Search Results (8,181)

The paper presents the findings of an analysis of a tank subjected to thermal effects caused by variations in air and liquid temperatures. The structural analysis focuses on the influence that thermal actions exert on the distribution of prestressing force. One of the important aspects addressed is the application of transient heat transfer analysis instead of the steady-state approach, allowing for a more accurate yet realistic representation of thermal effects within load combinations used to evaluate prestressing force. The study suggests that thermal actions should reflect the average annual temperatures of air and liquid separately, considering the transient thermal field. This hypothesis contradicts the standard approach. Numerical simulations using the finite element method were conducted in order to model transient heat transfer (CFD model) and the structural response of the tank (with axisymmetric shell model). The results indicated that temperature gradients across the tank wall may be linear or non-linear, varying with time and the amplitude of air temperature. Consequently, a modified formula for the reduced temperature gradient is proposed. The research emphasises the importance of incorporating transient thermal effects and the temperature-influenced distribution of prestressing force, which may have a significant impact on the safety of prestressed tanks. Full article

Gradient stiffness structures are increasingly recognized for their excellent energy absorption capabilities, particularly under challenging loading conditions. Most studies focus on varying the thickness of the structure in order to produce gradient stiffness. This work introduces an innovative approach to design honeycomb architectures with controlled gradient stiffness along the out-of-plane direction achieved by materials’ microstructure variations. The gradient is achieved by combining three types of thermoplastic polyurethane (TPU) materials: porous TPU, plain TPU, and carbon fiber (CF)-reinforced TPU. By varying the material distribution across the honeycomb layers, a smooth transition in stiffness is formed, improving both mechanical resilience and energy dissipation. To fabricate these structures, a dual-head 3D printer was employed with one head printed processed TPU with a chemical blowing agent to produce porous and plain sections, while the other printed a CF-reinforced TPU. By alternating between the two print heads and modifying the processing temperatures, honeycombs with up to three distinct stiffness zones were produced. Compression testing under out-of-plane loading revealed clear plateau and densification regions in the stress–strain curves. Pure CF-reinforced honeycombs absorbed the most energy at stress levels above ~4.5 MPa, while porous TPU honeycombs were more effective under stress levels below ~1 MPa. Importantly, the gradient stiffness honeycombs achieved a balanced energy absorption profile across a broader range of stress levels, offering enhanced performance and adaptability for applications like protective equipment, packaging, and automotive structures. Full article

The variable speed pump-turbine is usually used to adjust the rotational speed to improve the efficiency in turbine mode and change the input power in pump mode because its rotational speed can vary within a certain range. In order to explore the evolutions of pressure pulsation and flow patterns caused by changes in the rotational speeds, the steady operating conditions under different rotational speeds in turbine and pump modes were investigated by using three-dimensional numerical simulations. The results show that as the pump-turbine operates with the highest efficiency at the rated rotational speed, the change in the rotational speed leads to the variation in macro-parameters, deterioration of the flow patterns, and increase in pressure pulsations. In addition, under a certain guide vane opening, with the increase in the rotational speed, the torque, power, and discharge increase in the turbine mode, while these parameters decrease in the pump mode. And when the rotational speed is too high or too low, it causes an obvious increase in pressure pulsations. Full article

The problem of nonlinear elastic transverse oscillations of a beam moving along its axis and subjected to an axial compressive or tensile force is considered. A theoretical study is carried out using the asymptotic method of nonlinear mechanics KBM (Krylov–Bogolyubov–Mitropolsky). Using this methods, differential equations were obtained in a standard form, determining the law of variation in amplitude and frequency as functions of kinematic, force, and physico-mechanical parameters in both resonant and non-resonant regimes. The fourth-order Runge–Kutta method was applied for the oscillatory system numerical analysis. The computation of complex mathematical expressions and graphical representation of the results were implemented in the mathematical software Maple 15. The results obtained can be applied for engineering calculations of structures containing moving beams subjected to compressive or tensile forces. Full article

Shock–accelerated interfaces between fluids of different densities are prone to Richtmyer–Meshkov-type instabilities, whose evolution is strongly influenced by the incident shock Mach number. In this study, we present a systematic numerical investigation of the Mach number effect on the instability growth at a light–heavy fluid layer. The governing dynamics are modeled using the compressible multi-species Euler equations, and the simulations are performed with a high-order modal discontinuous Galerkin method. This approach provides accurate resolution of sharp interfaces, shock waves, and small-scale vortical structures. A series of two-dimensional simulations is carried out for a range of shock Mach numbers impinging on a sinusoidally perturbed light–heavy fluid interface. The results highlight the distinct stages of instability evolution, from shock–interface interaction and baroclinic vorticity deposition to nonlinear roll-up and interface deformation. Quantitative diagnostics—including circulation, enstrophy, vorticity extrema, and mixing width—are employed to characterize the instability dynamics and to isolate the role of Mach number in enhancing or suppressing growth. Particular attention is given to the mechanisms of vorticity generation through baroclinic torque and compressibility effects. Moreover, the analysis of controlling parameters, including Atwood number, layer thickness, and initial perturbation amplitude, broadens the parametric understanding of shock-driven instabilities. The results reveal that increasing shock Mach number markedly enhances vorticity generation and accelerates interface growth, while the resulting nonlinear morphology remains strongly sensitive to variations in Atwood number and perturbation amplitude. Full article

This study investigates interactions among morphology, word order, and syntactic directionality across 55 languages from 11 families. We quantify morphological richness (moving-average mean size of paradigm), word order flexibility (entropy), and syntactic directionality (dependency direction), linking linguistic structure to information-theoretic principles. Analyses show that morphological richness is only weakly related to word order entropy and does not provide a robust predictor after statistical correction. Rich morphology facilitates the predictability of syntactic functions. Languages with richer morphology consistently favor head-final structures, whereas minimally inflected languages lean toward head-initial patterns, indicating that syntactic directionality is more closely associated with morphological complexity than with surface word order. Overall, the findings indicate that languages maintain a balance between redundancy and flexibility in optimizing information transmission, providing quantitative evidence for efficiency-driven trade-offs in human language. Full article

In agile, adaptive, and hybrid project management, the Weighted Shortest Job First (WSJF) technique is increasingly being used to prioritize the most relevant business opportunities for organizations. However, this decision-making process often involves the evaluation of multiple interconnected factors whose interactions can influence outcomes in unforeseen ways. Traditional decision-making models tend to assume independence between variables for the sake of simplicity and tractability. In real-world contexts, however, variables rarely operate in isolation; their interdependence introduces complexities that challenge the validity, robustness, and practical applicability of conventional decision-making tools. The objective of this research is to address the problem of interdependence among WSJF variables. To achieve this, Fuzzy Cognitive Mapping (FCM) was applied to evaluate the impact and influence of interdependencies during the decision-making process. The findings demonstrate that incorporating FCM into WSJF yields a 76% correlation in prioritization order with the best outcomes, compared to linear WSJF, while revealing a 24% variation that highlights areas for further study. This evidence indicates that accounting for interdependence leads to more efficient and reliable decision-making than traditional approaches. Full article

The characterization of lithology within Quaternary aquifers holds significant geological importance for the protection, management, and utilization of groundwater resources, yet it continues to present considerable challenges. Indicator Kriging (IK) is a non-parametric, probability-based method of spatial interpolation. It considers the correlation and variability between data points, and its popularity stems from its alignment with geological experts’ principles. However, it still encounters issues in complex geological conditions. To address the limited capacity of conventional IK in reproducing geological variables within heterogeneous geological settings, this study develops an ordered IK method incorporating field variogram function parameters. This framework dynamically extends IK applications by integrating stratigraphic extension trends, requiring experts to formalize spatial variation trends into geological knowledge data, subsequently transformed into constraint parameters for interpolation. Estimation paths are determined via Euclidean distances between points-to-be-estimated and valid data, executing ordered IK following near-to-far and bottom-to-top principles. Results directly depict QLS formation spatial distributions or undergo expert modification for quantitative analysis, demonstrating superior integration of geological knowledge compared to empirical variogram fitting and partitioned IK estimation. The method reduces deviation from expert-interpreted spatial distributions while maintaining computational efficiency and multi-factor integration, with three case analyses confirming enhanced accuracy in lithology distribution reproduction and improved geostructural congruence in complex geological reconstruction. This approach revitalizes Kriging applications in complex geological research, synergizing domain cognition with computational efficacy to advance precision in geological characterization and support government decision-making. Full article

In order to protect the boundary columns once tension region form on shear walls subjected to seismic loads, a new shear wall system constructed by partial-connected crossing-stiffened corrugated steel plate shear walls (PCCSWs) is proposed and investigated. Numerical modeling of the PCCSWs was conducted and validated by a similar test on single-span two-story corrugated steel plate shear wall test specimen. Some key parameters, such as material properties, height-to-thickness ratio, wave length, and width of the crossing stiffeners, were then investigated through parametric analyses, and the results of PCCSWs were compared to the results of other types of steel shear walls. And a theoretical mechanical model was developed for predicting the ultimate capacity of the PCCSWs taking basis of the parametric results. Several findings can be concluded: (1) The finite element method (FEM) simulates buckling modes and the buckling positions of corrugated steel plates and boundary columns precisely, with the errors of initial stiffness and ultimate shear resistance being less than 10%, which proves the feasibility of the FEM. (2) The optimal values on such key parameters were the height-to-thickness ratio of 510~680 at the center, wave lengths of 360~480 mm, and varying widths of crossing stiffeners which are 64.41~136.89. (3) The relative errors between the theoretical and the numerical results were within 14.17%, and most of the variations were less than 10%, indicating the effectiveness of the developed mechanical model. Full article

Protected areas play a fundamental role in the implementation of international environmental strategies in order to ensure effective management systems that support the conservation of biodiversity and the provision of ecosystem services. However, the actual capacity of national parks to generate a specific “park effect” remains an open question. This study aims to assess whether the transformations observed in Italian national parks between 1960 and 2018 can be attributed to a specific park effect or are instead the result of other territorial dynamics. We analyzed long-term changes in land use and land cover (LUMCs) and variations in ecosystem services (ES), both inside and outside park boundaries, taking into account the SNAI classification. The results show a significant expansion of forest areas (+52%) and sparse vegetation (+56%), alongside a marked decline in arable land (−60%) and permanent crops (−26%). At the same time, the overall value of ES remains stable at around EUR 4 billion per year, with regulating services—accounting for 80% of the total—increasing by 20% between 1960 and 2018 and provisioning services declining by 41%. Italy’s national parks represent strategic socioecological laboratories capable of generating benefits both locally and globally. To fully realize this potential, more integrated management is needed, enabling their transformation from mere conservation areas to drivers of territorial resilience and social cohesion. Full article

Shipboard ballast water management systems (BWMS) commonly employ chlorine or other oxidants to treat ballast. Oxidant-based BWMS inject these biocides to meet a concentration threshold or target value that is lethal to most aquatic organisms. Resulting concentrations of total residual oxidant (TRO) may span two orders of magnitude between initial doses (e.g., ~10 mg L⁻¹) and discharged ballast, which must meet discharge limits (e.g., <0.1 mg L⁻¹). Here, we evaluated three TRO instruments (two colorimetric-based and one based on amperometry) that have been integrated into BWMS for use in shipboard applications. Our study quantified accuracy and precision using test waters along a range of temperatures and salinities, using a pipe loop to mimic in-line shipboard operations, where the instruments continuously sample and analyze circulating water. Linear regression analysis compared the instruments to a standard reference method along a range of concentrations relevant to oxidant-based BWMS. In general, measurements from the TRO sensors showed strong linear relationships to the reference method, but slopes of these relationships were significantly <1 in all but one instance. Precision—measured as the coefficient of variation—ranged from 2 to 4%. These initial tests occurred on units shipped directly from the manufacturer, immediately following calibration and quality checks, and in a controlled laboratory environment. Thus, in this context, our evaluations represent a “best-case” outcome. We recommend that laboratory studies (as described here) be paired with endurance trials and in-service monitoring to include tests in a shipboard environment. These trials should evaluate TRO instruments that are integrated with BWMS and functioning under normal ship operations, measuring both high (treated ballast) and low (neutralized discharge) concentrations of TRO. Shipboard trials in concert with frequent calibration checks will reduce the risks of under- or overestimating TRO concentrations, as both outcomes may harm the environment. Full article

This study investigates the dynamics of optical solitons for the variable-coefficient coupled higher-order nonlinear Schrödinger equation (VCHNLSE) enriched with $\beta$-derivatives. By employing an extended direct algebraic method (EDAM), we successfully derive explicit soliton solutions that illustrate the intricate interplay between nonlinearities and variable coefficients. Our approach facilitates the transformation of the complex NLS into a more manageable form, allowing for the systematic exploration of diverse solitonic structures, including bright, dark, and singular solitons, as well as exponential, polynomial, hyperbolic, rational, and Jacobi elliptic solutions. This diverse family of solutions substantially expands beyond the limited soliton interactions studied in conventional approaches, demonstrating the superior capability of our method in unraveling new wave phenomena. Furthermore, we rigorously demonstrate the robustness of these soliton solutions against various perturbations through comprehensive stability analysis and numerical simulations under parameter variations. The practical significance of this work lies in its potential applications in advanced optical communication systems. The derived soliton solutions and the analysis of their dynamics provide crucial insights for designing robust signal carriers in nonlinear optical media. Specifically, the management of variable coefficients and fractional-order effects can be leveraged to model and engineer sophisticated dispersion-managed optical fibers, tunable photonic devices, and ultrafast laser systems, where controlling pulse propagation and stability is paramount. The presence of $\beta$-fractional derivatives introduces additional complexity to the wave propagation behaviors, leading to novel dynamics that we analyze through numerical simulations and graphical representations. The findings highlight the potential of the proposed methodology to uncover rich patterns in soliton dynamics, offering insights into their robustness and stability under varying conditions. This work not only contributes to the theoretical foundation of nonlinear optics but also provides a framework for practical applications in optical fiber communications and other fields involving nonlinear wave phenomena. Full article

Bellows compensators are critical components in pipeline systems, designed to absorb thermal expansions, vibrations, and pressure reflections. Ensuring their operational reliability requires accurate prediction of the stress–strain state (SSS) and stability under internal pressure. This study presents a comprehensive mathematical model for analyzing corrugated bellows compensators, formulated as a boundary value problem for a system of partial differential equations (PDEs) within the Kirchhoff–Love shell theory framework. Two numerical approaches are developed and compared: a finite difference method (FDM) applied to a reduced axisymmetric formulation to ordinary differential equations (ODEs) and a finite element method (FEM) for the full variational formulation. The FDM scheme utilizes a second-order implicit symmetric approximation, ensuring stability and efficiency for axisymmetric geometries. The FEM model, implemented in Ansys 2020 R2, provides high fidelity for complex geometries and boundary conditions. Convergence analysis confirms second-order spatial accuracy for both methods. Numerical experiments determine critical pressures based on the von Mises yield criterion and linearized buckling analysis, revealing the influence of geometric parameters (wall thickness, number of convolutions) on failure mechanisms. The results demonstrate that local buckling can occur at lower pressures than that of global buckling for thin-walled bellows with multiple convolutions, which is critical for structural reliability assessment. The proposed combined approach (FDM for rapid preliminary design and FEM for final verification) offers a robust and efficient methodology for bellows design, enhancing reliability and reducing development time. The work highlights the importance of integrating rigorous PDE-based modeling with modern numerical techniques for solving complex engineering problems with a focus on structural integrity and long-term performance. Full article

With the growing significance of hydrogen in the global energy transition, research on its pricing mechanisms has become increasingly crucial. Focusing on hydrogen markets predominantly supplied by electrolytic production, this study proposes a nodal marginal hydrogen price decomposition algorithm that explicitly incorporates the time-delay dynamics inherent in hydrogen transmission. A four-dimensional price formation framework is established, comprising the energy component, network loss component, congestion component, and time-delay component. To address the nonconvex optimization challenges arising in the market-clearing model, an improved second-order cone programming method is introduced. This method effectively reduces computational complexity through the reconstruction of time-coupled constraints and reformulation of the Weymouth equation. On this basis, the analytical expression of the nodal marginal hydrogen price is rigorously derived, elucidating how transmission dynamics influence each price component. Empirical studies using a modified Belgian 20-node system demonstrate that the proposed pricing mechanism dynamically adapts to load variations, with hydrogen prices exhibiting a strong correlation with electricity cost fluctuations. The results validate the efficacy and superiority of the proposed approach in hydrogen energy market applications. This study provides a theoretical foundation for designing efficient and transparent pricing mechanisms in emerging hydrogen markets. Full article

In order to ensure the reliable operation of a gravity energy storage system and reduce a converter’s cost and power rating, this paper proposes a gravity energy storage system (GESS) based on a doubly fed induction generator (DFIG). To address the issues of low inertia and limited grid-support capability, a speed-adaptive droop control strategy is introduced. The droop curve can be adjusted automatically according to the speed variation. Thereby, the GESS can effectively provide grid support through rotor-speed control. A simulation model of the DFIG-based GESS is developed in MATLAB/Simulink 2024b, and the grid-support capability of the proposed control strategy is verified under various operating conditions. Full article