Catálogo de publicaciones - revistas

<jats:p>Spiking neural networks (SNNs) are widely used in many fields because they work closer to biological neurons. However, due to its computational complexity, many SNNs implementations are limited to computer programs. First, this paper proposes a multi-synaptic circuit (MSC) based on memristor, which realizes the multi-synapse connection between neurons and the multi-delay transmission of pulse signals. The synapse circuit participates in the calculation of the network while transmitting the pulse signal, and completes the complex calculations on the software with hardware. Secondly, a new spiking neuron circuit based on the leaky integrate-and-fire (LIF) model is designed in this paper. The amplitude and width of the pulse emitted by the spiking neuron circuit can be adjusted as required. The combination of spiking neuron circuit and MSC forms the multi-synaptic spiking neuron (MSSN). The MSSN was simulated in PSPICE and the expected result was obtained, which verified the feasibility of the circuit. Finally, a small SNN was designed based on the mathematical model of MSSN. After the SNN is trained and optimized, it obtains a good accuracy in the classification of the IRIS-dataset, which verifies the practicability of the design in the network.</jats:p>

<jats:p>We propose a cylindrical conformal transmitted metasurface for orbital angular momentum vortex wave generation. Formulas for calculating the phase distributions of cylindrical conformal transmitted metasurface is presented. A prototype of the proposed conformal transmitted metasurface is designed, fabricated and measured. Measured results shows that the proposed conformal transmitted metasurface can effectively generate vortex waves, which verifies the effectiveness of our method. The proposed method may pave the way of vortex wave generation with cylindrical conformal devices.</jats:p>

<jats:p>Copper ion conducting solid electrolyte Rb<jats:sub>4</jats:sub>Cu<jats:sub>16</jats:sub>I<jats:sub>6.5</jats:sub>Cl<jats:sub>13.5</jats:sub> was prepared by means of mechano-chemical method. The structure and morphology of the powder was investigated by x-ray diffraction and scanning electron microscopy. The grain size was estimated to be 0.2–0.9 μm and the ionic conductivity at room temperature was approximately 0.206 S/cm. The solid electrolyte Rb<jats:sub>4</jats:sub>Cu<jats:sub>16</jats:sub>I<jats:sub>6.5</jats:sub>Cl<jats:sub>13.5</jats:sub> was exploited for copper ion beam generation. The copper ion emission current of several nA was successfully obtained at acceleration voltages of 15 kV and temperature of 197 °C in vacuum of 2.1 × 10<jats:sup>−4</jats:sup> Pa. A good linear correlation between the logarithmic ion current (log <jats:italic>I</jats:italic>) and the square root of the acceleration voltage (<jats:italic>U</jats:italic> <jats:sub>acc</jats:sub>) at high voltage range was obtained, suggesting the Schottky emission mechanism in the process of copper ion beam generation.</jats:p>

<jats:p>Integrated cavity output spectroscopy (ICOS) is an effective technique in trace gase detection. The strong absorption due to the long optical path of this method makes it challenging in the application scenes that have large gas concentration fluctuation, especially when the gas concentration is high. In this paper, we demonstrate an extension of the dynamic range of ICOS by using a detuned laser combined with an off-axis integrating cavity. With this, we improve the upper limit of the dynamic detection range from 0.1% (1000 ppm) to 20% of the gas concentration. This method provides a way of using ICOS in the applications with unpredictable gas concentrations such as gas leak detection, ocean acidification, carbon sequestration, etc.</jats:p>

<jats:p>In the weak-magnetic-field approximation, we derived an expression of quadratic Zeeman shift coefficient of <jats:inline-formula> <jats:tex-math><?CDATA ${}^{3}{P}_{0}^{{\rm{o}}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mrow /> <mml:mn>3</mml:mn> </mml:msup> <mml:msubsup> <mml:mi>P</mml:mi> <mml:mn>0</mml:mn> <mml:mi mathvariant="normal">o</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_4_043101_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> clock state for <jats:sup>88</jats:sup>Sr and <jats:sup>87</jats:sup>Sr atoms. By using this formula and the multi-configuration Dirac–Hartree–Fock theory, the quadratic Zeeman shift coefficients were calculated. The calculated values <jats:italic>C</jats:italic> <jats:sub>2</jats:sub> = –23.38(5) MHz/T<jats:sup>2</jats:sup> for <jats:sup>88</jats:sup>Sr and the <jats:inline-formula> <jats:tex-math><?CDATA ${}^{3}{P}_{0}^{{\rm{o}}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mrow /> <mml:mn>3</mml:mn> </mml:msup> <mml:msubsup> <mml:mi>P</mml:mi> <mml:mn>0</mml:mn> <mml:mi mathvariant="normal">o</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_4_043101_ieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:italic>F</jats:italic> = 9/2, <jats:italic>M<jats:sub>F</jats:sub> </jats:italic> = ±9/2 clock states for <jats:sup>87</jats:sup>Sr agree well with the other available theoretical and experimental values, especially the most accurate measurement recently. In addition, the calculated values of the <jats:inline-formula> <jats:tex-math><?CDATA ${}^{3}{P}_{0}^{{\rm{o}}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mrow /> <mml:mn>3</mml:mn> </mml:msup> <mml:msubsup> <mml:mi>P</mml:mi> <mml:mn>0</mml:mn> <mml:mi mathvariant="normal">o</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_4_043101_ieqn5.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:italic>F</jats:italic> = 9/2, <jats:italic>M<jats:sub>F</jats:sub> </jats:italic> = ±9/2 clock states were also determined in our <jats:sup>87</jats:sup>Sr optical lattice clock. The consistency with measurements verifies the validation of our calculation model. Our theory is also useful to evaluate the second-order Zeeman shift of the clock transition, for example, the new proposed <jats:sup>1</jats:sup> <jats:italic>S</jats:italic> <jats:sub>0</jats:sub>, <jats:italic>F</jats:italic> = 9/2, <jats:italic>M<jats:sub>F</jats:sub> </jats:italic> = ±5/2–<jats:inline-formula> <jats:tex-math><?CDATA ${}^{3}{P}_{0}^{{\rm{o}}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mrow /> <mml:mn>3</mml:mn> </mml:msup> <mml:msubsup> <mml:mi>P</mml:mi> <mml:mn>0</mml:mn> <mml:mi mathvariant="normal">o</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_4_043101_ieqn6.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:italic>F</jats:italic> = 9/2, <jats:italic>M<jats:sub>F</jats:sub> </jats:italic> = ±3/2 transitions.</jats:p>

<jats:p>The scattering matrices of e + N<jats:sup>+</jats:sup> with <jats:italic>J<jats:sup>π</jats:sup> </jats:italic> = 1.5<jats:sup>+</jats:sup> in discrete energy regions are calculated using the eigenchannel R-matrix method. We obtain good parameters of multichannel quantum defect theory (MQDT) that vary smoothly as the function of the energy resulting from the analytical continuation property of the scattering matrices. By employing the MQDT, all discrete energy levels for N could be calculated accurately without missing anyone. The MQDT parameters (i.e., scattering matrices) can be calibrated with the available precise spectroscopy values. In this work, the optical oscillator strengths for the transition between the ground state and Rydberg series are obtained, which provide rich data for the diagnostic analysis of plasma.</jats:p>

<jats:p>We present a coherent population trapping clock system based on laser-cooled <jats:sup>87</jats:sup>Rb atoms. The clock consists of a frequency-stabilized CPT interrogation laser and a cooling laser as well as a compact magneto-optical trap, a high-performance microwave synthesizer, and a signal detection system. The resonance signal in the continuous wave regime exhibits an absorption contrast of ∼ 50%. In the Ramsey interrogation method, the linewidth of the central fringe is 31.25 Hz. The system achieves fractional frequency stability of <jats:inline-formula> <jats:tex-math> <?CDATA $2.4\times {10}^{-11}/\sqrt{\tau }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>2.4</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>11</mml:mn> </mml:mrow> </mml:msup> <mml:mo>/</mml:mo> <mml:msqrt> <mml:mi>τ</mml:mi> </mml:msqrt> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_4_043201_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, which goes down to 1.8 × 10<jats:sup>−13</jats:sup> at 20000 s. The results validate that cold atom interrogation can improve the long-term frequency stability of coherent population trapping clocks and holds the potential for developing compact/miniature cold atoms clocks.</jats:p>

<jats:p>The strongly coupled system composed of atoms, molecules, molecule aggregates, and semiconductor quantum dots embedded within an optical microcavity/nanocavity with high quality factor and/or low modal volume has become an excellent platform to study cavity quantum electrodynamics (CQED), where a prominent quantum effect called Rabi splitting can occur due to strong interaction of cavity-mode single-photon with the two-level atomic states. In this paper, we build a new quantum model that can describe the optical response of the strongly-coupled system under the action of an external probing light and the spectral lineshape. We take the Hamiltonian for the strongly-coupled photon–atom system as the unperturbed Hamiltonian <jats:italic> <jats:bold>H</jats:bold> </jats:italic> <jats:sub>0</jats:sub> and the interaction Hamiltonian of the probe light upon the coupled-system quantum states as the perturbed Hamiltonian <jats:italic> <jats:bold>V</jats:bold> </jats:italic>. The theory yields a double Lorentzian lineshape for the permittivity function, which agrees well with experimental observation of Rabi splitting in terms of spectral splitting. This quantum theory will pave the way to construct a complete understanding for the microscopic strongly-coupled system that will become an important element for quantum information processing, nano-optical integrated circuits, and polariton chemistry.</jats:p>

<jats:p>We investigate the ellipticity of the high-order harmonic generation from the oriented <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{H}}}_{2}^{+}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">H</mml:mi> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_4_043203_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> exposed to a linearly polarized laser field by numerically solving the two-dimensional time-dependent Schrödinger equation (2D TDSE). Numerical simulations show that the harmonic ellipticity is remarkably sensitive to the alignment angle. The harmonic spectrum is highly elliptically polarized at a specific alignment angle <jats:italic>θ</jats:italic> = 30°, which is insensitive to the variation of the laser parameters. The position of the harmonic intensity minima indicates the high ellipticity, which can be attributed to the two-center interference effect. The high ellipticity can be explained by the phase difference of the harmonics. This result facilitates the synthesis of a highly elliptical isolated attosecond pulse with duration down to 65 as, which can be served as a powerful tool to explore the ultrafast dynamics of molecules and study chiral light–matter interaction.</jats:p>

<jats:p>The high-order harmonic generation from an asymmetric molecular ion is theoretically investigated based on the Born–Oppenheimer model with two-dimensional electron dynamics. It is shown that the harmonic intensity changes periodically in elliptically polarized laser fields. The periodical character is ellipticity-dependent. By establishing the physical image, the periodicity of the harmonic intensity can be ascribed to the contributions of the ground state and the excited state. Furthermore, the electron dynamics from different electronic states can be selected via combining the elliptically polarized laser field with a static electric field. The harmonics dominated either by ground state or excited state are emitted once in an optical cycle in the combined laser field.</jats:p>