On a Powder Consolidation Problem
The problem of the consolidation of an aerated fine powder under gravity is considered. The industrial relevance of the problem is discussed and a mathematical model is introduced. The mathematical structure is that of a coupled system for three unknowns, pressure, stress, and height of the powder in the (axisymmetric) bunker containing it. The system itself consists of a parabolic PDE, an ODE, and an integral equation determining a free boundary corresponding to the height of the powder. Existence and uniqueness of a solution is established. A numerical method based on a formulation of the semidiscretized problem as an index 1 DAE is proposed and implemented. The feasibility of the approach is illustrated by computational results.
The effect of the gaseous phase on pressures in a cylindrical silo
Abstract When a fine powder is filled into a silo the gas trapped by the particles will take an appreciable time to escape and will cause an increase in the lateral pressure on the walls of the silo. A mathematical analysis of the problem is presented and numerical solutions are provided. The theoretical results are compared with model measurements and the implications for hopper design are discussed.
A Method For Geometric Processing Of Optical Satellite Images Using Automatically Determined Ground Control Information
Orthorectification is the process to convert imagery into map-accurate forms by removing sensor, satellite motion and terrain related geometric distortions from raw imagery and is one of the main pre-processing steps for application oriented evaluations. Although optical satellite data of high geometric resolution can be orthorectified to absolute geometric accuracies of about 5 m to several hundred meters - depending on the satellite mission - using the metadata information from the satellite data providers (e.g. satellite position, velocity and attitude at any instant of time during data acquisition, camera internal geometry), there is still a need to improve the geometric accuracy by using Ground Control Points (three dimensional real world coordinates, which have to be identified in the satellite image). The manual measurement of such Ground Control Points by operators is a time consuming work leading to a cost and time ineffective project completion. This paper proposes a method and procedure to automatically extract Ground Control Points from already existing orthorectified images of superior geometric quality (reference images), which are used to improve the geometric accuracy as well as to produce at least consistent data sets.