UAV-aided cellular networks,millimeter wave(mm-wave) communications and multi-antenna techniques are viewed as promising components of the solution for beyond-5G(B5G) and even 6G communications.By leveraging the power...UAV-aided cellular networks,millimeter wave(mm-wave) communications and multi-antenna techniques are viewed as promising components of the solution for beyond-5G(B5G) and even 6G communications.By leveraging the power of stochastic geometry,this paper aims at providing an effective framework for modeling and analyzing a UAV-aided heterogeneous cellular network,where the terrestrial base stations(TBSs) and the UAV base stations(UBSs) coexist,and the UBSs are provided with mm-wave and multi-antenna techniques.By modeling the TBSs as a PPP and the UBSs as a Matern hard-core point process of type Ⅱ(MPH-Ⅱ),approximated but accurate analytical results for the average rate of the typical user of both tiers are derived through an approximation method based on the mean interference-to-signal ratio(MISR) gain.The influence of some relevant parameters is discussed in detail,and some insights into the network deployment and optimization are revealed.Numerical results show that some trade-offs are worthy of being considered,such as the antenna array size,the altitude of the UAVs and the power control factor of the UBSs.展开更多
Beneficial microbes can improve soil health by promoting soil structure,nutrient cycling,and disease suppression.In addition,a wide array of rhizospheric microbes are responsible for producing metabolically active comp...Beneficial microbes can improve soil health by promoting soil structure,nutrient cycling,and disease suppression.In addition,a wide array of rhizospheric microbes are responsible for producing metabolically active compounds including various types of plant growth regulators.So,microbial biodiversity studies could contribute to the improvement of agricultural practices in deprived areas,such as the Pampean semiarid region.The vast majority of studies conducted on endophytic microorganisms have focused on intensive crop legume species.In contrast,little attention has been paid to microorganisms of native legumes,whose ecology is not directly affected by human action.In this study,endophytic microorganisms isolated from root nodules of a selected native legume of the genus Rhynchosia were characterized.Viable isolates were studied with a focus on their plant growth-pro-moting rhizobacteria(PGPR)properties.Considering the edaphic characteristics of the Pampean semiarid region,the isolates obtained were evaluated for their ability to grow under three salt stress conditions(50,100,and 200 mM NaCl)and four different pH values(6,7,8,and 9).Based on their PGPR activities,the selected strains were phylogenetically grouped using BOX-PCR.The results showed great variability among the isolates in terms of the characteristics studied.Native legumes manifested a wide endophytic variability and remarkable perfor-mance in PGPR activities.We conclude that they could be used as potential bioinoculants for legume cultivation,an excellent alternative to the use of chemical fertilizers that currently pollute the environment.展开更多
The recent advances in aqueous magnesium-ion hybrid supercapacitor(MHSC)have attracted great attention as it brings together the benefits of high energy density,high power density,and synchronously addresses cost and ...The recent advances in aqueous magnesium-ion hybrid supercapacitor(MHSC)have attracted great attention as it brings together the benefits of high energy density,high power density,and synchronously addresses cost and safety issues.However,the freeze of aqueous electrolytes discourages aqueous MHSC from operating at low-temperature conditions.Here,a low-concentration aqueous solution of 4 mol L^(-1) Mg(ClO_(4))_(2) is devised for its low freezing point(-67℃)and ultra-high ionic conductivity(3.37 mS cm^(-1) at-50℃).Both physical characterizations and computational simulations revealed that the Mg(ClO_(4))_(2) can effectively disrupt the original hydrogen bond network among water molecules via transmuting the electrolyte structure,thus yielding a low freezing point.Thus,the Mg(ClO_(4))_(2) electrolytes endue aqueous MHSC with a wider temperature operation range(-50℃–25℃)and a higher energy density of 103.9 Wh kg^(-1) at 3.68 kW kg^(-1) over commonly used magnesium salts(i.e.,MgSO_(4) and Mg(NO_(3))_(2))electrolytes.Furthermore,a quasi-solid-state MHSC based on polyacrylamide-based hydrogel electrolyte holds superior low-temperature performance,excellentflexibility,and high safety.This work pioneers a convenient,cheap,and eco-friendly tactic to procure low-temperature aqueous magnesium-ion energy storage device.展开更多
基金supported by National Natural Science Foundation of China (No.62001135)the Joint funds for Regional Innovation and Development of the National Natural Science Foundation of China(No.U21A20449)the Beijing Natural Science Foundation Haidian Original Innovation Joint Fund (No.L232002)
文摘UAV-aided cellular networks,millimeter wave(mm-wave) communications and multi-antenna techniques are viewed as promising components of the solution for beyond-5G(B5G) and even 6G communications.By leveraging the power of stochastic geometry,this paper aims at providing an effective framework for modeling and analyzing a UAV-aided heterogeneous cellular network,where the terrestrial base stations(TBSs) and the UAV base stations(UBSs) coexist,and the UBSs are provided with mm-wave and multi-antenna techniques.By modeling the TBSs as a PPP and the UBSs as a Matern hard-core point process of type Ⅱ(MPH-Ⅱ),approximated but accurate analytical results for the average rate of the typical user of both tiers are derived through an approximation method based on the mean interference-to-signal ratio(MISR) gain.The influence of some relevant parameters is discussed in detail,and some insights into the network deployment and optimization are revealed.Numerical results show that some trade-offs are worthy of being considered,such as the antenna array size,the altitude of the UAVs and the power control factor of the UBSs.
基金supported by Facultad de Ciencias Exactas y Naturales de la Universidad Nacional de La Pampa(FCEyN-UNLPam).
文摘Beneficial microbes can improve soil health by promoting soil structure,nutrient cycling,and disease suppression.In addition,a wide array of rhizospheric microbes are responsible for producing metabolically active compounds including various types of plant growth regulators.So,microbial biodiversity studies could contribute to the improvement of agricultural practices in deprived areas,such as the Pampean semiarid region.The vast majority of studies conducted on endophytic microorganisms have focused on intensive crop legume species.In contrast,little attention has been paid to microorganisms of native legumes,whose ecology is not directly affected by human action.In this study,endophytic microorganisms isolated from root nodules of a selected native legume of the genus Rhynchosia were characterized.Viable isolates were studied with a focus on their plant growth-pro-moting rhizobacteria(PGPR)properties.Considering the edaphic characteristics of the Pampean semiarid region,the isolates obtained were evaluated for their ability to grow under three salt stress conditions(50,100,and 200 mM NaCl)and four different pH values(6,7,8,and 9).Based on their PGPR activities,the selected strains were phylogenetically grouped using BOX-PCR.The results showed great variability among the isolates in terms of the characteristics studied.Native legumes manifested a wide endophytic variability and remarkable perfor-mance in PGPR activities.We conclude that they could be used as potential bioinoculants for legume cultivation,an excellent alternative to the use of chemical fertilizers that currently pollute the environment.
基金supported by Shenzhen Science and Technology Innovation Committee(Nos.JCYJ20190806145609284,GJHZ20190820091203667,JSGG20201102161000002,SGD-X20201103095607022)Guangdong Basic and Applied Basic Research Foundation(2020A1515010716)+1 种基金Guangdong Introducing Innovative and Entrepreneurial Teams Program(2019ZT08Z656)P.H.would like to acknowledge Shenzhen Science and Technology Program(KQTD20190929172522-248).
文摘The recent advances in aqueous magnesium-ion hybrid supercapacitor(MHSC)have attracted great attention as it brings together the benefits of high energy density,high power density,and synchronously addresses cost and safety issues.However,the freeze of aqueous electrolytes discourages aqueous MHSC from operating at low-temperature conditions.Here,a low-concentration aqueous solution of 4 mol L^(-1) Mg(ClO_(4))_(2) is devised for its low freezing point(-67℃)and ultra-high ionic conductivity(3.37 mS cm^(-1) at-50℃).Both physical characterizations and computational simulations revealed that the Mg(ClO_(4))_(2) can effectively disrupt the original hydrogen bond network among water molecules via transmuting the electrolyte structure,thus yielding a low freezing point.Thus,the Mg(ClO_(4))_(2) electrolytes endue aqueous MHSC with a wider temperature operation range(-50℃–25℃)and a higher energy density of 103.9 Wh kg^(-1) at 3.68 kW kg^(-1) over commonly used magnesium salts(i.e.,MgSO_(4) and Mg(NO_(3))_(2))electrolytes.Furthermore,a quasi-solid-state MHSC based on polyacrylamide-based hydrogel electrolyte holds superior low-temperature performance,excellentflexibility,and high safety.This work pioneers a convenient,cheap,and eco-friendly tactic to procure low-temperature aqueous magnesium-ion energy storage device.
