METADEX

This work presents a comparative study of the surface mechanical properties and tribological wear resistance of polymeric sliding materials. The authors focused on the application of polymeric materials in producing spare parts for vehicles that are still in use but for which original components are no longer manufactured or are disproportionately expensive compared to the vehicle’s market value. The subject of the study was frictional interactions between the timing chain and the sliding element. Three commercial materials were tested, designated: PA6G, PA6G+MoS2, PE 1000. A commercial lubricant PMO 5W40 Extreme 100 % (intended for vehicles without a particulate filters) was used. The coefficient of friction and wear were analyzed under dry friction and oil bath. The lowest coefficient of dry friction was obtained for the PA6 G, whereas PE 1000 exhibits the highest. Under oil lubrication, however, PE 1000 demonstrated the lowest coefficient of friction. Microscopic analysis of wear scars was performed. The extent of wear depends on the type of material used and the nature of the interaction (dry friction, oil-bath friction). Wear under dry friction was lower than under oil-bath conditions, possibly due to the influence of the Rebinder effect.

The rheological properties and stability of cement‐based materials determine the technological properties of concrete mixtures and significantly influence concrete properties. Polycarboxylate ether (PCE) and other plasticizing admixtures are widely used in construction practice to plasticize concrete mixtures. Experimental research on the rheological characteristics of cement mortar modified with PCE and air‐entraining admixtures (AIRs) was carried out with a rotation rheometer with coaxial cylinders and water bleeding tests. Herschel–Buckley or modified Bingham models were used to approximate experimental flow curves and assess rheological parameters such as yield stress, plastic viscosity, and shear thinning/thickening index. The rheological test was carried out at 5 and 90 min after mixing the cement mortar. The rheological test established that the modification of cement mortar by PCE in a dosage of 0.2% (in dry material) leads to a decrease in plastic viscosity of 25.0% with a reduction in water demand of 18% for the same workability. Modification of cement mortar by AIR in 0.3% dosage leads to a decrease in yield stress by 37.7% and a decrease in plastic viscosity by 35.4% compared to the control specimen without PCE. The combined modification by PCE and AIR admixtures shows a synergistic effect. It leads to a significant decrease in yield stress of cement mortar by 92.2% and a decrease in plastic viscosity to about 0  Pa·s. In addition, there is a significant coefficient of water bleeding reduction up to 0%, when additional water reduction was carried out in the mixture while maintaining the same workability. The cement mortar, with or without PCE and AIR, exhibited shear‐thinning characteristics for up to 90 min after mixing. The solid, liquid, and gas (air) phases’ influence yield stress and plastic viscosity in the analysis mixtures are presented in this paper. It has been established that a modified exponential Mooney dependency can be used to predict the yield stress and plastic viscosity of the modified cement mortar (both plasticized and air‐entrained).

The post-pandemic economic rebound has accelerated power demand. However, in a power generation system dominated thermal power plants, implementing the carbon peak strategy induces a contradiction between power supply and demand. This gives rise to the issues of the rational power allocation. To address this issue, based on enterprise micro-data, this study develops a model that allows power allocation across industrial enterprises to maximise their output. The ladder price is used for power redistribution seeking to ensure efficiency and fairness of the power allocation. Then, the utility theory is used to explore the effects of changes in the power use under different ladder prices. The paper relies on the unique dataset for Chinese enterprises. The results show that the proposed model renders power re-allocation among the enterprises (31 % of enterprises should reduce their power use, 32 % whereas should increase their power use by more than 50 %). By including the power cost in the model, significant differences were discovered between the optimal power use of three ladder price levels. This study provides recommendations for power allocation and the use of the ladder prices.

Sub-divisional errors (SDE) of linear encoders adversely affect mechanical equipment performance. Existing compensation methods often entail high costs or increased complexity. This research introduces an adaptive auto-compensation system for SDE reduction by minimize the factors of DC-offsets, deviation in amplitudes and phase disparities. The system has the advantage mitigate errors without significant additional expenses or complexity. Theoretical analysis of SDE and the experimental setup are discussed, alongside analytical data demonstrating the system's effectiveness.

The article proposes an assessment of the quantitative parameters of the crop using the analysis of mechanical vibrations. A demonstration of the investigation is shown for a situation where a support system in the field helps cucumbers grow vertically. The study was carried out by model- ing the yield of cucumbers. The greatest attention was paid to the frequencies of natural oscilla- tions. A developed numerical model of the support design is proposed and its natural oscillation frequencies are calculated using the finite element method (FEM). The results were confirmed by a physical experiment that actually simulates a numerical model.

This study investigates the mechanical properties of ceramic and photopolymer composites created using stereolithography (SLA) 3D printing. It aims to evaluate and compare the performance of two SLA materials: Liqcreate Composite-X and Phrozen's Water-Washable Resin, using dynamic flexural vibration tests to determine Young's modulus. Liqcreate Composite-X, a photopolymer resin with excellent mechanical properties, including high tensile and flexural strength, showed a first resonance frequency of 318 Hz and a Young's modulus of 0.93 x 1010 Pa. Phrozen's Water-Washable Resin, designed for easy post-processing, had a first resonance frequency of 210 Hz and a Young's modulus of 0.30 x 1010 Pa. In conclusion, Liqcreate Composite-X demonstrates superior mechanical performance, making it suitable for high-strength applications, while Phrozen's Water-Washable Resin, with lower mechanical properties, is more suited for less demanding uses. This study enhances the understanding and application of SLA-based ceramic composites in various engineering domains.

Low shear strength of historical masonry constructions is a matter of great concern, especially when these buildings are located in areas of high seismic risk. In recent years this issue has led to many investigations on the development of innovative reinforcement techniques. The application of cement mortar, commonly used in this type of reinforcements, involves a number of material incompatibility problems that could be overcome with the use of lime-based binder mortars. The present article presents the results of an experimental study on solid mock brick wallets reinforced with thin layers of mortar mixed with glass fibers; Diagonal compression tests have been carried out to determine the behaviour of the reinforced masonries, evaluated both in terms of shear strength and deformation capacity. Test results verify that the coating of mortar mixed with fibers is practically as effective as cement mortar regarding shear strength, while they improve deformation capacity.

In this paper, we show the approach to enhance the optical properties of the plasmonic nanowires from the perspectives of both field enhancement and tunability. Two different cases have been suggested for the consideration: the first one uses hollow-core metamaterial interface, while the other involves metallic nanowire metamaterial interface. It has been outlined, that the use of nanowire metamaterial interface allows for stretching the frequency range of surface wave existence from 500 THz (600 nm) to approximately 1000 THz (300 nm). Moreover, the nanowire metamaterial interface demonstrates better field confinement.

Recently, metal selective laser sintering (SLS) techniques have attracted lively interest as a promising technology, which offers a number of unique applications in manufacturing of metal parts with complex internal structure and geometry. However, unsatisfactory surface properties of as-manufactured SLS parts cause high cost of finish processing and restrict wider application of SLS products. The paper presents results of the study, which was taken to evaluate capability of laser processing to improve surface quality of SLS parts manufactured from powder maraging steel 1.2709 (X3NiCoMoTi 18-9-5). The properties of processed surfaces were assessed, and the main dependencies of the roughness, hardness, wear resistance, and phase composition on the main parameters of laser processing—scanning speed, laser power, and number of processing times—were determined. The roughness of surfaces was diminished up to ∼41%, the hardness was increased up to ∼88%, and the wear resistance was improved up to almost 4 times, as compared with surface of as-manufactured SLS part. The preliminary study has demonstrated that laser processing has considerable potential for improvement of surface conditions of steel additive manufactured parts.

Bringing clean and affordable energy to the market is one of the goals of sustainable development set by the United Nations. Thermal comfort is an important aspect of efficient energy use, which plays a crucial role in ensuring health and well-being in the built environment. The majority of energy in the building sector is consumed by microclimate systems that provide thermal comfort for occupants. Design strategies, such as passive and active solar and thermal mass utilisation, reduce heat demand. When aiming to optimise thermal comfort, a reasonable combination is important in order to increase the utilisation of clean renewable energy, while conserving other resources. In this paper, a method to generate design charts is proposed to assess early design options. It aids in the selection of design parameters, based on targeted seasonal thermal comfort as a function of a complex microclimate system. In order to explore the interaction between design variables, a TRNSYS simulation model was used. An analysis of comfort conditions (based on the EN ISO 7730 method) in building spaces was performed to assess functionality. The simulation model accounted for the thermal constant in building spaces, solar utilisation and gain through glass surfaces, solar collectors and active accumulation, energy transportation, and distribution efficiency. The presented case study results showed that the lack of space heating capacity (3/4 of the calculated quantity) could be compensated for by thermal mass and a solar thermal collector without compromising thermal comfort (the Percentage of people dissatisfied (PPD) was below 10%). The highest solar fraction (36%) was reached with the lowest fractions of space heating capacity (1/2 of the calculated quantity), due to increased demands, but this design option did not satisfy the thermal comfort conditions (PPD>17%).