Resonance Condition Research Articles

Nonreciprocal toroidal dipole resonance and one-way quasi-bound state in the continuum.

Bound states in the continuum (BICs) provide an alternative way of trapping light at nanoscale. Although the last 10 years have witnessed tremendous progress on BICs from fundamentals to applications, nonreciprocal BICs and their potential applications have not been fully exploited yet. In this study, we demonstrated a one-way quasi-BIC by leveraging an all-dielectric magneto-optical (MO) metasurface. We show that the key point for achieving a one-way quasi-BIC is to excite a magnetization-induced leaky resonance. Here we adopt the longitudinal toroidal dipole (TD) resonance characterized by a vortex distribution of head-to-tail magnetic dipoles parallel to the plane of the MO metasurface. We show that, by breaking the time-reversal symmetry, at critical conditions, the TD resonance can be enhanced in the forward channel and perfectly canceled in the time-reversed channel, resulting in a one-way quasi-BIC. The demonstrated phenomena hold significant promise for practical applications such as magnetic field optical sensing, nonreciprocal optical switching, isolation, and modulation.

Design and control of high-speed railway bridges equipped with an under-deck adaptive tensioning system

This work investigates the application of an external adaptive tensioning (EAT) system for high-speed railway (HSR) bridges. The design of HSR bridges involves strict displacement and acceleration limits, which typically results in oversizing. The EAT system comprises under-deck cables deviated by compressive struts that are equipped with linear actuators. Since the cable is eccentric to the bridge neutral axis, tensioning the under-deck cables by adjusting the length of the linear actuators generates a bending moment that counteracts the effect of the external loads. The response under variable loading is reduced by computing the actuator commands with a linear quadratic regulator (LQR). Numerical results show that active control through the EAT system allows satisfying displacement and acceleration limits, which otherwise cannot be met without increasing the stiffness and mass of the bridge. A significant reduction of the response is achieved when resonance conditions occur. In addition, peak stresses are significantly reduced, showing the potential for fatigue-life extension. Parametric analyses comparing different bridge depths and spans, EAT system dimensions, controller parameters and actuator placement are carried out to investigate system efficacy. Results show that the adaptive bridge solution can achieve up to 32% mass savings compared to an equivalent passive bridge.

On the Spatial and Temporal Evolution of EMIC Wave‐Driven Relativistic Electron Precipitation: Magnetically Conjugate Observations From the Van Allen Probes and CALET

AbstractElectromagnetic ion cyclotron (EMIC) waves have been shown to be able to drive strong electron precipitation, particularly at MeV energies. However, the spatio‐temporal evolution of both the waves and the resulting precipitation is still not well understood. Here we investigate the evolution of relativistic electron precipitation driven by EMIC waves through combined observations from the Van Allen Probes and the CALorimetric Electron Telescope experiment onboard the International Space Station. Two case studies are examined where EMIC waves near the magnetic equator and precipitation at low altitude were detected in close magnetic conjunction, both of which were confined to narrow radial regions but persisted multiple hours. These observations, combined with quasilinear calculations, confirm that long‐lived EMIC waves can drive hours‐long MeV electron precipitation loss. However, the magnitude of the precipitation varied significantly during one of the events, as resonance conditions, particularly plasma density, evolved.

Altering Spin Distribution of Tb2Pc3 via Molecular Chirality Manipulation.

Manipulating the chirality of the spin-polarized electronic state is pivotal for understanding many unusual quantum spin phenomena, but it has not been achieved at the single-molecule level. Here, using scanning tunneling microscopy and spectroscopy (STM/STS), we successfully manipulate the chirality of spin distribution in a triple-decker single-molecule magnet tris(phthalocyaninato)bis(terbium(III)) (Tb2Pc3), which is evaporated on a Pb(111) substrate via molecular beam epitaxy. The otherwise achiral Tb2Pc3 becomes chiral after being embedded into the self-assembled monolayer films of bis(phthalocyaninato)terbium(III) (TbPc2). The chirality of the spin distribution in Tb2Pc3 is manifested via the spatial mapping of its Kondo resonance state from its ligand orbital. Our first-principles calculations revealed that the spin and molecular chirality are associated with a small rotation followed by a structural distortion of the top Pc, consistent with the experimental observation. By constructing tailored molecular clusters with the STM tip, a single Tb2Pc3 molecule can be manipulated among achiral and differently handed chiral configurations of spin distributions reversibly. This paves the way for designing chiral spin enantiomers for fundamental studies and developing functional spintronic devices.

Nonlinear dynamics of soliton molecules, hybrid interactions and other wave solutions for the (3+1)-dimensional generalized Kadomtsev–Petviashvili–Boussinesq equation

This work plumbs the nonlinear dynamics of the ([Formula: see text])-dimensional generalized Kadomtsev–Petviashvili–Boussinesq equation (gKPBe), which is used to describe some interesting physical phenomena in the fields of fluids. The resonance conditions of the soliton molecules on the ([Formula: see text]), ([Formula: see text]) and ([Formula: see text]) planes are investigated and the soliton molecules are obtained on the basis of the N-soliton solutions that are extracted by virtue of the Hirota form. Furthermore, some novel hybrid interactions including the interaction between the soliton and soliton molecule, the interaction between the different soliton molecules are also explored. Finally, the sub-equation approach is exerted to explore the various wave solutions, which include the kinky wave, bright-dark wave and the singular periodic wave solutions. Correspondingly, the graphical descriptions of the attained solutions are drawn to present a better understanding of the physical attributes. The derived solutions can enlarge the exact solutions of the ([Formula: see text])-dimensional gKPBe and lead us to understand the nonlinear dynamic behaviors better.

Orbital angular momentum sensing of composite vortex light in a single-layer graphene system

This paper explores the impact of orbital angular momentum (OAM) in composite vortex light on the absorption and dispersion characteristics of a weak probe light interacting with a single-layer graphene system. Through systematic investigation, we demonstrate the exceptional control achievable over absorption and dispersion profiles by manipulating the OAM of light. Under resonance conditions for the probe light, transparent regions emerge in the spatial profile of probe absorption, and the number of these transparent regions can be precisely regulated by adjusting the OAM number of the composite vortex light. Conversely, in the case of off-resonance probe light, amplified regions surface in the absorption spectrum, with the number of these regions controllable by the OAM state of the composite vortex light. These findings hold significant implications for optical communication systems, offering a valuable tool for the detection and measurement of the OAM number of composite vortex light, and paving the way for advancements in tailored signal processing and communication technologies.

Laminar to turbulent transitions of pipe flows by resonances of natural frequencies of components of test sections

This investigation analyses special papers and doctoral theses that treat transitions of pipe flows as a resonance phenomenon of wave frequencies. These frequencies are natural frequencies of pipe flows, of components of the test section and of vortex ring formations. Resonance conditions are derived that show how the critical Reynolds number, Rec , depends on the volume of the plenum chamber, the pipe diameter, the pipe length, etc. The derived resonance relations were verified experimentally using the experimental data of the third author, yielding R e c ∼ 1 / V ple , R e c ∼ 1 / ( L D ) and other interesting results. These findings suggest that the laminar-to-turbulent transition has various modes and transitive dependences. To understand this fully, it is necessary to take all components of the test section involved into account. The test section considered in this paper consists of a mass flow controller to supply the airflow and a plenum chamber, followed by the actual pipe of interest. It is shown that all the components can contribute to the measured value of the critical Reynolds number of pipe flow transition.

Flow pattern evolution and flow-induced vibration response in multiphase flow within an M-shaped subsea jumper

The subsea jumper, a crucial pipeline connector facilitating liquid transport between underwater structures, experiences dynamic alterations in flow direction, rate, and phase volumes owing to its distinctive design. These complex flow characteristics can trigger flow-induced vibrations, potentially causing fatigue damage to the jumper. This paper explores the multiphase flow patterns (oil, gas, and water) in a rigid M-shaped subsea jumper under varied mixing velocities (2–4 m/s) and different volume fractions of each phase (0.1–0.7). It analyzes the factors influencing structural vibration response. The findings reveal diverse flow patterns within the jumper, each exhibiting distinct characteristics based on flow parameters. Concurrently, spatiotemporal oscillations from fluid dynamics impact each bend. Pressure on jumper walls gradually diminishes with changing flow direction. Furthermore, the study performs structural modal and frequency domain analyses of pulsating pressure to evaluate potential resonance conditions. The results of this paper contribute to a deeper understanding of the multiphase flow characteristics in jumpers, offering valuable insights to enhance the reliability of underwater oil and gas production.

Resonance theory of vibrational polariton chemistry at the normal incidence

Abstract We present a theory that explains the resonance effect of the vibrational strong coupling (VSC) modified reaction rate constant at the normal incidence of a Fabry–Pérot (FP) cavity. This analytic theory is based on a mechanistic hypothesis that cavity modes promote the transition from the ground state to the vibrational excited state of the reactant, which is the rate-limiting step of the reaction. This mechanism for a single molecule coupled to a single-mode cavity has been confirmed by numerically exact simulations in our recent work in [J. Chem. Phys. 159, 084104 (2023)]. Using Fermi’s golden rule (FGR), we formulate this rate constant for many molecules coupled to many cavity modes inside a FP microcavity. The theory provides a possible explanation for the resonance condition of the observed VSC effect and a plausible explanation of why only at the normal incident angle there is the resonance effect, whereas, for an oblique incidence, there is no apparent VSC effect for the rate constant even though both cases generate Rabi splitting and forming polariton states. On the other hand, the current theory cannot explain the collective effect when a large number of molecules are collectively coupled to the cavity, and future work is required to build a complete microscopic theory to explain all observed phenomena in VSC.

Large-scale magnetic field oscillations and their effects on modulating energetic electron precipitation

In this study, we present simultaneous multi-point observations of magnetospheric oscillations on a time scale of tens of minutes (forced-breathing mode) and modulated whistler-mode chorus waves, associated with concurrent energetic electron precipitation observed through enhanced BARREL X-rays. Similar fluctuations are observed in X-ray signatures and the compressional component of magnetic oscillations, spanning from ∼9 to 12 h in MLT and 5 to 11 in L shell. Such magnetospheric oscillations covering an extensive region in the pre-noon sector have been suggested to play a potential role in precipitating energetic electrons by either wave scattering or loss cone modulation, showing a high correlation with the enhancement in X-rays. In this event, the correlation coefficients between chorus waves (smoothed over 8 min), ambient magnetic field oscillations and X-rays are high. We perform an in-depth quasi-linear modeling analysis to evaluate the role of magnetic field oscillations in modulating energetic electron precipitation in the Earth’s magnetosphere through modulating whistler-mode chorus wave amplitude, resonance condition between chorus waves and electrons, as well as loss cone size. Model results further show that the modulation of chorus wave amplitude plays a dominant role in modulating the electron precipitation. However, the effect of the modulation in the resonant energy between chorus waves and energetic electrons due to the background magnetic field oscillations cannot be neglected. The bounce loss cone modulation, affected by the magnetic oscillations, has little influence on the electron precipitation modulation. Our results show that the low frequency magnetospheric oscillations could play a significant role in modulating the electron precipitation through modulating chorus wave intensity and the resonant energy between chorus waves and electron.

Fast generation of spin squeezing via resonant spin-boson coupling

We propose protocols for the creation of useful entangled states in a system of spins collectively coupled to a bosonic mode, directly applicable to trapped-ion and cavity QED setups. The protocols use coherent manipulations of the resonant spin-boson interactions naturally arising in these systems to prepare spin squeezed states exponentially fast in time. The resonance condition harnesses the full spin-boson coupling and thus avoids the slower timescales when operating in the off-resonance regime. We demonstrate the robustness of the protocols by analyzing the effects of natural sources of decoherence in these systems and show their advantage compared to more standard slower approaches where entanglement is generated with off-resonant spin-boson interactions.

Design and Effect of Resonant Ultrasonic Vibration-Assisted Laser Cladding (R-UVALC) on AlCrFeMnNi High-Entropy Alloy.

The design of the resonant ultrasonic vibration-assisted laser cladding (R-UVALC) setup involved employing finite element analysis (FEA) to simulate the ultrasonic transducer, horn, and workpiece in a resonance state. The impact of R-UVALC on AlCrFeMnNi high-entropy alloys was assessed using various ultrasonic vibration amplitudes of 0, 5, 10, and 15 µm, with a constant frequency of 20 kHz. Ultrasonic vibrations reduced pores and cracks and increased the clad breadth, melt pool wetting angle, and laser-clad layer consistency. The columnar elongated grains in proximity to the substrate surface underwent a size reduction and transformed into grains with a more equiaxed shape with the utilization of ultrasonic vibrations at an amplitude of 5 µm. Laser cladding performed without ultrasonic vibrations yields two phases: face-centered cubic (FCC) and body-centered cubic (BCC). However, when the coating is exposed to ultrasonic vibrations with an amplitude of 5 µm, it forms a solitary body-centered cubic (BCC) phase. The microhardness tripled compared to the substrate, and the most significant microhardness value was achieved at 5 µm of ultrasonic vibration. The friction coefficient was assessed at an ambient temperature, revealing that an ultrasonic amplitude yields the lowest friction coefficient, demonstrating the excellent wear resistance properties of the coating. The analysis of the 3D surface profile of the wear indicates that the use of ultrasonic aid with a 5 µm amplitude leads to reduced depth of scars, and the primary wear mechanism observed is abrasive and oxidative wear with fewer grooves and debris. In addition, XPS analysis revealed the presence of metal components in an oxidized condition, suggesting that the wear process is oxidative in nature. Integrating the R-UVALC setup into a resonance state can significantly enhance the efficiency of the laser cladding process in the laser cladding field.

Independently tunable dual Fano resonances based on plasmonic MIM Sagnac loop coupling Taiji resonator

In this paper, we first propose and demonstrate independently tunable dual Fano resonances based on a plasmonic structure composed of MIM (metal-insulator-metal) Sagnac loop with embedded Taiji resonator. An S-shaped crossover branch inside the Taiji ring resonator can tailor the propagating modes into their counter-propagating directions, finally tuning the number of whispering-gallery modes (WGMs) in Taiji resonator. Both Fano resonances originate from the interference between the discrete state generated from WGMs in Taiji resonator and continuous state from modes propagating in the plasmonic Sagnac loop. By stuffing a silver circle area (SCA) inside S-shaped branch, dual Fano resonances can be tuned independently as SCA has different sizes or locates at different places. Fano resonance would be influenced and shifted strongly when SCA locates at the energy intensity valley of WGM, while without any influence as SCA situates at the energy intensity peak of WGM. Thanks to the strong sub-wavelength light confinement of dual Fano resonances based on MIM plasmonic system, an optical refractometric sensor with figure of merit (FOM) of 100/RIU and high sensitivity of 1899 nm/RIU is demonstrated. Furthermore, this hybrid structure is also used for temperature sensing of ethanol with the maximal sensitivity of −0.793 nm/°C. This compact plasmonic Sagnac loop coupling Taiji resonator demonstrates impressive practical prospects for high-sensitivity biochemical sensors, nonlinear optics, and optical modulation.

Investigations into Higher-Frequency Hysteresis Current Controller for Supraharmonic Hybrid Active Filters

Hysteresis current controllers (HCCs) are extensively used in low-frequency power inverters and active power filters. Very little is known about their strengths and weaknesses when applied at supraharmonic frequencies. The major concern regarding the use of HCCs is their variable and uncontrollable switching frequencies. This results in difficulties in filter design, high switching losses, and the possibility of resonance conditions with power system elements. In this article, investigations are conducted on the application of HCCs in a hybrid filter for a 6 kHz matrix converter (MC)-coupled supraharmonic load. The effects of the MC-coupled load and VSC switches on the HCC’s switching frequency are analyzed. A novel mathematical model for obtaining a fixed-frequency HCC is presented. The model is verified in open- and closed-loop HCC control configurations for a three-phase hybrid active power filter (HAPF). Fast Fourier transform (FFT) analysis of the supply current after the implementation of the novel HCC-HAPF showed 2.31% of the 50 Hz fundamental. The analysis is verified in a MATLAB/Simulink environment.

Enantioselective Reduction of Noncovalent Complexes of Amino Acids with CuII via Resonant Collision-Induced Dissociation: Collision Energy, Activation Duration Effects, and RRKM Modeling.

Formation of noncovalent complexes is one of the approaches to perform chiral analysis with mass spectrometry. Enantiomeric distinction of amino acids (AAs) based on the relative rate constants of competitive fragmentations of quaternary copper complexes is an efficient method for chiral differentiation. Here, we studied the complex [CuII,(Phe,PhG,Pro-H)]+ (m/z 493) under resonant collision-induced dissociation conditions while varying the activation time. The precursor ion can yield two main fragments through the loss of the non-natural AA phenylglycine (PhG): the expected product ion [CuII,(Phe,Pro-H)]+ (m/z 342) and the reduced product ion [CuI,(Phe,Pro)]+ (m/z 343). Enantioselective reduction describes the difference in relative abundance of these ions, which depends on the chirality of the precursor ion: the formation of the reduced ion m/z 343 is favored in homochiral complexes (DDD) compared to heterochiral complexes (such as LDD). Energy-resolved mass spectrometry data show that reduction, which arises from rearrangement, is favored at a low collision energy (CE) and long activation time (ActT), whereas direct cleavage preferentially occurs at a high CE and short ActT. These results were confirmed with kinetic modeling based on RRKM theory. For this modeling, it was necessary to set a pre-exponential factor as a reference, so that the E0 values obtained are relative values. Interestingly, these simulations showed that the critical energy E0 required to form the reduced ion is comparable in both homochiral and heterochiral complexes. However, the formation of product ion m/z 342 through direct cleavage is associated with a lower E0 in heterochiral complexes. Consequently, enantioselectivity would not be caused by enhanced reduction in homochiral complexes but rather by direct cleavage being favored in heterochiral complexes.

Multispectral Narrowband Frustrated Total Internal Reflection Filter with Inclusions of Plasmonic Nanoparticles

A spatial-frequency thin-film filter with inclusions of nanoparticles operating in the visible range of the spectrum is investigated. The effect of nanoparticles embedded in the central and lateral layers of the frustrated total internal reflection filter on the spectral characteristics, considering the frequency dispersion, is investigated. It is shown that plasmonic effects cause the splitting of the filter bandwidth into a set of narrow-band spectral lines and the angular splitting of the incident beam into a set of output beams. It is demonstrated that due to the difference in the resonance conditions for s- and p-polarization waves, the spectral lines of transparency do not coincide, which indicates the possibility of using the filter as a polarizer.

Ruelle–Taylor resonances of Anosov actions

Combining microlocal methods and a cohomological theory developed by J. Taylor, we define for Anosov \mathbb{R}^{\kappa} -actions a notion of joint Ruelle resonance spectrum. We prove that these Ruelle–Taylor resonances fit into a Fredholm theory, are intrinsic and form a discrete subset of \mathbb{C}^{\kappa} , with \lambda=0 being always a leading resonance. The joint resonant states at 0 give rise to some new measures of SRB type and the mixing properties of these measures are related to the existence of purely imaginary resonances. The spectral theory developed in this article applies in particular to the case of Weyl chamber flows and provides a new way to study such flows.

Quantum chemical explanation and APT atomic charge index of substituent orienting effect proposed by DFT calculation and MO Theory

AbstractIn organic chemistry textbooks, the electron resonance states are used to explain the orienting effect of benzene substituent. However, these resonance states do not exist in the C6H5‐S + E+ electrophilic addition, so the resonance state discussions actually are meaningless. The density functional theory (DFT) calculation shows that the C6H5‐S + E+ addition follows the transition state theory and needs to overcome a barrier. Benzene molecule C6H6 has two degenerate highest occupied molecular orbitals (HOMOs), but after becoming substituted benzenes, the two HOMOs split to HOMO and HOMO‐1 with different orbital energies and electron distributions. It makes the addition barrier on two or three benzene ring carbons is low, and the addition rate is fast, but the barrier of other carbons is high, and the rate is slow. Therefore, substituent splits the two degenerate HOMOs of benzene molecule, which is the origin of substituent orienting effect. For the substituted benzenes with halogen group ‐X and electron‐releasing group, their HOMO images alone can determine that the two types of substituents are the ortho‐ and para‐orienting groups, but for the substituted benzenes with electron‐withdrawing group, their HOMO alone cannot determine whether the substituent is a meta‐orienting group. The study found that atomic polar tensor (APT) charges are a good judgment index of substituent orienting effect because based on its physic‐chemical model, the charges represent the number of active electrons on the benzene ring carbons. The DFT calculation gives the APT charges of 19 mono‐substituted and 12 di‐substituted benzenes and some aromatic molecules. The APT charges can all correctly determine their orienting effects, showing that APT atomic charge from quantum theoretical calculation is a good substituent orienting index.

Spectroscopic observation of Feshbach resonances in the tellurium dimer anion.

We report on the high-resolution photodetachment spectroscopy of the cryogenically cooled anionic tellurium dimer (Te2-). The high-resolution resonant photoelectron spectrum yields an accurate electron affinity of 16 689.7(92) cm-1 or 2.0693(11) eV for Te2. Two resonant states of Te2- anions have been identified, positioned at 1092(17) cm-1 below and 250(11) cm-1 above the photodetachment threshold, respectively. The spectra of resonant two-photon detachment (R2PD) and autodetachment from a specific vibrational level through a Feshbach resonance exhibit notable non-Franck-Condon behaviors. Using the spectroscopic data from the current experiment, the equilibrium bond distances and spectroscopic constants of the ground state and two electronically excited states of Te2- were determined.

Indications of electron emission from the deuteron-deuteron threshold resonance

Electron emission in the deuteron-deuteron reaction supporting existence of the single-particle threshold resonance in He4 has been observed for the first time. The measured electron energy spectrum and the electron-proton branching ratio agree very well with the assumed electron-positron pair creation decay of the 0+ resonance state to the ground state and the detailed Monte Carlo simulations of the experimental energy spectrum. Published by the American Physical Society 2024