Arctic quaternary ostracods and their use in paleoreconstructions

The paper deals with original and published data on fossil ostracodal assemblages from the Eurasian Arctic Kara, Laptev and Chuckchi seas. As a whole, six ecologically different assemblages were distinguished (freshwater, brackish water, marine of the inner, middle and outer shelves and upper continental slope), they replace each other upcore reflecting a gradual increase in water depth and distance from the coast. These assemblages are stable in the entire Arctic region and can be used for interpretation of environments in different Arctic areas

Experimental and Numerical Analysis of the Shear Ring.

The shear ring is dependent on a weak link that is activated in case of emergency situations. The failure of the weak link needs to be propagated in a controlled way and it is the only component in the tool that is allowed to brake. In an emergency attempt performed offshore, the current design of the shear ring did not shear at the required load. The testing of the ring was unsuccessful and the attempt caused failure instead on the surrounding parts of the main tool. The reasons behind this unsuccessful event were due to both the material and the geometry of the ring. A new design of the shear ring was proposed. The purpose of this master thesis was to evaluate the failure of both the old and new design. The theoretical analyses on the current design of the shear ring were performed with two methods; implicit and explicit. The results were compared to a physical test in order to evaluate the accuracy of the computational methods. The implicit method and the physical test provided similar results. The explicit gave slightly higher forces but it followed the same behavior as the physical test. Both experimental and theoretical analyses show that the current design of the shear ring gets stuck to the component below the ring. The value of the explicit method is the modeling of the damage and failure in a material. This cannot be performed by the implicit method. The theoretical analysis of the proposed design of the shear ring was performed with the explicit method using the shear failure model to simulate the failure of the ring. The shear failure criterion is robust and simple but this method requires a full stress train curve until failure. The proposed design of the shear ring broke in a predictable way.Säkerhetsringen är en komponent som skall gå sönder vid olyckshändelser eller oförberedda situationer för att skydda utrustning och miljö ute i havs. Därför är det viktigt att säkerhetsringen, vid rätt kraft, går sönder på ett förutbestämt sätt. Eftersom säkerhetsringen är den enda komponenten i verktyget som får gå sönder är det väldigt viktigt att denna process är kontrollerad. Vid ett test som utfördes ute till havs så gick inte den nuvarande konstruktionen på säkerhetsringen sönder på ett förutbestämt sätt. Testet av ringen var ej lyckosamt vilket orsakade skada på de omkringliggande delarna på huvudverktyget. Anledningarna bakom det misslyckade testet berodde på både materialval och geometrin på säkerhetsringen. En ny konstruktion på ringen togs fram. Den här uppsatsen har till uppgift att utvärdera brottet av den gamla och nya konstruktionen. De teoretiska analyserna på den nuvarande konstruktionen på säkerhetsringen genomfördes med två olika metoder, implicita och explicita metoden. Resultaten jämfördes med ett fysiskt test för att säkerställa träffsäkerheten av de båda beräkningsmetoderna. Implicita metoden och det fysiska testet påvisade liknande resultat. Den explicita metoden gav en aning högre krafter men det följde samma beteendemönster som det fysiska testet. Båda det fysiska testet och de teoretiska beräkningarna visade att ringen fastnade på komponenten direkt under den. Värdet av den explicita metoden är modelleringen av brott i ett material. Detta kan inte genomföras med den implicita metoden. De teoretiska beräkningarna på den föreslagna konstruktionen på säkerhetsringen genomfördes med den explicita metoden och ’’Shear failure’’ kriteriet för att simulera hur ringen går sönder. Detta kriterium är robust och simpelt men det kräver en dragprovkurva tills brott av det material som används. Den föreslagna konstruktionen på säkerhetsringen går sönder på uträknat sätt

Late Miocene ostracod assemblages from eastern Mediterranean coral reef complexes (central Crete, Greece)

Ostracods from ten Late Miocene coral reef complexes built by Siderastrea, Tarbellastrea and Porites, cropping out in the Messara Plain (southern Iraklion basin, central Crete), have been investigated and five assemblages have been recognised, which point to different marine environments: (1) assemblage from the basal sandy silts, dominated by very shallow inner-infralittoral species, such as Cyamocytheridea meniscus, Cyamocytheridea obstipa, Cyamocytheridea dertonensis, Cytheretta semiornata and Nonurocythereis seminulum; (2) assemblage from the coral reef complexes within which Grinioneis haidingeri, Aurila cicatricosa, Cimbaurila diecii, Tenedocythere cruciata, Pokornyella italica and Callistocythere quadrangula are dominant and point to a stable inner-infralittoral environment characterised by warm, quiet and well-oxygenated waters; (3) assemblage from the silts intercalated among the coral reef complexes, mainly characterised by Neomonoceratina laskarevi, Cytheridea acuminata, Phlyctenophora farkasi and Aurila albicans together with Callistocythere spp., Xestoleberis communis and Xestoleberis dispar, which points to a very shallow marine environment rich in aquatic vegetation; (4) assemblage from the upper silts, which records the absolute dominance of Xestoleberis species, reflecting a very shallow and highly-vegetated environment and (5) assemblage from the uppermost silty clays, dominated by Hemicytherura defiorei, Xestoleberis spp. and Palmoconcha dertobrevis, accompanied by Acanthocythereis hystrix, Cytherella scutulum, Bairdoppilata conformis, Semicytherura spp., Krithe sp., Cytheropteron alatum, Bythocypris sp. and Pseudocythere caudata, which suggest deeper marine environments probably located in the outer infralittoral/inner-circalittoral zones. The studied section has been dated by means of calcareous nannoplankton to be not younger than Zone MNN9 (Early Tortonian), which is the biostratigraphical datum recorded in the fine-grained deposits that overlie the coral reef complexes. An age not older than Tortonian can be inferred by the stratigraphical distribution of the recognized ostracods. Thus, the coral reef complexes have been tentatively referred to the Early Tortonian