4,957 research outputs found
Friction Boosted by Equilibrium Misalignment of Incommensurate Two-Dimensional Colloid Monolayers
Colloidal 2D monolayers sliding in an optical lattice are of recent
importance as a frictional system. In the general case when the monolayer and
optical lattices are incommensurate, we predict two important novelties, one in
the static equilibrium structure, the other in the frictional behavior under
sliding. Structurally, realistic simulations show that the colloid layer should
possess in full equilibrium a small misalignment rotation angle relative to the
optical lattice, an effect so far unnoticed but visible in some published
experimental moir\'e patterns. Under sliding, this misalignment has the effect
of boosting the colloid monolayer friction by a considerable factor over the
hypothetical aligned case discussed so far. A frictional increase of similar
origin must generally affect other incommensurate adsorbed monolayers and
contacts, to be sought out case by case.Comment: 9 pages, 11 figures (including Supplemental Material
Finite-temperature phase diagram and critical point of the Aubry pinned-sliding transition in a 2D monolayer
The Aubry unpinned--pinned transition in the sliding of two incommensurate
lattices occurs for increasing mutual interaction strength in one dimension
() and is of second order at , turning into a crossover at nonzero
temperatures. Yet, real incommensurate lattices come into contact in two
dimensions (), at finite temperature, generally developing a mutual
Novaco-McTague misalignment, conditions in which the existence of a sharp
transition is not clear. Using a model inspired by colloid monolayers in an
optical lattice as a test case, simulations show a sharp Aubry transition
between an unpinned and a pinned phase as a function of corrugation. Unlike
, the transition is now of first order, and, importantly, remains well
defined at . It is heavily structural, with a local rotation of moir\'e
pattern domains from the nonzero initial Novaco-McTague equilibrium angle to
nearly zero. In the temperature () -- corrugation strength () plane,
the thermodynamical coexistence line between the unpinned and the pinned phases
is strongly oblique, showing that the former has the largest entropy. This
first-order Aubry line terminates with a novel critical point , marked
by a susceptibility peak. The expected static sliding friction upswing between
the unpinned and the pinned phase decreases and disappears upon heating from
to . The experimental pursuit of this novel scenario is proposed.Comment: 9 pages, 9 figure
Comportamento meteorolĂłgico e sua influĂȘncia na vindima de 2004 na Serra GaĂșcha.
bitstream/item/59967/1/CNPUV-COM.TEC.-51.pdfISSN 1516-8093
CNN-based fast source device identification
Source identification is an important topic in image forensics, since it
allows to trace back the origin of an image. This represents a precious
information to claim intellectual property but also to reveal the authors of
illicit materials. In this paper we address the problem of device
identification based on sensor noise and propose a fast and accurate solution
using convolutional neural networks (CNNs). Specifically, we propose a
2-channel-based CNN that learns a way of comparing camera fingerprint and image
noise at patch level. The proposed solution turns out to be much faster than
the conventional approach and to ensure an increased accuracy. This makes the
approach particularly suitable in scenarios where large databases of images are
analyzed, like over social networks. In this vein, since images uploaded on
social media usually undergo at least two compression stages, we include
investigations on double JPEG compressed images, always reporting higher
accuracy than standard approaches
RAVEN: a GUI and an Artificial Intelligence Engine in a Dynamic PRA Framework
Increases in computational power and pressure for
more accurate simulations and estimations of accident scenario consequences are driving the need for Dynamic
Probabilistic Risk Assessment (PRA) [1] of very complex models. While more sophisticated algorithms and
computational power address the back end of this challenge, the front end is still handled by engineers that
need to extract meaningful information from the large amount of data and build these complex models.
Compounding this problem is the difficulty in knowledge transfer and retention, and the increasing speed of
software development. The above-described issues would have negatively
impacted deployment of the new high fidelity plant simulator RELAP-7 (Reactor Excursion and Leak
Analysis Program) at Idaho National Laboratory. Therefore, RAVEN that was initially focused to be the
plant controller for RELAP-7 will help mitigate future
RELAP-7 software engineering risks. In order to accomplish such a task Reactor Analysis
and V
Comportamento meteorolĂłgico e sua influĂȘncia na vindima de 2006 na Serra GaĂșcha.
bitstream/CNPUV/8188/1/cot067.pdfISSN 1516-8093
Inkjet printing of flexible organic electrodes for tissue engineering applications
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro TecnolĂłgico, Programa de PĂłs-graduação em CiĂȘncia e Engenharia de Materiais, FlorianĂłpolis, 2012A tecnologia de impressĂŁo por jato de tinta vem demonstrando ser capaz de imprimir todos os materiais necessĂĄrios para a fabricação de circuitos integrados, apresentando baixos custos de fabricação quando comparada Ă s tĂ©cnicas convencionais utilizadas com silĂcio. Com o advento da eletrĂŽnica orgĂąnica, uma ampla gama de materiais tornou-se disponĂvel e a fabricação de dispositivos com propriedades Ășnicas com a interface biolĂłgica Ă© agora possĂvel. Um exemplo importante Ă© a utilização de eletrodos metĂĄlicos revestidos com polĂmeros condutores implantados no sistema nervoso central, proporcionando estimulação elĂ©trica aos neurĂŽnios. Este trabalho relata a fabricação de dispositivos orgĂąnicos biocompatĂveis por meio da tecnologia de impressĂŁo por jato de tinta, utilizando-se uma nova combinação de materiais. Os dispositivos foram fabricados sobre um substrato de Parileno C (PaC), um polĂmero flexĂvel e biocompatĂvel. As linhas condutoras foram impressas utilizando-se uma tinta de nanopartĂculas de prata, enquanto os sĂtios ativos foram impressos usando-se uma tinta de poli (3,4-etilenodioxitiofeno)/poliestireno sulfonado (PEDOT: PSS). Para isolar o dispositivo final foi utilizada uma tinta de poliimida para imprimir uma espessa pelĂcula sobre o dispositivo, deixando pequenas janelas abertas sobre os sĂtios ativos de PEDOT:PSS. Caracterização elĂ©trica do dispositivo final e avaliação de sua interface com a biologia (testes de cultura de cĂ©lulas) foram realizadas. Os resultados mostram que um dispositivo biocompatĂvel e de baixo custo pode ser produzido por escrita direta sem quaisquer tĂ©cnicas de pre-patterning ou de auto-alinhamento, utilizando-se tintas orgĂąnicas. Abstract : Inkjet printing has been demonstrated to be able to print all materials required for integrated circuits at low costs when compared to conventional silicon processing. With the advent of organic electronics, a wide range of materials became available and the fabrication of devices with unique properties for interfacing with biology is now possible. One important example is the use of conducting polymer coatings on metal electrodes that are implanted in the central nervous system, which provides electrical stimulation of neurons. This work reports on the fabrication of biocompatible organic devices by means of inkjet printing with a novel combination of materials. The devices were fabricated on Parylene C (PaC), a biocompatible, flexible polymer substrate. The contact tracks were printed using a silver nanoparticle ink, while the active sites were inkjet printed using a poly (3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS) solution. To insulate the final device, a polyimide ink was used to print a thick film, leaving small opened windows upon the active sites. Electrical characterization of the final device and evaluation of its interface with biology (cells culture assays) were performed. The results show that inexpensive and biocompatible devices can be produced by direct writing without any pre-patterning or self-alignment techniques using organic inks
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