Papers by Keyword: Time Domain

Abstract: In view of badly transplanting of analog filter and low cost performance of digital filter for the washing out signal methods used by dynamic simulator, this paper proposed a computer intelligent time domain method. We decompose signal with the computer intelligence in the time domain, and convert the signal into the corresponding movement form respectively, then get the final result by overlaying them. The experimental results show that this method not only can achieve the effect of the traditional methods, better portability and faster computation speed, but also can be achieved directly on general computers.

Abstract: In practical applications, the DSSS signal has very low power spectral density, and its application range is very wide, so in the non cooperative communication, if on the premise that the spread spectrum sequence is unaware, how to detect and estimate the existence of DSSS signal is very important, this has very strong application background. This paper introduces the time domain correlation detection method of DSSS signal, through the simulation can validate that this way can detect the existence of signal; it lays the theoretical foundation for practical application.

Abstract: The analysis of mechanical systems (for example the mechanical systems of vehicles) vibration is permanently very topical. The vehicle dynamical properties are determined with the help of this analysis during a new vehicle design, or renewal of an older existing vehicle. The Eigen frequencies are characteristic for a vehicle construction. A vehicle mechanical system is excited with various types of loads in the operation and this is the reason why its individual parts oscillate. The aim of a dynamical analysis is not only to judge the influence of an excitation on the mechanical system, but also on the base of that analysis, to propose and to perform the construction changes of a vehicle for the detected negative state elimination or improvement.

Abstract: The input of road roughness, which affects the ride comfort and the handling stability of vehicle, is the main excitation for the running vehicle. The time history of the road roughness was researched with the random phases, based on the stationary power spectrum density of the road roughness determined by the standards. Through the inverse Fourier transform, the random phases can be used to get the road roughness in time domain, together with the amplitude. Then, the time domain simulation of the non-stationary random excitation when the vehicle ran at the changing speed, would also be studied based on the random phases. It is proved that the random road excitation for the vehicle with the changing speed is stationary modulated evolution random excitation, and its power spectrum density is the stationary modulated evolutionary power spectrum density. And the numerical results for the time history of the non-stationary random inputs were also provided. The time history of the non-stationary random road can be used to evaluate the ride comfort of the vehicle which is running at the changing speed.

Abstract: In this study, the modal identification methods based on time and frequency domain are summarized, and the working condition, identified accuracy and some fundamental idea of these approaches are discussed. By comparing the characteristic of different identification method, the identification technique based on ambient excitation is promising in bridges since it is difficult to measure the excitation information. Some challenge and key issues of modal identification of bridges are pointed out in the last part.

Abstract: An innovative asymmetric binary frequency shift keying (ABFSK) modulation format is presented and studied both in the time domain and frequency domain. First, the modulation function is demonstrated, it shows a quasi-continuous phase attribute and an ability of high speed data modulation. Second, the domain attribute is studied; it has a high degree of energy centralization. Thus, a narrow occupied bandwidth can be achieved after a proper filtering. Then, the finite spectrum can be conserved to improve spectrum efficiency.

Abstract: By taking the 3D Laplace equation as the basic governing equation, a mathematical model with respect to the interaction between linear waves and arbitrary 3D structures was founded. For the example of wave action with three cylinders, numerical results show that wave force F_x decrease and wave force F_y increase in each cylinder by incident wave direction from 0° to 60°; wave height on origin point increases with incident wave direction increasing for given layout and incident wave conditions.

Abstract: The bearing of rotating machinery often fails due to the frictional forces of rolling element, in the early stages of the faults, a series of ultrasound can be generated in short time intervals, which occur at bearing characteristic frequencies. Since the frequencies of ultrasonic signal are very high, they will lead to much higher computing burden when using the common technique of Fast Fourier Transforms (FFT) directly. In this paper, envelope detection technology and heterodyne technology which integrated in an ultrasonic data collection system are used to reduce the frequency effectively. To allow for the easier detection of the bearing faults, these two techniques has been used together with FFT. A verification research with respect to vibration analysis is carried out to analyze the effectiveness and superiority of ultrasonic data collection in time domain and frequency domain aspects respectively. Extensive experiments have been performed in an Alternating Current (AC) motor system, and the results indicated that this ultrasonic data collection system is as useful as vibration analysis system in diagnosing the faults of bearings. In addition, it is more sensitive in fault diagnosis in the early stages of the bearing faults than vibration acquisition system.

Abstract: The working mode of constant-pressure radial piston pump includes the mode of constant flow and constant pressure. The dynamic model of stator vibration was established and the analysis was made on the stator vibrating velocity in time domain to the two modes. Measurement mechanism was designed to test the vibration of stator of JB32H-type radial piston pump. It is concluded from the analysis and test results that the velocity of stator vibrates periodically on the two modes. The maximum amplitude on the mode of constant pressure is smaller than the one on the mode of constant flow. The conclusions are helpful to the noise control of piston pump.

Abstract: On account of the problem that traditional pipe leakage diagnosis method is not highly accuracy .this paper come up with a method that based on pipe leakage diagnosis method of neural network information fusion. Giving the stress wave time domain feature extraction index data algorithm and wavelet packet extraction each the frequency band energy algorithm, by comparing with these results of the pressure wave time domain feature index data, time-frequency extraction energy values and fault diagnosis of both information fusion ,which show the neural network information fusion method that is used for pipe leakage diagnosis that is feasible and effective.