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Artykuły w czasopismach na temat "Leader discharge"
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Rakov, V. A., M. D. Tran, Y. Zhu, et al. "New insights into the lightning discharge processes." Plasma Sources Science and Technology 31, no. 10 (2022): 104005. http://dx.doi.org/10.1088/1361-6595/ac9330.
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Abstract This review covers selected results of recent observations of lightning discharges performed across the entire electromagnetic spectrum (radiofrequency, optical, and energetic radiation) at the Lightning Observatory in Gainesville, Florida. The most important results include (a) characterization of the preliminary-breakdown, stepped-leader, and return-stroke processes in high-intensity (⩾50 kA) negative lightning discharges, (b) the first high-speed video images of bidirectional leader that made contact with the ground and produced a return stroke, (c) discovery of negative stepped leader branches colliding with the lateral surface of neighboring branches of the same leader, (d) new data on the occurrence context and properties of compact intracloud discharges, and (e) observation of a terrestrial gamma-ray flash that occurred during a bipolar cloud-to-ground lightning discharge. The results serve to improve our understanding of the physics of lightning with important implications for lightning modeling, lightning protection, and high-energy atmospheric physics studies.
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Das, Sayantan, and Udaya Kumar. "Modeling of Bi-Polar Leader Inception and Propagation from Flying Aircraft Prior to a Lightning Strike." Atmosphere 13, no. 6 (2022): 943. http://dx.doi.org/10.3390/atmos13060943.
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Lightning is one of the major environmental threats to aircraft. The lightning strikes during flying are mostly attributed to aircraft-triggered lightning. The first step toward designing suitable protective measures against lightning is identifying the attachment locations. For this purpose, oversimplified approaches are currently employed, which do not represent the associated discharge phenomena. Therefore, in this work, a suitable model is developed for simulating the inception and propagation of bi-polar leader discharge from the aircraft. Modeling of leader discharges requires field computation around the aircraft, which is carried out employing the Surface Charge Simulation Method (SCSM) combined with sub-modeling, which ensures the best accuracy of field computations near nosecone, wingtips, etc. A DC10 aircraft model is considered for the simulation. Simulations are performed for different pairs of leader inception points on aircraft using the developed model. Subsequently, corresponding ambient fields required for stable bi-polar discharge from aircraft are determined. These values are in the range of measured ambient fields reported in the literature. In summary, the present work has come up with a suitable model for simulating the bi-polar leader inception and propagation from the flying aircraft. Using the same, a detailed quantitative description of the discharge phenomena from the aircraft is provided.
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Ma, Xinyu, Chijie Zhuang, Zezhong Wang, and Rong Zeng. "Positive Leader Velocity and Discharge Current Considering Leader Branching Under Different Air Pressures." IEEE Transactions on Plasma Science 47, no. 5 (2019): 1939–43. http://dx.doi.org/10.1109/tps.2018.2886570.
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Belosheev, V. P. "Discharge leader self-organization on the water surface." Technical Physics 45, no. 7 (2000): 922–27. http://dx.doi.org/10.1134/1.1259749.
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Xie, Yaoheng, Yue Yishi, Huisheng Ye, Liu Yun, Yongheng Zhong, and Xiangeng Zhao. "The development characteristics of the discontinuous leader under the positive switching impulse with low rate of voltage rising." European Physical Journal Applied Physics 83, no. 2 (2018): 20802. http://dx.doi.org/10.1051/epjap/2018180103.
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Discontinuous leader development is the most important discharge process under the application of the switching impulse voltage with the low rate of voltage rising, which is of great significance to study the external insulation characteristics of ultra-high voltage (UHV) large scale air gap. Based on the CMOS high-speed camera, a discharge test with different operating impulse voltage is carried out by constructing a comprehensive observation platform of rod-plate air gap discharge, and a clear discontinuous leader development process picture is captured. Moreover, the leader current, injection charge and leader channel unit length charge, and their characteristics of the change trend are also obtained. Further analysis based on the experimental results shows that the discontinuous leader development under the action of the impulse voltage with low rate of voltage rising has two different laws. Finally, this paper uses the thermodynamic equation, combined with the test results, the channel temperature changes in the discontinuous leader development stagnation stage were calculated. The results show that the leader channel temperature is still greater than 1500 K in the hundreds of microsecond time scales in the leader stagnation stage, and the subsequent leader can continue to develop on the original leader channel.
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Qie, X., Y. Yu, C. Guo, P. Laroche, G. Zhang, and Q. Zhang. "Some features of stepped and dart-stepped leaders near the ground in natural negative cloud-to-ground lightning discharges." Annales Geophysicae 20, no. 6 (2002): 863–70. http://dx.doi.org/10.5194/angeo-20-863-2002.
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Abstract. Characteristics of the electric fields produced by stepped and dart-stepped leaders 200 µs just prior to the return strokes during natural negative cloud-to-ground (CG) lightning discharges have been analyzed by using data from a broad-band slow antenna system with 0.08 µs time resolution in southeastern China. It has been found that the electric field changes between the last stepped leader and the first return stroke could be classified in three categories. The first type is characterized by a small pulse superimposed on the abrupt beginning of the return stroke, and accounts for 42% of all the cases. The second type accounts for 33.3% and is characterized by relatively smooth electric field changes between the last leader pulse and the following return stroke. The third type accounts for 24.7%, and is characterized by small pulses between the last recognizable leader pulse and the following return stroke. On the average, the time interval between the successive leader pulses prior to the first return strokes and subsequent return strokes was 15.8 µs and 9.4 µs, respectively. The distribution of time intervals between successive stepped leader pulses is quite similar to Gaussian distribution while that for dart-stepped leader pulses is more similar to a log-normal distribution. Other discharge features, such as the average time interval between the last leader step and the first return stroke peak, the ratio of the last leader pulse peak to that of the return stroke amplitude are also discussed in the paper.Key words. Meteology and atmospheric dynamics (atmospheric electricity; lightning) – Radio science (electromagnetic noise and interference)
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Cooray, Vernon, Hasupama Jayasinghe, Marcos Rubinstein, and Farhad Rachidi. "The Geometry and Charge of the Streamer Bursts Generated by Lightning Rods under the Influence of High Electric Fields." Atmosphere 13, no. 12 (2022): 2028. http://dx.doi.org/10.3390/atmos13122028.
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The streamer bursts generated during the initiation and propagation of leaders play an important role in the creation and maintenance of hot discharge channels in air. The most important parameters related to streamer bursts in this respect are the length of the streamer bursts, their lateral extent and the charge associated with them. The lateral extent of the streamer bursts may play a significant role in deciding the path and the tortuosity of the discharge channels of laboratory discharges and lightning. The charges associated with the streamer bursts are needed in understanding the physical processes associated with the streamer-to-leader transition. In this paper, the length, the lateral extension and the charge of the streamer regions generated by grounded conductors when exposed to external electric fields are estimated. This estimation is based on two assumptions: (i) once a streamer is incepted, the streamer head follows the direction of maximum background electric field at the location of the streamer head and (ii) the streamer continues to extend along this direction until the potential drop along the streamer channel matches the potential drop caused by the background electric field between the initial and end points of the streamer channel. The same technique could be used to estimate the streamer bursts generated in laboratory discharges and lightning stepped leaders. It is shown that in estimating the geometry of the streamer region, it is necessary to include the spread of streamers caused by branching. Moreover, the charge associated with the streamer region increases as the frequency of branching increases. The results obtained confirm that the charge in the streamer region can significantly change the potential ahead of the streamer region from the background potential and this has to be taken into account in any study that simulates the initiation and propagation of lightning leaders. Since the streamer bursts of leaders control the direction and speed of the leaders, the technique we have used here could be implemented in lightning leader progression models.
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Keffer, C. W. "Waste Discharge Reduction Program Overview – Monsanto Agricultural Company." Water Science and Technology 24, no. 12 (1991): 29–32. http://dx.doi.org/10.2166/wst.1991.0367.
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Monsanto is committed to being a leader in reducing waste discharges to the environment. The Company announced in June 1988 a commitment to reduce air emissions of hazardous materials by 90% by the end of 1992. In addition, Monsanto Agricultural Company established a further goal to reduce the discharge of organic and hazardous inorganic materials to all environmental media. Projects have been identified for the Agricultural Company to achieve the 90% air emission reduction goal and to reduce projected 1995 waste discharges from 150 million pounds to 50 million pounds.
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Pei, Zhehao, Weijiang Chen, Xing Fan, et al. "The contribution of femtosecond laser filaments to positive and negative breakdown discharge in a long air gap." Physics of Plasmas 30, no. 4 (2023): 043511. http://dx.doi.org/10.1063/5.0138646.
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Discharges of different polarities develop in different modes, resulting in different guiding effects by femtosecond laser filaments. Knowledge of the contribution of laser filaments to positive and negative discharges is the basis of the laser-guided long-air-gap discharge technique. This study presents a direct comparison of the inception, propagation, and breakdown characteristics of discharges of both polarities. Long-air-gap discharge experiments under the switching impulses of both polarities are carried out under the same experimental conditions. Discharge modes and phases are also considered. The statistical results show that positive discharge inception voltages are transformed from a Weibull distribution into an exponential distribution under the influence of laser filaments, but there is little effect on the negative discharge inception voltage. The guidance probability of a positive discharge reaches 15% at most during the dark period stage, leading to little effect on the breakdown discharge probability. However, for negative discharges, the guidance probability can exceed 95%. An investigation of the filament contributions to both polarity discharges shows that the different migration directions of photoelectrons lead to a difference in the effects of laser filaments on inception voltages, and the difference in the connection of the two discharge passages leads to a difference in the guidance probability. Through the results of a simulation model, it is speculated that the connection condition for positive discharges is that the positive leader overlaps with the laser filaments, and, for negative discharges, the rod electrode is connected to the laser filaments through bi-directional discharge propagation.
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Molas, Michał, and Marcin Szewczyk. "Experimental Evaluation of 3D Tortuosity of Long Laboratory Spark Trajectory for Sphere-Sphere and Sphere-Plane Discharges under Lightning and Switching Impulse Voltages." Energies 14, no. 21 (2021): 7409. http://dx.doi.org/10.3390/en14217409.
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Evaluation of attractive areas of high- and ultra-high voltage power transmission lines to direct lightning strokes is based on modeling of propagating progress of the lightning leader approaching the transmission line. The aim of the modeling is to determine the effectiveness of lightning protection for a given line design. The statistical models are currently being developed to extend the conventional deterministic models by embracing the randomness of the discharge channel in space and hence to reproduce the statistical distribution of the striking points. These models require experimental data for understanding of the lightning leader development process and to validate the model across the measurement data. This paper reports on the measured trajectories of discharge channels of long laboratory sparks in various high voltage laboratory arrangements. The sparks were initiated by switching and lightning impulses with peak values ranging from 1200 kV to 3364 kV of positive and negative polarity for two types of high-voltage electrode systems (sphere-sphere and sphere-plane), arranged at distances of 3.3 m and 5.5 m from each other. Statistical distributions of angles describing trajectory of discharge channels in space are reported for a total number of 540 recorded discharges. The results can serve as reference measurement data to develop and evaluate the accuracy of simulation models incorporating statistical nature of the lightning leader development process.