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The stability of the electroosmotic flow of electrolyte-dielectric viscous liquids under the influence of the DC and AC electric fields along with the external pressure gradient is studied theoretically. Liquids are bounded by two infinite parallel plates. The lower wall bordering the electrolyte is assumed to be a charged surface, and the upper wall is electrically isolated. The charge at the lower boundary is assumed to be immobile, while the surface charge at the free surface is assumed to be mobile. In this paper, we study the micro- and nanosized liquid layers. The mathematical model is described by a nonlinear system of the Nernst-Planck-Poisson-Stokes partial differential equations with the appropriate boundary conditions on the solid surface, the electrolyte/dielectric interface, and on the upper wall. The pressure gradient is highly important for the stability of the flow. For the DC case, the external pressure could either stabilize and destabilize the flow depending on the relative directions of the electroosmotic flow and the pressure-driven flow. For the AC case, the dependence on the value of the external pressure is not monotonous for different wave numbers of perturbations, but, as a rule, the external pressure destabilizes the flow. As the frequency of the electric field increases, the one-dimensional solution of the problem becomes stable.

In this study, we demonstrate the thermal-stable characteristics of a metamorphic double -doped heterostructure field-effect transistor (MDDFET). The variations in drain current density and extrinsic transconductance of the studied device are as low as +0.3 and À2:5% from 300 to 420 K. When the temperature increases from 360 to 380 K, positive changes of transconductance and drain current are observed, which is different from that observed in most FETs. The thermal-stable characteristics can be attributed to the coupled wave function, inducing a larger carrier distribution in the undoped high-speed In 0:6 Ga 0:6 As region of the In 0:5 Ga 0:5 As/ þ /In 0:5 Ga 0:5 As/In 0:6 Ga 0:4 As/In 0:5 Ga 0:5 As/ þ /In 0:5 Ga 0:5 As channel when temperature increases.

The stability of the electroosmotic flow of the two-phase system electrolyte-dielectric with a free interface in the microchannel under an external electric field is examined theoretically. The mathematical model includes the Nernst-Plank equations for the ion concentrations. The linear stability of the 1D nonstationary solution with respect to the small, periodic perturbations along the channel, is studied. Two types of instability have been highlighted. The first is known as the long-wave instability and is connected with the distortion of the free charge on the interface. In the long-wave area, the results are in good agreement with the ones obtained theoretically and experimentally in the literature. The second type of instability is a short-wave and mostly connected with the disturbance of the electrolyte conductivity. The short-wave type of instability has not been found previously in the literature and constitutes the basis and the strength of the present work. It is revealed that with the increase of the external electric field frequency, the 1D flow is stabilized. The dependence of the flow on the other parameters of the system is qualitatively the same as for the constant electric field.

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