7 research outputs found
Quantum-Mechanical Histories and the Uncertainty Principle: I.Information-Theoretic Inequalities
This paper is generally concerned with understanding how the uncertainty
principle arises in formulations of quantum mechanics, such as the decoherent
histories approach, whose central goal is the assignment of probabilities to
histories. We first consider histories characterized by position or momentum
projections at two moments of time. Both exact and approximate (Gaussian)
projections are studied. Shannon information is used as a measure of the
uncertainty expressed in the probabilities for these histories. We derive a
number of inequalities in which the uncertainty principle is expressed as a
lower bound on the information of phase space distributions derived from the
probabilities for two-time histories. We go on to consider histories
characterized by position samplings at moments of time. We derive a lower
bound on the information of the joint probability for position samplings.
Similar bounds are derived for histories characterized by samplings of other
variables. All lower bounds on the information of histories have the general
form , where is a volume element of
history space, which we define, and is the volume of that space probed by
the projections. We thus obtain a concise and general form of the uncertainty
principle referring directly to the histories description of the system, and
making no reference to notions of phase space.Comment: 40 pages (revised uncorrupted version), Imperial College Preprint IC
92-93/2
Tactile device based on opto-mechanical actuation of liquid crystal elastomers
Nematic elastomers are promising materials for the fabrication of actuators due to their ability to reversibly contract and expand during phase transitions triggered by external stimuli. Thus, actuation can be produced on demand, forcing these phase changes. Here, we present a refreshable tactile device based on the opto-mechanical properties of liquid crystalline elastomers (LCE) with the capability to represent Braille characters and simplified graphical information. The actuators designed are based on the use of the stress gradient generated in the elastomer under illumination to exert a force on movable components. Additionally, hardware implementation and a communication software interface were developed to provide end users with a complete solution. Displacements of 0.8 mm with measured forces of up to 40 mN were reached without material degradation, proving not only the viability of the device but also the potential applications of this type of actuator.Scopu
Nematic opto-mechanical actuators for the fabrication of refreshable tactile systems
Nematic elastomers are promising materials for the fabrication of actuators due to their ability to reversibly contract and expand during phase transitions triggered by external stimuli. We present a refreshable tactile system based on the opto-mechanical properties of liquid-crystalline elastomers (LCE) composites, with the capability to represent Braille characters and graphic information. The actuators designed are based on the stress gradient generated in the elastomer under illumination to exert a force on movable components. Hardware implementation and communication software interface were developed too to provide end users with a complete solution. First tests prove not only the viability of the device, but also the potential applications of this type of actuators.Scopu