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Effects of phosphorus limitation on sinking velocities of phytoplankton during summer in the Changjiang River Estuary
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作者 Xinchi You Qiang Hao +6 位作者 Jie Zhu Wei Zhang Haiyan Jin Dewang Li Huanhong Ji Yu Ke Feng Zhou 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2024年第6期131-141,共11页
The sinking of phytoplankton is critical to organic matter transportation in the ocean and it is an essential process for the formation of coastal hypoxic zones.This study was based on a field investigation conducted ... The sinking of phytoplankton is critical to organic matter transportation in the ocean and it is an essential process for the formation of coastal hypoxic zones.This study was based on a field investigation conducted during the summer of 2022 in the Changjiang River(Yangtze River) Estuary(CJE) and its adjacent waters.The settling column method was employed to measure the sinking velocity(SV) of different size fractions of phytoplankton at the surface of the sea and to analyze their environmental control mechanisms.The findings reveal significant spatial variation in phytoplankton SV(-0.55-2.41 m/d) within the CJE.High-speed sinking was predominantly observed in phosphate-depleted regions beyond the CJE front.At the same time,an upward trend was more commonly observed in the phosphate-rich regions near the CJE mouth.The SV ranges for different sizefractionated phytoplankton,including micro-(>20 μm),nano-(2-20 μm),and picophytoplankton(0.7-2 μm),were-0.50-4.74 m/d,-1.04-1.59 m/d,and-1.24-1.65 m/d,respectively.Correlation analysis revealed a significant negative correlation between SV and dissolved inorganic phosphorus(DIP),implying that the influence of DIP contributes to SV.The variations in phytoplankton alkaline phosphatase activity suggested a significant increase in SV across all size fractions in the event of phosphorus limitation.Phytoplankton communities with limited photo synthetic capacity(maximum photochemical efficience,Fv/Fm <0.3) were found to have higher SV than that of communities with strong capacity,suggesting a link between sinking and alterations in physiological conditions due to phosphate depletion.The findings from the in situ phosphate enrichment experiments confirmed a marked decrease in SV following phosphate supplementation.These findings suggest that phosphorus limitation is the primary driver of elevated SV in the CJE.This study enhances the comprehension of the potential mechanisms underlying hypoxic zone formation in the CJE,providing novel insights into how nearshore eutrophication influences organic carbon migration. 展开更多
关键词 PHYTOPLaNKTON sinking velocity Changjiang River Estuary phosphorus limitation alkaline phosphatase
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Effects of nutrient limitations on the sinking velocity of Thalassiosira weissflogii
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作者 Jie Zhu Qiang Hao +2 位作者 Wei Zhang Yingying Ma Jiangning Zeng 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2024年第6期163-172,共10页
The sinking of diatoms is critic al to the formation of oceanic biological pumps and coastal hypoxic zones.However,little is known about the effects of different nutrient restrictions on diatom sinking.In this study,w... The sinking of diatoms is critic al to the formation of oceanic biological pumps and coastal hypoxic zones.However,little is known about the effects of different nutrient restrictions on diatom sinking.In this study,we measured the sinking velocity(SV) of Thalassiosira weissflogii using a new phytoplankton video observation instrument and analyzed major biochemical components under varying nutrient conditions.Our results showed that the SV of T.weissflogii under different nutrient limitation conditions varied substantially.The highest SV of(1.77±0.02) m/d was obtained under nitrate limitation,signific antly surpassing that under phosphate limitation at(0.98±0.13) m/d.As the nutrient limitation was released,the SV steadily decreased to(0.32±0.03) m/d and(0.15±0.05) m/d,respectively.Notably;under conditions with limited nitrate and phosphate concentrations,the SV values of T.weissflogii significantly positively correlated with the lipid content(P <0.001),with R^(2) values of 0.86 and 0.69,respectively.The change of the phytoplankton SV was primarily related to the intracellular compo sition,which is controlled by nutrient conditions but did not significantly correlate with transparent extracellular polymer and biosilica contents.The results of this study help to understand the regulation of the vertical sinking process of diatoms by nutrient restriction and provide new insights into phytoplankton dynamics and their relationship with the marine nutrient structure. 展开更多
关键词 nutrient limitation Thalassiosira weissflogii sinking velocity biochemical component lipid content
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Effects of urbanization and forest type on species composition and diversity,forest characteristics,biomass carbon sink,and their associations in Changchun,Northeast China:implications for urban carbon stock improvement
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作者 Yuanyuan Wang Xinzhu Dai +5 位作者 Xingling Chen Dan Zhang Guiqing Lin Yuanhang Zhou Tianyi Wang Yulong Cui 《Journal of Forestry Research》 SCIE EI CAS CSCD 2024年第2期146-162,共17页
Differences in forest attributes and carbon sequestration of each organ and layer between broadleaved and conifer forests of central and outer urban areas are not well-defined,hindering the precise management of urban... Differences in forest attributes and carbon sequestration of each organ and layer between broadleaved and conifer forests of central and outer urban areas are not well-defined,hindering the precise management of urban forests and improvement of function.To clarify the effect of two forest types with different urbanization intensities,we determined differences in vegetation composition and diversity,structural traits,and carbon stocks of 152 plots(20 m×20 m)in urban park forests in Changchun,which had the largest green quantity and carbon density effectiveness.We found that 1.1-fold thicker and healthier trees,and 1.6-to 2.0-fold higher,healthier,denser,and more various shrubs but with sparser trees and herbs occurred in the central urban forests(p<0.05)than in the outer forests.The conifer forests exhibited 30–70%obviously higher tree aboveground carbon sequestration(including stem and leaf)and 20%bigger trees,especially in the outer forests(p<0.05).In contrast,1.1-to 1.5-fold higher branch stocks,healthier and more diverse trees were found in broadleaved forests of both the inner and outer forests(p<0.05).Plant size and dominant species had similarly important roles in carbon stock improvement,especially big-sized woody plants and Pinus tabuliformis.In addition,a higher number of deciduous or needle species positively affected the broadleaved forest of the central urban area and conifer forest of the outer urban area,respectively.These findings can be used to guide precise management and accelerate the improvement of urban carbon function in Northeast China in the future. 展开更多
关键词 Species diversity Forest characteristics Biomass carbon sink Forest-type effect Urbanization effect Urban forests
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A comprehensive review on microchannel heat sinks for electronics cooling
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作者 Zhi-Qiang Yu Mo-Tong Li Bing-Yang Cao 《International Journal of Extreme Manufacturing》 SCIE EI CAS CSCD 2024年第2期133-162,共30页
The heat generation of electronic devices is increasing dramatically,which causes a serious bottleneck in the thermal management of electronics,and overheating will result in performance deterioration and even device ... The heat generation of electronic devices is increasing dramatically,which causes a serious bottleneck in the thermal management of electronics,and overheating will result in performance deterioration and even device damage.With the development of micro-machining technologies,the microchannel heat sink(MCHS)has become one of the best ways to remove the considerable amount of heat generated by high-power electronics.It has the advantages of large specific surface area,small size,coolant saving and high heat transfer coefficient.This paper comprehensively takes an overview of the research progress in MCHSs and generalizes the hotspots and bottlenecks of this area.The heat transfer mechanisms and performances of different channel structures,coolants,channel materials and some other influencing factors are reviewed.Additionally,this paper classifies the heat transfer enhancement technology and reviews the related studies on both the single-phase and phase-change flow and heat transfer.The comprehensive review is expected to provide a theoretical reference and technical guidance for further research and application of MCHSs in the future. 展开更多
关键词 microchannel heat sink thermal management of electronics microscale heat transfer heat transfer enhancement
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Effects of viscoelasticity on the stability and bifurcations of nonlinear energy sinks 被引量:1
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作者 A.MOSLEMI M.R.HOMAEINEZHAD 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2023年第1期141-158,共18页
Due to the increasing use of passive absorbers to control unwanted vibrations,many studies have been done on energy absorbers ideally,but the lack of studies of real environmental conditions on these absorbers is felt... Due to the increasing use of passive absorbers to control unwanted vibrations,many studies have been done on energy absorbers ideally,but the lack of studies of real environmental conditions on these absorbers is felt.The present work investigates the effect of viscoelasticity on the stability and bifurcations of a system attached to a nonlinear energy sink(NES).In this paper,the Burgers model is assumed for the viscoelasticity in an NES,and a linear oscillator system is considered for investigating the instabilities and bifurcations.The equations of motion of the coupled system are solved by using the harmonic balance and pseudo-arc-length continuation methods.The results show that the viscoelasticity affects the frequency intervals of the Hopf and saddle-node branches,and by increasing the stiffness parameters of the viscoelasticity,the conditions of these branches occur in larger ranges of the external force amplitudes,and also reduce the frequency range of the branches.In addition,increasing the viscoelastic damping parameter has the potential to completely eliminate the instability of the system and gradually reduce the amplitude of the jump phenomenon. 展开更多
关键词 VISCOELaSTICITY Burgers model nonlinear energy sink(NES) saddle-node bifurcation Hopf bifurcation
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Impact of Cattaneo-Christov Heat Flux in the Nanofluid Flow over an Inclined Permeable Surface with Irreversibility Analysis
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作者 Muhammad Ramzan Hina Gul 《Journal of Applied Mathematics and Physics》 2024年第4期1582-1595,共14页
This study discusses the magnetohydrodynamic nanofluid flow over an inclined permeable surface influenced by mixed convection, and Cattaeo-Christov heat flux. The heat transfer analysis is performed in the presence of... This study discusses the magnetohydrodynamic nanofluid flow over an inclined permeable surface influenced by mixed convection, and Cattaeo-Christov heat flux. The heat transfer analysis is performed in the presence of a heat source/sink and thermal stratification. To gauge the energy loss during the process, an irreversibility analysis is also performed. A numerical solution to the envisaged problem is obtained using the bvp4c package of MATLAB. Graphs are drawn to assess the consequences of the arising parameters against the associated profiles. The results show that an augmentation in the magnetic field and nanomaterial volume fraction results in an enhancement in the temperature profile. A strong magnetic field can significantly reduce the fluid velocity. The behavior of the Skin friction coefficient against the different estimates of emerging parameters is discussed. . 展开更多
关键词 Nanofluid Flow Cattaneo-Christov Heat Flux Permeable Surface Mixed Convection Heat Source/Sink thermal Stratification
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基于NSGA-Ⅱ遗传算法的Myring流线型量水槽体型优化设计
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作者 杨洋 张宽地 +3 位作者 姚田成 李柯 吕宏兴 王蒙 《农业机械学报》 EI CAS CSCD 北大核心 2024年第4期241-250,共10页
Myring流线型在水下航行器领域应用较为广泛,而量水槽在渠道中的受阻状态与潜水器潜行时受到的阻力情况具有一定的相似之处,因此本文借鉴潜水器的结构特点进行量水槽体型设计,探究量水槽受阻最小的较优线型。基于FLOW-3D软件,采用最优... Myring流线型在水下航行器领域应用较为广泛,而量水槽在渠道中的受阻状态与潜水器潜行时受到的阻力情况具有一定的相似之处,因此本文借鉴潜水器的结构特点进行量水槽体型设计,探究量水槽受阻最小的较优线型。基于FLOW-3D软件,采用最优拉丁超立方设计方法,以流线型的收缩段长度和锐度因子、扩散段长度和离去角为变量设计了40组数值模拟方案,得到对应的水头损失百分比和上游佛汝德数。以数值模拟变量为输入、结果为输出,训练RBF神经网络,结合NSGA-Ⅱ遗传算法获得Patero前沿解,通过TOPSIS评价法筛选出最优解并得出其线形参数:优化模型收缩段长度为45.9 cm、收缩段锐度因子为0.74、扩散段长度为49.2 cm、扩散段离去角为14.63°,并通过等比例缩放得到6组收缩比,在9组流量下进行模型试验分析水力性能。结果表明,优化后线型过流较顺畅,水力性能较优,预测结果和模拟结果误差不超过5%;不同工况下上游佛汝德数均小于0.5,满足测流规范要求,收缩比为0.58~0.66时各项水力性能均较优;基于临界流测流和量纲分析原理得到的测流公式精度较高,平均相对误差为2.09%。本研究证明了将流线型运用于量水槽领域研究以及通过神经网络和遗传算法寻优的可行性,优化后Myring流线型量水槽具有良好的性能和测流精度,在灌区渠道中具有较好的运用前景。 展开更多
关键词 流线型量水槽 体型优化 数值模拟 神经网络 NSGa-Ⅱ遗传算法
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Vibration control of fluid-conveying pipes: a state-of-the-art review 被引量:2
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作者 Hu DING J.C.JI 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2023年第9期1423-1456,共34页
Fluid-conveying pipes are widely used to transfer bulk fluids from one point to another in many engineering applications.They are subject to various excitations from the conveying fluids,the supporting structures,and ... Fluid-conveying pipes are widely used to transfer bulk fluids from one point to another in many engineering applications.They are subject to various excitations from the conveying fluids,the supporting structures,and the working environment,and thus are prone to vibrations such as flow-induced vibrations and acoustic-induced vibrations.Vibrations can generate variable dynamic stress and large deformation on fluid-conveying pipes,leading to vibration-induced fatigue and damage on the pipes,or even leading to failure of the entire piping system and catastrophic accidents.Therefore,the vibration control of fluid-conveying pipes is essential to ensure the integrity and safety of pipeline systems,and has attracted considerable attention from both researchers and engineers.The present paper aims to provide an extensive review of the state-of-the-art research on the vibration control of fluid-conveying pipes.The vibration analysis of fluid-conveying pipes is briefly discussed to show some key issues involved in the vibration analysis.Then,the research progress on the vibration control of fluid-conveying pipes is reviewed from four aspects in terms of passive control,active vibration control,semi-active vibration control,and structural optimization design for vibration reduction.Furthermore,the main results of existing research on the vibration control of fluid-conveying pipes are summarized,and future promising research directions are recommended to address the current research gaps.This paper contributes to the understanding of vibration control of fluid-conveying pipes,and will help the research work on the vibration control of fluidconveying pipes attract more attention. 展开更多
关键词 fuid-conveying pipe VIBRaTION passive control nonlinear energy sink(NES) active control semi-active control
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Multi-scenario Simulation for 2060 and Driving Factors of the Eco-spatial Carbon Sink in the Beibu Gulf Urban Agglomeration, China 被引量:5
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作者 QIN Menglin ZHAO Yincheng +3 位作者 LIU Yuting JIANG Hongbo LI Hang ZHU Ziming 《Chinese Geographical Science》 SCIE CSCD 2023年第1期85-101,共17页
Since China announced its goal of becoming carbon-neutral by 2060, carbon neutrality has become a major target in the development of China's urban agglomerations. This study applied the Future Land Use Simulation(... Since China announced its goal of becoming carbon-neutral by 2060, carbon neutrality has become a major target in the development of China's urban agglomerations. This study applied the Future Land Use Simulation(FLUS) model to predict the land use pattern of the ecological space of the Beibu Gulf urban agglomeration, in 2060 under ecological priority, agricultural priority and urbanized priority scenarios. The Integrated Valuation of Ecosystem Services and Trade-offs(In VEST) model was employed to analyse the spatial changes in ecological space carbon storage in each scenario from 2020 to 2060. Then, this study used a Geographically Weighted Regression(GWR) model to determine the main driving factors that influence the changes in land carbon sinking capacity. The results of the study can be summarised as follows: firstly, the agricultural and ecological priority scenarios will achieve balanced urban expansion and environmental protection of resources in an ecological space. The urbanized priority scenario will reduce the carbon sinking capacity. Among the simulation scenarios for 2060, carbon storage in the urbanized priority scenario will decrease by 112.26 × 10^(6) t compared with that for 2020 and the average carbon density will decrease by 0.96 kg/m^(2) compared with that for 2020. Carbon storage in the agricultural priority scenario will increase by 84.11 × 10^(6) t, and the average carbon density will decrease by 0.72 kg/m^(2). Carbon storage in the ecological priority scenario will increase by 3.03 × 10^(6) t, and the average carbon density will increase by 0.03 kg/m^(2). Under the premise that the population of the town will increases continuously, the ecological priority development approach may be a wise choice.Secondly, slope, distance to river and elevation are the most important factors that influence the carbon sink pattern of the ecological space in the Beibu Gulf urban agglomeration, followed by GDP, population density, slope direction and distance to traffic infrastructure.At the same time, urban space expansion is the main cause of the changes of this natural factors. Thirdly, the decreasing trend of ecological space is difficult to reverse, so reasonable land use policy to curb the spatial expansion of cities need to be made. 展开更多
关键词 Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model carbon sink multi-scenario simulation ecological space driving factor Beibu Gulf urban agglomeration
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Synthesis of new EVA graft copolymer and its pour point depressant performance evaluation for Daqing crude oil 被引量:4
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作者 伍丽娟 张帆 +1 位作者 关中原 郭淑凤 《Journal of Central South University》 SCIE EI CAS 2008年第S1期488-491,共4页
EVA was widely used as the pour point depressant for waxy oil.In order to improve its effect,some graft copolymerization methods should be used to modify EVA's property.EVA has long side chains and nitrogen polar ... EVA was widely used as the pour point depressant for waxy oil.In order to improve its effect,some graft copolymerization methods should be used to modify EVA's property.EVA has long side chains and nitrogen polar groups to enforce its adaptability and effect of waxy oil.The pure amine,maleicanhydride and their reaction product were tested using infrared spectra and the NMR spectral.The results show that when the modified EVA is added into oil,the wax deposits not only on the main chain but also on the side chains.And the polar groups have the function to avoid and resist the wax crystals connection each other to form the net.Using the reaction product of maleicanhydride and high carbonic amine(C12,C16,C18 amine) as the graft component,the toluene as the solvent and BPO as the initiator,the series of new EVA graft copolymer with special side chains are prepared under controlled condition.A series of cylmaleimide exist indeed in modified EVA and the highest grafted percentage is 18.8%.EVA-16,the new graft copolymer,is better than EVA about 3 ℃ more in depressant the pour-point of Daqing waxy crude oil. 展开更多
关键词 MODIFICaTION EVa COPOLYMER POUR POINT depressants performance evolution DaQING crud
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Influences of solid particles on the formation of the third phase crud during solvent extraction 被引量:6
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作者 ZHENG Qi RUAN Renman WEN Jiankang SONG Yongsheng DONG Qinghai WU Minglin YAO Guocheng 《Rare Metals》 SCIE EI CAS CSCD 2007年第1期89-96,共8页
The influences of solid particles in leach solution on the formation of the third phase crud during solvent extraction of copper were studied. Analyzed from the point of view of pH value and surface tension, the study... The influences of solid particles in leach solution on the formation of the third phase crud during solvent extraction of copper were studied. Analyzed from the point of view of pH value and surface tension, the study results showed that the solid particle is one of the most important contributors for the formation of the third phase crud. During solvent extraction, if the pH value was greater than 2.30, the number of solid particles in the mother solution increased, in which case the possibility of forming the third phase crud could also increase, and the interface tension value might grow in pace with the quantity of the third phase crud. 展开更多
关键词 solvent extraction solid particle the third phase crud surface tension
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Carbon Fluxes and Sinks:the Consumption of Atmospheric and Soil CO_2 by Carbonate Rock Dissolution 被引量:20
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作者 CAO Jianhua YUAN Daoxian +3 位作者 Chris GROVES HUANG Fen YANG Hui LU Qian 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2012年第4期963-972,共10页
Carbonate rock outcrops cover 9%-16% of the continental area and are the principal source of the dissolved inorganic carbon (DIC) transferred by rivers to the oceans, a consequence their dissolution. Current estimat... Carbonate rock outcrops cover 9%-16% of the continental area and are the principal source of the dissolved inorganic carbon (DIC) transferred by rivers to the oceans, a consequence their dissolution. Current estimations suggest that the flux falls between 0.1-0.6 PgC/a. Taking the intermediate value (0.3 PgC/a), it is equal to 18% of current estimates of the terrestrial vegetation net carbon sink and 38% of the soil carbon sink. In China, the carbon flux from carbonate rock dissolution is estimated to be 0.016 PgC/a, which accounts for 21%, 87.5%-150% and 2.3 times of the forest, shrub and grassland net carbon sinks respectively, as well as 23%-40% of the soil carbon sink flux. Carbonate dissolution is sensitive to environmental and climatic changes, the rate being closely correlated with precipitation, temperature, also with soil and vegetation cover. HCO3 in the water is affected by hydrophyte photosynthesis, resulting in part of the HCO~ being converted into DOC and POC, which may enhance the potential of carbon sequestration by carbonate rock dissolution. The possible turnover time of this carbon is roughly equal to that of the sea water cycle (2000a). The uptake of atmospheric/soil CO2 by carbonate rock dissolution thus plays an important role in the global carbon cycle, being one of the most important sinks. A major research need is to better evaluate the net effect of this sink in comparison to an oceanic source from carbonate mineral precipitation. 展开更多
关键词 carbonate rock carbon transfer carbon flux and sink exchange between inorganic carbon and organic carbon
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Diagnostic Study of Apparent Heat Sources and Moisture Sinks in the South China Sea and its Adjacent Areas during the Onset of 1998 SCS Monsoon 被引量:7
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作者 王世玉 钱永甫 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2000年第2期285-298,共14页
The apparent heat sources (?Q1 ?) and moisture sinks (?Q2 ?) are calculated based on the reanalyzed data of the South China Sea Monsoon Experiment (SCSMEX) from May 1 to August 31, 1998. It is found that the formation... The apparent heat sources (?Q1 ?) and moisture sinks (?Q2 ?) are calculated based on the reanalyzed data of the South China Sea Monsoon Experiment (SCSMEX) from May 1 to August 31, 1998. It is found that the formation and distribution of the atmospheric heat sources are important for the monsoon onset. The earlier onset of the SCS monsoon is the result of enduring atmospheric heating in the Indo–China Peninsula and South China areas. The atmospheric heating firstly appears in the Indo–China Peninsula area and the sensible heat is the major one. The 30–50 day periodic oscillation of atmospheric heat sources between the SCS area and the western Pacific warm pool has a reverse phase distribution before the middle of July and the low frequency oscillation of heat sources in SCS area has an obvious longitudinal propagation. The 30–50 day low frequency oscillation has vital modificatory effects on the summer monsoon evolution during 1998. Key words Apparent heat sources - Apparent moisture sinks - The South China Sea monsoon - Diagnostic Study Sponsored by the National Key Project of Fundamental Research “ SCSMEX” and the Research Fund for the Doctoral Program of Higher Education: “ Study of the Air-sea Interaction in the SCS Monsoon Region”. 展开更多
关键词 apparent heat sources apparent moisture sinks the South China Sea monsoon Diagnostic Study
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Dynamics and vibration reduction performance of asymmetric tristable nonlinear energy sink 被引量:2
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作者 Hongyan CHEN Youcheng ZENG +2 位作者 Hu DING Siukai LAI Liqun CHEN 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2024年第3期389-406,共18页
With its complex nonlinear dynamic behavior,the tristable system has shown excellent performance in areas such as energy harvesting and vibration suppression,and has attracted a lot of attention.In this paper,an asymm... With its complex nonlinear dynamic behavior,the tristable system has shown excellent performance in areas such as energy harvesting and vibration suppression,and has attracted a lot of attention.In this paper,an asymmetric tristable design is proposed to improve the vibration suppression efficiency of nonlinear energy sinks(NESs)for the first time.The proposed asymmetric tristable NES(ATNES)is composed of a pair of oblique springs and a vertical spring.Then,the three stable states,symmetric and asymmetric,can be achieved by the adjustment of the distance and stiffness asymmetry of the oblique springs.The governing equations of a linear oscillator(LO)coupled with the ATNES are derived.The approximate analytical solution to the coupled system is obtained by the harmonic balance method(HBM)and verified numerically.The vibration suppression efficiency of three types of ATNES is compared.The results show that the asymmetric design can improve the efficiency of vibration reduction through comparing the chaotic motion of the NES oscillator between asymmetric steady states.In addition,compared with the symmetrical tristable NES(TNES),the ATNES can effectively control smaller structural vibrations.In other words,the ATNES can effectively solve the threshold problem of TNES failure to weak excitation.Therefore,this paper reveals the vibration reduction mechanism of the ATNES,and provides a pathway to expand the effective excitation amplitude range of the NES. 展开更多
关键词 aSYMMETRIC nonlinear energy sink(NES) tristable vibration control po-tential barrier
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Anomalous Atmospheric Circulation, Heat Sources and Moisture Sinks in Relation to Great Precipitation Anomalies in the Yangtze River Valley 被引量:5
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作者 杨辉 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2001年第5期972-983,共12页
Using the summer (June to August) monthly mean data of the National Centers for Environmental Predictions (NCEP) - National Center for Atmospheric Research (NCAR) reanalysis from 1980 to 1997, atmospheric heat sources... Using the summer (June to August) monthly mean data of the National Centers for Environmental Predictions (NCEP) - National Center for Atmospheric Research (NCAR) reanalysis from 1980 to 1997, atmospheric heat sources and moisture sinks are calculated. Anomalous circulation and the vertically integrated heat source with the vertical integrated moisture sink and outgoing longwave radiation (OLR) flux are examined based upon monthly composites for 16 great wet-spells and 8 great dry-spells over the middle-lower reaches of the Yangtze River. The wind anomaly exhibits prominent differences between the great wet-spell and the great dry-spell over the Yangtze River Valley. For the great wet-spell, the anomalous southerly from the Bay of Bengal and the South China Sea and the anomalous northerly over North China enhanced low-level convergence toward a narrow latitudinal belt area (the middle-lower reaches of the Yangtze River). The southerly anomaly is connected with an anticyclonic anomalous circulation system centered at 22 degreesN, 140 degreesE and the northerly anomaly is associated with a cyclonic anomalous circulation system centered at the Japan Sea. In the upper level, the anomalous northwesterly between an anticyclonic anomalous system with the center at 23 degreesN, 105 degreesE and a cyclonic anomalous system with the center at Korea diverged over the middle-lower reaches of the Yangtze River. On the contrary, for the great dry-spell, the anomalous northerly over South China and the anomalous southerly over North China diverged from the Yangtze River Valley in the low level. The former formed in the western part of a cyclonic anomalous system centered at 23 degreesN, 135 degreesE. The latter was located in the western ridge of an anticyclonic anomalous system in the northwestern Pacific. The upper troposphere showed easterly anomaly that converged over the middle-lower reaches of the Yangtze River. A cyclonic anomalous system in South China and an anticyclonic system centered in the Japan Sea enhanced the easterly. Large atmospheric heat source anomalies of opposite signs existed over the western Pacific - the South China Sea, with negative in the great wet-spell and positive in the great dry-spell. The analysis of heat source also revealed positive anomalous heat sources during the great wet-spell and negative anomalous heat sources during the great dry-spell over the Yangtze River valley. The changes of the moisture sink and OLR were correspondingly altered, implying the change of heat source anomaly is due to the latent heat releasing of convective activity. Over the southeastern Tibetan Plateau- the Bay of Bengal, the analysis of heat source shows positive anomalous heat sources during the great wet-spell and negative anomalous heat sources during the great dry-spell because of latent heating change. The change of divergent wind coexisted with the change of heat source. In the great wet-spell, southerly divergent wind anomaly in the low level and northerly divergent wind anomaly in high-level are seen over South China. These divergent wind anomalies are helpful to the low-level convergence anomaly and high-level divergence anomaly over the Yangtze River valley. The low-level northerly divergent wind anomaly and high-level southerly divergent wind anomaly over South China reduced the low-level convergence and high-level divergence over the Yangtze River valley during the great dry-spell. 展开更多
关键词 anomalous atmospheric circulation heat sources and moisture sinks anomalies great precipitation anomalies in the Yangtze River valley
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Distribution Characteristics and Controlling Factors of Heavy Metals in Surface Sediments from the Bay-Island-Estuary System(BIES):A Case Study in Coastal Waters of Fujian Province,China
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作者 LIU Bo HU Rijun +4 位作者 WANG Yonghong LI Yi ZHU Longhai ZHANG Xiaodong YUAN Xiaodong 《Journal of Ocean University of China》 SCIE CAS CSCD 2023年第5期1253-1268,共16页
Based on the contents of six heavy metal elements in surface sediments from coastal areas of Fujian Province,the distribution characteristics and controlling factors of six heavy metals in a bay-island-estuary system(... Based on the contents of six heavy metal elements in surface sediments from coastal areas of Fujian Province,the distribution characteristics and controlling factors of six heavy metals in a bay-island-estuary system(BIES)were studied.This paper focuses on the influence of the hydrodynamic environment,and systematically discusses how grain size compositions,chemical environment,tidal current,ocean circulation and human activities influence the distribution and transportation of the heavy metals.The results indicated that the distribution and migration of Cu,Pb,Zn and Cr elements were mainly controlled by natural factors such as regional geological background,grain size compositions,and tidal residual currents.In contrast,As and Hg was mainly affected by human factors such as agriculture and industrial manufacturing.In the BIES,where the chemical environment exerted limited influence,the accumulation and migration of heavy metals are mainly influenced by human activities and enhanced by estuary processes as well as the complex sedimentary dynamic environment caused by many bays and islands. 展开更多
关键词 heavy metals sediments source to sink controlling factors hydrodynamic environment
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Spatial-temporal variations and driving factors of soil organic carbon in forest ecosystems of Northeast China
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作者 Shuai Wang Bol Roland +4 位作者 Kabindra Adhikari Qianlai Zhuang Xinxin Jin Chunlan Han Fengkui Qian 《Forest Ecosystems》 SCIE CSCD 2023年第2期141-152,共12页
Forest soil carbon is a major carbon pool of terrestrial ecosystems,and accurate estimation of soil organic carbon(SOC)stocks in forest ecosystems is rather challenging.This study compared the prediction performance o... Forest soil carbon is a major carbon pool of terrestrial ecosystems,and accurate estimation of soil organic carbon(SOC)stocks in forest ecosystems is rather challenging.This study compared the prediction performance of three empirical model approaches namely,regression kriging(RK),multiple stepwise regression(MSR),random forest(RF),and boosted regression trees(BRT)to predict SOC stocks in Northeast China for 1990 and 2015.Furthermore,the spatial variation of SOC stocks and the main controlling environmental factors during the past 25 years were identified.A total of 82(in 1990)and 157(in 2015)topsoil(0–20 cm)samples with 12 environmental factors(soil property,climate,topography and biology)were selected for model construction.Randomly selected80%of the soil sample data were used to train the models and the other 20%data for model verification using mean absolute error,root mean square error,coefficient of determination and Lin's consistency correlation coefficient indices.We found BRT model as the best prediction model and it could explain 67%and 60%spatial variation of SOC stocks,in 1990,and 2015,respectively.Predicted maps of all models in both periods showed similar spatial distribution characteristics,with the lower SOC in northeast and higher SOC in southwest.Mean annual temperature and elevation were the key environmental factors influencing the spatial variation of SOC stock in both periods.SOC stocks were mainly stored under Cambosols,Gleyosols and Isohumosols,accounting for 95.6%(1990)and 95.9%(2015).Overall,SOC stocks increased by 471 Tg C during the past 25 years.Our study found that the BRT model employing common environmental factors was the most robust method for forest topsoil SOC stocks inventories.The spatial resolution of BRT model enabled us to pinpoint in which areas of Northeast China that new forest tree planting would be most effective for enhancing forest C stocks.Overall,our approach is likely to be useful in forestry management and ecological restoration at and beyond the regional scale. 展开更多
关键词 Soil organic carbon stocks Forest ecosystem Spatial-temporal variation Carbon sink Digital soil mapping
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Buoyancy Effects in the Peristaltic Flow of a Prandtl-Eyring Nanofluid with Slip Boundaries
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作者 Hina Zahir 《Fluid Dynamics & Materials Processing》 EI 2023年第6期1507-1519,共13页
The interaction of nanoparticles with a peristaltic flow is analyzed considering a Prandtl-Eyring fluid under various conditions,such as the presence of a heat source/sink and slip effects in channels with a curvature... The interaction of nanoparticles with a peristaltic flow is analyzed considering a Prandtl-Eyring fluid under various conditions,such as the presence of a heat source/sink and slip effects in channels with a curvature.This problem has extensive background links with various fields in medical science such as chemotherapy and more in general nanotechnology.A similarity transformation is used to turn the original balance equations into a set of ordinary differential equations,which are then integrated numerically.The investigation reveals that nanofluids have valuable thermal capabilitises. 展开更多
关键词 Curved channel Prandtl-Eyring nanofluid slip conditions flexible walls heat source or sink mixed convection
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Survey on the Policy Evolution of China s Marine Carbon Sink and Carbon Trading Market
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作者 Jinghui YANG 《Meteorological and Environmental Research》 CAS 2023年第4期46-49,共4页
Climate change is currently the biggest environmental challenge facing sustainable development in human society,and it is an inherent requirement for achieving sustainable development by actively addressing climate ch... Climate change is currently the biggest environmental challenge facing sustainable development in human society,and it is an inherent requirement for achieving sustainable development by actively addressing climate change.Under the increasingly strict constraints of climate governance,developed countries such as the United States,European Union countries,and Japan have responded and actively formulated low-carbon development goals and policy measures that are in line with their national conditions.These policies mainly involve various fields such as low-carbon technology,energy conservation and emission reduction,and circular development,with clear policy guidance.In this paper,the evolution of policies on marine carbon sink and carbon trading in China is summarized,providing support for better understanding the background of formulating relevant international and domestic policies. 展开更多
关键词 Carbon sink Carbon trade OCEaN Policy investigation
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中国林业产权研究热点与变迁趋势——基于CiteSpace和VOSviewer的可视化分析
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作者 林若煊 黄丽 +1 位作者 郭铭杰 黄安胜 《科技和产业》 2024年第5期170-176,共7页
利用科学知识图谱方法梳理国内林业产权领域研究的热点主题及其变迁趋势,厘清林业产权领域研究的逻辑脉络。综合运用CiteSpace和VOSviewer软件,对中国知网(CNKI)学术期刊数据库中2001-2023年收录的1 540篇相关文献进行知识图谱分析。研... 利用科学知识图谱方法梳理国内林业产权领域研究的热点主题及其变迁趋势,厘清林业产权领域研究的逻辑脉络。综合运用CiteSpace和VOSviewer软件,对中国知网(CNKI)学术期刊数据库中2001-2023年收录的1 540篇相关文献进行知识图谱分析。研究发现:自2001年开始,该领域发文量呈现逐年渐进式增长,至2009年达到顶峰后趋于稳定,但领域内作者和发文机构之间的合作较为松散,且国内林业产权领域研究的发文机构相对集中于高校;结合林业产权领域的研究热点,可大致将该领域的研究内容归纳为关于林业产权制度、碳汇、林业产权交易和中国森林资源产权的研究;结合林业产权领域研究的历史脉络与演化趋势,可以将该领域研究分为3个阶段,包括探索阶段、横向拓展阶段和纵向延伸阶段。未来研究应把握“双碳”新特征,以此推进林业产权领域研究深入发展。 展开更多
关键词 集体林权 林业碳汇 森林碳汇 林权改革 研究综述
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