Browsing by Author "Lin, Guan-Yu"

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A Modified Deutsch-Anderson Equation for Predicting the Nanoparticle Collection Efficiency of Electrostatic Precipitators
(2012-10-01)
Lin, Guan-Yu
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Chen, Tzu-Ming
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Tsai, Chuen-Jinn
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環境工程研究所
;
Institute of Environmental Engineering
It is of great importance to mitigate nanoparticle exposure in the environment by using effective control devices. For controlling nanoparticles with the particle diameter (d(p)) < 100 nm in the air environment, electrostatic precipitators (ESPs) are widely used in many industries because of their low pressure drop and high removal efficiency. However, existing models cannot predict the nanoparticle collection efficiency very well. This is due to the partial charging effect, when some nanoparticles are not charged but penetrate through the ESPs, resulting in a decrease in the collection efficiency. In this study, a modified Deutsch-Anderson model was developed to predict the nanoparticle collection efficiency (eta, %), as well as that for particles with d(p) > 100 nm. The present model is eta(%) = [1 - exp(-A(N-De)(B)) + C(N-De) - (1 - alpha)] x 100%, where A, B, and C are regression coefficients, NDe is the modified Deutsch number, and a is the partial charging factor. Good agreement was obtained between the present predictions and experimental data published in the literature. It is expected that the modified equation can facilitate the design and scale-up of the ESPs for controlling nanoparticle emissions, as well as particle in all size ranges.
A parallel plate wet denuder for acidic gas measurement
(2008-08-01)
Tsai, Chuen-Jinn
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Lin, Guan-Yu
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Chen, Sheng-Chieh
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環境工程研究所
;
Institute of Environmental Engineering
A parallel plate wet denuder (PPWD) was designed and tested for acidic gas absorption in this studY. The PPWD is composed of two fi-osted glass plates coated with nano-TiO? particles. The gap of the plates is 4 inin, the active sinjace is 7.5 cut in width and 15 cin in height. The DI water is,flowing downward along the sulf ces to form a icn forni tvaterfilm to absorb the gas.flowing uptvard along the gap. The gas absorption efficiency and nienzory eft ct were tested using test gases of HF (3.573.80 ppb), HCl (0.48-15.63 pph), and HN03 (8.43-20.92 ppb) generatedfi-oni per"leation tubes at the flow rate of 5-10 Llinin, scrubbing DI water flow rate oj'].O n?Llnlilll plate, and PH = 6.8 -_ 0.3. The experiment was also conducted for HF and HCl with scrubbing water PH value ol'3.08 and 4.10 to examine the ffcct of PH oil the absorption efficiency. The experimental data at different.flow rates match with the theoretical values ver ' N7 well assuming peifect absorption condition (it the water filin when the scrubbing water PH = 6.8 +/- 0.3. The absorption efficiency of the three gases at the sampling flow rate of 5 Llinin was nearly 100% when the scrubbing water PH value was 6.8 +/- 0.3, but was ' found to decrease slightl ' v when the PH value of scrubbing tvater was reduced from 6.8 to 3.08, which indicates slight inodification of' peifect absorption condition at the water filin. The meniory cffect test showed that the rise time was 15 to 25 min and the fiall tinie was 10 to 25 iniiijbi- the three gases. Good un ft)rniit_v Qfthe tvater filin was observed during the 9-day ainbient air sampling for HF, 110, and HNO,, which indicates the applicabilitly (the present PPWD for ambient air sampling. (c) 2008 American Institute of Chemical Engineers.
An Efficient Conflict Detection Algorithm for Packet Classification
(2010)
Lee, Chun-Liang
;
Lin, Guan-Yu
;
Chen, Yaw-Chung
;
資訊工程學系
;
Department of Computer Science
Packet classification is essential for supporting advanced network services such as firewall, quality-of-service (QoS), and policy-based routing. The rules used by routers to classify packets are called packet filters. If two or more filters overlap, a conflict occurs and leads to ambiguity in packet classification. In this paper, we propose an algorithm which can efficiently detect and resolve filter conflicts by using tuple based search. The time complexity of the proposed algorithm is O(nW+S), and the space complexity is O(nW), where n is the number of filters, W is the number of bits in a header field, and S is the number of conflicts. We use the synthetic filter databases generated by ClassBench to evaluate the proposed algorithm. Simulation results show that the proposed algorithm can achieve better performance than the plane-sweep algorithm both in time and space, particularly for databases with larger numbers of conflicts.
An Efficient Conflict Detection Algorithm for Packet Filters
(2012-02-01)
Lee, Chun-Liang
;
Lin, Guan-Yu
;
Chen, Yaw-Chung
;
資訊工程學系
;
Department of Computer Science
Packet classification is essential for supporting advanced network services such as firewalls, quality-of-service (QoS), virtual private networks (VPN), and policy-based routing. The rules that routers use to classify packets are called packet filters. If two or more filters overlap, a conflict occurs and leads to ambiguity in packet classification. This study proposes an algorithm that can efficiently detect and resolve filter conflicts using tuple based search. The time complexity of the proposed algorithm is O(nW + s), and the space complexity is O(nW), where n is the number of filters, W is the number of bits in a header field, and s is the number of conflicts. This study uses the synthetic filter databases generated by Class-Bench to evaluate the proposed algorithm. Simulation results show that the proposed algorithm can achieve better performance than existing conflict detection algorithms both in time and space, particularly for databases with large numbers of conflicts.
An Efficient Single-Stage Wet Electrostatic Precipitator for Fine and Nanosized Particle Control
(2010)
Lin, Guan-Yu
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Tsai, Chuen-Jinn
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Chen, Sheng-Chieh
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Chen, Tzu-Ming
;
Li, Shou-Nan
In this study, an efficient parallel-plate single-stage wet electrostatic precipitator (wet ESP) with a width of 75 mm, effective precipitation length of 48 mm and gap of 9.0 mm was designed and tested to control fine and nanosized particles without the need of rapping. The collection plates are made of sand-blasted copper plates coated with TiO(2) nanopowder instead of hydrophilic membranes. Three gold wires (diameter: 100 mu m) were used as the discharge electrodes and a pulse jet valve was used to regularly purge the wires. The design of the present wet ESP is aimed at solving the problems of traditional dry ESPs: reduction of the collection efficiency due to particle deposition on the discharge electrodes and collection electrodes, back corona, and particle re-entrainment. The collection efficiency at initially clean and heavy particle loading conditions was tested and compared to a similar dry ESP. Experimental results showed that when the wet ESP was initially clean, the particle collection efficiency ranged from 96.9-99.7% for particles ranging from 16.8 to 615 nm in electrical mobility diameter at an aerosol flow rate of 5 L/min (residence time of 0.39 s) and an applied voltage of 4.3 kV. After heavy loading with TiO(2) nanopowder about 1.2 +/- 0.06 g/plate, the collection efficiency of the present wet ESP for corn oil particles was shown to reduce only slightly to 94.7-99.0% for particles from 16.8 to 615 nm in diameter.
An Online Parallel-Plate Wet Denuder System for Monitoring Acetic Acid Gas
(2010-10-01)
Ku, Yueh-Ping
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Yang, Caddie
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Lin, Guan-Yu
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Tsai, Chuen-Jinn
;
環境工程研究所
In air environments, acetic acid gas may lead to irritations, generate pungent odor, and cause objects to corrode. This paper examines an online parallel-plate wet denuder system to monitor gaseous acid at ppbv concentration levels. Denuder surfaces which comprised frosted glass plates coated with a thin layer of TiO(2) nanoparticles were covered by a thin film made of ultrapure water or 0.5 mM H(2)O(2) to absorb the test acetic gases that were generated from a small thermostatic evaporation tube. Denuder effluent was then injected automatically into an ion chromatography for real-time detection. The method was validated by comparing measured concentrations with those obtained simultaneously by using a well established impinger technique. Test results showed that the current technique is an efficient collector for gaseous acetic acid, achieving the collection efficiency between 93.8% to 96.4% by using ultrapure water film. It can monitor 0.9-698.0 ppbv gaseous acetic acid accurately in real-time with response time of 10 minutes, a detection limit of 1.2 ppbv and a time resolution of either 10 minutes or 20 minutes, depending on the concentration of the eluent used in the ion chromatography. The technique was applied successfully to measure the exposure concentration of acetic acid gas leaking from a fume hood in a laboratory.
Characteristic of nanoparticles generated from different nano-powders by using different dispersion methods
(2012-04-01)
Tsai, Chuen-Jinn
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Lin, Guan-Yu
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Liu, Chun-Nan
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He, Chi-En
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Chen, Chun-Wan
A standard rotating drum with a modified sampling train (RD), a vortex shaker (VS), and a SSPD (small-scale powder disperser) were used to investigate the emission characteristics of nano-powders, including nano-titanium dioxide (nano-TiO2, primary diameter: 21 nm), nano-zinc oxide (nano-ZnO, primary diameter: 30-50 nm), and nano-silicon dioxide (nano-SiO2, primary diameter: 10-30 nm). A TSI SMPS (scanning mobility particle sizer), a TSI APS (aerodynamic particle sizer), and a MSP MOUDI (micro-orifice uniform deposit impactor) were used to measure the number and mass distributions of generated particles. Significant differences in specific number and mass concentration or distributions were found among different methods and nano-powders with the most specific number and mass concentration and the smallest particles being generated by the most energetic SSPD, followed by VS and RD. Near uni-modal number or mass distributions were observed for the SSPD while bi-modal number or mass distributions existed for nano-powders except nano-SiO2 which also exhibited bimodal mass distributions. The 30-min average results showed that the mass median aerodynamic diameter (MMAD) and number median diameter (NMD) of the SSPD ranged 1.1-2.1 mu m and 166-261 nm, respectively, for all three nano-powders, which were smaller than those of the VS (MMAD: 3.3-6.0 mu m and NMD: 156-462 nm), and the RD (MMAD: 5.2-11.2 mu m and NMD: 198-479 nm). For nano-particles (electric mobility diameter < 100 nm), specific mass concentrations were nearly negligible for all three nano-powders and test methods. Specific number concentrations of nano-particles were low for the RD tester but were elevated when more energetic VS and SSPD testers were used. The quantitative size and concentration data obtained in this study is useful to elucidate the field emission and personal exposure data in the future provided that particle loss in the generation system is carefully assessed.
Drag Coefficient of a Spherical Particle Attached on the Flat Surface
(2011-10-01)
Liu, Chun-Nan
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Chien, Chih-Liang
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Lo, Chu-Chun
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Lin, Guan-Yu
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Chen, Sheng-Chieh
The previous analytical solution for the drag coefficient (C(d)) for a spherical particle attached on the flat surface, which was derived by O'Neill (1968), is only valid in the creeping flow conditions. It is important to extend O'Neill's formula to cover a wide range of particle Reynolds number (Re(p)). In this study, the drag coefficient was calculated numerically to cover Re(p) from 0.1 to 250. For a particle suspended in the air, an empirical drag coefficient exists, which is defined as C(d) = f x 24/Re(p), where f is a correction factor depending on Re(p). The applicability of the correction factor f for O'Neill's analytical equation for the spherical particle attached on the flat surface for Re(p) = 0.1 to 250 was examined in this study.
EEG Dynamics Reflect the Distinct Cognitive Process of Optic Problem Solving
(1970-01-01)
She, Hsiao-Ching
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Jung, Tzyy-Ping
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Chou, Wen-Chi
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Huang, Li-Yu
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Wang, Chia-Yu
"This study explores the changes in electroencephalographic (EEG) activity associated with the performance of solving an optics maze problem. College students (N = 37) were instructed to construct three solutions to the optical maze in a Web-based learning environment, which required some knowledge of physics. The subjects put forth their best effort to minimize the number of convexes and mirrors needed to guide the image of an object from the entrance to the exit of the maze. This study examines EEG changes in different frequency bands accompanying varying demands on the cognitive process of providing solutions. Results showed that the mean power of theta, alpha 1, alpha 2, and beta 1 significantly increased as the number of convexes and mirrors used by the students decreased from solution 1 to 3. Moreover, the mean power of theta and alpha 1 significantly increased when the participants constructed their personal optimal solution (the least total number of mirrors and lens used by students) compared to their non-personal optimal solution. In conclusion, the spectral power of frontal, frontal midline and posterior theta, posterior alpha, and temporal beta increased predominantly as the task demands and task performance increased."
Enhancement of Extrinsic Charging Efficiency of a Nanoparticle Charger with Multiple Discharging Wires
(2010)
Tsai, Chuen-Jinn
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Lin, Guan-Yu
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Chen, Hui-Lin
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Huang, Cheng-Hsiung
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Alonso, Manuel
A unipolar charger with multiple discharging wires has been developed and investigated to enhance the extrinsic charging efficiency of nanoparticles by using sheath air near the wall of the charger. The applied voltage of the charger ranged from +4.0 to +10 kV, corresponding to corona current from 0.02 to 119.63 mu A. Monodisperse NaCl particles of 10 similar to 50 nm and Ag particles of 2.5 similar to 10 nm in diameter were produced to test the performance of the charger with multiple discharging wires and to investigate the particle loss at different sheath flow rates, corona voltages and sheath air velocities. Results showed that the optimal efficiency in the charger was obtained at + 9 kV applied voltage, 10 L/min aerosol flow rate and 20 L/min sheath air flow rate. The extrinsic charging efficiency increased from 2.86% to 86.3% in the charger as the particle diameter increasing from 2.5 to 50 nm. The TDMA (tandem-differential mobility analyzer) technique was used to investigate the charge distribution, and the charge distributions in the exit were obtained at the optimal operating condition.
Fast and Memory Efficient Conflict Detection for Multidimensional Packet Filters
(2012)
Lee, Chun-Liang
;
Lin, Guan-Yu
;
Chen, Yaw-Chung
;
資訊工程學系
;
Department of Computer Science
Packet classification plays an important role in supporting advanced network services such as Virtual Private Networks (VPNs), quality-of-service (QoS), and policy-based routing. Routers classify incoming packets into different categories according to pre-defined rules, which are called packet filters. If two or more filters overlap, a conflict may occur and leads to ambiguity in packet classification. In this paper, we propose an algorithm which can efficiently detect and resolve filter conflicts. The proposed algorithm can handle filters with more than two fields, which is more general than algorithms designed for two-dimensional filters. We use the synthetic filter databases generated by Class Bench to evaluate the proposed algorithm. Compared with the bit-vector algorithm, simulation results show that the proposed algorithm can reduce the detection times by over 84% for 10 out of 12 filter databases, and only uses less than 26% of memory space.
High-efficiency wet electrocyclone for removing fine and nanosized particles
(2013-08-09)
Lin, Guan-Yu
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Le-Thi Cuc
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Lu, Wei
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Tsai, Chuen-Jinn
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Chein, Hung-Min
This study designed and tested a wet electrocyclone with high efficiency for long-term operation. The inner diameter of the collection electrode is 25 cm, and the discharge electrodes consist of seven circular discs with zigzag-shaped edges for particle charging and removal. The tip of the circular saw-type discs is 20 pin in diameter and the tip to the inner wall (collection electrode) spacing is 4 cm. Cleaning water near the inter wall was used to keep the collection electrodes clean. Experimental results showed that the collection efficiency of the present wet electrocyclone decreased with an increasing air flow rate. The efficiency for oleic acid (OA) particles was reduced only slightly from 78-92% to 75-90% for particles from 22.1 to 805 nm in electrical mobility diameter (d(p)) after 6 h of micro-Al2O3 loading test. In the field test, the collection efficiencies of the present wet electrocyclone for submicron SiO2 particles with mass concentration of 20-50 mg/m(3) were also found to keep higher than 93% for continuous 14-day operation. A modified Deutsch-Anderson model was developed to predict the charged particle collection efficiency (eta(elec,p), %) of nanoparticle as well as larger particles. The present model is eta(elec,p) (%) = 1 - exp{-[A(N-De(B)) + C(N-De) + D]} x 100%, where A, B, C and D are regression coefficients, and N-De is the modified Deutsch number. Good agreement was obtained between the present predictions and experimental data. (C) 2013 Elsevier B.V. All rights reserved.
Modeling and Validation of Nanoparticle Charging Efficiency of a Single-Wire Corona Unipolar Charger
(2011)
Chien, Chih-Liang
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Tsai, Chuen-Jinn
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Chen, Hui-Lin
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Lin, Guan-Yu
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Wu, Jong-Shinn
A single-wire corona unipolar aerosol charger with a sheath air to avoid particle loss was designed and experimental charging efficiencies were obtained at a fixed aerosol flow rate of 1 L/min using monodisperse silver nanoparticles of 2.5 to 20 nm in diameter. The charger has a cylindrical casing of 30 mm in inner diameter in which a gold wire of 50 mu m in diameter and 2 mm in length is used as the discharge electrode. A two-dimensional (2-D) numerical model was developed to predict nanoparticle charging efficiency in the unipolar charger. Laminar flow field was solved by using the Semi-Implicit Method for Pressure Linked Equations (SIMPLER method), while electric potential and ion concentration fields were solved on the basis of Poisson and convection-diffusion equations, respectively. The charged particle concentration fields and charging efficiencies were then calculated on the basis of the convection-diffusion equation in which ion-particle combination coefficient was calculated by Fuchs diffusion charging theory (Fuchs, N. A. (1963). On the Stationary Charge Distribution on Aerosol Particles in a Bipolar Ionic Atmosphere. Geophys. Pura. Appl., 56:185-193). Good agreement between predicted and experimental extrinsic charging efficiencies was obtained. Numerical results showed the advantage of using sheath air to minimize charged particle loss and indicated the location where major charged particle loss occurred. It is expected that the present model can be used to facilitate the design of more efficient corona-wire unipolar charger in the future.
Numerical Modeling of Nanoparticle Collection Efficiency of Single-Stage Wire-in-Plate Electrostatic Precipitators
(2010)
Lin, Guan-Yu
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Tsai, Chuen-Jinn
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環境工程研究所
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Institute of Environmental Engineering
The numerical models for predicting the collection efficiency of particles in the size range of 0.3 similar to 10.0 mu m in electrostatic precipitators (ESPs) have been well developed. However, for nanoparticles, or particles with the diameter below 100 nm, the existing models can't predict the collection efficiency very well because the electric field and ion concentration distribution were not simulated, or charging models were not adopted appropriately to calculate particle charges. In this study, a 2-D numerical model was developed to predict the nanoparticle collection efficiency in single-stage wire-in-plate ESPs. Laminar flow field was solved by using the Semi-Implicit Method for Pressure-Linked Equation (SIMPLER Method), while electric field strength and ion concentration distribution were solved based on Poisson and diffusion-convection equations, respectively. The charged particle concentration distribution and the particle collection efficiency were then calculated based on the convection-diffusion equation with particle charging calculated by Fuchs diffusion charging theory. The simulated collection efficiencies of 6-100 nm nanoparticles were compared with the experimental data of Huang and Chen (2002) for a wire-in-plate dry ESP (aerosol flow rate: 100 L/min, applied voltage: -15.5 similar to -21.5 kV). Good agreement was obtained. The simulated particle collection efficiencies were further shown to agree with the experimental data obtained in the study for a wire-in-plate wet ESP (Lin et al. 2010) (aerosol flow rate: 5 L/min, applied voltage: +3.6 similar to +4.3 kV) using monodisperse NaCl particles of 10 and 50 nm in diameter. It is expected that the present model can be used to facilitate the design of ESPs for nanoparticle control and electrostatic nanoparticle samplers.
Parallel plate denuder for gas absorption
(2008-06-12)
Tsai, Chuen-Jinn
;
Lin, Guan-Yu
This invention provides a high-efficiency parallel plate wet denuder (PPWD) for gas absorption, the absorption surfaces thereof are composed of two hydrophilic porous glass plates on which TiO2 particles are coated and subsequently are irradiated with UV light to form super-hydrophilic surfaces, so that it further enhances the formation of uniform water film and increases gas absorption efficiency. This invention can be used in the manual sampling devices for acidic/basic gases, the gas absorption equipments for acidic/basic gases and gas-particle denuder sampling devices, besides it can also be coupled with an ion chromatograph to make semi-continuous acidic/basic gas-particle monitors.
The Effect of Nanoparticle Convection-Diffusion Loss on the Transfer Function of an Aerosol Particle Mass Analyzer
(2014)
Lin, Guan-Yu
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Liao, Bo-Xi
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Tzeng, Neng-Jiun
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Chen, Chun-Wan
;
Uang, Shi-Nian
The existing theoretical response spectra of APM-3600 agree well with the experimental data for submicron particles larger than 100nm in the electrical mobility diameter but not for nanoparticles. In this study, a 2-D numerical model was developed to predict the transfer function and response spectra of APM-3600 based on the detailed simulation of flow and particle concentration fields. It was found that recirculation flows existed in the annular classifying region and APM\'s inlet and outlet regions, which led to enhanced convection-diffusion loss of nanoparticles compared to that without considering flow recirculation. As a result, the APM underestimates the mass of naonoparticles due to the shift of the peak position of the transfer function to a larger diameter than the targeted diameter. The response spectra calculated with the simulated transfer function agree well both in shapes and peak values with the experimental data present in a previous study for both nanoparticles and submicron particles larger than 100 nm. The predicted particle masses also agree well with the PSL\'s experimental data of the article.Copyright 2014 American Association for Aerosol Research
The Predictive Method for the Submicron and Nano-Sized Particle Collection Efficiency of Multipoint-to-Plane Electrostatic Precipitators
(2013-10-01)
Le, Thi-Cuc
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Lin, Guan-Yu
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Tsai, Chuen-Jinn
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環境工程研究所
;
Institute of Environmental Engineering
The multipoint-to-plane electrostatic precipitator (ESP) is one type of ESP devices used for the sampling and control of nanoparticles and sub-micron particles, with the advantage of a low pressure drop and high particle collection efficiency. Several empirical equations for predicting the particle collection efficiency are available in the literature, but most of them are only applicable to wire-in-plate ESPs. For ESPs with different discharge electrodes, the empirical equations are different since the ion concentration and electric fields are different. In this paper, a predictive method is developed to calculate the particle migration velocity and the particle collection efficiency equation eta(%) of multipoint-to-plane ESPs in the form of eta(%) = {1 - exp{-[beta(1)(N-De(beta 2)) + beta(3)(N-De) + beta(4)]}} x 100%, in which beta(1), beta(2), beta(3) and beta(4) are regression coefficients and N-De is the Deutsch number determined by the particle migration velocity. Good agreement is obtained between the present model predictions and the experimental particle collection efficiencies obtained from the literature. It is expected that the present model can be used to facilitate the design of efficient multipoint-to-plane ESPs for nanoparticle and sub-micron particles removal in the future.
Ultrafine Particles and PM2.5 at Three Urban Air Monitoring Stations in Northern Taiwan from 2011 to 2013
(2015-11-01)
Lin, Guan-Yu
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Lee, Guo-Rui
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Lin, Sih-Fan
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Hung, Yi-Hung
;
Li, Shih-Wei
In this study, long term measurements of PM2.5 and ultrafine particles (UFPs) for daily average mass concentration at Zhongshan (ZS), Sinjhuang (SJ), and Jhudong (JD) urban air monitoring stations were conducted from 2011 spring to 2013 autumn. The results showed that daily average UFPs mass concentrations in spring (average at 3 stations: 1.58 +/- 0.74 mu g m(-3)) and summer (average at 3 stations: 1.59 +/- 0.53 mu g m(-3)) were higher than those in autumn (average at 3 stations: 1.02 +/- 0.28 mu g m(-3)) and winter (average at 3 stations: 1.04 +/- 0.48 mu g m(-3)) due to the impacts by heavy traffic emission and new particle formation event. The effective density (rho(eff)) and dynamic shape factor (chi) for ultrafine particles (UFPs) were found to be 0.68 +/- 0.16 g cm(-3) and 2.06 +/- 0.19, respectively, suggesting that the particle morphology was irregular shape. Based on the calculated rho(eff) and chi, the average number and surface area concentration ratio of UFPs to those of PM2.5 at these monitoring stations was determined to be 89.0 +/- 5.5% and 42.1 +/- 12.8%, respectively, suggesting that UFPs contribute significantly to the health-relevant PM2.5 aerosol fraction in these stations.
Wet electrostatic precipitator with pulse jet for cleaning discharge wires
(2011-03-10)
Tsai, Chuen-Jinn
;
Lin, Guan-Yu
A wet electrostatic precipitator (ESP) is disclosed to have a housing, several discharge wires, two roughened collection electrodes coated with TiO2 or SiO2 nanoparticles, two porous metallic plates, and two roughened glass plates coated with TiO2 or SiO2 nanoparticles. The porous metallic plates and the glass plates coated with TiO2 or SiO2 nanoparticles located above the collection electrodes are used to enhance the uniformity of the water film. When particles are introduced into the ESP, they are charged by gas ions generated by corona discharge, and then migrate to collection electrodes due to electrostatic force. Finally, particles are removed by uniform water film flowing downward along the collection electrodes. Furthermore, pulse jet passing through the small holes on the collection plates is used to clean discharge wires, maintaining electric corona strength and prolonging the operation life.