Improvement of bearing strength of laminated composites by nanoclay and Z-pin reinforcement.

The bearing behavior of bolted composite joints is significantly poorer than that of their metallic counterparts. The objective of the present study was to examine ways of improving the bearing performance of bolted joints in carbon fibre reinforced epoxy laminates. Two strategies were examined, namely stiffening of the matrix using nanofillers and through- thickness reinforcement of the laminates using z- pins. The development of a nanoparticle reinforced matrix resin, and its performance in a composite loaded in bearing, was the focus of the first part of the study. A commercial nanoclay, I30E from Nanocor, was chosen as the reinforcement since the nanoclay particles are modified with long alkyl chain amines which improves dispersion in the epoxy resin. The c onditions for preparing nanocomposites based on the nanoclay were examined for two epoxy resin systems , DGEBA and TGDDM. Significant improvements in the elastic modulus were obtained , with a 20% increase being recorded w ith 8.4 phr nanoclay content in the DGEBA resin and a 50% increase with 20 phr nanoclay content in the TGDDM system. Carbon fibre reinforced laminates w ere prepared from nanoclay reinforced TGGDM matrix resin, using a vacuum assisted prepregging process. The bearing strength and stiffness of the laminated composites was improved by 7% and 15% respectively but the strain to failure was reduced. The addition of nanoclay to the matrix resin was found to change the failure mode. Enhancement of the bearing performance of laminates by through-thickness reinforcement (z-pins) was examined as the second strategy trialed in this thesis. The bearing strength, stiffness and energy to failure of carbon fibre laminates was found to increase progressively with increasing volume content of z-pins , with increases of 10%, 10% and 16%, respectively , being achieved at a z-pin volume content of 4%. No significant change in strength, stiffness or failure energy was observed when the z-pin diameter was changed from 0.28 to 0.51 mm at the same volume content

RESEARCH ON EXERCISES TO DEVELOP PROFESSIONAL PHYSICAL STRENGTH FOR MALE STUDENTS OF VOVINAM TEAM AT HO CHI MINH CITY UNIVERSITY OF SPORTS, VIETNAM

On the basis of synthesizing and analyzing the opinions and knowledge of experts, building exercises to develop professional fitness for male Vovinam students in the HCM City University of Sports team. The research has synthesized 27 exercises to develop strength of mind, including 7 supplementary exercises, 5 arm exercises, 9 leg exercises and 6 continuous exercises to be included in the training program in the 2020-2021 school year. The results after 1 year of the experiment showed that the exercises to develop mental strength for male Vovinam students increased.  Article visualizations

TEACHERS' EXPERIENCE WITH USING TEACHING TECHNIQUES TO PROMOTE CHILDREN'S MOTIVATION AND ENGAGEMENT IN A NON-FORMAL ENGLISH EDUCATIONAL SETTING

In this increasing globalized and internationalized world, teaching techniques reported to be effective in one country are more frequently adopted for use in other countries. However, these techniques may not yield similar effects across educational contexts. This article reports a study that (i) explored teaching techniques that teachers in commercial English Language Centres (CELC) in Southern Vietnam used to promote children’s learning motivation and engagement, (ii) examined why they adopted these teaching techniques and (iii) identified challenges associated with the use of these techniques. Content analysis of 21 semi-structured interviews with teachers from four CELC showed that teachers were frequently using games, picture flashcards, videos, miming, role play and storytelling for the mentioned purpose. The study also revealed several challenges for the use of these techniques associated with (i) teachers considering teaching in CELC as an extra job, (ii) educational norms and values ingrained in stakeholders’ perception, and (iii) practicality issues involved in their teaching. The article highlights that teachers’ adoption of a teaching technique was driven by their beliefs about its effectiveness, about expectations of important stakeholders, and about contextual factors that may affect the use of the technique

TEACHERS’ EXPERIENCE WITH USING TEACHING TECHNIQUES TO PROMOTE CHILDREN’S MOTIVATION AND ENGAGEMENT IN A NON-FORMAL ENGLISH EDUCATIONAL SETTING

In this increasing globalized and internationalized world, teaching techniques reported to be effective in one country are more frequently adopted for use in other countries. However, these techniques may not yield similar effects across educational contexts. This article reports a study that (i) explored teaching techniques that teachers in commercial English Language Centres (CELC) in Southern Vietnam used to promote children’s learning motivation and engagement, (ii) examined why they adopted these teaching techniques and (iii) identified challenges associated with the use of these techniques. Content analysis of 21 semi-structured interviews with teachers from four CELC showed that teachers were frequently using games, picture flashcards, videos, miming, role play and storytelling for the mentioned purpose. The study also revealed several challenges for the use of these techniques associated with (i) teachers considering teaching in CELC as an extra job, (ii) educational norms and values ingrained in stakeholders’ perception, and (iii) practicality issues involved in their teaching. The article highlights that teachers’ adoption of a teaching technique was driven by their beliefs about its effectiveness, about expectations of important stakeholders, and about contextual factors that may affect the use of the technique.  Article visualizations

Application of the Fenton-like agent based on magnetic iron and manganese oxide in the degradation process of paracetamol in water

A Fenton-like catalyst MnO2-Fe3O4/SiO2 is synthesized via a two-step approach. The prepared composite has a mesoporous structure and a high surface area of 190 m2/g. The XRD pattern describes a specific peak of Fe3O4 magnetite on the baseline of amorphous silica. Furthermore, the FTIR spectra not only show the height assigned to stretching vibrations of Si-O-Si bonds, and Fe–O–Fe connections but also exhibit a small peak that matches the Mn–O bonds. SEM images exhibit a porous network structure of the composites with some holes among 30 – 100 nm clusters. The activity of the catalyst is determined in a paracetamol degradation as a Fenton oxidation. The paracetamol removal efficiency is at 85.6% with the optimal condition as initial pH 3, catalyst dosage of 0.15 g/50mL and H2O2 concentration of 1 mL/50 mL. In addition, the catalyst can be reused at least 5 times with a low reduction of the catalytic activity from 85.6% to 80.8%. The experiment results open a direction that has high efficiency in the treatment process of excess paracetamol in pharmacy wastewater

Effect of natural auxin from portulaca grandiflora hook and Ipomoea batatas (L.) Poir on the formation adventitious roots in vitro of Plumbago zeylanica L.

Plumbago zeylanica L. is a traditional herbal that has been reported to treat on skin diseases. Furthermore, some researchers have found plumbagin extracted from roots of this species can prevent cancer cell development. In current study, stems of Plumbago zeylanica L. were cultured on MS medium with BA 1.0 mg/L and IAA (0.01-0.15 mg/L) or NAA (0.1-0.15 mg/L). After 8-week cultured, stems were transferred to MS medium with extracted from stems of Portulaca grandiflora Hook (2-10 ml/L) or extracted from stems of Ipomoea batatas (L.) Poir. The results showed that, the appropriate medium for shoot formation was in MS with BA and IAA 0.1 mg/L or NAA 0.1 mg/L. The adventitious roots in vitro were formatted in MS medium supplied with extracted from stems Portulaca grandiflora Hook or from stems of Ipomoea batatas (L.) Poir 6 ml/L. Simultaneously, after 8-week cultured, the adventitious roots were collected and plumbagin qualitative were analyzed with pure plumbagin of Sigma. As the results, plumbagin presents in adventitious roots cultured

A simple, effective, green method for regioselective 3-acylation of unprotected indoles

A fast and green method is developed for regioselective acylation of indoles in the 3-position without the need for protection of the NH position. The method is based on Friedel-Crafts acylation using acid anhydrides. The method has been optimized, and Y(OTf)3 in catalytic amounts is found to be the best catalyst together with the commercially available ionic liquid [BMI]BF4 (1-butyl-3-methylimidazolium tetrafluoro-borate) as solvent. The reaction is completed in a very short time using monomode microwave irradiation. The catalyst can be reused up to four times without significant loss of activity. A range of substituted indoles are investigated as substrates, and thirteen new compounds have been synthesized

Measuring citizen's satisfaction when using E-Government online public services: Lessons from Vietnam

This study aims to evaluate the factors affecting the satisfaction of citizen when using online public services through data collected from direct surveys of people. Research results show that Quality of online public services, Citizen's awareness, Privacy and security, Trust and accessibility affect citizen's satisfaction when using online public services. Based on these results, the study also gives some discussion and governance implications for researchers as well as policy-makers in improving citizen's satisfaction as well as attracting more users for online public services in Vietnam context

Rice farmers' perception and determinants of climate change adaptation measures: a case study in Vietnam

The study used Mann Kendall's and Sen's slope tests to elicit rice farmers' perceptions of climate change due to extreme weather occurrences and compared them to hydro-meteorological data. According to the findings, temperatures increased by 0.4 degrees during the last 35 years. While rainfall has increased, the pattern has been difficult to discern. The test results corroborated farmers' perceptions of increased heat spells, but rainfall frequency and intensity vary and are difficult to anticipate. Three adaptation strategies are frequently employed in the Nong Cong district: adjusting the seasonal calendar to alter transplanting and harvesting timing; increasing fertiliser and pesticide application; and changing variety to short-time kinds. Due to the interdependence of adaption techniques, the study used a multivariate probit model. The regression findings indicated that several relevant variables influence the decision to apply adaption methods. Numerous policy ideas for enhancing adaptation to climate change can be derived from the results of this study. District governments must improve their capacity to forecast weekly weather and train how to adapt production to climate change.Le Phuong Nam (Viet Nam National University of Agriculture (VNUA)), Nguyen Dang Que (National Academy of Public Administration (NAPA)), Nguyen Van Song (Viet Nam National University of Agriculture (VNUA)), Tran Thi Hoang Mai (Vinh University (VU)), Nguyen Thi Minh Phuong (Vinh University (VU)), Nguyen Thi Xuan Huong (Viet Nam National University of Forestry (VNUF)), Nguyen Cong Tiep (Viet Nam National University of Agriculture (VNUA)), Tran Ba Uan (Dien Bien Technical Economic College)Includes bibliographical references