This paper brings together two important but hitherto largely unrelated areas of the forecasting literature, density forecasting and forecast combination. It proposes a simple data-driven approach to direct combination of density forecasts using optimal weights. These optimal weights are those weights that minimise the ‘distance’, as measured by the Kullback-Leibler Information Criterion, betwe...

This experimental study shows the validity of Sheridan’s method in determining plasma density in low pressure, weakly magnetized, RF plasmas using ion saturation current data measured by a planar Langmuir probe. The ion density derived from Sheridan’s method which takes into account the sheath expansion around the negatively biased probe tip, presents a good consistency with the electron densit...

Real-valued functions of a real variable which are continuous with respect to the density topology on both the domain and the range are called density continuous. A typical continuous function is nowhere density continuous. The same is true of a typical homeomorphism of the real line. A subset of the real line is the set of points of discontinuity of a density continuous function if and only if...

As density functional theory conventionally assumes that the density of a chosen model system (e.g., the Kohn-Sham system) is the same as the exact one, one might expect that approximations to the exact density introduce supplementary errors by falsifying the density. In fact, this is not true: by modeling the exchange-correlation holes for all densities, density functional approximations avoid...

True Impostors offers an efficient method for adding a large number of simple models to any scene without having to render a large number of polygons. The technique utilizes modern shading hardware to perform ray casting into texture defined volumes. To achieve this, a virtual screen is set up in texture space for each impostor and inherits the same camera dependent orientation as the impostor....

The Renaissance architect, moral philosopher, cryptographer, mathematician, Papal adviser, painter, city planner and land surveyor Leon Battista Alberti provided the theoretical foundations of modern perspective geometry. Alberti’s work on perspective exerted a powerful influence on painters of the stature of Albrecht Dürer, Leonardo da Vinci and Piero della Francesca. But his Della pittura of ...