An explicit secular equation of Rayleigh waves propagating along an obliquely cut surface in a directional fiber-reinforced composite

The propagation of Rayleigh waves along an obliquely cut surface in a directional fiber-reinforced composite was studied recently by Ohyoshi [Ohyoshi T. Compos Sci Technol  2000; 60; 2191-6]. The author derived the secular equation of the wave, however, it is still implicit. In this paper, a fully explicit secular equation of the wave is obtained by using the method of first integrals. From it we immediately arrive at the secular equation of the wave for the case when the cut surface is parallel to the fiber direction. This secular equation is much more simple than the ones obtained recently by Cerv [Cerv J. Int Rev Mech Eng (IREME) 2008; 2; 762-72] and Cerv et al. [Cerv J et al. Composite Structures 2010; 92; 568-77]. Based on the obtained secular equations some approximate formulas for the velocity of Rayleigh waves are established and it is shown that they are good approximations. The explicit secular equations and the approximate formulas for the velocity derived in this paper are useful  for analyzing the effect of the material properties and the  orientation of the  fiber direction on the Rayleigh wave velocity, especially they are  powerful tools for solving the inverse problem: determining the  material parameters from the measured values of the velocity

Peer Interaction by English as a Foreign Language (EFL) Students in a Decision Making Task

Tasks are frequently used in English as a Foreign Language (EFL) classes. The sociocultural theory considers tasks to mediate learners through language. However, how a specific task can embrace such a claim remains an issue to explore. This study was set out to address the questions of how a decision making task stimulated interaction among peers and how it mediated knowledge construction. Thirty EFL junior college students forming fifteen pairs participated in the study. The recorded videos of their decision-making task performance were used for data analysis. The findings reveal that cumulative talk was present in all pairs’ recordings. While exploratory talk was not generated as frequently as cumulative talk, it tended to conduce to more language learning and knowledge construction. The findings also indicate that with the same task, peers interacted in different patterns and mediated each other by providing immediate assistance with English vocabulary and ideas

Linking Ethical Leadership to Employee Creative Performace: The Role of Leader-Member Exchange and Work Engagement

Purpose: The purpose of this research is to investigate the mediating role of leader-member exchange (LMX) and work engagement in the relationship between ethical leadership and creative performance.   Theoretical framework: The study is based on the theoretical foundation that ethical leadership positively influences creative performance. It further posits that this relationship is mediated by both leader-member exchange (LMX) and work engagement.   Design/Methodology/Approach: Data for this study was collected from a Vietnamese service firm, with a sample comprising 78 leaders and 354 employees. The collected data was analyzed using structural equation modeling (SEM) to examine the proposed relationships.   Findings: The findings of the study indicate a significant and positive correlation between ethical leadership and creative performance. Additionally, the study reveals that ethical leadership exerts an influence on both leader-member exchange (LMX) and work engagement, which subsequently enhance employees' demonstration of creativity in their work.   Research, practical & social implications: This research sheds light on the mediating mechanisms through which ethical leadership impacts creative performance. The findings highlight the importance of fostering positive leader-member relationships and promoting work engagement in order to enhance employees' creative behaviors. Practically, the study suggests that organizations should prioritize the development of ethical leadership qualities to foster a creative work environment. Moreover, the research contributes to the broader social implications by emphasizing the significance of ethical leadership in promoting creativity and innovation within organizations.   Originality/Value: This research contributes to the existing literature by examining the mediating role of leader-member exchange and work engagement in the relationship between ethical leadership and creative performance. The study provides valuable insights into the mechanisms through which ethical leaders can enhance creativity in the workplace. The findings of this research contribute to the understanding of the importance of ethical leadership and its impact on organizational outcomes, thereby adding to the originality and value of the study

Stakeholder Perceptions towards the Quality of Coursera MOOCs Blended Learning in Vietnam: A Qualitative Study

Coursera MOOCs blended learning (CMBL) has been implemented at a Vietnamese Higher Education Institute (HEI) since the Fall 2019 semester. Our case study, which shows how Coursera MOOCs and the traditional classroom may work together, is unique in the context of Vietnamese higher education. In this case, students must complete the courses and earn certifications through Coursera MOOCs to qualify for the HEI’s offline final examinations. Meanwhile, students also engage in offline mentoring sessions with their classmates and lecturers (mentors). By employing the Service Quality (SERVQUAL) and 3P models, the research was conducted to explore how key factors might influence the quality of CMBL. This research conducted semi-structured interviews and employed thematic analysis with thirty interview participants, including ten administrators, eleven lecturers, three curriculum developers, and six students across four campuses of the HEI. We found that assessment, learning outcomes, learning content, Coursera staff’s responsiveness, offline mentors’ responsiveness and assurance, interaction, and student satisfaction might have considerably significant relationships with the quality of CMBL. On the other hand, Coursera instructors and offline mentors’ reliability have insignificant relationships with the quality of CMBL. This study has both theoretical and practical implications for universities and academics. Regarding the theoretical implications, this qualitative study provides critical criteria to measure the quality of the CMBL. Regarding the practical implications, it provides implications for curriculum development, teaching and learning, and assessment to improve the quality of CMBL. However, the authors could not travel across Vietnam to conduct face-to-face interviews in 2021 due to the COVID-19 pandemic. Therefore, twenty-eight online interviews were conducted via Microsoft Teams and two email interviews. A downside of an online interview is that personal qualities that are critical to a study may be amended during the interview, forcing the researcher to rely on the participant’s words. Additionally, unlike a face-to-face interview, an email interview lacks simultaneous communication between the interviewer and the interviewee. Keywords: Higher Education Institution (HEI), blended MOOCs, Coursera MOOCs Blended Learning (CMBL), Coursera MOOCs, offline mentoring, sustainable developmen

Cytotoxic constituents from Vietnamese Pterospermum truncatolobatum Gagnep.

32-35Pterospermum truncatolobatum Gagnep. has long been used as a traditional medicine in Vietnam. Its crude extract showed cytotoxicity against human epidermal carcinoma (KB) cell lines. However, its chemical constituent and biological activity remains unknown. In the course of our investigation on the Vietnamese medicinal plants, four compounds, taraxerol (1), betulonic acid (2), -sitosterol (3) and eicosanoic acid (4) were purified from methanolic extract of P. truncatolobatum by silica gel column chromatography. Their structures were determined by spectral (Mass spectrometry and nuclear magnetic resonance) analysis and by comparison with the literature reports. Of which, betulonic acid (2) showed moderate cytotoxicity against all four cancer cell lines, KB, MCF7 (human breast carcinoma), LU (human lung carcinoma), and HepG2 (hepatocellular carcinoma)

How Digital Natives Learn and Thrive in the Digital Age: Evidence from an Emerging Economy

As a generation of ‘digital natives,’ secondary students who were born from 2002 to 2010 have various approaches to acquiring digital knowledge. Digital literacy and resilience are crucial for them to navigate the digital world as much as the real world; however, these remain under-researched subjects, especially in developing countries. In Vietnam, the education system has put considerable effort into teaching students these skills to promote quality education as part of the United Nations-defined Sustainable Development Goal 4 (SDG4). This issue has proven especially salient amid the COVID−19 pandemic lockdowns, which had obliged most schools to switch to online forms of teaching. This study, which utilizes a dataset of 1061 Vietnamese students taken from the United Nations Educational, Scientific, and Cultural Organization (UNESCO)’s “Digital Kids Asia Pacific (DKAP)” project, employs Bayesian statistics to explore the relationship between the students’ background and their digital abilities. Results show that economic status and parents’ level of education are positively correlated with digital literacy. Students from urban schools have only a slightly higher level of digital literacy than their rural counterparts, suggesting that school location may not be a defining explanatory element in the variation of digital literacy and resilience among Vietnamese students. Students’ digital literacy and, especially resilience, also have associations with their gender. Moreover, as students are digitally literate, they are more likely to be digitally resilient. Following SDG4, i.e., Quality Education, it is advisable for schools, and especially parents, to seriously invest in creating a safe, educational environment to enhance digital literacy among students

The impacts of lead recycling activities to human health and environment in Dong Mai craft village, Hung Yen, Vietnam

Lead (Pb) recycling activities in Dong Mai village, Chi Dao commune, Van Lam district, Hung Yen province have been taking place for more than 30 years. The development of recycling activities contributed to the improvement of the local economics. However, along with economic development, Dong Mai craft village is facing to serious pollution. Soil, air and water polluted by lead (Pb) caused food containing Pb at higher levels than allowed limit from 20 to 40 times. The pollution had the bad effect on human health in this village. The investigation results showed that 100 % of employee who participated on melting lead and 63.5 % of local children were poisoned by Pb. Besides, the local people got diseases relating to skin, eyes, etc. This situation requires the provincial authorities to find immediate solutions to reduce the impacts of Pb recycling activities to environment and human.Hoạt động tái chế chì của thôn Đông Mai, xã Chỉ Đạo, huyện Văn Lâm, tỉnh Hưng Yên đã diễn ra hơn 30 năm nay. Sự phát triển của nghề tái chế đã làm góp phần cải thiện kinh tế của địa phương. Tuy nhiên, cùng với sự phát triển kinh tế, làng nghề Đông Mai đã và đang đối mặt với ô nhiễm môi trường nghiêm trọng. Môi trường đất, nước không khí bị ô nhiễm bởi chì (Pb) dẫn đến thực phẩm nhiễm chì ở hàm lượng cao hơn mức cho phép từ 20- 40 lần. Sự ô nhiễm gây ra những ảnh hưởng xấu tới sức khỏe của người dân làng nghề. Kết quả điều tra cho thấy 100% công nhân tham gia nấu chì và 63.5% trẻ em địa phương bị nhiễm độc chì. Bên cạnh đó, người dân địa phương còn bị mắc của các loại bệnh ngoài da, bệnh về mắt, …. Tình trạng này đòi hỏi chính quyền địa phương phải tìm ra giải pháp khẩn cấp để giảm thiểu tác động của những hoạt động tái chế chì tới môi trường và con người

Evaluation Of Allelopathic Potential Of Cissus sicyoides Against the Growth Of Echinochloa Crus-Galli And Some Tested Plants

Many plant species in nature exert significant allelopathic potential as part of the defense mechanism system, many among their secondary metabolites (allelochemicals), including mineral constituents, which are responsible for the suppression of weeds and enhancing crop yield when directly incorporated into paddy fields. Cissus sicyoides is considered a high-potential allelopathic plant because of its invasion in nature and detected allelochemicals from the plant parts in some studies. The objective of this research was to exploit the allelopathic properties of C.sicyoides against paddy weeds and some indicator plants under laboratory bioassays and greenhouse conditions. The results demonstrated that C. sicyoides had significant inhibition on E. crus-galli, tested plants, and other paddy weeds. In the laboratory conditions, the extracts from C.sicyoides leaves inhibited the growth of Echinochloa crus-galli by 54.3%. The powders from C.sicyoides leaves inhibited the emergence of paddy weeds by approximately 100.0%. In the greenhouse conditions, the powders from C.sicyoides leaves by adding after 3 and 13 days inhibited the growth of E. crus-galli and the emergence of paddy weeds by 64.4%. Remarkably, negligible harmful effects on rice growth were observed. The findings of the study may provide useful information for the exploitation of this plant species to effectively control weeds in the rice fields for sustainable agriculture production

Evaluation of awake prone positioning effectiveness in moderate to severe COVID-19

Evidence mainly from high income countries suggests that lying in the prone position may be beneficial in patients with COVID-19 even if they are not receiving invasive ventilation. Studies indicate that increased duration of prone position may be associated with improved outcomes, but achieving this requires additional staff time and resources. Our study aims to support prolonged (≥ 8hours/day) awake prone positioning in patients with moderate to severe COVID-19 disease in Vietnam. We use a specialist team to support prone positioning of patients and wearable devices to assist monitoring vital signs and prone position and an electronic data registry to capture routine clinical data

Safety and efficacy of fluoxetine on functional outcome after acute stroke (AFFINITY): a randomised, double-blind, placebo-controlled trial

Background Trials of fluoxetine for recovery after stroke report conflicting results. The Assessment oF FluoxetINe In sTroke recoverY (AFFINITY) trial aimed to show if daily oral fluoxetine for 6 months after stroke improves functional outcome in an ethnically diverse population. Methods AFFINITY was a randomised, parallel-group, double-blind, placebo-controlled trial done in 43 hospital stroke units in Australia (n=29), New Zealand (four), and Vietnam (ten). Eligible patients were adults (aged ≥18 years) with a clinical diagnosis of acute stroke in the previous 2–15 days, brain imaging consistent with ischaemic or haemorrhagic stroke, and a persisting neurological deficit that produced a modified Rankin Scale (mRS) score of 1 or more. Patients were randomly assigned 1:1 via a web-based system using a minimisation algorithm to once daily, oral fluoxetine 20 mg capsules or matching placebo for 6 months. Patients, carers, investigators, and outcome assessors were masked to the treatment allocation. The primary outcome was functional status, measured by the mRS, at 6 months. The primary analysis was an ordinal logistic regression of the mRS at 6 months, adjusted for minimisation variables. Primary and safety analyses were done according to the patient's treatment allocation. The trial is registered with the Australian New Zealand Clinical Trials Registry, ACTRN12611000774921. Findings Between Jan 11, 2013, and June 30, 2019, 1280 patients were recruited in Australia (n=532), New Zealand (n=42), and Vietnam (n=706), of whom 642 were randomly assigned to fluoxetine and 638 were randomly assigned to placebo. Mean duration of trial treatment was 167 days (SD 48·1). At 6 months, mRS data were available in 624 (97%) patients in the fluoxetine group and 632 (99%) in the placebo group. The distribution of mRS categories was similar in the fluoxetine and placebo groups (adjusted common odds ratio 0·94, 95% CI 0·76–1·15; p=0·53). Compared with patients in the placebo group, patients in the fluoxetine group had more falls (20 [3%] vs seven [1%]; p=0·018), bone fractures (19 [3%] vs six [1%]; p=0·014), and epileptic seizures (ten [2%] vs two [<1%]; p=0·038) at 6 months. Interpretation Oral fluoxetine 20 mg daily for 6 months after acute stroke did not improve functional outcome and increased the risk of falls, bone fractures, and epileptic seizures. These results do not support the use of fluoxetine to improve functional outcome after stroke