Low Earth Orbit(LEO)multibeam satellites will be widely used in the next generation of satellite communication systems,whose inter-beam interference will inevitably limit the performance of the whole system.Nonlinear ...Low Earth Orbit(LEO)multibeam satellites will be widely used in the next generation of satellite communication systems,whose inter-beam interference will inevitably limit the performance of the whole system.Nonlinear precoding such as Tomlinson-Harashima precoding(THP)algorithm has been proved to be a promising technology to solve this problem,which has smaller noise amplification effect compared with linear precoding.However,the similarity of different user channels(defined as channel correlation)will degrade the performance of THP algorithm.In this paper,we qualitatively analyze the inter-beam interference in the whole process of LEO satellite over a specific coverage area,and the impact of channel correlation on Signal-to-Noise Ratio(SNR)of receivers when THP is applied.One user grouping algorithm is proposed based on the analysis of channel correlation,which could decrease the number of users with high channel correlation in each precoding group,thus improve the performance of THP.Furthermore,our algorithm is designed under the premise of co-frequency deployment and orthogonal frequency division multiplexing(OFDM),which leads to more users under severe inter-beam interference compared to the existing research on geostationary orbit satellites broadcasting systems.Simulation results show that the proposed user grouping algorithm possesses higher channel capacity and better bit error rate(BER)performance in high SNR conditions relative to existing works.展开更多
Aqueous zinc metal batteries feature intrinsic safety,but suffer from severe dendrite growth and water-derived side reactions.Many metal coatings have been explored for stabilizing Zn metal anode via a trialand-error ...Aqueous zinc metal batteries feature intrinsic safety,but suffer from severe dendrite growth and water-derived side reactions.Many metal coatings have been explored for stabilizing Zn metal anode via a trialand-error approach.Here,we propose an exercisable way to screen the potential metal coating on Zn anodes in view of de-polarization effect and dendrite-suppressing ability theoretically.As an output of this screening,cadmium(Cd) metal is checked experimentally.Therefore,symmetric ZnllZn cells using Cd coated Zn(Zn@Cd) exhibit an ultra-long cycle life of 3500 h(nearly 5 months) at a high current density of 10 mA cm^(-2),achieving a record-high cumulative capacity(35 A h cm^(-2)) compared to the previous reports.The full cells of Zn@Cd‖MnO_(2) display a markedly improved cycling performance under harsh conditions including a limited Zn supply(N/P ratio=1.7) and a high areal capacity(3.5 mA h cm^(-2)).The significance of this work lies in not only the first report of Cd coating for stabilizing Zn metal anode,but also a feasible way to screen the promising metal materials for other metal anodes.展开更多
Sea area is an important area of oil and gas exploration in China.It has been found that China's sea area mainly consists of coal type oil and gas,and the exploration of coal-bearing series source rocks has become...Sea area is an important area of oil and gas exploration in China.It has been found that China's sea area mainly consists of coal type oil and gas,and the exploration of coal-bearing series source rocks has become an important part of oil and gas exploration there.Through years of comprehensive geological research in China's sea area,it has been revealed that it has undergone multiple occurrences of tectonic opening and closing movements in varying degrees in the Paleogene,forming 26 Cenozoic sedimentary basins of various types,such as active continental margin,passive continental margin,transitional continental margin and drift rift basins.In the present study,it is observed for the first time that coal type source rocks are mainly developed in 14 continental margin basins in China's sea area,revealing that a very large C-shaped coal-bearing basin group developed there in the Cenozoic.Next,based on the coupling analysis of paleoclimate,paleobotany,paleogeography and paleostructure,it is observed that there are five coal-forming periods in China's sea area,namely the Paleocene,Eocene,early Oligocene,late Oligocene and Miocene-Pliocene,and the coal-forming age is gradually new from north to south.It is also found that the coal seams in the sea area are mainly developed in three coal-forming environments in Cenozoic,namely delta,fan delta and tidal flat-lagoon.The coal seams developed in different environments are characterized by thin thickness,many layers and poor stability.However,the coal-bearing series source rocks in China's sea area have a wide distribution range,very high thickness and large amount,thus forming a material basis for the formation of rich coal type oil and gas.展开更多
The ChatGPT,a lite and conversational variant of Generative Pretrained Transformer 4(GPT-4)developed by OpenAI,is one of the milestone Large Language Models(LLMs)with billions of parameters.LLMs have stirred up much i...The ChatGPT,a lite and conversational variant of Generative Pretrained Transformer 4(GPT-4)developed by OpenAI,is one of the milestone Large Language Models(LLMs)with billions of parameters.LLMs have stirred up much interest among researchers and practitioners in their impressive skills in natural language processing tasks,which profoundly impact various fields.This paper mainly discusses the future applications of LLMs in dentistry.We introduce two primary LLM deployment methods in dentistry,including automated dental diagnosis and cross-modal dental diagnosis,and examine their potential applications.Especially,equipped with a cross-modal encoder,a single LLM can manage multi-source data and conduct advanced natural language reasoning to perform complex clinical operations.We also present cases to demonstrate the potential of a fully automatic Multi-Modal LLM AI system for dentistry clinical application.While LLMs offer significant potential benefits,the challenges,such as data privacy,data quality,and model bias,need further study.Overall,LLMs have the potential to revolutionize dental diagnosis and treatment,which indicates a promising avenue for clinical application and research in dentistry.展开更多
Cu-based cathodes in aqueous batteries become very attractive in view of high theoretical capacity,moderate operation voltage and rich reserves of raw materials.However,their applications are obstructed by serious sid...Cu-based cathodes in aqueous batteries become very attractive in view of high theoretical capacity,moderate operation voltage and rich reserves of raw materials.However,their applications are obstructed by serious side reactions.The side reaction mainly arises from the spontaneous formation of Cu_(2)O,which occupies the electrode surface and lowers the reaction reversibility.Here,Na_(2)EDTA is introduced to address these issues.Both experimental results and theoretical calculations indicate that the Na_(2)EDTA reshapes the solvation structure of Cu^(2+)and modifies the electrode/electrolyte interface.Therefore,the redox potential of Cu^(2+)/Cu_(2)O is reduced and the surface of Cu is protected from H2O,thereby inhibiting the formation of Cu_(2)O.Meanwhile,the change in the solvation structure reduces the electrostatic repulsion between Cu^(2+)and the cathode,leading to high local concentration and benefiting uniform deposition.The results shed light on the applications of rechargeable Cu-based batteries.展开更多
Machin County is situated in the Sanjiangyuan Nature Reserve in the southeastern part of Qinghai Province.Influenced by the special topography and climate of the Qinghai-Tibet Plateau,Machin County has complex and div...Machin County is situated in the Sanjiangyuan Nature Reserve in the southeastern part of Qinghai Province.Influenced by the special topography and climate of the Qinghai-Tibet Plateau,Machin County has complex and diverse plant species.The vascular plant resources and diversity in Machin County were studied through field survey,literature review and specimen identification.The results show that there are 47 families and 127 genera and 256 species of vascular plants in the region,basically angiosperms,including those containing more species of the family Asteraceae,Buttercup,Genus Ginseng,Leguminosae and Rosaceae,and those containing more species of the genus Artemisia,Artemisia,Aster and Donzonia.In terms of life type,perennial herbs are the most dominant ones,accounting for 77.34%of the total number of species,followed by some annual(or biennial)herbs and shrub types.There are 191 species of medicinal vascular plants,accounting for 74.61%of the total number of species,including 48 species of Tibetan medicine.In terms of the medicinal parts of these plants,whole herb category is the most common one,followed by the root and rhizome category.Based on the investigation and research,we have proposed the conservation and utilization of plant resources in Machin County,Qinghai Province.展开更多
In this paper, we focus on the design of irregular QC-LDPC code based multi-level coded modulation(MLCM) scheme by jointly optimizing the component code rate and the degree distribution of the irregular QC-LDPC compon...In this paper, we focus on the design of irregular QC-LDPC code based multi-level coded modulation(MLCM) scheme by jointly optimizing the component code rate and the degree distribution of the irregular QC-LDPC component code. Firstly, the sub-channel capacities of MLCM systems is analyzed and discussed, based on which the optimal component code rate can be obtained. Secondly, an extrinsic information transfer chart based two-stage searching algorithm is proposed to find the good irregular QC-LDPC code ensembles with optimal component code rates for their corresponding sub-channels. Finally, by constructing the irregular QC-LDPC component codes from the designed ensembles with the aim of possibly enlarging the girth and reducing the number of the shortest cycles, the designed irregular QC-LDPC code based 16QAM and 64QAM MLCM systems can achieve 0.4 dB and 1.2 dB net coding gain, respectively, compared with the recently proposed regular QC-LDPC code based 16QAM and 64QAM MLCM systems.展开更多
There are 9 major coal-accumulating periods during geological history in China,including the Early Carboniferous,Late Carboniferous-Early Permian,Middle Permian,Late Permian,Late Triassic,Early-Middle Jurassic,Early C...There are 9 major coal-accumulating periods during geological history in China,including the Early Carboniferous,Late Carboniferous-Early Permian,Middle Permian,Late Permian,Late Triassic,Early-Middle Jurassic,Early Cretaceous,Paleogene and Neogene.The coal formed in these periods were developed in different coal-accumulating areas(CAA)including the North China,South China,Northwest China,Northeast China,the Qinghai–Tibet area,and China offshore area.In this paper,we investigated depositional environments,sequence stratigraphy,lithofacies paleogeography and coal accumulation pattern of five major coal-accumulating periods including the Late Carboniferous to Middle Permian of the North China CAA,the Late Permian of the South China CAA,the Late Triassic of the South China CAA,the Early-Middle Jurassic of the North and Northwest China CAA,and the Early Cretaceous in the Northeast China CAA.According to distribution of the coal-bearing strata and the regional tectonic outlines,we have identified distribution range of the coal-forming basins,sedimentary facies types and coal-accumulating models.The sequence stratigraphic frameworks of the major coal-accumulating periods were established based on recognition of a variety of sequence boundaries.The distribution of thick coals and migration patterns of the coal-accumulating centers in the sequence stratigraphic framework were analyzed.The lithofacies paleogeography maps based on third-order sequences were reconstructed and the distribution of coal accumulation centers and coal-rich belts were predicted.展开更多
With the development of multi-autonomous underwater vehicle(AUV) cooperative systems, the evaluation of their reliability is becoming more and more important. Aimed at the characteristics of the system, three reliabil...With the development of multi-autonomous underwater vehicle(AUV) cooperative systems, the evaluation of their reliability is becoming more and more important. Aimed at the characteristics of the system, three reliability indexes – standard entropy of rank distribution, all-terminal reliability and standard natural connectivity are determined in this paper. Topology structure and underwater acoustic communication are considered. The calculation methods of the three reliability indexes are proposed, and the characteristics of these indexes are analyzed. The reliability indexes of two multi-AUV cooperative systems are obtained as examples. Results show that these three indexes reflect different aspects of reliability for multi-AUV cooperative systems. This paper provides some methods to evaluate the reliability of multi-AUV cooperative systems, which is of practical value.展开更多
By the end of 2019,more than 220 gas fields had been discovered in the South China Sea.In order to accurately determine the geological characteristics of the large-and medium-sized gas fields in the South China Sea,th...By the end of 2019,more than 220 gas fields had been discovered in the South China Sea.In order to accurately determine the geological characteristics of the large-and medium-sized gas fields in the South China Sea,this study conducted a comprehensive examination of the gas fields.Based on the abundant available geologic and geochemical data,the distribution and key controlling factors of the hydrocarbon accumulation in the South China Sea were analyzed.The geological and geochemical features of the gas fields were as follows:(1)the gas fields were distributed similar to beads in the shape of a"C"along the northern,western,and southern continental margins;(2)the natural gas in the region was determined to be composed of higher amounts of alkane gas and less CO2;(3)the majority of the alkane gas was observed to be coal-type gas;(4)the gas reservoir types included structural reservoirs,lithologic reservoirs,and stratigraphic reservoirs,respectively;(5)the reservoir ages were mainly Oligocene,Miocene,and Pliocene,while the lithology was mainly organic reef,with some sandstone deposits;and(6)the main hydrocarbon accumulation period for the region was determined to be the late Pliocene-Quaternary Period.In addition,the main controlling factors of the gas reservoirs were confirmed to have been the development of coal measures,sufficient thermal evolution,and favorable migration and accumulation conditions.展开更多
With the development of multi-autonomous underwater vehicle(AUV) cooperative systems, the evaluation of their reliability is becoming more and more important. Since AUVs are always in motion, the reliability of the sy...With the development of multi-autonomous underwater vehicle(AUV) cooperative systems, the evaluation of their reliability is becoming more and more important. Since AUVs are always in motion, the reliability of the system is not stationary, but it varies with time. This paper studies the time-varying reliability evaluation indexes for multi-AUV cooperative systems. Aimed at elucidating the characteristics of the system, by considering the motion of the AUVs, two time dependent reliability evaluation indexes, natural connectivity and all-terminal reliability of the basic reliability indexes, are determined with the graph theory. Then the timevarying reliability of multi-AUV cooperative systems is evaluated combining with an actual example. This paper provides a method to evaluate the time-varying reliability of multi-AUV cooperative systems.展开更多
The solubilities of fluorene in Exxsol D30, Exxsol D40, and crude dimethyl ethylbenzene(DME) from 299.25 to 356.85 K were investigated using the gas chromatography(GC) observation technique. Solubility curves were obt...The solubilities of fluorene in Exxsol D30, Exxsol D40, and crude dimethyl ethylbenzene(DME) from 299.25 to 356.85 K were investigated using the gas chromatography(GC) observation technique. Solubility curves were obtained based on the results and correlated with the modified Apelblat and λh equations to provide a valid model to predict the dissolution thermodynamic properties of fluorene at different temperatures, which is important in separating fluorene by crystallization.展开更多
In the present study,the coal-rock organic facies of Oligocene Yacheng Formation of the marginal basin in the South China Sea were classified and divided.In addition,through the correlations of the large-scale coal-be...In the present study,the coal-rock organic facies of Oligocene Yacheng Formation of the marginal basin in the South China Sea were classified and divided.In addition,through the correlations of the large-scale coal-bearing basins between the epicontinental sea and the South China Sea,it was concluded that the coal forming activities in the South China Sea presented particularity and complexity.Furthermore,the coal forming mechanisms also presented distinctiveness.The marginal basins in the South China Sea consist of several large and complex rift or depression basins,which are distributed at different tectonic positions in the South China Sea.Therefore,the marginal basins in the South China Sea are not simple traditional units with onshore continental slopes extending toward the deep sea.The marginal basins are known to consist of multi-level structures and distinctive types of basins which differ from the continental regions to the sea.During the Oligocene,the existing luxuriant plants and beneficial conditions assisted in the development of peat.Therefore,the Oligocene was the significant period for the formation and aggregation of the peat.However,the peat did not form in unified sedimentary dynamic fields,but instead displayed multi-level geographical units,multiple provenance areas,instability,and nonevent characteristics.As a result,the marginal basins in the South China Sea are characterized by non-uniform peat aggregation stages.In another words,the majority of the peat had entered the marine system in a dispersive manner and acted as part of the marine deposits,rather than during one or several suitable coal-forming stages.These peat deposits then became the main material source for hydrocarbon generation in all of the marginal basins of the South China Sea.The study will be of much significance for the hydrocarbon exploration in the marginal basins of the South China Sea.展开更多
Catalytic CO_(2)conversion has witnessed a dynamic growth in recent decades.Various materials have been applied to reduce CO_(2)into fuels and value-added chemicals.Normally,the powder-based catalysts cannot be direct...Catalytic CO_(2)conversion has witnessed a dynamic growth in recent decades.Various materials have been applied to reduce CO_(2)into fuels and value-added chemicals.Normally,the powder-based catalysts cannot be directly utilized for CO_(2)conversion.Much attention was paid to the study of catalytic membranes in order to overcome this issue,since it is convenient for catalytic membranes to be employed in devices for practical applications.In this review,the recent research development of porous catalytic membranes for CO_(2)conversion is summarized.The preparations of representative porous catalytic membranes and their CO_(2)conversion methods,including electrocatalysis,photocatalysis,photoelectrocatalysis,thermalcatalysis and biocatalysis,are discussed in detail.This review is expected to provide deep understanding on the utilization of porous catalytic membranes for CO_(2)conversion.展开更多
Rationally manipulating surface reconstruction of catalysts for water oxidation,inducing formation and dynamic accumulation of catalytically active centers still face numerous challenges.Herein,the introduction of[Cr(...Rationally manipulating surface reconstruction of catalysts for water oxidation,inducing formation and dynamic accumulation of catalytically active centers still face numerous challenges.Herein,the introduction of[Cr(C_(2)O_(4))_(3)]^(3-)into NiFe LDHs by intercalation engineering to promote surface reconstruction achieves an advanced oxygen evolution reaction(OER)activity.In view of the weak electronegativity of Cr^(3+) in[Cr(C_(2)O_(4))_(3)]^(3-),the intercalation of[Cr(C_(2)O_(4))_(3)]^(3-)is expected to result in an electron-rich structure of Fe sites in NiFe LDHs,and higher valence state of Ni can be formed with the charge transfer between Fe and Ni.The optimized electronic structure of NiFe-[Cr(C_(2)O_(4))_(3)]^(3-)-LDHs with more active Ni^(3+) species and the expedited dynamic generation of Ni^(3+) (Fe)OOH phase during the OER process contributed to its excellent catalytic property,revealed by in situ X-ray absorption spectroscopy,Raman spectroscopy,and quasi-in situ X-ray photoelectron spectroscopy.With the modulated electronic structure of metal sites,NiFe-[Cr(C_(2)O_(4))_(3)]^(3-)-LDHs exhibited promoted OER property with a lower overpotential of 236 mV at the current density of 10 mA cm^(-2).This work illustrates the intercalation of conjugated anion to dynamically construct desired Ni^(3+) sites with the optimal electronic environment for improved OER electrocatalysis.展开更多
基金supported by the Key R&D Project of the Ministry of Science and Technology of China(2020YFB1808005)。
文摘Low Earth Orbit(LEO)multibeam satellites will be widely used in the next generation of satellite communication systems,whose inter-beam interference will inevitably limit the performance of the whole system.Nonlinear precoding such as Tomlinson-Harashima precoding(THP)algorithm has been proved to be a promising technology to solve this problem,which has smaller noise amplification effect compared with linear precoding.However,the similarity of different user channels(defined as channel correlation)will degrade the performance of THP algorithm.In this paper,we qualitatively analyze the inter-beam interference in the whole process of LEO satellite over a specific coverage area,and the impact of channel correlation on Signal-to-Noise Ratio(SNR)of receivers when THP is applied.One user grouping algorithm is proposed based on the analysis of channel correlation,which could decrease the number of users with high channel correlation in each precoding group,thus improve the performance of THP.Furthermore,our algorithm is designed under the premise of co-frequency deployment and orthogonal frequency division multiplexing(OFDM),which leads to more users under severe inter-beam interference compared to the existing research on geostationary orbit satellites broadcasting systems.Simulation results show that the proposed user grouping algorithm possesses higher channel capacity and better bit error rate(BER)performance in high SNR conditions relative to existing works.
基金supported by the National Nature Science Foundation of China (22105118)the Nature Science Foundation of Shandong Provinces (ZR2021QB095)the China Postdoctoral Science Foundation (2020TQ0183 and 2021M701979)。
文摘Aqueous zinc metal batteries feature intrinsic safety,but suffer from severe dendrite growth and water-derived side reactions.Many metal coatings have been explored for stabilizing Zn metal anode via a trialand-error approach.Here,we propose an exercisable way to screen the potential metal coating on Zn anodes in view of de-polarization effect and dendrite-suppressing ability theoretically.As an output of this screening,cadmium(Cd) metal is checked experimentally.Therefore,symmetric ZnllZn cells using Cd coated Zn(Zn@Cd) exhibit an ultra-long cycle life of 3500 h(nearly 5 months) at a high current density of 10 mA cm^(-2),achieving a record-high cumulative capacity(35 A h cm^(-2)) compared to the previous reports.The full cells of Zn@Cd‖MnO_(2) display a markedly improved cycling performance under harsh conditions including a limited Zn supply(N/P ratio=1.7) and a high areal capacity(3.5 mA h cm^(-2)).The significance of this work lies in not only the first report of Cd coating for stabilizing Zn metal anode,but also a feasible way to screen the promising metal materials for other metal anodes.
基金The Ministry of Land and Resources Project of Oil and Gas Resource Investigation and Evaluation under contract Nos XQ-2004-05 and XQ-2007-05the National Key Basic Research Program of China(973 Program)under contract No.2009CB219400+3 种基金the National Science and Technology Major Project under contract Nos 2008ZX05025,2011ZX05025 and2016ZX05026the National Natural Science Foundation under contract Nos 41872172 and 42072188the Research and Innovation Team Support Program of Shandong University of Science and Technology under contract No.2018TDJH101Hebei Provincial Resources Survey and Research Laboratory Open Foundation。
文摘Sea area is an important area of oil and gas exploration in China.It has been found that China's sea area mainly consists of coal type oil and gas,and the exploration of coal-bearing series source rocks has become an important part of oil and gas exploration there.Through years of comprehensive geological research in China's sea area,it has been revealed that it has undergone multiple occurrences of tectonic opening and closing movements in varying degrees in the Paleogene,forming 26 Cenozoic sedimentary basins of various types,such as active continental margin,passive continental margin,transitional continental margin and drift rift basins.In the present study,it is observed for the first time that coal type source rocks are mainly developed in 14 continental margin basins in China's sea area,revealing that a very large C-shaped coal-bearing basin group developed there in the Cenozoic.Next,based on the coupling analysis of paleoclimate,paleobotany,paleogeography and paleostructure,it is observed that there are five coal-forming periods in China's sea area,namely the Paleocene,Eocene,early Oligocene,late Oligocene and Miocene-Pliocene,and the coal-forming age is gradually new from north to south.It is also found that the coal seams in the sea area are mainly developed in three coal-forming environments in Cenozoic,namely delta,fan delta and tidal flat-lagoon.The coal seams developed in different environments are characterized by thin thickness,many layers and poor stability.However,the coal-bearing series source rocks in China's sea area have a wide distribution range,very high thickness and large amount,thus forming a material basis for the formation of rich coal type oil and gas.
基金supported by the Research and Development Program,West China Hospital of Stomatology,Sichuan University(RD-02-202107)Sichuan Province Science and Technology Support Program(2022NSFSC0743)Sichuan Postdoctoral Science Foundation(TB2022005)grant to H.Huang.
文摘The ChatGPT,a lite and conversational variant of Generative Pretrained Transformer 4(GPT-4)developed by OpenAI,is one of the milestone Large Language Models(LLMs)with billions of parameters.LLMs have stirred up much interest among researchers and practitioners in their impressive skills in natural language processing tasks,which profoundly impact various fields.This paper mainly discusses the future applications of LLMs in dentistry.We introduce two primary LLM deployment methods in dentistry,including automated dental diagnosis and cross-modal dental diagnosis,and examine their potential applications.Especially,equipped with a cross-modal encoder,a single LLM can manage multi-source data and conduct advanced natural language reasoning to perform complex clinical operations.We also present cases to demonstrate the potential of a fully automatic Multi-Modal LLM AI system for dentistry clinical application.While LLMs offer significant potential benefits,the challenges,such as data privacy,data quality,and model bias,need further study.Overall,LLMs have the potential to revolutionize dental diagnosis and treatment,which indicates a promising avenue for clinical application and research in dentistry.
基金financial support from the Natural Science Foundation of Shandong Province(ZR2021ZD05)the Outstanding Talents in Shandong University。
文摘Cu-based cathodes in aqueous batteries become very attractive in view of high theoretical capacity,moderate operation voltage and rich reserves of raw materials.However,their applications are obstructed by serious side reactions.The side reaction mainly arises from the spontaneous formation of Cu_(2)O,which occupies the electrode surface and lowers the reaction reversibility.Here,Na_(2)EDTA is introduced to address these issues.Both experimental results and theoretical calculations indicate that the Na_(2)EDTA reshapes the solvation structure of Cu^(2+)and modifies the electrode/electrolyte interface.Therefore,the redox potential of Cu^(2+)/Cu_(2)O is reduced and the surface of Cu is protected from H2O,thereby inhibiting the formation of Cu_(2)O.Meanwhile,the change in the solvation structure reduces the electrostatic repulsion between Cu^(2+)and the cathode,leading to high local concentration and benefiting uniform deposition.The results shed light on the applications of rechargeable Cu-based batteries.
文摘Machin County is situated in the Sanjiangyuan Nature Reserve in the southeastern part of Qinghai Province.Influenced by the special topography and climate of the Qinghai-Tibet Plateau,Machin County has complex and diverse plant species.The vascular plant resources and diversity in Machin County were studied through field survey,literature review and specimen identification.The results show that there are 47 families and 127 genera and 256 species of vascular plants in the region,basically angiosperms,including those containing more species of the family Asteraceae,Buttercup,Genus Ginseng,Leguminosae and Rosaceae,and those containing more species of the genus Artemisia,Artemisia,Aster and Donzonia.In terms of life type,perennial herbs are the most dominant ones,accounting for 77.34%of the total number of species,followed by some annual(or biennial)herbs and shrub types.There are 191 species of medicinal vascular plants,accounting for 74.61%of the total number of species,including 48 species of Tibetan medicine.In terms of the medicinal parts of these plants,whole herb category is the most common one,followed by the root and rhizome category.Based on the investigation and research,we have proposed the conservation and utilization of plant resources in Machin County,Qinghai Province.
基金supported by the National Key R&D Program of China(2017YFC0211503,2016YFC0207100)the Strategic Priority Research Program(A)of the Chinese Academy of Sciences(XDA23030300)+2 种基金the National Natural Science Foundation of China(21401200,51672273)the Open Research Fund of State Key Laboratory of Multi-phase Complex Systems(MPCS-2017-D-06)the Young Talent Project of the Center for Excellence in Regional Atmospheric Environment,CAS(CERAE201805)~~
基金supported by National Natural Science Foundation of China(No.61571061)
文摘In this paper, we focus on the design of irregular QC-LDPC code based multi-level coded modulation(MLCM) scheme by jointly optimizing the component code rate and the degree distribution of the irregular QC-LDPC component code. Firstly, the sub-channel capacities of MLCM systems is analyzed and discussed, based on which the optimal component code rate can be obtained. Secondly, an extrinsic information transfer chart based two-stage searching algorithm is proposed to find the good irregular QC-LDPC code ensembles with optimal component code rates for their corresponding sub-channels. Finally, by constructing the irregular QC-LDPC component codes from the designed ensembles with the aim of possibly enlarging the girth and reducing the number of the shortest cycles, the designed irregular QC-LDPC code based 16QAM and 64QAM MLCM systems can achieve 0.4 dB and 1.2 dB net coding gain, respectively, compared with the recently proposed regular QC-LDPC code based 16QAM and 64QAM MLCM systems.
基金This research was supported by the Project for the Survey of Land and Resources in China(1212010633901)National Natural Science Foundation of China(Grant No.41572090)。
文摘There are 9 major coal-accumulating periods during geological history in China,including the Early Carboniferous,Late Carboniferous-Early Permian,Middle Permian,Late Permian,Late Triassic,Early-Middle Jurassic,Early Cretaceous,Paleogene and Neogene.The coal formed in these periods were developed in different coal-accumulating areas(CAA)including the North China,South China,Northwest China,Northeast China,the Qinghai–Tibet area,and China offshore area.In this paper,we investigated depositional environments,sequence stratigraphy,lithofacies paleogeography and coal accumulation pattern of five major coal-accumulating periods including the Late Carboniferous to Middle Permian of the North China CAA,the Late Permian of the South China CAA,the Late Triassic of the South China CAA,the Early-Middle Jurassic of the North and Northwest China CAA,and the Early Cretaceous in the Northeast China CAA.According to distribution of the coal-bearing strata and the regional tectonic outlines,we have identified distribution range of the coal-forming basins,sedimentary facies types and coal-accumulating models.The sequence stratigraphic frameworks of the major coal-accumulating periods were established based on recognition of a variety of sequence boundaries.The distribution of thick coals and migration patterns of the coal-accumulating centers in the sequence stratigraphic framework were analyzed.The lithofacies paleogeography maps based on third-order sequences were reconstructed and the distribution of coal accumulation centers and coal-rich belts were predicted.
文摘With the development of multi-autonomous underwater vehicle(AUV) cooperative systems, the evaluation of their reliability is becoming more and more important. Aimed at the characteristics of the system, three reliability indexes – standard entropy of rank distribution, all-terminal reliability and standard natural connectivity are determined in this paper. Topology structure and underwater acoustic communication are considered. The calculation methods of the three reliability indexes are proposed, and the characteristics of these indexes are analyzed. The reliability indexes of two multi-AUV cooperative systems are obtained as examples. Results show that these three indexes reflect different aspects of reliability for multi-AUV cooperative systems. This paper provides some methods to evaluate the reliability of multi-AUV cooperative systems, which is of practical value.
基金The National Petroleum Major Projects under contract Nos 2016ZX05026,2011ZX05025 and 2008ZX05025the National Natural Science Foundation Major Research Program of China under contract No.91528303+3 种基金the National Program on Key Basic Research Project of China(973 Program)under contract No.2009CB219400the Key Laboratory Project of Gansu Province under contract No.1309RTSA041the National Natural Science Foundation of China under contract No.41872172the SDUST Research Found under contract No.2018TDJH101
文摘By the end of 2019,more than 220 gas fields had been discovered in the South China Sea.In order to accurately determine the geological characteristics of the large-and medium-sized gas fields in the South China Sea,this study conducted a comprehensive examination of the gas fields.Based on the abundant available geologic and geochemical data,the distribution and key controlling factors of the hydrocarbon accumulation in the South China Sea were analyzed.The geological and geochemical features of the gas fields were as follows:(1)the gas fields were distributed similar to beads in the shape of a"C"along the northern,western,and southern continental margins;(2)the natural gas in the region was determined to be composed of higher amounts of alkane gas and less CO2;(3)the majority of the alkane gas was observed to be coal-type gas;(4)the gas reservoir types included structural reservoirs,lithologic reservoirs,and stratigraphic reservoirs,respectively;(5)the reservoir ages were mainly Oligocene,Miocene,and Pliocene,while the lithology was mainly organic reef,with some sandstone deposits;and(6)the main hydrocarbon accumulation period for the region was determined to be the late Pliocene-Quaternary Period.In addition,the main controlling factors of the gas reservoirs were confirmed to have been the development of coal measures,sufficient thermal evolution,and favorable migration and accumulation conditions.
文摘With the development of multi-autonomous underwater vehicle(AUV) cooperative systems, the evaluation of their reliability is becoming more and more important. Since AUVs are always in motion, the reliability of the system is not stationary, but it varies with time. This paper studies the time-varying reliability evaluation indexes for multi-AUV cooperative systems. Aimed at elucidating the characteristics of the system, by considering the motion of the AUVs, two time dependent reliability evaluation indexes, natural connectivity and all-terminal reliability of the basic reliability indexes, are determined with the graph theory. Then the timevarying reliability of multi-AUV cooperative systems is evaluated combining with an actual example. This paper provides a method to evaluate the time-varying reliability of multi-AUV cooperative systems.
文摘The solubilities of fluorene in Exxsol D30, Exxsol D40, and crude dimethyl ethylbenzene(DME) from 299.25 to 356.85 K were investigated using the gas chromatography(GC) observation technique. Solubility curves were obtained based on the results and correlated with the modified Apelblat and λh equations to provide a valid model to predict the dissolution thermodynamic properties of fluorene at different temperatures, which is important in separating fluorene by crystallization.
基金The National Natural Science Foundation of China under contract Nos 41872172 and 41672096the Major National Science and Technology Projects under contract No.2016ZX05026007-004the Science Foundation of Shandong Province under contract No.ZR2019QD008
文摘In the present study,the coal-rock organic facies of Oligocene Yacheng Formation of the marginal basin in the South China Sea were classified and divided.In addition,through the correlations of the large-scale coal-bearing basins between the epicontinental sea and the South China Sea,it was concluded that the coal forming activities in the South China Sea presented particularity and complexity.Furthermore,the coal forming mechanisms also presented distinctiveness.The marginal basins in the South China Sea consist of several large and complex rift or depression basins,which are distributed at different tectonic positions in the South China Sea.Therefore,the marginal basins in the South China Sea are not simple traditional units with onshore continental slopes extending toward the deep sea.The marginal basins are known to consist of multi-level structures and distinctive types of basins which differ from the continental regions to the sea.During the Oligocene,the existing luxuriant plants and beneficial conditions assisted in the development of peat.Therefore,the Oligocene was the significant period for the formation and aggregation of the peat.However,the peat did not form in unified sedimentary dynamic fields,but instead displayed multi-level geographical units,multiple provenance areas,instability,and nonevent characteristics.As a result,the marginal basins in the South China Sea are characterized by non-uniform peat aggregation stages.In another words,the majority of the peat had entered the marine system in a dispersive manner and acted as part of the marine deposits,rather than during one or several suitable coal-forming stages.These peat deposits then became the main material source for hydrocarbon generation in all of the marginal basins of the South China Sea.The study will be of much significance for the hydrocarbon exploration in the marginal basins of the South China Sea.
基金supported by the Ministry of Education Singapore under the Academic Research Funds(RT12/19 and MOE-MOET2EP10120-0003)the Singapore National Research Foundation Investigatorship(NRF-NRFI2018-03)。
文摘Catalytic CO_(2)conversion has witnessed a dynamic growth in recent decades.Various materials have been applied to reduce CO_(2)into fuels and value-added chemicals.Normally,the powder-based catalysts cannot be directly utilized for CO_(2)conversion.Much attention was paid to the study of catalytic membranes in order to overcome this issue,since it is convenient for catalytic membranes to be employed in devices for practical applications.In this review,the recent research development of porous catalytic membranes for CO_(2)conversion is summarized.The preparations of representative porous catalytic membranes and their CO_(2)conversion methods,including electrocatalysis,photocatalysis,photoelectrocatalysis,thermalcatalysis and biocatalysis,are discussed in detail.This review is expected to provide deep understanding on the utilization of porous catalytic membranes for CO_(2)conversion.
基金support from the National Natural Science Foundation of China(51402100,21905088,21573066 and U19A2017)the Provincial Natural Science Foundation of Hunan(2020JJ5044,2022JJ10006)。
文摘Rationally manipulating surface reconstruction of catalysts for water oxidation,inducing formation and dynamic accumulation of catalytically active centers still face numerous challenges.Herein,the introduction of[Cr(C_(2)O_(4))_(3)]^(3-)into NiFe LDHs by intercalation engineering to promote surface reconstruction achieves an advanced oxygen evolution reaction(OER)activity.In view of the weak electronegativity of Cr^(3+) in[Cr(C_(2)O_(4))_(3)]^(3-),the intercalation of[Cr(C_(2)O_(4))_(3)]^(3-)is expected to result in an electron-rich structure of Fe sites in NiFe LDHs,and higher valence state of Ni can be formed with the charge transfer between Fe and Ni.The optimized electronic structure of NiFe-[Cr(C_(2)O_(4))_(3)]^(3-)-LDHs with more active Ni^(3+) species and the expedited dynamic generation of Ni^(3+) (Fe)OOH phase during the OER process contributed to its excellent catalytic property,revealed by in situ X-ray absorption spectroscopy,Raman spectroscopy,and quasi-in situ X-ray photoelectron spectroscopy.With the modulated electronic structure of metal sites,NiFe-[Cr(C_(2)O_(4))_(3)]^(3-)-LDHs exhibited promoted OER property with a lower overpotential of 236 mV at the current density of 10 mA cm^(-2).This work illustrates the intercalation of conjugated anion to dynamically construct desired Ni^(3+) sites with the optimal electronic environment for improved OER electrocatalysis.
