The Extragalactic Distance Database: Color-Magnitude Diagrams

The CMDs/TRGB (Color-Magnitude Diagrams/Tip of the Red Giant Branch) section of the Extragalactic Distance Database contains a compilation of observations of nearby galaxies from the Hubble Space Telescope. Approximately 250 (and increasing) galaxies in the Local Volume have CMDs and the stellar photometry tables used to produce them available through the web. Various stellar populations that make up a galaxy are visible in the CMDs, but our primary purpose for collecting and analyzing these galaxy images is to measure the TRGB in each. We can estimate the distance to a galaxy by using stars at the TRGB as standard candles. In this paper we describe the process of constructing the CMDs and make the results available to the public.Comment: 8 pages, 5 figures, 1 long table, submitted to Astronomical Journa

К вопросу о применении облачных технологий для организации онлайн-обучения в системе высшего образования

Application of advanced information and communication technologies (ICT) allows not only to improve the quality of education process but provides the teachers with completely new forms and possibilities of knowledge representation not possible when traditional methods of teaching are used. Nowadays, online learning is considered to be the most striking example of providing convergence of traditional and new potential methods of organizing educational process. Learning Management System (LMS) is considered to act as a specific platform online learning is based upon providing the possibilities for e-learning resources creation, adapted for online learning, integration of advanced forms of content presentation, interactive work, and educational content consolidation together with software related. The most effective way to organize LMS support in the current context is cloud computing application. The LMS is realized as cloud server providing the ability to scale the system depending on the increased number of users, centralized content storage and management. Access to the LMS can be made anywhere in the world, at any time, this allowing for easy development of individual educational curricula, thereby increasing the quality of education. In this respect, the LMS system is very convenient for teachers’ collaboration work within on-line learning process when they work with different institution and in different places. Cloud computing is undoubtedly a noteworthy approach to the organization of online learning, possessing a number of important advantages. This approach appears to have a potentially large scope of applicationПрименение современных информационно-коммуникационных технологий не только позволяет значительно повысить качество учебного процесса, но и обеспечивает совершенно новые возможности и формы представления знаний, недостижимые при традиционных методах обучения. На сегодняшний день онлайн-обучение является наиболее ярким примером применения подобного подхода, обеспечивая при этом конвергенцию традиционных и перспективных методов организации обучения. Платформой, посредством которой осуществляется онлайн-обучение, является система поддержки обучения (LMS – Learning Management System), которая предоставляет необходимые возможности по созданию образовательного контента, адаптированного для онлайн-обучения, интеграции в учебный процесс современных форм представления контента и взаимодействия со слушателями, а также консолидацию образовательного контента и связанного с ним программного обеспечения. В современных реалиях наиболее перспективным способом организации системы поддержки обучения LMS является применение облачных решений. В этом случае система LMS реализуется в виде так называемого облачного сервиса, что обеспечивает ряд преимуществ, в первую очередь – возможность масштабирования системы с увеличением числа пользователей с централизованным хранением и управлением контентом в то же самое время. Доступ к системе может в этом случае производиться из любой точки мира в любое удобное время, что позволяет легко выстраивать индивидуальные образовательные траектории для обучающихся, повышая тем самым качество обучения. Важным фактором является также и возможность распределенной работы преподавателей, например при их географической удаленности. Безусловно, применение технологий облачных вычислений (cloud computing) представляет собой интересное и очень перспективное направление при организации онлайн-обучения, обладающее рядом уникальных преимущест

Синтез управления и наблюдателя для слабо нелинейных систем на основе техники псевдолинеаризации

In this paper, an approach to the construction of nonlinear output tracking control on a finite time interval for a class of weakly nonlinear systems with state-dependent coefficients is considered. The proposed method of control synthesis consists of two main stages. At the first stage, a nonlinear state feedback regulator is constructed by using a previously proposed control algorithm based on the State Dependent Riccati Equation (SDRE). At the second stage, the problem of fullorder observer construction is formulated and then it is reduced to the differential game problem. The form of its solution is obtained with the help of the guaranteed (minimax) control principle, which allows to find the best observer coefficients with respect to a given functional considering the worstcase uncertainty realization. The form of the obtained equations made it possible to use the algorithm from the first stage to determine the observer matrix. The proposed approach is characterized by the nonapplicability of the estimation and control separation principle used for linear systems, since the matrix of observer coefficients turned out to be dependent on the feedback coefficients matrix. The use of numerical-analytical procedures for determination of observer and feedback coefficients matrices significantly reduces the computational complexity of the control algorithm. В работе для одного класса слабо нелинейных систем с зависящими от состояния коэффициентами рассматривается подход к построению нелинейного следящего управления по выходу на конечном интервале времени. Предложенный метод синтеза состоит из двух основных этапов. Сначала с помощью ранее предложенного автором алгоритма на основе уравнений Риккати, с зависящими от состояния коэффициентами (State Dependent Riccati Equation – SDRE), находится нелинейный регулятор по состоянию. На втором этапе ставится задача построения наблюдателя полного порядка, которая сводится к задаче дифференциальной игры. Вид её решения получен с помощью принципа гарантированного управления, позволяющего относительно заданного функционала найти наилучшие коэффициенты наблюдателя при наихудшей реализации неопределенностей. Однотипность полученных уравнений позволила для определения матрицы наблюдателя использовать алгоритм решения из первого этапа. Особенностями предложенного подхода являются отсутствие принципа разделения задач синтеза управления и наблюдения, который имеет место в линейных системах, поскольку матрица коэффициентов наблюдателя оказалась зависимой от матрицы коэффициентов обратной связи, и использование численно-аналитических процедур для определения этих матриц, что позволяет значительно снизить вычислительную сложность алгоритма управления.

Reflection resonances in surface-disordered waveguides: strong higher-order effects of the disorder

We study coherent wave scattering through waveguides with a step-like surface disorder and find distinct enhancements in the reflection coefficients at well-defined resonance values. Based on detailed numerical and analytical calculations, we can unambiguously identify the origin of these reflection resonances to be higher-order correlations in the surface disorder profile which are typically neglected in similar studies of the same system. A remarkable feature of this new effect is that it relies on the longitudinal correlations in the step profile, although individual step heights are random and thus completely uncorrelated. The corresponding resonances are very pronounced and robust with respect to ensemble averaging, and lead to an enhancement of wave reflection by more than one order of magnitude.Peer Reviewe

Lena Delta hydrology and geochemistry: long-term hydrological data and recent field observations

The Lena River forms one of the largest deltas in the Arctic. We compare two sets of data to reveal new insights into the hydrological, hydrochemical, and geochemical processes within the delta: (i) long-term hydrometric observations at the Khabarova station at the head of the delta from 1951 to 2005; (ii) field hydrological and geochemical observations carried out within the delta since 2002. Periods with differing relative discharge and intensity of fluvial processes were identified from the long-term record of water and sediment discharge. Ice events during spring melt (high water) reconfigured branch channels and probably influenced sediment transport within the delta. Based on summer field measurements during 2005–2012 of discharge and sediment fluxes along main delta channels, both are increased between the apex and the front of the delta. This increase is to a great extent connected with an additional influx of water from tributaries, as well as an increase of suspended and dissolved material released from the ice complex. Summer concentrations of major ion and biogenic substances along the delta branches are partly explained by water sources within the delta, such as thawing ice complex waters, small Lena River branches and estuarine areas

Cosmicflows-2: The Data

Cosmicflows-2 is a compilation of distances and peculiar velocities for over 8000 galaxies. Numerically the largest contributions come from the luminosity-linewidth correlation for spirals, the TFR, and the related Fundamental Plane relation for E/S0 systems, but over 1000 distances are contributed by methods that provide more accurate individual distances: Cepheid, Tip of the Red Giant Branch, Surface Brightness Fluctuation, SNIa, and several miscellaneous but accurate procedures. Our collaboration is making important contributions to two of these inputs: Tip of the Red Giant Branch and TFR. A large body of new distance material is presented. In addition, an effort is made to assure that all the contributions, our own and those from the literature, are on the same scale. Overall, the distances are found to be compatible with a Hubble Constant H_0 = 74.4 +-3.0 km/s/Mpc. The great interest going forward with this data set will be with velocity field studies. Cosmicflows-2 is characterized by a great density and high accuracy of distance measures locally, falling to sparse and coarse sampling extending to z=0.1.Comment: To be published in Astronomical Journal. Two extensive tables to be available on-line. Table 1 available at http://edd.ifa.hawaii.edu select catalog `Cosmicflows-2 Distances

Lyapunov analysis of the spatially discrete-continuous system dynamics

The spatially discrete-continuous dynamical systems, that are composed of a spatially extended medium coupled with a set of lumped elements, are frequently met in different fields, ranging from electronics to multicellular structures in living systems. Due to the natural heterogeneity of such systems, the calculation of Lyapunov exponents for them appears to be a challenging task, since the conventional techniques in this case often become unreliable and inaccurate. The paper suggests an effective approach to calculate Lyapunov exponents for discrete-continuous dynamical systems, which we test in stability analysis of two representative models from different fields. Namely, we consider a mathematical model of a 1D transferred electron device coupled with a lumped resonant circuit, and a phenomenological neuronal model of spreading depolarization, which involves 2D diffusive medium. We demonstrate that the method proposed is able reliably recognize regular, chaotic and hyperchaotic dynamics in the systems under study