Search Results (362)

In the digital environment, grooming—classified as a communication-based risk—has shown a steadily increasing frequency in recent years. In Hungary, increasing attention has been directed to the protection of children’s rights in the digital space in alignment with ensuring their online safety, with both parents and the state playing crucial roles in ensuring a safe digital presence. Within this context, the state bears a particular responsibility to educate not only children but also parents. This study explores how public policies and institutional programs in Hungary address the prevention of grooming and the reactive management of this harm through parental awareness. It examines existing measures aimed at expanding knowledge related to prevention and response, based on a qualitative analysis of the normative foundations of the state’s educational obligations and the relevant academic literature. The study relies on questionnaire data collected from parents of children aged 7 to 18 to examine the effectiveness of state measures and parents’ perceptions of them. The findings of the empirical research may support the development of state-led parental education programs and identify current gaps. As such, it can play a guiding role in shaping the direction of a future, large-scale investigation. Full article

The increasing demand for efficient aviation navigation system inspections has led to the use of Unmanned Aerial Vehicles (UAVs) as a flexible and cost-effective alternative to traditional manned aircraft. This study emphasizes the operational advantages of UAVs in transforming flight inspections, including Non-Directional Beacon (NDB) calibration. Following the successful performance evaluation of an NDB system in Banská Bystrica, Slovakia, using a manned aircraft, a UAV was deployed on the same flight path to validate its ability to replicate the procedure in terms of trajectory only, without performing any signal measurement. The UAV maintained accurate flight paths and continuous communication throughout the mission. A specialized rotatory system, operating at 868 MHz, enabled real-time tracking and ensured stable communication over long distances. The manned aircraft test revealed a maximum bearing deviation of 13.47° at 3.37 NM and a minimum received signal strength of −90 dBm, which approaches the ICAO threshold for en route navigation (±10°) but remains usable for diagnostic purposes. The UAV flight did not include signal capture but successfully completed the 40 NM profile with a circular error probable (CEP95) of 2.8 m and communication link uptime of 99.8%, confirming that the vehicle can meet procedural trajectory fidelity. These findings support the feasibility of UAV-based NDB inspections and provide the foundation for future test phases with onboard signal monitoring systems. Full article

Porous materials are characterized by the pore surface area (S) and volume (V) accessible to a confined fluid. For mesoporous materials NMR measurements of diffusion are used to assess the S/V ratio, because at short times, only the diffusivity of molecules in the adsorbed layer is affected by confinement and the fractional population of these molecules is proportional to the S/V ratio. For materials with sub-nanometer pores, this might not be true, as the adsorbed layer can encompass the entire pore volume. Here, using molecular simulations, we explore the role played by S and S/V in determining the dynamical behavior of two carbon-bearing fluids—CO₂ and ethane—confined in sub-nanometer pores of silica. S and V in a silicalite model representing a sub-nanometer porous material are varied by selectively blocking a part of the pore network by immobile methane molecules. Three classes of adsorbents were thus obtained with either all of the straight (labeled ‘S-major’) or zigzag channels (‘Z-major’) remaining open or a mix of a fraction of both types of channel blocked, resulting in half of the total pore volume being blocked (‘Half’). While the adsorption layers from opposite surfaces overlap, encompassing the entire pore volume for all pores except the intersections, the diffusion coefficient is still found to be reduced at high S/V, especially for CO₂, albeit not so strongly as would be expected in the case of wider pores. This is because of the presence of channel intersections that provide a wider pore space with non-overlapping adsorption layers. Full article

Ascorbic acid (AA) plays a multidimensional role in human physiological and pathological processes, and the detection of its urinary concentration facilitates the diagnosis of metabolic or kidney diseases. Visual detection exhibits minimal reliance on instrumentation and is suitable for on-site analysis in routine settings. Current visual colorimetric detection methods typically rely on enzymatic or nanozyme-based catalysis. Organic neutral radicals bearing unpaired electrons represent a class of materials exhibiting intrinsic responsiveness to redox stimuli. The tris (2,4,6-trichlorophenyl) methyl (TTM) radical has attracted widespread attention for its adjustable optical properties and sensitive response to external redox stimuli. We synthesized a novel radical TTM-DMODPA and applied it for non-catalytic colorimetric detection of AA. It not only enables quantitative AA measurement via UV-vis spectroscopy (linear range: 1.25–75 μmol/L, LOD: 0.288 μmol/L) but also facilitates instrument-free visual detection using smartphone cameras (linear range: 0–65 μmol/L, LOD: 1.46 μmol/L). This method demonstrated satisfactory performance in the measurement of AA in actual urine samples. Recovery rates ranged from 97.8% to 104.1%. Consequently, this work provides a portable and effective method for assessing AA levels in actual urine samples. Full article

Maintenance dredging produces large volumes of fine sediments that are commonly discarded, despite increasing pressure for beneficial reuse. Lime–cement stabilization offers one pathway, yet field performance is highly variable. This study juxtaposes two French marine dredged sediments—DS-F (low plasticity, organic matter (OM) ≈ 2 wt.%) and DS-M (high plasticity, OM ≈ 18 wt.%)—treated with practical hydraulic road binder (HRB) dosages. This is the first French study that directly contrasts two different DS types under identical HRB treatment and proposes practical boundary thresholds. Physical indexes (particle size, methylene-blue value, Atterberg limits, OM) were measured; mixtures were compacted (Modified Proctor) and tested for immediate bearing index (IBI). IBI, unconfined compressive strength, indirect tensile strength, and elastic modulus were determined. DS-F reached IBI ≈ 90–125%, UCS ≈ 4.7–5.9 MPa, and ITS ≈ 0.40–0.47 MPa with only 6–8 wt.% HRB, satisfying LCPC-SETRA class S2–S3 requirements for road subgrades. DS-M never exceeded IBI ≈ 8%, despite 3 wt.% lime + 6 wt.% cement. A decision matrix distilled from these cases and recent literature shows that successful stabilization requires MBV < 3 g/100 g, plastic index < 25%, OM < 7 wt.%, and fine particles < 35%. These thresholds permit rapid screening of dredged lots before costly treatment. Highlighting both positive and negative evidence clarifies the realistic performance envelope of soil–cement reuse and supports circular-economy management of DS. Full article

The influence of foundation pit excavation on the bearing behavior of concrete tubular piles at the pit bottom remains unclear. Based on the Vesic cavity expansion theory, this paper proposes a method for calculating pile driving resistance, which takes into account the residual effect of vertical pressure changes on earth pressure during excavation. Furthermore, relying on the statistical regularity between Qu/Pu (ratio of ultimate bearing capacity to ultimate cavity expansion pressure) and L/d (length-to-diameter ratio), theoretical formulas for calculating the ultimate bearing capacity of tubular piles before and after foundation pit excavation are established, with their reliability and influencing factors analyzed. This method only requires determining the L/d of the tubular piles and the theoretical value of pile driving resistance. With its simple parameter requirements, it is suitable for estimating the ultimate bearing capacity of tubular piles affected by excavation. By comparing the computed penetration resistance, earth pressure, and driving resistance of tubular piles with field measurements, the computed results show good agreement with field measurements, and the accuracy of the proposed method meets the requirements of engineering design, verifying its feasibility as an empirical method. The fitting results of the Q_u/P_u ratios indicate that the deviations between the measured and computed values are 4.17% and 5.64% before and after excavation, respectively. Additionally, L/d and L/H (ratio of pile length to excavation depth) significantly affect the earth pressure, driving resistance, and vertical bearing capacity of monopoles. Smaller L/d and L/H ratios lead to greater earth pressure on the pile and more pronounced effects on driving resistance and vertical bearing capacity. The development of this method offers an approach for estimating the ultimate bearing capacity of tubular piles before and after foundation pit excavation during preliminary design, thereby holding substantial engineering significance. Full article

Cylindrical retaining structures are widely adopted in intercity railway tunnel engineering due to their exceptional load-bearing performance, no need for internal support, and efficient utilization of concrete compressive strength. Measured deformation data not only comprehensively reflect the influence of construction and hydrogeological conditions but also directly and clearly indicate the safety and stability status of structure. Therefore, based on two geometrically similar cylindrical shield tunnel shafts in Shenzhen, the surface deformation, structure deformation, and changes in groundwater outside the shafts during excavation were analyzed, and the deformation characteristics under the soil–rock composite stratum were summarized. Results indicate that the uneven distribution of surface surcharge and groundwater level are key factors causing differential deformations. The maximum horizontal deformation of the shafts wall is less than 0.05% of the current excavation depth (H), occurring primarily in two zones: from H − 20 m to H + 20 m and in the shallow 0–10 m range. Vertical deformations at the wall top are mostly within ±0.2% H. Localized groundwater leakage in joints may lead to groundwater redistribution and seepage-induced fine particle migration, exacerbating uneven deformations. Timely grouting when leakage occurs and selecting joints with superior waterproof sealing performance are essential measures to ensure effective sealing. Compared with general polygonal foundation pits, cylindrical retaining structures can achieve low environmental disturbances while possessing high structural stability. Full article

The Dixi area of the Junggar Basin has favorable petroleum geological conditions, with the Cretaceous system representing one of the principal hydrocarbon-bearing strata. However, the genetic origin and mixing characteristics of natural gas across different tectonic zones remain insufficiently understood. In this study, a total of 65 natural gas samples were analyzed using molecular composition and stable carbon isotopic data to determine gas origins and quantify the contributions of different source rocks. A novel multivariate mathematical analysis method was developed and applied to convert compositional and isotopic data into quantitative parameters, enabling the accurate estimation of end-member mixing ratios in natural gas. This methodological innovation addresses the challenge of interpreting multi-source gas systems under complex geological conditions. The results show that the Cretaceous natural gas in the Dixi area is derived from three main sources, comprising both oil-type gas from Permian lacustrine source rocks and coal-type gas from Carboniferous coal-measure source rocks. The calculated mixing proportions exhibit significant spatial variation: in the northern Dixi area, coal-type gas dominates (67.8–84.3%), while the southern zone presents a broader mixture (25.6–68.4% coal-type gas). In the Dongdaohaizi Depression, oil-type gas is predominant, accounting for 89.4–97.7%. This study not only clarifies the genetic classification and mixing dynamics of natural gas in the Dixi area but also provides a quantitative framework for evaluating accumulation processes and source contributions in multi-source gas reservoirs. The proposed method offers valuable guidance for assessing resources and optimizing exploration strategies in the Junggar Basin and other similar basins. Full article

As a World Cultural Heritage site, the Beijing–Hangzhou Grand Canal is lined with historic and cultural cities that bear abundant historical and cultural connotations. It is of vital importance to address the issues of landscape homogenization, the disconnect between conservation measures and public needs, and other related challenges in the development of these cities. This study adopts a mixed-methods approach combining qualitative and quantitative research. By integrating subjective landscape evaluation with eye tracking analysis, the ancient city of Taierzhuang along the Beijing–Hangzhou Grand Canal was selected as the research subject to conduct an in-depth investigation into the visual experience and preferences for different types of landscapes in this area. The study yielded the following findings: There are significant differences in visual experiences among various types of landscapes in Taierzhuang Ancient City. Among them, participants exhibited the highest level of attention toward canal landscapes and the lowest toward heritage site landscapes. In terms of visual distribution differences, eye tracking heatmaps revealed that attention was primarily concentrated on architectural structures and water surface reflections. In the subjective evaluation analysis, canal cultural landscapes received the highest comprehensive score (4.39 points), followed by historical architectural landscapes (4.02 points), historical street landscapes (3.93 points), modern commemorative landscapes (3.72 points), and heritage site landscapes (3.69 points). Additionally, a significant correlation was found between eye tracking data and subjective evaluation results, validating the scientifically effective relationship between subjective assessments of historical cultural landscapes and eye tracking analysis. The findings of this study not only provide a scientific basis for landscape improvement and optimization in other canal-related historical and cultural cities but also offer new research methods and perspectives for the protection and development of other heritage landscapes. Full article

Remaining useful life (RUL) estimation of a bearing is a methodology to monitor rolling bearings for a system’s performance and reliability. It predicts the exact residual time without operational interruptions until complete bearing failure by training a deep learning model to predict the remaining time of working using extracted signal features. Extracting features is one of the most important subjects since its quality directly influences the performance of predicting RUL. Features should gradually and consistently increase over time and capture sudden deterioration within normalized specific thresholds. However, recent studies have not addressed feature extraction methods that consider all of these aspects. Moreover, some bearings exhibit a “self-healing” phenomenon, in which bearing conditions appear to temporarily improve, and this complicates the accurate representation of consistent performance degradation. However, very few studies have properly addressed this issue. Meanwhile, transfer learning is frequently used when training the RUL deep learning model because there is a lack of data for run-to-failure experiments. Most RUL estimation methodologies pre-train and apply deep learning models with supervised learning. But supervised transfer learning supposes that researchers already have access to end-of-life (EOL) data—often unavailable in industrial settings—limiting their practicality. To address these challenges, this paper proposes a novel semi-supervised transfer learning methodology that integrates an anti-self-healing health indicator (ASH-HI) with a transformer-based architecture. ASH-HI is a health indicator that quantifies the power spectrum density (PSD) difference between normal and abnormal states using skewness-based parameter selection, eliminating the need for manual parameter tuning. Also, it overcomes the self-healing problem by measuring the difference not only between normal and abnormal states but also between “correction” and abnormal states. Also, this paper presents a new semi-supervised transfer learning method without EOL information. The proposed methodology is validated using the PHM 2012, NASA IMS, and an experimental setup. This study is the first to attempt transfer learning using more than three datasets simultaneously, resulting in significantly improved performance. Full article

Fine spodumene particles are challenging to treat by froth flotation and are often discarded. An approach to recover the lithium-bearing mineral is to selectively aggregate fine spodumene into larger sizes that are amenable to recovery by flotation. This research investigated the aggregation behaviour of spodumene and the gangue minerals K-feldspar and quartz, using commercially available anionic polyacrylamide flocculants. Calcium ions were used as activators that facilitated the selective adsorption of the carboxylate groups in the anionic flocculants onto the spodumene surface. The calcium ions decreased the magnitude of the negative zeta potential and reversed the zeta potential to positive for spodumene and K-feldspar, but not for quartz, below pH 10. Calcium concentrations of 312.5 g/t enhanced the adsorption of anionic polymers onto spodumene and K-feldspar, inducing aggregation, while quartz was aggregated only above 5000 g/t. Increasing the polymer concentration increased the aggregate size for spodumene and K-feldspar, but had little effect on quartz. In situ sizing and turbidity measurements indicated the optimal conditions for spodumene aggregation were 625 g/t of calcium and 63–84 g/t of the 58% anionic-charged polyacrylamide at pH 8.5. The sedimentation results showed limited separation due to quartz entrapment in the aggregates. Anionic polyacrylamide flocculants with calcium activators can aggregate fine spodumene particles. Full article

Chloride-induced corrosion is a major contributor in the degradation of standardised steel-based products (e.g., rebars and fibres) commonly used for reinforcing concrete structures. Since cracked reinforced concrete elements are determined to be more susceptible to corrosion on the one hand, and fibres are effective in arresting crack growth and improving the post-cracking mechanical behaviour on the other hand, the use of fibres emerges as a promising strategy to enhance durability. This review is focused on the degradation of the load-bearing capacity, caused by chloride corrosion, in concrete elements reinforced with fibres and conventional rebar. Based on the recorded values of ultimate loads and the corresponding deflections in the reviewed studies, a lower decrease in the load-bearing capacity and less severe degradation of ductility were observed in elements where fibres (either steel or macro-synthetic) were used in combination with rebar compared with elements where only rebar was used. Furthermore, the recorded values of corrosion potential (E_corr), corrosion current density (i_corr) and gravimetric measurements indicated lower corrosion damage, delayed corrosion initiation and a prolonged propagation phase of corrosion. However, due to many differences in the methodology among the reviewed studies, the optimal fibre type or quantity cannot be identified unless more studies are performed. Full article

This paper addresses the problem of observability analysis and enhancement for UAV target localization and sensor bias estimation with bearing-only measurement. Inspired by the compound eye vision, a bio-inspired observability analysis method is proposed for stochastic systems. Furthermore, a performance metric that can be utilized in UAV trajectory optimization for observability enhancement of the target localization system is formulated based on maximum mean discrepancy. The performance metric and the distance of the UAV relative to the target are utilized as objective functions for trajectory optimization. To determine the decision variables (the UAV’s velocity and turn rate) for UAV maneuver decision making, a multi-objective optimization framework is constructed, and is subsequently solved via the nonlinear constrained multi-objective whale optimization algorithm. Finally, the analytical results are validated through numerical simulations and comparative analyses. The proposed method demonstrates superior convergence in both target localization and sensor bias estimation. The nonlinear constrained multi-objective whale optimization algorithm achieves minimal values for both generational distance and inverted generational distance, demonstrating superior convergence and diversity characteristics. Full article

Tracking targets with nonlinear motion patterns remains a significant challenge in state estimation. We propose an energy-adaptive stochastic gradient Hamiltonian sequential Monte Carlo (SGHSMC) filter that combines adaptive energy dynamics with efficient particle sampling. The proposed method features a novel energy function that automatically adapts to target dynamics while minimizing the need for resampling operations. By integrating Hamiltonian Monte Carlo sampling with stochastic gradient techniques, our approach achieves a 40% reduction in computational overhead compared to traditional particle filters while maintaining particle diversity. We validate the method through both simulation and experimental studies. The simulation employs a univariate nonstationary growth model, demonstrating improvements of 39% in tracking accuracy over the extended Kalman filter (EKF) and 29% over standard sequential Monte Carlo methods. The experimental validation uses a bearing-only tracking scenario with a quadrupedal robot executing complex maneuvers, tracked by high-precision angular measurement systems. In practical tracking scenarios, the SGHSMC filter achieves a 77% better accuracy than EKF while maintaining the computational efficiency suitable for real-time applications. The algorithm demonstrates effectiveness in scenarios involving rapid state changes and irregular motion patterns, offering a robust solution for challenging target tracking problems. Full article

Rolling bearing is an indispensable part of mechanical rotating parts, which plays an important role in reducing friction and ensuring the rotation accuracy of rotating parts. It is necessary to carry out a health assessment of the bearing. Current health assessment methods for rolling bearings only extract strongly related feature indicators and input them into the health assessment model without considering the profound impact external conditions have on the fluctuation of feature indicators, which will lead to an inaccurate health assessment. Besides, most methods evaluating the health of rolling bearings only consider the real-time index data but do not make full use of bearing maintenance data for reliability modeling and analysis, actually reducing the hierarchy and rationality of the health assessment. Therefore, this paper combines multivariate state estimation (MSET) and reliability analysis to evaluate the health of rolling bearings. Firstly, the health baseline of the rolling bearing under multi-speed conditions is established based on MSET, which collects the history health data of rolling bearings under various working conditions and learns the impact of working conditions on health data. Subsequently, Mahalanobis distance is used to measure the degree of deviation from the health baseline, and calculated Mahalanobis distance is input into the health mapping function to get the initial health score. Finally, combined with the reliability analysis correcting the initial score, the final health score is obtained, which can provide data support for intelligent operation and maintenance and a decision-making basis for equipment maintenance. The proposed health assessment method is validated using the bearing dataset from Case Western Reserve University and historical failure data of rolling bearings. The proposed method reduces speed-related influences in bearing health evaluation, dynamically adjusting the health assessment result through the reliability model to track performance degradation throughout the bearing’s service life. Full article