#### EUREKA: Physics and Engineering

Journal Information

ISSN / EISSN :
2461-4254 / 2461-4262

Current Publisher: OU Scientific Route (10.21303)

Total articles ≅ 279

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#### Latest articles in this journal

EUREKA: Physics and Engineering pp 42-51; doi:10.21303/2461-4262.2021.001693

**Abstract:**

Cracks that occur in rigid pavements include longitudinal cracks, transverse cracks, and corner cracks. The relatively large crack width not only spoils the aesthetics of the concrete structural elements but can also lead to structural failure. This study aims to determine the crack width of a rigid pavement concrete slab located above the subgrade which is considered a beam on an elastic foundation, so that a minimum rigid pavement concrete slab thickness can be recommended. The specimen will be observed at various thicknesses to obtain the optimum thickness. The load used is a centralized monotonous load, which represents the load of the truck vehicle. The research limitation is using a test object in the form of a concrete plate measuring 2000x600 mm which is placed on the ground with CBR=6 %. The quality of reinforced concrete slabs is fc'=40 MPa and fy=440.31 MPa. The thickness of the concrete slab varies between 100 mm, 150 mm, and 200 mm. The slab placed on the ground is then given a central loading in the form of a centralized monotonic load. The loading range starts from a load of 2–180 kN with a load interval of 2 kN. The experimental results show that the rigid pavement slab has a bending failure so that the crack pattern that occurs begins with the first crack on the underside of the slab. The crack pattern in terms of slab thickness variation has a similar pattern. The initial crack width on the slab is 0.04 mm. The thicker the slab smaller the crack width at the same load. Based on the maximum allowable crack width=0.3 mm. For loads between (80–100) kN (Road Class I, II, and III), a minimum thickness of rigid pavement slabs (70–80) mm is recommended. For loads between (130–140) kN, the minimum thickness of the rigid pavement slab (105–115) mm is recommended

EUREKA: Physics and Engineering pp 99-107; doi:10.21303/2461-4262.2021.001694

**Abstract:**

In this work, the optimal combinations of Al – Si in cast iron for cast parts for machine-building purposes were determined with the aim of subsequent selection of rational modes of modification and alloying, and the possibility of their implementation under industrial smelting conditions was checked. The graphical dependence Si=f (Al) is obtained, which is a set of optimal combinations of the content of Al and Si in cast iron, providing the maximum ultimate tensile strength UTS≈245 ... 334 MPa. The technological audit of the results of serial industrial smelting included the analysis of actual indicators, the calculation of sample distribution functions (mathematical expectation and dispersion) of the Al and Si content in the alloy, as well as the UTS value. The correspondence of the indicators of the content of Al and Si and the value of σ to the optimal values was assessed by testing the statistical hypotheses: H: M(Al)=Alopt, M(Si)=Siopt, M(σв)=σвopt.On the basis of the obtained results of the assessment of statistical characteristics and verification of hypotheses, it was established that at the chosen significance level α=0.05, the technological process of smelting satisfies the requirements of optimality in terms of the Si content, but in terms of the Al content, the technological process does not meet the requirements of optimality. The proposed procedure for choosing the optimal combinations of Al and Si makes it possible to choose the amount of correcting additives depending on the actual indicators of the chemical composition during the smelting process. To do this, it is necessary to assess the closeness of the actual composition to the optimal curve Si=f(Al) and choose the one that most satisfies the criteria of rationality. The latter can be the cost of ferroalloys, through which Al and Si are introduced

EUREKA: Physics and Engineering pp 87-98; doi:10.21303/2461-4262.2021.001310

**Abstract:**

Pig farming is a sector of animal husbandry, the development of which is great attention. The pork market occupies a large share in the trade in animal products. In the conditions of they do competition more efforts are made to improve the quality and reduce the cost of production. To achieve this goal, work is being done in several areas – development and expansion of the gene pool, improvement of the living environment in the premises for animal husbandry, reduction of energy costs. Along with the development of feeding technologies, it is necessary to create a suitable microclimate in the premises, in which the animals to realize their productive potential, which in turn is directly related to the use of heating and cooling systems. The design of these systems for both existing and new buildings is carried out according to generally accepted methodologies, which in turn require time for calculation and use of specialized software. The methodologies for determining the loads for heating and cooling of livestock buildings, in accordance with the current legislation in the Republic of Bulgaria, are compared with a new method proposed in this publication. The possibility to consider a livestock building from the point of view of the theory of heat exchange allows the use of the basic differential equations describing the dynamic interaction of the building with the environment. This description would be complete and complex to implement. Therefore, the method of dimensional analysis is used, which is based on generalized indicators, when fulfilling certain criteria of similarity. The aim of the new methodology is to shorten the design time and allow the rapid sizing of heating and cooling systems in livestock buildings. In developing the new methodology, the task was the proposed new approach to summarize the interaction of all physical parameters affecting the heat exchange between the building and the surrounding air, allowing to take into account changes in external (air temperature, wind speed, solar radiation intensity) and internal factors (heat given off by farm animals, lighting, process equipment and processes) affecting the heat exchange between the building and the ambient air

EUREKA: Physics and Engineering pp 52-65; doi:10.21303/2461-4262.2020.001414

**Abstract:**

In this study, the multi-objective optimization problem of turning process was successfully solved by a Taguchi combination method and MOORA techniques. In external turning process of EN 10503 steel, surface grinding process, the orthogonal Taguchi L9 matrix was selected to design the experimental matrix with four input parameters namely insert nose radius, cutting velocity, feed rate, and depth of cut. The parameters that were chosen as the evaluation criteria of the machining process were the surface roughness (Ra), the cutting force amplitudes in X, Y, Z directions, and the material removal rate (MRR). Using Taguchi method and MOORA technique, the optimized results of the cutting parameters were determined to obtain the minimum values of surface roughness and cutting force amplitudes in X, Y, Z directions, and maximum value of MRR. These optimal values of insert nose radius, cutting velocity, feed rate, and cutting depth were 1.2 mm, 76.82 m/min, 0.194 mm/rev, and 0.15 mm, respectively. Corresponding to these optimal values of the input parameters, the surface roughness, cutting force amplitudes in X, Y, Z directions, and material removal rate were 0.675 µm, 124.969 N, 40.545 N, 164.206 N, and 38.130 mm3/s, respectively. The proposed method in this study can be applied to improve the quality and effectiveness of turning processes by improving the surface quality, reducing the cutting force amplitudes, and increasing the material removal rate. Finally, the research direction was also proposed in this study

EUREKA: Physics and Engineering pp 108-123; doi:10.21303/2461-4262.2021.001691

**Abstract:**

The problem of transport management in a distributed logistics system "suppliers – consumers" is considered. Under the assumption of a random nature of transportation costs, an exact algorithm for solving this problem by a probabilistic criterion has been developed. This algorithm is implemented by an iterative procedure for sequential improvement of the transportation plan. The rate of convergence of a computational procedure to an exact solution depends significantly on the dimension of the problem and is unacceptably low in real problems. In this regard, an alternative method is proposed, based on reducing the original problem to solving a nontrivial problem of fractional-nonlinear programming. A method for solving this problem has been developed and substantiated. The corresponding computational algorithm reduces the fractional-nonlinear model to the quadratic one. The resulting problem is solved by known methods. Further, the original problem is supplemented by considering a situation that is important for practice, when in the conditions of a small sample of initial data there is no possibility of obtaining adequate analytical descriptions for the distribution densities of the random costs of transportation. In this case, the available volume of statistical material is sufficient only to estimate the first two moments of unknown distribution densities. For this marginal case, a minimax method for finding the transportation plan is proposed. The first step is to solve the problem of determining the worst distribution density with the given values of the first two moments. In the second step, the transportation plan is found, which is the best in this most unfavorable situation, when the distribution densities of the random cost of transportation are the worst. To find such densities, let’s use the modern mathematical apparatus of continuous linear programming

EUREKA: Physics and Engineering pp 32-41; doi:10.21303/2461-4262.2021.001686

**Abstract:**

To increase the efficiency of using railway transport, the possibility of using new designs of bogies, for example, Y25 under "wide gauge" wagons was considered. In order to substantiate the proposed solution, mathematical modeling of the dynamic loading of the hopper wagon Y25 bogies was carried out. A hopper wagon for the transportation of pellets and hot sinter model 20-9749 built by the State Enterprise "Ukrspetsvagon" (Ukraine) was chosen as a prototype. The simulation results showed that the use of Y25 bogies for hopper wagons allows to reduce the acceleration of its load-bearing structure, in comparison with the use of conventional 18100 bogies, by 36 %. Other performance indicators are also significantly improved. The use of Y25 bogies for hopper wagons with actual parameters allows to reduce the acceleration of its load-bearing structure, in comparison with the use of conventional 18100 bogies, by 28 %. The determination of the main indicators of the strength of the bearing structure of the hopper wagon Y25 bogie was carried out. The calculation was carried out in the SolidWorks Simulation software package (CosmosWorks), (France), which implements the finite element method. The calculations showed that the maximum equivalent stresses in the load-bearing structure of a hopper wagon with nominal parameters are 17 % lower than the stress acting in the load-bearing structure of a wagon on bogies 18–100 V of the load-bearing structure of a hopper wagon with actual parameters, the maximum equivalent stresses are 12 % lower per voltage in the load-bearing structure on bogies 18100. The conducted research will help to reduce the load on the load-bearing structures of hopper wagons in operation, improve the dynamics and strength indicators, as well as their service life

EUREKA: Physics and Engineering pp 137-142; doi:10.21303/2461-4262.2021.001687

**Abstract:**

In the article, on the basis of observational data the problems of the specific frequency of globular clusters are studied. Possible relationships between them and the absolute stellar magnitude of their host galaxy are considered, where the observational data published in the literature were presented. It should be noted that before us the relationship between the specific frequency and the absolute magnitude is shown as exponential functions. An empirical relationship between the specific frequency and the absolute value of the host galaxy were obtained and showed that the dependence of the specific frequency on the absolute magnitude is not linear, but has a quadratic function. It is also shown that the specific frequency determines the number of globular clusters in a given galaxy relative to our Galaxy. Also in the article, based on the results of studies of the specific frequency, some discussions are presented related to the origin and evolution of globular clusters. The results obtained show that the ratios of the specific frequency to the luminosity of the host galaxy are different. Variations in the specific frequency of elliptical galaxies are associated with variations in the mass-to-luminous flux ratio. This may be due to the fact that the number of globular clusters in spiral galaxies per unit of luminosity of the halo and not of the entire galaxy. Analysis of the observational data shows that the values of the specific frequency of spiral galaxies are 5–6 times less than that of giant elliptical ones. As a result of the results of studies of the specific frequency of the globular clusters, unsolved problems are listed and possible solutions are shown. It is noted that the problem posed will be solved even more accurately if it is considered by the types of galaxies

EUREKA: Physics and Engineering pp 66-77; doi:10.21303/2461-4262.2021.001722

**Abstract:**

High smoke emissions, nitrogen oxide and particulate matter typically produced by diesel engines. Diminishing the exhausted emissions without doing any significant changes in their mechanical configuration is a challenging subject. Thus, adding hydrogen to the traditional fuel would be the best practical choice to ameliorate diesel engines performance and reduce emissions. The air hydrogen mixer is an essential part of converting the diesel engine to work under dual fuel mode (hydrogen-diesel) without any engine modification. In this study, the Air-hydrogen mixer is developed to get a homogenous mixture for hydrogen with air and a stoichiometric air-fuel ratio according to the speed of the engine. The mixer depends on the balance between the force exerted on the head surface of the valve and the opposite forces (the spring and friction forces) and its relation to decrease and increase the fuel inlet. Computational fluid dynamics (CFD) analysis software was utilised to study the hydrogen and airflow behaviour inside the mixer, established by 3.2 L engine. The Air-hydrogen mixer is examined with different speeds of engine1000, 2000, 3000 and 4000 RPM. Results showed air-hydrogen mixture was homogenous in the mixer. Furthermore, the stoichiometric air-fuel ratio was achieved according to the speed of the engine, the developed mixer of the AIR-Hydrogen mixing process provides high mixing homogeneity and engines with stoichiometric air-fuel ratios, which subsequently contributes to the high levels of efficiency in engine operation. In summary, the current study intends to reduce the emissions of gases and offer a wide range of new alternative fuels usage. While the performance of the diesel engine with the new air-hydrogen mixer needs to be tested practically.

EUREKA: Physics and Engineering pp 124-136; doi:10.21303/2461-4262.2021.001708

**Abstract:**

One of the main problems of decision-making tasks is the need to take into account subjective expert assessments, the complete consistency of which is rare, and the choice of the best alternative. The complexity of the connections between the many-sided aspects of the decision-making situation and the lack of an accurate forecast of the consequences leads to the fact that when assessing and choosing alternatives, it is possible, and often necessary, to use and process qualitatively fuzzy estimates. In decision-making situations, when at least one of the elements (outcomes, criteria, preferences, expert opinions, etc.) is described qualitatively, indistinctly, there are problems of multi-criteria decision-making with fuzzy initial information. Let’s consider the solution to the problem of multi-criteria choice based on the rules of fuzzy conditional inference, which have the form of fuzzy statements, the conditions and conclusions of which, along with expert assessments of the criteria, are presented in the form of interval fuzzy numbers of the second type (IT2FN). The convolution of private implications in each statement is made according to Lukasiewicz's rule. To reduce the type and defuzzify the resulting IT2FN, the Karrnik-Mendel algorithm was used to construct the minimum and maximum centroids of nested fuzzy sets of the first type, which give an estimate of the utility interval for each alternative. To refine the obtained utility estimates, under conditions of incomplete definiteness of statements, using the generalized Bayesian inference mechanism, adjusted estimates of the utility intervals of alternatives are constructed. By comparing these intervals, a larger interval is determined and the corresponding alternative is taken as a solution to the problem under consideration. The application of the proposed approach to solving the problem of multicriteria selection of the most corroded section of a gas pipeline with ambiguous expert opinions is shown. To date, specific practical and theoretical results have been obtained for decision-making problems with fuzzy initial information

EUREKA: Physics and Engineering pp 19-31; doi:10.21303/2461-4262.2021.001689

**Abstract:**

To ensure the functioning of the energy system, coordination and increase the efficiency of its parts need new control mechanisms. Generation, transmission and consumption of electricity needed control mechanisms that include integration of self-organizing power and heat supply systems, built on multi-agent principle. Also they must correspond intellectual basis, monitoring and accumulation. This includes effectiveness assessment of the state and analysis of technical, technological and organizational management mechanisms. One of the main parts is interaction principles of energy systems in accordance with European Community policy at various levels at liberalized electricity market. In most developed countries, demand management programs are widely used as a means of harmonizing the modes of generation and consumption in the power supply system. The main direct methods are set in the form of electricity tariffs. Indirect methods are set in the form of programs to manage electricity demand and the possibility of their application to manage electricity demand. Methods for estimating the unevenness of the daily schedule of electricity consumption and the factors influencing the technological environment are presented. The work aims at scientific and applied problem – finding methods of estimation and features of managing the demand for electricity. The use of the proposed estimation methods of electricity consumption influence non-uniformity on the level of power supplies system losses based on Frize QF power and optimization of consumers’ operation modes in the power supply system is considered. Approaches and optimization mechanisms of the daily electricity consumption on the example of a residential complex with the possibility of energy accumulation are offered