African swine fever(ASF)is a devastating infectious disease in swine that is severely threatening the global pig industry.An efficacious vaccine is urgently required.Here,we used the Chinese ASFV HLJ/18 as a backbone ...African swine fever(ASF)is a devastating infectious disease in swine that is severely threatening the global pig industry.An efficacious vaccine is urgently required.Here,we used the Chinese ASFV HLJ/18 as a backbone and generated a series of genedeleted viruses.The virulence,immunogenicity,safety,and protective efficacy evaluation in specific-pathogen-free pigs,commercial pigs,and pregnant sows indicated that one virus,namely HLJ/18-7GD,which has seven genes deleted,is fully attenuated in pigs,cannot convert to the virulent strain,and provides complete protection of pigs against lethal ASFV challenge.Our study shows that HLJ/-18-7GD is a safe and effective vaccine against ASFV,and as such is expected to play an important role in controlling the spread of ASFV.展开更多
As a new generation of direct current(DC)transmission technology,voltage sourced converter(VSC)based high voltage direct current(HVDC)has been widely developed and applied all over the world.China has also carried out...As a new generation of direct current(DC)transmission technology,voltage sourced converter(VSC)based high voltage direct current(HVDC)has been widely developed and applied all over the world.China has also carried out a deep technical research and engineering application in this area,and at present,it has been stepped into a fast growing period.This paper gives a general review over China’s VSC based HVDC in terms of engineering technology,application and future development.It comprehensively analyzes the technical difficulties and future development orientation on the aspects of the main configurations of VSC based HVDC system,topological structures of converters,control and protection technologies,flexible DC cables,converter valve tests,etc.It introduces the applicable fields and current status of China’s VSC based HVDC projects,and analyzes the application trends of VSC based HVDC projects both in China and all over the world according to the development characteristics and demands of future power grids.展开更多
As a revolutionary industrial technology,additive manufacturing creates objects by adding materials layer by layer and hence can fabricate customized components with an unprecedented degree of freedom.For metallic mat...As a revolutionary industrial technology,additive manufacturing creates objects by adding materials layer by layer and hence can fabricate customized components with an unprecedented degree of freedom.For metallic materials,unique hierarchical microstructures are constructed during additive manufacturing,which endow them with numerous excellent properties.To take full advantage of additive manufacturing,an in-depth understanding of the microstructure evolution mechanism is required.To this end,this review explores the fundamental procedures of additive manufacturing,that is,the formation and binding of melt pools.A comprehensive processing map is proposed that integrates melt pool energy-and geometry-related process parameters together.Based on it,additively manufactured microstructures are developed during and after the solidification of constituent melt pool.The solidification structures are composed of primary columnar grains and fine secondary phases that form along the grain boundaries.The post-solidification structures include submicron scale dislocation cells stemming from internal residual stress and nanoscale precipitates induced by intrinsic heat treatment during cyclic heating of adjacent melt pool.Based on solidification and dislocation theories,the formation mechanisms of the multistage microstructures are thoroughly analyzed,and accordingly,multistage control methods are proposed.In addition,the underlying atomic scale structural features are briefly discussed.Furthermore,microstructure design for additive manufacturing through adjustment of process parameters and alloy composition is addressed to fulfill the great potential of the technique.This review not only builds a solid microstructural framework for metallic materials produced by additive manufacturing but also provides a promising guideline to adjust their mechanical properties.展开更多
Due to their high controllability and flexibility,DC power grids have broad application prospects in the fields of networking of renewable energy and the power supply for oceanic archipelagos and future cities.This pa...Due to their high controllability and flexibility,DC power grids have broad application prospects in the fields of networking of renewable energy and the power supply for oceanic archipelagos and future cities.This paper describes the system topology,control strategy,DC breaker configuration,and research,development and testing of converter valves and DC breaker equipment of the Zhoushan multi-terminal DC transmission system.Zhejiang Zhoushan has unique geographical and developmental features to demonstrate the irreplaceable technical advantages of a DC power grid for providing reliable power supply.The experience gained from the Zhoushan DC power grid project can offer valuable insights into the development and utilization of this technology worldwide.展开更多
FOXP3＋ regulatory T （Treg） cells are critical in maintaining immune tolerance and homeostasis of the immune system. The molecular mechanisms underlying the stability, plasticity and functional activity of Treg cell...FOXP3＋ regulatory T （Treg） cells are critical in maintaining immune tolerance and homeostasis of the immune system. The molecular mechanisms underlying the stability, plasticity and functional activity of Treg cells have been much studied in recent years. Here, we summarize these intriguing findings, and provide insight into their potential use or manipulation during Treg cell therapy for the treatment of autoimmune diseases, graft-versus-host disease （GVHD） and cancer.展开更多
A cycle model of an irreversible heat engine working with harmonic systems is established in this paper. Based on the equation of motion of an operator in the Heisenberg picture and semi-group approach, the first law ...A cycle model of an irreversible heat engine working with harmonic systems is established in this paper. Based on the equation of motion of an operator in the Heisenberg picture and semi-group approach, the first law of thermodynamics for a harmonic system and the time evolution of the system are obtained. The general expressions for several important parameters, such as the work, efficiency, power output, and rate of entropy production are derived. By means of numerical analysis, the optimally operating regions and the optimal values of performance parameters of the cycle are determined under the condition of maximum power output. At last, some special cases, such as high temperature limit and frictionless case, are dis-cussed in brief.展开更多
Microblogging provides a new platform for com- municating and sharing information among Web users. Users can express opinions and record daily life using microblogs. Microblogs that are posted by users indicate their ...Microblogging provides a new platform for com- municating and sharing information among Web users. Users can express opinions and record daily life using microblogs. Microblogs that are posted by users indicate their interests to some extent. We aim to mine user interests via keyword extraction from microblogs. Traditional keyword extraction methods are usually designed for formal documents such as news articles or scientific papers. Messages posted by mi- croblogging users, however, are usually noisy and full of new words, which is a challenge for keyword extraction. In this paper, we combine a translation-based method with a frequency-based method for keyword extraction. In our ex- periments, we extract keywords for microblog users from the largest microblogging website in China, Sina Weibo. The re- suits show that our method can identify users＇ interests accu- rately and efficiently.展开更多
By Mobile Edge Computing(MEC), computation-intensive tasks are offloaded from mobile devices to cloud servers, and thus the energy consumption of mobile devices can be notably reduced. In this paper, we study task off...By Mobile Edge Computing(MEC), computation-intensive tasks are offloaded from mobile devices to cloud servers, and thus the energy consumption of mobile devices can be notably reduced. In this paper, we study task offloading in multi-user MEC systems with heterogeneous clouds, including edge clouds and remote clouds. Tasks are forwarded from mobile devices to edge clouds via wireless channels, and they can be further forwarded to remote clouds via the Internet. Our objective is to minimize the total energy consumption of multiple mobile devices, subject to bounded-delay requirements of tasks. Based on dynamic programming, we propose an algorithm that minimizes the energy consumption, by jointly allocating bandwidth and computational resources to mobile devices. The algorithm is of pseudo-polynomial complexity. To further reduce the complexity, we propose an approximation algorithm with energy discretization, and its total energy consumption is proved to be within a bounded gap from the optimum. Simulation results show that, nearly 82.7% energy of mobile devices can be saved by task offloading compared with mobile device execution.展开更多
Bauxite in China remains an urgently needed resource largely dependent on imports. Based on the study of the newly- discovered Dazhuyuan bauxite deposit in northeastern Guizhou, we have found new enrichment of tungste...Bauxite in China remains an urgently needed resource largely dependent on imports. Based on the study of the newly- discovered Dazhuyuan bauxite deposit in northeastern Guizhou, we have found new enrichment of tungsten and lithium in bauxite, with the highest WO3 content up to 0.33% and the highest Li20 content up to 0.58%. The present paper reports the in- itial result, and the spatial distribution feature of W and Li in the ore body （with Li enriched mostly in the north part of the west limb of the Liyuan syncline, whereas W enriched mostly in the central part of the east limb）. The results suggest that it is necessary to delineate lithium and tungsten ore body independently, discuss the feasibility of its industrial utilization, and point out the new direction of synthetic appraisal for such kinds of traditional mineral resources, in order to forecast and assess bauxite resources in the region.展开更多
The ability to perform short-term traffic flow forecasting is a crucial component of intelligent transportation systems. However, accurate and reliable traffic flow forecasting is still a significant issue due to the ...The ability to perform short-term traffic flow forecasting is a crucial component of intelligent transportation systems. However, accurate and reliable traffic flow forecasting is still a significant issue due to the complexity and variability of real traffic systems. To improve the accuracy of short-term traffic flow forecasting, this paper presents a novel hybrid prediction framework based on Support Vector Regression （SVR） that uses a Random Forest （RF） to select the most informative feature subset and an enhanced Genetic Algorithm （GA） with chaotic characteristics to identify the optimal forecasting model parameters. The framework is evaluated with real-world traffic data collected from eight sensors located near the 1-605 interstate highway in California. Results show that the proposed RF- CGASVR model achieves better performance than other methods.展开更多
It is very important to understand the annular multiphase flow behavior and the effect of hydrate phase transition during deep water drilling. The basic hydrodynamic models, including mass, momentum, and energy conser...It is very important to understand the annular multiphase flow behavior and the effect of hydrate phase transition during deep water drilling. The basic hydrodynamic models, including mass, momentum, and energy conservation equations, were established for annular flow with gas hydrate phase transition during gas kick. The behavior of annular multiphase flow with hydrate phase transition was investigated by analyzing the hydrate-forming region, the gas fraction in the fluid flowing in the annulus, pit gain, bottom hole pressure, and shut-in casing pressure. The simulation shows that it is possible to move the hydrate-forming region away from sea floor by increasing the circulation rate. The decrease in gas volume fraction in the annulus due to hydrate formation reduces pit gain, which can delay the detection of well kick and increase the risk of hydrate plugging in lines. Caution is needed when a well is monitored for gas kick at a relatively low gas production rate, because the possibility of hydrate presence is much greater than that at a relatively high production rate. The shut-in casing pressure cannot reflect the gas kick due to hydrate formation, which increases with time.展开更多
According to differences in vegetation types and their coverage, combining the latest research, using theory and method on the value of vegetation ecosystem services, this paper not only calculated goods...According to differences in vegetation types and their coverage, combining the latest research, using theory and method on the value of vegetation ecosystem services, this paper not only calculated goods produced by different types of vegetation but also estimated the value of various vegetation ecosystem services and set up database, GIS and eco-account of vegetation ecosystem. The result was as follows: the value of vegetation's primary productivity, soil and fertility conservation, water conservation, CO 2 fixation and O 2 release was 199.6 billion yuan/a, 22.64 billion yuan/a, 22.66 billion yuan/a, 352.24 billion yuan/a and 374.19 billion yuan/a, respectively. The total value of ecosystem services was 968.33 billion yuan/a. The temperate deciduous broad-leaved forest had the highest contribution rate, accounting for 16.42%. The result of value can reflect regional reality more exactly.展开更多
The H5N8 avian influenza viruses have been widely circulating in wild birds and are responsible for the loss of over 33 million domestic poultry in Europe, Russia, Middle East, and Asia since January 2020. To monitor ...The H5N8 avian influenza viruses have been widely circulating in wild birds and are responsible for the loss of over 33 million domestic poultry in Europe, Russia, Middle East, and Asia since January 2020. To monitor the invasion and spread of the H5N8 virus in China, we performed active surveillance by analyzing 317 wild bird samples and swab samples collected from 41,172 poultry all over the country. We isolated 22 H5N8 viruses from wild birds and 14 H5N8 viruses from waterfowls. Genetic analysis indicated that the 36 viruses formed two different genotypes: one genotype viruses were widely detected from different wild birds and domestic waterfowls;the other genotype was isolated from a whopper swan. We further revealed the origin and spatiotemporal spread of these two distinct H5N8 virus genotypes in 2020 and 2021. Animal studies indicated that the H5N8 isolates are highly pathogenic to chickens, mildly pathogenic in ducks, but have distinct pathotypes in mice. Moreover, we found that vaccinated poultry in China could be completely protected against H5N8 virus challenge. Given that the H5N8 viruses are likely to continue to spread in wild birds, vaccination of poultry is highly recommended in high-risk countries to prevent H5N8 avian influenza.展开更多
Metabolic reprogramming is reported to be one of the hallmarks of cancer,which is an adaptive mechanism by which fast-growing cancer cells adapt to their increasing energy demands.Recently,extracellular vesicles(EVs)k...Metabolic reprogramming is reported to be one of the hallmarks of cancer,which is an adaptive mechanism by which fast-growing cancer cells adapt to their increasing energy demands.Recently,extracellular vesicles(EVs)known as exosomes have been recognized as crucial signaling mediators in regulating the tumor microenvironment(TME).Meanwhile,the TME is a highly heterogeneous ecosystem incorporating cancer cells,fibroblasts,adipocytes,endothelial cells,mesenchymal stem cells,and extracellular matrix.Accumulated evidence indicates that exosomes may transfer biologically functional molecules to the recipient cells,which facilitate cancer progression,angiogenesis,metastasis,drug resistance,and immunosuppression by reprogramming the metabolism of cancer cells and their surrounding stromal cells.In this review,we present the role of exosomes in the TME and the underlying mechanism of how exosomes exacerbate tumor development through metabolic reprogramming.In addition,we will also discuss the potential role of exosomes targeting metabolic process as biomarkers for tumor diagnosis and prognosis,and exosomes-mediated metabolic reprogramming as potential targets for cancer therapy.Furthermore,a better understanding of the link between exosomes and metabolic reprogramming,and their impact on cancer progression,would provide novel insights for cancer prevention and treatment in the future.展开更多
Xanthomonas oryzae pathovar oryzae(Xoo)uses transcription activator-like effectors(TALEs)to cause bacterial blight(BB)in rice.In turn,rice has evolved several mechanisms to resist BB by targeting TALEs.One mechanism i...Xanthomonas oryzae pathovar oryzae(Xoo)uses transcription activator-like effectors(TALEs)to cause bacterial blight(BB)in rice.In turn,rice has evolved several mechanisms to resist BB by targeting TALEs.One mechanism involves the nucleotide-binding leucine-rich repeat(NLR)resistance gene Xa1 and TALEs.Reciprocally,Xoo has evolved TALE variants,C-terminally truncated versions(interfering TALEs or iTALEs),to overcome Xa1 resistance.However,it remains unknown to what extent the two co-adaptive mechanisms mediate Xoo–rice interactions.In this study,we cloned and characterized five additional Xa1 allelic R genes,Xa2,Xa31(t),Xa14,CGS-Xo111,and Xa45(t)from a collection of rice accessions.Sequence analysis revealed that Xa2 and Xa31(t)from different rice cultivars are identical.These genes and their predicted proteins were found to be highly conserved,forming a group of Xa1 alleles.The XA1 alleles could be distinguished by the number of C-terminal tandemrepeats consisting of 93 amino acid residues and ranged from four in XA14 to seven in XA45(t).Xa1 allelic genes were identified in the 3000 rice genomes surveyed.On the other hand,iTALEs could suppress the resistance mediated by Xa1 allelic R genes,and iTALE genes were prevalent(95%)in Asian,but not in African Xoo strains.Our findings demonstrate the prominence of a defense mechanism in which rice depends on Xa1 alleles and a counteracting mechanismin which Xoo relies on iTALEs for BB.展开更多
To study the seepage and deformation characteristics of coal at high temperatures,coal samples from six different regions were selected and subjected to computed tomography(CT)scanning studies.In conjunction with ANSY...To study the seepage and deformation characteristics of coal at high temperatures,coal samples from six different regions were selected and subjected to computed tomography(CT)scanning studies.In conjunction with ANSYS software,3 D reconstruction of CT images was used for the establishment of fluidsolid conjugate heat transfer model and coal thermal deformation model based on the microstructures of coal.In addition,the structure of coal was studied in 2 D and 3 D perspectives,followed by the analysis of seepage and deformation characteristics of coal at high temperatures.The results of this study indicated that porosity positively correlated with the fractal dimension,and the connectivity and seepage performances were roughly identical from 2 D and 3 D perspectives.As the porosity increased,the fractal dimension of coal samples became larger and the pore-fracture structures became more complex.As a result,the permeability of coal samples decreased.In the meantime,fluid was fully heated,generating high-temperature water at outlet.However,when the porosity was low,the outlet temperature was very high.The average deformation of coal skeleton with different pore-fracture structures at high temperatures showed a trend of initial increase and subsequent decrease with the increase of porosity and fractal dimension.The maximum deformation of coal skeleton positively correlated with connectivity but negatively correlated with the fractal dimension.展开更多
Supplying an ever-growing world population with industrial raw materials,energy and clean water,and at the same time addressing the threats posed by global change,these are the two fundamental challenges facing mankin...Supplying an ever-growing world population with industrial raw materials,energy and clean water,and at the same time addressing the threats posed by global change,these are the two fundamental challenges facing mankind today.展开更多
Reducing carbon emissions in the power sector is critical for transitioning to a sustainable and low-carbon future.Estimating carbon efficiency of demand side response(DSR)in the power system is an important step towa...Reducing carbon emissions in the power sector is critical for transitioning to a sustainable and low-carbon future.Estimating carbon efficiency of demand side response(DSR)in the power system is an important step towards realizing potential environmental benefits.Marginal emission factor(MEF)is an effective tool for estimating incremental changes in carbon emissions as a result of a change in demand.However,estimation methods currently used for evaluating MEF can be improved upon,specifically,by factoring in the ramp-rate constraint of generators in the fuel cost based merit order dispatch.In this paper is described a new method for MEF assessment under ramp-rate constraints;the method is then compared with two conventional estimations in a British power system.Three fuel price scenarios are used to conduct a sensitivity analysis of MEFs to fuel prices.Conclusions are drawn that can pave the way for future improvements in estimating MEF in power systems.展开更多
With the eruption of big data,practical recommendation schemes are now very important in various fields,including e-commerce,social networks,and a number of web-based services.Nowadays,there exist many personalized mo...With the eruption of big data,practical recommendation schemes are now very important in various fields,including e-commerce,social networks,and a number of web-based services.Nowadays,there exist many personalized movie recommendation schemes utilizing publicly available movie datasets(e.g.,MovieLens and Netflix),and returning improved performance metrics(e.g.,Root-Mean-Square Error(RMSE)).However,two fundamental issues faced by movie recommendation systems are still neglected:first,scalability,and second,practical usage feedback and verification based on real implementation.In particular,Collaborative Filtering(CF)is one of the major prevailing techniques for implementing recommendation systems.However,traditional CF schemes suffer from a time complexity problem,which makes them bad candidates for real-world recommendation systems.In this paper,we address these two issues.Firstly,a simple but high-efficient recommendation algorithm is proposed,which exploits users1 profile attributes to partition them into several clusters.For each cluster,a virtual opinion leader is conceived to represent the whole cluster,such that the dimension of the original useritem matrix can be significantly reduced,then a Weighted Slope One-VU method is designed and applied to the virtual opinion leader-item matrix to obtain the recommendation results.Compared to traditional clusteringbased CF recommendation schemes,our method can significantly reduce the time complexity,while achieving comparable recommendation performance.Furthermore,we have constructed a real personalized web-based movie recommendation system,MovieWatch,opened it to the public,collected user feedback on recommendations,and evaluated the feasibility and accuracy of our system based on this real-world data.展开更多
The Fuling shale gas field in China is the largest shale gas field as well as the largest of its type discovered in any Lower Paleozoic formation.In this study,the geology and production of the upper and lower gas lay...The Fuling shale gas field in China is the largest shale gas field as well as the largest of its type discovered in any Lower Paleozoic formation.In this study,the geology and production of the upper and lower gas layers in the Fuling shale gas field are evaluated in terms of structure,shale quality,fault,initial production,and estimated ultimate recovery(EUR).The shale in the lower gas layer of the Jiaoshiba anticline is a high-quality reservoir,where the space is dominated by organic pores in kerogen,and the gas content is high.The shale gas wells reveal relatively high initial production and EUR.However,the shale in the upper gas layer of the Jiaoshiba anticline has reservoir space mainly composed of clay mineral pores and organic pores within bitumen,and the gas content is low.In terms of structure,primary gas migration may occur in the upper gas layer,resulting in free gas accumulation in the structural high,where the development effects are generally better than those in the structural low.The lower gas layer in the Pingqiao anticline,is the main interval for shale gas accumulation and development due to the high-quality shale.Under the influence of faults,the efficiency of exploration wells emplaced on top of the anticline is much lower a compared with those in the flanks.The residual synclines close to the Sichuan Basin,including the Baima and Baitao anticlines,are characterized by more recent uplifts,larger area,greater distance from the deep and large faults,and early fracture closure.Therefore,we recommend that the shale gas exploration and development should be carried out preferentially in areas close to the center of the residual synclines,featuring relatively high-pressure coefficient and moderate burial depth.展开更多
基金supported by the National Key R&D Program of China(2018YFC1200601)Applied Technology Research and Development Project of Heilongjiang Province(GA19B301)+1 种基金Key-Area Research and Development Program of Guangdong Province(2019B020211004)the grant from the State Key Laboratory of Veterinary Biotechnology Program(SKLVBP201801)。
文摘African swine fever(ASF)is a devastating infectious disease in swine that is severely threatening the global pig industry.An efficacious vaccine is urgently required.Here,we used the Chinese ASFV HLJ/18 as a backbone and generated a series of genedeleted viruses.The virulence,immunogenicity,safety,and protective efficacy evaluation in specific-pathogen-free pigs,commercial pigs,and pregnant sows indicated that one virus,namely HLJ/18-7GD,which has seven genes deleted,is fully attenuated in pigs,cannot convert to the virulent strain,and provides complete protection of pigs against lethal ASFV challenge.Our study shows that HLJ/-18-7GD is a safe and effective vaccine against ASFV,and as such is expected to play an important role in controlling the spread of ASFV.
基金This work was supported by National Natural Science Foundation of China(No.51261130471).
文摘As a new generation of direct current(DC)transmission technology,voltage sourced converter(VSC)based high voltage direct current(HVDC)has been widely developed and applied all over the world.China has also carried out a deep technical research and engineering application in this area,and at present,it has been stepped into a fast growing period.This paper gives a general review over China’s VSC based HVDC in terms of engineering technology,application and future development.It comprehensively analyzes the technical difficulties and future development orientation on the aspects of the main configurations of VSC based HVDC system,topological structures of converters,control and protection technologies,flexible DC cables,converter valve tests,etc.It introduces the applicable fields and current status of China’s VSC based HVDC projects,and analyzes the application trends of VSC based HVDC projects both in China and all over the world according to the development characteristics and demands of future power grids.
基金financial support of National Natural Science Foundation of China(No.51971149)the funding from Science and Technology Innovation Commission of Shenzhen(Nos.KQJSCX20180328095612712,GJHZ20190822095418365)+1 种基金Guangdong Basic and Applied Basic Research Foundation(Nos.2020A1515110869 and 2019A1515110515)Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone Shenzhen Park Project(No.HZQB-KCZYB-2020030)。
文摘As a revolutionary industrial technology,additive manufacturing creates objects by adding materials layer by layer and hence can fabricate customized components with an unprecedented degree of freedom.For metallic materials,unique hierarchical microstructures are constructed during additive manufacturing,which endow them with numerous excellent properties.To take full advantage of additive manufacturing,an in-depth understanding of the microstructure evolution mechanism is required.To this end,this review explores the fundamental procedures of additive manufacturing,that is,the formation and binding of melt pools.A comprehensive processing map is proposed that integrates melt pool energy-and geometry-related process parameters together.Based on it,additively manufactured microstructures are developed during and after the solidification of constituent melt pool.The solidification structures are composed of primary columnar grains and fine secondary phases that form along the grain boundaries.The post-solidification structures include submicron scale dislocation cells stemming from internal residual stress and nanoscale precipitates induced by intrinsic heat treatment during cyclic heating of adjacent melt pool.Based on solidification and dislocation theories,the formation mechanisms of the multistage microstructures are thoroughly analyzed,and accordingly,multistage control methods are proposed.In addition,the underlying atomic scale structural features are briefly discussed.Furthermore,microstructure design for additive manufacturing through adjustment of process parameters and alloy composition is addressed to fulfill the great potential of the technique.This review not only builds a solid microstructural framework for metallic materials produced by additive manufacturing but also provides a promising guideline to adjust their mechanical properties.
基金supported in part by the National Natural Science Foundation of China(No.51261130471)by the Science and Technology Research Project of the State Grid Corporation of China(No.SGRIPGKJ(2013)166).
文摘Due to their high controllability and flexibility,DC power grids have broad application prospects in the fields of networking of renewable energy and the power supply for oceanic archipelagos and future cities.This paper describes the system topology,control strategy,DC breaker configuration,and research,development and testing of converter valves and DC breaker equipment of the Zhoushan multi-terminal DC transmission system.Zhejiang Zhoushan has unique geographical and developmental features to demonstrate the irreplaceable technical advantages of a DC power grid for providing reliable power supply.The experience gained from the Zhoushan DC power grid project can offer valuable insights into the development and utilization of this technology worldwide.
文摘FOXP3＋ regulatory T （Treg） cells are critical in maintaining immune tolerance and homeostasis of the immune system. The molecular mechanisms underlying the stability, plasticity and functional activity of Treg cells have been much studied in recent years. Here, we summarize these intriguing findings, and provide insight into their potential use or manipulation during Treg cell therapy for the treatment of autoimmune diseases, graft-versus-host disease （GVHD） and cancer.
基金the National Natural Science Foundation of China(Grant No. 10465003) the Natural Science Foundation of Jiangxi Province(Grant No. 0412011)
文摘A cycle model of an irreversible heat engine working with harmonic systems is established in this paper. Based on the equation of motion of an operator in the Heisenberg picture and semi-group approach, the first law of thermodynamics for a harmonic system and the time evolution of the system are obtained. The general expressions for several important parameters, such as the work, efficiency, power output, and rate of entropy production are derived. By means of numerical analysis, the optimally operating regions and the optimal values of performance parameters of the cycle are determined under the condition of maximum power output. At last, some special cases, such as high temperature limit and frictionless case, are dis-cussed in brief.
文摘Microblogging provides a new platform for com- municating and sharing information among Web users. Users can express opinions and record daily life using microblogs. Microblogs that are posted by users indicate their interests to some extent. We aim to mine user interests via keyword extraction from microblogs. Traditional keyword extraction methods are usually designed for formal documents such as news articles or scientific papers. Messages posted by mi- croblogging users, however, are usually noisy and full of new words, which is a challenge for keyword extraction. In this paper, we combine a translation-based method with a frequency-based method for keyword extraction. In our ex- periments, we extract keywords for microblog users from the largest microblogging website in China, Sina Weibo. The re- suits show that our method can identify users＇ interests accu- rately and efficiently.
基金the National Key R&D Program of China 2018YFB1800804the Nature Science Foundation of China (No. 61871254,No. 61861136003,No. 91638204)Hitachi Ltd.
文摘By Mobile Edge Computing(MEC), computation-intensive tasks are offloaded from mobile devices to cloud servers, and thus the energy consumption of mobile devices can be notably reduced. In this paper, we study task offloading in multi-user MEC systems with heterogeneous clouds, including edge clouds and remote clouds. Tasks are forwarded from mobile devices to edge clouds via wireless channels, and they can be further forwarded to remote clouds via the Internet. Our objective is to minimize the total energy consumption of multiple mobile devices, subject to bounded-delay requirements of tasks. Based on dynamic programming, we propose an algorithm that minimizes the energy consumption, by jointly allocating bandwidth and computational resources to mobile devices. The algorithm is of pseudo-polynomial complexity. To further reduce the complexity, we propose an approximation algorithm with energy discretization, and its total energy consumption is proved to be within a bounded gap from the optimum. Simulation results show that, nearly 82.7% energy of mobile devices can be saved by task offloading compared with mobile device execution.
基金supported by Guizhou Bureau of Geology and Mineral Resources, under its co-operative program "Study on metallogeny and ore-control factors for the Dazhuyuan bauxite deposit in Wuchuan area", and Chinese Geological Survey Program (Grant No. 1212010633903)"
文摘Bauxite in China remains an urgently needed resource largely dependent on imports. Based on the study of the newly- discovered Dazhuyuan bauxite deposit in northeastern Guizhou, we have found new enrichment of tungsten and lithium in bauxite, with the highest WO3 content up to 0.33% and the highest Li20 content up to 0.58%. The present paper reports the in- itial result, and the spatial distribution feature of W and Li in the ore body （with Li enriched mostly in the north part of the west limb of the Liyuan syncline, whereas W enriched mostly in the central part of the east limb）. The results suggest that it is necessary to delineate lithium and tungsten ore body independently, discuss the feasibility of its industrial utilization, and point out the new direction of synthetic appraisal for such kinds of traditional mineral resources, in order to forecast and assess bauxite resources in the region.
基金supported by the Science and Technology Department of Sichuan Province of China (Nos. 2017JY0007, 2016JY0073, and 2016JZ0031)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministrythe Fundamental Research Funds for the Central Universities (No. ZYGX2015J063)
文摘The ability to perform short-term traffic flow forecasting is a crucial component of intelligent transportation systems. However, accurate and reliable traffic flow forecasting is still a significant issue due to the complexity and variability of real traffic systems. To improve the accuracy of short-term traffic flow forecasting, this paper presents a novel hybrid prediction framework based on Support Vector Regression （SVR） that uses a Random Forest （RF） to select the most informative feature subset and an enhanced Genetic Algorithm （GA） with chaotic characteristics to identify the optimal forecasting model parameters. The framework is evaluated with real-world traffic data collected from eight sensors located near the 1-605 interstate highway in California. Results show that the proposed RF- CGASVR model achieves better performance than other methods.
基金supported by the China National 863 Program (Grant No.2006AA09A106)the Doctoral Program of Higher Education of China (Grant No.20060425502)+1 种基金the National Natural Science Foundation of China (Grant No.50874116)Shandong Province Natural Science Foundation(Grant No.Z2007A01)
文摘It is very important to understand the annular multiphase flow behavior and the effect of hydrate phase transition during deep water drilling. The basic hydrodynamic models, including mass, momentum, and energy conservation equations, were established for annular flow with gas hydrate phase transition during gas kick. The behavior of annular multiphase flow with hydrate phase transition was investigated by analyzing the hydrate-forming region, the gas fraction in the fluid flowing in the annulus, pit gain, bottom hole pressure, and shut-in casing pressure. The simulation shows that it is possible to move the hydrate-forming region away from sea floor by increasing the circulation rate. The decrease in gas volume fraction in the annulus due to hydrate formation reduces pit gain, which can delay the detection of well kick and increase the risk of hydrate plugging in lines. Caution is needed when a well is monitored for gas kick at a relatively low gas production rate, because the possibility of hydrate presence is much greater than that at a relatively high production rate. The shut-in casing pressure cannot reflect the gas kick due to hydrate formation, which increases with time.
基金National Natural Science Foundation of China No.30070083+1 种基金 Ministry of Education of China No.2001DXM700012
文摘According to differences in vegetation types and their coverage, combining the latest research, using theory and method on the value of vegetation ecosystem services, this paper not only calculated goods produced by different types of vegetation but also estimated the value of various vegetation ecosystem services and set up database, GIS and eco-account of vegetation ecosystem. The result was as follows: the value of vegetation's primary productivity, soil and fertility conservation, water conservation, CO 2 fixation and O 2 release was 199.6 billion yuan/a, 22.64 billion yuan/a, 22.66 billion yuan/a, 352.24 billion yuan/a and 374.19 billion yuan/a, respectively. The total value of ecosystem services was 968.33 billion yuan/a. The temperate deciduous broad-leaved forest had the highest contribution rate, accounting for 16.42%. The result of value can reflect regional reality more exactly.
基金supported by the National Natural Science Foundation of China (31521005, 31672593)the Laboratory for Lingnan Modern Agriculture Project (NT2021007)+1 种基金the National Key Research and Development Program of China (2016YFD0500201)the China Agriculture Research System (CARS-41G12)
文摘The H5N8 avian influenza viruses have been widely circulating in wild birds and are responsible for the loss of over 33 million domestic poultry in Europe, Russia, Middle East, and Asia since January 2020. To monitor the invasion and spread of the H5N8 virus in China, we performed active surveillance by analyzing 317 wild bird samples and swab samples collected from 41,172 poultry all over the country. We isolated 22 H5N8 viruses from wild birds and 14 H5N8 viruses from waterfowls. Genetic analysis indicated that the 36 viruses formed two different genotypes: one genotype viruses were widely detected from different wild birds and domestic waterfowls;the other genotype was isolated from a whopper swan. We further revealed the origin and spatiotemporal spread of these two distinct H5N8 virus genotypes in 2020 and 2021. Animal studies indicated that the H5N8 isolates are highly pathogenic to chickens, mildly pathogenic in ducks, but have distinct pathotypes in mice. Moreover, we found that vaccinated poultry in China could be completely protected against H5N8 virus challenge. Given that the H5N8 viruses are likely to continue to spread in wild birds, vaccination of poultry is highly recommended in high-risk countries to prevent H5N8 avian influenza.
基金supported by National Natural Science Foundation of China(grant number 81901022).
文摘Metabolic reprogramming is reported to be one of the hallmarks of cancer,which is an adaptive mechanism by which fast-growing cancer cells adapt to their increasing energy demands.Recently,extracellular vesicles(EVs)known as exosomes have been recognized as crucial signaling mediators in regulating the tumor microenvironment(TME).Meanwhile,the TME is a highly heterogeneous ecosystem incorporating cancer cells,fibroblasts,adipocytes,endothelial cells,mesenchymal stem cells,and extracellular matrix.Accumulated evidence indicates that exosomes may transfer biologically functional molecules to the recipient cells,which facilitate cancer progression,angiogenesis,metastasis,drug resistance,and immunosuppression by reprogramming the metabolism of cancer cells and their surrounding stromal cells.In this review,we present the role of exosomes in the TME and the underlying mechanism of how exosomes exacerbate tumor development through metabolic reprogramming.In addition,we will also discuss the potential role of exosomes targeting metabolic process as biomarkers for tumor diagnosis and prognosis,and exosomes-mediated metabolic reprogramming as potential targets for cancer therapy.Furthermore,a better understanding of the link between exosomes and metabolic reprogramming,and their impact on cancer progression,would provide novel insights for cancer prevention and treatment in the future.
基金supported by the National Natural Science Foundation of China(31830072 to G.C.)the United States Department of Agriculture National Institute of Agriculture and Food(2017-67013-26521 to B.Y.)+1 种基金the Young Elite Scientist Sponsorship of the China Association for Science and Technology(2017QNRC001 to Z.J.)the Chinese National Transgenic Major Program(2016ZX08001-002 to G.C.).
文摘Xanthomonas oryzae pathovar oryzae(Xoo)uses transcription activator-like effectors(TALEs)to cause bacterial blight(BB)in rice.In turn,rice has evolved several mechanisms to resist BB by targeting TALEs.One mechanism involves the nucleotide-binding leucine-rich repeat(NLR)resistance gene Xa1 and TALEs.Reciprocally,Xoo has evolved TALE variants,C-terminally truncated versions(interfering TALEs or iTALEs),to overcome Xa1 resistance.However,it remains unknown to what extent the two co-adaptive mechanisms mediate Xoo–rice interactions.In this study,we cloned and characterized five additional Xa1 allelic R genes,Xa2,Xa31(t),Xa14,CGS-Xo111,and Xa45(t)from a collection of rice accessions.Sequence analysis revealed that Xa2 and Xa31(t)from different rice cultivars are identical.These genes and their predicted proteins were found to be highly conserved,forming a group of Xa1 alleles.The XA1 alleles could be distinguished by the number of C-terminal tandemrepeats consisting of 93 amino acid residues and ranged from four in XA14 to seven in XA45(t).Xa1 allelic genes were identified in the 3000 rice genomes surveyed.On the other hand,iTALEs could suppress the resistance mediated by Xa1 allelic R genes,and iTALE genes were prevalent(95%)in Asian,but not in African Xoo strains.Our findings demonstrate the prominence of a defense mechanism in which rice depends on Xa1 alleles and a counteracting mechanismin which Xoo relies on iTALEs for BB.
基金supported by the National Natural Science Foundation of China(Project Nos.51934004,51674158,51574158,and 51474106)the Major Program of Shandong Province Natural Science Foundation(ZR2018ZA0602)+2 种基金the Taishan Scholar Talent Team Support Plan for Advantaged&Unique Discipline Areasthe Science and technology support plan for Youth Innovation of colleges and universities in Shandong Province(2019KJH006)the special funds for Taishan scholar project(TS20190935)。
文摘To study the seepage and deformation characteristics of coal at high temperatures,coal samples from six different regions were selected and subjected to computed tomography(CT)scanning studies.In conjunction with ANSYS software,3 D reconstruction of CT images was used for the establishment of fluidsolid conjugate heat transfer model and coal thermal deformation model based on the microstructures of coal.In addition,the structure of coal was studied in 2 D and 3 D perspectives,followed by the analysis of seepage and deformation characteristics of coal at high temperatures.The results of this study indicated that porosity positively correlated with the fractal dimension,and the connectivity and seepage performances were roughly identical from 2 D and 3 D perspectives.As the porosity increased,the fractal dimension of coal samples became larger and the pore-fracture structures became more complex.As a result,the permeability of coal samples decreased.In the meantime,fluid was fully heated,generating high-temperature water at outlet.However,when the porosity was low,the outlet temperature was very high.The average deformation of coal skeleton with different pore-fracture structures at high temperatures showed a trend of initial increase and subsequent decrease with the increase of porosity and fractal dimension.The maximum deformation of coal skeleton positively correlated with connectivity but negatively correlated with the fractal dimension.
基金supported by the National Natural Science Foundation of China(42072168 and 41790450)the National Key Research and Development Program of China(2019YFC0605405)+1 种基金the Fundamental Research Funds for the Central Universities(2021YQDC04)support from International Continental Scientific Drilling Program。
文摘Supplying an ever-growing world population with industrial raw materials,energy and clean water,and at the same time addressing the threats posed by global change,these are the two fundamental challenges facing mankind today.
基金This work was supported in part by the EPSRC UK and the NSFC,through the ERIFT project(51261130471).
文摘Reducing carbon emissions in the power sector is critical for transitioning to a sustainable and low-carbon future.Estimating carbon efficiency of demand side response(DSR)in the power system is an important step towards realizing potential environmental benefits.Marginal emission factor(MEF)is an effective tool for estimating incremental changes in carbon emissions as a result of a change in demand.However,estimation methods currently used for evaluating MEF can be improved upon,specifically,by factoring in the ramp-rate constraint of generators in the fuel cost based merit order dispatch.In this paper is described a new method for MEF assessment under ramp-rate constraints;the method is then compared with two conventional estimations in a British power system.Three fuel price scenarios are used to conduct a sensitivity analysis of MEFs to fuel prices.Conclusions are drawn that can pave the way for future improvements in estimating MEF in power systems.
文摘With the eruption of big data,practical recommendation schemes are now very important in various fields,including e-commerce,social networks,and a number of web-based services.Nowadays,there exist many personalized movie recommendation schemes utilizing publicly available movie datasets(e.g.,MovieLens and Netflix),and returning improved performance metrics(e.g.,Root-Mean-Square Error(RMSE)).However,two fundamental issues faced by movie recommendation systems are still neglected:first,scalability,and second,practical usage feedback and verification based on real implementation.In particular,Collaborative Filtering(CF)is one of the major prevailing techniques for implementing recommendation systems.However,traditional CF schemes suffer from a time complexity problem,which makes them bad candidates for real-world recommendation systems.In this paper,we address these two issues.Firstly,a simple but high-efficient recommendation algorithm is proposed,which exploits users1 profile attributes to partition them into several clusters.For each cluster,a virtual opinion leader is conceived to represent the whole cluster,such that the dimension of the original useritem matrix can be significantly reduced,then a Weighted Slope One-VU method is designed and applied to the virtual opinion leader-item matrix to obtain the recommendation results.Compared to traditional clusteringbased CF recommendation schemes,our method can significantly reduce the time complexity,while achieving comparable recommendation performance.Furthermore,we have constructed a real personalized web-based movie recommendation system,MovieWatch,opened it to the public,collected user feedback on recommendations,and evaluated the feasibility and accuracy of our system based on this real-world data.
基金supported by the National Natural Science Foundation of China(Grant No.41872124 and 91755211)and several Sinopec in-house projects.We thank Sinopec Petroleum Exploration and Production Research Institute,Sinopec Exploration Company,Sinopec Jianghan Oilfield,and Sinopec East China Petroleum Company for valuable data and information.
文摘The Fuling shale gas field in China is the largest shale gas field as well as the largest of its type discovered in any Lower Paleozoic formation.In this study,the geology and production of the upper and lower gas layers in the Fuling shale gas field are evaluated in terms of structure,shale quality,fault,initial production,and estimated ultimate recovery(EUR).The shale in the lower gas layer of the Jiaoshiba anticline is a high-quality reservoir,where the space is dominated by organic pores in kerogen,and the gas content is high.The shale gas wells reveal relatively high initial production and EUR.However,the shale in the upper gas layer of the Jiaoshiba anticline has reservoir space mainly composed of clay mineral pores and organic pores within bitumen,and the gas content is low.In terms of structure,primary gas migration may occur in the upper gas layer,resulting in free gas accumulation in the structural high,where the development effects are generally better than those in the structural low.The lower gas layer in the Pingqiao anticline,is the main interval for shale gas accumulation and development due to the high-quality shale.Under the influence of faults,the efficiency of exploration wells emplaced on top of the anticline is much lower a compared with those in the flanks.The residual synclines close to the Sichuan Basin,including the Baima and Baitao anticlines,are characterized by more recent uplifts,larger area,greater distance from the deep and large faults,and early fracture closure.Therefore,we recommend that the shale gas exploration and development should be carried out preferentially in areas close to the center of the residual synclines,featuring relatively high-pressure coefficient and moderate burial depth.
