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Study on bubble and liquid velocities in an area-varying horizontal channel
Tran, Thanh Tram,Kim, Byoung Jae,Park, Hyun-Sik Elsevier 2018 Annals of nuclear energy Vol.118 No.-
<P><B>Abstract</B></P> <P>Two-fluid equations are widely used to simulate thermal-hydraulic phenomena in a nuclear reactor. Simulation accuracy depends on the modeling terms in the two-fluid equations. For a dispersed flow, the overall two-phase pressure drop by wall friction must be apportioned to each phase in proportion to the fraction of each phase (Kim et al., 2014). By applying this approach, the prediction of bubble phase velocity can be close to that of liquid for a fully developed flow in a horizontal pipe with a constant area. One may want to know what would happen in the area-varying channels. It is always true that the bubble density is much lower than the water density. Hence, the bubble would accelerate faster than the liquid in a nozzle in which the pressure decreases along the downstream; the bubbles would decelerate more quickly than the liquid in a diffuser in which the pressure increases along the downstream. The purpose of this study was to investigate those behaviors in an area-varying channel using the experimental data and MARS simulations. Experiments were made of turbulent bubbly flows in an area-varying horizontal channel. The velocities of two phases were measured with the help of the PIV technique. The experimental result showed that the two-phase velocities were no longer close to each other in the area-varying regions. The bubble was faster than the liquid in the nozzle region; in contrast, the bubble was slower than the liquid in the diffuser region. MARS code simulations were performed to assess the wall drag model. By replacing the original wall drag partition model in the MARS code with Kim’s one, the simulation results were consistent with experimental observations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bubble and water velocities in an area-varying channel are measured. </LI> <LI> The phase velocities are very close in the constant-area region. </LI> <LI> The bubble is faster than the water in the contraction region. </LI> <LI> The bubble is slower than the water in the diffuser region. </LI> <LI> Kim’s wall drag partition model well predicts experimental results. </LI> </UL> </P>
Tram-Anh Tran Nguyen,Sang-Geun Lee 한국중원언어학회 2021 언어학연구 Vol.0 No.58
This study investigated the characteristic distribution of hedges and intensifiers in argumentative essays of NESs and Vietnamese EFL learners to see if there is any positive or negative relation between writing qualities and the two rhetorical devices. By using both quantitative and qualitative analysis of 90 essays (30 from NESs, 30 from advanced Vietnamese EFL learners, and 30 from intermediate Vietnamese EFL learners), we obtained some meaningful findings. First, no significant difference was found between the NESs and the Vietnamese learners regarding the frequency of hedges and intensifiers. However, both the NESs and the advanced Vietnamese learners showed a tendency to use more hedges and fewer intensifiers than the intermediate Vietnamese learners. Second, hedges turned out to have a positive correlation with writing qualities while intensifiers were negatively related to writing scores. This study is significant from the ESL/EFL education in that it reveals a correlation between language proficiency and the use of hedges/intensifiers and that it helps ESL/EFL learners to more effectively use the two devices in academic writing.
유로단면이 변하는 수평관 내 기포류에서의 기포 및 액체 속도
찬탄짬(Tran Thanh Tram),김병재(Byoung Jae Kim),박현식(Hyun Sik Park) 한국가시화정보학회 2017 한국가시화정보학회지 Vol.15 No.3
The two-fluid equations are widely used to simulate two-phase flows in a nuclear reactor. For the two-fluid momentum equation, the wall and interfacial drag terms play an important role in predicting a two-phase flow behavior. Since the bubble density is much smaller than the water density, the bubble accelerates faster than the liquid in a nozzle. As a result, the bubble phase becomes faster than the liquid phase in the nozzle. In contrast, the opposite phenomena occur in the diffuser. The purpose of our study is to experimentally show these behaviors in an area-varying channel such as nozzle and diffuser. Experiments were made of turbulent bubbly flows in an area-varying horizontal channel. The velocities of the bubble and liquid phases were measured by the PIV technique. It was shown that the two-phase velocities were no longer close to each other in the area-varying regions. The bubble was faster than the liquid in the nozzle; in contrast, the bubble was slower than the liquid in the diffuser. Code simulations were also performed using the MARS code. By replacing the original wall drag model in the MARS code with Kim (1)’s wall drag partition model, we obtained the simulation results being consistent with experimental observations.
Using Syntax and Shallow Semantic Analysis for Vietnamese Question Generation
Phuoc Tran,Duy Khanh Nguyen,Tram Tran,Bay Vo 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.10
This paper presents a method of using syntax and shallow semantic analysis for Vietnamese question generation (QG). Specifically, our proposed technique concentrates on investigating both the syntactic and shallow semantic structure of each sentence. The main goal of our method is to generate questions from a single sentence. These generated questions are known as factoid questions which require short, fact-based answers. In general, syntax-based analysis is one of the most popular approaches within the QG field, but it requires linguistic expert knowledge as well as a deep understanding of syntax rules in the Vietnamese language. It is thus considered a high-cost and inefficient solution due to the requirement of significant human effort to achieve qualified syntax rules. To deal with this problem, we collected the syntax rules in Vietnamese from a Vietnamese language textbook. Moreover, we also used different natural language processing (NLP) techniques to analyze Vietnamese shallow syntax and semantics for the QG task. These techniques include: sentence segmentation, word segmentation, part of speech, chunking, dependency parsing, and named entity recognition. We used human evaluation to assess the credibility of our model, which means we manually generated questions from the corpus, and then compared them with the generated questions. The empirical evidence demonstrates that our proposed technique has significant performance, in which the generated questions are very similar to those which are created by humans.
Factors Affecting Entrepreneurial Intention of College Students: An Empirical Study from Vietnam
Thi Thuy An NGO,Phuong Thao TRUONG,Yen Linh TRAN,Thao Vy TRAN,Ngoc Tram TRAN,Ai My HUYNH,Thanh Truc HUYNH 한국유통과학회 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.5
The study aims to identify factors that influence university and college students’ entrepreneurial intentions in Vietnam’s Mekong Delta region. The study examines entrepreneurship mindset, subjective norm, capital sources, concept development assistance, personality qualities, and perceived behavioral control of university support for a student’s entrepreneurial aim. The research was conducted according to the quantitative method. The data was collected through an online survey with a sample size of 611 students from 19 universities and colleges in the Mekong Delta region. The methods that test the scale, including Cronbach Alpha Test, Structural Equation Modeling (SEM), are used to consider the correlation between the influence factors. The results of SEM analysis show that there are five main factors affecting students’ entrepreneurial intention with decreasing level of influence, including the source of capital, perceived behavioral control, business development support, entrepreneurial attitude, and educational support. Besides, the results indicate that the subjective norm, personality traits, and concept development support have no impact on the intention of students toward entrepreneurship. The research also reveals that the entrepreneurial intention of students at universities and colleges has a positive relationship and is significantly affected by capital source and perceived behavioral control.
Pd NHC complexes as catalyst for reductive carbonylation of nitrobenzene for generating urethanes
( Tran Anh Vy ),( Tram Thuy Huynh Nguyen ),( Tung Thanh Nguyen ),김용진 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Carbamates have been widely used due to their versatility such as intermediates in pharmaceuticals, pesticides, fertilizers or precursors of isocyanates. The conventional process for the production of carbamates involves the toxic usage of phosgene. The reductive of carbonylation of aromatic nitro compounds with carbon monoxide in the presence of alcohols has drawn much attention as a phosgene-free alternative to carbamates. There have been numerous attempts to afford carbamates from the reductive carbonylation of nitrobenzene facilitated by various complexes of transitional metals. In this research, N-heterocyclic carbene (NHC)-palladium(II) complexes have been investigated as active catalysts for the synthesis of carbamates. The results showed that the 97% yield of carbamates was obtained under the conditions at 1600C in 2 h in the presence of (NHC)-palladium(II) as main catalyst.
Dinh Tram Anh PHAN,Thi Thuy Ngan NGUYEN,Thi Khanh Nhi NGUYEN,Tran Thien An NGUYEN,Van Si Dan PHAN,Ngoc Phuong Thao HO,Kim Xuan DO,Trong Luan NGUYEN 한국유통과학회 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.5
The outbreak of the COVID-19 pandemic has had a significant impact on the Vietnamese economy. In the midst of a complex disease that compelled people to limit their interaction, customers’ shopping habits shifted from “offline” to “online” transactions. Mobile payments have also grown in popularity. The goal of this study is to figure out what factors influence the use of mobile payments by hotel clients in Can Tho after COVID-19. The research team also examines how those factors influence customers’ willingness to use mobile payment and makes recommendations to better the current situation. Primary data was collected from 227 persons using online surveys and processed with SPSS software for this study. To analyze the correlation relationship between the elements determining the intention to use, the Cronbach alpha, EFA, Correlation, and Regression methods used to assess the scale are applied. Perceived Trustworthiness, Perceived Usefulness, and Perceived Ease of Use all have positive effects on customers’ propensity to use, according to the findings. Perceived Security, on the other hand, has no bearing. The findings of this study have significant theoretical and practical implications for the development of mobile payment services in Can Tho, particularly following the implementation of COVID-19.