Location Of Maximum Amplitude Research Articles

Study on the Propagation Process Characteristics of Anisotropic Acoustic Waves in Shale Gas Well with the Reflection Rule of Lateral Fractures

Based on the acoustic wave finite element (AWFE) method, one can establish an AWFE method and study the influence of mechanical parameters on the shale reservoir acoustic wave propagation characteristics. The different crack characteristics and different crack multi-physical coupling phenomena are studied by using the AWFE method on shale gas reservoir cracks. To calculate the shape and position along the crack near a side borehole, the model parameters are compared with the simulation results. The reflection waveform characteristics of adjacent cracks are studied by using the AWFE method. By considering the borehole axis of symmetry, for an acoustic impedance discontinuous interface on one side of the two-dimensional axisymmetric AWFE, one can establish a borehole cross-crack and an arc cross-crack reflection interface model with the AWFE method. By processing the waveform data received by different receiving points under the same source distance, the parameters, such as the reflection wave time and the distribution laws of the crack in the shale reservoir, are obtained. To verify the validity of the research method, the propagation of a reflected acoustic wave from the reservoir fracture by the filling with different media was also studied. The results show that a reflection wave arrival time changing with the source ordinate and present law, by side borehole fracture morphology, showed a suitable consistency. The well cross-crack angle range is 10~20°, according to the wave arrival time calculated by the side borehole fracture dip. For the acoustic signal propagation in the shale formation anisotropy, they found that an acoustic signal is always in the direction of the elastic modulus, with a further larger spread, a location of maximum amplitude, and a 45-degree direction to the axis of symmetry. In the lateral and longitudinal distance from an acoustic source of the same two receiver signal waves, the receiver vibration amplitude is bigger, and there is less attenuation. With the increase in the anisotropic index, the inside ovality amplitude distribution of the signal amplitude in this model is higher. When a side borehole has an arc crack and a reflected wave to time to obtain the coordinates of a reflecting interface and to compare with the results of the calculation model, the crack in the center position, and the reflection point coordinates, the relative error is less than 5%. Finally, the AWFE method could provide a new idea for the identification of the crack properties and also could be an inverse calculation of the position and morphological characteristics of fractures near the side borehole.

Analysis on location of maximum vibration amplitude in panel flutter

When the panel is under limit cycle oscillation, the location of maximum vibration amplitude always locates at 0.75 of panel length under different dynamic pressure. However, this conclusion is drawn from engineer practice without further investigations on its theoretical basis. Thus, the current study focuses on the theoretical and mathematical basis of this problem. The pattern of the location of maximum amplitude is verified at first by using three numerical methods. Then, based on the law of energy conservation, the displacement function of linear panel oscillation is derived for theoretical investigation. The linear panel consists of two structural modes. Theoretical analysis shows that, under critical dynamic pressure, the generalized displacement responses of two structural modes have opposite phase, the same vibration amplitude and the same vibration frequency. As a result, the superposition of displacement function of two structural modes, which is the displacement function of panel, leads to the occurrence of maximum vibration amplitude at 0.7 of panel length. With more structural modes considered, the location of maximum moves to 0.75 of panel length.

조석 전파 특성을 활용한 한강하구 주요 수로의 지형학적 수렴과 바닥 마찰 간의 관계에 대한 연구

The basic research of the estuarine circulation at Gyeong-Gi bay has not been well studied up to now, although coastal development pressures have been continuously increased. To understand the oceanographic phenomena at the Han River estuary, it`s essential to understand the propagation characteristic of tidal wave which is the strongest external forcing in this region. In this study, we investigate the tidal wave propagation characteristics along the 3 major channels using observation data and numerical model. It is found that 3 channels are all hyper-synchronous and the most important physical factor controlling the tidal wave propagation is topographical convergence of estuary shape and friction. The result of analytic solution at ideal channel considering the topographical convergence and friction show that the contribution of physical role of convergence and friction varies at 3 different channel. And the ratio of convergence and friction at Yeomha channel is four times larger than Seokmo channel. Because of this effect, the location of maximum amplitude at Yeomha channel is showed up downward than Seokmo channel. The ratio of decreasing amplitude and increasing phase per unit distance between stations is bigger than Seokmo channel. Although 3 major channel show a hyper-synchronous pattern, Yeomha shows more frictionally dominant channel and Seokmo channel is more dominantly affected by convergence effect.

Measurement of pressure fluctuations in two-dimensional gas-solid fluidized beds at elevated temperatures.

Pressure fluctuations were measured in a two-dimensional gas-solid fluidized bed at temperatures ranging from 13 to 270°C. The random pressure fluctuation signals were studied on-line by the statistical method. The results indicate that the frequency spectrum, major frequency, and mean pressure amplitude depend considerably on the gas excess velocity and temperature. A probability density function of pressure fluctuations with two peaks was observed in the upper portion of the bed, indicating bubble eruption behavior at room temperature. The two peaks in the p.d.f. are transformed into a single peak at higher temperature, and the location of maximum amplitude also changes at higher temperature. Both measurements of pressure drop fluctuations and differential pressure fluctuations were used in this study, and the latter were found to be superior in the study of bubble behavior.

Conjectured Location of Maximum Amplitude in an All-Pass Sequence

Conjectured Location of Maximum Amplitude in an All-Pass Sequence