Financial threat, hardship and distress predict depression, anxiety and stress among the unemployed youths: a Bangladeshi multi-cities study

Introduction: Unemployment has a contributory role in the development of mental health problems and in Bangladesh there is increasing unemployment, particularly among youth. Consequently, the present study investigated depression, anxiety, and stress among recent graduates in a multi-city study across the country. Methods: A cross-sectional study was conducted among 988 Bangladeshi graduate jobseekers in six major cities of the country between August to November 2019. The measures included socio-demographics and life-style factors, study and job-related information, Economic Hardship Questionnaire, Financial Threat Scale, Financial Well-Being Scale, and Depression Anxiety Stress Scale-21. Results: Depression, anxiety and stress rates among the present sample were 81.1% (n=801), 61.5% (n=608) and 64.8% (n=640) respectively. Factors related to gender, age, socio-economic conditions, educational background, lack of extra-curricular activities, and high screen activity were significant risk factors of depression, anxiety, and stress. Structural equation modeling indicated that (while controlling for age, daily time spent on sleep study, and social media use), financial threat was moderately positively related to depression, anxiety, and stress. Financial hardship was weakly positively associated with depression, anxiety, and stress, whereas financial wellbeing was weakly negatively associated with depression, anxiety, and stress. Limitations: Due to the nature of the present study (i.e., cross-sectional study) and sampling method (i.e., convenience sampling), determining causality between the variables is not possible. Conclusions: The present results emphasized the important detrimental role of financial troubles on young people's mental health by showing that financial problems among unemployed youth predict elevated psychiatric distress in both men and women

Numerical modelling of oxy fuel combustion, the effect of radiative and convective heat transfer and burnout

In this study, a numerical investigation on the radiative and convective performance of the combustion of pulverised Russian coal having higher Calorific value in a 0.5 MWth combustion test facility (CTF) has been conducted for air and CO2-rich oxy-fired environment considering an IFRF Aerodynamically Air Staged Burner (AASB) configured with the furnace. This study is carried out considering a finite volume method (FVM) tool using AVL Fire version 2009.2 coupled with the user defined subroutines especially for the coal devolatilisation and char combustion modelling. This code is validated comparing the experimental radiative heat flux with the numerically predicted data and results show that reasonable agreement has been found with the measured radiative heat flux on the furnace wall. Different combustion environments were investigated including an air-fired as reference case and three recycled flue gas (RFG) fired combustion environments. The different cases are composed of varying recycled ratio (RR) between 65% and 75%. It was found that the flame temperature distribution for the reference case (air fired) and RR72% case were found to be similar. The flame temperature increased with O2concentration and decreasing RR. With the decrease of RR, the length of the flame is also shortened. The ignition condition improved with enriched O2concentration in the RR65% (O230.9%, CO269.2% by mass) case. The results show that radiative and convective heat flux is significantly manipulated by the RR. The position of peak radiative flux moves downstream with increasing RR due to increased mass flow rate and reduced O2at higher RR. With the increase of normalised total flow (NTF), mean flame temperature and exit temperature decreased whereas with the increase of normalised O2flow (NOF), mean flame temperature and exit temperature increase. The presented working range for the Russian coal, suggests that the air equivalent radiative heat flux can be obtained at a RR ≈ 71% while air equivalent flame temperature were observed at RR of 72%. Reasonable agreement has been obtained for unburned carbon in ash (CIA). An improved burnout was observed in RR conditions

CFD modelling of co-firing of biomass with coal under oxy-fuel combustion in a large scale power plant

Co-firing biomass is the principal means of mitigating the future energy crisis by expanding the use of renewable energy. Oxy-fuel combustion is the most capable technologies for carbon capture and storage (CCS) system. This paper presents a 3D numerical study considering co-firing concepts in a 550 MW tangentially fired furnace using a commercial CFD code AVL Fire ver.2009.2. Necessary subroutines were written and coupled with the code to account for chemical reactions, heat transfer, fluid and particle flow fields and turbulence. Due to irregularities of the biomass particle shape, a special drag effect was considered. Three different co-firing cases (20% biomass with 80% coal, 40% biomass with 60% coal and 60% biomass with 40% coal) were considered. All the co-firing cases were simulated under air-firing and three different oxy-firing cases (25% O2/75% CO2, 27% O2/73% CO2 and 29% O2/71% CO2). Level of confidence has been achieved by conducting a study on co-firing of biomass with coal in a 0.5 MW small scale furnace under air and oxy-fuel conditions. Similar findings have been observed in the present study which indicates the model can be used to aid in design and optimization of large-scale biomass co-firing under oxy-fuel conditions. This study enables the calculation of species transport and mixing phenomena and the simulation of ignition, combustion and emission formation in industrial furnace. Results were presented by the aerodynamics of burner flow, temperature distributions, gaseous emissions such as O2 and CO2 distributions. With the increase of biomass sharing, peak flame temperature reduced significantly. The dominant effect of the lower calorific value of biomass dampens the effect of volatile content contributing to lower temperature. Comparatively, improved burnout is observed for the improved oxy-fuel cases. But, the CFD model predicted a significant increase in unburned carbon in fly ash for the increase of biomass co-firing sharing. Overall, this study highlights the possible impact of changing the fuel ratio and combustion atmosphere on the boiler performance, underlining that minor redesign may be necessary when converting to biomass co-firing under air and oxy-fuel conditions

Thermal characterization of coal/straw combustion under air/oxy-fuel conditions in a swirl-stabilized furnace: a CFD modelling

Global warming is mainly due to increase of CO2 from fossil fuel based power generation in developed countries. The level of CO2 increase in the atmosphere is alarming. International effort imposed some strict obligations to control these emissions. To reduce the greenhouse gas emissions, shifting from coal based production to biomass resources is a must. The present study investigates the combustion behaviour of biomass (straw) compared with the coal combustion in air and O2/CO2 mixtures. Reference air-fuel and oxy-fuel (25%, 30% and 35% O2) cases were considered maintaining a constant thermal load of 30 kW in a semi-technical scale once-through swirl-stabilized furnace. The main objective of this study is to illustrate the impact on the combustion characteristics including flame temperature, burnout, and emissions for pure coal to pure biomass (straw) combusted in air and oxy-fuel atmospheres. Good agreement between the results obtained in this numerical work and results reported in literature was observed. This work has shown that significant changes occur to the fundamental combustion characteristics for straw when burned in the O2/CO2 atmosphere compared to air firing case. Comparatively higher flame temperatures were observed for oxy-firing case. The CO levels are predicted to decrease in the downstream section during oxy-fuel combustion compared to air-firing flames due to O2 availability. The burnout is reliably advanced during oxy-fuel combustion to 99.8% than air firing

Investigation of thermal performance and entropy generation in a helical heat exchanger with multiple rib profiles using Al2O3-water nanofluid

This research aims to assess the in detail thermal performance and entropy generation of a helical heat exchanger with multiple rib profiles and coil revolutions using water-based Al2O3 nanofluid with 5% concentration. A steady-state computational fluid dynamic model was used in determining the thermal and hydraulic parameters. The numerical model was validated with a numerical study and an experimental study. Three multiple rib profiles (2 rib, 3 rib and 4 rib) and three different coil revolutions (10, 20 and 30) were considered to design nine cases of heat helical exchangers. The geometrical effect was assessed and further represented as the streamlines, isotherms, overall Nusselt number, friction factor, thermal enhancement factor, and entropy generation. It is found that with the growth of coil revolutions the overall heat transfer rate and friction factor rise. The most efficient heat exchanger found in terms of thermal enhancement factor is 3 rib 10 revolutions with the value of 1.34. The entropy generation increases with the rise of the coil revolution. The maximum entropy generation increased by 19.5% for varying the coil revolution with a constant rib profile. Finally, this study is a guide of choosing an efficient heat transfer in terms of thermo-hydraulic performance

Finite Element Analysis of Aluminum Honeycombs Subjected to Dynamic Indentation and Compression Loads

The mechanical behavior of aluminum hexagonal honeycombs subjected to out-of-plane dynamic indentation and compression loads has been investigated numerically using ANSYS/LS-DYNA in this paper. The finite element (FE) models have been verified by previous experimental results in terms of deformation pattern, stress-strain curve, and energy dissipation. The verified FE models have then been used in comprehensive numerical analysis of different aluminum honeycombs. Plateau stress, σpl, and dissipated energy (EI for indentation and EC for compression) have been calculated at different strain rates ranging from 102 to 104 s−1. The effects of strain rate and t/l ratio on the plateau stress, dissipated energy, and tearing energy have been discussed. An empirical formula is proposed to describe the relationship between the tearing energy per unit fracture area, relative density, and strain rate for honeycombs. Moreover, it has been found that a generic formula can be used to describe the relationship between tearing energy per unit fracture area and relative density for both aluminum honeycombs and foams

Numerical modelling of unsteady flow behaviour in the rectangular jets with oblique opening

Vortex shedding in a bank of three rectangular burner-jets was investigated using a CFD model. The jets were angled to the wall and the whole burner was recessed into a cavity in the wall; the ratio of velocities between the jets varied from 1 to 3. The model was validated against experimentally measured velocity profiles and wall pressure tapings from a physical model of the same burner geometry, and was generally found to reproduce the mean flow field faithfully. The CFD model showed that vortex shedding was induced by a combination of an adverse pressure gradient, resulting from the diffuser-like geometry of the recess, and the entrainment of fluid into the spaces separating the jets. The asymmetry of the burner, a consequence of being angled to the wall, introduced a cross-stream component into the adverse pressure gradient that forced the jets to bend away from their geometric axes, the extent of which depended upon the jet velocity. The vortex shedding was also found to occur in different jets depending on the jet velocity ratio