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In this study, an on-line two-dimensional high-speed counter-current chromatography system based on a six-port valve was developed. Target-guided by ultrafiltration with high-performance liquid chromatography, the one-step isolation of three potential α-amylase inhibitors from Abelmoschus esculentus (L).Moench was achieved by employing the developed orthogonal system and extrusion elution mode. The purities of three potential α-amylase inhibitors were all over 95% as determined by high-performance liquid chromatography. Furthermore, UV, mass spectrometry and H NMR spectroscopy were applied to the structural identification of the isolated three target compounds, their structures were assigned as quercetin-3-O-sophoroside (i), 5,7,3',4'-tetrahydroxy flavonol-3-O-[β-d-rhamnopyranosil-(1→2)]-β-d-glucopyranoside (ii ) and isoquercitrin (iii), respectively. The Results demonstrated that the proposed method was highly efficient to screen and isolate enzyme inhibitors from complex natural products extracts, and on-line two-dimensional high-speed counter-current chromatography can effectively increase the peak resolution of target compounds.

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An off-line two-dimensional high-speed counter-current chromatography method combined with gradient and recycling elution mode was established to isolate terpenoids and flavones from the leaves of Andrographis paniculata (Burm. f.) Nees. By using the solvent systems composed of n-hexane/ethyl acetate/methanol/water with different volume ratios, five compounds including roseooside, 5,4'-dihydroxyflavonoid-7-O-β-d-pyranglucuronatebutylester, 7,8-dimethoxy-2'-hydroxy-5-O-β-d-glucopyranosyloxyflavon, 14-deoxyandrographiside, and andrographolide were successfully isolated. Purities of these isolated compounds were all over 95% as determined by high-performance liquid chromatography. Their structures were identified by UV, mass spectrometry, and (1) H NMR spectroscopy. It has been demonstrated that the combination of off-line two-dimensional high-speed counter-current chromatography with different elution modes is an efficient technique to isolate compounds from complex natural product extracts.

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In order to solve the thorny problem of maintenance and repair of cast-in-place monolithic track slab, a new type of prefabricated slab ballastless track structure is developed for ordinary sections and damping sections. This study uses dynamics software to establish a vehicle-ballastless track coupling dynamics model, to explore the dynamic properties of the new type of prefabricated ballastless track structure in ordinary and damping sections. The model is verified using field measurement to prove its reliability. Based on the results obtained in the study, the following conclusions are deduced: (1) The vertical displacement of the floating slab in the damping section is increased by 82.95 times compared with the ordinary section. However, the vertical acceleration of the tunnel wall is reduced by 90.48%, while the insertion loss of vertical vibration acceleration of the tunnel wall is 11.08 dB, which meets the requirements of the code (CJJ/T 191-2012). (2) As the stiffness of the damping cushion increases, the vertical displacements of the rail and track slab are reduced by 43.25% and 56.68%, respectively, while the insertion loss of the vertical vibration acceleration is reduced by 31.28%. (3) As the damping increases, the vertical acceleration of the tunnel wall increases by 75.96%, whereas the insertion loss of the vertical vibration decreases by 30.51%. When the damping or the stiffness of rubber cushion is greater than 0.132 MN·s/m3 or 0.0231 N/mm3, the damping does not meet requirements. (4) When the thickness of the floating slab is increased from 200 mm to 350 mm, the vertical accelerations of the floating slab and the tunnel wall are reduced by 35.79% and 41.35%, respectively, whereas the insertion loss of the vertical vibration acceleration is increased by 37.36%.