TỔNG HỢP VẬT LIỆU TiO2/rGO VÀ ỨNG DỤNG PHÂN TÍCH ĐỒNG THỜI CADIMI VÀ CHÌ BẰNG PHƯƠNG PHÁP VON – AMPE HOÀ TAN

In this paper, graphite powder was used to produce graphene oxide (GO), which was then reduced by ascorbic acid to gain reduced graphene oxide (rGO) with the Hummer method. Nano titanium dioxide (TiO2) is physically and chemically stable and used in numerous environmental applications. Reduced graphene oxide was modified with TiO2. The obtained TiO2/rGO was characterized by using X-ray diffraction, scanning electron microscopy and nitrogen adsorption/desorption isotherms. The synthesized material was applied to modify a glassy carbon electrode for the simultaneous determination of cadmium and lead with differential pulse anodic stripping voltammetry (DP-ASV). The method yielded a high sensitivity (0.329 ± 0.005 and 0.346 ± 0.004 μA/ppb for CdII and PbII), low detection limit (3.17 ppb and 2.42 ppb for CdII and PbII) and a good linear correlation between Ip and the metal concentration in the range of 6–80 ppb for both metals (R2 ≥ 0.998).Trong bài báo này, graphen oxit (GO) được tổng hợp từ bột graphit bằng phương pháp Hummer; GO được khử bằng axit ascorbic thành graphen  oxit dạng khử (rGO). Titan dioxit (TiO2) cấu trúc nano có tính ổn định vật lý và hóa học cao với nhiều ứng dụng, đặc biệt là trong lĩnh vực môi trường. Vật liệu TiO2/rGO được đặc trưng bằng nhiễu xạ tia X (XRD) và hiển vi điện tử quét (SEM) để chứng minh các đặc điểm hình thái của bề mặt chất hấp phụ. Quá trình hấp phụ – giải hấp phụ nitơ được sử dụng để xác định diện tích bề mặt riêng và độ xốp. Vật liệu vừa tổng hợp được ứng dụng để biến tính điện cực nền than thủy tinh nhằm xác định đồng thời hàm lượng cadimi và chì bằng phương pháp von-ampe hòa tan anot xung vi phân (DP-ASV). Độ nhạy của phương pháp đối với CdII và PbII là 0,329 ± 0,005 và 0,346 ± 0,004 μA/ppb. Giới hạn phát hiện đối với CdII và PbII là 3,17 và 2,42 ppb. Giữa Ip và nồng độ kim loại có tương quan tuyến tính tốt trong khoảng 6–80 ppb với R2 ≥ 0,998

ESSENTIAL SELF-TRAINING SKILLS TO BECOME AN INTERPRETER: ENGLISH-MAJORING STUDENTS’ PERCEPTION

Currently, interpreting has become a profession in high demand. This study surveyed students' perceptions of the essential self-training skills to become an interpreter. The study used a questionnaire to collect data collection tool which was a survey with 12 multiple-choice questions and 4 open-ended questions. 82 English–majoring students of High-quality program Batch 45 – at Can Tho University participated in the survey. The results show that students majoring in High-quality English Language perceive the importance of skills in interpreting: shorthand skills, listening comprehension skills, memorization skills, visualization skills, presentation skills, skills in using search engines, teamwork skills, multi-tasking skills, and pronunciation skills. Students also pointed out a number of skills that they think are equally important if they want to become an interpreter such as reflexes, situational skills, and contextual skills. On that basis, a number of measures of how to support students to develop their own training plans and hone their skills for their future careers are proposed.  Article visualizations

Recommendation Systems: A Systematic Review

This article presents a comprehensive and objective systematic review of existing research on recommendation systems with regards to core theory, latest studies, various applications, current attitudes, and potential future applications. The research is mainly based on exploring professional peer-reviewed studies and articles and using their abstracts to create a comprehensive and unbiased review of existing research. The following search terms were used to identify articles and studies for the research: recommendation systems; recommender systems; core theory of recommender systems; current attitudes towards recommendation systems; latest studies on recommendation systems; applications of recommendation systems; potential studies on recommendation systems; and future potential applications of recommendation systems. The research also used the advanced search filter to locate recent studies for comparison by limiting the search by year to find studies published from 2021 onwards. Most literature on this area highlights the importance of recommendation systems in almost all aspects of modern life. Specifically, recommendation systems have become critical components in business, health care, education, marketing, and social networking domains. Additionally, most studies identified reinforcement of learning and deep learning techniques as significant developments in the field. These techniques form the backbone of most modern recommendation systems. The primary concern that could hinder further evolution systems is their consequent filter bubble effects which many studies showed to be problematic. Healthcare is a central area that shows tremendous potential for these systems. Although recommender systems have been implemented in this domain, there remains a lot of untapped potential that, if unleashed, could revolutionize medicine and healthcare. But the problems facing these systems have to be tackled first to establish trust. Keywords: Recommendation systems, Recommender systems, Deep learning, Reinforcement learning DOI: 10.7176/CEIS/13-4-04 Publication date:August 31st 202

AN INVESTIGATION INTO THE COMMON ERRORS OF WORD FORM USED IN WRITING OF THE FRESHMEN: A CASE STUDY

English has been used all across the world, including in Vietnam. From middle school to high school and even university, Vietnamese students have numerous opportunities to engage with English grammar, but there is still a significant gap between their understanding and the correct application of English grammar. In fact, Grammar has a significant impact on the writing skills of Vietnamese students in general, and especially the first-year students of English majors who were not much exposed to writing in high school, so they are not yet used to writing at a higher level. The majority of errors in their writings are due to the influence of their mother tongue and a lack of frequent practice and their misuse of word forms, as a matter of fact, the expected results have not been satisfactory. Based on the general insight into the writing competence of the freshmen, the study titled “An investigation into the common errors of word forms made in the writings of the freshmen: A case study” was done with the English-major students. A close survey was deliberately done with 142 paragraphs written by the first-year students to investigate the common errors of word forms made in their writings. From what was collected, the study subsequently offered some suggestions for helping the students improve their writing skills.  Article visualizations

A SURVEY OF STUDENTS’ ABILITY OF IDENTIFYING ERRORS IN WRONG SOLUTIONS FOR THE MATHEMATICAL PROBLEMS RELATED TO THE MONOTONICITY OF FUNCTIONS

The monotonicity of a function plays an important role in the general mathematics curriculum in Vietnam, because it is considered as an effective tool for solving mathematical problems involved with the monotonic intervals of functions, their extreme, absolute maximum value and absolute minimum value. Normally, students commit errors in solving these problems because of their complexity and difficulty. In addition, specific characteristics of knowledge also make children make mistakes. The sample consisted of 362 students, and they had the task of identifying errors in false assumptions. From the results of the survey, it was found that when dealing with the monotonicity of the functions, students were still misled.  Article visualizations

Chemical Constituents and Bacterial Activity of Essential Oils of Five Wax Apples (Syzygium samarangense) from Dong Thap Province, Vietnam

In the present study, essential oils from the leaves of five varieties of wax apple trees, (\u27An Phuoc\u27, \u27Hoa An\u27, \u27Hong Dao\u27, \u27Sua\u27, and \u27Xanh Duong\u27) collected in Dong Thap Province, Vietnam were isolated using hydrodistillation, and their constituents were for the first time identified via gas chromatography - mass spectrometry. A total of 74 compounds from essential oils were identified. These compounds were classified into four clusters by hierarchical clustering analysis. The main constituents of the essential oils isolated from the leaves of five varieties of wax apple trees were o-cymene, α-cubebene, epizonarene, β-gurjunene, and α-selinene. The antibacterial activity of the essential oils isolated from the leaves of five varieties of wax apples were evaluated for the first time. The results showed that the essential oils could inhibit the growth of four tested microorganisms: Bacillus cereus, Escherichia coli, Salmonella enteritidis and Staphylococcus aureus

Chemical Constituents and Bacterial Activity of Essential Oils of Five Wax Apples (Syzygium samarangense) from Dong Thap Province, Vietnam

In the present study, essential oils from the leaves of five varieties of wax apple trees, (\u27An Phuoc\u27, \u27Hoa An\u27, \u27Hong Dao\u27, \u27Sua\u27, and \u27Xanh Duong\u27) collected in Dong Thap Province, Vietnam were isolated using hydrodistillation, and their constituents were for the first time identified via gas chromatography - mass spectrometry. A total of 74 compounds from essential oils were identified. These compounds were classified into four clusters by hierarchical clustering analysis. The main constituents of the essential oils isolated from the leaves of five varieties of wax apple trees were o-cymene, α-cubebene, epizonarene, β-gurjunene, and α-selinene. The antibacterial activity of the essential oils isolated from the leaves of five varieties of wax apples were evaluated for the first time. The results showed that the essential oils could inhibit the growth of four tested microorganisms: Bacillus cereus, Escherichia coli, Salmonella enteritidis and Staphylococcus aureus

Habenaria diphylla (Nimmo) Dalzell (Orchidaceae), new record for the flora of Vietnam

Habenaria diphylla (Nimmo) Dalzell is reported for the first time as a new discovery for the flora of Vietnam based on the specimens collected in Binh Chau-Phuoc Buu Nature Reserve, Ba Ria-Vung Tau Province. The present study provided the detailed characteristics of the species including detailed photographs of the morphological characteristics, the cross section of the leaf, inflorescence axis and root. Furthermore, the information about the species, including distribution, habitat, ecology and conservation status were also provided

Cider Production from King Mandarin (Citrus nobilis Lour.) and Its Antioxidant Activity

With the necessity of diversifying alcoholic beverages, cider has become a kind of drink that can fulfill this demand. This is because the cider will be diversified depending on the kinds of fruit that are chosen to be used for the cider fermentation. Therefore, this study aims to investigate the effects of dilution ratio, Brix, pH, and yeast concentration on the production of cider from king mandarin (Citrus nobilis Lour.), and to evaluate the analytical characteristics and antioxidant activity of the product. After the investigation, it can be claimed that the dilution of the juice causes the ethanol content to decrease, whereas the increase of Brix, pH, and yeast concentration makes the ethanol content increase. However, the proportional increase in the ethanol content with Brix, pH, and yeast concentration has its limitations. Specifically, when the Brix and the yeast concentrations were, respectively, higher than 16°Brix and 0.04%, the ethanol content tended to maintain the same. This is also the same when the pH was lower than 4.5. In addition, by using the DPPH and ABTS●+ methods, the antioxidant activity of cider is estimated to be lower than the one of the juice before fermentation, which is smaller than 3.78 times for the DPPH method and 3.76 times for the ABTS●+ method