1,817 research outputs found
High-dimensional Ising model selection using -regularized logistic regression
We consider the problem of estimating the graph associated with a binary
Ising Markov random field. We describe a method based on -regularized
logistic regression, in which the neighborhood of any given node is estimated
by performing logistic regression subject to an -constraint. The method
is analyzed under high-dimensional scaling in which both the number of nodes
and maximum neighborhood size are allowed to grow as a function of the
number of observations . Our main results provide sufficient conditions on
the triple and the model parameters for the method to succeed in
consistently estimating the neighborhood of every node in the graph
simultaneously. With coherence conditions imposed on the population Fisher
information matrix, we prove that consistent neighborhood selection can be
obtained for sample sizes with exponentially decaying
error. When these same conditions are imposed directly on the sample matrices,
we show that a reduced sample size of suffices for the
method to estimate neighborhoods consistently. Although this paper focuses on
the binary graphical models, we indicate how a generalization of the method of
the paper would apply to general discrete Markov random fields.Comment: Published in at http://dx.doi.org/10.1214/09-AOS691 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Towards Efficient Sensor Placement for Industrial Wireless Sensor Network
Industrial Wireless Sensor Network (IWSN) is the recent emergence in wireless technologies that facilitate industrial applications. IWSN constructs a reliable and self-responding industrial system using interconnected intelligent sensors. These sensors continuously monitor and analyze the industrial process to evoke its best performance. Since the sensors are resource-constrained and communicate wirelessly, the excess sensor placement utilizes more energy and also affects the environment. Thus, sensors need to use efficiently to minimize their network traffic and energy utilization. In this paper, we proposed a vertex coloring based optimal sensor placement to determine the minimal sensor requirement for an efficient network
Coreference detection of low quality objects
The problem of record linkage is a widely studied problem that aims to identify coreferent (i.e. duplicate) data in a structured data source. As indicated by Winkler, a solution to the record linkage problem is only possible if the error rate is sufficiently low. In other words, in order to succesfully deduplicate a database, the objects in the database must be of sufficient quality. However, this assumption is not always feasible. In this paper, it is investigated how merging of low quality objects into one high quality object can improve the process of record linkage. This general idea is illustrated in the context of strings comparison, where strings of low quality (i.e. with a high typographical error rate) are merged into a string of high quality by using an n-dimensional Levenshtein distance matrix and compute the optimal alignment between the dirty strings. Results are presented and possible refinements are proposed
Comparison of History Effects in Magnetization in Weakly pinned Crystals of high- and low-T Superconductors
A comparison of the history effects in weakly pinned single crystals of a
high YBaCuO (for H c) and a low
CaRhSn, which show anomalous variations in critical current
density are presented via tracings of the minor magnetization
hysteresis loops using a vibrating sample magnetometer. The sample histories
focussed are, (i) the field cooled (FC), (ii) the zero field cooled (ZFC) and
(iii) an isothermal reversal of field from the normal state. An understanding
of the results in terms of the modulation in the plastic deformation of the
elastic vortex solid and supercooling across order-disorder transition is
sought.Comment: Presented in IWCC-200
Minimum and maximum against k lies
A neat 1972 result of Pohl asserts that [3n/2]-2 comparisons are sufficient,
and also necessary in the worst case, for finding both the minimum and the
maximum of an n-element totally ordered set. The set is accessed via an oracle
for pairwise comparisons. More recently, the problem has been studied in the
context of the Renyi-Ulam liar games, where the oracle may give up to k false
answers. For large k, an upper bound due to Aigner shows that (k+O(\sqrt{k}))n
comparisons suffice. We improve on this by providing an algorithm with at most
(k+1+C)n+O(k^3) comparisons for some constant C. The known lower bounds are of
the form (k+1+c_k)n-D, for some constant D, where c_0=0.5, c_1=23/32=0.71875,
and c_k=\Omega(2^{-5k/4}) as k goes to infinity.Comment: 11 pages, 3 figure
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