Resonant System Research Articles

Heat transfer-deformation characteristics and fracture damage analysis during LN2 freeze-thaw process in different rank coals

Exploring the heat transfer and deformation characteristics of coal bodies of different coal ranks during the freeze-thaw process is of significant importance for analyzing the fracture mechanism under the effect of liquid nitrogen (LN2). This experiment targets lignite, bituminite, and anthracite under both saturated and dry conditions. A real-time temperature-strain monitoring system was employed to observe the heat transfer and deformation characteristics of coal samples with different ranks throughout the freeze-thaw cycle. Additionally, a nuclear magnetic resonance system was utilized to examine the characteristics of pore damage before and after fracturing. The findings reveal: (1) During the freeze-thaw process, the absolute value of the temperature evolution rate for dry coal samples shows a negative correlation with coal rank, indicating a close link between temperature diffusion and intrinsic coal properties like oxygen content and porosity. (2) For saturated coal samples, the absolute value of the temperature change rate during freezing decreases as the coal rank increases, with the opposite trend observed during thawing. The phase change effect of water in fractures during freezing can enhance internal temperature diffusion in the coal body, while it acts as an inhibitor during thawing. (3) Based on the trend of strain fluctuations, the coal body deformation process during the freeze-thaw cycle can be segmented into seven stages, summarizing the general mechanisms of deformation failure. (4) Under saturated conditions, the amplitude of elastic deformation for each sample is negatively correlated with coal rank, with the sequence for dry coal samples being bituminite > anthracite > lignite. (5) The formation of a sealed space at the beginning of freezing is identified as a necessary condition for deformation during the freeze-thaw process, with the formation and strength of the sealed space depending on the temperature diffusion rate, moisture content, and inherent properties of the coal sample.

Scattering and blow up for nonlinear Schrödinger equation with the averaged nonlinearity

We consider the 3-dimensional nonlinear Schrödinger equation (NLS) with average nonlinearity. This is a limiting model of NLS with strong magnetic confinement and a generalized model of the resonant system of NLS with a partial harmonic oscillator in terms of nonlinear power. We provide a new proof for the conservation law of kinetic energy and remove the restriction on nonlinearity. Moreover, in the case of focusing, super-quintic, and sub-nonic, we construct a new ground-state solution and classify the behavior of the solutions below the ground state. We demonstrate a sharp threshold for scattering and blow-up.

Functional analytic methods for discrete approximations of subwavelength resonator systems

Functional analytic methods for discrete approximations of subwavelength resonator systems

A space-adiabatic theorem for longitudinal and transversal wave motion analysis of graded metamaterials

The use of graded metamaterials is widespread in the fields of wave manipulation and energy harvesting. However, they have the drawback of causing energy scattering after a certain period due to wave reflection or trapping, known as the rainbow effect, in some cases. To address this issue, we extend the adiabatic theorem to the spatial modulation field to mitigate the impact of the rainbow effect, thereby enhancing transmission at the interface of graded metamaterials. Firstly, an analytical expression for the limiting gradient in the space-adiabatic theorem is derived. Then, it is applied to study the longitudinal wave motion in a spring-mass with graded resonators (SMGR) system and the transversal wave motion in a beam with graded resonators (BGR) system. The numerical study demonstrates that if the spatial gradient of system properties is small enough to satisfy the adiabatic theorem, wave scattering can almost be neglected, and transmission will experience a significant increase compared to the non-adiabatic case. Finally, the critical boundary between adiabatic and non-adiabatic cases is determined using the fitting method. This study introduces a design strategy for graded metamaterials, offering opportunities for communication, sensing, energy harvesting, and various other applications.

Customizing subwavelength stochastic light fields via structured spatial coherence in a high-NA resonator

Interaction of light in the high-numerical aperture (high-NA) systems is crucial for theoretical advances and applications such as superresolution imaging and optical nanofabrication. High coherence is demanded at this scale for intensity and spin profile sculpturing, since the underlying physics being wave interference. Here we report that, even for low-coherence light, 3D light features in a nanometer range can be generated by employing structured coherence states of the light beam in a high-NA resonator system. The generated structures, e.g., 3D helix intensity and transverse spin texture, can survive in rather incoherent optical fields at nanoscale. We also found that, counterintuitively, despite the substantial decrease in spatial coherence of the light field, the longitudinal electric field component and transverse spin density are instead enhanced. The applications of the observed twisted spectral density and spin structures may range from high-resolution imaging to metrology.

Piezoelectric Ultrasonic Local Resonant Ultra-Precision Grinding for Hard-Brittle Materials.

Hard-brittle materials are widely used in the optics, electronics, and aviation industries, but their high hardness and brittleness make it challenging for traditional processing methods to achieve high efficiency and superior surface quality. This study aims to investigate the application of ultrasonic local resonant grinding to sapphire to improve the efficiency and meet the requirements for the optical window in the surface roughness of the material. The resonant frequency of a piezoelectric ultrasonic vibration system and the vibration amplitude of a grinding head's working face were simulated and tested, respectively. The results of ultrasonic grinding experiments showed that the local resonant system reduced the surface roughness parameter (Ra) of sapphire to 14 nm and improved its surface flatness to 44.2 nm, thus meeting the requirements for the ultra-precision grinding of sapphire. Compared with a conventional resonant system, the surface roughness of the sapphire ground with the local resonant system was reduced by 90.79%, its surface flatness was improved by 81.58%, and the material removal rate was increased by 31.35%. These experimental results showed that ultrasonic local resonant grinding has better effects than those of conventional ultrasonic grinding in improving surface quality and increasing the material removal rate.

Unveiling the tradeoff between device scale and surface nonidealities for an optimized quality factor at room temperature in 2D MoS2 nanomechanical resonators

A high quality (Q) factor is essential for enhancing the performance of resonant nanoelectromechanical systems (NEMS). NEMS resonators based on two-dimensional (2D) materials such as molybdenum disulfide (MoS2) have high frequency tunability, large dynamic range, and high sensitivity, yet room-temperature Q factors are typically less than 1000. Here, we systematically investigate the effects of device size and surface nonidealities on Q factor by measuring 52 dry-transferred fully clamped circular MoS2 NEMS resonators with diameters ranging from 1 μm to 8 μm, and optimize the Q factor by combining these effects with the strain-modulated dissipation model. We find that Q factor first increases and then decreases with diameter, with an optimized room-temperature Q factor up to 3315 ± 115 for a 2-μm-diameter device. Through extensive characterization and analysis using Raman spectroscopy, atomic force microscopy, and scanning electron microscopy, we demonstrate that surface nonidealities such as wrinkles, residues, and bubbles are especially significant for decreasing Q factor, especially for larger suspended membranes, while resonators with flat and smooth surfaces typically have larger Q factors. To further optimize Q factors, we measure and model Q factor dependence on the gate voltage, showing that smaller DC and radio-frequency (RF) driving voltages always lead to a higher Q factor, consistent with the strain-modulated dissipation model. This optimization of the Q factor delineates a straightforward and promising pathway for designing high-Q 2D NEMS resonators for ultrasensitive transducers, efficient RF communications, and low-power memory and computing.

Application of a vibration resonance-assisted enhanced feedforward cascaded stochastic resonance system in bearing diagnostics

Extracting fault features from strong background noise is a key challenge in bearing diagnostics. Stochastic resonance (SR) has been widely applied in bearing diagnostics by utilizing noise to enhance useful signals. This paper proposes a feedforward cascaded system based on vibration resonance (VR) to assist in enhancing SR from the perspective of multi-system synergy, aiming to improve the performance of the SR system. Firstly, a matching steady-state potential function is designed to effectively alleviate the output saturation phenomenon. Then, by introducing a feedback term and VR, a feedforward cascaded system with band-pass characteristics is constructed, significantly enhancing the ability to suppress low-frequency interference. Finally, the proposed system is analyzed in the detection of simulated signals and actual bearing fault signals from the German PADERBORN dataset. The results demonstrate that the system outperforms two other SR systems and the Fast-Kurtogram method (FK), validating its performance and practicality.

Ultrathin metal-dielectric planar interface for high-performance photonic spin Hall effect

Abstract This study explores the photonic spin Hall effect (PSHE) with a focus on its sensitivity to incident wave polarization and physical parameter variations. Traditionally surface plasmonic resonance (SPR) systems mainly enhance H-polarized PSHE. However, our proposed method involves an ultrathin metal layer, capped with a glass dielectric layer on a glass substrate, to achieve high-performance PSHE for both H- and V-polarization waves. This high-performance PSHE in terms of enhancement in PSHE magnitudes arises from the simultaneous presence of SPR and waveguiding effects, resulting in the emergence of hybrid TE and TM modes. Investigating Au and Ag ultrathin metal layers, we find that the highest H-polarized PSHE occurs at ~1.52 × 10^6 nm and ~2.05 × 10^5 nm for Au and Ag, respectively. Similarly, for Vpolarized incident light, maximum enhanced PSHE is observed at ~1.58 × 10^5 nm and ~9.48 × 10^4 nm for Au and Ag, respectively. By adjusting the thickness of the metal and/or glass cap layer, precise control over PSHE amplitude and active polarization response is achievable. This research unveils unique capabilities for generating hybrid modes that enhance PSHE for both polarizations, offering a potential platform for developing tunable polarizationfavorable spin optics optoelectronic devices.

Exponentially localized interface eigenmodes in finite chains of resonators

AbstractThis paper studies wave localization in chains of finitely many resonators. There is an extensive theory predicting the existence of localized modes induced by defects in infinitely periodic systems. This work extends these principles to finite‐sized systems. We consider one‐dimensional, finite systems of subwavelength resonators arranged in dimers that have a geometric defect in the structure. This is a classical wave analog of the Su–Schrieffer–Heeger model. We prove the existence of a spectral gap for defectless finite dimer structures and find a direct relationship between eigenvalues being within the spectral gap and the localization of their associated eigenmode. Then, for sufficiently large‐size systems, we show the existence and uniqueness of an eigenvalue in the gap in the defect structure, proving the existence of a unique localized interface mode. To the best of our knowledge, our method, based on Chebyshev polynomials, is the first to characterize quantitatively the localized interface modes in systems of finitely many resonators.

Parameter-induced logical stochastic resonance in substrate potential with deformable sine-Gordon shape

Logical stochastic resonance (LSR) systems are physical nonlinear systems capable of robust Boolean logic operations under the influence of noise. While LSR systems suitable for electronic circuit implementation have been extensively studied, research on condensed matter LSR systems remains limited to constrained bistability with saturation characteristic. Considering the presence of periodic nonlinearities in many physical systems, a deformable sine-Gordon-shaped Remoissenet–Peyrard potential (RPP)-based LSR system is proposed for the first time in this work. Testing under both noise-free and noisy conditions proves the existence of parameter-induced LSR phenomena in the proposed system. Moreover, we find that a relatively wide potential well shape contributes to enhanced noise robustness in the RPP-based LSR system. Additionally, traditional polynomial nonlinearity-based LSR systems are compared with the proposed system. Regardless of whether the noise is Gaussian white noise or composite noise containing spiking pulses, the RPP-based LSR system exhibits superior robustness. The results demonstrate the exceptional advantages of the RPP-based LSR system and encourage further design of condensed matter LSR systems based on deformable periodic nonlinearities.

Nonintegrability of 3 DoF Hamiltonian Resonant Systems

We review a number of methods to prove nonintegrability of Hamiltonian systems and focus on 3 Degrees-of-Freedom (DoF) systems listing the known results for the prominent resonances. Associated with the Hamiltonian systems are the averaged-normal forms that provide us with geometric insight, approximations of orbits and measures of chaos. Symmetries do change the qualitative and quantitative pictures; we illustrate this for the 1:2:1 resonance with discrete symmetry in the 1st and 3rd DoF. In this case, the averaged-normal form is still nonintegrable, but it becomes integrable when adding discrete symmetry in all DoF. Apart from the short-periodic solutions obtained by averaging, we find many periodic solutions. There is numerical evidence of the presence of Šilnikov bifurcation which clarifies the presence of nonintegrability phenomena qualitatively and quantitatively.

Design of a locally resonant system to reduce noise inside the payload fairing of a launcher during the lift-off

The high sound pressure exerted on the payload during the launch of space vehicles can jeopardize its structural integrity. Given space and weight restrictions, designing fairing noise protection systems is not easy and the number of alternatives is limited, especially for small launchers. This work proposes the design of an acoustic protection based on an simultaneous increase of insulation and absorption in the system tailored to the payload fairing of a space launcher. To this end, the use of a panel made of Helmholtz resonators is investigated. The panel presents a deep subwavelength thickness, as well as a highly efficient acoustic protection (90% of absorption and 13 dB of Transmission Loss) over the frequency range of interest. The panel is designed by considering a reciprocal and non mirror symmetric transmission problem and the acoustic incidence from both sides of the panel. A high Transmission Loss in the frequency range of interest is then obtained when considering an incidence coming from the outside of the payload fairing, whereas the quasi-perfect absorption of acoustic waves is observed in the case where the incidence comes from the inside of the fairing. The panels are subsequently prototyped and their performance is experimentally evaluated. Measurements are correlated and discussed in view of the theoretical and numerical predictions. This mitigation approach sets a new trajectory for innovative noise reduction in small-scale space launchers.

Finite automated system to design a high efficiency LLC resonant converter system for 3 kW. PV solar array

A combination of electrical circuit design and the Finite Automation model leads to improved efficiency in terms of memory usage, computation time, and overall performance. LLC resonant converters are known for their high efficiency and ability to convert DC voltage from solar panels into the desired AC voltage for grid-tied or off-grid PV systems. However, designing, testing, and implementing LLC in a PV system requires careful consideration of various factors, including voltage and current requirements, resonant frequency, and compliance with standards and regulations. Eight cases are taken for this purpose with a special case of a 3kW-PV module. The major parameters for the LLC resonant Converter were 480-500V. as output voltage for 36-40V. input voltage range with a 39V. nominal voltage. The calculated coefficients for these values were as follows: A = C = 7.29, B = -50.58, D = -0.25, and E = -11. Combining LLC circuit design with FA, it is providing 94.5 % efficiency through selecting precise parameters that minimized overall calculated losses such as conductive and switching types. The right path and accepted words for different cases are given to provide several solutions with the correct path of design. ZVS and ZCS have been obtained through precise selection process of phase shift between Half Bridge of LLC circuit achieved by this design.

AEEFCSR: an adaptive ensemble empirical feed-forward cascade stochastic resonance system for weak signal detection

Abstract A novel adaptive ensemble empirical feed-forward cascade stochastic resonance (AEEFCSR) method is proposed in this study for the challenges of detecting target signals from intense background noise. At first, we create an unsaturated piecewise self-adaptive variable-stable potential function to overcome the limitations of traditional potential functions. Subsequently, based on the foundation of a feed-forward cascaded stochastic resonance method, a novel weighted function and system architecture is created, which effectively addresses the issue of low-frequency noise enrichment through ensemble empirical mode decomposition. Lastly, inspired by the spider wasp algorithm and nutcracker optimization algorithm, the spider wasp nutcracker optimization algorithm is proposed to optimize the system parameters and overcome the problem of relying on manual experience. In this paper, to evaluate its performance, the output signal-to-noise ratio (SNR), spectral sub-peak difference, and time-domain recovery capability are used as evaluation metrics. The AEEFCSR method is demonstrated through theoretical analysis. To further illustrate the performance of the AEEFCSR method, Validate the adoption of multiple engineering datasets. The results show that compared with the compared algorithms, the output SNR of the AEEFCSR method is at least 6.2801 dB higher, the spectral subpeak difference is more than 0.25 higher, and the time-domain recovery effect is more excellent. In summary, the AEEFCSR method has great potential for weak signal detection in complex environments.

Temperature Dependence of the Sensitivity of PVDF Pyroelectric Sensors to THz Radiation: Towards Cryogenic Applications.

The application of terahertz (THz) science in industrial technology and scientific research requires efficient THz detectors. Such detectors should be able to operate under various external conditions and conform to existing geometric constraints in the required application. Pyroelectric THz detectors are among the best candidates. This is due to their versatility, outstanding performance, ease of fabrication, and robustness. In this paper, we propose a compact pyroelectric detector based on a bioriented poled polyvinylidene difluoride film coated with sputtered metal electrodes for in situ absorption measurement at cryogenic temperature. The detector design was optimized for the registration system of the electron paramagnetic resonance (EPR) endstation of the Novosibirsk Free Electron Laser facility. Measurements of the detector response to pulsed THz radiation at different temperatures and electrode materials showed that the response varies with both the temperature and the type of electrode material used. The maximum signal level corresponds to the temperature range of 10-40 K, in which the pyroelectric coefficient of the PVDF film also has a maximum value. Among the three coatings studied, namely indium tin oxide (ITO), Au, and Cu/Ni, the latter has the highest increase in sensitivity at low temperature. The possibility of using the detectors for in situ absorption measurement was exemplified using two typical molecular spin systems, which exhibited a transparency of 20-30% at 76.9 cm-1 and 5 K. Such measurements, carried out directly in the cryostat with the main recording system and sample fully configured, allow precise control of the THz radiation parameters at the EPR endstation.

LCL/CLC Resonant Rectifier-Based Inductive Power Transfer Systems With Integrated Coil Structure and Inherent CC and CV Battery-Charging Profile

LCL/CLC Resonant Rectifier-Based Inductive Power Transfer Systems With Integrated Coil Structure and Inherent CC and CV Battery-Charging Profile

ХАРАКТЕРИСТИКИ РЕЗОНАНСНИХ СИСТЕМ ДЛЯ ОТРИМАННЯ ВИСОКОЇ НАПРУГИ НА НАВАНТАЖЕННІ ЄМНІСНОГО ТИПУ

The work is devoted to the comparative analysis of currents in inverter circuits of transformerless resonant and transformer resonant and non-resonant systems of the same power for obtaining high voltage on a capacitive load. The purpose of the work is to determine the type of system characterized by the smallest average operating current of the inverter switches. The dependence of the currents in the circuits of the inverters on the parameters of the resonant circuits was obtained, the results of calculations according to which allow us to state that the use of a transformerless circuit to ensure the same power of systems for obtaining high voltage on a capacitive type load will allow to almost halve the average operating current in the inverter circuit. Simulation modeling of the processes in the studied schemes was carried out, which confirms the obtained theoretical results. The use of high-voltage transformerless resonant systems to obtain high voltage on a capacitive load will allow to halve the nominal and maximum permissible current characteristics of the power elements of the converters. Ref. 10, fig. 3.

A novel exponential unsaturated bistable stochastic resonance-boosted incipient fault identification in rotating machineries

Abstract Stochastic resonance (SR) for weak fault detection stands as a significant constructive methodology leveraging noise in nonlinear information systems processing. In virtue of the SR technique in conjunction with coupled non-saturated nonlinear systems, an exponential unsaturated bistable stochastic resonance (EUBSR) model is developed to enhance output levels. By integrating the exponential monostable stochastic resonance system (ESR) and the unsaturated bistable stochastic resonance (UBSR) system through coupling coefficients, this model offers a broader spectrum of resonance characteristics. The performance of the EUBSR is evaluated based on the relevant indicators signal-to-noise ratio (SNR) and residence time distribution ratio. These indicators are treated as multi-objective functions, with the coati optimization algorithm employed to optimize both the parameters and coupling coefficients of the EUBSR model simultaneously. Moreover, the paper takes into account the interdependence of nonlinear systems and their interactions by considering both cascade and parallel models of the ESR and UBSR systems. Fault diagnosis is carried out on simulation signals and bearings to validate the effectiveness of the proposed EUBSR model. The results demonstrate that the EUBSR model surpasses not only its individual component models but also cascade and parallel models.

A tiny Drude scatterer can accurately model a coherent emitter in nanophotonics

Abstract We add a missing element to the set of directly computable scenarios of light-matter-interaction within classical numerical Maxwell solvers, i.e., light scattering from hybrid systems of resonators and individual Fourier-limited emitters. In particular, individual emitters are incorporated as tiny polarizable and resonant spherical scatterers. This emitter model is based on well-known extremal properties of Mie modes. The spherical emitter is made from an artificial Drude metal with ϵ ( ω ) = ϵ b − ω p 2 / ( ω 2 + i Γ ω ) ${\epsilon}(\omega )={{\epsilon}}_{b}-{\omega }_{p}^{2}/({\omega }^{2}+i{\Gamma }\omega )$ . By tuning ϵ b and ω p we adjust the resonance frequency and the Fourier-limited linewidth and by adjusting Γ we may add non-radiative damping or dephasing. This approach automatically reproduces the ideal text book coherent scattering cross-section of Fourier-limited two level quantum systems of σ 0 = 3λ 2/(2πϵ out) which is not possible with typically used Lorentz permittivities which only mimic optical resonances. Further, the emitter’s linewidth adopts to the surrounding optical local density of states (LDOS). To demonstrate this we successfully benchmark our approach with prominent examples from the literature.