Search Results (123)

A flywheel energy storage system (FESS) is a device that employs a high-speed rotating flywheel for energy storage, where the motor is a core component enabling the energy conversion. Since the motor rotor is integrated onto the flywheel rotor (FR), when the FESS operates, the vortex motion of the FR causes misalignment between the motor rotor and stator, and the resulting unbalanced magnetic pull (UMP) will induce changes in the vibration characteristics of the FR. This paper presents a permanent magnet synchronous motor (PMSM) designed for a FESS and analyzes the variation pattern of the UMP induced by rotor eccentricity in this motor utilizing the finite element method. Furthermore, the UMP is equivalently modeled using the motor stiffness, and a dynamic model of an active magnetically suspended rigid flywheel rotor that considers the UMP in the motor is established. In this study, the motor position offset ratio β is defined to quantify the axial distance between the motor position and the FR mass center. This paper analyzes the variation law of the vibration characteristics of the FR with the magnitudes of the UMP and the motor position offset ratio β using numerical calculations. Finally, the correctness of the calculated results is verified using experimental testing. This investigation demonstrates that the value of UMP fluctuates as the rotor’s rotation angle increases, while its average value exhibits a linear increasing trend with the growth in rotor eccentricity. As UMP and β increase, the first- and second-order critical speeds of FR exhibit a clear decreasing trend. Meanwhile, variations in these two factors also exert different influences on the vibration amplitude induced by the mass imbalance response of the FR. Therefore, when designing an active magnetically levitated flywheel energy storage system, the influence of motor parameters on the vibration characteristics of FR should be taken into consideration. Full article

Background and Objectives: Rhinosinusitis contributes to the development of sleep-disordered breathing (SDB) by causing nasal obstruction and airway inflammation; however, the extent to which treatment improves these conditions remains unclear. To address this, this study systematically evaluated the impact of rhinosinusitis-directed therapy on nasal symptoms, endoscopic findings, and sleep-related respiratory parameters. Materials and Methods: Methodologically, this systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. A comprehensive search was conducted across the PubMed, Medline, Web of Science, Science Direct, and Google scholar databases. Specifically, studies reporting pre- and post-treatment outcomes in patients with rhinosinusitis were included. Due to substantial clinical and methodological heterogeneity among the included studies, a quantitative meta-analysis was not performed; instead, findings were synthesized narratively. Results: Ultimately, fifteen studies met the inclusion criteria and demonstrated consistent improvements in sleep-related outcomes following the treatment of rhinosinusitis. Across the surgical and medical interventions, reductions in apnea-hypopnea index (AHI) and improvement in endoscopic findings were frequently reported. For instance, functional endoscopic sinus surgery (FESS) produced notable enhancements in sleep quality, daytime sleepiness, and sinonasal symptom scores in several studies, while biologic therapy and medical management also showed benefit in reducing nasal obstruction, rhinorrhea, and inflammatory markers. Conclusions: The available evidence suggests that rhinosinusitis treatment may be associated with improvements in measures of sleep-disordered breathing (SDB) and mucosal inflammation, although subjective nasal symptom outcomes were more variable across studies. Consequently, targeted sinonasal therapy may play an important role in reducing SDB burden, particularly in patients with inflammatory airway compromise. Full article

Flywheel energy storage systems impose high demands on the mechanical properties and structural integrity of rotors, particularly in high-speed applications. This study focuses on the numerical analysis of gravity casting of a steel rotor manufactured from low alloy 34CrMo4 steel, with the aim of identifying critical regions related to molten metal flow, solidification behaviour and shrinkage defect formation. Numerical simulations were calculated using a MAGMASOFT^® 5.5 software environment based on the finite volume method and included both mold filling and subsequent solidification and cooling stages. Flow stability, temperature field distribution and solidification characteristics were researched thoroughly. The results showed that optimization of the gating and feeding system lowered porosity under 2% within the casting and relocated shrinkage defects to the risers. At the same time, solidification directionality was improved and the Hot Spot value was reduced. From the perspective of casting quality, the proposed design represents the most suitable solution, despite a lower metal utilization rate. The analysed casting forms the structural body of a hybrid flywheel rotor intended for the subsequent integration of high-density tungsten segments. Full article

Flywheel energy storage systems (FESSs) offer millisecond-level response speed, making them highly suitable for providing system inertia/frequency support in emergency grid scenarios. However, the FESSs often have limited energy capacity due to their high capacity cost, which necessitates a comprehensive consideration between remaining stored energy and sustained support capability. Thus, this paper proposes a virtual synchronous generator (VSG) control strategy based on a multi-time-step model predictive control (MPC) that considering flywheel’s state of charge (SOC), which provides both emergency frequency support and autonomous flywheel energy recovery within a single integrated framework. First, a multi-time-step MPC with the objective function aiming for both fast frequency response and smooth power output is introduced to compensate the reference power generated by the VSG strategy. Second, an SOC-adaptive frequency weight function is designed and incorporated into the objective function to balance the frequency deviation and the inertia/frequency support duration. Furthermore, an SOC self-recovery strategy is developed, allowing the flywheel to autonomously adjust its SOC to the desired range when the FESS is not participating in frequency regulation. Finally, the proposed strategy is verified through comprehensive simulations on various scenarios, demonstrating that it can efficiently and rapidly meet the frequency regulation demands when the SOC is sufficient, as well as achieve the balances between the frequency regulation performance and the support continuity when the SOC is insufficient. Full article

Chronic rhinosinusitis (CRS) constitutes a multicausal inflammatory disease of the nose and paranasal sinuses, often associated with olfactory dysfunction (OD), a symptom that significantly impacts patients’ quality of life. OD in CRS was traditionally thought to be related to mechanical obstruction of the olfactory cleft, but is now considered to be multifactorial, involving conductive, inflammatory, and sensorineural mechanisms as well. Type-2 inflammatory response (high interleukins IL-4, IL-5, IL-13), eosinophilia, and increased IgE are involved in epithelial damage, impaired neurogenesis, and persistent olfactory loss, especially in chronic rhinosinusitis with nasal polyps (CRSwNP). In addition, peripheral chronic inflammation may also play a role in central neural remodeling, which may potentially affect olfactory function. Objective psychophysical testing is necessary to accurately assess olfactory function because self-reports may lack reliability. Management strategies aim at reducing inflammation and restoring sinonasal ventilation. First-line therapy with intranasal corticosteroids and short courses of systemic corticosteroids may be useful for symptomatic relief. Biologic agents directed against type-2 inflammation have demonstrated significant benefits in selected cases. Functional Endoscopic Sinus Surgery (FESS) plays an important role in the treatment of refractory CRS to restore the airflow and to improve the delivery of topical drugs. Olfactory outcomes following surgery, however, are variable and often incomplete, reflecting underlying inflammation and neuroepithelial damage. Disease recurrence, especially in type-2–driven CRS, affects long-term outcomes, underscoring the necessity to incorporate surgery in an individualized, endotype-informed treatment strategy. Full article

This paper presents a comparative analysis of Flywheel Energy Storage Systems (FESS) employing Permanent Magnet Synchronous Machines (PMSMs) and AC Brushless DC (AC-BLDC) machines for fast and efficient frequency regulation. The study examines their electromechanical behavior during the key operational stages of charging, standby, and discharging, with a focus on mitigating inrush current and enhancing overall system efficiency. MATLAB/Simulink models were developed to evaluate machine dynamics, electromagnetic behavior, and harmonic distortion during their operation. The results show that electromagnetic effects, particularly inrush current, commutation harmonics, and inverter limitations, significantly influence torque smoothness, efficiency, and overall system performance. PMSMs demonstrate superior torque quality, lower Total Harmonic Distortion (THD), and more stable energy conversion under Field-oriented Control (FOC), making it well suited for high-performance FESS applications. In contrast, the AC-BLDC machine exhibits higher torque ripple and elevated THD due to six-step commutation but offers a simpler drive topology and cost advantages. The findings offer practical insights for selecting machines and controllers in high-speed FESS designs and emphasize the importance of mitigating transient electromagnetic effects to enhance efficiency and reliability in modern grid support applications. Improved modeling incorporating magnetic saturation, frequency-dependent iron losses, and inverter constraints is essential for accurate performance prediction. Future work includes Hardware-In-the-Loop (HIL), Power-HIL validation, and DlgSILENT PowerFactory co-simulation to confirm dynamic performance under grid-connected operation. Full article

The increasing penetration of inverter-based renewable energy sources has significantly reduced system inertia, leading to faster frequency deviations in low-inertia power systems. This paper proposes an asynchronous distributed model predictive control (AD-MPC) strategy to coordinate flywheel energy storage systems (FESSs) and battery energy storage systems (BESSs) for enhanced frequency stability in low-inertia power grids. A modified IEEE 39-bus system integrating a 3 MW wind energy conversion system (WECS), a 2 MW PV solar unit, and an electric vehicle (EV) load emulator unit was simulated to evaluate the system performance of the controller under a 30% increase in load disturbance. The results show that the coordinated FESS–BESS operation using the proposed AD-MPC controller achieves faster frequency recovery and reduces frequency deviation by 4% compared to single storage configurations. The proposed approach demonstrates that the high-speed FESS can provide a rapid inertial response, while the BESS delivers primary frequency support, offering a promising solution for maintaining dynamic stability in future renewable-dominated power systems. Full article

To address the DC-link voltage control issue in flywheel energy storage systems (FESSs), a DC-link voltage control strategy using a capacitor-energy-based super-twisting sliding mode controller (CE-STSMC), integrated with a disturbance observer, is proposed in this article. First, an exponential term is incorporated into the STSMC algorithm to enhance its convergence rate. Then, the improved STSMC is employed as the voltage-loop controller to mitigate the insufficient anti-disturbance capability of conventional control methods. To improve the system robustness, a nonlinear disturbance observer (NDOB) is developed to estimate the load power. The estimated disturbance is further feedforward-compensated into the improved STSMC controller. Finally, experiments are carried out on a 2.2 kW FESS prototype under DC-link voltage step and sudden load-change conditions, which demonstrates the effectiveness and superiority of the proposed control strategy. Full article

To address DC-link voltage fluctuation, active-power imbalance between the machine side and the grid side, and double-frequency distortion in the grid current of a flywheel energy storage system (FESS) under symmetrical and asymmetrical voltage sag faults, this paper proposes a coordinated control strategy for the machine-side and grid-side converters to enhance low-voltage ride-through (LVRT) capability. Taking the DC-side energy imbalance as the coordination criterion, the machine-side converter adopts an online active-current-command reconstruction method based on cascaded limiting of DC-link voltage deviation. Under reactive-power-priority support and constrained active-power output on the grid side, the FESS can actively adjust its active-current command according to the DC-side energy state, thereby suppressing DC-link overvoltage/undervoltage and restoring the power balance between the machine side and the grid side. On the grid side, an improved linear active disturbance rejection control (LADRC) is introduced into the current inner loop. By optimizing the structure of the extended state observer, the observation and compensation capability for double-frequency disturbances is enhanced, thus improving grid-current quality under asymmetrical faults. In this way, power rebalancing between the machine side and the grid side, DC-link voltage stabilization, and grid-current disturbance suppression are incorporated into a unified coordinated control framework. Hardware-in-the-loop experimental results show that the proposed strategy can maintain DC-link voltage stability during both symmetrical and asymmetrical voltage sags, while keeping the maximum grid-current total harmonic distortion (THD) below 0.13%. Under asymmetrical voltage sag, the improved LADRC reduces the maximum interphase peak-current deviation from approximately 52 A under conventional PI control to 4.57 A, corresponding to a reduction of about 91.2%. These results indicate that the proposed strategy can effectively enhance DC-link voltage stabilization and improve grid-current quality during faults. Full article

Background and Objectives: Controlled hypotension during functional endoscopic sinus surgery (FESS) improves surgical field visibility but may pose a risk of subclinical cerebral hypoperfusion. Serum S100Β and neuron-specific enolase (NSE) are established biomarkers of glial and neuronal injury and may reflect perioperative neuroprotection associated with different anesthetic regimens. This study evaluated the effect of four anesthetic protocols on perioperative brain biomarker release during FESS. Materials and Methods: In this single-center, randomized, controlled trial, 88 adult patients (ASA I–III) undergoing FESS under moderately controlled hypotension (mean arterial pressure < 55 mmHg) were allocated to one of four groups: propofol–remifentanil, propofol–remifentanil with ketamine–magnesium, sevoflurane–remifentanil, or sevoflurane–remifentanil with ketamine–magnesium. Serum S100Β and NSE concentrations were measured at three timepoints: early intraoperatively, during hypotension, and at the end of surgery. Biomarker data were analyzed using nested ANOVA and linear mixed-effects models adjusted for relevant covariates. Secondary outcomes included recovery characteristics, surgical field quality, bleeding scores, and perioperative hemodynamics. Results: Baseline demographic and perioperative characteristics were comparable across groups. The group receiving sevoflurane–remifentanil combined with ketamine–magnesium showed the lowest S100B levels (p = 0.01 compared to the propofol–remifentanil group; p = 0.04 compared to the sevoflurane–remifentanil group). Additionally, NSE concentrations were markedly lower in both sevoflurane groups (sevoflurane–remifentanil and sevoflurane–remifentanil plus ketamine–magnesium) compared to the propofol–remifentanil group (p = 0.003 and p = 0.007, respectively). No intergroup differences were observed at baseline and surgical field quality, bleeding, and hemodynamic parameters did not differ significantly among groups. Recovery and extubation times were shortest with propofol–remifentanil, whereas ketamine–magnesium prolonged emergence. Conclusions: Anesthetic technique significantly influences perioperative brain biomarker release during FESS. Sevoflurane-based regimens, with or without ketamine–magnesium, demonstrate more favorable neurobiological profiles under controlled hypotension, although propofol-based anesthesia offers faster recovery. Full article

Against the backdrop of the global clean energy transition, this paper addresses the volatility of renewable energy like wind and PV power, focusing on magnetic suspended flywheel energy storage systems (FESS). It expounds FESS’s structure (flywheel body, magnetic suspension bearings, etc.) and working principles (charging, energy retention, discharging) and studies key technologies including rotor material selection, magnetic bearing classification/modeling, motor coordination, and heat dissipation. Challenges such as high material costs and magnetic bearing stability are pointed out, with prospects for developing FESS toward higher performance, lower cost, and multi-scenario integration to support the clean transformation of power systems. Full article

Functional endoscopic sinus surgery (FESS) is the gold-standard surgical treatment for chronic rhinosinusitis (CRS) not responding to appropriate medical therapy. Identifying the natural maxillary ostium (NMO) during FESS is often challenging due to the lack of definitive landmarks. To aid in the identification of the NMO, we describe and assess the feasibility of using a new surgical landmark, the infra-bullar groove (IBG), and evaluate its visibility and reproducibility during FESS. Methods: Video recordings of 41 maxillary antrostomy procedures in patients with varying severity of CRS were reviewed. Surgeons of different experience levels assessed IBG visibility and its termination at the NMO. Results: In video recordings where the ethmoid bulla was preserved during uncinectomy, the IBG and its connection to the NMO were successfully identified by all reviewers in 100% of analyzable cases. The mean time to IBG identification did not significantly differ among surgeons. The IBG was consistently more pronounced in cases with well-pneumatized bullae. Conclusions: Under controlled surgical conditions where the ethmoid bulla is preserved during uncinectomy, the IBG demonstrates high visibility and reproducibility for locating the NMO. However, further prospective studies are needed to establish its real-world utility and impact on surgical outcomes. Full article

Objectives: The aim of this study was to assess the role of functional endoscopic sinus surgery (FESS) in the treatment of chronic rhinosinusitis (CRS) in children with cystic fibrosis (CF). Methods: We performed a comprehensive review of the literature by searching PubMed/MEDLINE. Results: CRS affects most children with CF. Though subjective symptoms are variable, radiological and endoscopic examination demonstrated typical objective findings. FESS is recommended for children with significant nasal symptoms that do not respond to medical treatment. At present, there are no uniform criteria for timing and extension of surgery. Primary surgery includes nasal polypectomy and correction of any bone anatomical variants that reduce ventilation of paranasal sinuses predisposing to recurrent sinusitis and complications. In case of recurrences, revision surgery supports a more expanded surgical approach. Moreover, FESS can relieve symptoms, improve patients’ quality of life, manage complications, ameliorate the delivery of medical therapy, and reduce sinonasal and lung superinfections. Conclusions: FESS has emerged as a safe and effective procedure for the treatment of CRS in children with CF. Since children with CF and CRS are difficult-to-treat patients, a multidisciplinary approach in tertiary-care referral centers is required. Full article

Background/Objectives. Medical and social care professionals (MSCPs) are disproportionately affected by chronic occupational stress, placing them at elevated risk for autonomic dysregulation, affective disorders, and burnout. Method. This preliminary study includes data obtained from two samples. The data protocols were approved by University of Florida’s IRB (IRB202200233 approved 24 February 2023 and IRB202401217 approved on 2 October 2024) and registered at ClinicalTrials.gov (NCT05766852 and NCT06580119). With a total sample of 39 female MSCPs, we investigated the effects of the novel Somatic Psychoeducational Intervention (SPI), grounded in Polyvagal Theory, on autonomic reactivity, psychological distress symptoms, and salivary oxytocin levels. Participants engaged in a three- to four-week intervention integrating psychoeducation, interoceptive training, breathwork, and somatic movement. A subset was randomly assigned via a random number generator to allow for comparison of the intervention group (n = 8) to control group (n = 7). Results. Repeated measures ANOVA revealed increases in salivary oxytocin (η_p² = 0.46) and reductions in autonomic reactivity (η_p² = 0.24) and psychological distress symptoms (η_p² ranging from 0.24 to 0.47). Benefits were sustained at one-month follow-up. Subset analyses focused on participants receiving the intervention at the same time found that only the participants in the intervention group improved with regard to autonomic reactivity and symptoms of anxiety and depression. Correlational analyses showed that changes in oxytocin and autonomic reactivity were associated with mindfulness improvements, which in turn predicted symptom reduction. Conclusions. These preliminary findings support SPI as a potentially scalable intervention with neurophysiological and psychological benefits. However, high attrition and small subgroup sizes necessitate cautious interpretation. Full article

The increasing penetration of inverter-based renewable generation has reduced rotational inertia in power systems worldwide, causing steeper frequency drops after severe contingencies and increasing the risk of load shedding. In the Honduran context, this study evaluates the dynamic response of the National Interconnected System (NIS) operating in island mode through detailed DIgSILENT PowerFactory simulations, explicitly incorporating the national Under-Frequency Load Shedding (UFLS) scheme. Five disturbance scenarios were analyzed, including generation losses of 100 MW, 200 MW, and 262 MW, to assess the frequency support provided by Battery Energy Storage Systems (BESSs) and Flywheel Energy Storage Systems (FESSs). Results show that, in the base case, frequency decreased to 55.3 Hz during a 200 MW loss, confirming the system’s high vulnerability. The integration of a 75 MW BESS improved frequency stability to 58.74 Hz, preventing UFLS activation, while a 320 MW equivalent FESS provided only short-term inertial support with limited effectiveness. Quantitatively, the BESS reduced the minimum frequency, delayed UFLS activation by approximately 3.5 s, and provided sustained support, whereas the FESS contributed mainly during the first 5 s of the disturbance. In the most severe contingency (262 MW generation loss), the combined operation of BESS and FESS prevented total system collapse, improving the frequency nadir to 58.6 Hz. These results confirm that BESS provides more robust and sustained frequency support than FESS under the analyzed conditions, highlighting its effectiveness for improving system stability in low-inertia networks such as Honduras. The findings offer useful insights for future studies on storage integration and frequency regulation strategies. Full article