http://hdl.handle.net/10397/379 Search the Channel search http://repository.lib.polyu.edu.hk/jspui/simple-search http://hdl.handle.net/10397/5636 Title: Quasi-distributed strain sensing with white-light interferometry: a novel approach<br/><br/>Authors: Yuan, Libo; Zhou, Limin; Jin, Wei<br/><br/>Abstract: An optical fiber ring is used to generate multiple reference waves in a multiplexed fiber-optic Michelson-type sensor array. The array consists of N sensing segments connected in series along a single optical fiber path and is interrogated with a white-light interferometric technique. Experimental results with a two-sensor array are presented.<br/><br/>Description: DOI: 10.1364/OL.25.001074 Tue, 01 Aug 2000 00:00:00 GMT http://hdl.handle.net/10397/5597 Title: Antiferroelectric-like properties and enhanced polarization of Cu-doped K₀.₅Na₀.₅NbO₃ piezoelectric ceramics<br/><br/>Authors: Ke, Shanming; Huang, Haitao; Fan, Huiqing; Lee, H. K.; Zhou, Limin; Mai, Yiu Wing<br/><br/>Abstract: Abnormal evolution of ferroelectric hysteresis (P-E) loops was observed in Cu-doped K₀.₅Na₀.₅NbO₃ (KNN) ceramics. The 1 mol. % Cu-doped fresh sample exhibited double-loop-like characteristics, while the 1.5 and 2 mol. % Cu-doped KNN ceramics showed normal single loops. Electron paramagnetic resonance spectra verified the formation of non-switchable (Cu[sub Nb]‴−V[sub O]••) ′ (DC1) and non-polar (V[sub O]••−Cu [sub Nb]‴−V[sub O]••)• (DC2) defect complexes in these ceramics. According to the experimental results, it is suggested that DC1 would provide the driving force for domain back-switching, leading to the double P-E loops, while DC2 would contribute to the space charges. Dielectric aging behaviors of the samples also supported this mechanism. It is the competition between the DC1 and DC2 defect complexes that induced the observed compositional evolution of P-E loops in the Cu-doped KNN ceramics.<br/><br/>Description: DOI: 10.1063/1.4747212 Mon, 20 Aug 2012 00:00:00 GMT http://hdl.handle.net/10397/5386 Title: Mesoscopic theory of shear banding and crack propagation in metallic glasses<br/><br/>Authors: Zheng, Guangping; Li, M.<br/><br/>Abstract: We propose a phenomenological theory to model shear banding, shear-band propagation and branching on mesoscopic scales in metallic glasses by using Ginzburg-Landau formulism. The disordering caused by mechanical or thermal agitation is represented by atomic volume dilatation and used as an order parameter. This model captures several important features in the deformation process, namely, shear localization or banding, shear-band propagation and branching, and crack propagation and its velocity. We also assessed the relation between the crack propagation velocity and local heating and the connection between the serrated flow and shear band branching.<br/><br/>Description: DOI: 10.1103/PhysRevB.80.104201 Tue, 01 Sep 2009 00:00:00 GMT http://hdl.handle.net/10397/5369 Title: Effect of strain and deadlayer on the polarization switching of ferroelectric thin film<br/><br/>Authors: Wang, Jie; Xia, Yifan; Chen, Long-Qing; Shi, San-qiang<br/><br/>Abstract: The effect of misfit strain and deadlayer on the polarization switching of epitaxial ferroelectric thin film is investigated using a phase field model. Simulation results show that a compressive misfit strain increases the coercive field and remanent polarization of ferroelectric thin film with deadlayers, whereas a tensile misfit strain decreases these factors. The presence of a deadlayer between the ferroelectric thin film and the electrode prevents charge compensation on the ferroelectric surface and reduces the coercive field and remanent polarization of the film. A periodic a/c/a/c multiple domain structure is found in ferroelectric thin film with tensile misfit strain when there is no deadlayer. However, when a deadlayer is present in the film, the c domains vanish and the out-of-plane component of polarization degrades. The degradation of the out-of-plane polarization makes ferroelectric thin films with tensile misfit strain and deadlayers lose their ferroelectric property in the thickness direction, which can be attributed to the combined effects of the deadlayer and tensile strain. The coercive field and remanent polarization of ferroelectric thin film decrease with the thickness of the deadlayer.<br/><br/>Description: DOI: 10.1063/1.3664913 Thu, 01 Dec 2011 00:00:00 GMT