Ballast Resistor Research Articles

Complex dynamics in an atmospheric pressure glow discharge in helium: transition from stationary to periodic oscillatory, and fully chaotic states

Abstract This work deals with the numerical study of spontaneous temporal oscillations in an atmospheric pressure glow discharge (APGD) in helium. The transition of helium APGD from stationary to periodic oscillatory state through the Hopf bifurcation, and further from periodic to chaotic oscillations through period-doubling bifurcations is explored. The choice of the discharge and external electric circuits parameters is guided by the relevant experiments. The ballast resistance and supply voltage of the external circuit play the role of control parameters. The method is based on the stability analysis of stationary states of the discharge. 

The stability diagram predicting parameter regimes at which stable and oscillatory states of the APGD can be expected is obtained. The effects of the discharge parameters (such as the gas gap, secondary electron emission coefficients, and capacitance in the external electric circuit) on the bifurcation curves are identified. 

The Lorenz map and corresponding period-doubling bifurcation diagram characterizing transition to chaotic oscillations in helium APGD with an increase in the control parameter are derived. The value of the capacitance in the external circuit plays a critical role in the dynamical behavior of the discharge. Decreasing its value contributes to the dissipation/damping of the system, whereas increasing it enhances the irregular behavior of the system.

Ignition process of the plasma scalpel in normal saline: Numerical simulation and comparison to experiment

In this paper, the ignition process of the plasma scalpel is characterized by means of numerical simulation, shadowgraphy, and voltage–current measurements. The ignition process involves two phases: the pre-breakdown phase and the breakdown phase. Our study shows that in the pre-breakdown phase, the vapor layer is first generated around the corners of the active electrode and then gradually extends to cover the entire active electrode. Once the active electrode is fully covered by the vapor layer, the electric field reaches a maximum of 7.3 × 106 V m−1, which can cause discharge in the vapor layer. At this moment, the thickness of the vapor layer is approximately 100 μm. In the breakdown phase, the maximum electron density reaches 1018–1019 m−3. The plasma dissipates about 60% of the total power which is up to 125 W, thus enabling efficient cutting. In addition, we simulate the discharge characteristics of cutting various biological tissues. The results show that under the same voltage level, the higher the conductivity of biological tissues, the greater the discharge current. The biological tissues act as ballast resistors in equivalent circuits.

Hysteresis between gas breakdown and plasma discharge

In direct-current (DC) discharge, it is well known that hysteresis is observed between the Townsend (gas breakdown) and glow regimes. Forward and backward voltage sweep is performed using a one-dimensional particle-in-cell Monte Carlo collision (PIC-MCC) model considering a ballast resistor. When increasing the applied voltage after reaching the breakdown voltage (Vb), transition from Townsend to glow discharges is observed. When decreasing the applied voltage from the glow regime, the discharge voltage (Vd) between the anode–cathode gap can be smaller than the breakdown voltage, resulting in a hysteresis, which is consistent with experimental observations. Next, the PIC-MCC model is used to investigate the self-sustaining voltage (Vs) in the presence of finite initial plasma densities between the anode and cathode gap. It is observed that the self-sustaining voltage coincides with the discharge voltage obtained from the backward voltage sweep. In addition, the self-sustaining voltage decreases with increased initial plasma density and saturates above a certain initial plasma density, which indicates a change in plasma resistivity. The decrease in self-sustaining voltage is associated with the electron heat loss at the anode for the low pd (rarefied) regime. In the high pd (collisional) regime, the ion energy loss toward the cathode due to the cathode fall and the inelastic collision loss of electrons in the bulk discharge balance out. Finally, it is demonstrated that the self-sustaining voltage collapses to a singular value, despite the presence of a initial plasma, for microgaps when field emission is dominant, which is also consistent with experimental observations.

JTC online comprehensive fault diagnosis method based on angle feature and linear trend feature

Aiming at the problem of incompatibility of the fault diagnosis method between JTC (Jointless Track Circuit) compensation capacitor and tuning zone, based on the amplitude envelope mathematical model of induced voltage of locomotive signal, an online comprehensive fault diagnosis algorithm for multi-compensation capacitor and tuning equipment fault was proposed. It is characterized by the angle of the tangent vector of the amplitude envelope at the compensation capacitor and the linear trend within the three compensation capacitor sections close to the transmitter when the tuning device fails, the angle feature and linear trend feature are extracted to determine the fault type. Experimental results show that the proposed algorithm can accurately detect multi-compensation capacitor faults and tuning equipment faults with high accuracy and high efficiency, especially the sudden multi-compensation capacitor faults and tuning zone unit breaking faults. The accuracy of the algorithm for JTC fault diagnosis is verified under different signal-to-noise ratio and ballast resistance fluctuation, which shows that the algorithm has strong applicability.

THERMAL BUCKLING ON CURVED AND TANGENT RAILWAYS: PARAMETRIC STUDY

AbstractThis study investigates the thermal buckling in railway infrastructures, which can cause derailments and safety risks. The research analyses the influence of various parameters on thermal buckling, focusing on misalignment and ballast resistance. Using a finite element model, curved and tangent tracks are simulated, considering rail sections, sleeper materials, fastener stiffness and initial imperfections. Results demonstrate that ballast resistance is the most critical factor, with compacted ballast increasing buckling temperatures by up to 127%. Additionally, rail imperfections significantly impact temperature increases. A new design guide is proposed for operating conditions under different conditions.

Detailed yield assessment of carbon nanostructures synthesized by submerged arc discharge in water

Submerged arc discharge in water (SADW) is one of the most effective methods for the synthesis of high-quality carbon nanostructures (CNSs). Despite the numerous published studies on SADW, systematic data on yield is still lacking. The SADW runs as a succession of stable and unstable zones, but the influence of these zones on its yield has not yet been explored. The CNSs were synthesised in a SADW facility with a micro-positioning system controlled by current feedback, stabilisation via ballast resistance, and data recorded by a five-parameter correlated measurement system. The synthesis products were characterised by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) adsorption isotherms. In this study, an approach is presented to determine the SADW yield by analysing the correlation between the process parameters recorded with the experimental setup and gravimetric measurements. In the work, the relationship between the formation of the different CNSs and the stable and unstable zones is discussed. The yield was determined at a current of 30 A, which is considered the optimal current for CNSs synthesis, and the estimation obtained indicates that it is in the range of 1%–1.3%. The energy consumption to produce CNSs was assessed to be around 80 kJ.mg−1. The results obtained contribute to clarifying some of the factors that influence yield and how to optimise it. This work provides a useful reference point for future work associated with CNS synthesis using SADW.

Генератор пар импульсов противоположной полярности с повышенной мощностью с применением сумматора на нерегулярно-включенных полосковых линиях

A pulse pair generator with a subnanosecond front is considered, in which pulses of opposite polarity are created by separate generators, and then supplied to the bridge combiner of the original design (on suspended striplines). For the first time in devices of this type, an output power of 18 watts was achieved. A distinctive feature of this structure is that a half of the power of the generators is dissipated on the ballast resistor (due to the alternating appearance of pulses at the inputs of the combiner). To partially compensate for this effect, a half-standard (25 ohms) input resistance of the adder is selected. In the current circuit of generators it leads to an increase in power takeoff from them. The generators themselves are made on step recovery diodes (SRD) according to a scheme close to the traditional one, but differ by a diode circuit at the output, which eliminates penetration of parasitic lobes of a pulse of opposite polarity to the output and protects the SRD from the action of the pulse of the neighboring generator. The shaper is used in experiments to study nonlinear scattering.

Experimental investigation of the period-adding bifurcation route to chaos in plasma.

Since the characteristic timescales of the various transport processes inside the discharge plasma span several orders of magnitude, it can be regarded as a typical fast-slow system. Interestingly, in this work, a special kind of complex oscillatory dynamics composed of a series of large-amplitude relaxation oscillations and small-amplitude near-harmonic oscillations, namely, mixed-mode oscillations (MMOs), was observed. By using the ballast resistance as the control parameter, a period-adding bifurcation sequence of the MMOs, i.e., from L^{s} to L^{s+1}, was obtained in a low-pressure DC glow discharge system. Meanwhile, a series of intermittently chaotic regions caused by inverse saddle-node bifurcation was embedded between the two adjacent periodic windows. The formation mechanism of MMOs was analyzed, and the results indicated that the competition between electron production and electron loss plays an important role. Meanwhile, the nonlinear time series analysis technique was used to study the dynamic behavior quantitatively. The attractor in the reconstructed phase space indicated the existence of the homoclinic orbits of type Γ^{-}. In addition, by calculating the largest Lyapunov exponent (LLE), the chaotic nature of these states was confirmed and quantitatively characterized. With the decrease in the ballast resistance, the return map of the chaotic state gradually changed from the nearly one-dimensional single-peak structure to the multibranch structure, which indicates that the dissipation of the system decreased. By further calculating the correlation dimension, it was shown that the complexity of the strange attractors increased for higher-order chaotic states.

Static Characteristics of Magnetic Modulation DC Converters with Analog Filter

The paper examines the most important requirements for current converters, the features of magnetic modulation converters, and identifies their fundamental and design features. The paper considers the principle of constructing converters for contactless DC measurement and their disadvantages of converters, methods of current measurement using magnetic modulation current converters, in which the magnetic permeability of a core made of ferromagnetic material is modulated. The influence of the parameters of the elements of a magnetic modulation current converter with an analog filter on their static characteristics and the influence of modulation on the static characteristics of the sensor have been determined. It has been revealed that the discrete operation of the magneto-modulation DC converter does not affect its static characteristics and the nonlinearity due to the type of modulation also does not affect the static characteristics of the sensor. The most important requirement for the operation of a magneto-modulation DC converter for autonomous power supplies with recharging buffer batteries is the formation of a static characteristic with the specified properties: linearity, sensitivity and the required range of operating currents. An analytical expression for the static characteristic is obtained in the form of the dependence of the output voltage on the values of T1 and T2 for the basic version of a magnetic modulation DC converter with an analog low-pass filter. Curves of the static characteristics of the magneto-modulation DC converter have been constructed for different values of the resistance of the ballast resistor R, as well as curves of the static characteristics of the magneto-modulation DC converter for different values of the supply voltage E. Analytical expressions for the static characteristics of a magneto-modulation DC converter based on magnetic transistor multivibrators with pulse-width modulation, curves of their characteristics and the output voltage of a magnetic modulation DC converter with a digital output and a discrete filter have been obtained.

Influence of the ballast resistor on the current-voltage characteristics in the cathodic subregimes of the plasma-driven solution electrolysis

Influence of the ballast resistor on the current-voltage characteristics in the cathodic subregimes of the plasma-driven solution electrolysis

Uninsulated Track Circuit Parameter Adjustment and Ballast Resistance Analysis

Uninsulated track circuits are increasingly used in railroad signaling equipment, but the external environment dramatically influences operating conditions. Using the relationship between uninsulated track circuits and ballast resistance, an equivalent four-terminal network model of track circuit transmission characteristics is constructed based on uniform transmission line theory to analyze the influence law of ballast resistance on track surface current. It also makes corresponding adjustments to the track circuit parameters to ensure that the track circuit can work reliably in all four different operating conditions to ensure the safety of railroad transportation.

Fundamental study on rapid detection of the insufficient lateral resistance of ballasted railway tracks by dynamic loading

To resume trains operation as soon as possible after disasters, it is necessary to quickly find out locations of ballasted railway with insufficient lateral ballast resistance. In this study, a new method was proposed to evaluate the lateral ballast resistance using dynamic lateral excitation. The dynamic method was performed on 1/9-scale ballasted railway models with ballast densities of 1.5 and 1.6 g/cm3. The simple harmonic excitation was generated from a pair of 20g flywheels, and the accelerations of the vibrator and the central sleeper were recorded by sensors attached on the central sleeper and the vibrator, respectively. Based on the obtained data sets, maximum accelerations as well as the maximum amplitudes of the lateral displacements of the vibrator and the central sleeper were analysed. It was found that the maximum accelerations of the vibrator were higher than those of the central sleepers. This was also true for the maximum amplitude of the lateral displacements. The ratio of the maximum amplitude of the lateral displacement of the central sleeper to that of the vibrator was evaluated. It was found that the amplitude ratio of the track model with the ballast density of 1.5 g/cm3 was higher than that with the ballast density of 1.6 g/cm3. This implies that the difference in the lateral ballast resistance owing to the difference in the ballast density may be detected based on the evaluation of the amplitude ratio.

A Novel Toolbox for Induced Voltage Prediction on Rail Tracks Due to AC Electromagnetic Interference Between Railway and Nearby Power Lines

AC electromagnetic interference (EMI) between railway and nearby power lines causes serious concerns about railway personnel and equipment safety. The AC EMI analysis is usually conducted by complex computer simulation software to estimate induced voltages on rail tracks, and induced voltages can be further used for safety evaluation. However, such analysis becomes especially difficult at the transmission line routing stage when only limited information of railway and power lines is available. To overcome this challenge, a novel regression model-based toolbox is developed in this paper to predict induced voltages on rail tracks. To develop this toolbox, the dataset acquisition is critical due to very limited research done in this area. The novel dataset is produced by our newly developed AC EMI study method, where variations of several essential factors are considered, including the power line's current, the separation distance between power lines and railway, the ballast resistance, and the length of rail tracks. Two models are eventually chosen to predict induced voltages: “Gaussian process regression” with “matern 3/2” kernel function; and a tri-layered “neural network” model with “sigmoid” activation function. To improve the accuracy, hyperparameters of the regression algorithms are optimized by Bayesian optimization. The toolbox is accurate and easy-to-use, and is currently in use by Manitoba Hydro, Canada.

Improving the energy efficiency of wind turbines for charging batteries

The article describes the method for determining the optimal angular velocity and the number of turns of the generator winding on permanent magnets powered by a wind turbine operating in specific operating conditions according to the wind speed regime. The optimization criterion is the maximum potential of energy that can be used to charge the battery. The permissible power of the generator and wind turbine, current and battery charging voltage are accepted as limiting factors. The restriction is provided by connecting a ballast resistor to the generator output. The power developed by the turbine is determined taking into account the wind energy utilization factor, which depends on the angular velocity of its shaft and wind speed. Two variants of power limitation are compared: by limiting the angular velocity by aerodynamic means and by stopping the wind turbine. The return of energy to charging in both cases is determined taking into account the distribution of wind speeds, obeying the Weibull probability distribution law. As an example, the calculation of the possible annual power generation for charging a battery with a capacity of 200 A∙h with a voltage of 24 volts from a synchron generator with a number of poles of 48 driven by a wind turbine with a radius of 2 meters, operating in an area with an average wind speed of 5 m/s. The calculation shows that for the parameters and operating conditions of the electrical installation used in the example, the maximum annual energy output (3.3 × 103 kWh) is observed at optimal 11 turns of the winding at each of the poles of the generator. The deviation of the number of turns from the optimal one in both directions by 2 times leads, with the same dimensions of the wind turbine, to a decrease in annual energy output by 3...5 times, which is a clear proof of the need to carry out such a calculation for each specific wind turbine.

Effect of Random Lateral Ballast Resistance on Force-Deformation Characteristics of CWR with a Small-Radius Curve

To address the randomness of lateral ballast resistance in the field and its effect on the force-deformation behavior of Continuous Welded Rail (CWR) with small-radius curves, field tests were first conducted to investigate longitudinal and lateral ballast resistance on a 250 m-radius curve. It was found that the lateral ballast resistance follows a normal distribution based on the Shapiro-Wilk test. A finite element model of a small-radius curve CWR track was then established based on actual field conditions, and the force-deformation characteristics were analyzed under thermal loading. The results showed that it is of great significance to incorporate the randomness of the lateral ballast resistance as the deformation mode is closer to the actual field situation. In particular, attention should be given to areas where the lateral ballast resistance is weak. The research presented here has significant implications for railway maintenance practice.

Evolution of Negative Corona in the Discharge-Current Limitation Mode: Transition from the Pulsed-Periodic Mode to Steady-State Burning

The evolution of burning modes of a weak-current corona discharge in a diode filled with atmospheric air, having a pointed cathode and a flat anode, has been investigated. A theoretical description is performed in terms of an axisymmetric multifluid plasma model, including the kinetics of 9 types of particles and 25 plasma-chemical reactions. A discharge in a gap 10 mm long, with a needle-like cathode having a tip curvature radius of 100 μm, a source voltage of 8 kV, a ballast capacitance of 100 pF and a circuit ballast resistance of 1 MΩ, is described in detail. It is shown, both experimentally and theoretically, that the discharge has a lifetime of 180 μs and occurs in four clearly different stages under these conditions: (1) dark breakdown delay phase (0–20 μs); (2) Trichel pulse phase with a variable on–off time ratio and quasi-steady-state corona current component (20–80 μs); and (3) intermediate phase of monotonically rising weak current (80–130 μs), which ends with a vibrational transition to the (4) steady-state phase (130–180 μs), having a typical structure of glow discharge. The tendencies to a change in the corona discharge parameters with a variation in the feed voltage are analyzed. The results of theoretical calculations are in good agreement with the experimental data.

Effect of material composition of diamond field emission array cathodes on quality of transversely shaped beams

Diamond field emitter array field emission cathodes (DFEA FECs) are attractive for the next generation of injectors due to their ability to produce transversely shaped beams without the need for complex masking or laser schemes. However, reliability of this cathode technology remains a challenging issue as principal mechanisms guiding and allowing for output beam shaping remained poorly understood. This paper reports the results of testing two DFEA FECs with the same pattern and emitter tip geometry. Although both cathodes were able to sustain gradients of 44 MV/m and produce maximum output integral charge of 0.5 nC per radio frequency pulse, their emission patterns were different. One cathode did not produce a shaped beam, while the other one did. This difference was explained by the extent of the local variations of the diamond material across the arrays as discovered by spatially resolved Raman spectroscopy. The main practical takeaways were (i) tip sharpness was not a prerequisite for producing a shaped beam and instead (ii) material characteristics resulting in different cathode ballast resistance affected emission spatial uniformity across the array and hence the beam shaping.

Influence of the electron field emission on the magnetized direct current high-pressure discharge

The influence of electron field emission on the sub-normal mode of a magnetized direct current high-pressure helium discharge is analyzed using the two-dimensional axisymmetric fluid model. It is observed that in spite of accounting for a more intense electron emission mechanism, discharge still operates in the sub-normal mode. However, the field emission driven discharge is characterized by a smaller discharge voltage and a larger discharge current. For large values of the electric field enhancement factor, the discharge voltage can be as low as ∼40 V, and the discharge current is a few amperes. It is also seen that for large values of the field enhancement factor and small values of the ballast resistor, rather dense plasma (density ∼ 1017 m−3) can be generated on the nanosecond time scale.

Combined effect of supported and unsupported sleepers on lateral ballast resistance in ballasted railway track

The lateral resistance of a ballast bed significantly affects the lateral stability of ballasted railway tracks. Hence, a precise evaluation of the lateral ballast resistance is essential for predicting rail buckling potential. Differential ballast settlement can cause the sleeper bottom to separate from the ballast, thereby causing the sleeper to become an “unsupported sleeper” suspended from the rail. The gap between the ballast and sleeper bottom results in zero frictional force at the bottom, which reduces the lateral ballast resistance. However, sleepers near unsupported sleepers are subjected to the additional weight of the unsupported sleepers and the rail load borne by the unsupported sleepers. Consequently, they become over-supported. Additional loads may change the lateral ballast resistance of the supported sleepers. Previous studies did not consider the combined effects of supported and unsupported sleepers on the lateral ballast resistance. Therefore, in this study, experiments are conducted on 1/5-scale ballasted track models to investigate these combined effects. Analytical methods for evaluating the lateral ballast resistance when panels incorporate both supported and unsupported sleepers are presented. Pullout tests conducted on panels incorporating supported and unsupported sleepers reveal that unsupported sleepers adversely affect the lateral ballast resistance. The lateral ballast resistance decreases as the number of unsupported sleepers increases, irrespective of sleeper type. Moreover, the analytical results reveal that the lateral ballast resistance of the panel is underestimated when only the decrease in the lateral ballast resistance due to unsupported sleepers is considered. Meanwhile, the analyses considering the combined effects of supported, unsupported, and over-supported sleepers provide reasonable estimates of the lateral ballast resistance, similar to the experimental results. This indicates the importance of comprehensively considering the effects of the support conditions of the sleepers on the lateral ballast resistance to estimate rail buckling potential.

Experimental analysis of ballast bed state in newly constructed railways after tamping and stabilizing operation

Before the operation of newly constructed railways, tamping and stabilizing machines should be used to improve the quality of ballast beds. With the expansion of the railway network and increase of speeds and axle loads, higher quality and efficiency for tamping and stabilizing operation are required. However, previous studies did not involve the effects and parameters of three-sleeper tamping and stabilizing operation under complex working conditions. In the paper, the effect of a three-sleeper tamping and stabilizing machine on the ballast bed state has been studied by performing field experiments. The effect of important factors, including tamping modes, stabilizing frequency, and track lifting amount, are discussed in detail. The results show that the tamping operation on newly constructed railways causes a reduction of the lateral resistance by 56.5 % and a reduction of lateral resistance work by 64.9 %. After the stabilizing operation, the lateral resistance and lateral resistance work are increased by 168.6 % and 209.8 %, respectively. The tamping and stabilizing operation can significantly increase the support stiffness of ballast beds, which meets the requirements of train operation. Meanwhile, 2X tamping mode is more beneficial to improve ballast resistance. Besides, it is reasonable for a stabilizing frequency of 25 Hz to be used for newly constructed railways. The track lifting amount also has a large effect on the ballast bed quality, and it is recommended to keep the lift amount in the range of 20 mm ∼ 30 mm to achieve a better tamping quality.