327 research outputs found
Non-ergodic Intensity Correlation Functions for Blinking Nano Crystals
We investigate the non-ergodic properties of blinking nano-crystals using a
stochastic approach. We calculate the distribution functions of the time
averaged intensity correlation function and show that these distributions are
not delta peaked on the ensemble average correlation function values; instead
they are W or U shaped. Beyond blinking nano-crystals our results describe
non-ergodicity in systems stochastically modeled using the Levy walk framework
for anomalous diffusion, for example certain types of chaotic dynamics,
currents in ion-channel, and single spin dynamics to name a few.Comment: 5 pages, 3 figure
Sign-time distribution for a random walker with a drifting boundary
We present a derivation of the exact sign-time distribution for a random
walker in the presence of a boundary moving with constant velocity.Comment: 5 page
The impact of environmental effects on AGN: a decline in the incidence of ionized outflows
AGN have been generally considered to be less frequent in denser environments
due to the lower number of galaxy-galaxy interactions and/or the removal of
their gas-rich reservoirs by the dense intergalactic medium. However, recent
observational and theoretical works suggest that the effect of ram-pressure
stripping might reduce the angular momentum of their gas, causing it to infall
towards the super massive black hole (SMBH) at their centre, activating the AGN
phase. In this work we explore the connection between environment and nuclear
activity by evaluating the variation in the incidence of ionized outflows in
AGN across different environments. We select a sample of optical AGN
from the Sloan Digital Sky Survey Data Release 13 that we match with the group
catalogue from Lim et al. 2017. We further probe their environment through the
projected distance to the central galaxy of the group/cluster and the projected
surface density to the 5th neighbour (). We find that at lower masses
(M), the fraction of ionized outflows is significantly
lower in satellite (%) than in isolated (%) AGN. The fraction of
outflows in all satellite AGN decreases towards closer distances to the
central, whereas only the lower-mass ones display a significant decline with
. Although this study does not include AGN in the densest regions of
galaxy clusters, our findings suggest that AGN in dense environments accrete
less gas than those in the field potentially due to the removal of the gas
reservoirs via stripping or starvation, consistent with a negative connection
between environment and AGN activity. We propose that the observed change in
the incidence of outflows towards denser regions of groups and clusters could
contribute to the higher gas metallicities of cluster galaxies compared to
field ones, especially at lower masses.Comment: 9 pages, 6 figures, Accepted for publication in Astronomy and
Astrophysic
Large-Deviation Functions for Nonlinear Functionals of a Gaussian Stationary Markov Process
We introduce a general method, based on a mapping onto quantum mechanics, for
investigating the large-T limit of the distribution P(r,T) of the nonlinear
functional r[V] = (1/T)\int_0^T dT' V[X(T')], where V(X) is an arbitrary
function of the stationary Gaussian Markov process X(T). For T tending to
infinity at fixed r we find that P(r,T) behaves as exp[-theta(r) T], where
theta(r) is a large deviation function. We present explicit results for a
number of special cases, including the case V(X) = X \theta(X) which is related
to the cooling and the heating degree days relevant to weather derivatives.Comment: 8 page
A new method for measuring and calibrating cinema audio systems for optimal sound quality
The aim of this research is to utilize new methodologies and technology in order to gain insight into how the modern cinema audio system could be calibrated to provide improved audio performance. To this end, both objective and subjective measurements were developed to better understand the audio preferences of listeners, the requirements of the audio systems inclusive of the acoustic environment, and how the two are related.
Part of the data for this research was derived from a survey of re-recording mixers regarding their use and opinion of the current SMPTE standard. The survey confirmed anecdotal information suggesting that re-recording mixers use high-end pre-emphasis to compensate for the severe roll-off induced by the SMPTE X-curve. It is also noted that the re-recording mixers' opinions of how well their mix translates from dub-stage to cinema is correlated to how many years they have spent in the industry.
The aim of this research is to utilize new methodologies and technology in order to gain insight into how the modern cinema audio system could be calibrated to provide improved audio performance. To this end, both objective and subjective measurements were developed to better understand the audio preferences of listeners, the requirements of the audio systems inclusive of the acoustic environment, and how the two are related.
Part of the data for this research was derived from a survey of re-recording mixers regarding their use and opinion of the current SMPTE standard. The survey confirmed anecdotal information suggesting that re-recording mixers use high-end pre-emphasis to compensate for the severe roll-off induced by the SMPTE X-curve. It is also noted that the re-recording mixers' opinions of how well their mix translates from dub-stage to cinema is correlated to how many years they have spent in the industry.
To further understand listener preference to in-room responses curves, a series of listening tests utilizing the BRS system were conducted using various sized cinemas, seating positions within the cinemas, audio tracks (including those mixed on a SMPTE calibrated dub-stage) and target curves. The overwhelming outcome was that regardless of cinema size, seating position or audio track utilized; the "curve" that listeners preferred is a relatively flat 0.9dB/octave slope with a 6.5dB bass boost below 105Hz and a -2.5dB roll off above 2.5kHz. Of the 5 target curves presented, the SMPTE X-curve place fourth with scores very near the low-rated perceptual anchor. This calls into question the notion of the X-curve providing "ideal" translation between dub-stage and cinema and in fact, challenges the concept of translation all together.
Research was completed in an effort to identifying the number of microphone positions required, along with their placement, in order to accurately capture a cinema's response for calibration purposes. A novel experiment utilizing anechoic loudspeaker data as a guideline for
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analysis demonstrated that, with proper data, the number of microphones and their positions plays a less critical factor in determining the room response. The collected data shows that even with as few as 4 microphones at varied positions, the resultant room response will trend towards the anechoic data above 1kHz. From around 300Hz to 1kHz, there is evidence of seat effects that may be resolved through randomizing the microphone heights. Below 300Hz, the room becomes the dominating factor and more than 5 microphone positions will be required to properly identify any problems
Critical dimensions of the diffusion equation
We study the evolution of a random initial field under pure diffusion in
various space dimensions. From numerical calculations we find that the
persistence properties of the system show sharp transitions at critical
dimensions d1 ~ 26 and d2 ~ 46. We also give refined measurements of the
persistence exponents for low dimensions.Comment: 4 pages, 5 figure
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