A nonlinear equation for ionic diffusion in a strong binary electrolyte

The problem of the one dimensional electro-diffusion of ions in a strong binary electrolyte is considered. In such a system the solute dissociates completely into two species of ions with unlike charges. The mathematical description consists of a diffusion equation for each species augmented by transport due to a self consistent electrostatic field determined by the Poisson equation. This mathematical framework also describes other important problems in physics such as electron and hole diffusion across semi-conductor junctions and the diffusion of ions in plasmas. If concentrations do not vary appreciably over distances of the order of the Debye length, the Poisson equation can be replaced by the condition of local charge neutrality first introduced by Planck. It can then be shown that both species diffuse at the same rate with a common diffusivity that is intermediate between that of the slow and fast species (ambipolar diffusion). Here we derive a more general theory by exploiting the ratio of Debye length to a characteristic length scale as a small asymptotic parameter. It is shown that the concentration of either species may be described by a nonlinear integro-differential equation which replaces the classical linear equation for ambipolar diffusion but reduces to it in the appropriate limit. Through numerical integration of the full set of equations it is shown that this nonlinear equation provides a better approximation to the exact solution than the linear equation it replaces.Comment: 4 pages, 1 figur

From screen to shelf : perspectives on independent distribution

Of the three broadly defined sectors which make up the British film industry, the academy has tended to focus its attention on production and exhibition, giving comparatively short shrift to matters of distribution. Certainly, the current role of the independent distributor in the UK is, to say the least, under-examined. Academic interest in the work of the distributor tends to stop at their marketing campaigns and, as an extension, their attempts to connect with and sell a film to the public. The relationship between the distributor and the exhibitor, and the process of negotiation which takes place between them, have been largely ignored. Since around 1999, with the burgeoning of the DVD market, UK distributors have gradually expanded their home entertainment divisions, becoming as invested in the retail sector as is the music industry and devoting as much energy (if not as much money) to a film’s release on DVD as to its theatrical launch. Again, academic material on the video and DVD industries is scant, with those studies which do exist, such as Paul McDonald’s Video and DVD Industries (2007), focusing primarily on the US and the major studios

Effects of wing leading-edge flap deflections on subsonic longitudinal aerodynamic characteristics of a wing-fuselage configuration with a 44 deg swept wing

An investigation was conducted to determine the effects of wing leading-edge flap deflections on the subsonic longitudinal aerodynamic characteristics of a wing-fuselage configuration with a 44 deg swept wing. The tests were conducted at Mach numbers from 0.40 to 0.85, corresponding to Reynolds numbers (based on wing mean geometric chord) of 2.37 x 1,000,000 to 4.59 x 1,000,000 and at angles of attack from -3 deg to 22 deg. The configurations under study included a wing-fuselage configuration and a wing-fuselage-strake configuration. Each configuration had multisegmented, constant-chord leading-edge flaps which could be deflected independently or in various combinations

Studies of various factors affecting drag due to lift at subsonic speeds

Drag and lift of thin swept wings at subsonic speed

PRESSURE DISTRIBUTIONS OVER THE FORWARD PORTION OF THE PROJECT FIRE SPACE-VEHICLE CONFIGURATION AT MACH NUMBERS FROM 0.25 TO 0.60

Pressure distributions over forward portion of project fire space-vehicle configuration at subsonic spee

A dual-beam actinic light source for photosynthesis research

Simulation of photosynthetic process in plants is accomplished by using two separate and identical optical channels that provide independently adjustable wavelengths (filters), shutter sequencing, and control intensity of illumination. In addition to experiments using electron paramagnetic resonance spectroscopy, system may be applicable to other types of research in photosynthetic field

Magnetic shell enhancements during magnetic disturbances

Magnetic shell enhancements during magnetic field disturbances from Langmuir probe observations of electron density on Ariel I satellit