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

Formation of system of support of development of small youth business

The results of the research of youth entrepreneurship problems have been adduced. Institutions and programs of its support have been considered. Measures to eliminate the identified problems of attracting young people to entrepreneurship have been recommended. The formation of a new program of support «Acceleration of youth entrepreneurship» and the creation of coordination centers in the subjects of the Russian Federation «Regional youth center» have been off red. The model of the system of support of small youth entrepreneurship, which will increase entrepreneurial activity among young people and create new jobs, has been presented

Development of the A/H6N1 influenza vaccine candidate based on A/Leningrad/134/17/57 (H2N2) master donor virus and the genome composition analysis using high resolution melting (HRM)

The avian influenza viruses of H6N1subtype present a potential danger for humans. The cold-adapted (ca) reassortant influenza virus А/17/herring gull/Sarma/2006/887 (H6N1) was obtained in chicken embryos by the genetic reassortment based on the coldadapted A/Leningrad/134/17/57 (H2N2) master strain. The genome composition of the obtained reassortant was analyzed by means of real-time PCR with the high resolution melting (HRM) analysis using the intercalating fluorescent dye EvaGreen. Analysis of the gene segments showed that the reassortant А/17/herring gull/Sarma/2006/887 (H6N1) contains the internal proteins coding genes (PB2, PB1, PA, NP, M, and NS) of the master donor virus and the surface antigens coding genes of the A/herring gull/Sarma/51c/2006 (H6N1) avian influenza virus. The study of the phenotypic properties showed that the virus А/17/herring gull/Sarma/2006/887 (H6N1) is temperature sensitive (ts), ca in chicken embryos, and attenuated in mice when administered intranasally. This reassortant can be recommended as a live influenza vaccine candidate for humans.The avian influenza viruses of H6N1subtype present a potential danger for humans. The cold-adapted (ca) reassortant influenza virus А/17/herring gull/Sarma/2006/887 (H6N1) was obtained in chicken embryos by the genetic reassortment based on the coldadapted A/Leningrad/134/17/57 (H2N2) master strain. The genome composition of the obtained reassortant was analyzed by means of real-time PCR with the high resolution melting (HRM) analysis using the intercalating fluorescent dye EvaGreen. Analysis of the gene segments showed that the reassortant А/17/herring gull/Sarma/2006/887 (H6N1) contains the internal proteins coding genes (PB2, PB1, PA, NP, M, and NS) of the master donor virus and the surface antigens coding genes of the A/herring gull/Sarma/51c/2006 (H6N1) avian influenza virus. The study of the phenotypic properties showed that the virus А/17/herring gull/Sarma/2006/887 (H6N1) is temperature sensitive (ts), ca in chicken embryos, and attenuated in mice when administered intranasally. This reassortant can be recommended as a live influenza vaccine candidate for humans

Very high frequency gravitational wave background in the universe

Astrophysical sources of high frequency gravitational radiation are considered in association with a new interest to very sensitive HFGW receivers required for the laboratory GW Hertz experiment. A special attention is paid to the phenomenon of primordial black holes evaporation. They act like black body to all kinds of radiation, including gravitons, and, therefore, emit an equilibrium spectrum of gravitons during its evaporation. Limit on the density of high frequency gravitons in the Universe is obtained, and possibilities of their detection are briefly discussed.Comment: 14 page

Wavelength and intensity dependence of multiple forward scattering at above-threshold ionization in mid-infrared strong laser fields

The nonperturbative role of multiple forward scattering for Coulomb focusing in mid-infrared laser fields and its dependence on a laser intensity and wavelength are investigated for low-energy photoelectrons at above-threshold ionization. We show that high-order rescattering events can have comparable contributions to the Coulomb focusing and the effective number of rescattering depends weakly on laser parameters in the classical regime. However, the relative contribution of the forward scattering to the Coulomb focusing and the Coulomb focusing in total decrease with the rise of the laser intensity and wavelength

Atmospheric Gravity Perturbations Measured by Ground-Based Interferometer with Suspended Mirrors

A possibility of geophysical measurements using the large scale laser interferometrical gravitational wave antenna is discussed. An interferometer with suspended mirrors can be used as a gradiometer measuring variations of an angle between gravity force vectors acting on the spatially separated suspensions. We analyze restrictions imposed by the atmospheric noises on feasibility of such measurements. Two models of the atmosphere are invoked: a quiet atmosphere with a hydrostatic coupling of pressure and density and a dynamic model of moving region of the density anomaly (cyclone). Both models lead to similar conclusions up to numerical factors. Besides the hydrostatic approximation, we use a model of turbulent atmosphere with the pressure fluctuation spectrum f^{-7/3} to explore the Newtonian noise in a higher frequency domain (up to 10 Hz) predicting the gravitational noise background for modern gravitational wave detectors. Our estimates show that this could pose a serious problem for realization of such projects. Finally, angular fluctuations of spatially separated pendula are investigated via computer simulation for some realistic atmospheric data giving the level estimate 10^{-11} rad/sqrt(Hz) at frequency 10^{-4} Hz. This looks promising for the possibility of the measurement of weak gravity effects such as Earth inner core oscillations.Comment: 13 pages, 4 pigures, LaTeX. To be published in Classical and Quantum Gravit

Расчёт поправочных коэффициентов при измерении твёрдости по Виккерсу на неплоской поверхности

The exact determination of Vickers HV hardness is important for determining of the product material mechanical properties. An important aspect of measuring HV is to obtain its values on a non-planar surface. Regulatory documents contain table values of correction factors K which depend on the surface shape (convex or concave, spherical or cylindrical), its curvature (diameter D) and hardness (arithmetic mean d of indentation diagonal lengths) but this does not solved the problem. The K values for d/D ratios not given in the tables are determined by interpolation from the closest to the measured tabulated d/D values. The error in the representation of these tabulated d/D values is fully included in the error of determining the K coefficient for the measured d/D ratio. The aim of the work was to simplify the calculation of correction factors K for Vickers hardness measurements on non-planar surfaces and to reduce the calculation error compared to the methodology governed by the regulations.The method presented is based on a statistical analysis of K coefficients, presented in regulatory documents for cases considered in the form of tables. The sufficiency of using of a quadratic power function for approximating K(d/D) dependences and the necessity of fulfilling the physically justified condition K ≡ 1 at zero curvature of tested surface have been substantiated. Simplification of calculation of K coefficient and decrease of calculation error in comparison with the recommended in the regulatory documents obtaining of K value by linear interpolation relative to two adjacent table values are shown.The reduction of the calculation error in comparison with the calculation recommended in the regulatory documents occurred because of the reason that when calculating by the developed formulas, the error in the value of the calculated for a specific value of d/D coefficient K is averaged over all n values of d/D given in the table of GOST for a given surface. That is, the error is reduced by a factor of about √n 2 in comparison with the calculation according to the regulated procedure. This is illustrated by the above numerical data and an example of the use of the method.The obtained formulas for calculation of correction coefficients K when measuring hardness HV on spherical and cylindrical (concave and convex) surfaces are reasonable to use for automatic calculation of HV on items with a non-planar surface.Точное определение твёрдости HV по Виккерсу важно для определения механических свойств материала изделий. Важным аспектом измерения HV является получение её значений на неплоской поверхности. Включение в нормативные документы табличных значений поправочных коэффициентов К, зависящих от формы (выпуклая или вогнутая, сферическая или цилиндрическая) поверхности, её кривизны (диаметра D) и твёрдости (среднего арифметического d длин диагоналей отпечатка) не решает проблему. Значения К для отношений d/D, не приведённых в таблицах, определяют интерполяцией от ближайших к измеренному табличных значений d/D. Погрешность представления этих табличных значений d/D полностью включается в погрешность определения искомого коэффициента К для измеренного отношения d/D. Цель работы – упрощение расчёта поправочных коэффициентов К при измерении твёрдости по Виккерсу на неплоских поверхностях и снижение погрешности расчёта по сравнению с методикой, регламентированной нормативными документами.Разработка основана на статистическом анализе коэффициентов К, представленных в нормативных документах для рассмотренных случаев в виде таблиц. Обоснована достаточность использования квадратичной степенной функции для аппроксимации зависимостей К(d/D) и необходимость выполнения физически обоснованного условия К ≡ 1 при нулевой кривизне испытуемой поверхности. Показано упрощение расчёта коэффициента К и снижение погрешности расчёта по сравнению с рекомендованным в нормативных документах получением значения К линейной интерполяцией относительно двух соседних табличных значений.Снижение погрешности расчёта по сравнению с расчётом, рекомендованным в нормативных документах, происходит за счёт того, что при расчёте по разработанным формулам погрешность в значении рассчитанного для конкретного значения d/D коэффициента К усредняется по всем n значениям d/D, приведённым в таблице ГОСТа для данной поверхности. То есть снижается примерно в √n 2 раз по сравнению с расчётом по регламентированной методике. Это иллюстрируют приведённые численные данные и пример использования методики.Полученные формулы для расчёта поправочных коэффициентов К при измерении твёрдости HV на сферических и цилиндрических (вогнутых и выпуклых) поверхностях целесообразно использовать для автоматического расчёта HV на изделиях с неплоской поверхностью

Методика определения эффективной толщины цементированного слоя стали

Highly loaded transmission gears are cemented and hardened. An important parameter of the hardened cemented layer is its effective thickness hef . Metal banding and the unavoidable instrumental error in hardness measuring have a great influence on the reliability of hef determination. The purpose of this article was to develop a methodology to improve the reliability of determining of the effective thickness hef of the hardened layer in steel after carburizing and quenching.The value of hef is the distance h from the surface of the product to the hardness zone of 50 HRC. The article substantiates that approximation of hardness change from the distance h to the product surface will allow to obtain a more reliable dependence of hardness change in the investigated area when making hardness measurements in a wider range of distance h. Therefore, to increase the reliability of hef determination, results of the HV0.5 hardness measurement in an extended range of changes in h in the vicinity of the analyzed zone were used. The HV0.5 measurement results are converted to HRC hardness values using the formula recommended by the international standard. The HRC(h) distribution of HRC hardness values in the measurement area is interpolated by a second-degree polynomial which physically correctly reflects the change in metal hardness in the analyzed area. The resulting polynomial is used to determine of the distance hef at which the hardness takes on a value of 50 HRC. The methodology was used to determine the hef of an 18KhGT steel gear wheel after carburizing and quenching. It is shown that results of two independent measurements of the hef sample differ from each other by 0.003 mm. This is significantly less than the permissible error of 0.02 mm of the hef determination according to the standard technique. The error of hef determination is reduced by extending the range of variation of h and statistically valid interpolation of the monotonic change in hardness with the distance from the surface of the item in the measurement area. The developed method of determining the effective thickness hef of the hardened steel layer consists in determining the distribution of its hardness in the expanded vicinity of the hef area, approximating the obtained dependence by a polynomial of the second degree and solving the square equation obtained with its use. The technique provides a significant reduction in the influence of the structural banding of the metal and the inevitable error in measuring hardness on the result of determining the hef . Its application will allow to optimize the cementation regimes of gear wheels to increase their service life.Высоконагруженные зубчатые колёса трансмиссий подвергают цементации и закалке. Важным параметром упрочнённого цементированного слоя является его эффективная толщина hef . Большое влияние на достоверность определения hef оказывают полосчатость металла и неизбежная инструментальная погрешность измерения твёрдости. Цель работы – разработка методики повышения достоверности определения эффективной толщины hef упрочнённого слоя в стали после цементации и закалки.За величину hef принимают расстояние h от поверхности изделия до зоны с твёрдостью 50 HRC. В работе обосновано, что аппроксимация изменения твёрдости от расстояния h до поверхности изделия позволит получить более достоверную зависимость изменения твёрдости в исследуемой зоне при проведении измерений твёрдости в более широком диапазоне расстояний h. Поэтому для повышения достоверности определения hef использованы результаты измерения твёрдости HV0,5 в расширенном диапазоне изменений h в окрестности анализируемой зоны. Результаты измерения HV0,5 пересчитаны в значения твёрдости HRC по формуле, рекомендованной международным стандартом. Распределение HRC(h) значений твёрдости HRC в области измерения интерполировано полиномом второй степени, физически верно отражающим изменение твёрдости металла в анализируемой зоне. Полученный полином использован для определения расстояния hef , при котором твёрдость принимает значение 50 HRC. Методика использована для определения hef зубчатого колеса из стали 18ХГТ после цементации и закалки. Показано, что результаты двух независимых измерений hef образца отличаются друг от друга на 0,003 мм. Это существенно меньше допустимой погрешности 0,02 мм определения hef по стандартной методике. Погрешность определения hef снижена за счёт расширения диапазона изменения h и статистически обоснованной интерполяции монотонного изменения твёрдости с расстоянием от поверхности изделия в области измерения.Разработанная методика определения эффективной толщины hef упрочнённого слоя стали заключается в определении распределения её твёрдости в расширенной окрестности области hef , аппроксимации полученной зависимости полиномом второй степени и решении полученного с его использованием квадратного уравнения. Методика обеспечивает существенное снижение влияния структурной полосчатости металла и неизбежной погрешности измерения твёрдости на результат определения hef . Её применение позволит оптимизировать режимы цементации зубчатых колёс для повышения ресурса их эксплуатации