Search Results (107)

Precise fault localization for high-speed railway continuous transmission lines is indispensable for sustaining power supply reliability and mitigating power outages. This study presents a novel fault localization approach that uses low-voltage information obtained from box-type substations distributed along continuous transmission lines. The proposed scheme relies on the distribution features of the positive-to-negative sequence voltage ratio ($r_{PNV}$) measured at the low-voltage terminals of box-type substations. Results reveal that the magnitude of $r_{PNV}$ gradually declines from the main substation to the fault location in the fault upstream area, while it stays nearly unchanged in the downstream section. Based on this feature, the faulted section is initially determined by means of the nearest neighbor clustering method. Subsequently, the precise fault location is calculated by solving equations that combine the sequence voltage ratio at the fault point with the measurements obtained from the main substation and box-type substations downstream of the fault. The proposed method requires only asynchronous low-voltage measurements, eliminates the need for fault impedance modeling, and is applicable to various asymmetric faults. Simulation tests under different fault types, fault resistances (up to 2000 Ω), noise conditions, and neutral grounding modes demonstrate that the method achieves high accuracy and robustness. Full article

Continuous monitoring of forest biomass is indispensable for establishing transparent carbon budgets and ensuring sustainable forest management toward achieving carbon neutrality. While satellite data has traditionally been used for wide-area biomass estimation, signal saturation in high-biomass regions has posed a significant challenge to accuracy. To address this saturation issue and enhance the precision of carbon budget estimations, this study develops a new methodology for estimating forest above-ground biomass (AGB). First, a training dataset was constructed by integrating airborne LiDAR data from across Japan with various satellite datasets, such as PALSAR-2 and Sentinel-2. Machine learning (XGBoost) was then employed to generate a nationwide canopy height map, achieving a high coefficient of determination ($R^2=0.594$). Subsequently, allometric equations with parameters optimized for specific forest types (evergreen coniferous, evergreen broadleaf, deciduous coniferous, and deciduous broadleaf) were derived from the relationship between estimated canopy height and AGB to create a nationwide AGB map. Validation results indicated that the resulting AGB map demonstrated higher estimation accuracy ($R^2=0.265$) compared to existing global products (ESA CCI Biomass), with significant improvements in mitigating underestimation (saturation) in high-biomass areas. By combining canopy height estimation with forest-type-specific allometry, this approach enables high-precision mapping that reflects the unique characteristics of Japanese forests and is expected to contribute to more reliable carbon budget assessments. Full article

This paper investigates the thermal buckling behavior of a four-edge simply supported bimodular functionally graded rectangular thin plate subjected to thermal loads. Unlike existing studies, this work introduces the bimodular effect into the thermal buckling analysis of functionally graded thin plates for the first time, accounting for the influence of tension–compression modulus on the critical temperature difference. The problem is challenging due to the complexity of materials and the nonlinearity of structural thermal buckling. For the theoretical analysis, we propose a simplified mechanical model which contains the four important assumptions: there exists a neutral plane in bending; the influence of shear stresses may be neglected; the membrane effect and bending effect are considered separately; and there are two different buckling regimes: a compression-dominated pre-buckling state and a bending-dominated post-buckling state. Three types of thermal loading cases are considered, including uniform temperature rise, linear temperature gradient through the thickness, and nonlinear temperature distribution satisfying Fourier’s law of heat conduction. Within the framework of the simplified mechanical model, the pre-buckling membrane forces, equilibrium equations, and stability equations are derived, thus obtaining a closed-form analytical expression for the critical buckling temperature difference under three different temperature rise modes. The reliability of the present analytical model is validated through comparison with finite element results. Furthermore, a detailed parametric study is conducted to reveal the influences of aspect ratio, width-to-thickness ratio of plate, bimodular indices, and gradient parameters of materials on the critical temperature difference. The results provide a theoretical basis for the thermal stability design of bimodular functionally graded plates operating in high-temperature environments. Full article

Soil salinization poses a severe threat to global wheat production, yet the physiological mechanisms underlying photosynthetic responses to neutral, alkaline, and combined salt stress remain poorly understood. This study systematically evaluated the photosynthetic physiology and salt tolerance of six spring wheat genotypes under three types of salt stress at varying concentrations. By integrating phenotypic data, gas exchange parameters, chlorophyll fluorescence indices, and biomass measurements, and applying structural equation modeling and multivariate analysis, key traits regulating biomass were identified. The results revealed significant interactions among salt stress type, genotype, and concentration on photosynthetic parameters. Structural equation modeling analysis revealed that under neutral salt stress, both gas exchange parameters and chlorophyll content had significant direct effects on seedling biomass, with standardized path coefficients of 0.421 and 0.400, respectively. Under alkaline and combined salt stresses, only chlorophyll content showed a significant direct effect on biomass, with standardized path coefficients of 0.873 and 0.790, respectively. Multiple regression analysis further identified key photosynthetic factors influencing growth under different stress types. Under neutral salt stress, phi (Ro) and E significantly affected biomass, whereas under alkaline and combined salt stresses, biomass was primarily co-regulated by phi (Ro) and phi (Eo). Based on a comprehensive evaluation of salt tolerance index, damage index, and biomass response, genotypes W06 and W02 exhibited the strongest overall salt tolerance. This study systematically elucidates the differential response mechanisms of photosynthesis in spring wheat under distinct salt stress types, providing an important theoretical basis and elite germplasm resources for breeding salt-tolerant wheat varieties. Full article

Current carbon accounting in the power sector often relies on annual average emission factors, which suffer from ill-defined system boundaries, update delays, and insufficient temporal granularity. To address these limitations, this study introduces a high-spatiotemporal-resolution dynamic measurement model for grid carbon emission factors, grounded in carbon emission flow theory. Applied to a regional grid in northern China, the model employs nodal carbon–emission–flow balance to construct system-level matrix equations. This approach accurately traces the spatiotemporal transmission paths of carbon emissions, enabling refined, node-level, and hourly carbon accounting. A case study demonstrated that our model significantly outperformed existing static methods based on interprovincial power exchange in both resolution and accuracy. The results revealed pronounced spatiotemporal heterogeneity in grid emission factors: diurnal fluctuations reach up to 45% in maximum deviation, closely coupled with renewable energy output, while spatial disparities between high- and low-emission regions reach a factor of 4.7, highlighting the critical roles of generation mix and grid topology. This study confirms that high-resolution emission factors effectively overcome the biases of traditional methods, providing a critical data foundation for green electricity trading, demand-side response, and regionally differentiated emission-reduction policies. Our approach offers key methodological and policy insights for building new-type power systems and advancing carbon neutrality goals. Full article

This paper investigates a class of implicit neutral fractional integro-differential equations of Volterra–Fredholm type. The equations incorporate a tempered fractional derivative in the Caputo sense, along with both retarded (delay) and advanced arguments. The problem is formulated on a time domain segmented into past, present, and future intervals and includes nonlinear mixed integral operators. Using Banach’s contraction mapping principle and Schauder’s fixed point theorem, we establish sufficient conditions for the existence and uniqueness of solutions within the space of continuous functions. The study is then extended to general Banach spaces by employing Darbo’s fixed point theorem combined with the Kuratowski measure of noncompactness. Ulam–Hyers–Rassias stability is also analyzed under appropriate conditions. To demonstrate the practical applicability of the theoretical framework, explicit examples with specific nonlinear functions and integral kernels are provided. Furthermore, detailed numerical simulations are conducted using MATLAB-based specialized algorithms, illustrating solution convergence and behavior in both finite-dimensional and Banach space contexts. Full article

The current manuscript is concerned with the uniqueness and existence of a solution for a new class of $\Phi$-Hilfer fractional neutral functional integro-differential equations ($\Phi$-HFNFIDEs) with terminal conditions. Firstly, employing Babenko’s approach, we convert the aforesaid equation under consideration into an analogous integral equation. More precisely, using the multivariate Mittag-Leffler function, Banach contraction principle, and Krasnoselskii’s fixed-point theorem, we derive some conditions that guarantee the uniqueness and the existence of the solutions. For an illustration of our results in this manuscript, two examples are provided as well. Full article

The paper investigates the oscillation, zero-convergence, and solutions of second-order neutral delay difference equations containing three nonlinear delayed terms with different growth rates. By using positivity and monotonicity conditions on an auxiliary function along with divergence-type conditions on the coefficient sequences of the neutral and delayed terms, the paper establishes new criteria that guarantee oscillation or convergence of all solutions. These novel findings extend and enhance several of the existing oscillation criteria established by the literature. Suggestions for further investigation are included with illustrative examples. Full article

The study examines the impact of social innovation on sustainability in rural organizations in southern Sonora, within a context where these entities face economic, social, and environmental challenges that constrain regional development. The research addresses the limited understanding of how social innovation contributes to the sustainability of rural organizations in developing regions, which is an area still insufficiently explored in the existing literature. A quantitative correlational design was employed, using a 34-item questionnaire administered to 200 members of rural organizations in southern Sonora, Mexico. Sociodemographic data were processed using IBM SPSS version 23, and a structural equation model was constructed with SmartPLS V 4.0 to analyze the relationships among the variables. The results indicate a neutral trend in the responses, indicating a limited implementation of social innovation practices, likely associated with the small size, low level of development, and restricted technological capacity of these organizations, most of which are micro or small enterprises with limited infrastructure. Regarding the impact of social innovation dimensions on sustainability, the strongest effect was found in the social impact dimension, followed by type of innovation, economic viability, replicability, and intersectoral collaboration, with the latter showing the weakest effect. It is concluded that five hypotheses were accepted and one—related to intersectoral collaboration—was rejected, providing evidence on how social innovation contributes to the sustainable strengthening of rural organizations. These findings advance the theoretical understanding of social innovation in rural contexts and offer practical implications for the design of policies and management strategies aimed at enhancing sustainability within local development processes. Full article

Accurate estimation of forest stand carbon storage is critical for assessing ecosystem functions and informing sustainable forest management. Most existing models depend heavily on stand age, a strategy that is often unreliable in natural forests, and they typically ignore species interactions, limiting their applicability across forest types. To overcome these issues, we developed a dynamic carbon storage model based on the Richards equation that replaces stand age with a growth interval period (defined as the time difference between two successive growth stages, T_n = T₂ − T₁) and explicitly incorporates site quality and species composition. This approach enables consistent estimation for both natural and plantation forests. Using field data from six dominant tree species in Wuyishan City, Fujian Province, we calibrated and validated the model through five-fold cross-validation. It achieved high accuracy, with an efficiency coefficient (EA) above 99% and a relative mean absolute error (RMA) under 7%, effectively reflecting how site conditions and mixed-species structures influence carbon dynamics. Total forest carbon storage in the study area was estimated at 7.32 million tons. Simulations show a gradual decline in carbon accumulation over time, consistent with natural growth saturation in aging stands. Scenario analyses further identified practical zones for sustainable harvesting in major plantation types, underscoring the model’s management relevance. The model does not yet include climate variability, disturbances, or below-ground carbon pools. Adding these components in future work would strengthen its utility for regional carbon assessment and support more robust carbon-neutral forestry planning. Full article

This work analyses the existence, uniqueness, and Ulam-type stability of neutral fractional functional differential equations with recursively defined state-dependent delays. Employing the Caputo fractional derivative of order $\alpha \in (0,1)$ with respect to a strictly increasing function $\phi$, the analysis extends classical results to nonuniform memory. The neutral term and delay chain are defined recursively by the solution, with arbitrary continuous initial data. Existence and uniqueness of solutions are established using Krasnosel’skii’s fixed point theorem. Sufficient conditions for Ulam–Hyers stability are obtained via the Volterra-type integral form and a $\phi$-fractional Grönwall inequality. Examples illustrate both standard and nonlinear time scales, including a Hopfield neural network with iterated delays, which has not been previously studied even for integer-order equations. Fractional neural networks with iterated state-dependent delays provide a new and effective model for the description of AI processes—particularly machine learning and pattern recognition—as well as for modelling the functioning of the human brain. Full article

In this work, we adopted an approach similar to that of Chatzarakis’, by transforming the oscillation analysis of third-order differential equations into an equivalent first-order problem. A key generalization in our study is the extension coefficient $b\left(t\right)$ from the range $0\le b\left(t\right)\le 1$ to $b\left(t\right)\ge 1$. Moreover, we established several oscillation criteria applicable to the canonical and non-canonical cases. Our conclusions complement and extend the oscillation theory for third-order delay differential equations. Several examples are provided to illustrate our results. Full article

This paper investigates the existence of square-mean S-asymptotically $(\omega ,c)$-periodic solutions for a class of neutral impulsive stochastic differential equations driven by fractional Brownian motion, addressing the challenge of modeling long-range dependencies, delayed feedback, and abrupt changes in systems like biological networks or mechanical oscillators. By employing semigroup theory to derive mild solution representations and the Banach contraction principle, we establish sufficient conditions–such as Lipschitz continuity of nonlinear terms and growth bounds on the resolvent operator—that guarantee the uniqueness and existence of such solutions in the space ${\mathcal{S}AP}_{\omega ,c}([0,\infty ),L^2(\Omega ,\mathbb{H}))$. The important results demonstrate that under these assumptions, the mild solution exhibits square-mean S-asymptotic $(\omega ,c)$-periodicity, enabling robust asymptotic analysis beyond classical periodicity. We illustrate these findings with examples, such as a neutral stochastic heat equation with impulses, revealing stability thresholds and decay rates and highlighting the framework’s utility in predicting long-term dynamics. These outcomes advance stochastic analysis by unifying neutral, impulsive, and fractional noise effects, with potential applications in control theory and engineering. Full article

This research work presents a techno-economic assessment of biodiesel production with non-standard waste cooking oil (WCO) (brown grease of small restaurants, yellow grease of households) and semi-open Chlorella sp. microalgal cultivation, which covers the problematic areas of scale and cost-efficiency in sustainable biodiesel production. Cost-effective biodiesel feedstock research has been motivated by the urgency of finding sustainable sources of energy. With base-catalyzed transesterification optimized by ANOVA and response surface methodology (RSM), the present study recorded biodiesel yields of up to 99.08% in household WCO (at optimum conditions; 55 °C, 3.3 mg/g NaOH, ethanol) and 96.61% in restaurant WCO (at optimum conditions; 54 °C, 1.5 mg/g NaOH, methanol) compared to 28.6% in Chlorella sp. (semi-open photobioreactors). Concerning the two types of WCO feedstocks, the obtained equations are able to compute the biodiesel viscosity and yield, in good correlation with the experimental values, in relation to the temperature and ratio of catalyst to oil/alcohol solution. The assessed household WCO has better yield and quality as it contains fewer impurities, whereas the restaurant WCO needed to be further purified, driving up the prices. Although Chlorella biodiesel is carbon neutral, its production and extraction costs are higher, making it less economically feasible for biodiesel production. Economic analysis showed that the capital costs of household WCO, restaurant WCO, and Chlorella sp. are USD 190,000, USD 220,000, and USD 720,000, respectively, based on 1,000,000 L/year as biodiesel production rate. Low capital costs as well as byproduct glycerol income of the two investigated types of WCO play a role in their low payback periods (0.23–0.91 years) and high ROI (110–444.4%). The analysis highlights the economic and environmental benefits of WCO, especially household WCO, as a scalable biodiesel feedstock, which provides new insights into process optimization and sustainable biodiesel strategies. To enhance its sustainability and cost-effectiveness and contribute to the transition to renewable biofuels globally, future studies need to emphasize energy reduction in microalgae production and purification of restaurant WCO. Full article

This study introduces a theoretical and computational framework for modeling acoustic wave propagation in defective concrete, with applications to non-destructive testing and structural health monitoring. The formulation is based on a coupled system of evolutionary hyperbolic equations, where internal defects are explicitly represented as localized energetic sources or sinks. A key contribution is the definition of a coercivity coefficient, which quantifies the energetic effect of defects and enables their classification as stabilizing, neutral, or dissipative. The model establishes a rigorous relationship between defect morphology, spatial distribution, and the global energetic stability of the material. Numerical simulations performed with an explicit finite-difference time-domain scheme confirm the theoretical predictions: the normalized total energy remains above $95\%$ for stabilizing defects (${\mu }_i>0$), decreases by about $10\%$ for quasi-neutral cases (${\mu }_i\approx 0$), and drops below $50\%$ within $200\mathsf{\mu }\mathrm{s}$ for dissipative defects (${\mu }_i<0$). The proposed approach reproduces the attenuation and phase behavior of classical Biot-type and Kelvin–Voigt models with deviations below $5\%$ while providing a richer energetic interpretation of local defect dynamics. Although primarily theoretical, this study establishes a physically consistent and quantitatively validated framework that supports the development of predictive ultrasonic indicators for the energetic classification of defects in concrete structures. Full article