Search Results (26)

This paper establishes a new stochastic SIR epidemic model that incorporates telegraph noise and Lévy noise to simulate the complex environmental disturbances affecting disease transmission. Given the susceptibility of epidemic spread to environmental noise and its intricate dynamics, an adaptive sliding mode controller based on an integral sliding surface and an adaptive control law is proposed. This controller is capable of stabilizing the constructed model and effectively suppressing the spread of the disease. The main contributions of this paper include the following: establishing a comprehensive and realistic stochastic SIR model that accounts for the complex impacts of telegraph noise (symbolizing periodic environmental changes) and Lévy noise (representing sudden environmental shocks) on the dynamics of disease transmission; employing T-S fuzzy modeling, which considers the design of fuzzy rules and the symmetry of membership functions, to ensure linearization of the model; constructing an integral sliding surface and designing an adaptive sliding mode controller for the fuzzy-processed model. Finally, the effectiveness of the proposed control method is validated through numerical simulations. Full article

A complex study was performed of the disturbances in geophysics parameters that were observed during a short-term period of earthquake preparation. On 4 March 2024, an $M6.1$ earthquake (N 42.93, E 76.966) occurred with the epicenter 12.2 km apart from the complex of geophysical monitoring. Preparation of the earthquake we detected in real time, 8 days prior to the main shock, when a characteristic cove-like decrease appeared in the gamma-ray flux measured 100 m below the surface of the ground, which observation indicated an approaching earthquake with high probability. Besides the gamma-ray flux, anomalies connected with the earthquake preparation were studied in the variation of the Earth’s natural pulsed electromagnetic field (ENPEMF) at very low frequencies (VLF) $f=7.5$ kHz and $f=10.0$ kHz and at ultra-low frequency (ULF) in the range of 0.001–20 Hz, as well as in the shift of Doppler frequency (DFS) of the ionospheric signal. A drop detected in DFS agrees well with the decrease in gamma radiation background. A sequence of disturbance appearance was revealed, first in the variations of ENPEMF in the VLF band and of the subsurface gamma-ray flux, both of which reflect the activation dynamic of tectonic processes in the lithosphere, and next in the variation of DFS. Two types of earthquake-connected effects may be responsible for the transmission of the perturbation from the lithosphere into the ionosphere: the ionizing gamma-ray flux and the ULF/VLF emission, as direct radiation from the nearby earthquake source. In the article, we emphasize the role of medium ionization in the propagation of seismogenic effects as a channel for realizing the lithosphere–ionosphere coupling. Full article

Spasticity is a common complication after spinal cord injury (SCI) that significantly diminishes quality of life and complicates daily management. As a hallmark of upper motor neuron lesions, spasticity emerges through a complex post-injury process involving the resolution of spinal shock, an imbalance between excitatory and inhibitory signaling, and maladaptive neuronal plasticity, leading to hyperreflexia and chronic spasticity. Severe spasticity frequently results in pain, sleep disturbances, and marked functional impairments. This review systematically integrates motor neuron alterations with corresponding muscle manifestations, providing a comprehensive analysis of the brain–spinal cord–muscle pathway in spasticity pathogenesis. Through an in-depth analysis of the pathological and physiological changes in motor neurons post-SCI, this review offers a novel perspective that unveils the intrinsic mechanisms underlying spasticity formation, thereby establishing a robust theoretical foundation for developing targeted therapeutic strategies. Full article

Efficient wastewater treatment with high-quality effluent and minimal operational costs and carbon emissions is vital for safeguarding the ecological environment and promoting human health. However, the wastewater treatment process is extremely complicated due to the characteristics of multiple treatment mechanisms, high disturbance variability and nonlinear behaviors; therefore, optimizing the wastewater treatment process through intelligent control is a long-standing challenge for researchers and operators. Machine learning models are regarded as effective tools for wastewater treatment with better simulating and controlling complex nonlinear behaviors. With the aid of bibliometric analysis, this paper aimed to summarize worldwide research progress and trends in the application of machine learning to wastewater treatment among 1226 related publications. The findings indicate that China and the United States are the two leading countries, with publications of 342 and 209, respectively, while the United States is an outstanding global collaboration leader in this field. Research institutions and authors are mainly from developing countries, and China accounts for the largest proportion of these. The analysis of journal and cited journal contributions report that almost all of the top 10 journals in publications belong to the Q1 quartile (9/10). Overall, future research will likely focus on developing systematic, strong and multi-objective models for wastewater treatment. A hybrid model could take advantage of two or more machine learning models or mechanistic models, which have been verified as excellent models for tackling limited data. Thus, predicting the pollutants in the effluent rather than the influent using hybrid models is attracting increasing attention because effective prediction contributes to reducing the loading shock of influent sharp fluctuation to wastewater treatment effluent quality. Also, the development of advanced data acquirement devices and the AI model prediction with partially default data should also be another focus of future research. Full article

Pulse detonation engines (PDEs) have become a transformative technology in the field of aerospace propulsion due to the high thermal efficiency of detonation combustion. However, initiating detonation waves within a limited space and time is key to their engineering application. Direct initiation, though theoretically feasible, requires very high critical energy, making it almost impossible to achieve in engineering applications. Therefore, indirect initiation methods are more practical for triggering detonation waves that produce a deflagration wave through a low-energy ignition source and realizing deflagration to detonation transition (DDT) through flame acceleration and the interaction between flames and shock waves. This review systematically summarizes recent advancements in DDT methods in pulse detonation engines, focusing on the basic principles, influencing factors, technical bottlenecks, and optimization paths of the following: hot jet ignition initiation, obstacle-induced detonation, shock wave focusing initiation, and plasma ignition initiation. The results indicate that hot jet ignition enhances turbulent mixing and energy deposition by injecting energy through high-energy jets using high temperature and high pressure; this can reduce the DDT distance of hydrocarbon fuels by 30–50%. However, this approach faces challenges such as significant jet energy dissipation, flow field instability, and the complexity of the energy supply system. Solid obstacle-induced detonation passively generates turbulence and shock wave reflection through geometric structures to accelerate flame propagation, which has the advantages of having a simple structure and high reliability. However, the problem of large pressure loss and thermal fatigue restricts its long-term application. Fluidic obstacle-induced detonation enhances mixing uniformity through dynamic disturbance to reduce pressure loss. However, its engineering application is constrained by high energy consumption requirements and jet–mainstream coupling instability. Shock wave focusing utilizes concave cavities or annular structures to concentrate shock wave energy, which directly triggers detonation under high ignition efficiency and controllability. However, it is extremely sensitive to geometric parameters and incident shock wave conditions, and the structural thermal load issue is prominent. Plasma ignition generates active particles and instantaneous high temperatures through high-energy discharge, which chemically activates fuel and precisely controls the initiation sequence, especially for low-reactivity fuels. However, critical challenges, such as high energy consumption, electrode ablation, and decreased discharge efficiency under high-pressure environments, need to be addressed urgently. In order to overcome the bottlenecks in energy efficiency, thermal management, and dynamic stability, future research should focus on multi-modal synergistic initiation strategies, the development of high-temperature-resistant materials, and intelligent dynamic control technologies. Additionally, establishing a standardized testing system to quantify DDT distance, energy thresholds, and dynamic stability indicators is essential to promote its transition to engineering applications. Furthermore, exploring the DDT mechanisms of low-carbon fuels is imperative to advance carbon neutrality goals. By summarizing the existing DDT methods and technical bottlenecks, this paper provides theoretical support for the engineering design and application of PDEs, contributing to breakthroughs in the fields of hypersonic propulsion, airspace shuttle systems, and other fields. Full article

The evolution form of the flow field generated via the impact of a muzzle jet on a constrained moving body changes from the state of fully free-spatial development to that of constrained development, and it involves the problem of interference, owing to the spatiotemporal coupling of various kinds of shock waves and vortices. Against this backdrop, the authors use the dynamic mesh method to establish two models for simulating the flow field and exploring the mechanism of development and the characteristics of propagation of disturbances induced via the shock waves as the muzzle jet impacts a constrained moving body. The results show that the muzzle jet exhibited a circumferentially asymmetric shape under the influence of the constrained track. The shock wave leaned towards the upper part of the muzzle, and its speed of propagation above the muzzle was higher than that below the muzzle. Meanwhile, the vortex that should have been present below the muzzle disappeared, and it was replaced with a separation line. Changes in the pressure of the flow field and important parameters of the moving body also became more complex due to the influence of the constrained track. Full article

This paper presents a WENO-based upwind rotated lattice Boltzmann flux solver (WENO-URLBFS) in the finite difference framework for simulating compressible flows with contact discontinuities and strong shock waves. In the method, the original rotating lattice Boltzmann flux solver is improved by applying the theoretical solution of the Euler equation in the tangential direction of the cell interface to reconstruct the tangential flux so that the numerical dissipation can be reduced. The fluxes at each interface are evaluated using a weighted summation of lattice Boltzmann solutions in two local perpendicular directions decomposed from the direction vector so that the stability performance can be improved. To achieve high-order accuracy, both fifth and seventh-order WENO reconstructions of the flow variables in the characteristic spaces are carried out. The order accuracy of the WENO-URLBFS is evaluated and compared with the traditional Lax–Friedrichs scheme, Roe scheme, and the LBFS by simulating the advection of the density disturbance problem. It is shown that the fifth and seventh-order accuracy can be achieved by all considered flux-evaluation schemes, and the present WENO-URLBFS has the lowest numerical dissipation. The performance of the WENO-URLBFS is further examined by simulating several 1D and 2D examples, including shock tube problems, Shu–Osher problems, blast wave problems, double Mach reflections, 2D Riemann problems, K-H instability problems, and High Mach number astrophysical jets. Good agreements with published data have been achieved quantitatively. Moreover, complex flow structures, including shock waves and contact discontinuities, are successfully captured. The present WENO-URLBFS scheme seems to present an effective numerical tool with high-order accuracy, lower numerical dissipation, and strong robustness for simulating challenging compressible flow problems. Full article

The hydraulic support liquid supply system provided power for the hydraulic support, serving as the core to ensure safe support of the coal mining face and to maintain continuous, efficient, and stable advancement of the coal mining operations. The hydraulic support faced complex loads while operating on the fully mechanized mining face. To meet the requirement of rapidly following the coal mining machine’s movement, numerous actuators of the hydraulic support frequently performed sequential actions, and the liquid demand of the hydraulic support varied strongly over time, causing the hydraulic system to endure constant pressure and flow shocks, making it difficult to ensure the production efficiency and equipment reliability of comprehensive working face. This study analyzed the pressure and flow characteristics of the liquid supply system during the periodic actions of the hydraulic support. To address the strong time-varying load and liquid demand during the simultaneous actions of the hydraulic support, an Extended State Observer (ESO) was designed for observation and compensation. An Active Disturbance Rejection Control (ADRC) method suitable for the configuration of a rapid pump-controlled liquid replenishment and pressure stabilization system was proposed, and a co-simulation model of the mechanical and control systems was developed by comparing indicators such as the pressure fluctuation amplitude and the execution time of the hydraulic support actions. The pressure stabilization control effects of the ADRC method, the PID control method, and the traditional multi-pump coordinated liquid supply mode under typical time-varying conditions were analyzed and compared. A simulation test system was constructed to validate the results, demonstrating that the ADRC rapid fluid replenishment and pressure stabilization control method can suppress load disturbances, reduce the system pressure fluctuation amplitude by 20.8%, and shorten the hydraulic support operation time by 2.6%. Full article

Shock wave boundary/layer interactions (SWBLIs) are critical in high-speed aerodynamic flows, particularly within supersonic regimes, where unsteady dynamics can induce structural fatigue and degrade vehicle performance. Conventional measurement techniques, such as pressure-sensitive paint (PSP), face limitations in frequency response, calibration complexity, and intrusive instrumentation. Similarly, MEMS-based sensors, like Kulite^® sensors, present challenges in terms of intrusiveness, cost, and integration complexity. This study presents a flexible, lightweight polyvinylidene fluoride (PVDF) piezoelectric sensor array designed for high-resolution wall-pressure measurements in SWBLI research. The primary objective is to optimize low-frequency pressure fluctuation detection, addressing SWBLI’s need for accurate, real-time measurements of low-frequency unsteadiness. Fabricated using a double-sided screen-printing technique, this sensor array is low-cost, flexible, and provides stable, high-sensitivity data. Finite Element Method (FEM) simulations indicate that the sensor structure also has potential for high-frequency responses, behaving as a high-pass filter with minimal signal attenuation up to 300 kHz, although the current study’s experimental testing is focused on low-frequency calibration and validation. A custom low-frequency sound pressure setup was used to calibrate the PVDF sensor array, ensuring uniform pressure distribution across sensor elements. Wind tunnel tests at Mach 2 verified the PVDF sensor’s ability to capture pressure fluctuations and unsteady behaviors consistent with those recorded by Kulite sensors. The findings suggest that PVDF sensors are promising alternatives for capturing low-frequency disturbances and intricate flow structures in advanced aerodynamic research, with high-frequency performance to be further explored in future work. Full article

On 22 January 2024, at 18 UT, a strong earthquake (EQ), Mw = 7, occurred with the epicenter at 41°N, 79°E. This seismic event generated a complex response, the elements of which correspond to the concept of lithosphere–atmosphere–ionosphere coupling through electromagnetic processes. While flying over the EQ area on the night-ide of the Earth, the tandem of low-orbiting Swarm satellites observed small-scale irregularities in the plasma density with an amplitude of ~1.5 × 10⁴ el/cm³, which are likely associated with the penetration of the coseismic electric field into the ionosphere. The local anomaly was detected against the background of a global increase in total electron content, TEC (although geomagnetic indices remained quiet), since the moment of EQ coincided with the ionospheric response to a solar flare. In the troposphere, specific humidity decreased while latent heat flux and aerosol optical depth increased, all exhibiting the co-located disturbances that can be attributed to the effect of increased air ionization rates, resulting in greater electrical conductivity in the near-Earth boundary layer. Anomalies started developing over the epicenter the day before and maximized on the day of the main shock and aftershocks. Full article

The aim of this study is to delve into the intricate the mechanism through which alterations in currency exchange rates give rise to shifts in inflation rates, while taking into careful consideration the country’s economic cycle. In order to accomplish this objective, we used a dataset that spanned from 1 January 1999 to 1 July 2023, focusing our analytical lens on three specific geographic areas, namely the Eurozone, the United Kingdom, and Canada. In our pursuit of understanding this complex relationship, we employed the Markov Switching Vector Autoregressive model. Our research outcomes can be succinctly encapsulated as follows: in the initial stages, particularly during phases characterized by robust economic growth, the transmission of exchange rate effects onto inflation levels appeared to exhibit a partial impact across all geographic areas under examination. However, during periods marked by economic downturns, both the United Kingdom and Canada displayed a distinctly more comprehensive transmission of these effects. Moreover, the prevailing projections for the forthcoming time horizon, across all the countries encompassed by our study, strongly indicate the onset of an expansionary phase that is projected to extend over a span of 25 months. Lastly, concerning the implications of unexpected disturbances or shocks, it is noteworthy that the response of exchange rates to inflation induced shocks was neither immediate nor as pronounced as the corresponding reaction of inflation to sudden shifts in exchange rates. Full article

Currently, Mediterranean forests are experiencing the deleterious effects of global warming, which mainly include increased temperatures and decreased precipitation in the region. Relict Abies pinsapo fir forests, endemic in the southern Iberian Peninsula, are especially sensitive to these recent environmental disturbances, and identifying the genes involved in the response of this endangered tree species to climate-driven stresses is of paramount importance for mitigating their effects. Genomic resources for A. pinsapo allow for the analysis of candidate genes reacting to warming and aridity in their natural habitats. Several members of the complex gene families encoding late embryogenesis abundant proteins (LEAs) and heat shock proteins (HSPs) have been found to exhibit differential expression patterns between wet and dry seasons when samples from distinct geographical locations and dissimilar exposures to the effects of climate change were analyzed. The observed changes were more perceptible in the roots of trees, particularly in declining forests distributed at lower altitudes in the more vulnerable mountains. These findings align with previous studies and lay the groundwork for further research on the molecular level. Molecular and genomic approaches offer valuable insights for mitigating climate stress and safeguarding this endangered conifer. Full article

In the context of an increasingly interconnected global economy, deciphering the complex ripple effects of external financial disruptions on national economies is a task of utmost significance. This article dives deep into the intricate repercussions of such disturbances on the macroeconomic dynamics of China using the example of the potential insolvency of a Silicon Valley bank. Grounded in empirical scrutiny, we leverage data spanning from Q1 2000 to Q1 2022 and the analytical utility of the impulse response function to illuminate our findings. We find that external financial tumult triggers a global recession, adversely impacting China’s export-driven economy while simultaneously unsettling aggregate output, employment levels, and wage stability. Simultaneously, these disruptions induce variability in consumption tendencies, investment trajectories, and import volumes and inject instability into interest rate paradigms. We also acknowledge the potential for currency depreciation and bank insolvency incidents to induce inflationary stresses, primarily by escalating the costs of imports. However, these inflationary tendencies may be offset by the concomitant economic slowdown and diminished demand inherent to global recessions. Importantly, the tightening of global credit conditions, coupled with existing financial ambiguities, may obstruct investment initiatives, curtail imports, and exert influence on both risk-free and lending interest rates. Our investigation also probes into the response of the Chinese government’s monetary policy to these external financial shocks. Despite the vital role of monetary policy in alleviating the impacts of these shocks, the potential secondary effects on China’s domestic economy warrant attention. Our study underscores the imperative of proper policy design rooted in a profound understanding of the intricate economic interdependencies for effective management and mitigation of the potentially detrimental consequences of such financial upheavals on China’s macroeconomic resilience within the tapestry of a tightly knit global financial ecosystem. Full article

Forest ecosystems are increasingly subject to disturbances, such as extreme (climate) events, fires and pathological outbreaks, which exert significant (and still poorly quantified) economic impacts, despite their intrinsic resilience. How forest management addresses these challenges will have profound effects on human health, environmental diversity, (ecological and economic) productivity and the ability of forest ecosystems to recovery from exogenous shocks. Assuming forests as ensuring ecosystem services that are vital to society and human well-being, in addition to providing wood material, a better knowledge of forest ecosystems appears a key requirement to delineate a developmental strategy that guarantees environmental protection objectives and achievement of climate and energy targets. In the context of Sustainable Development Goals of the United Nations 2030 Agenda, the information available on forest management practices in Europe still seems not completely suitable to provide a comprehensive overview of ecosystem conditions, their economic value, and their biodiversity. Based on a literature review, the present contribution focuses on recent dynamics of the forestry sector in Europe, delineating the inherent complexity in the environmental-economic nexus. Additionally, the extensive use of a key natural resource such as wood exerts social implications for local districts adapting to ecological change—from climate warming to landscape transformations. In line with earlier studies, our paper confirms the role of the technical-economic dimension of forestry in sustainable development paths of districts and regions, affecting together (i) short-term economic dynamics, (ii) the growth prospects of the sector, (iii) the organization of the supply chain, (iv) the interconnections between companies, and (v) investment strategies at large. One of the major issues is the low reliability of official statistics to provide a coherent picture of the actual status of forest resources. At the same time, forestry practices are pivotal in maintaining habitats and species while increasing the timber production that remains (too) sustainable. This is the policy direction constantly given by the European Commission to stimulate over time public bodies and private (in whose hands is about 60% of European forests) to start virtuous paths in the circular economy with considerable repercussions in terms of additional jobs, recycled materials, mt of CO₂ equivalent avoided, and increase in community added value. In this context, forestry should assure a more ‘holistic’ contribution to sustainable development paths at various spatial scales. This means concentrating on both economic and environmental targets based on the identification of significant (ecological-economic) dimensions that may delineate future lines of investigation and policy intervention, while increasing between member countries and regional authorities. Full article

This work investigates a hypersonic turbulent boundary layer over a $7^{°}$ half angle cone at a wall-to-total temperature ratio of 0.1, $M_{\infty }=7.4$ and $R{e}_{\infty m}=4.2\times {10}^6$ m${}^{-1}$, in terms of density fluctuations and the convection velocity of density disturbances. Experimental shock tunnel data are collected using a multi-foci Focused Laser Differential Interferometer (FLDI) to probe the boundary layer at several heights. In addition, a high-fidelity, time-resolved Large-Eddy Simulation (LES) of the conical flowfield under the experimentally observed free stream conditions is conducted. The experimentally measured convection velocity of density disturbances is found to follow literature data of pressure disturbances. The spectral distributions evidence the presence of regions with well-defined power laws that are present in pressure spectra. A framework to combine numerical and experimental observations without requiring complex FLDI post-processing strategies is explored using a computational FLDI (cFLDI) on the numerical solution for direct comparisons. Frequency bounds of 160 kHz $<f<1$ MHz are evaluated in consideration of the constraining conditions of both experimental and numerical data. Within these limits, the direct comparisons yield good agreement. Furthermore, it is verified that in the present case, the cFLDI algorithm may be replaced with a simple line integral on the numerical solution. Full article