of unilamellar and highly monodisperse liposomes in a 3D chaotic-advection microdevice. Process of high mass productivity in which mixing conditions are not the only parameter to control liposome synthesis.
Recent advances in integrated solid-state nanopore sensors
Authors: Rahman Mahmudur , Sampad Mohammad Julker Neyen , Hawkins Aaron , Schmidt Holger
Published: June 2021

Nanopores are powerful single molecule sensors that have a wide range of applications from single molecule biophysics to medical diagnostics. This review covers all aspects of nanopore sensor integration into increasingly complex lab-on-chip systems.
A trinuclear Zn(ii) Schiff base azido compound: synthesis, structure and exploration of antimicrobial activity
Authors: Ghosh Mrinmoy , Biswas Samik , Roy Moumita , Biswas Saptarshi , Ghosh Pameli , Koner Subratanath , Mandal Supratim , Saha Sandip
Published: June 2021

The synthesis, characterization, X-ray crystal structure and antimicrobial activity of a trinuclear zinc(ii) complex have been explored.
Electromagnetic field-assisted cell-laden 3D printed poloxamer-407 hydrogel for enhanced osteogenesis
Authors: Dutta Sayan Deb , Bin Jin , Ganguly Keya , Patel Dinesh K. , Lim Ki-Taek
Published: June 2021

3D bioprinted ‘mini-tooth’ respond to low voltage-frequency electromagetic fields (EMFs) stimulation and promote differentiation of apical papilla stem cells (SCAPs).
Size-controlled synthesis of porous ZnSnO3 nanocubes for improving formaldehyde gas sensitivity
Authors: Zheng Jiaoling , Hou Huanhuan , Fu Hao , Gao Liping , Liu Hongjie
Published: June 2021

The size of the ZnSnO3 nanocubes is about 100 nm with the corresponding specific surface area of 70.001 m2 g−1. A gas sensor based on porous ZnSnO3 nanocubes shows high sensitivity and selectivity to formaldehyde.
Enhancing the removal efficiency of methylene blue in water by fly ash via a modified adsorbent with alkaline thermal hydrolysis treatment
Authors: Dinh Nga Thi , Vo Linh Ngoc Hoang , Tran Ngoc Thi Thanh , Phan Tuan Dinh , Nguyen Duc Ba
Published: June 2021

High efficiency of methylene blue adsorbent from waste coal fly ash by treatment with alkaline thermal hydrolysis.
Phase behavior and surface tension of soft active Brownian particles
Authors: Lauersdorf Nicholas , Kolb Thomas , Moradi Moslem , Nazockdast Ehssan , Klotsa Daphne
Published: June 2021

We study quasi two-dimensional, monodisperse systems of active Brownian particles (ABPs) for a range of activities, stiffnesses, and densities.
Active sites provided by the surface autocatalytic effect and quantum confinement for stable and efficient photocatalytic hydrogen generation
Authors: Jia Ruiming , Gui Qingfeng , Sui Lina , Huang Yan , Lu Honggang , Dong Hongzhou , Ma Shuai , Gan Zhixing , Dong Lifeng , Yu Liyan
Published: June 2021

A metal-free photocatalyst is constructed by anchoring the ultrasmall SiC NCs on carbon nitride nanosheets for efficient and durable hydrogen generation.
A 3D printed Ga containing scaffold with both anti-infection and bone homeostasis-regulating properties for the treatment of infected bone defects
Authors: Wang Minqi , Yang Yiqi , Chi Guanghao , Yuan Kai , Zhou Feng , Dong Liang , Liu Haibei , Zhou Qinghui , Gong Weihua , Yang Shengbing , Tang Tingting
Published: June 2021

A dual-functional 3D printed scaffold with both anti-infection and bone homeostasis-regulating properties for infected bone defect treatment.
The formation process of five-component Cu–In–Zn–Se–S nanocrystals from ternary Cu–In–S and quaternary Cu–In–Se–S nanocrystals via gradually induced synthesis
Authors: Guan Zhongyuan , Ye Haihang , Lv Peiwen , Wang Lijin , Zhang Jing , Zou Bin , Tang Aiwei
Published: June 2021

The growth mechanism and optical properties were studied systematically for multinary Cu-based chalcogenide NCs including ternary Cu–In–S NCs, quaternary Cu–In–Se–S NCs, and five-component Cu–In–Zn–Se–S NCs.
Molecular basis for recognition of the Group A Carbohydrate backbone by the PlyC streptococcal bacteriophage endolysin
Authors: King Harley , Ajay Castro Sowmya , Pohane Amol Arunrao , Scholte Cynthia M. , Fischetti Vincent A. , Korotkova Natalia , Nelson Daniel C. , Dorfmueller Helge C.
Published: June 2021

Endolysins are peptidoglycan (PG) hydrolases that function as part of the bacteriophage (phage) lytic system to release progeny phage at the end of a replication cycle. Notably, endolysins alone can produce lysis without phage infection, which offers an attractive alternative to traditional antibiotics. Endolysins from phage that infect Gram-positive bacterial hosts contain at least one enzymatically active domain (EAD) responsible for hydrolysis of PG bonds and a cell wall binding domain (CBD) that binds a cell wall epitope, such as a surface carbohydrate, providing some degree of specificity for the endolysin. Whilst the EADs typically cluster into conserved mechanistic classes with well-defined active sites, relatively little is known about the nature of the CBDs and only a few binding epitopes for CBDs have been elucidated. The major cell wall components of many streptococci are the polysaccharides that contain the polyrhamnose (pRha) backbone modified with species-specific and serotype-specific glycosyl side chains. In this report, using molecular genetics, microscopy, flow cytometry and lytic activity assays, we demonstrate the interaction of PlyCB, the CBD subunit of the streptococcal PlyC endolysin, with the pRha backbone of the cell wall polysaccharides, Group A Carbohydrate (GAC) and serotype c-specific carbohydrate (SCC) expressed by the Group A Streptococcus and Streptococcus mutans, respectively.
Boundary feedback stabilization of a semilinear model for the flow in star-shaped gas networks
Authors: Gugat Martin , Giesselmann Jan
Published: June 2021

The flow of gas through a pipeline network can be modelled by a coupled system of 1-d quasilinear hyperbolic equations. In this system, the influence of certain source terms that model friction effects is essential. Often for the solution of control problems it is convenient to replace the quasilinear model by a simpler semilinear model. In this paper, we analyze the behavior of such a semilinear model on a star-shaped network. The model is derived from the diagonal form of the quasilinear model by replacing the eigenvalues by the sound speed multiplied by 1 or −1 respectively. Thus in the corresponding eigenvalues the influence of the gas velocity is neglected, which is justified in the applications since it is much smaller than the sound speed in the gas. For a star-shaped network of horizontal pipes for suitable coupling conditions we present boundary feedback laws that stabilize the system state exponentially fast to a position of rest for sufficiently small initial data. We show the exponential decay of the L2-norm for arbitrarily long pipes. This is remarkable since in general even for linear systems, for certain source terms the system can become exponentially unstable if the space interval is too long. Our proofs are based upon an observability inequality and suitably chosen Lyapunov functions. At the end of the paper, numerical examples are presented that include a comparison of the semilinear model and the quasilinear system.
A brief review of (multi-scale) modelling approaches to segregation
Authors: Thornton Anthony
Published: June 2021

Segregation in dense granular flows is a large problem in many areas of industry and the natural environment. In the last few years an advection-diffusion style framework has been shown to capture segregation in many geometries. Here, we review the different ways such a framework has been obtained by different authors, compare the forms and make recommendations for the best form to use. Finally, we briefly outline some of the remaining open-questions.
An average model for disordered sphere packings
Authors: Yanqui Calixtro
Published: June 2021

In this paper, an assembly of disordered packings is considered as a suitable set of packing cells of ordered spheres. In consequence, any of its parameters can be obtained by averaging the values of the set. Namely, the density of a packing of ordered spheres is described by two variables: the angle of the base, and the angle of the inclined edge of the associated parallelepiped. Then, the density of a packing of disordered spheres is obtained by averaging the angle of the base, and the subsequent averaging of the other angle, according to the kind of strain induced by the experiment. The average packing yields the density limits of loose sphere assemblies achieved by a process of fluidization and sedimentation in air, in water, and in viscous liquid at zero gravitational force. It also models the close sphere assemblies shaped by gentle tapping, vertical shaking, horizontal and multidirectional vibrations. The theory allows to elucidate the mechanism of each of the limits, as, for example, the metastable columns of spheres in the loosest packing, as well as the random close packing, and crystallization. The limits obtained coincide very well with the published experimental, numerical and theoretical data.
Discharge of soft and hard grains and their mixtures from 2D silos
Authors: Wang Jing , Harth Kirsten , Stannarius Ralf , Fan Bo , Börzsönyi Tamás
Published: June 2021

The outflow characteristics of hard grains from containers with narrow basal openings have been extensively studied. Recently, it was shown that soft, low-frictional grains can behave qualitatively different from the behavior of rigid grains. We compare experimentally the discharge of monodisperse hard spheres, soft spheres and mixtures of both from a quasi-two dimensional (2D) silo. The experiments demonstrate the remarkable consequences of the addition of few hard particles to a soft particle ensemble, as well as the gradual transition between the two limiting cases of pure one-component materials.
Discharge of a 2D magnetic silo
Authors: Thorens Louison , Viallet Maud , Måløy Knut Jørgen , Bourgoin Mickaël , Santucci Stéphane
Published: June 2021

We investigate experimentally the discharge of a 2D-silo, a Hele-Shaw cell, filled with a mono layer of ferromagnetic grains submitted to an external magnetic field B perpendicular to the cell plane. In this case the magnetic pair interactions are repulsive. We show that the granular flow rate decreases systematically with the amplitude of the external magnetic field applied. Interestingly, while the output flow rate remains constant during an experiment, we reveal very large spatio-temporal fluctuations of the packing density within the cell, particularly evident for magnetic field of high amplitudes.
Modelling of scour formation using SedFoam, continuum approach
Authors: Ghzayel Alaa , Beaudoin Anthony , Jarny Sebastien
Published: June 2021

SedFOAM is a two-phase flow solver built upon consecutive laws, based on the CFD toolbox OpenFOAM. The sediment body is considered as a continuum phase. The intergranular and fluid stresses are modeled with the dense granular flow rheology and the k–ϵ turbulent model, respectively. The model setup will be based on an experimental study on the scour due to a water jet subjected to lateral confinement. A comparison study will be made based on precise experimental data by Martino et al. (2019) that will show the advantages and defaults of SedFoam. The objective of this work is to reproduce the digging and filling cycle of the scour formation due to the water jet in a confined canal. The first numerical results show that it needs to use 3D numerical simulations because of the fluctuation of the jet direction induced by the presence of a driven flow cavity.
Analytical solutions for dense, inclined, granular flow over a rigid, bumpy base
Authors: Jenkins James , Berzi Diego
Published: June 2021

We first phrase a boundary-value problem for a dense, steady, fully-developed, gravitational flow of identical inelastic spheres over in inclined bumpy base in the absence of sidewalls. We then obtain approximate analytical solutions for the profiles of the solid volume fraction, the strength of the velocity fluctuations, and the mean velocity of the flow. We compare these with those obtained in numerical solutions of the exact equations.
From Darcy to Gaussian to fully mobilised grain flow in a confined channel
Authors: Morgan Miles , Sandnes Bjørnar
Published: June 2021

Fluid-driven grain flow through a confined channel filled with non-buoyant grains is herein observed to exist in three regimes according to total imposed flow rate. (1) At low imposed flow rates, no grain flow occurs as the fluid stress is insufficient to mobilise the grains and Darcy flow is observed. (2) At a sufficient imposed flow rate, grains begin to flow at the top of the channel with self-similar Gaussian velocity profiles that become faster and encroach deeper into the channel with increased flow rate. (3) At high flow rates, significant grain flow occurs at the base of the channel, distorting the Gaussian profile, resulting in a gradual transition towards a more symmetric, full-channel flow. Each regime, and the transitions between them, is discussed in relation to experimental grain velocity measurements.
Granular segregation on the rubble-pile asteroid Itokawa
Authors: Ghosh Sohanjit , Sharma Ishan , Dhingra Deepak
Published: June 2021

We investigate the dynamics of regolith on rubble-pile asteroids to explain granular processes observed in reality. In particular, we explain how the appearance of boulders on the surface of asteroid Itokawa could have resulted from a size sorting process in granular media called the Brazil Nut Effect (BNE). The Discrete Element Method (DEM) is implemented to perform numerical simulations of the BNE in a micro-gravity environment caused by inter-particle collisions during seismic vibrations. Firstly, we present the results of how the BNE depends on the magnitude of surface gravity. It is estimated that segregation processes on Itokawa occur over much longer time-scales (in the order of a few hundred years) than the same processes would require in the presence of a strong gravitational field, like on Earth. Secondly, we also find that the size sorting could also result from kinetic sieving encountered during granular avalanches. Finally, we discuss how the void-filling mechanism becomes more efficient when there is a higher relative size difference between the boulders and the surrounding grains. Our model has important implications in understanding the resurfacing of Itokawa by trying to explain one of the many complex geophysical processes that occur in such unique conditions.
Micromechanics of slow granular flows
Authors: Gautam Ravi , Nott Prabhu R.
Published: June 2021

It has been contemplated for a long time that dense granular materials flow in a stick-slip manner, and large fluctuations in the stresses are associated with it. However, the particle scale mechanics for this type of macroscopic motion has not been understood so far. We have analyzed the time evolution of contact networks from particle dynamics simulations and found that the rate of change of elastic energy of the packing can distinguish the stick regimes and the slip events. The isostatic criterion (number of contacts for a minimally stable particle) has been used to construct a cascade failure mechanism which reveals that the effect of the random breaking of contacts due to applied shear can be system-spanning for some cases. The size of the cascade failures follows a power law that explains experimentally observed large fluctuations is stresses. We expect that this power law distribution can connect the microstructure of a granular packing to its mechanical response.
Relative entropy of freely cooling granular gases. A molecular dynamics study
Authors: Megías Alberto , Santos Andrés
Published: June 2021

Whereas the original Boltzmann’s H-theorem applies to elastic collisions, its rigorous generalization to the inelastic case is still lacking. Nonetheless, it has been conjectured in the literature that the relative entropy of the velocity distribution function with respect to the homogeneous cooling state (HCS) represents an adequate nonequilibrium entropy-like functional for an isolated freely cooling granular gas. In this work, we present molecular dynamics results reinforcing this conjecture and rejecting the choice of the Maxwellian over the HCS as a reference distribution. These results are qualitatively predicted by a simplified theoretical toy model. Additionally, a Maxwell-demon-like velocity-inversion simulation experiment highlights the microscopic irreversibility of the granular gas dynamics, monitored by the relative entropy, where a short “anti-kinetic” transient regime appears for nearly elastic collisions only.
Highly strained mixtures of bidimensional soft and rigid grains: an experimental approach from the local scale
Authors: Barés Jonathan , Cárdenas-Barrantes Manuel , Cantor David , Azéma Émilien , Renouf Mathieu
Published: June 2021

Granular systems are not always homogeneous and can be composed of grains with very diﬀerent mechanical properties. To improve our understanding of the behavior of real granular systems, in this experimental study, we compress 2D bidisperse systems made of both soft and rigid grains. By means of a recently developed experimental set-up, from the measurement of the displacementfield we can follow all the mechanical observables of this granular medium from the inside of each particle up-to the whole system scale. We are able to detect the jamming transition from these observables and study their evolution deep in the jammed state for packing fractions as high as 0.915. We show the uniqueness of the behavior of such a system, in which way it is similar to purely soft or rigid systems and how it is diﬀerent from them. This study constitutes thefirst step toward a better understanding of mechanical behavior of granular materials that are polydisperse in terms of grain rheology.
Influence of the coefficient of restitution on the classification of granite sand using an elutriator
Authors: Borsa Eugenia , Petit H. Andrés , Piña Juliana , Paulo Cecilia I. , Irassar E. Fabián
Published: June 2021

The objective of this work was to measure the coefficient of restitution of fine granite sand dust (passing sieve ASTM N°30) and to study its influence on the prediction of classification parameters in an elutriator device. Three types of restitution coefficients were evaluated in the computational fluid dynamic model: experimental, elastic, and half the experimental value. The influence of process variables, such as the inclination angle of the equipment and the air inlet velocity, on the efficiency of the obtained fine and coarse fractions was also studied. The results indicate that the coefficient of restitution significantly influences the efficiency parameters calculated for the inclined tests, given the greater contact that exists between the particles and the equipment wall. The experimental value of the coefficient achieved almost total congruence with the coarse fraction collected for the tested velocities. For the vertical tests, the variation of the coefficient did not show significant differences for both collected fractions. The results obtained in this work allowed to gain a deeper insight into the studied gas-solid systems, and to improve the numerical predictions on fine particles classification processes widely used in the ceramic, mining and metallurgical industries.
Energy dissipation of a particle colliding on a flat surface
Authors: Fernández Fabricio Éric , Piva Marcelo Fabián , Martino Román Gustavo , Aguirre María Alejandra
Published: June 2021

To gain an understanding of the factors affecting the interaction of one grain with its environment as it reaches equilibrium, we study a particle bouncing off a flat surface. The bouncing of the particle leads to dissipation that is usually characterized with t, the coefficient of restitution, defined as the ratio between the velocity component that is normal to the contact surface just before impact (Vn) and the same component, but immediately after the collision (Vn’), i.e. related to a kinetic energy corresponding to motion in the normal direction. We will show how d is affected by energy stored in other degrees of freedom and transferred to kinetic energy that leads to an increase in normal velocity after the impact Vn’, and therefore to, ɛ >1. For this purpose, the evolution of potential, translational kinetic energy and rotational kinetic energy is analysed during the whole relaxation process and just before and after each collision for two different types of particle, a disk and a faceted particle.
Impact of sample scaling on shear strength: coupled effects of grains size and shape
Authors: Linero-Molina Sandra , Azéma Emilien , Estrada Nicolas , Fityus Stephen , Simmons John , Lizcano Arcesio
Published: June 2021

Size limitations of geotechnical testing equipment often require that samples of coarse granular materials have to be scaled in order to be tested in the laboratory. Scaling implies a convenient modification of the particle size distribution (PSD) to reduce particle sizes. However, it is well known that particle size and shape may be correlated in nature, due to geological factors (as an example). By means of two-dimensional contact dynamics simulations, we analyzed the effect of altering the size span on the shear strength of granular materials when particle size and shape are correlated. Two different systems were considered: one made of only circular particles, and the second made of size-shape correlated particles. By varying systematically the size span we observed that the resulting alteration of material strength is not due to the change in particle sizes. It results instead from the variation of the particle shapes induced by the modification of the PSD, when particle size and particle shape are correlated. This finding suggests that particle shape distribution is a higher order factor than PSD for the shear strength of granular materials. It also highlights the importance of particle shape quantification in soil classification and the case for its consideration in activities such as sampling, subsampling, and scaling of coarse materials for geotechnical testing
Cohesion of bird nests
Authors: Andrade-Silva Ignacio , Godefroy Théo , Pouliquen Olivier , Marthelot Joel
Published: June 2021

One striking difference between aggregates of flexible frictional fibres and other granular materials like rigid spheres is the effective cohesion of their assembly. While glue or capillary bridges are needed to shape aggregates of spherical particles and build sandcastles, for fibres, no need for glue to build a nest. Here we study an assembly of mono disperse flexible fibres. We first use X-ray microtomography to characterise the geometry of the initial assembly, the number of contact points and mean curvatures of the fibres. Using forcedisplacement measurements, we characterise the macroscopic cohesive strength of the aggregate by varying the geometry of the fibres, the fibres mechanicals properties and the packing of the preparation. Finally, we relate the macroscopic mechanical behaviour of the assembly with the filament reorganisation at the microscopic scale.
Contact evolution in granular materials with inherently anisotropic fabric
Authors: Pinzón Gustavo , Andò Edward , Tengattini Alessandro , Viggiani Gioacchino , Desrues Jacques
Published: June 2021

This paper presents the results of two triaxial compression tests performed on approximately 9×103 oblate spheroids (lentils) with different initial orientations with respect to the loading axis (approximately 30° and 60°). Typical stress-strain information is complemented with x-ray tomography scans every 1 % strain. Starting from an initial labelling of particles, a new technique is used to obtain unprecedented detail of tracking of all the particles through time. This rich dataset is analysed from the perspective of inter-particle contacts (building on previous metrological work on this subject) revealing that the mean contact orientation in both samples rotates towards the direction of σ1 at a rate depending on the initial orientation. Different trends are observed for the alignment of contact orientation, with a significant evolution observed in the sample prepared at 30° which is not as pronounced as in the other sample.
Analysis of particle dynamics in a pin mill by Discrete Element Method
Authors: Goh Wei Pin , Ghadiri Mojtaba
Published: June 2021

Milling is an important process for tailoring the particle size distribution for enhanced attributes, such as dissolution, content uniformity, tableting, etc., especially for active pharmaceutical ingredients and excipients in pharmaceutical industries. Milling performance of particulate solids depends on the equipment operating conditions (geometry, process conditions and input energy etc.) as well as material properties (particle size, shape, and mechanical properties, such as Young’s modulus, hardness and fracture toughness). In this paper the particle dynamics in a pin mill is analysed using Discrete Element Method (DEM), combined with a novel approach for assessing particle breakability by single particle impact testing. A sensitivity analysis is carried out addressing the effect of the milling conditions (rotational speed and feed particle flow rate), accounting for feed mechanical properties on the breakage behaviour of the particles. Particle collision energy spectra are calculated and shown to have a distribution with the upper tail end being close to the maximum energy associated with the collision with the rings. Breakage is primarily due to collisions with the rings, except for large particles that are comparable in size with the gap between the rings, nipping is also a contributory breakage mechanism.
High compressibility caused by particle breakage: a DEM investigation
Authors: Stasiak Marta , Richefeu Vincent , Combe Gaël , Zghondi Jad , Armand Gilles
Published: June 2021

This paper summarises the numerical and experimental studies of brittle, hollow, cylindrical particles, called shells. It addresses the influence of shell properties both at the particle and assembly scales. Extreme compressibility has been recorded in the oedometer tests. Due to the large internal porosity of the shell, the breakage phenomena lead to highly compressive deformations with a significant stress dissipation. Using the Discrete Element Method (DEM), we have investigated in depth the micro-mechanical phenomena governing this macroscopic response. By quantifying the breakage and separating the double-porosity of the material, the foundations of a future constitutive model have been established throughout a simple prediction model applicable to the engineering practice.
Packing density of bi-disperse mixtures under one-dimensional compression
Authors: Guida Giulia , Casini Francesca
Published: June 2021

This work aims to investigate the effect of fines in different type of bi-disperse grain size distributions in terms of minimum/maximum density, compressibility and crushing. The material adopted is the Light Expanded Clay Aggregate (LECA), an artificial granular material characterized by light, porous and crushable grains. The bi-disperse grading are firstly analysed in terms of packing density, measuring experimentally the minimum and the maximum porosity for different combination of sizes and volume proportions. Then, some selected mixtures are subjected to one-dimensional compression tests up to high pressures. Evolution of grain size due to grain crushing phenomena and compressibility are therefore measured and interpreted. Finally a theoretical model is adopted in order to predict the mechanical material response accounting grain crushing and granular microstructure.
An investigation of collisions of liquid coated particles
Authors: Danczyk Megan , Fullard Luke , Holland Daniel
Published: June 2021

The presence of even small amounts of liquid between particles dramatically changes the dynamics of collisions. This study considers granular collisions between two particles coated with a thin layer of viscous liquid, such that the capillary number is high and viscous forces dominate. High-speed particle tracking velocimetry was used to experimentally study the collisions of two smooth spheres with and without liquid coatings. We then use these experiments to examine four theoretical models that describe the collisions. A key challenge when modelling viscous forces is that the force which is predicted as particles approach each other scales with the inverse of the distance, i.e. tends to infinity. Most existing models impose a limit to the viscous force. One recent model instead assumes a hard sphere collision. These fundamentally different approaches produce different rebound outcomes. A fair match between experiments and simulations was obtained when using the hard sphere collision model, but only if an empirically-fitted glass transition pressure model was used to describe the minimum approach distance.
Detecting vorticity in cohesive deformable granular material
Authors: Bouillanne Olivier , Mollon Guilhem , Saulot Aurélien , Descartes Sylvie , Serres Nathalie , Demmou Karim , Chassaing Guillaume
Published: June 2021

Numerical models of granular materials are useful in tribology, and can be used to predict wear and friction in contacts. DEM-like simulations are used to model particles of third-body, which are partly wear debris from rubbing bodies. It has been shown that the third-body particles can have different flow regimes, depending on their mechanical properties. Among the different characteristics of flow regimes, agglomerate size seems to be crucial. A method based on vortex analysis used in fluid mechanics allows characterizing this cluster size. The results show that different vortex sizes can be observed during the simulation. In particular, it is observed that some vortexes of a characteristic size persist over time, and could be representative of agglomerates. These results pave the way for a better characterisation of the different flow regimes.
Non-monotonic Mpemba effect in binary molecular suspensions
Authors: Gómez González Rubén , Garzó Vicente
Published: June 2021

The Mpemba effect is a phenomenon in which an initially hotter sample cools sooner. In this paper, we show the emergence of a non-monotonic Mpemba-like effect in a molecular binary mixture immersed in a viscous gas. Namely, a crossover in the temperature evolution when at least one of the samples presents non-monotonic relaxation. The influence of the bath on the dynamics of the particles is modeled via a viscous drag force plus a stochastic Langevin-like term. Each component of the mixture interchanges energy with the bath depending on the mechanical properties of its particles. This discrimination causes the coupling between the time evolution of temperature with that of the partial temperatures of each component. The non-monotonic Mpemba effect—and its inverse and mixed counterparts—stems from this coupling. In order to obtain analytical results, the velocity distribution functions of each component are approximated by considering multitemperature Maxwellian distributions. The theoretical results derived from the Enskog kinetic theory show an excellent agreement with direct simulation Monte Carlo (DMSC) data.
On water waves generated by gravity driven granular collapse
Authors: Sarlin Wladimir , Morize Cyprien , Sauret Alban , Gondret Philippe
Published: June 2021

Tsunami-like waves can arise from large-scale geological events such as the collapse of a mountain flank or a volcano into a lake or an ocean. We here mimic this situation at the laboratory scale. The landslide is modeled by the sudden release of a rectangular granular column, which impacts a still water layer and generates a wave. Through experiments varying both the column dimensions and the initial water depth, three regimes of nonlinear waves of different shapes are reported. The amplitude and width of the generated waves are governed by a local Froude number based on the velocity of the granular front at the water surface.
Shear bands in dense fault gouge
Authors: Casas Nathalie , Mollon Guilhem , Daouadji Ali
Published: June 2021

Earthquakes happen with frictional sliding, by releasing all the stresses accumulated in the prestressed surrounding medium. The geological fault gouge, coming from the wear of previous slips, acts on friction stability and plays a key role in this sudden energy release. A large part of slip mechanisms are influenced, if not controlled, by the characteristics and environment of this tribological “third body”. A 2D granular fault (mm scale) is implemented with Discrete Element Modelling (DEM). A displacement-driven model with dry contact is studied to observe kinematics and properties of the slipping zone. Increasing the length of the granular media increases the slip needed to weaken the friction from friction peak to steadystate. Low-angle Riedel shear bands are mostly observed. Their number increases with the inter-particle friction coefficient, which also influences shear bands formation in their orientation angle (higher friction leads to higher angle with the main slip direction).
Coupled DEM-FDM simulation of cone penetration tests in coarse grained soils
Authors: Kidane Mussie , Peña Olarte Andrés Alfonso , Cudmani Roberto
Published: June 2021

The numerical modelling of geotechnical problems often poses major challenges when large displacements and strain localization are involved. Conventional continuum mechanical approaches like the finite element method (FEM) or the finite difference method (FDM) suffer from mesh distortion and numerical inaccuracy when large deformations are involved. In addition, they require the use of appropriate constitutive models to simulate the soil behaviour. The distinct element method is a promising alternative for large deformation analyses. It does not have the limitations resulting from the numerical discretization of the continuumand not need a constitutive model since the macroscopic response results from the individual particle interaction. However, the maximum number of particles and therefore the domain of the simulation is nowadays limited by the available computational capacity. To overcome this limitation, a coupled DEM-FDM approach is proposed used to optimize the number of particles for a combined numerical domain consisting of areas of large and small displacements. The performance of the coupled DEM-FDM approach is investigated by simulating cone penetration tests in coarse grained soils.
Investigation of laser-powder interaction in laser powder bed fusion process in additive manufacturing
Authors: Li Erlei , Wang Lin , Zou Ruiping , Yu Aibing , Zhou Zongyan
Published: June 2021

Laser powder bed fusion (LPBF) is one of the most promising additive manufacturing (AM) technologies to fabricate metal components using laser beams. To understand the underlying thermal and physical phenomena in LPBF process, discrete element method (DEM) is applied to generate the randomly packed powder, then computational fluid dynamics (CFD) coupled with volume of fluid (VOF) is adopted to simulate the laser-powder interaction. The penetration and multiple reflection of laser rays is traced. The physics of melting and solidification is captured. The temperature profile indicates the laser travel path and the adsorption and transmission of laser rays with the powder. The wetting behaviour of the melt pool driven by the capillary forces leads to the formation of pores at the connection zone. It has been demonstrated that the developed model can capture the laser-powder interaction for further understanding of LPBF process.
DEM examination of SPT correction factors
Authors: Zhang Ningning , Arroyo Marcos , Ciantia Matteo , Gens Antonio
Published: June 2021

The Standard Penetration Test (SPT) is the most widely used method for dynamic testing of soils. The test is simple and robust but difficult to control and not fully standardized. As a result, experimental results typically show large variations and poor repeatability. To mitigate that correction factors such as energy normalization and rod length have been introduced in SPT practice. This study provides an examination of the two correction factors using models based on the discrete element method (DEM).
Acoustic localisation in a two-dimensional granular medium
Authors: Levy dit Vehel Victor , Haddjeri Ange , Ramos Osvanny
Published: June 2021

We focus on localizing the source of acoustic emissions within a compressed two-dimensional granular ensemble of photoelastic disks, having as main information the arrival times of the acoustic signal to 6 sensors located in the boundaries of the system. By estimating, thanks to the photoelasticity of the grains, the wave speed at every point of the structure, we are able to compute the arrival times from every point of the system to the sensors. A comparison between the arrival time differences between every set of computed values to those from the actual measurements allows finding the source of the acoustic emissions.
Embedded inertial sensor for tracking projectile impact on granular media
Authors: Köstler Stefan , Zhao Jinchen , Lyu Chen , Völkel Simeon , Huang Kai
Published: June 2021

Due to the opacity of most granular materials, it is often desirable to have three dimensional (3D) particle tracking techniques beyond optical imaging to explore granular dynamics. Using inertial measurement units (IMU) embedded in a projectile, we obtain the trajectory of projectile impacting on a granular medium under microgravity using tri-axial acceleration and angular velocity data. In addition to the standard algorithm for reconstruction, we emphasize solutions to various sources of error to determine projectile trajectory accurately.
Optimaler Schutz für die Hände
Authors: Nadler Sylvia
Published: June 2021

Die Hände sind das wichtigste Instrumentarium des OP-Personals und müssen deshalb gut geschützt werden. Obwohl die meisten OP-Handschuhe ausreichend Schutz bei den gängigen Anwendungen bieten, können von den Handschuhmaterialien unterschiedliche Risiken für den Träger sowie für Patienten ausgehen. Unsere Autorin erklärt, welche Aspekte bei der Auswahl des richtigen Handschuhs zu beachten sind.
Nickel-Catalyzed Regiodivergent Reductive Hydroarylation of Styrenes
Authors: He Yuli , Zhu Shaolin , Xue Yuhang , Chen Jian , Song Peihong
Published: June 2021

We report a ligand-controlled nickel-catalyzed reductive hydroarylation of styrenes with predictable and controllable regioselectivity. With a diamine ligand, the reaction produces selective linear hydroarylation products. Alternatively, with a chiral PyrOx ligand, branch-selective enantioenriched 1,1-diarylalkane products are obtained. Preliminary mechanistic results are consistent with a reductive Heck process.
Toward exascale whole-device modeling of fusion devices: Porting the GENE gyrokinetic microturbulence code to GPU
Authors: Germaschewski K. , Allen B. , Dannert T. , Hrywniak M. , Donaghy J. , Merlo G. , Ethier S. , D'Azevedo E. , Jenko F. , Bhattacharjee A.
Published: June 2021

GENE solves the five-dimensional gyrokinetic equations to simulate the development and evolution of plasma microturbulence in magnetic fusion devices. The plasma model used is close to first principles and computationally very expensive to solve in the relevant physical regimes. In order to use the emerging computational capabilities to gain new physics insights, several new numerical and computational developments are required. Here, we focus on the fact that it is crucial to efficiently utilize GPUs (graphics processing units) that provide the vast majority of the computational power on such systems. In this paper, we describe the various porting approaches considered and given the constraints of the GENE code and its development model, justify the decisions made, and describe the path taken in porting GENE to GPUs. We introduce a novel library called gtensor that was developed along the way to support the process. Performance results are presented for the ported code, which in a single node of the Summit supercomputer achieves a speed-up of almost 15× compared to running on central processing unit (CPU) only. Typical GPU kernels are memory-bound, achieving about 90% of peak. Our analysis shows that there is still room for improvement if we can refactor/fuse kernels to achieve higher arithmetic intensity. We also performed a weak parallel scalability study, which shows that the code runs well on a massively parallel system, but communication costs start becoming a significant bottleneck.
The combination of targeted vaccination and ring vaccination
Authors: Li Weiqiang , Zhou Jin , Jin Zhen , Lu Jun-an
Published: June 2021

Complex networks have become an important tool for investigating epidemic dynamics. A widely concerned research field for epidemics is to develop and study mitigation strategies or control measures. In this paper, we devote our attention to ring vaccination and targeted vaccination and consider the combination of them. Based on the different roles ring vaccination plays in the mixed strategy, the whole parameter space can be roughly divided into two regimes. In one regime, the mixed strategy performs poorly compared with targeted vaccination alone, while in the other regime, the addition of ring vaccination can improve the performance of targeted vaccination. This result gives us the more general and overall comparison between targeted and ring vaccination. In addition, we construct a susceptible–infected–recovered epidemic model coupled with the immunization dynamics on random networks. The comparison between stochastic simulations and numerical simulations confirms the validity of the model we propose.
Inclination of self-interstitial dumbbells in molybdenum and tungsten: A first-principles study
Authors: Suzudo T. , Tsuru T.
Published: June 2021

Body-centered-cubic (BCC) transition metals are ubiquitous structural materials, and their mechanical degradation under irradiation is significantly influenced by the stability and mobility of the lattice defects. In this study, we analyzed the self-interstitial atoms (SIAs) in BCC molybdenum (Mo) and tungsten (W) in comparison with other BCC transition metals utilizing the first-principles method; particularly, we focused on uncommon dumbbells whose direction are inclined from 〈111〉 toward 〈110〉 on the {110} plane. Such a direction is not stable in the group 5 BCC metals (i.e., vanadium, niobium, and tantalum) or in α-iron. Our first-principles relaxation simulations indicated that inclined dumbbells were more energetically favored than common 〈111〉 dumbbells in Mo, while this is not necessarily the case for W. However, a certain degree of lattice strain, such as shear or expansive strain, could make inclined dumbbells more favored also in W, suggesting that the lattice strain can substantially influence the migration barrier of SIAs in these metals because inclined dumbbells generally have a larger migration barrier than 〈111〉 dumbbells. We also elucidated the mechanism of the inclination using the electronic charge density; the charge density map of the perfect crystals suggested that the anti-bonding state of electrons along the 〈111〉 direction is likely to cause the instability of 〈111〉 dumbbells, and the charge density map near dumbbells suggested how 〈111〉 dumbbells are inclined toward the 〈110〉 direction.
Vibration-mediated energy transport in bacterial reaction center: Simulation study
Authors: Bubilaitis Vytautas , Rancova Olga , Abramavicius Darius
Published: June 2021

Exciton energy relaxation in a bacterial Reaction Center (bRC) pigment–protein aggregate presumably involves emission of high energy vibrational quanta to cover wide energy gaps between excitons. Here, we assess this hypothesis utilizing vibronic two-particle theory in modeling of the excitation relaxation process in bRC. Specific high frequency molecular vibrational modes are included explicitly one at a time in order to check which high frequency vibrations are involved in the excitation relaxation process. The low frequency bath modes are treated perturbatively within Redfield relaxation theory. The analysis of the population relaxation rate data indicates energy flow pathways in bRC and suggests that specific vibrations may be responsible for the excitation relaxation process.