Search Results (10)

Due to the asymmetry of pass profiles, F-section steel is prone to defects such as overfilling, underfilling, and twisting during production, which significantly deteriorates the dimensional accuracy, mechanical properties, and surface quality of products. To mitigate the occurrence of such defects, this study established a thermo-mechanical coupled three-dimensional finite element model for the finishing rolling process of F-section steel using ABAQUS 2022 incorporating the actual operating conditions of the steel plant’s production line. By analyzing the stress–strain fields of each pass, it was found that the maximum deformation of the rolled piece is concentrated at the junctions of the inner leg with the flange, the inner leg with the web, and the outer leg with the web. Additionally, underfilling was observed at the legs and flanges of the pass in each rolling sequence. Based on these findings, an in-depth analysis was conducted on the effects of friction coefficient, tension configuration, rolling temperature, and web reduction on pass filling degree. Conditions of low friction, small reduction, and high temperature facilitate the smooth filling of metal in the leg cavity; in contrast, conditions of high friction, large reduction, and low temperature promote the filling of surface metal and an increase in spread. Maintaining a low-tension state is a common favorable condition for improving the pass filling degree of both the legs and the surface. When the friction coefficient is 0.2, tension is 0, rolling temperature is 1040 °C, and web reduction is 4 mm, the pass filling degrees of the inner and outer legs reach their maximum values of 99.88% and 99.16%, respectively. When the friction coefficient is 0.4, tension is 0, rolling temperature is 1010 °C, and web reduction is 4 mm, the pass filling degrees of the upper and lower surfaces are maximized, reaching 98.95% and 98.22%, respectively. These findings provide data support and theoretical guidance for addressing defects encountered in F-section steel production. Full article

In road engineering, road construction requires a large amount of natural aggregate; its substitution with recycled construction-solid-waste aggregate not only saves resources but also reduces the burden on the environment. The main components of construction solid waste are concrete blocks and brick slag; the breakability of the latter can affect the performance of mixed recycled aggregate, which hinders the use of construction solid waste in road engineering applications. To analyze the applicability of recycled construction-solid-waste aggregate containing brick slag aggregate in the subgrade layer, the effect of brick aggregate content on the CBR (California bearing ratio) and crushing value of mixed recycled aggregates was evaluated based on laboratory tests, and the field compaction quality of the recycled aggregates was analyzed. The results show that the 9.5–19 mm mixed recycled aggregate samples were crushed to a higher degree during the compaction process. A brick aggregate content less than 40% had little effect on the performance of mixed recycled construction-solid-waste aggregate. It is recommended to use a 22 t road roller for five passes (two weak vibrations + two strong vibrations + one weak vibration) at a speed of 3 km/h in the main compaction stage of the subgrade filling. Full article

Silicon-based photovoltaic (PV) cells are currently the most prevalent and cost-effective solution for solar energy generation. Given their dominance in the market and the extensive research dedicated to them, they are ideal targets for efficiency enhancement through innovative yet straightforward methods. This study explores the potential for improving the efficiency of these cells by managing the PV’s temperature using an infrared (IR) filter. The filter allows photons that can generate free electron–hole pairs to pass while reflecting those with wavelengths below the semiconductor bandgap, which otherwise contribute to performance degradation. Various techniques were applied, including I–V analysis, impedance measurements, and atmospheric scanning electron microscope (Air-SEM) observations, to examine the temperature’s impact on silicon PVs. By integrating IR filters, the results showed a 3% increase in the fill factor and a temperature reduction of approximately 10 degrees Celsius. These findings highlight the potential of this cooling approach for silicon cells, which can enhance the cell’s longevity and efficiency, paving the way for future industrial applications. Full article

Rough- and intermediate-rolled composite billets and finished clad rebars were cut using flying shears. The law of metal rheology and the mechanism of composite interface generation during clad rebar formation were then investigated using metallographic microscopy, electron backscatter diffraction, and scanning electron microscopy. The radial deformation trend of the clad rebars was greater than that of HRB400 rebars and “ears” were more likely to appear during the rolling process. The widths of the decarburization and composite zones and diffusion distances of each element decreased as the cumulative reduction rate increased. Furthermore, as deformation increased, the number of oxides on the composite interface significantly decreased, the proportion of recrystallized grains increased, and the grains became more refined. These changes led to increases in the bond and tensile strengths of the composite interface. According to the research above, the pass filling degree should be within 0.85–0.9 and the cumulative reduction rate should be over 80% when rolling clad rebars. Full article

The debate on the primary cross-curricular skills or fundamental competencies that must be improved in higher education has increased in the last few years. This is especially important in the new distant learning environments, which bring new challenges to the educational process. Econometric models have been designed to explain the students’ academic performance, which has been measured using their qualifications average, the number of failed subjects, passed subjects, and withdrawn subjects, and the level of progress, among other indicators, to try to understand the influence of variables such as students’ self-esteem, reading comprehension, English proficiency level, and performance in a mathematics-related subject on the students of accountant auditor program from Pontificia Universidad Católica de Valparaiso. Students were asked to fill in a questionnaire to collect data on the psychological and pedagogical variables, while the socio-economic and socio-demographic data were collected from the university. The results have shown that the most significant variables in the development level of this skill type are socio-demographic and socio-economic characteristics. Some of the psychological and pedagogical variables that have, to a lesser degree, some influences are self-regulation in the learning process and the self-perception of anxiety levels. Lastly, some recommendations to intervene in the students’ learning process are presented with the objective of achieving a higher level of development in this type of competences. Full article

The construction of undercrossing roads often has an adverse effect on the upper existing railway line, and can cause an uneven subsidence of the crossed section. In response to the influence of new road construction on the existing high-speed railway bridge, a highway passing under an existing high-speed railway bridge was taken as the research object. Based on the FLAC3D finite difference software, a computational model of new roads undercrossing a high-speed railway bridge was established to analyze the structural deformation response of a high-speed railway bridge. The results show that the excavation of foundation pits during new road construction causes an overall upward heaving of the soil layers between the pits, with a greater amount of heaving near the high-speed railway piers than that at other locations. Meanwhile, a degree of upward displacement of the high-speed railway bridge piers occurred. The filling of a road base structure generates an additional stress greater than the original consolidation pressure, inducing an overall subsidence of the soil layers between the pits. The final deformation during construction of new roads undercrossing the high-speed railway bridge shows that the displacement of adjacent piles is manifested as an overall settlement and as a horizontal displacement to the side of soil excavation. Full article

The aim of current in vitro research was to determine the effect of hydrothermal accelerated aging on the mechanical properties and wear of different commercial dental resin composites (RCs). In addition, the effect of expiration date of the composite prior its use was also evaluated. Five commercially available RCs were studied: Conventional RCs (Filtek Supreme XTE, G-aenial Posterior, Denfil, and >3y expired Supreme XTE), bulk-fill RC (Filtek Bulk Fill), and short fiber-reinforced RC (everX Posterior). Three-point flexural test was used for determination of ultimate flexural strength (n = 8). A vickers indenter was used for testing surface microhardness. A wear test was conducted with 15,000 chewing cycles using a dual-axis chewing simulator. Wear pattern was analyzed by a three-dimensional (3D) noncontact optical profilometer. Degree of C=C bond conversion of monomers was determined by FTIR-spectrometry. The specimens were either dry stored for 48 h (37 °C) or boiled (100 °C) for 16 h before testing. Scanning electron microscopy (SEM) was used to evaluate the microstructure of each material. Data were analyzed using ANOVA (p = 0.05). Hydrothermal aging had no significant effects on the surface wear and microhardness of tested RCs (p > 0.05). While flexural strength significantly decreased after aging (p < 0.05), except for G-aenial Posterior, which showed no differences. The lowest average wear depth was found for Filtek Bulk Fill (29 µm) (p < 0.05), while everX Posterior and Denfil showed the highest wear depth values (40, 39 µm) in both conditions. Passing the expiration date for 40 months did not affect the flexural strength and wear of tested RC. SEM demonstrated a significant number of small pits on Denfil’s surface after aging. It was concluded that the effect of accelerated aging may have caused certain weakening of the RC of some brands, whereas no effect was found with one brand of RC. Thus, the accelerated aging appeared to be more dependent on material and tested material property. Full article

Financial performance and financial equilibrium are two key aspects that should be monitored by any business manager interested in passing the test of time and overcoming unpredictable events such as economic crises. The organic link between financial performance and financial equilibrium has rarely been studied in the long run for companies listed on the stock market. The present article fills this gap in the literature by examining the degree to which financial performance influenced long-term financial equilibrium using data from 34 major companies publicly traded on the New York Stock Exchange and operating around the world in a wide variety of industries and sectors. The period of analysis spread over a decade (2007Q1–2020Q3) in order to cover two major crises that have marked the dawn of the third millennium and occurred relatively close to one another: the 2008 financial meltdown and the COVID-19 pandemic crisis. By means of panel data modelling, the study showed that the short-term and long-term financial equilibria of these public companies measured by current ratio, quick ratio and debt to equity ratio were significantly impacted by different financial performance indicators. The study addresses various implications of the empirical results and lays out avenues for future research. Full article

The novel microwave quasi-elliptic bandstop filter, which uses the initially uncoupled strip transmission lines, is considered in this work. The proposed filter is based on the reentrant structure, where the metallic body with a floating potential is asymmetric. Generally speaking, the internal and external dielectric fillings must have their unequal relative permittivities. As a result, additional symmetrical reflection zeros are reached at the lower and upper pass bands of the stop band leading to the quasi-elliptic function response that improves the filter selectivity. The general transverse electromagnetic (TEM) circuit model for the proposed filter in terms of a series connection of the multi-ports is presented and then used to predict the initial electrical and geometrical parameters. An experimental printed circuit prototype has been manufactured and evaluated to validate the design concept. The measured filter parameters correlate well with the simulation-derived ones and that increases the degree of freedom in the fabrication of microwave frequency selective components. Full article

Quantificationally describing weathering process and characterizing particle breakage are important in predicting the behavior of coarse-grained soil (e.g., weathered granite). In order to comprehensively understand the mechanical properties of weathered granite and provide references for reasonable evaluation of the engineering properties of subgrade filling in mountains, a series of tests—X-ray diffraction, sieving, heavy compaction, large-scale triaxial, and field compaction tests—were carried out in this research. Based on the weathering process parameters (m and r) of in-situ granite samples at two typical sections of weathered granite mountains obtained by using previous grading equation, the mathematical model of weathering process with depth was proposed and the variation laws of weathering process with depth were described. The results show that, with an increase in burying depth of mountain profile (h) of weathered granite, the geological year’s parameter (m) decrease by power function, but the geometric progression constants (r) increase by power function. Some factors affecting the particle breakage properties of compacted weathered granite were evaluated by using relative breakage (B_r). Especially, the effect of field compaction condition (such as thickness of loose paving layer and number of vibratory rolling passes) on particle breakage was analyzed creatively. Through laboratory and field tests, it was found that particle gradation, mineral composition, compaction effect, stress level, and number of rolling passes significantly affected the particle breakage characteristics of weathered granite. Furthermore, it is worthy of attention that the weathered granite in this paper showed obvious particle breakage characteristics under weak compaction effect and at low stress levels and over-compaction could result in a decrease in the degree of compaction of a certain thickness of loose paving layer filled with weathered granite. Findings in this research can provide a theoretical basis for evaluating the physical properties and mechanical behavior of weathered granite as subgrade fillings. Full article