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Technical solutions and algorithms for implementation of multi-hop relay in cellular networks are discussed. Multi-hop relay networks have improved capacity and coverage compared to legacy cellular networks.

The dealing/recycling of Ni‐containing wastewater pollution has aroused great attention both from environmental science and resource utilization perspectives. Herein, a classic CaFe‐layered double hydroxide (CaFe‐LDH) stabilizer, which exhibits a super‐stable mineralization efficiency for removing Ni2+ ions with a maximum saturated removal capacity of 321 mg g−1 is prepared. This stabilizer can remove not only 10 000 mg L−1 Ni2+ ions to a few mg L−1, but also 1 mg L−1 Ni2+ ions to 2 µg L−1. Moreover, the CaFe‐LDH shows great mineralization capability for the real Ni‐containing electroplating solution. It is demonstrated by ex situ X‐ray diffraction and extended X‐ray absorption fine structure characterization that the isomorphous substitution of Ca2+ by Ni2+ in the laminate of LDH dominates the mineralization process, and the CaFe‐LDH is transformed to the corresponding NiCaFe‐LDH accordingly. Further application of the resultant NiCaFe‐LDH shows improved electrocatalytic oxygen evolution reaction and photocatalytic CO2 reduction activities. This work paves great way for Ni2+ ion removal from wastewater and utilization of the recycled Ni resource. [ABSTRACT FROM AUTHOR]

Hydrazine (N2H4) is considered as one of the most potential energy storage materials in liquid fuel cells, as it contains high energy and power density, and the high‐efficiency oxidation of N2H4 in fuel cells has drawn great attention. However, the most used catalysts are expensive noble metal catalysts, thus the development of highly efficient non‐noble metal catalysts is crucial to reduce the cost of hydrazine oxidation in practical industry. Herein, we synthesized a series of CoFe‐layered double hydroxides (CoFe‐LDHs) intercalated with different anions via a simple one‐step co‐precipitation method for the electrooxidation of hydrazine. Through altering the intercalated anions of CoFe‐LDHs, the defects and the electronic structure can be well controlled, and the catalytic performance for the electrooxidation of hydrazine were well promoted by using NO3− intercalated into CoFe‐LDH compared with other anions (like Cl−, BO33−, CO32−). This work developed a series of hydrazine electrooxidation catalysts and established the relationship between the intercalated anions, the fine structure of the catalyst and the electrocatalytic performance. [ABSTRACT FROM AUTHOR]

For many years, Beijing has suffered from severe air pollution. At present, fine particulate matter (PM2.5) pollution in the winter and ozone (O3) pollution in the summer constitute serious environmental problems. In this study, the combination of a comprehensive air quality model with particulate matter source apportionment technology (CAMx-PAST) and monitoring data was used for the high-spatial resolution source apportionment of secondary inorganic components (SNA: SO42−, NO3−, and NH4+) in PM2.5; their corresponding precursor gases (SO2, NO2, and NH3); and O3 in the winter and summer over Beijing. Emissions from residents, industry, traffic, agriculture, and power accounted for 54%, 25%, 14%, 5%, and 2% of PM2.5 in the winter, respectively. In the summer, the emissions from industry, traffic, residents, agriculture, and power accounted for 42%, 24%, 20%, 10%, and 4% of PM2.5, respectively. The monthly transport ratio of PM2.5 was 27% and 46% in the winter and summer, respectively. The regional transport of residential and industrial emissions accounted for the highest proportion of PM2.5. The regional transport of emissions had a significant effect on the SO42− and NO3− concentrations, whereas SO2 and NO2 pollution were mainly affected by local emissions, and NH4+ and NH3 were mainly attributed to agricultural emissions. Industrial and traffic sources were two major emission sectors that contributed to O3 pollution in Beijing. The monthly transport ratios of O3 were 31% and 65% in the winter and summer, respectively. The high-spatial resolution regional source apportionment results showed that emissions from Langfang, Baoding, and Tangshan had the greatest impact on Beijing's air pollution. This work's methods and results will provide scientific guidance to support the government in its decision-making processes to manage the PM2.5 and O3 pollution issues. [ABSTRACT FROM AUTHOR]

Air-breathing hypersonic flight vehicles are highly airframe/propulsion integrated, especially the outer and inner flows of the flight vehicles are very complicated and interact strongly with each other, considerable difficulties should be solved rationally in ground testing. Therefore, it is of great necessity to conduct researches on the related experimental methodology. This paper presents a brief analysis of main aerodynamic issues concerned with air-breathing hypersonic flight vehicles as well as associated experimental testing requirements, in which three typical types of experimental testing are focused on, they are performance testing of airframe/propulsion integrated vehicles, experiment of boundary layer transition with trips, and arc-heated facility testing of sharp leading edges. Besides, an overview of wind tunnel research methodologies both in China and abroad is included. This paper also provides critical similarity parameters that need to be ensured for the three types of experiments mentioned above, followed by an influence analysis of those key parameters that are difficult to achieve in ground testing. Based on the testing capability of the current test facilities, three typical wind tunnel experimental methods have been put forward, along with an effective method of acquiring accurate aerodynamic performance of the airframe/propulsion integrated vehicles in particular. The research materials presented should provide a useful guideline on the aerothermal and aerodynamic experimental research on hypersonic flight vehicles. [ABSTRACT FROM AUTHOR]

Fast electron/ion transport and cycling stability of anode materials are key factors for achieving a high rate performance of battery materials. Herein, we successfully fabricated a carbon-coated Mo 2 C nanofiber (denoted as laser Mo 2 C@C) as the lithium ion battery anode material by laser carbonization of PAN-PMo 12 (PAN = Polyacrylonitrile; PMo 12 = H 3 PMo 12 O 40 ). The highly graphitized carbon layer in laser Mo 2 C@C effectively protects Mo 2 C from agglomeration and flaking while facilitating electron transfer. As such, the laser Mo 2 C@C electrode displays an excellent electrochemical stability under 5 A g -1 , with a capacity up to 300 mA h g -1 after 3000 cycles. Furthermore, the extended X-ray absorption fine structure results show the existence of some Mo vacancies in Mo 2 C@C. Density functional theory calculations further prove that such vacancies make the defective Mo 2 C@C composites energetically more favorable for lithium storage in comparison with the intact Mo 2 C.

In this paper, the circulation background, the characteristics of meteorological elements configuration in the boundary layer and the stable meteorological conditions in two precipitation episodes (during February 19-21, 2015 and February 10-13, 2016, respectively) within the Beijing-Tianjin-Hebei region are compared and analyzed. Data from conventional meteorological observations, air quality monitoring, reanalysis and numerical models are used. The results show that before the two precipitation processes in 2015 and 2016, the circulations in the middle and high latitudes of Asia and Europe demonstrate "two troughs and one ridge". Besides, the weather is stable and the pollutant concentration is relatively high. During the precipitation, the circulation is relatively stable for the episode in 2015, and no obvious change in the synoptic system is observed. However, during the episode in 2016, the formation of blocking high and the enhancement of the average ridge in western Asia cause obvious change in the circulation. The simulation results show that significant removal can be detected in both cases, and the PM 2.5 wet deposition fluxes are 647 g/ha and 486 g/ha, respectively, with the removal in 2015 slightly stronger than that in 2016. The removal and dissipation of pollutants is determined by the atmospheric diffusion conditions and the precipitation, especially in the former episode. In the case of February 2016, good diffusion conditions and the precipitation demonstrate obvious PM 2.5 removal effect. In the case of February 2015, the longstanding calm wind with high humidity and the physical quantity configuration in the lower mixed layer lead to the poor pollutant removal., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Authors.)