Search Results (4,908)

Growing concerns about global climate change and its negative consequences for communities have put immense pressure on the building industry, which is one of the primary sources of greenhouse gas emissions. Due to the environmental issues associated with the manufacture of sustainable construction materials, alkali-activated concrete (AAC) has emerged as a competitive alternative to cement. To predict the compressive strength (CS) of AAC, four machine learning (ML) models, namely, Convolutional Neural Network (CNN), Long Short-Term Memory (LSTM), Random Forest (RF), and Extreme Gradient Boosting (XGBoost), were employed in this study using 193 data points. The input variables include Precursor “P” (kg/m³), Blast Furnace Slag “BFS ratio”, Sodium hydroxide “Na” (kg/m³), silicate modulus “Ms”, water content “W” (kg/m³), fine aggregate “FA” (kg/m³), coarse aggregate “A” (kg/m³), and curing time “CT” (day), with CS (MPa) as the output variable. The dataset was checked for stationarity and then normalized to decrease data redundancy and increase integrity. Furthermore, three model combinations were developed based on the relationship between the input and target variables. The XGB-M3 model outperformed all other models with a high degree of accuracy, according to the study’s findings. Specifically, the Pearson correlation coefficient (PCC) was 0.9577, and the mean absolute percentage error (MAPE) was 14.95% during the calibration phase. SHAP, an explainable AI approach that provides interpretable insights into complex AI systems by assigning feature importance to model predictions, was employed. Results suggest the higher predictions from the XGB-M3 and RF-M3 models were largely driven by curing time (CT). Full article

Detecting changes in the permittivities of materials has important applications in electronic information, materials science, biomedicine, and many other fields. However, existing detection methods are limited by factors such as sample thickness and resonance intensity, making it difficult to achieve sensitive dielectric constant detection at desired frequency bands. This paper proposes a method for detecting the dielectric constant changes in samples based on destructive interference of spoof surface plasmon polaritons (SSPPs) in a dual-path transmission structure, which forms a characteristic absorption peak at the SSPPs’ cutoff frequency. Specifically, by utilizing the dependence of the SSPPs’ phase on the periodic unit, a constant π phase difference is formed at the cutoff frequency through the periodic unit number difference between the two paths, resulting in a cutoff frequency absorption peak. When the sample is coated on the SSPPs’ dual-path structure, the boundary conditions are altered, leading to a cutoff frequency shift, thereby enabling dielectric constant detection at the specified frequency. Simulation results show that, with proper structural design, the normalized characteristic frequency shift reaches 10.8%/${\epsilon }_S$ and further demonstrates dramatic robustness against initial phase difference, sample thickness and sample loss. In summary, this work provides a novel high-precision and high-robustness method for detecting dielectric constant changes in samples at specified frequencies. Full article

A micro-cavity based on phase-change material is a very important strategy for the realization of tunable absorption and conversion of terahertz waves. In this work, a tunable terahertz metamaterial absorber based on the phase-change material germanium–antimony–tellurium (GST) is demonstrated. The device features a metal–insulator–metal triple-layer structure, where the dynamic switching of absorption characteristics is achieved via thermally controlled GST phase transition. In the amorphous state, the absorber exhibits a single absorption peak at 7.7 THz. Upon crystallization, the absorption switches to dual peaks at 5.1 THz and 8.3 THz, achieving near-perfect absorption in both states. Full-wave electromagnetic simulations and theoretical analysis based on a multiple-reflection interference model indicate that this performance tuning originates from the GST-phase-transition-induced change in the equivalent optical cavity length. This corresponds to a switch between two resonant modes: coupled inner–outer ring resonance and independent outer ring resonance. These results provide a foundation for developing dynamically tunable terahertz devices with promising applications in terahertz communications, imaging, and sensing. Full article

With the accelerated transformation of green shipping and the advancement of ship electrification, lithium-ion batteries have become the core solution for ship propulsion due to their advantages of high energy density and zero emission. Efficient thermal management serves as a key technical support to ensure the safe and stable operation of batteries, extend their service life, and mitigate the risk of thermal runaway. Lithium-ion batteries accumulate heat during discharge, and pure phase change material (PCM) cooling systems are limited by low thermal conductivity, leading to excessive battery temperature rise and poor temperature uniformity. To address this problem, RT42 (a paraffin-based PCM with a melting temperature range of 311.15–316.15 K) was selected as the PCM in this study. The battery thermal management system (BTMS) coupling RT42 with a three-dimensional fin network structure was designed. Numerical simulations were conducted via ANSYS Fluent, and the enthalpy-porosity method was adopted to simulate the PCM phase change process. The effects of fin distribution, spacing and layer number on BTMS performance were systematically investigated and compared. Results show that the heat transfer process in the PCM can be significantly improved due to the three-dimensional fin network, and the battery maximum temperature can be reduced by 7.53 K compared with the pure PCM system. This study provides theoretical support for the design and optimization of high-efficiency BTMS. Full article

Phase change material (PCM)-based latent heat storage (LHS) systems help address the mismatch between renewable energy supply and thermal demand. However, their practical implementation is constrained by the strongly nonlinear and multiphysics nature of phase change, which makes high-fidelity simulations and real-time applications computationally expensive. This review examines mathematical reduced-order modeling (ROM) as an effective strategy to overcome this limitation by combining physics-based simplifications, projection methods, interpolation techniques, and data-driven models for PCM-based LHS systems. While physical simplifications (such as dimensional reduction and effective property approximations) represent an important first layer of model reduction, the primary focus of this work is on the mathematical ROM methodologies that operate on the governing equations after such physical simplifications have been applied. The review covers approaches including two-temperature non-equilibrium and analytical thermal-resistance models, Proper Orthogonal Decomposition (POD), CFD-derived look-up tables, kriging and ε-NTU grey/black-box metamodels, and machine-learning methods such as artificial neural networks and gradient-boosted regressors trained from CFD data. These ROM techniques have been applied to packed beds, PCM-integrated heat exchangers, finned enclosures, triplex-tube systems, and solar thermal components, achieving speed-ups from tens to over 80,000 times faster than full CFD simulations while maintaining prediction errors typically below 5% or within sub-Kelvin temperature deviations. A critical comparative analysis exposes the fundamental trade-off between interpretability, data dependence, and computational efficiency, leading to a practical decision-making framework that guides method selection for specific applications such as design optimization, real-time control, and system-level simulation. Remaining challenges—including accurate representation of phase change nonlinearity, moving phase boundaries, multi-timescale dynamics, generalization across geometries, experimental validation, and integration into industrial workflows—motivate a structured roadmap for future hybrid physics–machine learning developments, standardized validation protocols, and pathways toward industrial deployment. Full article

Wire Arc Additive Manufacturing (WAAM) has emerged as a promising additive manufacturing technique due to its high deposition rate and low material cost. WAAM is increasingly adopted in various industries for the production of large-scale metal components, yet optimizing productivity without sacrificing mechanical integrity remains a critical challenge, particularly for low-carbon steels. This study systematically investigates the influence of key WAAM parameters—welding current (100–350 A) and travel speed (5–30 mm/s) on the deposition stability, microstructure, and mechanical properties of thin walls made of low-carbon Fe–0.09 C–1.10 Cr–1.47 Mn–0.59 Si–0.56 Mo–0.11 Ni–0.23 V steel. A stable processing window for defect-free wall fabrication was established for currents of 100–250 A, while higher currents of 300–350 A resulted in melt pool instability and geometrical distortions due to excessive heat input. Microstructural characterization revealed a dual-phase structure consisting of allotriomorphic ferrite (ALF) and acicular ferrite (AF) in all samples. The microstructural evolution was critically governed by variations in the cooling time in the critical temperature range of 800 °C to 500 °C (t_8/5) within the thermal cycles, a direct consequence of the heat input quantified through volumetric energy density. Low heat input at 100 A, 5 mm/s promoted a microstructure with minimal ALF fraction of ~10%, whereas high heat input at 350 A, 30 mm/s induced significant ferrite recrystallization and coarsening, increasing ALF fraction to ~55%. These microstructural changes directly affected mechanical properties: YS/UTS decreased from 512 MPa/668 MPa to 401 MPa/602 MPa, respectively. Concurrently, the deposition rate increased substantially from ~1.6 kg/h to ~6.3 kg/h. The results demonstrate a critical trade-off between productivity and mechanical performance, providing a practical framework for parameter selection in WAAM-fabricated low-carbon steel components. Full article

This study addresses a critical methodological gap in evaluating building envelope performance in hot, arid climates, the overreliance on annual energy indicators, which fail to capture transient thermal behavior during peak-load periods. In such environments, instantaneous heat gains, their intensity, and temporal distribution are decisive factors for cooling demand, occupant comfort, and grid stability. To overcome this limitation, a dynamic evaluation framework—the Thermal Adaptation Rating (TAC) system—is proposed. TAC integrates three interrelated indices—peak temperature reduction (ΔT_peak), relative peak cooling load reduction (ΔP_peak, %), and peak thermal delay (Δt_delay), representing thermal damping, load intensity mitigation, and temporal redistribution, respectively. A typical residential building in Karbala was modeled in DesignBuilder using the EnergyPlus engine, with inputs documented and calibration performed against real consumption data following ASHRAE standards (MBE and CV(RMSE)) to ensure reliability. The study examined advanced envelope systems, including thermochromic glass (TG), phase-change materials (PCMs), aerogel materials (AMs), and hybrid combinations. Results revealed that while AM achieved the greatest annual energy savings, its impact on instantaneous cooling load was limited. PCM, by contrast, effectively mitigated and delayed peak loads, enhancing thermal comfort (PMV/PPD). Hybrid systems, particularly TG-PCM, delivered the most balanced performance, simultaneously reducing peak cooling load and shifting its occurrence to reshape the cooling demand curve during critical periods. These findings demonstrate that annual indices alone are insufficient for evaluating envelope performance in extreme climates. Peak-condition analysis, expressed in terms of instantaneous cooling load, as operationalized through TAC, provides a more accurate representation of thermal behavior and offers a practical tool to guide envelope design decisions in hot, dry regions. Full article

The decline of fossil fuel resources and the negative impact of fuel combustion on the environment are forcing scientists to develop new technologies for producing functional carbon materials with various useful properties. This work is devoted to a detailed study of the transformations of monosaccharides, glucose and levoglucosan, during hydrothermal carbonization, aimed at the formation of carbon microspheres. Hydrochars were obtained at temperatures of 200, 250, and 300 °C and characterized using SEM, Py-GC/MS, and elemental analysis. Changes in the chemical composition of the liquid phase were studied, depending on the HTC temperature and precursor concentration. Expanded knowledge of microsphere formation enriches information on the mechanism of monosaccharide transformation for the production of new carbon materials through synthesis from inexpensive precursors. Full article

The increasing global demand for oil and gas, together with the depletion of shallow reservoirs, has driven exploration toward deep and ultra-deep formations characterized by high-temperature and high-pressure (HTHP) conditions. In such environments, conventional drill pipes often experience thermal stress, corrosion, and mechanical degradation, which can reduce drilling efficiency and compromise operational reliability. Thermal insulated drilling pipes (TIDPs) have therefore emerged as an effective solution to minimize heat transfer between drilling fluids and the surrounding formation. This review summarizes recent advances in TIDP materials, structural design strategies, fabrication technologies, and critical performance. Relevant studies were collected from major scientific databases, including Web of Science and Google Scholar, with a focus on insulation materials, coating technologies, and thermal management approaches used in drilling systems. The analysis indicates that advanced insulation systems, including polymer-based coatings, silica aerogels, vacuum-insulated layers, and phase-change materials, can significantly enhance thermal management in drilling operations. These technologies can reduce heat loss by approximately 40–60% (i.e., 400–600 W·m⁻²) and maintain drilling-fluid temperature differentials of 10–18 °C under HTHP conditions. In addition, fabrication techniques such as plasma spraying, composite fabrication, and additive manufacturing enable the development of multifunctional insulation systems with improved thermal, mechanical, and corrosion-resistant properties. Hybrid TIDP systems integrating nanocomposites and advanced polymers show strong potential for improving drilling safety and efficiency. However, challenges related to durability, scalability, and cost remain, highlighting the need for further research on multilayer insulation architectures and sustainable materials. Full article

The incorporation of phase change materials in concrete is a practical strategy that holds great promise for enhancing the energy efficiency of buildings and reducing CO₂ emissions. However, the direct contact between phase change materials and cement interferes with the cement hydration reaction, leading to a significant reduction in the mechanical strength of cementitious composites. To encapsulate polyethylene glycol and prevent leakage, this study developed a shape-stabilized phase change aggregate via the cold-bonding method and the vacuum impregnation method. The nanoscale pore structure of the aggregate was regulated by adjusting the biochar content to enhance the phase-change material loading capacity. The phase change aggregate was characterized by indicators including crushing strength and water absorption. Meanwhile, its microstructure, the correlations between nano-sized hydration products, chemical compatibility, and phase change properties were analyzed. The fabricated phase change aggregate has a crushing strength of over 5 MPa, latent heat of 42.84 J/g, and phase change temperature of 29.17 °C while also exhibiting good mechanical properties and thermal energy storage performance. The compressive strength of phase change concrete can meet the strength requirements for structural building material. Moreover, phase change aggregate contributed to reduced CO₂ emissions during service, with favorable economic and low-carbon benefits over its service life, demonstrating good performance in both economic efficiency and CO₂ emission reduction. Full article

Thermal management is critical for maintaining the safety and performance of lithium-ion batteries. Phase change materials (PCMs) have been widely studied as passive cooling media due to their high latent heat capacity, but major technical challenges remain due to their relatively low thermal conductivity and nanoparticle sedimentation in composite systems. In this work, a composite phase change material (PCM) consisting of paraffin wax, a microencapsulated phase change material (MicroPCM 28D), and nano carbon black is developed to enhance thermal stability and suppress particle sedimentation through increased viscosity of the PCM matrix. Five capsule geometries fabricated by fused filament fabrication (FFF) 3D printing are experimentally investigated under airflow velocities ranging from 0 to 10 m s⁻¹. Wind tunnel experiments with infrared thermography are used to evaluate the thermal response of the PCM capsules. The results show that airflow velocity and capsule geometry strongly influence heat dissipation behavior. Compared with conventional wax composites, the MicroPCM 28D composite capsules reduce peak temperature by approximately 2–4 °C under airflow velocities of 0–10 m/s. These findings provide insights into geometry-regulated convection and stable composite PCM design for lithium-ion battery thermal management systems. Full article

Hybrid-electric propulsion and alternative energy carriers are being considered to mitigate the climate impact of short-range regional aviation. Within this framework, the HERA (Hybrid Electric Regional Architecture) project investigates advanced propulsion architectures for a next-generation 72 passenger regional platform. This work presents a cradle-to-grave Life Cycle Assessment of two HERA reference configurations and compares them with a conventional 70 passenger turboprop representative of current service aircraft. The analysis focuses on lithium–sulphur batteries, proton exchange membrane fuel cells, liquid hydrogen storage tanks, and electric motors. The assessment is implemented through a parametric LCA tool supported by a detailed Life Cycle Inventory based on Ecoinvent v3.8 and evaluated using ReCiPe 2016 midpoint indicators. The system boundary includes raw material extraction, manufacturing and assembly, operation under defined mission profiles, maintenance with component replacement, and End-of-Life (EoL) treatment. Results show that the operational phase remains the main driver of climate change impacts, exceeding 95% of total CO₂ equivalent emissions across configurations. The battery-based hybrid reduces fuel consumption but increases manufacturing and maintenance burdens. The fuel cell configuration shows a more balanced life cycle profile, with platinum identified as a critical hotspot. Full article

The crystal structure regulation of Ti₃O₅ by Al₂O₃ doping and its effect on the optical properties of TiO₂ films prepared by electron beam evaporation were systematically studied. Ti₃O₅ coating materials with different Al₂O₃ doping contents (0–50 at%) were prepared by vacuum melting, and the corresponding TiO₂ films were deposited on K9 glass substrates via electron beam vacuum evaporation. The phase structure, phase transition temperature, chemical composition and optical properties of the materials and films were characterized by XRD, DSC, EDS, XPS, UV-Vis and AFM. Results show that Al₂O₃ doping induces the phase transition of Ti₃O₅ from a room-temperature stable β-phase to a high-temperature stable λ-phase, with complete transition at 5 at% doping. Al³⁺ with a smaller ionic radius causes lattice contraction and local distortion of Ti₃O₅, enabling stabilization at room temperature of the λ-phase. For TiO₂ films, 12.5 at% doping is the optimal state with the stable composition transfer under this condition. With the increase in Al₂O₃ doping content, the refractive index and extinction coefficient of TiO₂ films decrease continuously, while the optical band gap and surface roughness show an increasing trend. The changes in optical properties are mainly ascribed to the low refractive index of Al₂O₃, lattice compressive strain effect and oxygen vacancy passivation induced by Al³⁺. This study clarifies the regulation effect of Al₂O₃ doping on Ti₃O₅ phase transition and TiO₂ film optical properties, and provides theoretical basis and experimental reference for the doping modification of TiO₂ films and their practical applications in consumer electronics and optical filter devices. Full article

The particle size of aggregate is a key factor affecting the mechanical properties and deformation capacity of cemented gangue filling body. In this study, coal gangue with a particle size range of (0.05, 20) mm was sieved into six groups of aggregate particles. Based on the Talbot gradation theory, cubic specimens with gradation indices n = 0.3, 0.4, 0.5, 0.6, and 0.7 were prepared for acoustic emission (AE) monitoring tests. The microstructure of the filling body was analyzed, and the failure characteristics and damage evolution laws of the cemented gangue filling body with different gradation indices were explored. The results show that the compressive strength reaches its maximum when n = 0.5. As the gradation index increases, the compressive strength of the specimens first increases and then decreases, and the specimens shift from primarily experiencing cleavage failure to shear failure. The curve of cumulative AE ringing count shows a bimodal distribution pattern, with both surge points and fracture points coexisting. The surge points can be regarded as precursor signals of backfill failure. The spatiotemporal evolution of AE events exhibits complex phased changes. An excessively small gradation index tends to form micropores and striped microcracks, reducing the compactness of the microstructure. An excessively large gradation index can lead to the formation of penetrative weak channels. A reasonable gradation index enables the mutual interlocking of aggregate particles, constructing a stable three-dimensional spatial skeleton structure. The dynamic trend of damage in the filling body can be captured based on AE analysis, and reverse guidance can be provided for parameter optimization of Talbot gradation, achieving a dynamic closed loop of “gradation design-AE monitoring-damage assessment-parameter optimization”. This not only enriches the application scenarios of acoustic emission analysis in graded materials, but also provides a new research approach and technical method for gradation design and safety assessment in scenarios where particle sizes are missing in practical engineering. Full article

This article presents a newly excavated Iron Age IIA cult room from Tel Lachish (Sanctuary BBE4) and examines its significance for the study of the organization of religious practice, situating this case within the broader corpus of Iron Age I–IIA local sanctuaries in Judah and the southern Levant. The evidence suggests that early Iron Age ritual practice was organized primarily at the level of extended kin groups, materialized in modest intramural cult rooms embedded within residential neighborhoods. These spaces reflect decentralized forms of religious authority, contrasting with the temple-centered ritual systems of the Bronze Age and with the increasing centralization of cult and religious authority in later phases of the Iron Age. By situating the Lachish evidence within a broader diachronic and regional framework, the study explores changing relationships between household ritual practices, kin-based social organization, and the development of state-level religious institutions in early Judah. Full article