Equivalence of the Impedance Method and the Method of Amplitude‐Frequency Characteristics for Investigations of Vibrations in Hydraulically Powered Supports

Two approaches to investigation of hydroelastic shock absorbers ensuring an efficient decrease in vibrations and noise in mobile machines have been presented. It has been shown that the parameters obtained by the method of amplitudefrequency characteristics more accurately correspond to the parameters of the physical model than the data computed with the impedance method.     

Effects of a Metal–Insulator–Metal Contact on the Antenna in a Radar Monitoring System

Theoretical and experimental studies have been performed on the scattering by a horn antenna containing a metal–insulator–metal contact having a nonlinear voltage–current characteristic, which lies at the flange joint between the waveguide components. The effects of the contact are examined as regards the performance of the radar antenna system.     

Working Standard of the Unit of Power of Electromagnetic Waves in the Frequency Range of 37.5–220 GHz

Measurement Techniques - We show the possibility of application of the bolometric converters of microwave power, included in the State Primary Standard of the unit of power of electromagnetic waves...     

Evanescent Wave Transport and Shot Noise in Graphene: Ballistic Regime and Effect of Disorder

We have investigated electrical transport and shot noise in graphene field effect devices. In large width over length ratio W/L graphene strips, we have measured shot noise at low frequency (f=600–850 MHz) in the temperature range of 4.2–30 K. We observe a minimum conductivity of $\frac{4e^{2}}{\pi h}$ and a finite and gate dependent Fano factor reaching the universal value of $\frac{1}{3}$ at the Dirac point, i.e. where the density of states vanishes. These findings are in good agreement with the theory describing that transport at the Dirac point should occur via evanescent waves in perfect graphene samples with large W/L. Moreover, we show and discuss how disorder and non-parallel leads affect both conductivity and shot noise.     

Frequency–Time Method of Processing Phase Measurements in Geophysics

A frequency–time method is proposed for analyzing geophysical phase information whose implementation approaches the results of the operation of an ideal filter. The method is based on the principle of expanding an observed signal over a system of basis functions. The procedure developed makes it possible to determine the phase of the signal and to estimate the operational stability of the phase measuring system. The procedure can be used when designing geophysical measuring devices utilizing optical phase measurements.     

Dynamic Frequency-Interference Method of Measuring the Wavelength–Frequency Ratio of Lasers

The frequency-interference method of measurement of the wavelength–frequency ratio of lasers is investigated. A wavelength-dependent frequency shift is formed as a consequence of the Doppler effect produced by rotation of a reflector. The optical circuits and signal detection circuit are presented.     

Characterization of the Properties of Barium–Strontium Titanate Films and Controlled Elements Based on Them in the Frequency Range of 1–60 GHz

Technical Physics Letters - The electrical properties of barium–strontium titanate films and tunable capacitors based on them are studied in a wide frequency range. The dielectric losses in...     

Frustrated Phase Separation in the Overdoped Regime of “123” High-Tc Superconductors

Recent inelastic neutron scattering measurements revealed the crystal-field (CF) spectra of the overdoped R_{1 – y} Ca_yBa₂Cu₃O₇ (R = Ho, Er; 0 < y < 0.25) high-T _c superconductors to consist of two spectral components associated with the optimally doped and the overdoped domains. Increase of the Ca concentration does not affect the local charge density of domains, but changes the spectral weight of the components. In the sense of this two-phase picture, which was established earlier for the underdoped region, there is a smooth crossover between the under- and overdoped parts of the phase diagram. The charge origin of the observed superposition effect is confirmed by the systematic analysis of the concentration dependences of the CF parameters for both Ho- and Er-based compounds. Therefore, the local charge inhomogeneity in the CuO₂ planes of high-T _c cuprates is a characteristic feature of the doping process, which depends neither on the way to introduce doping nor on the doping level.     

On Randomization Techniques for the Suppression of Unwanted Moiré Patterns in Images Generated by a Scanning System with a Periodic Amplitude Defect

Arrays of motifs, such as are found in half-tone images, may exhibit moiré fringes when they are generated by a scanning system which introduces a periodic amplitude defect. It is shown that the fringes may be eliminated in the continued presence of the defect by a one-dimensional randomization of the positions of the motifs. The necessary Fourier theory is presented, and elimination of a particular moiré pattern is demonstrated for four probability-density functions.     

Modeling the Process of Liquid Flow in the System “Formation–Pipeline”

Journal of Engineering Physics and Thermophysics - A model of the process of nonstationary motion of a liquid in the conjugate system “formation–pipeline” has been constructed,...     

Heat Transfer in Turbulent Rayleigh–Bénard Convection Below the Ultimate Regime

A Rayleigh–Bénard cell has been designed to explore the Prandtl (Pr) dependence of turbulent convection in the cross-over range 0.7<Pr<21 and for the full range of soft and hard turbulences, up to Rayleigh number Ra?10¹¹. The set-up benefits from the favourable characteristics of cryogenic helium-4 in fluid mechanics, in situ fluid property measurements, and special care on thermometry and calorimetric instrumentation. The cell is cylindrical with diameter/height=0.5. The effective heat transfer Nu(Ra, Pr) has been measured with unprecedented accuracy for cryogenic turbulent convection experiments in this range of Rayleigh numbers. Spin-off of this study include improved fits of helium thermodynamics and viscosity properties. Three main results were found. First the Nu(Ra) dependence exhibits a bimodality of the flow with 4–7% difference in Nu for given Ra and Pr. Second, a systematic study of the side-wall influence reveals a measurable effect on the heat transfer. Third, the Nu(Pr) dependence is very small or null: the absolute value of the average logarithmic slope (d ln Nu/d ln Pr)_Ra is smaller than 0.03 in our range of Pr, which allows to discriminate between experiments with contradictory results [Ashkenazi et al., Phys. Rev. Lett. 83, 3641 (1999)] [Ahlers et al., Phys. Rev. Lett. 86, 3320 (2001)].     

End-of-Line Waveguide Thermistor Power Meters in the Frequency Range 16.7–37.5 GHz

Measurement Techniques - In this study, a multiprobe end-of-line converter, which is a part of a waveguide thermistor wattmeter, was developed. This converter functions to improve the power...     

Fast and robust estimation of the multivariate errors in variables model

In the multivariate errors in variables models, one wishes to retrieve a linear relationship of the form y=β ^t x+α, where both x and y can be multivariate. The variables y and x are not directly measurable, but observed with measurement error. The classical approach to estimate the multivariate errors in variables model is based on an eigenvector analysis of the joint covariance matrix of the observations. In this paper, a projection-pursuit approach is proposed to estimate the unknown parameters. The focus is on projection indices based on half-samples. These lead to robust estimators which can be computed using fast algorithms. Fisher consistency of the procedure is shown, without the need to make distributional assumptions on the x-variables. A simulation study gives insight into the robustness and the efficiency of the procedure.