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[Display omitted] • Plastic waste valorization into water filtration membranes with a trimodal structure. • Acid-catalyzed oxidation enhances the hydrophilicity, improving water flow rates. • The macrovoids allows efficient water passage while cavities serve as oil reservoirs. • Membranes recycle for 10 cycles, maintaining 84 – 94 % oil–water separation efficiency. Polyolefin waste is among the most generated yet least recycled. Despite its potential as a feedstock of superhydrophobic membranes for organic solvent filtration, it remains a challenge to achieve high selectivity and permeability for viscous oils. In this study, we valorized polyolefin waste into trimodal water filtration membranes through acid-catalyzed oxidation and a void inducer. This approach enabled the creation of membranes with exceptional wettability and strength, characterized by a combination of micropores, macrovoids (30 – 70 µm), and cavities (150 – 200 µm). The acid-catalyzed oxidation introduced oxygen moieties into the membrane structure, resulting in a reduced water contact angle, improved hydrophilicity, and increased permeability. The micropores facilitated capillary action, macrovoids enabled efficient water passage, and cavities acted as oil reservoirs, for optimal oil–water separation. Various membranes were synthesized using low-density and high-density polyethylene (PE), polypropylene (PP), and their blend. The obtained results were compared with commercial membranes, revealing a flow rate of 43 ml/min, a retention capacity of 261 mg, and an oil removal efficiency ranging from 84 – 94 %. Furthermore, the membranes exhibited recyclability, demonstrating stability over at least 10 cycles. This hybrid process transforms plastic waste into trimodal water filtration membranes, achieving a balance between superoleophilicity and hydrophilicity. [ABSTRACT FROM AUTHOR]

• A portable device is devised for high-quality GPR data collection in shield tunnels. • RTM algorithm is applied to reconstruct the cavities behind shield tunnel segments. • A field measurement in a subway tunnel verifies the effectiveness of RTM algorithm. • A band-pass filter is designed to effectively remove interfering joint clutters. Ground penetrating radar (GPR) has been widely used for detecting cavities and other hidden defects behind reinforced shield tunnel linings. Migration can collapse diffractions and reconstruct the geometries of cavities behind the tunnel, thus aiding accurate interpretation of the GPR data. However, clutters from a segment joint could be misjudged as a cavity in the reconstructed GPR images. In this paper, a band-pass filter is designed to effectively remove interfering joint clutters. Laboratory experiments were carried out in the circumference and longitudinal directions on two full-scale shield tunnel models, in which cavities were buried behind the tunnel lining. Different migration algorithms are tested on the laboratory GPR data, and the results show that the reverse time migration (RTM) algorithm outperforms traditional diffraction stack and Kirchhoff algorithms. RTM can reconstruct both the accurate geometry and location of the cavity behind the lining. The phase of the reflection signal from an air-filled cavity is opposite to that of a water-filled cavity. A portable inspection device is designed to acquire high-quality GPR data in a real shield tunnel. A field measurement in a subway tunnel verifies the effectiveness of the GPR system and the RTM algorithm, and two cavities were found behind the vault and shoulder of the tunnel, respectively. It is concluded that the RTM of GPR data can be used for detecting and characterizing cavities behind shield tunnel segments. [ABSTRACT FROM AUTHOR]

• The spontaneous ignition was investigated for compressed hydrogen jets suddenly entering cavities. • Cavities enhanced the formation of multidimensional shock waves and complicated flow patterns. • The effect of release pressure on the ignition time and position was studied. The release of pressurized hydrogen jets can lead to spontaneous ignition, which poses a major challenge to the safe utilization of hydrogen energy. Previous studies have primarily focused on the spontaneous ignition of pressurized hydrogen released into tubes. However, in real industrial scenarios, pressurized hydrogen is usually released into the atmosphere or a complex equipment environment. Therefore, the effect of obstacles on spontaneous ignition needs to be considered. In this study, the spontaneous ignition of sudden releases of pressurized hydrogen entering various cavity shapes was modeled using the standard k-ω turbulence model, the eddy dissipation concept (EDC) model and a detailed 21-step chemistry model. The effects of the cavities on the jet flow fields and the spontaneous ignition were analyzed for various cavity shapes and release pressures. For the pressures considered in this study, the cylindrical cavity did not lead to ignition. The highest hydrogen jet temperature occurred in the contact region due to the shock wave reflection, after which spontaneous ignition could not occur due to the flow divergence. The pressurized hydrogen entering hemispherical and conical cavities enhanced the hydrogen-air mixing which led to combustible regions and the formation of multidimensional shock waves, which significantly increased the spontaneous ignition probability. The cavities created a high-temperature region inside the cavity that experienced ignition but the flames did not spread out of the cavity. The conical cavity produced lower flame temperatures than the hemispherical cavity but prolonged the flame lifetime. Higher initial hydrogen release pressures resulted in more violent multidimensional shock wave interactions and higher contact surface temperatures, which lead to earlier ignition times but with little impact on the initial location of the spontaneous ignition. The results of this study provide a scientific foundation for hydrogen safety codes, safe equipment designs and the development of industry codes and standards. [ABSTRACT FROM AUTHOR]