Nonlinear acoustic waves in channels with variable cross sections

The point symmetry group is studied for the generalized Webster-type equation describing non-linear acoustic waves in lossy channels with variable cross sections. It is shown that, for certain types of cross section profiles, the admitted symmetry group is extended and the invariant solutions corresponding to these profiles are obtained. Approximate analytic solutions to the generalized Webster equation are derived for channels with smoothly varying cross sections and arbitrary initial conditions.Comment: Revtex4, 10 pages, 2 figure. This is an enlarged contribution to Acoustical Physics, 2012, v.58, No.3, p.269-276 with modest stylistic corrections introduced mainly in the Introduction and References. Several typos were also correcte

Quaternary palynostratigraphy of the Pechora Sea

By combining the lithologic, original palynologic and published micropaleonthological data we reconstructed paleogeographical events On the Pechora shelf during the Younger Dryas and Holocene time. Our paleoenvironmental reconstructions are based On the regularities in formation of pollen-and-spores assemblages in the surface sediments of the Pechora Sea. The main stages in paleogeography of the Pechora Sea during the Late Pleistocene were emphasized. The Late Valdai sediments in the Pechora Sea region were accumulated under the influence of fluvioglacial flows probably from the melting ice cap on Kolguev Island and, also, coastal glaciers. Climate deterioration considerably changed coastal vegetation as reflected in the depleted taxonomic and quantitative composition of palynospectra. The pollen data suggest that Open steppe-like plant communities with Artemisia, Poaceae, Asteraceae and Caryophyllaceae dominated dry ecotopes On watersheds, whereas tundra-like communities with Betula nana, arctic Salix, Dryas, Saxifraga, Carex and Brassicaceae were common in more humid coastal lowlands. The overlying silts and loamy sands are believed to have been accumulated during early deglaciation, i.e., Older Dryas and Alleröd. During this phase the glacial sedimentation was rather rapidly replaced by a glaciomarine deposition. Progressive climate warming caused prominent changes in coastal vegetation. Discontinuous treeless tundra-steppe associations were replaced by dwarf and shrub ernik tundra. A "complex vegetation cover" of forest-tundra apparently existed in the northern part of the Kola Peninsula and in the Northern Dvina Lowland. By the end of the Alleröd alder-bushes and horsetails occupied riverbanks, and spruce occurred in the forest-tundra communities on the adjacent hinterland

НЕОБХІДНІСТЬ РОЗВИТКУ ВОЛОНТЕРСЬКОГО РУХУ СЕРЕД СТУДЕНТІВ-МЕДИКІВ

 The given article deals with the work of volunteer team under the aegis ofBerdyanskMedicalCollege and covers the necessity of development of volunteer movement among medical students.  У статті повідомляється про роботу волонтерської бригади Бердянського медичного коледжу та про необхідність розвитку волонтерського руху серед студентів-медиків

Evaluation of the inbreeding effect on the milk productivity of Holstein cows

Inbreeding is an integral part of breeding work today. However, its effect on the economically valuable traits of animals is not identical. The research was carried out in LLC "Вreeding plant «Pushkinskoe» Bolsheboldinsky district of the Nizhny Novgorod region. The data have been obtained from the primary zootechnical records and database «SELEX» – Dairy cattle (n = 950). The animals were divided into 4 groups depending on the degree of inbreeding. Cows with the close degree of inbreeding had the maximum milk yield (9877.9 kg), those with the mild degree had minimal milk yield (9338.11 kg). An increase in the degree of inbreeding had a negative effect on the fat content in milk, which led to its decrease from 3.85 % in the group with outbred animals to 3.64 % in the group with the close degree of inbreeding. There were no significant differences in the protein content in milk between the groups. The lactation stability coefficient decreases as the degree of inbreeding increases. The variability coefficient of milk yield in animals with the close degree of inbreeding is lower than the other groups (10.53 %), the coefficient varies within 5 % according to the fat content in all groups and in terms of protein content in milk within 1.3-2.2 %. Distant and mild inbreeding has a weak positive relationship with milk yield (r = +0.015 and +0.028), close inbreeding leads to its decrease (r = -0.098). Inside the groups, having inbred connections, аn increase in the inbreeding degree leads to a very slight increase in fat content (r = +0.016-0.129) and the lactation stability coefficient (r = +0.063-0.164), the influence of the degree of inbreeding on the protein content in milk is not identical. The relationship between milk yield and fat content in outbred animals is weakly positive (r = +0.26), in cows with mild and distant degree of inbreeding is weakly negative (r = +0.057-0.121), in the group with a close degree it becomes closely negative (r = - 0.677)

Determination of the electric field strength of high-voltage substations

The electric field strength is one of the main factors influencing sensitive microprocessor equipment and personnel on power stations and substations, power lines. Determining its level is an important applied task for ensuring the safe operation of electrical installations. The aim is to develop calculation relationships for determining the electric field strength created by the busbar of high-voltage substations in the working areas of personnel. The solution of the problem was based on the use of the method of equivalent charges to determine the strength of the electric field created by the complex busbar of high-voltage substations. Methodology. The development was based on solving the problem of the potential of the electric field of a point charge located in a dielectric half-space for a cylindrical coordinate system. By representing the electrode in the form of a set of point charges and subsequent integration, an expression for calculating the potential is obtained, created by a busbar of arbitrary orientation of finite length in an analytical form. Using the principle of superposition of fields and the definition of the derivative, expressions were obtained for calculating the vertical component of the electric field strength at given heights. Results. Based on the obtained expressions, using Visual Basic, the simulation of the distribution of the electric field strength under a three-phase power line with a voltage of 150 kV was performed. Comparison with the known calculation results obtained on the basis of analytical expressions for infinitely long conductors showed that the obtained expressions have an error of no more than 7%. The scientific novelty lies in the fact that for the first time expressions were obtained for determining the electric field strength created by a system of electrodes of finite length, based on the analytical method for solving differential equations. Practical significance. The proposed technique is implemented as a test module of the LiGro specialized software package, which allows modeling complex busbar systems typical for power stations and substations and power lines. A test calculation was carried out for an operating substation of regional electric networks with a voltage class of 110 kV. By comparing the duration of the calculation of switchgears with a diagonal of about 500 m, it was found that the calculation time in the LiGro complex based on the analytical method is several tens of times less than the calculation based on the finite element method. In addition, a more powerful computer was used for the end element simulation.В електричних станціях та підстанціях, лініях електропередачі напруженість електричного поля є одним з головних факторів впливу на чутливе мікропроцесорне обладнання та персонал. Визначення її рівня є важливою прикладною задачею для забезпечення безпечної експлуатації електроустановок. Мета роботи – розробка розрахункових співвідношень для визначення напруженості електричного поля, що створюється ошиновкою високовольтних підстанцій в робочих зонах персоналу. Розв'язання задачі базувалося на використанні методу еквівалентних зарядів для визначення напруженості електричного поля, створюваного складною ошиновкою високовольтних підстанцій. Методика. В основу розробки покладено розв’язання задачі про потенціал електричного поля точкового заряду, розташованого в діелектричному наппівпросторі, для циліндричної системи координат. Шляхом представлення електроду у вигляді множини точкових зарядів та подальшого інтегрування отримано вираз для розрахунку потенціалу, що створений ошиновкою довільної орієнтації кінцевої довжини в аналітичному вигляді. Використовуючи принцип суперпозиції полів і визначення похідної, отримано вирази для розрахунку вертикальної складової напруженості електричного поля на заданих висотах. Результати. На основі отриманих виразів за допомогою Visual Basic виконано моделювання розподілу напруженості електричного поля під трифазною лінією електропередачі напругою 150 кВ. Порівняння з відомими результатами розрахунків, отриманими на основі аналітичних виразів для нескінченно довгих провідників, показало, що отримані вирази мають похибку не більше 7%. Наукова новизна полягає в тому, що вперше отримано вирази для визначення напруженості електричного поля, створюваного системою електродів скінченної довжини, на основі аналітичного методу розв’язування диференціальних рівнянь. Практична значимість. Запропонований спосіб реалізовано у вигляді тестового модулю спеціалізованого програмного комплексу LiGro, що дозволяє виконувати моделювання складних систем ошиновок, характерних для електричних станцій та підстанцій і ліній електропередачі. Виконано тестовий розрахунок для діючої підстанції регіональних електричних мереж класом напруги 110 кВ. Шляхом порівняння тривалості розрахунку розподільчих пристроїв з діагоналлю близько 500 м встановлено, що час розрахунку в комплексі LiGro на основі аналітичного методу в декілька десятків разів менший, ніж розрахунок на основі методу кінцевих елементів. Крім того, для моделювання методом кінцевих елементів використовувався комп’ютер з більш потужними характеристиками

Effect of Al2O3 and CaF2 additives on the viscosity of conventional cryolite melts

The viscosity of cryolite melts of conventional composition NaF–AlF3–CaF2–Al2O3 was studied by rotational viscometry using the FRS 1600 high-temperature rheometer. The cryolite ratio of the NaF–AlF3 melt was 2.1, 2.3, and 2.5; the Al2O3 content varied from 2 to 6.6, and CaF2 – from 0 to 8 wt%. The measurements were carried out in the temperature range from liquidus to 1200 °C. The conditions for the laminar flow of the investigated melts were determined, based on the measurements of the cryolite melts viscosity as a function of the shear rate at a constant temperature. A shear rate of 12 ± 1 s–1 was chosen for studying the viscosity temperature dependence for all samples. The viscosity temperature dependence of cryolite melts is described by a linear equation. The temperature coefficient b in this equation has negative values and varies in the range of (–0.01)–(–0.06) mPa·s/deg. It was found that the viscosity of cryolite melts of conventional composition in the range of operating temperatures of aluminum electrolysis (950–970 °C) varies from 2.5 to 3.7 mPa·s (depending on the composition and temperature). The viscosity of cryolite-alumina melts increases with the rise of alumina content: 1 wt% Al2O3 increases the viscosity, on average, by 1%. However, the influence of CaF2 is more significant: the addition of 1 wt% CaF2 leads to an increase in viscosity by 3%. A decrease in the CR of the melt by 0.1 (in the range of 2.1–2.5) leads to a decrease in the viscosity of cryolite melts by 2.3%. A viscosity regression equation for the cryolite melts of conventional composition as a function of several independent parameters (temperature, CR, CaF2 and Al2O3 content) is obtained by the multivariable approximation of experimental data. The equation satisfactorily (within 1.5%) describes the viscosity of conventional industrial electrolytes and can be used for estimation of their viscosity