The Experts below are selected from a list of 39954 Experts worldwide ranked by ideXlab platform

Andreas Seibel - One of the best experts on this subject based on the ideXlab platform.

  • From Software Traceability to Global Model Management and Back Again
    2011 15th European Conference on Software Maintenance and Reengineering, 2011
    Co-Authors: Andreas Seibel
    Abstract:

    In the past, traceability was concerned with tracing requirements also known as requirements traceability. Meanwhile, Model-driven engineering (MDE) becomes popular and in this context, requirements traceability evolved to a more general software traceability, which is about tracing any relationship between software artifacts. Due to increasing heterogeneity and complexity of MDE, Global Model management (GMM) becomes indispensable to MDE. In state-of-the-art GMM approaches, traceability is primarily concerned with tracing Model transformations, which generate traceability information as side-effect. However, this is only a subset of the capabilities of software traceability. My hypothesis is that GMM can benefit from software traceability by applying software traceability techniques into the context of GMM. Thus, I will consider GMM from a traceability perspective and show new possibilities to GMM that arise from taking in this perspective.

Evangelos Gogolides - One of the best experts on this subject based on the ideXlab platform.

  • a Global Model for sf6 plasmas coupling reaction kinetics in the gas phase and on the surface of the reactor walls
    Journal of Physics D, 2009
    Co-Authors: George Kokkoris, Apostolos Panagiotopoulos, Andy Goodyear, Mike Cooke, Evangelos Gogolides
    Abstract:

    Gas phase and reactor wall-surface kinetics are coupled in a Global Model for SF6 plasmas. A complete set of gas phase and surface reactions is formulated. The rate coefficients of the electron impact reactions are based on pertinent cross section data from the literature, which are integrated over a Druyvesteyn electron energy distribution function. The rate coefficients of the surface reactions are adjustable parameters and are calculated by fitting the Model to experimental data from an inductively coupled plasma reactor, i.e. F atom density and pressure change after the ignition of the discharge. The Model predicts that SF6, F, F2 and SF4 are the dominant neutral species while and F? are the dominant ions. The fit sheds light on the interaction between the gas phase and the reactor walls. A loss mechanism for SFx radicals by deposition of a fluoro-sulfur film on the reactor walls is needed to predict the experimental data. It is found that there is a net production of SF5, F2 and SF6, and a net consumption of F, SF3 and SF4 on the reactor walls. Surface reactions as well as reactions between neutral species in the gas phase are found to be important sources and sinks of the neutral species.

John P. Verboncoeur - One of the best experts on this subject based on the ideXlab platform.

  • Investigation of the Similarity Law in Discharges at High Pressure Using A Kinetic Global Model
    2017 IEEE International Conference on Plasma Science (ICOPS), 2017
    Co-Authors: Yangyang Fu, John P. Verboncoeur, Janez Krek, Guy Parsey, Andrew Christlieb, Xinxin Wang
    Abstract:

    A kinetic Global Model framework (KGMf) has been developed and used to investigate the similarity law in discharges at high pressure. Keeping the pd (gas pressure × linear dimension) unchanged, the electron and ion densities in the steady state are calculated while the geometrical similar volume increases from micron scale (500μm) to millimeter scale (2.5mm) and at the pressure decreases from 760Torr to 152Torr, correspondently. In the Model, electrons, positive ions and fourteen excited levels of argon atom are considered, and the transition of excitations, three-body collisions, and stepwise ionizations, which are forbidden processes from the similarity law are included and excluded, respectively1-3. The simulation results showed that within the forbidden processes the normalized density relations are below the predicted relations from the similarity law, which is attributed to the nonlinear impact of forbidden processes. Without the forbidden processes, the parameter relations are in good agreement with the theoretical prediction from the similarity law. The KGMf has the potential for deeper studies on similarity law at high pressure, such as gas mixtures with other volume and surface processes.

  • Global Model for High Power Microwave Breakdown at High Pressure
    2008 IEEE International Power Modulators and High-Voltage Conference, 2008
    Co-Authors: Sang Ki Nam, John P. Verboncoeur
    Abstract:

    A major limiting factor in transmission of high power microwave radiation is dielectric window breakdown. Dielectric window breakdown from vacuum multipactor to collisional microwave discharge has been investigated using the PIC/MCC Model for noble gases. The effect of a wide spectrum of reaction kinetics is very important in molecular gases like oxygen or air. However, it is not practical to investigate breakdown in molecular gases including detailed reaction kinetics using particle simulation due to the computational expense. Therefore, a fast volume-averaged Global Model was developed for the purpose of investigating the effect of reaction kinetics and plasma parameters for multiple species needed to Model molecular gases. Since the Global Model is a fluid-based Model, it requires specification of the electron energy distribution function (EEDF). Most Global Models assume a Maxwellian distribution for the electron energy distribution function. The electrons, however, are not in equilibrium in most discharges unless the electron-electron collision is dominant. The assumption of a Maxwellian EEDF produces inaccurate reaction rate coefficients for the plasma discharge and results in incorrect plasma parameters especially at high pressure. We examine the effect of the EEDF on the Global Model and develop a method to find the proper approximation of the EEDF to improve fidelity of the prediction of the high power microwave breakdown at high pressure. An application of the improved Global Model to oxygen and air breakdown is presented.

  • Effect of electron energy distribution function on the Global Model for high power microwave breakdown at high pressures
    2008 IEEE International Vacuum Electronics Conference, 2008
    Co-Authors: John P. Verboncoeur
    Abstract:

    Most volume-averaged Global Models assume a Maxwellian distribution for the electron energy distribution function (EEDF) in plasma discharges. The electrons, however, are not in the equilibrium in most discharges unless the electron-electron collision is dominant. The assumption of a Maxwellian EEDF can result in inaccurate reaction rate coefficients for the plasma discharge and lead to the wrong breakdown behavior prediction. Since the collisional plasma properties strongly depend on those coefficients, they are important to predict the plasma breakdown properly. This work will demonstrate the effect of the EEDF on the Global Model and propose a method to find an approximation of the EEDF that can improve the fidelity of the Global Model for prediction of high power microwave (HPM) breakdown in the high pressure regime.

P Peter J Bruggeman - One of the best experts on this subject based on the ideXlab platform.

  • Global Model of low temperature atmospheric pressure he h2o plasmas
    Plasma Sources Science and Technology, 2010
    Co-Authors: Dingxin Liu, P Peter J Bruggeman, Felipe Iza, Mingzhe Rong, M G Kong
    Abstract:

    A detailed Global Model of atmospheric-pressure He + H2O plasmas is presented in this paper. The Model incorporates 46 species and 577 reactions. Based on simulation results obtained with this comprehensive Model, the main species and reactions are identified, and simplified Models capable of capturing the main physicochemical processes in He + H2O discharges are suggested. The accuracy of the simplified Models is quantified and assessed for changes in water concentration, input power and electrode configuration. Simplified Models can reduce the number of reactions by a factor of similar to 10 while providing results that are within a factor of two of the detailed Model. The simulation results indicate that Penning processes are the main ionization mechanism in this kind of discharge (1-3000 ppm of water), and water clusters of growing size are found to be the dominant charged species when the water concentration is above similar to 100 ppm. Simulation results also predict a growing electronegative character of the discharge with increasing water concentration. The use of He + H2O discharges for the generation of reactive oxygen species of interest in biomedical applications and the green production of hydrogen peroxide are also discussed. Although it would be unrealistic to draw conclusions regarding the efficacy of these processes from a zero-dimensional Global Model, the results indicate the potential suitability of He + H2O plasmas for these two applications.

Randhir Singh - One of the best experts on this subject based on the ideXlab platform.

  • Development of a New Global Model for Estimating One-Minute Rainfall Rate
    IEEE Transactions on Geoscience and Remote Sensing, 2018
    Co-Authors: Randhir Singh, Rajat Acharya
    Abstract:

    One-minute rain rate exceeded for 0.01% of an average year (known as R0.01) is an important parameter, which is required in rain fade Models for planning both satellite and terrestrial links, especially in the microwave and millimeter-wave bands. This paper presents the development of a new Global Model for estimating high-resolution R0.01. The Model is developed using the Climate Hazards Group Infrared Precipitation with Stations (CHIRPS), ERA-Interim reanalyzed total precipitable water, and the cumulative distribution functions of the measured R0.01 via genetic algorithm. The newly proposed Model performs better than the International Telecommunication Union Radio Sector (ITU-R) recommendation and widely used ITU-R P.837-6 Model, particularly over the tropical regions, where ITU-R P.837-6 strongly underestimates R0.01. Overall, when compared to ITU-R P.837-6, the estimated R0.01 by the proposed Model is improved by ~15%. Furthermore, the proposed Model can provide R0.01 with a much higher spatial resolution (~5 km) as compared to ITU-R P.837-6 (~110 km). Another key advantage of the proposed Model over ITU-R P.837-6 is that the inputs required for this Model are readily available from meteorological database as well as from space-based observing system. This paper also investigated the long-term (1981-2016) trends in R0.01. The analysis revealed significant increasing trends in R0.01 over most parts of the globe, India and northern part of Southern America exhibited the strongest (~0.5 mm.year-1) increasing trends. It is anticipated that R0.01 obtained with the newly proposed Model will have large implications in rain attenuation Modeling for planning both terrestrial and earth-satellite microwave links.

  • Early Detection of Cyclogenesis Signature Using Global Model Products
    IEEE Transactions on Geoscience and Remote Sensing, 2014
    Co-Authors: Sanjeev Kumar Singh, C. M. Kishtawal, Neeru Jaiswal, Randhir Singh
    Abstract:

    High-resolution Global Forecast System (GFS) Model products are used to detect the earliest tropical cyclogenesis (TCG) signature over the North Indian Ocean (NIO). In order to identify the formation of tropical cyclones (TCs) in the Model forecast fields, three parameters, namely, low-level relative vorticity, genesis potential parameter, and wind circulation pattern matching index, are examined in this paper. The detection of TCG in the GFS Model is performed for 14 TCs that developed in the NIO during the 2008-2011 period. The results show that the wind circulation pattern matching index provides the most reliable guidance (high probability of detection, i.e., approximately 0.92, in a 24-h forecast with relatively few false alarms) for identifying TC formation over the NIO.