26 results about "Angular frequency" patented technology

The embodiment of the invention discloses a harmonic compensation method for an angle error of a magnetic encoder, and the method comprises the steps: enabling the magnetic encoder to rotate at a constant speed in a setting mode, collecting sine and cosine signals outputted by the magnetic encoder, and carrying out the calculation through CORDIC, thereby obtaining an initial angle sequence containing a fundamental wave error and a harmonic wave error; extracting each harmonic component through an adaptive wave trap, constructing a harmonic compensation polynomial, and storing each coefficient; in an application mode, a magnetic encoder signal is collected in real time, a current initial angle value is solved, a harmonic compensation amount is calculated according to a current fundamental wave angular frequency and a stored coefficient, and an accurate angle value is obtained by subtracting the compensation amount from the initial angle value. According to the method, external reference signals and a large amount of storage space are not needed, each harmonic error is directly eliminated through a harmonic compensation polynomial, and approximate errors caused by traditional linear interpolation are avoided; and the compensation precision can be improved only by increasing polynomial terms, and the storage requirement is not obviously increased.

The invention discloses a network construction type energy storage parameter adaptive control method for improving transient stability. The method comprises the following steps: determining a rated angular frequency of a network construction type energy storage system, measuring a current operation angular frequency, and calculating an angular frequency deviation and an angular frequency change rate; the VSG output active power is measured, and the active power deviation is calculated in combination with the mechanical power instruction value; dividing a system oscillation period into four oscillation intervals; calculating a damping coefficient reference value and a rotational inertia reference value by using the maximum mechanical torque of the VSG system, the maximum angular frequency offset allowed by the system and the maximum active power output by the system; calculating real-time rotational inertia and a damping coefficient according to the oscillation interval in combination with the adjustment coefficient; and the rotational inertia and the damping coefficient controlled by the VSG are adjusted. According to the method, the defect that transient stability and dynamic response are difficult to consider by fixed parameters in traditional virtual synchronous generator control is overcome, the frequency overshoot is remarkably reduced, and the recovery time is shortened.

The invention discloses an electric energy metering method and device based on harmonic self-adaptive observation and zero point tracking type SOGI-FLL. The electric energy metering method comprises the following steps: step 1, carrying out ADC sampling on voltage and current signals of a power grid; 2, performing frequency rapid estimation on the voltage signal based on a zero point tracking frequency-locked loop, and obtaining a fundamental wave angular frequency of a power grid in real time; step 3, constructing adaptive observers of voltage and current by using the fundamental wave angular frequency, and estimating parameters of fundamental waves, harmonic waves and direct current components in voltage and current signals in real time through an adaptive law based on Lyapunov stability; 4, according to the parameter estimation value, the amplitude and phase of the voltage and current are calculated; and step 5, calculating active power and reactive power of each harmonic based on the voltage and current amplitudes and phases obtained in the step 4, and summing to obtain total active power and total reactive power so as to realize metering of active electric energy and reactive electric energy. According to the invention, rapid and accurate metering of fundamental wave and harmonic wave electric energy under complex working conditions is realized.

The present application relates to the technical field of marine winch metering and control in marine operation equipment, and discloses a compensation method for dynamic error of marine winch metering. By synchronously sampling the angular displacement and the acceleration along the rope direction, the rope length sequence is converted to obtain the rope length vector and the acceleration vector in the window; the discrete angular frequency is set according to the sampling point and the period, the sine cosine base function is generated to form the harmonic orthogonal base, and the rope length sequence is projected and reconstructed to obtain the harmonic component of each frequency; the power spectrum analysis is performed on the acceleration sequence, the dominant frequency of vibration is identified according to the power spectrum, and the upper limit of high-frequency disturbance is determined, and the harmonic component is accumulated in the frequency not higher than the upper limit to obtain the low-frequency trend rope length sequence; the rope length is first reduced by the low-frequency trend value and then reduced by the high-frequency error component to form the error vector and the compensated rope length sequence, the double compensation of the winch metering error is realized, the rope length change and the vibration disturbance are separated under the time-frequency structure, and the metering precision and the real-time performance are improved.

The application discloses a laser radar correction method and device based on an angular frequency field, a storage medium and electronic equipment, and the method comprises the following steps: controlling a laser radar to emit sinusoidal modulation light to irradiate a whiteboard, acquiring four-phase original intensity data and displacement increment values; reconstructing a phase sequence for each pixel and estimating an angular frequency, and forming an angular frequency distribution of a full field of view; establishing an analytical coupling model of the angular frequency and a rotation matrix according to the distribution, an internal parameter matrix and a whiteboard normal vector, solving a rotation matrix estimation value by using a least square method, and combining an initial normal distance to calculate a translation vector estimation value; calculating real distances of each pixel to a whiteboard point according to the rotation and translation estimation values, recalibrating phase zero point offset and fixed mode phase noise, and generating a correction lookup table; and outputting the rotation, translation parameters and the lookup table. According to the application, a pattern target is not needed, and only a whiteboard and a guide rail are used to restore external parameters, system errors introduced by tilting are reduced, and the ranging and point cloud reconstruction precision are improved.

The invention relates to the technical field of wave making, in particular to a wave making method based on an underwater flat plate longitudinal pushing type wave maker. Wave surface equations of different wave surface positions are constructed according to the obtained geometric parameters of the wave maker and the motion parameters of the underwater flat plate; according to the input target wave parameter, determining the wave number of the target wave and the underwater flat plate amplitude required for generating the target wave; if the target wave is a regular wave, controlling an underwater flat plate to longitudinally move according to a simple harmonic motion rule according to the flat plate amplitude; and if the target wave is an irregular wave containing N angular frequency components, introducing a random phase, and driving the underwater flat plate to perform multi-frequency synthetic vibration according to the flat plate amplitude corresponding to each angular frequency component. According to the method, the wave surface equation of vertical movement of the two-dimensional underwater flat plate structure is derived based on the potential flow theory, and the transfer function is obtained by using the equation, so that accurate generation of regular waves and irregular waves can be realized through the underwater flat plate.

The application provides a flow field reconstruction and deduction method based on K-A theorem, and belongs to the technical field of ship hydrodynamics. First, multi-dimensional data such as the direction, amplitude, period, frequency and flow velocity of irregular waves are collected and integrated into high-dimensional wave vectors. Then, the KAN network with B-spline curve as a learnable function is used to map the high-dimensional input into a low-dimensional parameter list, obtain the amplitude, angular frequency and initial phase of the dominant equivalent regular wave, calculate the decoupling target function by constructing an equivalent wave superposition model, compare the decoupling target function with the true value to obtain a loss function, and then optimize the network parameters by backward propagation until convergence. Finally, based on the network output parameters, a wave superposition model is constructed to represent the real wave in the form of a series of interpretable regular waves superimposed in time sequence, so that efficient and accurate flow field reconstruction and deduction are realized.

The invention discloses a joint inversion three-dimensional quality factor method, which comprises the following steps of: acquiring average attenuation travel time through an initial three-dimensional quality factor (Q value) and an average attenuation travel time formula, and acquiring a theoretical frequency spectrum amplitude at the frequency by combining a plurality of initial values including corner frequency, field effect, low-frequency amplitude and frequency and an amplitude formula; converting the displacement frequency spectrum amplitude in the frequency domain into an observation frequency spectrum amplitude in a natural logarithm domain, and obtaining a residual vector formula in combination with a theoretical frequency spectrum amplitude; a formula obtained after meshing of the seismic wave three-dimensional propagation speed and the initial Q value in the average attenuation travel time formula is substituted into a residual vector formula, smooth constraint and damping parameters are added to obtain a new residual vector formula, and the new residual vector formula is solved to obtain a value of a parameter disturbance quantity; superposing the values to the plurality of initial values to obtain a plurality of new initial values of the next round of iteration; and substituting the initial three-dimensional Q value back to a residual vector formula to obtain a residual vector, and taking the new initial three-dimensional Q value as a target three-dimensional Q value when a difference value between the residual vector and the amplitude meets a condition.

The invention relates to an angular sensor comprising: a resonator (2) capable of supporting a radial mode of vibration with respect to an axis of symmetry of the resonator (2); transducers (5.1, 5.2, 6.1, 6.2) for delivering a first measurement signal and a second measurement signal concerning a deformation of the resonator (2) in a first direction and a second direction, respectively, said directions being orthogonal to one another in a reference frame of the mode of vibration, and for applying a force to the resonator (2) in these two orthogonal directions; and an electronic processing circuit (7) electrically connected to the transducers (5, 6) and designed to determine, on the basis of the measurement signals, an estimate (Formula) of an angular speed applied to the angular sensor and to output control signals for the transducers (6.1, 6.2) in order to generate and keep a vibration of the resonator (2) at a frequency corresponding substantially to a theoretical natural angular frequency ω0 and with a substantially constant amplitude a and a substantially zero quadrature component q, by processing an amplitude servo-control error X p — a 0 where X p is an amplitude servo-controlled to an amplitude setpoint a 0 , a quadrature servo-control error Y q , an angle estimation error Y p and a phase estimation error X q , characterized in that the electronic processing circuit (7) is designed to carry out compensation that makes the errors insensitive to a variable angular speed of the sensor taking into account the theoretical natural angular frequency ω0 and the estimate of the angle of the angular sensor.

The invention discloses a method, device and equipment for determining an earthquake reflection coefficient, a medium and a product. The method comprises the following steps: acquiring an actually measured seismic record, and determining an original amplitude spectrum corresponding to a target frequency band from the actually measured seismic record; the target frequency band comprises a plurality of angular frequencies; determining at least two main frequencies based on the target frequency band; determining a frequency division recording amplitude spectrum corresponding to the main frequency based on the plurality of angular frequencies, the main frequency and a preset frequency band width, and determining a wavelet amplitude spectrum corresponding to the main frequency based on the plurality of angular frequencies and the main frequency; and based on the original amplitude spectrum, the frequency division record amplitude spectrum corresponding to each main frequency and the wavelet amplitude spectrum, determining a seismic reflection coefficient corresponding to the actually measured seismic record. The problem that in the prior art, seismic wavelets are extracted from seismic records, and the seismic reflection coefficient is reversely deduced through an inversion method, so that the accuracy of determining the seismic reflection coefficient is poor is solved, and the effect of improving the accuracy of determining the seismic reflection coefficient is achieved.

This invention discloses a wave generation control method and apparatus for wave generators deployed at both ends in a wave testing tank. First, the target positions and target angular frequencies of two wave trains are determined based on the target function, which can be wave attenuation, bidirectional wave generation, or focused wave generation. Then, the propagation times of the two wave trains are calculated respectively. Based on the propagation times, the target activation time of the corresponding wave generator is determined. Finally, the corresponding wave generator is activated at the target activation time, generating the corresponding waves based on the target wave height and target angular frequency. In this invention, each end of the wave generators deployed at both ends can independently control wave generation at each end. Based on the synergistic effect of the wave generators deployed at both ends, wave propagation and superposition are controlled, accurately generating focused waves and simulating the effect of concentrated waves on marine structures.

The geosynchronous orbit debris inclination vector evolution calculation method disclosed by the application comprises the following steps: firstly, calculating the influence of the J2 term of the earth's non-spherical perturbation on the change rate of the inclination debris, calculating the angular frequency of the geosynchronous orbit debris inclination vector, the period of the precession and the angular rate of the precession under the influence of the J2 term; then, calculating the frequency of the geosynchronous orbit debris inclination vector precession, the period of the precession and the angular rate of the precession caused by the sun's gravity and the moon's gravity respectively; finally, synthesizing and calculating the different angular frequencies, the periods of the inverse precession and the angular rates of the precession. The geosynchronous orbit debris inclination vector evolution calculation method disclosed by the application separately calculates the effects of the J2 term of the earth and the sun and the moon, and compared with the traditional geosynchronous orbit debris inclination vector evolution calculation method which adopts complete numerical calculation, the method has the advantages of fast calculation speed and can be used for the analysis and calculation of the long-term evolution of the geosynchronous orbit debris orbit.

The application discloses a method for exciting polarization medium transient electromagnetic forward fast selection of central frequency, and belongs to the technical field of geophysical prospecting, and comprises the following steps: firstly, determining three-dimensional forward time step iteration parameters and a central frequency range, and constructing a Cole-Cole model; then, sequentially performing Padé series approximation on the discrete central frequency vector and the angular frequency vector at each frequency point to obtain an expansion format of each frequency point; respectively calculating time domain pulse responses of the expansion format and the Cole-Cole model and relative errors thereof, obtaining a two-dimensional distribution of the relative errors, expanding the Cole-Cole model by using the Padé series approximation method, and starting three-dimensional forward calculation of the Cole-Cole model with the exciting polarization effect. The application can provide a fast central frequency selection method for developing three-dimensional forward calculation of transient electromagnetic waves in the underground polarized medium, and is the basis of geophysical transient electromagnetic prospecting.

A method for measuring low-frequency angle dynamic characteristics of an inertial measurement combination based on a three-axis turntable comprises the following steps: mounting the inertial measurement combination on the three-axis turntable, rotating the inertial measurement combination, and sampling angular position information of the three-axis turntable and pulse output of the inertial measurement combination at a certain frequency; performing difference calculation on the pulse output of the inertial measurement combination obtained by sampling in each direction to obtain a pulse difference after the common-mode error is eliminated; calculating the triaxial angular position of the inertial measurement combination based on the pulse difference after the common-mode error is eliminated; fourier transform is carried out on the angular position information of the three-axis turntable and the three-axis angular position of the inertial measurement combination to obtain an amplitude spectrum and a phase spectrum of the three-axis turntable and the inertial measurement combination, and an angular frequency is calculated based on the maximum value in the amplitude spectrum of the angular position of the three-axis turntable and the serial number of the maximum value in the amplitude spectrum; meanwhile, the gain and the phase difference of the inertial measurement combination relative to the maximum value in the amplitude spectrum of the angular position of the three-axis turntable are calculated.

The invention discloses a navigation ship motion parameter extraction method based on wave height time sequence data. Two measuring points are arranged on the same side of a ship navigation main channel by adopting a wave height sensor; the method comprises the following steps: acquiring ship traveling wave time-wave height data in a channel by using double measuring points, and constructing a basic signal set; performing frequency spectrum domain conversion and purification processing on the basic signal set by combining short-time Fourier transform with noise threshold filtering to obtain an effective wave system frequency spectrum matrix; angular frequencies of two measuring points are extracted by adopting a dynamic window peak value detection method in combination with linear fitting aiming at transverse waves, and slopes of the two measuring points are extracted by frequency spectrum matrix binaryzation and improved Hough transform aiming at scattered waves; the ship navigational speed is inverted based on the angular frequency, the vertical distance between the ship and the measuring point is deduced in combination with the scattered wave slope, the navigational direction angle is deduced according to double-measuring-point geometric analysis, the navigational speed, the ship position and the course angle parameters are output, and navigational ship dynamic monitoring without active signal dependence is achieved. According to the invention, high-precision and high-reliability ship dynamic monitoring in a complex scene is realized.

The invention belongs to the technical field of rotary transformer signal processing, and particularly relates to a rotary transformer envelope signal correction decoding method and system, and the method comprises the steps: demodulating an output signal of a rotary transformer through frequency shift, and obtaining a sine envelope signal and a cosine envelope signal; the method comprises the following steps: collecting a sine envelope signal and a cosine envelope signal based on a preset sampling frequency, carrying out offline parameter estimation, firstly estimating an envelope angular frequency estimation value of the envelope signal, and then estimating an amplitude estimation value, a phase offset estimation value and a direct current offset estimation value of the envelope signal by using the envelope angular frequency estimation value; a sine envelope signal and a cosine envelope signal are collected, and online non-ideal envelope signal correction and angular position decoding are carried out. According to the method and the system for correcting and decoding the envelope signal of the rotary transformer, the influence of a harmonic term in the envelope signal is fully considered by adopting an angular frequency off-line estimation method based on a self-adaptive notch filter and system identification.

The invention relates to a damping characteristic evaluation method, device and system of a power system, and relates to the technical field of power systems. The method comprises the steps of obtaining power data and angular frequency data of a generator set in a preset time period, generating a first variable quantity curve according to the power data, determining first characteristic information of the first variable quantity curve, generating a second variable quantity curve according to the angular frequency data, and determining second characteristic information of the second variable quantity curve, determining a power variable quantity matrix according to the first characteristic information, determining an angular frequency variable quantity matrix according to the second characteristic information, determining an equivalent admittance coefficient according to the power variable quantity matrix and the angular frequency variable quantity matrix, and evaluating the damping characteristic of the generator set by using the equivalent admittance coefficient to obtain an evaluation result. According to the scheme, the accuracy of evaluating the damping characteristics is improved.

The invention relates to a seismic wave forward modeling method and device based on a viscoelastic medium and electronic equipment. The method comprises the following steps: acquiring viscoelastic medium parameters of a stratum to construct a viscoelastic wave fluctuation equation; acquiring a wave equation based on a viscoelastic wave wave equation, and constructing a second-order Green displacement tensor based on the viscoelastic medium density, the angular frequency and a Green function of a scalar wave equation; the method comprises the following steps: acquiring a first coefficient expression of a second-order green displacement tensor based on a geometric model of a viscoelastic medium, introducing a frequency-dependent complex velocity, constructing a green function based on the complex velocity, and acquiring a first solving subitem based on the green function and the first coefficient expression; based on Hooke's law and the first solving subitem, obtaining a second solving subitem; obtaining a frequency domain viscoelastic medium boundary integral equation on the basis of the first solving subitem and the second solving subitem; and performing discrete solution on the frequency domain viscoelastic medium boundary integral equation to obtain the displacement and stress of the seismic wave in the propagation process. And calculation errors can be reduced.

The invention provides a flow field reconstruction and deduction method based on the K-A theorem.The method belongs to the technical field of ship hydrodynamics, and comprises the steps that firstly, multi-dimensional data such as the direction, the amplitude, the period, the frequency and the flow speed of irregular waves are collected and integrated into a high-dimensional wave vector, and then a KAN with a B spline curve as a learnable function is used for obtaining a high-dimensional wave vector; high-dimensional input is mapped into a low-dimensional parameter list, the amplitude, the angular frequency and the initial phase of dominant equivalent regular waves are obtained, a loss function is obtained by constructing an equivalent wave superposition model, calculating a decoupling objective function and comparing the decoupling objective function with a true value, then network parameters are optimized through back propagation until convergence, and finally, the optimal network parameters are obtained. A wave superposition model is constructed based on network output parameters, real waves are represented in the form that a series of interpretable regular waves are superposed on a time sequence, and efficient and accurate flow field reconstruction and deduction are achieved.

The invention relates to the field of power electronic control, and discloses a virtual synchronous generator parameter adaptive control method and a medium, and the method comprises the steps: calculating the active power and reactive power outputted by a VSG; establishing a small signal model based on the VSG, obtaining a function relationship between the damping ratio and the natural angular frequency of the VSG and the rotational inertia and the damping coefficient, and determining value boundaries of the rotational inertia and the damping coefficient; a meta-heuristic optimization algorithm is adopted to carry out optimization in the value boundary to solve the reference rotational inertia and the reference damping coefficient of the output system under the steady-state working condition; setting an angular velocity change rate threshold value and an angular velocity variation threshold value; monitoring the angular velocity change rate and the angular velocity change quantity of the system in real time; when the angular velocity change rate or the angular velocity variable quantity exceeds a corresponding threshold value, obtaining a final rotational inertia and a final damping coefficient according to a preset self-adaptive control rule; and generating a voltage reference signal of the VSG based on the final rotational inertia and the damping coefficient. According to the invention, the problem of slow convergence of adaptive control is avoided.

Systems and methods include a method for determining wave propagation speed. Spatio-temporally-sampled data for electromagnetic (EM) wave propagation through a fluid in a conduit is acquired for different instants of time from each antenna of an array of antennas distributed at predetermined locations. A k-ω plot plotting curves having a kinematic relationship ω=ck is generated based on the spatio-temporally-sampled data and using a spectral-based algorithm, where ω is an angular frequency of a spectral component of EM disturbances, k is a wavenumber, and c is an unknown speed of the EM wave propagation. A spectral ridge on the curves is identified using the k-ω plot. Parameters for calculating a slope of the spectral ridge are determined. The slope of the spectral ridge is determined. The speed of EM wave propagation is determined assuming a relation between the speed of EM wave propagation and the slope of the spectral ridge.

The invention discloses a hemispherical resonator gyroscope angular rate error online compensation method based on a frequency modulation technology, and belongs to the field of hemispherical resonator gyroscope control. The problems that a traditional angular rate online error compensation method is low in damping non-uniform error recognition accuracy and poor in compensation effect are solved. According to the invention, through systematic closed-loop processes of preparation, modulation, demodulation, identification and compensation, dynamic real-time correction of angular rate errors caused by inherent defects such as uneven damping in the hemispherical resonator gyroscope is realized. The method specifically comprises the following steps: extracting angular frequency information of backward and forward rotation traveling waves by using a frequency modulation technology, and updating the inverse of an error coefficient vector and a covariance matrix in each modulation period through an online recursive identification algorithm, so as to accurately calculate a damping non-uniform error of the current period and carry out immediate compensation. The method is mainly used for accurately identifying the angular rate of the hemispherical resonator gyroscope.

The invention relates to the technical field of anti-overturning safety monitoring, and discloses an anti-overturning safety monitoring system for a derrick rotary supporting mechanism, which realizes real-time monitoring of the operating state of a derrick by collecting attitude parameters, load parameters, motion parameters and environmental wind parameters and inputting nominal anti-overturning rigidity and overturning moment limit. Calculating an external upsetting moment, a peak value and a time change rate according to load, motion and wind power information; the equivalent time delay and the right half plane zero point corresponding angular frequency are obtained through frequency domain identification, the beat frequency is calculated in combination with the working condition parameters, the wind speed signals are subjected to spectral analysis to determine the representative frequency of the gust main energy region, and the frequency band coincidence index is obtained through comparison. And solving an equivalent moment gap according to the equivalent time delay, the structural parameters and the external upsetting moment change rate, correcting an external upsetting moment peak value to obtain a corrected peak value, and performing safety judgment according to the corrected peak value, the upsetting moment limit and the frequency band coincidence index.

The invention provides a three-dimensional sound source positioning imaging method, device and equipment based on a two-dimensional convex array and a medium, and the method comprises the steps: obtaining a time domain signal p (r, phi, y, t) passively received by a two-dimensional convex array ultrasonic transducer in a sound velocity non-uniform medium, the array elements of the two-dimensional convex array ultrasonic transducer are distributed on a cylindrical surface, and a cylindrical coordinate reference system is (r, phi, y, t); r is the extrapolation radius of the probe of the two-dimensional convex array ultrasonic transducer, and R is the distribution surface where the array elements of the convex array ultrasonic transducer are located; according to the time domain signal p (r, phi, y, t), determining the sound velocity distribution of a propagation medium, and generating an aligned sound velocity diagram to determine the slowness u (r, phi, y) of the medium; the time domain signal p (r, phi, y, t) is converted in the time t, the circumferential direction phi and the longitudinal direction y, a spiral wave spectrum Pn (r, ky, omega) is generated, omega represents the time angular frequency, n is the circumferential wavelength, and ky is the longitudinal wavelength; and according to the spiral wave spectrum Pn (r, ky, omega) and the medium slowness u (r, phi, y), determining a frequency domain sound field of a next layer, and according to the frequency domain sound field, generating a passive sound image I (r, phi, y). The scheme can accurately position the sound source.

The invention provides a sub-hyper-synchronous oscillation detection method and system based on a tunable wave trap, and a medium, and the method comprises the steps: enabling a DC digital filter to be in cascade connection with the tunable digital wave trap, and obtaining a single-frequency oscillation signal detector; constructing an energy function based on the oscillation signal to be detected and the output of the single-frequency oscillation signal detector by taking the notch angular frequency of the tunable notch filter as an independent variable; and adopting a gradient descent method, carrying out iterative updating on the negative gradient direction of the independent variable along the energy function at a fixed step length, and searching the minimum value of the energy function: when the gradient of the energy function to the independent variable is zero, determining the corresponding angular frequency as the angular frequency of the oscillation signal to be measured. The implementation process is simple and easy to implement, the calculated amount is small, implementation is easy, and real-time accurate detection of the sub-hyper-synchronous oscillation signal can be achieved.

Techniques for determining a damping rate of unforced oscillations of a meniscus are disclosed. An example method includes receiving input describing a shape of a container, physical parameters of a liquid inside the container, and an equilibrium shape of the meniscus. The method also includes generating a mesh conforming to the shape of the container and generating a discrete version of a continuous eigenvalue problem based on this mesh. The method also includes computing, at appropriate mesh nodes, values for pressure, velocity components, and meniscus surface deformation corresponding to a suitable number of least-damped late-time oscillation modes of the liquid and computing an angular frequency and damping rate of these least-damped late-time oscillation modes from the discrete version of the continuous eigenvalue problem. The method also includes identifying the mode that has the lowest damping rate and computing a liquid relaxation time by inverting the damping rate of the identified mode.