248 research outputs found
Equation of state SAHA-S meets stellar evolution code CESAM2k
We present an example of an interpolation code of the SAHA-S equation of
state that has been adapted for use in the stellar evolution code CESAM2k. The
aim is to provide the necessary data and numerical procedures for its
implementation in a stellar code. A technical problem is the discrepancy
between the sets of thermodynamic quantities provided by the SAHA-S equation of
state and those necessary in the CESAM2k computations. Moreover, the
independent variables in a practical equation of state (like SAHA-S) are
temperature and density, whereas for modelling calculations the variables
temperature and pressure are preferable. Specifically for the CESAM2k code,
some additional quantities and their derivatives must be provided. To provide
the bridge between the equation of state and stellar modelling, we prepare
auxiliary tables of the quantities that are demanded in CESAM2k. Then we use
cubic spline interpolation to provide both smoothness and a good approximation
of the necessary derivatives. Using the B-form of spline representation
provides us with an efficient algorithm for three-dimensional interpolation.
The table of B-spline coefficients provided can be directly used during stellar
model calculations together with the module of cubic spline interpolation. This
implementation of the SAHA-S equation of state in the CESAM2k stellar structure
and evolution code has been tested on a solar model evolved to the present. A
comparison with other equations of state is briefly discussed. The choice of a
regular net of mesh points for specific primary quantities in the SAHA-S
equation of state, together with accurate and consistently smooth tabulated
values, provides an effective algorithm of interpolation in modelling
calculations. The proposed module of interpolation procedures can be easily
adopted in other evolution codes.Comment: 8 pages, 5 figure
Synthesis and characterisation of nanocrystalline ZrN PVD coatings on AISI 430 stainless steel
The nanocrystalline films of zirconium nitride have been synthesized using ion-plasma vacuum-arc deposition technique in combination with high-frequency discharge (RF) on AISI 430 stainless steel at 150oC. Structure examinations X-ray fluorescent analysis (XRF), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) with microanalysis (EDS), and transmission electron microscopy (TEM), nanoidentation method – were performed to study phase and chemical composition, surface morphology, microstructure and nanohardness of coatings. The developed technology provided low-temperature coatings synthesis, minimized discharge breakdown decreasing formation of macroparticles (MPs) and allowed to deposit ZrN coatings with hardness variation 26.6…31.5 GPa. It was revealed that ZrN single-phase coatings of cubic modification with finecrystalline grains of 20 nm in size were formed
Anti-corrosion ceramic coatings on the surface of Nd-Fe-B repelling magnets
The results of vacuum-arc deposition of thin ZrO₂coatings to protect the surface of Nd-Fe-B permanent magnets used as repelling devices in orthodontics are presented. The structure, phase composition and mechanical properties of zirconium dioxide films have been investigated by means of SEM, XRD, EDX, XRF and nanoindentation method. It was revealed the formation of polycrystalline ZrO₂ films of monoclinic modification with average grain size 25 nm. The influence of the ZrO₂ coating in terms of its barrier properties for corrosion in quasi-physiological 0.9 NaCl solution has been studied. Electrochemical measurements indicated good barrier properties of the coating on specimens in the physiological solution environment
ОПТИМАЛЬНАЯ СХЕМА ПРОКЛАДКИ СБОРНЫХ ПОЕЗДОВ
The authors consider methods to find optimal scheme of routing for single wagon load trains for different railway sections. Three variants of allocation of a pair of such trains and consequences of stoppage of the wagons at the stations of loading and unloading are considered. Those variants are studied from the point of view of the advantages for traffic control. The comparison of computed data gives opportunity to make certain conclusions on the selection of a scheme that gives better results and less car stoppage.Авторы рассматривают методику поиска оптимальной схемы прокладки сборных поездов на железнодорожных участках. С позиций грамотно налаженного управления движением и получаемых от этого выгод в статье оцениваются три варианта размещения поездных пар и сопутствующие им последствия простоя вагонов на станциях погрузки-выгрузки. Сопоставление расчетных данных позволяет сделать выводы о том, какая из представленных схем организации дает действительно наилучшие результаты при построении наиболее рациональных графиков и сведении к минимуму простаивания вагонной техники.
A synoptic comparison of the MHD and the OPAL equations of state
A detailed comparison is carried out between two popular equations of state
(EOS), the Mihalas-Hummer-Dappen (MHD) and the OPAL equations of state, which
have found widespread use in solar and stellar modeling during the past two
decades. They are parts of two independent efforts to recalculate stellar
opacities; the international Opacity Project (OP) and the Livermore-based OPAL
project. We examine the difference between the two equations of state in a
broad sense, over the whole applicable rho-T range, and for three different
chemical mixtures. Such a global comparison highlights both their differences
and their similarities.
We find that omitting a questionable hard-sphere correction, tau, to the
Coulomb interaction in the MHD formulation, greatly improves the agreement
between the MHD and OPAL EOS. We also find signs of differences that could stem
from quantum effects not yet included in the MHD EOS, and differences in the
ionization zones that are probably caused by differences in the mechanisms for
pressure ionization. Our analysis do not only give a clearer perception of the
limitations of each equation of state for astrophysical applications, but also
serve as guidance for future work on the physical issues behind the
differences. The outcome should be an improvement of both equations of state.Comment: 33 pages, 26 figures. Corrected discussion of Basu & Antia, 2004,
ApJ, 606, L85-L8
Modeling Pdx:Biy nanoclusters and predicting their catalytic activity in the glucose oxidation reaction into gluconic acid
A Precision Measurement of Nuclear Muon Capture on 3He
The muon capture rate in the reaction mu- 3He -> nu + 3H has been measured at
PSI using a modular high pressure ionization chamber. The rate corresponding to
statistical hyperfine population of the mu-3He atom is (1496.0 +- 4.0) s^-1.
This result confirms the PCAC prediction for the pseudoscalar form factors of
the 3He-3H system and the nucleon.Comment: 13 pages, 6 PostScript figure
The Role of Birds as Potential Reservoirs of West Nile Virus in the Territory of the Russian Federation
Submitted are the materials on epizootiology of West Nile Fever in birds, taking into account their migration. Described are the characteristics of WNF in wild and synanthropic birds. Ecological relationships between birds, mosquitoes, ticks and West Nile virus are analyzed. Main autumn bird migratory directions are characterized and the data on WNF monitoring in birds in different geographical regions of Russia are presented
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