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Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / The histology, histochemistry arxi fine structure of the tubular glands of the isthmus region of the hen's oviduct were studied during various phases of the egg laying cycle. Numerous tubular glands were found in the lamina. propria of the isthmus region. These glands consisted of a single layer of pyramidal epithelial cells. Histochemical studies showed the presence of large secretory granules in the apical region of the cytoplasm of the gland cells. 'lhese granules were composed of neutral mucopolysaccharides and sul:fur-ccmtaining proteins and were especially abundant during active secretory phases of the egg laying cycle. [TRUNCATED] / 2031-01-01

Student Number : 9306442N - PhD thesis - School of Electrical and Information Engineering - Faculty of Engineering and the Built Environment / This thesis describes the design, construction and evaluation of a prototype modified tubular linear synchronous motor. The linear motor has a long static primary and a short permanent magnet mobile secondary. The design is unique in that a tubular topology has been modified to allow access to the moving secondary section. This modification means that this design can be used in long distance applications. The application for this research is the use of linear motors in rope-less vertical trans- portation systems in ultra deep level mines. The design of the linear motor has been analysed from an electrical, magnetic, mechanical and thermal perspective. Finite Element Analysis was used to predict the performance of the linear motor. The design of the secondary section has been optimised to produce the greatest possible thrust force while reducing the effects of the cogging forces. The linear motor has been tested extensively and the results correlate with theoretical predictions from the Finite Element Analysis. This project proves that the modified tubular lin- ear synchronous motor is a viable technology that can be used in rope-less vertical transportation systems.

Tese de mestrado. Engenharia mecânica. Faculdade de Engenharia. Universidade do Porto. 2005

The tubular welded joints used in the construction of Offshore structures can experience millions of variable amplitude wave induced stress cycles during their operational life. Fatigue has been identified as the main cause of degradation of structural integrity in these structures. As a result, fatigue is an important consideration in their design. Jack-up legs are made from a range of high strength steels with yield strengths up to 70OMPa. These steels are thought to exhibit fatigue resistance properties which are different when compared with conventional fixed platform steels such as BS 4360 50D and BS 7191 355D. The difference in their behaviour was heightened by the discovery, in the late 80s and early 90s, of extensive cracking around the spud can regions of several Jack-ups operating in the North Sea. It was thought that these steels may be more susceptible to hydrogen cracking and embrittlement. There was the additional requirement to study their behaviour under realistic loading conditions typical of the North Sea environment. This thesis contains results of an investigation undertaken to assess the performance of a typical high strength weldable Jack-up steel under realistic loading and environmental conditions. Details of the methodology employed to develop a typical Jack-up Offshore Standard load History (JOSH) are presented. The factors which influence fatigue resistance of structural steels used in the construction of Jack-up structures are highlighted. The methods used to model the relevant factors for inclusion in JOSH are presented with particular emphasis on loading and structural response interaction. Results and details of experimental variable amplitude corrosion fatigue (VACF) tests conducted using JOSH are reported and discussed with respect to crack growth mechanisms in high strength weldable Jack-up steels. Different fracture mechanics models for VACF crack growth prediction are compared and an improved generalised methodology for fast assessment of Offshore structural welded joints is proposed.

The bulge forming process is a method for shaping tubular components using an internal hydrostatic pressure combined with an axial compressive force. Initial investigations involved carrying out an extensive literature survey to determine the components which could be formed and the types of machines which have been used. Subsequent to this, initial tests were carried out using a previously designed die and tool block in conjunction with a compression testing machine. In these tests copper tubes were formed into expander/reducers and cross pieces by manual adjustment of the axial force and internal pressure. Having obtained experience of the difficulties associated with this die and toolblock, and the loading requirements necessary for theforming process, a new bulge forming machine was designed. The design of the machine was based on the following main criteria: (i) The machine should be free standing and self contained. (ii) The axial deformation of the ends of the tube blank should besynchronised to allow the bulge to form centrally on the tube. (iii) The internal bulge forming pressure should be externallycontrollable during the forming process. (iv) The design should incorporate facilities for subsequent automatic control using a micro-processor/computer. On the basis of these requirements, a machine was designed, built andcommissioned. After correcting a few problems encountered in the commissioning of the machine, a series of tests were carried out, forming tee and cross pieces from copper tube of two different wall thicknesses. These were found to be fairly easy to produce on this new machine. From the resulting components, formed at various combinations of internal pressure and axial compressive force, the limits for a successful forming operation were established. Further analysis of these components was then undertaken to evaluate the effects of the internal pressure and axial compressive force on the bulge height and the wall thickness in the deformation zone. From these results, which have been illustrated graphically, the greatest effect on the resulting bulge can seen to be the axial compressive force. An extension of a theoretical analysis has also been presented, which predicts the wall thickness distribution around the bulge zone. Comparison of these predictions with the experimental wall thickness distributions shows fairly good agreement, especially at the root and tip of the side branch.

This study investigated the bonding technique for the joining together of tubular sections which are under axial loading. In particular the yielding of polymers was studied and the criterion which was eventually used in the analyses was a modification of the Von Mises one. The Paraboloidal criterion accommodates differences in tensile and compressive yield strengths and accounts for any dependence of yielding on the hydrostatic component of the applied stress state. The yielding behaviour of the thin layer of the adhesive epoxy resin was analysed and it has been shown that the prediction of the adhesive strength is affected by the progress of the yield. Comparisons between the Paraboloidal and the Von Mises yield criteria have also been applied to a modified tubular joint involving threads within the bonded region. It is suggested that the prediction of the stresses at yield, using the modified criterion have a greater credibility compared with those of the Von Mises. The paraboloidal yield criterion has been implemented correctly in a standard finite element package ABAQUS. The author has made use of the "user subroutine" facility which allows a user of ABAQUS to write a sub-program defining the material constitutive relations to be used in an analysis.

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