A new form of producing and sharing knowledge has emerged as an international(United States of America,Asia,and Europe) research collaboration,known as the Long-Term Ecological Research(LTER) Network.Although Africa b...A new form of producing and sharing knowledge has emerged as an international(United States of America,Asia,and Europe) research collaboration,known as the Long-Term Ecological Research(LTER) Network.Although Africa boasts rich biodiversity,including endemic species,it lacks the long-term initiatives to underpin sustainable biodiversity managements.At present,climate change may exacerbate hunger and poverty concerns in addition to resulting in ecosystem degradation,land use change,and other threats in Africa.Therefore,ecosystem monitoring was suggested to understanding the effects of climate change and setting strategies to mitigate these changes.This paper aimed to investigate ecosystem monitoring ground sites and address their coverage gaps in Africa to provide a foundation for optimizing the African Ecosystem Research Network(AERN) ground sites.The geographic coordinates and characteristics of ground sites-based ecosystem monitoring were collected from various networks aligned with the LTER implementation in Africa.Additionally,climatic data and biodiversity distribution maps were retrieved from various sources.These data were used to assess the size of existing ground sites and the gaps in description,ecosystems and biomes.The results reveal that there were 1089 sites established by various networks.Among these sites,30.5%,27.5%,and 28.8% had no information of area,year of establishment,current status,respectively.However,68.0% of them had an area equal to or greater than 1 km2.Sites were created progressively over the course of the years,with 68.9% being created from 2000 to 2005.To date,only 41.5% of the sites were operational.The sites were scattered across Africa,but they were concentrated in Eastern and Southern Africa.The unbalanced distribution pattern of the sites left Central and Northern Africa hardly covered,and many unique ecosystems in Central Africa were not included.To sustain these sites,the AERN should be based on operational sites,seeking secure funding by establishing multiple partnerships.展开更多
The Zagwe period is believed to be the richest and most artistic period of Ethiopian civilization since the conversion of Ezana though its achievements have been virtually consigned to obscurity. One of the ideologica...The Zagwe period is believed to be the richest and most artistic period of Ethiopian civilization since the conversion of Ezana though its achievements have been virtually consigned to obscurity. One of the ideological weapons which aggravated this obscurity is arguably the deep-rooted allegiance of the Kebra Nagest to the Solomonic dynasty. Contemporary researchers on Kebra Nagest seem to have underestimated the ideological onslaught of the Kebra Nagest on the Zagwe period that their contributions to the medieval Ethiopian civilization have been virtually shrouded in mystery. Thus, expatriate and compatriot authorities on the medieval Ethiopian cultural history are called upon to revisit the impacts oftbe Kob~ NSg^gt on the Zagwe period from the other end of the telescope, thereby, to reconstruct the unsung achievements of Ag^w civilization.展开更多
Horizontal fracture-simulated completions remain the most reliable method of producing hydrocarbons from shale formations. The vast majority of unconventional wells are completed using the “Plug and Perf” method. Th...Horizontal fracture-simulated completions remain the most reliable method of producing hydrocarbons from shale formations. The vast majority of unconventional wells are completed using the “Plug and Perf” method. This method involves using either a coiled tubing (CT) with a positive displacement motor or a jointed pipe to mill out composite plugs after fracturing operations are completed. An estimated average of 120,000 composite plugs is installed in the US alone each year. Bridge plug drillouts from milling operations tend to accumulate in horizontal wells and can cause stuck pipe incidents and loss of well control. Efficient removal of composite plugs’ debris is crucial in achieving operational efficacies and full production potential. This paper provides an overview of the various bridge plug drillouts cleaning practices adopted in horizontal wells. It discusses several case histories, showcasing how operators solved cleanout challenges. Developed mechanistic models to better understand hole cleaning are also reviewed. As more unconventional wells are being set at more extensive depths, an economical and optimized coiled tubing process becomes increasingly important. This paper focuses on delivering a more conclusive set of recommendations to increase efficiency and improve current composite plug coiled tubing cleaning-milling practices, increase operational efficiency and reduce cost.展开更多
Insects are not only the most species-rich group on Earth, they also play numerous crucial roles in ecosystem functioning and the global economy. The conservation of insect diversity is therefore a topic of global imp...Insects are not only the most species-rich group on Earth, they also play numerous crucial roles in ecosystem functioning and the global economy. The conservation of insect diversity is therefore a topic of global importance. However, insects are mostly ignored by "biodiversity" research; for example, relationships between insect diversity and vegetation or climate change remain widely unknown. This paper makes suggestions for further research into insect diversity patterns based on two typical forest types in northern China: Changbai Mountain, northeast China and Dongling Mountain, central northern China. Plants and climate have been well studied in these areas but substantial knowledge gaps prevail in relation to insect diversity patterns. It is therefore important to investigate insect biodiversity patterns in these regions.展开更多
基金Under the auspices of National Natural Science Foundation of China(No.31161140355)
文摘A new form of producing and sharing knowledge has emerged as an international(United States of America,Asia,and Europe) research collaboration,known as the Long-Term Ecological Research(LTER) Network.Although Africa boasts rich biodiversity,including endemic species,it lacks the long-term initiatives to underpin sustainable biodiversity managements.At present,climate change may exacerbate hunger and poverty concerns in addition to resulting in ecosystem degradation,land use change,and other threats in Africa.Therefore,ecosystem monitoring was suggested to understanding the effects of climate change and setting strategies to mitigate these changes.This paper aimed to investigate ecosystem monitoring ground sites and address their coverage gaps in Africa to provide a foundation for optimizing the African Ecosystem Research Network(AERN) ground sites.The geographic coordinates and characteristics of ground sites-based ecosystem monitoring were collected from various networks aligned with the LTER implementation in Africa.Additionally,climatic data and biodiversity distribution maps were retrieved from various sources.These data were used to assess the size of existing ground sites and the gaps in description,ecosystems and biomes.The results reveal that there were 1089 sites established by various networks.Among these sites,30.5%,27.5%,and 28.8% had no information of area,year of establishment,current status,respectively.However,68.0% of them had an area equal to or greater than 1 km2.Sites were created progressively over the course of the years,with 68.9% being created from 2000 to 2005.To date,only 41.5% of the sites were operational.The sites were scattered across Africa,but they were concentrated in Eastern and Southern Africa.The unbalanced distribution pattern of the sites left Central and Northern Africa hardly covered,and many unique ecosystems in Central Africa were not included.To sustain these sites,the AERN should be based on operational sites,seeking secure funding by establishing multiple partnerships.
文摘The Zagwe period is believed to be the richest and most artistic period of Ethiopian civilization since the conversion of Ezana though its achievements have been virtually consigned to obscurity. One of the ideological weapons which aggravated this obscurity is arguably the deep-rooted allegiance of the Kebra Nagest to the Solomonic dynasty. Contemporary researchers on Kebra Nagest seem to have underestimated the ideological onslaught of the Kebra Nagest on the Zagwe period that their contributions to the medieval Ethiopian civilization have been virtually shrouded in mystery. Thus, expatriate and compatriot authorities on the medieval Ethiopian cultural history are called upon to revisit the impacts oftbe Kob~ NSg^gt on the Zagwe period from the other end of the telescope, thereby, to reconstruct the unsung achievements of Ag^w civilization.
文摘Horizontal fracture-simulated completions remain the most reliable method of producing hydrocarbons from shale formations. The vast majority of unconventional wells are completed using the “Plug and Perf” method. This method involves using either a coiled tubing (CT) with a positive displacement motor or a jointed pipe to mill out composite plugs after fracturing operations are completed. An estimated average of 120,000 composite plugs is installed in the US alone each year. Bridge plug drillouts from milling operations tend to accumulate in horizontal wells and can cause stuck pipe incidents and loss of well control. Efficient removal of composite plugs’ debris is crucial in achieving operational efficacies and full production potential. This paper provides an overview of the various bridge plug drillouts cleaning practices adopted in horizontal wells. It discusses several case histories, showcasing how operators solved cleanout challenges. Developed mechanistic models to better understand hole cleaning are also reviewed. As more unconventional wells are being set at more extensive depths, an economical and optimized coiled tubing process becomes increasingly important. This paper focuses on delivering a more conclusive set of recommendations to increase efficiency and improve current composite plug coiled tubing cleaning-milling practices, increase operational efficiency and reduce cost.
基金the China Bureau of Foreign Experts and the Ministry of Education of China (111 Program, Grant 2008-B08044)the Key Basic Research Project "973" (2010CB951301-5)the Chinese Academy of Sciences’ Fellowship for Young International Scientists (Fellowship Number 2010Y1SA16)
文摘Insects are not only the most species-rich group on Earth, they also play numerous crucial roles in ecosystem functioning and the global economy. The conservation of insect diversity is therefore a topic of global importance. However, insects are mostly ignored by "biodiversity" research; for example, relationships between insect diversity and vegetation or climate change remain widely unknown. This paper makes suggestions for further research into insect diversity patterns based on two typical forest types in northern China: Changbai Mountain, northeast China and Dongling Mountain, central northern China. Plants and climate have been well studied in these areas but substantial knowledge gaps prevail in relation to insect diversity patterns. It is therefore important to investigate insect biodiversity patterns in these regions.