Disturbance Frequency Research Articles

A Transient Damping Improvement Strategy for Enhancing Grid-Connected Active Power Response Performance of VSG

The given power and grid frequency disturbances can cause transient oscillations and steady-state deviations in the output power of a virtual synchronous generator (VSG), which can be effectively addressed by adding transient damping. However, this approach may result in significant power overshoot. This article proposes an improved VSG control strategy based on transient electromagnetic power feedback compensation and a small-signal model reduction scheme. Firstly, the grid-connected active closed-loop small-signal models of typical VSG control and transient damping VSG control are established, respectively. The transient oscillation suppression mechanism of active power is revealed through root locus and frequency response analyses, and the power overshoot characteristics of the two control strategies are analysed by combining them with the system of zero points. Secondly, the active transient feedback compensation method and the small-signal model reduction design method are introduced in detail. Finally, comparative analysis experiments are conducted using the Matlab/Simulink and hardware-in-the-loop experimental platform. It is verified that the proposed control strategy can suppress transient oscillations in active power, prevent steady-state deviations, and effectively mitigate the power overshoot problem of the system.

Interannual variation of summer southwest monsoon rainfall over the monsoon core regions of the eastern Bay of Bengal and its relationship with oceans

The study looked at how summer monsoon rainfall in the eastern Bay of Bengal area changes from year to year due to Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO). Study used rainfall data and sea surface temperature data to see these variations. It's found that during ENSO positive phase, rainfall decreased in the eastern coastal region of the Bay of Bengal but increased in the northern Indo-Myanmar region. The opposite happened during ENSO negative phase. The study used a special analysis method called EOF and Morlet wavelet power-spectrum analysis to look for important patterns in the rainfall data and did correlation analysis to understand what causes abnormal rainfall in these regions. The study also found that the local convection and water vapor flux during ENSO positive phase are related to the anomalous rainfall in the Monsoon Core region. Rainfall is made stronger by the unusual anticyclone circulation in the upper troposphere. A strong/weak Mainland Indochina southwest monsoon (MSwM) in the positive or negative phase of ENSO can bring excess/less moisture to wet/dry the local southwest summer rainfall. In northern Indo-Myanmar, the anomalous rainfall is not only relied on the intensity of the MSwM but also the frequency of western disturbances also influences the regional rainfall, and further study need to develop.

Prevalence and risk factors of training-related abdominal injuries: A multicenter survey study

PurposeThis study aims to identify the prevalence and risk factors of military training-related abdominal injuries and help plan and conduct training properly. MethodsThis questionnaire survey study was conducted from October 2021 to May 2022 among military personnel from 6 military units and 8 military medical centers and participants’ medical records were consulted to identify the training-related abdominal injuries. All the military personnel who ever participated in military training were included. Those who refused to participate in this study or provided an incomplete questionnaire were excluded. The questionnaire collected demographic information, type of abdominal injury, frequency, training subjects, triggers, treatment, and training disturbance. Chi-square test and t-test were used to compare baseline information. Univariate and multivariate regression analyses were used to explore the risk factors associated with military training-related abdominal injuries. ResultsA total of 3058 participants were involved in this study, among which 1797 (58.8%) had suffered training-related abdominal injuries (the mean age was 24.3 years and the service time was 5.6 years), while 1261 (41.2%) had no training-related abdominal injuries (the mean age was 23.1 years and the service time was 4.3 years). There were 546 injured patients (30.4%) suspended the training and 84 (4.6%) needed to be referred to higher-level hospitals. The most common triggers included inadequate warm-up, fatigue, and intense training. The training subjects with the most abdominal injuries were long-distance running (589, 32.8%). Civil servants had the highest rate of abdominal trauma (17.1%). Age ≥ 25 years, military service ≥ 3 years, poor sleep status, and previous abdominal history were independent risk factors for training-related abdominal injury. ConclusionMore than half of the military personnel have suffered military training-related abdominal injuries. Inadequate warm-up, fatigue, and high training intensity are the most common inducing factors. Scientific and proper training should be conducted according to the factors causing abdominal injuries.

Composite Disturbance Suppression Strategy for Current Loop of HSPMSG Based on High Frequency Disturbance Observer

Composite Disturbance Suppression Strategy for Current Loop of HSPMSG Based on High Frequency Disturbance Observer

Визначення предикторів стійких порушень серцевого ритму у військовослужбовців із тяжким перебігом міокардиту

The aim – to study heart rhythm and conduction disturbances in different localization and distribution of myocardial lesions in combatants with severe myocarditis based on the results of a 6-month follow-up.Materials and methods. 46 male military personnel with a severe course of acute myocarditis (AM) with a reduced ejection fraction (EF) of the left ventricle (LV) (≤ 40 %) with an average age of (35,1±2,4) years were examined. Examinations were carried out in the 1st month after the onset of symptoms of myocarditis and after 6 months of observation. The diagnosis of myocarditis and the severe course of the disease were established on the basis of the Recommendations for the diagnosis and treatment of myocarditis of the All-Ukrainian Association of Cardiologists of Ukraine. All patients underwent for 24-hour ECG monitoring with analysis of the frequency and spectrum of rhythm and conduction disturbances and cardiac magnetic resonance (CMR) imaging with contrast analysis of the topography of the lesion and counting the number of LV segments affected by inflammatory changes and LV segments with the presence of late gadolinium enhancement (LGE).Results and discussion. When comparing the results of heart MRI with the data of daily ECG monitoring, a clear association of the presence of frequent ventricular extrasystoles (VE) and paroxysms of non-sustained ventricular tachycardia (NSVT) with the localization of LGE in the interventricular septum (IS) was established – among patients with LGE lesions at the onset of AM more than in a third (37.0 %) had frequent VE, and NSVT paroxysms, which increase the risk of developing life-threatening ventricular arrhythmias, were detected in 25,9 % of cases. After 6 months of observation in the presence of LGE in the IS, the frequency of detection of frequent VE and NSVT paroxysms was also significantly higher compared to other localization of the lesion and amounted to 20,0 and 13,3 %, respectively. With the help of correlation analysis, an associative relationship was revealed between the presence of LGE in the IS and the presence of frequent VE and NSVT paroxysms in the debut of myocarditis – r=0.73 (р<0.01) and r=0.66 (р<0,01) respectively, and also after 6 months of observation – r=0.65 (р<0.01) and r=0.59 (р<0.05), respectively. According to the results of the multivariate regression analysis, predictors of frequent VE persistence after 6 months were: LVEF ≤30 %; LV end-diastolic volume index ≥105 ml/m2; presence of inflammatory changes in ≥5.0 LV segments; presence of LGE in ≥4.0 LV segments and its presence in the IS, determined in the 1st month from the onset of the disease. The predictors NSVT paroxysms persistence after 6 months were the same factors with the exception of LV EF, and, according to the value of the β coefficient (β=1.302; p<0.001), the most significant contribution was the presence of LGE in the IS.Conclusions. In combatants with severe myocarditis, the presence of late gadolinium enhancement in the interventricular septum is an additional risk factor for the persistence of frequent ventricular extrasystoles and paroxysms of non-sustained ventricular tachycardia during 6 months, while the presence of late gadolinium enhancement in the posterior and lateral walls of the left ventricle has no reliable relationship with the presence of rhythm and conduction disorders. On the basis of multivariate regression analysis, predictors of frequent ventricular extrasystoles and paroxysms of non-sustained ventricular tachycardia persistence were established in combatants with myocarditis.

Optimization research on control strategies for photovoltaic energy storage systems considering multi-mode operation

In this paper, a selective input/output strategy is proposed for improving the life of photovoltaic energy storage (PV-storage) virtual synchronous generator (VSG) caused by random load interference, which can sharply reduce costs of storage device. The strategy consists of two operating modes and a power coordination control method for the VSGs. Firstly, a selective VSG input strategy is proposed based on the magnitude of disturbances, a method of offline solving model equation is used for determine the VSG input time. An online method is used for matching the disturbance frequency variations, which enables a selective VSG startup method, allowing the grid to prioritize the utilization of the generator's physical inertia. Secondly, a dynamic VSG exit strategy is developed based on dynamic frequency characteristics to prevent secondary oscillations in the frequency recovery phase of the PV-storage VSG following grid disturbances. This strategy is crucial as grid variations may affect energy storage lifespan and reduce frequency recovery speed. Finally, the proposed approach is validated for correctness and effectiveness through computer simulations and semi-physical experiments using the NI-PXI + LabVIEW platform. Through the above optimization and research, the selective start of VSG is realized, the energy storage life is improved, the capacity of charge and discharge cycles is reduced by 37.82 % compared with the strategy without investment and withdrawal, and the life loss in the secondary charge and discharge process of PV-storage VSG is avoided, which is conducive to frequency recovery.

Identifying mechanistic links between sleep disturbance and binge eating: the role of depressed mood

ABSTRACT Global sleep disturbance is robustly linked with a subjective sense of loss-of-control over eating (LOC). Depressed mood has been proposed as a mechanism to explain the bi-directional relationship between sleep disturbance and LOC eating. The current study evaluated whether sleep disturbance indirectly affects LOC eating via depressed mood. Adults seeking treatment for a DSM-5 binge-spectrum eating disorder (e.g. bulimia nervosa, binge-eating disorder) were recruited (n = 79) and asked to complete self-report questionnaires assessing sleep disturbance and depression, and a semi-structured interview assessing LOC eating. Tests of indirect effects evaluated the effect of depressed mood on the association between global sleep disturbance and LOC frequency covarying for BMI and parent study. A significant indirect effect of depressed mood on the association between global sleep disturbance and frequency of LOC eating was identified (Est = 1.519, S.E. = 0.859, p = .033). The indirect effect of depressed mood on the association between sleep disturbance and LOC eating may indicate that depressed mood serves as a mechanistic link between sleep disturbance and LOC eating. The findings offer preliminary support for adjunctive treatments targeting both sleep disturbance and depressed mood for LOC eating. Future research should explore these pathways in a larger clinical sample.

Adaptive complex coefficient‐filtered extended states observer type three‐phase enhanced phase‐locked loop

AbstractThis paper proposes an adaptive complex coefficient filtered (CCF) full order extended state observer (ESO) type three phase enhanced phase locked loop (EPLL), which is employed in matrix reactance frequency converter (MRFC) for rotating vectors measurement estimation. EPLL phase detector was analysed first to track not only the rad frequency and transient phase, but also the amplitude of the rotating vectors. Full order ESO can filter out more high frequency disturbance, so it can track frequency and phase more accurately than proportion and integration algorithm. CCF modules were analysed in theory to attenuate the disturbance within two times of the EPLL's cut‐off frequency. The whole adaptive CCF‐ESO‐EPLL design, including stability and parameter tuning were then interpreted. The proposed CCF‐ESO‐EPLL adapts the estimated frequency with CCF to attenuate the MRFC switching non‐linear disturbance as well as unknown disturbance by the full order ESO. The MRFC topology necessary measured vectors, as well as the input side reactive power adjustment capacity, were discussed. The theoretical conclusion has been verified on a MRFC prototype. The proposed CCF‐ESO‐EPLL has less parameter tuning, less computation resource requirement, better steady and dynamic performance, and outstanding disturbance robustness.

Mitochondrial DNA damage, repair and copy number dynamics of Sclerophytum sp. (Anthozoa: Octocorallia) in response to short-term abiotic oxidative stress

As a consequence of global climate change, the increasing frequency of environmental disturbances and surplus oxidative stress experienced by coral reefs will likely contribute to phase shifts from stony to soft corals. Mitochondrial response to reactive oxygen species (ROS) -induced oxidative damage appears pivotal for bioenergetic adaptation and recovery during environmental stress, partly governed by mitochondrial DNA copy number. Unlike other animals, octocorals possess unique mitogenomes with an intrinsic DNA mismatch repair gene, the mtMutS, that is likely to have a role in mitochondrial response and mtDNA damage recovery. Yet, there is a general lack of stress response studies on octocorals from a mitochondrial perspective. Here we evaluate the mitochondrial response of the octocoral Sclerophytum sp. subjected to acute elevated temperature and low pH, and its putative competence to reverse oxidative mtDNA damage caused by exogenous agents like hydrogen peroxide (H2O2). Temporal changes in mtDNA copy number and mtDNA damage and recovery were monitored. Both short-term thermal and low pH stress applied independently instigated mtDNA damage and affected mtDNA copy number differently, while mtMutS gene was significantly upregulated during low pH stress. mtDNA damage caused by H2O2 insult was observed to be promptly reversed in Sclerophytum sp., and a higher mtDNA copy number was associated with lower mtDNA damage. These findings provide insights into the potential role of mtMutS gene in conferring resilience to octocorals, the relevance of mtDNA copy number, and emphasize the importance of better understanding the mitochondrial stress response of cnidarians in the context of climate change.

Modeling of a six-degree-of-freedom magnetic levitation platform actuated by noncontact Lorentz forces

In this study, the modeling of a six-degree-of-freedom (DOF) magnetic levitation platform actuated by noncontact Lorentz forces was analyzed. First, an analytic model of the actuator forces was studied, and the magnetic flux density in the working gap of the actuators was established using the Image Method, Ampere molecular hypothesis, and Biot–Savart law. The dynamics model of the floater actuated by the actuators was then built using the Newton–Euler method. Moreover, the double-pendulum chaotic nonlinear system of the hoisted floater was simplified as a single-DOF system, in which the interaction effects between two DOFs were considered. Furthermore, modeling of the platform control system was performed, which included an acceleration measuring unit with six uniaxial accelerometers, a position measuring unit with three two-dimensional PSDs, and a control unit that decouples the six-DOF control. Finally, an experimental setup was built to perform ground tests on the platform. The results verified the platform modeling; translational and rotational positioning accuracies were approximately 5 μm and 40 μrad at the six DOFs, respectively, and the vibrational suppression efficiencies were greater than 90% for low frequency disturbances. Moreover, Kalman estimators and disturbance observers were introduced into the controller to estimate the movement of the floater and observe the direct disturbance. Simulation testing demonstrated a significant improvement in the vibration-suppression performance of the platform.

Optimizing active distribution microgrids with multi-terminal soft open point and hybrid hydrogen storage systems for enhanced frequency stability

The recent increased interest in active distribution microgrids has complicated the process of reaching stable generation with the presence of distributed generators (DGs). These challenges can be handled by employing multi-terminal soft open points (SOPs), which can further boost system performance compared to the conventional two-terminal SOP, especially with present system disturbances. At the same time, hydrogen energy storage has drawn increased attraction to strengthen power grid stability and flexibility. This paper uses a hybrid-based energy storage device that employs an electrolyzer and fuel cell means with a hydrogen tank to absorb or generate power through multi-terminal SOP based on desired grid requirements. This work also offers a novel implementation of a hybrid jellyfish search and particle swarm optimization (HJPSO) applied to model predictive controllers (MPCs) to provide a solution regarding frequency control issues for multiple microgrids comprised of hybrid micro-turbines and renewable generators with the presence of storage devices. Furthermore, different forms of nonlinearity and actual data measurements for the implemented renewable generators are incorporated to attain further realistic analysis. The transient behavior of the studied microgrid is substantially augmented via the suggested control scheme. Referring to the modern grid codes and standards, the frequency operation limits in a specific range. This requirement has been preserved throughout the entire simulations, including uncertainty analysis, assessing the capabilities of multi-terminal SOP in providing frequency disturbance ride-through for the operating active hybrid distribution microgrid under various operating conditions.

Evaluation of Urban Resilience and Its Influencing Factors: A Case Study of the Yichang–Jingzhou–Jingmen–Enshi Urban Agglomeration in China

With the increasing frequency of various uncertainties and disturbances faced by urban systems, urban resilience is one of the vital components of the sustainability of modern cities. An indicator system is constructed to measure the resilience levels of the Yichang–Jingzhou–Jingmen–Enshi (YJJE) urban agglomeration during 2010–2023 based on four domains—economy, ecology, society, and infrastructure. This paper analyzes the spatiotemporal differentiation of resilience in YJJE in conjunction with the entropy weight method, Getis–Ord Gi* model, and robustness testing. Then, the factor contribution model is used to discern key driving elements of urban resilience. Finally, the CA-Markov model is implemented to predict urban resilience in 2030. The results reveal that the values of resilience in YJJE increase at a rate of 3.25%/a and continue to rise, with the differences among cities narrowing over the examined period. Furthermore, the urban resilience exhibits a significant spatially heterogeneity distribution, with Xiling, Wujiagang, Xiaoting, Yidu, Zhijiang, Dianjun, Dangyang, Yuan’an, Yiling, and Duodao being the high-value agglomerations of urban resilience, and Hefeng, Jianli, Shishou, and Wufeng being the low-value agglomerations of urban resilience. The marked heterogeneity of resilience in the YJJE urban agglomeration reflects the disparity in economic progress across the study area. The total amount of urban social retail, financial expenditure per capita, GDP per capita, park green space area, urban disposable income per capita, and number of buses per 10,000 people surface as the key influencing factors in relation to urban resilience. Finally, the levels of resilience among cities within YJJE will reach the medium level or higher than medium level in 2030. Xiling, Wujiagang, Xiaoting, Zhijiang, Dianjun, Dangyang, and Yuan’an will remain significant hot spots of urban resilience, while Jianli will remain a significant cold spot. In a nutshell, this paper can provide scientific references and policy recommendations for policymakers, urban planners, and researchers on the aspects of urban resilience and sustainable city.

Sleep and lucid dreaming in adolescent athletes and non-athletes

ABSTRACT During lucid dreaming (LD), dreamers are aware of experiencing a dream and may consciously influence its content. This study used an online questionnaire to investigate the LD frequency and applications in 193 adolescent athletes and non-athletes (17.40 ± 2.09 years; 46% athletes, 54% controls). Given the critical role that sleep plays in adolescent health, development, and performance, associations of LD with various sleep parameters were also explored. LD is prominent in adolescents (67.4% experienced it at least once, 30.0% once a month or more, 12.9% at least once a week), but similar in terms of frequency and uses between athletes and non-athletes. A higher proportion of those who practiced sports/dance during LD reported improved waking self-efficacy (57.1%) over sport performance (42.9%). There was no indication that chronotype preference may influence LD nor that LD may be detrimental to adolescent sleep. Athletes and controls had similar sleep durations, daytime sleepiness, and sleep disturbances frequency, but athletes reported higher sleep quality. Despite, on average, meeting the minimum sleep recommendation guidelines for their age, a relatively large proportion of adolescents did not attain sufficient sleep, particularly on weeknights (47.4% 14–17 years; 20.0% 18–21 years), suggesting that restricted sleep remains prevalent in adolescent populations.

Seal dynamics of supercritical carbon dioxide turbine with the uncertain rotor nonlinear motion

The actual rotor motion and seal dynamics are nonlinear and uncertain. The uncertain effects include the seal flow and the rotor system parameters. While the influence of system parameters makes it more difficult to accurately predict the seal dynamics. A rotor nonlinear whirling model was established to achieve the synchronous solution of rotor motion and seal simulation. The coupling effect between rotor system parameters and seal aerodynamic performance was adopted. The actual seal dynamics for SCO2 turbine were obtained and evaluated by the numerical finite difference method. In the rotor nonlinear whirling model, the rotor has the uncertain continuous free motion. The influence of the system main parameters, such as elastic recovery stiffness and unbalanced mass force, on seal dynamics is revealed. And the dynamic coefficients beyond the artificial specific disturbance frequency are shown. The results show that the rotor nonlinear whirling can better predict the seal dynamics. The rotation speed, elastic recovery stiffness and unbalanced mass eccentricity have different significant effects on seal dynamics.

Associations between masturbation frequency, anxiety, and sleep disturbances during the COVID-19 era.

The COVID-19 pandemic has markedly influenced people's lifestyle and sexual behaviors, including masturbation patterns. This study delved into how masturbation frequency could impact anxiety levels, sleep quality, and somatic symptoms post-masturbation among Chinese adults during this period. From December 2022 to January 2023, we conducted a cross-sectional survey, gathering data via WenJuanXing, a leading online survey platform in China. This platform facilitated the recruitment of a diverse cohort, spanning various age groups and geographical locations. Masturbation frequency among participants was subjectively categorized into three levels: 'lesser' (a few times over the past year), 'moderate' (once to three times a month), and 'greater' (weekly to almost daily). To assess anxiety levels and sleep quality, we employed the Generalized Anxiety Disorder 7-item (GAD-7) scale and the Pittsburgh Sleep Quality Index (PSQI), respectively. Among 1500 participants, we received 1423 valid responses. Among these, 65% (n = 930) reported engaging in masturbation in the past year, of whom 87.5% reported subjectively experiencing various levels of fatigue post-masturbation. These 930 responses were subsequently analyzed in-depth (e.g., non-parametric test and pathway analysis), with ages ranging from 18 to 54 years (mean age = 30.5, SD = 7.42). Notably, our findings indicate that participants with greater masturbation frequency exhibited higher anxiety levels [GAD-7 median score: 6 (lesser) vs. 4 (moderate) vs. 8 (greater), p < 0.001, Cohen's f = 0.41] and poorer sleep quality [PSQI median score: 5 (lesser) vs. 4 (moderate) vs. 7 (greater), p < 0.001, Cohen's f = 0.46]. A rough positive correlation between masturbation frequency and PSQI score was also observed (β = 0.16, p < 0.001). These results suggest potential mental and sleep benefits at moderate frequencies, especially in contrast to greater frequencies. However, the cross-sectional design and subjective categorization of masturbation frequency in our study limit our ability to draw definitive causal conclusions. These limitations highlight the need for future longitudinal research employing more precise categorizations of masturbation behavior, such as frequency, to delve deeper into these relationships and understand their underlying mechanisms.

Sleep Disturbances and Co-sleeping in Italian Children and Adolescents with Autism Spectrum Disorder.

The current study aimed (1) to provide an analysis of the frequency and prevalence of sleep disturbances in a large Italian sample of children and adolescents with ASD, detecting specific predictors of the presence/absence of sleep disorders, (2) to examine the phenomenon of co-sleeping within a subgroup of participants with ASD. A total of 242 children and adolescents with ASD (194 males, mean age 5.03 ± 3.15years) were included. After the diagnostic procedure, caregivers were requested to complete the Sleep Disturbance Scale for Children (SDSC) to assess sleep disorders among participants. The presence of co-sleeping was investigated in a subgroup of 146 children and adolescents with ASD. An elevated or clinically relevant global score for sleep disorders (≥ 60) was found in 33% of participants. The most prevalent sleep disorder in our group was related to difficulties with sleep onset and sleep maintenance (~ 41% of cases). Sleep disturbances were predicted by higher intelligence quotient (IQ)/developmental quotient (DQ), increased internalizing problems, and elevated parental stress. The subgroup of participants engaged in co-sleeping (N = 87) were younger and had lower IQ/DQ scores, reduced adaptive functioning, and diminished psychological wellbeing than the non-co-sleeping group. Our findings are consistent with the current literature highlighting that insomnia is the most widespread sleep problem associated with ASD. The relationship between IQ/DQ and sleep alterations is a crucial topic that deserves additional research. Future studies should assess sleep by objective measures such as EEG topography to better understand the mechanisms underlying sleep alterations in this neurodevelopmental disorder.

Stabilizing Large-Scale Electric Power Grids with Adaptive Inertia

The stability of ac power grids relies on ancillary services that mitigate frequency fluctuations. The electromechanical inertia of large synchronous generators is currently the only resource to absorb frequency disturbances on subsecond time scales. Replacing standard thermal power plants with inertialess new renewable sources of energy (NREs) therefore jeopardizes grid stability against, e.g., sudden power-generation losses. To guarantee system stability and compensate the lack of electromechanical inertia in grids with large penetrations of NREs, virtual synchronous generators, which emulate conventional generators, have been proposed. Here, we propose a novel control scheme for virtual synchronous generators, where the provided inertia is large at short times—thereby absorbing faults as efficiently as conventional generators—but decreases over a tunable time scale to prevent coherent frequency oscillations from setting in. We evaluate the performance of this adaptive-inertia scheme under sudden power losses in large-scale transmission grids. We find that it systematically outperforms conventional electromechanical inertia and that it is more stable than previously suggested schemes. Numerical simulations show how a quasioptimal geographical distribution of adaptive-inertia devices not only absorbs local faults efficiently but also significantly increases the damping of interarea oscillations. Our results show that the proposed adaptive-inertia control scheme is an excellent solution to strengthen grid stability in future low-inertia power grids with large penetrations of NREs. Published by the American Physical Society 2024

An improved derivative‐based phase‐locked loop for single‐phase grid synchronization under abnormal grid conditions

SummaryGenerating a quadrature signal in a single‐phase system using a second‐order generalized integrator (SOGI) requires accurate frequency information. The standard SOGI phase‐locked loop (PLL) includes frequency feedback to the SOGI. However, during grid abnormalities such as voltage sag/swell and phase angle jumps, the SOGI‐PLL faces frequency disturbances that propagate to the phase detector (PD) and affects the quadrature signal generator (QSG). Furthermore, the SOGI‐PLL having two loops dependent on each other creates loop coupling phenomena; either a change in phase or frequency affects each other. SOGI‐PLL is tuning sensitive, as the SOGI block has a gain that needs to be adjusted, increases the complexity, and affects the performance of the system. There is a trade‐off between SOGI gain and PLL parameters that needs to be considered for adequate parameter design to provide accurate grid synchronization while maintaining the stability of the system. To attain better performance, researchers have proposed derivative‐based PLL (DPLL). The conventional DPLL faces challenges to noise and harmonics amplification. This paper presents an improved DPLL for single‐phase grid synchronization under adverse grid conditions. The improved derivative‐based PLL (IDPLL) comprises two improved derivative‐based quadrature signal generator (IDQSG) blocks to extract the phase‐error information for accurately estimating phase and frequency. The detailed mathematical modeling and bode plot for the IDQSG and IDPLL are presented. The proposed IDQSG eliminates the requirement of gain tuning, hence reducing complexity. Moreover, there is no interdependent loop in the IDPLL, which significantly improves the dynamic performance. A hardware setup is developed to evaluate the performance of the system in real‐time. The experimental results are obtained using an field programmable gate array (FPGA)‐based controller.

On the dependence of the thermal module of elasticity of a two-component magnetic fluid on frequency, concentration and magnetic field

Purpose. Study of the dependence of the thermal modulus of elasticity of a two-component magnetic fluid on the magnitude of the magnetic field strength, the frequency of external disturbance and the volumetric concentration of magnetic particles.Method. The research method is based on the kinetic theory of liquid systems. Based on previously constructed kinetic equations for one-particle and two-particle distribution functions and a microscopic expression for the heat flux vector, an explicit dynamic expression for the thermal modulus of elasticity of magnetic fluids is obtained. In fast processes in liquids, heat transfer occurs in waves and their propagation is similar to the propagation of second sound in helium II. The thermal modulus of elasticity in liquids appears at high frequencies and ensures the propagation of second sound. The expression for the thermal modulus of elasticity consists of potential and kinetic parts, taking into account structural and translational relaxation processes, respectively. To study the thermoelastic properties of magnetic fluids, appropriate expressions of potential interaction energies were selected for each subsystem, allowing for numerical calculations.Results. Numerical calculations of the frequency and concentration dependence of the dynamic thermal modulus of elasticity in the presence of an external magnetic field in a kerosene-based magnetic fluid were carried out. The calculation results show that an increase in the influence of external disturbances leads to a nonlinear increase in the thermal modulus of elasticity in the magnetic fluid. An increase in the volume concentration of magnetic particles and an increase in the magnetic field strength also led to a nonlinear increase in the thermal modulus of elasticity in the magnetic fluid.Conclusion. It has been established that, due to taking into account translational and structural relaxation processes, the region of frequency dispersion of the thermal elastic modulus is wide. Numerical calculations carried out at different values of the external magnetic field and the volume concentration of magnetic particles showed that although an increase in the magnetic field and concentration of magnetic particles leads to an increase in the thermal modulus of elasticity, their increase does not affect the change in the frequency dispersion region.

Prevalence and Associated Risk Factors of Insomnia Among Adults in Riyadh, Saudi Arabia.

Background Insomnia is a common sleep disorder with significant effects on physical and mental health. This study aimed to document the prevalence of insomnia and its associated risk factors among adults in Riyadh, Saudi Arabia. Materials and methods A cross-sectional study was conducted in Riyadh using the Sleep Condition Indicator Questionnaire (SCIQ). Data were collected from 548 participants. The inclusion criteria encompassed adults aged 18 and above living in Riyadh, Saudi Arabia. Information on sociodemographic characteristics, medical history, and sleep patterns was gathered through a translated eight-itemSCIQ (score ≤16=insomnia). Statistical analysis involved descriptive and inferential statistics using IBM SPSS Statistics for Windows, Version 27.0 (Released 2020; IBM Corp., Armonk, New York, United States). Results The findings revealed a significant prevalence of insomnia, affecting 219 individuals (40%). Insomnia was significantly associated with the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria, including difficulty initiating or maintaining sleep, frequency of sleep disturbances, significant distress, and duration of sleep disturbances (p<0.001 for each). The highest prevalence of insomnia was observed in the 40-60-year age group (n=91, 45.7%, p=0.014), among smokers (n=27, 60%, p=0.0063), and among obese individuals (n=20, 54.1%, p=0.035). Additionally, insomnia was strongly associated with anxiety (n=49, 66.2%, p<0.001), depression (n=27, 54%, p=0.033), and hypertension (n=24, 58.5%, p=0.011). Conclusion This study highlighted the high prevalence of insomnia among adults in Riyadh, particularly among older adults, smokers, and those with chronic health conditions. These findings underscore the need for targeted interventions to address insomnia and its associated risk factors. Future research should focus on longitudinal studies to establish causal relationships and explore the impacts of lifestyle and genetic factors on insomnia.