Search Results (92)

Background: Exercise-induced bronchoconstriction (EIB) is common in athletes, being more frequent in outdoor endurance-based/long-distance sports. We followed a World-Class marathon paddler’s season with recurrent episodes of EIB, which intensified during cold exposure workouts. This unique immunophenotype profile during the season and its variations were reflected in acute and chronic inflammatory markers. Methods: A longitudinal case study was conducted with blood sampling obtained from a single paddler after overnight fasting at three timepoints: T1 (beginning of season, after 15-day rest period), T2 (post-Winter National Championship), and T3 (post-Summer National Championship). Complete blood counts and lymphocyte immunophenotyping were performed using automated hematology analysis and multiparametric flow cytometry. Results: The total numbers of leukocytes (T1: 6.3; T2: 5.0; T3: 5.5 × 10⁹/L), neutrophils (3.1; 2.5; 2.8 × 10⁹/L), and lymphocytes (2.4; 1.8; 2.2 × 10⁹/L) declined between T1 and T2, followed by a partial recovery at T3. In contrast, monocyte counts exhibited the reverse pattern (0.41; 0.62; 0.31 × 10⁹/L). The two T cell subsets (αβ and γδ) remained relatively stable, showing only minor seasonal fluctuations. CD19+ B cells, initially at very low levels, increased steadily as the season progressed (0.05; 0.07; 0.16 × 10⁹/L). During T2, the proportion of memory lymphocytes (CD45RO+) rose, while naive cells (CD45RA+) declined; this trend was subsequently inverted at M3. Although the CD4+/CD8+ ratio varied over time, it consistently stayed below the normal reference range established for healthy controls (0.50; 0.83; 0.60 for T1, T2, and T3, respectively). Conclusions: The immune assessment of the World-Class marathon paddler revealed transient immunosuppression early in the season, marked by reduced neutrophils, a low CD4+/CD8+ ratio, and diminished CD19+ lymphocytes. Over time, immune parameters showed signs of recovery, indicating a temporary imbalance that did not impair the athlete’s physical performance. Conclusions: This case study of an elite marathon kayaker revealed transient immune fluctuations across a competitive season, including early immunosuppression (low neutrophils, CD4+/CD8+ ratio 0.50, and minimal CD19+ B cells) followed by partial recovery mid- and late-season. Despite persistently inverted CD4+/CD8+ ratios suggesting chronic immune dysregulation, the athlete maintained competitive performance, highlighting the temporary nature of these changes and emphasizing that regular immune monitoring can help optimize health and performance in elite athletes. Full article

This paper proposes a battery emulator based on a bidirectional non-inverting buck-boost power electronics converter. With the capability of bidirectional operation, it can emulate both charging and discharging processes. The proposed emulator is controlled with the advanced I² dual current-mode control (I²DCMC) algorithm, combined with a feedforward control, which ensures fast and accurate tracking of the voltage and current characteristics of the batteries. The emulator is universal in terms of the various mathematical models of the batteries, which can be implemented in real time. It has no limitations regarding different battery types. Detailed analysis and the design procedure of the proposed battery emulator are presented. The performances of the emulator are validated with simulation and experimental results for three battery types: polymer Li-ion, conventional Li-ion, and lead–acid battery. Both steady and transient states are analyzed, especially transitions between charging and discharging phases. The possibility of simple time scaling of charging/discharging processes is successfully achieved and demonstrated, which is very important in making tests faster, with preserved battery characteristics. Considering its low-cost and user-friendly operation, the proposed emulator can be a good alternative to the real batteries in experimental tests of different power electronics systems. The prototype, which is developed for the experimental verification of the emulator, is designed for and limited to the research of lower power ratings systems of up to 100 W. It is suitable in education to easily demonstrate the behavior of the batteries in multiple scenarios in controlled laboratory conditions. Full article

Neonatal screening programs for inborn errors of metabolism are essential for early diagnosis and intervention. However, false-positive results can cause unnecessary psychological stress for caregivers. This study investigated the emotional impact on a small number of caregivers in Oita Prefecture in Japan, whose infants received false-positive screening results for very long-chain acyl-CoA dehydrogenase deficiency (VLCADD). Particular attention was given to caregivers’ concerns regarding episodes of transient fasting suggestive of nutritional deficiency, as well as their perspectives on appropriate feeding practices for newborns. Nineteen infants in Oita Prefecture were identified as having elevated acylcarnitines, which were later confirmed as false positives. Of these cases, 11 mothers consented to participate in a survey and long-term growth evaluation using health check records. Thirty children with normal screening results were included as controls. While no differences in physical growth were found between groups by 3.5 years of age, some mothers of false-positive infants reported persistent anxiety. Their concerns included regret for inadequate breastfeeding and latent adverse effects on long-term growth or development. Conversely, caregivers’ anxiety diminished over time as they directly observed their infants’ normal growth and development. No regret was expressed regarding breastfeeding, and concerns about VLDCAD were not observed. Caregivers’ responses may help reduce their psychological burden. Full article

To thoroughly analyze the high-frequency and high-amplitude electromagnetic disturbances generated during disconnector operation, this paper proposes an equivalent modeling approach based on dynamic arc behavior. The model incorporates the resistance, inductance, and capacitance characteristics of the arc and consists of four main modules: arc reignition, arc extinction, arc resistance control, and switch control. Complete logical coordination among these modules is designed to enhance the model’s performance in terms of dynamic response and modeling accuracy compared to traditional methods. By systematically comparing simulation results with experimental data and conventional model outputs, the effectiveness and reliability of the proposed model in accurately reflecting the operational characteristics of disconnectors are validated. Furthermore, a comparative analysis of transient waveform characteristics from both experiment and simulation is conducted, with key parameters extracted and probability density functions constructed. The results demonstrate the high-precision fitting capability of the model and further reveal the statistical distribution patterns of very fast transient overvoltage single-pulse characteristics. Full article

Very fast transient overvoltage (VFTO) is characterized by short wavefront time, high amplitude and wide frequency. VFTO poses a threat to the safe operation of power equipment. In order to suppress the harmful effects of VFTO transmission on power equipment, a new type of busbar based on the structure of “inductance + resistance” has been designed, which is called a “damping busbar”. In this study, the equivalent circuit of a damping bus including spurious parameters was developed. These stray parameters are formed between the GIS enclosure and the damping bus, and between the disk insulators and the damping bus. A damping bus simulation model was established based on the equivalent circuit to carry out analysis of the relationship between the structural parameters of the damping bus and the inductance generated by the damping bus. The simulation results showed that the number of turns plays a decisive role in bus inductance, and the relationship between the number of turns and inductance is approximately linear. Comparative analysis of multiple waveforms was carried out before and after the addition of damping buses to the GIS on a 550 kV test rig. The test data showed that the average amplitude of VFTO decreased by 20.36% after the installation of the damping bus, the number of breakdowns decreased by about 66.7%, and there was no obvious high frequency in the measured waveform after installation. In short, the damping busbar had a good suppression effect on the amplitude and frequency of VFTO, and reduced the number of breakdowns. This technique provides a novel solution for VFTO suppression. Full article

The very fast transient overvoltage (VFTO) is characterized by steep wavefronts, high amplitude, and wide spectrum. These characteristics can lead to partial discharges or insulation breakdowns in potted insulators, which can lead to localized overheating or turn-to-turn insulation damage in transformers. The strong electromagnetic radiation generated by VFTO may also interfere with relay protection and communication systems, triggering risks to grid operation. This paper introduces the existing mainstream VFTO suppression methods, such as damping resistance method, disconnecting switch operation method, inductive method, etc., from the aspects of circuit structure, parameter design and suppression effect, and focuses on the influence of the material selection, parameter adjustment, and mounting structure adjustment of ferrite ring on VFTO suppression effect. In addition, the lightning arrester method and the method of utilizing overhead lines for VFTO suppression are also briefly discussed. The article concludes with a comparison of the advantages and disadvantages of each method and an outlook on the future research direction of VFTO suppression technology. Full article

Due to increasing decentralized power applications, power electronics are gaining importance, also in distribution grids. Since their scope of investigation is diverse, their versatile models and their use in grid calculations are important. In this work, a three-phase grid-synchronous inverter with an LCL filter is considered. It is defined as a component of the “Extended Node Method” to make it applicable in this node-based transient grid calculation method. Because the component stucture always looks the same and the construction of the grid system of equations always follows the same, straightforward process, the model can be applied easily and several times to large network calculations. Furthermore, an approach is developed for how inverter control algorithms are interconnected with the method’s results in the time domain. This allows for the fast analysis of converter control schemes in different grid topologies. To evaluate its accuracy, the developed approach is compared to equivalent calculations with Simulink and shows very good agreement, also for steep transients. In the long term, this model is intended to bridge the gap to other DC systems like electrochemical components and to gas and heating networks with the Extended Node Method. Full article

Simulations of the pump response time refer to the determination of the time constant of the transient process when the flow and pressure change. The changes mentioned in the standards are precisely defined and prescribed by the “MIL-P-19692E” norms. The simulation showed that the time constants are within the permissible limits prescribed by these norms. The diagram shows the responses for the considered pump and for the case when the flow changes from Q_n to Q_min and changes from Q_min to Q_n. The time constants t₁ and t₂ are defined on the diagrams, with the parameters that the pump has. In addition, the standards define the pressure jump that occurs during the transient process as well as time constants. From the flow change diagram, it can be seen that the flow change is also very fast and takes place in time intervals shorter than 0.1 s. By evaluating the size of the time constants, t₁ and t₂, it can be concluded that they have a value below 0.05 s, which meets the regulations in that area. Also, the size of the jump pressure meets the regulations because it is only 1.2 M Pa above the nominal pressure. Full article

Operating overvoltage occurs when the pantograph or main breaker of an electric locomotive is operated, which is prone to causing insulation failure of high-voltage equipment. The HX_D1 electric locomotive is taken as the research object in this paper to explore the characteristics and influencing factors of operating overvoltage. Under pantograph lifting, main breaker closing, main breaker opening, and pantograph dropping, operating overvoltage waveform in the high-voltage system is recorded by a high-speed oscilloscope and resistance–capacitance voltage divider to analyze the overvoltage characteristics and distribution law. Tested data show that the amplitude of operating overvoltage is in the range of 80 to 330 kV with ultra-high steepness, which is similar to the Very Fast Transient Overvoltage (VFTO) in power systems. The maximum overvoltage during the entire test occurred during the main breaker closing and its amplitude is 328.60 kV with a steepness of 4.21 × 10⁴ kV/μs. The max overvoltage of the other operations (pantograph lifting, main breaker opening, and pantograph dropping) are 280.60 kV, 194.73 kV, and 305.56 kV with ultra-high steepness. High-amplitude overvoltage is predominantly located at the pantograph, while the low-amplitude sort is mainly observed around other high-voltage equipment. The result indicates that operating overvoltage belongs to ultra-fast transient overvoltage and its amplitude and steepness are higher than existing research. Full article

When the electric locomotive pantograph is dropping, the interruption of pantograph catenary contact causes electromagnetic oscillation and arcing. The frequent arc burning that occurs due to charge accumulation results in the amplitude of overvoltage increasing gradually, posing a threat to locomotive high-voltage equipment. However, the physical mechanisms and characteristics of overvoltage are still unclear. This paper proposes a simulation model of operating overvoltage due to a dropping pantograph based on the pantograph–catenary arc and variable capacitance. Distributed RLC electromagnetic oscillation is considered, which allows the real-time calculation of arc resistance and capacitance. Under the same working conditions, the error between the simulation and test results is less than 4.0%, which proves the credibility of the model. The variation law of overvoltage under different dropping speeds or catenary phases was investigated, which shows the max amplitude is 298.20 kV and steepness is 2096.80 kV/μs at 0.30 m/s speed. The waveform shows the characteristics of high amplitude and high steepness, similar to very fast transient overvoltage (VFTO). There is a sinusoidal relationship between the catenary phase and overvoltage amplitude. The closer the catenary phase to 90°, the higher the overvoltage amplitude. The research has important guiding significance for the overvoltage formation mechanism of a traction power supply system and the insulation coordination design of high-voltage equipment. Full article

Energy harvesting from energy sources is a rapidly developing cost-effective and sustainable technique for powering low-energy consumption devices such as wireless sensor networks, RFID, IoT devices, and wearable electronics. Although these devices consume very low average power, they require peak power bursts during the collection and transmission of data. These requirements are satisfied by the use of energy-storage devices such as batteries or supercapacitors (SCs). Batteries offer significantly higher energy density but are subject to regular replacement, thermal runaway risk, and environmental concerns. On the other hand, SCs provide over a million-fold increase in capacitance compared to a traditional capacitor of the same volume. They are considered as the energy-storing devices that bridge the gap between conventional capacitors and batteries. They also offer fast charging times, a long lifecycle, and low equivalent series resistance (ESR). Most importantly, they are capable of handling the high transient currents produced by energy harvesters and provide a stable power source for external loads. This study encompasses a brief exploration of the three fundamental SC types. Then, the discussion delves into the integration of SCs into energy harvesting applications. The collective knowledge presented aims to guide future research endeavors fostering the development of novel energy harvesting systems using SCs. Full article

PANDORA (Plasmas for Astrophysics Nuclear Decays Observation and Radiation for Archaeometry) is an INFN project aiming at measuring, for the first time, possible variations in in-plasma $\beta$-decay lifetimes in isotopes of astrophysical interest as a function of thermodynamical conditions of the in-laboratory controlled plasma environment. Theoretical predictions indicate that the ionization state can dramatically modify the $\beta$-decay lifetime (even of several orders of magnitude). The PANDORA experimental approach consists of confining a plasma able to mimic specific stellar-like conditions and measuring the nuclear decay lifetime as a function of plasma parameters. The $\beta$-decay events will be measured by detecting the $\gamma$-ray emitted by the daughter nuclei, using an array of 12 HPGe detectors placed around the magnetic trap. In this frame, plasma parameters have to be continuously monitored online. For this purpose, an innovative, non-invasive multi-diagnostic system, including high-resolution time- and space-resolved X-ray analysis, was developed, which will work synergically with the $\gamma$-rays detection system. In this contribution, we will describe this multi-diagnostics system with a focus on spatially resolved high-resolution X-ray spectroscopy. The latter is performed by a pin-hole X-ray camera setup operating in the 0.5–20 keV energy domain. The achieved spatial and energy resolutions are 450 µm and 230 eV at 8.1 keV, respectively. An analysis algorithm was specifically developed to obtain SPhC (Single Photon-Counted) images and local plasma emission spectrum in High-Dynamic-Range (HDR) mode. Thus, investigations of image regions where the emissivity can change by even orders of magnitude are now possible. Post-processing analysis is also able to remove readout noise, which is often observable and dominant at very low exposure times (ms). Several measurements have already been used in compact magnetic plasma traps, e.g., the ATOMKI ECRIS in Debrecen and the Flexible Plasma Trap at LNS. The main outcomes will be shortly presented. The collected data allowed for a quantitative and absolute evaluation of local emissivity, the elemental analysis, and the local evaluation of plasma density and temperature. This paper also discusses the new plasma emission models, implemented on PIC-ParticleInCell codes, which were developed to obtain powerful 3D maps of the X-rays emitted by the magnetically confined plasma. These data also support the evaluation procedure of spatially resolved plasma parameters from the experimental spectra as well as, in the near future, the development of appropriate algorithms for the tomographic reconstruction of plasma parameters in the X-ray domain. The described setups also include the most recent upgrade, consisting of the use of fast X-ray shutters with special triggering systems that will be routinely implemented to perform both space- and time-resolved spectroscopy during transient, stable, and turbulent plasma regimes (in the ms timescale). Full article

The thermal characterization of power devices is an inevitable task in the industry. Thermal transient testing is one of the major tools for this characterization, as it is not only capable of giving information about the actual thermal parameters but may also reveal the root cause of potential device failures. The testing may occur on single packages or modules on a dedicated standard test bench, or “in situ”, in an actual assembly. The testing process itself is very fast in both cases, on the order of seconds, but the transient measurement needs to be preceded by a calibration step to determine the temperature dependence of a temperature-sensitive parameter (TSP) of the semiconductor device. This may require a long time, as the device has to be measured at many stabilized temperatures, which in the case of power devices may take hours. It also has to be considered that, especially in “in situ” measurements, reaching the highest device temperatures of power devices may even damage other parts of the surrounding electronics. Moreover, the temperature distribution inside a module will be different at calibration time than during operation with the same junction temperature, as bond wires and copper traces do not reach the chip temperature in the latter case. This paper presents a methodology that can be used to replace the lengthy measurement of one parameter at many temperatures with a fast single I–V characteristics measurement at room temperature. Physics-based calculations assign a unique temperature-sensitive parameter to each item of interest in the system. After the presentation of the theoretical background, the usability of the method is demonstrated by verifying measurements on silicon power devices. Full article

The aging of supercapacitors (SCs) depends on several factors, with temperature being one of the most important. When this is high, degradation of the electrolyte occurs. The impurities generated in its decomposition reduce the accessibility of the ions to the porous structure on the surface of the electrode, which reduces its capacity and increases its internal resistance. In some applications, such as electric vehicles whose storage system consists of SCs, fast chargers, which supply very high power, are used. This can lead to an increase in temperature and accelerated aging of the cells. Therefore, it is important to know how the temperature of the SCs evolves in these cases and what parameters it depends on, both electrical and thermal. In this contribution, mathematical formulae have been developed to determine the evolution of the temperature in time and its maximum value during the transient state. The formulae for obtaining the mean and maximum temperature, once the thermal steady state (TSS) has been reached, are also shown, considering that the charger cells are recharged from the grid at a constant current. Based on this formulation, the thermal analysis of a specific case is determined. Full article

For the application of high-frequency current detection in power systems, such as very fast transient current, lightning current, partial discharge pulse current, etc., current sensors with a quick response are indispensable. Here, we propose a high-frequency magnetoelectric current sensor, which consists of a PZT piezoelectric ceramic and Metglas amorphous alloy. The proposed sensor is designed to work under d₁₅ thickness-shear mode, with the resonant frequency around 1.029 MHz. Furthermore, the proposed sensor is fabricated as a high-frequency magnetoelectric current sensor. A comparative experiment is carried out between the tunnel magnetoresistance sensor and the magnetoelectric sensor, in the aspect of high-frequency current detection up to 3 MHz. Our experimental results demonstrate that the d₁₅ thickness-shear mode magnetoelectric sensor has great potential for high-frequency current detection in smart grids. Full article