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M.Ing. / Timber is an organic, orthotropic material of which the strength is currently not fully utilised in structural designs. Most design codes treat timber as an isotropic material with special clauses to compensate for the weaker strength across the grain. Several safety factors are used to accommodate the large variations in the strength of timber. In the orthotropic approach presented here, the unidirectional properties of timber are assumed as constant. It is also assumed that the large strength variation which is observed between samples of the same group, can mostly be attributed to the grain slope variation in a sample. The finite element method is employed to model grain slopes around a predetermined defect in a sample. The sample is then forced to fail at this defect, and the finite element model is then analyzed at the failure load to determine which stress combination led to the failure. Initial unidirectional material strengths are used in a failure criterion to evaluate the critical stress combination. The method of least squares is used to fit the predicted strength against the experimental strength. In this process new values are found for the unidirectional material strengths. The process is then repeated to determine whether another stress combination is not more critical than the original choice. As soon as the numerically acquired material strengths stabilise, it is compared with known values. The results indicate that the strength of a timber section can be predicted on the grounds of the observed fibre directions if the unidirectional material strengths are known.

This thesis explores the effect of some parameters on the breaking strain, strength and the shape of the stress-strain curve of bovine leather as revealed by uniaxial tensile tests. The parameters explored are fatliquoring, moisture content, strain rate and cyclic stressing. A basic mechanical model of a simple two-dimensional weave is created and used to describe the effect of such a weave on the shape of the stress-strain curve. It is found that fatliquoring lubricates and opens up the fibre structure and thereby makes the weave more extensible. The increase in the extensibility depends on the direction in which samples are cut and therefore the manner in which the fibres are orientated. Patliquoring is observed to increase the degree to which fibres pull out at break. There are indications that the strength of fatliquored leather decreases with time of storage, while the extensibility increases. The effect of the strain rate on the breaking strain, the tensile strength and the shape of the stress-strain curve is not very clear. The stressing and releasing leather decreases the strength of leather when the fibres are orientated preferentially along the direction of the applied stresses, but has an insignificant effect in the transverse direction. It is concluded that the degree of lubrication in a weave and the orientation of the fibre bundles significantly influence the performance of leather in a test. Both moisture and fatliquoring lubricate the weave. In both the cases the degree of fibre adhesions in a weave is decreased. A well lubricated weave allows its constituent fibres to slide and align along the direction of the applied stresses, and this tends to occur before the fibres themselves areextended. Cyclic testing, at low strains, ruptures fibre adhesions and as a result induces permanent set and makes a hide softer. Most of the work done in breaking the fibre adhesion is done in the first cycle.

There are two ways that attentional resources can be aligned in visual space. They can be "pulled" automatically by stimulus cues, or "pushed" in a more strategic manner by the observer in response to information cues. The present study was designed to determine if the ability to align attention in these two ways changes throughout the course of the lifespan. Subjects (6, 8, 10, 23, and 73 years) were tested in two conditions. In the first, subjects were presented with a stimulus cue (a dot that appears briefly at a target location) prior to the presentation of a target. Attention was automatically aligned to a possible target location in response to the stimulus cue. In the second, an arrow was presented prior to the target, allowing the subject to align attention strategically in response to the cue. Cues were either valid or invalid predictors of target location, cue-target SOA was varied so the time course for the effective use of both types of cues was measured and compared. Eye movements were monitored to control for confounding developmental differences in vision. In a second experiment, lifespan changes in the interaction between the two forms of orienting were assessed by presenting subjects with both cues on each trial. The location information provided by each cue could be either compatible or incompatible with each other. The results of both experiments suggest that the ability to align attention automatically changes very little from early childhood through old age. Strategic attention alignment becomes more efficient in early adulthood. Children have difficulty sustaining attention at locations specified by information cues and seniors have difficulty using the information rapidly. Both children and seniors are less able to use information cues when stimulus cues are also available where as young adults can use both. These findings suggest that separate mechanisms are required to implement attention alignments to automatic and strategic cues. / Arts, Faculty of / Psychology, Department of / Graduate

An experimental investigation into the stress-strain behavior of an undisturbed sensitive clay is presented. The stress-strain characteristics of both drained and undrained triaxial tests are considered. The drained and undrained shear strengths are compared for both the maximum principal stress difference and the maximum effective principal stress ratio failure criteria. An attempt is made to correlate the drained and undrained shear strength through the use of energy equations which account for volume change. The magnitude of pore pressures that develop during drained tests is estimated, and a brief discussion of the effect of rate of strain on the behavior of the clay is also included. The soil tested was a sensitive laminated silty-clay of marine origin. The experimental work consisted of standard strain-controlled triaxial compression tests performed on saturated, normally consolidated, 2.8 ins. by 1.4 ins. diameter samples. The strain rate in both the drained and undrained tests was 0.5 percent per hour, except for one drained test sheared at 2.5 percent per hour. All consolidation and drained shear was conducted under a back pressure of 10 lbs./sq. in. Drainage was permitted from both ends of the sample but no filter paper side drains were used. Pore pressures were measured at the base of the sample using a Bishop and Henkel null-indicator. The samples were sheared until approximately 30 percent axial strain had been developed or until failure had occurred. A discussion of the testing procedures is included. The results of the investigation indicated that the sensitivity of the clay is of primary importance in determining the behavior of soil under load. A relationship between void ratio and strength that is independent of stress path does not exist in undisturbed sensitive clays, nor does there appear to be a common drained and undrained strength envelope at the maximum principal stress difference failure criterion. Application of the Bishop and Rowe energy corrections to the drained strength obtained at the maximum effective principal stress ratio did not yield the same effective strength envelope as that determined from undrained tests at the same failure criterion, but the value of M (the slope of the q(w)-pˈ curve) in the Roscoe, Schofield, and Thurairajah energy equation was approximately constant. The uncorrected effective angle of shearing resistance, ⌽ˈ, was found to be a function of failure criterion and drainage condition. The strain at which failure occurred in drained tests, although decreasing with increase in consolidation stress, was large, indicating that the generally accepted failure criteria of maximum principal stress difference and maximum effective principal stress ratio are not satisfactory for sensitive clay. Although calculations showed that pore pressures were developed at low strains in drained tests, increasing the rate of strain from 0.5 percent per hour to 2.5 percent per hour did not noticeably affect the strength or stress-strain behavior of the 2.8 ins. by 1.4 ins. diameter samples. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Creep and recovery tests in compression parallel to the grain were conducted on 2 in. by 2 in. Douglas-fir specimens 4 in. long at four different levels of moisture. Specimens were loaded in stages up to a predetermined load. Instantaneous axial and lateral deformation as well as creep measurements were taken at each stage. Creep was observed over periods ranging from five minutes to twenty-five hours. Similarly, recovery was observed during unloading at successively lower stress levels. There are indications that creep as well as negative creep and negative recovery were mainly due to moisture present in the cell walls. Creep, In general, appeared to be more marked in the green specimens than in the intermediate and air-dry conditions. The only oven-dry specimen showed less creep than the air-dry specimens. Results also show that the values of the coefficient of lateral deformation(formula omitted) (both radial and tangential), during the load rise were entirely different from those during the period of creep, indicating that the corresponding deformations were entirely different. The µ’s for the change In load were always higher than those for the periods of creep. All specimens tested showed a recovery of more than 50% of the longitudinal creep. This indicates that creep in wood is made up of two parts, recoverable and permanent creep. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The present research was conducted to determine the influence of cultural factors upon cognitive assessment of Thematic Apperception Test cards. In the first study, a sample, consisting of 100 Japanese students, identified the major perceptual impact of TAT cards by specifying from a list of five alternative categories the one which best described a given card. The data were quantified by the uncertainty measure (H) in order to provide an indication of the ambiguity of each TAT card. The comparative Canadian data were obtained from Kuechler's (1961) study. A comparison of the rank order of the TAT cards for ambiguity yielded a significant correlation between sexes within a given culture; cross-cultural comparisons indicated that only the Japanese male rankings agreed with the male and female Canadian ratings. The Japanese female rankings did not relate to the Canadian rankings. To determine whether the connotative meaning of TAT cards is dependent upon cultural factors, a second study was conducted. Seventy Japanese students and 85 Canadian students rated each TAT card on twelve bipolar semantic scales which represented the general connotative factors of evaluation, potency and activity. The mean judgements for each TAT card against each semantic scale were correlated. Similarly, the rank orders of the general factors were correlated. High correlations obtained from these comparisons provide evidence for the validity of the placements of the semantic scales within their general factors. On the other hand, with the exception of the "meaningful-meaningless" semantic scale for the Japanese sample, the semantic space of connotative meanings generated by the scales of evaluation I and II are dissimilar. Osgood's hypothesis that evaluation, activity and potency are distinct general factors was not upheld. Finally, the correlation between the rankings of the TAT cards, based on the uncertainty measure and the semantic scales, were determined. The results showed that ambiguous cards are viewed as "active" and "potent" by Canadian subjects. Contrary to expectation, evaluation II correlated positively with degree of ambiguity. These findings are, however, unique to the Canadian groups: with one minor exception, Japanese semantic factor rankings did not correlate with ambiguity rankings. Such results most clearly demonstrate cultural influences on the relations between ambiguity and connotative correlates of pictorial stimuli. To provide a comprehensive picture of the influence of culture and sex on the semantic differential results, a Chi square analysis was applied cross culturally and between sexes. It was found that a greater distinction exists between cultures than between sexes in the same culture. An important finding was that cultural differences were expressed more significantly on the semantic scales than on the cards per se. It may be concluded that the semantic correlates of ambiguity only hold for the Canadian sample and that Japanese males are closer than Japanese females to Canadian individuals. The results generally support the hypothesis of cultural influence upon an individual's manner of cognitive responses to perceptual stimuli. / Arts, Faculty of / Psychology, Department of / Graduate

The present study was designed to investigate the reliability of the Frostig Developmental Test of Visual Perception with retarded subjects. The Frostig test is divided into five subtests involving visuo-perceptual tasks and measurements. This study computed reliability coefficients on all the subtests as well as on the total scores. The Peabody Picture Vocabulary Test and the Frostig Developmental test of Visual Perception were also correlated in an attempt to assess an aspect of Frostig validity. The sixty retarded subjects used in this study were divided into groups on the basis of both chronological and mental age, and the test-retest method of reliability assessment was used. The results of this study indicate that the total test scores of the Frostig Developmental Test of Visual Perception are reliable when dealing with the perceptual performance of retarded subjects. The stability of the subtest shows greater variation than does that of the total scores. The subtests of Eye-Motor Coordination and Form Constancy yielded the most variable results and it is evident that with the population studied, these subtests cannot be considered stable enough to be individually, diagnostically, useful. The Peabody Picture Vocabulary correlation with the Frostig Developmental Test of Visual Perception of .537 was significant at the .01 level. / Arts, Faculty of / Psychology, Department of / Graduate

The high speed 2-stroke cycle engine designed for high power-to-weight ratio is relatively inefficient at part throttle. It would be advantageous to incorporate a simple method of allowing extra air to enter the cylinder prior to the fresh mixture, thus stratifying the charge and increasing the proportion of the air-fuel mixture retained in the cylinder at part loads while not deleteriously affecting the maximum power at full throttle. A series of tests, on an engine fitted with a reed valve connecting the atmosphere to the passageway leading to intake ports, were carried out with varying amounts of extra air, the results showed that power, speed, thermal efficiency, and fuel trapping efficiency gave increases at nearly all settings, but with a large excess of extra air, the air-fuel ratio through the carburetor had to be decreased to maintain stable operation. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The primary purpose of this study was the comparison of the rank orders of Thematic Apperception Test cards scaled by three different methods of ambiguity. An additional problem was the comparison of these ambiguity rank orders with personality variables drawn from the literature. For the first method of perceptual ambiguity five descriptive statements for each TAT card were used to obtain the proportional agreement of eighty-four judges on which of these statements was most expressive of what they saw in the card. The degree of agreement of the judges provided the basis for numerical indices and subsequent rank orders by ambiguity. The validity of the descriptive categories was determined by comparing the proportional agreement found in this study with the frequency with which the statements occurred in the original study. A comparison of ranks based on these data showed a greater than 99 per cent validity for the categories. The second method of ambiguity utilized fourteen need concerns rank ordered for each TAT card. The proportional agreement of the judges on the first ranking need was used In order to determine an index of ambiguity and the cards rank ordered on that basis. The agreement of the judges on all fourteen ranks was determined by the average intercorrelation. The rank order of the TAT cards based on the average Inter-correlation indices was compared with the rank order derived from the choice of first rank. All rank orders of the TAT cards, when compared as to sex differences, correlated highly, indicating that the sexes do not appreciably differ in their perceptual and schematic reactions. The rank orders based on the descriptive statements were compared with those based on the rank order of need concerns. The lack of rank order correlation between the two methods led to the conclusion that ambiguity values of TAT cards differ, when they are based on perceptual reactions, from those based on schematic activity which is involved in the ranking of the needs. A third method of scaling the ambiguity of TAT cards is based on the subjective consensus of judges on the number of interpretations for each card. The rank order of this method was correlated with the rank orders by perceptual ambiguity and themata ranking. A lack of comparability with both methods was accounted for by the theory that in the subjective consensus method the global judgement of the subjects relied on both perceptual reactions and schematic processes and is therefore not comparable with ranks based on either the perceptual reaction or the schematic process alone. A comparison of the perceptual and schematic ambiguity rank orders was made with quantitative data from TAT research. It was found that neither perceptual nor schematic ambiguity varied with the productivity of themes, the total number of words, or the emotional tone of TAT stories. No covariance was found between personality revealingness and levels of perceptual or schematic ambiguity. The mean number of emotional words and the number of statements going beyond the pure description of the cards showed no significant correlation with levels of perceptual or schematic ambiguity. Similarly, behavioral response patterns and problems induced by the TAT cards revealed no commensurate variation with schematic and perceptual ambiguity. The lack of correlation with personality variables was explained by the fact that in all instances, the data are the result of complex psychological functions, including both perceptual and schematic functions, and are therefore not comparable to ambiguity rank orders based on perceptual reactions or schematic reactions alone. / Arts, Faculty of / Psychology, Department of / Graduate