Search

In order to explore the impact of moisture on the mechanical properties of coal, the triaxial compression tests of raw coal with different moisture contents are carried out by using the triaxial servo-controlled seepage equipment for thermal-hydro- mechanical coupling in coal containing methane. Based on elastic damage mechanics, the damage variables of coal with different moisture contents are deduced, and the damage constitutive model of coal under hydro-mechanical coupling is established, the deformation characteristics of coal with different moisture contents are obtained. The results show that: (1) the deformation and failure process of coal under different moisture contents are similar, which can be divided into pre-peak stress stage, post-peak stress stage and residual stress stage; (2) as the moisture content increases, the peak stress, elastic modulus and brittleness of coal decrease, but the Poisson's ratio increases; (3) the damage constitutive model of coal can better represent the deformation characteristics of coal in the complete stress-strain process under different moisture contents, which is suitable for the analysis of the triaxial compressive stress-strain of coal under different moisture contents; (4) both the damage correction coefficient q and the damage constitutive coefficient n determine the curve shape of the damage constitutive model. The damage correction coefficient reflects the characteristics of residual deformation of coal, and the damage constitutive coefficient reflects different degrees of post-peak strain softening of the stress-strain curve.

Guizhou province, located in the southwest China, is one of the richest biodiversity regions, meanwhile, is also one of the hardest-hit areas by alien invasive species. A comprehensive understanding of the invasive alien plants species composition and distribution can provide a scientific basis for the prevention, early warning and integrated management, to improve the ability of alien invasive species prevention and control. In this study, Guanling Buyi and Miao autonomous county, located in the central Guizhou province, and Huishui county, located in the south-central Guizhou province were selected as the investigation sites. Investigation was conducted in 74 sampling sites of Guanling county and 64 sampling sites of Huishui county using quadrat sampling method, to figure out the species composition, obtain the distribution pattern information (habitats and distribution frequency), then analyze their origin, life type by referring to the literature. In this study, 24 families 56 species of agricultural alien invasive plants were found through field investigation, among which Asteraceae was the dominant family (Guanling: 29.55%, Huishui: 33.33%), followed by Amaranthaceae (Guanling: 13.64%, Huishui: 11.11%), Fabaceae (Guanling: 6.82%, Huishui: 6.67%), Solanaceae (Guanling: 6.82%, Huishui: 4.44%), with mainly herbaceous species (Guanling: 80.85%, Huishui: 86.96%). The escaped Verbena bonariensis Linnaeus and Myriophyllum aquaticum Verdcourt were found in Guizhou for the first time in the wild, confirming their invasive characteristics. Furthermore, Ageratina adenophora (Sprengel) R. M. King & H. Robinson, Bidens pilosa Linnaeus, Erigeron annuus (Linnaeus) Persoon, Alternanthera philoxeroides (Martius) Grisebach, Erigeron canadensis Linnaeus, Geranium carolinianum Linnaeus, Galinsoga parviflora Cavanilles were classified as malignant agricultural alien invasive plants in these two counties, which widely distributing in the sampling sites. Agricultural alien invasive plants had adapted to various habitats and mainly distributed in the frequently anthropogenic disturbance habitats including wastelands, farmlands, roadsides, which had caused threats to the agroecosystem, human activities and natural ecosystems. The alien invasive plants has great species diversity, wild distribution range, strong adaptability, fast reproduction speed and strong reproductive ability in this two counties. Authors suggest that people should take the systematically investigation of the agricultural alien invasive plants in Guizhou province, and strengthen the monitoring and dynamic spread trend research of malignant alien invasive species, to provide scientific basis for the prevention, early warning and integrated management of alien invasive plants. [ABSTRACT FROM AUTHOR]

We report a phosphine-directed ruthenium-catalyzed C8-selective alkylation of naphthalenes with alkenes. This protocol provides straightforward access to a large library of electron-rich C8-alkyl substituent 1-naphthphosphines, which outperformed common commercial phosphines and their precursors in the Pd-catalyzed Suzuki–Miyaura coupling of aryl bromides with alkylboronic acid. [ABSTRACT FROM AUTHOR]

Oppositional Defiant Disorder (ODD) is characterized as a pattern of noncompliant, argumentative, angry, hostile and defiant behavior. In order to explore the symptoms and the affecting factors of ODD upon one child families with grandparents education, 29 group interview data (each group including ODD children, parents, teachers) were collected through one-to-one and face-to-face interviewing. The analysis revealed that: (i) ODD has great negative internalizing and externalizing problems in that such children were easy to be irritated and in general disobeyed both their parents and teacher, and tended to beat peers; (ii) ODD families had problems of parentification, scapegoat, cross-generation coalition, hierarchical structure, and multigenerational transmission; and (iii) they had such problems as whole family ODD level (e. g., low cohesion), interaction level (e. g., control, inconsistent) and parent individual level psychology (inferiority and compensation). [ABSTRACT FROM AUTHOR]