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Since the beginning of the COVID-19 outbreak in Spring 2020, universities around the world have quickly adopted online teaching as an emergency measure. Informed by activity theory, the present qualitative case study aims to better understand the nature of the rapid institutional transition and its impact on academics' pedagogical experiences during this period. A multiple set of qualitative data was collected in a national university in South Korea that rapidly made the online transition, following government directives in February 2020. This article provides useful accounts of the changes that occurred in interconnected teaching activity systems at the university while adopting online teaching, highlighting the complex factors underpinning individual academics' experiences. The sudden shift in institutional teaching activities and conditions created a range of contradictions that were experienced as dilemmas by academics, the main subject of the activity systems. The results demonstrate that two groups of university faculty, separately identified as novice online teachers and expert online teachers, faced different dilemmas and challenges. An essential lesson learned from this analysis is the need for a more holistic, realistic, and sensitive approach to emergency teaching scenarios that may enable educational institutions to better respond to such emergencies in the future.

While much is discussed of the challenges that educators and their institutions have been facing during COVID-19, there is little reported about how students have been coping with the challenges. In this short piece, we present preliminary data on university students' perceptions of online learning and teaching during the pandemic. Our findings from a student course satisfaction survey, conducted in two universities during the 2020 summer term (June through August), reveal that students have been more resilient than is often assumed. In light of these findings as well as the reflections of authors in a previous issue of "Distance Education," we will discuss some important implications for distance education scholarship.

The power graph of a finite group is the graph whose vertex set is the group, two distinct elements being adjacent if one is a power of the other. The enhanced power graph of a finite group is the graph whose vertex set consists of all elements of the group, in which two vertices are adjacent if they generate a cyclic subgroup. In this paper, we give a complete description of finite groups with enhanced power graphs admitting a perfect code. In addition, we describe all groups in the following two classes of finite groups: the class of groups with power graphs admitting a total perfect code, and the class of groups with enhanced power graphs admitting a total perfect code. Furthermore, we characterize several families of finite groups with power graphs admitting a perfect code, and several other families of finite groups with power graphs which do not admit perfect codes.

It is difficult to determine the main microscopic factors controlling reservoir quality due to the strong microscopic heterogeneity of tight sandstone reservoirs, which also makes it difficult to distinguish dominant reservoirs. At the same time, there are fewer experimental samples available, and data collected from relevant research are thus worth paying attention to. In this study, based on the experimental results of high-pressure mercury injection of 25 rock samples from Chang 6 reservoir in the Wuqi area, Lasso dimensionality reduction was used to reduce the dimensionality of 14 characteristic parameters to 6, which characterize the microscopic pore structure, while a combination of different kernel functions was used to construct the multi-kernel function of the multi-kernel model to be determined. A multi-kernel support vector machine (MK-SVM) model was established for unsupervised learning of microscopic pore structure characteristic parameters that affect reservoir quality. By optimizing the hyperparameters of the model and obtaining the optimal decision function, the tight sandstone reservoirs were classified into classes I, II and III, and the classification results were verified. The results show that the accuracy of the proposed reservoir classification method is as high as 86%, which can effectively reduce the time loss and save labor costs. It provides an effective method for the comprehensive evaluation of tight sandstone reservoirs. [ABSTRACT FROM AUTHOR]

Since the beginning of the COVID-19 outbreak in Spring 2020, universities around the world have quickly adopted online teaching as an emergency measure. Informed by activity theory, the present qualitative case study aims to better understand the nature of the rapid institutional transition and its impact on academics' pedagogical experiences during this period. A multiple set of qualitative data was collected in a national university in South Korea that rapidly made the online transition, following government directives in February 2020. This article provides useful accounts of the changes that occurred in interconnected teaching activity systems at the university while adopting online teaching, highlighting the complex factors underpinning individual academics' experiences. The sudden shift in institutional teaching activities and conditions created a range of contradictions that were experienced as dilemmas by academics, the main subject of the activity systems. The results demonstrate that two groups of university faculty, separately identified as novice online teachers and expert online teachers, faced different dilemmas and challenges. An essential lesson learned from this analysis is the need for a more holistic, realistic, and sensitive approach to emergency teaching scenarios that may enable educational institutions to better respond to such emergencies in the future. [ABSTRACT FROM AUTHOR]