Trade-related R&D Spillovers in Vietnamese Manufacturing

Thang Ngoc Bach 한국국제경제학회 2018 International Economic Journal Vol.32 No.3

This study aims to examine how Vietnamese manufacturing could benefit from R&D investment locally and from OECD countries through trade during a period marked with major trade liberalisations. Using the industry-level data during 2000–2009, it finds that the foreign R&D has accounted for the most part of the R&D spillovers in the sector, with a larger proportion earning from the other foreign industries’ R&D. The domestic industries’ own R&D has improved the sector’s total factor productivity, but in a relatively smaller magnitude compared to the foreign sources. In examining the localised effects of R&D spillovers in Vietnamese manufacturing, the results reiterate the important roles of trade-embedded foreign R&D spillovers from Japan, the US, South Korea, and Germany in the sector’s total factor productivity growth. These findings altogether give support to foreign technology diffusion as a major conduit for growth prospects in Vietnamese manufactures.

Adaptive Cuckoo Search Algorithm for Short-Term Fixed-Head Hydrothermal Scheduling Problem with Reservoir Volume Constraints

Bach Hoang Dinh,Thang Trung Nguyen,Dieu Ngoc Vo 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.5

This paper present three versions of Cuckoo Search Algorithm (CSA) including conventional Cuckoo Search Algorithm (CSA), modified CSA (MCSA) and adaptive CSA (ACSA) for solving the fixed head short-term hydrothermal scheduling (ST-HTS) problem where the reservoir volume constraints and nonconvex fuel cost function of thermal unit as well as the power losses in transmission line are taken into account. Among the applied methods, ACSA is first developed in the study by performing two modifications on second new solution generation via the action of an alien egg to be abandoned. In the ACSA, all initial solutions or all solutions at the end of the previous iteration are evaluated and sorted into two kinds of solution, good solutions with lower fitness function and bad solutions with higher fitness function. The implementation of the first new solution generation first via Lévy flights in the ACSA is carried out similarly to that in MCSA. However, at the second new solution generation the ACSA evaluates the current solutions to choose the best one and use the information of the best one with a random solution to generate the second new solutions via the action of an alien egg to be abandoned. In addition, the probability of an alien egg discovery is considered an adaptive variable, which is set to the largest value at the beginning and decreased as the iteration is increased. Due to the adaptive value of the parameter, the ACSA can search an optimal solution but the trial runs are significantly decreased compared to CSA and MCSA. The performance of the ACSA is validated by testing on two systems and comparing with CSA, MCSA and other existing methods available in the paper.

Controllable synthesis of MoS₂/graphene low-dimensional nanocomposites and their electrical properties

Long, Le Ngoc,Thi, Pham Tan,Trung Kien, Pham,Trung, Pham Thanh,Ohtani, Masataka,Kumabe, Yoshitaka,Tanaka, Hirofumi,Ueda, Shigenori,Lee, Hyoyoung,Thang, Phan Bach,Khai, Tran Van Elsevier 2020 APPLIED SURFACE SCIENCE - Vol.504 No.-

<P><B>Abstract</B></P> <P>In this study, a novel hydrothermal route has been developed for the synthesis of MoS<SUB>2</SUB>/graphene composite with controllable structures, in which ammonium molybdatetetrahydrate, as-prepared graphene oxide (GO), and thioacetamide were used as staring materials. Effects of Mo<SUP>4+</SUP>-to-C precursor ratios and crystalline time on the structures, components and morphologies of MoS<SUB>2</SUB>/graphene were investigated. MoS<SUB>2</SUB>/graphene samples were characterized using XRD, FESEM, HRTEM, FTIR, Raman spectroscopy, HAADF-STEM/EDS, HXPES and electrical measurements. The results show that petal-like MoS<SUB>2</SUB> nanostructures with ultrathin petals (~1–10 layers) and coexistence of 1T- and 2H-MoS<SUB>2</SUB> phases can be synthesized on graphene surface in a short time (~2 h). Comparison of crystallization conditions, we found that the crystallization time had a significant effect on the size of the MoS<SUB>2</SUB> nanopetals. The shorter the reaction time is, the thinner the petal-like MoS<SUB>2</SUB> nanoscale is. On the other hand, by adjusting the ratios of Mo<SUP>4+</SUP>to C (denoted as: MoS<SUB>2</SUB>/C (1:2), MoS<SUB>2</SUB>/C (3:2), MoS<SUB>2</SUB>/C (2.5:1) and MoS<SUB>2</SUB>/C (3:1)), different MoS<SUB>2</SUB>/graphene architectures including “sandwich-liked”, “layer–by–layer” and “anchored” can be obtained. On the basis of these results, a possible growth mechanism of MoS<SUB>2</SUB>nanopetals on GO was proposed. Interestingly, the as-synthesized material depicts its memristive behavior through the Volt-Ampere characteristics, suggesting a potential application in logic memory devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel hydrothermal route has been developed for the synthesis of MoS<SUB>2</SUB>/graphene composite with controllable structures. </LI> <LI> The effects of Mo<SUP>4+</SUP>-to-C precursor ratios and crystalline time on properties of MoS<SUB>2</SUB>/graphene were investigated by FESEM, HRTEM, XRD, FTIR, Raman spectroscopy, HAADF-STEM/EDS and HXPES. </LI> <LI> The memristive properties of the MoS<SUB>2</SUB>/graphenenanocomposite were presented. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Optimal Generation Coordination of Hydrothermal System

Ly Huu Pham,Thang Trung Nguyen,Dieu Ngoc Vo,Bach Hoang Dinh 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.5

This paper presents the use of an enhanced version of conventional cuckoo search algorithm (ECSA) for solving optimal generation coordination of hydrothermal system where the objective is to minimize both fuel cost and emission, and the hydro model is represented as a quadratic function of water discharge with respect to generation. The ECSA method is built for the optimal operation based on several modifications on conventional Cuckoo search algorithm (CSA). In the ECSA method, by evaluating the fitness of all initial eggs they are divided into two parts including the high quality one with lower fitness value and bad quality one with higher fitness value. The ECSA is tested on several systems and obtained results from the ECSA are compared those from other methods. The comparison reveals that the ECSA is so efficient for the considered problem.

Electrical Conduction and Resistance Switching Mechanisms of Ag/ZnO/Ti Structure

Trung Do Nguyen,Kim Ngoc Pham,Vinh Cao Tran,Duy Anh TuanNguyen,Bach Thang Phan 한국전기전자학회 2013 전기전자학회논문지 Vol.17 No.3

We investigated electrical conduction and resistance switching behavior of the Ag/ZnO/Ti structures for random access memory devices. These films were prepared on glass substrate by dc sputtering technique at room temperature. The resistance switching follows unipolar switching mode with small switching voltages (0.4 V – 0.6 V). Two electrical conduction mechanisms dominating the LRS and HRS are Ohmic and trap-controlled space charge limited current, respectively. These both conductions are consistent with the filamentary model. Based on the filamentary model, the switching mechanism was also interpreted.

Electrical Conduction and Resistance Switching Mechanisms of Ag/ZnO/Ti Structure

Nguyen, Trung Do,Pham, Kim Ngoc,Tran, Vinh Cao,TuanNguyen, Duy Anh,Phan, Bach Thang Institute of Korean Electrical and Electronics Eng 2013 전기전자학회논문지 Vol.17 No.3

We investigated electrical conduction and resistance switching behavior of the Ag/ZnO/Ti structures for random access memory devices. These films were prepared on glass substrate by dc sputtering technique at room temperature. The resistance switching follows unipolar switching mode with small switching voltages (0.4 V - 0.6 V). Two electrical conduction mechanisms dominating the LRS and HRS are Ohmic and trap-controlled space charge limited current, respectively. These both conductions are consistent with the filamentary model. Based on the filamentary model, the switching mechanism was also interpreted.

Technical Efficiency of Small And Medium Manufacturing Firms in Vietnam: Parametric and Non-Parametric Approaches

( Nguyen Khac Minh ),( Giang Thanh Long ),( Bach Ngoc Thang ) 한국경제학회 2007 The Korean Economic Review Vol.23 No.1

Correlation between crystallinity and resistive switching behavior of sputtered WO3 thin films

Thi Bang Tam Dao,Kim Ngoc Pham,Yi-Lung Cheng,김상섭,Bach Thang Phan 한국물리학회 2014 Current Applied Physics Vol.14 No.12

The as-depositedWO3 thin films were post-annealed at different temperatures (300 C and 600 C) in air to investigate a correlation between crystallinity and switching behavior of WO3 thin films. Associating the results of XRD, FTIR, XPS and FESEM measurements, the annealing-caused crystallinity change contributes to the variation of the switching behaviors of theWO3 thin films. The as-depositedWO3 films with low crystalline structure are preferred for random Ag conducting path, resulting in large switching ratio but fluctuating IeV hysteresis, whereas the annealedWO3 films with crystallized compact structure limits Ag conducting path, favoring the stable IeV hysteresis but small switching ratio. It is therefore concluded that electrochemical redox reaction-controlled resistance switching depends not only on electrode materials (inert and reactive electrodes) but also on crystallinity of host oxide.

Drug resistance and the genotypic characteristics of rpoB and katG in rifampicin- and/or isoniazid-resistant Mycobacterium tuberculosis isolates in central Vietnam

Thi Binh Nguyen Nguyen,Thi Kieu Diem Nguyen,Van Hue Trương,Thi Tuyet Ngoc Tran,van Bao Thang Phan,Thi Tuyen Nguyen,Hoang Bach Nguyen,Viet Quynh Tram Ngo,Van Tuan Mai,Paola Molicotti 질병관리본부 2023 Osong Public Health and Research Persptectives Vol.14 No.5

Objectives: Tuberculosis (TB) and drug-resistant TB (DR-TB) are national health burdens in Vietnam. In this study, we investigated the prevalence of rifampicin (RIF) and/or isoniazid (isonicotinic acid hydrazide, INH) resistance in patients with suspected TB, and applied appropriate techniques to help rapidly target DR-TB. Methods: In total, 1,547 clinical specimens were collected and cultured using the BACTEC MGIT system (Becton Dickinson and Co.). A resazurin microtiter assay (REMA) was used to determine the proportions of RIF and/or INH resistance. A real-time polymerase chain reaction panel with TaqMan probes was employed to identify the mutations of rpoB and katG associated with DR-TB in clinical isolates. Genotyping of the identified mutations was also performed. Results: A total of 468 Mycobacterium tuberculosis isolates were identified using the REMA. Of these isolates, 106 (22.6%) were found to be resistant to 1 or both antibiotics. Of the resistant isolates, 74 isolates (69.8%) were resistant to isoniazid (INH) only, while 1 isolate (0.94%) was resistant to RIF only. Notably, 31 isolates (29.24%) were resistant to both antibiotics. Of the 41 phenotypically INH-resistant isolates, 19 (46.3%) had the Ser315Thr mutation. There were 8 different rpoB mutations in 22 (68.8%) of the RIF-resistant isolates. The most frequently detected mutations were at codons 531 (37.5%), 526 (18.8%), and 516 (6.3%). Conclusion: To help prevent new cases of DR-TB in Vietnam, it is crucial to gain a comprehensive understanding of the genotypic DR-TB isolates.