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《Physics letters. A》2020,384(35):126893
Here, the thermoelectric (TE) properties of Na0.74CoNbxO2 () compounds are investigated experimentally and computationally. The experimental measurements are conducted in K. Positive sign of Seebeck coefficient for both the compounds indicates the dominating p-type character. The maximum experimental values of ZT are observed as ∼ 0.12 and ∼ 0.19 at 620 K for and , respectively. The experimental transport properties of these compounds are understood by employing spin-polarized GGA+U (= 4 eV) electronic structure calculations on compound. On the basis of best experimental and computational matching of transport properties, we have estimated ZT till 1200 K computationally. The highest calculated values of ZT are ∼ 1.36 and ∼ 1.22 at 1200 K for and , respectively. The optimum value of efficiency for is calculated as ∼ 6.4%, whereas it reaches ∼ 7.5% for . 相似文献
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Using azimuthally symmetrized cylindrical coordinates, we consider some position-dependent mass (PDM) charged particles moving in position-dependent (PD) magnetic and Aharonov–Bohm flux fields. We focus our attention on PDM-charged particles with (i.e., the PDM is only radially dependent) moving in an inverse power-law-type radial PD-magnetic fields . Under such settings, we consider two almost-quasi-free PDM-charged particles (i.e., no interaction potential, ) endowed with and . Both yield exactly solvable Schrödinger equations of Coulombic nature but with different spectroscopic structures. Moreover, we consider a Yukawa-type PDM-charged particle with moving not only in the vicinity of the PD-magnetic and Aharonov-Bohm flux fields but also in the vicinity of a Yukawa plus a Kratzer type potential force field . For this particular case, we use the Nikiforov-Uvarov (NU) method to come out with exact analytical eigenvalues and eigenfunctions. Which, in turn, recover those of the almost-quasi-freePDM-charged particle with for . Energy levels crossings are also reported. 相似文献
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《Physics letters. A》2020,384(31):126811
Y2WO6 ceramics were fabricated via a solid-state reaction method and investigated structure stability, densification, microstructure, and dielectric properties at microwave frequency range. Y2WO6 crystallized in a monoclinic structure and stabilized to 1500 ∘C, beyond which the decomposition of Y6WO12 occurred. Y2WO6 ceramic could be sintered into a compact bulk at 1450 ∘C, which was characterized by a high relative density ∼ 97.6% and a dense microstructure. The favorable dielectric performances were achieved at 1450 ∘C with a relative permittivity , a quality factor GHz ( GHz), and a temperature coefficient of resonant frequency ppm/∘C. The MW properties of Y2WO6 suggest that it could be useful candidate material for low-loss dielectric resonators. 相似文献
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《Physics letters. A》2020,384(36):126930
We consider quantum bosons with contact interactions at the Lowest Landau Level (LLL) of a two-dimensional isotropic harmonic trap. At linear order in the coupling parameter g, we construct a large, explicit family of quantum states with energies of the form , where and are integers. Any superposition of these states evolves periodically with a period of until, at much longer time scales of order , corrections to the energies of order may become relevant. These quantum states provide a counterpart to the known time-periodic behaviors of the corresponding classical (mean field) theory. 相似文献
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《Physics letters. A》2019,383(22):2652-2657
The equilibrated grain boundary groove shape of solid Al in equilibrium with Al-Sn-Mg eutectic liquid was observed by using a Bridgman type directional solidification apparatus. The ratio of the thermal conductivity of the equilibrated liquid to the thermal conductivity of solid Al has been obtained as 0.91. In addition, the average Gibbs-Thomson coefficient, , the solid-liquid interfacial energy, and the grain boundary energy, , in the Al/Al-Sn-Mg system have been calculated from the measured grain boundary shapes. 相似文献
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《Physics letters. A》2020,384(13):126265
The exact solvability and impressive pedagogical implementation of the harmonic oscillator's creation and annihilation operators make it a problem of great physical relevance and the most fundamental one in quantum mechanics. So would be the position-dependent mass (PDM) oscillator for the PDM quantum mechanics. We, hereby, construct the PDM creation and annihilation operators for the PDM oscillator via two different approaches. First, via von Roos PDM Hamiltonian and show that the commutation relation between the PDM creation and annihilation operators, , not only offers a unique PDM-Hamiltonian but also suggests a PDM-deformation in the coordinate system. Next, we use a PDM point canonical transformation of the textbook constant mass harmonic oscillator analog and obtain yet another set of PDM creation and annihilation operators, hence an “apparently new” PDM-Hamiltonian is obtained. The “new” PDM-Hamiltonian turned out to be not only correlated with but also represents an alternative and most simplistic user-friendly PDM-Hamiltonian, ; , that has never been reported before. 相似文献
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This paper deploys the Convolutional Neural Network (CNN) to learn and set the statistical test in Spectrum Sensing (SS) task of multiple primary user (PU) sources in massive uncalibrated antennas of secondary users (SU) sharing the same spectrum resources. The proposed deep learning-based SS method (DL-SS) is based on the CNN architecture that has the capability of extracting features of the sample covariance matrices (SCMs) that are given as the network input, improving the overall performance and robustness. The proposed CNN-SS method is compared with nine recent multiple-antennas SS methods, namely the arithmetic–geometric detector (AGM), John’s detector (JD), sphericity detector (SD), generalized likelihood test (GLRT), locally most powerful invariant test (LMPIT), maximum–minimum eigenvalue detector (MME), covariance detector (CAV), Hadamard detector (HD) and volume detector (VD) methods; besides, the proposed method is also compared with five recent state-of-art CNN-based SS methodologies. Performance-complexity trade-off of the proposed and reference SS methods are corroborated via Monte Carlo Simulations (MCS). The proposed CNN-SS method under uncalibrated massive antennas reveals substantial benefits w.r.t. the reference methods and is competitive with others CNN-SS methodologies, both in terms of complexity and performance, achieving detection probability of under very low false alarm probability . Under different figures of merit, the performance of the CNN-based SS detector has revealed to be indubitably superior regarding the state-of-art SS detectors. However, the proposed CNN-based SS detector presents relative computational complexity increases. Hence, to be effective, such a superior operational performance requires a very efficient processing structure in the SU base stations. 相似文献
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Singly-excited states of the two-electron atom cease being bound when (from above), the outer orbital becoming infinitely diffuse. The asymptotic relations where , are demonstrated to hold. Here, is a hydrogenic s orbital with principal quantum number . New, more nuanced light is shed on the already challenged dogma that the Pauli principle keeps the electrons further apart in the triplet than in the corresponding singlet. 相似文献
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