Search Results (263)

In view of the depletion of high-grade magnesite resources in China, this study presents a comparative analysis of two industrial fused magnesia products produced via a flotation–fusion route. A low-grade magnesite (DSQLM-3, MgO 41.48 wt.%) was upgraded by reverse flotation to a concentrate (FDSQLM-3, MgO 47.55 wt.%) with >97% SiO₂ removal. Two fused magnesia samples (FM-1 from natural high-grade ore DSQLM-1; FFM-3 from concentrate FDSQLM-3) were produced under identical arc-furnace melting (2800 °C, 4 h), followed by natural cooling. Although FFM-3 showed higher MgO (97.61 vs. 97.25 wt.%), its bulk density was comparable to FM-1 (3.45 vs. 3.46 g/cm³). XRD/Rietveld refinement and SEM-EDS indicated that CMS dominated the Ca–silicate assemblage in FM-1, whereas β/γ-C₂S was observed in FFM-3, coinciding with a higher CaO/SiO₂ (C/S) ratio (2.85 vs. 0.68). Image analysis further showed higher grain boundary microcrack metrics in FFM-3. These observations are consistent with reports in the literature stating that the β → γ transformation of C₂S during cooling involves ~12% volume expansion that can contribute to cracking; however, cooling history and composition were not independently controlled in this industrial comparison, so the relationships are interpreted as data-supported associations rather than isolated causality. The results suggest that beneficiation strategies may benefit from managing residual oxide balance (especially C/S ratio) in addition to reducing total impurities. Mechanical and thermomechanical properties were not measured and should be evaluated in future work. Full article

This study develops a green, high-performance, cement-based grout by replacing manufactured sand with iron tailings sand (ITS) at ratios of 0–50% to address resource depletion. Fluidity, mechanical strength, and expansion rates were experimentally evaluated to determine engineering feasibility. The results indicate that while ITS inclusion reduces fluidity due to particle morphology, it significantly enhances compressive strength through a physical filling effect. Specifically, the 30% replacement group achieved a peak 28-day compressive strength of 100.4 MPa. Comprehensive analysis identifies 40% as the optimal replacement rate, where the grout strictly satisfies relevant industry specifications regarding fluidity, early strength, and volume stability. This research demonstrates the practical significance of utilizing industrial solid waste to produce high-performance sleeve grout for prefabricated construction. Full article

To study the sulfate corrosion behavior of potassium magnesium phosphate cement (PMPC) paste, the sulfate content, strength, and length of PMPC specimens were measured at different corrosion ages under 5% Na₂SO₄ solution soaking conditions, and the phase composition and microstructure were analyzed. The conclusion is as follows: In PMPC specimens subjected to one-dimensional SO₄²⁻ corrosion, the relation between the diffusion depth of SO₄²⁻ (h) and the SO₄²⁻ concentration (c (h, t)) can be referred by a polynomial very well. The sulfate diffusion coefficient (D) of PMPC specimens was one order of magnitude lower than Portland cement concrete (on the order of 10⁻⁷ mm²/s). The surface SO₄²⁻ concentration c (0, t), the SO₄²⁻ computed corrosion depth h₀₀, and D of FM2 specimen containing 20% fly ash (FA) were all less than those of the FM0 specimen (reference). At 360-day immersion ages, the c (0, 360 d) and h₀₀ in FM2 were obviously smaller than those in FM0, and the D of FM2 was 64.2% of FM0. The strengths of FM2 specimens soaked for 2 days (the benchmark strength) were greater than those of FM0 specimens. At 360-day immersion ages, the residual flexural/compressive strength ratios (360-day strength/benchmark strength) of FM0 and FM2 specimens were all larger than 95%. The volume linear expansion rates (S_n) of PMPC specimens continued to increase with the immersion age, and S_n of FM2 specimen was only 49.5% of that of the FM0 specimen at 360-day immersion ages. The results provide an experimental basis for the application of PMPC-based materials. Full article

Voluntary carbon markets (VCMs) are growing rapidly but remain structurally fragmented due to verification delays, lifecycle opacity, inconsistent metadata, and capital mobilisation bottlenecks. While blockchain is often proposed as a digitalisation layer to improve transparency and traceability, this paper reframes tokenisation as a sector-aware financial infrastructure capturing the full lifecycle of carbon credits. Rather than treating it as a digital overlay, this study argues that tokenisation functions as a modular, automated architecture capable of absorbing sector-specific frictions within VCMs. Drawing on 1495 registry-compliant projects from the Berkeley Voluntary Offsets Database (BVOD v2025-06), the study develops the sector tokenisation opportunity matrix (STOM). This diagnostic framework maps registry-derived indicators—issuance volume, credit retirement ratio, and average credits per project—to three tokenisation functions: market expansion, retirement acceleration, and structuring for scale and fragmentation. STOM reveals how tokenisation can address VCM fragmentation by mobilising capital, reinforcing lifecycle integrity, and enabling assets to be packaged across diverse project types. By linking friction diagnostics to governance-sensitive infrastructure design, the research proposes a sector-aware blueprint for climate finance infrastructure and positions tokenisation as a strategic tool for scaling high-integrity climate action. Full article

Large-format additive manufacturing (LFAM) is a manufacturing process in which high volumes of material are extruded in a layer-by-layer fashion to create large structures with often complex geometries. The Loci-One system, operated and developed by Loci Robotics Inc., is an LFAM-type system that was used to print single-bead walls of 20% by weight carbon fiber reinforced acrylonitrile butadiene styrene (CF-ABS) using various print parameter inputs. This study observed the influence of bead width and layer time on thermomechanical performance via material characterization techniques that accounted for the complex microstructure of LFAM parts to develop a better understanding of parameter–structure–property relationships. Printed parts were characterized by measuring the coefficient of thermal expansion (CTE) and interlayer strength. Near the edges of the printed beads, microscopy revealed a “thinning effect” experienced by a shell composed primarily of highly oriented fiber as the bead width was increased; however, this effect was diminished with a higher shear rate. The CTE results demonstrated the influence of mesostructure on the thermomechanical response. Increased shear rates were expected to lower CTE in the x-direction due to a higher ratio of fiber oriented in the print direction, but this relationship was not always observed. For the larger bead widths printed at higher shear rates, the randomly oriented fiber at the core dominated the thermomechanical response and increased CTE overall in the x-direction. A heat transfer model was developed for this work to determine how much time was required for the deposited bead to cool to the glass transition temperature. Interlayer strength results revealed a rapid decrease once the printed layer time exceeded the time required for the extrudate to cool below the glass transition temperature. Full article

High-volume fly ash (FA) mitigates the expansion of magnesium oxide (MgO), and the uneven regional distributions of high-quality FA collectively limit the application of roller-compacted concrete admixed with MgO (M-RCC). This study evaluated the autoclave expansion and compressive strength of MgO-admixed cement paste and mortar, wherein phosphorus slag (PS) was used to partially or fully replace FA. The expansion mechanism within the MgO-FA-PS system was explored. Results show that the autoclave expansion of the mortar increased as the proportion of PS replacing FA rose. At a replacement ratio of 33% (i.e., 20% of the total mass of cementitious materials), the mortar maintained the same ultimate MgO dosage (8%) as the control specimen, yet exhibited a 12.7% increase in expansion and an 8.8% decrease in strength. The mechanism is that PS is less efficient than FA in reducing the pore solution alkalinity, thereby promoting the formation of more brucite. The growth pressure of brucite crystals expands the internal gaps in the matrix and coarsens the pore size, resulting in greater expansion and reduced compressive strength. The results of this study can provide theoretical and technical insights for the application of PS in M-RCC. Full article

The excellent thermal performance, quiet operation, and fuel flexibility of free-piston Stirling machines enable their broad application potential in sectors such as aerospace, distributed power generation, and industrial waste heat utilization. The impact of structural parameters on the output characteristics of the free-piston Stirling engine was investigated using a parametric MATLAB model based on an isothermal thermodynamic approach. Parameters such as the dead volume ratios (χ_H, χ_K, χ_R), temperature ratio τ, sweep volume ratio k, piston phase angle a_dr, and minimum pressure angle θ were evaluated for their effects on the dimensionless power Z. The results indicate that the dead volume ratio in the cold space χ_K has the most significant influence on system performance, followed by the hot space χ_H, while the regenerator χ_R exhibits a comparatively weaker effect. All three parameters demonstrate the existence of optimal design intervals. The dimensionless power Z decreases monotonically with increasing dead volume ratio. Moreover, this decline is intensified at higher temperature ratios τ, indicating that the influence of dead volume becomes more significant under larger τ values. The interaction between these parameters can be described by $Z=0.0037{\tau }^2-0.0045\tau +0.0021$. An excessively large sweep volume ratio k tends to degrade the system’s output performance. An empirical correlation between k and the dimensionless power can be established as follows $Z=1.53(1-e^{-3.37k})+0.01$. A moderate increase in the piston phase angle a_dr and a reduction in the minimum pressure angle θ contribute to improved system performance by enlarging the p-v diagram area and enhancing the utilization of gas expansion. The relationship between a_dr and the dimensionless power Z follows a linear trend, expressed as $Z=0.341a_{dr}-0.2104$. A well-defined functional relationship exists between the minimum pressure angle θ and the dimensionless power output Z, which can be expressed as $Z=2.18\times {10}^{-4}{\theta }^2-0.0261\theta +0.7065$. A coupling regulation mechanism and design strategy have been developed to facilitate the coordinated optimization of multiple parameters in free-piston Stirling engines, which delivers theoretical guidance that is expected to support the engineering implementation of next-generation, high-performance Stirling technologies. Full article

Cultivation practices such as fruit thinning and soil management with ground covers are commonly applied in Citrus orchards, yet their physiological impact on young trees remains poorly documented. This study evaluated the effects of manual fruit thinning and weed-control mesh on vegetative growth, fruit development, and leaf mineral composition of Citrus sinensis L. Osbeck cv. ‘Navelina’ grafted on Citrus macrophylla. A six-month field experiment was conducted in southeastern Spain under semi-arid Mediterranean conditions using six treatments that combined different soil coverage and subsurface drainage systems. After physiological fruit drop, trees were standardized to ten fruits per plant. Vegetative parameters (canopy and trunk dimensions), fruit growth (size, juice content), and foliar nutrient concentrations were monitored. Trees with ground cover showed significantly greater canopy expansion and juice yield compared to uncovered controls. A negative correlation between fruit number and canopy-to-fruit volume ratio highlighted the trade-off between vegetative vigor and fruit load. Foliar analysis revealed lower micronutrient concentrations (Fe, Mn, B, Zn) in uncovered trees, suggesting reduced nutritional status. These findings demonstrate that combining early thinning with weed-control mesh promotes vegetative vigor, improves juice yield, and enhances nutrient uptake, providing practical insights for optimizing orchard establishment and early Citrus productivity in water-limited environments. Full article

Based on the need for safe disposal of hazardous waste incineration fly ash (HFA), this study evaluated the solidification/stabilization (S/S) performance of silicate cement, sodium dihydrogen phosphate (NaH₂PO₄), and sodium dimethyl dithiocarbamate (SDD) used individually and in combination. The raw HFA failed the leaching test for Pb, Zn, Cd, and Ni, with their concentrations exceeding the GB16889-2024 limits by factors of 3.1, 2.45, 1.67, and 1.1, respectively. While cement (150% dosage) effectively immobilized Pb, and Cd with >90% leaching reduction, it resulted in significant volume expansion (2.7-fold). NaH₂PO₄ excelled in Pb stabilization (100% efficiency at 20% dosage) via insoluble phosphate formation but required high doses. SDD effectively chelated Zn (63.4% efficiency at 5% dosage) but was less effective for Pb and costly. A synergistic combination of 5% cement, 15% SDD, and 10% NaH₂PO₄ was identified as the possible optimal formulation, successfully immobilizing all heavy metals within regulatory limits. This combined approach minimized dosage, controlled volume expansion ratio (R_VE) (~1.31), and reduced cost. The low initial dioxin content (7.6 ng TEQ/kg) was unaffected by S/S treatments and remained compliant. Mechanistic analyses (XRD, FTIR, SEM-EDS) confirmed the formation of C-S-H gels from cement, insoluble phosphates from NaH₂PO₄, and metal chelates from SDD, collectively transforming the HFA into a compact, low-porosity matrix conducive to safe disposal. This stabilization and solidification strategy not only achieves the safe disposal of hazardous waste incineration fly ash but also contributes to the goals of sustainable waste management by reducing the environmental footprint of treatment processes and minimizing the final disposal volume. Full article

This study addresses the challenge of low working gas ratios in China’s underground gas storage (UGS) facilities by optimizing geomechanical evaluations to enable safe pressure increases and capacity expansion. Through mini-fracturing tests conducted at the Liaohe Gas Storage Group, a cross-validated analytical framework was established, integrating the square-root-of-time, Geomechanical (G) function, and flow-back pressure–volume methods. This framework enables precise determination of the dynamic maximum safe pressure, effectively balancing storage efficiency against the risks of fracture and fault activation. The results indicate that the minimum horizontal stress is 37% higher in the caprock than in the reservoir, confirming the integrity of the natural stress barrier. A mere 0.39% discrepancy in interpretation results validates the consistency of the methodology. The derived three-dimensional (D) in situ stress model reveals that the upper sandstone section exhibits 15–20% higher horizontal stress than deeper intervals, acting as a secondary barrier against fracture propagation. Theoretically, we propose a ‘stress differential gradient sealing’ mechanism to explain the buffering effects observed in the sandstone–mudstone transition zone. Practically, we developed a standardized testing protocol for complex geological conditions, which achieved a 15% increase in the maximum safe operating pressure at the Liaohe facility. This study provides critical insights for optimizing gas storage operations. Full article

Differing from traditional isobaric combustion, a pulse detonation-based ramjet (PD-Ramjet) was proposed in this study to enhance the efficiency of traditional ramjets. By using a two-dimensional numerical simulation method, the filling process and detonation initiation process of the hydrogen/air stoichiometric mixture in channels equipped with typical flameholders were studied under the inflow condition of a ramjet combustor, and the influences of the typical flameholders on the filling process and detonation initiation process were analyzed. Single cavity, sudden expansion cavity, central cavity, and V-shaped groove were chosen as typical ramjet flameholders. The simulation and analysis results indicated that the flameholders would affect the filling effect, and the blocking ratio had a great influence on the filling process. The hydrogen volume discharged from the outlet of the channel and the time for mixed gas to reach the outlet were related to the blocking ratio and the cavity aft wall inclination angle. The detonation initiation process revealed that the flameholders promoted the generation of detonation waves. Contrastingly, the detonation wave could not be initiated in the channel without flameholders despite the better filling effect. Moreover, different flameholders would change the position of high-pressure point formation and the time for generating the stable detonation wave. On the whole, the sudden expansion cavity had a lower blockage ratio and also gave consideration to the filling effect and detonation initiation characteristic, making it the most suitable flameholder structure for PD-Ramjet in this study. Full article

SDG Indicator 11.3.1 assesses urban land use efficiency (LUE) through the ratio of the land consumption rate (LCR) to the population growth rate (PGR), or LCRPGR. However, its methodology is restricted to two-dimensional built-up area expansion, excluding vertical development and limiting insight into the structural mechanisms underlying efficiency outcomes. This study aims to integrate vertical urban growth into SDG 11.3.1 monitoring to improve the interpretation of efficiency outcomes. We introduce the Built-up Area–Built-up Volume (BUA–BUV) trajectory framework, which embeds vertical growth into LUE monitoring. The framework represents urban growth as trajectories in normalized BUA–BUV space and classifies them by prevailing built form (horizontal, balanced, vertical) and growth modality (expansion or intensification). This classification is then coupled with LCRPGR to link efficiency outcomes with spatial structure. We apply the framework to 10,856 urban centres worldwide using Global Human Settlement Urban Centre Database (GHS-UCDB 2025) data from 1980 to 2020. Results show that inefficient growth (LCRPGR > 1) dominated, affecting 69% of centres during 1980–2000 and 52% during 2000–2020, while inefficiency linked to demographic decline (LCRPGR ≤ 0) rose from 9% to 20%. Efficient centres (0 < LCRPGR ≤ 1) increased from 22% to 29%. Across all efficiency classes, BUA–BUV trajectories revealed a prevailing pattern of horizontal expansion, with similar LCRPGR values associated with structurally divergent growth paths. Vertically intensifying development was rare, even among efficient centres. The BUA–BUV framework embeds structural context into efficiency assessments, thereby strengthening SDG 11.3.1 monitoring and informing policies for compact and sustainable urbanization. Full article

Soil stabilization is a key process in geotechnical engineering, particularly for expansive clay soils that exhibit low strength and high volume-change potential. This study examines the use of waste tire powder (WTP) and autoclaved aerated concrete powder (ACP) as sustainable soil additives to improve mechanical performance while promoting sustainable waste recycling. Clayey soils from the Çorlu/Tekirdağ region were blended with varying proportions of WTP and ACP, and their properties were evaluated through Standard Proctor compaction, unconfined compressive strength (UCS), and California bearing ratio (CBR) tests. The results showed that UCS increased from 3.7 MPa to 4.5 MPa with 5% ACP, while CBR values rose from 21.3% to 29.8% with 17% ACP addition. Incorporating 2% WTP enhanced elasticity and reduced brittleness, although higher WTP contents (4%) lowered cohesion and strength. The optimum formulation, 2% WTP + 5% ACP, produced balanced improvements in strength, stiffness, and deformation resistance. The novelty of this research lies in establishing a hybrid stabilization mechanism that combines the elastic contribution of WTP with the pozzolanic bonding of ACP. Beyond technical improvements, recycling these industrial by-products mitigates environmental pollution, reduces disposal costs, and provides economic benefits. Thus, this study advances both the scientific understanding and practical application of sustainable soil stabilization. Full article

Objectives: Rapid maxillary expansion (RME) is widely used in orthodontics to correct transverse maxillary deficiencies. Beyond its skeletal and dental effects, RME may influence upper airway dimensions and respiratory function, particularly in growing individuals. This study aimed to evaluate the impact of RME on pulmonary function in adolescents using spirometric measurements. Materials and Methods: Fifteen adolescent patients (8 females, 7 males; mean age: 13.93 ± 2.89 years) diagnosed with maxillary transverse constriction underwent orthodontic treatment with acrylic-bonded RME appliances over a mean duration of 3.56 ± 0.67 months. Respiratory function was assessed via spirometry at baseline (T0) and one day after appliance removal (T1). Parameters recorded included peripheral oxygen saturation (SpO₂), forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), FEV₁/FVC ratio, and vital capacity (VC). Data were analyzed using the paired-samples t-test (for normally distributed variables) or the Wilcoxon signed-rank test (for non-normal distributions), with statistical significance set at p < 0.05. Results: Following RME treatment, all respiratory parameters showed a consistent upward trend but did not reach statistical significance. SpO₂ increased from 96.98 ± 0.96% to 97.01 ± 0.98% (p = 0.925). VC rose from 2.86 ± 1.07 L to 3.03 ± 0.80 L (p = 0.626). The FEV₁/FVC ratio improved from 90.88 ± 12.17% to 92.34 ± 7.37% (p = 0.742). Mean FEV₁ increased from 2.61 ± 0.72 L to 2.72 ± 0.68 L (p = 0.518), while FVC rose from 2.87 ± 0.75 L to 2.96 ± 0.69 L (p = 0.547). No adverse effects were reported during the treatment period. Conclusions: This study identified a non-significant but consistent trend toward improved pulmonary function following RME in adolescents. These preliminary findings should be considered hypothesis-generating rather than confirmatory evidence, as none of the outcomes reached statistical significance. While the observed upward trends in oxygen saturation, lung volumes, and expiratory performance suggest potential respiratory benefits, larger-scale, controlled, and long-term studies incorporating both spirometric and anatomical airway assessments are needed to validate these observations. Full article

Understanding and modeling the effect of magnetic fields on flows that present separation properties, such as those over a backward-facing step (BFS), is critical due to its role in metallurgical processes, nuclear reactor cooling, plasma confinement, and biomedical applications. This study examines the hydrodynamic and magnetohydrodynamic numerical solution of an electrically conducting fluid flow in a backward-facing step (BFS) geometry under the influence of an external, uniform magnetic field applied at an angle. The novelty of this work lies in employing an in-house finite-volume solver with a collocated grid configuration that directly applies a Newton–like method, in contrast to conventional iterative approaches. The computed hydrodynamic results are validated with experimental and numerical studies for an expansion ratio of two, while the MHD case is validated for Reynolds number $Re=380$ and Stuart number $N=0.1$. One of the most important findings is the reduction in the reattachment point and simultaneous increase in pressure as the magnetic field strength is amplified. The magnetic field angle with the greatest influence is observed at $\phi =\pi /2$, where the main recirculation vortex is substantially suppressed. These results not only clarify the role of magnetic field orientation in BFS flows but also lay the foundation for future investigations of three-dimensional configurations and coupled MHD–thermal applications. Full article