Part Of Technology Research Articles

Photoelasticity of crystals with the scheelite structure: quantum mechanical calculations.

We report a complete set of elastic, piezooptic and photoelastic tensor constants of scheelite crystals CaMoO4, BaMoO4, BaWO4 and PbWO4 determined by density functional theory (DFT) calculations using the quantum chemical software package CRYSTAL17. The modulation parameter, i.e. the change in the crystal optical path normalized by thickness and mechanical stress, was calculated based on piezooptic and elastic compliance tensor constants. For the geometries of the most effective piezo-optic interactions, this parameter reaches rather large values (16-17) × 10-12 m2 N-1. Anisotropy of the photoelastic and acoustooptic effects is explored by means of indicative surfaces, considering the directions of light propagation and polarization, the direction of uniaxial compression or lattice distortion caused by the propagation of the acoustic wave. DFT calculations indicate BaWO4 and PbWO4 crystals as the most effective acousto-optic materials, predicting the figure of merit constant M2 ∼ 20 × 10-15 s3 kg-1. The methodology proposed combines the DFT calculations and photoelasticity caused by uniaxial compression of the crystal lattice, with particular emphasis on its anisotropy. It can be considered as part of optical engineering aimed at preliminary assessment of the photoelastic properties of crystal materials, thus assisting in their selection for synthesis and relevant applications.

Corrosion fatigue behavior of cast iron in simulated combustion product solutions of ammonia and methanol fuels

The clean fuels of ammonia and methanol are used to replace diesel in shipbuilding industry, but there exists corrosion risk for the engine parts in combustion products. The corrosion fatigue behavior of cylinder liners cast iron in simulated combustion product solutions of ammonia, methanol and diesel fuels were investigated. The corrosion rate and corrosion fatigue sensitivity in the three simulated solutions are ammonia fuel < diesel fuel < methanol fuel. The type B graphite causes more severe matrix corrosion than type A flake graphite, and the ternary phosphorus eutectic has no significant effect on corrosion. For ammonia fuel, fatigue damage is dominated by stress concentration induced by flake graphite and phosphorous eutectic. For methanol and diesel, fatigue damage is mainly dominated by corrosion process induced by flake graphite.

Narrative Review and Guide: State of the Art and Emerging Opportunities of Bioprinting in Tissue Regeneration and Medical Instrumentation.

Three-dimensional printing was introduced in the 1980s, though bioprinting started developing a few years later. Today, 3D bioprinting is making inroads in medical fields, including the production of biomedical supplies intended for internal use, such as biodegradable staples. Medical bioprinting enables versatility and flexibility on demand and is able to modify and individualize production using several established printing methods. A great selection of biomaterials and bioinks is available, including natural, synthetic, and mixed options; they are biocompatible and non-toxic. Many bioinks are biodegradable and they accommodate cells so upon implantation, they integrate within the new environment. Bioprinting is suitable for printing tissues using living or viable components, such as collagen scaffolding, cartilage components, and cells, and also for printing parts of structures, such as teeth, using artificial man-made materials that will become embedded in vivo. Bioprinting is an integral part of tissue engineering and regenerative medicine. The addition of newly developed smart biomaterials capable of incorporating dynamic changes in shape depending on the nature of stimuli led to the addition of the fourth dimension of time in the form of changing shape to the three static dimensions. Four-dimensional bioprinting is already making significant inroads in tissue engineering and regenerative medicine, including new ways to create dynamic tissues. Its future lies in constructing partial or whole organ generation.

Dynamic Stiffness Measurements of Road Pavements by Means of Impact Hammer in a Non-Resonant Configuration

The different sources of noise in a vehicle have long been known, and they include noise from the engine and other mechanical parts, aerodynamic noise, and rolling noise. More specifically, the latter concerns the interaction between the tire and the road surface, and so it is also known as Tire–Road Noise (TRN). One of the parameters influencing TRN is pavement stiffness. The empirical measurement of pavement stiffness, and in particular, its frequency spectrum (dynamic stiffness), is not easy to determine, and only in the last decade have studies emerged about this subject. In these works, two different instrumental chains are employed as follows: the impact hammer one and the dynamic exciter (shaker) one, which has established itself over time as a reference. The objective of this work is to develop a system for the dynamic stiffness measurements of road pavements using the impact hammer capable of producing a similar performance to the shaker while minimizing costs. During the work, a measurement aid device named Test Automation Device (TAD) was designed and implemented to increase the quality of the measurements. In line with the practical execution of the measurement, the analysis and the representation of the results were optimized to obtain results that adhere to the stiffness model proposed in the literature. In the present paper, the TAD, the measurement optimization work, the data analysis performed, and the proposed representation method will be described. Finally, we will present the results obtained and possible future perspectives.

EFFECTIVE REMOVAL OF EXHAUST VALVE DEPOSITS USING HIGHER ALCOHOL WITH GUTTER OIL IN SINGLE CYLINDER DIESEL ENGINE

This study examined a CIDI engine's exhaust valve. while excessive silt builds up on the exhaust system walls, especially while driving in an urban area, or when there are leaks in the vacuum or exhaust pipes, the valve has a tendency to become stuck. To determine the amount of deposition buildup on the exhaust valve, the engine was operated at a constant speed and load. Regarding this, to find out how three tested fuels—DF, DF90GO10, and DF70GO15Pn15—affect long-term endurance tests, a single-cylinder diesel engine was chosen and tested for 200 hours on each fuel sample. The results of the analysis showed that the exhaust valve's running surface was severely damaged. The results demonstrated that DF90WCO10 generated comparatively more deposits, especially on the exhaust valve. Additionally, the deposits formed on important engine parts, including intake/exhaust valves, when DF90WCO10 was employed had a completely different elements composition and structure than when DF and DF70GO15Pn15 were used. In contrast to both fuels, it was found that adding n-pentanol as a ternary mix produced less deposits. Overall, the inclusion rate of waste cooking oil showed that deposits were more common, especially on the valves, and that they were also more likely to be brittle and moist.

Structural and sewage characteristics of practical rural sewage collection systems in underdeveloped mountainous areas

Rural sewage collection systems are important parts of rural sewage engineering and the conditions in underdeveloped mountainous areas are not conducive to the construction and operation of conventional rural sewage collection systems. This study investigated and analyzed the practical rural sewage collection system in an underdeveloped mountainous area, and found that the diameters of the public rural sewers in the region were mostly DN300 and DN500, the relative depth was generally <0.3, and the frequency of siltation was 6 %. The concentration of chemical oxygen demand (COD), suspended solids (SS) and ammonia nitrogen in the rural sewage collection system was relatively high, and the pollution degree of the sewage could be reflected through the conductivity, turbidity, dissolved oxygen and oxidation reduction potential, so as to realize the rapid monitoring of the rural sewage characteristics and ensure the normal operation of the terminal treatment facilities. The removal capacity of COD and SS in sewers and ditches was different. It is suggested to strengthen the operation and maintenance of the collection system, optimize the design parameters of the collection system and evaluate the concentration of influent pollutants in the treatment facilities to improve the effectiveness of rural sewage treatment.

Osteogenic Differentiation of Adipose Tissue-Derived Mesenchymal Stem Cells on Composite Polymeric Scaffolds: A Review.

The mesenchymal stem cells (MSCs) are the fundamental part of bone tissue engineering for the emergence of reconstructive medicine. Bone tissue engineering has recently been considered a promising strategy for treating bone diseases and disorders. The technique needs a scaffold to provide an environment for cell attachment to maintain cell function and a rich source of stem cells combined with appropriate growth factors. MSCs can be isolated from adipose tissue (ASCs), bone marrow (BM-MSCs), or umbilical cord (UC-MSCs). In the present study, the potential of ASCs to stimulate bone formation in composite polymeric scaffolds was discussed and it showed that ASCs have osteogenic ability in vitro. The results also indicated that the ASCs have the potential for rapid growth, easier adipose tissue harvesting with fewer donor site complications and high proliferative capacity. The osteogenic differentiation capacity of ASCs varies due to the culture medium and the addition of factors that can change signaling pathways to increase bone differentiation. Furthermore, gene expression analysis has a significant impact on improving our understanding of the molecular pathways involved in ASCs and, thus, osteogenic differentiation. Adding some drugs, such as dexamethasone, to the biomaterial composite also increases the formation of osteocytes. Combining ASCs with scaffolds synthesized from natural and synthetic polymers seems to be an effective strategy for bone regeneration. Applying exopolysaccharides, such as schizophyllan, chitosan, gelatin, and alginate in composite scaffolds enhances the osteogenesis potential of ASCs in bone tissue regeneration.

Parametric optimization and sensitivity analysis of the integrated Taguchi-CRITIC-EDAS method to enhance the surface quality and tensile test behavior of 3D printed PLA and ABS parts.

3D printing is a popular and cost-effective method for producing lightweight engineering parts with enhanced characteristics and detailed prototypes. Nevertheless, the quality of the print can be diminished by the selection of improper parameter settings. This investigation explored the impact of printing factors on the tensile behavior of polylactic acid (PLA) and Acrylonitrile Butadiene Styrene (ABS) specimens. Experimental investigations were conducted to investigate the effects of infill pattern (grid, 2D, and 3D honeycomb), layer thickness (0.10, 0.15, and 0.20mm), infill percentage (30%, 50%, and 70%), and printing material on surface roughness and tensile characteristics where an irregular dependency was identified. In this scenario, the Evaluation based on Distance from Average Solution (EDAS) Method was integrated with Taguchi and Criteria Importance through Inter-criteria Correlation (CRITIC) to prevent inconsistent judgments with a minimal number of experiments. PLA printed parts with 2D honeycomb design, 0.10mm layer thickness, and 50% infill provided the optimum results within the declared boundary conditions. The robustness and sensitivity of the employed MCDM method were assessed through a comprehensive analysis. The weights determined through other techniques, including the equal method, principal component analysis (PCA), and Entropy, were subsequently compared to CRITIC. The results indicated a stronger correlation between PCA and CRITIC. Furthermore, the Pearson correlation matrix results indicated that EDAS was significantly correlated with the MOORA method in comparison to the other methods (ARAS, WASPAS, GRA, COPRAS, and CODAS).

Optimization of Tool Usage Range for Aircraft Engine Parts Machining Using Power Monitoring and K-means Algorithm

Optimization of Tool Usage Range for Aircraft Engine Parts Machining Using Power Monitoring and K-means Algorithm

Effect of operating conditions on mechanical properties of engine parts of quarry and metallurgical production machines

Effect of operating conditions on mechanical properties of engine parts of quarry and metallurgical production machines

Determining rational complex modifying and alloying additives to improve the mechanical characteristics of gray cast iron

The object of this study is the mechanical properties and parameters of the cast iron microstructure. The task to solve was to ensure high mechanical properties of cast iron for mechanical engineering part. To this end, a working hypothesis was put forward, which assumed the possibility of increasing mechanical properties by selecting complex additives based on modifiers and alloying ferroalloys. The effect of 4 groups of additives was investigated: group 1 – ferrochrome (FeCr025) and silicocalcium (SiCa-30), group 2 – ferrotitanium (FТі35) and ferroboral (FEB6), group 3 – ferrotitanium (FТі35) and ferrochrome (FeCr025), group 4 – ferroboral (FEB6) and silicocalcium (SiCa-30). They were introduced into the liquid metal in different percentages in the amount of 3 % of the mass of liquid cast iron. The following mechanical characteristics were selected: flexural strength (σ, MPa), tensile strength (UTS, MPa), deflection arrow (f, mm), hardness (HB), and whitening. It was determined that the strength characteristics of cast iron treated with ferroalloys of group 1 reach a maximum at about 40 % silicocalcium in the composition of the additive. The tensile strength of cast iron reaches about 320 MPa, the bending strength is about 710 MPa, the deflection arrow is 4.5 mm, and the hardness corresponds to the HB250 level. The fact of competition of hardness and other mechanical properties was established in the range of silicocalcium content in the modifier composition up to 40 %. Thus, it was established that it is the combination FeCr025+SiCa-30 with the ratio of components of 40:60, respectively, that is rational. The revealed regularities of changes in the amount of carbides, the size of graphite, and the amount of ferrite when using different additives allow us to explain patterns in the formation of mechanical properties of cast irons. Owing to this, it becomes possible to identify the mechanism of formation of properties, ensuring purposeful regulation of the quality of cast iron

Using a 3D system for control of parts during repairs

The development of scientifi c hypotheses and approaches to improving the strategy for maintenance and repair of agricultural machinery is one of the current areas in the agro-industrial complex, as it is of paramount importance in the technical support of the machine and tractor fl eet throughout the entire life cycle of machines. Research of methods and means of monitoring parts of automotive and tractor internal combustion engines during defect detection and repair with the development of an automated interactive system with software for monitoring these parameters, using the example of a connecting rod of the K-744 tractor engine.

A systematic review of deep learning applications in database query execution

Modern database management systems (DBMS), primarily designed as general-purpose systems, face the challenging task of efficiently handling data from diverse sources for both analytical services and online transactional processing (OLTP). The volume of data has grown significantly, with distributions ranging from linear to highly skewed, sometimes involving very slow changes or rapid, intensive updates. Recent research in this field has been significantly influenced by advances in machine learning (ML), particularly deep learning (DL), and these developments have led to the application of various ML algorithms to enhance the efficiency of different parts of the query execution engine. While previous research studies were mostly focused on identifying drawbacks to individual components, such as the query optimizer, there is a notable lack of studies examining the applicability and effectiveness of various machine learning approaches across multiple aspects of the query execution engine. This article aims to provide a systematic review of approaches that apply deep learning models at various levels within the query execution engine. We categorize these approaches into three groups based on how such models are applied: improving performance of index structures and consequently data manipulation algorithms, query optimization tasks, and externally controlling query optimizers through parameter tuning. Furthermore, we discuss the key challenges associated with implementing deep learning algorithms in DBMS.

DETERMINATION OF THE FREQUENCY OF NATURAL OSCILLATIONS OF THE ELEMENTS OF THE MECHANICAL SYSTEM OF THE MOTOR CARRIAGE ROLLING STOCK

Of particular importance is the problem of operational reliability and durability of locomotive power units (diesel engines), which equip a significant portion of freight and passenger rolling stock operating on non-electrified railway networks in Ukraine. This necessitates conducting computational and experimental studies of the stress-strain state of critical diesel engine parts and assemblies, among which the camshaft holds a special place. At the same time, such studies require, as one of the stages, measures aimed at developing an appropriate mathematical model that considers the peculiarities of formation of accumulating torque moments in the camshaft subsystem. Therefore, research aimed at developing a mathematical model that considers the design features of the mechanical system of a multi-cylinder locomotive diesel engine and allows obtaining simulation results of the camshaft stress state close to operational indicators should be considered relevant. The article highlights an approach to modeling torque accumulation in the diesel engine camshaft subsystem using a mathematical model developed by the authors, which takes into account the design features of the mechanical system of modern traction rolling stock. A structural-functional scheme of the locomotive power unit (LPU) mechanical system is presented, which was developed to study the interaction between its subsystems, the description of which is paramount among the series of stages in studying the loaded state of the LPU mechanical system elements. This scheme contains several subsystems, namely: the camshaft subsystem; cylinder modules; crankshaft; transmission mechanism; and auxiliary equipment. Its analysis allowed noting that loads in the camshaft subsystem are formed from the action of input torque and accumulation of series torque moments, which in turn include loads in the sections of valve gear cam mechanisms and high-pressure fuel pump drives. The presented results show the modeling of torque formation in the sections of intake and exhaust valves of the valve gear mechanism, fuel cams, and in the section of the camshaft drive gear. Generalized formulas are provided, which allowed obtaining arrays of torque moments in the sections of valve gear cam mechanisms and high-pressure fuel pump drives. It is noted that the formation of torque layering across cylinder modules occurs in accordance with the design features of the LPU mechanical system. Recommendations for further use of the obtained results are provided.

A novel recast layer in situ thinning method for film cooling holes in fast EDM drilling

As the main machining method of film cooling holes, fast EDM (electrical discharge machining) drilling has the defect that the thickness of a recast layer is difficult to control, which can severely affect the service life of a turbine blade on the aero engine parts. In order to reduce the thickness of a recast layer in fast EDM drilling while ensuring machining precision and efficiency, a novel recast layer in situ thinning method, which uses the precision-controlled discharge erosion and tiny energy layer-by-layer thinning strategy, is proposed. Moreover, the recast layer removal mechanism, as well as the influence of this method on fast EDM drilling are systemically investigated, thereby, the optimal combination of machining parameters with different electrode diameters of the in situ thinning method is obtained. Machining results show that with the proposed method, the maximum and average thickness of the recast layer can be well controlled within 2.5 μm and 2 μm, with the highest reduction rate of the recast layer reaching 85.39%, which greatly improves the machining quality of film cooling holes of a turbine blade.

Analysis of Contact Wheel and Tool Interaction in Belt Grinding

The belt grinding process is gaining an increasing importance in the industrial sector. Due to its high flexibility regarding the range of workpiece materials and its adaptability to various, even geometrically complex workpiece shapes and designs, belt grinding has a broad field of applications. Typical application cases for this process include sealing surfaces on housing and engine parts, the production of camshafts and crankshafts as well as cylinders with high concentricity accuracy. Despite the extensive application of belt grinding in the manufacturing industry, the respective interactions between grinding belt and contact wheel of the process have not been holistically investigated. Therefore, this article focuses on the deformation of the contact wheel as well as the deformation during the interaction between the contact wheel and the grinding belt. This includes the flattening of the tool under grinding normal force Fn and deformation under centrifugal forces. The empirical data is intended to provide insights into the relationship between tool deformation and elastic effective depth of cut ae.

Formation of Gas Turbine Engine Parts from Heat-Resistant Alloys by the Pressure Method with Torsion under Isothermal Conditions (Technology and Equipment)

Formation of Gas Turbine Engine Parts from Heat-Resistant Alloys by the Pressure Method with Torsion under Isothermal Conditions (Technology and Equipment)

Towards backward compatibility of ADRC: revisiting classical state-feedback control with integral compensator

In this paper, the problem of backward compatibility of active disturbance rejection control (ADRC) is investigated. The goal is to contextualize ADRC to deliver its interpretations from the established field of linear control systems. For this study, a control algorithm, denoted here as integral disturbance rejection control (IDRC), is considered that combines classical state-feedback control with an integral compensator. At first, an interpretation of ADRC is involved in terms of existing state-space control approaches. Next, a transition to the frequency domain is performed, which is justified as a significant part of practical control engineering is conducted in that domain. For assumed specific plant structures, both ADRC and IDRC are then holistically compared in terms of transfer function representation and frequency characteristics, as well as steady-state convergence conditions. Such a juxtaposition helps to highlight the similarities and differences of both approaches, whereas the utilized bandwidth parameterization is shown to bring the control system to the same form, thus indicating some interesting practical aspects. Finally, the theoretical results concerning both considered control structures are validated in a set of numerical simulations and experiments conducted on a laboratory hardware testbed.

Confined Truths and Cognitive Ecologies: When the Social Pursuit of Questioning Becomes Unreliable

AbstractThe capacity to distinguish reliable or rationally believable claims from a huge pool of views available within the public arena has never been as critical an issue as it is today. We live in a world full of bizarre, unwarranted beliefs and conspiracy theories, some of which may seem, at least on the face of it, quite well justified. Moreover, some of them may even turn out to be true. This poses a significant social-epistemological as well as practical problem. Here I propose to single out a group of beliefs known as confined truths. These are true beliefs belonging to a pathological question-answer system. The paper first provisionally articulates this idea and then makes the case for an ecological account of questioning and answering, thought of as social pursuits made possible by the capacity for problematization. The latter shall be characterized as part of cognitive engineering or niche construction. In the final part of the paper, various possible dysfunctionalities of the social/ecological pursuit of problematization are elicited and suitable examples thereof are briefly discussed.

Development and verification of material models in modeling of wave strain hardening and additive synthesis processes

BACKGROUND: The creation of competitive machine parts capable of withstanding standard and increased operational loads is an urgent task in mechanical engineering. Developing additive synthesis technologies together with strengthening technologies make it possible to create such products with high load-bearing capacity. However, to improve the efficiency of these technologies, it is necessary to create theoretical models of the processes taking place. The article presents the results of the first stage of creating complex theoretical models of the combined 3DMP process and wave strain hardening (WSH) required for designing technological processes for manufacturing engine parts and brake systems of automotive equipment. . AIMS: Creation and assessment of the adequacy of material models used in finite element modeling of additive synthesis processes with subsequent hardening. MATERIALS AND METHODS: Theoretical models of the material were created in the ANSYS software package, which allows for multidisciplinary calculations. The experimental data required for preparing the models were obtained by testing tensile samples manufactured using standardized methods. The hardness of materials was studied using a KB 30S automatic hardness tester. The adequacy of additive synthesis modeling was assessed based on the distribution of temperature fields. The adequacy of material models for the VDU process was assessed based on the sizes of individual plastic indentations and the distribution diagrams of the depth and degree of hardening in the surface layer. RESULTS: Theoretical models of the following materials were developed: steel, stainless steel, bronze alloy, titanium alloy, aluminum alloy. The theoretical data obtained from the modeling results have a high level of significance. The studies were conducted for various thermal (in the range from +20ºС to +800ºС) and deformation modes. Graphical results of theoretical and experimental studies allow us to obtain a qualitative assessment of the processes under study with the required accuracy. CONCLUSIONS: As a result of the assessment of the adequacy of the developed models, it was established that the discrepancy between the empirical and theoretical data does not exceed 7.4%. The obtained models of materials are statistically significant and can be correctly applied in further studies.