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Deep coalbed methane (CBM) has become one of the most significant potential sources of natural gas in China. However, the exploration and development of deep CBM in China is still in an initial stage, and its accumulation-forming characteristics require further study. Therefore, taking the No. 8 deep coal seam in the central-eastern region of Ordos Basin as an example, this study investigated the geologic characteristics of CBM accumulations to establish a numerical model. The evolution of the burial and accumulation of CBM in the area was reconstructed. The modeling results suggest that the No. 8 coal seam experienced continuous subsidence from the Late Cretaceous to the Triassic, alternating subsidence and uplift during the Jurassic, rapid burial throughout the Early Cretaceous, and continuous uplift since the Late Cretaceous. The coal reached its maximum maturity at the end of the Early Cretaceous. Furthermore, CBM generation in the region was divided into four stages of thermal events—biogenic and early thermogenic gas, cracking of light oil into gas, cracking of the remaining kerogen into gas, and hydrocarbon generation ceasing—which accelerated coal maturity and generation. The adsorption capacity presented an overall declining trend prior to the end of the Cretaceous, followed by a rapid increase since the Late Cretaceous. As for adsorption mass evolution, the CBM successively underwent unsaturated minor adsorption, unsaturated rapid-rising adsorption, saturated decreasing adsorption, and saturated rising adsorption. The in-situ gas mass was found to be controlled by a combination of generation, adsorption, and expulsion of hydrocarbons, with its present-day value being 9–29 × 104 t/km2 and the corresponding gas volume per ton of coal being 12–28 m3/t. Moreover, free gas evolution initially showed an increasing trend, followed by a decline, ultimately accounting for 11%–28% of the total gas content.

Abstract Perovskite photovoltaics have been shown to recover, or heal, after radiation damage. Here, we deconvolve the effects of radiation based on different energy loss mechanisms from incident protons which induce defects or can promote efficiency recovery. We design a dual dose experiment first exposing devices to low-energy protons efficient in creating atomic displacements. Devices are then irradiated with high-energy protons that interact differently. Correlated with modeling, high-energy protons (with increased ionizing energy loss component) effectively anneal the initial radiation damage, and recover the device efficiency, thus directly detailing the different interactions of irradiation. We relate these differences to the energy loss (ionization or non-ionization) using simulation. Dual dose experiments provide insight into understanding the radiation response of perovskite solar cells and highlight that radiation-matter interactions in soft lattice materials are distinct from conventional semiconductors. These results present electronic ionization as a unique handle to remedying defects and trap states in perovskites.

Abstract In this paper, we present an effective prismatic mesh generation method for viscous flow simulations. To address the prismatic mesh collisions in recessed cavities or slit areas, we exploit 3D tensors controlled anisotropic volume harmonic field to generate prismatic meshes. Specially, a well-fitting tetrahedral mesh is first constructed to serve as the discrete computation domain of volume harmonic fields. Then, 3D tensors are exploited to control the volume harmonic field that better fits the shape geometry. From the topological perspective, the generation of the prismatic mesh can be treated as a topology-preserved morphing of the viscous wall. Therefore, iso-surfaces in the volume harmonic field should be homeomorphic to the viscous wall while fitting its shapes. Finally, a full prismatic mesh can be induced by estimating the forward directions and visible regions in the volume harmonic field. Moreover, to be compatible with different simulation situations, the thickness of prismatic meshes should be variable. Our approach provides local adjustable thickness of prismatic meshes, which can be achieved by controlling local 3D tensors. The proposed anisotropic volume harmonic field based prismatic meshes are efficient and robust, and a full prismatic mesh can be guaranteed without low quality collisions. Various experiments have shown that our proposed prismatic meshes have obvious advantages in terms of efficiency and effectiveness.

The performance of a metal halide perovskite single crystal is governed by the defect density. Here, the authors report a high quality single crystal perovskite grown by a ligand-assisted solution process with DPSI achieving 23-fold smaller trap density than that without DPSI.

With the advent of big data era and the enhancement of computing power, Deep Learning has swept the world. Based on Convolutional Neural Network (CNN) image classification technique broke the restriction of classical image classification methods, becoming the dominant algorithm of image classification. How to use CNN for image classification has turned into a hot spot. After systematically studying convolutional neural network and in-depth research of the application of CNN in computer vision, this research briefly introduces the mainstream structural models, strengths and shortcomings, time/space complexity, challenges that may be suffered during model training and associated solutions for image classification. This research also compares and analyzes the differences between different methods and their performance on commonly used data sets. Finally, the shortcomings of Deep Learning methods in image classification and possible future research directions are discussed.

Abstract Perovskite quantum dots (QDs) are of interest for solution‐processed lasers; however, their short Auger lifetime has limited lasing operation principally to the femtosecond temporal regime the photoexcitation levels to achieve optical gain threshold are up to two orders of magnitude higher in the nanosecond regime than in the femtosecond. Here the authors report QD superlattices in which the gain medium facilitates excitonic delocalization to decrease Auger recombination and in which the macroscopic dimensions of the structures provide the optical feedback required for lasing. The authors develope a self‐assembly strategy that relies on sodiumd—an assembly director that passivates the surface of the QDs and induces self‐assembly to form ordered three‐dimensional cubic structures. A density functional theory model that accounts for the attraction forces between QDs allows to explain self‐assembly and superlattice formation. Compared to conventional organic‐ligand‐passivated QDs, sodium enables higher attractive forces, ultimately leading to the formation of micron‐length scale structures and the optical faceting required for feedback. Simultaneously, the decreased inter‐dot distance enabled by the new ligand enhances exciton delocalization among QDs, as demonstrated by the dynamically red‐shifted photoluminescence. These structures function as the lasing cavity and the gain medium, enabling nanosecond‐sustained lasing with a threshold of 25 µJ cm–2.

The rock physics model of coalbed methane (CBM) reservoir is significant for the study of CBM content. However, because of the adsorption and dissociation of the CBM reservoir, it is difficult to establish models. In addition, the studies on rock physics modeling of the CBM reservoir are scarce. This paper proposes the basic modeling process. First, the coal rock minerals and methane in adsorbed state are used to calculate elastic parameters of coal rock matrix. Then, the differential equivalent medium model is used to get elastic parameters of the dry rock skeleton. The free methane is mixed with water, and finally the Gassmann equation is applied to obtain elastic parameters of the CBM reservoir model. The study on the CBM reservoir rock physics model's response characteristics has found that there is a sensitive negative correlation between CBM content and P-wave velocity and density. The higher CBM content goes with larger absolute values of intercept, gradient, and seismic amplitude, because their seismic attributes are more sensitive to higher CBM content, whereas the response characteristics are opposite with the lower CBM content. The relationship among the CBM content and absolute values of intercept, gradient, and seismic amplitude in the real data of Qinshui Basin is largely consistent with the response characteristics of the established rock physics model, indicating that the CBM reservoir rock physics model proposed in this paper has a certain feasibility, and the response characteristics of its intercept, gradient, and seismic amplitude are more sensitive to predicting CMB reservoirs.

We propose a newmethod to generate surface quadrilateralmesh by calculating a globally defined parameterization with feature constraints. In the field of quadrilateral generation with features, the cross field methods are wellknown because of their superior performance in feature preservation. The methods based on metrics are popular due to their sound theoretical basis, especially the Ricci flow algorithm. The cross field methods' major part, the Poisson equation, is challenging to solve in three dimensions directly. When it comes to cases with a large number of elements, the computational costs are expensive while the methods based on metrics are on the contrary. In addition, an appropriate initial value plays a positive role in the solution of the Poisson equation, and this initial value can be obtained from the Ricci flow algorithm. So we combine the methods based on metric with the cross field methods. We use the discrete dynamic Ricci flow algorithm to generate an initial value for the Poisson equation, which speeds up the solution of the equation and ensures the convergence of the computation. Numerical experiments show that our method is effective in generating a quadrilateral mesh for models with features, and the quality of the quadrilateral mesh is reliable. [ABSTRACT FROM AUTHOR]

The article discusses the study of the color-pure red light-emitting diodes based on two-dimensional lead-free perovskites. Topics discussed include high-efficiency, lead-free (PEA)2SnI4 perovskite LEDs (PeLEDs) with color coordinates (0.708, 0.292) that fulfill the Rec. 2100 specification for red emitters; and the improved films and the reduced Sn4+ content enable PeLEDs with an external quantum efficiency of 5% and an operating half-life exceeding hours at an initial brightness.

The combined use nanotechnology and medical technologies holds great promise for the development and improvement of various theranostic media. Here, based on a facile hydrothermal method, polyethyleneimine (PEI) functionalized YbPO4:Er up-conversion porous nanospheres (UCPSs) were fabricated, which combined the capabilities of up-conversion luminescence (UCL)/X-ray computed tomography (CT) bimodal imaging and drug delivery. The resulting hydrophilic PEI functionalized YbPO4:Er UCPSs (PEI-UCPSs) showed uniform morphology and high crystallinity. Moreover, PEI-UCPSs possessed high drug loading capacity because of their large specific surface area, which was confirmed by the Brunauer--Emmett--Teller (BET) experiment. Cellular experiments indicated that the PEI-UCPSs had low cytotoxicity and confirmed the performance of the pH-mediated cancer targeting of PEIUCPSs@DOX. Importantly, because of the ideal UCL property and high CT contrast both in vitro and in vivo, YbPO4:Er PEI-UCPSs could be used as an optical probe and a contrast agent for optical and CT imaging, forming a promising platform for simultaneous bioimaging and drug delivery. [ABSTRACT FROM AUTHOR]