bluuebunny/crossref_metadata_2025_split huggingface dataset:
The relationship between solid–liquid interface interaction and gelling capacity of h-BN 2D material: a rheological study
Authors: Zhang Ruochong , Cao Wenhui , Xia Yu , Zhang Haojie , Ding Qi , Xu Xuefeng , Hu Litian 
Published: December 2021

Abstract
Diurea modified h-BN nanosheet is a novel kind of 2D gelator that could gel the lubricating oils under the stimulus of ultrasound. Morphological analyzations in previous study confirmed that the ultrasound induced layer-by-layer (LBL) structure of BN gelator is critical for the gelation. However, the elastic response in LBL structure, which is crucial for the formation of a stable gel system, has not been explicitly illustrated yet. The challenge is that the LBL gelator structure is based on 2D material and thus lacks vertical linkage between gelator layers, which is significantly different from the traditional gel systems that generally possess highly crosslinked gelator network. In this work, by investigating the viscoelastic behavior of the BN-based gel via rheometer, it is found the solid–liquid interface interaction, which is regulated by the diurea molecular structure in the BN gelator, is the key factor for triggering the stable elastic response in the LBL structure, and the elasticity mainly originates from the interface interaction induced bending deformation of h-BN 2D material. The findings further elucidate the gelling mechanism of BN gelators and enlighten the structure design of ultrasound-responsive gelator based on 2D materials.
Prior knowledge of potential energy and the understanding of quantum mechanics
Authors: Krijtenburg-Lewerissa Kim , Pol Henk , Brinkman Alexander , van Joolingen Wouter 
Published: December 2021

Abstract
Quantum mechanics (QM) has become part of many secondary school curricula. These curricula often do not include the mathematical tools for a formal, mathematical introduction of QM. QM therefore needs to be taught at a more conceptual level, but making secondary school students understand counterintuitive QM concepts without introducing mathematical formalism is a challenge. In order to accept QM, students not only have to see the need of it, but also have to see that QM is understandable and logical. Dutch secondary school students are familiar with potential energy (PE) in the context of gravitational and elastic energy. Therefore, the introduction of QM by using the potential wells and tunneling with emphasis on students’ prior knowledge of PE could be a way to make QM more understandable and logical. To explore this, we investigated the relation between the understanding of energy diagrams and the understanding of the potential well and tunneling. A module was created to promote students’ understanding of PE in classical context. Then, a quasi-experimental intervention was used, in which the experimental group received additional lessons using the module on classical energy diagrams before being taught QM. Two tests were developed in order to determine students’ understanding of PE and QM. The results of the tests showed that the experimental group not only had better understanding of PE diagrams, but also of QM even before they were being taught QM. Analysis of the tests also showed that there was a significant correlation between the understanding of PE diagrams and the understanding of QM. Therefore, the results of this study indicate that emphasis on PE can be used to reduce the gap between students’ prior knowledge and QM.
We know the way: learning the secrets of celestial navigation from ancient travellers
Authors: Spathopoulos Vassilios McInnes 
Published: December 2021

Abstract
Educators are constantly looking for new ways to inspire students to actively engage with science. Learning how to navigate by using the stars, sun and moon can be one of the first steps for pupils, students and the general public to cultivate an interest in astronomy. With this in mind, an online platform based on the Google Earth and Stellarium software has been developed. It presents basic celestial navigation techniques that were first devised and deployed by the ancient Phoenicians and Greeks, the Vikings and the Polynesian travellers. Both software applications are free to use and are available in web versions, making them easily accessible to anyone with an internet connection. The user undertakes a set of predefined tasks that take him/her on a fascinating journey both around the world and back in time.
Spatial aspects of spin polarization of structurally split surface states in thin films with magnetic exchange and spin–orbit interaction
Authors: Nechaev I A , Krasovskii E E 
Published: December 2021

Abstract
A theoretical study is presented of the effect of an in-plane magnetic exchange field on the band structure of centrosymmetric films of noble metals and topological insulators. Based on an ab initio relativistic k ⋅ p theory, a minimal effective model is developed that describes two coupled copies of a Rashba or Dirac electronic system residing at the opposite surfaces of the film. The coupling leads to a structural gap at

Γ

¯

and causes an exotic redistribution of the spin density in the film when the exchange field is introduced. We apply the model to a nineteen-layer Au(111) film and to a five-quintuple-layer Sb2Te3 film. We demonstrate that at each film surface the exchange field induces spectrum distortions similar to those known for Rashba or Dirac surface states with an important difference due to the coupling: at some energies, one branch of the state loses its counterpart with the oppositely directed group velocity. This suggests that a large-angle electron scattering between the film surfaces through the interior of the film is dominant or even the only possible for such energies. The spin-density redistribution accompanying the loss of the counterpart favors this scattering channel.
Synchronization or cluster synchronization in coupled Van der Pol oscillators networks with different topological types
Authors: Shuai Wang , Yong Li 
Published: December 2021

Abstract
In this paper, we discuss the mechanism of synchronization or cluster synchronization in the coupled van der Pol oscillator networks with different topology types by using the theory of rotating periodic solutions. The synchronous solutions here are transformed into rotating periodic solutions of some dynamical systems. By analyzing the bifurcation of rotating periodic solutions, the critical conditions of synchronous solutions are given in three different networks. We use the rotating periodic matrix in the rotating periodic theory to judge various types of synchronization phenomena, such as complete synchronization, anti-phase synchronization, periodic synchronization, or cluster synchronization. All rotating periodic matrices which satisfy the exchange invariance of multiple oscillators form special groups in these networks. By using the conjugate classes of these groups, we obtain various possible synchronization solutions in three networks. In particular, we find symmetry has different effects on synchronization in different networks. The network with more types of symmetry has more elements in the corresponding group, which may have more types of synchronous solutions. However, different types of symmetry may get the same type of synchronous solutions or different types of synchronous solutions, depending on whether their corresponding rotating periodic matrices are similar.
Exploring physical features of anisotropic quark stars in Brans-Dicke theory with a massive scalar field via embedding approach *
Authors: Errehymy Abdelghani , Mustafa G. , Khedif Youssef , Daoud Mohammed 
Published: December 2021

Abstract
The main aim of this study is to explore the existence and salient features of spherically symmetric relativistic quark stars in the background of massive Brans-Dicke gravity. The exact solutions to the modified Einstein field equations are derived for specific forms of coupling and scalar field functions using the equation of state relating to the strange quark matter that stimulates the phenomenological MIT-Bag model as a free Fermi gas of quarks. We use a well-behaved function along with the Karmarkar condition for class-one embedding as well as junction conditions to determine the unknown metric tensors. The radii of strange compact stars viz., PSR J1416-2230, PSR J1903+327, 4U 1820-30, CenX-3, and EXO1785-248, are predicted via their observed mass for different values of the massive Brans-Dicke parameters. We explore the influences of the mass of scalar field

, coupling parameter

, and bag constant

on state determinants and perform several tests on the viability and stability of the constructed stellar model. Conclusively, we find that our stellar system is physically viable and stable as it satisfies all the energy conditions and necessary stability criteria under the influence of a gravitational scalar field.
Investigation of the relation between space-weather parameters and Forbush decreases automatically selected from Moscow and Apatity cosmic ray stations during solar cycle 23
Authors: Alhassan Jibrin Adejoh , Okike Ogbonnaya , Chukwude Augustine Ejikeme 
Published: December 2021

Abstract
We present the results of an investigation of the relation between space-weather parameters and cosmic ray (CR) intensity modulation using algorithm-selected Forbush decreases (FDs) from Moscow (MOSC) and Apatity (APTY) neutron monitor (NM) stations during solar cycle 23. Our FD location program detected 408 and 383 FDs from MOSC and APTY NM stations respectively. A coincident computer code employed in this work detected 229 FDs that were observed at the same Universal Time (UT) at the two stations. Out of the 229 simultaneous FDs, we formed a subset of 139 large FDs(%) ≤ − 4 at the MOSC station. We performed a two-dimensional regression analysis between the FD magnitudes and the space-weather data on the two samples. We find that there were significant space-weather disturbances at the time of the CR flux depressions. The correlation between the space-weather parameters and decreases in galactic cosmic ray (GCR) intensity at the two NM stations is statistically significant. The implications of the present space-weather data on CR intensity depressions are highlighted.
Simulation analysis of a method to improve data-transmission performance of Nanshan 26m Radio Telescope based on Software-Defined Networks
Authors: Wang Jie , Zhang Hai-Long , Wang Na , Ye Xin-Chen , Wang Wan-Qiong , Li Jia , Zhang Meng , Zhang Ya-Zhou 
Published: December 2021

Abstract
Data Center of Xinjiang Astronomical Observatory (XAO-DC) commenced operating in 2015, and provides services including archiving, releasing and retrieving precious astronomical data collected by the Nanshan 26m Radio Telescope (NSRT) over the years, and realises the open sharing of astronomical observation data. The observation data from NSRT are transmitted to XAO-DC 100 km away through dedicated fiber for long-term storage. With the continuous increase of data, the static architecture of the current network cannot meet NSRT data-transmission requirements due to limited network bandwidth. To get high-speed data-transmission using the existing static network architecture, a method for reconstruction data-transmission network using Software-Defined Networks (SDN) is proposed. Benefit from the SDNʼs data and control plane separation, and open programmable, combined with the Mininet simulation platform for experiments, the TCP throughput (of single thread) was improved by ∼24.7%, the TCP throughput (of multi threads) was improved by ∼9.8%, ∼40.9%, ∼35.5% and ∼11.7%. Compared with the current network architecture, the Latency was reduced by ∼63.2%.
LAMOST medium-resolution spectral survey of Galactic nebulae (LAMOST-MRS-N): subtraction of geocoronal Hα emission
Authors: Zhang Wei , Wu Hong , Wu Chao-Jian , Ren Juan-Juan , Chen Jian-Hun , Hsia Chih-Hao , Wu Yu-Zhong , Zhu Hui , Shi Jian-Rong , Bai Zhong-Rui , Qi Zhao-Xiang , Zhao Yong-Heng , Hou Yong-Hui 
Published: December 2021

Abstract
We introduce a method of subtracting geocoronal Hα emissions from the spectra of LAMOST medium-resolution spectral survey of Galactic nebulae (LAMOST-MRS-N). The flux ratios of the Hα sky line to the adjacent OH λ6554 single line do not show a pattern or gradient distribution in a plate. More interestingly, the ratio is well correlated to solar altitude, which is the angle of the Sun relative to the Earthʼs horizon. It is found that the ratio decreases from 0.8 to 0.2 with the decreasing solar altitude from –17 to –73 degree. Based on this relation, which is described by a linear function, we can construct the Hα sky component and subtract it from the science spectrum. This method has been applied to the LAMOST-MRS-N data, and the contamination level of the Hα sky to nebula is reduced from 40% to less than 10%. The new generated spectra will significantly improve the accuracy of the classifications and the measurements of physical parameters of Galactic nebulae.
X-ray source population in the polar ring galaxy NGC 660 as observed by Chandra
Authors: Nazri Nurnabilah , Annuar Adlyka 
Published: December 2021

Abstract
We present Chandra observations of the nearby polar ring galaxy NGC 660 to study its X-ray source population. Based on our analysis, we detected a total of 23 X-ray sources in the 0.5−8 keV band, with luminosities ranging from ∼1037 to ∼1039 erg s−1. Twenty-two of these sources are located off-nuclear and have luminosities below the ultraluminous X-ray source (ULX) threshold value of L
0.5−8 keV < 1039 erg s−1, suggesting that they are likely to be X-ray binary (XRB) candidates. The remaining source is located at the center of the galaxy, suggesting it is an active galactic nucleus (AGN). However, we estimated that four of the detected sources could be associated with background objects. Based on the source count rates in each of the Chandra observations, we found evidence for variability in nine of the 23 sources, including the AGN. However, further investigation with spectral analysis suggested no significant differences in the AGN luminosities between the observations. The X-ray luminosity distribution of the galaxy was found to be generally lower than that expected from previous studies on star forming and collisional ring galaxies. No ULX was also detected in the galaxy, in contrast with what was expected from the galaxyʼs SFR and metallicity (i.e., SFR = 14.43 ± 0.19 M
⊙ yr−1 and Z = 0.94 ± 0.01 Z
⊙, respectively). These results suggest a deficit in the X-ray sources detected. Based on source hardness ratio distribution, we found evidence that the fainter sources have a harder source spectrum, indicating higher absorption. This further suggests that there could be more X-ray sources that were not detected in the galaxy due to significant obscuration.
New photometric studies for two deep, low-mass ratio overcontact binaries: Y Sex and V1363 Ori
Authors: Yang Yuan-Gui , Wang Shuang , Yuan Hui-Yu , Dai Hai-Geng 
Published: December 2021

Abstract
We present new photometry for two contact binaries, Y Sex and V1363 Ori, which were observed by three small telescopes in China. By using the W-D method, the absolute parameters are updated from new BVR light curves and previous radial velocity curves. Results identify that two binaries are deep, low-mass ratio (DLMR) overcontact binaries with q ⩽ 0.25 and f ⩾ 50%. From the temperature-luminosity diagram, the primary components are slightly evolved main-sequence stars, whose evolutionary ages are ∼2.51 Gyr for Y Sex and ∼3.56 Gyr for V 1363 Ori, respectively. From the (O − C) curves, it is found that the orbital periods may be undergoing secular increase with cyclic variations, which may be interpreted either by magnetic activity cycles or by the light-time orbit effect. With period increasing, this kind of DLMR overcontact binaries, such as Y Sex and V1363 Ori, will evolve into the rapid-rotating single stars.
What causes the absence of pulsations in Central Compact Objects in supernova remnants?
Authors: Wu Qi , Pires Adriana M. , Schwope Axel , Xiao Guang-Cheng , Yan Shu-Ping , Ji Li 
Published: December 2021

Abstract
Most young neutron stars belonging to the class of Central Compact Objects (CCOs) in supernova remnants do not have known periodicities. We investigated seven such CCOs to understand the common reasons for the absence of detected pulsations. Making use of XMM-Newton, Chandra, and NICER observations, we perform a systematic timing and spectral analysis to derive updated sensitivity limits for both periodic signals and multi-temperature spectral components that could be associated with radiation from hotspots on the neutron star surface. Based on these limits, we then investigated for each target the allowed viewing geometry that could explain the lack of pulsations. We find that it is unlikely (< 10−6) to attribute that we do not see pulsations to an unfavorable viewing geometry for five considered sources. Alternatively, the carbon atmosphere model, which assumes homogeneous temperature distribution on the surface, describes the spectra equally well and provides a reasonable interpretation for the absence of detected periodicities within current limits. The unusual properties of CCOs with respect to other young neutron stars could suggest a different evolutionary path, as that proposed for sources experiencing episodes of significant fallback accretion after the supernova event.
Method for differential phase delay resolution of phase referencing VLBI technique and its experimental verification
Authors: Zhou Huan , Yan Jian-Guo , Xu De-Zhen , Huang Yong , Li Hai-Tao 
Published: December 2021

Abstract
The phase referencing Very Long Baseline Interferometry (VLBI) technique is a newly developed tool to measure the angular position of a deep space exploration probe in the plane-of-the-sky. Through alternating observations between the probe and a nearby reference radio source, their accurate relative angular separation can be obtained from the radio images generated by this technique. To meet the requirements of the current orbit determination software, differential delay should be firstly derived from those radio images. A method to resolve the differential phase delay from the phase referencing VLBI technique is proposed in this paper, and as well the mathematical model for differential phase ambiguity resolution is established. This method is verified with practical measurement data from the Chang’E-3 mission. The differential phase delay between the Chang’E-3 lander and rover was derived from the phase referencing VLBI measurements, and was then imported into the Shanghai astronomical observatory Orbit Determination Program (SODP) to calculate the position of the rover relative to the lander on the lunar surface. The results are consistent with those acquired directly from radio images, indicating that the differential phase ambiguity has been correctly resolved. The proposed method can be used to promote applications of the phase referencing VLBI technique in future lunar or deep space explorations, and more accurate orbit determination becomes promising.
Crystallization and mechanical properties of carbon nanotube/continuous carbon fiber/metallocene polypropylene composites
Authors: Tan Hongsheng , Guo Xiuxue , Tan Hao , Zhang Qinglu , Liu Changheng , Shen Penghui , Qiao liang , Yan Xu , Jing Liyue 
Published: December 2021

Abstract
In this work, a high fluidity polypropylene prepared with the metallocene catalyst (mPP) was used as matrix, carbon nanotube (CNT) and continuous carbon fiber (CCF) were added to prepare composites, and their mechanical properties, melting and crystallization behavior were investigated. In the mechanical properties, the effects of tension force in the preparation process and compatibilizer maleic anhydride grafted polypropylene (MAPP) on the tensile strength of the composites were researched. The results show that the tensile strength of the composites increases first and then decreases with the increase of tractive force. In addition, the melting and crystallization behaviors and dynamic mechanical behaviors of mPP, CNT/mPP and CNT/CCF/mPP composites were characterized and studied by a differential scanning calorimetry (DSC) and dynamic mechanical analyzer (DMA). The results show that the melting point (T
m), crystallization temperature (T
c) and storage modulus (E′) of CNT/mPP are all increased by adding 1 wt% CNT, especially the T
c is increased by 8.8 °C. It shows that after CNT was added to mPP as inorganic carbon material, it plays a prominent role in heterogeneous nucleation. After CCF was composited with CNT/mPP, the composites with CCF content of 30 and 42 wt% were prepared, and their T
m, T
c, crystallinity (X
c) and E′ were all improved, especially E′ was greatly improved, such as the initial E′ was increased by 5.64 and 11.74 times. Even at the end of the curve, the E′ of the composites with CF is still significantly higher than that of mPP and CNT/mPP. It indicates that adding CCF will greatly improved the deformation resistance and load deformation temperature of mPP.
Prediction of permeability of five-harness satin fabric by a modified Kozeny constant determined from experiments
Authors: Park Dong-Cheol , Yu Tianyu , Park Soo-Jeong , Shin Do-Hoon , Kim Yun-Hae 
Published: December 2021

Abstract
Permeability is a critical parameter not only in flow simulation analysis but also in liquid composite molding process. When a liquid resin is infused into a dry preform, the impregnation is mainly characterized by the permeability. The permeability of a dry preform can be obtained through theoretical and experimental methods. In the theoretical estimation of permeability, the effects of fiber arrangement as well as fabric type and form for various types of preforms are not sufficiently reflected in the calculation. Thus, there is a gap between the theoretical and experimental permeability. Recently, experimental determination has been gaining considerable attention as a mean to obtain accurate permeability values; however, it requires a number of trials. In this study, the permeability of the Hexforce G0926 5HS (five-harness satin) carbon fabric preform is estimated using representative theoretical prediction models, the Gebart and Kozeny–Carman equations. In addition to the Kozeny–Carman permeability (using the Kozeny constant values from literature), the Kozeny constant obtained through experiments was used to obtain a modified Kozeny–Carman permeability. All three calculated permeabilities were compared and verified with the fabric manufacturer’s reference value. The results showed that the modified Kozeny–Carman permeability using the experimentally determined Kozeny constant was closest to the reference value at 57% fiber volume fraction. Further, the predicted permeability was compared with other experimental permeability values from literature over the 40%–65% range of fiber volume fraction. We found that the modified Kozeny–Carman permeability once again came closest to the literature values. Finally, an optimized fitting equation was proposed to replace the Kozeny–Carman equation for predicting the permeability of Hexforce G0926 5HS carbon fabric over the 40%–65% fiber volume fraction range.