bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantum chemical study of 5,5-dimethyl-1,3-dioxane isomerization to 2,2-dimethyl-3-methoxypropanal, - the general reaction scheme
Authors: Kurilova E I , Kantor E A 
Published: June 2021

Abstract
The results of quantum chemical simulation by B3PW91 method in the 6-31G(d,p) basis for formation of 2,2-dimethyl-3-methoxypropanal from 5,5- dimethyl- 1,3- dioxane in the presence of proton are given. The proposed reaction scheme involves protonation of the parent molecule - formation of the oxonium ion, breaking of C-0 bond with receipt of alkoxycarbenium ion, rearrangement of the alkoxycarbenium ion by two successive 1,3-displacement or 1,5 displacement of positive charge, deprotonation of the oxycarbenium ion with formation of the reaction product. Data on the structure and energy characteristics of molecular products, ions, and transition states are obtained not only for the states characterized minimum Gibbs energy (G298, δG298, δG#
298), but also for possible conformers and transitions between them. Based on the calculations, an energy diagram is drawn up in accordance with the general reaction scheme.
Comparison of the estimated activation barriers (δG#
298) for implementation of the reaction in two stages (1,3-migrations) and one-stage 1,5-migration showed that they are comparable in size, the difference is about 2 kcal/mol. Since conversion of 5,5- dimethyl- 1,3- dioxane to 2,2-dimethyl-3-methoxypropanal is an endothermal reaction with heat absorption of 3.4 kcal/mol, it can be assumed that in real conditions transformation of ions as per the reaction coordinate will include both two-stage and one-stage conversion of alkoxycarbenium ion to the oxycarbenium ion.
Verification method of strength of refractory slings for positioning and holding after exposure to a heated metal rod
Authors: Prostakishin D A , Antonova V A , Gadzhiev R S , Ya Barvina A 
Published: June 2021

Abstract
In the introduction of this work, three types of safety systems are considered when working at height. Hazardous factors have been identified that affect the safety of the user, depending on the components of the safety systems and their resistance to high temperatures. The purpose of this work is to improve safety in hazardous sectors of industry, construction and other types of work where increased protection of PPE components from sources of elevated temperatures is required, when working with gas and electric welding, as well as the resistance of materials to sparks from mechanical power tools. In the main part of the article, a new test methodology for refractory slings for positioning and holding was introduced, tests were carried out and the method was adjusted. The experience of the fire sector was borrowed, and in particular, the method in clause 9.8 from GOST R 53268-2009 Firefighting equipment was transferred and adapted. Fire rescue belts General technical requirements. Test methods”. The conclusions of adaptation and application of this method to other components of personal protective equipment are made.
Prospects for the use of nanofluids in heating systems
Authors: Sheremet E O , Uvarov V A , Nikulin N Y , Dudinskih S V 
Published: June 2021

Abstract
The desire to create new, improved working fluids for heat and mass transfer systems in the industry is gaining momentum. Now more and more researchers are being attracted to analyze the use of nanofluids in heating systems due to their improved thermal and physical properties. Nanofluids are a new type of dispersed fluids that consist of a carrier fluid in the form of which water can act, as well as polymer solutions and organic liquids, and solid particles, which are mainly particles of chemically stable metals and their oxides. The heat transfer characteristics of modern liquids are significantly improved by the addition of nanoscale solid particles with a diameter of less than 100 nm. Such liquids can be considered as promising applications in such areas as solar collectors, heat pipes, nuclear reactors, electronic cooling systems, automobile radiators, etc. The paper (publication) describes nanofluids as new energy-efficient types of working fluids for heat transfer. The most promising developments in the field of creating nanofluids from the point of view of increasing the heat transfer coefficient are presented and analyzed. Further possible promising ways of studying nanofluids are formulated.
Heat treatment of mandrel steel for pipes’ piercing
Authors: Gevorgyan G , Pachurin G , Mukhina M , Kozinov D 
Published: June 2021

Abstract
Seamless pipes are mainly used in the oil, gas and defense industry, what places special demands on its reliability and safety. It is very important to select the steel grade and heat treat the mandrels for flashing and cross rolling of seamless pipes in order to ensure the required operational characteristics. The work is devoted to the substantiation of the choice of 4Kh5MF1S steel and the development of the technological cycle of manufacturing mandrels of increased strength for sheet and transverse-spiral rolling of seamless pipes. The optimal combination of strength and ductility of this steel during heat treatment was established, which includes quenching at 1070 ° C and tempering in the temperature range of 650-700 ° C. Based on the analysis of the structure and mechanical characteristics, an optimal mode of heat treatment of steel 4Kh5MF1S was proposed: quenching from 1070 °C in oil and tempering for 2 hours at the temperature of 650-700 °C, which makes it possible to recommend it for use as a heat-resistant structural material for highly loaded metal products with the yield stress o0.2 from 750 to 1000 MPa.
Verification method of material stability of fire-resistant slings for holding and positioning against an open flame
Authors: Prostakishin D A , Zherdev K V , Gadzhiev R S , Ya Barvina A 
Published: June 2021

Abstract
In the introduction of this work, the problem of the lack of test methods for personal protective equipment against falls from a height (hereinafter PPE), used in the areas associated with direct contact of PPE components with sources of elevated temperatures, is disclosed. The experience of the fire sector was adopted with fire tests for the impact of materials used in the production of PPE products in contact with an open flame. A number of tests were carried out on refractory slings for holding and positioning and the results obtained with a positive approbation of the method. The purpose of this work is to improving overall safety when working at height, to identify weak zones of protection of components of safety systems from various external factors that negatively affect them. Work was carried out and conclusions have been drawn about the application of this method on refractory slings for holding and positioning. One of the important requirements of customers of these slings in production is the resistance of materials of safety systems to the interaction of components in an environment of high temperatures. The conclusion of this work is the relevance of the application of this technique to the PPE sector, in particular to refractory slings for holding and positioning.
Determination of the efficiency of a complex of dust removal systems for industrial enterprises
Authors: Kireev V M , Minko V A , Goltsov A B , Seminenko A S 
Published: June 2021

Abstract
In various industries, there are often technological processes that are characterized by the release of dust into the working area. This dust is the cause of various diseases of the workers of the enterprise. To maintain the required air parameters in terms of the dust factor in industrial premises, it is necessary to use a complex of systems, including an aspiration system, a centralized vacuum dust removal system and general ventilation. Each of the listed systems will fulfill its specific task, but their efficiency and productivity are interrelated. There are numerous works that consider the operation of systems separately, however, the final concentration of dust in the room, in the end, will depend on their simultaneous operation. The article presents a developed method for calculating the efficiency of a complex of dedusting systems, which will allow at the design stage to assess the concentration of dust in the air of industrial premises and, if necessary, make the necessary adjustments.
Remaining Service Life Evaluation of Nuclear Power Plants Construction Steel Elements
Authors: Bausk E A , Volchuk V M , Uzlov O V 
Published: June 2021

Abstract
The paper is devoted to investigation of S235J2 steel quality criteria variation during thirty years’ service life as a part of construction of power-generation unit #1 of Zaporizhia Nuclear Power Plant (NPP). The microstructure of the steel has been evaluated by fractal methods. Fractal size of the steel structure has higher correlation to mechanical properties of the steel compared to microstructure analysis. During service life of the steel YTS ranging 10.01% (24.9 MPa), UTS ranging 9.42% (39.5 MPa), while elongation ranging 43.16% and Reduction of area ranging 39.58%. These values can be explained by strain ageing of the S235J2 steel during service life. It has been stated that fractal size of pearlite and strength have good correspondence (YTS has fractal model correlation coefficient R² = 0.6194, while UTS has R² = 0.8068). The correspondence of ferrite fractal size to ductility has been calculated (Elongation has fractal model correlation coefficient R² = 0.6493 and Reduction of area has R² = 0.5258). Analysis of the S235J2 quality criteria fractal models let the range quality criteria depends on fractal size of the ferrite-pearlite structure of the steel. Experimental results prove the possibility of usage the fractal models for predicting remaining life of the steel constructions at NPP. Therefore, the fractal modelling may be assumed as a promising nondestructive test method for NPP.
Model of the kinetics of aging of paint and varnish coatings of cement concrete
Authors: Loganina V I 
Published: June 2021

Abstract
Information on the kinetics of aging of coatings is presented.The process of moistening was considered as one of the particular cases of aging. During incubation period there is a slight increase, and possibly a decrease in defectiveness. The duration of the incubation period is 0.2 -0.5 of the entire durability.The active stage of damage accumulation begins after the incubation period. In the active stage of accumulation of damages, significant changes occur in the structure and properties of the coating (change in color, shine , cracking, etc.).Determined that the beginning of the active stage of accumulation of lesions coincides in time with the first significant changes in the surface area of the coating. It was found that there is a correlation between the experimental data on the kinetics of damage accumulation, the degree of chalking, and surface area. It lies in the fact that the active stage of damage accumulation coincides with the beginning of chalking of coatings. An analytical dependence is proposed that makes it possible to estimate the area of the defective surface of the coating during aging. The dependence of the level of damage accumulation on the duration of tests can be described by a logistic curve (or Pearl curve)
Analysis of karst protective slab foundations taking into account the features of the base modeling
Authors: Shebunyaev A N , Yudina I M 
Published: June 2021

Abstract
This paper presents a practical application of the improved method for calculating of slab foundations designed in karst rock areas. The method implementation is associated with the application of the updated analytical model taking into account behavior patterns of the ground base in the karst hole zone. The analytical solution obtained in the closed-form in the nonlinear formulation, allowed to obtain two key parameters of the foundation bed in the zone being studied - ? and ????. The dependence to determine the size of the weakening zone around the karst sinkhole area - ? and the developed criterion for the quantitative change of the coefficient of subgrade reaction ???? in the zone of this weakening made it possible to propose a bilinear model of the interaction of the “foundation slab - base” system. The parameters of the base weakening obtained as a result of the problem solution have a wide range of changes depending on the physical and mechanical characteristics of the base soils and can be used for engineering calculations of slab foundations designed in karst areas. The comparative analysis of the calculations made according to the proposed and normative methods showed a substantial under-reinforcement of the foundation slab projected in the karst-hazardous zone.
Attenuating acoustic pulse propagation in multilayered rods
Authors: Karakozova A I 
Published: June 2021

Abstract
The problem of seismic activity and carrying out anti-seismic measures is extremely urgent at the present time. A large number of regions are more or less earthquake-prone and sometimes new regions, in which seismic activity has not been recorded before, fall into this category. Various methods of seismic load reduction are used to build new structures and support existing structures in these areas. The seismic load is transmitted to the structure through the foundation, therefore one of the effective ways to reduce it is to change the properties of the foundation. If instead of soil, which perfectly transmits impulses of seismic load, fill in a certain order with material that dampens these impulses - the desired effect can be achieved. The article analyzes the way of how one-dimensional pulse becomes attenuated in a multilayer rod. The layers in the rod are arranged in a periodical order and have contrasting acoustic properties. Numerical analysis is carried out using the finite element method. A pulse hitting the interface between the media undergoes multiple reflection and refraction, which causes damping in a purely mechanical system. The analysis shows that the larger the difference in acoustic properties between adjacent layers, the higher the attenuation of acoustical properties becomes.
Abnormal setting of Portland cement
Authors: Rakhimbaev Sh M , Tolypina N M , Anikanova T V , Khakhaleva E N 
Published: June 2021

Abstract
It is proposed to distinguish the false setting from the abnormal one, considering the false as a variety of the latter. With false setting, the start of setting occurs in a short time, but then it spontaneously disappears, reappearing after a while. Such cements, in which the beginning of setting occurs faster than 50 minutes, and the end – after 5-12 hours, are proposed to be called abnormal cements. It is shown that when the start time of setting is more than 50 ∼ 60 minutes, the probability of abnormal setting decreases sharply. The kinetics of structure formation of cements with different setting patterns is considered. Methods for the identification of abnormal setting by the setting interval (τfinal – τstart)/τstart > 3, the kinetics of structure formation, heat release, and changes in the activity of calcium ions in the liquid phase of cement paste of normal density are proposed. It is shown that the measurement of the kinetics of heat release and the activity of Ca 2+ ions in the liquid phase of cement paste is of great interest for the development of automated and rapid control of the presence of anomalies during setting. It is established that the mixture of the inhibitor and the booster of the setting acts according to the rule of additivity, the use of mineral additives of acidic composition weakens the abnormal properties of cement systems. To combat the belated anomaly, it is necessary to monitor the properties of the cement 1-2 days before its application.
Physico-chemical efficiency of mineral additives of various compositions in cement systems
Authors: Nizina T A , Balykov A S , Korovkin D I , Volodin V V 
Published: June 2021

Abstract
Management of the pore volume and the mineral-morphological state of the hardening system through the use of chemical and mineral additives introduced both separately and in complexes is considered to be one of the defining directions of cement system structure formation. Currently, the nomenclature of mineral modifiers includes a wide list of materials of natural, artificial, and technogenic origin. The purpose of this study was to establish the influence regularities of mineral additives of various compositions (siliceous (microsilica, diatomite, opoka), aluminosilicate (metakaolin, fly ash), sulfoaluminate (expanding sulfoaluminate modifier), carbonate (microcalcite)) on the physical-mechanical properties of cement systems, with the identification of the most effective modifiers. According to the results of experimental studies, the influence of modifiers on the activity of the mixed cement binder, water demand, water-holding capacity and mobility of the cement paste was revealed. Condensed non-compacted microsilica, metakaolin and expanding sulfoaluminate modifier were selected as the most promising mineral additives.
Renovation of five-storey residential buildings of the first mass series in the regions of Russia. Problems and solutions
Authors: Chereshnev I V , Chereshneva N V 
Published: June 2021

Abstract
The paper examines the problem associated with the reconstruction of residential buildings and the renovation of the territory of residential development of the first mass series. The issues of the current state of the five-storey housing stock in the regions of Russia are highlighted. On the example of the city of Volgograd, an architectural and spatial assessment of the development of residential development of the city is given. Attention is focused on the issues of building blocks and neighborhoods with five-story houses of the first standard series. The socio-economic, architectural and planning parameters of residential sections and apartments are analyzed in detail. Structural and planning deficiencies affecting the level of comfort of the housing stock are identified. During the discussion, the search for possible solutions related to the renovation and improvement of a five-storey residential development is shown. The evaluation of the operational qualities of the experimental construction allowed determining the complex methodological basis of possible reconstructive measures, combined in three main technological directions: renovation of the territory of a five-storey housing stock by demolishing individual buildings or entire blocks; renovation, which is based on major repairs of the housing stock without interfering with the architectural and structural system of a five-stored building; renovation aimed at changing the architectural and planning structure of residential buildings by adding additional volumes. The ways of implementation of technological directions of reconstruction of five-storey buildings that increase their compliance with the requirements of sustainability are considered.
Gas using efficiency in heating boilers for individual consumers
Authors: Beloglazova T N , Romanova T N 
Published: June 2021

Abstract
Gas boilers for heating of individual consumers is used in all regions of Russia. Gas boilers are characterized by higher efficiency unlike on other types of organic fuels. Using dry natural gas reduces the polluting emissions into the atmosphere. A significant variety of gas boilers for individual heat supply meets the needs of consumers. The main requirements for individual heat supply from gas boilers are safety, economy, high efficiency, ease of use. These requirements are met by using gas with specified properties that meets standards. The required gas parameters for the consumer are provided due to the availability and functioning of the gas distribution system in the settlements. For the safety and efficiency of gas boilers, proper organization of air exchange in the room is necessary. To determine the efficiency of domestic gas boilers, the influence of the temperature of the air used in the combustion process is considered. Boilers with open the combustion chamber use internal air. Outside air is used in boilers with a closed combustion chamber. The study determines how the efficiency of a gas boiler changes at different temperatures outside air during the heating period. Losses of flue gases and chemical incomplete burning were taken into account when calculating the efficiency of gas boilers. The calculation was made taking into account the physical heat introduced by the air for burning. The study considered gas boilers with a heating capacity of 20, 30, 50, 100kW at a nominal operating mode. The annual effect of gas fuel saving is presented for natural dry gas with a calorific value of 34MJ/cub m.
The ALEX17 diurnal cycles in complex terrain benchmark
Authors: Sanz Rodrigo J , Santos P , Chávez Arroyo R , Avila M , Cavar D , Lehmkuhl O , Owen H , Li R , Tromeur E 
Published: June 2021

AbstractThe NEWA ALEX17 experiment was conducted with the objective of characterizing the wind conditions upstream of the Alaiz Test Site for the validation of flow models. From the intensive operational period, a case study has been selected for a Wakebench benchmark consisting of four consecutive days with relatively persistent winds from the North. The validation is centered around a 118-m mast at the Alaiz site and six additional masts located along the valley and at the lee side of a ridge delimiting a 8-km long area of interest. The benchmark is a follow-up of the GABLS3 diurnal cycle benchmark in flat terrain to test mesoscale-to-microscale transient and steady-state modeling methodologies in the assessment of stability-dependent bin-averaged wind conditions. Meso-micro methodologies reduce the wind speed mean bias from 32%, at 3-km mesoscale, to ±5%. Beyond mean bias mitigation, these initial results demonstrate the added value of meso-micro coupling at reproducing non conventional wind conditions at the test site like high-shear low-level jets in stable conditions and negative wind shear in unstable conditions. The benchmark also discusses the challenges of each meso-micro methodology going forward.
Stability of Floating Wind Turbine Wakes
Authors: Kleine V G , Franceschini L , Carmo B S , Hanifi A , Henningson D S 
Published: June 2021

Abstract
Floating offshore wind turbines (FOWTs) are the next frontier in offshore wind energy, allowing exploration of deep-water regions previously unavailable to fixed-foundation turbines. Since offshore turbines operate in lower turbulence levels, the intrinsic hydrodynamic unstable modes of the tip vortices can have even more relevance than in onshore turbines. For floating turbines, platform motion induced by wind and wave loads can trigger vortex instabilities, modifying the wake structure, possibly influencing the flow reaching downstream wind turbines. In the present paper, we study those effects by the means of numerical simulations and their comparison with analytical studies. In our simulations, the wind turbine blades are modeled as actuator lines in the incompressible Navier–Stokes equations. Heave motion with different amplitudes and frequencies are studied. The effect of increasing amplitude is to advance the onset of vortex interaction. For the lower frequency of heave motion, several vortices coalesce to form a large flow structure. High amplitude of oscillations in the streamwise velocity were observed due to these flow structures, which may increase fatigue or induce high amplitude motion on downstream turbines. The number of vortices that interact, as other qualitative phenomena of the numerical simulation, were well predicted by a simple stability model of two-dimensional row of vortices. The disturbances imposed by the heave motion were also compared to the eigenvectors resulting from linear stability theory for helical vortices and the predicted growth rates for the wavenumbers resulting from this comparison were consistent with the model of a row of vortices. These results motivate further studies to understand the impact of the larger flow structures on downstream turbines.