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Dynamic responses of underground arch structures subjected to conventional blast loads: Curvature effects

Chen H. L., Xia Z. C., Zhou J. N., Fan H. L., Jin F. N.

Archives of Civil and Mechanical Engineering

2013

Vol. 13, no. 3

322--333

The present study explored dynamic responses of underground circular arch structures subjected to subsurface conventional denotation. Analytical solutions were obtained through the modal superposition method. The soil–structure interaction, behaving as an interfacial damping, was included and the effect of different soils was investigated. Two soil–structure interaction models were discussed and compared. In Model I, the curvature of the structure surface and the arrival time difference were considered, while in Model II, the curvature of the structure surface was ignored but the arrival time difference to the structure was considered. Due to the complexity of the arch structure, a simplified structure model, neglecting the effect of shear and rotary inertia, was employed. The time histories of displacement, velocity and acceleration were predicted. Distributions of maximum moment and displacement were plotted using the result of responses. Blast loads in elastic designs were suggested and potential failure modes were predicted. Considering the curvature effect, Model I suggested greater reflection factors and dynamic loads subjected to the arch. Safety of structure could be evaluated by the results of responses. For safety purpose, the protective structures are better to be constructed in a site with small acoustic impedance and a large attenuation factor.

Simultaneous separation and analysis of two bioactive xanthones in the Tibetan medicinal plant Gentianopsis paludosa (Hook. f.) Ma by micellar electrokinetic capillary chromatography

Cheng Y. Q., Zhang Y. X, Qi S. D., Chen H. L., Chen X. G.

Acta Chromatographica

2010

Vol. 22, no. 4

637--650

1,7-Dihydroxy-3,8-dimethoxyxanthone (X1) and 1,8-dihydroxy-3,7-dimethoxyxanthone (X2) are two important xanthones of the Tibetan medicinal plant Gentianopsis paludosa (Hook. f.) Ma. They are very similar in structure, the only difference being exchange of OH and OCH 3 at the 7 and 8 positions. By calculations based on the geometry of the molecules using the MM+ force field, the different distances between the hydroxyl groups of the two xanthones were obtained (4.64774 Å for X2 and 7.19412 Å for X1), therefore, the two hydroxyl groups of X1 should freely interact with more water molecules than those of X2 in aqueous solution. In other words, X2 is more hydrophobic than X1. Micellar electrokinetic capillary chromatography (MEKC) was therefore chosen for separation of the compounds. The optimum separation conditions were: 20 mM borate + 20 mM SDS (pH 9.8) as running buffer, 17.5 kV applied potential, and detection wavelength 260 nm. The two xanthones were well separated in 9.0 min, with Gaussian peak shapes. The repeatability of the MEKC method (expressed as RSD) for X1 and X2 was 0.9 and 1.1%, respectively, for migration time, and 3.1 and 1.4% for peak area. The limits of detection ( S/N = 3) were 0.41 μg mL -1 for X1 and 0.82 μg mL -1 for X2. The recovery of the MEKC method for the two xanthones was also satisfactory.