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Characteristics of Riverbed Configuration Affected by River-crossing Structures
Takeyoshi Chibana,Daisuke Harada,Kimiko Yamashita,Tatsuya Asai 대한토목학회 2012 KSCE Journal of Civil Engineering Vol.16 No.2
In the middle reaches of gravel-bed rivers, the formation of alternate or linguoid bars provides a diverse microhabitat for many kinds of creatures, much as with riffle pools and dry riverbed areas. The riverbed configuration, however, is completely altered by river-crossing structures, such as weirs or drop structures, installed in a river channel. In this study, both a large river and a small stream that have many river-crossing structures were targeted, and the characteristic feature of the topography in a river channel was investigated. Consequently, there was clarification that a similar pattern of topography was created in both rivers. The elevation gap between the bank and the riverbed was largest just downstream of a river-crossing structure but decreased in the flow direction and disappeared upstream of the next structure. Contrastingly, the width of the low-flow channel was narrowest just downstream of a river-crossing structure and gradually increased in the flow direction. The implication was that the longitudinal profile of the bank was determined by significant past floods and the low-flow channel was gradually created by small floods afterwards. Based on these results, we conclude that a change of river-crossing structure height is effective to manage the floodplain for habitat control, and the installation of large boulder is also effective to restore the low-flow channel.
Seesaw lepton masses and muon g-2 from heavy vector-like leptons
Lee Hyun Min,Song Jiseon,Yamashita Kimiko 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.12
We propose a model for the vector-like lepton to explain the small muon mass by a seesaw mechanism, based on leptonspecific two Higgs doublet models with a local U(1)' symmetry. There is no bare muon mass for a nonzero U(1)' charge of the leptophilic Higgs doublet, so the physical muon mass is generated due to the mixing between the vector-like lepton and the muon after the leptophilic Higgs doublet and the dark Higgs get VEVs. In this scenario, the non-decoupling effects of the vector-like lepton give rise to leading contributions to the muon g − 2 , thanks to the light Z' and the light dark Higgs boson. We discuss various constraints on the model from lepton flavor violation, electroweak precision and Higgs data, as well as collider searches.