increasing requirement of energy density. Among these alternatives to the conventional lithium-ion batteries, lithium-sulfur (Li-S) batteries are of particular interest due to their high theoretical gravimetric energy density (2500 Wh kg −1 ) and natural abundance of sulfur. [1] Selenium (Se), as an element that also belongs to the chalcogen group in periodic table, has been recently proposed as a promising cathode material. [2][3][4][5] In spite of the lower theoretical gravimetric capacity of Se (675 mAh g −1 ), the volumetric capacity of Se (3253 mAh cm −3 ) is comparable to that of S (3467 mAh cm −3 ). Moreover, Se possesses an electronic conductivity that is ≈20 orders of magnitude higher than S, which enables a higher utilization rate, better kinetics and higher loading of active materials in electrode. These advantages make Se a promising candidate of cathode materials for high energy lithium battery.The Li-Se electrochemistry highly depends on the organic electrolyte. In ether-based electrolytes, the Se cathode operated via solidliquid-solid mechanism suffers from the dissolution of reaction intermediates-lithium polyselenide, resulting in the continuous leakage of active materials and shuttle reaction between cathode and anode. [4][5][6] Using the carbonate-based electrolytes that seldom dissolve lithium polyselenide intermediates is a potential strategy to address this problem occurred in Li-Se batteries. [7] However, because of the irreversible reactions between the nucleophilic long-chain polysulfide anions (Se 2− or Se 2− ) and carbonate molecules, the bulk Se cathode even prepared with nanostructured Se active materials is incompatible with these electrolytes. [5,8,9] Recently, it was found that the Se confined in CMK-3 matrix can perform well with carbonate electrolytes. [2] By forming the space-confined Se chains in pores of carbon hosts, the Se molecules can are directly converted to Li 2 Se without the lithium polyselenide intermediates. [10] Moreover, the terminal Se molecules in helical Se x are preferentially attacked by Li + , enabling a higher electrochemical activity than the ring structure. [11] Inspired by this work, various carbon hosts have also been demonstrated for Li-Se batteries. Compared to the mesoporous carbon/Se (MeC/Se) [12][13][14] and hierarchical porous carbon/Se cathodes, [15][16][17] the MiC/Se cathodes such as metal-organic framework-derived MiC, [18][19][20] graphitic MiC Embedding the fragmented selenium into the micropores of carbon host has been regarded as an effective strategy to change the Li-Se chemistry by a solid-solid mechanism, thereby enabling an excellent cycling stability in Li-Se batteries using carbonate electrolyte. However, the effect of spatial confinement by micropores in the electrochemical behavior of carbon/selenium materials remains ambiguous. A comparative study of using both microporous (MiC) and mesoporous carbons (MeC) with narrow pore size distribution as selenium hosts is herein reported. Systematic investigations reveal that the high Se ut...

li length of the wedge k turbulent kinetic energy m 0 captured airflow Δm bleeding massflow m b Δm/m 0 , relative bleeding massflow M 0 Mach number of the freestream M s0 starting Mach number M r0restarting Mach number p 0 static pressure of the freestream p 3 mass-averaged static pressure at the exit of the isolator T 0 static temperature of the freestream T 3 mass-averaged static temperature at the exit of the isolator δ i angle of the wedge ϕ mass-captured coefficient π p 3 /p 0 , static pressure ratio τ T 3 / T 0 , static temperature ratio σ total-pressure recovery coefficient θ A b /A 0 , bleeding rate ε turbulent dissipation rate η kinetic energy efficiency ABSTRACT A series of mixed-compression hypersonic inlets at different bleeding rates were simulated at different freestream conditions in this paper. The unstart/restart characteristics of hypersonic inlets were analysed and the reasons why the unstart/restart phenomenon is in existence is presented. The unstart/restart characteristics of hypersonic inlets at different bleeding rates were given. The effects of boundary-layer bleeding on the performance parameter (masscaptured coefficient, total-pressure recovery coefficient), starting and restarting Mach number of hypersonic inlets were discussed. In conclusion, boundary-layer bleeding can improve the performance parameter of hypersonic inlets, and can reduce the starting and restarting Mach number, and can broad the operation range of the hypersonic inlet. NOMENCLATUREA b area of the bleeding shown in Fig. 13 A 0 area shown in Fig. 13 d difference between M s0 and M r0

Inlet start/unstart detection is one of the most important issues of hypersonic inlets and is also the foundation of protection controls of scramjets. In ground and flight tests, it is inevitably to introduce the sensor noises to the measurement system. How to overcome or weaken the influence of the sensor noises and the outer disturbances is an important issue to the control system of the engine. To solve this problem, the 2D inner steady flow of hypersonic inlets was numerically simulated in different freestream conditions and backpressures, and two different inlet unstart phenomena were analysed. The membership function for hypersonic inlet start/unstart can be obtained by using probabilistic output support vector machine, and the algorithm of multiple classifiers fusion is introduced. The variations of the classification accuracy with the intensity of the sensor noises and the number of the classifier were discussed respectively. In conclusion, it is useful to introduce the algorithm of support vector machine and multiple classifiers fusion to overcome or weaken the influence of the sensor noises on the classification accuracy of hypersonic inlet start/unstart. The number of the practical fusion classifiers needs a tradeoff between the fusion classification accuracy and the complexity of the classification system.

No abstract

Nonaqueous potassium-ion batteries (KIBs) have been regarded as a promising alternative energy system to lithium-ion batteries, due to the abundance of the K resource and unique electrochemical properties. However, exploring suitable KIB cathode materials remains a great challenge, owing to the much larger size of the K ion than that of the Li ion. Here, a series of layered vanadates have been developed as cathodes for KIBs to elucidate the key factors that determine the electrochemical performance of KIBs, including the interlayer distance between adjacent (100) planes (d 100) and preintercalated cations. Compared to NH4V3O8 nanowires with a d 100 of 7.80 Å, (NH4)0.5V2O5 nanowires with a wider d 100 of 9.52 Å show a faster K+ diffusion and much higher reversible capacity. The preintercalation of potassium ions into V-O slabs is also crucial to the stability of the structure of vanadates, which leads to better electrochemical cycling stability in K0.5V2O5 than that in (NH4)0.5V2O5 and NH4V3O8 nanowires. These findings reveal the great potential of the vanadate cathode in future KIBs and provide a new direction to rationally design a stable layered intercalation compound for practical KIBs.