Space/air communications have been envisioned as an essential part of the next-generation mobile communication networks for providing highquality global connectivity. However, the inherent broadcasting nature of wirel...Space/air communications have been envisioned as an essential part of the next-generation mobile communication networks for providing highquality global connectivity. However, the inherent broadcasting nature of wireless propagation environment and the broad coverage pose severe threats to the protection of private data. Emerging covert communications provides a promising solution to achieve robust communication security. Aiming at facilitating the practical implementation of covert communications in space/air networks, we present a tutorial overview of its potentials, scenarios, and key technologies. Specifically, first, the commonly used covertness constraint model, covert performance metrics, and potential application scenarios are briefly introduced. Then, several efficient methods that introduce uncertainty into the covert system are thoroughly summarized, followed by several critical enabling technologies, including joint resource allocation and deployment/trajectory design, multi-antenna and beamforming techniques, reconfigurable intelligent surface(RIS), and artificial intelligence algorithms. Finally, we highlight some open issues for future investigation.展开更多
With the rapid development of urban road traffic and the increasing number of vehicles,how to alleviate traffic congestion is one of the hot issues that need to be urgently addressed in building smart cities.Therefore...With the rapid development of urban road traffic and the increasing number of vehicles,how to alleviate traffic congestion is one of the hot issues that need to be urgently addressed in building smart cities.Therefore,in this paper,a nonlinear multi-objective optimization model of urban intersection signal timing based on a Genetic Algorithm was constructed.Specifically,a typical urban intersection was selected as the research object,and drivers’acceleration habits were taken into account.What’s more,the shortest average delay time,the least average number of stops,and the maximum capacity of the intersection were regarded as the optimization objectives.The optimization results show that compared with the Webster method when the vehicle speed is 60 km/h and the acceleration is 2.5 m/s^(2),the signal intersection timing scheme based on the proposed Genetic Algorithm multi-objective optimization reduces the intersection signal cycle time by 14.6%,the average vehicle delay time by 12.9%,the capacity by 16.2%,and the average number of vehicles stop by 0.4%.To verify the simulation results,the authors imported the optimized timing scheme into the constructed Simulation of the Urban Mobility model.The experimental results show that the authors optimized timing scheme is superior to Webster’s in terms of vehicle average loss time reduction,carbon monoxide emission,particulate matter emission,and vehicle fuel consumption.The research in this paper provides a basis for Genetic algorithms in traffic signal control.展开更多
目的探讨尿白细胞介素-17(IL-17)、中性粒细胞明胶酶相关脂质运载蛋白(NGAL)与高迁移率族蛋白B1(HMGB1)水平在狼疮性肾炎(LN)中的变化及其临床意义。方法选取三亚中心医院收治的LN患者106例,即Ⅱ型,Ⅲ型,Ⅳ型,Ⅴ型和Ⅵ型分别为18,17,43...目的探讨尿白细胞介素-17(IL-17)、中性粒细胞明胶酶相关脂质运载蛋白(NGAL)与高迁移率族蛋白B1(HMGB1)水平在狼疮性肾炎(LN)中的变化及其临床意义。方法选取三亚中心医院收治的LN患者106例,即Ⅱ型,Ⅲ型,Ⅳ型,Ⅴ型和Ⅵ型分别为18,17,43,21和7例。采用SLE病情活动指数(SLEDAI)评分将106例LN患者分为LN稳定组(n=37,SLEDAI评分<10分)和LN活动组(n=69,SLEDAI评分≥10分),采用酶联免疫吸附法测定各组尿IL-17,NGAL及HMGB1水平。应用ROC曲线分析尿IL-17,NGAL及HMGB1水平预测活动性LN的价值。结果LN组尿IL-17(146.30±38.24ng/L vs 48.70±11.25ng/L),NGAL(230.72±65.20ng/ml vs 27.36±6.40ng/ml)和HMGB1(21.73±6.25μg/L vs 3.46±1.20μg/L)水平均明显高于对照组,差异均有统计学意义(t=15.826,18.847,14.715,均P<0.001)。LN活动组尿IL-17(171.42±45.26ng/L vs 120.28±26.70ng/L),NGAL(257.63±69.24ng/ml vs 196.35±47.38ng/ml)和HMGB1(27.16±7.83μg/L vs 16.15±4.17μg/L)水平均明显高于LN稳定组,差异均有统计学意义(t=10.264,13.718,9.516,均P<0.001)。不同分型LN患者尿IL-17,NGAL及HMGB1水平均明显高于对照组(F=8.615,12.217,8.295,P<0.001),且Ⅴ~Ⅵ型组和Ⅳ型组尿IL-17,NGAL及HMGB1水平均明显高于Ⅱ~Ⅲ型组(P<0.001),差异有统计学意义。ROC曲线显示,IL-17,NGAL及HMGB1三项联合预测活动性LN的曲线下面积(0.918,95%CI:0.856~0.982)最大,其敏感度(92.6%)和特异度(86.5%)较好。结论LN患者尿IL-17,NGAL及HMGB1水平明显升高,且与LN活动性及病理分型相关,三项联合预测活动性LN具有较高的价值。展开更多
Cinnamomum camphora(L.)J.Presl.(Laurales:Lauraceae)is widely cultivated as an important landscape tree species in many urban areas in South China,especially in Shanghai City.Pagiophloeus tsushimanus Morimoto has becom...Cinnamomum camphora(L.)J.Presl.(Laurales:Lauraceae)is widely cultivated as an important landscape tree species in many urban areas in South China,especially in Shanghai City.Pagiophloeus tsushimanus Morimoto has become a destructive insect pest of C.camphora plantations in Shanghai,but the biological and ecological traits of this pest remain largely unknown.In this study,we investigated the damage and life history and determined the larval instar of P.tsushimanus.The results indicated that P.tsushimanus is a monophagous weevil pest,and C.camphora is the unique host tree species.C.camphora plantations in all administrative districts of Shanghai have been seriously damaged by P.tsushimanus.Adults often aggregate for feeding on the tender bark of twigs and occasionally on newly emerged buds.After experiencing damage,the twigs shrink and crack and the buds will shrink.Adults tend to repeatedly mate and oviposit,and all females lay single eggs at a time.Eggs will be covered with a mixture of secretions and wood chips by female adults.Larvae(1 st-2 nd instar)feed on the phloem,while 3 rd-5 th instar can bore into the phloem and the cambium.Massive tunnels,including three shapes(inverted"L",inverted"T",and inverted"Z"),were observed in the trunk of each tree,and resulted in swelling of the outer bark.P.tsushimanus has one life cycle per year in Shanghai.Both adults and larvae(3 rd-5 th instar)overwinter from early November to early April.Adults overwinter in grooves on the underside of branches or at branch nodes,and larvae overwinter in tunnels.Five larval instars of P.tsushimanus were determined according to Dyar’s and Crosby’s rules.The biological traits and life history of P.tsushimanus have been identified and can provide guidance in terms of pest control and plantation management.展开更多
Hydrogen evolution reaction(HER) plays a key role in generating clean and renewable energy. As the most effective HER electrocatalysts, Pt group catalysts suffer from severe problems such as high price and scarcity. I...Hydrogen evolution reaction(HER) plays a key role in generating clean and renewable energy. As the most effective HER electrocatalysts, Pt group catalysts suffer from severe problems such as high price and scarcity. It is highly desirable to design and synthesize sustainable HER electrocatalysts to replace the Pt group catalysts. Due to their low cost, high abundance and high activities, cobalt-incorporated N-doped nanocarbon hybrids are promising candidate electrocatalysts for HER. In this report, we demonstrated a robust and eco-friendly host-guest approach to fabricate metallic cobalt nanoparticles embedded in N-doped carbon fibers derived from natural silk fibers. Benefiting from the onedimensional nanostructure, the well-dispersed metallic cobalt nanoparticles and the N-doped thin graphitized carbon layer coating, the best Cobased electrocatalyst manifests low overpotential(61 mV@10 mA/cm^2) HER activity that is comparable with commercial 20% Pt/C, and good stability in acid. Our findings provide a novel and unique route to explore high-performance noble-metal-free HER electrocatalysts.展开更多
基金supported in part by the National Natural Science Foundation of China(NSFC)under grant numbers U22A2007 and 62171010the Beijing Natural Science Foundation under grant number L212003.
文摘Space/air communications have been envisioned as an essential part of the next-generation mobile communication networks for providing highquality global connectivity. However, the inherent broadcasting nature of wireless propagation environment and the broad coverage pose severe threats to the protection of private data. Emerging covert communications provides a promising solution to achieve robust communication security. Aiming at facilitating the practical implementation of covert communications in space/air networks, we present a tutorial overview of its potentials, scenarios, and key technologies. Specifically, first, the commonly used covertness constraint model, covert performance metrics, and potential application scenarios are briefly introduced. Then, several efficient methods that introduce uncertainty into the covert system are thoroughly summarized, followed by several critical enabling technologies, including joint resource allocation and deployment/trajectory design, multi-antenna and beamforming techniques, reconfigurable intelligent surface(RIS), and artificial intelligence algorithms. Finally, we highlight some open issues for future investigation.
基金supported by the joint NNSF&FDCT Project Number (0066/2019/AFJ)joint MOST&FDCT Project Number (0058/2019/AMJ),City University of Macao,Macao,China.
文摘With the rapid development of urban road traffic and the increasing number of vehicles,how to alleviate traffic congestion is one of the hot issues that need to be urgently addressed in building smart cities.Therefore,in this paper,a nonlinear multi-objective optimization model of urban intersection signal timing based on a Genetic Algorithm was constructed.Specifically,a typical urban intersection was selected as the research object,and drivers’acceleration habits were taken into account.What’s more,the shortest average delay time,the least average number of stops,and the maximum capacity of the intersection were regarded as the optimization objectives.The optimization results show that compared with the Webster method when the vehicle speed is 60 km/h and the acceleration is 2.5 m/s^(2),the signal intersection timing scheme based on the proposed Genetic Algorithm multi-objective optimization reduces the intersection signal cycle time by 14.6%,the average vehicle delay time by 12.9%,the capacity by 16.2%,and the average number of vehicles stop by 0.4%.To verify the simulation results,the authors imported the optimized timing scheme into the constructed Simulation of the Urban Mobility model.The experimental results show that the authors optimized timing scheme is superior to Webster’s in terms of vehicle average loss time reduction,carbon monoxide emission,particulate matter emission,and vehicle fuel consumption.The research in this paper provides a basis for Genetic algorithms in traffic signal control.
文摘目的探讨尿白细胞介素-17(IL-17)、中性粒细胞明胶酶相关脂质运载蛋白(NGAL)与高迁移率族蛋白B1(HMGB1)水平在狼疮性肾炎(LN)中的变化及其临床意义。方法选取三亚中心医院收治的LN患者106例,即Ⅱ型,Ⅲ型,Ⅳ型,Ⅴ型和Ⅵ型分别为18,17,43,21和7例。采用SLE病情活动指数(SLEDAI)评分将106例LN患者分为LN稳定组(n=37,SLEDAI评分<10分)和LN活动组(n=69,SLEDAI评分≥10分),采用酶联免疫吸附法测定各组尿IL-17,NGAL及HMGB1水平。应用ROC曲线分析尿IL-17,NGAL及HMGB1水平预测活动性LN的价值。结果LN组尿IL-17(146.30±38.24ng/L vs 48.70±11.25ng/L),NGAL(230.72±65.20ng/ml vs 27.36±6.40ng/ml)和HMGB1(21.73±6.25μg/L vs 3.46±1.20μg/L)水平均明显高于对照组,差异均有统计学意义(t=15.826,18.847,14.715,均P<0.001)。LN活动组尿IL-17(171.42±45.26ng/L vs 120.28±26.70ng/L),NGAL(257.63±69.24ng/ml vs 196.35±47.38ng/ml)和HMGB1(27.16±7.83μg/L vs 16.15±4.17μg/L)水平均明显高于LN稳定组,差异均有统计学意义(t=10.264,13.718,9.516,均P<0.001)。不同分型LN患者尿IL-17,NGAL及HMGB1水平均明显高于对照组(F=8.615,12.217,8.295,P<0.001),且Ⅴ~Ⅵ型组和Ⅳ型组尿IL-17,NGAL及HMGB1水平均明显高于Ⅱ~Ⅲ型组(P<0.001),差异有统计学意义。ROC曲线显示,IL-17,NGAL及HMGB1三项联合预测活动性LN的曲线下面积(0.918,95%CI:0.856~0.982)最大,其敏感度(92.6%)和特异度(86.5%)较好。结论LN患者尿IL-17,NGAL及HMGB1水平明显升高,且与LN活动性及病理分型相关,三项联合预测活动性LN具有较高的价值。
基金supported by the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX19_1077)the Science and Technology Commission of Shanghai Municipality(18,391,903,200)the Shanghai Landscaping&City Appearance Administrative Bureau(G161206)。
文摘Cinnamomum camphora(L.)J.Presl.(Laurales:Lauraceae)is widely cultivated as an important landscape tree species in many urban areas in South China,especially in Shanghai City.Pagiophloeus tsushimanus Morimoto has become a destructive insect pest of C.camphora plantations in Shanghai,but the biological and ecological traits of this pest remain largely unknown.In this study,we investigated the damage and life history and determined the larval instar of P.tsushimanus.The results indicated that P.tsushimanus is a monophagous weevil pest,and C.camphora is the unique host tree species.C.camphora plantations in all administrative districts of Shanghai have been seriously damaged by P.tsushimanus.Adults often aggregate for feeding on the tender bark of twigs and occasionally on newly emerged buds.After experiencing damage,the twigs shrink and crack and the buds will shrink.Adults tend to repeatedly mate and oviposit,and all females lay single eggs at a time.Eggs will be covered with a mixture of secretions and wood chips by female adults.Larvae(1 st-2 nd instar)feed on the phloem,while 3 rd-5 th instar can bore into the phloem and the cambium.Massive tunnels,including three shapes(inverted"L",inverted"T",and inverted"Z"),were observed in the trunk of each tree,and resulted in swelling of the outer bark.P.tsushimanus has one life cycle per year in Shanghai.Both adults and larvae(3 rd-5 th instar)overwinter from early November to early April.Adults overwinter in grooves on the underside of branches or at branch nodes,and larvae overwinter in tunnels.Five larval instars of P.tsushimanus were determined according to Dyar’s and Crosby’s rules.The biological traits and life history of P.tsushimanus have been identified and can provide guidance in terms of pest control and plantation management.
基金supported by the National Natural Science Foundation of China (NSFC) (Grant No. 21203137, 51573166)the Natural Science Foundation of Zhejiang Province (Grant No. LQ16E020005)
文摘Hydrogen evolution reaction(HER) plays a key role in generating clean and renewable energy. As the most effective HER electrocatalysts, Pt group catalysts suffer from severe problems such as high price and scarcity. It is highly desirable to design and synthesize sustainable HER electrocatalysts to replace the Pt group catalysts. Due to their low cost, high abundance and high activities, cobalt-incorporated N-doped nanocarbon hybrids are promising candidate electrocatalysts for HER. In this report, we demonstrated a robust and eco-friendly host-guest approach to fabricate metallic cobalt nanoparticles embedded in N-doped carbon fibers derived from natural silk fibers. Benefiting from the onedimensional nanostructure, the well-dispersed metallic cobalt nanoparticles and the N-doped thin graphitized carbon layer coating, the best Cobased electrocatalyst manifests low overpotential(61 mV@10 mA/cm^2) HER activity that is comparable with commercial 20% Pt/C, and good stability in acid. Our findings provide a novel and unique route to explore high-performance noble-metal-free HER electrocatalysts.
