Lasers for modern linear measurements

Three definitions of the meter are given. The role of lasers in the last definition is shown.A He-Ne/I ₂ laser is examined in ample detail. Baltic State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 106–108, August, 1999.     

Effect of noise and vibration on the performance of a particle concentration laser meter and optimization of its parameters

Spurious illumination penetrating into a gas duct adversely affects the performance of a laser gage measuring the concentration of solid particles dispersed in the air flow. The noise and gas duct vibration caused by the noise and vibration of the flow driver and other sources mechanically connected to the gas duct modulate the spurious radiation so that it may generate a signal that is perceived as a useful one by a photodetector. The noise-and vibration-modulated spurious illumination, as well as its optical-to-electric conversion with consideration for the spectral characteristics and the connection of the photodetector to the laser gage, is analyzed. From the amplitude and frequency properties of real noise and vibration sources causing the gas duct walls, on which the laser gage is mounted, to vibrate, the effect of the parasitic illumination is estimated. The operating parameters of a laser gage with double amplitude modulation and subsequent double synchronous detection, which make it possible to considerably improve its noise immunity, are proposed.     

Stability of rotation of a vane in a flow

The results of investigation of the stability of permanent rotation of a four-blade vane on a weightless rod in the flow of a homogeneous medium are discussed. The rod rotates about a fixed point where a spherical joint is situated. The vane rotates about the second joint fixed at the other end of the rod. The stability of permanent rotation of the vane is studied when the rod coincides with the dynamic symmetry axis of the vane. The results are compared with the one-joint case. It is shown that increasing the number of degrees of freedom leads to “diminishing” the stability domain projection onto the corresponding subspace of parameters. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 11, No. 7, pp. 73–95, 2005.     

An LGN-303 frequency-stabilized He-Ne laser with a modulating attachment

The operating principle and elements of the construction of an LGN-303 frequency-stabilized He-Ne laser with a modulating attachment are considered. The basic parameters of the laser are presented, and some recommendations are given concerning the use of a modulating attachment in He-Ne lasers stabilized with the aid of an iodine absorption cell.     

The effect of the back reflections in an optical discriminator of a double-mode laser

Lidar sounding of iodine molecules were performed at pressures lower than 1 torr. The differential cross-section of fluorescence and the absorption cross-section of iodine molecules at a wavelength of 532 nm were been obtained.     

Compensation of Magnetic Field Instabilities in Field Cycling NMR by Reference Deconvolution

Performing a nuclear magnetic resonance (NMR) experiment in an unstable magnetic field causes fluctuations in the NMR frequency, leading to a loss of reproducibility and an effective shortening of the free induction decay after data averaging. Reference deconvolution allows the compensation of field fluctuations via simultaneous measurement of an internal or external reference signal. The technique was applied to compensate the effect of field fluctuations in a resistive electromagnet used for fast field cycling NMR. An external sample was chosen as the reference.     

On the Possibility of Conversion of Alcohols to Ketones and Aldehydes by Phosphinoboranes R2PBR′R′′: A Computational Study

Can phosphinoboranes promote hydrogenation of carbonyl moieties? By means of B3LYP and MPW1K density functional calculations the likelihood of the oxidation of alcohols by phosphinoboranes R₂PBR′₂ ( 1 ) was explored. As a proof‐of‐principle, a theoretical study that tests the reversibility of the alcohol oxidation is reported. The potential of 1 as a metal‐free hydrogenation mediator is discussed for a series of hydrogen sources such as primary and secondary alcohols.