bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fallback in bipolar planetary nebulae?
Authors: Baan Willem A. , Imai Hiroshi , Orosz Gabor 
Published: December 2021

Abstract
The subclass of bipolar Planetary Nebulae (PNe) exhibits well-defined low-power outflows and some shows shock-related equatorial spiderweb structures and hourglass structures surrounding these outflows. These structures are distinctly different from the phenomena associated with spherical and elliptical PNe and suggest a non-standard way to simultaneously energise both kinds of structures. This paper presents evidence from the published literature on bipolar PN Hb 12 and other sources in support of an alternative scenario for energising these structures by means of accretion from material shells deposited during earlier post-AGB and pre-PNe evolutionary stages. In addition to energising the bipolar outflow, a sub-Eddington accretion scenario could hydrodynamically explain the spiderweb and outer hourglass structures as oblique shockwaves for guiding the accreting material into the equatorial region of the source. Estimates of the accretion rate resulting from fallback-related spherical accretion could indeed help to drive a low-power outflow and contribute to the total luminosity of these sources.
Chemical abundances of three new Ba stars from the Keck/HIRES spectra
Authors: Liu Shuai , Wang Liang , Shi Jian-Rong , Wu Zhen-Yu , Yan Hong-Liang , Gao Qi , Li Chun-Qian 
Published: December 2021

Abstract
Based on high resolution, high signal-to-noise (S/N) ratio spectra from Keck/HIRES, we have determined abundances of 20 elements for 18 Ba candidates. The parameter space of these stars is in the range of 4880 ≤ T
eff ≤ 6050 K,

2.56
≤
log

g
≤
4.53

dex

and − 0.27 ≤ [Fe/H] ≤ 0.09 dex. It is found that four of them can be identified as Ba stars with [s/Fe] > 0.25 dex (s: Sr, Y, Zr, Ba, La, Ce and Nd), and three of them are newly discovered, which include two Ba giants (HD 16178 and HD 22233) and one Ba subgiant (HD 2946). Our results show that the abundances of α, odd and iron-peak elements (O, Na, Mg, Al, Si, Ca, Sc, Ti, Mn, Ni and Cu) for our program stars are similar to those of the thin disk, while the distribution of [hs/ls] (hs: Ba, La, Ce and Nd, ls: Sr, Y and Zr) ratios of our Ba stars is similar to those of the known Ba objects. None of the four Ba stars show clear enhancement in carbon including the known CH subgiant HD 4395. It is found that three of the Ba stars present clear evidence of hosting stellar or sub-stellar companions from the radial velocity data.
New continuum and polarization observations of the Cygnus Loop with FAST I. Data processing and verification
Authors: Sun Xiao-Hui , Meng Mei-Niang , Gao Xu-Yang , Reich Wolfgang , Jiang Peng , Li Di , Yan Hui-Rong , Li Xiang-Hua 
Published: December 2021

Abstract
We report on the continuum and polarization observations of the Cygnus Loop supernova remnant (SNR) conducted by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). FAST observations provide high angular resolution and high sensitivity images of the SNR, which will help to disentangle its nature. We obtained Stokes I, Q and U maps over the frequency range of 1.03 – 1.46 GHz split into channels of 7.63 kHz. The original angular resolution is in the range of

∼

3

′

−
∼

3

′

.8

, and we combined all the data at a common resolution of

4

′

. The temperature scale of the total intensity and the spectral index from the in-band temperature-temperature plot are consistent with previous observations, which validates the data calibration and map-making procedures. The rms sensitivity for the band-averaged total-intensity map is about 20 mK in brightness temperature, which is at the level of confusion limit. For the first time, we apply rotation measure (RM) synthesis to the Cygnus Loop to obtain the polarization intensity and RM maps. The rms sensitivity for polarization is about 5 mK, far below the total-intensity confusion limit. We also obtained RMs of eight extragalactic sources, and demonstrate that the wide-band frequency coverage helps to overcome the ambiguity of RM determinations.
Does ADS 9346 have a low-mass companion?
Authors: Kiyaeva Olga V. , Khovritchev Maxim Yu. , Kulikova Agrippina M. , Narizhnaya Natalya V. , Vasilyeva Tatyana A. , Apetyan Arina A. 
Published: December 2021

Abstract
Based on the photographic and CCD observations of the relative motion of the A and B components of the binary system ADS 9346 obtained with the 26-inch refractor of Pulkovo Observatory during 1979–2019, we discover an invisible companion associated with star A. Comparison of the ephemerides with the positional and spectroscopic observations allowed us to calculate the preliminary orbit of the photocenter (P = 15 yr). The minimal mass of the companion is approximately 0.13 M
⊙. The existence of the invisible low-mass companion is implied by the IR-excess based on IRAS data. To confirm this, additional observations of the radial velocity near the periastron need to be carried out.
LAMOST Time-Domain survey: first results of four K2 plates
Authors: Wang Song , Zhang Hao-Tong , Bai Zhong-Rui , Yuan Hai-Long , Xiang Mao-Sheng , Zhang Bo , Hou Wen , Zuo Fang , Du Bing , Li Tan-Da , Yang Fan , Cui Kai-Ming , Wang Yi-Lun , Li Jiao , Kovalev Mikhail , Li Chun-Qian , Tian Hao , Zong Wei-Kai , Han Heng-Geng , Liu Chao , Luo A-Li , Shi Jian-Rong , Fu Jian-Ning , Bi Shao-Lan , Han Zhan-Wen , Liu Ji-Feng 
Published: December 2021

Abstract
From Oct. 2019 to Apr. 2020, LAMOST performed a time-domain (TD) spectroscopic survey of four K2 plates with both low- and medium-resolution observations. The low-resolution spectroscopic survey acquired 282 exposures ( ≈ 46.6 h) over 25 nights, yielding a total of about 767 000 spectra, and the medium-resolution survey took 177 exposures ( ≈ 49.1 h) over 27 nights, collecting about 478 000 spectra. More than 70%/50% of low-resolution/medium-resolution spectra have signal-to-noise ratio higher than 10. We determine stellar parameters (e.g., T
eff, log g, [Fe/H]) and radial velocity (RV) with different methods, including LASP, DD-Payne and SLAM. In general, these parameter estimations from different methods show good agreement, and the stellar parameter values are consistent with those of APOGEE. We use the Gaia DR2 RV values to calculate a median RV zero point (RVZP) for each spectrograph exposure by exposure, and the RVZP-corrected RVs agree well with the APOGEE data. The stellar evolutionary and spectroscopic masses are estimated based on the stellar parameters, multi-band magnitudes, distances and extinction values. Finally, we construct a binary catalog including about 2700 candidates by analyzing their light curves, fitting the RV data, calculating the binarity parameters from medium-resolution spectra and cross-matching the spatially resolved binary catalog from Gaia EDR3. The LAMOST TD survey is expected to represent a breakthrough in various scientific topics, such as binary systems, stellar activity, stellar pulsation, etc.
Deep double descent: where bigger models and more data hurt*
Authors: Nakkiran Preetum , Kaplun Gal , Bansal Yamini , Yang Tristan , Barak Boaz , Sutskever Ilya 
Published: December 2021

Abstract
We show that a variety of modern deep learning tasks exhibit a ‘double-descent’ phenomenon where, as we increase model size, performance first gets worse and then gets better. Moreover, we show that double descent occurs not just as a function of model size, but also as a function of the number of training epochs. We unify the above phenomena by defining a new complexity measure we call the effective model complexity and conjecture a generalized double descent with respect to this measure. Furthermore, our notion of model complexity allows us to identify certain regimes where increasing (even quadrupling) the number of train samples actually hurts test performance.
Augmenting physical models with deep networks for complex dynamics forecasting*
Authors: Yin Yuan , Le Guen Vincent , Dona Jérémie , de Bézenac Emmanuel , Ayed Ibrahim , Thome Nicolas , Gallinari Patrick 
Published: December 2021

Abstract
Forecasting complex dynamical phenomena in settings where only partial knowledge of their dynamics is available is a prevalent problem across various scientific fields. While purely data-driven approaches are arguably insufficient in this context, standard physical modeling-based approaches tend to be over-simplistic, inducing non-negligible errors. In this work, we introduce the APHYNITY framework, a principled approach for augmenting incomplete physical dynamics described by differential equations with deep data-driven models. It consists of decomposing the dynamics into two components: a physical component accounting for the dynamics for which we have some prior knowledge, and a data-driven component accounting for errors of the physical model. The learning problem is carefully formulated such that the physical model explains as much of the data as possible, while the data-driven component only describes information that cannot be captured by the physical model; no more, no less. This not only provides the existence and uniqueness for this decomposition, but also ensures interpretability and benefit generalization. Experiments made on three important use cases, each representative of a different family of phenomena, i.e. reaction–diffusion equations, wave equations and the non-linear damped pendulum, show that APHYNITY can efficiently leverage approximate physical models to accurately forecast the evolution of the system and correctly identify relevant physical parameters. The code is available at https://github.com/yuan-yin/APHYNITY.
Hausdorff dimension, heavy tails, and generalization in neural networks*
Authors: Şimşekli Umut , Sener Ozan , Deligiannidis George , Erdogdu Murat A 
Published: December 2021

Abstract
Despite its success in a wide range of applications, characterizing the generalization properties of stochastic gradient descent (SGD) in non-convex deep learning problems is still an important challenge. While modeling the trajectories of SGD via stochastic differential equations (SDE) under heavy-tailed gradient noise has recently shed light over several peculiar characteristics of SGD, a rigorous treatment of the generalization properties of such SDEs in a learning theoretical framework is still missing. Aiming to bridge this gap, in this paper, we prove generalization bounds for SGD under the assumption that its trajectories can be well-approximated by a Feller process, which defines a rich class of Markov processes that include several recent SDE representations (both Brownian or heavy-tailed) as its special case. We show that the generalization error can be controlled by the Hausdorff dimension of the trajectories, which is intimately linked to the tail behavior of the driving process. Our results imply that heavier-tailed processes should achieve better generalization; hence, the tail-index of the process can be used as a notion of ‘capacity metric’. We support our theory with experiments on deep neural networks illustrating that the proposed capacity metric accurately estimates the generalization error, and it does not necessarily grow with the number of parameters unlike the existing capacity metrics in the literature.
Meta-optimization of the parameters for the gravitational search algorithm in chemical kinetics problems
Authors: Enikeeva L V , Shvareva E N , Dubovtsev D A , Gubaydullin I M 
Published: December 2021

Abstract
The paper considers the selection of the optimal parameters of the heuristic algorithm, which is used for mathematical modeling of the chemical-technological process. This adjustment of the algorithm parameters is called meta-optimization. The gravity search algorithm is used as a heuristic algorithm. Meta-optimization is performed by a genetic algorithm. The meta-optimization is tested on the problem of modeling the process of propane pre-reforming. It is shown that setting even one parameter of a heuristic algorithm is a time-consuming operation. The article presents the results of the numerical solution of the meta-optimization algorithm.
Computer simulation of block polymerization of 1,6-Hexanediol Diacrylate
Authors: Shakiryanov E D 
Published: December 2021

Abstract
In this paper, a computer model of the block three-dimensional free-radical polymerization of 1,6-Hexanediol Diacrylate (HDDA) is proposed. The model of the reaction system is based on an ideal mixing reactor. The reaction process is modeled by the Monte Carlo method. Accounting for the diffusion inhibition of the reaction is described using the free volume model. An adequate description of the experimental data of the calculated conversion rate curve is obtained. The nature of the change in the rate constant of the growth reaction with increasing conversion is shown.
Algorithm for numerical simulation of electron density and stochastically convecting high latitude ionosphere
Authors: Vlaskov G 
Published: December 2021

Abstract
The problem of modeling the inhomogeneities of the electron density in the polar ionosphere at the level of the F - layer is considered. It is known that the distribution of ionospheric plasma changes under the action of the electric field of large-scale magnetospheric convection. Since the electric field undergoes significant fluctuations in the auroral zone, it is proposed to use the Monte Carlo method to solve this problem, simulating the process of plasma motion, like the Wiener one with deterministic drift.
Vertical turbulent exchange structure and parametrization for 3D shallow water hydrodynamics models
Authors: Sukhinov A I , Chistyakov A E , Protsenko S V , Protsenko E A 
Published: December 2021

Abstract
The work describes research of vertical turbulent exchange structure and parametrization for 3D shallow water hydrodynamics models. In this paper, the coefficients of horizontal turbulent exchange are calculated using a whole set of averaging periods of turbulent velocity pulsations. Using experimental data on the pulsations of the velocity components, the coefficient of vertical turbulent exchange was calculated on the basis of various approaches to its parameterization, based on the analysis of the obtained coefficient distributions, the most adequate parameterization of the coefficient was selected, which is used in the software package. The distribution of the vertical turbulent exchange coefficient obtained in a numerical experiment was compared with the results of full-scale measurements, and the calculation results obtained using the mathematical statistics apparatus were analysed.
Research of strength capabilities of building steels under temperature effects
Authors: Vernezi N L , Kosenko E E , Kosenko V V , Demchenko D B , Cherpakov A V 
Published: December 2021

Abstract
The use of information technologies in construction makes it possible to assess the strength capabilities of various classes of reinforcement in order to use the full strength potential of steels laid down at the production stage. The information obtained during the study of the properties of steels is important both for building structures and for metals used in the manufacture of load-bearing car bodies, in the construction of which high-strength steels are also used. In terms of the quality of the steels produced, the Russian industry is among the leaders in the world along with the largest European companies. The high characteristics of steel make it possible to expand the range of their application, both in conditions of elevated and in conditions of low temperatures.
Stability of a nonlinear thermoelastic plate
Authors: Volokitin G I , Moiseev D V 
Published: December 2021

Abstract
The problem of loss of stability of a circular plate under lateral compression in an inhomogeneous temperature field is considered. The theory of superposition of a small deformation on a finite one is used. A similar approach to the study of the equilibrium bifurcation of nonlinear thermoelastic bodies was used in the following works.
Three-dimensional integro-differential model of unstationary hydrodynamic process in a liquid-metal pool of underwater arc welding
Authors: Rybalkin E , Yagyaev E , Bogutsky V , Shron L 
Published: December 2021

Abstract
Wet underwater arc welding is now widely used. At the same time, obtaining high-quality welds with this welding method is an urgent scientific and technical problem due to their saturation with hydrogen and oxygen and the formation of pores. One of the promising directions for solving this issue is the use of an external electromagnetic effect on the liquid metal in the weld pool in order to control the movements of the molten metal flows to improve the degassing processes of welded joints. It is possible to estimate the parameters and efficiency of external electromagnetic influence by means of mathematical modeling of related electromagnetic, hydrodynamic and thermal processes occurring in the welding installation. The article proposes a three-dimensional integro-differential model of a non-stationary hydrodynamic process occurring in the liquid metal of a weld pool in an underwater arc welding system with an external electromagnetic effect. For the equations of hydrodynamics boundary value problems are formed, which, using potential theory, are reduced to a system of integro-differential equations for the vorticity function in the volume of a liquid conductor and a simple vector layer on its surface. For a numerical solution, the resulting system of integro-differential equations is approximated by an algebraic system according to the Krylov-Bogolyubov method. This system of equations makes it possible to determine the velocity field in the liquid metal of the weld pool for any welding modes.
Formalization of requirements for assembly of high-precision units during process design of production of multi-product machining systems
Authors: Nazaryev A , Bochkarev P , Gumarov G 
Published: December 2021

Abstract
This article considers the improvement of mathematical and methodological support of the implementation of an enlarged block of design procedures of the analysis of requirements of the assembly of high-precision products of the complex of design procedures of the system of accounting requirements for the assembly in the design of manufacturing methods of machining. The proposed modernization will allow to more efficiently perform of the design dimensional analysis of a high-precision assembly unit in an automated fashion and choose rational manufacturing methods of machining of parts in the system of automated sequencing of manufacturing methods during process design of the production of multi-nomenclature machining complexes. In addition, the proposed solutions allow for the expansion of digitalization of designing preproduction and process design and the transition to intelligent production systems. The problem posed in the presented study is relevant, since the proposed solutions allow for the expansion of digitalization of designing preproduction and process design and the transition to intelligent production systems in the future.
Investigation of piston ring wear engines by the mathematical statistics method
Authors: Khachkinayan A , Zharkov Yu , Zubkov V , Novakovich V , Ermakov V 
Published: December 2021

Abstract
Improving the reliability and durability of internal combustion engines makes it possible to increase productivity and reduce the cost of operation. The study of nature and magnitude of piston rings wear is relevant and represents a scientific novelty. During the operation of internal combustion engines, it is almost impossible to determine the influence of various factors on the wear rate and the resource of piston rings. One of the most accurate ways to study the wear intensity and the service life values of internal combustion engines piston rings during operation is the statistical method. The method of mathematical statistics allows us to study the nature and magnitude of individual parts wear with a sufficient degree of accuracy, to determine the main causes of wear, to outline ways of increasing the parts wear resistance, to establish durability criteria, to reasonably assign standard service life of parts and plan the parts need for any period with a given probability, with climatic conditions being taking into account. The article presents the collected statistical material on the internal combustion engines piston rings wear of construction and road vehicles operated at construction sites of Rostov region. It has been processed according to the normal Gauss law and data on the wear and service life of piston rings are obtained. The obtained experimental data on the wear of piston rings in height are reliable to the distribution law and can be used to determine the intensity of engines piston rings wear at repair enterprises.
Experimental studies of vibroacoustic characteristics of the basic structure parts of the traction rolling stock and transportation technological vehicles
Authors: Yaitskov I , Nazaretov A , Kochetkov A 
Published: December 2021

Abstract
The paper presents the obtained results of the vibration studies, particularly, the structural elements of the railway rolling stock, created at the driver workplaces, structures of the internal combustion engines, hoods, frames while moving and a stationary machine, which determine the vibration spectral composition and propose the specific engineering solutions for the noise and vibration protection system.
Heat recovery in the refrigeration equipment of dining cars
Authors: Voron O A , Patenyan A A , Yu Rostokin A 
Published: December 2021

Abstract
The paper investigates the major parameters of the existing refrigeration equipment of dining cars, as well as analyzes the latest trends in the development of refrigeration equipment, taking into account the changing requirements of legislation and environmental standards. Besides, it compares several systems with different refrigerants. Finally, our study introduces the possibilities of exploiting a transcritical system with heat recovery.
Methodology of the selection of effective dipping and control over the filling depth of open-textured construction materials
Authors: Nikolaev SV , Benin AV , Popov AM 
Published: December 2021

Abstract
It is determined that for the combination of the dipping process with the ultrasound control it is necessary to carry out the optimization of the filling speed and the precision of control over the dipping depth, to determine the optimum frequency of the ultrasound emission which satisfies the speed and the dipping measurement precision of the sample with the hydrophobic agent. On the basis of the performed multiobjective optimization, experimental results for the dipping and the control over the dipping stage of porous materials by the solution in the uniform acoustic field alignment charts are received for the selection of the rational frequency of ultrasound fluctuations which allow regulating and/or optimizing dipping and control processes over the material filling depth subject to customer tasks. The selection methodology of effective values of parameters of the acoustic field providing the combination of filling processes and the control over the depth of the dipped material filling is well-reasoned.