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Borehole drillstring waves play an important role in geotechnical and exploration applications. Coupled waves are simulated inside and outside a real drillstring in borehole. The drillstring is considered a system with variable geometry. We simulated coupled waves in three domains: inner mud, drillstring, and annular mud. Each mode has a characteristic wave propagation velocity. A consequence of this coupling effect is that waves from the downhole tool can be partially reflected and converted to other modes at a discontinuity in the formation stiffness or in the annular cross section that can cause a significant reduction of the transmitted wave energy. Examples of application are reported.

We study the coupling of a semiconductor device, modeled by means of an energy-transport model, with an electric network, when thermal effects are taken into account. In this case, the network can be described by two concurrent topologies, one related to the transfer of electric current, and the other one related to the heat transfer. A mathematical model is proposed for this complex coupling.

An unified Generalised Beam Theory (GBT) approach to the stability and vibration analyses of arbitrary orthotropic thin-walled members is formulated. The main steps required to establish the GBT system of homogeneous differential equations are first described and discussed. Then, the derived GBT matrices are physically interpreted, i.e., their terms are related to the member mechanical properties. Finally, the GBT equations are used to investigate the local and global stability/vibration behaviour of orthotropic (laminated plate) thin-walled channel members. The relevant buckling/vibration modes are identified and the associated bifurcation stresses/natural frequencies are evaluated.

Every kinds of cluster radioactivities have different radioactive features depending on their emitted clusters and daughters nuclei. Thus each decay process can be treated as a radioactive channel, and the channels can be coupled to each other. Therefore some channels are abated or strengthen due to the coupling effects. Here we attempt to find out a way to evaluate the influence of each channel, and then introduce a physical quantity M_i to express this effect.