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Sulfuric acid corrosion is a non-negligible problem affecting the durability of concrete materials. To explore the mechanism of sulfuric acid corrosion on the fracture performance and microstructure of concrete, three-point bending test was utilized to analyze the evolutionary characteristics of the crack mouth opening displacement and the fracture toughness of concrete corroded by sulfuric acid. Scanning electron microscope and energy-dispersive spectrometer were utilized to analyze the characteristics of microscopic morphology and corrosion products of concrete corroded by sulfuric acid. The result shows that the fracture evolution of concrete can be divided into four stages: nonlinear development stage, linear development stage, deceleration expansion stage, and accelerated expansion stage. In purified water environment, the peak fracture load and fracture toughness of concrete is positively related to corrosion time. In sulfuric acid corrosion environment, the peak fracture load and fracture toughness of concrete are negatively related to corrosion time and concentrations of sulfuric acid solution. Microscopic experiments show that the interior of concrete is less affected by sulfuric acid corrosion, and the structure is relatively dense compared with the surface. The expansion crystal ettringite formed at the fracture surface of the concrete specimen during sulfuric acid corrosion was the main reason for the durability reduction of concrete. [ABSTRACT FROM AUTHOR]

During tunnel boring machine (TBM) construction, the rock breaking effect of the disc cutter in complex formations affects the progress and cost of the entire project. Therefore, it is necessary to better understand the rock breaking mechanism of TBM in complex formations. In this study, matrix discrete element method (MatDEM) software is used to study the rock breaking mechanism of the disc cutter at the interface of soil and rock. Based on the theoretical study and analysis of rock breaking process of the disc cutter in the soil-rock composite formations, the three-dimensional dynamic rock breaking process of the disc cutter in soil-rock formations with different rock dip angles (0°, 15°, 30°, 45°, 60°, 75°) is simulated by using MatDEM, and the simulation results are analyzed from three aspects: the unit force, the fracture number of unit connection, and the system energy. The main conclusions are as follows: when the disc cutter is used to roll and break the rock at the soil-rock interface of composite formations, the unit force and the fracture number of unit connection are positively related to the contact area S of the rock and blade at the front edge of the disc cutter. The energy to break the rock by the disc cutter is mainly affected by the broken rock volume per unit time Vdt. The greater the Vdt is, the more energy the disc cutter needs to break the rock is. The total force P is affected by the contact area S (β, t). The change of the maximum total force is small when β = 15°, 30°, and 45°, and is obviously lower at 60° and 75°, respectively. [ABSTRACT FROM AUTHOR]

Entecavir (ETV) is approved by the Food and Drug Administration for the treatment of chronic hepatitis B in 2005. ETV monohydrate (ETV‐H) is used as drug substance in pharmaceutical industry. In this work, ETV‐H is prepared in pure water. The single crystal structure of ETV‐H is originally reported by Jiang and Liu in 2009 and shows a layered structure in ETV‐H crystal. Then ETV‐H is first studied by density functional theory method at B3LYP/6‐311+G(d,p) level. The optimized geometric parameters of ETV‐H agree well with the reported single crystal data and theoretical vibrational frequencies are consistent with experimental spectra. Molecular electronic potential and natural bond orbital results exhibit the molecular connection properties of the layered structure. The theoretical calculated dihedral angles between two ETV molecules are 177.6° and 176.8°, indicating that two ETV molecules are almost in the same plane. The theoretical calculated interlayer space is 16.4 Å, which is similar to the calculated interlayer space 16.7 Å using X‐ray diffraction result according to Bragg's law. These calculated results further illustrate the existence of the layered structure in ETV‐H crystal. This study may provide an idea for the future drug research. [ABSTRACT FROM AUTHOR]