Resonant Branch Research Articles

Measurement of the resonant and nonresonant branching ratios in Ξc0→Ξ0K+K−

Using the entire data sample of $980$ $fb^{-1}$ integrated luminosity collected with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider, we present an amplitude analysis measuring the branching fractions of the Cabibbo-allowed, $W$-exchange resonant decay $\Xi_{c}^{0} \rightarrow \Xi^{0} \phi (\to K^+ K^-)$ with a polarized $\phi$ and the non-resonant decay via a direct process $\Xi_{c}^{0} \rightarrow \Xi^{0} K^+ K^-$. We present these measurements, relative to the normalization mode $\Xi^{-}\pi^{+}$, and find branching ratios $\frac{\mathcal{B}(\Xi_{c}^{0} \rightarrow \Xi^{0} \phi (\rightarrow K^{+}K^{-}))}{\mathcal{B}(\Xi_{c}^{0} \rightarrow \Xi^{-} \pi^{+})} = 0.036 \pm 0.004 (stat.) \pm 0.002 (syst.)$ and $\frac{\mathcal{B}(\Xi_{c}^{0} \rightarrow \Xi^{0} K^{+} K^{-})}{\mathcal{B}(\Xi_{c}^{0} \rightarrow \Xi^{-} \pi^{+})} = 0.039 \pm 0.004 (stat.) \pm 0.002 (syst.)$ which suggest that only minor cusping peaks occur in the combinatorial background of $\Omega^{*-} \to \Xi^{0}K^{-}$ due to these $\Xi_{c}^{0}$ decays.

Flow-induced cross-flow vibrations of long flexible cylinder with an upstream wake interference

Flow-induced vibration (FIV) of a flexible cylinder with an upstream wake interference at a subcritical Reynolds number is numerically investigated in this study. Two cylinders are installed in a tandem arrangement with the tandem separation between the cylinder centers set at 5.0 diameters. The downstream cylinder is flexible and placed in the wake of the stationary rigid upstream cylinder. A quasi-three-dimensional fluid-structure interaction (FSI) numerical methodology that couples the strip theory-based Lagrangian discrete vortex method with the finite-element method (FEM) for structural dynamics is developed to simulate the FIV response of the flexible cylinder with the upstream wake interference. The vortex-induced vibration (VIV) of an identical isolated cylinder is also numerically simulated as a contrast. This numerical study characterizes the dynamic response of the cylinder FIV with the upstream wake interference and sheds light on the FSI mechanisms responsible for the structural dynamic response. With the upstream wake interference, the cylinder FIV response shows two features distinct from the isolated VIV response: the vibration of large amplitude during the modal resonance branch transition and the extension of the modal resonance branch. The hydrodynamic coefficients database is constructed by the rigid cylinder forced vibration experiment to help explain the FSI properties of the FIV dynamic response. The lower added mass coefficient for the FIV with the upstream wake interference than the VIV of the isolated cylinder guarantees the synchronization between the vortex shedding frequency and the “true” natural frequency of the structure persisting to higher reduced velocity in a certain modal resonance response branch. The excitation coefficient distribution indicates that the cylinder FIV with the upstream wake interference reaches higher amplitude at high reduced velocity, instead of ceasing resonance as the isolated cylinder. The numerical wake visualization is shown and used to explain the correlation between the distribution of hydrodynamic coefficients along the cylinder span and the wake vortex mode. It is found that the upstream wake interference effect is strongly correlated with the vortex–structure interaction pattern between the upstream wake vortices and the downstream motion. When the upstream vortex impinges on the downstream cylinder and splits into subvortices, the effect of the upstream wake interference acting on the downstream cylinder reduces. When the downstream cylinder enters the gap between the upstream vortices over the entire vibration process, the upstream wake has a stronger interference effect on the downstream FIV response.

Broadband terahertz polarization converter with anomalous reflection based on phase gradient metasurface

In order to expand the application situation of the polarization converter in terahertz band, a broadband polarization converter based on phase gradient metasurface is proposed for simultaneously manipulating the polarization and the wavefront of the reflected wave in terahertz region. Consisting of six different “H”-shaped resonators which can tune the phase and the polarization respectively, the polarization converter is able to deflect the normally incident terahertz wave with an anomalous reflection angle while changing the polarization. Geometric rotation and resonant frequency modulation constitute the phase variation of the unit, which can be superimposed on each other without interference. The simulation results show that the reflecting angle from 0.40 to 0.60 THz varies from 39° to 22° with side lobe level lower than −14 dB. Specific elucidation for high polarization conversion ratio is discussed through reflection phase and resonant branch analysis. Compared to the conventional polarization converter, the proposed one has an advantage in propagation manipulating, which reveals its potential application in THz detection, imaging and sensing, etc.

Probing the top-Higgs sector with composite Higgs models at present and future hadron colliders

We study the production of toverline{t}h and toverline{t} hh at hadron colliders, in the minimal Composite Higgs Models, based on the coset SO(5)/SO(4). We explore the fermionic representations 5 and 14. A detailed phenomenological analysis is performed, covering the energy range of the LHC and its High Luminosity upgrade, as well as that of a future 100 TeV hadron collider. Both resonant and non-resonant production are considered, stressing the interplay and complementary interest of these channels with each other and double Higgs production. We provide sets of representative points with detailed experimental outcomes in terms of modification of the cross sections as well as resonance masses and branching ratios. For non-resonant production, we gauge the relative importance of Yukawa, Higgs trilinear, and contact toverline{t} hh vertices to these processes, and consider the prospect for distinguishing the fermion representations from each other and from the Standard Model. In the production of top partners, we find that the three-body decay channel W+W–t becomes significant in certain regions of parameter space having a degenerate spectrum, and is further enhanced by increasing the top partner’s mass. This motivates both higher energy machines as well as the need to go beyond the current analysis performed for the searches for these resonances.

Internal resonance in the higher-order modes of a MEMS beam: experiments and global analysis

This work investigates the dynamics of a microbeam-based MEMS device in the neighborhood of a 2:1 internal resonance between the third and fifth vibration modes. The saturation of the third mode and the concurrent activation of the fifth are observed. The main features are analyzed extensively, both experimentally and theoretically. We experimentally observe that the complexity induced by the 2:1 internal resonance covers a wide driving frequency range. Constantly comparing with the experimental data, the response is examined from a global perspective, by analyzing the attractor-basins scenario. This analysis is conducted both in the third-mode and in fifth-mode planes. We show several metamorphoses occurring as proceeding from the principal resonance to the 2:1 internal resonance, up to the final disappearance of the resonant and non-resonant attractors. The shape and wideness of all the basins are examined. Although they are progressively eroded, an appreciable region is detected where the compact cores of the attractors involved in the 2:1 internal resonance remain substantial, which allows effectively operating them under realistic conditions. The dynamical integrity of each resonant branch is discussed, especially as approaching the bifurcation points where the system becomes more vulnerable to the dynamic pull-in instability.

Experimental and theoretical investigation of the 2:1 internal resonance in the higher-order modes of a MEMS microbeam at elevated excitations

We analyze the dynamics induced by a 2:1 internal resonance between the third (second symmetric) and the fifth (third symmetric) mode of a MEMS microbeam. An extensive experimental investigation is conducted, where forward and backward sweeps are systematically acquired up to elevated excitations. As ramping the voltage, a change along the forward sweep of the resonant branch is noted. This is analyzed via the combined use of different analytical and numerical tools, which show a phase shift between the modes involved in the 2:1 internal resonance. Constantly referring to the experimental data, simulations examine the underlying features of the system's behavior. The dynamics observed in the experimental frequency sweeps are part of a more complex scenario, where different attractors appear and coexist. The experimental behavior bifurcation chart is reported and compared with simulations, which offers a comprehensive view of the 2:1 internal resonance activation. The concurrence of numerical results and experimental data confirms on the effective actuality of these complex features in safe conditions, along wide ranges of the parameters space.

Two-to-one internal resonance in the higher-order modes of a MEMS beam: Experimental investigation and theoretical analysis via local stability theory

The present study is focused on the dynamics of a microbeam-based MEMS device and analyzes its behavior in the neighborhood of the third natural frequency. An extensive experimental investigation is conducted. The main resonant and non-resonant branches span a wide range of coexistence. The 2:1 internal resonance is activated between the third and fifth modes, in which case the device exhibits complex and intriguing dynamics. The experimental data are examined in depth using various analytical and numerical tools. Alongside with the experiments, theoretical simulations are developed, where the main features of the internal resonance are properly represented and the contribution of each mode is discussed. The main steps of the progression of the 2:1 internal resonance are highlighted and the possibility of more complex internal resonances is explored, where different higher modes are involved.

High-Gain Switched-Capacitor DC-DC Converter With Low Count of Switches and Low Voltage Stress of Switches

This paper presents a novel concept of a high-voltage-gain DC-DC converter. The converter is made up of switched capacitors and passive resonant branches. A significant reduction in the count of switches and low voltage stress on the switches is achieved in this proposed converter topology, in comparison to that of a classical SC series-parallel converter. It is essential from the cost, volume, and efficiency of the converter standpoint. The reduction in the count of switches is threefold. The highest voltage stress on the switches depends on the output voltage and is decreased in the proposed converter as well, as the output voltage is divided into two series-connected capacitors. The presented results demonstrate the operation of the converter with the use of resonant branches, its switching strategies, voltage stresses of switches, efficiency, voltage gain, and output voltage regulation as well as the zero-voltage switching (ZVS) operation. The paper also presents novel issues related to analytical loss modeling, extended concepts of topology, converter start-up, and operation during transient states. The demonstrated concept of the converter, the analytical discussion and its design, as well as the experimental setup and results clearly demonstrate the optimization achievements.

Observation of Standing Spin Waves in a van der Waals Magnetic Material.

Spin waves are studied for data storage, communication, and logic circuits in the field of spintronics based on their potential to substitute electrons. The recent discovery of magnetism in 2D systems such as monolayer CrI3 and Cr2 Ge2 Te6 has led to a renewed interest in such applications of magnetism in the 2D limit. Here, direct evidence of standing spin waves is presented along with the uniform precessional resonance modes in the van der Waals magnetic material, CrCl3 . This is the first direct observation of standing spin-wave modes, set up along a thickness of 20mm, in a van der Waals material. Standing spin waves are detected in the vicinity of both branches, optical and acoustic, of the antiferromagnetic resonance. Magnon-magnon coupling and softening of resonance modes with temperature enable extraction of interlayer exchange field as a function of temperature.

Antisite disorder in the battery material LiFePO4

We report detailed magnetometry and high-frequency electron spin resonance (HF-ESR) measurements which allow detailed investigation on Li-Fe antisite disorder in single-crystalline LiFePO$_4$, i.e., exchange of Fe$^{2+}$- and Li$^+$-ions. The data imply that magnetic moments of Fe$^{2+}$-ions at Li-positions do not participate in long-range antiferromagnetic order in LiFePO$_4$ but form quasi-free moments. Anisotropy axes of the magnetic moments at antisite defects are attached to the main crystallographic directions. The local character of these moments is confirmed by associated linear resonance branches detected by HF-ESR studies. Magnetic anisotropy shows up in significant zero-field splittings of $\Delta = 220(3)$~GHz, $\Delta'\sim50$~GHz and a highly anisotropic $g$-factor, i.e., $g_\mathrm{a} = 1.4$, $g_\mathrm{b} = 2.0$, and $g_\mathrm{c} = 6.3$. We demonstrate a general method to precisely determine Fe-antisite disorder in LiFePO$_4$ from magnetic studies which implies a density of paramagnetic Fe$^{2+}$-ions at Li-positions of 0.53\%.

Neutron Spin Resonance in a Quasi-Two-Dimensional Iron-Based Superconductor.

The neutron spin resonance is generally regarded as a key to understanding the magnetically mediated Cooper pairing in unconventional superconductors. Here, we report an inelastic neutron scattering study on the low-energy spin excitations in a quasi-two-dimensional iron-based superconductor KCa_{2}Fe_{4}As_{4}F_{2}. We have discovered a two-dimensional spin resonant mode with downward dispersions, a behavior closely resembling the low branch of the hourglass-type spin resonance in cuprates. While the resonant intensity is predominant by two broad incommensurate peaks near Q=(0.5,0.5) with a sharp energy peak at E_{R}=16 meV, the overall energy dispersion of the mode exceeds the measured maximum total gap Δ_{tot}=|Δ_{k}|+|Δ_{k+Q}|. These results deeply challenge the conventional understanding of the resonance modes as magnetic excitons regardless of underlining pairing symmetry schemes, and it also points out that when the iron-based superconductivity becomes very quasi-two-dimensional, the electronic behaviors are similar to those in cuprates.

Influence of Spurious Modes on the Efficiency of Piezoelectric Transformers: A Sensitivity Analysis

An analysis of the efficiency degradation resulting from spurious modes in piezoelectric transformers (PTs) is presented in this article. Circuit analysis is performed on PT equivalent circuit models with both a single resonant branch and with two resonant branches (spurious mode included), allowing the efficiency degradation from a spurious mode to be analyzed. Multiple sensitivity analyses were then performed, highlighting frequency difference (between modes) and characteristic impedance of the spurious resonant circuit (√L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) as critical design parameters for minimizing efficiency degradation from spurious modes. These two parameters are further analyzed to determine optimum design conditions to ensure minimal efficiency degradation. Results of this analysis provide a method of estimating whether a spurious mode will degrade efficiency and consequently provide a method for improving PT designs.

Microwave dynamics of the stoichiometric and bond-disordered anisotropic S=1 chain antiferromagnet NiCl2−4SC(NH2)2

We studied electron spin resonance in a quantum magnet NiCl2-4SC(NH2)2, demonstrating a field-induced quantum phase transition from a quantum-disordered phase to an antiferromagnet. We observe two branches of the antiferromagnetic resonance of the ordered phase, one of them has a gap and the other is a Goldstone mode with zero frequency at a magnetic field along the four-fold axis. This zero frequency mode acquires a gap at a small tilting of the magnetic field with respect to this direction. The upper gap was found to be reduced in the doped compound Ni(Cl(1-x)Br(x))2-4SC(NH2)2 with $x=0.21$. This reduction is unexpected because of the previously reported rise of the main exchange constant in a doped compound. Further, a nonresonant diamagnetic susceptibility $\chi^{\prime}$ was found for the ordered phase in a wide frequency range above the quasi-Goldstone mode. This dynamic diamagnetism is as large as the dynamic susceptibility of the paramagnetic resonance. We speculate that it originates from a two-magnon absorption band of low-frequency dispersive magnon branch.

Study of a piezoelectric plate based self-sustained electric and electromechanical oscillator

This work deals with the electrical characterization of a piezoelectric plate and its use to generate self-sustained electrical and mechanical oscillations. An experimental frequency-impedance curve of the piezoelectric plate is obtained leading to the electric equivalent of the piezoelectric plate constituted of a capacitive branch in parallel with many RLC resonant branches. The values of the electric components for each branch are determined using the resonant and anti-resonant frequencies. It is demonstrated theoretically that these branches can be understood in terms of vibration modes of the plate; each of which has its own resonant frequency. It is then demonstrated theoretically and experimentally that putting the piezoelectric plate in series with a resistor presenting a nonlinear I − V characteristics having a negative slope, autonomous oscillations of the Van der Pol type can be observed. A theoretical development has led to the appearance of self-sustained periodic and mixed modes mechanical oscillations of the plate deflection.

Vortex-induced vibrations of an elliptic cylinder of low mass ratio: Identification of new response branches

The classical resonance branches that construct the response of a freely vibrating circular or elliptic cylinder at low Reynolds numbers, Re, are “initial” and “lower.” The existence of additional response branches, if any at low Re via alteration of controlling parameters, is unavailable in the literature. In this computational work, relating to a low mass ratio (m* = 1) and zero damping, i.e., m*ζ = 0 transverse-only vortex-induced vibrations of an elliptic cylinder over Re = 50–180, four response branches that are unreported in the literature are identified. The lock-in at such a low mass ratio is non-classical, and the new response branches are resolved close to the lock-in boundaries. These additional branches are designated as extended initial branch, extended lower branch, terminal branch, and quasi-periodic desynchronization branch. The method proposed by Kumar et al. [“Identification of response branches for oscillators with curved and straight contours executing VIV,” Ocean Eng. 164, 616–627 (2018b)] has been employed to identify the branches by locating the Re region concerning the change of slope and discontinuous jumps of oscillation frequency. It is further shown that branching at a low mass ratio depends on structural damping, oscillator shape, and degree-of-freedom.

Design of a Frequency Reconfigurable Broadband THz Antenna Based on the Vanadium Dioxide

In this article, the design of a frequency reconfigurable broadband THz antenna based on vanadium dioxide (VO2) is investigated. Instead of being fed by the microstrip line directly, a windmill-shaped feeding structure is designed to provide a proximity-coupled feeding method. Many modes with contiguous resonant frequencies can be excited to obtain the wideband performance. The proposed antenna combines gold with metamaterial VO2. Thanks to insulator-metal phase transition characteristic of VO2 at phase transition temperature (68 °C), we can change the length of the resonant branches to realize frequency reconfiguration by changing the external temperature (T). The simulated results illustrate that when T = 50 °C (State I), such an antenna has a bandwidth of 35.2% (7.01–10 THz) with S11 below − 10 dB, and a maximum gain of 6.62 dBic. When T = 80 °C (State II), it has a bandwidth of 21.8% (5.77–7.18 THz) with S11 below − 10 dB, and a maximum gain of 4.49 dBic. Thus, we realize a design of a proximity-coupled antenna with reconfigurable wideband over the THz band.

Research on effect of circuit parameters on breaking characteristics of mechanical DC circuit breaker

Whether fault current can be broken quickly and reliably depends on dynamic characteristics of LC resonant commutation branch of mechanical DC circuit breaker.Thereby, the breaking characteristics of mechanical DC circuit breaker based on LC resonant commutation are studied in this paper. The topological structure and action time sequence of mechanical DC circuit breaker based on LC resonant commutation are introduced firstly. Transient voltage and transient current equations of mechanical DC circuit breaker based on LC resonant commutation are deduced on the basis. The influence of fast mechanical switch contact gap, resonant capacitor C, charging voltage of resonant capacitor C, resonant inductance L, solid-state switch turn-on time and other parameters on fault current, breaking time and other breaking characteristics are studied finally, thereby providing feasibility basis for parameter design of LC resonant commutation branch.

Design of a tunable omnidirectional circularly polarized antenna based on VO 2

In this article, a VO2-based tunable omnidirectional circularly polarized (CP) antenna is designed. The proposed antenna combines copper and metamaterial VO2. By utilizing the characteristics of insulator-metal phase transition of VO2, we can change the length of the resonant branches to achieve tunable working bandwidth. The proposed antenna is composed of a modified floor loaded with VO2 and copper resonant branches, a top patch with slits, and 14 shorting vias connecting the top path and bottom floor. Different from the traditional electric controlled antennas, antennas based on metamaterial VO2 do not need to design complicated circuit structures and can be easily tailored by the external temperature (T). The simulated results illustrate that when T ≥ 68°C (state I), the proposed antenna has a 10-dB impedance bandwidth of 15.9% (2.09-2.45 GHz), and a 3-dB axial ratio (AR) bandwidth of 23.4% (2.04-2.58 GHz). When T < 68°C (state II), it has a bandwidth of 6.5% (2.38-2.54 GHz) with S11 below −10 dB, and a bandwidth of 19.9% (2.39-2.92 GHz) with AR below 3 dB.

Optimized Resonant Converter by Implementing Shunt Branch Element as Magnetizing Inductance of Transformer in Electric Vehicle Chargers

An optimized resonant converter with zero-voltage switching over an extensive range of loading is proposed to integrate renewable energy sources to an onboard charger. In conventional resonant circuit, high-frequency transformer (HF) parasitic components are used as tank circuit, this degrades the performance due to non-optimal magnetic components. Here, the HF transformer is fabricated with optimized resonant tank circuit shunt branch inductance ( $L_p$ ) as magnetizing inductance, hence eliminating the need for shunt branch inductance. The proposed resonant converter circuit design is optimized for minimum kilovoltampere rating and better voltage regulation with both duty cycle and frequency control (mixed control method). Furthermore, the performance of the converter at a very light load is improved using the proposed control method. Incorporating a low- $R_{\text{DS}}(\text{ON})$ silicon carbide mosfet and softly turning off the switches for a wide load variation minimizes conduction and switching losses and improves efficiency. Using powder core for the design of the tank circuit reduces magnetic losses. A 3-kW prototype of the converter is built to verify the performance from no load to full load. The highest efficiency of the proposed converter is 98.6%, attained at 50% full load.

Gigahertz Frequency Antiferromagnetic Resonance and Strong Magnon-Magnon Coupling in the Layered Crystal CrCl_{3}.

We report broadband microwave absorption spectroscopy of the layered antiferromagnet CrCl_{3}. We observe a rich structure of resonances arising from quasi-two-dimensional antiferromagnetic dynamics. Because of the weak interlayer magnetic coupling in this material, we are able to observe both optical and acoustic branches of antiferromagnetic resonance in the GHz frequency range and a symmetry-protected crossing between them. By breaking rotational symmetry, we further show that strong magnon-magnon coupling with large tunable gaps can be induced between the two resonant modes.