Stereotypical Images of STEM Professionals and STEM Career Interests in Chinese Elementary School Students

This study investigated stereotypical images of STEM professions and STEM career interest in Chinese elementary school students. The relationships between stereotypical images of STEM professionals and STEM career interests were also determined. Data for this study was gathered from two elementary schools in China, forming a convenience sample of 318 students enrolled from 3rd to 6th grade. Quantitative data of stereotypes about STEM professionals’ social skills, positive images of STEM professionals, views on STEM implications for society, and STEM career interests were gathered by a questionnaire with Likert scale. Follow-up structured interviews were performed with 12 participants. Elementary school students had strong stereotypes about STEM professionals’ social skills, slightly deep positive image of STEM professionals, and very positive views on STEM implications for society. However, their STEM career interests were not very high. Besides, elementary school students’ stereotypes about STEM professionals’ social skills have minor negative effects on their STEM career interests. Their positive image of STEM professionals and views on STEM implications for society have significant correlation with their STEM career interests

Experimental Study on the Damage Mechanism of Reinforced Concrete Beams Based on Acoustic Emission Technique

The purpose of this paper is to investigate the developmental process of internal damage in prestressed concrete beams under static loading conditions. We conducted static loading tests on two prestressed reinforced concrete beams and one ordinary reinforced concrete beam. Acoustic emission (AE) technology was employed to dynamically monitor the entire process of the test beams simultaneously. The energy and ring count AE characteristic parameters were studied, and the frequency domain characteristics of acoustic emission signals from three test beams were analyzed. The actual failure process of the test beams was compared with the AE characteristic parameters and the waveform frequency distribution. Furthermore, the corresponding relationships between the actual failure process and the AE characteristic parameters were analyzed. Additionally, the frequency distribution of waveforms was examined. The obtained data, including deflection, strain, and prestress variation within the beams, were combined with theoretical calculations to explore the damage development law of simply supported reinforced concrete beams during the entire failure process. Comparative studies revealed a strong correlation between the actual failure processes of the three test beams and the AE characteristic parameters as well as the waveform frequency distribution. The strain variation trend of the ordinary reinforced concrete beam closely matched the AE signal characteristics, with the critical load often occurring at around 40% of the ultimate load. The strain and deflection variations of the prestressed reinforced concrete beams exhibited a robust correspondence with the AE signal characteristics. The critical load typically manifested at approximately 80% of the ultimate load. The ultimate load of the prestressed reinforced concrete beams decreased by approximately 20% under cyclic loading conditions compared to hierarchical loading

Research on quantitative evaluation of morphological characteristic of coarse aggregates

©, 2015, Tongji University. All right reserved. To obtain the most reasonable quantitative index of the morphological characteristic of coarse aggregates, Los Angeles (LA) abrasion tester without steel balls was employed to change the shape of aggregate particles with size of 4.75-9.5 mm, 9.5-13.2 mm, 13.2-16 mm, 16-19 mm, respectively. Abrasion cycles were 0, 600, and 1200. Through the self-developed morphology analysis system of coarse aggregate (MASCA), the values of 6 quantitative indexes (aspect, convexity ratio, roughness, angularity parameter, roundness, fractal dimension) were calculated. Their sensitivity to the change of particle morphology was compared using the method of binary variance. The results show that fractal dimension is the optimal quantitative index to evaluate the morphological characteristic of coarse aggregates. At last, AC-16, SAC-16, SMA-16 mixture specimens were fabricated with the different morphological characteristics of coarse aggregates obtained by abrasion, respectively. The rutting and penetration shear tests were conducted for validation, and test results indicate that the fractal dimension has a good correlation with high temperature performance of asphalt mixture

The Effect of Morphological Characteristic of Coarse Aggregates Measured with Fractal Dimension on Asphalt Mixture’s High-Temperature Performance

The morphological properties of coarse aggregates, such as shape, angularity, and surface texture, have a great influence on the mechanical performance of asphalt mixtures. This study aims to investigate the effect of coarse aggregate morphological properties on the high-temperature performance of asphalt mixtures. A modified Los Angeles (LA) abrasion test was employed to produce aggregates with various morphological properties by applying abrasion cycles of 0, 200, 400, 600, 800, 1000, and 1200 on crushed angular aggregates. Based on a laboratory-developed Morphology Analysis System for Coarse Aggregates (MASCA), the morphological properties of the coarse aggregate particles were quantified using the index of fractal dimension. The high-temperature performances of the dense-graded asphalt mixture (AC-16), gap-graded stone asphalt mixture (SAC-16), and stone mastic asphalt (SMA-16) mixtures containing aggregates with different fractal dimensions were evaluated through the dynamic stability (DS) test and the penetration shear test in laboratory. Good linear correlations between the fractal dimension and high-temperature indexes were obtained for all three types of mixtures. Moreover, the results also indicated that higher coarse aggregate angularity leads to stronger high-temperature shear resistance of asphalt mixtures