A theoretical model of a wake of a body towed in a stratified fluid at large Reynolds and Froude numbers

International audienceThe objective of the present paper is to develop a theoretical model describing the evolution of a turbulent wake behind a towed sphere in a stably stratified fluid at large Froude and Reynolds numbers. The wake flow is considered as a quasi two-dimensional (2-D) turbulent jet flow whose dynamics is governed by the momentum transfer from the mean flow to a quasi-2-D sinuous mode growing due to hydrodynamic instability. The model employs a quasi-linear approximation to describe this momentum transfer. The model scaling coefficients are defined with the use of available experimental data, and the performance of the model is verified by comparison with the results of a direct numerical simulation of a 2-D turbulent jet flow. The model prediction for the temporal development of the wake axis mean velocity is found to be in good agreement with the experimental data obtained by Spedding (1997)

ВЛИЯНИЕ МОДИФИКАТОРОВ НА РЕОЛОГИЧЕСКИЕ И ТЕРМИЧЕСКИЕ СВОЙСТВА БОРОСИЛИКАТНЫХ СТЕКОЛ

Results of research for the glass system Na2O-K2O-B2O3-SiO2 at 2:1 molar ratio of K2O/Na2O modifiers are presented. It has been found that increasing (K2O+Na2O)/B2O3 ratio in glass compositions leads to higher low-temperature viscosity and viscosity gradient in the range of 109-104Pa-s. The established temperature dependences of viscosity allow to optimize borosilicate glass compositions with predetermined characteristics, as well as technological parameters of their synthesis and formation.Представлены результаты исследования стекол системы Na2O-K2O-B2O3-SiO2 при молярном соотношении модификаторов K2O/Na2O, равном 2:1. Установлено, что рост соотношения (K2O+Na2O)/B2O3 в составе стекол вызывает увеличение низкотемпературной вязкости и градиента вязкости в интервале значений 109-104 Па-с. Установленные температурные зависимости вязкости позволяют оптимизировать составы боросиликатных стекол с заданными характеристиками, а также технологические параметры их синтеза и формования

High-index glass for the products of ophthalmologic optics

The results of development of high-index glass for the products of ophthalmologic optics on the basis of the systems Li2O – RO – B2O3– SiO2and K2O – TiO2– SiO2are presented. It is shown that the formation of complexes [TiO4/2O] 2– K2 + in glass of the system K2O – TiO2– SiO2interferes with the formation of the chromophorecenters Fe 2+ – O – Ti 4+ and allows to receive colorless glass at amount of TiO2to 30 mol.%. The compositions of glass with a refractive index 1.65 and 1.70 at density no more than 2.91 g/cm 3 are developed. It allows to recommend them for the production of the facilitated lenses with a high optical force

Glass-ceramic cement for vacuum-tight joint

Synthesis of fusible glass of ZnO – PbO – B[2]O[3] system at the maintenance of components, wt %: B[2]O[3] – 10–45; ZnO – 5–40; PbO – 50–85 is carried out. It was established that stability of a vitreous state is defined by a ratio of ZnO / (PbO + B [2]O[3]) in the glass composition. Dependences of thermal and rheological characteristics of glass systems of ZnO – PbO – B[2]O[3] from a chemical composition are studied. The increase in the maintenance of B[2]O[3] superseded by PbO causes the essential growth of viscosity and decreas e of its gradient. The components able to reduce viscosity are arranged in the following way: B[2]O[3]→ZnO →PbO. By the results of research of glass rheological properties of ZnO – PbO – B[2]O[3] system, the area of glass compositions with viscosity less than 10{5} Pa · s at a temperature not over 450°C that provides the demanded spreadability indicators is defined. Regulation of indicators of TCLE is reached by creation of compositions glass – a crystal filler. Influence of such crystal filler as zircon, spodumene, cordierite on properties of composite glass-ceramic cement is re searched. The target TCLE indexes being equal to (77 ± 1) · 10{–7} K{–1} are achieved by the introduction of a spodumene. The composite glass-ceramic cement, intended for vacuum-tight connections of fiber-optical elements with a metal frame was developed. TCLE indexes of the glass-ceramic cement are equal to 77.2 · 10{–7} K{–1}, that coordinates it with TCLE containing a fiber-optical element. Temperature of composite glass-ceramic cement soldering is 450 ± 5°C, temperature of its deformation – 520 ± 5°C

Application of X-Ray Fluorescence Analysis to Determine the Elemental Composition of Tissues from Different Ovarian Neoplasms

x-ray fluorescence analysis, endometrioid cancer, mucinous cancer, serous carcinoma, ovarian tissues, microelements.We present the results of x-ray fluorescence analysis of tissues from healthy ovaries and from ovaries with different pathologies: benign and borderline tumors, mucinous and endometrioid cancers, serous carcinomas. We determine the average copper, zinc, calcium, selenium, cadmium, lead, and mercury levels. We observed that in the benign ovarian tumors, we see a significant decrease in the cadmium, mercury, and lead levels compared with healthy tissues. In the borderline neoplasms, the copper level is reduced relative to zinc (Cu/Zn), cadmium, mercury, and lead, and also the zinc concentration is increased. In the ovarian carcinomas, we observed changes in the ratio of the chemical elements in the tumor tissues, depending on the histologic type. The results obtained can be used for differentiation, diagnosis, and adjustment of treatment for different ovarian neoplasms

FIELD AND NUMERICAL STUDY OF THE WIND-WAVE REGIME ON THE GORKY RESERVOIR

The paper describes the study of wind-wave regime at the Gorky reservoir. A series of field experiments (carried out from May to October in 2012–2015) showed that the values of the drag coefficient CD for a middle-sized reservoir in the range of moderate and strong winds are approximately 50 % lower than its values typical of the ocean conditions. The obtained parameterization of CD was implemented in the wave model WAVEWATCH III to receive the correct wave forecasts for a middle-sized reservoir. Statistical distribution of the wind speeds and directions called for consideration of wind field heterogeneity over the Gorky reservoir. It was incorporated using the wind forcing from atmospheric model WRF to WAVEWATCH III. Homogeneous wind forcing from the experimental data was compared with heterogeneous wind forcing from WRF. The need for further improvement of the quality of wind and wave prediction is discussed