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Comments on "Non-existence of Shilnikov chaos in continuous-time systems"

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Applied Mathematics and Mechanics(English Edition) 2013年第9期34卷 1175-1176页

作者： A.ALGABA F.FERNANdeZ-SANCHEZ M.MERINO A.J.RODRIGUEZ-LUIS departamento de Matematicas Centro de Investigacion de Fisica Teorica y Matematica FIMATUniversity of Huelva departamento de Matematica Aplicada II E.S.IngenierosUniversity of Sevilla Camino de los Descubrimientos s/n

A paper, ＂Non-existence of Shilnikov chaos in continuous-time systems＂ was published in the journal Applied Mathematics and Mechanics （English Edition）. The authors gave sufficient conditions for the non-existence of homoclinic and heteroclinic orbits in an nth-order autonomous system. Unfortunately, we show in this comment that the proof presented is erroneous and the result is invalid. We also provide two counterexamples of the wrong criterion stated by the authors.

关键词： homoclinic chaos heteroclinic chaos non-existence of Shilnikov chaos

Spectroscopic investigations on Yb^3+ doped and Pr^3+/Yb^3+ codoped tellurite glasses for photonic applications

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Journal of Rare Earths 2021年第1期39卷 33-42,I0002页

作者： M.Seshadri M.J.V.Bell V.Anjos Y.Messaddeq Grupo de Engenharia e Espectroscopia de Materiais Departamento de Fisica-ICEUniversidade Federal de Juiz de ForaJuiz de ForaMG36036-900Brazil Centre d'Optique Photonique et Laser2375 Rue de la TerrasseUniversite LavalQuebecQCG1V 0A6Canada

In this work we repo rt on structural and spect roscopic properties of Yb^3+doped and Pr^3+/Yb^3+co-doped TeO2-Bi2 O3-ZnO-Li2 O-Nb2 O5(TBZLN)tellurite *** and stretching modes of TeO2 and Te-OH bond(strong and weak)were analysed from the deconvolution of observed Raman and FT-IR *** on the absorption measurements,the energy bands of Yb^3+and Pr^3+ions are *** spectroscopic properties for the radiative transitions of Yb^3+and Pr^3+ions were reported using McCumber and Judd-Ofelt *** emission bands originating from 3 P1 and 3 P0 to lower lying levels of Pr^3+were registered under 447 nm *** emission band around 1334 nm assigned to the Pr3:1 G4→3 H5 was observed when excited at 980 *** stimulated emission cross-section(σemi(λ))and effective linewidth(Δλeff)for the 3 P1→3 H6,3 P1→3 H5,3 P0→3 H6,3 P0→3 F2,3 P1→3 F3,3 P1→3 F4,3 P0→3 F4 and 1 G4→3 H5 transitions of Pr^3+are *** luminescence in Pr^3+/Yb^3+codoped glass upon 980 nm excitation was *** resonant transfer processes between Yb^3+and Pr^3+ions are presented and *** chromaticity co-ordinates were also evaluated from the visible emission spectra showing that Pr^3+/Yb^3+co-doped glass may be suitable for the development of yellow-orange(λexc=447 nm)and near white light(λexc=980 nm)emitting devices in photonics.

关键词： Rare earth ions Tellurite glass Spectroscopic properties Upconversion luminescence

Comparison of Electron Acceleration Ability of SiO_2 and ZnS fromZnS∶Er Transient Electroluminescence

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Journal of Rare Earths 2006年第3期24卷 298-301页

作者：张福俊徐征刘玲孟立建 Key Laboratory of Luminescence and Optical Information Ministry of Education Institute of Optoelectronic Technology Beijing Jiaotong University Beijing 100044 China Key Laboratory of Luminescence and Optical Information Ministry of Education Institute of Optoelectronic Technology Beijing Jiaotong University Beijing 100044 ChinaDepartmento de Fisica Instituto Superior de Engenharia do Porto 4200-072 Porto Protugal departmento de fisica Instituto Superior de Engenharia do Porto 4200-072 Porto Protugal

The acceleration ability of electrons in SiO2 and ZnS was compared through the variation of emission intensity based on ZnS ： Er electroluminescence during the reverse of polarity of sinusoidal voltage. In order to avoid the influence of work function of electrode, cathodal and anodal materials were ITO （indium tin oxide）. The ratio of maximum emission intensity under positive and negative half period is 2.18. This result demonstrates that the electron acceleration ability of SiO2 is 2.18 times stronger than that of ZnS.

关键词： electron acceleration rare earths

Engineering magnetic nanostructures with inverse hysteresis loops

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Nano Research 2016年第8期9卷 2347-2353页

作者： Beatriz Mora Nastassia Soriano Carolina Redondo Alberto Arteche David Navas Rafael Morales Dpto. de Quimica-fisica Universidad del Pais Vasco UPWEHU 48940 Leioa Spain IFIMUP-IN and dept. fisica e Astronomia Universidade do Porto 4169007 Porto Portugal Dpto. de Qulmica-Ffsica & BCMaterials Universidad del Pals Vasco UPV/EHU 48940 Leioa Spain IKERBASQUE Basque Foundation for Science 48011 Bilbao Spain

Top-down lithography techniques allow the fabrication of nanostructured elements with novel spin configurations, which provide a new route to engineer and manipulate the magnetic response of sensors and electronic devices and understand the role of fundamental interactions in materials science. In this study, shallow nanostructure-patterned thin films were designed to present inverse magnetization curves, i.e., an anomalous magnetic mechanism characterized by a negative coercivity and negative remanence. This procedure involved a method for manipulating the spin configuration that yielded a negative coercivity after the patterning of a single material layer. Patterned NiFe thin films with trench depths between 15%-25% of the total film thickness exhibited inverse hysteresis loops for a wide angular range of the applied field and the trench axis. A model based on two exchange-coupled subsystems accounts for the experimental results and thus predicts the conditions for the appearance of this magnetic behavior. The findings of the study not only advance our understanding of patterning effects and confined magnetic systems but also enable the local design and control of the magnetic response of thin materials with potential use in sensor engineering.

关键词： magnetic nanostructures magnetic patterning effects inverted loops negative coercivity negative remanence

Attosecond twisted beams from high-order harmonicgeneration driven by optical vortices

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High Power Laser Science and Engineering 2017年第1期5卷 12-19页

作者： Carlos Hernandez-Garcia Laura Rego Julio San Roman Antonio Picon Luis Plaja Grupo de Investigacion en Aplicaciones del Laser y Fotonica Departamento de Fisica AplicadaUniversity of SalamancaE-37008SalamancaSpain Argonne National Laboratory Argonne1L 60439USA

Optical vortices are structures of the electromagnetic field with a spiral phase ramp about a point-phase singularity,carrying orbital angular momentum(OAM). Recently, OAM has been imprinted to short-wavelength radiation through high-order harmonic generation(HHG), leading to the emission of attosecond twisted beams in the extreme-ultraviolet(XUV) regime. We explore the details of the mapping of the driving vortex to its harmonic spectrum. In particular, we show that the geometry of the harmonic vortices is convoluted, arising from the superposition of the contribution from the short and long quantum paths responsible of HHG. Finally, we show how to take advantage of transverse phase-matching to select twisted attosecond beams with different spatiotemporal properties.

关键词： attosecond science extreme-ultraviolet vortices high harmonic generation orbital angular momentum twisted beams vortexbeams

Characterisation of Photocathodes Based on Pb Thin Film deposited by UV Pulsed Laser Ablation

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Journal of Materials Science & Technology 2014年第1期30卷 37-40页

作者： Francisco Gontad Antonella Lorusso Giancarlo Gatti Massimo Ferrario Laura Gioia Passione Luana Persano Nicola Lovergine Alessio Perrone Istituto Nazionale di fisica Nucleare e Università del Salento Università del Salento Dipartimento di Matematica e Fisica "E.De Giorgi" Laboratori Nazionali di Frascati Istituto Nazionale di Fisica Nucleare Center for Biomolecular Nanotechnologies Istituto Italiano di Tecnologia Dipartimento di Ingegneria dell'Innovazione Università del Salento National Nanotechnology Laboratory(NNL)

This work deals with the deposition of lead （Pb） thin films by the UV pulsed laser ablation technique, for their further use as photocathode devices in superconducting radio frequency guns. Scanning electron microscopy and atomic force microscopy analyses were performed to study the morphological features of Pb thin films deposited on Si （100） and Nb substrates. The films showed a granular structure with a nearly fully covered surface only for that one deposited on Nb substrate. X-ray diffraction measurements indicate the growth of polycrystalline Pb thin films with a preferential orientation along （111） planes. Results of the photoemission performance of Pb thin film deposited on Nb substrate showed a very encouraging average value of quantum efficiency of 6 x 10-5 through a single-photon absorption process, promoting further studies in the realisation of Pb photocathodes by this technique.

关键词： Pulsed laser deposition Lead thin film Metallic photocathodes Quantum efficiency

Relativistic Landau quantization in the spiral dislocation spacetime

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Communications in Theoretical Physics 2021年第2期73卷 68-72页

作者： A V D M Maia K Bakke departamento de fisica Universijade Federal da ParaibaCaixa Postal 500858051-900Joao PessoaPBBrazil

We analyse the interaction of a relativistic electron with a uniform magnetic field in the spiral dislocation *** show that analytical solutions to the Dirac equation can be obtained,where the spectrum of energy corresponds to the relativistic Landau *** also analyse the influence of the spiral dislocation on the relativistic Landau levels by showing that there exists an analogue of the Aharonov–Bohm effect for bound states.

关键词： spiral dislocation spacetime relativistic Landau quantization Aharonov-Bohm effect relativistic wave equations Dirac equation

Movement initiation of millimeter particles on a rotating rough surface: The role of adhesion

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Particuology 2020年第6期18卷 92-99页

作者： Karina de los Angeles Valenzuela Aracena Rodolfo O.Unac Irene Ippolito Ana M.Vidales INFAP CONICETDepartamento de FisicaFacultad de Ciencias Fisico Matematicas y NaturalesUniversidad Nacional de San LuisEjercito de los Andes 950D5700HHWSan LuisArgentina Universidad de Buenos Aires Facultad de IngenieriaGrupo de Medios PorososPaseo Colon 850C1063ACV Buenos AiresArgentina

We performed experiments to determine the critical moment for movement initiation of a millimeter bead on a rotating rough *** corresponding critical angular velocities were measured for glass and stainless-steel ball bearings over two different rough surfaces with glued glass beads.A basic theoretical analysis was developed to explain the observed *** the expectation of a simple approach with the presence of the obstacles offered by a rough surface could be sufficient to describe the problem,we prove here that the sole con sideration of these obstacles,and even friction,are insufficient to explain the results in the range of a few-millimeter glass *** the thermodynamic work of adhesion between surfaces is significant,the adhesion forces must be considered in the force balance for particle detachment:.This effect is a determinant for describing theoretically and numerically the dynamics of millimeter particles.

关键词： detachment Adhesion Centrifugation

Seasonality Variability and Periodicities for Ultra-deep Earthquakes Worldwide

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Open Journal of Earthquake Research 2019年第1期8卷 1-18页

作者： Marilia Hagen Anibal Azevedo Retired Universidade Federal Fluminense Instituto de Fisica Niteroi Brazil faculdade de Ciências Aplicadas da Unicamp S&atilde o Paulo Brazil

Our last study found that deepest-depth earthquakes with larger magnitudes (M6 or above) showed seasonality, which is dependent on the area searched. The main results indicated strong evidence that the causes for the delays in enhancements along the period investigated were due to the tectonics also, not only the season. Therefore, if the inquiry was about an area in Northern Hemisphere, the season in which the increases occurred is different than the season in the Southern Hemisphere. Also, higher latitudes in the Northern Hemisphere or around the Equator, displayed seasonality similarly where the tremors appear to increase during the Spring and Summer. This did not happen to the Southern Hemisphere where disturbances and anomalies occurred without showing much connection to the seasons in the analyzed period. However, some of the regions presented periodicities independent from the seasons.

关键词： Seasons Subduction Zones Earthquakes Periodicity South Hemisphere