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Efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional electrocatalysts have been pursued for decades. Meanwhile, single metal atoms embedded in a two-dimensional material substrate (2D-substrate) have emerged as an outstanding catalyst. Herein, we report on computational ORR/OER efficiencies of a series of single atom catalyst systems, with a nitrogen-doped boron phosphide monolayer (N3-BP) as the 2D-substrate, and with Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rh, Pd, Ir, and Pt as the single-atom subject (M). In brief, our density functional theory results show that the overpotentials for ORR/OER are low for CoN3-BP, NiN3-BP, and PtN3-BP, with {ηORR; ηOER} of {0.36; 0.42 V}, {0.29; 0.44 V}, and {0.32; 0.25 V}, respectively. The relevant attributes such as the chemical stability of the 2D-substrate in the ORR/OER environments, immobilization of the single-atom subject on the 2D-substrate, and mechanisms of the ORR/OER activity and the catalyst recovery on the MN3-BP catalysts were carefully examined. The key to the comparative study is how the electronic states of the reaction center near the Fermi level of the catalytic system match the frontier orbitals of ORR/OER reaction intermediates. In short, our method predicts the ORR/OER catalytic efficiencies of novel catalysts via a single-atom/2D-substrate design strategy.

A sparse reconstruction algorithm for near-mainlobe jamming suppression is proposed in this paper, which can suppress the mainlobe towed jamming (MTJ) effectively and extract the distance and direction of the target. Firstly, the orthogonal matching pursuit (OMP) algorithm is adopted to estimate the MTJ information containing direction, amplitude and phase, then the jamming reconstruction is obtained. Secondly, the MTJ can be suppressed when the received signal is eliminated the jamming is reconstructed. Thirdly, the sparse Bayesian learning is employed to obtain the information of the target and jamming residue, such as direction and distance. Usually, the target only occupies 2 or 3 range units in a certain direction, while the jamming occupies all range units in a certain direction. Hence, the target and jamming residue can be distinguished by this priori knowledge. Hence, the target information can be obtained.

Redox-responsive core-crosslinked copolymers were synthesized based on poly(e-caprolactone) (PCL) and poly(ethylene glycol) (PEG) via “A~A + B3~” strategy and Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. It is a feasible method for large-scale preparing redox-responsive core-crosslinked copolymers by crosslinking PCL-based disulfide bond-containing A-PCL-A macromonomers and PEG-based telechelic B3~ macromonomers. The core-crosslinked copolymers can form stable micelles through self-assembly in aqueous solution and exhibit reduction-cleavage responsibility in reductive medium. Further, their doxorubicin (DOX)-loaded micelles exhibit desirable reduction-triggered release performance in vitro. The cellular proliferation inhibition against A549 cells indicates their enhanced anticancer activity in comparison to free DOX. The redox-responsive core-crosslinked copolymers are expected to be used in smart delivery vehicles of anti-cancer drugs.

China is the world largest producer and consumer of rice. With stagnant yields, resource depletion, labor shortages direct-seed rice (DSR) is gaining the interest of rice producers in southern China. This study investigates the impact of the adoption of DSR on rice yield and net rice income of Chinese farmers. We use plot-level data from four provinces in southern China. Results indicate that rice yield increase by 3.1% for DSR adopters and by 0.7% if puddled transplanted rice (PTR) producers adopted DSR method. Finally, we find that net rice income increased by 66% if PTR method plots switched to DSR method. Adoption of DSR should be encouraged by policymakers.

In this paper, a sparse estimation algorithm for the radar target range and direction under strong mainlobe blanket jamming conditions is presented. This algorithm can effectively suppress multiple strong mainlobe blanket jammings (multi-MLJs) and extract the information about target distance and direction. First, the space domain adaptive processing for the received signal in each row (or column) is adopted to suppress multi-MLJs. Second, the sparse Bayesian learning is employed to obtain the information of the target distance and elevation (or azimuth). In addition, the proposed method still has an effective performance under the error condition and the applicable conditions of the new algorithm based on the performance analysis are provided in this paper.

Complex fracture systems including natural fractures and hydraulic fractures exist in shale gas reservoir with fractured horizontal well development. The flow of shale gas is a multi-scale flow process from microscopic nanometer pores to macroscopic large fractures. Due to the complexity of seepage mechanism and fracture parameters, it is difficult to realize fine numerical simulation for fractured horizontal wells in shale gas reservoirs. Mechanisms of adsorption–desorption on the surface of shale pores, slippage and Knudsen diffusion in the nanometer pores, Darcy and non-Darcy seepage in the matrix block and fractures are considered comprehensively in this paper. Through fine description of the complex fracture systems after horizontal well fracturing in shale gas reservoir, the problems of conventional corner point grids which are inflexible, directional, difficult to geometrically discretize arbitrarily oriented fractures are overcome. Discrete fracture network model based on unstructured perpendicular bisection grids is built in the numerical simulation. The results indicate that the discrete fracture network model can accurately describe fracture parameters including length, azimuth and density, and that the influences of fracture parameters on development effect of fractured horizontal well can be finely simulated. Cumulative production rate of shale gas is positively related to fracture half-length, fracture segments and fracture conductivity. When total fracture length is constant, fracturing effect is better if single fracture half-length or penetration ratio is relatively large and fracturing segments are moderate. Research results provide theoretical support for optimal design of fractured horizontal well in shale gas reservoir.

Basis pursuit of sparse decomposition is adopted to discriminate and identify the target echo with two kinds of mainlobe jamming named time-delay repeater jamming and smeared spectrum (SMSP) jamming, which can produce multiple false targets. The main idea is to extract their pulsed differences. The signal model is first transformed to an underdetermined matrix equation, the dictionary is constructed by the function form of the target echo, and then the matrix equation is solved by replacing the l 0 norm problem via the l 1 norm problem. The identification of time-delay repeater jamming and the target echo is by the difference of the pulse width. Identifying SMSP jamming and the target echo is by the difference of the chirp rate. The proposed algorithm is particularly relevant to the case that the signals are overlapped. Finally, simulation results demonstrate the efficacy of the proposed method and they show that the method outperforms the conventional time–frequency representation method.

Inspired by natural materials, sacrificial bonds have been successfully applied in the design of flexible shape memory polymers (SMPs). However, thermal oxidative stability of these SMPs is worth to be concerned because it is inevitable for the applications. Herein, model shape memory rubber composite was prepared by adding ZnCl2 and sulfur into nitrile butadiene rubber (NBR). Dual crosslinking networks with sacrificial bonds, composed of Zn2+-CN coordination bonds, was constructed in NBR composite, which endowed itself a good shape memory property in air, water and even oil. Through 20-day thermal oxidation at 100 °C, Zn2+-CN coordination bonds were partially dissociated and ZnCl2 agglomerations were gradually dissolved into rubber matrix. The growth of covalent crosslinking density accompanied with chains scission during aging. Excessive growth in covalent crosslinking density and the loss of coordination bonds induced a rapid ductile-brittle transition of NBR composite in mechanical tests. Ruptured chains developed an additional relaxation with Zn2+ ions to broaden glassy transition of rubber matrix through aging, which increased the shape fixing ratio of NBR composite and descended its recovery ratio. Moreover, the shape recovery processes were obviously slowed down owing to aging. These novel findings reveal that thermal-oxidative aging processes change the architecture of dual crosslinking networks and affect shape memory behaviors of modeled rubbers which are practically useful for the lifetime of their products.

In this paper, to suppress the digital radio frequency memory (DRFM) false target jamming, we introduce a jamming recognition-based method. The method first extracts mixed target and jamming samples, then computes adaptive weights by subsections of mixed samples, finally recognizes the jamming samples according to the adaptive power residue (APR) criterion. Numerical examples are provided which verify the effectiveness of the proposed method.

The basis pursuit algorithm of sparse decomposition is used to recover and discriminate the target echo and the jamming signal which have different time-delay and pulse width. The key is to construct an atomic dictionary. The recoveries in both the noiseless case and in the noisy case are considered. The noiseless case adopts linear programming. The noisy case adopts quadratic programming. Since the recovery is sensitive to the noise, the solution to the noisy case is unstable. More importantly, densely false targets, including the case that two signals are overlapped in the temporal domain, can also be recovered. Finally, simulations verifies the results.

It is common to use Moving Target Detection (MTD) to compete with passive clutter. When there are jamming and clutter at the same time, it is necessary to apply Adaptive Sidelobe Canceller (ASLC) before MTD. However, the weight noise caused by ASLC brings about the large surplus of clutter in the MTD process, which affects the performance of MTD. Therefore, two methods, diagonal loading based (DL-based) ASLC and MTD processing ahead of ASLC, are proposed in this paper to solve this problem. Simulation results indicate that the proposed methods can improve the performance of MTD.