Batteries which use dissolved redox-active species, such as redox flow batteries (RFBs), are often considered to be constrained in their operation and energy density by the solubility limit of the redox species. Here, we show that soluble redox active electrolytes can be reversibly cycled deeply into the precipitation regime, permitting higher effective concentrations, energy densities, and lower costs. Using aqueous sodium polysulfide negative electrolytes cycled in the nominal Na 2 S 2 to Na 2 S 4 capacity range as an example, we show that the effective solubility can be increased from 5 M in the fully-dissolved state to as much as 10 M using the precipitation strategy. Stable cycling was observed at 8 M concentration over more than 1600h at room temperature. We also analyze the range of polysulfide electrochemical stability, and characterize the precipitate composition. This enhanced effective concentration approach may be generalized to other redox chemistries that utilize solubilized reactants, and may be especially useful for long-duration storage applications where slow charge-discharge rates allow equilibration of precipitated species with the redox-active solution.
12 kV vacuum circuit breaker (CB) is one of the most important components in the power distribution system. Its mechanical reliability plays a quite important role in the safety and stability of the power system. In order to solve the problem of poor accuracy caused by information redundancy and irrelevant interference in time domain, frequency domain and time-frequency domain features of CB mechanical vibration signal, a new intelligent fault diagnosis method based on ReliefF and PSO-BP neural network is proposed. The ReliefF algorithm is used for automatic feature selection to maximum the correlation between the input and output of the model. In order to get the minimum false alarm rate and the highest detection rate, the top sensitive features are selected. To identify faults more accurately, the initial weights and threshold parameters of BP neural network (BPNN) are optimized by PSO to solve the problem that BPNN tends to fall into local optimum and improve the diagnosis performance. The effectiveness of the proposed method for CB fault diagnosis was verified by orthogonal tests.
The ClO2-/ClO2 electrochemical reaction is shown to be highly reversible in acidic, near-neutral, and alkaline electrolytes while using low-cost carbon electrodes. Its equilibrium potential (0.954 V vs SHE) is pH-independent and enables high aqueous cell voltages of 1.38-2.15 V when used as a positive electrode with negative electrodes such as Zn, Fe, or S. This anion redox couple may enable low-cost aqueous rechargeable batteries free of resource-constrained metals, here demonstrated in prototype Zn-NaClO2 full cells. The rapid reaction kinetics and stability of the ClO2 phase at low temperatures also suggests that chlorite-based batteries may be favorable for applications in cold environments.
A selective fluorescent sensor FNE3 with a high signal-to-background ratio was constructed for microalbumin quantitative detection and drug visualization.
The wave structural characteristics and arrangement have a significant effect on the mass transfer performance and also on the performance stability of the flow field. This study investigates the impact of wave structural characteristics and arrangement on the mass transfer performance and stability of four Proton Exchange Membrane Fuel Cell (PEMFC) models with equal channel volumes but completely different wave structural characteristics. Moreover, the oxygen transfer performance and water drainage performance of four wave structures are investigated using the equivalent mass transfer method and the volume of fluid (VOF) method, respectively, and the non-uniformity coefficient is used as an index to evaluate the performance fluctuation amplitude of the PEMFC during long-term operation. Results indicate that wave structures can effectively improve the mass transfer performance and stability of the PEMFC. In addition, the wave structure arranged longitudinally has the best effect on improving PEMFC performance. Further research has found that the concave wave flow channel has the better mass transfer performance and stability among the longitudinal wave flow channels, and the concave wave flow channel has a 2.48% higher average velocity, 0.23% lower water content, 34.20% higher power density and much better current stability than the convex wave flow channel.
According to highway engineering construction in district the highway construction technology is elaborated form several aspects such as the choosing of raw materials, the determination of construction plan, construction technology's improvement, type selection of mechanical equipment, quality control and so on. In the highway construction the using of new method and equipments enhance the construction quality and this article bring references for highway construction in future.
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With the growing capability of wireless communication and hardware, it is possible to envision networks comprising of a large number of mobile nodes. This kind of networks needs a scalable solution to rapidly deploy and organize these nodes into a functional network. In this paper, we present a clustering scheme based on the Kautz digraph to efficiently solve this problem. We defined nodes identifiers as Kautz strings and used Breadth-First-Search via post-order to travel a well-defined address tree for clusters creation. By formal proof and experimental simulations, our clustering scheme can achieve good performance and effectiveness.
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