Search Results (3,076)

Aiming at the trajectory tracking control problem caused by the coupling of strong nonlinearity, parameter uncertainty and unknown disturbances in rigid robotic arms, this paper proposes an adaptive robust model predictive control (APRMPC) scheme. This study aims to fill the gap in the existing literature by proposing a dedicated control framework capable of simultaneously and effectively handling parameter uncertainty, unmodeled dynamics, and external disturbances, while ensuring constraint satisfaction. Firstly, a dynamic model of a three-degree-of-freedom robotic arm was established based on the Lagrange equation; secondly, this paper designs a deep integration mechanism of adaptive law and robust predictive control: by designing a parameter adaptive algorithm to estimate the system uncertainty online and feedforward compensate it to the predictive model, the impact of model mismatch is significantly reduced; meanwhile, for the estimated residuals and unknown disturbances, feedback gain was introduced and the control input was designed based on the robust invariant set theory, achieving unified parameter identification, disturbance suppression and rolling optimization within a single framework. This paper strictly proves the feasibility and stability of the control scheme. Finally, the simulation experiments based on MATLAB show that, compared with the traditional MPC and PID methods, the APRMPC algorithm can achieve higher accuracy and stronger robustness in trajectory tracking under various working conditions, effectively resolving the inherent contradiction between the weak robustness of the traditional MPC and the large buffering of sliding mode control, and verifying the value of the proposed scheme in filling the gap in related literature. Full article

In gas reservoirs, high gas velocity causes significant inertial effects, leading to a nonlinear relationship between pressure gradient and velocity, especially near wellbores or fractures. In such cases, Darcy’s law is inadequate, and the Forchheimer equation is commonly used to model nonlinear flow behavior. Although the Forchheimer equation improves simulation accuracy for high-velocity flow in porous media, incorporating it into conventional numerical simulations greatly increases computational time, as nonlinear flow equations must be solved over the entire reservoir. This difficulty is exacerbated in heterogeneous fractured reservoirs, where complex fracture–matrix interactions and localized high-velocity flow complicate solving nonlinear equations. To address this, this work proposes a fast numerical simulation method based on diffusive time of flight (DTOF). By using DTOF as a spatial coordinate, the original three-dimensional flow equations incorporating the Forchheimer equation are reduced to a one-dimensional form, enhancing computational efficiency. DTOF represents the diffusive time for a pressure disturbance from a well to reach a specific reservoir location and can be efficiently computed by solving the Eikonal equation via the fast marching method (FMM). Once the DTOF field is obtained, the three-dimensional problem is transformed into a one-dimensional problem. This dimensionality reduction enables fast and reliable modeling of nonlinear high-velocity gas transport in complex reservoirs. The proposed method’s results show good agreement with those from COMSOL Multiphysics, confirming its accuracy in capturing nonlinear gas flow behavior. Full article

The world is far from meeting the goals of the Paris Agreement of limiting the rise of global temperature to below 1.5 °C, with dire consequences for Small Island Developing States (SIDS) in particular. If SIDS are to address their climate vulnerabilities through policy-induced resilience building, they need to have a robust governance framework in place that coherently addresses climate change adaptation and disaster risk reduction. What would such a governance framework look like? To address this question, we carried out a systematic literature review of papers published between 1992 and 2023. Our review reveals that the governance around climate change adaptation and disaster risk reduction is relatively weak in SIDS. However, the analysis of barriers and enablers unveils the contours of a proposed three-tiered governance framework, the application of which needs to be contextualised: Tier 1 comprises three key pillars: Policy Planning, Institutional Arrangements, and Laws and Regulations; Tier 2 identifies the principles of transparency, accountability, equity, legitimacy, and subsidiarity; the core pillars and the principles are nested within a broader Tier 3 comprising democratic processes (rule of law), religious and cultural values, and political commitment. In order for SIDS to fight the existential threat of climate change, the proposed framework will allow SIDS to better understand their climate governance framework and deliver low-carbon, climate resilient development within the broader ambit of sustainable development. This framework also addresses the weakness in previous studies, which consider dimensions, principles, and enabling an environment of good governance on equal footing. We illustrate this framework using the analogy of the lotus flower. Full article

Thermoset composites are a fast-growing waste stream that resists conventional reusing routes. Water is the principal ageing agent for epoxy-based thermoset materials that bind high-pressure piping, wind-turbine blades and aircraft skins, yet its action is deceptively complex: a rapid, reversible plasticisation is often followed by a far slower, irreversible chemical hydrolysis. Here we bridge that gap to access a reliable diagnosis inspection. Gravimetric immersion tests (from 8 to 93 °C, up to more than a year) and in situ FTIR spectroscopy were performed on four industrial DGEBA networks (two amine-cured matrices and two anhydride-cured matrices that hydrolyse). This 2 + 2 design isolates reversible from irreversible changes and exposes the individual signatures of diffusion, specific sorption and bond scission. The data are rationalised with a compact three-contribution model that superposes Fickian diffusion through nano-voids, adsorption site saturation through hydrogen bonds and a power-law hydrolysis term sharing global Arrhenius parameters. Since the parameters retain clear physical meaning, the approach can be extrapolated to service temperatures, providing a fast, transparent tool for lifetime prediction and for separating recoverable plasticisation from permanent chemical degradation in critical epoxy infrastructure. Full article

Introduction: Global crises such as the COVID-19 pandemic have posed a critical challenge to education and have hampered progress towards sustainability in higher education. Therefore, the present study aimed to examine the impact of pandemic crisis management on the sustainability of higher education. Methods: This research was based on a mixed approach and, in terms of the nature of the data, consisted of two qualitative and quantitative phases. Qualitative data based on the grounded theory were collected through semi-structured interviews with 25 university leaders. The statistical population in the quantitative section consisted of 240 employees and faculty members from agricultural faculties in Tehran province, and the resulting data were analyzed using structural equation modeling. Results: Qualitative data were examined through three phases: open, axial, and selective coding, resulting in the identification of 393 open codes, including 98 ideas across eight primary themes. After validating the model obtained from the qualitative phase, all relationships between variables were confirmed through path analysis. The findings indicated the advancement and enhancement of six factors: the creation of laws and regulations, financial resources, infrastructure, communication and collaboration, human resource management, and social capital, which facilitated the promotion of pandemic crisis management. Likewise, pandemic crisis management affects the sustainability of higher education. Discussion: This research helps to document the pandemic crisis management model of agricultural colleges so that the sustainability of higher education can be achieved through understanding the conditions and strategies of pandemic crisis management. Also, this paper expands the knowledge about the management of the pandemic, which necessitates the sustainability of the functioning of the higher education system. Full article

Focusing on the mining-induced fracture development characteristics of Weakly Cemented Overburden (WCO) in Ultra-Thick Coal Seam (UTCS) extraction, this study, based on the 1101 first mining face in Xinjiang’s Zhundong Coalfield, systematically investigates the dynamic evolution law of the water-conducting fracture zone (WCFZ) in WCO by employing similarity simulation, quantitative characterization using Fractal Dimension (D), and surface borehole exploration and borehole imaging technology. The results show that existing prediction equations for the WCFZ have poor applicability in the study area, with significant fluctuations in prediction outcomes. Similarity simulation reveals that Thick Soft Rock Layers (TS) guide and control fracture development, with the D exhibiting a “step-like” evolution. After the first rupture of TS1, the peak D reaches 1.49, stabilizing between 1.36 and 1.37 after full extraction. The height of the WCFZ increases non-linearly with the advance of the working face, reaching a maximum of 189 m, with a fracture-to-mining ratio of 10.5. Based on D fluctuations and extension patterns, the fracture development is divided into three stages, initial development, vertical propagation, and stabilization, clarifying its spatial evolution. Field measurements indicate a WCFZ height ranging from 161 to 178 m, with a fracture-to-mining ratio of 9.73–12.18, showing only a 6.2% error compared to the simulation results, which verifies the reliability of the experiment. This study reveals the evolution mechanism of the WCFZ during mining in UTCS and WCO in the Zhundong area, providing a theoretical basis and practical guidance for mine disaster prevention and control, as well as safe and efficient mining. Full article

This study systematically investigates settlement sites that record living patterns of ancient humans, aiming to reveal the interactive mechanisms of human–environment relationships. The core issues of landscape archeology research are the surface spatial structure, human spatial cognition, and social practice activities. This article takes the Han Dynasty settlement site in Sanyangzhuang, Neihuang County, Anyang City, Henan Province, as a typical case. It comprehensively uses ArcGIS 10.8 spatial analysis and remote sensing image interpretation techniques to construct spatial distribution models of elevation, slope, and aspect in the study area, and analyzes the process of the Yellow River’s ancient course changes. A regional historical geographic information system was constructed by integrating multiple data sources, including archeological excavation reports, excavated artifacts, and historical documents. At the same time, the sequences of temperature and dry–wet index changes in the study area during the Qin and Han dynasties were quantitatively reconstructed, and a climate evolution map for this period was created based on ancient climate proxy indicators. Drawing on three dimensions of settlement morphology, architectural spatial organization, and agricultural technology systems, this paper provides a deep analysis of the site’s spatial cognitive logic and the ecological wisdom it embodies. The results show the following: (1) The Sanyangzhuang Han Dynasty settlement site reflects the efficient utilization strategy and environmental adaptation mechanism of ancient settlements for land resources, presenting typical scattered characteristics. Its formation mechanism is closely related to the evolution of social systems in the Western Han Dynasty. (2) In terms of site selection, settlements consider practicality and ceremony, which can not only meet basic living needs, but also divide internal functional zones based on the meaning implied by the orientation of the constellations. (3) The widespread use of iron farming tools has promoted the innovation of cultivation techniques, and the implementation of the substitution method has formed an ecological regulation system to cope with seasonal climate change while ensuring agricultural yield. The above results comprehensively reflect three types of ecological wisdom: “ecological adaptation wisdom of integrating homestead and farmland”, “spatial cognitive wisdom of analogy, heaven, law, and earth”, and “agricultural technology wisdom adapted to the times”. This study not only deepens our understanding of the cultural value of the Han Dynasty settlement site in Sanyangzhuang, but also provides a new theoretical perspective, an important paradigm reference, and a methodological reference for the study of ancient settlement ecological wisdom. Full article

Soil electrical resistivity is a fundamental parameter in various geotechnical, agricultural, environmental, and engineering applications, as it directly depends on the soil’s moisture content and physical properties. Understanding this relationship is crucial for improving the safety and efficiency of electrical installations. This study analyzes the relationship between soil electrical resistivity and gravimetric moisture content in three soil types, sandy, clayey, and silty, with the aim of comparing the performance of different predictive models under controlled laboratory conditions. Seven fitting models were evaluated, Logarithmic Spline, Radial Basis Function (RBF), Locally Estimated Scatterplot Smoothing (LOESS), Least Absolute Shrinkage and Selection Operator (LASSO), Ridge Regression (RIDGE), Power Law and a segmented equation, using metrics such as Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE) and coefficient of determination $R^2$ . The Spline and RBF models showed excellent accuracy and near-zero errors in all soils, although their applicability is limited by the lack of an explicit formulation and by the fact that, as interpolation methods, they do not guarantee predictive capacity outside the experimental dataset. Therefore, their use should be restricted to controlled laboratory conditions, as field variability factors can significantly alter soil resistivity responses. Among the explicit models, the Segmented Equation obtained a MAPE of 6.14% (sandy), 15.1% (clayey), and 13.16% (silty), with $R^2$ values of 0.91, 0.93, and 0.89, respectively, demonstrating good performance and functionality. The Power Law model, although showing an $R^2$ close to 0.96, presented significant overestimations, especially in silty soils (MAPE > 187%). The LASSO model yielded inconsistent predictions with percentage errors exceeding 120% in silty soils. In conclusion, nonparametric models provide excellent accuracy, while the segmented equation stands out as the best explicit alternative for estimating resistivity with reasonable precision. Full article

Accurate prediction of gas pipeline incidents through risk factor interdependencies is critical for proactive safety management. This study develops a hybrid SARIMA–association rule mining (ARM) framework integrating time-series forecasting with causal pattern decoding, using 60-month U.S. pipeline incident records (2010–2024) from the Pipeline and Hazardous Materials Safety Administration (PHMSA) database, covering leaks, mechanical punctures, and ruptures. Seasonal Autoregressive Integrated Moving Average (SARIMA) modeling with six-month rolling-window validation achieves precise leak forecasts (MAPE = 14.13%, MASE = 0.27) and reasonable mechanical damage predictions (MAPE = 31.21%, MASE = 1.15), while ruptures exhibit pronounced stochasticity. Crucially, SARIMA incident probabilities feed Apriori-based ARM, revealing three failure-specific mechanisms: (1) ruptures predominantly originate from natural force damage, with underground cases causing economic losses (lift = 3.70) and aboveground class 3 incidents exhibiting winter daytime ignition risks (lift = 2.37); (2) leaks correlate with equipment degradation, where outdoor meter assemblies account for 69.7% of fire-triggering cases (108/155 incidents) and corrosion dominates >50-year-old pipelines; (3) mechanical punctures cluster in pipelines <20 years during spring excavation, predominantly occurring in class 2 zones due to heightened construction activity. These findings necessitate cause-specific maintenance protocols that integrate material degradation laws and dynamic failure patterns, providing a decision framework for pipe replacement prioritization and seasonal monitoring in high-risk zones. Full article

Background and Aims: In recent decades, lifestyle patterns have undergone significant transformations, particularly in low- and middle-income countries (LMICs). These changes have contributed to a dual nutritional crisis characterized by the coexistence of undernutrition and overweight/obesity, commonly referred to as the Double Burden of Malnutrition (DBM). Compounding this issue is the persistent prevalence of parasitic infections, due to poor personal hygiene and sanitation practices which further exacerbate nutritional imbalances, creating what is now recognized as the Triple Burden of Malnutrition (TBM). This review aims to explore the evolving lifestyle factors that have contributed to the emergence of the DBM and to examine its intersection with parasitic infections. The focus is particularly on South Asian low- and middle-income countries, where these overlapping burdens present a significant public health challenge. By highlighting the interconnectedness of malnutrition, obesity, and parasitic diseases, this study seeks to provide a comprehensive understanding of the current nutritional landscape in South Asian LMICs and to inform future health interventions and policies. Methods: This study was conducted using published and unpublished secondary data that are available on websites and other printed materials. One of the main requirements is date, with 2013 being regarded as the initiative’s landmark. Another crucial factor is the availability of the entire article. For this study, only research publications published in English were taken into consideration. Zotero was used for compilation. The majority of the analysis was performed using percentages and ratios. A thorough evaluation of all the studies’ methodology, design, execution, and reporting was performed in order to spot any systematic flaws in this study. Results: Only 45 of the 105 full-text papers that were screened met the requirements for inclusion. Of these studies, 15 satisfied the inclusion and exclusion requirements. The results show that China, with a comparatively higher income level status, has more prevalence of overweight and obesity among children (11.5%) and women (34.6%) than India (2.1% of OWOB among children and 20.6% among women). Nepal stands behind China and India with 1.2% of OWOB among children and between them with 22.2% OWOB among women. Interestingly, among the three South Asian nations, India has the highest stunting, wasting, and underweight among children (38.4%, 21%, and 35.7%, respectively) followed by Nepal (35.8%, 9.7%, and 27%) and China (8.1%, 2%, and 2.5%). This study finds no significant difference in the prevalence of intestinal parasitic infections among OWOB and underweight populations. This review finds that the DBM along with parasitic infections has resulted in a Triple Burden of Malnutrition, which is currently a major public health issue in low- and middle-income countries in South Asia. Discussion: The various types of malnutrition were once thought of and treated as distinct public health problems, but the new understanding is that undernutrition and overnutrition are linked, and that in order for policy solutions to be successful, double-duty measures that simultaneously address multiple dimensions must be put in place. When the DBM is combined with parasite illnesses, it becomes the Triple Burden of Malnutrition, which is the primary cause of the financial burden in LMICs. China has the worst obesity problem, yet it also has more obesity-related laws and intervention programs than India and Nepal combined. All three nations, however, have failed to stop or deal with the dramatic increase in OWOB over the last 20 years. For effective implementation and results, genetic and psychological factors must also be taken into account when developing policies and programs to tackle the obesity epidemic, undernutrition, and parasite diseases. Conclusions: The prevalence of the DBM has been rising globally, with South Asia seeing a faster rate of increase. A growing DBM is favorably correlated with national economic development. In South Asian LMICs, the DBM combined with parasite diseases has resulted in a Triple Burden of Malnutrition, a debilitating illness. Full article

Schrödinger’s operator relations combined with Einstein’s special relativistic energy-momentum equation produce the linear Klein–Gordon partial differential equation. Here, we extend both the operator relations and the energy-momentum relation to determine new families of nonlinear partial differential relations. The Planck–de Broglie duality principle arises from Planck’s energy expression $e=h\nu$, de Broglie’s equation for momentum $p=h/\lambda$, and Einstein’s special relativity energy, where h is the Planck constant, $\nu$ and $\lambda$ are the frequency and wavelength, respectively, of an associated wave having a wave speed $w=\nu \lambda$. The author has extended these relations to a family that is characterised by a second fundamental constant $h^{\prime }$ and underpinned by Lorentz invariant power-law particle energy-momentum expressions. In this note, we apply generalized Schrödinger operator relations and the power-law relations to generate a new family of nonlinear partial differential equations that are characterised by the constant $\kappa =h^{\prime }/h$ such that $\kappa =0$ corresponds to the Klein–Gordon equation. The resulting partial differential equation is unusual in the sense that it admits a stretching symmetry giving rise to both similarity solutions and simple harmonic travelling waves. Three simple solutions of the partial differential equation are examined including a separable solution, a travelling wave solution, and a similarity solution. A special case of the similarity solution admits zeroth-order Bessel functions as solutions while generally, it reduces to solving a nonlinear first-order ordinary differential equation. Full article

The three-soft coal seam, characterized by its soft and fractured lithology, is prone to significant drilling trajectory deviation during construction, severely compromising gas drainage efficiency and posing potential safety hazards. In order to clarify the variation law of the drilling trajectory of the three-soft coal seam, this paper takes the 14205 working face of a mine in Guizhou Province as the engineering background, monitors and analyzes the drilling inclination and the change in the inclination, and then studies the influencing factors of the drilling deviation. During on-site drilling and coring operations and data monitoring, the formation lithology and fragmentation conditions were clarified, and the trajectories of gas drainage drilling holes at 15°, 30°, 45°, 60°, 75°, and 90° were obtained. It was observed that when the hole inclination is 15° or 90°, the change Δ value of the hole inclination is close to 0°. When the hole inclination is 30° or 75°, the change Δ value of the hole inclination is close to 2.5°. When the hole inclination is 45° or 60°, the change Δ value of the borehole inclination angle is close to 4.5°. The curve of the change Δ value of the borehole inclination angle and the borehole inclination angle was obtained by calculation and fitting, and the whole presents a quadratic function distribution. It was inferred that when the inclination angle of the borehole is 50°, the change Δ value of the inclination angle of the borehole reaches the maximum value, which is close to 5°, that is, the deflection of the gas drainage borehole is the largest. With the help of this curve, the deflection was predicted, controlled, and reduced. The AHP analysis model was used to rank the importance of the influencing factors of the borehole trajectory, and it was clear that the main controlling factor of the borehole deflection is the geological factor. This study provides a basis for obtaining the drilling deflection law and determining the appropriate drilling deflection control and correction technology. Full article

If evaluated solely by Raz’s criteria, Dworkin’s interpretive theory of law indeed faces a crisis of authority justification. This controversy stems from their divergent understandings of the nature of authority. By drawing on Gadamer’s philosophical hermeneutics to interrogate the rational foundation of prejudice, the rational essence of authority is re-exposed. Authority is a rational and free activity, tied to recognition, and manifests as the possibility of being justified through reasoning. Dworkin’s methodological approach provides a robust justification for legal authority, which manifests in three key dimensions. First, the very act of interpretation demonstrates recognition that authority constitutes a rational activity, thereby affirming that the establishment of legal authority represents a voluntary, autonomous, and reason-governed enterprise. Second, the interpretive theory of law correlates with the be-earned character of authority across three constitutive aspects: its susceptibility to justifiability, its normative demand for justification, and its substantive realization through justificatory practices. Third, the substantive content of interpretive theory corresponds to the epistemic features of authoritative justification—including its informational properties, scope of application, communal dimensions, and capacity for adaptive rationalization. Consequently, contra Raz’s critique, Dworkin’s theoretical framework successfully provides a coherent account of legal authority’s justificatory foundations. Full article

As concrete exhibits localized strain softening, for example, under tension, fracture-energy consistency is essential for obtaining mesh-insensitive results of finite-element (FE) analyses. Accordingly, element- and structural-level parametric studies of uniaxial tensile behavior are performed within an FE framework coupling the Concrete Damaged Plasticity (CDP) model, the Crack Band Theory, and the Newton–Raphson solver in Abaqus. The effects of several CDP parameters and the mesh size are quantified using a sensitivity index ($SI$). A damage evolution law with several tensile parameters is proposed for energy consistency in addition to scaling of the softening strain. Besides tensile strength, elastic modulus, and an estimated uniaxial stress–strain curve, three key parameters are validated: the ratio between fracture energy from pure tension in the crack band and that from direct-tension tests, and two mesh-independent damage evolution parameters. An inverse calibration is proposed, in which the damage parameters and the fracture-energy ratio are identified in one-element ($SI\le 5\%$) and multi-element models, respectively. With these calibrations, the tensile response of the crack band is obtained, and multi-element analyses achieve mesh insensitivity when meshes are not smaller than the crack-band width. For finer meshes violating continuum assumptions, the initial damage rate parameter is reduced to preserve energy consistency. Full article

A complex operating environment and high operating temperature lead to the uneven temperature field distribution of key components of the molten salt Linear Fresnel collector in a way that compromises the collector’s safety and stability. To investigate the influence of different working conditions on the temperature field of the molten salt Linear Fresnel collector under multi-physical field conditions, this study develops a three-dimensional numerical model based on ANSYS that integrates the loading of solar radiation and thermal–fluid coupling, compares and verifies the accuracy of the model through the collector field data of the actual operation, and systematically analyzes the distribution characteristics of the receiver tube and outlet temperature field and its rule of change. The results show that temperatures of the receiver tube and exit during operation exhibit pronounced non-uniform distribution characteristics, in which the inlet flow rate of the molten salt and intensity of solar irradiation have the most critical influence on the temperature distribution throughout the receiver tube and its exit, and the heat transfer temperature difference between the molten salt and heat conduit wall is reduced as the inlet temperature raises, which makes the receiver tube and molten salt outlet temperature gradient slightly reduced. This study not only supplements and improves the numerical simulation study of the molten salt Linear Fresnel collector under complex working conditions but also reveals the distribution law of the temperature field between the receiver tube and the outlet, which provides adequate numerical support for the safe and stable operation of the collector. Full article