Evolution of Dentary Diastema in Iguanodontian Dinosaurs     

Katsuhiro KUBOTA  Yoshitsugu KOBAYASHI 《《地质学报》英文版》2009,83(1)

The dentary diastema of iguanodontians has been considered to be related to its unique jaw mechanism for herbivorous adaptation.The dentary and diastema lengths of iguanodontians were measured and compared to elucidate the evolution of iguanodontian diastema.A gap in ratios between most non-hadrosaurid iguanodontians and hadrosaurids was observed,suggesting that all non- hadrosaurid iguanodontians,expect for Ouranosaurus nigeriensis and Protohadros byrdi,lack a diastema or have a short diastema,although ...  相似文献   

Densification and grain coarsening of melting snow     

周石硚  中尾正义  桥本重将  坂井亚规子  成田英器  石川信敬 《极地研究(英文版)》2003,14(1)

1　IntroductionSnowdensificationiscriticalforcalculationsinengineering glaciology,snowavalancheforecasting ,springflooding,andotherpracticalaspects.Itisalsoimportantforinterpretingicecoredataincludingthosetakenfromratherwarmsiteswheresurfacelay ersexperiencemelting ,sinceitwouldaffectthechangeofannuallayerthicknesswithtime.Whileextensivestudies(e.g .AndersonandBenson 1 963 ;Bader1 960 ,1 962 ;Koji ma 1 95 4,1 95 5 ,1 95 6,1 95 7,1 95 8,1 95 9,1 964;Keeler 1 967;Gow 1 975 ;MaenoandE binuma 1…  相似文献   

VARIATION OF FLOW AND ROUGHNESS CHARACTERISTICS IN FLUVIAL RIVERS     

Tutomu Kishi Professor  Hokkaido Institute of Technology  Japan 《国际泥沙研究》1991,(3)

The flow and roughness characteristics of fluvial rivers vary in accordance with the properties of the bed configurations. In field rivers, sand waves with different characteristic lengths are often formed simultaneously. This kind of bed configurations can hardly be observed in the flume experiments. In the present research, the bed configurations are classified into three types according to the type of bar and the characteristics of the resistance to flow are analysed in relation to the type of bar.  相似文献   

THE INTERLINKAGE OF LARGE-SCALE SYSTEMS BETWEEN HIGH AND LOW LATITUDES RELATED TO PROPAGATION OF THE PLANETARY WAVE AROUND EAST ASIA IN SUMMER   总被引：1，自引：0，他引：1  

王亚非  藤吉康志 《Acta Meteorologica Sinica》2002,(3)

This study has reviewed recent studies about impact of the Rossby wave propagation on theweather of East Asia.Then,we have focused on the northward progression of the subtropical highaffected by the propagations and their interaction.The following results are obtained:(1)The twokinds of meridional Rossby wave propagations often affect the East Asian weather in summer,which propagate in two conflicting directions(northwest-southeastward and southwest-northeast-ward).This is considered as the interaction of the large-scale systems between high and lowlatitudes with wave propagation,especially to the circulation systems around East Asia.(2)Thenorthward progression of the subtropical high is largely restrained,aecompanied by the southwardshift of the convective activity in middle latitudes,under the strong and persistent Rossby wavepropagation from high to low latitudes.And the opposite role could be found in the Rossby wavepropagation from low to high latitudes.  相似文献