Forecasting of phase behavior and PVT-properties of natural gas is one of the major tasks during the developing and operation of gas and gas condensate fields. Each stage – from an exploration to ...transportation and storage of gas is followed by continuous changes of thermobaric conditions. This causes changes of thermodynamic properties of gas, one of which is compressibility factor. The comparative study of the existing theoretical methods of compressibility factor determination is given in the presented work: based on the equation of state and empirical correlations. Besides, the alternative approach based on molecular dynamics simulations with the Lennard-Jones potential is offered. The analysis of the received results is carried out on the basis of 165 experimental data for 5 various mixtures of natural gas covering temperatures of 310.9 – 344.4 K and pressure range of 7.074 - 48.443 MPa. The statistical analysis shows that the molecular dynamics method shows the minimum error and is suitable for determination of z-factor of mixtures with methane content more than 90%. For mixtures with the high content of carbon dioxide the Peng-Robinson equation of state with shift-parameter shows the minimum error.
Straw tubes with resistive cathode and cathode readout were successfully manufactured and tested. The straw tubes were manufactured by ultrasonic welding technique. The resistive cathode electrode ...was made of diamond like carbon (DLC). The possibility of cathode signal readout from external strip electrodes was successfully demonstrated. The event coordinate along the straw can be accurately determined by applying center of gravity method to the individual strip signals.
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The characteristics of neutron scintillation detectors built on monolithic and heterogeneous scintillators containing
6
Li were studied. The detectors were tested on a thermal neutron beam and on a ...stand with a source of γ-quanta
60
Co. To process the signals received from the detector with a monolithic scintillator, three different γ-radiation discrimination algorithms were used: registration of pulses at a constant threshold and selection according to the pulse shape using two digital signal separation methods: charge integration and pulse duration measurement. For a homogeneous scintillator, pulse shape selection methods work approximately the same when separating thermal neutrons and γ-quanta and are significantly inferior to the method of registration at a constant threshold. In this case, the quality of the
n
/γ separation is worse than the result obtained with a heterogeneous scintillator when recording at a constant threshold. The purpose of the work is to compare the results of using digital methods for discrimination of gamma-quanta with the results obtained using heterogeneous scintillators.
The kinetics of internal mass transfer in the course of evaporation of liquids in elastic capillary systems in which the transverse dimensions of the pores can both decrease and increase on exposure ...to intense thermal effect is investigated. Structural transformations in a material arise as a result of its dehydration. It is assumed that the channel radius changes simultaneously over the entire length, synchronously with the interface motion. Three schemes are possible in principle: a uniform change during the process, a faster change in the initial stage, and, conversely, a faster change in the closing stage. The time-limited additional thermal effect during the period that makes the main contribution to the overall duration of the process is capable of substantially enhancing mass transfer with minimum energy consumption.
A two-way evaporation of liquids from conical channels has been studied . The influence of the temperature gradient on the mass transfer process has been considered. An approximation expression for ...the temperature coefficient of evaporation has been derived and algorithm for calculating the system drainage time is developed. The double-sided vaporization from conical channels at an axial temperature gradient has been investigated in detail. Expressions for temperature coefficient of evaporation has been obtained and a computational algorithm for vaporization velocity has been developed. The obtained results allow estimating the duration of drying for materials with through pores of any type under conditions of uneven heating.
Heterogeneous nucleation in extended states of liquid argon with a solid particle is studied with molecular dynamics methods. The rupture strength of cavitation in the liquid is determined as a ...function of the energy of interaction between molecules of liquid and those of solid inclusion. The influence of solid particle sizes on the nucleation process is explored.
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A Monte Carlo model of the thermal-neutron scintillation detector based on NE 912 lithium glass has been created and verified. The simulation was validated by comparing its result to experimental ...data from a prototype detector exposed to thermal-neutron and γ-ray beams. The light yield in the scintillator for a captured thermal neutron, the quenching factor, and the decay times of the scintillator were determined. The accuracy in reproducing the pulse shapes obtained in the experiment is sufficient to allow analysis of experimental data and estimation of the efficiency of
n
/γ discrimination techniques. Based on the simulation, it is possible to develop detector models with a low γ-ray sensitivity using heterogeneous composite scintillators with various geometries.
The paper presents the results of an experimental study of the current dependence of samples of silicon structures with dielectric insulation (SSDI) on voltage, and describes the features of the flow ...of currents of extremely high density in these structures. A study of the processes of self-organization of electron-hole plasma in SSDI manufactured using SDI technology and an analysis of the obtained results have been performed. The temperature Ti of intrinsic conductivity, which was 860 K, was experimentally determined at a current density of less than 2(104 A/cm2, which exceeds the temperature in the structures made by “silicon on insulator” (SOI) technology by more than 200 K. It is shown that the current causes an intense Joule heating of these structures, an emergence of their own conductivity and the electron-hole plasma formation. A plasma stratification is accompanied by a glow in the form of symmetrically located red spots. The appearance of each new spot is accompanied by the formation of an S-shaped area on the volt-ampere characteristic, which is a typical manifestation of the current cord formation. The current cord occurs if the characteristics of the current dependence on the voltage (I-U) of SSDI structures deviate from the Ohm's law, having an S-shape. The appearance of cords is inherent to materials, in particular semiconductors, with the electrical conductivity increasing rapidly with temperature growth, due to the increase in charge carrier concentration. The obtained results are compared to authors’ earlier results of studies of light emission from the structures produced by SOI technology. It was found that the effects in the SOI structures occur at lower current density values than in the SSDI structures.
Data analysis of an experiment in which photon splitting in atomic fields was observed is presented. The experiment was performed at the tagged photon beam of the ROKK-1M facility at the VEPP-4M ...collider. In the energy region of 120-450 MeV, statistics of 1.6x10(9) photons incident on the BGO target was collected. About 400 candidate photon-splitting events were reconstructed. Within the attained experimental accuracy, the experimental results are consistent with the calculated exact atomic-field cross section. The predictions obtained in the Born approximation differ significantly from the experimental results.
A
bstract
We present the study of the decay
J/ψ
→
ρπ
. The results are based on of 5.2 million
J/ψ
events collected by the KEDR detector at the VEPP-4M collider. The branching fractions are measured ...to be
B
(
J/ψ
→
ρπ
) = (2
.
072 ± 0
.
017 ± 0
.
062) ∙ 10
−
2
and
B
(
J/ψ
→
π
+
π
−
π
0
) = (1
.
878 ± 0
.
013 ± 0
.
051) ∙ 10
−
2
, where the first uncertainties are statistical and the second systematic. Our results are more precise than the previous relative measurements.
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