A Unified Flow Solver (UFS) has been developed for simulations of rarefied, transitional and continuum flows based on direct numerical solution of the Boltzmann equation coupled to kinetic schemes of gas dynamics. The UFS uses dynamically adaptive mesh and automatic domain decomposition into kinetic and continuum domains based on continuum breakdown criteria. This paper describes UFS extensions...

Degradation of RF accelerating cavities caused by field emission currently limits the design of future linear accelerators. When field emission is the problem, foreign particles often deserve the blame, but they can be ”processed” away if the cavity electric field is high enough to initiate voltage breakdown near the particle site, in which case the troublesome particle vaporizes, leaving behin...

This paper presents a new concept for an active high voltage insulation system with dynamic and adaptive features. The governing principle is based on surface charge accumulation on dielectrically covered electrodes in air under atmospheric pressure. This accumulation results in a charge-induced electric field component which steers the field distribution within the system advantageously. At eq...

A novel gas ionization sensor using Pd nanoparticle-capped ZnO (Pd/ZnO) nanorods as the anode is proposed. The Pd/ZnO nanorod-based sensors, compared with the bare ZnO nanorod, show lower breakdown voltage for the detected gases with good sensitivity and selectivity. Moreover, the sensors exhibit stable performance after more than 200 tests for both inert and active gases. The simple, low-cost,...

Two methods can be used to suppress multipacting in a rectangular coupler waveguide. The slotted waveguide method calls for opening slots on the broad walls in the wave propagation direction that perturb the resonance and trap multipacting electrons. The DC magnetic bias method utilizes a solenoid coil wrapped around the waveguide to generate a mild DC magnetic field in the waveguide space that...

We present a detailed derivation of the renormalization group equations for two dimensional electromagnetic Coulomb gases whose charges lie on a triangular lattice (magnetic charges) and its dual (electric charges). The interactions between the charges involve both angular couplings and a new electromagnetic potential. This motivates the denomination of “elastic” Coulomb gas. Such elastic Coulo...

The residual biodegradation products of wheat straw lignin attacked by Cyathus stercoreus for thirty days were identified. Low-molecualr-weight nonvolatile materials constituted less than 5% of the total 14C released from labeled lignin. In this portion, syringic acid, vanillic acid, p-hydroxy benzoic acid, acetic acid, and 2-methoxy-succinic acid were found. The majority of the water-soluble b...