Pitch Excitation Research Articles

Nonlinear Vibration of Multi-Surface Liquid in a Rectangular Tank Subjected to Pitching Excitation

The nonlinear characteristics of multi-surface liquid motion in a rectangular tank are investigated. The rectangular tank is divided into two parts by the partition, which is perpendicular to the bottom of the tank and does not reach the bottom. The nonlinearity of the liquid surface oscillation is considered in the response analysis of the sloshing motion. The nonlinear ordinary differential equations governing the liquid surface oscillation are derived. The time histories of the liquid surface displacement are calculated to the harmonic pitching excitations. An experiment was conducted using a model tank. A fairly good agreement was found between the theoretical and experimental results. It is shown that the nonlinear analysis is important for estimating the sloshing phenomena.

Nonlinear Liquid Oscillation in an Annular Cylindrical Tank Subjected to Pitching Excitation.

Nonlinear liquid motion in a partially filled annular cylindrical tank, in response to a pitching excitation, is investigated. The nonlinearity of the liquid surface oscillation is considered in the response analysis of the sloshing motion. Basic equations are derived by employing the variational principle. The nonlinear ordinary differential equations governing the liquid surface oscillation are then derived by applying Galerkin's method to the basic equations. The effects of the ratio of inner radius to outer one on liquid surface oscillation are discussed. The time histories of the liquid surface displacement are calculated to the harmonic pitching excitations. An experiment was conducted using a model tank. A good agreement was found between the theoretical and experimental results. It is shown that the nonlinear analysis is important for estimating the sloshing responses.

The Nonlinear Sloshing of Liquid in Tank With Pitching

In this paper, a method used to analyze the sloshing of liquid in a tank subjected to forced pitching and (or) yawing oscillation is presented. First, a variational principle for a liquid in a container under pitching and (or) yawing oscillation is proposed. Based on the preceding variational principle and new Lagrangian, the nonlinear sloshing of liquid in a circle cylindrical tank under pitching excitation is studied analytically for the first time.

Cross-spectral methods with applications to speech processing

Cross-spectral methods were first presented in the mid-1980’s as a method for accurately estimating stable parameters such as modem baud rate and carrier frequencies. The stability of these signal parameters makes it possible to integrate large amounts of data to accurately estimate parameters even under degraded conditions. Since biological signals, such as speech, are not stationary, classical analysis methods, including normal cross-spectral methods, are poorly suited to the problem. Presented here are methods which take advantage of the structure of speech and the phase properties of the Fourier transform. They are based on the cross-spectral methods of the 80’s, but have the advantage that these newer methods provide good accuracy and resolution for nonstationary signals such as speech. In addition, they provide a simple method for taking advantage of signal structure, such as the harmonic properties of speech, which results from the quasi-periodic pitch excitation. Specific problems addressed are accurate pitch and formant estimation, and problems such as blind recovery of carrier frequencies for single side band AM radio transmissions.

ピッチング励振を受ける直方体容器内液面のパラメトリック振動

Three-dimensional nonlinear liquid motion in a rigid rectangular tank partially filled with liquid, in response to pitching excitation, is investigated. In the case that symmetric modes are dominant, the nonlinear ordinary differential equations governing the liquid surface oscillation are derived by applying Galerkin's method to the basic equations. It is confirmed that vertical excitation causes parametric excitation. In addition, it is noted that pitching excitation also causes parametric excitation when the pitching axis does not intersect the vertical line passing the center of the tank bottom. An experiment was conducted using a model tank. Good agreement was found between the theoretical and experimental results.

Generation of wideband speech from bandlimited speech by use of an autocorrelation function

A high quality of speech sound is requested in speech communication circuits. This requirement, however, is not satisfied in telephone and mobile communication circuits. This paper proposes a new method to generate a lower speech signal from bandlimited speech (300–3400 Hz). A short-time autocorrelation function (ACF) is calculated on a speech waveform where the amplitude is compressed with a square root. A period is determined from the ACF. The period of the ACF is employed as an output signal. This signal is low-pass filtered and added to the original bandlimited signal. On the other hand, the higher band signal is synthesized by a pitch excitation formant synthesizer with fixed formant frequencies. The synthesized signal is filtered with BPF (3.4–7 kHz) and added to the original. Those processes are repeated with every pitch period. Short sentences uttered by two males and two females are assessed with a preference test. Synthesized speech is compared with bandlimited natural speech where the lowest frequency is varied between 0 and 300 Hz. The hearing test reveals that the proposed method provides a speech signal that is equivalent to the bandlimited signal where the limit of low frequency is 100–200 Hz.

Pitching Response of an Anchored Viscous Liquid Bridge to Bottom and/or Top Disc Excitation

AbstractThe response of an anchored viscous liquid bridge to different pitching top and/or bottom excitation has been determined. The pressure, the velocity distribution and free surface displacement are obtained for synchronous, counter‐excited and one‐sided pitching excitation as a function of the dimensionless forcing frequency Ωa2/v. The contactlines at the rim of the upper and lower discs are considered to be anchored there. In synchronous pitching excitation only the even resonances show response peaks, while in a counter‐excited system only odd resonances appear, which is in contrast to axial excitation modes. For one‐sided excitation all resonances appear.

Digital speech coder having optimized signal energy parameters

A speech coder and decoder methodology wherein pitch excitation and codebook excitation source energies (100) are represented by parameters that are readily transmissible with minimal transmission capacity requirements. The parameters are the long term energy value, a short term correction factor which is applied to the long term energy value to match the short term energy, and proportionality factor(s) that specify the relative energy contribution of the excitation sources to the short term energy value (101).

Three-Dimensional Sloshing Analysis in a Rectangular Tank Subjected to Pitching Excitation.

Three-dimensional nonlinear liquid motion in a rigid rectangular tank partially filled with liquid, in response to pitching excitation, is investigated. The nonlinear ordinary differential equations governing the liquid surface oscillation are derived by applying Galerkin's method to basic equations. The fundamental modes in two horizontal directions of the tank are considered dominant in the admissible functions that are assumed to be represented by combining the modal functions obtained by the linearization analysis. The nonlinear coupling characteristics of two dominant modes are discussed. Calculations are presented for the time histories of the liquid surface displacement to the harmonic pitching excitation. It is shown that the three-dimensional nonlinear analysis is important for estimating the sloshing responses in a rectangular tank when the aspect ratio of the tank is an integer.

A helical microwave antenna for welding plaque during balloon angioplasty

A catheter-based microwave helix antenna has been developed in an attempt to improve the long-term success of balloon angioplasty treatment of arteriosclerosis. When the balloon is inflated to widen vessels obstructed with plaque, microwave power is deposited in the plaque, heating it, and thereby fixing it in place. By optimizing the helix pitch angle and excitation frequency, the antenna radiation pattern can be adjusted to deposit microwave power preferentially in the plaque while avoiding overheating the healthy artery. The optimal power deposition patterns of helical antennas are analytically computed for four-layered concentric and four-layered nonconcentric cylindrical geometries, which model symmetric and asymmetric occluded arteries. Experiments were performed on occluded artery phantom models with a prototype antenna for both symmetric and asymmetric models, which matched the theoretical predictions well, indicating almost complete power absorption in the low-water-content simulated plaque.

Anchored edge pitching response of a spinning frictionless liquid column due to bottom and/or top excitation

The response of an anchored spinning frictionless liquid bridge to different pitching top and/or bottom excitation has been determined. The free surface displacement is obtained for synchronous, counter-excited and one-sided pitching excitation as a function of the dimensionless forcing frequency\(\bar \Omega = \Omega /\sqrt {\sigma /(\varrho \alpha ^3 )}\). The contactlines at the rim of the upper and lower discs are considered to be anchored. In synchronous pitching excitation only the even resonances show response peaks, while in a counter-excited system only odd resonances appear, which is in contrast to axial excitation modes. For one-sided excitation, all reasonances appear. Because of the different natural frequencies in direction of spin and opposite to it double peaks are present in the responses.

Wear-toll quality 4.8 kbps speech codec

A speech codec operating at low data rates uses an iterative method to jointly optimize pitch and gain parameter sets. A 26-bit spectrum filter coding scheme may be used, involving successive subtractions and quantizations. The codec may preferably use a decomposed multipulse excitation model, wherein the multipulse vectors used as the excitation signal are decomposed into position and amplitude codewords. Multipulse vectors are coded by comparing each vector to a reference multipulse vector and quantizing the resulting difference vector. An expanded multipulse excitation codebook and associated fast search method, optionally with a dynamically-weighted distortion measure, allow selection of the best excitation vector without memory or computational overload. In a dynamic bit allocation technique, the number of bits allocated to the pitch and excitation signals depend on whether the signals are "significant" or "insignificant". Silence/speech detection is based on an average signal energy over an interval and a minimum average energy over a predetermined number of intervals. Adaptive post-filter and the automatic gain control schemes are also provided. Interpolation is used for spectrum filter smoothing, and an algorithm is provided for ensuring stability of the spectrum filter. Specially designed scalar quantizers are provided for the pitch gain and excitation gain.

Response of an anchored frictionless liquid bridge to pitching bottom and/or top excitation

The natural frequencies and response of a circular cylindrical liquid bridge consisting of incompressible and non-viscous liquid has been determined. Three cases of pitching excitations have been treated: synchronous- and counter-excitation of the end discs, as well as the pitching excitation of only one end disc. The contact lines were considered to be anchored at the end discs.

8 kbit/s short and medium delay speech codecs based on CELP coding

AbstractThis paper discusses two speech‐coding algorithms at around 8 kbit/s. These algorithms both use pre‐selection in the codebook search and training for the conjugate structured random codebook. One has short‐delay time that can dispense with echo‐control equipment. This algorithm is robust against channel errors by using LPC analysis separated from pitch excitation, although LPC parameters are derived from the locally decoded signal. The other algorithm has medium‐delay time and meets all the requirements of the ITU‐T (formerly CCITT) 8 kbit/s speech coding standard. The performance of these codecs is evaluated using signal to noise ratio (SNR), pair comparison tests with a modulated noise reference unit (MNRU), and Mean Opinion Score (MOS). The major applications of these codecs are personal handy phone systems and FPLMTS.

Measurement Around a Rotor Blade Excited in Pitch, Part 1: Dynamic Inflow

This is the first of two papers describing experiments on a two-bladed rotor in hover, under controlled pitch excitation. Measurements of the inflow to the rotor are described, first under steady conditions, and then under prescribed 4-per-rev pitch excitation. The high data rates, data acquisition techniques and data quality required for this experiment are demonstrated, including 4-per-rev velocity variations due to 1-degree pitch oscillation, extracted over a single period of rotor revolution at 600rpm. The steady case results agree with lifting-line-based analytical predictions except in the tip region, as expected. The excited-blade case shows the 4-per rev velocity perturbation, and the dependence on the phase of the excitation. Spectral analysis of the LDV data shows multiple harmonics of the excitation frequency. The rate of pitch change is seen to be high enough to produce substantial hysteresis effects, whose variation with radial position is measured. The hysteresis is seen to arise from the inboard shed vorticity, and to decay towards the tip. NOMENCLATURE f frequency, in Hz. G(f) Spectral density, in dB. r Radial coordinate, with origin at the center of the rotor hub. R Rotor radius. z Axial coordinate, with origin at the center of the rotor hub, positive going downstream. Vz Inflow velocity in m/s, perpendicular to the tip path plane; positive going downstream.

Parametric Vibration of Liquid Surface in a Circular Cylindrical Tank Subjected to Pitching Excitation.

Nonlinear sloshing motion of the liquid in a partially filled circular cylindrical tank is investigated. The tank is subjected to horizontal, vertical and pitching excitations. The nonlinear ordinary differential equations governing the liquid surface oscillation are derived by applying Galerkin's method. It is confirmed that the vertical excitation causes the parametric excitation. In addition, it is noted that the pitching excitation also causes the parametric excitation when the pitching axis does not intersect the symmetrical axis of the circular cylindrical tank. The time histories of the liquid surface displacement are calculated to the harmonic pitching excitations. An experiment is carried out using a model tank. A fairly good agreement was found between the theoretical and experimental results. It is shown that, even if the tank is only subjected to the pitching excitation, the amplitude of liquid surface oscillation grows owing to parametric resonance.

Effects of Higher Order Radial Modes upon Nonlinear Sloshing in a Circular Cylindrical Tank Subjected to Pitching Excitation.

Nonlinear sloshing motion of the liquid in a partially filled circular cylindrical tank is investigated. The tank is subjected to horizontal, vertical and pitching excitations. The nonlinear ordinary differential equations governing the liquid surface oscillation are derived by applying Galerkin's method to the basic equations. The higher order radial modes are considered in the admissible functions which are assumed to be represented by combining the modal functions obtained by the linearization analysis. The effects of these higher order modes on liquid surface oscillation are discussed. The time histories of the liquid surface displacement to the harmonic pitching excitations are calculated. An experiment is carried out using a model tank. The usefulness of the present nonlinear analysis was demonstrated by comparing the theoretical results with the experimental ones. It is shown that the higher order radial modes play an important role in estimating the liquid surface displacement.

Effects of Higher Order Radial Modes upon Nonlinear Sloshing in a Circular Cylindrical Tank Subjected to Vertical Excitation.

Parametric vibration of the liquid surface in a partially filled circular cylindrical tank is investigated. The tank is subjected to horizontal, vertical and pitching excitations. Nonlinearity of the liquid surface oscillation is considered in the response analysis of the sloshing motion. The nonlinear and parametric ordinary differential equations, governing the axisymmetric liquid surface oscillation and including the higher order radial modes, are derived by applying Galerkin's method. It is confirmed that the vertical excitation causes the parametric excitation. In addition, it is noted that the pitching excitation also causes the parametric excitation when the pitching axis does not intersect the symmetrical axis of the circular cylindrical tank. The time histories of the liquid surface displacement to the harmonic vertical excitations are calculated in cases where the dominant mode is axisymmetric and where it has nodal radiuses. An experiment was conducted using a model tank. Good agreement was found between the theoretical and experimental results.

Frequency Response of Sloshing in a Circular Cylinirical Tank Subjected to Pitching Excitation.

Frequency responses of stable planar and rotary motions in a partially tilled circular cylindirical tank, subjected to a pitching excitation at a frequency in the neighborhood of the lowest resonant frequency, are investigated. The nonlinearity of the liquid surface oscillation and the nonlinear coupling between the dominant modes and other modes(e.g., an axisymmetric mode) are considered in the response analysis of the sloshing motion. The equations governing the amplitude of those two types of liquid surface motions are derived and the stability analysis of each motion is conducted. An experiment was carried out using a model tank. Good agreement was found between the theoretical and experimental results. It is shown that the nonlinear analysis is important for estimating the sloshing responses.

Nonlinear Liquid Oscillation in an Elastic Circular Cylindrical Tank Subjected to Pitching Excitation.

Nonlinear liquid motion in an elastic circular cylindrical tank partially filled with liquid, in response to pitching excitation, is investigated. The nonlinearity of liquid surface oscillation and the elastic wall deformation caused by the liquid pressure are considered in the response analysis of sloshing motion. Basic equations are derived by employing the variational principle. Free vibration analysis of the linearized system confirms that the influence of wall deformation on sloshing motion is negligible. The time histories of the liquid surface displacement and the deformation of the tank are calculated to the harmonic pitching excitations. An experiment was conducted using a model tank. A fairly good agreement was found between the theoretical and experimental results. It is shown that the nonlinear analysis is important for estimating sloshing responses.