Resonance Problem Research Articles

Numerical investigation of wave actions on two side by side boxes in close proximity using IMLPG_R method

The capability of the Meshless Local Petrov Galerkin method to understand the gap resonance between two side-by-side fixed boxes in close proximity is reported in this study. The present paper focuses on bilge-shaped boxes, the draft of the downstream box, and various hydrodynamic aspects of the gap resonance problem. Both regular wave and focused wave are used in this study. The piston mode resonance frequencies for different model configurations are determined by conducting regular wave tests within the range of 0.625 Hz to 1.54 Hz. The effect of wave steepness is also discussed. Near the resonance frequency, the model configuration having round bilge shapes showed a 77% increase in wave amplification when compared to square bilge shape. Similarly, horizontal and vertical forces on boxes also showed a significant increase in the case of round bilge configuration. For the different model configurations tested, an increase in the draft of the downstream body is found to amplify free surface elevation in the gap by 19% near gap resonance frequency. The reasons for various distinctive behavior for wave amplification inside the narrow gap and force acting on the boxes are explained with the help of instantaneous velocity and vorticity from the numerical simulation. The paper also discusses the water column in the narrow gap excited with a focused transient wave group. A four-phase combination method is then used to extract the first-order and higher-order harmonics of free surface elevation in the narrow gap and the forces acting on the boxes to analyze the influence.

Dynamic Design of the Test Bench of Electric Vehicle Motor

In order to avoid the resonance of the bench and the laboratory floor, it is necessary to carry out vibration analysis and dynamic design on the motor test bench. Firstly, the lightweight target and the constraint conditions related to the rigid body modal frequency and elastic modal frequency of the platform are set, and the structure of the platform is optimized. Then, the three-dimensional model of the whole bench is built and the finite element is meshed to carry out modal analysis. The optimized modal analysis results show that the natural frequencies of the designed bench will not be excited by various vibration excitation forces at the set speed of motor test, the vibration isolation rate of the lower bracket reaches more than 52% (except that the vibration isolation rate of the lower bracket is 36.30% at 1000 rpm), which effectively eliminates the resonance problem between the bench and foundation during motor NVH test, and the normal performance of motor and NVH test can be effectively ensured.

N-th Order Functional Problems with Resonance of Dimension One

We consider the nonlinear n-th order boundary value problem Lu=u(n)=f(t,u(t),u′(t),…,u(n−1)(t))=Nu given arbitrary bounded linear functional conditions Bi(u)=0, i=1,…,n and develop a method that allows us to study all such resonance problems of order one, as well as implementing a more general constructive method for deriving existence criteria in the framework of the coincidence degree method of Mawhin. We demonstrate applicability of the formalism by giving an example for n=4.

Simulation of Multiple-Quantum NMR Dynamics of Spin Dimer on Quantum Computer

Dynamics of spin dimers in multiple quantum NMR experiment is studied on the 5-qubit superconducting quantum processor of IBM Quantum Experience for the both pure ground and thermodynamic equilibrium (mixed) initial states. The work can be considered as a first step towards an application of quantum computers to solving problems of magnetic resonance. This article is dedicated to Prof. Klaus Möbius and Prof. Kev Salikhov on the occasion of their 85th birthdays.

Spin Temperature and Dynamic Nuclear Polarization. From the History of Researches (1953 – 1983)

An attempt is proposed in the most concise form to provide the reader with a history of research and applications of dynamic nuclear polarization (DNP). The main attention is paid to the first three decades of DNP research, and the history of the discovery and development of multiparticle DNP and its relationship with the spin temperature approximation are outlined in some detail. The article emphasizes the role of such researchers as Anatol Abraham, Maurice Goldman, Michel Borghini, Thomas Wenckebach, Vadim Atsarkin, Boris Provotorov, Maya Rodak, Mortko Kozhushner, Levan Buishvili, Givi Khutsishvili. As far as possible, the contributions of many other scientists are considered. The establishment of a uniform temperature for nuclear spins due to the effect of spin diffusion was first proposed by Nicholas Blombergen in 1949. The content of the article is based on the bibliography available in the public domains, in particular on the memoirs of the research participants, and first of all on the materials of Atsarkin's 1978 review in Sov. Phys. Uspekhi and on the oral history of the development of the multiparticle concept of DNP effects, recorded from the speeches of the participants of the Moscow seminar "Problems of Magnetic Resonance" in 2001. A simplified description of the effects of DNP and a summary of the history of their discovery is given in section “Introduction”. The shortest biographical data and portraits of participants in the DNP study are given in Appendix 1, and a selected bibliography on the problems of DNP and spin temperatures is given in Appendix 2. The bibliography divided into four sections according to the time and type of publication (I - historical research, memoirs; II – monographs, reviews; III - original publications 1953 - 1983; IV – some original publications of a later time, mainly during the transformation of DNP into an method for the implementation of nuclear magnetic spectroscopy and tomography in the interests of chemistry, biochemistry and medicine). The widespread use of DNP methods is evidenced, for example, by the fact, that by now company Bruker BioSpin has installed about 50 gyrotron based spectrometers for DNP operating upto 593 GHz worldwide to date.

Grid-connected resonance analysis of half-wavelength transmission system with wind power and photovoltaic power supply

New energy centers such as wind power and photovoltaic power generation are generally too far away from the load center. Half wavelength AC transmission technology can solve this problem. However, harmonics may be generated when new energy is connected to half wavelength transmission system. Harmonics will do harm to the normal operation of power grid. Therefore, this harmonic resonance problem is studied in this paper. Firstly, this paper expounds the principles of classical resonance analysis method and modal analysis method, and explains the advantages of modal analysis method through analysis and calculation. Then, the grid connected resonance of large-scale wind farm and photovoltaic power station connected to half wavelength transmission system is studied by modal analysis method. The effects of transmission line length, the number of groups of wind power and photovoltaic inverters on typical modal harmonic resonance are analyzed. The results show that the length of half wavelength transmission line and outgoing line only affect the low-frequency harmonic resonance of some modes; The length of collector cable has an effect on the harmonic resonance of each typical mode; The number of wind power and photovoltaic inverter groups has an impact on the harmonic resonance of some modes, but will not change the location of resonance.

Improved active damping control strategy and closed-loop parameter design for LCL grid-connected inverter

In this paper, an active damping control strategy based on capacitance and voltage feedback is proposed to solve the resonance problem of three-phase LCL inverter grid-connected system. To solve the problem that the parameters of active damping control strategy are complicated and need to be adjusted repeatedly, a parameter design method is proposed in this paper, which is simple to implement and does not need to be adjusted repeatedly. Finally, the effectiveness of the control strategy and parameter design method is verified by experiments.

Collocation Methods for High-Order Well-Balanced Methods for Systems of Balance Laws

In some previous works, two of the authors introduced a technique to design high-order numerical methods for one-dimensional balance laws that preserve all their stationary solutions. The basis of these methods is a well-balanced reconstruction operator. Moreover, they introduced a procedure to modify any standard reconstruction operator, like MUSCL, ENO, CWENO, etc., in order to be well-balanced. This strategy involves a non-linear problem at every cell at every time step that consists in finding the stationary solution whose average is the given cell value. In a recent paper, a fully well-balanced method is presented where the non-linear problems to be solved in the reconstruction procedure are interpreted as control problems. The goal of this paper is to introduce a new technique to solve these local non-linear problems based on the application of the collocation RK methods. Special care is put to analyze the effects of computing the averages and the source terms using quadrature formulas. A general technique which allows us to deal with resonant problems is also introduced. To check the efficiency of the methods and their well-balance property, they have been applied to a number of tests, ranging from easy academic systems of balance laws consisting of Burgers equation with some non-linear source terms to the shallow water equations—without and with Manning friction—or Euler equations of gas dynamics with gravity effects.

Resonance Avoidance Control Algorithm for Semi-Submersible Floating Offshore Wind Turbine

In this study, a resonance avoidance control algorithm was designed to address the tower resonance problem of a semi-submersible floating offshore wind turbine (FOWT) and the dynamic performance of the wind turbine, floater platform, and mooring lines at two exclusion zone ranges were evaluated. The simulations were performed using Bladed, a commercial software for wind turbine analysis. The length of simulation for the analysis of the dynamic response of the six degrees of freedom (DoF) motion of the floater platform under a specific load case was 3600 s. The simulation results are presented in terms of the time domain, frequency domain, and using statistical analysis. As a result of applying the resonance avoidance control algorithm, when the exclusion zone range was ±0.5 rpm from the resonance rpm, the overall performance of the wind turbine was negatively affected, and when the range was sufficiently wide at ±1 rpm, the mean power was reduced by 0.04%, and the damage equivalent load of the tower base side–side bending moment was reduced by 14.02%. The tower resonance problem of the FOWT caused by practical limitations in design and cost issues can be resolved by changing the torque control algorithm.

"Subsynchronous Resonance Problems in an Integrated Power System".(Dept.E)

"Subsynchronous Resonance Problems in an Integrated Power System".(Dept.E)

A Canonical Transformation to Eliminate Resonant Perturbations. I.

Abstract We study dynamical systems that admit action-angle variables at leading order, which are subject to nearly resonant perturbations. If the frequencies characterizing the unperturbed system are not in resonance, the long-term dynamical evolution may be integrated by orbit-averaging over the high-frequency angles, thereby evolving the orbit-averaged effect of the perturbations. It is well known that such integrators may be constructed via a canonical transformation, which eliminates the high-frequency variables from the orbit-averaged quantities. An example of this algorithm in celestial mechanics is the von Zeipel transformation. However, if the perturbations are inside or close to a resonance, i.e., the frequencies of the unperturbed system are commensurate; these canonical transformations are subject to divergences. We introduce a canonical transformation that eliminates the high-frequency phase variables in the Hamiltonian without encountering divergences. This leads to a well-behaved symplectic integrator. We demonstrate the algorithm through two examples: a resonantly perturbed harmonic oscillator and the gravitational three-body problem in mean motion resonance.

Parameter co-design of active damping loop and grid current controller for a 3-phase LCL-filtered grid-connected inverter

Under non-ideal grid conditions, especially the harmonic grid condition, the proportional resonant controller with multiple harmonic resonant controllers (HR-PR controller) is recommended to provide high quality grid currents for the 3-phase LCL-filtered grid-connected inverter. Besides, in order to solve the resonance problem, the active damping loop with the grid-side currents feedback only is preferred. However, parameters of the HR-PR controller and the active damping loop both affect the performance of LCL filter resonance suppression and stability of the inverter, which is analyzed in this paper. Moreover, the stability constraint and the resonance suppression constraint is derived to maintain the good ability of LCL filter resonance suppression and satisfy the stability requirements of the inverter. Considering the wide control bandwidth for the HR-PR controller, a co-design method of the active damping loop and HR-PR controller is proposed in this paper. By introducing the Lagrange multiplier method, the proposed co-design method obtains the optimized parameters for the active damping loop and grid currents controller in z-domain appropriately. A prototype of 3-phase LCL-filtered three-level neutral point clamped grid-connected inverter is established to validate the proposed method.

Bounded resonant problems driven by fractional Laplacian

In this paper we study the existence of nontrivial solutions for the fractional Laplacian resonance problem with a bounded nonlinearity via Morse theory and a penalization technique.

Resonance Capture for a Mercurian Orbiter in the Vicinity of Sun

In this work, the problem of resonance caused by some gravitational potentials due to Mercury and a third body, namely the Sun, together with some non-gravitational perturbations, specifically coronal mass ejections and solar wind in addition to radiation pressure, are investigated. Some simplifying assumptions without loss of accuracy are employed. The considered force model is constructed. Then the Delaunay canonical set is introduced. The Hamiltonian of the problem is obtained then it is expressed in terms of the Deluanay canonical set. The Hamiltonian is re-ordered to adopt it to the perturbation technique used to solve the problem. The Lie transform method is surveyed. The Hamiltonian is doubly averaged. The resonance capture is investigated. Finally, some numerical simulations are illustrated and are analyzed. Many resonant inclinations are revealed.

Design and Performance Study of Clutch Disc Assembly of Wide-Angle, Large-Hysteresis, Multistage Damper

The clutch is an important component of the vehicle driveline system. One of its major functions is to attenuate or eliminate the torsional vibration and noise of the driveline system caused by the engine. Based on experiments of vibration damping under different vehicle conditions, the structure and functional principle of a clutch-driven disc assembly for a wide-angle, large-hysteresis, multistage damper is investigated in this study using an innovative combined approach. Furthermore, a systematic integration of key technologies, including wide-angle low-stiffness damping technology, large-hysteresis clutch technology, a novel split pre-damping structure technology, damping structure technology for component cushioning, and multistage damping structure technology, is proposed. The results show that the total torsional angle of the wide-angle large-hysteresis, multistage damper is more than twice that of the traditional clutch damper. The multistage damping design allows a better consideration of various damping requirements under different vehicle conditions, which can effectively address problems of severe idle vibrations and torsional resonance that occur under idled and accelerated conditions. Meanwhile, the use of a large-hysteresis structure and wear-resistant materials not only improves the vibration damping performance, but also prolongs the product service life, consequently resulting in multi-faceted optimization and innovative products.

Convergence analysis of a Galerkin boundary element method for electromagnetic resonance problems

In this paper a convergence analysis of a Galerkin boundary element method for resonance problems arising from the time harmonic Maxwell’s equations is presented. The cavity resonance problem with perfect conducting boundary conditions and the scattering resonance problem for impenetrable and penetrable scatterers are treated. The considered boundary integral formulations of the resonance problems are eigenvalue problems for holomorphic Fredholm operator-valued functions, where the occurring operators satisfy a so-called generalized Gårding’s inequality. The convergence of a conforming Galerkin approximation of this kind of eigenvalue problems is in general only guaranteed if the approximation spaces fulfill special requirements. We use recent abstract results for the convergence of the Galerkin approximation of this kind of eigenvalue problems in order to show that two classical boundary element spaces for Maxwell’s equations, the Raviart–Thomas and the Brezzi–Douglas–Marini boundary element spaces, satisfy these requirements. Numerical examples are presented, which confirm the theoretical results.

Research on transmission mechanism of harmonics in cable lines

The high cabled rate of urban power grid aggravates the risk of resonance and harmonic amplification. In addition, the system side of DC receiving end urban power grid contains converter station high-power harmonic sources, while the user side contains other nonlinear user harmonic sources. There are two-way conduction characteristics of harmonics in transmission lines. The problem of resonance and harmonic amplification in distribution network is aggravated by high cable ratio. Therefore, the response of the system side injected harmonic voltage at the end of the line and the potential harmonic amplification problem after the user side injected harmonic current are studied respectively. The influence of key factors (line type, length, load rate and power factor) on harmonic propagation is analyzed. The characteristic harmonic of converter station is not amplified and the most severe condition of amplification is summarized. The harmonic limit of the harmonic injection terminal is also proposed.

Metanalysis of alloplastic materials versus autologous fat for injection augmentation pharyngoplasty treatment of velopharyngeal insufficiency

BackgroundVelopharyngeal insufficiency (VPI) can cause resonance, speech and feeding problems. While reconstructive palatoplasty and surgical pharyngoplasty techniques are the mainstay of treatment for severe VPI, injection augmentation pharyngoplasty offers a minimally invasive approach in patients with mild-to-moderate VPI. MethodsWe conducted a systematic review of the literature available on PubMed and Embase from 1990 to 2019 including studies that addressed VPI, incompetence, or dysfunction managed with injection augmentation. Patient demographics, etiology of VPI, injection material, volume of injection, number of injections, complications and both subjective and objective outcomes were recorded. ResultsTwenty-nine studies met our inclusion criteria encompassing 587 patients, ages 3–75 years (mean = 16) who underwent injection pharyngoplasty. Injection materials included glutaraldehyde cross-linked (GAX) collagen (n = 5), calcium hydroxyapatite (n = 36), dextranomer and hyaluronic acid (n = 72) and autologous fat (n = 471). Follow-up averaged 15.4 months (range = 2–60 months). Functional improvements in nasality were recorded in a large proportion of patients (0.79, 95% CI 0.75 to 0.82). However, a greater proportion of patients in the synthetic materials group demonstrated either reduced or resolved hypernasality compared with those receiving autologous fat injections (χ2 = 7.035, n = 91/103 vs. 255/338, p = 0.008). Complete velopharyngeal gap closure post-injection was achieved at a higher frequency with injection of synthetic materials compared with autologous fat (χ2 = 11.270, n = 61/69 vs. 58/91 p = 0.001).r ConclusionInjection pharyngoplasty offers a minimally invasive alternative intervention for treatment of VPI secondary to small velopharyngeal gaps. Patients treated with synthetic materials experienced a greater improvement in velopharyngeal closure and a corresponding improvement in resonance balance.

Harmonic Mitigation Using Passive Harmonic Filters: Case Study in a Steel Mill Power System

In this study, we mitigated the harmonic voltage in a power system that contained the roughing mill (RM) and finishing mill (FM) motor drives. AC/DC converter type RM drive is a non-linear, large-capacity varying load that adversely affects power quality, e.g., a flicker, voltage distortion, etc. The voltage drop can be compensated within a certain limit by using the proper capacity of a power capacitor bank. In addition, the voltage distortion can be controlled as per the guidelines of IEEE Std. 519 using the passive harmonic filter corresponding to the characteristic harmonics of the motor drive load. The passive harmonic filter can provide an economical solution by mitigating the harmonic distortion with a proper reactive power supply. However, at the planning level, attention should be paid to avoid system overvoltage that is caused by the leading power under light load conditions and also the problem of parallel resonance between the harmonic filter and the step-down transformer. In addition, when designing the filter reactor, the K-factor and peak voltage must be considered; the filter capacitor also requires a dielectric material that considers the harmonic peak voltage. The purpose of this study was to acquire a better understanding of the filter applications as well as verify the field measurement, analysis, and design of harmonic filters together with its performance.

Nasalance Scores for Normal Persian-Speaking Girls

Background: Obtaining normative nasalance scores is essential in the process of assessing and treating resonance disorders. The purpose of this study was to obtain nasalance scores in Persian-speaking girls aged 4-6 years and investigate the age-related differences. Materials and Methods: All participants (n=40) were screened to identify any overt problems relating to resonance, hearing, voice quality, or speech and language skills. The mean nasalance scores were obtained from normal-speaking girls during the repetition of the Persian version of the Simplified Nasometric Assessment Procedures (SNAP) test subtests. The Nasometer II (model 6450) was used to obtain the nasalance scores. Results: The mean nasalance score for the SNAP test subtests was obtained. Group mean and standard deviation (SD) nasalance scores of girls for oral and nasal sentences were 12.59±3.74 and 50.52±6.39, respectively. There was no significant difference between age groups (4, 5 and 6 years old) (P<0.05). Conclusion: Our results provided normative nasalance scores based on the SNAP test that can be used for the evaluation and treatment of resonance problems in Persian-speaking girls.