Transient Recovery Research Articles

Alternation of the Mode Synchronization and Desynchronization in Ultrafast Fiber Laser

AbstractUltrafast fiber lasers offer a unique opportunity to implement optically a Poincaré mapping in the phase space of a variety of complex dissipative dynamical systems operating far from the equilibrium. Understanding of such complex optical dynamical systems revealing, for instance, ultrafast dynamics of the dissipative solitons (DSs) and more complex regimes is important for advancing specification and performance of the mode‐locked lasers used in a vast number of applications ranging from spectroscopy and medicine to metrology and telecom. Here, using the mode‐locked fiber laser as a test‐bed, the Shilnikov‐type ultrafast dynamics taking the form of randomly switching between noise‐like pulsing and quasi‐continuous‐wave regimes is experimentally demonstrated. The transient coherence recovery is revealed, during which the noise‐like pulse (NLP) is transformed into a coherent DS state and then returned to an incoherent NLP state. The demonstrated alternation of mode synchronization and desynchronization is both of practical importance for developing new types of partially mode‐locked lasers and of the fundamental interest for the nonlinear science in the context of revealing routes to the turbulence in distributed nonlinear systems.

Effect of Bapta and Dysferlin's C2A Domain on Recovery of Ca2D Transients After Osmotic Shock in Dysferlin-Null Myofibers

Effect of Bapta and Dysferlin's C2A Domain on Recovery of Ca2D Transients After Osmotic Shock in Dysferlin-Null Myofibers

Detection of the natural frequency of transmission power lines applying S-transform on Transient Recovery Voltage

This paper presents a new approach for detecting the natural frequency of transmission power lines applying S-transform on Transient Recovery Voltage (TRV). TRV usually appears between terminals of a circuit breaker during an isolation of a fault. The TRV phenomenon contains wideband frequency information such as the natural frequency of the system that depends not only on the electrical transmission line characteristics but also on the location of the fault. S-transform was applied to the TRV signal and the energy content in the time-frequency contours was evaluated using Parseval's theorem. This analysis ensures the accurate identification of the natural frequency of the resulting system by locating the maximum relative of the energy content. The case studies studied involved taking actual systems and using frequency-dependent phase models. The experiments were performed to show that the proposed approach can robustly determine the frequency associated with the parameters of the line. Different cases were considered: distances, inception angles, fault resistances, circuit breakers and models of electric arc. The simulation results demonstrate that using S-transform to analyse TRV provides a simple and reliable method for determining the natural frequency and opens a new way for studying the behaviour of protections and faults in power systems.

Dynamic Alterations of Brain Injury, Functional Recovery, and Metabolites Profile after Cerebral Ischemia/Reperfusion in Rats Contributes to Potential Biomarkers.

Cerebral ischemia-reperfusion (I/R) is characterized by initial transient cerebral ischemia followed by reperfusion. Various pathophysiological processes are involved in brain injury and functional recovery during cerebral I/R. There are few studies on dynamic metabolic process after cerebral I/R. The present study was to observe dynamic alteration of brain injury, functional recovery, and metabolites after cerebral I/R in rats and discover potential metabolic markers. The cerebral I/R model was established by middle cerebral artery occlusion (MCAO) for 90min, following reperfusion in rats. The results of cerebral infarction area, cerebral edema, and behavior test showed that there were dynamic changes in brain injury and functional recovery at different periods after cerebral I/R. Further analysis showed that the brain injury was severe on the first day of cerebral I/R, and there was a significant functional recovery from the 7th day of cerebral I/R, followed by an aggravation trend of brain injury from the days 7 to 28. Furthermore, Matrix-assisted laser desorption ionization mass spectrometry imaging analysis showed that the expression of ATP, glucose, and citric acid on 7th day was the highest during cerebral I/R, which indicated that energy metabolism and oxidative phosphorylation played important roles during cerebral I/R. In addition, the untargeted metabolomic results showed that the level of isocitric acid, the ratio of oxyglutaric acid/glutamic acid, and the level of pyruvic acid associated with the TCA cycle were also the highest on the 7th day during cerebral I/R, which indicated that the transient spontaneous recovery of ischemic brain on the 7th day after ischemia-reperfusion might be related to oxidative phosphorylation and energy metabolism in the brain in this period. In conclusion, the results suggest that some small molecule metabolites participate in the brain injury and functional recovery during cerebral I/R, which is of great significance to the development of therapeutic drugs and diagnostic markers.

Solution-processed TiO2 as a hole blocking layer in PEDOT:PSS/n-Si heterojunction solar cells

The junction properties at the solution-processed titanium dioxide (TiO2)/n-type crystalline Si(n-Si) interface were studied for poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/n-Si heterojunction solar cells by the steady-state photovoltaic performance and transient reverse recovery characterizations. The power conversion efficiency could be increased from 11.23% to 13.08% by adjusting the layer thickness of TiO2 together with increasing open-circuit voltage and suppressed dark saturation current density. These findings originate from the enhancement of the carrier collection efficiency at the n-Si/cathode interface. The transient reverse recovery characterization revealed that the surface recombination velocity S was ∼375 cm/s for double TiO2 interlayer of ∼2 nm thickness. This value was almost the same as that determined by microwave photoconductance decay measurement. These findings suggest that solution-processed TiO2 has potential as a hole blocking layer for the crystalline Si photovoltaics.

Two-dimensional kinetic simulation of plasma dynamics in the post-arc stage of vacuum circuit breakers

In this paper, the plasma decay process is simulated with a two-dimensional kinetic model. The charged particles including electrons and singly charged copper ions are processed with the particle-in-cell method, and the electric field is solved in cylindrically symmetric coordinates. When the residual magnetic field is not taken into consideration, electrons react to the transient recovery voltage instantaneously, leaving an ion sheath in the vicinity of the postarc cathode where the electric field is significantly enhanced. The sheath expanding velocity increases as the overall plasma density decreases. Charged particles move not only along the axial direction but also toward the shield of the arc chamber. When the shield is at postarc cathode potential, the radial expansion of electrons is reduced, while that of ions is facilitated. In addition, postarc current is higher than that in simulation with the shield at postarc anode potential. These results are consistent with those in previously published works. When the axial magnetic field is applied, electrons rotate around the magnetic lines and instabilities develop, resulting in density fluctuations. Besides that, the postarc current is higher than those in the case without the magnetic field.

Генераторные выключатели для атомных электростанций

A comparative analysis of the characteristics of foreign and domestic generator circuit breakers is carried out. The necessity of developing a domestic generator circuit breaker for newly constructed nuclear power plants with a power unit capacity of over 1200 MW is shown. The most promising solution is the development of hybrid generator circuit breakers using main contacts, vacuum circuit breakers and controlled arresters. The scheme and operation of elements of hybrid circuit breakers in modes of shutdown of three
phase short
circuit current is resulted. The developed mathematical model of hybrid breakers consisting of generator, busbar and transformer for power plant and given transients disable the short
circuit current in different modes. It is proposed to develop hybrid circuit breakers to replace oil and air circuit breakers at the stages of modernization of nuclear power plants, and in the new construction it is advisable to use generator circuit breakers, as a prototype of which the gas-insulated device developed by ABB is given. Basic electrical formulas for estimation of the switching capacity of the circuit breaker of the generator in the amplitude of the current gap three
phase short
circuit current, degree of asymmetry, amplitude and rate of rise of transient recovery voltage formulated.&nbsp

Methodology to find and mitigate Transient Recovery Voltages (T.R.V) considering various abnormal scenarios: A case study of IEEE-39 bus system

Methodology to find and mitigate Transient Recovery Voltages (T.R.V) considering various abnormal scenarios: A case study of IEEE-39 bus system

Self‐adaptive fractional‐order LQ‐PID voltage controller for robust disturbance compensation in DC‐DC buck converters

AbstractThis paper presents a state‐dependent self‐tuning fractional control strategy for a DC‐DC buck converter in order to enhance its output voltage regulation and disturbance attenuation capability. The proposed control scheme primarily employs a ubiquitous proportional‐integral‐derivative (PID) controller, where gains are optimally selected using a linear‐quadratic state‐space tuning approach. The optimal PID controller is then augmented with fractional‐order integral and derivative operators in order to improve the controller's degrees‐of‐freedom as well as the system's overall time‐domain performance. The fractional controller's robustness against bounded exogenous disturbances, contributed by the input fluctuations and load‐step transients, is further enhanced by adaptively modulating the fractional‐orders of the integro‐differential operators as a smooth nonlinear function of controlled‐variable's error‐dynamics. An online dynamic adjustment law, comprising of a zero‐mean Gaussian function of error and its derivative, is used to individually update the two fractional orders after every sampling interval. The error derivative is evaluated by measuring the output capacitor's current in order to compensate the noise injected by parasitic impedance. The other controller parameters are tuned via particle‐swarm‐optimization algorithm. The proposed self‐adaptive control strategy renders rapid transits, minimum transient recovery time, and minimal fluctuations around steady state in the response. Its efficacy is validated through hardware in‐the‐loop experiments conducted on a buck converter prototype.

A Novel Adaptive Model Predictive Control Based Three-Phase Inverter Current Control Method

This paper proposes a novel current control method based on Model Predictive Control (MPC) for three-phase inverters. The proposed method is based on an Adaptive MPC (A-MPC) with a PWM modulation. An innovative model parameter estimation and modification method is also proposed, leading to enhanced control accuracy. Comparing with traditional current control methods, such as PI and PR control, the proposed method has better dynamic performance. The transient dynamics, i.e., recovery time and overshoot, have been considerably improved. Simulation and experimental results are presented to validate the effectiveness of the proposal.

Switching Behaviour of a Series Connection of a Vacuum Interrupter and a Gas Circuit Breaker

After being in the focus of sciences' and industry's research and development activities for many years, the investigation of possible SF6 gas-alternatives has been even more intensified after the revision of the European F-Gas regulation 517/2014. As natural gases yield a significantly lower dielectric strength in comparison to SF6, new challenges arise for the design of high voltage switchgear. Vacuum interrupters are environmentally friendly, reliable and able to withstand steep rising transient recovery voltages. In the last years, first installations of switchgear based on vacuum switching technology in sub-transmission level are in operation. One option for the realization of a SF6 free high voltage switchgear for transmission level is the combination of a gas circuit breaker filled with an atmospheric gas with a vacuum interrupter in a hybrid switchgear. In this contribution the voltage distribution and switching behavior of a hybrid circuit breaker is experimentally investigated.

A new realistic transient model for restrike/prestrike phenomena in vacuum circuit breaker

Vacuum circuit breakers (VCBs) are increasingly used in power systems. During the operation of a circuit breaker (CB), several incidents such as prestrike, restrike and current chopping might happen which cause erosion in the contacts of the CB and high frequency inrush current. The evaluation of these transients are highly important due to their influence on the switching overvoltage, as well as their dependency to the statistical behavior of the dielectrics. Accordingly, this paper presents a new realistic model for VCBs with respect to the three factors as follows: I-probabilistic breakdown voltage, II-probabilistic operation-velocity and III-nonlinear movement of the contacts. The results based on the proposed model have been compared with other published-experiments and those obtained based on the conventional model in the Helmer circuit. The results are indicated that ignoring the probabilistic behavior of the parameters or linear consideration for breakdown voltage led to the imprecise estimation of transient parameters such as transient recovery voltage (TRV), rate of rise of recovery voltage (RRRV) and the number of breakdowns. The results indicated that using the improved model led to a 60% and 20% change in TRV peak and RRRV, respectively.

Study of the stagnation region in HV gas-blast interrupters with synchronous gas injection

According to modern trends in the development of HV gas blast circuit breakers GCB (such as increasing of rated voltage per break) a stagnation region in GCB rises and GCB interrupting ability is reduced. The zone of stagnation has the dominant influence on a thermal-dielectric recovery, since some quantity of hot gas medium remains in this region during the transient voltage recovery wave. The paper studies the stagnation region deformation in double-flow gas-blast interrupters with synchronous gas injection. The interaction between gas jet and the stagnation zone in the vicinity of current zero is discussed. Numerical analysis of basic gas flow with synchronous gas injection between arc contacts of the arc quenching chamber is presented.

Alopecia totalis and universalis long-term outcomes: a review.

Alopecia totalis (AT) and universalis (AU) represent the most severe subtypes of alopecia areata with more dramatic features and worse prognosis. The goal of this review is to identify all studies with long-term prognostic data on patients with AT and AU and provide a long-term outcome estimate. The PubMed database was queried to identify all articles discussing the long-term prognosis of AT and AU. A total of nine articles discussing long-term recovery rates of AT and AU were identified. The articles described 689 (162=AT, 245=AU, 282=not specified) total patients. Six of the nine studies identified complete recovery as a potential end point in a total of 375 (39=AT, 75=AU, 261=not specified) patients. According to these studies 8.5% (32/375) of AT and AU patients achieved complete recovery. A larger proportion of patients will obtain at least transient recovery periods of partial or total hair regrowth. The poor long-term outcomes of AT and AU may cause patients to lose hope with treatment. Response to treatment is often unpredictable, and physicians should be aware of the prognosis and its effects in order to properly counsel patients.

P1598Electrophysiological and structural characterization of acute atrial myocardial infarction

Abstract Background Atrial myocardial infarction may be a risk for atrial fibrillation. However, the electrophysiological and structural characteristics of the infarcted atrial myocardium are not well known. This study aimed to analyse the changes in local atrial electrograms and myocardial structure in an experimental model of isolated atrial myocardial infarction. Methods Five anesthetized, open-chest pigs were submitted to 4 hours of acute atrial myocardial ischemia induced by direct surgical clamping of atrial coronary branches originating from the right coronary artery. In all cases, we recorded simultaneously the 12-lead surface electrocardiogram (ECG) and the epicardial mapping of local atrial electrograms (17 x 12.5 mm patches containing 128 electrodes, with 1 mm inter-electrode distance) in a region close to the occluded branches and in control non-treated atria. The changes in local atrial QRS-ST segment and the amplitude of the P-wave of the ECG were sequentially analysed (Figure). The hearts were removed and processed for anatomopathological examination. Results Selective atrial coronary branch occlusion induced a patchy atrial myocardial necrosis with an irregular and abrupt border zone (circled areas in the Figure). During the first 15 min of ischemia, the local atrial electrograms showed increasing R waves, widening of QRS complex, and ST segment elevation leading to monophasic potentials (maximal ST segment at 30 min: from 0.2±0.7 mV to 1.9±1.4 mV, ANOVA p<0.01). This period was followed by a phase of transient electrical recovery characterized by disappearance of monophasic potentials, reduction of ST segment elevation, and recovery of local electrical activation. After 60 min of occlusion, monophasic potentials reappeared and the magnitude of ST segment elevation decreased progressively during the ensuing 3 hours. The spatial transition from areas with monophasic potentials to normal electrograms encompassed 1 or 2 electrodes. The surface ECG showed increased duration of the P-wave (lead II at 3h occlusion: from 73.2±4.5 ms to 88.9±15.5 ms, ANOVA p<0.05) with absence of ST segment changes. Atrial arrhythmias were not observed. Structural and electrical atrial changes Conclusion Selective occlusion of atrial coronary branches induced patchy atrial myocardial necrosis with abrupt anatomical and electrical border zone. The overt QRS and ST segment changes in local atrial electrograms resembled those described in acute ventricular myocardial ischemia, and were associated with widening of the P-wave on the surface ECG. Although acute ischemic arrhythmias were not observed, the atrial structural alterations might set the substrate for re-entrant arrhythmias late after the healing over process. Acknowledgement/Funding Supported by grants from ISCI-MINECO (FISPI17/00069), CIBERCV (CB16/11/00276), FEDER and Fundaciό “La Maratό” TV3 (20150830).

An Integrated DC–DC Converter With Segmented Frequency Modulation and Multiphase Co-Work Control for Fast Transient Recovery

This paper presents a fully integrated voltage-controlled oscillator (VCO)-based switched-capacitor (SC) 15-phase dc–dc converter in 65-nm CMOS. We propose two transient-enhancement techniques: segmented frequency modulation (SFM) and multiphase co-work (MCW) control to reduce the latency of the VCO-based control loop and shorten the SC dc–dc converter’s transient response time. The SFM can improve the heavy-to-light load transient by dynamically increasing the charge pump discharge current by nine times, while the MCW can enhance the light-to-heavy load recovery by synchronously combining three interleaved flying capacitors together during the transient state. We designed the 15-phase interleaved converter to support an output voltage of 1 V from a 2.4-V input supply, delivering up to 138 mA of load current, which takes only 25/29 ns for output voltage recovering to the steady state from heavy-to-light/light-to-heavy load transients, respectively. It obtains a peak efficiency of 82.8% and maintains the efficiency above 80% from 31 mA to the maximum load current. The SC dc–dc converter chip occupies 0.61 mm2, and its output power density is 240 mW/mm2.

Design of Dual-Sampling and Adaptive Predictive PID Controller for Buck DC–DC Converters

In this paper, based on the combination scheme of dual-sampling and adaptive predictive PID control, a digital controller for improving the transient performance of Buck DC–DC converters is designed. Due to the inherent loop delay in analog-to-digital (A/D) conversion, the calculation process of the digital controller and digital pulse width modulator (DPWM) of conventional digitally-controlled Buck DC–DC converters limits the system bandwidth and this makes the transient response lower. The designed digital controller can reduce the delay time in analog-to-digital converter (ADC), the digital controller and DPWM of digitally-controlled Buck DC–DC converters. Adaptive predictive control is used to eliminate the delay time of ADC and the digital controller, while dual-sampling scheme is used to reduce the delay time of DPWM in this paper. These are two new control schemes, and they show better performance in improving the transient response than other existing control schemes. Both simulation and experimental results demonstrate that the designed digital controller based on dual-sampling and adaptive predictive PID control is effective in improving the transient performance of Buck DC–DC converters. During experimental verification, for a load step between 0.5[Formula: see text]A and 1.0[Formula: see text]A, the fastest transient recovery time and the overshoot voltage are found to be 102[Formula: see text][Formula: see text]s and 120[Formula: see text]mV, respectively. Compared with the conventional digital PID controller, the transient recovery time and the overshoot voltage of the digital controller designed in this paper are decreased by 40.0% and 27.3%, respectively.

Analysis on the Self-Sustained Oscillation of SiC MOSFET Body Diode

Under certain conditions, self-sustained oscillation may occur during reverse recovery transient of high-side silicon carbide (SiC) MOSFET body diode in the half-bridge circuit. In this article, two distinct positive feedback mechanisms that can excite the self-sustained oscillation are identified based on the double-pulse test. To investigate the instability of the two types of oscillation, a small signal ac model of the half-bridge circuit is proposed. With the model utilized, the parametric sensitivities of various parameters on the self-sustained oscillation are analyzed. The analyses reveal the oscillatory criteria, which provides effective guidelines to prevent the oscillation. In the end, the oscillation prevention guidelines are validated by the experiment. The experimental results demonstrate that the proposed theoretical treatment can provide reasonable guidelines to suppress the two types of self-sustained oscillation.

Traction Injury of Recurrent Laryngeal Nerve During Thyroidectomy.

Loss of the neuromonitoring signal (LOS) during thyroidectomy signifies recurrent laryngeal nerve (RLN) injury, which is one of the common complications, especially by traction injury. Transient intraoperative LOS means spontaneous recovery of nerve function during surgery or within 6-month post-surgery. Few articles discuss intraoperative recovery time and transient LOS, and there is no consensus on the risk factors for RLN traction injury and its recovery course; thus, we wanted to determine the maximum intraoperative recovery time. This retrospective study included patients who had undergone thyroidectomies at Tainan National Cheng Kung University Hospital between January 2015 and August 2018. A total of 775 patients (with 1000 nerves at risk) who underwent intermittent intraoperative neuromonitoring during thyroidectomy were included in this study. The LOS nerves were divided into 4 groups based on the LOS subtype and the intraoperative status of the recovery. The postoperative vocal cord function was determined by thyroid ultrasound and/or laryngoscope. All the patients would be followed up postoperatively in 2-3days, 1week, 2weeks, and 4-6weeks. LOS occurred in 67 of 775 (8.6%) patients and in 70 of 1000 nerves at risk (7.0%). There were 2 in 70 nerves (2.9%) with LOS type 1 (segmental nerve traction injury) with intraoperative recovery (Group 1), 5 (7.1%) with LOS type 1 without intraoperative recovery (Group 2), 47 (67.1%) with LOS type 2 (global injury) with intraoperative recovery (Group 3), and 16 (22.8%) with LOS type 2 without intraoperative recovery (Group 4). All LOS type 1 (segmental nerve injury) nerves had pathologic lesions near the RLN or vagus nerve, but none had invaded the nerves (p < 0.05). The resolving time intraoperatively in the 2 patients in Group 1 was 5min and 10min, respectively. The resolving time intraoperatively in Group 3 was 1-20min, and the average time was 4.8min. In Group 2, 3 injured nerves recovered within 6weeks postoperatively, and 2 nerves in 12weeks. In Group 4, all the 16 injured nerves recovered within 6weeks postoperatively. Applying intermittent intraoperative neuromonitoring during thyroidectomy, traction recurrent laryngeal nerve injury still happened in 7.0%. 70% of the injured nerves recovered the function intraoperatively after releasing the traction, and the longest duration of recovery is 20min.

Post-Arc Characteristics of High-Current Arcs in Vacuum Circuit-Breakers

The post-arc (PA) characteristics of vacuum arcs in transverse magnetic field contacts are studied for short-circuit currents of up to 123 kA peak and transient recovery voltages below 875 V. The measured PA currents are interpreted in terms of an Electric Resistance Model and the models of Andrews-Varey, Langmuir-Child, and Slepian-Schmelzle. Whereas in the late PA period, the calculations do not agree well with the measurements, the PA behavior is well described in the early period after current-zero. It is concluded that the PA discharge is amplified by ionization of metal vapor particles in the boundary sheath due to electron impact.