Resonance Phase Research Articles

Denoising sphere‐valued data by relaxed total variation regularization

AbstractCircle‐ and sphere‐valued data play a significant role in inverse problems like magnetic resonance phase imaging and radar interferometry, in the analysis of directional information, and in color restoration tasks. In this paper, we aim to restore ‐sphere‐valued signals exploiting the classical anisotropic total variation on the surrounding ‐dimensional Euclidean space. For this, we propose a novel variational formulation, whose data fidelity is based on inner products instead of the usually employed squared norms. Convexifying the resulting non‐convex problem and using ADMM, we derive an efficient and fast numerical denoiser. In the special case of binary (0‐sphere‐valued) signals, the relaxation is provable tight, that is, the relaxed solution can be used to construct a solution of the original non‐convex problem. Moreover, the tightness can be numerically observed for barcode and QR code denoising as well as in higher dimensional experiments like the color restoration using hue and chromaticity and the recovery of SO(3)‐valued signals.

Resonant frequency, phase and power estimation in a broadband substrate integrated waveguide two- channel T- type power divider using adaptive network-based fuzzy inference system

Resonant frequency, phase and power estimation in a broadband substrate integrated waveguide two- channel T- type power divider using adaptive network-based fuzzy inference system

Fast inspirals and the treatment of orbital resonances

Abstract Extreme mass ratio inspirals (EMRIs), where a compact object orbits a massive black hole, are a key source of gravitational waves for the future Laser Interferometer Space Antenna (LISA). Due to their small mass ratio, ε ~ 10-4 -- 10-7 , the binary evolves slowly and EMRI signals will be in-band for years. Additionally, astrophysical EMRIs are expected to have complex dynamics featuring both spin-precession and eccentricity. A standard approach to modelling these inspirals is via the method of osculating geodesics (OG) which we employ along with a toy model for the gravitational self-force. Using this method requires resolving tens of thousands radial and polar orbital librations over the long duration of the signal which makes the inspiral trajectory expensive to compute.In this work we accelerate these calculations by employing Near-Identity (averaging) Transformations. 
However, this averaging technique breaks down at orbital resonances where the radial and polar frequencies are an integer ratio of each other. Thus, we switch to a partial averaging transformation in the vicinity of the resonance where the dynamics are characterised by the slow evolution of the so-called ``resonant phase". Additionally, we develop an optimal switching criterion to minimise the computation time while maximising accuracy. We find the error in the waveform phase is improved from O(ε-1/2) in the fully averaged scheme to O(ε4/7) in the switching scheme. At the same time, this scheme improves the scaling of the computation time from being inversely proportional to ε using OG, to a very weak scaling with ε. This results in a speed-up of at least two orders of magnitude for LISA EMRIs with room for further optimisation.

Stability and Spin Waves of Skyrmion Tubes in Curved FeGe Nanowires.

In this work, we investigate the influence of curvature on the dynamic susceptibility in FeGe nanowires, both curved and straight, hosting a skyrmionic tube texture under the action of an external bias field, using micromagnetic simulations. Our results demonstrate that both the resonance frequencies and the number of resonant peaks are highly dependent on the curvature of the system. To further understand the nature of the spin wave modes, we analyze the spatial distributions of the resonant mode amplitudes and phases, describing the differences among resonance modes observed. The ability to control the dynamic properties and frequencies of these nanostructures underscores their potential application in frequency-selective magnetic devices.

The Challenges of Piezoelectric Actuators and Motors Application in a Space Environment

Piezoelectric actuators and motors are increasingly essential for space applications due to their precision, compactness, and efficiency. This review explores their advantages over traditional actuators, emphasizing their minimal electromagnetic interference, high responsiveness, and operational reliability in harsh space environments. This study highlights the challenges posed by space conditions such as vacuum, microgravity, extreme temperatures, and radiation, which require robust design and material considerations. A comprehensive review of missions using piezo actuators, including their operating principles, material advancements, and innovative designs tailored for space conditions. In addition, numerical calculations were performed by COMSOL Multiphysics 5.6 software with the aim of analyzing the impact of temperature variations typical of the low Earth orbit (LEO) on the electromechanical properties of the piezoelectric transducer. The results indicate significant variations in the characteristics of the resonant frequency, impedance, and phase frequency in a temperature range from −20 °C to 40 °C, emphasizing the importance of accounting for thermal effects in the design. The calculations show that advantages which are proposed by piezoelectric motion systems must be combined with adaptability to harsh environmental conditions and call for further research to enhance their robustness and performance for broader application in future space missions.

Design of main parameter of modular multilevel converter applied in power grid simulator

Abstract In the context of application in a power grid simulator, we investigated the parameter design issues of several crucial components of the Modular Multilevel Converter (MMC) topology applied to the power grid simulator system. These components include the bridge arm inductance and submodule capacitance. Based on the fundamental circuit of the MMC applied to the power grid simulator system, we introduced an equal discharge time constant H. We analyzed the capacitor voltage fluctuation rate and the equivalent capacitance discharge time constant “H”, discovering that they still exhibit an inversely proportional relationship across different engineering scenarios. Consequently, a general method for determining submodule capacitance parameters was proposed, and in conjunction with previous engineering parameters, recommended values for an equal discharge time constant of 40 ms were provided. Furthermore, we introduced the concepts of double-frequency circulating resonant angular frequency and phase resonant angular frequency, outlining the principles for determining the bridge arm reactance values. Through the analysis of corresponding parameters in previous engineering studies, universally applicable recommended values for the bridge arm reactance parameters were proposed, considering the unit resonant angular frequency as the power grid frequency angular frequency 1.0ω.

Piezoelectric temperature acoustic sensor of LiNbO3 crystal fibers operating at radio frequencies

This study focuses on the growth and characterization of crystalline LiNbO3 (LN) piezoelectric fibers pulled by the Laser Heated Pedestal Growth (LHPG) technique. The electrical properties of the fibers were investigated using an impedance analyzer, which yielded values for resonance frequency, anti-resonance frequency, and phase angle. Subsequently, elastic constants and coupling factor were determined through calculations based on thickness resonance modes. The accuracy of the resonance method was validated through numerical simulations utilizing COMSOL software, demonstrating a close agreement between experimental and simulated results. Additionally, a temperature sensing was conducted, subjecting the fibers to a wide temperature range from 30 °C to 236 °C to assess their sensitivity to temperature variations. The coupling factors of K = 0.37 for LN-1 and K = 0.35 for LN-2 demonstrated efficient performance of the crystalline fibers. Furthermore, the numerical simulations exhibited strong correlation between simulated and experimental data. The sensitivity analysis revealed the potential of LN fibers for temperature sensor applications, exhibiting a sensitivity of −87 Hz.°C−1. These findings underscore the promise of LN piezoelectric fibers in advanced sensing technologies.

Anisotropic Sensing Performance in a High-Sensitivity Surface Plasmon Resonance Sensor Based on Few-Layer Black Phosphorus.

Few-layer black phosphorus (FLBP) is a highly promising material for high sensitivity label-free surface plasmon resonance (SPR) sensors due to its exceptional electrical, optical, and mechanical properties. FLBP exhibits inherent anisotropy with different refractive indices along its two main crystal orientations, the zigzag and armchair axes. However, this anisotropic property is often overlooked in FLBP-based sensors. In this study, we conducted a comprehensive investigation of the SPR reflectivity and phase in a BK7-Ag-FLBP structure to understand the influence of the stacking sequence and the number of FLBP layers on the sensing performance. Clear resonant angle shifts caused by different stacking sequences of FLBP could be observed both theoretically and experimentally. In the theoretical study, the highest reflective and phase sensitivities were achieved with a 12-layer black phosphorus (BP) structure. The reflectivity sensitivity reached 287.9°/refractive index units (RIU) with the zz stacking 12-layer BP film exhibiting a sensitivity 76°/RIU higher than the ac stacking structure. Similarly, the phase sensitivity reached 1162°/RIU with the zz stacking 12-layer BP structure showing a sensitivity 276.9°/RIU higher than the ac stacking structure. The electric field distribution of the 12-layer BP structure with four different stacking sequences has also been analyzed. In the experiment study, the well-known Attenuated Total Reflection (ATR) θ-2θ SPR setup is utilized to detect the reflectivity and phase of BK7-Ag-FLBP structures. The FLBP samples with the same thickness but different stacking sequences show significant resonant angle shift (0.275°) and maximum phase difference variation (34.6°). The FLBP sample thickness and crystal orientations have been demonstrated using the angular-resolved polarized Raman spectroscopy (ARPRS). These theoretical and experimental results provide strong evidence that the stacking sequences of FLBP have a significant impact on the sensing performance of SPR sensors. By harnessing the anisotropic properties of materials like FLBP, novel structures of anisotropic-2D material-based SPR sensors could open up exciting possibilities for innovative applications.

Static topological mechanics with local resonance

The locally resonant band gaps that lie in the vicinity of resonant frequency have been extensively employed in metamaterials for ultralow-frequency wave control, such as vibration isolation, negative refraction, superlensing, and cloaking. The combination of local resonance and band topology allows for the broadband tunable topological boundary modes, ranging from audible to ultrasonic frequencies. Recently, nontrivial topological boundary modes have been reported in static mechanical systems beyond frequency-based wave dynamics, in which the band gap is typically Bragg-like. In this paper, the concept of local resonance is extended from dynamic to static systems where the inertial effects are absent, and is leveraged to customize the topological modes. We impart a pseudo-mass to the static systems and retrieve the locally resonant band gap. The eigenvalues and associated bulk deformation fields of the topological mode can be tailored by shifting the pseudo-resonant frequency. Moreover, an effective non-reciprocity is achieved by passively breaking the lattice symmetry, and its cooperation with local resonances enables the static metamaterial to shield eccentric deformations and selectively filter boundary loads. All of these models are experimentally validated in an assembled truss-like lattice. This study is expected to provide a platform for exploring locally resonant topological phases without relying on wave motion.

Damped kink motions in a system of two solar coronal tubes with elliptic cross sections

Aims. This study is motivated by observations of coordinated transverse displacements in neighboring solar active region loops, addressing specifically how the behavior of kink motions in straight two-tube equilibria is impacted by tube interactions and tube cross-sectional shapes. Methods. We worked with linear, ideal, pressureless magnetohydrodynamics. Axially standing kink motions were examined as an initial value problem for transversely structured equilibria involving two identical, field-aligned, density-enhanced tubes with elliptic cross sections (elliptic tubes). Continuously nonuniform layers were implemented around both tube boundaries. We numerically followed the system response to external velocity drivers, largely focusing on the quasi-mode stage of internal flows to derive the pertinent periods and damping times. Results. The periods and damping times that we derive for two-circular-tube setups justify the available modal results found with the T-matrix approach. Regardless of cross-sectional shapes, our nonuniform layers feature the development of small-scale shears and energy accumulation around Alfvén resonances, indicative of resonant absorption and phase mixing. As with two-circular-tube systems, our configurational symmetries still make it possible to classify lower-order kink motions by the polarization and symmetric properties of the internal flows; hence, such motions are labeled as S​x and Ax. However, the periods and damping times for two-elliptic-tube setups further depend on cross-sectional aspect ratios, with Ax motions occasionally damped less rapidly than S​x motions. We find uncertainties up to ∼20% (∼50%) for the axial Alfvén time (the inhomogeneity lengthscale) if the periods (damping times) computed for two-elliptic-tube setups are seismologically inverted with canonical theories for isolated circular tubes. Conclusions. The effects of loop interactions and cross-sectional shapes need to be considered when the periods, and in particular the damping times, are seismologically exploited for coordinated transverse displacements in adjacent coronal loops.

Why the Laplace Resonant Angle is So Special

We analyze adjacent local pairs of mean-motion resonances (MMRs) between three orbiting bodies designed to produce a Laplace resonant phase angle φ L or one of its multiples N φ L, where integer N ≥ 2. This assumption yields a concrete pattern of Laplace resonances, very few of which (with angles φ L and 2φ L) have been observed in actual (extra)solar subsystems. All other MMRs face issues of proximity or remoteness of the orbits (they are too close or too far apart). We highlight one as yet unobservable MMR in each N-sequence for which these issues appear to be less acute.

Metasurface-based wide-angle reflective metalens with consistently constant focusing efficiency

Terahertz (THz) communication technology has drawn a lot of attention due to advancements in global research and aspirations for 6G communication as well as the development of THz technology. It is desirable to have a reflective metalens that can gather light from many directions and focus it at a fixed place. We employed the diffractive neural network (DNN) to design a wide-angle metasurface-based reflective metalens in order to meet this technical need. This reflective metalens is capable of consistently and efficiently reflecting incident light from a wide angle of incidence and focusing it into one spot. The DNN is used to quantitatively optimize the phase distribution of the reflective metalens and the resonance phase modulation approach is adopted to develop the unit structure. Both simulation and experimentation in a 220 GHz environment were used to confirm the reflective metalens's functionality. Through increased wide-angle reflection and directional focusing homogeneity and efficiency, the suggested technology offers a practical means of addressing the problems associated with 6G communication.

Experimental Characterization of RF-SQUIDs Based Josephson Traveling Wave Parametric Amplifier Exploiting Resonant Phase Matching Scheme

Experimental Characterization of RF-SQUIDs Based Josephson Traveling Wave Parametric Amplifier Exploiting Resonant Phase Matching Scheme

WITHDRAWN: The periodic evolution of the resonant mode in a lossy microfiber coil resonator with three turns

The periodic evolution of the resonant mode in a lossy microfiber coil resonator with three turns is unraveled, and two types of loss conditions are assumed to investigate the characteristics of resonant mode with respect to the coupling state by means of numerical modeling. Under a given loss condition, the resonant mode exhibits periodic evolution between normal resonance, white-light cavity effect and resonance mode splitting as the change of the phase shift and coupling state. When the coupling state exceeds a certain threshold under a specific loss coefficient, the microfiber coil resonator predominantly exhibits normal resonance with characteristics akin to a single-ring resonator. Once the coupling state decreases to this threshold and matches the loss, white-light cavity effect will be activated. Moreover, as the coupling state falls below this threshold, the degeneracy of the resonance mode is raised and the resonant phase undergoes a bifurcation. The excitation conditions for each resonant mode have been derived, and the critical coupling conditions exist for both normal resonance and mode splitting in the case of relatively small losses. It’s found that there exists a threshold loss at which the critical coupling states of normal resonance and mode splitting coincide with the condition of white-light cavity effect. The characteristics of each mode have also been discussed.

Four-channel near-field focusing metasurface lens based on frequency-polarization multiplexing

In response to the issue of traditional near-field focusing metasurfaces having a single working frequency band and limited focusing functionality, this paper proposes a four-channel focusing metasurface based on frequency-polarization multiplexing. Utilizing the principles of anisotropy and metasurface resonant phase, a metasurface unit composed of two sets of orthogonal resonators was designed. The designed units have independent transmission amplitude and phase at 15 GHz and 23 GHz, with the transmission phase of the two sets of resonators encoded in 2-bit and 1-bit based on phase differences of 90° and 180°, respectively. Based on the units, combined with the focusing principle of metasurface lenses and the principle of phase superposition, a four-channel near-field focusing metasurface lens was designed. The lens is composed of 20 × 20 units, measuring 200 × 200 mm2. Numerical simulations and experimental results demonstrate that the designed metasurface lens achieves single-point and dual-points focusing at 15 GHz under x- and y-polarized wave incidence, with the focus at the z = 70 mm plane and a maximum focusing efficiency of 48.5%. At 23 GHz under x- and y-polarized wave incidence, metasurface lens focuses electromagnetic waves at different positions, with the focus at the z = 80 mm plane and a maximum focusing efficiency of 27.8%. The metasurface lens designed by this method is expected to find applications in fields such as Medical Sensing, Microwave Imaging, and Integrated Optics.

Polarization-insensitive wide-angle resonant acousto-optic phase modulator.

Phase modulators are commonly used devices in optics. Free-space phase modulators are typically constructed from optically anisotropic crystals exhibiting the Pockels effect. To preserve the light's polarization state as it propagates through the crystal, it is essential to align the polarization and the angle of incidence of the light with respect to the crystal. In this study, we demonstrate the feasibility of constructing free-space resonant phase modulators with a broad acceptance angle and minimal dependence on the polarization state of light using an acousto-optic approach. These modulators operate in the megahertz frequency range, require modest power levels, have aperture sizes exceeding 1 cm2, and feature sub-millimeter thickness.

Amplitude and phase modulation with electric quadrupole radiation

Optical metasurfaces can be used to realize various peculiar optical effects, and their mechanisms of the controlling optical phase can be roughly categorized into three types: resonant phase, geometric phase, and propagation phase, also known as the dynamic phase. Multiple mechanisms can be employed to manipulate the phase and amplitude of one metasurface. Therefore, discovering more profound and diverse methods can provide additional degrees of application freedom. This paper proposes a control principle based on electric multipole expansion. We found that for a unit structure formed by dual-metal bars on a metasurface, the radiation of its dipole is equivalent to the interference results of the dual-metal bars. Moreover, the radiation of the quadrupole enables independent control for amplitude and phase. Therefore, we used quadrupole radiation to manipulate the phase and amplitude of the light and even investigated some simple applications, including the realization of focusing light and anomalous refraction. Such a new mechanism of controlling light, combined with other methods, can provide significant insights into achieving challenging goals, like steganography and multifunctional metasurfaces.

Spinet-QSM: model-based deep learning with schatten p-norm regularization for improved quantitative susceptibility mapping.

Quantitative susceptibility mapping (QSM) provides an estimate of the magnetic susceptibility of tissue using magnetic resonance (MR) phase measurements. The tissue magnetic susceptibility (source) from the measured magnetic field distribution/local tissue field (effect) inherent in the MR phase images is estimated by numerically solving the inverse source-effect problem. This study aims to develop an effective model-based deep-learning framework to solve the inverse problem of QSM. This work proposes a Schatten -norm-driven model-based deep learning framework for QSM with a learnable norm parameter to adapt to the data. In contrast to other model-based architectures that enforce the l -norm or l -norm for the denoiser, the proposed approach can enforce any -norm ( ) on a trainable regulariser. The proposed method was compared with deep learning-based approaches, such as QSMnet, and model-based deep learning approaches, such as learned proximal convolutional neural network (LPCNN). Reconstructions performed using 77 imaging volumes with different acquisition protocols and clinical conditions, such as hemorrhage and multiple sclerosis, showed that the proposed approach outperformed existing state-of-the-art methods by a significant margin in terms of quantitative merits. The proposed SpiNet-QSM showed a consistent improvement of at least 5% in terms of the high-frequency error norm (HFEN) and normalized root mean squared error (NRMSE) over other QSM reconstruction methods with limited training data.

Exploring resonance theory and uncontrollability during co-creative art making: A qualitative study among cancer patients.

Co-creation, characterised by artists and patients creating a joint work of art, may support patients with the integration of life events, such as living with cancer, into their life story. In the process of co-creation, resonance relationships between patients, artists and material may evolve that support such integration. Using the framework of resonance theory, we aim to investigate if and how patients move through the three phases of resonance during a process of co-creation and explore the role of uncontrollability in this process. Ten patients who received cancer treatment with palliative intent completed co-creation processes, which were audio recorded. These recordings were imported in Atlas-Ti and analysed by applying content analysis. We searched for the three phases of resonance, Being affected, touched and moved; Self-efficacy and responding; Adaptive transformation. We additionally searched for signs of uncontrollability. Patients used 4-8 sessions (median 5 sessions) with a duration 90-240 min per session (median duration 120 min). We found that patients move through the three phases of resonance during co-creation processes. Uncontrollability both presents a challenge and an invitation to integrate experiences of contingency into one's life narrative. Patients express self-recognition and the experience of contingency in their work of art. Integration of experiences of contingency into a life narrative can be supported by the process of co-creation of art, which invites patients to relate to their illness, their environment and themselves. The phases of resonance in combination with uncontrollability as a continuously present factor, provide a means to both study and support the integration of experiences of contingency into the life narrative.

Gradient-based surface nuclear magnetic resonance for groundwater investigation

In medical magnetic resonance imaging, spatial localization (imaging) is based upon the application of controlled magnetic field gradients on top of the main magnetic field to spatially modulate the frequency and/or phase of the nuclear magnetic resonance (NMR) signal across the volume of investigation. In this work, we have applied similar physical principles to produce controlled magnetic field gradients during surface NMR-based groundwater investigations. In this approach, a gradient pulse of variable amplitude or duration is applied immediately after the excitation pulse to cause predictable phase encoding of the NMR signal as a function of depth. This approach is also applicable to emerging surface NMR detection methods that use a prepolarization field with fast nonadiabatic turn-off to generate detectable NMR signals from the shallow subsurface. In this case, the gradient pulse is applied after terminating the prepolarization field and provides a heretofore unavailable means of localizing the NMR response as a function of depth. The application of gradients can also be combined with tip-angle-based modulation to yield higher imaging resolution than can be achieved through either gradient- or tip-angle-based imaging alone. We implemented this new gradient-based capability into a surface NMR gradient generation accessory that is compatible with the GMR-Flex instrument and developed surface NMR-specific forward modeling and linear inverse models. We validated the accuracy of this novel gradient-based sNMR technology using computer simulations, experiments using a small pool filled with a discrete layer of bulk water, and field experiments at well-characterized groundwater test sites along Ebey Island, WA, and Larned, KS. The gradient-based sNMR imaging observations were compared with high-resolution direct push NMR results observed at these sites. The results of computer simulations and field experiments indicate improvements in both the detection (signal-to-noise ratio) and spatial resolution of shallow subsurface water content using gradient-based surface NMR, compared with traditional surface NMR imaging methods.