Formation of complex radiation defects in irradiated materials

The principles of formation of the complex vacancy defects (V-clusters), their ensembles and patterns of formation of superlattices of the V-clusters are determined. The inclusion of the drift component of the elementary defects into the field of elastic stresses of the V-cluster in the analysis allowed describing its genesis and development adequately. The mechanisms of motion of the V-clusters in the material are described in detail, considering their interaction with each other. The authors have developed the original physical and mathematical formalism within which it has become possible to describe the order-disorder phase transition when an ensemble of clusters chaotically distributed in the irradiated solid transforms into an ordered coherent superlattice. The critical point of the phase transition and the parameters of the defect lattice itself are determined. They are confirmed by the experimental results. The ordering process in this system is understood as the motion of the undamped wave of order parameter through the material, while other configuration states of the V-cluster ensemble constitute rapidly damping fluctuations. The article also shows the mechanism of linking the symmetry of the V-cluster superlattice to the symmetry of the initial crystal.

La derive dans l’évaluation de l’incertitude

Taking into account the instrumental drift in the uncertainty of measurement does not benefit at this time from a provided bibliography. Although an abundant literature (standards, articles, samples collections, etc.) dealing with the estimation of uncertainty by the GUM method exists, the question of the drift component is often avoided or inaccurate, usually limited to a point-to-point deviation divided by 2√3, which is based on an erroneous hypothesis and clearly confines to being immobile. The choice of a rectangular probability law supposes that the greatest variation observed is necessarily the greatest observable variation; in other words, during the observed history (sometimes reduced to two calibration certificates), we noted the maximum drift of which the instrument could be the object. If the method is effectively statistically questionable, it becomes completely useless as soon as a modification takes place; especially when the periodicity optimization (variable calibration frequency) is used or when the points are changed from one calibration to another, in number or level. We propose here an alternative method which intends to correct these defects and is at once compatible with the principles of the GUM and easily automatable.

Coordinate dependent diffusion analysis of phosphorus diffusion profiles in gallium doped germanium

We have analyzed phosphorus diffusion profiles in an In0.01Ga0.99As/In0.56Ga0.44P/Ge germanium structure during phosphorus co-diffusion with gallium for synthesis of the germanium subcell in multi-junction solar cells.. Phosphorus diffused from the In0.56Ga0.44P layer simultaneously with gallium diffusion into the heavily gallium doped germanium substrate thus determining the specific diffusion conditions. Most importantly, gallium and phosphorus co-diffusion produces two p–n junctions instead of one. The phosphorus diffusion profiles do not obey Fick’s laws. The phosphorus diffusion coefficient DP depth distribution in the specimen has been studied using two methods, i.e., the Sauer–Freise modification of the Boltzmann–Matano method and the coordinate dependent diffusion method. We show that allowance for the drift component in the coordinate dependent diffusion method provides a better DP agreement with literary data. Both methods suggest the DP tendency to grow at the heterostructure boundary and to decline closer to the main p–n junction. The DP growth near the surface p–n junction the field of which is directed toward the heterostructure boundary and its decline near the main p–n junction with an oppositely directed field, as well as the observed DP growth with the electron concentration, suggest that the negatively charged VGeP complexes diffuse in the heterostructure by analogy with one-component diffusion.

Wind Influence on the Formation of Nearshore Currents in the Southern Baltic: Numerical Modelling Results

A two-dimensional numerical model was used for a simulation of vertical average longshore currents generated by both wind friction and wind-wave action in the nearshore zone. The modelling domain includes the southern part of the Baltic Proper (all boundaries were closed). Wind, uniform in space and varying in time, was the only forcing in the model. The correlation coefficient higher than 0.8 was obtained by model calibration versus the field measurements of currents conducted at the Lubiatowo field station (southern Baltic) during about 1.5 months in 2006. Comparative simulations of total currents including both wind-induced drift and wave components, and of total currents including only a wind-induced drift component, showed that the input of the drift component into currents in the nearshore zone is greater than commonly believed.Wind-induced drift strongly dominates outside the zone of wave transformation, and its input into the total resulting currents remains noticeable even in a zone between the shoreline and the depth of the first wave breaking. Thus, wind-induced drift constitutes up to 50% of the resulting longshore currents for longshore winds and no less than 20% of the longshore component of currents for winds at 45 degrees to the longshore direction.

Heuristic Reduction of Gyro Drift for Personnel Tracking Systems

The paper pertains to the reduction of measurement errors in gyroscopes used for tracking the position of walking persons. Such tracking systems commonly use inertial or other means to measure distance travelled, and one or more gyros to measure changes in heading. MEMS-type gyros or IMUs are best suited for this task because of their small size and low weight. However, these gyros have large drift rates and can be sensitive to accelerations. The Heuristic Drift Reduction (HDR) method presented in this paper estimates the drift component and eliminates it, reducing heading errors by almost one order of magnitude.