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| 2. |
- Bravo, L, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 3. |
- Tabiri, S, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 7. |
- Mishra, A, et al.
(författare)
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Diminishing benefits of urban living for children and adolescents' growth and development
- 2023
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 615:7954, s. 874-883
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Tidskriftsartikel (refereegranskat)abstract
- Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.
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| 11. |
- Babayev, Rafig, et al.
(författare)
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Computational characterization of hydrogen direct injection and nonpremixed combustion in a compression-ignition engine
- 2021
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 46:35, s. 18678-18696
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Tidskriftsartikel (refereegranskat)abstract
- With the revived interest in hydrogen (H ) as a direct combustion fuel for engine applications, a computational study is conducted to assess the characteristics of H direct-injection (DI) compression-ignition (CI) non-premixed combustion concept. Development of a CFD modeling using CONVERGE CFD solver focuses on hydrogen's unique characteristics by utilizing a suitable numerical method to reproduce the direct H injection phenomena. A grid sensitivity study is performed to ensure the fidelity of results with optimal cost, and the models are validated against constant-volume optical chamber and diesel engine experimental data. The present study aims to contribute to the future development of DICI H combustion engines, providing detailed characterization of the combustion cycle, and highlighting several distinct aspects of CI nonpremixed H versus diesel combustion. First, unlike the common description of diesel sprays, hydrogen jets do not exhibit significant flame lift-off and air entrainment near injector nozzle, and the fuel-air interface is drastically more stratified with no sign of premixing. It is also found that the DICI H combustion concept is governed first by a free turbulent jet mixing phase, then by an in-cylinder global mixing phase. The former is drastically more dominant with the DICI H engine compared to conventional diesel engines. The free-jet mixing is also found to be more effective that the global mixing, which indicates the need to completely rethink the optimization strategies for CI engines when using H as fuel. 2 2 2 2 2 2 2 2
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| 12. |
- Babayev, Rafig, 1995, et al.
(författare)
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Computational comparison of the conventional diesel and hydrogen direct-injection compression-ignition combustion engines
- 2022
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 307
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Tidskriftsartikel (refereegranskat)abstract
- Most research and development on hydrogen (H2) internal combustion engines focus on premixed-charge spark ignition (SI) or diesel-hydrogen dual-fuel technologies. Premixed charge limits the engine efficiency, power density, and safety, while diesel injections give rise to CO2 and particulate emissions. This paper demonstrates a non-premixed compression-ignition (CI) neat H2 engine concept that uses H2 pilots for ignition. It compares the CI H2 engine to an equivalent diesel engine to draw fundamental insights about the mixing and combustion processes. The Converge computational fluid dynamics solver is used for all simulations. The results show that the brake thermal efficiency of the CI H2 engine is comparable or higher than diesel, and the molar expansion with H2 injections at TDC constitutes 5–10 % of the total useful work. Fuel-air mixing in the free-jet phase of combustion is substantially higher with H2 due to hydrogen's gaseous state, low density, high injection velocity, and transient vortices, which contribute to the 3 times higher air entrainment into the quasi-steady-state jet regions. However, the H2 jet momentum is up to 4 times lower than for diesel, which leads to not only ineffective momentum-driven global mixing but also reduced heat transfer losses with H2. The short H2 flame quenching distance may also be inconsequential for heat transfer in CI engines. Finally, this research enables future improvements in CI H2 engine efficiency by hypothesizing a new optimization path, which maximizes the free-jet phase of combustion, hence is totally different from that for conventional diesel engines.
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| 13. |
- Babayev, Rafig, 1995, et al.
(författare)
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Computational optimization of a hydrogen direct-injection compression-ignition engine for jet mixing dominated nonpremixed combustion
- 2022
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 23:5, s. 754-768
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen (H2) nonpremixed combustion has been showcased as a potentially viable and preferable strategy for direct-injection compression-ignition (DICI) engines for its ability to deliver high heat release rates and low heat transfer losses, in addition to potentially zero CO2 emissions. However, this concept requires a different optimization strategy compared to conventional diesel engines, prioritizing a combustion mode dominated by free turbulent jet mixing. In the present work, this optimization strategy is realized and studied computationally using the CONVERGE CFD solver. It involves adopting wide piston bowl designs with shapes adapted to the H2 jets, altered injector umbrella angle, and an increased number of nozzle orifices with either smaller orifice diameter or reduced injection pressure to maintain constant injector flow rate capacity. This work shows that these modifications are effective at maximizing free-jet mixing, thus enabling more favorable heat release profiles, reducing wall heat transfer by 35%, and improving indicated efficiency by 2.2 percentage points. However, they also caused elevated incomplete combustion losses at low excess air ratios, which may be eliminated by implementing a moderate swirl, small post-injections, and further optimized jet momentum and piston design. Noise emissions with the optimized DICI H2 combustion are shown to be comparable to those from conventional diesel engines. Finally, it is demonstrated that modern engine concepts, such as the double compression-expansion engine, may achieve around 56% brake thermal efficiency with the DICI H2 combustion, which is 1.1 percentage point higher than with diesel fuel. Thus, this work contributes to the knowledge base required for future improvements in H2 engine efficiency.
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| 14. |
- Babayev, Rafig, 1995, et al.
(författare)
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Double compression-expansion engine (DCEE) fueled with hydrogen: Preliminary computational assessment
- 2022
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Ingår i: Transportation Engineering. - : Elsevier BV. - 2666-691X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen (H2) is currently a highly attractive fuel for internal combustion engines (ICEs) owing to the prospects of potentially near-zero emissions. However, the production emissions and cost of H2 fuel necessitate substantial improvements in ICE thermal efficiency. This work aims to investigate a potential implementation of H2 combustion in a highly efficient double compression-expansion engine (DCEE). DICI nonpremixed H2 combustion mode is used for its superior characteristics, as concluded in previous studies. The analysis is performed using a 1D GT-Power software package, where different variants of the DICI H2 and diesel combustion cycles, obtained experimentally and numerically (3D CFD) are imposed in the combustion cylinder of the DCEE. The results show that the low jet momentum, free jet mixing dominated variants of the DICI H2 combustion concept are preferred, owing to the lower heat transfer losses and relaxed requirements on the fuel injection system. Insulation of the expander and removal of the intercooling improve the engine efficiency by 1.3 and 0.5%-points, respectively, but the latter leads to elevated temperatures in the high-pressure tank, which makes the selection of its materials harder but allows the use of cheaper oxidation catalysts. The results also show that the DCEE performance is insensitive to combustion cylinder temperatures, making it potentially suitable for other high-octane fuels, such as methane, methanol, ammonia, etc. Finally, a brake thermal efficiency of 56% is achieved with H2 combustion, around 1%-point higher than with diesel. Further efficiency improvements are also possible with a fully optimized H2 combustion system.
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| 15. |
- Dominguez-Valentin, M, et al.
(författare)
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No Difference in Penetrance between Truncating and Missense/Aberrant Splicing Pathogenic Variants in MLH1 and MSH2: A Prospective Lynch Syndrome Database Study
- 2021
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Ingår i: Journal of clinical medicine. - : MDPI AG. - 2077-0383. ; 10:13
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Tidskriftsartikel (refereegranskat)abstract
- Background. Lynch syndrome is the most common genetic predisposition for hereditary cancer. Carriers of pathogenic changes in mismatch repair (MMR) genes have an increased risk of developing colorectal (CRC), endometrial, ovarian, urinary tract, prostate, and other cancers, depending on which gene is malfunctioning. In Lynch syndrome, differences in cancer incidence (penetrance) according to the gene involved have led to the stratification of cancer surveillance. By contrast, any differences in penetrance determined by the type of pathogenic variant remain unknown. Objective. To determine cumulative incidences of cancer in carriers of truncating and missense or aberrant splicing pathogenic variants of the MLH1 and MSH2 genes. Methods. Carriers of pathogenic variants of MLH1 (path_MLH1) and MSH2 (path_MSH2) genes filed in the Prospective Lynch Syndrome Database (PLSD) were categorized as truncating or missense/aberrant splicing according to the InSiGHT criteria for pathogenicity. Results. Among 5199 carriers, 1045 had missense or aberrant splicing variants, and 3930 had truncating variants. Prospective observation years for the two groups were 8205 and 34,141 years, respectively, after which there were no significant differences in incidences for cancer overall or for colorectal cancer or endometrial cancers separately. Conclusion. Truncating and missense or aberrant splicing pathogenic variants were associated with similar average cumulative incidences of cancer in carriers of path MLH1 and path_MSH2.
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| 17. |
- Glasbey, JC, et al.
(författare)
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- 2021
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swepub:Mat__t
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