bluuebunny/crossref_metadata_2025_split huggingface dataset:
Systematic variation of design aspects for a significant increase in thermal fracture resistance of alumina microthrusters
Authors: Åkerfeldt Erika , Klintberg Lena , Thornell Greger 
Published: June 2021

Abstract
Because of thermal stresses occurring upon rapid heating or cooling, microcomponents made from high-temperature co-fired ceramics (HTCC) often fail at temperatures far below what the materials can withstand per se. This work investigates how resistance to thermal fracture in HTCC microcomponents can be increased by improving the component design, aiming at increasing the thermal performance of a microthruster with integrated heaters. The effect of four design parameters: component and cavity geometries (circular or square), heater location (central or peripheral), and addition of embedded platinum layers, on thermal fracture resistance was investigated through a full factorial designed experiment. Components of different designs were manufactured, and their thermal fracture resistance tested by rapid heating until failure. Peripheral heater location and presence of embedded platinum layers were seen to improve resistance to thermal fracture, whereas the shape of the component and the cavity did not significantly affect thermal performance. The most favourable design was then used for a cold gas microthruster that was fabricated and evaluated with respect to thermal fracture resistance. The microthruster survived rapid heating up to 1460 °C and was operated as a cold gas thruster at temperatures up to 772 °C, which is more than twice the maximum temperatures previously reported for alumina microthrusters.
Riemannian geometry and automatic differentiation for optimization problems of quantum physics and quantum technologies
Authors: Luchnikov Ilia A , Krechetov Mikhail E , Filippov Sergey N 
Published: June 2021

Abstract
Optimization with constraints is a typical problem in quantum physics and quantum information science that becomes especially challenging for high-dimensional systems and complex architectures like tensor networks. Here we use ideas of Riemannian geometry to perform optimization on the manifolds of unitary and isometric matrices as well as the cone of positive-definite matrices. Combining this approach with the up-to-date computational methods of automatic differentiation, we demonstrate the efficacy of the Riemannian optimization in the study of the low-energy spectrum and eigenstates of multipartite Hamiltonians, variational search of a tensor network in the form of the multiscale entanglement-renormalization ansatz, preparation of arbitrary states (including highly entangled ones) in the circuit implementation of quantum computation, decomposition of quantum gates, and tomography of quantum states. Universality of the developed approach together with the provided open source software enable one to apply the Riemannian optimization to complex quantum architectures well beyond the listed problems, for instance, to the optimal control of noisy quantum systems.
On the primordial information available to galaxy redshift surveys
Authors: McQuinn Matthew 
Published: June 2021

Abstract
We investigate the amount of primordial information that can be reconstructed from spectroscopic galaxy surveys, as well as what sets the noise in reconstruction at low wavenumbers, by studying a simplified universe in which galaxies are the Zeldovich displaced Lagrangian peaks in the linear density field. For some of this study, we further take an intuitive linearized limit in which reconstruction is a convex problem but where the solution is also a solution to the full nonlinear problem, a limit that bounds the effectiveness of reconstruction. The linearized reconstruction results in similar cross correlation coefficients with the linear input field as our full nonlinear algorithm. The linearized reconstruction also produces similar cross correlation coefficients to those of reconstruction attempts on cosmological N-body simulations, which suggests that existing reconstruction algorithms are extracting most of the accessible information. Our approach helps explain why reconstruction algorithms accurately reproduce the initial conditions up to some characteristic wavenumber, at which point there is a quick transition to almost no correlation. This transition is set by the number of constraints on reconstruction (the number of galaxies in the survey) and not by where shot noise surpasses the clustering signal, as is traditionally thought. We further show that on linear scales a mode can be reconstructed with precision well below the shot noise expectation if the galaxy Lagrangian displacements can be sufficiently constrained. We provide idealized examples of nonlinear reconstruction where shot noise can be outperformed.
The effect of finite halo size on the clustering of neutral hydrogen
Authors: Umeh Obinna , Maartens Roy , Padmanabhan Hamsa , Camera Stefano 
Published: June 2021

Abstract
Post-reionisation 21cm intensity mapping experiments target the spectral line of neutral hydrogen (HI) resident in dark matter haloes. According to the halo model, these discrete haloes trace the continuous dark matter density field down to a certain scale, which is dependent on the halo physical size. The halo physical size defines an exclusion region which leaves imprints on the statistical properties of HI. We show how the effect of exclusion due to the finite halo size impacts the HI power spectrum, with the physical boundary of the host halo given by the splashback radius. Most importantly, we show that the white noise-like feature that appears in the zero-momentum limit of the power spectrum is exactly cancelled when the finite halo size is taken into consideration. This cancellation in fact applies to all tracers of dark matter density field, including galaxies. Furthermore, we show that the exclusion due to finite halo size leads to a sub-Poissonian noise signature on large scales, consistent with the results from N-body simulations.
Self-similar orbit-averaged Fokker-Planck equation for isotropic spherical dense clusters (iii) Application to Galactic globular clusters
Authors: Ito Yuta 
Published: June 2021

Abstract
Fitting parametric models to globular clusters’ structural profiles has been essential for the study of stellar dynamics. It provides their important structural parameters, such as the concentrations and core radii of the clusters. However, existing parametric models can apply only to non-collapsing-core clusters in the early relaxation-evolution stage. Hence, a single parametric model cannot provide globular clusters’ structural parameters in both the early and late evolution stages. We have recently found an accurate spectral solution for the self-similar orbit-averaged Fokker-Planck (OAFP) equation to model collapsingcore clusters at the late evolution stage. The present work establishes a new parametric model by combining the self-similar OAFP- and polytropic- models. Although it is a single-mass and isotropic model, the new model applies to at least fifty-five Galactic globular clusters with resolved cores in all the evolution stages. As a main result, we show the characteristics of the relaxation times against the concentrations of the clusters. We also affirm that the structures of low-concentration clusters are polytropic in the Milky Way.
A new class of viable and exact solutions of EFEs with Karmarkar conditions: an application to cold star modeling
Authors: Pant Neeraj , Govender Megandhren , Gedela Satyanarayana 
Published: June 2021

Abstract
In this work we present a theoretical framework within Einstein’s classical general relativity which models stellar compact objects such as PSR J1614–2230 and SAX J1808.4–3658. The Einstein field equations are solved by assuming that the interior of the compact object is described by a class I spacetime. The so-called Karmarkar condition arising from this requirement is integrated to reduce the gravitational behaviour to a single generating function. By appealing to physics we adopt a form for the gravitational potential which is sufficiently robust to accurately describe compact objects. Our model satisfies all the requirements for physically realistic stellar structures.
Physical and orbital properties of the stellar system HIP 43766
Authors: Widyan Hatem , Aljboor Hussam 
Published: June 2021

Abstract
In this paper, we present the analysis of the stellar binary system HIP 43766 to determine its properties. We rely on dynamical modeling and atmospheric modeling with recent data to determine the orbital solution and the physical properties of the system. There is a consistency between observed and synthetic photometry obtained using atmospheric modeling. The calculated dynamical mass sum of the system ranged between 1.691 and 2.609 solar masses, while it ranges between 2.0 and 2.1 as estimated utilizing atmospheric modeling. This could be due to inaccuracy in estimating the orbit, which could be modified with future observations with more relative positional measurements. The parameters of the system and the position of the components on the evolutionary tracks show that the system consists of F5 and G5 subgiant stars, mostly formed by fragmentation. A dynamical mass sum is predicted for the system.
Pollution tracks of r-process material in [Sr/Ba] vs. [Ba/Fe] space for the early Galaxy
Authors: Han Wan-Qiang , Yang Guo-Chao , Zhang Lu , Cui Wen-Yuan , Niu Ping , Wen Fang , Zhang Bo 
Published: June 2021

Abstract
In the early Galaxy, elemental abundances of the extremely metal-poor (EMP) stars contain abundant information about the neutron-capture nucleosynthesis and the chemical enrichment history. In this work, we study the abundance characteristics of Sr and Ba for the EMP stars in the [Sr/Ba] vs. [Ba/Fe] space. We find that there are three boundaries for the distribution region of the EMP stars. The weak r-process star CS 22897–008 lies on the upper end and the main r-process stars lie on the right end of the region. Near the right boundary of the distribution region, there is an Fe-normal belt. For the EMP stars in the belt, element Fe dominantly originates from the normal massive stars. The low-Sr stars ([Sr/Fe]≤−0.3) distribute in the region of the lower left of the Fe-normal belt and their Fe should originate partly from the prompt inventory. We find that the formation of the lower boundary of the distribution region is due to the pollution of the main r-process material and the formation of the right boundary could be explained by the combination of the weak r- and main r-process material. Furthermore, the formation of the left boundary is due to the pollution of the weak r-process material. Although the [Sr/Ba] ratios are related to the relative importance of the weak r-process material, the scatter of [Sr/Ba] ratios for the EMP stars mainly depends on the abundance ratio of the weak r-process.
Absolute parameters and observed flares in the M-type detached eclipsing binary 2MASS J04100497+2931023
Authors: Meng Gang , Zhang Li-Yun , Pi Qing-Feng , Long Liu , Han Xianming L. , Prabhakar Misra 
Published: June 2021

Abstract
The eclipsing binary 2MASS J04100497+2931023 (J04100497+2931023) is classified its spectral type of M0 ± 2V on basis of a low-resolution spectral survey by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). The low-resolution spectra exhibit strong single-peak emission in the Hα line. We obtained the radial velocities of this binary by means of the Cross-Correlation Function method from the LAMOST medium-resolution spectra. Both components of J04100497+2931023 indicate strong emissions in the Hα line. We performed follow-up photometric observations of J04100497+2931023 using the Xinglong 85 cm telescope of National Astronomical Observatories, Chinese Academy of Sciences. We obtained its full light curve in VRI filters. We first determined their absolute parameters from simultaneously radial velocity and light curves by the Wilson-Devinney program. From our new light curves, we detected three flares for the first time, including one convective flare. The amplitudes, durations, energies, and spectral indices of three flares were also determined. J04100497+2931023 was monitored for approximately 29 h, which indicates that the flare rate is 0.1 flare per hour. We conclude that J04100497+2931023 is a low-mass detached eclipsing binary with strong magnetic activity.
New open clusters found by manual mining of data based on Gaia DR2
Authors: Casado Juan 
Published: June 2021

Abstract
The physical nature of a series of 20 new open clusters is confirmed employing existing data on putative star members, mainly from the second Gaia Data Release (DR2). The clusters were discovered as overdensities of stars by visual inspection of either photographic DSS plates or proper motion plots of random source fields. The reported objects are not present in the most comprehensive or recent catalogs of stellar clusters and associations. For all of them, clumps of comoving stars are revealed in the proper motion space. The parallaxes of the clumped stars are compatible with the real existence of open clusters over narrow ranges of distances. Surface density calculations, free of most noise from non-member sources, allow differentiating a cluster core and an extended cluster corona in some instances. Color-magnitude diagrams generally show a definite main sequence that allows confirmation of the physical existence of the clusters and some of their characteristics. Two of the new clusters seem to form a double system with a common origin. Several of the new clusters challenge the claim of near completeness of the known OC population in the distance range from 1.0 to 1.8 kpc from the Sun (Kharchenko et al.).
Radio frequency interference detection based on the AC-UNet model
Authors: Yan Rui-Qing , Dai Cong , Liu Wei , Li Ji-Xia , Chen Si-Ying , Yu Xian-Chuan , Zuo Shi-Fan , Chen Xue-Lei 
Published: June 2021

Abstract
Radio frequency interference (RFI) is a serious issue in radio astronomy. This paper proposes a U-Net network model with atrous convolution to detect RFI. Using the ability of convolutional neural networks to extract image features of RFI, and learning RFI distribution patterns, the detection model of the RFI is established. We use observational data containing real RFIs obtained by the Tianlai telescope to train the model so that the model can detect RFI. Calculate the probability of a data point being RFI pixel by pixel, and set a threshold. At the same time the dropout layer was added to avoid overfitting problems. If the predicted probability of a data point exceeds the threshold, it is considered that there is RFI, and if the predicted probability of a data point does not exceed the threshold, then it is considered that there is no RFI, so that the part of the image with RFI is flagged. Experimental results show that this approach can achieve satisfactory accuracy in the detection of radio observation images with a small amount of RFI.
Methodology for in-flight flat-field calibration of the Lyman-alpha solar telescope (LST)
Authors: Li Jing-Wei , Li Hui , Li Ying , Feng Li , Huang Yu , Zhao Jie , Lu Lei , Ying Bei-Li , Xue Jian-Chao 
Published: June 2021

Abstract
Flat-field reflects the non-uniformity of the photometric response at the focal plane of an instrument, which uses digital image sensors, such as Charge Coupled Device (CCD) and Complementary Metal-Oxide-Semiconductor (CMOS). This non-uniformity must be corrected before being used for scientific research. In this paper, we assess various candidate methods via simulation using available data so as to figure the in-flight flat-field calibration methodology for the Lyman-alpha Solar Telescope (LST). LST is one of the payloads for the Advanced Space-based Solar Observatory (ASO-S) mission and consists of three instruments: a White-light Solar Telescope (WST), a Solar Disk Imager (SDI) and a dual-waveband Solar Corona Imager (SCI). In our simulations, data from the Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) mission are used. Our results show that the normal KLL method is appropriate for in-flight flat-field calibration of WST and implementing a transmissive diffuser is applicable for SCI. For the in-flight flat-field calibration of SDI, we recommend the KLL method with off-pointing images with defocused resolution of around 18″, and use the local correlation tracking (LCT) algorithm instead of limb-fitting to determine the relative displacements between different images.
The first photometric analysis and period investigation of the K-type W UMa type binary system V0842 Cep
Authors: Li Yu-Yang , Li Kai , Liu Yuan 
Published: June 2021

AbstractV0842 Cep is a W UMa-type binary star that has been neglected since its discovery. We analysed theVRcIclight curves, obtained by the 1 m telescope at Weihai Observatory of Shandong University, using the Wilson-Devinney code. V0842 Cep was found to be a shallow contact binary system (f= 8.7%) with a mass ratio of 2.281. Because its orbital inclination is greater than 80°, the photometric results are reliable. A period study is included which reveals a continually decreasing orbital period (dpdt= 1.50(±0.42)×10−7d yr−1). This trend could be attributed to the angular momentum loss via stellar wind.
The HI gas and star formation in star-forming galaxies selected from ALFALFA
Authors: Lei Feng-Jie , Wu Hong , Zhu Yi-Nan , Lam Man I. , Zhou Zhi-Min 
Published: June 2021

Abstract
This paper presents the results of Hα imaging of 169 galaxies randomly selected from the α.40 - SDSS catalog. The sample has excluded all low surface brightness galaxies (LSBGs) whose central surface brightness in B band (μ0(B)) fainter than 22.5 mag arcsec−2. It can be used as the counterparts sample to LSBGs. We observed their Hα and R band images by using the 2.16 m telescope at the Xinglong Observatory of the National Astronomical Observatories, Chinese Academy of Sciences (NAOC). The main goal of this work is to present the properties of those galaxies, together with Hα flux and star formation-, gas-, stellar mass- surface density. In addition, we confirm the correlations among HI content, stellar mass and star formation in ALFALFA galaxies. The HI mass increases with stellar mass, and the slope slows down at the higher stellar mass. The overall trend was that the specific star formation rate (sSFR) decreases with stellar mass, and the sSFR dropped sharply when the stellar mass is close to 1010.3 ∼ 1010.5
M
⊙. The weak correlation between SFR/MHI and M
HI implies the HI contribute little to star formation. Our sample, which are mostly star-forming galaxies, follows the revisited Kennicutt-Schmidt law as well as the Kennicutt-Schmidt law.
Spectral deconvolution analysis on Olivine-Orthopyroxene mixtures with simulated space weathering modifications
Authors: Han Hui-Jie , Lu Xiao-Ping , Jiang Te , Hsia Chih-Hao , Yang Ya-Zhou , Zhang Peng-Fei , Zhang Hao 
Published: June 2021

AbstractOlivine and pyroxene are important mineral end-members for studying the surface material compositions of mafic bodies. The profiles of visible and near-infrared spectra of olivine-orthopyroxene mixtures systematically vary with their composition ratios. In our experiments, we combine the RELAB spectral database with new spectral data obtained from some assembled olivine-orthopyroxene mixtures. We found that the commonly-used band area ratio (BAR, Cloutis et al.) does not work well on our newly obtained spectral data. To investigate this issue, an empirical procedure based on fitted results by a modified Gaussian model is proposed to analyze the spectral curves. Following the new empirical procedure, the end-member abundances can be estimated with a 15% accuracy with some prior mineral absorption features. In addition, the mixture samples configured in our experiments are also irradiated by pulsed lasers to simulate and investigate the space weathering effects. Spectral deconvolution results confirm that low-content olivine on celestial bodies is difficult to measure and estimate. Therefore, the olivine abundance of space weathered materials may be underestimated from remote sensing data. This study may be utilized to quantify the spectral relationship of olivine-orthopyroxene mixtures and further reveal their correlation between the spectra of ordinary chondrites and silicate asteroids.
Partitioning the Galactic halo with Gaussian Mixture Models
Authors: Liang Xi-Long , Chen Yu-Qin , Zhao Jing-Kun , Zhao Gang 
Published: June 2021

AbstractThe Galactic halo is supposed to form from merging with nearby dwarf galaxies. In order to probe different components of the Galactic halo, we have applied the Gaussian Mixture Models method to a selected sample of metal poor stars with [Fe/H] < –0.7 dex in the APOGEE DR16 catalogue based on four-parameters, metallicity, [Mg/Fe] ratio and spatial velocity (VR,Vϕ). Nine groups are identified with four from the halo (group 1, 3, 4 and 5), one from the thick disk (group 6), one from the thin disk (group 8) and one from dwarf galaxies (group 7) by analyzing their distributions in the ([M/H], [Mg/Fe]), (VR,Vϕ), (Zmax,eccentricity), (Energy,Lz) and ([Mg/Mn], [Al/Fe]) coordinates. The rest of the two groups are respectively caused by observational effect (group 9) and the cross section component (group 2) between the thin disk and the thick disk. It is found that in the extremely outer accreted halo (group 1), stars born in the Milky Way cannot be distinguished from those accreted from other galaxies either chemically or kinematically. In the intermediate metallicity of −1.6 < [Fe/H] < –0.7 dex, the accreted halo is mainly composed of the Gaia-Enceladus-Sausage substructure (group 5), which can be easily distinguished from group 4 (the in-situ halo group) in both chemical and kinematic space. Some stars of group 4 may come from the disk and some disk stars can be scattered to high orbits by resonant effects as shown in theZmaxversus Energy coordinate. We also displayed the spatial distribution of main components of the halo and the ratio of accreted components do not show clear relation to the Galactic radius.
Time Borrowing Flip-Flop architecture for error masking in near threshold voltage regime
Authors: Raj Abhinav , Arora Diwakar , Chaurasia Aman , Indu S. 
Published: June 2021

Abstract
This As dynamic delay variability increases with near-threshold voltage operation, wide timing margins need to be integrated in DVFS (Dynamic Voltage and Frequency Scaling) when deciding the frequency of operation to ensure reliable and error-free operation. Hence the maximum frequency (which is already low) in near-threshold operation is limited by these timing margins. Online methodologies for the resilience of temporal arrangement errors facilitate the recovery of temporal arrangement margins, increasing efficiency and/or energy consumption. This study presents a method for the resilience of online temporal arrangement errors that masks temporal arrangement errors by borrowing time from the phases of serial pipelines. Planned style, while not instruction replay or roll-back support, will recover temporal arrangement margins.