Search Results (550)

This paper presents a PSCAD-based analysis of short-circuit faults and protection characteristics in a real distribution-level microgrid that integrates a 1 MWh battery energy storage system (BESS) with a 500 kW power conversion system (PCS) and a 500 kW photovoltaic (PV) plant connected to a 22.9 kV feeder. While previous studies often rely on simplified inverter models, this paper addresses the critical gap by integrating actual manufacturer-defined control parameters and cable impedances. This allows for a precise analysis of sub-millisecond transient behaviors, which is essential for developing robust protection schemes in inverter-dominated microgrids. The PSCAD model is first verified under grid-connected steady-state operation by examining PV output, BESS power, and grid voltage at the point of common coupling. Based on the validated model, DC pole-to-pole faults at the PV and ESS DC links and a three-phase short-circuit fault at the low-voltage bus are simulated to characterize the fault current behavior of the grid, BESS and PV converters. The DC fault studies confirm that current peaks are dominated by DC-link capacitor discharge and are strongly limited by converter controls, while the AC three-phase fault is mainly supplied by the upstream grid. As an initial application of the model, an instantaneous current change rate (ICCR) algorithm is implemented as a dedicated DC-side protection function. For a pole-to-pole fault, the ICCR index exceeds the 100 A/ms threshold and issues a trip command within 0.342 ms, demonstrating the feasibility of sub-millisecond DC fault detection in converter-dominated systems. Beyond this example, the validated PSCAD model and associated data set provide a practical platform for future research on advanced DC/AC protection techniques and protection coordination schemes in real BESS–PV microgrids. Full article

Future lunar south pole missions face dual challenges of highly variable illumination and rugged terrain that directly constrain rover mobility and energy sustainability. To address these issues, this study proposes a dynamic illumination-constrained spatio-temporal A* (DIC3D-A*) path-planning algorithm that jointly optimizes terrain safety and illumination continuity in polar environments. Using high-resolution digital elevation model data from the Lunar Reconnaissance Orbiter Laser Altimeter, a 1300 m × 1300 m terrain model with 5 m/pixel spatial resolution was constructed. Hourly solar visibility for November–December 2026 was computed based on planetary ephemerides to generate a dynamic illumination dataset. The algorithm integrates slope, distance, and illumination into a unified heuristic cost function, performing a time-dependent search in a 3D spatiotemporal state space. Simulation results show that, compared with conventional A* algorithms considering only terrain or distance, the DIC3D-A* algorithm improves CSDV by 106.1% and 115.1%, respectively. Moreover, relative to illumination-based A* algorithms, it reduces the average terrain roughness index by 17.2%, while achieving shorter path length and faster computation than both the Rapidly-exploring Random Tree Star and Deep Q-Network baselines. These results demonstrate that dynamic illumination is the dominant environmental factor affecting lunar polar rover traversal and that DIC3D-A* provides an efficient, energy-aware framework for illumination-adaptive navigation in upcoming missions such as Chang’E-7. Full article

This paper presents a kind of dual-channel coupled radial magnetic field resolver (DCCRMFR). The exciting winding and signal winding of this resolver adopt the structure of orthogonal phase. The number of turns and distribution of the four phase signal winding have been designed. The rotor has a double-wave magnetic conductive material structure. The variable reluctance mechanism between the stator and the rotor is derived by analytical method, and the feasibility of changing the coupling area for variable reluctance is obtained. The inductance of DCCRMFR was theoretically derived through the winding function method and combined with the finite element simulation method to obtain the inductance variation law and verify the correctness of the resolver design. Then simulation analysis was conducted on the output signal of DCCRMFR to extract the total harmonic distortion (THD) of the envelope of the electromotive force (EMF) output from the signal winding. Taking THD as the optimization objective, the optimized DCCRMFR simulation model is obtained by analyzing the air-gap length between the stator and the rotor and the thickness ratio of rotor. Finally, experimental measurements were conducted on a prototype model of a two pole pairs DCCRMFR, and the measurement results were compared and analyzed with simulation results to verify the correctness of the structural design and optimization of this DCCRMFR. Full article

To further satisfy the extreme operating conditions of electric tractors, a pole-changing double-sided excitation permanent magnet vernier motor (PC-DPMVM) is proposed evolving from the existing PC-SPMVM in this paper. Half of the rotor PMs are transferred to the stator small slots, while a consequent-pole rotor structure and stator PM structure can be obtained. Firstly, the simulation and experiments of the existing PC-SPMVM are introduced, which shows the deficiency of the maximum torque output. Then, the evolution process of the proposed PC-DPMVM is illustrated. The rotor modulation and stator modulation behaviors of the PC-DPMVM are introduced based on airgap field modulation theory. The main working PM flux density harmonics are deduced further. Next, electromagnetic performance comparisons are made between two PC-PMVMs by using finite element method, and the results reveal that the proposed PC-DPMVM has superior torque output compared with the PC-SPMVM, while the speed regulation abilities of the two motors are similar. It can be concluded that two extra operation regions can be obtained for the PC-DPMVM according to the comparison of torque-speed curve of the two motors. Full article

Objectives: Against common belief, mandibular condyle fractures are not that rare, with morbidity rates ranging from 19 to 52%, depending on actual literature sources. Practitioners try to improve the surgical techniques applied to obtain the most satisfactory anatomical and functional effect. The purpose of this study is to identify the relationships that affect bone loss around screws and plates in mandibular condylar process fractures treated surgically using the Open Reduction and Internal Fixation (ORIF) technique. Materials and Methods: Our research covered 276 fractures of the base, low and high neck of the condylar process. No formal sample size calculation was performed; the study enrolled patients treated at the Department during the last 4 years, based on informed consent granted both prospectively and retrospectively compares to the actual treatment time. The study group was selected based on injury type and the ability to implement surgical treatment. The imaging modality selected for the study was computed tomography (CT), which was assessed in each case by the same operator. Therefore, there was no need to account for inter-rater variability in the results. Based on CT scans, we studied various parameters, including bone healing in the fracture area, bone loss in the screws and plates area, change in the length of the mandibular ramus following osteosynthesis and on the opposite side after 12 months, as well as deformities of the mandibular head. Results: Using screws and plates is the gold standard for treating mandibular condylar process fractures. The number of screws used affects the bone loss ratio around head of the screw. Another factor that impacts the results achieved is the distance from the plate edge to the lateral pole of the mandibular head. Statistical evaluation indicated that proximity to the lateral pole is a risk factor for bone resorption at the plate edge. Conclusions: Based on the collected data, it is possible to predict bone loss, determine the location and selection of plates and screws, as well as to plan the procedure, achieving the lowest possible loss rates. Full article

Lead-free K_0.5Bi_0.5TiO₃ (KBT) ceramics were prepared using a finely tuned convectional solid-state reaction method. Their phase transitions in unpoled and poled states were examined. The temperature-dependent evolution of the reflections sensitive to structural changes and their 2Θ-positions indicated two temperature-driven phase transitions: tetragonal–tetragonal at about 200 °C, and tetragonal–cubic at around 400 °C. These structural transformations are further corroborated by studies examining Raman spectroscopy, dielectric properties, and mechanical properties. It was demonstrated that a prior E-field poling process significantly influences the polar state, causing an increase in the local degree of order, as well as the transformation of the cubic phase into the tetragonal one. This stabilizes and widens the temperature range of the ferroelectric phase. It was found that phase transformations in KBT are accompanied by a softening of the mechanical behavior similarly to improper ferroelastic transformations. The results demonstrate that KBT possesses favorable structural, dielectric, and mechanical characteristics, making it a potential candidate for electronic applications. The present study provides a clear understanding of the multi-scale structural behavior in multi-phase KBT, bridging micro-heterogeneity behaviors and macro-properties, and demonstrates an effective method of tuning the properties of KBTs by E-poling with a low electric field. Full article

During the operation of the magnetic fluid sealing device, a large amount of heat is generated due to the viscous friction of the magnetic fluid, causing the shaft to deform and thus affecting the sealing effect. This paper explores the thermal expansion effect of the magnetohydrodynamic sealing device under the working conditions of an axle diameter of 1030 mm and a maximum rotational speed of 700 r/min. The temperature distribution law under the action of a magnetic field, the influence of thermal deformation caused by temperature on the sealing performance, and the influence of the selection of shaft and pole shoe materials on the magnetic fluid sealing device were studied. Research findings show that in magnetic fluid sealing, an increase in system temperature can enhance the sealing effect, but it will cause thermal expansion of the rotating shaft and change the gap. By adopting a combination of different materials for the rotating shaft and the pole shoe, the sealing performance can be optimized and improved. Full article

Based on the long-stator permanent magnet linear synchronous motor (PMLSM), motor structures with different pole–slot ratios are designed by changing the distribution of armature windings. A magnetic field analytical model of the motor is developed, the no-load magnetic field characteristics of the motor are calculated, and the results are compared and verified with those obtained by the finite element analysis (FEA). The influences of back-electromotive force (EMF) and armature reaction on the no-load magnetic field under different slots are studied. Through fast Fourier transform, the harmonic characteristics of the magnetic field in different structures are analyzed. Then, the cogging force and thrust characteristics generated by the motor in different structures are compared. The research results provide certain references for motor design. Full article

(1) Background: Each generation’s approach to private-sphere environmentalism is shaped by distinct historical and socio-economic contexts, values, educational opportunities, and living conditions. The aim of this article is to identify differences on this issue among four generations (BB, X, Y, Z) of Poles. (2) Methods: An online survey was conducted on a quota sample of 1000 individuals, with each generation represented by 250 participants. The sample was balanced across generations in terms of gender, education, and place of residence. (3) Results: The top private-sphere environmental behavior was waste segregation (M = 5.1, SD = 1.23), followed by using reusable bags (M = 4.92, SD = 1.2) and reducing energy use (M = 4.57, SD = 1.2). The older the generation, the higher the score in the private-sphere environmentalism index (F = 33.3 (3, 996), p < 0.001). Significant predictors of the private-sphere environmental behaviors (PSE) index were age, gender, environmental concern, and perceived self-impact on the environment, and the final hierarchical regression model explained 38% of the variance in the PSE index. (4) Conclusions: These results underscores the need to account for generational contexts when developing behavior-change strategies and sustainability policies aligned with SDG 12. Full article

Zephyranthes tubispatha is an Amaryllidaceae species with high ornamental potential, whose seed dispersal coincides with periods of high temperatures (HTs) and long photoperiods. While supraoptimal temperatures (>28 °C) have been shown to induce thermoinhibition, the effect of light on germination dynamics has not yet been explored. The aim was to study the effect of different exposure times to white light (WL) and different light qualities, as well as the interaction with HT, on seed germination. Changes in the endogenous levels of several phytohormones, responses to pharmacological treatments, and O₂^.− production in the embryo were analyzed to gain an understanding of the underlying physiological mechanisms. Our results suggest the presence of a negative photoblastic response of the high-irradiance (HIR) type. Fluridone (an ABA synthesis inhibitor) restored germination in light-exposed seeds to levels close to the dark control, highlighting the importance of ABA content for photoinhibition. The preincubation period at HT (33 °C) significantly influenced germination behavior and photosensitivity at optimal temperature (20 °C). Thermoinhibition depends on changes in phytohormone balance and/or sensitivity, rather than on their absolute concentration. Unlike thermoinhibition, photoinhibition was not associated with the suppression of O₂^.− production in the embryonic root pole, confirming that these environmental signals utilize different regulatory pathways. Full article

The temperature–frequency dependence of dielectric permittivity in Na_0.5Bi_0.5TiO₃ (NBT) -based compositions displays a diffused, frequency-independent maximum along with a frequency-dependent shoulder below this maximum. This behavior deviates from that of both classical ferroelectrics and conventional relaxor ferroelectrics, and its interpretation is further complicated by challenges in linking it to known structural phase transitions. This study proposes a new interpretation of the dielectric behavior of NBT-based materials through a comparative analysis of temperature–frequency permittivity data in both unpoled and poled NBT samples and 0.95Na_0.5Bi_0.5TiO₃–0.05CaTiO₃ solid solution over a broad frequency range (10 Hz–100 MHz). Results reveal that the steep permittivity change between the maximum and shoulder—accompanied by pronounced thermal hysteresis—can be attributed to a phase transition between two non-ferroelectric phases. When this contribution is excluded, the dielectric response aligns with classical relaxor ferroelectric behavior. To reconcile this with other known properties of NBT, the “breathing” model is employed, offering a unified framework for understanding its relaxor-like characteristics. Full article

This paper presents the validation of a voltage balancing converter for a bipolar DC microgrid designed to ensure reliable operation in both grid-connected and islanded modes. This microgrid includes unipolar constant power loads (CPL), a unipolar Battery Energy Storage System (BESS), and local PV generation. The BESS converter employs a V–I droop strategy using only inductor current feedback, reducing sensing requirements while maintaining plug-and-play capability and ensuring smooth transitions between connected and islanded modes. In such a microgrid, the voltage balancing converter regulates the differential voltages under severe unbalanced load conditions and during transients caused by changes in unipolar loads and sources. The experimental results validate the voltage balancing strategy across various scenarios in a small-scale prototype. The results show tight voltage regulation under unbalanced conditions, and smooth transitions during load transients and unintentional islanding, even if there is no dc voltage source in one of the poles of the bipolar dc bus. For both conditions, the imbalance between the unipolar voltages is less than 0.5% of the total bipolar voltage. Full article

The ionospheric E layer (90–150 km altitude) significantly influences ionospheric dynamics and plays a crucial role in radio wave propagation. The Tibetan Plateau, as the “Third Pole,” affects E-layer morphology due to its unique topographical factors. Given the limited systematic studies in this high-altitude region, this study analyzes E-layer spatiotemporal characteristics and their controlling mechanisms over the Tibetan Plateau and adjacent regions. We analyzed foE (critical frequency of E-layer) data from six ionospheric observation stations across the Tibetan Plateau and neighboring areas during 2013–2023, covering a complete solar cycle from solar minimum to maximum. Combined with sunspot numbers as solar activity indicators, we systematically examined diurnal, seasonal, and solar cycle variations to understand regional E-layer behavior patterns. Daytime foE values significantly exceed nighttime values, demonstrating strong solar control. Spatially, Kunming shows the strongest daytime E-layer intensity with peak values reaching 3.12 MHz, while Urumqi exhibits the weakest at 2.94 MHz. Daytime foE values decrease with increasing latitude, whereas nighttime values show opposite latitudinal trends, indicating pronounced diurnal distribution asymmetry. Kunming displays the largest day-night foE variation amplitude, while Urumqi shows the smallest changes. Notably, most stations exhibit E-layer intensity peaks in July rather than June when solar zenith angles are minimum, differing from typical mid-low latitude seasonal behavior. These patterns may be related to complex vertical atmospheric coupling influenced by the region’s unique topography, which could affect the spatiotemporal distribution of the E-layer over the Tibetan Plateau. Full article

Smartphone-based fundus cameras and telemedicine are an opportunity for accessing ocular health inequalities in under-resourced areas. The objective of this study is to evaluate the prevalence of retinal findings in a community in the Amazon and propose strategies to enhance ocular health. A retrospective study was conducted in a riverside community. Retinal photos from the posterior pole and optic disc were captured using a portable fundus camera. All photos and data were analyzed remotely by a retina specialist. The final sample was 107 participants, aged 52 ± 17. Retinal findings were detected in 37.4% (95%CI 28.7–46.8) of the sample; the three main retinal findings were epithelial changes (10.3%, 95%CI 5.6–17.1), chorioretinal scars (8.4%, 95%CI 4.2–14.8), and dry age-related macular degeneration (7.5%, 95%CI 3.6–13.6). This study detected retinal alterations in a similar prevalence to that of other under-resourced areas. Telemedicine is an opportunity to address health inequities, especially in ophthalmology, through relatively low-cost portable devices, supporting clinical decisions in areas with low health access; however, maintaining assistance after implementation is a challenge. Enhancing medical education and training local non-specialized health professionals in risk assessment, device handling, and data base use is reasonable to ensure follow-up. Full article

The tooth harmonics caused by stator slots are a major factor leading to low motor efficiency, high temperature rise and severe vibration. The application of a magnetic slot wedge (MSW) can effectively mitigate the adverse effects of the stator slot on the motor. However, it should also be noted that the MSW may be subject to the action of electromagnetic forces during motor operation and thus has a risk of falling off. In order to comprehensively analyze the impact of MSW on the electromagnetic and reliability performance of the motor, this paper selected three types of MSW with relative permeabilities of 5, 10 and 15 to be applied in a high-power line-start permanent magnet synchronous motor (LSPMSM). The effects of these three types of MSWs on the electromagnetic performance of the motor and the changes in the electromagnetic force acting on the MSW were studied. Finally, the research content of the paper was verified on a 630 kW, 6 kV, 4-pole LSPMSM, providing a reference for the selection and application of MSW in motors. Full article