Browsing by Author "Vroulis, George"
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Item Circumferential waves on rough cylindrical shells(1970) Vroulis, George; Hayre, Harbhajan S.; Sinclair, Rex; Schneider, William P.; Finch, Robert D.; Blumberg, RandolphThe theory of acoustic scattering and in particular circumferential waves on statistically rough surfaces of air-filled aluminum cylindrical shells [...]Item Identification of simple geometrical objects from their backscattered pattern(1968) Vroulis, George; Hayre, H. S.; Michaels, Edward L.; Finch, Robert D.Both theoretical and experimental work were done in the areas of scattering of incident wave and the generating of creeping waves on simple geometrical objects. Acoustic plane waves of continuous or short pulse form were used in the experimental work where city water was used as the propagation medium. The targets were cylinders, spheres, and cones made out of aluminum, stainless steel, and maple wood, and their dimensions ranged from 10 to 60 wavelengths, which was selected to be 1.5 millimeters. The transducers used as transmitter and receiver were resonant at a frequency of 1 megacycle but these were excited at frequencies lying between 850 to 1050 kilocycles. In the first part of the experimental work, the targets were suspended in water by a thin piano wire support, whereas in the second part these were either completely or partially buried in glazing putty. The backscattered fields for both the continuous and the pulsed wave transmission cases were recorded. The results were compared with the theoretical predictions, and in the cases of spheres and the cylinders, the comparisons were quite satisfactory, while in others the complexity of the target and its orientation imposed some difficulties. In an effort to identify an object by its backscattered field pattern, it was necessary to write two computer programs which would scan and analyze the experimental data. The first program compares the polar data of the bistatic case and the second one analyzes the return of the monostatic pulsed case. Each program identifies a simple geometrical object in the form of the probability of its identification being the same as that for which the reference data was taken. All the experimental data is also presentedin the forms of diagrams and actual photographs of the oscilloscope traces with an adequate explanatory discussion. Finally a method of simulating creeping waves, in weightless environment is suggested (for future satellite laboratories) and compared with Bogush's method.Item Structure, process, and individual differences in the comprehension and recall of prose(1981) Thomas, Diane; Malin, Jane T.; Cofer, Charles N.; Doughtie, Eugene B.; Foorman, Barbara R.; Vroulis, GeorgeThe issue of how individuals understand and remember information from prose passages has been a topic of interest in psychology since Bartlett's pioneering work. Remembering, was published in 1932. The concept of remembering as an active, constructive process that is guided by abstract, organizational frameworks or "schemata" has become familiar now, and many psychologists are interested in investigating the nature of these schemata and in specifying how they are implemented during retrieval. Handler and Johnson (1977, 79) have proposed that retrieval schemata for prose are based on subjects' shared knowledge about the well-formedness of stories, and on ideal, rule-governed relations existing between individual story propositions. They propose that these syntactic schemata are major determinants of a subject's recall output. They report that subjects make predictable omissions and errors in recall when the actual text does not conform to the specifications of the ideal story grammar. The present study was designed to test this model further and to explore the effect of two processing variables, the mode of presentation of the story material (ORAL and WRITTEN) and subjects' reading ability level, on memory for prose passages. Two types of stories, a simple, relatively well-formed work and a longer, ambiguous passage were used as stimulus materials. An analysis of the recall protocols was was made with respect to the frequency of errors and omissions made by subjects in recalling both story types. The results were considered in the light of Handler and Johnson's pre dictions about recall. An expanded and more rigorous recall scoring system than that utilized by Handler and Johnson (1977) was developed for this purpose. This system allows for scoring categories that include attempts by the recaller to increase the coherence and meaningfulness of the story during recall as well as scoring for categories of omissions and errors. Data on inter and intra-rater reliability using this system are also reported. The results of the present study did not support the predictions made by Handler and Johnson (1977, 79) concerning subjects' recall performance. Recall performance was affected by the mode in which the prose materials were presented and by individual competencies in processing information in a given mode. These results are not wel1-accounted for by syntactic structural models such as the one proposed by Handler and Johnson (1977, 79), and other models that do consider task demands, processing capacity, and individual abilities to organize information were found to be better predictors of recall performance. The present system of scoring recall protocols was also used to explore the nature of the processing differences across modes of presentation and within groups who differ in their ability to comprehend material in the written mode. A model of the way in which readers and listeners attempt to meet processing demands was proposed based on the characteristic omissions and errors made by each group during recall. The differences noted between readers of varying skill levels was explored in a similar way. These differences seemed to involve the ability of better readers to hierarchically organize the story propositions and to construct coherent macrostructures even in the absence of coherence in the text base. Poor readers were less skilled at using information in the text to "fill in the gaps" in text structure and did not appear to be able to organize important elements of the text to facilitate recall. Educational procedures to enhance these skills in poor readers were suggested. The usefulness of employing the present scoring system to discriminate cognitive processing differences in clinical subject populations was also considered.