102 research outputs found
Successive Wyner-Ziv Coding Scheme and its Application to the Quadratic Gaussian CEO Problem
We introduce a distributed source coding scheme called successive Wyner-Ziv
coding. We show that any point in the rate region of the quadratic Gaussian CEO
problem can be achieved via the successive Wyner-Ziv coding. The concept of
successive refinement in the single source coding is generalized to the
distributed source coding scenario, which we refer to as distributed successive
refinement. For the quadratic Gaussian CEO problem, we establish a necessary
and sufficient condition for distributed successive refinement, where the
successive Wyner-Ziv coding scheme plays an important role.Comment: 28 pages, submitted to the IEEE Transactions on Information Theor
Multiple Description Quantization via Gram-Schmidt Orthogonalization
The multiple description (MD) problem has received considerable attention as
a model of information transmission over unreliable channels. A general
framework for designing efficient multiple description quantization schemes is
proposed in this paper. We provide a systematic treatment of the El Gamal-Cover
(EGC) achievable MD rate-distortion region, and show that any point in the EGC
region can be achieved via a successive quantization scheme along with
quantization splitting. For the quadratic Gaussian case, the proposed scheme
has an intrinsic connection with the Gram-Schmidt orthogonalization, which
implies that the whole Gaussian MD rate-distortion region is achievable with a
sequential dithered lattice-based quantization scheme as the dimension of the
(optimal) lattice quantizers becomes large. Moreover, this scheme is shown to
be universal for all i.i.d. smooth sources with performance no worse than that
for an i.i.d. Gaussian source with the same variance and asymptotically optimal
at high resolution. A class of low-complexity MD scalar quantizers in the
proposed general framework also is constructed and is illustrated
geometrically; the performance is analyzed in the high resolution regime, which
exhibits a noticeable improvement over the existing MD scalar quantization
schemes.Comment: 48 pages; submitted to IEEE Transactions on Information Theor
Application of cover-free codes and combinatorial designs to two-stage testing
AbstractWe study combinatorial and probabilistic properties of cover-free codes and block designs which are useful for their efficient application as the first stage of two-stage group testing procedures. Particular attention is paid to these procedures because of their importance in such applications as monoclonal antibody generation and cDNA library screening
Simulation of Main Memory Database Recovery
In a main memory database (MMDB), the primary copy of the database may reside permanently in a volatile memory. When a system failure occurs, the database must be reloaded efficiently from archive memory into main memory. This paper presents four different reload schemes and the simulation models constructed to compare the algorithms. Simulation results indicate that the reload scheme based on freguency of data access gives the best overall performance in terms of transaction response time and system throughput.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Assessing the uncertainties of model estimates of primary productivity in the tropical Pacific Ocean
Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Marine Systems 76 (2009): 113-133, doi:10.1016/j.jmarsys.2008.05.010.Depth-integrated primary productivity (PP) estimates obtained from satellite
ocean color based models (SatPPMs) and those generated from biogeochemical ocean
general circulation models (BOGCMs) represent a key resource for biogeochemical and
ecological studies at global as well as regional scales. Calibration and validation of these
PP models are not straightforward, however, and comparative studies show large
differences between model estimates. The goal of this paper is to compare PP estimates
obtained from 30 different models (21 SatPPMs and 9 BOGCMs) to a tropical Pacific PP
database consisting of ~1000 14C measurements spanning more than a decade (1983-
1996). Primary findings include: skill varied significantly between models, but
performance was not a function of model complexity or type (i.e. SatPPM vs. BOGCM);
nearly all models underestimated the observed variance of PP, specifically yielding too
few low PP (< 0.2 gC m-2d-2) values; more than half of the total root-mean-squared
model-data differences associated with the satellite-based PP models might be accounted
for by uncertainties in the input variables and/or the PP data; and the tropical Pacific
database captures a broad scale shift from low biomass-normalized productivity in the
1980s to higher biomass-normalized productivity in the 1990s, which was not
successfully captured by any of the models. This latter result suggests that interdecadal
and global changes will be a significant challenge for both SatPPMs and BOGCMs.
Finally, average root-mean-squared differences between in situ PP data on the equator at
140°W and PP estimates from the satellite-based productivity models were 58% lower
than analogous values computed in a previous PP model comparison six years ago. The
success of these types of comparison exercises is illustrated by the continual modification
and improvement of the participating models and the resulting increase in model skill.This research was supported by a grant from the National Aeronautics and Space Agency
Ocean Biology and Biogeochemistry program (NNG06GA03G), as well as by numerous
other grants to the various participating investigator
What Should We Agree on about the Repugnant Conclusion?
The Repugnant Conclusion served an important purpose in catalyzing and inspiring the pioneering stage of population ethics research. We believe, however, that the Repugnant Conclusion now receives too much focus. Avoiding the Repugnant Conclusion should no longer be the central goal driving population ethics research, despite
its importance to the fundamental accomplishments of the existing literature
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