Lion dance is a popular folk activity in China,and is traditionally associated with joyful celebrations since it is thought to bring riches and good fortune.Dancers in lion costumes jump back and forth while integrati...Lion dance is a popular folk activity in China,and is traditionally associated with joyful celebrations since it is thought to bring riches and good fortune.Dancers in lion costumes jump back and forth while integrating Chinese martial arts and acrobatics to the sounds of drums,cymbals,and resounding gongs.Such performances draw huge crowds,which always adds to a joyous mood.Lion dancer Liang Jiali,28,from Foshan City in south China’s Guangdong Province,carries the ancient tradition on poles of various heights.She was chosen at the age of seven to join the only elite women’s team in China,the Shunde Women’s Lion Dance Troupe.She has been attached to the male-dominated art genre for 21 years now.展开更多
In this paper,a streamline diffusion F.E.M. for linear Sobolev equations with convection dominated term is given.According to the range of space time F.E mesh parameter h ,two choices for artifical diffusion par...In this paper,a streamline diffusion F.E.M. for linear Sobolev equations with convection dominated term is given.According to the range of space time F.E mesh parameter h ,two choices for artifical diffusion parameter δ are presented,and for the corresponding computation schemes the stability and error estimates in suitable norms are estabilished.展开更多
In this paper,we investigate a streamline diffusion finite element approxi- mation scheme for the constrained optimal control problem governed by linear con- vection dominated diffusion equations.We prove the existenc...In this paper,we investigate a streamline diffusion finite element approxi- mation scheme for the constrained optimal control problem governed by linear con- vection dominated diffusion equations.We prove the existence and uniqueness of the discretized scheme.Then a priori and a posteriori error estimates are derived for the state,the co-state and the control.Three numerical examples are presented to illustrate our theoretical results.展开更多
The hydrodynamic conditions present in a river delta's formation are a highly important factor in the variation between its sedimentary regulation and characteristics. In the case of the lacustrine basin river-dom...The hydrodynamic conditions present in a river delta's formation are a highly important factor in the variation between its sedimentary regulation and characteristics. In the case of the lacustrine basin river-dominated delta, water level fluctuations and fluviation, are both important controlling factors of the sedimentary characteristics and reservoir architecture. To discuss the effects of water level fluctuation on sediment characteristics and reservoir architecture of this delta, the Fangniugou section in the east of the Songliao Basin was selected for study. Based on an outcrop investigation of the lacustrine basin river-dominated delta, combining with an analysis of the major and trace chemical elements in the sediments to determine the relative water depth, through architecture bounding surfaces and lithofacies division, sedimentary microfacies recognition and architectural element research, this work illustrated the effects of water level fluctuation on the reservoir architecture and established sedimentary models for the lacustrine basin river-dominated delta under various water level conditions. The results show that there are 8 lithofacies in the Fangniugou section. The fan delta front, which is the main object of this study, develops four sedimentary microfacies that include the underwater distributary channel, river mouth bar, sheet sand and interdistributary bay. The effects of water level fluctuation on different orders geographic architecture elements are respectively reflected in the vertical combination of the composite sand bodies, the plane combination of the single sand bodies, the particle size changes in the vertical of hyperplasia in the single sand body, the coset and lamina. In the case of the sand body development of the petroliferous basin, varying water level conditions and research locations resulted in significant variation in the distribution and combination of the sand bodies in the lacustrine basin.展开更多
In this paper the large deviation results for partial and random sums Sn-ESn=n∑i=1Xi-n∑i=1EXi,n≥1;S(t)-ES(t)=N(t)∑i=1Xi-E(N(t)∑i=1Xi),t≥0 are proved, where {N(t);t ≥ 0} is a counting process of non-...In this paper the large deviation results for partial and random sums Sn-ESn=n∑i=1Xi-n∑i=1EXi,n≥1;S(t)-ES(t)=N(t)∑i=1Xi-E(N(t)∑i=1Xi),t≥0 are proved, where {N(t);t ≥ 0} is a counting process of non-negative integer-valued random variables, and {Xn; n ≥ 1} are a sequence of independent non-negative random variables independent of {N(t); t ≥ 0}. These results extend and improve some known conclusions.展开更多
Stability of infinite matrices has important applications to spline approximation, wavelets, Gabor time-frequency analysis, etc. In this paper, perturbation analysis for convolution dominated infinite matrices was stu...Stability of infinite matrices has important applications to spline approximation, wavelets, Gabor time-frequency analysis, etc. In this paper, perturbation analysis for convolution dominated infinite matrices was studied by introducing an idea of lp-stability at infinity. For infinite matrices in the Gohberg-Baskakov-Sjostrand class, a practical criterion for the lp-stability at infinity of convolution dominated infinite matrices on Zd under perturbation of compact operators was given.展开更多
Objective The Early Cretaceous sediments are well-exposed in southern Jilin Province,and yield abundant invertebrate and plant fossils,including the typical EosestheriaEphemeropsis trisetalis-Lycoptera(E-E-L)assembl...Objective The Early Cretaceous sediments are well-exposed in southern Jilin Province,and yield abundant invertebrate and plant fossils,including the typical EosestheriaEphemeropsis trisetalis-Lycoptera(E-E-L)assemblage of the Jehol Biota(Shao Tiequan et al.,2017).However,vertebrate fossils,especially tetrapods,are extremely rare and there is no formal documents on these fossils.Recently,a new fossil site dominated by fishes and turtles has been discovered in the middle part of the展开更多
In this short article, the upwind and central compact finite difference schemes for spatial discretization of the first-order derivative are analyzed. Comparison of the schemes is provided and the best discretization ...In this short article, the upwind and central compact finite difference schemes for spatial discretization of the first-order derivative are analyzed. Comparison of the schemes is provided and the best discretization scheme for convection dominated problems is suggested.展开更多
In this paper a mixed finite element method for the convection dominated diffusion problems with small parameter ε is presented,the effect of the parameter ε on the approximation error is considered and a su...In this paper a mixed finite element method for the convection dominated diffusion problems with small parameter ε is presented,the effect of the parameter ε on the approximation error is considered and a sufficient condition for optimal error estimates is derived.The paper also shows that under some conditions,the standard finite element method only gives a bounded solution,however the mixed finite element method gives a convergent one. Received March 1,1997. 1991 MR Subject Classification: 65N30,65M15.展开更多
2008 Fabrics China Creation Competition, oriented with the theme of promoting product innovation, turns out to be one of the most influential and authoritative
Harmful cyanobacterial blooms cause many ecological disasters worldwide. During the development of cyanobacterial blooms, the diversity and domination of cyanobacterial taxa are of a particular concern. In this study,...Harmful cyanobacterial blooms cause many ecological disasters worldwide. During the development of cyanobacterial blooms, the diversity and domination of cyanobacterial taxa are of a particular concern. In this study, the microbial community structure within a water system, such as in Yuqiao Reservoir and Haihe River in Tianjin City, China, was compared by using next-generation sequencing. A total of 5 001 operational taxonomic units were obtained and clustered from filtered 16 S rDNA V3–V4 region sequences. The cyanobacterial and microbial structures greatly differed in these two water areas. Microcystis was dominant in Yuqiao, whereas Synechococcus was dominant in Haihe. Proteobacteria species were dominant among all detected samples. The relative abundances of Bacteroidetes and Planctomycetes were higher in Yuqiao Reservoir than in Haihe River, whereas Firmicutes and Verrucomicrobia were relatively abundant in Haihe River. Further analyses indicated that the domination of both cyanobacteria was strongly related to several environmental factors, such as total nitrogen, total phosphorus, and dissolved oxygen, reflecting the role of trophic states in shaping the dominance of cyanobacterial taxa. The present study provided the example for Microcystis and Synechococcus dominance along a cyanobacterial bloom in north China. Applying highthroughput sequencing could offer a wide field of vision in analyzing microbial community structures.展开更多
1. Introduction Over the five centuries since Copernicus, the focus of planetary science has transitioned from the visible realm to the invisible. In the more than 60 years following the advent of the space age, our a...1. Introduction Over the five centuries since Copernicus, the focus of planetary science has transitioned from the visible realm to the invisible. In the more than 60 years following the advent of the space age, our ability to comprehend planets has grown from the gravitational forces to electromagnetic forces.展开更多
In this paper,a compact mathematical model having an elegant structure,together with a generic control framework,are proposed for generic power systems dominated by power converters that are interconnected through a p...In this paper,a compact mathematical model having an elegant structure,together with a generic control framework,are proposed for generic power systems dominated by power converters that are interconnected through a passive transmission and distribution(T&D)grid,by adopting the port-Hamiltonian(pH)systems theory and the fundamental circuit theory.The models of generic T&D lines are developed and then the model of a generic T&D grid is established.With the proposed control framework,the controlled converters are proven to be passive and Input-to-State Stable(ISS).The compact mathematical model is scalable and can be applied to power systems with multiple power electronic converters with generic passive controllers,passive local loads,and different types of passive T&D lines connected in a meshed configuration without self-loops,so it is very generic.Moreover,the resulting power system is proven to be ISS as well.The analysis is carried out without assumptions on constant frequency/voltage,constant loads,and/or lossless networks,except the need of passivity for all parts involved,and without using the Clarke/Park transformations or the graph theory.To simplify the presentation,three-phase balanced systems are adopted but the results can be easily adapted for single-phase or unbalanced three-phase systems.展开更多
The popularization of smartphones and the acceleration of their replacement lead to a surge in mobile phone disposal.How to recycle waste mobile phones efficiently becomes a major problem in today’s society.The“Inte...The popularization of smartphones and the acceleration of their replacement lead to a surge in mobile phone disposal.How to recycle waste mobile phones efficiently becomes a major problem in today’s society.The“Internet+”recycling mode is an effective way to solve this problem.The recycling process of waste mobile phones involves retailers,manufacturers,third parties and other recycling parts.Retailers have natural advantages compared with other parts because of their perfect sales network and logistics system.The system dynamics model for“Internet+”recycling of waste mobile phones dominated by retailers is constructed,and the Vensim software is used to simulate the influence of changes in two key factors in“Internet+”recycling environment:Annual operating cost of online platform and offline unit logistics cost on retailers’recycling volume and recycling profit.The results show that the investment of online platform operation cost is conducive to the increase of retailers’online waste mobile phone recycling volume and recycling profit,while the investment of offline logistics cost increases retailers’online waste mobile phone recycling volume,but reduces the recycling profit.展开更多
We prove large deviation results on the partial and random sums s n =Σ i=1 n X i , n?1; S(t)=Σ i=1 N(t) X i , t?0, where {N(t);t?0} are non-negative integer-valued random variables and {X n ;n?1} are independent non...We prove large deviation results on the partial and random sums s n =Σ i=1 n X i , n?1; S(t)=Σ i=1 N(t) X i , t?0, where {N(t);t?0} are non-negative integer-valued random variables and {X n ;n?1} are independent non-negative random variables with distribution, F n , of X n , independent of {N(t);t?0}. Special attention is paid to the distribution of dominated variation.展开更多
The action of wind on the sea surface plays an important role in the noise generation mechanism.Sea surface wind speed can be estimated accurately provided there is an accurate understanding of the relationship betwee...The action of wind on the sea surface plays an important role in the noise generation mechanism.Sea surface wind speed can be estimated accurately provided there is an accurate understanding of the relationship between the ocean ambient noise and wind speed.Many measurements and analyses of the wind dependence of ambient noise have been conducted.The approximate empirical rule given by Wenz[1]states that in the frequency band between 0.5and 5 kHz,the ambient sea-noise spectrum levels decrease展开更多
In this paper, we study variational discretization for the constrained optimal control problem governed by convection dominated diffusion equations, where the state equation is approximated by the edge stabilization G...In this paper, we study variational discretization for the constrained optimal control problem governed by convection dominated diffusion equations, where the state equation is approximated by the edge stabilization Galerkin method. A priori error estimates are derived for the state, the adjoint state and the control. Moreover, residual type a posteriori error estimates in the L^2-norm are obtained. Finally, two numerical experiments are presented to illustrate the theoretical results.展开更多
Aims Free-surface flow-constructed wetland is a powerful means for the reduction of contaminants from agricultural runoff.Wetlands dominated by submerged aquatic vegetations(SAVs)may take up nutrients,particularly pho...Aims Free-surface flow-constructed wetland is a powerful means for the reduction of contaminants from agricultural runoff.Wetlands dominated by submerged aquatic vegetations(SAVs)may take up nutrients,particularly phosphorus(P),from surface flow with high efficiency.The objective of this study was to assess P removal performance by the SAV community under high and low P concentrations.Methods Weekly or biweekly inflow and outflow water samples were collected from four small constructed wetlands(test cells)planted with SAV in South Florida,USA,between September 1999 and September 2001.These test cells were divided into two groups,with the north test cells receiving a higher inflow total phosphorus(TP)concentration(average=75 lg l^(-1))than the south test cells receiving a lower TP concentration(average=23 lg l^(-1)).Limerock(LR)berms were installed in two of these test cells to allow an evaluation of the efficiency of this physical barrier to enhance wetland performance.Important findings North test cells displayed high TP removal of;60%while the removal efficiency of the south test cells was only;20%.Soluble reactive phosphorus concentrations in both north and south test cells were sequestered down to near-detection limit.High removal efficiencies for particulate phosphorus were also observed in the north test cells.The LR berms at the two test cells were found to be associated with decreases of an average TP removal of 2 lg l^(-1).Outflow TP concentration did not increase with inflow TP concentration,but increased with nominal hydraulic loading rates.Findings from this study demonstrated high P removal from inflow water containing high TP concentration by the SAV wetland and the importance of hydraulic regime to wetland performance.展开更多
To investigate the dominant species and interspecific association in the phytoplankton community of the Feiyun River basin in Zhejiang Province,East China,the main stream and the Shanxi Zhaoshandu Reservoir in the dow...To investigate the dominant species and interspecific association in the phytoplankton community of the Feiyun River basin in Zhejiang Province,East China,the main stream and the Shanxi Zhaoshandu Reservoir in the downstream were chosen as the study area,for which 22 sampling sites were designated.Sampling was conducted in September 2021,January,May,and July 2022.Phytoplankton species were identified from both quantitative samples and in-vivo observations.Phytoplankton was quantified by direct counting.Results show that there were 98 species belonging to 6 phyla and 78 genera.In addition,to clarify the niches of the dominant phytoplankton species and their interspecific association,the dominance index was calculated,and a comprehensive analysis was conducted including niche width,niche overlap value,ecological response rate,overall association,chi-square test,and the stability.The phytoplankton community exhibited characteristics of a Cyanobacteria-Chlorophyta-Diatom type community,showing higher diversity in spring and lower diversity in summer.Among 11 dominants phytoplankton species from 3 phyla,both frequency and dominance degree varied seasonally,of which Microcystis sp.was the dominant species in Spring,Autumn,and Winter.The niche widths of the dominant species ranged from 0.234 to 0.933,and were categorized into three groups.The niche overlap values of the 11 dominant species ranged from 0.359 to 0.959,exhibiting significant seasonal differences-highest in winter followed by autumn,spring,and summer in turn.The overall correlation among dominant species in all four seasons revealed a non-significant negative association,resulting in an unstable community structure.A significant portion(84.2%)of species pairs displayed positive associations,suggesting a successional pattern where Diatoms dominated while other dominant species shared resources and space.Despite this pattern,stability measurements indicated that the dominant species community remained unstable.Therefore,careful monitoring is recommended for potential water environment issues arising from abnormal proliferation of dominant species in the watershed during winter.This research built a theoretical foundation with a data support to the early warning of eutrophication and provided a reference for water resources management in similar watersheds along the eastern coast of China.展开更多
The estuarine areas are under frequent influence from freshwater intrusion and ocean currents,in which zooplankton species are diversified and variable as they are sensitive to physio-chemical variations in water.Ther...The estuarine areas are under frequent influence from freshwater intrusion and ocean currents,in which zooplankton species are diversified and variable as they are sensitive to physio-chemical variations in water.Therefore,understanding the relationships between zooplankton and environmental factors help us know the water quality.To achieve co-existence with species in similar ecological group or habit,they could inevitably alter themselves to fit the ecology and adjust the function according to the competitive exclusion in ecological theory.However,information of the co-existence of dominant species in the Changjiang(Yangtze)River estuary(CRE)and adjacent waters remains scarce.We explored the relationships between dominant zooplankton and environmental factors in the study region in spring-summer from 2016 to 2020,involving particularly the composition of dominant species,ecological groups,their relationships with environmental factors,and co-existence of important species,using the non-multidimensional scale analysis(nMDS)method and redundancy analysis.Results show that Labidocera euchaeta and Tortanus vermiculus were dominant species in the study scope.The turnover rate of dominant zooplankton was greater(>50%)in spring while the species number was higher in summer.The dominant species were estuarine,offshore,and eurytopic based on the adaptation to salinity.In spring,the ecological groups were dominated by estuarine species,while in summer by estuarine and offshore species.In addition,the nMDS showed that the dominant species in the same ecological group were more dispersed and not prominently clustered;the dominant species were staggered among different ecological groups.The temperature,salinity,pH,dissolved oxygen,and chlorophyll a were the main environmental factors on the distribution of the dominant species in spring,while in summer were dissolved oxygen,temperature,salinity,and pH.The domination of medusae of Nemopsis bachei and Pleurobrachia globosa in zooplankton community in spring,and the continuous decrease in abundance of L.euchaeta reflected the effects of local climate change.The temperature and salinity changes in different years and the subsequent response of zooplankton reflected the influence of freshwater intrusion and/or ocean currents.Zooplankton in similar ecological habits exhibited the competitive exclusion in terms of co-existence.展开更多
文摘Lion dance is a popular folk activity in China,and is traditionally associated with joyful celebrations since it is thought to bring riches and good fortune.Dancers in lion costumes jump back and forth while integrating Chinese martial arts and acrobatics to the sounds of drums,cymbals,and resounding gongs.Such performances draw huge crowds,which always adds to a joyous mood.Lion dancer Liang Jiali,28,from Foshan City in south China’s Guangdong Province,carries the ancient tradition on poles of various heights.She was chosen at the age of seven to join the only elite women’s team in China,the Shunde Women’s Lion Dance Troupe.She has been attached to the male-dominated art genre for 21 years now.
基金Supported by the National Natural Sciences Foundation of China(1 8971 0 51 )
文摘In this paper,a streamline diffusion F.E.M. for linear Sobolev equations with convection dominated term is given.According to the range of space time F.E mesh parameter h ,two choices for artifical diffusion parameter δ are presented,and for the corresponding computation schemes the stability and error estimates in suitable norms are estabilished.
基金supported by the National Basic Research Program under the Grant 2005CB321701the National Natural Science Foundation of China under the Grants 60474027 and 10771211.
文摘In this paper,we investigate a streamline diffusion finite element approxi- mation scheme for the constrained optimal control problem governed by linear con- vection dominated diffusion equations.We prove the existence and uniqueness of the discretized scheme.Then a priori and a posteriori error estimates are derived for the state,the co-state and the control.Three numerical examples are presented to illustrate our theoretical results.
基金Project(2011ZX05009-002)supported by the National Key Oil&Gas Project,ChinaProject(15CX06010A)supported by the Fundamental Research Funds for the Central Universities,China
文摘The hydrodynamic conditions present in a river delta's formation are a highly important factor in the variation between its sedimentary regulation and characteristics. In the case of the lacustrine basin river-dominated delta, water level fluctuations and fluviation, are both important controlling factors of the sedimentary characteristics and reservoir architecture. To discuss the effects of water level fluctuation on sediment characteristics and reservoir architecture of this delta, the Fangniugou section in the east of the Songliao Basin was selected for study. Based on an outcrop investigation of the lacustrine basin river-dominated delta, combining with an analysis of the major and trace chemical elements in the sediments to determine the relative water depth, through architecture bounding surfaces and lithofacies division, sedimentary microfacies recognition and architectural element research, this work illustrated the effects of water level fluctuation on the reservoir architecture and established sedimentary models for the lacustrine basin river-dominated delta under various water level conditions. The results show that there are 8 lithofacies in the Fangniugou section. The fan delta front, which is the main object of this study, develops four sedimentary microfacies that include the underwater distributary channel, river mouth bar, sheet sand and interdistributary bay. The effects of water level fluctuation on different orders geographic architecture elements are respectively reflected in the vertical combination of the composite sand bodies, the plane combination of the single sand bodies, the particle size changes in the vertical of hyperplasia in the single sand body, the coset and lamina. In the case of the sand body development of the petroliferous basin, varying water level conditions and research locations resulted in significant variation in the distribution and combination of the sand bodies in the lacustrine basin.
基金Supported by the Science Foundation of the Education Committee of Anhui Province(0505101).
文摘In this paper the large deviation results for partial and random sums Sn-ESn=n∑i=1Xi-n∑i=1EXi,n≥1;S(t)-ES(t)=N(t)∑i=1Xi-E(N(t)∑i=1Xi),t≥0 are proved, where {N(t);t ≥ 0} is a counting process of non-negative integer-valued random variables, and {Xn; n ≥ 1} are a sequence of independent non-negative random variables independent of {N(t); t ≥ 0}. These results extend and improve some known conclusions.
基金National Natural Science Foundation of China(No.10971023)Fundamental Research Funds for the Central Universities of China
文摘Stability of infinite matrices has important applications to spline approximation, wavelets, Gabor time-frequency analysis, etc. In this paper, perturbation analysis for convolution dominated infinite matrices was studied by introducing an idea of lp-stability at infinity. For infinite matrices in the Gohberg-Baskakov-Sjostrand class, a practical criterion for the lp-stability at infinity of convolution dominated infinite matrices on Zd under perturbation of compact operators was given.
基金supported by the National Natural Science Foundation of China(grants No.41202012 and 41172009)China Geological Survey(grant No.1212011120149)+1 种基金the Project ‘‘111’’,China(grant No.B-06008)Shandong University of Science&Technology Research Fund(grant No.2015TDJH101)
文摘Objective The Early Cretaceous sediments are well-exposed in southern Jilin Province,and yield abundant invertebrate and plant fossils,including the typical EosestheriaEphemeropsis trisetalis-Lycoptera(E-E-L)assemblage of the Jehol Biota(Shao Tiequan et al.,2017).However,vertebrate fossils,especially tetrapods,are extremely rare and there is no formal documents on these fossils.Recently,a new fossil site dominated by fishes and turtles has been discovered in the middle part of the
文摘In this short article, the upwind and central compact finite difference schemes for spatial discretization of the first-order derivative are analyzed. Comparison of the schemes is provided and the best discretization scheme for convection dominated problems is suggested.
文摘In this paper a mixed finite element method for the convection dominated diffusion problems with small parameter ε is presented,the effect of the parameter ε on the approximation error is considered and a sufficient condition for optimal error estimates is derived.The paper also shows that under some conditions,the standard finite element method only gives a bounded solution,however the mixed finite element method gives a convergent one. Received March 1,1997. 1991 MR Subject Classification: 65N30,65M15.
文摘2008 Fabrics China Creation Competition, oriented with the theme of promoting product innovation, turns out to be one of the most influential and authoritative
基金Supported by the International Science&Technology Cooperation Program of China(No.2013DFA71340)the National Natural Science Foundation of China(No.51779247)
文摘Harmful cyanobacterial blooms cause many ecological disasters worldwide. During the development of cyanobacterial blooms, the diversity and domination of cyanobacterial taxa are of a particular concern. In this study, the microbial community structure within a water system, such as in Yuqiao Reservoir and Haihe River in Tianjin City, China, was compared by using next-generation sequencing. A total of 5 001 operational taxonomic units were obtained and clustered from filtered 16 S rDNA V3–V4 region sequences. The cyanobacterial and microbial structures greatly differed in these two water areas. Microcystis was dominant in Yuqiao, whereas Synechococcus was dominant in Haihe. Proteobacteria species were dominant among all detected samples. The relative abundances of Bacteroidetes and Planctomycetes were higher in Yuqiao Reservoir than in Haihe River, whereas Firmicutes and Verrucomicrobia were relatively abundant in Haihe River. Further analyses indicated that the domination of both cyanobacteria was strongly related to several environmental factors, such as total nitrogen, total phosphorus, and dissolved oxygen, reflecting the role of trophic states in shaping the dominance of cyanobacterial taxa. The present study provided the example for Microcystis and Synechococcus dominance along a cyanobacterial bloom in north China. Applying highthroughput sequencing could offer a wide field of vision in analyzing microbial community structures.
基金supported by the National Natural Science Foundation of China (Grant Nos.42241106,42388101)。
文摘1. Introduction Over the five centuries since Copernicus, the focus of planetary science has transitioned from the visible realm to the invisible. In the more than 60 years following the advent of the space age, our ability to comprehend planets has grown from the gravitational forces to electromagnetic forces.
基金supported by NSF,USA,under award#1810105 and Foundation for Research Support of the State of Rio Grande do Sul(FAPERGS),BR,under grant number 21/2551-0002158-6,CfP PqG.2021。
文摘In this paper,a compact mathematical model having an elegant structure,together with a generic control framework,are proposed for generic power systems dominated by power converters that are interconnected through a passive transmission and distribution(T&D)grid,by adopting the port-Hamiltonian(pH)systems theory and the fundamental circuit theory.The models of generic T&D lines are developed and then the model of a generic T&D grid is established.With the proposed control framework,the controlled converters are proven to be passive and Input-to-State Stable(ISS).The compact mathematical model is scalable and can be applied to power systems with multiple power electronic converters with generic passive controllers,passive local loads,and different types of passive T&D lines connected in a meshed configuration without self-loops,so it is very generic.Moreover,the resulting power system is proven to be ISS as well.The analysis is carried out without assumptions on constant frequency/voltage,constant loads,and/or lossless networks,except the need of passivity for all parts involved,and without using the Clarke/Park transformations or the graph theory.To simplify the presentation,three-phase balanced systems are adopted but the results can be easily adapted for single-phase or unbalanced three-phase systems.
基金Supported by National Social Science Foundation“Research on the Innovation and Promotion Strategy of China’s E-waste Recycling Model under the‘Internet+’Strategy”(18BGL182)。
文摘The popularization of smartphones and the acceleration of their replacement lead to a surge in mobile phone disposal.How to recycle waste mobile phones efficiently becomes a major problem in today’s society.The“Internet+”recycling mode is an effective way to solve this problem.The recycling process of waste mobile phones involves retailers,manufacturers,third parties and other recycling parts.Retailers have natural advantages compared with other parts because of their perfect sales network and logistics system.The system dynamics model for“Internet+”recycling of waste mobile phones dominated by retailers is constructed,and the Vensim software is used to simulate the influence of changes in two key factors in“Internet+”recycling environment:Annual operating cost of online platform and offline unit logistics cost on retailers’recycling volume and recycling profit.The results show that the investment of online platform operation cost is conducive to the increase of retailers’online waste mobile phone recycling volume and recycling profit,while the investment of offline logistics cost increases retailers’online waste mobile phone recycling volume,but reduces the recycling profit.
基金This work was supported in part by the National Natural Science Foundation of China(Grant Nos.10071058,70273209) the Ministry of Education of China.The authors are grateful to the referees for their comments and suggestions,which led to the present imp
文摘We prove large deviation results on the partial and random sums s n =Σ i=1 n X i , n?1; S(t)=Σ i=1 N(t) X i , t?0, where {N(t);t?0} are non-negative integer-valued random variables and {X n ;n?1} are independent non-negative random variables with distribution, F n , of X n , independent of {N(t);t?0}. Special attention is paid to the distribution of dominated variation.
基金supported by the National Natural Science Foundation of China(Grant Nos.11434012,41561144006,and 11404366)
文摘The action of wind on the sea surface plays an important role in the noise generation mechanism.Sea surface wind speed can be estimated accurately provided there is an accurate understanding of the relationship between the ocean ambient noise and wind speed.Many measurements and analyses of the wind dependence of ambient noise have been conducted.The approximate empirical rule given by Wenz[1]states that in the frequency band between 0.5and 5 kHz,the ambient sea-noise spectrum levels decrease
基金support of the Chinese and German Research Foundations through the Sino-German Workshop on Applied Mathematics held in Hangzhou in October 2007support of the German Research Foundation through the grants DFG06-381 and DFG06-382+1 种基金support of the National Basic Research Program under the Grant 2005CB321701the National Natural Science Foundation of China under the Grant 60474027 and 10771211
文摘In this paper, we study variational discretization for the constrained optimal control problem governed by convection dominated diffusion equations, where the state equation is approximated by the edge stabilization Galerkin method. A priori error estimates are derived for the state, the adjoint state and the control. Moreover, residual type a posteriori error estimates in the L^2-norm are obtained. Finally, two numerical experiments are presented to illustrate the theoretical results.
文摘Aims Free-surface flow-constructed wetland is a powerful means for the reduction of contaminants from agricultural runoff.Wetlands dominated by submerged aquatic vegetations(SAVs)may take up nutrients,particularly phosphorus(P),from surface flow with high efficiency.The objective of this study was to assess P removal performance by the SAV community under high and low P concentrations.Methods Weekly or biweekly inflow and outflow water samples were collected from four small constructed wetlands(test cells)planted with SAV in South Florida,USA,between September 1999 and September 2001.These test cells were divided into two groups,with the north test cells receiving a higher inflow total phosphorus(TP)concentration(average=75 lg l^(-1))than the south test cells receiving a lower TP concentration(average=23 lg l^(-1)).Limerock(LR)berms were installed in two of these test cells to allow an evaluation of the efficiency of this physical barrier to enhance wetland performance.Important findings North test cells displayed high TP removal of;60%while the removal efficiency of the south test cells was only;20%.Soluble reactive phosphorus concentrations in both north and south test cells were sequestered down to near-detection limit.High removal efficiencies for particulate phosphorus were also observed in the north test cells.The LR berms at the two test cells were found to be associated with decreases of an average TP removal of 2 lg l^(-1).Outflow TP concentration did not increase with inflow TP concentration,but increased with nominal hydraulic loading rates.Findings from this study demonstrated high P removal from inflow water containing high TP concentration by the SAV wetland and the importance of hydraulic regime to wetland performance.
基金Supported by the National Key Scientific Research Project(No.2018YFC1508200)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX 23_0714)+1 种基金the China Scholarship Council(No.202206710066)the Construction Project of Wenzhou Hydrology High quality Development Pilot Zone(No.WZSW-GZLFZXXQ-202105)。
文摘To investigate the dominant species and interspecific association in the phytoplankton community of the Feiyun River basin in Zhejiang Province,East China,the main stream and the Shanxi Zhaoshandu Reservoir in the downstream were chosen as the study area,for which 22 sampling sites were designated.Sampling was conducted in September 2021,January,May,and July 2022.Phytoplankton species were identified from both quantitative samples and in-vivo observations.Phytoplankton was quantified by direct counting.Results show that there were 98 species belonging to 6 phyla and 78 genera.In addition,to clarify the niches of the dominant phytoplankton species and their interspecific association,the dominance index was calculated,and a comprehensive analysis was conducted including niche width,niche overlap value,ecological response rate,overall association,chi-square test,and the stability.The phytoplankton community exhibited characteristics of a Cyanobacteria-Chlorophyta-Diatom type community,showing higher diversity in spring and lower diversity in summer.Among 11 dominants phytoplankton species from 3 phyla,both frequency and dominance degree varied seasonally,of which Microcystis sp.was the dominant species in Spring,Autumn,and Winter.The niche widths of the dominant species ranged from 0.234 to 0.933,and were categorized into three groups.The niche overlap values of the 11 dominant species ranged from 0.359 to 0.959,exhibiting significant seasonal differences-highest in winter followed by autumn,spring,and summer in turn.The overall correlation among dominant species in all four seasons revealed a non-significant negative association,resulting in an unstable community structure.A significant portion(84.2%)of species pairs displayed positive associations,suggesting a successional pattern where Diatoms dominated while other dominant species shared resources and space.Despite this pattern,stability measurements indicated that the dominant species community remained unstable.Therefore,careful monitoring is recommended for potential water environment issues arising from abnormal proliferation of dominant species in the watershed during winter.This research built a theoretical foundation with a data support to the early warning of eutrophication and provided a reference for water resources management in similar watersheds along the eastern coast of China.
基金Supported by the Innovation Team Project of Ecological Environment Monitoring and Restoration of Fishery Waters in the East China Sea of the Chinese Academy of Fishery Sciences(No.2020TD14)the National Basic Research Program of China(973 Program)(No.2010CB429005)。
文摘The estuarine areas are under frequent influence from freshwater intrusion and ocean currents,in which zooplankton species are diversified and variable as they are sensitive to physio-chemical variations in water.Therefore,understanding the relationships between zooplankton and environmental factors help us know the water quality.To achieve co-existence with species in similar ecological group or habit,they could inevitably alter themselves to fit the ecology and adjust the function according to the competitive exclusion in ecological theory.However,information of the co-existence of dominant species in the Changjiang(Yangtze)River estuary(CRE)and adjacent waters remains scarce.We explored the relationships between dominant zooplankton and environmental factors in the study region in spring-summer from 2016 to 2020,involving particularly the composition of dominant species,ecological groups,their relationships with environmental factors,and co-existence of important species,using the non-multidimensional scale analysis(nMDS)method and redundancy analysis.Results show that Labidocera euchaeta and Tortanus vermiculus were dominant species in the study scope.The turnover rate of dominant zooplankton was greater(>50%)in spring while the species number was higher in summer.The dominant species were estuarine,offshore,and eurytopic based on the adaptation to salinity.In spring,the ecological groups were dominated by estuarine species,while in summer by estuarine and offshore species.In addition,the nMDS showed that the dominant species in the same ecological group were more dispersed and not prominently clustered;the dominant species were staggered among different ecological groups.The temperature,salinity,pH,dissolved oxygen,and chlorophyll a were the main environmental factors on the distribution of the dominant species in spring,while in summer were dissolved oxygen,temperature,salinity,and pH.The domination of medusae of Nemopsis bachei and Pleurobrachia globosa in zooplankton community in spring,and the continuous decrease in abundance of L.euchaeta reflected the effects of local climate change.The temperature and salinity changes in different years and the subsequent response of zooplankton reflected the influence of freshwater intrusion and/or ocean currents.Zooplankton in similar ecological habits exhibited the competitive exclusion in terms of co-existence.