Search Results (1,179)

This paper presents the design, structural optimization, and two-dimensional (2D) technology computer-aided design (TCAD) simulation of a gallium nitride (GaN) vertical Merged P-i-N/Schottky (MPS) diode incorporating a multi-drift-layer doping profile, composite SiO₂/Si₃N₄ passivation, and field-plate (FP) termination. The proposed device is constructed on an n⁺-GaN substrate with a three-sub-layer n-type drift region and a p-GaN/p⁺-GaN anode region. Systematic TCAD simulations are performed to investigate the dependences of key performance metrics—including knee voltage (V_knee), specific on-resistance (R_on), breakdown voltage (BV), reverse leakage current (J_leak), and Baliga’s figure of merit (BFOM)—on the Schottky metal work function, multi-drift-layer doping concentration, drift-layer thickness, Schottky-to-PN contact length ratio (γ_w), operating temperature, and reverse recovery switching transients. Results demonstrate that the MPS architecture effectively decouples forward conduction loss from reverse blocking capability, overcoming the conventional R_on–BV trade-off. The optimal doping profile (n_mm = 2 × 10¹⁵, n_m = 2 × 10¹⁵, n = 1 × 10¹⁶ cm⁻³) achieves a BFOM of ~31.97 GW·cm⁻² with BV ≈ 5.98 kV and R_on ≈ 1.12 mΩ·cm². Joint doping–thickness optimization further identifies a graded doping profile (n_mm = 2 × 10¹⁵, n_m = 5 × 10¹⁵, n = 1 × 10¹⁶ cm⁻³) combined with layer thicknesses (T_nmm, T_nm, T_n) = (4.49, 5, 20) μm as the overall optimum, achieving BFOM = 55.36 GW·cm⁻² (BV = 6.61 kV, R_on = 0.79 mΩ·cm²)—a +73% improvement, governed by the punch-through/field-stop design principle. The optimal contact ratio of γ_w = 1.33 yields a BFOM of 38.71 GW·cm⁻². Temperature analysis confirms a positive BV temperature coefficient due to drift-region-limited avalanche breakdown, and the BFOM improves monotonically from 33.31 to 37.82 GW·cm⁻² between 200 K and 450 K. Mixed-mode switching simulations show that increasing γ_w substantially reduces reverse recovery charge (Q_rr), demonstrating the strong potential of the proposed MPS diode for high-voltage, high-frequency, and high-temperature power electronic applications. Full article

Concrete contributes significantly to global CO₂ emissions due to high energy demand for cement production. This research integrates multiple advanced ensemble ML-based prediction models by combining experimental evaluation, explainable framework, and life cycle sustainability analysis for SCM (supplementary cementitious materials)-incorporated concrete mixtures. A comprehensive experimental program was conducted to evaluate the compressive and tensile strength of concrete revealing that the hybrid mix of GF4 with a 40% replacement level of cement with fly ash (FA) and ground granulated blast furnace slag (GGBFS) exhibited optimum synergistic performance due to balanced hydration kinetics and improved microstructure characteristics. For computational model development, a k-fold cross validation technique was deployed to evaluate robustness across multiple data partitions and to control overfitting in models. Model performance was assessed through multiple metrics including R², RMSE, and MAE with particular emphasis on the gap between training and testing performance. The best performing model was optimized using Particle Swarm Optimization (PSO) and Bayesian Optimization (BO) techniques providing an additional safeguard against overfitting. Shapley Additive Explanation (SHAP) interpretation revealed w/b ratio and curing age as key parameters for compressive strength, while fine aggregate content and curing age influenced tensile strength. For compressive strength, XGBoost model performed well with an R² value of 0.879 which was increased to 0.918 with the PSO optimization technique. For tensile strength, the Gradient Boosting model was selected with an R² value of 0.840 which was optimized to 0.879 after the PSO optimization technique. Moreover, life cycle assessment was performed to evaluate the environmental impacts in terms of embodied carbon and energy associated with concrete mixes. The hybrid GF4 mix demonstrated a 36% reduction in embodied carbon compared to the control mix, indicating strong potential for low carbon concrete applications. This integrated research contributes to the advancement of green construction practices and supports global efforts to reduce atmospheric impacts through the circular use of industrial byproducts. Full article

This work investigates Ferro-Rock concrete as a carbon-negative alternative to ordinary Portland cement (OPC), which accounts for 5–9% of global CO₂ emissions, and evaluates its viability as a sustainable construction material. Ferro-Rock is an iron-based binder comprising recycled iron powder, fly ash, metakaolin, limestone powder, and oxalic acid. This is enhanced by a carbonation reaction in which iron particles react with CO₂ and water to form iron (II) carbonate (FeCO₃), the main binding phase, thereby locking in atmospheric CO₂. The experimental program was divided into two groups. Group 1 studied 100% Ferro-Rock binders with different types of aggregate, specimen sizes, and CO₂ curing periods (0–6 days) with a new locally manufactured stainless steel curing chamber that provided a controlled CO₂ environment of 99.9% and 1.2–1.5 bar gauge pressure. Group 2 investigated Ferro-Rock as a partial cement replacement at 0%, 5%, 10%, 15% and 20% levels of substitution with 5% increments. The 7 and 28 days of compressive, flexural and indirect tensile strengths were determined. The results showed the Ferro-Rock with 100% iron ductile waste aggregates (Mix F4) achieved a 28-day compressive strength of 5.5 MPa, 37.5% higher than the standard Ferro-Rock reference mix. The optimum replacement range of Group 2 was 5–10% with an increase in compressive strength by 5–10%, flexural strength by 11%, and indirect tensile strength by 16% over the OPC control. When replacement exceeded 25%, the bonding was weakened, and all strength measures decreased significantly, reaching a 46% reduction in compressive strength at 50% substitution. Scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDS) microstructural analysis verified the gradual formation of the iron carbonate crystalline phase and provided mechanistic insights into the observed strength trends. Fully cured Ferro-Rock specimens sequestered as much as 11% CO₂ by weight, with a verifiably carbon-negative profile that no OPC-based system can match. Full article

Reliable nursery production is essential for producing ex situ planting stock of the locally threatened mangrove Lumnitzera littorea in Can Gio, Vietnam. We evaluated 12-month seedling performance using two nursery substrates—CTI (topsoil) and CTII (mixed substrate)—and salinity-structured irrigation regimes: C, a dynamic river/tidal water plus freshwater reference regime and seven fixed-salinity treatments (E1–E7: 0, 10, 15, 20, 25, 30, and 35‰). Each substrate–regime combination comprised three replicate cells of 40 seedlings (N = 1920). The primary endpoints were month 12 survival (SR12), seedling height among survivors (H12), and root collar diameter among survivors (Do12). Statistical inference was confined to E1–E7; C was retained as a descriptive operational reference. For E1–E7, substrate and regime significantly affected SR12 and H12, whereas Do12 varied by regime but not by substrate; no substrate × regime interaction was detected. SR12 declined sharply at 30–35‰, especially under CTI, and the high-salinity H12 and Do12 estimates were based on few survivors. CTII outperformed topsoil alone, particularly for survival and survivor-conditioned height. The findings support conservative nursery guidance for Can Gio: use a mixed substrate and avoid sustained high fixed-salinity irrigation, without extending the inference to a species-wide salinity optimum or post-planting field performance. Full article

The increase in CO₂ concentration in the atmosphere can be attributed to various anthropogenic activities. Soils play a significant role in climate regulation, particularly through the storage of atmospheric carbon in soil organic matter. The main aim of the study was to examine the effects of site conditions on soil CO₂ flux in middle-aged stands of pedunculate oak (Quercus robur L.). A three-year study was conducted in three middle-aged stands within different subtypes of Chernozem. One of these stands is a windbreak (RŠ), while the other two stands (VN and DE) belong to larger forest complexes. Air samples were collected using the closed-chamber technique and analyzed using gas chromatography. The linear mixed-effects model (LMM) revealed that soil temperature, soil moisture, and location had significant effects on soil CO₂ flux (p < 0.05), whereas the effect of year was not significant (p > 0.05). The results showed that there was a higher temperature sensitivity of soil respiration (Q₁₀) in the windbreak (RŠ) compared to the other two stands (VN and DE). The mean annual carbon loss through soil respiration for all stands was assessed to be approximately 3.24 ± 0.12 t C ha⁻¹ yr⁻¹. These findings suggest that lower soil CO₂ flux in stands growing under optimal site conditions may indicate a more favorable carbon balance compared to stands growing outside their ecological optimum. Full article

A composite warm-mix additive (PNSK) was developed to improve asphalt workability by reducing viscosity while maintaining rheological performance at both high and low temperatures. The warm-mix asphalt binders (PWMA) were analyzed using an integrated approach combining conventional property tests with rheological analysis. Results showed that penetration, softening point, and ductility improved. The viscosity-reduction effect was enhanced with increasing PNSK dosage, yet the benefit plateaued beyond 11% content. Additionally, the adhesion strength between asphalt and aggregate began to decrease after 11% dosage, with 12% serving as the critical threshold for adhesion deterioration. Consequently, the optimal dosage was determined to be 11% based on comprehensive consideration of all factors. LAS results demonstrated that 11%PWMA exhibited lower strain sensitivity and superior fatigue resistance at low-to-intermediate temperatures, with fatigue life increasing by nearly an order of magnitude under low strain at 20 °C. MSCR results revealed that under low stress, 11%PWMA exhibited significantly lower non-recoverable creep compliance (J_nr) and higher percent recovery (R) than the 70^#, especially in the high-temperature range (54–66 °C), demonstrating superior resistance to permanent deformation. However, 11%PWMA exhibited temperature-strain sensitivity characteristics under high-temperature, high-strain conditions, representing an inherent characteristic of WMA technology. Full article

This study examined the foaming characteristics of asphalt and their effects on the performance of cold recycled mixtures. The expansion ratio and half-life were used to evaluate effects of asphalt type, foaming temperature, and water content. The influence of asphalt content, gradation, cement content, curing time, and mixing water on mechanical properties and water stability was analyzed. The results indicate that asphalt type is the key factor affecting foaming performance. CNOOA asphalt showed optimal foaming at 160 °C with 2% water, achieving an expansion ratio of 27 and a half-life over 30 s. Optimal asphalt contents for gradations A and B are 3.5% and 2.5%, respectively. A 1.5% cement content provides the best performance balance. Dry and wet indirect tensile strengths increased by 91.18% and 205.56% after 3-day curing. The optimal mixing water ranges are 60–90% and 70–80% of optimum moisture content for gradations A and B. Curing time has the most significant influence on performance, followed by cement and asphalt content. This study provides a theoretical basis for optimizing foamed asphalt cold recycling. Full article

The decoupling of physical loading configurations from dynamic temperature control in cold-chain logistics exposes supply chains to severe thermal compliance risks and exponential cost penalties. To address this structural gap, this study formulated the Cold Chain Unitization Loading Optimization Problem (CCULP). We propose a mixed-integer linear programming (MILP) model that integrates continuous-time heat-transfer dynamics—including door-opening impulse disturbances—and Q10-driven quality-decay kinetics as endogenous constraints within the hierarchical assignment of perishable goods to insulated containers, pallets, and vehicles. By treating container thermal resistance as a core decision variable, the model operationalizes a “prevention-first” economic strategy. To solve this NP-hard problem, we developed a Temperature-Aware Heuristic Algorithm (TAHA) that embeds a forward-Euler temperature simulation loop directly into the combinatorial search. Computational experiments on instances up to 100 SKU types demonstrate that TAHA achieves near-optimal solutions (within 0.7% of the MILP proven optimum) while converging 63 times faster than a genetic algorithm benchmark. Moreover, compared with traditional geometry-centric heuristics, TAHA’s proactive container-polarization strategy effectively eliminates the “penalty cliff,” yielding up to a 25.9% reduction in total system cost on Large-scale instances, almost entirely attributable to the elimination of temperature-violation penalties. Sensitivity analyses further confirm TAHA’s robustness under extreme environmental stress (e.g., 40 °C ambient temperatures) and frequent logistical disturbances, offering an integrated framework for proactive risk mitigation and for reducing food loss in sustainable temperature-controlled distribution. Full article

The low-pressure environment at aircraft cruising altitudes severely degrades lithium battery performance, yet the effectiveness and mechanisms of air-cooling thermal management under such conditions remain poorly understood. This study systematically investigates the coupled thermal, electrical, and material responses of NCM523/graphite ternary batteries under forced air-cooling at three pressures (96 kPa, 77 kPa, 58 kPa) and varying wind speeds (0–10 m/s) during 4C charge/6C discharge cycling. Air cooling reduces the maximum surface temperature by up to 14.2 °C and maintains the temperature difference below 5 °C, even at 58 kPa. An optimal wind speed of 6 m/s extends cycle life by 71% at 58 kPa (from 45 to 77 cycles), suppresses resistance growth, and preserves discharge capacity. Further increasing the wind speed paradoxically accelerates degradation. Post-mortem analyses reveal that appropriate air cooling mitigates cathode particle fragmentation, restores cation mixing (I₀₀₃/I₁₀₄ from 1.07 to 1.63 for 58 kPa), reduces transition metal dissolution, and suppresses solid electrolyte interface (SEI) thickening. This work establishes an optimum air velocity for low-pressure battery cooling and provides mechanistic insights into preserving electrode structural integrity, offering design guidelines for safe battery thermal management in electric aircraft. Full article

Copper slag (CS) was considered a major by-product produced from the copper refining industry, which estimates about 2.2 to 3 tons generated during the production of every one ton of copper. At the same time, continuous dumping and improper disposal of this byproduct have led to serious environmental problems, especially due to the leaching of heavy metals into soil and water. This review carefully studies the potential of CS as a sustainable construction material through a clear distinction of its performance, especially when used as a fine aggregate and as a supplementary cementitious material (SCM). Due to the presence of higher content of iron and silica, higher hardness, and very low water absorption, it was found that CS helps in improving the density and durability of concrete. When used as a fine aggregate, CS enhances workability, strength, and durability at an optimum level of about 40%, mainly due to better particle packing and reduced pore connectivity. On the other hand, when used as an SCM, CS contributes to long-term strength through pozzolanic reactions and the formation of C–S–H gel, but its replacement level should be limited to about 20% to avoid loss of early-age strength caused by reduced alkalinity. In terms of durability, the use of CS can reduce water absorption by up to 60%, lower chloride penetration, and improve resistance to sulfate attack. Environmental Life Cycle Assessment studies show that CS can reduce global warming potential by about 12–19% and also decrease overall energy consumption. Statistical validation using multi-criteria decision analysis (MCDA) and separate regression modeling with an R² value of about 0.965, which supports these optimum replacement levels up to 40% for fine aggregate and 20% for cement, providing a good balance between strength, durability, environmental benefits, and cost. Overall, this review shows that CS is a valuable and multi-functional material that supports circular economy practices when used with a proper mix design based on specific applications. Full article

This study considers the potential of utilizing waste glass powder as a sustainable additive to improve the characteristics of clay subgrade soils. A comprehensive experimental program was designed, wherein a selected clay soil was amended with four distinct contents of glass powder that were finely ground: 0%, 3%, 6%, and 9% by weight. The primary objective was to evaluate the resultant improvements in soil strength and the enhanced interfacial bond between the treated subgrade and an overlying Type B granular subbase layer, which was further reinforced with an SS2 Geogrid. To characterize these effects, a suite of laboratory tests was performed, including the Modified Proctor Test, Atterberg Limits Test, California Bearing Ratio (CBR) test, and a large-scale direct shear test. A specially made large-scale instrument for direct shear was employed for the interface testing. The results demonstrate a clear positive correlation between the proportion of glass powder and the improvement in geotechnical properties. The most significant enhancement was observed at the 9% inclusion rate, which yielded a 6.6% increase in the maximum dry density and a substantial 49% improvement in the CBR value. Concurrently, this optimal mix design resulted in a 14% reduction in optimum moisture content, alongside notable decreases in the swelling and plasticity indices by 33% and 39%, respectively, confirming the efficacy of glass powder in stabilizing the clay subgrade. Full article

This research aims to study the compressive behavior of concrete with partial replacement of fine aggregate by recycled rubber. In addition, the mechanical capacity of these concretes will be analyzed when reinforced by carbon fibers (CFRP) and basalt (BFRP) confinement. To carry out the work, 48 cylindrical test specimens were made, corresponding to 4 mixes, with different percentages of recycled rubber by volume (0%, 10%, 20%, and 30%). The compressive behavior of unreinforced concrete with and without recycled rubber, reinforced concrete made from concrete with and without recycled rubber previously taken to failure, and reinforced concrete with and without recycled rubber without prior failure were evaluated in order to assess the influence of concrete quality before placing the reinforcement. The results show that replacing fine aggregate with recycled rubber in concrete reduces its strength and stiffness, increasing its ductility, with the optimum replacement percentage being 10%. On the other hand, confining concrete with FRP (BFRP and CFRP) improves its strength and ductility compared to unconfined concrete, obtaining similar values regardless of the initial strength of the reinforcing concrete. Confining concrete with CFRP achieves strength improvements of 26% compared to reinforcement with BFRP. Full article

Wireless sensor networks increasingly support time-critical monitoring applications, where coverage optimization must often be performed under limited computational resources. This work addresses a previously underexplored WSN coverage problem involving range-free, angular-limited sensors with transmitter-induced sensing degradation and discrete sector orientation. We formulate a mixed combinatorial problem that jointly optimizes $K$-out-of-$N$ sensor activation and sector assignment under strict feasibility constraints. A constraint-aware genetic algorithm with repair-based feasibility enforcement is proposed and validated against the global optimum obtained via exhaustive enumeration, enabling direct quantification of optimality. The repair mechanism corrects infeasible offspring after each genetic operation to guarantee that exactly K sensors remain active, eliminating the need for penalty-based constraint handling. A brute-force search is used to establish the global optimum of our small-scale scenario, serving as a ground-truth optimality benchmark for evaluating the proposed method. The purpose of this comparison is not to assess competitiveness against other metaheuristic algorithms, but to quantify how closely the proposed approach approximates the true optimal solution under strict problem constraints. The constraint-aware genetic algorithm is developed using an integer chromosome encoding, two initialization strategies, two crossover pairing schemes, elitism, and per-gene mutation, combined with alternative constraint-handling strategies. Two experimental series evaluate the impact of population size, crossover method, mutation probability, and constraint handling using problem-specific metrics, alongside convergence and fitness statistics. The proposed algorithm reliably reaches near-optimal solutions with significantly reduced computational cost when compared to exhaustive search. By integrating problem-specific constraints directly into the process, the proposed evolutionary optimization method effectively balances solution quality and execution time, making it well suited for scenarios requiring rapid sensor reconfiguration. Full article

Network function virtualization (NFV) enables flexible service deployment by implementing network functions as software, with service function chains (SFCs) linking virtual network functions (VNFs) in a specific order to deliver end-to-end services. However, ensuring SFC resilience against large-scale disasters that can disrupt entire disaster zones (DZs) remains a significant challenge. In this paper, we study the multipath disaster-resilient SFC deployment problem, aiming to minimize the total bandwidth and computing resource overhead by jointly optimizing VNF placement, multipath routing, and protection mechanisms, subject to DZ-disjoint constraints. We formulate this problem as a Mixed-Integer Nonlinear Programming (MINLP) model and prove it to be NP-hard. To solve it efficiently, we propose a two-stage adaptive deployment approach; the first stage employs heuristic rules to generate a set of candidate paths satisfying DZ-disjoint constraints, and the second stage leverages deep reinforcement learning to intelligently place VNFs along these candidate paths, approximating the global optimum. Simulation results on real network topologies demonstrate that, compared to traditional dedicated protection strategies and a state-of-the-art exact algorithm, the proposed approach reduces resource overhead by up to 20% while effectively guaranteeing SFC disaster resilience, exhibiting good scalability and online deployment potential. Full article

The global construction sector, a major consumer of virgin raw materials, is under increasing pressure to transition from a linear to a circular economy model. Marble waste, generated in large quantities during quarrying, cutting, and polishing operations, represents a promising secondary resource for sustainable construction applications. This systematic review was conducted in accordance with the PRISMA 2020 reporting guidelines to critically evaluate the utilization of marble waste in concrete and other building materials. A comprehensive literature search was performed using major scientific databases, and relevant studies published between 2000 and 2025 were analyzed. The findings consistently indicate that marble waste performs most effectively as a fine aggregate replacement at 10–20%, resulting in improved compressive strength, pore refinement, and durability. As a cement substitute, the optimum replacement level is generally 5–10%, beyond which dilution effects may adversely affect strength development. The performance is primarily attributed to improved particle packing and microstructural refinement. This review further highlights future pathways for industrial-scale implementation, mix optimization, standardisation, and policy integration to accelerate circular construction practices. These findings support the potential of marble waste as a sustainable material in advancing circular economy principles in the construction industry. Full article