Short-range stationary patterns and long-range disorder in an evolution equation for one-dimensional interfaces

A novel local evolution equation for one-dimensional interfaces is derived in the context of erosion by ion beam sputtering. We present numerical simulations of this equation which show interrupted coarsening in which an ordered cell pattern develops with constant wavelength and amplitude at intermediate distances, while the profile is disordered and rough at larger distances. Moreover, for a wide range of parameters the lateral extent of ordered domains ranges up to tens of cells. This behavior is new in the context of dynamics of surfaces or interfaces with morphological instabilities. We also provide analytical estimates for the stationary pattern wavelength and mean growth velocity

Non-linear ripple dynamics on amorphous surfaces patterned by ion-beam sputtering

Erosion by ion-beam sputtering (IBS) of amorphous targets at off-normal incidence frequently produces a (nanometric) rippled surface pattern, strongly resembling macroscopic ripples on aeolian sand dunes. Suitable generalization of continuum descriptions of the latter allows us to describe theoretically for the first time the main nonlinear features of ripple dynamics by IBS, namely, wavelength coarsening and non-uniform propagation velocity, that agree with similar results in experiments and discrete models. These properties are seen to be the anisotropic counterparts of in-plane ordering and (interrupted) pattern coarsening in IBS experiments on rotating substrates and at normal incidence.Comment: 5 pages, 3 figure

Anomalous scaling in a non local growth model in the Kardar-Parisi-Zhang universality class

We study the interface dynamics of a discrete model to quantitatively describe electrochemical deposition experiments. Extensive numerical simulations indicate that the interface dynamics is unstable at early times, but asymptotically displays the scaling of the Kardar-Parisi-Zhang universality class. During the time interval in which the surface is unstable, its power spectrum is anomalous; hence the behaviors at length scales smaller than or comparable with the system size are described by different roughness exponents. These results are expected to apply to a wide range of electrochemical deposition experiments.Comment: REVTEX (4 pages) and three figures (postscript), to be published in PRE (rapid communication, March, 1998

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Possible origin for the experimental scarcity of KPZ scaling in non-conserved surface growth

8 pages, 1 figure.-- PACS nrs.: 68.35.Ct; 64.60.Ht; 81.15.Gh; 81.15.Pq.-- MSC2000 codes: 82D20, 35Q53.Dedicated to H.E. Stanley on the occasion of his 60th birthday.Zbl#: Zbl 1001.82109The Kardar–Parisi–Zhang (KPZ) equation is generically expected to describe the scaling properties of rough surfaces growing in the absence of conservation laws. However, very few experimental realizations are known of this universality class. Here we focus on the role of instabilities, whether of diffusional origin or other, as physical mechanisms hindering the observation of KPZ scaling. Examples are drawn from various growth processes, such as electrochemical deposition (ECD), chemical vapor deposition (CVD), and erosion by ion-beam sputtering. We moreover consider an interface equation which, starting from the corresponding constitutive equations, can be derived to describe growth by either ECD or CVD depending on the interpretation of the quantities appearing. This approach makes contact with phenomenological parameters, and suggests that a more generic description of non-conserved growth may be provided by the Kuramoto–Sivashinsky equation and generalizations thereof. In this case, the experimental scarcity of KPZ scaling would be due to exceedingly long transients determined by the instabilities that occur.Work partially supported by DGES (Spain) Grant No. BFM2000-0006.Publicad

Comment on "Kinetic roughening of ion-sputtered Pd(001) surface: beyond the Kuramoto-Sivashinsky model"

1 page, no figures.-- PACS nrs.: 68.55.–a, 05.45.–a, 64.60.Cn, 79.20.Rf.A comment on the Letter by T. C. Kim et al., Phys. Rev. Lett. 92, 246104 (2004), http://dx.doi.org/10.1103/PhysRevLett.92.246104. The authors of the Letter offer a reply.This work has been partially supported by MECD (Spain) Grants No. BFM2003-07749-C05, No. -05 (M. C.), and No. -01 (R. C.).Publicad

Transients due to instabilities hinder Kardar-Parisi-Zhang scaling: a unified derivation for surface growth by electrochemical and chemical vapor deposition

4 pages, no figures.-- PACS nrs.: 68.35.Ct, 64.60.Ht, 81.15.Gh, 81.15.Pq.We propose a unified moving boundary problem for surface growth by electrochemical and chemical vapor deposition, which is derived from constitutive equations into which stochastic forces are incorporated. We compute the coefficients in the interface equation of motion as functions of phenomenological parameters. The equation features the Kardar-Parisi-Zhang (KPZ) nonlinearity and instabilities which, depending on surface kinetics, can hinder the asymptotic KPZ scaling. Our results account for the universality and the experimental scarcity of KPZ scaling in the growth processes considered.This work has been supported by DGES (Spain) Grant No. BFM2000-0006.Publicad

Anti Spoofing Face Detection Technique based on Transfer Learning Convolutional Neural Networks and Real-Time Facial Landmark Detection*

International audienceDespite the fact that current Facial Recognition (FR) models like FaceNet or many AI Web Services (e.g. AWS Rekognition) work very well recognizing people using One-shot learning, they are not able to detect if the face in front of the camera is genuine or not (e.g. face in a video replay). This is critical because many serious consequences may happen if anybody could successfully attack financial or government services that work with facial recognition system. This problem is known as Spoofing Attack and many state-of-art papers in computer vision focus in detecting noise, use Local Binary Patterns, use special hardware that measure depth or light reflection with different colors on faces, but new approaches of Deep Learning can make possible an end-to-end learning such as Transfer Learning (CNNs). The main contribution of this work-in-progress is that it uses a new embedded system that only works with face recognition techniques and were tested in 3 different datasets: CASIA, MSU USAA and a local dataset we prepared and named UNI-PUCP that shares attributes with CASIA Attack, Replay Mobile, MSU USAA and SiW dataset

Kinetic roughening in a realistic model of non-conserved interface growth

We provide a quantitative picture of non-conserved interface growth from a diffusive field making special emphasis on two main issues, the range of validity of the effective small-slopes (interfacial) theories and the interplay between the emergence of morphologically instabilities in the aggregate dynamics, and its kinetic roughening properties. Taking for definiteness electrochemical deposition as our experimental field of reference, our theoretical approach makes use of two complementary approaches: interfacial effective equations and a phase-field formulation of the electrodeposition process. Both descriptions allow us to establish a close quantitative connection between theory and experiments. Moreover, we are able to correlate the anomalous scaling properties seen in some experiments with the failure of the small slope approximation, and to assess the effective re-emergence of standard kinetic roughening properties at very long times under appropriate experimental conditions.Comment: Journal of Statistical Mechanics: Theory & Experiment, in pres