유기물로 개질한 나노점토-폴리(에틸렌 테레프탈레이트) 복합재료의 기계적 특성

( Hai Anh Thi Le ),박용태 ( Yong Tae Park ) 한국복합재료학회 2023 Composites research Vol.36 No.4

고분자 기반 복합재료는 가볍고 우수한 물성을 가지고 있기 때문에, 단일 소재가 갖기 어려운 물성을 충족하기 위한 방법으로서 그 수요는 급격하게 증가되고 있다. 그에 따라, 크기가 1-100 nm를 갖는 입자를 고분자 기지에 분산시켜 제작하는 고분자 나노 복합재료에 대한 연구가 많이 진행되고 있다. 그리고, 나노입자 강화 복합재의 기지 재료로 열가소성 수지를 사용한 복합재료 연구를 많이 진행하고 있다. 본 연구를 통해 세틸트리메틸 암모늄브로마이드(CTAB)으로 층간 물질을 개질한 유기 나노 점토가 포함된 폴리(에틸렌 테레프탈레이트)(PET) 기반 나노 복합체를 제조하였다. 다양한 나노 점토 중에서, 질석 (vermiculite, VMT)은 저가이며 풍부한 매장량과 고유의 물성으로 인해 고분자 재료의 기계적 및 열적 특성을 증가시키는 연구들이 수행되고 있다. 하지만, VMT의 강한 층간 결합으로 인해 고분자 기지 내에서 박리 및 분산 성능이 낮아 그 활용이 제한되었다. 본 연구에서는 나노 점토의 함유량에 따른 기계적 물성을 인장 시험으로 확인하였고, 나노 점토 입자가 PET 기재 내에 분산되는 정도를 TEM 단면 사진으로 평가하고, 그리고 질소 가스 차단 특성을 측정하였다. Because polymer-based composites are lightweight and have excellent properties, their demand is growing rapidly as a way to fulfill properties that are difficult to achieve with a single material. As a result, there has been a lot of research on polymer nanocomposites, which are made by dispersing particles with a size of 1-100 nm in a polymer matrix. In addition, many nanocomposites using thermoplastic resins as matrix materials are being studied. In this study, poly(ethylene terephthalate) (PET)-based nanocomposites containing organic nanoclays modified with cetyltrimethylammonium bromide (CTAB) as interlayer materials were prepared. Among various nanoclays, vermiculite (VMT) has been studied to increase the mechanical and thermal properties of polymeric materials due to its low cost, abundant reserves and unique properties. However, the strong interlayer bonding of VMT has limited its utilization due to its poor exfoliation and dispersion performance within polymer matrices. In this study, the mechanical properties of the VMT content were confirmed by tensile tests, the dispersion of VMT particles in the PET matrix was evaluated by TEM cross-sectional images, and the nitrogen gas barrier properties were evaluated.

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.

Production of high purity rare earth mixture from iron-rich spent fluid catalytic cracking (FCC) catalyst using acid leaching and two-step solvent extraction process

Le-Phuc Nguyen,Yen Thi Hai Pham,Phuong Thuy Ngo,Tri Van Tran,Loc Vinh Tran,Nam Thi Hoai Le,Luong Huu Nguyen,Tung Thanh Dang,Duc Anh Nguyen,Marco Wenzel,David Hartmann,Karsten Gloe,Jan J. Weigand,Klaus 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.5

Acid leaching and a two-step solvent extraction procedure were developed to produce high purity mixture of La and Ce from iron-rich spent FCC catalyst discharged from Dzung Quat refinery (Vietnam). Acid leaching of the spent catalyst with 2M HNO3 and a solid-to-liquid ratio of 1/3 at 80 oC in 1 h dissolved almost 90% of La while 12% of Al and 25% of Fe were transferred to the leachate. The extraction of RE metals and main impurities such as Al and Fe by a mixture of di-2-ethylhexyl phosphoric acid (D2EHPA) and tributyl phosphate (TBP) was investigated. Experiments showed that it was necessary to remove Fe before extracting RE and the optimum extraction conditions for a high recovery of RE while 0% of Al extraction were pH1, contact time=10min, and D2EHPA/TBP volume ratio= 4 : 1. At these conditions, the extraction yields of La(III) and Ce(III) were 72% and 89%, respectively. A two-step solvent extraction was developed to achieve a high purity of RE mixture, which included (1) the removal of impurity Fe by 25% (v/v) diisooctyl phosphinic acid (DiOPA) in n-octane for 140 min, (2) the extraction of rare earths by a mixture of di-2-ethylhexyl phosphoric acid (D2EHPA) and tributyl phosphate (TBP) in n-octane for 10 min without the need for adjusting the pH of the leaching solution.

Tobacco Access and Availability for Vietnamese School Children (aged 13-15): Results from the Global Youth Tobacco Use Survey (GYTS) 2014 in Viet Nam

Le, Thi Kim Anh,Bui, Thi Tu Quyen,Hoang, Van Minh,Kim, Bao Giang,Phan, Thi Hai,Doan, Thu Huyen,Luong, Ngoc Khue,Nguyen, Tuan Lam,Pham, Thi Quynh Nga Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.no.sup1

Efforts to reduce tobacco use among school children need to be based on understanding of access to cigarettes by these subjects because previous studies indicated that enforcement of laws for controlling tobacco sales seems to not affect teen/school children because they can obtain cigarettes from different sources. This paper aims to describe access to and availability of cigarettes among school students (aged 13-15 years old) according to the data from GYTS Vietnam 2014. In GYTS, a national school-based survey of students of grades 8-10, our findings showed that about 15% school children are current smokers who smoke at home, and that they could easily buy cigarettes from stores (63.2%), or someone else (27.8%), or street vendors (9%). Notably, over 85% of school children answered that they were not refused because of their age. This high percentage was nearly the same in the North (85.7%), the Centre (92.5%), and the South (89.7%) of Viet Nam. These findings show that it is quite easy for school children to obtain cigarettes and this is a crucial challenge for policy makers aiming to reduce tobacco use among youth in general and school-age students in particular.

Adaptive hierarchical sliding mode control using an artificial neural network for a ballbot system with uncertainties

Hai Le Xuan,Quoc-Dong Hoang,Soon Geul Lee,Dat Pham Xuan,Hoang Tran Viet,Minh Pham Van,Hung Pham Van,Hung Pham Viet,PHAM DUC TUAN,Duc Anh Nguyen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2

Ballbots, which have been studied for over ten years, are under-actuated mobile robots that operate using the inverted pendulum paradigm. Controlling a ballbot poses a number of challenges, including maintaining the stable upright posture from the ground in all directions and making sure it follows the desired trajectory. External factors such as a minor change in contact surface properties or fabrication errors can affect the system's stabilization and transfer capabilities. In this study, an adaptive hierarchical sliding mode control algorithm based on an artificial neural network is developed to make the ballbot robust to external factors. The use of the proposed controller ensures system stability despite uncertainties including friction, accidental centrifugal forces and gravity that occur when the ballbot follows the reference trajectory. The system stability is guaranteed on the basis of Lyapunov theory. Control efficiency and robot stability under system uncertainties are demonstrated by numerical simulation.

Factors Affecting Accounting Policy Choice: Evidence from Small and Medium Enterprises in Vietnam

DOAN, Anh Thi Thuy,LE, Binh Thi Hai,LE, Nguyet Thi My,DANG, Ly Ai Korea Distribution Science Association 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.9

The purpose of this study is to determine the direction and significance of variables influencing small and medium enterprises (SMEs) decisions regarding accounting policy in Vietnam. Research data was collected through a survey of 296 subjects, including chief accountants, accountants, managers, and lecturers with practical experience in accounting work at enterprises. With the help of specialized software SPSS, determining the impact of factors on the choice of accounting policy of enterprises is done through a multivariate regression model with control tools Cronbach's alpha determination, EFA factor analysis, and Pearson correlation analysis. Research results show that there are seven factors affecting the choice of accounting policy in Vietnamese SMEs; in which, the factors information technology, legal environment, information demand, manager's awareness, and accounting qualification have a positive impact; and two factors are tax pressure, and financial leverage have a negative impact on accounting policy choice. These results are consistent with most of the previously published studies. However, in contrast to many previous studies, our research shows that accounting's psychological factor does not affect the accounting policy choice. This is consistent with the characteristics of SMEs in Vietnam because the role of accountants is not appreciated in the business.

Determinants of Access to Green Finance in Vietnam: An Empirical Research

Lam Hai LE,Anh Hoang Thi PHAM 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.9

Green finance plays an important role in environmental protection missions and fighting climate change. The Environment Fund in Vietnam is the main channel of preferential capital offered to firms for environmental protection. Unfortunately, it was previously unknown which criteria influenced these companies’ ability to obtain green financing. Using a survey method, we collected data through a structured questionnaire of 203 respondents that represent firms that had received concessional loans from 26 Environment Funds. A Multiple Linear Regression model was used to examine the determinants of access to concessional loans for environmental protection. We found relationships between age, size, ownership type, and industry sector, and access to green finance. Third-party guarantees were a significant factor in financing through Environment Funds. Moreover, we found commercial environmental projects face fewer green financing obstacles. Surprisingly, showing audited financial statements does not mitigate the information asymmetry between firms and these financial institutions. These findings suggest that Environment Funds should classify environmental project types to develop appropriate lending policies. In emerging markets, enterprises need to build a trusted relationship with financial institutions so that they can replace asset-based lending techniques, thereby increasing the firms’ accessibility to green finance.

Appropriation of Protocol for Laparoscopic Pancreaticoduodenectomy in Treatment of Periampullary Cancer

( Minh Hai Pham ),( Quan Anh Tuan Le ),( Hoang Bac Nguyen ),( Quang Hung Vu ),( Thai Ngoc Huy Tran ),( Hang Dang Khoa N Guyen ),( Thi Ngoc Sang Duong ),( Van Toan Tran ) 대한간학회 2020 춘·추계 학술대회 (KASL) Vol.2020 No.1

Aims: Laparoscopic pancreaticoduodenectomy (LPD) is considered as a safe and effective procedure in well - selected patients and appropriate surgical technique. Our aim is to evaluate suitability of using protocol for LPD in treatment of periampullary cancer at a single team. Methods: case series Results: Indication for LPD included 37 cases with resectable tumors which were classified basing on NCCN. All witness evaluation risk of complications with PREPARE score, ASA and evaluation risk of postoperative pancreatic fistula (POPF) with FRS classification. There were 2 open conversions because of vein resections, accounting for 5.4%. Standard lymphadenectomy was performed in all of 37 cases. In term of PREPARE score, major complications (Clavien - Dindo >= III) were 17.8%, 0% and 0% (5/28, 0/5 and 0/2 cases) in low risk, intermediate risk and high risk group, respectively. All of cases had ASA I or II. POPF happened 11.1% (1/9), 4.1% (1/24) and 50% (1/2) in low risk, intermediate risk and high risk group, respectively. Frozen section was needed for R0 margin. Retrieved lymph nodes was 8 - 18 with 12 lymph nodes in average. Conclusions: Indication for LPD with resectable tumors is acceptable. ASA I or II is a safe measure to select patient for LPD. FRS classification shows appropriation to evaluate risk of POPF.

Prenylated isoflavones from Cudrania tricuspidata inhibit NO production in RAW 264.7 macrophages and suppress HL-60 cells proliferation

Tuan Anh, Hoang Le,Tuan, Do Thanh,Trang, Do Thi,Tai, Bui Huu,Nhiem, Nguyen Xuan,Yen, Pham Hai,Kiem, Phan Van,Minh, Chau Van,Duc, Tran Minh,Kang, Hee Kyoung,Kim, Youn Chul,Kim, Young Ho Taylor Francis 2017 Journal of Asian natural products research Vol.19 No.5

Novel 3,4-dihydro-4-oxoquinazoline-based acetohydrazides: Design, synthesis and evaluation of antitumor cytotoxicity and caspase activation activity

Huan, Le Cong,Tran, Phuong-Thao,Phuong, Cao Viet,Duc, Phan Huy,Anh, Duong Tien,Hai, Pham The,Huong, Le Thi Thu,Thuan, Nguyen Thi,Lee, Hye Jin,Park, Eun Jae,Kang, Jong Soon,Linh, Nguyen Phuong,Hieu, Tr Elsevier 2019 Bioorganic chemistry Vol.92 No.-

<P><B>Abstract</B></P> <P>In search for novel small molecules with antitumor cytotoxicity via activating procaspase-3, we have designed and synthesized three series of novel (E)-<I>N</I>′-benzylidene-4-oxoquinazolin-3(4<I>H</I>)-yl)acetohydrazides (<B>5a-j, 6a-h,</B> and <B>7a-h)</B>. On the phenyl ring ò the benzylidene part, three different substituents, including 2-OH-4-OCH<SUB>3</SUB>, 4-OCH<SUB>3</SUB>, and 4-N(CH<SUB>3</SUB>)<SUB>2</SUB>, were introduced, respectively. Biological evaluation showed that the acetohydrazides in series <B>5a-j</B>, in which the phenyl ring of the benzylidene part was substituted by 2-OH-4-OCH<SUB>3</SUB> substituent, exhibited potent cytotoxicity against three human cancer cell lines (SW620, colon; PC-3, prostate; NCI-H23, lung). Most of the compounds, in this series, especially compounds <B>5c, 5b</B> and <B>5h,</B> also significantly activated caspase-3 activity. Among these, compound <B>5c</B> displayed 1.61-fold more potent than PAC-1 as caspase-3 activator. Cell cycle analysis showed that compounds <B>5b</B>, <B>5c</B>, and <B>5h</B> significantly arrested the cell cycle in G1 phase. Further apoptotic studies also demonstrated compounds <B>5b</B>, <B>5c</B>, and <B>5h</B> as strong apoptotic cell death inducers. The docking simulation studies showed that these compounds could activate procaspase <I>via</I> chelating Zn<SUP>2+</SUP> ion bound to the allosteric site of the zymogen.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel (<I>E</I>)-<I>N</I>′-benzylidene-2-(4-oxoquinazolin-<I>3(4H)-yl</I>)acetohydrazides were synthesized. </LI> <LI> The acetohydrazides <B>5a-i</B> exhibited potent cytotoxicity against three human cancer cell lines. </LI> <LI> A number of cytotoxic compounds exhibited good caspase activation activity. </LI> <LI> The cytotoxic compounds were shown to arrest cells at G1 phase. </LI> <LI> The cytotoxic compounds were shown as strong apoptotic inducers. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>