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Energy Exchange During Electron Emission from Carbon Nanotubes: Considerations on Tip Cooling Effect and Destruction of the Emitter

M. Dionne, S. Coulombe, and J. Meunier
Department of Chemical Engineering, McGill University, Montreal, Quebec, Canada

Murphy and Good general theory for electron emission from metal surfaces was used to predict the field-emission capabilities of ideal arrays of vertically aligned carbon nanotubes (VACNT). The Nottingham effect was taken into account in order to explain experimental observation of a localized cooling of the VACNT tips during field emission and the total destruction of very short emitters at ...

Densification and Shape Change of Calcined High Level Waste During Hot-Isostatic Pressing

T. Burnett, and D. Lower
CH2M-WG Idaho, LLC
The Idaho Cleanup Project at the Idaho National Laboratory
Idaho Falls, ID

Hot Isostatic Pressing (HIP) has been selected as a means of treating calcined high level waste (HLW). The process combines high temperature and pressure to densify the HLW in to a mineral similar to the geologic formulation of granite. This study uses COMSOL to predict densification and shape deformation of a stainless steel can filled with HLW. Two approaches were used to model ...

Numerical Study of the Self-ignition of Tetrafluoroethylene in a 100-dm3-reactor

F. Ferrero[1], M. Kluge[1], R. Zeps[1], T. Spoormaker[2]
[1]BAM Federal Institute for Materials Research and Testing, Berlin, Germany
[2]Chairman PlasticsEurope Fluoropolymers TFE Safety Task Force, Du Pont De Nemours, Dordrecht, The Netherlands

The self-ignition of tetrafluoroethylene (TFE) caused by contact with hot surfaces has been analyzed with the help of simulations performed with COMSOL Multiphysics®. The current study focuses on large-scale heated reactors for the industrial production of polytetrafluoroethylene (PTFE) from TFE at high pressures. Simulations of the self-heating and consequent self-ignition of TFE in a 100-dm3 ...

Modeling of Space-Charge Effects in 3D Thermionic Devices

P. Zilio [1], W. Raja [2], A. Alabastri [3], R. Proietti Zaccaria [2]
[1] Istituto Italiano di Tecnologia, Italy
[2] Istituto Italiano di Tecnologia, Italy
[3] Rice University, USA

The formation of space charge clouds is a well known problem that affects thermionic emitters in regimes of high current emission. Although some analytical models have been presented, suitable for 1D geometries, the modeling of the problem in complex 3D structures remains a challenge due to the mutual coupling between electron trajectories and field they produce. Here we propose a model able to ...

A Time Dependent Dielectric Breakdown (TDDB) Model for Field Accelerated Low-K Breakdown Due To Copper Ions

R. Achanta, J. Plawsky, and W. Gill
Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA

We have simulated the copper ion concentration and internal electric field profiles in a dielectric material by solving the transient continuity/Poisson equations using COMSOL Multiphysics. We have shown that failure of dielectrics can be modeled if we assume that failure in Cu/SiO2/Si devices occurs due to a pile-up of copper ions at the cathode and the subsequent increase in electric field ...

Simulating Wear in Disc Brakes - new

N. H. Elabbasi[1], M. J. Hancock[1], S. B. Brown[1]
[1]Veryst Engineering, LLC., Needham, MA, USA

Wear is a complex phenomenon relevant to many problems involving frictional contact, such as mechanical brakes, seals, metal forming, and orthopedic implants. The rate of wear depends on the properties of the contacting materials and operating conditions. One widely used model of wear is Archard’s law, which relates the rate of material removal due to wear to the contact pressure, sliding ...

3D Multiphysics Modeling of Bulk High-Temperature Superconductors for Use as Trapped Field Magnets - new

M. Ainslie[1], J. Zou[1], D. Hu[1], D. Cardwell[1]
[1]Department of Engineering, University of Cambridge, Cambridge, UK

The authors are currently investigating the use of bulk high temperature superconductors as trapped field magnets (TFMs) in order to increase the electrical and magnetic loading of an axial gap, trapped flux-type superconducting electric machine. In electric machines, the use of superconducting materials can lead to increases in efficiency, as well as power density, which results in reductions ...

Numerical Modeling of Sampling Airborne Radioactive Particles Methods from the Stacks of Nuclear Facilities in Compliance with ISO 2889 - new

P. Geraldini[1]
[1]Sogin Spa, Rome, Italy

The main objective of this study is to verify the compliance of an ongoing nuclear facilities stack design with the ISO 2889 requirements, during normal and off-normal conditions. In particular, with the numerical simulations, they have been identify well-mixed sample locations along the chimney and the compliance with the International Standard requirements as result of stack flow rate and ...

High Frequency Magnetohydrodynamic Calculations in COMSOL

N. Kleinknecht, and S. A. Halvorsen
Teknova AS
Kristiansand, Norway

In many metallurgical processes metals are (heated and) stirred by an oscillating external magnetic field. The magnetic field induces electric currents in the metal and the currents interact with the magnetic field to create a force, the Lorentz force. For high frequencies induction only takes place in an electromagnetic boundary layer due to the skin effect and the force is confined within this ...

Modeling of Straight Jet Dynamics in Electrospinning Process

R. Pandya [1], A. Kumar [2], V. Runkana [1],
[1] Tata Research Development and Design Centre, Tata Consultancy Services, Pune, India
[2] Indian Institute of Technology, Delhi, India

Electrospinning is a process where high voltage is applied to produce polymer fibers of nanoscale diameter. Various polymers have been used for this process in molten form or as a solution with an appropriate solvent such as glycerol. The melt solidifies while the solvent evaporates to produce fibers. The fibers produced have properties such as high surface to volume ratio and a molecular ...