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Accelerating CFD–DEM simulation of processes with wide particle size distributions

Particuology 2014年第1期12卷 113-121页

作者： Tamir Brosh Haim Kalman Avi Levy Pearlstone Centre for Aeronautical engineering Studies Department of Mechanical Engineering Ben-Gurion University of the Negev School of Mechanical and Systems engineering Stephenson Building Claremont Road Newcastle University

Sizereduction systems have been extensively used in industry for many years. Nevertheless, reliable engi neering tools to be used to predict the comminution of particles are scarce. Computational fluid dynamics （CFD）discrete element model （DEM） numerical simulation may be used to predict such a complex phe nomenon and therefore establish a proper design and optimization model for comminution systems, They may also be used to predict attrition in systems where particle attrition is significant. Therefore, empirical comminution functions （which are applicable for any attrition/comminution process）, such as： strength distribution, selection, equivalence, breakage, and fatigue, have been integrated into the three dimensional CFDDEM simulation tool. The main drawback of such a design tool is the long computational time required owing to the large number of particles and the minute timestep required to maintain a steady solution while simulating the flow of particulate materials with very fine particles. The present study developed several methods to accelerate CFDDEM simulations： reducing the num ber of operations carried out at the singleparticle level, constructing a DEM grid detached from the CFD grid enabling a no binary search, generating a subgrid within the DEM grid to enable a no binary search for fine particles, and increasing the computational timestep and eliminating the finest particles in the simulation while still tracking their contribution to the process. The total speedup of the simulation process without the elimination of the finest particles was a factor of about 17. The elimination of the finest particles gave additional speedup of a factor of at least 18. Therefore, the simulation of a grinding process can run at least 300 times faster than the conventional method in which a standard no binary search is employed and the smallest particles are tracked.

关键词： Computational fluid dynamicsDiscrete element modelSearch algorithmIncreased time-step

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Surroundings affect slip length dynamics in nanoscale friction through contact stiffness and damping

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Friction 2023年第2期11卷 216-227页

作者： Simona SKURATOVSKY Liron AGMON Enrico GNECCO Ronen BERKOVICH department of Chemical engineering Ben-Gurion University of the NegevBeer-Sheva 8410501Israel Marian Smoluchowski Institute of Physics Jagiellonian UniversityLojasiewicza 11Krakow 30-348Poland Ilze Katz Institute for Nanoscience and Technology Ben-Gurion University of the NegevBeer-Sheva 8410501Israel

Friction force microscopy (FFM) explores the interaction in a sliding contact on the nanoscale, providing information on the frictional dynamics and lateral contact stiffness with lattice resolution. Recent FFM measurements on a NaCl crystal immersed in liquid (ethanol) surroundings displayed an increase of the effective contact stiffness, K_(eff), with the applied load, differently from similar measurements performed under ultra-high vacuum (UHV) conditions, where K_(eff) showed negligible load dependency. Additionally, under UHV conditions multiple slip length friction with increasing load was reported, while in ethanol surroundings only single (lattice unit length) slips were observed. Our current understanding of this behavior relates the transition from single jumps to multiple jumps dynamics to the normal load (manifested through the amplitude of the interaction potential at the contact, U0) and to the damping of the system. Here we have incorporated the effect of the load dependency on both U0 and K_(eff) within Prandtl‒Tomlinson based simulations, accompanied by variations in the damping coefficient of the system. Introducing the experimentally observed load dependency to K_(eff) resulted indeed in single slip jumps at critical damping, while multiple slip jumps were obtained at constant K_(eff). The average slip length increased with the normal load, particularly when the system became underdamped. Our work provides a glimpse on the relation between the characteristic observables in atomic-scale sliding friction (maximal slip forces, stiffness, and slip dynamics) with respect to their governing parameters (corrugation energy, effective stiffness, and damping). While common understanding in nanotribology relates the effect of surrounding media mainly to the interaction potential at the contact, here we show that the media can also greatly affect the elastic interaction, and consequently play an important role on the transition from single to multiple stick-s

关键词： friction force microscopy(FFM) nanoscale friction multiple jumps Prandtl‒Tomlinson model effective stiffness damping

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Single-shot circular dichroism spectroscopy

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Light(Science & Applications) 2022年第6期11卷 1021-1022页

作者： Alina Karabchevsky ben-gurion university of the negev School of Electrical and Computer EngineeringDepartment of Photonics and ElectroopticsBeer-Sheva 8410501Israel

Circular dichroism spectroscopy can be optimized to measure the scattering circular dichroism response of a single chiral nanostructure with a single shot.

关键词： circular dichroism spectroscopy

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An Optimization Framework for Travel Pattern Interpretation of Cellular Data

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International Journal of Transportation Science and Technology 2013年第3期2卷 167-182页

作者： Sarit Freund Hillel Bar-Gera department of industrial engineering ben-gurion university of the negev P.O.Box 653Beer-Sheva 84105

Collection of travel data by traditional survey methods is costly,thus limiting the amount of data being collected,as well as their frequency and *** technologies offer new types of data collection *** particular,cellular systems generate substantial amounts of data,including records regarding the connection between handsets(phones)and base stations(antenna).These records,collected by cellular service providers for various internal purposes,may provide an excellent source of information regarding travel,with several critical advantages relative to traditional travel surveys:low cost,large sample,long duration,and high response *** data has some limitations too,particularly with respect to accuracy and traveler identity;therefore,such data cannot provide a complete replacement for traditional surveys,but it can complement and enhance *** paper explores methods for identifying travel patterns from cellular data.A primary challenge in this research is to provide an interpretation of the raw data that distinguishes between activity durations and travel durations.A novel framework is proposed for this purpose,based on a grading scheme for candidate interpretations of the raw data.A genetic algorithm is used to find interpretations with high grades,which are considered as the most reasonable *** proposed method is tested on a dataset of records covering 9454 cell-phone users over a period of one *** evaluation of the resulting interpretations is presented.

关键词： antenna travel Cellular

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Turbulent Melt Flow in a Helical Channel of an Inductive Pump

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Journal of Iron and Steel Research International 2012年第S1期19卷 566-568页

作者： A.Kapusta B.Mikhailovich L.Reymal B.Tilman Center for MHD Studies Ben-Gurion University of the NegevBeer-ShevaIsrael department of Mechanical engineering Ben-Gurion University of the NegevBeer-ShevaIsrael Mahyd and Co TallinnEstonia

In contrast to Ref.[1]studying MHD processes in a helical channel induced by a vertical rotating electric current layer,in the present report we examine another version with the rotating electric current layer orthogonal to the helical channel axis,which leads to an increase in melt velocity with the growing pitch angle α of the helical channel.

关键词： vertical coordinate system helical channel pitch angle external friction model electromagnetic body force flow velocity.

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Turbulent Melt Flow Excited by Amplitude-andFrequency Modulated RMF

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Journal of Iron and Steel Research International 2012年第S1期19卷 483-486页

作者： A.Kapusta M.Khavkin Sh.Lesin B.Mikhailovich B.Tilman Center for MHD Studies Ben-Gurion University of the NegevBeer-ShevaIsrael department of Mechanical engineering Ben-Gurion University of the NegevBeer-ShevaIsrael Energetics Technologies Ltd OmerIsrael

We examine MHD processes arising in melts placed in vessels of circular and rectangular cross-sections under the action of amplitude-and-frequency modulated rotating magnetic *** is established that besides the mean t... 详细信息

关键词： rotating magnetic field amplitude-and-frequency modulation electromagnetic body force velocity field velocity oscillation external friction model

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Soft thermal nanoimprint lithography using a nanocomposite mold

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Nano Research 2018年第5期11卷 2705-2714页

作者： Viraj Bhingardive Liran Menahem Mark Schvartzman department of Materials engineering Isle Katz Institute of Nanoscale Science and Technology Ben-Gurion University of the Negev P.O. Box 653 Beer-Sheva 8410501 Israel

Soft nanoimprint lithography has been limited to ultraviolet （UV） curable resists. Here, we introduce a novel approach for soft thermal nanoimprinting. This unprecedented combination of the terms ＂soft＂ and ＂thermal＂ for nanoimprinting became possible thanks to an innovative nanocomposite mold consisting of a flexible polydimethylsiloxane （PDMS） substrate with chemically attached rigid relief features. We used soft thermal nanoimprinting to produce high-resolution nanopatterns with a sub-100 nm feature size. Furthermore, we demonstrate the applicability of our nanoimprint approach for the nanofabrication of thermally imprinted nanopattems on non-planar surfaces such as lenses. Our new nanofabrication strategy paves the way to numerous applications that require the direct fabrication of functional nanostructures on unconventional substrates.

关键词： soft lithography nanoimprint lithography polydimethylsiloxane(PDMS) non-planar substrates

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Detection and upconversion of three-dimensional MMW/THz images to the visible

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Photonics Research 2016年第6期4卷 306-312页

作者： Avihai Aharon(Akram) Daniel Rozban Avi Klein Amir Abramovich Yitzhak Yitzhaky Natan S.Kopeika department of Electrical and Electronic engineering Ariel University department of Electrical and Computer engineering Ben-Gurion University of the Negev department of Electro-Optical engineering Ben-Gurion University of the Negev

We present an inexpensive technique to obtain a three-dimensional(3D) millimeter wave(MMW) and terahertz(THz) image using upconversion. In this work we describe and demonstrate a method for upconversion of MMW/THz radiation to the visual band using a very inexpensive miniature glow discharge detector(GDD) and a silicon photodetector. We present MMW/THz upconversion images based on measuring the visual light emitting from the GDD rather than its electrical current. The results show better response time and better sensitivity compared to the electronic detection performed previously. Furthermore, in this work we perform frequency modulation continuous wave(FMCW) radar detection based on this method using a GDD lamp, with a photodetector to measure GDD light emission. By using FMCW detection, the range in addition to the intensity at each pixel can be obtained,thus yielding the 3D image. The GDD acts as a heterodyne mixer not only electronically but also optically. The suggested 3D upconversion technique using the GDD is simple and inexpensive and has better performance compared to other MMW/THz imaging systems suggested in the literature. This method provides minimum detectable signal power that is about 6 orders of magnitude better than similar plasma systems due to the very large internal signal gain deriving from the much smaller electrode separation and resulting in much higher plasma electric field.

关键词： THz Detection and upconversion of three-dimensional MMW/THz images to the visible FMCW

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Engineered exosome hybrid copper nanoscale antibiotics facilitate simultaneous self-assembly imaging and elimination of intracellular multidrug-resistant superbugs

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Chinese Chemical Letters 2024年第7期35卷 319-324页

作者： Zengchao Guo Weiwei Liu Tengfei Liu Jinpeng Wang Hui Jiang Xiaohui Liu Yossi Weizmann Xuemei Wang State Key Laboratory of Digital Medical engineering School of Biological Science and Medical EngineeringSoutheast UniversityNanjing 210096China department of Chemistry Ben-Gurion University of the NegevBeer-Sheva 8410501Israel

With the increasing emergence of bacterial infections,especially multidrug-resistant(MDR)bacteria,poses an urgent *** study demonstrated a novel multifunctional nanotheranostics platform developed by the strategic integration of both in-situ bio-assembly imaging and target bacteria *** the introduction of copper ions into bacteria,the Cu^(2+)could spontaneously bio-selfassembled into a multifunctional copper nanoclusters(NCs)which efficiently enhanced epigallocatechin gallate(EGCG)uptake into *** visualizing the bacteria,the developed theranostic nanoplatform exhibited highly efficient disinfection activities with negligible side effects as reflected by higher cell viability and insignificant hemolytic ***,the exosomal formulation of EGCG integrated with Cu^(2+)showed an increased intracellular antibacterial activity,which could eliminate most of the methicillin-resistant Staphylococcus aureus(MRSA)phagocytosed by macrophages,guide macrophages toward M2-like phenotype polarization and alleviate inflammation,without exhibiting obvious cytotoxicity on host *** regimen could be viewed as an effective strategy for the sterilization of intractable bacterial infections.

关键词： In situ self-assembled Exosome Antibacterial agents Bioimaging Intracellular infection

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Novel Methodologies for Preventing Crack Propagation in Steel Gas Pipelines Considering the Temperature Effect

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Structural Durability & Health Monitoring 2025年第1期19卷 1-23页

作者： Nurlan Zhangabay Ulzhan Ibraimova Marco Bonopera Ulanbator Suleimenov Konstantin Avramov Maryna Chernobryvko Aigerim Yessengali department of Architecture and Urban Planning Mukhtar Auezov South Kazakhstan UniversityShymkent160012Kazakhstan department of industrial Civil and Road Construction Mukhtar Auezov South Kazakhstan UniversityShymkent160012Kazakhstan Mechanics Sound&Vibration LaboratoryDepartment of Civil EngineeringCollege of EngineeringNational Taiwan UniversityTaipei10617Taiwan department of Reability&Dynamic Strength A.Pidhornyi Institute of Mechanical Engineering Problems of National Academy of Sciences of UkraineKharkiv61046Ukraine

Using the software ANSYS-19.2/Explicit Dynamics,this study performedﬁnite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crack,strengthened by steel wire *** effects of the thread tensile force of the steel winding in the form of single rings at the crack edges and the wires with different winding diameters and pitches were also *** results showed that the strengthening was preferably executed at a minimum value of the thread tensile force,which was 6.4%more effective than that at its maximum *** analysis of the inﬂuence of the winding dia-meters showed that the equivalent stresses increased by 32%from the beginning of the crack growth until the wire *** increment in winding diameter decelerated the disclosure of the edge crack and reduced its length by 8.2%.The analysis of the inﬂuence of the winding pitch showed that decreasing the distance between the winding turns also led to a 33.6%reduction in the length of the straight crack and a 7.9%reduction in the maximum stres-ses on the strengthened pipeline *** analysis of the temperature effect on the pipeline material,within a range from-40℃ to+50℃,resulted in a crack length change of up to 5.8%.As the temperature dropped,the crack length *** such a temperature range,the maximum stresses were observed along the cen-tral area of the crack,which were equal to 413 MPa at+50℃ and 440 MPa at-40℃.The results also showed that the presence of the steel winding in the pipeline signiﬁcantly reduced the length of crack propagation up to 8.4 times,depending on the temperature effect and design parameters of *** work integrated the existing methods for crack localization along steel gas pipelines.

关键词： Crack propagation ﬁnite-element internal pressure prestressing steel gas pipeline temperature effect

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