Development of Piping Stress Analysis Guideline for Neste Jacobs' Projects

The aim of this research was to develop a piping stress analysis guideline to be widely used in Neste Jacobs Oy’s domestic and foreign projects. The company’s former guideline to performing stress analysis was partial and lacked important features, which were to be fixed through this research. The development of the guideline was based on literature research and gathering of existing knowledge from the experts in piping engineering. Case study method was utilized by performing stress analysis on an existing project with help of the new guideline. Piping components, piping engineering in process industry, and piping stress analysis were studied in the theory section of this research. Also, the existing piping standards were studied and compared with one another. By utilizing the theory found in literature and the vast experience and know-how collected from the company’s employees, a new guideline for stress analysis was developed. The guideline would be widely used in various projects. The purpose of the guideline was to clarify certain issues such as which of the piping would have to be analyzed, how are different material values determined and how will the results be reported. As a result, an extensive and comprehensive guideline for stress analysis was created. The new guideline more clearly defines formerly unclear points and creates clear parameters to performing calculations. The guideline is meant to be used by both new and experienced analysts and with its aid, the calculation process was unified throughout the whole company’s organization. Case study was used to exhibit how the guideline is utilized in practice, and how it benefits the calculation process.

Monolithic zirconium dioxide as a full contour restorative material: With special emphasis on the optical and mechanical properties

Full contour monolithic zirconia restorations have shown an increased popularity in the dental field over the recent years, owing to its mechanical and acceptable optical properties. However, many features of the restoration are yet to be researched and supported by clinical studies to confirm its place among the other indirect restorative materials This series of in vitro studies aimed at evaluating and comparing the optical and mechanical properties, light cure irradiance, and cement polymerization of multiple monolithic zirconia material at variable thicknesses, environments, treatments, and stabilization. Five different monolithic zirconia materials, four of which were partially stabilized and one fully stabilized were investigated. The optical properties in terms of surface gloss, translucency parameter, and contrast ratio were determined via a reflection spectrophotometer at variable thicknesses, coloring, sintering method, and after immersion in an acidic environment. Light cure irradiance and radiant exposure were quantified through the specimens at variable thicknesses and the degree of conversion of two dual-cure cements was determined via Fourier Transform Infrared spectroscopy. Bi-axial flexural strength was evaluated to compare between the partially and fully stabilized zirconia prepared using different coloring and sintering methods. Surface characterization was performed using a scanning electron microscope and a spinning disk confocal microscope. The surface gloss and translucency of the zirconia investigated were brand and thickness dependent with the translucency values decreasing as the thickness increased. Staining decreased the translucency of the zirconia and enhanced surface gloss as well as the flexural strength of the fully stabilized zirconia but had no effect on partially stabilized zirconia. Immersion in a corrosive acid increased surface gloss and decreased the translucency of some zirconia brands. Zirconia thickness was inversely related to the amount of light irradiance, radiant exposure, and degree of monomer conversion. Type of sintering furnace had no effect on the optical and mechanical properties of zirconia. Monolithic zirconia maybe classified as a semi-translucent material that is well influenced by the thickness, limiting its use in the esthetic zones. Conventional acid-base reaction, autopolymerizing and dual-cure cements are recommended for its cementation. Its desirable mechanical properties give it a high potential as a restoration for posterior teeth. However, close monitoring with controlled clinical studies must be determined before any definite clinical recommendations can be drawn.