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Ferroelectric tunnel junctions (FTJs) as the artificial synaptic devices have been considered promising for constructing brain-inspired neuromorphic computing systems. However, the memristive synapses based on the flexible FTJs have been rarely studied. Here, we report a flexible FTJ memristor grown on a mica substrate, which consists of an ultrathin ferroelectric barrier of BiFeO3, a semiconducting layer of ZnO, and an electrode of SrRuO3. The obtained flexible FTJ memristor exhibits stable voltage-tuned multi-states, and the resistive switchings are robust after 103 bending cycles. The capability of the FTJ as a flexible synaptic device is demonstrated by the functionality of the spike-timing-dependent plasticity with bending, and the accurate conductance manipulation with small nonlinearity (−0.24) and low cycle-to-cycle variation (1.77%) is also realized. Especially, artificial neural network simulations based on experimental device behaviors reveal that the high recognition accuracies up to 92.8% and 86.2% are obtained for handwritten digits and images, respectively, which are close to the performances for ideal memristors. This work highlights the potential applications of FTJ as flexible electronics for data storage and processing.

Persulfate-based nonradical oxidation processes (PS-NOPs) are appealing in wastewater purification due to their high efficiency and selectivity for removing trace organic contaminants in complicated water matrices. In this review, we showcased the recent progresses of state-of-the-art strategies in the nonradical electron-transfer regimes in PS-NOPs, including design of metal and metal-free heterogeneous catalysts, in situ/operando characterization/analytical techniques, and insights into the origins of electron-transfer mechanisms. In a typical electron-transfer process (ETP), persulfate is activated by a catalyst to form surface activated complexes, which directly or indirectly interact with target pollutants to finalize the oxidation. We discussed different analytical techniques on the fundamentals and tactics for accurate analysis of ETP. Moreover, we demonstrated the challenges and proposed future research strategies for ETP-based systems, such as computation-enabled molecular-level investigations, rational design of catalysts, and real-scenario applications in the complicated water environment. Overall, this review dedicates to sharpening the understanding of ETP in PS-NOPs and presenting promising applications in remediation technology and green chemistry.

To assess groundwater nitrate contamination and its human health risks, 489 unconfined groundwater samples were collected and analyzed from Zhangjiakou, northern China. The spatial distribution of principle hydrogeochemical results showed that the average concentrations of ions in descend order was HCO3−, SO42−, Na+, Ca2+, Cl−, NO3−, Mg2+ and K+, among which the NO3− concentrations were between 0.25 and 536.73 mg/L with an average of 29.72 mg/L. In total, 167 out of 489 samples (~ 34%) exceeded the recommended concentration of 20 mg/L in Quality Standard for Groundwater of China. The high NO3− concentration groundwater mainly located in the northern part and near the boundary of the two geomorphic units. As revealed by statistical analysis, the groundwater chemistry was more significantly affected by anthropogenic sources than by the geogenic sources. Moreover, human health risks of groundwater nitrate through oral and dermal exposure pathways were assessed by model, the results showed that about 60%, 50%, 32% and 26% of the area exceeded the acceptable level (total health index>1) for infants, children, adult males and females, respectively. The health risks for different groups of people varied significantly, ranked: infants> children> adult males>adult females, suggesting that younger people are more susceptible to nitrate contamination, while females are more resistant to nitrate contamination than males. To ensure the drinking water safety in Zhangjiakou and its downstream areas, proper management and treatment of groundwater will be necessary to avoid the health risks associated with nitrate contamination.

Unmanned Aerial Vehicles (UAVs) play a vital role in military warfare. In a variety of battlefield mission scenarios, UAVs are required to safely fly to designated locations without human intervention. Therefore, finding a suitable method to solve the UAV Autonomous Motion Planning (AMP) problem can improve the success rate of UAV missions to a certain extent. In recent years, many studies have used Deep Reinforcement Learning (DRL) methods to address the AMP problem and have achieved good results. From the perspective of sampling, this paper designs a sampling method with double-screening, combines it with the Deep Deterministic Policy Gradient (DDPG) algorithm, and proposes the Relevant Experience Learning-DDPG (REL-DDPG) algorithm. The REL-DDPG algorithm uses a Prioritized Experience Replay (PER) mechanism to break the correlation of continuous experiences in the experience pool, finds the experiences most similar to the current state to learn according to the theory in human education, and expands the influence of the learning process on action selection at the current state. All experiments are applied in a complex unknown simulation environment constructed based on the parameters of a real UAV. The training experiments show that REL-DDPG improves the convergence speed and the convergence result compared to the state-of-the-art DDPG algorithm, while the testing experiments show the applicability of the algorithm and investigate the performance under different parameter conditions.

Microplastics (MPs) are ubiquitous in the environment and are infiltrating the food chain, causing potential risks to living beings. However, current methods of MP removal from an aqueous environme...

Porous metal nanostructures exhibit excellent catalytic properties due to their high surface-to-volume ratios and abundant catalytic active sites. However, it is still challenging to control nanopores density and structural features in a facile route and the preparation of porous alloy nanorods for catalytic application has not been well explored. In this work, we demonstrate a synthetic strategy to fabricate highly porous Au–Ag alloy nanorods (P-AuAgNRs) by critically dealloying Ag atoms from homogeneous solid Au–Ag alloy nanorods (AuAgNRs). Combining the merits of the tunable plasmonic properties of noble metal nanorods, excellent stabilities of alloys, and superior catalytic activities of porous structures, we use the P-AuAgNRs as a Raman probe for the in situ monitoring of the catalytic oxidation of 3,3’,5,5’ tetramethylbenzidine (TMB) and reduction of 4-nitrothiophenol (4-NTP). We also compare their composition-dependent catalytic activities. The results show that P-AuAgNRs possess superior chemical stability and higher catalytic activity than those of core-shell structures due to synergistic structural and chemical mechanisms. This strategy provides a predictive design approach for the next-generation alloy catalysts with high-performance.

Graphitized nanodiamonds (ND) exhibit outstanding capability in activating peroxymonosulfate (PMS) for the removal of aqueous organic micropollutants (OMPs). However, controversial observation and interpretation regarding the effect of graphitization degree on ND's activity and the role of singlet oxygen (1O2) in OMP degradation need to be clarified. Herein, we investigated graphitized ND-mediated PMS activation. Experiments show that the activity of ND increases first and then decreases with the monotonically increased graphitization degree. Further experimental and theoretical studies unveil that the intensified surface graphitization alters the degradation mechanism from singlet oxygenation to an electron-transfer pathway. Moreover, for the first time, we applied a self-constructed, time-resolved phosphorescence detection system to provide direct evidence for 1O2 production in the PMS-based system. This work not only elucidates the graphitization degree-dependent activation mechanism of PMS but also provides a reliable detection system for in situ analysis of 1O2 in future studies.

e-MnO2 effectively activates peroxymonosulfate (PMS) for the efficient degradation of emerging pollutants. e-MnO2 was synthesized by a facile thermal-treatment method and its long-term stability and efficiency for the elimination of emerging pollutants, including sulfamethoxazole (SMX), sulfachloropyridazine (SCP), sulfamethazine (SMT), ciprofloxacin (CIP), and azithromycin (AZI), from aqueous media were evaluated. e-MnO2 was found to activate PMS more efficiently than α-MnO2, β-MnO2, or δ-MnO2, owing to its high − OH-group content, unique structure, and high surface area. Sulfate (SO4•−), hydroxyl (•OH), and superoxide (O2•−) radicals, as well as singlet oxygen (1O2) were generated, with O2•− acting as the 1O2 precursor. The e-MnO2/PMS system proved to be effective in the pH range of 3.5–9.0 and the rate of SMX degradation was not significantly affected by the presence of inorganic anions or natural organic matter. The proposed pathway for the activation of PMS by e-MnO2 includes inner-sphere interactions between e-MnO2 and PMS, and electron transfer to PMS via the MnIII ↔ MnIV redox cycle, which generates reactive oxygen species. These findings provide new insight into PMS activation by less-toxic metal oxides as catalysts and demonstrate that Mn-based materials can be used to effectively treat water matrices containing emerging pollutants.

We report the fabrication of highly ordered Nb2O5 nanochannel film (Nb2O5-NCF) onto niobium foil by an anodization method. After thermal treatment, the obtained Nb2O5-NCF with rich oxygen vacancies exhibits electrochemical N2 reduction reaction (NRR) activity with an NH3 yield rate of 2.52 × 10−10 mol cm-2 s-1 and a faradaic efficiency of 9.81% at −0.4 V (vs. RHE) in 0.1 mol/L Na2SO4 electrolyte (pH 3.2). During electrocatalytic NRR, the Nb2O5-NCF takes place electrochromism (EC), along with a crystalline phase transformation from pseudo hexagonal phase to hexagonal phase owing to H+ insertion. This results in the reduced NRR activity due to the decrease of oxygen vacancies of hexagonal phase Nb2O5, which can be readily regenerated by low-temperature thermal treatment or applying an anodic potential, showing superior recycling reproducibility.

This paper investigates, for the first time, the thermo-elastic responses of a functionally graded (FG) graphene nanoplatelets (GPLs) reinforced composite (FG-GPLRC) closed cylindrical shell under a temperature field due to steady-state thermal conduction along thickness direction. A comprehensive thermo-elastic model covering various thermal boundary conditions (TBCs) is established. Analytical solutions for both radial stress and hoop stress of the shell are derived based on the plane hypothesis and displacement continuity conditions between the cylindrical shell and hemispherical ends. A parametric study is conducted to investigate the effects of GPL distribution pattern, weight fraction and geometry as well as TBCs on thermal stresses and deformation of the shell. It is found that GPL distributions V and O are preferred patterns for both FG-GPLRC cylindrical shell and hemispherical ends, respectively. The closed FG-X-GPLRC cylindrical shell with higher GPL concentration has higher thermal conductivity consequently higher thermal stresses. The research findings are of practical importance for the applications and design of closed FG-GPLRC shells in a variety of engineering sectors.

Vanadium dioxide (VO2) is known as a typical 3d-orbital transition metal oxide exhibiting the metal-to-insulator-transition (MIT) property near room temperature. However, their electronic applications have been challenged by the quality and uniformity of VO2 thin films. In this work, we demonstrate the high sensitivity in the valence charge of vanadium and the MIT properties of the VO2 thin films to the deposition temperature. This observation indicates the necessity to eliminate the inhomogeneity in the temperature distribution of substrate during the vacuum-deposition process of VO2. In addition, a high thermoelectric power factor (PF, e.g., exceeding 1 μWcm−1K−2) was achieved in the metallic phase of the VO2 thin films and this value is comparable to typical organic or oxide thermoelectric materials. We believe this high PF enriches the potential functionality in thermoelectric energy conversions beyond the existing electronic applications of the current vacuum-grown VO2 thin films.

Developing all-solid-state Z-scheme systems with highly active photocatalysts are of huge interest in realizing long-term solar-to-fuel conversion. Here we reported an innovative hybrid of {110}-oriented CeO2 nanorods with edge-enriched bicrystalline 1T/2H-MoS2 coupling as efficient photocatalysts for water splitting. In the composites, the metallic 1T phase acts as an excellent solid state electron mediator in the Z-scheme, while the 2H phase and CeO2 are the adsorption sites of the photosensitizer and reactant (H2O), respectively. Through optimal structure and phase engineering, 1T/2H-MoS2@CeO2 heterojunctions simultaneously achieve high charge separation efficiency, proliferated density of exposed active sites, and excellent affinity to reactant molecules, reaching a superior hydrogen evolution rate of 73.1 μmol/h with an apparent quantum yield of 8.2% at 420 nm. Furthermore, density functional theory calculations show that 1T/2H-MoS2@CeO2 possesses the advantages of intensive electronic interaction from the built-in electric field (negative MoS2 and positive charged CeO2) and reduced H2O adsorption/dissociation energies. This work sheds light on the design of on-demand noble-metal-free Z-scheme heterostructures for solar energy conversion.

Sewage sludge was subjected to hydrothermal fueling (HTF) (330 °C for 40 min), obtaining hydrochar at 13.5 MJ kg−1. The higher heating value (HHV) of the raw sludge was related to its fatty acid content. The results showed that although the higher heating value (HHV) of the raw sludge was related to its fatty acid content, with the intensification of HTF, the increase in aliphatic/cyclic amino acids determined the production of HHV in the hydrochar. In order to increase the content of fatty acids and amino acids, the sludge was fermented. However, the Bacteroidetes consumed the organic matter too early, which was detrimental to the production of HHV. Therefore, appropriate sludge fermentation is recommended to restrict excessive Bacteroidetes proliferation, decompose lipids to saturated fatty acids, and convert proteins to aliphatic/cyclic amino acids to increase the efficiency of converting sludge to fuel. HIGHLIGHTS Hydrochar of 13.5 MJ/kg produced at 330 °C for 40 min can be used as fuel.; HHV of sludge relates to fatty acids, while HHV of hydrochar relates to amino acids.; Saturated fatty acids, aliphatic & cyclic amino acids play a role in HHV production.; Over-proliferation of Bacteroidetes harmful to HHV production is to be controlled.

As a novel zero-dimensional (0D) material, metal carbides and/or carbonitrides (MXenes) quantum dots (MQDs) show unique photoluminescence properties and excellent biocompatibility. However, due to the limited synthesis methods and research to date, many new features have yet to be uncovered. Here, to explore their new properties and expand biological applications, chlorine and nitrogen co-doped Ti3C2 MXene quantum dots (Cl, N-Ti3C2 MQDs) were designed and synthesized, and their hydroxyl radical scavenging properties were investigated for the first time, revealing outstanding performance. Cl, N-Ti3C2 MQDs was directly stripped from bulk Ti3AlC2 by electrochemical etching, while N and Cl are successfully introduced to carbon skeleton and Ti boundaries in the etching process by electrochemical reactions between selected electrolytes and Ti3C2 skeleton, respectively. The obtained Cl, N-Ti3C2 MQDs exhibit large surface-to-volume ratio due to small particle size (ca.3.45 nm) and excellent higher scavenging activity (93.3 %) and lower usage (12.5 μg/mL) towards hydroxyl radicals than the previous reported graphene-based nanoparticles. The underlying mechanism of scavenging activity was also studied based on the reduction experiment with potassium permanganate (KMnO4). The reducing ability of the intrinsic Ti3C2 structure and electron donation of double dopants are the main contributors to the outstanding scavenging activity.

Addressing microstructure-property relations of polymer nanocomposites is vital for designing advanced dielectrics for electrostatic energy storage. Here, we develop an integrated phase-field model to simulate the dielectric response, charge transport, and breakdown process of polymer nanocomposites. Subsequently, based on 6615 high-throughput calculation results, a machine learning strategy is schemed to evaluate the capability of energy storage. We find that parallel perovskite nanosheets prefer to block and then drive charges to migrate along with the interfaces in x-y plane, which could significantly improve the breakdown strength of polymer nanocomposites. To verify our predictions, we fabricate a polymer nanocomposite P(VDF-HFP)/Ca2Nb3O10, whose highest discharged energy density almost doubles to 35.9 J cm−3 compared with the pristine polymer, mainly benefit from the improved breakdown strength of 853 MV m−1. This work opens a horizon to exploit the great potential of 2D perovskite nanosheets for a wide range of applications of flexible dielectrics with the requirement of high voltage endurance.

Glucose and ball-milled α-Al2O3 mixed powder was hydrothermal treated to synthesize Al2O3/C mixture, which was directly heated to 1700–1750 °C for 10 min holding in N2. Fine and single phase AlON powders were successfully fast prepared by one-step carbothermal reduction and nitridation (CRN). With aggregation of as-purchased α-Al2O3 being effectively disconnected by ball milling, α-Al2O3 particles were perfectly coated with carbon by hydrothermal treatment, which inhibited coalescence of Al2O3 during heating and enabled fast formation of AlON to further shorten holding duration. As a result, one-step fast fabricated pure AlON powder has fine primary particles with weak interconnections. At 170 rpm, powders were ball-milled to D50 ≤ 1.00 μm for 4 h, and D50 = 0.33 μm for 24 h. Moreover, primary particle size is controllable by adjusting holding time, synthesis temperature and heating speed. One-step CRN method provides a practical way to prepare pure AlON powder with the required primary particles.

An imprinted electrospun fiber membrane was developed for the detection of volatile organic acids, which are key components of human body odor. In this study, hexanoic acid (HA) was selected as the target, polymethyl methacrylate (PMMA) was used as the substrate, and colorimetric detection of HA was achieved by a bromocresol purple (BCP) chromogenic agent. The results showed that the morphology of the fiber membrane was uniform and continuous, and it showed excellent selectivity and specificity to HA. Photographs of the color changes before and after fiber membrane adsorption were recorded by a camera and quantified by ImageJ software by the difference in gray value (ΔGray). This method is simple, intuitive, and low cost and has great potential for application in human odor analysis.

Controlling the structural order of nanoparticles (NPs), morphology, and composition is of paramount significance in tailoring the physical properties of nanoassembly. However, the commonly reported symmetrical nanocomposites often suffer an interference or sacrifice of the photophysical properties of the original components. To address this challenge, we developed a novel type of organic-inorganic Janus nanocomposite (JNCP) with an asymmetric architecture, offering unique features such as the precisely controlled localization of components, combined modular optical properties, and independent stimuli. As a proof of concept, JNCPs were prepared by incorporating two photoacoustic (PA) imaging agents, namely an organic semiconducting dye and responsive gold nanoparticles (AuNP) assembly in separate compartments of JNCP. Theoretical simulation results confirmed that the formation mechanism of JNCPs arises from the entropy equilibrium in the system. The AuNP assembly generated a PA images with the variation of pH, while the semiconducting molecule served as an internal PA standard agent, leading to ratiometric PA imaging of pH. JNCP based probe holds great potential for real-time and accurate detection of diverse biological targets in living systems.

High resolution and wide color gamut are two key requirements for novel display technologies. Owing to the distinguishing advantages over conventional displays, such as intrinsic wide color gamut and the possibility to achieve high resolution, quantum dot light-emitting diodes (QLED) have drawn considerable attention in recent years. On the other hand, indium phosphide quantum dots (InP QDs) have shown a great potential as a replacement for cadmium selenide (CdSe) QDs in display applications due to the inherent toxicity of cadmium-based QDs. In this study, we investigate a top-emission InP-based green QLED with optimized angular distribution. By adjusting the electrical and optical architecture, the device exhibits improved properties with a maximum current efficiency of 30.1 cd/A and a narrowed full width at half maxima (FWHM)of 31 nm, which are the best results ever reported to our knowledge.

The vast drylands of the Asian interior were an integral part of a transcontinental network connecting east to west, that acted periodically as corridors and routeways for human migration. However, our understanding of the prehistoric human occupation of and interaction with this inhospitable environment has been hindered by a lack of direct evidence from settlements. Here we present the results of the first systematic study of archaeological material and radiocarbon dates from newly-discovered Bronze Age settlements in the hyper-arid Lop Nur region, in the eastern Tarim Basin. The studied settlement (the North Loulan Settlement, NLS), apparently associated with the prehistoric Xiaohe Culture, which is known from the Xiaohe and Gumugou cemeteries, is especially significant for the study of the prehistoric desert-oasis civilization in the drylands of the Asian interior, because it is quite different from any of the contemporary cultures in the surrounding regions. Based on a synthesis of Bayesian-modeled radiocarbon dates, the age of the NLS falls within the range of ca. 2051–1774 BC. Our field investigations indicate that the inhabitants of the site occupied semi-subterranean/semi-cave dwellings on the upper part of high yardangs, suggesting that they were able to utilize island-like yardangs in order to adapt to lake or wetland terrains. The new chronological framework for the Xiaohe cultural sites indicates that the NLS was the first Xiaohe settlement in the Tarim Basin. The earliest settlers, who were influenced by oriental culture, may have migrated to the NLS along the eastern or northeastern corridors. Later, there was the migration of populations westward along rivers.

In this study, we report an efficient fabrication method for the membrane of a metal-organic framework (MOF) (Kgm-OEt) which is one kind of kagome-type MOF with a two-dimensional (2D) sheet structure having one-dimensional (1D) channels suitable for separation of H2 from other larger gases. The Kgm-OEt seed layer was created on an Al2 O3 substrate using layer-by-layer (LBL) growth, then a membrane was fabricated by secondary growth. The membrane on a 3-aminopropyltriethoxysilane (APTEs)-treated substrate obtained in this method was continuous and defect-free with the crystal orientation suitable for gas transportation, while the membrane grown on an unmodified substrate was loosely packed with unfavorable crystal orientation.

N-Tosylhydrazones have proven to be versatile synthons over the past several decades. However, to our knowledge, the construction of isoxazolines based on N-tosylhydrazones has not been examined. Herein, we report the first demonstrations of [2 + 2 + 1] cycloaddition reactions that allow the facile synthesis of isoxazolines, employing N-tosylhydrazones, tert-butyl nitrite (TBN) and alkenes as reactants. This process represents a new type of cycloaddition reaction with a distinct mechanism that does not involve the participation of nitrile oxides. This approach is both general and practical and exhibits a wide substrate scope, nearly universal functional group compatibility, tolerance of moisture and air, the potential for functionalization of complex bioactive molecules and is readily scaled up. Both control experiments and theoretical calculations indicate that this transformation proceeds via the in situ generation of a nitronate from the coupling of N-tosylhydrazone and TBN, followed by cycloaddition with an alkene and subsequent elimination of a tert-butyloxy group to give the desired isoxazoline., A novel [2 + 2 + 1] cycloaddition of N-tosylhydrazones, tert-butyl nitrite and alkenes was successfully established, which allowed facile construction of a wide range of isoxazolines.

With advances in nanotechnology, nanowires have gained worldwide attention because of their novel properties and promising applications. Among them, silicon nitride (Si3N4) nanowires have attracted increasing attention due to their excellent performance and huge application potential. In this review, various synthesis methods of Si3N4 nanowires are introduced in detail, and then the growth mechanisms are also stated. Subsequently, the novel properties of Si3N4 nanowires including mechanical, optical, electrical, thermal, and wetting performance are highlighted. Applications corresponding to performance are also summarized later, such as composites, field emitters, field-effect transistors (FETs), photodetectors, photocatalysts, and microwave absorbers. Finally, the contents of this article are concluded and outlooks of future research directions are stated. This article reviews the recent advances and provides the prospects and challenges of Si3N4 nanowires.

Rate and product control are crucial for a chemical process and are useful in a wide range of applications. Traditionally, thermodynamic parameters, such as temperature or pressure, have been used to control the chemical reactions. Here, by using the fabrication of a hollow MnxFeyO4 nanostructure as a model system, we report an experimental tuning of both chemical reaction rate and product by a high magnetic field. A 12 times magneto-acceleration of the galvanic replacement (GR) reaction was observed. Moreover, it is first demonstrated that a magnetic field can unravel and accelerate the hidden Kirkendall effect (KE) in addition to the pristine GR reaction. With coaction of magneto-tuned KE and GR, not only the rate but also the composition as well as magnetic property of the products could be modulated. These observations suggest that not only is a magnetic field a variable parameter that cannot be ignored, but also it can effectively control both rate and product in a chemical reaction, which provides a new route for chemical process controlling and shape/composition designing in material synthesis.

Aerobic oxidation of 5-Hydroxymethylfurfural (HMF) to 2,5-Diformylfuran (DFF) using O2 gas represents a sustainable approach for valorization of lignocellulosic compounds. As manganese dioxide (MnO2) is validated as a useful oxidation catalyst and many crystalline forms of MnO2 exist, it is critical to explore how the crystalline structures of MnO2 influence their physical/chemical properties, which, in turn, determine catalytic activities of MnO2 crystals for HMF oxidation to DFF. In particular, six MnO2 crystals, α-MnO2, β-MnO2, γ-MnO2, δ-MnO2, e-MnO2, and λ-MnO2 are prepared and investigated for their catalytic activities for HMF oxidation to DFF. With different morphologies and crystalline structures, these MnO2 crystals possess very distinct surficial chemistry, redox capabilities, and textural properties, making these MnO2 exhibit different catalytic activities towards HMF conversion. Especially, β-MnO2 can produce much higher DFF per surface area than other MnO2 crystals. β-MnO2 could achieve the highest CHMF = 99% and YDFF = 97%, which are much higher than the reported values in literature, possibly because the surficial reactivity of β-MnO2 appears to be highest in comparison to other MnO2 crystals. Especially, β-MnO2 could exhibit YDFF > 90% over 5 cycles of reusability test, and maintain its crystalline structure, revealing its advantageous feature for aerobic oxidation of HMF to DFF. Through this study, the relationship between morphology, surface chemistry, and catalytic activity of MnO2 with different crystal forms is elucidated for providing scientific insights into design, application and development of MnO2-based materials for aerobic oxidation of bio-derived molecules to value-added products.

To explore the correlation between the stress corrosion sensitivity and formation processing for high-strength Al-Zn-Mg alloy, extrusion surface and the matrix were investigated by microstructural characterizations, electrochemistry, and stress corrosion cracking (SCC) tests. Larger, but with low density and discontinuity, grain boundary precipitates (GBPs, − 60 nm and − 3.7% area fraction) and intermetallic particles (IMPs, − 0.5% area fraction) were achieved in the secondary recrystallized (SR) coarse-grained layer compared with the non-recrystallized matrix. The maximum Volta potential differences between the IMPs and Al matrix were about 373 mV, causing the pitting initiation by micro-galvanic effect. The decreased pitting density and the low residual stress in the SR layer reduced the available initiation sites for SCC. Thus, the SR layer acted as a barrier layer to reduce the SCC susceptibility of the extruded Al-Zn-Mg alloy in Cl−-containing environments.

Green bond is a relatively new fixed-income financial instrument created to fund sustainable development projects. Since green and conventional bonds can both bring benefits to investors and given that China has become an important but unique green bond market, it is of great significance to explore the relationship between Chinese green and conventional bond markets. Using the monthly data from 2010 to 2019, we investigate the dependence structure between Chinese green bond market and five conventional bond markets, namely treasury, interbank, financial, high-yield corporate, and enterprise bond markets. The dependence structure is investigated using Gumbel Rotated Gumbel (GRG) copula with Markov-switching that allows for a more thorough analysis. The dependence under extreme market conditions is analyzed using tail dependence coefficients, whereas the dependence under normal market conditions is examined using quantile-based dependence measures. The results show that although the green bond market is positively correlated with all the five conventional bond markets, the degree of positive dependence differs under extreme and normal market conditions.

In the present paper, a novel method was developed to predict the dynamic recrystallization (DRX) behavior during hot rolling based on machine learning in combination with physical models of niobium (Nb) micro-alloyed steels. It has been demonstrated that the comprehensive modeling could accurately predict the DRX behavior under different compositional and processing conditions, which not only exhibited higher precisions but also was in better agreement with physical metallurgical principles than traditional methods.

A ring-width series was developed from Dahurian larch (Larix gmelinii) in the northeastern forest area of Inner Mongolia, China. By analyzing the relationships between tree-ring data and climate records, an August-September mean maximum temperature (T89) series during 1845 and 2012 was reconstructed based on a simple linear regression equation. This reconstructed series explained 40.9% variance of the observed temperature from 1959 to 2012. The reconstructed T89 series was consistent with the historical disaster events caused by extreme climate (e.g., flood, frost disaster, and cold damage). Besides, the temperature comparisons showed that the year in which the warm months (April-September) in northeast China began to warm up has latitude differences. It started with a gradual delay from north to south, starting 1980 in the south region, after 1950 AD in the central region and after 1940 in the north region. Our study can enrich high-resolution temperature series in Northeast China and help clarify the characteristic of recent warming in northeast China.

We report that continuous MOF films with highly controlled thickness (from 44 to 5100 nm) can be deposited over length scales greater than 80 centimeters by a facile, fast, and cost-effective spray-coating method. Such success relies on our discovery of unprecedented perfectly dispersed colloidal solutions consisting of amorphous MOF nanoparticles, which we adopted as precursors that readily converted to the crystalline films upon low-temperature in situ heating. The colloidal solutions allow for the fabrication of compact and uniform MOF films on a great deal of substrates such as fluorine-doped tin oxide, glass, SiO2 , Al2 O3 , Si, Cu, and even flexible polycarbonate, widening their technological applications where substrates are essential. Despite the present work focuses on the fabrication of uniform cobalt-(2-methylimidazole)2 and zinc-(2-methylimidazole)2 films, our findings mark a great possibility in producing other high-quality MOF thin films on a large scale.

Root pile is a new type of pile that improves the load carrying capacity by roots penetrating into soils. To carry out the nonlinear settlement analysis of such a root pile in multilayered soils, the hyperbolicity-based load transfer model is in this paper reformulated to account for the discontinuities between the segments with and without roots. The procedure to determine the model parameters for root piles is presented accordingly. The feasibility and reliability of such a proposed modified hyperbolic model for nonlinear settlement analysis of root piles in multilayered soils are verified by a numerical case and two real experimental cases. The numerical case study shows that the root pile does increase the pile load carrying capacity to some extent. In a parametric study based on this numerical case, it can be found that the bearing capacity of root piles increases along with the increase in the root number, size, depth and the elastic modulus of the surrounding soil. The loading test results on two real root piles sited in Chizhou Yangtze River Bridge, China, are used to further verify the proposed method. Comparing with other analytical methods, it is demonstrated that the proposed method incorporated with the proposed modified hyperbolic model can achieve a better agreement with the measured ones especially in a large loading stage.

The seismic rotational stability analysis of waterfront retaining walls can be found in the existing literature, which adopted the limit equilibrium theory and was based on the moment balance of th...

Stitched composite materials are emerging as a promising material due to their high interlaminar strength, combined performance and light weight. The mechanical properties of stitch yarns are very essential for stitched composite structures. In this study, the tensile behaviors of the twisted fiber yarn in stitched composites were investigated experimentally, analytically and numerically. Two kinds of cross-sectional area of twisted yarn are proposed and discussed. The paper presents an intersecting circle model to describe the cross-section of twisted fiber yarns, and a physics-based theoretical model to predict the effective tensile moduli. The numerical models take into account the cross-sectional characteristic and the twist architecture. The investigation shows that: the sum of each fiber area should be used for experimental analysis; and the cross-sectional area surrounded by the yarn profile should be used for theoretical predictions and finite element (FE) simulations. The relative errors of the prediction method and the FE simulation are less than 2% and 1%, respectively. The friction between the fibers is derived, and the effect of friction on mechanical properties is discussed. The investigation method will serve as a fundamental component of twisted fiber bundle/yarn analysis.

Let f 1 , f 2 be two fixed distinct holomorphic cuspidal Hecke eigenforms of level 1 and respective weights κ 1 , κ 2 with κ 1 ≡ κ 2 ( mod 4 ) . Let L ( s , f 1 ⊗ χ ) , L ( s , f 2 ⊗ χ ) denote the corresponding twisted L-functions associated to f 1 , f 2 twisted by a primitive Dirichlet character χ modulo q. In this paper, we obtain a lower bound for the 2kth moment of the product of two twisted L-functions at the central value for all sufficiently factorable q including 99.9% of all admissible moduli q, i.e., for any natural number k, ∑ ⁎ χ mod q ( L ( 1 / 2 , f 1 ⊗ χ ) L ( 1 / 2 , f 2 ⊗ χ ) ‾ ) 2 k ≫ k ψ ( q ) ( log ⁡ q ) 2 k 2 ( log ⁡ log ⁡ q ) − 4 k 2 , where ψ ( q ) denotes the number of primitive characters modulo q and the asterisk restricts the summation to all primitive characters, which coincides with the remark of Blomer and Milicevic [1] .

Three sesquiterpene-based meroterpenoids psiguamers A–C (1–3) with new skeletons were isolated from Psidium guajava leaves. Compounds (±)-1 and (±)-2 were two pairs of humulene-derived meroterpenoids bearing a rare methylated benzoylphloroglucinol unit, while 3 was an unprecedented adduct of bicyclogermacrene and methylated benzoylphloroglucinol. Their structures were determined based on comprehensive analyses of spectroscopic data, calculated electronic circular dichroism (ECD) spectra, total synthesis, and X-ray crystallographic data. The biomimetic synthesis of (±)-1 and (±)-2 was achieved. Compound (+)-1 exhibited cytotoxic activities against five human tumor cell lines (HCT-116, HepG2, BGC-823, A549, and U251), with IC50 values of 2.94, 9.01, 6.45, 5.42, and 5.33 μmol/L, respectively.

To remove the harmful dye Congo red (CR) from water, porous Fe2O3 Al2O3 composite was designed using a sol-gel and an organic solvent sublimation drying (OSSD) strategy. The composite contained mainly γ-Al2O3, together with various amounts of γ-Fe2O3, α-Fe2O3, and/or AlFeO3 if Fe/Al and heating strategy were properly controlled. It has high specific surface areas ranging from 126 to 210 m2/g. Its pores (10–30 nm) were formed between the homogeneously mixed Fe2O3 and Al2O3 spherical nano particles. Its CR adsorption behaviour was affected by such factors as pH, initial CR concentration and contact time, and had reached a maximum equilibrium adsorption capacity of ~941 mg/g under the neutral pH condition (~7.5) and an initial CR concentration of 100 mg/L. Such adsorption behaviour obeyed the Weber-Morris intra-particle diffusion, pseudo-second-order kinetic and Freundlich isotherm models, suggesting that the adsorption behaviour was kinetically limited by the intra-particle diffusion and chemical adsorption steps and it was likely to be multi-layer adsorption. Furthermore, it also showed a magnetization of around 3.48–5.51 emu/g under the magnetic field (3T), ensuring decent magnetic properties for recycling. This work may provide new insights for the efficient removal of organic dyes.

In this work, solar-heating-induced temperature-based photocatalytic hydrogen evolution reaction (PC-HER) of different photocatalysts (TiO2 P25, g-C3N4, and their loaded Pt) was comprehensively stu...

Replacing conventional metal–N4 moieties with different coordination structures is a promising strategy to tailor the activity and selectivity of single-atom catalysts (SACs). However, for CO2 elec...

The construction of C(sp3)–N bonds via direct radical–radical cross-coupling under benign conditions is a desirable but challenging approach. Herein, the cross-coupling of alkyl and amidyl radicals...

Nitrogen and sulfur co-doped graphene (N,S-G) is activated using ZnCl2, KOH, and CO2 to develop different defects and functionalities. The modified carbo-catalysts are used to activate peroxymonosu...

In this study, neutral salt spray accelerated corrosion test of copper–aluminium composite under 0–125A DC current was carried out under 5% concentration. The effect of corrosion behaviour on copper–aluminium composite by DC current was carried out by a scanning electron microscope (SEM) with energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS), weight-loss method and electrochemical analysis. The results show that the current can accelerate the corrosion rate. Meanwhile, the current temperature effect can reduce the corrosion rate. The current caused directional migration of ions resulting in different corrosion products on positive and negative poles of specimen, and the corrosion degree on the positive pole was more serious. The galvanic corrosion mechanism at the copper–aluminium interface is different from the pitting corrosion mechanism far away from the interface, and the latter is more affected by DC current.

Summary In this study, we used two-photon polymerization 3D printing technology to successfully print the first true pore-scale rock proxy of Berea sandstone with a submicrometer resolution. Scanning electron microscope (SEM) and computed tomography (CT) images of the 3D-printed sample were compared with the digital file used for printing to verify the rock’s internal structures. Petrophysical properties were estimated with a digital rock physics (DRP) model based on the 3D-printed sample's initial pore network. The results show that our 3D-printing workflow was able to reproduce true-scale 3D porous media such as Berea sandstone with a submicrometer resolution. With a variety of materials and geometric scaling options, 3D printing of nearly identical rock proxies provides a method to conduct repeatable laboratory experiments without destroying natural rock samples. Rock proxy experiments can potentially validate numerical simulations and complement existing laboratory measurements.

Based on regional geology, 2D seismic and ocean drilling data, the formation of the Eratosthenes Seamount (ESM) and its surrounding isolated platforms, types of organic reefs and hydrocarbon accumulation conditions in the eastern Mediterranean were analyzed through fine tectonic interpretation and seismic facies study, and the future exploration targets were pointed out. The formation and evolution of the ESM and its peripheral isolated platforms are highly related to the open and close of the Neotethyan ocean. The precursors of the ESM and its peripheral isolated platforms are both horst-type fault blocks formed in the Middle Triassic–Early Jurassic intracontinental rift stage. The ESM and its peripheral isolated platforms underwent continued and inherited carbonate build-ups during the Middle Jurassic intercontinental rift stage, the Late Jurassic–Late Cretaceous Turonian passive drift stage, and Late Cretaceous Senonian–Miocene subduction stage, as well as medium-slight inversion transformation beginning in the Late Miocene Messinian caused by the closure of the Neotethyan ocean. Three types of isolated platforms formed controlled by variant paleo-tectonic settings: the first type is composed of a single patch-like reef controlled by a small-scale and narrow horst-type fault block, the second type consists of a single atoll controlled by a middle-scale and wide horst-type fault block, and the third type is comprised of multiple reef-beach complexes controlled by a large-scale and broad paleo-high. The first two types universally developed in the highs of the alternate sag-uplift structural zones on the south and west of Eratosthenes, and the third type only developed in the ESM. As a result of fluctuation of sea level, two sequences of reef build-ups, i.e. the Middle Jurassic Bajocian–Upper Cretaceous Turonian and the Miocene, developed in the ESM as well as the highs in the alternate sag-uplift structural zones on the south and west of Eratosthenes. Drillings have confirmed that the first two types of isolated platforms with a single patch-like reef and a single circle-like reef have good conditions for natural gas accumulations. The isolated platform of reef-beach complexes in the ESM also has accumulation potentials of natural gas and is worth prospecting.

Thermal compression testing was investigated using the Gleeble 3800 thermal simulator, and thermal deformation behavior of particle-reinforced titanium matrix composites (TMCs) was studied under deformation temperatures of 750–900 °C, strain rates of 0.001–1 s−1, and experimental deformation of 60%. According to obtained flow stress curves, the hot deformation characteristics were analyzed. Based on the Arrhenius hyperbolic sinusoidal model, the constitutive equation at high temperature was established. Based on the theory of dynamic material models, a hot processing map of TMCs at high temperature was established, and the peak region of power dissipation rate and the instability region in the hot processing map were both determined. At the same time, the corresponding microstructures in the peak power dissipation rate and rheological instability regions were observed. The results showed that flow stress decreased with increasing deformation temperature and increased with increasing strain rate. The thermal deformation activation energy of titanium matrix composites was 301.8 kJ/mol. The Ti-6Al-4V/(TiB + TiC) composites possessed only one instability zone under high-temperature compression at a strain of 0.5, with corresponding temperatures at 750–840 °C and strain rates at 0.1–1 s−1. The optimal thermal deformation parameters included corresponding temperatures of 830–880 °C and strain rates of 0.001–0.05 s−1. The microstructures corresponding to optimal hot working parameters in processing maps were more homogeneous than the microstructures in the instability zone, including the distribution uniformity of reinforcement and the degree of dynamic recrystallization, and no instability phenomena including abnormal grain growth, microcracks or intensive fracture of reinforcements were found, indicating that the hot processing map had a positive guiding effect on the option of desirable material thermal-working parameters.

Hydraulic fracturing is a key technology for increasing the permeability of coal seams and improving the extraction effect of coalbed methane. Exploring the parameters that represent the infiltration effect is an essential part of the optimization process of hydraulic fracturing. In this work, based on a similarity principle design, a hydraulic fracturing test was carried out on large raw coal samples using an indoor hydraulic fracturing physical simulation test system. Based on the distribution of primary cracks in the coal samples, the law of crack extension during hydraulic fracturing was studied. The stress variations before and after hydraulic fracturing of the coal seams were monitored, and the stress transfer laws during confining pressure loading and hydraulic fracturing were investigated. The experiment showed that the new fissures in the fracturing process are more likely to extend to the primary fissure development area. When the applied coal body stress exceeds the strength of the coal sample body, the internal cracks in the coal sample are completely penetrated. During this complete penetration, the energy accumulated by pressure water injection is continuously released, and the count detected by the acoustic emission increases sharply. The coal is mainly subjected to compressive stress during the confining pressure loading process, whereas the coal body is mainly subjected to a shear stress during the hydraulic fracturing process. Both the stresses can be transferred through the coal samples. When the stress increase during hydraulic fracturing is greater than the confining load, the overall effect is due to different stresses. As the cracks continue to expand and extend during hydraulic fracturing, the stress transfer effect becomes weaker. Through the exploration of the law of crack extension and stress transmission, this experiment showed that large-scale physical simulation experiments in a laboratory setting can help effectively simulate on-site hydraulic fracturing conditions. The test method and results reported herein provide a reference and basis for the design and optimization of on-site hydraulic fracturing parameters.

The water impurities and corrosion products of the nuclear power plant structure form sludge outside the steam generator tube (SGT), which decreases the energy exchange efficiency resulting in tremendous economic loss and may lead to serious defects posing a threat to the safe operation. Thus, it is critical to efficiently inspect the deposition of sludge outside SGT. This work reveals that the sludge sample of a nuclear power plant has little conductivity and relative permeability about 2.88. Based on the electromagnetic properties of the sludge, we proposed a novel probe with array tunnel magnetoresistance (TMR) sensors for inspection of magnetic field disturbed by the presence of sludge outside the SGT. The principle of the method and the parameters of the probe were studied using a 3D finite element method (FEM) model. It is seen that the signal amplitude of the offset sensor configuration is stronger than that of the probe with non-offset sensor setup and the offset design avoids the disadvantage of non-sensitive to symmetry sludge. Further, it is observed that the sludge inspection performance is better at a lower excitation frequency, i.e. 1 kHz. The TMR sensors provide superior image quality at the low excitation frequency. A prototype probe is manufactured and tested. Sludge samples prepared according to the realistic fouling scenarios in steam generator were tested by the probe. The experimental results validate the feasibility of the probe and demonstrate the advantage of enhancing signal to noise ratio (SNR) of imaging by suppressing the background signal of tube support plate structure under the low excitation frequency.

Hydrophobic interactions mediated by nonpolar molecular fragments in water are influenced by local chemical and physical contexts in ways that are not yet fully understood. Here, we use globally amphiphilic (GA) β-peptides (GA-Lys and GA-Arg) with stable conformations to explore if replacement of β3-homolysine (βLys) with β3-homoarginine (βArg) influences the hydrophobically driven assembly of these peptides in bulk aqueous solution. The studies were conducted in 10 mM triethanolamine buffer at pH 7, where both βLys (ammonium) and βArg (guanidinium) side chains are substantially protonated. Comparisons of light scattering measurements and cryo-electron micrographs before and after the addition of 60 vol% MeOH indicate very different outcomes of the hydrophobically driven assembly of AcY-GA-Lys versus AcY-GA-Arg (AcY denotes an N-acetylated-β3-homotyrosine (βTyr) at each N-terminus). Nuclear magnetic resonance and analytical ultracentrifugation confirm that AcY-GA-Lys assembles into large aggregates in aqueous buffer, whereas AcY-GA-Arg at comparable concentrations forms only small oligomers. Titration of AcY-GA-Arg into aqueous solutions of AcY-GA-Lys reveals that the driving force for AcY-GA-Lys association is far stronger than that for AcY-GA-Arg association. We discuss these results in the light of past experimental observations involving single molecule force measurements with GA β-peptides and hydrophobically driven dimerization of conventional peptides that form a GA α-helix upon dimerization (but do not display the Lys versus Arg trend predicted by extrapolating from the earlier AFM studies with β-peptides). Overall, our results establish that the identity of proximal cationic groups, ammonium versus guanidinium, profoundly modulates the hydrophobically driven self-assembly of conformationally stable β-peptides in bulk aqueous solution.

Hydrothermal treatment (HT) is a promising technology to enhance anaerobic digestion (AD) of municipal sludge. However, the capacity of pre- and inter-stage HT (i.e., HT-AD and AD-HT-AD, respectively) to enhance the digestibility of municipal sludge has not been sufficiently explored. This study compared the efficacy of pre- and inter-stage HT performed from 90 to 185°C to enhance methane production from a mixture of primary sludge and waste activated sludge using mesophilic (35°C) biochemical methane potential tests. In both configurations, sludge solubilization increased with HT temperature. HT-AD, and to a greater extent AD-HT-AD, increased the release of ammonium nitrogen. Even though HT at 185°C dramatically increased sludge solubilization, the overall specific methane yield with HT at 185°C was lower than or comparable to that at lower HT temperatures in the HT-AD and AD-HT-AD configurations, respectively. Up to 155°C HT, the overall specific methane yield with the HT-AD configuration was higher by 4.9%-8.3% compared to the AD-HT-AD configuration. However, when the HT energy was considered, compared to the control (i.e., AD of sludge without HT), the net energy gain (ΔE) decreased as the HT temperature increased, becoming negative at an HT of 185°C. The AD-HT-AD configuration resulted in a higher overall volatile solids destruction (by 8.1 to 20.1%). In conclusion, for municipal sludge with a relatively high ultimate digestibility, as was the case in this study, HT-AD is preferable as it has a smaller footprint and is easier to operate than the AD-HT-AD configuration. However, given the significantly higher volatile solids destruction in the AD-HT-AD configuration, compared to the HT-AD configuration, AD-HT-AD may be more beneficial considering post-AD sludge handling processes. PRACTITIONER POINTS: Hydrothermal treatment (HT) increased the rate and extent of methane production from municipal sludge mixture. 155°C was the optimal temperature for either pre- or inter-stage HT to increase biogas production. Pre- and inter-stage HT resulted in comparable ultimate methane production. Pre-stage HT is preferable to inter-stage HT (smaller footprint, easier to operate). AD-HT-AD resulted in significantly higher volatile solids destruction compared to the HT-AD configuration.

The ancient Loulan kingdom in northwest China was a key transportation hub along the ancient Silk Road. What determined the burial practice in Loulan is a mystery as many of the tombs were constructed atop approximately 20-m-high yardangs in the north of the ancient city of Loulan. This paper includes the first attempt to provide a geoarchaeological perspective on this problem. A representative section (3.8 m) from the tomb area was investigated using optically stimulated luminescence (OSL) dating and grain size analyses to reconstruct environmental changes. Results show that the section was formed during Loulan's early development stage (approximately from the second century BC to the first century AD) in the wake of lacustrine-fluvial hydrology fluctuation. Radiocarbon dating suggests that the tombs were also constructed during the period. Therefore, our reconstruction indicates that the landscape of the burial area was dominated by extensive island-like yardangs within a lake or wetland. We argue that the burial practice was influenced by the yardang's location high above the wetland/flooded area. People would generally prefer cemeteries in the area to avoid disturbance to the bodies from the fluctuating water table.