2,664 research outputs found
Synchronization recovery and state model reduction for soft decoding of variable length codes
Variable length codes exhibit de-synchronization problems when transmitted
over noisy channels. Trellis decoding techniques based on Maximum A Posteriori
(MAP) estimators are often used to minimize the error rate on the estimated
sequence. If the number of symbols and/or bits transmitted are known by the
decoder, termination constraints can be incorporated in the decoding process.
All the paths in the trellis which do not lead to a valid sequence length are
suppressed. This paper presents an analytic method to assess the expected error
resilience of a VLC when trellis decoding with a sequence length constraint is
used. The approach is based on the computation, for a given code, of the amount
of information brought by the constraint. It is then shown that this quantity
as well as the probability that the VLC decoder does not re-synchronize in a
strict sense, are not significantly altered by appropriate trellis states
aggregation. This proves that the performance obtained by running a
length-constrained Viterbi decoder on aggregated state models approaches the
one obtained with the bit/symbol trellis, with a significantly reduced
complexity. It is then shown that the complexity can be further decreased by
projecting the state model on two state models of reduced size
Ethical reflection in dentistry: first steps at the Faculty of Dental Surgery of Toulouse.
International audienceThe goal of this work is to contribute to ethical reflection in the dental profession through the example of a survey of ethical reflection and ethical issues in dentistry conducted at the dental school of Toulouse. A written survey was given to the heads of departments and to the sixth-year students and also to the dental faculty at the hospital dental clinic in order to estimate their level of understanding and concern about these topics
PĂ©trole : du carbone pour la croissance:Ătude spĂ©ciale
La chute du prix du Brent de 50 % en
six mois ouvre des perspectives favo-
rables aux économies importatrices de pé
trole, Ă la condition toutefois quâelle
soit durable. Ă lâhorizon 2016, la situ
ation dâexcĂšs dâoffre sur le marchĂ©,
alimentée par le développement de la
production de pétrole de schiste aux
Ătats-Unis et lâ
absence de rĂ©action de lâOPEP po
ur contrecarrer cet essor, va
dans ce sens. La production non-conven
tionnelle américaine, dont la rentabi-
litĂ© nâest plus assurĂ©e en deçà du seui
l de 60 dollars le ba
ril, subit certes le
contrecoup de la baisse des prix, mais lâ
ajustement de la production dâici Ă deux
ans ne ferait pas remonter le
prix Ă son niveau dâavant-choc.
Les outils de modélisation opératio
nnels de lâOFCE, les modĂšles macro-
Ă©conomĂ©triques pour lâĂ©conomie française
e-mod.fr
et
ThreeMe
permettent
dâĂ©valuer les rĂ©percussions globales de
ce choc sur lâĂ©conomie, mais aussi les
transferts dâactivitĂ© dâun secteur Ă un
autre ainsi que lâim
pact environnemental
dâune consommation dâhydrocarbures ac
crue. En adaptant lâarchitecture de
e-mod.fr
aux caractĂ©ristiques de consommation, dâimportation et de produc-
tion dâhydrocarbures, les simulations
ont été étendues au
x grandes Ă©conomies
développées.
Ă lâexception des Ătats-Unis, lâimpact posi
tif est significatif et assez similaire
pour tous les pays. LâĂ©conomie amĂ©ricai
ne bĂ©nĂ©ficie, comme ses consĆurs, des
mĂȘmes effets positifs, mais la chute du pr
ix du pétrole, qui frappe de plein fouet
lâactivitĂ© de production de pĂ©trole non-
conventionnel, pĂšse
sur la croissance et
tempĂšre lâeffet final du contrechoc. Les
variantes présentées
ici produisent des
résultats comparables à ceux issus des modÚles utilisés par les grandes institu-
tions internationales. Il en ressort que la
baisse du prix du pĂ©trole sâavĂšre bien
ĂȘtre un choc positif pour la croiss
ance mondiale, mais malheureusement pas
pour lâenvironnement
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