21,057 research outputs found
Voltage-Induced Friction with Application to Electrovibration
Due to the growing interest in robotic and haptic applications, voltage-induced friction has rapidly gained in importance in recent years. However, despite extensive experimental investigations, the underlying principles are still not sufficiently understood, which complicates reliable modeling. We present a macroscopic model for solving electroadhesive frictional contacts which exploits the close analogy to classical adhesion theories, like Johnson-Kendall-Roberts (JKR) and Maugis, valid for electrically neutral bodies. For this purpose, we recalculate the adhesion force per unit area and the relative surface energy from electrostatics. Under the assumption of Coulomb friction in the contact interface, a closed form equation for the friction force is derived. As an application, we consider the frictional contact between the fingertip and touchscreen under electrovibration in more detail. The results obtained with the new model agree well with available experimental data of the recent literature. The strengths and limitations of the model are clearly discussed.TU Berlin, Open-Access-Mittel – 201
Characterisation of the potential of frequency modulation and optical feedback locking for cavity-enhanced absorption spectroscopy
A combination of optical feedback self-locking of a continuous-wave
distributed feedback diode laser to a V-shaped high finesse cavity, laser phase
modulation at a frequency equal to the free spectral range of the V-cavity and
detection of the transmitted laser beam at this high modulation frequency is
described for possible application in cavity-enhanced absorption
spectroscopy.In order to estimate an absorbance baseline noise of laser
intensity and frequency modulated light triplet passed through the V-cavity in
open air, a 1.5-cm long optical cell filled by C2H2 at low pressure was placed
behind the cavity output mirror. The performance of the setup was evaluated
from the experimental bandwidth normalised relative intensity noise on the
cavity output and the frequency modulation absorption signals induced by C2H2
absorption in the 1.5-cm cell. From these data we estimate that the
noise-equivalent absorption sensitivity of 2.1*10^-11 cm^-1 Hz^-1/2 by a factor
of 11.7 above a shot-noise limit can be achieved for C2H2 absorption spectra
extracted from the heterodyne beat signals recorded at the transmission maxima
intensity peaks of the successive TEM00 resonances.Comment: 18 pages, 8 figures, submitted to Appl. Phys. B 28.07.201
Collective cyclotron motion of the relativistic plasma in graphene
We present a theory of the finite temperature thermo-electric response
functions of graphene, in the hydrodynamic regime induced by electron-electron
collisions. In moderate magnetic fields, the Dirac particles undergo a
collective cyclotron motion with a temperature-dependent relativistic cyclotron
frequency proportional to the net charge density of the Dirac plasma. In
contrast to the undamped cyclotron pole in Galilean-invariant systems (Kohn's
theorem), here there is a finite damping induced by collisions between the
counter-propagating particles and holes. This cyclotron motion shows up as a
damped pole in the frequency dependent conductivities, and should be readily
detectable in microwave measurements at room temperature. We also discuss the
large Nernst effect to be expected in graphene.Comment: 16 pages, 2 figures; calculation of giant Nernst effect in graphene
adde
Walking the Talk in Multiparty Bargaining: An Experimental Investigation
We study the framing effects of communication in multiparty bargaining. Communication has been shown to be more truthful and revealing than predicted in equilibrium. Because talk is preference-revealing, it may effectively frame bargaining around a logic of fairness or competition, moving parties on a path toward or away from equal-division agreements. These endogenous framing effects may outweigh any overall social utility effects due to the mere presence of communication. In two experiments, we find that non-binding talk of fairness within a three-party, complete-information game leads toward off-equilibrium, equal division payoffs, while non-binding talk focusing on competitive reasoning moves parties away from equal divisions. Our two studies allow us to demonstrate that spontaneous within-game dialogue and manipulated pre-game talk lead to the same results.communication, fairness, bargaining
- …