The present work deals with modes and mechanisms of failure in compression of angleply laminates. Experimental results were obtained from 42 angle-ply IM7/8551-7a specimens with a lay-up of [ (±9) / (=F9)] 6s where 9, the off-axis angle, ranged from 0° to 90°. The results showed four failure modes, these modes being a function of off-axis angle. Failure modes include fiber compression, inplane transverse tension, inplane shear, and inplane transverse compression. Excessive interlaminar shear strain was also considered as an important mode of failure. At low off-axis angles, experimentally observed values were considerably lower than published strengths. It was determined that laminate imperfections in the form of layer waviness could be a major factor in reducing compression strength. Previously developed linear buckling and geometrically nonlinear theories were used, with modifications and enhancements, to examine the influence of layer waviness on compression response. The wavy layer is described by a wave amplitude and a wave length. Linear elastic stress-strain response is assumed. The geometrically nonlinear theory, in conjunction with the maximum stress failure criterion, was used to predict compression failure loads and failure modes for the angle-ply laminates. A range of wave lengths and amplitudes were used. It was found that for 0° S 9 S 15° failure was most likely due to fiber compression. For 15° < 9 oS 35° failure was most likely due to inplane transverse tension. For 35° < e ~ 70° failure was most likely due to inplane shear. For e > 70° failure was most likely due to inplane transverse compression. The fiber compression and transverse tension failure modes depended more heavily on wave length than on wave amplitude. Thus using a single parameter, such as a ratio of wave amplitude to wave length, to describe waviness in a laminate would be inaccurate. Throughout, results for AS4/3502, studied previously, are included for comparison. At low off-axis angles, the AS4/3502 material system was found to be less sensitive to layer waviness than IM7 /8551-7 a. Analytical predictions were also obtained for laminates with waviness in only some of the layers. For this type of waviness, laminate compressive strength could also be considered a function of which layers in the laminate were wavy, and where those wavy layers were. Overall, the geometrically nonlinear model correlates well with experimental results. / Master of Science

To investigate the changes in glycolipid biosynthesis during early embryogenesis mouse F9 teratocarcinoma cells were induced to differentiate in vitro in the presence of retinoic acid. Control embryonal carcinoma cells and their differentiated derivatives, RNF9 cells, were metabolically-radiolabeled with [6-3H]galactose or [6-3H]glucosamine, and their glycolipids were compared. The neutral and acidic glycolipid fractions from both cell lines were subjected to ozonolysis and alkali fragmentation or endoglycoceramidase digestion to release the glycolipid-derived oligosaccharides. The neutral oligosaccharides were separated according to size by gel filtration and high performance liquid chromatography. These analyses indicated that differentiated F9 cells synthesized less high molecular weight oligosaccharides (containing more than 5 sugar residues) relative to controls. Serial lectin affinity chromatography on columns of immobilized Helix pomatia. Wisteria f1oribunda. Griffonia simplicifolia-I and Ricinus communis-' agglutinins followed by reduction and permethylation revealed that globoside (GaINAcβ1, 3Galα1, 4Galβ1, 4Glc) and lactose (Galβ1,4Glc) are the principal glycolipid-derived oligosaccharides synthesized by F9 and RNF9 cells. An increased biosynthesis of these components was observed in RNF9 cells relative to controls. These changes paralleled the reduced biosynthesis of Forssman pentasaccharide (GaiNAcα 1 ,3GaINAcβ1 ,3Galα1 ,4Galβ1 ,4Glc) reported previously. Normalization of the incorporation of 3H-monosaccharides in glycolipid-derived oJigosaccharides to the number of cells indicated a 2-6 fold increase in the incorporation of radioactive precursors in RAlF9 cells relative to F9 controls, suggesting that an enhancement in glycosphingolipid biosynthesis accompanies the differentiation of F9 cells. The monosialylganglioside-derived oligosaccharides obtained from F9 and RAlF9 cells were separated by anion exchange chromatography. A reduced biosynthesis of high molecular weight components was observed in RAlF9 cells when compared with undifferentiated F9. Lectin affinity chromatography on immobilized Maackia amurensis agglutinin followed by reduction and permethylation indicated a dramatic increase in the synthesis of GM1 (Galβ1,3Ga1NAcβ1,4[NeuAcα2,3] Galβ1,4Glc) and GM3 (NeuAcα2,3Galβ1,4Glc) in RAlF9 cells relative to controls. These changes were accompanied by a decrease in the synthesis of sialyltetrasaccharide a (NeuAcα2,3Galβ1 ,3GlcNAcβ1 ,3Galβ1,4Glc) and sialylparagloboside (NeuAcα2,3Galβ1 ,4GlcNAβ1 ,3Galβ1 ,4Glc) in the differentiated cells. These observations are in agreement with previous reports in leukemic and human embryonal carcinoma cell lines and may be related to the growth arrest and antigenic changes associated with F9 differentiation. In the work reported herein, serial lectin affinity chromatography in concert with permethylation analysis prove to be powerful methods for the isolation and characterization of glycolipid-derived oligosaccharides. The application of these methods has allowed the unequivocal identification of main glycosphingolipid components as well as of some representing less than 1 % of the total glycolipids synthesized by two cell lines. This information should provide the basis for further studies involving glycosyltransferas. / Master of Science

This research assessed the effects of inconsistencies in graphic direct manipulation interfaces. Objective and subjective measurement techniques were employed to determine how inconsistencies affected performance in an Apple Macintosh-based computer application called “The Personal Organizer.” Three groups of 11 participants, all familiar with the Macintosh computer, were given a set of similar tasks on different versions of the application in a pretest (control version), treatment (control or one of two inconsistent versions), post-test (control version) experimental design. Performance was measured using two objective measures: task completion time and the number of input control actions. Analysis of variance and correlational procedures were used to interpret these measures. A set of 29 bipolar semantic differentials were used to form a subjective measure of consistency. The linear sum of the scores on a subset of these items was used to create a composite measure of consistency. An analysis of variance procedure was performed on the composite measure, called the Preference Index. Results show that time and subjective measures are not identical in their ability to discriminate between inconsistent versions of the interface. It is concluded that the inconsistency of the interface has different effects on subject’s ability to complete tasks as compared to subject’s ability to rate interface consistency. Interface designers should be aware that subjective ratings of interface consistency need to be collected in concert with objective performance measures to assess the effects of graphical user interface inconsistencies upon human performance. / Master of Science

The purpose of this study is to investigate the primary factors which control the engineering behavior of silts. The methods of classifying silts at present do not provide much basis to infer how silts will behave in the field for design purposes. In the course of this research study, series of UU and CU triaxial test results of different silt samples were gathered to investigate the factors that control the strength parameters of silts. Effective and total stress strength interpretation were done on the test results. The effective stress friction angle were evaluated using the CU triaxial test results. Undrained strength parameters were determined from the CU and UU triaxial test results, and comparison were performed using the undrained strength ratio S_u/p. Silt samples which exhibit dilative behavior during undrained shear make it difficult to define failure. Because of this behavior, the test results were interpreted using different failure criteria to assess the effective stress friction angle and the undrained strength parameters. Test results indicate that the effective stress friction angle can be evaluated using the CU triaxial test will little uncertainty. The undrained shear strength of silt samples are influenced by the type of failure criteria. The results indicate that a unique undrained shear strength can not be determined because the samples get stronger with increasing strain. A reliable method of evaluating the undrained shear strength of silt samples is to determine the relationship between the undrained strength ratio and the changes in pore pressure. / Master of Science

The disposal of water treatment residual has received little attention due to a lack of regulation, funding, and concern about their environmental impacts. Many treatment plants discharge alum residual directly into nearby water courses or dewater them for landfilling. If suitable land is available, land application of residual is cost effective and has the potential for negligible effects on the environment and may prove to be a long-term solution to the disposal problem. This research project investigated the effects of land application of alum residual on crops or vegetation grown on fine loamy Slagle soil (<i>siliceous, thermic aquic hapludults</i>). Prior research identified the reduction in plant available P as a potential concern. During summer months. many water treatment plants also add powdered activated carbon (PAC) during the treatment process to prevent taste and odor problems. The PAC ultimately ends up in the residual and alters its chemical characteristics. The effects of land-applied PAC residual on plant growth was also investigated. Fescue (<i>festuca arundinacae</i>) yields decreased with increased residual addition. Lime addition did not Significantly effect fescue yield. Reductions in plant yield were attributed to a reduction in plant available phosphorus (P) in soils receiving higher residual loadings. Supplemental fertilization was able to overcome the P availability problem. The presence of manganese in the residual did not adversely affect plant yields. Likewise, incorporation of spent PAC into the residual did not reduce yields. / Master of Science

Juvenility and flowering requirements were examined in Coreopsis grandiflora 'Sunray', C. lanceolata 'Early Sunrise', and Chrysanthemum x superbum 'G. Marconi' and 'Snow Lady'. C. grandiflora 'Sunray' and C. lanceolata 'Early Sunrise' grown from seed under continuous short days (SD) did not flower. 'Sunray' remained vegetative in long days (LD); however, LD induced flowering in 70 to 100% of the 'Early Sunrise' plants moved from SD to LD at true leaf stages beginning with 0 (cotyledons only) and progressing at 2 or 3 leaf increments to 24 leaves. The loss of juvenility in 'Early Sunrise' was gradual, with fastest flowering from onset of LD, 46 days, occurring when plants were transferred to LD at the 16 leaf stage. Plants moved to LD at six leaves flowered most rapidly from time of seeding, 84 days. Total leaf number at first flower increased as leaf number at transfer to LD increased. Chrysanthemum x superbum 'G. Marconi' was relatively unresponsive to LD, whereas all 'Snow Lady' plants flowered in LD treatments except the 24 leaf stage, which had 70% flowering. Although no 'G. Marconi' plants flowered under SD, 90% of the 'Snow Lady' plants flowered in continuous SD. In 'Snow Lady', transfer to LD at the cotyledon stage promoted fastest flowering from time of seeding, 75 days, and produced plants with the fewest number of leaves at first flower. Histological examination of apices of C. x superbum 'Snow Lady' revealed floral initiation in all 5 plants sampled following 3 weeks of LD. Initiation in SD started after the fifth week and was evident in all 5 plants sampled after the ninth week of SD. The effects of chilling and a limited number of inductive photoperiods was examined in all 4 cultivars. Four months of natural outdoor chilling followed by at least 6 LD, promoted 40 to 100% flowering in Coreopsis grandiflora 'Sunray' and Chrysanthemum x superbum 'G. Marconi'. Chilling followed by SD increased flowering in each cultivar as compared to continuous SD with no chilling. The effects of limited inductive photoperiod (LIP) were evident in both Coreopsis cultivars, but not seen in either cultivar of C. x superbum. LIP inhibited stem elongation by approximately 10 cm in the chilled Coreopsis cultivars and also in C. lanceolata 'Early Sunrise' grown from seed with no chilling. LIP did not affect the scape length of either chilled or unchilled plants. / Master of Science

LaRC-TPI, an aromatic thermoplastic polyimide, and Kapton®, a poly(pyromellitimide) were exposed to oxygen, argon and ammonia plasmas as pretreatments for adhesive bonding. Chemical changes which occurred in the surface as a result of the plasma treatments were investigated using x-ray photoelectron spectroscopy (XPS) and infrared reflection-absorption spectroscopy (IR-RAS). Water contact angle analysis was utilized to characterize the changes in surface wettability, and the ablative effects of the plasmas were monitored using ellipsometry and high resolution scanning electron microscopy (HR-SEM). Both XPS and IR-RAS results revealed the formation of polar functional groups at the surface. Contact angle analysis showed enhanced water wettability of the plasma-treated surfaces. As monitored by ellipsometry, oxygen and argon plasmas were seen to be highly ablative, whereas an ammonia plasma was only moderately so. HR-SEM micrographs revealed texturized surfaces in the case of oxygen and argon plasmas, but not in the case of ammonia plasma. Oxygen and argon plasmas appear to react with the polyimides via a fragmentation/oxidation mechanism, forming a loosely attached layer composed of low molecular weight polymer chains. The effect of ammonia plasma is postulated to be imide ring-opening resulting in the formation of amide functional groups. The 180° peel test was utilized to determine the receptability of the plasma-treated polyimide surfaces toward bonding with other polymeric materials. Adhesives used were a pressure sensitive acrylate and poly(ether sulfone). The pressure sensitive adhesive, although not representing a realistic bonding situation, does represent a system which presents the least disturbance to the plasma-modified layer, allowing the physical nature of the plasma-treated surface to be probed. The peel test values of the pressure sensitive adhesive/plasma-treated polyimide systems fell below the level of the non-treated controls, regardless of the plasma treatment used. Peel surface analysis revealed the presence of polyimide on the pressure sensitive adhesive failure surface, indicating failure in the plane of a weak boundary layer created by plasma. The removal of the weak boundary layer by solvent treatment restored the peel values to the level of the controls. Bonding of Kapton® films with poly(ether sulfone) showed an opposite trend; peel strengths of the plasma-treated samples all showed improvements versus the non plasma-treated control. Plasma treatments of LaRC-TPI which had been deliberately contaminated with mold release and high density polyethylene illustrated showed that plasma treatments are not always detrimental to adhesion. It was shown that the physical as well as the chemical nature of a polymer surface is critical to the level of adhesion which can be achieved. / Master of Science

The objective of this thesis is to verify the "base test method" for uplift loading of C- and Z-purlin supported, standing seam metal building roof systems. To achieve this end, eight sets of full-scale roof system tests were conducted. Each test set consisted of a single span base test and a three-span, multi-purlin line, confirming test. The base test method for uplift loading, in its present form, did not prove to be an effective method for determining the failure load of a multispan, multi-purlin line, standing seam roof system. Suggestions are made for possible modifications to the method. / Master of Science

The static strength and long-term performance of composite hip prostheses under complex mechanical and environmental loading conditions are studied through theoretical modelling and experimental investigations. Two static strength models, namely, a cantilever beam model and an elastic foundation model, were developed using a strength of materials approach, and were transformed into an operating computer code which can be used for stress analysis and engineering design of composite prostheses. The predictions of the two models are shown to be in very good agreement with experimental data. A dynamic, mechanistic cumulative damage model that is capable of predicting the residual strength and life of a composite prosthesis under cyclic loading was also developed, based on a 'Critical Element Model' and the static strength models, and was transformed into an operating computer code. The predictions by the dynamic model are, in general, within engineering accuracy when compared to the experimental data. A test fixture was designed to perform fatigue tests on the composite prostheses. A total of nine prostheses were fatigue tested. Several nondestructive evaluation (NDE) techniques were used to assess fatigue damage development in the specimens tested. Among all the NDE techniques used, x-ray radiography and a surface replication technique were shown to be most effective qualitatively. Destructive tests were also performed on selected specimens, the results are complimentary to the information obtained from the NOE tests. / Master of Science

The dynamics of two three-degree-of-freedom systems with quadratic nonlinearities are studied. The first system has two simultaneous two-to-one internal resonances. The second has a combination internal resonance. In both cases the response to a primary resonant excitation of the third mode is studied. The method of multiple time scales is used to obtain the equations that govern the amplitudes and phases of the first system. Then the fixed points of these equations are obtained and their stability is determined. The fixed points undergo Hopf bifurcations, and the overall system response can be periodic or periodically, quasiperiodically, or chaotically modulated. The method of the time-averaged Lagrangian is used to obtain the equations that govern the amplitudes and phases of the second system. The fixed points of these equations are obtained and their stability is determined. These fixed points undergo Hopf bifurcations, and the overall system response can be periodic or a two- or three-torus. / Master of Science