Determination of the three-dimensional velocity vector using the laser doppler measurements of unevenly sampled components

This paper describes the method for determining the three-dimensional velocity vector of the flow using the laser Doppler measurements of unevenly sampled components. This method is based on the filtering and linear interpolation of the measured velocity components in the circuit channels. It is shown in the numerical simulation and physical experiment that the method error does not exceed 2% and the results of interpolation with respect to the closest points are several times greater.     

Optoelectronic method of contactless reconstruction of the surface profile of complexly shaped three-dimensional objects

An optoelectronic method of contactless reconstruction of the surface profile of complexly shaped threedimensional objects with the use of structured light, phase triangulation, and a steady-state method of identification of interference patterns by means of stepwise shift is considered. Analytic estimates as well as estimates obtained experimentally (using the newly developed measurement system) of the error in measurements of surface profile with the use of the proposed method are presented.     

A 1-THz superconducting hot-electron-bolometer receiver for astronomical observations

In this paper, we describe a superconducting hot-electron-bolometer mixer receiver developed to operate in atmospheric windows between 800-1300 GHz. The receiver uses a waveguide mixer element made of 3-4-nm-thick NbN film deposited over crystalline quartz. This mixer yields double-sideband receiver noise temperatures of 1000 K at around 1.0 THz, and 1600 K at 1.26 THz, at an IF of 3.0 GHz. The receiver was successfully tested in the laboratory using a gas cell as a spectral line test source. It is now in use on the Smithsonian Astrophysical Observatory terahertz test telescope in northern Chile.     

Correlating Nanocrystalline Structure with Electronic Properties in 2D Platinum Diselenide

Platinum diselenide (PtSe₂) is a 2D material with outstanding electronic and piezoresistive properties. The material can be grown at low temperatures in a scalable manner, which makes it extremely appealing for many potential electronics, photonics, and sensing applications. Here, the nanocrystalline structure of different PtSe₂ thin films grown by thermally assisted conversion (TAC) is investigated and is correlated with their electronic and piezoresistive properties. Scanning transmission electron microscopy for structural analysis, X-ray photoelectron spectroscopy (XPS) for chemical analysis, and Raman spectroscopy for phase identification are used. Electronic devices are fabricated using transferred PtSe₂ films for electrical characterization and piezoresistive gauge factor measurements. The variations of crystallite size and their orientations are found to have a strong correlation with the electronic and piezoresistive properties of the films, especially the sheet resistivity and the effective charge carrier mobility. The findings may pave the way for tuning and optimizing the properties of TAC-grown PtSe₂ toward numerous applications.     

Oxidation of SrFe12O19-based solid solutions with double heterovalent cation substitution

The effect of oxidizing annealing on the phase composition, microstructure, and magnetic properties of solid solutions based on Pb-containing strontium M hexaferrite is studied. The solid solutions prepared by different methods (ceramic route and glycol-citrate sol-gel process) are shown to differ in composition. Oxidizing annealing (air, 500–700°C) of single-phase materials leads to the formation of nanometer-sized (10–20 nm) equiaxed precipitates on some of the faces of the (initially smooth) hexaferrite grains. In some cases, such precipitates form chains running over the entire surface of the hexaferrite grain. Some of the annealed solid solutions contain a second phase, which has not been identified. Annealing slightly increases the coercive force of the solid solutions (by 2 to 25%, depending on their composition), which may be due to oxidation-induced second-phase precipitation or phase segregation of the solid solution within the hexaferrite grains.     

High-speed processing of phase images with parallel computations

An algorithm is proposed for processing phase images with the use of computing power of graphics processing units (GPUs) for 3D geometry measurements by means of phase triangulation. It is shown that implementation of the phase image decryption algorithm on the GPU is faster by more than 100 times than on the central processing unit (CPU). Practical implementation of the proposed approach can substantially improve the performance of phase triangulation methods.     

A 1.3-THz Balanced Waveguide HEB Mixer for the APEX Telescope

In this paper, we report about the development, fabrication, and characterization of a balanced waveguide hot electron bolometer (HEB) receiver for the Atacama Pathfinder EXperiment telescope covering the frequency band of 1.25-1.39 THz. The receiver uses a quadrature balanced scheme and two HEB mixers, fabricated from 4- to 5-nm-thick NbN film deposited on crystalline quartz substrate with an MgO buffer layer in between. We employed a novel micromachining method to produce all-metal waveguide parts at submicrometer accuracy (the main-mode waveguide dimensions are 90 times 180 mum ). We present details on the mixer design and measurement results, including receiver noise performance, stability and ldquofirst-lightrdquo at the telescope site. The receiver yields a double-sideband noise temperature averaged over the RF band below 1200 K, and outstanding stability with a spectroscopic Allan time more than 200 s.