Telerobotics: problems and research needs

With major emphasis on simulation, a university laboratory telerobotics facility permits problems to be approached by groups of graduate students. Helmet-mounded displays provide realism; the slaving of the display to the human operator's viewpoint gives a sense of `telepresence' that may be useful for prolonged tasks. Using top-down 3-D model control of distant images allows distant images to be reduced to a few parameters to update the model used for display to the human operator in a preview model to circumvent, in part, the communication delay. Also, the model can be used as a format for supervisory control and permit short-term local autonomous operations. Image processing algorithms can be made simpler and faster without trying to construct sensible images from the bottom. Control studies of telerobots lead to preferential manual control modes and, in this university environment, to basic paradigms for human motion and thence, perhaps, to redesign of robotic control, trajectory path planning, and rehabilitation prosthetics. Speculation as to future industrial drives for this telerobotic field suggests efficient roles for government agencies such as NASA     

The evolution of moderately close and moderately wide binaries

We discuss evolutionary processes in binaries where the primary becomes a red giant with a deep convective envelope before it fills its Roche lobe. Such binaries (late Case B or late Case C, if they evolve conservatively) ought to suffer drastic mass transfer, on a hydrodynamic timescale. In some circumstances this may lead to a common envelope, spiral-in, and finally either a very short-period binary or coalescence. But there appear to be other circumstances in which the outcome is an ordinary Algol, or a wide binary with a white dwarf companion as in Barium stars and some symbiotics. We try to demonstrate that stellar-wind mass loss, enhanced one or two orders of magnitude by tidal interaction with a companion, can vitally affect the approach to RLOF, and indeed may prevent RLOF in binaries with periods over 1000 d. Such mass loss is probably accompanied by angular momentum loss, by magnetic braking combined with tidal friction. The result is that it will not be easy to predict definitively the outcome of evolution in a given zero-age binary.     

Three R's of radar: recollections, remonstrances, and ruminations

The author describes his experiences in the early days in radar, working on a radar landing system called ground control approach (GCA). He discusses for the disparity between the short time from conception to worldwide deployment of that system and today's 10- to 15-year cycle, as well as GCA's high (100%) availability, and identifies the factors responsible. The author goes on to argue that the radar community has a history of overselling what radar can do. He forecasts future trends and concludes with a few things he has learned over the years     

Ferri project: technologies to support advanced transportationsystems

The authors present the plan under discussion in Italy between the government entities and Aeritalia, the leading Italian aerospace company, for the technology development needed to support advanced transportation systems. The plan centers around the following areas: thermal protection and control; advanced structures and materials; guidance, navigation, and control; and tests and computation methods. Experimental activities needed to support the development of such systems and the difficulties involved are examined     

Effect of wall suction on leading edge contamination

This paper is devoted to an experimental study of swept wing leading edge contamination by the turbulence emanating from the wing-wall junction. The main objective is to delay the contamination onset by applying surface suction along the attachment line. Two series of experiments are described; the first one was performed in a small wind tunnel at CERT ONERA, the second one was carried out in the F2 wind tunnel at Le Fauga Mauzac centre. Hot film measurements showed that leading edge contamination could be delayed up to very large Reynolds numbers. We also studied the behaviour of the relaminarized boundary layer downstream of the sucked region, along the span as well as in the chordwise direction.     

Problems related to non-linear variations of surface tension

Generally, the tension at a liquid/gas interface is decreasing with temperature. For aqueous solution of alcohol, alkylammonium chloride in water, some binary metallic alloys and nematic liquid crystals the surface tension presents an extremum as a function of temperature. The influence of this property on the hydrodynamic stability and on the surface tension induced flows is studied as well theoretically as experimentally.     

Laboratory experiments of magnetospheric interest

Space-related laboratory experiments can play an important role as a complement to observations and active experiments in the magnetosphere. Excluding laboratory experiments for mere developing or testing of techniques for space experiments, we may distinguish between two major types: (1) partial scale model experiments and (2) experiments for clarifying basic plasma physical processes known or expected to be important in the magnetosphere (but without the ambition to simulate actual space configurations). The limitations and potentialities of both types are discussed and examples of experiments are given. It is concluded that there should be an increasing need for the experiments of the second type. In particular, they are needed for the clarification of the response of a thin plasma to electric fields and its ability to carry electric currents. This encompasses such key questions as the nature and role of anomalous resistivity (and electron runaway in its presence), the possible formation of double layers (and the acceleration processes associated with them) and rapid dissipation of magnetic-field energy.     

Frame Synchronization in the Presence of Errors and Erasures

An approach to the problem of achieving frame synchronization in the presence of jamming or other large disturbances is presented. It is assumed that the disturbance can be detected at the receiver, which then erases the corresponding bits and passes this information to the synchronizer. A synchronization algorithm designed to operate in the presence of both erasures and background errors is described and evaluated for a representative set of system parameters. This algorithm is shown to have a significant advantage over an algorithm which does not use the location information inherent in the erasure model.