Buckling of a continuous beam resting on a tensionless elastic foundation

In this paper, a solution is presented to the buckling problem of a continuous beam resting on a tensionless foundation model that was proposed by Winkler and by Reissner.     

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.     

Structural aspects of controllability and observability—I. tensorial aggregation

The classical criteria for controllability and observability are given a tensorial formulation which is then extended into Boolean form directly related to a digraph interpretation of system structure. This is examined in detail with particular reference to group theoretic aspects, invariant properties under transformation, the term rank test and the existence of zero eigenvalues.Within this framework the structural design concepts of potential controllability and observability are presented in generalised terms.     

Structural aspects of controllability and Sobservability—II. digraph decomposition

The graph theoretic aspects of controllability and observability are examined and related to the tensorial formulation of Part I of the paper. Particular emphasis is given to the significance of the system digraph decomposition and the relevance of this to certain system algebraic properties of interest in control theory.     

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.     

The effects of extraneous speech on visual vigilance performance of children

First-grade males performed a 30-min visual vigilance task under 5 conditions of auditory background stimulation. The 5 conditions consisted of (1) continuous conversation, in which subjects listened to a tape of conversation spliced so that there were no intervals of silence lasting longer than 3 sec; (2) continuous reverse, in which subjects heard the continuous conversation tape played in reverse; (3) intermittent conversation, in which subjects heard alternating segments of conversation and silence; (4) intermittent reverse, in which subjects heard alternating segments of reverse conversation and silence; and (5) silence control. Compared with silence or continuous stimulation, intermittent stimulation produced better detection regardless of whether or not it was meaningful. High achievers made more correct detections than low achievers, but only in the second and third time periods. Few subjects made errors of commission.     

The elimination of hypo from photographic images

It is very difficult, if not impossible, to remove the last traces of hypo from photographic papers by any known procedure of washing. The sulfur in the residual hypo ultimately, and especially under abnormal conditions of temperature and humidity, combines with the silver image to form yellowish brown silver sulfide. This phenomenon is known as sulfiding or “fading” of the image. The various factors which affect the rate of fading of images and the washing out of hypo from films and papers are outlined.Chemical methods of hypo elimination have been proposed from time to time but the majority of these have not been satisfactory because they tend to leave substances such as thionates in the photographic material, which are equally as difficult to wash out as hypo and which also tend to sulfide or fade the silver image. A new hypo eliminator is recommended consisting of two volatile chemicals, hydrogen peroxide and ammonia. This eliminator oxidizes the hypo to sodium sulfate, which is inert and soluble in water, while any excess eliminator evaporates on drying.Two formulas and treatments are proposed: (1) Complete elimination of hypo for use by the professional, advanced amateur, and photofinisher who demand the highest standard of photographic quality in their prints.(2) Almost complete elimination of hypo (less than o.oi milligram per square inch).Since the conditions to which prints will be subjected are rarely known in advance, use of the “complete elimination treatment” is advised in all cases.