RELATION BETWEEN ANN-CATEGORIES AND RING CATEGORIES

Phung, Che Thi Kim,Quang, Nguyen Tien,Thuy, Nguyen Thu Korean Mathematical Society 2010 대한수학회논문집 Vol.25 No.4

There are different categorifications of the notion of a ring such as Ann-category due to N. T. Quang, ring category due to M. M. Kapranov and V. A. Voevodsky. The main result of this paper is to prove that every axiom in the definition of a ring category, but the axiom $x_0 = y_0$, can be deduced from the axiomatics of an Ann-category.

A hydrogeological and geochemical review of groundwater issues in southern Vietnam

Quang Khai Ha,김강주,Nam Long Phan,Thanh Huy Phung,이진원,Viet Ky Nguyen,Chu Nam Phan 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.6

Southern Vietnam is known as one of the most vulnerable areas to climate change in the world due to its low elevation and flat topography, heavy groundwater use, and dense population. This paper introduces hydrogeological conditions and critically reviews groundwater issues that southern Vietnam faces by summarizing previous literatures. Issues that this paper covers include groundwater use and associated phenomenon, acid sulfate soils, the occurrence of saline groundwaters, seawater intrusion, land subsidence, groundwater acidification, and groundwater contamination by nitrate, ammonium, and trace metals such as As, Fe, Mn, Al, Cd, and Pb. This paper shows that most of these issues are inter-related and essentially linked with the unique hydrogeological setting of the study area. However, many of these problems have also been triggered or aggravated by human activities that use water resources and land. Issues such as those of As contamination and groundwater acidification are connected with the aquifer characteristics that are generally confined and rich in organics and pyrite. However, groundwater salinization, acidification, groundwater level declining, land subsidence, and high heavy metal concentrations are in large part caused by human activities such as well installation and heavy groundwater abstraction. While previous studies have proposed artificial recharge as a promising means of mitigating groundwater issues in the study area, the development of techniques that help minimizing aquifer disturbances is also likely required.

Factor Affecting Customers Satisfaction About Banking Services: Evidence from Agribank, Vietnam

NGUYEN, Dung Thi,NGUYEN, Ha Quang,PHUNG, Hanh My Tran,THAN, Hoang Viet Korea Distribution Science Association 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.6

Today, customer satisfaction is the most important issue for Vietnamese banks. There are numerous factors that influence bank customers' satisfaction. The study investigates the factors that influence customer satisfaction with deposit services at the Vietnam Bank for Agriculture and Rural Development (Agribank) in Bac Giang province, Vietnam, and analyses the impact of each component. The authors used 5-point Likert scales to assess whether elements were related to the factors determining consumer satisfaction with Agribank's deposit service. To perform this study, exploratory factor analysis (EFA) and multiple regression were used to find factors determining customer satisfaction with Agribank services. Customers that use deposit services at Agribank in Bac Giang province, Vietnam, provided samples of 300 survey questionnaires for this study. SPSS software is used to examine the data. Customers' satisfaction with Agribank's deposit service is influenced by six factors, including reliability, responsiveness, service capabilities, empathy, tangible means, and service price, according to the study. This finding also offers some recommendations for improving service quality in local Vietnamese banks to gain a competitive advantage.

An Analysis of Factors Impacting Vietnam's Coffee Exports: An Approach from the Gravity Model

PHUNG, Quang Duy,NGUYEN, Tai Cong Korea Distribution Science Association 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.8

This paper uses the gravity model estimated by the random effect method to analyze the factors affecting Vietnam's coffee export turnover for the period 2007-2020 major markets according to statistics from the General Statistics Office and the General Department of Customs. Coffee export turnover was collected from the General Statistics Office, General Department of Customs, and Vietnam Cacao Coffee Association. The authors calculated the price of coffee based on output and export value from data on coffee export turnover; the authors calculated the economic gap based on population and Gross Domestic Product data (reference: geographic distance metrics on the website: http://www.distancefromto.net/countries.php) and other data was collected based on the databases of the Food and Agriculture Organization of the United Nations, the International Monetary Fund, and World Bank organizations. The results of the study show that from 2007 to 2020, the factors of Vietnam's export price of coffee, geographical distance, Gross Domestic Product of the importing country and Gross Domestic Product of Vietnam, the population of Vietnam, the economic gap between Vietnam and the importing country, the openness of the economy, all have an impact on Vietnam's coffee export turnover. Finally, some conclusions about the policy's impact are made based on the empirical results of the paper.

A New and Effective Controller for Inductor Motor Drives using Direct–Decoupling Methodology based on exact linearization algorithm and Adaptive Back Stepping Technology

Anh Tuan DINH,Phung Quang NGUYEN,Minh-Duc LE 제어로봇시스템학회 2010 제어로봇시스템학회 국제학술대회 논문집 Vol.2010 No.10

Control of Inductor Motors is a difficult task because of the motors’ non-linear nature. Hence, the Inductor Motors are usually expressed by complicated non-linear models. This paper presents a new and effective method for modeling stator current and estimating rotor flux of an induction motor by applying Direct?ecoupling Methodology. A nonlinear control approach with full state feedback linearization has been used to construct the decoupling form of the induction motors. A new current controller named “irect-decoupling” based on exact linearization algorithm of the motor current model has been proposed. The obtained linear system in a new state-space is very convenient to design the current controller and the rotor flux estimator for induction motors. A linear Kalman filter has also been derived to construct an observer for rotor flux. Effectiveness of the new adaptive backstepping controller for induction motors and Kalman filter for observation of rotor flux has been verified by simulations and experiments in wide ranges of motor speed. Simulations and experiment results show clearly that the rotor flux can be well estimated in all operating conditions and performance of induction motors under all dynamic modes can be improved by using the new developed controller.

Understanding the COVID-19 Infodemic: Analyzing User-Generated Online Information During a COVID-19 Outbreak in Vietnam

Ha-Linh Quach,Thai Quang Pham,Ngoc-Anh Hoang,Dinh Cong Phung,Viet-Cuong Nguyen,Son Hong Le,Thanh Cong Le,Dang Hai Le,Anh Duc Dang,Duong Nhu Tran,Nghia Duy Ngu,Florian Vogt,Cong-Khanh Nguyen 대한의료정보학회 2022 Healthcare Informatics Research Vol.28 No.4

Objectives: Online misinformation has reached unprecedented levels during the coronavirus disease 2019 (COVID-19) pandemic. This study analyzed the magnitude and sentiment dynamics of misinformation and unverified information about public health interventions during a COVID-19 outbreak in Da Nang, Vietnam, between July and September 2020. Methods: We analyzed user-generated online information about five public health interventions during the Da Nang outbreak. We compared the volume, source, sentiment polarity, and engagements of online posts before, during, and after the outbreak using negative binomial and logistic regression, and assessed the content validity of the 500 most influential posts. Results: Most of the 54,528 online posts included were generated during the outbreak (n = 46,035; 84.42%) and by online newspapers (n = 32,034; 58.75%). Among the 500 most influential posts, 316 (63.20%) contained genuine information, 10 (2.00%) contained misinformation, 152 (30.40%) were non-factual opinions, and 22 (4.40%) contained unverifiable information. All misinformation posts were made during the outbreak, mostly on social media, and were predominantly negative. Higher levels of engagement were observed for information that was unverifiable (incidence relative risk [IRR] = 2.83; 95% confidence interval [CI], 1.33–0.62), posted during the outbreak (before: IRR = 0.15; 95% CI, 0.07–0.35; after: IRR = 0.46; 95% CI, 0.34-0.63), and with negative sentiment (IRR = 1.84; 95% CI, 1.23–2.75). Negatively toned posts were more likely to be misinformation (odds ratio [OR] = 9.59; 95% CI, 1.20–76.70) or unverified (OR = 5.03; 95% CI, 1.66–15.24). Conclusions: Misinformation and unverified information during the outbreak showed clustering, with social media being particularly affected. This indepth assessment demonstrates the value of analyzing online “infodemics” to inform public health responses.