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Imaging through random media is a pervasive issue in many areas. Recently, deep learning (DL) has shown strong capability in speckle reconstruction, especially in extracting the correlation properties of speckle patterns. However, in practical imaging scenarios, most DL methods need numerous training data to adapt to various imaging condition changes. Here, we develop an S-CNN-based phase conjugation method in imaging through random media. Specifically, we propose the amplitude-phase distortion model to characterize the light scattering process. Then, we further develop a scattering convolutional neural network (S-CNN) based on our model to map speckle patterns to scattered light fields in the changed imaging conditions. Finally, we reconstruct the object through phase conjugation. We quantitatively validated the imaging performance of S-CNN-based phase conjugation imaging, meeting the possible changes of practical imaging conditions, encompassing unseen types of different sparse objects, different diffusers, different detection positions, and different apertures on the imaging path. We found that the Jaccard index (JI), Pearson correlation coefficient (PCC), and structural similarity measure (SSIM) in different physical scenarios were increased by more than 21%, 22%, and 8%, compared with digital CNN. The proposed method provides a new optical imaging system that can be adapted to accommodate various condition changes in practical imaging scenarios and paves the way for an all-optical imaging system in imaging through random media. • Deep learning methods need lots of data to adapt to various imaging conditions. • Physical parameters enable S-CNN to map speckles to scattered light fields. • S-CNN-based phase conjugation adapts to accommodate various imaging conditions. • S-CNN-based phase conjugation has better performance in changed conditions. • S-CNN-based phase conjugation does not need large amounts of training data. [ABSTRACT FROM AUTHOR]

To explore the durability and erosion mechanism of biomass-coal mixed combustion ash geopolymer backfill (BCCGB) under compound salt erosion, the appearance, mass loss, unconfined compressive strength (UCS), microscopic morphology and erosion products of BCCGB under compound salt erosion were studied by means of dry and wet (WD) cycle tests, microscopic tests and molecular dynamics, and the erosion mechanism of SO 4 2-, Cl- and Mg2+ was revealed at the ionic scale. The results showed that after 30 WD cycles, BCCGB remained solid, no large amount of aggregate was exposed, and produced Na 2 SO 4 ·10H 2 O crystals. The mass loss rate was 0.93 %, and the UCS decreased by 33.2 %. The erosion products were CaSO 4 ·2H 2 O (gypsum), ettringite (AFt), calcium chloro-aluminate hydrate (Friedel's salt) and magnesium silicate hydrate (M-S-H). SO 4 2-, Cl- and Mg2+ bind or replace Ca2+ in calcium silicate hydrate (C-S-H), Cl- erosion was mainly aimed at free calcium, SO 4 2- and Mg2+ erosion were mainly aimed at structural calcium. In this process, changes in Coulomb forces and van der Waals forces occur, which is an endothermic and exothermic energy dynamic equilibrium process, and the presence of Cl- inhibits the diffusion of SO 4 2- and Mg2+, and the order of the diffusion coefficient was Cl- >SO 4 2- >Mg2+. Stability of erosion products: Friedel salt > Gypsum and AFt > M-S-H. [Display omitted] • The mechanism of compound salt erosion is revealed from nanometric scale. • The interaction between ions in the process of compound erosion is analyzed. • Cl- erosion targeted free calcium, SO 4 2- and Mg2+ erosion targeted structural calcium. • It is found that compound erosion is an energy dynamic equilibrium process. [ABSTRACT FROM AUTHOR]

• This study presents a novel strategy that integrates a grating with a metasurface to develop highly sensitive spectrometers for CO 2 detection. By leveraging the dispersion characteristics of the grating alongside the off-axis convergence capabilities of the metasurface at various wavelengths, this coupling approach facilitates the construction of an optical system with hyperdispersive properties. This methodology not only improves spectral resolution but also achieves a more effective balance between the off-axis convergence angle and focusing efficiency. • The designed element achieves a spectral resolution of 450 pm at a central wavelength of 1605 nm, with a focusing efficiency of 47.75%. The overall dimensions of the system are 5×5×6.6 mm³. Compared to traditional spectrometers, it reduces the number of required components, enhances portability and durability, and can be integrated with photosensitive elements, offering the potential for constructing compact and high-performance spectrometric systems. • The designed element not only enables the precise analysis of specific wavelengths related to CO2 gas absorption lines, but it also has potential applications across various fields, including portable smart wearables, environmental monitoring, medical diagnostics, and industrial process control, especially in areas that require portable high-performance spectrometers. Off-axis reflective optical systems are commonly used to minimize the dimensions of spectrometers. However, despite sophisticated off-axis reflective designs, constructing systems with excellent spectral and spatial resolutions, particularly those that can be used for CO 2 gas detection in space-based spectrometers, necessitates maintaining a significant overall instrument size. The metasurface is an innovative optical device that can enable spectrometer miniaturization. For CO 2 spectral detection in the near-infrared spectral range of 1590–1620 nm, this study proposes a device that integrates a grating with a metasurface for off-axis convergence within the relevant wavelength range. The grating facilitates primary spectral dispersion, whereas the metasurface enables off-axis convergence at different wavelengths. Grating–metasurface coupling effectively enhances the spectral resolution of the spectrometer, mitigating any efficiency losses caused by excessive off-axis angles. The proposed strategy exhibits high potential for on-chip integrated photonics and the fabrication of small-size spaceborne spectrometers. [ABSTRACT FROM AUTHOR]