Search

In this paper, a numerical simulation on the interaction between the double cathode spot craters in the vacuum arc is carried out. By establishing a double-cathode spot ablation model, the crater development process when two spots coexist is simulated, and the formation mechanism of cathode spot groups is analyzed. The simulation results show that the two cathode spots appearing on the flat electrode would squeeze each other to form a liquid metal ridge, which changed the ablation morphology of the cathode spots. When the double-spot arc craters appear simultaneously, the metal ridge will be squeezed into a straight line, otherwise, when the spots appear one after another, the liquid metal ridge will shift toward the side of the spot that appears first. The relative experimental results are adopted to compare with the simulation results. By comparison, it is found that the morphology of the multi-spot crater in the experiment is in agreement with the simulation results. [ABSTRACT FROM AUTHOR]

A 3D transient model of a cathode-spot crater and droplet formation in a vacuum arc is developed. The model includes mass, momentum, heat transfer (energy), current continuity and potential equations. Using the energy flux density, current density and pressure as external parameters, the shape of the cathode-spot crater and the temperature, velocity, potential and current density distributions at each time step are determined via numerical simulation. Under symmetrical conditions, the 3D simulation results are highly consistent with those from the previous 2D model. The new cathode spot tends to appear in the direction in which the protrusion is largest because the liquid-metal velocity is lower and the liquid-metal ridge radius is larger in this direction. The effect of the external transverse magnetic field is considered by using a symmetric space function to represent the pressure and energy flux density of the plasma cloud. Simulation results show that even small changes in the plasma cloud distribution have a significant impact on the cathode-spot crater process and droplet formation. Since the pressure is asymmetric, the crater becomes asymmetric and the new cathode spot tends to appear opposite to the direction of the Ampere force. Based on this phenomenon, a possible explanation for the retrograde motion phenomenon of cathode spots is proposed. [ABSTRACT FROM AUTHOR]

In this article, the model including cathode spot process and deuterium desorption process on zirconium deuterium cathode is developed. Five kinds of particle fluxes on cathode surface and three mechanisms affecting deuterium diffusion in cathode are considered. The model not only describes the deformation of cathode metal, but also describes the variation of deuterium concentration with time. On pure zirconium cathode, the mean charge state is larger but on zirconium deuterium cathode, the total ion number density is larger since there are additional deuterium ions, and simulation results show the discharge currents are very close on the two cathodes, the energy flux density on ZrD0.66 cathode is larger so cathode spot crater develops faster on ZrD0.66 cathode. Ablation rates caused by different mechanisms are calculated and the results show in cathode spot development process, mass loss caused by evaporation is ignored, most of the liquid metal will resolidify on cathode surface, and droplets are the main reason for cathode ablation. The ablation rates due to the ejection of droplets are close to experimental results. The ratios of deuterium ion from different mechanisms in this process are also calculated and it is 93.5% in simulation. Simulation results are in agreement with the other researchers’ works. [ABSTRACT FROM AUTHOR]

Abstract: A common approach when reconstructing a 3D model from medical images is to do segmentation and registration manually and reconstruct these images in Maya or other 3D modeling software. To afford an effective interaction with serially sectioned medical images and reconstructed 3D models, we propose VRKidney. This medical simulation software acts as a common VR tools on computer for man-machine interaction. By integrating image registration, segmentation and reconstruction, VRKidney provides a fast registration and segmentation method using ITK and an interactive manipulation using VTK. This paper discusses the implementation of VRKidney for serially sectioned images and 3D models of human kidney and provides an initial evaluation of the usability of VRKidney in virtual human functions simulation. [Copyright &y& Elsevier]

The adsorptions of fixed groups −COOH, −OH, −CN, −NH 2 and −SH of dye molecules on three kinds of SnO 2 (110) surfaces were systematically investigated by first principle calculations. It is found that the adsorptions of five fixed groups on three kinds of SnO 2 (110) surfaces are chemical adsorption which includes both dissociative adsorption and non-dissociative adsorption. The most stable adsorption configuration of the five fixed groups on three kinds of SnO 2 (110) surfaces is bidentate chelate adsorption configuration of COOH group on Pt-doped SnO 2 (110) surface with adsorption energy of −3.265 eV. Thus, −COOH group is a promising fixed group of dye molecules for the preparation of dye-sensitized solar cells (DSSCS). At the same time, the Pt-doped SnO 2 photo-anode shows optimal adsorption performance, which provides theoretical basis for the design and application of SnO 2 dye-sensitized cells. [ABSTRACT FROM AUTHOR]