Coral reefs are integral components of tropical coastal marine ecosystems that have considerable capacity to mitigate extreme flows and marine floods caused by storms and tsunamis. However, limited studies on coral reef efficacy in reducing such flows, coupled with variable roughness coefficient characteristics, hinder their broader utilization in sustainable engineering applications for societal benefit. In this study, we conducted comprehensive experimental investigations to examine flow–coral interactions and the flow energy reduction capabilities of coral reefs. Three-dimensional-printed coral reefs were used to simulate actual coral reefs, providing a scalable and environmentally responsible approach for studying nature-based coastal protection systems. Flow characteristics within the coral reef were investigated through flow depth and velocity measurements taken at the front of, over, and behind the reef. Analysis was performed considering nondimensional parameters, i.e., the Froude number (Fr), the depth effect (DE; ratio of flow depth to coral height), and the size effect (SE; ratio of coral length to coral height), to assess the flow energy reduction under different coral combinations and flow conditions. Spatial variations in flow depth over the reef showed that fast and shallow flows exhibited a reduction gradient toward the back of the reef. The findings revealed a substantial reduction in flow depth and velocity, reaching up to 27.5% and 25%, respectively, at the back boundary of the coral. Two-layered velocity analyses showed that the velocity over the top of corals could be six times higher than that through the coral reef structure for deep flows. Manning’s roughness coefficient varied considerably from 0.03 to 0.26. Overall, this study contributes to sustainable coastal engineering by demonstrating how bio-inspired coral reef structures can be applied to reduce flow energy and enhance coastal resilience in an environmentally adaptive manner.

For runoff-generated debris flow continuum mechanics-based early warning models, the computational unit must satisfy the homogeneity assumption of continuum mechanics. Although traditional grid cells meet the homogeneity assumption as computational units, they segment channel geomorphological functional reaches, weaken the clustered mobilization of sediment sources, and constrain efficiency due to grid-by-grid calculations. To address these limitations, we construct a Froude number (Fr) calculation model constrained by key factors such as the channel cross-sectional geometry and topographic parameters. The absolute deviation of Fr is used as a criterion for homogeneity within the computational unit. By combining critical shear stress theory and velocity perturbation, physical thresholds for the criteria are derived. A physical model-based method for automatically delineating homogeneous channel units (CUj) is proposed, ensuring that the geometric features and hydrodynamic parameters within CUj are homogeneous, while ensuring heterogeneity between adjacent CUj. Comprehensive multi-scale validation in Yeniu Gully, a typical debris flow catchment in Wenchuan County, demonstrates that parameters such as longitudinal gradient, cross-sectional area, flow depth, and shear stress remain relatively homogeneous within each CUj but differ significantly between adjacent CUj. Furthermore, the proposed method can stably characterize key channel geomorphological functional units, such as bends, confluences, abrupt width changes, longitudinal gradient changes, erosion segments, and deposition segments. Sensitivity analysis demonstrates that the method satisfies both robustness and universality under various conditions of rainfall intensity, runoff coefficient, and Manning’s roughness coefficient. Even under the most unfavorable extreme conditions, the accuracy of CUj delineation exceeds 88.64%, indicating high reliability and suitability for deployment in various debris flow catchments. The proposed framework for defining CUj resolves the conflict in traditional computational units between the “continuum model homogeneity requirement” and “geomorphological functional unit continuity,” providing a more rational and efficient computational environment for runoff-generated debris flow continuum mechanics-based early warning models.

This study assesses the hydraulic roughness of periwinkle shell and Rapana venosa gabions to ascertain their appropriateness for hydraulic engineering applications. Laboratory tests were performed utilizing a rectangular flume (0.6 m wide, 0.45 m deep, and 5.0 m long) in the Niger Delta region, where periwinkle shells are prevalent. Flow discharges between 0.015 and 0.045 m³/s were introduced, with matching measurements taken for velocity, flow depth, and hydraulic radius. The Manning's roughness coefficient (n) and the Darcy–Weisbach friction factor (f) was calculated from the observed data. The findings indicated that periwinkle shell gabions exhibited elevated roughness values, with Manning’s n varying from 0.034 to 0.041 and the friction factor f ranging from 0.045 to 0.052. Conversely, Rapana venosa gabions had reduced values, with n varying from 0.028 to 0.033 and f between 0.038 and 0.044. The findings demonstrate that periwinkle shells offer enhanced flow resistance and energy dissipation, rendering them effective for erosion-prone channels and flood control systems. In contrast, Rapana venosa gabions demonstrated more favorable flow conditions, appropriate for irrigation canals and conveyance systems. The study indicates that shell-based gabions offer a cost-efficient and sustainable alternative to traditional aggregates, facilitating waste reutilization in hydraulic infrastructure.

ABSTRACT Accurate assessment of rock mass strength is crucial in rock mass engineering due to its significant impact on project safety and economic viability. Improper evaluation of rock mass parameters can lead to potential risks or costly inefficiencies. In this study, an attempt was made to integrate the Hoek-Brown criterion and Barton-Bandis criterion to describe the strength of rock mass with non-persistent joints using a new analysis model framework. Further, a new quantitative evaluation method for the geological strength index (GSI) was proposed based on joint persistence factor, joint roughness coefficient, and residual friction angle. Rock core samples containing representative joints were selected from boreholes at the Yingliangbao Hydropower Station. The surfaces of these joints were then subjected to 3D laser scanning, and embedded into cubic cement molds for direct shear testing. Then, GSI values at different parts of the main powerhouse were obtained, with a mean of 62.3 and a standard deviation of 10.99. Furthermore, a Bayesian framework was employed to quantify the uncertainty of the proposed GSI model. By incorporating in-situ data, the analysis yields a posterior probability distribution for the GSI value, providing a more realistic assessment of rock mass quality.

ABSTRACT Uniaxial compression tests instrumented with acoustic emission and digital image correlation systems were conducted to explore the failure behaviors of unbolted and bolted jointed specimens. The jointed specimens were fabricated by 3D printing with a fixed inclination angle of 45° and five joint roughness coefficients (JRC) values: 2.88, 7.47, 11.86, 15.37, and 19.15. For unbolted jointed specimens, as JRC increased from 2.88 to 19.15, the increments in strength, elastic modulus, and failure strain were 19.99 MPa, 6.95 × 10 −3 , and 0.52 GPa, respectively. Bolting produced a marked increase in failure strain for jointed specimens with JRC = 2.88 and 7.47; the bolting‐induced gains in strength, elastic modulus, and failure strain diminished as JRC increased. Both increasing JRC and bolting led to a larger total number of cracks and a stabilization of the b‐value. As the JRC increased, the failure mode of jointed specimens shifted from joint sliding to matrix tensile‐splitting. Bolting exacerbated joint wear and increases promoted the formation of tensile cracks within the matrix. The bolts in jointed specimens with JRC = 2.88 and 7.47 were sheared off, whereas those in specimens with JRC = 15.37 and 19.15 underwent bending deformation. Higher JRC values increased the ratio of axial to vertical deformation in the bolts.

Ni‐rich NiTi is a distinctive functional smart alloy well‐suited for biomedical and aerospace applications, owing to its exceptional thermomechanical properties, biocompatibility, and corrosion resistance. The wear resistance and long‐term service life of NiTi alloys are strongly dependent on their phase transformation behavior, which is intrinsically linked to microstructural evolution. In this context, the present study investigates the critical role of Ti 3 Ni 4 precipitates in governing phase transformation kinetics, microstructure, and tribological performance through controlled aging treatments at 450 °C and 650 °C. Results reveal that Ti 3 Ni 4 precipitation significantly hardens the alloy, inhibiting martensitic phase transformation while substantially improving wear resistance compared to precipitate‐free conditions, despite exhibiting higher surface roughness and friction coefficient. In contrast, the absence of Ti 3 Ni 4 precipitates (achieved by aging at 650 °C) accelerates the thermally induced transformation rate by 78% but severely degrades wear resistance, increasing both wear rate and wear depth by 67%. The findings establish a microstructure–property framework for tailoring Ni‐rich NiTi shape memory alloys: Ti 3 Ni 4 ‐rich microstructure optimizes wear‐critical applications, while unprecipitated microstructure favors rapid phase transformation. This work advances the design of NiTi alloys by decoupling the antagonistic effects of precipitates on transformation kinetics and wear performance, offering actionable guidelines for application‐specific heat treatments.

Understanding the shear behavior of the interface between surrounding rock and backfill is of significant engineering importance for enhancing stope stability in cemented tailings backfill mining. However, the evolutionary mechanisms of shear properties and damage under varying mechanical conditions remain insufficiently studied. This investigation employed tailings and surrounding rock from a Guangdong tailings pond, with basic mechanical parameters determined through laboratory tests. Numerical models of the rock-backfill composite were developed using PFC2D, considering different shear rates (0.3, 0.6, and 0.9 mm/min), lateral confinement levels (0.5, 1.0, and 1.5 MPa), and roughness coefficients. The analysis compared the interface’s peak and residual shear strengths, revealed crack evolution patterns, and explored damage mechanisms using acoustic emission monitoring and energy dissipation theory. Key findings include the following: (1) Shear stress–displacement curves under all conditions exhibited three stages, ascending, shearing-off, and sliding, with distinct peak and residual strengths. (2) Increasing lateral confinement, shear rate, and roughness transformed failure from localized to global sliding, with cracks occurring at the interface and propagating into the backfill. (3) Cumulative acoustic emission events increased with all three factors, with lateral confinement showing the most substantial effect on interface energy accumulation (83% increase). These results provide theoretical support for assessing interface stability in deep backfilled stopes.

The flow regime in channels or in surface water at lowland territories during the growing season is often very strongly influenced by the occurrence of aquatic vegetation. As a result of global warming, temperatures are rising, and for this reason, the year-round water growth in the warmest regions of Slovakia - Záhorská lowlands. Lowland streams flow mostly in important agricultural areas of the country, where fertilizers can greatly affect water quality and promote the growth of aquatic vegetation. Another factor affecting the occurrence of aquatic vegetation is the small slope of water flows in lowland areas, and the resulting small flow velocities in the flow. There is a settling of carried particles in the stream, an increase in the thickness of the bottom sediments and thus an improvement in the conditions for the growth of aquatic vegetation. From a hydrodynamic point of view, water plants alter the size and distribution of flow velocities at a large rate; they increase the stream bed roughness and decrease the discharge capacity of a stream. This study investigates flow resistance in the Malina stream, located in the Zahorská lowland of western Slovakia, with a particular emphasis on refining the estimation of Manningʼs n in vegetated stream and analyses impact of aquatic vegetation density on the dynamics of flow process by evaluation of the roughness coefficient value obtained from different methods (measurements in streams/open channels; empirical equations; tables of the roughness coefficients; photographics catalogs; Cowan´s method). Measurements performed during vegetation season (from April to September) along the part of the Malina stream were used for determination of the roughness coefficient value for different extents of river bed overgrowth during the year.

A Derivative-Orthogonal Wavelet Multiscale Method for Elliptic Equations with Rough Diffusion Coefficients

Decoupling elevation errors from pipe roughness calibration in hydraulic network models.

This study addresses the growing need for architectural environments that support stable navigation and perception performance of service robots as their deployment expands. Based on the principles of Evidence-Based Design (EBD), the research investigates correlations between robotic performance and the physical properties of architectural finishing materials. While conventional EBD has focused on human responses, evidence concerning environmental factors that influence robotic sensors and locomotion remains limited. This study examines service robot performance indicators, perception accuracy, path stability, and collision rate and relates them to material properties such as reflectance, coefficient of friction, surface roughness, illuminance uniformity, and transparency. The findings indicate that reflectance and lighting uniformity are critical determinants of sensor recognition, while friction and surface roughness strongly affect navigation stability. In addition, transparent obstacles and lighting conditions act as moderating factors that impact both perception and mobility. As a foundational investigation, this study provides baseline evidence for a correlation-based evaluation framework that can inform future design, construction, and operational guidelines for robot-friendly built environments.

The parameter optimization of marine hydrodynamic models currently relies predominantly on expert empirical knowledge, but the quantitative indicators and weighting mechanisms for rapid calibration remain unclear due to inherent model uncertainties and complexities. This study addresses these challenges through expert questionnaires that collect fuzzy evaluations of calibration criteria, developing an integrated methodology combining the theory of axiomatic fuzzy set (AFS) with principal component analysis (PCA). Numerical case studies quantify calibration indicator weights and assess critical parameter impacts, revealing that bathymetry and roughness coefficients predominantly govern simulation accuracy. Elevated roughness conditions demonstrate two regimes: (1) at 1–2 × baseline roughness, strong positive correlations (with a coefficient of determination R2 increased by up to 0.568 compared to baseline) confirm effective model-data matching for tidal levels/currents; (2) beyond 2 × baseline roughness, progressive correlation decay accompanies increasing coefficients, indicating amplified simulation–measurement discrepancies. Notably, under reduced roughness conditions, high accuracy persists during spring/mid-tide phases but significantly diminishes during neap tides, demonstrating enhanced roughness sensitivity in low-tidal energy regimes.

Effects of Offset Displacement and Joint Roughness Coefficient (JRC) on the Real Contact Area of Mismatched Rock Joints

The objective of this in vitro study was to evaluate and correlate the wear resistance of three additively manufactured dental restorative materials using three wear test methods. ball-on-disc, block-on-ring, and linear reciprocation. Three polished or glazed restorative materials were divided into four groups and subjected to wear testing under 49 N and 70 N loads, submerged in artificial saliva to simulate 48 months of in vivo wear. Vertical loss, step-height, surface roughness and friction coefficient were recorded. Correlation and statistical analyses were conducted. Ball-on-disc and reciprocative methods exhibited an overall weak positive correlation, while reciprocation vs. block-on-ring had weak to negative correlations. Three-way ANOVA indicated a significant effect of material type on vertical loss values (P < 0.03). Reciprocation caused higher surface roughness for Crowntec Plus and VarseoSmile Plus (P < 0.05), but not for MFH C&B (P > 0.05). Friction coefficient remained clinically acceptable across all methods. Increased load (49 N to 70 N) minimally impacted wear but affected surface roughness. Materials exhibited varying wear performance based on the testing method used. Weak correlations were observed across wear tests in most instances, with increases in load having minimal impact on wear outcomes and variable impact on surface roughness depending on the testing method.

The fatigue of wood mortise–tenon (M–T) joints commonly results from the looseness of the joints when subjected to long-term cyclic load. It is of critical importance to comprehensively understand the fatigue of M–T joints to know what occurs in M–T joints However, fatigue evolution progression (FEP) of M–T joints has been rarely studied. This study mainly aimed to investigate the FEP of the roughness of mortise (RM) and tenon (RT), and the friction coefficient of the non-glued round-end beech wood M–T joint when subjected to cyclic load to provide basic data for numerically modelling the FEP of the M–T joint. The effects of cyclic load amplitude (CLA) (150 N, 200 N, 250 N, and 300 N) and cyclic load count (CLC) (25%, 50%, 75%, and 100% fatigue life) on RM, RT, and the friction coefficient were investigated. The results demonstrate that the CLA and CLC have significant effects on RM, RT, and the friction coefficient of the M–T joint. The RM, RT, and friction coefficient of the M–T joint decrease non-linearly as the CLA and CLC increase, complying with the power law function. The RM, RT, and friction coefficient of M–T joints are reduced by a large margin within the CLC of the initial 25% fatigue life, and these reductions decelerate from a CLC of 75% to 100% for all CLAs. The relationships between the friction coefficient and RM and RT at each CLA can be well fitted by a quadratic model during FEP. This study provides a new insight to comprehensively understand the FEP of the round-end M–T joint and supplies basic data for numerically modelling the FEP of the M–T joint.

ABSTRACT Dual-hole blast experiments were conducted, and the fracture processes on the specimens’ free surfaces were captured. The fracture surface roughness coefficient (FSRC) was quantitatively analysed to assess the degree of blast-induced surface irregularity. To further investigate the dynamic response, 3D finite element models were built in LS-DYNA to simulate stress wave propagation, stress response, and damage evolution under varying delay initiation conditions. The results revealed that at zero or short delay times, a unified fracture zone was formed. Cracks are mainly concentrated in the central region, following an uneven distribution. In contrast, longer delay times led to more independent fracture processes between the holes. The first blast hole provides initial cracks or damage zones for the second hole, resulting in a more uniform crack distribution. Under short-delay initiation, stress waves interacted in the collision zone between the two holes, resulting in localised stress enhancement that promoted crack propagation within this region. The relatively low FSRC values observed between adjacent blast holes further confirmed that stress wave superposition facilitated crack coalescence, thereby improving the continuity and smoothness of the blast contour. Moreover, crack propagation from the first blast hole was found to influence the second hole’s fracturing behaviour, with secondary cracks preferentially extending along pre-existing paths rather than initiating new radial fractures.

Accurate estimation of Manning’s roughness coefficient (n) is vital for hydrological modeling and optimizing furrow irrigation systems, yet traditional methods remain limited due to spatial-temporal variability, the need for expert users, the inherent limitations of hydraulic equations, and labor-intensive measurements. This study introduces a novel algorithm that integrates high-resolution image processing with machine learning techniques to dynamically predict n during advance and storage phases in bare furrows. Three scenarios were evaluated: (i) full-field data (including inflow/outflow rates, advance/recession times, infiltration, slope, soil moisture, furrow images and etc.), (ii) images only, and (iii) images plus selected field data (inflow rate, slope, cross-sectional area, clod size and irrigation events). Manning’s n was computed using the SIPAR_ID model and Manning’s equation in advance and storage phases, yielding ranges of 0.017–0.636 (advance phase) and 0.015–0.317 (storage phase), with respective means of 0.083 and 0.054. The Random Forest algorithm in Scenario (i) achieved near-perfect performance (99% precision, recall, and F1-score), while Scenario (iii) preserved 95–96% accuracy with significantly reduced data inputs. Notably, excluding hydraulic variables (Scenario ii) led to a ~ 50% performance drop, highlighting their importance. This approach offers a robust, cost-effective solution for n estimation, bridging the gap between precision, practicality, and real-time application in sustainable water management and precision agriculture.

When jointed rock masses are in a high-stress environment, the roughness of the joints is the key factor controlling their shear strength. Their loading behavior is also different from the constant normal load (CNL) conditions controlled in conventional laboratories; rather, they follow the constant normal stiffness (CNS) conditions. To investigate the effects of normal stiffness and roughness on the shear mechanical properties of unfilled joint surfaces, shear tests were simulated using PFC3D (5.0) software under CNS conditions. The effects of normal stiffness of 0 (constant normal stress of 4 MPa), 0.028 GPa/m (low normal stiffness), 0.28 GPa/m (medium normal stiffness), and 2.8 GPa/m (high normal stiffness), and joint roughness coefficients (JRC) of 2~4 (low roughness), 10~12 (medium roughness), and 18~20 (high roughness) on the shear stress, normal stress, normal deformation, surface resistance index, and block failure characteristics of the joint surface were obtained. The results indicate that for different combinations of normal stiffness—JRC—the shear simulation process primarily exhibits three deformation stages: linear stage, yield stage, and post-peak stage. Shear stress increases initially and then decreases as shear displacement increases. When normal stiffness is no less than 0.28 GPa/m, both normal stress and JRC increase gradually with increasing JRC and normal stiffness. When the normal stiffness is no greater than 0.028 GPa/m, the normal stress shows no significant change. The normal displacement changes from “shear contraction” to “shear expansion” with increasing shear displacement and from positive to negative values while the displacement gradually increases; the maximum normal displacement decreases with increasing normal stiffness and increases with increasing JRC. The peak SRI value increases with increasing JRC and decreases with increasing normal stiffness. As normal stiffness increases, the number of tensile cracks for JRC 2~4 first decreases and then increases, while the number of shear cracks gradually increases; for JRC 10~12 and 18~20, both the number of shear cracks and tensile cracks increase with increasing normal stiffness. This paper simulates the actual mechanical environment of deep underground joints to expound the influence of normal stiffness and joint roughness on the stability of deep rock masses. The research results can provide certain theoretical references for predicting the stability of deep surrounding rocks and the stress of support structures.

Spatiotemporal variations of Manning’s roughness coefficient in the estuary of Langsa River based on field measurements and hydraulic modeling

Calibration of Manning’s roughness coefficients for Shallow-water flows on complex bathymetries using optimization algorithms and surrogate neural network models