238 research outputs found

    Virtual Instrument of Harmonics Detection Based on Neural Network Adaptive Filters

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    This study investigated the adaptive detection principle based on a single artificial neuron, and constructed a method for detecting harmonics using the artificial neural network technique. Based on the established method, and by comprehensively processing the obtained harmonics data using the LabVIEW software-developing environment of the virtual instrument, the harmonic waves were detected and analyzed. Finally, the analysis of current ball crusher harmonics verified that the designed system was effective

    The Effect of CO2 Phase on Oil Displacement in a Sandstone Core Sample

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    CO2 sequestration in saline aquifers and hydrocarbon reservoirs is a promising strategy to reduce CO2 concentration in the atmosphere and/or enhance hydrocarbon production. Change in subsurface conditions of pressure and temperature and CO2 state is likely to have a significant impact on capillary and viscous forces, which, in turn, will have a considerable influence on the injection, migration, displacement, and storage capacity and integrity of CO2 processes. In this study, an experimental investigation has been performed to explore the impact of fluid pressure, temperature, and injection rate, as a function of CO2 phase, on the dynamic pressure evolution and the oil recovery performance of CO2 during oil displacement in a Berea sandstone core sample. The results reveal a considerable impact of the fluid pressure, temperature, and injection rate on the differential pressure profile, cumulative produced volumes, endpoint CO2 relative permeability, and oil recovery; the trend and the size of the changes depend on the CO2 phase as well as the pressure range for gaseous CO2–oil displacement. The residual oil saturation was in the range of around 0.44–0.7; liquid CO2 gave the lowest, and low-fluid-pressure gaseous CO2 gave the highest. The endpoint CO2 relative permeability was in the range of about 0.015–0.657; supercritical CO2 gave the highest, and low-pressure gaseous CO2 gave the lowest. As for increasing fluid pressure, the results indicate that viscous forces were dominant in subcritical CO2 displacements, while capillary forces were dominant in supercritical CO2 displacements. As temperature and CO2 injection rates increase, the viscous forces become more dominant than capillary forces

    Adaptive Exponential Synchronization of Coupled Complex Networks on General Graphs

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    We investigate the synchronization in complex dynamical networks, where the coupling configuration corresponds to a weighted graph. An adaptive synchronization method on general coupling configuration graphs is given. The networks may synchronize at an arbitrarily given exponential rate by enhancing the updated law of the variable coupling strength and achieve synchronization more quickly by adding edges to original graphs. Finally, numerical simulations are provided to illustrate the effectiveness of our theoretical results

    Understanding the interplay of capillary and viscous forces in CO2 core flooding experiments

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    Interaction between capillary and viscous forces significantly affects the flow instability in immiscible displacement, which is usually investigated by visualization of flow patterns in 2d porous micromodels or in 3d system equipped with X-ray CT. However, in most practical applications, visualization of flow in porous media is not possible and the pressure signal is often as one of the important sources of information. Core flooding experiments were implemented in this study to investigate the interplay of capillary and viscous effects by analysis of differential pressure. Water and crude oil were employed as defending fluid, and different states of CO2 were injected as invading fluid. The inlet was set as the constant injection flow rate while the outlet as the constant pressure. In viscous-dominated displacement, differential pressure evidently depends on the injection rate and the pressure decline curve is fitted by a power function. The exponent of the function is found to be significantly larger at the crossover between capillary-dominated and viscous-dominated regions. In capillary-dominated displacement, the pressure profile is characterized by a pressure jump at the beginning and intermittent fluctuations during the displacement. Further analysis by wavelet decomposition indicates a transition point existing in standard deviation of pressure fluctuations when the displacement is transformed from capillary-dominated to viscous-dominated. The experimental results are finally verified by a macroscopic capillary number, which characterizes the interaction between capillary and viscous forces at a critical value of , agreeing well with the Log Nca-Log M phase diagram