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1. chinaXiv:201910.00060 [pdf]

Reinvestigation of the scaling law of the windblown sand launch velocity with a wind tunnel experiment

ZHANG Yang1; LI Min; WANG Yuan; YANG Bin
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

Windblown sand transport is a leading factor in the geophysical evolution of arid and semi-arid regions. The evolution speed is usually indicated by the sand transport rate that is a function of launch velocity of sand particle, which has been investigated by the experimental measurement and numerical simulation. However, the obtained results in literatures are inconsistent. Some researchers have discovered a relation between average launch velocity and wind shear velocity, while some other researchers have suggested that average launch velocity is independent of wind shear velocity. The inconsistence of launch velocity leads to a controversy in the scaling law of the sand transport rate in the windblown case. On the contrary, in subaqueous case, the scaling law of the sand transport rate has been widely accepted as a cubic function of fluid shear velocity. In order to explain the debates surrounding the windblown case and the difference between windblown and subaquatic cases, this study reinvestigates the scaling law of the vertical launch velocity of windblown transported sand particles by using a dimensional analysis in consideration of the compatibility of the characteristic time of sand particle motion and that of air flow. Then a wind tunnel experiment is conducted to confirm the revisited scaling law, where the sand particle motion pictures are recorded by a high-speed camera and then the launch velocity is solved by the particle tracking velocimetry. By incorporating the results of dimensional analysis and wind tunnel experiment, it can be concluded that, the ratio of saltons number to reptons number determines the scaling law of sand particle launch velocity and that of sand transport rate, and using this ratio is able to explain the discrepancies among the classical models of steady sand transport. Moreover, the resulting scaling law can explain the sand sieving phenomenon: a greater fraction of large grains is observed as the distance to the wind tunnel entrance becomes larger.

submitted time 2019-10-26 Cooperative journals:《Journal of Arid Land》 Hits1654Downloads1095 Comment 0

2. chinaXiv:201804.01251 [pdf]

Fossil gibbons (Mammalia, Hylobatidae) from the Pleistocene of Chongzuo, Guangxi Zhuang Autonomous Region, China

ZHANG Ying-Qi; JIN Chang-Zhu; WANG Yuan; Alejandra ORTIZ; HE Kai; Terry HARRISON
Subjects: Geosciences >> Geology

Recent fieldwork at Pleistocene cave sites in the Chongzuo area in Guangxi Zhuang Autonomous Region has yielded 33 isolated teeth of fossil hylobatids. Comparisons indicate that the teeth can all be referred to a single species of Nomascus, but the material is insufficient to assign it to a particular species. The molars are slightly larger on average than those of extant species of Nomascus, but unlike contemporary great apes from the Pleistocene of southern China, the hylobatids do not seem to have undergone a change in dental size through time. Nomascus is not present in the Chongzuo area today, but historical records indicate that the genus may have been widely distributed across southern China in the recent past.

submitted time 2018-04-04 Cooperative journals:《古脊椎动物学报》 Hits6316Downloads1956 Comment 0

3. chinaXiv:201711.01902 [pdf]

Taxonomic revision of lizards from the Paleocene deposits of the Qianshan Basin, Anhui, China

DONG Li-Ping; Susan E. EVANS; WANG Yuan
Subjects: Biology >> Zoology

Although the Late Cretaceous lizard fauna of China and Mongolia is relatively well-known, information on Paleocene lizards from the same region is currently limited. Several species of lizards have been reported from the Paleocene Wanghudun and Doumu formations of Qianshan Basin on the basis of fragmentary specimens, namely Agama sinensis Hou, 1974, Anhuisaurus huainanensis Hou, 1974, Anqingosaurus brevicephalus Hou, 1976, Changjiangosaurus huananensis Hou, 1976, Qianshanosaurus huangpuensis Hou, 1974, and Tinosaurus doumuensis Hou, 1974. In this paper, we review all the reported material of these taxa with the aid of new technology, including CT scanning, and according to current views of squamate relationships and classification. Revised descriptions and classifications are given for each taxon, leading to changes in our understanding of faunal composition. This, in turn, reveals greater morphological and ecological diversity among the Paleocene lizards of the Qianshan Basin, including the occurrence of a varaniform (IVPP V 22767), and the reinterpretation of Anqingosaurus as a possible burrower. Further work on the Paleocene Qianshan lizards is ongoing and the discovery of new specimens may help to solve the puzzles these strange lizards have posed.

submitted time 2017-11-07 Cooperative journals:《古脊椎动物学报》 Hits1958Downloads882 Comment 0

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