Tesis: "Atmospheric discharges"

1

Chirokov, Alexandre V. Fridman Alexander. "Stability of atmospheric pressure glow discharges /". Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/657.

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2

Rusterholtz, Diane. "Nanosecond Repetitively Pulsed Discharges in Atmospheric Pressure Air". Phd thesis, Ecole Centrale Paris, 2012. http://tel.archives-ouvertes.fr/tel-00997397.

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Nanosecond Repetitively Pulsed (NRP) discharges in atmospheric pressure air have many potential applications. Spark NRP discharges have applications in plasma assisted combustion. These discharges tend to stabilize lean flames which produce less NOx. Furthermore, an increase of several hundreds of Kelvins in less than 20 ns has been observed following NRP spark discharges, which could be used to create nanomaterials. NRP glow discharges, while creating an important number of actives species such as atomic oxygen, do not heat the ambient gas, which allows them to be used in temperature-sensitive applications such as bio-decontamination. In the first part of this thesis, we validate experimentally the mechanism that was proposed to explain the ultrafast heating observed. Time-resolved measurements of the absolute densities of two excited states of nitrogen and of the gas temperature have been performed with calibrated Optical Emission Spectroscopy. The second part of the thesis deals with the NRP glow regime. We have shown that its existence depends on several parameters, gas temperature and pressure, voltage across the electrodes, inter-electrode distance, pulse duration, radius of curvature of the electrodes. This regime had not been observed for temperatures lower than 750 K so far. Thanks to a detailed parametrical experimental study and the analysis of the obtained results, we have succeeded in identifying the NRP glow regime at ambient temperature and we observe a new type of "multi-channel" glow regime.

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3

Deng, Xu-Tao. "Stable atmospheric glow discharges : computational study and applications". Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/36172.

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This thesis describes a study of stable atmospheric pressure glow discharges through both a PC-based numerical simulation of their dynamics and exploratory experiments for establishing their decontamination efficacy. The numerical work is based on a one-dimensional fluid model with a commonly adopted hydrodynamic approximation that assumes electron equilibrium with the local electric field. Two gas systems are considered, namely pure helium and helium-nitrogen mixture, and our simulation results agree well with relevant experimental data. Also the numerical study establishes a specific frequency range within which stable helium atmospheric pressure dielectric-barrier glow discharges can be generated, and unravels two distinct plasma disruption mechanisms when the plasma excitation is outside the above mentioned frequency range. Further explored is possible plasma power saving that can be achieved by means of pulsed excitation. It is shown that significant power saving of up to 40% can be achieved by a combination of wave-shaping and pulse-width reduction. Finally through preliminary exploratory experiments, it is shown that atmospheric pressure glow discharge is biologically lethal to food-borne microorganisms and when further developed can form the basis for a novel food decontamination technology.

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4

Hasan, Mohammad. "Numerical modelling of atmospheric pressure plasma jet discharges". Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/2046221/.

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Atmospheric-pressure plasma discharges (APPJs) have been one of the main active research topics of low temperature plasmas since they were firstly reported a decade ago. Their compactness, their ability to operate at ambient conditions (atmospheric pressure and room temperature), and their simplicity (no complex or expensive vacuum equipment are required) makes them very promising sources of active chemical species for a variety of applications, ranging from sterilisation of surfaces to space thrusters. Optimising APPJs to suit particular applications requires deep understanding of the plasma dynamics involved in their operation, which is an active field of research from experimental and numerical approaches. Because both approaches have practical limitations, the difference between the simulated conditions and the experimental conditions has become wide. One particular aspect of this difference is the time scales of the phenomena studied. In most numerical studies the time scale considered is in the order of hundreds of nanoseconds, while experiments are conducted under steady state conditions. In this work, a numerical model is built to study the behaviour of an APPJ discharge on relatively longer times compared to other numerical studies. The longer time scale in this work covers two consecutive periods of an applied pulsed DC waveform (up to 40 s), compared to only the pulse-on time for a single pulse in most other works. The study presented here considered two jet configurations, an open jet configuration and a surface configuration. The afterglow of the open jet configuration is studied, where it is shown that the absence of the applied potential causes the electrons to diffuse strongly from the plasma channel created in the pulse-on time, causing an increase by almost two orders of magnitude in the density of the negative ions. An increase in the density of the positive ions is also observed in the afterglow, which is attributed to Penning ionisation between the helium metastables and the molecules of air (O2 iv and N2). The study also shows that the characteristics of the discharge in the second period are noticeably influenced by the residuals from the first period. With respect to the surface configuration, the study presented in this work focuses on the fluxes of the active species to the surface. It is reported that the flux of the positive ions to the surface occurs mainly during the pulse-on time, with its maximum value coinciding with the location of the plasma bullet at a given time. The flux of the negative ions however occurs mainly during the pulse-off time at locations on the surface where no surface charge is deposited during the pulse-on time. In the second period, the deposited negative surface charge deposited in the previous period causes a decrease of the flux of negative ions to the surface. Whereas the residual plasma from the previous period causes an increase in the flux of positive ions to the surface where the residual plasma is in contact with it. The other topic of interest in this work is the induction of turbulence in APPJ due to the presence of the plasma, where it is shown that the plasma affects the background flow by electrohydrodynamic forces and by gas heating. It is shown than neither the EHD forces nor the gas heating by the plasma are capable of accelerating the flow to change the flow regime. Thus, a new explanation is proposed to explain the induction of turbulence by the plasma in APPJs.

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5

Shi, Jianjun. "Experimental and theoretical studies of atmospheric glow discharges". Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/7982.

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This thesis presents the experimental and theoretical studies of nonthermal and stable atmospheric-pressure glow discharges. With the excitation frequency in the kilohertz range, a uniform and stable glow discharge has been successfully produced in atmospheric helium without the usually indispensable dielectric barrier. For this barrier-free cold atmospheric discharge, there are two discharge events occurring, respectively, in the voltage-rising and the voltage-falling phases, and in general they compete with each other. This distinct feature is illustrated through a detailed fluid simulation. For direct current atmospheric glow discharges, their cathode fall region is shown to depend critically on the discharge current density. For atmospheric glow discharges excited at 13.56 MHz on the other hand, we present observations that after gas breakdown, the discharge evolves from the normal glow mode to the abnormal glow mode and then through the recovery mode back to the normal glow mode. The operation modes, namely the a mode and the y mode, in radio-frequency atmospheric glow discharges are investigated with a one-dimensional, self-consistent continuum model. This model is evaluated by comparing our numerical results with experimental data and other simulation results in literature. It is shown that gas ionization is volumetric in the a mode and localized in the boundary region between the sheath and the bulk plasma in the y mode. The stable operation regime in the a mode is found to have a positive differential conductivity, and can be expanded to higher discharge current density without compensating plasma reactivity by increasing the excitation frequency. Furthermore this plasma stability-reactivity balance is also studied for radio-frequency atmospheric glow microdischarges.

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6

Buntat, Zolkafle. "Ozone generation using electrical discharges : a comparative study between pulsed streamer discharge and atmospheric pressure glow discharge". Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/14556.

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This thesis deals with an investigation into atmospheric pressure glow discharge and pulsed streamer discharge techniques of ozone generation, in an attempt to compare their performances in the generation of a high concentration and high yield of ozone. It is motivated by the desire to exploit further the ability and potential possessed by both techniques for ozone generation and to provide support to the increased demand for ozone in many areas of application. Chapter 1 of the thesis provides a brief history into the application of ozone. In Chapter 2, a basic understanding of the gas discharge is given for both thermal and non-thermal plasm as, and the theory 0 f non-thermal plasma is presented. The different types of electric discharges commonly used for ozone generation are explained. A review of the effect of both the physical configuration and the electrical parameters on the ozone yield and concentration is presented in Chapter 3, with the three main parameters that limit the efficiency of the production being highlighted. The second part of the thesis describes a thorough experimental investigation. In Chapter 4, a study is made of the stability of the atmospheric pressure glow discharge (APGD) which is found to be more stable when perforated electrodes are used rather than a fine steel wire mesh. Following this, a comparative study between APGD and pulsed streamer discharge (PSD) is presented in Chapter 5. A detailed investigation into both APGD and PSD in air is described. The effects of varying the input voltage, gap distance, chamber length, air flow rate and gas residence time are all used to evaluate the performance of both techniques. The PSD is found to generate a higher concentration but with a lower ozone yield. On the other hand, the APGD generates a lower concentration but with a higher yield. Chapter 6 presents the effect of a cross magnetic field on an AC corona and the PSD techniques and its influence on ozone generation. Results show no apparent effect of the magnetic field in either technique. Chapter 7 describes the use of dimensional analysis in investigating the effect of the electrical and the discharge configuration parameters on ozone production in oxygen by means of a PSD. Ozone destruction factors are taken into account in the model, and predicted results are shown to be in good agreement with experimental findings.

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7

Balcon, Nicolas y nicolas balcon@gmail com. "Atmospheric pressure Radio Frequency discharges, diagnostic and numerical modeling". The Australian National University. Research School of Physical Sciences and Engineering, 2008. http://thesis.anu.edu.au./public/adt-ANU20080318.234936.

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The aim of this thesis is to investigate the properties of a Radio Frequency capacitive discharge at atmospheric pressure in argon. In these conditions where the pressure x distance product is around 150 Torr.cm, the discharge usually consists of several locally hot filaments. By pulsing the RF generator with an appropriate width and period, it was found possible to control the filament to glow transition in order to obtain a diffused and stable plasma.¶ The 2 mm gap between the electrodes is open to the ambient air and fed with argon via one hundred submillimetric holes regularly spread on the surface of the top electrode. This configuration allows on-line surface treatment of polymer films without having to turn the discharge off between successive samples. An important and lasting improvement of the polymer wettability is quickly obtained without risk of damage. The plasma diagnostic methods are emission spectroscopy and electric measurements. The Stark broadening of the Balmer β transition line of atomic hydrogen is measured to determine a plasma density of 10^15/cm3 in the filamentary mode. The glow mode density estimation was based on power balance yielding a density of 5×10^11/cm3. Emission line ratios between neutrals and Ar+ ions are used in the Saha equation to calculate the electron temperature. It results in an approximation of 1.3 eV for the glow mode and 1.7 eV for the filaments.¶ A unidimensional self-consistent fluid model is developed to gain insight into the homogeneous discharge behaviour. Poissons equation for the electric field is coupled to the first moments of the Boltzmann equation (continuity equation, drift-diffusion equation and energy equation). Transport and reaction coefficients are obtained from the mean energy of the electrons.¶ The model is applied to a reduced argon kinetic with the main ionization and excitation processes. Simulation results are in agreement with experimental measurements. The atmospheric pressure RF discharge is similar to a lower pressure RF discharge for which the ionization occurs mainly inside the oscillating sheaths where electrons are the most energetic

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8

Walsh, James L. "Ultra-short pulsed non-equilibrium atmospheric pressure gas discharges". Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/15140.

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This thesis presents experimental studies of various non-thermal atmospheric pressure gas discharges generated using short pulsed excitation as an alternative to widely used sinusoidal excitation. Several pulse generators are detailed that provide high voltage pulses ranging from hundreds of microseconds to less than ten nanoseconds in duration. A key enabler to the generation of a stable discharge is a suitably high repetition rate; this prerequisite precludes many conventional pulsed power technologies. Fortunately, recent advances in semiconductor technology have made it possible to construct solid state switches capable of producing high voltage pulses with repetition rates of many kilohertz. Pulsed excitation introduces many opportunities to tailor the applied voltage and consequently enhance the discharge which are not possible with sinusoidal excitation sources. Through detailed electrical and optical analysis it is shown that pulsed excitation is not only more energy efficient than a comparable sinusoidal source but produces a higher flux of excited species that are essential in many applications. When pulse widths are reduced to a sub-microsecond timescale a novel barrier-free mode of operation is observed. It is shown that diffuse large area plasmas are easily produced at kilohertz repetition rates without the usually indispensable dielectric barriers. Experimental results show that a short pulse width prevents the onset of the undesirable glow-to-arc transition thus introducing an added degree of stability. A further benefit of pulsed excitation is the ability to produce gas discharges with a high instantaneous peak power yet low average power consumption, resulting in a high density plasma that exhibits roomtemperature characteristics. Finally, as an acid test to highlight the many benefits of pulsed excitation several real-world applications are considered. It is shown that in all cases pulsed gas discharges provide real benefits compared to their sinusoidal counterparts.

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9

Balcon, Nicolas. "Atmospheric pressure radio frequency discharges, diagnostic and numerical modeling /". View thesis entry in Australian Digital Thesis, 2007. http://thesis.anu.edu.au/public/adt-ANU20080318.234936/index.html.

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10

Li, Sirui. "Atmospheric non-thermal plasma discharges for cleaning and bio-decontamination". Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27572.

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It has been shown that non-thermal plasma has great potential for chemical oxidation and bacterial inactivation. However, the mechanism of plasma-induced oxidation and bactericidal effects is not fully understood, and optimisation of the non-thermal plasma treatment is required to improve the efficiency of this technology. This research presents an investigation into the oxidation and bio-decontamination capabilities of steady-state corona discharges and impulsive transient plasma discharges in atmospheric air. Degree of decolorisation of blue dye by plasma discharges was obtained and used for evaluation of the oxidation efficiency of these discharges. The Gram-positive and Gram-negative bacteria, Staphylococcus aureus and Escherichia coli, respectively, were used for investigation of the bio-decontamination capability of the plasma discharges. It has been shown that conditions such as air humidity, electrode topology, and voltage levels may affect the efficiency of plasma treatment. The obtained results show that the oxidation and inactivation effects depend on the amount of charge delivered by the plasma. The charge-dependent decolorisation and inactivation rates of plasma discharge treatment, which indicate the oxidation efficiency and inactivation efficiency, were obtained and analysed. Different decolorisation and inactivation rates were achieved with various electrode topologies and energisation polarities. This study also investigated the production of reactive species by atmospheric plasma discharges. Ozone concentration was measured during the decolorisation and inactivation tests. The production of OH radicals by the plasma discharges have also been obtained in this study using terephthalic acid as the chemical probe. The obtained results confirm that the reactive oxygen species play a major role in the plasma discharge treatment. In addition, an attempt of using TiO2 as a catalyst to enhance oxidation and bio-decontamination effects of the plasma discharge treatment has been made. TiO2 was revealed to have the potential to improve the oxidation efficiency of atmospheric plasma discharges. The results obtained and presented in this thesis will help in optimisation of non-thermal plasma systems for chemical and biological decontamination.

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11

Bless, Frédéric. "Investigation of atmospheric-pressure plasma discharges for thin film deposition". Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2050119/.

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Gas-phase polymerisation of different monomers has been studied for an atmospheric plasma jet predominantly using quadrupole mass spectrometry. Thin film depositions were made and analysed using XPS and TOF-SIMS. Time-resolved and time-averaged measurements were performed to understand more deeply the paths of plasma polymerisation at atmospheric pressure and in ambient air. Continuous wave and pulse DC jets were both investigated. Results show the importance of positive ions in polymerisation and support the step growth formation for the creation of heavy oligomers. Negative ions are also important and depend far more on the signal frequency, more precisely on the off-time duration, than the positive ions. Another study was performed on an adaptable plasma system for atomic layer deposition allowing deposition of oxides at room temperature. Results show a high quality of Al2O3 films realised at room temperature with air as an oxygen-rich gas with the use of a custom-built surface discharge plasma reactor.

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12

Seidelmann, Lukas Josef Wilfried. "Atmospheric pressure dielectric barrier discharges for the surface modification of polypropylene". Thesis, Manchester Metropolitan University, 2015. http://e-space.mmu.ac.uk/608794/.

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Polypropylene films are widely used as packaging materials for foodstuffs, since they offer excellent barrier properties against polar substances, high elasticity, mechanical strength, transparency and chemical stability. However, the relatively low surface energy of polypropylene represents a major issue for the adhesion of printing inks and labels. To improve printability it is necessary to perform a surface activation process. In the presented work, the atmospheric pressure dielectric barrier discharge (DBD) in nitrogen is investigated as a surface treatment method to increase the surface energy of biaxially orientated polypropylene foils. This technology creates a non-thermal plasma by applying strong electrical fields to a gas between two electrodes. The reactive species of the plasma forms new electronegative chemical groups on the surface and also etches the surface of the substrate. Both effects lead to an increase of the surface energy of the plasma treated polymer films. The crosslinking of polymer chains is also a possible effect caused by the plasma treatment. A new plasma rig was designed for this project, including a closed plasma chamber, two different parallel electrode configuration (flat or sawtooth electrodes) and a reel-to-reel system for the transport of the polypropylene foil. The designed system allows to adjust the sizes of the gas gap and the thickness of the dielectric. In addition, the plasma chamber can be filled with every gas or gas mixture wanted. A D-optimal design of experiments approach was utilised to study the influence of the power applied to the electrodes, the size of the gas gap and the thickness of the dielectric on the wettability of the treated polymer films. Furthermore, a flat electrode and a sawtooth electrode configuration are compared to each other. The findings of this work clearly indicate that the sawtooth electrode configuration is superior regarding the consumed electrical power and the wettability of the treated films. The optimal setting for the plasma treatment with the sawtooth electrode configuration are a low gas gap and a high power applied to the electrodes. The thickness of the dielectric has no influence on the wettability of the treated film. However, the increase of the dielectric thickness leads to an increase of the consumed power. These findings were transferred to an industrial process, where the polymer foils were treated in a nitrogen atmosphere with admixtures of CO2, N2O and C2H2 in the ppm range under the founded optimal conditions. A significant difference in the surface energies of these samples could not be identified by contact angles measurement, but all samples showed a significantly reduced hydrophobic recovery rate in comparison to samples treated by the in the industry more conventional plasma treatment in air. The DBD surface treatment in nitrogen is therefore an important improvement for the industrial production, because the treated packaging foils can be stored longer before they are processed further without the need to refresh the surface treatment. The low hydrophobic recovery of the samples treated in the nitrogen plasma is connected to an intensified crosslinking of the polymer chains on the surface of the treated polypropylene films.

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13

Liu, Dawei. "Experimental and numerical study of radio frequency atmospheric pressure glow discharges". Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/13987.

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Radio frequency (rf) atmospheric pressure glow discharges (APGDs) have received growing attention for their exciting scope of new science and their immense potential for widespread applications. While geometrically similar to conventional low-pressure discharges used in the semiconductor industry for decades, rf APGDs present new physics that require investigation. This thesis presents an experimental and computational study of helium rfAPGDs aimed at making a contribution to the current understanding of these discharges and enabling their optimization for different applications. The timely interest and significance of this work is highlighted by the publication of different parts of this thesis in 10 peer-reviewed international journals. Starting with the electron trapping in rf APGDs, the thesis looks into the electron heating mechanism responsible for sustaining the discharges, the influence of the rf excitation frequency on the discharge characteristics, the role of impurities in the discharge chemistry as well as the evolution of the discharge as the size is reduced down to microplasma dimensions. The findings of this research are based on the synergistic use of electrical measurements, optical diagnostics and self-developed computational models. With the knowledge gained from this thesis, rf-APGDs can be readily used for a wide-range of applications including biological decontaminations, nanostructure fabrication and portable gas analyzers.

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14

Pechereau, François. "Numerical simulation of the interaction of atmospheric pressure plasma discharges with dielectric surfaces". Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-00978523.

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In this Ph.D. thesis, we have carried out 2D numerical simulations to study the influence of dielectric surfaces on the propagation dynamics of plasma discharges at atmospheric pressure. First we have improved the computational efficiency of the discharge code used in this work in implementing parallelization techniques and more efficient numerical schemes. Second we have studied the dynamics of an air discharge at atmospheric pressure in a point-to-plane geometry with a dielectric layer on the cathode plane. Then, we have studied the influence of a dielectric layer obstacle in the inter-electrode gap. We have shown that depending on the characteristics of the dielectric layer and the amplitude and polarity of the applied voltage, a second discharge may reignite or not below the dielectric in the second air gap. The comparison of simulation results with experiments has shown that in a point-to-plane geometry with a sharp point and a high over-voltage, a single conical discharge structure is observed. A good agreement on the discharge diameter and propagation velocity has been obtained. With a dielectric obstacle in the gap, the simulated reignition dynamics is faster than in the experiments. To improve the agreement, we have studied the influence of several physico-chemical processes. Finally, we have studied the dynamics of discharges in dielectric tubes at atmospheric pressure. For a He -N2 mixture, we have put forward the importance of three body reactions. Last, the influence of the tube radius on the structure of discharges in He - N2 and air is discussed.

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15

Nemschokmichal, Sebastian [Verfasser]. "Temporal and spatial characterisation of nitrogen metastables in atmospheric pressure barrier discharges / Sebastian Nemschokmichal". Greifswald : Universitätsbibliothek Greifswald, 2013. http://d-nb.info/1045036803/34.

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16

Pencheva, Mariana. "Modelling of atmospheric pressure argon plasmas: application to capacitive RF and surface microwave discharges". Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209451.

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This work is focused on modelling of atmospheric pressure high frequency (HF) discharges operated at relatively low power densities. Two types of devices are considered – the radio frequency capacitively coupled atmospheric pressure plasma jet and the microwave discharge sustained by surface electromagnetic waves. They are addresses as the plasma shower and the surface-wave discharge (SWD). Both of the considered devices operate in argon at atmospheric pressure (p = 1 bar). However, the difference in the frequency of the power coupling mechanism induces a big difference in plasma properties. This implies also that different modelling approaches have to be employed.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

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17

Tholin, Fabien. "Numerical simulation of nanosecond repetitively pulsed discharges in air at atmospheric pressure : Application to plasma-assisted combustion". Phd thesis, Ecole Centrale Paris, 2012. http://tel.archives-ouvertes.fr/tel-00879856.

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In this Ph.D. thesis, we have carried out numerical simulations to study nanosecond repetitively pulsed discharges (NRPD) in a point-to-point geometry at atmospheric pressure in air and in H2-air mixtures. Experimentally, three discharge regimes have been observed for NRPD in air at atmospheric pressure for the temperature range Tg = 300 to 1000 K: corona, glow and spark. To study these regimes, first, we have considered a discharge occurring during one of the nanosecond voltage pulses. We have shown that a key parameter for the transition between the discharge regimes is the ratio between the connection-time of positive and negative discharges initiated at point electrodes and the pulse duration. In a second step, we have studied the dynamics of charged species during the interpulse at Tg = 300 and 1000 K and we have shown that the discharge characteristics during a given voltage pulse remain rather close whatever the preionization level (in the range 109-1011 cm��3) left by previous discharges. Then, we have simulated several consecutive nanosecond voltage pulses at Tg = 1000 K at a repetition frequency of 10 kHz. We have shown that in a few voltage pulses, the discharge reaches a stable quasi-periodic glow regime observed in the experiments. We have studied the nanosecond spark discharge regime. We have shown that the fraction of the discharge energy going to fast heating is in the range 20%- 30%. Due to this fast heating, we have observed the propagation of a cylindrical shockwave followed by the formation of a hot channel in the path of the discharge that expands radially on short timescales (t < 1 _s), as observed in experiments. Then we have taken into account an external circuit model to limit the current and then, we have simulated several consecutive pulses to study the transition from multipulse nanosecond glow to spark discharges. Finally the results of this Ph.D. have been used to find conditions to obtain a stable glow regime in air at 300 K and atmospheric pressure. Second we have studied on short time-scales (t_ 100_s) the ignition by a nanosecond spark discharge of a lean H2-air mixture at 1000 K and atmospheric pressure with an equivalence ratio of _ = 0:3. We have compared the relative importance for ignition of the fast-heating of the discharge and of the production of atomic oxygen. We have shown that the ignition with atomic oxygen seems to be slightly more efficient and has a completely different dynamics.

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18

Farouk, Tanvir Iqbal Farouk Bakhtier Friedman Alexander. "Modeling and simulations of DC and RF atmospheric pressure non-thermal micro plasma discharges : analysis and applications /". Philadelphia, Pa. : Drexel University, 2009. http://hdl.handle.net/1860/3002.

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19

Halethimmanahally, Thejaswini C. [Verfasser]. "Atmospheric-Pressure Dielectric Barrier Discharges: Synthesis and Deposition of Organic plasma polymers and their characterizations / Thejaswini C. Halethimmanahally". Greifswald : Universitätsbibliothek Greifswald, 2012. http://d-nb.info/1028455658/34.

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20

Ito, Yosuke. "Studies on Microplasmas in Coaxial Dielectric Barrier Discharges and Their Application to Thin Film Deposition at Atmospheric Pressure". 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120872.

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21

Schmidt, Jacob Brian. "Ultrashort Two-Photon-Absorption Laser-Induced Fluorescence in Nanosecond-Duration, Repetitively Pulsed Discharges". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437694779.

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22

Tyl, Clémence. "Study of the memory effect in atmospheric pressure townsend discharges in nitrogen with addition of oxidizing gas : temporally and spatially resolved electrical and optical characterizations". Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30296.

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Les procédés plasma utilisant des décharges à barrières diélectriques (DBD) à pression atmosphérique sont une bonne alternative aux plasmas froids à basse pression pour de nombreuses applications comme le traitement de surface, le dépôt de couches minces, la stérilisation etc. En effet, ils permettent de s'affranchir des systèmes de pompage et donc de réaliser des traitements sur de grandes surfaces directement implantables sur des lignes de production. Cependant, les DBD sont généralement filamentaires, ce qui conduit à des dépôts non homogènes. Dans certaines conditions expérimentales (géométrie, nature du gaz, excitation etc.), on peut néanmoins obtenir une décharge homogène conduisant à un traitement homogène des surfaces. Néanmoins, les caractéristiques des DBD homogènes ne sont pas identiques en tout point de l'espace, notamment en raison du flux de gaz, mais aussi dans le cas de matériaux diélectriques avec un gradient de propriétés ou dans le cas de décharges auto-organisées. Afin de mieux caractériser la distribution spatiale de la décharge, un outil de mesure de densités locales de courant a été développé au cours de cette thèse. En effet, les mesures électriques sont un bon outil de caractérisation de la décharge donnant accès à de nombreux paramètres (courant de décharge, tension gaz, puissance dissipée etc.). Néanmoins, le courant mesuré est intégré sur toute la surface des électrodes. Pour pouvoir mesurer les courants localement, l'électrode de masse de la cellule de décharge de dimension 3×3 cm2 a été divisée en 64 segments, et un système d'acquisition a été développé afin de pouvoir acquérir les 64 courants mesurés simultanément avec une fréquence d'échantillonnage suffisante pour le traitement des données. Ce nouvel outil de diagnostics électriques peut être corrélé temporellement et spatialement à des mesures optiques par caméra intensifiée iCCD couplée à différents filtres optiques, donnant des informations sur les densités de certaines espèces dans le plasma. L'objectif de cette thèse est de mieux comprendre la dissipation de puissance locale et de caractériser plus finement les espèces mises en jeu et les différents régimes de décharge, notamment l'obtention d'un régime homogène. Les DBD homogènes sont initiées par un claquage de type Townsend. Pour cela, une source de production d'électrons est nécessaire entre deux décharges, quand le champ électrique est inférieur au champ de claquage. Ce claquage est lié à un effet mémoire d'une décharge à l'autre, visible sur les mesures électriques, avec un saut du courant de décharge. Les hypothèses sur l'origine de cet effet mémoire peuvent être séparées en deux catégories.[...]
Plasma processes at atmospheric pressure using Dielectric Barrier Discharges (DBD) are a good alternative to low pressure non-thermal plasma processes for various applications such as surface treatment, thin-film coating, sterilization etc. Indeed, they can be operated without complex vacuum facilities and allow the treatment of large surfaces that can be implemented directly into assembly lines. However, DBDs are usually filamentary, leading to non-homogeneous depositions on the treated surfaces. In certain condition depending on the experimental parameters (geometry, gas nature, power supply, etc.), a homogeneous discharge can be obtained leading to a uniform surface treatment. Nevertheless, even in the homogeneous mode, the DBDs properties are not necessarily the same at any point on the discharge surface, because of the gas flow circulation in particular, but also in case of materials with a properties gradient, or in case of self-organization phenomena. In order to better characterize the spatial distribution of the discharge, a new local electrical diagnostic tool to measure the local current densities has been developed during this thesis. Indeed, electrical measurements are widely used to characterize the DBDs as they give access to various parameters such as the gas voltage, discharge current, dissipated power etc. However, the measured current is integrated on all the surface of the electrodes. To be able to measure the local currents, the 3×3 cm2 ground electrode from the discharge cell has been divided into 64 segments, and a data acquisition system has been developed in order to simultaneously acquire the 64 measured currents with a high enough sampling rate for the data processing. This new electrical diagnostic tool can be correlated in time and space with optical measurements with an intensified iCCD camera, coupled with optical filters, to obtain information on the densities of some species in the plasma. The aim of this thesis is to better understand to local power dissipation, and to refine the characterization of the involved species in the different discharge regimes, especially to obtain a homogeneous regime. Homogeneous DBDs are ignited by a Townsend breakdown. For a Townsend breakdown to occur, a production source of seed electrons is necessary between two discharges, when the electric field is lower than the breakdown voltage. This breakdown is related to a memory effect from one discharge to the following one, that is visible on the electrical measurements with a discharge current jump. The hypotheses on the memory effect origin can be separated into two categories.[...]

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23

Ueno, Keisuke. "A study of microho1low cathode discharge plasmas by laser absorption spectroscopy of excited helium atoms". Kyoto University, 2019. http://hdl.handle.net/2433/242494.

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Silva, Valeria Cristiane. "Sensor para medição do campo eletrico". [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259374.

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Orientador: Jose Pissolato Filho
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Este trabalho apresenta a elaboração e a construção de um sensor utilizado na detecçãode intensidade de campo elétrico e consequentemente de descargas atmosféricas. O sensor de diâmetro igual a 10 cm é constituído por uma placa girante composta por quatro aletas, que tem seu movimento de rotação controlado por um mini motor de 12000 rpm, e uma placa fixa, denominada placa de medição, composta por oito aletas que são responsáveis por produzir uma tensão alternada referente ao campo elétrico ao qual o sensor está submetido. Quando o rotor (placa girante) gira sobre o estator (placa de medição), ele expõe a placa de medição ao campo elétrico e isola-o deste campo quando está sobre ele. Dessa forma corta-se o campo elétrico normal estático ou que varia muito lentamente. O medidor de campo elétrico (EFM - do inglês Eletric Field Mill ) cria um campo "variável" que irá induzir uma carga elétrica no estator. A magnitude e polaridade da carga são dependentes da magnitude e polaridade do campo elétrico. A placa de medição gera um sinal da ordem de milivolts, sendo necessário a utilização de amplificadores para torná-lo significante para análise. O sinal amplificado será então digitalizado e enviado à um software para visualização dos dados gerados pelo sensor. Neste trabalho apresenta-se também um estudo sobre origem de cargas nas nuvens, formação de tempestade, assim como formação e classificação dos raios.
Abstract: This paper presents the development and construction of a sensor used to detect intensity of electric field and consequently of lightning. The sensor diameter of 10 cm consists of a plate consisting of four revolving vanes that has its rotation controlled by a small motor to 12000 rpm and a fixed plate, called a measuring board, composed of eight vanes that are responsible for produce a alternating voltage electric field concerning which the sensor is subjected. When the rotor (revolving vanes) turns on the stator (plate measurement), it exposes the plate for measuring the electric field alone, and the field when this is over it. Thus is cut to the normal static electric field or which varies very slowly. The electric field meter (EFM - the English Electric Field Mill) creates a field "variable" that will induce an electric charge in the stator. The magnitude and polarity of the load are dependent on the magnitude and polarity of the electric field. The measurement plate generates a measurement signal of the order of millivolts, requiring the use of amplifiers to make it significant for analysis. The amplified signal is then digitized and sent to a software for visualization of data generated by the sensor. In this work it is also a study of origin of cargoes in the clouds, formation of storm as well as training and classification of rays.
Mestrado
Energia Eletrica
Mestre em Engenharia Elétrica

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25

Zocher, Maria Katja Verfasser], Michael [Akademischer Betreuer] Lalk, Jürgen F. [Akademischer Betreuer] Kolb, Michael [Gutachter] Lalk, Jürgen F. [Gutachter] Kolb y Timo H. J. [Gutachter] [Niedermeyer. "Extraction of bioactive primary and secondary Metabolites from Microalgae by atmospheric pressure Plasmas and pulsed Discharges in Water / Maria Katja Zocher ; Gutachter: Michael Lalk, Jürgen F. Kolb, Timo Niedermeyer ; Michael Lalk, Jürgen F. Kolb". Greifswald : Universität Greifswald, 2019. http://d-nb.info/1202111319/34.

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26

Zocher, Maria Katja [Verfasser], Michael Akademischer Betreuer] Lalk, Jürgen F. [Akademischer Betreuer] Kolb, Michael [Gutachter] Lalk, Jürgen F. [Gutachter] Kolb y Timo H. J. [Gutachter] [Niedermeyer. "Extraction of bioactive primary and secondary Metabolites from Microalgae by atmospheric pressure Plasmas and pulsed Discharges in Water / Maria Katja Zocher ; Gutachter: Michael Lalk, Jürgen F. Kolb, Timo Niedermeyer ; Michael Lalk, Jürgen F. Kolb". Greifswald : Universität Greifswald, 2019. http://d-nb.info/1202111319/34.

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Zocher, Maria Katja [Verfasser], Michael [Akademischer Betreuer] Lalk, Jürgen F. Akademischer Betreuer] Kolb, Michael [Gutachter] Lalk, Jürgen F. [Gutachter] Kolb y Timo H. J. [Gutachter] [Niedermeyer. "Extraction of bioactive primary and secondary Metabolites from Microalgae by atmospheric pressure Plasmas and pulsed Discharges in Water / Maria Katja Zocher ; Gutachter: Michael Lalk, Jürgen F. Kolb, Timo Niedermeyer ; Michael Lalk, Jürgen F. Kolb". Greifswald : Universität Greifswald, 2019. http://nbn-resolving.de/urn:nbn:de:gbv:9-opus-34358.

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Terra, Victor Scartezini. "Avaliação de mecanismos não convencionais de instabilização de encostas: o papel das poropressões de ar". Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/6797.

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Natural disasters related to landslides have caused thousands of deaths and left tens of thousands homeless people around the world. Landslides can occur in most cases due to factors related to water infiltration on soil, causing a raise in the positive pore-water pressure. But what is often observed is that both water infiltration and the reduction of negative pore-water pressure due to water infiltration are not, in practice, enough to justify some of the observed landslides. Some less conventionals mechanisms, such as lightning, are not, usually, taken in consideration in a failure analysis, but can contribute to the factor of safety reduction. This paper aims to study the effects of atmospheric discharges in the stability of natural slopes of residual soils. Partial differential equations governing the coupled flow of pore-water and pore-air are developped. The numerical modeling is made with the FlexPDE software, version 6. The results show that there is a raise on pore-air pressure inside the soil due to atmospheric discharge. However, the raise of pore-air pressure works both in the raise of the apparent cohesion and the reduction on net pressure. It is concluded that any failure due to atmospheric discharge will present a shallow slip surface.
Desastres naturais relacionados a deslizamentos de massas de terra já causaram milhares de mortes e dezenas de milhares de desabrigados no mundo inteiro. Os deslizamentos podem ocorrer em sua maioria devido aos fatores provenientes da infiltração de água no solo, gerando aumento das poropressões positivas de água. Mas o que se observa frequentemente, é que a infiltração e a redução das poropressões negativas muitas vezes não são, na prática, o suficiente para justificar todos os escorregamentos observados. Mecanismos menos convencionais como descargas atmosféricas e o aumento das poropressões de ar consequentes do efeito Lisse normalmente não são levados em consideração em análises de ruptura, mas podem contribuir para a diminuição do fator de segurança de taludes. Esta pesquisa tem como objetivos, portanto, estudar como os efeitos do avanço da frente de infiltração e das descargas atmosféricas irão afetar a estabilidade de taludes em encostas naturais de solos residuais. Além disso, cita-se como objetivos secundários o desenvolvimento de modelos numéricos para análises acopladas de fluxo de água e ar, e a verificação desses modelos por meio de análises de validação. Um estudo detalhado de como a onda de choque e os gradientes de temperatura de descargas atmosféricas se comportam ao atingir a superfície terrestre é desenvolvido para que se possam definir as condições de fronteira do problema. Equações diferenciais parciais acopladas para fluxo de água e ar são desenvolvidas. As análises são feitas com o auxílio do programa FlexPDE, versão 6. Os resultados mostraram que há um aumento das poropressões de ar na massa de solo provenientes de descargas atmosféricas ou do efeito Lisse. No entanto, tais acréscimos de poropressão de ar trabalham tanto a favor do ganho de coesão aparente como como na diminuição das tensões líquidas. No estudo da influência do aumento das poropressões de ar como consequência de descargas atmosféricas conclui-se que eventuais rupturas de taludes causadas por isso serão rasas. Com relação ao estudo do aumento de poropressão de ar em taludes como consequência do efeito Lisse, conclui-se que os acréscimos de poropressão de ar serão maiores na massa de solo quando mais próximo da saturação estiver o solo.

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29

Cockenpot, Sabine. "Caractérisation des processus aux interfaces air-eau et sédiment-eau pour la quantification des apports d’eaux souterraines par le radium et le radon". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4331/document.

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Les apports d’eaux souterraines (Submarine Groundwater Discharge : SGD) peuvent constituer des apports considérables d'eau et de nutriments ou de contaminants en zone côtière. Le suivi des radio-éléments (radon, radium) dans ces zones permet de tracer les apports de SGD et leurs bilans de masse permettent de quantifier leurs flux. Cette méthode est utilisée depuis des années, mais les termes des bilans aux interfaces restent difficiles à appréhender. L'objectif de cette thèse est d'apporter des précisions sur ces termes afin de permettre une meilleure quantification des flux de SGD. Pour l'interface air-eau, les flux de dégazage du radon vers l'atmosphère ont été estimés pour différentes conditions de vent sur l’étang de Berre. Un dégazage permanent, même sans vent, a été mis en évidence. Pour l'interface sédiment-eau, nous décrivons une méthode de calcul et d’évaluation du flux diffusif du radon et proposons une nouvelle approche pour estimer celui du radium. Dans la lagune de Mar Menor, les flux de SGD estimés sont 5 à 200 fois plus élevés que les apports d'eau par les rivières et sont majoritairement causés par de la recirculation d’eau à travers les sédiments. Pour la première fois les suivis de radio-éléments ont été combinés à un modèle hydrodynamique, ce qui a permis de localiser précisément les SGD. L'étude du système karstique de la source de la calanque de Port-Miou a mis en évidence un système bicouche de la colonne d'eau. La combinaison des bilans en radio-éléments, d'eau et de sel nous a permis d'estimer un débit de la source très proche de celui mesuré par différence de pression, attestant ainsi de la fiabilité de cette méthode pour les systèmes karstiques
Submarine Groundwater Discharges (SGD) may represent important inputs of water, nutrients as well as contaminants to the coastal zone. Monitoring radionuclides (radon, radium) in those areas allows to trace SGD inputs while their fluxes may be quantified through their mass balances. This method has been used for many years, even though the terms from the mass balance at these interfaces remain difficult to manage. The objective of this thesis is to develop methods to better describe and evaluate these terms, in order to get a better quantification of SGD fluxes. For the air-water interface, the radon atmospheric fluxes have been estimated for different wind conditions on the Berre lagoon. A permanent flux, even without wind, has been highlighted. For the sediment-water interface, new methods are proposed here in order to calculate and evaluate the radon diffusive flux, as well as a new approach for estimating the radium diffusive flux. In the Mar Menor, the estimated SGD fluxes are 5 to 200 times higher than water river inputs and are predominantly caused by lagoon water recirculation through sediments forced by tidal pumping. For the first time, the monitoring of radionuclides in this lagoon was combined to a hydrodynamic model, allowing to locate precisely the SGD inputs. The study of the karstic spring of the Port-Miou calanque shows a two-layer system in the water column. The combination of radionuclides, water and salt mass balances leads to calculate a spring flux similar to the one measured by pressure gradient, which confirms the reliability of this method for karstic systems

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30

Li, Ya. "Contribution à l'étude de l'influence des décharges de couronne sur la perte de volume d'une aspérité de glace portée à un potentiel élevé /". Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1993. http://theses.uqac.ca.

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Thomazella, Rogério [UNESP]. "Implementação computacional para avaliar os níveis de sobretensões atmosféricas induzidas em linhas de distribuição". Universidade Estadual Paulista (UNESP), 2004. http://hdl.handle.net/11449/90810.

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O presente trabalho visa o desenvolvimento de uma ferramenta computacional confiável na análise e estimação dos níveis de tensões induzidas em linhas de distribuição. Neste contexto, utilizam-se ferramentas computacionais consolidadas, como o ATP (Alternative Transients Program), que combinado a um software desenvolvido em Visual Basic, permitem quantificar e avaliar o nível de sobretensões nas linhas de distribuição. Por meio de modificações nas técnicas clássicas de modelagem das descargas atmosféricas, foi possível a construção de um software em Visual Basic capaz de quantificar os valores das tensões induzidas em linhas de distribuição finitas. A avaliação dos níveis de sobretensões induzidas nas mesmas foi implementada pela associação deste software a um programa de simulação (ATP), a fim de se obter resultados fidedignos deste transitório. Tais resultados foram utilizados para se avaliar o desempenho das...
The present work aims at the development of a trustworthy computacional tool in the analysis and estimate of the levels of induced overvoltage in distribution network. In this context, consolidated computacional tools are used, as ATP (Alternative Transients Program), that combined with a software developed in Visual Basic (beginner's all-purpose symbolic instruction code), they allow to quantify and to evaluate the level of overvoltage in the distribution network. By the means of modifications in the classic techniques of modeling of the atmospheric discharges, the construction of a software in Visual Basic was possible to quantify the values of the induced overvoltage in a finite... (Complete abstract click electronic access below)

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32

Richard, Frédéric. "Etude et caracterisation d'une decharge electrique glissante dans l'air a pression atmospherique". Orléans, 1995. http://www.theses.fr/1995ORLE2061.

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Les arcs glissants qui se deplacent dans un ecoulement de gaz entre deux electrodes profilees en forme de tuyere permettent d'obtenir a la pression atmospherique et aux pressions plus elevees des plasmas hors equilibre caracterises a la fois par de fortes densites electroniques (superieures a 10#1#4 cm#-#3) et des champs electriques eleves de l'ordre de 10#4 v/m. Ces dispositifs sont interessants et prometteurs pour de nombreuses applications industrielles dans le domaine de la plasma chimie (destruction des composes organiques volatils (cov), desulfuration des gaz et reduction de h#2s, valorisation du methane, transformation du protoxyde d'azote n#2o en no#x). Ce travail porte sur l'etude d'une telle decharge alimentee a partir d'une source electrique continue, dans l'air a pression atmospherique. Plusieurs methodes de diagnostics ont ete utilisees (photographie rapide avec une camera dtc intensifiee, capteurs optoelectroniques, mesures electriques, spectrometrie moleculaire). Les resultats obtenus ont montre que le comportement de ces decharges peut etre decrit a l'aide de modeles relativement simples et ont permis de mettre en evidence les differents parametres importants qui caracterisent le fonctionnement du dispositif (debit de gaz, tension, intensite du courant, distance minimale des electrodes). L'arc glissant peut etre decrit comme un fin cordon de plasma (diametre 1 mm) a haute temperature (6000 k), entoure d'une gaine plasmagene a plus basse temperature (3000 k) hors equilibre et contenant de nombreuses especes moleculaires excitees. Celui-ci se deplace et s'allonge sous l'effet des forces d'entrainement exercees par le flux de gaz. Une difference de vitesse importante entre le gaz et l'arc glissant produit un refroidissement efficace et deplace le regime de fonctionnement depuis le regime d'arc vers un regime de decharge luminescente. La tension aux bornes de l'arc augmente proportionnellement a son allongement et la tension maximale atteinte, correspond a la tension de claquage au col des electrodes (tension de paschen) qui provoque l'amorcage d'un nouvel arc. Cette etude constitue un progres significatif dans la connaissance des phenomenes physiques associes a l'arc glissant. Cependant, le dernier chapitre de ce travail qui est consacre a l'etude de la formation de no#x dans l'arc, revele l'ampleur du travail restant a accomplir pour maitriser parfaitement les phenomenes physico-chimiques intervenant dans ce type de decharge

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33

Urabe, Keiichiro. "Spectroscopic Study of Dielectric Barrier Discharge at Atmospheric Pressure". 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157532.

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Cao, Zhi. "Large-scale spatially extended atmospheric pressure plasma". Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6688.

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This thesis presents experimental studies of low-temperature atmospheric pressure plasma sources with generic ability to effectively treat large-scale three-dimensional (3D) objects. The reported large-scale plasma sources are developed through parallelisation of single plasma jets. This strategy outshines the other reported strategies for treatment of uneven surfaces by being able to produce spatially extended plasma directly onto the surface of heavily three-dimensional objects. Comparable studies of the design of elemental plasma jets bring out a hybrid electrode configuration, the capillary-ring jet, as the best elemental jet to be used in the parallelisation. It is found that the introduction of a ballast resistor to the individual jet circuit or built-in capacitance is important to assure the jet-to-jet synchronism, stability and uniformity. Electrical and optical analyses of one-dimensional (1D) array of atmospheric pressure plasma jets demonstrate robust temporal and spatial jet-to-jet uniformity both for flat and sloped surfaces. Hexagonally-arranged two-dimensional (2D) arrays of atmospheric pressure plasma jets show good level of insusceptibility to variations of the downstream samples in their physical dimensions as well as structural and material properties. The reaction chemistry impact area of a 2D 37-jet array is estimated to be 18.6 cm2. These confirm the plasma jet arrays as a viable option as large-scale atmospheric plasma sources, well suited for many processing applications including plasma medicine. The spatially separated dual-frequency excitation further benefits the plasma jet in that separate control of different important plasma parameters is possible. Enhanced plasma properties achieved by the dual-frequency offer greater potential to the jet arrays.

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Zepka, Gisele dos Santos. "Estudo para o desenvolvimento de um previsor descargas elétricas atmosféricas aplicado à região costeira do estado do Rio de Janeiro". reponame:Repositório Institucional da FURG, 2005. http://repositorio.furg.br/handle/1/3445.

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Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia Oceânica, Escola de Engenharia, 2005.
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The atmospheric dynamics evidently is very complex. There are many macro and micron scales processes and meteorological variables involved in the atmospheric physical phenomena. The storms with electrical dischargesare distinguished, among these phenomena, by the damage consequences to the human beings, directly or indirectly. Many researchers have pursued the possibility of forecasting the occurrence of a storm with electrical discharges, principally in the last three decades. However, there are not improvements in forecast performance, mainly due to phenomenon complexity. The main objective of the present dissertation was to accomplish a study to determine the viability or not of constructing a forecast system of atmospheric electrical discharges from artificial intelligence techniques, specifically artificial neural networks (NN). The base of the system was constituted of numerical simulations results of the atmospheric dynamics obtained from the mesoscale model MM5. It was identified meteorological variables (outputs of MM5) that would have some correlation with the electrical discharges. These variables act as input in the NN, which generate the forecast, consisting in the number of electrical discharges that will reach the ground some posterior time to the relative time of the simulated atmospheric fields. The region chosen for this study includes the state of Rio de Janeiro, the south of Espírito Santo, the southeast of Minas Gerais and the AtlanticOcean. Besides possessing a detection system of electrical discharges, this region contains the most important concentration of oil platforms of Brazil, being strategic to better know the atmospheric behavior in this place. Before developing the forecast system based on NN, some comparative tests were made using the MM5 simulation results and GOES infrared imagery, in order to survey the model prognostic capability. The forecast system showed reasonable results, indicating that the NN application may be a promising way to the electrical discharge forecast. However, it is necessary a better investigation, mainly with relation to the accomplishment of others tests with a bigger set of electrical discharges real data.
A dinâmica da atmosfera é evidentemente bastante complexa. Muitos são os processos físicos de macro e micro escalas e as variáveis meteorológicas envolvidos nos fenômenos atmosféricos. As tempestades com descargas elétricas destacam-se, dentre estes fenômenos, pelas conseqüências danosas causadas aos seres humanos, direta ou indiretamente. Diversos pesquisadores têm procurado investigar a possibilidade de prever a ocorrência de tempestades com descargas elétricas, principalmente nas úl timas três décadas, entretanto, progressos na performance da previsão ainda não foram alcançados devido à complexidade do fenômeno. O principal objetivo da presente dissertação foi realizar um estudo para determinar a viabilidade ou não de construir um sistema de previsão de descargas elétricas atmosféricas a partir de técnicas de inteligência artificial, mais precisamente redes neurais artificiais (RNA). A base do sistema constituiu-se de resultados de simulações numéricas da dinâmica atmosférica obtidos com o modelo de mesoescala MM5. Variáveis meteorológicas (saídas do MM5), que teriam alguma correlação com as descargas elétricas, foram identificadas e selecionadas como entradas na RNA, a qual gera a previsão, isto é, o número de descargas elétricas que atingirá o solo algum tempo posterior ao tempo relativo dos campos atmosféricos simulados. A região escolhida para este estudo, abrangendo o Estado do Rio de Janeiro, o sul do Estado do Espírito Santo, o sudeste do Estado de Minas Gerais e o Oceano Atlântico, além de possuir um sistema de detecção e monitoramento de descargas elétricas, contém a mais importante concentração de plataformas de petróleo do Brasil, sendo, portanto, estratégico conhecer melhor o seu comportamento atmosférico. Antes de desenvolver o sistema de previsão baseado em RNA, alguns testes comparativ os foram realizados usando resultados de simulação do MM5 e imagens infravermelhas de satélite geoestacionário, a fim de aferir a capacidade preditiva do modelo. O sistema de previsão apresentou resultados razoáveis, indicando que a aplicação da RNA é um cami nho promissor na previsão de descargas elétricas. Contudo, faz-se necessária uma mel hor investigação, principalmente quanto à realização de outros testes com um conjunto maior de dados reais de descargas elétricas.

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36

Buruiană, Marian-Daniel. "Atmospheric precipitations, water discharge and inundations in the Moldavian plain". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0251/document.

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À cause du caractère torrentiel de la plupart des rivières de la Plaine de la Moldavie, on a encore des difficultés pour gérer le risque associé à l'écoulement maximal, spécialement sur les affluents des cours d'eau principaux. Constamment, il y a des risques associés à l'écoulement maximal et aux ruissellements sur les pentes, même si le bassin de Jijia, le principal cours d'eau qui traverse la Plaine de la Moldavie, a de nombreuses accumulations réalisées entre les années 60 et 90 et même s’il est un des plus aménagés rivières, avec dizaines de kilomètres de digues et régularisations. L’intention de réaliser une thèse de doctorat ayant le titre « Les aléas associées aux précipitations et les inondations dans la Plaine de la Moldavie » est apparue comme une nécessité d’identifier les risques naturels et d’évaluer les actions anthropiques de la perspective risque – bénéfice, afin de gérer de manière efficiente les ressources naturelles ou d’élaborer des projets de développement durable. Même si les crues sont des phénomènes normaux, répétables, qui font partie du processus d’écoulement dans le lit d’une rivière, les inondations représentent, à notre époque, l’une des causes principales des pertes matérielles et humaines. La Plaine de la Moldavie se situe au nord-est du Plateau de la Moldavie, entre le couloir de Prut et les plateaux de Suceava et Bârlad. Enregistrant une altitude moyenne de 125 m et une altitude maximale de 265 m dans la Colline Cozancea, la Plaine de la Moldavie a été, le long du temps, très bien étudiée par des géographes réputés. Le sens de plaine est lié à l’usage agricole, à l’altitude, aux tchernosiomes, à la végétation de forêt et de steppe, au régime d’écoulement des eaux, etc. Afin de réaliser une analyse réelle et exacte de la distribution spatiale des quantités de précipitations, on a utilisé les données issues des observations pluviométriques pendant la période 1960 – 2011 dans 32 stations météorologiques ou postes pluviométriques (9 stations météorologiques et 23 postes pluviométriques), localisées à l’intérieur de la Plaine de la Moldavie, mais aussi dans son immédiate proximité. En ce qui concerne la vulnérabilité de la Plaine de la Moldavie face à l’intensité des pluies d’été, on observe que la moitié nord de la plaine présente une vulnérabilité intermédiaire, et que la moitié sud est fortement vulnérable. Dans la Plaine de la Moldavie, le degré de vulnérabilité donné par l’intensité des pluies d’été monte sur la direction générale ONO – SSE. Les pluies torrentielles ont une grande contribution pluviométrique qui, cumulée au niveau d’un mois, nous a donné la possibilité d’enregistrer entre 172,1 mm en juillet 1991 à Botosani et 277,2 mm en juin 1985 à Iasi. L’intervalle mai – septembre reste avec les plus fortes probabilités que des pluies torrentielles déversant grandes, voire, parfois, exceptionnelles quantités de précipitations tombent. L’analyse statistique de l’écoulement maximal dans la Plaine de la Moldavie a été réalisée à base des données enregistrées dans la période 1950-2011, aux principales stations hydrométriques. La variabilité multi annuelle des débits maximaux met en évidence le fait que, au niveau des bassins hydrographiques de la zone analysée, on a enregistré des années dans lesquelles se sont produits les débits maximaux les plus élevés (1954, 1969, 1975, 1980, 2008, 2010) et, aussi des années quand les valeurs des débits maximaux ont été un peu plus basses (1959, 1963, 1964, 1986). Entre 1960 et 2011, les crues les plus significatives enregistrées dans la Plaine de la Moldavie se sont produites, généralement, pendant l’été, dans les mois de juin et juillet. Après une analyse spatiale basée sur les SIG, plus précisément, d’intersection entre les bandes d’inondabilité (à différentes probabilités de dépassement) et les contours des localités situées dans la Plaine de la Moldavie, on peut identifier les localités potentiellement affectables par les crues
One of the major challenges of this century is represented by climatic changes and their influence upon the environment. In the case of Romania, the orographic barrier plays the most important role in the delineation of surplus or deficient areas as refered to humidity. In the western and central regions of Romania, with oceanic influences, there is an surplus of humidity, while in the southern, south-eastern and eastern regions, with continental influences, there is a deficient humidity that generates dryness phenomena and drought. Non-the-less, we notice, in the last years, contrast situations with particularities in those regions affected by dryness and drought where there is an surplus of humidity. Climatic change at global or local level represent a major problem and induce concern among researchers from various disciplines (meteorology, climatology, geomorphology, ecology, hydrology, biology, medicine, sociology etc.) in consideration of change that might produce major setbacks in all the life domains and the socio-economic activities. In this respect, knowledge, research and investigation at detailed level of local and regional meteorological conditions that induce triggering situations for atmospheric hazards generating risks, human and economic losses, sometimes hard to estimate, develop in significant and full of concern attitudes in contemporary times. In the Moldavian Plain, due to the torrential character of most of the rivers, maximum discharge risk management is still difficult for the tributary/secondary streams. Even if the Jijia watershed, with the main stream of the Moldavian Plain, dispalys numerous water storages since 1960 to 1990, being one of the most systematized hydrographic basins, with tens of kilometers of dams and enbankments, the risks of maximum channel discharge and hillside discharge is still present. The intention of realizing a doctoral study on the Atmospheric precipitations, water discharge and inundations in the Moldavian Plain comes as a result of concerns in this respect and need to identify the natural risks and to evaluate the human activities as a perspective of risk – benefit for the efficient management of natural resources or in the attempt to favour sustainable development. Although floods are natural phenomena, with time repetability, as discharge processes along riverbeds, inundations represent, in modern times, one of the main causes of human and material losses. The analyses of the obtained maps regarding annual precipitations quantities in the Moldavian Plain reveal the decreasing trend from west to east, along with the decrease in overall altitudes and lower frequencies of humid air masses to the east (drier air masses), compared to more humid, Atlantic, air masses to the west. Torrential rains are atmospheric phenomena with short duration influence but with great intensity, upon the environment via erosion and flooding. They consist in increased precipitation quantities on short time intervals, sudden change of intensity along with extension of duration. As far as the vulnerability of the Moldavian Plain to the suumer rains we notice that the northern half displays an intermediate vulnerability while the southern half diplays a higher vulnerability. We also notice that for the whole space east, south-east and south of the Carpathians is vulnerable to an apreciable extent to torrential rains with intermediate and high intensities. In figure 5.32 we also observe that in those areas where oceanic influences predominate, rains have a less violent character and in those areas where continental influence pedominate (as the case of the Moldavian Plain) torrentail rains have a more violent character. In the Moldavian Plain the degree of vulnerability of torrential summer rains increases from WNW to SSE. Torrential rains bring a great pluviometric input that can reach a monthly quantity of 172.1 mm in July at Botosani and 277.2 mm in June 1985 at Iasi

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37

Zhang, Yiyun S. M. Massachusetts Institute of Technology Department of Aeronautics and Astronautics. "Pulsed nanosecond dielectric barrier discharge in nitrogen at atmospheric pressure". Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127118.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 85-87).
Small power devices are of strong interest as many electronics are made more compact. Those portable power sources are widely used in aerospace applications such as small UAVs and satellite thrusters. Typically, these portable devices rely on batteries, but small power generators based on hydrocarbon fuel micro-combustors have much higher energy densities. However, flame instability and extinction are difficult to avoid at small scales. Because of the high surface to volume ratio, significant heat loss and radical quenching at the walls take place. To address this challenge, plasma has shown capabilities in facilitating combustion through thermal, kinetic and transport effects. In this work, a preliminary study of plasma discharge at atmospheric pressure is conducted as the first step to understand Plasma-Assisted Combustion (PAC) at micro scales.
Among various electric discharge mechanisms, Dielectric Barrier Discharge (DBD) is chosen due to its ability to generate non-thermal plasma at atmospheric pressure with a simple geometry and a low power consumption. Repetitive Pulsed Nanosecond Discharge (RPND) technique is also studied. It provides repetitive high voltage pulses on the order of 10 - 20 nanoseconds and is a common technique in non-equilibrium plasma generation. A 1D DBD model is constructed for a volume discharge. It couples particle continuity equations with Poisson's equation, and solves for electric field and charged particle number densities. The numerical model is discretized in space and time to obtain charged particles evolution and electric properties. The model is firstly validated with open literature for both AC and RPND, and is then applied to our DBD setup at atmospheric pressure. In addition, a nitrogen (and air) discharge experiment is designed and operated with RPND.
Preliminary results show the capability to generate sustainable and uniform plasma at atmospheric pressure. The appearance is that of a uniform glow plasma free of micro-discharges. Several experimental findings help to understand the discharge physics and set a foundation for future applications in micro-scale combustion.
by Yiyun Zhang.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics

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38

Voloshko, Andrey. "Nanoparticle formation by means of spark discharge at atmospheric pressure". Thesis, Saint-Etienne, 2015. http://www.theses.fr/2015STET4011/document.

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Au cours de la dernière décennie, les nanoparticules métalliques ont trouvé de nombreuses applications dans divers domaines tels que l'optique, la photonique, la catalyse, la fabrication de matériaux, les énergies renouvelables, l'électronique, la médecine et même les cosmétiques. Les nouveaux développements de ces applications nécessitent des méthodes de synthèse de nanoparticules fiables donnant une grande quantité de nanoparticules aux propriétés spécifiques. Les méthodes à base de plasma, tels que des décharges d'étincelles et d’arcs sont parmi les plus prometteuses car elles permettent une augmentation considérable de la vitesse de production et une diminution des coûts. Le contrôle de ces processus est cependant toujours difficile et nécessite de nombreuses études détaillées, à la fois expérimentales et théoriques. Dans cette thèse, les décharges d'étincelles sont étudiées numériquement. L'objectif principal est de mieux comprendre les principaux mécanismes impliqués dans la décharge d'étincelle avec un faible écartement d’électrodes et sous pression atmosphérique. Ensuite, sur la base de la modélisation détaillée proposée, la quantité de nanoparticules produites ainsi que leur distribution en taille est prédite et est comparée avec les résultats expérimentaux correspondants. Dans le modèle proposé, seules les conditions initiales, la géométrie du système et les propriétés du matériau sont utilisés comme paramètres d'entrée. Une décharge d’étincelle unique est divisée en plusieurs unités selon les échelles spatiales et temporelles des processus physiques comme suit: modèles de (i) flux plasma, (ii) décharge, (iii) hydrodynamique, (iv) couche cathodique, (v) érosion d’électrode et (vi) formation de nanoparticules. Les résultats du modèle combiné sont ensuite comparés à la fois avec d'autres résultats théoriques et à des résultats expérimentaux. Enfin, les possibilités d'optimisation de la production de nanoparticules par décharge d'étincelles sont proposées sur la base de la variation des paramètres expérimentaux et sur l'analyse de la quantité de particules produites et de leur taille moyenne
During last decade, metal nanoparticles have found many applications in various areas, such as optics, photonics, catalysis, material manufacturing, renewable energy, electronics, medicine and even cosmetics. Further development of these applications requires reliable nanoparticle synthesis methods providing a large amount of nanoparticle with required properties. Plasma-based methods, such as spark and arc discharges are among the most promising since they allow a considerable increase in the production rate and a decrease in costs. The control over these processes is, however, still challenging and requires many detailed studies, both experimental and theoretical. In this thesis, spark discharge is investigated numerically. The main objective is to better understand main mechanisms involved in spark discharge with a short gap under atmospheric pressure. Then, based on the proposed detailed modeling, the amount of the produced nanoparticles, their size distribution should be predicted and compared with the corresponding experimental results. In the proposed model, only initial conditions, geometry of the system and material properties are used as input parameters. A single spark event is divided into several units according to localization and time scales of physical processes as follows: (i) streamer model, (ii) discharging model, (iii) hydrodynamic model, (iv) cathode layer model, (v) electrode erosion model and (vi) nanoparticle formation model. The results of the combined model are then compared both with other theoretical and experimental results. Finally, possibilities of optimization the nanoparticle production by spark discharge are proposed based on the variation of the experimental parameters and on the analysis of the resulted particle yield and mean size

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39

Dascalescu, Lucian. "Comportement de granules conducteurs en champ électrique mono-ionisé dans l'air atmosphérique". Université Joseph Fourier (Grenoble ; 1971-2015), 1994. http://www.theses.fr/1994GRE10088.

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L'objectif de ce travail a ete d'etudier les phenomenes physiques mis en jeu lors des mouvements de granules conducteurs spheriques ou cylindriques, de taille millimetrique, dans des champs electriques continus ou intermittents, entre electrodes distantes de quelques centimetres, dans l'air atmospherique. L'etude a ete effectuee en champ harmonique puis en presence des decharges de type couronne positives ou negatives. Un logiciel fonde sur la methode des elements de frontiere a ete utilise pour calculer la charge acquise par un granule, la force agissant sur celui-ci et le renforcement du champ electrique qu'il produit, lorsqu'il est en contact avec ou a proximite d'une electrode plane. On a evalue les conditions d'apparition d'une decharge electrique entre un granule charge et une electrode de polarite opposee, et analyse les circonstances dans lesquelles la presence d'un petit objet conducteur provoque le claquage de l'air ionise. En utilisant plusieurs dispositifs experimentaux (electrodes pointe-plan, fil et cylindre coaxiaux, matrice de pointes plan) on a determine le champ de decollement des granules de formes, de dimensions et de masses volumiques variees. Les experiences ont permis egalement de mesurer les tensions de claquage de l'air entre electrodes de configurations diverses, en presence d'un granule conducteur fixe ou mobile. Un modele mathematique a ete propose afin de decrire par calcul numerique les mouvements des granules et les claquages engendres par ceux-ci. L'influence des divers parametres electriques (niveau de la haute tension, densite de la charge d'espace) ou mecaniques (coefficient de rebond des granules sur une electrode) a ete etudiee systematiquement. La meilleure comprehension des phenomenes physiques acquise lors de ce travail a contribue a realiser des ameliorations a des installations industrielles telles que les separateurs electrostatiques

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40

Thomazella, Rogério. "Implementação computacional para avaliar os níveis de sobretensões atmosféricas induzidas em linhas de distribuição /". Bauru : [s.n.], 2004. http://hdl.handle.net/11449/90810.

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Orientador: André Nunes de Souza
Banca: Ivan Nunes da Silva
Banca: Luiz Gonzaga Campos Porto
Resumo: O presente trabalho visa o desenvolvimento de uma ferramenta computacional confiável na análise e estimação dos níveis de tensões induzidas em linhas de distribuição. Neste contexto, utilizam-se ferramentas computacionais consolidadas, como o ATP (Alternative Transients Program), que combinado a um software desenvolvido em Visual Basic, permitem quantificar e avaliar o nível de sobretensões nas linhas de distribuição. Por meio de modificações nas técnicas clássicas de modelagem das descargas atmosféricas, foi possível a construção de um software em Visual Basic capaz de quantificar os valores das tensões induzidas em linhas de distribuição finitas. A avaliação dos níveis de sobretensões induzidas nas mesmas foi implementada pela associação deste software a um programa de simulação (ATP), a fim de se obter resultados fidedignos deste transitório. Tais resultados foram utilizados para se avaliar o desempenho das... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The present work aims at the development of a trustworthy computacional tool in the analysis and estimate of the levels of induced overvoltage in distribution network. In this context, consolidated computacional tools are used, as ATP (Alternative Transients Program), that combined with a software developed in Visual Basic (beginner's all-purpose symbolic instruction code), they allow to quantify and to evaluate the level of overvoltage in the distribution network. By the means of modifications in the classic techniques of modeling of the atmospheric discharges, the construction of a software in Visual Basic was possible to quantify the values of the induced overvoltage in a finite... (Complete abstract click electronic access below)
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41

Léveillé, Valérie 1977. "A miniature atmospheric pressure glow discharge torch for localized biomedical applications /". Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102676.

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This thesis presents the design and characterization of a novel pulsed miniature capacitively-coupled Atmospheric Pressure Glow Discharge Torch (APGD- t) aimed at localized biomedical applications. Amplitude modulation of the 13.56 MHz carrier signal allows to continuously vary the power level applied to the APGD-t. Typically, the APGD-t produces a plasma jet with a 150-500 μm diameter and ≈2.5 mm length. Helium (He) is the plasma-forming gas with a flow rate ranging from 0.5 to 1.5 slm. The use of a small capillary electrode enhances the electric field, lowering the breakdown voltage (typically 220 Vpk-to-0) and allows the injection of small amounts (0-50 sccm) of a source of reactive species (O2) downstream of the plasma-forming region, in the plasma afterglow. The O2 is electronically dissociated in the plasma afterglow to create atomic oxygen (O) with no effect on the electrical properties. A ratio of 0.3% v/v, O2/He generates a maximum in O production.
Careful electrical probe measurements and circuit analyses reveal the strong effect of commercial passive voltage probes on the total load impedance of the APGD-t circuit. The larger the probe capacitance and cable length, the larger the component of the phase angle between the load voltage and circuit current signals induced by the probe. The calibration of the phase angles induced by the voltage probes allows to estimate that a resistive power of ~0.24-1 W is dissipated in the APGD- t under nominal operating conditions.
The gas kinetic and atomic He excitation temperatures, and the electron density near the APGD-t nozzle exit are estimated at ≈323 K, ≈1914 K and ≈1011 cm-3, respectively. This confirms that the APGD-t plasma jet near the nozzle exit is in a non-thermal equilibrium state. The emission spectroscopy study reveals the entrainment of air molecules (N2, O2 and H2O) in the plasma jet, and that their excitation by the plasma creates new reactive species (O and OH). A preliminary survey of the chemical reactions taking place in the plasma afterglow reveals that metastable He as well as OH, O, O2(a1Δg), O2(b1Σg+), N2, N2+ and O3 are plasma species that can reach and react with organic or biological surfaces located a few mm downstream of the APGD-t nozzle exit. This thesis demonstrates that the APGD-t is a promising tool for localized biomedical applications.

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42

Lee, Kyoung Ook. "Coaxial Atmospheric Pressure Plasma Discharge for Treatment of Filaments and Yarns". NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-12242007-142129/.

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Characteristics of non-thermal atmospheric-pressure plasma generated in a coaxial cylindrical Dielectric-Barrier Discharge (DBD) were investigated for application in treatment of polymer and 100% un-mercerized cotton yarns. The discharge characteristics were investigated by measuring the electrical parameters and utilization of developed plasma circuit models to obtain plasma electron temperature, number density and the electron-neutral collision frequency. The experiments were conducted in helium and oxygenated helium plasma in absence and presence of yarns. The discharge is capacitively-coupled and is induced by an audio-frequency, 4.5 kHz, oscillating voltage. The electrical voltage-current (V-I) characteristics optimized for plasma processing, by the oxygen and helium flow rate ratio, was found to be about 40sccm for oxygen flow. Optical emission spectroscopy (OES) was used to determine the plasma composition and to evaluate plasma temperature and number density. The plasma electron number density decreased from 2.2 x 10^16 to 1.4 x 10^16 per cubic meter when oxygen flow rate was increased to 100sccm in a 10,000sccm helium flow, while the electron temperature increased from 0.15 to 0.4 eV for the same increase in oxygen flow rate. It was also found that the plasma experiences some streamers and that the streamer?s electron temperature has a wide range between 0.5 to 2 eV. The optimized oxygen flow rate for polymer yarn processing was found to be 40sccm in a 10,000sccm helium flow.

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43

Lindon, Michael Allen. "CO2 Dissociation using the Versatile Atmospheric Dielectric Barrier Discharge Experiment (VADER)". Thesis, West Virginia University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3618122.

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As of 2013, the Carbon Dioxide Information Analysis Center (CDIAC) estimates that the world emits approximately 36 trillion metric tons of Carbon Dioxide (CO₂) into the atmosphere every year. These large emissions have been correlated to global warming trends that have many consequences across the globe, including glacial retraction, ocean acidification and increased severity of weather events. With green technologies still in the infancy stage, it can be expected that CO₂ emissions will stay this way for along time to come. Approximately 41% of the emissions are due to electricity production, which pump out condensed forms of CO₂. This danger to our world is why research towards new and innovative ways of controlling CO₂ emissions from these large sources is necessary.

As of now, research is focused on two primary methods of CO₂ reduction from condensed CO₂ emission sources (like fossil fuel power plants): Carbon Capture and Sequestration (CCS) and Carbon Capture and Utilization (CCU). CCS is the process of collecting CO₂ using absorbers or chemicals, extracting the gas from those absorbers and finally pumping the gas into reservoirs. CCU on the other hand, is the process of reacting CO₂ to form value added chemicals, which can then be recycled or stored chemically.

A Dielectric Barrier discharge (DBD) is a pulsed, low temperature, non-thermal, atmospheric pressure plasma which creates high energy electrons suitable for dissociating CO₂ into its components (CO and O) as one step in the CCU process. Here I discuss the viability of using a DBD for CO₂ dissociation on an industrial scale as well as the fundamental physics and chemistry of a DBD for CO₂ dissociation. This work involved modeling the DBD discharge and chemistry, which showed that there are specific chemical pathways and plasma parameters that can be adjusted to improve the CO₂ reaction efficiencies and rates. Experimental studies using the Versatile Atmospheric dielectric barrier Discharge ExpeRiment (VADER) demonstrated how different factors, like voltage, frequency and the addition of a photocatalyst, change the efficiency of CO₂ dissociation in VADER and the plasma chemistry involved.

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44

Algwari, Q. Th. "Plasma jet formation and interactions between atmospheric pressure dielectric barrier discharge jets". Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545999.

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45

Papa, Brian D. "Large-scale ice discharge events in a pure ice sheet model". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81421.

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Sediment cores in the North Atlantic show evidence of periodic large-scale ice discharge events between 60 kyr and 10 kyr before present. These so-called Heinrich Events (HEs) occurred with a typical period between 5 kyr and 10 kyr. During each HE, a significant amount of ice was discharged from the Laurentide ice sheet into the North Atlantic. This input of freshwater through the melting of icebergs is thought to have strongly reduced the strength of the Atlantic thermohaline circulation.
One theory for HEs is that they are due to an internal oscillation of the ice sheet under constant forcing. This implies that past multi-millennial scale climate variations in the North Atlantic region may have been driven by variations in the Laurentide ice sheet and were not externally forced by climate change or sea level variations. A second theory for HEs requires some variable external forcing on an unstable ice sheet to produce a discharge event.
Using the 3-D ice sheet model of Marshall and Clarke (1997a,b), which includes ice sheet dynamics and thermodynamics, the possibility of internal oscillations within an ice sheet is verified and an analysis of the mechanisms associated with these oscillations is performed. The bed topography and strain heating are found to be critical for the formation and development of fast moving ice streams, which lead to large iceberg calving. In addition, the calving parameterization is found to be an important factor in the ability of the model to periodically discharge large amounts of ice.

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46

Chan, Yi-kei y 陳伊祺. "Nutrient input of Tolo Harbour by river, atmospheric deposition and submarine groundwater discharge". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46732718.

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47

Vieira, Marcos Stefanelli. "Influência das edificações na propagação de ondas eletromagnéticas geradas por descargas atmosféricas". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-15072016-150045/.

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Descargas atmosféricas representam uma das principais causas de interrupção no fornecimento de energia para os consumidores, e embora tenham efeitos mais intensos quando incidem diretamente nas redes elétricas, é o caso das descargas indiretas que chama mais atenção, já que elas ocorrem com maior frequência. Tanto as primeiras descargas que geralmente ocorrem com maior intensidade de corrente, quanto as descargas subsequentes que têm menor tempo de frente associado, irradiam campos eletromagnéticos que ao se acoplarem com as redes elétricas geram surtos que podem causar tanto a interrupção do fornecimento de energia quanto danos a equipamentos. A presença de edifícios na região de incidência da descarga atmosférica afeta a propagação das ondas irradiadas, criando diferentes padrões de campos resultantes, os quais são responsáveis por sobretensões induzidas. Embora tanto a descarga atmosférica em si quanto a caracterização do ambiente ao seu redor sejam de natureza complexa para sua representação, ferramentas computacionais bem estruturadas podem representar o fenômeno de forma satisfatória, como é o caso da ferramenta computacional desenvolvida neste trabalho utilizando o método das diferenças finitas no domínio do tempo. O presente trabalho apresenta dois estudos para verificação da influência de edificações na propagação de campo irradiado por descargas atmosféricas. O primeiro estudo avaliou o comportamento das componentes do campo elétrico e do campo magnético irradiados, comparando resultados obtidos com e sem a presença de edificações numa pequena região. Tanto os parâmetros geométricos dos três edifícios considerados neste estudo, como a permissividade e a condutividade elétrica do solo e dos edifícios, foram variados para identificar a sua influência nos campos irradiados. Os resultados mostraram diferentes comportamentos das componentes dos campos resultantes em função da variação desses parâmetros, observando-se inversão de polaridade, oscilações na forma de onda e tanto redução quanto aumento do valor de campo. O segundo estudo avaliou um caso mais geral em que a componente vertical de campo elétrico foi tomada em nove pontos diferentes de uma região tipicamente urbana, com a presença de 102 edifícios. Os valores de campo avaliados em cada ponto, dez metros acima do solo, consideraram a incidência aleatória de 28 descargas atmosféricas distintas, cada uma atingindo o topo de um dado edifício. Os resultados desse segundo estudo mostraram que exceto nos casos em que a descarga atmosférica ocorre próximo do ponto analisado, há reduções significativas do campo elétrico vertical. Desta forma é possível perceber que não apenas a existência de edifícios, mas a sua concentração com diferentes características elétricas e geométricas, podem influenciar significativamente a propagação de campo irradiado. Os valores calculados a partir da ferramenta desenvolvida podem ser usados em conjunto com modelos de acoplamento, para o cálculo de sobretensões induzidas em redes elétricas, em situações realistas com configurações mais complexas.
Atmospheric discharges represent one of the main causes of interruption in power supply to consumers, and although they have more intense effects when direct impact on energy lines, are the case of indirect discharges that draws more attention, since they occur more frequently. Both the first discharges, occurring generally with greater intensity of current, as subsequent discharges that have shorter front time associated, radiate electromagnetic fields which engage with the electrical networks generating surges that can cause so much disruption of power supply as damage to the equipment. The presence of buildings in the lightning incident area affects the propagation of the radiated waves, creating different patterns of resultant fields, which are responsible for induced overvoltages. Although both the lightning itself and characterization of the surrounding environment are of a complex nature for its representation, structured computational tools can represent satisfactorily the phenomenon, such as the software tool developed here using the finite difference time domain method. This work presents two studies to verify the influence of buildings in the propagation of lightning irradiated field. The first study assessed the behavior of the components of the electric field and magnetic field irradiated, by comparing results obtained with and without the presence of buildings in a small region. Both the geometric parameters of the three buildings considered in this study, as the permittivity and electrical conductivity of the soil and buildings, were changed to identify their influence on radiated fields. The results showed different behaviors of the components of the resulting field due to the variation of these parameters, observing polarity inversion, oscillations in the waveform and either a reduction or increase of the field value. The second study evaluated a more general case where the vertical component of the electric field was taken at nine different points of a typical urban area, in the presence of 102 buildings. The field values evaluated at each point, ten meters above the ground, considered the effect of 28 different random lightning, which hit the top of a given building. The results of this second study showed that except in cases where atmospheric discharge occurs near the analyzed point, there are significant reductions of the vertical electric field. Thus it can be seen that not only the existence of buildings, but its concentration with different electrical and geometrical characteristics, can significantly influence the propagation of irradiated field. The values calculated from the developed tool can be used in conjunction with coupling models for calculating induced overvoltages on power lines, in realistic situations with complex configurations.

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48

Yonson, Sara. "Cell treatment and surface functionalization using the atmospheric pressure glow discharge plasma torch (APGD-t)". Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99551.

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The atmospheric pressure glow discharge plasma torch (APGD-t ) was used to treat cell cultures to investigate potential reactions with biological tissue. The plasma jet successfully detached HAAE-1 and HepG2 cells from a culture surface. The cells surrounding the void did not show any morphological damage after treatment. The detached HepG2 cells were transplanted to a new vessel, where they reattached. A viability assay showed the transplanted cells had functioning mitochondria up to 7 days after exposure to the plasma jet. These cells were also shown to have a permeabilized cell membrane for 4 hours after treatment, with resealing of the cell membrane occurring within 24 hours of transplantation. This work could be useful for localized tissue removal, and the injection of foreign DNA and RNA into cells for gene therapy.
In separate experiments, sterilized bacterial grade polystyrene (BGPS) was functionalized with the plasma jet to improve cell adhesion. The contact angle of treated BGPS decreased from 93° to 35°, likely due to the addition of polar oxygen and nitrogen groups to the surface. The width of the functionalized track was visualized using the adhesion of HAAE-1 cell cultures, and was found to correspond to approximately double the diameter of the plasma jet. Direct plasma micropatterning using the APGD-t could replace the masks and chemicals required in present photolithographic techniquesIn separate experiments, sterilized bacterial grade polystyrene (BGPS) was functionalized with the plasma jet to improve cell adhesion. The contact angle of treated BGPS decreased from 93° to 35°, likely due to the addition of polar oxygen and nitrogen groups to the surface. The width of the functionalized track was visualized using the adhesion of HAAE-1 cell cultures, and was found to correspond to approximately double the diameter of the plasma jet. Direct plasma micropatterning using the APGD-t could replace the masks and chemicals required in present photolithographic techniques.

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49

Kerr, Maria. "The grafting of collagen to medically relevant polymers through an atmospheric pressure dielectric barrier discharge". Thesis, University of Ulster, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536466.

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Wolkenhauer, Arndt. "Plasma treatment of wood and wood-based materials by dielectric barrier discharge at atmospheric pressure /". Göttingen : Sierke, 2009. http://d-nb.info/993076556/04.

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