Search for light dark matter from atmosphere in PandaX-4T

We report a search for light dark matter produced through the cascading decay of $\eta$ mesons, which are created as a result of inelastic collisions between cosmic rays and Earth's atmosphere. We introduce a new and general framework, publicly accessible, designed to address boosted dark matter specifically, with which a full and dedicated simulation including both elastic and quasi-elastic processes of Earth attenuation effect on the dark matter particles arriving at the detector is performed. In the PandaX-4T commissioning data of 0.63 tonne$\cdot$year exposure, no significant excess over background is observed. The first constraints on the interaction between light dark matter generated in the atmosphere and nucleus through a light scalar mediator are obtained. The lowest excluded cross-section is set at $5.9 \times 10^{-37}{\rm cm^2}$ for dark matter mass of $0.1$ MeV$/c^2$ and mediator mass of 300 MeV$/c^2$. The lowest upper limit of $\eta$ to dark matter decay branching ratio is $1.6 \times 10^{-7}$

A Search for Light Fermionic Dark Matter Absorption on Electrons in PandaX-4T

We report a search on a sub-MeV fermionic dark matter absorbed by electrons with an outgoing active neutrino using the 0.63 tonne-year exposure collected by PandaX-4T liquid xenon experiment. No significant signals are observed over the expected background. The data are interpreted into limits to the effective couplings between such dark matter and electrons. For axial-vector or vector interactions, our sensitivity is competitive in comparison to existing astrophysical bounds on the decay of such dark matter into photon final states. In particular, we present the first direct detection limits for an axial-vector (vector) interaction which are the strongest in the mass range from 25 to 45 (35 to 50) keV/c$^2$

Mechanistic studies of corrosion of pipeline steel under coating

Bibliography: p. 180-191Some pages are in colour

Safety evaluation method for flexible composite gathering and transmission pipelines of oil and gas in shifting dune areas

As the flexible composite pipelines in the shifting dune areas are easy to be suspended and displaced, it is necessary to perform a comprehensive evaluation on the safety of oil and gas pipelines to ensure their safe and stable operation. Thus, with a polyester fiber flexible reinforced composite pipeline as the example, analysis was conducted for the ultimate bearing capacity of the flexible composite pipelines under the action of suspension and lateral compression caused by the shifting sand dunes. In addition, based on the axial tensile test results, the failure process of flexible composite pipelines and the characteristic strain values under the different states of yield, reinforcement and shrinkage were identified. Combined with the finite element analysis method, the failure evaluation basis of the "ultimate slope" of suspended pipeline in the sand and the "limited displacement" of pipelines under the lateral compression of quicksand were proposed. Further, the evaluation method for flexible composite pipelines in the shifting sand areas was established, which could provide technical support for the safe operation of oil and gas pipelines in the desert areas