Experimental study of thermally induced oscillations of gaseous helium

Results of a study of thermally induced oscillations of helium gas in semi-open and closed tubes are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 3, pp. 453–457, September, 1984.     

Recovering the Architecture of Links in a Chain of Three Unidirectionally Coupled Systems Using the Granger-Causality Test

Technical Physics Letters - We propose a method for reconstructing links in a chain of unidirectionally coupled systems by means of three tests for estimating direct and mediated coupling with the...     

Synthesis and study of thin TiO<Subscript>2</Subscript> films doped with silver nanoparticles for the antireflection coatings and transparent contacts of photovoltaic converters

Problems associated with the deposition and studies of the properties of thin titanium-dioxide films doped with silver nanoparticles, which can be used as antireflection coatings and transparent contacts in the fabrication of solar cells, are analyzed. The method of deposition onto a rotating substrate is used for synthesis. The structural and optical properties and the surface morphology of the TiO₂–Ag films are examined. It is shown that the concentration of Ag nanoparticles in the reaction mixture affects the thickness of the resulting films, their refractive index, and their conductivity. The introduction of Ag nanoparticles into titanium-dioxide films gives rise to an absorption band at 420–430 nm, associated with the plasmon resonance in silver. Calcination at 400°C leads to a decrease in the intensity of this absorption band.     

Study of shock-wave flows in the channel by schlieren and background oriented schlieren methods

The results of recording gas flow in a shock tube by the schlieren and background oriented schlieren (BOS) methods after initiating a pulsed (surface or volume) discharge are presented. Simultaneous recording of the flow field by the two methods allows a complete qualitative and quantitative analysis of the shock-wave processes resulting from the interaction of a pulse discharge with high-velocity flow. The vector displacement field of the BOS method was determined by the cross-correlation method. The density field was obtained by solving the Poisson equation with special boundary conditions. It was shown that the BOS method yields a good quality map of the flow structure that corresponds to the classical schlieren method and provides reliable quantitative results except in areas of high gradients. A modification of the BOS method was proposed and tested to measure the density jump at the shock-wave front. Recording was performed at an angle to the plane of the wave front. Various Schemes of processing of digital flow images were tested. The proposed method provides a resolution of large density gradients at the shock-wave front. The obtained quantitative results are consistent with the calculated values.     

Discretization of the profiles of large cylindrical products in analysis of shape deviations with allowance for evaluations of the curvature

The error caused in the determination of the departure from roundness by profile discretization is studied. Corresponding estimates of the chord-length discretization with ana priori error allow the minimum number of points uniformly distributed on the profile that must be chosen to obtain a given accuracy. Translated from Izmeritel'naya Tekhnika, No. 1, pp. 42–47, January, 1997.