Impact Of Density Variations Research Articles

Exploring the role of mean-field potentials and short-range wave function behavior in the adiabatic connection.

In this article, we explore the construction of Hamiltonians with long-range interactions and their corrections using the short-range behavior of the wave function. A key aspect of our investigation is the examination of the one-particle potential, kept constant in our previous work, and the effects of its optimization on the adiabatic connection. Our methodology involves the use of a parameter-dependent potential dependent on a single parameter to facilitate practical computations. We analyze the energy errors and densities in a two-electron system (harmonium) under various conditions, employing different confinement potentials and interaction parameters. The study reveals that while the mean-field potential improves the expectation value of the physical Hamiltonian, it does not necessarily improve the energy of the system within the bounds of chemical accuracy. We also delve into the impact of density variations in adiabatic connections, challenging the common assumption that a mean field improves results. Our findings indicate that as long as energy errors remain within chemical accuracy, the mean field does not significantly outperform a bare potential. This observation is attributed to the effectiveness of corrections based on the short-range behavior of the wave function, a universal characteristic that diminishes the distinction between using a mean field or not.

ACCNT: A Metallic-CNT-Tolerant Design Methodology for Carbon Nanotube VLSI: Analyses and Design Guidelines

We present analyses for ACCNT (pronounced as “accent”), which is a solution to the metallic-nanotube problem that does not require any metallic-nanotube removal of any kind. ACCNT uses asymmetrically correlated carbon nanotubes to achieve metallic-nanotube tolerance, delivering high ON-OFF ratios while preserving current drive. We analyze the ACCNT methodology in terms of its tradeoffs and explore optimizations that may serve as future design guidelines. We also investigate circuit-level considerations and the impact of density variation on the ACCNT design. We find that ACCNT can improve the yield of a one-million transistor chip from 0% (conventional CNT design) up to 99% at a cost of 3.3× area overhead if the fraction of semiconducting CNTs is improved to 99.9%.

Impact of density on the hydraulics of peat filters

Peat filters have been used to treat septic tank effluents from domestic and commercial sources, landfill leachate, and acid mine drainage. A better understanding of the hydraulics and impact of the organic loading on these types of systems will enhance the application of peat filter systems. This paper presents the results of a field study to evaluate the hydraulics of a peat filter used to treat the septic tank effluent from a public school west of Ottawa, Ontario, Canada. The filter was instrumented with tensiometers and transducers to monitor the pore-water pressures in response to a pulse of septic tank effluent. Samples of peat were collected to determine the dry density profile with depth. The soil moisture retention curve, effective porosity, and hydraulic conductivity as a function of dry density were determined in laboratory experiments. A one-dimensional unsaturated flow model was used to predict the pressure response due to a pulse. Two model scenarios were evaluated to demonstrate the impact of density variations on model simulations. Model simulations that accounted for dry density variations with depth measured in the field more accurately simulated the pressure responses measured in the field.Key words: unsaturated flow, peat, filters, septic, modelling, density.

Ignition and anomalous transport processes

Using a modified version of the 1½-D BALDUR transport code, important aspects of the time evolution of D-T plasmas in a compact, high field tokamak of the Ignitor type with strong Ohmic heating are investigated. For the canonical electron heat transport, a generalization of the Coppi-Mazzucato-Gruber diffusion for axisymmetric toroidal geometry is assumed as well as alpha particle heating contributions; this reproduces the power dependent degradation of confinement observed in present-day auxiliary heated experiments. Anomalous ion heat conductivity is based on the existence of the ηi mode halfway out in the discharge, with an assumed spatial dependence of the transport magnitude superimposed on a parameter scaling related to wave breaking in the direction perpendicular to the magnetic field. The particle density profiles are held fixed, and convective energy fluxes are ignored. Results from three model examples associated with the set of transport coefficients are considered, and the impact of variations in density, conductivity magnitudes, resistivity, plasma impurity level and flux surface equilibrium configuration on the approach to ignition is discussed.