Search Results (126)

Numerous dark linear recurrent features called Recurring Slope Lineae (RSL) are observed on Martian surfaces, hypothesized as footprints of high-salinity liquid flow. This paper experimentally examined this “wet hypothesis” by analyzing the aspect ratios (length/width) of the flow traces on the granular material column to investigate how they vary with the granular material column, liquid and its flow rate, and inclination. While pure water produced low aspect ratios (<1.0) on the Martian regolith simulant column, high-salinity fluid (CaCl₂(aq)) traces exhibited significantly higher aspect ratios (>4.0), suggesting that pure water alone is insufficient to explain RSL formulation. Furthermore, the aspect ratios of high-salinity fluid traces on Martian regolith simulants were among the highest observed across all studied granular materials with similar particle sizes, aligning closely with actual RSL observed on Martian slopes. The results further suggest that variable ARs of actual RSL at the given slope can partly be explained by variable flow rates of high-salinity flow as well as salinity (i.e., viscosity) of flow. The results can be attributed to the unique granular properties of Martian regolith, characterized by the lowest permeability and Beavers–Joseph slip coefficient among the studied granular materials. This distinctive microstructure surface promotes surface flow over Darcy flow within the regolith column, leading to a narrow and long-distance feature with high aspect ratios observed in Martian RSL. Thus, our findings support that high-salinity flows are the primary driver behind RSL formation on Mars. Our study suggests the presence of salts on the Martian surface and paves the way for further investigation into RSL formulation processes. Full article

Poly[bis(4-phenyl) (2,5,6-trimethylphenyl) amine (PTAA), as a hole transfer material, has been widely used in perovskite solar cells (PSCs). However, the optimal solvent for preparing the PTAA solution and coating the PTAA layer is still uncertain. In this work, we investigated three types of organic solvents (toluene, chlorobenzene and dichlorobenzene) for processing PTAA layers as the hole transport layer in PSCs. Based on the experimental verification and molecular dynamics simulation results, all the evidence indicated that toluene performs best among the three candidates. This is attributed to the significant polarity difference between toluene and PTAA, which leads to the formation of a uniform surface morphology characterized by granular protuberances after spin coating. The contact area of the hole transfer layer with the surface aggregation is increased in reference to the rough surface, and the hydrophilicity of the PTAA layer is also increased. The improvement of these two aspects are conducive to the effective interfacial charge transfer. This leads to the generation of more photocurrent. The PSCs employing toluene-processed PTAA exhibit an average power conversion efficiency (PCE) of 19.1%, which is higher than that of PSCs using chlorobenzene- and dichlorobenzene-processed PTAA (17.3–17.9%). This work provides a direct optimization strategy for researchers aiming to fabricate PSCs based on PTAA as a hole transport layer and lays a solid foundation for the development of high-efficiency inverted PSCs. Full article

The construction industry, characterized by high energy consumption and carbon emissions, plays a pivotal role in climate change mitigation. This paper employs bibliometric analysis, based on 282 articles from the SCIE and SSCI in the Web of Science spanning 1992–2022, to explore research trends and themes in Carbon Emissions of Construction Industry (CECI). A manual review was conducted to identify challenges and possibilities concerning accounting scales, objects, boundaries, and methods in CECI research. Key findings include (1) temporal and thematic evolution, with a notable increase in research activity since 2015, primarily focusing on energy efficiency, sustainable development, green building technologies, and policy evaluation; (2) scale-specific gaps, as 80.7% of studies are conducted at macro (national/regional) or micro (building/material) levels, while city-scale analyses are significantly underrepresented, with only 13 articles identified; (3) object granularity deficiencies, with 74.8% of studies not distinguishing between building types, resulting in rural residential, educational, and office buildings being significantly underrepresented; (4) system boundary limitations, as few studies account for emissions from building demolition or the disposal and recycling of construction waste, indicating a substantial gap in life-cycle carbon assessments. Furthermore, the predominant reliance on the carbon emission factor method, along with embedded assumptions in accounting processes, presents challenges for improving carbon accounting accuracy. This review synthesizes insights into prevailing research scales, object classifications, system boundaries, and methodological practices, and highlights the urgent need for more granular, lifecycle-based, and methodologically diverse approaches. These findings provide a foundation for advancing CECI research toward more comprehensive, accurate, and context-sensitive carbon assessments in the construction sector. Full article

The recovery of green waste and biomass presents a significant challenge in the 21st century. In this context, this study aims to valorize waste generated by the fruit juice processing industry at the N’Gaous unit (composed of the orange peel, fibers, pulp, and seeds) as an adsorbent to eliminate an anionic dye and to enhance its adsorption capacity through thermal activation at 200 °C and 400 °C. The aim is also to determine the parameters for the adsorption process including contact time (0–120 min), solution pH (2–10), initial dye concentration (50–700 mg/L), and adsorbent dosage (0.5–10 g/L). The adsorption tests showed that waste activated at 400 °C (AR400) demonstrated a higher efficiency for removing indigo carmine (IC) from an aqueous solution than waste activated at 200 °C (AR200) and unactivated waste (R). The experimental maximum adsorption capacities for IC were 70 mg/g for unactivated waste, 500 mg/g for waste activated at 200 °C, and 680 mg/g for waste activated at 400 °C. These tests were conducted under conditions of pH 2, an equilibrium time of 50 min, and an adsorbent concentration of 1 g/L. The analysis of the kinetic data revealed that the pseudo-second-order model provides the best fit for the experimental results, indicating that this mechanism predominates in the sorption of the pollutant onto the three adsorbents. In terms of adsorption isotherms, the Freundlich model was found to be the most appropriate for describing the adsorption of dye molecules on the R, AR200, and AR400 supports, owing to its high correlation coefficient. Before adsorption tests, the powder R, AR200 and AR400 were characterized by various analyses, including Fourier transform infrared (FTIR), pH zero charge points and laser granularity for structural evaluation. According to the results of these analyses, the specific surface area (SSA) of the prepared material increases with the increase in the activation temperature, which expresses the increase in the adsorption of material activated at 400 °C, compared with materials activated at 200 °C and the raw material. Full article

Due to the significantly increasing demand for plastic components, it has become necessary to investigate polymer recycling solutions to eliminate their adverse environmental impact. The focus of this study is to examine the feasibility of recycling polypropylene and a thermoplastic elastomer up to five times using additive manufacturing. This study also focuses on the production and evaluation of the quality of hybrid components based on polypropylene and thermoplastic elastomers. A thermomechanical recycling approach is used, which involves subjecting polymers to thermal and mechanical processes to obtain a usable material form after each recycling cycle. Additive manufacturing was used to produce specimens using the material in both filament and granular form. The thermal, mechanical, and rheological properties of the specimens were characterized by means of various analytical techniques, including tensile test, impact test, optical microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, dynamic scanning calorimetry, and rheological tests in order to study the degradation characteristics of the recycled polymers. The results generally indicate that the chosen recycling procedure causes only slight alterations in the material properties by means of thermal and rheological tests, while impacting mechanical properties and printability. Full article

In the western Tarim Basin, Carboniferous granular dolostones deposited on a carbonate platform contain a small amount of terrigenous materials of sand-size fraction, agglomerated clay minerals, or similar phases. However, the role of terrigenous materials on dolomitization is still unclear. The aim of this study was to reveal the dolomitization mechanism. The granular dolomites have small crystal size, earthy yellow color, and fabric-retentive texture, with relatively good order. These features indicate dolomites precipitated during early diagenesis. The ratio of rare earth elements (RREs) abundance of the stable isotopes ⁸⁷Sr/⁸⁶Sr relative to Post-Archean Australian Shale (PAAS) normalized patterns was used to study the source of the dolomitizing fluids. The composition of REEs is characterized by heavy rare earth (HREE) enrichment (average Nd_SN/Yb_SN = 0.83). There is a positive (La/La*)_SN anomaly and slightly positive (Gd/Gd*)_SN and (Y/Y*)_SN anomaly; δ¹⁸O of seawater in fractionation equilibrium with granular dolostones was from −2.8‰ to 1.7‰ PDB, implying the dolomitizing fluid was contemporary, slightly evaporated seawater. The granular dolostones on the relatively thick shoals were subject to subaerial exposure before pervasive dolomitization, with evidence that the input of detrital kaolinite predated the formation of dolomites. Higher ⁸⁷Sr/⁸⁶Sr values and ∑REE in granular dolostones than the values in equivalent limestones indicate that dolomitization was related to terrigenous materials. Within the terrigenous materials, the negative-charged clay minerals may have catalyzed the dolomitization, resulting in dramatically decreased induction time for precipitation of proto-dolomites. A greater amount of terrigenous materials occurred on the shoals at the sea level fall, resulting from enhanced river entrenchment and downcutting. As a result, after subaerial exposure, the penesaline water flow through the limy allochems sediments lead to dolomitization, with the catalysis of illite on relatively thick shoals. Full article

Lateritic soils, characterized by complex mineralogy, a high degree of weathering, and a distinctive structure, are widely distributed in tropical regions. However, their use in pavement layers is often restricted due to conservative soil classification methods that may not fully represent their mechanical potential. This study evaluates the geotechnical behavior of a lateritic clay from a small town in São Paulo, referred to in this article as Purple Clay, with a focus on its permanent deformation (PD) and resilient modulus (RM). Repeated load triaxial tests, along with X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM), were conducted to assess the soil’s mechanical response and microscopic structure. The results indicated that the high concentration of iron oxides contributed to increased cohesion and mechanical strength. When compacted at intermediate Proctor energy, the Purple Clay exhibited RM values comparable to some granular materials reported in the literature, highlighting its potential for pavement applications. However, under higher stress levels, PD was up to 42% greater than that of reference materials, emphasizing the influence of loading conditions on its behavior. Full article

The wettability of granular solids is a critical parameter in numerous industrial applications, including enhanced oil recovery, advanced material coatings, and nanotechnology. However, traditional methods for assessing wettability, such as contact angle measurements, face significant challenges when applied to heterogeneous or porous solids. This study proposes a rheological methodology as an alternative approach to determine the wettability of granular solids, focusing on bentonite clay modified via sodium dodecylbenzene sulfonate adsorption. Aqueous and oily suspensions of bentonite with varying degrees of hydrophobicity were characterized using viscosity measurements, oscillatory amplitude sweeps, and thixotropic recovery tests. For the system under study, a bentonite concentration of 8% ensures optimal rheological behavior. Furthermore, the adsorption isotherm provides a reliable means of determining varying degrees of solid coverage. The results demonstrated clear correlations between surface coverage and rheological behavior, with increasing hydrophobicity leading to reduced viscosity and viscoelasticity in aqueous systems and a shift toward Newtonian flow behavior in oily systems. These findings were supported by traditional contact angle measurements, which confirmed the relationship between surfactant adsorption and enhanced hydrophobicity. The proposed rheological methodology overcomes the limitations of conventional wettability assessments and provides a new approach for characterizing and optimizing the interfacial properties of particulate systems. This work has broad implications across industries such as petroleum, coatings, and material science, offering a novel pathway for designing systems with tailored wettability and flow characteristics. Full article

Discontinuities in rock mass are usually considered to be important influencing factors for shear failure. As a type of granular material, the macroscopic mechanical behavior of rock masses is closely related to the anisotropy of the contact network. This paper uses the discrete element method (DEM) to simulate direct shear tests of specimens with different joint inclinations and analyzes the evolution of shear-induced fabric anisotropy and contact force anisotropy during the shear process. Three anisotropic tensors $a_{ij}^c$, $a_{ij}^n$ and $a_{ij}^t$ are defined to characterize the anisotropic behavior of granular materials. The macroscopic mechanical behavior of the specimens is explained from the micromechanical level combined with the evolution laws of the microcracks and energy of the specimens. The research results indicate that, after the appearance of microcracks in the specimens, the joint inclination leads to changes in their macroscopic mechanical behavior such as peak shear stress, peak displacement and failure mode by affecting the development of the fabric and contact anisotropy of the specimens. Meanwhile, a decrease in fabric and contact anisotropy often indicates specimen failure. Full article

This research study aims to study and investigate the corrosion rate, hot tensile properties, and microstructures of SSDS 2507 and AISI 316 gas tungsten arc dissimilar weldments. Three separate samples were developed with frequencies of 2, 4, and 6 Hz using the pulse arc mode technique. The tensile characteristics were assessed at two distinct temperatures (27 °C and 350 °C) in order to examine the behavior of the welded structure. Mechanical characterization such as hardness measurement and corrosion behavior were studied. The metallurgical characteristics of pulsed and continuous current weldments were examined using microscopes (optical and scanning), revealing variations across different zones. At the 4 Hz pulse frequency, the material exhibited improved tensile qualities compared to constant arc welding. The microstructures indicated that the fusion zone in the pulsed arc weldment consisted of a balanced mixture of inter-granular austenite and ferrite phases. A better corrosion resistance rate of 0.0487 mm/year was observed in the pulsed arc weldment compared to both the SSDS2507 base metal and the constant arc weldment. Specifically, at a temperature of 27 °C, the ultimate tensile strength was 695 MPa, whereas at a temperature of 350 °C, the tensile strength was 475 MPa. The weld strength of the pulsed arc weldment exhibited a 15.8% improvement in comparison to the constant arc weldment. The surface hardness value increased to 240 HV compared to the constant arc weldment, which had an HV of 225. Full article

The mesquite tree (Prosopis juliflora) is cultivated across 500,000 hectares in the semi-arid region of Brazil, primarily aimed at recovering degraded areas in the northeastern part of the country, which represents 15.7% of the national territory. However, its economic potential remains underutilized. Mesquite pods are particularly rich in carbohydrates, making them a promising raw material for bioethanol production. This study investigates the production of first-generation bioethanol from mesquite pods as feedstock. Mature pods were sourced from local producers in Sumé Town, located in the Cariri Paraibano microregion of Brazil. Sugar extraction from the mesquite pods involved hydration followed by pressing, with the extracted juice adjusted to a pH of 4.3 and soluble solids (°Brix) concentrations corrected to 20, 18, and 16. The juice was then subjected to fermentation using different yeast strains (fresh yeast, granular yeast, and FLNF CA-11) at a concentration of 25 g L⁻¹. Alcoholic fermentation was carried out in a batch system, with measurements of cell concentration (biomass), soluble solids (°Brix), ethanol concentration (°GL), and pH taken at 2 h intervals over a 20 h period. The best physicochemical characterization of bioethanol was obtained using the LNF CA-11 yeast at 20 °Brix, producing a biofuel that met Brazilian legal standards set by the National Petroleum Agency (ANP). The bioethanol had a colorless appearance and was free of impurities, with a titratable acidity of 28.2 mg of acetic acid, electrical conductivity of 282.33 µS m⁻¹, a specific mass of 809 kg m⁻³, an alcohol content of 95.5 °GL, a pH of 6.28, and no evaporation residue in 100 mL. Additionally, the highest bioethanol yield was achieved with broth fermented at 18 °Brix and LNF CA-11 yeast. These results highlight the potential of mesquite pods as a renewable energy alternative, especially relevant in the context of the global climate crisis; the growing need to reduce dependence on fossil fuels; and the need to reduce environmental problems; and they promote the added-value and use of this product. Full article

The microstructure and impact toughness of a steel material subjected to multi-layer and multi-pass welding with varying secondary peak temperatures were investigated using welding thermal simulation. The detailed microstructures and fracture morphologies were examined by SEM, TEM, and EBSD. When the secondary peak temperature reaches 650 °C, the microstructure resembles that of a primary thermal cycle at 1300 °C, characterized by coarse grains and straight grain boundaries. As the temperature increases to 750 °C, chain-like structures of bulky M/A (martensite/austenite) constituents form at grain boundaries, widening them significantly. At 850 °C, grain boundaries become discontinuous, and large bulky M/A constituents disappear. At 1000 °C, smaller austenitic grains form granular bainite during cooling. However, at 1200 °C, grain coarsening occurs due to the significant increase in peak temperature, accompanied by a lath martensite structure at higher cooling rates. In terms of toughness, the steel exhibits better toughness at 850 °C and 1000 °C, with ductile fracture characteristics. Conversely, at 650 °C, 750 °C, and 1200 °C, the steel shows brittle fracture features. Microscopically, the fracture surfaces at these temperatures exhibit quasi-cleavage fracture characteristics. Notably, chain-like M/A constituents at grain boundaries significantly affect impact toughness and are the primary cause of toughness deterioration in the intercritical coarse-grained heat-affected zone. Full article

Ground liquefaction potential analysis is a fundamental characterization in areas with continuous seismic activity, such as Ecuador. Geotechnical liquefaction studies are usually approached from dynamic penetration tests, which pose problems both in their correct execution and in their evaluation. Our research involves analyzing dynamic penetration tests and microtremor geophysical surveys (horizontal-to-vertical spectral ratio technique, HVSR) for analyzing the liquefaction potential at the base of the San Marcos dam, a reservoir located in Cayambe canton (Ecuador). Based on the investigations performed at the time of construction of the dam (drilling and geophysical refraction profiles) and the application of 20 microtremor observation stations via the HVSR technique, an analysis of the safety factor of liquefaction (SF_liq) was conducted using the 2001 Youd and Idriss formulation and the values of the standard penetration test (SPT) applied in granular materials (sands). In addition, the vulnerability index (K_g) proposed by Nakamura in 1989 was analyzed through the HVSR records related to the ground shear strain (GSS). The results obtained in the HVSR analysis indicate the presence of a zone of about 100 m length in the central part of the foot of the dam, whose GSS values identified a condition of susceptibility to liquefaction. In the same area, the SPT essays analysis in the P-8A drill hole also shows a potential susceptibility to liquefaction in earthquake conditions greater than a moment magnitude (M_w) of 4.5. That seismic event could occur in the area, for example, with a new activity condition of the nearby Cayambe volcano or even from an earthquake from the vicinity of the fractured zone. Full article

Recent advancements in railway construction have emphasized environmental sustainability, integrating considerations of environmental impact into the planning and execution of infrastructure projects to reduce costs and mitigate adverse effects. This study investigates the use of steel slag as a sustainable alternative for railway ballast, grounded in shakedown theory. The characterization of the aggregates was performed in accordance with NBR 5564 and AREMA standards, confirming that the material meets most requirements. The mechanical behavior of the ballast was analyzed under cyclic loading conditions, assessing permanent deformation and the material’s ability to achieve stability (shakedown). Triaxial tests with repeated loading simulated real railway conditions, applying vertical stresses up to 600 kPa and confining pressures ranging from 35 to 200 kPa. The results indicate that steel slag aggregates exhibited promising performance, with seven specimens achieving stable deformation levels, characterized by residual deformations of less than 2.5 mm. Notably, these specimens approached deformations on the order of ${10}^{-7}$, indicating stability under cyclic loading. Furthermore, a comparative analysis of shakedown criteria proposed by various authors revealed variations in limits for granular materials, enhancing the understanding of steel slag aggregate behavior. The experimental results were validated through numerical simulations conducted with Systrain software 2.0, which simulated a loading condition of 32.5 tons per axle, confirming the observations with maximum principal stresses ranging from 166 to 184 kPa in the ballast. The analysis showed that steel slag aggregates can withstand stress levels higher than those of granodiorite, reinforcing their viability as a sustainable alternative for railway ballast. Full article

Excessive consumption of natural resources to meet the growing demands of building and infrastructure projects has put enormous stress on these resources. On the other hand, a significant quantity of soil is excavated for development activities across the globe and is usually treated as waste material. This study explores the potential of excavated soils in the Brittany region of France for its reuse as earthen construction materials. Characterization of soil recovered from building sites was carried out to classify the soils and observe their suitability for earthen construction materials. These characteristics include mainly Atterberg limits, granulometry, organic matter and optimum moisture content. Soil samples were separated into fine and coarse particles through wet sieving. The percentage of fines (particles smaller than 0.063 mm) in studied soil samples range from 28% to 65%. The methylene blue value (MBV) for Lorient, Bruz and Polama soils is 1, 1.2 and 1.2 g/100 g, and French classification (Guide de terrassements des remblais et des couches de forme; GTR) of soil samples is A1, B5 and A1, respectively. The washing of soils with lower fine content helps to recover excellent-quality sand and gravel, which are a useful and precious resource. However, residual fine particles are a waste material. In this study, three soil formulations were used for manufacturing earth blocks. These formulations include raw soil, fines and restructured soil. In restructured soil, a fine fraction of soil smaller than 0.063 mm was mixed with 15% recycled sand. Restructuring of soil fine particles helps to improve soil matrix composition and suitability for earth bricks. Compressed-earth blocks of 4 × 4 × 16 cm were manufactured at a laboratory scale for flexural strength testing by using optimum molding moisture content and compaction through Proctor normal energy. Compressive strength tests were performed on cubic blocks of size 4 × 4 × 4 cm. Mechanical testing of bricks showed that bricks with raw soil had higher resistance with a maximum of 3.4 MPa for Lorient soil. Removal of coarse particles from soil decreased the strength of bricks considerably. Restructuring of fines with recycled sand improves their granular skeleton and increases the compressive strength and durability of bricks. Full article