Spatial Effects of Interaction of a Shock with a Lateral Low-Density Gas Channel

Three-dimensional interaction of a shock with lateral low-density gas channel of round, elliptic or rectangular cross-section is numerically studied using Euler’s equations. The structure of formed shock wave precursor is described in detail. Internal shear layer instabilities in three-dimensional flow are shown to develop faster than in axisymmetric case. Moderate amplification of high-pressure jet cumulation effect is noted for elliptic and rectangular channel cases. Dependence of precursor growth rate on cross-section shape is studied. It is found that stretching of cross-section shape significantly increases the duration of linear precursor growth phase.     

Microgravity Test Complex for Mobile and Portable Optical Frequency Standards

Measurement Techniques - Herein, the application of optical quantum standards (quantum sensors) based on cold atoms in satellite navigation is discussed. The advantages of placing quantum sensors...     

Combustible Gas Cylinder Detonation upon Incident Shock Focusing

Technical Physics Letters - Two-dimensional interaction of a shock in air with elliptic area (two-dimensional gas bubble) filled with propane-oxygen mixture with addition of heavy gas is...     

A Study of (In,Ga,Al)As/GaAs Quantum-Dot Heterostructures by X-ray Diffraction and Total Reflection

The structure of (In,Ga,Al)As/GaAs stacks with one to three layers of self-assembled InAs quantum dots is studied by high-resolution x-ray diffractometry and x-ray reflectometry. It is shown that the quantum dots are almost pyramidal in shape. It is found that (i) a first InAs layer, 2.7 ML thick, is invariably produced with a faceted surface and (ii) vertical coupling of quantum dots and superlattice formation do occur (with three quantum-dot layers). It is demonstrated that combining the two methods provides researchers with more reliable structural data.     

Optical Frequency Standard Based on Strontium Cold Atoms

Measurement Techniques - We present the results obtained in the course of the development of an optical frequency standard based on cold 87Sr atoms. We describe the parameters of experimental...