bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the k-ary Euclid for tuples of integers
Authors: Amer Ismail , Ishmukhametov Sh T
Published: November 2019

In our paper we discuss the k-ary Euclid Algorithm for counting the great common divisor (GCD) of two or more integers and suggest some improvements. This gives us a possibility to parallelize and speed up the calculating of GCD, which has a variety of applications in the Number Theory, Modular Arithmetic and the Cryptography Algorithms such as RSA, ElGamal encryption system and others.
Classification of sociotechnical landscapes on the basis of analogies of cortege codes of indicators
Authors: Artemenko M V , Budanov V G , Korenevskiy N A
Published: November 2019

Now new technologies within the Industry 4.0 develop. Convergence of various applications of applied mathematics for a research of a synergetic coevolution the sociotechnical landscapes (STL) is intensified. STL is presented in the form of a taxonomical ontologic matrix which elements are symbols of the Cartesian work of sets social the practician and digital technologies. The train of indicator signs which is unambiguously characterizing levels of tension of STL is applied to classification of STL. The method of coding of indicator signs for calculation of value of the qualifier based on calculation of a binary code on function of accessory of each sign which carrier is the natural logarithm of a relative deviation of nominal rate of sign from registered is described. The reversibility of formation of the qualifier allows carrying out decrease in dimension of feature space without information losses. Results of researches STL of Kursk region are given in work (the train was presented by 20 indicators). The conclusion about prospects of application of the considered applied method of the mathematical analysis of the solution of classification tasks is drawn.
Integral equation of a dipole antenna located vertically at the interface between two media
Authors: Artem’ev V V , Sochilin A V , Eminov S I
Published: November 2019

The article presents the derivation of the integral equation for a cylindrical perfectly conducting symmetric vibrator located vertically at a certain height from the interface of the two media. An example of numerical calculation is considered.
The generalization of shift operator related Bessel differential operator
Authors: Britvina L E , Ignatenko V V
Published: November 2019

We introduce the generalized shift operator related to the Bessel differential operator and the Hankel integral transform. It generalizes the operator introduced by J Delsarte and studied by J. Delsarte, B.M. Levitan and Ya.I. Zhitomirskii. The considered operator is not the generalized shift operator of the Levitan’s type. The basic properties of the shift operator are proved. The visualization of shift action is given.
Pseudorandom amplitude-phase-shift keyed signals with irregular bi-level amplitude spectrum for moving target detection
Authors: Bystrov N E , Zhukova I N , Chebotarev S D
Published: November 2019

This paper considers the target locating against the clutter background in radars with quasi-continuous mode of transmission and reception on common aerial of signals with pseudorandom amplitude- and phase-shift keying. Pseudorandom amplitude-phase-shift keyed signals with irregular bi-level amplitude spectrum are proposed for use. The high-level spectrum components of returns from the moving and stationary targets can be partially overlapped. It is proposed to perform the frequency rejection of high-level components of the stationary targets before the correlation signal processing. As a result, significant part of the energy of interfering reflections is cut out and just a small part of the energy of the useful signal is lost. The signal-to-clutter ratio increases. The synthesis method of pseudorandom amplitude-phase-shift keyed signal with irregular bi-level amplitude spectrum is considered. The spectrum of the synthesized signals is analyzed. Increase of the signal-to-clutter ratio was obtained in the processing of signals with frequency interference rejection. The result of detection modeling of a moving target against the background of reflections from a stationary object is presented.
What is reverse debugging? Classification of reverse debugging methods
Authors: Dmitriev D S , Dovgalyuk P M , Makarov V A
Published: November 2019

The article discusses an approach to speeding up the search complex errors in software – reverse debugging. In this approach, debugging is divided into two phase. The first phase is to save the behaviour to a log file. The second phase is the reproduction of behaviour and the search for errors. During the second phase, both past and future program states can be examined. The article describes methods that support this approach and general principles for such methods and their differences. A classification of reverse debugging methods is proposed by debugging scope and replay scope. Examples of modern reverse debugging tools and their place in the proposed classification are given.
About the values of generating polynomials of cyclotomic classes
Authors: Edemskiy V A , Tsurina A S
Published: November 2019

The trace representation of sequences is a powerful tool for the analysis and for the design of pseudorandom sequences. Z. Dai et al. (2011) reduce the problem of determining trace representation of series of binary eth power residue sequences to that of determining the values of generating polynomials of cyclotomic classes. We derive the values of generating polynomials of cyclotomic classes of order 4, 6, 8 and consequently solve three problems pointed by Z. Dai et al. In fact, we study the discrete Fourier transform of cyclotomic sequences of order 4, 6, 8.
Synthesis of the streaming network with optimal adjustment placement of different-sized radio elements on the surface of the construct
Authors: Elkanova L M , Baichorova A N , Botasheva F Iu
Published: November 2019

Streaming networks have a wide range of options for practical application: information flows in information and communications networks, transport traffic, electrical power systems. The tasks of large dimension, including those which are associated with finding the frequency-optimum traffic, should be solved by the decomposition method. The paper considers the algorithm of the “pinwheel” decomposition of the installation and switching space and synthesis of the streaming network with optimal adjustment placement of different-sized radio elements on the surface of the construct.
The heat conduction model involving two temperatures on the segment with Wentzell boundary conditions
Authors: Goncharov N S , Sviridyuk G A
Published: November 2019

According to the theory of relatively p-bounded operators, we study the Heat Conduction model involving two temperatures for isotropic material, which describes, the rate of change of internal energy due to the movement of the heat flux form one medium to its complement with general Wentzell boundary conditions. In particular, we consider spectrum of one-dimensional Laplace operator on the segment [0,1] with general Wentzell boundary conditions. We examine the relative spectrum in one-dimensional Heat Conduction equation involving two temperatures, and construct the resolving group in the Cauchy-Wentzell problem with general Wentzell boundary conditions. In the paper, these problems are solved under the assumption that the initial space is a contraction of the space L
2(0,1).
How to solve the Maxwell equations?
Authors: Granovsky Ya I
Published: November 2019

This paper contains the general solution for potential Aμ
of electromagnetic field with given sources. It consists of two terms having clear physical sense and includes gauge additive.
Additive-multiplicative fixed-pattern noise model of an IR photodetector, taking into account the exposure time
Authors: Kornyshev N P , Senin A S
Published: November 2019

The article discusses the additive-multiplicative fixed-pattern noise model of the infrared photodetector and a new way of its compensation, invariant to a change in exposure time. Examples of images showing the effectiveness of a new method for compensating fixed-pattern noise when the exposure time of a photodetector is changed are given.
Measuring blood flow velocity with a magnetic label
Authors: Lobekin V N , Leontiev V S , Petrov R V , Bichurin M I , Rebinok A V , Sulimanov R A
Published: November 2019

The article describes the method of measuring blood flow velocity by a non-invasive method of magnetizing blood with a magnetic pulse and detecting a magnetized substance using a magnetoelectric magnetic field sensor. The influence of the magnetic field on the parameters of blood and blood flow is considered. The methods of measuring blood flow velocity are considered, the distinguishing features of each method are given. The use of a magnetoelectric composite structure of bidomain lithium niobate\nickel\metglas is proposed as a sensitive element for detecting blood flow velocity.
Electronic structure of stishovite SiO2
Authors: Manyakin M D , Kurganskii S I
Published: November 2019

Electronic structure calculation of the stishovite as close packing SiO2 modification was performed with the use of the linearized augmented plane wave method in framework of Wien2k code. Band diagram, total and partial density of states were calculated. X-ray emission Si K and Si L2,3 spectra characterizing valence band were obtained. By “core hole” approximation XANES Si L2,3 was calculated. X-ray stishovite spectra reveals good agreement with the experimental data. The explanations are given for the observed density of states and emission spectra fine structure features.
Pseudo-random sequences with nonmaximal length based on the shift register and reducible polynomial
Authors: Pesoshin V A , Kuznetsov V M , Rakhmatullin A K
Published: November 2019

We consider nonhomogeneous pseudorandom sequences of nonmaximal length formed by a shift register with linear feedback (Fibonacci generators), and with internal half-adders (Galois generators). As a basis, we consider characteristic polynomial raised to the power of n of a form

φ

(
x
)

=

φ
0

m

(
x
)

φ
1

(
x
)

, where φ0 (x) and φ1 (x) are primitive polynomials respectively raised to the power of m
1 and m
1, m
0 · m + m
1 = n. We discovered periodic polynomial structures. Examples demonstrate a diversity of generated practical sequences, which are organized and ordered from elements of direct and inverse M-sequences. We investigated probabilistic properties of the formed sequences.
The identifying hidden data features problem solution
Authors: Petrova S Y , Boikova M A
Published: November 2019

In the article, we considered recommender models based on matrix factorization demonstrate excellent performance in collaborative filtering. The standard Matrix Factorization approach in MLlib deals with clear ratings. To work with implicit data, we used the trainImplicit method. To simulate the processing of real-time data streams, we used the Spark Streaming library, which is responsible for receiving data from the input source and converting the raw data into a discretized stream discretized stream (DStream) consisting of Spark RDD. The rank parameter determines the number of hidden features in the low rank approximation matrices. As a rule, the greater the number of factors, the better, but for a large number of users or elements, it will directly affect the memory usage of the computing system and the amount of data required for training. Therefore, in our problem it was a compromise solution.
A discerning algorithm for authorization
Authors: Petrova S Y , Eminov S I
Published: November 2019

In the article, we consider a discerning authorization algorithm that eliminates the contradictions in the assignment of access rights to security principals in complex infrastructures, which are using concepts such as group and inheritance. It also can use for the identification of security risks and it ensures that the security risk assessments produce consistent, valid and comparable results.
The rotation of methane molecules in the crystalline state above and below the temperature of the phase α-β transition
Authors: Prokhorov A Yu , Leont’eva A V , Dmitriev Yu A
Published: November 2019

The work is devoted to the study of rotational features of methane molecules in the methane solid state in different temperature ranges. We formulated earlier, the concept of the description of collective rotational motion of the CH
4 molecules with the use of a topon quasi-particle. This approach received a new experimental confirmation in papers by Yu. A. Dmitriev and N. P. Benetis on studying by electron paramagnetic resonance (EPR) quantum mechanical rotation of CH
3 radicals matrix isolated in solid methane and in a work by P. Pyykko using nuclear magnetic resonance (NMR) technique to test rotation of host molecules in methane at temperatures of orientational ordering (below the α−β transition). Comparison with the behavior of the CH
3 radical in other orientation-ordered matrices, CO
2, N
2, CO, N
2
O suggests that the observed change in the barrier at such low temperatures is associated with the reorientation of the methane matrix molecules, which, provided that their orientation ordering is preserved, is possible only as a result of collective tunnel rotation.
Modelling of microwave filters based on LTCC
Authors: Rychko A R , Telina I S , Petrov E V , Popov V V
Published: November 2019

Microwave filters made according to the technology of low-temperature co-fired ceramics (LTCC) are considered. The main features of LTCC technology are described. The parameters of the domestic glass-ceramic material are given. The stages of designing an integrated microwave filter, all elements of which are in the volume of ceramics, are considered. In the course of this work, a model of a LTCC microwave filter with a nominal frequency of 300 MHz was developed taking into account the parameters of domestic materials. According to the modeling outcomes, conclusions were made.
Size dependence of the melting temperature and mechanisms of the coalescence/sintering on the nanoscale
Authors: Samsonov V M , Alymov M I , Talyzin I V , Vasilyev S A
Published: November 2019

We have proposed to use the nanoparticle (NP) melting temperature Tm
to distinguish between the coalescence and sintering processes on the nanoscale. According to our molecular dynamics results, obtained on Au NPs, the coalescence of nanoproplets may be interpreted as a hydrodynamic phenomenon on the nanoscale, and the characteristic coalescence time τ is a linear function of the initial particle radius r
0. In turn, the sintering of two crystalline NPs (T < Tm
) relates to a grain boundary formation as a result of an alignment of the crystallographic orientations of the sintering NPs, and in this case a dependence of τ on r
0 has not been revealed.
On the mechanical stability conditions for nanoparticles in vacuum and under an external pressure
Authors: Sdobnyakov N Yu , Samsonov V M , Bazulev A N
Published: November 2019

A condition of the mechanical stability of non-volatile nanoparticles in a chemically inert medium is derived from the non-negativity of the second variation of the Helmholtz free energy of the ‘small object - gaseous medium’ system. Two cases have been analyzed: (i) a non-volatile nanoparticle with the surface tension depending on its radius; (ii) a limiting case of bigger objects when the surface tension corresponds to its constant macroscopic value. It has been shown that the external pressure should increase stability of nanoparticles. However, the effect under consideration should be noticeable at high pressures only.
Errors of the most popular functionals in the calculation of the electron energy and enthalpy of formation of compounds
Authors: Turovtsev V V , Orlov Yu D , Kaplunov I A , Fedina Yu A , Zubkov V V
Published: November 2019

The calculation of the total electron energy Etotal
and the enthalpy of formation

Δ
f

H

298

0

of the compounds GeO2, C2H6, NH2CHO, C6H6, C5H5N and C6H4O2 has been performed using methods B1LYP, B1PW91, B3LYP, BHandH, BHandHLYP, BLYP, BP, CAMY-B3LYP, HTBS, KMLYP, LCY-BLYP, LCY-BP86, LCY-PBE, LDA, M06, M06-2X, M06-HF, M06L, mPBE, mPW, MPW1K, MPW1PW, O3LYP, OLYP, OPBE, OPBE0, PBE, PBE0, PBEsol, PW91, revPBE, revTPSS, RPBE, TPSS, TPSSH, X3LYP and HF in the slater basis QZ4P, aug-TZ2P and TZ2P, as well as DZ, and the errors of calculation of Etotal
and Δ

Δ
f

H

298

0

at the variation limit were determined. The QZ4P basis set and the settings of the ADF program were configured so that these errors can be attributed to the structure of DFT functionals. The dependence of the Etotal
and

Δ
f

H

298

0

based on type (size) of the basis set was studied. It has been demonstrated that the functional M06 has the smallest error independent from the incomplete basis set, and the optimal combinations are DFT/TZ2P, where DFT = OPBE, X3LYP, B3LYP, revTPSS, M06L, M06, TPSS, CAMY-B3LYP.
Calculation of some types of phase diagrams of binary solutions in the framework of the generalized lattice model
Authors: Zakharov M A
Published: November 2019

A brief review of the methods of calculation of the basic types of binary phase diagrams is done in the framework of the generalized lattice model. The construction of binary phase diagrams with unlimited and limited solubility of the components in the solid state, the phase diagrams of the eutectic types is considered.
Complex index of a system’s quality for a set of observations
Authors: Zhgun T V
Published: November 2019

This paper discusses the solution to the problem of constructing latent complex indexes of a change in a system’s quality for several observations in the absence of training. The algorithm for constructing complex indexes is implemented with the definition of non-random variables of the principal component characterizing the structure of the system under discussion. The algorithm uses a new approach to choose the principal component number, determine the weights of the considered variables and subsystems, and to determine the information content of the complex index based on the selected signal-to-noise ratio parameter. The algorithm was used to obtain complex indexes of quality of life for Russia’s constituent entities for 2007-2016.
Method for evaluating the robustness of rankings generated by composite indices
Authors: Zhgun T V
Published: November 2019

Characteristics of the quality of many systems in the economics, politics, society is in the form of a composite index, take the form of a linear composite index that linearly aggregates over several dimensions using a weight vector. The construction of the complex indexes of a system can be considered as the task of extracting the useful signal from the background noise. The signal in this case is the weights of the linear convolution of the indicators, which should reflect the structure of the system being evaluated. Principal component analysis determines the structure of the principal components for successive observations differently. The reason for this may be the presence of fatal errors in the data used. A modification of the principal component method that takes into account the presence of errors in the data used determines the structure of the system unambiguously. If the nature of the aggregation method of variables and the choice of weights adequately reflect the system quality model, then to study the reliability of the composite index, it is necessary to investigate the stability of ratings over time. The consequence of stability is on average a slight change (increment) in the rating of objects for different measurements. This increment can be a posteriori estimated by a set of observations on the proposed dispersion criterion. The results of assessing the stability of different integral characteristics by this criterion are given. Complex indexes, calculated by the author’s method, show good stability.
Distribution functions for continuous medium without probability hypotheses
Authors: Zubkov V V
Published: November 2019

A non-probabilistic interpretation of the distribution functions is obtained. The cases of instantaneous and retarded interactions are considered. The derivation is based on the use smoothing operator that does not change the symmetry of the equation of motion with respect to time inversion.
Extending Geostationary Orbit Missions for Lunar Observations
Authors: Silva William R. , Terra Maisa de O. , Celestino Claudia C. , de Melo Cristiano F.
Published: November 2019

This work investigates an alternative strategy to exploit future communications satellite generations including a final stage of lunar observations. For that, we explore impulsive transfers between geostationary orbits and lunar gravitational capture orbits in a full 4-body dynamical model with the Sun, Earth, Moon and spacecraft. Criteria to seek natural transfer orbits between the geostationary orbit and the vicinity of the Moon are defined considering escape properties of trajectories of the Circular Restricted Three Body Problem (CR3BP) as a guide. Namely, we select initial conditions of the 4-body model with energies that favors Earth-Moon transfers that remain around the Moon for a long time. As a case of study, we selected the current Brazilian geostationary satellite Star One C4. After a broad analysis of initial conditions and their transport behavior, we select potential transfers that reaches a near vicinity of the GEO orbit with an sufficiently small inclination with respect to the terrestrial equator. Time evolution of candidate solutions are analyzed and Δν budget and propellant mass are computed. As well as some current proposals for space debris mitigation, our strategy requires that additional mass of propellant besides onboard propulsion systems to perform final maneuvers have to be foreseen in the design of future generations of these communication satellites.
Orbits around the dwarf planet Haumea
Authors: Jean Carvalho P. S.
Published: November 2019

The dwarf planet Haumea is a very interesting celestial body due to the characteristics of its physical form and also the recently observed ring. A Kuiper Belt object, Haumea is a triaxial ellipsoid with dimensions of approximately 513 × 852 × 1161 (km), with a mass of 4.006 × 1021 kg and a rotation period of 3.915341h. The dwarf planet Haumea has its system formed by two natural satellites, the moons Namaka and Hi’iaka. We have presented an analysis of orbits around the dwarf planet Haumea taking into account the influences of the perturbations of its nonsphericity (J2, J4, C22
). We have found that the C22
term and the rotation rate of Haumea have contributed strongly to reduce the variation rate of the periapsis radius of the spacecraft. We have calculated the spherical harmonics of Haumea taking into account the most current values for the semi-axes of the ellipsoid and we have presented a comparison with the values of the harmonics found in other works.
An implementation of the weighted essential non-oscillatory scheme for numerical approximations of the pressureless gas dynamics equations
Authors: Jung SungKi
Published: November 2019

In this study, the Weighted Essential Non-Oscillatory (WENO) scheme is implemented for numerical approximations of the pressureless gas dynamics equations. The Harten-Lax-van Leer-Contact (HLLC) approximate Riemann solver serves as a basic building block with the fifth order WENO scheme involving the first order Lax-Friedrichs scheme as a flux limiter for the numerical stability. In particular, the WENO scheme suppressed the oscillatory around the delta shock waves and the flux limiter guaranteed the positivity of densities around the vacuum. Lastly, numerical testes for one-dimensional problems are presented for capturing the delta shock waves and vacuum.
Equilibrium points stability analysis for the asteroid 21 Lutetia
Authors: Mota Marcelo Lisboa , Rocco e Evandro Marconi
Published: November 2019

This work investigates the stability of the equilibrium points that occur around the asteroid (21) Lutetia, assuming that this body has a constant velocity of rotation and is immersed in a gravitational field, whose force of attraction presents a perturbation with respect to the central force due to the irregular mass distribution of the asteroid. For the calculation of the potential, as well as of the effective potential, was used the method of the expansion of the potential in series, associated to the asteroid decomposition in tetrahedral elements. The zero velocity curves for a massless particle orbiting the gravitational environment were analyzed. The linearized dynamic equation in the vicinity of the equilibrium points, the associated characteristic equation, and the Jacobi constant were calculated. The validation of the results was ratified by simulations of trajectories around these equilibrium points, considering the gravitational field modelled. It should be emphasized the general nature of the procedures adopted in this work, that is, they can be applied to any other asteroid.
Particle-in-cell model of the helicon plasma thruster experiment at the University of Brasilia
Authors: Miranda Rodrigo A. , da Trindade Daniel B. , Luz Jhéssica M. N. de J. , Costa Sarah da , Ferreira José L.
Published: November 2019

In this paper we describe a numerical model of a helicon plasma thruster device currently under development at the Laboratory of Plasmas at the University of Brasilia. The two-dimensional model is obtained by representing the device using a cylindrical geometry, and neglecting variations in the azimuthal direction. The computational code solves the electrostatic equations and the equations of motion of charged particles self-consistently using the particle-in-cell approach. Our model predicts the emergence of a structure similar to a current-free double-layer in the plasma, which has been detected in similar experiments.
Propagation of the trajectories for reentry spherical debris including rotation, melting fragmentation and voxel method
Authors: Murcia P J O , Guedes U T V , Prado A F B D
Published: November 2019

It is estimated that more than 22.000 objects are in orbit around the Earth, with a total mass of 8.400.000 kg. These numbers consider only objects with dimensions above 10 cm and some non-operational, but still orbiting satellites without control (debris). The debris represent a hazard to operational satellites and aerospace operations due to the high probability of collisions. Due to the interaction of the debris with the atmosphere of the Earth and the solar activity, they began to lose energy and finally decay. During the de-orbit process, the debris fall into the Earth’s atmosphere at hypersonic speeds and these objects can break-up and/or be fragmented due to the aerodynamics, thermal and structural loads. It is important to obtain the trajectory and attitude of any fragment to determine the possible survival mass, impact area, hazard conditions and risks to the population, the air traffic control, and infrastructure. In this case, it is implemented a computational code to integrate the equations of motion to propagate the dynamics and kinematics of spherical debris or propellant tanks. It is also analyzed the results of trajectories with six degrees of freedom, atmospheric winds, and Magnus effect. A voxel method is implemented to analyze the tanks heat transfer, surface temperature and structures stress. To determine and observe the influence of the rotation and the Magnus force in six reentry spherical bodies, three materials are selected; aluminum alloy, due to its application in many aerospace structures; titanium and graphite epoxy I, due to their highest melting point and specific heat. Generally, these materials are used in tanks and rocket motors. More than 62 trajectories were simulated. The mathematical model and computational code were validated in three degrees of freedom. Results are compared with data from other computational tools available in the scientific literature. The results show a good approximation with reported cases of study. New results are generated in the simulations of rotational bodies, due to the influence of aerodynamic forces in the trajectory and the changes in the stagnation regions. Due to the implementation of wind and rotation of the debris, the fragments increased the survivability and the dispersion area.
The use of Design of experiments to calculate the influence of planet oblateness in the temporary gravitational capture
Authors: Siqueli Guilherme A. , Antônio F. B. A. Prado , Solórzano Carlos R. H.
Published: November 2019

This paper presents the study of the influence of the oblateness of one planet in the temporary gravitational capture of a particle (or a spacecraft) around the main celestial body of the system. The gravitational capture is a physical phenomenon where a celestial body (or a spacecraft), initially in a hyperbolic orbit with positive energy with respect to the main body of the system, is captured by another celestial body, changing the energy of the orbit to negative during a determined time. In this way, we have a temporary capture of this body or spacecraft. In the case of a spacecraft, it is possible to make this capture permanent by the application of a propulsion system to the spacecraft. This technique is done with savings over the traditional maneuvers performed without the support of the temporary capture, so it can help mission designers in the planning of the mission. As an example, the system used in the present paper is composed by the Sun-Jupiter-particle, and this system is modeled by the circular restricted three-body problem (CR3BP) plus the oblateness of Jupiter. To determine the effects of the oblateness in the dynamics of the particle, it is used the design of experiments to generate the data for a global analysis of the model. The oblateness of the planet is varied to show the effects of this parameter.
Simulations without data updates using analytical attitude propagator GSAM for spin stabilized satellites
Authors: Zanardi M C , Mota V , Borderes-Motta G
Published: November 2019

The objective of this work is to validate the GSAM propagator using new data provided by the National Institute for Space Research (INPE) from SCD1 and SCD2 data collection satellites, with emphasis on long interval simulations without daily data updates. Originally, only 40 days of data were available to test the program, constraining any attempts to measure its precision more accurately. Recently, over two decades of data regarding both satellites’ orbital and attitude parameters were provided, allowing further studies and validation of the program. The rotational motion equations are composed by the gravity gradient torque, aerodynamic torque, solar radiation pressure torque, residual and eddy current magnetic torques, the latter using a dipole geomagnetic model. The results are considered fitting when the mean deviation between the calculated variables and the real satellite data stay within 0.5° for the right ascension and declination angles and 0.5 rpm for the spin velocity. Intervals that meet the required precision were found for all years, from three to up to 15 days of simulation without data update. The consistent detection of such intervals further corroborate the use of the propagator to estimate the orientation of the satellites studied in their missions.
Database on detected stellar occultations by small outer Solar System objects
Authors: Braga-Ribas F , Crispim A , Vieira-Martins R , Sicardy B , Ortiz J L , Assafin M , Camargo J I B , Desmars J , Lecacheux J , Santos-Sanz P , Duffard R , Benedetti-Rossi G , Gomes-Júnior A R , Morgado B , Rommel F L , Margoti G , Pereira C L
Published: November 2019

Observation of stellar occultation by objects of the Solar System is a powerful technique that allows measurements of size and shape of the small bodies with accuracies in the order of the kilometre. In addition, the occultation star probes the surroundings of the object, allowing the study of putative rings/debris or atmosphere around it. Since 2009, more than 60 events by trans-Neptunian and Centaur objects have been detected, involving more than 34 different bodies. Some remarkable results were achieved, such as the discovery of rings around Chariklo and Haumea, or the high albedo of Eris, the lack of global atmosphere around Makemake and the discovery of the double shape of 2014 MU69, among others. After the release of Gaia catalogues, predictions became more accurate, leading to an increasing number of successful observations of occultation events. To keep track of the results achieved with this technique, we created a database to gather all the detected events worldwide. The database is presented as an electronic table (http://occultations.ct.utfpr.edu.br/), where the main information obtained from any occultation by small outer solar system objects are listed. The structure and term definitions used in the database are presented here, as well as some simple statistics that can be done with the available results.
Hall plasma thruster development for micro and nano satellites
Authors: Ferreira J L , Martins A A , Miranda R A , Porto M C F , Coelho H O
Published: November 2019

Hall thrusters are one of the most successful electric thrusters for space application that has been developed until now. The Plasma Physics Laboratory of the University of Brasília (UnB) has been developing a Permanent Magnet Hall Thruster (PHALL) for the Brazilian Space Program since 2004. Recently we have achieved important experimental results satisfying our initial goals of generating a force above 40 mN with powers around 620 W. We will discuss in this article possible applications of this thruster to nano and microsatellites with powers above 50 W. Meanwhile, a complete description is given of our present and future installations where the new thruster will be tested; taking advantage of our new 1.5 m diameter vacuum chamber (the old chamber had 0.5 m in diameter), which intends to test our thruster in the most realistic conditions, including mounting and testing on a 3U CubeSat structure, which is where we intend to start testing our thruster in a real mission in space.
Evaluation of orbital decay of a satellite at low altitude due to atmospheric drag as a function of solar activity
Authors: Macêdo C F C , Rocco E M
Published: November 2019

Artificial satellites in low Earth orbit have as main disturbance the atmospheric drag, which is a non-conservative disturbance that causes the satellite to lose orbital energy due to the friction with the air. Basically, the drag force is a function of the velocity, the local air density and the satellite’s constructive parameters. The air density is a function of altitude, longitude, latitude, geomagnetic index and solar activity. Solar storms are responsible for a wide range of terrestrial effects, especially in damage to telecommunications systems. Another relevant effect of solar activity is the variation in the volume of the atmosphere and consequently in the value of the air density for a given altitude, longitude and latitude. This work provides an initial approach, through simulation, in the engineering effort to deal with this disturbance.
The role of the mean and forced eccentricities in the secular dynamic of circumbinary planets
Authors: Zoppetti F.A. , Beaugé C. , Leiva A.M.
Published: November 2019

Within the framework of the Restricted Three Body Problem (RTBP), we consider the orbital evolution of a circumbinary (CB) planet. We develop a simple analytical model to explain the mean behaviour of the planetary eccentricity and better identify the nature of the main contributors of eccentricity oscilations. Our theory is validated by comparing with N-body simulation. We analyse the effect of including dissipative forces in our theory and compare with a N-body simulation in which the dissipative force is the interaction with a protoplanetary disc. Finally, we use our model to explain dynamical maps in the CB region and distinguish domains where the secular dynamics dominate over the resonant perturbations.
New adsorbent materials on the base of minerals and industrial waste
Authors: Kotova Olga
Published: November 2019

At present, when environmental problems become more pronounced, we need to find special solutions. One of the ways is to use cheap adsorbents that do not need to be restored. An example of developing a class of adsorbent materials is technology for synthesizing nanotubes from refractory ilmenite-leucoxene ore. Another example of the development of a class of zeolite as advanced materials is the technology of their synthesis from ashes of thermal power plants. Synthesis conditions create necessary parameters of adsorption properties to remove heavy metals and radionuclides. “Clean” technologies are formed to replace natural and commercial zeolite. Production of such materials at the national level can be an important source of profit, can create new jobs and increase competitiveness of the industry.
The Influence of Cr doping on the Structural and Magnetic Properties of HoMnO3 Multiferroic Ceramics
Authors: Ibrahim J. F. M. , Mergen A. , Parlak Umut , Kurovics Emese
Published: November 2019

In this research single-phase Cr-doped HoMnO3 ceramics were synthesized via solid state reaction method. The structural and magnetic characteristics of the prepared samples were examined using various characterization techniques, including x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and vibrating sample magnetometer (VSM). All samples exhibit single phase that emphasized by SEM and XRD. Magnetic properties of the prepared samples at low temperature (10K) showed the presence of different magnetic characteristics. The change in magnetic behavior could probably occur due to slight decrease in the unit cell volume that leads to a structural distortion in the lattice. Cr-doped HoMnO3 could be a good candidate with a better ferromagnetic property for practical multiferroic applications.
Computer simulation of damage to metal-ceramic composites under shock loading
Authors: Karakulov V V , Smolin I Yu , Kulkov S N
Published: November 2019

In this work the results of studying of the mechanical behaviour of metal-ceramic composites with an aluminium matrix on mesoscale level are submitted. Computer simulation of mechanical reaction of representative volume of composite material, considered as ensemble of the interacting structural elements (ceramic particles and metal matrix), is used for studying processes of the nucleation and growth of damages on mesoscale level of metal-ceramic composites under the loading by shock pulses. The sizes of representative volume give the possibilities to enter effective mechanical parameters of a composite material. The mechanical behaviour of aluminium matrix is described by the model of the damaged elastic-plastic medium. The model of the damaged brittle solid is used for ceramics. The problem is solved in 2D statement with application of finite-difference method. The results of computer simulation show that the local tensile stresses can appear in unloading wave and can cause damages in ceramic particles. In the region of composite where two opposing unloading waves interacts (spall zone) the calculation predicts the existence of cracked ceramic particles, local damages in metal matrix and existence of mesoscale and macro-scale cracks.
Electrochemical study of the corrosion inhibition effect of 3-cyanophenyl compound on 420 martensitic stainless steel in strong acid media
Authors: Loto Roland T. , Ayozie Bryan U. , Loto Cleophas A.
Published: November 2019

The corrosion inhibition performance of 3-cyanophenyl organic compound on heat treated 420 martensitic stainless steel in 6 M H2SO4was evaluated through potentiodynamic polarization test, ATR-FTIR spectroscopy and adsorption isotherm studies. Results obtained proves the compound to be effective with highest inhibition performance value of 99.4%. The inhibition property was determined to be mixed type inhibition with significant anodic inhibition tendencies. Adsorption of the compound onto the steel was through chemisorption mechanism in agreement with the Langmuir and Freundlich isotherms models at correlation coefficients of 1 and 0.7570. The transmittance of detected functional groups of 3-cyanophenyl diminished at distensible wavelengths because of excellent surface coverage and adsorption of the compound onto the steel
Comparative investigations of the selective Co etching from hardmetal support layer of diamond coating
Authors: Rugóczky Peter , Muránszky Gábor , Lakatos János
Published: November 2019

Selective cobalt etching from WC–Co composite usually carry out prior diamond deposition was investigated. Diluted Caro’s acid as primarily utilized etching reagent was used. The cobalt and tungsten dissolution from hardmetals (HM) were determined as a function of time and a comparison were done in case of different grade hardmetals. For comparison beside the hardmetals the pure metallic cobalt and binderless, plasma sprayed tungsten carbide dissolution also has been tested. Hot filament chemical vapor deposition (HFCVD) technic was used to investigate the diamond nucleation on the differently pre-treated samples. The investigation highlighted for that: a) the selective cobalt etching can due to the different rate of dissolution of the two components, however the dissolution of the WC was not zero, b) the dissolution rate governed by the composite substance structure by the pore size which has formed during the selective dissolution process, therefore the dissolution rate of both components was found to be influenced by the grain size of WC and the cobalt content of the hardmetal. c) The removed cobalt quantity from the hardmetal surface has strong effect on the diamond nucleation during HFCVD method. Based on this research a better understanding of the mechanism of the pre-treatment and a chance for optimizing the selective cobalt etching from hardmetals prior diamond deposition will be achieved.
Formation of metastable zirconium oxides using pulsed laser deposition of ZrO based target
Authors: Křenek Tomáš , Mikysek Petr , Pola Michal , Vála Lukáš , Melaré Estela , Jandová Věra , Vavruňková Veronika , Rieger David
Published: November 2019

There is a growing interest about the possibilities for preparation of various zirconium oxides from scientific as well as application point of view. Laser ablation of solid target consisting of sintered grains of metallic hexagonal Zr3O and monoclinic ZrO2 results in evaporation of Zr, O species (ions, atoms) and subsequent deposition of Zr-O film. Ta and Cu have been used as substrates. The films were analyzed by SEM-EDX, Raman and FTIR spectroscopy and X-ray diffraction. SEM analysis revealed µm/sub-µm sized roundshape and ring-like objects on continuous coat. Using Raman spectroscopy broad peaks which can suggest partial laser induced amorphization of Zr-O deposits were detected. FTIR spectroscopy shows bands which are assignable to Zr-O vibration of nanostructured zirconia. X-ray diffraction analysis provides more explicit assignment of deposited phases where the deposit on Ta exhibits presence of monoclinic ZrO2, oxygen deficient rhombohedric Zr3O and interestingly indicates presence of high-pressure orthorhombic ZrO2 phase. The coat on Cu consists of monoclinic ZrO2, rhombohedric Zr3O, and metastable tetragonal ZrO2 phase.
Synthesis and Characterization of Carbon Nanosheets from Stinging Nettle (Urtica Dioica)
Authors: Nuilek K , Simon A , Baumli P
Published: November 2019

Extensive research in nanotechnology has allowed us to improve and revolutionize technology and industry. This had led to an interest in the synthesis of other forms of carbon nanomaterial, such as graphene, fibre, carbon nanotubes and particles. Nowadays, a variety of carbon materials is available offering the flexibility to modify carbon properties. Therefore, the manufacture of carbon materials in different shapes is a likely way to take advantage of the morphology and relate it to the properties of the carbon nanomaterial. Stinging nettle is a new material to study for the production of carbon nanostructured materials. In this research, carbon nanosheets were successfully prepared from stinging nettle (nettle stem and leaf) using potassium hydroxide (KOH), sulphuric acid (H2SO4) and thermal treatment. This method is simple for producing carbon nanosheets from natural materials. Treating the nettle stem with KOH (solid) produces carbon nanosheets with a thickness of ∼159.2– 252.3 nm, while KOH (solute) treatment led to thinner nanosheets (∼70.43–111.2 nm). SEM micrographs of the nettle leaf with KOH (solute) activation show a smooth surface and clearly reveal the formation of carbon nanosheets. However, in the samples activated by KOH (solute) a greater number of micropores were found on the wall. The microstructure and morphology of the samples were investigated by scanning electron microscopy (SEM), the chemical composition was analysed by energy-dispersive X-ray spectrometry (EDS).
Band Structure of Phononic Crystal Consist of Hollow Aluminum Cylinders in Different Media; Finite Element Analysis
Authors: Ozer Zafer , Demir Mehtap , Mamedov Amirullah M. , Ozbay Ekmel
Published: November 2019

In this study, we investigated band structure of a 2D Phononic Crystal (PnC) which was consist of hollow aluminum cylinders in different media. To validate the finite element predictions, we made a square lattice PnC which has lattice constant a = 14mm, outer radius r1
= 5mm and inner radius r2
= 4mm of cylinders. In our experimental measurement, by using a signal generator software, we sent 100 Hz-20kHz sine signal for 5 seconds duration from speaker to the PnC where placed 1m away from. With the help of a microphone, we recorded the sound in front of the PnC (Pin
) and backside the PnC (Pout
). Then we were converted our recording into frequency domain by standard FFT algorithm, we calculated the Transmission Loss value according to the formula TL = 20*
log10
(Pout
/ Pin
) and obtained the experimental Transmission Loss. After experimental validation, we conducted band structure analysis of different combination of the 2D PnC by finite element method.
Application of finite element method (FEM) to study stress-strain state and distribution of temperatures in cutting zone in turning of various structural materials by carbide tools with coatings of various composition and architecture
Authors: Vereschaka Alexey , Mokritskii Boris , Mokritskaya Elena , Sharipov Oleg , Sotova Catherine
Published: November 2019

The paper considers simulation of cutting process conditions and state of a metal-cutting tool using the finite element method (FEM). The study considered the distribution of normal equivalent and tangential stresses in workpiece material during turning of aluminum-deformable alloy G-AlMg5 (DIN 1725) and copper C11000. Based on the calculated stress values, the values of plastic strains of the workpiece material were determined throughout the whole process of turning with the necessary time sampling of the process. The distribution of temperatures in cutting zone during turning of steel 5135 by carbide tools with coatings of different composition and thickness was studied. The obtained results were compared with the data obtained during the corresponding cutting tests. The paper considered the influence of such coating parameters as thickness, element composition and architecture on distribution of temperatures in a workpiece, cutting tool and chips during the cutting process.