Bifurcations in the theory of current transfer to cathodes of dc discharges and observations of transitions between different modes

General scenarios of transitions between different spot patterns on electrodes of dc gas discharges and their relation to bifurcations of steady-state solutions are analyzed. In the case of cathodes of arc discharges, it is shown that any transition between different modes of current transfer is related to a bifurcation of steady-state solutions. In particular, transitions between diffuse and spot modes on axially symmetric cathodes, frequently observed in the experiment, represent an indication of the presence of pitchfork or fold bifurcations of steady-state solutions. Experimental observations of transitions on cathodes of dc glow microdischarges are analyzed and those potentially related to bifurcations of steady-state solutions are identified. The relevant bifurcations are investigated numerically and the computed patterns are found to conform to those observed in the course of the corresponding transitions in the experiment

Impact stresses and deformations in spherical shells Final report

Spherical shell dynamic response on colliding with special elastic impact surface with stress wave analysi

Modelling excited species and their role on kinetic pathways in the non-oxidative coupling of methane by dielectric barrier discharge

Acknowledgments We acknowledge and greatly appreciate the assistance from Dr. Mihailova from Plasma Matters B.V. in working with the software Plasimo and from Dr Marcus Campbell Bannerman from the University of Aberdeen for providing access to the computational cluster used for carrying out the simulations in this work. The work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) New Investigator Award, grant no. EP/R031800/1.Peer reviewedPostprin

Modelling cathode spots in glow discharges in the cathode boundary layer geometry

Self-organized patterns of cathode spots in glow discharges are computed in the cathode boundary layer geometry, which is the one employed in most of the experiments reported in the literature. The model comprises conservation and transport equations of electrons and a single ion species, written in the drift-diffusion and local-field approximations, and Poisson’s equation. Multiple solutions existing for the same value of the discharge current and describing modes with different configurations of cathode spots are computed by means of a stationary solver. The computed solutions are compared to their counterparts for plane-parallel electrodes, and experiments. All of the computed spot patterns have been observed in the experiment.info:eu-repo/semantics/publishedVersio

3D modelling of self-organized patterns of spots on anodes of DC glow discharge

Self-organized patterns of spots on a at metallic anode in a cylindrical glow dis- charge tube are simulated self-consistently. A standard model of a glow discharge is used, comprising conservation and transport equations for a single species of ion and electrons, written with the use of the drift-diffusion and local-field approximations, and the Poisson equation. The computation domain is the region from the anode to the discharge column; only processes in the near-anode region are considered. Multiple solutions, existing in the same range of discharge current and describing modes with and without anode spots, are computed by means of a stationary solver. The computed spots exhibited unexpected behavior. A reversal of the local anode current density in the middle of each of the spots was found, i.e. mini-cathodes are formed inside the spots. The solutions do not fit into the conventional pattern of self-organization in bistable nonlinear dissipative systems; e.g. the modes are not joined by bifurcations

Stability of coordination polymers in water: state of the art and towards a methodology for nonporous materials

A mini review on the study concerning water stability of coordination polymers (CPs) is presented. Next, following the procedure proposed recently by Gelfand and Shimizu (Dalton Trans 45:3668-3678, 2016) the stability of three cysteine (Cys)containing CPs is investigated. The stability of studied CPs decreases in the order: Zn(Cys)(2)>Mg(Cys)(2)>Ca(Cys)(2) H2O. For the latternever reported before, the structure is additionally determined and it is proved that water is located in the first coordination sphere. It is shown that for nonporous CPs, in contrast to the porous ones, the immersion in water at 20 degrees C is more drastic for studied solids than the harsh humid conditions (80 degrees C at 90% R.H.). Finally all materials are assigned to the hydrolytic stability groups and it is concluded that the stability of studied CPs correlates well with the standard reduction potentials. This leads to the conclusion that the application of more inert metal as a node causes larger stability of studied CPs

Development of a device to simulate tooth mobility

Objectives: The testing of new materials under simulation of oral conditions is essential in medicine. For simulation of fracture strength different simulation devices are used for test set-up. The results of these in vitro tests differ because there is no standardization of tooth mobility in simulation devices. The aim of this study is to develop a simulation device that depicts the tooth mobility curve as accurately as possible and creates reproducible and scalable mobility curves. Materials and methods: With the aid of published literature and with the help of dentists, average forms of tooth classes were generated. Based on these tooth data, different abutment tooth shapes and different simulation devices were designed with a CAD system and were generated with a Rapid Prototyping system. Then, for all simulation devices the displacement curves were created with a universal testing machine and compared with the tooth mobility curve. With this new information, an improved adapted simulation device was constructed. Results: A simulations device that is able to simulate the mobility curve of natural teeth with high accuracy and where mobility is reproducible and scalable was developed

Computing DC discharges in a wide range of currents with COMSOL MultiPhysics: time-dependent solvers vs. stationary solvers

The benefits of the usage of stationary over time-dependent solvers of COMSOL Multiphysics in the modelling of DC discharges are explored and demonstrated using as examples glow and high pressure arc discharges; in particular, it is investigated whether time-dependent solvers can be used for a systematic computation of different modes of these discharges. It has been found that most modes of both glow and high-pressure arc discharges cannot be computed in the whole range of their existence by a time-dependent solver. Further, time-dependent solvers are unsuitable for a computation of all the states belonging to the retrograde sections of the current-voltage characteristics of the modes, so the discharge manifests hysteresis, which, in principle, can be observed in the experiment.info:eu-repo/semantics/publishedVersio

Toward a Reliable Wave Hindcast/Forecast in the Bering Sea

1. To validate the quality of available wind products through application of the WAM model Cycle 4.5 and satellite observations. 2. To analyze effects of high resolution atmospheric model downscaling and data assimilation. 3. To analyze summer surface wave condition in the Bering Sea during the years, 2007-2011. 4. To explore the possibility of developing a new algorithm for a dynamically constrained minimizing function without employing the adjoint of the dynamical system