CURRENT SITUATION INVESTIGATION AND COUNTERMEASURE RESEARCH OF STUDENTS’ ONLINE LEARNING DURING THE EPIDEMIC PERIOD: A CASE STUDY OF ZHEJIANG PROVINCE, CHINA

A survey of 538 students in 6 primary and secondary schools and colleges in Hangzhou, Ningbo and Jiaxing, Zhejiang Province, China has found: (1) Chinese schools suspended offline teaching in February-May, 2020 due to the novel coronavirus outbreak. All students studied online at home and 93% of them studied 2-7 hours a day online on average. Among all of them, students in primary schools spent least time online and college students spent most time. The science courses in middle school accounted for 46% of total studied courses, English accounted for 17%, and university major courses accounted for 21%. Furthermore, students spent 1-7 hours per day on watching TV and playing video games, and 1-4 hours on homework to review lessons. (2) After the end of the epidemic in China, more than 51% of students are still studying online for 1-4 hours a day, the epidemic situation has made online teaching in China popularized 10-20 years in advance, and students' online learning has become normal. (3) 32% of students like to study online, and they think that online class has the following advantages: numerous high-quality courseware that can be learned at any time anywhere, easy to communicate, save the time to go and from school, high learning efficiency, and online tutoring class charges are cheaper than offline ones. (4) The proportion of students who feel neutral and dislike the online study account for 56% and 9% respectively; they think online learning has the following problems: the online courses provided by schools are boring but they were forced to learn, and also have to clock in, which cannot bring the advantages of online education; the price of online tutoring course is very high; communication is not as easy as offline; the submission and correction of homework is more complicated than offline, and the learning effect is not good; students’ eyesight is decreased rapidly; online examination is not allowed. (5) 21% of parents are very supportive of online teaching, 62% of parents think it is acceptable, 17% of parents do not support or oppose, the reason for opposition is that their children do not have enough self-control, online learning effect is more difficult to ensure, eyesight loss is faster and so on. Therefore, the following countermeasures are put forward: (1) students are ought to be guided to pay attention to online learning; (2) to strengthen the reform of teaching methods, improve courseware quality, control teaching time, and leave students time for notes to ensure recess; (3) reduce video and broadcast courses, advocate live courses, strengthen the communication and interaction between teachers and students; (4) reform to simplify the online homework submission method, explore a reasonable online examination model; (5) strengthens the home-school cooperation, encourages the supervision function of parents, and strengthens the online teaching results. Article visualizations

Scaling BDD-based timed verification with simulation reduction

Digitization is a technique that has been widely used in real-time model checking. With the assumption of digital clocks, symbolic model checking techniques (like those based on BDDs) can be applied for real-time systems. The problem of model checking real-time systems based on digitization is that the number of tick transitions increases rapidly with the increment of clock upper bounds. In this paper, we propose to improve BDD-based verification for real-time systems using simulation reduction. We show that simulation reduction allows us to verify timed automata with large clock upper bounds and to converge faster to the fixpoint. The presented approach is applied to reachability and LTL verification for real-time systems. Finally, we compare our approach with existing tools such as Rabbit, Uppaal, and CTAV and show that our approach outperforms them and achieves a significant speedup.No Full Tex

Expression of immune-response genes in lepidopteran host is suppressed by venom from an endoparasitoid, Pteromalus puparum

<p>Abstract</p> <p>Background</p> <p>The relationships between parasitoids and their insect hosts have attracted attention at two levels. First, the basic biology of host-parasitoid interactions is of fundamental interest. Second, parasitoids are widely used as biological control agents in sustainable agricultural programs. Females of the gregarious endoparasitoid <it>Pteromalus puparum </it>(Hymenoptera: Pteromalidae) inject venom along with eggs into their hosts. <it>P. puparum </it>does not inject polydnaviruses during oviposition. For this reason, <it>P. puparum </it>and its pupal host, the small white butterfly <it>Pieris rapae </it>(Lepidoptera: Pieridae), comprise an excellent model system for studying the influence of an endoparasitoid venom on the biology of the pupal host. <it>P. puparum </it>venom suppresses the immunity of its host, although the suppressive mechanisms are not fully understood. In this study, we tested our hypothesis that <it>P. puparum </it>venom influences host gene expression in the two main immunity-conferring tissues, hemocytes and fat body.</p> <p>Results</p> <p>At 1 h post-venom injection, we recorded significant decreases in transcript levels of 217 EST clones (revealing 113 genes identified <it>in silico</it>, including 62 unknown contigs) derived from forward subtractive libraries of host hemocytes and in transcript levels of 288 EST clones (221 genes identified <it>in silico</it>, including 123 unknown contigs) from libraries of host fat body. These genes are related to insect immune response, cytoskeleton, cell cycle and apoptosis, metabolism, transport, stress response and transcriptional and translational regulation. We verified the reliability of the suppression subtractive hybridization (SSH) data with semi-quantitative RT-PCR analysis of a set of randomly selected genes. This analysis showed that most of the selected genes were down-regulated after venom injection.</p> <p>Conclusions</p> <p>Our findings support our hypothesis that <it>P. puparum </it>venom influences gene expression in host hemocytes and fat body. Specifically, the venom treatments led to reductions in expression of a large number of genes. Many of the down-regulated genes act in immunity, although others act in non-immune areas of host biology. We conclude that the actions of venom on host gene expression influence immunity as well as other aspects of host biology in ways that benefit the development and emergence of the next generation of parasitoids.</p