EARLY KYIV OBSERVATIONS OF ASTEROIDS: ANALYSIS AND NEW REDUCTION WITH TYCHO-2 AND GAIA CATALOGS

For more than 50 years, the continuous photographic observations of asteroids have been carried outwith telescopes of the Astronomical Observatory of the Taras Shevchenko National University of Kyiv and the Main Astronomical Observatory of the National Academy of Sciences of Ukraine. About 3,000 photographic plates were obtained, some of which were exposed in 1908. We collected the data on more than 5,500 positions and magnitudes of asteroids on these astroplates taking into account all results of the processing of observations available in various publications and in the Minor Planet Center database. All positional data were compared with JPL ephemeris and analyzed. From different series of asteroid observations the values of positional accuracy were obtained, depending on the methods of measuring and processing the plates and reference catalogs of stars. In order to systematically improve the obtained asteroid positions, we evaluated the possibilities of reprocessing some of the earliest asteroid observations applying the modern star high accuracy catalogs. Using the Tycho-2, Gaia DR2, and Gaia EDR3 as the reference catalogs, the 590 astroplates exposed on the MAO NASU Double Long-Focus Astrograph (DLA) in 1952-1986 were reprocessed based on old plate measurements. All newly determined and previous original asteroid positions were compared with the JPL ephemeris. The comparison results show an improvement in the systematic and random components of the accuracy of coordinates for new positions of asteroids. When comparing the new positions of the asteroids determined in the Tycho-2 and Gaia catalog systems, no significant changes in accuracy were found.

Detection of radio signals against the background of strong electromagnetic noise in transport

The problem of detecting a useful signal in the presence of a strong background noise is considered. To solve it, a statistical approach is used, based on a change in the level of chaos in the system when an additional random or deterministic process occurs, which is probabilistically independent from a set of stochastic phenomena that form background noise. It is shown that the occurrence of this process changes the level of entropy of the measured signal; this fact is the basis of the applied mathematical algorithm. It is based on the elements of the Fourier transform apparatus for the probability density with an appropriate choice of a nonlinear function of the random process under study. The proposed approach, based on variations in the randomness in the system in the presence of a useful signal, makes it possible to record its presence against the background of noise components even at low signal-to-noise ratios. The effectiveness of the method is confirmed both by theoretical justification and by the calculations presented in this work. The condition for the implementation of the technique described in the article, which does not impose restrictions on the studied physical fields and frequency ranges, is the comparability of the width of the probabilistic distribution of the desired useful signal with several intervals of discreteness of the measuring equipment. One of the results of this work is a high sensitivity to the emergence of independent random components.

Account for the Full Extent of Esophagus Motion in Radiation Therapy Planning: A Preliminary Study of the IRV of the Esophagus

ObjectiveAccounting for esophagus motion in radiotherapy planning is an important basis for accurate assessment of toxicity. In this study, we calculated how much the delineations of the esophagus should be expanded based on three-dimensional (3D) computed tomography (CT), four-dimensional (4D) average projection (AVG), and maximum intensity projection (MIP) scans to account for the full extent of esophagus motion during 4D imaging acquisition.Methods and MaterialsThe 3D and 4D CT scans of 20 lung cancer patients treated with conventional radiotherapy and 20 patients treated with stereotactic ablative radiation therapy (SBRT) were used. Radiation oncologists contoured the esophagus on the 3DCT, AVG, MIP and 25% exhale scans, and the combination of the esophagus in every phase of 4DCT. The union of all 4D phase delineations (U4D) represented the full extent of esophagus motion during imaging acquisition. Surface distances from U4D to 3D, AVG, and MIP volumes were calculated. Distances in the most extreme surface points (1.5 cm most superoinferior, 10% most right/left/anteroposterior) were used to derive margins accounting only for systematic (delineation) errors.ResultsEsophagus delineations on the MIP were the closest to the full extent of motion, requiring only 6.9 mm margins. Delineations on the AVG and 3D scans required margins up to 7.97 and 7.90 mm, respectively. The largest margins were for the inferior, right, and anterior aspects for the delineations on the 3D, AVG, and MIP scans, respectively.ConclusionDelineations on 3D, AVG, or MIP scans required extensions for representing the esophagus’s full extent of motion, with the MIP requiring the smallest margins. Research including daily imaging to determine the random components for the margins and dosimetric measurements to determine the relevance of creating a planning organ at risk volume (PRV) of the esophagus is required.

EXPERIMENTAL RESEARCH INTENSITY OF OSCILLATIONS AGRICULTURAL MACHINE-TRACTOR UNITS

Smoothness of movement of agricultural units is one of the important operational indicators of their work which is estimated on influence of fluctuations (translational vertical, cross, angular longitudinal, etc.) The article presents the method and results of experimental assessment of the smoothness of the movement of the bridge agricultural unit, which moves in the footsteps of a constant technological track. Studies of the smoothness of the bridge unit showed that the graphs of normalized correlation functions of vertical oscillations of the bridge agricultural tool developed by us in its motion in the wake of a constant technological track is characterized by a function containing along with random components harmonic, which are expressed by attenuating periodic oscillations. The frequency spectrum of oscillations of the agricultural tool core is concentrated in the range from 0 to 20 s–1, which agrees with the frequency range 0…0.3 cm−1 in which the variances of oscillations of the irregularities of the profile of the traces of the technological track are concentrated. The length of the correlation connection is approximately 0.25 s, which is equal to 0.25 m at the speed of the agricultural tool within 1.0 m / s.The obtained result is explained by the fact that the main spectrum of oscillations of the profile irregularities has a periodicity that corresponds to the step of ground engagement of the tires of the wheels of the agricultural tool. The research confirmed the effectiveness of the method of estimating the intensity of vertical oscillations of an agricultural unit by a measuring and registration complex based on a tablet computer with Android operating system with built-in accelerometer sensors and Accelerometer Meter application.

EXPERIMENTAL RESEARCH OF MICRORELIEF SOIL SURFACES OF PERMANENT TECHNOLOGICAL TRACK

A promising direction for further development of agriculture not only in Ukraine but also in the world is the introduction of innovative technologies, to which we should include the track system of agriculture. The movement of transport and energy vehicles on the aligned compacted trace of the constant technological track causes undesirable and uncharacteristic vibrations for agricultural machinery. The latter are due to the influence of the microprofile of the constant technological track, which has a significant negative impact on the degree of comfort and efficiency of the operator, operational and technological indicators, reliability and smoothness of machines. The method and results of experimental automated estimation of the microprofile of irregularities of traces of the constant technological track are presented in the article. Experimental studies of the microprofile of irregularities of the traces of the constant technological track have shown that the standard deviation of the irregularities of the profile is ± 0.84 According to their internal structure, the inequalities of the profile of traces of the constant technological track are characterized by a function that contains, along with random components, the harmonic ones, which are expressed by attenuating periodic oscillations of the normalized correlation function. The main share of variances of oscillations of the irregularities of the profile of the traces of the technological track is concentrated in the frequency range from 0… 0.3 cm − 1. The generator of formation of irregularities of a longitudinal profile of soil traces of a constant technological track are parameters of ground hooks of tires of wheels of the cars moving on it.This is confirmed by the fact that the length of the correlation of the ordinates of the irregularities of the profile of the traces of a constant technological track in the conditions of tests of the bridge agricultural tool of the new design is about 0.18 m, which corresponds to the pitch of its tires.

Impact of the ISM magnetic field on GRB afterglow polarization

Linear polarization has been measured in several GRB afterglows. After a few days, polarization arises from the forward shock emission which depends on the post-shock magnetic field. The latter can originate both from compression of existing fields, here the ISM magnetic field, and from shock generated instabilities. For short GRBs, previous modelling of the polarization arising from the forward shock considered a random field fully or partially confined to the shock plane. However, the ISM magnetic field likely consists of both random and ordered components. Here we study the impact of a more realistic magnetic field having both ordered and random components. We present our semi-analytical model and compute polarization curves arising for different magnetic field configurations. We find that the presence of an ordered component, even significantly weaker than the random one, has distinct signatures that could be detectable. In the presence of an ordered component not in the observer plane, we show that: i) for an observer inside the jet, the polarization angle θp either remains constant during all the afterglow phase or exhibits variations smaller than the 90○ swing expected from a random component solely, ii) for an off-axis observer, the polarization angle evolves from $\theta _p^{\max }$, before the jet break to its opposite after the jet break. We also find that the upper limit polarization for GRB170817 requires a random field not fully confined to the shock plane and is compatible with an ordered component as large as half the random one.

Subgraph Network Random Effects Error Components Models: Specification and Testing

This paper develops a subgraph random effects error components model for network data linear regression where the unit of observation is the node. In particular, it allows for link and triangle specific components, which serve as a basal model for modeling network effects. It then evaluates the potential effects of ignoring network effects in the estimation of the coefficients’ variance-covariance matrix. It also proposes consistent estimators of the variance components using quadratic forms and Lagrange Multiplier tests for evaluating the appropriate model of random components in networks. Monte Carlo simulations show that the tests have good performance in finite samples. It applies the proposed tests to the Call interbank market in Argentina.