By pushing computation,cache,and network control to the edge,mobile edge computing(MEC)is expected to play a leading role in fifth generation(5G)and future sixth generation(6G).Nevertheless,facing ubiquitous fast-grow...By pushing computation,cache,and network control to the edge,mobile edge computing(MEC)is expected to play a leading role in fifth generation(5G)and future sixth generation(6G).Nevertheless,facing ubiquitous fast-growing computational demands,it is impossible for a single MEC paradigm to effectively support high-quality intelligent services at end user equipments(UEs).To address this issue,we propose an air-ground collaborative MEC(AGCMEC)architecture in this article.The proposed AGCMEC integrates all potentially available MEC servers within air and ground in the envisioned 6G,by a variety of collaborative ways to provide computation services at their best for UEs.Firstly,we introduce the AGC-MEC architecture and elaborate three typical use cases.Then,we discuss four main challenges in the AGC-MEC as well as their potential solutions.Next,we conduct a case study of collaborative service placement for AGC-MEC to validate the effectiveness of the proposed collaborative service placement strategy.Finally,we highlight several potential research directions of the AGC-MEC.展开更多
We describe patterns of buttress formation and development in eleven tree species at Lawachara National Park, Bangladesh. Forty-five percent of trees of these 11 species had buttresses. Artocarpus chaplasha Roxb. show...We describe patterns of buttress formation and development in eleven tree species at Lawachara National Park, Bangladesh. Forty-five percent of trees of these 11 species had buttresses. Artocarpus chaplasha Roxb. showed maximum （87%） buttress formation, whereas Alstonia scholaris （L.） R. Br. did not show any buttress. Buttresses were recorded in 20%-40% of trees of six species and 40%-60% of trees in three species. Mean length and height of buttress varied among the species and ranged from 0.37-4.37 m and 0.71-2.13 m, respectively. Buttress height, mean buttress length, total buttress length, and total length plus length of secondaries increased with DBH （diameter at breast height） and tree height. Buttress number did not increase with DBH or tree height. Under-storey and mid-canopy trees produced less developed buttresses than did emergent trees （p〈0.01）. Wood density showed moderate effects on buttress characters （p〈0.05）, while the slope of the land did not. Canopy category was a primary regulating factor for tree buttressing, suggesting that buttresses are mechanical adaptations of trees to counter physical stresses.展开更多
While deltas fed by seasonal rivers are common in modem sedimentary environments,their characteristics remain unclear as compared to those fed by perennial rivers.This study identifies a small delta discharged by a se...While deltas fed by seasonal rivers are common in modem sedimentary environments,their characteristics remain unclear as compared to those fed by perennial rivers.This study identifies a small delta discharged by a seasonal stream flowing into Daihai Lake,in northern China,which is driven by ephemeral and high-energy flood events.Detailed 3D facies architecture was analyzed using ground-penetrating radar (GPR) and sedimentary logs from outcrop and trenches.Four types of radar surfaces,including truncations of underlying inclined strata,weak reflections,and depositional surface of downlap and onlap,were identified.Six radar facies (highangle obliquetangential,low-angle subparallel,gently plane parallel,plane-parallel,chaotic,and continuous strong reflection) were identified based on distinctive reflections,including amplitude,continuity,dip,and termination patterns.Five depositional units (Unit A to E) were documented from proximal to distal delta.Seasonal discharge signatures include significant grain-size decrease over short distance,abundant Froude supercritical flow sedimentary structures,poorly developed barforms,and small-scale scour and fill structures.Records of lake-level and sediment budget were evaluated over the past 60 years.In highstand stage (1960- 1980),amalgamated channel (Units A and B),and delta front (Unit C) were deposited.In slope stage (1980-1996),the lower deposits (Units A,B,C) were eroded by Unit D with a distinct truncation surface.In lowstand stage,most eroded sediments bypassed the incised channel and accumulated in the distal part,in which a new depositional unit was formed (Unit E).The model demonstrates that deltas fed by seasonal rivers tend to accumulate large amounts of sediments carried by high magnitude floods within short periods.展开更多
This paper examines general composition problems in modernist architecture by means of a close analysis of the formal principles and devices at work in two exemplary mid twentieth century projects, De Vore House by Lo...This paper examines general composition problems in modernist architecture by means of a close analysis of the formal principles and devices at work in two exemplary mid twentieth century projects, De Vore House by Louis Kahn （1901-1974） and House II by Peter Eisenman （1932）. The goal of the paper is to inaugurate a larger research project into the design processes and spatial-formal effect at work in modernist architecture. The methodology is primarily visual, and postulates a range of form relationships for the creation and interpretation of works of architecture. Following an introduction to the research problem, an analysis of the case study projects is undertaken according to three themes： plan disposition, ambiguity in wall and column relations, and volume as impacting on movement. A concluding section summarizes the findings and suggests future lines of research. The paper＇s significance lays in its contributions to discussions around architectural practice at a specific moment in modernist architecture＇s mid twentieth century trajectory, to our understanding of a number of formal strategies and their resulting architectural effects, and to scholarship on the practice and theories of Kahn and Eisenman.展开更多
基金supported in part by the National Natural Science Foundation of China under Grant 62171465,62072303,62272223,U22A2031。
文摘By pushing computation,cache,and network control to the edge,mobile edge computing(MEC)is expected to play a leading role in fifth generation(5G)and future sixth generation(6G).Nevertheless,facing ubiquitous fast-growing computational demands,it is impossible for a single MEC paradigm to effectively support high-quality intelligent services at end user equipments(UEs).To address this issue,we propose an air-ground collaborative MEC(AGCMEC)architecture in this article.The proposed AGCMEC integrates all potentially available MEC servers within air and ground in the envisioned 6G,by a variety of collaborative ways to provide computation services at their best for UEs.Firstly,we introduce the AGC-MEC architecture and elaborate three typical use cases.Then,we discuss four main challenges in the AGC-MEC as well as their potential solutions.Next,we conduct a case study of collaborative service placement for AGC-MEC to validate the effectiveness of the proposed collaborative service placement strategy.Finally,we highlight several potential research directions of the AGC-MEC.
文摘We describe patterns of buttress formation and development in eleven tree species at Lawachara National Park, Bangladesh. Forty-five percent of trees of these 11 species had buttresses. Artocarpus chaplasha Roxb. showed maximum （87%） buttress formation, whereas Alstonia scholaris （L.） R. Br. did not show any buttress. Buttresses were recorded in 20%-40% of trees of six species and 40%-60% of trees in three species. Mean length and height of buttress varied among the species and ranged from 0.37-4.37 m and 0.71-2.13 m, respectively. Buttress height, mean buttress length, total buttress length, and total length plus length of secondaries increased with DBH （diameter at breast height） and tree height. Buttress number did not increase with DBH or tree height. Under-storey and mid-canopy trees produced less developed buttresses than did emergent trees （p〈0.01）. Wood density showed moderate effects on buttress characters （p〈0.05）, while the slope of the land did not. Canopy category was a primary regulating factor for tree buttressing, suggesting that buttresses are mechanical adaptations of trees to counter physical stresses.
基金the National Natural Science Foundation of China (Grant No.41602117)the opening foundation of the Key Laboratory of Marine Sedimentology & Environmental Geology,SOA (No.MASEG201706).
文摘While deltas fed by seasonal rivers are common in modem sedimentary environments,their characteristics remain unclear as compared to those fed by perennial rivers.This study identifies a small delta discharged by a seasonal stream flowing into Daihai Lake,in northern China,which is driven by ephemeral and high-energy flood events.Detailed 3D facies architecture was analyzed using ground-penetrating radar (GPR) and sedimentary logs from outcrop and trenches.Four types of radar surfaces,including truncations of underlying inclined strata,weak reflections,and depositional surface of downlap and onlap,were identified.Six radar facies (highangle obliquetangential,low-angle subparallel,gently plane parallel,plane-parallel,chaotic,and continuous strong reflection) were identified based on distinctive reflections,including amplitude,continuity,dip,and termination patterns.Five depositional units (Unit A to E) were documented from proximal to distal delta.Seasonal discharge signatures include significant grain-size decrease over short distance,abundant Froude supercritical flow sedimentary structures,poorly developed barforms,and small-scale scour and fill structures.Records of lake-level and sediment budget were evaluated over the past 60 years.In highstand stage (1960- 1980),amalgamated channel (Units A and B),and delta front (Unit C) were deposited.In slope stage (1980-1996),the lower deposits (Units A,B,C) were eroded by Unit D with a distinct truncation surface.In lowstand stage,most eroded sediments bypassed the incised channel and accumulated in the distal part,in which a new depositional unit was formed (Unit E).The model demonstrates that deltas fed by seasonal rivers tend to accumulate large amounts of sediments carried by high magnitude floods within short periods.
文摘This paper examines general composition problems in modernist architecture by means of a close analysis of the formal principles and devices at work in two exemplary mid twentieth century projects, De Vore House by Louis Kahn （1901-1974） and House II by Peter Eisenman （1932）. The goal of the paper is to inaugurate a larger research project into the design processes and spatial-formal effect at work in modernist architecture. The methodology is primarily visual, and postulates a range of form relationships for the creation and interpretation of works of architecture. Following an introduction to the research problem, an analysis of the case study projects is undertaken according to three themes： plan disposition, ambiguity in wall and column relations, and volume as impacting on movement. A concluding section summarizes the findings and suggests future lines of research. The paper＇s significance lays in its contributions to discussions around architectural practice at a specific moment in modernist architecture＇s mid twentieth century trajectory, to our understanding of a number of formal strategies and their resulting architectural effects, and to scholarship on the practice and theories of Kahn and Eisenman.
