39095893
Comparison of hierarchical and marginal likelihood estimators for binary outcomes
Abstract Likelihood estimation in random-effect models is often complicated because the marginal likelihood involves an analytically intractable integral. Numerical integration such as Gauss–Hermite quadrature is an option, but is generally not recommended when the dimensionality of the integral is high. An alternative is the use of hierarchical likelihood, which avoids such burdensome numerical integration. These two approaches for fitting binary data are compared and the advantages of using the hierarchical likelihood are discussed. Random-effect models for binary outcomes and for bivariate binary-continuous outcomes are considered.
9799056
Fitting via alternative random-effect models
When there are two alternative random-effect models leading to the same marginal model, inferences from one model can be used for the other model. We illustrate how a likelihood method for fitting models with independent random effects can be applied to seemingly very different models with correlated random effects. We also discuss some merits of using these alternative models.
206579905
Improving multistage network performance under uniform and hot-spot traffics
The major performance drawbacks of multistage interconnection networks are due to link contention and message blockage. To remedy this problem, the authors propose a switch design which uses two independent routes between each input port and each output port within a switch. With proper routing control mechanisms, the adverse effect on link conflicts can be greatly reduced. Various simulations are used to illustrate the performance improvement of this new design under both uniform and hot-spot traffic patterns.<<ETX>>
14857474
Optimal design and use of retry in fault-tolerant computer systems
In this paper, a new method is presented for (i) determining an optimal retry policy and (ii) using retry for fault characterization, which is defined as classification of the fault type and determination of fault durations. First, an optimal retry policy is derived for a given fault characteristic, which determines the maximum allowable retry durations so as to minimize the total task completion time. Then, the combined fault characterization and retry decision, in which the characteristic of a fault is estimated simultaneously with the determination of the optimal retry policy, are carried out. Two solution approaches are developed: one is based on point estimation and the other on Bayes sequential decision analysis.
Numerical examples are presented in which all the durations associated with faults (i.e., active, benign, and interfailure durations) have monotone hazard rate functions (e.g., exponential Weibull and gamma distributions). These are standard distributions commonly used for modeling and analyses of faults.
26477941
A novel direction-finding method for cyclostationary signals
We develop a method based on the phase-SCORE algorithm of Agee et al. (Proc. IEEE 78 (April 1990) 753) to achieve direction finding for cyclostationary signals. Using the weight obtained from the phase-SCORE algorithm, we construct a subspace orthogonal to the subspace spanned by the direction vectors of uncorrelated signals of interest (SOIs). Finding the directions of the uncorrelated SOIs is then performed according to a subspace-fitting concept. For coping with the coherence between SOIs, we incorporate the proposed method with the well-known spatial smoothing algorithm of Shan et al. (IEEE Trans. Acoust. Speech Signal Process ASSP-33 (August 1985) 806) to alleviate the performance degradation due to coherence. Simulation examples for illustration and comparison are also provided.
14229192
Ranking Documents in Thesaurus-Based Boolean Retrieval Systems
Abstract In this paper we investigate document ranking methods in thesaurus-based boolean retrieval systems, and propose a new thesaurus-based ranking algorithm called the Extended Relevance (E-Relevance) algorithm. The E-Relevance algorithm integrates the extended boolean model and the thesaurus-based relevance algorithm. Since the E-Relevance algorithm has all the desirable properties of the extended boolean model, it avoids the various problems of previous thesaurus-based ranking algorithms. The E-Relevance algorithm also ranks documents effectively by using term dependence information from the thesaurus. We have shown through performance comparison that the proposed algorithm achieves higher retrieval effectiveness than the others proposed earlier.
39597503
Dynamic Load Sharing in Distributed Database Systems