Effect Of Waveform Distortion Research Articles

High accuracy and resolution damage detection for concrete based on novel virtual correlation imaging method and embedded piezoelectric sensing technology

This paper presents a novel virtual correlation imaging (VCI) method to reduce the adverse effects of stress wave distortion and realize high accuracy and resolution damage imaging based on the sparse stress wave data collected by embedded piezoceramic transducers. Specifically, a compensation function is first constructed in the VCI method based on the frequency response characteristic of damage-induced scattering signals. Then, the constructed compensation function is emitted as the virtual excitation signal in the simulation space via virtual channels. To automatically compensate for the effect of waveform distortion, a virtual correlation operator is developed based on the scattering signal and its corresponding virtual received signal to design the imaging function. Finally, the practicability of the proposed VCI method is investigated on a concrete specimen with two successively drilling holes under laboratory conditions. The results indicate that, compared with the conventional damage imaging methods, the proposed VCI method can effectively decrease the adverse effect of distorted probing stress waves on damage localization accuracy and spatial resolution during the imaging process.

Pressure pulse wave attenuation model coupling waveform distortion and viscous dissipation for blockage detection in pipeline

AbstractSafety issues are always a major concern in the oil and gas transportation facilities. Equipment damages are frequently encountered due to solid deposition such as gas hydrate deposition. A fast and efficient detection of the location, length, and rate of the accumulating blockage will significantly help relieve the potential risk. Most existing pressure wave‐based models suffer the difficulty to properly predict the blockage percentage arising from the ignorance of the wave attenuation. In the present work, an attenuation model to describe the transportation of the pressure pulse wave in gas is developed; the effects of waveform distortion and absorption as a result of the nonlinear effect and viscous dissipation are collectively considered for the first time. A simplified procedure to couple the wave attenuation in the model is proposed. The results show that the model can remarkably improve the prediction accuracy of blockage percentage by reducing the errors from −9.0% to −4.2%. Moreover, the attenuation process of the pressure pulse wave is determined to consist of three stages. The effect of waveform distortion on amplitude mainly occurs in the second stage, when our proposed model shows an improved prediction. The performance of the proposed model will help the early warning of the blockage in the pipelines and effectively avoid the potential injury and financial loss.

Parallel interaction protocol for electromagnetic and electromechanical hybrid simulation

A new hybrid simulator is presented, which comprises a transient stability (TS) simulator interfaced with an electromagnetic transients (EMT) simulator. It can simulate very large networks with TS simulator-like speed, while delivering EMT simulator-like accuracy on key components, while running in real time or in accelerated time modes. In the accelerated time mode, the simulator can be used as a system operation tool, offering extended contingency lists (such as mal-operation of power electronic devices) for dynamic security assessment. In real-time operation, the simulator can be interfaced with real control system hardware for detailed study, including the effects of waveform distortion and mal-operation of switching devices. Much of the development work in this area has been based on a serial communication protocol whereby each of the two different simulators runs in turn. However, a serial-protocol-based hybrid simulator cannot meet the real-time requirement of continuous operation of the EMT simulator. A parallel protocol is proposed, whereby both simulators run continuously, such that real-time operation is feasible. The feasibility of the proposed hybrid simulator is demonstrated by case studies, which show very good comparison between the parallel and series protocols, as well as with an EMTP benchmark.

Gaussian approach for performance evaluation of optically preamplified receivers with arbitrary optical and electrical filters

A Gaussian approach (GA), which takes into account the influence of arbitrary optical and electrical filters, is proposed to analytically evaluate the performance of optically preamplified receivers. This GA also takes into account the effects of waveform distortion in the signal and in the signal-amplified spontaneous emission beat noise. Exact expressions for the mean and variance of the current at the decision circuit input are derived, which explicitly present the dependence on the optical and electrical filter transfer functions and take into account the presence or absence of a polariser. This GA is computationally much faster and simpler than more rigorous methods and the accuracy of its sensitivity estimates is investigated for different optical and electrical filters. It is shown that the GA predicts the optimal optical filter bandwidth very reasonably. Discrepancies below 1.2 dB are found between its sensitivity estimates and rigorous estimates. The assessment of the optical filter detuning impact on the receiver sensitivity is also investigated with this GA. Discrepancies less than 1 dB are found between the GA estimates and rigorous estimates. The GA sensitivity estimate's accuracy is also investigated in the presence of intersymbol interference (ISI) and very accurate predictions are obtained by the GA for significant ISI.

Effect of waveform distortion on sonic boom noise penetration into a flat ocean

The penetrating underwater sound field due to an N-shaped sonic boom incident on a flat ocean surface is well described by existing theory. However, in realistic situations, most of the waves that hit the surface are not perfect N waves but are distorted by such processes as atmospheric turbulence. In the present research, N waves are created that contain the same amount of energy as experimentally measured sonic booms produced by aircraft in the U.S. Air Force. Each signature is input to an algorithm recently presented by Sparrow and Ferguson [AIAA Paper 97-0486 (1997)] to calculate the respective underwater sound fields. By comparing the underwater wave shapes and plots of peak pressure with respect to depth, initial results of the effect of waveform distortion on sonic boom noise penetration into a flat ocean are determined. Preliminary figures show that waveform distortions at the surface cause a slightly greater penetration depth underwater. However, the magnitude of the effect is dependent on the incident sonic boom. [Work supported by Armstrong Laboratory, Air Force Materiel Command, USAF, under Grant No. F41624-96-1-0003.]

Effect of waveform distortion on protective relays

Effect of waveform distortion on protective relays

Error rate performance in high‐speed gmsk transmission on mobile satellite channel

AbstractIn high‐speed digital transmission in mobile satellite and land mobile communications, one of the serious problems is the effect of waveform distortion due to the frequency‐selective fading. This paper considers the GMSK modulation system, which is considered as useful as the modulation scheme for digital mobile communication.The effect of the waveform distortion produced by the time‐delay spread of the scattered interfering waves in the Nakagami‐Rice fading channel is considered and the bit error rate is calculated theoretically. Numerical examples of bit error rate performance are illustrated. It is shown that the bit error rate is improved when there is an average delay time or a time‐delay spread in the scattered interfering wave, compared with the case without a delay. However, the effect is relatively small.