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The C2H2 + OH reaction is an important acetylene oxidation pathway in the combustion process, as well as a typical multi-well and multi-channel reaction. Here, we report an accurate full-dimensional machine learning-based potential energy surface (PES) for the C2H2 + OH reaction at the UCCSD(T)-F12b/cc-pVTZ-F12 level, based on about 475 000 ab initio points. Extensive quasi-classical trajectory (QCT) calculations were performed on the newly developed PES to obtain detailed dynamic data and analyze reaction mechanisms. Below 1000 K, the C2H2 + OH reaction produces H + OCCH2 and CO + CH3. With increasing temperature, the product channels H2O + C2H and H + HCCOH are accessible and the former dominates above 1900 K. It is found that the formation of H2O + C2H is dominated by a direct reaction process, while other channels belong to the indirect mechanism involving long-lived intermediates along the reaction pathways. At low temperatures, the C2H2 + OH reaction behaves like an unimolecular reaction due to the unique PES topographic features, of which the dynamic features are similar to the decomposition of energy-rich complexes formed by C2H2 + OH collision. The classification of trajectories that undergo different reaction pathways to generate each product and their product energy distributions were also reported in this work. This dynamic information may provide a deep understanding of the C2H2 + OH reaction. [ABSTRACT FROM AUTHOR]

When radar receivers adopt digital channelization, it is prone to generating a cross-channel split signal, the rabbit ear effect, and a transition band repeated signal, leading to errors in radar signal sorting or identification. The pulse-splitting model and detection method proposed in this paper can model split pulses and identify them in radar pulse streams, facilitating the merging of split pulses to enhance sorting and identification performance. Firstly, the mechanism of splitting pulse generation is deeply analyzed, and the splitting site theory is proposed. Then, the split pulse signal model and the split pulse number statistical model based on geometric distribution are constructed, which are used to guide the construction of simulation data of split pulse flow with different characteristics. Furthermore, a time-domain convergence degree (TCD) index is proposed to characterize the pulse split phenomenon. At the same time, in order to avoid a large number of threshold searching problems in pulse-splitting detection, an empirical formula for the pulse-splitting detection threshold based on the TCD is given to quickly determine whether there is a pulse train split problem. The selected measured radar pulse stream is verified to follow a geometric distribution at a significance level of 0.05. The proposed method achieved a detection accuracy of at least 99.55% on the simulation dataset and at least 95.68% on the experimental dataset, validating the rationality of pulse-splitting modeling and the effectiveness of the detection method. [ABSTRACT FROM AUTHOR]

The study of crude oil oxidation characteristics is fundamental to the design of ignition in situ combustion. Experimentation is the most crucial method for studying the oxidation characteristics of crude oil. Aiming to address the challenges posed by high temperature, high pressure, and rapid temperature changes during the combustion of crude oil, a dynamic simulation system for high-temperature and high-pressure ignition is designed. In order to study the oxidation characteristics of the crude oil ignition process, we conducted experiments using a high-temperature and high-pressure dynamic ignition simulation device. The experiments focused on determining the ignition point of crude oil under different pressure conditions, oil–water ratios, heating rates, gas injection rates, and other relevant characteristics. The kinetic model for the oxidation process of crude oil ignition was established. The kinetic parameters were calculated for different ignition conditions and the apparent activation energy for each oxidation stage was determined. Additionally, the stability of in situ combustion was evaluated under various ignition parameters. The results show that the Arrhenius curves for crude oil exhibit noticeable differences in the HTO (high-temperature oxidation) and LTO (low-temperature oxidation) regions. The curves demonstrate good linearity in the HTO region, with correlation coefficients exceeding 0.9. Moreover, the apparent activation energies in the HTO region range from 8.01 to 26.7 kJ/mol. The apparent activation energies and finger front factors were calculated for the HTO stage under different pressure conditions. The results showed that, as the pressure increased, the autoignition point, inflection point temperature, and apparent activation energy of the crude oil decreased. This suggests that increasing the pressure can enhance the HTO of the crude oil. The spontaneous ignition point of the crude oil exhibited an upward trend as the heating rate increased. Additionally, the maximum temperature during the combustion process generally increased with the heating rate, reaching a maximum temperature of 453.1 °C. The tests demonstrated that the simulation system is capable of real-time monitoring and recording of oxidation parameters during the combustion process of crude oil. This system can provide essential data for project implementation and numerical simulation. [ABSTRACT FROM AUTHOR]