Search Results (139)

This study uses life cycle analysis (LCA) to evaluate the environmental impacts of co-firing bituminous coal with agricultural biomass waste, such as coconut and rice husks, emphasising circular economy principles. Seven experimental scenarios with different coal-to-biomass ratios were designed, ranging from pure coal to pure biomass. The results show that Scenario B (100% rice husk) achieved the best overall environmental performance, with the lowest global warming potential (300 kg CO₂ equivalent), eutrophication potential (4.742 kg PO₄ equivalent), and smog formation potential (0.012 kg C₂H₄ equivalent). Additionally, Scenario F (15% biomass mix) recorded the lowest acidification potential (57.39 kg SO₂ eq), indicating that even partial substitution can yield significant environmental benefits. In contrast, Scenario C (100% coal) exhibited the highest acidification (164.08 kg SO₂ eq) and eutrophication (8.82 kg PO₄ eq) potential. Overall, the results demonstrate that co-firing biomass waste significantly reduces pollutant emissions compared to burning coal alone. This study highlights the effectiveness of biomass waste co-firing in mitigating environmental impacts, promoting resource recovery, and supporting a sustainable energy transition within a circular economy framework. Full article

Predicting the blow-off (BO) is critical for characterising the operability limits of gas turbine engines. In this study, the applicability of a low-order extinction prediction modelling, which is based on a stochastic variant of the Imperfectly Stirred Reactor (ISR) approach, to predict the lean blow-off (LBO) curve and the extinction conditions in a hydrogen Rich-Quench-Lean (RQL)-like swirl combustor is investigated. The model predicts the blow-off scalar dissipation rate (SDR), which is then extrapolated using Reynolds-Averaged Navier–Stokes (RANS) cold-flow simulations and simple scaling laws, to determine the critical blow-off conditions. It has been found that the sISR modelling framework can predict the BO flow split ratio at different global equivalence ratios, showing a reasonable agreement with the experimental data. This further validates sISR as an efficient low-order modelling flame extinction tool, which can significantly contribute to the development of robust hydrogen RQL combustors by enabling the rapid exploration of combustor operability during the preliminary design phases. Full article

According to the World Health Organization (WHO), indoor air quality (IAQ) is becoming a serious global concern due to its significant impact on human health. However, not all relevant health parameters are currently regulated. For example, particle number concentration (PNC) and its associated carbonaceous species, such as black carbon (BC), which are classified as carcinogenic by the International Agency for Research on Cancer (IARC), are not currently regulated. Compared with IAQ studies in other types of buildings, studies focusing on IAQ in hospitals or other healthcare facilities are scarce. Therefore, this study aims to evaluate the impact of these outdoor pollutants, among others, on the indoor environment of a hospital under different atmospheric conditions. To identify the seasonal influence, two different periods of two consecutive seasons (summer 2020 and winter 2021) were selected for the measurements. Regulated pollutants (NO, NO₂, O₃, PM₁₀, and PM_2.5) and nonregulated pollutants (PM₁, PNC, and equivalent BC (eBC)) in outdoor air were simultaneously measured indoor and outdoor. This study also investigated the impact of indoor activities on indoor air quality. In the absence of indoor activities, outdoor sources significantly contribute to indoor traffic-related pollutants. Indoor and outdoor (I-O) measurements showed similar behavior, but indoor concentrations were lower, with peak levels delayed by up to two hours. Seasonal variations in indoor/outdoor ($\mathrm{I}/\mathrm{O}$) ratios were lower for particles than for associated gaseous pollutants. Particle infiltration depended on particle size, with it being higher the smaller the particle size. Indoor activities also significantly affected indoor pollutants. PM_x (especially PM₁₀ and PM_2.5) concentrations were mainly modulated by walking-induced particle resuspension. Vertical eBC profiles indicated a relatively well-mixed environment. Ventilation through open windows rapidly altered indoor air quality. Outdoor-dominant pollutants (PNC, eBC, and NO_X) had $\mathrm{I}/\mathrm{O}$ ratios ≥ 1. Staying in the room with an open window had a synergistic effect, increasing the $\mathrm{I}/\mathrm{O}$ ratios for all pollutants. Higher I/O ratios were associated with turbulent outdoor conditions in both unoccupied and occupied conditions. Statistically significant differences were observed between stable (TKE ≤ 1 m² s⁻²) and unstable (TKE > 1 m² s⁻²) conditions, except for NO₂ in summer. This finding was particularly significant when the wind direction was westerly or easterly during unstable conditions. The results of this study highlight the importance of understanding the behavior of indoor particulate matter and related pollutants. These pollutants are highly variable, and knowledge about them is crucial for determining their health effects, particularly in public buildings such as hospitals, where information on IAQ is often limited. More measurement data is particularly important for further research into I-O transport mechanisms, which are essential for developing preventive measures and improving IAQ. Full article

This study investigates the effects of diffusion modeling and swirl intensity on flow fields and NO emissions in CH₄/NH₃ non-premixed swirling flames using large eddy simulations (LESs). Simulations are performed for a 50/50 ammonia–methane blend at three global equivalence ratios of 0.77, 0.54, and 0.46 and two swirl numbers of 8 and 12, comparing the unity Lewis number (ULN) and mixture-averaged diffusion (MAD) models against the experimental data includes OH-PLIF and ON-PLIF reported in a prior study by the KAUST group. Both models produce similar flow fields, but the MAD model alters the flame structure and species distributions due to differential diffusion (DD) and limitations in its Flamelet library. Notably, the MAD library lacks unstable flame branch solutions, leading to extensive interpolation between extinction and stable branches. This results in overpredicted progress variable source terms and reactive scalars, both within and beyond the flame zone. The ULN model better reproduces experimental OH profiles and localizes NO formation near the flame front, whereas the MAD model predicts broader NO distributions due to nitrogen species diffusion. Higher swirl intensities shorten the flame and shift NO production upstream. While a low equivalence ratio provides enough air for good mixing, lower ammonia and higher NO contents in exhaust gases, respectively. Full article

The 83rd session of the IMO Maritime Environment Protection Committee (MEPC 83) approved a global pricing mechanism for the shipping industry, with formal adoption scheduled for October 2025. Proposed mechanisms include the International Maritime Sustainable Fuels and Fund (IMSF&F) and a combined approach integrating GHG Fuel Standards with Universal GHG Contributions (GFS&UGC). This study developed a model based on the marginal abatement cost curve (MACC) methodology to assess the cost-effectiveness of alternative fuels under both mechanisms. Sensitivity analyses evaluated the impacts of fuel prices, carbon prices, and the GHG Fuel Intensity (GFI) indicator on MAC. Results indicate that implementing the GFS&UGC mechanism yields higher net present values (NPVs) and lower MACs compared to IMSF&F. Introducing universal GHG contributions promotes a comparatively fairer transition to sustainable shipping fuels. Investments in zero- or near-zero-fueled (ZNZ) ships are unlikely to be recouped by 2050 unless carbon prices rise sufficiently to boost revenues. Bio-Methanol and bio-diesel emerged as the most cost-competitive ZNZ options in the long term, while e-Methanol’s poor competitiveness stems from its extremely high price. Both pooling costs and universal GHG levies significantly reduce LNG’s economic viability over the study period. MACs demonstrated greater sensitivity to fuel prices (P_fuel) than to carbon prices (P_carbon) or GFI within this study’s parameterization scope, particularly under GFS&UGC. Ratios of P_carbon%/P_fuel% in equivalent sensitivity scenarios were quantified to determine relative price importance. This work provides insights into fuel selection for shipping companies and supports policymakers in designing effective GHG pricing mechanisms. Full article

Background/Objectives: The maternal mortality ratio is one of the global health indicators, and cardiopathies are the leading indirect causes of maternal deaths. Proper management of pregnant women with heart disease is crucial, as the severity of these conditions can lead to complications during the perinatal period. This study aimed to evaluate the rate of severe maternal morbidity and associated factors in pregnant women with heart disease. Methods: A retrospective cohort study was conducted at a referral hospital in São Paulo from 2008 to 2017, including pregnant women with heart disease who underwent procedures in the obstetric center (n = 345). Sociodemographic, obstetric, and pre-existing conditions were analyzed, along with life-threatening conditions, near-miss events, and maternal deaths. Heart diseases were classified according to the World Health Organization (WHO) guidelines, and health indicators were calculated using WHO-recommended formulas. The Chi-square test or Likelihood Ratio test (p < 0.05) was used to compare severe maternal morbidity among women with heart disease. Results: The mean age of participants was 29.1 ± 7.29 years; most were white (58.8%), had completed high school (37.9%), and were married (71.6%). The most frequent pre-existing conditions were hypertension (9.6%) and diabetes mellitus (9.3%). The mean gestational age at admission/delivery was 37 weeks. According to the WHO classification, most women were classified as “II/III” (31.6%). Life-threatening conditions included hemorrhagic complications (13.9%), hypertensive complications (5.8%), clinical complications (19.7%), and severe management conditions (31.6%). Near-miss events occurred in 6.4% of patients, with clinical criteria in 2.9%, laboratory criteria in 4.3%, and management criteria in 3.5%. The cesarean section rate was 51%. Patients classified as WHO III and IV presented more severe management conditions (p < 0.0001), and those in WHO IV had a higher occurrence of near-miss events (p = 0.0001). Maternal mortality was 0.9% (n = 3). Conclusions: The incidence of severe maternal morbidity was 25 cases (22 near-miss events + 3 maternal deaths), equivalent to 2.86 per 1000 live births, and was significantly associated with WHO classifications III and IV. Full article

Ammonia combustion has garnered increasing attention due to its potential as a carbon-free fuel. Globally swirling flow in a rectangular furnace generates flameless conditions by high flue gas recirculation. The reverse air injection (RAI) technique enabled stable swirling flameless combustion of pure ammonia without auxiliary methods. Experiments with pure ammonia combustion in a swirling flameless furnace demonstrated an operable equivalence ratio (ER) range of 0.3–1.05, extending conventional flammability limits of pure ammonia as a fuel. NO emissions were reduced by 40% compared to conventional combustion, with peak concentrations of 1245 ppm at ER = 0.71 and near-zero emissions at ER = 1.05. Notably, flameless combustion exhibited lower temperature sensitivity in NO formation; however, the ER has a serious effect. Developing a simplified reaction model for ammonia combustion is crucial for computational fluid dynamics (CFD) research. A reduced kinetic mechanism comprising 36 reactions and 16 chemical species was introduced, specifically designed for efficient and precise modeling of pure ammonia flameless combustion. Combustion simulation using the eddy dissipation concept (EDC) approach confirmed the mechanism’s predictive capability, maintaining acceptable accuracy across the operating conditions. Full article

Ammonia (NH₃) and hydrogen (H₂) are considered promising fuels for the power sector’s decarbonization. Their combustion is capable of producing energy with zero direct CO₂ emissions, and ammonia can act as a stable energy H₂ carrier. This study numerically investigates the design and implementation of staged combustion of a mixture of NH₃/H₂ by means of CFD simulations. The investigation employed the single-phase flow RANS governing equations and the eddy dissipation concept (EDC) combustion model, with the incorporation of a detailed kinetic mechanism. The combustion chamber operates under the RQL (rich–quench–lean) combustion regime. The first stage operates under rich conditions, firing mixtures of ammonia in air, enriched by hydrogen (H₂) to enhance combustion properties in a swirl and bluff-body stabilized burner. The secondary stage injects additional air and hydrogen to mitigate unburnt ammonia and NO_x emissions. Simulations of the first stage were performed for a thermal input ranging from 4 kW to 8 kW and flames with an equivalence ratio of 1.2. In the second stage, additional hydrogen is injected with a thermal input of either 1 kW or 2 KW, and air is added to adjust the global equivalence ratio to 0.6. Full article

This numerical study addressed the multi-objective optimization of a rocket-type Pulse Detonation Engine nozzle. The Pulse Detonation Engine consisted of a constant length, constant diameter cylindrical section plus a nozzle that could be either convergent, divergent, or convergent–divergent. The space of five design variables contained: equivalence ratio of the H2-Air mixture, convergent contraction ratio, divergent expansion ratio, dimensionless nozzle length, and convergent to divergent length ratio. The unsteady Euler-type numerical solver was quasi-one-dimensional with variable cross-sectional area. Chemistry was simulated by means of a one-step global reaction. The solver was used to generate three coarse five-dimensional data tensors that contained: specific impulse based on fuel, total impulse, and nozzle surface area, for each configuration. The tensors were decomposed using the High Order singular Value Decomposition technique. The eigenvectors of the decompositions were used to generate continuous descriptions of the data tensors. A genetic algorithm plus a Gradient Method optimization algorithm acted on the densified data tensors. Five different objective functions were considered that involved specific impulse based on fuel, total impulse, and nozzle surface area either separately or in doublets/triplets. The results obtained were discussed, both qualitatively and quantitatively, in terms of the different objective functions. Design guidelines were provided that could be of interest in the growing area of Pulse Detonation Engine engineering applications. Full article

Background: Age-related vascular stiffening increases cardiovascular risk by altering ventricular–arterial coupling (VAC). Physical activity, a modifiable factor, may improve cardiovascular health. This pilot study evaluated the relationship between physical activity evaluation and VAC, measured by the carotid–femoral pulse wave velocity to global longitudinal strain (cfPWV/GLS) ratio, in a Romanian primary care cohort. Methods: The prospective cohort analysis was performed on 81 adults (49 females, mean age 50.27 ± 12.93 years). Physical activity was quantified through anamnesis using metabolic equivalents (METs) according with Compendium of Physical Activities, and patients were stratified into four groups: G1 (METs < 1.5, n = 39), G2 (METs = 1.5–2.9, n = 2), G3 (METs = 3–5.9, n = 23), and G4 (METs ≥ 6, n = 17). Demographic and echocardiographic data were recorded to explore associations between physical activity and VAC. Results: The cfPWV/GLS ratio differed significantly across groups (p = 0.012), with the lowest values present in the moderate-intensity group (G3). VAC ≥ 0.391 can predict sedentary lifestyles (AUC = 0.730; CI: 0.617–0.833, p > 0.001). Multivariate analysis revealed that age, arterial age, and hypertension independently predict VAC. Conclusions: Higher physical activity is inversely associated with VAC (cfPWV/GLS ratio) and can predict sedentary lifestyles. Encouraging moderate-to-vigorous exercise in primary care may improve cardiovascular function and aid prevention. Full article

The amendment to MARPOL Annex VI, which limits the sulfur content in marine fuels to a maximum of 0.5 wt.%, came into effect in January 2020. This includes reducing sulfur oxide (SO_X) emissions and establishing nitrogen oxide (NO_X) emission standards (Tiers I, II, and III) based on the ship’s engine type and construction date. Furthermore, the regulations require oil tankers to control volatile organic compound (VOC) emissions and prohibit the installation of new equipment containing ozone-depleting substances. After a four-year exploration phase, global shipping companies still lack consistent evaluation criteria for the selection and use of alternative fuels, resulting in divergence across the industry. According to the latest data, methanol can reduce NO_X, SO_X, and particulate matter (PM) emissions by approximately 80%, 99%, and 95%, respectively, compared to traditional heavy fuel oil. Furthermore, green methanol has the potential for near-zero greenhouse gas emissions and can meet the stringent standards of Emission Control Areas. Therefore, this study adopts a cost-benefit analysis method to evaluate the feasibility and implementation benefits of two promising strategies: methanol dual fuel and very low-sulfur fuel oil (VLSFO). A 6600-TEU container ship was selected as a representative case, and the evaluation was conducted by replacing an older ship with a newly built one. The reductions in total pollutants and CO₂-equivalent emissions of the container ship, as well as the cost-effectiveness of each specific strategy, were calculated. This study found that, in the first five years of operation, the total incremental cost of Vessel A, which uses 100% VLSFO, will be significantly lower than that of Vessel B, which uses a blend of 30% e-methanol + 70% VLSFO as fuel. Furthermore, compared to a scenario without any improvement strategies, the total incremental cost for Vessels A and B will increase by 69.90% and 178.15%, respectively, over five years. Vessel B effectively reduced the total greenhouse gas emission equivalent (CO₂e) of CO₂, CH_4, and N₂O by 24.72% over five years, while Vessel A reduced the CO₂e amount by 12.18%. Furthermore, the cost-benefit ratio (CBR) based on total pollutant emission reduction is higher for Vessel A than for Vessel B within five years of operation. However, in terms of the cost-effectiveness of CO₂e emission reduction, the CBR of Vessel A becomes lower than Vessel B after 4.7 years of operation. Therefore, Vessel A’s strategy should be considered a short-term option for reducing CO₂e within 4.7 years, whereas the strategy of Vessel B is more suitable as a long-term solution for more than 4.7 years. Full article

Carbon capture and storage (CCS) technologies are employed to mitigate global warming by removing carbon from the atmosphere. To enhance carbon capture efficiency, nanoparticles have gained considerable attention as catalysts due to their large surface area, tunable properties, regeneration, and enhanced reactivity. However, it poses some challenges, such as nanoparticle aggregation and reduced effectiveness in sustainable solvents like seawater. To address these limitations and promote an environmentally sustainable method for carbon capture, this study evaluates the CO₂ capture efficiency of seawater using nickel nanoparticles (NiNPs) coated with polyvinylpyrrolidone (PVP) as a catalyst. We examined the time-dependent size variations of CO₂ bubbles in a flow-focusing microchannel using high-speed bubble-based microfluidics, directly associated with transitory CO₂ dissolution into the surrounding solution. We hypothesized that smaller polymer-coated NiNPs, due to their higher surface-to-volume ratio, can enhance CO₂ solubility and capture rates under identical environmental conditions. To verify this, polymer-coated NiNPs of three different sizes—5 nm, 10 nm, and 20 nm—were synthesized and tested. The experiments revealed that 5 nm NiNPs achieved a CO₂ dissolution rate of 77%, in contrast to 71% for 10 nm and 43% for 20 nm particles. These findings validate the hypothesis, demonstrating that smaller nanoparticles facilitate more effective CO₂ capture using equivalent material quantities, thereby potentially improving the overall efficiency of CO₂ reduction. This innovative approach contributes to advancing NiNP-based catalysts for saltwater-based CO₂ capture. Full article

This study investigates the combustion dynamics of methane in a dual swirl combustor, focusing on improving combustion efficiency and understanding flow features. Methane, as a conventional fuel, offers high energy content and relatively low carbon emissions compared to other hydrocarbons, making it a promising choice for sustainable energy solutions. Accurate numerical models are essential for the optimization of combustion processes, particularly in the design of combustion engines utilizing methane. In this work, we employ a partially premixed combustion model based on a mixture fraction and progress-variable approach to simulate methane combustion dynamics. Turbulent behavior is modeled using Detached-Eddy Simulation (DES), with the DLR dual swirl combustor serving as the geometric model. The simulations are performed at a global equivalence ratio of 0.65 for partially premixed methane. The results show good validation against experimental data, including time-averaged velocity components, turbulent fluctuations, mixture fraction, and temperature profiles. Additionally, the analysis of instantaneous flow features reveals the presence of a precessing vortex core. This study provides a robust numerical methodology, validated against experimental data, offering valuable insights into the combustion behavior of methane in dual swirl combustors and its industrial applicability. Full article

Background: Bicomponent split microfiber reusable wipers and flat mops are innovative textiles used to hygienically clean healthcare surfaces and, hence, reduce hospital-acquired infections. Sustainability improvements are reflected as reduced energy and mass requirements over a life cycle. Methods: The environmental impacts of reusables were compared to disposable equivalents using standard life cycle assessment procedures. Results: With information from 80 hospitals, disposable flat mops and wipers were used at a higher rate than reusable counterparts; the disposable/reusable ratio was 2.3:1 for wipers and 2.5:1 for flat mop pads. Bicomponent split microfiber reusable products had lower impacts (65–95%) in all categories considered: global warming potential, natural resource energy, blue water use, and solid waste production. Discussion: Results reinforce other studies that compare reusable and disposable textile options in healthcare. Laundry energy is an important driver of energy use for reusables. The energy associated with water consumption for disposables’ supply chains is significantly greater than net water consumption for reusables laundry. Conclusions: Selecting disposables versus bicomponent split microfiber reusable flat mops and wipers increases these specific environmental life cycle assessment (LCA) impacts by 320% to 2000%, which is clearly not an environmental sustainability improvement. Group Purchasing Organizations may be barriers to hospital adoption of these reusables. Full article

Maize is a critical crop for global food security, yet excessive nitrogen (N) application, while sustaining yields, leads to reduced nitrogen use efficiency (NUE), and the application of controlled-release fertilizer (CRF) is one of the effective options to achieve sustainable maize production while improving NUE. This study evaluated the long-term effects of CRF with varying N input rates on maize growth using low-cost UAV-RGB imaging. UAV-RGB images were captured in different growth stages, and the non-canopy background was removed using the maximum between-class algorithm (OTSU). Eleven vegetation indices were constructed from the images to analyze maize growth under different N treatments. The results indicated that a single application of CRF with an equivalent N input rate to conventional treatment yielded significantly better outcomes. The optimal controlled-release N ratio was 40% of the total N input, increasing maize yield by 6.73% and NUE by 15%. Indices such as NRI, NBI, ARVI, RGBVI, ExR, ExG, and ExGR effectively reflected plant N status, with R² values exceeding 0.856 for yield estimation across growth stages. UAV-RGB imaging proved to be a viable method for rapid N status monitoring, aiding in the optimization of N management in maize production. Full article