Search Results (7,477)

Chalcopyrite and molybdenite exhibit similar surface wettability and high floatability, which has long hindered their efficient and selective separation in mineral processing. In this work, the novel chalcopyrite depressant 2-mercapto-5-benzoimidazole sulfonate dihydrate (2MBI5SA) was investigated for its effect on the flotation behavior of chalcopyrite and molybdenite. Compared with the conventional depressant sodium sulfide (Na₂S), 2MBI5SA exhibited stronger selective depression toward chalcopyrite; under conditions yielding a Mo recovery of 81.46% and a Mo grade of 4.46%, the Cu recovery decreased to 13.03%. To clarify the origin of this selectivity, interfacial properties were systematically characterized using adsorption measurements, contact angle measurements, zeta potential measurements, FTIR, XPS, and SEM-EDS, and the adsorption mechanism was further elucidated using SCC-DFTB calculations. The results demonstrate that 2MBI5SA chemisorbs onto the chalcopyrite surface via bidentate coordination, forming a stable adsorption layer that effectively suppresses chalcopyrite flotation. Moreover, structure−function relationship analysis confirmed that introducing hydrophilic and ionizable functional groups into the collector framework can convert a collector into a selective depressant, thereby providing new insights into the rational design of selective organic depressants with potential environmental advantages over conventional highly toxic inorganic depressants. Full article

This study examines the low-speed impact response of Nomex honeycomb-core sandwich structures using an approach combining experimental tests and three-dimensional numerical modeling. A finite element model was developed using Abaqus/Explicit to predict contact force, displacement, damage evolution, and absorbed energy under different impact configurations. The influence of core density, skin thickness, and impactor geometry was analyzed to identify the parameters governing impact resistance and energy dissipation mechanisms. The numerical results show good agreement with experimental measurements, with maximum relative differences between 7.3% and 8.3% for the maximum force and between 1.8% and 4.3% for the absorbed energy. Core density appears to be a determining factor: the D144 configuration reaches a maximum force of approximately 4400 N, compared to 2600 N for the D80 configuration, representing an increase of approximately 69%. However, sensitivity analysis indicates that skin thickness exerts the most dominant overall influence on load-bearing capacity; increasing this thickness from 0.2 mm to 1.2 mm leads to a fivefold increase in maximum force (from 1800 N to over 10,000 N) and a significant rise in absorbed energy (from 20 J to 105 J). The geometry of the impactor strongly controls the damage modes and stress distribution. A 60° conical impactor promotes localized deformation and rapid perforation, while a 70° angle offers a better compromise between local resistance and progressive energy absorption. At 80°, the stresses are distributed over a larger surface area, which delays perforation. The geometry of the impactor strongly controls the spatial distribution of damage modes. A sharper 60° conical impactor induces highly localized core crushing and rapid skin perforation, while a 70° angle offers a better compromise between local resistance and progressive energy absorption. At 80°, the stresses are distributed over a wider area, promoting diffuse damage and delaying perforation. These results show that the combined optimization of core density, skin thickness, and the impactor–structure interaction is an effective way to improve the impact tolerance of lightweight sandwich structures intended for aerospace, automotive, and marine applications. Full article

Tooth crack, as a typical fault, directly affects the meshing characteristics of gears, which causes abnormal vibration and noise during the gear meshing process, with some even threatening the operational safety of the mechanical device. Meanwhile, the mapping relation between the tooth crack and the actual meshing characteristics is still unclear under the tooth surface morphology and lubrication properties. Aiming at this issue, an integrated time-varying meshing stiffness (I-TVMS) model with cracks is proposed under the complex and variable working conditions. Based on the potential energy method, the analytical expressions with cracks are derived and calculated, and, then, the variation laws of I-TVMS under different crack parameters, tooth surface morphology, and structural and excitation parameters are investigated. Combined with the healthy tooth, the crack increases the contact load on the tooth surface, and reduces the oil film thickness, which decreases the I-TVMS of the cracked tooth. The greater the crack depth and torque is, the smaller the oil film thickness, and the weaker the I-TVMS fluctuation will be. The influence of the crack angle depends on the crack type and meshing region. The tooth-root crack is more sensitive in the single-tooth region, whereas the tooth surface crack shows a larger change only in the double-tooth mean value. When the crack location transitions from the tooth root to the tooth top, the stiffness attenuation gradually weakens. Full article

Hall-effect sensors are pervasive in magnetic-field measurement applications, including current sensing and position detection, owing to their excellent compatibility with standard CMOS processes. However, the inherent offset and temperature drift of silicon-based Hall elements remain a paramount obstacle to achieve high precision. This paper presents a fully integrated angle sensor chip that addresses this challenge. Implemented in a 0.35 μm CMOS process, the sensor incorporates four cross-shaped Hall elements arranged in an orthogonal array as a non-contact Hall-permanent magnet configuration, which enables absolute angular encoding across a full 0–360° range. Experimental characterisation demonstrates a low noise floor of 0.087° (3σ), validating the effectiveness of the proposed architecture for high-accuracy angular measurement. Full article

Water leakage in underground construction works is a prominent and persistent quality defect, particularly for the joint between the foundation slab and prestressed anti-floating anchors or piles. Previous studies have focused on optimizing the structural details to improve impermeability, while overlooking water seepage caused by insufficient adhesion at the interface between the polyethylene (PE) sheath and concrete. Therefore, this study aimed to enhance this interfacial adhesion through the hydrophilic modification of PE, thereby improving the impermeability of anti-floating anchors or piles prestressed with retarded-bond tendons. Physical blending modification was adopted in which hydrophilic PE granules were incorporated into ordinary PE. The variations in the water contact angle and mechanical properties of PE were analyzed at contents ranging from 0% to 8%. Adhesion strength tests were conducted to evaluate the changes in the interfacial adhesion strength between ordinary PE, modified PE, and concrete with different cement grades. Water impermeability tests were performed to measure the impermeability grades of concrete specimens reinforced with unbonded, ordinary retarded-bond, and modified retarded-bond prestressing tendons. The results showed that with increasing hydrophilic PE granule content, the hydrophilicity of PE improved markedly, while its mechanical properties improved slightly. A content of 8% hydrophilic PE granules is recommended. Debonding occurs between ordinary PE and concrete, whereas the adhesion strength of hydrophilic PE to concrete gradually increases with the cement grade. The impermeability grade of concrete with modified retarded-bond prestressing tendons is six grades higher than that with ordinary retarded-bond prestressing tendons, reaching P8. This indicates that the incorporation of hydrophilic PE granules significantly improves the impermeability of anti-floating anchors or piles prestressed with retarded-bond tendons. Full article

Background/Objectives: Distal chevron metatarsal osteotomy (DCMO) is one of the most commonly performed procedures for hallux valgus (HV) correction. Although medial eminence resection is routinely performed during DCMO, the effect of its timing on lateral translation, angular correction, and osteotomy contact area remains unclear. The aim of this study was to assess how the timing of medial eminence resection affects lateral translation, angular correction, and osteotomy contact area. Methods: Patient-specific first metatarsal models were generated from computed tomography data of 14 patients with HV using three-dimensional printing. Four groups were established according to medial eminence resection timing (before or after osteotomy) and lateral translation strategy (fixed 7 mm translation or preservation of a 5 mm contact width). DCMO was simulated in all specimens. Osteotomy contact area and the first metatarsal axis change angle (MACA) were measured and compared between the groups. Results: Under the fixed 7 mm translation condition, delaying medial eminence resection until after osteotomy resulted in a significantly larger osteotomy contact area than resection before osteotomy (236.50 ± 37.78 vs. 201.07 ± 22.54 mm²; p < 0.001). When lateral translation was limited by preservation of a 5 mm osteotomy contact width, delayed medial eminence resection achieved significantly greater angular correction (MACA: 20.71 ± 1.64° vs. 15.36 ± 1.45°; p < 0.001), while maintaining a comparable osteotomy contact area. Conclusions: Delaying medial eminence resection until after DCMO may allow greater lateral translation and angular correction while preserving osteotomy contact area in HV correction. Full article

Electrochemical impedance spectroscopy (EIS) is a powerful, non-destructive tool for evaluating ion-selective electrode (ISE) membrane condition. This work investigated EIS for identifying degradation mechanisms in all-solid-state Pb²⁺-selective electrodes. Graphene-containing PVC membranes deposited on glassy carbon electrodes were exposed to synthetic urine, river water, and seawater (24 h and 1 week) and to mechanical damage (cutting, needle puncture, or both). Degradation was assessed using EIS, potentiometric measurements, contact-angle analysis, profilometry, and SEM. River water and urine exposure decreased hydrophobicity, increased roughness, and produced fouling deposits. Seawater caused only minor morphological and wettability changes, though impedance data showed increased membrane hydration due to high ionic strength. Mechanical damage substantially disrupted membrane integrity, causing pronounced impedance changes, increased potential drift, and reduced analytical performance. Fouling and mechanical damage produced distinct electrochemical signatures: fouling mainly affected surface properties, while mechanical damage altered the membrane–transducer interface, increasing capacitance and reducing resistance. Notably, needle-punctured electrodes retained a near-Nernstian response despite clear impedance changes and reduced long-term stability, showing that EIS detects defects invisible to conventional calibration. These results confirm EIS as a sensitive method for distinguishing fouling from physical damage, useful for early degradation detection and lifetime monitoring of all-solid-state ISEs. Full article

Agro-industrial residues are an important source of bioactive compounds with interesting properties for textile applications. Bio-based formulations were developed by incorporating cationic starch and bacterial cellulose with extracts obtained from agro-industrial residues (oregano (OS) and thyme stems (TSs), spent hops (SHs) and rice husk (RH)), through ultrasound-assisted and water bath extraction. The extract from OS obtained by the water bath showed the highest antioxidant activity (25,272 μM Trolox), and when incorporated into textiles, it also enabled a high antioxidant activity of 85%. A high antioxidant activity was also recorded in TS extract (21,063 μM TX), where the functionalized textiles achieved an antioxidant activity of 89%. However, a decrease to 20% in antioxidant activity was recorded after washing. The functionalization with RH extracts enabled the development of hydrophobic textiles, exhibiting static water contact angles above 140, which was maintained after washing. Textiles functionalized with OS and TS extracts achieved excellent UV protection (UPF > 50). Even after washing, the textiles pre-treated with the commercial fixation maintained UPF > 50. Overall, this study demonstrates the potential for valorising agro-industrial residues into functional textiles within a sustainable and circular bioeconomy approach. Full article

Existing buckling stiffness tests usually load the ski boot in a manner that changes with the buckling angle of the boot cuff. As a result, the direction of the applied force changes as the cuff bends, which can cause a deviation between the measured force and the actual acting force and can influence the test result. In this study, a new buckling stiffness test device was designed and constructed. By introducing a translational-rod loading structure, the device keeps the loading force perpendicular to the prosthetic-foot loading rod throughout the test. Tests were conducted at a room temperature of 15 °C, with a fixed force-arm length of L = 0.31 m and a standard binding tension of F = 40 N, thereby improving the consistency of load-angle measurement. A binding-force adjustment unit was also designed through computer-aided design, and the standard binding force was determined through subjective comfort tests involving 20 skiers, enabling consistent control of the tightness state of the ski boot. Theoretically, the expression for ski-boot buckling stiffness was established using an equivalent torsional-spring model. Under small-angle and quasi-static conditions, the equivalent buckling stiffness was represented as a linear relationship between the applied load and the normalized deflection angle. The experimental results show that, within the loading range of 60–260 N, the relationship between load and deformation exhibited good linearity, with coefficients of determination of 0.986–0.996. Repeatability tests showed that the coefficients of variation of load and deflection-angle measurements were controlled within 0.40–1.48% and 6.92–8.26%, respectively, and the relative expanded uncertainty of equivalent buckling stiffness was 7.33–11.93%. These results indicate that the device has good stability. Although the fitted curves showed slight nonzero intercepts, these mainly originated from clamping error, contact effects, and sensor zero drift, and did not affect stiffness identification. Overall, the device can provide stable and reliable buckling stiffness measurement and offers an effective method for evaluating ski-boot performance. Full article

Loess has a metastable microstructure and high water sensitivity. When exposed to water, it undergoes rapid structural damage and disintegration, posing significant risks to the stability and durability of geotechnical structures such as foundations and slopes. Unconfined compressive strength (UCS) tests, direct shear tests, uniaxial tensile strength tests, and slake durability tests were conducted to evaluate the treatment performance. Optical microscopy and SEM were used to characterize the changes in microstructure to explain the potential reinforcement mechanism. The results show that microbial-induced carbonate precipitation (MICP) treatment leads to substantial improvement. Compared with untreated loess, the UCS, cohesion, internal friction angle, and uniaxial tensile strength increased by 370%, 663%, 43.7%, and 480%, respectively. Empirical refinements to the Mohr-Coulomb criterion were established to relate the measured UCS and uniaxial tensile strength to their theoretical values predicted from cohesion and friction angle. Both correlation models achieved R² > 0.82, quantifying the additional structural strength contributed by bio-cementation. At the same time, the treatment significantly improved water stability, and the slaking index was reduced from 100% to less than 20%. Microstructural analysis shows that precipitated calcium carbonate crystals bond soil particles at contact points and fill inter-particle pores, constructing a bonding framework, which enhances the mechanical strength and water stability of the soil mass. These research results further illustrate the potential of MICP in enhancing the performance of loess in engineering projects. Full article

This study investigates titanium oxynitride (TiO_xN_y) coatings deposited by reactive magnetron sputtering on 316L stainless steel substrates in an Ar–N₂–O₂ gas mixture at a fixed N:O ratio of 1.6. The coatings were deposited under three reactive magnetron sputtering regimes with Ar flow rates of 33, 28, and 26 sccm and corresponding substrate biases of −50, −100, and −150 V, respectively, while the N₂ and O₂ flow rates were kept constant at 10 and 6 sccm. The coatings exhibited a dense microstructure, with thicknesses ranging from 2.13 to 5.51 μm. X-ray diffraction analysis revealed the formation of a multiphase structure comprising TiN, TiO_xN_y, and TiO. The deposition regime had a significant influence on the functional properties of the coatings. The lowest friction coefficients (µ ≈ 0.26–0.28) and stable tribological behavior were characteristic of the Ar26 sample. The highest corrosion resistance was observed for the Ar28 sample, with a corrosion current density of i_corr = 2.82 × 10⁻⁷ A/cm² and a corrosion rate of v_corr = 0.00573 mm/year. All coatings exhibited hydrophilic surface behavior, with contact angles of 50–57°, which may be relevant for further evaluation in biomedical surface applications. Thus, the structure and functional properties of TiO_xN_y coatings can be regulated by selecting an appropriate deposition regime, including the Ar flow rate, relative reactive gas fraction, and substrate bias. However, additional biological tests, including cytotoxicity, hemocompatibility, endothelialization, and platelet adhesion studies, are required before conclusions about vascular implant applicability can be made. Full article

In professional water polo, understanding the effects of ball wettability on game dynamics is essential but remains insufficiently investigated. This research aims to evaluate how the surface wettability of various professional water polo balls could influence their behavior during play. The study employed a combination of laboratory measurements to assess the wettability of multiple ball brands using the sessile drop method under standardized conditions. FTIR spectroscopy was also performed to characterize the surface chemical composition and support the interpretation of wettability differences observed in contact angle measurements. Performance-related parameters, including static contact angle values and droplet behavior during measurement, were analyzed in relation to surface chemistry and material composition. Significant variability in wettability was observed across different ball brands. These differences indicate that surface properties may play an important role in modulating ball–water interaction mechanisms, which are influenced by both chemical composition and surface morphology. Based on these results, we propose including wettability-related parameters in the official water polo equipment guidelines, which currently cover only size, weight, and material composition. This adjustment could help standardize ball behavior across competitive play, leading to more consistent and fair conditions. This study extends current knowledge of the physical factors influencing sports performance and suggests practical improvements to enhance fairness and quality in water polo competitions. Full article

Aluminum corrosion in acidic media leads to accelerated material degradation and significant economic losses. This study evaluated the aqueous extract of yerba mate (Ilex paraguariensis) as a green inhibitor for aluminum corrosion in 0.5 M HCl at temperatures (298–323 K) and extract concentrations (1%, 2.5%, and 5% v/v). The extract was characterized by FTIR, and its inhibitory performance was assessed using weight loss measurements, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and contact angle analysis. Gravimetric results showed a decrease in corrosion rate with increasing extract concentration, reaching a maximum inhibition efficiency of 94% at 308 K and 5% v/v. The increase in activation energy in the presence of the inhibitor suggested the formation of an energy barrier associated with adsorption on the aluminum surface. Polarization studies indicated that the extract behaves as a mixed-type inhibitor, while EIS revealed an increase in charge transfer resistance and the formation of a protective adsorbed film. SEM images confirmed reduced corrosion damage, and contact angle measurements indicated increased surface hydrophobicity. The inhibition mechanism followed Langmuir adsorption behavior, suggesting adsorption of organic species at the aluminum–solution interface. These findings demonstrate that yerba mate extract is an effective corrosion inhibitor. Full article

Human gait analysis is a key component of rehabilitation medicine, enabling objective assessment of patient recovery. In crutch-assisted locomotion, however, conventional forearm crutches operate as passive devices, providing no quantitative information on load distribution or patient adherence to partial weight-bearing (PWB) prescriptions. This work presents the design and dynamic validation of a sensorized forearm crutch system for biomechanical monitoring during assisted gait. The proposed device combines a force-sensing module based on a full Wheatstone bridge strain-gauge configuration with a 6-axis inertial measurement unit (IMU) to capture both axial load and crutch orientation. Sensor fusion was implemented through a complementary filter to estimate pitch and roll angles under dynamic conditions. The system was calibrated through static loading procedures and validated against reference instrumentation, including an optoelectronic motion capture system and an instrumented dual-belt treadmill with force platforms. Unlike previous studies relying on stationary force platforms that capture discrete steps and may alter natural gait, this validation approach enabled continuous, stride-by-stride force and orientation measurements without restricting foot placement. Experimental trials were conducted with unimpaired participants performing assisted gait using 2-point and 3-point patterns at two partial weight-bearing levels (20% and 40% body weight) and two walking speeds (0.80 m/s and 1.20 m/s). Dynamic validation showed good agreement with the treadmill reference, with force RMSE values of $9.33\pm 1.70$ N for the left crutch and $12.90\pm 2.85$ N for the right crutch, and with coefficients of determination of $R^2=0.9956$ and $R^2=0.9927$, respectively. Orientation RMSE values were $1.08\pm 0.44$° (roll, right), $2.06\pm 0.56$° (roll, left), $1.79\pm 0.55$° (pitch, right), and $1.66\pm 0.37$° (pitch, left). Beyond validation accuracy, the system enabled extraction of a set of quantitative biomechanical descriptors directly from crutch signals, axial load, cadence, crutch contact variability, load asymmetry, pitch asymmetry, and crutch stance/swing asymmetries, characterizing walking stability, bilateral coordination, and gait regularity during continuous assisted locomotion. These results demonstrate the feasibility of integrating force and inertial sensors into forearm crutches to enable quantitative monitoring of assisted gait, with potential applications in rehabilitation assessment and real-time feedback. Full article

The release of microplastic fibers from synthetic textiles during domestic laundering is a major contributor to aquatic pollution. Nanomaterial-based surface treatments have recently emerged as a potential route for minimizing microfiber shedding. This study investigates the use, for the first time, of metal oxide nanoparticles (TiO₂, ZnO, MgO) functionalized with fatty acids (oleic acid (OA) and stearic acid (SA)) as microfiber-retaining agents. The nanoparticles were modified via a simple adsorption process at room temperature, monitored by zeta potential analysis, and confirmed by DSC-TG and FTIR-ATR analysis. When applied to polyester fabrics during simulated washing cycles, the hydrophobicity of the polyester surface coated with functionalized nanoparticles was assessed via contact angle measurements, and the effect on microfiber shedding was evaluated by the filtration of wastewater and by weighing the mass of fibers retained in the filters. ZnO and MgO nanoparticles treated with stearic and oleic acid demonstrated a significant reduction in fiber shedding compared to commercial laundry detergent (approximately 46–70%). In contrast, fatty acid adsorption onto TiO₂ was less efficient (reduction in microfiber release ~23%), and the TiO₂-based systems showed limited improvement in microfiber shedding, possibly due to insufficient hydrophobic interaction. These results demonstrate that fatty acid functionalization of low-cost inorganic nanoparticles is a promising strategy for mitigating microfiber pollution in laundry effluents. Full article