bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gravitational instability with dust charge gradient and ion drag forces in unmagnetized dusty plasma
Authors: Dolai Bivash , Prajapati R P 
Published: November 2020

Abstract
The influence of dust charge gradient force and ion drag force on the fragmentation of unmagnetized, self-gravitating dust cloud has been studied. The thermal electrons satisfy the Boltzmann relation, while inertialess ions are affected by the ion-neutral collisions. The dynamics of dusty fluid are modified by ion drag, charge gradient, and gravitational forces. The onset criterion of pinching instability and gravitational instability is derived. The pinching instability depends upon the critical ion drag coefficient and dust charge variation parameter. In the laboratory complex plasma, with finite dust charge variations, the ion drag coefficient larger than the critical value causes pinching instability. This results in the fragmentation of the dusty cloud, which is affected due to the dust charge variations. The ion drag coefficient has destabilizing, while the dust charge variation parameter has stabilizing influence on the growth rate of the linear gravitational instability. The results have been discussed to understand the dust cloud collapse in the astrophysical system.
Modeling and analysis of a coupled novel nonlinear magneto-electro-aeroelastic lumped model for a flutter based energy harvesting system
Authors: Zaheri Abdehvand Mehran , Seyed Roknizadeh Seyed Alireza , Sedighi Hamid Mohammad 
Published: November 2020

Abstract
The present paper investigates the modeling and analysis of a novel aeroelastic energy harvesting system using magneto-electro-elastic (MEE) material considering the nonlinear elastic effects of the structure. The main aim of using this group of composite materials, as compared to common piezoelectric materials used in aeroelastic harvesters, is to increase the harvested electrical power. The proposed model to improve energy harvesting is composed of a rigid airfoil connected to an elastic beam, with the elastic beam covered by one or two layers of MEE material and two electrodes connected to the top and bottom of the MEE layers to harvest the electric potential from the generated electric field. An external coil was also provided around the oscillating beam to induce the electrical energy generated by the magnetic field established within the MEE layer. Firstly, simulating the harvesting system as a discrete model considering bending and torsional cubic nonlinear springs, the governing equations are extracted using the constitutive equations of MEE materials, Gauss’s law, and Faraday’s law of induction through Hamilton’s principle. Next, the effects of different design parameters are evaluated to find their optimal values to maximize the generated power as well as the harvester stability. Finally, a comparison is made between the considered MEE harvester and a piezo-aeroelastic (PA) energy harvester, indicating the superiority of the proposed MEE energy harvester.
Statistical properties of radio flux densities of solar flares
Authors: Wang Lu , Liu Si-Ming , Ning Zong-Jun 
Published: November 2020

Abstract
Short timescale flux variations are closely related to the energy release process of magnetic reconnection during solar flares. Radio light curves at 1, 2, 3.75, 9.4, and 17 GHz of 209 flares observed by the Nobeyama Radio Polarimeter from 2000 to 2010 are analyzed with a running smooth technique. We find that the impulsive component (with a variation timescale shorter than 1 s) of 1 GHz emission of most flares peaks at a few tens of solar flux unit and lasts for about 1 minute and the impulsive component of 2 GHz emission lasts a shorter period and peaks at a lower flux level, while at the three high frequency channels the occurrence frequency of flares increases with the decrease of the flux density up to the noise level of the corresponding background. However, the gradual components of these emissions have similar duration and peak flux density distributions. We also derive the power spectrum on different timescales and a normalized wavelet analysis is used to confirm features on short timescales. At a time resolution of 0.1 s, more than ∼60% of these radio light curves show significant flux variation on 1 s or shorter time scales. This fraction increases with the decrease of frequency and reaches ∼100% at 1 GHz, implying that short timescale processes are universal in solar flares. We also study the correlation between the impulsive radio flux densities and soft X-ray fluxes obtained with the GOES satellites and find that more than 65% of the flares with an impulsive component have their impulsive radio emission reach a peak value ahead of the soft X-ray fluxes and this fraction increases with the radio frequency.
Estimating up-limits of eccentricities for the binary black holes in the LIGO-Virgo catalog GWTC-1
Authors: Yun Qian-Yun , Han Wen-Biao , Wang Gang , Yang Shu-Cheng 
Published: November 2020

Abstract
In the first Gravitational-Wave Transient Catalogue of LIGO and Virgo, all events are announced having zero eccentricity. In the present paper, we investigate the performance of SEOBNRE, which is a spin-aligned eccentric waveform model in time-domain. By comparing with all the eccentric waveforms in SXS library, we find that the SEOBNRE coincides perfectly with numerical relativity data. Employing the SEOBNRE, we re-estimate the eccentricities of all black hole merger events. We find that most of these events allow a possibility for existence of initial eccentricities at 10 Hz band, but are totally circularized at the observed frequency (≳ 20 Hz). The upcoming update of LIGO and the next generation detector like Einstein Telescope will observe the gravitational waves starting at 10 Hz or even lower. If the eccentricity exists at the lower frequency, then it may significantly support the dynamical formation mechanism taking place in globular clusters.
Gravitational wave sensitivity curve of pulsar timing arrays affected by correlated noises
Authors: Liu Shu , Tong Ming-Lei 
Published: November 2020

Abstract
The detection of gravitational waves (GWs) by pulsar timing arrays (PTAs) is not only a very important supplementation of the verification of general relativity but also a new window to study the evolution of supermassive binary black holes and the early universe. However, so far the detection sensitivity of PTAs is not good enough to catch signals of GWs due to the disturbance of various noises. In this paper we explore the influences of the correlated noises caused by the reference clock errors and solar system ephemeris errors in pulsar timing on the detection of stochastic gravitational waves background (GWB). We demonstrate the power-law integrated sensitivity curves of GWB detection under the impacts from these correlated noises. From the simulated data, we find that the influence of different reference time-scale is non-negligible, and the influence is even quite huge if one uses a very old version of solar system ephemeris. However, the impact from these correlated noises on the sensitivity curve is very limited for the real observational data released by international pulsar timing arrays (IPTA). We also calculate the signal-to-noise ratios based on the theoretical GW amplitude permitted by observations. Moreover, we study how the detection sensitivity increases with more pulsar number and longer observation.
Chinese sunspot drawings and their digitization – (III) quasi-biennial oscillation of the hand-drawn sunspot records
Authors: Wan Miao , Zeng Shu-Guang , Zheng Sheng , Lin Gang-Hua 
Published: November 2020

Abstract
Quasi-biennial Oscillations (QBOs) of the Sun have a significant meaning as a benchmark of solar cycle, not only for understanding the dynamo action but also in terms of space weather prediction. In this paper, the hand-drawn sunspot images recorded from the Purple Mountain Observatory are used to investigate the solar QBOs and the Gnevyshev gap of the sunspot relative numbers (Rs) and group sunspot numbers (Rg) during the period 1954–2011. The main results are as follows: (1) both the Rs and Rg exhibit similar periods including the 22-year magnetic cycle, the 11-year Schwabe cycle, and the QBOs modes; (2) the reconstructed QBOs of both data sets exhibit coherent behavior and tend to have a high amplitude during the maximum phase of each solar cycle; (3) the Gnevyshev gap is produced by the superposition of the QBOs and the 11-year Schwabe cycle, and the Rs is better to study the variation of the Gnevyshev gap rather than the Rg.
Optimized finite-build stellarator coils using automatic differentiation
Authors: McGreivy N. , Hudson S.R. , Zhu C. 
Published: November 2020

Abstract
A new stellarator coil design code is introduced that optimizes the position and winding pack orientation of finite-build coils. The new code, called flexible optimized curves in space using automatic differentiation (AD) and finite build (FOCUSADD), performs gradient-based optimization in a high-dimensional, non-convex space. The derivatives with respect to parameters of finite-build coils are easily and efficiently computed using AD. FOCUSADD parametrizes coil positions in free space using a Fourier series and uses a multi-filament approximation to the coil winding pack. The orientation of the winding pack is parametrized with a Fourier series and can be optimized as well. Optimized finite-build coils for a Wendelstein 7-X (W7-X)-like stellarator are found, and compared with filamentary coil results. The final positions of optimized finite-build W7-X-like coils are shifted, on average, by approximately 2.5 mm relative to optimized filamentary coils. These results suggest that finite-build effects should be accounted for in the optimization of stellarators with low coil tolerances.
Assessment of the durability of corrosion-damaged prefabricated reinforced concrete structures
Authors: Tamrazyan A G , Koroteev D D 
Published: November 2020

Abstract
During exploitation, reinforced concrete structures are under the influence of an aggressive environment, as a result of which they are damaged and destroyed. The durability of structures depends on the nature of its interaction with aggressive environmental factors, which is described using general models of external influences, such as the action of loads, climatic, aggressive and other influences and their combinations. An example of calculating durability based on corrosion of concrete and reinforcement is given. The selected protective layer and the diameter of the reinforcement were checked in case of general corrosion. The average value of the service life in years was determined on the basis of carbonization of the protective layer of concrete and the formation of cracks in it. The methods for predicting the service life of reinforced concrete structures are analysed. The service life of the structure is determined taking into account the assessment of the technical condition of the structure according to external signs. In theoretical terms, the influence of various factors by the introduction of a multifactorial measure of damage is shown. The calculations for predicting the service life of structures and for determining the durability are analysed. The example of calculating the probabilistic service life is considered.
Effect of silica fume on the ultrasonic pulse velocity of cemented sand
Authors: Shooshpasha I , Hasanzadeh A , Kharun M 
Published: November 2020

Abstract
One of the geotechnical engineering strategies for dealing with weak soils in a construction site is to modify their mechanical properties with the aid of soil improvement techniques. Chemical stabilization of soil using cement is one of these effective approaches that can considerably enhance workability and shear strength parameters of soil. However, very limited investigations have been carried out to reveal the effect of silica fume on the ultrasonic pulse velocity (UPV) and the ultrasonic stiffness (Eu) of cement-treated sandy soil. For this purpose, in the present research, a series of UPV tests were performed on sand-cement-silica fume specimens. The cement percentages were 3, 5 and 7% and silica fume contents were 0, 0.25, 0.5 and 1% by weight of dry sand. The cylindrical samples were prepared and cured for 3, 7, 14, 28, 42 and 56 days and tested. The results show that inclusion of silica fume to the cemented sand increases UPV and Eu which this enhancement is more pronounced at longer ages.
Factors influencing the critical piles length in reinforced slope
Authors: Shooshpasha I , Amirdehi H A , Kharun M 
Published: November 2020

Abstract
In this research, the performance of a homogeneous slope reinforced with one row of piles is studied using coupled numerical analysis and the method of shear strength reduction as implemented in the finite element analysis software, ABAQUS. Parametric studies are performed by changing geometric and strength parameters such as piles head conditions, piles location and the soil cohesion to assess their influence on the slope stability. For each of these parameters, the safety factor of the slope and the piles critical length was assessed. The results indicates the performance level of piles with different head conditions will not be similar; so that hinged and fixed heads are the most effective and cause the piles critical length to reduce, whilst free heads are less effective. The optimum location of the piles depends on their length, but regardless of the piles head type, the maximum increase of the safety factor is achieved when the piles are located in the mid-section of the slope. In addition to this, various levels of soil cohesion do not affect the piles optimum location, whilst cause significant changes in their critical length and increase rate of safety factor.
The impact of section properties on thin walled beam sections with restrained torsion
Authors: Gebre T H , Galishnikova V V 
Published: November 2020

Abstract
In this paper the influence of section properties on thin walled beam sections with restrained torsion is studied by considering the angle of twisting for non-uniform torsion. The study is based on the governing equation for non-uniform torsion of thin-walled beam of open and closed cross-sections, including the restrained behavior. The hyperbolic shape functions is used to generate the general solution for homogenous equation as it gives the exact results in accordance with the analytical solution. This study is focused on a bar subjected to torsion with warping of wide-ranging open and closed cross-sections with different value of characteristics number for torsion. The impact of the characteristics number for torsion on different section type is studied and evaluated. The obtained results are compared based on the influence of section properties on the components of the total applied torsion and presented graphical for different value of characteristics number for torsion.
Numerical study of free vibration behaviour of filled tool holder using epoxy-granite
Authors: Kashyzadeh K R , Ghorbani S 
Published: November 2020

Abstract
This paper presents a computer simulation focused on identifying the effect of cutting tool construction and damping material on its natural frequency. To this end, nine cutting tools with different cross-section of tool holder filled up with high damping material were presented. The free vibration analysis performed by ANSYS Workbench indicated that vibration amplitude decreases in cutting tools with epoxy-granite compared to that of conventional cutting tool. The relationship between the first and second natural frequencies with the length and diameter of the absorber chamber reveals that increase in diameter and length will reduce the natural frequency. Moreover, Multiple Regression Technique (MRT) was used to present a new equation for calculating the first natural frequency of filled tool holder via the dimensions of epoxy-granite cell. Next, various cases of filled tool holder were analysed based on Taguchi method. The results of the Taguchi sensitivity analysis showed the effect of length parameter (58%) on the natural frequency is more than the effect of diameter parameter (42%) on it. Moreover, it is also concluded that the natural frequency is more effectively reduced if the part between tool head and first tightening screw is filled with an increased volume of the absorbent.
Influence of environmental factors on the processes of biodegradation of vinylester composites
Authors: Kablov E N , Erofeev V T , Dergunova A V , Deraeva E V , Svetlov D A 
Published: November 2020

Abstract
Polymer composite materials based on various binders are widely used in the construction industry. Polymer composites are characterized by high performance. Of great interest is the study of more economical compared to other polymers vinylester composites. They are successfully used in the US and European countries. In Russia, the use of polyester resin as a binder is not as common as abroad. At the same time, the influence of environmental factors on the biodegradation of vinyl ester polymer composites has not been sufficiently studied to date. This study is devoted to the study of the biostability of vinyl-ether composites under the influence of environmental factors. The most significant are the processes of atmospheric aging of materials, which include a complex effect of climatic and environmental factors. The study of changes in the species composition of microflora and indicators of resistance of composites, depending on their composition and operating conditions in the conditions of the seacoast.
Behavior of conventional and fibered concrete shear walls during earthquake, an analytical simulation in SAP2000
Authors: Kharun M , Koroteev D D , Hemati Bahar M , Huang J , Kamrunnaher Mimi 
Published: November 2020

Abstract
The investigation of this paper was about non-liner behavior of shear walls against seismic wave by using conventional and fibered concrete. Case of earthquake study was Iripina 1980, Italy with Ms = 6.9 and fourth kind of shear walls with glass fiber, basalt fiber, steel fiber concrete and conventional concrete shear walls simulated in SAP2000 with dynamic analysis method. Analysis shows that glass fiber concrete and conventional concrete shear walls had similar behavior, also these shear walls had more suitable response. All shear walls behavior were same at the beginning of earthquake but at the end of earthquake basalt and steel fiber concretes had a lot of displacement. Furthermore, behavior of steel fiber concrete shear wall could not return at the last moments of earthquake. Beside modulus of elasticity and compressive strength had most effect on reaction of shear walls such that modulus of elasticity was the cause of doing linear behavior of shear walls during all times of earthquake, on the other hand compressive strength had most efficiently in dissipation energy. Best result in earthquake was with conventional concrete due to modulus of elasticity and compressive strength.
Strength of frozen soils during thawing
Authors: Ya Maslikova O , Debolsky V K , Ionov D N , Gritsuk I I , Sinichenko E K 
Published: November 2020

Abstract
More than a third of the Earth’s surface is subject to seasonal or prolonged soil frosts, and the recent warming of the climate requires revision of the construction standards in the conditions of permafrost because under heavy load in low-strength soils, there is a high risk of mobility of thawing rock and collapse of the construction structures, which is fraught with disastrous consequences. For design tasks it is necessary to know the behavior of frozen soils under certain changing conditions. This creates new requirements related to the degradation of permafrost and, as a result, the criteria for strength and stability of soils suitable for construction are changing. Calculation of loads during construction in the permafrost zone requires a special approach in each specific case, since it is impossible to make a single model in connection with the variety of soils and the history of their freezing. Soil typization does not give a clear picture at negative temperatures, since the transition “water-ice-water” in the soil changes the behavior of the grounds, and the unpredictability of climatic changes affecting this process greatly complicates the task. In the hydraulic laboratory of the RUDN University, a series of experiments was conducted for various types of soil subject to load, in order to determine the main parameters affecting the stability of soils during thawing, and to give approximate recommendations regarding the use of these soils as bases.
Application Analysis of WF / HDPE Composite in Landscape Design
Authors: Sun Qinghui , Lai Yibing , Shi Huiquan 
Published: November 2020

Abstract
Based on the brief introduction of the basic concept of landscape design, the anti-aging properties of WF / HDPE composite with UV-326 absorbent and WF / HDPE composite with UV-P absorbent were compared, It is concluded that the UV-P modified WF / HDPE composite can replace the UV-326 modified WF / HDPE composite in landscape design, The effects of UV-P and UV-326 contents on the aging resistance of WF / HDPE composites were analyzed. The application of UV-P modified WF / HDPE composite in modern landscape design is presented, and the structure and application place of paving board are introduced.
Applicability of Epoxy Materials for Repairing Wet and Underwater Concrete
Authors: Lu Zhihua 
Published: November 2020

Abstract
Concrete structures in wet or underwater environment are damaged by erosion of water medium and other external factors for a long time. The working environment is bad, and they need to be repaired in time after diseases occur. Otherwise, it will have a serious impact on the safe use and durability of the whole structure. Because there is a large amount of water in the construction environment, the repair and reinforcement of such structures often need wet or underwater construction. Based on the above background, the purpose of this study is to study the applicability of epoxy materials for wet and underwater concrete repair. In this study, the influence of steel sheet, substrate and surface treatment on the underwater bonding ability was discussed. The EM underwater performance of different curing agent and curing agent compounding was studied. The basic principle of curing agent compounding was put forward, and the comprehensive performance of EM optimized formula was tested. The results show that the underwater properties of different curing agents are very different, but it is difficult for a single curing agent to meet the comprehensive performance requirements; the use of different kinds of curing agent compounding technology is an effective means to improve its underwater properties, but the effect of different compounding methods is significantly different, when using the modified alicyclic amine and phenolic amine compounding system, After optimization, the water pull-down shear strength of epoxy solution is 20.1mpa, air pull-shear strength is 22.7mpa, air tensile strength is 41.6mpa, air compressive strength is 100.9mpa, elastic modulus is 2.53gpa, the underwater positive pull bonding strength of epoxy mortar is 4.31mpa and the failure mode is cohesive failure of base mortar block. The underwater long-term bonding performance of epoxy mortar is excellent, After immersion for one year, the strength of the specimens has not decreased significantly, which can fully meet the actual engineering needs.