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In this study the influence of cell tilting on flow dynamics and heat transport is explored experimentally within a rectangular cell (aspect ratios Γ x = 1 and Γ y = 0.25). The measurements are carried out over a wide range of tilt angles (0 β π/2 rad) at a constant Prandtl number (Pr 6.3) and Rayleigh number (Ra 4.42 × 10 9 ). The velocity measurements reveal that the large-scale circulation (LSC) is sensitive to the symmetry of the system. In the level case, the high-velocity band of the LSC concentrates at about a quarter of the cell width from the boundary. As the cell is slightly tilted (β 0.04 rad), the position of the high-velocity band quickly moves towards the boundary. With increasing β, the LSC changes gradually from oblique ellipse-like to square-like, and other more complicated patterns. Oscillations have been found in the temperature and velocity fields for almost all β, and are strongest at around β 0.48 rad. As β increases, the Reynolds number (Re) initially also increases, until it reaches its maximum at the transition angle β = 0.15 rad, after which it gradually decreases. The cell tilting causes a pronounced reduction of the Nusselt number (Nu). As β increases from 0 to 0.15, 1.05 and π/2 rad, the reduction of Nu is approximately 1.4 %, 5 % and 18 %, respectively. Over the ranges of 0 β 0.15 rad, 0.15 β 1.05 rad and 1.05 β π/2 rad, the decay slopes are 8.57 × 10 −2 , 3.27 × 10 −2 and 0.24 rad −1 , respectively.

Alkali metal−sulfur/selenium batteries have attracted much attention because they offer promising high energy density. However, the shuttle effect of the polysulfide dissolutions, poor electrical conductivity, and relatively large volume variations greatly hinder their potential applications. Herein, a novel organic carbon/selenium sulfide (OC/SeS 2 ) composite has been prepared by a one-step in situ method by heating the mixture of commercial polyacrylonitrile (PAN) with selenium sulfide powder in vacuum. The carbonized PAN matrix with an N-doped carbon ring structure could effectively confine SeS 2 in the form of small molecules and regulate its electronic structure. The superior sodium/potassium storage performance of the OC/SeS 2 composite electrodes stems from their rational chemical structure design, including high electrical conductivity of the N-doped organic carbon network and chemical binding with SeS 2 molecules. As a result, the OC/SeS 2 cathode delivers a reversible capacity of 416 mAh g −1 after 700 cycles for sodium-ion batteries and 216 mAh g −1 after 500 cycles for potassium-ion batteries at 0.5 A g −1 , respectively. These findings could open a new window to develop selenium sulfide cathode for metal−sulfur/selenium batteries.

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Summary In order to study the fatigue crack growth (FCG) of self‐compacting concrete, in this paper, the 100 mm × 100 mm × 400 mm specimens with a 30‐mm initial notch were used for three‐point bending test under three different stress levels (0.75, 0.8, and 0.85) and three different loading frequencies (0.5, 1, and 2 Hz), and the acoustic emission (AE) technique was used for monitoring the FCG. According to the results, the changes of the crack mouth opening displacement, the stiffness, and the effective crack length all present three obvious stages with the increase of fatigue cycles. According to Paris law, under the same stress level, the increase of loading frequency results in the increase of fatigue life and the decrease of FCG rate, but the curves of da/dN are approximately parallel under different loading frequencies. Furthermore, the research results of characteristic parameters of AE show that cumulative hits, counts and energy show three stages, which are similar to the change of stiffness, and there is a failure point in the curves of cumulative counts and cumulative energy. The cumulative laws of hits and counts can be used to well describe the FCG, and the b value can be used to analyze the three stages of fatigue fracture. Therefore, the AE technology can be used to monitor the FCG in concrete engineering.

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