Search Results (1,012)

The objective of this study is to mitigate the bottom-out failure and improve the energy absorption of conventional helmet liners during high-energy impacts, thereby reducing the risk of head injuries. To this end, a locally reinforced Primitive-type triply periodic minimal surface (P-TPMS) energy-absorbing liner is proposed for the helmet forehead region, which facilitates progressive energy dissipation through layer-by-layer buckling deformation. A finite element model of a helmet–head coupling was created based on a previously verified high-fidelity head model and subsequently validated against the ECE 22.06 standard drop-test methodology. Three critical design parameters—outer protective layer thickness, triply periodic minimal surface (TPMS) unit cell size, and wall thickness—were optimized employing the Box–Behnken Design (BBD) response surface methodology, resulting in quadratic regression models for the head injury criteria (HIC) and peak linear acceleration (PLA) with good fit ($R^2$ > 0.97). Optimal parameter combinations were established using multi-objective optimization, with protective efficacy carefully assessed from both head dynamic response and biomechanical response perspectives. The ideal P-TPMS liner possesses an outer protective layer thickness of 14.95 mm, a TPMS unit cell size of 12.23 mm, and a wall thickness of 3.93 mm. Compared to the traditional expanded polystyrene (EPS) liner, the optimized P-TPMS liner significantly reduces HIC (by ∼16%) and PLA (by ∼14%) while extending the impact duration. More critically, it transitions both intracranial pressure and brain tissue strain below their respective clinical injury thresholds, substantially lowering the risks of skull fracture and mild traumatic brain injury (mTBI). The P-TPMS construction facilitates continuous energy dissipation during impacts via incremental layer-by-layer buckling deformation, hence extending impact duration and markedly improving helmet protective efficacy. These findings offer theoretical foundations and technical direction for the creation of localized heterogeneous liner designs in advanced high-performance helmets, although the results are limited to frontal flat-anvil impact conditions. Full article

Strong seismic waves induced by drill-and-blast tunnel excavation threaten the structural integrity of adjacent existing tunnels; however, prevailing safety evaluation methods mostly simplify tunnel linings as homogeneous continua, failing to accurately characterize the meso-scale uncoordinated dynamic response between rebar and concrete under blast impact. To fill this research gap, a 1:1 full-scale separated three-dimensional finite element model of reinforced concrete composite linings was established using the LS-DYNA explicit dynamic numerical algorithm, which was verified by previous 1:25 scaled physical model tests. This study systematically quantifies the spatiotemporal evolution of lining dynamic responses under two core parameters—tunnel clear distance (10 m to 60 m) and single-delay detonating charge quantity (10.8 kg to 28.8 kg)—to validate the response differences between materials. It is abstracted that the structural failure is dominated by axial tensile stress, with the embedded rebar being significantly more sensitive to internal stress surges (reaching 3.5 times the peak stress of concrete), while the concrete is more sensitive to particle vibration velocity amplification, a mismatch that is particularly acute within a 30 m clear distance. This study highlights the severe interfacial stress gradient between rebar and concrete, providing an indirect but critical indicator for the potential risk of interface debonding under adjacent blasting, and offers a quantitative theoretical basis for extending safety assessments from macro-surface vibration control to refined meso-scale internal stress monitoring. Full article

Cosmic large-scale structure formation is commonly described in terms of the evolution of density fluctuations and correlation statistics. However, such approaches primarily characterize amplitude variations and do not directly capture the spatial rearrangement of mass distributions. Recent developments based on optimal transport theory have introduced a complementary perspective, in which structure formation is understood as a transport process in the space of probability measures equipped with Wasserstein geometry. In this work, we extend this framework by introducing transport–information geometry, which unifies transport geometry with information geometry. Within this formulation, cosmological states are represented as elements of the product space of probability measures and statistical manifolds, allowing gravitational mass transport and generative deformations associated with galaxy formation to be treated in a unified manner. Using entropic optimal transport, we demonstrate that Wasserstein geometry and Kullback–Leibler-based information geometry are connected within a single mathematical structure, leading to a geometric interpretation of cosmological evolution as a coupled transport–information process endowed with a dual-affine structure. In this picture, gravitational evolution corresponds to generative deformation associated with e-geometry, while observational processes, including finite sampling and survey selection, are described as mixing and projection in m-geometry. This dual-affine cosmology provides a unified framework in which gravitational transport, galaxy bias, observational effects, and nonlinear multi-stream structures are consistently incorporated. The resulting formulation offers a systematic basis for cosmological inference, data analysis, and stochastic descriptions of structure formation. Full article

Steel–concrete composite beams are widely used in bridge infrastructure but are vulnerable to deterioration due to uniform and pitting corrosion, particularly at the lower flange. This study investigates the flexural behavior of corroded steel–normal strength concrete (NSC) composite beams and evaluates rehabilitation using ultra-high-performance concrete (UHPC) slab replacement, with and without additional steel plate strengthening. A comprehensive finite element analysis was conducted considering three beam spans (5, 7, and 9 m), two corrosion types, and three corrosion levels. The results indicate that both corrosion types significantly reduce flexural capacity due to cross-sectional loss, with pitting corrosion causing greater strength reduction than uniform corrosion at the same weight loss because of stress concentration effects. Replacing the NSC slab with a UHPC slab effectively restores and often enhances load-carrying capacity beyond that of intact beams while reducing dead load, demonstrating the superiority of the proposed rehabilitation approach. The combined use of UHPC slab replacement and welded steel plate strengthening provides the greatest improvement, revealing a strong synergistic effect. A case study of a corroded steel bridge in Pennsylvania confirms the practical applicability of the method, showing that UHPC-based rehabilitation increases the load rating from below unity to above unity. These findings highlight UHPC as an efficient and sustainable solution for extending the service life of aging steel bridges. Full article

This work presents a graded investigation of $\mathrm{\Theta }$-superderivations within the framework of Lie superalgebras, generalizing the $\mathrm{\Theta }$-derivation concept from ordinary Lie algebras to graded settings. For a given Lie superalgebra $\mathfrak{g}$, a linear mapping $\phi$ qualifies as a $\mathrm{\Theta }$-superderivation where $\mathrm{\Theta }$ is a superderivation such that $\phi \left([\eta ,\xi ]\right)=[\phi \left(\eta \right),\xi ]+{(-1)}^{\left|\phi \right|\left|\eta \right|}[\eta ,\mathrm{\Theta }\left(\xi \right)]$ for all homogeneous elements $\eta ,\xi \in \mathfrak{g}$. This formulation simultaneously encompasses ordinary superderivations and even components of graded centroids. We demonstrate that the collection ${sDer}^{*}\left(\mathfrak{g}\right)$ of all $\mathrm{\Theta }$-superderivations naturally carries the structure of a Lie superalgebra and admits the decomposition ${sDer}^{*}\left(\mathfrak{g}\right)=sDer\left(\mathfrak{g}\right)+C_{\overline{0}}\left(\mathfrak{g}\right)$, where $sDer\left(\mathfrak{g}\right)$ denotes the superderivation algebra and $C_{\overline{0}}\left(\mathfrak{g}\right)$ represents the even part of the graded centroid. For perfect or centerless Lie superalgebras, this sum becomes direct. In the particular case of finite-dimensional simple Lie superalgebras over algebraically closed fields of characteristic zero, we establish ${sDer}^{*}\left(\mathfrak{g}\right)=ad\left(\mathfrak{g}\right)\oplus \mathbb{F}·{id}_{\mathfrak{g}}$. Furthermore, a semidirect product decomposition ${sDer}^{*}\left(\mathfrak{g}\right)\cong sDer\left(\mathfrak{g}\right)⋉C_{\overline{0}}\left(\mathfrak{g}\right)$ holds whenever the center vanishes. Concrete illustrations involving the Heisenberg superalgebra, the super-Virasoro algebra, and low-dimensional examples are provided, complete with explicit matrix representations. Our findings extend classical derivation and centroid theories to the superalgebraic realm, laying groundwork for future implications in deformation theory and supersymmetric quantum mechanics. Full article

One of the interesting properties of the two-dimensional potential problem is that solutions of the Laplace equation remain solutions of the Laplace equation when subjected to a conformal transformation. While this result was established long ago, the consequences within computational mechanics have not been fully explored. Here, we demonstrate for the first time that in a finite element formulation of the potential problem, the stiffness matrix remains invariant under a conformal mapping. This holds even when the mapped domain extends to infinity. Furthermore, by introducing the local flux in a finite element method, we find that the fundamental boundary eigensolutions also are invariant under a conformal mapping transformation by using a special weight function related to the Jacobian of the transformation. A series of computational examples is presented to emphasize the most important characteristics of conformal mappings within the finite element method and to demonstrate convergence of the computational results. Included are two exterior problems, the latter of which permits determination of the tearing stress intensity factor for a crack in an infinite plate. Full article

Pumping stations serve as the foundation platform for large-scale vertical fluid machinery, and their structural dynamics directly govern the vibration levels and long-term reliability of the installed pump units. In low-head vertical pumping stations, the interaction among the massive underwater substructure, flexible above-ground powerhouse, and surrounding backfill soil creates a complex dynamic system whose behavior remains insufficiently characterized. This study presents a comprehensive dynamic analysis of a large-scale vertical pumping station using a high-fidelity three-dimensional finite element model that incorporates the powerhouse superstructure, submerged concrete substructure, and backfill soil. Modal analysis under four boundary condition scenarios—varying in soil participation and interface contact conditions—systematically quantifies the influence of soil–structure interaction on natural frequencies and mode shapes. Resonance verification against three primary excitation sources—rotational frequency (4.917 Hz), blade passage frequency (24.583 Hz), and rotor–stator interaction frequency (196.667 Hz)—is extended from the first 50 modes to the 400th mode to assess potential high-order resonance risks. Results show that the roof slab, with its large span and low stiffness, exhibits the highest vibration susceptibility. For the rotational frequency, modes 4–12 fall below the 20% code-specified safety margin but rapidly exceed the threshold thereafter. For the blade passage frequency, the separation ratio decreases progressively with increasing mode order within the first 50 modes, and the extended analysis up to the 400th mode shows that the separation ratio remains well above 20% throughout modes 51–400. Consequently, no substantial resonance risk exists for the blade passage frequency within the entire computed range. The rotor–stator interaction frequency remains safely separated with margins exceeding 95%. These findings demonstrate the profound influence of soil–structure interaction and confirm that, despite a decreasing trend in frequency separation at higher orders, the blade passage frequency poses no substantial resonance risk up to the 400th mode. This work provides a rigorous analytical framework for vibration-informed design and optimization of pump foundation systems, with direct implications for the reliability and operational safety of large-scale vertical fluid machinery. Full article

The Vertical Shaft Machine (VSM) method is increasingly used in ultra-deep prefabricated shafts. However, as its application extends into hard ground, existing segment designs still largely follow soft soil experiences, resulting in insufficient material utilization and poor economic efficiency. Based on the first VSM shaft in South China, this study establishes a refined finite element model validated by field monitoring and subsequently constructs a structural response database. A GA-XGBoost surrogate model combined with the SHAP method quantifies the contributions of key parameters—concrete strength, rebar diameter, and steel plate thickness—to shaft structural stress. Following the optimization objective of reducing material consumption while maintaining the overall structural performance of the original design, an optimization scheme for Ring 0 reinforcement is proposed. Results show that SHAP analysis effectively identifies the contribution ranking of each parameter to the structural response: for Ring 0, concrete strength contributes the most while rebar diameter shows low sensitivity; for the cutting edge ring, steel plate thickness and concrete strength contribute significantly, whereas tie bars show the lowest sensitivity. After optimization of Ring 0, reinforcement consumption per linear meter of segment is reduced by 43.43 kg, and steel content decreases by 57.91 kg/m³. Verification confirms that the stress distribution remains largely unchanged and crack width meets specification limits. Tie bars in the cutting edge ring play an irreplaceable structural role during concrete pouring and should not be directly optimized. The proposed scheme reduces material consumption while ensuring structural safety, offering a reference for optimizing VSM shaft segment structures in hard ground conditions. Full article

This paper presents an extended combined experimental and numerical study on the vibration comfort assessment of a modern timber-framed public utility building. The research focuses on a lightweight skeleton floor system, representing a typical high-frequency floor. In situ vibration measurements were conducted under various walking excitations (single and multiple pedestrians) to determine key vibration parameters. Post-processing, which yielded root mean square accelerations and velocities, was performed using a custom-developed code in the Mathematica package. A finite element model was prepared in Dlubal RFEM 6 using shell and beam elements with offsets. The dynamic characteristics obtained from the FE modal analysis showed high consistency with the experimental data, with a relative error of approximately 5 % for the fundamental frequency. The vibration comfort was assessed using two distinct methodologies: the JRC report and the SCI P354 guide. Both approaches positively verified the floor’s vibration comfort, confirming its suitability for the intended use. The study demonstrates that the JRC methodology is more straightforward and unambiguous for engineering practice. Furthermore, the results indicate that simplified FE models provide a reliable basis for predicting vibration modes and calculating mode shape factors, which are essential for the correct interpretation of local measurements in existing buildings. Full article

A graph G is locally irregular if every two adjacent vertices have distinct degrees and is locally irregular-connected if for every two vertices u and v of G, there is a locally irregular $u-v$ path in G. For a finite set S of two or more positive integers with maximum element k, it is known that there exists a graph of order $k+1$ with degree set S. This result is extended by showing that there is a locally irregular-connected graph of order $k+1$ with degree set S. Characterizations are established for all locally irregular-connected graphs of cycle rank at most 2. All sets S of positive integers are determined for which there is a locally irregular-connected graph of cycle rank at most 2 with degree set S. The minimum order of a locally irregular-connected graph with a prescribed degree set is determined as well. Other results and open questions are also presented. Full article

Stray-current corrosion from DC-electrified railways drives premature failure of buried metallic infrastructure (pipelines, foundations, tunnel reinforcement), causing resource waste, repair-driven carbon emissions and service disruptions that undermine the sustainability of urban transit corridors. Conventional impressed-current cathodic protection (ICCP) design relies on uniform-anode rules of thumb or closed commercial codes that cannot quantify the trade-off between protection uniformity, energy use and hardware cost. We present an open MATLAB framework that couples a custom 3D finite element method (FEM) solver with multi-objective particle swarm optimisation (MOPSO) and minimises three competing objectives simultaneously: total impressed current, RMS deviation from the protection target, and number of active anodes. A laboratory-calibrated coupling factor ($\mathrm{CF}=1.98$, consistent with the image-method prediction of 2 for a highly conductive pipe inclusion) absorbs the pipe–soil interface kinetics into a single direct FEM solve, and a pre-computed Green’s-function basis accelerates each MOPSO evaluation by more than two orders of magnitude. The solver is validated against an instrumented prototype with RMSE $=14.9$ mV across ten Cu/CuSO₄ saturated reference electrode (CSE) measurements, and applied to a 500 m DC traction line. At an identical total current of 20.30 A across five anodes, the optimised design achieves an RMSE of 86.6 mV against the $-850$ mV NACE target, whereas a conventional uniform layout produces severe over-protection (RMSE $=1107$ mV)—a twelve-fold reduction. The framework is recommended as a transparent, reproducible engineering tool that simultaneously extends pipeline service life and reduces rectifier energy demand, supporting UN Sustainable Development Goals 9 and 11 for sustainable urban-rail infrastructure. Full article

The classical earth pressure theories, such as Coulomb’s and Rankine’s, are derived based on the assumption that the backfill soil extends infinitely behind a retaining wall. However, in many practical engineering situations, the backfill width is limited, and the failure wedge cannot fully develop as assumed in these classical solutions, which leads to inaccuracies in the estimation of the active earth pressure. To address this issue, this study investigates the active earth pressure under a narrow backfill width through numerical simulations and theoretical analysis. A finite element model was developed in PLAXIS 2D to examine the effects of parameters such as the backfill width-to-height ratio and the internal friction angle of the soil on the active earth pressure. Based on the numerical results, a theoretical model was formulated by discretizing the soil into blocks, formulating equilibrium equations for each block, and considering the interactions between adjacent blocks. The distribution and point of application of the active earth pressure were then computed using the finite difference method. Finally, the theoretical predictions were validated through comparisons with numerical results and previous studies. Full article

To address the problems of easy cracking and the difficulty in balancing construction schedule and structural quality in the construction of ultra-long concrete slabs, this paper takes the ultra-long floor slab project of an inpatient building in the Science City Campus of Chongqing University Cancer Hospital as the research object, and conducts research on temperature and crack control in the construction of the alternative bay method. The key structural mechanical parameters are determined through theoretical calculation. The temperature and deformation changes during the whole process of concrete pouring are tracked by combining on-site monitoring and finite element simulation, and the effects of different construction parameters are compared and analyzed. The results show that when the alternative bay method is adopted, the overall temperature distribution of the floor slab is uniform, and there are obvious differences in deformation at different positions. The center of the first-poured slab has smaller deformation, the beam side has larger deformation, the later-poured slab has larger overall deformation, and tensile deformation occurs on both sides of the construction joint. Reasonably dividing the pouring blocks, optimizing the pouring sequence and extending the pouring interval can significantly reduce the tensile deformation of concrete and alleviate stress concentration. This study confirms that the alternative bay method can effectively reduce the risk of temperature-induced cracking in ultra-long floor slabs and provide technical reference for seamless construction of similar above-ground structures. Full article

Hard ceramic coatings are essential for extending the performance of metal parts under the extreme heat and stress found in aerospace and defense environments. There is a major knowledge gap regarding this topic in the current literature. While there has been significant research on individual fabrication methods or specific coating materials separately, no previous review has combined experimental lifecycle data with a broad computational design approach that covers the entire design-to-deployment process. This review fills that gap by offering a unified roadmap from integrated computational materials engineering (ICME) to machine learning (ML). This roadmap speeds up the rational design of coatings for next-generation aerospace systems. The practical importance of this framework is its clear use in gas turbine engine qualification, hypersonic vehicle thermal protection, and landing gear surface engineering. It can cut down on experimental trial-and-error cycles by allowing ML-guided composition screening and condition-based maintenance through digital twin integration. The main ceramic material systems, tungsten carbide (WC), boron nitride (BN), boron carbide (B₄C), silicon carbide (SiC), alumina (Al₂O₃), and zirconia (ZrO₂), are examined for their protective roles in aerospace-grade alloys. A key contribution is the multiscale computational framework that includes density functional theory, molecular dynamics, finite element analysis, and ML-driven inverse design. Together, these methods improve predictions for thermal breakdown, multi-axial stress responses, and coating lifetime. Future research should focus on ultra-high-temperature ceramics, multifunctional self-healing coatings, and surface engineering methods driven by data. Full article

Overhead distribution systems may experience concurrent wind and rainfall loading during typhoon events, but most existing studies still emphasize individual components, single-hazard descriptions, or network-level consequences. To address this gap, this paper develops a probabilistic assessment framework for distribution pole–line segments exposed to compound typhoon wind–rain hazards. A three-dimensional finite-element model of a representative segment with three poles, two spans, and three-phase conductors is constructed, and uncertainties in structural properties and loading-related coefficients are incorporated explicitly. Correlated turbulent wind histories are synthesized using the Davenport spectrum and harmonic superposition method, whereas rainfall actions are represented through an impact-based raindrop spectrum formulation. Nonlinear dynamic analyses are performed for multiple combinations of basic wind speed and rainfall intensity, and the resulting peak conductor tension and pole-base bending moment are used as engineering demand parameters. Logarithmic probabilistic demand models are then fitted to derive failure-probability surfaces for the conductor, the pole, and the pole–line segment. Segment failure is defined through the maximum normalized demand among the central pole and the six connected conductors, thereby extending the assessment from component-level failure to local segment-level risk. The results show that basic wind speed governs the overall evolution of failure probability, whereas rainfall acts as a secondary but non-negligible amplifying factor that shifts the probability transition zone toward lower wind-speed levels. For the adopted configuration, the segment-level failure probability is governed mainly by pole response. Additional model checks and event-based comparisons support the consistency of the proposed segment-level probability formulation. The proposed methodology can support risk screening, warning-threshold setting, and maintenance decision making for overhead distribution systems subjected to compound meteorological hazards. Full article