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Query: UMLS:C0016632 (Fox)
 1,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this Letter we propose a closed-form expression for the average bit error rate of intensity modulation/direct detection free-space optical systems employing dual-branch equal-gain combining and operating over turbulence channels. To offer a realistic error performance of the considered system we assume that both branches undergo independent but not necessarily identically distributed gamma-gamma fading. Our newly developed formula is obtained in terms of the bivariate H-Fox function, which can be readily evaluated based on its two-fold Mellin-Barnes representation. Numerically evaluated and computer simulation results are presented that verify the accuracy of the proposed mathematical analysis.
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PMID:Formula for the average bit error rate of free-space optical systems with dual-branch equal-gain combining over gamma-gamma turbulence channels. 2345 64

The trend of rising scores on intelligence tests raises important questions about the comparability of variation within and between time periods. Descriptions of the processes that mediate selection of item responses provide meaningful psychological criteria upon which to base such comparisons. In a recent paper, Fox and Mitchum presented and tested a cognitive theory of rising scores on analogical and inductive reasoning tests that is specific enough to make novel predictions about cohort differences in patterns of item responses for tests such as the Raven's Matrices. In this paper we extend the same proposal in two important ways by (1) testing it against a dataset that enables the effects of cohort to be isolated from those of age, and (2) applying it to two other inductive reasoning tests that exhibit large Flynn effects: Letter Series and Word Series. Following specification and testing of a confirmatory item response model, predicted violations of measurement invariance are observed between two age-matched cohorts that are separated by only 20 years, as members of the later cohort are found to map objects at higher levels of abstraction than members of the earlier cohort who possess the same overall level of ability. Results have implications for the Flynn effect and cognitive aging while underscoring the value of establishing psychological criteria for equating members of distinct groups who achieve the same scores.
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PMID:Confirming the cognition of rising scores: Fox and Mitchum (2013) predicts violations of measurement invariance in series completion between age-matched cohorts. 2480 78