Unassisted System Research Articles

Design and Evaluation of a Haptic Computer-Assistant for Telemanipulation Tasks

This paper introduces a computer-assisted teleoperation system, where the control over the teleoperator is shared between a human operator and computer assistance in order to improve the overall task performance. Two units, an action recognition and an assistance unit are introduced to provide context-specific assistance. The action recognition unit can evaluate haptic data, handle high sampling rates, and deal with human behavior changes caused by the actived haptic assistance. Repairing of a broken hard drive is selected as scenario and three different task-specific assistance functions are designed. The overall computer-assisted teleoperation system is evaluated in two steps: first, the performance of the action recognition unit is evaluated and then, the performance of the integrated computer-assisted teleoperation system is compared with an unassisted system by means of a user study with 15 participants. Overall action recognition rates of about 65% are achieved. Multivariate paired comparisons show that the computer-assisted teleoperation system significantly reduces the human effort and damage possibility compared with a teleoperation system without assistance.

The dissociation of low energy 1,2-propanediol ions: an intriguing mechanism revisited

The fascinating unimolecular chemistry of ionized 1,2-propanediol, CH 3C(H)OHCH 2OH ·+, 1, has been re-examined using computational chemistry (ab initio MO and density functional theories) in conjunction with modern tandem mass spectrometric and 13C labelling experiments. The calculations allow a considerable simplification of a previously proposed complex mechanism (Org. Mass Spectrom., 23 (1988) 355). Again, the central intermediates are proposed to be stable hydrogen bridged ion—dipole complexes, but our present calculations indicate that the key transformation now is the rearrangement CH 3C(H)OH +···O(H)-CH 2 . → CH 3C(H)OH +··· .OCH 3, which can best be viewed as the cation-catalyzed 1,2-hydrogen shift .CH 2OH → CH 3O ., a rearrangement which does not occur so easily in the unassisted system. Another important process is the electron transfer CH 3C(H)O···CH 3OH ·+ → OCH(CH 3) ·+···O(H)CH 3 which allows proton transfer to generate CH 3OH 2 + + CH 3CO .. Other dissociation processes (loss of CH 3 ., H 2O, H 2O + CH 3 ., H 2O + CH 4) are interpreted in terms of Bohme's ‘methyl cation shuttle’ (J. Am. Chem. Soc., 118 (1996) 4500) taking place in ion-dipole complexes. The most stable intermediate is the hydrogen bridged ion-dipole complex CH 2CHOH .+···O(H)CH 3, which is the reacting configuration for loss of methanol.