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Maeta, S., Y. Kamitani, M. Yoshiura i T. Nukuto. "Behavior of the discrete energy states". IEEE Transactions on Dielectrics and Electrical Insulation 8, nr 3 (czerwiec 2001): 461–68. http://dx.doi.org/10.1109/94.933365.
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Rasulov, V. R., R. Ya Rasulov, M. A. Mamatova i F. Qosimov. "Semiclassical theory of electronic states in multilayer semiconductors. Part 2". Journal of Physics: Conference Series 2388, nr 1 (1.12.2022): 012158. http://dx.doi.org/10.1088/1742-6596/2388/1/012158.
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Abstract The electronic states in multilayer semiconductors are studied theoretically in the semiclassical approximation. In this case, the Schrödenger equation is solved, where the potential is expanded into a series along the coordinate and is limited by the first four terms. It is shown that, in this case, the energy spectrum takes on discrete values, and the bending of the energy spectrum increases as the size quantization order increases.
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Rasulov, V. R., R. Ya Rasulov, M. A. Mamatova i F. Qosimov. "Semiclassical theory of electronic states in multilayer semiconductors. Part 1". Journal of Physics: Conference Series 2388, nr 1 (1.12.2022): 012156. http://dx.doi.org/10.1088/1742-6596/2388/1/012156.
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Abstract States of electrons in multilayer semiconductor structures are theoretically investigated in the semiclassical approximation, where one-electron wave functions of the stationary Schrödinger equation are calculated in the presence of various types of potential, which is a slowly varying function of the coordinate. It is determined that the energy spectrum of electrons in the potential in the quadratic approximation takes discrete values and the steepness of the energy spectrum depends on the parameters of the expansion of the potential in coordinates.
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SOUZU, Y., i M. TSUKADA. "ELECTRONIC STATES OF MONOLAYER GRAPHITE COADSORBED WITH ALKALI ATOMS ON Ni(111) SURFACE". Surface Review and Letters 04, nr 06 (grudzień 1997): 1337–40. http://dx.doi.org/10.1142/s0218625x97001772.
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The energy bands of the monolayer graphite (MG) on a Ni(111) surface, and that coadsorbed with alkali atoms, are calculated by the discrete variational Xα method. The π bands at the K point of the original MG show various different features depending on the alkali species and the structure parameters. For the case of the Na and Cs ternary system, the surface reconstruction of the Ni substrate is indicated.
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Ji, Xiaoli, Xiaoyu Tan, Tongbo Wei, Hongxi Lu, Junxi Wang, Fuhua Yang i Jinmin Li. "Discrete energy states induced broadband emission from self-assembly InGaN quantum dots". Optical Materials 94 (sierpień 2019): 237–40. http://dx.doi.org/10.1016/j.optmat.2019.05.049.
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Kheifets, Anatoli. "Revealing the Target Electronic Structure with Under-Threshold RABBIITT". Atoms 9, nr 3 (13.09.2021): 66. http://dx.doi.org/10.3390/atoms9030066.
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The process of reconstruction of attosecond beating by interference of two-photon transitions (RABBITT) reveals the target atom electronic structure when one of the transitions proceeds from below the ionization threshold. Such an under-threshold RABBITT resonates with the target bound states and thus maps faithfully the discrete energy levels and the corresponding oscillator strengths. We demonstrate this sensitivity by considering the Ne atom driven by the combination of the XUV and IR pulses at the fundmanetal laser frequency in the 800 and 1000 nm ranges.
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Li, Zhi, Jincheng Zhuang, Li Wang, Haifeng Feng, Qian Gao, Xun Xu, Weichang Hao i in. "Realization of flat band with possible nontrivial topology in electronic Kagome lattice". Science Advances 4, nr 11 (listopad 2018): eaau4511. http://dx.doi.org/10.1126/sciadv.aau4511.
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The energy dispersion of fermions or bosons vanishes in momentum space if destructive quantum interference occurs in a frustrated Kagome lattice with only nearest-neighbor hopping. A discrete flat band (FB) without any dispersion is consequently formed, promising the emergence of fractional quantum Hall states at high temperatures. Here, we report the experimental realization of an FB with possible nontrivial topology in an electronic Kagome lattice on twisted multilayer silicene. Because of the unique low-buckled two-dimensional structure of silicene, a robust electronic Kagome lattice has been successfully induced by moiré patterns after twisting the silicene multilayers. The electrons are localized in the Kagome lattice because of quantum destructive interference, and thus, their kinetic energy is quenched, which gives rise to an FB peak in the density of states. A robust and pronounced one-dimensional edge state has been revealed at the Kagome edge, which resides at higher energy than the FB. Our observations of the FB and the exotic edge state in electronic Kagome lattice open up the possibility that fractional Chern insulators could be realized in two-dimensional materials.
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Arutyunyan, Rafael V., i Alexander V. Osadchy. "The Systems of Volume-Localized Electron Quantum Levels of Charged Fullerenes". Journal of Nanomaterials 2018 (3.12.2018): 1–10. http://dx.doi.org/10.1155/2018/7526869.
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The existence of a system of short-lived, discrete, volume-localized electron quantum levels in positively charged fullerenes is theoretically and numerically demonstrated using the example of fullerenes C60 and C20. Unlike experimentally and theoretically well-studied electron states localized in a thin surface layer, these electron states are due to the flat part of the Coulomb potential of a positively charged fullerene sphere. The energy width of the system of such discrete volume-localized levels depends on the charge and increases with increasing charge. For C60+1, the energy width is 0.16 a.u. and increases up to 0.9 a.u. for fullerene C60+10. Thus, the electrons captured on these discrete levels of fullerene form a sort of short-lived superheavy “nanoatom” or “nanoion,” in which the electrons are localized inside a positively charged spherical “nucleus” with an atomic mass of 240 a.u. for C20 and 720 a.u. for C60. Numerous published papers have demonstrated theoretically and experimentally the existence of metastable positively charged C60 fullerenes with a charge of +10 or more, which suggests the possibility of experimental observation of the considering system of volume-localized electronic states. In conclusion, questions are discussed and estimates are made of the possibility of generating coherent radiation at these transitions.
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Schuler, Bruno, Katherine A. Cochrane, Christoph Kastl, Edward S. Barnard, Edward Wong, Nicholas J. Borys, Adam M. Schwartzberg, D. Frank Ogletree, F. Javier García de Abajo i Alexander Weber-Bargioni. "Electrically driven photon emission from individual atomic defects in monolayer WS2". Science Advances 6, nr 38 (wrzesień 2020): eabb5988. http://dx.doi.org/10.1126/sciadv.abb5988.
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Quantum dot–like single-photon sources in transition metal dichalcogenides (TMDs) exhibit appealing quantum optical properties but lack a well-defined atomic structure and are subject to large spectral variability. Here, we demonstrate electrically stimulated photon emission from individual atomic defects in monolayer WS2 and directly correlate the emission with the local atomic and electronic structure. Radiative transitions are locally excited by sequential inelastic electron tunneling from a metallic tip into selected discrete defect states in the WS2 bandgap. Coupling to the optical far field is mediated by tip plasmons, which transduce the excess energy into a single photon. The applied tip-sample voltage determines the transition energy. Atomically resolved emission maps of individual point defects closely resemble electronic defect orbitals, the final states of the optical transitions. Inelastic charge carrier injection into localized defect states of two-dimensional materials provides a powerful platform for electrically driven, broadly tunable, atomic-scale single-photon sources.
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ORTEGA, J. E., F. J. HIMPSEL, G. J. MANKEY i R. F. WILLIS. "QUANTUM WELL STATES IN METALLIC THIN LAYERS". Surface Review and Letters 04, nr 02 (kwiecień 1997): 361–70. http://dx.doi.org/10.1142/s0218625x97000365.
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When going from the bulk solid to a thin film of nanometer dimensions, the electronic structure becomes discretized in the perpendicular direction. These discrete states, also called thin film states and quantum well states, are clearly distinguished in photoemission experiments as two-dimensional and thickness-dependent modulations of the bulk spectra, although their observation is limited to highly perfect epitaxial systems. The photoemission data are well explained in the framework of a simple model for the electron wave function in a quantum well state. Thin film states become spin-polarized when growing on ferromagnetic substrates. Furthermore, spin-polarized, thickness-dependent modulations at a given energy lead to spin-dependent periodic oscillations of the density of states as a function of thickness, which are found to be responsible for the oscillatory coupling observed in magnetic multilayers.
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Teterin, Anton, Mikhail Ryzhkov, Yury Teterin, Ernst Kurmaev, Konstantin Maslakov, Kirill Ivanov, Victor Fedorenko i Lyudmila Elohina. "X-ray spectroscopy study of ThO2 and ThF4". Nuclear Technology and Radiation Protection 25, nr 1 (2010): 8–12. http://dx.doi.org/10.2298/ntrp1001008t.
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The structure of the X-ray photoelectron, X-ray O(F)Ka-emission spectra from ThO2 and ThF4 as well as the Auger OKLL spectra from ThO2 was studied. The spectral structure was analyzed by using fully relativistic cluster discrete variational calculations of the electronic structure of the ThO8 D4h) and ThF8 (C2) clusters reflecting thorium close environment in solid ThO2 and ThF4. As a result it was theoretically found and experimentally confirmed that during the chemical bond formation the filled O(F)2p electronic states are distributed mainly in the binding energy range of the outer valence molecular orbitals from 0-13 eV, while the filled O(F)2s electronic states - in the binding energy range of the inner valence molecular orbitals from 13-35 eV. It was shown that the Auger OKLL spectral structure from ThO2 characterizes not only the O2p electronic state density distribution, but also the O2s electronic state density distribution. It agrees with the suggestion that O2s electrons participate in formation of the inner valence molecular orbitals, in the binding energy range of 13-35 eV. The relative Auger OKL2-3L2-3 peak intensity was shown to reflect quantitatively the O2p electronic state density of the oxygen ion in ThO2.
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ARISTOV, V. YU, G. LE LAY, M. GREHK, V. M. ZHILIN, A. TALEB-IBRAHIMI, G. INDLEKOFER i P. SOUKIASSIAN. "CESIUM-INDUCED QUANTIZED 2D ELECTRON CHANNEL ON THE InAs(110) SURFACE". Surface Review and Letters 02, nr 06 (grudzień 1995): 723–29. http://dx.doi.org/10.1142/s0218625x95000650.
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We present the first clear evidence of electron emission arising directly from a quantized two-dimensional electron channel from the InAs (110) surface covered by a few Cs atoms (≈ 0.01 Cs ML). Spectral features observed by photoemission spectroscopy using synchrotron radiation reveal discrete-energy electronic states resulting from quantization in the direction normal to the surface. The electron photoemission originates from the vicinities of [Formula: see text] points in the first and second surface Brillouin zones corresponding to the bottom of the conduction band. These findings are in agreement with self-consistent theoretical energy-level calculations using a jellium-like model.
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Radwanski, R. J., D. M. Nalecz i Z. Ropka. "Charge and crystal field electronic states in CeRh2Si2 and Ba2IrO4". Journal of Physics: Conference Series 2164, nr 1 (1.03.2022): 012058. http://dx.doi.org/10.1088/1742-6596/2164/1/012058.
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Abstract We point out the scientific importance of the increasing evidence for the existence of the discrete low-energy meV-energy states in compounds containing atoms with incomplete 4f, 5f, 3d shells and recently in iridates (5d shell). We point out that the realized charge state of the 3d/4f/5f/4d/5d atoms/ions in oxides is very close to the formal one obtained within the ionic model. In Ba2IrO4 the charge states are very close to Ba2+, Ir4+ and O2−. In CeRh2Si2, which is intermetallic and considered as a Kondo-lattice antiferromagnet, by detailed analysis of temperature dependence of the specific heat we have proved the realization of the trivalent charge state of practically all cerium ions. In the magnetic state, below TN of 36 K, the Kramers doublet becomes split and there appears a spin gap growing to 6 meV at T = 0 K.
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Chen, Li Qun, i Zheng Chen Qiu. "The Effect of a Light Impurity on the Electronic Structure of Dislocations in NiAl". Defect and Diffusion Forum 318 (lipiec 2011): 23–32. http://dx.doi.org/10.4028/www.scientific.net/ddf.318.23.
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The effect of light impurities (C, N) upon the electronic structure of the [100](010) edge dislocation core in NiAl single crystals is investigated by using the Dmol and the discrete variational method within the framework of density functional theory. The impurity segregation energy, interatomic energy and charge distribution are calculated, and the effects of impurity atoms upon the dislocation motion are discussed. The energy analysis shows that both C and N atoms can stabilize the [100](010) edge dislocation core, and prefer to occupy the interstitial site in the Center-Ni dislocation core. Meanwhile, the impurity atoms can form strong bonding states with their neighboring host atoms via hybridization between the 2p orbitals of the impurity atom and the 3d4s4p orbitals of the host Ni atoms; as well as between the 2p orbitals of the impurity atom and the 3s3p orbitals of the host Al atoms. The strong interaction between impurity atom and host atoms in the dislocation core may improve the strength of NiAl single crystals.
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Teterin, Yury, Konstantin Maslakov, Mikhail Ryzhkov, Anton Teterin, Kirill Ivanov, Stepan Kalmykov, Vladimir Petrov i Dmitry Suglobov. "Electronic structure and chemical bond nature in Cs2PuO2Cl4". Nuclear Technology and Radiation Protection 30, nr 2 (2015): 99–112. http://dx.doi.org/10.2298/ntrp1502099t.
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X-ray photoelectron spectral analysis of dicaesiumtetrachlorodioxoplutonate (Cs2PuO2Cl4) single crystal was done in the binding energy range 0-~35 eV on the basis of binding energies and structure of the core electronic shells (~35 eV-1250 eV), as well as the relativistic discrete variation calculation results for the PuO2Cl4 (D4h). This cluster reflects Pu close environment in Cs2PuO2Cl4 containing the plutonyl group PuO2. The many-body effects due to the presence of cesium and chlorine were shown to contribute to the outer valence (0-~15 eV binding energy) spectral structure much less than to the inner valence (~15 eV- ~35 eV binding energy) one. The filled Pu 5f electronic states were theoretically calculated and experimentally con- firmed to present in the valence band of Cs2PuO2Cl4. It corroborates the suggestion on the direct participation of the Pu 5f electrons in the chemical bond. The Pu 6p atomic orbitals were shown to participate in formation of both the inner and the outer valence molecular orbitals (bands), while the filled Pu 6p and O 2s, Cl 3s electronic shells were found to take the largest part in formation of the inner valence molecular orbitals. The composition of molecular orbitals and the sequence order in the binding energy range 0-~35 eV in Cs2PuO2Cl4 were established. The quantitative scheme of molecular orbitals for Cs2PuO2Cl4 in the binding energy range 0-~15 eV was built on the basis of the experimental and theoretical data. It is fundamental for both understanding the chemical bond nature in Cs2PuO2Cl4 and the interpretation of other X-ray spectra of Cs2PuO2Cl4. The contributions to the chemical binding for the PuO2Cl4 cluster were evaluated to be: the contribution of the outer valence molecular orbitals -66 %, the contribution of the inner valence molecular orbitals -34 %.
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DYADYURA, KONSTANTIN, LIUDMYLA HREBENYK, TIBOR KRENICKY i TADEUSZ ZABOROWSKI. "MODELING OF THE MANUFACTURING SYSTEMS STATE IN THE CONDITIONS OF THE LEAN PRODUCTION". MM Science Journal 2021, nr 2 (2.06.2021): 4408–13. http://dx.doi.org/10.17973/mmsj.2021_6_2021024.
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This article investigates the hierarchy of the manufacturing system, which consists of a set of interrelated processes aimed at converting information, knowledge, energy, materials, and other resources into value for the consumer based on the principles of lean production. Modern manufacturing systems are becoming more and more complex to manage. The problems that need to be solved are associated with a significant number of time-varying parameters, large time delays, high non-linearity of processes, and a complex relationship between input and output parameters. Depending on the parameters of internal components and characteristics of external conditions, the state of manufacturing systems can change in an unpredictable manner. The paper considers many types of discrete states in which the system can be. The estimation of the probability of finding the manufacturing system in any of the given states was carried out using discrete Markov analysis. The article also presents the results of studies of possible transitions between states in which the production system is presented in the form of a transition matrix.
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Li, Jie, Yi Zhou, Leining Zhang i Hui Li. "Characteristic electron transport on pyridine-linked molecular devices with graphene nanoribbons electrodes and gold electrodes". Functional Materials Letters 09, nr 05 (październik 2016): 1650067. http://dx.doi.org/10.1142/s1793604716500673.
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The electrodes in the molecular devices play a crucial role in creating functional organic electronic devices. We employed the first-principles calculations to investigate the conjugated pyridine-terminated molecule-4, 4[Formula: see text]-vinylenedipyridine attached to monolayer zigzag graphene nanoribbons (ZGNRs) and Au electrodes. Results show that the ZGNRs-based device exhibits excellent electrical properties. It has larger equilibrium conductance or stronger transmission capacity due to higher strength of individual channel and stronger delocalization of electronic states at the Fermi level. The transmission of two devices near the Fermi level is influenced by resonant electron transport through the discrete energy and the edge states. Comparatively, different from the rising trend of gold-based device with the increasing voltage, the current of the device with ZGNRs electrodes changes in a completely different way with the augment of the applied voltage, exhibiting a negative differential resistance effect unexpectedly. The changing trends of the current through two devices are elucidated by the evolution of the transmission peak nearest to the Fermi level.
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ROY, H. V., F. PATTHEY, P. FAYET, W. D. SCHNEIDER i B. DELLEY. "EVOLUTION OF THE ELECTRONIC AND GEOMETRIC STRUCTURES OF SIZE-SELECTED Pt AND Pd CLUSTERS DEPOSITED ON Ag(110) OBSERVED BY PHOTOEMISSION". Surface Review and Letters 03, nr 01 (luty 1996): 943–47. http://dx.doi.org/10.1142/s0218625x96001698.
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Mass-selected Ptn and Pdn (n=1–15) clusters, generated by ion bombardment, are deposited at room temperature in submonolayer quantities on Ag(110) single-crystal surface and characterized by electron spectroscopy (XPS, UPS). Different sites, reflected in the Pt-5d and Pd-4d binding energies, are observed as a function of the substrate temperature, indicating clearly the surface-subsurface atom exchange processes. The monodispersed clusters indicate individual discrete electronic structure features of the Pt-5d and Pd-4d emission. For the monomers virtual bound-state formation as in dilute (3%) PtAg and PdAg alloys is observed. With increasing cluster size, firstly, the increasing splitting between the bonding-like and antibonding-like d-states reflects the increase in cohesive energy due to molecular interaction, and secondly, the shift of the center of gravity of the d-emission towards the Fermi energy indicates the trend to transition-metal formation.
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ROY, H. V., J. BOSCHUNG, P. FAYET, F. PATTHEY i W. D. SCHNEIDER. "PHOTOEMISSION STUDY OF THE ELECTRONIC STRUCTURE OF SIZE-SELECTED Ptn — CLUSTERS DEPOSITED ON Ag(110)". International Journal of Modern Physics B 07, nr 01n03 (styczeń 1993): 556–59. http://dx.doi.org/10.1142/s0217979293001177.
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We report on a photoemission study (XPS, UPS) of the evolution of the electronic structure with cluster size of Pt n ( n = 1-10) clusters deposited on a Ag(110) single crystal surface. The clusters are produced by Xe-ion bombardment of a Pt target. The ionized clusters are mass-selected by a quadrupole mass spectrometer and guided to the substrate by an RF-mode only quadrupole. The substrate is in the center of the analysis chamber allowing in-situ characterization of the supported clusters. Photoemission spectra taken on submonolayer quantities of mass-selected monodispersed Pt clusters indicate individual discrete electronic structure features of the Pt 5d emission. In the atomic-like limit virtual bound state formation with different 5d3/2 and 5d5/2 line broadening is observed which points to an energy dependent Vsd hopping matrix element in agreement with theoretical predictions. With increasing cluster size the splitting between the bonding-like and antibonding-like Pt 5d states reflects the Pt-Pt interaction. The shift of the center of gravity of the Pt 5d state towards the Fermi energy and their concomittant broadening indicate the trend to Pt-metal formation.
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Qiu, Zheng Chen, i Li Qun Chen. "First-Principles Investigation of the Alloying Effect of Mn and Cr in the Kink on the Edge Dislocation in BCC Iron". Defect and Diffusion Forum 272 (marzec 2008): 61–70. http://dx.doi.org/10.4028/www.scientific.net/ddf.272.61.
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Using the first-principles self-consistent discrete variational method based on density functional theory, we investigated the energetics and the electronic structure of 3d impurity Mn and Cr in the kink on the [100](010) edge dislocation in bcc iron. The calculations of binding energies show that both Mn and Cr can stabilize the system containing kink. We also calculate the structural energy, the interatomic energy, the local density of states and the charge density difference. The results indicate that both Mn and Cr in the kink can enhance the interatomic interaction between the impurity atom and the neighboring Fe atoms due to the hybridization of impurity d-Fe d orbitals. The introduction of the Mn and Cr impurity leads to a strong pinning effect on the dislocation motion in bcc iron, which may explain the solid solute hardening of Mn and Cr.
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Teterin, Yury, Konstantin Maslakov, Mikhail Ryzhkov, Anton Teterin, Kirill Ivanov, Stepan Kalmykov i Vladimir Petrov. "X-ray photoelectron spectra structure and chemical bonding in AmO2". Nuclear Technology and Radiation Protection 30, nr 2 (2015): 83–98. http://dx.doi.org/10.2298/ntrp1502083t.
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Quantitative analysis was done of the X-ray photoelectron spectra structure in the binding energy range of 0 eV to ~35 eV for americium dioxide (AmO2) valence electrons. The binding energies and structure of the core electronic shells (~35 eV-1250 eV), as well as the relativistic discrete variation calculation results for the Am63O216 and AmO8 (D4h) cluster reflecting Am close environment in AmO2 were taken into account. The experimental data show that the many-body effects and the multiplet splitting contribute to the spectral structure much less than the effects of formation of the outer (0-~15 eV binding energy) and the inner (~15 eV-~35 eV binding energy) valence molecular orbitals. The filled Am 5f electronic states were shown to form in the AmO2 valence band. The Am 6p electrons participate in formation of both the inner and the outer valence molecular orbitals (bands). The filled Am 6p3/2 and the O 2s electronic shells were found to make the largest contributions to the formation of the inner valence molecular orbitals. Contributions of electrons from different molecular orbitals to the chemical bond in the AmO8 cluster were evaluated. Composition and sequence order of molecular orbitals in the binding energy range 0-~35 eV in AmO2 were established. The experimental and theoretical data allowed a quantitative scheme of molecular orbitals for AmO2, which is fundamental for both understanding the chemical bond nature in americium dioxide and the interpretation of other X-ray spectra of AmO2.
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Ciano, Chiara, Michele Virgilio, Luigi Bagolini, Leonetta Baldassarre, Andrea Rossetti, Alexej Pashkin, Manfred Helm i in. "Electron Population Dynamics in Optically Pumped Asymmetric Coupled Ge/SiGe Quantum Wells: Experiment and Models". Photonics 7, nr 1 (18.12.2019): 2. http://dx.doi.org/10.3390/photonics7010002.
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n-type doped Ge quantum wells with SiGe barriers represent a promising heterostructure system for the development of radiation emitters in the terahertz range such as electrically pumped quantum cascade lasers and optically pumped quantum fountain lasers. The nonpolar lattice of Ge and SiGe provides electron–phonon scattering rates that are one order of magnitude lower than polar GaAs. We have developed a self-consistent numerical energy-balance model based on a rate equation approach which includes inelastic and elastic inter- and intra-subband scattering events and takes into account a realistic two-dimensional electron gas distribution in all the subband states of the Ge/SiGe quantum wells by considering subband-dependent electronic temperatures and chemical potentials. This full-subband model is compared here to the standard discrete-energy-level model, in which the material parameters are limited to few input values (scattering rates and radiative cross sections). To provide an experimental case study, we have epitaxially grown samples consisting of two asymmetric coupled quantum wells forming a three-level system, which we optically pump with a free electron laser. The benchmark quantity selected for model testing purposes is the saturation intensity at the 1→3 intersubband transition. The numerical quantum model prediction is in reasonable agreement with the experiments and therefore outperforms the discrete-energy-level analytical model, of which the prediction of the saturation intensity is off by a factor 3.
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Mizuta, Hiroshi. "Three-Dimensional S-Matrix Simulation of Single-Electron Resonant Tunnelling Through Random Ionised Donor States". VLSI Design 6, nr 1-4 (1.01.1998): 103–6. http://dx.doi.org/10.1155/1998/85748.
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This paper presents a numerical study of single-electron resonant tunnelling (RT) assisted by a few ionised donors in a laterally-confined resonant tunnelling diode (LCRTD). The 3D multi-mode S-matrix simulation is performed newly introducing the scattering potential of discrete impurities. With a few ionised donors being placed, the calculated energy-dependence of the total transmission rate shows new resonances which are donor-configuration dependent. Visualised electron probability density reveals that these resonances originate in RT via single-donor-induced localised states. The I-V characteristics show current steps of order 0.1 nA per donor before the main current peak, which is quantitatively in good agreement with the experimental results.
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Zhou, Yong-Qiang, Lei Dai i Suo-Ping Li. "Performance Analysis of Multiple Relays Cooperative Truncated Automatic Repeat Request in Wireless Sensor Networks". Sensor Letters 17, nr 9 (1.09.2019): 733–38. http://dx.doi.org/10.1166/sl.2019.4138.
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In this paper, we research the performance of direct and non-direct multiple relays cooperative truncated automatic repeat request (D/ND-MRCT-ARQ) protocols in wireless sensor networks (WSNs). We propose a method that named discrete time Markov chain (DTMC) with N + 2 states, which could obtain the throughput formulas of D/ND-MRCT-ARQ protocols. Furthermore, we solve the mathematical expressions of the average transmission delay of both protocols by truncating the number of packet retransmission. In addition, we derive energy efficiency formulas of both protocols under considering the different power consumption of each node. Simulation results demonstrate that the proposed D-MRCT-ARQ protocol achieve higher throughput and energy efficiency while fewer average packet transmission delay, as compared with the ND-MRCT-ARQ protocol.
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Barcelos, Raphael J., Maurício A. Corrêa i João Carlos Basilio. "Predictability of Discrete-Event Systems with Cycles of States Connected with Unobservable Events". Journal of Control, Automation and Electrical Systems 31, nr 4 (19.04.2020): 842–49. http://dx.doi.org/10.1007/s40313-020-00594-9.
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Kolwas, Krystyna. "Optimization of Coherent Dynamics of Localized Surface Plasmons in Gold and Silver Nanospheres; Large Size Effects". Materials 16, nr 5 (22.02.2023): 1801. http://dx.doi.org/10.3390/ma16051801.
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Noble metal nanoparticles have attracted attention in recent years due to a number of their exciting applications in plasmonic applications, e.g., in sensing, high-gain antennas, structural colour printing, solar energy management, nanoscale lasing, and biomedicines. The report embraces the electromagnetic description of inherent properties of spherical nanoparticles, which enable resonant excitation of Localized Surface Plasmons (defined as collective excitations of free electrons), and the complementary model in which plasmonic nanoparticles are treated as quantum quasi-particles with discrete electronic energy levels. A quantum picture including plasmon damping processes due to the irreversible coupling to the environment enables us to distinguish between the dephasing of coherent electron motion and the decay of populations of electronic states. Using the link between classical EM and the quantum picture, the explicit dependence of the population and coherence damping rates as a function of NP size is given. Contrary to the usual expectations, such dependence for Au and Ag NPs is not a monotonically growing function, which provides a new perspective for tailoring plasmonic properties in larger-sized nanoparticles, which are still hardly available experimentally. The practical tools for comparing the plasmonic performance of gold and silver nanoparticles of the same radii in an extensive range of sizes are also given.
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Dixon, J. M., J. A. Tuszyński i M. L. A. Nip. "The One-Electron Energies of a Neutral Zinc Atom Evaluated Using Nonlinear Field Theoretical Methods: Comparison with Hartree–Fock Calculations". International Journal of Modern Physics B 11, nr 03 (30.01.1997): 263–94. http://dx.doi.org/10.1142/s0217979297000319.
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The Method of Coherent Structures (MCS) has been used, as an example of a sufficiently complex atomic system, to determine the one-electron eigenvalues of a neutral zinc atom. An ensemble procedure is used in MCS to properly account for spatial correlations even for a relatively small number of particles. The MCS is a semiclassical approach, but the essentially Fermionic character of the electrons emerges via physical boundary conditions on the choice of classical field. We interpret the classical field as a coherent state envelope which partly determines the effective potential in which quantum fluctuations take place. We find that three distinct régimes of behaviour of the classical field exist depending on the magnitude of the effective Coulomb repulsion, μ. When μ<μ0, a critical value, those classical fields which correspond to certain discrete values of μ are physically acceptable normalisable bound charge states. When μ<μ0 and does not correspond to the discrete values, classical solutions exhibit a damped oscillatory behaviour typical of charged "ring" waves. For μ>μ0, corresponding to an excess of electronic charge, only a small fraction of the charge, represented by a few oscillations about the nucleus, remains attracted to this centre while the remainder escapes from the nucleus. Parameters representing the repulsive energy strength and energy shifts agree well with trends in the Slater parameter F 0(2s,2p) as a function of atomic number Z and also Moseley's Law. Agreement is also obtained with the first-principles form of charge density at small distances from the nucleus as given by Kato's Theorem and also at large distances as outlined by March. The usefulness and validity of this approach has been shown by comparing such energies with those determined by a Hartree–Fock–Slater (HF) method which is well known to satisfactorily account for many specific details of the level structure of atoms. Good agreement with HF has been obtained for both shell positions and energy ordering of states within a shell.
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Husain, Mudassir M., i Maneesh Kumar. "First-Principles Modeling of the Smallest Molecular Single Electron Transistor". Journal of Atomic, Molecular, Condensate and Nano Physics 2, nr 1 (30.07.2015): 33–39. http://dx.doi.org/10.26713/jamcnp.v2i1.270.
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Using first-principles method the charging energy has been calculated; of the smallest single electron transistor (SET) consisting of only two carbon atoms while operating in coulumb blockade regime. The ethyne (C2H2) molecule is acting like a quantum dot (with discrete energy levels) and is weakly coupled to the gold electrodes (continuum). The quantum effects are significant and the conduction of current takes place through incoherent method via electron tunneling. The electronic levels of the molecule determine the electron transport properties. The molecule may be in several charged states from +2 to -2. It has been observed that the HOMO-LUMO gap is strongly reduced in solid state environment with metallic electrodes, as compared to the vacuum. This reduction is attributed to the image charges generated in the source and drain electrodes. This results in strong localization of charges in the molecule, a phenomenon addressed earlier. The charging energy has been calculated in vacuum and in SET environment. The interaction between molecule and the electrodes is treated self-consistently through Poisson equation. The charge stability diagram of the smallest molecular SET has been obtained.
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Lypkivskyi, K. O., i A. G. Mozharovskyi. "COMBINED TRANSFORMER-AND-SWITCHES EXECUTIVE STRUCTURE STRUCTURE OF A TWO-FUNCTION CONVERTER WITH DISCRETE-TIME CONTROL". Tekhnichna Elektrodynamika 2022, nr 5 (18.08.2022): 29–33. http://dx.doi.org/10.15407/techned2022.05.029.
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Power supply systems with transformer-and-switches executive structures have a prominent place in the power supply systems of electrical and electro technological equipment. Voltage converters based on them with discrete-time control of semiconductor switches are characterized by high energy performance and the absence of distortions in the operating states of the output voltage and input current. The constant increase in the range and number of electricity consumers that require the use of such converters for their standardized operation, encourages their appropriate improvement, in particular to expand functionality. The peculiarities of forming a combined transformer- and-switches executive structure of a two-function converter for a rectified current power supply system, which is characterized by increased efficiency of semiconductor devices and lower losses in them, are investigated. Possible and expedient ranges of regulation of output voltage of such converters are defined. References 12, tables 2, figures 4.
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Sakamoto, Hironori, Bei Ma, Ken Morita i Yoshihiro Ishitani. "Raman study of the quantum interference of multiple discrete states and a continuum of states in the phonon energy region of semiconductors: examples ofp-type Ga0.5In0.5P films". Journal of Physics D: Applied Physics 49, nr 37 (18.08.2016): 375107. http://dx.doi.org/10.1088/0022-3727/49/37/375107.
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Yao, Jie, i Ai-Di Zhao. "Advances in detection and regulation of surface-supported molecular quantum states". Acta Physica Sinica 71, nr 6 (2022): 060701. http://dx.doi.org/10.7498/aps.71.20212324.
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Single molecular systems are typical quantum confinement systems, which have rich electronic states, photon states and spin states due to their discrete energy levels, localized orbitals and diverse chemical structures. The states determined by quantum mechanics in these molecular systems make it possible to serve as great physical entities for future quantum information technology. The detection and manipulation of quantum states on a single molecule scale are beneficial to the bottom-up construction of quantum devices. Owing to the highly limited spatial localization of single molecular systems, it is difficult to accurately address and manipulate them with conventional macroscopic characterization methods. Scanning tunneling microscope (STM) is such a powerful tool that it can achieve high-resolution real-space imaging as well as spectroscopic investigation, with the ability to <i>in-situ</i> manipulating the individual atoms or molecules. It can also work jointly with various near-field or external field characterization techniques, making it a most important technique for precisely detecting and manipulating quantum properties at a single molecule level. In this paper, we review recent research progress of quantum states of surface-supported single molecules and relevant structures based on scanning tunneling microscopy. We start from the methods for the synthesis of molecular structures with desired quantum states, and then we review the recent advances in the local spin states for single molecular systems and the optical properties of single molecules serving as a single-photon source. An emerging family of molecular nanographene systems showing intriguing topological properties and magnetic properties is also reviewed. In the last part, we summarize the research progress made recently and prospect the future development of the quantum states at a single molecular level.
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Zhao, Li, Wei Li i Yajie Li. "Research on Dual Security Control for a Non-Linear CPS with Multi-Objective Constraints under DoS Attack and Actuator Fault: An Active-Passive Attack-Tolerant Approach". Journal of Control Science and Engineering 2022 (18.02.2022): 1–19. http://dx.doi.org/10.1155/2022/1734593.
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Based on the discrete event-triggered communication scheme (DETCS), a codesign method of dual security control and communication for the non-linear cyberphysical system (CPS) with denial-of-service (DoS) attack and actuator fault is studied under multi-objective constraints. First, to effectively distinguish DoS attacks with different energy levels, the DoS attack detection method is established based on the maximum allowable delay of the system. Second, a non-linear CPS dual security control framework that integrates active-passive attack tolerance for DoS attack and active fault tolerance for actuator fault is constructed. Third, the low-energy DoS attack is regarded as a special kind of time delay, and a robust observer for the estimation of system states and actuator fault is designed, and a codesign method of passive attack tolerance, active fault tolerance, and communication is proposed. Furthermore, a correction compensation algorithm of control quantity is proposed for high-energy DoS attack based on the PID idea to make active-passive attack tolerance more effective. Finally, the effectiveness of the proposed method is verified by the simulation of a quadruple-tank model.
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Nikonov, S. V., i A. S. Chikhachev. "Discrete nature of self-consistent equilibrium states of an electron beam in a longitudinal magnetic field". Radiophysics and Quantum Electronics 29, nr 3 (marzec 1986): 192–97. http://dx.doi.org/10.1007/bf01037622.
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Sindona, Antonello, Michele Pisarra, Mario Gravina, Cristian Vacacela Gomez, Pierfrancesco Riccardi, Giovanni Falcone i Francesco Plastina. "Statistics of work and orthogonality catastrophe in discrete level systems: an application to fullerene molecules and ultra-cold trapped Fermi gases". Beilstein Journal of Nanotechnology 6 (18.03.2015): 755–66. http://dx.doi.org/10.3762/bjnano.6.78.
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The sudden introduction of a local impurity in a Fermi sea leads to an anomalous disturbance of its quantum state that represents a local quench, leaving the system out of equilibrium and giving rise to the Anderson orthogonality catastrophe. The statistics of the work done describe the energy fluctuations produced by the quench, providing an accurate and detailed insight into the fundamental physics of the process. We present here a numerical approach to the non-equilibrium work distribution, supported by applications to phenomena occurring at very diverse energy ranges. One of them is the valence electron shake-up induced by photo-ionization of a core state in a fullerene molecule. The other is the response of an ultra-cold gas of trapped fermions to an embedded two-level atom excited by a fast pulse. Working at low thermal energies, we detect the primary role played by many-particle states of the perturbed system with one or two excited fermions. We validate our approach through the comparison with some photoemission data on fullerene films and previous analytical calculations on harmonically trapped Fermi gases.
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Rauwel, Protima, Augustinas Galeckas, Martin Salumaa, Frédérique Ducroquet i Erwan Rauwel. "Photocurrent generation in carbon nanotube/cubic-phase HfO2 nanoparticle hybrid nanocomposites". Beilstein Journal of Nanotechnology 7 (26.07.2016): 1075–85. http://dx.doi.org/10.3762/bjnano.7.101.
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A hybrid material consisting of nonfunctionalized multiwall carbon nanotubes (MWCNTs) and cubic-phase HfO2 nanoparticles (NPs) with an average diameter of 2.6 nm has been synthesized. Free standing HfO2 NPs present unusual optical properties and a strong photoluminescence emission in the visible region, originating from surface defects. Transmission electron microscopy studies show that these NPs decorate the MWCNTs on topological defect sites. The electronic structure of the C K-edge in the nanocomposites was probed by electron energy loss spectroscopy, highlighting the key role of the MWCNT growth defects in anchoring HfO2 NPs. A combined optical emission and absorption spectroscopy approach illustrated that, in contrast to HfO2 NPs, the metallic MWCNTs do not emit light but instead expose their discrete electronic structure in the absorption spectra. The hybrid material manifests characteristic absorption features with a gradual merger of the MWCNT π-plasmon resonance band with the intrinsic defect band and fundamental edge of HfO2. The photoluminescence of the nanocomposites indicates features attributed to combined effects of charge desaturation of HfO2 surface states and charge transfer to the MWCNTs with an overall reduction of radiative recombination. Finally, photocurrent generation under UV–vis illumination suggests that a HfO2 NP/MWCNT hybrid system can be used as a flexible nanodevice for light harvesting applications.
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IGUCHI, KAZUMOTO. "π-ELECTRONS IN A SINGLE STRAND OF DNA: A PHENOMENOLOGICAL APPROACH". International Journal of Modern Physics B 18, nr 13 (20.05.2004): 1845–910. http://dx.doi.org/10.1142/s0217979204025051.
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We revisit the problem of the electronic properties of a single strand of DNA, formulating the Hückel approximation for π-electrons in both the sugar-phosphate backbone chain and the π-stacking of nitrogenous bases in a single strand of DNA where the nitrogenous bases are adenine (A), guanine (G), cytosine (C) and thymine (T), respectively. We calculate the electronic band structure of π-electrons: (i) in the single nitrogenous base molecules such as A, G, C and T, (ii) in the single sugar-phosphate molecule, (iii) in the single nucleotide systems such as A, G, C, T with the single sugar-phosphate group, and (iv) in the system of a single strand of DNA with an infinite repetition of a nucleotide such as A, G, C and T, respectively. We find the following: In the case of (i), there is an energy gap between the energy levels for the HOMO and LUMO in the nitrogenous base. This guarantees the semiconducting character of the bases as a mother material. In the case of (ii), there are the HOMO localized at the oxygen site with a double bond and the LUMO localized around the phosphorus atom, which have a quite large energy gap. In the case of (iii), the energy levels for the HOMO and LUMO of the nitrogenous base remain almost the same as those of the nucleotide, while those of the sugar-phosphate group remain the same as well. The HOMO of the sugar-phosphate group exists right below the HOMO of the nitrogenous base. Therefore, comparing the energy levels for the HOMOs of the nitrogenous base group with those of the sugar-phosphate group, the nitrogenous base group behaves as a donor while the sugar-phosphate group behaves as an acceptor. In the case of (iv), there are energy bands and band gaps for the extended states in the nitrogenous base group and the sugar-phosphate group as well as the discrete levels for the localized states at the phosphate site in the spectrum. There is a transition from semiconductor to semimetal as the π-electron hopping between the nitrogenous bases of nucleotide is increased. The details of the above will be discussed in the present paper. Thus, we show the powerfulness of the Hückel theory in the study of DNA as well, although this theory is, at the first glance, oversimplified and purely phenomenological.
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Teterin, Yury, Konstantin Maslakov, Mikhail Ryzhkov, Anton Teterin, Kirill Ivanov, Stepan Kalmykov, Vladimir Petrov i Dmitry Suglobov. "Valence XPS structure and chemical bond in Cs2UO2Cl4". Nuclear Technology and Radiation Protection 31, nr 1 (2016): 37–50. http://dx.doi.org/10.2298/ntrp1601037t.
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Quantitative analysis was done of the valence electrons X-ray photoelectron spectra structure in the binding energy (BE) range of 0 eV to ~35 eV for crystalline dicaesium tetrachloro-dioxouranium (VI) (Cs2UO2Cl4). This compound contains the uranyl group UO2. The BE and structure of the core electronic shells (~35 eV-1250 eV), as well as the relativistic discrete variation calculation results for the UO2Cl4(D4h) cluster reflecting U close environment in Cs2UO2Cl4 were taken into account. The experimental data show that many-body effects due to the presence of cesium and chlorine contribute to the outer valence (0-~15 eV BE) spectral structure much less than to the inner valence (~15 eV-~35 eV BE) one. The filled U5f electronic states were theoretically calculated and experimentally confirmed to be present in the valence band of Cs2UO2Cl4. It corroborates the suggestion on the direct participation of the U5f electrons in the chemical bond. Electrons of the U6p atomic orbitals participate in formation of both the inner (IVMO) and the outer (OVMO) valence molecular orbitals (bands). The filled U6p and the O2s, Cl3s electronic shells were found to make the largest contributions to the IVMO formation. The molecular orbitals composition and the sequence order in the binding energy range 0 eV-~35 eV in the UO2Cl4 cluster were established. The experimental and theoretical data allowed a quantitative molecular orbitals scheme for the UO2Cl4 cluster in the BE range 0-~35 eV, which is fundamental for both understanding the chemical bond nature in Cs2UO2Cl4 and the interpretation of other X-ray spectra of Cs2UO2Cl4. The contributions to the chemical binding for the UO2Cl4 cluster were evaluated to be: the OVMO contribution - 76%, and the IVMO contribution - 24 %.
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Cheriet, Ahmed, Abdeldjebar Hazzab, Abdelkader Bekri, Hicham Gouabi, Mohamed Habbab, Miloud Rezkallah, Ambrish Chandra i Hussein Ibrahim. "Novel strategy for fault e-diagnosis of wind energy conversion systems using wavelet analysis based on Rt-Lab and Arduino". International Journal of Power Electronics and Drive Systems (IJPEDS) 14, nr 2 (1.06.2023): 1085. http://dx.doi.org/10.11591/ijpeds.v14.i2.pp1085-1097.
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The diagnosis of wind energy conversion systems (WECS) turns out to be necessary because of their relatively high cost of operation and maintenance. Wind turbines are hard-to-access structures, and they are often located in remote areas. Therefore, a remote diagnosis (e-diagnosis) is required. This paper proposes an alternative approach for the e-diagnosis of a WECS based on the discrete wavelet transform (DWT) and frequency analysis of the aero generator stator currents. To validate this approach, real-time hardware in the loop (HIL) is used to simulate in real-time the mathematical model of the induction generator on the OPAL-RT OP5600 platform to generate the stator currents and the rotor speed. The DWT is applied to the current signal, to generate the DWT signal, which has a huge number of points that are not supported for direct transmission by the Arduino Mega RobotDyn because of its limited sample time. The absolute values of the DWT peak points (MDWT) are sent as point’s packages form to the diagnosis station via the ESP8266 integrated Wi-Fi board of the Arduino Mega RobotDyn to monitor the SCIG states and determine the number of broken bars.
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CSENKI, ATTILA. "SPECIFIED DEMAND PATTERNS FOR FINITE MARKOV SYSTEMS IN DISCRETE AND CONTINUOUS TIME WITH ILLUSTRATIVE EXAMPLES". International Journal of Reliability, Quality and Safety Engineering 13, nr 06 (grudzień 2006): 547–64. http://dx.doi.org/10.1142/s0218539306002422.
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We consider systems whose time–dependent behaviour can be described by a Markov chain with a finite state space. There is a finite set of subsets of the state space given and every point in the time interval under consideration is associated with one of these subsets, thereby definig a demand (or usage) pattern. Closed form expressions are derived for the probability of a demand pattern being satisfied, in both, discrete and continuous time. Known reliability measures are identified as special cases. We illustrate the theory on two examples: the first is a system comprising three power transmission lines, the second is a small computer system consisting of four units, each in one of the states up or down. The demand patterns cover a four–week period.
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Tarucha, Seigo. "Transport in Quantum Dots: Observation of Atomlike Properties". MRS Bulletin 23, nr 2 (luty 1998): 49–53. http://dx.doi.org/10.1557/s0883769400031274.
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Recent advances in nanofabrication technologies have enabled us to fabricate semiconductor quantum dots in which electrons are three-dimensionally confined. These quantum dots are often referred to as artificial atoms since their electronic properties—for example the ionization energy and discrete excitation spectrum—resemble those of real atoms. Electrons bound to a nucleus potential encounter sufficiently strong effects of quantum-mechanical confinement and mutual Coulomb interactions that they are well arranged in ordered states, and this leads to the arrangement of atoms in the periodic table. It is well known in atom physics that the threedimensional spherically symmetric potential around atoms gives rise to the shell structure 1s, 2s, 2p, 3s, 3p,…. The ionization energy has a large maximum for atomic numbers 2, 10, 18,…. Up to atomic number 23, these shells are filled sequentially. Hund's rule determines whether a spin-down or a spin-up electron is added. This article describes how closely we can approach the electronic properties of real atoms through the use of semiconductor quantum dots.Both the effects of quantum confinement and Coulomb interaction become strong in quantum dots when the dot size is comparable to the electron wavelength and contains just a few electrons. The consequence of these factors on transport have only recently been studied in vertical-dot devices, which contain a dot located between source and drain contacts by means of heterostructure tunnel barriers because the few-electron regime is only accessible in the vertical-dot device. Studies include transport measurements through submicron resonant tunneling devices and submicron gated resonant-tunneling devices, and capacitance measurements on submicron double-barrier structures. However quantum-dot devices usually contain some disorder—for instance because of impurities or when the shape of the dot is irregular—which readily causes sample specific inhomogeneity in the electronic properties. Clean quantum dots, in the form of regular disks, have only recently been fabricated in a semiconductor heterostructure (Figure 1), and have been used to study the atomlike properties of artificial atoms.
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Ahmad, Awais, M. Mazhar Rathore, Anand Paul, Won-Hwa Hong i HyunCheol Seo. "Context-Aware Mobile Sensors for Sensing Discrete Events in Smart Environment". Journal of Sensors 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/7283831.
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Over the last few decades, several advancements in the field of smart environment gained importance, so the experts can analyze ideas for smart building based on embedded systems to minimize the expense and energy conservation. Therefore, propelling the concept of smart home toward smart building, several challenges of power, communication, and sensors’ connectivity can be seen. Such challenges distort the interconnectivity between different technologies, such as Bluetooth and ZigBee, making it possible to provide the continuous connectivity among different objects such as sensors, actuators, home appliances, and cell phones. Therefore, this paper presents the concept of smart building based on embedded systems that enhance low power mobile sensors for sensing discrete events in embedded systems. The proposed scheme comprises system architecture that welcomes all the mobile sensors to communicate with each other using a single platform service. The proposed system enhances the concept of smart building in three stages (i.e., visualization, data analysis, and application). For low power mobile sensors, we propose a communication model, which provides a common medium for communication. Finally, the results show that the proposed system architecture efficiently processes, analyzes, and integrates different datasets efficiently and triggers actions to provide safety measurements for the elderly, patients, and others.
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Kumar, Sandeep, Anal K. Jha i K. Prasad. "Green synthesis and characterization of Ag1/2Al1/2TiO3 nanoceramics". Materials Science-Poland 33, nr 1 (1.03.2015): 59–72. http://dx.doi.org/10.1515/msp-2015-0006.
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AbstractSingle phase silver aluminum titanate (Ag1/2Al1/2)TiO3, later called AAT, nanoceramic powder (particle size 2 to 7.5 nm) was synthesized by a low-cost, green and reproducible tartaric acid gel process. X-ray, FT-IR, energy dispersive X-ray and high resolution transmission electron microscopy analyses were performed to ascertain the formation of AAT nanoceramics. X-ray diffraction data analysis indicated the formation of monoclinic structure having the space group P2/m(10). UV-Vis study revealed the surface plasmon resonance at 296 nm. Dielectric study revealed that AAT nanoceramics could be a suitable candidate for capacitor applications and meets the specifications for “Z7R” of Class I dielectrics of Electronic Industries Association. Complex impedance analyses suggested the dielectric relaxation to be of non-Debye type. To find a correlation between the response of the real system and idealized model circuit composed of discrete electrical components, the model fittings were performed using the impedance data. Electric modulus studies supported the hopping type of conduction in AAT. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in AAT. The ac conductivity data were used to evaluate the density of states at Fermi level and minimum hopping length of the compound.
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Bouhamed, Omar, Manar Amayri i Nizar Bouguila. "Weakly Supervised Occupancy Prediction Using Training Data Collected via Interactive Learning". Sensors 22, nr 9 (21.04.2022): 3186. http://dx.doi.org/10.3390/s22093186.
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Accurate and timely occupancy prediction has the potential to improve the efficiency of energy management systems in smart buildings. Occupancy prediction heavily depends on historical occupancy-related data collected from various sensor sources. Unfortunately, a major problem in that context is the difficulty to collect training data. This situation inspired us to rethink the occupancy prediction problem, proposing the use of an original principled approach based on occupancy estimation via interactive learning to collect the needed training data. Following that, the collected data, along with various features, were fed into several algorithms to predict future occupancy. This paper mainly proposes a weakly supervised occupancy prediction framework based on office sensor readings and occupancy estimations derived from an interactive learning approach. Two studies are the main emphasis of this paper. The first is the prediction of three occupancy states, referred to as discrete states: absence, presence of one occupant, and presence of more than one occupant. The purpose of the second study is to anticipate the future number of occupants, i.e., continuous states. Extensive simulations were run to demonstrate the merits of the proposed prediction framework’s performance and to validate the interactive learning-based approach’s ability to contribute to the achievement of effective occupancy prediction. The results reveal that LightGBM, a machine learning model, is a better fit for short-term predictions than known recursive neural networks when dealing with a limited dataset. For a 24 h window forecast, LightGBM improved accuracy from 38% to 50%, which is an excellent result for non-aggregated data (single office).
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Araújo, Kathleen, i David Shropshire. "A Meta-Level Framework for Evaluating Resilience in Net-Zero Carbon Power Systems with Extreme Weather Events in the United States". Energies 14, nr 14 (14.07.2021): 4243. http://dx.doi.org/10.3390/en14144243.
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Important changes are underway in the U.S. power industry in the way that electricity is sourced, transported, and utilized. Disruption from extreme weather events and cybersecurity events is bringing new scrutiny to power-system resilience. Recognizing the complex social and technical aspects that are involved, this article provides a meta-level framework for coherently evaluating and making decisions about power-system resilience. It does so by examining net-zero carbon strategies with quantitative, qualitative, and integrative dimensions across discrete location-specific systems and timescales. The generalizable framework is designed with a flexibility and logic that allows for refinement to accompany stakeholder review processes and highly localized decision-making. To highlight the framework’s applicability across multiple timescales, processes, and types of knowledge, power system outages are reviewed for extreme weather events, including 2021 and 2011 winter storms that impacted Texas, the 2017 Hurricane Maria that affected Puerto Rico, and a heatwave/wildfire event in California in August 2020. By design, the meta-level framework enables utility decision-makers, regulators, insurers, and communities to analyze and track levels of resilience safeguards for a given system. Future directions to advance an integrated science of resilience in net-zero power systems and the use of this framework are also discussed.
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Kulik, Anatoliy, Kostiantyn Dergachov, Sergiy Pasichnik i Dmytro Sokol. "Rational control of the temperature of vortex energy separator under destabilizing influence". RADIOELECTRONIC AND COMPUTER SYSTEMS, nr 3 (4.10.2022): 47–66. http://dx.doi.org/10.32620/reks.2022.3.04.
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The object of study in this article is the formation process of a rational control of the temperature of a vortex energy separator under destabilizing influences. The subject matter of the article is the process of forming a dichotomous tree by two-digit predicates from diagnostic models a vortex energy-separator device as a rational control object when destabilizing influences appear, and its further recovery. The goal is to develop an analytical approach to the formation of digital algorithms for the rational control of cold and hot air flow temperatures of a vortex energy separator. The tasks are to study the features of the process in the vortex energy-separator device; to describe a rational control system of the vortex energy-separator device; to analyze the experimental characteristics of the vortex energy-separator device; to form linear mathematical models of the nominal mode of the vortex energy-separator device; to develop linear diagnostic models that describe the inoperable states of the vortex energy separator as a rational control object; to form logical signs of diagnosing using diagnostic models, to develop recovering algorithms for the vortex energy separator. The methods used are transfer functions, discrete state space, forming production rules, two-digit predicate equations, dichotomous trees, diagnosing and recovering the operability of dynamic objects. The following results were obtained: the vortex energy-separation process features analysis, the rational control system structure and function description, the experimental characteristics analysis, the development of mathematical models, diagnostic and recovering tool development for the emergency operation process of a vortex energy separator as a rational control object for a given destabilizing influence set. Conclusions. Scientific novelty is the development of an analytical approach to the development of rational control of the vortex separation process of the air flow under the significant influence of various kinds of destabilizing influences.
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Sun, Shuai, Mario Miscuglio, Xiaoxuan Ma, Zhizhen Ma, Chen Shen, Engin Kayraklioglu, Jeffery Anderson, Tarek El Ghazawi i Volker J. Sorger. "Induced homomorphism: Kirchhoff’s law in photonics". Nanophotonics 10, nr 6 (22.03.2021): 1711–21. http://dx.doi.org/10.1515/nanoph-2020-0655.
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Abstract When solving, modeling or reasoning about complex problems, it is usually convenient to use the knowledge of a parallel physical system for representing it. This is the case of lumped-circuit abstraction, which can be used for representing mechanical and acoustic systems, thermal and heat-diffusion problems and in general partial differential equations. Integrated photonic platforms hold the prospective to perform signal processing and analog computing inherently, by mapping into hardware specific operations which relies on the wave-nature of their signals, without trusting on logic gates and digital states like electronics. Here, we argue that in absence of a straightforward parallelism a homomorphism can be induced. We introduce a photonic platform capable of mimicking Kirchhoff’s law in photonics and used as node of a finite difference mesh for solving partial differential equation using monochromatic light in the telecommunication wavelength. Our approach experimentally demonstrates an arbitrary set of boundary conditions, generating a one-shot discrete solution of a Laplace partial differential equation, with an accuracy above 95% with respect to commercial solvers. Our photonic engine can provide a route to achieve chip-scale, fast (10 s of ps), and integrable reprogrammable accelerators for the next generation hybrid high-performance computing. Summary A photonic integrated platform which can mimic Kirchhoff’s law in photonics is used for approximately solve partial differential equations noniteratively using light, with high throughput and low-energy levels.
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Uppal, Ali Arshad, Manuel C. R. M. Fernandes, Sérgio Vinha i Fernando A. C. C. Fontes. "Cascade Control of the Ground Station Module of an Airborne Wind Energy System". Energies 14, nr 24 (10.12.2021): 8337. http://dx.doi.org/10.3390/en14248337.
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An airborne wind energy system (AWES) can harvest stronger wind streams at higher altitudes which are not accessible to conventional wind turbines. The operation of AWES requires a controller for the tethered aircraft/kite module (KM), as well as a controller for the ground station module (GSM). The literature regarding the control of AWES mostly focuses on the trajectory tracking of the KM. However, an advanced control of the GSM is also key to the successful operation of an AWES. In this paper we propose a cascaded control strategy for the GSM of an AWES during the traction or power generation phase. The GSM comprises a winch and a three-phase induction machine (IM), which acts as a generator. In the outer control-loop, an integral sliding mode control (SMC) algorithm is designed to keep the winch velocity at the prescribed level. A detailed stability analysis is also presented for the existence of the SMC for the perturbed winch system. The rotor flux-based field oriented control (RFOC) of the IM constitutes the inner control-loop. Due to the sophisticated RFOC, the decoupled and instantaneous control of torque and rotor flux is made possible using decentralized proportional integral (PI) controllers. The unknown states required to design RFOC are estimated using a discrete time Kalman filter (DKF), which is based on the quasi-linear model of the IM. The designed GSM controller is integrated with an already developed KM, and the AWES is simulated using MATLAB and Simulink. The simulation study shows that the GSM control system exhibits appropriate performance even in the presence of the wind gusts, which account for the external disturbance.
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DOBRODEY, N. V., L. I. ZIEGELMAN, V. G. ZAVODINSKY i I. A. KUYANOV. "NONEMPIRICAL CLUSTER STUDY OF THE Au ADSORPTION ON THE Si(111) SURFACE". Surface Review and Letters 01, nr 02n03 (sierpień 1994): 273–84. http://dx.doi.org/10.1142/s0218625x94000278.
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The nonempirical discrete-variational method of local density approximation was used to study the electronic structure and the most stable position of a single Au atom for the Si(111)–Au chemisorption system. Only the symmetric adsorption sites (H3, T4, "on-top") were considered. The three fold hollow site has been found to be energetically the most favorable position with the vertical distance between adsorbed Au atom and the topmost silicon atom plane of 1.59 Å, binding energy of 4.76 eV and vertical vibrational mode of 87 cm –1. The photoemission spectra were calculated and compared with the experimental spectra. Although the calculations suggest that Au atom can not penetrate under the silicon surface, the possibility has been shown for Au atom to replace the surface silicon atom upon the adsorption. The results of the calculations are discussed in connection with the existing models for initial stages of the Au growth on the Si(111) surface.
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Nazemi, Adel, Omid Salari, Mohammad Tavakoli Bina, Masoud Kazemi i Bahman Eskandari. "Predictive Control for Reduced Structure Multilevel Converters: Experimenting on a Seven Level Packed U-Cell". International Journal of Power Electronics and Drive Systems (IJPEDS) 7, nr 2 (1.06.2016): 568. http://dx.doi.org/10.11591/ijpeds.v7.i2.pp568-582.
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Recently, a branch of multilevel converters is emerged, in which their ‘reduced structure’ topologies use lower number of devices compared to the available topologies. To get a cost efficient converter, lower number of components as well as high quality waveforms, multilevel converters with a ‘reduced structure’ (MCRS) are suitable for high/medium power systems. Also, utilizing the fast microprocessors available today, applications of predictive control in power converters are of very powerful and attractive alternatives to classical controllers. This paper proposes a finite control set model-based predictive control (FCS-MPC) for load current regulation and capacitor voltage balancing for a typical MCRS. A case study considered, three-phase seven level packed U-cell (PUC), which is among reduced structure multilevel converters. A discrete model of the system is derived, and a predictive model-based control is developed according to this model in order to predict the future behavior of the system for all possible switching states; then, the switching state that optimized the cost function is selected. The feasibility of the proposed FCS-MPC strategy for a seven level PUC is evaluated based on simulations with MATLAB/ SIMULINK. Moreover, experimental validation of the proposed control system on a 5 kVA PUC is examined through DSP implementation<strong>.</strong>
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Lei, Yan, Xiaojie Liang, Dingwu Zhou, Tao Qiu, Kaixin Wang i Yue Wu. "Effect of Particle Diameter on Primary Breakup of High-Pressure Diesel Spray Atomization: A Study Based on Numerical Simulations Using the Eulerian–Lagrangian Model". Energies 16, nr 1 (26.12.2022): 238. http://dx.doi.org/10.3390/en16010238.
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The coupling of Eulerian and Lagrangian methods in the Eulerian–Lagrangian Spray Atomization (ELSA) approach is critical. This study proposes an equation for the primary breakup particle diameter D of a diesel fuel spray and adopts it as a key transition criterion for coupling. A three-dimensional diesel spray is modeled by the large-eddy simulation (LES) approach. This improved ELSA simulation was conducted using various transition criteria for particle diameter Dcr. The results show that fuel spray experiences two stages: stage I, when a liquid column appears without a dispersed phase, and stage II, when primary breakup occurs with many discrete particles. Although Dcr has little influence on the macro-spray characteristics, such as top penetration distance S and spray cone angle θ, it has significant effects on discrete particles, such as their number, average diameter, distribution and location, and spray cone area. Dcr should be determined on the basis of actual operating conditions.