Search Results (66)

Spontaneous combustion in fire-affected coal seams can degrade coal quality, alter rock mechanical parameters and reduce mining profitability. Traditional pit limit optimization methods ignore coal fire-induced quality degradation, ignore the coupling effect of economic fluctuation and slope stability, and lack quantitative optimization for fire-affected open-pit mines. Here, we optimize loss-reducing mining boundaries for the southern fire-affected highwall in the first mining district of the Dananhu No. 2 Mine, Hami, Xinjiang. The aim is to move beyond binary decisions that either sterilize or fully extract fire-affected reserves. We instead integrate economic return, slope stability and coal-price uncertainty into a single boundary-optimization framework. First, we established a three-dimensional Cartesian coordinate system for the study area. We then modeled and fitted the coal-seam roof and floor using MATLAB-based multiple integration, reducing edge errors in solid surfaces. Laboratory analyses of borehole coal samples defined how calorific value varied with advance distance. These data were used to derive the coal-quality curve. Net mining profit was then formulated as the objective function, replacing the conventional stripping-ratio criterion. Profit was calculated across advance distances to identify the economically optimal boundary. Mechanical parameters of thermally altered rocks were obtained from laboratory deformation tests. Rhino and FLAC3D 6.0 were then used to evaluate three-dimensional slope stability at critical locations. Coal-price perturbation scenarios were finally introduced to test the sensitivity of net profit and optimal advance distance. Under the baseline coal price, the slope remained stable at an advance distance of 193 m. At this boundary, net profit reached a maximum of RMB 676.608 million. The southern surface boundary contracted by 47 m relative to the initial boundary, reducing unnecessary land disturbance. Sensitivity analysis showed that lower coal prices sharply reduced both the optimal advance distance and maximum net profit. When coal price decreased by 30%, the optimal advance distance contracted to approximately 116.9 m. Maximum net profit fell to approximately RMB 248.239 million. Higher coal prices expanded the optimal boundary outward. Once coal price reached approximately 128.7 yuan/t, or 18.5% above baseline, the optimum reached the upper constraint of 240 m. Net profit then increased substantially with further price growth. These results provide a quantitative basis for dynamic boundary optimization and disturbance-reducing extraction in fire-affected open-pit coal mines. Full article

This paper investigates the static stability of a thin plate with elastically restrained boundaries in an axial channel flow. The fluid forces, including two-sided wall effects, are derived using a method that combines the potential-flow equation, the method of images, and operator theory. By incorporating Chebyshev polynomials with the energy method, a fluid–structure coupling model with variable boundary stiffness is established. The critical dynamic pressure, instability modes, and pressure distributions are calculated for different channel parameters and torsional spring stiffnesses. The results show that reducing the channel height or moving the plate away from the channel centerline decreases the critical dynamic pressure. A reduction in the torsional spring stiffness also leads to a monotonic decrease in the critical pressure. The channel walls have a negligible effect on the relative reduction in critical pressure caused by boundary relaxation. In addition, trailing-edge relaxation has a stronger influence on the critical dynamic pressure than leading-edge relaxation, because the negative pressure near the relaxed leading edge does negative work and thus provides a stabilizing effect. Full article

The use of the stress intensity factor K to characterize the severity of crack tip stress fields is widespread throughout engineering. The relationship between K and the crack growth rate is then usually represented empirically by a straight line Paris law relationship on logarithmic axes. This study develops an analytical relationship between the two by linking crack growth to the accumulation of fatigue damage ahead of the moving crack tip. A stress-based fatigue model was used, with inputs from plastic 2D plane stress FE analyses representing an edge crack by a sharp semi-circular notch. Stress–distance profiles ahead of the crack tip were extracted at the maximum and minimum points of a range of fatigue loading cycles. These were then used with data from smooth specimen LCF tests to predict the build-up of fatigue damage at regularly spaced locations ahead of the crack tip and hence crack growth rates. Full da/dN–ΔK curves were generated for the nickel-based superalloy RR1000 at 20 °C with loading R-ratios of 0, −1 and 0.5. The R = 0 and R = −1 crack growth rate predictions agreed well with experimental data, as did the steeper growth rate slope calculated at R = 0.5. The method was then extended to predict overload behaviour. Full article

Owing to its exceptional mechanical and electrical properties, graphene is regarded as an ideal sensing material for piezoresistive pressure sensors. However, vacancy defects inevitably introduced during graphene preparation and transfer significantly alter its electrical characteristics and piezoresistive performance. Based on first-principles calculations, this work systematically investigates the influence of mono-, di-, and tri-vacancy defects on the electrical and piezoresistive properties of graphene. The results indicate that di- and tri-vacancy defects reconstruct into 5-8-5 and 5-10-5 configurations during relaxation. Mono-, di-, and tri-vacancy defects effectively open bandgaps in graphene, yielding values of 0.62, 0.48, and 0.72 eV, respectively. The mono-vacancy introduces localized defect states near the Fermi level, the di-vacancy shifts the Dirac point from K to M, and the tri-vacancy moves it along the K-Γ path, eventually placing it between K and Γ. The application of strain not only widens the bandgap of defective graphene but also induces the movement of defect energy levels toward the band edges in the mono-vacancy system. All three defect types enhance the piezoresistive effect, with the tri-vacancy defect showing the most pronounced enhancement—boosting the gauge factor by a factor of 5.58. These findings provide a theoretical foundation for optimizing graphene-based pressure sensors. Full article

Modern software systems have implemented calculation techniques that allow numerical modeling of the icing of various aerodynamic objects and show themselves well when modeling the icing of objects at subsonic speeds. This paper describes a technique that is used to solve the problem of icing the profile of a NASA SC (2)-0714 airfoil streamlined by a supersonic gas stream. A feature of modeling this class of problems is the consideration of factors that arise when moving at high speeds: at supersonic flight speed, aerodynamic heating of the surface above 0 °C is observed, which is accompanied by a high intensity of impinging supercooled water droplets on this surface. The results of the numerical solution of the NASA SC (2)-0714 airfoil icing problem showed that even at a positive airfoil surface temperature, ice shapes can grow at the leading edge due to intense deposition of supercooled droplets. Full article

In order to solve the zoom delay issue for high-magnification zoom optical systems, a voice coil motor (VCM) is used to achieve rapid zooming. In this paper, the structural design of VCMs is systematically analyzed through magnetic field numerical computations. Firstly, finite element method (FEM) is used to analyze magnetic field of single magnets, and simulations correspond to experimental results. Both FEM and equivalent magnetic charge (EMC) results confirm that increasing magnet thickness while reducing its lateral dimensions will contribute to magnetic enhancement. Furthermore, the influence of structural parameters VCM is analyzed, validating the yoke’s critical role in suppressing edge effects and optimizing magnetic circuit efficiency, and optimal yoke thickness and magnet width range are determined. Moreover, a simple EMC calculation method is proposed for rapid and accurate determination of the magnetic field distribution in the VCM air gap. Optimal structural parameters of VCM are determined for a 40× rapid zoom lens with cost and space limitations. Driving force F_drive = 5.58 N is about 5 times the demand force F_d = 1.06 N, and the prototype fabrication of the rapid zoom lens is successfully accomplished. Moving group reaches 35.4 mm destination within 0.18 s, and photographs confirm that the rapid zoom system achieves 100-ms-level short/long-focus transition. Rapid zoom lens shows great potential in applications including security surveillance, industrial visual inspection, and intelligent logistics management. Full article

Spatial big data about human mobility have been employed intensively in understanding human spatial activity patterns, which is a central topic in many applications. Available research on spatial clustering patterns of human activities has been investigated mainly based on similarities of locations and temporal attributes of spatial trajectories. These methods are not effective in revealing human groups who move among spaces at different locations but with the same functions. Function, as one semantic attribute of spaces, is a major driver of most human movements. This work investigates human clustering based on space functions of trajectory stay points in human mobility data using graph embedding. Firstly, typical functions of spaces are categorized into 35 types in our research area, which is a university campus. Human trajectories based on Wi-Fi networks were collected as test data. Then, human networks are built among human individuals. Each individual is taken as a node in the network, and an edge is built between two nodes if the corresponding individuals stay in spaces of the same type of function longer than a specific time duration. The graph embedding algorithm is used to calculate feature vector representations of nodes in the network, which can capture complex relationships among nodes through biased random walks. K-means clustering is applied to classify the feature vectors, which reveals potential behavioral pattern similarities of individuals concerning the functions of their staying spaces. The elbow method and silhouette score of clusters are used to determine an appropriate number of clusters. Three scenarios were designed based on three specific time durations, and random walk-biased parameters were fine-tuned to improve the clustering performance. Results reveal typical clusters and correlation between clusters and typical space functions. Full article

Forest–grassland ecotones refer to the transitional area between forest and grassland ecosystems. Previous studies mainly focus on environmentally sensitive features and landscape risk pressures caused by edge effects, ignoring the landscape restoration and stability changes brought about by high species diversity. In this study, we calculated the landscape stability in the forest–grassland ecotone of the Greater Khingan Mountains in Inner Mongolia, China from 1990 to 2020, analyzed the changing trends and spatial migration dynamics of the landscape stability, and revealed the potential driving factors and spatial heterogeneity of dominant driving factors for the changes in landscape stability. The results indicated that the dominant landscapes in the study area changed from forests and grasslands in 1990 to forest-dominated landscapes in 2020, and the landscape stability gradually improved from a lower level to a higher level. The stability gradually expanded from the center to the northeast and southwest edges, exhibiting a ribbon sprawl pattern, and the stable center gradually moved to the northeast from 1990 to 2020. Climate factors were the main driving forces affecting the changes in landscape stability in the study area. Different dominant driving factors showed various spatial heterogeneity over time. In the northern part of the forest–grassland ecotone, precipitation, and NDVI had positive correlations with landscape stability, while the opposite was true in the south. In addition, the area of landscape stability in the south that was positively correlated with temperature and NDVI gradually expanded over time. This study analyzed the unique ecological advantages of the forest–grassland ecotones from the perspective of landscape stability changes, which will be facilitated in the ecological assessments and restoration of the forest–grassland ecotones. Full article

Moving in straight lines is a behaviour that enables organisms to search for food, move away from threats, and ultimately seek suitable environments in which to survive and reproduce. This study explores a vision-based technique for detecting a change in heading direction using the Milky Way (MW), one of the navigational cues that are known to be used by night-active insects. An algorithm is proposed that combines the YOLOv8m-seg model and normalised second central moments to calculate the MW orientation angle. This method addresses many likely scenarios where segmentation of the MW from the background by image thresholding or edge detection is not applicable, such as when the moon is substantial or when anthropogenic light is present. The proposed YOLOv8m-seg model achieves a segment mAP@0.5 of $84.7\%$ on the validation dataset using our own training dataset of MW images. To explore its potential role in autonomous system applications, we compare night sky imagery and GPS heading data from a field trial in rural South Australia. The comparison results show that for short-term navigation, the segmented MW image can be used as a reliable orientation cue. There is a difference of roughly 5–10° between the proposed method and GT as the path involves left or right 90° turns at certain locations. Full article

As the carrier of electric energy transmission, transmission lines undertake the important task of electric energy distribution and transfer. However, with the increasing frequency of construction using large machinery such as tower cranes and excavators under the transmission channels, transmission line accidents occur frequently. Therefore, this paper proposes a refined identification method for the hidden dangers of external damage in transmission lines based on the generation of effective regions driven by vanishing points. The comprehensive and accurate perception of external damage targets through the perception model of scene elements based on slicing-aided hyperinference was realized. Secondly, the accuracy and robustness of the calculation of the transmission line’s vanishing point were improved based on Canny edge detection and Hough linear detection. The effective region on the visual images was generated by combining the vanishing point and the bottom of transmission tower coordinates. Finally, the relative position relationship between areas with hidden dangers of external damage and the effective warning regions were compared, and the refined identification of hidden dangers was realized. The experimental data show that the proposed method realized a perception accuracy of 82.9% in identifying hidden dangers of external damage caused by ground- and aerial-moving targets, which shows better detection performance and practical value compared with the existing method. Full article

The construction of anatase/rutile heterojunctions in TiO₂ is an effective way of improving the CO₂ photoreduction activity. Yet, the origin of the superior photocatalytic performance is still unclear. To solve this issue, the band edges between anatase and rutile phases were theoretically determined based on the three-phase atomic model of (112)_A/II/(101)_R, and simultaneously the CO₂ reduction processes were meticulously investigated. Our calculations show that photogenerated holes can move readily from anatase to rutile via the thin intermediated II phase, while photoelectrons flowing in the opposite direction may be impeded due to the electron trapping sites at the II phase. However, the large potential drop across the anatase/rutile interface and the strong built-in electric field can provide an effective driving force for photoelectrons’ migration to anatase. In addition, the II phase can better enhance the solar light utilization of (112)_A/(100)_II, including a wide light response range and an intensive optical absorption coefficient. Meanwhile, the mixed-phase TiO₂ possesses negligible hydrogenation energy (CO₂ to COOH*) and lower rate-limiting energy (HCOOH* to HCO*), which greatly facilitate CH₃OH generation. The efficient charge separation, strengthened light absorption, and facile CO₂ reduction successfully demonstrate that the anatase/rutile mixed-phase TiO₂ is an efficient photocatalyst utilized for CO₂ conversion. Full article

Urban green space (UGS) has been recognized as a key factor in enhancing the urban ecosystem balance, particularly in arid areas. It is often considered an effective means to mitigate the urban heat island (UHI) effect. In this study, the reference comparison method was utilized to optimize the process of nighttime lighting data; the random forest classification method was employed to extract UGS data; and the radiative transfer method was applied in land surface temperature (LST) inversion. Additionally, moving window analysis was conducted to assess the robustness of the results. The objective of this research was to analyze the spatial distribution characteristics of UGS and LST and to explore their bivariate local spatial autocorrelations by calculating four landscape metrics, including the aggregation index (AI), edge density (ED), patch density (PD), and area-weighted mean shape index (Shape_am). It was found that the distribution of UGS in the study area was uneven, with higher temperatures in the eastern and western regions and lower temperatures in the central and southern regions. The results also revealed that ED, PD, and Shape_am were negatively correlated with LST, with correlation coefficients being −0.469, −0.388, and −0.411, respectively, indicating that UGS in these regions were more effective in terms of cooling effect. Conversely, AI was found to be positively correlated with LST (Moran’ I index of 0.449), indicating that surface temperatures were relatively higher in regions of high aggregation. In essence, the fragmented, complex, and evenly distributed green patches in the study area provided a better cooling effect. These findings should persuade decision makers and municipal planners to allocate more UGS in cities for UHI alleviation to improve quality of life and enhance recreational opportunities. Full article

Landslides recurrently cause severe damage and, in some cases, the full disruption of many highways in mountainous areas, which can last from a few days to even months. Thus, there is a high demand for monitoring tools and precipitation data to support highway alignment selections before construction. In this study, we proposed a new system highway alignment selection method based on coherent scatter InSAR (CSI) and ~1 km high-spatial-resolution precipitation (HSRP) analysis. Prior to the CSI, we calculated and analyzed the feasibility of Sentinel-1A ascending and descending data. To illustrate the performance of the CSI, CSI and SBAS–InSAR were both utilized to monitor 80 slow-moving landslides, which were identified by optical remote-sensing interpretation and field investigation, along the Barkam–Kangting Highway Corridor (BKHC) in southwestern China, relying on 56 Sentinel-1A descending images from September 2019 to September 2021. The results reveal that CSI has clearer deformation signals and more measurement points (MPs) than SBAS-InSAR. And the maximum cumulative displacements and rates of the landslides reach −75 mm and −64 mm/year within the monitoring period (CSI results), respectively. Furthermore, the rates of the landslides near the Jinchuan River are higher than those of the landslides far from the river. Subsequently, to optimize the highway alignment selection, we analyzed the spatiotemporal evolution characteristics of feature points on a typical landslide by combining the −1 km HSRP, which was calculated from the 30′ Climatic Research Unit (CRU) time-series datasets, with the climatology datasets of WorldClim using delta spatial downscaling. The analysis shows that the sliding rates of landslides augment from the back edge to the tongue because of fluvial erosion and that accelerated sliding is highly related to the intense precipitation between April and September each year (ASP). Consequently, three solution types were established in our method by setting thresholds for the deformation rates and ASPs of every landslide. Afterward, the risk-optimal alignment selection of the BKHC was finalized according to the solution types and consideration of the construction’s possible impacts. Ultimately, the major problems and challenges for our method were discussed, and conclusions were given. Full article

In the fast-moving world of information and communications technologies, one significant issue in metropolitan cities is water scarcity and the need for an intelligent water distribution system for sustainable water management. An IoT-based monitoring system can improve water distribution system management and mitigate challenges in the distribution network networks such as leakage, breakage, theft, overflow, dry running of pumps and so on. However, the increase in the number of communication and sensing devices within smart cities has evoked challenges to existing communication networks due to the increase in delay and energy consumption within the network. The work presents different strategies for efficient delay and energy offloading in IoT-integrated water distribution systems in smart cities. Different IoT-enabled communication network topology diagrams are proposed, considering the different water network design parameters, land cover patterns and wireless channels for communication. From these topologies and by considering all the relevant communication parameters, the optimum communication network architecture to continuously monitor a water distribution network in a metropolitan city in India is identified. As a case study, an IoT design and analysis model is studied for a secondary metropolitan city in India. The selected study area is in Kochi, India. Based on the site-specific model and land use and land cover pattern, delay and energy modeling of the IoT-based water distribution system is discussed. Algorithms for node categorisation and edge-to-fog allocation are discussed, and numerical analyses of delay and energy models are included. An approximation of the delay and energy of the network is calculated using these models. On the basis of these study results, and state transition diagrams, the optimum placement of fog nodes linked with edge nodes and a cloud server could be carried out. Also, by considering different scenarios, up to a 40% improvement in energy efficiency can be achieved by incorporating a greater number of states in the state transition diagram. These strategies could be utilized in implementing delay and energy-efficient IoT-enabled communication networks for site-specific applications. Full article

The authors of this article analyzed the problem of logistic robotics. This paper presents a method for robot navigation in a known environment. The method consists of two steps. The first step is to model the system, assign vector marks to the prominent edges of the virtual environment map, and direct the robot to reach these marks. The second step is to enable the robot to execute a specific task based on the given paths and deal with the local obstacles avoidance independently. The identification of the prominent point, the computation of the vector mark, and optimal path calculation are performed on the computer model using colored Petri nets in the software ‘Centaurus CPN’. The proposed approach was extended to simulate the work of a logistic robot, which has to take boxes and deliver them to certain places in storages. The experimental investigation has shown that the simulated mobile robots with the proposed navigation system were efficiently moving along the planned path. The analysis of the vector tree reveals that it takes 0.389 s to compute and graphically represent it. The occupation of certain places in storages is visualized and shown in experimental graphics. Full article