Impact of gaps in the asteroseismic characterization of pulsating stars. I. On the efficiency of pre-whitening

It is known that the observed distribution of frequencies in CoRoT and Kepler {\delta} Scuti stars has no parallelism with any theoretical model. Pre-whitening is a widespread technique in the analysis of time series with gaps from pulsating stars located in the classical instability strip such as {\delta} Scuti stars. However, some studies have pointed out that this technique might introduce biases in the results of the frequency analysis. This work aims at studying the biases that can result from pre-whitening in asteroseismology. The results will depend on the intrinsic range and distribution of frequencies of the stars. The periodic nature of the gaps in CoRoT observations, just in the range of the pulsational frequency content of the {\delta} Scuti stars, is shown to be crucial to determine their oscillation frequencies, the first step to perform asteroseismolgy of these objects. Hence, here we focus on the impact of pre-whitening on the asteroseismic characterization of {\delta} Scuti stars. We select a sample of 15 {\delta} Scuti stars observed by the CoRoT satellite, for which ultra-high quality photometric data have been obtained by its seismic channel. In order to study the impact on the asteroseismic characterization of {\delta} Scuti stars we perform the pre-whitening procedure on three datasets: gapped data, linearly interpolated data, and ARMA interpolated data. The different results obtained show that at least in some cases pre-whitening is not an efficient procedure for the deconvolution of the spectral window. therefore, in order to reduce the effect of the spectral window to the minimum it is necessary to interpolate with an algorithm that is aimed to preserve the original frequency content, and not only to perform a pre-whitening of the data.Comment: 27 pages, 47 figures Tables and typos fixe

Fractal analysis applied to light curves of δ\delta Scuti stars

Fractal behaviour, i.e. scale invariance in spatio-temporal dynamics, have been found to describe and model many systems in nature, in particular fluid mechanics and geophysical related geometrical objects, like the convective boundary layer of cumulus cloud fields, topographic landscapes, solar granulation patterns, and observational astrophysical time series, like light curves of pulsating stars. The main interest in the study of fractal properties in such physical phenomena lies in the close relationships they have with chaotic and turbulent dynamic. In this work we introduce some statistical tools for fractal analysis of light curves: Rescaled Range Analysis (R/S), Multifractal Spectra Analysis, and Coarse Graining Spectral Analysis (CGSA), an FFT based algorithm, which can discriminate in a time series the stochastic fractal power spectra from the harmonic one. An interesting application of fractal analysis in asteroseismology concerns the joint use of all these tools in order to develop classification criteria and algorithms for {\delta}-Scuti pulsating stars. In fact from the fractal and multi-fractal fingerprints in background noise of light curves we could infer on different mechanism of stellar dynamic, among them rotation, modes excitation and magnetic activity.Comment: 13 pages, 10 figure

Design of a Segmentation and Classification System for Seed Detection Based on Pixel Intensity Thresholds and Convolutional Neural Networks

Due to the computational power and memory of modern computers, computer vision techniques and neural networks can be used to develop a visual inspection system of agricultural products to satisfy product quality requirements. This chapter employs artificial vision techniques to classify seeds in RGB images. As a first step, an algorithm based on pixel intensity threshold is developed to detect and classify a set of different seed types, such as rice, beans, and lentils. Then, the information inferred by this algorithm is exploited to develop a neural network model, which successfully achieves learning classification and detection tasks through a semantic-segmentation scheme. The applicability and satisfactory performance of the proposed algorithms are illustrated by testing with real images, achieving an average accuracy of 92% in the selected set of classes. The experimental results verify that both algorithms can directly detect and classify the proposed set of seeds in input RGB images. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG

Seismology of beta Cephei stars: differentially-rotating models for interpreting the oscillation spectrum of nu-Eridani

A method for the asteroseismic analysis of beta Cephei stars is presented and applied to the star nu Eridani. The method is based on the analysis of rotational splittings, and their asymmetries using differentially-rotating asteroseismic models. Models with masses around 7.13 M_sun, and ages around 14.9 Myr, were found to fit better 10 of the 14 observed frequencies, which were identified as the fundamental radial mode and the three L=1 triplets g, p, and p. The splittings and aymmetries found for these modes recover those provided in the literature, except for p. For this last mode, all its non-axysimmetric components are predicted by the models. Moreover, opposite signs of the observed and predicted splitting asymmetries are found. If identification is confirmed, this can be a very interesting source of information about the internal rotation profile, in particular in the outer regions of the star. In general, the seismic models which include a description for shellular rotation yield slightly better results as compared with those given by uniformly-rotating models. Furthermore, we show that asymmetries are quite dependent on the overshooting of the convective core, which make the present technique suitable for testing the theories describing the angular momentum redistribution and chemical mixing due to rotationally-induced turbulence.Comment: 11 pages, 9 figures, 8 tables. ApJ (in press

Resistive switching and charge transport mechanisms in ITO/ZnO/p-Si devices

[EN] The resistive switching properties of ITO/ZnO/p-Si devices have been studied, which present well-defined resistance states with more than five orders of magnitude difference in current. Both the high resistance state (HRS) and the low resistance state (LRS) were induced by either sweeping or pulsing the voltage, observing some differences in the HRS. Finally, the charge transport mechanisms dominating the pristine, HRS, and LRS states have been analyzed in depth, and the obtained structural parameters suggest a partial re-oxidation of the conductive nanofilaments and a reduction of the effective conductive area.This work was financially supported by the Spanish Ministry of Economy and Competitiveness (Project Nos. TEC2012-38540-C02-01 and TEC2016-76849-C2-1-R). O.B. also acknowledges the subprogram "Ayudas para Contratos Predoctorales para la Formacion de Doctores" of the Spanish Ministry of Economy and Competitiveness for economical support. X.P., C.L., and C.G. are grateful to C. Frilay for his expertise in the maintenance of the sputtering kit used for the growth of the ZnO films.Blázquez, O.; Frieiro, J.; López-Vidrier, J.; Guillaume, C.; Portier, X.; Labbé, C.; Sanchis Kilders, P.... (2018). Resistive switching and charge transport mechanisms in ITO/ZnO/p-Si devices. Applied Physics Letters. 113(18):1-6. https://doi.org/10.1063/1.50469111611318I. G. Baek , M. S. Lee , S. Sco , M. J. Lee , D. H. Seo , D.S. Suh , J. C. Park , S. O. Park , H. S. Kim , I. K. Yoo , U.I. Chung , and J. T. Moon , in IEDM Technical Digest. IEEE International Electron Devices Meeting, 2004 ( IEEE, 2004), pp. 587–590.Waser, R., & Aono, M. (2007). Nanoionics-based resistive switching memories. Nature Materials, 6(11), 833-840. doi:10.1038/nmat2023Kaeriyama, S., Sakamoto, T., Sunamura, H., Mizuno, M., Kawaura, H., Hasegawa, T., … Aono, M. (2005). A nonvolatile programmable solid-electrolyte nanometer switch. IEEE Journal of Solid-State Circuits, 40(1), 168-176. doi:10.1109/jssc.2004.837244Strukov, D. B., & Likharev, K. K. (2005). CMOL FPGA: a reconfigurable architecture for hybrid digital circuits with two-terminal nanodevices. Nanotechnology, 16(6), 888-900. doi:10.1088/0957-4484/16/6/045Mehonic, A., Cueff, S., Wojdak, M., Hudziak, S., Jambois, O., Labbé, C., … Kenyon, A. J. (2012). Resistive switching in silicon suboxide films. Journal of Applied Physics, 111(7), 074507. doi:10.1063/1.3701581Mehonic, A., Vrajitoarea, A., Cueff, S., Hudziak, S., Howe, H., Labbé, C., … Kenyon, A. J. (2013). Quantum Conductance in Silicon Oxide Resistive Memory Devices. Scientific Reports, 3(1). doi:10.1038/srep02708Pickett, M. D., Medeiros-Ribeiro, G., & Williams, R. S. (2012). A scalable neuristor built with Mott memristors. Nature Materials, 12(2), 114-117. doi:10.1038/nmat3510Jo, S. H., Chang, T., Ebong, I., Bhadviya, B. B., Mazumder, P., & Lu, W. (2010). Nanoscale Memristor Device as Synapse in Neuromorphic Systems. Nano Letters, 10(4), 1297-1301. doi:10.1021/nl904092hVescio, G., Crespo-Yepes, A., Alonso, D., Claramunt, S., Porti, M., Rodriguez, R., … Aymerich, X. (2017). Inkjet Printed HfO2-Based ReRAMs: First Demonstration and Performance Characterization. IEEE Electron Device Letters, 38(4), 457-460. doi:10.1109/led.2017.2668599Valov, I. (2013). Redox-Based Resistive Switching Memories (ReRAMs): Electrochemical Systems at the Atomic Scale. ChemElectroChem, 1(1), 26-36. doi:10.1002/celc.201300165Martín, G., González, M. B., Campabadal, F., Peiró, F., Cornet, A., & Estradé, S. (2017). Transmission electron microscopy assessment of conductive-filament formation in Ni–HfO2–Si resistive-switching operational devices. Applied Physics Express, 11(1), 014101. doi:10.7567/apex.11.014101Simanjuntak, F. M., Panda, D., Wei, K.-H., & Tseng, T.-Y. (2016). Status and Prospects of ZnO-Based Resistive Switching Memory Devices. Nanoscale Research Letters, 11(1). doi:10.1186/s11671-016-1570-yKim, J., & Yong, K. (2011). Mechanism Study of ZnO Nanorod-Bundle Sensors for H2S Gas Sensing. The Journal of Physical Chemistry C, 115(15), 7218-7224. doi:10.1021/jp110129fYuan, Q., Zhao, Y.-P., Li, L., & Wang, T. (2009). Ab Initio Study of ZnO-Based Gas-Sensing Mechanisms: Surface Reconstruction and Charge Transfer. The Journal of Physical Chemistry C, 113(15), 6107-6113. doi:10.1021/jp810161jSeo, J. W., Park, J.-W., Lim, K. S., Yang, J.-H., & Kang, S. J. (2008). Transparent resistive random access memory and its characteristics for nonvolatile resistive switching. Applied Physics Letters, 93(22), 223505. doi:10.1063/1.3041643Rahaman, S. Z., Maikap, S., Chiu, H.-C., Lin, C.-H., Wu, T.-Y., Chen, Y.-S., … Tsai, M.-J. (2010). Bipolar Resistive Switching Memory Using Cu Metallic Filament in Ge[sub 0.4]Se[sub 0.6] Solid Electrolyte. Electrochemical and Solid-State Letters, 13(5), H159. doi:10.1149/1.3339449Simanjuntak, F. M., Panda, D., Tsai, T.-L., Lin, C.-A., Wei, K.-H., & Tseng, T.-Y. (2015). Enhancing the memory window of AZO/ZnO/ITO transparent resistive switching devices by modulating the oxygen vacancy concentration of the top electrode. Journal of Materials Science, 50(21), 6961-6969. doi:10.1007/s10853-015-9247-ySimanjuntak, F. M., Prasad, O. K., Panda, D., Lin, C.-A., Tsai, T.-L., Wei, K.-H., & Tseng, T.-Y. (2016). Impacts of Co doping on ZnO transparent switching memory device characteristics. Applied Physics Letters, 108(18), 183506. doi:10.1063/1.4948598Simanjuntak, F. M., Panda, D., Tsai, T.-L., Lin, C.-A., Wei, K.-H., & Tseng, T.-Y. (2015). Enhanced switching uniformity in AZO/ZnO1−x/ITO transparent resistive memory devices by bipolar double forming. Applied Physics Letters, 107(3), 033505. doi:10.1063/1.4927284Liu, Q., Guan, W., Long, S., Jia, R., Liu, M., & Chen, J. (2008). Resistive switching memory effect of ZrO[sub 2] films with Zr[sup +] implanted. Applied Physics Letters, 92(1), 012117. doi:10.1063/1.2832660Shuai, Y., Zhou, S., Bürger, D., Helm, M., & Schmidt, H. (2011). Nonvolatile bipolar resistive switching in Au/BiFeO3/Pt. Journal of Applied Physics, 109(12), 124117. doi:10.1063/1.3601113Chen, J.-Y., Hsin, C.-L., Huang, C.-W., Chiu, C.-H., Huang, Y.-T., Lin, S.-J., … Chen, L.-J. (2013). Dynamic Evolution of Conducting Nanofilament in Resistive Switching Memories. Nano Letters, 13(8), 3671-3677. doi:10.1021/nl4015638Hubbard, W. A., Kerelsky, A., Jasmin, G., White, E. R., Lodico, J., Mecklenburg, M., & Regan, B. C. (2015). Nanofilament Formation and Regeneration During Cu/Al2O3 Resistive Memory Switching. Nano Letters, 15(6), 3983-3987. doi:10.1021/acs.nanolett.5b00901Liu, Q., Sun, J., Lv, H., Long, S., Yin, K., Wan, N., … Liu, M. (2012). Real-Time Observation on Dynamic Growth/Dissolution of Conductive Filaments in Oxide-Electrolyte-Based ReRAM. Advanced Materials, 24(14), 1844-1849. doi:10.1002/adma.201104104Zhu, X., Wu, H.-Z., Qiu, D.-J., Yuan, Z., Jin, G., Kong, J., & Shen, W. (2010). Photoluminescence and resonant Raman scattering in N-doped ZnO thin films. Optics Communications, 283(13), 2695-2699. doi:10.1016/j.optcom.2010.03.006Cerqueira, M. F., Vasilevskiy, M. I., Oliveira, F., Rolo, A. G., Viseu, T., Ayres de Campos, J., … Correia, R. (2011). Resonant Raman scattering in ZnO:Mn and ZnO:Mn:Al thin films grown by RF sputtering. Journal of Physics: Condensed Matter, 23(33), 334205. doi:10.1088/0953-8984/23/33/334205Marchewka, A., Roesgen, B., Skaja, K., Du, H., Jia, C.-L., Mayer, J., … Menzel, S. (2015). Nanoionic Resistive Switching Memories: On the Physical Nature of the Dynamic Reset Process. Advanced Electronic Materials, 2(1), 1500233. doi:10.1002/aelm.201500233Krzywiecki, M., Grządziel, L., Sarfraz, A., Iqbal, D., Szwajca, A., & Erbe, A. (2015). Zinc oxide as a defect-dominated material in thin films for photovoltaic applications – experimental determination of defect levels, quantification of composition, and construction of band diagram. Physical Chemistry Chemical Physics, 17(15), 10004-10013. doi:10.1039/c5cp00112aMurgatroyd, P. N. (1970). Theory of space-charge-limited current enhanced by Frenkel effect. Journal of Physics D: Applied Physics, 3(2), 151-156. doi:10.1088/0022-3727/3/2/308Electron emission in intense electric fields. (1928). Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, 119(781), 173-181. doi:10.1098/rspa.1928.0091Özgür, Ü., Alivov, Y. I., Liu, C., Teke, A., Reshchikov, M. A., Doğan, S., … Morkoç, H. (2005). A comprehensive review of ZnO materials and devices. Journal of Applied Physics, 98(4), 041301. doi:10.1063/1.1992666Kaidashev, E. M., Lorenz, M., von Wenckstern, H., Rahm, A., Semmelhack, H.-C., Han, K.-H., … Grundmann, M. (2003). High electron mobility of epitaxial ZnO thin films on c-plane sapphire grown by multistep pulsed-laser deposition. Applied Physics Letters, 82(22), 3901-3903. doi:10.1063/1.1578694Gall, D. (2016). Electron mean free path in elemental metals. Journal of Applied Physics, 119(8), 085101. doi:10.1063/1.4942216Lee, W., Park, J., Kim, S., Woo, J., Shin, J., Choi, G., … Hwang, H. (2012). High Current Density and Nonlinearity Combination of Selection Device Based on TaOx/TiO2/TaOx Structure for One Selector–One Resistor Arrays. ACS Nano, 6(9), 8166-8172. doi:10.1021/nn3028776Kwon, D.-H., Kim, K. M., Jang, J. H., Jeon, J. M., Lee, M. H., Kim, G. H., … Hwang, C. S. (2010). Atomic structure of conducting nanofilaments in TiO2 resistive switching memory. Nature Nanotechnology, 5(2), 148-153. doi:10.1038/nnano.2009.456Choi, B. J., Torrezan, A. C., Strachan, J. P., Kotula, P. G., Lohn, A. J., Marinella, M. J., … Yang, J. J. (2016). High‐Speed and Low‐Energy Nitride Memristors. Advanced Functional Materials, 26(29), 5290-5296. doi:10.1002/adfm.201600680Sun, X. (2006). Designing efficient field emission into ZnO. SPIE Newsroom. doi:10.1117/2.1200602.0101Hu, C., Wang, Q., Bai, S., Xu, M., He, D., Lyu, D., & Qi, J. (2017). The effect of oxygen vacancy on switching mechanism of ZnO resistive switching memory. Applied Physics Letters, 110(7), 073501. doi:10.1063/1.4976512Gul, F., & Efeoglu, H. (2017). Bipolar resistive switching and conduction mechanism of an Al/ZnO/Al-based memristor. Superlattices and Microstructures, 101, 172-179. doi:10.1016/j.spmi.2016.11.043Blázquez, O., Martín, G., Camps, I., Mariscal, A., López-Vidrier, J., Ramírez, J. M., … Garrido, B. (2018). Memristive behaviour of Si-Al oxynitride thin films: the role of oxygen and nitrogen vacancies in the electroforming process. Nanotechnology, 29(23), 235702. doi:10.1088/1361-6528/aab744Bersuker, G., Gilmer, D. C., Veksler, D., Kirsch, P., Vandelli, L., Padovani, A., … Nafría, M. (2011). Metal oxide resistive memory switching mechanism based on conductive filament properties. Journal of Applied Physics, 110(12), 124518. doi:10.1063/1.367156

A comprehensive asteroseismic modelling of the high-amplitude delta Scuti star RV Arietis

We present a comprehensive asteroseismic study of the double-mode high-amplitude delta Scuti star HD 187642 (RV Arietis). The modelling includes some of the most recent techniques: 1) effects of rotation on both equilibrium models and adiabatic oscillation spectrum, 2) non-adiabatic study of radial and non-radial modes, 3) relationship between the fundamental radial mode and the first overtone in the framework of Petersen diagrams. The analysis reveals that two of the observed frequencies are very probably identified as the fundamental and first overtone radial modes. Analysis of the colour index variations, together with theoretical non-adiabatic calculations, points to models in the range of [7065,7245] K in effective temperature and of [1190, 1270] Myr in stellar age. These values were found to be compatible with those obtained using the three other asteroseismic techniques.Comment: accepted for publication in A&