Small Reactance Research Articles

Electron series resonance excited in the 27.12 MHz magnetron sputtering discharge

Abstract Electron series resonance (ESR) excited in a 27.12 MHz magnetron sputtering discharge was investigated. By analyzing the discharge impedances, the imaginary part of the impedance was found to undergo a transition from capacitive to inductive at varying radio-frequency (RF) power, and the conditions for ESR excitation were satisfied at 27.12 MHz magnetron sputtering. By analyzing the discharge current and its higher-order harmonics, the near-sinusoidal current waveform and weak second-order harmonic were obtained, showing a weak nonlinear effect of the RF current. However, for the magnetron sputtering discharge, the nonuniform magnetic field has a significant effect on the sheath width and transverse current, making the sheath thinner and the transverse current smaller. As a result, a small capacitive reactance was obtained, and the inductive reactance was easily canceled. Therefore, the ESR excited in the 27.12 MHz magnetron sputtering was caused by the strong effect of the nonuniform magnetic field and the weak second-order current harmonic (H2). By estimating the ESR frequency ω res,B , the second-order current harmonic (54.24 Hz) was found to be responsible for ESR excitation.

Respiratory function after 30+ years following sulfur mustard exposure in survivors in Sweden.

Sulfur mustard (SM) exposure causes acute and chronic respiratory diseases. The extent of small airway dysfunction (SAD) in individuals exposed to SM is unclear. This study evaluated and compared SAD in SM-exposed and SM-unexposed participants using noninvasive lung function tests assessing small airway function. This retrospective cohort study involved SM-exposed (n = 15, mean age: 53 ± 8 years) and SM-unexposed (n = 15, mean age: 53 ± 7 years) Kurdish-Swedish individuals in Sweden. Small airway resistance and reactance were assessed using impulse oscillometry (IOS). Nitrogen (N2) multiple breath washout (MBW) was employed to assess lung ventilation heterogeneity. The gas-exchanging capacity of the lungs was assessed using the diffusing capacity of the lungs for the carbon monoxide (DLCO) test. Lung function outcomes were reported as absolute values and z-scores. Group comparisons were performed using the Mann-Whitney U test. No statistically significant differences in age, height, or body mass index were observed between the two groups. IOS showed significantly increased small airway resistance, while N2MBW exhibited significantly increased global and acinar ventilation heterogeneity in SM-exposed individuals compared to that in unexposed individuals. SAD was identified in 14 of 15 SM-exposed individuals, defined as at least one abnormal IOS difference between resistance at 5 and 20 Hz (R5-R20) and/or area of reactance (AX) or N2MBW lung's acinar zone (Sacin), and DLCO adjusted to the alveolar volume (DLCO/VA) outcome. Of these 14 individuals, only 5 demonstrated concordant findings across the IOS and N2MBW tests. Exposure to SM was positively associated with long-term impairment of respiratory tract function in the small airways in the majority of the previously SM-exposed individuals in the present study. Furthermore, both IOS and N2MBW should be employed to detect SAD in SM-exposed survivors as they provide complementary information. Identifying and characterizing the remaining pathology of the small airways in survivors of SM exposure is a first step toward improved treatment and follow-up.

Analysis of fault current and overvoltage at the neutral point of [formula omitted]800 kV High-Voltage DC converter transformer

In order to enhance the security of ±800 kV High-Voltage DC (HVDC) system, it is needed to consider and analyze the grounding mode of the neutral point of converter transformer. Different neutral grounding modes have different inhibitory effects on the current of transmission lines when faults occur, and also produce different overvoltages at the neutral point. Therefore, this paper first analyzes the influence of converter transformer on fault current and neutral point voltage in three cases of ungrounded, direct grounding and via small reactance grounding. Through the analysis, it is known that the neutral grounding via small reactance is the most suitable for the HVDC transmission system. Then the model of ±800 kV bipolar HVDC transmission system is built in PSCAD/ EMTDC simulation software and analyzed under two typical conditions of grounding overvoltage and breaking overvoltage. By comparing several cases of converter transformer neutral point grounding directly, via 5Ω, 10Ω, 17Ω, 20Ω and 25Ω reactance grounding, it is found that grounding via small reactance can effectively suppress fault current. However, with the increase of the resistance value, the inhibitory effect will gradually weaken and cause the increase of the neutral point overvoltage.

Evaluation of lightning overvoltage at neutral point of HVDC converter transformer based on EMTP

In order to ensure the safe and stable operation of high voltage direct current (HVDC) systems, this paper studies the lightning overvoltage at the neutral point of the HVDC converter transformer. The work first introduces the basic types of lightning overvoltage based on the CIGRE Benchmark 500 kV HVDC transmission system which is modeled in the electromagnetic transient program (EMTP) software. The high-frequency model of the HVDC transmission system is considered where lightning overvoltage at the converter transformer neutral point is studied at different values of the small reactance connected at neutral point grounding and different lightning strike locations. Although increasing the small reactance value can effectively suppress the lightning current, the lightning overvoltage will gradually increase. When the neutral point is grounded by 11 Ω small reactance, the lightning overvoltage is most serious, where the peak value can reach 415 kV. Also, the farther the lightning strike position from the converter transformer, the smaller the lightning overvoltage.

High-flow nasal cannula improves respiratory impedance evaluated by impulse oscillometry in chronic obstructive pulmonary disease patients: a randomised controlled trial

Non-pharmacological treatment with high-flow nasal cannula (HFNC) may play a vital role in treatment of patients with chronic obstructive pulmonary disease (COPD). To evaluate the efficacy of HFNC, impulse oscillation system (IOS) is a new noninvasive technique in measuring the impedance of different portions of lungs. It shows higher sensitivity in contrast to conventional pulmonary function tests (PFT). However, whether IOS is an appropriate technique to evaluate the efficacy of HFNC in improving the impedance of small airways or peripheral lung in patients with COPD is still unclear. We enrolled 26 stable COPD participants randomised into two groups receiving HFNC or nasal cannula (NC) for 10 min followed by a 4-week washout period and crossover alternatively. IOS was used to detect the difference of respiratory impedance after HFNC or NC interventions. IOS parameters, PFT results, transcutaneous partial pressure of carbon dioxide, peripheral oxygen saturation, body temperature, respiratory rate, pulse rate, and blood pressure at the time of pre-HFNC, post-HFNC, pre-NC, and post-NC, were collected and analysed using SPSS (version 25.0, IBM, Armonk, NY, USA). The IOS measurement indicated that HFNC significantly improved R5, R5% predicted, R5–R20, X5-predicted, and Fres compared with NC, whereas no significant difference was observed through the PFT measurement. The beneficial effect of HFNC in improving small airway resistance and peripheral lung reactance compared with that of NC in patients with stable COPD was confirmed through IOS measurement.Trial registration: ClinicalTrials.gov NCT05130112 22/11/2021.

Linearity-Enhanced Quasi-Balanced Doherty Power Amplifier With Mismatch Resilience Through Series/Parallel Reconfiguration for Massive MIMO

A reconfigurable series/parallel quasi-balanced Doherty power amplifier (QB-DPA) is presented with a unique capability of maintaining high linearity and high efficiency against load mismatch, which is highly desirable for massive multiple-input–multiple-output (MIMO) and active array applications. Based on the new QB-DPA topology derived from an ideal balanced amplifier, it is, for the first time, discovered that QB-DPA can be reconfigured between series- and parallel-DPA modes by setting the isolation-port loading to the ground and open circuit, respectively, and exchanging the roles of main and auxiliary amplifiers. Expanding from the ideal Doherty modes, the isolation port can be loaded with small reactance (susceptance) for linearity enhancement of series (parallel) QB-DPA. Furthermore, by leveraging the symmetry of series and parallel modes with complementary sensitivities to load impedance/admittance, it is theoretically proved that the QB-DPA can be strongly mismatch-resilient. Based upon the comprehensive and conclusive theoretical analysis, a physical prototype demonstration is practically presented using the GaN technology at 3.5 GHz. In modulated measurement using Long-Term Evolution (LTE) signals, the developed QB-DPA exhibits excellent linearity, e.g., <1.6% error vector magnitude (EVM) and high average efficiency of 45% at the rated averaged power in the nominal 50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> condition, which compares favorably with state of the art. More importantly, through only a two-state adaption (using silicon-on-insulator (SOI)-based switches) of reactive loading at the output isolation port together with optimized gate biasing, the high linearity (<4% EVM) and average efficiency (>31%) can be experimentally maintained up to 2.5:1 of voltage standing wave ratio.

Intratracheal budesonide/surfactant attenuates hyperoxia-induced lung injury in preterm rabbits.

Recent clinical trials have shown improvements in neonatal outcomes after intratracheal administration of a combination of budesonide/surfactant (ITBS) in infants at risk of bronchopulmonary dysplasia. However, the effect of ITBS on lung function and alveolar structure is not known. We aimed to determine the effect of ITBS on lung function, parenchymal structure, and inflammatory cytokine expression in a relevant preterm animal model for bronchopulmonary dysplasia. Premature neonatal rabbits were administered a single dose of ITBS on the day of delivery and exposed to 95% oxygen. Following 7 days of hyperoxia, in vivo forced oscillation and pressure-volume maneuvers were performed to examine pulmonary function. Histological and molecular analysis was performed to assess alveolar and extracellular matrix (ECM) morphology, along with gene expression of connective tissue growth factor (CTGF), IL-8, and CCL-2. ITBS attenuated the functional effect of hyperoxia-induced lung injury and limited the change to respiratory system impedance, measured using the forced oscillation technique. Treatment effects were most obvious in the small airways, with significant effects on small airway resistance and small airway reactance. In addition, ITBS mitigated the decrease in inspiratory capacity and static compliance. ITBS restricted alveolar septal thickening without altering the mean linear intercept and mitigated hyperoxia-induced remodeling of the ECM. These structural changes were associated with improved inspiratory capacity and lung compliance. Gene expression of CTGF, IL-8, and CCL-2 was significantly downregulated in the lung. Treatment with ITBS shortly after delivery attenuated the functional and structural consequences of hyperoxia-induced lung injury to day 7 of life in the preterm rabbit.

Analysis on Short Circuit Current Limiting Effect of Installing Small Reactance in 500kV Autotransformer’s Neutral-point

For the condition that single-phase short circuit current exceeds three-phase short circuit current occurs on some of Shandong 500kV substations’ 220kV bus, this paper studies the principle of limiting 500kV autotransformer’s short circuit current by installing small reactance. Considering that installing small reactance at 500kV autotransformer’s neutral point influences the zero sequence circuit, this paper suggests to configure independent relay protection on small reactance which aims at supervision the short circuit current and improving reliability. Protection setting for neutral-grounding small reactance is proposed. Simulation results and protection setting software show the effect of limiting short circuit current by installing small neutral-point reactance.

Microwave Tunneling and Robust Information Transfer Based on Parity-Time-Symmetric Absorber-Emitter Pairs.

Robust signal transfer in the form of electromagnetic waves is of fundamental importance in modern technology, yet its operation is often challenged by unwanted modifications of the channel connecting transmitter and receiver. Parity-time- (PT-) symmetric systems, combining active and passive elements in a balanced form, provide an interesting route in this context. Here, we demonstrate a PT-symmetric microwave system operating in the extreme case in which the channel is shorted through a small reactance, which acts as a nearly impenetrable obstacle, and it is therefore expected to induce large reflections and poor transmission. After placing a gain element behind the obstacle, and a balanced lossy element in front of it, we observe full restoration of information and overall transparency to an external observer, despite the presence of the obstacle. Our theory, simulations, and experiments unambiguously demonstrate stable and robust wave tunneling and information transfer supported by PT symmetry, opening opportunities for efficient communication through channels with dynamic changes, active filtering, and active metamaterial technology.

Design of a Combined Screening and Damping Layer for a 10-MW-Class Wind Turbine HTS Synchronous Generator

This paper is focused on the design of a single protection layer to cover both the screening and damping characteristics of a large-scale high-temperature superconducting (HTS) wind turbine synchronous generator under sudden short-circuit conditions. Due to small synchronous reactance of HTS generators, short-circuit condition causes substantial fault current in the stator windings, which produces high unbalance variable magnetic field as well as substantial mechanical fluctuations issues. The former one can lead to unstable condition for HTS field windings, due to induced ac loss and field overcurrent, and the latter one can produce large fluctuations on the generator rotational speed and rotor torque angle. The proposed protection layer is designed in a way that not only screening capability is provided for the HTS windings by preventing unbalance magnetic field penetration, but desirable damping ratio is also achieved so that the fluctuations are suppressed in a proper transient time. A 10-MW-class HTS synchronous generator is modeled and simulated using finite element method under different short-circuit conditions. The temperature variation study and field overcurrent analysis are provided to show the compatibility of the proposed model. In addition, magnetic force distribution and static eccentricity fault detection analyses are provided, which guarantee the proper dynamic performance of the studied generator using the proposed protection layer. Simulation results confirm that with the proposed protection layer, both the screening and damping characteristics of the 10-MW-class HTS generator are obtained and proper transient dynamic responses are deduced for wind power applications.

A cavity-by-cavity description of the aeroacoustic instability over a liner with a grazing flow

This paper presents a two-dimensional (2-D) cavity-by-cavity description of a convective instability near a lined wall with low dissipation due to the coupling of hydrodynamic modes with resonance of the wall. For a liner consisting of an array of deep cavities periodically placed along a duct containing a mean shear flow, the acoustic and hydrodynamic disturbances are described by the linearized Euler equations. The Bloch modes and the scattering matrix of periodic cells are used to examine the instability over the liner. The unstable Bloch mode is due to the coupling of a hydrodynamic mode in the shear flow with the cavity resonance. It is demonstrated that even when all the transverse modes are stable in the duct–cavity system, i.e. when the Kelvin–Helmholtz instability of the shear flow over the cavities does not occur, such an instability over the liner can still exist. The unstable Bloch wave, excited by the incident sound wave at the upstream part of the liner, convectively grows along the liner, and regenerates sound near the downstream edge of the liner with a sound level higher than the incident sound level. It is shown that a homogenized approach, where the wall effect is described by a homogeneous impedance, can also explain the unstable behaviour above the liner. It reveals that a small wall resistance and a small and positive reactance are two necessary conditions for such an instability.

Algorithm for adaptive single‐phase reclosure on shunt‐reactor compensated extra high voltage transmission lines considering beat frequency oscillation

The existing technique of fault state recognition for adaptive single-phase reclosure is severely impacted by the transient beat frequency oscillations after the secondary arc being extinguished in a shunt-reactance compensated line, due to the resonance between the equivalent capacitors and compensating inductors. The characters of fault phase terminal voltage and neutral small reactance voltage are analysed, and the differences of fault phase terminal voltage between the two fault states at recovery voltage stage are compared. Considering that there are some misjudged zones caused by beat frequency oscillation on the fault phase voltage, the neutral small reactance voltage is taken as a base value, and the ratio which uses the difference of calculated and measured on fault phase terminal voltage to neutral small reactance voltage is detected through a beat frequency cycle. Only when all ratios are >1 at the sampling points, a permanent fault is identified. If the ratio of a sampling point is <;1, the transient fault is identified, and the reclosing command is issued after a determined delay. The simulation results show that the algorithm can distinguish the fault state under different compensation degrees effectively, and be free of different loads, fault locations and fault resistances.

Research on Neutral Grounding Reactance Allocation with MCR

For the arc current generated during the reclosing of the high-voltage transmission system, small reactance configuration compensation and control strategy. By the magnetically controlled reactor is researched. First analyzing the principle that high-pressure single-circuit and double-circuit on the same pole line suppresses arc current, then establishing the magnetron controlled reactor equivalent model in PSCAD, on this basis, establishing simulation using magnetron reactors to suppress secondary arc current circuit under the conditions of high voltage transmission lines , designing and implementing of a magnetic valve controllable reactor inhibition of arc current physics experiments under of a low-voltage experimental conditions analoging high-voltage actual line condition. At last, the comparison of PSCAD simulation waveform and physics experiments of Power Quality the analyzer topas2000 and oscilloscope output verify the magnetic valve controllable reactor to suppress the arc current theory feasibility and effectiveness.

Comparison of Three Magnet Array-type Rotors in Surface Permanent Magnet-type Vernier Motor

Surface permanent magnet-type vernier motors with three magnet array-type rotors (parallel magnetized type, repulsion type, and Halbach type) are compared based on the pull-out torque. It was clarified that increasing the rotor radius increases the pull-out torque at a fixed three-phase alternating voltage. The mechanism for the pull-out torque increase on each magnet array type was different, when the effects of the increase were analyzed based on an induced electromotive force and a synchronous reactance. As a result, the design of the Halbach-type rotor was found to be especially effective for achieving high pull-out torque, because this array type achieves a large induced electromotive force E0 and a small synchronous reactance xs.

Investigation the Performance of Axial Channel Rotor in Inset Permanent Magnet Synchronous Machine

An electrical machine is constructed with some holes or axial hollows in the rotor core for special purpose. The effects of axial hole in the proposed Inset Permanent Magnet Machine (Inset PMSM) with eight radial poles are analyzed by the magnetic flux density in air gap. The characteristics associated with magnetic flux density of every magnet poles in the air gap, magnetic flux losses in the rotor teeth, density magnetic flux in the rotor core surface and torque of the machine are also investigated and compared. Results show small direct reactance and less area in the proposed axial channel rotor core compared with the convention Inset PMSM. It imply to a lighter weight and high efficiency machine design. The finite element simulation shows the magnetic flux density per pole in air gap of the proposed rotor structure remain constant or may be a little bit drop compared with the conventional machine.

초전도 한류모듈 내 고온초전도 선재 배치에 따른 교류손실 변화

Usually, the AC loss from the superconducting element of an SFCL due to the load current is very small because it is composed of the combination of bifilar windings with very small reactance. Although the AC loss is small enough, we should be albe to predict for the design and control of the cryogenic system. In fact, an SFCL for the transmission voltage class may not generate ignorable AC loss because of the inevitable space between the HTS wires for the high voltage insulation and cryogenic efficiency. To measure the AC loss dependency on the space between the 2G HTS wires with the width of 4.4 mm, we prepared an experimental setup which could adjust the distance between the wires. We used two 500-mm length HTS wires in parallel and applied the current in the opposite direction for each wire to simulate a part of a current limiting module for a high voltage SFCL. We also put two couples of voltage taps at the ends of each wire and a cancel coil in the voltage measurement circuit to compensate the reactive component from the voltage taps. In this condition, we varied the distance between the wires to investigate the change of the transport current loss. A similar experimental study with HTS wire with the width of 12 mm is now in progress.

Development of a REBCO Superconducting Transformer With Current Limiting Function

A single-phase 10 kVA transformer was designed and fabricated with RE1Ba2Cu30O7-δ (REBCO, RE: Rare Earth) superconducting tapes to quantitatively investigate the transition phenomenon of REBCO superconducting tapes to normal state due to a fault excess current. The voltage ratio was 1:1 and the rated voltage was 393 V. It had four windings. The primary and secondary windings had auxiliary windings in addition to main ones respectively. The main and auxiliary windings were connected in parallel in the both sides. The addition of the auxiliary windings made it possible to observe the induced normal resistances in the respective main ones individually. First usual performance tests were carried out and a stable operation as designed was confirmed. In steady state almost all of the current flowed in the main windings due to the small leakage reactance between them. At a sudden short-circuit test, the main windings quenched due to excess current over the critical current and the current was reduced to one fortieth as compared with the case of no current limiting function. It was clarified the whole of the main windings did not shift to normal state though the current exceeded the critical current all over the length and the induced normal zone was almost proportional to the primary voltage.

Study of 10 MW-Class Wind Turbine Synchronous Generators With HTS Field Windings

We study the electro-magnetic design of 10 MW-class wind turbine generator with high temperature superconducting field winding by using the FEM analysis. The design examples are presented and the generator characteristics are investigated. The 10 MW-class HTS wind turbine generator is considered to be feasible from the stand point of the electro-magnetic design. In this study, 8-pole and 12-pole generators are investigated. From the results, it is considered that the 8-pole design is preferable compared with the 12-pole design. The analysis also reveals the small synchronous reactance of the HTS wind turbine generator. Therefore, proper protection is necessary for the large short circuit current.

Design and Analysis of a Multiport Circuit for Shaping Sub-Nanosecond Pulses

In this study, a coupled-line coupler was evaluated for its potential to shape sub-nanosecond ultra-wideband (UWB) pulses. The coupler was shown to exhibit a natural tendency to differentiate sub-nanosecond pulses, owing to its bandpass nature. Next, a Schottky detector diode was applied to confirm that the small parasitic reactance in the coupler gives rise to the differentiation behavior. The unconventional application of a coupler and Schottky diode towards signal differentiation culminated in the development of a novel UWB generator that simultaneously produces: a square waveform that has a 20%-80% rise time of 850 ps, a Gaussian waveform that has a pulse duration of 100 ps, and a monocycle waveform that has a 80 ps rise time between its peaks. These waveforms were obtained by taking advantage of the dc isolation of the coupled line structure and using step recovery diodes to compress the edges of a 14 MHz sinusoidal source. The resulting multiport circuit for simultaneous shaping of sub-nanosecond pulses (MCS3P) showed good agreement between measured and simulated results.

Comparison of Time-Domain Impedance Boundary Conditions for Lined Duct Flows

impedance of liners. This part of the model, however, is limited to single frequency sound source in its present form. The EHR is based on the z‐transformation of the corresponding impedance function for the Extended Helmholtz Resonator in the frequency‐domain. The implementations of the two models in the numerical simulation tool with the DRP scheme are discussed in details. The results from the both models in general agree notably well with each other. However, in one case, the results from the two models dier significantly due to the presence of strongly attenuated modes, which renders the approximations of the EFI invalid. The validation and verification of both models are carried out for the latest NASA impedance tube experiment and the generic aero‐engine frequency domain results of Rienstra and Eversman. In addition, an impedance eduction technique based on the EHR and the optimization process has been developed. This further extends applications of the time‐domain models. The simultaneous optimization of all frequencies considered in the NASA’s impedance tube experiments results in a physically reasonable set of parameters for the EHR. The fitted terminal impedances and the measured mean flow profiles are used for the impedance eduction. The numerical results of both models for the generic aero‐engine inlet test case with higher azimuthal modes also compare well if the same flow assumptions and eigenvalues are used as for the frequency domain methods. Overall both models give a similar physical behavior, but the EHR requires smaller time steps in the case of small face sheet reactances.