China Journal of Chinese Materia Medica,2020,Vol 45,No. 03
This study was to investigate the chemical constituents from the whole plant Corydalis edulis. The chemical constituents were separated and purified by macroporous resin D101, silica gel, Sephadex LH-20, ODS, and semi-preparative HPLC. Their structures were determined based on the physicochemical properties and spectroscopic data. Four compounds were isolated from the dichloromethane and water extracts of the whole plant C. edulis, and identified as 6′- β-D-xylosylicariside B2 ( 1), (3 S,5 R,6 S,7 E)-5,6-epoxy-3-hydroxy-7- megastigmen-9-one ( 2), loliolide ( 3), and 5,5′-dimethoxybiphenyl-2,2′-diol ( 4), respectively. Compound 1 was a new compound, and its absolute configuration was established by electronic circular dichroism (ECD) calculation. Compound 4 was obtained from the plants of Papaveraceae family for the first time. Compounds 2 and 3 were isolated from the plant in genus Corydalis for the first time.
Feasibility Analysis on Key Technologies to Cope with High Water Pressure and Long Distance of Subsea Shield Tunnel
Tunnel Construction,2020,Vol 40,No. 05
The sea-crossing tunnels are developing rapidly in China. The proposed Qiongzhou Strait Passage and Bohai Strait Passage will face technical difficulties such as ultra-long distance and ultra-high water pressure tunneling. In the current research and practice, the water pressure of shield tunneling is about 0.8 MPa, and the distance of one tunneling is within 8 km. Based on the engineering background of the Qiongzhou Strait Middle Line Shield Tunnel(water pressure of 1.2 MPa, tunneling length of 12 km), the engineering analogy and construction key technologies are used to analyze the feasibility of high-pressure long-distance shield tunneling technology to solve the problem of safe tunneling and safe service during the operation of the shield tunnel under high water pressure. The following technologies, i. e., shield active tool change, passive saturation diving belt pressure tool change, integrated tool change technology for freezing and strengthening in extraordinary state and the comprehensive technology of replaceable seal, are put forward, which can guarantee the shield tunneling for long distance. Meanwhile, an ultra-high water pressure shield composite segment lining and a combination of internal and external waterproof structures are proposed to ensure the safe operation of the shield segment structure under ultra-high water pressure.
Another estimation method for the variable capital depreciation rate: based on the maximum likelihood estimation of Chinese provincial capital depreciation
Economic Research Journal,2020,Vol 55,No. 01
At present, the literature on depreciation rates in China mainly considers the national depreciation rate, which is often used to replace provincial rates and is fixed across years. We construct a method to estimate the variable depreciation rates of provincial-level areas (hereinafter referred to as provinces) in China using observable provincial depreciation and considering the economic depreciation caused by technological progress. In addition, the capital stock of provinces in China during 1990–2015 is calculated. We use a different method to estimate the variable depreciation rates of provinces in China. The relationship between capital stock and the level of capital embodied technological progress is first obtained. Then, a mathematical model of depreciation rate, growth rate, and capital embodied technological progress is constructed using the AK production function, and the variable depreciation rate function is obtained. The variable depreciation rate model with capital depreciation as the explained variable is constructed using the perpetual inventory and matrix operation methods, and the variable depreciation rate is estimated by the maximum likelihood method. We set 1990 as the initial year of the capital stock of provinces mainly for ease of measurement. The values for the capital stock of provinces in 1990 as calculated by various scholars are quite different, so it is difficult to choose a calculated value, but their mean value can be used as a reference value. Based on the calculated capital stock, investment, and capital depreciation of provinces in 1990, the maximum likelihood estimation of the variable depreciation rate model is carried out. To estimate the variable depreciation rate more accurately, we use an iterative method to estimate the variable depreciation rate model. After one simple and three complex models are estimated, the estimated parameter values of such a complex model tend to converge smoothly. The variable depreciation rates of provinces in China are obtained from the estimated values of the parameters of the econometric model. Capital embodied technological progress of provinces during 1990–2015 is also calculated. To test the reliability of the maximum likelihood estimation of small samples, the Monte Carlo method is used to test the parameter estimation of the variable depreciation rate model. According to the complex model of 31 estimated provinces, the estimated GDP growth rate coefficients of 21 provinces are positive; those of 10 provinces are negative. Based on the relationship between the parameters of the complex model, we calculate the capital embodied technological progress of provinces and sort them in ascending order, and we find results consistent with the economic reality of provinces in China. According to our estimation from 1991 to 2015, variable depreciation rates in China differ between provinces and across years. If the national depreciation rate is used to replace the provincial depreciation rate in China, it may fail to correctly reflect the depreciation rate of each province, and capital stock calculated from the national depreciation rate will deviate from the real capital stock of provinces. The value of 1990–2015 provincial capital stock calculated based on the initial capital stock, investment, and estimated variable depreciation rates using our method falls between the capital stock values calculated in the literature. This shows that the estimated depreciation rates of provinces and the calculated capital stock values in this paper are effective and reliable. We construct a mathematical model of the capital depreciation rate, growth rate, and capital embodied technological progress, and we adopt the AK production function, which is favorable for estimating capital depreciation rates. To analyze the relationship among the depreciation rate, technological progress, and economic growth, we must further improve the production function.
CIESC Journal,2020,Vol 71,No. 04
Using ammonium tungstate, cerium nitrate hexahydrate, and urea as raw materials, CeO 2–WO 3/g-C 3N 4 catalyst was prepared by the melting method, and the samples were characterized by XRD, UV–Vis, TEM, PL, and XPS. XRD characterization results show that the introduction of CeO 2 can improve the dispersion of active component WO 3 on g-C 3N 4. XPS characterization indicates the good oxygen storage and release capacity of Ce 4+/Ce 3+ is conducive to the formation of oxygen vacancy and reactive oxygen species. The PL characterization also indicates that the introduction of CeO 2 can capture electrons and thus inhibits photogenic electron–hole pair recombination. The introduction of CeO 2 for the catalytic activity of compound photocatalysis was investigated by oxidation and desulfurization experiment, the high-pressure sodium lamp was used to simulate visible light source, using the mixture of n-heptane and dibenzothiophene (DBT) as a simulation oil. Experimental results show that in the reaction conditions of 80 °C, O/S molar ratio 5.0, 5% (mass fraction) CeO 2 payload, 180 min, the conversion rate of DBT in n-heptane under the catalysis of CeO 2-WO 3/g-C 3N 4 is 86.4%, higher than that under the catalysis of WO 3/g-C 3N 4 (72.9%). The characterization results and oxidation desulfurization experiments show that the introduced CeO 2 can interact well with WO 3/g-C 3N 4, thus improving the activity of the composite photocatalyst.
CIESC Journal,2020,Vol 71,No. 02
A series of TiO 2 nanotube arrays (TNAs) with different diameters and roughness were prepared by electrochemical anodization method by changing the fluoride ion concentration [0.4%, 0.3%, 0.2% (mass)] and applied voltage (15, 25, 35, 45 V). The scanning electron microscopy (FESEM) and atomic force microscopy (AFM) results showed that the wall thickness of the prepared TNAs increased and the roughness decreased with the decrease in fluoride ion concentration in the electrolyte. The effects of surface roughness and diameter on the surface mechanical properties of TNAs and the interaction of Cytochrome C (Cyt C) were studied by AFM characterization. The results show that the adhesion is proportional to the contact area. With the increase in the diameter of the TNAs, the wall thickness decreases; the effective contact area between TNAs and Cyt C increases first and then decreases; the forces of Cyt C with TNAs also increase first and then decrease. The roughness decreases when the diameter is fixed; the effective area of TNAs increases; the interaction force also increases. It can be seen that the surface roughness and effective contact area of TNAs can be effectively controlled by changing the fluoride ion concentration of the electrolyte, which is further beneficial to promoting the interaction with protein molecules.