bluuebunny/crossref_metadata_2025_split huggingface dataset:
R+RG gravity with maximal Noether symmetry
Authors: Pokrovsky Yu E 
Published: November 2021

Abstract
A Noether symmetric, 3rd order polynomial in the Riemann curvature tensor
R
αβμν
extension of the General Relativity (GR) without cosmological constant (R+RG gravity) is suggested and discussed as a possible fundamental theory of gravity in 4-dimensional space-time with the geometric part of the Lagrangian to be

L

R
+
R
G

=

−
g

2
k

R

(

1
+

G

G
P

)

. Here

k
=

8
π

G
N

c
4

is the Einstein constant,

g
=
det

(

g

μ
ν

)

,

g

μ
ν

- the metric tensor, GN
- the Newton constant, c - the speed of light,

R
=

R

μ
ν

μ
ν

- the Ricci scalar,

G
=

R
2

−
4

R

μ
ν

R

μ
ν

+

R

α
β
μ
ν

R

α
β
μ
ν

- the Gauss-Bonnet topological invariant, and GP
- a new constant of the gravitational self-interaction to model the cosmological bounce, inflation, accelerated expansion of the Universe, etc. The best fit to the Baryon Acoustic Oscillations data for the Hubble parameter H (z) at the redshifts z<2.36 leads to

G
P

1
/
4

=

(

0.557
±
0.014

)

T
p

c

−
1

with the mean square weighted deviation from the data about 3 times smaller than for the standard cosmological (ΛCDM) model. Due to the self-gravitating term ∼RG the respective Einstein equation in the R+RG gravity contains the additional (tachyonic in the past and now) scalar (spin = 0) graviton and the perfect geometric fluid tensor with pressure-and matter-like terms equal to the respective terms in the ΛCDM model at |z| 1. Some predictions of this R+RG gravity for the Universe are also done.
Multiworld motives by closed time-like curves
Authors: Shepelin A V , Rostom A M , Tomilin V A , Il’ichov L V 
Published: November 2021

Abstract
We propose a new model, entitled S-CTC, for description of quantum systems in the presence of CTC – closed time-like curves. The model is based on the viewpoint on any quantum state as an observer’s state of knowledge of the system preparation procedure. We compare and contrast our S-CTC model with D-CTC and P-CTC models and show that S-CTC shares special quantum features with both D-CTC and P-CTC. As far as the interaction of the quantum system with itself coming from the future concerns, S-CTC is formally equivalent to P-CTC. On the other hand, when calculating outcome probabilities for a measurement within the time interval between the entrance and exit of CTC, S-CTC becomes equivalent to D-CTC. Both these models require the concept of alternative realities (worlds) where different measurement outcomes are recorded and alternative connections of these realities by CTC.
The principle of materiality of space and the theory of fundamental fields
Authors: Zhuravlev V M 
Published: November 2021

Abstract
The work formulates the principle of materiality of space and on its basis a brief critical analysis of the general ideology of the Special and General Theories of Relativity is carried out. The connection of the new principle with the previously developed Topological Theory of Fundamental Fields (TTFF) is considered. A method of constructive implementation of the principle of materiality in the framework of the physical theory of fundamental fields is considered. General equations of the dynamics of markers of material points of physical space are derived and their physical meaning is established.
Didactic Engineering as a research method in physics teaching
Authors: Prada-Núñez R , Gamboa-Suárez A A , Avendaño-Castro W R 
Published: November 2021

Abstract
Several mathematical concepts have application in physics; this paper reports the results of a pedagogical investigation based on the methodology known as didactic engineering, which has been proposed with the aim of improving the skills exhibited by a group of eleventh grade students from a private institution in the interpretation of kinematic graphs. The concept of the slope of the straight line and how this mathematical concept can represent velocity or acceleration according to the variables considered in the kinematics graph provided was enhanced in the pedagogical intervention. This methodology offers a process of internal validation, after comparing the results obtained in a knowledge test at two different points in time (pre-test and post-test). The results allowed us to identify improvements in all students in terms of basic kinematics graph interpretation skills, and a group of students stood out by advancing in more complex reasoning and interpretation processes. These results contribute to the improvement of the pedagogical practices of Physics teachers at secondary and middle school levels, making them more competent when they enter higher education.
Physics in architecture projects, a perfect match on Alamillo’s bridge by Santiago Calatrava
Authors: Acuña-Prada M C , Coronel-Ruiz L K , Prada-Nuñez R 
Published: November 2021

AbstractThe Alamillo’s bridge by Santiago Calatrava was studied, who develops projects and structures with morphological, sculptural, and conceptual aspects associated with physics and contemporary architecture, through experimentation with forms of nature, the movement of the human body and, materials such as steel and reinforced concrete. The methodological framework corresponded to a documentary study that determined the importance of the bridge from its historical context as part of the infrastructure of the 1992 Universal Exposition in Seville, as well as the analysis of the physical concepts used in its design and construction; and, a quantitative-descriptive study applied to the seventh semester students of the Architecture program of the Universidad Francisco de Paula Santander, Colombia, which determined their level of recognition of the physical concepts of this project. As a finding, it is highlighted that this bridge applied physical concepts such as: aerodynamics, torsion, compression, tension, traction, and gravitation, in compliance with its formal-aesthetic design criteria, and those students recognize the physical concepts, design and technical characteristics-formal, typical of the project. Likewise, it was determined that this urban landmark represents a comprehensive solution that solves the structure and form through solutions associated with the field of engineering, architecture, and physics.
Underlying variables in the understanding of movement in engineering students
Authors: Suárez O J , Gamboa-Suárez A A , Hernández-Suárez C A 
Published: November 2021

Abstract
This article describes the understanding of motion by active students taking Newtonian physics for engineering, supported by active learning, during the pandemic due to COVID-19; in addition, an unsupervised predictive model of learning achievement was constructed from variables identified using the principal component analysis technique on the responses. the instrument used is the modified test of understanding graphs-kinematics comprehension. students from two universities in Bogotá, Colombia participated. The results show a lower level of accuracy in students in remote face-to-face mode, compared to the reference group of physical presence; by way of reflection, the forced educational experiment implies resizing the teaching activity in the teaching and learning of movement.
Comparison of analytical methods and numerical methods in modeling the physical phenomenon of heat conduction with free radiation
Authors: Nolasco Serna C , Afanador Garcia N , Guerrero Gómez G 
Published: November 2021

Abstract
The development of mathematical setting for modeling heat conduction phenomena in the presence of radioactive effects is well known. The importance in the study of heat conduction in relation to radioactive effects is relevant in several engineering applications such as combustion, materials science, fluid mechanics and other areas. This research is based on the mathematical model of the heat equation to study the physical phenomenon of heat transfer along a metal bar with slightly insulated sides with the effect of free radiation. To calculate the temperature function that allows modeling the heat transfer process along the bar, the Fourier series solution is constructed step by step, in addition an alternative method of calculating the temperature by using the explicit numerical method is given. The calculation of the temperature along the bar is compared by analytical and numerical method by computing the percentage error and different temperature profiles are plotted to verify the fit of the two approaches. The methods developed throughout the research can be extended to other types of physical phenomena that are useful in related research and in education in engineering subjects such as fluid mechanics and heat transfer.
Modeling of heat transport phenomena using the equations of mathematical physics
Authors: Nolasco Serna C , Afanador Garcia N , Guerrero Gómez G 
Published: November 2021

AbstractThe study of physical phenomena that include conservative principles is part of the research field of the equations of mathematical physics. To deepen in methods to solve the equations of mathematical physics is a contribution in understanding the modeling of applications in different areas. This research studies the physical phenomenon of heat transport with convection from the viewpoint of modeling with differential equations. The advantage of working with equations is to apply the techniques of mathematical analysis and numerical methods to obtain the temperature function. In the research, the solution of the heat transport model is computed according to the analytical method of separable variables in order to represent the temperature function as a trigonometric series. With the help of a simple numerical method, it is possible to derive a scheme of calculation of the temperature function. By performing a case study, the methods are compared, and their fit is verified by simulation.
Analysis of linear and non-linear effects in the frequency domain for a three-channel optical transmission system
Authors: Galvis-Velandia J E , Puerto-López K , Ramírez-Mateus J 
Published: November 2021

Abstract
This paper presents the analysis of a wavelength division multiplexer communication system in the frequency domain, with the objective of visualizing the incidence of the linear phenomena of attenuation and chromatic dispersion, together with the phenomenon of phase self-modulation, the Kerr electro-optical effect and fourth wave mixing. The analyzed system consists of a laser transmitter with a Mach-Zender modulator and a standard G.625b single-mode fiber link transmitting three optical signals of 10 mW, 25 mW and 50 mW at a fundamental wavelength of 1550 nm at a rate of 10 Gbps. This system is analyzed through a graphical user interface programmed by the authors in the Python environment, which calculates the parameters corresponding to each phenomenon and graphically represents the transmission results at distances of 50 km and 100 km. The analysis methodology consists of varying the spectral separation of the transmitted channels, initially considering a spectral separation of 2 nm and subsequently a spectral separation of 0.2 nm, observing as a result that the harmonics generated by the fourth wave mixing phenomenon considerably alter the spectral density of the transmitted signals, since the energy of the harmonics is equal to the power of the transmitted signals. On the other hand, with the spectral spacing of 0.2 nm, it is obtained that, although the harmonics alter the spectral density waveform, the bandwidth is not compromised by these additional signals.
Applications of differential equations to model the physical phenomenon of heat transfer with an internal energy source
Authors: Cadena-Morales J J , López-Castro C A , Alba-Maldonado J M 
Published: November 2021

Abstract
The mathematical modeling of the physical phenomenon of conduction in the presence of heat sources has various uses in engineering ranging from heat diffusion, pollution generation in large cities and chemical reactions. From the mathematical theory, the study of physical phenomena with the presence of heat is approached from techniques of polynomial approximation, analysis of variations and numerical methods. In this research a mathematical model is proposed to study the heat conduction in a metal bar with a heat source. In the first part of the work, by the application of the method of the parameter variation, the exact solution of the mathematical model is calculated. Subsequently, by means of a case study of the physical phenomenon of heat conduction with internal energy source, with the use of computational simulation, the convergence of the Fourier series linked to the physical phenomenon is shown. The mathematical method proposed in the paper can be applied to other physical phenomena such as wave propagation, electric potential, and chemical reactions.
FM-CW compact reflectometer using DDS signal generation
Authors: Silva A. , Dias J. , Santos J. , da Silva F. , Gonçalves B. 
Published: November 2021

Abstract
A prototype of a compact coherent fast frequency sweeping RF back-end is being developed at IPFN-IST using commercial Monolithic Microwave Integrated Circuits (MMIC). On this work we present the usability of this concept of compact reflectometry associated with a Direct Digital Synthesis (DDS) source. Flexibility is one of the design goals for the back-end prototype, so that it can easily match the required frequency range. The backend alone covers the NATO J-band (10 GHz to 20 GHz) and is designed to drive external full band frequency multipliers, resulting in an ultra-wideband coverage of up to 140 GHz. FM-CW radar precision is strongly dependent on the probing source linearity. DDS nowadays plays an important role in signal generation in many fields of applications for communication systems as well as in radar technology. Modern DDSs are fully integrated, low-cost, single chip solutions that only need an external clock source for generating sinusoidal output signals up to several gigahertz. The DDS benefits from the totally digital generation of the output signal, which allows full control of the signal’s frequency and phase, both with very high precision and resolution. Recent implementations feature automatic sweeping capability, thus allowing the DDS to generate very linear and agile frequency chirps, assuming a high quality and constant frequency reference clock source. We propose to implement a DDS signal generation solution with the capability of a full band sweep in 1 μs. On the receiver side the IF and reference signals will be digitised allowing the use of high flexible data processing techniques. Input/output signals will allow the synchronisation of several systems.
Aerosol–light interactions reduce the carbon budget imbalance
Authors: O’Sullivan Michael , Zhang Yuan , Bellouin Nicolas , Harris Ian , Mercado Lina M , Sitch Stephen , Ciais Philippe , Friedlingstein Pierre 
Published: November 2021

Abstract
Current estimates of the global land carbon sink contain substantial uncertainties on interannual timescales which contribute to a non-closure in the global carbon budget (GCB) in any given year. This budget imbalance (BIM) partly arises due to the use of imperfect models which are missing or misrepresenting processes. One such omission is the separate treatment of downward direct and diffuse solar radiation on photosynthesis. Here we evaluate and use an improved high-resolution (6-hourly), gridded dataset of surface solar diffuse and direct fluxes, over 1901–2017, constrained by satellite and ground-level observations, to drive two global land models. Results show that tropospheric aerosol–light interactions have the potential for substantial land carbon impacts (up to 0.4 PgCyr-1 enhanced sink) at decadal timescales, however large uncertainties remain, with models disagreeing on the direction of change in carbon uptake. On interannual timescales, results also show an enhancement of the land carbon sink (up to 0.9 PgCyr-1) and subsequent reduction in BIM by 55% in years following volcanic eruptions. We therefore suggest GCB assessments include this dataset in order to improve land carbon sink estimates.
On scalar products and form factors by separation of variables: the antiperiodic XXZ model
Authors: Pei Hao , Terras Véronique 
Published: November 2021

Abstract
We consider the XXZ spin-1/2 Heisenberg chain with antiperiodic boundary conditions. The inhomogeneous version of this model can be solved by separation of variables, and the eigenstates can be constructed in terms of Q-functions, solution of a Baxter TQ-equation, which have double periodicity compared to the periodic case. We compute in this framework the scalar products of a particular class of separate states which notably includes the eigenstates of the transfer matrix. We also compute the form factors of local spin operators, i.e. their matrix elements between two eigenstates of the transfer matrix. We show that these quantities admit determinant representations with rows and columns labelled by the roots of the Q-functions of the corresponding separate states, as in the periodic case, although the form of the determinant are here slightly different. We also propose alternative types of determinant representations written directly in terms of the transfer matrix eigenvalues.
Comparison of cost indicators of Ukrainian wind farms with cost indicators of wind energy global producers
Authors: Podhurenko V , Kutsan Yu , Terekhov V 
Published: November 2021

Abstract
Efficiency improvement in wind conversion field is the most critical scientific-and-technical problem, which is chiefly settled by increasing the power of wind turbines. A new technique was pioneered for determining the efficiency of wind turbines operation in the wind conditions of the Northern Black Sea region of Ukraine. It is found out that the main parameters that have an impact on the cost of electricity are as follows: the cost of a wind turbine itself and annual electric energy production. The cost indicators of wind turbines of the Ukrainian wind farms were defined in the wind conditions of the Northern Black Sea region in 2018, according to which it was ascertained that the cost of electric energy generated in Ukraine was by 17 % cheaper as compared to the world cost value. In illustration of application of the first ever developed technique, we have made the assessment of effective operation of the Ukrainian wind farms in the years of 2019 – 2020. The results obtained bear compelling evidence as to the correlations between the cost of produced electric energy and the size of wind turbines. In view of the above, application of wind turbines of super-large sizes in the conditions of the Northern Black Sea area of Ukraine (as well as in other regions of the world) is hardly expedient due to increase in the cost of electric power generated by them.
The impact of climate change on the investment attractiveness of agricultural enterprises
Authors: Davydenko N , Titenko Z , Buriak A , Polova O 
Published: November 2021

Abstract
The trend of climate change has a direct impact on the economic development of any country. Ukraine is an agrarian country and climatic conditions have a direct impact on its economic stability. The purpose of this work is to highlight the tightness of climate change and their direct impact on the development of the agricultural sector of Ukraine’s economy on the example of a particular agricultural enterprise and develop recommendations for adapting the enterprise to climate change. The conducted research clearly shows the negative consequences of climate change and the forms of their manifestation, which threaten not only the studied enterprise, but also the agricultural sector of Ukraine. It is established that the main ones are the following: instability of temperature indicators, soil degradation and the spread of diseases and pests of crops.
“Green” finance as a modern tool for social and environmental security
Authors: Cheberyako O V , Varnalii Z S , Borysenko O A , Miedviedkova N S 
Published: November 2021

Abstract
The article is devoted to the study of the essence of “green” finance and is intended to give an idea of the existing “green” financial instruments and problems of their application in Ukraine, to outline ways to improve the use of “green” financial instruments to ensure social and environmental security. The study calls for a review and improvement of practices in the use of “green” financial instruments, taking into account the international experience. The research paper is structured as follows: firstly, theoretical approaches to the essence of “green” finance are disclosed; secondly, the impact of “green” finance on social and environmental security is considered; thirdly, “green” finance is examined financial instruments to enhance national security in both the environmental and social spheres. The results of the study allowed to provide directions for the development of “green” finance in the context of social and environmental security in Ukraine, in particular, to strengthen the use of public-private partnerships, climate risk insurance and investment in education to create a skilled labor force in “green” finance.
Environmental component of socially responsible policy of multinational companies
Authors: Privarnikova I , Zinchenko O , Meshko N , Apalkova V 
Published: November 2021

Abstract
The article is aimed at studying environmental responsibility of multinational enterprises in electronics and IT sectors. The main aspects of environmental policy of global business enterprises have been systematized, their characteristics for such high-tech market leaders as Alphabet Inc, IBM and Intel Corporation have been given. Corporate policies have been analyzed and compared in three aspects of environmental activity of the companies selected for this study: waste recycling, energy use and environmental impact. The results of the analysis of eco-responsible companies’ practices show that each company forms management style and tools by implementing environmental responsibility, but none of them has managed to hold higher positions in the ranking of business environmental responsibility. Reserves for activating eco-oriented companies’ policy in IT sector have been identified.
Circular law as a legal basis for a circular economy
Authors: Mikichurova O V , Vlialko I V 
Published: November 2021

Abstract
The article is devoted to the study of the legal basis for the development of the circular economy, clarifying the essence of the concept of circular law, and analysis of international and national legal acts in this area. Research has shown humanity’s awareness of modern global threats and its gradual movement from the traditional to circular economic model. The legal basis for such a transition lies in circular law, which is a set of legal norms that define and regulate social relations in the field of circular economy. The article explores legal acts in the field of circular economy at the universal, regional and national levels across the globe. The main purpose of the article is to analyze the legal basis for the development of the circular economy. International law is currently being enriched with a number of new legal acts devoted to this subject matter. This may indicate the emergence of a new branch of international law – a circular law. An increased attention of international financial institutions towards financing of circular projects stipulates the further development and spread of the circular concept.