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• Porous single-crystal NTP micro-sized framework coated with conductive carbon nano-layer (NTP@C) is designed. • The carbon coating enhances conductivity of NTP@C, and protects it from O2 erosion serves as a protective phase. • Regulations in both the dissolved O2 content and pH values of aqueous Na2SO4 electrolyte are conducted. • The NTP@C displays superb electrochemical properties in the optimized Na2SO4 electrolyte (N2 purged and pH = 8.0). • The NTP@C based full devices exhibit high energy density and cycling stability with the optimum electrolyte. NASICON-type NaTi 2 (PO 4) 3 (NTP) is one of the most competitive anode materials for aqueous sodium-ion batteries (ASIBs), thanks to its unique three-dimensional open framework structure, high ionic conductivity and good chemical stability. However, the low electrical conductivity of NTP and the oxygen reduction induced side reactions seriously affect its practical applications. To well address the above issues, the synergistic regulation strategy in electrode materials and electrolytes is motivatively put forward. The porous single-crystal NTP micro-sized framework coated with conductive carbon nano-layer (denoted as NTP@C) is designed with significantly improved electronic conductivity and structural stability. With further regulations in both the dissolved oxygen content and pH values of aqueous Na 2 SO 4 electrolyte, the enhanced reversible capacities and cyclic stability especially at high rates are achieved by effectively alleviating side reactions. As a result, the fabricated NTP@C anode is optimized with a high-rate capability and remarkable long-duration electrochemical stability in the N 2 -purged aqueous Na 2 SO 4 electrolyte with pH = 8.0. Furthermore, the assembled NTP@C//Na 0.44 MnO 2 ASIBs exhibit high energy density of ∼40.0 Wh kg‒1 along with excellent cycling stability. More significantly, our work provides an insightful guideline for rational construction of other advanced aqueous rechargeable batteries. Hierarchical porous single-crystal NaTi 2 (PO 4) 3 @C framework is first designed, and exhibits enhanced electrochemical Na+-storage properties in half/full cells with detailed regulation in both the dissolved oxygen content and pH values of electrolytes, when evaluated a competitive anode platform for aqueous sodium-ion batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

The effects of the exit convergent ratio on the propagation behavior (i.e., initiation processes and propagation characteristics) of rotating detonations utilizing liquid kerosene have been experimentally investigated by varying the exit convergent ratio from 1 to 10 (i.e., CR = 1, 1.25, 1.67, 2.5, 5 and 10) and the mass flow rate of oxidizer. Oxygen-enriched air with an oxygen volume fraction of 40% and kerosene have been used as oxidizer and fuel, respectively, which are supplied into the combustion chamber through an atomizer-slit configuration. Experimental results indicate that rotating detonation waves can be initiated and propagate with different propagation modes under different exit convergent ratios. Three different propagation modes have been obtained, i.e., a deflagration mode, an ignition failure mode and a stable detonation mode. Moreover, the results show that the convergent ratio significantly influences the propagation modes, and when the combustion chamber outlet with a smaller convergent ratio is employed, stable rotating detonation waves can be obtained easily. In addition, it is observed that the time of establishment of the detonation wave increases with the convergent ratio. • Effects of the exit convergent ratio on the propagation characteristics have been studied. • Three fundamental operating modes have been observed at different conditions. • Stable rotating detonations can be obtained easily with a smaller convergent ratio. • The influence of the exit convergent ratio on the initiation time has been investigated. [ABSTRACT FROM AUTHOR]

Nanopore electrochemical sensors have been developed to detect various emerging pollutants at the single-molecule level with high sensitivity and specificity due to their high resolution in past three decades, which is of great significance for emerging hazardous pollutants control. Electrochemical detection methods based on nanopore technology are primarily divided into two categories: resistive-pulse and rectification sensing. The main detection mechanism of the resistive-pulse method is based on the volume exclusion effect generated when the analyte enters through the nanopore, and it involves three primary detection strategies. The first approach involves nanopore technology for direct pollutant detection, where pollutant structure and concentration information is assessed based on nanopore-generated ionic current's blockade strength, duration, and frequency. The second strategy relies on weak intermolecular interactions when direct detection of pollutants is challenging. Molecular probes interact with target molecules to enhance detection sensitivity and achieve specific recognition. The third strategy is based on the biological/chemical reaction of pollutant molecules, through indirect detection method to achieve specific detection of target pollutant molecules. Additionally, relies on changes in surface charge polarity or nanopore spatial structure induced by the analyte molecules to achieve the detection of target molecules within the nanopore. This work demonstrates the research progress achieved in the application of nanopore electrochemical sensing technology to high-sensitivity detection of hazardous pollutants, utilizing the unique confined spatial characteristics of nanopores, combined with biorecognition techniques and principles of electrochemical reactions. [ABSTRACT FROM AUTHOR]

Abstract To explore an effective way for the nozzle design of a pulse detonation rocket engine (PDRE), theoretical and experimental researches have been carried out. The exhaust process and optimal converging/diverging area ratios of a nozzle were theoretically analyzed. Pressure and velocity fluctuations of the exhaust flow were considered to be the major issues. A fluidic solution which employs nitrogen flows in the nozzle throat and divergent section has been tested. The fluidic nozzle is able to adjust the effective area ratios according to the incoming flow. The effective convergent area ratio varied from 2.0 to 2.2, and the divergent one varied from 5.0 to 1.8. It is proved that the fluidic nozzle effectively improved the propulsive performance of the engine. A maximum average thrust increase of 137.8% was obtained in proper conditions. Highlights • A key-points nozzle design method for the PDRE was carried out. • Effect of a fluidic nozzle on the propulsive performance of a PDRE was validated. • Thrust and specific impulses were discussed in details. [ABSTRACT FROM AUTHOR]

To reduce hardware complexity and increase operating frequency, a simplified double-frequency scheme has been developed to obtain high-frequency detonations for pulse detonation rocket engines based on the valved and valveless schemes. This study focuses on characteristics of this simplified scheme. The critical points where detonations transit to deflagrations are considered at different operating conditions to clarify the lower boundaries of stable operations. Experimental results indicate that an ideal buffer zone may not be formed similar to the traditional valved schemes. Comparisons with the valveless scheme without the purge process show that the upper limits of oxidizer percentages are consistent to ensure stable operations, which implies that the present scheme operates potentially as the valveless mode. Detailed studies on the employed solenoid valves and impacts of retonations on the upstream passages demonstrate that solenoid valves are not able to realize intermittent supply control effectively. It is concluded that practical operations utilizing solenoid and rotary valves to control periodic supplies may also operate under a valveless scheme actually with a different upper limit of oxygen percentage in oxidizer. [ABSTRACT FROM AUTHOR]

To provide preferable operating conditions for biomass carbonization, the carbonization properties of maize straw, cotton stalk and poplar wood were investigated in nitrogen atmosphere by segmented heating process at different final temperatures of 300–800 °C for 1 h. Segmented heating carbonization contributes to higher ratio of mass and energy yields than a constant temperature/linear heating process with final temperature of around 300 °C. The fuel properties and characteristics of raw and carbonized biomass were analysed systematically. Increasing carbonization temperature, the fuel ratios of the obtained chars rise exponentially, and the profile of atomic H/C ratio versus atomic O/C ratio approximately decreases linearly. There are small changes of sulphur and nitrogen content in the chars. To provide an estimation method for higher heating value for torrefied/carbonized biomass, a new correlation is proposed based on ultimate analysis. The correlation is H H V = 19.9579 + 0.1284 C + 0.3355 H − 0.1209 O − 1.3836 N − 5.4680 S , which is validated through experimental data. The correlation has a low level of errors, that the correlation efficient, mean absolute error, average absolute error and average bias error are 0.971, − 6.75 × 10 − 6 MJ, 1.2% and 0.02% respectively. This work will make a contribution to the biomass pretreatment process. [ABSTRACT FROM AUTHOR]