Experimental Investigation on Forced Convection Heat Transfer Augmentation Using Annular Blockages

Abstract— Heat exchangers have several industrial and engineering applications. The design procedure of heat exchangers is quite\ud \ud complicated, as it needs exact analysis of heat transfer rate and pressure drop estimations apart from issues such as long-term\ud \ud performance and the economic aspect of the equipment. Whenever inserts are used for the heat transfer enhancement, along with the\ud \ud increase in the heat transfer rate, the pressure drop also increases. This increase in pressure drop increases the pumping cost. Therefore\ud \ud any augmentation device should optimize between the benefits due to the increased heat transfer coefficient and the higher cost\ud \ud involved because of the increased frictional losses.\ud \ud Experimental work on heat transfer augmentation using annular blockages. Inserts when placed in the path of the flow of the\ud \ud fluid, create a high degree of turbulence resulting in an increase in the heat transfer rate and the pressure drop. The work includes the\ud \ud determination of friction factor and heat transfer coefficient for various annular blockages and annular blockages having different\ud \ud diameter. The results of annular blockages having different diameter have been compared with the values for the plain tube. Four\ud \ud annular blockages (di=20%, 30%, 40% & 50% reduction in outer diameter) are used in the study

Selection functions of strong lens finding neural networks

Convolution Neural Networks trained for the task of lens finding with similar architecture and training data as is commonly found in the literature are biased classifiers. An understanding of the selection function of lens finding neural networks will be key to fully realising the potential of the large samples of strong gravitational lens systems that will be found in upcoming wide-field surveys. We use three training datasets, representative of those used to train galaxy-galaxy and galaxy-quasar lens finding neural networks. The networks preferentially select systems with larger Einstein radii and larger sources with more concentrated source-light distributions. Increasing the detection significance threshold to 12$\sigma$ from 8$\sigma$ results in 50 per cent of the selected strong lens systems having Einstein radii $\theta_\mathrm{E}$ $\ge$ 1.04 arcsec from $\theta_\mathrm{E}$ $\ge$ 0.879 arcsec, source radii $R_S$ $\ge$ 0.194 arcsec from $R_S$ $\ge$ 0.178 arcsec and source S\'ersic indices $n_{\mathrm{Sc}}^{\mathrm{S}}$ $\ge$ 2.62 from $n_{\mathrm{Sc}}^{\mathrm{S}}$ $\ge$ 2.55. The model trained to find lensed quasars shows a stronger preference for higher lens ellipticities than those trained to find lensed galaxies. The selection function is independent of the slope of the power-law of the mass profiles, hence measurements of this quantity will be unaffected. The lens finder selection function reinforces that of the lensing cross-section, and thus we expect our findings to be a general result for all galaxy-galaxy and galaxy-quasar lens finding neural networks.Comment: Submitted to MNRA

Spotting Solid Oxide Fuel Cell Degradation Effects by Electron Microscopy

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 - August 2, 201

Trajectories of eating behavior during COVID-19 lockdown: Longitudinal analyses of 22,374 adults

Background & aims: The COVID-19 pandemic has led to the implementation of stay-at-home and lockdown measures. It is currently unknown if the experience of lockdown leads to long term changes in individual's eating behaviors. The objectives of this study were: i) to derive longitudinal trajectories of change in eating during UK lockdown, and ii) to identify risk factors associated with eating behavior trajectories. Method: Data from 22,374 UK adults from the UCL COVID-19 Social study (a panel study collecting weekly data during the pandemic) were analyzed from 28th March to 29th May 2020. Latent Class Growth Analysis was used to derive trajectories of change in eating. These were then associated with prior socio-economic, health-related and psychological factors using multinomial regression models. Results: Analyses suggested five trajectories, with the majority (64%) showing no change in eating. In contrast, one trajectory was marked by persistently eating more, whereas another by persistently eating less. Overall, participants with greater depressive symptoms were more likely to report any change in eating. Loneliness was linked to persistently eating more (OR ¼ 1.07), whereas being single or divorced, as well as stressful life events, were associated with consistently eating less (OR ¼ 1.69). Overall, higher education status was linked to lower odds of changing eating behavior (OR ¼ 0.54e0.77). Secondary exploratory analyses suggest that participants self-reported to have overweight were more commonly categorised into the group consistently eating more, whereas participants with underweigh persistently ate less. Conclusion: In this study, we found that one third of the sample report changes in quantities eaten throughout the first UK lockdown period. Findings highlight the importance of adjusting public health programs to support eating behaviors in future lockdowns both in this and potential future pandemics. This is particularly important as part of on-going preventive efforts to prevent nutrition-related chronic diseases

TEM investigation on zirconate formation and chromium poisoning in LSM/YSZ cathode

Cell durability is a crucial technological issue for SOFC commercialization, and considerable progress has been made in recent years. A number of degradation pathways have been established, amongst which microstructural changes, poisoning effects and formation of less conductive phases. In this study, transmission electron microscopy was used to observe submicron-scale effects on selected cathode zones of an anode supported cell tested in SOFC stack repeat element configuration. The test has been performed with a dedicated segmented test bench, at 800°C for 1900h, which allowed to spatially resolve degradation processes, and therefore to improve their correlation with localized post-test analysis. Evidence is presented of reaction products (mainly SrZrO3) at the LSM/YSZ interfaces as well as of contaminants, in particular Cr, but also Si. A polarized cell segment is compared to an unpolarized one, to assess any influence of cathode polarizatio

Electrochemical performance of Nd1.95NiO4+δ cathode supported microtubular solid oxide fuel cells

Nd1.95NiO4+δ (NNO) cathode supported microtubular cells were fabricated and characterized. This material presents superior oxygen transport properties in comparison with other commonly used cathode materials. The supporting tubes were fabricated by cold isostatic pressing (CIP) using NNO powders and corn starch as pore former. The electrolyte (GDC, gadolinia doped ceria based) was deposited by wet powder spraying (WPS) on top of pre-sintered tubes and then co-sintered. Finally, a NiO/GDC suspension was dip-coated and sintered as the anode. Optimization of the cell fabrication process is shown. Power densities at 750°C of ~40 mWcm-2 at 0.5V were achieved. These results are the first electrochemical measurements reported using NNO cathode-supported microtubular cells. Further developments of the fabrication process are needed for this type of cells in order to compete with the standard microtubular solid oxide fuel cells (SOFC).The authors thank grant MAT2009-14324-C02-01 and MAT2012-30763, financed by the Spanish Government (Ministerio de Ciencia e Innovación) and Feder program of the European Community, for funding the project.Peer Reviewe

Food fussiness and food neophobia share a common etiology in early childhood

BACKGROUND: 'Food fussiness' (FF) is the tendency to be highly selective about which foods one is willing to eat, and emerges in early childhood; 'food neophobia' (FN) is a closely related characteristic but specifically refers to rejection of unfamiliar food. These behaviors are associated, but the extent to which their etiological architecture overlaps is unknown. The objective of this study was to quantify the relative contribution of genetic and environmental influences to variation in FF and FN in early childhood; and to establish the extent to which they share common genetic and environmental influences. METHOD: Participants were 1,921 families with 16-month-old twins from the Gemini birth cohort. Parents completed the Child Eating Behaviour Questionnaire which included three FF items and four FN items. Bivariate quantitative genetic modeling was used to quantify: (a) genetic and environmental contributions to variation in FF and FN; and (b) the extent to which genetic or environmental influences on FF and FN are shared across the traits. RESULTS: Food fussiness and FN were strongly correlated (r = .72, p < .001). Proportions of variation in FF were equally explained by genetic (.46; 95% CI: 0.41-0.52) and shared environmental influences (.46; 95% CI: 0.41-0.51). Shared environmental effects accounted for a significantly lower proportion of variation in FN (.22; 95% CI: 0.14-0.30), but genetic influences were not significantly different from those on FF (.58, 95% CI: 0.50-0.67). FF and FN largely shared a common etiology, indicated by high genetic (.73; 95% CI: 0.67-0.78) and shared environmental correlations (.78; 95% CI: 0.69-0.86) across the two traits. CONCLUSIONS: Food fussiness and FN both show considerable heritability at 16 months but shared environmental factors, for example the home environment, influenced more interindividual differences in the expression of FF than in FN. FF and FN largely share a common etiology

Fabrication and performance of Nd1.95NiO4+δ (NNO) cathode supported microtubular solid oxide fuel cells

Trabajo presentado al 10th European Solid Oxide Fuell Cell Forum celebrado en Lucerna (Suiza) del 26 al 29 de Junio de 2012.Microtubular SOFC present significant advantages in comparison with the traditional planar SOFC configuration. In particular, the tubular design facilitates sealing and also reduces thermal gradients. As a consequence, rapid starts up times are possible. In addition, another advantage of the microtubular configuration is their higher power density per unit volume. Due to these properties, those devices are especially attractive for portable applications. There has been a great interest in microtubular SOFCs in the recent years, mainly using anode supported cells. Electrolyte supported cells have also been reported, but there are relatively few investigations using the cathode as the support. In the present paper, Nd1.95NiO4+δ (NNO) has been chosen as the cathode support, as it presents superior oxygen transport properties in comparison with other commonly used cathode materials, such as LSCF or LSM, and these material has been proven as an excellent cathode for SOFC and SOEC applications. Results on the fabrication and characterization of NNO cathode supported SOFC will be presented. The tubes were fabricated by cold isostatic pressing (CIP) using NNO powders and corn starch as the pore former. The electrolyte (GDC based) was deposited by wet powder spray (WPS) on top of the pre-sintered tubes and then co-sintered. Finally, a NiOGDC paste was dip-coated as the anode. Optimization of the fabrication process as well as the electrochemical performance of single cells will be further discussed.The authors thank grant MAT2009-14324-C02-01, financed by the Spanish Government (Ministerio de Ciencia e Innovación) and Feder program of the European Community, for funding the project. M.A.L.-B. thanks the JAE program (CSIC) for financial support.Peer Reviewe

Genetic and environmental influences on food preferences in adolescence

Background: Food preferences vary substantially among adults and children. Twin studies have established that genes and aspects of the shared family environment both play important roles in shaping children's food preferences. The transition from childhood to adulthood is characterized by large gains in independence, but the relative influences of genes and the environment on food preferences in late adolescence are unknown. Objective: The aim of this study was to quantify the contribution of genetic and environmental influences on food preferences in older adolescents. Design: Participants were 2865 twins aged 18-19 y from the TEDS (Twins Early Development Study), a large population-based cohort of British twins born during 1994-1996. Food preferences were measured by using a self-report questionnaire of 62 individual foods. Food items were categorized into 6 food groups (fruit, vegetables, meat or fish, dairy, starch foods, and snacks) by using factor analysis. Maximum likelihood structural equation modeling established genetic and environmental contributions to variations in preferences for each food group. Results: Genetic factors influenced a significant and substantial proportion of the variation in preference scores of all 6 food groups: vegetables (0.54; 95% CI: 0.47, 0.59), fruit (0.49; 95% CI: 0.43, 0.55), starchy foods (0.32; 95% CI: 0.24, 0.39), meat or fish (0.44; 95% CI: 0.38, 0.51), dairy (0.44; 95% CI: 0.37, 0.50), and snacks (0.43; 95% CI: 0.36, 0.49). Aspects of the environment that are not shared by 2 twins in a family explained all of the remaining variance in food preferences. Conclusions: Food preferences had a moderate genetic basis in late adolescence, in keeping with findings in children. However, by this older age, the influence of the shared family environment had disappeared, and only aspects of the environment unique to each individual twin influenced food preferences. This finding suggests that shared environmental experiences that influence food preferences in childhood may not have effects that persist into adulthood