bluuebunny/crossref_metadata_2025_split huggingface dataset:
STABILIZATION OF QUALITY AND PRODUCTIVITY OF GRINDING OF EXTENDED CYLINDRICAL SURFACES OF SHAFTS WITH PETAL CIRCLES
Authors: Бишутин С.Г. , Шупиков И.Л. 
Published: May 2021

Статья посвящена проблеме стабилизации показателей лепесткового шлифования протяженных цилиндрических заготовок для исключения влияния изнашивания инструмента на качество и производительность данной обработки. Представлены результаты исследований влияния изнашивания абразивного инструмента на процессы съема металла и формирования шероховатости обрабатываемой поверхности при лепестковом шлифовании. Более интенсивно изнашиваются круги большей зернистости, причем стойкость инструментов зернистостью 12…20 (ГОСТ 3647- 80 (в ред. 1995 г.)) в 2…3 раза выше кругов зернистостью 40…50 и составляет 5...10 минут. Приведены данные по стойкости лепестковых шлифовальных кругов с учетом основных факторов процесса обработки. Установлено, что скорость съема металла при шлифовании неизношенными лепестковыми кругами зернистостью от 12 до 40 составляет 130...270 мм/мин, параметр шероховатости Ra находится в пределах от 0,4 до 3,0 мкм, Sm - от 0,08 до 0,20 мм. Значения параметров шероховатости обрабатываемой поверхности вследствие изнашивания инструмента возрастают до 2-3 раз, а скорость съема материала с течением времени непрерывно уменьшается и может стать равной нулю. Предлагается стабилизировать показатели лепесткового шлифования путем непрерывного или периодического увеличения деформации (натяга) инструмента в процессе абразивной обработки, что позволит поддерживать на необходимом уровне требуемое число режущих зерен
The article is devoted to the problem of stabilization of indices of petal grinding of extended cylindrical billets in order to exclude the effect of tool wear on the quality and productivity of this treatment. We present the results of studies of influence of abrasive tool wear on processes of metal removal and formation of roughness of treated surface during petal grinding. Circles of greater grain wear more intensively, and the resistance of instruments with grain 12... 20 (GOST 3647- 80 (ed. 1995)) is 2...3 times higher than circles with grain 40...50 and is 5...10 minutes. We give the data on resistance of blade grinding wheels taking into account the main factors of the processing process. We found that the rate of metal removal when grinding with unworn petal circles with grain size from 12 to 40 is 130...270 mm/min, the roughness parameter Ra can vary in the range from 0.4 to 3.0 μm, Sm - from 0.08 to 0.20 mm. The values of the roughness parameters of the treated surface due to wear of the tool increase by 2-3 times, and the rate of material removal over time continuously decreases and can become zero. We proposed to stabilize the indicators of petal grinding by continuous or periodic increase of deformation of the tool during abrasive processing, which will allow one to maintain the required number of cutting grains at the required level
First Observations of Anomalous Cosmic Rays in to 36 Solar Radii
Authors: Rankin J. S. , McComas D. J. , Leske R. A. , Christian E. R. , Cohen C. M. S. , Cummings A. C. , Joyce C. J. , Labrador A. W. , Mewaldt R. A. , Posner A. , Schwadron N. A. , Strauss R. D. , Stone E. C. , Wiedenbeck M. E. 
Published: May 2021

Abstract
NASA’s Parker Solar Probe mission continues to travel closer to the Sun than any prior human-made object, with an expected closest approach of <10 solar radii (<0.046 au) by 2024. On board, the Integrated Science Investigation of the Sun instrument suite makes unprecedented in situ measurements of energetic particles in the near-Sun environment. The current low level of solar activity offers a prime opportunity to measure cosmic rays closer to the Sun than ever before. We present the first observations of anomalous cosmic rays in to 36 solar radii (0.166 au), focusing specifically on helium. Our results indicate a strong radial intensity gradient of ∼25 ± 5%/au over energies of ∼4 to ∼45 MeV/nuc. These values are larger than prior observations, further out in the heliosphere, and come at a unique time in our understanding and modeling of particle transport and acceleration, particularly as both Voyagers have crossed the heliopause and IBEX has accumulated a full solar cycle of observations. Thus, continued measurements of cosmic rays by Parker Solar Probe will play a critical role in linking past observations with our present knowledge and significantly advancing our understanding of cosmic ray transport in the heliosphere.
Effects of Photoionization and Photoheating on Lyα Forest Properties from Cholla Cosmological Simulations
Authors: Villasenor Bruno , Robertson Brant , Madau Piero , Schneider Evan 
Published: May 2021

Abstract
The density and temperature properties of the intergalactic medium (IGM) reflect the heating and ionization history during cosmological structure formation, and are primarily probed by the Lyα forest of neutral hydrogen absorption features in the observed spectra of background sources. We present the methodology and initial results from the Cholla IGM Photoheating Simulation (CHIPS) suite performed with the graphics process unit–accelerated Cholla code to study the IGM at high, uniform spatial resolution maintained over large volumes. In this first paper, we examine the IGM structure in CHIPS cosmological simulations that include IGM uniform photoheating and photoionization models where hydrogen reionization is completed early or by redshift z ∼ 6. Comparing with observations of the large- and small-scale Lyα transmitted flux power spectra P(k) at redshifts 2 ≲ z ≲ 5.5, the relative agreement of the models depends on scale, with the self-consistent Puchwein et al. IGM photoheating and photoionization model in good agreement with the flux P(k) at k ≳ 0.01 s km−1 at redshifts 2 ≲ z ≲ 3.5. On larger scales, the P(k) measurements increase in amplitude from z ∼ 4.6 to z ∼ 2.2, faster than the models, and lie in between the model predictions at 2.2 ≲ z ≲ 4.6 for k ≈ 0.002–0.01 s km−1. We argue that the models could improve by changing the He ii photoheating rate associated with active galactic nuclei to reduce the IGM temperature at z ∼ 3. At higher redshifts, z ≳ 4.5, the observed flux P(k) amplitude increases at a rate intermediate between the models, and we argue that for models where hydrogen reionization is completed late (z ∼ 5.5–6), resolving this disagreement will require inhomogeneous or “patchy” reionization. We then use an additional set of simulations to demonstrate that our results have numerically converged and are not strongly affected by varying cosmological parameters.
A Search for Cloud Cores Affected by Shocked Carbon Chain Chemistry in L1251
Authors: Liu 刘 X.-C. 训川 , Wu Y. , Zhang 张 C. 超 , Chen X. , Lin L.-H. , Qin S.-L. , Liu T. , Henkel C. , Wang J. , Liu H.-L. , Yuan J. , Yuan L.-X. , Li J. , Shen Z.-Q. , Li D. , Esimbek J. , Wang K. , Li L.-X. , Kim Kee-Tae , Zhu L. , Madones D. , Inostroza-Pino N. , Meng F.-Y. , Zhang T. , Tatematsu K. , Xu Y. , Ju B.-G. , Kraus A. , Xu F.-W. 
Published: May 2021

Abstract
We searched for shocked carbon chain chemistry (SCCC) sources with C3S abundances surpassing those of HC5N toward the dark cloud L1251, using the Effelsberg telescope at the K band (18–26 GHz). L1251-1 and L1251-3 are identified as the most promising SCCC sources. The two sources harbor young stellar objects. We conducted mapping observations toward L1251-A, the western tail of L1251, at λ ∼ 3 mm with the Purple Mountain Observatory 13.7 m and the Nobeyama Radio Observatory 45 m telescopes in lines of C2H, N2H+, CS, HCO+, SO, HC3N, and C18O as well as in CO 3–2 using the James Clerk Maxwell Telescope (JCMT). The spectral data were combined with archival data including Spitzer and Herschel continuum maps for further analysis. Filamentary substructures labeled as F1–F6 were extracted in L1251, with F1 being associated with L1251-A hosting L1251-1. The peak positions of dense gas traced by HCO+ are misaligned relative to those of the dust clumps. Episodic outflows are common in this region. The twisted morphology of F1 and velocity distribution along L1251-A may originate from stellar feedback. SCCC in L1251-1 may have been caused by outflow activities originated from the infrared source IRS1. The signposts of ongoing SCCC and the broadened line widths of C3S and C4H in L1251-1 as well as the distribution of HC3N are also related to outflow activities in this region. L1251-1 (IRS1) together with the previously identified SCCC source IRS3 demonstrate that L1251-A is an excellent region to study SCCC.
Investigating X-Ray Sources during the Epoch of Reionization with the 21 cm Signal
Authors: Ma Qing-Bo , Ciardi Benedetta , Eide Marius B. , Busch Philipp , Mao Yi , Zhi Qi-Jun 
Published: May 2021

Abstract
Heating of neutral gas by energetic sources is crucial for the prediction of the 21 cm signal during the epoch of reionization. To investigate differences induced on the statistics of the 21 cm signal by various source types, we use five radiative transfer simulations that have the same stellar UV emission model and varying combinations of more energetic sources, such as X-ray binaries (XRBs), accreting nuclear black holes (BHs), and hot interstellar medium emission (ISM). We find that the efficient heating from the ISM increases the average global 21 cm signal while reducing its fluctuations and thus power spectrum. A clear impact is also observed in the bispectrum in terms of scale and timing of the transition between a positive and a negative value. The impact of XRBs is similar to that of the ISM, although it is delayed in time and reduced in intensity because of the less efficient heating. Due to the paucity of nuclear BHs, the behavior of the 21 cm statistics in their presence is very similar to that of a case when only stars are considered, with the exception of the latest stages of reionization, when the effect of BHs is clearly visible. We find that differences between the source scenarios investigated here are larger than the instrumental noise of SKA1-low at z ≳ 7–8, suggesting that in the future it might be possible to constrain the spectral energy distribution of the sources contributing to the reionization process.
Evidence for a Cosmic-Ray Gradient in the IM Lup Protoplanetary Disk
Authors: Seifert Richard A. , Cleeves L. Ilsedore , Adams Fred C. , Li Zhi-Yun 
Published: May 2021

Abstract
Protoplanetary disk evolution is strongly impacted by ionization from the central star and local environment, which collectively have been shown to drive chemical complexity and are expected to impact the transport of disk material. Nonetheless, ionization remains a poorly constrained input to many detailed modeling efforts. We use new and archival ALMA observations of N2H+ 3–2 and H13CO+ 3–2 to derive the first observationally motivated ionization model for the IM Lup protoplanetary disk. Incorporating ionization from multiple internal and external sources, we model N2H+ and H13CO+ abundances under varying ionization environments and compare these directly to the imaged ALMA observations by performing non-LTE radiative transfer, visibility sampling, and imaging. We find that the observations are best reproduced using a radially increasing cosmic-ray (CR) gradient, with low CR ionization in the inner disk, high CR ionization in the outer disk, and a transition at ∼80–100 au. This location is approximately coincident with the edge of spiral structure identified in millimeter emission. We also find that IM Lup shows evidence for enhanced UV-driven formation of HCO+, which we attribute to the disk’s high flaring angle. In summary, IM Lup represents the first protoplanetary disk with observational evidence for a CR gradient, which may have important implications for IM Lup’s ongoing evolution, especially given the disk’s young age and large size.
FRBs Lensed by Point Masses I. Lens Mass Estimation for Doubly Imaged FRBs
Authors: Chen Xuechun , Shu Yiping , Zheng Wenwen , Li Guoliang 
Published: May 2021

Abstract
Fast radio bursts (FRBs) are bright radio transient events with durations on the order of milliseconds. The majority of FRB sources discovered so far have a single peak, with the exception of a few showing multiple-peaked profiles, the origin of which is unknown. In this work, we show that the strong lensing effect of a point mass or a point mass + external shear on a single-peak FRB can produce double peaks (i.e., lensed images). In particular, the leading peak will always be more magnified and hence brighter than the trailing peak for a point-mass lens model, while the point-mass + external shear lens model can produce a less magnified leading peak. We find that, for a point-mass lens model, the combination of lens mass M and redshift z

l
in the form of M(1 + z

l
) can be directly computed from two observables—the delayed time Δt and the flux ratio of the leading peak to the trailing peak R. For a point-mass + external shear lens model, upper and lower limits in M(1 + z

l
) can also be obtained from Δt and R for a given external shear strength. In particular, tighter lens mass constraints can be achieved when the observed R is larger. Lastly, we show the process of constraining lens mass using the observed values of Δt and R of two double-peaked FRB sources, i.e., FRB 121002 and FRB 130729, as references, although the double-peaked profiles are not necessarily caused by strong lensing.
First-principles Prediction of X-Ray Polarization from Magnetic Reconnection in High-frequency BL Lacertae Objects
Authors: Zhang Haocheng , Li Xiaocan , Giannios Dimitrios , Guo Fan 
Published: May 2021

Abstract
Relativistic magnetic reconnection is a potential particle acceleration mechanism for high-frequency BL Lac objects (HBLs). The Imaging X-ray Polarimetry Explorer (IXPE) scheduled to launch in 2021 has the capability to probe the evolution of magnetic field in HBLs, examining the magnetic reconnection scenario for the HBL flares. In this paper, we make the first attempt to self-consistently predict HBL X-ray polarization signatures arising from relativistic magnetic reconnection via combined particle-in-cell and polarized radiation transfer simulations. We find that although the intrinsic optical and X-ray polarization degrees are similar on average, the X-ray polarization is much more variable in both the polarization degree and angle (PD and PA). Given the sensitivity of the IXPE, it may obtain one to a few polarization data points for one flaring event of nearby bright HBLs Mrk 421 and 501. However, it may not fully resolve the highly variable X-ray polarization. Due to temporal depolarization, where the integration of photons with variable polarization states over a finite period of time can lower the detected PD, the measured X-ray PD can be considerably lower than the optical counterpart or even undetectable. The lower X-ray PD than the optical thus can be a characteristic signature of relativistic magnetic reconnection. For very bright flares where the X-ray polarization is well resolved, relativistic magnetic reconnection predicts smooth X-ray PA swings, which originate from large plasmoid mergers in the reconnection region.
The Old Moving Groups in the Field of Taurus
Authors: Liu Jiaming , Fang Min , Tian Hao , Liu Chao , Yang Chengqun , Xue XiangXiang 
Published: May 2021

Abstract
In this work, we present a systematic search for stellar groups in the Taurus field by applying the DBSCAN algorithm to the data from Gaia DR2. We find 22 groups, consisting of 8 young groups (Groups 1–8) at ages of 2–4 Myr and distances of ∼130–170 pc, and 14 old groups (Groups 9–22) at ages of 8–49 Myr and distances of ∼110–210 pc. We characterize the disk properties of group members and find 19 new disk-bearing stars, 8 of which are in the young groups with 11 others belonging to the comparatively old groups at the ages of 8–11 Myr. We characterize the accretion properties of the group members with Hα emission lines in their Large Sky Area Multi-Object Fibre Spectroscopic Telescope spectra, and discover one source in Group 10 at an age of 10 Myr which still shows accretion activity. We investigate the kinematic relations among the old groups, find that Group 9 is kinematically related to the known Taurus members, and exclude any kinematic relations between Groups 10–22 and the known Taurus members.
Radial Velocities in the Fields of RR Lyr Variables NO Cas, NR Lyr, and V1176 Sgr
Authors: Barnes Thomas G. , Jeffery Elizabeth , Skillen Ian , Montemayor Thomas J. 
Published: May 2021

Abstract
We report 14 radial velocities for three field stars located near the RR Lyrae variables NO Cas, NR Lyr, and V1176 Sgr. We identified the three field stars using Gaia Early Data Release 3. Two of these stars confirm the Gaia radial velocities. The third has no previously published radial velocity.
L’idée libérale en question
Authors: Bujon Anne-Lorraine 
Published: May 2021

Alors que le libéralisme est une force structurante de notre modernité, l’hostilité contemporaine à l’idée libérale repose sur des contresens qu’il convient de corriger. Le libéralisme est en effet une tradition plurielle, capable de se renouveler et de se combiner avec d’autres courants de pensée politique. Timothy Garton Ash le définit comme « une quête interminable pour déterminer le meilleur moyen de bien vivre ensemble dans les conditions de la liberté » . N’est-il pas temps de le rénover, pour ainsi mieux le défendre ?
Des enseignants qui res(is)tent : dynamiques identitaires et investissement du champ de l’enseignement professionnel au Québec
Authors: Grossmann Sophie 
Published: May 2021

Le phénomène d’abandon de la profession enseignante interroge chercheurs et décideurs nord-américains régulièrement depuis plusieurs décennies. En écho à la déscolarisation qui affecte le métier d’élève, la question du décrochage des enseignants au cours des premières années de leur carrière mobilise par ailleurs les acteurs universitaires et scolaires chargés de la formation et de l’accompagnement des enseignants dans leur intégration professionnelle. Outre les problématiques globales qui affectent l’entrée dans la profession enseignante au Québec (complexité et charge de travail, précarité, etc.), des facteurs spécifiques à la formation professionnelle au secondaire complexifient le processus de transition professionnelle dans ce secteur d’enseignement (notamment la rapidité avec laquelle s’effectue le passage du métier à l’enseignement et la rupture que constituerait le saut d’un champ professionnel à un autre). Partant d’une inversion de la perspective sur le décrochage, la présentation s’attardera à des enseignants qui, échappant aux déterminismes, persévèrent en formation professionnelle au-delà des cinq ans fatidiques. Comment apprécier la transition qu’ont opérée ces enseignants entre un avant dans leur métier et un après dans l’enseignement ? Partant d’entrevues approfondies recueillies auprès d’une vingtaine d’enseignants de la formation professionnelle au secondaire, l’analyse porte sur les processus de transition professionnelle au regard des itinéraires des enseignants dans leur(s) métier(s) et en enseignement.
Peut-on modéliser les activités physiques en éducation physique et sportive en termes de problématisation ? L’exemple de la course de haies
Authors: Bas Alain Le 
Published: May 2021

Dans cet article, nous questionnerons les résultats d’une recherche antérieure en didactique de la course de haies (INRP, 1995)2 en mobilisant la théorie de la problématisation et essaierons de tester les hypothèses théoriques que constituent les cinq caractéristiques de la problématisation telles que les définit Michel Fabre : - un processus multidimensionnel, impliquant position, construction et résolution de problèmes, - une recherche de l’inconnu à partir du connu, - une dialectique de faits, d’idées, d’expériences et de théories, - une pensée contrôlée par des normes (intellectuelles, techniques, programmatiques), - une schématisation fonctionnelle du réel qui renonce à tout embrasser et à reproduire la réalité. Nous considérerons que le processus multidimensionnel représente la caractéristique de l’activité de problématisation dans la mesure où il en précise les différentes opérations, que « les normes prédéfinies » apparaissent comme des contraintes balisant le champ de la problématisation et que les autres items de la proposition originelle sont les conditions de la fonctionnalité du processus. L’adaptabilité des comportements moteurs s’exprime dans la capacité à identifier, à caractériser, à résoudre un problème, à stabiliser des réponses adaptées, à reconnaître un problème pour lequel on a une solution. Nous essaierons de voir comment en éducation physique, et précisément en course de haies, la prise en compte de la problématisation permet de repenser l’apprentissage et de l’opérationnaliser.
Situations et savoirs dans la pratique de classe
Authors: Rey Bernard 
Published: May 2021

Une idée très répandue dans le monde éducatif affirme que c’est en s’affrontant à des situations que les élèves apprennent. Le présent texte tente de saisir quelles caractéristiques il faut attribuer à la notion de situation pour donner cohérence à cette idée. Comment concevoir les situations pour que du rapport des élèves à elles, des savoirs puissent émerger ? Il analyse les difficultés ainsi rencontrées et fait apparaître la nature des relations entre les notions de situation, de compétence et de savoir. Il débouche sur l’importante distinction qu’il convient d’établir entre contexte et situation.
Du concept de situation dans les didactiques de l’histoire, de la géographie et de l’éducation à la citoyenneté
Authors: Audigier François 
Published: May 2021

Après avoir connu une fortune certaine dans son association avec le terme de problème, le concept de situation se voit à nouveau remis au premier rang des préoccupations didactiques avec l’arrivée des curriculums par compétences. Ces dernières appellent nécessairement une réflexion renouvelée sur les situations. En effet, les compétences sont construites et mises en œuvre en situation. Elles portent aussi sur des objets spécifiques. Ainsi, l’histoire, la géographie et l’éducation à la citoyenneté, principales disciplines de sciences sociales présentes à l’école obligatoire, étudient les actions humaines dans les sociétés présentes et passées. Le terme de situation renvoie donc à deux réalités différentes : la situation d’enseignement telle qu’elle est organisée et mise en œuvre par l’enseignant et la réalité sociale présente ou passée qui est étudiée. Dans ce texte, l’auteur dessine un parcours qui, depuis l’examen de quelques aspects des relations entre compétences et situations, le conduit à proposer deux fois deux distinctions pour décrire, comprendre et analyser les situations d’enseignement-apprentissage. Pour ce dernier moment, il s’appuie sur une recherche menée par une équipe de Suisse romande sur l’Education en vue du développement durable.
Manhunt : Unabomber : conversation avec une cabane, une boîte aux lettres et un feu tricolore
Authors: Espinosa Laurence 
Published: May 2021

Les séries TV peuvent devenir des « terrains » au sens anthropologique, dans un dialogue avec la philosophie de Stanley Cavell. Et ces terrains engagent la subjectivité du chercheur comme les autres terrains anthropologiques. Ainsi la série Manhunt : Unabomber dit Cavell dans ses mots, ses images et ses sons. La cabane, la boite aux lettres et le feu tricolore, personnages – objets, disent Henry David Thoreau, le scepticisme, le langage ordinaire, la voix ou le perfectionnisme moral. L’écran nous rapproche et nous perd au rythme de la conversation qui affleure.