Harmonic Resonance Frequencies Research Articles

Cure State Sensing of Polymethylmethacrylate Using a Vibrating Axial Probe.

A new axially vibrating sensor based on an audio voice coil transducer and a lead zirconate titanate (PZT) piezoelectric disc microphone was developed as a probe for the measurement of in vitro rheological fluid properties, including curing progress for polymethylmethacrylate (PMMA) mixtures with important uses as bone cement in the field of orthopedics. The measurement of the vibrating axial sensor's acoustic spectra in PMMA undergoing curing can be described by a damped harmonic oscillator formalism and resonant frequency (ca. 180 Hz) shift can be used as an indicator of curing progress, with shifts to the blue by as much as 14 Hz. The resonant frequency peak was measured in 19 different 4.0 g PMMA samples to have a rate of shift of 0.0462 ± 0.00624 Hz·s-1 over a period of 400 s while the PMMA was in a dough state and before the PMMA transitioned to a hard-setting phase. This transition is unambiguously indicated by this sensor technology through the generation of a distinct circa 5 kHz high-Q under-damped ring-down response.

Harmonic impedance optimization scheme for multi‐resonance systems to suppress resonance

AbstractHarmonic resonance is caused by harmonic source matching resonance frequency and presents the characteristics of decentralization and whole network in modern grids. The current resonance suppression methods mainly focus on reducing the harmonic source, and are suitable for single‐site and small‐scale grids. This paper presents a new method for suppressing parallel resonance at system level. The holistic harmonic resonance is suppressed by reducing the harmonic impedance. In addition, new resonances are prevented by weakening the coupling between resonance and non‐resonance frequencies. The resonance modal analysis and resonance frequency shift (RFS) are employed to optimize harmonic impedance. Simulation results indicate that the capacitance parameter has higher sensitivity and is theoretically more suitable for RFS. Considering the accuracy of modal frequency sensitivity, a variable‐limit genetic algorithm for iteration is proposed. The validity of the proposed method was verified using an IEEE 14‐bus test network.

Characterization of harmonic modes and parasitic resonances in multi-mode superconducting coplanar resonators

Planar superconducting microwave transmission line resonators can be operated at multiple harmonic resonance frequencies. This allows covering wide spectral regimes with high sensitivity, as it is desired, e.g., for cryogenic microwave spectroscopy. A common complication of such experiments is the presence of undesired “spurious” additional resonances, which are due to standing waves within the resonator substrate or housing box. Identifying the nature of individual resonances (“designed” vs “spurious”) can become challenging for higher frequencies or if elements with unknown material properties are included, as is common for microwave spectroscopy. Here, we discuss various experimental strategies to distinguish designed and spurious modes in coplanar superconducting resonators that are operated in a broad frequency range up to 20 GHz. These strategies include tracking resonance evolution as a function of temperature, magnetic field, and microwave power. We also demonstrate that local modification of the resonator, by applying minute amounts of dielectric or electron spin resonance-active materials, leads to characteristic signatures in the various resonance modes, depending on the local strength of the electric or magnetic microwave fields.

Quantitative Harmonic Amplification Analysis in Electric Railway Traction Power Supply Systems

Background: Harmonic resonance is one of the apprehensive power quality problems in electric railway traction power supply systems. Harmonic resonances result in big harmonic voltage distortions or harmonic currents. Different harmonic resonance frequencies existing in a power system possess varying propagation areas and amplification levels. The frequency scan analysis technique and the resonance mode analysis technique are the two most commonly used methods. The frequency scan analysis technique can reveal whether resonance exists and determine the resonance frequency. Resonance mode analysis technique can further identify the location where a resonance can be most easily initiatedand observed. However, there are still few studies on the quantitative analysis of harmonic propagation and resonance amplification in traction power supply systems. Methods: The model of the all-parallel autotransformer-fed system in the high-speed railway is built accurately, then a quantitative analysis method based on harmonic electrical distance is used to study the harmonic propagation characteristics and propagation severities caused by electric trains, and analyses in detail the influence of the number of lines, the number of trains, and the location of the train on the severity of resonance amplification. Results: The results of case studies reveal the traction power supply system harmonic propagation characteristics and amplification severities and system parameter sensitivities in a quantitative way, validating the effectiveness and superiority of the quantitative analysis method. Conclusion: Compared with the resonance mode analysis method and the frequency scan analysis method, at a harmonic resonance frequency point, the quantitative analysis method can quantitatively reveal the harmonic propagation area and amplification level at each bus of the traction power supply system. Meanwhile, it is simple and practical.

Online-Harmonic-Detection-Based System Stabilization Function for Grid-Forming Inverters Under Various Grid Conditions

In power systems with grid-forming inverters (GFMs), small-signal instability issues could occur due to harmonic excitation, impedance interactions, and poor inverter control design. There mainly exist two types of stability issues based on the frequency range. One is the low-frequency resonance (0 – 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f₀</i> Hz) and the other is the high-frequency harmonics (above 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f₀</i> Hz), where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f₀</i> is the system fundamental frequency. By assuming that the low-frequency related controls are well designed, this paper addresses the high-frequency harmonic issues. The goal is to develop a system stabilization function (SSF) to eliminate any high-frequency stability issues under various grid conditions without affecting predefined low-frequency behaviors. The idea is to conduct the inverter passivation test at the system harmonic resonant frequency so that the corresponding harmonic instability can be removed. To achieve this, the resonant frequency of the harmonic instability is detected first, and then if the magnitude of the resonant component exceeds the threshold value, the proposed SSF will be enabled, thus the system would be stabilized. Both simulation and experimental tests are conducted to validate the effectiveness of the proposed approach.

Mechanism analysis and suppression method of high frequency harmonic resonance in VSC-HVDC

This paper introduces the basic situation of high frequency harmonic resonance in Guangxi on April 10, 2017, which is based on the Luxi back-to-back voltage source converter based high voltage direct current transmission (VSC-HVDC) project in China. Firstly, the harmonic amplification mechanism and its key links in the event are analyzed in detail and verified by simulation. Secondly, the relationship among high frequency harmonic resonance, voltage feedforward control loop and system harmonic impedance is obtained, and the formulas among voltage feedforward control parameters, system harmonic impedance and high frequency harmonic resonance frequency amplitude are deduced. Then, a method to suppress high frequency harmonic resonance by adding a reasonably filter to the voltage feedforward control loop is proposed. Finally, the effectiveness of the proposed method in this paper is verified by simulation and field operation.

An improved harmonic resonance mode analysis method for distribution power grid

Harmonic resonance endangers seriously safe and reliable operation of power grid and an appropriate resonance harmonic analysis method is of great importance. The traditional mode analysis method is a kind of main method to analyze harmonic resonance of power grid so to obtain various harmonic information such as resonance frequency, maximum excitation node and observation node as well as participation factor. However, its calculation efficiency is lower and has no way to judge accurately the maximum excitation node in the harmonic resonance of the distribution power grid. The improved mode analysis method proposed in this paper combines the frequency spectrum analysis with the traditional mode analysis method, and the condition of whether the harmonic resonance could occur at the determined excitation node at resonance frequency is added. Taking the distribution power grid in Bonan Oil area of Shengli Oilfield as an example, this paper analyzes the harmonic resonance of distribution network by using traditional mode analysis method and improved mode analysis method respectively. By comparing the analysis results of the two methods, the superiority of the improved mode analysis method is verified. The analysis of harmonic resonance of distribution network in Bonan Oil area shows that the improved mode analysis method proposed in this paper can accurately determine the harmonic resonance frequency and the highest excitation node of distribution network, while the traditional mode analysis method could not accurately judge the highest excitation node. In addition, the calculation time of the improved mode analysis method is only 17% of that of the traditional mode analysis method, which greatly improves the analysis efficiency.

Synthesis, spectroscopic characterization, molecular docking and in vitro cytotoxicity investigations on 8-Amino-6-Methoxy Quinolinium Picrate: a novel breast cancer drug

Density Functional Theory (DFT) studies of the 8-Amino-6-Methoxy Quinolinium Picrate (8A6MQP) molecule have been carried out with extensive and accurate investigations of detailed vibrational and spectroscopic investigations as well as validated experimentally. The 8A6MQP sample was synthesized and characterized using FT-IR, FT-Raman, FT-NMR and UV-Vis spectroscopic techniques. Subsequently, the optimized molecular structure and harmonic resonance frequencies of the molecule were computed based on DFT/B3LYP method with a 6-311G++(d,p) basis set using the Gaussian 09 program. The experimental and calculated vibrational wavenumbers were assigned. The absorption spectrum of the molecule was computed in the liquid phase (ethanol), which exhibits n to л* electronic transition and compared with the observed UV-Vis spectrum. Frontier molecular orbital analysis shows the molecular reactivity and kinetic stability of the molecule. The Mulliken atomic charge distribution and molecular electrostatic potential surface analysis of the molecule validate the reactive site of the molecule. The natural bond orbital analysis proves the bioactivity of the molecule. Molecular docking analysis indicates that the 8A6MQP molecule inhibits the action of DNA topoisomerase 2-alpha protein, which is associated with breast cancer. In addition, the in vitro cytotoxicity analysis of the 8A6MQP molecule against human cervical cancer cell lines (ME180) and human breast cancer cell lines (MDA MB 231) were determined by MTT assay, which evidences that the title molecule exhibits higher inhibition against the breast cancer cell lines compared to that of cervical cancer cell lines. Hence, the present study paves the way for the development of novel drugs in the treatment of breast cancer. Communicated by Ramaswamy H. Sarma

A gray-box harmonic resonance frequency identification method of multiple-inverter-fed power system oriented to system designers

This paper presents a gray-box harmonic resonance frequency identification method of multiple-inverter-fed power system, which enables modal analysis oriented to system designers based on only frequency response data provided by diverse vendors or measured by frequency scanning. First, admittance transfer functions of all grid-connected inverters (GCIs) are fitted using Matrix Pencil Method-Vector Fitting (MPM-VF) combined method. Then, node admittance matrix (NAM) is formed according to the topology of whole system. Finally, harmonic resonance frequency along with changes in number of GCIs are identified by NAM-based modal analysis (MA). The proposed gray-box identification method is implemented in a typical multiple-inverter-fed power system. The correctness of harmonic resonance frequency identification results and the effectiveness of the presented method are verified by simulation results obtained in Matlab/Simulink platform and OPAL-RT digital real-time simulation platform. Based on the identification results, a more stable and better power quality multiple-inverter-fed power system can be built by system designers though avoiding the appearance of harmonic sources with corresponding resonance frequency.

Fundamental limits and optimal estimation of the resonance frequency of a linear harmonic oscillator

All physical oscillators are subject to thermodynamic and quantum perturbations, fundamentally limiting measurement of their resonance frequency. Analyses assuming specific ways of estimating frequency can underestimate the available precision and overlook unconventional measurement regimes. Here we derive a general, estimation-method-independent Cramer Rao lower bound for a linear harmonic oscillator resonance frequency measurement uncertainty, seamlessly accounting for the quantum, thermodynamic and instrumental limitations, including Fisher information from quantum backaction- and thermodynamically driven fluctuations. We provide a universal and practical maximum-likelihood frequency estimator reaching the predicted limits in all regimes, and experimentally validate it on a thermodynamically limited nanomechanical oscillator. Low relative frequency uncertainty is obtained for both very high bandwidth measurements (≈10−5 for τ = 30 μs) and measurements using thermal fluctuations alone (<10−6). Beyond nanomechanics, these results advance frequency-based metrology across physical domains.

Simulation Analysis of Emulsion Droplet Excited by Chaotic Frequency Pulse Electric Field

The frequency of the chaotic pulse electric field is random in a limited range, which can be adjusted and controlled, thus can effectively cover the harmonic resonance frequency of the droplets in the oil, and realize the efficient coalescence and demulsification of the droplets. In this study, the chaotic frequency pulse electric field is constructed by embedding the chaotic sequence into the pulse interval with the Chaotic-Pulse-Position Modulation method, and the vibration dynamics simulation model of the emulsion droplet in the chaotic frequency electric field is established. The vibration dynamics response of the emulsion droplet under the action of the chaotic frequency pulse electric field is obtained by numerical calculation, and the dynamic analysis, phase diagram analysis and maximum Lyapunov exponent calculation of the response output are carried out. It is found that under the action of chaotic frequency pulse electric field, the emulsion droplet can obtain large tensile deformation at high frequency, but relatively small at low frequency, and the fluctuation is stable, which can qualitatively and quantitatively identify the chaotic vibration characteristics of the droplet.

Spectroscopic, quantum chemical and molecular docking studies on 1-amino-5-chloroanthraquinone: A targeted drug therapy for thyroid cancer

The DFT studies of the 1-Amino-5-chloro-anthraquinone (ACAQ) molecule have been carried out with extensive and accurate investigations of detailed vibrational and spectroscopic investigations and validated by experimentally. The optimized molecular structure and harmonic resonance frequencies were computed based on DFT/B3LYP method with 6-311G++(d,p) basis set using the Gaussian 09 program. The experimental and calculated vibrational wavenumbers were assigned on the basis of PED calculations using VEDA 4.0 program. The 13C NMR isotropic chemical shifts of the molecule were calculated using Gauge-Invariant-Atomic Orbital (GIAO) method in DMSO solution and compared with the experimental data. The absorption spectrum of the molecule was computed in liquid phase (ethanol), which exhibits л to л* electronic transition and compared with observed UV–Vis spectrum. Frontier molecular orbitals analysis shows the molecular reactivity and kinetic stability of the molecule. The Mulliken atomic charge distribution and molecular electrostatic potential surface analysis of the molecule validate the reactive site of the molecule. The natural bond orbital analysis proves the bioactivity of the molecule. Molecular docking analysis indicate that ACAQ molecule inhibits the action of c-Met Kinase protein, which is associated with the thyroid cancer. Hence, the present study pave the way for the development of novel drugs in the treatment of thyroid cancer.

Dynamic features of a non-polarized Erbium-doped fiber ring laser subjected to external cavity-loss modulation

An experimental study of an Erbium-doped fiber ring laser subjected to external cavity-loss modulation using a loudspeaker as the modulator has been carried out and analyzed via modulation of the driving amplitude and frequency in the range of 1–20 kHz. The linear and non-linear (chaotic) dynamical behaviors have been observed from the bifurcation, time domain and frequency domain diagrams presented. The bifurcation diagram showed that the loss modulated laser is more sensitive to the acoustic wave generated from the loudspeaker when the driving amplitude is < 200 mV and < 1000 mV (< 16.5 mW and < 82.5 mW optical power). At driving amplitudes of 500 mV – 1000 mV (41.25 mW – 82.5 mW optical power), the ring laser system behaves like a damped non-linear oscillator. Optical bi-stability was also observed in the bifurcation diagrams near or exactly at the fundamental resonance frequency and first super harmonic resonance frequency. The availability of different control parameters during external cavity-loss modulation in an Erbium doped fiber laser makes the study of its non-linear response features easy in a very precise way. The control parameters considered in this paper are the driving amplitude and the modulation frequency.

The Vibration Behavior of Sub‐Micrometer Gas Vesicles in Response to Acoustic Excitation Determined via Laser Doppler Vibrometry

AbstractThe ability to monitor sub‐micrometer gas vesicles' (GVs) vibration behavior to nonlinear buckling and collapse using laser Doppler vibrometry is reported, providing a precise noncontact technique for monitoring the motion of sub‐micrometer objects. The fundamental and first harmonic resonance frequencies of the vesicles are found to be 1.024 and 1.710 GHz, respectively. An interparticle resonance is furthermore identified at ≈300 MHz, inversely dependent upon the agglomerated GV size of around 615 nm. Most importantly, the vesicles amplify and broaden input acoustic signals at far lower frequencies—for example, 7 MHz—associated with medical and industrial applications, and they are found to transition from a linear to nonlinear response at 150 kPa and to collapse at 350 kPa or greater.

Optimal Positioning of Power Quality Meters for Monitoring Potential Conditions of Harmonic Resonances in a MV Distribution System

This research proposes an optimized allocation methodology of power quality (PQ) meters in medium voltage (MV) distribution system (DS), considering the potential harmonic resonance conditions. The allocation methodology uses the harmonic resonance mode analysis (HRMA) to calculate the critical modal impedances and identify the harmonic resonance frequencies. Thereby, using the HRMA, it is possible to build a binary observability matrix, which contains the information of nodes' observability for potential harmonic resonance frequencies. The allocation problem is modeled as a constraint integer linear programming that minimizes the number of necessary PQ meters, ensuring the complete observation of the determined harmonic resonance frequencies. The final feasible solution indicates the best locations to install the PQ meters, considering the harmonic resonance conditions, which include distinct operation scenarios of the DS, regarding the capacitor banks of the customers for power-factor correction. The allocation algorithm was applied in two test DSs, based on a CIGRÉ MV network and on the IEEE 34-node test feeder. The results show that four PQ meters are required to completely monitor the potential harmonic resonance frequencies in both the test DSs. It is also shown that the final allocation solution is applicable even for certain variability of the considered capacitor banks.

The vibration behavior of submicron gas vesicles in response to acoustic excitation as determined via laser doppler vibrometry

Gas vesicles (GVs) are remarkably stable nano-sized gas-filled protein shells proven effective in ultrasonic imaging. The many potential benefits of GVs arise from their strong gas equilibrium at a submicron size as produced by bacteria or algae, producing significant contrast in ultrasound imaging. The actual vibration behavior of GVs, including buckling and collapse, is poorly understood since the GVs are too small for observation methods of sufficient speed to produce details of the GV deformation during exposure to ultrasound. Traditional optical or acoustic microscopy methods are, in any case, not useful, and ex-situtransmission electron microscopy produces useful images but without sufficient time resolution. We propose to instead use laser Doppler vibrometry (LDV) to observe the vibration behavior of GVs. Employing interferometry, LDV offers a far better spatiotemporal resolution. While the typical GV is smaller than 1 μm, an agglomeration of GVs may be used with the LDV to produce a measurable displacement response from a controlled, acoustically delivered pressure. In this talk, we report the fundamental and first harmonic resonance frequencies of GVs and vibration to buckling and collapse at the clinically relevant frequency of 6.5 MHz. We also compare these results with predictions from classic theories of bubble and particle oscillations and finite difference-based computations.

DC-side harmonic analysis and DC filter design in hybrid HVDC transmission systems

Hybrid high-voltage direct current (HVDC) transmission is a new transmission structure that uses line commutated converter (LCC) at the rectifier side and voltage source converter (VSC) at the inverter side. This study proposes a method to calculate DC side harmonic currents of hybrid HVDC transmission systems and design filters to mitigate DC-side low-frequency voltage pulsations. First, an equivalent harmonic analysis model of modular multilevel converter (MMC) is deduced according to the relationship among different harmonic components. The harmonic voltage expressions at DC side of 12-pulse LCC are deduced by combining the three-pulse harmonic voltage source model and FFT decomposition. On this basis, the expressions for harmonic currents are derived by multiplying the harmonic voltage transfer function and transfer admittance equation of DC network and are solved for the inverse Laplace transform. Two different types of DC filters are designed according to the requirements of DC filter on decaying specific order harmonic currents. The influence of partial element decay on the transfer characteristic of filter is analyzed, and appropriate partial component dissipation parameters are applied. The decay pole near the harmonic resonance frequency is configured to achieve reasonable DC-filtering results. Simulation results of a hybrid HVDC transmission system demonstrate the effectiveness of the proposed analysis model and filter design method.

New Insights into χ(3) Measurements: Comparing Nonresonant Second Harmonic Generation and Resonant Sum Frequency Generation at the Silica/Aqueous Electrolyte Interface

Historically, different pH-dependent behaviors at the mineral oxide/aqueous electrolyte interface have been observed by nonresonant second harmonic generation (SHG) and resonant sum frequency gener...

Impedance-based analysis of harmonic instabilities in HVDC-connected Offshore Wind Power Plants

HVDC-connected Offshore Wind Power Plants (OWPPs) with a large number of power converters are prone to instabilities due to interactions with converter controllers. This paper analyzes harmonic instabilities in OWPPs connected through HVDC due to interactions with the offshore HVDC converter and the wind turbine converters. An impedance-based model is used to represent a detailed OWPP with fully-rated converter based wind turbines, including the offshore HVDC converter, wind turbine converters, submarine cables and transformers of the offshore AC grid. Harmonic stability is evaluated both from the grid connection point of the offshore HVDC converter and the WT grid side converters. As a result, the influence that parameters of converter control systems and the offshore grid configuration have on harmonic resonant frequencies and stability conditions is analyzed in depth through a sensitivity analysis. Active damping implemented as a feed-forward control is coordinated in all converters to mitigate the harmonic instabilities. Examples of harmonic instabilities and active damping application are validated with time domain simulations in PSCAD/EMTDC.

Theoretical and experimental study of gradient-helicoid metamaterial

Resonance based acoustic metamaterials and metasurfaces exhibit outstanding phase modulation capabilities with high transmission coefficient, but it is rather confined to the neighborhood of fundamental or harmonic resonant frequencies. Based on the impedance-matched gradient material, we theoretically and experimentally study a gradient index helicoid metamaterial that can modulate sound wavefront with nearly perfect transmission over a broad bandwidth. Taking advantage of the linear spectral phase shifting, a thin flat metalens is constructed to demonstrate sound focusing with the extraordinary transmission for more than 1/3 octave band. It is anticipated that this engineered material may be used in ultrasonography, ultrasound surgery, and DNA fragmentation. Moreover, with the flexible adjustment of effective parameters, it can be an ideal alternative to the anisotropic inhomogeneous medium and has much better stiffness.