bluuebunny/crossref_metadata_2025_split huggingface dataset:
Programming Ozobots for teaching astronomy
Authors: Balaton Mariana , Cavadas Jorge , Simeão Carvalho Paulo , Lima J J G 
Published: May 2021

Abstract
Experimental teaching is essential for a good understanding of science, especially on Physics. Practical activities play an important role for engaging students with science, mainly when they interact directly with equipment, collect experimental data with computers and/or use interactive software for data analysis. In this work, we present the use of low-cost mini-robots as an ‘object-to-think-with’ for teaching and learning with technology. The activity concerns programming the robots to make them run in circular paths, record videos of their trajectories and analyse them with Tracker Software, to boost the study of Astronomy contents. This kind of practical activity develops multiple skills in students and is usually very well accepted because it involves robots, programming, manipulating technology and for raising topics that are difficult to understand in real-life observations, making them cognitively accessible to the vast majority of students. In this practical activity, students are asked to create the robot programming code and make a video recording (with a smartphone) of the robots’ trajectories, mediated by the teacher, who assists in the construction of the experimental activity and analysis of the data obtained. The results will allow students to understand Kepler’s laws of planetary motion and why some planets seem to have an apparent retrograde motion as seen from the Earth, a problem that arose in IV BC and was only officially solved by the Copernicus heliocentric model, published in 1543, the year of his death.
Impact of the I-value of diamond on the energy deposition in different beam qualities
Authors: Kaveckyte Vaiva , Carlsson Tedgren Åsa , Fernández-Varea José M 
Published: May 2021

AbstractDiamond detectors are increasingly employed in dosimetry. Their response has been investigated by means of Monte Carlo (MC) methods, but there is no consensus on what mass densityρ, mean excitation energyIand number of conduction electrons per atomnceto use in the simulations. The ambiguity occurs due to its seeming similarity with graphite (both are carbon allotropes). Except for the difference inρbetween crystalline graphite (2.265 g cm−3) and diamond (3.515 g cm−3), their dielectric properties are assumed to be identical. This is incorrect, and the two materials should be distinguished: (ρ= 2.265 g cm−3,I= 81.0 eV,nce= 1) for graphite and (ρ= 3.515 g cm−3,I= 88.5 eV,nce= 0) for diamond. Simulations done with the MC codepenelopeshow that the energy imparted in diamond decreases by up to 1% with respect to ‘pseudo-diamond’ (ρ= 3.515 g cm−3,I= 81.0 eV,nce= 0) depending on the beam quality and cavity thickness. The energy imparted changed the most in cavities that are small compared with the range of electrons. The difference in the density-effect term relative to graphite was the smallest for diamond owing to an interplay effect thatρ,Iandncehave on this term, in contrast to pseudo-diamond media when eitherρorIalone were adjusted. The study also presents a parameterized density-effect correction function for diamond that may be used by MC codes like EGSnrc. Theestarprogram assumes thatnce= 2 for all carbon-based materials, hence it delivers an erroneous density-effect correction term for graphite and diamond. Despite the small changes of the energy imparted in diamond simulated with two differentIvalues and expected close-to-negligible deviation from the published small-field output correction data, it is important to pay attention to material properties and model the medium faithfully.
Development of a new piezoelectric galvanometer scanner: fabrication, operation, and measurements
Authors: Chiu Ya-Chu , Lin Chi-Ying , Yen Chien-Yu , Huang Yu-Hsi 
Published: May 2021

Abstract
Our objective in this study was to overcome the size and complexity of existing galvanometers by developing a direct-drive galvanometer based on the deformation of a double-layer ceramic piezoelectric disc with mirrored surface. The resulting device is extremely compact (0.41 mm), light weight, and highly responsive. The performance of the galvanometer was evaluated using an electronic speckle interferometer to characterize vibration mode characteristics. The voltage and input frequency can be adjusted to match the vibration amplitude and vibration mode required for practical galvanometer operations. Using a position sensitive detector, we recorded changes in the position of a light spot generated by a single-point laser by which to track changes in the optical path imposed by the galvanometer. Experiments using graphics drawn by an open-loop control system verified the performance of the device.
Prediction of crystal structures and motifs in the Fe–Mg–O system at Earth’s core pressures
Authors: Wang Renhai , Sun Yang , Wentzcovitch Renata M , Zheng Feng , Fang Yimei , Wu Shunqing , Lin Zijing , Wang Cai-Zhuang , Ho Kai-Ming 
Published: May 2021

Abstract
Fe, Mg, and O are among the most abundant elements in terrestrial planets. While the behavior of the Fe–O, Mg–O, and Fe–Mg binary systems under pressure have been investigated, there are still very few studies of the Fe–Mg–O ternary system at relevant Earth’s core and super-Earth’s mantle pressures. Here, we use the adaptive genetic algorithm (AGA) to study ternary Fe
x
Mg
y
O
z
phases in a wide range of stoichiometries at 200 GPa and 350 GPa. We discovered three dynamically stable phases with stoichiometries FeMg2O4, Fe2MgO4, and FeMg3O4 with lower enthalpy than any known combination of Fe–Mg–O high-pressure compounds at 350 GPa. With the discovery of these phases, we construct the Fe–Mg–O ternary convex hull. We further clarify the composition- and pressure-dependence of structural motifs with the analysis of the AGA-found stable and metastable structures. Analysis of binary and ternary stable phases suggest that O, Mg, or both could stabilize a BCC iron alloy at inner core pressures.
The smooth distributions of the surface states in a semi-bounded medium with an abruptly change in characteristics in dependence on the field amplitude
Authors: Savotchenko S E 
Published: May 2021

Abstract
The wave equation with the stepwise nonlinear coefficient on the semi-axis is considered. The boundary problems allowing to obtain the exact solutions of such nonlinear wave equation are proposed. Obtained solutions describe the features of the field localization near the surface covered with fully shielding film in the medium with an abruptly change in characteristics depending on the field. Five types of the surface states with the same structure but different amplitudes, phases, characteristic localization lengths and positions of the domain boundary are found. The features of the wave distributions and the influence of control parameters such as the threshold value of the switching field, surface amplitude and their derivatives on the wave characteristics are analyzed. The change in control parameters allows us to vary the position of the domain boundary.
Exact Anti-Self-Dual four-manifolds with a Killing symmetry by similarity transformations
Authors: Paliathanasis Andronikos 
Published: May 2021

Abstract
We study the group properties and the similarity solutions for the constraint conditions of anti-self-dual null Kähler four-dimensional manifolds with at least a Killing symmetry vector. Specifically we apply the theory of Lie symmetries to determine all the infinitesimal generators of the one-parameter point transformations which leave the system invariant. We use these transformations to define invariant similarity transformations which are used to simplify the differential equations and find the exact form of the spacetime. We show that the constraint equations admit an infinite number of symmetries which can be used to construct an infinite number of similarity transformations.
On the magnetized 3D flow of hybrid nanofluids utilizing nonlinear radiative heat transfer
Authors: Waqas Hassan , Farooq Umar , Alghamdi Metib , Muhammad Taseer , Alshomrani Ali Saleh 
Published: May 2021

Abstract
This article analyzes the heat transfer, non-linear thermal radiation, the Cattaneo-Christov heat flux model and velocity slip effects in hybrid nanofluid flow over a 3D moving sheet. The hybrid type nanoparticles like Ag-Cu and MoS2 and GO are suspended in working liquid. Hybrid nanoliquid is homogeneous-mixture with novel physical and chemical structures making it a promising option for improving thermal efficiency. Hybrid nanoliquids have high ability to absorb and preserve the hydrogen because of their very huge unique surface-area and distinctive and unusual nature of an each nanostructure. Nanostructure carbon atoms like graphite, graphene and few metals like molybdenum and magnesium have recently been found to store hydrogen due to their larger storage-capacity and the higher dehydrogenation and hydrogenation speeds. The system of the mathematical relation in PDEs form is converted to system of ODEs by employing suitable variables. The bvp4c tool available in computational software MATLAB is used for solving the dimensionless ordinary differential system. Furthermore, the flow expectations for each physical flow parameter like

0.1
≤
α
≤
1.2
,

0.4
≤
β
≤
1.2
,

2.0
≤
P
r
≤
5.0
,

0.1
≤
γ
≤
1.2
,

0.2
≤
R
e
≤
0.8
,

0.1
≤
M
≤
1.2
,

0.0
≤
R
d
≤
0.8
,

0.1
≤
E
c
≤
0.4
,

0.1
≤
N
r
≤
1.2
,

0.2
≤

ϕ

1

=

ϕ

2

≤
0.5.
,

0.1
≤
Ω
≤
0.6
,

1.5
≤

θ

w

≤
1.8
,

are discussed. The physical consequence of flow parameters against subjective flow fields are graphically highlighted with physical justifications. The vitality of prominent parameters against velocity field and temperature distribution is illustrated through graphs. The velocity field diminishes with a larger velocity slip parameter. The velocity field is enhanced by the higher estimations of the Grashof number. The consequence of temperature ratio parameter on thermal field is delineated. By enhancing the thermal relaxation parameter, the thermal field reduces.
Dynamic behaviors of a star-coupled underdamped system with multiplicative quadratic noise and periodic excitation
Authors: Li Pengfei , Tang Zeyu , Zhang Qian , Zhang Wei 
Published: May 2021

Abstract
The star-coupled linear underdamped system subject to multiplicative quadratic noise and periodic sinusoidal excitation are considered. The multiplicative noise is modeled as a quadratic polynomial function of symmetric trichotomous noise. Firstly, the stability conditions of the system and the stationary solution of the mean field are deduced by establishing the differential equations of the mean field. Then the synchronization conditions of the principal and general particles are obtained respectively. These conditions are beneficial for studying the collective behavior of the system and the motion characteristics of particles in different situations. Then the output signal-to-noise ratio of the coupled system is derived in detail for the first time. Moreover, the dynamic behaviors of the system are analyzed by analytical results and numerical simulations, including the collective behavior under different conditions, and the concrete influence of parameters on the output signal-to-noise ratio.
Parisi-Sourlas-like dimensional reduction of quantum gravity in the presence of observers
Authors: Podolskiy Dmitriy , Barvinsky Andrei O. , Lanza Robert 
Published: May 2021

Abstract
We show that in the presence of disorder induced by random networks of observers measuring
covariant quantities (such as scalar curvature) (3+1)-dimensional
quantum gravity exhibits an effective dimensional reduction at large spatio-temporal scales, which is
analogous to the Parisi-Sourlas phenomenon observed for quantum field theories
in random external fields. After averaging over disorder associated with observer networks, statistical properties of the latter determine both the value of gravitational constant and the effective cosmological constant in the model. Focusing on the dynamics of infrared degrees of freedom we find that
the upper critical dimension of the effective theory is lifted
from D
cr = 1+1 to D
cr = 3+1 dimensions.
Testing clockwork axion with gravitational waves
Authors: Chiang Cheng-Wei , Lu Bo-Qiang 
Published: May 2021

Abstract
We investigate the gravitational waves (GWs) produced from the Peccei-Quinn (PQ) phase transition associated with the clockwork axion. The PQ phase transition can be first-order when the dimension-6 operator is included into the scalar potential. The GWs from the PQ phase transition at scale in the range of 103-106 GeV are detectable for the BBO and ALIA interferometers. The LISA and Taiji interferometers can probe the GWs from the PQ scale f ≤ 104 GeV, while the GW signals from the scale f ≥ 105 GeV can be detected by the ground-based GW observatories ET and CE. We find that the parameter space κm
∼ 0.06-0.001, κl
∼ 0.04-0.001, and ε ∼ 0.1-0.01 at the scale f = 105 GeV and most of the parameter regions at the scale f = 106 GeV
have been excluded by the LIGO O2 run. The LIGO O3 and design phases can further probe the remaining parameter space.
We show that the GWs from the annihilation of domain walls with a PQ scale f ≃ 2 × 105 GeV can induce the
stochastic signals with the right amplitude for the NANOGrav 12.5-year observations, but having a steeper spectral slope than the observations.
The LIGO O3 run has the opportunity of detecting the GW signals from the first-order PQ phase transition around this scale.
Wavelike propagation of quorum activation through a spatially distributed bacterial population under natural regulation
Authors: Patel Keval , Rodriguez Coralis , Stabb Eric V , Hagen Stephen J 
Published: May 2021

Abstract
Many bacteria communicate using diffusible pheromone signals known as autoinducers. When the autoinducer concentration reaches a threshold, which requires a minimum population density or ‘quorum’, the bacteria activate specific gene regulatory pathways. Simple diffusion of autoinducer can activate quorum-dependent pathways in cells that are located at substantial distances from the secreting source. However, modeling has predicted that autoinducer diffusion, coupled with positive feedback regulation in autoinducer synthesis, could also allow a quorum-regulated behavior to spread more rapidly through a population by moving as a self-sustaining front at constant speed. Here we show that such propagation can occur in a population of bacteria whose quorum pathway operates under its own natural regulation. We find that in unstirred populations of Vibrio fischeri, introduction of autoinducer at one location triggers a wavelike traveling front of natural bioluminescence. The front moves with a well-defined speed ∼2.5 mm h−1, eventually outrunning the slower diffusional spreading of the initial stimulus. Consistent with predictions from modeling, the wave travels until late in growth, when population-wide activation occurs due to basal autoinducer production. Subsequent rounds of waves, including waves propagating in the reverse direction, can also be observed late in the growth of V. fischeri under natural regulation. Using an engineered, lac-dependent strain, we show that local stimuli other than autoinducers can also elicit a self-sustaining, propagating response. Our data show that the wavelike dynamics predicted by simple mathematical models of quorum signaling are readily detected in bacterial populations functioning under their own natural regulation, and that other, more complex traveling phenomena are also present. Because a traveling wave can substantially increase the efficiency of intercellular communication over macroscopic distances, our data indicate that very efficient modes of communication over distance are available to unmixed populations of V. fischeri and other microbes.
Enhancement for P300-speller classification using multi-window discriminative canonical pattern matching
Authors: Xiao Xiaolin , Xu Minpeng , Han Jin , Yin Erwei , Liu Shuang , Zhang Xin , Jung Tzyy-Ping , Ming Dong 
Published: May 2021

Abstract

Objective. P300s are one of the most studied event-related potentials (ERPs), which have been widely used for brain–computer interfaces (BCIs). Thus, fast and accurate recognition of P300s is an important issue for BCI study. Recently, there emerges a lot of novel classification algorithms for P300-speller. Among them, discriminative canonical pattern matching (DCPM) has been proven to work effectively, in which discriminative spatial pattern (DSP) filter can significantly enhance the spatial features of P300s. However, the pattern of ERPs in space varies with time, which was not taken into consideration in the traditional DCPM algorithm. Approach. In this study, we developed an advanced version of DCPM, i.e. multi-window DCPM, which contained a series of time-dependent DSP filters to fine-tune the extraction of spatial ERP features. To verify its effectiveness, 25 subjects were recruited and they were asked to conduct the typical P300-speller experiment. Main results. As a result, multi-window DCPM achieved the character recognition accuracy of 91.84% with only five training characters, which was significantly better than the traditional DCPM algorithm. Furthermore, it was also compared with eight other popular methods, including SWLDA, SKLDA, STDA, BLDA, xDAWN, HDCA, sHDCA and EEGNet. The results showed multi-window DCPM preformed the best, especially using a small calibration dataset. The proposed algorithm was applied to the BCI Controlled Robot Contest of P300 paradigm in 2019 World Robot Conference, and won the first place. Significance. These results demonstrate that multi-window DCPM is a promising method for improving the performance and enhancing the practicability of P300-speller.
Overview of the II International Conference on Metrological Support of Innovative Technologies – ICMSIT-II-2021
Authors: Antokhina Yu A , Ovodenko A A , Okrepilov V V , Kovalev I V , Voroshilova A A 
Published: May 2021

Abstract
The overview describes the main directions and results of the II International Conference “ICMSIT-II-2021” held in St. Petersburg in March 3-6, 2021. It gives the details about the participants and the proceedings. The anchor partner of Krasnoyarsk Science and Technology City Hall was St. Petersburg State University of Aerospace Instrumentation. A description of the main trends in modern innovative technologies, engineering and industrial physics as well as in the development of the third International Forum “Metrological Support of Innovative Technologies” by the St. Petersburg State University of Aerospace Instrumentation is given in the overview.
Building of a digital model of aluminum electrolysis modes
Authors: Vereschagina E A , Zolkin A L , Lavrov E A , Fakhertdinova D I , Dragulenko V V 
Published: May 2021

Abstract
The article discusses the issues of constructing a digital model of aluminum electrolysis modes. This model allows to achieve the specified criteria of the production process on the basis of scientific processing of historical data accumulated during the industrial production of aluminum at factories using a mathematical apparatus as well as to obtain recommendations on the values of control parameters. The study is aimed at achieving the business goals of the company’s management in particular on increasing of the profits by improving the quality and quantity of products with reduced production costs.
Competence-based approach in the training of physicists
Authors: Vasylyshyn Vitalii , Yekimov Sergey , Svitlana Nakhod , Yuliya Voytsekhovska , Otroshchenko Nataliia , Gavrilko Tetiana , Zheludenko Maryna , Mikheev Andriy , Tetiana Vynnyk 
Published: May 2021

Abstract
Competence is the ability of an individual to solve various practical tasks, a set of knowledge, skills and abilities required to perform a specific practical activity. The use of intersubject connections during the training of physicists, in our opinion, will make it possible to prepare specialists with a broad Outlook and good qualifications. The knowledge acquired in this way will allow future physicists to compete more successfully in the labor market. This may be important if, due to certain circumstances, it is not possible to work in a previously acquired specialty, this will allow you to choose a new profession in which you will be able to maximize the use of previously acquired competencies, as well as make the choice of a new profession more consciously.
Modeling the interaction of PbSe nanoparticles
Authors: Zakharov P V , Lutsenko I S , Markidonov A V , Cherednichenko A I 
Published: May 2021

Abstract
In this work, the interaction of two PbSe nanoparticles is studied by means of atomistic modeling within the framework of the molecular dynamics method. The considered model consisted of two nanoparticles, each of which contained 5398 atoms. The interaction between particles was described by means of the Leonardo-Jones pair potential supplemented by the Coulomb interaction. The paper considers the effect of temperature on the process of combining nanoparticles depending on the distance between them. Attention is paid to the deformation of PbSe particles. At the initial stage of model relaxation, diffusion processes occur along the surface of nanoparticles due to the presence of polarly charged (111) planes on the crystal surface. This process is accompanied by deformation of particles along the axis of mutual arrangement of PbSe. There is a tendency to an increase in deformation with increasing temperature. The tendency of increasing deformation with increasing distance between particles is characteristic. The presence of PbSe near the second particle leads to an increase in deformation with increasing temperature. The maximum deformation of the particles increased by 5%, compared to a single particle, where the deformation is due only to its own dipole moment.
Application of artificial intelligence and digital technologies in the organization of the educational process of specialists in the field of physics, engineering and metrology
Authors: Shamina S V , Munister V D , Zolkin A L , Verbitskiy R A , Dragulenko V V 
Published: May 2021

Abstract
The article deals with the problems and the importance of modern advanced learning. A model of teaching for students mastering programs of secondary and higher vocational education, based on the terminal-matrix approach, which includes the integration of several related disciplines, is proposed. The importance of artificial intelligence methods in engineering, physical, engineering education is substantiated by the example of checking of research results.
Modeling of rotational oscillations in a diesel locomotive wheel-motor block
Authors: Djanikulov Akhat T , Mamayev Sherali I , Kasimov Obidjon T 
Published: May 2021

Abstract
This article highlights the importance of the effective movement of the rolling stock and the coefficient of friction between the wheels and rails in their use. Factors affecting wheel friction with the rails were considered. During the study, the dependence of the coupling coefficient between the wheel and the rails on the speed of movement was considered. Accordingly, it was found that the coefficient of adhesion decreases with increasing speed.
One of the scenarios of transition to the turbulent mode of the flow of liquid crystals
Authors: Denisova O A 
Published: May 2021

Abstract
The article presents the results of an experimental study of the transition to a turbulent flow regime of thin layers of nematic liquid crystals (4-octyl-4’-cyanobiphenyl) with a thickness of 20-125 μm at temperature of 39° C. The cell we used was a “sandwich”, which was assembled from three translucent glass plates separated by narrow strips of gaskets. Shear effects on the cell were carried out by the pendulum method with a frequency of 190 Hz, the phoner method was used. The analysis of the amplitude dependence of the optical signal, its spectrum, as well as the amplitude dependence of the width of the spectrum showed that low-frequency modes appear in the fluctuation spectrum, which lead to the appearance of periodic convection in the nematic liquid crystal layer.