Хаотический потенциал заряженных дислокаций в гетероконтактах III-нитридов

In this work, the structure of the chaotic potential in heterocontacts of III-nitrides, caused by the electrostatic field of charged dislocations, is studied. Taking into account the spatial dispersion of the dielectric response of a two-dimensional electron gas, the amplitude and scale of the chaotic potential in the contact plane are determined. The dependence of the parameters of the chaotic potential on the surface states density and the concentration of dislocations is shown.

Stress Tensor and Gradient of Hydrostatic Pressure in the Contact Plane of Axisymmetric Bodies Under Normal and Tangential Loading

The Hertzian contact theory, as well as most of the other classical theories of normal and tangential contact, provides displacements and the distribution of normal and tangential stress components directly in the contact surface. However, other components of the full stress tensor in the material may essentially influence the material behaviour in contact. Of particular interest are principal stresses and the equivalent von Mises stress, as well as the gradient of the hydrostatic pressure. For many engineering and biomechanical problems, it would be important to find these stress characteristics at least in the contact plane. In the present paper, we show that the complete stress state in the contact plane can be easily found for axially symmetric contacts under very general assumptions. We provide simple explicit equations for all stress components and the normal component of the gradient of hydrostatic pressure in the form of one-dimensional integrals.

New Generation of Mobile Platform of Service Robot for Motion along Vertical Walls

The paper sums up results achieved during in the last few years of the development and research of service robots aiming their use for service applications on vertically oriented walls with predominantly smooth contact surfaces having minimal altitude unevenesses within the range ± 5 mm. Two robot generations are described step by step, and both of them use the same mechanical principle of the patented system of motion. The system uses the intermittent motion when positions of the robot legs and body alternate cyclically, and the appropriate gripping force of a holding-down system is realized by vacuum. As compared with the first version, the current one allows legs to move independent in part. In that way it is possible to compensate better variations of parallelism between a contact plane of the robot holding-down system and a vertical wall. Moreover, the robot is provided with a rotary unit making possible a rotation on the axis going through the robot center and being perpendicular to the contact plane, which guarantees a change in the robot orientation in the plane. As for drives, very compact rotary actuating mechanisms (servo drives) are used, having a high ratio of power parameters in relation to weight and dimensions, combined with a control based on an industrial PC.