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- Schumacher, A. E., et al.
(författare)
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Global age-sex-specific mortality, life expectancy, and population estimates in 204 countries and territories and 811 subnational locations, 1950–2021, and the impact of the COVID-19 pandemic : a comprehensive demographic analysis for the Global Burden of Disease Study 2021
- 2024
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Ingår i: The Lancet. - : Elsevier B.V.. - 0140-6736 .- 1474-547X. ; 403:10440, s. 1989-2056
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Tidskriftsartikel (refereegranskat)abstract
- Background: Estimates of demographic metrics are crucial to assess levels and trends of population health outcomes. The profound impact of the COVID-19 pandemic on populations worldwide has underscored the need for timely estimates to understand this unprecedented event within the context of long-term population health trends. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 provides new demographic estimates for 204 countries and territories and 811 additional subnational locations from 1950 to 2021, with a particular emphasis on changes in mortality and life expectancy that occurred during the 2020–21 COVID-19 pandemic period. Methods: 22 223 data sources from vital registration, sample registration, surveys, censuses, and other sources were used to estimate mortality, with a subset of these sources used exclusively to estimate excess mortality due to the COVID-19 pandemic. 2026 data sources were used for population estimation. Additional sources were used to estimate migration; the effects of the HIV epidemic; and demographic discontinuities due to conflicts, famines, natural disasters, and pandemics, which are used as inputs for estimating mortality and population. Spatiotemporal Gaussian process regression (ST-GPR) was used to generate under-5 mortality rates, which synthesised 30 763 location-years of vital registration and sample registration data, 1365 surveys and censuses, and 80 other sources. ST-GPR was also used to estimate adult mortality (between ages 15 and 59 years) based on information from 31 642 location-years of vital registration and sample registration data, 355 surveys and censuses, and 24 other sources. Estimates of child and adult mortality rates were then used to generate life tables with a relational model life table system. For countries with large HIV epidemics, life tables were adjusted using independent estimates of HIV-specific mortality generated via an epidemiological analysis of HIV prevalence surveys, antenatal clinic serosurveillance, and other data sources. Excess mortality due to the COVID-19 pandemic in 2020 and 2021 was determined by subtracting observed all-cause mortality (adjusted for late registration and mortality anomalies) from the mortality expected in the absence of the pandemic. Expected mortality was calculated based on historical trends using an ensemble of models. In location-years where all-cause mortality data were unavailable, we estimated excess mortality rates using a regression model with covariates pertaining to the pandemic. Population size was computed using a Bayesian hierarchical cohort component model. Life expectancy was calculated using age-specific mortality rates and standard demographic methods. Uncertainty intervals (UIs) were calculated for every metric using the 25th and 975th ordered values from a 1000-draw posterior distribution. Findings: Global all-cause mortality followed two distinct patterns over the study period: age-standardised mortality rates declined between 1950 and 2019 (a 62·8% [95% UI 60·5–65·1] decline), and increased during the COVID-19 pandemic period (2020–21; 5·1% [0·9–9·6] increase). In contrast with the overall reverse in mortality trends during the pandemic period, child mortality continued to decline, with 4·66 million (3·98–5·50) global deaths in children younger than 5 years in 2021 compared with 5·21 million (4·50–6·01) in 2019. An estimated 131 million (126–137) people died globally from all causes in 2020 and 2021 combined, of which 15·9 million (14·7–17·2) were due to the COVID-19 pandemic (measured by excess mortality, which includes deaths directly due to SARS-CoV-2 infection and those indirectly due to other social, economic, or behavioural changes associated with the pandemic). Excess mortality rates exceeded 150 deaths per 100 000 population during at least one year of the pandemic in 80 countries and territories, whereas 20 nations had a negative excess mortality rate in 2020 or 2021, indicating that all-cause mortality in these countries was lower during the pandemic than expected based on historical trends. Between 1950 and 2021, global life expectancy at birth increased by 22·7 years (20·8–24·8), from 49·0 years (46·7–51·3) to 71·7 years (70·9–72·5). Global life expectancy at birth declined by 1·6 years (1·0–2·2) between 2019 and 2021, reversing historical trends. An increase in life expectancy was only observed in 32 (15·7%) of 204 countries and territories between 2019 and 2021. The global population reached 7·89 billion (7·67–8·13) people in 2021, by which time 56 of 204 countries and territories had peaked and subsequently populations have declined. The largest proportion of population growth between 2020 and 2021 was in sub-Saharan Africa (39·5% [28·4–52·7]) and south Asia (26·3% [9·0–44·7]). From 2000 to 2021, the ratio of the population aged 65 years and older to the population aged younger than 15 years increased in 188 (92·2%) of 204 nations. Interpretation: Global adult mortality rates markedly increased during the COVID-19 pandemic in 2020 and 2021, reversing past decreasing trends, while child mortality rates continued to decline, albeit more slowly than in earlier years. Although COVID-19 had a substantial impact on many demographic indicators during the first 2 years of the pandemic, overall global health progress over the 72 years evaluated has been profound, with considerable improvements in mortality and life expectancy. Additionally, we observed a deceleration of global population growth since 2017, despite steady or increasing growth in lower-income countries, combined with a continued global shift of population age structures towards older ages. These demographic changes will likely present future challenges to health systems, economies, and societies. The comprehensive demographic estimates reported here will enable researchers, policy makers, health practitioners, and other key stakeholders to better understand and address the profound changes that have occurred in the global health landscape following the first 2 years of the COVID-19 pandemic, and longer-term trends beyond the pandemic. Funding: Bill & Melinda Gates Foundation.
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| 4. |
- Atashipour, Rasoul, 1983, et al.
(författare)
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On the boundary layer phenomenon in bending of thick annular sector plates using third-order shear deformation theory
- 2010
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Ingår i: Acta Mechanica. - : Springer Science and Business Media LLC. - 1619-6937 .- 0001-5970. ; 211:1-2, s. 89-99
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Tidskriftsartikel (refereegranskat)abstract
- In this article, the bending equations of thick annular sector plates are extracted based on the third-order shear deformation theory. Using a function, called boundary layer function, the coupled system of equations is converted into two decoupled equations. These equations are used to find a closed form solution for bending of thick transversely isotropic annular sector plates. It is shown that the solution of one of the decoupled equations has a boundary layer behavior like that of Mindlin plate theory. It is seen that the value of the boundary layer function for third order shear deformation theory is higher than that of the Mindlin theory. Thus, variations of stress components in the edge zone of the plate are more significant. Also, as in the Mindlin plate theory, there exist no boundary layer, a weak boundary layer, and a strong boundary layer effect for simply supported, clamped, and free edges, respectively.
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| 5. |
- Jomehzadeh, E., et al.
(författare)
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An analytical approach for stress analysis of functionally graded annular sector plates
- 2009
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Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275 .- 0261-3069. ; 30:9, s. 3679-3685
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, an exact analytical approach is used for bending analysis of functionally graded (FG) annular sector plates. The governing equilibrium equations are obtained based on the first order shear deformation plate theory. Introducing an analytical method, the coupled governing equilibrium equations are replaced by independent equations in term of transverse deflection and a new function. Using an equivalent flexural rigidity, the solutions of FG annular sector plates can be easily extracted from equation of homogeneous annular plates. Also, it is shown that the present method can provide accurate results. Finally, the effects of power of functionally graded material (FGM), plate thickness, inner to outer radius ratio and boundary conditions on the deflection and stresses of a functionally graded annular sector plate are studied.
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| 6. |
- Saidi, A.R., et al.
(författare)
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Exact analytical solution for bending analysis of functionally graded annular sector plates
- 2009
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Ingår i: International Journal of Engineering. - 1025-2495 .- 1735-9244. ; 22:3, s. 307-316
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Tidskriftsartikel (refereegranskat)abstract
- In this article, an exact levy solution is presented for bending analysis of a functionally graded (FG) annular sector plate. The governing equilibrium equations are obtained based on the classical plate theory. Introducing an analytical method for the first time, the three coupled governing equilibrium equations are replaced by an independent equation in term of transverse deflection. This equation which is a forth-order partial differential equation is similar to the governing equilibrium equation of a homogeneous isotropic annular sector plate. Using an equivalent flexural rigidity, the solutions of FG annular sector plates can be easily extracted from equation of homogeneous annular plates. Finally, the effects of the exponents of the power functions, aspect ratio, inner to outer radius ratio and boundary conditions on the mechanical behavior of a functionally graded annular sector plate are discussed.
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| 7. |
- Saidi, A.R., et al.
(författare)
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Exact elasticity solutions for thick-walled functionally graded spherical pressure vessels
- 2009
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Ingår i: International Journal of Engineering. - 1025-2495 .- 1735-9244. ; 22:4, s. 405-416
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, exact closed-form solutions for displacement and stress components of thick-walled functionally graded (FG) spherical pressure vessels are presented. To this aim, linear variation of properties, as an important case of the known power-law function model is used to describe the FG material distribution in thickness direction. Unlike the pervious studies, the vessels can have arbitrary inner to outer stiffness ratio without changing the function variation of FGM. After that, a closed-form solution is presented for displacement and stress components based on exponential model for variation of properties in radial direction. The accuracy of the present analyses is verified with known results. Finally, the effects of non-homogeneity and different values of inner to outer stiffness ratios on the displacement and stress distribution are discussed in detail. It can be seen that for FG vessels subjected to internal pressure, the variation of radial stress in radial direction becomes linear as the inner stiffness becomes five times higher than outer one. When the inner stiffness is half of the outer one, the distribution of the circumferential stress becomes uniform. For the case in which the external pressure is applied, as the inner to outer shear modulus becomes lower than 1/5, the value of the maximum radial stress is higher than external pressure.
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| 8. |
- Saidi, A.R., et al.
(författare)
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Reformulation of Navier equations for solving three-dimensional elasticity problems with applications to thick plate analysis
- 2009
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Ingår i: Acta Mechanica. - : Springer Science and Business Media LLC. - 1619-6937 .- 0001-5970. ; 208:3-4, s. 227-235
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a new reformulation of the Navier equations of motion is introduced for solving the known three-dimensional elastostatics and elastodynamics problems. At first, three decoupled equations in terms of displacement components and three decoupled equations in terms of rotation components are obtained. These equations are also invariant with respect to the choice of the coordinate system. In order to solve a three-dimensional elasticity problem based on the presented formulation, one of the three equations in terms of displacement components and the corresponding rotation equation should be solved independently. Using some relations, the other two displacement components can be obtained in terms of the mentioned displacement and rotation component. In order to verify the relations, the closed-form solutions are obtained for deflection and natural frequencies of the thick rectangular plate. The numerical results are compared with available results in the literature and it can be seen that the results of the present study are identical to those of the previous works.
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