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Effects of the extrusion parameters on microstructure,texture and room temperature mechanical properties of extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy

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International Journal of Minerals,Metallurgy and Materials 2025年第1期32卷 136-146页

作者： Chenjin Zhang Guangyu Yang Lei Xiao Zhiyong Kan Jing Guo Qiang Li Wanqi Jie state key laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China College of Materials science and Engineering Fuzhou UniversityFuzhou 350108China College of Chemistry and environmental science Qujing Normal UniversityQujing 655011China

Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusion speeds(3 and 6 mm/s).The experimental results exhibited that the grain sizes after extrusion were much finer than that of the homogenized alloy,and the second phase showed streamline distribution along the extrusion direction(ED).With extrusion temperature increased from 260 to 320℃,the microstructure,texture,and mechanical properties of alloys changed *** dynamic recrystallization(DRX)degree and grain sizes enhanced as the extrusion ratio increased from 10:1 to 30:1,and the strength gradually decreased but elongation(EL)*** the extrusion speed increased from 3 to 6 mm/s,the grain sizes and DRX degree increased significantly,and the samples presented the typical-rare-earth(RE)*** alloy extruded at 260℃ with extrusion ratio of 10:1 and extrusion speed of 3 mm/s showed the tensile yield strength(TYS)of 213 MPa and EL of 30.6%.After quantitatively analyzing the contribution of strengthening mechanisms,it was found that the grain boundary strengthening and dislocation strengthening played major roles among strengthening *** results provide some guidelines for enlarging the industrial application of extruded Mg-RE alloy.

关键词： Mg-rare earth alloys extrusion temperature extrusion ratio extrusion speed strengthening mechanisms

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Carbon fluxes in the China Seas: An overview and perspective

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science China Earth sciences 2018年第11期61卷 1564-1582页

作者： Qian LIU Xianghui GUO Zhiqiang YIN Kuanbo ZHOU Elliott Gareth ROBERTS Minhan DAI state key laboratory for marine environmental science Xiamen University

This paper aims to provide an overview of regional carbon fluxes and budgets in the marginal seas adjacent to *** "China Seas" includes primarily the South China Sea, East China Sea, Yellow Sea, and the Bohai Sea. Emphasis is given to CO_2 fluxes across the air-sea interface and their controls. The net flux of CO_2 degassing from the China Seas is estimated to be9.5±53 Tg C yr^(-1). The total riverine carbon flux through estuaries to the China Seas is estimated as 59.6±6.4 Tg C yr^(-1). Chinese estuaries annually emit 0.74±0.02 Tg C as CO_2 to the atmosphere. Additionally, there is a very large net carbon influx from the Western Pacific to the China Seas, amounting to ～2.5 Pg C yr^(-1). As a first-order estimate, the total export flux of particulate organic carbon from the upper ocean of the China Seas is 240±80 Tg C yr^(-1). This review also attempts to examine current knowledge gaps to promote a better understanding of the carbon cycle in this important region.

关键词： Air-sea CO2 fluxes marine biogeochemistry Marginal seas Ocean carbon cycle China Seas

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Microbial D-amino acids and marine carbon storage

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science China Earth sciences 2016年第1期59卷 17-24页

作者： ZHANG Zi Lian ZHENG Qiang JIAO Nian Zhi state key laboratory of marine environmental science Institute of Marine Microbes and EcospheresXiamen University

In nature, there are two conformational types of amino acids: L- and D-isomers. The L-amino acids are the predominant form and are used mainly for protein synthesis, while the D-amino acids are few in quantity but more diverse in terms of their biological functions. D-amino acids are produced by many marine microbes, which are important players in carbon and energy cycles in the ocean. As the major constituent of the marine organic carbon pool, D-amino acids can persist in the water column for a long time before being further transformed by chemical or biological processes or transported through physical processes(such as absorption and aggregation). This article reviews the microbial synthesis of D-amino acids, their physiological function and metabolism in microbes, and the contribution of D-amino acids as a carbon source to the oceanic carbon reservoir.

关键词： Microbe D-amino acid Dissolved organic carbon marine carbon storage

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Membrane preconcentration of iron in seawater samples and on-site determination in spectrophotometry

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Chinese Journal of Oceanology and Limnology 2012年第2期30卷 315-320页

作者：彭园珍袁东星黄勇明姜涛刘宝敏 state key laboratory of marine environmental science Environmental Science Research CenterXiamen University

A novel method for on-site determination of trace iron was developed using membrane preconcentration and spectrophotometric detection. Fe（II）-ferrozine complex was reacted with cetyltrimethylammonium bromide （CTAB） to form a Fe（II）-ferrozine-CTAB paired compound, which was collected on a membrane by filtration under vacuum. The membrane was immersed in 2 mL of ethanol-nitric acid and the absorbance of the solution measured for quantitative analysis. Various factors affecting the iron collection and determination were investigated. With different sample preconcentration volumes, the range of determination was broadened to 0.5-120 ~tg/L. The detection limit of this method reached 0.19 ktg/L and the recoveries were between 97.2 and 109% when the concentration enrichment was about 45. The relative standard deviation （n = 7） was 1.9% for samples containing 10 ~g/L Fe. Twelve seawater samples were analyzed on-site using the proposed method, and two were also analyzed in inductively coupled plasma mass spectrometry. No significant difference was shown between the two methods by the Student＇s t-test. The method has also been used on-site for iron enrichment experiments with phytoplankton and concluded to be simple, accurate and inexpensive.

关键词： iron membrane filtration spectrophotometric detection

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Spatial and temporal variations of Synechococcus and picoeukaryotes in the Taiwan Strait,China

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Chinese Journal of Oceanology and Limnology 2009年第1期27卷 22-30页

作者：黄邦钦林学举洪华生 state key laboratory of marine environmental science and environmental science Research Center Xiamen University

The size-fractionated phytoplankton biomass, and the spatial and temporal variations in abundance of Synechococcus (SYN) and picoeukaryotes (PEUK) were measured in the Taiwan Strait during three cruises (August 1997, February-March 1998, and August 1998). The results show that picophytoplankton and nanophytoplankton dominate the phytoplankton biomass, in average of 38% and 40%, respectively. SYN and PEUK varied over time in abundance and carbon biomass, greater in summer than in winter, in range of (7.70–209.2)×106 and (0.75–15.4)×106 cells/cm2 in the abundance, and 1.93–52.3 and 1.57–32.4 μgC/cm2 in the carbon biomass, for SYN and PEUK, respectively. The horizontal distributions of both groups were diurnal but heterogeneous in abundance, depending on the groups and layer of depths. Temperature is the key controlling factor for picophytoplankton distribution (especially in winter) in the Strait.

关键词： Synechococcus picoeukaryotes picophytoplankton spatial and temporal variations theTaiwan Strait

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Effect of environmental factors on the complexation of iron and humic acid

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Journal of environmental sciences 2015年第1期27卷 188-196页

作者： Kai Fang Dongxing Yuan Lei Zhang Lifeng Feng Yaojin Chen Yuzhou Wang state key laboratory of marine environmental science College of the Environment and Ecology Xiamen University

A method of size exclusion chromatography coupled with ultraviolet spectrophotometry and off-line graphite furnace atomic absorption spectrometry was developed to assess the complexation properties of iron（Fe） and humic acid（HA） in a water environment. The factors affecting the complexation of Fe and HA, such as ionic strength, pH, temperature and UV radiation, were investigated. The Fe–HA complex residence time was also studied. Experimental results showed that pH could influence the deprotonation of HA and hydrolysis of Fe, and thus affected the complexation of Fe and HA. The complexation was greatly disrupted by the presence of NaCl. Temperature had some influence on the complexation. The yield of Fe–HA complexes showed a small decrease at high levels of UV radiation, but the effect of UV radiation on Fe–HA complex formation at natural levels could be neglected. It took about 10 hr for the complexation to reach equilibrium, and the Fe–HA complex residence time was about 20 *** of Fe and HA reached a maximum level under the conditions of pH 6, very low ionic strength, in the dark and at a water temperature of about 25°C, for 10 hr. It was suggested that the Fe–HA complex could form mainly in freshwater bodies and reach high levels in the warm season with mild sunlight radiation. With changing environmental parameters, such as at lower temperature in winter or higher pH and ionic strength in an estuary, the concentration of the Fe–HA complex would decrease.

关键词： Iron Humic acid Complexation Size exclusion chromatography Graphite furnace atomic absorption spectrometry

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Diagnostic model construction and example analysis of habitat degradation in enclosed bay:Ⅲ. Sansha Bay habitat restoration strategy

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Chinese Journal of Oceanology and Limnology 2015年第2期33卷 477-489页

作者：孙芃于格陈照章胡建宇刘光兴徐东晖 key laboratory of marine environmental science and Ecology College of Environmental Science and EngineeringOcean University of China state key laboratory of marine environmental science College of Ocean & Earth ScienceXiamen University

Unbalanced inputs and outputs of material are the root cause of habitat degradation in Sansha Bay,Fujian Province,China. However,the cumulative pollution varies in different geographic locations and natural conditions in the enclosed bay. In this study,hydrodynamic conditions,sediment characteristics,and aquaculture methods were recognized as the underlying causes of spatial heterogeneity in the distribution of nitrogen and phosphorous pollutants,the two major controlling factors of habitat degradation in the bay area. In order to achieve the goal of balancing nutrient inputs and outputs in Sansha Bay,we developed a feasible and practical zone restoration strategy for reasonable adjustment and arrangement of aquaculture species and production scale in accordance with varying hydrodynamic conditions and sediment characteristics in six sub-bay areas(sub-systems). The proposed zone restoration strategy lays a solid foundation for habitat restoration and management in Sansha Bay.

关键词： habitat degradation restoration strategy cumulative pollution Sansha Bay

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Nitrogen addition promotes soil carbon accumulation globally

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science China Life sciences 2025年第01期 284-293页

作者： Xuemei Yang Suhui Ma Erhan Huang Danhua Zhang Guoping Chen Jiangling Zhu Chengjun Ji Biao Zhu Lingli Liu Jingyun Fang Institute of Ecology College of Urban and Environmental Sciencesand Key Laboratory for Earth Surface Processes of the Ministry of EducationPeking University Ministry of Education key laboratory for Transboundary Ecosecurity of Southwest China School of Ecology and Environmental ScienceYunnan University state key laboratory of Vegetation and environmental Change Institute of BotanyChinese Academy of Sciences

Soil is the largest carbon(C) reservoir in terrestrial ecosystems and plays a crucial role in regulating the global C cycle and climate *** nitrogen(N) deposition has been widely considered as a critical factor affecting soil organic carbon(SOC) storage, but its effect on SOC components with different stability remains unclear. Here, we analyzed extensive empirical data from 304 sites worldwide to investigate how SOC and its components respond to N addition. Our analysis showed that N addition led to a significant increase in bulk SOC(6.7%), with greater increases in croplands(10.6%) and forests(6.0%) compared to grasslands(2.1%). Regarding SOC components, N addition promoted the accumulation of plant-derived C(9.7%–28.5%) over microbial-derived C(0.2%), as well as labile(5.7%) over recalcitrant components(–1.2%), resulting in a shift towards increased accumulation of plant-derived labile C. Consistently, N addition led to a greater increase in particulate organic C(11.9%) than mineral-associated organic C(3.6%), suggesting that N addition promotes C accumulation across all pools, with more increase in unstable than stable pools. The responses of SOC and its components were best predicted by the N addition rate and net primary productivity. Overall, our findings suggest that N enrichment could promote the accumulation of plant-derived and non-mineral associated C and a subsequent decrease in the overall stability of soil C pool, which underscores the importance of considering the effects of N enrichment on SOC components for a better understanding of C dynamics in soils.

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AFLP analysis of genetic variation among three natural populations of horseshoe crab Tachypleus tridentatus along Chinese coast

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Chinese Journal of Oceanology and Limnology 2011年第2期29卷 284-289页

作者：许茜陈菲单锦城张肇坚陈彦柯才焕 state key laboratory of marine environmental science College of Oceanography and Environmental ScienceXiamen University state key laboratory of marine Pollution and Department of Biology and Chemistry City University of Hong Kong

The AFLP(amplified fragment length polymorphism) technique was used to analyze and compare the genetic diversity of Tachypleus tridentatus from three south-eastern coastal sites of China(Pingtan,Hong Kong and Beihai).Eight pairs of primers generated 361 loci,including 285 polymorphic *** ratio of polymorphic loci was 96.97%.Nei's genetic diversity index was 0.420 8 and the Shannon information index was 0.607 5,both of which were higher than that reported for many other *** results show that the genetic diversity detected was mainly caused by individual differences within a *** distance showed that the rational division of the three geographic populations of *** along the south-eastern coast of China was not significant,in which the genetic distance was not proportional to the geographic *** three horseshoe crab populations may belong to a large group,and had a high degree of genetic *** high level of genetic diversity obtained from the present AFLP analysis may be due to the large effective population size of the species in Chinese waters.

关键词： Tachypleus tridentatus population genetic variation AFLP (amplified fragment lengthpolymorphism)

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Diagnosis of CO2 dynamics and fluxes in global coastal oceans

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National science Review 2020年第4期7卷 786-797页

作者： Zhimian Cao Wei Yang Yangyang Zhao Xianghui Guo Zhiqiang Yin Chuanjun Du Huade Zhao Minhan Dai state key laboratory of marine environmental science and College of Ocean and Earth sciences Xiamen University

Global coastal oceans as a whole represent an important carbon sink but, due to high spatial–temporal variability, a mechanistic conceptualization of the coastal carbon cycle is still under development, hindering the modelling and inclusion of coastal carbon in Earth System Models. Although temperature is considered an important control of sea surface p CO2, we show that the latitudinal distribution of global coastal surface p CO2does not match that of temperature, and its inter-seasonal changes are substantially regulated by non-thermal factors such as water mass mixing and net primary production. These processes operate in both ocean-dominated and river-dominated margins, with carbon and nutrients sourced from the open ocean and land, respectively. These can be conceptualized by a semi-analytical framework that assesses the consumption of dissolved inorganic carbon relative to nutrients, to determine how a coastal system is a CO2source or sink. The framework also finds utility in accounting for additional nutrients in organic forms and testing hypotheses such as using Redfield stoichiometry, and is therefore an essential step toward comprehensively understanding and modelling the role of the coastal ocean in the global carbon cycle.

关键词： CO2 dynamics and fluxes coastal ocean ocean-dominated margin river-dominated ocean margin carbon cycle

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