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Solitons are self-reinforcing localized wave packets that manifest in the major areas of nonlinear science, from optics to biology and Bose–Einstein condensates. Recently, optically driven dissipative solitons have attracted great attention for the implementation of the chip-scale frequency combs that are decisive for communications, spectroscopy, neural computing, and quantum information processing. In the current understanding, the generation of temporal solitons involves the chromatic dispersion as a key enabling physical effect, acting either globally or locally on the cavity dynamics in a decisive way. Here, we report on a novel class of solitons, both theoretically and experimentally, which builds up in spectrally confined optical cavities when dispersion is practically absent, both globally and locally. Precisely, the interplay between the Kerr nonlinearity and spectral filtering results in an infinite hierarchy of eigenfunctions which, combined with optical gain, allow for the generation of stable dispersion-less dissipative solitons in a previously unexplored regime. When the filter order tends to infinity, we find an unexpected link between dissipative and conservative solitons, in the form of Nyquist-pulse-like solitons endowed with an ultra-flat spectrum. In contrast to the conventional dispersion-enabled nonlinear Schrödinger solitons, these dispersion-less Nyquist solitons build on a fully confined spectrum and their energy scaling is not constrained by the pulse duration. Dispersion-less soliton molecules and their deterministic transitioning to single solitons are also evidenced. These findings broaden the fundamental scope of the dissipative soliton paradigm and open new avenues for generating soliton pulses and frequency combs endowed with unprecedented temporal and spectral features. A novel class of solitons, which builds up in spectrally confined optical cavities when dispersion is practically absent, is revealed both theoretically and experimentally, opening new avenues for generating soliton pulses and frequency combs endowed with unprecedented temporal and spectral features.

Ultrawideband beamforming is essential for next-generation radar and communication systems, however, the instantaneous bandwidth of phase-shifter-based phased array antennas (PAAs) is limited by beam squint. Photonic true-time-delay (TTD) beamformers offer a potential solution, yet their practical deployment is hindered by complex delay-line architectures. Here, we report a frequency-comb-steered photonic quasi-TTD beamforming approach that eliminates delay lines by leveraging frequency-diverse arrays and photonic microwave mixing arrays. This enables squint-free beamforming and continuous beam steering for widely used linear frequency modulation (LFM) waveforms, effectively delivering infinite spatial resolution. We present 16-element linear and 4×4 planar PAA prototypes, achieving 6 GHz instantaneous bandwidth across the entire Ku-band. Furthermore, we demonstrate integrated sensing and communication capabilities, including inverse synthetic aperture radar imaging with 2.6 × 3.0 cm resolution and 4.8 Gbps wireless transmission. This work establishes a compact, robust, and scalable architecture for ultrawideband, large-scale photonic PAAs, paving the way for future integrated radar and communication systems. Ultrawideband beamforming is essential for next generation radar and communication. Here, authors demonstrate a photonic beamforming approach using frequency combs that enables beamforming and continuous beam-steering of LFM waveforms, supporting high-performance integrated sensing and communication.

The phenomenon of coherence resonance (CR) in two typical kinds of fractional van del Pol oscillator is investigated. For the first model, the damping term of the ordinary van der Pol oscillator is replaced by a fractional-order damping. While in the second model, the fractional-order damping is instead of the inertia term of the ordinary van der Pol oscillator. In the first model, there is obvious CR by adjusting the noise intensity. The resonance frequency mainly depends on the value of the fractional-order but it is almost independent of the noise intensity when the noise intensity is small, but change with the noise intensity when the noise intensity lies in a slightly large range. However, the resonance frequency of the ordinary van der Pol oscillator does not influence by the noise. In addition, with the increase of the fractional-order, the resonance frequency decreases monotonicity. Whereas, the resonance amplitude is a nonmonotonic function of the fractional-order. When the fractional oscillator deviates from the ordinary one, the resonance amplitude is much greater. In the second model, CR occurs only when the fractional oscillator is very close to the ordinary van der Pol oscillator. Comparing CR in the first model with that in the second model, we find that the value of the fractional-order can be taken over a much larger range to induce CR for the first one. The study shows that the inertia term is an indispensable factor in causing CR phenomenon while the fractional-order damping only changes the resonance frequency in different kinds of van der Pol oscillators. Graphic abstract Coherence resonance phenomenon in the fractional van der Pol oscillator under different values of the fractional-order and noise intensity.

The numerical simulation method is used to mimic the outflow field of 30 ° Ahmed model. The accuracy of the simulation method is verified by comparing with the wind tunnel test results. Based on the aerodynamic characteristics of the wind tunnel model, the impact of Ahmed on the structure is explored by combining the numerical simulation method of Ahmed model. The results show that the fold structure has more significant effect on lift and less effect on aerodynamic resistance.

This paper describe an approach to optimize the economy of electric vehicles’fast charging station investment with service satisfaction be constraints. An optimized model is proposed to study the relationship between the number of charge devices and economy of investment, which is based on the internal rate of return. Some service index like the queuing time and queuing length based on queuing theory are calculated to make sure the result reasonable and attainable for both investors and customers. At last, an example based on a conventional traffic flow and service intensity is simulated on Matlab to prove the effectiveness of the model.

Solitons are self-reinforcing localized wave packets arising from a balance of linear and nonlinear effects. This definition encompasses the interplay of nonlinear gain and loss, leading to the concept of dissipative solitons that has been instrumental in understanding the wide variety of mode locking phenomena in ultrafast optics. To date, most studies have involved the group velocity dispersion as a key ingredient for soliton generation. Here, we report on a novel kind of soliton, both theoretically and experimentally, which builds up in spectrally confined cavities when dispersion is practically absent. Precisely, the interplay between the Kerr nonlinearity and spectral filtering results in an infinite hierarchy of eigenfunctions which, combined with optical gain, allow for the generation of stable dispersion-less dissipative solitons in a previously uncharted regime. When the filter order tends to be infinite, we find an unexpected link between dissipative and conservative solitons, in the form of Nyquist-pulse-like solitons endowed with an ultra-flat spectrum. In contrast to the dispersion-enabled solitons, these dispersion-less Nyquist solitons build on a fully confined spectrum and their energy scaling is not constrained by the pulse duration. This study broadens the fundamental scope of dissipative soliton physics and opens new avenues for engineering optical solitons endowed with superior temporal and spectral features.

We have found two kinds of ultra-sensitive vibrational resonance in coupled nonlinear systems. It is particularly worth pointing out that this ultra-sensitive vibrational resonance is a transient behavior caused by transient chaos. Considering long-term response, the system will transform from transient chaos to periodic response. The pattern of vibrational resonance will also transform from ultra-sensitive vibrational resonance to conventional vibrational resonance. This article focuses on the transient ultra-sensitive vibrational resonance phenomenon. It is induced by a small disturbance of the high-frequency excitation and the initial simulation conditions, respectively. The damping coefficient and the coupling strength are the key factors to induce the ultra-sensitive vibrational resonance. By increasing these two parameters, the vibrational resonance pattern can be transformed from an ultra-sensitive vibrational resonance to a conventional vibrational resonance. The reason for different vibrational resonance patterns to occur lies in the state of the system response. The response usually presents transient chaotic behavior when the ultra-sensitive vibrational resonance appears and the plot of the response amplitude versus the controlled parameters shows a highly fractalized pattern. When the response is periodic or doubly-periodic, it usually corresponds to the conventional vibrational resonance. The ultra-sensitive vibrational resonance not only occurs at the excitation frequency, but it also occurs at some more nonlinear frequency components. The ultra-sensitive vibrational resonance as a transient behavior and the transformation of vibrational resonance patterns are new phenomena in coupled nonlinear systems.

Microwave phased array antennas (PAAs) are very attractive to defense applications and high-speed wireless communications for their abilities of fast beam scanning and complex beam pattern control. However, traditional PAAs based on phase shifters suffer from the beam-squint problem and have limited bandwidths. True-time-delay (TTD) beamforming based on low-loss photonic delay lines can solve this problem. But it is still quite challenging to build large-scale photonic TTD beamformers due to their high hardware complexity. In this paper, we demonstrate a photonic TTD beamforming network based on a miniature microresonator frequency comb (microcomb) source and dispersive time delay. A method incorporating optical phase modulation and programmable spectral shaping is proposed for positive and negative apodization weighting to achieve arbitrary microwave beam pattern control. The experimentally demonstrated TTD beamforming network can support a PAA with 21 elements. The microwave frequency range is \\(\\mathbf{8\\sim20\\ {GHz}}\\), and the beam scanning range is \\(\\mathbf{\\pm 60.2^\\circ}\\). Detailed measurements of the microwave amplitudes and phases are performed. The beamforming performances of Gaussian, rectangular beams and beam notch steering are evaluated through simulations by assuming a uniform radiating antenna array. The scheme can potentially support larger PAAs with hundreds of elements by increasing the number of comb lines with broadband microcomb generation.

Modal crosstalk is the main bottleneck in MMF-enabled optical datacenter networks with direct detection. A novel time-slicing-based crosstalk-mitigated MDM scheme is first proposed, then theoretically analyzed and experimentally demonstrated.

Load model identification using small disturbance data is studied. It is proved that the individual load to be identified and the rest of the system forms a closed-loop system. Then, the impacts of disturbances entering the feedforward channel (internal disturbance) and feedback channel (external disturbance) on relationship between load inputs and outputs are examined analytically. It is found out that relationship between load inputs and outputs is not determined by load itself (feedforward transfer function) only, but also related with equivalent network matrix (feedback transfer function). Thus, load identification is closed loop identification essentially and the impact of closed loop identification cannot be neglected when using small disturbance data to identify load parameters. Closed loop load model identification can be solved by prediction error method (PEM). Implementation of PEM based on a Kalman filtering formulation is detailed. Identification results using simulated data demonstrates the correctness and significance of theoretical analysis.