External uniform electric field removing flexoelectric effect in epitaxial ferroelectric thin films

Using the modified Landau-Ginsburg-Devonshire thermodynamic theory, it is found that the coupling between stress gradient and polarization, or flexoelectricity, has significant effect on ferroelectric properties of epitaxial thin films, such as polarization, free energy profile and hysteresis loop. However, this effect can be completely eliminated by applying an optimized external, uniform electric field. The role of such uniform electric field is shown to be the same as that of an ideal gradient electric field which can suppress the flexoelectricty effect completely based on the present theory. Since the uniform electric field is more convenient to apply and control than gradient electric field, it can be potentially used to remove the flexoelectric effect induced by stress gradient in epitaxial thin films and enhance the ferroelectric properties.Comment: 5 pages, 3 figure

A damage index based damage recognition and localization algorithm of high accuracy

Composite laminates are widely used due to the advantages of low density, high specific modulus and specific strength, strong internal damping and excellent chemical stability. Invisible damage by impact and fatigue such as matrix crack, internal delamination and fiber break may lead to sharp decline of structural strength and stability and finally makes composite structural failure. This paper proposes a damage index weighted average localization algorithm (DIA), which can realize a quick damage identification and damage localization of high accuracy. The proposed algorithm does not require damage imaging, and thus has the potential of realizing Structural Health Monitoring on line and in situ. Pre-experiments of real impact damages and artificial bonded bolt are done on composite laminates of small sizes. At last, to reduce experiment cost, the bolts are bonded on laminates to replace real impact damage for validation of DIA. Damage identification is successfully realized with damage localization error lower than 5 mm. A regular PZT arrangement with fewer sensors verifies that 6 sensors are enough for localization error of 20 mm and a random PZT arrangement with one or two sensors missing from the initial sensor array will not influence the localization accuracy

20-O-β-d-Xylopyranos­yl(1→6)-β-d-glucopyranosyl-20(S)-protopanaxadiol methanol solvate

The title compound, C41H70O12·CH4O, was prepared by microbial transformation. Within the steroid skeleton of the mol­ecule, three six-membered rings exhibit a chair conformation, while the five -membered ring adopts an envelope conformation. The two pyranosyl rings also adopt chair conformations. The mol­ecules are held together by an extensive O—H⋯O hydrogen-bonding network