МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ ДИНАМИКИ ДВИЖЕНИЯ ЮБКИ ПОРШНЯ В ЦИЛИНДРЕ ДВИГАТЕЛЯ ВНУТРЕННЕГО СГОРАНИЯ

There examined method theoretical research of sectional piston skirt hydrodynamic lubrication, and influence of piston and connection rod groups options on it.В статье рассмотрена методика проведения теоретического исследования гидродинамической смазки юбки составного поршня, и влияние на нее конструктивных параметров деталей поршневой и кривошипно-шатунной групп

Экспериментальное исследование напряженно-деформированного состояния юбки поршня двигателя внутреннего сгорания на безмоторном стенде

The article describes the features developed by the authors of the profiling method of the piston skirt, provides the main parameters that affect the lubrication conditions of the piston skirt and the magnitude of mechanical losses. In computational studies, the basic formulas are given for determining the thickness of the oil layer in a piston skirt - cylinder sleeve conjunction to assess the nature of friction. To determine the deformations, the finite element method is used on the spatial model of the piston. To verify the finite element model, a stand for experimental studies was developed. The article describes the developed stand, the methodology and results of experimental studies of the stress-strain state of the two-piece piston skirt obtained at this stand and a comparative analysis of the results of the calculated and experimental studies of the stress-strain state of the two-piece piston skirt of a diesel engine. The research results showed that the developed stand can be used to verify mathematical models for calculating the stress-strain state of the piston skirt in the pilot production of internal combustion engine pistons to accelerate and reduce the cost of the piston design development process, as well as the results of experimental studies obtained at the stand, can be used as initial data for the developed mathematical model of the dynamics of the movement of the piston and the profiling of the piston skirt.В статье представлены особенности разработанной авторами методики профилирования юбки поршня, приведены основные параметры, влияющие на условия смазывания юбки поршня и величину механических потерь. В расчетных исследованиях даны основные формулы для определения толщины масляного слоя в сопряжении «юбка поршня - цилиндр» для оценки характера трения. Для определения деформаций используется метод конечных элементов на пространственной модели поршня. Для верификации конечно-элементной модели был разработан стенд для экспериментальных исследований. В статье описаны разработанный стенд, методика проведения и результаты экспериментальных исследований напряженно-деформированного состояния юбки составного поршня, полученные на данном стенде, выполнен сравнительный анализ результатов расчетных и экспериментальных исследований напряженно-деформированного состояния юбки составного поршня дизеля. Исследование показало, что разработанный стенд может применяться для верификации математических моделей расчета напряженно-деформированного состояния юбки поршня в опытном производстве поршней двигателя внутреннего сгорания для ускорения и удешевления процесса разработки их конструкции. Результаты экспериментальных исследований, полученные на стенде, также могут быть использованы в качестве исходных данных для разработанной математической модели динамики движения поршня и профилирования юбки поршня

Auger decay of degenerate and Bose-condensed excitons in Cu2_2O

We study the non-radiative Auger decay of excitons in Cu$_2$O, in which two excitons scatter to an excited electron and hole. The exciton decay rate for the direct and the phonon-assisted processes is calculated from first principles; incorporating the band structure of the material leads to a relatively shorter lifetime of the triplet state ortho excitons. We compare our results with the Auger decay rate extracted from data on highly degenerate triplet excitons and Bose-condensed singlet excitons in Cu$_2$O.Comment: 15 pages, revtex, figures available from G. Kavoulaki

Fine structure of excitons in Cu2_2O

Three experimental observations on 1s-excitons in Cu$_2$O are not consistent with the picture of the exciton as a simple hydrogenic bound state: the energies of the 1s-excitons deviate from the Rydberg formula, the total exciton mass exceeds the sum of the electron and hole effective masses, and the triplet-state excitons lie above the singlet. Incorporating the band structure of the material, we calculate the corrections to this simple picture arising from the fact that the exciton Bohr radius is comparable to the lattice constant. By means of a self-consistent variational calculation of the total exciton mass as well as the ground-state energy of the singlet and the triplet-state excitons, we find excellent agreement with experiment.Comment: Revised abstract; 10 pages, revtex, 3 figures available from G. Kavoulakis, Physics Department, University of Illinois, Urban

Quantum saturation and condensation of excitons in Cu2_2O: a theoretical study

Recent experiments on high density excitons in Cu$_2$O provide evidence for degenerate quantum statistics and Bose-Einstein condensation of this nearly ideal gas. We model the time dependence of this bosonic system including exciton decay mechanisms, energy exchange with phonons, and interconversion between ortho (triplet-state) and para (singlet-state) excitons, using parameters for the excitonic decay, the coupling to acoustic and low-lying optical phonons, Auger recombination, and ortho-para interconversion derived from experiment. The single adjustable parameter in our model is the optical-phonon cooling rate for Auger and laser-produced hot excitons. We show that the orthoexcitons move along the phase boundary without crossing it (i.e., exhibit a ``quantum saturation''), as a consequence of the balance of entropy changes due to cooling of excitons by phonons and heating by the non-radiative Auger two-exciton recombination process. The Auger annihilation rate for para-para collisions is much smaller than that for ortho-para and ortho-ortho collisions, explaining why, under the given experimental conditions, the paraexcitons condense while the orthoexcitons fail to do so.Comment: Revised to improve clarity and physical content 18 pages, revtex, figures available from G. Kavoulakis, Physics Department, University of Illinois, Urban

Predicting the Amplitude of a Solar Cycle Using the North-South Asymmetry in the Previous Cycle: II. An Improved Prediction for Solar Cycle~24

Recently, using Greenwich and Solar Optical Observing Network sunspot group data during the period 1874-2006, (Javaraiah, MNRAS, 377, L34, 2007: Paper I), has found that: (1) the sum of the areas of the sunspot groups in 0-10 deg latitude interval of the Sun's northern hemisphere and in the time-interval of -1.35 year to +2.15 year from the time of the preceding minimum of a solar cycle n correlates well (corr. coeff. r=0.947) with the amplitude (maximum of the smoothed monthly sunspot number) of the next cycle n+1. (2) The sum of the areas of the spot groups in 0-10 deg latitude interval of the southern hemisphere and in the time-interval of 1.0 year to 1.75 year just after the time of the maximum of the cycle n correlates very well (r=0.966) with the amplitude of cycle n+1. Using these relations, (1) and (2), the values 112 + or - 13 and 74 + or -10, respectively, were predicted in Paper I for the amplitude of the upcoming cycle 24. Here we found that in case of (1), the north-south asymmetry in the area sum of a cycle n also has a relationship, say (3), with the amplitude of cycle n+1, which is similar to (1) but more statistically significant (r=0.968) like (2). By using (3) it is possible to predict the amplitude of a cycle with a better accuracy by about 13 years in advance, and we get 103 + or -10 for the amplitude of the upcoming cycle 24. However, we found a similar but a more statistically significant (r=0.983) relationship, say (4), by using the sum of the area sum used in (2) and the north-south difference used in (3). By using (4) it is possible to predict the amplitude of a cycle by about 9 years in advance with a high accuracy and we get 87 + or - 7 for the amplitude of cycle 24.Comment: 21 pages, 7 figures, Published in Solar Physics 252, 419-439 (2008

The ^4He trimer as an Efimov system

We review the results obtained in the last four decades which demonstrate the Efimov nature of the $^4$He three-atomic system.Comment: Review article for a special issue of the Few-Body Systems journal devoted to Efimov physic

The haemadsorption at african swine fever (review)

The capability of causing haemadsorption at African swine fever (ASF) virus (ASFV) reproduction in swine bone marrow cell cultures, leukocytes or continuous cells in the presence of swine erythrocytes is characteristic of the majority of the virus isolates (W.A. Malmquist, D. Hay, 1960). This trait is used for ASF diagnosis based on autohaemadsorption in porcine blood, the virus titration in cell culture, and selection of its attenuated variants in vitro (A.D. Sereda et al., 2014). The haemadsorption inhibition assay (HIA) in tandem with the bioassay using the disease-resistant pigs is applied for seroimmunotype-based classification of ASFV isolates (N.I. Mitin et al., 1985). The heterogeneity of an ASFV population for quantitative haemadsorption characteristic (like «dense», «moderate» or «loose») is a phenotypic trait of ASFV isolates, strains and/or variants (V. Makarov et al., 2016). Also, the proportion of the circumference of red blood cells as observed at their contact with infected macrophages serves as another quantifiable feature of haemadsorption. Some quantitative differences in HIA activity levels of swine blood sera are determined in the assays carried out using virulent reference variants and their attenuated derivatives, and the obtained results require some interpretation. The loss of ability to induce haemadsorption is not critical for ASFV reproduction and often accompanied by a decrease in the pathogen virulence levels. Hence, as a rule, attenuated ASFV variants are prepared through a selection by limiting dilution from populations of virulent isolates of the virus clones that are characterized by a reduced potential to induce haemadsorption (D.V. Kolbasov et al., 2014). In the course of the virus reproduction, haemadsorption precedes the exocytosis. Virions do not play a significant role in the mechanism of haemadsorption, nevertheless, their interaction with erythrocyte membranes promotes the virus dissemination throughout the swine organism and more effective introduction into the gut cells of ticks (L.K. Dixon et al., 2004). ASFV haemadsorbing potentiality is determined by highly glycosylated transmembrane protein CD2v (J.M. Rodríguez et al., 1993). Probably, nonhaemadsorbing avirulent isolates emerge as a result of some shift of the open reading frames for EP402R and EP153R encoding the CD2v and lectin-like proteins, respectively (D.A. Chapman et al., 2008). An assumption is made that the haemadsorption phenomenon is due to an interaction between carbohydrate residues of glycoproteins of ASFV oligosaccharides and lectin-like receptors of swine red blood cells

Effect of Optical and Structural Parameters of Thermal Barrier Coatings of the Combustion Chamber on Working Processes of a Diesel

The paper describes the bulk mean thermodynamic parameters of the combustion space in the diesel engine cylinder during the whole operating cycle adjusted consideration the features of heat transfer between the working fluid and the combustion chamber wall made of (or coated) thermal barrier materials using semitransparent ceramics. The novelty of this study is a simulation of convective and radiant heat exchange by the forming gas atmosphere and the generating soot microparticle cloud near heat insulated walls with a temperature regime determined by the significant influence of the optical parameters of thermal barrier materials or coatings. The total thermal radiant flux within the IR long and short wavelength range was modeled as a part of the convective-radiant heat flux. The temperature regime of insulation material (with a transparency band up to sim 3-4 mu m) was mainly determined by exposure of penetrating radiation component ( 1-2 mu m) primarily from red-hot soot particles. For the first time, the model developed by the authors suggests the study of convective and radiant processes in different locations within the chamber due to the temperature regime of the exposed semitransparent thermal barrier coatings with subsurface (internal) radiant thermal source with the power which is independently determined by its microstructure and optical parameters. The proposed physical model based on the independent impact of the long and short wavelength components allowed the authors to modify the traditional semi-empirical approximation of by including (for example, in the Annand formula) the real value without any correlating constants. The remaining additive radiant part used for solving a nonlinear problem of radiant-conductive heat transfer within the wall with TBC to determine its specified surface temperature Tw for further iterative and cyclic calculations depending on the angular rotation rate of the engine crankshaft. © 2019 IEEE