3,235 research outputs found
Optimization of Green-Times at an Isolated Urban Crossroads
We propose a model for the intersection of two urban streets. The traffic
status of the crossroads is controlled by a set of traffic lights which
periodically switch to red and green with a total period of T. Two different
types of crossroads are discussed. The first one describes the intersection of
two one-way streets, while the second type models the intersection of a two-way
street with an one-way street. We assume that the vehicles approach the
crossroads with constant rates in time which are taken as the model parameters.
We optimize the traffic flow at the crossroads by minimizing the total waiting
time of the vehicles per cycle of the traffic light. This leads to the
determination of the optimum green-time allocated to each phase.Comment: 8 pages, 6 eps figures, more explanation added. To appear in EPJ
Asymptotics of Randomly Weighted u- and v-statistics: Application to Bootstrap
This paper is mainly concerned with asymptotic studies of weighted bootstrap
for u- and v-statistics. We derive the consistency of the weighted bootstrap u-
and v-statistics, based on i.i.d. and non i.i.d. observations, from some more
general results which we first establish for sums of randomly weighted arrays
of random variables. Some of the results in this paper significantly extend
some well-known results on consistency of u-statistics and also consistency of
sums of arrays of random variables. We also employ a new approach to
conditioning to derive a conditional CLT for weighted bootstrap u- and
v-statistics, assuming the same conditions as the classical central limit
theorems for regular u- and v-statistics
Minimising the heat dissipation of quantum information erasure
Quantum state engineering and quantum computation rely on information erasure
procedures that, up to some fidelity, prepare a quantum object in a pure state.
Such processes occur within Landauer's framework if they rely on an interaction
between the object and a thermal reservoir. Landauer's principle dictates that
this must dissipate a minimum quantity of heat, proportional to the entropy
reduction that is incurred by the object, to the thermal reservoir. However,
this lower bound is only reachable for some specific physical situations, and
it is not necessarily achievable for any given reservoir. The main task of our
work can be stated as the minimisation of heat dissipation given probabilistic
information erasure, i.e., minimising the amount of energy transferred to the
thermal reservoir as heat if we require that the probability of preparing the
object in a specific pure state be no smaller than
. Here is the maximum
probability of information erasure that is permissible by the physical context,
and the error. To determine the achievable minimal heat
dissipation of quantum information erasure within a given physical context, we
explicitly optimise over all possible unitary operators that act on the
composite system of object and reservoir. Specifically, we characterise the
equivalence class of such optimal unitary operators, using tools from
majorisation theory, when we are restricted to finite-dimensional Hilbert
spaces. Furthermore, we discuss how pure state preparation processes could be
achieved with a smaller heat cost than Landauer's limit, by operating outside
of Landauer's framework
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