A comprehensive introduction to the boundary state approach to Dirichlet branes is given. Various examples of BPS and non-BPS Dirichlet branes are discussed. In particular, the non-BPS states in the duality of type IIA on K3 and the heterotic string on T 4 are analysed in detail.PACS numbers: 1125, 1125H, 1125S * Lectures given at the TMR network school on 'Quantum aspects of gauge theories, supersymmetry and quantum
Piezoelectric properties of grain-oriented bismuth layer structured compound CaBi 4 Ti 4 O 15 ceramics and their temperature dependencies were studied. The grain-oriented CaBi 4 Ti 4 O 15 ceramics were fabricated by the templated grain growth method. The highly preferentially (00l) oriented CaBi 4 Ti 4 O 15 ceramics were obtained and their Lotgering (00l) orientation degree was almost 100%. The electromechanical coupling coefficient of the longitudinal vibration mode (k 33 ) was approximately three times as large as that of the nonoriented specimen, and the temperature coefficient of resonant frequency (| f r − T C|) was the same as that of the nonoriented specimen. The 24 vibration mode is separated from the 15 vibration mode in the thickness shear vibration of the grain-oriented ceramics. The electromechanical coupling coefficient k 15 of the grain-oriented specimen was twice as large as k 15 of the nonoriented ceramics, while, k 24 was one-third that of k 15 of the nonoriented specimen. The | f r − T C| of the 15 vibration mode of the grain-oriented specimen was half that of the 15 vibration mode in the nonoriented ceramics, and that of the 24 vibration mode of the oriented specimen was much larger than that of the 15 vibration mode in the nonoriented ceramics.
The effect of the angle between the vibration direction and the oriented direction on high-power characteristics was investigated for h001i-textured SrBi 2 Nb 2 O 9 (SBN) ceramics in the longitudinal mode (33 mode). Specimens with their long side formed at angles of 90 and 45 to the h001i-oriented direction were fabricated from a 95%-textured SBN ceramic. Their high-power characteristics were compared with those of a randomly oriented specimen. In the case of the specimen with a 90 angle, the resonant frequency was almost constant during high-vibration-velocity driving. On the other hand, the resonant frequency of the specimen with a 45 angle decreased with increasing vibration velocity as did that of the randomly oriented SBN specimen. Therefore, it is considered that the excellent high-power characteristics of highly textured ceramics depend on the vibration direction for the h001i-textured ceramics. The angle between the vibration direction and the h001i-oriented direction is important in the excellent high-power characteristics of textured SBN ceramics.
Abstract-The high-power piezoelectric characteristics in h001i oriented ceramics of bismuth layer structured ferroelectrics (BLSF), SrBi(2)Nb(2)O(9) (SBN), (Bi,La)(4)Ti(3)O(12) (BLT), and CaBi(4)Ti(4)O(15) (CBT), were studied by a constant voltage driving method. These textured ceramics were fabricated by a templated grain growth (TGG) method, and their Lotgering factors were 95%, 97%, and 99%, respectively. The vibration velocities of the longitudinal mode (33-mode) increased proportionally to an applied electric field up to 2.5 m/s in these textured BLSF ceramics, although, the vibration velocity of the 33-mode was saturated at more than 1.0 m/s in the Pb(Mn,Nb)O(3)-PZT ceramics. The resonant frequencies were constant up to the vibration velocity of 2.5 m/s in the SBN and CBT textured ceramics; however, the resonant frequency decreased with increasing over the vibration velocity of 1.5 m/s in the BLT textured ceramics. The dissipation power density of the BLT was almost the same as that of the Pb(Mn,Nb)O(3)-PZT ceramics. However, the dissipation power densities of the SBN and CBT were lower than those of the BLT and Pb(Mn,Nb)O(3)-PZT ceramics. The textured SBN and CBT ceramics are good candidates for high-power piezoelectric applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.