Search Results (2,123)

Accurate lesion segmentation in ultrasound images remains challenging because of severe speckle noise, low tissue contrast, ambiguous boundaries, and substantial variations in lesion morphology and scale. To address these limitations, we propose RDPA-UNet, an enhanced U-shaped network that integrates differential-path feature modeling with multi-scale contextual aggregation. First, a residual convolutional backbone equipped with Group Normalization is employed to facilitate feature propagation and stabilize optimization under small-batch training. Second, a Differential-Path Feature (DPF) block is introduced to jointly encode local-detail and dilated-context responses from different receptive fields. Their element-wise absolute difference is explicitly modeled to quantify cross-receptive-field response discrepancies and provide complementary structural information for subsequent feature fusion. Third, a Residual Multi-scale Atrous Spatial Pyramid Pooling (RMASPP) bottleneck aggregates high-level semantic information across multiple receptive fields and refines the fused representation, thereby improving the delineation of lesions with heterogeneous sizes and irregular contours. The proposed method was evaluated on the BUSI, DDTI, and Hemangioma datasets, as well as under a mixed-data setting, using five-fold cross-validation. RDPA-UNet achieved mean Dice scores of 78.30%, 77.05%, 83.58%, and 77.08%, together with mean IoU scores of 69.45%, 66.05%, 74.12%, and 67.10%, respectively. It achieved the highest mean Dice and IoU scores across all four dataset settings and obtained the lowest mean HD95 on BUSI, DDTI, and the mixed-data setting, while achieving the second-best HD95 on Hemangioma. Ablation experiments further demonstrated the effectiveness and complementarity of residual encoding, differential-path feature modeling, and multi-scale contextual aggregation. These results indicate that RDPA-UNet provides robust lesion segmentation performance across heterogeneous ultrasound datasets while maintaining competitive boundary-localization accuracy. Full article

Generative AI has advanced architectural and landscape layout generation, but regional gardens still lack formal spatial representations, controllable generation of intrinsic spatial prototypes, and domain-aligned evaluation methods. This study presents a theory-informed proof of concept for structured translation, conditional generation, and evaluation of Lingnan courtyard garden layouts. Based on classical Lingnan garden theory, 63 plans are encoded through five semantic layers: period style, spatial structure, organization mode, courtyard type, and constituent elements. The resulting multimodal dataset pairs normalized color-coded plans with structured prompts. A latent diffusion model fine-tuned using low-rank adaptation supports boundary-constrained generation. A multi-level evaluation framework combines spatial-prototype label ablation, expert relevance assessment, and element-proportion analysis. Empirical results show that structured spatial labels improve generation controllability: the structural-label hit rate reaches 78.8% (vs. 19.4% for element-only controls), and the organizational-label hit rate reaches 52.1% (vs. 13.6%). Structural control is stronger, whereas precise organizational relationships remain difficult to generate. This study establishes a traceable pathway from regional garden knowledge encoding to generative control and evaluation, provides an open and reusable dataset, and offers a methodological reference for the digital preservation of regional architectural and landscape heritage. Full article

Prestressed and post-tensioned concrete structural elements constitute approximately 43.4% of modern bridge infrastructure, representing 58.2% of the total bridge surface area due to their long-span capabilities. Despite their structural efficiency, evaluating residual post-tensioning forces and diagnosing localized degradation within internally grouted tendons—such as localized stress corrosion cracking (SCC), grout voids, and moisture infiltration—remains a critical challenge due to geometric confinement and high material attenuation. This paper presents a non-destructive Structural Health Monitoring (SHM) methodology optimized for the continuous and periodic assessment of post-tensioned anchorage zones under operational traffic loads. The proposed Identification of Active Anomalies (IAA) system integrates the Acoustic Emission (AE) method with unsupervised machine learning to classify multi-mechanism structural degradation. By implementing a mathematically transparent k-means clustering framework initialized via the k-means++ heuristic, high-velocity multi-parameter AE data streams are partitioned within an n-dimensional Euclidean feature space. The scientific novelty of this work lies in its real-scale validation on an operational, highly complex cable-stayed bridge, establishing a previously unpublished acoustic signature database (the 2025 Signal Database). The empirical validity of the algorithm’s predictive boundaries was confirmed through forensic physical inspections and material sampling during a major structural rehabilitation in 2026, which corroborated the active corrosion states within heavily confined post-tensioned anchorage blocks. Furthermore, extracted AE pattern classes are explicitly correlated with structural crack opening widths, enabling real-time tracking of macro-defect propagation, anchorage slippage, and active micro-structural corrosion. Full article

A residual multilayer perceptron (ResNetMLP) surrogate framework is presented to predict the broadband radiated sound power spectra of submerged circular cylindrical shells. The surrogate maps the shell mean radius, wall thickness, and longitudinal excitation position to the unit-force sound power spectra generated by a high-fidelity frequency-domain solver. The trained model is deployed within a diagonal power superposition scheme using equivalent nodal forces derived from an unsteady computational fluid dynamics surface pressure field. Comparing surrogate predictions with direct diagonal vibroacoustic calculations confirms the high predictive accuracy within the diagonal approximation. Crucially, a key limitation of sound power-based surrogates is highlighted: because acoustic power is a quadratic scalar quantity, it cannot capture phase-coherent load interaction, providing a clear rationale for future pressure-based surrogate formulations. Full article

Against the backdrop of high-quality development in rural tourism, issues such as landscape homogenization and insufficient coordination among diverse stakeholders have become increasingly prominent, creating a marked disparity with the requirements for distinctive and differentiated development in rural revitalization. This paper aims to investigate how actor-networks drive the dynamic evolution of rural tourism landscapes through translation mechanisms, and to illuminate the agentic role of non-human elements in this process, thereby addressing the core question of why the same set of local resources generates distinct landscape forms across different developmental stages. To this end, this study takes the Mayangxi Ecotourism Area in Fujian as a case study and, drawing on actor-network theory, employs qualitative research methods including in-depth interviews, participant observation, and grounded theory to systematically analyze the phased evolutionary characteristics, actor-network translation logic, and underlying operational mechanisms of rural tourism landscape creation. The findings reveal that: (1) the creation of the Mayangxi rural tourism landscape has successively undergone three major developmental stages—landscape construction, landscape integration, and landscape optimization—during which human and non-human actors, through a complete translation mechanism, drive the continuous iteration of the actor-network, with non-human elements playing a significant agentic role throughout the landscape’s evolution; (2) the local landscape creation has formed a closed-loop operational mechanism of “base activation → network construction → network iteration → sustainable operation,” which effectively supports the sustainable development of rural tourism landscapes. This study addresses the analytical limitations of existing rural landscape research, which tends to focus on human-centered interactions while overlooking the value of non-human elements, expands the application boundaries of actor-network theory in the field of rural tourism, and provides practical guidance for differentiated landscape creation in China’s rural tourism development. Full article

Nanocrystalline (NC) alloys hold significant promise as structural alloys due to their superior mechanical properties over the traditional coarser grained microcrystalline alloys. Often, there is an optimal range of mean grain size for most metals about which maximum material strength can be realized. In the context of NC alloys, stabilization of the grain size in this optimal range is one of the primary synthesis challenges. A large volume fraction of NC alloy microstructure is occupied by grain boundaries (GBs). Since GBs increase the internal surface energy of the system, during solidification and grain growth phases, there is a tendency to minimize GBs through grain coarsening. However, in NC alloys, phenomena like GB–solute segregation and solute precipitation are active and mitigate grain growth and thus stabilize the desired small grains. Numerically modeling these phenomena of GB–solute interactions, and the evolution of these stabilized GBs under mechanical load, is of immense interest to the NC alloy community. To enrich the numerical modeling formulations available in this space, we present here a phase-field-method-based numerical framework to model GB segregation, solute precipitation and effect of external loading on NC alloys. While some of these effects have been modeled in isolation, a unified treatment of the solute–GB segregation-related effects and its coupling with mechanics has not be considered in the literature. We present a three-dimensional, finite element method (FEM)-based, finite-strain phase-field formulation for modeling grain evolution and microstructure stabilization in NC alloys. Beyond the formulation and its computational implementation, various case studies demonstrate the applicability of this framework. Further, thermodynamic and kinetic arguments are provided based on the evolution of GB energy to explain the effects of solute drag, GB pinning and mechanical deformation. Full article

Equal-leg angle-steel members are widely used as main load-bearing and bracing members in transmission towers. Under elevated-temperature environments such as mountain fires and forest fires, the elastic modulus and strength of steel degrade significantly, which may reduce the overall stability capacity of compression members and even lead to instability failure. To investigate the stability performance of equal-leg angle-steel members made of Q420 steel at uniform elevated temperatures, a shell-element finite-element model was established in Abaqus by considering temperature-dependent material properties of steel. Parametric analyses were carried out under constant compressional loading and uniform heating for the cases of pinned–pinned, fixed–fixed and eccentric–pinned conditions. The effects of slenderness ratio, stability load ratio, section dimension, and initial imperfection amplitude on the critical temperature were systematically analyzed. The results show that the critical temperature decreases significantly with increasing stability load ratio. The eccentric–pinned condition leads to a higher critical temperature than the other two conditions. The initial geometric imperfection will reduce the fire resistance of members. Based on the critical temperature method, design curves of the critical temperature for three boundary conditions were developed using the finite-element results, which are demonstrated to be more accurate than the existing Chinese and European codes. Full article

This study presents a numerical investigation of natural convection in a two-dimensional inclined square cavity filled with air and subjected to differential heating. The effects of the Rayleigh number and cavity inclination on heat transfer and flow behavior were investigated for 10³ ≤ Ra ≤ 10⁹ and inclination angles of 0°, 15°, 30°, and 45°. The dimensionless Navier–Stokes and energy equations were solved using the finite-element method under the Boussinesq approximation with a steady laminar formulation. A structured quadrilateral mesh with boundary-layer refinement was employed near the differentially heated walls. Mesh-refinement tests and comparisons with benchmark data for the classical square cavity were used to assess the numerical accuracy of the model. The results show that the average Nusselt number increases with the Rayleigh number, reflecting the progressive intensification of buoyancy-driven heat transfer. The effect of inclination is non-monotonic and depends on the Rayleigh number. At Ra = 10⁴, the highest average Nusselt number is obtained at 45°, whereas for Ra ≥ 10⁵, the maximum is consistently observed at 15°. At Ra = 10⁹, the average Nusselt number is 54.475, 55.617, 53.224, and 49.408 for inclination angles of 0°, 15°, 30°, and 45°, respectively. The results indicate that moderate cavity inclination can enhance heat transfer by favorably modifying the interaction between buoyancy and the imposed thermal gradient, whereas larger inclinations progressively reduce the heat-transfer rate. The present results provide a systematic characterization of the coupled effects of Rayleigh number and cavity inclination within the scope of the steady two-dimensional formulation considered. Full article

We study the linear continuous interior penalty finite element method (CIP-FEM) for the two-dimensional Helmholtz equation on nonconvex polygonal obstacle domains with mixed Dirichlet and impedance boundary conditions. Re-entrant corners reduce the global regularity below $H^2\left(\mathrm{\Omega }\right)$ and require a corner-sensitive treatment of the CIP stabilization term. Using a wavenumber-explicit regular–singular decomposition, we establish exact consistency of the CIP formulation under this reduced regularity. We also prove the critical-order penalty-seminorm estimate $|I_h{S}_j{|}_J \lesssim h^{{\alpha }_j}$ for the Scott–Zhang quasi-interpolant of the cut-off corner singular functions. Combining this estimate with endpoint Scott–Zhang approximation and wavenumber-explicit bounds for the regular and singular components yields ${\inf }_{v_h \in V_h}\parallel u-v_h{\parallel }_{h,k} \lesssim (kh + k^{\alpha -1/2}{h}^{\alpha }){\parallel f\parallel }_{0,\mathrm{\Omega }}$. A Schatz-type duality argument then yields the corresponding quasi-optimal error estimate $\parallel u-u_h{\parallel }_{h,k} \lesssim (kh + k^{\alpha -1/2}{h}^{\alpha }){\parallel f\parallel }_{0,\mathrm{\Omega }}$ under the sufficient resolution condition $k^{2}h \le \delta$, where $\delta$ is independent of k and h. Discrete uniqueness is proved independently of this condition. Numerical experiments support the predicted corner-singularity behavior; for the tested problems with the fixed penalty value $\gamma = 0.1$, they show smaller errors than the standard FEM on some relatively coarse meshes in the high-wavenumber pre-asymptotic regime. The present analysis does not separately identify an additive pollution error term. Full article

Background/Objectives: The 3′ untranslated region (3′ UTR) integrates cleavage and polyadenylation signals, microRNA targets, RNA-binding-protein sites, and RNA secondary structure, but the organizational levels that remain conserved during long-term sequence evolution are poorly understood. Methods: We analyzed the ras85D 3′ UTR in 37 drosophilid taxa. Substitution rates were estimated by maximum likelihood and RelTime; insertions and deletions were reconstructed with ARPIP and summarized as insertion–deletion evolutionary localizations (IELs). Mobile-element candidates were detected with CENSOR/Repbase, and evolutionarily conserved motifs (ECMs) with MEME/MAST. Functional and structural annotations were integrated for Drosophila melanogaster, Drosophila yakuba, and Drosophila virilis and tested using permutation-based coverage, distance, boundary-neighborhood, and multilayer architecture analyses. Results: The 2247-column alignment yielded 959 block events (710 deletions and 249 insertions). Among 63 positive-length ingroup branches, 16 were deletion-enriched, three were insertion-enriched, and one showed bidirectional turnover. Thirty-four IELs projected to 27 D. melanogaster loci and were associated with ECMs. The final registry contained 390 primary functional objects and 1135 RNAfold-predicted structural segments. Predicted weakly conserved miRNA target sites were depleted in ECM_15 and ECM_11, whereas none of 12 Functional Distance tests was significant. APA objects were enriched near predicted structural-segment boundaries (O/E = 5.21; FDR = 0.00761). SAME_MULTILOOP_INTERVAL showed reduced between-context variance (0.276× null; FDR = 0.0233), and the DIFFERENT_MULTILOOP_ARMS − SAME_MULTILOOP_INTERVAL contrast was significant (p = 0.00149; FDR = 0.00447). Conclusions: The ras85D 3′ UTR evolves as a mosaic system in which extensive deletion-biased sequence turnover coexists with conserved regulatory landmarks, recurrently remodeled local neighborhoods, and context-dependent structural–functional architectures. Full article

Digital rock technology is essential for characterizing the petrophysical properties of tight reservoirs. However, conventional construction methods often yield models with insufficient pore connectivity due to low porosity and complex nanopore structures. To address this limitation, we propose a novel connectivity algorithm for isolated pore systems. First, a digital rock model is constructed using a random particle packing algorithm that integrates high-resolution SEM parameters, including kaolinite particle morphologies and randomly distributed microfractures. Subsequently, the connectivity algorithm sequentially links isolated pore clusters to the largest continuous pore system, forming an interconnected channel. Pore network extraction reveals that the algorithm produces significantly denser and more continuous structures, with pore–throat size distributions aligning well with experimental observations. Single-phase flow simulations demonstrate that the enhanced model yields porosity and permeability values consistent with laboratory measurements, whereas unenhanced models deviate substantially. To further advance microscale flow characterization, we derive explicit fitting formulas for the dimensionless conductivity of canonical pore cross-sections (equilateral triangle, square, and circle) considering water film boundary layer (WFBL) effects. These formulations are based on a comprehensive parametric study using the ab initio finite element method, followed by regression analysis to yield closed-form expressions. Two-phase flow simulations reveal that the WFBL increases residual saturations, reduces relative permeabilities, and decreases waterflooding displacement efficiency, with effects being more pronounced during secondary imbibition. This integrated approach provides a robust framework for constructing representative digital rock models of tight reservoirs and offers essential theoretical support for accurately modeling nanoscale flow behaviors in complex subsurface systems. Full article

This study investigates the vibro-acoustic behavior of a thin square aluminum plate with a central clamped hole, inspired by splash cymbal configurations. The structural dynamics are analyzed using finite element method (FEM) modal and frequency response function (FRF) simulations, while experimental measurements validate the modal characteristics. A semi-analytical Rayleigh–Ritz model is also employed to estimate the natural frequencies and provide an additional reference for comparison. Excellent agreement is observed between the predicted and measured resonance frequencies and overall dynamic response. Acoustic radiation is evaluated through coupled structural–acoustic analyses using a Rayleigh integral formulation and an indirect variational boundary element method (BEM). The sound pressure radiated to a field point above the plate is compared with the FEM-derived FRF results. The results demonstrate a correlation between structural vibration and acoustic response, with variations in radiation efficiency influenced by the central clamp and higher-frequency modal behavior. The Rayleigh approach shows good agreement but exhibits numerical noise and overprediction of modal contributions. In contrast, the BEM provides smoother responses and more physically consistent results. These findings are relevant for noise control, vibration reduction, and sound synthesis applications in mechanical systems. Full article

Cylindrical liquid-storage tanks are important engineering structures, and ring ribs play a key role in enhancing their stiffness and fundamental frequency. The complex ring ribs, end plates, and fluid–structure coupling make rapid frequency calculation and structural design challenging. This paper develops a circumferential-harmonic FEM/BEM method based on generator-line discretization for fast computation of coupled frequencies in liquid-storage tanks. The cylindrical shell, end plates, and ring ribs are discretized along their generators, with element matrices derived via an energy method. A corresponding boundary-element formulation for the internal fluid is developed based on potential flow theory, and the fluid added-mass matrix is obtained from the fluid–structure coupling boundary to solve the coupled frequencies. The results agree well with those of commercial software, verifying the method’s accuracy. Compared with commercial software, the proposed method is more efficient. The influence of ring ribs on the fundamental frequency is further analyzed, and an optimal distribution is obtained using a genetic algorithm. The results can provide references for the design and rapid calculation of cylindrical liquid-storage tanks. Full article

In this study, the vibration characteristics of microbeams subjected to thermal loads and electric field effects under non-ideal boundary conditions were investigated. The non-ideal boundary conditions are modeled as a linear combination of ideal fixed and simply supported boundary conditions. The weighting factor, k, is defined as a measure of deviation from the ideal boundary conditions. To determine the influence of the boundary conditions, both non-ideal fixed and non-ideal simply supported beams were examined. The equations of motion of the system are derived using Hamilton’s principle, and the Method of Multiple Scales, a perturbation technique, is applied to obtain approximate analytical solutions for both linear and nonlinear vibration responses. The effects of thermal loads, electric field influence, and non-ideal boundary conditions on the natural frequencies were investigated. The results demonstrate that the natural frequencies vary significantly with changes in the weighting factor, k. To address operational reliability, a formal probabilistic sensitivity and uncertainty analysis using Monte Carlo simulations is integrated, quantifying how uncertainties in geometrical and thermal parameters propagate to structural instability. Furthermore, a theoretical framework for calibrating the abstract boundary parameter via Finite Element Model updating is introduced. These results indicate that idealized boundary condition assumptions may lead to significant inaccuracies in the design and reliability assessment of micro-electromechanical systems (MEMSs) operating under the combined effects of thermal and electric fields. Relying solely on idealized support assumptions may result in significant failure (damage) predictions owing to the underestimation of thermally induced buckling and electrical pull-in risks arising from assembly imperfections. Furthermore, a probabilistic sensitivity analysis is implemented to quantify how parameter uncertainties propagate through the system, bridging the gap between pure deterministic modeling and operational reliability. Full article

Flexible membrane structures, such as solar sails and membrane reflectors, rely on accurate characterization of in-plane prestress for structural reliability and functional performance. This study proposes a Boundary Virtual Load Method (BVLM) for the semi-analytical prediction of prestress fields in corner-tensioned rectangular membranes. An initial corner-dominated radial stress field is constructed by superposing the stress solutions generated by four corner loads. Residual normal stresses along the nominally free edges are then evaluated, and boundary virtual loads of equal magnitude and opposite direction are introduced to approximate the zero-normal-traction condition. Polynomial representations of these virtual-load distributions are incorporated into the Airy stress-function framework, yielding a boundary-corrected closed-form prestress solution. Comparisons with finite element results for three membrane configurations show that BVLM accurately captures the principal spatial characteristics and aspect-ratio-dependent evolution of the prestress field while requiring substantially lower computational cost for the cases examined. The predicted prestress fields are further incorporated into a free-vibration model that accounts for the added mass of the surrounding air. The resulting natural frequencies generally reproduce the experimentally measured modal-frequency trends, although mode-dependent discrepancies are observed for several modes. The 12 frequency comparisons yield a mean absolute relative error of $8.46\%$, indicating reasonable overall agreement for the approximate analytical formulation. These comparisons provide an indirect dynamic consistency assessment rather than a direct validation of the spatial prestress field. BVLM therefore offers an efficient framework for prestress analysis, preliminary vibration prediction, and parametric design of corner-tensioned membranes. Full article