Papers by Keyword: BN

Paper TitlePage

Authors: I.Y. Al-Qaradawi, F.A. El Khangi, P.C. Rice-Evans
Authors: Jian Hui Liu, Jing Lin Zhang, Ming Di Jin
Abstract: To solve the problems caused by the complex failure mechanisms in hydraulic brake failure systems and the uncertain linkages between fault type and fault symptoms, a method of Bayesian network (BN) is offered for failure diagnosis. A statistical strategy is adopted there in this algorithm on the rule base provided by many experts to discard the weak causal relationship rules while keep the relatively strong ones during the BN structure learning, and a BN-based model of layered architecture is established for fault diagnosis of hydraulic braking failure systems. Experimental data analysis shows that the Bayesian network fault diagnosis model has higher accuracy than fuzzy logic diagnosis method, effectively solving the uncertainties in fault diagnosis.
Authors: Jeong Won Kang, Ho Jung Hwang
Abstract: We have investigated the single-wall boron-, aluminum- and gallium-nitride nanotubes using atomistic simulations based on the Tersoff potential. The Tersoff potential for III-nitride effectively describes the properties of III-nitride nanotubes. Structures, energetic and nanomechanics of III-nitride nanotubes were investigated and compared with each other. Young’s moduli of III-N nanotubes were lower than that of CNT. Though the graphite-like sheet formation of AlN was very difficult, since the elastic energy per atom to curve the sheet into cylinder for AlN was very low, if graphite-like sheets of AlN were formed, the extra cost to produce the tubes would be very low
Authors: Jian Peng Dou, Xiao Lin Liu, Jing Tao Ma, Xu Ping Lin
Abstract: Recently, ceramic composites with low dielectric constant, low loss tangent, high flexural strength and high thermal shock resistance have received a considerable attention as candidate materials for certain high speed radome. In this paper, Si3N4-BN ceramic composites were fabricated by dry-press processing and cold isostatic pressing, with α-Si3N4 and BN as starting powder, Al2O3 and Yb2O3 as sintering additives, PMMA as pore-forming agenSubscript textt. After sintering for 2 h at 1750°C, porous Si3N4-BN ceramic composites with a three-point bending strength of 50~120MPa and a dielectric constant of 3.2~4.4 at 7~18 GHz frequency were obtained. The sintered body was mainly β-Si3N4 grains; BN was dispersed in the grains. The formation of β-Si3N4 grains was demonstrated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) respectively. Furthermore, the influence of the BN content on the dielectric and mechanical properties was also studied. The porous Si3N4-BN ceramic composites showed a lower dielectric constant and shrinkage. For above excellent properties, Si3N4-BN ceramic composites have been became one of the most hopeful candidate materials for high speed radome.
Authors: Tao Zhang, Hai Yun Jin, Rui Zhou, Ji Feng Zhao, Zhi Hao Jin
Abstract: The relationship between the processing technology and the dielectric property of the laminated AlN/h-BN ceramic composites has been studied. The results showed that the main polarization mechanism of laminated ceramic composites in low frequency range is space charge polarization at the interface of AlN layer and BN layer. Due to the affection of porosity, the permittivity increases and the dielectric loss decreases with increasing the hot pressing temperature. The permittivity increases and the dielectric loss decreases with increasing thickness ratio of different layer., Both permittivity and dielectric loss increase with increasing the content of AlN doping in BN layer.
Authors: Bao Lin Liu, Rong Jun Liu, Chang Rui Zhang, Ying Bin Cao
Abstract: 2.5D SiC/SiC composites with and without BN interphase coating were fabricated by VSI process from SiC/C preforms that were produced after 3, 4 and 5 PIP C cycles, respectively. The effect of the BN interphase coating and PIP C cycles on the mechanical properties and microstructure of the composites was investigated. The results indicated that the composites with or without BN interphase coating exhibited catastrophic fracture behavior. Both the excess residual carbon and BN interphase coating played a positive role in protecting the SiC fibers from silication by vapor silicon, which accounted for the less obvious fibers pull-out phenomenon that occurred in the composites. The PIP cycles had an influence on the residual porosity and the content of the newly developed SiC in the composites, and therefore the mechanical properties of the composites were influenced. The composites fabricated from preforms after 4 PIP C cycles and containing BN interphase coating have a flexural strength of 122.5 MPa and a modulus of 86.5 GPa.
Authors: Jing Ao, Chun Mei Li, Zhi Qian Chen, Jin Wang
Abstract: The structural properties and elastic constants of (B1-xCx)(N1-xCx) (x=0.0, 0.2, 0.4 and 0.6) are calculated by the ultra-soft pseudo-potentials within the generalized gradient approximation and local density approximation in frame of density functional theory with virtual crystal approximation. The elastic constants, the aggregate elastic modulus, poisson’s ratio, energy gap and hardness are computed too. The energy band structure, DOS, and Hellmann-Feynman stresses are also examined in details.
Authors: Jing Ao, Ai Ling Ding, Chun Mei Li, Feng Li, Jin Wang, Zhi Qian Chen
Abstract: The thermodynamic properties of (B1-xCx)(N1-xCx) (x=0, 0.25, 0.5) are calculated by the ultra-soft pseud-potentials within local density approximation in frame of density functional theory with virtual crystal approximation and using the quasi-harmonic Debye model. The normalized relative volume V/V0, bulk modulus, thermal expansion coefficient α and heat capacity were computed with different temperature and pressure. Meanwhile the lower limit of the thermal conductivity κmin is also examined in details.
Authors: S. Siegel, M. Hermann, G. Putzky
Showing 1 to 10 of 28 Paper Titles