Resonance Frequency Detuning Research Articles

The coupling effect of temperature and Rb-Xe in NMR sensor

The nuclear magnetic resonance (NMR) sensor is the atomic sensor which has the advantages of high accuracy, high sensitivity, small size, etc., and has broad application prospects in the field of inertial navigation. Temperature is one of the important parameters that determine the ultimate performance of NMR sensor including temperature fluctuations, temperature gradients, and temperature uniformity. Among them, temperature fluctuations give rise to the resonance frequency detuning, which not only shifts the carrier frequency, but also affects the alkali metal magnetic field perceived by the Xe nuclei. The accuracy and sensitivity of NMR sensor were limited as consequence of temperature fluctuations on account of its temperature sensitivity. In this paper, we have demonstrated a model of the coupling effect of temperature and Rb-Xe to analyze the influence of temperature fluctuations on the resonance frequency detuning of Xe nuclei. On the one hand, this model has analyzed the resonance frequency detuning caused by the Rb-Xe coupling effect in the NMR sensor demodulation system, whose fitting degree between theoretical analysis and experimental results is achieved 99.78%. On the other hand, it has analyzed the resonance frequency detuning caused by the magnetic field generated by the alkali metal atoms, which is associated with temperature fluctuations and experienced by Xe nuclei. The fitting degree of theoretical model of the coupling effect of temperature and Rb-Xe is achieved 99.87%. These works have provided a valuable scheme for enhancing the ultimate performance of NMR sensor and future applications.

Analysis of carbon content in direct-write plasmonic Au structures by nanomechanical scanning absorption microscopy

In this work, a novel chemical composition characterization method of direct-write focused electron beam-induced deposition (FEBID) gold nanostructures is presented. The reliable determination of the chemical content for nanostructures has been challenging due to its limited interaction volume. We hereby propose an alternative technique for measuring the chemical composition of nanostructures with limited volume. By measuring the differences in the optical absorption of the nanostructure due to the differences in the chemical composition with the resonance frequency detuning of a nanomechanical resonator and the assistance of analytical optical modeling, we demonstrate the possibility of characterizing the carbon content in the (FEBID) gold nanostructures. From our characterization method, the post-purification process with water successfully reduced the carbon content from ∼65 at. % to ∼20 at. %. This method presents a new technique for the chemical analysis of nanostructures.

Sensitivity Analysis of Inductive Power Transfer Systems With Voltage-Fed Compensation Topologies

The output characteristics and the transfer efficiencies of inductive power transfer (IPT) systems are affected by (but not limited to) the variation of parameters such as, variable load, misalignment between the primary and secondary coils, and resonance frequency detuning. This paper first analyzes the resonant conditions of all voltage-fed compensation topologies in IPT systems to achieve the load-independent voltage transfer characteristic at load-independent zero phase angle frequency. With these conditions, the parameters sensitivity to the key performance factors of the S-SP, LCC-S, LCC-P, and double-sided LCC compensated IPT systems are systematically investigated when considering the losses in coils and compensation networks. Comparisons of the quantitative sensitivity analysis and experimental results for all IPT systems are made in terms of the voltage transfer ratio and efficiency. These analyses can provide guidance for the selection of superior compensation networks to minimize the additional converter effort and simplify the control algorithm of closed-loop IPT systems.

Vibration Reduction of Mistuned Bladed Disks Via Piezoelectric-Based Resonance Frequency Detuning

This paper extends the resonance frequency detuning (RFD) vibration reduction approach to cases of turbomachinery blade mistuning. Using a lumped parameter mistuned blade model with included piezoelectric elements, this paper presents an analytical solution of the blade vibration in response to frequency sweep excitation; direct numerical integration confirms the accuracy of this solution. A Monte Carlo statistical analysis provides insight regarding vibration reduction performance over a range of parameters of interest such as the degree of blade mistuning, linear excitation sweep rate, inherent damping ratio, and the difference between the open-circuit (OC) and short-circuit (SC) stiffness states. RFD reduces vibration across all degrees of blade mistuning as well as the entire range of sweep rates tested. Detuning also maximizes vibration reduction performance when applied to systems with low inherent damping and large electromechanical coupling.

Switch Triggers for Optimal Vibration Reduction Via Resonance Frequency Detuning

Resonance frequency detuning (RFD) reduces vibration of systems subjected to frequency sweep excitation by altering the structural stiffness state as the excitation frequency passes through resonance. This vibration reduction technique applies to turbomachinery experiencing changes in rotation speed, for example, on spool-up and spool-down, and can be achieved through the inclusion of piezoelectric material and manipulation of its electrical boundary conditions. Key system parameters—the excitation sweep rate, modal damping ratio, electromechanical coupling coefficient, and, most importantly, the switch trigger that initiates the stiffness state switch (represented here in terms of excitation frequency)—determine the peak response dynamics. This paper exploits an analytical solution to a nondimensional single degree-of-freedom equation of motion to provide this blade response and recasts the equation in scaled form to include the altered system dynamics following the stiffness state switch. An extensive study over a range of sweep rates, damping ratios, and electromechanical coupling coefficients reveals the optimal frequency switch trigger that minimizes the peak of the blade response envelope. This switch trigger is primarily a function of the electromechanical coupling coefficient and the phase of vibration at which the switch occurs. As the coupling coefficient increases, the frequency-based switch trigger decreases, approximately linearly with the square of the coupling coefficient. Furthermore, as with other state-switching techniques, the optimal stiffness switch occurs on peak strain energy; however, the degradation in vibration reduction performance associated with a switch occurring at a nonoptimal phase is negligible for slow sweep rates and low modal damping.

Tracking Frequency Resonant Coupling Energy Wireless Transmission Research

The problem of transceiver coil resonance frequency detuning is solved tentatively on resonant coupling energy wireless transmission in this paper. The circuit model of the wireless transmission system of the resonant coupling electrical energy is first studied, the relationship between the parameters of the system and the transmission efficiency of the various parts is analyzed, and yhe studies have shown that the change in the amount of the transmitting coil inductance greater impact on the transmission efficiency, while the receiving coil inductance change in the amount of efficiency small, and thus the proposed phase locked loop frequency tracking technology, to ensure that the transceiver coil resonant frequency to ensure that the transmission efficiency of the system. The feasibility of the design frequency tracking system is verified with the experimental results.

Piezoelectric-Based Vibration Reduction of Turbomachinery Bladed Disks via Resonance Frequency Detuning

Piezoelectric-based resonance frequency detuning can alleviate unwanted vibration of turbomachinery blades, thus reducing the dangers of high-cycle fatigue while also decreasing the blade weight. This semiactive approach applies to structures that are subjected to frequency-sweep excitation and involves altering the structural stiffness (here, by switching the piezoelectric electrical boundary conditions) to avoid a resonant condition, thus limiting the blade response. Detuning requires two switches per resonance/excitation frequency crossing, including a switch back to the original the original state,many fewer than other semiactive approaches that require four switches per cycle of vibration.Resonance frequencydetuningapplies to anymode of vibrationwith apositive electromechanical coupling coefficient, and it provides the greatest normalized vibration reduction for slow sweeps, low damping, and high coupling coefficient. Yet even for amoderate sweep rate 10 4 andmodal damping 0:1%, optimally detuning a structure with an electromechanical coupling coefficient k 10% provides the same vibration reduction as increasing either the sweep rate ormodal damping by an order of magnitude.With a lower sweep rate 10 5 and modal damping 0:01%, detuning with a coupling coefficient of only k 3% provides equivalent vibration reduction as an order of magnitude increase in sweep rate or modal damping.

The resonance interaction of vibrational modes in one-dimensional nonlinear lattices

Resonances of vibrational modes were for the first time revealed for the example of the one-dimensional random Morse lattice. The observation of resonances was possible because of lattice deformation, when, at certain relative deformation values, vibrational modes satisfied the conditions of double (m i ω i + m j ω j = 0) or triple (m i ω i + m j ω j + m k ω k = 0) resonances. Of all the resonances observed, the resonance with the frequency ratio ω2: ω1 = 2: 1 was studied in detail. The dependences of mode lifetimes and the degree of energy exchange between them on such parameters as resonance frequency detuning, excitation energy level, etc. were determined. A model of two nonlinearly coupled harmonic oscillators was considered in detail on the assumption of a one-to-one correspondence between oscillators and vibrational modes. A consideration of the model problem of oscillators revealed analytic dependences of the dynamic behavior of vibrational modes on control parameters. Excellent agreement between the numerical results for the Morse lattice and analytic conclusions was obtained. It was shown that, for the Fermi-Pasta-Ulam lattice, the resonance interaction of vibrational modes was controlled by the same rules as with the Morse lattice.

Local electrical dissipation imaged by scanning force microscopy

The low internal damping of micromachined monolithic silicon levers with integrated probe tip has been exploited to detect nonconservative components in the interaction forces between the probe tip and sample. This is accomplished by monitoring the mechanical Q while scanning the surface. The gap width was controlled by keeping the lever’s resonance frequency detuning, caused by the gradient of the force between tip and surface, fixed to a preset value. Nonconservative components are present even in Coulomb attraction since, whenever a voltage is applied between tip and substrate, currents are induced by the lever’s oscillation leading to Joule dissipation of energy at a rate that depends on the local conductivity. Strong damping contrast was observed in layered GaAs/AlGaAs semiconductor heterostructures. It depended on the type of material, dopant concentration, illumination, and the applied voltage. Damping variations were resolved over distances of less than 20 nm.