Sichuan Institute of Building Research

In the context of the rise of online education, learners have generated large-scale learning behavior records in open education platforms providing sufficient material for educational data mining. In this paper, based on edX open education dataset, 11 features representing learners' learning status are downscaled by principal component analysis technique, learners are clustered based on learning status and using the proposed K-means clustering algorithm, and the number of clusters is determined by the aggregation coefficient method. The experimental results show that the aggregation coefficient peaks when the number of clusters is 4. Therefore, the optimal teaching state is categorized into 4 types of spaces, which are general learning space, negative learning space, interactive learning space, and active learning space. Finally, on the basis of the clustering results, corresponding teaching enhancement strategies are proposed for the strengths and weaknesses of the groups. The method proposed in the article can identify and analyze students' learning status in real time and accurately, improve teachers' mastery of students' classroom performance, and provide a new research idea and technical reserve for the development of open education.

The keys to implementing the child-friendly concept lies in enhancing community livability, particularly by advocating for low-carbon travel. Currently, communities are still insufficiently considering children’s needs, with many activity spaces and facility layouts failing to meet the requirements for low-carbon travel. Using Shuangliu District in Chengdu as a case study, this research employed both random forest and logistic regression models to examine the effects of travel distance and road environment on children’s travel mode choices. The findings reveal that travel distance holds the highest relative importance in influencing children’s selection of neighborhood activity travel modes, accounting for 22.48%. Additionally, a nonlinear relationship and threshold effect exist between travel distance and certain travel modes, with approximately 3 km serving as the critical intersection point for walking, cycling, and car. Furthermore, feature such as road smoothness, the availability of sidewalks, and traffic density significantly enhance the probability of children choosing to walk to child-friendly facilities. This research seeks to bridge the gap by examining how facility distribution influences travel mode choice and identifying key feature that help urban planners design child-friendly, sustainable urban environments.

In this study, a microbially induced calcium carbonate precipitation (MICP) technique has been proposed as an alternative to traditional cementitious strategy for filling rock fractures to improve rock strength and reduce permeability. We investigate calcium carbonate (CaCO3) precipitation characteristics and flow channel evolution within artificial fractures treated with MICP to gain insights into the fundamental mechanisms underlying microbially induced mineralization in rock fractures with varying initial apertures and joint roughness coefficients. CaCO3 precipitation occurs within small-scale artificial fractures, which are formed by a transparent polymethyl methacrylate top plate and either a smooth or rough acrylonitrile butadiene styrene base plate. The evolution behavior of the flow channels is captured—both temporally and spatially—by using a high-resolution camera employing time-lapse photography, and the spatial distribution of CaCO3 precipitation throughout the base plate is accurately quantified by using a three-dimensional laser scanner. The results reveal that in the smooth fracture, the yield and distribution ranges of the biomineralization products increase as the aperture increases and gradually stabilize at the critical aperture. Two critical aperture intervals (referred to A and B) are identified under a constant staged injection strategy: 1.4–1.5 and 1.1–1.2 mm, respectively. The rate and efficiency of CaCO3 precipitation experience significant changes when the fracture aperture is outside the aforementioned two intervals. Within the rough fracture, the convex–concave structure simulating rough fluctuations of the fracture surface distributed on the base plate significantly facilitate the precipitation of CaCO3 on its surface. An interesting observation is that the flocs in the suspension transport stage can be impeded by gas bubbles; therefore, the location of CaCO3 precipitation could be controlled to some extent by changing the location of the gas bubbles incorporated during precipitation, indicating the potential of gas bubbles as nucleation sites to promote CaCO3 crystallization. The transport and settling of flocs, as well as the formation, clogging, and unclogging of flow channels, are explained at the microscopic level.