Breakdown Phase Research Articles

Collective excitations at non-equilibrium phase transition in metabolically active red blood cells

Collective excitations of superconductors and superfluids have been extensively studied in condensed matter physics, while recent experimental advances have made it possible to study the non-equilibrium dynamics of human blood. Here, we show that some dynamic quantitative metrics calculated for the ion fluxes of two isolated peripheral blood droplets that were spatially separated by the presence of a semiconductor exhibited the characteristic features of a quasi-particle (or collective excitation) at a critical point. In the experiment, the spontaneous peak, which indicates order, appeared at a physiological (hereafter: critical) temperature of 36 °C in the human blood. The ordering effect, which was still present in the weak magnetic field of 350 mT, disappeared above the critical magnetic field of approximately 500 mT, suggesting a dynamic Meissner effect in the system (henceforth “dynamic” means derived from the “time series” – a series of real numbers). Moreover, a superconducting gap ratio of approx. 2.91 was found below the upper limit (4) of the BCS theory for weak coupling. Both these effects indicate the existence of a “superconducting” (ion) environment that is conducive to the emergence of quasiparticles. While the dynamic structure of the time series is substantially isotropic at temperatures beyond the phase transition, the system undergoes symmetry breakdown and non-equilibrium phase transition at a critical state. The designated series of dynamic variables can be used in medicine, inter alia, in screening tests as new indicators describing the patient's health.

Core-double-shell structured BT@TiO2@PDA and oriented BNNSs doped epoxy nanocomposites with field-dependent nonlinear electrical properties and enhancing breakdown strength

Field-grading polymer nanocomposites have drawn significant attention in high voltage electrical industries due to their excellent nonlinear conductive or dielectric properties. But composites with both nonlinear properties are rarely reported, and desirable nonlinear performance associated with excess fillers in the composite is at the expense of electric breakdown strength. In this work, BaTiO3 nanoparticles were decorated successively using double-shell layers of TiO2 and polydopamine, which are developed as novel nanofillers (BT@TiO2@PDA) for field-grading applications. Subsequently, BNNSs were prepared by liquid phase exfoliation, serving as the inhibitor of breakdown phase growth in the composites. Finally, novel epoxy nanocomposites (EP/BT@TiO2@PDA-OB) with BT@TiO2@PDA and oriented BNNSs were fabricated by a simple hot-pressing method. Results show that the hierarchically designed nanoparticles can make the composites possess not only nonlinear dielectric properties due to high εr of BT and improved interfacial polarization, but also nonlinear conductive properties resulted from the organic semiconductor PDA shell. Nonlinear effective medium theory (EMT) was utilized to explain the nonlinear dielectric properties, and the hopping transport model considering Pool-Frenkel effect was applied to explain the nonlinear conductive properties. In addition, electric breakdown tests reveal that EP/BT@TiO2@PDA-OB has significantly enhanced breakdown strength (45.7 kV/mm) as compared to that of pristine epoxy resin (29.4 kV/mm) and EP/BT@TiO2@PDA-RB (randomly dispersed BNNSs, 36.2 kV/mm). It is expected that these results can open new avenues for the design of novel composites with both nonlinear conductive properties and dielectric properties as well as high breakdown strength.

Development of full electromagnetic plasma burn-through model and validation in MAST

This paper describes the improvement of the electromagnetic plasma burn-through model. Full circuit equations describing the currents in solenoid, poloidal field coils, and toroidally conducting passive structures have been integrated into the differential equation system of the plasma energy and particle balances in DYON. This enables consistent calculation of the time-evolving loop voltage at a plasma position only using operation signals in a control room, which are current (or voltage) waveforms in solenoid and poloidal field coils and prefill gas pressure. The synthetic flux loop data calculated in the modelling agrees well with the measurement in MAST, confirming the validity of the loop voltage calculation. The electromagnetic modelling also enables calculation of 2D time-evolving poloidal magnetic flux map, thereby modelling the plasma volume evolution during the plasma break-down and burn-through phase. Only using the control room operation signals used in 34 ohmic start-up discharges with the direct induction start-up scenario in MAST, the electromagnetic plasma burn-through modelling has reproduced the time-evolution of plasma current, electron density and temperature, and plasma volume, showing a reasonable level of agreement with experimental measurement.

Renegotiating problematic relationships: An art-based sculpting method to address reactivity across disciplines

This article details an art-based sculpting method designed to assist professionals in exploring reactivity and difficulties within therapeutic relationships. The authors describe the Four-Phase Sculpting Method (FPSM), research specific to the method and how it was adapted for use in clinical practice, education, training and professional development. The FPSM addresses challenging relationships through the creation of a three-dimensional sculpture in four distinct phases: a creation phase, breakdown phase, mending phase and renegotiation phase. During these phases, emotions are given a form and explored through a continual process of dialoguing and witnessing. Research outcomes indicate that the method promotes transformation of thoughts and feelings, resulting in a greater understanding of the self and others. The authors discuss the FPSM and how they incorporated it into a variety of academic and professional settings over the past several years. Furthermore, the authors provide an overview of interdisciplinary applications of the FPSM.

Evaluation of the spatiotemporal unsteady characteristics of the tip leakage vortex based on a direct numerical simulation database

The spatiotemporal evolution of the tip clearance vortical structures behind a flat hydrofoil immersed in a turbulent boundary layer over a flat plate was investigated by means of direct numerical simulation, with focus on the unsteady behaviors of the tip-leakage vortex (TLV) and their effects on the flow blockage. It is found that the TLV evolutionary processes can be characterized by three typical phases: the formation phase, the vortex wandering phase, and the vortex splitting and breakdown phase. In the second phase, the TLV is subject to the wall-normal low-frequency wandering motion, which is excited by the induced vortex. The abrupt increase in vortex wandering intensity near the trailing edge of the hydrofoil can be attributed to the frequent occurrence of vortex splitting and breakdown events in the third phase. The time-averaged vortex intensity of the TLV increases gradually in the first and second phases. On the other hand, instantaneous vortex intensity shows an initially decreasing and then increasing trend, as a result of the breakdown of the TLV and the formation of the secondary TLV, respectively. In addition, the investigation of flow blockage caused by the TLV indicates that along the streamwise direction, the time-averaged blockage area and blockage coefficient both follow an exponential distribution. The present results provide a qualitative and quantitative characterization for the spatiotemporal evolution of the TLV, which is critical for improving the efficiency loss and mechanical vibration caused by the unsteady behaviors of the TLV.

Investigation of Mechanical and Physical Behaviours of Polyester Resin Matrix from Recycled Polyethylene Terephthalate with Bamboo Fibre

In this research article, we investigate the physical and mechanical properties of composites comprised of unsaturated polyester resin (UPR) and recycled polyethylene terephthalate (PET) with 10% to 40% volume of bamboo fibre (BF). Chemical evaluation of BF revealed that BF has a cellulose content of 49.86%, hemicellulose content of 25.17%, and lignin content of 7.14%. As the UPR’s different connections, FTIR identified an interconnecting framework between the styrene monomer (ST) and the unsaturated polyester (UP). It was found by TGA-DTG that there were two breakdown phases. UPR’s physical and mechanical properties were found to be affected by increasing the amount of fibre in the material, with the water absorption rising from 0.7% to 2.81% and the density (1214.38 to 1168.83 kg/m), flexural strength (51.81 to 28.92 MPa), flexural modulus (2.78 to 2.83 GPa), and tensile strength (9.71 to 3.86 MPa) all decreasing at the same time. On the other hand, the hardness increased from 82.4 Shore D to 67.9 Shore D. Fibre distribution flaws in the UPR were found, affecting the composites' mechanical characteristics. By repurposing two waste products, this study helps create new materials that are better for the surroundings.

Numerical characterization of the breakdown process of dc-driven micro-discharges sustained by thermionic emission

Because of the larger surface-area-to-volume ratio, micro-discharges can be sustained by surface emission processes. If the cathode is heated, a micro-discharge can be sustained mainly by thermionic emission. However, we still know little about how this kind of plasma is ignited and sustained. In order to explore the breakdown process of dc-driven micro-discharge sustained by thermionic emission, a one-dimensional implicit particle-in-cell/Monte Carlo collision method is adopted, coupled with the external circuit and thermionic emission model. The breakdown process of micro-discharge lasts about 8 , and this process can be roughly divided into two phases, i.e. pre-breakdown and breakdown phase. The dynamic plasma parameters during the evolution process are analyzed, such as particle density, electron energy distribution function, electric potential, average particle temperature, and particle current density. The plasma electrical characteristics as well as the article and power balance, are also presented to show the evolutionary features of the whole gas breakdown process.

Influence of Temperature on Lightning Performance of Mineral Oil

This article deals with the influence of temperature on the lightning impulse breakdown voltage (LI BDV) of mineral oil in a non-uniform electric field. The experiments were performed in point–plane electrode arrangements under a standard lightning impulse voltage of negative polarity. The LI BDV for the temperatures of 20, 40, 60, 80, 100 and 110 °C was measured using a step method with registration of the light signals emitted during pre-breakdown and breakdown phases. The average propagation velocity was also determined. The results confirm that the mineral oil tested under LI voltage behaves similarly to AC voltage-based stress. The LI BDV increases with temperature up to 100 °C and then tends to decrease. The results demonstrated that viscosity dependent processes are responsible for increasing the LI BDV with temperature up to the 100 °C; and liquid vapor formation processes are responsible for decreasing the LI BDV at temperatures equal to and higher than 100 °C.

Microsecond Electrical Breakdown in Water: Advances Using Emission Analysis and Cavitation Bubble Theory.

Electrical discharges in water are a subject of major interest because of both the wide range of potential applications and the complexity of the processes. This paper aimed to provide significant insights to better understand processes involved during a microsecond electrical discharge in water, especially during the propagation and the breakdown phases. Two different approaches were considered. The first analysis focused on the emission produced by the discharge during the propagation using fast imaging measurements and spatially resolved optical emission spectroscopy. The excited species H, O, and OH were monitored in the whole interelectrode gap. The second analysis concerned the thermodynamic conditions induced by the breakdown of the discharge. The time evolution of the bubble radius was simulated and estimation of the initial pressure of the cavitation bubble was performed using the Rayleigh–Plesset model. Values of about 1.7 × 107 Pa and 1.2 × 108 Pa were reported for the cathode and anode regimes, respectively. This multidisciplinary approach constitutes a new step to obtain an accurate physical and chemical description of pin-to-pin electrical discharges in water.

Determining metal elements in liquid samples using laser-induced breakdown spectroscopy and phase conversion technology.

A phase conversion technology, involving the loading of brine samples with anionic polyacrylamide (APAM) colloidal droplets, is proposed to detect metal elements rapidly and accurately in liquid samples using laser-induced breakdown spectroscopy. The experimental conditions were optimized by comparing the obtained emission intensities and the signal-to-noise ratios, including the concentration of APAM, volume ratio of APAM solution to sample, delay time, and lens-to-sample distance (LTSD). Three kinds of complex brine samples with slightly soluble salts were used to test the analytical performance of the proposed method. The results show that the discrepancies of the concentrations of Li, Sr and Ca were 0.74-3.59%, compared with those obtained using inductively coupled plasma-optical emission spectrometry. This suggests that the proposed method can successfully determine metal elements in liquid samples, featuring short sample preparation time (less than 20 min), small sample volume (10 μL), and simple operation (no adsorption).

Two Stages Thermal and Catalytic Cracking of Polyethylene Terephthalate to Fuel Production

PET (polyethylene terephthalate) is made up of polymerized repeating units of the ethylene terephthalate monomer (C10H8O4). PET is a recyclable plastic with the number 1 as its identification code. PET, which has a molecular weight of 192 gm/mole and contains 62.5 percent carbon, 33.3 percent oxygen, and 4.2 percent hydrogen, is utilized as synthetic fiber, polyester, plastic packaging, and soft drink containers all over the world. The main purpose of this study is to convert PET waste into liquid hydrocarbon fuel. Because PET use has risen significantly over the world, and the bulk of garbage is thrown into the soil rather than recycled, posing an environmental risk. During the heat breakdown phase, PET decomposes. It creates very strong and solid non-biodegradable terephthalic acid and benzoic acid complexes. To obtain liquid hydrocarbon fuel from PET, at 250-300℃, calcium hydroxide Ca(OH)2 is used as a catalyst in this study.

A transport model describing how defect accumulation leads to intrinsic dielectric breakdown and post-breakdown conduction

A charge transport model, originally developed for simulating time-dependent dielectric breakdown (TDDB) behavior at the interconnect level, was modified and extended to also apply to the current-voltage (I-V) behavior in the post-breakdown region. The model allows one to simulate the current-voltage characteristics of the dielectric material from its pristine state, through the wear-out and breakdown phase, and into the post-breakdown region. The systematic transition from the insulator region to the conductor-like region is visualized through the intrinsically generated trap distribution evolution. A percolation starts forming near the anode at a critical trap concentration of 5 × 1026m−3 for the system under study and proceeds directionally, towards the cathode. Soft breakdown occurs when the percolation path front reaches the cathode with a trap volume fraction of 0.15, close to the theoretical value of 0.16. Hard breakdown, at the switching point, is associated with the completion of a vacancy-type percolation path and saturation of the trap concentration. A power law relationship with a power of 2 is found between the system's conductance and the trap concentration near the anode between the critical point and the switching point. A predicted linear post-breakdown region following the breakdown event along with a weak temperature dependence agrees well with experimental observations.

Understanding the Relationship between State-of-Charge and Structural Fragility in Ni-Rich Layered Materials for Lithium Batteries

Lithium batteries are at the frontier of energy storage. Co-free, Ni-rich layered transition metal oxide (TMO) materials have gained interest within the past decade due to their low cost and increased practical capacity. The challenge with employing these layered oxide cathodes is their inherent structural fragility, facilitated by metal cation migration and lattice oxygen loss. Upon charging, the redox center becomes oxidized, generating thermodynamically favorable electron transfer pathways between the electrolyte and the layered oxide. This transfer pathway is mainly due to the TM3d-O2p orbital hybridization perturbation during battery charging.Surface reconstruction and the structural reordering that accompanies it can undesirably influence the cathode – electrolyte interphase, leading to enhanced electrolyte degradation pathways that can minimize Coulombic efficiency. Electrolyte decomposition occurs at the oxide cathode surface, but can lead to bulk electronic and structural changes of the layered oxide, chemomechanical breakdown, and irreversible phase transformations.In this study, we focus on understanding the interplay between bulk phase transitions and surface instability with respect to electrolyte chemical decomposition. We use novel galvanostatic cycling parameters, extensive electron microscopy, and synchrotron X-ray techniques to decouple chemical and electrochemical electrolyte decomposition pathways to understand their role in Co-free, Ni-rich oxide cathode degradation. This work allows us to decouple surface and bulk chemistries at the cathode – electrolyte interphase to inform further insight into optimal Ni-rich oxide cathode design.

Phase-Field Modeling to Investigate the Influence of Nano-Filler Properties on Composite Breakdown Strength and Discharge Energy Density

Composite materials have wide range of energy storage applications where high energy density is desirable. Inclusion of nano-fillers with low electrical conductivity in the polymers have been associated with the improvement in breakdown strength and hence the discharge energy density. A phase-field model is developed to investigate the influence of nano-filler properties, shape and volume fraction on the breakdown phase evolution, breakdown strength and discharge energy density. The model is validated with the experimental results from literature. The results reveal that the inclusion of nano-filler (nano-sheets) with lower electrical conductivity as compared to polymer, result in the increase of breakdown strength. The results also show that nano-fillers with high dielectric constant would result in high discharge energy density. This increase in discharge energy density comes at the expense of decrease in breakdown strength. This work reports strategies on choosing suitable nano-filler material (and shape) for specific polymer material.

The effects of air flow on the nanosecond pulsed pin-to-pin discharge dynamics in atmosphere-pressure air

Investigation of the breakdown phase of a nanosecond pulsed pin-to-pin discharge in air at atmosphere pressure with different gas flow rates is carried out. The experimental results show that the air flow leads to increase in the breakdown delay time. The effect of air flow rate on the current growth rates and streamer channel appearance at the beginning of breakdown is observed, which indicates that the redistribution and decrease in the densities of reactive species produced by previous discharges are playing the main role in the discharge delay time. When 15 standard liters per minute (slm) air flow is used and pulse frequency is 1 kHz, the discharge current reaches a peak of about 0.5 A, then it decreases to 0.4 A and lasts for about 70 ns, and then the discharge current starts to increase rapidly at a rate of >0.1 A/ns. For pulse frequency of 8 kHz or nitrogen as working gas, the discharge current increases monotonically. Besides, the difference of the gas temperature for the cases of 0 and 15 slm is measured, and the result indicates that the difference of the gas temperature should not be the main contributor to the difference of the breakdown delay time. Detailed analysis shows that the appearance of the first current peak is due to the fast detachment of O2−. Finally, simulation results show that the ionization rate for the case of 15 slm is also more significantly delayed than the case of 0 slm, which is consistent with the measured discharge current waveform.

Thermal-hydraulic analysis of the DEMO CS coil designed by CEA

The superconducting Central Solenoid (CS) of the EU-DEMO tokamak coil will comprise five modules, labeled CSU3, CSU2, CS1, CSL2 and CSL3, situated vertically one above the other. The central CS1 module will be operated under the most severe conditions, i.e. the largest mechanical loads and magnetic field. Two alternative designs of the CS1 module are being developed by the CEA and EPFL-SPC teams. The CS1 module designed by CEA is double-pancake wound using a Nb3Sn Wind&React Cable-in-Conduit Conductor with a central cooling channel. Our work presents the thermal-hydraulic study of the CEA design of the CS1 module based on the EU-DEMO 2018 baseline. The first part of our analysis includes simulations of the CS1 behavior at normal operating conditions, aimed at the estimation of the minimum temperature margin. This part consists of two stages, namely: (i) simulations of the whole simplified “4 points” CS current scenario (not including the breakdown), and (ii) preliminary simulations of the breakdown phase. The second part is focused on quench simulations aimed at the assessment of the maximum hot-spot temperature. The analysis is performed using the THEA code by CryoSoft. We consider the realistic magnetic field and strain profiles along the conductor, heat transfer between neighboring turns and heat loads due to the AC coupling losses. Power of AC coupling losses in all performed simulations is computed based on the effective values of magnetic field and three trial values of the parameter nτ (100 ms, 200 ms and 400 ms). We assume that quench is initiated at the beginning of pre-magnetization phase and we take into account heat generation due to AC losses during the current dump. Minimum temperature margin during the whole simplified current scenario is larger than the 1.5 K acceptance criterion for all considered nτ values. Preliminary simulations of the breakdown phase indicate that the minimum ΔTmarg may drop below 1.5 K, even for the lowest considered nτ value, which calls for attention and requires further more detailed studies. The calculated hot-spot temperatures in all considered cases were safely below the 150 K acceptable limit.

Breakdown Phase in the GOLEM Tokamak and Its Impact on Plasma Performance

The effect of the breakdown phase on subsequent plasma parameters in GOLEM tokamak is investigated remotely. The dependence of the breakdown voltage and the breakdown time on the time delay between the switchings-on of a toroidal magnetic field Bt and a toroidal electric field Et for different groups of the pressure magnitudes is built. The performed experiments have shown that, for GOLEM tokamak, the shorter the temporal delay, the better are the mean plasma parameters. In addition, the breakdown phase is discussed in more details. In the discussion, the avalanche phase of the breakdown is analyzed. The dominant mechanism of particle losses during the avalanche phase, future steps, and tasks are discussed and set. The experiments on studying the breakdown phase have been carried out remotely on GOLEM tokamak by undergraduate students of V.N. Karazin Kharkiv National University.

“STRING” TYPE OF BARRIERLESS PLASMA CHEMICAL REACTOR FOR GENERATION OZONE FROM AIR

The efficiency of ozone generation for barrierless plasma chemical reactors with different cathode designs was compared. The characteristics of ozone generation for a plasma chemical reactor with a string-type cathode in comparison with the previously developed star-shaped cathode for different combinations of bias and pulsed components of voltage have been investigated. The special feature of the operation of a plasma-chemical reactor with a string cathode is revealed. There is consisting in the absence of dependence of the transition of the discharge combustion mode into the spark breakdown phase from the presence of a bias voltage.

Recording the breakdown phase of a 4 m rod-plane air insulation under positive standard switch impulse voltages

Air insulation is widely used as the external insulation of power transmission lines. The performance of air insulation is a concern. The breakdown voltage of rod-plane air insulation with a certain length is often used to evaluate the performance of the air insulation with the length. The breakdown voltage of rod-plane air insulation is determined by the discharge phase termed breakdown phase. The breakdown phase of a 4 m rod-plane air insulation under positive standard switch impulse voltages was recorded by a high-speed camera and reported in this paper. The breakdown phase would help to deepen the understanding of air insulation.

Experimental Analysis of Breakdown With Nanosecond Pulses for Spark-Ignition Engines

The influence of pulse rise rate and pulse duration for ignition purposes in engines is investigated. A constant volume cell is used to characterize the breakdown voltage under nanosecond pulsed voltages with automotive sparkplugs having electrode gaps ranging from 0.2 mm to 1 mm. Two pulse generators are used to compare pulses with durations of 10 ns and 50 ns. Different pulse amplitudes are used, and air gaps with breakdown voltages ranging from 4 kV to 15 kV are investigated. The cell is filled with synthetic air with densities gap distances products that are relevant for internal combustion engines. This study shows that the pulse shape and rise rate influence the breakdown voltage. Under pulsed discharge, the breakdown voltage is always above the static breakdown voltage. The probability of pulsed discharge breakdown increases as both the pulse amplitude and duration increases. Furthermore, the breakdown voltage value increases with increasing pulse rise rate. The delay time between reaching the static breakdown voltage and the actual breakdown voltage decreases with increasing overvoltage. The delay time is constituted by statistical and formative times. Both the statistical and formative times decrease with increasing overvoltage. For ignition purposes, the pulse rise rate should be as high as possible to deliver a larger energy input in the breakdown phase. Furthermore, for reduced electrode erosion, the pulse duration should be short (10-20 ns) to reduce the probability for a transition to an arc.