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The Use of Microwaves, Plasma and Laser for Wood Modification
Published in Dick Sandberg, Andreja Kutnar, Olov Karlsson, Dennis Jones, Wood Modification Technologies, 2021
Dick Sandberg, Andreja Kutnar, Olov Karlsson, Dennis Jones
In addition to this “direct” chemical activation of the wood surface, two “indirect” activation methods have emerged: the use of a corona discharge and of plasma modification. A corona discharge is a process whereby current passes from an electrode with a high potential into a neutral fluid, usually air, and causes the fluid (air) to ionise, generating a plasma around the electrode. The ions generated pass to nearby areas of lower potential (such as a wooden surface), pass the charge to nearby areas of low potential or recombine to form neutral gas molecules. More recently, plasma treatment has come to replace corona treatment, mainly because of the low intensity often associated with a corona discharge, which can have only a limited impact on the surface. It is technically possible to increase the energy of the corona discharge, but this would increase the temperature of the wood being treated and this might have an undesirable effect.
Load Flow over Power Transmission Lines
Published in J.C. Das, Power System Analysis, 2017
The corona discharges form when the electrical field intensity exceeds the breakdown strength of air and local ionization occurs. There are a number of factors at which the corona forms, which include conductor diameter, conductor type (the smoother the conductor surface, the higher the critical disruptive voltage assuming the same diameter), line configuration, and weather. Corona will form when an electrode is charged to sufficiently high voltage from a power frequency source. The mechanism of corona formation is different for the positive and negative half cycles. The negative cycle tends to produce short-duration pulses of current up to 1 mA, lasting for 0.03 μs. The corona noise generated by negative charged electrode tends to be of low level compared to the noise generated by a positive charged electrode. The corona inception voltage is given by
High-sensitivity gas sensor for chemicals leak in transportation
Published in Amir Hussain, Mirjana Ivanovic, Electronics, Communications and Networks IV, 2015
Dongjie Zhao, Jun Liu, Fang Yan, Yan Xu, Lei Wang
The initial step in FAIMS sensor response to CWAs is the formation of gas-phase ions from sample vapor. The traditional ionization source of the FAIMS is a 10mCi radioactive 63Ni foil with a halflife of about 85 years, which provides stable operation, and does not require an external power supply. However, radioactive ionization source is needed to make regular leak test and special safety regulations(Guharay et al. 2008). Several other alternative ionization methods have been reported, such as photoionization by ultraviolet light, laser multiphoton ionization, electrospray for liquid samples, corona discharge (CD), and so on. Corona discharge is one of the electrical discharges developed by the ionization gas around a sharp conductor, which occurs when the electric fields are strongly nonuniform and insufficient to cause completely electrical breakdown. CD in IMS is systemically designed and optimized by Tabrizchi(2000). According to the article, both better sensitivity and higher signal-to-noise ratio can be achieved. CD is a promising method to replace 63Ni, which is available in some producing instruments including IMS, MS (Eiceman & Karpas 2005).
Partial Discharge Detection and Localization in Power Transformers based on Acoustic Emission: Theory, Methods, and Recent Trends
Published in IETE Technical Review, 2021
Viral B. Rathod, Ganesh B. Kumbhar, Bhavesh R. Bhalja
Four types of partial discharge defects are shown in Figure 1 [2]. Internal Discharges: It occurs in voids or cavities within the solid or liquid insulating material.Surface Discharges: It appears at the boundary of the different insulating materials.Corona Discharges: It occurs due to the non-uniform (inhomogeneous) electric fields at the sharp points of the electrodes under high voltage either in air, liquid, or other gaseous insulating material.Treeing: It occurs due to the continuous impact of discharges in the solid insulating material, which forms a conducting channel.
Characteristics and potential human health hazards of charged aerosols generated by high-voltage power lines
Published in International Journal of Occupational Safety and Ergonomics, 2019
Joon-Sig Jung, Jae Won Lee, Rajitha Kawshalya Mailan Arachchige Don, Duck Shin Park, Seung Cheol Hong
We found that the average effective level at the HVPL sites was 59.8%, which was about 2.7 times higher than that at the control site (21.5%). This means that charged aerosols were more often present at the exposed sites than at the non-exposed site, indicating that charged aerosols were locally generated. Charged aerosols were more likely to cause condensation of other nearby harmful substances, such as gases, heavy metals and bacteria. This result is similar to the findings of a previous study, where 25 of 41 sites adjacent to HVPLs were dominated by positive ions, while the remaining 16 sites were dominated by negative ions [13]. Corona discharge occurs when the air around a charged body is ionized beyond a threshold value (direct current [DC] 30 kV/cm, AC 21 kV/cm) based on the power line density. In other words, there is a local isolated breakdown of a strong electric field between electrodes. Sites A and B were located directly beneath and within 10 m of HVPLs, so these sites may have been closer to the power source than the other exposed sites. However, more research needs to be conducted on this topic.
Research on electrostatic shielding characteristics of electrostatic precipitator
Published in Journal of the Air & Waste Management Association, 2022
Bing Chen, Shiqing Li, Yongheng Guo, Hongjiao Li, Wenning Zhou, Baiqian Liu
In addition, as shown in Figure 6, this study further verified the relationship between corona current (I) and applied voltage (kV) by comparing with the experimental results obtained by Kasdi (2016). The results show that there is a good agreement between the simulated value of this model and the experimental measured value of Kasdi (2016). The model also accurately predicts the change of the corona current when the wire-to-wire distance changes. It can be seen from Figure 6 that the corona current increases with the increase of the wire-to-wire distance. Due to the effect of electrostatic shielding, the reduction of the wire-to-wire distance will cause the corona current to decrease.