bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass sensitivity of Langmuir-Blodgett monolayer film coated surface acoustic wave resonators to volatile organic solvents
Authors: Ivanov G R , Avramov I D , Strijkova V J , Marinov Y G , Vlakhov T E , Bogdanova E , Hadjichristov G B 
Published: February 2021

Abstract
Langmuir-Blodgett (LB) monolayer films deposited from a Dipalmytoyl Phosphatidyl Ethanolamine head labelled with Nitrbenzoxadiazole (DPPE-NBD), have been studied for their ability to be used as sensing layer for chemical gas sensors. DPPE-NBD molecules are known for their similarity to bio membrane molecules. Therefore, it is expected that they can serve as a matrix for immobilization of proteins, enzymes, aptamers, while preserving their function for selective reaction with organic analytes. In this study, LB monolayers of DPPE-NBD were deposited on Rayleigh Surface Acoustic Wave (RSAW) resonant devices working at 411 MHz and simultaneously on ultra-flat Si wafer substrates for Atomic Force Microscopy (AFM) inspection. Depositions were carried out both at a low surface pressure where the liquid-expanded phase dominates, and at a high surface pressure, where the liquid-condensed (solid) phase dominates. AFM topography reveals the liquid and solid phase coexistence as well as the formation of 3D pyramids of 3 to 30 nm height and 50 to 1000 nm in diameter. In a vapour sensing experiment, the RSAW devices were exposed subsequently to vapours of 6 volatile organic compounds (VOCs) and water. The most significant resonant frequency shift of 225 kHz which corresponds to 11.42 ng mass change was observed with chloroform vapours when the substrate with the solid phase LB monolayer was used as a sensing layer. Adsorption and desorption of the vapours was very fast (a few seconds) and completely reversible. The higher-pressure deposited LB film demonstrates higher sensitivity to all gases. Mechanisms of this behaviour are discussed.
Scientific instrument for creation of effective Cooper pair mass spectroscopy
Authors: Mishonov T M , Varonov A M 
Published: February 2021

Abstract
We describe electronic instruments for creation of effective Cooper pair spectroscopy. The suggested spectroscopy requires study of electric field effects on the surface of cleaved superconductors. The electronic instrument reacquires low noise amplifier with 106 amplitude amplification which we have formerly used for study of Johnson-Nyquist and Schottky noises. The nonspecific amplifier is followed by high-Q tunable resonance filter based on schematics of general impedance converter topology which is also and innovative device. The work of the device is based on the Manhattan equation of operational amplifier. After a final nonspecific amplification the total amplification can exceed 109 and in such a way sub-nano-volt signals can be reliably detected. In short the observation of new effects in condensed matter physics leads to creation of new generation of electronic equipment.
Interaction of solitons with a qubit in an anisotropic Heisenberg spin chain with first and second-neighbor interactions
Authors: Varbev S , Boradjiev I , Kamburova R , Chamati H 
Published: February 2021

Abstract
Solitons provide a promising means to control the state of a spin-qubit in quantum information technology. In this paper, we consider the anisotropic interaction between a soliton, propagating in a ferromagnetic Heisenberg spin chain and a spin-

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2

particle (qubit). The spin chain exhibits an on-site anisotropy and spin-spin nearest-neighbor and next-nearest-neighbor interactions. The Bloch sphere picture is employed to investigate the spin-

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dynamics. We found that increasing the anisotropic and the second neighbor interactions leads to an increase of the deviation of the spin-

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particle from its initial state.
Origin of the magnetic exchange in insulators: Localized vs. delocalized electrons
Authors: Georgiev M , Chamati H 
Published: February 2021

Abstract
The present study focuses on the fundamental physical principles underlying the exchange interactions between two metallic centers in magnetic insulators. Using the variational method in conjunction with the Heisenberg model, we demonstrate that the exchange symmetry is tightly related to the magnetism of the considered system and that the electrons’ distributions affect the corresponding exchange interactions.
Bound Soliton–Defect Spin States in Anisotropic Ferromagnetic Chains
Authors: Kamburova R S , Primatarowa M T 
Published: February 2021

Abstract
The interaction of soliton with an impurity spin in a discrete anisotropic ferromagnetic chain is studied. The defect spin in our model is characterized by modification of the exchange interaction with its neighbors. A perturbed nonlinear Schrödinger (NLS) equation for the spin amplitude is derived on the basis of a semiclassical and a continuum approximation. A specific feature of this type of defect is that it leads to perturbations to all terms of the NLS equation. Localized soliton-defect spin solutions are obtained for the case of dark and bright solitons and their stability is analyzed.
Dilute nitrides heterostructures grown by liquid phase epitaxy for solar cells applications
Authors: Donchev V , Milanova M 
Published: February 2021

Abstract
In this paper, we present a study on liquid phase epitaxy (LPE) grown dilute nitride GaAsSbN layers and p-i-n heterostructures for use in multijunction solar cells. The composition of the layers and chemical bonding of Sb and N in the compounds were determined by energy- dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The electrical properties of the grown samples were characterized by Hall effect measurements. Nominally undoped layers are n-type with Hall carrier concentration of 5 × 1016cm-3. Mg was successfully used as acceptor dopant for obtaining closely compensated layers with electron concentration of 1015 cm-3 as well as p-type layers with high free hole concentrations in the range (5-7) × 1018cm-3. Temperature-dependent photoluminescence spectra at low and high excitation were measured to evaluate the optical quality and identify localized states in the grown layers. Non-contact surface photovoltage method provided information about the absorption characteristics of the GaAsSbN layers. A series of GaAs/GaAsSbN/GaAs heterostructures based on closely compensated i-GaAsSbN have been also grown by LPE. The red limit of the structures determined from surface photovoltage measurements was extended down to 1.2 eV. Single junction p-i-n solar cells with area 0.16 cm2 were performed based on the grown structures. A power conversion efficiency of 4.1 % was measured for the fabricated cells under AM1.5 air global conditions.
Solution deposition of ZnO thin films
Authors: Stankova S , Volobujeva O , Dikov Hr , Ganchev M 
Published: February 2021

Abstract
A solution deposition technique is investigated as an approach for formation of nanostructured ZnO films with tailored geometric shape and aspect ratio, electrical conductivity, and high optical transmittance. Having in mind thermodynamic particulars of ZnO precipitation from aqueous solutions, we show deposition of thin films of intrinsic ZnO with well-defined hexagonal wurtzite structure and with high optical transmittion in the visible region. Deposition of doped layers of Al:ZnO with aluminium concentration up to 3 wt% does not cause degradation of the wurtzite structure and sheet resistance of the films is near 8.0*102 Ω / □. After applying thermal annealing, the absorption edge gets sharper and optical band gap is found to be near 3.26 eV for direct transitions. Addition of the ethanol in the aqueous deposition solution leads to formation of ZnO nanostructured films with trigonal configuration.
Renewable energy resources in the system of sustainable development of Carpathian region of Ukraine
Authors: Arkhypova L M , Mandryk O M , Moskalchuk N M , Prykhodko M M , Radlovska K O 
Published: February 2021

Abstract
The scientific novelty presented in this paper is to substantiate the extension of the resource potential of renewable energy sources in the Carpathian region with the creation of a set of maps in the geographic information system “Map Info”. For each type of renewable energy (solar, wind, small hydropower) a number of technical issues and advantages, technological ecologically safe priorities are defined. The detailed regional calculation of wind, solar, hydropower potential for the Carpathian region of Ukraine has been performed. The spatial limitations and possibilities of introducing renewable energy sources in the sustainable development of the region are scientifically substantiated. Renewable energy scenarios are proposed.
Investigation of the separation of combed heap of winter wheat
Authors: Lezhenkin O M , Halko S V , Miroshnyk O O , Vershkov O O , Lezhenkin I O , Suprun O M , Shchur T G , Kruszelnicka W , Kasner R 
Published: February 2021

Abstract
The article deals with the problem of separation of combed heap of winter wheat with an experimental working unit consisting of a segregator and a sieve. In order to expand the range of information on the qualitative side of the functioning of the working unit, it is suggested to introduce an additional assessment parameter – the impurity separation efficiency coefficient. Experimental studies of the technological process of the working unit were carried out using the mathematical theory of experimental design, where the response function was represented by the functional dependence of the change in the impurity separation efficiency coefficient on the specific feed of the combed heap, the oscillation frequency of the working unit and the diameter of the sieve openings. To conduct the experimental studies, the Box-Behnken design was selected. Verification of the significance of the obtained coefficients according to Student’s t-test showed that all the coefficients were significant. The adequacy of the model was assessed according to Fisher’s test. As a result of the calculations, it was established that the model was adequate and could be used for further research.
The separation assessment of small-seeded mixtures of agricultural crops
Authors: Kovalyshyn S , Ptashnyk V , Shvets O , Ivashchyshyn F , Nester B , Kasner R , Urbańska P 
Published: February 2021

Abstract
The paper confirms that the effective separation of small-seeded mixtures of crops can be achieved if we use electrical separation methods that take into account the difference in electrical conductivity and dielectric constant of the components, their ability to receive and give a charge etc. Having examined electrical conductivity and polarization properties of winter oilseed rape and Galium aparine seeds by the method of impedance spectroscopy, it was found out that the frequency dependence of the real part of their complex resistance is of the same type and has a decreasing character. The maximum capacity of winter oilseed rape is 50 % higher than the corresponding capacity of Galium aparine, and the maximum accumulation of charge by seeds is observed in the frequency band for which the real part of the complex resistance takes close values for both Galium aparine and winter oilseed rape. The revealed difference in electrical conductivity and dielectric constant of the studied seeds of winter oilseed rape and Galium aparine causes different charges, which is one of the main conditions for their effective separation in electric separators, which use an electric field of corona discharge as an additional working body.
A bar model of a temporary wooden support used to remove deflections of buildings
Authors: Gromysz K 
Published: February 2021

Abstract
The deflection of buildings located in mining areas is removed by uneven raising of the overground part of the structure by means of supports consisting of a hydraulic piston jack and a stack of underpinning elements. Temporary supports may also consist of stacks of wooden elements only. The article presents a bar model of a temporary support consisting of a stack of elements. The model, which is described by a differential, second-order equation, allows to determine horizontal displacements. It was demonstrated that the unintended eccentricity and the initial curvature of the element have influence on such displacements. In addition, the effect of the load transmitted by the deformed adjacent supports is important. The model presented can be used to determine the limit load capacity of temporary supports due to unintended horizontal displacements of the structure. The model therefore allows to design safely the removal of building structures’ deflections.
Experimental stand and researches on pantograph-catenary contact force control using chaos theory
Authors: Rusu-Anghel S , Mezinescu S S , Lihaciu I C 
Published: February 2021

Abstract
Due to the oscillating behaviour of the pantograph and the catenary during the movement of the locomotive, the contact force changes to wide limits, resulting in electrical sparks with consequences: premature wear of the contact wire, electromagnetic disturbances, energy loss. Suitable control of the contact force at speeds exceeding 160 km/h may diminish these effects. Due to the particularities of the pantograph-catenary system and many random external factors, existing control methods do not always give the best results. The authors’ research has shown that the contact force signal contains a chaotic component that can be offset by chaos theory methods. Their own studies have demonstrated theoretically and by simulation that this approach can largely eliminate the separating the pantograph from the catenary and will lessen excessive forces. Experimental research, conducted by the authors and presented in this article, has been done in laboratory conditions on a specially built test stand and confirms that this new approach to active pantograph control produces superior results to existing methods.
Comparative study between the melting process of an aluminum batch and a steel batch in a high frequency induction furnace
Authors: Iagăr A , Popa G N , Diniş C M 
Published: February 2021

Abstract
In this work we analyzed a laboratory induction furnace, having a small capacity, fed by a high-frequency static converter. The measurements were carried out in the case of an aluminum batch, and a steel batch, using the power quality analyzer CA8334B. We studied the influence of the type, temperature and amount of processed material, on the electrical parameters of induction furnace during the melting process. Large electromagnetic disturbances (harmonic currents, current unbalances, reactive power consumption) were recorded, especially during the preheating period of crucible and the first stage of heating, when the furnace worked at low power, for the both batches. The experiments allowed the elaboration of some measures for optimization of melting process in the analyzed induction furnace, in terms of efficiency and mitigation of electromagnetic disturbances.
Ozone and anions generator for disinfection of enclosed spaces
Authors: Popa G N , Popa L , Diniş C M 
Published: February 2021

Abstract
After the pandemic of SARS-CoV-2, people’s lives will be different. It seems that in the next period, due to the spread of SARS-CoV-2 virus worldwide, all objects, surfaces and spaces that people come in contact with must be disinfected frequently. At the same time, the atmosphere in closed spaces must be disinfected because the transmission of the virus through the air is made easier. It seems that an effective method of disinfection (viruses, bacteria, etc.) is the use of ozone generators. Ozone in the air over a certain dose affects the human respiratory system.
It is known the role of anions on human health, especially given that the vast majority will spend time indoors. Staying in homes for long periods of time has negative effects on the humans body.
The paper presents and analyze ozone, anions, and the their generators. It is presented a generator that can produce both ozone (measured with an electrochemical sensor) at a certain concentration for limited periods of time, as well as anions in high concentrations that have a beneficial effect on humans health. Air quality is measured (with an electrochemical sensor), and in conditions of low quality, the generator can provide higher concentrations of anions. The ozone and anions generator is controlled with microcontroller development board. The flowchart of the program used in the microcontroller is presented.
Experimental analysis of the influence of clogging on the filtration process for internal combustion engines
Authors: Bucevschi R , Socalici V , Budiul Berghian A , Birtok Băneasă C 
Published: February 2021

Abstract
This article presents the analysis of the laboratory tests results carried out to investigate the effects of the clogging phenomenon developed at internal combustion engine filters. A classical filter module from an aspirated engine was used to carry out the tests, composed of air ducts, filter housing and a standard panel filter element made of paper, mounted on the test stand designed by the authors, for analysis of flow state parameters in dynamic mode.
Modular load-bearing structures for the study of interactions between the soil and working parts of agricultural machines
Authors: Cardei P , Constantin N , Sfîru R , Muraru V , Condruz P 
Published: February 2021

Abstract
The authors outline in this article the principles underlying the conception and design of modular load-bearing structures (MLBS) for the study of the interaction between soil and the agricultural machinery working bodies for the inter-study study of 3D CAD design. It presents the main scientific problems faced by agricultural machines for soil works, main reasons for the conception and realization of this machine or category of machines. It also presents the scientific but also economic reasons for the modulation or modular design of this machine, an operation that has led to several possible working variants, which require power sources for traction of different values. It also presents the multifunctionality acquired through the possibility of using work parts and their supports of different types and mountable on the structure in different formations.
Experimental research with the help of thermal derivatographic analysis on coal powder that can be blowed in the furnace
Authors: Caloian V , Vlad E M , Oancea V , Hritac M , Plopeanu E F , Pandelescu C , Rucai V , Constantin N 
Published: February 2021

Abstract
In an integrated steel flow, the costs related to the consumption of metallurgical coke represent approx. 25% of the production cost of the shards obtained by continuous casting. As the price of coal returns to about 50% of that of coke, the technology of insufflating coal dust at the blast furnaces mouths, which transfers the coking process to the blast furnace, can reduce the cost of slag by 4-5%. It cannot be used to blow into the furnace any type of coal. The coal used must meet certain requirements, based on its physical and chemical properties. By thermo-derivatographic analysis, important properties of coals can be established. The authors present in this paper the results of thermal derivatographic analyzes performed on certain types of coal.
Experimental research on the effect of additives on the sintering process of alumina-based refractory materials
Authors: Vlad E M , Buzduga R V , Buzduga M D , Caloian V , Plopeanu E F , Pandelescu C , Dobrescu C , Constantin N 
Published: February 2021

Abstract
This experimental study refers to the obtaining of refractory materials based on alumina, by adding different amounts of TiO2 and MnO2, as sintering agents, to the initial mixtures of raw materials (alumina, chamotte), followed by the sintering of the mass’s different temperatures between 1300 ºC and 1700 ºC. The effects of the use of additives on the sintering temperature, as well as on the microstructure and, consequently, on the properties of the sintered materials were analysed on both the added and non-added ceramic samples, considered as comparative benchmarks.
Building a blockchain for aviation maintenance records
Authors: Andrei A G , Balasa R , Costea M L , Semenescu A 
Published: February 2021

Abstract
The objective of this paper was to create a proof of concept for a blockchain application in aviation world, with an emphasis on improving the aircraft maintenance traceability. It is well known that aviation industry manages incredible complex systems, where failure is not an option. This industry needs blockchain technology not only for safety improvements but also for a new business model where airline companies can deliver more trust and more transparency to their customers.
Nowadays, the passengers who are the end customers, cannot evaluate an airline company from the point of view of fleet maintenance. Bad or uncomplete maintenance are premises for an undesired accident. Moreover, aircraft investigators and auditors are experiencing difficulties in understanding how an aircraft was operated. Thinking of forecasting defects, models of predictive maintenance cannot be developed if accurate data are not available. All these can be changed with the implementation of the proposed blockchain application.
Beside the theoretical explanations, the scope of this work was also to put in practice the main blockchain features and develop on a small scale, a real decentralized blockchain application using Python programming language. The script was designed to run on a localhost machine and store maintenance records and relevant parameters for the process of tracking an airplane’s lifespan in a chain of interconnected blocks.
Therefore, the traditional approach in the data management is no longer an option for the aviation industry.
Methane combustion kinetic schemes in FlowVision software
Authors: Krikunova A I 
Published: February 2021

Abstract
The two-step chain reaction of methane combustion in air is integrated into the FlowVision software package. The conical flame numerical simulation under normal conditions using the built-in single-step chemical reaction was performed. A comparative analysis of the numerical results for one- and two-step schemes, as well as experimental results was made.
Estimation of the flux density of galactic comets in the Orion–Cygnus branch based on number of shield volcanoes on Venus, craters on Mars and marine basins on the Moon
Authors: Barenbaum A A , Shpekin M I 
Published: February 2021

Abstract
Based on data on shield volcanoes of Venus and the distribution of craters on Mars and sea basins on the Moon, the flux density of galactic comets in the Orion–Cygnus branch was calculated. The comets flux density is 5 × 10−10 year−1 km−2. This value was used to estimate the number, energy and fallings frequency of galactic comets on terrestrial planets in the period from ≈ 5 to 1 million years ago. The article shows, that the falls of such comets can explain the phenomena of “newest uplifts of Earth’s crust” and “young volcanism” on Earth, the appearance of shield volcanoes on Venus, the asymmetric structure of Mars, as well as origin of large craters, seas and mascons on the Moon, Mars and Mercury. A hypothesis of formation on the Moon of the South Pole–Aitken basin by galactic comets is proposed.