Maximum a posteriori estimation through simulated annealing for binary asteroid orbit determination

This paper considers a new method for the binary asteroid orbit determination problem. The method is based on the Bayesian approach with a global optimisation algorithm. The orbital parameters to be determined are modelled through an a posteriori distribution made of a priori and likelihood terms. The first term constrains the parameters space and it allows the introduction of available knowledge about the orbit. The second term is based on given observations and it allows us to use and compare different observational error models. Once the a posteriori model is built, the estimator of the orbital parameters is computed using a global optimisation procedure: the simulated annealing algorithm. The maximum a posteriori (MAP) techniques are verified using simulated and real data. The obtained results validate the proposed method. The new approach guarantees independence of the initial parameters estimation and theoretical convergence towards the global optimisation solution. It is particularly useful in these situations, whenever a good initial orbit estimation is difficult to get, whenever observations are not well-sampled, and whenever the statistical behaviour of the observational errors cannot be stated Gaussian like.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Societ

Mechanisms of Microwave Absorption in Carbon Compounds from Shungite

According to SEM, X-ray phase analysis, Raman scattering data features of nanostructural changes in shungite carbon structure were found when processing shungite in 52 % hydrofluoric acid. It is found that conductivity increases up to the values of electrical graphite and absorption of microwave radiation also increases at frequencies up to 40 GHz, which, along with dielectric losses, is due to intense processes of both scattering at laminar carbon structures and absorption of electromagnetic energy. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3365

Surface-enhanced optical third-harmonic generation in Ag island films

Surface-enhanced optical third-harmonic generation (THG) is observed in silver island films. The THG intensity from Ag nanoparticles is enhanced by more than two orders of magnitude with respect to the THG intensity from a smooth and homogeneous silver surface. This enhancement is attributed to local plasmon excitation and resonance of the local field at the third-harmonic wavelength. The diffuse and depolarized component of the enhanced THG is associated with the third-order hyper-Rayleigh scattering in a 2-D random array of silver nanoparticles.Comment: 4 pages, 2 figure

The boundary value problem of determining hydrogen concentration and the stress state in a titanium shell

Decreasing physical and mechanical properties of materials in contact with an aggressive environment is one of the factors determining the strength and service life of various structures. In this paper, the effect of a hydrogen-containing medium on the mechanical properties and stress state of a titanium alloy shell is shown. For this purpose, the diffusion boundary-value problem is solved and the distribution of hydrogen concentration over the shell wall thickness is determined. Then the boundary-value problem of statics is solved, and the stress state of the shell structure is determined before and after hydrogenation. The object of study is presented in the form of a shell of revolution loaded with internal pressure and working in a hydrogen-containing medium. © 2019 Author(s)

Cytomorphometric indicators of the gingiva epitheliocytes of patients with ischemic heart disease on the background of taking acetylsalicylic acid

The aim is to study the cytological and morphometric characteristics of gingiva epitheliocytes in patients with IHD who are constantly taking ASA drugs. To determine the dental status, 92 patients aged 40-60 years who are on outpatient treatment of IHD were examined. An in-depth scientific study was conducted and the results of cytomorphometric indicators of the gingiva epitheliocytes of patients with ischemic heart disease, constantly taking acetylsalicylic acid drugs, were presente