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Some implementation characteristics of the Independent Modal-Space Control method are considered. It is shown that the control method is completely robust with respect to modeling errors and plant truncation effects. The globally optimal control of distributed systems requires distributed actuators. Instead of using distributed actuators, the distributed control is approximated with discrete actuators. Since the distributed control is closely approximated, the closed-loop poles are computed as a perturbation of the distributed control. The discrete actuators are located such that the control spillover is minimized. / M.S.

Experimental measurements ol N₂ resonant charge transfer cross sections were performed. It was found that the energy of electrons used to produce the N₂⁺ ions is an important variable with respect to cross section. An examination of the experimental precision was performed and it was found that the precision of measurement was insufficient to determine the exact form of this relationship. The effect of ion energy (collisional energy) was too small to be seen. Modulated detection was used to improve precision and permit measurement at high noise levels. A description of the apparatus is provided. Consideration of other systems and the suitability of their resonant charge transfer reactions for experimental investigation is discussed. Various theoretical models for estimation of cross section were examined. / M.S.

The architect deals intimately with the concept of time, space, and light. He realizes the separation between the visible world and the invisible world. The architect tries to bridge that gap. This thesis attempts to use architecture to explore issues presented. It allows for a meeting place for individuals as well as a meeting place for the body and its spirit. / M. Arch.

Deep groove and angular con tact 25 and 30 mm bore ball bearings were tested to high speeds using air-oil mist lubrication. Test conditions included cooling air flow rates of 1.5, 3.0, and 6.0 scfm (0.05, 0.10, and 0.20 kg/min), thrust loads of 50, 75, and 100 lb (222, 334, and 445 N), and a constant radial load of 25 lb (111 N). Steady-state bearing outer race temperature was recorded at various speeds under each set of test conditions. Maximum ON values of 1.9 x 10⁶, 1.5 x 10⁶, 1.4 x 10⁶, and 1.26 x 10⁶ were achieved on the 30 mm deep groove, the 25 mm deep groove, the 25 mm angular contact, and the 30 mm angular contact bearings, respectively. Tests were usually terminated when the stabilized outer race temperature reached approximately 200°F (366 K) although the 30 mm deep groove bearing was operated to 240°F (389 K). A cooling air flow rate of 1.5 scfm (0.05 kg/min) was judged not adequate for high speed bearing operation under the tested conditions. An outer-race temperature prediction equation, based on a regression analysis of the test results, is presented for each test bearing. / M.S.

Two sizes (2x4 and 2x10) and two grades (2250f-1.9E and No. 2 KDl5) of Southern Pine lumber having three different test span lengths of 30, 90 and 120 inches were tested in tension parallel-to-grain. Results obtained from the tests indicated that the tensile strengths of the 30-inch test specimens were significantly higher than the tensile strengths of the 90- and 120-inch test specimens. A tensile strength-length effect model was developed for generating tensile strength values of lumber taking the length effect into consideration. The model generates tensile strength values for lumber longer than 30 inches in multiples of 30 inches, ie. 60-, 90- 120-inch lengths. The two sizes and two grades of Southern Pine lumber formed the data base for developing the model. The tensile strength-length effect model utilized an MOE variability model which generated serially correlated MOE's along 30-inch segments for a piece of lumber using a second order Markov model. The segment MOE values were then used in a first-order Markov model to generate serially correlated tensile strength residuals for each 30-inch segment. The segment MOE values and the segment tensile strength residuals were then inputted into a weighted least squares regression to obtain the tensile strength parallel-to-grain for each 30-inch segment. The tensile strength of the generated piece of lumber was then determined using the weakest-link concept; the minimum segment tensile strength value was selected as the tensile strength of the generated piece of lumber. / Master of Science

Distortions and changes in orientation of a 30° wye pile assembly were monitored in an attempt to improve our understanding of this critical connection in cellular cofferdams. Main cell, arc cell and common wall hoop tensions were simulated by applying axial loads to the three wye legs. Loads and displacements were monitored by a microcomputer aided data acquisition system. All of the behaviors studied exhibited some dependence on the ratio between the forces applied to the main and arc cell legs of the wye. Applied loads varied in magnitude and proportion, and the assembly re-oriented to new equilibrium positions. These positions were found to be predictable by solving three non-linear equilibrium equations of a statically determinate model. Common wall tension was observed to exceed main cell tension by 10-80% depending on the ratio of applied loads. Interlock load-deformation responses were measured for interlocks at which connecting piles were not coaxial. Wye angle deformations were found to be very small in the test loading range. The results of this investigation may be useful in developing parameters for and comparing results from finite element models of cellular cofferdams. / M.S.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Experiments were conducted on smooth specimens to study the closure behavior of short cracks at high cyclic strains under completely reversed cycling. Testing procedures and methodology, and closure measurement techniques, are described in detail. The strain levels chosen for the study cover from predominantly elastic to grossly plastic strains. Crack closure measurements were made at different crack lengths. The study reveals that, at high strains, cracks close only as the lowest stress level in the cycle is approached. The crack opening was observed to occur in the compressive part of the loading cycle. The applied stress needed to open a short crack, under high strain was found to be less than for cracks under small scale yielding. For increased plastic deformations, the value of σ_op/σ_max is observed to decrease and approaches the value of R. Comparison of the experimental results with existing analysis has been made and indicates the limitations of the small scale yielding approach where gross plastic deformation behavior occurs. / M.S.

A series of four water-blown flexible polyurethane foams was produced in which the water content was varied from 2 to 5 pph at a constant isocyanate index of 110. A portion of each foam was thermally compression molded into a plaque. The morphology of the foams and plaques was investigated using DMS, DSC, FTIR, TEM, SEM, swelling, WAXS, and SAXS. A high degree of phase separation occurs in these foams and the degree of phase separation is independent of water (hard segment) content. In the foam with the lowest water content the morphology is similar to that of typical segmented urethane elastomers. Small hard segment domains are present with a correlation distance of roughly 7.0 nanometers. When the water content is increased a binodal distribution of hard segments appears. There are the small hard segment domains typical of segmented urethane elastomers as well as large hard segment aggregates greater than 100 nanometers in diameter. The large domains are thought to be aggregates of polyurea that precipitated during the manufacture of the foam. The foam making process successfully incorporated the trifunctional polyols into a network indicating a high degree of polymerization for the hydroxyl-isocyanate reaction. Unreacted isocyanate is present in the foams a month after curing. It is believed to be trapped in the large urea aggregates. WAXS patterns of the foams suggest hard segment ordering that may be of a paracrystalline nature but certainly lacking in true crystallinity. / Master of Science