Search Results (2,050)

Decarbonizing the transportation sector requires quick adoption of low-carbon energy carriers, with green hydrogen becoming a promising option for zero/low-emission mobility. Hydrogen refueling stations powered by renewable energy sources present a practical way to cut down lifecycle greenhouse gases and ease grid congestion. Nonetheless, most existing photovoltaic (PV)-based hydrogen production systems focus solely on electrical aspects, overlooking thermal energy flows and temperature effects that greatly impact PV and Electrolyzer performance. This study provides a thorough techno-economic evaluation of a hybrid PV/photovoltaic-thermal (PVT) green hydrogen system for refueling stations. The simulation framework models the combined electrical, thermal, and hydrogen subsystems under realistic conditions, incorporating rooftop PV/PVT collectors, battery storage, a water Electrolyzer, and hydrogen storage. Thermal energy from the PVT is used to pre-heat Electrolyzer feedwater, lowering electricity demand for hydrogen production and boosting PV efficiency via active cooling. Hydrogen production follows a demand-driven control strategy based on randomly generated stochastic daily refueling events. Three configurations are compared: (i) grid-only electrolysis, (ii) PV-only assisted electrolysis, and (iii) fully integrated PV/PVT-assisted electrolysis. The results show that the integrated PV/PVT setup significantly increases self-consumption, autarky rate, and overall efficiency, while lowering reliance on grid electricity and hydrogen production costs. Developed case studies highlight the economic feasibility and real-world viability of PV/PVT-assisted (decentralized) hydrogen refueling infrastructure. Full article

To address the issues of high cutting temperatures and severe tool wear during titanium alloy machining, this study proposes a hybrid surface modification strategy combining micro-textures and multicomponent titanium nitride (TiN)-based coatings on cemented carbide tools. Using YG8 cemented carbide as the substrate, micro-dimple textures were fabricated by fiber laser, and three coatings with different architectures (TiAlSiN, TiSiN/TiAlN, and TiSiN/TiAlSiN/TiAlN) were deposited via multi-arc ion plating technology. Based on a two-factor (texture diameter and texture spacing) and three-level orthogonal experiment, the evolution behaviors of surface morphology, phase composition, and mechanical properties of the textured multicomponent TiN-based coatings were systematically characterized and comparatively analyzed. The results reveal that: compared to the monolithic-structured TiAlSiN coating, the TiSiN/TiAlSiN/TiAlN and TiSiN/TiAlN composite coatings with multilayered composite structures can effectively relieve the residual stress inside the film–substrate system, and significantly suppress the phenomena of coating cracking and localized spallation caused by irregular protrusions of the recast layer at the micro-texture edges. X-ray diffraction (XRD) and crystallite size analyses indicate that the amorphous Si₃N₄ phase promoted by the Si element in the composite coatings effectively impedes the growth of TiN columnar crystals, achieving significant grain refinement. Mechanical property tests confirm that the existence of multicomponent composite interfaces effectively hinders dislocation movement. Among them, the textured TiSiN/TiAlSiN/TiAlN composite coating exhibits the optimal comprehensive performance; its microhardness, nanohardness, and H/E ratio (characterizing the resistance to plastic deformation) are increased by 17.94%, 8%, and approximately 45%, respectively, compared to those of the textured TiAlSiN coating. This study deeply elucidates the synergistic strengthening and toughening mechanisms between micro-texture parameters and the internal structures of the coatings, providing important theoretical guidance and experimental data support for the surface design of long-lifespan tools oriented towards the high-efficiency machining of titanium alloys. Full article

Introduction: Advancements in thermo-mechanical surface treatment of endodontic nickel–titanium (NiTi) instruments introduced another aspect of variation. Particularly related to their metallurgy, which influences their behaviour in relation to temperature. This is clinically significant, considering the variation in the temperatures inside the root canal during instrumentation. This study aimed to compare the effects of different temperatures on the bending stiffness, cyclic fatigue resistance, and cutting efficiency of two reciprocating heat-treated NiTi files: R-Motion (RM) and WaveOne Gold (WOG). Methodology: Bending stiffness was examined in a temperature-controlled water bath, measuring the maximum force in Newtons during a 3 mm tip horizontal displacement. The cyclic fatigue resistance was tested in a simulated stainless-steel canal (35° curvature, 6 mm radius) in dynamic mode at 22 °C, 37 °C, and 45 °C. Time to fracture (TTF) and length of fractured fragment were recorded, and representative samples were examined using scanning electron microscopy. The cutting efficiency was assessed using bovine bone slabs measuring 1.5 mm in thickness and 15 mm in width. The files were activated in reciprocation mode for three minutes while resting on the upper surface of the slab, while submerged in a water bath maintained at 22 °C, 37 °C, or 45 °C. The maximum cutting depth was measured in millimetres under magnification. Additionally, Differential Scanning Calorimetry (DSC) analysis was performed for three specimens of each file type. Results: RM exhibited significantly higher TTF, longer fractured fragments, and smaller cutting depths than WOG across all temperatures. The RM was significantly stiffer at 37 °C and 45 °C only. For each file type, increasing the temperature was associated with a significant increase in stiffness (p < 0.01), except for WOG between 22 °C and 37 °C (p = 0.199). The TTF was significantly higher in RM at 22 °C, while the TTF in WOG increased significantly with lower temperatures. No effect was observed on the length of the fractured fragment. Lower temperatures were also associated with reduced cutting efficiency in both files. Conclusions: Temperature has a significant impact on the properties and performance of RM and WOG and should be considered during instrumentation. File design has a greater influence on their strength and cutting ability than their transformation behaviour related to heat treatment. Full article

This study presents the results of shell-side pressure drop calculations for a model shell-and-tube heat exchanger with an inner shell diameter of 200 mm and an effective tube length of 518 mm. The tube bundle consisted of 85 copper tubes (12/10 mm) arranged in a staggered layout with a pitch ratio of 1.5. The exchanger contained nine segmental baffles with a 25% cut, spaced 48 mm apart. The mean temperature of the hot water flowing on the shell side was 69 °C, and the mass flow rate varied in the range of 1–6 kg/s. In particular, the effects of the tube bundle diameter, nozzle diameter, and sealing strips on the pressure drop were investigated. The calculations employed the extended Bell–Delaware method and the VDI method. The results were compared with calculations performed using Aspen EDR and with numerical simulations carried out in OpenFOAM and Ansys Fluent. The comparison shows that the difference in total pressure drop estimation can reach up to 40% depending on the method used. Full article

The design and main parameters of a plasma–chemical reactor containing two compartments are presented. One compartment houses a vacuum-arc evaporator, while the other houses a planar magnetron. The compartments are separated by a diaphragm with a dosing slot for injecting copper vapor into the TiN synthesis compartment. The conditions for the synthesis of superhard TiN-Cu composite coatings are experimentally determined. Based on established process parameters for TiN synthesis in a nitrogen-containing plasma by Ti evaporation using a vacuum-arc discharge, it is proposed to apply TiN-Cu coatings by injecting Cu vapor into the TiN synthesis area and sputtering Cu using a magnetron discharge. XRD analyses of both TiN and TiN-Cu coatings show the presence of WC, Ti₂C, and TiN. EDS analysis confirms 5.57 at. % copper on the surface of the TiN-Cu coating. Real-life operating tests of TiN-Cu coatings on replaceable WC-TiC-Co (79/15/6 wt.%) alloy hexagonal inserts used for cutting 40Kh steel revealed that applying the TiN-Cu coating extends the tool life of WC-TiC-Co inserts by about 2.5 times compared with uncoated tools. Cutting force measurements on TiN-Cu-coated inserts showed no vibration or noise during cutting, driven by a reduced friction coefficient and improved heat dissipation at the contact zone between the cutting edge and the workpiece, thereby lowering the temperature in that area. Full article

Binary-cycle geothermal plants are inherently limited by thermodynamics, forcing operators to reinject fluids at temperatures that are still valuable for direct heating. This process results in substantial exergetic waste. While prior research has examined efficiency at the level of individual plants, this study introduces a regional-scale framework to convert these facilities into multi-purpose energy hubs. The research focuses on Türkiye’s Western Anatolia Graben, a region with high geothermal activity that, paradoxically, remains dependent on fossil fuels. By combining meteorological records with operational plant data, we evaluated the existing housing stock of 983,277 residences across 14 districts and modeled the heating requirements for a targeted capacity of 468,719 residences that the proposed system can serve. The results indicate that the currently wasted thermal load in 10 specific districts, including key centers such as Sarayköy and Alaşehir, is sufficient to cover peak winter heating demands without fossil fuel backup. Although the infrastructure requires a significant initial investment of $4.51 billion, the project demonstrates long-term viability with a Levelized Cost of Heat (LCOH) of 62.94 USD/MWh and a payback period of 10.43 years. Beyond economic considerations, the system serves as a major decarbonization tool, capable of cutting residential CO₂ emissions by 1.7 million tons annually (a 47.7% reduction). These findings suggest that policy incentives should move away from electricity-only models toward integrated reservoir management to maximize resource efficiency. Full article

This paper presents the results of calculations of the shell-side heat transfer coefficient and pressure drop for a shell-and-tube heat exchanger with an inner shell diameter of 200.2 mm and an effective tube length of 518 mm. The exchanger contained 85 copper tubes (12/10 mm), arranged in a staggered layout with a pitch ratio of 1.5. It was equipped with nine segmental baffles, with a 25% baffle cut and a baffle spacing of 48 mm. The inlet temperature of the hot water flowing through the shell, and the mass flow rate, were varied in the ranges of 35–79 °C and 1–3 kg/s, respectively. The calculations were performed using the extended Bell–Delaware method, the VDI (Gaddis–Gnielinski) method, and the Aspen Exchanger Design and Rating. CFD simulations were performed using the OpenFOAM and Ansys Fluent software packages. The calculated results were then compared with the available experimental data. The findings showed that the VDI method generated the greatest overestimation of the heat transfer coefficient and underestimated the pressure drop, whereas the extended Bell–Delaware method demonstrated the highest agreement with the experimental data. Full article

Ventricular septal defect (VSD) occluders commonly rely on permanent nitinol frameworks, which may contribute to long-term mechanical mismatch and late complications. Here, we developed a tissue-compliant composite membrane by embedding a 3D-printed poly(vinyl alcohol) (PVA) grid within a shape-memory poly(glycerol dodecanedioate) (PGD) matrix. Grid spacing was varied from 0.1 to 0.5 mm to tune reinforcement density. FTIR indicated that PVA was incorporated mainly through physical interlocking rather than new covalent bonding. The composite preserved near-body-temperature shape recovery. In water at 37 °C, PVA reinforcement increased tensile modulus and fracture strength, although swelling also increased. Finite-element analysis and benchtop occlusion testing consistently showed lower deformation, less strain localization, and smaller bulge height for PGD–PVA than for PGD alone. In vitro assays showed low cytotoxicity, low hemolysis, and prolonged plasma recalcification time. A 12-week pilot degradation study showed that the faster mass loss observed in initial samples was mainly caused by exposed PVA cut edges; after switching to a fully encapsulated design, static mass loss became similar across groups, and dynamic PBS agitation produced about 10% mass loss at 12 weeks. These results support PGD–PVA as a reinforced membrane strategy for polymeric occluders. Full article

To address the issues of high cutting temperature and insufficient heat dissipation during the machining of γ-TiAl alloys, this study systematically investigates the effects of three cooling strategies—dry cutting, flood cooling, and high-pressure cooling—on tool wear and surface integrity. The variations in tool wear, surface morphology, surface roughness, surface defects, microstructure, and microhardness were analyzed in detail. The experimental results indicate that adhesive wear is the dominant wear mechanism under all three cooling conditions. Owing to its superior penetration capability, high-pressure cooling significantly suppresses tool wear, although it may induce groove wear. In terms of surface integrity, high-pressure cooling significantly improves the machined surface quality while reducing surface defects, plastic deformation, and work hardening. Compared with dry cutting, the surface roughness decreases by approximately 9.1%–39.0%, the thickness of the plastically deformed layer is reduced by up to 50.74%, and the degree of work hardening decreases by approximately 11.5%–14.5%. With increasing cutting speed, the surface roughness, plastically deformed layer thickness, and degree of work hardening increase under all three cooling conditions; however, high-pressure cooling still maintains the best overall performance at high cutting speeds. These results indicate that high-pressure cooling effectively suppresses thermo-mechanical coupling in the cutting zone by enhancing coolant penetration and lubrication, thereby providing an efficient approach to reducing tool wear and improving the surface quality of machined γ-TiAl alloys. Full article

The Dongqiyishan W-polymetallic deposit is a large porphyry deposit in the Beishan region, Inner Mongolia. Based on cross-cutting relationships of veins and distinct mineral assemblages, the hydrothermal evolution of the Dongqiyishan deposit can be divided into three mineralization stages, with corresponding characteristic alteration types: (1) early W mineralization stage, dominated by potassic–sodic alteration; (2) main W mineralization stage, characterized by extensive phyllic alteration; and (3) post-W-mineralization hydrothermal stage, associated with quartz–fluorite–calcite alteration. This study employs an integrated approach, including molybdenite Re-Os dating, microthermometry of fluid inclusions, and H-O-S isotopic analyses, to investigate the genesis of the deposit. The results show that: (1) the metallogenic age of the deposit is 222.2 ± 1.5 Ma (MSWD = 0.58; Middle Triassic), which was likely caused by the northward subduction of the Paleo-Tethys Ocean; (2) the metallogenic fluids of Stage I (homogenization temperature 350~400 °C, salinity 6.0~8.0 wt.% NaCl eqv.) and Stage II (homogenization temperature 300~350 °C, salinity 4.0~6.0 wt.% NaCl eqv.) are mainly from magmatic water, and Stage III (homogenization temperature 225~275 °C, salinity 4.0~8.0 wt.% NaCl eqv.) has a mixed fluid of magmatic water and meteoric water; (3) the ore-forming materials were mainly derived from magma, which is supported by the S isotopic results (δ³⁴S = −0.5‰~1.6‰, average 0.93‰); (4) mineralization depths calculated through fluid inclusions are 0.52–1.60 km (Stage I), 0.70–1.80 km (Stage II) and 0.10–0.49 km (Stage III); and (5) Stage I W precipitation was likely driven by fluid boiling and water–rock interaction, Stage II W precipitation by water–rock interaction principally, and Stage III fluorite precipitation by water–rock interaction plus fluid cooling. This research provides theoretical guidance for W-polymetallic prospecting in the Beishan of Inner Mongolia. Full article

The results of the development and practical application of a comprehensive system for studying gear cutting processes are presented. The processes are traditional hobbing, modern power skiving, and radial-circular methods. Carrying out these processes is based on the gear teeth continuous generating method using complex kinematics. This complicates the analysis, description and modeling of the processes. The developed system provides for a logical sequence of step-by-step modeling and simulation of interrelated processes and phenomena accompanying gear processing. Reproducing volumetric chips and calculating their parameters provides the basis for determining deformation and contact processes, cutting forces, elastic deformations, machining accuracy and energy costs per operation. After establishing the operation to overcome friction and heat flows, the degree of heating and the temperature of the working surfaces are calculated to predict tool wear and its service life. Based on the parametric non-uniformity of the considered processes, the intensity of oscillations and vibrations of gear cutting machines is predicted, and their impact on the quality of gear surfaces and the accuracy of gears is determined. These approaches enable the study of such processes at the level of individual teeth and blades during cutting. They also allow gear cutting technology and cutting tools to be optimized according to the most important criteria and performance assessments. Full article

To address the challenges of winter pavement icing and the disposal of organic waste, this study developed a sustained-release deicing filler utilizing biochar derived from spent coffee grounds (SCGs). The material was synthesized through high-temperature carbonization, followed by physical adsorption of chloride salts and surface hydrophobic modification to control release rates. The study made asphalt mixtures and replaced normal mineral filler with the SCG material by volume at ratios of 0%, 50%, 75%, and 100% to test road and deicing performance. Wheel-tracking tests showed that the additive improved high-temperature stability and dynamic stability went up by 27.04% at the 75% replacement level. Salt dissolving created voids and slightly lowered water stability at high dosages, but all performance numbers still met the current engineering rules. Rutting slab tests at −5 °C showed the 100% replacement mix cut snow coverage to 11.43% in 60 min and proved it works for deicing. Pull-out tests measure the bond strength between ice and pavement at −5 °C, −7 °C, and −9 °C. The SCG deicing material weakens ice sticking and the bond strength for the 100% group at −5 °C was 0.35 kN, which is about 57.8% lower than the control asphalt. The bond strength of the deicing mix at −9 °C was still lower than the normal mix at −5 °C. This big drop in stickiness means the pavement stops ice from packing hard and makes mechanical removal easier. This study shows that the prepared deicing materials exhibit excellent sustained-release performance and snow-melting efficiency while ensuring satisfactory road performance. SCG deicing materials can effectively reduce snow accumulation on road surfaces in winter, lower the difficulty of ice-layer removal, and realize the sustainable utilization of SCGs. Full article

Green façades are acknowledged as passive strategies that reduce heat accumulation, enhance biodiversity, improve particulate matter absorption and provide psycho-physiological benefits for users. However, evaluations of their thermal performance—accounting for seasonality, vegetation density, and leaf characteristics—remain incomplete. This study addresses this gap by assessing two green façade typologies on a sample building located in Northern Italy (Cfa climate). ENVI-met microclimate simulations compared a bare wall with vegetated façades featuring Hedera helix (evergreen) and Parthenocissus tricuspidata (deciduous) across four orientations and seasonal conditions, considering the sample building and the immediate surrounding outdoor space. Both species reduced wall-surface temperatures (T₀) and improved outdoor thermal comfort perception (PET), influenced by LAI dynamics, foliage persistence, and façade orientation. Results indicate that Parthenocissus tricuspidata achieved the greatest cooling effect during hot periods due to higher LAI, with absolute T₀ reductions of up to 22.1 °C on southern façades and 30.0 °C on western façades. In these orientations, PET improvements reached up to 3.0 °C (south) and 8.0 °C (west). Conversely, Hedera helix ensured stable year-round performance and performed better on northern façades during colder periods. The results stress the need for integrated design that aligns plant choice with orientation and seasonal growth to optimize thermal performance, cut cooling demands, and improve outdoor comfort. Full article

This study investigates the factors affecting surface integrity during the machining of near-β Ti-5553, a critical material in the aerospace and defense industries. Considering this alloy as a difficult-to-machine material, the turning process was examined by analyzing the effects of cutting speed, feed rate, and cooling strategy (dry, conventional, and 30 MPa/High-Pressure cooling) on cutting force, temperature, surface roughness, and residual stress. The primary novelty of this research lies in its integrated approach: rather than evaluating surface integrity metrics in isolation, it simultaneously models interrelated responses to residual stress, cutting temperature, cutting force, and surface roughness under high-pressure coolant (HPC) conditions. Furthermore, it introduces a robust machine learning framework that uniquely applies data augmentation (Gaussian jittering and interpolation) to overcome the conventional constraints of limited experimental machining data, providing a highly accurate predictive tool. The experimental data were expanded using data augmentation methods (Gaussian jittering and interpolation) and modeled using five different machine learning algorithms (Extra Trees, Random Forest, Gradient Boosting, KNN, and AdaBoost). The results revealed that cooling pressure plays a dominant role, particularly in residual stress (importance score: 0.926) and cutting temperature (0.657). It was observed that high-pressure cooling (HPC) reduces thermal gradients, thereby lowering tensile stresses and improving surface integrity. When algorithm performances were compared, the Extra Trees and Random Forest models achieved the most accurate predictions after hyperparameter optimization. Specifically, the optimized Extra Trees regressor demonstrated exceptional predictive capability for residual stress, achieving an accuracy of 98.47%, a remarkably high coefficient of determination (R² = 0.9997), and a minimal Mean Squared Error (MSE = 6.8289). These quantitative results confirm that the proposed machine learning framework provides a highly reliable and precise tool for controlling surface quality in HPC- assisted machining. Full article

Water-based drill cuttings generated during onshore natural gas development are complex solid wastes that may pose environmental risks if improperly managed. This study evaluates the feasibility of reutilizing water-based drill cuttings as pavement base materials after stabilization using a novel composite stabilizer composed of cement, stabilizer liquid agent, and water-reducing powder (CLP stabilizer). Mix proportion optimization was conducted through compaction and 7-day unconfined compressive strength tests, followed by evaluation of road performance, including strength, compressive rebound modulus, water stability, and temperature shrinkage, with stabilized powder stabilized soil as a control. Microstructural characteristics were analyzed using X-ray diffraction and scanning electron microscopy, and environmental safety was assessed through heavy metal leaching tests and background soil investigation. The results show that the optimal mixture ratio of curing agent (5% cement + 2% liquid stabilizer + 8% superplasticizer powder) satisfies the strength requirement for pre-drilling road bases, exhibiting superior performance compared to the control group. When the stabilizer dosage reaches 9%, the 7-day unconfined compressive strength achieves a maximum of 3.38 MPa, representing a 51% increase over the control group. At a stabilizer dosage of 12%, the splitting tensile strength reaches a peak value of 0.901 MPa, showing a 60.3% improvement. These results indicate enhanced deformation resistance, water stability, and reduced temperature shrinkage rates. Microstructural analysis indicates that the formation of calcium silicate hydrate (C-S-H) gel and ettringite (AFt phase) leads to a denser structure and enhanced durability. Heavy metal concentrations comply with relevant standards, demonstrating controllable environmental risks and supporting sustainable pavement base application. Full article