Sand cay is a special kind of islet formed by coral detritus and bioclast, which is common in Nansha Islands of China. Some sand cays play an important role in ocean strategy and economy, but surprisingly we know litt...Sand cay is a special kind of islet formed by coral detritus and bioclast, which is common in Nansha Islands of China. Some sand cays play an important role in ocean strategy and economy, but surprisingly we know little about them, especially those recently formed sand cays. In this research, we monitor migration of a new sand cay in Nanxun Jiao（Gaven Reef） using a series of Quick Bird and World View-2 satellite images between June 2006 and August 2013. We conduct a regression between migration distance and wind observational data to examine the migration patterns of the new sand cay. The migration distance is calculated based on the sand cay locations extracted based on Normalized Difference Water Index（NDWI）. The wind observational data downloaded from NOAA are reformed into four wind direction vectors. Based on the results of regression, we concluded that the migration of the new sand cay on Nanxun Jiao was significantly associated with the east, west and north wind.East wind was the main influence factor of the migration; its impact strength was almost twice as the west and north wind. The south wind has little effect on the migration of the sand cay, which is partly blocked by the artificial structure in the south.展开更多
Given the socio-economic consequences associated with declaring areas of ocean protected in order to achieve conservation objectives, this paper contributes to the growing global need to assess Marine Protected Areas ...Given the socio-economic consequences associated with declaring areas of ocean protected in order to achieve conservation objectives, this paper contributes to the growing global need to assess Marine Protected Areas (MPAs) as an effective management tool. It adds to the current body of knowledge on MPA effectiveness by conducting an evaluation of the Tobago Cays Marine Park (TCMP), located in St. Vincent and the Grenadines (SVG) in the eastern Caribbean, using a modified MPA effectiveness framework. Due to the limited information existing about the current performance of this MPA, this assessment also provides needed insight on the effect that the TCMP is having on the marine ecosystem, as well as its overall management performance. By comparing the performance of the MPA over a 10-year span (2007 and 2016), the results indicate that overall, the TCMP could be described as having limited success when key management categories of context, planning, input, process, output and outcomes are evaluated. In particular, efforts dedicated to planning, process and outcomes are assessed as deficient. Furthermore, the analysis revealed that efforts to realize the stated goals relating to conservation, public awareness and public education were being neglected. However, considerable effort was being expended by TCMP staff on achieving the remaining goal focusing on deriving economic benefits from touristic activities in the Park. Preliminary field research examining the effects of the TCMP on the abundance and density of an economically important species, Lobatus gigas, (commonly referred to as the queen conch) showed the TCMP as having no effect towards conch protection. The results and recommendations of this study, combined with continued monitoring of a recommended targeted suite of indicators, could contribute to better-informed adaptive MPA management, leading to progress towards the achievement of the stated goals for the TCMP.展开更多
It has been conjectured that there is a hamiltonian cycle in every finite connected Cayley graph.In spite of the difficulty in proving this conjecture,we show that almost all Cayley graphs are hamiltonian.That is,as t...It has been conjectured that there is a hamiltonian cycle in every finite connected Cayley graph.In spite of the difficulty in proving this conjecture,we show that almost all Cayley graphs are hamiltonian.That is,as the order n of a group G approaches infinity,the ratio of the number of hamiltonian Cayley graphs of G to the total number of Cayley graphs of G approaches 1.展开更多
Beach rock,which forms at the intertidal zone,is a natural barrier to protect beach and island from wave erosion. The formation mechanism of beach rocks is significant in the study of surface carbonate diagenesis and ...Beach rock,which forms at the intertidal zone,is a natural barrier to protect beach and island from wave erosion. The formation mechanism of beach rocks is significant in the study of surface carbonate diagenesis and protection of island. Beach rocks in Qilian Islets and Cays were formed about 500–700 a BP,neither its composition nor sedimentary structure experienced intense post-reformation.Beach rocks in Qilian Islets and Cays are mainly composed of reef-building skeletal fragments and bioclasts without terrigenous sediments. This study focused on the types and morphologies of cements in beach rocks of Qilian Islets and Cays,and its cementation mechanisms and influencing factors. Biological activities,such as micritization caused by microbial activities and algae binding action,play an important role in the initial stage of bioclast transformation and promote the subsequent early marine and early meteoric cementation. Acicular aragonite induced by early marine cementation is well developed in beach rocks,especially in those samples from Medium Islet. Early meteoric cementation is not common as marine cementation,generally presenting granular and meniscus cements. The main factors affecting the formation and development of beach rocks in Qilian Islets and Cays include sediment source,hydrodynamic condition,climate,sea level change and anthropogenic impacts.展开更多
Isotope eff ects are pivotal in understanding silicate melt evaporation and planetary accretion processes.Based on the Hertz-Knudsen equation,the current theory often fails to predict observed isotope fractionations o...Isotope eff ects are pivotal in understanding silicate melt evaporation and planetary accretion processes.Based on the Hertz-Knudsen equation,the current theory often fails to predict observed isotope fractionations of laboratory experiments due to its oversimplified assumptions.Here,we point out that the Hertz-Knudsen-equation-based theory is incomplete for silicate melt evaporation cases and can only be used for situations where the vaporized species is identical to the one in the melt.We propose a new model designed for silicate melt evaporation under vacuum.Our model considers multiple steps including mass transfer,chemical reaction,and nucleation.Our derivations reveal a kinetic isotopic fractionation factor(KIFF orα)αour model=[m(^(1)species)/m(^(2)species)]^(0.5),where m(species)is the mass of the reactant of reaction/nucleation-limiting step or species of diffusion-limiting step and superscript 1 and 2 represent light and heavy isotopes,respectively.This model can eff ectively reproduce most reported KIFFs of laboratory experiments for various elements,i.e.,Mg,Si,K,Rb,Fe,Ca,and Ti.And,the KIFF-mixing model referring that an overall rate of evaporation can be determined by two steps jointly can account for the eff ects of low P_(H2)pressure,composition,and temperature.In addition,we find that chemical reactions,diffusion,and nucleation can control the overall rate of evaporation of silicate melts by using the fitting slope in ln(−ln f)versus ln(t).Notably,our model allows for the theoretical calculations of parameters like activation energy(E_(a)),providing a novel approach to studying compositional and environmental eff ects on evaporation processes,and shedding light on the formation and evolution of the proto-solar and Earth-Moon systems.展开更多
基金National Sea Islands Protection and Management Programme
文摘Sand cay is a special kind of islet formed by coral detritus and bioclast, which is common in Nansha Islands of China. Some sand cays play an important role in ocean strategy and economy, but surprisingly we know little about them, especially those recently formed sand cays. In this research, we monitor migration of a new sand cay in Nanxun Jiao（Gaven Reef） using a series of Quick Bird and World View-2 satellite images between June 2006 and August 2013. We conduct a regression between migration distance and wind observational data to examine the migration patterns of the new sand cay. The migration distance is calculated based on the sand cay locations extracted based on Normalized Difference Water Index（NDWI）. The wind observational data downloaded from NOAA are reformed into four wind direction vectors. Based on the results of regression, we concluded that the migration of the new sand cay on Nanxun Jiao was significantly associated with the east, west and north wind.East wind was the main influence factor of the migration; its impact strength was almost twice as the west and north wind. The south wind has little effect on the migration of the sand cay, which is partly blocked by the artificial structure in the south.
文摘Given the socio-economic consequences associated with declaring areas of ocean protected in order to achieve conservation objectives, this paper contributes to the growing global need to assess Marine Protected Areas (MPAs) as an effective management tool. It adds to the current body of knowledge on MPA effectiveness by conducting an evaluation of the Tobago Cays Marine Park (TCMP), located in St. Vincent and the Grenadines (SVG) in the eastern Caribbean, using a modified MPA effectiveness framework. Due to the limited information existing about the current performance of this MPA, this assessment also provides needed insight on the effect that the TCMP is having on the marine ecosystem, as well as its overall management performance. By comparing the performance of the MPA over a 10-year span (2007 and 2016), the results indicate that overall, the TCMP could be described as having limited success when key management categories of context, planning, input, process, output and outcomes are evaluated. In particular, efforts dedicated to planning, process and outcomes are assessed as deficient. Furthermore, the analysis revealed that efforts to realize the stated goals relating to conservation, public awareness and public education were being neglected. However, considerable effort was being expended by TCMP staff on achieving the remaining goal focusing on deriving economic benefits from touristic activities in the Park. Preliminary field research examining the effects of the TCMP on the abundance and density of an economically important species, Lobatus gigas, (commonly referred to as the queen conch) showed the TCMP as having no effect towards conch protection. The results and recommendations of this study, combined with continued monitoring of a recommended targeted suite of indicators, could contribute to better-informed adaptive MPA management, leading to progress towards the achievement of the stated goals for the TCMP.
基金Supported by the National Natural Science Foundation of China,Xinjiang Educational Committee and Xinjiang University.
文摘It has been conjectured that there is a hamiltonian cycle in every finite connected Cayley graph.In spite of the difficulty in proving this conjecture,we show that almost all Cayley graphs are hamiltonian.That is,as the order n of a group G approaches infinity,the ratio of the number of hamiltonian Cayley graphs of G to the total number of Cayley graphs of G approaches 1.
基金supported by the National Natural Science Foundation of China (Nos. 41672107, 41372119, 41440040)supports provided by the Marine Environmental Observation and Research Station at the Xisha Islands, the South China Sea Institute of Oceanology, CAS during the fieldwork
文摘Beach rock,which forms at the intertidal zone,is a natural barrier to protect beach and island from wave erosion. The formation mechanism of beach rocks is significant in the study of surface carbonate diagenesis and protection of island. Beach rocks in Qilian Islets and Cays were formed about 500–700 a BP,neither its composition nor sedimentary structure experienced intense post-reformation.Beach rocks in Qilian Islets and Cays are mainly composed of reef-building skeletal fragments and bioclasts without terrigenous sediments. This study focused on the types and morphologies of cements in beach rocks of Qilian Islets and Cays,and its cementation mechanisms and influencing factors. Biological activities,such as micritization caused by microbial activities and algae binding action,play an important role in the initial stage of bioclast transformation and promote the subsequent early marine and early meteoric cementation. Acicular aragonite induced by early marine cementation is well developed in beach rocks,especially in those samples from Medium Islet. Early meteoric cementation is not common as marine cementation,generally presenting granular and meniscus cements. The main factors affecting the formation and development of beach rocks in Qilian Islets and Cays include sediment source,hydrodynamic condition,climate,sea level change and anthropogenic impacts.
基金supported by Chinese NSF project(42,130,114)the strategic priority research program(B)of CAS(XDB41000000)the pre-research Project on Civil Aerospace Technologies No.D020202 funded by Chinese National Space Administration(CNSA)and Guizhou Provincial 2021 Science and Technology Subsidies(No.GZ2021SIG).
文摘Isotope eff ects are pivotal in understanding silicate melt evaporation and planetary accretion processes.Based on the Hertz-Knudsen equation,the current theory often fails to predict observed isotope fractionations of laboratory experiments due to its oversimplified assumptions.Here,we point out that the Hertz-Knudsen-equation-based theory is incomplete for silicate melt evaporation cases and can only be used for situations where the vaporized species is identical to the one in the melt.We propose a new model designed for silicate melt evaporation under vacuum.Our model considers multiple steps including mass transfer,chemical reaction,and nucleation.Our derivations reveal a kinetic isotopic fractionation factor(KIFF orα)αour model=[m(^(1)species)/m(^(2)species)]^(0.5),where m(species)is the mass of the reactant of reaction/nucleation-limiting step or species of diffusion-limiting step and superscript 1 and 2 represent light and heavy isotopes,respectively.This model can eff ectively reproduce most reported KIFFs of laboratory experiments for various elements,i.e.,Mg,Si,K,Rb,Fe,Ca,and Ti.And,the KIFF-mixing model referring that an overall rate of evaporation can be determined by two steps jointly can account for the eff ects of low P_(H2)pressure,composition,and temperature.In addition,we find that chemical reactions,diffusion,and nucleation can control the overall rate of evaporation of silicate melts by using the fitting slope in ln(−ln f)versus ln(t).Notably,our model allows for the theoretical calculations of parameters like activation energy(E_(a)),providing a novel approach to studying compositional and environmental eff ects on evaporation processes,and shedding light on the formation and evolution of the proto-solar and Earth-Moon systems.
