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Liquefaction susceptibility and deformation characteristics of saturated coral sandy soils subjected to cyclic loadings-a critical review 被引量:1
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作者 Chen Guoxing Qin You +3 位作者 Ma Weijia Liang Ke Wu Qi C.Hsein Juang 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2024年第1期261-296,共36页
Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and respons... Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities.This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades.The focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy soils.In particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics.Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments. 展开更多
关键词 liquefaction susceptibility dynamic deformation characteristics coral sandy soil cyclic loading review and prospect
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Validating the use of ROS-scavenging bacteria as probiotics to increase coral resilience to thermal stress
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作者 Xiaoyu TANG Qingsong YANG +5 位作者 Ying ZHANG Hanzhang WANG Juan LING Haiyan SUN Junde DONG Yanying ZHANG 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2024年第4期1242-1260,共19页
Thermal stress causes the overproduction and toxic accumulation of reactive oxygen species(ROS),which seems to be correlated with coral bleaching and,ultimately,death.The reduction of ROS concentration within the cora... Thermal stress causes the overproduction and toxic accumulation of reactive oxygen species(ROS),which seems to be correlated with coral bleaching and,ultimately,death.The reduction of ROS concentration within the coral holobiont could minimize the effects of thermal stress and support efforts to reduce coral decline globally.In the current study,we explored the physiological responses of Pocillopora damicornis to ROS-scavenging bacteria inoculation as well as the microbiome restructuring that correlates with P.damicornis’s resilience to thermal stress after probiotic inoculation.Inoculation of corals with ROS-scavenging bacteria enhanced coral health and reduced ROS concentration.Furthermore,the enhanced coral thermal resistance promoted by ROS-scavenging bacteria was also correlated with an overall coral microbiome restructuring.In addition,the complex network relationships between bacteria and Symbiodiniaceae in corals after ROS-scavenging bacteria inoculation contributed to corals’resilience to high temperatures.Besides,coral heat tolerance bacterial biomarkers,such as Myxococcota,were enriched in corals with added ROS-scavenging bacteria.Collectively,our findings validate the selected ROS-scavenging bacteria as coral probiotics that could help corals resist thermal stress on a short timescale.Additionally,our data contribute to our understanding of the potential interactions between different members of the coral holobiont and the use of probiotics as tools to aid coral restoration efforts. 展开更多
关键词 coral beneficial microorganisms for corals(BMCs) Symbiodiniaceae thermal stress coral bleaching
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Coral records of Mid-Holocene sea-level highstands and climate responses in the northern South China Sea
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作者 Yuanfu Yue Lichao Tang +1 位作者 Kefu Yu Rongyong Huang 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2024年第2期43-57,共15页
High-resolution sea-level data and high-precision dating of corals in the northern South China Sea(SCS)during the Holocene provide a reference and historical background for current and future sea-level changes and a b... High-resolution sea-level data and high-precision dating of corals in the northern South China Sea(SCS)during the Holocene provide a reference and historical background for current and future sea-level changes and a basis for scientific assessment of the evolutionary trend of coral reefs in the SCS.Although sporadic studies have been performed around Hainan Island in the northern SCS,the reconstructed sea level presents different values or is controversial because the indicative meaning of the sea-level indicators were neither quantified nor uniform criteria.Here,we determined the quantitative relationship between modern living coral and sea level by measuring the top surfaces of 27 live Porites corals from the inner reef flat along the east coast of Hainan Island and assessed the accuracy of results obtained using coral as sea-level indicators.Additionally,three in situ fossil Porites corals were analyzed based on elevation measurements,digital X-ray radiography,and U-Th dating.The survey results showed that the indicative meanings for the modern live Porites corals is(146.09±8.35)cm below the mean tide level(MTL).It suggested that their upward growth limit is constrained by the sea level,and the lowest low water is the highest level of survival for the modern live Porites corals.Based on the newly defined indicative meanings,6 new sea-level index points(SLIPs)were obtained and 19 published SLIPs were recalculated.Those SLIPs indicated a relative sea level fluctuation between(227.7±9.8)cm to(154.88±9.8)cm MTL between(5393±25)cal a BP and(3390±12)cal a BP,providing evidences of the Mid-Holocene sea-level highstand in the northern SCS.Besides that,our analysis demonstrated that different sea-level histories may be produced based on different indicative meanings or criteria.The dataset of 276 coral U-Th ages indicates that coral reef development in the northern SCS comprised the initial development,boom growth,decline,and flourishing development again.A comparison with regional records indicated that synergistic effects of climatic and environmental factors were involved in the development of coral reefs in the northern SCS.Thus,the cessation of coral reef development during the Holocene in the northern SCS was probably associated with the dry and cold climate in South China,as reflected in the synchronous weakening of the ENSO and East Asian summer monsoon induced by the reduction of the 65°N summer insolation,which forced the migration of the Intertropical Convergence Zone. 展开更多
关键词 northern South China Sea Middle Holocene sea-level highstand Porites corals climate response
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A machine learning-based strategy for predicting the mechanical strength of coral reef limestone using X-ray computed tomography
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作者 Kai Wu Qingshan Meng +4 位作者 Ruoxin Li Le Luo Qin Ke ChiWang Chenghao Ma 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第7期2790-2800,共11页
Different sedimentary zones in coral reefs lead to significant anisotropy in the pore structure of coral reef limestone(CRL),making it difficult to study mechanical behaviors.With X-ray computed tomography(CT),112 CRL... Different sedimentary zones in coral reefs lead to significant anisotropy in the pore structure of coral reef limestone(CRL),making it difficult to study mechanical behaviors.With X-ray computed tomography(CT),112 CRL samples were utilized for training the support vector machine(SVM)-,random forest(RF)-,and back propagation neural network(BPNN)-based models,respectively.Simultaneously,the machine learning model was embedded into genetic algorithm(GA)for parameter optimization to effectively predict uniaxial compressive strength(UCS)of CRL.Results indicate that the BPNN model with five hidden layers presents the best training effect in the data set of CRL.The SVM-based model shows a tendency to overfitting in the training set and poor generalization ability in the testing set.The RF-based model is suitable for training CRL samples with large data.Analysis of Pearson correlation coefficient matrix and the percentage increment method of performance metrics shows that the dry density,pore structure,and porosity of CRL are strongly correlated to UCS.However,the P-wave velocity is almost uncorrelated to the UCS,which is significantly distinct from the law for homogenous geomaterials.In addition,the pore tensor proposed in this paper can effectively reflect the pore structure of coral framework limestone(CFL)and coral boulder limestone(CBL),realizing the quantitative characterization of the heterogeneity and anisotropy of pore.The pore tensor provides a feasible idea to establish the relationship between pore structure and mechanical behavior of CRL. 展开更多
关键词 coral reef limestone(CRL) Machine learning Pore tensor X-ray computed tomography(CT)
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A novel relationship between elastic modulus and void ratio associated with principal stress for coral calcareous sand
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作者 Ran Gao Jianhong Ye 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第3期1033-1048,共16页
Elastic moduli,e.g.shear modulus G and bulk modulus K,are important parameters of geotechnical materials,which are not only the indices for the evaluation of the deformation ability of soils but also the important bas... Elastic moduli,e.g.shear modulus G and bulk modulus K,are important parameters of geotechnical materials,which are not only the indices for the evaluation of the deformation ability of soils but also the important basic parameters for the development of the constitutive models of geotechnical materials.In this study,a series of triaxial loading-unloading-reloading shear tests and isotropic loading-unloadingreloading tests are conducted to study several typical mechanical properties of coral calcareous sand(CCS),and the void ratio evolution during loading,unloading and reloading.The test results show that the stress-strain curves during multiple unloading processes are almost parallel,and their slopes are much greater than the deformation modulus at the initial stage of loading.The relationship between the confining pressure and the volumetric strain can be defined approximately by a hyperbolic equation under the condition of monotonic loading of confining pressure.Under the condition of confining pressure unloading,the evolution of void ratio is linear in the e-lnp0 plane,and these lines are a series of almost parallel lines if there are multiple processes of unloading.Based on the experimental results,it is found that the modified Hardin formulae for the elastic modulus estimation have a significant deviation from the tested values for CCS.Based on the experimental results,it is proposed that the elastic modulus of soils should be determined by the intersection line of two spatial surfaces in the G/K-e-p’/pa space(pa:atmosphere pressure).“Ye formulation”is further proposed for the estimation of the elastic modulus of CCS.This new estimation formulation for soil elastic modulus would provide a new method to accurately describe the mechanical behavior of granular soils. 展开更多
关键词 coral calcareous sand(CCS) Elastic shear modulus Elastic bulk modulus Triaxial test Estimation formulation Ye formulation
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Microbiome Engineering:A Promising Approach to Improve Coral Health 被引量:1
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作者 Jie Li Qingsong Yang +7 位作者 Junde Dong Michael Sweet Ying Zhang Cong Liu Yanying Zhang Xiaoyu Tang Wenqian Zhang Si Zhang 《Engineering》 SCIE EI CAS CSCD 2023年第9期105-116,共12页
The world’s coral reefs are threatened by the cumulative impacts of global climate change and local stressors.Driven largely by a desire to understand the interactions between corals and their symbiotic microorganism... The world’s coral reefs are threatened by the cumulative impacts of global climate change and local stressors.Driven largely by a desire to understand the interactions between corals and their symbiotic microorganisms,and to use this knowledge to eventually improve coral health,interest in coral microbiology and the coral microbiome has increased in recent years.In this review,we summarize the role of the coral microbiome in maintaining a healthy metaorganism by providing nutrients,support for growth and development,protection against pathogens,and mitigation of environmental stressors.We explore the concept of coral microbiome engineering,that is,precise and controlled manipulation of the coral microbiome to aid and enhance coral resilience and tolerance in the changing oceans.Although coral microbiome engineering is clearly in its infancy,several recent breakthroughs indicate that such engineering is an effective tool for restoration and preservation of these valuable ecosystems.To assist with identifying future research targets,we have reviewed the common principles of microbiome engineering and its applications in improving human health and agricultural productivity,drawing parallels to where coral microbiome engineering can advance in the not-too-distant future.Finally,we end by discussing the challenges faced by researchers and practitioners in the application of microbiome engineering in coral reefs and provide recommendations for future work. 展开更多
关键词 coral reef restoration coral holobiont Beneficial microorganisms for corals BLEACHING Microbiome engineering
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Coral reef ecological pump for gathering and retaining nutrients and exporting carbon:a review and perspectives 被引量:1
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作者 Linbin Zhou Yehui Tan Liangmin Huang 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2023年第6期1-15,共15页
How coral reefs with high productivity and biodiversity can flourish in oligotrophic tropical oceans has inspired substantial research on coral reef ecosystems.Increasing evidence shows that similar to water in an oas... How coral reefs with high productivity and biodiversity can flourish in oligotrophic tropical oceans has inspired substantial research on coral reef ecosystems.Increasing evidence shows that similar to water in an oasis in the desert,there are stable nutrient supplies to coral reefs in oligotrophic oceans.Here,with emphasis on the fluxes of organic matter,we summarize at the ecosystem level(1)the multiple input pathways of external nutrients,(2)the storage of nutrients in reef organisms,(3)the efficient retaining and recycling of dissolved and particulate organic matter within coral reef ecosystems,(4)the distinctly high phytoplankton productivity and biomass inside and near oceanic coral reefs,and(5)the export of reef-related organic carbon to adjacent open oceans.These properties enable coral reefs to function as ecological“pumps”for gathering nutrients across ecosystems and space,retaining and recycling nutrients within the ecosystem,supporting high phytoplankton productivity,and exporting organic carbon to adjacent open oceans.Particularly,the high phytoplankton productivity and biomass make waters around coral reefs potential hotspots of carbon export to ocean depths via the biological pump.We demonstrate that organic carbon influx is vital for coral reef ecosystems’carbon budget and carbon export.The concept of the coral reef ecological pump provides a framework to improve the understanding of the functioning of the coral reef ecosystem and its responses to disturbance.Prospects of the coral reef ecological pump in coral reef studies are discussed in changing oceans driven by human activities and global change in the Anthropocene. 展开更多
关键词 Darwin’s Paradox coral reef NUTRIENTS coral reef ecological pump carbon export ocean carbon cycle
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Effects of biochar-amended alkali-activated slag on the stabilization of coral sand in coastal areas 被引量:1
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作者 Xiaole Han Ningjun Jiang +4 位作者 Fei Jin Krishna RReddy Yijie Wang Kaiwei Liu Yanjun Du 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2023年第3期760-772,共13页
Coral sand is widely encountered in coastal areas of tropical and subtropical regions.Compared with silica sand,it usually exhibits weaker performance from the perspective of engineering geology.To improve the geomech... Coral sand is widely encountered in coastal areas of tropical and subtropical regions.Compared with silica sand,it usually exhibits weaker performance from the perspective of engineering geology.To improve the geomechanical performance of coral sand and meet the requirement of foundation construction in coastal areas,a novel alkali activation-based sustainable binder was developed.The alkaliactivated slag(AAS)binder material was composed of ground granulated blast-furnace slag(GGBS)and hydrated lime with the amendment of biochar,an agricultural waste-derived material.The biocharamended AAS stabilized coral sand was subjected to a series of laboratory tests to determine its mechanical,physicochemical,and microstructural characteristics.Results show that adding a moderate amount of biochar in AAS could improve soil strength,elastic modulus,and water holding capacity by up to 20%,70%,and 30%,respectively.Moreover,the addition of biochar in AAS had a marginal effect on the sulfate resistance of the stabilized sand,especially at high biochar content.However,the resistance of the AAS stabilized sand to wet-dry cycles slightly deteriorated with the addition of biochar.Based on these observations,a conceptual model showing biochar-AAS-sand interactions was proposed,in which biochar served as an internal curing agent,micro-reinforcer,and mechanically weak point. 展开更多
关键词 coral sand Soil stabilization BIOCHAR Alkali activation
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Chemical diversity of scleractinian corals revealed by untargeted metabolomics and molecular networking
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作者 Jiying Pei Yuxia Zhou +4 位作者 Shiguo Chen Kefu Yu Zhenjun Qin Ruijie Zhang Yitong Wang 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2023年第11期127-135,共9页
The chemical diversity of scleractinian corals is closely related to their physiological,ecological,and evolutionary status,and can be influenced by both genetic background and environmental variables.To investigate i... The chemical diversity of scleractinian corals is closely related to their physiological,ecological,and evolutionary status,and can be influenced by both genetic background and environmental variables.To investigate intraspecific variation in the metabolites of these corals,the metabolomes of four species(Pocillopora meandrina,Seriatopora hystrix,Acropora formosa,and Fungia fungites)from the South China Sea were analyzed using untargeted mass spectrometry-based metabolomics.The results showed that a variety of metabolites,including amino acids,peptides,lipids,and other small molecules,were differentially distributed among the four species,leading to their significant separation in principal component analysis and hierarchical clustering plots.The higher content of storage lipids in branching corals(P.meandrina,S.hystrix,and A.formosa)compared to the solitary coral(F.fungites)may be due to the high densities of zooxanthellae in their tissues.The high content of aromatic amino acids in P.meandrina may help the coral protect against ultraviolet damage and promote growth in shallow seawater,while nitrogen-rich compounds may enable S.hystrix to survive in various challenging environments.The metabolites enriched in F.fungites,including amino acids,dipeptides,phospholipids,and other small molecules,may be related to the composition of the coral's mucus and its life-history,such as its ability to move freely and live solitarily.Studying the chemical diversity of scleractinian corals not only provides insight into their environmental adaptation,but also holds potential for the chemotaxonomy of corals and the discovery of novel bioactive natural products. 展开更多
关键词 scleractinian coral chemical diversity metabolomics molecular networking environmental adaptation
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Refined mathematical model for the breaching of concrete-face sand-gravel dams due to overtopping failure
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作者 QIU Wen LI Yan-long +2 位作者 WEN Li-feng WANG Jing YIN Qiao-gang 《Journal of Mountain Science》 SCIE CSCD 2023年第3期670-687,共18页
Overtopping is one of the main reasons for the breaching of concrete-face sand-gravel dams(CFSGDs).In this study,a refined mathematical model was established based on the characteristics of the overtopping breaching o... Overtopping is one of the main reasons for the breaching of concrete-face sand-gravel dams(CFSGDs).In this study,a refined mathematical model was established based on the characteristics of the overtopping breaching of CFSGDs.The model characteristics were as follows:(1)Based on the Renormailzation Group(RNG)k-εturbulence theory and volume of fluid(VOF)method,the turbulent characteristics of the dam-break flow were simulated,and the erosion surface of the water and soil was tracked;(2)In consideration of the influence of the change in the sediment content on the dam-break flow,the dam material transport equation,which could reflect the characteristics of particle settlement and entrainment motion,was used to simulate the erosion process of the sand gravels;(3)Based on the bending moment balance method,a failure equation of the concrete face slab under dead weight and water load was established.The proposed model was verified through a case study on the failure of the Gouhou CFSGD.The results showed that the proposed model could well simulate the erosion mode of the special vortex flow of the CFSGD scouring the support body of the concrete face slab inward and reflect the mutual coupling relationship between the dam-break flow,sand gravels,and concrete face slabs.Compared with the measured values,the relative errors of the peak discharge,final breach average width,dam breaching duration,and maximum failure length of the face slab calculated using the proposed model were all less than 12%,thus verifying the rationality of the model.The proposed model was demonstrated to perform better and provide more detailed results than three selected parametric models and three simplified mathematical models.The study results can aid in establishing the risk level and devising early warning strategies for CFSGDs. 展开更多
关键词 Concrete-face sand-gravel dam OVERTOPPING Dam-break flow Concrete face slab failure Refined mathematical model
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Dynamic Impact Compressive Behavior Investigation of Sisal Fiber-reinforced Coral Seawater Concrete
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作者 MA Haiyan TAN Yongshan +2 位作者 YU Hongfa YUE Chengjun ZHANG Yan 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS CSCD 2023年第5期1034-1043,共10页
Split Hopkinson pressure bar(SHPB)was used to investigate the dynamic compressive properties of sisal fiber reinforced coral aggregate concrete(SFCAC).The results showed that,with the increase of strain rate,the dynam... Split Hopkinson pressure bar(SHPB)was used to investigate the dynamic compressive properties of sisal fiber reinforced coral aggregate concrete(SFCAC).The results showed that,with the increase of strain rate,the dynamic compressive strength,peak strain and toughness index of SFCAC are all greater than its static properties,indicating that SFCAC is a kind of rate-sensitive material.When the sisal fiber was blended,the failure mode showed obvious ductility.At high strain rates,the SFCAC without sisal fiber specimen was comminuted,and the SFCAC showed a"cracked without breaking"state.The results indicated that the sisal fiber played a significant role in reinforcing and strengthening the properties of concrete.The finite element software LS-DYNA was used to simulate two working conditions with strain rates of 78 and 101 s-1.The stressstrain curves and failure patterns obtained were in good agreement with the experimental results. 展开更多
关键词 coral aggregate concrete sisal fiber dynamic compressive strain-rate effect
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Compressive Strength of Basic Magnesium Sulfate Cement Coral Aggregate Concrete(MCAC)on Non-Destructive Testing
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作者 GUO Jianbo YU Hongfa +3 位作者 MA Haiyan CHANG Yun MEI Qiquan ZHANG Yan 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS CSCD 2023年第5期1086-1095,共10页
Basic magnesium sulfate cement coral aggregate concrete(MCAC)is a new type of concrete consisting of basic magnesium sulfate cement,coarse coral aggregate,coral reef sand and seawater.The rebound hammer(RH),the ultras... Basic magnesium sulfate cement coral aggregate concrete(MCAC)is a new type of concrete consisting of basic magnesium sulfate cement,coarse coral aggregate,coral reef sand and seawater.The rebound hammer(RH),the ultrasonic pulse velocity(UPV)and the compressive strength(fcu)tests of 14 sets of cube specimens of the MCAC after 28 d of aging were conducted.The impact of the content and length of sisal fiber on the relationship between the fcu-RH and the fcu-UPV was determined.A mathematical model was established to predict the strength of the MCAC using the UPV,RH,and comprehensive UPV/RH methods and to obtain the curves of test strength.The applicability of the test strength curves of ordinary portland concrete(OPC),light-weight aggregate concrete(LAC),and coral aggregate concrete(CAC)to MCAC was assessed.The results showed that the test strength curves of OPC,LAC and CAC were inappropriate to determine the strength of MCAC using non-destructive method.The relative standard error of the curves of test strength of the RH method and the comprehensive method met the specifications,whereas that of the UPV method did not. 展开更多
关键词 non-destructive testing basic magnesium sulfate cement coral aggregate corcrete ultrasonic pulse velocity rebound hammer specific test strength curves
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珊瑚礁生态系统固碳过程及储碳机制研究进展 被引量:1
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作者 黄晖 袁翔城 +3 位作者 宋严 李颖心 周伟华 龙爱民 《热带海洋学报》 CAS CSCD 北大核心 2024年第3期13-21,共9页
珊瑚礁生态系统在全球碳循环和气候变化中发挥着重要作用。珊瑚礁生态系统是潜在的蓝色碳汇,我国珊瑚礁总面积约占全球的11%,每年的固碳量大约在3.5×10^(6)~4.5×10^(6)t之间。珊瑚礁生态系统的总储碳量非常巨大,同时珊瑚礁生... 珊瑚礁生态系统在全球碳循环和气候变化中发挥着重要作用。珊瑚礁生态系统是潜在的蓝色碳汇,我国珊瑚礁总面积约占全球的11%,每年的固碳量大约在3.5×10^(6)~4.5×10^(6)t之间。珊瑚礁生态系统的总储碳量非常巨大,同时珊瑚礁生态系统作为碳库在碳交易中具有非常大的潜在应用价值。文章综述了珊瑚礁生态系统中的固碳过程及储碳机制,包括碳酸盐泵、生物泵和微型生物碳泵,阐述了三种碳泵的研究进展。同时,针对目前研究存在的不足和问题,提出未来研究方向,以期为南海岛礁珊瑚礁生态系统的保护和管理提供科学依据。 展开更多
关键词 珊瑚礁 生态系统 固碳 碳酸盐泵 生物泵 微型生物碳泵
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不同形状的珊瑚砂颗粒沉降试验研究 被引量:1
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作者 陈杰 蒋超 +1 位作者 蒋昌波 姚震 《泥沙研究》 CAS CSCD 北大核心 2024年第1期8-15,共8页
珊瑚砂在液体中的沉速是反映泥沙运动特性的一个重要物理量。由于珊瑚砂形状多样,套用现有的珊瑚砂沉速公式进行计算并不合适。针对珊瑚砂颗粒开展形状分析,将珊瑚砂颗粒分成枝棒状、片状和块状3种形状,然后开展单颗粒沉降试验。基于试... 珊瑚砂在液体中的沉速是反映泥沙运动特性的一个重要物理量。由于珊瑚砂形状多样,套用现有的珊瑚砂沉速公式进行计算并不合适。针对珊瑚砂颗粒开展形状分析,将珊瑚砂颗粒分成枝棒状、片状和块状3种形状,然后开展单颗粒沉降试验。基于试验数据,分析不同形状珊瑚砂颗粒的沉降特性,与各家理论公式计算结果进行比较分析,选取经典的珊瑚砂颗粒沉速公式,引入颗粒形状系数进行公式修正,从而推求了枝棒状、片状和块状珊瑚砂颗粒的阻力系数和沉降速度公式。该公式充分考虑不规则珊瑚砂颗粒形状的影响,具有更高的计算精度和适用性。 展开更多
关键词 珊瑚砂 颗粒形状 沉降速度 阻力系数
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三亚凤凰岛造礁石珊瑚迁移效果研究
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作者 张浴阳 刘骋跃 +4 位作者 俞晓磊 罗勇 周天成 练健生 黄晖 《热带海洋学报》 CAS CSCD 北大核心 2024年第3期177-186,共10页
造礁石珊瑚既是构成珊瑚礁生态系统中的关键功能生物,也是国家二级保护野生动物,其数量的快速衰退已引起了广泛关注,因此近年来我国对造礁石珊瑚以及珊瑚礁生态系统的保护正在逐步加强。海岸工程易对周边的珊瑚礁造成严重影响,实施保护... 造礁石珊瑚既是构成珊瑚礁生态系统中的关键功能生物,也是国家二级保护野生动物,其数量的快速衰退已引起了广泛关注,因此近年来我国对造礁石珊瑚以及珊瑚礁生态系统的保护正在逐步加强。海岸工程易对周边的珊瑚礁造成严重影响,实施保护性迁移是降低工程对造礁石珊瑚影响的重要手段。为研究海南热带海域造礁石珊瑚迁移方法以及迁移保护的效果,我们对三亚凤凰岛二期项目拆除工程影响海域内的造礁石珊瑚实施了保护性迁移及监测。迁移造礁石珊瑚个体共计16634株,包括鹿角珊瑚属、牡丹珊瑚属、滨珊瑚属等18属造礁石珊瑚种类。迁移个体分别迁移至鹿回头海域6210株与西岛海域10424株。迁移珊瑚采用了三种移植方法,分别为铆钉移植、小型移植礁体移植与直接摆放。在迁移至鹿回头和西岛两地8个月后,迁移珊瑚平均存活率均在80%以上,两地迁移珊瑚的总存活率为86.24%。调查的结果显示,铆钉移植的方法存活率最高,小型移植礁体和直接摆放的两种移植方法存活率稍低。迁移至西岛的珊瑚8个月平均生长了3.03cm,的增长率为23.31%,而鹿回头迁入的珊瑚平均生长了6.15cm,增长率为58.74%,高于迁移至西岛的珊瑚。迁移采用的三种移植方法的8个月的存活率均高于75%,并且珊瑚的生长速率较好,说明珊瑚适应迁入区环境。由以上结果来看,此次保护性迁移珊瑚数量多,涉及的珊瑚种类广,在迁移后经受过两次台风的影响,迁移结果具有一定的代表性。本研究中,珊瑚迁移的效果达到了保护受拆除工程影响的造礁石珊瑚的目的,可为未来的珊瑚迁移性保护提供重要经验。 展开更多
关键词 造礁石珊瑚 珊瑚礁保护 珊瑚迁移 三亚珊瑚礁 凤凰岛
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Stressed Coral Reef Identification Using Deep Learning CNN Techniques
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作者 S.P.Aruna M.Thamarai 《Journal of Electronic & Information Systems》 2023年第2期1-9,共9页
Deep learning is a machine learning technique that allows the computer to process things that occur naturally to humans.Today,deep learning techniques are commonly used in computer vision to classify images and videos... Deep learning is a machine learning technique that allows the computer to process things that occur naturally to humans.Today,deep learning techniques are commonly used in computer vision to classify images and videos.As a result,for challenging computer vision problems,deep learning provides state of the art solutions to it.Coral reefs are an essential resource of the earth.A new study finds the planet has lost half of its coral reefs since 1950.It is necessary to restore and prevent damage to coral reefs as they play an important role in maintaining a balance in the marine ecosystem.This proposed work helps to prevent the corals from bleaching and restore them to a healthy condition by identifying the root cause of the threats.In the proposed work,using deep learning CNN techniques,the images are classified into Healthy and Stressed coral reefs.Stressed coral reefs are an intermediate state of coral reef between healthy and bleached coral reefs.The pre-trained models Resnet50 and Inception V3 are used in this study to classify the images.Also,a proposed CNN model is built and tested for the same.The results of Inception V3 and Resnet50 are improved to 70%and 55%by tuning the hypermeters such as dropouts and batch normalisation.Similarly,the proposed model is tuned as required and obtains a maximum of up to 90%accuracy.With large datasets,the optimum amount of neural networks and tuning it as required brings higher accuracy than other methods. 展开更多
关键词 Stressed coral reef Deep learning Convolutional neural network Pre-trained models
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《西沙群岛珊瑚岛(礁)地区岩土工程勘察标准》研究与编制
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作者 杨永康 杨武 +2 位作者 谢书领 王影 冯春燕 《岩土工程技术》 2024年第1期37-40,共4页
为适应和满足西沙群岛珊瑚岛(礁)工程建设的需要,使珊瑚岛(礁)岩土工程勘察有据可依,总结了西沙群岛岩土工程勘察项目实践经验和研究成果,通过资料收集、分析与研究,编制了《西沙群岛珊瑚岛(礁)地区岩土工程勘察标准》(DBJ46—060—2022... 为适应和满足西沙群岛珊瑚岛(礁)工程建设的需要,使珊瑚岛(礁)岩土工程勘察有据可依,总结了西沙群岛岩土工程勘察项目实践经验和研究成果,通过资料收集、分析与研究,编制了《西沙群岛珊瑚岛(礁)地区岩土工程勘察标准》(DBJ46—060—2022)。介绍标准的编制背景、编制的工作流程、标准的主要内容和重点研究内容,探讨需要进一步研究的内容。 展开更多
关键词 西沙群岛 珊瑚岛(礁) 珊瑚碎屑砂土 珊瑚礁灰岩
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聚丙烯纤维增强珊瑚混凝土韧性试验研究
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作者 易金 王磊 +2 位作者 李增 张继旺 池俊生 《建筑材料学报》 EI CAS CSCD 北大核心 2024年第10期913-921,共9页
采用聚丙烯纤维(PPF)对珊瑚混凝土进行增韧和降脆处理.结果表明:适当增加PPF的掺量或长度能在一定程度上提升珊瑚混凝土的抗弯强度与抗拉强度;当PPF长度过长或掺量过大时,PPF卷曲或聚团会引起珊瑚混凝土的局部缺陷,降低增韧效果;PPF增... 采用聚丙烯纤维(PPF)对珊瑚混凝土进行增韧和降脆处理.结果表明:适当增加PPF的掺量或长度能在一定程度上提升珊瑚混凝土的抗弯强度与抗拉强度;当PPF长度过长或掺量过大时,PPF卷曲或聚团会引起珊瑚混凝土的局部缺陷,降低增韧效果;PPF增强珊瑚混凝土的拉伸应力-应变曲线符合三线性本构模型,极限拉应变提升了52%~333%,延性指数高达10.89;尽管PPF能显著提升珊瑚混凝土的韧性,但也可能导致其密实度和抗压强度有所降低,建议在实际应用中精确控制PPF的掺量和长度,以确保珊瑚混凝土既能获得所需的韧性,又能保持适当的密实度和抗压强度. 展开更多
关键词 珊瑚混凝土 聚丙烯纤维 抗拉强度 韧性 应变
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珊瑚海岛包气带中氮磷的迁移、转化和累积规律
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作者 李莉 张盼 +3 位作者 赵志伟 张赛 龚星 许庭浩 《中国环境科学》 EI CAS CSCD 北大核心 2024年第10期5776-5787,共12页
珊瑚海岛包气带中氮磷的迁移转化直接影响海岛地下水质量和土壤结构.通过XRD和SEM分析,明确了珊瑚砂特殊的CaCO_(3)物相成分和多孔形貌特征.采用静态吸附实验明确了珊瑚砂对N、P的吸附机理;通过短期连续降雨和长期间歇降雨模拟柱实验分... 珊瑚海岛包气带中氮磷的迁移转化直接影响海岛地下水质量和土壤结构.通过XRD和SEM分析,明确了珊瑚砂特殊的CaCO_(3)物相成分和多孔形貌特征.采用静态吸附实验明确了珊瑚砂对N、P的吸附机理;通过短期连续降雨和长期间歇降雨模拟柱实验分别研究了N、P在珊瑚砂中的运移机制和不同深度剖面N的转化和P的累积规律.结果表明,珊瑚砂对NH_(4)^(+)和DIP的平均吸附量为192mg/kg和2051.75mg/kg,吸附模型分别符合可逆线性吸附和Freundlich等温吸附模型;NH_(4)^(+)的运移机制可由线性平衡CDE模型解释,低浓度DIP的运移过程符合含衰减项的双点位化学非平衡模型;而高浓度DIP的运移过程无法由模型拟合,结合pH值推测了其与CaCO_(3)发生的溶解沉淀平衡反应.长期降雨条件下,结合微生物分析得出土壤中存在N_(2)→NH_(4)^(+)→NO_(2)^(-)→NO_(3)^(-)→N_(2)/DON的氮转化路径,存在地下水氮污染的风险,而DIP则以非溶解态磷形式被固定,其长期累积可能对土壤结构不利.简言之,N、P在珊瑚海岛包气带中的迁移、转化、累积方面具有特殊性,明确其规律可为海岛生态建设中的环境风险控制提供科学依据. 展开更多
关键词 珊瑚砂 静态吸附 氮磷运移 HYDRUS-1D 微生物
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珊瑚礁生态学研究现状和展望
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作者 黄晖 俞晓磊 +1 位作者 黄林韬 江雷 《热带海洋学报》 CAS CSCD 北大核心 2024年第3期3-12,共10页
珊瑚礁生态系统是海洋生态系统的重要组成部分,在维持海洋生态平衡和生物多样性上扮演着重要角色。本文通过文献检索手段,归纳了当前国际和国内珊瑚礁生态学领域的发展现状。国际上关注的主要方面包括全球变化与珊瑚礁生态系统、珊瑚共... 珊瑚礁生态系统是海洋生态系统的重要组成部分,在维持海洋生态平衡和生物多样性上扮演着重要角色。本文通过文献检索手段,归纳了当前国际和国内珊瑚礁生态学领域的发展现状。国际上关注的主要方面包括全球变化与珊瑚礁生态系统、珊瑚共生关系的建立与维持、珊瑚礁生物系统发育与进化、珊瑚礁生物多样性及其物种分布格局、珊瑚礁生态系统保护与管理等;国内关注的主要方面包括全球变化与珊瑚礁生态系统、全球变化背景下的珊瑚–虫黄藻共生体、珊瑚共生关系多样性、人类活动与南海珊瑚礁生态系统、珊瑚礁生物多样性及其群落格局等。珊瑚礁生态学研究的未来发展趋势将更加注重全球变化背景下的珊瑚与珊瑚礁生态系统、珊瑚共生机制、边缘珊瑚礁以及珊瑚礁保护与修复。未来我国珊瑚礁生态学研究需提升全球视野,加强国内与国际合作,深入机制挖掘,完善系统研究,增强珊瑚礁保护与修复研究。 展开更多
关键词 珊瑚礁生态学 研究现状 发展趋势和对策
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