Search Results (7,939)

The presence of secondary electromagnetic waves (EMWs) results in EMW pollution and a large need for EMW-shielding materials. Therefore, new, lightweight, flexible, chemically resistant, and durable EMW shielding materials are demanded, while graphene and its derivatives meet the above-mentioned requirements. Among graphene derivatives, N-doped graphene exhibits promising electrical properties for shielding applications, although achieving sufficient N-incorporation in the graphene sheets remains a challenge. Herein, we produced graphene oxide using the modified Hummers’ method (GO) and the electrochemical exfoliation of highly ordered pyrolytic graphite. These two GO samples were thermally treated at 500 °C and 800 °C under a pure NH₃ gas for 1 h. UV-Vis, infrared, and Raman spectroscopies and X-ray diffraction, elemental, and thermogravimetric analyses were used to investigate the structural properties of modified GO. One of the highest levels of N-doping of GO was measured (11.25 ± 0.08 at%). The modification under a NH₃ atmosphere leads to simultaneous N-doping and reduction of graphene, resulting in the formation of electrically conductive and EMW shielding materials. Density functional theory (DFT) revealed the effect of heteroatoms on the energy band gap of GO. The cluster corresponding to N-doped rGO had a reduced bandgap of 0.77 eV. Full article

Meso-scale combustors face persistent challenges in sustaining stable combustion and efficient heat transfer due to high surface-to-volume ratios and attendant heat losses. In contrast, larger outlet diameters exhibit weaker recirculation and more diffused temperature zones, resulting in reduced combustion efficiency and thermal confinement. The behavior of non-premixed flames in meso-scale combustor has been investigated through a comprehensive numerical study, utilizing computational fluid dynamics (CFD) under stoichiometric natural gas (methane)–air conditions; three outlet configurations (6 mm, 8 mm, and 10 mm) were analysed to evaluate their impact on temperature behaviour, vortex flow, swirl intensity, and central recirculation zone (CRZ) formation. Among the tested geometries, the 6 mm outlet produced the most robust central recirculation, intensifying reactant entrainment and mixing and yielding a sharply localised high-temperature core approaching 1880 K. The study highlights the critical role of geometric parameters in governing heat release distribution, with the 6 mm configuration achieving the highest exhaust temperature (920 K) and peak wall temperature (1020 K), making it particularly suitable for thermoelectric generator (TEG) integration. These findings underscore the interplay between combustor geometry, flow dynamics, and heat transfer mechanisms in meso-scale systems, providing valuable insights for optimizing portable power generation devices. Full article

Water alternating gas (WAG) flooding is a relatively mature technology for enhanced oil recovery (EOR). It combines the advantages of water flooding and gas flooding to maintain reservoir pressure and effectively mitigate the issues of high mobility ratio and fingering, demonstrating preferable application prospects. However, the evaluation of its development effect faces the challenges of complexity and lack of adaptability attributed to the multiple interactions of various factors involved in WAG flooding. Moreover, there are few studies evaluating the development effect of producers. Therefore, the traditional hierarchical analysis process (AHP) is improved in this study to fill the gap in this technological field. This process is combined with the entropy weight method (EWM) to establish a coupled evaluation model. Subsequently, this study classifies the contribution weights of producers and proposes adjustment suggestions for the primary development contradictions. This study finds that the contribution weight of producers to the well group indicates that the development effect of producers is no longer influenced by a single factor, but is determined by the coupling effect of geological, engineering, and development factors. By constructing a coupled model and fully utilizing on-site data to objectively characterize the underground production situation, the development effect of producers can be more accurately reflected. Finally, a closed-loop optimization system for evaluating the development effect and potential of producers with WAG flooding is established, laying a theoretical foundation for dynamic analysis and development adjustment of on-site engineers. Full article

With the world facing the twin pressures of a warming climate and an ever-increasing amount of waste, it is becoming increasingly clear that we need to rethink the way we generate energy and use materials. Despite growing awareness, our energy systems are still largely dependent on fossil fuels and characterized by a linear ‘take-make-dispose’ model. This leaves us vulnerable to supply disruptions, rising greenhouse gas emissions, and the depletion of critical raw materials. Hydrogen is emerging as a potential carbon-free energy vector that can overcome both challenges if it is produced sustainably from renewable sources. This study reviews hydrogen production from a circular economy perspective, considering industrial, agricultural, and municipal solid waste as a resource rather than a burden. The focus is on the reuse of waste as a catalyst or catalyst support for hydrogen production. Firstly, the role of hydrogen as a new energy carrier is explored along with possible routes of waste valorization in the process of hydrogen production. This is followed by an analysis of where and how catalysts from waste can be utilized within various hydrogen production processes, namely those based on using fossil fuels as a source, biomass as a source, and electrocatalytic applications. Full article

The sulfur dioxide removal in thermoelectric plants occurs through flue gas desulfurization (FGD), which produces waste that needs to be correctly disposed of. This exploratory research aims to characterize waste obtained from an FGD plant in Candiota, Rio Grande do Sul, Brazil, and evaluate its potential as alternative mineral source in obtaining alkali-activated materials (AAM). The dried and processed waste was called FGD-D, and AAM was produced by mixing FGD-D with sodium-based alkaline activating solutions. The amounts of FGD at formulations ranged from 31.6 (F1) to 38.9 wt.% (F4), and the use of metakaolin was not necessary. The results show that the chemical composition of FGD-D is composed mainly of calcium oxides (38 wt.%), sulfur (22 wt.%), and silica (19 wt.%). Crystalline phases and a high amorphous fraction were identified in the residual samples. The use of FGD-D in AAM proved to be an alternative mineral source, showing an exothermic reaction with subsequent rapid hardening and increased compressive strength values ranged from 7.7 ± 1.3 Mpa for F1 to 14.4 ± 1.8 Mpa for F4 at seven days. The results demonstrate the potential of using FGD-D in AAM formulations, opening positive perspectives for a more sustainable destination for these residual materials. Full article

Propolis is a substance produced by bees from the collection of plant resins, with a chemical composition that varies according to the available flora and region, and it has several biological activities. Stingless bee propolis is often produced in reduced amounts, posing a challenge to the study of their volatile compounds, as traditional hydrodistillation extraction would demand more raw propolis than available. These bees collect resins from various sources, resulting in a variable composition, so a standardized reproducible method is fundamental for their analysis. Headspace solid-phase microextraction (HS-SPME), associated with gas chromatography, appears to be an efficient alternative for the analysis of these volatiles. In this study, the GC-MS results of three types of SPME fibers were compared to those of extracts obtained by hydrodistillation to evaluate their efficiency in representing the composition of essential oils from (geo)propolis of different species. The extraction time and temperature were also standardized. Among the fibers tested, PDMS/DVB extracted the volatiles in a similar manner to the essential oil obtained by hydrodistillation for all the samples tested, indicating this to be the best choice of fiber coating for propolis volatile extraction and analysis. Full article

Reppe’s ethynylation of formaldehyde uses coal-based acetylene to produce commercially valuable 1,4-butynediol with a silica-supported copper oxide-bismuth oxide catalyst. Cuprous acetylide (Cu₂C₂) is generally accepted to be the catalytically active phase, which is formed in situ from the CuO-Bi₂O₃/SiO₂ pre-catalyst under ethynylation conditions. The catalytic performance and stability of this sensitive Cu₂C₂ phase are evaluated by long-term experiments (up to 240 h) and by catalyst recycling (10 cycles of 22 h). Powder X-ray diffraction and Raman spectroscopy are found to be the best and the only applicable analytical tools for qualitative evaluation of Cu₂C₂’s crystallinity, purity, and morphology during in situ formation and for phase transformations during the ethynylation. They were continuously correlated with the catalytic performance (1,4-butynediol yield determined by gas chromatography). No catalyst deactivation was observed, indicating outstanding catalyst stability. Observed structural changes within the active Cu₂C₂ phase have obviously limited influence on the catalytic cycle and performance. Full article

The rapid increase in global warming requires that sustainable energy choices aimed at achieving net-zero greenhouse gas emissions be implemented as soon as possible. This objective, emerging from the European Green Deal and the UN Climate Action, could be achieved by using clean and efficient energy sources such as hydrogen produced from nuclear power. “Renewable” hydrogen plays a fundamental role in decarbonizing both the energy-intensive industrial and transport sectors while addressing the global increase in energy consumption. In recent years, several strategies for hydrogen production have been proposed; however, nuclear energy seems to be the most promising for applications that could go beyond the sole production of electricity. In particular, nuclear advanced reactors that operate at very high temperatures (VHTR) and are characterized by coolant outlet temperatures ranging between 550 and 1000 °C seem the most suitable for this purpose. This paper describes the potential use of nuclear energy in coordinated and coupled configurations to support clean hydrogen production. Operating conditions, energy requirements, and thermodynamic performance are described. Moreover, gaps that require additional technology and regulatory developments are outlined. The intermediate heat exchanger, which is the key component for the integration of nuclear hybrid energy systems, was studied by varying the thermal power to determine physical parameters needed for the feasibility study. The latter, consisting of the comparative cost evaluation of some nuclear hydrogen production methods, was carried out using the HEEP code developed by the IAEA. Preliminary results are presented and discussed. Full article

Environmental emissions from the maritime sector, including CO₂, NO_x, and SO_x, contribute significantly to global air pollution and climate change. The International Maritime Organization (IMO) has set a target to reduce greenhouse gas emissions from international shipping to reach zero GHG by 2050 compared to 2008 levels. To meet these goals, the IMO strongly encourages the transition to alternative fuels, such as hydrogen, ammonia, and biofuels, as part of a broader decarbonization strategy. This study presents a comparative analysis of converting conventional diesel engines to dual-fuel systems utilizing alternative fuels such as methanol or natural gas. The methodology of this research is based on theoretical calculations to estimate various types of emissions produced by conventional marine fuels. These results are then compared with the emissions generated when using methanol and natural gas in dual-fuel engines. The analysis is conducted using the EVER ALOT container ship as a case study. The evaluation focuses on both environmental and economic aspects of engines operating in natural gas–diesel and methanol–diesel dual-fuel modes. The results show that using 89% natural gas in a dual fuel engine reduces nitrogen oxides (NO_x), sulfur oxides (SO_x), carbon dioxide (CO₂), particulate matter (PM), and carbon monoxide (CO) pollutions by 77.69%, 89.00%, 18.17%, 89.00%, and 30.51%, respectively, while the emissions percentage will be 77.78%, 91.00%, 54.67%, 91.00%, and 55.90%, in order, when using methanol as a dual fuel with percentage 91.00% Methanol. This study is significant as it highlights the potential of natural gas and methanol as viable alternative fuels for reducing harmful emissions in the maritime sector. The shift toward these cleaner fuels could play a crucial role in supporting the maritime industry’s transition to low-emission operations, aligning with global environmental regulations and sustainability goals. Full article

Bacterial leaf spot, particularly in chili peppers, is major concern worldwide, particularly in chili peppers. Enhancing pepper resistance to bacterial leaf spot addresses a key agricultural challenge while minimizing chemical usage. In this study, the efficacy of plant resistance inducers (PRIs) in controlling bacterial leaf spot in peppers was evaluated through molecular and secondary metabolite analyses. Pepper plant seedlings were treated with salicylic acid (SA), acibenzolar-S-methyl, β-aminobutyric acid, chitosan, Bacillus subtilis B01, and B. velezensis CH6 and inoculated with Xanthomonas euvesicatoria pv. euvesicatoria. Disease severity was assessed, and the expression level of genes (PR-1, PR-2, PR-4, and CAT) and the abundance of secondary metabolites were analyzed via quantitative PCR (qPCR) and gas chromatography-mass spectrometry (GC-MS), respectively. Soil drenching with B. subtilis B01 produced the best effects, reducing the disease severity by 80% and significantly inducing PR-1 expression 24–48 h post-treatment. SA was similarly effective in inducing systemic acquired resistance (SAR), while β-aminobutyric acid primed antioxidative defenses through sustained catalase (CAT) expression, and chitosan induced PR-4. GC-MS analysis revealed secondary metabolites associated with systemic resistance pathways including SAR and induced systemic resistance (ISR). Herein, B. subtilis B01 and SA were identified as potent resistance inducers that reduce the disease severity of bacterial leaf spot and activate key defense pathways in pepper plants. These findings contribute to the development of sustainable, integrated disease management strategies. Full article

Rapid on-site detection of chemical warfare agents (CWAs) is vital for security and environmental monitoring. In this work, copper(I) oxide (Cu₂O) nanowire (NW) chemiresistors were investigated as gas sensors for low-concentration organophosphorus chemical warfare agent (CWA) simulants. The NWs were hydrothermally synthesized and deposited onto microheater platforms, enabling them to operate at elevated working temperatures. Their sensing performance was tested against a range of vapor-phase simulants, including dimethyl methylphosphonate (DMMP), triethyl phosphate (TEP), diethyl ethylphosphonate (DEEP), diphenyl phosphoryl chloride (DPPCl), parathion, diethyl phosphite (DEP), diethyl adipate (DEA), and cyanogen chloride (ClCN). Fully oxidized P(V) simulants (DMMP, DEEP, TEP) produced modest, predominantly reversible responses (~3–6% RR). On the contrary, DPPCl and DEP induced the strongest relative responses (RR −94.67% and >200%, respectively), accompanied by irreversible surface modification as revealed by SEM and EDS. ClCN produced a substantial but reversible negative response (RR −9.5%), consistent with transient oxidative interactions. Surface poisoning was confirmed after exposure to DEP and DPPCl, which left phosphorus or chlorine residues on the Cu₂O surface. These results highlight both the promise and limitations of Cu₂O NW chemiresistors for selective CWA detection. Full article

Controlling dissolved nitrogen is critical to meeting increasingly stringent steel quality targets, yet the variable kinetics of gas absorption and removal across production stages complicate real-time decision-making. Leveraging a total of 291 metal samples, the research applied ordinary least squares (OLS) regression, enhanced by cointegration diagnostics, to develop four stage-specific models covering pig iron after desulfurization, crude steel in the basic oxygen furnace (BOF) before tapping, steel at the beginning and end of secondary metallurgy processing. Predictor selection combined thermodynamic reasoning and correlation analysis to produce prediction equations that passed heteroscedasticity, normality, autocorrelation, collinearity, and graphical residual distribution tests. The k-fold cross-validation method was also used to evaluate models’ performance. The models achieved an adequate accuracy of 77.23–83.46% for their respective stages. These findings demonstrate that statistically robust and physically interpretable regressions can capture the complex interplay between kinetics and the various processes that govern nitrogen pick-up and removal. All data are from U. S. Steel Košice, Slovakia; thus, the models capture specific setup, raw materials, and production practices. After adaptation within the knowledge transfer, implementing these models in process control systems could enable proactive parameter optimization and reduce laboratory delays, ultimately minimizing excessive nitrogenation in finished steel. Full article

This article presents a proposal for blending natural gas and biogas with a control system with feedback to ensure a constant mixture density. To achieve this, we propose the following: a mathematical model to determine the gas density based on its composition; a control system whose main components are a gas mixer, valves, and a natural gas storage tank to regulate the biogas density, where its inputs are gases from biomass plants and the natural gas grid; mathematical models to calculate the volume of natural gas required in the storage tank. It is assumed that the composition at the outlet of the biogas plants is measured and that there are no losses of any kind; a case study simulation is then performed. All models consider random variation in gas composition over time. The main results are as follows: (a) reduced natural gas consumption, the promotion of biogas production and use and of mixtures of lower methane compared to natural gas, and the facilitation of the pumping of the gas mixtures; (b) all the biogas produced is used; (c) different piping, sources, storage tanks, consumers, and mixer schemes, considering the concepts of cities, microgrids, smart grids, and smart cities. Full article

In the context of reservoir monitoring, time-lapse (4D) full-waveform inversion (FWI) of seismic data can potentially estimate reservoir changes with high resolution. However, most existing field-data applications are carried out with isotropic, and often acoustic, FWI algorithms. Here, we apply a time-lapse FWI methodology for transversely isotropic (TI) media with a vertical symmetry axis (VTI) to offshore streamer data acquired at Pyrenees field in Australia. We explore different objective functions, including those based on global correlation (GC) and designed to mitigate errors in the source signature (SI, or source-independent). The GC objective function, which utilizes mostly phase information, produces the most accurate inversion results by mitigating the difficulties associated with amplitude matching of the synthetic and field data. The SI FWI algorithm is generally more robust in the presence of distortions in the source wavelet than the other two methods, but its application to field data is hampered by reliance on amplitude matching. Taking anisotropy into account provides a better fit to the recorded data, especially at far offsets. In addition, the application of the anisotropic FWI improves the flatness of the major reflection events in the common-image gathers (CIGs). The 4D response obtained by FWI reveals time-lapse parameter variations likely caused by the reservoir gas coming out of solution and by the replacement of gas with oil. Full article

This work aims to present tes-thermo, a Python library developed to solve thermodynamic equilibrium problems using the Gibbs energy minimization approach. The library is a variant of TeS v.3, a standalone executable developed for the same purpose. The tool formulates the chemical equilibrium problem of combined phases as a nonlinear programming problem, implemented using Pyomo (Python Optimization Modeling Objects) and solved with IPOPT (Interior Point OPTimizer). To validate the tool and demonstrate its robustness, the supercritical water gasification (SCWG) of methanol and ethanol was investigated. The Peng–Robinson equation of state was employed to account for non-idealities in the gas phase. Experimental and simulated data from the literature were used for validation, and, in both cases, the results were satisfactory, with root mean square errors consistently below 0.23. The SCWG processes studied revealed that hydrogen production is favored by increasing temperature and decreasing pressure. For both methanol and ethanol, increasing the carbonaceous substrate fraction in the feed promotes hydrogen formation; however, it also leads to reduced hydrogen relative yield due to the enhanced formation of methane and carbon monoxide under these conditions. Consequently, although hydrogen production increases, the hydrogen molar fraction in the dry gas stream tends to decrease with the higher substrate content. As expected, the SCWG of methanol produces more hydrogen and less carbon monoxide compared to ethanol under similar conditions. This behavior is consistent with the higher carbon content in ethanol, which favors reactions leading to carbon oxides. In summary, tes-thermo proves to be a robust and reliable tool for conducting research and studies on topics related to thermodynamic equilibrium. Full article