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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.
Ship's Propulsion Using The Weis-Fogh Mechanism
Michihisa, Tsutahara,Takeyoshi, Kimura,Ro, Kideok 國立統營水産專門大學 附設 水産科學硏究所 1989 수산과학연구소보고 Vol.1 No.-
A two-dimensional model of the Weis-Fogh Mechanism, which is a mechanism of hovering flight of small insects, is applied to ship propulsion. A model of the propulsion mechanism consisting of one or two wings in a square channel is proposed. The thrust and the drag on the wing, which are defined, respectively, the force in the direction of progress of the ship and that of movement of the wing, are measured. The propulsive efficiency is calculated and is high when the moving speed of the wing is small compared with the advancing speed of the ship. A model ship equipped with this propulsion mechanism is made and working tests performed. The applicability of this propulsion mechanism to actual ships is expected to be good.
김용태,안봉영,Takeyoshi Uchida,Mahmoud Elgazery 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.3
An international comparison of ultrasound power measurements was conducted among the ultrasoundlaboratories of the Korea Research Institute of Standards and Science (KRISS), the NationalMetrology Institute of Japan (NMIJ) and the National Institute of Standards (NIS, Egypt). Themeasurand for comparison is the electro-acoustic radiation conductance G, which is defined as theamount of ultrasound power divided by the square of the input signal voltage to the transducer. The reference device is an ultrasonic transducer, model number KRISS-2MHz-14LN, manufacturedby KRISS using a Lithium-Niobate (LiNbO3) piezoelectric single crystal. This comparison, referencenumber KN.U-K2, was piloted by KRISS, including the preparation of the protocol and thereference device, and the analysis of measurement results by the participants. This paper reportsthe comparison results.