167 research outputs found
Physiological aspects of educational training adaptation of students
20 healthy male and female students of Artsakh State University aged 18-20 years have participated in an experiment to study the mechanisms of training adaptation. Surveys were conducted during the academic semester in 2 stages: the non-examination period (March-April) - Monday and Friday, before and after school and during the examination period (May-June) - before and after the exam. In order to study the impact of mental stress a survey was also conducted among students once they complete mental or intellectual Eysenck test. A psychological testing of students was carried out to identify the level of intelligence (IQ) by Eysenck, personal and situational anxiety by Spielberger and health, activity, mood by SAN (HAM) questionnaire. Basic hemodynamic parameters were measured: heart rate, systolic and diastolic blood pressure. ECG examination was conducted using R.M. Baevsky's cardio-ervalography method. Comparative analysis of the dynamics of the studied parameters showed that the process of adaptation of students to the teaching load is accompanied by periods of decline during non-examination period, more vividly expressed when doing mental or intellectual work, and tension of the studied parameters during the examination period
Transfer ionization and its sensitivity to the ground-state wave function
We present kinematically complete theoretical calculations and experiments
for transfer ionization in HHe collisions at 630 keV/u. Experiment and
theory are compared on the most detailed level of fully differential cross
sections in the momentum space. This allows us to unambiguously identify
contributions from the shake-off and two-step-2 mechanisms of the reaction. It
is shown that the simultaneous electron transfer and ionization is highly
sensitive to the quality of a trial initial-state wave function
Emission Spectrum of a Dipole in a Semi-infinite Periodic Dielectric Structure: Effect of the Boundary
The emission spectrum of a dipole embedded in a semi-infinite photonic
crystal is calculated. For simplicity we study the case in which the dielectric
function is sinusoidally modulated only along the direction perpendicular to
the boundary surface plane. In addition to oscillations of the emission rate
with the distance of the dipole from the interface we also observed that the
shape of the emission spectrum srongly depends on the \em initial \em phase
of the dielectric modulation. When the direction of light propagation inside
the periodic structure is not normal to the boundary surface plane we observed
aditional singularities in the emission spectrum, which arise due to different
angle-dependence of the Bragg stop-band for and polarizations.Comment: 14 pages, 6 figures, to appear in Phys Rev
A metallic phase in quantum Hall systems
The electronic eigenstates of a quantum Hall (QH) system are chiral states.
Strong inter-Landau-band mixings among these states can occur when the
bandwidth is comparable to the spacing of two adjacent Landau bands. We show
that mixing of localized states with opposite chirality can delocalize
electronic states. Based on numerical results, we propose the existence of a
metallic phase between two adjacent QH phases and between a QH phase and the
insulating phase. This result is consistent with non-scaling behaviors observed
in recent experiments on quantum-Hall-liquid-to-insulator transition.Comment: 5 pages, 3 figures. Will be published in Phys. Rev. Let
Dynamics of Boltzmann Q-Learning in Two-Player Two-Action Games
We consider the dynamics of Q-learning in two-player two-action games with a
Boltzmann exploration mechanism. For any non-zero exploration rate the dynamics
is dissipative, which guarantees that agent strategies converge to rest points
that are generally different from the game's Nash Equlibria (NE). We provide a
comprehensive characterization of the rest point structure for different games,
and examine the sensitivity of this structure with respect to the noise due to
exploration. Our results indicate that for a class of games with multiple NE
the asymptotic behavior of learning dynamics can undergo drastic changes at
critical exploration rates. Furthermore, we demonstrate that for certain games
with a single NE, it is possible to have additional rest points (not
corresponding to any NE) that persist for a finite range of the exploration
rates and disappear when the exploration rates of both players tend to zero.Comment: 10 pages, 12 figures. Version 2: added more extensive discussion of
asymmetric equilibria; clarified conditions for continuous/discontinuous
bifurcations in coordination/anti-coordination game
Conductance distribution between Hall plateaus
Mesoscopic fluctuations of two-port conductance and four-port resistance
between Hall plateaus are studied within a realistic model for a
two-dimensional electron gas in a perpendicular magnetic field and a smooth
disordered potential. The two-port conductance distribution is concave
between and and is nearly flat between and . These
characteristics are consistent with recent observations. The distribution is
found to be sharply peaked near the end-points and . The
distribution functions for the three independent resistances in a four-port
Hall bar geometry are, on the other hand, characterized by a central peak and a
relatively large width.Comment: 11 pages, 5 ps figures, submitted to Phys. Rev.
Scaling Properties of Conductance at Integer Quantum Hall Plateau Transitions
We investigate the scaling properties of zero temperature conductances at
integer quantum Hall plateau transitions in the lowest Landau band of a
two-dimensional tight-binding model. Scaling is obeyed for all energy and
system sizes with critical exponent nu =7/3 . The arithmetic average of the
conductance at the localization-delocalization critical point is found to be
_c = 0.506 e^2 / h, in agreement with the universal longitudinal conductance
predicted by an analytical theory. The probability distribution of the
conductance at the critical point is broad with a dip at small G.Comment: 4 pages, 3 postscript figures, Submitted to PR
Two-terminal conductance fluctuations in the integer quantum Hall regime
Motivated by recent experiments on the conductance fluctuations in mesoscopic
integr quantum Hall systems, we consider a model in which the Coulomb
interactions are incorporated into the picture of edge-state transport through
a single saddle-point. The occupancies of `classical' localised states in the
two-dimensional electron system change due to the interactions between
electrons when the gate voltage on top of the device is varied. The
electrostatic potential between the localised states and the saddle-point
causes fluctuations of the saddle-point potential and thus fluctuations of the
transmission probability of edge states. This simple model is studied
numerically and compared with the observation.Comment: 6 pages with 3 figures. To be published in Physical Review
- …