Rethinking infant knowledge: toward an adaptive process account of successes and failures in object permanence tasks

Infants seem sensitive to hidden objects in habituation tasks at 3.5 months but fail to retrieve hidden objects until 8 months. The authors first consider principle-based accounts of these successes and failures, in which early successes imply knowledge of principles and failures are attributed to ancillary deficits. One account is that infants younger than 8 months have the object permanence principle but lack means-ends abilities. To test this, 7-month-olds were trained on means-ends behaviors and were tested on retrieval of visible and occluded toys. Means-ends demands were the same, yet infants made more toy-guided retrievals in the visible case. The authors offer an adaptive process account in which knowledge is graded and embedded in specific behavioral processes. Simulation models that learn gradually to represent occluded objects show how this approach can account for success and failure in object permanence tasks without assuming principles and ancillary deficits.     

The formal-CAFE methodology and model checking patterns in the specification of e-commerce systems

Electronic commerce is an important application that has evolved significantly recently. However, electronic commerce systems are complex and difficult to be correctly designed. Guaranteeing the correctness of an e-commerce system is not an easy task due to the great amount of scenarios where errors occur, many of them very subtle. In this work we presents a methodology that uses formal-method techniques, specifically symbolic model checking, to design electronic commerce applications and to automatically verify them. Also, a model checking pattern hierarchy has been developed—it specifies patterns to construct and verify the formal model of e-commerce systems. We consider this research the first step to the development of a framework, which will integrate the methodology, an e-commerce specification language based on business rules, and a model checker. Adriano Pereira received the B.S. and M.S. degrees in computer science in 2000 and 2002, respectively, and he is currently pursuing the Ph.D. degree in computer science from the Federal University of Minas Gerais, Belo Horizonte, Brazil. His current interests are on performance analysis and modeling of e-business and distributed systems, and formal methods. Mark Song received the B.S., M.S. and Ph.D. degrees in computer science from the Federal University of Minas Gerais, Belo Horizonte, Brazil. His current interests are on distributed systems and formal methods – especially BMC (Bounded Model Checking). Gustavo Franco received the B.S. and M.S. degrees in computer science in 2001 and 2004, respectively, from the Federal University of Minas Gerais, Belo Horizonte, Brazil. His research was on modeling the user behavior of e-business and distributed systems, and formal methods. Actually his current interests are on software engeneering and project management of IT projects.     

Cigarette smoking and submaximal exercise test duration in a biracial population of young adults: the CARDIA study

Symptom-limited, graded exercise treadmill testing was performed by 4,968 white and black adults, ages 18-30 yr, during the baseline examination for the Coronary Artery Risk Development in Young Adults (CARDIA) study. Compared with nonsmokers, the mean exercise test duration of smokers was 29-64 s shorter depending on race/gender group (all P < 0.001), but mean duration to heart rate 130 (beats.min-1) ranged from 20-50 s longer (P < 0.05). In each race/gender group, test duration to heart rates up to 150 was 15-35 s longer (P < 0.05) in smokers than in nonsmokers after adjustment for age, sum of skinfolds, hemoglobin, and physical activity score. The mean maximum heart rate was lower in smokers than in nonsmokers (difference ranging from 6.7 beats.min-1 in white men to 11.2 beats.min-1 lower in black women, P < 0.001), although maximum rating of perceived exertion was nearly identical in smokers and nonsmokers. Chronic smoking appears to blunt the heart rate response to exercise, so that exercise duration to submaximal heart rates is increased even though maximal performance is impaired. This may result from downloading of beta-receptors caused by smoking. Smoking status should be considered in the evaluation of physical fitness data utilizing submaximal test protocols, or else the fitness of smokers relative to nonsmokers is likely to be overestimated.     

Spatial shape error concealment for object-based image and video coding

In this paper, an original spatial shape error-concealment technique, to be used in the context of object-based image and video coding schemes, is proposed. In this technique, it is assumed that the shape of the corrupted object at hand is in the form of a binary alpha plane, in which some of the shape data is missing due to channel errors. From this alpha plane, a contour corresponding to the border of the object can be extracted. However, due to errors, some parts of the contour will be missing and, therefore, the contour will be broken. The proposed technique relies on the interpolation of the missing contours with Bézier curves, which is done based on the available surrounding contours. After all the missing parts of the contour have been interpolated, the concealed alpha plane can be easily reconstructed from the fully recovered contour and used instead of the erroneous one improving the final subjective impact.     

Surveillance test policy optimization through genetic algorithms using non-periodic intervention frequencies and considering seasonal constraints

In order to maximize systems average availability during a given period of time, it has recently been developed a non-periodic surveillance test optimization methodology based on genetic algorithms (GA). The fact of allowing non-periodic tests turns the solution space much more flexible and schedules can be better adjusted, providing gains in the overall system average availability, when compared to those obtained by an optimized periodic test scheme. This approach, however, turns the optimization problem more complex. Hence, the use of a powerful optimization technique, such as GA, is required.Considering that some particular features of certain systems can turn it advisable to introduce other specific constraints in the optimization problem, this work investigates the application of seasonal constraints for the set of the Emergency Diesel Generation of a typical four-loop pressurized water reactor in order to planning and optimizing its surveillance test policy. In this analysis, the growth of the blackout accident probability during summer, due to electrical power demand increases, was considered. Here, the used model penalizes surveillance test interventions when the blackout probability is higher.Results demonstrate the ability of the method in adapting the surveillance test policy to seasonal constraints. The knowledge acquired by the GA during the searching process has lead to test schedules that drastically minimize test interventions at periods of high blackout probability. It is compensated by more frequent redistributed tests through the periods of low blackout probability in order to improve on the overall average availability at the system level.