Physics of Particle Detection

In this review the basic interaction mechanisms of charged and neutral particles are presented. The ionization energy loss of charged particles is fundamental to most particle detectors and is therefore described in more detail. The production of electromagnetic radiation in various spectral ranges leads to the detection of charged particles in scintillation, Cherenkov and transition radiation counters. Photons are measured via the photoelectric effect, Compton scattering or pair production, and neutrons through their nuclear interactions. A combination of the various detector methods helps to identify elementary particles and nuclei. At high energies absorption techniques in calorimeters provide additional particle identification and an accurate energy measurement.Comment: 32 pages, LaTeX, 21 figure

Tumour Therapy with Particle Beams

Photons are exponentially attenuated in matter producing high doses close to the surface. Therefore they are not well suited for the treatment of deep seated tumours. Charged particles, in contrast, exhibit a sharp increase of ionisation density close to the end of their range, the so-called Bragg-peak. The depth of the Bragg-peak can be adjusted by varying the particle's energy. In parallel with the large energy deposit the increase in biological effectiveness for cell killing at the end of the range provides an ideal scalpel for the surgeon effectively without touching the surface tissue. Consequently proton therapy has gained a lot of ground for treating well localized tumours. Even superior still are heavy ions, where the ionisation pattern is increased by the square of their charge.Comment: 12 pages, Latex, 11 figure

A Developmental Organization for Robot Behavior

This paper focuses on exploring how learning and development can be structured in synthetic (robot) systems. We present a developmental assembler for constructing reusable and temporally extended actions in a sequence. The discussion adopts the traditions of dynamic pattern theory in which behavior is an artifact of coupled dynamical systems with a number of controllable degrees of freedom. In our model, the events that delineate control decisions are derived from the pattern of (dis)equilibria on a working subset of sensorimotor policies. We show how this architecture can be used to accomplish sequential knowledge gathering and representation tasks and provide examples of the kind of developmental milestones that this approach has already produced in our lab

Hadronic Structure Functions of the Photon Measured at LEP

The measurements of hadronic structure functions of the photon based on the reaction ee --> ee gamma^(*)(P^2) gamma^*(Q^2)--> ee hadrons are discussed.Comment: 9 pages, 6 figures, Conference contribution to DIS 2000, 25-30 April 2000, Liverpool, England, to appear in the Proceeding

CAD-based 3-D object recognition

Journal ArticleWe propose an approach to 3-D object recognition using CAD-based geometry models for freeform surfaces. Geometry is modeled with rational B-splines by defining surface patches and then combining these into a volumetric model of the object. Characteristic features are then extracted from this model and subjected to a battery of tests to select an "optimal" subset of surface features which are robust with respect to the sensor being used (e.g. laser range finder versus passive stereo) and permit recognition of the object from any viewing position. These features are then organized into a "strategy tree" which defines the order in which the features are sought, and any corroboration required to justify issuing a hypotheses. We propose the use of geometric sensor data integration techniques as a means for formally selecting surface features on free-form objects in order to build recognition strategies. Previous work has dealt with polyhedra and generalized cylinders, whereas here we propose to apply the method to more general surfaces

High-level planning for dextrous manipulation

Journal ArticleThe development of mechanical end effectors capable of dextrous manipulation is a rapidly growing and quite successful field of research. It has in some sense put the focus on control issues, in particular, how to control these remarkably anthropomorphic manipulators to perform the deft movement that we take for granted in the human hand. The objective of this paper is the creation of a framework within which constraints involving the manipulator, the object, and the hand/object interaction can be exploited to direct a goal oriented manipulation. The analysis here is targeted for the Utah/MIT dextrous manipulator, but will support any general purpose dextrous manipulation system?

Task defined grasp force solutions

Journal ArticleForce Control for dextrous manipulation has been approached algebraically with a great deal of success, however, the computational burden created when such approaches are applied to grasps consisting of many contacts is prohibitive. This paper describes a procedure which restricts the complexity of the algebraic system of equations, and makes use of mathematical programming techniques to select a solution which is optimal with respect to an objective function. The solution is constrained by contact surface friction properties and the kinematic limitations of the hand. The application of the procedure to the selection of minimal internal grasp forces which allow the application of task defined external forces is described. Examples of the procedure are presented