A quantitative study on meiofauna was carried out along a transect throughout the Changjiang Estuary＇ s oxygen minimum zone （OMZ） in the East China Sea. There exist two distinct station groups in the OMZ： the fine...A quantitative study on meiofauna was carried out along a transect throughout the Changjiang Estuary＇ s oxygen minimum zone （OMZ） in the East China Sea. There exist two distinct station groups in the OMZ： the fine-grained hypoxic area and the more fine-grained anoxie area. Meiofauna abundance ranged from （ 101.5±31.0） ind./cm^2 （ hypoxie area） to （369.9±123.9） ind./cm^2（ anoxic area） along the transect. Free-living marine nematodes were the numerically dominant meiofauna at every station. The anoxic area differed significantly in meiofauna abundance and vertical distribution pattern from the hypoxic area. Within the anoxic area, nematodes abundance increased and amounted to over 90% of the total meiofauna; about 50% of nematodes were found in the 2-5 and 5-8 cm layers. At hypoxie stations, about over 85 % were restricted to the top 2 cm. Benthic eopepod abundance and dominance decreased consistently with the oxygen gradient. The pattern of meiofauna biomass was similar to that of abundance. The correlation analysis of the meiofauna numbers and environmental parameters indicated that abundance and biomass of total meiofauna and nematodes had significant or highly significant （ P 〈 0.05 or P 〈 0.01 ） correlations with Chl a and Pha a, but no significant （ P 〉 0.05 ） correlations with bottom-water oxygen （ BWO2 ）. On the other hand, there was a highly significant positive correlation between benthic eopepod abundance and bottom-water oxygen （P 〈 0.05 ）. The investigation on the nematode community structure indicated that two different nematode communities existed in hypoxic and anoxic areas. In certain way, the shift in nematode species composition distinguishes the anoxia to hypoxia. Nematode diversity was generally lower within the anoxic stations than the hypoxic ones, but the difference was not significant. Indices of the nematode community structure varied in relation to the bottom-water oxygen together with bottom-water temperature, Chl a concentration and median grain size of sediment.展开更多
A genetic algorithm (GA)-based method is proposed to solve the nonlinearoptimization problem of minimum zone cylindricity evaluation. First, the background of the problemis introduced. Then the mathematical model and ...A genetic algorithm (GA)-based method is proposed to solve the nonlinearoptimization problem of minimum zone cylindricity evaluation. First, the background of the problemis introduced. Then the mathematical model and the fitness function are derived from themathematical definition of dimensioning and tolerancing principles. Thirdly with the least squaressolution as the initial values, the whole implementation process of the algorithm is realized inwhich some key techniques, for example, variables representing, population initializing and suchbasic operations as selection, crossover and mutation, are discussed in detail. Finally, examplesare quoted to verify the proposed algorithm. The computation results indicate that the GA-basedoptimization method performs well on cylindricity evaluation. The outstanding advantages concludehigh accuracy, high efficiency and capabilities of solving complicated nonlinear and large spaceproblems.展开更多
As a serious consequence of ocean warming and increased stratification,a rapid decrease in dissolved oxygen(DO)content of the world’s oceans has attracted more and more attention recently.In open oceans,the decline o...As a serious consequence of ocean warming and increased stratification,a rapid decrease in dissolved oxygen(DO)content of the world’s oceans has attracted more and more attention recently.In open oceans,the decline of DO is characterized by the expansion of oxygen minimum zones(OMZs)in the ocean interior.Vast OMZs exist within the mesopelagic zones of the Tropical Western Pacific(TWP),but have gained very little attention.In this study,we focus on characteristics of OMZs in three typical seamounts areas(named Y3,M2,and Kocebu,respectively)of the TWP.Based on distributions of DO,the OMZs of the three seamounts areas are very different in scope,thickness,and the minimum oxygen content.The significantly different characteristics of OMZs at the seamounts are mainly because they are located in regions affected by different ventilation and consumption characteristic.To quantitatively describe the intensity of OMZs,a parameter,IOMZ,is firstly proposed.According to this quantitative parameter,the intensity order of OMZs for the three seamounts areas is Kocebu>M2>Y3.Potential biogeochemical effects of OMZs in the three seamounts areas are discussed using IOMZ.With higher IOMZ,the degradation of particulate organic carbon(POC)tends to be lower.Yet because of the limited data,their relationship still need more research to prove.However,if this relationship holds in global oceans,the presence of seamounts would—under climate warming with expanding OMZs—promote vertical transport of POC resulting in an enhanced biological pump.Our study provides a new way to quantitatively study the impact of OMZs on the efficiency of biological pump.展开更多
The oxygen minimum zones(OMZs)are globally expanding,yet the variation pattern of microbial communities related to dissolved oxygen levels remain unclear.Spatial variability of bacterial diversity and community compos...The oxygen minimum zones(OMZs)are globally expanding,yet the variation pattern of microbial communities related to dissolved oxygen levels remain unclear.Spatial variability of bacterial diversity and community composition(repre sented by 16 S rRNA)of six stations was investigated within the water column in the seamount area of Tropical Western Pacific Ocean(TWPO)in May 2019.The seawater has dissolved oxygen(DO)concentration of 3.01-6.68 mg/L and the core of the oxygen minimum zones was located between the depths of 650 m and 1750 m.The bacterial alpha-diversity showed unimodal pattern with the decreasing DO with depths and peaked in the upper oxycline(UO)of OMZs.The bacterial community structure of the mixed layer(ML)and the bottom layer clustered and separated from each other,while those of UO and the OMZ core(OM)clustered and overlapped.Overall,bacterial community composition transitioned from being Alphaproteobacteria and Gammaproteobacteria-dominant in ML to being Gammaproteobacteria and Nitrososphaeria/Deltaproteobacteria-dominant in UO and OM,and then changed to being Clostridia and unidentified Actinobacteria-dominant in the bottom layer.Moreover,both bacterial alpha-diversity and the abundant classes fitted varying sectioned functions with DO.The DO solely explained 40.37%of the variation of bacterial community composition among layers(P<0.001).The predicted function profiling showed that the water column was predominant by chemoheterotrophy,cyanobacteria,and photoautotrophy in ML,by chemoheterotrophy and nitrate/sulfide cycling in UO and OM,and by chemoheterotrophy and ferme ntation in the bottom layer.Our findings revealed the DO-associated variation in bacterial diversity and community composition,and help to clarify the potential responses of microbes and their involved biogeochemical processes to the expansion and intensification of OMZs.展开更多
The mathematical modeling for evaluation of the sphericity error is proposed with minimum radial separation center. To obtain the minimum sphericity error from the form data, a geometric approximation technique was de...The mathematical modeling for evaluation of the sphericity error is proposed with minimum radial separation center. To obtain the minimum sphericity error from the form data, a geometric approximation technique was devised. The technique regarded the least square sphere center as the initial center of the concentric spheres containing all measurement points, and then the center was moved gradually to reduce the radial separation till the minimum radial separation center was got where the constructed concentric spheres conformed to the minimum zone condition. The method was modeled firstly, then the geometric approximation process was analyzed, and finally,the software for data processing was programmed. As evaluation example, five steel balls were measured and the measurement data were processed with the developed program. The average iteration times of the approximation technique is 4.2, and on average the obtained sphericity error is 0. 529μm smaller than the least square solution,with accuracy increased by 7. 696%.展开更多
Utilizing the convex hull theory, a novel minimum zone circle （MZC） method, named im- proved minimum zone circle （IMZC） was developed in this paper. There were three steps for IMZC to evaluate the roundness error....Utilizing the convex hull theory, a novel minimum zone circle （MZC） method, named im- proved minimum zone circle （IMZC） was developed in this paper. There were three steps for IMZC to evaluate the roundness error. Firstly, with the convex hull algorithm, data points on the circle contour were categorized into two sets to determine two concentric circles which contained all points of the contour. Secondly, vertexes of the minimum circumscribed circle and the maximum inscribed circle were found out from the previously determined two sets, and then four tangent points for de- termining the two concentric circles were also found out. Lastly, according to the evaluation using the MZC method, the roundness error was figured out. In this paper l IMZC was used to evaluate roundness errors of some micro parts. The evaluation results showed that the measurement precision using the IMZC method was higher than the least squared circle （LSC） method for the same set of data points, and IMZC had the same accuracy as the traditional MZC but dramatically shortened com- putation time. The computation time of IMZC was 6. 89% of the traditional MZC.展开更多
基金the Ministry of Science and Technology of China under contract Nos 2002CB412400,G1999043709the National Natural Science Foundation of China under contract No.40176033.
文摘A quantitative study on meiofauna was carried out along a transect throughout the Changjiang Estuary＇ s oxygen minimum zone （OMZ） in the East China Sea. There exist two distinct station groups in the OMZ： the fine-grained hypoxic area and the more fine-grained anoxie area. Meiofauna abundance ranged from （ 101.5±31.0） ind./cm^2 （ hypoxie area） to （369.9±123.9） ind./cm^2（ anoxic area） along the transect. Free-living marine nematodes were the numerically dominant meiofauna at every station. The anoxic area differed significantly in meiofauna abundance and vertical distribution pattern from the hypoxic area. Within the anoxic area, nematodes abundance increased and amounted to over 90% of the total meiofauna; about 50% of nematodes were found in the 2-5 and 5-8 cm layers. At hypoxie stations, about over 85 % were restricted to the top 2 cm. Benthic eopepod abundance and dominance decreased consistently with the oxygen gradient. The pattern of meiofauna biomass was similar to that of abundance. The correlation analysis of the meiofauna numbers and environmental parameters indicated that abundance and biomass of total meiofauna and nematodes had significant or highly significant （ P 〈 0.05 or P 〈 0.01 ） correlations with Chl a and Pha a, but no significant （ P 〉 0.05 ） correlations with bottom-water oxygen （ BWO2 ）. On the other hand, there was a highly significant positive correlation between benthic eopepod abundance and bottom-water oxygen （P 〈 0.05 ）. The investigation on the nematode community structure indicated that two different nematode communities existed in hypoxic and anoxic areas. In certain way, the shift in nematode species composition distinguishes the anoxia to hypoxia. Nematode diversity was generally lower within the anoxic stations than the hypoxic ones, but the difference was not significant. Indices of the nematode community structure varied in relation to the bottom-water oxygen together with bottom-water temperature, Chl a concentration and median grain size of sediment.
基金This project is supported by National Natural Science Foundation of China (No.59975025)
文摘A genetic algorithm (GA)-based method is proposed to solve the nonlinearoptimization problem of minimum zone cylindricity evaluation. First, the background of the problemis introduced. Then the mathematical model and the fitness function are derived from themathematical definition of dimensioning and tolerancing principles. Thirdly with the least squaressolution as the initial values, the whole implementation process of the algorithm is realized inwhich some key techniques, for example, variables representing, population initializing and suchbasic operations as selection, crossover and mutation, are discussed in detail. Finally, examplesare quoted to verify the proposed algorithm. The computation results indicate that the GA-basedoptimization method performs well on cylindricity evaluation. The outstanding advantages concludehigh accuracy, high efficiency and capabilities of solving complicated nonlinear and large spaceproblems.
基金the Science&Technology Basic Resources Investigation Program of China(No.2017FY100802)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA19060401)the National Natural Science Foundation of China(No.91958103)。
文摘As a serious consequence of ocean warming and increased stratification,a rapid decrease in dissolved oxygen(DO)content of the world’s oceans has attracted more and more attention recently.In open oceans,the decline of DO is characterized by the expansion of oxygen minimum zones(OMZs)in the ocean interior.Vast OMZs exist within the mesopelagic zones of the Tropical Western Pacific(TWP),but have gained very little attention.In this study,we focus on characteristics of OMZs in three typical seamounts areas(named Y3,M2,and Kocebu,respectively)of the TWP.Based on distributions of DO,the OMZs of the three seamounts areas are very different in scope,thickness,and the minimum oxygen content.The significantly different characteristics of OMZs at the seamounts are mainly because they are located in regions affected by different ventilation and consumption characteristic.To quantitatively describe the intensity of OMZs,a parameter,IOMZ,is firstly proposed.According to this quantitative parameter,the intensity order of OMZs for the three seamounts areas is Kocebu>M2>Y3.Potential biogeochemical effects of OMZs in the three seamounts areas are discussed using IOMZ.With higher IOMZ,the degradation of particulate organic carbon(POC)tends to be lower.Yet because of the limited data,their relationship still need more research to prove.However,if this relationship holds in global oceans,the presence of seamounts would—under climate warming with expanding OMZs—promote vertical transport of POC resulting in an enhanced biological pump.Our study provides a new way to quantitatively study the impact of OMZs on the efficiency of biological pump.
基金the National Natural Science Foundation of China(No.91958103)the Science&Technology Basic Resources Investigation Program of China(No.2017FY100802)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA19060401)。
文摘The oxygen minimum zones(OMZs)are globally expanding,yet the variation pattern of microbial communities related to dissolved oxygen levels remain unclear.Spatial variability of bacterial diversity and community composition(repre sented by 16 S rRNA)of six stations was investigated within the water column in the seamount area of Tropical Western Pacific Ocean(TWPO)in May 2019.The seawater has dissolved oxygen(DO)concentration of 3.01-6.68 mg/L and the core of the oxygen minimum zones was located between the depths of 650 m and 1750 m.The bacterial alpha-diversity showed unimodal pattern with the decreasing DO with depths and peaked in the upper oxycline(UO)of OMZs.The bacterial community structure of the mixed layer(ML)and the bottom layer clustered and separated from each other,while those of UO and the OMZ core(OM)clustered and overlapped.Overall,bacterial community composition transitioned from being Alphaproteobacteria and Gammaproteobacteria-dominant in ML to being Gammaproteobacteria and Nitrososphaeria/Deltaproteobacteria-dominant in UO and OM,and then changed to being Clostridia and unidentified Actinobacteria-dominant in the bottom layer.Moreover,both bacterial alpha-diversity and the abundant classes fitted varying sectioned functions with DO.The DO solely explained 40.37%of the variation of bacterial community composition among layers(P<0.001).The predicted function profiling showed that the water column was predominant by chemoheterotrophy,cyanobacteria,and photoautotrophy in ML,by chemoheterotrophy and nitrate/sulfide cycling in UO and OM,and by chemoheterotrophy and ferme ntation in the bottom layer.Our findings revealed the DO-associated variation in bacterial diversity and community composition,and help to clarify the potential responses of microbes and their involved biogeochemical processes to the expansion and intensification of OMZs.
基金Supported by National Natural Science Foundation of China(No.50175081) andTianjin Municipal Science and Technology Commission (No.0431835116).
文摘The mathematical modeling for evaluation of the sphericity error is proposed with minimum radial separation center. To obtain the minimum sphericity error from the form data, a geometric approximation technique was devised. The technique regarded the least square sphere center as the initial center of the concentric spheres containing all measurement points, and then the center was moved gradually to reduce the radial separation till the minimum radial separation center was got where the constructed concentric spheres conformed to the minimum zone condition. The method was modeled firstly, then the geometric approximation process was analyzed, and finally,the software for data processing was programmed. As evaluation example, five steel balls were measured and the measurement data were processed with the developed program. The average iteration times of the approximation technique is 4.2, and on average the obtained sphericity error is 0. 529μm smaller than the least square solution,with accuracy increased by 7. 696%.
基金Supported by the National Nature Science Foundation of China ( 51075035 )Beijing Training Program for the Talents( 210D00911000002)
文摘Utilizing the convex hull theory, a novel minimum zone circle （MZC） method, named im- proved minimum zone circle （IMZC） was developed in this paper. There were three steps for IMZC to evaluate the roundness error. Firstly, with the convex hull algorithm, data points on the circle contour were categorized into two sets to determine two concentric circles which contained all points of the contour. Secondly, vertexes of the minimum circumscribed circle and the maximum inscribed circle were found out from the previously determined two sets, and then four tangent points for de- termining the two concentric circles were also found out. Lastly, according to the evaluation using the MZC method, the roundness error was figured out. In this paper l IMZC was used to evaluate roundness errors of some micro parts. The evaluation results showed that the measurement precision using the IMZC method was higher than the least squared circle （LSC） method for the same set of data points, and IMZC had the same accuracy as the traditional MZC but dramatically shortened com- putation time. The computation time of IMZC was 6. 89% of the traditional MZC.
基金Acknowledgment The research was supported by the Natural Science Foundation of Fujian Province, China （Grant No. 2010J01293） and the National Natural Science Foundation of China （Grant No. 51075160）.
