Suchergebnisse

A fracture criterion is newly proposed to evaluate fracture behavior and predict fracture initiation of metal materials in different complicated stress states for four different fracture mechanisms including quasicleavage fracture, normal fracture with void, shear fracture with void, and shear fracture without void. The dominant factors of these four different mechanisms are distinct, so it is impossible to capture all features of fracture initiation under different stress states with a single criterion, and different functions are necessary to predict fracture initiation of different mechanisms. In the new fracture criterion, different branches of the fracture criterion have been proposed corresponding to different fracture mechanisms. Quasicleavage fracture and normal fracture with void are described as a function of the principal stress, shear fracture with void is a function of the stress triaxiality and maximal shear stress, and shear fracture without void is only controlled by the maximal shear stress. The new fracture criterion is applied to predict the fracture initiation site and the fracture direction of nodular cast iron QT400-15 in combined tension-torsion tests. Predicted results are compared with experimental results to validate the performance of the new criterion in the intermediate stress triaxiality between 0 and 1/3. The new criterion is also applied to predict the crack initiation site and the direction of crack initiation of LY12 aluminium alloy and HY130 mild steel in mixed mode fracture tests to validate the performance of the new criterion in the high stress triaxiality. The new fracture criterion gives consistent results for these materials in a wide stress triaxiality range. It is shown that the new fracture criterion is a better supplement to the deficiency of fracture mechanics and also a better amendment to traditional strength theory in complicated stress states. Therefore, the new fracture criterion is recommended to be utilized to evaluate the fracture initiation of metal structures in nuclear waste storage and other engineering applications.

Long-term immersion was adopted to explore the damage deterioration and mechanical properties of granite under different chemical solutions. Here, granite was selected as the candidate of parent rocks for nuclear waste storage. The physical and mechanical properties of variation regularity immersed in various chemical solutions were analyzed. Meanwhile, the damage variable based on the variation in porosity was used in the quantitative analysis of chemical damage deterioration degree. Experimental results show that granite has a significant weakening tendency after chemical corrosion. The fracture toughnessKIC, splitting tensile strength, and compressive strength all demonstrate the same deteriorating trend with chemical corrosion time. However, a difference exists in the deterioration degree of the mechanical parameters; that is, the deterioration degree of fracture toughnessKICis the greatest followed by those of splitting tensile strength and compressive strength, which are relatively smaller. Strong acid solutions may aggravate chemical damage deterioration in granite. By contrast, strong alkaline solutions have a certain inhibiting effect on chemical damage deterioration. The chemical solutions that feature various compositions may have different effects on chemical damage degree; that is,SO42-ions have a greater effect on the chemical damage in granite thanHCO3-ions.

Environment and Natural Resources Economics: Overview -- Environmental Resource Benefit Assessment -- Environmental Resource Allocation Efficiency and Sustainable Development -- Carbon Neutrality and Environmental Governance -- Replenishable but Depletable Resource: Water -- A Fixed and Versatile Resource: Land Resources -- Renewable and Globally Scarce Resources: Agricultural and Food Resources -- Storable and Renewable Resources: Forest Resources -- Depletable and Nonrenewable Energy Resources: Coal and Oil Resources -- Renewable and Common Resources: Marine Fishery Resources. .

Establishing multi-scale optimal water allocation modes which takes the enhancement of utilization efficiency as core is a research hotspot for the international water resources management of river basins. This book aims to introduce how to compile the first set of county-level IO tables involving resources and environment accounts with integrated datasets which contains the spatio-temporal data of water and land resources, ecology and social economy in the river basin and to construct an integrated Computable General Equilibrium (CGE) model with resources and environment accounts embedded, which can be used to quantitatively depict the key process parameters of the water-ecology-social economy coupling system. Thus, this book can provide decision support for integrated river basin management, and scientific support for the sustainable development of social economy, eco-environment and water resources

BACKGROUND: Inequalities in early childhood development (ECD) tend to persist into adulthood and amplify across the life course. To date, little research on inequalities in early childhood care and development in low/middle-income countries has been available to guide governments, donors and civil society in identifying which young children and families should be targeted by policies and programmes to improve nurturing care that could prevent them from being left behind. METHODS: Using data from 135 Demographic and Health Surveys and Multiple Indicator Cluster Surveys between 2010 and 2018, we assessed levels and trends of inequalities in exposure to risks of stunting or extreme poverty (under age 5; levels in 85 and trends in 40 countries), early attendance of early care and education programmes (36–59 months; 65 and 17 countries), home stimulation (36–59 months; 62 and 14 countries) and child development according to the Early Childhood Development Index (36–59 months; 60 and 13 countries). Inequalities within countries were measured as the absolute gap in three domains—child gender, household wealth and residential area—and compared across regions and country income groups. RESULTS: 63% of children were not exposed to stunting or extreme poverty; 39% of 3–4-year olds attended early care and education; and 69% received a level of reported home stimulation defined as adequate. Sub-Saharan Africa had the lowest proportion of children not exposed to stunting or extreme poverty (45%), attending early care and education (24%) and receiving adequate home stimulation (47%). Substantial gaps in all indicators were found across country income groups, residential areas and household wealth categories. There were no significant reductions in gaps over time for a subset of countries with available data in two survey rounds. CONCLUSIONS: Available data indicate large inequalities in early experiences and outcomes. Efforts of reducing these inequalities must focus on the poorest families and those living in rural areas in ...