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A thermodynamic model for calculating the operating process in the cylinder of a spark-ignition engine with internal mixture formation and stratified air-fuel charge based on the volume balance method was developed. The model takes into account the change in the working fluid volume during the piston movement in the cylinder. The equation of volume balance of internal mixture formation processes during direct fuel injection into the engine cylinder was compiled. The equation takes into account the adiabatic change in the volume of the stratified air-fuel charge, consisting of fuel-air mixture volume and air volume. From the heat balance equation, the change in the fuel-air mixture volume during gasoline evaporation in the fuel stream and from the surface of the fuel film due to external heat transfer was determined. Basic equations of combustion-expansion processes of the stratified air-fuel charge were derived, taking into account three zones corresponding to combustion products, fuel-air mixture and air volumes. The equation takes into account the change in the working fluid volume due to heat transfer and heat exchange between the zones and the walls of the above-piston volume. Dependences for determining the temperature in the three considered zones and pressure in the cylinder were obtained. Graphs of changes in the volumes of the combustion products, fuel-air mixture and air zones with the change of the above-piston volume in partial load modes (n=3,000 rpm) were plotted. With increasing load from bmep=0.144 MPa to bmep=0.322 MPa, at the moment of fuel ignition, the volume of the fuel-air mixture increases from 70 % to 92 % of the above-piston volume. At the same time, the air volume decreases from 30 % to 8 %. Analysis of theoretical and experimental indicator diagrams showed that discrepancies in the maximum combustion pressure do not exceed 5 %

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A procedure was developed for isolation and determination of the isotope composition and content of U and Pu on the ultrasmall level in environmental samples of technogenic origin, characterized by a small mass (up to 0.l g) and complex macrocomposition. The procedure is based on isotope dilution and mass-spectrometric measurement of the isotope ratios (IDMS). Subnanogram quantities of U and Pu were isolated using a modification of resin bead technique, involving sorption on a limited number of anion exchanger beads and allowing, after desorption, analysis of the solutions containing the selectively isolated nanogram quantities of U or 10 312 310 315 g of Pu. The measurements were carried out on thermal ionization mass spectrometers manufactured in Ukraine and Russia with a modernized ion registration system utilizing a position-sensitive detector based on microchannel plates. Uranium was analyzed by the laser luminescence method suitable for measuring fractions of nanograms of U accurately to within 10%. This procedure, combining highly sensitive methods of isolation of ultrasmall quantities of U and Pu with the mass-spectrometric method of analysis, is applied at the Radium Institute (acting as a national laboratory of IAEA) and at the Institute of Analytical Instrument Designing, Russian Academy of Sciences, in analysis of inspection samples submitted by IAEA for monitoring the activity of nuclear facilities under the Treaty on Nonproliferation of Nuclear Weapons.

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