bluuebunny/crossref_metadata_2025 huggingface dataset:
The numerical solution of the space-time fractional diffusion equation involving the Caputo-Katugampola fractional derivative
Authors: Bouchama Kaouther , Arioua Yacine , Merzougui Abdelkrim
Published: July 2021

In this paper, a numerical approximation solution of a space-time fractional diffusion equation (FDE), involving Caputo-Katugampola fractional derivative is considered. Stability and convergence of the proposed scheme are discussed using mathematical induction. Finally, the proposed method is validated through numerical simulation results of different examples.
Inference on semiparametric multinomial response models
Authors: Khan Shakeeb , Ouyang Fu , Tamer Elie
Published: July 2021

We explore inference on regression coefficients in semiparametric multinomial response models. We consider cross‐sectional, and both static and dynamic panel settings where we focus throughout on inference under sufficient conditions for point identification. The approach to identification uses a matching insight throughout all three models coupled with variation in regressors: with cross‐section data, we match across individuals while with panel data, we match within individuals over time. Across models, we relax the Indpendence of Irrelevant Alternatives (or IIA assumption, see McFadden (1974)) and allow for arbitrary correlation in the unobservables that determine utility of various alternatives. For the cross‐sectional model, estimation is based on a localized rank objective function, analogous to that used in Abrevaya, Hausman, and Khan (2010), and presents a generalization of existing approaches. In panel data settings, rates of convergence are shown to exhibit a curse of dimensionality in the number of alternatives. The results for the dynamic panel data model generalize the work of Honoré and Kyriazidou (2000) to cover the semiparametric multinomial case. A simulation study establishes adequate finite sample properties of our new procedures. We apply our estimators to a scanner panel data set.
A unified framework for efficient estimation of general treatment models
Authors: Ai Chunrong , Linton Oliver , Motegi Kaiji , Zhang Zheng
Published: July 2021

This paper presents a weighted optimization framework that unifies the binary, multivalued, and continuous treatment—as well as mixture of discrete and continuous treatment—under a unconfounded treatment assignment. With a general loss function, the framework includes the average, quantile, and asymmetric least squares causal effect of treatment as special cases. For this general framework, we first derive the semiparametric efficiency bound for the causal effect of treatment, extending the existing bound results to a wider class of models. We then propose a generalized optimization estimator for the causal effect with weights estimated by solving an expanding set of equations. Under some sufficient conditions, we establish the consistency and asymptotic normality of the proposed estimator of the causal effect and show that the estimator attains the semiparametric efficiency bound, thereby extending the existing literature on efficient estimation of causal effect to a wider class of applications. Finally, we discuss estimation of some causal effect functionals such as the treatment effect curve and the average outcome. To evaluate the finite sample performance of the proposed procedure, we conduct a small‐scale simulation study and find that the proposed estimation has practical value. In an empirical application, we detect a significant causal effect of political advertisements on campaign contributions in the binary treatment model, but not in the continuous treatment model.
Average crossing time: An alternative characterization of mean aversion and reversion
Authors: Donaldson John B. , Mehra Rajnish
Published: July 2021

This study compares and contrasts the multiple characterizations of mean reversion in financial time series as regards the restrictions they imply. This is accomplished by translating them into statements about an alternative measure, the “Average Crossing Time” or ACT. We argue that the ACT measure, per se, provides not only a useful benchmark for the degree of mean reversion/aversion, but also an intuitive, and easily quantified sense of one time series being “more strongly mean‐reverting/averting” than another. We conclude our discussion by deriving the ACT measure for a wide class of stochastic processes and detailing its statistical characteristics. Our analysis is principally undertaken within a class of well‐understood production based asset pricing models.
Antecedents Influencing the Adoption of Collaborative Learning Social-Media Platforms Among Thai University Students During the Covid-19 ‘New Normal’ Era
Authors: Phuthong Thadathibesra
Published: July 2021

There are benefits and challenges related to the recent worldwide Covid-19-driven surge of social-media collaborative learning in higher education. This research examines the antecedents influencing this ‘new normal’ phenomenon among university students to provide a causal model of understanding. This study was based on a purposive sample; a questionnaire was completed by 371 university students. The analysis of the data obtained using applied structural equation modelling of the partial least-squares technique, it was found that the most influential antecedents included collaborative capability and perceived enjoyment. Based on the results, we recommend that, owing to the turbulent and changing requirements of social distancing and distance learning, educational institutions and stakeholders invest in the improvement of implied social-media collaboration and learning platforms.
Developing Interactive Digital Mathematics Book with Multi Representation Approach for Deaf Students
Authors: Suarsana I Made
Published: July 2021

Mathematics learning objectives for deaf students are not different from normal students, but their learning approach is not the same. Learning materials for deaf students should be made simple and equipped with multi representation. With the development of ICT, multi representation has become easy and inexpensive. Therefore, the purpose of this study was to develop an interactive digital book with a multi representation approach for deaf students. This study was carried out using 3 initial stages of 4-D research and development design (define, design, develop, and disseminate). Media feasibility is determined based on the results of expert validation, practicality test, and a passing grade. The average score of book validation by the material expert was 2.92 (97.3%), learning design expert was 2.97 (99%), media expert was 2.99 (99.7%), and language expert was 2.78 (92.7%), so it can be said that the book met the validity criteria. The average score of the practicality test by students was 4.24 (84.8%) and teachers were 4.35 (87%), so it can be said that the book met the practicality criteria. The average passing grade was 83.34%, so the book met the effectiveness criteria. By meeting validity, practicality, and effectiveness criteria, it can be concluded that the digital book met the feasibility criteria as mathematical learning materials for VII-grade deaf students.
Online Learning Using Block-based Programming to Foster Computational Thinking Abilities during the COVID-19 Pandemic
Authors: Amnouychokanant Virawan , Boonlue Surapon , Chuathong Saranya , Thamwipat Kuntida
Published: July 2021

The COVID 19 pandemic has affected global education. In Thailand, all educational institutions temporarily closed to prevent the spread of COVID-19. However, teaching and learning still need to be continued. It is necessary to switch the learning activities to online learning. In this study, we designed online learning activities for developing computational thinking (CT) of students and carried out an experiment with 90 participants (first-year students enrolled in a Bachelor of Education Program in educational technology and communications at King Mongkut's University of Technology Thonburi). At the beginning of the experiment, all participants were asked to take a CT test to measure their CT. The test is consistent with other CT tests under validation. During the sessions, all participants were taught by Thunkable. After the experiment, they took the CT test again. The results show that by improving CT through block-based programming projects, students’ performance improved significantly. In conclusion, block-based programming and working in pairs are combinations that can potentially help students to perform better, in turn affecting their performance in projects.
An Investigation of Learners’ Perception of an Online Intercultural Communicative Competence (ICC) Training Model
Authors: Shen Lemin
Published: July 2021

Developing students’ Intercultural communicative competence (ICC) has been viewed as the English as a foreign language teachers’ responsibility in the globalized world, especially after the birth of COVID-19 pandemic. Amidst the flourishing development of ICC cultivation studies, a noted absence is on the study of how to actualize ICC in the online teaching based English language teaching. This study, by presenting a pedagogical case, explores the application of the online ICC training model, and focuses on how the online teaching can be established at the four teaching stages, namely, attitude development, knowledge construction, skills practice, and reflection. Attitude development is a pre-class activity to motivate students’ learning curiosity. In the stage of knowledge construction, various kinds of Massive Open Online Courses (MOOCs) are selected as teaching resources for students to learn the key concepts and theories for the course. Skills practice requires students to make full use of WeChat or Bulletin Board System (BBS) to have online intercultural encounter, in this process students practice both their linguistic and intercultural communicative competence. The last stage provides chances for both students and teacher to rethink about their learning and teaching and move to the new circle of teaching stages. An eight-weeks’ action research with a class of second-grade English Majors in a Chinese university has been conducted. Questionnaire and interview are the main methods for data collection, combined with teacher and students’ reflective journals. The results of both quantitative and qualitative evaluation show that adopting online-teaching may serve as an effective way to develop students’ ICC during epidemic and in the future.
Applying the MCMSI for Online Educational Systems Using the Two-Factor Authentication
Authors: Ahmed Shaymaa Taha , Kadhim Qusay Kanaan , Alsultani Hamid Sadeq Mahdi , Abd almahdy Widyan Salman
Published: July 2021

 

This paper researches the evolution process of what is called two-factor authentication technique and its adaptation related to the educational system through the Internet. This technique is a measure of security employed, particularly in scopes which have valuable information like bank services. It witnesses developments so far as today, in parallel with the developments occurring in technology. Since this technique consists of two phases, the security is going to be developed. Today, bank services, devices using the Internet of things, tickets of public transportation and lots of other scopes are utilized. In the information field, the researchers and scientists always update the techniques of two-factor authentication to resist the attacks related to security. Last years, the researchers studied novel technologies like behavioral biometric or biometrics. The training through the Internet may become much more useful than going to someplace to study a specific course. Mostly, the participants in the trainings through the Internet get many certificates for success, participation, etc. The principal problem is how to certify the truthiness of the participant who desires to get the certification. In this paper, and by researching the techniques of two-factor authentication, the Mimic Control Method with Sound Intensity (MCMSI) is proposed to be used for the training through the Internet.
Bending Strength of Fiber Metal Laminate Based on Abaca Fiber Reinforced Polyester and Aluminum Alloy Metal Sheet
Authors: Iqbal Mohd , Satrianda M.S. , Firsa Teuku , Azan Said Amir , Abhang Laxman B.
Published: July 2021

The Fiber Metal Laminate (FML) discussed here was made from Fiber Reinforced Polymer (FRP) composite, laminated by aluminum alloy sheet. The FRP composite panel was made from abaca fiber and polyester resin matrix. The objective was to study the bending strength of the FML with different fiber content. Five panels of abaca FRP were prepared using hand-lay-up methods. The weight content of the fiber in the panels were 0%, 3.56%, 5.18%, 8.94% and 12.22% respectively. The aluminum alloy sheet was laminated to the composite panel using epoxy super glue. The density of the FMLs were measured to confirm the fiber content in the panels. The bending specimen were prepared based on ASTM D-7264. The bending strength that represented by flexural stress of the FML panels were 53.15, 56.44, 46.80, 63.53 61.48 and 49.57 MPa, respectively. The result of the experiment showed that the content of abaca fiber significantly affects the bending strength of the FML. The highest bending strength (63.53 MPa) was produced by the FML with 5.18% fiber content. The result of the study showed that the bending strength of abaca FML was 19.5% higher than commercial FML (53.15 MPa). It was an indication that abaca fiber could be used to substitute the glass fiber in commercial FML.
Immobilization of Silver Nanoparticles on Chitosan-Coated Silica-Gel-Beads and the Antibacterial Activity
Authors: Hidayat Muhammad Iqbal , Adlim Muhammad , Maulana Ilham , Zulfajri Muhammad
Published: July 2021

Silver nanoparticles (Ag0) have attracted the most attention due to their broad antimicrobial application and outstanding activity. The silver nanoparticles are usually in colloidal form, then immobilization the colloid onto solid support is still interesting to explore. In this work, a new method for silver colloidal nanoparticle immobilization on silica gel beads (SiG), which was then symbolized as Ag0-[chi-SiG] was conducted and characterized successfully. The finding proved that SiG must be coated with three chitosan film layers to give stable support for silver nanoparticles. This coating method caused the chitosan completely covered SiG, and the chitosan film provides coordination bonding for silver ions. The most appropriate solvent for silver ion impregnation on the surface of chi-SiG is methanol compared to other solvents. Tungsten lamp as the photo-irradiation, which is low cost and environmentally friendly has been proven effective for silver ion reduction, as shown by silver metal colloid UV-Vis surface plasmon resonance at 400-700 nm. Ag0-[chi-SiG] showed the antibacterial properties of inhibiting the growth Staphylococcus aureus and Escherichia coli; then it provides the potential application for antibacterial filter material. According to the weight comparison between antibacterial standard and Ag content, then Ag0-[chi-SiG] has two and five times higher of exhibiting zone for each bacteria.
Permanent Deformation and Fatigue of Semi Flexible Pavement Incorporating Waste Tire Rubber and Natural Zeolite
Authors: Hamzani Hamzani , Munirwansyah Munirwansyah , Hasan Muttaqin , Sugiarto Sugiarto , Zulfhazli Zulfhazli
Published: July 2021

Due to repeated loads, the pavement structures will experience repeated stresses and strains resulting in permanent deformation even though the working loads are still smaller than the design load. The permanent deformation will lead to cracking and fatigue failure with the life of the pavement. This phenomenon can be reduced by increasing the stiffness, flexibility, durability, stability and water absorption of the pavement. Material modification including the utilization of waste tire rubber (WTR) and natural zeolite is one of the efforts to increase those parameters in semi flexible pavement (SFP). The aim of this study therefore, to assess the deformation and fatigue failure of SFP incorporating WTR and natural zeolite under cyclic loading. The WTR was used as an additive at the level of 3% of asphalt content while natural zeolite was used as cement replacement at the 0, 5, 15 and 25% replacement levels. Permanent deformation tests were conducted by applying wheel tracking loads with the pressure of 6.4 ± 0.15 kg/cm2 on the surface of the specimens with 1260 cycles per hour while fatigue tests were conducted on the simple supported beams with the span length of 30 cm by applying forth point loading at the frequency of 10 Hz. The test results showed that the best performance in sustaining cyclic loading was achieved at the zeolite content of 5%.
Failure Analysis of a Fractured Leaf Spring as the Suspension System Applied on the Dump Truck
Authors: Husaini Husaini , Liza Rizqi Handayani , Ali Nurdin , Muammar Sadrawi
Published: July 2021

A spring is a component which is designed to have relatively low stiffness compared to normal rigid rods, thereby making it possible to accept certain forces that are charged. A leaf spring is an important suspension component for heavy vehicles, as a failure of the leaf spring can cause severe if not fatal accidents. This study aims to investigate the factors that cause leaf spring failure in the form of a 125 PS dump truck vehicle suspension system. The method employed incorporated experimental and finite element analyses. The experimental work included visual observations, observation using a scanning electron microscope (SEM), hardness testing, and microstructure testing. Leaf spring modelling was conducted using Autodesk Inventor 2017 software, and the finite element analysis (FEA) was performed using Siemens ™ FEMAP V12.0.1 application software to calculate the maximum stress and strain that occurred near the crack tip of the leaf spring. The results from the analysis indicated that the cause of the fracture that occurred in leaf spring No. 3 was due to a defect discovered on the surface of the leaf spring. Based on the observations of the fracture surface, it is revealed that the cause of failure was due to the cyclic load experienced by the components during operation which caused crack propagation beginning from micro-cracks until reaching a significant dimension to cause a final fracture. In addition, the overload imposed on the leaf springs also caused maximum stress on the springs to increase, thus accelerating the failure of the leaf springs. Further results also showed that the value of the stress intensity factor, KI = 29.15 MPa.m1/2 was greater than the value of fracture toughness, KIC = 23 MPa.m1/2 of the spring material.
Flexural Resistance Analysis on Hot Asphalt Mixtures with Wire Mesh Placement Modeling as Reinforcement
Authors: Ismy Romaynoor , Husaini Husaini , Sofyan M. Saleh , Isya M.
Published: July 2021

Flexural resistance is the ability of a specimen to withstand force in two pedestals with vertical axis until it is broken. Flexible pavement is a type of pavement which is very dependent with pavement course underneath. The dependency of flexible pavement in both base course and subgrade makes this pavement difficult to apply in unstable soil. Using wire mesh course as reinforcement is considerably able to raise the flexural resistance. This study is aimed to analyze flexural resistance value in hot mix by using wire mesh course as reinforcement. The study is conducted by applying experimental method with designing four types of wire mesh laying models in hot mix using three points flexural test equipment. Based on the study result, it is found that hot mix with wire mesh laying 30 mm from specimen surface is the best model type with 291,85 KN flexural resistance value with 8 mm of deflection depth. In this laying, it can be concluded that wire mesh course can raise up the flexural resistance up to 35,41% compared to the hot mix without wire mesh course.
Research of Safe Technology of Impregnation of Heated Reinforcing Materials with Binder
Authors: Kondratiev Andrii , Haidachuk Oleksandr , Tsaritsynskyi Anton
Published: July 2021

Prepreg manufacturing process is one of the most important preparatory technological processes, quality of which has the decisive influence on the physical, mechanical, processing and operational characteristics of the finished composite product. However, manufacturing of prepregs is associated with a number of harmful factors, negatively affecting the participants in the technological process and the environment. Consequently, significant additional costs are required in order to ensure specified maximum permissible levels and concentrations of the harmful products released by the components of polymeric composite materials in the product manufacturing process. The paper deals with the study of peculiarities and efficiency of impregnation of the heated reinforcing material using solvent-free binder. The method for predicting the optimal process parameters of binder solutions for impregnation of prepregs, taking into account the safety of production activity, has been developed. The problem of thermal conductivity from the heated reinforcing material to the binder, which allowed establishing the law of temperature distribution over the depth of the impregnating bath, depending on the duration of continuous impregnation, has been solved. It is found that the binder, with the duration of impregnation even within one working shift, heats up to the temperatures excluding the formation of centers of exothermic polymerization reaction in it. It indicates the availability of the effective regimes of impregnation using the method under study. The paper proposes the practical ways of improvement of the investigated method of impregnation by varying the wavelength, programmed change of the temperature of the reinforcing material at the entry to the bath, and setting of the optimal coordinates of the binder supply as it is drawn in the process of continuous impregnation of the reinforcing material.
The Deformable and Strength Characteristics of Nanocomposites Improving
Authors: Sierikova Olena , Koloskov Volodymyr , Degtyarev Kirill , Strelnikova Olena
Published: July 2021

Mechanical properties of composites and nanocomposites have been considered in the assumptions of linear elasticity. To describe the nanoscale contact between matrices and inclusions on the interface surface, the conditions of ideal contact and non-classical Gurtin-Murdoch conditions have been implemented. The influence of shapes and relative sizes of inhomogeneities and matrices of representative volumes on the effective elasticity modulus of nanocomposites has been treated. Matrices in the form of cube and cylinder of finite sizes and inhomogeneity in the form of spheres and fibers have been considered. Finite element-based calculation models have been generalized to composites with distributed nanoinclusions of random and ordered orientation. The resulting models create the informative base for nanocomposites synthesis technologies with improved deformable and strength characteristics.
Thermodynamics of Solid-Phase Exchange Reactions Limiting the Subsolidus Structure of the System MgO-Al2O3-FeO-TiO2
Authors: Borisenko Oksana , Logvinkov Sergey , Shabanova Galina , Myrgorod Oksana
Published: July 2021

The basis of modern materials science is multicomponent systems, on their basis it is possible to create various combinations of phases in structural materials with a set of specified properties. The investigated system MgO-Al2O3-FeO-TiO2 is promising for the production of periclase-spinel refractories used as lining of rotary kilns during cement clinker firing, which are highly resistant to chemical corrosion when exposed to a gas environment and cement clinker components; thermomechanical stresses. However, in the reference literature and scientific articles, no information was found on the structure of the four-component diagram of the state of the MgO-Al2O3-FeO-TiO2 system, partial elements of its structure are given only in the composition of multicomponent systems [1-3]. Thus, research to the study of the subsolidus structure of the MgO-Al2O3-FeO-TiO2 system, which is the physicochemical basis for the development of compositions of periclase-spinel refractories, is urgent.
Synthesis of ActivaTED Carbon from Plant Raw Materials by a Self-Activation Modified Method
Authors: Malovanyy Myroslav , Bordun Ihor , Ableeva Iryna , Krusir Galina , Sahdeeva Olha
Published: July 2021

In order to increase environmental safety and reduce the cost of production, a modified method of self-activation for the synthesis of activated carbon from plant wastes - cherry stones and wheat straw. A 5% solution of orthophosphate acid was used as an additional activator. Synthesis of activated carbon at temperatures of 600 °C, 700 °C and 800 °C was performed. It was found that coal from cherry stones has a production of 1.3-1.6 times higher than the production of activated carbon from wheat straw. The obtained coal was studied by electron microscopy and the method of isothermal adsorption / desorption of nitrogen. It is shown that all synthesized coal has a well-developed porous structure, which is determined mainly by micropores. An increase in the synthesis temperature leads to an increase in the specific surface area, the volume of micro-and mesopores and a decrease in the average pore radius. The reduction of the average pore radius for activated carbon from cherry stones occurs at lower temperatures compared to coal from wheat straw.
Utilization of Galvanic Enterprises Sewage
Authors: Chernyshova Liudmyla , Movchan Sergei , Epoyan Stepan
Published: July 2021

A method for obtaining refractories based on inorganic glue as a reaction product of sludge from electroplating shops with sulfuric and phosphoric acids, which was tested by the authors in laboratory and industrial conditions in the article, is presents. After drying at a certain temperature, the manufactured samples are tested for strength. Properties of refractories based on inorganic glue are characterized by increased water resistance due to treatment with a cement solution. Based on experimental studies, the authors are presents the results of testing samples for strength with dry and wet aluminum-oxide abrasive. According to the test results, it was found that the specific density of the obtained samples increased from 0,57 to 0,9 g/cm3 with increasing glue content, while the strength decreased. Compositions with a low glue content had for the most strength.
Ash-Slag Waste of the Coal-Fired Thermal Power Plant as a Resource for the Construction Industry
Authors: Kolokhov Viktor , Moroz Lina , Romin Andrey , Kovregin Volodymyr
Published: July 2021

The article presents a study of the physical and technical properties of ash and slag waste Coal Power Plant. The main problem when using ash-slag mixtures is the variability of the particle size distribution of the material. Determining the characteristics of slag stored in the dumps of thermal power plants will help to choose the separation methods of this material, to address the disposal and accumulation of industrial waste, to expand the scope of their application. The obtained research results of physical and technical properties of waste of the Coal TPP testify to wide potential in the further use in many branches of the industry. Possible applications include fillers for concrete, materials for sandblasting (abrasive material), raw materials for the metallurgical industry, additives for the manufacture of binders, etc.
Technology Placement of Drilling Waste Storage with the Use of Soil Cement Screens
Authors: Mykhailovska Olena V. , Zotsenko Mykola L.
Published: July 2021

The authors of the article analyze the known technological solutions for the disposal of waste from drilling wells. The authors propose a technological solution for the arrangement of drilling waste storage from soil-cement elements with the installation of soil-cement coating. Filling the storage facility with waste is proposed to be carried out with layers of drilling mud, soil, ash. Used a layer of fly ash to reduce humidity, if it differs from the optimum. The thickness of the layers was chosen based on ensuring optimal humidity. The authors propose to add ash from the Mykolayiv thermal power plant in the amount of 5 wt.% By weight of cement when installing the walls and covering the sludge storage from soil cement. It is established that with increasing the shelf life of samples in water up to 180 days, the average compressive strength of soil cement samples increases. If we compare without additives and with the addition of the appropriate percentage of removal ash, the value of strength increases by 12-15%.
Research of Technical and Economic Properties of Material of Porous Fuel Briquettes from the Solid Combustible Waste Impregnated with Liquid Combustible Waste
Authors: Kondratenko Olexandr , Koloskov Volodymyr , Kovalenko Svitlana , Derkach Yuriy
Published: July 2021

The study evaluates the impact of the enterprise for production of industrial electronics on the components of the environment, in particular the lithosphere of Kharkiv by solid and liquid combustible waste. The environmental protection technology by the method of waste disposal of solid and liquid combustible substances by improving the technology of production and storage of fuel briquettes with improved ingredient composition, utilization of thermal energy from their combustion in a solid fuel boiler and purification of its exhaust gases been developed. A new ingredient composition of the fuel briquettes has been developed and the technology of their storage has been improved, and a feasibility study has been provided. Rational values of mass-size, technical and economic properties of the fuel briquettes taking into account properties of materials of their solid and liquid components has been defined.
Fine-Grained Concrete for Repair and Restoration of Building Structures
Authors: Shyshkina Alexandra , Shyshkin Alexander
Published: July 2021

It is determined that the active components of modern concrete are active mineral fillers, such as microsilica, meta-kaolin, ash-bearing or compositions from them, as well as superplasticizers. The optimal combination of these additive modifiers allows you to control the rheological properties of concrete mixtures and to modify the structure of the cement stone in such a way as to provide concrete properties that provide high operational reliability of structures. However, they have certain disadvantages that hamper their widespread use. The purpose of the research is to determine the effect of reaction powders applied simultaneously with colloidal surfactant, on the strength of powdered concrete and the rate of its formation.
Experiment Planning for Prospective Use of Barium-Containing Alumina Cement for Refractory Concrete Making
Authors: Myrgorod Oksana , Shabanova Galina , Ruban Artem , Shvedun Viktoriia
Published: July 2021

The prospect of further use of refractory concrete based on barium-containing alumina cement was justified, with the help of a simplex-lattice method of the experiment planning, the granulometric composition of concrete was selected and its physical, mechanical and technical properties were determined, which exceed the properties of the used analogues.
Development of a Bitumen-Polymer Composition, Resistant to Atmospheric Influences, Based on Petroleum Bitumen and their Properties Study
Authors: Cherkashina Anna , Lavrova Inna , Lebedev Vladimir
Published: July 2021

In the work the bituminous-polymeric composition stable against action of external factors is designed taking into account literature-patent researches and industrial needs. The basic physical-mechanical and thermophysical properties of the designed bituminous-polymeric composition are investigated, and also change of water absorption, shrinkage with time and flammability is studying. The technology of manufacturing bitumen-polymer composition in production is described. The designed bituminous-polymeric composition on some indicators, in particular on heat resistance and flexibility is better than existing analogs that allows its introduction.
Analysis of the Effect of Mechanical Oscillations Generated during Welding on the Structure of Ductile Constituent of Products Made of Steel 10G2FB
Authors: Tsymbal Bohdan , Ziborov Kyrylo , Rott Nataliia , Fedoryachenko Sergey
Published: July 2021

Under open construction, the requirements to welding processes are very critical since reliable connections requires complex, costly and sometimes impossible processes that involve fixed machines and devices. Therefore, in such cases it is important to carry out welding work using mechanical vibrations. Elastic oscillations in the weld metal result in uniform crystallization of the melt and formation of a dispersed structure. This also results in enhancement of diffusion processes while promoting degassing process in weld metal.
Investigation of the Influence of the Physical Properties of Landfill Soils on the Stability of Slopes in the Context of Solving Civil Security Problems
Authors: Rashkevich Nina , Shevchenko Roman , Khmyrov Ihor , Soshinskiy Alexandr
Published: July 2021

The paper presents the results of laboratory studies of the influence of the physical properties of landfill soils on the stability of slopes, namely, the determination of mechanical properties – the angle of internal friction, specific adhesion, and the shear angle of experimental landslide blocks under conditions of different humidity, density and temperature; determination of physical properties – humidity, temperature and density on the fact of shear of the experimental blocks, taking into account the gradual increase in humidity. The results of laboratory tests are processed using the classical statistical method. This made it possible to confirm the reliability of the mathematical model, which includes the solution of individual tasks for assessing the physical properties of landfill soils, and the corresponding methodology developed on its basis for preventing emergencies associated with shear of landfill soils at potentially hazardous burial sites for solid domestic waste.
Regarding the Formation of Wood Material Fire Protection and the Mechanism of its Action
Authors: Likhnyovskyi Ruslan , Tsapko Yuriy , Kovalenko Vitalii , Ivashyna Natalia
Published: July 2021

The theoretical aspects of wood material fire protection formation by esterification reactions are considered in the article. The reactivity of polysaccharides and polymers from which wood material is composed has been confirmed by the FTIR method. The IR spectra of the original standard samples of lignin and microcrystalline cellulose were taken and after treatment with solutions with concentrations of 10% of the mass. orthophosphoric (Н3РО4) and oxyethylene diphosphonic (CH3C(OH)(H2PO3)2) acids. Electron scanning microscopy revealed the crystallization of inorganic salts on the wood material surface, which play the role of flame retardants, as well as a film of organopolymer (polyhexamethylene guanidine polyphosphate), which forms a foamed layer of coke when heated. Thermogravimetric analysis (TGA) and gas chromatography (GC) methods show the mechanism of action of fire protection provided to wood material. The formation of foamed coke is visually shown and the results on the effectiveness of fire protection on the example of wood material treatment with a mixture of diammonium phosphate and ammonium sulfate are obtained.
Research of Pyrophoric Compounds in Order to Reduce their Hazard
Authors: Korovnikova Natalia , Oliinik Volodymyr , Dubyna Oleksandr
Published: July 2021

The constantly growing content of sulfur compounds and the increased water content in the extracted oil enhances the aggressiveness of the environments in which the technological equipment of oil depots and pipelines operates, resulting in a higher number of emergencies in the equipment of oil refineries. Thus, one of the most urgent problems is the corrosion damage to oil storage equipment and the associated consequences of flammable pyrophoric compounds formation. Finely dispersed flammable sulfides with organic impurities are formed in the equipment of the diesel fuel distillate hydrotreating unit thus accumulating on the bottoms and walls of tanks and reservoirs. This negatively affects the material balance of the hydrotreating process and increases fire and explosion hazards of the whole hydrotreating process at the refinery. For the first time, the elemental composition of pyrophoric deposits formed while storing petroleum products in the LCh-24-2000 unit was experimentally investigated. These sulfides are a flammable component of the equipment in the hydrotreating process, where diesel fuel distillates rotate. The obtained results of the test study as for the prevention of pyrophores spontaneous combustion indicate that hydrogen peroxide solutions have the highest efficiency. The practical significance of the results is in the use of experimental studies on the spontaneous combustion of pyrophoric samples in the development of the equipment cleaning terms during the hydrotreating process from pyrophoric deposits at the refinery. The experimental results of testing the ability of chemicals to prevent pyrophores spontaneous combustion can be used to reduce the risk of spontaneous combustion of pyrophoric compounds.
Features of Evaluation of Fire Resistance of Reinforced Concrete Ribbed Slab under Combined Effect "Explosion-Fire"
Authors: Vasilchenko Alexey , Danilin Olexandr , Lutsenko Tatiana , Ruban Artem
Published: July 2021

Calculations using the example of a reinforced concrete ribbed slab have shown that if, as a result of an explosion, due to cracks that have arisen, a part of the compressed concrete layer is turned off, then even while maintaining the bearing capacity of the slab, its fire resistance is significantly reduced. It is shown that on the basis of the proposed methodology for studying the behavior of bending elements under the combined effect of "explosion-fire", it is possible to take into account the necessary parameters of reinforced concrete ribbed slabs in the design and operation of structures of hazardous operations industrial facilities. Also, the proposed technique makes it possible to predict a relatively safe amount of explosive in the technological process of an hazardous operations industrial facility, without leading to catastrophic consequences.
Enhancing the Fire Resistance of Concrete Structures by Applying Fire-Retardant Temperature-Resistant Metal Coatings
Authors: Korytchenko Kostyantyn , Samoilenko Dmytro , Dubinin Dmytro , Kucherskyi Vladyslav , Krivoruchko Yevhen
Published: July 2021

The issues relating to an increase in the fire-resistance of concrete structures by applying (heat dissipating) fire-retardant and fire resistant metal coatings onto them was considered. The experimental investigation data obtained for the heating rate of the brick coated with the aluminum layer as heat dissipating coating were given. The investigation was carried out through the comparison of a time-dependent change in the temperature of the material coated with the aluminum layer with the temperature of uncoated material. The obtained research results proved a decrease in the heating rate of the coated brick exposed to the thermal irradiation.
Research of Fire Resistance of Elements of Steel Frames of Industrial Buildings
Authors: Hvozd Viktor , Tishchenko Eugene , Berezovskyi Andriy , Sidnei Stanislav
Published: July 2021

The article considers and analyses the methods by which it is possible to carry out research to determine the fire resistance of elements of steel frames of industrial buildings. It is determined that it is expedient to use the means of computational fluid dynamics, which has no limitations due to the high cost, complexity, environmental friendliness and complexity in comparison with real experiments. In order to conduct the most reliable computational experiments, mathematical models of temperature and mechanical reaction to the thermal effect of fire were created, taking into account the equations of thermal conductivity, systems of differential equations of stress-strain state of solids in their numerical implementation based on the finite element method. The solution of mathematical models was carried out using computational fluid dynamics, which describes the process of heat and mass transfer in test fire furnaces during the determination of fire resistance of steel structures. According to the results of computational experiments it is shown that the limiting state of loss of bearing capacity of vertical and horizontal structures occurs due to the formation of a zone of plastic deformations taking into account the associative theory of plasticity. According to the results of computational experiments, the dependence of the limit of fire resistance on the level of applied load to structures, which is close to linear, was revealed. Based on the obtained dependences and the corresponding graphs, a technique is developed based on the use of maximum deformations of the elements with the corresponding fixation of the limit state on the loss of fire resistance in terms of bearing capacity by bending this curve.
Electrochemical Synthesis of Crystalline Niobium Oxide
Authors: Ryshchenko Igor , Lyashok Larisa , Vasilchenko Alexey , Ruban Artem , Skatkov Leonid
Published: July 2021

Features of creation of porous nanostructured oxides of transition materials on an example of niobium are considered. It has been experimentally shown that variation in anodizing modes makes it possible to obtain non-porous and porous amorphous anodic oxide films (AOF) and films of the crystalline type. It is determined that the process of AOF formation on niobium, as well as its structure and properties depend on such parameters as the type of electrolyte, anodizing voltage, activator concentration, the duration of the process. It is confirmed that the presence of an activator in the electrolyte is a necessary and decisive factor in the process of forming a nanostructured anode oxide layer. To obtain a nanostructured surface of niobium oxide, a necessary condition is the introduction of fluoride into the electrolyte, but also an important task is to determine the type of compound with which F– ions are introduced into the electrolyte. It has been experimentally determined that the optimal solution for the rapid growth of porous crystalline oxide is a solution consisting of a background electrolyte in the form of 1M H2SO4 with the addition of a fluoride ion activator in the form of 0.5M NaF. The increase in the activator accelerates the formation of the crystal structure on the surface of niobium. It is shown that higher voltage and longer anodizing time leads to an increase in the size of microcones and their number on the surface of niobium. Optimal for the formation of porous crystalline oxide is a voltage of 60 V in the electrolyte 1M H2SO4 + 0.5M NaF for 2 hours.
Research of the Influence of Silicate Fillers on Water Absorption and Microstructure of Styrene-Acrylic Dispersion Coatings
Authors: Saienko Natalia Vyacheslavovna , Bikov Roman , Skripinets Anna , Demidov Dmitriy Vasilevich
Published: July 2021

Permeability is important to ensure the protective properties of coatings based on styrene-acrylic dispersions. This indicator characterizes the complex of insulating properties of coatings, their ability to prevent the penetration of liquids, vapors and gases from the environment to the surface to be protected. It was studied the effect of aluminosilicate microspheres, which are characterized by the hydrophilic nature of the surface and highly dispersed silicate filler aerosil with a hydrophobised surface on the water absorption of styrene-acrylic coatings. Decreased of water absorption of styrene-acrylic coatings filled with aluminosilicate microspheres with the introduction of hydrophobised aerosil is linked to the fact that the fine aerosil with a high specific surface area provides the formation of a more densely packed structure. Thus, partially filling the interspherical space, which is formed by particles of microspheres with a diameter of 10-100 μm and reduces the surface defect of the styrene-acrylic coating. Localization on the surface of defective structures of particles of hydrophobised aerosil leads to a decrease in wetting of defective structures with water. Resulting deteriorating wetting the surface of the styrene-acrylic coating. Micrographs were taken to assess the nature of the distribution of aerosil on the surface of the styrene-acrylic coating. The analysis of the obtained micrographs confirms that the introduction of microspheres form large agglomerates, between which there are vacancies, which will negatively affect the technological and operational properties of the developed coatings. At the same time, the introduction of aerosil allows to obtain a more orderly structure, which allows to obtain a coating with lower internal stresses, increased aggregate stability and, as a consequence, with improved technological and operational properties.
Planning an Experiment for Low-Cycle Fatigue under Conditions Deep Cooling
Authors: Medved Ivan , Kovregin Volodymyr , Myrgorod Oksana , Lysenko Andrii
Published: July 2021

In the elements of structures with a limited resource during operation, significant cyclic stresses can occur, reaching and exceeding the yield strength; the results of an experimental study of the effect of the magnitude of preliminary plastic deformations on the strength and durability of structural alloys under low-cycle loading can be of undoubted interest for practice. The use of experimental planning methods in the study of the influence of the maximum cycle stresses and the magnitude of the preliminary permanent deformation on the low-cycle fatigue of 03Kh13AG19 chromium-manganese steel at T = 4.2 K under pulsating tension showed that these methods can be successfully used.
A novel mouse model simulating transurethral laser vaporization prostatectomy
Authors: Zhang Heng , Tian Ye , Yang Bing , An Ling-Yue , Xia Shu-Jie , Luo Guang-Heng
Published: July 2021

Benign prostatic hyperplasia (BPH) is a common disease in elderly men, and transurethral laser prostatectomy (TULP) has been widely used in the clinic to remove bladder outlet obstruction caused by BPH. Previous animal models for wound repair after prostatectomy have many limitations, and there have been no previous reports of a mouse model of TULP. Therefore, this study aimed to establish a novel mouse model of TULP. Twelve healthy adult Kunming (KM) mice received transurethral laser vaporization prostatectomy with a 200-μm thulium laser. The mice were sacrificed, and wound specimens from the prostatic urethra and bladder neck were harvested at 1 day, 3 days, 5 days, and 7 days after surgery. Hematoxylin-eosin (HE) and immunohistochemistry were applied to confirm the establishment of the mouse TULP model. One day after the surgery, urothelium expressing uroplakin (UPK) was absent in the urethral wound site, and a large number of necrotic tissues were found in the wound site. There was no UPK-positive urothelium in the wound 3 days after surgery. At 5 days after surgery, monolayer urothelium expressing UPK was found in the wound site, indicating that the re-epithelization of the wound had been completed. On the 7th day after surgery, there were multiple layers of urothelium with UPK expression, indicating that the repair was completed. It is feasible to establish a mouse TULP model by using a microcystoscope system and a 200-μm thulium laser.