Collisional excitation of interstellar molecules

An effective straight-line trajectory (EST) approach has been proposed for computation of collision-induced rotational line widths (half widths at half maximum) and excitation rates in case of atom-molecule system under the frame work of Smithet. al. (1976) formalism and molecule-molecule systems under the framework of a normalized semi-classical perturbative approach. An arbitrary multiplication factor RX with its optimum value can be used as a measure of significance of the curved trajectories of the colliding particles. The EST approach has been tested for HCL-Ar system and further applied to CO-He, CO-H₂, and OCS-H₂ systems of interstellar interest. The line width computations in case of HCl–Ar system are in accordance with the trend of the experimental values. The results obtained by the present approach are in good agreement with the theoretical computations using semi-perturbative approach. The present approach provides significant information about the lower and upper bound of the collision-induced rates even for the perturbers in rotationally excited states. The EST approach is not expensive in nature. It can be generalized for vibrational-electronic excitations.     

Analytic characterization of measurement uncertainty and initial orbit determination on orbital element representations

This paper presents an approach to characterize the uncertainty associated with the state vector obtained from the Herrick-Gibbs orbit determination approach using transformation of variables. The approach is applied to estimate the state vector and its probability density function for objects in low Earth orbit using sparse observations. The state vector and associated uncertainty estimates are computed in Cartesian coordinates and Keplerian elements. The approach is then extended to accommodate the $J_2$ perturbation where the state vector is written in terms of mean orbital elements. The results obtained from the analytical approach presented in this paper are validated using Monte Carlo simulations and compared with the often utilized similarity transformation for Kepler, mean, and nonsingular elements. The measurement uncertainty characterization obtained is used to initialize conventional nonlinear filters as well as operate a Bayesian approach for orbit determination and object tracking.     

On upper limits for gravitational radiation

A procedure with a Bayesan approach for calculating upper limits to gravitational wave bursts from coincidence experiments with multiple detectors is described, where the detection efficiency for small signals is taken into consideration. The Bayesan approach to the upper limit estimation is confronted with the unified approach for the case when no events are observed in presence of a non-zero background.     

An observational approach to the early stages of stellar evolution

During the last three decades an observational approach has been applied at the Byurakan Astrophysical Observatory to the problems of the evolution of astronomical bodies and systems. In contradiction to the traditional point of view, assuming that the processes of condensation are dominant in the Universe, this approach makes use of the observed predominance of expansions, ejections, and explosions.In the past, the observational approach has led to the prediction of an expansion of some stellar associations confirmed later by the analysis of observations. It became clear that the stellar associations are very young systems where the star-formation process is still continuing. The new approach has also led to the concept of the activity of galactic nuclei. The observational approach considers as a phenomenon of primary importance the formation of nebulae as a consequence of the activity of dense bodies (nebulae surrounding the novae, planetary nebulae, supernova remnants, cometary nebulae, and the diffuse nebulae in OB-associations).The new approach in application to the early stages of stellar evolution is discussed. The T Tauri-stage is considered as a phase following the more dense protostellar state. The flare stars are regarded as the next phase of evolution. The phenomena of fuors (FU Ori-type brightenings) can be considered as an expression of the same tendency (the transformation of dense matter into a rarefied state).     

Probability approach to the ballistic models of superluminal radio sources

Probability approach is considered in order to examine the plausibility of ballistic model explanation of superluminal phenomenon in extragalactic sources. It is shown that this approach is less probable for the explanation of observed data.     

A more exact expression for the gravitational deflection of light,derived using material medium approach

The deflection of a ray of light passing close to a gravitational mass is generally calculated from the null geodesic which the light ray (photon) follows. However, there is an alternate approach, where the effect of gravitation on the ray of light is estimated by considering the ray to be passing through a material medium. Calculations have been done in this paper, following the latter approach, to estimate the amount of deflection due to a static non-rotating mass. The refractive index of such a material medium, has been calculated in a more rigorous manner in the present work, and the final expression for the amount of deflection calculated here is claimed to be more exact than all other expressions derived so far, using material medium approach. Based on this expression, the amount of deflection for a sun grazing ray has also been calculated. The exact amount of deflection can be performed in a number of ways, without the material medium approach. However, the method presented here using the material medium approach and without any weak field approximation is believed to be original.     

Application of the atomic configuration probability to the equilibrium calculation

This is an extension study of the grand canonical approach of the equation of state to the equilibrium calculation for radiative opacities. We discuss the construction of atomic configurations from the ion stages and excitation states of atoms. The atomic configuration is essentially important to the grand canonical approach, and also useful to the radiative opacity calculation. We present the complete formalism for the calculation of atomic configuration probabilities and population fractions. We show that the grand canonical approach provides a shortcut in the computation of thermodynamic equilibrium. We mainly discuss its use in two cases for the equilibrium calculation.     

Parallel Construction of Nonlinear Force-Free Fields

A numerical approach to calculating nonlinear force-free fields is presented. The approach is similar to Sakurai (1981) being a current-field iteration scheme using the integral solution to Ampere's law (the Biot–Savart law). However, the method of solution presented here is simpler than Sakurai's approach, in that the field is directly constructed on a grid without the intermediate solution of a large system of nonlinear equations. The method also permits straightforward implementation on parallel computers. Results of applying the method to a number test cases, including boundary conditions with substantial currents, are presented.     

On the expansions of intermediate orbit for general planetary theory

Intermediate orbit for general planetary theory is constructed in the form of multivariate Fourier series with numerical coefficients. The structure and efficiency of the derived series are illustrated by giving various statistical properties of the coefficients.The ability of the recently proposed elliptic function approach to compress the Fourier series representing the intermediate orbit is investigated. Our results confirm that when mutual perturbations of a pair of planets are considered the elliptic function approach is quite efficient and allows one to compress the series substantially. However, when perturbations of three or more planets are under study the elliptic function approach does not give any advantages.     

The heating of coronae

Probably the most significant breakthroughs in understanding the heating of coronae have emerged from a global electrodynamics approach. Although this approach ties together A.C. (resonant) and D.C. (non-resonant) heating mechanisms, the detailed physics of the dissipation process is still not clearly understood.     

The Parameterization of the Ground State and Its Applications to Planetary Systems

Natural systems tend to minimize their energy. Hence an important problem in astrophysics is the parametrization of the ground state. In this context a quantum statistical approach is very useful. The problem of the variational approximation of the density matrix is extended towards a parametrization of the ground state. With an analogy to the semiclassical approach, a classical approach to the variational principle in the parametrization of the ground state is elucidated and its applications are discussed. We find that planetary systems tend to have circular orbits in an effort to attain the ground state. The results of this paper may be useful for the modern problem of detecting planets around bright stars.     

The redshift-space power spectrum in the halo model

Recently there has been a lot of attention focused on a virialized halo-based approach to understanding the properties of the matter and galaxy power spectrum. We show that this model allows a natural treatment of the large- and small-scale redshift-space distortions, which we develop here, which extends the pedagogical value of the approach.     

Astro-WISE interfaces

From a simple text interface to a graphical user interfaces—Astro-WISE provides the user with a wide range of possibilities to interact with the information system according to the user’s tasks and use cases. We describe a general approach to the interfacing of a scientific information system. We use this approach to create a number of services, which allows the user to browse the data stored in the system, to process the data and to exchange the newly created images and catalogs with the users within the system and wider astronomical community. Reusability of interfaces and services is another important feature of our approach. It reduces the time and resources spent to interface other information systems created from Astro-WISE.     

Tidal gravitational redshifts of spectral lines in geometrodynamics

An alternative approach is proposed for the study of the non-cosmological redshifts. The approach is based on the radiation formulation of the tidal gravitation acceleration in geometrodynamics and the spacetime curvature around the massive objects. The resulting formalism can be used to study the object mass and the gravitation magnitude from the observed spectral lines with redshifts.     

Dynamic planning of navigation determinations of airspace and missile objects in an automated flight test control system

This study considers an approach to planning navigation determinations of airspace and missile objects in the course of preparing for and carrying out an active flight test in an automated flight test control system. The approach is based on special information and mathematical software. The performance indices of the navigation determination subsystem are studied. Results of simulated modeling are provided.     

TOC信息的广播控制算法

研究了广播TOC信息时的控制算法和控制方法。在一个罗兰C信道上，可以单一广播TOC信息，也可以与差分GNSS信息交替广播。分析了交替广播时的信息的有效性和可用性。给出了TOC信息帧帧头位置序号的递推公式，并提出了相应的控制方法。     

1900 Draconid Trail Activity in 2011 and the Prospects for 2014

The article provides an explanation of stronger than expected by the Author Draconids 2011 activity basing on the assumption of unusually high density of 1900 trail of the comet 21P Giacobini-Zinner. Also, a revised prediction for Draconids 2014 is presented, which should also be caused by 1900 trail. For this prediction a “vertical trails” approach is used. This approach is described in the article.     

Bayesian galaxy shape measurement for weak lensing surveys – I. Methodology and a fast-fitting algorithm

The principles of measuring the shapes of galaxies by a model-fitting approach are discussed in the context of shape measurement for surveys of weak gravitational lensing. It is argued that such an approach should be optimal, allowing measurement with maximal signal-to-noise ratio, coupled with estimation of measurement errors. The distinction between likelihood-based and Bayesian methods is discussed. Systematic biases in the Bayesian method may be evaluated as part of the fitting process, and overall such an approach should yield unbiased shear estimation without requiring external calibration from simulations. The principal disadvantage of model fitting for large surveys is the computational time required, but here an algorithm is presented that enables large surveys to be analysed in feasible computation times. The method and algorithm is tested on simulated galaxies from the Shear TEsting Programme (STEP).