bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the alidade thermal behavior on the pointing accuracy of a large radio telescope
Authors: Wei Shan-Xiang , Kong De-Qing , Wang Qi-Ming 
Published: August 2021

Abstract
The alidade’s non-uniform temperature field of a large radio telescope is very obvious under solar radiation. Estimating a radio telescope’s pointing errors, caused by the alidade deformation under solar radiation, is significant to improve the telescope’s pointing accuracy. To study the effect of the alidade thermal behavior on the pointing accuracy of a large radio telescope, a temperature experiment is first carried out in a 70-m radio telescope on a sunny day. According to the measured results, the temperature distribution rule of the alidade is summarized initially. In addition, the alidade’s temperature field is calculated by finite element thermal analysis. The simulated results are proved to be in good agreement with the experimental results. Finally, the alidade deformation under solar radiation is computed by finite element thermal-structure coupling analysis. The telescope’s pointing errors caused by alidade deformation are estimated via the alidade’s node displacements. The final results show that the effect of alidade thermal behavior on the telescope’s elevation pointing errors Δ ε
2 + Δ εr
is much more than the effect on the telescope’s cross-elevation pointing errors Δ ε
1. The maximum of Δ ε
2 + Δ εr
is more than 45″, while the maximum of Δ ε
1 is less than 6″. This study can provide valuable references for improving the pointing accuracy of large radio telescopes.
A triplet of the only pulsation mode detected in the DAV star G132–12
Authors: Su Wen-Chao , Fu Jian-Ning , Chen Jian-Xing , Fox-Machado Lester , Zhao Shi-Jie , Ayala-Loera Carmen , Wang Jiang-Tao , Pan Yang 
Published: August 2021

Abstract
Hydrogen atmosphere pulsating white dwarfs, also known as DAV stars, are the most abundant type of pulsating white dwarfs. High-temperature DAV stars in general exhibit a small number of pulsation modes and stable frequencies. G132–12 is one of the pulsating hydrogen atmosphere white dwarf stars which lies close to the blue edge of the instability strip. Previous researches reported that G132–12 might have only one pulsation mode with the period of 212.69 s. To study the pulsation properties of G132–12 in detail, we carried out a bi-site observation campaign in October 2019. Time series photometric data were collected during around 154 h in total. A Fourier analysis reveals three frequencies which are identified as the triplet of an l = 1 g-mode pulsation with the period of 212.499 s. The rotational period is derived as P
rot = 35.0 ± 6.7 h and the inclination of the rotational axis to the line of sight is 70°. G132–12 could be an ideal target for measuring the cooling scale of this white dwarf star with only one excited pulsation mode detected.
Effects of solar radiation pressure on asteroid surface hopping transfers for high area/mass ratio rovers
Authors: Dong Chuan-Jun , Yang Hong-Wei , Li Shuang , Liu Xue-Wen 
Published: August 2021

Abstract
The high area/mass ratio hopping rovers have potential applications in future asteroid surface exploration. This paper systematically investigates the effects of solar radiation pressure (SRP) on ballistic surface hopping transfers for the asteroid 101955 Bennu. Effects of SRP on the traveled distance and the trajectory design of hopping transfers are analyzed and summarized. The simulation results indicate that it is necessary to take SRP into account to ensure the success of hopping transfers and the proper use of SRP can help design the trajectories of hopping transfers with low initial impulses and short transfer times. It also reveals the potential possibility in using SRP to control the post-hopping transfers with specific control policies in the future surface exploration of asteroids.
Correction of the temperature effect in calibration of a solar radio telescope
Authors: Geng Li-Hong , Tan Cheng-Ming , Yan Yi-Hua , Tan Bao-Lin , Liu Dong-Hao , Dun Jin-Ping 
Published: August 2021

AbstractThis work analyzes the annual fluctuation of the observation data of the Mingantu Solar radio Telescope (MST) in S, C and X bands. It is found that the data vary with local air temperature as the logarithmic attenuation of equipment increases with temperature and frequency. A simplified and effective calibration method is proposed, which is used to calibrate the MST data in 2018–2020, while the correction coefficients are calculated from data in 2018–2019. For S, C and X bands, the root mean square errors of one polarization are 2.7, 5.7 and 20 sfu, and the relative errors are 4%, 6% and 8% respectively. The calibration of MUSER and SBRS spectra is also performed. The relative errors of MUSER at 1700 MHz, SBRS at 2800 MHz, 3050 MHz and 3350 MHz are 8%, 8%, 11% and 10% respectively. We found that several factors may affect the calibration accuracy, especially at X-band. The method is expected to work for other radio telescopes with similar design.
A study on universal observation control system and its application for LAMOST
Authors: Wang Zheng , Tian Yuan , Li Jian , Cao Zi-Huang , Zhao Yong-Heng 
Published: August 2021

Abstract
The observatory control system (OCS), a part of automated control of Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST), runs on the CentOS6 platform and implements the communication between modules based on Common Object Request Broker Architecture (CORBA). However, CORBA is complicated and has limited development support; moreover, the official support for CentOS6 has ended. OCS inherently has some shortcomings such as the over-concentration of control and the blocking of device status processing, which hinder the realization of automated observation control of LAMOST. Therefore, this study designs and implements a universal observation control system (UOCS) for optical telescopes. The UOCS takes the device command as the basic execution unit, controls the device execution logic using observation script, controls the observation logic by event-driven messaging, and realizes mutual decoupling between modules via a distributed control mode, thereby ensuring high system robustness. The UOCS performs significantly better than OCS in terms of the observation performance, operator complexity, and communication error. Currently, UOCS is applied to the automated control of some devices and subsystems in LAMOST observation. It will be applied to the automated observation control of Multi-channel Photometric Survey Telescope by 2021.
Analysis and compensation of the reflector antenna pointing error under wind disturbance
Authors: Xu Qian , Zhang Jie , Wang Zhao-Yu , Pan Huan-Zhi 
Published: August 2021

Abstract
A large reflector antenna has been widely used in satellite communications, gravitational wave detection, galaxy origin observation and other fields due to its narrow beam and high gain. With the increase of the antenna aperture and the improvement of the working frequency, the requirements for the pointing accuracy of an antenna are also rising. However, the effect of environmental load on the deformation of the antenna structure, which in turn affects its beam pointing, has become a key problem to be solved urgently in the antenna engineering applications. The key issue to solving this problem involves accurately estimating the pointing error caused by the structural deformation and designing an effective controller that is based on the structural deformation. In this paper, we first establish a dynamic model for antenna structure based on the modal superposition method. The model is then modified by using modal characteristics and the dynamic displacement information of the sampling points to achieve the purpose of accurately estimating the structural deformation. Secondly, by considering the influence of the deformation of the rotating shaft and the reflector surface on the pointing accuracy, a control-oriented pointing error analysis model is established for estimating the pointing error caused by the environmental load in real time. Thirdly, based on considering the influence of the shaft deformation on the error compensation, the feedback error amount is decoupled and corrected to improve the accuracy of the compensation error. Finally, this paper analyzes and verifies the 65 m S/X-band dual reflector antenna with a numerical example. We consider a fluctuating wind with an average wind speed of 10 m s−1 as an example, which results in a maximum pointing error of 55.82″ as calculated by the antenna theoretical model, whereas the maximum pointing error as predicted by our model is 68.27″. The pointing error after compensating for the cause of the environmental load with the modified controller is reduced to 10.57″, which effectively improves the antenna pointing performance.
Stellar dynamical modeling - accuracy of 3D density estimation for edge-on axisymmetric galaxies
Authors: Long Richard J. , Lu Sheng-Dong , Xu Dan-Dan 
Published: August 2021

Abstract
From Rybicki’s analysis using the Fourier slice theorem, mathematically it is possible to reproduce uniquely an edge-on axisymmetric galaxy’s 3D light distribution from its 2D surface brightness. Utilizing galaxies from a cosmological simulation, we examine the ability of Syer and Tremaine’s made-to-measure method and Schwarzschild’s method for stellar dynamical modeling to do so for edge-on oblate axisymmetric galaxies. Overall, we find that the methods do not accurately recover the 3D distributions, with the made-to-measure method producing more accurate estimates than Schwarzschild’s method. Our results have implications broader than just luminosity density, and affect other luminosity-weighted distributions within galaxies, for example, age and metallicity.
High-α-Metal-Rich stars in the LAMOST-MRS survey and its connection with the galactic bulge
Authors: Zhang Hao-Peng , Chen Yu-Qin , Zhao Gang , Zhao Jing-Kun , Liang Xi-Long , Li Hai-Ning , Wu Ya-Qian , Luo Ali , Wang Rui 
Published: August 2021

Abstract
We report the detection of a large sample of high-α-metal-rich stars on the low giant branch with 2.6 < log g < 3.3 dex in the LAMOST-MRS survey. This special group corresponds to an intermediate-age population of 5 – 9 Gyr based on the [Fe/H]-[C/N] diagram and age-[C/N] calibration. A comparison group is selected to have a solar α ratio at super metallicity, which is young and has a narrow age range around 3 Gyr. Both groups have thin-disk like kinematics but the former shows slightly large velocity dispersions. The special group shows a larger extension in a vertical distance toward 1.2 kpc, a second peak at smaller Galactic radius and a larger fraction of super metal rich stars with [Fe/H] > 0.2 than the comparison group. These properties strongly indicate its connection with the outer bar/bulge region at R = 3 – 5 kpc. A tentative interpretation of this special group is that its stars were formed in the X-shaped bar/bulge region, close to its corotation radius, where radial migration is the most intense, and brings them to present locations at 9 kpc and beyond. Low eccentricities and slightly outward radial excursions of its stars are consistent with this scenario. Its kinematics (cold) and chemistry ([α/Fe] ∼ 0.1) further support the formation of the instability-driven X-shaped bar/bulge from the thin disk.
Overview of the results from divertor experiments with attached and detached plasmas at Wendelstein 7-X and their implications for steady-state operation
Authors: Jakubowski M. , Endler M. , Feng Y. , Gao Y. , Killer C. , König R. , Krychowiak M. , Perseo V. , Reimold F. , Schmitz O. , Pedersen T.S. , Brezinsek S. , Dinklage A. , Drewelow P. , Niemann H. , Otte M. , Gruca M. , Hammond K. , Kremeyer T. , Kubkowska M. , Jabłoński S. , Pandey A. , Wurden G. , Zhang D. , Bozhenkov S. , Böckenhoff D. , Dhard C.P. , Baldzuhn J. , Gradic D. , Effenberg F. , Kornejew P. , Lazerson S. , Lore J. , Naujoks D. , Puig Sitjes A , Schlisio G. , Ślęczka M. , Wenzel U. , Winters V. , the W7-X Team  
Published: August 2021

Abstract
Wendelstein 7-X (W7-X), the largest advanced stellarator, is built to demonstrate high power, high performance quasi-continuous operation. Therefore, in the recent campaign, experiments were performed to prepare for long pulse operation, addressing three critical issues: the development of stable detachment, control of the heat and particle exhaust, and the impact of leading edges on plasma performance. The heat and particle exhaust in W7-X is realized with the help of an island divertor, which utilizes large magnetic islands at the plasma boundary. This concept shows very efficient heat flux spreading and favourable scaling with input power. Experiments performed to overload leading edges showed that the island divertor yields good impurity screening. A highlight of the recent campaign was a robust detachment scenario, which allowed reducing power loads even by a factor of ten. At the same time, neutral pressures at the pumping gap entrance yielded the particle removal rate close to the values required for stable density control in steady-state operation.
A study on aluminum metal matrix preforms forging into double-hub flange
Authors: Agrawal M , Singh S 
Published: August 2021

Abstract
The present article presents investigation of deformation characteristics during forging (closed-die) of SiCp AMC. The preform (cylindrical) fabricated via liquid metal stir casting manufacturing route were located centrally in closed-die set with respect to its axis and forged into axi-symmetric double-hub flange component. Initial experiments were conducted to examine the mechanical characterization of the AMC preforms under consideration, which also included investigations into interfacial frictional conditions and stress-strain behaviour of the AMC material. Under a controlled die-travel till the die corners were filled completely, during forging of the preforms, corresponding height reductions and die loads were recorded. The complete deformations were considered in two stages, i.e. free barreling and constrained distortion stages. The theoretical expressions (generalized using ‘Upper Bound’ technique) for strain rates, velocity field, various energy dissipations along with average die loads for all the deformation modes considered in the present study were formulated. The variation in die loads, die cavity fills and energy dissipations due to the effect of preform aspect ratio and die velocity were critically examined and experimentally compared the results.
An Acquaintance to Text-Steganography and its Methods
Authors: Singh A P , Moudgil S , Rani S 
Published: August 2021

Abstract
In this research paper discussion will be going on upon text steganography. As the word ‘steganography’ is very well known amongst human beings, considering that, this research paper will highlight the term ‘Text Steganography’. Defining steganography, that an individual can hide data into/within or behind text, images, audio, and video would not be inappropriate. Digital steganography is a modern approach and necessity of digital security system. Digital Text steganography is a distinct factor of digital steganography. Various types of Text steganography will have been discussed further.
Effect of load on the wear behaviour of Al2O3 HVOF sprayed coating
Authors: Meena SL , Tyagi Ankit , Murtaza Qasim , Walia R.S. , Niranjan MS 
Published: August 2021

Abstract
Al2O3 HVOF sprayed coating has been deposited with controlled process parameters. SEM characterization was used to characterize the deposited coating. Wear, Residual stresses, COF and hardness, are studied at variable load of 40, 50, 60 and 70N. Surface morphology of Al2O3 HVOF coating shows a molten and un-molten powder with curved laminar structure and confirm homogeneous coating. Experimental results revealed that with increase in load wear, hardness, residual stresses, and COF results were enhanced at higher load (70N). Experimental result shows wear value reduces to 80 microns and COF decreased to 0.25, while hardness and residual stresses increased to 470 HV and -20 MPa respectively. The experimental test results reveal that decrease in COF and wear may be occurs oxide layer formation or due to tribo-film formation under increasing load condition
Cloud and mobile computing: the age of virtual internet space
Authors: Singh Dhaneshwar , Madaan Rosy , Panda Supriya P 
Published: August 2021

Abstract
This century is described as Cloud Computing Technology over the Information Technology Business. Cloud computing advancement mostly relies on the Internet possesses the most advanced planning of computation. It records as piles of correlated and schmoozed hardware, software, and internet infrastructure. It blends grid computing and other computing as a community. A short overview of cloud computing is obtained from this research paper by consulting several papers on cloud technologies. The substance conveyed by this represents the perspective of shaping IT businesses and the idea of cloud computing.
A review paper on hypervisor and virtual machine security
Authors: Aalam Zunaid , Kumar Vinod , Gour Surendra 
Published: August 2021

AbstractA hypervisor is a computer programme or software that facilitates to create and run multiple virtual machines. It is also known as Virtual Machine Manager (VMM). Due to their popularity, it exploits the attack surface, because the Hypervisor code contains much vulnerability. Since the Hypervisor is a core element of any cloud computing service, it is always on the top priority of the attackers. There are many Software (open source) and Hardware-based Solutions are available in the market to monitor and control the hypervisor activities. This paper summarizes various types of attacks, vulnerabilities, security issues and challenges related to hypervisor and virtual machines.
Blockchain Technology, Its Applications and Open Research Challenges
Authors: Kaushal Rajesh Kumar , Kumar Naveen , Panda Surya Narayan 
Published: August 2021

Abstract
Blockchain is a technology that operates on distributed peer-to-peer network and is widely adopted by large number of organizations due to its attractive features such as highly secured, transparent, traceable, low transaction fee, no need of central authority and confidentiality. There are lot of confusions and myths regarding the blockchain technology as it is emerging technology and too complex in nature. This paper is aimed at revealing blockchain technology in depth along with its applications and open research challenges. The past published literature was reviewed to achieve the objectives. The study found that apart from cryptocurrency, blockchain is also suitable for other applications such as smart cities, supply chain, healthcare, smart transportation and authenticating IoT (Internet of Things) devices. This study is also disclosing various open research challenges such as scalability issues, huge power consumption and delay in completing transactions. This paper is also sharing the mitigation approaches and the future of blockchain with smart contracts.
Experimental Analysis of Porter Governor Mechanism in Dynamics of Machinery Laboratory
Authors: Hasan Ali 
Published: August 2021

Abstract
This work is done in the Machine Dynamics Laboratory of Mechanical Engineering Department. All the observations have been recorded using universal governor apparatus set up available in the laboratory. The author studied both the actual as well as theoretical parameters of the porter governor given to the students to perform their experiments. Author noted that, at M= 1, 2 and 3 kg, the actual sensitivity of given porter governor are 24, 11 and 24% respectively. The actual average sensitivity comes to a value of 20%. While with the help of calculations, the theoretical sensitivity of given porter governor are 23, 17 and 8% respectively. The theoretical average sensitivity comes to a value of 16%. Here, it is to be noted that in both the cases, the sensitivity of the studied governor is constant. The research covers both the experimental and numerical approached. The results of this paper may serve a model for researchers in doing research work as per specific necessity in the early stage of their work.
Digital Image Forensic based on Machine Learning approach for Forgery Detection and Localization
Authors: Monika  , Passi Abhiruchi 
Published: August 2021

Abstract
Machine learning for multimedia forensic is a new way of image forgery detection due to its amazing features of fast forgery detection. Compared with existing techniques of Deep Learning and Convolution Neural Network (“CNN”), machine learning improves security in the specific forged region under various test conditions. Some researchers use Support Vector Machine (“SVM”) and k-nearest neighbors (k-NN) algorithms to detect forgeries and another category uses unsupervised classification, including self-organization feature map (SOFM) and fuzzy c-means. But there occurs a need to address the detection speed improvement under the present scenario. The proposed algorithm has been developed using a machine learning approach to improve detection speed by pre-processing of feature extraction and feature reduction using “DWT” and “PCA” where data is trained by support vector machine (“SVM”) to provide quick results under various test conditions. This work specifies different image attacks like all types of geometric transformation, post-processing operations, etc., and presents efficiency in forgery detection and localization in case of multiple forgeries.
Exploration of machine learning methods for prediction and assessment of soil properties for agricultural soil management: a quantitative evaluation
Authors: Motia Sanjay , Reddy SRN 
Published: August 2021

Abstract
Soil is a heterogeneous and complex natural resource that is the factual basis of almost all agriculture production activities. The soil’s inherent nutrients or physiochemical properties help the researchers better understand the soil ecosystem dynamics and play a crucial role in guiding farmland decision-makers in their routine decisions. Therefore, the accurate forecasting of soil leads to improved and better soil health management (SHM). The recent advances in sensing and computational technologies have led to the expanding accessibility of farmland data either obtained distantly or proximally. The increasing availability of massive data and unreservedly accessible open-source algorithms have prompted a quickened use of machine learning (ML) procedures to investigate soil conditions. Therefore, to understand the usage of ML techniques in exploring soil properties and related applications, this paper concentrates on reviewing and analyzing ML techniques precisely to predict and assess soil properties for improved decisions on agricultural SHM. The article also explores various other vital factors like algorithms, implementation tools, and performance metrics employed in numerous soil assessment application domains and different challenges and future research directions for SHM using ML techniques. The detailed assessment concludes that the response for ML in the prediction and evaluation of soil properties for SHM is very promising for the sustainable growth of agriculture.