114,331 research outputs found
Webtechno-G/corona-tr-modeling: Corona Modelleme Metrikleri
No full textTürkiye Corona Metrikleri Şemas
Measurement and analysis of electric potential decay in corona charged low-density polyethylene films
Get PDFIn this paper, corona charged LDPE film was tested using a standard static potential monitor and the pulsed electro-acoustic (PEA) technique to observe the surface potential decay. A wide range of voltages and different corona charging times, different sample thicknesses and multi-layer films were used to demonstrate influential factors for surface potential decay. These provide a direct experimental evidence to support the bulk transport process. An important finding from the PEA results is that bipolar charge injection takes place during corona charging process and in subsequently decay process. The new evidence challenges the existing surface potential decay models which were developed based on a single charge carrier injection
Bactericidal effect of corona discharges in atmospheric air
No full textThe present paper explores the possibilities of using impulsive and steady-state corona discharges for bio-decontamination operations. A high tension tubular corona electrode was stressed with positive or negative dc voltage with magnitude up to 26 kV, and a grounded mesh was used as an opposite electrode. Different operational regimes of this corona generator were investigated for the production of ozone in air flow and the inactivation of microorganisms. The test microorganisms used in this work were Escherichia coli and Staphylococcus aureus, populations of which were seeded onto agar plates. These bacterial plates were located behind the grounded mesh electrode to assess bactericidal efficacy. The results show that corona discharges have a strong bactericidal effect, for example positive flashing corona discharges were able to reduce populations of the test microorganism by 94% within a 30-60 sec time interval. Negative steady-state corona discharges also produce noticeable bactericidal effect, reducing population of E. coli and S. aureus by more than 97% within 120 sec energisation interval. The bactericidal efficiency of different corona discharge modes and its correlation with ozone levels produced by these discharges is discussed. The results obtained in this work will help in the design and development of compact plasma systems for environmental application
Charge transport mechanisms in corona charged polymeric materials
No full textPolymeric materials have been widely used as an insulator due to their excellent electrical properties, light weight and low cost. Surface potential measurement is one of the simplest and low cost tools to gauge electrical properties of materials. Once charged, the surface charges or surface potential tend to decay over a period of time, and the exact pattern of the decay represents the characteristic of the material. For corona charged sample, it has been observed that the potential of sample with an initial high surface potential decays faster than that with an initial lower surface potential, known as the cross-over phenomenon. Various theories and models have been proposed to explain the phenomenon. The common feature of these models is that they are all based on single charge carrier injection from corona charged surface. With the recent experimental results on comparing different types of ground of corona charged low density polyethylene sample, bipolar charge injection from both electrodes has been verified. Based on this fact, a new model based on bipolar charge injection has been proposed. In this thesis, the detail of the new model was tested both experimentally and numerically. The new simulation results show that several features experimentally observed can be readily revealed using the bipolar charge injection model. More importantly, the modelling can illustrate charge dynamics across the sample and allows one to extract parameters that are associated with material properties. The effect on different charging polarities and charging times were also discussed in the thesis. Additionally, experiments have been done to nano polyimide materials and the results clearly show that adding different amounts of nano-particles can change the material's electrical property
Measurement of surface potential decay of corona-charged polymer films using the pulsed electroacoustic method
No full textIn this paper, the pulsed electroacoustic (PEA) technique that allows the determination of space charge in a dielectric material has been used to monitor the electrical potential decay of corona-charged polyethylene films of different thicknesses. To prevent possible disturbance on the surface charge during the PEA measurements, two thin polyethylene films were placed on both sides of the corona-charged sample. Charge profiles measured at different times were used to calculate the potential across the sample. The obtained potential decay was compared with the potential measured using the conventional method. A good agreement has been obtained. More importantly, the charge profile obtained using the PEA technique indicates that bipolar charge injection has taken place
The influence of TiO<sub>2</sub> nanoparticle incorporation on surface potential decay of corona-resistant polyimide nanocomposite films
No full textPI nanocomposite films containing surface modified nanoparticles by employing silane coupling agent were prepared using in-situ dispersion polymerization process. The surface potential decay measurements on films were investigated over the different negative corona-charged voltages and times in a controlled environment where temperature and relative humidity were kept at 21 ºC and 45%, respectively. There is a significant change in the surface potential decay characteristics after nano-fillers were introduced into polyimide. The surface potential decay pattern depends also on the amount of nano-fillers. The possible surface potential decay and corona resistance mechanisms responsible for the observed phenomena were discussed
A new model for surface potential decay of corona-charged polymers
Get PDFSurface potential measurement provides a useful tool to gauge the electrical properties of materials. It has been observed that the potential of a sample with an initial high surface potential decays faster than that with an initial lower surface potential, known as the cross-over phenomenon. The phenomenon was found a few decades ago and various theories and models have been proposed. A common feature of the existing models is based on single charge carrier injection from a corona-charged surface. With our recent space charge measurement results on corona-charged samples, double injection from both electrodes has been verified. Based on this new fact, a new model based on bipolar charge injection is proposed and initial numerical simulation reveals that the surface potential cross-over phenomenon can occur under bipolar charge injection
Effects of the Presence or Absence of a Protein Corona on Silica Nanoparticle Uptake and Impact on Cells
No full textNanoparticles enter cells through active processes, thanks to their capability of interacting with the cellular machinery. The protein layer (corona) that forms on their surface once nanoparticles are in contact with biological fluids, such as the cell serum, mediates the interactions with cells in situ. As a consequence of this, here we show that the same nanomaterial can lead to very different biological outcomes, when exposed to cells in the presence or absence of a preformed corona. In particular, silica nanoparticles exposed to cells in the absence of serum have a stronger adhesion to the cell membrane and higher internalization efficiency, in comparison to what is observed in medium containing serum, when a preformed corona is present on their surface. The different exposure conditions not only affect the uptake levels but also result in differences in the intracellular nanoparticle location and impact on cells. Interestingly, we also show that after only one hour of exposure, a corona of very different nature forms on the nanoparticles exposed to cells in the absence of serum. Evidence suggests that these different outcomes can all be connected to the different adhesion and surface properties in the two conditions.Irish Research Council for Science, Engineering and TechnologyEuropean Research Counci
Decay of Electric Charge on Corona Charged Polyethylene
No full textIn this paper, the surface potential decay of corona-charged low density polyethylene (LDPE) films has been investigated. It has been found that for the same sample thickness the faster decay occurs in the sample with a higher charging voltage. For the same charging voltage, the surface potential in the thinner sample shows rapid decay. Our new evidence from both the surface potential measurement on multilayer samples and space charge measurement suggests the surface potential decay is a bulk limited process. More importantly, space charge measurement indicates double injection has taken place during corona charging process
LA FUNZIONE BENEFICIO NETTO IN UN PROGRAMMA DI INTERVENTI PER UN PIANO MANUNTENTORIO STRADALE
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