Анализ и выбор методики оценки рисков отказов магистральных нефтепроводов

Объектом исследования является напряженно-деформированное состояние линейной части подземного нефтепровода. Цель работы – проанализировать методику оценки рисков отказов нефтепроводов, основанную на определении их напряженно-деформированного состояния, и применить ее к конкретному участку нефтепровода для повышения уровня надежности. В работе рассмотрены подходы к оценке конструктивной надежности нефтепровода и основные параметры, определяющие его напряженно-деформированное состояние. В результате работы проведен расчет напряженно-деформированного состояния подводного перехода участка 379-383 км трассы магистрального нефтепровода "Александровское – Анжеро-Судженск" и сделан вывод об уровне риска его отказа.The object of the research is the stress-strain state of the line section of the buried oil pipeline. The purpose of the work is to analyze the methodology for assessing the risks of oil pipeline failures based on the determination of their stress-strain state and use it to a specific section of oil pipeline to increase the level of reliability. The approaches to an estimation of constructive reliability of oil pipeline and the basic parameters defining its stress-strain state are considered in the work. As a result of the work, the stress-strain state of the underwater crossing of section 379-383 km of the route of the Alexandrovskoye-Anzhero-Sudzhensk main oil pipeline was calculated and a conclusion was made about the level of risk of its failure

Microtensile bond strength of resin-post interfaces created with interpenetrating polymer network posts or cross-linked posts

Objective: The purpose of this study was to evaluate the microtensile strength of composite bonded to interpenetrating polymer network (IPN) or cross-linked glass fibre posts and to observe the failure modes by using light and scanning electron microscopy. Methods: Twenty posts containing IPN resin matrix and 20 posts containing cross-linked epoxy polymer matrix were used for testing. One half of the posts from each type was treated with Stick Resin, the other half was treated with OptiBond. Composite resin was used to build up a block on the bonding surface. Tensile strength data was analysed statistically using the non-parametric Kaplan-Meier survival analysis. The distribution of failure modes as a function of post type/bonding agent was evaluated using the ?² test. Results: The mean tensile strength values were lower for the groups bonded with OptiBond and higher for the groups bonded with Stick Resin (p = 0.017), the type of post used had no statistical significance (p = 0.263). All the IPN posts showed cohesive failure within the post The cross-linked posts demonstrated a higher number of adhesive failures and lower number of cohesive failures within the post (?² = 0.0001). Conclusions: Stick Resin was more effective than OptiBond in bonding composite cores to fibre posts. Post fracture was the failure mode of IPN posts, debonding of the composite core was the failure mode of most of cross-linked posts. These different failure modes may appear clinically in endodontically treated teeth restored with the post types tested in this study

Which White Wire? A Multi-centre Randomised Controlled Trial on Alignment Efficiency and Colour Performance

AIMS: To evaluate the alignment efficiency and colour performance of four coated nickel-titanium aligning archwires over an eight-week period. The aim was to establish whether the latest aesthetic archwires have dispelled their reputation. SUBJECTS AND METHOD: One hundred and twenty participants requiring fixed appliance orthodontic treatment had each dental arch randomly allocated to one of four interventions: (1) Forestadent® BioCosmetic® 0.017 inch (2) Forestadent® Titanol® Cosmetic 0.016 inch (3) TP Orthodontics Aesthetic 0.014 inch (4) Ortho Organizers® Tooth Tone® 0.016 inch. The archwires were ligated and remained in situ for an eight week period. Changes in Little's Irregularity Index were measured on dental casts using digital callipers and retrieved archwires were measured for colour change (ΔE) and coating loss. Colour assessments were made using digital photography and Adobe® Photoshop®, with ΔE values computed using the CIE L*a*b* system. Coating loss was measured by analysing digitally scanned images and using Autodesk® AutoCAD®. RESULTS: One hundred and nineteen patients (74 females, 45 males) completed the trial. Significant alignment was achieved in all groups, however, one-way ANOVA showed no difference in alignment efficiency among the four groups. All four archwires showed significant mean colour change and coating loss after clinical use. One-way ANOVA showed a statistically significant difference between the archwires for ΔE (P = 0.001), with Titanol Cosmetic showing the greatest statistically significant colour change. There was no statistically significant difference between the archwires for coating loss. CONCLUSION: There was no difference in alignment efficiency amongst the coated archwires used, however there was appreciable colour change and coating loss after clinical use of coated aligning archwires. The aesthetic properties of these coated archwires are not ideal