Search Results (298)

The present investigation presents the field measurement and prediction of tunneling-induced surface ground settlement in Tianjin Metro Line 7, China. The cross-section of a metro tunnel exhibits circular symmetry, thereby making it suitable for tunneling with a circular shield machine. The ground surface may deform during the tunneling stage. In the early stage of tunneling, few measurement data can be collected. To obtain a better usable prediction model, two kinds of neural networks according to the model-agnostic meta-learning (MAML) scheme are presented. One kind of deep learning strategy is a combination of the Back-Propagation Neural Network (BPNN) and the MAML model, named MAML-BPNN. The other prediction model is a mixture of the MAML model and the Long Short-Term Memory (LSTM) model, named MAML-LSTM. Founded on several measurement datasets, the prediction models of the MAML-BPNN and MAML-LSTM are successfully trained. The results show the present models possess good prediction ability for tunneling-induced surface ground settlement. Based on the coefficient of determination, the prediction result using MAML-LSTM is superior to that of MAML-BPNN by 0.1. Full article

Span-wise homogeneous supersonic cavity flows display complicated structures due to shear layer breakdown, flow acoustic resonance, and even non-linear hydrodynamic-acoustic interactions. In practical applications, such as aircraft bays, the cavity is of finite width and has doors, both of which introduce distinctive phenomena that couple with the shear layer at the cavity lip, further modulating shear layer bifurcations and tonal mechanisms. In particular, asymmetric states manifest as ‘tornado’ vortices with significant practical consequences on the design and operation. Both inward- and outward-facing leading-wedge doors, resulting in leading edge shocks directed into and away from the cavity, are examined at select opening angles ranging from $22.5°$ to $90°$ (fully open) at Mach 1.6. The computational approach utilizes the Reynolds-Averaged Navier–Stokes equations with a one-equation model and is augmented by experimental observations of cavity floor pressure and surface oil-flow patterns. For the no-doors configuration, the asymmetric results are consistent with a long-time series DDES simulation, previously validated with two experimental databases. When fully open, outer wedge doors (OWD) yield an asymmetric flow, while inner wedge doors (IWD) display only mildly asymmetric behavior. At lower door angles (partially closed cavity), both types of doors display a successive bifurcation of the shear layer, ultimately resulting in a symmetric flow. IWD tend to promote symmetry for all angles observed, with the shear layer experiencing a pitchfork bifurcation at the ‘critical angle’ ($67.5°$). This is also true for the OWD at the ‘critical angle’ ($45°$), though an entirely different symmetric flow field is established. The first observation of pitchfork bifurcations (‘critical angle’) for the IWD is at $67.5°$ and for the OWD, $45°$, complementing experimental observations. The back wall signature of the bifurcated shear layer (impingement preference) was found to be indicative of the 3D cavity dynamics and may be used to establish a correspondence between 3D cavity dynamics and the shear layer. Below the critical angle, the symmetric flow field is comprised of counter-rotating vortex pairs at the front and back wall corners. The existence of a critical angle and the process of door opening versus closing indicate the possibility of hysteresis, a preliminary discussion of which is presented. Full article

The South Shetland Islands and Antarctic Peninsula (SHETPENANT region) constitute a geodynamically active area shaped by the interaction of major tectonic plates and active magmatic systems. This study analyzes GNSS time series spanning from 2017 to 2024 to investigate surface deformation associated with the 2020–2021 seismic swarm near the Orca submarine volcano. Horizontal and vertical displacement velocities were estimated for the preseismic, coseismic, and postseismic phases using the CATS method. Results reveal significant coseismic displacements exceeding 20 mm in the horizontal components near Orca, associated with rapid magmatic pressure release and dike intrusion. Postseismic velocities indicate continued, though slower, deformation attributed to crustal relaxation. Stations located near the Orca exhibit nonlinear, transient behavior, whereas more distant stations display stable, linear trends, highlighting the spatial heterogeneity of crustal deformation. Stress and strain fields derived from the velocity models identify zones of extensional dilatation in the central Bransfield Basin and localized compression near magmatic intrusions. Maximum strain rates during the coseismic phase exceeded 200 $\mathrm{\nu }$strain/year, supporting a scenario of crustal thinning and fault reactivation. These patterns align with the known structural framework of the region. The integration of GNSS-based displacement and strain modeling proves essential for resolving active volcano-tectonic interactions. The findings enhance our understanding of back-arc deformation processes in polar regions and support the development of more effective geohazard monitoring strategies. Full article

Rock slopes exhibiting anti-inclined interbedded strata have widespread distribution and complex deformation mechanisms. In this study, we used a physical model test with basal friction to replicate the evolution process of the slope deformation. Digital Image Correlation (DIC) and Particle Image Velocimetry (PIV) methods were used to capture the variation in slope velocity and displacement fields. The results show that the slope deformation is conducted by bending of soft rock layers and accumulated overturning of hard blocks along numerous cross joints. As the faces of the rock columns come back into contact, the motion of the slope can progressively stabilize. Destruction of the toe blocks triggers the formation of the landslides within the toppling zone. The toppling fracture zones form by tracing tensile fractures within soft rocks and cross joints within hard rocks, ultimately transforming into a failure surface which is located above the hinge surface of the toppling motion. The evolution of the slope deformation mainly undergoes four stages: the initial shearing, the free rotation, the creep, and the progressive failure stages. Full article

In the purpose of enhancing solar cell efficiency and sustainability, zinc selenide (ZnSe) and silicon (Si) play indispensable roles, offering a compelling combination of stability and transparency while also highlighting their abundant availability. This study utilizes the SCAPS_1D tool to explore diverse heterojunction setups, aiming to solve the nuanced correlation between key parameters and photovoltaic performance, therefore contributing significantly to the advancement of sustainable energy solutions. Exploring the performance analysis of heterojunction solar cell configurations employing ZnSe and Si elements, various configurations including SnO₂/ZnSe/p_Si/p⁺_Si, SnO₂/CdS/p_Si/p⁺_Si, TiO₂/ZnSe/p_Si/p⁺_Si, and TiO₂/CdS/p_Si/p⁺_Si are investigated, delving into parameters such as back surface field thickness (BSF), doping concentration, operating temperature, absorber layer properties, electron transport layer properties, interface defects, series and shunt resistance. Among these configurations, the SnO₂/ZnSe/p_Si/p⁺_Si configuration with a doping concentration of 10¹⁹ cm⁻³ and a BSF thickness of 2 μm, illustrates a remarkable conversion efficiency of 22.82%, a short circuit current density (J_sc) of 40.33 mA/cm², an open circuit voltage (V_oc) of 0.73 V, and a fill factor (FF) of 77.05%. Its environmentally friendly attributes position it as a promising contender for advanced photovoltaic applications. This work emphasizes the critical role of parameter optimization in propelling solar cell technologies toward heightened efficiency and sustainability. Full article

The evolution of telecommunications and radars in the terrestrial and space domains is introducing new specifications for antennas that have difficulty meeting today’s phased arrays. Breakthrough technologies must be introduced to push back the limits not only in beam steering and beam forming, but also in frequency bandwidth, conformation, and multifunctionality. Indeed, the representation of radiating surfaces (Huygens) by arrays of point sources (a century ago!) is the poorest approximation of the rigorous solution, with well-known limitations. The proposed approach starts from the rigorous expression of the field radiated by any antenna obtained using the equivalence principle on any closed surface Sc surrounding the antenna. Important approximations are introduced to apply this rigorous result to the design of beam-agile multisource antennas that require sampling of the radiating Sc surface. The proposed approach samples the Sc surface by slicing it into small piecewise surfaces. For the fabrication of these small surfaces, structures called “pixels” deduced from the s have been designed. Many applications are proposed and compared with array solutions. Full article

This study focuses on the investigation of the Tepehan landslide triggered by the 6 February 2023, Kahramanmaraş earthquake in Türkiye. The overall goal of this study is to understand the slope condition and simulate the failure considering pre- and post-event geometry. Topographic variations in the landslide area were analyzed using digital elevation models (DEMs) derived from the Sentinel-1 Synthetic Aperture Radar (SAR) satellite data and geospatial analysis. Slope stability analyses were conducted over a representative alignment, including assessments of soil structure, geological history, and field features. A limit equilibrium back-analysis was performed under both static and pseudo-static conditions, where an earthquake load coefficient was considered in the analyses. A total of five scenarios were evaluated to determine factors of safety (FoS) based on fully softened and residual strength parameters. The resulting critical slip surfaces from the simulations were compared with the geomorphometric analysis, necessitating the adjustment of the subsurface hard clay layer for residual conditions. The analyses revealed that the slope behaves as a delayed first-time landslide, with bedding planes acting as localized weak layers, reducing mobilized shear strength. This integrated remote sensing–geotechnical approach advances landslide hazard evaluation by enhancing the precision of slip surface identification and post-seismic slope behavior modeling, offering a valuable framework for similar post-disaster geohazard assessments. Full article

Bifacial solar cells are the leading technology, and the number of steps in the manufacturing process influences the processing time and production cost. The goal of this paper is to optimize the boron back surface field (B-BSF) produced with reduced thermal steps and to analyze its influence on the electrical parameters and bifaciality coefficients of p-type bifacial PERT solar cells. The boron diffusion and a silicon oxide layer grown as a phosphorus diffusion barrier were carried out in a single thermal step, according to the patent granted BR102012030606-9. The sheet resistance of the emitter and B-BSF were not affected by the reduced thermal steps, demonstrating the effectiveness of the silicon oxide layer as a barrier to phosphorus diffusion in the boron-doped side. The short-circuit current density with incident irradiance on the boron-doped side was impacted by the B-BSF sheet resistance, affecting the efficiency and the maximum power bifaciality coefficient. The high recombination in the pp⁺ region limited the maximum power bifaciality coefficient to approximately 0.7, which is typical in p-type solar cells. Considering the achieved results, the boron and phosphorus diffusion performed with reduced thermal steps produces bifacial p-PERT solar cells with typical bifaciality, avoiding two thermal steps for silicon oxide growth and chemical etching and cleaning. Full article

(1) Background: This study aims to provide a viable theoretical framework for wetland ecological restoration in the lower reaches of the Yellow River within the city of Kaifeng, China. (2) Methods: Using remote sensing and image interpretation to identify the long-term evolution characteristics of wetlands in the study area and analyzing the impact of runoff, riverway changes, and groundwater flow fields in the lower reaches of the Yellow River on wetland conditions along the Yellow River. (3) Results: With natural wetland as its major wetland type, the study area saw an increase in the total wetland area from 2000–2021. Among others, the total area of artificial wetlands increased by 43%, while that of flooding wetlands in natural wetlands decreased by 37%. Surface water discharge and water level saw a year-by-year drop. Moreover, the significant wandering and oscillations of riverways led to a direct impact on the area and stability of tidal flat wetlands. After 2010, affected by rainfall and exploitation, the groundwater level declined sharply. The degraded areas of artificial wetlands were mainly distributed at the northern embankment of the Yellow River, where the groundwater burial depth decreased significantly. In contrast, at the southern embankment, for the sake of the irrigation canal diverted from the Yellow River, new back river depressions had formed and helped build a more stable ecological environment. Yellow River water levels and discharge directly impacted the area of rivers and flooding wetlands. The decline in groundwater levels led to the degradation of ponds in artificial wetlands. (4) Conclusions: The reduction of groundwater exploitation and an adequate supply of diverted Yellow River water were conducive to the development of wetlands in the back river depressions on the outside of the Yellow River embankment. Full article

The surface-borehole transient electromagnetic method exhibits significant advantages in identifying deep targets, as its closer distance to subsurface targets results in more pronounced effective anomalies when compared to surface-based techniques. The grounded-wire source TEM demonstrates enhanced capabilities for deep exploration, featuring increased penetration depth, enhanced signal response, superior resolution, and minimized volume effects, which render it especially effective for examining intricate deep reservoirs. This study utilizes a time-domain finite-element method with unstructured tetrahedral grids to conduct three-dimensional numerical simulations of grounded-wire source SBTEM in complex terrains, capitalizing on the flexibility and precision of this method for modeling detailed geological structures. A comparative analysis of electromagnetic field responses between conductive and high-resistivity targets indicates that the detection capability of magnetic field components decreases more markedly than that of the vertical electric field Ez as the burial depth of the target increases. The grounded-wire source SBTEM exhibits enhanced sensitivity and better identification capabilities for conductive targets when compared to high-resistivity alternatives. The present research represents a detailed analysis of the impact of complex terrain on the detection capabilities of grounded-wire source SBTEM, utilizing electromagnetic response simulations of typical three-dimensional complex geological models. The results provide robust theoretical backing and empirical evidence for an enhanced understanding of subsurface resource exploration. Full article

We present a two-dimensional reconstruction of blocking frequency indices in the Atlantic-European region spanning the last 400 years. Our approach is based on a simple field reconstruction scheme similar to the principal component regression method. The particularity of our reconstruction scheme is that we select the blocking predictors using observed and reconstructed surface temperature and precipitation gridded data based on the correlation stability criteria. This approach avoids the problem of non-stationarity between predictand and predictors that commonly affects the quality of climate field reconstructions. First, we reconstruct the blocking field back to 1891 using observed gridded surface temperature and precipitation data. Then, the reconstruction is extended back in time to 1602 using seasonal-resolution paleo-reanalysis temperature and precipitation fields. The reconstruction is validated against various observed blocking frequency fields and climate reconstruction indices. The methodology presented in this study offers an opportunity for extracting paleo-weather signals from seasonal-resolution gridded datasets, which enables an improved understanding of the forcing of low-frequency variability for atmospheric blockings and related extremes. Full article

Copper zinc tin sulfide (commonly known as CZTS) solar cells (SCs) are gaining attention as a promising technology for sustainable electricity generation owing to their cost-effectiveness, availability of materials, and environmental advantages. The goal of this study is to enhance CZTS SC performance by adding a back surface field (BSF) layer. SC capacitance simulator software (SCAPS) was used to examine three different configurations. Another option is to replace the cadmium sulfide (CdS) buffer layer with a titanium dioxide (TiO₂) layer. The results demonstrate that the reduced graphene oxide (rGO) BSF layer increases the conversion efficiency by 25.68% and significantly improves the fill factor, attributed to lowering carrier recombination and creating a quasi-ohmic contact at the interface between the metal and semiconductor. Furthermore, replacing the CdS buffer layer with TiO₂ offers potential efficiency gains and mitigates environmental concerns associated with the toxicity of CdS. The results of this investigation could enhance the efficiency and viability of CZTS SCs for future energy applications. However, it is observed that BSF layers may become less effective at elevated temperatures due to increased recombination, leading to reduced carrier lifetime. This study underlines valuable insights into optimizing CZTS SC performance through advanced material choices, highlighting the dual benefits of improved efficiency and reduced environmental impact. Full article

Self-cleaning coatings for solar mirrors aim to reduce water usage for cleaning, cut down on maintenance costs for solar fields, and lower the overall electricity production costs in concentrated solar power (CSP) systems. Various approaches have been developed for mirrors with back surface (BSM) and front surface (FSM) architectures, all sharing the characteristic that the self-cleaning coating serves as the outermost layer, acting as a “skin” that protects against fouling. A recent trend in this field is to enhance this “skin” with sensing capabilities, allowing it to self-monitor its performance in terms of soiling or failure, contributing to the digitalization of solar fields and CSP technology. Building on previous work with auxetic aluminum nitrides and ZnO transparent composites, which were developed to replace alumina as the self-cleaning layer in BSMs, this study explores the potential of adding sensing properties to these coatings. The approach leverages the piezoelectric properties of the materials, which can be linked to dust accumulation and surface soiling, as well as their electrical resistive behavior, which can help monitor potential failures. The promising d33 values of sputtered piezoelectric AlN and the tailored electrical properties of ZnO composites, combined with their self-cleaning effects and optical clarity across the full solar spectrum, suggest that these coatings could serve as an intelligent, self-aware skin for solar mirrors. Full article

Manual material handling, a common practice in various industries, often involves moving or lifting heavy objects, placing significant physical strain on workers, especially in the lower back. A prime example is manhole cover removal, which typically requires handling heavy weights, potentially leading to lower back muscle strain. This study investigates the effectiveness of a passive exoskeleton in reducing ergonomic risks during manhole cover removal. Twenty able-bodied workers participated, performing the task with and without extractor tools in the field. Techniques such as surface electromyography and inertial measurement units were employed to measure muscle activity and body posture using the Rapid Entire Body Assessment (REBA). This study compared muscle activities and REBA scores under different conditions: manually lifting covers, using an in-house lever tool, and using a sledgehammer and a pick bar tool named Jake, both with and without an exoskeleton. Results revealed that the in-house Lever tool was the safest and most efficient method, resulting in the lowest muscle activities and REBA scores, regardless of exoskeleton use. Interestingly, the exoskeleton significantly reduced muscle strain when using the Jake tool. These findings indicate that while the Lever tool is optimal for this task, passive exoskeletons can effectively lower ergonomic risks associated with more physically demanding tools. Full article

Modern multi-junction solar cell technology offers a pathway to achieving consistent and high photovoltaic conversion efficiencies through enhanced solar spectrum absorption. Indeed, during the last years, the industries of solar cells have focused on optimizing device structures, utilizing both robust and delicate materials to maximize their performances. This paper presents the modeling and optimization of the electrical and structural properties of high-efficiency InGaP/GaAs double-junction solar cells, specifically without employing an anti-reflective coating. This developed structure has been achieved by introducing a buffer layer in the lower layer and incorporating an upper back surface field layer into the investigated cell structure. Furthermore, the optimization conducted in this paper using Silvaco-Atlas software (version 2018) under the AM1.5G spectrum reveals that the proposed InGaP/GaAs tandem cell configuration exhibits significant performance, reaching conversion efficiency of 41.585%. It can be said that this adapted structure yields a short-circuit current density of 21.65 mA/cm², an open-circuit voltage of 2.319 V, and a filling factor of 84.001%. Whereas this newly optimized structure demonstrates its effectiveness in enhancing solar cell efficiency performance, presenting highly promising results with potential significance for the devices’ optical and electrical properties. Full article