Source Of Disturbance Research Articles

The Phase Structure of Wave Disturbances Excited by a Pulsating Source at the Interface of a Liquid Flow of Finite Depth and an Ice Sheet

The floating ice sheet determines the dynamic interaction between the ocean and the atmosphere, affects the dynamics of the sea surface and subsurface waters, since the ice sheet and the entire mass of liquid under it participate in the general vertical movement. The paper investigates the phase structure of wave fields arising at the interface between ice and a flow of homogeneous liquid of finite thickness when flowing around a localized pulsating source of disturbances. The ice sheet is modeled by a thin elastic plate, the deformations of which are small, and the plate is physically linear. An integral representation of the solution is obtained, and the results of calculations of dispersion dependencies and phase patterns for various parameters of wave generation are presented. It is shown that the main parameters determining the characteristics of the amplitude-phase structure of wave disturbances of the ice sheet surface are ice thickness, flow velocity, and pulsation frequency. Numerical calculations demonstrate that when the flow velocities, ice thickness, and frequency change, there is a noticeable qualitative restructuring of the phase patterns of the excited long-range wave fields at the ice-liquid interface.

Reducing low-frequency noise radiation from a concrete box girder bridge using acoustic short circuits

Low-frequency noise (20–200 Hz) radiated from concrete box girder bridges on urban viaduct railway lines is a significant source of disturbance to nearby residents. Many researchers have investigated methods which can be used to effectively reduce this bridge noise. Currently, most of the methods are based on the principles of vibration isolation and/or absorption. This paper, after modelling and analysing the contributions of various parts of a concrete box girder bridge to the total noise radiated from the bridge, presents a study on the potential in bridge noise control of making holes to create acoustic short circuits on the bridge wings. It is found that by this means the bridge noise can be reduced by up to 6.8 dB at standard-specified measurement points. Additionally, a 3dB-effectiveness distance ratio design method for acoustic short-circuiting is proposed, which effectively reduces bridge noise and achieves stable noise reduction outcomes.

Near‐Real‐Time Identification of the Source of Ionospheric Disturbances

Near‐Real‐Time Identification of the Source of Ionospheric Disturbances

Calculation of Single and Multiple Low Reynolds Number Free Jets with a Lattice-Boltzmann Method

Numerical calculations of low-Reynolds-number freejets with a Lattice Boltzmann Method are presented. The calculated-time-averaged axial velocity of a round jet with Re=1030 matches experimental data, including the length of transition from laminar to turbulent flow. Special care was needed for the inlet conditions in order to reproduce the vena contracta phenomenon. The results for round jets with Re=1000/1500/2000 show good agreement with Finite Difference Method calculations from the literature. In principle, there is a strong sensitivity to the inlet conditions, suggesting a need in future experimental work to measure in detail the velocity profiles and turbulence quantities at the nozzle outlet. The application of turbulence at the inflow boundary of the calculation domain is often used to emulate sources of disturbances in experiments. The present study demonstrates the need to investigate the impact of turbulence level and length scale at inlet independent of each other. Finally, the calculation for a bundle of nine jets with a square inlet led to the finding that the velocity decay of the central jet is maximal when the spacing between the jets is ca. one jet diameter.

On space–time diversity in shock train self-excited oscillation mode during wide-range evolution in a scramjet isolator

The shock train self-excited oscillation can induce combustor instabilities and reduce engine margin. In a dual-mode scramjet, the shock train undergoes a complete evolution process, exhibiting structural changes closely tied to this inherent unsteadiness. This study aims to elucidate the space–time diversity in shock train self-excited oscillation mode and the underlying mechanisms during wide-range evolution. The experimental investigations were conducted at Ma = 1.95, capturing the complete evolution of the shock train. The results indicate the evolution can be categorized into three regimes based on structural characteristics. In regime I, the shock region gradually forms, followed by the occurrence of the mixing region in regime II. Regime III corresponds to inlet unstart. In regime II, isolator outlet pressure fluctuations exhibit higher frequency and lower amplitude compared to regime I, while the shock motion demonstrates lower frequency and higher amplitude. The shock train behaves in a large-scale, low-frequency (1.53 times the duct height, 10 Hz) unsteady motion in regime II, posing a potential threat to engine operation. Coherence and phase analysis reveal the disturbance source originates downstream. Proper orthogonal decomposition modal analysis shows two oscillation modes: low-frequency components correspond to shock motion, and high-frequency components correspond to pressure fluctuations across the entire pseudoshock. The propagating of downstream disturbance differs between the two regimes. In regime I, the shock train exhibits rigid-body motion synchronously. In regime II, the relative motion between each shock wave and the cumulative effect of pressure disturbance lead to frequency decay upstream, amplifying the shock train motion.

Characteristic analysis of India-Burma trough events and its impact on winter precipitation in South and East Asia: Based on objective identification

Abstract During the boreal winter, the India-Burma trough (IBT), a shortwave trough system primarily positioned over the northern Bay of Bengal, exerts a significant synoptic scale variation and impact on precipitation in South and East Asia. This study utilizes the 6-hourly ERA5 dataset to objectively identify and track 714 IBT events from 1981 to 2019. On average, IBT occurred about 54.7 days per year, with an average of 18.3 events annually and lasting around 2.5 days. IBT events are classified into two types: local and eastward-moving. Local IBTs manifest in the middle and lower troposphere with a vertical temperature structure of warm-over-cold, whereas the signals of the eastward-moving IBTs extend from the lower to the upper troposphere, exhibiting cold anomalies vertically. The impacts on winter precipitation in South and East Asia differ significantly between these two IBT types. Local IBTs are primarily linked with the eastward propagation of wave disturbances along the subtropical westerly jet, while eastward-moving IBTs are associated with robust disturbance sources from mid-high latitudes and jointly modulated by the consequent eastward propagation of Rossby wave trains along northern and southern branches of the westerly jet streams. Precipitation anomalies during local IBTs are typically positive (negative) in the Indochina Peninsula and southwestern China (Indian Peninsula), whereas eastward-moving IBTs correlate with more intense and widespread precipitation in South and East Asia, with a pronounced band of anomalies from the Indochina Peninsula to southern China.

Acoustic detection of Unmanned Aerial Vehicles in flight with respect to the signal-to-noise ratio using machine learning

Nowadays, unmanned Aerial vehicles (UAV) are more and more commonly found in the world for a variety of activities. It has become an important task to detect and classify them in order to manage their potential malicious intentions. Current detection and classification methods mostly rely on feature extraction and the use of artificial neural networks that can be heavily impacted by the signal-to-noise ratio (SNR). The approach proposed aims to solve a two-class problem (presence or absence of an UAV) by extracting information on the content of the acoustic source, and then presenting it as input to a neural network. The features used are strongly inspired by the harmonic sound emitted by UAV. Attention is also given on the SNR of the scene. Indeed, various disturbing sources such as trains, helicopters or footsteps are involved from an open library. These signals are added to our recordings of UAVs in flight by tuning their amplitude to obtain different SNRs. The aim is to establish the performance of the detection system as a function of the SNR of the scene.

A preliminary analysis of long-term self-reported sleep disturbance attributed to wind turbines and modelled outdoor nightly average wind turbine sound pressure level

The World Health Organization (WHO) Environmental Noise Guidelines provide source-based annual average nighttime sound pressure level (Lnight) recommendations. For non-aircraft sources the recommendation for self-reported high sleep disturbance (HSD) is the Lnight associated with an absolute prevalence of 3%HSD. The Guideline Development Group (GDG) reported that no Lnight recommendation could be provided for wind turbines because the evidence available was inadequate. In the current study, outdoor wind turbine Lnight at each dwelling was calculated following international standards. Questionnaires were completed between May and September 2013 by individuals aged 18-79y (606 males, 632 females), randomly selected from households 0.25 to 11.22 kilometers from operational wind turbines. Calculated Lnight ranged from <25 dB(A) to 46 dB(A). When the source of sleep disturbance was unspecified, the mean prevalence of HSD was 13.3% overall and unrelated to Lnight (p = 0.53). As Lnight increased, the prevalence of identifying wind turbines as one of the causes of sleep disturbance increased from 0% below 25 dB(A) to 3.8% (95% CI 1.9% to 7.4%) between 40-46 dB(A) (p = 0.01) . The WHO's 3%HSD threshold was estimated to occur for wind turbine Lnight between 38-39 dB(A).

Motivating Mechanisms of the South Asian Jet Wave Train by Disturbances over the North Atlantic in Winter

Abstract This study investigated the motivation of the South Asian jet wave train (SAJW) and its underlying mechanism, by distinguishing different evolutions of disturbance sources over the North Atlantic. The disturbance sources propagate along the SAJW toward the western North Pacific in the propagating cases, while they are constrained over the North Atlantic and Europe in the interrupted cases. The possible motivating mechanisms are disclosed in the perspectives of energy dispersion and background potential vorticity gradient (PVG) affecting energy attraction. In the propagating cases, wave energy propagates eastward over the North Atlantic and converges into the Mediterranean Sea and Middle East, leading to the amplification and development of the wave train. The enhancement of PVG over south Europe–Mediterranean Sea is a key factor attracting such eastward propagation, which is associated with the positive PV anomaly over north Europe driven by the diabatic heating of precipitation. In the interrupted cases, energy dispersion is more divergent over the North Atlantic because of the weaker PVG, resulting in the failure of the SAJW excitement. The impacts of the SAJW on the temperature and precipitation along its path are evident, with the modulated snow depth agreeing more with temperature rather than precipitation except over the Tibetan Plateau. Hence, understanding the motivating mechanism of the SAJW is essential for improving weather forecasts over subtropical Eurasia by using the disturbances over the North Atlantic.

Decoupling method of self-gravity compensation based on spherical multipole expansion for space gravitational wave detectors

In space gravitational wave detection missions, the gravity and its gradients produced by the spacecraft on the two Test Masses (TMs) are commonly referred to as the Self-Gravity(SG). It is an important source of TM disturbances in gravitational wave detection and other drag-free space missions and will affect the TM acceleration noise in many ways. The SG can be reduced by adding Balance Masses (BMs). But for typical space gravitational wave detectors, in which the sensitive axes of the two TMs are at an angle of 60°, the couplings of different SG components of two TMs make the gravity compensation process complicated in practice, which is normally an iterative process. This paper analyses the correspondence between the SG components of the two TMs and the spherical harmonics of different orders, and proposes a compensation method based on spherical multipole expansion. This method allows independent design of the BMs for most of the main SG components, without couplings and iterations. To verify this method, a self-gravity compensation simulation is carried out by using a demonstrating spacecraft structural model for TianQin gravitational wave detection mission. Three sets of BMs are designed on the outer surface of the inertial sensor vacuum chamber, to compensate for the two linear accelerations and one linear gradient that exceed the requirements. The results show that the SG components after compensation are two orders of magnitude lower than the initial level, and all the components meet the preliminary requirements of TianQin mission. This study could provide reference for the engineering design and development of the spacecraft and inertial sensor payload for space gravitational wave detection missions.

Evaluation of water environment quality in a typical wetland on the Qinghai-Tibet Plateau using positive matrix factorization and self-organizing map

The Qinghai-Tibet Plateau (QTP), the world's largest plateau, harbors rich lake resources but is ecologically fragile. Vulnerable river ecosystems in these areas face significant threats from environmental and anthropogenic pressures. Thus, comprehensive water quality monitoring is essential prior to conservation efforts. This study focuses on the Selin Co International Wetland in Tibet, a model of natural wetland ecosystems. We employed methods including water quality assessment, source apportionment, and clustering analysis to evaluate the water environment. Results from the Water Quality Index (WQI) indicate overall good water quality; however, parameters such as COD, DO, TN, TP, and As require monitoring for potential exceedance. Positive Matrix Factorization (PMF) analysis reveals that the primary sources of substances are identified as natural sources (37.17%), animal disturbance sources (32.93%), and anthropogenic activities (22.31%). The results of the water source analysis using the PMF and the cluster analysis based on the self-organizing map (SOM) indicate that natural and geographical environmental factors are the primary determinants of water quality, with minimal influence from human activities. This research emphasizes the importance of these natural influences, providing a scientific foundation for the protection and management of wetlands in the QTP, which is critical for ensuring regional water resource security.

Joint probabilistic modeling approach for harmonic and three-phase unbalanced disturbance sources

Harmonics and three-phase imbalance are two common disturbances in power systems that interact with and affect each other, leading to more complex impacts on power system performance. To comprehensively and accurately analyze the distribution and interaction mechanisms of harmonics and three-phase imbalance, this study investigated the joint emission level of harmonic and three-phase unbalanced disturbance sources (H-TU-DS). This paper proposes a joint probabilistic emission level modeling approach. The power, harmonic, and three-phase unbalanced data of H-TU-DS are multidimensional, and the feature dataset is filtered by calculating multiple correlation coefficients to achieve dimensionality reduction without losing data information. Considering the different operating characteristics of the H-TU-DS, an improved fuzzy C-means (FCM) algorithm is applied to classify operating conditions, enabling a comprehensive and accurate analysis of the joint emission level. Based on the nonparametric kernel density function, joint probability modeling of H-TU-DS is performed using an adaptive bandwidth improvement method, effectively enhancing the accuracy of the modeling process. Finally, the effectiveness and accuracy of the proposed methods for feature dataset filtering, operating condition classification, and joint probability modeling are demonstrated through comparisons with both simulated and actual data. The proposed model facilitates the prediction and assessment of the impact of H-TU-DS on power quality after grid connection, enabling the effective prevention of power-quality problems through advanced treatment.

Mathematical Nonlinear Graph Theory Topology Layer Model for Photoelectric Tracking System

The performance of the photoelectric tracking system mainly depends on the tracking accuracy. In order to achieve the purpose of high precision tracking, controlling the power dragging device, the main component of the photoelectric tracking system, is the main means to achieve this purpose. In order to improve the tracking speed and accuracy of photoelectric tracking systems, the author proposed a mathematical nonlinear graph theory topology layer model for photoelectric tracking systems. The topology layer model and the motion node servo mechanism model of the photoelectric tracking system are studied, and the two-stage disturbance sources that affect the tracking stability are analyzed. The results show that the interference estimation error range designed by the author reaches 0.003 through comparison, it can be seen that the estimation error designed by the author is significantly smaller than the ESO estimation error, and the buffeting is small. Through comparison, it can be concluded that the estimation error of the algorithm and the disturbance observer designed by the author are significantly smaller than the estimation error of ESO, and the buffeting is small, and they have strong compensation ability for the disturbance of different frequencies. The interference observer can quickly and accurately estimate the interference and prove its stability. The effectiveness of the proposed observer and disturbance observer is fully demonstrated. The finite time integrated site selection mode disturbance observer (F-ISMDOB) is designed to quickly estimate and compensate for equivalent interference, and effectively improves the anti-interference performance of the system structure layer.

No evidence of mutations associated with anticoagulant resistance in gene Vkorc1 in brown and black rats from Barcelona

Synanthropic rodents such as the brown rat (Rattus norvegicus) and black rat (Rattus rattus) are a source of disturbance in urban areas and the focus of control programs. Control measures often rely on anticoagulant rodenticides, but their broad use is compromised by the emergence of resistance. Here we studied the prevalence of anticoagulant resistance genotypes in the Vkorc1 gene in rats in the metropolitan area of Barcelona. In this area, part of the management practices to control brown rats include anticoagulant rodenticide use, but rodenticides with different active ingredients are used in rotation. Brown rats were sampled from the sewage system during two periods: from December 2016 to November 2017 when difenacoum and brodifacoum were used, and from August 2021 to July 2022 when bromadiolone was used. Because black rats have just recently been detected in Barcelona, we only studied them during the latter sampling period, with samples obtained from a control action carried out in a green urban area. Exon 3 of the Vkorc1 gene was characterized in both species, while exon 1 was additionally analyzed in black rats. Synonymous mutations, not resulting in amino-acid changes, were found in both exons, indicating no evidence of anticoagulant resistance in the rats of Barcelona. This finding indicates that the current rodent management plan in Barcelona, which involves anticoagulant rotation for brown rats and the use of life capture traps in specific situations for black rats, has helped to prevent the emergence of resistance to anticoagulant rodenticides in rats in Barcelona. Future actions should aim to diversify the control measures included in the rodent management plan.

Green’s Tensor of BIOT’s Equations by Stationary Oscillations

Various mathematical models of deformable solids mechanics are used in the study of seismic processes in the earth's crust. The processes of waves propagation are most studied in elastic media. But these models do not take into account many real properties of the ambient array. These are, for example, the presence of groundwater, which complicates the construction and operation of surface and underground structures, affect the magnitude and distribution of stresses. Models, which take into account the water saturation form the earth's crust structures, the presence of gas bubbles, etc., are multi-component medium. A variety of multicomponent media, the complexity of the processes associated with their deformation, lead to a large difference in the methods of analysis and modelling used in the solution of wave problems. In this paper the processes of wave propagation in a two-component Biot medium under the action of periodic forces of various forms are considered. Using the Fourier transform of generalized functions, fundamental solutions are constructed - the Green's tensor of the Biot equations and its properties are studied. This tensor describes the process of propagation of harmonic waves of a fixed frequency in spaces of dimension N = 1,2,3 under the action of power sources concentrated at the origin of coordinates, described by a singular delta function. On its basis, generalized solutions of these equations are constructed under the action of various sources of periodic disturbances, which are described by both regular and singular generalized functions. For regularly acting forces, integral representations of solutions are given, which can be used to calculate the stress-strain state of a porous water-saturated medium

Light Pollution: To What Extent We are Concerned About

Light pollution is now a global problem with a catastrophic impact on human health, environment, ecology, plant life cycle, and animals. Some nations have enacted laws aimed at limiting light pollution. Unfortunately, there is no such regulation in Bangladesh, and if there is, it is not being enforced. In this study, an attempt has been made to investigate people's perceptions of light pollution in Bangladesh. This study collected three hundred forty samples using a convenient sampling technique. Descriptive statistics were employed to analyze the data. Among the sources, the respondents identified commercial light, fireworks, light from the market, and light from billboards as the major sources of light pollution. Besides light from the neighbor's house, own domestic light, events light, and light from home were assumed to be the significant disturbing light sources. Findings showed that most respondents agreed with the hazardous impact of light pollution on human health, animals, the environment, and the ecosystem. Among the possible solutions, respondents recommended developing awareness, limiting light at night-time, cutting off unnecessary lights, and reducing the frequent use of decorative lights. Results conclude that people have a sound understanding and good perception of light pollution. So the associate agents can take appropriate steps toward light pollution control.

The Behavioral Responses of Geoffroy’s Spider Monkeys to Drone Flights

Drones are increasingly used for monitoring wildlife, and it is therefore necessary to evaluate their impact on animal behavior. According to the landscape of fear framework, animals assess and respond to perceived risks in their environment by adjusting their behavior and space use to avoid potential threats. Understanding how drones influence risk perception is thus crucial to avoid generating stress and altering the animal’s natural behavior. Geoffroy’s spider monkeys (Ateles geoffroyi) are endangered arboreal primates, but information on their distribution and abundance is scarce throughout their geographical distribution. Drones can aid to rapidly obtain such information, but data of their impact on the monkeys are needed to design surveys that minimize disturbance (i.e., any interference or modification of the natural behavior of the monkeys caused by the presence and operation of drones). Here, we evaluated whether drone flights influenced the following spider monkey behaviors: agonistic displays, self-scratching, whinny vocalizations, feeding, resting, social interactions, and moving. We also evaluated the effect of three flight parameters, flight height (35, 50 m above ground level), speed (2, 4 m/s), and distance to the drone (“close”, “medium”, and “far”) on spider monkey behavior and examined whether repeated exposure to drones resulted in tolerance (i.e., lack of a behavioral response). We found that drone flights influenced only agonistic displays and resting and that the only flight parameter affecting behaviors was the distance between the monkeys and the drone. We found that spider monkeys developed a tolerance to drone flights only for agonistic displays. Based on our results, we suggest that spider monkeys do not perceive drone flights as major sources of disturbance (such as predators) in the short term, and that drone monitoring can be a viable option to study this species if adequate flight protocols are implemented.

Electromagnetic Disturbance Source Modeling Scheme and its Interference Estimation of Medium–Low-Speed Maglev Train Interior

Magnetic fields from the linear motor, suspended electromagnet, and collector shoe arcing are the three main electromagnetic interference (EMI) sources for the medium–low-speed maglev train interior. Under their collective influence, the field intensity may exceed the standard threshold, consequently affecting the operational reliability of the train system. However, in previous studies, the EMI sources were analyzed separately, and studies regarding the influence of factors such as the motor states and the train body (TB) shielding against arcing EMI were lacking. Therefore, in this paper, all three EMI source are considered, and an EM disturbance source modeling scheme is proposed using the COMSOL software platform. Its effectiveness is demonstrated and the train interior magnetic field is analyzed, primarily with respect to prior simulations and tests. Subsequent analyses enable a comparative assessment of the individual contributions of each EMI source to the overall interference, considering the EMI control standards. The influence of other EMI source parameters, such as different motor states, is analyzed, and the potential for modifying the material composition and structural thickness of the TB is explored to determine the appropriate EMI inhibition strategy.

A Method for Locating Wideband Oscillation Disturbance Sources in Power Systems by Integrating TimesNet and Autoformer

A Method for Locating Wideband Oscillation Disturbance Sources in Power Systems by Integrating TimesNet and Autoformer

Influence of nature reserve road traffic disturbance on soil carbon

PurposeRoad traffic has long been recognized as a considerable source of ecological disturbance, compromising the integrity of natural ecosystems from their pristine baseline state. Pollutant deposition from vehicular emissions significantly contributes to environmental contamination, while associated human activities exacerbate ecosystem disruptions. In designated conservation zones, including nature reserves, land-use practices such as pastoralism and agriculture are subject to regulation. Nevertheless, the influence of road traffic on ecosystem structure and processes, particularly concerning carbon (C) sequestration and its spatial heterogeneity, warrants further research. This consideration is critically relevant in the understanding the intricate C fractions and their dynamic interplay with environmental factors. Materials and methodsIn this study, we meticulously selected four distinct locations along a principal roadway within a national reserve. For each site, experimental measuring 2 m * 2 m were established at intervals of 2 m, 10 m, 20 m, 30 m, 40 m, and 50 m from the road's edge. Observational data were accrued during the peak of the vegetative growth seasons in August of both 2020 and 2021. Within each plot, soil and cut-ring samples were procured for comprehensive analysis of soil carbon fractions (Total Carbon, TC, g/kg; Carbon Density, g/m2; Readily Oxidizable Carbon, ROC, g/kg; Dissolved Organic Carbon, DOC, mg/kg; Microbial Biomass Carbon, MBC, mg/kg; Cumulative Mineralization Carbon, CMC, mg(CO2-C)*(kg*soil)−1; Soil Inorganic Carbon, SIC, g/kg), chemical properties (pH; Electrical Conductivity, EC, us/cm; Soil Organic Matter, SOM), and physical properties (Soil Water, SW, %; Bulk Density, BD, g/cm3; area conditions). Vegetation metrics, including above-ground biomass (AGB) and below-ground biomass (BGB), species composition, height, and coverage, were meticulously documented. The four sites were replicated, culminating in 24 uniformly oriented plots to mitigate wind influence. ResultsOur analysis revealed that C stock, as determined by TC and C density increased with distance from the road edge, reaching a peak at approximately 30 m (TC: 19.43 g/kg, C density: 39.26 g/m2, SOM: 27.57 g/kg), followed by a subsequent decline. At the 30 m distance, there was a 60.6 %, 41.2 %, and 38.7 % enhancement in TC, C density, and SOM, respectively, compared to the 2 m distance, and a 23.9 %, 25.9 %, and 19.8 % increase relative to the 50 m distance. Levels of DOC, MBC, and CMC exhibited an upward trend from the road edge to 50 m, suggesting more favorable microbiological conditions in less disturbed locales. SEM demonstrated that SIC is directly influenced by BGB (β = −0.31), pH (β = 0.46), and labile C components (β = 0.56), culminating in a reduction of total C storage (total effect, β = −0.28). The dynamic changes of soil C stocks were primarily explained directly by soil labile C (β = 0.475, p < 0.001), and indirectly by vegetation biomass (β = 0.460) and pH (β = −0.570), and were closely correlated with ROC (0.54, the highest eigenvalue among Labile_C). ConclusionThe findings suggest that the buffering effect of the roadside in these nature reserves up to a distance of 30 m has an signficant impact on C stock, and that C losses attributable to biochemical processes and laible soil C fractions may contribute to diminished C levels in less disturbed zones 50 m away from the road. Our findings also substantiate the moderate disturbance hypothesis, particularly in the milieu of road traffic within the Hulunbuir Nature Reserve, Mongolia. A moderate distance from roadways enhances soil C storage compared to areas near the road or undisturbed natural landscapes.