The oxide-semiconductor interface is a key element of MOS transistors, which are widely used in modern electronics. In silicon electronics, SiO2 is predominantly used. The miniaturization requirement raises a problem regarding the growing of heterostructures with ultrathin oxide layers. Two structural models of interface between crystalline Si and cristobalite SiO2 are studied by using DFT-based computer modelling. The structures of several Si/SiO2 superlattices (SL), with layer thicknesses varied within 0.5–2 nm, were optimized and tested for stability. It was found that in both models the silicon lattice conserves its quasi-cubic structure, whereas the oxide lattice is markedly deformed by rotations of the SiO4 tetrahedra around axes perpendicular to the interface plane. Based on the analysis of the calculated total energy of SLs with different thicknesses of the layers, an assessment of the interface formation energy was obtained. The formation energy is estimated to be approximately 3–5 eV per surface Si atom, which is close to the energies of various defects in silicon. Elastic strains in silicon layers are estimated at 5–10%, and their value rapidly decreases as the layer thickens. The elastic strains in the oxide layer vary widely, in a range of 1–15%, depending on the interface structure.

176Wrestling makes a demand to regulate the static and dynamic balance; therefore, improvement of this function was observed in wrestlers [1,2]. Improvement of balance function is observed not only in wrestlers but also in other athletes [2], especially when physical exercises are performed under strict conditions (e.g., in gymnasts) [3]. However, evaluation of the static bal ance control in healthy persons under normal quiet conditions of a bipedal stance with the eyes open often fails to reveal distinctions between nonathletes and skilled athletes, such as gymnasts [3,4] and ballet dancers [5]. This may be caused by the simplicity and low specificity of the tests, as well as by the low demands to the systems of balance control under the testing conditions. The system that controls postural balance is known to compensate the weakness of some components or subsystems and provide rather efficient regulation of the vertical posture under usual noncom plicated conditions [6].Physical fatigue, which deteriorates balance con trol, is one of the factors important for muscular activ ity [7]. The fatigue induced metabolic factors accu mulate in the working muscles and systemic circula tion; they are capable of reducing the muscular sensitivity [8] and balance control [7]. Hence, we expect that the difference in the parameters of balance control between the athlete and control group is the most pronounced during physical exercise and the sta bility of the bipedal stance under the influence of fatigue is reduced to a lower extent in athletes, which is related to their working capacity and the rate of recovery. METHODSSambo wrestlers (n = 31) with qualification levels of a first rank athlete and master of sports of Russia participated in our study. Their average age was 23.1 ± 3.9 years; their experience of sambo wrestling was 12 ± 5 years. The average weekly physical exercise was 14.3 ± 5.5 h for the previous month. The control group consisted of healthy students (n = 40) not involved in any sport, who were 20.3 ± 2.3 years old. They matched the athletes in body weight (75.9 ± 13.2 and 70.6 ± 12.2 kg) and height (176.0 ± 8.6 and 177.9 ± 6.8 cm).The function of balance control was studied using a Stabilan 1 02 posturographic hardware and software system (Ritm, Russia); swaying of the center of pres sure (CP) was studied. Postural stability was evaluated Abstract-Control of static balance was studied in wrestlers (n = 31) in the normal state and against the back ground of physical fatigue, i.e., before and after a bicycle PWC 170 test, respectively. The static balance was evaluated using a Ritm force platform (Russia) during normal basic stance (BS) and static strain (half squat ting position (HS) with the eyes open). Before physical exercise, i.e., during BS, the differences in postural control of the center of pressure (CP) between athletes and control subjects (n = 40) were nonsignificant. In the HS position, both linear and angular sway velocities of CP (LSV and ASV, respectively) were significantly lower in wrestlers (p...

A method is introduced for determination of a vector network analyzer's calibration residual errors for measurement of the reflection coefficient. The method utilizes unscented Kalman filtering and spline interpolation time domain techniques. All three residual errors are calculated by processing the measured reflection coefficient of a single verification device, such as an air line terminated with a short or open network. The proposed method shows particular advantages when the use of a long verification line is impractical (e.g. at the wafer-level), or for measurements at low frequency ranges or similar cases when the resolution of conventional time domain methods is low.Experimental studies were conducted for two frequency ranges and in coaxial and on-wafer measurement environment. The proposed algorithm is a good candidate for a wide range of practical applications especially for measurement uncertainty estimation of cost-effective vector network analyzers.Index Terms -Vector network analyzer (VNA), verification, residual error box, unscented Kalman filters (UKF).

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