Abstract Conventional structural dampers are constrained by inherent limitations: viscoelastic dampers demonstrate low initial stiffness, reducing their effectiveness under wind loads and minor earthquakes; friction dampers provide considerable energy dissipation but often induce significant residual deformations; and self-centering dampers based on nickel–titanium shape memory alloys (Ni–Ti SMAs) effectively mitigate residual displacements yet are hindered by prohibitively high material costs, which restricts their widespread application. To holistically address these challenges, this study proposes a novel self-centering wedge-shaped friction and viscoelastic composite damper that incorporates cost-effective copper-based SMAs. Initially, the effects of solution treatment temperature and cyclic thermal loading on the mechanical behavior of Cu-based SMA bolts were systematically investigated. Subsequently, the configuration and working principle of the proposed damper were described in detail. Furthermore, quasi–static cyclic tests were conducted to assess its hysteretic behavior, self-centering capability, and energy dissipation characteristics. Finally, a comprehensive numerical investigation was performed to systematically quantify the influence of key parameters—including loading frequency, bolt preload, bolt diameter, wedge surface friction coefficient, and wedge slope height—on the damper’s cycle performance. The experimental and numerical results collectively indicate that bolt preload contributes to the most substantial enhancement in initial stiffness, with an increase of up to 585%. A critical transition in performance is observed at wedge slope heights between 8 mm and 10 mm. Although a higher friction coefficient improves the equivalent viscous damping ratio, it compromises the self-centering capability. Moreover, increased loading frequency enhances energy dissipation but leads to an increase in residual displacements.

Impact of equivalence ratio on soot emissions from turbofan combustor during takeoff and ground idle status

Optical and numerical investigation of global equivalence ratio effects on combustion and flame propagation in active pre-chamber methanol turbulent jets

The Zhundong coalfield in Xinjiang contains vast reserves and is a crucial source of thermal coal. However, the Zhundong coal has a high content of alkali and alkaline earth metals, which makes it prone to ash deposition and slagging in boilers, thereby limiting its large-scale utilization. Fluidized-bed preheating is an emerging clean combustion technology that can reduce the slagging and fouling risks associated with high-alkali coal by modifying its fuel properties. This study employs circulating fluidized-bed preheating technology to treat high-alkali coal, with a focus on investigating the effect of the preheated air equivalence ratio on fuel preheating modification. Through microscopic characterization of both the raw coal and preheated char, the release and transformation behaviors of elements and substances during the preheating process are revealed. The results demonstrate that fluidized preheating promotes alkali metal precipitation, and increasing the preheated air equivalence ratio (λPr) enhances gas production and elemental release, with a volatile fraction mass conversion of up to 84.57%. As the λPr value increased from 0.28 to 0.40, the average temperature in the preheater riser increased from 904 °C to 968 °C. Compared to the raw coal, the specific surface area of the preheated char was enhanced by a factor of 3.6 to 9.1 times, with a more developed pore structure and less graphitization, thus enhancing the surface reactivity of the preheated char. The increase in λPr also facilitated the conversion from pyrrolic nitrogen to pyridinic nitrogen, thus improving combustion performance and facilitating subsequent nitrogen removal. These findings provide essential data support for advancing the understanding of preheating characteristics in high-alkali coal and for promoting the development of efficient and clean combustion technologies tailored for high-alkali coal.

Dialkyl carbonates (DACs) have emerged as renewable alternative fuels, attracting considerable interest from researchers in their combustion characteristics. Compared with short-chain DACs, longer-chain DACs have a higher lower-heating value and are more reactive at low temperatures, making them more promising alternatives to diesel. Although extensive studies have been conducted on short-chain DACs, research on longer-chain DACs remains limited. This study conducted the first experimental and modeling investigation into the oxidation chemistry of the longer-chain dibutyl (DBC) and dipentyl (DPeC) carbonates using a jet-stirred reactor (JSR). The mole fractions of the reactants and oxidation products were measured at three equivalence ratios of 0.5, 1.0, and 2.0 within a temperature range of 500-1100 K. Notably, the results revealed that both DBC and DPeC exhibited a pronounced negative temperature coefficient (NTC) behavior, which was absent in short-chain DACs. A detailed kinetic mechanism was developed and validated against the experimental data. Furthermore, a comprehensive analysis of reaction pathways and sensitivity was performed based on the newly developed mechanism. The difference in the oxidation reactivity of DACs with a changed carbon chain length is also illustrated in detail. Analysis of the reaction path reveals that at low temperatures, the fuel molecules are primarily consumed through H-abstraction reactions, generating fuel radicals. A considerable amount of ketohydroperoxides (KHPs) undergo decomposition reactions to form alkyl radicals. The subsequent chain-branching pathways of both the primary fuel radicals and the alkyl radicals contribute to the pronounced low-temperature oxidation reactivity observed for DBC and DPeC. The sensitivity analysis indicates that H-abstraction reactions by OH radicals exert the most significant promoting effect at low temperatures, while the chain-terminating reactions of the key ROO species in both fuel and alkane oxidation chemistry exhibit notable inhibiting effects.

Abstract Porous media burners offer significant advantages due to their high efficiency and low emissions. Nevertheless, a substantial challenge in the field of porous media burner research pertains to the precise control of crucial operating parameters, with the objective of further reducing pollutant emissions while maintaining combustion stability. The establishment of a numerical model of a cylindrical porous media burner enabled the simulation of the premixed combustion process, with a focus on the analysis of the effects of equivalence ratio, inlet velocity, and temperature on combustion characteristics and pollutant emissions. The findings of the study demonstrate that augmenting the equivalence ratio and inlet velocity results in elevated flame temperature and heightened NO and CO emissions. Conversely, an increase in inlet temperature has been shown to enhance both flame and outlet temperatures while concomitantly reducing pollutant emissions. The system reveals the variation patterns of combustion stability and emission characteristics across various operating conditions, with the findings offering theoretical support for optimizing burner design and operational control. This finding is of considerable significance for the achievement of highly efficient, low-pollution combustion.

A field experiment was conducted in 2019–2020 and 2020–2021 at Rogoza, Fala, and Brežice in Slovenia to examine the biological viability of a mixed intercropping system and the effect of winter catch crops (WCCs) on maize growth parameters. The experiment included Italian ryegrass (IR) in pure stands, fertilized with nitrogen (N) in spring (70 kg N ha−1), mixtures of crimson clover and red clover 50:50 (C), and intercropping between IR and C (IR+C). Neither mixture was fertilized with N in spring. We evaluated different competition indices and biological efficiency. Relative crowding coefficient (RCC) and actual yield loss (AYL) exceeded 1, indicating a benefit of IR+C intercropping. The IR in intercropping was more aggressive, as indicated by positive aggressivity (A) and a competitive ratio (CR) > 1, and it dominated over C in IR+C (that had negative A values and CR < 1). The competitive balance index (Cb) differed from zero, the relative yield total (RYT) was 2.24, the land equivalent coefficient (LEC) exceeded 0.25, the area–time equivalent ratio (ATER) exceeded 1, and land use efficiency (LUE) exceeded 100%. IR+C exhibited the highest total aboveground dry matter yield of maize (29.22 t ha−1), the highest nitrogen content in dry matter grain yield of maize (206.35 kg ha−1), the highest nitrogen and potassium content in maize stover (105.7 and 105.7 kg ha−1, respectively), and the highest nitrogen and potassium content in the total aboveground dry matter of maize (312 and 267.3 kg ha−1, respectively). The C/N ratio in dry matter yield of IR was 45.35, and in IR+C it was 33.43, which means that the mixture had a positive effect on nutrient release in maize. The ryegrass–clover mixture, according to the calculated biological indices, had advantages over pure stands and had a positive effect on maize yield.

IntroductionOptimizing nutrient cycling in diversified cropping systems is essential for sustainable agriculture. While intercropping legumes with cereals can enhance complementary resource use, the interaction between phosphorus (P) fertilization and such systems in restructuring rhizosphere microbiomes and driving synergistic productivity gains in alkaline soils remains unclear.MethodsWe conducted a long-term field experiment, integrating amplicon sequencing with comprehensive agronomic and soil analyses to investigate this interaction in a maize-peanut intercropping system under P fertilization.ResultsPhosphorus fertilization significantly increased the yields of intercropped maize (by 52.12%) and peanut (by 43.60%), while simultaneously enhancing the intercropping yield advantage (IYA; +60.77%) and land equivalent ratio (LER; +2.54%). Soil P availability was the dominant environmental driver, explaining 73.46% and 84.39% of the variance in bacterial and fungal community structure, respectively. Phosphorus addition and intercropping selectively enriched keystone functional taxa, including the nitrifying bacterium Nitrospirae and the saprophytic fungus Mortierellomycota, whose abundances correlated strongly with improved soil nutrient availability and crop performance. Concurrently, intercropping suppressed the pathogen-rich phylum Ascomycota.DiscussionOur findings demonstrate that the synergy between P fertilization and intercropping enhances crop productivity through a microbiome-mediated mechanism. This synergy restructures the rhizosphere community into a functionally beneficial state, fostering a self-reinforcing plant–microbe–soil feedback loop. This study provides a mechanistic framework for developing integrated, microbiome-informed management strategies to support sustainable agricultural intensification.

Limited research has explored how fines content impacts static liquefaction at critical state in soils with different stress histories using the equivalent void ratio concept, especially when considering fabric techniques. This study bridges this gap through undrained triaxial tests analyzing the effects of fines content and stress history on critical state behavior in clean and silty sand specimens. Specimens were reconstituted with systematically varied fines content, packing densities, and fabric techniques. Results showed that for a given stress history and initial density, dry pluviated specimens displayed a consistent decline in critical state shear strength as fines content increased. In contrast, moist-tamped specimens exhibited an opposite trend, with increasing low-plastic fines significantly enhancing shear strength across all parameters. Stress history was found to increase critical shear strength in all cases. Furthermore, the equivalent granular void ratio concept unified steady-state/critical state data into a single relationship in the e* - log (p’) space, termed the equivalent steady-state line, particularly for dry pluviated specimens. These findings advance understanding of sand-fines mixture behavior, including flow potential and mechanisms influenced by stress history.

In the steel industry, reheating furnaces are a significant source of carbon emissions. Co-firing natural gas and ammonia in reheating furnaces reduces carbon emissions and mitigates ignition difficulties and the limited flammability range of ammonia. This research develops a three-dimensional model for combustion, fluid dynamics, and heat transfer in a reheating furnace to investigate slab heating and emission with a natural gas/ammonia blended fuel. Numerical results demonstrate that, under constant calorific value conditions, the average temperature of the discharged slab decreases following ammonia blending, with the greatest temperature differential of 110 K achieved at a 10% ammonia blending ratio. Moreover, as the ammonia blending ratio increases from 0 to 40%, the mass fraction of CO first rises and subsequently declines, ultimately decreasing by 18%. Meanwhile, the CO2 emissions at the outlet decrease by 17.6% to 40.7%. The mass fraction of unburned NH3 rises to 0.0271, whilst NOx emissions diminish from 49.47 ppm to 14.23 ppm. These changes are attributed to the low combustion efficiency and burning rate of ammonia, coupled with the reduced furnace temperature during ammonia-blended combustion, which weakens radiative heat transfer. Thus, optimizing the equivalence ratio along with applying hydrogen can improve the thermal efficiency of the reheating furnace. This study provides insight into the operational characteristics of a full-scale walking-beam reheating furnace operating under natural gas-ammonia co-firing conditions, providing theoretical guidance for enhancing the thermal efficiency of furnaces.

ABSTRACT The supersonic combustion of ethylene in a pylon-cavity configuration with curved pylons was studied numerically. A curvature at the trailing edge of the standard pylon was added, and the injection was performed along the rear surface of the pylon. A total of four pylon configurations were tested, including the standard pylon. The freestream conditions corresponding to the Mach numbers within 5 to 6 were considered in the current study with an equivalence ratio of 0.3. The unsteady Reynolds Averaged Navier-Stokes simulations were carried out using, an open-source finite volume solver. A 9-species 10-step reaction mechanism developed for scramjet combustor conditions was implemented for the chemical kinetics. The SST k − ω turbulence model was used as a closure for the Reynolds stresses and the Turbulent-Chemistry-Interaction was captured using the Partially Stirred Reactor model. The numerical scheme used in the study was validated using the experimental wall pressure and CH* chemiluminescence from the literature. The results showed that curved pylons produce better combustion efficiency than the standard pylon. The Takeno Flame Index was used for the identification of premixed and non-premixed combustion modes. The flame modes were also found to be affected by the curvature effects. As the bottom curvature angle decreased, the overall heat release power was found to be increased. The pylon with the lowest curvature angle produced about 15% higher heat release power than the standard pylon. The turbulent flame regime diagram in Damköhler and turbulent Reynolds number coordinates was analyzed. The flame was found to occur in the Perfectly Stirred Reactor/Laminar chemistry regime due to the relatively large chemical time scales associated with the ethylene combustion.

The integration of sweetpotato (Ipomoea batatas (L.) Lam) with legumes provides innovative cropping systems that enhance land use, crop yields, soil health, and climate change adaptation among farmers in Malawi. Declining soil fertility, crop yields, and shrinking productive land continue to affect agricultural productivity and food security. Sustainable intensification of sweetpotato production is therefore essential. This study assessed sweetpotato–pigeonpea intensification options for productivity and land use efficiency in Malawi. Experiments were conducted at Chitedze, Baka, and Chitala during the 2020/2021 and 2021/2022 cropping seasons. Five spatial arrangements—(i) sole sweetpotato, (ii) sole pigeonpea (Cajanus cajan (L.)), (iii) sweetpotato–pigeonpea (1:1), (iv) sweetpotato–pigeonpea (2:1), and (v) sweetpotato–pigeonpea within row (SP-PP_row)—were evaluated using a randomized complete block design in a split-plot arrangement with three replications. Analysis of variance was performed, and means were separated by LSD₀.₀₅. Land equivalent ratio (LER) and Absolute Mixture Effect (AME) were used to determine productivity. Cropping systems, locations, and seasons significantly influenced all measured parameters. Intercropping is more productive than sole cropping, with LERs exceeding one (LER &gt; 1), indicating a yield advantage. The 1:1 and 2:1 arrangements showed the highest yield advantages of 3.57 and 2.55 tha⁻¹ above sole cropping, contributing 71% and 31% to total land productivity, respectively. Sweetpotato–pigeonpea intercropping enhanced land use efficiency, productivity, and pest and disease suppression, offering potential to improve food security, dietary diversity, and farmer incomes. The 1:1 and 2:1 arrangements are recommended for sustainable and productive farming systems in Malawi. Keywords: Sweetpotato - legume, intercropping, pigeonpea, productivity, yield, land use efficient

Thermochemical conversion of oil palm empty fruit bunch into fuel gas in a fluidized bed gasifier.

Heavy metal exposure and all health outcomes: An umbrella review of meta-analyses.

Prediction of equivalent damping ratio for round-ended hollow railway bridge piers with variable sections based on GA-BP neural network and quasi-static test

Numerical studies on the effects of the supporting struts and center equivalence ratio on flow field and fuel mixing performance in a circular axisymmetric combustor

ABSTRACT Soil organic carbon (SOC) accrual is vital for mitigating climate change and building resilient agriculture ecosystems. Introducing agricultural practices based on crop diversification is crucial for efficient nutrient stoichiometric management and crop productivity. Therefore, this study aimed to evaluate the effects of different strip intercropping systems on SOC management, SOC and total nitrogen (TN) stocks, carbon management indices (CMI), as well as carbon, nitrogen and phosphorus (P) stoichiometry. Results indicated that SOC and total N were increased across all intercropping systems compared to monocropping. The land equivalent ratio (LER) ranged from 1.29 to 1.36, with a maximum value in the sesame–guar intercropping system, indicating yield advantage over monocropping. Total N and SOC stocks were enhanced by 96% and 66% during millet–mungbean and sesame–soybean intercropping, while maximum SOC mineralisation (32%) was observed in millet–mungbean intercropping. Sesame–mungbean increased the soil active carbon and CMI by 65%–163%, followed by millet–mungbean (50%–109%), sesame–soybean (64%–80%) and sesame–guar (63%–75%) in comparison with the sole cropping. Narrowed soil C:N and N:P ratios were found with strip intercropping, highlighting N and P mineralisation, which enhanced carbon accumulation, as compared to the mono‐cropping system. Increasing active carbon levels and nutrient availability such as nitrate and phosphate favour SOC storage due to reduced decomposition of stable carbon. However, soil C:N stoichiometry showed an exponentially declined nonlinear relationship with SOC stock, signifying that nitrogen availability played a critical role in soil carbon stabilisation. In contrast, the positive association of soil N:P ratio with SOC stock highlighted that balanced nitrogen is vital for SOC accumulation relative to phosphorus. It was concluded that legume strip intercropping inclusion in cereal crops enhances SOC stock, carbon management indices and optimises crop yield by enhancing soil multifunctionality while maintaining soil nutrient stoichiometry, particularly for low carbon agroecosystem.

Research on the explosion dynamics and mechanism of locally premixed methanol vapor/hydrogen blended gas in a semi-enclosed space: Effect of equivalent ratio and hydrogen blended ratio

This study conducted numerical simulations to enhance particle combustion and reduce drag by increasing blockage in a solid rocket scramjet combustor. The simulation was performed using the Eulerian–Lagrangian model, under flight conditions of Mach 6 at 25 km, with an equivalence ratio of 0.56. Ramps of different heights were installed near the exit of the combustor to act as a throat and alter the blockage ratio. The results indicate that higher ramps increase blockage, resulting in higher temperature and pressure. With higher blockage, the reaction rates of kinetics-controlled particles significantly accelerate due to the increased temperature and pressure. In contrast, the reaction rates of diffusion-controlled particles remain relatively unchanged. Nevertheless, the combustion efficiency of both particles is enhanced owing to the longer residence time. Higher blockage increases the wave drag due to the intensified shock train. However, the calculation of Rayleigh loss indicates that increasing blockage reduces the heat drag by a maximum of 77.42%, even with more heat release. Despite the additional drag caused by the introduction of ramps, the overall total pressure loss is decreased by up to 10.67% (with 35 mm ramps). These findings provide novel insights for the design of solid rocket scramjet engines with high performance.

Thermal protection is a crucial issue for Combined-Cycle Engines (CCE) in advanced propulsion systems. Uneven flow distribution and localized heat transfer deterioration limit the application of parallel cooling channels in CCE under multimodal operating conditions. The pin-fin structure presents a promising approach for the next-generation regenerative cooling channel design. The flow and supercritical-pressure heat transfer behavior of hydrocarbon fuel flowing in pin-fin regenerative cooling channels were investigated in this work via large eddy simulations and experiments. Detailed analyses of flow turbulence, vortex structures, and thermal fields were conducted for three distinct pin-fin geometries (circular, elliptic, and square). Results indicated that the square pin-fin configuration exhibits the highest thermal performance factor, with a Thermal Performance Factor 3.5 times greater than that of the iso-parallel channel and reduces the wall temperature by ∼40%. The heat transfer is enhanced by impingement cooling resulting from the horseshoe vortex near the leading edge of the fin and the unsteady Kármán vortex after the flow separation point, which increases the turbulent intensity of the shear layer. The elliptical pin-fin exhibits comparable heat transfer to the circular one while inducing only 19% of the pressure drop. Ground-based direct-connect thermal test at a simulated flight Mach number of 6 was conducted to verify the heat transfer efficiency of the pin-fin cooling plates. Experiment results demonstrated that the average temperature on the heating surface of the square pin-fin regenerative cooling plate can be reduced up to 27% compared to that of the iso-parallel cooling plate, while the non-uniform circumferential temperature distribution caused by uneven flow distribution can also be significantly mitigated. Effects of coolant mass flow rate, combustion equivalence ratio, and coolant pressure on heat transfer efficiency decrease successively. This work provides quantitative design guidelines and fundamental insights for implementing high-efficiency, lightweight pin-fin regenerative cooling channels in advanced CCE.