Three-dimensional interconnected graphene network-based high-performance air electrode for rechargeable zinc‒air batteries

Although zinc-air batteries(ZABs)are regarded as one of the most prospective energy storage devices,their practical application has been restricted by poor air electrode performance.Herein,we developed a free-standing air electrode that is fabricated on the basis of a multifunctional three-dimensional interconnected graphene network.Specifically,a three-dimensional interconnected graphene network with fast mass and electron transport ability,prepared by catalyzing growth of graphene foam on nickel foam and then filling reduced graphene oxide into the pores of graphene foam,is used to anchor iron phthalocyanine molecules with atomic Fe-N_(4)sites for boosting the oxygen reduction during discharging and nanosized FeNi hydroxides for accelerating the oxygen evolution during charging.As a result,the obtained air electrode exhibited an ultra-small electrocatalytic overpotential of 0.603 V for oxygen reactions,a high peak power density of 220.2mWcm^(-2),and a small and stable charge-discharge voltage gap of 0.70 V at 10mA cm^(-2)after 1136 cycles.Furthermore,in situ Raman spectroscopy together with theoretical calculations confirmed that phase transformation of FeNi hydroxides takes place fromα-Ni(OH)_(x)toβ-Ni(OH)_(x)toγ-Ni^((3+δ)+)OOH for the oxygen evolution reaction and Ni is the active center while Fe enhances the activity of Ni active sites.

A New Approach for the Health Assessment of River Systems Based on Interconnected Water System Networks

Interconnected river system networks is a national water conservancy strategy in China and focus of research. Here we discuss the classification system, material and energy exchange between rivers and lakes, various dynamic flows and ecological functions of river-lake interconnected relationships. We then propose a novel method for the health assessment of river systems based on interconnected water system networks. In a healthy river system there is ＂material and energy exchange＂ and it is the first and foremost relationship of material and energy exchange between rivers and lakes. There are unobstructed various ＂flows＂ between rivers and lakes including material flows （water, dissolved substances, sediments, organisms and contaminants）, energy flows （water levels, flow and flow velocity）, information flows （information generated with water flows, organisms and human activities） and value flows （shipping, power generation, drinking and irrigation）. Under the influences of na- ture and human activity, various flows are connected by river-lake interconnection to carry material and energy exchange between rivers and lakes to achieve river-lake interactions. The material and energy exchange between rivers and lakes become one of the approaches and the direct driving forces of changes in river-lake interconnected relationships. The benignant changes in river-lake interconnected relationship tend to be in relatively steady state and in ideal dynamic balance.

Performance Analysis of Interconnected Communication Networks

As the means for communication of users in different communication networks and network resource sharing, communication network interconnection has been paid great attention to in recent years. The performance analysis of internetworks is very important in communication network interconnection, for it is the basis for the study of other problems concerned. The main contribution of this paper is a wide and deep study of performance of internetwork, the construction of systematic performance analysis method for arbitrary internetworks, and of queuing model for gateways. In this paper, the performance analysis of internetwork with arbitrary topology is studied for the first time, and a new method - Node Equivalence of Subnetworks (NES) is proposed. The key step of this method is the node equivalence of subnetworks of all kinds, so we first deeply study the node equivalence, and develop two models for node equivalence. Then we study the node equivalence of CSMA/CD and SLOTTED ALOHA systems by using these models. The results show that the NES method is a systematic method which is suitable for performance analysis of any type of internetworks. The proposed equivalence models is usable with good approximation. The queuing model of gateway is first widely studied in this paper. The queuing model for gateways with packet fragmentation and reassembly is studied for the first time and the analysis method, proposed. In the analysis, two modeling tools, Reversed Switched Poisson Process (RSPP) and Switched Determined Process (SDP), are proposed and RSPP/M/1 queue and SDP/D/1 queue, analyzed. A new method-minislot method is proposed and used for the study of SDP/D/1 queue and performance of ATM multiplexer. In this paper, the interdeparture time distribution of ATM network under some input traffic models is studied and the expression, derived. These results can be used for both performance evaluation of ATM network and the performance of ATM networks interconnected with other networks. We also propose an approximate analysis method for queuing networks with priority service and the queuing networks with packet fragmentation and reassembly.

ON THE CONDITIONAL EDGE CONNECTIVITY OF ENHANCED HYPERCUBE NETWORKS

Let G =（V, E） be a connected graph and m be a positive integer, the conditional edge connectivity λ;is the minimum cardinality of a set of edges,if it exists, whose deletion disconnects G and leaves each remaining component with minimum degree δ no less than m. This study shows that λ;(Q;) = 2 n,λ;(Q;) = 4 n-4（2 ≤ k ≤ n-1, n ≥ 3） for n-dimensional enhanced hypercube Q;. Meanwhile, another easy proof about λ;（Q;） = 4 n-8, for n ≥ 3 is proposed. The results of enhanced hypercube include the cases of folded hypercube.

Optimizing oxygen redox kinetics of M-N-C electrocatalysts via an in-situ self-sacrifice template etching strategy

The accessibility and mass transfer between catalytic sites and substrates/intermediates are essential to a catalyst's overall performance in oxygen electrocatalysis based energy devices.Here,we present an“in-situ self-sacrifice template etching strategy”for reconstructing MOF-derived M-N-C catalysts,which introduces micro-meso-macro pores with continuous apertures in a wide range and a central hollowout structure to optimize the electrochemical oxygen redox kinetics.It is realized via one-step pyrolysis of ZIF-8 single crystal epitaxially coating on a multi-functional template of the Fe,Co co-loaded mesoporous ZnO sphere.The ZnO core is reduced during the general pyrolysis of ZIF-8 into M-N-C and acts as a pore former to etch the surrounding ZIF-8 shell into diverse channels anchoring highly exposed Fe and Co-based active sites with edge enrichment.The redesigned catalyst reveals apparent structural benefits towards enhanced oxygen redox kinetics as bifunctional cathode catalysts of rechargeable zinc-air battery compared with the primitive bulk M-N-C catalysts and the mixture of commercial Pt/C and Ir/C.The unique structure-based activity advantages,the omitted template removal step and good template compatibility during synthesis make the strategy universal for the channel engineering of electrocatalysts.

Chinese Water Resource Management and Application of the Harmony Theory

Chinese water resource management （CWRM） has passed through four stages： infancy, initial development, rapid development, and formation. In the last of these stages some problems persist and will affect management performance. CWRM was a decentralised, imperfectly codified and weakly implemented system that lacked a sound market policy, rational water prices, water conservation awareness, technical support and a performance appraisal system. The government of China proposed two new strategies in 2009： the Three Red Lines and the Interconnected River System Network （IRSN）. This paper analyses these two strategies and reflects on new CWRM concepts. Both strategies strive for the sustainable utilisation of water resources and human-water harmony. The concepts, quantification method and application of harmony theory to water resources management is discussed. Applications of harmony theory to water resources management include （i） harmony between humans and nature; （ii） a harmony strategy for water resources management; （iii） a rational allocation model for water resources among different areas and departments based on harmony theory; （iv） harmony-based water allocation issues associated with transboundary rivers; （v） harmony-based interbasin water transfer problems; and （vi） harmony-based control of pollution discharge. We conclude by discussing how harmony theory and its applications provide an appropriate pathway for water resource management in China.

Interconnected graphene scaffolds for functional gas sensors with tunable sensitivity

In this work,the interconnected graphene scaffolds are prepared by three-dimensional(3 D)printing for multifunctional gas detection with tunable sensitivity.The scaffolds with regularly aligned graphene conductive networks exhibit significant mechanical strength and high electrical stability to multi-direction deformation,which can be attributed to the typical core-shell structure of graphene and PVP.The resistance of the free-standing scaffolds can realize the real-time response to H_(2) O and NO_(2),and the relative resistance change to 100 ppm H_(2) O and 100 ppm NO_(2) can reach 2%and 2.5%,respectively.The charge doping of the oxidizing gases is considered to be the main reason for various response sensitivities of the scaffolds with different orthogonal layers,in which the interconnected conductive network can generate a large specific surface area and significantly improving the adsorption of the target gases and the transfer of charge.The controllable fabrication of regular structure has appropriately great potential for further optimizations and applications in gas detection.