The aim of the research was to optimize the effectiveness of student learning based on experimental work in chemistry classes in Slovenian primary schools. To obtain evidence about how experimental ...work is implemented during regular chemistry classes, experimental work was videotaped during 19 units of chemistry lessons at 12 Slovenian primary schools from the pool of randomly selected schools. Altogether 332 eight-grade students were involved in the investigation, with an average age of 14.2 years. Students were videotaped during chemistry lessons, and their worksheets were collected afterward. The 12 chemistry teachers, who conducted lessons in these schools, were interviewed before the lessons; their teaching plans were also collected. The collected data was analyzed using qualitative methods. The results indicate that many teachers in Slovenian primary schools are not fully aware of the potential of experimental work integrated into chemistry lessons for the development of students' experimental competence. Further research of the value of different kinds of training to support teachers for the use of experimental work in chemistry teaching is needed.
Nanoplastics (<1000 nm), raise concerns regarding their potential effects and associated risks. These particles exhibit unique characteristics including diverse buoyancy and colloid behaviour, with ...additional challenges on processing and detection, and on their interaction with aquatic organisms. Consequently, laboratory experiments on nanoplastics can at times lack appropriate experimental controls or quality criteria and may not generate relevant data for conducting reliable risk assessments or capturing environmental realism. This study aimed to review and discuss the methodological challenges involved in assessing the effects of nanoplastics on aquatic organisms and provides recommendations for optimising experimental approaches. We discuss the major challenges and best practices when experimenting with nanoplastics, the current methods for detection of nanoplastics in internal tissues and assess translocation, and the pressing needs for nanoplastics risk assessment. We recommend the development of a rigorous quality criteria framework to advise researchers when designing experimental work, and to ensure suitability of data for risk assessment.
Display omitted
•Nanoplastics pose potential risks due to their unique characteristics.•Nanoplastics processing, detection, and colloid behaviour add experimental challenges.•Lack of quality criteria and appropriate controls limit suitable data for risk assessment.•There is a lack of a quality criteria framework to guide researchers.•We highlight methodological challenges and provide recommendations.
•A novel experimental data set for numerical model validation.•Experimental data uncertainty analysis.•Wide range of the experimental data for validation of the mathematical model dedicated for ...modelling particulate flows.•Validation of DEM approach against experimental data.
Display omitted
Significant effort has been exerted on developing fast and reliable numerical models for modeling particulate flow; this is challenging owing to the complexity of such flows. To achieve this, reliable and high-quality experimental data are required for model development and validation. This study presents the design of a novel test-rig that allows the visualization and measurement of particle flow patterns during the collision of two particle streams. Valuable data sets are provided for the validation of numerical models dedicated to granular flows. The experimental work was conducted for three particle distributions and different configurations of the test rig setup. Additionally, a standard discrete element method for modeling particle transport was applied to the test-rig configuration and the effects of the material spring constant on the predicated flow patterns are investigated. An additional purpose of these simulations was also to collect necessary data for further collision model validation, developed based on a reduced-order technique.
•Thermal performance of lightweight blocks incorporating textile waste was analysed.•Different percentages of textile waste were added to the cementitious mixtures.•Higher thermal stability is ...obtained for higher textile waste percentage.•Higher thermal resistance value is achieved for higher textile waste percentages.•The obtained results revealed the suitability for thermal insulation purposes.
Textile industry is one of the most important sectors of the global economy, but at the same rate as production, millions of tons of textile waste (TW) are generated worldwide, causing negative impacts on the environment. To mitigate CO2 emissions and TW landfilled, its reuse and recycling are considered promising in fulfilling the circular economy principles. Furthermore, its valorization as building materials components may be a contribution towards sustainable construction. Studies already developed in this domain demonstrate that more research work is needed so the suitability of TW as building insulation materials can be assessed. In this context, it is intended with the research work here presented to propose cement-based lightweight blocks (LWB) incorporating TW and discuss their application as insulation materials purposes.
The studied TW was fabric leftovers from the textile industry, constituted by 70 % wool, 25% viscose, and 5% elastane. TW percentages of 6.25%, 8.16%, and 8.75% were considered in the cement mixture composition of LWB1, LWB2 and LWB3, respectively, and their influence on the LWB thermal performance was analyzed. The LWB thermal performance characterization was carried out by analyzing heat fluxes, inner surface temperatures, thermal transmission coefficients, and infrared thermal imaging. The obtained results revealed their suitability for thermal insulation applications. Values of 0.34 m2°C/W, 0.61 m2°C/W, and 0.67 m2°C/W were estimated for the thermal resistance of LWB1, LWB2 and LWB3, respectively, achieving higher thermal stability when higher percentage of TW is incorporated in the cementitious mixture composition. A comparison of the LWB with currently available building materials, such as simple masonry walls and insulating concrete forms, was also performed showing promising results for the proposed textile waste-based materials.
Various industrial applications, including rotating and reciprocating machinery, depend on gears. Therefore, a sudden breakdown of the gears could result in substantial financial losses. Due to this, ...extensive studies have focused on defect diagnosis. Both machinery maintenance decisions and preventive maintenance techniques have been aided by vibration analysis. An increased vibration is a warning sign that a machine is about to malfunction or break down. Observing and evaluating the machine's vibration pulses can identify the nature and extent of the issue and, as a result, predict when the machine will fail. The vibration signal may identify gearbox defects early on and diagnose its problems. Hence, this research highlights the main crucial steps that can be followed for defect detection and identification, mainly based on vibration analysis methodologies. It provides an application methodology for various signal-processing techniques used successfully in rotating machinery. The study briefly explains the applied methods to diagnose problems that depend on hybrid artificial intelligence approaches, such as fuzzy sets, expert systems, and neural networks. The key aspect of the present paper is the parametric comparison of the performance of various artificial Intelligence systems used in rotary machines. As such, the paper reports a comprehensive study of the gearbox defect diagnosis and provides useful analysis, which would be helpful for the usage of such techniques in the engineering industry.
•The experimental validation and numerical applications were reviewed for moisture separator modeling.•The advantage and disadvantage of Eulerian-Eulerian and Lagrangian-Eulerian methods were ...compared.•An optimization design of moisture separator was performed by numerical modeling.
The applications of numerical simulation can provide detailed information about the droplet behaviors that is useful to study the performance of the system of Moisture Separator (MS). In this study, the simulation results and new findings of MS modeling are reviewed under the framework of both Eulerian-Eulerian (EE) and Lagrangian-Eulerian (LE) methods. In addition, the experimental work on MS performance since the 1980s is carefully examined. First, we analyze the experimental test of the working performance of the most commonly used MS. The flow pattern, structure design, separation efficiency and pressure drop by the experiment work are summarized. Second, we provide the simulation findings of flow patterns, like droplet generation, droplet collision and droplet-wall impaction under the framework of the LE method. Third, we systematically show the simulation results of the droplet and the steam velocity field, void fraction distribution, separation efficiency and pressure drop. We find that the EE method is efficient to study a relative large scale of MS, such as swirl-vane separator. For the LE method, we find that the entire life of a droplet is easily to be tracked. Further, we verify that the accuracy of simulated separation efficiency of a mini-type cyclone can be increased by using the droplet collision model. Moreover, we introduce the simulation result of a separation system, which proves that numerical methods could be applied to optimize the design of MS for commercial market. Finally, the study concludes with the future directions needed to develop both EE and LE methods for MS modeling.
U-bar loop connections have traditionally been used to establish structural continuity between wall-elements in precast concrete buildings. However, recent advancements have introduced the looped ...wire rope connection as a viable alternative due to its installation benefits. While the strength of the connection itself has been investigated thoroughly, the anchoring of the looped wire ropes inside the wall-element remains under-investigated.
This paper presents an experimental study including 66 experiments focusing on the anchorage and associated failure mechanisms of looped wire ropes. The experimental study investigates various design parameters such as the embedment length of the looped wire rope, the u-bar in the concrete element, concrete compressive strength, the comparison between an embedded bolt and looped wire rope, and the size of the test specimen, which represents the distance between wire ropes in a wall element and the wall thickness.
On the basis of the experimental evidence, a mechanical model is developed based on the principles of rigid plastic modelling. This model key design parameters into account and provides an understanding of the anchorage of looped wire ropes. The model, backed by a detailed analysis of failure mechanisms using digital image correlation, provides an improvement in predicting the anchorage capacity of looped wire ropes in concrete wall elements.
•Comprehensive experimental programme on the anchorage capacity of looped wire ropes.•Analysis of failure mechanisms with Digital Image Correlation.•The failure begins as T-shape crack development followed by reinforcement activation.•A rigid plastic model is presented and shows good agreement with failure mechanisms.
In this study, natural heat convection caused by centric and vertically eccentric long horizontal cylinders under the influence of vibration is experimentally investigated. The internal wall of the ...annulus is heated and kept at a constant heat flux, while the outside wall is cooled and maintained at a constant temperature. The vibration frequency impacts the annular convection heat transfer process and the effects of the Rayleigh number, heat flow, and eccentricity. This work employed a moderate, laminar-ranging Rayleigh number from (5×104 to 6.48×106), while the eccentricity range is varied from (-0.667, 0, and+0.667). The investigation is carried out at five different frequencies (0, 2, 5, 10, 15, and 20 Hz); therefore, it was decided to compare the case under the same circumstances in both the absence and presence of vibration. The present results' verification worked exceptionally well in concordance with previous studies. When heat fluxes are considered, the study demonstrates that the temperature difference along the gap (radial difference) between the two cylinders significantly decreases for negative as opposed to positive eccentricities for each Rayleigh number. For different eccentricities, it was discovered that the temperature difference decreased as the Rayleigh number increased. Along with these reductions, the temperature difference was promoted as the vibration frequency increased, which is significant at (20 Hz) within the range considered for controlling parameters. It was also observed that the decrease in temperature difference is higher for the negative eccentric position than for the centric and positive positions. At vertical positive eccentricity at a low Rayleigh number, the gain in vibrational average Nusselt number caused by applying vibration had a minimum value of 22.50601475%, While at the higher value of the Rayleigh number, the maximum increase in negative vertical eccentricity was 86.66933125%. However, the gain in the average Nusselt number depends on the position of the heated inner cylinder, the Rayleigh number, and the vibrational frequency.
PDF
