Glassy carbon electrode modified with ex-in-situ gold film – A simple and effective working electrode for As(III) determination by using differential pulse anodic stripping voltammetry

An easy-to-make new working electrode, an ex-in-situ AuF/GCE, was developed for trace As(III) detection. A gold film electrode prepared ex-situ was re-plated in-situ during each arsenic deposition step by adding Au(III) into the analyte solution. The factors affecting arsenic stripping response, namely, gold film preparation conditions, electrolyte concentration, electrode cleaning potential, cleaning time, deposition potential, and deposition time, were investigated. Compared with the traditional gold film electrodes prepared ex-situ, the new electrode has better precision and linearity of arsenic differential pulse anodic stripping voltammetry responses. For a deposition time of 90 s at –200 mV, the new electrode exhibits a sensitivity, a limit of detection (3-Sigma), a limit of quantitation of 0.103 μA·L·μg–1, 0.4 μg·L–1, and 1.3 μg·L–1, respectively

Research on Aeroelasticity Phenomenon in Aeronautical Engineering

Aeroelasticity phenomena arise when structural deformations induce changes on aerodynamic forces due to airplane structures that are not completely rigid. The additional aerodynamic forces cause an increase in the structural deformations, which leads to greater aerodynamic forces in a feedback process. These interactions may become smaller until reaching a condition of equilibrium or may diverge catastrophically if resonance occurs. Flutter is an instability aeroelasticity phenomenon which is the most difficult to predict. In this chapter, a numerical method and an experimental method were realized to predict aeroelastic response and characteristic parameters of a wing structure. The numerical method was firstly developed based on the interaction between computational fluid dynamic and computational structural dynamic methods using a coupling system, fluid–solid interaction (FSI), in the ANSYS software. Then, an experiment was set up in suitable conditions to study aeroelasticity characteristics with the goal of comparing the numerical results with the experimental results on the same wing structure at low speed. After that, a developed code based on immersed boundary method (IBM) was realized to predict aeroelasticity response and characteristic parameters of the wing structure. AGARD 445.6 wing model was chosen for this developed procedure at high speed. Obtained results were compared to other numerical and experimental results

FACTORS INFLUENCING THE INTENTION TO USE MOBILE MONEY: A STUDY IN BUSINESSES IN HANOI, VIETNAM

Abstract The government's and people's expectations for the successful implementation of this activity are significant, but the scientific basis for its implementation remains limited. This study, the first of its kind in Vietnam since the aforementioned decision, aims to clarify the factors influencing consumer usage of Mobile Money, focusing on businesses in Hanoi, Vietnam. Mobile Money, a form of mobile wallet not linked to bank accounts, represents a new transaction method in Vietnam, catering to consumers' reduced use of cash. This research examines the factors affecting the intention to use Mobile Money among employees of businesses in Hanoi. To achieve this goal, the author relies on the Theory of Reasoned Action (TRA), the Theory of Planned Behavior (TPB), the Technology Acceptance Model (TAM), and risk perception variables to design the research model. With a sample of 479 employees who intend to use Mobile Money, hypotheses are tested using a multivariate regression model through quantitative analysis with IBM SPSS Statistics 20.0. The research results identify five factors that positively influence the intention to use Mobile Money: Perceived Ease of Use, Trust, Security and Privacy, Social Influence, and COVID-19 Risk Perception. The factor of Perceived Usefulness does not have a significant impact in this case. Particularly, heightened risk perception regarding COVID-19 or social instability leads to an increased intention to use Mobile Money. This study provides guidance to Mobile Money service providers on how to enhance users' intention to use their services. Additionally, it underscores how factors related to diseases or societal instability can alter or even disrupt initial intention or behavior models

Influence des conditions d'entrée/sortie pour un jet plan impactant une surface concave au milieu confiné

L'étude de l'influence des conditions d'entrée/sortie pour un jet plan impactant une surface concave au milieu confiné est présentée. L'écoulement est décrit à partir des champs moyens de vitesse et des valeurs turbulentes obtenues par vélocimétrie par imagerie de particules (PIV) classique ( 5000 champs). Les paramètres fixés de cette étude sont le nombre de Reynolds (Reb = 3200), la hauteur d'impact (H/b = 7) et la courbure relative (Dc/b = 5). Les résultats mettent clairement en évidence l'influence des conditions d'entrée/sortie pour un jet plan impactant une surface concave au milieu confiné. Le changement de condition de sortie (e passant de 0 à 10 mm) modifie fortement la structure du jet et la position moyenne du point d'impact. Du point de vue instationnaire cela se caractérise par un jet qui oscille fortement lorsque la sortie est libre alors que le jet se stabilise en position basse dans le cas d'une sortie obstruée

SỬ DỤNG AXIT OXALIC LÀM CHẤT CHUẨN ĐỂ XÁC ĐỊNH NHU CẦU OXI HÓA HỌC BẰNG PHƯƠNG PHÁP ĐUN HỒI LƯU KÍN – TRẮC QUANG

Potassium hydrogen phthalate (KHP) is used as a standard to determine the chemical oxygen demand (COD) with the closed reflux-colourimetric method (colourimetric method). Besides KHP, it is possible to utilize oxalic acid for this purpose. After boiling at 150 °C for more than 30 minutes in H2SO4 containing Ag2SO4, K2Cr2O7 reacts completely with H2C2O4 at a molar ratio of 1:3. The experimentally determined chemical oxygen demand of H2C2O4 coincides with its theoretical value at 16.0 mg O2/mole H2C2O4. The average COD values of two river water samples, determined with the colourimetric method by using KHP standard and oxalic acid, are not statistically different. Oxalic acid can be used as a standard to determine COD with the colourimetric method.Kali hydro phthalate (KHP) được dùng làm chất chuẩn để xác định nhu cầu oxi hóa học (COD) bằng phương pháp đun hồi lưu kín – trắc quang (phương pháp trắc quang). Ngoài KHP, có thể sử dụng axit oxalic cho mục đích này. Sau khi đun hơn 30 phút ở 150 °C trong môi trường H2SO4 chứa Ag2SO4, K2Cr2O7 sẽ phản ứng hoàn toàn với H2C2O4 theo tỷ lệ mol 1:3. Nhu cầu oxi hóa học của H2C2O4 đã xác định bằng thực nghiệm hoàn toàn trùng khớp với giá trị nhu cầu oxi lý thuyết của hợp chất này là 16,0 mg O2/mol H2C2O4. Nhu cầu oxi hóa học trung bình của hai mẫu nước sông xác định bằng phương pháp trắc quang với hai đường chuẩn dùng KHP và axit oxalic không khác nhau về mặt thống kê. Như vậy, có thể sử dụng axit oxalic làm chất chuẩn để xác định COD bằng phương pháp đã nêu

TECHNICAL ASSESSMENT OF GAMMA-AMINO BUTYRIC ACID (GABA) PRODUCTION FROM RICE BRAN

This research focused on technical assessment of GABA production from rice bran through fermentation by Lactobacillus brevis. Influence of operating pressure on separation of GABA by nanofiltration membrane was investigated and 4 bar was suitable for the nanofiltration process. The purification of GABA by nanofiltration with constant feed volume was carried out and purity of GABA reached 4.8 folds, compared to feed, at 5 volumes of added water. At 40 of concentration factor in concentration of GABA solution by nanofiltration with full recycle of retentate, content of GABA reached 49.8 g/L. The production of GABA from defatted rice bran at pilot scale was carried out at 1,000 L/batch (equal to 200 kg of rice bran) of fermentation. Estimation of mass balance showed that, with 200 kg of defatted rice bran, 7.0 kg of GABA powder was obtained. Results indicated that, it is potential to produce GABA from rice bran through the fermentation by Lactobacillus brevis

Antibacterial activity of crude methanolic and fractionated extracts of Aaptos suberitoides

In this research, we at the first time assessed antibacterial effects of methanolic crude and fractionated extracts from the marine sponge, Aaptos suberitoides against three bacterial strains including E. coli., S. aureus, B. cereus. The anti-bacterial assays were carried out by the disc diffusion method to test the anti-bacterial activity of different concentrations of methanolic crude of A. suberitoides against the indicator bacterial pathogens. The results indicated that extracts of A. suberitoides exhibited anti-microbial activity against all tested bacterial strains in concentrationdependent manner. Moreover, we showed that the majority of the active compound was in the polar fractions

Sorting or supporting teachers? An exploration of the imbalanced role of classroom observation in the development and assessment of Vietnamese secondary schoolteachers

In 2018, Vietnam’s National Teacher Education Programme established a new framework for schoolteachers’ professional development. Classroom observation was the dominant method used for teacher monitoring, assessment and development. This paper explores the use and impact of current classroom observation policy and practice on novice teachers in Vietnamese secondary schools. Our study draws on qualitative data from 35 semi-structured interviews across four provinces. Our findings revealed ongoing policy-practice tensions, with the prioritisation and dominance of classroom observation as an assessment tool for sorting rather than supporting teachers. These tensions were indicative of a wider policy-practice disconnect enshrined in recent reform by the Ministry of Education and Training that advocated the adoption of lesson study as the preferred national approach in schools. However, the experiences of our participants reflected a very different picture in practice that reinforced traditional hierarchies of power associated with evaluative models of observation that are designed to standardise and rank teachers’ classroom performance rather than develop the quality of teaching. Instead of the more collaborative and collegial ethos typically associated with inquiry-based approaches like lesson study, observation was being used largely as a high-stakes assessment, resulting in increased levels of anxiety and stress among teachers

The role of classroom observation in the development and assessment of schoolteachers in Vietnam: a review of national policy and research

This paper focuses on the role of classroom observation in the development and assessment of schoolteachers in Vietnam through a narrative review of current policy and cognate research literature. The overall aim of this review was twofold. Firstly, to contribute to a growing bank of Vietnam-based studies to maximise the value of the insights from this scholarly work into recent policy reforms on teachers’ professional development in Vietnam. Secondly, to widen access and exposure to published work on the topic in Vietnamese that is not readily accessible to English-speaking scholars. This review revealed a long history and engrained culture of using observation as a teacher performance evaluation tool. In recent years, there have been policy reforms and research studies that have repositioned observation as a tool for teacher learning and development. However, the implementation of these reforms has been inconsistent across Vietnam, along with recent reform having encountered resistance from a culture of compliance in schools. This paper identifies some of the key issues that policy makers and educational leaders need to address in practice in order to ensure the effective and meaningful implementation of the reforms relating to the use of observation for learning and developmental purposes