Computational methods for ideal compressible flow

Conservative dissipative difference schemes, the recognition and representation of discontinuities, and multidimensional methods are discussed

Ray tracing algorithms for zonal radiative heat transfer

Целью работы является повышение точности и быстродействия методов трассировки лучей и учета наличия препятствий на пути излучения в системах со сложной геометрией. Выполнено сравнительное исследование методов трассировки лучей для расчета зонального теплообмена, а также разработаны программы, реализующие трассировку лучей известными методами. Показано, что стандартный метод трассировки сквозь неравномерную сетку, как наиболее удобную структуру данных для лучистого теплообмена, приводит к проблеме пропадания лучей. Разработан робастный метод трассировки лучей, решающий данную проблему и обладающий немного лучшим быстродействием. Разработан новый алгоритм пересечения прямой с выпуклым многогранником. Алгоритм дает решение проблемы пересечения при неизвестном списке граней многогранника, которая часто возникает в задачах САПР и геометрических вычислениях в реальном времени. Все описываемые алгоритмы реализованы в виде программ и готовы к использованию. Полученные результаты могут применяться в моделировании теплообмена, компьютерной графике, САПР и визуализации результатов расчета.The aim of this work is increasing accuracy and performance of ray tracing and obstructions handling in systems of complex geometry. Known ray tracing methods are compared in context of radiative heat transfer. Methods of ray tracing and radiative view factors evaluation are implemented in computer programs. It is shown that the standard ray tracing with non uniform mesh (the most suitable geometrical structure for radiative heat transfer) fails with loss of some rays in geometry. Robust ray tracing algorithm is developed that solves the problem. The algorithm is also slightly faster than the standard one. New ray – convex polyhedron intersection algorithm is developed. It solves the intersection problem if polyhedron faces are unknown – usual case in CAD and real-time calculations. All described algorithms are implemented as computer programs and are ready to use. Obtained investigation results can be applied in modeling of radiative heat transfer, computer graphics, CAD and scientific visualization.Программа развития УрФУ на 2013 год (п.1.2.2.3

Spectral properties of XRBs in dusty early-type galaxies

We present spectral properties of a total of 996 discrete X-ray sources resolved in a sample of 23 dusty early-type galaxies selected from different environments. The combined X-ray luminosity function of all the 996 sources within the optical \D of the sample galaxies is well described by a broken power law with a break at 2.71$\times$\te \lum and is close to the Eddington limit for a 1.4\Msun neutron star. Out of the 996, about 63\p of the sources have their X-ray luminosities in the range between few\tim\ts to 2.0 \tim \tn \lum and are like normal LMXBs; about 15-20\p with luminosities $<$ few \tim 10$^{37}$ \lum are either super-soft or very-soft sources; while the remainder represents ULXs, HMXBs or unrelated heavily absorbed harder sources. More XRBs have been detected in the galaxies from isolated regions while those from rich groups and clusters host very few sources. The X-ray color-color plot for these sources has enabled us to classify them as SNRs, LMXBs, HMXBs and heavily absorbed AGNs. The composite X-ray spectra of the resolved sources within \D region of each of the galaxies are best represented by a power law with the average photon spectral index close to 1.65. The contribution of the resolved sources to the total X-ray luminosity of their host is found to vary greatly, in the sense that, in galaxies like NGC 3379 the XRB contribution is about 81\p while for NGC 5846 it is only 2\p. A correlation has been evidenced between the cumulative X-ray luminosity of the resolved sources against the star formation rate and the Ks band luminosity of the target galaxies indicating their primordial origin.Comment: 15 Pages, 6 Figures & 2 Tables, Accepted for publication in New Astronom

Methods for Software Visualization of Large Graph Data Structures

In this paper, three different methods for software visualization of large graph structures, respectively Rectangle, Intersection and Combined are presented. The basic concepts for using software development environments are outlined. Their capabilities for visual designing and event-oriented programming are discussed. A brief analysis of the basic features of the environment used to develop the ClipRect Monitor application is made. The main functions of this software are also presented. All experimental results in this study are generated with this application. According to the methodology, six graphs are prepared to determine the effectiveness of the three methods. The number of vertices and the edges of these graphs are proportional to the size of the drawing area (canvas). The drawing areas are also six and have different sizes, such that each subsequent area has a height and width twice the size of the previous one. Besides, for all areas, the width/height ratio is exactly 16:9. This ratio is widely used in monitors as well as laptops, mobile phones and tablets. The largest drawing area that the ClipRect Monitor application scanned during the experiments is 128 000 x 72 000 pixels. This scan is performed for graph G_6 with 1 415 vertices and 100 000 edges. The visualization area is diagonally positioned relative to the drawing area. For each visualization area, each of the three methods, respectively Rectangle, Intersection and Combined is performed. The Combined method executes the Rectangle method first and then the Intersection method. The results show that the Intersection method was the slowest compared to the other two methods in terms of the number of edges of the graph that are analyzed. When the visualization area is internal to the drawing area, the Rectangle method performs better than the Combined method. The Rectangle method gives the best result in terms of time for analysis and drawing of the edges of the graph. The Combined method combines the characteristics of the other two methods. This method is optimal in terms of the time of analysis of the need to draw the edges of the graph relative to the number of drawn edges

Human-like Planning for Reaching in Cluttered Environments

Humans, in comparison to robots, are remarkably adept at reaching for objects in cluttered environments. The best existing robot planners are based on random sampling of configuration space- which becomes excessively high-dimensional with large number of objects. Consequently, most planners often fail to efficiently find object manipulation plans in such environments. We addressed this problem by identifying high-level manipulation plans in humans, and transferring these skills to robot planners. We used virtual reality to capture human participants reaching for a target object on a tabletop cluttered with obstacles. From this, we devised a qualitative representation of the task space to abstract the decision making, irrespective of the number of obstacles. Based on this representation, human demonstrations were segmented and used to train decision classifiers. Using these classifiers, our planner produced a list of waypoints in task space. These waypoints provided a high-level plan, which could be transferred to an arbitrary robot model and used to initialise a local trajectory optimiser. We evaluated this approach through testing on unseen human VR data, a physics-based robot simulation, and a real robot (dataset and code are publicly available 1 ). We found that the human-like planner outperformed a state-of-the-art standard trajectory optimisation algorithm, and was able to generate effective strategies for rapid planning- irrespective of the number of obstacles in the environment

Engineering evaluations and studies. Volume 2: Exhibit B, part 1

Ku-band communication system analysis, S-band system investigations, payload communication investigations, shuttle/TDRSS and GSTDN compatibility analysis are discussed