Experimental investigation on fracturing effects in hydraulic sand fracturing with acoustic emission and 3d laser scanning.

Due to the extremely low permeability of shale reservoirs, large-scale reservoir fracturing is required. Hydraulic fracturing is one of the most important technologies in shale gas exploration and development. In this paper, the acoustic emission energy and the number of location and fracture surface morphology of specimens before and after fracture are studied through hydraulic sand fracturing test. The test results show that: (1) the energy ratio obtained during hydraulic fracturing without proppant is the smallest, and increasing the confining pressure, as well as reducing the displacement and viscosity of the fracturing fluid will cause the energy ratio to decrease. From the perspective of acoustic emission energy, the proppant play an important role in the generation of fractures during hydraulic sand fracturing; (2) when the confining pressure increases, the number of shale specimens before and after rupture is the largest, but the total number of locating events is smaller than the sanding ratio increased; there is no proppant hydraulic fracturing, the number of specimens before and after the rupture is the largest. And the total number reached the minimum, indicating that the proppant can play an important role in the hydraulic sand fracturing test; (3) the sand is relatively large, the specific surface and standard deviation both reach the maximum, indicating that the fracture surface roughness is the largest under the test condition, and the fracturing effect is the best, but the specific surface and standard deviation are the minimum when fracturing without proppant, so indicating that the fracture surface fracturing effect is the worst at this time.

Delay in Seeking Medical Attention and Diagnosis in Chinese Melanoma Patients: A Cross-Sectional Study.

Melanoma is a highly malignant skin tumor, and prolonged delay in seeking medical attention (DSMA) and delay in diagnosis (DD) may result in poor prognoses. Through a web-based questionnaire, we explored the related factors affecting the DSMA and DD of melanoma in a Chinese population. A total of 112 valid answer sheets were received. After obtaining the relevant information, we analyzed the factors associated with DSMA and DD. The median time of DSMA was 8.0 (quartiles: 1.0, 29.3) months, and the median of patients' DD was 1.0 (quartiles: 1.0, 8.3) month. The subsequent analysis showed that DSMA and DD were positively correlated to age and negatively correlated to education background and annual household income. Patients with a history of tumors or previous health-seeking behavior because of other skin lesions had significantly longer DSMA than those without. Patients who sought medical help at general tertiary hospitals for the first time had a significantly shorter DD than those who chose other hospitals. Our study found that DSMA and DD are associated with factors such as age, education, income, and patients' histories. Secondary prevention of Chinese melanoma should be strengthened to reduce DSMA and DD to improve patients' prognoses.

Study of the Mechanical Properties of Alkali-Activated Solid Waste Cementitious Materials at the Interface.

The paper uses alkali-activated slag and fly ash as cementitious materials to pour and repair concrete. Their modification on the bonding surface of new and old concrete is studied. The new and old concrete composite specimens were prepared. The split tensile strength test of the new and old concrete specimens along the interface was carried out, and the test results of different alkali-stimulated slag and fly ash concrete as repair materials were compared and analyzed. The influence of activator modulus and other factors on the bond strength of new and old concrete interfaces was studied, and the law of its strength change was explored. The research results show that with the gradual increase in the amount of fly ash minerals, the splitting tensile strength presents a trend of first increasing and then decreasing. When the amount is 50%, the splitting surface partly occurs on the old concrete. It shows that the bonding effect is the best at this content; the alkali excitation modulus gradually increases, and the splitting tensile strength shows a downward trend. When the activator modulus is 1.3, more gelatinous substances can be observed in the section of the specimen. These overlap each other to form a tight material skeleton structure; a comparative analysis of the bonding strength of the new and old concrete interfaces with different interface agents and without interface agents showed that the alkali-activated solid waste cementitious material has the best repair performance and greater bonding strength when the water-to-binder ratio is 0.3.