Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The anisotropic physical property is the most noteworthy feature of crystals. In this paper, the subscript change method is used to analyze the sign changes of different tensors describing physical properties in uniaxial crystals. The distribution of some physical properties in special point groups exhibits non-symmetry in eight quadrants, which should arouse the attention of crystal research. The difference between the crystallographic and physical coordinate systems and the lack of crystal symmetry operations are considered to be the origins of the non-symmetry. In order to avoid ambiguities and difficulties in characterizing and applying crystal physical properties, eight quadrants in space should be clarified. Hence, we proposed to utilize piezoelectric properties to define the positive direction of optical coordinate axis prior to the research and applications of optical properties.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>High-performance interrogation systems for optical fiber sensors are extensively required in applications of environmental condition monitoring. In this article, we propose and demonstrate a Michelson interferometer (MI) interrogation system based on optoelectronic oscillator (OEO). The frequency of the OEO is related to the free spectral range (FSR) of the MI. Thus, when the FSR of the MI varies with the change of the external physical factors, the frequency of the OEO would shift and can be used for interrogation. We demonstrate that the temperature sensitivity and interrogation resolution are 35.35 MHz/℃ and 0.012 ℃, respectively. Such OEO-based scheme enables wavelength-to-frequency mapping and promises the wide linear interrogation range, high-resolution and high-speed interrogation.</jats:p>

<jats:p>Norovirus is one of the most common causes of viral gastroenteritis in the world, causing significant morbidity, deaths, and medical costs. In this work, we look at stochastic modelling methodologies for norovirus transmission by water, human to human transmission and food. To begin, the proposed stochastic model is shown to have a single global positive solution. Second, we demonstrate adequate criteria for the existence of a unique ergodic stationary distribution <jats:inline-formula> <jats:tex-math><?CDATA ${\Re}_{{\mathfrak{s}}}^{0}\gt 1$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>ℜ</mml:mi> <mml:mi mathvariant="fraktur">s</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:mo>&gt;</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_2_020202_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> by developing a Lyapunov function. Thirdly, we find sufficient criteria <jats:italic>ℜ<jats:sub>s</jats:sub> </jats:italic> &lt; 1 for disease extinction. Finally, two simulation examples are used to exemplify the analytical results. We employed optimal control theory and examined stochastic control problems to regulate the spread of the disease using some external measures. Additional graphical solutions have been produced to further verify the acquired analytical results. This research could give a solid theoretical foundation for understanding chronic communicable diseases around the world. Our approach also focuses on offering a way of generating Lyapunov functions that can be utilized to investigate the stationary distribution of epidemic models with nonlinear stochastic disturbances.</jats:p>

<jats:p>A multi-hop nondestructive teleportation scheme independent of channel parameters based on Bell pairs is presented, where the coefficients of the quantum channel are unknown to all the communication nodes. With Bell measurement and channel matching technology the unknown channel parameters can be eliminated probabilistically with the help of the intermediate nodes. Then the source node Alice can teleport an unknown state to the remote destination node Bob. In our scheme the teleportation is generalized first to the scenario independent of channel parameters, which makes the requirement of quantum channel reduced. Our scheme still preserves the initial unknown state even if this teleportation fails. Moreover, performance analysis shows that our scheme has a higher communication efficiency.</jats:p>

<jats:p>Continuous-variable quantum key distribution (CVQKD) allows legitimate parties to extract and exchange secret keys. However, the tradeoff between the secret key rate and the accuracy of parameter estimation still around the present CVQKD system. In this paper, we suggest an approach for parameter estimation of the CVQKD system via artificial neural networks (ANN), which can be merged in post-processing with less additional devices. The ANN-based training scheme, enables key prediction without exposing any raw key. Experimental results show that the error between the predicted values and the true ones is in a reasonable range. The CVQKD system can be improved in terms of the secret key rate and the parameter estimation, which involves less additional devices than the traditional CVQKD system.</jats:p>

<jats:p>We numerically study a one-dimensional, nonlinear lattice model which in the linear limit is relevant to the study of bending (flexural) waves. In contrast with the classic one-dimensional mass-spring system, the linear dispersion relation of the considered model has different characteristics in the low frequency limit. By introducing disorder in the masses of the lattice particles, we investigate how different nonlinearities in the potential (cubic, quadratic, and their combination) lead to energy delocalization, equipartition, and chaotic dynamics. We excite the lattice using single site initial momentum excitations corresponding to a strongly localized linear mode and increase the initial energy of excitation. Beyond a certain energy threshold, when the cubic nonlinearity is present, the system is found to reach energy equipartition and total delocalization. On the other hand, when only the quartic nonlinearity is activated, the system remains localized and away from equipartition at least for the energies and evolution times considered here. However, for large enough energies for all types of nonlinearities we observe chaos. This chaotic behavior is combined with energy delocalization when cubic nonlinearities are present, while the appearance of only quadratic nonlinearity leads to energy localization. Our results reveal a rich dynamical behavior and show differences with the relevant Fermi–Pasta–Ulam–Tsingou model. Our findings pave the way for the study of models relevant to bending (flexural) waves in the presence of nonlinearity and disorder, anticipating different energy transport behaviors.</jats:p>

<jats:p>Since the advent of three-dimensional photonic integrated circuits, the realization of efficient and compact optical interconnection between layers has become an important development direction. A vertical interlayer coupler between two silicon layers is presented in this paper. The coupling principle of the directional coupler is analyzed, and the traditional method of using a pair of vertically overlapping inverse taper structures is improved. For the coupling of two rectangular waveguide layers, a pair of nonlinear tapers with offset along the transmission direction is demonstrated. For the coupling of two ridge waveguide layers, a nonlinear taper in each layer is used to achieve high coupling efficiency. The simulation results show that the coupling efficiency of the two structures can reach more than 90% in a wavelength range from 1500 nm to 1650 nm. Moreover, the crosstalk is reduced to less than –50 dB by using multimode waveguides at intersections. The vertical interlayer coupler with a nonlinear taper is expected to realize the miniaturization and dense integration of photonic integrated chips.</jats:p>

<jats:p>Nearfield acoustic holography in a moving medium is a technique which is typically suitable for sound sources identification in a flow. In the process of sound field reconstruction, sound pressure is usually used as the input, but it may contain considerable background noise due to the interactions between microphones and flow moving at a high velocity. To avoid this problem, particle velocity is an alternative input, which can be obtained by using laser Doppler velocimetry in a non-intrusive way. However, there is a singular problem in the conventional propagator relating the particle velocity to the pressure, and it could lead to significant errors or even false results. In view of this, in this paper, nonsingular propagators are deduced to realize accurate reconstruction in both cases that the hologram is parallel to and perpendicular to the flow direction. The advantages of the proposed method are analyzed, and simulations are conducted to verify the validation. The results show that the method can overcome the singular problem effectively, and the reconstruction errors are at a low level for different flow velocities, frequencies, and signal-to-noise ratios.</jats:p>

<jats:p>The relation between friction mechanism and force chains characteristics has not yet been fully studied in the powder metallurgy research area. In this work, a uniaxial compression discrete element model is established based on the compaction process of ferrous powder. Furthermore, the correlation mechanism between force chains and the friction mechanism during powder compaction is investigated. The simulation results reveal a strong correlation between the variation of the friction coefficient and the evolution of force chains. During the powder compaction, the friction coefficient would eventually tend to be stable, a feature which is also closely related to the slip ratio between particles. The side wall friction and the friction between particles would have an important effect on the direction of force chain growth in about one-third of the area near the side wall. The research results provide theoretical guidance for improving the densification process of the powder according to the force chain and friction.</jats:p>

<jats:p>With the increasing maturity of automatic driving technology, the homogeneous traffic flow will gradually evolve into the heterogeneous traffic flow, which consists of human-driving and autonomous vehicles. To better study the characteristics of the heterogeneous traffic system, this paper proposes a new car-following model for autonomous vehicles and heterogeneous traffic flow, which considers the self-stabilizing effect of vehicles. Through linear and nonlinear methods, this paper deduces and analyzes the stability of such a car-following model with the self-stabilizing effect. Finally, the model is verified by numerical simulation. Numerical results show that the self-stabilizing effect can make the heterogeneous traffic flow more stable, and that increasing the self-stabilizing coefficient or historical time length can strengthen the stability of heterogeneous traffic flow and alleviate traffic congestion effectively. In addition, the heterogeneous traffic flow can also be stabilized with a higher proportion of autonomous vehicles.</jats:p>