bluuebunny/crossref_metadata_2025 huggingface dataset:
Artificial modelling of unsaturated tests considering the suction control on porous collapsible clay
Authors: Ruge J C
Published: November 2019

Soils with a tendency to show phenomena of collapsibility generally have a susceptibility to be controlled by partial saturation, due to its structural configuration which reveal in some cases bonds of cementing minerals, that can be broken in process of wetting. This cementation is governed by the lateritic genesis, as well as for a microporal predominance. Laboratory tests that intend to reproduce the unsaturated condition, need a suction control to simulate properly the levels of stress required in the sample, according with the in-situ stresses presents in the soil mass. However, these tests are difficult to have access to given that they have a complicated assembly and can last several days (even months), due to the benefit in the resistance imposed by the suction on the soil. For this reason, it is extremely important to validate numerically by means of an appropriate constitutive law, at least at the laboratory level, the unsaturated response of a material. In this case a collapsible porous clay of lateritic origin, cause the high dependency of specialized laboratory tests can lead to non-necessaries delayed researches, that can impact in the economy of any project. In this research, an emphasis is placed on the numerical simulation of partially saturated tests through a hypoplastic constitutive model that involves suction in its mathematical formulation. The results are oriented to show the dependence of the suction with the shear strength of the material.
Multicriteria analysis of methane mitigation options on offshore oil and gas production platforms
Authors: Barbosa R , Guimarães C , Serra E , Bellon D , Martínez-Amariz A
Published: November 2019

The oil and gas exploration and production sector are one of the most significant methane emitters through fossil fuel combustion and fugitive emissions. In Brazil, there are few studies focused on the mitigation of methane in the oil sector. The objective of the present work is to use a multicriteria analysis methodology to compare different methane mitigation technologies applicable to offshore oil and gas platforms. In the study, six different mitigation options were compared through the analytic hierarchy process methodology, considering environmental, financial and operational criteria. The results were calculated for each mitigation option considering the scores of each criterion and their respective relative weights, obtained in the prioritization of the elements. This unique score obtained through the analytic hierarchy process made it possible to compare the mitigation alternatives. The alternative that received the best score considering the evaluated criteria was the recovery of vapor from cargo tanks associated with methane reuse, being highlighted mainly due to its high potential for mitigation.
Software to determine the viscosity and honey’s purity using a ball viscometer
Authors: Angelone J P , González N , Adarme J , Rueda S , Cristiano K L , Herrera J R , Triana D A
Published: November 2019

Physics is a science that studies the laws and properties of the universe and everything in it. However, it is more interesting when it is applied to the solution of problems that influence economic and social development. In our case, applied to beekeeping to ensure the purity of honey. Some producers or intermediaries add sugar or water to honey to reduce costs and improve their income affecting the final consumer. Therefore, in this research work, an experimental methodology was proposed combined with the development of software to determine the viscosity of honey with aggregates (sugar and water) and without those, considering that the experimental methodology used here, does not alter the properties of honey. With a ball viscometer and using honey as a viscous medium, times that took metal spheres to pass through the sample tube with different densities were measured. The times were analyzed and synthesized with the application to obtain the viscosity in real-time of the different types of honey, allowing to discern which ones were pure and which had water or sugar aggregates.
Using scattering theory to calculate the ground state energy of lithium atom
Authors: Alcalá Varilla L A , Torres Hoyos F , Pérez Pitalua D L
Published: November 2019

The problem of bound states of atoms with many electrons does not have an analytic solution; therefore, standard methods of approximation are utilized to solve it, and among them, we can find the variational method, the perturbation method and the Hartree Fock method. Said methods may be very difficult to implement and may take a great amount of computational time, even when they are applied to the lithium atom. An alternative method that is considerably easier to implement is proposed in this paper. This involves considering the Hamiltonian for the lithium atom as a collision between an electron and an ionized lithium atom; in this way, the energy of the lithium atom is the sum of energies of a helium atom (with nuclear charge Z = 3) and the energy that an electron needs to be bound to an ionized lithium atom in a collision process. The Quantum Collision Theory under the focus of Jost function was used to calculate the bound state energies of one electron with an ionized lithium atom. Using this approach, we calculated the ground state energy of lithium atom with an error with respect to the experimental value of 0.3%. This error is very low; therefore, the proposed method produces very good results and it can be taken as basis to study atoms with more electrons. Hopefully, In the future, this method could be part of quantum physics books because it is a novel method to observe the formation of atoms.
Computational study of a glow discharge device
Authors: Pacheco Y Q , Barragán Y F , Parada-Becerra F F , Tsygankov P A , Orozco E A
Published: November 2019

The glow discharge is the basis of conventional techniques used to improve the tribological properties of materials, such as the generation of thin films using ionic beams and the sputtering process for the treatment of surfaces. This work focuses on the numerical study of the glow discharge in a system composed of a cylindrical quartz chamber containing argon gas, whose length and radius are 20 cm and 2.5 cm, respectively. Said chamber is limited by two copper electrodes whose potentials are 0 V (Anode) and -500 V(Cathode), respectively. In order to analyze this time-independent discharge, the generation of secondary electrons allowing the discharge to be self-sustained as well as the manifestation of fixed regions, among others, numerical modeling is carried out by using the Plasma Module of COMSOL Multiphysics software. The presented results in this paper can be useful to understand, design and build new technologies focused on the area of treatment of surfaces.
Numerical study of linear plasma dynamics in a spherical tokamak
Authors: López J E , Orozco E A , Dugar-Zhabon V D
Published: November 2019

The magnetohydrodynamic equilibrium is the starting point to study macro- instabilities in a confined plasma; for the particular case, where the system is axially symmetric, the static and stationary equilibrium is due by the Grad-Shafranov equation. We present the equilibrium state for a toroidal plasma confined by a spherical Tokamak with aspect ratio A ∼1.6, total plasma current 1.3 MA and beta parameter β ∼0.35. The Grad-Shafranov equation is solved numerically in a rectangular region of the poloidal plane, using the finite differences method under a successive over-relaxation scheme. Profiles of poloidal magnetic flux, pressure, safety factor and magnetic field are presented. Subsequently, by using the resistive magnetohydrodynamic model, said equilibrium is subjected to perturbations in the velocity to study the dynamics of the plasma in the linear regime. The plasma dynamics simulation is carried out under a fourth order finite difference scheme for the spatial derivatives and implementing the Runge-Kutta algorithm as a temporal integrator. The results show that the perturbations are located in the plasma outer edge; however, some poloidal modes move toward the central zone around the magnetic axis.
Simulation of the electron dynamics in a magnetron sputtering device with equipotential and non-equipotential cathode
Authors: Tsygankov P A , Orozco E A , Dugar-Zhabon V D , López J E , Cárdenas P A
Published: November 2019

The magnetron sputtering of cathode material is one of the ways of producing a thin film deposition on solid surfaces and maintaining the cathode system under a certain potential. Recently, some experimental study of a magnetron sputtering system with the segmented cathode at different electric potential on each segment has been conducted. It allows the system productivity regarding the rate of deposition to be over the volt-ampere current limitations imposed on each segment. The physical processes associated with generating and sustaining it in this system are complex and have not been explained so far from a theoretical point of view. In this work, we present a computational study of the electron dynamics in the simple particle approximation which is found in a two-segments magnetron discharge under the influence of both the magnetic field and the segment electric potentials of 750 V and 500 V. The fields are calculated by using comsol multiphysics ®. The particle dynamics is studied through numerical solution of the Newton-Lorentz equation. The simulations show that the Hall current symmetry is determined by the electrode segments geometry. The obtained results are checked through the simulations fulfilled to maintain the cathode system at the same potential.
Smart operator for the human liver automatic segmentation, present in medical images
Authors: Vera M , Sáenz F , Huérfano Y , Gelvez-Almeida E , Vera M I , Salazar-Torres J , Valbuena O
Published: November 2019

The segmentation of the human body organ called liver is a highly challenging problem due to the noise, artifacts and the low contrast exhibited by the anatomical structures located around the liver and that are present in digital images, generated by any modality of medical images. The main modalities are: ultrasound, nuclear emission, magnetic resonance and the gold standard called multi-slice computed tomography. In this paper, with the objective of to address this problem, we consider multi-slice computed tomography images and we propose an automatic strategy based on two phases. In the first phase, a digital filtering bank is used for diminishing the noise effect and the artifacts impact in the quality of images. In the second phase, called liver detection, we use a smart operator based on least squares support vector machines for generating both the morphology and the volume of liver. The application of this strategy allows generating the morphology of the liver in a precise and efficient manner as it was demonstrated by the metrics used to assess its performance. These results are very important in clinical-surgical processes where both the shape and volume of liver are vital for monitoring some liver diseases that can affect the normal liver physiology.
Left atrial appendage automatic segmentation, in computed tomography images
Authors: Huérfano Y , Vera M , Vera M I , Valbuena O , Gelvez-Almeida E , Salazar-Tores J , Molina V
Published: November 2019

The left atrial appendage is one of the anatomical places where most frequently blood thrombi occur. When migrating from the appendage, these thrombi, become blood emboli that, potentially, can compromise the physiology and/or anatomy of cardiac or cerebral blood vessels, being able to generate cerebrovascular events. The left atrial appendage segmentation is very difficult due, mainly, to its location and the identical densitometric information presents into of this appendage and around of the left atrium. In this paper, an automatic technique is proposed to segment this appendage with the purpose of generating important information to the procedure called left atrial appendage surgical closure. This information is linked to the volume and the diameters of the left atrial appendage. The technique consists of a digital pre-processing stage, based on filtering processes and definition of a region of interest and, of one segmentation stage that considers a clustering method. The results are promising and they allow us to calculate useful quantitative variables when characterizing the most lethal appendix of the human body represented by the mentioned appendage. These results are very important in clinical processes where both the shape and volume of this appendage are vital for detecting and monitoring some vascular diseases such as cardiac embolism, arterial hypertension and stroke, among others.
Usefulness of digital images segmentation in pulmonary transplantation
Authors: Gelvez-Almeida E , Huérfano Y , Vera M , Vera M I , Valbuena O , Salazar-Torres J
Published: November 2019

In the presence of pulmonary pathologies such as chronic obstructive pulmonary disease, diffuse pulmonary disease and cystic fibrosis, among others, it is common to require the removal or replacement of a portion of lungs. There are several requirements for both donors and organ receivers (recipients) established in the literature. May be the main one is the volume that the donor’s lungs occupy in the thoracic cavity. This parameter is vital because if the volume of the lungs exceeds the thoracic cavity of the recipients the transplant, logically, is unfeasible for physical reasons such as the incompatibility between the receiver lung volume and the donor lung volume. In this sense, the present paper proposes the creation of a hybrid technique, based on digital image processing techniques application to raise the quality of the information related to lungs captured in three-dimensional sequences of computed tomography and for generating the morphology and the volumes of the lungs, belonging to a patient. During the filtering stage median, saturated and gradient magnitude filters are applied with the purpose of addressing the noise and artefacts images problems; whereas during the segmentation stage, methods based on clustering processes are used to extract the lungs from the images. The values obtained for the metric that assesses the quality of the hybrid computational technique reflect its good performance. Additionally, these results are very important in clinical processes where both the shapes and volumes of lungs are vital for monitoring some lung diseases that can affect the normal lung physiology.
Semi-automatic detection of the evolutionary forms of visceral leishmaniasis in microscopic blood smears
Authors: Salazar J , Vera M , Huérfano Y , Vera M I , Gelvez-Almeida E , Valbuena O
Published: November 2019

Leishmaniasis is a complex group of diseases caused by obligate unicellular and intracellular eukaryotic protozoa of the leishmania genus. Leishmania species generate diverse syndromes ranging from skin ulcers of spontaneous resolution to fatal visceral disease. These syndromes belong to three categories: visceral leishmaniasis, cutaneous leishmaniasis and mucosal leishmaniasis. The visceral leishmaniasis is based on the reticuloendothelial system producing hepatomegaly, splenomegaly and lymphadenopathy. In the present article, a semiautomatic segmentation strategy is proposed to obtain the segmentations of the evolutionary shapes of visceral leishmaniasis called parasites, specifically of the type amastigote and promastigote. For this purpose, the optical microscopy images containing said evolutionary shapes, which are generated from a blood smear, are subjected to a process of transformation of the color intensity space into a space of intensity in gray levels that facilitate their subsequent preprocessing and adaptation. In the preprocessing stage, smoothing filters and edge detectors are used to enhance the optical microscopy images. In a complementary way, a segmentation technique that groups the pixels corresponding to each one of the parasites, presents in the considered images, is applied. The results reveal a high correspondence between the available manual segmentations and the semi-automatic segmentations which are useful for the characterization of the parasites. The obtained segmentations let us to calculate areas and perimeters associated with the parasites segmented. These results are very important in clinical context where both the area and perimeter calculated are vital for monitoring the development of visceral leishmaniasis.
An ontological model based on the ontology driven architecture paradigm for a middleware in the management of nano-devices in a smart environment
Authors: Lopez-Pacheco A , Aguilar J , Puerto E , García R
Published: November 2019

In this paper is proposed an ontology framework for an autonomic reflective middleware for the management of nanodevices, which is based on the ontology-driven architecture paradigm. In this paper are presented the different levels of the ontology driven architecture model. At the first level, the computation independent model level defines the different ontologies of the nanotechnology domain, like a taxonomy of nanodevices, among others. The second level is the platform independent model level, where are defined the different ontologies for the deployment of the platform, which are the autonomic computation for the autonomous behavior of the middleware, data analytics that describes the analysis process of nanodata, and service-oriented architecture because the autonomic reflective middleware is defined as a multi-agent system oriented by services.
Analytical and experimental determination of gravity and moment of inertia using a physical pendulum
Authors: Cristiano K L , Triana D A , Ortíz R , Pico M , Estupiñán A F
Published: November 2019

Searching to encourage and increase the desire of students to seek a vocation in the study of engineering and science, we wanted to implement and validate experimentally and numerically, the study of the movement of a mechanical oscillator using, in this case, a physical pendulum, formed by a bar and a disk. In this article has done the study the physical pendulum, combining a methodology that involves an experimental arrangement and the implementation of simulations developed in Python, with the aim objective of offering to students a visual and interactive experience, so that they can understand in a simpler way topics covered in the theoretical physics course, in such a way that is different from the typical physical-mathematical formalism. This study was carried out with low cost materials and easy access, in addition to the great social impact that I had against the acceptance and assessment by the students with whom this work was applied. This work was developed in three phases: first, to measure the period of oscillation of a physical pendulum experimentally. Second, the approach of the analytical model to compare with the experimental results. Third, the development of a dynamic simulator according to the predictions of the theoretical model. The students found a didactic and different way of studying the physical pendulum. Finally, it was possible to demonstrate a self-consistency between the experimental and numerical results of the system studied in this work.
Rainwater volume at the Alberto Santos Buitrago school in El Socorro, Colombia
Authors: Torrado K A , Duran L M , Cristancho S L , Quintanilla E , Céspedes E , Tiria L C
Published: November 2019

This study calculated the volume of capturable rainwater over a three-month period at the Alberto Santos Buitrago school in the municipality of El Socorro, Colombia. Rainwater is frequently an under-developed natural resource, due to the minimal investment by public entities, and to the lack of awareness and education of the local inhabitants in this regard. Due to the significant climatic changes occurring across Colombia, however, new interest has arisen in utilizing this resource. The Universidad de Santander, Bucaramanga, Colombia, and the Universidad Libre in El Socorro, Colombia, have joined forces to promote projects focused upon the use of these resources to ameliorate the condition of vulnerable green areas, which tend to deteriorate during dry summer months, as occurred during this study, due to local geographic conditions and the impacted population; in these case young, low-income students of this rural municipality. Such a water storage and distribution system could also serve a valuable role in the school’s sanitary facilities, and for cleaning public areas, with a total of 35.01 m3 of rainwater collected on school roofs. Nevertheless, upon the delivery of the results of the current study, a significant lack of interest was evident on the part of the directors of public institutions in implementing this type of sanitary system. It is thus necessary for the community itself to commit to incentivizing and promoting the implementation and improvement of these new mechanisms.
Impact of technology on the evolution of sports training
Authors: Vera-Rivera J L , Ortega-Parra A J , Ramírez-Ortiz Y A
Published: November 2019

This research work aimed to analyze through research results in some sports how the application of technology affects the diagnosis and planning of sports training. within the methodology, different types of theoretical methods were used, such as analysis and synthesis, the logical history that, through the findings found in different specialized databases, allowed us to find different positions and theoretical references that allow us to affirm that winning in national and international competitions is the product of conducting a well-planned interdisciplinary work, the use of methods such as quasi-experimental that is based on the pre-test, the pedagogical intervention and the post-test was carried out through the use of the technological implementation used in sport as it is through sport machines such as contact platforms, linear encoders, sports preparation software, tablets, and mobile devices that facilitate the roles of the coach and his interdisciplinary group that through technology demonstrates have better results in the data processing, evaluations, and treatment of injuries of their athletes. The work allows managing evaluative information of different sports disciplines about the level of physical, technical, and tactical preparation and other aspects of sports preparation that access to identify characteristics of sports performance of the athlete. A descriptive and application research approach was assumed that through a training plan allows to capture and generate key information for the identification and characterization of the most important aspects of the control and monitoring of the athlete as they are actors (individual, institutional, corporate), that includes elements of personal data, results of physical, technical, tactical tests and thus, having reliable data that allow us to predict results in different sports competitions As results the specific requirements expressed in user stories were obtained and the strengths and weaknesses of the athletes understudy taking into account that the social impact is to be able to use sports development mechanisms that help the orientation and selection of sports talent found in the different slums and neighborhoods of the region which will allow through sport a comprehensive education and environmental care through a sports and pedagogical process that allows it to grow economically not only in the sale of services that can be generated with the use of state of the art technology but with the economic projection of what can be worth a high-performance athlete. In conclusion, reliable information was obtained, for the realization and control of different training plans generating inputs for decision-making in the approach of different possibilities seeking to solve very particular aspects of the computerized and disciplinary management of sport, the use of technology applied to sports training represents a significant advance in reducing costs, time and processes in the training of athletes with a view to professional sports.
Development of a technological platform for teaching and training in competitive programming contests
Authors: Lázaro Carrillo G Y , Delgado León A M , Vera Contreras M J , Vera-Rivera F H
Published: November 2019

The competitive programming contests are competitions where the programming capacity and algorithm of the participants are measured. The objective of this work was to develop and implement a framework to formalize the working methodology of the competitive programming study group of the Universidad Francisco de Paula Santander and to develop a web-based training platform to monitor the work carried out within the study group. The intention with this platform is to give the students the tools they need to carry out their training, from the platform the student can study, can practice, can compete, and can improve their skills both in competitive programming, as well as in areas of programming and computer science. This work was carried out following an iterative methodology composed of the following phases: initially, the project has been formalized, analysis of the problem, preliminary details, and formation of the state of the art and theoretical reference. Then, the initial state of the group is diagnosed, a solution is proposed. After refining this solution proposal. Once implemented, information and metrics are gathered and the results are analyzed, already with a functional framework and a web platform, to detect problems and improvements, restarting the phases, for improving in each step those aspects that can be enhanced. The results obtained in the national and international contest have improved considerably and the participation and satisfaction of the students who are part of the study group were increased. The technological platform developed constitutes a confluence point for the study group, and a clear guideline to follow to advance in the process of continuous improvement that allows the university to achieve the best results in national and international programming competitions.
Bloch lines in thin films with perpendicular magnetic anisotropy and intermediate quality factor
Authors: Izmozherov I M , Zverev V V , Baykenov Erlan Zh.
Published: November 2019

Bloch lines (BLs) are linear topological defects of magnetic domain walls structure, studied well for bubble domain materials. We investigate its structure and role in magnetization reversal for thin ferromagnetic films with perpendicular magnetic anisotropy and intermediate quality factor. We observe vertical BLs with Bloch points and U-shaped structures with vertical and horizontal parts in three-dimensional micromagnetic simulations for Q = 0.34. Also we suggest analytical model functions, describing 3D magnetization distribution in domain walls with BLs.
Solitons in The Domain Structure of an Easy-Axis Ferromagnet
Authors: Kiselev V V , Raskovalov A A
Published: November 2019

We obtain new solutions of the Landau-Lifshitz model by the inverse scattering technique. They describe solitons strongly associated with the domain structure of an easy-axis ferromagnet. Solitons serve as elementary carriers of macroscopic shifts of the structure and are, under certain conditions, nuclei of the magnetic reversal of a material. We show, that the inhomogeneous elliptic precession of magnetization in a soliton core leads to oscillations of the neighbouring domain walls of the structure. We study the behavior of immobile solitons in the domain structure, which are more simple to observe in experiment. We investigate the structure of solitons near the boundaries of their existence.
Magnetic component of mixing enthalpy for BCC Fe-Cr alloys: ab initio based model
Authors: Mirzaev D A , Mirzoev A A
Published: November 2019

The standard magnetic model in the current CALPHAD modelling is based on the Inden–Hillert–Jarl model and can be used to ferromagnetic and antiferromagnetic alloys. In this work, we demonstrate that this model can also be applied to alloys with more complicated forms of magnetism. The concept of ‘effective magnetic moment’ has been introduced as a measure of the maximum magnetic entropy. To calculate this quantity, it is necessary to know the local magnetic moments on the atoms of the components. A case study on the Fe –Cr system has been performed by Density Functional Theory (DFT) formalism at 0 K. It is shown that the CALPHAD modelling using the concept of effective magnetic moment leads to good agreement with the data of ab-initio modeling of the magnetic contribution to the mixing energy of Fe-Cr alloys.
Two types of 3-d metals nanowires: synthesis, structure and properties
Authors: Zagorskiy D , Doludenko I , Zhigalina O , Ivanov I , Muslimov A , Cherkasov D , Biziaev D , Bukharaev A
Published: November 2019

Matrix synthesis based on etched-track membranes was used for fabrication of two type of nanowires (NWs) – homogeneous (alloys – Fe-Co and Fe-Ni) and heterogeneous – layered NWs (Ni/Cu and Co/Cu). Parameters of galvanic process and features of electrodeposition were determined. X-ray analysis demonstrated the two-phase structure of alloys with low concentration of Fe and step-type changing of cell-parameter with changing of metals concentration ratio in alloy NWs. Topography of NWs was determined by SEM: NWs’ diameter were higher than pores size due to metal oxidation or expansion. Elemental analysis demonstrated that composition of Fe-Co NWs is equal to composition of electrolyte, while for Fe-Ni Fe concentration in NWs is higher; this difference increases with concentration of Fe. TEM allows to evaluate the length of metal segments in layer NWs, to estimate their concentration (pure Cu and mixed Co or Ni). Magnetic-Force microscopy allows to correspond structure and domain size. External field could change magnetization, but only partly – due to mutual influence of NWs.
Magnetism of amorphous Dy-Tb-Co-type films
Authors: Balymov K G , Kudyukov E V , Vas’kovskiy V O , Adanakova O A , Kulesh N A , Stepanova E A , Rusalina A S
Published: November 2019

In this work a systematic study of magnetic properties of amorphous TbxCo100-x and DyxCo100-x films is presented. In a composition range 15 < x < 40 at. %, temperature dependencies of spontaneous magnetization in a temperature interval 5 – 300 K as well as low-temperature 5 K hysteresis loops in magnetic field up to ±70 kOe have been obtained. We demonstrated, that the experimental results can be interpreted in a framework of a model considering a variable sperimagnetic cone angle of rare earth atoms up to 150°. A series of Tb-Dy-Co films with a composition close to Laves phase has been obtained. We demonstrated that the variation of rare earth content with Co content fixed does not lead to a systematic lowering of magnetic hysteresis.
The Kondo effect in 2D electron gas of magnetically undoped AlGaN/GaN high-electron-mobility transistor heterostructures
Authors: Chumakov N K , Chernykh I A , Davydov A B , Ezubchenko I S , Grishchenko Yu V , Lev L L , Maiboroda I O , Strocov V N , Valeyev V G , Zanaveskin M L
Published: November 2019

Unusual observation of the Kondo effect in two-dimensional electron gas (2DEG) of magnetically undoped AlGaN/GaN high-electron-mobility transistor heterostructures is reported. The temperature-dependent zero-field resistivity data exhibited an upturn below 120 K, while the standard low-temperature weak-localization behaviour was revealed at T → 0. Magnetotransport characterization was carried out in the magnetic fields up to 80 kOe, applied perpendicular to the 2DEG plane, in the temperature range 1.8 ÷ 300 K. Negative low-temperature magnetoresistance with a magnitude of order of 1 % was detected. The data set is analysed in the frame of the multichannel Kondo model for d0-magnetic materials.
Experimental and numerical analysis of magnetic susceptibility of the tetranuclear heterometallic SMM complexes [Me2
IIFe2
III(L)4(OH)2⋅EtOH)2⋅(Et2O)2], Me = Co, Ni with dicubane structure
Authors: Starichenko D , Shvachko Yu , Anokhin A , Kuznetsov A
Published: November 2019

Magnetic susceptibilities of the two isostructural heterometallic complexes, [Me2
IIFe2
III(L)4(OH)2,(EtOH)2,(Et2O)2], Me = Co, Ni, with triketonate ligands L = dianion of 1,1,1,7,7,7-hexa-fluoroheptane-2,4,6-trione, were studied experimentally and theoretically. Extended theoretical analysis included a phenomenological approach as well as quantum calculations in several numerical schemes. Magnetic ground states of Co2
IIFe2
III(L)4 and Ni2
IIFe2
III(L)4 complexes were resolved as an interplay of two intrinsic superexchange interactions with the constants J
FeFe and J
CoFe/J
NiFe. The first system was described by two non interacting AFM-coupled pairs Co-Fe with J
CoFe = - 4.2 cm−1 and zero-field splitting parameter D = -0.15 cm−1. The second one revealed the ferromagnetic coupling between the AFM dimers, J
NiFe = -12.1 cm−1, J
FeFe = 1.3 cm−1 and D = -0.5 cm−1.
The influence of the interlayer on the magnetic and structural properties of three-layer systems
Authors: Shalygina E , Kharlamova A , Efremova S , Makarov A , Kurlyandskaya G , Svalov A
Published: November 2019

This article is dedicated to the influence analysis of the thickness and composition of nonmagnetic intermediate layers, t
NM, on the magnetic and structural properties of Co/Mo/Co, Co/Si/Co, Co/Bi/Co and Fe1/PDP/Fe2 thin-film systems, as well as comparing the mechanisms of exchange interaction between ferromagnetic, FM, layers through NM spacers. The thicknesses of Co layers are equal to 5.0 nm and the thickness of Fe layers is varied from 14.0 to 50.0 nm. The thickness of NM layers, depending on its composition, is changed from 0.2 to 50.0 nm. It is found that the hysteresis loops for some samples measured in a magnetic field applied parallel to the easy magnetization axis have a rectangular form and for others – more complex two-step ones. The saturation field, HS, of Co/Mo/Co, Co/Si/Co and Co/Bi/Co samples oscillates in magnitude. These data are explained by the presence of exchange coupling between the Co layers through a NM spacer. Fe1/PDP/Fe2 samples have a two-step hysteresis loops, which at t
PDP ≥ 10 nm are explained by the exchange coupling between the Fe layers through the PDP layer, and at t
PDP > 10 nm - by the magnetostatic interaction between the Fe layers due to the difference in their thickness.
Magnetic properties of GdCo-Al2O3 composite films
Authors: Gorkovenko A N , Lepalovskij V N , Vas’kovskiy V O
Published: November 2019

The purpose of this work was to synthesize and study magnetic properties of composite films consisting of Gd-Co ferrimagnetic system and Al2O3 dielectric matrix. GdCo-Al2O3 films of different composition were synthesized by magnetron co-sputtering of Gd, Co, and Al2O3 targets in an Ar atmosphere. Investigation of magnetic properties was carried out using a vibrating sample magnetometer in the temperature range from 10 to 300 K. The obtained results showed that in the composite system with a volume of dielectric material exceeding 50% a superparamagnetic state is realized, indicating granular microstructure. In this case, the granules show signs of ferrimagnetic ordering.
Magnetic properties of Fe-Bi films
Authors: Patrin G S , Yakovchuk V Yu , Yarikov S A , Shiyan Ya G , Furdyk V P , Patrin K G
Published: November 2019

In the paper the results of experimental studies of film structures in the Fe-Bi system are presented. By the method of electron magnetic resonance, it is shown that for bilayer structures the magnetic state depends on the order of deposition of the magnetic and non-magnetic layers. In the three-layer structures, the effect of exchange bias was found, the magnitude of that depends on the thickness of the bismuth layer.
Non-equilibrium vortex annealing of structural disorder in the critical relaxation of diluted two-dimensional XY-model
Authors: Popov Ivan S , Popova Anna P , Prudnikov Pavel V
Published: November 2019

The study of the effects of aging in the non-equilibrium critical relaxation of a two-dimensional XY-model with a non-equilibrium vortex annealing of structural disorder has been carried out. Two-time dynamic dependencies of the spin-spin and defect-defect autocorrelation functions C
SS (t,t
w) and C
DD (t,t
w) are obtained for the entire Berezinskii low-temperature phase T < T
BKT(p), for a wide range of waiting times t
w and spin concentrations p. Near the BKT phase transition point T
BKT (p), the dynamic dependencies C
DD(t,t
w) become uniform with time. However, with a decrease in temperature in the low-temperature phase T < T
BKT (p), this relaxation uniformity breaks down, and C
DD(t,t
w) does not exhibit canonical aging properties. The formation of a declining family of dynamical scaling curves is clearly observed at large observation times t – t
w which may indicate the presence of an asymptotic scaling dependence of C
DD (t, t
w).
Temperature dependence of the interphase interaction energy of core/shell nanoparticles
Authors: Anisimov S V , Afremov L L , Petrov A A
Published: November 2019

Within the framework of the Ising model, in the direct exchange interaction approximation by the “average spin” method, the constant of the interphase exchange interaction A(T), which determines the exchange bias field, is estimated. It was shown that A(T) ~ e(−T/T
0), where the characteristic temperature T
0 is determined by the constant of the exchange interaction between the atoms of the core and the shell.
The role of the semiconductor layer in the exchange-bias film structure of CoNi / Si / FeNi / Si with a spin spring effect
Authors: Kobyakov A V , Turpanov I A , Patrin G S , Yushkov V I , Yarikov S A , Volochaev M N , Zhivaya Ya A
Published: November 2019

CoNi / Si / FeNi / Si structures were synthesized by ion-plasma sputtering. A negative hysteresis loop bias was detected at the thickness of the silicon layer was less than 2 nm and the temperature was less than 100 K. A positive hysteresis loop bias was detected at the thickness of the silicon layer was more than 2 nm and the temperature greater than 100K.
Microwave refraction coefficient in nanocomposites and nanostructures in magnetic field
Authors: Perov D , Rinkevich A , Nemytova O
Published: November 2019

Microwave refraction coefficient is studied for two types of composites and for metallic (CoFe)/Cu nanostructures. Nanocomposites of the first type are prepared on the base of artificial opal matrices with embedded particles of nickel-zinc ferrite and metallic cobalt. The introduced particles are sized from 5 to 60 nm. The composite material of the second type is prepared of permalloy flakes sized about 2 – 50 μm placed into epoxy amine matrix. At frequencies of centimeter and millimeter waveband the magnetic field dependences of transmission and reflection coefficients have been measured. The complex refractive coefficients are obtained as a function of magnetic field. The complex refraction coefficient can be expressed via the effective dielectric permittivity and magnetic permeability. Analysis of magnetic field dependences of refraction coefficient shows that strong variations are observed near ferromagnetic resonance. For metallic nanostructures there are also variations of the refraction coefficient caused by giant magnetoresistive effect.
The reason of occurrence of a longitudinal residual induction of steel spindle after circular magnetization
Authors: Reutov Yu
Published: November 2019

A special attention is paid to the possibility of appearance of a longitudinal residual magnetic flux leakage (MFL) field in the tested ferromagnetic spindle after its circular magnetization. The reasons of appearance of this field and experimental verification of the interpretation are given. When the occurrence of such field is unacceptable, the spindle has to be demagnetized.
Magnetic non-destructive testing of residual stresses in low carbon steels
Authors: Stashkov A , Nichipuruk A , Kuleev V , Schapova E
Published: November 2019

A new calibration-free magnetic method and a measuring system for residual stresses monitoring in low carbon steels have been developed. The method is based on the fact that during the action of compressive stresses in the material an “easy plane” magnetic texture appears. Magnetic texture affects the processes of magnetization reversal of the testing object in such a way that two or three maxima on the curves of differential μd(H) or reversible μrev(H) magnetic permeabilities appear. The fields of the maxima are associated with the magnetoelastic field and residual stresses. To increase the reliability of testing results and simplify the evaluation of residual stresses in testing objects, it was proposed to use the method of subtracting experimental μd(H) curves measured in the zones of action of compressive stresses and in the object under test without stresses. The method can also be used to estimate residual tensile stresses that are the most dangerous for steel structures.
Highly effective system for excitation and reception of Lamb waves in ferromagnets
Authors: Mikhailov A V , Gobov Yu L , Smorodinskii Ya G
Published: November 2019

The paper presents the concept of a highly efficient system for excitation and reception of Lamb waves in ferromagnets. Methods for creating large polarizing fields allowing to increase the efficiency of generation and reception of Lamb waves in ferromagnets and the principles of unidirectional electromagnetic-acoustic transducers are proposed. The results obtained in this work can be used in the development of devices for non-destructive testing of the long ferromagnetic objects.
The influence of zero-to-tension loading on magnetic and acoustic properties of 08G2B hot-rolled steel
Authors: Gorkunov E S , Povolotskaya A M , Zadvorkin S M , Putilova E A , Mushnikov A N , Bazulin E G
Published: November 2019

The paper reports on the results of studying the effect of the number of zero-to-tension loading cycles, with an amplitude approximately corresponding to conventional yield strength, on the acoustic and magnetic parameters of the 08G2B hot-rolled pipe steel, including its longitudinal and transverse magnetostrictions. The parameters uniquely varying with the number of cycles have been determined, and this principally enables these parameters to be used for the development of nondestructive methods of testing fatigue degradation in the material of structures made of the steel under study.
Terahertz-infrared spectroscopy of single crystalline m-type hexaferrite BaTixFe12-xO19
Authors: Yegiyan S R , Alyabyeva L N , Torgashev V I , Vinnik D A , Gudkova S A , Prokhorov A S , Dressel M , Gorshunov B P
Published: November 2019

We have studied polarization-dependent broad-band dielectric response of single-crystalline Ti-substituted barium hexaferrites BaTixFe12-xO19, x=0.64., 0.75, 1.1, in the frequency range from 10 to 8000 cm−1 and at temperatures from 5 to 300 K. In addition to a rich set of phonon resonances located at frequencies from 90 to 800 cm−1 we observed an unusual low-energy response (terahertz region, 10-100 cm−1) stemming from two different effects: relaxational process and second order spin-orbit coupling in Fe2+ ground state, that may set up new prospects for doped hexaferrites in terahertz technologies.
Concept of using composite multiferroic structure magnonic crystal - ferroelectric slab as memory unit
Authors: Matveev O , Morozova M , Romanenko D
Published: November 2019

In the present work, it is proposed to use as a memory cell with random access a new type of memristor - a multiferroic wave memristor based on structures type magnonic crystal-ferroelectric. Main feature of propagating excitations trough such structure is band gap formation: Bragg band gap that position in spectrum depends on the polarization of ferroelectric. Thus, information from ferroelectric is read as a result of signal transmission / attenuation at frequency of band gap. In present work theoretical model of spin waves propagating in structure magnonic crystal-ferroelectric is developed. Results of an experimental study of the propagation of spin-wave excitations in such structure are given.
Magnetic properties of Ho0.9Er0.1Fe3(BO3)4
Authors: Gudim Irina , Demidov Andrey , Eremin Eugene , Temerov Vladislav , Shukla Dinesh
Published: November 2019

The magnetic properties of Ho0.9Er0.1Fe3(BO3)4 ferroborate with the competing Ho–Fe and Er–Fe exchange couplings have been experimentally and theoretically investigated. The measured magnetic characteristics (Ma,c
(B), χa,c
(T)) and observed features are interpreted using a single theoretical approach based on the molecular-field approximation and calculations within the crystal-field model of the rare-earth ion. Interpretation of the experimental data includes determination of the crystal-field parameters for Ho3+ and Er3+ ions in Ho0.9Er0.1Fe3(BO3)4 and parameters of the Ho–Fe and Er–Fe exchange couplings.
Effects of long storage in La-Sr manganites with pared divalent and quadrivalent substituents for manganese
Authors: Karpasyuk V K , Badelin A G , Derzhavin I M , Estemirova S Kh , Merkulov D I
Published: November 2019

The results of investigation on the ageing of ceramic manganites La1-cSrcMn0.90Ni0.05Ge0.05O3+γ and La1-cSrcMn0.90Zn0.05Ti0.05O3+γ (c = 0.15, 0.17, 0.19) during long-term storage at normal conditions are presented. Unit cell volume of all manganites having rhombohedral structure decreased over time. The width of X-ray diffraction reflexes from (Ni,Ge)-compositions varied irregularly within the measurement error, and the width of reflexes from (Zn,Ti)-contained manganites decreased significantly. Magnetization of all samples increased in the end of storage period. Curie point of compositions with c > 0.17 exhibited some trend of increase. Ageing leaded to the lowering of “metal-semiconductor” transition temperature in (Ni,Ge)-substituted manganites. (Zn,Ti)-contained compositions showed only semiconductor behavior in investigated temperature range from 100 to 300 K, and the changes of their magnetic parameters were most considerable. The increase in magnetization and Curie point reached 7.5 % and 11 %, respectively. Possible mechanisms of ageing in considered materials are discussed in terms of oxidation processes, formation of microinhomogeneities and relaxation of internal stresses.
Magnetoelectric structure with integrated current carrying electrodes
Authors: Burdin D A , Saveliev D V , Fetisov Yu K , Ekonomov N A , Chashin D V
Published: November 2019

Various methods of magnetoelectric effect excitation in a composite structure consisting of ferromagnetic and piezoelectric layers are investigated and compared, such as: by ac magnetic field of electromagnetic coil, by ac current flowing through external conductive strip, by ac current flowing through the ferromagnetic layer, and by as current flowing through electrode of the piezoelectric layer. It is shown that ac current flowing through the ferromagnetic layer effectively excites both linear and nonlinear magnetoelectric effects due to absence of demagnetization. Specific dependence of the voltage harmonics on the permanent magnetic field under the structure excitation by ac current are observed and explained.
Thickness dependence of conductivity in Bi2Se3 topological insulator
Authors: Chistyakov V V , Domozhirova A N , Huang J C A , Marchenkov V V
Published: November 2019

The electrical resistivity of thin films of a topological insulator of Bi2Se3 with a thickness of 10 nm to 75 nm, single crystal of Bi2Se3 with thickness of 0.65 mm in the temperature range from 4.2 to 300 K was measured. A size effect in the electrical conductivity of Bi2Se3 films was observed, i.e. linear dependence of the conductivity of the sample on its inverse thickness. It was suggested that similar effects should be observed in other TIs and systems with non-uniform distribution of direct current over the cross section of the sample.