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Compressive sampling matching pursuit (CoSaMP), as a conventional algorithm requiring system sparsity and sensitive to step size, was improved in this paper by approximating the sparsity with adaptive variable step size. In the proposed algorithm (CoSaMP with variable step size abbreviated as Vss-CoSaMP), the idea of approximating sparsity with adaptive step size was borrowed from the sparsity adaptive matching pursuit (SAMP) algorithm to determine the sparsity for the CoSaMP algorithm. The applicability of the CoSaMP algorithm was therefore expanded considerably. On this basis, a step size reduction was added as the iteration termination condition of an orthogonal frequency division multiplexing (OFDM) system. An adaptive variable step size algorithm was then put forward to address the CoSaMP algorithm’s sensitivity to step size. It could realize the required precision at different initial step sizes. A simulation was carried out to analyze the influence of pilot number and step size in an OFDM system on the algorithm. The algorithms, including SAMP, CoSaMP, and Vss-CoSaMP, were compared with two sparse channels, revealing that the Vss-CoSaMP algorithm overcame the problem of the CoSaMP algorithm, that is, the impossibility to forecast the channel sparsity. With the adaptive step size, the proposed algorithm could reach and achieve better accuracy than the CoSaMP algorithm. Additionally, the proposed algorithm was superior over the SAMP algorithm in terms of reconstruction, mean square error (MSE), and bit error ratio (BER).

Covalent organic frameworks (COFs) have emerged as promising renewable electrode materials for LIBs and gained significant attention, but their capacity has been limited by the densely packed 2D layer structures, low active site availability, and poor electronic conductivity. Combining COFs with high-conductivity MXenes is an effective strategy to enhance their electrochemical performance. Nevertheless, simply gluing them without conformal growth and covalent linkage restricts the number of redox-active sites and the structural stability of the composite. Therefore, in this study, a covalently assembled 3D COF on Ti3C2 MXenes (Ti3C2@COF) is synthesized and serves as an ultralong cycling electrode material for LIBs. Due to the covalent bonding between the COF and Ti3C2, the Ti3C2@COF composite exhibits excellent stability, good conductivity, and a unique 3D cavity structure that enables stable Li+ storage and rapid ion transport. As a result, the Ti3C2-supported 3D COF nanosheets deliver a high specific capacity of 490 mAh g−1 at 0.1 A g−1, along with an ultralong cyclability of 10,000 cycles at 1 A g−1. This work may inspire a wide range of 3D COF designs for high-performance electrode materials. [ABSTRACT FROM AUTHOR]

Rechargeable metal‐ion batteries (MIBs) beyond lithium‐ion batteries based on Na, K, Mg, and Al metal electrodes which are earth‐abundant and low‐cost have been developed for large‐scale energy storage systems. MXenes, a type of transition metal carbides, nitrides, and carbonitrides, are discovered as electrodes for MIBs owing to their distinctive properties of large‐scale ultrathin conductive 2D structures, adjustable surface functional groups, regulable interlayer spacing, and high specific surface area. Herein, the properties of MXenes are summarized and the recent progress on MXene‐based materials for diversified MIBs (Li, Na, K, Mg, and Al‐ion batteries) is introduced. The main focus is on the synthesis and applications of MXene‐based materials in MIBs, and their roles in electrochemical reactions. Further examples are provided to demonstrate the significant function of MXene‐based composite as active materials, substrates, collectors, and precursors in different MIBs, highlighting the enormous potential of MXene‐based materials to construct advanced electrodes. This review expects to offer a deep understanding of the relationship between the electrochemical performance and the MXene‐based electrodes, which will promote more novel and creative breakthroughs in the MXenes‐based electrodes for MIBs. [ABSTRACT FROM AUTHOR]

Water deficit episodes impact apple (Malus domestica) productivity through challenging the trees' water status, the influence of extreme high temperature climate has become increasingly prominent in recent years. Rootstocks can bestow specific properties on the fruit trees such as the resistance to drought stress. However, the related hydraulic mechanisms in response to water deficit have not been fully understood. Herein, five rootstocks (SH6, GM256, M9, M26, and MM106) were examined under water limitation. The hydraulic conductance of root (Kroot), shoots (Kshoot), and stems (Kstem‐shoot) in the five rootstocks reduced slightly during drought stress. Whereas the leaf water potential and photosynthesis of five rootstocks decreased dramatically when they were exposed to drought stress. Additionally, the Kshoot and Kstem‐shoot were strongly correlated with the total plant leaf area. Aquaporins (AQPs) involved in the symplastic water transport pathway, the PIP2:1, TIP1:1, and TIP2:2 mRNA levels of all genotypic rootstocks showed significant regulation under drought stress. We examined the relationships among photosynthesis, apoplastic, and symplastic water movement pathways to achieve a comprehensive understanding of rootstocks' hydraulic strategy for improving drought adaptation. The PIP2:1 and TIP2:1 in leaves were more sensitive to root hydraulic conductance in response to drought stress. Furthermore, the coordinated relationship existed in leaf‐specific conductance of shoot (Kl‐shoot) and transpiration rate (Tr) under drought stress in the rootstocks. Overall, the drought resistance in the five dwarfing rootstocks is associated with the rapid re‐establishment of water‐related traits, and the effect of the canopy on the drought resistance in apple rootstocks merits much more attention. [ABSTRACT FROM AUTHOR]

A composite electrode of carbon nanotube CNT@Mn3O4 nanocable was successfully synthesized via direct electrophoretic deposition onto a copper foil, followed by calcination. By uniformly depositing Mn3O4 nanoparticles on CNTs, a nanocable structure of CNT@Mn3O4 can be formed, where the CNT acts as a "highway" for electrons and ions to facilitate fast transportation. Moreover, capacitive energy storage processes play a crucial role in lithium (Li) storage, especially during high scan rates. The significant contribution of capacitance is highly advantageous for the rapid transfer of Li+ ions, which ultimately results in an improved reversible capacity and prolonged cycle stability of the battery. A high specific capacity of 1367 mAh g−1 was maintained over 300 charge–discharge cycles at a current density of 1 A g−1, indicating excellent capacity retention and an extended cycle life. Furthermore, the synthesis process was facile and cost-effective, obviating the need for complex procedures such as mixing and pasting. Additionally, no binder was required, thereby enhancing battery quality efficiency. [ABSTRACT FROM AUTHOR]

The subcritical transition in a two-dimensional channel flow is characterized by the emergence of localized wave packet (LWP). In this paper, the nonlinear nonmodal optimization method is used, and when the target time is long enough the minimal seed, the minimal-energy perturbation triggering the transition is found to be the localized wave packet tilted upstream with energy scaling as R e − 3.8 for R e > 2500. The formation of LWP from a minimal seed includes three stages. First, the disturbance kinetic energy of the minimal seed increases to a local maximum through a transient growth governed by the Orr mechanism, and second, large scale vortex structures are generated due to the nonlinear forcing mainly contributed by the wave components and causes a streamwise symmetry breaking, i.e., a long but weak upstream tail and a strong downstream front are formed. As a result, the perturbation structure approaches the unstable lower branch solution and is attracted and captured at the last stage by the stable upper branch solution of LWP in the phase space. [ABSTRACT FROM AUTHOR]

An easy and scalable synthetic route was proposed for synthesis of a high-energy stable anode material composed of carbon-coated Si nanoparticles (NPs, 80 nm) confined in a three-dimensional (3D) network-structured conductive carbon nanotube (CNT) matrix (Si/CNT@C). The Si/CNT@C composite was fabricated via in situ polymerization of resorcinol formaldehyde (RF) resin in the co-existence of Si NPs and CNTs, followed by carbonization at 700 °C. The RF resin-derived carbon shell (~10 nm) was wrapped on the Si NPs and CNTs surface, welding the Si NPs to the sidewall of the interconnected CNTs matrix to avoid Si NP agglomeration. The unique 3D architecture provides a highway for Li+ ion diffusion and electron transportation to allow the fast lithiation/delithiation of the Si NPs; buffers the volume fluctuation of Si NPs; and stabilizes solid–electrolyte interphase film. As expected, the obtained Si/CNT@C hybrid exhibited excellent lithium storage performances. An initial discharge capacity of 1925 mAh g−1 was achieved at 0.1 A g−1 and retained as 1106 mAh g−1 after 200 cycles at 0.1 A g−1. The reversible capacity was retained at 827 mAh g−1 when the current density was increased to 1 A g−1. The Si/CNT@C possessed a high Si content of 62.8 wt%, facilitating its commercial application. Accordingly, this work provides a promising exploration of Si-based anode materials for high-energy stable lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Although LiFePO4 has the advantages of low raw material cost, excellent safety, and cycle performance, it remains challenging to achieve high-rate and low-temperature long cycling performance. To this context, porous hierarchical carbon-coated LiFePO4/Ti3C2@C composites for lithium-ion battery cathodes are successfully synthesized through in situ solvothermal method confined growth. LiFePO4 nanoparticles are uniformly grown in situ between highly conductive Ti3C2 layers to form a surface-point-surface porous hierarchical conductive network. The accordion-like-structured Ti3C2 can provide fast ion and electron conduction channels and effectively inhibit the agglomeration of the LiFePO4 nanoparticles. These phenomena are beneficial to improve the high-rate performance, cycle stability, and low-temperature performance of LiFePO4/Ti3C2. LiFePO4/Ti3C2@C delivers a high initial discharge capacity of 120 mAh g−1 at 5 C. LiFePO4/Ti3C2@C shows excellent low-temperature performance with discharge capacity of 47.7 mAh g−1 and a perfect capacity retention of 99.2%, over 200 cycles at 1 C under − 20 °C. [ABSTRACT FROM AUTHOR]

A multistage architecture with molybdenum nitride and oxide quantum dots (MON-QDs) uniformly grown on nitrogen-doped graphene (MON-QD/NG) is prepared by a facile and green hydrothermal route followed by a one-step calcination process for lithium ion batteries (LIBs). Characterization tests show that the MON-QDs with diameters of 1–3 nm are homogeneously anchored on or intercalated between graphene sheets. The molybdenum nitride exists in the form of crystalline Mo2N (face-centered cubic), while molybdenum oxide exists in the form of amorphous MoO2 in the obtained composite. Electrochemical tests show that the MON-QD/NG calcinated at 600 °C has an excellent lithium storage performance with an initial discharge capacity of about 1753.3 mAh g−1 and a stable reversible capacity of 958.9 mAh g−1 at current density of 0.1 A g−1 as well as long-term cycling stability at high current density of 5 A g−1. This is due to the multistage architecture, which can provide plenty of active sites, buffer volume changes of electrode and enhance electrical conductivity as well as the synergistic effect between Mo2N and MoO2. [ABSTRACT FROM AUTHOR]

Aiming at improving the method of underwater target recognition, this paper proposes a method to estimate the micro-Doppler spectrum parameters of propeller by using inverse Radon transform, so as to obtain the characteristic parameters of propeller. This paper firstly analyzes the basic concepts of micro-Doppler and inverse Radon transform, then defines the algorithm steps of inverse Radon transform for propeller parameter estimation and carries out simulation. The simulation results show that this method can effectively estimate the propeller rotational speed, blade number, blade length and initial spatial position. [ABSTRACT FROM AUTHOR]

The dry soil layer (DSL), as a typical indicator for degradation in soil water supply capacity and soil drought, could provide important information for land use and reconstruction in semiarid and arid areas. However, the traditional index of DSL assessment neglected the water absorption characteristics and drought resistance of different crops and lacked uniformity and comparability. These may misjudge the occurrence and severity of the DSL and bring uncertainty to land development and vegetation selection. In this study, the DSL severity of the main production zone of apples in the Chinese Loess Plateau was reassessed using new plant physiological indices covering the next 60 years (2020–2080) under four general circulation models. Physiological indices were established based on the response of leaf net photosynthetic (TPN) and transpiration rate (TTR) to soil available water which is the difference between soil moisture and permanent wilting point (n = 113). The environment policy integrated climate (EPIC) model was used to predict future soil water dynamics and drought yield loss (YL). The results showed that TPN and TTR significantly slowed down the accumulation of DSL severity quantitative index (QI, based on thickness moisture and formation depth of DSL) and enhanced the correlation between DSL and YL, which correlation coefficient increased from 0.51 to 0.73 and 0.64. Forming serious DSL (QI >0.5) has slowed from 2040 to 2055 years. Moreover, future climate change accumulatively reduced 9.95%–14.18% of the YL. These results indicated that the traditional method overestimated the environmental contradiction between economic benefits and eco‐hydrology of apple orchards, which could send unreliable messages to policymakers to restrict further development of apple industries. This study emphasized that evaluating DSL based on plant physiological threshold reflected better soil desiccation level and YL, which will contribute to further study of the sustainable development of fragile ecosystems. [ABSTRACT FROM AUTHOR]

Ceftriaxone sodium (CS) is a commonly used antibiotic drug that is frequently detected in surface water and sewage plant drainage. To enhance the adsorption performance of the adsorbent resin for CS, the amino-modified oxygenated ultra-high cross-linked adsorbent resin GNH-01 was prepared by Friedel-Crafts reaction and chemical modification using a low cross-linked polystyrene-divinylbenzene resin (CMCPS) as the backbone. Characterization analysis showed that the resin surface has loose small pores, large specific surface area, and abundant for-vacancy structure, and the surface is rich in oxygen- and nitrogen-containing functional groups. The effects of time, temperature, initial concentration, solution pH and resin dosage on the adsorption effect were investigated with CS as the target pollutant, and the adsorption mechanism was proposed in combination with the adsorption kinetics. The results showed that the best adsorption effect was achieved at an initial concentration of 40 mg/L, a dosage of 1 g/L, a temperature of 30 ° and pH 6.18(Qe=38.62 mg/g, removal rate 96.55%). The kinetic study showed that the adsorption process was in good agreement with the proposed secondary kinetic equation (R²>0.98). CS was both physisorbed and chemisorbed on the resin. The introduction of functional groups enhanced the adsorption performance of the resin due to the charge interaction between the adsorbent and CS. In addition, the hydrogen bonding interaction also increased the adsorption amount of the adsorption process. The Box-Behnken model of response surface method was used to optimize the experimental conditions, and the effects of the factors and their interactions on the adsorption effect were explored to determine the optimal adsorption conditions. Using 5.00% NaOH solution as its desorption solution, the GNH-01 resin was regenerated with good effect and could be reused. This study provides a mechanistic basis and data support for the application in CS wastewater resource treatment. [ABSTRACT FROM AUTHOR]