Resonance Stabilization Research Articles

A nonlinear analysis of electrically forced vibrations of piezoelectric plates with viscous damping near the thickness-shear mode

Based on the theory of nonlinear piezoelectricity, an approximate solution for electrically forced nonlinear thickness-shear vibrations of piezoelectric plates is introduced. The model considers an infinite piezoelectric plate subjected to an alternative voltage, incorporating 3rd-order and 4th-order elastic constants and viscous damping under finite deformation. The system's differential equations for steady-state forced vibrations are derived from the nonlinear pure thickness-shear vibration problem, and transformed so that the new electrical boundary conditions are free. After the application of Galerkin's method, the transformed differential equations lead to a cubic equation, capturing the nonlinear current-frequency curves of AT-cut quartz plates without the need of the quality factor Q, due to the introduced viscous damping. When the damping effect is ignored, the frequency response curves of the AT-cut quartz plate under a specific voltage are confirmed with the existing literature. The study emphasizes the presence of the critical voltage and the importance of the fourth-order elastic constant (c6666) in the stability, revealing lower c6666 values correspond to improved stability. Additionally, a proposed algorithm efficiently determines critical voltages for resonator stability.

Geometry effects in Impact Echo Signals - why traditional time-frequency filtering fails to remove them

Impact Echo signals can sometimes contain a lot of noise, even though the wavelength of the investigated modes is in the order of the specimen thickness. A special type of noise signals are the so-called geometry effects. These effects occur when the lateral dimensions of the investigated structure are not much larger than its thickness. This study compares signals with and without geometry effects using various types of signal processing methods such as classical fast Fourier transform, short-time Fourier transform, and the continuous wavelet transform. Results show that signals without geometry effects have a much more stable resonance frequency, whereas the main frequency content in Impact Echo signals containing geometry effects typically oscillates between two or more discrete frequencies. As this oscillation lasts for the entirety of the signals, traditional time-frequency filters will likely not be capable to remove geometry effects from Impact Echo signals. Resonance frequencies in Impact Echo signals unaffected by geometry effects are much more stable, with no fluctuation or oscillation over time. By comparing time-frequency representations of signals obtained at the same spot with different impactors, it is observed that the peak frequency at the beginning of each signal is similar for all three measurements. This result suggests that, for signals heavily affected by geometry effects, the beginning of the signal, which is usually neglected during Impact Echo inspection, could provide useful information regarding the thickness of the inspected structure. Two ways of obtaining thickness information from the signal beginning are presented and results are compared using a dataset from a reference specimen: one method uses classical Fourier transform of the signal beginning and the other approach uses the maximum frequency determined from the continuous wavelet transform. The results for both approaches show that the Impact Echo signal beginning contains depth information, which could prove valuable for evaluations of noisy datasets.

On the transverse stability of smooth solitary waves in a two-dimensional Camassa–Holm equation

We consider the propagation of smooth solitary waves in a two-dimensional generalization of the Camassa–Holm equation. We show that transverse perturbations to one-dimensional solitary waves behave similarly to the KP-II theory. This conclusion follows from our two main results: (i) the double eigenvalue of the linearized equations related to the translational symmetry breaks under a transverse perturbation into a pair of the asymptotically stable resonances and (ii) small-amplitude solitary waves are linearly stable with respect to transverse perturbations.

Carbene-Assisted Arene Ring-Opening.

Despite the significant achievements in dearomatization and C-H functionalization of arenes, the arene ring-opening remains a largely unmet challenge and is underdeveloped due to the high bond dissociation energy and strong resonance stabilization energy inherent in aromatic compounds. Herein, we demonstrate a novel carbene assisted strategy for arene ring-opening. The understanding of the mechanism by our DFT calculations will stimulate wide application of bulk arene chemicals for the synthesis of value-added polyconjugated chain molecules. Various aryl azide derivatives now can be directly converted into valuable polyconjugated enynes, avoiding traditional synthesis including multistep unsaturated precursors, poor selectivity control, and subsequent transition-metal catalyzed cross-coupling reactions. The simple conditions required were demonstrated in the late-stage modification of complex molecules and fused ring compounds. This chemistry expands the horizons of carbene chemistry and provides a novel pathway for arene ring-opening.

Investigation of Resonance Frequency and Stability of Solutions in a Continuous Rotor System

Investigation of Resonance Frequency and Stability of Solutions in a Continuous Rotor System

Multi-mode stable, high peak power Nd:YAG laser device for laser cleaning

High average power and peak power solid-state lasers are of great interest in the field of laser cleaning. In this research, a high peak power laser with over 400 W average power using a multi-mode stable resonator in a diode-pumped Nd:YAG master oscillator power amplifier has been demonstrated. A maximum peak power over 1.08 MW was achieved at a repetition frequency of 5 kHz. Delivery fiber with a 400 µm core diameter was utilized for flexible laser transmission. A prototype of the laser cleaning system was developed and inspiring application effects for paint and mold cleaning were achieved.

Low phase noise cavity transmission self-injection locked diode laser system for atomic physics experiments

Lasers with high spectral purity are indispensable for optical clocks and for the coherent manipulation of atomic and molecular qubits in applications such as quantum computing and quantum simulation. While the stabilization of such lasers to a reference can provide a narrow linewidth, the widely used diode lasers exhibit fast phase noise that prevents high-fidelity qubit manipulation. In this paper, we demonstrate a self-injection locked diode laser system that utilizes a high-finesse cavity. This cavity not only provides a stable resonance frequency, it also acts as a low-pass filter for phase noise beyond the cavity linewidth of around 100 kHz, resulting in low phase noise from dc to the injection lock limit. We model the expected laser performance and benchmark it using a single trapped 40Ca+-ion as a spectrum analyzer. We show that the fast phase noise of the laser at relevant Fourier frequencies of 100 kHz to >2 MHz is suppressed to a noise floor of between −110 dBc/Hz and −120 dBc/Hz, an improvement of 20 to 30 dB over state-of-the-art Pound-Drever-Hall-stabilized extended-cavity diode lasers. This strong suppression avoids incoherent (spurious) spin flips during manipulation of optical qubits and improves laser-driven gates when using diode lasers in applications involving quantum logic spectroscopy, quantum simulation, and quantum computation.

Vector form intrinsic finite element analysis for nonlinear parametric resonances of planar beam structures

The parametric resonance of a beam structure may lead to a disastrous consequence. To assess the safety of a structure, structural engineers need a straightforward and practical method to calculate the large-amplitude nonlinear parametric resonance responses of the beam structure. This paper proposes a newly developed vector form intrinsic finite element (VFIFE) calculation scheme to analyse the nonlinear parametric resonance of planar beam structures. By taking into account the geometric stiffness effect of the internal axial force for the frame element, a new relationship between internal nodal forces and deformation components is first established based on the VFIFE principle and the parametric resonance mechanism of frame structures. A numerical example of a portal frame is presented to demonstrate the efficacy of this new calculation scheme. A parametric resonance test of the cantilever beam is conducted to verify the applicability of the VFIFE method. The numerical results show that the proposed scheme can well simulate the nonlinear phenomena of parametric resonances. The numerical predictions are consistent with the experimental observations. A filtering-based finite-time Lyapunov exponent approach is presented to determine the stability boundary of the structure. The numerical stability boundary of parametric resonance agrees well with the experimental boundary. Possible causes of deviations between the numerical and experimental results are discussed. The proposed VFIFE scheme is a simple and effective means of analysing the stability and nonlinear responses of the parametric resonance of planar beam structures.

[Fe(NCMe)6](BF4)2 is a bifunctional catalyst for styrene aziridination by nitrene transfer and heterocycle expansion by subsequent dipolar insertion

The solvated iron(II) salt [Fe(NCMe)6](BF4)2 (Me = methyl) is shown to be a bifunctional catalyst with respect to aziridination of styrene. The salt serves as an active catalyst for nitrene transfer from PhINTs to styrene to form 2-phenyl-N-tosylaziridine (Ph = phenyl; Ts = tosyl, –S{O}2–p-C6H4Me). The iron(II) salt also acts as a Lewis acid in non-coordinating CH2Cl2 solution, to catalyze heterolytic CN bond cleavage of the aziridine and insertion of dipolarophiles. The 1,3-zwitterionic intermediate is presumably supported by interaction of the metal dication with the anion, and by resonance stabilization of the carbocation. Nucleophilic dipolarophiles then insert to give a five-membered heterocyclic ring. The result is a two-step cycloaddition, formally [2 + 1 + 2], that is typically regiospecific, but not stereospecific. This reaction mechanism was confirmed by conducting a series of one-step, [3 + 2] additions of unsaturated molecules into pre-formed 2-phenyl-N-tosylaziridine, also catalyzed by [Fe(NCMe)6](BF4)2. Relevant substrates include styrenes, carbonyl compounds and alkynes. These yield five-membered heterocylic rings, including pyrrolidines, oxazolidines and dihydropyrroles, respectively. The reaction scope appears limited only by the barrier to formation of the dipolar intermediate, and by the nucleophilicity of the captured dipolarophile. The bifunctionality of an inexpensive, earth-abundant and non-toxic catalyst suggests a general strategy for one-pot construction of heterocyclic rings, as demonstrated specifically for pyrrolidine ring formation.

Topological characterizations on hexagonal and rectangular tessellations of antikekulenes and its computed spectral, nuclear magnetic resonance and electron spin resonance characterizations

AbstractTessellations of antikekulenes are of interest from the standpoints of antiaromaticity, ring currents, unusual ‐electron characteristics, magnetism and their highly reactive nature. Although precursors of antikekulenes have been synthesized, up to now synthesis of antikekulenes has been proven to be formidably difficult. Yet they are predicted to have intriguing properties and their antiaromatic nature together with a combination of four and six‐membered rings makes them intriguing candidates for theoretical indices. In the present study, we have computed the topological indices of antikekulene by employing graph‐theoretical cut methods that simplify the parent tessellations of antikekulenes into simpler graphs. We have derived exact mathematical expressions of several topological descriptors for hexagonal and rectangular antikekulene structures. Furthermore we have obtained the graph‐spectral properties, algebraic structure counts, resonance stabilization and delocalization energies as well as nuclear magnetic resonance and electron spin resonance spectroscopic patterns of the two tessellations of antikekulenes.

Optimizing the beam quality of high-energy pulse mid-IR Fe:ZnSe laser

The mid-IR Fe:ZnSe laser has gained widespread attention due to its enormous potential with high-energy output. However, applications of Fe:ZnSe laser are limited by the beam quality. To optimize the beam quality of high-energy pulse Fe:ZnSe laser, this study presents a method of using spatial filtering in the resonator. Based on the theory of the ABCD transfer matrix and simulation of resonator stability and beam radius properties, the structure of the resonator was designed. Additionally, we study the output properties of Fe:ZnSe laser with different aperture diameters. We demonstrate when the aperture diameter D = 0.5 mm, the Fe:ZnSe laser output energy is 45.7 mJ and the beam quality is Mx2=2.11, My2=2.29, which is the best beam quality of using a pulse-pumped source to our knowledge. This method will guide for optimizing the beam quality of high-energy pulse mid-IR laser.

Abstract 3105: Computational integration with phage library to optimize clones of DEFB4A antibodies for cancer diagnostics and therapeutics

Abstract DEFB4A, a human beta-defensin, functions as a potential cancer biomarker, with elevated expression observed in various cancers, making it a candidate for diagnostic and prognostic applications. Additionally, its role in immune modulation suggests that DEFB4A may hold promise as a target for novel cancer treatments, particularly in the context of immunotherapy. This study aimed to develop a stable and high-affinity DEFB4A antibody for clinical and pre-clinical use. To achieve this, a combination of high-diversity phage libraries and computation-assisted analysis was employed to generate single-chain variable fragments (ScFv) clones specifically targeting DEFB4A. This research presents a robust approach for the generation of DEFB4A-targeting single-chain variable fragments (ScFv) from a phage library characterized by a high diversity of 109 unique clones and high titer of 1013 cfu/mL. Computational optimization was then applied to enhance the affinity, stability, and expression of these candidates through rational design and virtual mutagenesis programs. The binding activity of the optimized mutants was validated using biophysical methods such as surface plasmon resonance (SPR) and thermal stability assays. The process showed a remarkable 100-fold increase in affinity and stability. Additionally, the selected ScFv clone was further employed in immunohistochemistry (IHC) to detect DEFB4A in breast, prostate, and gastric cancers, showing higher expression levels compared to initial clones. This study highlights the synergy of high-diversity phage libraries and computational methods in crafting DEFB4A antibodies with enhanced affinity, stability, and expression. The findings advance the field of antibody engineering, emphasizing the crucial integration of experimental and computational approaches. This work lays the groundwork for the development of high-performance biologics with diagnostic and prognostic applications across diverse cancer types. Furthermore, it demonstrates the possibility of integrating computational approaches in antibody development, offering the promise of expediting the process in the future. Citation Format: Yichen Guo, Jina Yom, Andy (Xi) Han, Zhaoying Guo, Eden Zewdu, Rachel Gonzalez, Tianli Qu, Bailey Gilmore, Xuan Liu, Wei Fu, Xiaomin Hu. Computational integration with phage library to optimize clones of DEFB4A antibodies for cancer diagnostics and therapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3105.

28.02 W LD side-pumped CW laser operated at 2.8 µm in YSGG/Er:YSGG/YSGG crystal.

We demonstrated a 978 nm laser diode (LD) side-pumped YSGG/Er:YSGG/YSGG composite crystal with a size of Ф 3 mm × 65 mm and continuous-wave (CW) mode. By optimizing resonator length and output mirror transmittance, a maximum output power of 28.02W is generated, corresponding to slope efficiency of 17.55% and optical-optical efficiency of 12.29%, respectively. The thermal focal lengths are obtained by resonator stability condition. The laser wavelength is centered near 2.8 µm. Moreover, the beam quality factors M x2/M y2 are fitted to be 8.14 and 7.35, respectively. The above results indicate that a high-performance 2.8µm CW laser can be achieved by LD side-pumped YSGG/Er:YSGG/YSGG composite crystal with excellent heat dissipation ability, which promotes effectively the development and applications of the mid-infrared solid-state lasers.

Impact of Laser Cavity Configurations and Pump Radiation Parameters on the Characteristics of High-Energy Yellow Raman Lasers Based on Potassium Gadolinium Tungstate Crystals

In this paper, the influence of pump radiation parameters and laser resonator configurations on the characteristics of high-energy 589 nm KGW Raman lasers is investigated and explained. The best energy efficiency is obtained in lasers with a flat resonator, while the best angular characteristics are obtained in lasers with an unstable resonator. The use of stable spherical resonators results in the worst energy and angular characteristics. The angular divergence in lasers with flat cavities increases with pump intensity because of wing growth, whereas the core width remains unchanged. The structure of the wings is recorded and analyzed.

Tunable and stable micro-ring resonator based on thin-film lithium tantalate

As ferroelectric materials, lithium tantalate and lithium niobate share similar material characteristics, such as a high Pockels effect and nonlinear optical coefficients. When compared to lithium niobate, lithium tantalate offers a higher optical damage threshold, a broader transparent window, and lower birefringence, making it a promising candidate for high-performance electro-optical photonic integrated devices. In this study, we design and successfully fabricate micro-ring resonators on an acoustic-grade lithium-tantalate-on-insulator wafer, demonstrating their tunability and dynamic modulation capabilities. Experimental results indicate that the achieved thin-film lithium tantalate based micro-ring resonator exhibits an intrinsic Q-factor of 8.4 × 105, corresponding to a waveguide propagation loss of 0.47 dB/cm and a tuning efficiency of 1.94 pm/V. More importantly, as compared to those based on thin-film lithium niobate, a much weaker photorefractive effect and drift phenomenon around the 1550 nm wavelength under a direct-current drive are observed in the present fabricated thin-film lithium tantalate micro-rings with a silicon oxide over-cladding and a tuning electrode on top.

Realizing quasi-bound states in the continuum with stable resonant wavelength through compensation mechanism

All-dielectric metasurfaces underpinned by the physics of bound states in the continuum (BICs) have surged interest due to their spectral selectivity and strong light confinement. In this work, We propose a compensation mechanism for SP-BIC with stable resonance wavelength and controllable Q-factor. Here we take metasurfaces consisting of four nano-square disks as an example to break the symmetry of the unit cell by both x-compensation and y-compensation, respectively, and the resonance wavelengths are stable. The results show that the four nanodisks are excited in two modes with x-compensation and y-compensation when only C2 symmetry is preserved, and in one mode with x-compensation and y-compensation when only σx symmetry is preserved. Multiple decomposition results show that the loop dipole and magnetic dipole dominate the modes that retain only C2 symmetry excitation. In contrast, the magnetic dipole dominates the mode that retains only the σx symmetry excitation. Both modes excited by the compensation mechanism have stable resonances with high q-factors under the condition of preserving only C2 symmetry or only σx symmetry. Metasurfaces realized by the compensation mechanism may find promising applications in enhanced light-matter interactions such as lasers, sensing, strong coupling, and nonlinear harmonic generation.

Vinylic C-H Activation of Styrenes by an Iron-Aluminum Complex.

The oxidative addition of sp2 C-H bonds of alkenes to single-site transition-metal complexes is complicated by the competing π-coordination of the C═C double bond, limiting the examples of this type of reactivity and onward applications. Here, we report the C-H activation of styrenes by a well-defined bimetallic Fe-Al complex. These reactions are highly selective, resulting in the (E)-β-metalation of the alkene. For this bimetallic system, alkene binding appears to be essential for the reaction to occur. Experimental and computational insights suggest an unusual reaction pathway in which a (2 + 2) cycloaddition intermediate is directly converted into the hydrido vinyl product via an intramolecular sp2 C-H bond activation across the two metals. The key C-H cleavage step proceeds through a highly asynchronous transition state near the boundary between a concerted and a stepwise mechanism influenced by the resonance stabilization ability of the aryl substituent. The metalated alkenes can be further functionalized, which has been demonstrated by the (E)-selective phosphination of the employed styrenes.

Delay-Tracking Loop for Frequency Estimation of Grid-Interfaced Inverter Under Distorted Conditions

Fast and accurate frequency estimation is difficult for grid-interfaced inverter under distorted grid conditions with off-nominal frequency. A popular solution considers the multiple second-order generalized integrator-based frequency-locked loop yet can hardly achieve a fast dynamic response under significant phase jump and voltage sag. Another solution uses an adaptive sliding window filter with an additional frequency estimator. However, it is challenging to handle numerical instability due to the adjusting marginally-stable resonator and the accumulation error. This letter proposes a delay-tracking loop to overcome these problems. This loop allows the delay length to track the frequency with an inherent harmonics rejection at off-nominal frequency. At the same time, the fast response speed is maintained, and the marginally stable resonator is avoided. Comparative experimental results validate the above claims.

Identification of the Electrogenerated Hidden Nitrenium Ions by In Situ Mass Spectrometry.

The identification of the electrogenerated reactive intermediates is essential for an in-depth understanding of the electroredox processes. Although various short-lived intermediates are well characterized by coupling electrochemistry with mass spectrometry (EC/MS), many electrogenerated transient species (τ < 1 μs) are still rarely captured by the currently available EC/MS approaches. Here, we present a low-delay coupling device, which was constructed by decorating a microelectrode into the front tip of a microsized ion emitter. For the first time, the in situ detection of a previously hidden intermediate, i.e., the transient nitrenium ion of carbazole (τ = 333 ns), was achieved. The electrochemical generation of indole nitrenium ion, whose half-life is estimated to be shorter compared to the carbazole nitrenium ion due to less resonance stabilization, was also confirmed by direct observation. This clog-free microelectrode/ion emitter is cheap and easy to fabricate and offers a general and powerful approach to monitoring the fast reactions of electrogenerated reactive intermediates. We believe that our integrated EC/MS approach holds substantial potential for broad applicability, particularly in probing the intricate and ultrafast electroredox processes occurring at the electrode-solution interface.

Strong coupling between excitons and quasi-bound states in the continuum mode with stable resonance wavelength in the near-infrared region

Strong coupling between photons and excitons gives rise to Rabi splitting and hybridized states. These exhibit spectral anticrossing behavior and ultrafast energy exchange, demonstrating remarkable nanophotonic properties and offering exciting application possibilities. Herein, we propose a metasurface based on dimeric MoTe2 nanodisks for flexible control of the strong coupling between quasi-bound states in the continuum (QBIC) and excitons in the near-infrared region. It was found that introducing a gap perturbation transforms the BIC into a QBIC with a stable resonance wavelength, and the gap width can be used to customize its Q-factor. We confirmed that the upper limit of the Q-factor for achieving strong coupling is 500 in this QBIC metasurface system. It is noted that the wavelength of the QBIC mode and exciton peak are stable, so the coupling strength can be easily adjusted using the disturbance parameters. Moreover, significant Rabi splitting and typical anticrossing behavior were observed when the thickness and radius of the dimeric MoTe2 nanodisks were varied. The Rabi splitting value was 170 meV for f0=1.0. This work provides a useful solution for strong coupling in the near-infrared region, which may pave the way toward tunable near-infrared exciton polariton devices with high compatibility.