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1

Experiment and validation of local bearing capacity for reactive powder concrete confined with high-strength spirals

100%

Li S. , Zheng W. , Zhou W. , Jiang Z. , Wang Y.

Archives of Civil and Mechanical Engineering

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2022

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tom Vol. 22, no. 1

art. no. e40, 2022

EN

In this study, ten reactive powder concrete (RPC) specimens confined by high-strength spirals loaded over a limited area are used to investigate their behaviour and determine their local bearing capacity. The crack, wedge, and failure characteristics of RPC are discussed based on tests and simulation. The index of pressure versus deformation is used to evaluate the loading stages. The ratio of the cracking load to the ultimate load varies from 34 to 60%. A wedge pyramid is formed ahead of the bearing plate when approaching the ultimate load; thereafter, it slips downward, splitting the concrete below. The high-strength spirals did not yield even under the ultimate load. According to the test data, all the existing models for predicting the local bearing capacity are nonconservative. In this case, the effect of the actual stress caused by high-strength spirals is considered to further modify the existing calculation models when high-strength spirals are used, and a simple empirical equation for calculating the local bearing capacity of the RPC is developed. The equation and the models modified as described are verified experimentally.

2

Acidic Corrosion Behaviour of Niobium-Added Welding Overlays Fabricated by Self-Shielded Metal-Cored Wires

86%

Liu D. , Wu Y. , Long W. , Wei P. , Wang R. , Zhou W.

Archives of Metallurgy and Materials

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2023

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tom Vol. 68, iss. 3

887--894

EN

Both corrosion and abrasion remove materials from some engineering components such as impact coal crusher hammers, pulverizer rings, chute liner, and rolls or molds. Intensive research has been done on improving the wear resistance of high chromium alloys, however, studies into corrosion resistance of high chromium alloys are insufficient. In order to determine the amount of ferroniobium addition in the wire to achieve the best corrosion resistance, and find out the mechanism of ferroniobium enhancing the corrosion resistance of the welding overlays, the high-Cr iron-based welding overlays with different niobium addition were fabricated by using self-made self-shielded metal-cored wires and their acidic corrosion resistance in 3.5 wt.% NaCl solution + 0.01 mol/L HCl solution were investigated by electrochemical corrosion test. The microstructure and corrosion morphology were characterized by OM, SEM, XRD and EDS. The polarization curves and values of Icorr, Ecorr and Rc indicate the corrosion resistance is at the highest with 3.6 wt.% niobium addition, and at the lowest when the niobium addition is 10.8 wt.%. The corrosion of welding overlay occurs in the matrix of microstructure. With the increase of niobium addition from 3.6 wt.% to 10.8 wt.%, the proportion of network eutectic structure in the welding overlay is increased. Up to 10.8 wt.%, the microstructure is transformed from hypereutectic structure into eutectic one, leading to a higher acceleration of corrosion rate. When niobium addition reaches 14.4 wt.%, the welding overlay is transformed into a hypoeutectic structure. The addition of niobium element consumes carbon element in the alloy, which makes the increase of chromium content in the final solidified matrix, leading to an improvement in corrosion resistance.

3

Combining the synchrosqueezing generalized S-transform of variational mode decomposition with the Teager-Kaiser energy operator to calculate the attenuation gradient for identifying oil and gas reservoirs

86%

Yan H. , Zhou H. , Wang Y. , Wu N. , Zhou W. , Zhou J.

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tom Vol. 71, no. 2

795--812

EN

Because of the limited resolution of conventional time–frequency analysis algorithms, they are also limited to calculate attenuation gradients that describe oil and gas reservoirs. We propose an advanced method for calculating the attenuation gradient that combines the synchrosqueezing generalized S-transform of variational mode decomposition with the Teager–Kaiser energy operator. SSVGST takes advantage of the synchrosqueezing generalized S-transform to focus the longitudinal resolution of the time–frequency domain and variational mode decomposition for adaptive signal segmentation in the frequency domain. Thus, SSVGST can be used to improve the time–frequency resolution of seismic signals, and the Teager–Kaiser energy operator is used to enhance the extracted attenuation gradient and highlight oil and gas regions effectively. The time–frequency focusing ability of SSVGST was verified by using a synthetic signal and theoretical model. Experimental results with the model and field data showed that the combination of SSVGST with the Teager–Kaiser energy operator suppressed the fuzzy energy caused by the low resolution of conventional time–frequency analysis algorithms and could locate reservoirs accurately and effectively.

4

Antitumor chemical constituents of Toddalia asiatica (Linn) Lam root bark and its rational alternative medicinal parts by multivariate statistical analysis

86%

Luo C. , Liu J. , Liang Y. , Shen X. , Zhang X. , Zhou W.

Acta Chromatographica

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2021

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tom Vol. 33, no. 2

153--161

EN

Toddalia asiatica (Linn) Lam (T. asiatica) as a traditional Miao medicine was investigated to find rational alternative medicinal parts for T. asiatica root bark and its antitumor chemical constituents by quantitative pharmacognostic microscopy, high performance liquid chromatography (HPLC) fingerprint and multivariate statistical analysis. A bivariate correlation analysis method based on microscopic characteristics and content of chemical constituents was established for the first time, there were some regular discoveries between powder microscopic characteristics and common chromatographic peaks of T. asiatica through quantitative pharmacognostic microscopy, cork cells, calcium oxalate square crystal, brown clump, starch granule and phloem fiber, as powder microscopic characteristics may be placed where the main chemical constitutes were enriched. Scores plot of principal component analysis (PCA) and dendrogram of hierarchical clustering analysis (HCA) showed that 18 T. asiatica samples were distinguished correctly, clustered clearly into two main groups as follows: S01∼S03 (root bark) and S07∼S09 (stem bark) in cluster 1, S04∼S06 and S10∼S18 in cluster 2. Nineteen common peaks were obtained in HPLC fingerprint of T. asiatica, loadings plot of PCA indicated seven compounds played important roles in different part of samples (P10 > P08 > P07 > P14 > P16 > P17 > P19), peaks 04, 06, 07, 08, 10 were identified as hesperidin, 4-methoxycinnamic acid, toddalolactone, isopimpinlline and pimpinellin. MTT assay was used to determine the inhibitory activity of different medicinal parts of T. asiatica on human breast cancer MCF-7 cells, all parts of T. asiatica had different inhibitory effects on MCF-7 cell lines, root and stem barks of T. asiatica showed the best inhibitory activity. The relationship between chemical constituents and the inhibitions on MCF-7 cell had been established, significant antitumor constituents of T. asiatica were identified by correlation analysis, the order of the antitumor effect of the main compounds was P07 (toddalolactone) > P16 > P06 (4-methoxycinnamic acid), P11 > P18 > P10 (pimpinellin) > P08 (isopimpinellin) > P01 > P19 > P14 > P04 (hesperidin) > P17, which were antitumor chemical constituents of T. asiatica root bark. T. asiatica stem bark was the most rational alternative medicinal part for T. asiatica root bark.

5

CF–PK–PD analysis of natural hemostatic compounds from Toddalia asiatica (Linn) Lam root bark in rats

72%

Zhang X. , Liu J. , Sun W. , Shen X. , Gong X. , Wang C. , Liang Y. , Zhou W.

Acta Chromatographica

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2021

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tom Vol. 33, no. 3

261--269

EN

Natural hemostatic compounds from Toddalia asiatica (Linn) Lam (T. asiatica) root bark had been investigated by a novel strategy, chemical fingerprint–pharmacokinetic–pharmacodynamic (CF–PK–PD) for the first time in this study. The extract sample of T. asiatica root bark was subdivided into petroleum ether (PE), ethyl acetate (EA) and n-butanol (n-B) sample by reagent extraction, EA sample showed significant hemostatic activity using prothrombin time (PT), activated partial thromboplastin time (APTT) and fibrinogen (FIB) as evaluation indexes from rat plasma of PK experiment in hemorrhagic rat model. CF analysis was adopted to assist us to discover six natural compounds from T. asiatica root bark in actual rat plasma after sample treatment by Ultra Performance Liquid Chromatography-Electrospray Ionization (UPLC-ESI) MS, there were only lomatin and 5-methoxy-8-hydroxy psoralen showing significant hemostatic effect (P < 0.05) mainly through endogenous coagulation pathway and fibrinolytic system. In PK–PD study, six compounds in EA sample exhibited relatively rapid absorption and slow elimination characteristics. The mean Tmax and t1/2β of isopimpinellin and pimpinellin were 1.74 and 0.59 h, 5.31 and 6.89 h in rats. On the basis of Sigmoid–Emax model, PK–PD related curves of FIB in hemorrhagic rat model after treatment of T. asiatica root bark were obtained. Predicted Emax, EC50 and ke0 of FIB under isopimpinellin were 4.87 mg/mL, 1.39 μg/mL and 0.81 1/h; predicted Emax, EC50 and ke0 of FIB under pimpinellin were 4.29 mg/mL, 2.47 μg/mL and 0.77 1/h. In conclusion, hemostatic compounds from T. asiatica root bark had been materialized, there were lomatin, isopimpinellin, pimpinellin and 5-methoxy-8-hydroxy psoralen at least as its main active substances through coagulation pathways and fibrinolytic system. CF–PK–PD method as a promising method was worthy of follow-up opening, application in pharmaceutical research.