Experimental and numerical analysis of imbibition processes in a corrugated capillary tube

Spontaneous imbibition is a capillary-driven flow phenomenon that exists widely in nature and is important for several industries. Recently, Tolman length has been introduced to improve the classical Lucas-Washburn imbibition model, in order to alleviate the deviations in calculating the capillary pressure. However, imbibition experiments to measure Tolman length have been scarce. In addition, the fluid-wall friction has a considerable impact on the imbibition process, while it is often ignored. In this work, imbibition experiments under specific conditions are carried out to measure the values of Tolman length, and the fluid-wall friction is taken into consideration in the equilibrium equation. The water uptake model in  fractures is adopted to make corrections to the rise of water level. The experimental results show that Tolman length decreases first and then rises with the increasing curvature radius of liquid-gas interface. The data reveal that the Tolman length-based model can better describe the real imbibition processes than the classical Lucas-Washburn model.Cited as: Wang, J., Salama, A., Kou, J. Experimental and numerical analysis of imbibition processes in a corrugated capillary tube. Capillarity, 2022, 5(5): 83-90. https://doi.org/10.46690/capi.2022.05.0

5d SCFTs from Isolated Complete Intersection Singularities

In this paper, we explore the zoo of 5d superconformal field theories (SCFTs) constructed from M-theory on Isolated Complete Intersection Singularities (ICIS). We systematically investigate the crepant resolution of such singularities, and obtain a classification of rank $\leqslant 10$ models with a smooth crepant resolution and smooth exceptional divisors, as well as a number of infinite sequences with the same smoothness properties. For these models, we study their Coulomb branch properties and compute the flavor symmetry algebra from the resolved CY3 and/or the magnetic quiver. We check the validity of the conjectures relating the properties of the 5d SCFT and the 4d $\mathcal{N}=2$ SCFT from IIB superstring on the same singularity. When the 4d $\mathcal{N}=2$ SCFT has a Lagrangian quiver gauge theory description, one can obtain the magnetic quiver of the 5d theory by gauging flavor symmetry, which encodes the 5d Higgs branch information. Regarding the smoothness of the crepant resolution and integrality of 4d Coulomb branch spectrum, we find examples with a smooth resolved CY3 and smooth exceptional divisors, but fractional 4d Coulomb branch spectrum. Moreover, we compute the discrete (higher)-symmetries of the 5d/4d SCFTs from the link topology for a few examples.Comment: v2, 87 page

Sound event localization and classification using WASN in Outdoor Environment

Deep learning-based sound event localization and classification is an emerging research area within wireless acoustic sensor networks. However, current methods for sound event localization and classification typically rely on a single microphone array, making them susceptible to signal attenuation and environmental noise, which limits their monitoring range. Moreover, methods using multiple microphone arrays often focus solely on source localization, neglecting the aspect of sound event classification. In this paper, we propose a deep learning-based method that employs multiple features and attention mechanisms to estimate the location and class of sound source. We introduce a Soundmap feature to capture spatial information across multiple frequency bands. We also use the Gammatone filter to generate acoustic features more suitable for outdoor environments. Furthermore, we integrate attention mechanisms to learn channel-wise relationships and temporal dependencies within the acoustic features. To evaluate our proposed method, we conduct experiments using simulated datasets with different levels of noise and size of monitoring areas, as well as different arrays and source positions. The experimental results demonstrate the superiority of our proposed method over state-of-the-art methods in both sound event classification and sound source localization tasks. And we provide further analysis to explain the reasons for the observed errors

A Squeeze-and-Excitation and Transformer based Cross-task System for Environmental Sound Recognition

Environmental sound recognition (ESR) is an emerging research topic in audio pattern recognition. Many tasks are presented to resort to computational systems for ESR in real-life applications. However, current systems are usually designed for individual tasks, and are not robust and applicable to other tasks. Cross-task systems, which promote unified knowledge modeling across various tasks, have not been thoroughly investigated. In this paper, we propose a cross-task system for three different tasks of ESR: acoustic scene classification, urban sound tagging, and anomalous sound detection. An architecture named SE-Trans is presented that uses attention mechanism-based Squeeze-and-Excitation and Transformer encoder modules to learn channel-wise relationship and temporal dependencies of the acoustic features. FMix is employed as the data augmentation method that improves the performance of ESR. Evaluations for the three tasks are conducted on the recent databases of DCASE challenges. The experimental results show that the proposed cross-task system achieves state-of-the-art performance on all tasks. Further analysis demonstrates that the proposed cross-task system can effectively utilize acoustic knowledge across different ESR tasks

A study for using CO2 to enhance natural gas recovery from tight reservoirs

A comprehensive study is presented on the interfacial behavior of all participating phases in a scenario of using carbon dioxide (CO2) to enhance the recovery of natural gas in tight sandstone reservoirs. Natural gas condensate is contacted with carbon dioxide at increasing pressure in order to determine the minimum miscibility pressure (MMP) by the vanishing interfacial tension method. Close to the MMP at higher temperature, some compounds of the mixture are extracted leaving a heavy oil fraction that remains immiscible. As the second reservoir liquid, formation water is extracted by CO2 from a tight sandstone sample and subsequently applied as a sessile drop for assessment of the wetting behavior inside the reservoir in the presence of injected CO2. The contact angle has been observed to increase with increasing CO2 pressure. It has been further observed that water contact angle on a gas shale increased with increasing CO2 pressure more rapidly. The results suggest that CO2 could clear gas flow path blocked by water and gas condensate. As a consequence, the recovery of natural gas would increase. This could also create a greater potential for CO2 storage in gas-depleted reservoirs

Water uptake in parallel fractures

   Water uptake in rock fractures caused by rainfall plays a significant role in slope stability analysis. Since the fracture network system has complicated structures and multiple scales, the models based on the averaged system cannot account for these properties. On the other hand, a model describing a single fracture with fractal characteristics and surface roughness fails to deal with the case of multiple fractures at spatial scales. In this study, a fracture-network model is established to account for the complex structures and multiple scales of fractures. By considering the connectivity between fractures and the limited area of aquifer, capillary pressure formulations in different fractures are derived based on the Young-Laplace equation, and the final water level under specific rainfall conditions is also obtained. The cross-section shapes and exhaust conditions of rainwater infiltration have important influences on the final water level. The results indicate that the final water level is proportional to the ratio of perimeter to cross-section area when the fracture is a cylinder, and a circular pipe can reduce water level elevation in the fracture system.Cited as: Wang, J., Zhu, X., Pan, Y., Kou, J., Sun, S. Water uptake in parallel fractures. Capillarity, 2021, 4(1): 1-12, doi: 10.46690/capi.2021.01.0