When considering a class of Turing machines that halt when started from a blank tape, busy beavers for that class, as coined by Tibor Radó, are those Turing machines which eventually halt after the maximum number of steps (or after producing the maximum number of non-blank symbols). Finding for a class of Turing machines the busy beaver champion (for any of the two competitions) is of course un...

This work examines how awareness systems, a class of technologies that support sustained and effortless communication between individuals and groups, can support family communication. Going beyond the evaluation of specific design concepts, this paper reports on three studies that aimed to answer the following research questions: (a) Do families want to be aware of each other through the day? O...

The present investigation deals with performance analysis of single server preemptive priority retrial queue with immediate Bernoulli feedback. There are two types of customers are considered, which are priority customers and ordinary customers. The priority customers do not form any queue and have an exclusive preemptive priority to receive their services over ordinary customers. After complet...

Abstract In this paper, a new discrete-time GeomX /G/1 queue model with multiple vacations is analyzed. The Probability Generating Function (P.G.F.) of the queue length is obtained by using the method of an embedded Markov chain, and the mean of the queue length is obtained by using L’Hospital rule. Then the P.G.F. of the busy period is derived, and the probabilities for the system being in a b...

In a parity judgment task, the ERPs at parietal electrode sites become more negative as more mental rotation has to be executed. This article provides a review of the empirical evidence regarding this amplitude modulation. More specifically, experiments are reported that validate both the functional relationship between mental rotation and the amplitude modulation as well as the temporal relati...

We investigated whether concurrent processing of a tone (T1) interferes with early sensory-perceptual processing of a visual target (T2) in variants of the psychological refractory period paradigm using the event-related potential (ERP) method and 70-channel electroencephalographic recordings. T1, which required a speeded response, was presented in all trials. In half of the trials, T1 was foll...

M. A. Van Selst, E. Ruthruff, and J. C. Johnston (1999) found that practice dramatically reduced dual-task interference in a Psychological Refractory Period (PRP) paradigm with 1 vocal response and 1 manual response. Results from 3 further experiments using the highly trained participants of M. A. Van Selst et al. (1999) support 4 main conclusions: (a) A processing bottleneck exists even after ...

The apparently deleterious effect of aging on dual-task performance is well established, but there is little agreement about the source of this effect. Studies of the psychological refractory period (PRP) indicate that young adults can flexibly control dual-task performance through task-coordination strategies. Thus, the performance of older adults might differ from young adults because older a...

Why is the human brain fundamentally limited when attempting to execute two tasks at the same time or in close succession? Two classical paradigms, psychological refractory period (PRP) and task switching, have independently approached this issue, making significant advances in our understanding of the architecture of cognition. Yet, there is an apparent contradiction between the conclusions de...