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Phase Inversion Kinetics of Polymer Ionic Liquid Solutions in Relation with Membrane Morphology and Macrovoid Formation
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Field trips as gateways to out-of-school learning: perspectives and practices among preschool teachers*
No full textThis qualitative study addresses preschool teachers' beliefs and practices regarding field trips emphasizing their role as gateways to out-of-school learning. Engaging 20 preschool teachers, with observations of six during field trip activities, the research highlights the teachers' recognition of the substantial educational benefits that field trips offer in early childhood education. Participants emphasized that field trips provide valuable opportunities for learning, fostering several chances to think and act in diverse out-of-school settings. Despite their positive beliefs, practical implementations may be hindered by limited time, resources, and security concerns. The current study was concluded with recommendations aimed at reducing these barriers and enriching the benefits of out-of-school learning through field trips
Influence of conventional and supramolecular gellants on the rheological properties of JP-10 gel fuels
No full textThe effects of a conventional gellant and different types of supramolecular gellants on the rheological properties of JP-10 gel fuels are studied. Various concentrations of 1,2:5,6-di-O-isopropylidene-D-mannitol (IPM) and 1,2:5,6-di-O-cyclohexylidene-D-mannitol (CHM) supramolecular gellants are utilized for the preparation of JP-10 based gel fuels, and their rheological properties are compared with those of a conventional molecular gellant (Thixatrol ST (TST)) based gel fuel. Rheological characterization results show that all gellant types can create a gel structure within JP-10 fuel, including the TST-based gel fuel with a gellant concentration of 1.0 wt%, since their tans values are significantly lower than 1. The lowest tans values, hence the most significant solid-like behavior, were obtained for the TST-based gel fuels. However, the highest stiffness values were obtained for the CHM gellant-based JP-10 gel fuels, and the lowest stiffness values were obtained for the TST-based JP-10 gel fuels
Iron impurities drive Zn-rich phase formation in CdZnTe crystals
No full textThe yield of detector-grade CdZnTe (CZT) crystals remains limited by impurity segregation during traveling heater method (THM) growth. Here we investigate the role of unintentional Fe impurities in driving Zn-rich phase formation near the last-to-freeze region of CZT ingots. Infrared microscopy revealed the progressive evolution of opaque domains into needle-like structures. XPS analysis identified Zn enrichment on those opaque domains, and three-dimensional ToF-SIMS mapping demonstrated Fe accumulation within these domains. The co-localization of Fe and Zn phases suggests that Fe impurities facilitate heterogeneous nucleation and growth of Zn-rich inclusions. Such impurity-decorated phases act as recombination centers, compromising carrier transport and detector performance. These findings provide the first direct evidence linking Fe segregation to Zn-phase formation and highlight the importance of feedstock purification and growth optimization for improving CZT detector yield
Crystal plasticity modelling of time-dependent strain accumulation of stainless steel at room temperature
No full textThe mechanical integrity of structural materials under cyclic loading conditions is vital for various industries. 304L stainless steel parts often undergo cyclic loading and stress hold periods resulting in time-dependent strain accumulation. In this work, effects of mean stress and stress hold periods on strain ratcheting are examined using crystal plasticity modelling. A representative volume element (RVE) consisting of 200 grains is subjected to various loadings in the DAMASK framework, employing an isotropic-kinematic hardening model. Simulations are performed under three types of stress-controlled loading conditions: low-cycle fatigue (LCF), creep-fatigue interaction (CFI) with cyclic stress holds, and fatigue after long hold (FLH). Cyclic loadings ranged from symmetric to non-symmetric loading with high mean stress. The model is validated through comparison with experimental ratcheting data. For LCF loading, high mean stresses lead to pronounced ratcheting, while symmetric loading results in significant hardening in the early stages of cyclic loading. Cyclic hold periods in CFI loading amplify strain accumulation by enabling sustained slip activity during hold phases. Long hold periods of FLH loading induce significant strain accumulation which continues to increase with extended hold duration but saturates during following cyclic loading. Quantitative and qualitative comparisons with relevant experimental data demonstrate that the simulations effectively capture ratcheting trends under various loading conditions
Physical performance of flexible pavement system with and without a Portland-cement-concrete (PCC) slab for geofoam embankments
No full textPavement system design for geofoam block embankments requires special solution due to their low California Bearing Ratio (CBR) values. Hence, the use of a reinforced Portland-cement-concrete (PCC) slab atop the geofoam block assemblage is considered as a practical approach to increase the stiffness of the pavement. On the other hand, the PCC slab has some inherent disadvantages such as construction delay due to curing. A thicker pavement system without a PCC slab can be a potential alternative. Hence, the performance of flexible pavement systems with and without PCC slab were investigated using the accelerated pavement test (APT) program in detail. Two 3.75 m-wide and 10 m-long pavements were constructed in a test bed, and a controlled wheel load was applied using a 3-axle, 37.72-ton truck that traveled with an average speed of 16.5 km/h. The test was terminated, when rutting reached to steady deformation pattern at 1299 passes (3897 axle repetitions), which is equal to 20,264.4 equivalent single axle loads (ESAL). The test program also included plate load tests (PLT) and falling weight deflectometer (FWD) tests. The full-scale APT results showed that flexible pavement systems without a PCC slab for geofoam block embankments can be a viable option
Performance enhancement of Savonius hydrokinetic turbines: the role of twisted blade profiles
No full textSavonius Hydrokinetic Turbines (SHTs) are widely recognized for their simplicity, cost-effectiveness, and adaptability to slow flow conditions. However, conventional SHT designs face limitations, including low efficiency and significant torque fluctuations. The adoption of twisted/helical blade profiles has emerged as a potential solution to enhance turbine performance by reducing torque fluctuations and improving power output. A review of the existing literature reveals that studies focusing on blade twist angles are limited. To address this, the present study systematically investigates the impact of a broader range of blade twist angles (15-90 degrees) on SHT performance using computational fluid dynamics (CFD). Key performance metrics, including the torque coefficient (CT) and power coefficient (CP), were evaluated, and numerical accuracy was ensured through mesh independence and time step independence studies. The developed CFD model was validated against experimental results obtained from the literature to confirm the model's ability to capture flow dynamics. The results show that the SHT with a 45 degrees blade twist achieves a maximum CP of 0.252, an increase of 3.81 % over the conventional design, and reduces torque fluctuations by 9.38 %. Meanwhile, the 60 degrees blade twist demonstrates comparable CP values but achieves a further 7.28 % reduction in torque fluctuations compared to SHTs with a 45 degrees blade twist
Api-TRACE: A system for honey bee tracking in a constrained environment to study bee learning process and the effect of lithium on learning
No full textLearning is an adaptive behavior that improves the performance of bees in foraging, dance communication, predator avoidance, and other tasks. Any deficiencies in learning could be detrimental to the long-term survival of the bee colony. The passive avoidance task is a fundamental procedure for investigating learning. We introduce Api-TRACE, a computer vision-aided system for analyzing avoidance assays. Api-TRACE tracks individual bees from the video footage of the assay and detects the moments when they are exposed to a stimulus. The algorithm provides the stimulus exposure duration and learning profiles of each individual bee, enabling fast and detailed analysis of the results. The electric shock avoidance assay (ESAA) is one of the most common experimental methods for assessing learning. We designed an apparatus for the ESAA using readily available hardware and 3D-printed components. Honey bee behavioral analyses are easily performed and automated with Api-TRACE and our easy-to-build apparatus. Our system enables large-scale studies on how environmental factors, chemicals, and other agricultural inputs affect bee learning, providing data to help protect bee health and, therefore, agricultural productivity. We used Api-TRACE and an experimental apparatus to investigate the effect of lithium on bee learning success in passive avoidance and reversal learning paradigms through an ESAA. Lithium is a potential chemical for combating Varroa, a bee (Apis) parasite, and a well-known medication for treating bipolar disorder. It is known that lithium alters learning in humans and other animals. Before the experiment, we treated the bees with a sucrose solution with 0, 5, 25, and 125 mM LiCl ad libitum. Our results indicated a decrease in learning performance with increasing lithium doses in the reversal phase but not in the acquisition phase of the ESAA