scholarly journals Space astrometry prospects and limitations

1986 ◽  
Vol 114 ◽  
pp. 369-382
Author(s):  
J. Kovalevsky ◽  
F. Mignard ◽  
M. Froeschlé
Keyword(s):  
Relativistic Effects ◽  
Second Order ◽  
Point Of View ◽  
Wide Field ◽  
Theoretical Point ◽  
Small Field ◽  
Light Deflection ◽  
Celestial Bodies ◽  
Space Astrometry ◽  
Magnitude Improvement

Among the few parameters that describe the generalized space time metrics, astrometric techniques are essentially sensitive to the displacement of the apparent positions of celestial bodies. This includes the relativistic light deflection and aberration. The possibilities of small field and wide field astrometry in measuring these effects are described. The case of the second order aberration terms is considered with some detail from the theoretical point of view, both for stellar and planetary aberration. New results are presented in the latter case.A section is devoted to a description of the existing space astrometry projects among which Space Telescope and HIPPARCOS are approved but will not contribute significantly to relativistic studies. Several “second generation” projects exist that aim at 2 or 3 orders of magnitude improvement in precision. They would yield results on second order relativistic effects and may be used to determine masses of some single stars. However, the present state of engineering of space astrometric missions has permitted to identify several limitations of the present and future missions. They will not all be readily suppressed and one should be very careful in assessing now their potentialities. It seems however that interferometric techniques have more chance to reach the 10−4 and 10−5 arc second precision than the imaging methods.

scholarly journals UNCERTAIN PROBABILITIES

2006 ◽  
Vol 1 ◽  
pp. 377
Author(s):  
O. Uzhga-Rebrov
Keyword(s):  
Second Order ◽  
Point Of View ◽  
Sufficient Information ◽  
Uncertain Information ◽  
Theoretical Point ◽  
Knowledge Processing ◽  
Additional Information ◽  
Lack Of Information ◽  
Uncertainty Representation ◽  
Random Events

The uncertainty of probabilistic evaluations results from the lack of sufficient information and/or knowledge underlying those random events. Uncertainty representation in the form of second order probability distribution or interval evaluations does not cause any objections from the theoretical point of view. On the other hand, what is worthy in the second order probabilities is that they allow one to model a real uncertainty of subjective probabilistic evaluations resulting from the lack of information and/or knowledge. Processing of uncertain information regarding probabilistic evaluations can help make a validated decision about the collection of additional information aimed to remove completely or to reduce the existing uncertainty.

Reactivity Analysis of the AunAgm (6 ≤ n + m ≤ 12) Bimetallic Clusters with Selected Proportions

2013 ◽  
Vol 1548 ◽  
Author(s):  
Bertha Molina ◽  
Jorge R. Soto ◽  
Francisco E. Rojas ◽  
Jorge J. Castro
Keyword(s):  
Bimetallic Nanoparticles ◽  
Population Analysis ◽  
Relativistic Effects ◽  
Point Of View ◽  
Pure Gold ◽  
Theoretical Point ◽  
Binary Clusters ◽  
Relativistic Approach ◽  
Ag Clusters ◽  
M 12

ABSTRACTIt is well known that Au-Ag bimetallic nanoparticles have better performance in catalytic processes compared to their counterpart pure clusters. The improvement in their catalytic properties has been attributed to a kind of synergy between the gold and silver atoms that has not been fully understood. Unlike pure clusters, there are very few studies on the catalytic behavior of the Au-Ag binary nanoparticles. From the theoretical point of view, in the subnanometer regimen, the bimetallic Au-Ag clusters present a challenging problem, since by combining the different gold and silver relativistic effects, a variety of skeletal geometric structures and homotopic distributions are obtained. In particular, pure gold has favorable planar structure even up to 16 atoms, while silver begins to favor 3D arrangements from 5-7 atoms. This dissimilar behavior produces a diverse population of 2D and 3D coexisting binary clusters, whose properties strongly depend of the Au/Ag mixing ratio. In this work we use the relativistic approach ZORA-DFT to model the AunAgm (with 4 ≤ (n + m) ≤ 12) binary nanoclusters in selected proportions (1:1, 3:1, 5:1) in the gas-phase and we study their reactivity from the descriptors based in the condensed Fukui indexes obtained from an NBO electronic population analysis.

scholarly journals Relativistic Considerations for Precession and Nutation

1998 ◽  
Vol 11 (1) ◽  
pp. 173-176
Author(s):  
S.A. Klioner ◽  
M. Soffel
Keyword(s):  
General Relativity ◽  
Rotational Motion ◽  
Earth Rotation ◽  
Equations Of Motion ◽  
Relativistic Effects ◽  
Point Of View ◽  
Extended Body ◽  
The Earth ◽  
Celestial Bodies

Abstract The whole scope of problems related with the rotational motion of celestial bodies is briefly discussed. Relativistic modeling of the Earth rotation is considered from a conceptual point of view. Relativistic effects in rotational equations of motion of an extended body in general relativity are discussed. Numerical values of the effects are given.

scholarly journals Rotational Motion of Celestial Bodies in the Relativistic Framework

1999 ◽  
Vol 172 ◽  
pp. 435-436
Author(s):  
Sergei A. Klioner ◽  
Michael Soffel
Keyword(s):  
General Relativity ◽  
Rotational Motion ◽  
Relativistic Effects ◽  
Operational Definition ◽  
Point Of View ◽  
Newtonian Mechanics ◽  
Extended Body ◽  
International Astronomical ◽  
Celestial Bodies ◽  
Relativistic Framework

There are several important reasons to consider relativistic effects in rotational motion of celestial bodies. General Relativity is now recommended by the International Astronomical Union and International Union of Geodesy and Geophysics as a theoretical framework for modeling of high-precision observational data. On the other hand, various geodynamical observations provide data which are widely used for testing General Relativity itself.In Newtonian mechanics it is well known how to describe rotational motion of an extended body. In General Relativity this is a rather subtle issue. The concept of a precessing extended rigid body in general relativity encounters fundamental difficulties and cannot be introduced even in the first post-Newtonian approximation. From a practical point of view, however, the rotational motion of the Earth even at the Newtonian level is defined operationally through the time-dependence of geocentric quasi-inertial coordinates of observing sites. An analogous operational definition can be applied in general relativity. To this end, we need a set of physically adequate reference systems.

scholarly journals Data for Weak Lines

1995 ◽  
Vol 10 ◽  
pp. 574-576
Author(s):  
A. Hibbert
Keyword(s):  
Oscillator Strength ◽  
Hubble Space Telescope ◽  
Relativistic Effects ◽  
Electric Dipole Transition ◽  
Point Of View ◽  
Oscillator Strengths ◽  
Theoretical Point ◽  
Dipole Matrix Element

Weak lines, being unsaturated, are particularly important for the determination of interstellar abundances of elements. From a theoretical point of view, there are several possible causes of an electric dipole transition having a small oscillator strength. In some cases, several contributions to the dipole matrix element substantially cancel (e.g. the 1808 Å line Si II), while in other cases, the oscillator strength would be zero but for the inclusion of small relativistic effects (e.g. the intersystem 1909 Å line in C. II).For weak lines, the interstellar abundances depend on the oscillator strength (calculated or measured) and the equivalent width (observed). The increased resolution of the Goddard High Resolution Spectrograph on board the Hubble Space Telescope provides for many lines equivalent widths of much greater precision than was previously available. This situation presents a challenge to theorists to improve the quality of their calculations of oscillator strengths.Such calculations are difficult for weak transitions, especially when the cause is cancellation. Of course, with larger and more powerful computer a vailable, it is possible to undertake more extensive calculations. But the quality of observational data now makes it imperative for theorists not merely to do a better calculation than before, but to give a considered estimate of the accuracy of the results. Since there are no effective theoretical methods for obtaining rigorous bounds to oscillator strengths which could give a useful guide to accuracy, theoretical estimates of accuracy can be achieved only by undertaking a systematic sequence of calculations of increasing complexity, while ensuring that no significant contributions to the calculations are omitted.

Timber Auctions in the Context of the Modern Auction Theory

2007 ◽  
pp. 86-94
Author(s):  
A. Manakov
Keyword(s):  
Theoretical Analysis ◽  
Auction Theory ◽  
Point Of View ◽  
Theoretical Point ◽  
English Auction ◽  
Analysis And Evaluation

The article provides theoretical analysis and evaluation of the timber auctions reforms in Russia. The author shows that the mechanism of the "combined auctions", which functioned until recently, is more appropriate from the theoretical point of view (and from the point of view of the Russian practice) as compared to the officially approved format of the English auction.

A novel cryptosystem based on abstract automata and Latin cubes

2015 ◽  
Vol 52 (2) ◽  
pp. 221-232
Author(s):  
Pál Dömösi ◽  
Géza Horváth
Keyword(s):  
Block Cipher ◽  
Finite Automata ◽  
Theoretical Background ◽  
Point Of View ◽  
Theoretical Point ◽  
Transition Matrices ◽  
Encryption And Decryption ◽  
Secret Keys ◽  
Automata Network ◽  
Fully Functioning

In this paper we introduce a novel block cipher based on the composition of abstract finite automata and Latin cubes. For information encryption and decryption the apparatus uses the same secret keys, which consist of key-automata based on composition of abstract finite automata such that the transition matrices of the component automata form Latin cubes. The aim of the paper is to show the essence of our algorithms not only for specialists working in compositions of abstract automata but also for all researchers interested in cryptosystems. Therefore, automata theoretical background of our results is not emphasized. The introduced cryptosystem is important also from a theoretical point of view, because it is the first fully functioning block cipher based on automata network.

Graffiti als Version und Subversion–Praxen kultureller Re-Regulierung und die Möglichkeit von Gratiforschung

2010 ◽  
Vol 55 (2) ◽  
pp. 11-25 ◽  
Author(s):  
Bernd Dollinger
Keyword(s):  
Social Life ◽  
Point Of View ◽  
Theoretical Point ◽  
Research Practice ◽  
Wird Eine ◽  
Multiple Perspectives

Der Beitrag geht von Versuchen aus, integrative Perspektiven einer überaus heterogenen Graffitiforschung zu bestimmen. In Auseinandersetzung insbesondere mit Bruno Latours Ansatz des »Iconoclash« wird eine kulturtheoretische Referenz bestimmt, die Graffiti als Version identifiziert, d. h. als semiotisch orientierte Veränderung räumlich situierter Ordnungs- und Regulierungspraxen. Ihnen kann, wenn auch nicht zwingend, eine subversive Qualität zukommen. Durch die Ausrichtung am Konzept einer Version wird beansprucht, Forderungen einer normativ weitgehend abstinenten, nicht-essentialistischen und für komplexe Fragen der Identitäts- und Raumpolitik offenen Forschungspraxis einzulösen.<br><br>The contribution attempts to integrate multiple perspectives of current largely heterogeneous graffiti scholarship. Referring to Bruno Latour’s concept »iconoclash«, we discuss graffiti from a cultural-theoretical point of view as a »version«. It appears as a semiotically oriented modification of spatially situated practices that regulate social life. Often, but not necessarily, these practices involve subversive qualities. The concept of »version« facilitates a non-normative and non-essentialist strategy of research. This enables an explorative research practice in which the complex matters of identity and space politics that are associated with graffiti can be addressed.

scholarly journals How Digital Inclusion Increase Opportunities for Young People: Case of NEETs from Bulgaria, Romania and Turkey

2021 ◽  
Vol 13 (14) ◽  
pp. 7894
Author(s):  
Gabriela Neagu ◽  
Muhammet Berigel ◽  
Vladislava Lendzhova
Keyword(s):  
Data Analysis ◽  
Rural Areas ◽  
Secondary Data ◽  
Point Of View ◽  
Multidimensional Analysis ◽  
Theoretical Point ◽  
Digital Inclusion ◽  
Virtual Mobility ◽  
Alternative Research ◽  
High Share

This paper examines the perspectives of rural NEETs in the information society. Our analysis focuses on the situation of three European countries—Bulgaria, Romania, and Turkey—characterized by a high share of rural areas and a population of NEETs. From a methodological point of view, we use alternative research methods (secondary data analysis) with statistical methods (simple linear regression). From a theoretical point of view, we will opt for a multidimensional analysis perspective: the theory of digital divide, digital inclusion, virtual mobility, etc. Through data analysis, we expect to obtain a more complete and detailed picture of the ICT situation in rural areas (level of digital skills, level of digital inclusion) to demonstrate the importance of ICT in optimizing virtual mobility for the living conditions of the population, especially the NEET population.

scholarly journals Verbena officinalis Verbenaceae (Lamiales): a new plant model system for phyllotaxis research

2021 ◽  
Author(s):  
Beata Zagórska-Marek ◽  
Magdalena Turzańska ◽  
Klaudia Chmiel
Keyword(s):  
Vascular System ◽  
Cumulative Effect ◽  
Point Of View ◽  
Theoretical Point ◽  
Inflorescence Axis ◽  
Organ Identity ◽  
Lateral Organ ◽  
Complex Relationships ◽  
Secondary Transitions

AbstractPhyllotactic diversity and developmental transitions between phyllotactic patterns are not fully understood. The plants studied so far, such as Magnolia, Torreya or Abies, are not suitable for experimental work, and the most popular model plant, Arabidopsis thaliana, does not show sufficient phyllotactic variability. It has been found that in common verbena (Verbena officinalis L.), a perennial, cosmopolitan plant, phyllotaxis differs not only between growth phases in primary transitions but also along the indeterminate inflorescence axis in a series of multiple secondary transitions. The latter are no longer associated with the change in lateral organ identity, and the sequence of phyllotactic patterns is puzzling from a theoretical point of view. Data from the experiments in silico, confronted with empirical observations, suggest that secondary transitions might be triggered by the cumulative effect of fluctuations in the continuously decreasing bract primordia size. The most important finding is that the changes in the primary vascular system, associated with phyllotactic transitions, precede those taking place at the apical meristem. This raises the question of the role of the vascular system in determining primordia initiation sites, and possibly challenges the autonomy of the apex. The results of this study highlight the complex relationships between various systems that have to coordinate their growth and differentiation in the developing plant shoot. Common verbena emerges from this research as a plant that may become a new model suitable for further studies on the causes of phyllotactic transitions.

Sign in / Sign up

Export Citation Format

Share Document