Showing papers in "Eureka: Physics and Engineering in 2022"

Development of fully superconducting 5 MW aviation generator with liquid hydrogen cooling

Abstract: The use of liquid hydrogen as a fuel will be inevitable in the aviation of the future. This statement means that manufacturers will also implement liquid hydrogen for cooling all superconducting aviation equipment of an electric propulsion system. The development of fully electric aircraft is the most promising solution in this case. Scientists from the Department of electrical machines and power electronics of Moscow aviation institute have conducted calculations and theoretical researches of critical specific mass-dimensional parameters (MW/ton and MW/m3 at 21 K) of fully superconducting aviation synchronous generator of the electric propulsion system. The results are in this article. The article discusses the results 3D finite element modeling (FEM) simulation of a 5 MW fully superconducting synchronous generator with combined excitation. Superconducting armature and axial excitation windings based on second generation high temperature superconductors (HTS-2G) are located on the stator, which makes it possible to contactlessness and the absence of sliding seals. A dry gap will reduce gas-dynamic losses and increase the nominal peripheral speed of the rotor. The use of liquid hydrogen as a coolant makes it possible to significantly increase the linear load of the generator, and high current densities to reduce the cross-sectional area of the coils, which will make it possible to place them in individual cryostats in the future. Individual cryostats will allow to remove the heat release of magnetic losses from the cryogenic zone and reduce the consumption of refrigerant. For the purpose of internal redundancy of the HTS coils, the machine has a complete set of reserve winding made of ultrapure aluminum, also cooled by liquid hydrogen. If the superconducting coils get out of the stand, the generator will provide 15 % power on standby

Development of free water knock-out tank by using internal heat exchanger for heavy crude oil

Abstract: Reactivation of an old oil well can be explicitly calculated to maximize crude oil production. The biggest challenge with the activation process is the crude oil content in old wells, which is not feasible to meet the specified minimum standards. In the case of the Bunian oil field, Indonesia, the crude oil produced has high water content. It causes a decrease in the quality of production and also hinders production capacity. The production scheme applied to the Bunian field has a storage tank that functions to reduce water content using the gravity method, but this is less effective. Let’s modify the storage tank into a heat exchanger tank through the engineering design process and labeled it as a free water knockout tank (FWKO). The FWKO is made of a multi-pass tube heat exchanger. The experiments are conducted through three phases’ tests before deciding the final design. From the test, the change in water content is varied with temperature differences of the working fluid and crude oil. The lowest water content is obtained at 0.5 % at final tests. After analyzing the characteristic of each test result, the final design is taken by adjusting the suitable working fluid temperature and pressure. Finally, by using suitable parameters, the average water content of crude oil is decreased up to the minimum requirement (<0.1 %). The design of FWKO is considered simple with an excellent performance and can adapted easily. The FWKO able to process crude oil with water content <20 %, where it suitable for waxy oil well. The working fluid can be processed both in liquid and gas state. Furthermore, the heating source for the working fluid is gained from the gas flare by using thermic heater. Thus, it does not require an extra heating source for the heat exchanger

Influence of structural solutions of an improved brake cylinder of a freight car of railway transport on its load in operation

Abstract: The object of research is the processes of occurrence, perception and redistribution of loads in the design of the car brake cylinder in operation. To compensate for angular shifts of the brake cylinder rod at its maximum exit from the housing, improvement measures are proposed. This improvement consists in the use of a safety element to limit the angular movements of the rod when leaving the body. The load of the brake cylinder rod during its angular displacements is determined. The condition for ensuring the strength of the rod is obtained. The optimal parameters of the pipe of the safety element (limiter) of the brake cylinder rod were determined by its allowable moment of resistance. For the possibility of moving the levers interacting with the stem, special windows are provided in the limiter. It is proposed to fix the limiter to the cover by welding. To determine the strength of the brake cylinder, a calculation was made using the finite element method. The results of a robust calculation showed that the maximum equivalent stresses occur in the brake cylinder cover and amount to 118.5 MPa. Therefore, the strength of the brake cylinder is ensured. A feature of the obtained results is that the proposed improvement can be applied not only at the stage of designing a brake cylinder, but also at the stage of modernization. The sphere of practical use of the obtained results is railway transport. The conditions for the practical use of the results are the absence of deformations of the brake cylinder rod. The research carried out will help to improve the efficiency of rolling stock brakes, ensure traffic safety, increase rolling stock speeds, deliver goods, etc. Also, the conducted research will contribute to the creation of developments to improve the reliability of the rolling stock brakes

The effect of adding natural materials waste on the mechanical properties and water absorption of epoxy composite using grey relations analysis

Abstract: Recently, there has been a tendency for scientific studies to deal with natural materials as fillers and reinforcement for polymer composites, which are used in many different applications due to their environmentally friendly properties when compared to synthetic materials. The current study aims to preserve the environment by dealing with natural materials and their influence on the mechanical properties and water absorption property of the polymer composites. In this study, epoxy composites were produced from local natural sourced non-hazardous raw natural materials using grey relational analysis (GRG). The materials used for fabrication include micro-filler of pollen palm 50 μm, seashell 75 μm and epoxy resin. Nine different composites were prepared using pollen palm and seashell as reinforcement material by varying the wt % of the micro-filler. Rule of the mixture was used for formulation and wt % of (0.5, 1 and 1.5) % reinforcement and 99.5, 99 and 98.5 % epoxy (binder) were used for composites. Grey relational analysis was conducted in order to scale the multi-response performance to a single response. The results indicate that optimum performance can be achieved with the addition of 1.5 wt % micro-filler of seashell, which achieved the first rank, while the second rank achieved by 0.5 wt % micro-filler of palm pollen and seashell when compared to other composites. The addition of micro-fillers has improved greatly the mechanical properties of epoxy composites. The loading of micro-fillers has influenced the water absorption property of composites based epoxy in ascending order

A research on application of the measurement of alternatives and ranking according to compromise solution method for multi-criteria decision making in the grinding process

Abstract: The efficiency of cutting methods in general and the grinding method in particular is evaluated through many parameters such as surface roughness, machining productivity, system vibrations, etc. The machining process is considered highly efficient when it meets the set requirements for these parameters such as ensuring the small surface roughness, small vibrations, and high productivity, etc. However, for each specific machining condition, sometimes the set criteria for the output criteria are opposite. In these cases, it is required to solve the Multi-Criteria Decision Making (MCDM) which means making the decision to ensure the harmonization of all criteria. In this study, a study on multi-criteria decision making in the grinding process of 9CrSi steel using CBN grinding wheels is presented. The experimental process was carried out with sixteen experiments according to an orthogonal matrix that designed by the Taguchi method. The workpiece velocity, feed rate, and depth of cut were changed in each experiment. At each experiment, the responses were determined including surface roughness (Ra), the vibration of the grinding wheel shaft in the three directions, corresponding to Ax, Ay, and Az, and material removal yield (Q). Four determination methods of weights for criteria were used. The Measurement of Alternatives and Ranking according to Compromise Solution (MARCOS) method was applied for multi-criteria decision making. The objective of this study is to identify an experiment that simultaneously ensures the small values of Ra, Ax, Ay, and Az and large value Q

A real-time defect detection in printed circuit boards applying deep learning

Abstract: Inspection of defects in the printed circuit boards (PCBs) has both safety and economic significance in the 4.0 industrial manufacturing. Nevertheless, it is still a challenging problem to be studied in-depth due to the complexity of the PCB layouts and the shrinking down tendency of the electronic component size. In this paper, a real-time automated supervision algorithm is proposed to test the PCBs quality among different scenarios. The density of the PCBs layout and the complexity on the surface are analyzed based on deep learning and image feature extraction algorithms. To be more detailed, the ORB feature and the Brute-force matching method are utilized to match perfectly the input images with the PCB templates. After transferring images by aiding the RANSAC algorithm, a hybrid method using modern computer vision algorithms is developed to segment defective areas on the PCBs surface. Then, by applying the enhanced Residual Network –50, the proposed algorithm can classify the groove defects on the surface mount technology electronic components which minimum size up to 1x3 mm. After the training process, the proposed system is capable to categorize various types of overproduced, recycled, and cloned PCBs. The speed of the quality testing operation maintains at a high level with an average precision rate up to 96.29 % in case of good brightness conditions. Finally, the computational experiments demonstrate that the proposed system based on deep learning can obtain superior results and it outperforms several existing works in terms of speed, precision, and robustness

Development of the project of modular prefabricated buildings

Abstract: The issues of working design with the construction of modular prefabricated buildings, with the minimization of cold bridges are revealed. Cold bridges are typical for prefabricated buildings with inadequate attention to the design of both load-bearing metal and enclosing structures, as well as their connections. Connections should not pass through its cross section both zero and negative temperatures. As a result, an original project of two modular buildings was developed from easily prefabricated metal structures and wall structures with light mineral wool filling. This project is also intended for sharply continental regional natural and climatic conditions (regardless of the geographical location on the territory of Kazakhstan – south-eastern Kazakhstan, central, eastern or western Kazakhstan. In winter, natural and climatic conditions are similar in these areas). As a result of this study, it was found that the developed project meets the requirements of thermal insulation – at the interface of the supporting and enclosing structures. The thermal insulation requirements of the above structures are important to eliminate the dew point and consequently the formation of moisture and mold in all structures. In turn, mold and other microorganisms, as studies show, adversely affect the health and normal stay of people in the premises, both during the night and during the day. Many developers do not consider these factors in prefabricated buildings. These buildings are intended for various industries. For example, in healthcare, these are mobile hospitals. In military camps – buildings of temporary residence as barracks, etc.

Developing an algorithm for monitoring gas generators of hydrogen storage and supply systems

Abstract: In relation to the main element of the hydrogen storage and supply system based on the hydro-reacting composition – the gas generator – an algorithm for its control has been developed. The development of such an algorithm is carried out in three stages. At the first stage, the problem of formalizing the hydrogen generation process is solved. Formalization of this process is carried out using the transfer function of the gas generator. The use of the criterion for the minimum error of the mismatch of the given amplitude-frequency characteristics of the gas generator allows to represent its transfer function in the form of a transfer function of the inertial link. At the second stage, the problem of determining the conditions for the occurrence of self-oscillations in the pressure stabilization subsystem is solved. A prerequisite for the emergence of a self-oscillating mode of operation of the hydrogen storage and supply system is the presence of a relay static characteristic of the pressure sensor. For the characteristic parameters of such a system, the ranges of values of the parameters of self-oscillations, frequencies and amplitudes, are determined. For these parameters, analytical expressions are obtained, which include the main parameters of the pressure stabilization subsystem in the hydrogen storage and supply system. At the third stage, the problem of forming a gas generator control algorithm is solved. As a test action in the implementation of the control algorithm, self-oscillations in the pressure stabilization subsystem are used. The control algorithm for the gas generator of the hydrogen storage and supply system includes determining the parameters of self-oscillations and comparing their values with the values obtained a priori. A typical diagram of a hydrogen storage and supply system is presented, in which the developed gas generator control algorithm is implemented

Design and practice of simple first-order all-pass filters using commercially available IC and their applications

Abstract: First-order all-pass filter circuits, both non-inverting and inverting, could be the focus of this article, which could include the design and implementation of first-order all-pass filter circuits. Using a standard integrated circuit (IC): AD830, as well as a single resistor and a single capacitor, the proposed first-order all-pass filters could well be built. The AD830 is an integrated circuit (IC) manufactured by Analog Devices Corporation that is available for purchase. The pole frequency and phase response of the proposed all-pass filters could well be directly modified by attuning the resistor in the circuit. Aside from that, the output voltage has a low impedance, making it appropriate for use in voltage-mode circuits. In addition, the proposed first-order all-pass filter is used to design the multiphase sinusoidal oscillator, which serves as an example of an application wherein the oscillation condition can be adjusted without impacting the frequency. The gain and phase responses of the proposed all-pass filters, as well as their phase response adjustment, time-domain response, and total harmonic distortion of signals, are all shown via computer simulation using the PSPICE software, as well as their experimental results. For the proposed circuits, a statistical analysis is coupled with a Monte Carlo simulation to estimate the performance of the circuits. In accordance with the results of this study, a theoretical design suitable for developing a worksheet for teaching and learning in electrical and electronic engineering laboratories has already been developed

Characterization of WO3 thin films deposited by spray pyrolysis technique and its role in gas sensing

Abstract: The work investigated in this paper focused on the fabrication of WO3 films by the spray pyrolysis technique, and different analyses were made to find optimized samples for studying properties suitable for the application of gas sensing. The substrate temperature is the most important parameter among other spray parameters for the synthesis of thin films hence WO3 thin films were deposited on glass substrates by maintaining the substrate temperature at 350 ºC, 450 ºC, 550 ºC, and 650 °C using compressed air as a carrier gas. The influence of the substrate temperature on the structural, morphological, compositional, and optical properties of the WO3 thin films has been justified using XRD data. Good and enhanced crystallinity is observed for the film deposited at a substrate temperature of 550 ºC. The nonconventional properties were studied by different investigations and confirmed by past research work. The manipulation of surface morphology with the different deposition temperatures is monitored. Only the characteristic peaks of W and O are present in the fabricated WO3 thin films. The optical activity of about 70 to 80 % of the selected sample in the visible region (300 to 1200 nm) is found. The selective absorption activity of light in the ultraviolet region and visible region is checked. The obtained IR bands confirmed the inter bridge stretching and bending modes of W-O and O-W-O. A high response towards ammonia compared to other test gases is exhibited. The repeatability of WO3 towards NH3 over three periodic sensing cycles, response, and recovery time has also been discussed. From all the characteristic studies, it has been suggested that the fabricated WO3 thin films have been used in the health care field to detect the toxic NH3 gas

The effect of Clathrin protein addition on increasing the number of electrons in organic Dye-Sensitized Solar Cell (DSSC)

Abstract: Dye-Sensitized Solar Cell (DSSC) is a solar cell that uses dyes to convert sunlight into electricity, which has a wide absorption spectrum, is inexpensive and environmentally friendly. Visible light sensitive dyes are used in Dye-Sensitized Solar Cell (DSSC) types to generate electricity. Natural sensitive dyes that are commonly used in DSSC are chlorophyll derived from plants. Chlorophyll is a source of electrons which will be excited when exposed to light, resulting in an electric current in the DSSC. The most basic problem in Dye-Sensitized Solar Cell (DSSC) is that the number of electrons produced is still lower than that of silicon solar cells. This is due to the high recombination process of free electrons due to limited diffusion of electrons trapped at the boundary between TiO2 particles caused by less than optimal contact between particles. Clathrin is a protein that plays an important role in the formation of the vesicle layer which is responsible for the transport of molecules in cells. As a protein that plays an important role in the cell transport system, Clathrin can bind to ions in order to transport cells. This study has proven that the addition of Clathrin protein to the DSSC layer can increase the number of electrons generated in the DSSC. The method used in this study was to vary the addition of Clathrin content to TiO2, namely the Clathrin concentration of 0 %, 25 %, 50 % and 75 %. The results showed that increasing the Clathrin content would increase the electric current and the number of electrons generated by the DSSC, namely the 75 % Clathrin content with an electric current of 5,247 mA and the number of electrons was 3.28x1016

Development of object detection and classification with YOLOv4 for similar and structural deformed fish

Abstract: Food scarcity is an issue of concern due to the continued growth of the human population and the threat of global warming and climate change. Increasing food production is expected to meet the challenges of food needs that will continue to increase in the future. Automation is one of the solutions to increase food productivity, including in the aquaculture industry, where fish recognition is essential to support it. This paper presents fish recognition using YOLO version 4 (YOLOv4) on the "Fish-Pak" dataset, which contains six species of identical and structurally damaged fish, both of which are characteristics of fish processed in the aquaculture industry. Data augmentation was generated to meet the validation criteria and improve the data balance between classes. For fish images on a conveyor, flip, rotation, and translation augmentation techniques are appropriate. YOLOv4 was applied to the whole fish body and then combined with several techniques to determine the impact on the accuracy of the results. These techniques include landmarking, subclassing, adding scale data, adding head data, and class elimination. Performance for each model was evaluated with a confusion matrix, and analysis of the impact of the combination of these techniques was also reviewed. From the experimental test results, the accuracy of YOLOv4 for the whole fish body is only 43.01 %. The result rose to 72.65 % with the landmarking technique, then rose to 76.64 % with the subclassing technique, and finally rose to 77.42 % by adding scale data. The accuracy did not improve to 76.47 % by adding head data, and the accuracy rose to 98.75 % with the class elimination technique. The final result was excellent and acceptable

Research on selection of abrasive grain size and cutting parameters when grinding of interrupted surface using aluminum oxide grinding wheel with ceramic binder

Abstract: In this article, a study on intermittent surface grinding using aluminum oxide grinding wheel with ceramic binder is presented. The testing material is 20XH3A steel (GOST standard – Russian Federation). The testing sample has been sawn 6 grooves, with the width of each groove of 10 mm, the grooves are evenly distributed on the circumference of sample. The testing sample resembles a splined shaft. An experimental matrix of nine experiments has been built by Taguchi method, in which abrasive grain size, workpiece speed, feed rate and depth of cut were selected as input variables. At each experiment, surface roughness (Ra) and roundness error (RE) have been measured. Experimental results show that the aluminum oxide and ceramic binder grinding wheels are perfectly suitable for grinding intermittent surface of 20XH3A steel. Data Envelopment Analysis based Ranking (DEAR) method has been used to solve the multi-objective optimization problem. The results also showed that in order to simultaneously ensure minimum surface roughness and RE, abrasive grain size is 80 mesh, workpiece speed is 910 rpm, feed rate is 0.05 mm/rev and depth of cut is 0.01 mm. If evaluating the grinding process through two criteria including surface roughness and RE, depth of cut is the parameter having the greatest effect on the grinding process, followed by the influence of feed rate, workpiece speed, and abrasive grain is the parameter having the least effect on the grinding process. In addition, the effect of each input parameter on each output parameter has also been analyzed, and orientations for further works have also been recommended in this article

On the eventual periodicity of fractional order dispersive wave equations using RBFS and transform

Abstract: In this research work, let’s focus on the construction of numerical scheme based on radial basis functions finite difference (RBF-FD) method combined with the Laplace transform for the solution of fractional order dispersive wave equations. The numerical scheme is then applied to examine the eventual periodicity of the proposed model subject to the periodic boundary conditions. The implementation of proposed technique for high order fractional and integer type nonlinear partial differential equations (PDEs) is beneficial because this method is local in nature, therefore it yields and resulted in sparse differentiation matrices instead of full and dense matrices. Only small dimensions of linear systems of equations are to be solved for every center in the domain and hence this procedure is more reliable and efficient to solve large scale physical and engineering problems in complex domain. Laplace transform is utilized for obtaining the equivalent time-independent equation in Laplace space and also valuable to handle time-fractional derivatives in the Caputo sense. Application of Laplace transform avoids the time steeping procedure which commonly encounters the time instability issues. The solution to the transformed model is then obtained by computing the inversion of Laplace transform with an appropriate contour in a complex space, which is approximated by trapezoidal rule with high accuracy. Also since the Laplace transform operator is linear, it cannot be used to transform non-linear terms therefore let’s use a linearization approach and an appropriate iterative scheme. The proposed approach is tasted for some nonlinear fractional order KdV and Burgers equations. The capacity, high order accuracy and efficiency of our approach are demonstrated using examples and resultsRBFs Methods

Study of the secondary characteristics of the bistatic scattering of a combined object in a covert radar surveillance system

Abstract: The emergence of new means of attack, reconnaissance and methods of sabotage imposes special requirements on the technical means of protecting important state facilities (ISF). Modern trends in the construction of ISF physical protection systems are the integration of engineering barriers, perimeter signaling and detection tools. Detection tools should provide covert receipt of information about the approach of the intruder in "distant" intrigues. To do this, it is possible to use technical means built on the principle of semi-active bistatic radar with an external illumination source. However, in order to identify intruders in the ISF protection zone, it is necessary to have a priori information about the radar visibility of the combined location objects. The combined object is typically a complex object having both metallic and dielectric elements. To this end, a technique has been developed for estimating the radar cross-section (RCS) of combined objects in the field of external illumination. The electromagnetic field (EMF) scattered by a combined object in the meter and decimeter wavelength ranges is calculated as a coherent sum of fields, taking into account their phase, scattered by its metal and dielectric elements. This made it possible to take into account the electromagnetic interaction of the elements of the combined object. The method of integral equations (IE) was used to find the current density and magnetic field strength. The scatter diagrams of the person-intruder, the person-intruder in personal armor protection (PAP) under different conditions of irradiation and reception and illumination frequencies are obtained and analyzed. This made it possible to evaluate the effect of metallic elements on the scatter diagram of the combined object. The obtained a priori information is of significant practical importance at the stage of optimizing signal processing algorithms and designing new means of covert detection

Expert opinion-based multi objective optimization: an application in plasma coating technology

Abstract: Multi-objective optimization is a very important activity which is applied in many different fields. When solving this problem, it is important to determine weights for criteria. If the weight of criteria is determined according to dry mathematical formulas, the opinion of researchers will be ruined. On the contrary, if the weight of criteria is determined according to the subjective opinion of researchers, it is also easy to make mistakes. This study applies a method of determining the weight of criteria based on experts' opinions and conditions must be also strictly satisfied, thereby both of the above limitations have been remedied. Such method is known as FUCOM (FUll COonsistency Method). An application example was carried out for multi-objective optimization in the plasma coating process. Plasma coating is a modern coating technology. This method is increasingly used in many different fields. However, determining the value of technological parameters to ensure the quality of high-quality products is a very complicated job. In order to ensure many requirements of the product, it is necessary to determine the optimal value of the technological parameters. Four criteria to evaluate a coating process include the adhesion strength of the coating, the shear strength of the coating, the tensile strength of the coating, and the porosity of the coating. The task of multi-objective optimization in this study is to determine the values of three input parameters (including: spray current intensity, powder feed flow, and spray distance) to ensure that the desired values of the four criteria are simultaneously achieved. After the weight of criteria is determined by the FUCOM method, the multi-objective optimization problem has been solved. Experiments to verify the optimal results were also conducted, thereby demonstrating the correctness of the methodology. The optimal values of the technology parameters (spray current intensity, powder feed flow, and spray distance) have been determined to be 568.69 A, 31.87 g/min, and 170.19 mm, respectively

Controllability and stability capacity of a roll pair motion research

Abstract: The process of deriving the equation of the perturbed motion of a roll pair during the processing of leather material is discussed in the article, taking into account the influence of dynamic factors. It is shown that one of the reasons for the unstable stress state on the contact surfaces in the roller mechanism are dynamic factors arising from inaccuracies in the manufacture of its individual parts, assembly defects, and the occurrence of an oscillatory process in the roller mechanism, as well as due to the non-uniform thickness of the processed material at its gripping during starting and stopping the machine. Methods for determining optimal controls are shown; they provide asymptotic stability of the unperturbed motion of a roll pair and the torque applied to the upper roll as a function of generalized coordinates.It is shown that the width of the contact strip of the clamp, which depends on the radii of the rolls and the hardness of the coatings, has a significant effect on the efficiency of the rolls. The larger the shaft radius, the lower the actual pressure per unit contact area. It is shown that the squeezing efficiency increases with the improvement of the conditions for the removal of the squeezable liquid from the rolls (with their horizontal arrangement), with an increase in its temperature and a decrease in viscosity. Efficiency decreases with increasing material speed and thickness. It is shown that the width of the contact strip of the clamp, which depends on the radii of the shafts and the stiffness of the coatings, has a significant impact on the efficiency of the shafts. The larger the shaft radius, the lower the actual pressure per unit contact area

Synthesis and characterization of MgB2 superconductors with carbon nanotubes (CNTs) and tin (Sn) addition

Abstract: MgB2/CNT is a promising candidate for superconducting wire application due to its excellent mechanical properties and carbon nanotube’s low density. However, strong interfacial adhesion between the CNT reinforcement and the MgB2 matrix is difficult to manage. Therefore, this study examines the synthesis and characterization of magnesium diboride (MgB2) superconductors with carbon nanotubes (CNTs) and tin (Sn) addition. Determining the proper method and combination of CNT & Sn affects MgB2 superconductors is crucial. Raw materials of magnesium (Mg), boron (B), Sn, and multi-walled carbon nanotubes (MWCNTs) were used for a solid-state reaction process to determine the proper synthesis method and the effect of CNT on superconductors’ critical temperature. Each sample was obtained by weighing the raw material first, followed by hand grinding with agate mortars for 3 hours. The pelletization was then conducted by using a compact pressing machine with a pressure of 350 MPa. The compacted samples were then sintered at 800 °C for 2 hours either through the vacuum or PIST process. Finally, all were characterized, and MgB2 was discovered to be the dominant phase with minor impurity phases such as MgO, Mg, Mg2Sn, C, and Sn. Based on SEM morphological analysis, the grain boundaries of sample A1 were more precise than B2. In both, the grain size also varies, and the distribution of elements is uneven. Subsequently, Cryogenic Magnet Characterization indicated that at 40 K, almost all samples possess superconducting characteristics. For future studies, the potential impact of MgB2 on critical current density (Jc) and magnetic density (Hc) in several commercial applications such as Magnetic Resonance Imaging (MRI), magnetic levitation, and transformers needs to be investigated

Increasing the mechanical properties of structural cast iron for machine-building parts by combined Mn – Al alloying

Abstract: The object of research in this work was cast iron for machine-building parts, alloyed with Al. The possibility of improving the mechanical properties of cast iron by choosing the optimal Mn – Al combinations, depending on the carbon content in the cast iron, was determined. The study was carried out on the basis of available retrospective data of serial industrial melts by constructing the regression equation for the ultimate strength of cast iron in the three-factor space of the input variables C – Mn – Al. The optimization problem was solved by the ridge analysis method after reducing the dimension of the factor space by fixing the carbon content at three levels: C = 3 %, C = 3.3 %, and C = 3.6 %. It was found that the maximum values of the ultimate strength are achieved at the minimum level of carbon content (C = 3%) and are in the range of values close to 300 MPa. In this case, the Al content is in the range (2.4–2.6) %, and the Mn content is about 0.82 %. With an increase in the carbon content, there is a tendency to a decrease in the content of Mn and Al in the alloy, which is necessary to ensure the ultimate strength close to 300 MPa. The results of the ridge analysis of the response surface also showed that at the upper limit of the carbon content (C = 3.6%), it is not possible to reach the ultimate strength of 300 MPa in the existing range of Mn and Al variation. All solutions are verified for the following ranges of input variables C = (2.94–3.66) %, Mn = (0.5–1.1) %, Al = (1.7–2.9) %. Graphical-analytical descriptions of the optimal Mn – Al ratios are obtained, depending on the actual content of carbon in the alloy, which make it possible to purposefully select the optimal melting modes by controlling the tensile strength of the alloy

Decısıon makıng for car selectıon ın Vıetnam

Abstract: Mid-priced cars (segment B) are attracting the attention of middle-income families in Vietnam. They often consider choosing one of three vehicles from three different manufacturers, consisting of Hyundai Accent 1.4AT, Toyota Vios 1.5G, and Honda City 1.5L. This study was carried out to rank those three cars. Twelve criteria for rating each car provided by the dealer were used. These criteria are both qualitative and quantitative, and also fall into all three types, including max, min and another (“Yes”, “No”). The importance of each criterion was determined by experts in a survey. They are all knowledgeable about cars. Two multi-criteria decision making (MCDM) methods including R (A simple ranking method for multi-attribute decision making in the industrial environment) and CURLI (Collaborative Unbiased Rank List Integration) method were applied for ranking. This is the first work that has used both methods mentioned above. The result revealed that the rank of the alternatives is the same when both the methods were used. This result gives us a certain confidence when choosing a car. Accordingly, Honda City 1.5L is ranked first. R and CURLI not only succeeded in ranking cars in this study, but also promise to be successful when used in other situations. Moreover, other criteria for evaluating the vehicle options that have not been surveyed in this study are mentioned in the last section of this paper. They need to be further considered to include in other next studies for car selection

Analysis of three-layer gasket performance affected by flange surface

Abstract: Gaskets are components that play a very important role in piping connections to prevent leakage. Several factors affect the performance of the gasket, one of which is the contact surface of the flange. The quality of the contact surfaces in the connection also influences the leakage rate of each connection, therefore the gasket sealing performance is assessed by the rate of leakage that occurs. As a result, the surface roughness of the flange has an effect on sealing. This study examines the capability of a three-layer corrugated metal gasket to prevent leakage when the outside layer thickness and flange roughness are adjusted. The feature of three-layer corrugated metal gasket was elucidated using the finite element analysis (FEA) and experimental method. The leak rate was tested using a helium leak quantity test experimentally. The gasket was constructed with oxygen-free copper (C1020) as the outside layer and SUS304 as the base layer, and it was structured in a three-layer pattern with no bonding. A mold press was used to make the gasket. The simulation method applies finite element analysis software to investigate the correlation between contact stress, contact width, surface thickness and surface roughness. The projected results matched the experiment results fairly well. A three-layer corrugated metal gasket shows improvement capability to prevent leakage than a single gasket (standard). The gasket three-layer shows sealing performance improvement that leakage did not occur in low axial force 40 kN for all surface roughness test. In terms of sealing, a three-layer gasket with a low thickness ratio works well. Surface roughness of the flange has no influence on the three-layer gasket

Numerical simulation of nitrogen oxide formation in dust furnaces

Abstract: Even though natural sources of air pollution account for over 50 % of sulphur compounds, 93 % of nitrogen oxide which are the most dangerous artificial anthropogenic sources of air pollution and primarily associated with the combustion of fossil fuel. Coal-fired thermal power plants and industrial fuel-burning plants that emit large quantities of nitrogen oxides (NО and NО2), solids (ash, dust, soot), as well as carbon oxides, aldehydes, organic acids into the atmosphere pollute the environment in majority. In the present work, a mathematical model and a scheme for calculating the formation of nitrogen oxide has been developed. Also, the dependence of the rate of release of fuel nitrogen from coal particles at the initial stage of gasification and content of volatiles has been obtained. The main regularities of the formation of NOx at the initial section of the flame in the ignition zone of the swirl burner flame during the combustion of Ekibastuz coal have been revealed. Modern environmental requirements for the modernization of existing and the creation of new heat and power facilities determine the exceptional relevance of the development of effective methods and constructions to reduce emissions of nitrogen oxides, sulfur oxides and ash to 200, 300, and 100 mg/nm3 at a=1.4. The dust consumption in all experiments was kept constant and amounted to 0.042 g/s, as well as with the results of calculating the thermal decomposition of the Ekibastuz coal dust, the recombination of atomic nitrogen into nitrogen molecules, and the kinetics of the formation of fuel nitric oxide. It was found that despite the presence of oxygen in Ekibastuz coal for gases Odaf=11.8 % in an inert atmosphere, nitrogen oxides are not formed

The development a fully-balanced current-tunable first-order low-pass filter with Caprio technique

Abstract: This paper presents the development and design of a fully-balanced current-tunable first-order low-pass filter with Caprio technique, which could include the design and implementation of a first-order low-pass filter circuits. The filter consists of six bipolar junction transistor (BJT) and a single capacitor. The filter construction uses a bipolar junction transistor (BJT) as the main device and a single capacitor. A fully-balanced current-tunable first-order low-pass filter with Caprio technique developed. The architecture of the circuit is quite simple and proportional, symmetrical with signs of difference. Circuits developed into integrated circuits act like basic circuits for frequency filter circuits, current modes with Caprio techniques, obtained by improving the first-order low-pass filter for signal differences with incoming impedances. Adjusting the parameters of the circuit with the caprio technique achieves the optimal parameter value for correcting the total harmonic distortion value. The results of testing the operation of the circuit, a fully-balanced current-tunable first-order low-pass filter with Caprio technique developed and designed using the PSpice program. The simulation results showed good results in line with predicted theoretical analysis. The sensitivity of the device to the center frequency (ω0) response is low and independent of variables, the angular frequency is linear with wide current adjustment throughout the sweeping range of a wide frequency range, with a wide range of over tree orders of magnitude. Therefore, fully-balanced current-tunable first-order low-pass filter developed is very suitable to apply various applications regarding low frequency signal filtration, for example in biomedical systems, for example.

Experimental study of the effect of brake drum cooling grooves on motorcycle braking performance

Abstract: Some important indicators in the braking system performance on a motorcycle are the braking temperature and stopping distance. High temperatures due to frictional heat in the drum brake can decrease the braking force and cause a slip. To improve braking performance, an effective strategy is needed to reduce the drum temperature and shorten the stopping distance. This study aims to analyze the effect of cooling grooves on the standard brake drum to decrease the drum brake temperature and the length of stopping distance. The measurements were compared to the standard drum brake as a reference, and two types of the modified ones to increase the braking performance by adding the slant-grooved and a straight grooved on brake drum. Braking is performed by providing a compressive load of two kg on the brake pedal for three cases of motorbike speed: 20, 40, and 60 km/hour. The results show that the brake drum with straight cooling grooves provides better braking performance compared to other drum brakes. For a speed of 60 km/h, the temperature of the straight grooved brake is 3.5 ºC. The stopping distance is 29.1 % shorter compared to the standard one. It shows that adding cooling grooves on drum brake can increase the effectiveness of motorcycle braking performance at various speeds. The results show that the brake drum with straight cooling grooves provides better braking performance compared to other drum brakes

Detection of the synergetic influence of chemical and microbiological factors on the properties of concrete constructions at chemical plants during the long-term service

Abstract: Long-term operation of reinforced concrete structures in the conditions of chemical enterprises has a powerful negative impact on the physical and chemical properties of concrete, which leads to its destruction. The aim of this research is to determine the effect of biological and chemical corrosion on concrete structures in the workshop for the production of titanium dioxide by the sulphate method and the storage of finished products. In particular, chemical production for the synthesis of titanium dioxide by the sulfate method causes the rapid course of chemical (acid and sulfate) and microbiological (thionic bacteria and microscopic fungi) corrosion processes. These corrosion processes reinforce each other according to a synergistic principle. As a result, temperature-programmed desorption mass spectrometry (TPD MS) and scanning electron microscopy have experimentally proven the presence and spatial localization of colonies of thionic bacteria and microscopic fungi in concrete structures. Correlations between the intensity of biochemical corrosion and the depth of damage to the microstructures of concrete structures have been established. Moreover, a change in the chemical composition of concrete in the workshop for the production of titanium dioxide (increased SO2 content and reduced CO2) and the formation of gypsum crystals (CaSO4 2H2O) as a result of the dissimilation of microorganisms was established. Also, in the storage room for finished products, calcium citrate crystals and a violation of the formation of calcium carbonate are formed in the surface layers of concrete. In addition, the results of the study can be used to develop antimicrobial and anticorrosive protective agents to stop the biochemical corrosion of concrete in a chemical plant

Heat transfer analysis cabinet-type ERK solar dryer machine for drying agricultural products

Abstract: The Cabinet-type ERK solar dryer is manufactured by a temperature distribution process so that the temperature inside the appliance is well distributed. The cabinet-type ERK solar dryer comprises several components to maintain the water content, including a drying oven, air blower, heat-resistant pipe, hot water pump, thermostat, heat exchanger, and heater. These tools are used to convert heat radiation into conduction or convection so that the dried agricultural products' water content is relatively low. The data needed to show the quality of the tool include temperature on temperature received by the wall (Tw), absorbent plate (Tp) and room temperature (Tr). And as for other supporting data including the environmental air/ ambient temperature (Ta) and solar irradiation (I) for optimal tool usage time. The experiment results for 5.5 hours, as many as 23 measurements with time interval 15 minutes, obtained a relatively unchanged temperature distribution. During that time, the average temperature received by the wall (Tw) was 41.26 °C, while the middle plate temperature (Tp) was 40.65 °C and room temperature (Tr) was 40.71 °C. Thus, the temperature in the Cabinet-type ERK solar dryer is well distributed. The distribution percentage between wall temperature and plate temperature is 98.52 %, while wall temperature and room temperature are 98.67 %. The result indicates that the Cabinet-type ERK solar dryer is potential as a drying device for agricultural commodities. It is hoped that the Cabinet-type ERK solar dryer will be an alternative to a drying system that can improve the quality of agricultural commodities for farmers in Indonesia

Experimental study of the correlation for turbulent burning velocity at subatmospheric pressure

Abstract: Turbulent burning velocity is one of the most relevant parameters to characterize the premixed turbulent flames. Different correlation has been proposed to estimate this parameter. However, most of them have been obtained using experimental data at atmospheric pressure or higher. The present study is focused on obtaining a correlation for the turbulent burning velocity using data at sub-atmospheric pressure. The turbulent burning velocity was experimentally calculated using the burner method, where turbulent premix flames are generated in a Bunsen burner. Stoichiometric and lean conditions were evaluated at a pressure of 0.85 atm and 0.98 atm, whereas the turbulence intensity was varied for each condition. Perforated plates and a hot-wire anemometer were used to generate and measure the turbulence intensity. Schlieren images were used to obtain the average angle of the flame and calculate the turbulent burning velocity. Experiments and theory show that the turbulent deflagration rate decrease as pressure decrease. The turbulent deflagration speed decreased by up to 16 % at 0.85 atm concerning atmospheric conditions for the same turbulence intensity, discharge velocity, and ambient temperature, according to the experimental results. The comparison among the experimental results at sub-atmospheric conditions and the correlations reported in the literature exposes prediction issues because most of them are fitted using data at atmospheric conditions. A general correlation is raised between turbulent burning velocity (ST), laminar burning velocity (SL) and turbulence intensity (u’) proposed from the experimental data. This correlation has the form For sub-atmospheric and atmospheric conditions, the coefficients were determined

Modeling the convective component of the heat flow from a spill fire at railway accidence

Abstract: A significant number of emergencies that occur in the chemical, processing and transport industries begin with an accidental spill and ignition of a flammable liquid. In this case, the spread of fire to neighboring objects is of particular danger. When developing fire protection measures in areas where flammable liquids are stored, as a rule, heat transfer from a fire only by radiation is taken into account. But in some cases, the convection component of the heat flow can make a significant contribution to the overall heat transfer. Ignoring it can lead to an erroneous assessment of the safety of an industrial facility. In the paper, a model of the distribution of velocity and temperature in the upward flow, rising above the spill of a burning liquid, is constructed. The model is based on the system of Navier-Stokes equations, which, by means of simplifications, is reduced to a non-linear second-order differential equation of the parabolic type. The properties of the combustion site determine the boundary conditions of the first kind. In this case, the spill of a flammable liquid can have any shape. The presence of wind is taken into account by introducing a stable horizontal component of the flow velocity. For the numerical solution of the equation, the method of completed differences is used. The dependence of the kinematic viscosity on the flow temperature is taken into account. An empirical formula is used as the relationship between temperature and speed. It is shown that the presence of wind leads to an inclination of the ascending flow. The angle of inclination is not constant and increases with distance from the combustion source due to a decrease in speed and cooling of the flow. An estimate of the coefficient of convection heat transfer convection of the tank wall with ascending flows over the combustion source is constructed. It is shown that the coefficient of convection heat transfer increases with increasing wind speed

Development of spreadsheet simulation models of gas cylinders inventory management

Abstract: The solution of the problem of managing the inventory of an enterprise whose activities are related to the purchase and sale of gas cylinders is considered. To solve the problem, it was necessary to investigate and choose the best inventory management strategy that provides the minimum value of the average inventory balance in the warehouse with the established upper limit of the average deficit. The problem of determining the best strategy is presented as a discrete programming problem, the required variables of which depend on the replenishment method. With a periodic replenishment strategy, the controlled variables are the volume of the delivery line and the delivery interval, with a threshold one, the minimum inventory level and the volume of the delivery line. Let’s also consider replenishment with a predicted inventory level, where the delivery level and the minimum inventory level are used as control variables. Three tabular simulation models with a given delivery time and random demand are proposed. Using the Chi-square test, it was found that the quantity demanded has a normal distribution law. By carrying out computational experiments, the optimal values of controlled variables were determined. The best objective function values were obtained using a model with a predicted inventory level and a threshold replenishment strategy. Experiments conducted on the basis of historical data have shown the advantage of the two model strategies compared to the strategy currently used in the enterprise. The use of a model with a predictable inventory level would reduce the average inventory balance by 46 %, and, consequently, save working capital. The results of the study can be useful for managers of enterprises whose activities are related to inventory management

Development of the methodological approaches for the attitude control system of the Earth remote sensing satellite in the conditions of the onboard equipment partial failures

Abstract: The spacecraft controllability of the angular motion is possible only with operability of the attitude and orbit control system (AOCS) of the spacecraft, sensors, actuators and the spacecraft power system. However, there is a rather significant probability of failure of this equipment during the operation of the spacecraft. This is especially observed after half of the spacecraft's lifetime or because of emergency situations. There is a problem which is connected with providing the maximum performance of the AOCS in case of partial failures of their actuators (reaction wheels (RW), magnetorquer rods (MGTR), etc.). Thus, the purpose of this work is the development and synthesis of special algorithms for spacecraft angular motion control in the emergency situations which are connected with RWs partial failures and restrictions of onboard electricity consumption. The approach of synthesis of this control algorithms is based on using mobile control methods which allow to reserve RWs by MGTRs. There are different variants of control loops depending on MGTRs turning on combinations. There were proposed two types of control switching functions: time-periodic and switching by deviation. Also was proposed a methodology of controller synthesis using these switching functions. Using this methodology and computer simulation, it was shown the possibility of providing angular nadir orientation and stabilization of the spacecraft with maximum 1−1.5 deg error in case of time-periodic switching functions implementation. Switching by deviation allows to reduce onboard electricity consumption for 25−30 % comparing with using time-periodic switching. However, the accuracy of stabilization significantly lower in case of switching by deviation. Considering these estimates, the corresponding methodological recommendations were formulated for use switching functions depending on emergency