Leader discharge stepping in dry and humid air

2020 ◽  
Author(s):  
Alejandro Malagón-Romero ◽  
Alejandro Luque
Keyword(s):  
Electric Field ◽  
Heating Rate ◽  
Electron Density ◽  
Water Molecules ◽  
High Humidity ◽  
Geophysical Research ◽  
Humid Air ◽  
Dry Air ◽  
Spark Discharges ◽  
Streamer Corona

<p>Long spark discharges of about one meter and natural lightning show a polarity asymmetry.  While positive discharges propagate continuously, negative discharges propagate in a stepped manner. This stepped propagation is mediated by the so-called space stem, an isolated region in the streamer corona of depleted electron density and enhanced electric field. Kostinskiy et al. 2018 [1] reported the stepping of positive leaders under high humidity conditions and Malagón-Romero et al. 2019 [2] showed that positive leader steps, if they exist, would be shorter and thus harder to observe in experiments. </p><p>In this work we present the results of our simulations for the evolution of a space stem precursor [2] under dry and humid air conditions. These results show that the presence of water molecules enhances the electric field and the heating rate of the space stem, reaching 2000 K considerably faster than in dry air. This could make feasible the stepping of positive leader discharges under high humidity conditions as observed by Kostinskiy et al. 2018 [1].</p><p> </p><p>[1] Kostinskiy, A. Y., Syssoev, V. S., Bogatov, N. A., Mareev, E. A., Andreev, M. G., Bulatov, M. U., & Rakov, V. A. (2018). Abrupt elongation (stepping) of negative and positive leaders culminating in an intense corona streamer burst: Observations in long sparks and implications for lightning. Journal of Geophysical Research: Atmospheres, 123, 5360–5375. </p><p>[2] Malagón-Romero, A., & Luque, A. (2019). Spontaneous emergence of space stems ahead of negative leaders in lightning and long sparks. Geophysical Research Letters, 46, 4029–4038. https://doi.org/10.1029/ 2019GL082063</p>

scholarly journals Tungsten Oxide Based Sensor for Oxygen Detection

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 952 ◽  
Author(s):  
Wangi Sari ◽  
Simon Leigh ◽  
James Covington
Keyword(s):  
Metal Oxide ◽  
Linear Relationship ◽  
Tungsten Oxide ◽  
Spin Coating ◽  
Low Temperatures ◽  
Oxygen Sensor ◽  
High Response ◽  
Humid Air ◽  
Dry Air ◽  
Oxygen Detection

In this paper we report on the development tungsten oxide based chemiresistive sensors for the monitoring of oxygen at low temperatures (T ≤ 400 °C) in dry and humid air. The sensors were deposited onto alumina substrate by a combination of spin coating and a photolithographic process to define the sensing area. Our results show that the sensors comply with a linear relationship over a 0 to 20% concentration range, with a high response towards oxygen. The highest response was observed at 350 °C (ΔR/Ra = 7.8) in humid and in dry air (ΔR/Ra = 18). This result is a significant improvement over our previous experiments and we believe to take the concept of a metal-oxide based oxygen sensor a step closer.

scholarly journals The Impact of the Electric Field on Surface Condensation of Water Vapor: Insight from Molecular Dynamics Simulation

Nanomaterials ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 64 ◽  
Author(s):  
Qin Wang ◽  
Hui Xie ◽  
Zhiming Hu ◽  
Chao Liu
Keyword(s):  
Molecular Dynamics ◽  
Water Vapor ◽  
Electric Field ◽  
Intermolecular Forces ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Attraction Force ◽  
Condensation Rate ◽  
Shape Transformation ◽  
The Impact

In this study, molecular dynamics simulations were carried out to study the coupling effect of electric field strength and surface wettability on the condensation process of water vapor. Our results show that an electric field can rotate water molecules upward and restrict condensation. Formed clusters are stretched to become columns above the threshold strength of the field, causing the condensation rate to drop quickly. The enhancement of surface attraction force boosts the rearrangement of water molecules adjacent to the surface and exaggerates the threshold value for shape transformation. In addition, the contact area between clusters and the surface increases with increasing amounts of surface attraction force, which raises the condensation efficiency. Thus, the condensation rate of water vapor on a surface under an electric field is determined by competition between intermolecular forces from the electric field and the surface.

scholarly journals Research on Electromagnetic Sensitivity Properties of Sodium Chloride during Microwave Heating

2020 ◽  
Vol 39 (1) ◽  
pp. 54-62
Author(s):  
Hua Chen ◽  
Junjiang Chen ◽  
Weijun Wang ◽  
Huan Lin
Keyword(s):  
Sodium Chloride ◽  
Electric Field ◽  
Water Content ◽  
Heating Rate ◽  
Microwave Heating ◽  
Resonant Cavity ◽  
Relative Dielectric Constant ◽  
Heating System ◽  
Heating Process ◽  
Heating Efficiency

AbstractThe multimode resonant cavity is the most common cavity. The material often shows on selective heating performance during the heating process due to the effect of microwave heating having a closely relationship with the electromagnetism parameters. This paper is based on finite difference time domain method (FDTD) to establish the electromagnetic-thermal model. The electromagnetic sensitivity property parameters of sodium chloride including relative dielectric constant, loss angle tangent and water content of sodium chloride is studied during the heating and drying process. The heating rate and the electric field distribution of sodium chloride, at the different water content, were simulated with the electromagnetic characteristic parameters changing. The results show that with the electromagnetic sensitivity property parameters varying, the electric field strength, heating rate and steady-state temperature of the heating material will all have a variety in the cavity. Some measures are proposed to improve the heating efficiency and ensure the stability of the microwave heating system in the industrial application.

Hormones Nanofiltration in Carbon Nanotubes and Boron Nitride Nanotubes Using Uniform External Electric Field Through Molecular Dynamics

2021 ◽  
Vol 21 (11) ◽  
pp. 5499-5509
Author(s):  
Rosely Maria dos Santos Cavaleiro ◽  
Tiago da Silva Arouche ◽  
Phelipe Seiichi Martins Tanoue ◽  
Tais Souza Sá Pereira ◽  
Raul Nunes de Carvalho Junior ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Boron Nitride ◽  
Electric Field ◽  
Field Potential ◽  
Boron Nitride Nanotubes ◽  
Attractive Potential ◽  
Water Molecules ◽  
Computer Simulation Study ◽  
Simulation Time

Hormones are a dangerous group of molecules that can cause harm to humans. This study based on classical molecular dynamics proposes the nanofiltration of wastewater contaminated by hormones from a computer simulation study, in which the water and the hormone were filtered in two single-walled nanotube compositions. The calculations were carried out by changing the intensities of the electric field that acted as a force exerting pressure on the filtration along the nanotube, in the simulation time of 100 ps. The hormones studied were estrone, estradiol, estriol, progesterone, ethinylestradiol, diethylbestrol, and levonorgestrel in carbon nanotubes (CNTs) and boron nitride (BNNTs). The most efficient nanofiltrations were for fields with low intensities in the order of 10-8 au and 10-7 au. The studied nanotubes can be used in membranes for nanofiltration in water treatment plants due to the evanescent field potential caused by the action of the electric field inside. Our data showed that the action of EF in conjunction with the van der Walls forces of the nanotubes is sufficient to generate the attractive potential. Evaluating the transport of water molecules in CNTs and BNNTs, under the influence of the electric field, a sequence of simulations with the same boundary conditions was carried out, seeking to know the percentage of water molecules filtered in the nanotubes.

Nasal Mucosal Temperature after Exposure to Cold, Dry Air and Hot, Humid Air

2003 ◽  
Vol 123 (7) ◽  
pp. 851-856 ◽  
Author(s):  
Kristina Liener ◽  
Richard Leiacker ◽  
Jörg Lidemann ◽  
Gerhard Rettinger ◽  
Tilman Keck
Keyword(s):  
Humid Air ◽  
Dry Air ◽  
Exposure To Cold

scholarly journals The Variation of Factor of Enhancement in Nucleation Rate with Electric Field for Water Vapour and Ice

2020 ◽  
Vol 10 (2) ◽  
pp. 221-223
Keyword(s):  
Electric Field ◽  
Water Vapour ◽  
Electric Fields ◽  
Nucleation Rate ◽  
Water Molecules ◽  
Saturation Ratio

the nucleation rate is the parameter to judge the effect of electric field on nucleation of water vapour and ice glaciation. In the presence of electric field the total nucleation is the sum of nucleation due to electric field and nucleation due to diffusion of water molecules. Thus we can say the nucleation rate is enhanced by the factor of RE. This is known as factor of enhancement in nucleation rate. In the present work we will calculate the factor of enhancement in nucleation rate for water vapour and ice on temperature 268 K at different electric fields as a function of super saturation ratio.

scholarly journals Factors affecting the temperature increasing rate in arc-shaped bamboo pieces during high-frequency heating

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 2656-2667
Author(s):  
Feihu Chang ◽  
Yanhe Liu ◽  
Bin Zhang ◽  
Wansi Fu ◽  
Pengfei Jiang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Moisture Content ◽  
Electric Field ◽  
Heating Rate ◽  
High Frequency ◽  
Great Influence ◽  
Chord Length ◽  
High Frequency Electric Field ◽  
Frequency Electric Field ◽  
Frequency Heating

In the process of applying the high-frequency heating technology to bamboo heat treatment, controlling the material temperature has a great influence on the quality of bamboo forming. Therefore, research on the heat transfer mechanism of high-frequency heating of arc-shaped bamboo pieces is of great importance. In this paper, the influence of different moisture content, chord length, and plate voltage on the heating rate of arc-shaped bamboo pieces under high-frequency electric field were studied. The moisture content of bamboo had the most remarkable effect on the heating rate. With increased moisture content, the temperature rose faster. The selection of the plate voltage had an obvious influence on the heating. If the voltage was low, the heating rate was too slow, the heating time was long, or the voltage was high, it was easy to cause electric field breakdown and damage the bamboo pieces. As the chord length decreased, the heating rate gradually increased. When the radian of the arc-shaped bamboo pieces could be ignored, the heating rate was the fastest. The results showed that under certain conditions, the arc-shaped bamboo pieces showed a good heat treatment effect in a high-frequency electric field.

scholarly journals Regional energy and water budget of a precipitating atmosphere over ocean

2021 ◽  
pp. 1-56
Author(s):  
Seiji Kato ◽  
Norman G. Loeb ◽  
John T. Fasullo ◽  
Kevin E. Trenberth ◽  
Peter H. Lauritzen ◽  
...  
Keyword(s):  
Heating Rate ◽  
Water Budget ◽  
Diabatic Heating ◽  
Water Mass ◽  
Phase Changes ◽  
Water Phase ◽  
Global Ocean ◽  
Dry Air ◽  
Regional Energy ◽  
Atmospheric Column

AbstractEffects of water mass imbalance and hydrometeor transport on the enthalpy flux and water phase on diabatic heating rate in computing the regional energy and water budget of the atmosphere over ocean are investigated. Equations of energy and water budget of the atmospheric column that explicitly consider the velocity of liquid and ice cloud particles, and rain and snow are formulated by separating water variables form dry air. Differences of energy budget equations formulated in this study from those used in earlier studies are 1) diabatic heating rate depends on water phase, 2) diabatic heating due to net condensation of non-precipitating hydrometeors is included, and 3) hydrometeors can be advected with a different velocity from the dry air velocity. Convergence of water vapor associated with phase change and horizontal transport of hydrometeors is to increase diabatic heating in the atmospheric column where hydrometeors are formed and exported and to reduce energy where hydrometeors are imported and evaporated. The process can improve the regional energy and water mass balance when energy data products are integrated. Effects of enthalpy transport associated with water mass transport through the surface are cooling to the atmosphere and warming to the ocean when the enthalpy is averaged over the global ocean. There is no net effect to the atmosphere and ocean columns combined. While precipitation phase changes regional diabatic heating rate up to 15Wm-2, the dependence of the global mean value on the temperature threshold of melting snow to form rain is less than 1 Wm-2.

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