An unprecedented intramolecular remote
C–H activation via
sequential 1,4-palladium migration with an aromatic ring as a conveyor
has been described. This reaction provides an efficient route to construct
diverse polycyclic frameworks in moderate to good yield via palladium-catalyzed
remote C–H activation/alkene insertion, arylation, alkenylation,
and the Heck reaction. The preliminary mechanistic studies revealed
that the 1,4-palladium migration process was reversible.
Coral mud is widely distributed in the South China Sea. Studying deformation laws of coral mud is important to the infrastructure development in the South China Sea. In this article, a one-dimensional oedometer test of coral mud under near-natural conditions is performed. The exponential fitting model, Burgers model and ODGM model are used to analyse the time-strain relationship of coral mud under different vertical pressures. The self-fitting accuracy and prediction accuracy of the three models under different vertical pressures are compared. Then, the number of data points used in the model was reduced, and the associated change in accuracy and model stability of the three models were analysed. The study found that the ODGM model has high self-fitting, high prediction accuracy, and a high model stability when the number of data points is reduced, which describe the long-term nonlinear deformation of coral mud more accurately.
Coral mud is a special rock and sediment mass and is widely distributed in the South China Sea. Studying the deformation of coral mud is important for infrastructure development in the South China Sea. When choosing a model to describe the long-term deformation of coral mud, it is difficult for a simple nonlinear deformation model to accurately and universally describe the complex deformation processes of the sediment; a complex model is too time-consuming and difficult to apply to practical engineering. In this article, based on a classical element model, the Burgers model, certain elements are modified in combination with one-dimensional oedometer tests under normally consolidated situations. Then, combined with an unloading and reloading test, the modified Burgers model is further improved, and a modified Burgers model considering stress history is obtained. The modified Burgers model considering the stress history only has four parameters, all of which have practical physical significance, which makes the model easy to use. Different loading times and cyclic loading and unloading tests prove that the model has good stability and can, not only simulate the deformation characteristics of sediment, but can also provide good variation rules for the parameters.
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