4,467 research outputs found
Evidential-EM Algorithm Applied to Progressively Censored Observations
Evidential-EM (E2M) algorithm is an effective approach for computing maximum
likelihood estimations under finite mixture models, especially when there is
uncertain information about data. In this paper we present an extension of the
E2M method in a particular case of incom-plete data, where the loss of
information is due to both mixture models and censored observations. The prior
uncertain information is expressed by belief functions, while the
pseudo-likelihood function is derived based on imprecise observations and prior
knowledge. Then E2M method is evoked to maximize the generalized likelihood
function to obtain the optimal estimation of parameters. Numerical examples
show that the proposed method could effectively integrate the uncertain prior
infor-mation with the current imprecise knowledge conveyed by the observed
data
Rate coefficients for rovibrational transitions in H_2 due to collisions with He
We present quantum mechanical and quasiclassical trajectory calculations of
cross sections for rovibrational transitions in ortho- and para-H_2 induced by
collisions with He atoms. Cross sections were obtained for kinetic energies
between 10^-4 and 3 eV, and the corresponding rate coefficients were calculated
for the temperature range 100<T<4000 K. Comparisons are made with previous
calculations.Comment: 21 pages, 2 figures, AAS, eps
Self-assembly of iron nanoclusters on the Fe3O4(111) superstructured surface
We report on the self-organized growth of a regular array of Fe nanoclusters
on a nanopatterned magnetite surface. Under oxidizing preparation conditions
the (111) surface of magnetite exhibits a regular superstructure with
three-fold symmetry and a 42 A periodicity. This superstructure represents an
oxygen terminated (111) surface, which is reconstructed to form a periodically
strained surface. This strain patterned surface has been used as a template for
the growth of an ultrathin metal film. A Fe film of 0.5 A thickness was
deposited on the substrate at room temperature. Fe nanoclusters are formed on
top of the surface superstructure creating a regular array with the period of
the superstructure. We also demonstrate that at least the initial stage of Fe
growth occurs in two-dimensional mode. In the areas of the surface where the
strain pattern is not formed, random nucleation of Fe was observed.Comment: 6 pages, 3 figure
Precedence-type Test based on Progressively Censored Samples
In this paper, we introduce precedence-type tests for testing the hypothesis that two distribution functions are equal, which is an extension of the precedence life-test rst proposed by Nelson (1963), when the two samples are progressively Type-II censored. The null distributions of the test statistics are derived. Critical values for some combination of sample sizes and censoring schemes for the proposed tests are presented. Then, we present the exact power functions under the Lehmann alternative, and compare the exact power as well as simulated power (under location-shift) of the proposed precedence test based on nonparametric estimates of CDF with other precedence-type tests. We then examine the power properties of the proposed test procedures through Monte Carlo simulations. Two examples are presented to illustrate all the test procedures discussed here. Finally, we make some concluding remarks.Precedence test; Product-limit estimator; Type-II progressive censoring; Life-testing; level of significance; power; Lehmann alternative; Monte Carlo simulations
Use of Energy in Data-Track Association and State Estimation in Multitarget-Multisensor Problems
A coarse test and a fine test have been formulated for use in multiple sensor-multiple target data-track association. Various forms of energies are used in these tests to pick the proper data to be associated with any target. Numerical experiments which involve the use of a decentralized Kalman filter scheme are presented. The experiments show the effectiveness of the two test
Fuzzy Logic in Restructurable Flight Control Systems
In this paper, a fuzzy logic controller (FLC) is proposed for restructurable flight control systems. The role of the FLC is to stabilize the aircraft upon a fault occurrence. The FLC derives pitch/roll/yaw controls from a generic knowledge base characterized by 49 if-then rules. A linearized model representative of a modern jet fighter provides the basis for the numerical simulation. Simulated faults include various degrees of surface loss at the right stabilator, combined with reduced ailerons and rudder control power. The FLC accomplishes the stabilization task under test conditions without any knowledge of the system parameters. The numerical results demonstrate the potential of the FLC as a suitable control algorithm that bridges the critical gap between the fault occurrence and the full implementation of the new control la
Stochastic Analysis of a Churn-Tolerant Structured Peer-to-Peer Scheme
We present and analyze a simple and general scheme to build a churn
(fault)-tolerant structured Peer-to-Peer (P2P) network. Our scheme shows how to
"convert" a static network into a dynamic distributed hash table(DHT)-based P2P
network such that all the good properties of the static network are guaranteed
with high probability (w.h.p). Applying our scheme to a cube-connected cycles
network, for example, yields a degree connected network, in which
every search succeeds in hops w.h.p., using messages,
where is the expected stable network size. Our scheme has an constant
storage overhead (the number of nodes responsible for servicing a data item)
and an overhead (messages and time) per insertion and essentially
no overhead for deletions. All these bounds are essentially optimal. While DHT
schemes with similar guarantees are already known in the literature, this work
is new in the following aspects:
(1) It presents a rigorous mathematical analysis of the scheme under a
general stochastic model of churn and shows the above guarantees;
(2) The theoretical analysis is complemented by a simulation-based analysis
that validates the asymptotic bounds even in moderately sized networks and also
studies performance under changing stable network size;
(3) The presented scheme seems especially suitable for maintaining dynamic
structures under churn efficiently. In particular, we show that a spanning tree
of low diameter can be efficiently maintained in constant time and logarithmic
number of messages per insertion or deletion w.h.p.
Keywords: P2P Network, DHT Scheme, Churn, Dynamic Spanning Tree, Stochastic
Analysis
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