Dynamic and quasi-static models for analysis of a pipe lay spread are presented in the paper. Depending on the type of a pipe, spooling it on a big drum (reel) may cause plastic deformations. When the pipe is reeled out at sea, again it undergoes plastic deformations. In order to model such a nonlinear behaviour, a model, which includes both elasto-plastic material characteristics and large deformations, is required. Discretisation of the pipe is performed by means of the Rigid Finite Element Method (RFEM), which allows us to study static and dynamic problems, taking into account required properties of the model. Different sea conditions are simulated and analysed. It is shown how operational conditions can limit the ability of laying operation by a dedicated vessel, due to an unstable system response. The second part of the paper presents an upgrade of a passive reel drive by application of an active drive. In the model used for control applications, the pipe is modelled by a neural network. This allows us to perform a real-time calculations. In this fast-response calculation model, nonlinear aspects of the system are taken into account. The improvements in a pipe laying vessel performance are presented by some results of numerical simulations. The conclusions are also formulated. 相似文献
The notion of remote element synthesis has recently been modified to explain the presence of nucleogenetic isotopic anomalies
and decay products of short-lived nuclides by injection of a small amount ofexotic nucleogenetic material. Even with this modification, remote element synthesis seems inconsistent with the following observations:
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Evidence of coupled variations in the chemical and isotopic compositions of the source material for meteorites.
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Residual coupling of chemical and isotopic heterogeneities across planetary distances in the solar system today.
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The mass-fractionation relationship seen across isotopes of elements in the planetary system, in the solar wind, and in solar
flares.
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Linkage of short-lived radioactivities with isotopic anomalies and with physical properties of their host grains, as expected
for early condensate of fresh stellar debris.
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Temporal and spatial distributions of short-live nuclides and their decay products.
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Mirror-image (+ and −) isotopic anomalies in meteorite grains that sum to “normal” isotopic ratios, as expected of unmixed
products of the same nuclear reactions that produced our bulk elements.
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The lac supporting evidence for “presolar” grains or nearby stars that injectedexotic material into the early solar nebula.
In this study, dynamic behavior and earthquake resistance of Alibey earth dam was investigated. The dam was modeled with four
node plane-strain finite elements (FE) and displacement-pore pressure coupled FE analyses were performed. Nonlinear material
models such as pressure dependent and independent multi yield materials were implemented during the analyses. Transient dynamic
FE analyses were performed with Newmark method. The Newton-Raphson solution scheme was adopted to solve the equations. Liquefaction
and/or cyclic mobility effects were considered during the analysis. For the FE analyses, OpenSees (Open System for Earthquake
Engineering Simulation) framework was adopted. 相似文献