Recently,orthogonal time frequency space(OTFS)was presented to alleviate severe Doppler effects in high mobility scenarios.Most of the current OTFS detection schemes rely on perfect channel state information(CSI).Howe...Recently,orthogonal time frequency space(OTFS)was presented to alleviate severe Doppler effects in high mobility scenarios.Most of the current OTFS detection schemes rely on perfect channel state information(CSI).However,in real-life systems,the parameters of channels will constantly change,which are often difficult to capture and describe.In this paper,we summarize the existing research on OTFS detection based on data-driven deep learning(DL)and propose three new network structures.The presented three networks include a residual network(ResNet),a dense network(DenseNet),and a residual dense network(RDN)for OTFS detection.The detection schemes based on data-driven paradigms do not require a model that is easy to handle mathematically.Meanwhile,compared with the existing fully connected-deep neural network(FC-DNN)and standard convolutional neural network(CNN),these three new networks can alleviate the problems of gradient explosion and gradient disappearance.Through simulation,it is proved that RDN has the best performance among the three proposed schemes due to the combination of shallow and deep features.RDN can solve the issue of performance loss caused by the traditional network not fully utilizing all the hierarchical information.展开更多
Photochemical smog characterized by high concentrations of ozone(O_(3)) is a serious air pollution issue in the North China Plain(NCP)region,especially in summer and autumn.For this study,measurements of O_(3),nitroge...Photochemical smog characterized by high concentrations of ozone(O_(3)) is a serious air pollution issue in the North China Plain(NCP)region,especially in summer and autumn.For this study,measurements of O_(3),nitrogen oxides(NO_(x)),volatile organic compounds(VOCs),carbon monoxide(CO),nitrous acid(HONO),and a number of key physical parameters were taken at a suburban site,Xianghe,in the NCP region during the summer of 2018 in order to better understand the photochemical processes leading to O_(3)formation and find an optimal way to control O_(3)pollution.Here,the radical chemistry and O_(3)photochemical budget based on measurement data from 1−23 July using a chemical box model is investigated.The daytime(0600−1800 LST)average production rate of the primary radicals referred to as RO_(x)(OH+HO2+RO2)is 3.9 ppbv h−1.HONO photolysis is the largest primary RO_(x)source(41%).Reaction of NO2+OH is the largest contributor to radical termination(41%),followed by reactions of RO2+NO2(26%).The average diurnal maximum O_(3)production and loss rates are 32.9 ppbv h−1 and 4.3 ppbv h−1,respectively.Sensitivity tests without the HONO constraint lead to decreases in daytime average primary RO_(x)production by 55%and O_(3)photochemical production by 42%,highlighting the importance of accurate HONO measurements when quantifying the RO_(x)budget and O_(3)photochemical production.Considering heterogeneous reactions of trace gases and radicals on aerosols,aerosol uptake of HO2 contributes 11%to RO_(x)sink,and the daytime average O_(3)photochemical production decreases by 14%.The O_(3)-NO_(x)-VOCs sensitivity shows that the O_(3)production at Xianghe during the investigation period is mainly controlled by VOCs.展开更多
Public bulletin boards are widely used in various public places,but due to the large size of the billboards,it is not easy to carry,and the traditional billboards are integrated,when the billboards need to be transfer...Public bulletin boards are widely used in various public places,but due to the large size of the billboards,it is not easy to carry,and the traditional billboards are integrated,when the billboards need to be transferred,the limited storage space of the vehicle needs to be occupied It is extremely inconvenient,and at night,the traditional bulletin boards need to install additional light sources to illuminate them,which greatly increases energy consumption.Based on this paper designed a new structure of the bulletin board,this structure can make the bulletin board when not in use completely folded up and easy to carry,and in use can be completely unfolded and in the bottom of the added retractable support leg structure can be placed anywhere,and according to the terrain or human will to adjust the height.A solar panel is placed on the top of the bulletin board,which can store solar energy during the day and supply energy to the LED lights on the top at night for lighting,which saves energy and is very environmentally friendly.展开更多
A new family of two-dimensional （2D） topological insulators （TIs） comprising g-TIA （A = N, P, As, and Sb） monolayers constructed by T1 and group-V elements is predicted by first-principles calculations and molec...A new family of two-dimensional （2D） topological insulators （TIs） comprising g-TIA （A = N, P, As, and Sb） monolayers constructed by T1 and group-V elements is predicted by first-principles calculations and molecular-dynamics （MD） simulations. The geometric stability, band inversion, nontrivial edge states, and electric polarity are investigated to predict the large-gap quantum spin Hall insulator and Rashba-Dresselhaus effects. The MD results reveal that the g-T1A monolayers remain stable even at room temperature. The g-T1A （A = As, Sb） monolayers become TIs under the influence of strong spin-orbit couplings with large bulk bandgaps of 131 and 268 meV, respectively. A single band inversion is observed in each g-T1A （A = As, Sb） monolayer, indicating a nontrivial topological nature. Furthermore, the topological edge states are described by introducing a sufficiently wide zigzag-nanoribbon. A Dirac point in the middle of the bulk gap connects the valence- and conduction-band edges. The Fermi velocity near the Dirac point with a linear band dispersion is -0.51 × 106 m/s, which is comparable to that of many other 2D nanomaterials. More importantly, owing to the broken inversion symmetry normal to the plane of the g-T1A films, a promising Rashba-Dresselhaus effect with the parameter up to 0.85 eV-A is observed in the g-T1A （A = As, Sb） monolayers. Our findings regarding 2D topological g-T1A monolayers with room-temperature bandgaps, intriguing topological edge states, and a promising Rashba-Dresselhaus effect are of fundamental value and suggest potential applications in nanoelectronic devices.展开更多
Eco-toxicity investigation of polymer materials was considered extremely necessary for their potential menace,which was widely use as mulching materials in agricultural.In this study,polyethylene(PE),polystyrene(PS)an...Eco-toxicity investigation of polymer materials was considered extremely necessary for their potential menace,which was widely use as mulching materials in agricultural.In this study,polyethylene(PE),polystyrene(PS)and synthetic biomaterials-Ecoflex and cellulose were applying into soil cultivated with two potential indicator plants species:oat(A v ena sati v a)and red radish(Raphanus sativum).Variety of chemical,biochemical parameters and enzyme activity in soil were proved as effective approach to evaluate polymers phytotoxicity in plant-soil mesocosm.The F-value of biomass,pH,heavy metal and electoral conductivity of Raphanus behaved significant different from T0.Significant analysis results indicated biodegradation was fast in PE than PS,besides,heavy metals were dramatically decrease in the end implied the plant absorption may help decrease heavy metal toxicity.The increase value at T2 of Dehydrogenase activity(0.84 higher than average value for Avena&0.91 higher for Raphanus),Metabolic Index(3.12 higher than average value for Avena&3.81 higher for Raphanus)means during soil enzyme activity was promoted by biodegradation for its heterotrophic organisms’energy transportation was stimulated.Statistics analysis was carried on Biplot PC1(24.2%of the total variance),PC2(23.2%of the total variance),versus PC3(22.8%of the total variance),which indicated phosphatase activity and metabolic index was significant correlated,and high correlation of ammonium and protease activity.Furthermore,the effects were more evident in Raphanus treatments than in Avena,suggesting the higher sensitivity of Raphanus to polymers treatment,which indicate biodegradation of polymers in Raphanus treatment has produced intermediate phytotoxic compounds.展开更多
Spatiotemporal continuity of surface water datasets widely known for its significance in the surface water dynamic monitoring and assessments,are faced with drawbacks like cloud influence,which hinders the direct extr...Spatiotemporal continuity of surface water datasets widely known for its significance in the surface water dynamic monitoring and assessments,are faced with drawbacks like cloud influence,which hinders the direct extraction of data from time-series remote sensing images.This study proposes a Time-series Surface Water Reconstruction method(TSWR).The initial stage of this method involves the effective use of remote sensing images to automatically construct multi-stage surface water boundaries based on Google Earth Engine(GEE).Then,we reconstructed regions the reconstruction of regions with missing water pixels using the distance relationship between the multi-stage water boundaries in previous and later periods.When applied to 10 large rivers around the world,this method yielded an overall accuracy of 98%for water extraction,an RMSE of 0.41 km2.Furthermore,time-series reconstruction tests conducted in 2020 on the Lancang and Danube rivers revealed a significant improvement in the image availability.These findings demonstrated that this method could not only be used to accurately reconstruct the surface water distribution missing water images,but also to depict a more pronounced time variation characteristic.The successful application of this method on GEE demonstrates its importance for use on large scales or in global studies.展开更多
Quantum spin Hall （QSH） insulator is a new class of materials that is quickly becoming mainstream in condensed-matter physics. The main obstacle for the development of QSH insulators is that their strong interaction...Quantum spin Hall （QSH） insulator is a new class of materials that is quickly becoming mainstream in condensed-matter physics. The main obstacle for the development of QSH insulators is that their strong interactions with substrates make them difficult to study experimentally. In this study, using density functional theory, we discovered that MoTe2 is a good match for a GeI monolayer. The thermal stability of a van der Waals GeI/MoTe2 heterosheet was examined via molecular-dynamics simulations. Simulated scanning tunneling microscopy revealed that the GeI monolayer perfectly preserves the bulked honeycomb structure of MoTe2. The GeI on MoTe2 was confirmed to maintain its topological band structure with a sizable indirect bulk bandgap of 0.24 eV by directly calculating the spin Chern number to be -1. As expected, the electron mobility of the GeI is enhanced by MoTe2 substrate restriction. According to deformation- potential theory with the effective-mass approximation, the electron mobility of GeI/MoTe2 was estimated as 372.7 cm^2·s^-1·V^-1 at 300 K, which is 20 times higher than that of freestanding GeI. Our research shows that traditional substrates always destroy the topological states and hinder the electron transport in QSH insulators, and pave way for the further realization and utilization of QSH insulators at room temperature.展开更多
基金supported by Beijing Natural Science Foundation(L223025)National Natural Science Foundation of China(62201067)R and D Program of Beijing Municipal Education Commission(KM202211232008)。
文摘Recently,orthogonal time frequency space(OTFS)was presented to alleviate severe Doppler effects in high mobility scenarios.Most of the current OTFS detection schemes rely on perfect channel state information(CSI).However,in real-life systems,the parameters of channels will constantly change,which are often difficult to capture and describe.In this paper,we summarize the existing research on OTFS detection based on data-driven deep learning(DL)and propose three new network structures.The presented three networks include a residual network(ResNet),a dense network(DenseNet),and a residual dense network(RDN)for OTFS detection.The detection schemes based on data-driven paradigms do not require a model that is easy to handle mathematically.Meanwhile,compared with the existing fully connected-deep neural network(FC-DNN)and standard convolutional neural network(CNN),these three new networks can alleviate the problems of gradient explosion and gradient disappearance.Through simulation,it is proved that RDN has the best performance among the three proposed schemes due to the combination of shallow and deep features.RDN can solve the issue of performance loss caused by the traditional network not fully utilizing all the hierarchical information.
基金This work was supported by grants from the National Key Research and Development Program of China(Grant No.2017YFC0210003).
文摘Photochemical smog characterized by high concentrations of ozone(O_(3)) is a serious air pollution issue in the North China Plain(NCP)region,especially in summer and autumn.For this study,measurements of O_(3),nitrogen oxides(NO_(x)),volatile organic compounds(VOCs),carbon monoxide(CO),nitrous acid(HONO),and a number of key physical parameters were taken at a suburban site,Xianghe,in the NCP region during the summer of 2018 in order to better understand the photochemical processes leading to O_(3)formation and find an optimal way to control O_(3)pollution.Here,the radical chemistry and O_(3)photochemical budget based on measurement data from 1−23 July using a chemical box model is investigated.The daytime(0600−1800 LST)average production rate of the primary radicals referred to as RO_(x)(OH+HO2+RO2)is 3.9 ppbv h−1.HONO photolysis is the largest primary RO_(x)source(41%).Reaction of NO2+OH is the largest contributor to radical termination(41%),followed by reactions of RO2+NO2(26%).The average diurnal maximum O_(3)production and loss rates are 32.9 ppbv h−1 and 4.3 ppbv h−1,respectively.Sensitivity tests without the HONO constraint lead to decreases in daytime average primary RO_(x)production by 55%and O_(3)photochemical production by 42%,highlighting the importance of accurate HONO measurements when quantifying the RO_(x)budget and O_(3)photochemical production.Considering heterogeneous reactions of trace gases and radicals on aerosols,aerosol uptake of HO2 contributes 11%to RO_(x)sink,and the daytime average O_(3)photochemical production decreases by 14%.The O_(3)-NO_(x)-VOCs sensitivity shows that the O_(3)production at Xianghe during the investigation period is mainly controlled by VOCs.
基金College Students Innovation and Entrepreneurship Project(S202214435012).
文摘Public bulletin boards are widely used in various public places,but due to the large size of the billboards,it is not easy to carry,and the traditional billboards are integrated,when the billboards need to be transferred,the limited storage space of the vehicle needs to be occupied It is extremely inconvenient,and at night,the traditional bulletin boards need to install additional light sources to illuminate them,which greatly increases energy consumption.Based on this paper designed a new structure of the bulletin board,this structure can make the bulletin board when not in use completely folded up and easy to carry,and in use can be completely unfolded and in the bottom of the added retractable support leg structure can be placed anywhere,and according to the terrain or human will to adjust the height.A solar panel is placed on the top of the bulletin board,which can store solar energy during the day and supply energy to the LED lights on the top at night for lighting,which saves energy and is very environmentally friendly.
文摘A new family of two-dimensional （2D） topological insulators （TIs） comprising g-TIA （A = N, P, As, and Sb） monolayers constructed by T1 and group-V elements is predicted by first-principles calculations and molecular-dynamics （MD） simulations. The geometric stability, band inversion, nontrivial edge states, and electric polarity are investigated to predict the large-gap quantum spin Hall insulator and Rashba-Dresselhaus effects. The MD results reveal that the g-T1A monolayers remain stable even at room temperature. The g-T1A （A = As, Sb） monolayers become TIs under the influence of strong spin-orbit couplings with large bulk bandgaps of 131 and 268 meV, respectively. A single band inversion is observed in each g-T1A （A = As, Sb） monolayer, indicating a nontrivial topological nature. Furthermore, the topological edge states are described by introducing a sufficiently wide zigzag-nanoribbon. A Dirac point in the middle of the bulk gap connects the valence- and conduction-band edges. The Fermi velocity near the Dirac point with a linear band dispersion is -0.51 × 106 m/s, which is comparable to that of many other 2D nanomaterials. More importantly, owing to the broken inversion symmetry normal to the plane of the g-T1A films, a promising Rashba-Dresselhaus effect with the parameter up to 0.85 eV-A is observed in the g-T1A （A = As, Sb） monolayers. Our findings regarding 2D topological g-T1A monolayers with room-temperature bandgaps, intriguing topological edge states, and a promising Rashba-Dresselhaus effect are of fundamental value and suggest potential applications in nanoelectronic devices.
基金The National Natural Science Foundation of China(Grant No.81673366)the National Key Science Research Program of China(973 Program,Grant No.2015CB932100)
基金supported by the National Natu-ral Science Foundation of China(Nos.4197071831,41630645,41573126 and 41703115)the National Special Environ-mental Protection Foundation for Technology Exploit of China(No.2014EG166135).
文摘Eco-toxicity investigation of polymer materials was considered extremely necessary for their potential menace,which was widely use as mulching materials in agricultural.In this study,polyethylene(PE),polystyrene(PS)and synthetic biomaterials-Ecoflex and cellulose were applying into soil cultivated with two potential indicator plants species:oat(A v ena sati v a)and red radish(Raphanus sativum).Variety of chemical,biochemical parameters and enzyme activity in soil were proved as effective approach to evaluate polymers phytotoxicity in plant-soil mesocosm.The F-value of biomass,pH,heavy metal and electoral conductivity of Raphanus behaved significant different from T0.Significant analysis results indicated biodegradation was fast in PE than PS,besides,heavy metals were dramatically decrease in the end implied the plant absorption may help decrease heavy metal toxicity.The increase value at T2 of Dehydrogenase activity(0.84 higher than average value for Avena&0.91 higher for Raphanus),Metabolic Index(3.12 higher than average value for Avena&3.81 higher for Raphanus)means during soil enzyme activity was promoted by biodegradation for its heterotrophic organisms’energy transportation was stimulated.Statistics analysis was carried on Biplot PC1(24.2%of the total variance),PC2(23.2%of the total variance),versus PC3(22.8%of the total variance),which indicated phosphatase activity and metabolic index was significant correlated,and high correlation of ammonium and protease activity.Furthermore,the effects were more evident in Raphanus treatments than in Avena,suggesting the higher sensitivity of Raphanus to polymers treatment,which indicate biodegradation of polymers in Raphanus treatment has produced intermediate phytotoxic compounds.
基金The National Natural Science Foundation of China(Grant No.81673366)the National Key Science Research Program of China(973 Program,Grant No.2015CB932100)
基金The research was funded by the National Natural Science Foundation of China[grant no 42171283]the Major Science and Technology Projects of Qinghai Province[grant no 2021-SF-A6]+1 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)[grant number 2019QZKK0202]Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA19090120].
文摘Spatiotemporal continuity of surface water datasets widely known for its significance in the surface water dynamic monitoring and assessments,are faced with drawbacks like cloud influence,which hinders the direct extraction of data from time-series remote sensing images.This study proposes a Time-series Surface Water Reconstruction method(TSWR).The initial stage of this method involves the effective use of remote sensing images to automatically construct multi-stage surface water boundaries based on Google Earth Engine(GEE).Then,we reconstructed regions the reconstruction of regions with missing water pixels using the distance relationship between the multi-stage water boundaries in previous and later periods.When applied to 10 large rivers around the world,this method yielded an overall accuracy of 98%for water extraction,an RMSE of 0.41 km2.Furthermore,time-series reconstruction tests conducted in 2020 on the Lancang and Danube rivers revealed a significant improvement in the image availability.These findings demonstrated that this method could not only be used to accurately reconstruct the surface water distribution missing water images,but also to depict a more pronounced time variation characteristic.The successful application of this method on GEE demonstrates its importance for use on large scales or in global studies.
基金This work is supported by the National Basic Research Program of China （No. 2013CB632401）, National Natural Science Foundation of China （Nos. 21333006, 11374190, and 1140418）, and Program of Introducing Talents of Discipline to Universities （111 Program） （No. 297B13029）. We also thank the Taishan Scholar Program of Shandong Province.
文摘Quantum spin Hall （QSH） insulator is a new class of materials that is quickly becoming mainstream in condensed-matter physics. The main obstacle for the development of QSH insulators is that their strong interactions with substrates make them difficult to study experimentally. In this study, using density functional theory, we discovered that MoTe2 is a good match for a GeI monolayer. The thermal stability of a van der Waals GeI/MoTe2 heterosheet was examined via molecular-dynamics simulations. Simulated scanning tunneling microscopy revealed that the GeI monolayer perfectly preserves the bulked honeycomb structure of MoTe2. The GeI on MoTe2 was confirmed to maintain its topological band structure with a sizable indirect bulk bandgap of 0.24 eV by directly calculating the spin Chern number to be -1. As expected, the electron mobility of the GeI is enhanced by MoTe2 substrate restriction. According to deformation- potential theory with the effective-mass approximation, the electron mobility of GeI/MoTe2 was estimated as 372.7 cm^2·s^-1·V^-1 at 300 K, which is 20 times higher than that of freestanding GeI. Our research shows that traditional substrates always destroy the topological states and hinder the electron transport in QSH insulators, and pave way for the further realization and utilization of QSH insulators at room temperature.
