Search Results (169)

Integrated urban–rural development is an inevitable requirement of regional development. Developing green industries based on rural ecological resources are important approaches to promoting urban–rural integration. The National Key Ecological Function Zones (NKEFZ) policy focuses on safeguarding national ecological security. However, whether the resulting ecological improvements can, through the realization of ecological value, provide momentum for urban–rural integration remains unclear in existing research. This study uses a sample of 284 prefecture-level cities in China from 2006 to 2023, treating the establishment of NKEFZ as a quasi-natural experiment. First, the study constructs a “Driving-constraining” bidirectional theoretical framework, and then uses the entropy weight method to measure the level of urban–rural integration, which is selected by 18 sub-indicators from the populational, spatial, and economic dimensions. Finally, a multi-period difference-in-differences (DID) model is constructed to test the impact of NKEFZ on urban–rural integration, and the transmission mechanisms and heterogeneity are explored. The results indicate the following: (1) Following the implementation of the NKEFZ policy, it shows an overall inhibitory trend on urban–rural integration, consequently slowing the progress of urban–rural integration. The inhibitory effects are particularly pronounced in spatial and economic integration dimensions, and these results are robust. (2) Constrained industrial upgrading and increased fiscal pressure on local governments are the main mechanisms behind the slowed urban–rural integration. (3) Due to differences in policy coverage and the heterogeneous characteristics of city locations, the negative effects of the policy are more pronounced in cities with a high proportion of key ecological function counties, as well as in prefecture-level cities in central and western regions. Based on these findings, it is suggested to promote high-quality urban–rural integration in eco-priority areas through pathways such as developing ecological industries, improving the ecological compensation system, and clarifying central–local collaborative governance. Full article

We investigate the thermodynamic properties of a generalized de Sitter-like configuration. This investigation proceeds in two essential steps: (1) first, we construct a spacetime whose energy–momentum tensor asymptotically reproduces quintessence while maintaining isotropic pressures, despite being fueled by a nonconstant energy–momentum tensor; (2) second, we define a finite domain of validity for the solution, within which an additional Cauchy horizon emerges. Afterwards, we analyze the thermodynamic behavior of this configuration and compare it with the standard de Sitter case. Our results indicate that the extra parameter introduced in the metric does not lead to a positive specific heat; this value remains negative, suggesting that the role of such a parameter is thermodynamically nonessential. Full article

Amidst the accelerating trend of population aging, addressing regional disparities in basic elderly care services (BECS for short) and identifying the key obstacles to their development have become crucial prerequisites for development. Taking urgent transformation measures is indispensable for enhancing the quality of fundamental senior care provisions and advancing the attainment of the United Nations Sustainable Development Goals (SDGs for short) by 2030. However, the extant literature does not have a sufficient understanding of the evolution of differences, spatial correlations, and sources of obstacles. Therefore, this paper takes the period from 2021 to 2023 as the investigation period and comprehensively applies the entropy weight method, Dagum Gini coefficient, kernel density estimation, Moran Index, and obstacle degree model to conduct a systematic analysis of BECS in China. Quantitative results obtained from the research demonstrate that the level of BECS in China follows the pattern of eastern > western > central > northeastern regions. The overall difference slightly increases, and the differences within and between regions vary. The kernel density estimation results are highly consistent with the current landscape of the level of BECS in China, and the spatial correlation and aggregation characteristics are obvious. It was also found that the main obstacles in the quasi-measurement layer (including the indicator layer) were concentrated in the dimension of welfare subsidies. Based on this, a policy combination proposal is put forward in terms of strengthening the construction of a multi-subject supply network, promoting the cross-regional coordinated development of human, financial, and material factors, and enhancing the government’s governance capacity, with the aim of increasing Chinese contributions to improving the level of BECS and achieving the United Nations 2030 Sustainability Goals on schedule. Full article

Pb (II) contamination in wastewater represents a grave threat to the environment and ecosystems. Consequently, there is an urgent need to prepare low-cost and highly efficient Pb (II) adsorbents. To address this need, abundant and low-cost natural silica-based desert sand (DS) was innovatively utilized as a carrier to develop efficient and selective Pb (II) adsorbents. Modified desert sand (MDS) was first prepared via 1 M HCl pretreatment for 2 h and subsequent KH550 silane modification. Pb (II)-imprinted composites (Pb (II)-IIP@MDS) were then fabricated via ion-imprinted polymerization, using Pb (II) as the template ion and N-hydroxymethacrylamide (NHMA)/hydroxyethyl methacrylate (HEMA) as dual functional monomers with a molar ratio of 1:1. The synthesized Pb (II)-IIP@MDS was comprehensively characterized by X-ray photoelectron spectrometer (XPS), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). The adsorption capacity, selectivity, and reusability of this material for lead ions were evaluated through three experiments conducted within the optimized pH range of 6–7, with error bars indicated. In adsorption isotherm experiments, the initial Pb (II) concentration ranged from 50 to 500 mg·L⁻¹, conforming to the Langmuir model (R² = 0.992), with a theoretical maximum adsorption capacity reaching 107.44 mg·g⁻¹; this indicates that the adsorbate forms a monolayer adsorption on the homogeneous imprinted sites. Kinetics data indicate that the process best fits a quasi-first-order kinetic model (R² ≥ 0.988), while the favorable quasi-second-order kinetic fit (R² ≥ 0.982) reflects the synergistic effect of physical diffusion and ion-imprinting chemistry, reaching equilibrium within 120 min. Thermodynamic parameters (ΔH⁰ = 12.51 kJ·mol⁻¹, ΔS⁰ = 101.19 J·mol⁻¹·K⁻¹, ΔG⁰ < 0) confirmed endothermic, entropy-increasing, spontaneous adsorption. In multicomponent systems, Pb (II)-IIP@MDS showed distinct Pb (II) selectivity. It retained 80.3% adsorption efficiency after eight cycles. This work provides a promising strategy for fabricating low-cost, high-performance Pb (II) adsorbents, and Pb (II)-IIP@MDS stands as a practical candidate for the remediation of Pb (II)-contaminated wastewater. Full article

Statistical modeling is fundamentally based on probability distributions, which can be discrete or continuous and univariate or multivariate. This review focuses on the methods used to construct these distributions, covering both traditional and newly developed approaches. We first examine classic distributions such as the normal, exponential, gamma, and beta for univariate data, and the multivariate normal, elliptical, and Dirichlet for multidimensional data. We then address how, in recent decades, the demand for more flexible modeling tools has led to the creation of complex meta-distributions built using copula theory. Full article

This paper examines the nonlinear behavior of the generalized stochastic intermediate dispersive velocity (SIdV) equation, which has been widely analyzed in a non-noise deterministic framework but has yet to be studied in any depth in the presence of varying forcing strength and noise types, in particular how it switches between periodic, quasi-periodic, and chaotic regimes. A stochastic wave transformation reduces the equation to simpler ordinary differential equations to make soliton overlap analysis feasible to analyze soliton robustness under deterministic and stochastic conditions. Lyapunov exponents, power spectra, recurrence quantification, correlation dimension, entropy measures, return maps, and basin stability are then used to measure the effect of white, Brownian, and colored noise on attractor formation, system stability, and spectral correlations. Order–chaos transitions as well as noise-induced complexity are more effectively described by bifurcation diagrams and by Lyapunov spectra. The results of this experiment improve the theoretical knowledge of stochastic nonlinear waves and offer information that will be useful in the fields of control engineering, energy harvesting, optical communications, and signal processing applications. Full article

Background: Asymmetrical load carrying can impair balance and increase fall risk, especially in older adults. This study compared postural control in 33 older (mean age 72.2 ± 11.0 years) and 27 younger (mean age 33.5 ± 15.8 years) adults. Methods: Participants performed three 20 s quiet standing trials on a force plate: no load, 3 kg left shoulder load, and 3 kg right shoulder load. Center-of-pressure (COP) variability, range, mean velocity, and sample entropy were computed. This was a quasi-experimental study with a mixed-design ANOVA (Group as between-subjects factor; Load and Plane as within-subjects factors). Results: Younger adults showed better overall stability than older adults across conditions. Older adults had larger COP range than younger adults with no load and with the right-sided load. Notably, no significant difference in COP range was found between groups with the left-sided load. Key statistical findings included the significant Load × Group interaction (F(2, 116) = 3.9, p = 0.024, η_p² = 0.06) for COP range. Conclusions: A small asymmetrical load on the left side may be associated with postural control in older adults, possibly through familiar sensory cues. Conversely, a right-sided load appears to negatively impact their balance. These findings highlight the differential effects of load side on postural control in older individuals. Full article

India’s aviation sector, crucial for connectivity, economic growth, and national integration, faces sustainability measurement challenges focused solely on carbon emissions. This study proposes the Aviation Sustainability Performance Index (ASPI-India), spanning four pillars: Environmental Stewardship, Social Responsibility, Governance Maturity, and Economic Resilience. Measurable indicators are derived from regulatory filings, commercial flight databases, geospatial tracking, and targeted surveys. Data sources include DGCA safety audits, AAI operational statistics, ADS-B flight path data, and passenger satisfaction surveys from 2010 to 2024. Fixed-effects panel models link ASPI-India to operational and financial outcomes like load factor stability, CASK, and credit rating resilience. Quasi-experimental designs exploit policy shocks through difference-in-differences estimation. Factor analysis validates the four-pillar structure, and robustness checks compare entropy, PCA, and equal weighting. Results show that a one-standard-deviation increase in ASPI-India improves load factor stability, ancillary revenue share, and credit terms, especially for carriers with diversified route networks. The framework provides actionable insights for airlines, regulators, and investors to embed sustainability in aviation management. Full article

Hypersonic glide targets (HGTs) pose significant challenges for radar tracking due to complex maneuver strategies and time-varying statistics of measurement noise. Conventional single-model tracking methods are generally insufficient to fully capture maneuver modes, while existing multiple-model methods face trade-offs between model set completeness and computational efficiency. In addition, existing tracking methods struggle to cope with the non-Gaussian noise during hypersonic flight. To overcome these limitations, a Hierarchical Adaptive Moment Matching (HAMM) multiple-model method is proposed in this paper. Firstly, a comprehensive model set is constructed to cover characteristic maneuver modes. Subsequently, a hierarchical multiple-model framework is developed where: (1) a coarse model set is dynamically adapted by multi-frame posterior probability evolution and Rényi divergence criteria; (2) a fine model set is generated based on the moment matching method. Furthermore, the minimum error entropy cubature Kalman filter (MEECKF) is proposed to suppress the non-Gaussian measurement noise with high stability. Monte Carlo simulations demonstrate that the proposed method achieves improved positioning accuracy and faster convergence. Full article

Prenatal maternal stress (PS) is a risk factor for adverse offspring neurodevelopment. Heart rate variability (HRV) complexity provides a non-invasive marker of maternal autonomic regulation and may be influenced by mind–body interventions such as Yoga. In this quasi-randomized controlled trial, 28 chronically stressed pregnant women were followed from the second trimester until birth: 14 participated in weekly Hatha Yoga with electrocardiogram (ECG) recordings, and 14 received standard obstetric care with monthly ECGs. Group allocation was based on availability, with participants unaware of their assignment at enrollment. HRV complexity was assessed first with Sample Entropy and Entropy Rate and then expanded to 94 HRV metrics spanning temporal, frequency, nonlinear, and information-theoretical domains. All metrics were covariate-adjusted (maternal age, BMI, gestational age), standardized, and analyzed using timepoint-specific principal component analysis (PCA). From this, a unified HRV index was derived. Analyses revealed that HRV metric relationships changed dynamically across pregnancy, with PCA loadings shifting from frequency toward complexity measures in late gestation. The mixed effects model identified a significant time x group interaction effect (p = 0.041). These findings suggest a restructuring of HRV signal-analytical domains with advancing pregnancy attributable to Yoga and highlight the utility of advanced HRV analysis frameworks for future, larger trials. Full article

A Y-doped AlCoCrFeNi_2.1 eutectic high-entropy alloy was fabricated via powder bed fusion-laser melting/metal (PBF-LB/M), and the effects of the rare-earth element Y on its microstructure and mechanical properties were investigated. The results indicate that Y addition preserves the fine eutectic microstructure inherent to the PBF-LB/M process, while inducing lattice distortion within the face-centered cubic (FCC) matrix and promoting grain refinement. During solidification, Y facilitates heterogeneous nucleation and, due to its strong affinity with Al, increases both the volume fraction of the body-centered cubic (BCC) phase and the proportion of high-angle grain boundaries. X-ray diffraction (XRD) analysis further confirms that Y suppresses the formation of the ordered B2 phase. Tensile testing reveals that Y doping improves the tensile strength from 1383 MPa to 1475 MPa and enhances the elongation from 13.0% to 16.3%. Fractography shows a transition from quasi-cleavage to ductile fracture mode, indicating that Y significantly enhances the strength–ductility synergy of the alloy. Full article

The stability and mechanical properties of (TiZrHf)_1−x(AB)_x (AB = NbTa, NbMo, MoTa) refractory high-entropy alloys have been investigated by combining the first-principles with special quasi-random structure (SQS) method. It is found that with the increase in solute concentration x, the ΔH_mix of (TiZrHf)_1−x(AB)_x (AB = NbMo, MoTa) linearly decreases, whereas both ΔH_mix and ΔS_mix of (TiZrHf)_1−x(NbTa)_x increase initially and subsequently decrease, with the crossover occurring at x = 0.56. The ΔH_mix of (TiZrHf)_1−x(NbTa)_x and (TiZrHf)_1−x(AB)_x (AB = NbMo, MoTa) alloys are larger and lower than that of TiZrHf, respectively, while the ΔS_mix of all (TiZrHf)_1−x(AB)_x is larger than that of TiZrHf. The formation possibility parameter Ω of all (TiZrHf)_1−x(AB)_x (AB = NbMo, MoTa) first decreases sharply, followed by a gradual decrease. And the local lattice distortion (LLD) parameter δ remains relatively stable around x = 0.56 for all cases, after which it decreases sharply until x = 0.89. The δ value of (TiZrHf)_1−x(AB)_x is higher than that of TiZrHf for x < 0.56 but becomes lower beyond this composition. The valence electron concentration (VEC), a possible indicator for a single-phase solution, of (TiZrHf)_1−x(AB)_x increases nearly linearly, while the formation energy ΔH_f of (TiZrHf)_1−x(AB)_x shows the opposite tendency, except for (TiZrHf)_0.67(NbTa)_0.33. Furthermore, the VEC of all (TiZrHf)_1−x(AB)_x alloys increases, whereas their ΔH_f decreases compared to that of TiZrHf. The ideal strength σ_p of (TiZrHf)_1−x(AB)_x increases linearly, reaching approximately 2.12 GPa. The bulk modulus (B), elastic modulus (E), and shear modulus (G) also exhibit linear increases, and their values in all (TiZrHf)_1−x(AB)_x alloys are higher than those of TiZrHf, with some exceptions. The Cauchy pressure (C₁₂–C₄₄) and Pugh’s ratio G/B of all (TiZrHf)_1−x(AB)_x alloys increase, whereas the Poisson’s ratio ν exhibits the opposite trend. Moreover, the C₁₂–C₄₄ and G/B ratio of TiZrHf are lower and higher, respectively, than those of (TiZrHf)_1−x(AB)_x, and the ν of TiZrHf is lower than that of (TiZrHf)_1−x(AB)_x. This study provides valuable insights for the design of high-performance TiZrHf-based refractory high-entropy alloys. Full article

Deterministic chaos in optically injected semiconductor lasers (OILs) has attracted significant attention due to its relevance in secure communications, entropy generation, and photonic applications. However, existing studies often rely on low-resolution parameter sweeps or include noise contributions that obscure the intrinsic nonlinear dynamics. To address this gap, we investigate a noise-free OIL model and construct high-resolution chaos maps across the injection strength and frequency detuning parameter space. Chaos is characterized using two complementary approaches for computing the largest Lyapunov exponent: the Rosenstein time-series method and the exact variational method. This dual approach provides reliable and reproducible detection of deterministic chaotic regimes and reveals a rich attractor landscape with alternating bands of periodicity, quasi-periodicity, and chaos. The novelty of this work lies in combining high-resolution mapping with rigorous chaos indicators, enabling fine-grained identification of dynamical transitions. The results not only deepen the fundamental understanding of nonlinear laser dynamics but also provide actionable guidelines for exploiting or avoiding chaos in photonic devices, with potential applications in random chaos-based communications, number generation, and optical security systems. Full article

Precise electricity consumption forecasting and anomaly detection constitute fundamental requirements for maintaining grid reliability in smart power systems. While consumption patterns demonstrate quasi-periodic behavior with region-specific fluctuations influenced by environmental factors, existing approaches may fail to systematically model these dynamic variations or quantify environmental impacts. This limitation results in a compromised prediction accuracy and ambiguous anomaly identification. To overcome these challenges, we propose a novel Multi-Task Graph Attention Network (MGAT) framework leveraging an adaptive entropy analysis. Our methodology comprises four key innovations: (1) the temporal decomposition of consumption data with entropy-based adaptive clustering into predictable low-entropy components (processed via multi-scale attention networks) and volatile high-entropy components; (2) the graph-based representation of high-entropy fluctuations through numerical correlation encoding, complemented by temporal environmental graphs quantifying external influences; (3) the hierarchical fusion of environmental and fluctuation graphs via a specialized Graph Attention Autoencoder that jointly models dynamic patterns and environmental dependencies; (4) the integrated synthesis of all components for simultaneous consumption prediction and anomaly detection. Experiments verify the MGAT’s performance in both forecasting precision and anomaly identification compared to conventional methods. Full article

In this work, we explore a class of spherically symmetric black hole (BH) solutions within the framework of modified gravity, focusing on a non-ghost-free $f(R,G)$ theory coupled to a scalar field. We present a novel black hole geometry that arises as a deformation of the Schwarzschild solution and analyze its physical and thermodynamic properties. Our results show that the model satisfies stability conditions, with the Ricci scalar R, as well as its first and second derivatives, remaining positive throughout the spacetime. The solution admits multiple horizons and exhibits strong curvature singularities compared to those in general relativity. Furthermore, it supports a non-trivial scalar field potential. A comprehensive thermodynamic analysis is performed, including evaluations of the entropy, temperature, heat capacity, and quasi-local energy. We find that the black hole exhibits thermodynamic stability within certain ranges of model parameters. In addition, we investigate geodesic deviation and derive the conditions necessary for stability within the $f(R,G)$ gravitational framework. Full article