Dynamic Disturbances Research Articles

Forest Disturbance and Restoration in China's North-South Transition Zone: A Case from the Funiu Mountains

Accurate monitoring and assessment of forest disturbance and recovery dynamics are essential for sustainable forest management, particularly in ecological transition zones. This study analyzed forest disturbance and recovery patterns in China’s Funiu Mountains from 1991 to 2020 by integrating the LandTrendr algorithm with space-time cube analysis. Using Landsat time series data and the Geodetector method, we examined both the spatiotemporal characteristics and driving factors of forest change across three periods. The results showed that (1) between 1991 and 2020, the study area experienced 131.19 km2 of forest disturbance and 495.88 km2 of recovery, with both processes most active during the 1990s; (2) spatiotemporal analysis revealed that both disturbance and recovery patterns were predominantly characterized by cold spots, suggesting relatively stable forest conditions despite localized changes; (3) human activities were the primary drivers of forest disturbance in the early period, while forest recovery was consistently influenced by the combined effects of topographic conditions and precipitation. Additionally, forest fires emerged as an important factor affecting both disturbance and recovery patterns after 2010. These findings enhance our understanding of forest dynamics in transition zones and provide empirical support for regional forest management strategies. The results also highlight the importance of considering both spatial and temporal dimensions when monitoring long-term forest changes.

Intracranial pressure monitoring in patients with spontaneous onset of orthostatic headache.

Spontaneous intracranial hypotension (SIH) is a debilitating disorder, with an estimated annual incidence of 3.7 per 100,000. Diagnosing SIH can be challenging for clinicians, as patients frequently present with normal investigation findings. Intracranial pressure (ICP) monitoring has been proposed as a valuable tool for patients with orthostatic headaches that are highly suggestive of SIH but have inconclusive investigation results. The primary objective of this study was to determine the proportion of patients with spontaneous orthostatic headaches and normal diagnostic work-up who exhibited abnormal ICP monitoring results. This single-centre, retrospective observational study was conducted at a tertiary referral centre specialising in SIH and CSF dynamics disorders. Consecutive patients with spontaneous orthostatic headaches and inconclusive diagnostic work-up who underwent 24-hour ICP monitoring were considered eligible. The 24-hour ICP monitoring followed a standardised protocol, measuring median ICP and pulse amplitude (a marker of brain compliance) during the daytime, nighttime, and over the entire 24-hour period. Specific cut-offs for low and high ICP states were predetermined based on the best available current evidence. Thirty-eight patients (23 females, mean age 41 years ± 14SD) were identified. All patients had orthostatic headaches with a spontaneous onset. The mean duration of symptoms was 46 months ± 36SD. ICP monitoring identified 3 patients (7.9%) with low ICP (mean of the median 24-hour ICP - 2 mmHg ± 2SD) and 6 patients (15.8%) with high ICP (mean of the median 24-hour ICP 9 mmHg ± 3SD). Obvious CSF dynamics disturbances were excluded in the remaining 29 patients (76.3%, mean of the median 24-hour ICP 3 mmHg ± 3SD). The only clinical feature that was more common in patients with abnormal ICP compared to patients with normal ICP results was audiovestibular disturbance, namely aural fullness or muffled hearing (67% versus 17%, p = 0.015). There were no complications from the ICP monitoring procedure for any patient. When appropriately selected, patients with a clinical picture highly suggestive of SIH, who have a negative diagnostic work-up, may benefit from consideration of invasive ICP monitoring. Moreover, a significant minority of patients with orthostatic headache may paradoxically have a high CSF pressure state, which can be detected using ICP monitoring. Portions of this work were presented in abstract and oral presentation form at the Twenty-eighth Anglo-Dutch Migraine Association meeting (08/06/2018), the Tenth Meeting of the International Society for Hydrocephalus and Cerebrospinal Fluid Disorders (20/10/2018; Bologna, Italy), the Society of British Neurological Surgeons 2018 Autumn Meeting (19/09/2018; London, United Kingdom), and the European Association of Neurosurgical Societies 2023 congress (27/09/2023; Barcelona, Spain). This work is also part of the doctoral thesis of one of the authors (LD).

Role of calcium overload-mediated disruption of mitochondrial dynamics in offspring neurotoxicity due to methylmercury exposure during pregnancy and lactation.

Methylmercury (MeHg) is a potent neurotoxicant with neurodevelopmental toxicity that is widely ingested into the body through drinking water and food. MeHg crosses the placental barrier and accumulates in the brain of the fetus, affecting the growth and development of the central nervous system. Although it has been demonstrated that MeHg induces neuronal calcium overload in the rat cerebral cortex, the role of calcium overload in MeHg-induced neurodevelopmental toxicity remains unclear. Here, we used ICR-pregnant mice and their resulting offspring and administered the BAPTA-AM calcium antagonist to investigate the molecular mechanisms by which MeHg exposure during gestation and lactation affects neurodevelopment. We found that exposure to MeHg during gestation and lactation resulted in developmental arrest and neurobehavioral dysfunction in the offspring, with calcium overload, disturbed mitochondrial dynamics, and apoptosis. However, the calcium overload inhibitor BAPTA-AM rescued MeHg-induced neurodevelopmental damage, attenuated the onset of calcium overload, reduced mitochondrial kinetic disturbances and apoptosis. Meanwhile, the activation of the CaM/CaMKII/DRP1 signaling pathway induced by calcium overload was inhibited, and the interaction between DRP1 and BAX was attenuated, which alleviated apoptosis to a certain extent. In summary, our study suggests that MeHg-induced calcium overload may induce disturbed mitochondrial dynamics through activation of the CaM/CaMKII/DRP1 signaling pathway, resulting in neuronal apoptosis.

Shorter and inflexible intrinsic neural timescales of the self in schizophrenia.

Schizophrenia is hypothesized to involve a disturbance in the temporal dynamics of self-processing, specifically within the interoceptive, exteroceptive, and cognitive layers of the self. This study aimed to investigate the intrinsic neural timescales (INTs) within these self-processing layers among people with schizophrenia. We conducted a functional magnetic resonance imaging (fMRI) study to investigate INTs, as measured by the autocorrelation window, among people with schizophrenia and healthy controls during both resting-state and task (memory encoding and retrieval) conditions. We obtained data from the UCLA Consortium for Neuropsychiatric Phenomics data set and preprocessed using fMRIPrep. We included 45 people with schizophrenia and 65 healthy controls. Compared with controls, participants with schizophrenia exhibited significantly shorter INTs across all 3 self-processing layers during rest (p < 0.05). In addition, those with schizophrenia showed less INT shortening during task states, leading to reduced rest-task differences in INT across all self-processing layers (p < 0.05). We observed similar patterns of shortened INTs in primary sensory and motor regions. We included people with schizophrenia taking medication, which may influence INTs; our study was also limited by the relatively slow temporal resolution of the fMRI data and the higher variability of the autocorrelation function in the schizophrenia group, compared with the control group. Our findings suggest that schizophrenia is characterized by a global temporal disturbance of the self, manifesting as shorter and inflexible INTs across self-processing and sensorimotor regions. These results support the hypothesis that schizophrenia involves a fundamental disruption in the temporal integration of neural signals, contributing to the core self-disturbance observed in the disorder.

Experiment research on the control method of automatically retained entry by roof cutting pressure relief within thick hard main roof longwall top coal caving panel

To address the large deformation of goaf-side entries resulting from intense dynamic pressure, a method involving automatically retained entry by roof cutting pressure relief (ARERC) technology is proposed for use in thick and hard main roof longwall top coal caving (THLTCC) panel. Both physical and numerical model experiments have been conducted to verify the effectiveness of ARERC technology in controlling deformation. The evolution laws of stress and deformation in the surrounding rocks of the retained entry and the mechanism of pressure relief by roof cutting are analyzed. Results indicate that this technique optimizes the roof structure of the roadway and interrupts roof stress transfer between the retained entry and goaf. Consequently, the maximum vertical stress on the roof-cutting side of the retained entry roof is generally lower than on the uncut side. The retained entry deformation undergoes four distinct stages behind the panel: the pressure relief stage, deformation stage, compaction stable stage and stabilization stage. Notably, the deformation stage exhibits the highest deformation rate for the roadway. Therefore, it is recommended to utilize single hydraulic props for temporary support during the deformation stage to prevent damage to the retained entry caused by dynamic pressure disturbance. Based on the above analysis, several recommendations are provided for the field application of ARERC technology. Finally, the results from engineering application show the effectiveness of ARERC technology in controlling the deformation of the goaf-side entry. This ARERC technology can be extended to other coal mines with similar geological conditions.

Dynamic Event-Triggered Active Disturbance Rejection Formation Control for Constrained Underactuated AUVs

Dynamic Event-Triggered Active Disturbance Rejection Formation Control for Constrained Underactuated AUVs

Results of endoscopic examination of the respiratory system in dogs

The article describes the technique of performing an endoscopic examination of the respiratory system in 24 patients. Indications for the study were any deviations from normal breathing, the presence of cough or spontaneous reverse sneezing, parenchymal diseases (alveolar, interstitial), noisy or labored breathing in brachycephalic breeds, as well as for assessing dynamic disturbances in the caliber of the respiratory tract in patients with clinical signs indicating this (cough like "goose cackle"). All patients belonged to different age groups and did not contact each other. The patient was positioned ventrally on the table, the table had a longitudinal slope from the endoscopist, i.e. the patient's head was slightly higher than the back of the body. The position of the examined animals "on the stomach" was used, which is considered generally accepted, in order to avoid any possible gravitational effects on the respiratory system. During the examination, the tracheal bifurcation was assessed for pathological changes (expansion, compression, mucosal infiltration, collapse, etc.), and then all lobar bronchi and as many segmental and subsegmental bronchi as possible were assessed (the latter, accessible for examination, vary depending on the diameter of the bronchoscope used and the patient's size). The picture in healthy dogs was V-shaped, with no signs of compression of the main bronchi or bronchial collapse. In the presence of inflammatory processes, these structures acquired a U-shape, usually accompanied by deterioration in the visibility of the vessels of the submucosal layer. The information content of the data obtained during bronchoscopy, in comparison with other methods of diagnosing respiratory diseases, can be considered one of the most preferable and justified methods, over other diagnostic methods.

Study of failure characteristics of cavern surrounding rock mass based on dynamic disturbance true triaxial modeling test

Study of failure characteristics of cavern surrounding rock mass based on dynamic disturbance true triaxial modeling test

Assessing the impact of rainfall, topography, and human disturbances on nutrient levels using integrated machine learning and GAMs models in the Choctawhatchee River Watershed.

Nutrient pollution caused by excessive total nitrogen (TN) and total phosphorus (TP) is a significant environmental challenge globally, threatening water quality and ecosystem health. This study investigates the interplay between rainfall, topography, and human disturbances in shaping TN and TP dynamics, aiming to identify critical factors driving nutrient pollution. Using integrated machine learning and statistical approaches, including Self-Organizing Maps (SOMs), Generalized Additive Models (GAMs), and logistic regression, the study reveals that rainfall acts as a dominant dilution factor, reducing nutrient concentrations and explaining 72.8% of TN variance and 55.6% of TP variance. Conversely, steep slopes and human-disturbed land use are positively correlated with nutrient levels but are moderated by rainfall's mitigating effect. Logistic regression further confirms rainfall's predictive significance, achieving high classification accuracy for TN (AUC=0.82) and TP (AUC=0.76). The identification of Critical Source Areas (CSAs) highlights priority regions for intervention, demonstrating the utility of the proposed framework for targeting water quality improvement measures. By integrating spatial and statistical modeling, this study provides actionable solutions and contributes to advancing water quality management strategies through enhanced understanding of natural and anthropogenic influences on nutrient pollution.

Assessment of hemo- and cerebrospinal fluid dynamics disorders in idiopathic normal pressure hydrocephalus according to MRI data: a prospective study

INTRODUCTION: Idiopathic normal pressure hydrocephalus (NPH) is a condition characterized by enlargement of the cerebral ventricles and an isolated disturbance of cerebrospinal fluid dynamics, the etiology and pathogenesis of which are still not fully determined.OBJECTIVE: To evaluate changes in hemo- and cerebrospinal fluid dynamics in idiopathic normal pressure hydrocephalus according to phase-contrast MRI data.MATERIALS AND METHODS: Three groups of subjects were formed: patients with NPH (12 people), elderly volunteers with atrophic ventriculomegaly (15 people), a group of healthy volunteers (15 people). For each subject, the data from a routine MRI study, the volumes of gray, white matter and cerebrospinal fluid were assessed, and the volume-velocity characteristics of CSF and blood flows at several levels were calculated.Statistics: For quantitative indicators of cerebrospinal fluid dynamics, the median (Me), 25% and 75% percentiles, and interquartile range were calculated. An intergroup assessment of the significance of differences was carried out using the Mann-Whitney U test and nonparametric multivariate analysis of variance MANOVA.RESULTS: Individual neuroimaging markers of IGT were determined, as well as an increase in the volume-velocity characteristics of CSF flow at the level of the cerebral aqueduct (p&lt;0.01, with a predominance of the retrograde component) in comparison with the control group and patients with atrophic ventriculomegaly. Multidirectional changes in the volume of intracranial venous outflow were revealed in the study groups: in patients with IGT – a decrease in outflow along the straight sinus by 1.4 times (p&lt;0.01), in patients with atrophic ventriculomegaly – a decrease in outflow along the superior sagittal sinus by 1.3 times (p&lt;0.05).DISCUSSION: The data obtained show a significant impairment of cerebrospinal fluid dynamics in patients with NPH, in contrast to elderly volunteers with age-related atrophy and replacement expansion of the cerebrospinal fluid spaces at the level of the brain aqueduct, and also indicates the importance of the venous link in maintaining intracranial volumetric interactions.CONCLUSION: The combined use of a routine protocol and phase-contrast MRI techniques made it possible to identify a number of neuroimaging, hemo- and CSF dynamic changes in patients with NPH in comparison with healthy volunteers, and also, most importantly, with patients of comparable age with the presence of replacement ventriculomegaly against the background of atrophy.

A high-speed MPPT based horse herd optimization algorithm with dynamic linear active disturbance rejection control for PV battery charging system

This study first proposes an innovative method for optimizing the maximum power extraction from photovoltaic (PV) systems during dynamic and static environmental conditions (DSEC) by applying the horse herd optimization algorithm (HHOA). The HHOA is a bio-inspired technique that mimics the motion cycles of an entire herd of horses. Next, the linear active disturbance rejection control (LADRC) was applied to monitor the HHOA’s reference voltage output. The LADRC, known for managing uncertainties and disturbances, improves the anti-interference capacity of the maximum power point tracking (MPPT) technique and speeds up the system’s response rate. Then, in comparison to the traditional method (perturb & observe; P&O) and metaheuristic algorithms (conventional particle swarm optimization; CPSO, grasshopper optimization; GHO, and deterministic PSO; DPSO) through DSEC, the simulations results demonstrate that the combination HHOA-LADRC can successfully track the global maximum peak (GMP) with less fluctuations and a quicker convergence time. Finally, the experimental investigation of the proposed HHOA-LADRC was accomplished with the NI PXIE-1071 Hardware-In-Loop (HIL) prototype. The output findings show that the effectiveness of the provided HHOA-LADRC may approach a value higher than 99%, showed a quicker rate of converging and less oscillations in power through the detection mechanism.

Adaptive dual-loop trajectory tracking control of marine surface vehicles in the presence of kinematic and dynamic disturbances

Adaptive dual-loop trajectory tracking control of marine surface vehicles in the presence of kinematic and dynamic disturbances

Predefined-Time Enhanced Antidisturbance Attitude Control for Rigid–Liquid Coupled Launch Vehicles

High-precision and fast-response attitude control of launch vehicles plays an increasingly important role in numerous space launch missions, ensuring the efficiency of space transportation. However, disturbances caused by liquid sloshing and external environments degrade the control performances seriously. Because of the complicated coupling with control inputs and angular acceleration, the dynamics of liquid sloshing disturbance are highly uncertain. Therefore, it is urgent to develop novel disturbance estimation methods for launch vehicles by thoroughly analyzing disturbance dynamics. In this paper, an observer-based predefined-time attitude control method aimed at achieving precise and rapid estimation of liquid sloshing disturbance and other external disturbances is proposed. More specifically, a prescribed-time reduced-order state observer is proposed for estimating the liquid sloshing disturbance and the unmeasurable system state, leveraging the specific characteristics and inherent coupling relations of liquid sloshing disturbance. Additionally, a prescribed-time extended state observer is introduced for estimating external disturbances and nonlinear terms. Subsequently, by employing a predefined-time output feedback controller, a composite control law is proposed to enhance the antidisturbance capabilities of rigid–liquid coupled launch vehicles. Finally, simulation examples are presented to illustrate the effectiveness of the proposed method.

Designing of a wide-area power system stabilizer using an exponential distribution optimizer and fuzzy controller considering time delays

In this paper, explore the effectiveness of a new Wide Area Fuzzy Power System Stabilizer (WAFPSS), optimized using the Exponential Distribution Optimization (EDO) algorithm, and applied to an IEEE three-area, six-machine power system model. This research primarily focuses on assessing the stabilizer’s capability to dampen inter-area oscillations, a critical challenge in power grid operations. Through extensive simulations, the study demonstrates how the WAFPSS enhances stability and reliability under a variety of operational conditions characterized by different communication delay patterns. The application of the proposed stabilizer on this specific IEEE model provides a detailed insight into its performance in real-world scenarios, illustrating its adaptability and effectiveness in managing dynamic disturbances. The simulation results reveal that the proposed WAFPSS achieves significant reductions in the Integral Time Squared Error (ITSE), with improvements of 94.1%, 97.02%, and 98.18% in three distinct cases, showcasing its superior damping capability and robustness. The findings indicate that the advanced optimization techniques provided by the EDO algorithm significantly improve the stabilizer’s response, ensuring robust power system performance. This integration of WAMS with sophisticated control systems using fuzzy logic presents a strategic solution to managing the complexities faced by modern power networks, optimizing their stability in the face of increasing renewable integration and fluctuating demand.

Harmonic coupling characteristics of inverters with dynamic disturbances based on harmonic state space

Harmonic coupling characteristics of inverters with dynamic disturbances based on harmonic state space

Model-Free Speed Control for Pumping Kite Generator Systems Based on Nonlinear Hyperbolic Tangent Tracking Differentiator

This paper investigates the emerging field of grid-connected wind-powered pumping kite generator system (PKGS), focusing on the challenges associated with the generator/motor speed control. Conventional use of proportional–integral (PI) controllers faces difficulties in meeting requirements for dynamic response, tracking performance, stability, and disturbance rejection encountered in this technology, notably the periodical variation in the rotational speed reference in maximum power point tracking in generation phases and the dynamic response for the step reference in transient ones. To overcome these limitations, a model-free controller (MFC) approach is introduced, also known as intelligent PID controllers. Unlike traditional methods, MFC does not rely on a control model of the system and adapts to uncertainties and disturbances through online estimation based on the system’s input–output behavior. To further improve the control performances, a tracking differentiator based on a nonlinear hyperbolic tangent function is integrated in the MFC. The effectiveness of the proposed strategy is proved through simulations in MATLAB/Simulink. The results highlight the superior performances of the proposed MFC approach in terms of speed control accuracy, response time, and robustness.

Adaptive model predictive controller for power regulation and load reduction in large wind turbines

Pitch control is related to the efficient energy conversion and safe operation of wind turbine, which is a challenging control issue because of the highly nonlinear dynamics of wind turbine, system constraints and stochastic environmental disturbances, etc. In this article, we propose the adaptive model predictive pitch control strategy based on linear parameter varying (LPV) model to solve the pitch control issue of large-scale wind turbine. Firstly, a high-fidelity LPV model is constructed to approximate the high-nonlinearity dynamics of wind turbine. The gap metric theory is introduced to optimize the selection of local models. Based on the proposed LPV model, an adaptive model predictive controller with linear time-varying Kalman filter is designed for large-scale wind turbine. The benchmark 5 megawatt (MW) wind turbine model provided by FAST is employed to evaluate the controller performance. The results show that, compared with the traditional gain scheduling proportional–integral control strategy, the proposed control strategy can achieve better power regulation and load reduction performance under gust, step and turbulent wind.

Spatial Distribution Dynamics of Sensory Disturbances in the Treatment of Obesity-Related Meralgia Paresthetica Using Transcutaneous Electrical Nerve Stimulation.

Background: To date, there have been no studies on the dynamics of areas of pain, paraesthesia and hypoesthesia after the use of various transcutaneous electrical nerve stimulation in the treatment of meralgia paresthetica. Methods: In this pilot study, we observed 68 patients with obesity-related bilateral meralgia paresthetica. Pain syndrome, paraesthesia symptoms, and hypoesthesia were evaluated using 10-point scores. In addition, pain drawing (PD) was used to determine the area of the spatial distribution of pain syndrome and paraesthesia symptoms, and body drawing was used to determine the area of hypoesthesia. Sham TENS was performed in the control group, and effective TENS was performed in the treatment group. The treatment group consisted of two subgroups. One subgroup underwent HF-LA TENS, and the second subgroup underwent LF-HA TENS. Results: Despite the greatest analgesic effect observed from HF-LA TENS, which was assessed using scoring methods, during and after treatment, the reduction in the area of pain and paraesthesia symptoms and the area of hypoesthesia was moderate, short-term, and reversible. In contrast, LF-HA TENS had a pronounced analgesic and sustained anti-paraesthesia effect, manifested by a noticeable decrease in pain and paraesthesia symptoms area in PD, gradually increasing during the first 2 months of follow-up and accompanied by an irreversible prolonged decrease in the area of hypoesthesia. Conclusion: The areas of paraesthesia and hypoesthesia correlate with affective reactions to long-term chronic pain, which noticeably regress under the influence of LF-HA TENS compared to HF-LA TENS.

Fundamental investigation of process stabilization through combined modification of milling tools with structured functional surfaces and asymmetric dynamic properties

AbstractDisturbance factors, such as self-excited tool vibrations, limit the performance of modern machining processes and thus restrict the quality, productivity, and sustainability of industrially manufactured components. Tools with functional flank-face structures as well as asymmetric dynamic properties represent two approaches that are capable of reducing such dynamic disturbances. Since up to now both approaches have solely been investigated separately, a hybrid concept was developed, applied, and evaluated that combines both techniques and exploits synergistic effects. It was shown that the compliance of milling tools can be specifically adjusted by appropriate dimensioning of laterally inserted grooves on the tool shank. In addition, a preparation of the cutting edges, e.g. applying surface structures, are still feasible. The effect of such a hybrid tool modification was evaluated based on in-process measurements and workpiece analyses. An increase of the process stability and, thus material removal rate of 85% compared to non-modified tools could be achieved, which also exceeded the stabilizing potential of tools that include only one modification approach.

Bifenthrin causes disturbance in mitochondrial dynamics and bioenergetic system in human embryonic kidney cells (HEK 293).

Bifenthrin causes disturbance in mitochondrial dynamics and bioenergetic system in human embryonic kidney cells (HEK 293).