Effect of Surface Finish Material on Wetting Property of Sn-Xwt.%Ag Solder

Quoc Vu Bui,Bo-In Noh,Seung-Boo Jung 한국표면공학회 2008 한국표면공학회 학술발표회 초록집 Vol.2008 No.-

Influence of Concentration X on the Microstructure and the Electrical Properties of La{1-x} PrxNiO3 Thin Films

Vu Quoc VIET,민병준,김헌정 한국물리학회 2017 새물리 Vol.67 No.6

The La$_{1-x}$Pr$_x$NiO$_3$ (LPNO) films were grown on SrTiO$_3$ (STO) substrates via the pulsed laser deposition (PLD) method. The influence of the concentration x on the microstructure and the electrical properties of the LPNO films was investigated. The LPNO films with different concentrations x from 0 to 0.3 were fabricated under an oxygen partial pressure of 100 mTorr at a substrate temperature of 750 $^{\circ}$C and an energy density of 1.0 J/cm$^2$. The textures, morphologies and electrical properties of the LPNO films were characterized by using X-ray diffraction, atomic force microscopy (AFM), and electrical resistivity measurements. The LPNO films were shown to be c-axis oriented, and the LPNO films with x = 0.2 and 0.3 exhibited an upturns at T = 40 K and 50 K, respectively.

Molecular and Clinicopathological Features of Gastrointestinal Stromal Tumors in Vietnamese Patients

Quoc Dat Ngo,Quoc Thang Pham,Dang Anh Thu Phan,Anh Vu Hoang,Thi Ngoc Ha Hua,Sao Trung Nguyen 대한병리학회 2019 Journal of Pathology and Translational Medicine Vol.53 No.6

Background: Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal neoplasms of the gastrointestinal tract. Management of GIST patients is currently based on clinicopathological features and associated genetic changes. However, the detailed characteristics and molecular genetic features of GISTs have not yet been described in the Vietnamese population. Methods: We first identified 155 patients with primary GIST who underwent surgery with primary curative intent between 2011 and 2014 at University Medical Center at Ho Chi Minh City, Vietnam. We evaluated the clinicopathological features and immunohistochemical reactivity to p53 and Ki-67 in these patients. Additionally, KIT genotyping was performed in 100 cases. Results: The largest proportion of GISTs was classified as high-risk (43.2%). Of the 155 GISTs, 52 (33.5%) were positive for Ki-67, and 58 (37.4%) were positive for p53. The expression of Ki-67 and p53 were correlated with mitotic rate, tumor size, risk assessment, and tumor stage. Out of 100 GIST cases, KIT mutation was found in 68%, of which 62 (91.2%) were found in exon 11, two (2.9%) in exon 9, and four (5.8%) in exon 17. No mutation in exon 13 was identified. Additionally, KIT mutations did not correlate with any clinicopathological features. Conclusions: The expression of Ki-67 and p53 were associated with high-risk tumors. Mutations in exon 11 were the most commonly found, followed by exon 17 and exon 9. Additionally, KIT mutation status was not correlated with any recognized clinicopathological features.

Tunneling random access memory with Van der Waals heterostructures

Quoc An VU,Young Hee LEE,Woo Jong YU 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

Tuning Carrier Tunneling in van der Waals Heterostructures for Ultrahigh Detectivity

Vu, Quoc An,Lee, Jin Hee,Nguyen, Van Luan,Shin, Yong Seon,Lim, Seong Chu,Lee, Kiyoung,Heo, Jinseong,Park, Seongjun,Kim, Kunnyun,Lee, Young Hee,Yu, Woo Jong American Chemical Society 2017 NANO LETTERS Vol.17 No.1

<P>Semiconducting transition metal dichalcogenides (TMDs) are promising materials for photodetection over a wide range of visible wavelengths. Photodetection is generally realized via a phototransistor, photoconductor, p-n junction photovoltaic device, and thermoelectric device. The photodetectivity, which is a primary parameter in photo detector design, is often limited by either low photoresponsivity or a high dark current in TMDs materials. Here, we demonstrated a highly sensitive photodetector with a MoS2/h-BN/graphene heterostructure, by inserting a h-BN insulating layer between graphene electrode and MoS2 photoabsorber the dark-carriers were highly suppressed by the large electron barrier (2.7 eV) at the graphene/h-BN junction while the photocarriers were effectively tunneled through small hole barrier (1.2 eV) at the MoS2/h-BN junction. With both high photocurrent/dark current ratio (>10(5)) and high photoresponsivity (180 AW(-1)), ultrahigh photodetectivity of 2.6 x 10(13) Jones was obtained at 7 nth. thick h-BN, about 100-1000 times higher than that of previously reported MoS2-based devices.</P>

Adaptive Terminal Sliding Mode Control by Identifying Uncertain and Mutated Disturbance with Reference Model

Vu Quoc Huy,Tran Ngoc Binh 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.4

Nonlinear systems with certain parameters afected by sudden and uncertain disturbance are identifed by systematic state errors from the reference model. The identifcation algorithm is used to design an adaptive terminal sliding mode controller. The coefcient of the switching control component is automatically adjusted according to the deviation of the system state from the sliding surface. The proposed control method makes the state of the system converge to zero but not to converge to the state of the reference model. Simulation results have proved the efectiveness of the algorithm

Electronics and Optoelectronics Based on Two-Dimensional Materials

Quoc An Vu,유우종 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.1

Recently, with the emergence of two-dimensional (2D) materials such as graphene, transition metal dichalcogenides, and hexagonal boron nitride, various studies on electronic and optoelectronic devices based on them have been carried out. In this review article, we discuss the representative studies on electronic and optoelectronic devices based on 2D materials and their heterostructures. Accordingly, we brie y overview the unique properties of typical 2D materials and their van der Waals heterostructures and thereafter present an in-depth review of their advantages for electronics and optoelectronics. The opportunities and challenges presented by them for future electronics and optoelectronics are discussed.

Factors Influencing Cost Overruns in Construction Projects of International Contractors in Vietnam

VU, Thong Quoc,PHAM, Cuong Phu,NGUYEN, Thu Anh,NGUYEN, Phong Thanh,PHAN, Phuong Thanh,NGUYEN, Quyen Le Hoang Thuy To Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.9

A construction project is a designed product made up of labors, materials, and installations in the project positioned on the ground and may include the underground and ground section, and the section in water or on the water surface. It is a civil, industrial, transport, agricultural and rural development, infrastructure, or some other. A key phase in the life cycle of these construction projects is the implementation when building products are made directly with workers, equipment, materials, and managers. If there is a lack of management experience, information, and problem-solving solutions to tackle the risks faced by contractors, especially foreign ones, will fail in controlling the project's cost. This study was conducted with investigations, discussions, and evaluation of the factors that lead to cost overruns in the construction projects of international contractors in Vietnam. The principal component analysis (PCA) showed that those factors that influence cost overruns these construction projects fall into five general groups, including factors related to (i) the owners, (ii) the foreign contractors, (iii) the subcontractors and suppliers, (iv) state management, and (v) the project itself. Besides, the study proposes solutions to limit cost overruns in construction projects and improve the profitability of international contractors in Vietnam.

Specific Domain Pattern of ε-Fe₂O₃ Thin Films Grown on Yttrium-Stabilized Zirconia (100) as a Nucleation Site for α-Fe₂O₃

Viet, Vu Quoc,Adeyemi, Salawu Yusuff,Son, Won Huyk,Rhyee, Jong-Soo,Lee, Nam-Suk,Kim, Heon-Jung American Chemical Society 2018 Crystal Growth & Design Vol.18 No.6

<P>This study examined the phase competition and critical thickness of ε-Fe<SUB>2</SUB>O<SUB>3</SUB> in epitaxial ε-Fe<SUB>2</SUB>O<SUB>3</SUB> thin films grown on a (100)-oriented yttrium-stabilized zirconia (YSZ) substrate using a pulsed laser deposition technique. The maximum critical thickness was found to be ∼20 nm for a single phase of ε-Fe<SUB>2</SUB>O<SUB>3</SUB> at the optimal laser spot size without impurities. Above this critical thickness, (00l)-oriented α-Fe<SUB>2</SUB>O<SUB>3</SUB> begins to appear along with ε-Fe<SUB>2</SUB>O<SUB>3</SUB>, eventually dominating in the thicker samples. These results suggest that the stability of ε-Fe<SUB>2</SUB>O<SUB>3</SUB> films are influenced by the appearance of a specific domain pattern, which becomes a favorable nucleation site for α-Fe<SUB>2</SUB>O<SUB>3</SUB>. The ε-Fe<SUB>2</SUB>O<SUB>3</SUB> films grown on the YSZ (100) substrate have a larger saturation moment than ε-Fe<SUB>2</SUB>O<SUB>3</SUB> grown on SrTiO<SUB>3</SUB> (111), and its coercive field approaches 1/4 of the maximum coercive field of ε-Fe<SUB>2</SUB>O<SUB>3</SUB> nanoparticles.</P><P>Plane view of ε-Fe<SUB>2</SUB>O<SUB>3</SUB> and α-Fe<SUB>2</SUB>O<SUB>3</SUB> unit cells on a YSZ (001) substrate oriented along the <I>c</I>-direction. Edge structure of two ε-Fe<SUB>2</SUB>O<SUB>3</SUB> domains sharing a horizontal line is a possible nucleation site for α-Fe<SUB>2</SUB>O<SUB>3</SUB>. Formation of this structure limits stable growth of ε-Fe<SUB>2</SUB>O<SUB>3</SUB> on the YSZ (001)</P> [FIG OMISSION]</BR>

The Effect of Institutions on Productivity Spillovers from FDI to Domestic Firms: Evidence in Vietnam

Huynh Quoc Vu,Pham Thi Bich Ngoc,Nguyen Le Hoang Thuy To Quyen 사람과세계경영학회 2022 Global Business and Finance Review Vol.27 No.3

Purpose: The purpose of this study is to investigate the impact of formal institutions and their components on productivity spillovers from FDI enterprises to domestic firms’ TFP in developing countries like Vietnam. Design/methodology/approach: The study, conducted in two steps to explore the relationship, is to estimate the firm's TFP in accordance with the semi-parametric method of Levisohn and Petrin (2003). Regression is in accordance with the equation with panel data and adjusted by Driscoll and Kraay standard errors. An unbalanced panel data, related to more than 61,600 Vietnamese manufacturing firms from 2012 to 2017, is combined with the Provincial Institutional Quality Survey (PAPI index) and IO table. Findings: The local institutions have a positive impact on promoting learning ability and increasing productivity of domestic firms, especially small and medium enterprises (SMEs) that take better advantage of this effect. Vertical linkages with FDI enterprises assist local firms to increase productivity while horizontal linkages bring in negative effects. Domestic enterprises with high productivity (in the top 25%) receive positive spillover effects from horizontal linkages and vertical linkages and gain positive impacts of the institution on productivity whereas the group of low-productivity enterprises records negative impacts. This research highlights those enterprises operating in the region where institutions have transparency, accountability, participation in comments and effective corruption control can absorb spillovers and improve their productivity as well as the transparency and corruption control are recognized as having a positive impact through horizontal linkages. Research limitations/implications: With the limitation of research data being conducted only on manufacturing enterprises, there is a lack of data on the impact of service enterprises. The study only stops at understanding the impact of formal institutional effects on productivity spillovers whereas informal institutional effects will be studied in the future. Furthermore, the productivity spillovers of FDI enterprises are explored in general besides other FDI forms that will have different productivity spillovers like offshore. From the results of this study, the governments of developing countries should improve their institutions to encourage local enterprises to take the advantage of spillover effects from FDI enterprises as well as pay more attention to regional factors by supplementing development priority policies based on the capacity of each region. Institutional quality at provincial level has a positive impact on productivity spillovers; consequently, it is essential to have policies for further institutional improvement. Originality/value: This is the first research paper on the impact of the institutional factor at provincial level on firm’s productivity in developing countries like Vietnam. Theoretically, the impact of formal institutions on spillover effects from FDI enterprises is also clarified. In addition, our findings have implications for local economic development policies: vertical linkages promote domestic firms to increase their productivity while horizontal linkages of FDI enterprises in the same industry generate adverse impacts. This paper suggests some feasible solutions for SMEs in developing countries towards their productivity improvement.