Institution
Center for Theoretical Studies, University of Miami
About: Center for Theoretical Studies, University of Miami is a based out in . It is known for research contribution in the topics: Gauge theory & Clifford algebra. The organization has 196 authors who have published 543 publications receiving 11173 citations.
Papers published on a yearly basis
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TL;DR: The dynamics of pedestrian crowds is surprisingly predictable and the corresponding computer simulations are a valuable tool for developing optimized pedestrian facilities and way systems.
Abstract: Although pedestrians have individual preferences, aims, and destinations, the dynamics of pedestrian crowds is surprisingly predictable. Pedestrians can move freely only at small pedestrian densities. Otherwise their motion is affected by repulsive interactions with other pedestrians, giving rise to self-organization phenomena. Examples of the resulting patterns of motion are separate lanes of uniform walking direction in crowds of oppositely moving pedestrians or oscillations of the passing direction at bottlenecks. If pedestrians leave footprints on deformable ground (for example, in green spaces such as public parks) this additionally causes attractive interactions which are mediated by modifications of their environment. In such cases, systems of pedestrian trails will evolve over time. The corresponding computer simulations are a valuable tool for developing optimized pedestrian facilities and way systems.
771 citations
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University of Cambridge1, Monash University2, Centre national de la recherche scientifique3, University of Bonn4, Harish-Chandra Research Institute5, University of Paris6, University of Turin7, Center for Theoretical Studies, University of Miami8, KEK9, University of Barcelona10, Spanish National Research Council11, University of Montpellier12, CERN13, Stanford University14, University of Edinburgh15, Fermilab16, ETH Zurich17, University of Southampton18, University of Zaragoza19, University of Würzburg20, Moscow State University21, Durham University22, Sapienza University of Rome23, Paul Scherrer Institute24
TL;DR: Extensions of the conventions of the first SLHA are proposed to include various generalisations: the minimal supersymmetric standard model with violation of CP, R-parity, and flavour, as well as the simplest next-to-minimal model.
418 citations
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TL;DR: This work explores the ultimate limit in paradigmatic cases of optimal control theory, and demonstrates that it coincides with the maximum speed limit allowed by quantum evolution.
Abstract: Optimal control theory is a promising candidate for a drastic improvement of the performance of quantum information tasks. We explore its ultimate limit in paradigmatic cases, and demonstrate that it coincides with the maximum speed limit allowed by quantum evolution.
404 citations
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TL;DR: A model of pedestrian motion is developed that takes into account pedestrian motion and orientation and the concomitant feedbacks with the surrounding environment and is able to reproduce many of the observed large-scale spatial features of trail systems.
Abstract: Many human social phenomena, such as cooperation1,2,3, the growth of settlements4, traffic dynamics5,6,7 and pedestrian movement7,8,9,10, appear to be accessible to mathematical descriptions that invoke self-organization11,12. Here we develop a model of pedestrian motion to explore the evolution of trails in urban green spaces such as parks. Our aim is to address such questions as what the topological structures of these trail systems are13, and whether optimal path systems can be predicted for urban planning. We use an ‘active walker’ model14,15,16,17,18,19 that takes into account pedestrian motion and orientation and the concomitant feedbacks with the surrounding environment. Such models have previously been applied to the study of complex structure formation in physical14,15,16, chemical17 and biological18,19 systems. We find that our model is able to reproduce many of the observed large-scale spatial features of trail systems.
373 citations
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Heidelberg University1, Trinity College, Dublin2, University of Cambridge3, Autonomous University of Madrid4, Université Paris-Saclay5, Spanish National Research Council6, University of Zaragoza7, University of Nottingham8, RWTH Aachen University9, Kessler Foundation10, Istituto Italiano di Tecnologia11, Georgia Institute of Technology12, University of Grenoble13, Dresden University of Technology14, Polytechnic University of Turin15, University of Zurich16, Bielefeld University17, University of Strasbourg18, Technical University of Denmark19, Swiss Federal Laboratories for Materials Science and Technology20, Ikerbasque21, University of Erlangen-Nuremberg22, Technische Universität München23, Bundeswehr University Munich24, University of Bern25, University of Patras26, Foundation for Research & Technology – Hellas27, Center for Theoretical Studies, University of Miami28, École Polytechnique Fédérale de Lausanne29, University of Ulm30, University of Eastern Finland31, Aristotle University of Thessaloniki32, University of Manchester33, Polish Academy of Sciences34, Aalto University35, University of Castilla–La Mancha36, ShanghaiTech University37, University of Exeter38, Chalmers University of Technology39, Warsaw University of Technology40, University of Trieste41, Queen Mary University of London42, University of Trento43, Instituto Politécnico Nacional44, University of the Basque Country45, Chemnitz University of Technology46, Charles University in Prague47, University of Jena48, University of Texas at Dallas49
TL;DR: In this article, the authors present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures, adopting a 'hands-on' approach, providing practical details and procedures as derived from literature and from the authors' experience, in order to enable the reader to reproduce the results.
Abstract: © 2020 The Author(s). We present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures. We adopt a 'hands-on' approach, providing practical details and procedures as derived from literature as well as from the authors' experience, in order to enable the reader to reproduce the results. Section I is devoted to 'bottom up' approaches, whereby individual constituents are pieced together into more complex structures. We consider graphene nanoribbons (GNRs) produced either by solution processing or by on-surface synthesis in ultra high vacuum (UHV), as well carbon nanomembranes (CNM). Production of a variety of GNRs with tailored band gaps and edge shapes is now possible. CNMs can be tuned in terms of porosity, crystallinity and electronic behaviour. Section II covers 'top down' techniques. These rely on breaking down of a layered precursor, in the graphene case usually natural crystals like graphite or artificially synthesized materials, such as highly oriented pyrolythic graphite, monolayers or few layers (FL) flakes. The main focus of this section is on various exfoliation techniques in a liquid media, either intercalation or liquid phase exfoliation (LPE). The choice of precursor, exfoliation method, medium as well as the control of parameters such as time or temperature are crucial. A definite choice of parameters and conditions yields a particular material with specific properties that makes it more suitable for a targeted application. We cover protocols for the graphitic precursors to graphene oxide (GO). This is an important material for a range of applications in biomedicine, energy storage, nanocomposites, etc. Hummers' and modified Hummers' methods are used to make GO that subsequently can be reduced to obtain reduced graphene oxide (RGO) with a variety of strategies. GO flakes are also employed to prepare three-dimensional (3d) low density structures, such as sponges, foams, hydro- or aerogels. The assembly of flakes into 3d structures can provide improved mechanical properties. Aerogels with a highly open structure, with interconnected hierarchical pores, can enhance the accessibility to the whole surface area, as relevant for a number of applications, such as energy storage. The main recipes to yield graphite intercalation compounds (GICs) are also discussed. GICs are suitable precursors for covalent functionalization of graphene, but can also be used for the synthesis of uncharged graphene in solution. Degradation of the molecules intercalated in GICs can be triggered by high temperature treatment or microwave irradiation, creating a gas pressure surge in graphite and exfoliation. Electrochemical exfoliation by applying a voltage in an electrolyte to a graphite electrode can be tuned by varying precursors, electrolytes and potential. Graphite electrodes can be either negatively or positively intercalated to obtain GICs that are subsequently exfoliated. We also discuss the materials that can be amenable to exfoliation, by employing a theoretical data-mining approach. The exfoliation of LMs usually results in a heterogeneous dispersion of flakes with different lateral size and thickness. This is a critical bottleneck for applications, and hinders the full exploitation of GRMs produced by solution processing. The establishment of procedures to control the morphological properties of exfoliated GRMs, which also need to be industrially scalable, is one of the key needs. Section III deals with the processing of flakes. (Ultra)centrifugation techniques have thus far been the most investigated to sort GRMs following ultrasonication, shear mixing, ball milling, microfluidization, and wet-jet milling. It allows sorting by size and thickness. Inks formulated from GRM dispersions can be printed using a number of processes, from inkjet to screen printing. Each technique has specific rheological requirements, as well as geometrical constraints. The solvent choice is critical, not only for the GRM stability, but also in terms of optimizing printing on different substrates, such as glass, Si, plastic, paper, etc, all with different surface energies. Chemical modifications of such substrates is also a key step. Sections IV-VII are devoted to the growth of GRMs on various substrates and their processing after growth to place them on the surface of choice for specific applications. The substrate for graphene growth is a key determinant of the nature and quality of the resultant film. The lattice mismatch between graphene and substrate influences the resulting crystallinity. Growth on insulators, such as SiO2, typically results in films with small crystallites, whereas growth on the close-packed surfaces of metals yields highly crystalline films. Section IV outlines the growth of graphene on SiC substrates. This satisfies the requirements for electronic applications, with well-defined graphene-substrate interface, low trapped impurities and no need for transfer. It also allows graphene structures and devices to be measured directly on the growth substrate. The flatness of the substrate results in graphene with minimal strain and ripples on large areas, allowing spectroscopies and surface science to be performed. We also discuss the surface engineering by intercalation of the resulting graphene, its integration with Si-wafers and the production of nanostructures with the desired shape, with no need for patterning. Section V deals with chemical vapour deposition (CVD) onto various transition metals and on insulators. Growth on Ni results in graphitized polycrystalline films. While the thickness of these films can be optimized by controlling the deposition parameters, such as the type of hydrocarbon precursor and temperature, it is difficult to attain single layer graphene (SLG) across large areas, owing to the simultaneous nucleation/growth and solution/precipitation mechanisms. The differing characteristics of polycrystalline Ni films facilitate the growth of graphitic layers at different rates, resulting in regions with differing numbers of graphitic layers. High-quality films can be grown on Cu. Cu is available in a variety of shapes and forms, such as foils, bulks, foams, thin films on other materials and powders, making it attractive for industrial production of large area graphene films. The push to use CVD graphene in applications has also triggered a research line for the direct growth on insulators. The quality of the resulting films is lower than possible to date on metals, but enough, in terms of transmittance and resistivity, for many applications as described in section V. Transfer technologies are the focus of section VI. CVD synthesis of graphene on metals and bottom up molecular approaches require SLG to be transferred to the final target substrates. To have technological impact, the advances in production of high-quality large-area CVD graphene must be commensurate with those on transfer and placement on the final substrates. This is a prerequisite for most applications, such as touch panels, anticorrosion coatings, transparent electrodes and gas sensors etc. New strategies have improved the transferred graphene quality, making CVD graphene a feasible option for CMOS foundries. Methods based on complete etching of the metal substrate in suitable etchants, typically iron chloride, ammonium persulfate, or hydrogen chloride although reliable, are time- and resourceconsuming, with damage to graphene and production of metal and etchant residues. Electrochemical delamination in a low-concentration aqueous solution is an alternative. In this case metallic substrates can be reused. Dry transfer is less detrimental for the SLG quality, enabling a deterministic transfer. There is a large range of layered materials (LMs) beyond graphite. Only few of them have been already exfoliated and fully characterized. Section VII deals with the growth of some of these materials. Amongst them, h-BN, transition metal tri- and di-chalcogenides are of paramount importance. The growth of h-BN is at present considered essential for the development of graphene in (opto) electronic applications, as h-BN is ideal as capping layer or substrate. The interesting optical and electronic properties of TMDs also require the development of scalable methods for their production. Large scale growth using chemical/physical vapour deposition or thermal assisted conversion has been thus far limited to a small set, such as h-BN or some TMDs. Heterostructures could also be directly grown.
330 citations
Authors
Showing all 196 results
Name | H-index | Papers | Citations |
---|---|---|---|
Pietro Faccioli | 132 | 1378 | 89795 |
George Japaridze | 82 | 382 | 22222 |
Feng Liu | 75 | 628 | 21983 |
Francesco Iachello | 65 | 249 | 20401 |
Joachim Wambsganss | 59 | 310 | 13732 |
Pratim Kumar Chattaraj | 58 | 440 | 13868 |
Xingao Gong | 57 | 256 | 12747 |
O. Fadiran | 55 | 130 | 12798 |
Tommaso Calarco | 53 | 192 | 9077 |
David Blaschke | 52 | 575 | 11370 |
Rohini M. Godbole | 50 | 287 | 10282 |
N. Mukunda | 43 | 205 | 6542 |
Daniele Binosi | 39 | 169 | 5445 |
Javier L. Albacete | 37 | 92 | 6820 |
Stefano Giorgini | 35 | 77 | 9565 |