Three-dimensional CuO nanoflowers were prepared on the surface of flexible Cu foil (CuO@Cu) by a chemical deposition method. The morphology and composition of CuO nanoflowers were examined by scanning electron microscopy and x-ray diffraction spectroscopy, respectively. The electrochemical supercapacitive properties of CuO nanoflowers were investigated by cyclic voltammetry, galvanostatic charge-discharge measurements and electrochemical impedance spectroscopy (EIS). Electrochemical tests indicated that the optimized product showed a high specific capacitance of 284.5 F g À1 at the current density of 0.5 mA cm À2 . EIS analysis indicated that the CuO nanoflowers exhibited good conductivity and very low internal resistance. The cyclability of the electrode demonstrates a 20% loss in capacitance over 1000 cycles. Thus, the results revealed that CuO nanoflower active materials hold the potential for electrochemically stable supercapacitors.
Uma série de compostos simétricos e assimétricos de 2,5-dissubstituídos 1,3,4-oxadiazol foram sintetizados eficientemente a partir do ciclodesidratação das diacilhidrazinas, usando a sílica suportada com o diclorofosfato, como recuperador do ciclodesidratação sem solvente e sob irradiação por microondas. Este processo tem vantagens de ser não corrosivo e nem poluente, apresenta ainda velocidade acelerada, alto rendimento e simples procedimento experimental.A series of symmetrical and unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles were efficiently synthesized from the cyclodehydration of diacylhydrazines by using silica-supported dichlorophosphate as a recoverable cyclodehydrant in solvent-free medium under microwave irradiation. This protocol has advantages of no corrosion, no environmental pollution, accelerated rate, high yield and simple work-up procedure.
The microstructures of FeCoNiCrCu high entropy alloy were investigated under directional solidification. The results showed that only diffraction peak corresponding to a FCC crystal structure was observed in the directionally solidified FeCoNiCrCu alloy. With increasing solidification rate, the interface morphology would grows in planar, cellular and dendrite. Comparing the potentiodynamic polarization of as-cast and directionally solidified FeCoNiCrCu high entropy alloy in a 3.5%NaCl solution, it is clearly reveals that the corrosion resistance of directionally solidified FeCoNiCrCu alloy is superior to that of the as-cast FeCoNiCrCu alloy.
Different forms of δ–MnO2 were constructed with their reduction sites anchored on non-support or other supports. Morphology, composition, and electrochemical properties of MnO2 and its hybrids were analyzed. Results revealed that MnO2/reduced graphene oxide (rGO) layered hybrid showed a higher BET surface area due to the synergistic effect on the introduction of rGO and the morphologic transformation of anchored MnO2. MnO2/rGO–2 exhibits a higher ratio of Mn3+: Mn4+ content, a better adsorption performance for O2, and a lower charge-transfer resistance when respect to pristine δ–MnO2. Compared with other MnO2/rGO hybrids, porous MnO2/rGO-2 layered hybrid exhibits the best electrochemical property: a closer four-electron process (3.95), a more positive E
onset
(0.92 V vs RHE), and superior long-term durability (98.5% after 25,000 s). Especially, a mechanically reusable Mg–air battery with MnO2/rGO–2 cathode catalyst only exhibits a 5% decay for 264 h.
Performance analysis is crucial for designing predictable and cost-efficient sensor networks. Based on the network calculus theory, we propose a flow-based traffic splitting strategy and its analytical method for worst-case performance analysis on cluster-mesh sensor networks. The traffic splitting strategy can be used to alleviate the problem of uneven network traffic load. The analytical method is able to derive close-form formulas for the worst-case performance in terms of the end-to-end least upper delay bounds for individual flows, the least upper backlog bounds, and power consumptions for individual nodes. Numerical results and simulations are conducted to show benefits of the splitting strategy as well as validate the analytical method. The numerical results show that the splitting strategy enables much better balance on network traffic load and power consumption. Moreover, the simulation results verify that the theoretic bounds are fairly tight.
In order to measure the flame height (Lf), the image processing method was employed. The jet flame image was captured by the common-used digital camera. The resolution (C, with the unit of mm/pixel) of the pixel of the digital camera was calibrated by metric scale. The jet flame image was then successively processed by ROI (region of interest) processing, gray processing, binarization and edge detection. Through the image processing, the pixels where the flame root and the flame tip were located was detected. The flame region expressed in pixels can be easily obtained by the difference between the flame root (X1) and the flame tip(X2). The flame height (Lf) was calculated by multiplying the difference in pixels (Lp= X2-X1) with the resolution of pixel (in millimetres per pixel). Using the proposed method, the flame heights of the pulverized coal jet flame at the high temperature air combustion condition were measured. The effect of experimental parameters on the flame heights of the coal jet flame was discussed.
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