Nanostructured Fe 2

In the present work, a method combining arc plasma evaporation of a metal followed by oxidation in air was developed to produce nanosized metal oxide based composites in large scale. As an example, Fe2O3 based nanocomposites were prepared through such a method. With increasing the oxidation temperature, α-Fe2O3 content in the composites increases, while γ-Fe2O3 and residual α-Fe contents decrease. As anode materials for lithium batteries, the electrochemical properties of nanosized Fe2O3 composites were tested. It was found that the anode materials changed to tiny crystallites and then followed by grain growth during the galvanostatic charge/discharge cycles. A capacity rising was observed for the composites obtained at 400°C and 450°C, which was more prominent with increasing the oxidation temperature. Among these composites, the one obtained at 450°C showed the best performance: a specific capacity of 507.6 mAh/g remained after 150 cycles at a current density of 200 mA/g, much higher than that of the commercial nano-Fe2O3 powder (~180 mAh/g after 30 cycles)

Nonlinearity and Fractal Properties of Climate Change during the Past 500 Years in Northwestern China

By using detrended fluctuation analysis (DFA), the present paper analyzed the nonlinearity and fractal properties of tree-ring records from two types of trees in northwestern China, and then we disclosed climate change characteristics during the past 500 years in this area. The results indicate that climate change in northwestern China displayed a long-range correlation (LRC), which can exist over time span of 100 years or longer. This conclusion provides a theoretical basis for long-term climate predictions. Combining the DFA results obtained from daily temperatures records at the Xi’an meteorological observation station, which is near the southern peak of the Huashan Mountains, self-similarities widely existed in climate change on monthly, seasonal, annual, and decadal timescales during the past 500 years in northwestern China, and this change was a typical nonlinear process

Improve TCP performance in Ad Hoc netwoks

Standard TCP misinterpret mobility loss in Ad hoc network as congestion loss, thus, it reduce the TCP performance by invoking unnecessary congestion control action. In this paper, we propose two approaches, simELFN (an variation of TCP-ELFN) and TCP-FSR (an variation of TCP-F). They can distinguish the essence of packet loss and avoid multiple consecutive dupACKs. Analyses and simulations show that they can achieve better TCP performance in Ad hoc network.Keywords: Ad hoc Networks; simELFN; TCP-FSR; TCP performance

Microwave-assisted rapid preparation of hollow carbon nanospheres@TiN nanoparticles for lithium-sulfur batteries

Highly conductive titanium nitride (TiN) has a strong anchoring ability for lithium polysulfides (LiPSs). However, the complexity and high cost of fabrication limit their practical applications. Herein, a typical structure of hollow carbon nanospheres@TiN nanoparticles (HCNs@TiN) was designed and successfully synthesized via a microwave reduction method with the advantages of economy and efficiency. With unique structural and outstanding functional behavior, HCN@TiN-S hybrid electrodes display not only a high initial discharge capacity of 1097.8 mA h g−1 at 0.1C, but also excellent rate performance and cycling stability. After 200 cycles, a reversible capacity of 812.6 mA h g−1 is still retained, corresponding to 74% capacity retention of the original capacity and 0.13% decay rate per cycle, which are much better than those of HCNs-S electrodes

Synthesis of nanoflower-shaped MXene derivative with unexpected catalytic activity for dehydrogenation of sodium alanates.

Surface group modification and functionalization of two-dimensional materials in many cases are deemed as effective approaches to achieve some distinctive properties. Herein, we present a new nanoflower-shaped TiO2/C composite which was synthesized by in situ alcoholysis of two-dimensional layered MXene (Ti3C2(OHxF1-x)2) in a dilute HF solution (0.5 wt %) for the first time. Furthermore, it is demonstrated that it bestows a strong catalytic activity for the dehydrogenation of NaAlH4. The results show that the NaAlH4 containing 10 wt % A0.9R0.1-TiO2/C (containing 90% anatase TiO2 and 10% rutile TiO2) composite merely took ∼85 min to reach a stable and maximum dehydrogenation capacity of ∼3.08 wt % at 100 °C, and it maintains stable after ten cycles, which is the best Ti-based catalyst for the dehydrogenation of NaAlH4 reported so far. Theoretical calculation confirms that this C-doping TiO2 crystals remarkably decreases desorption energy barrier of Al-H bonding in NaAlH4, accelerating the breakdown of Al-H bonding. This finding raises the potential for development and application of new fuel cells

Hydrogenated core-shell MAX@K2Ti8O17 pseudocapacitance with ultrafast sodium storage and long-term cycling.

Sodium-ion batteries are considered alternatives to lithium-ion batteries for energy storage devices due to their competitive cost and source abundance. However, the development of electrode materials with long-term stability and high capacity remains a great challenge. Here, this paper describes for the first time the synthesis of a new class of core-shell MAX@K2Ti8O17 by alkaline hydrothermal reaction and hydrogenation of MAX, which grants high sodium ion-intercalation pseudocapacitance. This composite electrode displays extraordinary reversible capacities of 190 mA h g-1 at 200 mA g-1 (0.9 C, theoretical value of ~219 mA h g-1) and 150 mA h g-1 at 1000 mA g-1 (4.6 C). More importantly, a reversible capacity of 75 mA h g-1 at 10 000 mA g-1 (46 C) is retained without any apparent capacity decay even after more than 10 000 cycles. Experimental tests and first-principle calculations confirm that the increase in Ti3+ on the surface layers of MAX@K2Ti8O17 by hydrogenation increases its conductivity in addition to enhancing the sodium-ion intercalation pseudocapacitive process. Furthermore, the distorted dodecahedrons between Ti and O layers not only provide abundant sites for sodium-ion accommodation but also act as wide tunnels for sodium-ion transport

HiTrust: building cross-organizational trust relationship based on a hybrid negotiation tree

Small-world phenomena have been observed in existing peer-to-peer (P2P) networks which has proved useful in the design of P2P file-sharing systems. Most studies of constructing small world behaviours on P2P are based on the concept of clustering peer nodes into groups, communities, or clusters. However, managing additional multilayer topology increases maintenance overhead, especially in highly dynamic environments. In this paper, we present Social-like P2P systems (Social-P2Ps) for object discovery by self-managing P2P topology with human tactics in social networks. In Social-P2Ps, queries are routed intelligently even with limited cached knowledge and node connections. Unlike community-based P2P file-sharing systems, we do not intend to create and maintain peer groups or communities consciously. In contrast, each node connects to other peer nodes with the same interests spontaneously by the result of daily searches

Facile synthesis of TiN nanocrystals/graphene hybrid to chemically suppress the shuttle effect for lithium-sulfur batteries

Herein, we present a microwave reduction strategy for the synthesis of reduced-graphene-oxide (rGO) supported TiN nanoparticle hybrid (TiN/rGO) under N2 atmosphere. The method involves GO reduction, metal oxide reduction and nitridation reaction in one single step. Due to TiN high conductivity and good interfacial affinity between it and lithium polysulfides (LiPSs), the prepared TiN/rGO-Sulfur (TiN/rGO-S) cathodes demonstrate rapid charge transfer, lower polarization, faster surface redox reaction kinetic and enhanced stability cycling performance than rGO-Sulfur (rGO-S) and TiO2/rGO-Sulfur (TiO2/rGO-S) cathodes. The initial capacity reaches 1197.6 mA h g−1 with a reversible capacity of 888.7 mA h g−1 being retained after 150 cycles at 0.1 C