Pub Date : 2019-10-14DOI: 10.21122/2227-1031-2019-18-5-386-394
Y. Aliakseyeu, A. Korolyov, A. S. Budnitskiy, Dai Wenqi
A great attention has been recently paid to development of ultrasound technologies for treatment of blood vessels throughout the world. Authors of the paper have developed a new effective treatment method and ultrasound equipment that allow to carry out destruction of intravascular formations with simultaneous increase in elasticity of a vascular wall together with cardiologists from Belarusian Medical Academy of Postgraduate Education and Republican Scientific and Practical Center “Cardiology”. Advantages of the method are absence of necessity in surgical intervention, low probability of complications, low cost of treatment. The main component of the developed ultrasonic equipment is a tube-type stepped concentrator-waveguide having a spherical tip at a distal end with a single axial hole of 0.5 mm-diameter and three radial holes of 0.3 mmdiameter located at an angle of 120° relative to each other. The main effect for application of the concentratorwaveguide is achieved by ultrasonic vibromechanical action of a spherical tip on intravascular formation with subsequent removal of destruction products by their aspiration from a vascular bed. An additional effect is provided due to cavitation action on vascular formation and vessel walls by flow of fluid supplied via an internal cavity of the stepped concentratorwaveguide through the holes in the spherical tip. This contributes to a significant improvement in elastic properties of a vascular wall in atherosclerosis and diabetes. It is necessary to ensure high accuracy and quality of surfaces for the formed microholes in order to achieve maximum efficiency of the cavitation jet impact on intravascular formations and on the vascular wall. According to the analysis results on specific features of existing methods for small-diameter hole shaping, an electrochemical hole cutting method has been proposed which allows to obtain accurate micro-holes with a diameter of 0.3 mm and high surface quality in parts of small cross section and rigidity. The paper presents results of study on effect of electrochemical holes cutting parameters (voltage, concentration and consumption of electrolyte) on size and shape of the formed microholes. Main modes of electrochemical holes cutting process have been developed which allow to form micro-holes in a spherical tip of a tubular concentrator-waveguide with required accuracy, dimensions and shape.
{"title":"Electrochemical Cutting of Micro-Holes in Tubular Stepped Concentrator-Waveguide for Medical Purposes","authors":"Y. Aliakseyeu, A. Korolyov, A. S. Budnitskiy, Dai Wenqi","doi":"10.21122/2227-1031-2019-18-5-386-394","DOIUrl":"https://doi.org/10.21122/2227-1031-2019-18-5-386-394","url":null,"abstract":"A great attention has been recently paid to development of ultrasound technologies for treatment of blood vessels throughout the world. Authors of the paper have developed a new effective treatment method and ultrasound equipment that allow to carry out destruction of intravascular formations with simultaneous increase in elasticity of a vascular wall together with cardiologists from Belarusian Medical Academy of Postgraduate Education and Republican Scientific and Practical Center “Cardiology”. Advantages of the method are absence of necessity in surgical intervention, low probability of complications, low cost of treatment. The main component of the developed ultrasonic equipment is a tube-type stepped concentrator-waveguide having a spherical tip at a distal end with a single axial hole of 0.5 mm-diameter and three radial holes of 0.3 mmdiameter located at an angle of 120° relative to each other. The main effect for application of the concentratorwaveguide is achieved by ultrasonic vibromechanical action of a spherical tip on intravascular formation with subsequent removal of destruction products by their aspiration from a vascular bed. An additional effect is provided due to cavitation action on vascular formation and vessel walls by flow of fluid supplied via an internal cavity of the stepped concentratorwaveguide through the holes in the spherical tip. This contributes to a significant improvement in elastic properties of a vascular wall in atherosclerosis and diabetes. It is necessary to ensure high accuracy and quality of surfaces for the formed microholes in order to achieve maximum efficiency of the cavitation jet impact on intravascular formations and on the vascular wall. According to the analysis results on specific features of existing methods for small-diameter hole shaping, an electrochemical hole cutting method has been proposed which allows to obtain accurate micro-holes with a diameter of 0.3 mm and high surface quality in parts of small cross section and rigidity. The paper presents results of study on effect of electrochemical holes cutting parameters (voltage, concentration and consumption of electrolyte) on size and shape of the formed microholes. Main modes of electrochemical holes cutting process have been developed which allow to form micro-holes in a spherical tip of a tubular concentrator-waveguide with required accuracy, dimensions and shape.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2019-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74422264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-13DOI: 10.21122/2227-1031-2019-18-4-330-338
N. S. Gurinenko, E. I. Batyanovskiy
The paper presents results of research aimed at developing a new semi-functional concrete additive that provides an increase in rate and level of its strength growth while reducing energy costs to accelerate hardening process, as a basis for reducing energy intensity in manufacturing of concrete and reinforced concrete products and structures. Experimentally a rational ratio of components for a polyfunctional additive has been found of mass cement: a superplasticizer based on polycarboxylate resins (for example, “Stachement 2000” or “Relamiks PC”) – 0.5 %, ultradispersed microsilica (SiO2) – 1.0 %, sodium sulfate (Na2SO4), hardening accelerator – 0.5 %, aluminum sulfate (Al2(SO4)3), sealing additive structure ‒ 0.25 %. The mentioned components ensure the largest increase in strength of cement stone and structural heavy concrete. Results of derivatographic and X-ray phase analyses have shown that strength growth is based on formation of a fine-crystalline form of low-base crystalline silicates of CSH-silicate group, which complements traditionally formed C2SH by the reaction of threeand two-calcium silicate cement with water, as well as it is based on an increase in the number of neoplasms due to the reaction of Ca(OH)2 with amorphous SiO2 and ettringite 3CaO × Al2O3 × 3CaSO4 × 32H2O, being formed due to reactions with cement aluminates these are accelerating-compacting additive components, that in total provides an increase in density and strength of cement stone. While having the case with concrete, the effect is complemented by hardening the zone of contact between aggregate surface and cement stone due to the reaction between Ca(OH)2 and SiO2. These effects have been confirmed by growth (up to 38 %) of water which is chemically bound with cement in presence of a multifunctional additive in samples of cement stone, which is characterized by the largest strength. While using standardized testing methods, effectiveness of a multifunctional additive has been experimentally confirmed and it has been expressed in growth of quality characteristics and properties of structural heavy concrete: compressive strength – up to 40–60 %, flexural strength – up to 15 %, reduction of shrinkage – up to 50 % and water absorption – by 1.5–2 times, increase in frost resistance from brand F250 to F500, water resistance – from W6–W8 to W20.
{"title":"Influence of Polyfunctional Additive on Hardening Process and Properties of Cement Concrete","authors":"N. S. Gurinenko, E. I. Batyanovskiy","doi":"10.21122/2227-1031-2019-18-4-330-338","DOIUrl":"https://doi.org/10.21122/2227-1031-2019-18-4-330-338","url":null,"abstract":"The paper presents results of research aimed at developing a new semi-functional concrete additive that provides an increase in rate and level of its strength growth while reducing energy costs to accelerate hardening process, as a basis for reducing energy intensity in manufacturing of concrete and reinforced concrete products and structures. Experimentally a rational ratio of components for a polyfunctional additive has been found of mass cement: a superplasticizer based on polycarboxylate resins (for example, “Stachement 2000” or “Relamiks PC”) – 0.5 %, ultradispersed microsilica (SiO2) – 1.0 %, sodium sulfate (Na2SO4), hardening accelerator – 0.5 %, aluminum sulfate (Al2(SO4)3), sealing additive structure ‒ 0.25 %. The mentioned components ensure the largest increase in strength of cement stone and structural heavy concrete. Results of derivatographic and X-ray phase analyses have shown that strength growth is based on formation of a fine-crystalline form of low-base crystalline silicates of CSH-silicate group, which complements traditionally formed C2SH by the reaction of threeand two-calcium silicate cement with water, as well as it is based on an increase in the number of neoplasms due to the reaction of Ca(OH)2 with amorphous SiO2 and ettringite 3CaO × Al2O3 × 3CaSO4 × 32H2O, being formed due to reactions with cement aluminates these are accelerating-compacting additive components, that in total provides an increase in density and strength of cement stone. While having the case with concrete, the effect is complemented by hardening the zone of contact between aggregate surface and cement stone due to the reaction between Ca(OH)2 and SiO2. These effects have been confirmed by growth (up to 38 %) of water which is chemically bound with cement in presence of a multifunctional additive in samples of cement stone, which is characterized by the largest strength. While using standardized testing methods, effectiveness of a multifunctional additive has been experimentally confirmed and it has been expressed in growth of quality characteristics and properties of structural heavy concrete: compressive strength – up to 40–60 %, flexural strength – up to 15 %, reduction of shrinkage – up to 50 % and water absorption – by 1.5–2 times, increase in frost resistance from brand F250 to F500, water resistance – from W6–W8 to W20.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2019-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86925196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-13DOI: 10.21122/2227-1031-2019-18-4-303-310
P. I. Yukhnevskiy, N. Dimitriadi
The paper substantiates scientific background for development of lubricant compositions used in moulds for concrete products with high-quality surface. It has been shown that consideration of interaction between air bubbles, lubricant and liquid phase of modified concrete is of great importance. A release agent must allow air to migrate to a certain extent and leave “formwork – concrete mix” interface. In this regard the lubricant must have low viscosity. In addition, the lubricant should give maximum hydrophobization to a mould and have minimal adhesion in respect of the concrete mix. Additives of hydrophobic substances in liquid lubricants significantly reduce surface porosity of products. Chemical plasticizing additives and, in particular, additives of polycarboxylate type substantially reduce surface tension of liquid sгж, thereby they significantly reduce work for fixing an air bubble on concrete surface and contribute to its ejection. In addition, adsorbed molecules of the chemical additives interfere with interaction of cement paste particles and mould surface. Polycarboxylate additive molecules diffuse from a diffuse layer of the concrete mix, fill capillaries in the lubricant film, reduce its viscosity, act as additives that regulate spreading of lubricant and facilitate removal of air bubbles in a surface layer. Experimental studies of the combined effect while using low viscosity grease based on vegetable oils and modifying additives have confirmed the above provisions. The polycarboxylate-based additive has made the greatest impact on reduction of concrete surface porosity and content of all types of pores in the concrete has been approximately at the same level.
{"title":"About Synergistic Effect of Lubricant and Chemical Additives on Obtaining Quality Surface of Concrete Products","authors":"P. I. Yukhnevskiy, N. Dimitriadi","doi":"10.21122/2227-1031-2019-18-4-303-310","DOIUrl":"https://doi.org/10.21122/2227-1031-2019-18-4-303-310","url":null,"abstract":"The paper substantiates scientific background for development of lubricant compositions used in moulds for concrete products with high-quality surface. It has been shown that consideration of interaction between air bubbles, lubricant and liquid phase of modified concrete is of great importance. A release agent must allow air to migrate to a certain extent and leave “formwork – concrete mix” interface. In this regard the lubricant must have low viscosity. In addition, the lubricant should give maximum hydrophobization to a mould and have minimal adhesion in respect of the concrete mix. Additives of hydrophobic substances in liquid lubricants significantly reduce surface porosity of products. Chemical plasticizing additives and, in particular, additives of polycarboxylate type substantially reduce surface tension of liquid sгж, thereby they significantly reduce work for fixing an air bubble on concrete surface and contribute to its ejection. In addition, adsorbed molecules of the chemical additives interfere with interaction of cement paste particles and mould surface. Polycarboxylate additive molecules diffuse from a diffuse layer of the concrete mix, fill capillaries in the lubricant film, reduce its viscosity, act as additives that regulate spreading of lubricant and facilitate removal of air bubbles in a surface layer. Experimental studies of the combined effect while using low viscosity grease based on vegetable oils and modifying additives have confirmed the above provisions. The polycarboxylate-based additive has made the greatest impact on reduction of concrete surface porosity and content of all types of pores in the concrete has been approximately at the same level.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2019-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89361785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-13DOI: 10.21122/2227-1031-2019-18-4-284-291
S. Leonovich, E. E. Shalyi, L. Kim
Reinforcement corrosion of marine and coastal hydraulic structures due to chloride aggression and concrete carbonization leads to a sharp decrease in structure safety. The reinforcement is subjected to a depassivation process as soon as a chloride concentration on its surface exceeds a certain threshold concentration, or the pH value in a concrete protective layer is decreased to a threshold value due to carbonation. Electrochemical reactions are realized with formation of corrosion products due to penetration of oxygen up to reinforcement surface. This leads to cracking of the concrete protective layer and decrease in reinforcement cross-section. The paper proposes a method for predicting a complex degradation of reinforced concrete structures with due account of various mechanisms of corrosion wear that allows to develop efficient methods for improvement of structure durability and maintainability which are operated in the marine environment. A methodology for forecasting of reinforced concrete service life prediction has been developed under a combined effect of carbonization and chloride aggression while using finite-difference and probability models. The paper takes into account initiation periods of reinforcement corrosion and propagation periods for conditions of Sakhalin shelf zone. Field surveys of Kholmsk and Korsakov port facilities are presented in the paper. Carbonization front and chloride content have been estimated according to depth of the concrete protective layer. The paper proposes a model that allows to determine an average period prior to repair while taking into account rate of concrete protective layer degradation caused by simultaneous action of two corrosion processes: carbonization and chloride aggression.
{"title":"Reinforced Concrete under the Action of Carbonization and Chloride Aggression: a Probabilistic Model for Service Life Prediction","authors":"S. Leonovich, E. E. Shalyi, L. Kim","doi":"10.21122/2227-1031-2019-18-4-284-291","DOIUrl":"https://doi.org/10.21122/2227-1031-2019-18-4-284-291","url":null,"abstract":"Reinforcement corrosion of marine and coastal hydraulic structures due to chloride aggression and concrete carbonization leads to a sharp decrease in structure safety. The reinforcement is subjected to a depassivation process as soon as a chloride concentration on its surface exceeds a certain threshold concentration, or the pH value in a concrete protective layer is decreased to a threshold value due to carbonation. Electrochemical reactions are realized with formation of corrosion products due to penetration of oxygen up to reinforcement surface. This leads to cracking of the concrete protective layer and decrease in reinforcement cross-section. The paper proposes a method for predicting a complex degradation of reinforced concrete structures with due account of various mechanisms of corrosion wear that allows to develop efficient methods for improvement of structure durability and maintainability which are operated in the marine environment. A methodology for forecasting of reinforced concrete service life prediction has been developed under a combined effect of carbonization and chloride aggression while using finite-difference and probability models. The paper takes into account initiation periods of reinforcement corrosion and propagation periods for conditions of Sakhalin shelf zone. Field surveys of Kholmsk and Korsakov port facilities are presented in the paper. Carbonization front and chloride content have been estimated according to depth of the concrete protective layer. The paper proposes a model that allows to determine an average period prior to repair while taking into account rate of concrete protective layer degradation caused by simultaneous action of two corrosion processes: carbonization and chloride aggression.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2019-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78092800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-13DOI: 10.21122/2227-1031-2019-18-4-269-273
Ya. N. Kovalev, D. Y. Alexandrov
A problem of efficient resource usage in road branch continues to be one of the most complicated issues and requires an intensification in investigation process pertaining to possibilities for production of road construction materials of low resource intensity with high physical and mechanical properties. Technogenic wastes of the Belarusian enterprises are rather various and they need a detailed investigation. Application of such methods as IR spectrometry, probe microscopy, study of of geometric characteristics of particles and fibers make it possible to determine more active centres and reveal micro-defects that influence on strength of adhesion bond at the boundary of “fiber – binder” and physical and mechanical properties of ready-mixed asphalt concrete. Nature of basalt fiber presupposes mainly physical character of adhesion interaction at the boundary of phase separation. An increase of technogenic waste activity to enhance adhesion contacts up to chemisorption level is possible only due to preliminary fiber processing which includes cleaning, removal of foreign inclusions, etching, drying, probable sorting-out and fluffing. Industrial approbation of such technological process is not possible without development of a corresponding module or a plant. Disperse reinforment causes changes in composition and technology of sand asphalt concrete. An increase in specific surface of an aggregate, necessity of uniform distribution of fiber in terms of volume determine the required need in a binder, procedure and regimes for component mixing. Grain composition of the aggregate can be represented by crush screening and natural sand of mixture of these materials. Requirements to properties of sand disperse-reinforced asphalt concrete are formed on the basis of operational conditions and layer arrangement of the material in the design of a surface dressing. The disperse-reinforced sand asphalt concrete can perform functions of a superfine protective layer, a levelling layer or a crack stopping layer which is resistant to fatigue crack formation.
{"title":"Сonceptual Fundamentals for Technology of Sand Disperse-Reinforced Asphalt Concrete","authors":"Ya. N. Kovalev, D. Y. Alexandrov","doi":"10.21122/2227-1031-2019-18-4-269-273","DOIUrl":"https://doi.org/10.21122/2227-1031-2019-18-4-269-273","url":null,"abstract":"A problem of efficient resource usage in road branch continues to be one of the most complicated issues and requires an intensification in investigation process pertaining to possibilities for production of road construction materials of low resource intensity with high physical and mechanical properties. Technogenic wastes of the Belarusian enterprises are rather various and they need a detailed investigation. Application of such methods as IR spectrometry, probe microscopy, study of of geometric characteristics of particles and fibers make it possible to determine more active centres and reveal micro-defects that influence on strength of adhesion bond at the boundary of “fiber – binder” and physical and mechanical properties of ready-mixed asphalt concrete. Nature of basalt fiber presupposes mainly physical character of adhesion interaction at the boundary of phase separation. An increase of technogenic waste activity to enhance adhesion contacts up to chemisorption level is possible only due to preliminary fiber processing which includes cleaning, removal of foreign inclusions, etching, drying, probable sorting-out and fluffing. Industrial approbation of such technological process is not possible without development of a corresponding module or a plant. Disperse reinforment causes changes in composition and technology of sand asphalt concrete. An increase in specific surface of an aggregate, necessity of uniform distribution of fiber in terms of volume determine the required need in a binder, procedure and regimes for component mixing. Grain composition of the aggregate can be represented by crush screening and natural sand of mixture of these materials. Requirements to properties of sand disperse-reinforced asphalt concrete are formed on the basis of operational conditions and layer arrangement of the material in the design of a surface dressing. The disperse-reinforced sand asphalt concrete can perform functions of a superfine protective layer, a levelling layer or a crack stopping layer which is resistant to fatigue crack formation.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2019-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88877745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-13DOI: 10.21122/2227-1031-2019-18-4-319-329
И. И. Полевода, С. М. Жамойдик, Д. С. Нехань, Д. С. Батан
The paper presents a complex of laboratory and theoretical studies of physical and mechanical properties in centrifuged concrete while using samples of sectoral cross-section which are cut in layers from a finished product. A post made of concrete having B40 grade for compression strength and manufactured while using centrifugation with the help of РТЦ-5 machine. Assessment of heterogeneity across section thickness has been carried out by visual determination of composition changes in cross section, determination of strength, density of the obtained concrete samples, and water content over cross section of concrete mix. According to the results of a visual study on composition of a concrete structure it has been revealed that 1/8 part of the structure (from an inner surface) does not have a large aggregate. Later, as it moves to periphery, there is an increase in coarse aggregate and a decrease in size and number of cells between grains of gravel. An analysis of experimental data has shown that properties of the centrifuged concrete in samples being sawn in layers change significantly: density of concrete in samples of an inner layer is lower by 8 % than in samples of an outer layer, and compressive strength of concrete – by 34 %, water content of concrete mixture of samples of the inner layer has turned out to be by 43 % higher than in samples of the outer layer. Approximating curves showing regularities of changes in density, concrete strength, water content of concrete mixture over thickness have been constructed in the paper. Linear and exponential equations have been obtained that describe changes in physical and mechanical properties of centrifuged concrete over section depending on structure properties as a whole, which, taking into account the obtained correction factors k1 and k2, can be used with an acceptable level of confidence in practical calculations of centrifuged concrete structures. Relationship between strength of centrifuged concrete varying over cross section and action of a centrifugal force of inertia has been revealed in the paper. An equation has been obtained that relates the strength of centrifuged concrete to its density. Analysis of the research results makes it possible to assert that the main source of loading perception in centrifuged concrete structures is outer layers.
{"title":"Study of Physical and Mechanical Properties of Centrifuged Concrete","authors":"И. И. Полевода, С. М. Жамойдик, Д. С. Нехань, Д. С. Батан","doi":"10.21122/2227-1031-2019-18-4-319-329","DOIUrl":"https://doi.org/10.21122/2227-1031-2019-18-4-319-329","url":null,"abstract":"The paper presents a complex of laboratory and theoretical studies of physical and mechanical properties in centrifuged concrete while using samples of sectoral cross-section which are cut in layers from a finished product. A post made of concrete having B40 grade for compression strength and manufactured while using centrifugation with the help of РТЦ-5 machine. Assessment of heterogeneity across section thickness has been carried out by visual determination of composition changes in cross section, determination of strength, density of the obtained concrete samples, and water content over cross section of concrete mix. According to the results of a visual study on composition of a concrete structure it has been revealed that 1/8 part of the structure (from an inner surface) does not have a large aggregate. Later, as it moves to periphery, there is an increase in coarse aggregate and a decrease in size and number of cells between grains of gravel. An analysis of experimental data has shown that properties of the centrifuged concrete in samples being sawn in layers change significantly: density of concrete in samples of an inner layer is lower by 8 % than in samples of an outer layer, and compressive strength of concrete – by 34 %, water content of concrete mixture of samples of the inner layer has turned out to be by 43 % higher than in samples of the outer layer. Approximating curves showing regularities of changes in density, concrete strength, water content of concrete mixture over thickness have been constructed in the paper. Linear and exponential equations have been obtained that describe changes in physical and mechanical properties of centrifuged concrete over section depending on structure properties as a whole, which, taking into account the obtained correction factors k1 and k2, can be used with an acceptable level of confidence in practical calculations of centrifuged concrete structures. Relationship between strength of centrifuged concrete varying over cross section and action of a centrifugal force of inertia has been revealed in the paper. An equation has been obtained that relates the strength of centrifuged concrete to its density. Analysis of the research results makes it possible to assert that the main source of loading perception in centrifuged concrete structures is outer layers.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2019-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84669386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-13DOI: 10.21122/2227-1031-2019-18-4-292-302
M. M. Mordzich
Theoretical and experimental investigations have resulted in obtaining an effective insulating and structural material (claydite foam concrete) that is not subjected to slump and shrinkage in the range of main grades used in construction in terms of average density D300–D700, characterized by 5–31 % greater strength and 8–27 % elasticity modulus, as well as a higher (£30.7 %) level of vapor permeability and moisture return (by 17.4–46.7 %) with lower values (by 10.0–83.2 %) of water absorption, sorption moisture and thermal conductivity in comparison with aerated concrete of autoclave hardening and foam concrete of equal density. A three-stage technology has been developed for preparing claydite foam concrete. At the first stage cement dough is prepared and if it is necessary an optimum amount of hardening accelerator (1 % CaCl2 from cement mass) and additives condensing cement stone structure (1 % Al2SO4 from cement mass ) are introduced into it, they prevent slump of a binder (foam concrete) during the subsequent hardening, and in combination with 0.5 % from cement mass “Hydroxypropylmethylcellulose УСК-200 TT” – and shrinkage of foam and claydite foam concrete during the subsequent drying. At the second stage, the binder is aerated while introducing protein-based foam agent (Laston) into the cement dough in an optimal amount (depending on the given density) 0.5–1.3 % from the cement mass; and at the third stage, expanded clay gravel is introduced into prepared foam concrete mixture (in rational amount of approximately 0.7–0.8 m3 per 1 m3 of claydite foam concrete) with continuous mixing for 60–90 seconds. Methodologies for calculation of foamand claydite foam concrete compositions have been developed; molding modes of expanded clay foam concrete with high degree of homogeneity (variation coefficient of density and strength uk £ 6.2 % in the process of manufacturing molding with layer height up to 1500 mm) have been justified that confirms efficiency of the proposed technology.
{"title":"Technology and Physico-Mechanical Properties of Claydite Foam Concrete for Monolithic and Prefabricated Construction","authors":"M. M. Mordzich","doi":"10.21122/2227-1031-2019-18-4-292-302","DOIUrl":"https://doi.org/10.21122/2227-1031-2019-18-4-292-302","url":null,"abstract":"Theoretical and experimental investigations have resulted in obtaining an effective insulating and structural material (claydite foam concrete) that is not subjected to slump and shrinkage in the range of main grades used in construction in terms of average density D300–D700, characterized by 5–31 % greater strength and 8–27 % elasticity modulus, as well as a higher (£30.7 %) level of vapor permeability and moisture return (by 17.4–46.7 %) with lower values (by 10.0–83.2 %) of water absorption, sorption moisture and thermal conductivity in comparison with aerated concrete of autoclave hardening and foam concrete of equal density. A three-stage technology has been developed for preparing claydite foam concrete. At the first stage cement dough is prepared and if it is necessary an optimum amount of hardening accelerator (1 % CaCl2 from cement mass) and additives condensing cement stone structure (1 % Al2SO4 from cement mass ) are introduced into it, they prevent slump of a binder (foam concrete) during the subsequent hardening, and in combination with 0.5 % from cement mass “Hydroxypropylmethylcellulose УСК-200 TT” – and shrinkage of foam and claydite foam concrete during the subsequent drying. At the second stage, the binder is aerated while introducing protein-based foam agent (Laston) into the cement dough in an optimal amount (depending on the given density) 0.5–1.3 % from the cement mass; and at the third stage, expanded clay gravel is introduced into prepared foam concrete mixture (in rational amount of approximately 0.7–0.8 m3 per 1 m3 of claydite foam concrete) with continuous mixing for 60–90 seconds. Methodologies for calculation of foamand claydite foam concrete compositions have been developed; molding modes of expanded clay foam concrete with high degree of homogeneity (variation coefficient of density and strength uk £ 6.2 % in the process of manufacturing molding with layer height up to 1500 mm) have been justified that confirms efficiency of the proposed technology.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2019-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74776367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-13DOI: 10.21122/2227-1031-2019-18-4-339-349
Y. Popova
The use of information technologies and, in particular, information training systems increases capacity of both a teacher and a student to achieve their goals in an educational process, taking into account individual characteristics of each and providing opportunities for continuing education. The paper proposes and considers a new automated learning management system, called CATS (Care About the Students). The proposed system covers all components of the educational process, allows to conduct an electronic journal of visiting and defending laboratory works, distribute topics and monitor progress of course and diploma projects (creating automatically task sheets with subsequent export to MS Word editor). The CATS LMS makes it possible to test students’ knowledge in control and self-education modes, to form electronic educational and methodical complexes, to inform students about topics of lecture and practical classes with the possibility of downloading relevant materials, to provide educational content in SCORM format, developed by teachers around the world. Working in the CATS system, it is possible to exchange messages with students and teachers, to monitor progress and process of studying in respect of the proposed material by students, to check accomplished assignments of students for plagiarism. The system under consideration also takes into account specificity of training at a technical higher education institution, providing for work with an integrated project management system and ability to submit bugs. The CATS LMS has been implemented as a web application using modern technologies and it is available in the local network within the whole university at [172.16.11.72:2020].
利用信息技术，特别是信息训练系统，可以提高教师和学生在教育过程中实现其目标的能力，同时考虑到每个人的个人特点，并提供继续教育的机会。本文提出并考虑了一种新的自动化学习管理系统——CATS (Care About The Students)。拟议的系统涵盖了教育过程的所有组成部分，允许进行访问和捍卫实验室工作的电子期刊，分发主题和监控课程和文凭项目的进展(自动创建任务表，随后导出到MS Word编辑器)。CATS LMS可以在控制和自我教育模式下测试学生的知识，形成电子教育和系统综合体，向学生提供讲座和实践课程的主题，并可以下载相关材料，以SCORM格式提供由世界各地的教师开发的教育内容。在CATS系统中，我们可以与学生和老师交换信息，监控学生的学习进度和过程，以及检查学生完成的作业是否抄袭。所考虑的系统还考虑了技术高等教育机构培训的特殊性，提供了具有集成项目管理系统和提交错误能力的工作。CATS LMS已作为使用现代技术的web应用程序实现，并可在整个大学的本地网络中使用[172.16.11.72:2020]。
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Pub Date : 2019-07-02DOI: 10.21122/2227-1031-2019-18-3-256-264
O. Saraiev, S. Danez
The paper presents investigation methods which are aimed at increasing an accuracy in determination of parameters for movement of vehicles in the reconstruction process of road traffic accidents. The problems with a target to improve a method for calculation of vehicle movement speed and location coordinates at different time moments have been solved in the paper. In order to determine more accurately nature of vehicle damage and their location on carriageway, a laser scanning method has been applied which makes it possible to reduce an error while determining dimensions and distances, and to shorten time for an inspection of the road traffic accident place. The presence of a scanned image in three-dimensional form allows more accurately to simulate nature and angle concerning approach of vehicles prior to a collision. A methodological support for determination of vehicle movement parameters has been developed on the basis of the recorded data from driving video recorders (DVRs). It has been established that an error in measuring a speed of movement for vehicles will depend on quality of a video image, length of the investigated area and range of possible speeds. A relative error will be the higher, the smaller we have vehicle speed range and length of the investigated section. A mathematical model of vehicle speed change in a differential form has been compiled and solved in the paper. The model allows to calculate a speed of motion at different time moments with respect to recording from driving video recorders. In addition, the developed methodology permits more accurately to determine coordinates of vehicle location on a photoand video image. This is especially important while determining places of pedestrian-road accident or vehicle collision location of the collision or the place of collision with regard to the edge of carriageway. Unlike subjective research methods when initial data for carrying out auto-technical investigations are established by interviewing witnesses and the accused, the proposed methods make it possible to permit reconstruction of a road traffic accident exclusively by objective methods with the help of automated technical means.
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Pub Date : 2019-07-02DOI: 10.21122/2227-1031-2019-18-3-185-194
G. A. Vershina, L. E. Reut
The paper considers a technological process for production of sealing rings by winding a band work-piece on a cylindrical caliber mandrel with subsequent endurance under load and further cutting of a spiral in rings and also studies the possibility to obtain products while using a method for cold forming of a work-piece which excludes thermal stabilization operation. Taking into account the fact that fluorine plastic is a high-plastic material even at very low temperatures such technology looks quite real. Therefore winding of a band on a mandrel, endurance of a spiral work-piece without heating but under conditions of force action within the time which is necessary for completion of relaxation processes, and the subsequent cutting in rings will allow to obtain finished ring products of the required size. However fluoroplastic has specific mechanical properties and a number of specific features which are revealed during deformation process. Its deformation behavior considerably differs from behavior of low-molecular materials and therefore it requires a solid approach while using the existing theoretical base and developing calculation methodologies. While taking into consideration the fact that fluorine plastic is high density material and has structure with high degree of crystallinity, the mechanism of deformation behavior in it under conditions of a force field is mainly similar to metal behavior that allows to use methods and approaches for calculation of fluoroplastic products which are accepted in mechanics of solid bodies. However the applied calculating formulae require a certain correction and adaptation to specific features of mechanical fluoroplastic properties, one of which is its various rigidity at stretching and compression that is revealed in case of winding band work-piece on a mandrel. Fluorine plastic is a material with various modularity and its rigidity is higher during compression than under stretching and consequently in the case of band bending a neutral axis of section is displaced from the center of gravity to the area of compressed fibers, and the area of stretching is increasing. High elasticity at stretching and increase of this area lead to large accumulation of elastic deformations causing springing after unloading and changes in size of a finished product. These facts must be taken into account while calculating and designing a mandrel tool, it is also necessary to keep in mind various modularity of a material and possibility that a section being led to an uniform rigidity may take some other shape due to this. Calculation methodologies have been developed by the authors for both versions of section that take into consideration directly or indirectly a material with various modularity and which do not contradict each other and which are rather precisely proved by experimental data.
{"title":"Specific Features of Fluoroplastic Band Bending with Due Account of Various Modularity of Material","authors":"G. A. Vershina, L. E. Reut","doi":"10.21122/2227-1031-2019-18-3-185-194","DOIUrl":"https://doi.org/10.21122/2227-1031-2019-18-3-185-194","url":null,"abstract":"The paper considers a technological process for production of sealing rings by winding a band work-piece on a cylindrical caliber mandrel with subsequent endurance under load and further cutting of a spiral in rings and also studies the possibility to obtain products while using a method for cold forming of a work-piece which excludes thermal stabilization operation. Taking into account the fact that fluorine plastic is a high-plastic material even at very low temperatures such technology looks quite real. Therefore winding of a band on a mandrel, endurance of a spiral work-piece without heating but under conditions of force action within the time which is necessary for completion of relaxation processes, and the subsequent cutting in rings will allow to obtain finished ring products of the required size. However fluoroplastic has specific mechanical properties and a number of specific features which are revealed during deformation process. Its deformation behavior considerably differs from behavior of low-molecular materials and therefore it requires a solid approach while using the existing theoretical base and developing calculation methodologies. While taking into consideration the fact that fluorine plastic is high density material and has structure with high degree of crystallinity, the mechanism of deformation behavior in it under conditions of a force field is mainly similar to metal behavior that allows to use methods and approaches for calculation of fluoroplastic products which are accepted in mechanics of solid bodies. However the applied calculating formulae require a certain correction and adaptation to specific features of mechanical fluoroplastic properties, one of which is its various rigidity at stretching and compression that is revealed in case of winding band work-piece on a mandrel. Fluorine plastic is a material with various modularity and its rigidity is higher during compression than under stretching and consequently in the case of band bending a neutral axis of section is displaced from the center of gravity to the area of compressed fibers, and the area of stretching is increasing. High elasticity at stretching and increase of this area lead to large accumulation of elastic deformations causing springing after unloading and changes in size of a finished product. These facts must be taken into account while calculating and designing a mandrel tool, it is also necessary to keep in mind various modularity of a material and possibility that a section being led to an uniform rigidity may take some other shape due to this. Calculation methodologies have been developed by the authors for both versions of section that take into consideration directly or indirectly a material with various modularity and which do not contradict each other and which are rather precisely proved by experimental data.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2019-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89833721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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