Two-stage joint non-causal filtering and segmentation of nonuniform images

The optimal and quasioptimal algorithms of two-stage non-causal filtering and segmentation of nonuniform images distorted by additive interference with independent values of samples have been synthesized on the basis of the mathematical tools of mixed Markov discrete time processes. The first stage involves the performance of one-dimensional joint filtering and segmentation of nonuniform images along rows and columns. The second stage involves the combining of estimates computed at the first stage. The analysis of the quasioptimal algorithm was performed by using the computer statistical simulation of model example.     

Analogs of purine nucleosides. 3. Alkoxyalkylation of hypoxanthine by the silyl method

The reaction of bis(trimethylsilyl)hypoxanthine with methyl trichloromethyl ether has been investigated. 1-Methoxymethyl-, 7-methoxymethyl-, and 9-methoxymethyl-hypoxanthine, as well as 1,7-, 1,9-, and 3,7-bismethoxymethylhypoxanthine, have been isolated from the reaction mixture. The structures of the isomers have been established on the basis of an analysis of their UV, IR, ¹H NMR, ¹³C NMR, and ¹⁵N NMR spectra. The influence of the conditions under which the reaction is carried out on the yield of the alkylation products and the isomeric composition of the reaction mixture has been studied.For report 2, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 518–524, April, 1986.     

A study of reaction rates of (n, f ) , (n, \gamma) and (n, 2n) reactions in natU and 232Th by the neutron fluence produced in the graphite set-up (GAMMA-3) irradiated by 2.33 GeV deuteron beam

Spallation neutrons produced in the collision of a 2.33GeV deuteron beam with a large lead target are moderated by a thick graphite block surrounding the target and used to activate the radioactive samples of ^natU and Th put at three different positions, identified as holes “a”, “b” and “c” in the graphite block. Rates of the (n, f), (n, $ \gamma$ and (n, 2n) reactions in the two samples are determined using the gamma spectrometry. The ratios of the experimental reaction rates, R (n, 2n)/R (n, f), for ²³²Th and ^natU are estimated in order to understand the role of the (n, x n) kind of reactions in Accelerator-Driven Sub-critical Systems. For the Th-sample, the ratio is ～ 54 (10)% in the case of hole “a” and ～ 95 (57)% in the case of hole “b” compared to 1.73(20)% for hole “a” and 0.710(9)% for hole “b” in the case of the ^natU sample. Also the ratio of fission rates in uranium to thorium, ^natU (n, f)/ ²³²Th (n, f), is ～ 11.2 (17) in the case of hole “a” and 26.8(85) in hole “b”. Similarly, the ratio ²³⁸U (n, 2n)/ ²³²Th (n, 2n) is 0.36(4) for hole “a” and 0.20(10) for hole “b” showing that ²³²Th is more prone to the (n, x n) reaction than ²³⁸U . All the experimental reaction rates are compared with the simulated ones by generating neutron fluxes at the three holes from MCNPX 2.6c and making use of the LA150 library of cross-sections. The experimental and calculated reaction rates of all the three reactions are in reasonably good agreement. The transmutation power, P _norm as well as P _norm/P _beam of the set-up is estimated using the reaction rates of the (n, $ \gamma$ and (n, 2n) reactions for both the samples in the three holes and compared with some of the results of the “Energy plus Transmutation” set-up and TARC experiment.     

Triple-deck theory in transonic flows and boundary layer stability

An analysis of the lower branch of the neutral curve for the Blasius boundary layer leads to a perturbed velocity field with a triple-deck structure, which is a rather unexpected result. It is the asymptotic treatment of the stability problem that has a rational basis, since it is in the limit of high Reynolds numbers that the basic flow has the form of a boundary layer. The principles for constructing a boundary layer stability theory based on the triple-deck theory are proposed. Although most attention is focused on transonic outer flows, a comparative analysis with the asymptotic theory of boundary layer stability in subsonic flows is given. The parameters of internal waves near the lower branch of the neutral curve are associated with a certain perturbation field pattern. These parameters satisfy dispersion relations derived by solving eigenvalue problems. The dispersion relations are investigated in complex planes.     

Electron magnetic resonance and magnetooptical studies of nanoparticle-containing borate glasses

We report electron magnetic resonance (EMR) and magnetooptical studies of borate glasses of molar composition 22.5K₂O-22.5Al₂O₃-55B₂O₃ co-doped with low concentrations of Fe₂O₃ and MnO. In as-prepared samples the paramagnetic ions, as a rule, are in diluted state. However, in the case where the ratio of the iron and manganese oxides in the charge is 3/2, magnetic nanoparticles with characteristics close to those of manganese ferrite are formed already at the first stage of the glass preparation, as evidenced by both magnetic circular dichroism (MCD) and EMR. After thermal treatment all glasses show characteristic MCD and EMR spectra, attesting to the presence of magnetic nanoparticles, predominantly including iron ions. Preliminary EXAFS measurements at the Fe K-absorption edge show an emergence of nanoparticles with a structure close to MnFe₂O₄ after annealing the glasses at 560 °C.By computer simulating the EMR spectra at variable temperatures, a superparamagnetic nature of relatively broad size and shape distribution with the average diameter of ca. 3-4 nm. The characteristic temperature-dependent shift of the apparent resonance field is explained by a strong temperature dependence of the magnetic anisotropy in the nanoparticles.The formation of magnetic nanoparticles confers to the potassium-alumina-borate glasses magnetic and magneto-optical properties typical of magnetically ordered substances. At the same time, they remain transparent in a part of the visible and near infrared spectral range and display a high Faraday rotation value.     

Fissile radionuclides in thyroid of the inhabitants of the gomel region in belarus and peculiarities of their distribution

Severe radiation damages with the following substitution of connective tissue are the effect of high doses in microvolumes of the thyroid. Calcium, strontium and uranium deposited into these sections was more as compared to a normal tissue of the thyroid. An estimation of the microdistribution of fissile radionuclides was carried out using the method of fragmental radiography. The analysis of tracks done visually using a microscope magnification of 300 revealed the local density of fission fragments up to 10³ mm⁻². The irradiation of the surrounded cells which contain the hidden genetic damages, initiated by radioiodine, does not exclude their possible promoter role in thyroid cancerogenesis.     

Asymptotic behavior of solutions of the Orr-Sommerfeld equations in regions adjacent to two branches of the neutral curve

The asymptotic behavior of the upper and lower branches of the neutral stability curve of a boundary layer found by Lin [1] was determined more accurately by various authors [2–4], who, on the basis of the linearized Navien-Stokes equations, analyzed the higher approximations in the Reynolds number R. In the limit R , neutral perturbations have wavelengths that exceed in order of magnitude the boundary layer thickness. The long-wavelength asymptotic behavior of the Orr-Sommerfeld equation is, in particular, of interest because the characteristic solutions of the linearized equations of free interaction (triple-deck theory) [5–7] are a limiting form of Tollmierr-Schlichting waves in an incompressible fluid with critical layers next to the wall [8–9]. At the same time, the dispersion relation, which is identical to the secular equation of the Orr-Sommerfeld problem, contains an entire spectrum of solutions not considered in the earlier studies [2–4]. The first oscillation mode in the spectrum may be either stable or unstable. In the present paper, solutions are constructed for each of the subregions (including the critical layer) into which the perturbed velocity field in the linear stability problem is divided at large Reynolds numbers. Dispersion relations describing the neighborhood of the upper and lower branches of the neutral curve for the boundary layer are derived. These relations, which contain neutral solutions as a special case, go over asymptotically into each other in the unstable region between the two branches.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 3–11, July–August, 1984.