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In order to ensure safety and efficient state of nuclear power plant in the long time operation, it is necessary to figure out the acceptance table of defects of the primary loop to meet the requirement of rapid assessment in engineering. It is necessary to do the fracture mechanics and plastic limit load analysis for the cracked pipe. Through numerical simulation analysis, the rationality of adopting plastic limit load as the critical state of austenitic stainless steel structure with good fracture toughness is demonstrated. Based on the criterion of non-decreasing the plastic limit load in design state, the acceptance standard of defects for the austenitic stainless steel pipe is established in this paper. The results show that the defect acceptance size of the primary circuit pipe is close to that in the ASME code, but much larger than that of the RSE-M code, and the RSE-M code is too conservative.

The macroscopic structural fractures (joints) and geostress distribution characteristics of coal reservoirs are important factors affecting the exploitation of coalbed methane (CBM). In this study, the joints in the sedimentary strata of the Dahebian block in Liupanshui area, Guizhou Province were investigated. Directional coal samples were collected for observation and statistical analysis of coal microfractures, the paleotectonic stress fields of the study area were reconstructed, and the tectonic evolution was elucidated. The geostress distribution characteristics of the target coal seam (coal seam No. 11, P3l) in the study area were analyzed using the finite element numerical simulation method. The results indicate that the structural evolution of the Dahebian syncline in the study area can be divided into two stages. The Late Jurassic–Early Cretaceous stage (Early Yanshanian) is the first stage. Affected by the sinistral strike slip of the Weining–Ziyun–Luodian (WZL) fault zone, the derived stress field in the study area exhibits maximum principal stress (σ1) in the NEE–SWW direction. The Late Cretaceous stage (Late Yanshanian) is the second stage. Affected by the dextral strike slip of the WZL fault zone, the derived stress field exhibits σ1 in the NNW–SSE direction. The folds and faults formed in the first stage were modified by the structural deformation in the second stage. The dominant strikes of joints in the sedimentary strata are found to be in the NW–NNW (300°–360°) and NE (30°–60°) directions, with dip angles mostly ranging from 60° to 90°. The dominant strikes of coal microfractures are in the NW (285°–304°) and NE (43°–53°) directions. The distribution of geostress in the study area is characterized by high levels of geostress in the syncline center, decreasing towards the surrounding periphery. The overall trend of the geostress contour line is similar to the shape of the syncline and is influenced by folds and faults. The σ1 of coal seam No. 11 is vertical stress. The prediction results show that the joint density of coal seam No. 11 in the block is 36–50 joints/m, and the shape of the joint density contour line is also affected by the axial direction of the Dahebian syncline and the surrounding faults. The variation in coal seam joint density and the control effect of geostress on joints opening or closing affects the permeability of coal reservoirs. The study results provide significant guidance for the exploitation of CBM. [ABSTRACT FROM AUTHOR]

Functional materials revealing mechanochromism behaviors are in high demand for potential applications. Here, we report a 1 : 1 cocrystal of naphtho[2,1-b]benzofuran (BNF) and 1,2,4,5-tetracyanobenzene (TCNB) that displayed a reversible crystal transition (of α- and β-forms) with a resulting change in emission color. The slight differences in cell dimensions, slipping angles between stacking columns, and TCNB orientation enabled this cocrystal to be a sensitive mechanochromic luminescent material. The α-form cocrystal showed significant bathochromic shifts upon being subjected to grinding or isotropic compression, and returned to the original state upon subsequently being subjected to a heating or fuming treatment. Based on detailed spectroscopic and structural analyses, the observed changes in luminescence were mainly attributed to the crystal having undergone a transformation at low pressure and then having formed an amorphous state as a result of damage to its structure. [ABSTRACT FROM AUTHOR]

Organic donor-acceptor complexes as new organic semiconductor class have attracted wide attention, due to their potential applications in functional optoelectronics. Herein, we present two new charge transfer cocrystals of di-cyanodiazafluorene -perylene (DCPE) and di-cyanodiazaflfluorene-pyrene (DCPY) through a rational cocrystal-engineering strategy. Although they are both 1 : 1 mixed stacking cocrystals with similar chemical structures, the DCPE cocrystal possesses a non-centrosymmetric space group and narrower band gap compared to DCPY cocrystal, because of the non-covalent bonding variation. The electrostatic potential accumulated in the lateral facets leads to highly twisted DCPE nanobelts, and the small band gap causes near infrared fluorescence. Meanwhile, the DCPY crystals with centrosymmetric space groups and weaker intermolecular interactions exhibited an untwisted morphology and red emission. This study will be helpful for the design and understanding of functional cocrystal materials that can be used in flexible micro/nano-mechanics, mechanical energy, and optical devices., (© 2022 Wiley-VCH GmbH.)