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Structure and Properties for 28 GHz Microwave Sintered PZT Nanocomposites
Tajima, Ken-ichi,Hwang, Hae-Jin,Sando, Mutsuo,Niihara, Koichi The Korean Ceramic Society 1998 The Korean journal of ceramics Vol.4 No.4
Dense $ Pb(Zr, Ti)O_3(PZT)/Al_2O_3$ nanocomposites were prepared by the 28 GHz microwave heating method and conventional electric furnace sintering. Electrical and mechanical properties of the composites were investigated. The fracture strength of the PZT composites with 0.1vol% $Al_2O_3$ was significantly improved in both sintering methods. Smaller grain size and effective reinforcement of the PZT matrix by the second phase were considered to be responsible for the excellent fracture strength. Planar electromechanical coupling factor Kp of the composites sintered by 28GHz microwave heating was higher than that of the materical prepared by the conventional route. It seemed that the control of the reaction between PZT and $Al_2O_3$ by the microwave rapid sintering resulted in the high piezoelectric properties.
Electronic state of MgB2 superconductor
S.Tajima,T.Masui,H.Uchiyama,J.W.Quilty,Yu.Eltsev,S.Lee,A.Yamamoto,H.Mori 한국물리학회 2002 Current Applied Physics Vol.2 No.4
Thanks to the high quality single crystals of MgB2, we have measured various physical properties to extract important features ofthe electronic state in this superconductor. The electron density maps calculated from a precise X-ray diraction analysis and theband dispersions determined by the angle-resolved photoemission spectroscopy demonstrate that the boron orbitals play a centraldicated in resistivity and Raman scattering spectra. Although the multi-band structure signicantly aects various normal stateproperties, no clear multi-gap feature can be observed in the Raman scattering spectra belowTc.. 2002 Elsevier Science B.V. All rights reserved.
Keiji Tajima,Hirokazu. Ishiguro,Toshihiko Aso 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.4
This paper describes a study on improving redundancy in a 240 m span steel Pratt truss bridge. Redundancy was evaluated from two perspectives. The fi rst perspective was how many members would induce bridge collapse owing to their own damage, and the second perspective was how many members would be damaged owing to another member’s damage. Members corresponding to these two perspectives were widely present throughout the subject truss bridge. As a measure to improve redundancy of the subject truss bridge, the method of installing alternative load paths by retrofi tting additional braces was studied. Three proposals with diff erent geometry of the additional braces were compared, and "X bracing", which equipped X-shaped braces by adding braces in the opposite direction to the existing diagonal member, demonstrated excellent performance. In addition, the eff ect of the method retrofi tting the cable along the member was also studied. Next, the placement patterns of "X bracing" on 18 truss panels of the subject truss bridge were examined using an optimization technique. It was clarifi ed that examination of the placement for the additional braces was important for the effi cient improvement of redundancy, and that the optimum placement of X bracing was in the alternating areas. Finally, the buckling gusset plate of the I-35 W bridge was also in the alternating area, suggesting that reinforcement of the alternating area might be important for redundancy of truss bridges.