Ladder realizations of multivariable positive real functions

Necessary and sufficient conditions are obtained for the realization of an m-variable positive real function (PRF) as the impedence function of a resistively-terminated ladder network of m lossless two-ports connected in cascade. Each two-port is a single-variable lossless ladder with all of its transmission zeros either at the origin or at finity. Conditions are also obtained when each of the two-ports is a Fujisawa-type lowpass ladder.     

An analysis of the role of users in the total r&d portfolios of scientific instrument firms

This paper describes a real-time investigation of the total new product portfolios of nine product departments in the scientific instrument industry. It was found that within these portfolios only a few new products represented a major advance in functional performance. Most new products offered only incremental performance improvement, and many ‘new’ products were direct copies of competitors ' offerings.The scientific instrument innovation process is described in seven stages: recognition of need, invention of solution, prototype development, use in application, precommercial information dissemination, product engineering, and commercialization. In those cases where users were involved in the majority of the first five stages of the innovation process, the innovation was either a major functional improvement or a minor improvement that had not been initiated as a direct response to a competitor's product introduction. Direct copies and minor improvements that were competitive responses are notable for the absence of user involvement in the innovation process.Finally, the decision of a manufacturer to commercialize an innovation was unrelated to the level of user activity in the prior stages of the innovation process.     

Polynomial Root Clustering

A sequence of tests on derived polynomials to be strictly Hurwitz polynomials is shown to be equivalent to a given (typically real) polynomial having all its zeros in an open sector, symmetric with respect to the real axis, in the left half-plane. The number of tests needed is at most 1 + ?(ln k)/(ln 3)?, where k is the integer associated with the central angle π/k of the sector. An extension of this result on the sector as a region of root clustering is given which shows that only a limited number of tests are needed to verify that the roots are clustered in a region composed as the intersection of a set of primative (sector-like) regions. The results reported evolve from application of a collection of mappings on the complex plane defined by a particular collection of Schwarz-Christoffel transformations.     

Radial localization of odors by human newborns.

To study sensitivity to radial location of an odor source, 20 human newborns, ranging from 16 to 130 hours of age, were presented with a small amount of ammonium hydroxide. The odor source was placed near the nose slightly to the left or right of midline, with its position randomized over repeated trails. Direction of headturn with respect to the odor location and diffuse motor activity were scored from the videotape recordings of the newborns' behavior. It was found that as a group, the newborns turned away from the odor source more frequently than they turned toward it. The tendency to turn away from the odor was stronger in infants who displayed less motor activity after the response. Newborns also exhibited a right bias in the direction of the head movements. It is concluded that a spatially appropriate avoidance response is present in the neonate and that the newborn is innately sensitive to the radial location of an odor.     

Effects of social comparison on aggression and regression in groups of young children.

The influence of negative, equal, and positive social comparison and of nonsocial comparison upon 4- and 5-year-old black children's subsequent aggressive and regressive behavior in 3-member groups was investigated. The group behavior of boys included more physical agression following negative social comparison than the other treatments, and their group behavior also consisted of more nonverbal teasing behavior following the negative comparison treatment than that of the equal and nonsocial comparison groups. When the behavior of the nontarget partners was controlled, children initiated more physical aggression, nonverbal teasing, and regression after experiencing negative social comparison with the partners than after following the other treatments. There was some evidence to support the reciprocal influence of children's aggressive behavior on each other, particularly for boys following imbalanced social comparison treatments.     

Self-evaluation, social reinforcement, and academic achievement of black and white schoolchildren.

Black and white male schoolchildren covertly evaluated their own performance at a verbal task administered by black and white male experimenters. It was hypothesized that academically successful children would be predisposed to appraise themselves favorably, whereas relatively unsuccessful pupils would be biased toward self-criticism. The covert self-evaluations were assumed to represent at internalization of early experiences of predominantly positive or negative social reinforcement from adult socializing agents. The predicition for self-criticism was upheld in the white experimenter condition but not in the black experimenter condition. Relationships consistent with the theory were found between subjects' self-appraisals and their retrospective reports of positive and negative reinforcements received from parents and teachers in various typical situations. These relationships were more evident for black subjects than for white subjects. The extent to which children's self-praise and self-criticism mediated affect was assessed by means of a color conditioning technique. Contrary to predicition, possibly due to the easy nature of the experimental task.     

Problématique dans l'apprentissage de la mathématique

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