Characteristics Of Disturbances Research Articles

Analysis of co-seismic ionospheric disturbance of the Qinghai Mw 7.4 earthquake on May 21, 2021

ABSTRACT In this study, the total electron content (TEC) was extracted from Global Navigation Satellite System (GNSS) data provided by the Crustal Movement Observation Network of China (CMONOC). The ionospheric disturbances related to the Qinghai earthquake on 21 May 2021 were analysed. Significant coseismic ionospheric disturbances (CIDs) were observed near the earthquake epicentre. To further investigate the propagation characteristics of ionospheric anomalies associated with this earthquake, the epicentral area was divided into eight regions, each corresponding to a 45° sector, to analyse the characteristics of ionospheric disturbances. Firstly, based on the spatial and temporal characteristics of the slant total electron content, different degrees of ionospheric disturbances were identified at various time intervals after the earthquake. Secondly, the earthquake generated two types of coseismic ionospheric disturbances at the epicentre. The first type, with velocities of approximately 1.4 km s− 1, 1.8 km s− 1, and 1.0 km s− 1, were triggered by acoustic waves generated by the ground surface rupture induced by the earthquake. The second type, with velocities of about 0.8 km s− 1, represented another form of ionospheric disturbance induced by acoustic waves from the ground surface rupture. Thirdly, the ionospheric anomaly was most pronounced within the 90°–135° sector relative to the epicentre, corresponding to the southeast direction from the epicentre. Finally, based on the data from 15 GNSS stations at the epicentre, the coseismic deformation displacement of the earthquake was determined, with a maximum displacement of 0.24 m, and the leptokurtic slip characteristics of the earthquake were revealed.

Seasonal-diurnal features of the medium-scale traveling ionospheric disturbances characteristics in the Asian Region of Russia During years of moderate solar activity

Based on data from a network of oblique-incidence sounding radio paths at mid-latitudes in the Asian region of Russia, a high (up to 40−50%) average-daily recording probability of the medium-scale traveling ionospheric disturbances in years of moderate solar activity has been identified. The daily variation in the recording probability of these disturbances at mid-latitude radio paths in the Asian region of Russia has a pronounced seasonal dependence. For the winter season, there is a daily maximum probability, reaching 100% on some days. In the summer season, it occurs at night hours of local time at the midpoint of the corresponding radio path. The most likely reason for this is the transition from winter to summer pattern of the atmosphere zonal circulation.

Analysis of Ionospheric Disturbances Due to Cyclones in Geraldton City of Australia

Abstract A typhoon is a natural disaster that has the potential to cause damage and cause loss of life. On April 2, 2021, the tropical cyclone Seroja formed, reaching typhoon class category 3, which was characterized by a maximum wind speed of 140 km/s on April 11, 2021. Tropical cyclones reached typhoon class when the wind speed exceeded 119 km/h. Typhoon can generate Acoustic Gravity Waves which can cause Concentric Traveling Ionosphere Disturbances (CTIDs). One effort that can be made to mitigate typhoon disasters is to analyze the time when ionospheric disturbances are detected, which can be observed through changes in TEC values by utilizing GNSS technology. The propagation of the GNSS signal from the satellite to the receiver experiences a delay when passing through the ionosphere layer, which can be used to obtain the Total Electron Content (TEC) value. TEC is the number of electrons in a cylindrical vertical column with a cross-section of 1 m 2 along the line of sight. CTIDs due to typhoon Seroja were detected at around 09:00 UTC by GPS 9 at ~0.2 TECU. Interestingly, the CTIDs caused by typhoon Seroja were detected before the typhoon landed in Australia. It is hoped that additional information and variables regarding the comparison of the characteristics of ionospheric disturbances due to typhoons and earthquakes can be used to develop an early warning system for disasters in the future.

A hybrid predictive model with an error-trigger adjusting method of thermal load in super-high buildings

The precise prediction of thermal load has consistently garnered attention owing to its significant impact on energy conservation in buildings. The methodologies employed primarily concentrate on modeling within steady-state conditions, utilizing time-series data or mechanism model on fixed parameters. However, given the pronounced time-varying and multifaceted disturbance characteristics associated with building loads, current approaches exhibit constrained efficacy in addressing abrupt fluctuations in demand load and managing data noise. This limitation consequently undermines the accuracy of predictions. This paper proposes a novel hybrid model and an error-trigger adjusting strategy for predicting the thermal load in super-high buildings. The model is constructed by combining a thermodynamic model and an error cancellation model. The former, derived from an examination of the variations of material and energy in buildings, is proposed in the form of an approximate resistance-capacitance structure. The latter is developed using a wavelet threshold denoising technique, in conjunction with a convolutional neural network and a long short-term memory network. A self-adaptive state transition algorithm has been proposed, which relies on dynamically adjusting factors within the feasible region to optimize the selection of unknown parameters in the thermodynamic model. To enhance the flexibility of the hybrid model in effectively respond to the intricacies and fluctuations within the thermal conditions of buildings, an error-trigger adaptive updating strategy and a parameter calibration method based on sensitivity analysis are established. The real-world application results demonstrate the effectiveness of the presented hybrid model and the adjusting strategy.

Photovoltaic output prediction based on VMD disturbance feature extraction and WaveNet

Traditional photovoltaic (PV) forecasting methods often overlook the impact of the correlation between different power fluctuations and weather factors on short-term forecasting accuracy. To address this, this paper proposes a PV output forecasting method based on Variational Mode Decomposition (VMD) disturbance feature extraction and the WaveNet model. First, to extract different feature variations of the output and enhance the model’s ability to capture PV power fluctuation details, VMD is used to decompose the PV output time series, obtaining IMFs modes representing output disturbances and quasi-clear sky IMF modes. Then, to reveal power changes, especially the underlying patterns of disturbances and their relationship with weather factors, K-means clustering is applied to the IMF modes representing output disturbances, clustering the disturbance IMFs into different power change feature clusters. This is combined with Spearman correlation analysis of weather factors and the construction of an experimental dataset. Finally, to enhance the model’s learning ability and improve short-term output forecasting accuracy, the WaveNet model is employed during the forecasting phase. Separate WaveNet models are constructed and trained with the corresponding datasets, and the total PV output forecast is obtained by superimposing the predictions of different IMF modes. Experimental results are compared with traditional methods, demonstrating a significant improvement in forecasting accuracy, with a Mean Absolute Percentage Error (MAPE) error of 6.94%, highlighting the effectiveness of our method and providing strong technical support for the refined management and intelligent forecasting of PV energy.

Guaranteed Disturbance Compensation and Robust Fault Detection Based on Zonotopic Evaluation

ABSTRACTIn the context of model‐based fault detection, it is crucial to achieve strong robustness against disturbance and noise. However, the existing robust fault detection methods typically address disturbance and noise in a centralized manner to enhance robustness, which may cause some conservatism since the dynamic characteristics of disturbance and noise are considerably different. In addition, most of the existing model‐based fault detection method is implemented with constant thresholds, which may further introduce conservatism. In this context, this paper proposes a guaranteed disturbance compensation and robust fault detection method based on zonotopic evaluation for the discrete‐time systems subject to unknown but bounded disturbance and noise. To this end, a disturbance compensation controller is developed based on technology to obtain guaranteed control performance. Moreover, the control performances with or without disturbance compensation are analyzed based on zonotopes. By considering the disturbance dynamic characteristics, an extended fault detection observer (EFDO) is created to pursue robustness to disturbance, noise, and sensitivity to fault simultaneously. Meanwhile, a multi‐objective EFDO is devised by exploiting the index and index as the criteria within the finite‐frequency domain. Furthermore, the zonotopic residual evaluation is further deployed to generate the residual boundary, which helps to reduce the conservatism of fault detection. The superiority of the proposed method is theoretically analyzed. Simulation results also validate the effectiveness and superiority of the proposed method in disturbance compensation fault detection.

Mechanism analysis on a type of limit induced oscillation for single‐machine infinite‐bus system of PMSG with positive damping

AbstractThe mechanism of oscillations that occur in the system connected to renewable energy sources is complex, generally including negative damping oscillation, limit induced oscillation etc. Combining with the dynamic characteristics of the low‐dimensional system after limit working, this paper analyses the mechanism of a type of limit induced oscillation that occurs when the output of the DC voltage outer loop continuously touches the limit for single‐machine infinite‐bus system of permanent magnet synchronous generator with positive damping under a large disturbance. Specific study as follows: firstly, a non‐smooth state space model of single‐machine infinite‐bus system of permanent magnet synchronous generator with nonlinear state limit (clarified as a Filippov system) is established. Secondly, the small disturbance characteristics of the system are analysed when the limit does not work. Thirdly, the piecewise dynamic description of the system is analysed with the limit working, and the reason that the final contraction of the system to an eight‐dimensional manifold is explained based on mathematical derivation and physical characteristics. Finally, the characteristics of equilibrium point of the system in a low‐dimensional manifold are analysed when the limit continuously working, revealing that the existence of a pair of conjugate unstable eigenvalues in the low‐dimensional system is the reason of system oscillation.

Review of domestic inventions on methods for diagnostics of postural disorders of the musculoskal system

The development of the musculoskeletal system depends on many components of anatomically determined changes in the body, the structure of movement patterns and the mechanisms of action involved in it. Postural disorders can arise as a result of various reasons and be a source of further changes in the body, influencing the development of compensatory changes and functional transformations of the motor sphere. Diagnosis of the state of the musculoskeletal system is an urgent task, through which many somatic changes can be corrected or compensated in a timely manner. This article reviews patent documents from databases such as FIPS, Orbit, Google patents over the past 30 years. It was revealed that the study of postural disorders is carried out in four areas of study: visual assessment in a standing position; diagnostic methods using stabilometric platforms; characteristics of disturbances in the assessment of muscle electrical potentials and analysis of the kinematics of motor actions during movement. In their content aspect, these diagnostic methods are focused on the quantitative and qualitative characteristics of the location of the boundaries of the regions of bone segments, the center of gravity of the body and the parameters of its movement during motor action; assessment of electromyographic indicators of coordination of muscle efforts in static and dynamic positions; analysis of the biomechanics of movement patterns with consideration of various components of the motor act.

Internal Model‐Based Anti‐Disturbances Low‐Level Control for Drones Considering Actuator Dynamics

ABSTRACTLow‐level control plays a critical role in the overall flight performance of drones. Despite some progress, existing methods do not adequately consider the complex electromechanical characteristics of actuators and aerodynamic disturbances of propellers, which deteriorates low‐level control performance. To tackle these issues, we propose a new nonlinear low‐level controller for higher precision control. First, a high‐precision low‐level model that integrates the actuator dynamics and angular velocity dynamics is presented. Based on this model, a dynamic compensator is designed using the internal model method to handle aerodynamic disturbances. Next, a high‐gain observer is designed to estimate the actuator states without adding new sensors, and an observer‐based low‐level controller is proposed through a recursive design process. Finally, the local asymptotic stability of the closed‐loop system is analyzed. The effectiveness and superiority of the proposed method are validated through simulations and physical experiments.

Revisit compressible plane Couette and Poiseuille instability: Spectrum features of disturbances and dominant instability

Understanding the instability of compressible shear flows is of both academic interest and practical importance for predicting transition in such flows. In this paper, the linear stability of compressible plane Couette flow and Poiseuille flow in temporal mode is revisited, with emphasis on spectrum features of disturbances and dominant instability at different Mach numbers. The disturbance spectra of different discrete modes are presented, including acoustic modes (i.e., even modes II, IV, etc. and odd modes I, III, etc.) and viscous modes. The results show that as wavenumber increases, the even modes are first synchronized with the viscous branch when their phase velocities are a bit larger than zero, and subsequently synchronized with odd modes when their phase velocities coincide with each other. The synchronizations cause branching of the dispersion curves, and the even modes have several maxima of growth rate. The low-wavenumber maximum (with phase velocity close to zero) is associated with viscous instability and the higher-wavenumber maxima correspond to inviscid instability. Depending on the flow parameters, the branching topology may involve multimodes, which is different from the spectrum branching observed in hypersonic boundary layer. In compressible Couette flow, the mode-II viscous and inviscid instabilities dominate the instability at different Mach numbers. In compressible plane Poiseuille flow, multiple instability modes coexist, including the viscous Tollmien-Schlichting (TS) mode, the acoustic viscous instability modes II and IV and acoustic inviscid instability modes I and III. As Mach number increases (i.e., from incompressible to hypersonic), the mode TS, II, IV, and III would successively dominate the Poiseuille-flow instability. These results yield a comprehensive understanding of the disturbance spectrum and modal instability in compressible plane Couette and Poiseuille flows.

Active disturbance rejection control for four-wire inverters in standalone renewable resources-based microgrid — islanded microgrids ADRC-based control

This paper presents an active disturbance rejection control (ADRC) approach for three-phase four-legs voltage source inverters (FL-VSIs) in a standalone renewable energy resources (RES)-based islanded microgrid. The key purpose of the proposed approach is to improve the control robustness against load-side disturbances, power supply parameters uncertainties, and faulty operating conditions. Indeed, a notable benefit of ADRC is its ability to operate effectively without the need for precise knowledge of disturbance characteristics or accurate modeling and FL-VSI parameters. As compared with conventional PI controllers, this advanced control strategy allows improving the voltage waveforms quality and conforming to existing power quality standards and metrics while using only output voltage sensors. Extensive simulations on Matlab/Simulink software have been conducted to assess the effectiveness of the proposed approach.

Study on the acoustic disturbance characteristics of the spray flame

The axial sound field was added to the ethanol spray flame as a perturbation element to study the dynamic response and combustion characteristics. A forced acoustic field is applied to a small oscillating flame. In cases where the frequency of the external sound field matches the eigenfrequency, even small amplitude self-excited flames demonstrate significant instability. As the intensity of the sound field increases, the amplitude of pressure oscillations sharply rises, and the pressure and flame heat release oscillations are in-phase. When the sound field operates at frequencies other than the eigenfrequency, it has an inhibitory effect on the evaporation and combustion process of ethanol droplets. Consequently, intensifying the sound field leads to a reduction in both the area of the evaporation combustion zone and the axial temperature of the flame. The CO formation is influenced by both temperature and the sound field, showing a pattern of increasing and then decreasing with the increase of sound intensity. Additionally, NOx generation exhibits higher emission concentrations in low-temperature and short flames, which is more likely to prompt NOx and is not closely related to frequency.

High stability enhanced ultrasonic microfluidic structure with flexible tip coupled bubbles

Ultrasonic microfluidic technology is a technique that couples high-frequency ultrasonic excitation to microfluidic chips. To improve the issues of poor disturbance effects with flexible tip structures and the susceptibility of bubbles to thermal deformation, we propose an enhanced ultrasonic microchannel structure that couples flexible tips with bubbles aiming to improve the disturbance effects and the stability duration. Firstly, we used finite element analysis to simulate the flow field distribution characteristics of the flexible tip, the bubble, and the coupling structure and obtained the steady-state distribution characteristics of the velocity field. Next, we fabricated ultrasonic microfluidic chips based on these three structures, employing 2.8 μm polystyrene microspheres as tracers to analyze the disturbance characteristics of the flow field. Additionally, we analyzed the bubble size and growth rate within the adhering bubbles and coupling structures. Finally, we verified the applicability of the coupling structure for biological samples using human red blood cells (RBCs). Experimental results indicated that, compared to the flexible tip and adhering bubble structures, the flow field disturbance range of the coupling structure increased by 439.53% and 133.48%, respectively; the bubble growth rate reduced from 14.4% to 3.3%. The enhanced ultrasonic microfluidic structure proposed in this study shows great potential for widespread applications in micro-scale flow field disturbance and particle manipulation.

Symposium Highlight: PULMONARY LYMPHATICS HISTORY, ANATOMY, AND PATHOPHYSIOLOGY: EMERGING KNOWLEDGE AND A LOOK TO THE FUTURE

Central lymphatic disorders of the lung have not received intense investigation. Lymphatic system physiology is presented in the context of historical developments and basic lung lymphatic anatomy is reviewed followed by emerging characteristics of primary and secondary pathophysiological disturbances of lymphatic involvement in a number of pulmonary diseases including Gorham-Stout disease, pulmonary edema and infections and inflammatory conditions including lymphangioleiomyomatosis (LAM). The future includes potential molecular targeting of lymphangiogenesis or lymphatic vessels for interventional occlusion. This article is an amalgamation of presentations at the 2023 ISL International Congress of Lymphology, Genoa, Italy in a special symposium on central and regional lymphatic system in health and disease and as part of a Special Symposium on the Lymphatic system of the Heart and Lung in Health and Disease at the 26th International Congress of Lymphology meeting held in Barcelona, Spain, September 2017, which has been updated to 2024.

Comparison of depression with anxious distress and melancholic depression from the perspective of psychomotor disturbance.

In the DSM-5, it is specified that severe cases of major depressive disorder with anxious distress (ANXD) may be accompanied with motor agitation. Agitation, on the other hand, is one of the main characteristics of major depressive disorder with melancholic features (MEL). The purpose of this study was to compare ANXD and MEL in terms of psychomotor disturbance. A total of 106 patients with major depressive disorder were included in the study. Psychomotor disturbance was assessed using the CORE measure. The associations of ANXD and MEL with the CORE measure subscales of psychomotor retardation, agitation, and noninteractiveness were analyzed using multivariate logistic analysis. Retardation scores (odds ratio [OR] = 0.63, 95% confidence interval [CI] = 0.52-0.77) were associated with fewer diagnoses of ANXD, whereas agitation scores (OR = 2.23, 95% CI = 1.60-3.13) were associated with more diagnoses of ANXD. Both noninteractiveness (OR = 1.23, 95% CI = 1.06-1.42) and agitation (OR = 1.27, 95% CI = 1.02-1.58) scores were associated with increased diagnoses of MEL. Among the characteristics of psychomotor disturbance, agitation is a common feature of both ANXD and MEL, and ANXD and the agitated type of MEL may be overlapping concepts. On the other hand, ANXD is distinguished from the retarded type of MEL by its low level of retardation, whereas MEL but not ANXD is characterized by noninteractiveness.

Resistance of Australian fish communities to drought and flood: implications for climate change and adaptations

Climate change‐induced extreme weather and related drought and flood conditions are heterogeneous across space and time. The variability in location, timing, and magnitude of rainfall can alter how species respond to the drought and flood disturbances. To further complicate this matter, when droughts end they are often followed by extreme flooding, which are rarely considered as a disturbance (Humphries et al. 2024), let alone assessed with its own heterogeneity. Consequently, it is difficult to quantify impacts on ecological communities across large spatiotemporal scales without considering flood‐drought disturbance characteristics in sequence (Burton et al. 2020). We hypothesized that native organisms have evolved resistance to withstand repeated cycles of drought‐flood disturbances, and that established non‐native species have adapted to persist in novel conditions. To test this, we fit spatiotemporal models of species occurrence with local rainfall patterns as covariates in the drought and flood impacted Murray‐Darling basin in Australia during the decade long Millenium Drought, and its recovery period. During these drought conditions, river‐floodplain organisms in the Murray‐Darling became localized in refugia that limited longitudinal and lateral connectivity (Bond et al. 2008), and following flooding the same organisms were exposed to dispersal and recruitment opportunities (Humphries et al. 2020), as well as to hypoxic blackwater events that lead to the mortality of aquatic organisms (Small et al. 2014). At the basin‐scale we found that the range size of most native and non‐native fishes were highly resistant to the extreme drought and post‐flood conditions. At local scales, species richness, or detection, actually increased under drought conditions. Both findings highlight the resistance of species to climate change driven extreme weather, which opens new questions on community adaptations.

Impact of peripheral venoarterial extracorporeal membrane oxygenation support for heart failure on systemic hemodynamics and aortic blood flow

Peripheral venoarterial extracorporeal membrane oxygenation (VA-ECMO) is an advanced temporary life support system for patients with refractory cardiogenic shock or severe cardiopulmonary failure. However, the reperfusion of oxygenated blood into the arterial system via a peripheral artery will induce substantial hemodynamic changes that might contribute to the development of complications. In this study, we developed two types of computational models to quantify the hemodynamic changes induced by the peripheral VA-ECMO support for systolic heart failure (HF) of various severities. One was a lumped-parameter model used for exploring the optimal workload of extracorporeal membrane oxygenation (ECMO) for a specific severity of HF, whereas the other one was a geometrical multiscale model capable of simulating the detailed flow field in the aorta while accounting for the hemodynamic coupling of VA-ECMO with the cardiovascular system. Numerical results revealed that the retrograde transmission of ECMO-supplied blood flow toward the heart not only considerably inhibited cardiac output but also induced marked flow disturbance and regionally high or oscillatory wall shear stress (WSS) in the aorta that may increase the risk of thrombosis and vascular dysfunction. The major characteristics of flow disturbance and spatial distribution of abnormal WSS were codetermined by the cardiac function and workload of ECMO while less influenced by the morphology of aorta. These findings emphasized the importance of tuning the workload of ECMO based on patient-specific cardiac function to balance the amount of blood oxygenation support by ECMO against the risk of complications associated with hemodynamic abnormalities.

Spatio-temporal features of ionospheric disturbances resulting from March 2023 geomagnetic storm: Comparisons with March 2015 St. Patrick’s Day storm

This study explores the ionospheric disturbances induced by the March 2023 geomagnetic storm, offering insights into the complex interplay between space weather events and the Earth’s upper atmosphere. In this regard, data from ionospheric maps (global and regional electron contents) and topside plasma density (provided by the Swarm satellites) have been used. Furthermore, the findings are compared with those of the March 2015 St. Patrick’s Day storm of solar cycle 24, which exhibited notably similar onset conditions. The Global Electron Content (GEC) displays substantial positive surges in the African, Pacific, and American sectors, with a notable enhancement in the American sector on March 24, 2023. During the recovery phase (March-23 storm), negative storm effects are observed across all longitudinal sectors, with greater intensity at low-latitudes compared to mid-latitudes. Moreover, the study highlights discrepancies in positive storm effects when compared to the St. Patrick’s Day storm. During the March-2023, there was no positive storm effect observed in the pacific mid-latitude regions. This longitudinal difference in occurrence of positive storm may be attributed to potential influences from variations in the z-component of the interplanetary magnetic field and energy inputs into the magnetosphere. A super fountain effect is observed exclusively in the American sectors during both storms, exhibiting a noticeable hemispheric asymmetry. The non-uniform planetary distribution of disturbed thermospheric winds likely played a major role in the ionospheric asymmetry in the American region during the 2023 event.

Estimation of abnormal states in shunt capacitor banks using transient disturbance feature extraction

Shunt capacitor banks are essential for reactive power compensation, ensuring voltage stability, and reducing system losses. These banks consist of multiple units with components in series and parallel. A few component failures do not immediately affect the safe operation of the capacitor bank, but component breakdown can lead to voltage redistribution. Under combined factors such as system overvoltage and equipment aging, and others can trigger an avalanche effect causing capacitor breakdown, resulting in significant safety accident risks. Practical operation experience shows that partial component breakdown generates many transient disturbance signals. Quantitative analysis of these signals can detect capacitor bank anomalies early. This paper proposes the quantitative extraction of transient disturbance characteristics using the Prony algorithm and estimates the phase and number of capacitors that break down to judge capacitor anomalies. The simulation part verifies the theoretical analysis and detection algorithm’s correctness through numerical simulations and PSCAD (Power Systems Computer Aided Design) electromagnetic transient simulations. The numerical simulations consider different signal lengths, noise levels, attenuation coefficients, and oscillation frequencies. In the PSCAD simulation environment, verification models are built under varying sampling frequencies, numbers of breakdown components, signal lengths, and signal-to-noise ratios. These simulation results verify the accuracy of the detection algorithm under different conditions.

A study on the wake structure of an ascending submersible with silk flexible appendages using continuous wavelet transform and dynamic mode decomposition

This study proposed a new method for installing silk flexible appendages on the surface of the submersible to modify the wake structure of ascending submersibles, and explored a method of drag reduction of ascending submersible. A comparative analysis of the flow structure of submersibles with varying appendage lengths was conducted to understand the disturbance characteristics of the wake flow structure of submersible, and the high-speed particle image velocimetry (PIV) measurement experiment was conducted at a Reynolds number of 6456. Analysis of the time-averaged flow field showed that the flexible appendages could disrupt the two large-scale vortices in the wake of the submersibles during the sailing process, but this ability diminished with increasing appendage length. Furthermore, continuous wavelet transform (CWT) and dynamic mode decomposition (DMD) were used to analyze the mechanism behind this phenomenon. The analysis results showed that flexible appendages based on CWT had an inhibitory effect on large-scale flow, and this effect gradually decreased with increasing appendage length. The results indicate that the flexible appendages can disrupt the wake vortex structure, reduce vortex energy, and facilitate the transition from large-scale vortex to small-scale vortex. Additionally, excessive disturbance is generated in the wake region when the flexible appendage is too long, hindering the shedding of small-scale vortices and resulting in an increase.