Search Results (4,471)

Pressure swing adsorption (PSA) is a viable method for separating hydrogen from gas mixtures, an important aspect of long-term hydrogen storage in depleted gas fields. This study explores optimizing a 12-step PSA process for recovering high-purity hydrogen from varying compositions of hydrogen–methane mixtures, simulating the conditions likely encountered during hydrogen storage and recovery. Step-time optimization was performed on four different hydrogen–methane mixtures using the toPSAil simulation package—an open-source dynamic PSA simulator developed by researchers at the Georgia Institute of Technology—integrated with a particle swarm optimization (PSO) algorithm. The goal was to develop an optimization framework that can reliably identify PSA step times for different operating scenarios and satisfy specified purity and recovery constraints under fluctuating wellhead feed conditions. The optimization converged within 25–30 iterations, even in high-contaminant, low-pressure scenarios, where PSA performance is traditionally weak. The product purity in the optimized cycles was above 99.1% with more than 80% recovery for all cases, while fuel cell quality (99.7%) hydrogen was achieved in two out of the four scenarios. The purge-to-feed ratio of the best-performing cycles was between 0.07 and 0.32. These findings show the potential of the proposed approach in overcoming the difficulty of designing PSA cycles for non-constant gas compositions and achieving a hydrogen purification process suitable for variable feed conditions. The workflow generates a large synthetic dataset that can support surrogate or hybrid modeling. The results can help advance research in other gas separation areas with non-constant conditions, like flue gas or biogas purification. Full article

Clogging is the main mechanism that deteriorates the hydraulic functionality of permeable pavements, particularly in porous asphalt mixtures (PAM). This study evaluated the hydraulic impact of sediments from three peri-urban micro-watersheds in the Boyacá region of Colombia on the infiltration capacity of PAM. Road infrastructure and drainage conditions were analysed using orthophotos and field inspections to identify geomorphological factors that favour sediment transport toward the roadway. Annual erosion rates were estimated using the Universal Soil Loss Equation (USLE), and sediments were characterized both within the watersheds and at their outlet onto the road. Hydraulic performance was assessed through laboratory tests using a Falling Head Permeameter, complemented by field infiltration measurements with a Modified Cantabrian Infiltrometer (0.25 m²). Results showed erosion rates of up to 7.9 t/ha·year and infiltration losses above 90% under clogged conditions. A partial hydraulic recovery of around 40% was observed after maintenance, particularly when sediments exhibited a higher sand fraction. These findings demonstrate that combining USLE-based erosion modelling with controlled hydraulic testing provides a robust framework for evaluating clogging risks in peri-urban roads and offers new evidence on the hydraulic behaviour of PAM exposed to non-urban sediments in the design and maintenance of sustainable pavements. Full article

This paper presents the design, modeling, and experimental validation of a capacitive tactile sensor specifically conceived to sense shear-driven contact dynamics in robotic manipulation. The proposed device is a layered flexible capacitive structure, in which controlled tangential interactions are induced. The electrode design maximizes sensitivity to shear motion and promotes an isotropic response with respect to slip direction, thereby addressing two key limitations that affect the majority of existing slip-sensing technologies. An analytical model was developed to describe the essential relationship between shear-induced displacements and the electrical response, providing insight into the design parameters and supporting the selection of geometry and materials. To test the sensor in real conditions, a dedicated capacitive readout circuit based on high-frequency excitation and synchronous demodulation was developed to robustly acquire capacitance variations while rejecting static offsets and parasitic effects. Several formulations for the interposed dielectric layer material were investigated, including viscous fluids and composite mixtures with high-permittivity nanoparticles, with the aim of improving electrical sensitivity while preserving mechanical stability. Experimental results obtained under controlled loading and sliding conditions demonstrate that the sensor is highly sensitive to changes in contact state and tangential interaction dynamics. The sensor responded consistently to both load-induced shear and slip-related phenomena, enabling the reliable monitoring of contact dynamics rather than binary slip detection. A proof-of-concept integration into a robotic finger confirms the suitability of the proposed approach for grasp monitoring. Full article

Three-dimensional printing (3DP) has gained increasing attention in construction as a means of addressing labor shortages and improving efficiency. Various studies have investigated fiber-reinforced mortars for 3DP. However, only a few studies have examined mixture design strategies aimed at controlling early structural build-up, and the relationships between early structural build-up, printability, and interlayer stability remain largely unexplored. This study aimed to establish a practical method for evaluating the static yield stress and early buildability of 3DP mortars under construction-site conditions. Vane shear and 15-stroke flow tests were conducted to assess the static and dynamic behavior of mortars incorporating polyvinyl alcohol (PVA) fibers, and their compressive and flexural strengths were also evaluated. According to the results, the vane shear test sensitively captured the rheological changes associated with variations in fiber content and superplasticizer dosage. The addition of PVA fibers increased the maximum shear stress of the mortar, resulting in atypical static yield stress development compared to fiber-free mortars. While the 15-stroke flow test further elucidated flowability, the vane shear test revealed a stronger correlation between mechanical properties and overall buildability. Thus, vane shear testing can be reliably used to assess early-age structural build-up and interlayer stability in 3DP mortars for optimizing print performance. Full article

Ultra-high-performance concrete exhibits excellent mechanical performance but relies on a high binder content, resulting in substantial carbon emissions. This study investigates sustainable ultra-high-performance concrete incorporating sewage sludge ash, aiming to balance mechanical performance, environmental safety, and life-cycle impacts within an integrated material system. High volumes of sewage sludge ash were incorporated into ultra-high-performance concrete under autoclave curing, with mixture proportions designed based on particle packing theory. Fresh properties, mechanical performance, shrinkage behavior, microstructural characteristics, heavy-metal leaching, as well as life-cycle environmental and economic impacts were systematically evaluated. The incorporation of porous sewage sludge ash modified the pore structure of ultra-high-performance concrete, thereby enabling a substantial reduction in cement content. At a sewage sludge ash replacement level of 60%, life-cycle assessment results indicate a 42.7% reduction in carbon emissions while maintaining a compressive strength of approximately 147 MPa under autoclave curing, remaining within a practically viable range for ultra-high-performance concrete. This confirms that sewage sludge ash can be safely incorporated into ultra-high-performance concrete, delivering a favorable sustainability–performance trade-off alongside significant environmental and economic benefits. Full article

Rollpave technology offers an efficient and low-disruption solution for pavement rehabilitation but has not yet been widely implemented in practice. This review aims to provide a comprehensive overview of rollpave technology by examining performance evaluation methods, material design strategies, and construction workflows, and identifying its advantages and limitations to support practical application. Recent advances in rollpave pavement technology are reviewed, including flexural performance testing methods and evaluation criteria for rollable pavement materials, as well as the design of flexible asphalt mixtures and interlayer bonding materials. Construction techniques across different stages of rollpave implementation are summarized, and existing engineering case studies are reviewed. The advantages and limitations of rollpave technology are evaluated in comparison with other pavement construction and rehabilitation approaches, and current research focuses are discussed. The review indicates that pavement performance requirements can be achieved through the development of specialized modified asphalt binders and optimized mixture designs. On-site installation relies on coordinated operation of multiple devices to ensure adequate interfacial bonding between new and existing layers; however, current practices are largely experience-based and lack standardized guidelines. It is believed that rollpave technology demonstrates unique advantages for rapid pavement repair and emergency rehabilitation, but there are still challenges related to material and structural design, on-site installation, and cost-effectiveness that remain, limiting large-scale adoption. Future research could focus on establishing technical standards, developing specialized equipment, and enhancing multifunctional integration. Full article

Reactive powder concrete (RPC) delivers outstanding mechanical performance and durability; however, it is commonly hindered by high cement consumption, elevated embodied carbon emissions, and high material costs. To mitigate these drawbacks, this study develops a low-carbon, cost-effective RPC incorporating high-volume class-F fly ash, a reduced silica fume dosage, conventional river sand, and an optimized steel fiber system. A systematic mix design framework, combining particle packing density with paste rheology optimization, was employed to balance workability, strength, and durability. The optimized mixtures were evaluated for compressive, splitting tensile, and flexural strength, as well as durability-related metrics, including water absorption rate and resistance to chloride penetration. Environmental impact and cost-effectiveness were further quantified via embodied carbon accounting and strength-normalized performance indices. The results show that well-designed high-volume fly ash RPC can achieve compressive strengths above 130 MPa while maintaining excellent impermeability, alongside substantial reductions in both material cost and carbon footprint relative to conventional RPC. In addition, mixed-size steel fibers further enhance mechanical performance through multi-scale crack bridging. Overall, this work provides a practical route to decouple ultra-high performance from high environmental burden, supporting the sustainable deployment of RPC in infrastructure engineering. Full article

High reclaimed asphalt pavement (RAP) half-warm mix asphalt (HWMA) mixtures provide a low-energy alternative for pavement repair but often suffer from insufficient binder activation and reduced mechanical performance at low production temperatures. This study develops a high-RAP (73.8%) half-warm repair mixture using a dual-additive system comprising a rejuvenator and a low-temperature composite additive. The mixture was designed to enable effective mixing and compaction at temperatures as low as 60 °C. The optimized formulation achieved a 5.84 kN Marshall stability, 7.0% voids in total mixture, 80% retained Marshall stability after moisture conditioning, and approximately 1100 passes/mm dynamic stability. Temperature sensitivity analysis showed that stability increased from 4.50 kN at 50 °C to 9.20 kN at 90 °C with corresponding VTM reduction from 15.2% to 4.8%. The results demonstrate that a high-RAP HWMA repair mixture can satisfy mechanical and durability requirements while being produced at substantially reduced temperatures, supporting practical and sustainable pavement maintenance applications. The study further provides mixture-scale evidence that a dual-additive strategy can stabilize high-RAP mixtures under very low half-warm production temperatures (≈60–70 °C), which are representative of rapid repair conditions and remain insufficiently investigated in existing WMA–RAP research. Full article

Diet is a major, modifiable determinant of cardiometabolic, cancer, and inflammatory disease risk, yet individuals frequently exhibit substantial heterogeneity in metabolic and clinical responses to similar dietary exposures. Genetic susceptibility and its interplay with diet plausibly contribute to this variability, motivating gene–diet (G×D) interaction research and the broader ambition of precision nutrition. Translation has lagged, however, because interaction effects are typically modest, context-dependent, and difficult to reproduce, particularly in the presence of pervasive dietary measurement error, heterogeneous exposure definitions, and stringent multiplicity correction. A methodologically oriented synthesis is presented across eight domains of contemporary G×D epidemiology: classical regression interaction models; efficient study designs; dietary assessment and measurement error; dietary patterns, mixtures, and non-linear modeling; genome-wide and polygenic approaches; causal inference frameworks; multi-omics integration; and machine learning. Central concepts include the recognition that “interaction” is a scale-dependent estimand and that transparent reporting of coding choices and effect-modification metrics—including additive interaction when relevant for public health interpretation—is essential. Credible inference further depends on high-quality, harmonized dietary phenotyping with explicit energy adjustment and, where feasible, biomarker calibration, alongside robust control of population structure and gene–diet correlation using ancestry adjustment, mixed models, and family-based designs. Genome-wide and polygenic risk-based approaches expand discovery potential but require disciplined multiplicity strategies, discovery-replication workflows, and explicit evaluation of portability and equity across ancestries. Causal inference methods can strengthen etiologic interpretation when assumptions are defensible and sensitivity analyses are routinely implemented. Multi-omics and machine learning may enhance mechanistic and predictive insight, but only under rigorous quality control, validation, and reproducible pipelines. Overall, harmonized measurement, clear estimands, multi-ancestry replication, and integrated evidence pipelines are pivotal for producing robust and actionable G×D evidence. Full article

Performance deterioration and unstable operation are common when multistage centrifugal pumps handle gas–liquid mixtures. Here, we investigate a two-stage centrifugal pump over a wide speed range and inlet gas volume fractions (IGVFs) using experiments and CFD. The two-phase flow is simulated with a Eulerian–Eulerian two-fluid approach (liquid as the continuous phase; gas as a dispersed bubbly phase with a representative bubble diameter of 0.3 mm). Turbulence is closed using the SST k–ω model for the liquid phase and the built-in dispersed-phase turbulence treatment in ANSYS CFX. Transient pressure signals are analyzed in the time and frequency domains (FFT) to assess how rotational speed affects void-fraction distribution, overall performance, and the dominant unsteady components within the adopted modeling framework. The results show that IGVF primarily controls gas accumulation in the impeller passages: as IGVF increases, the gas phase evolves from dispersed bubbles to a central core, whereas speed mainly alters the detailed morphology via centrifugal effects. Similarity-law scaling is strongly speed-dependent in this pump: agreement is better at higher speeds and deteriorates at lower speeds where viscous effects become more influential. The dominant unsteady content also changes with speed, shifting from low-speed broadband features associated with gas redistribution to high-speed periodic components linked to blade–vane rotor–stator interaction (RSI). In addition, the downstream stage exhibits more uniform void fraction and more regular periodic signatures, consistent with an inter-stage flow-rectification effect. These observations provide practical guidance for hydraulic design and variable-speed operation of multistage pumps under gas entrainment. Full article

This study investigates the application of artificial intelligence for predicting the compressive strength of a high-performance, eco-efficient engineered cementitious composite (ECC), designated mix S8-1, A. The composite incorporates supplementary cementitious materials and alternative aggregates derived from recycled glass waste. The binder system combines waste glass powder and silica fume, while the aggregate fraction includes recycled cobalt glass. An extensive experimental program involving 14 mixtures tested at 7, 28, 56, 90, and 120 days was performed to establish the reference mechanical and rheological properties. Mix S8-1, A achieved strength class C60/75 and workability corresponding to consistency class S4. To substantiate long-term performance, microstructural and chemical analyses were conducted on specimens preserved since 2011, using scanning electron microscopy (SEM) and X-ray fluorescence (XRF). The results confirmed a stable, densified microstructure, evidencing the long-term durability of the patented ECC formulation. For predictive modeling, a shallow feedforward artificial neural network with three hidden layers was developed and trained on 70 dataset entries representing mixture proportions and curing ages. Model performance was evaluated using cross-validation, achieving a coefficient of determination (R²) of 0.968, a mean absolute error of 1.96 MPa, and a root mean square error of 2.52 MPa. The results demonstrate that AI-based approaches can accurately predict the compressive strength of high-performance, environmentally sustainable ECCs incorporating recycled glass constituents, supporting both performance optimization and resource-efficient material design. Full article

The buildings and construction sector is a major contributor to global environmental impact, accounting for 34% of global energy demand and 37% of energy- and process-related CO₂ emissions in 2022. This context motivates the development of alternative construction materials with lower embodied energy and reduced environmental impact. In this study, vibrocompressed calcium sulfate prefabricated elements were developed and experimentally evaluated as an alternative to conventional concrete-based units. Unlike traditional gypsum molding processes, the proposed vibrocompression route enables the production of semi-dry mixtures with reduced water content, allowing rapid demolding and palletization within 10–20 min. The study was designed as a process-validation campaign under real industrial production conditions (LOREV 1010/A), combined with an initial technical characterization of the manufactured units. The experimental program focused on manufacturing feasibility and on the initial physical and mechanical characterization of the prefabricated elements, including aggregate granulometric control, dry density, normalized compressive strength, and microstructural observations. Under the selected process conditions, the units reached normalized compressive strength values of up to 2.90 N/mm² and dry density values of approximately 1228 kg/m³, indicating technical suitability for non-load-bearing applications. From a process-route perspective, the cement-free formulation and the use of gypsum-based aggregates support the technical plausibility of a more circular construction system. The environmental and economic implications of the proposed system are discussed from a preliminary process perspective and should be quantified in future life cycle and techno-economic assessments. Full article

This study investigates the properties of concrete incorporating recycled aggregates (RAs) for rigid pavement applications. A 15-point three-level experimental design was used to vary three composition factors: Portland cement substitution with fly ash (FA), and dosages of a superplasticizer (SP) and polypropylene fibers (PFs). A set of experimental–statistical models (ES models) was developed to predict the concrete strength, abrasion and frost resistance (FR), water absorption (WA), and global warming potential (GWP). This study aimed to develop a material that achieves both adequate mechanical performance for pavement applications and enhanced environmental sustainability by incorporating RAs and FA. The results demonstrate that replacing up to 13% of cement with FA does not compromise the splitting tensile strength or FR. For non-fibrous concrete, this substitution increases FR by approximately 50 freeze–thaw cycles. Application of PFs (2.4–3 kg/m³) enhances splitting tensile strength by 14–16% and improves FR by about 50 cycles. Using response surface methodology (RSM), optimal concrete compositions were identified that meet all target criteria: compressive strength ≥ 40 MPa, flexural strength ≥ 5 MPa, FR ≥ F200 (cycles), and abrasion resistance (AR) ≤ 0.5 g/cm², while simultaneously minimizing GWP. An additional optimum composition was determined by imposing a constraint on splitting tensile strength of ≥4.5 MPa. This graphical optimization approach, utilizing two-factor interaction diagrams, provides an effective and visual methodology for practical concrete mixture design. The novelty of the method lies in the discretization of the factor space, which enables efficient identification of optimal concrete mixture compositions. Full article

Isobutane is a key feedstock for alkylate production. For separating an equimolar isobutane/n-butane mixture with 2 mol% ethane, two conventional designs are reported in the literature: a single water-cooled condenser (SC) and a dual condenser system with refrigeration (DC). This study proposes two vapor recompression retrofit configurations, SC-VR and SC-PHVR (with preheating), to improve energy efficiency and enable electrification. Economic and environmental performance were evaluated using total annualized cost (TAC) and CO₂ emissions. Compared with SC and DC schemes, SC-VR reduces CO₂ emissions by 49 and 52%, while SC-PHVR delivers higher reductions of 64 and 66%. A sensitivity analysis of electricity prices across 3-, 5-, and 10-year payback periods indicates the most favorable performance at 10 years. At 16.67 USD/GJ, SC-PHVR lowers TAC by 22 and 25%; in contrast, SC-VR provides marginal savings. At 24.03 USD/GJ, SC-VR is not economically competitive, whereas SC-PHVR continues to outperform the conventional cases, with TAC reductions of 8% and 4%. Both retrofit options significantly reduce emissions, with SC-PHVR offering the best economic performance. Finally, the proposed configurations enable the complete electrification of the de-isobutanizer system, eliminating reliance on fossil-based thermal utilities, which allows the use of renewable sources in line with the decarbonization efforts. Full article

The separation of xenon (Xe) and krypton (Kr) is very important for industrial applications and environmental protection. However, the lack of permanent dipoles, low polarizabilities arising from their spherical nature, and similar kinetic diameters make their efficient separation by porous adsorbents exceptionally challenging. This study explored the effects of pore geometry and surface polarity of a series of aluminum-based metal–organic frameworks (CAU-10-H, MIL-160, KMF-1, CAU-23) on Xe/Kr separation performance using a heteroatom engineering strategy. These MOFs are composed of AlO₆ clusters and bent dicarboxylic acid linkers, enabling us to systematically investigate the effects of pore size and heteroatom types on Xe/Kr separation performance. Among them, MIL-160 has a polar linker based on furan, showing the best balance performance. At 298 K and 1.0 bar, the uptake of Xe is 4.12 mmol g⁻¹ and the IAST selectivity is 7.63 for a Xe/Kr (20/80) mixture. The practical performance was verified by dynamic breakthrough experiments, which yielded a long Xe breakthrough time of 42.9 min g⁻¹. Grand Canonical Monte Carlo (GCMC) simulations and first-principles density functional theory (DFT) calculations revealed that the enhanced performance originates from cooperative confinement and polarization effects, with the furanyl oxygen atoms providing optimal Xe-binding sites. This work clarifies the structure–property relationships governing Xe/Kr separation in aluminum-based MOFs (Al-MOFs), highlighting the potential of heteroatom engineering for designing efficient noble gas adsorbents. Full article