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Estimation Process (estimation + process)

Distribution by Scientific Domains

Engineering	33%

Selected Abstracts

Informational intra-group influence: the effects of time pressure and group size

EUROPEAN JOURNAL OF SOCIAL PSYCHOLOGY, Issue 1 2008
Bryan L. Bonner
The judgments of groups have immense impact on our daily lives. This paper theorizes that three families of intra-group influence affect the collective estimation process. These different forms of influence map to different levels of task demonstrability, or the extent to which correct answers are transparent to problem-solvers. When demonstrability is low, group estimates are disproportionately influenced by proposals closer to the intra-group mean (centrality). When demonstrability is high and groups are small, group decisions are disproportionately influenced by proposals closer to the correct answer (accuracy). Finally, when demonstrability is high and groups are larger, group decisions are disproportionately influenced by proposals offered by generally more accurate individuals across a set of judgments (expertise). Three laboratory studies support our predictions with regard to informational influence in cooperative groups. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Kalman filtering over wireless fading channels,How to handle packet drop,

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 18 2009
Yasamin Mostofi
Abstract In this paper we consider estimation of dynamical systems over wireless fading communication channels using a Kalman filter. We show the impact of the stochastic communication noise on the estimation process. We furthermore show how noisy packets should be handled in the receiver. More specifically, we illustrate the impact of the availability of a cross-layer information path on the optimum receiver design. In the absence of a cross-layer information path, it was shown that packet drop should be designed to balance information loss and communication noise in order to optimize the performance. In the presence of a cross-layer path, we show that keeping all the packets will minimize the average estimation error covariance. We also derive the stability condition in the presence of noisy packets and show that it is independent of the shape of the communication noise variance or availability of a cross-layer information path. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Carrier phase recovery for turbo-coded systems with pre-coded GMSK modulation

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2008
Zhuo Wu
Abstract A carrier phase recovery scheme suited for turbo-coded systems with pre-coded Gaussian minimum shift keying (GMSK) modulation is proposed and evaluated in terms of bit-error-rate (BER) performance. This scheme involves utilizing the extrinsic information obtained from the turbo-decoder to aid an iterative carrier phase estimation process, based on a maximum-likelihood (ML) strategy. The phase estimator works jointly with the turbo-decoder, using the updated extrinsic information from the turbo-decoder in every iterative decoding. A pre-coder is used to remove the inherent differential encoding of the GMSK modulation. Two bandwidths of GMSK signals are considered: BT=0.5 and 0.25, which are recommended by the European Cooperation for Space Standardization (ECSS). It is shown that the performance of this technique is quite close to the perfect synchronized system within a wide range of phase errors. This technique is further developed to recover nearly any phase error in [,,,+,] by increasing the number of phase estimators and joint decoding units. This, however, will increase the complexity of the system. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Predator functional response and prey survival: direct and indirect interactions affecting a marked prey population

JOURNAL OF ANIMAL ECOLOGY, Issue 1 2006
DAVID A. MILLER
Summary 1Predation plays an integral role in many community interactions, with the number of predators and the rate at which they consume prey (i.e. their functional response) determining interaction strengths. Owing to the difficulty of directly observing predation events, attempts to determine the functional response of predators in natural systems are limited. Determining the forms that predator functional responses take in complex systems is important in advancing understanding of community interactions. 2Prey survival has a direct relationship to the functional response of their predators. We employed this relationship to estimate the functional response for bald eagle Haliaeetus leucocepalus predation of Canada goose Branta canadensis nests. We compared models that incorporated eagle abundance, nest abundance and alternative prey presence to determine the form of the functional response that best predicted intra-annual variation in survival of goose nests. 3Eagle abundance, nest abundance and the availability of alternative prey were all related to predation rates of goose nests by eagles. There was a sigmoidal relationship between predation rate and prey abundance and prey switching occurred when alternative prey was present. In addition, predation by individual eagles increased as eagle abundance increased. 4A complex set of interactions among the three species examined in this study determined survival rates of goose nests. Results show that eagle predation had both prey- and predator-dependent components with no support for ratio dependence. In addition, indirect interactions resulting from the availability of alternative prey had an important role in mediating the rate at which eagles depredated nests. As a result, much of the within-season variation in nest survival was due to changing availability of alternative prey consumed by eagles. 5Empirical relationships drawn from ecological theory can be directly integrated into the estimation process to determine the mechanisms responsible for variation in observed survival rates. The relationship between predator functional response and prey survival offers a flexible and robust method to advance our understanding of predator,prey interactions in many complex natural systems where prey populations are marked and regularly visited. [source]

Continuous Soluble Ziegler-Natta Ethylene Polymerizations in Reactor Trains, 2 , Estimation of Kinetic Parameters from Industrial Data

MACROMOLECULAR REACTION ENGINEERING, Issue 2 2008
Marcelo Embiruçu
Abstract We show that it is possible to estimate kinetic parameters for complex mechanistic polymerization models from available industrial data. A methodology is developed for efficient handling and reconciliation of industrial data and is then applied to allow estimation of kinetic parameters for industrial ethylene polymerizations performed in reactor trains using soluble Ziegler-Natta catalysts. The parameter estimation procedure is formulated as a nonlinear optimization procedure subject to hard and soft model and process constraints. Parameter estimates obtained for the catalyst system allow a very good description of actual industrial data used during the estimation process and also allow very good prediction of process performance when completely new operating conditions are considered. It is concluded that complex phenomenological models can be successfully fitted to actual industrial processes without the need to carry out extensive experimental tests in the laboratory. [source]

Do Children in Rural Areas Still Have Different Access to Health Care?

THE JOURNAL OF RURAL HEALTH, Issue 1 2009
Results from a Statewide Survey of Oregon's Food Stamp Population
ABSTRACT:,Purpose: To determine if rural residence is independently associated with different access to health care services for children eligible for public health insurance. Methods: We conducted a mail-return survey of 10,175 families randomly selected from Oregon's food stamp population (46% rural and 54% urban). With a response rate of 31%, we used a raking ratio estimation process to weight results back to the overall food stamp population. We examined associations between rural residence and access to health care (adjusting for child's age, child's race/ethnicity, household income, parental employment, and parental and child's insurance type). A second logistic regression model controlled for child's special health care needs. Findings: Compared with urban children (reference = 1.00), rural children were more likely to have unmet medical care needs (odds ratio [OR] 1.48, 95% confidence interval [CI] 1.07-2.04), problems getting dental care (OR 1.36, 95% CI 1.03-1.79), and at least one emergency department visit in the past year (OR 1.42, 95% CI 1.10-1.81). After adjusting for special health care needs (more prevalent among rural children), there was no rural-urban difference in unmet medical needs, but physician visits were more likely among rural children. There were no statistically significant differences in unmet prescription needs, delayed urgent care, or having a usual source of care. Conclusions: These findings suggest that access disparities between rural and urban low-income children persist, even after adjusting for health insurance. Coupled with continued expansions in children's health insurance coverage, targeted policy interventions are needed to ensure the availability of health care services for children in rural areas, especially those with special needs. [source]