bluuebunny/crossref_metadata_2025 huggingface dataset:
Probing fundamental losses in nanostructured Ta3N5 photoanodes: design principles for efficient water oxidation
Authors: Nandal Vikas , Pihosh Yuriy , Higashi Tomohiro , Minegishi Tsutomu , Yamada Taro , Seki Kazuhiko , Sugiyama Masakazu , Domen Kazunari
Published: June 2021

Detailed numerical simulations are performed to probe performance loss mechanisms and limiting parameters of Ta3N5-NRs based photoanodes. Device modelling enables the development of design strategies to realize efficient solar water oxidation.
Anti-obesity effects ofGrifola frondosathrough the modulation of lipid metabolismviaceramide in mice fed a high-fat diet
Authors: Jiang Xue , Hao Jie , Liu Zijian , Ma Xueting , Feng Yuxin , Teng Lirong , Li Yu , Wang Di
Published: June 2021

In high-fat-diet fed mice, Grifola frondosa alleviated hepatic steatosis and the inflammatory response, and counteracted obesity-induced insulin resistanceviaits inhibition of Cer related to down-regulation of TLR4/NF-κB signaling.
Associations between caseinophosphopeptides and theaflavin-3,3′-digallate and their impact on cellular antioxidant activity
Authors: Jiang Yike , Jin Weiping , Li Jessica , Huang Qingrong
Published: June 2021

The interactions between caseinophosphopeptides (CPPs) and theaflavin-3,3’-digallate (TF-3) and the consequent impacts on the cellular antioxidant activity of TF-3 have been investigated in this study.
Asymmetric D–A–D′ Scaffold inducing distinct mechanochromic luminescence
Authors: Yang Huifang , Fu Zhiyuan , Wang Sai , Liu Haichao , Zhou Jianwei , Wang Kai , Wu Xiugang , Yang Bing , Zou Bo , Zhu Weiguo
Published: June 2021

Two novel distinct multi-stimuli responsive mechanochromic luminescence (MCL) materials were prepared with an asymmetric D–A–D′ scaffold.
Recent advances on the removal of dyes from wastewater using various adsorbents: a critical review
Authors: Dutta Soumi , Gupta Bramha , Srivastava Suneel Kumar , Gupta Ashok Kumar
Published: June 2021

This review is focused on the origin of dye pollutants, their ecotoxicological effects and adsorptive removal using various types of adsorbents.
Flexible electrochromic devices prepared on ultra-thin ITO glass
Authors: Schott Marco , Niklaus Lukas , Müller Christine , Bozkaya Begüm , Giffin Guinevere A.
Published: June 2021

Electrochromic devices (ECDs) containing iron-based metallo-supramolecular polymers (Fe-MEPE) and Prussian blue (PB) as electrode materials, polymer electrolyte and flexible ultra-thin ITO glass as transparent conductive substrate are demonstrated.
A mini DNA–RNA hybrid origami nanobrick
Authors: Zhou Lifeng , Chandrasekaran Arun Richard , Yan Mengwen , Valsangkar Vibhav A. , Feldblyum Jeremy I. , Sheng Jia , Halvorsen Ken
Published: June 2021

A mini DNA–RNA hybrid origami nanobrick with overall size close to 12 nanometer showed high resistance to nuclease digestion.
Co-assembly and multicomponent hydrogel formation upon mixing nucleobase-containing peptides
Authors: Giraud Tristan , Bouguet-Bonnet Sabine , Stébé Marie-José , Richaudeau Lionel , Pickaert Guillaume , Averlant-Petit Marie-Christine , Stefan Loic
Published: June 2021

Mixing hybrid DNA-nucleobase-containing peptide derivatives to finely modulate structural, physicochemical and mechanical multicomponent hydrogel properties.
Research progress of environmentally friendly marine antifouling coatings
Authors: Liu Mengyue , Li Shaonan , Wang Hao , Jiang Rijia , Zhou Xing
Published: June 2021

The antifouling mechanisms and research progress in the past three years of environmentally friendly marine antifouling coatings are introduced in this work.
A practical route to 2-iodoanilines via the transition-metal-free and base-free decarboxylative iodination of anthranilic acids under oxygen
Authors: Rong Nianxin , Yuan Yongsheng , Chen Huijie , Yao Changguang , Li Teng , Wang Yantao , Yang Weiran
Published: June 2021

A new approach for synthesizing 2-iodoanilines via the transition-metal-free and base-free decarboxylative ortho-C–H iodination of anthranilic acids with a combination of KI and I2 as the halogen donor and catalyst under oxygen has been developed.
Highly twisted carbazole-borane derivatives: B–N stereodynamic analysis and consequences on their emission properties
Authors: Pecorari Daniel , Mazzanti Andrea , Gianvittorio Stefano , Foschi Simone , Stagni Stefano , Fiorini Valentina , Mancinelli Michele
Published: June 2021

The manuscript describes the stereodynamic features of amino bis-mesityl-boranes bearing carbazole and benzocarbazole as donor heterocycles, and how they influence the photophysical properties.
The rationality of using core–shell nanoparticles with embedded internal standards for SERS quantitative analysis based glycerol-assisted 3D hotspots platform
Authors: Wang Xiao-An , Shen Wei , Zhou Binbin , Yu Daoyang , Tang Xianghu , Liu Jinhuai , Huang Xingjiu
Published: June 2021

3D hotspots matrix SERS platform in water with the assistance of 2.5% v/v glycerol has been constructed and then used in investigating the rationality of using core–shell nanoparticles with embedded internal standards for SERS quantitative analysis.
Quercetin-gold nanorods incorporated into nanofibers: development, optimization and cytotoxicity
Authors: Mahmoud Nouf N. , Qabooq Haneen , Alsotari Shrouq , Tarawneh Ola A. , Aboalhaija Nour H. , Shraim Sawsan , Alkilany Alaaldin M. , Khalil Enam A. , Abu-Dahab Rana
Published: June 2021

Incorporating GNR-Quer into a mixture of 21% PLGA LMWT and 23% poloxamer 407 produced smooth, intact and uniform electrospun nanofibers with enhanced mechanical properties and hydration potential.
An XPS study of HCN-derived films on pyrite surfaces: a prebiotic chemistry standpoint towards the development of protective coatings
Authors: Pérez-Fernández Cristina , Ruiz-Bermejo Marta , Gálvez-Martínez Santos , Mateo-Martí Eva
Published: June 2021

Alkaline hydrothermal environment led to a NH4CN-based film with protective corrosion properties on the highly reactive pyrite surface.
Magnetic Fe3O4@CoFe-LDH nanocomposite heterogeneously activated peroxymonosulfate for degradation of azo-dye AO7
Authors: Sun Dapeng , Li Chuang , Lu Shengsen , Yang Qingfeng , He Chiquan
Published: June 2021

A novel core@shell magnetic nanocomposite Fe3O4/CoFe-layered double hydroxide was successfully synthesized by the co-precipitation method, and then employed as an efficient heterogeneous catalyst for activation of peroxymonosulfate in removal of azo-dye acid orange 7.
Preparation and characterization of polydopamine/melamine microencapsulated red phosphorus and its flame retardance in epoxy resin
Authors: Cheng Chen , Lu Yanling , Ma Weining , Li Shaojie , Yan Jun , Du Shiguo
Published: June 2021

Red phosphorus was coated by a polydopamine/melamine composite shell structure, which constituted an intumescent flame retardant with superior flame retardance and smoke suppression performance for epoxy resin.
Iron porphyrin-catalyzed N-trifluoroethylation of anilines with 2,2,2-trifluoroethylamine hydrochloride in aqueous solution
Authors: Ren Shuang , Xu Guiming , Guo Yongjia , Liu Qiang , Guo Cancheng
Published: June 2021

An iron porphyrin-catalyzed N-trifluoroethylation of anilines has been developed with 2,2,2-trifluoroethylamine hydrochloride as the fluorine source.
Halogen-free ionic liquids as high performance extractants for phenols separation
Authors: Yang Yufeng , Liu Qing , Chen Aibing , Ji Youan
Published: June 2021

In this work, five halogen-free ionic liquids (HFILs) were designed and employed to separate phenols from simulated oils, and all of them showed excellent separation performance.
The Heck reaction of allylic alcohols catalysed by an N-heterocyclic carbene-Pd(ii) complex and toxicity of the ligand precursor for the marine benthic copepod Amphiascoides atopus
Authors: Cárdenas Jorge , Gaviño Ruben , García-Ríos Eréndira , Rios-Ruiz Lucero , Puello-Cruz Ana C. , Morales-Serna Francisco Neptalí , Gómez Samuel , López-Torres Adolfo , Morales-Serna José Antonio
Published: June 2021

A 1,2,3-triazol-5-ylidene (aNHC)-based palladium(ii) complex formed in situ has been found to be an efficient catalyst in the formation of C–C bonds.
A MOF-74(Ni) derived partially oxidized Ni@C catalyst for SO2 electro-oxidation integrated with solar driven hydrogen evolution
Authors: Guo Jin-Han , Wei Xuming , Sun Wei-Yin
Published: June 2021

An efficient partially oxidized Ni@C (po-Ni@C) catalyst was developed for SO2 electro-oxidation reaction (SO2OR). Also, a solar to hydrogen electrolyzer was established base on the catalyst and delivered ∼25 mA current powered by a 1 V solar cell.
Recent advances in wearable self-powered energy systems based on flexible energy storage devices integrated with flexible solar cells
Authors: Zhao Jiangqi , Zha Jiajia , Zeng Zhiyuan , Tan Chaoliang
Published: June 2021

The recent advances in wearable self-powered energy systems based on flexible energy storage devices integrated with flexible solar cells for various applications are summarized.
Effects of NiO addition on sintering and proton uptake of Ba(Zr,Ce,Y)O3−δ
Authors: Huang Yuanye , Merkle Rotraut , Maier Joachim
Published: June 2021

Proton conducting Ba(Zr,Ce,Y)O3−δ: solid state reactive sintering with NiO, transient liquid phase, complex phase evolution, increased grain size, density and decreased proton uptake.
A broadband optical pH sensor using upconversion luminescence
Authors: Suresh K. , Bankapur Aseefhali , Chidangil Santhosh , Madhyastha Harishkumar , Sa-kai Kentaro , George Sajan D.
Published: June 2021

A non-contact optical pH and temperature sensor of the surrounding fluid medium based on the luminescence of an optically trapped single upconversion nanoparticle inside a microfluidic channel.
Luminescence-colour-changing sensing toward neurological drug carbamazepine in water and biofluids based on white light-emitting CD/Ln-MOF/PVA test papers
Authors: Li Yuxin , Sun Mingao , Yang Yang , Meng Hong , Wang Qiaoe , Li Chensha , Li Guangming
Published: June 2021

Nanomolar-level carbamazepine in water and biofluids has been determined using a white-light-emitting test paper via luminescence-colour-changing sensing.
A low-cost and green-solvent-processable hole-transport material enabled by a traditional bidentate ligand for highly efficient inverted perovskite solar cells
Authors: Huang Jiachen , Yang Jie , Li Dan , Sun Huiliang , Su Mengyao , Ji Xiaofei , Li Bolin , Li Bangbang , Liao Qiaogan , Han Dongxue , Yan He , Niu Li , Wang Dong , Guo Xugang
Published: June 2021

A bidentate ligand 1,10-phenanthroline enables a green-solvent-processable low-cost hole-transport materialM1, which efficiently passivates the Pb2+ion defects of perovskite toward high-performance inverted perovskite solar cells.
Seed shape-controlled, facet-selective growth of superspiky gold nanocrystals for biosensing applications
Authors: Li Jianqin , Lin Hangduo , Zhang Xiaolin , Li Ming
Published: June 2021

Seed shape-controlled synthesis of superspiky Au nanocrystals is reported using different shaped Au seeds, showing excellent plasmonic sensing and surface-enhanced Raman scattering sensing performances.
Stem cell sprays for neurological injuries: a perspective
Authors: Woods William , Evans Daisy , Mogas Barcons Aina , Tzerakis Nikolaos , Adams Christopher , Maitreyi Chari Divya
Published: June 2021

Injuries to the brain and spinal cord have major clinical consequences with high costs for healthcare systems. Neural cell transplantation therapies have significant translational potential to promote regeneration post-injury with clinical trials commencing for various pathologies. However, there are challenges associated with current clinical approaches used for systemic or direct delivery of transplant cells to neural tissue in regenerative applications. These include risks associated with surgical microinjection into neural tissue (e.g. haemorrhage, cell clumping) and high cell loss due to systemic clearance or with cell passage through fine gauge needles into densely packed neural tissue. This article presents lines of evidence supporting the concept that cell spray delivery technology can offer significant translational benefits for neural transplantation therapy, versus current cell delivery methods. Potential benefits include rapid/homogenous cell delivery, release over large surface areas, minimal invasiveness, compatibility with neurosurgical procedures in acute injury, no predictable clinical complications and the capacity to combine cell therapies with drug/biomolecule delivery. Accordingly, we consider that the development of cell spray delivery technology represents a key goal to develop advanced cell therapies for regenerative neurology.
Friction torque field distribution of a permanent‐magnet spherical motor based on multi‐physical field coupling analysis
Authors: Li Haolin , Li Guoli , Wang Qunjing , Ju Bin , Wen Yan
Published: June 2021

Non‐linear friction between the rotor and the rotor support mandrels would occur during the movement of the permanent‐magnet spherical motor (PMSpM). The friction which varies with the position causes PMSpM jitter or even stop it when running at low speeds, and the system operation accuracy is reduced. To solve these problems, this work proposes a parameter identification method of the Coulomb friction model. First, a dynamics model with the Coulomb friction of PMSpM is established by using generalised Euler angles and the Lagrangian energy method. Then, a parameter identification method of the Coulomb friction model based on COMSOL Multi physics coupled simulation and MEMS experiment is proposed to obtain the friction torque data of the PMSpM. Finally, the friction torque compensation in a closed‐loop control experiment is completed by using the friction data. The results show that the accuracy of trajectory tracking control is significant, and the error is reduced by 49.32%. Hence, the distribution of the friction torque field is accurate and effective.
Vulnerability analysis of secondary control system when microgrid suffering from sequential denial‐of‐service attacks
Authors: Wang Bingyu , Sun Qiuye , Wang Rui , Dong Chaoyu
Published: June 2021

The objective of the microgrid secondary control system (MSCS) is to regulate frequency and voltage and allocate active and reactive power among distributed generations in the microgrid. Sequential denial‐of‐service (DoS) attacks have a lasting impact that reduce the vulnerability of the MSCS. A vulnerability assessment method is proposed for when the microgrid experiences DoS attacks. The sequence model of attack actions and N–1 contingency actions are proposed to find the traversal expression. With the traversal method, vulnerable factors of the microgrid can be interpreted by the proposed comprehensive vulnerability metric, which provides an intuitive and easy way to understand the vulnerability of the MSCS. The metric is composed of four basic indicators concerning not only final states of the microgrid when a DoS attack ends, but also the dynamic process of the microgrid. To test the proposed metric, two mitigation methods with the purpose of mitigating the impact on the physical system caused by DoS attacks are proposed: the self‐adaptive coefficient method and the fault‐tolerance method. Finally, a 33‐node microgrid platform with eight distributed generations has been built to test the proposed vulnerability assessment method. From the analysis results, nodes with a high cyber‐degree are vulnerable and the fault‐tolerance method can provide a better mitigation result with an average metric of 9.41 compared with the self‐adaptive coefficient method with a metric of 9.03.
A user selection algorithm for aggregating electric vehicle demands based on a multi‐armed bandit approach
Authors: Hu Qinran , Zhang Nianchu , Quan Xiangjun , Bai Linquan , Wang Qi , Chen Xinyi
Published: June 2021

In systems with high penetration of renewables, demand side resources have been aggregated to facilitate system operation. However, the natural uncertainty and randomness of users' behaviour may deteriorate the demand aggregation performance, including a large mismatch from the expected aggregation target and unnecessary cost while executing aggregation. Here, the most fast‐growing demand side resource, electric vehicle is targeted, and an algorithm based on a multi‐armed bandit approach is proposed to aggregate those electric vehicle demands. In the proposed multi‐armed bandit model, each electric vehicle user's behaviour is viewed as two arms. Then, a combinatorial upper confidence bound mixed sorting algorithm, which selects the optimal set of users participating in demand aggregation, is developed. The case studies show that the proposed method can reduce the demand aggregation mismatch and eliminate the unnecessary cost. Additionally, it can be observed that the user experience is also improved.
Study of Fischer–Tropsch-type reactions on chondritic meteorites
Authors: Cabedo V. , Llorca J. , Trigo-Rodriguez J. M. , Rimola A.
Published: June 2021

Context.How simple organic matter appeared on Earth and the processes by which it transformed into more evolved organic compounds, which ultimately led to the emergence of life, is still an open topic. Different scenarios have been proposed, the main one assumes that simple organic compounds were synthesized, either in the gas phase or on the surfaces of dust grains, during the process of star formation and they were incorporated into larger bodies in the protoplanetary disk. The transformation of these simple organic compounds in more complex forms is still a matter of debate. Recent discoveries have pointed to catalytic properties of dust grains present in the early stellar envelope, which can nowadays be found in the form of chondrites. The significant infall of chondritic meteorites during the early periods of Earth suggests that the same reactions could have taken place in certain environments on the Earth’s surface, with conditions more favorable for organic synthesis.

Aims.This work attempts to synthesize simple organic molecules, such as hydrocarbons and alcohols via Fischer–Tropsch-type reactions supported by different chondritic materials under early-Earth conditions, to investigate if organic synthesis can likely occur in this environment and to determine what the differences are in selectivity when using different types of chondrites.

Methods.Fischer–Tropsch-type reactions are investigated from mixtures of CO and H2at 1 atm of pressure on the surfaces of different chondritic samples. The different products obtained are analyzed in situ by gas chromatography.

Results.Different Fischer–Tropsch reaction products are obtained in quantitative amounts. The formation of alkanes and alkenes being the main processes. The formation of alcohols also takes place in a smaller amount. Other secondary products were obtained in a qualitative way.

Conclusions.Chondritic material surfaces have been proven as good supports for the occurrence of organic synthesis. Under certain circumstances during the formation of Earth, they could have produced a suitable environment for these reactions to occur.
Flows of cohesive granular media
Authors: Mandal Sandip , Gans Adrien , Nicolas Maxime , Pouliquen Olivier
Published: June 2021

Cohesive granular media have broad applications in industries. However, our understanding of their flow behavior is still limited compared to dry granular media, although rich knowledge about their static and plastic properties has been gained. In this paper, we provide some insights into the flow behavior of cohesive granular media from our recent numerical studies using an inclined plane and a plane shear cell. We evidence that the cohesive nature of flows is significantly affected by material properties of the particles like stiffness and inelasticity in addition to the inter-particle adhesion and introduce the concept of “effective” adhesion, which incorporates the effects of these three variables. We propose constitutive relations involving dimensionless inertial number and “effective” cohesion number, based on the “effective” adhesion to describe the rheology. We also show that increasing adhesion increases the hysteresis in granular media, evidencing the existence of a prominent shear weakening branch in the friction coefficientversusinertial number rheological curve. Moreover, we reveal that this increasing hysteresis gives rise to the increasing occurrence of shear banding instability, pointing to the increasing possibility of jamming in cohesive granular media. Finally, we present a promising experimental approach to investigate the flow behavior of cohesive granular materials, based on a simple method of preparing a long time stable medium with a controlled adhesion between particles.
A micro-mechanical compaction model for granular mix of soft and rigid particles
Authors: Cárdenas-Barrantes Manuel , Cantor David , Barés Jonathan , Renouf Mathieu , Azéma Emilien
Published: June 2021

We use bi-dimensional non-smooth contact dynamics simulations to analyze the isotropic compaction of mixtures composed of rigid and deformable incompressible particles. Deformable particles are modeled using the finite-element method and following a hyper-elastic neo-Hookean constitutive law. The evolution of the packing fraction, bulk modulus and particle connectivity, beyond the jamming point, are characterized as a function of the applied stresses for different proportion of rigid/soft particles and two values of friction coefficient. Based on the granular stress tensor, a micro-mechanical expression for the evolution of the packing fraction and the bulk modulus are proposed. This expression is based on the evolution of the particle connectivity together with the bulk behaviour of a single representative deformable particle. A constitutive compaction equation is then introduced, set by well-defined physical quantities, given a direct prediction of the maximum packing fractionφmaxas a function of the proportion of rigid/soft particles.
Sample preparation of dense granular materials Influence of void ratio e and coordination number Z* on the mechanical behaviour at failure
Authors: Nawaz Shah , Combe Gaël
Published: June 2021

This paper presents a Discrete Element Method (DEM) study of assemblies of 5041 frictional discs, with periodic boundary conditions and confined by an external isotropic load. In order to generate samples with different internal state variables like the void ratio and coordination number, we present two different numerical procedures. The first technique, which has been widely used in the literature for many years, consists in controlling the coefficient of friction between particles to adjust the density of the samples, which directly influences the coordination number. The second technique is inspired by the previous one but adds an extra step of dynamic mixing with intergranular contacts lubrication. This makes it possible to control quasi independently the void ratio and the coordination number in the case of dense samples. These two types of samples are subjected to simple shear to analyse the influence of the sample preparation procedure on their macroscopic mechanical behaviour.
Exploring shear-induced segregation in controlled-velocity granular flows
Authors: Jing Lu , Ottino Julio M. , Lueptow Richard M. , Umbanhowar Paul B.
Published: June 2021

Particle segregation in geophysical and industrial granular flows is typically driven by gravity and shear. While gravity-induced segregation is relatively well understood, shear-induced segregation is not. In particular, what controls segregation in the absence of gravity and the interplay between shearand gravity-driven segregation remain unclear. Here, we explore the shear-induced segregation force on an intruder particle in controlled-velocity granular flows where the shear profile is systematically varied. The shear-induced segregation force is found to be proportional to the shear rate gradient, which effectively pushes the large intruder from lower to higher shear rate regions. A scaling law is developed for the segregation force that is accurate over a wide range of overburden pressures and shear rates, and hence inertial numbers.
Acoustic radiation patterns of the silo music phenomenon
Authors: Hernández-Juárez J.R. , Serrano D.A. , López-Villa A. , Medina A.
Published: June 2021

In this work, we apply the theory of radiation and reception of acoustic waves in the analysis of the acoustic contributions of the silo music phenomenon. The length portion of the silo where the silo music phenomenon occurs is considered a continuous line source. The continuous line source modeled as a simple acoustic source permits the analysis of the acoustic far field, interpreting the polar graphics of the beam patterns of the acoustic contributions. We propose to apply this technique in the silo design to diminish adverse acoustic effects during the discharge process of granular materials. Additionally, we present calculations of the sound pressure level of the silo music phenomenon.
Improved evaluation of granular media flows using an X-ray scanning compatible cone-plate setup
Authors: Farmani Zohreh , Wang Jing , Stannarius Ralf , Bieberle Martina , Barthel Frank , Hampel Uwe , Dijksman Joshua A.
Published: June 2021

To understand the typically heterogeneous flowing behavior of granular materials, it is important to combine flow tests with three-dimensional imaging. To probe the flow behavior of granular materials over a wide range of flow rates, it is imperative to be able to impose such flow rates in a well controlled manner while performing imaging tests that are compatible with all imposed flow rates. Achieving both flow control and bulk imaging capacity is challenging for a number of reasons. Here, we describe the design of a setup in which we are able to do imaging while imposing a constant overall shear rate on a granular material. We characterize the setup in which flow tests will be performed, which consists of a bottom-driven cone-plate or double-cone design. We show that the setup can be integrated in x-ray microtomography devices to aid particle tracking based flow measurements. The design is also compatible with typical rheometer setups. We also perform high speed imaging of a granular flow in an ultra-fast x-ray scanner, for which we provide proof-of-principle data in a simplified shear setup. The designed flow geometry is also compatible with said high speed imaging facility, where particle image velocimetry can be employed to extract quantitative flow field data.
Silo discharge: influence of the particle shape on the velocity profiles
Authors: Escudero Florencia , Villagrán Olivares Marcela Camila , Uñac Rodolfo , Vidales Ana María , Benito Jesica
Published: June 2021

Experiments on the discharge of a silo with an inclined outlet are performed using flattened seeds in order to evaluate the validity of a previous theoretical formulation developed in our work group [1]. In that description, funnel flow regime is assumed to be based on a free fall parabolic arc. The shape of this arc is described with a parameter which is the only one involved in the flow rate formulation. An experimental analysis of the behavior of this parameter is carried out based on the geometry and shape of the grains within the silo. Also, video analysis of the silo discharge is performed in order to investigate the velocity profiles at the outlet of the hopper for these non-spherical particles. Experiments are contrasted with analytical predictions derived from the proposed formulation in order to assess and discuss its validity for the case of flattened particles.
DEM simulations of quasi-two-dimensional flow of spherical particles on a heap without sidewalls
Authors: Ray Neiladri Sekhar , Khakhar Devang V.
Published: June 2021

Surface flows of granular materials find several important applications in both nature as well as industry. The effect of sidewalls on such flows is known to be large. Here, we study the rheology of such flows on a quasi two-dimensional heap without sidewalls, at different mass flow rates. It is seen that the surface angle of the heap, for all the mass flow rates, is the same and corresponds to the neutral angle. System variables such as the velocity, volume fraction and stresses are reported as a function of depth from the free surface of the heap. The friction coefficient and volume fraction are also studied as a function of the scaled local shear rate and these are also found to be independent of the mass flow rate. The behaviour observed in the present work is different from that reported in previous studies of surface flows with side walls.
Fracture, aggregation and segregation in dry, granular flows
Authors: Jenkins James T. , Larcher Michele
Published: June 2021

Particle fracture, the formation of small particles as the result of the breakage of large ones, and aggregation, the formation of large particles as the result of the combination of small ones, have important implications in industry (e.g. food processing, pharmaceutical production) and geophysics (e.g., snow avalanches and rock debris flows). Also, the presence of particles of different size that result from fracture and aggregation can induce segregation, resulting in the migration of large and small particles to different regions of the flow. Here, we formulate simple models for fracture and agglomeration and analyze the evolution of measures of the relative concentration of two sizes of spheres due the combined effects of fracture, aggregation, and segregation in dense, dry, granular flows. Particle breakage and combination is influenced by the frequency of collisions, by the local number density of the spheres, and by the particle kinetic energy. Segregation is predicted using a kinetic theory proposed by Larcher & Jenkins [2].
Modulated segregation of a bidisperse granular mixture due to recirculation currents
Authors: Mayeden Kwami Adem , Kolb Evelyne , Deboeuf Stéphanie , Jop Pierre
Published: June 2021

A bidisperse medium of large sand particles and small glass beads is mixed in a cylindrical vessel that is put in rotational motion around an eccentric static rod. The subsequent segregation occurring in the system is investigated primarily at the free-surface where the large particles concentration globally increases towards a limit value while oscillating. In order to gain deeper understanding of the intrinsic mechanisms causing the segregation, we also explore the dynamics in the bulk. Average residual bulk displacements fields both vertically and orthoradially could then be measured and show a secondary flow that counteracts the segregation process.
Axisymmetric landslides on top-shaped asteroids
Authors: Banik Deepayan , Gaurav Kumar , Sharma Ishan
Published: June 2021

Spin rates of minor planets or asteroids are known to have been affected by several agents including but not limited to tidal fly-bys, impacts and solar radiation. Surface processes like landslides occur as a result of such rotational changes. We study the evolution of landslides on top-shaped rubble pile asteroids like 101955 Bennu and 162173 Ryugu, with the underlying core modeled as two solid cones fused back to back. Using a depth averaged avalanche theory applicable to granular flows we solve for axisymmetric landslides occurring at various spin rates and regolith friction. Static regions on the surface corresponding to different spin rates are identified from an equilibrium analysis. We then solve for landslides initiated at different latitudes. It is found that landslides equilibrate at lower latitudes as the spin rate is increased. Beyond a critical spin rate regolith is shed from the equator. This critical spin is higher for a lower value of the semi-apex angle of the cone.
Magnetically heated granular gas in a low-gravity environment
Authors: Yu Peidong , Schröter Matthias , Adachi Masato , Sperl Matthias
Published: June 2021

Magnetic forces are used to heat up thousands of spherical particles under low-gravity. This long range external excitation, combined with the induced particle-particle interactions, results in a homogeneous spatial distribution of the particles. Comparisons with predictions of kinetic theories can hence be carried out. Haff’s cooling law is verified qualitatively, while the measured cooling time scale is quantitatively different from the prediction. The high velocity tail of the velocity distribution during homogeneous cooling state (HCS) is measured, while the expected cluster formation after HCS can not be verified by our experiment.
Music of grain crushing with the Discrete Element Method
Authors: Zeng Li , Peña Olarte Andres Alfonso , Cudmani Roberto
Published: June 2021

A series of compression tests on agglomerates of microspheres representing a single grain are conducted to investigate the impact of heterogeneity on the acoustic emissions (AE) generation. The grain heterogeneity is realized by using a Weibull shape parameter-augmented traditional discrete element method (DEM). During the compression process the development of the micro-cracks, and the magnitude and location of the AE events are tracked and recorded. Through a 3D visualization of the AE events, their location and the clustered broken bonds are identified. The current study demonstrates the potential of AE measurements to track changes in the fabric and structure of granular materials. The results of this DEM study will contribute to clarify the mechanism of particle breakage and its consideration in practical applications.
Taming the Janssen effect
Authors: Thorens Louison , Måløy Knut Jørgen , Bourgoin Mickaël , Santucci Stéphane
Published: June 2021

We investigate both experimentally and theoretically the apparent mass of a ferromagnetic granular assembly filling a cylindrical container and submitted to a magnetic fieldB, aligned vertically along the silo. We show that the mass of the ferromagnetic granular column depends strongly on the applied magnetic field. Notably, our measurements deviate strongly from the exponential saturation of the measured mass as a function of the true mass of the grain packing, as predicted by Janssen [H.A. Janssen, Vereins Eutscher Ingenieure Zeitschrift, 1045 (1895)]. In particular, the measured mass of tall columns decreases systematically as the amplitude of the magnetic field increases. We rationalize our experimental findings by considering the induced magnetic dipole-dipole interactions within the whole packing. We show the emergence of a global magnetic radial force along the walls of the silos, fully determined by the external magnetic field. The resulting tunable frictional interactions allows a full control of the effective mass of the ferromagnetic granular column.
Aerodynamic and impact thresholds for cohesive mixture of sand and non-volatile liquid
Authors: Besnard Jean-Baptiste , Valance Alexandre , Dupont Pascal , Ould El Moctar Ahmed
Published: June 2021

The moisture has been recognized to have a significant influence on the initiation movement of sand by wind and consequently on sand transport rates. The pertinent literature regarding these phenomena is sparse and current available theoretical and empirical models exhibit considerable disagreement regarding the magnitude of moisture effects. We believe that these discrepancies comes from the fact that the moisture levels are not well controlled neither properly measured and are susceptible to strongly vary over time due to evaporation. To get rid of the variability of moisture content due to evaporation, we propose a new approach based on the use of non-volatile liquid, namely silicon oil instead of water. This insures a proper control of the liquid content and the production of reliable data concerning the variation of the transport threshold with liquid content.
Slow and intermittent stress relaxation of biomass granular media
Authors: Thevenon Florent , Devulapalli Bharath , Marchand Muriel , Melkior Thierry , de Ryck Alain
Published: June 2021

In the present work, the relaxation of several wood powders has been investigated in an annular shear cell. It is found that the slow logarithmic relaxation commonly observed for various materials including granular materials is interrupted by large events. Their frequency and amplitude are investigated with respect to particle size and stress-history by measuring stresses and strain. These large events during the relaxation appear to be controlled by the deformation. The coarser the particles are, the bigger is the deformation of the powder bed between two fast relaxation events and during the event.
Liquid migration in flowing granular materials
Authors: Hagen Thijmen , Luding Stefan , van der Meer Devaraj , Magnanimo Vanessa , Jarray Ahmed
Published: June 2021

In partially wet granular beds, liquid migrates between particles due to collisions and contacts. This, in turn, influences the flow behaviour of the granular bed. We investigate liquid redistribution in moving monodisperse particles in a rotating drum using Discrete Element Method (DEM) simulations. For weak capillary forces, liquid re-distribution, induced by the continuous flow of particles, leads to concentration of the liquid in the core of the bed, where the flow is quasi-static. High capillary forces reduce the surface flow speed and granular temperature. This decreases liquid bridges rupturing in the flowing layer, allowing the liquid to remain in the outer region of the bed.
Particles bed morphology under an oscillating stiff and flexible plates
Authors: Prati Anna , Larcher Michele , Jenkins James T. , La Ragione Luigi
Published: June 2021

We analyse the different morphologies induced by an oscillating plate above an erodible bed. We present some data describing how the shape and the stiffness of the plate affects the main features of the generated heap. We investigate several configurations with different geometries, frequencies and the amplitudes. Some preliminary results are available, in which the role of the flexibility of the plate is taken in account. Unlike the rigid plate in which a proper oscillation induces the formation of one heap, the morphology of the bed is now characterized by more than one heap due to a different pressure profile induced by a flexible plate.
How does static granular matter re-arrange for different isotropic strain rate?
Authors: Luding Stefan
Published: June 2021

The question of how soft granular matter, or dense amorphous systems, re-arrange their microstructure under isotropic compression and de-compression, at different strain rates, will be answered by particle simulations of frictionless model systems in a periodic three-dimensional cuboid. Starting compression below jamming, the systems experience the well known jamming transition, with characteristic evolutions of the state variables elastic energy, elastic stress, coordination number, and elastic moduli. For large strain rates, kinetic energy comes into play and the evolution is more dynamic. In contrast, at extremely slow deformation, the system relaxes to hyper-elastic states, with well-defined elastic moduli, in static equilibrium between irreversible (plastic) re-arrangement events, discrete in time. Small, finite strains explore those reversible (elastic) states, before larger strains push the system into new states, by irreversible, sudden re-arrangements of the micro-structure.
Elastic wave velocity and attenuation in granular material
Authors: Jia Fan , Cheng Hongyang , Liu Sihong , Magnanimo Vanessa
Published: June 2021

Discrete Elements Method simulations are carried out to investigate waves propagation in isotropic, frictional granular media. The focus is on the effects of confining pressure, microstructure and input frequency on both wave velocity and attenuation. The latter is described via the seismic quality factor Q and three different measurement approaches are compared, in time and frequency domain. The simulation data validate previous findings on the scaling of wave velocity with confining pressure and coordination number. The quality factor Q shows a non-monotonic behavior with input frequency.
Geometrical network of granular materials under isochoric cyclic shearing
Authors: Yang Ming , Taiebat Mahdi , Mutabaruka Patrick , Radjai Farhang
Published: June 2021

We use three-dimensional particle dynamics simulations to investigate the microstructure evolution of granular material subjected to isochoric cyclic shearing, driving the system to a liquefaction state. The cyclically sheared assembly presents a realistic macroscopic response as observed in physical experiments. By analyzing the contact network evolution in the post-liquefaction period, we show that the onset of liquefaction state is characterized by a sudden drop of coordination number and a fragile particle connectivity network. The simulation suggests a critical coordination number for exiting the liquefaction state. Evolution of fabric anisotropy combined with coordination number implies the isotropic and anisotropic gain or loss of contacts at certain durations of a post-liquefaction loading cycle.
Numerical simulations of cone penetration in cemented sandstone
Authors: Rakhimzhanova Aigerim , Thornton Colin , Amanbek Yerlan , Zhao Yong
Published: June 2021

In this study, three-dimensional simulations of cone penetration tests (CPT) in cemented sandstone have been investigated using the Discrete Element Method (DEM). We generated the realistic grain size distribution of sandstone in the numerical simulations using the Ustyurt-Buzachi Sedimentary Basin samples. Numbers of numerical CPT tests at different bond strength values were performed with the penetrometer vertically moved down at a constant rate. The results of the real-world particle size distribution show that the cone penetration resistance and side friction increase with increasing depths; and with increase in bond strength the cone resistance and side friction decrease, while the friction ratio increases. The result of numerical CPT tests in cemented sandstone was found to be in good agreement with the Soil Behaviour Type (SBT) classification system from CPT data.
Effect of the coefficient of restitution and friction in the granular Leidenfrost effect in the absence of gravity. A numerical study
Authors: Schiochet Nasato Daniel , Briesen Heiko
Published: June 2021

In this study the granular Leidenfrost effect in the absence of gravity is investigated numerically by means of the discrete element method. Apart from identifying the phenomena, a parametric study to quantify the influence of the coefficient of restitution and friction in the packing fraction of the granular media is carried on numerically. Surprisingly, both the coefficient of restitution and the coefficient of friction exhibit an influence of the same magnitude in the packing fraction of the granular system, which has not been reported in experiments and simulation of granular Leidenfrost regime under gravity or microgravity conditions.
Discrete element simulations of load transfer mechanisms for a reinforced granular embankment submitted to loading cycles
Authors: Silvani Claire , Ramadan Mo’men , Villard Pascal , Briançon Laurent
Published: June 2021

A discrete element study of a reinforced granular embankment by rigid inclusions, submitted to cyclic loadings is presented. The discrete element method (based on molecular dynamics method) is used to understand the load transfer mechanisms into the granular layer (just above the inclusions) during cyclic loadings. The microscale study showed that the soil above the rigid inclusions retrieve the larger forces, illustrating on the role of the granular layer as a load transfer layer, while the settlement of both the granular layer and loading slab increase with loading. The efficiency of load transfer to piles and ability (capacity of the granular material to postpone the overloads to the piles) decreases with cycling, but keeping high values at the end of cycles. The transfer of forces in the granular layer is achieved by two mechanisms, interacting together (inverted pyramid above rigid inclusions and arching), confirming results found in the literature.
Quasistatic response of loose cohesive granular materials
Authors: Lammali Walid , Roux Jean-Noël , Tang Anh-Minh
Published: June 2021

DEM-simulated model cohesive assemblies of spherical grains of diameterd, with contact tensile strengthF0, once prepared in loose states, are quasistatically subjected to growing isotropic pressureP, and then to triaxial compression, maintaining lateral stresses σ2= σ3=Pwhile increasing axial stress σ1=P+qand strain є1. Reduced pressureP*=d2P/F0varies from 0.1 (cohesion dominated case, for which systems typically equilibrate with solid fraction Ф ≃ 0.35), to large values for which the cohesionless behavior is retrieved. In triaxial compression, while the moderate strain response (є1~ 0.1) is influenced by initial coordination numbers and mesoscale heterogeneities, the approach to the critical state, as bothq(deviator) and Ф steadily increase, gets slower for smallerP*. Critical ratioq/P strongly increases for decreasingP*, as roughly predicted in an “effective stress” scheme. Anomalously small elastic moduli are observed in the gel-like structures. While extensive geometric rearrangements take place, no shear banding is observed. Loose cohesive granular assemblies are thus capable of large quasistatic stable plastic strains and ductile rupture.
Injury Incidence and Severity in Musical Theatre Dance Students: 5-year Prospective Study
Authors: Stephens Nicola , Nevill Alan M. , Wyon Matthew Alexander
Published: June 2021

Dance injury research has mainly focused on ballet and modern dance with little data on musical theatre dancers. The purpose was to assess the incidence and severity of injuries in a musical theatre dance college over a 5-year period; 198 pre-professional musical theatre dancers (3 cohorts on a 3-year training course) volunteered for the study; 21 students left the course over the study period. Injury aetiology data were collected by an in-house physiotherapy team. Differences between academic year and sex were analysed using a Poisson distribution model; significant difference was set at p≤0.05. In total, 913 injuries were recorded, and more injuries occurred in academic year 1 than year 2 and 3. Overall injury incidence was 1.46 injuries per 1000 hours (95% CI 1.34, 1.56); incidence significantly decreased between year 1, 2 and 3 (p<0.05). There was no significant sex difference for incidence or severity. Most injuries were classified as overuse (71% female, 67% male). Pre-professional musical theatre dancers report a high proportion of lower limb and overuse injuries comparable to other dance genres. Unlike other studies on pre-professional dancers, injury incidence and severity decreased with academic year, even though workload increased across the course.