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Copyright of Journal of Scientific & Technical Applications / Revista de Aplicación Científica & Técnica is the property of ECORFAN-Mexico S.C. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We investigate the observational appearance of spherically symmetric black holes in perfect fluid dark matter (PFDM), with the celestial sphere and an accretion disk being light sources. For the celestial sphere model, we show the variations in black holes' appearance from different angles. And for an optically thin accretion disk, the intensity observed can be characterized by the redshift factor and the transfer functions. Then we investigate the angular dependencies for a resting and rotating accretion disk, respectively. It is found that as the observation angle increases, the blue-shift effect of black holes in rotating accretion disks becomes more pronounced. Our study may provide new insights into the physical characteristics of PFDM black holes and their surrounding environment. [ABSTRACT FROM AUTHOR]

Copyright of Dynamis is the property of Dynamis - Facultad de Medicina de la Universidad de Granada and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the aim is to simulate night-sky images for use in star-sensor designing software. For this purpose, a comprehensive and precise algorithm was developed to simulate night sky images based on the ideal pinhole method and the use of Gaussian distribution functions. Then, in order to create more realism, sources of random and systematic errors, the elongated images due to the high dynamics of the platform, as well as the asymmetric back-lighting of the moon, the sun, and the planets of the solar system have been simulated. Finally, considering the importance of realism in the problem-solving simulation approach, the use of precision ray tracking method as an alternative to the ideal pinhole method is suggested.

In this article we trace the scientific and cultural history of the astrolabe, a mechanical instrument used in the past for astronomical measurements and navigational purposes. The story of the astrolabe is interesting from several points of view, since it intertwines mathematical developments, geographical explorations, changing worldviews, and different cultures and civilizations. In our explorations, we move from the early understanding of the world due to the Greeks, to the loss of their work, its rediscovery, the reception of Arab thinkers in Western natural philosophy, and, finally, to the new European culture that emerged with the end of the Middle Ages and the beginning of the early Renaissance. We present a mathematical analysis of how the Celestial Sphere can be represented on the plane through the stereographic projection: this is the consequence of some geo-metrical results of Apollonius, together with later refinements, whose first traces appear in the work of Al-Farghānī. [ABSTRACT FROM AUTHOR]

A Legendrian link is called a déjà vu link if its components can be connected by a positive Legendrian isotopy but this isotopy cannot be embedded. This is the contact geometric analogue of a pair of events in a spacetime such that there are déjà vu moments on every future-directed timelike path between them. We construct déjà vu links in several geometrically relevant situations and discuss their basic properties. [ABSTRACT FROM AUTHOR]

There are many different ways of rendering 3D objects into two dimensions. Different kinds of projections are able to represent things like size, areas, distances or perspective, realistically. One particular kind of projection used for representing spheres and circles on spheres in two dimensions (i.e. some maps of the earth or celestial sphere) is stereographic projection. Stereographic projection has two important characteristics that differentiate it from other kinds of projections: it preserves circles and angles. This paper discloses the construction of the stereographic projection of the celestial sphere over Belgrade as the clock face of the astronomical clock. This astronomical clock will be capable to present the motion, as seen from the Earth, of the Sun, Moon, Ecliptic and the phases of the Moon during the year. Moreover, the hours of the sunrise, noon and sunset will be clearly observed on the stereographic dial of the astronomical clock.

Lenticular galaxy NGC3 has been chosen to study the surface photometry using griz filter. The data where obtained from the seventh Sloan Digital Sky Survey (SDSS) Data Release seven (DR7), and main the image reduction was done by the pipeline of SDSS. The work was achieved by the ELLIPS task from the STSDAS ISOPHOTE package in the Image Reduction and Analysis Facility (IRAF).The overall structure of the galaxy (a bulge, a bar, isophotal contour maps, together with a bulge to disk decomposition of the galaxy images where achieved, Also, the photometric properties (the disk position angle, ellipticity, B4 and inclination of the galaxy) where estimated. [ABSTRACT FROM AUTHOR]

The article offers information on the theory of aphorism. Topics discussed include interpretation of one aphorism opens a plurality of worlds in hermeneutics; intersection of the celestial sphere with a plane tangent to the earth's surface; and aphorism as against the architectonic systems of philosophy.

There are many different ways of rendering 3D objects into two dimensions. Different kinds of projections are able to represent things like size, areas, distances or perspective, realistically. One particular kind of projection used for representing spheres and circles on spheres in two dimensions (i.e. some maps of the earth or celestial sphere) is stereographic projection. Stereographic projection has two important characteristics that differentiate it from other kinds of projections: it preserves circles and angles. This paper discloses the construction of the stereographic projection of the celestial sphere over Belgrade as the clock face of the astronomical clock. This astronomical clock will be capable to present the motion, as seen from the Earth, of the Sun, Moon, Ecliptic and the phases of the Moon during the year. Moreover, the hours of the sunrise, noon and sunset will be clearly observed on the stereographic dial of the astronomical clock. [ABSTRACT FROM AUTHOR]

The systematic differences between the trigonometric parallaxes of the Hipparcos and TGAS catalogues have been investigated using spherical harmonics. The most significant harmonics in the expansion have been determined. The distribution of the parallax difference dispersion in various regions of the celestial sphere has also been studied. The distribution of the rms deviation has the simplest form in the ecliptic coordinate system. [ABSTRACT FROM AUTHOR]

Abstract We transform superstring scattering amplitudes into the correlation functions of primary conformal fields on two-dimensional celestial sphere. The points on celestial sphere are associated to the asymptotic directions of (light-like) momenta of external particles, with the Lorentz group realized as the S L (2 , C) conformal symmetry of the sphere. The energies are dualized through Mellin transforms into the parameters that determine dimensions of the primaries. We focus on four-point amplitudes involving gauge bosons and gravitons in type I open superstring theory and in closed heterotic superstring theory at the tree-level. [ABSTRACT FROM AUTHOR]

This paper traces the roots of the scientific tradition of astronomy in a classical century that marked the rise of Islamic civilization in the midst of Western darkness in a philosophical-historical perspective. The study focussed on translation activities in the eighth century to the peak of astronomical scientific activity that is divided into two major schools; the astronomical-mathematical school of the East and the astronomical-philosophical schools of the Western world to the Islamic Caliphate. The Greek astronomical tradition is basically dominated by Aristotelian thought that states that the universe is organized into a set of concentric spheres each carrying a star and spinning around the earth. The Earth is still and becomes the center of the universe. Ptolemy adopted the two basic principles of Aristotle, ie the earth dwells at the center of the universe and the motion of heavenly bodies must be represented by a set of perfectly uniform circular motions. From the results of historical studies on the development of Muslim astronomy in the classical century can be seen that the peak of scientific progress in the Western world can not be separated from the point of zenit for the advancement of science developed by Muslim scientists. Efforts made by Western scientists in enriching the astronomical treasury is inseparable from the step of translation through intensive scientific studies that gave birth to a variety of monumental works in the history of astronomy. Tulisan ini melacak akar tradisi ilmiah astronomi pada abad klasik yang menandai majunya peradaban Islam di tengah-tengah kegelapan Barat dalam perspektif historis-filosofis. Kajian difokuskan pada aktivitas penerjemahan pada abad kedelapan hingga puncak kegiatan ilmiah astronomis yang terbagi dalam dua mazhab besar; mazhab astronomis-matematis di Timur dan mazhab astronomis-filosofis di dunia Barat pada kekhalifahan Islam. Tradisi astronomi Yunani pada dasarnya didominasi pemikiran Aristotelian yang menyatakan bahwa alam semesta diatur menjadi satu set bola konsentris masing-masing membawa bintang dan berputar di sekitar bumi. Bumi berposisi diam dan menjadi pusat alam semesta. Ptolemeus mengadopsi kedua prinsip dasar Aristoteles tersebut, yaitu bumi diam di pusat alam semesta dan gerak benda-benda langit harus diwakili oleh satu set gerakan melingkar sempurna yang seragam. Dari hasil kajian historis atas perkembangan astronomi muslim pada abad klasik dapat diketahui bahwa puncak kemajuan ilmu pengetahuan di dunia Barat tidak lepas dari titik zenit atas kemajuan ilmu pengetahuan yang dikembangkan oleh ilmuwan Muslim. Upaya yang dilakukan ilmuwan Barat dalam memperkaya khazanah astronomi tidak terlepas dari langkah penerjemahan melalui pengkajian ilmiah yang intensif sehingga melahirkan berbagai karya-karya monumental dalam sejarah astronomi.

The act of projecting data sampled on the surface of the celestial sphere onto a regular grid on the plane can introduce error and a loss of information. This paper evaluates the effects of different planar projections on non-Gaussian statistics of weak lensing convergence maps. In particular we investigate the effect of projection on peak counts and Minkowski Functionals (MFs) derived from convergence maps and the suitability of a number of projections at matching the peak counts and MFs obtained from a sphere. We find that the peak counts derived from planar projections consistently overestimate the counts at low SNR thresholds and underestimate at high SNR thresholds across the projections evaluated, although the difference is reduced when smoothing of the maps is increased. In the case of the Minkowski Functionals, V 0 is minimally affected by projection used, while projected V 1 and V 2 are consistently overestimated with respect to the spherical case. [ABSTRACT FROM AUTHOR]

The present article is the result of a research work of the Degree in Mathematics in the scope of the Tutorial Education Program - PET. The work deals with concepts of Spherical Trigonometry, which has several fields of applications between mathematics and physics, related to cartographic problems, navigation and astronomy. The goal is to explore problems of astronomy applications of celestial bodies by making use of trigonometry concepts in the sphere to study positions and directions of stars in terms of a celestial sphere. In order to reach this objective, the article presents concepts of a smaller distance between two points in the sphere, a triangle of position that is the spherical triangle, the fundamental relation known as law of cosines, the Celestial Sphere, its elements, its coordinates in the equatorial system, horizontal system and time system. Thus, the work seeks to encourage students and teachers to work on Spherical Geometry in the classroom. [ABSTRACT FROM AUTHOR]

Meteor showers are recognized from the concentration of their radiant distribution on the celestial sphere, and their similar speeds. It has been pointed out that the dispersion of the radiants depends on the velocity of and the spread in velocities between individual stream meteoroids. For meteor showers with low speeds at the Earth, the dispersion can become so large that the shower becomes hard to recognize (Sato and Watanabe, 2014). In this paper, we apply a technique described in Sato and Watanabe (2014) which transforms radiants from a geocentric to a heliocentric frame. The technique is applied to detect two low speed meteor showers, the Phoenicids and the June Bootids, which otherwise would be very difficult to recognize as true meteor showers. [ABSTRACT FROM AUTHOR]

Recently a boundary energy-momentum tensor T has been constructed from the soft graviton operator for any 4D quantum theory of gravity in asymptotically flat space. Up to an 'anomaly' which is one-loop exact, T generates a Virasoro action on the 2D celestial sphere at null infinity. Here we show by explicit construction that the effects of the IR divergent part of the anomaly can be eliminated by a one-loop renormalization that shifts T . [ABSTRACT FROM AUTHOR]

A new fast algorithm for autonomous star identification in the general lost-in-space case is developed based on optimized catalog. The proposed method takes advantage of singular value decomposition method and the accuracy angular separation information. The central idea is that a unique pattern is created for each of guide star so that the pattern recognition is simple and straightforward and the index entry reaches minimum. The unique pattern is comprised of ellipticity and angular separations between pivot star and adjacent stars. The method for selecting adjacent stars of pivot star and how to rank them is presented. Three series of simulations each of which included more than ten thousand star tracker orientations were performed by dividing the entire celestial sphere into small regions. The results support the validity of the proposed method that achieves higher identification rate with 99.999%. [ABSTRACT FROM AUTHOR]

A great circle route (GCR) is the shortest route on a spherical earth model. Do we have a visual diagram to handle the shortest route? In this paper, a graphical method (GM) is proposed to solve the GCR problems based on the celestial meridian diagram (CMD) in celestial navigation. Unlike developed algebraic methods, the GM is a geometric method. Appling computer software to graph, the GM does not use any equations but is as accurate as using algebraic methods. In addition, the GM, which emphasizes the rotational surface, can depict a GCR and judge its benefit. [ABSTRACT FROM AUTHOR]

This article discusses the place and date of origin, the earlier whereabouts, and subsequent travels of an unsigned and undated early European astrolabe (International Instrument Checklist IIC #0191) now preserved in Oxford, in the Museum of the History of Science. After taking into consideration earlier descriptions, it investigates the evidence given by the astrolabe concerning its localisation and dating, and suggests a possible itinerary of this instrument. In the Appendix a full description of the astrolabe is provided. [ABSTRACT FROM AUTHOR]

The celestial globe is an early astronomical instrument that gives a realistic view of the heavens and the stars and can simulate the celestial motion, but has some disadvantages such as difficulties in construction, transportation and in carrying out measurements. The astrolabe is an evolution of the celestial globe; it represents the celestial sphere projected onto the plane, retaining the celestial ratios. It provides accurate measurements and helps in solving a great variety of astronomical problems. The aim of this paper is to show how various processes have been transferred from the celestial globe to the astrolabe, determining the form of each part of the astrolabe. [ABSTRACT FROM AUTHOR]

We probe the anisotropy of the large-scale structure (LSS) with the WISE-2MASS catalogue. This analysis is performed by a directional comparison of the galaxy number counts through the entire celestial sphere once systematic effects, such as star-galaxy separation and foregrounds contamination, are properly taken into account. We find a maximal hemispherical asymmetry whose dipolar component is A = 0.0507 ± 0.0014 towards the (l, b) = (323°, -5°) direction, whose result is consistent with previous estimations of our proper motion in low and intermediate redshifts, as those carried out with Type Ia Supernovae and similar LSS catalogues. Furthermore, this dipole amplitude is statistically consistent (p-value = 0.061) with mock catalogues simulated according to the expected Λ cold dark matter density fluctuations, in addition to observational biases such as the incomplete celestial coverage and anisotropic sky exposure. Our results suggest, therefore, that there is no strong evidence for anomalous anisotropy in the LSS, given the limitations and systematics of current data, in the concordance model scenario. [ABSTRACT FROM AUTHOR]

Very Long Baseline Interferometry (VLBI) is a space-geodetic technique that is uniquely capable of direct observation of the angle of the Earth's rotation about the Celestial Intermediate Pole (CIP) axis, namely UT1. The daily estimates of the difference between UT1 and Coordinated Universal Time (UTC) provided by the 1-h long VLBI Intensive sessions are essential in providing timely UT1 estimates for satellite navigation systems and orbit determination. In order to produce timely UT1 estimates, efforts have been made to completely automate the analysis of VLBI Intensive sessions. This involves the automatic processing of X- and S-band group delays. These data contain an unknown number of integer ambiguities in the observed group delays. They are introduced as a side-effect of the bandwidth synthesis technique, which is used to combine correlator results from the narrow channels that span the individual bands. In an automated analysis with the c5++ software the standard approach in resolving the ambiguities is to perform a simplified parameter estimation using a least-squares adjustment (L2-norm minimisation). We implement L1-norm as an alternative estimation method in c5++. The implemented method is used to automatically estimate the ambiguities in VLBI Intensive sessions on the Kokee–Wettzell baseline. The results are compared to an analysis set-up where the ambiguity estimation is computed using the L2-norm. For both methods three different weighting strategies for the ambiguity estimation are assessed. The results show that the L1-norm is better at automatically resolving the ambiguities than the L2-norm. The use of the L1-norm leads to a significantly higher number of good quality UT1-UTC estimates with each of the three weighting strategies. The increase in the number of sessions is approximately 5% for each weighting strategy. This is accompanied by smaller post-fit residuals in the final UT1-UTC estimation step. [ABSTRACT FROM AUTHOR]