Parameter control for enhanced peak-to-valley current ratio in a MoS₂/MoTe₂ van der Waals heterostructure

Duong, Ngoc Thanh,Bang, Seungho,Lee, Seung Mi,Dang, Dang Xuan,Kuem, Dong Hoon,Lee, Juchan,Jeong, Mun Seok,Lim, Seong Chu The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.26

<P>The <I>I</I>ds-<I>V</I>ds properties of a van der Waals cross-junction of few layered MoS2/MoTe2 were investigated, and the physical device parameters were altered in order to transform the conduction mechanism from thermionic emission to interband tunneling. The pristine heterostructure demonstrated rectification behavior of typical p-n junction diodes, because of the p-type and n-type nature of MoTe2 and MoS2, respectively. Lowering the contact resistance between the metal and channel materials, by changing the electrode metals from Au to Pd and Ti, alone did not give rise to carrier conduction through the hetero-interband tunneling between MoTe2 and MoS2. In addition to the reduction in contact resistance, the chemical doping of MoS2 using Benzyl Viologen (BV) achieves hetero-interband tunneling between MoTe2 and MoS2, which probably narrows the depletion layer by degenerating MoS2. The peak-to-valley ratio of the tunneling current of the BV-doped heterostructure of MoS2/MoTe2 is about 4.8, which is comparable to that of the commercially available Si tunneling diode.</P>

Modulating the Functions of MoS₂/MoTe₂ van der Waals Heterostructure <i>via</i> Thickness Variation

Duong, Ngoc Thanh,Lee, Juchan,Bang, Seungho,Park, Chulho,Lim, Seong Chu,Jeong, Mun Seok American Chemical Society 2019 ACS NANO Vol.13 No.4

<P>Various functional devices including <I>p-n</I> forward, backward, and Zener diodes are realized with a van der Waals heterostructure that are composed of molybdenum disulfide (MoS<SUB>2</SUB>) and molybdenum ditelluride (MoTe<SUB>2</SUB>) by changing the thickness of the MoTe<SUB>2</SUB> layer and common gate bias. In addition, the available negative differential transconductance of the heterostructure is utilized to fabricate a many-valued logic device that exhibits three different logic states (<I>i.e.</I>, a ternary inverter). Furthermore, the multivalued logic device can be transformed into a binary inverter using laser irradiation. This work provides a comprehensive understanding of the device fabrication and electronic-device design utilizing thickness control.</P> [FIG OMISSION]</BR>

The Effect of Financial Restructuring on the Overall Financial Performance of the Commercial Banks in Vietnam

DUONG, Tam Thanh Nguyen,PHAN, Hai Thanh,HOANG, Tien Ngoc,VO, Tien Thuy Thi Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.9

The study investigates and measures the impact of financial restructuring on overall financial performance of commercial banks in Vietnam. Survey data for this research were collected from audited financial reports of 28 commercial banks in Vietnam, for the period from 2008 to 2018. In the study, we have built a model of econometric regression with the dependent variable being financial results measured through ROA and ROE. The research methods used include Pooled Ordinary Least Square Model (POLS), Fixed Effects Model (FEM), Random Effects Model (REM), and different Generalized Method of Moments (GMM). The results showed that the account payables restructuring and owners' equity restructuring are much needed. Increasing the owners' equity, decreasing the account payables would improve the overall financial performance, bad debts restructuring to decrease bad debts would also improve the financial performance as well. However, the financial restructuring in the period 2012-2015 and 2016-2018, indeed worsen the financial performance during those times. The findings of this study suggest that the evaluation of the financial performance after restructuring of commercial banks in Vietnam must be based on longer data. At the same time, it is necessary to examine differences between various banking groups to draw accurate conclusions on financial performance.

Effect of adding non-ferromagnetic nanoparticles to grain boundary on coercivity of sintered Nd-Fe-B magnet

Thanh, Pham Thi,Van Duong, Nguyen,Yen, Nguyen Hai,Ngoc, Nguyen Huy,Lam, Nguyen Mau,Hau, Kieu Xuan,Yu, Seong Cho,Dan, Nguyen Huy ELSEVIER 2018 Current Applied Physics Vol.18 No.3

<P>In this work, we investigated the influence of additional compounds of Nd-Cu-Al, Dy-Nb-Al, Dy-Zr-Al and Nb-Cu-Al on coercivity of sintered Nd-Fe-B magnets. The additional nanoparticles with size in the range of 40-80 nm was mixed with the micrometer Nd-Fe-B powder before sintering process. The results show that the coercivity of the sintered Nd-Fe-B magnets can be improved by introducing additional nanoparticles to their grain boundaries. The improvement of the coercivity of the magnets is clearly dependent on composition and fraction of the additional compounds. While the Dy-Nb-Al, Dy-Zr-Al and Nb-Cu-Al compounds degrade the coercivity of the sintered Nd-Fe-B magnets, the Nd-Cu-Al nanoparticles considerably improve this quantity. The coercivity the sintered Nd16.5Fe77B6.5 magnets has been enhanced about 40% by adding 3 wt% of the Dy-free compound of Nd40Cu30Al30. (C) 2017 Elsevier B.V. All rights reserved.</P>

A HYBRID METHOD FOR INTEGRATING MULTIPLE ONTOLOGIES

Duong, Trong Hai,Nguyen, Ngoc Thanh,Jo, Geun Sik Taylor Francis 2009 Cybernetics and systems Vol.40 No.2

<P> While there has been a variety of research focusing on ontology integration based on simple techniques (e.g., element- or structure-level techniques), the hybrid approaches combining the simple techniques have not been explored. In this paper we describe a hybrid method to integrate multiple ontologies in several levels, such as the element level, internal structure, and relational structure. A semantic supporting environment (SSE) combining special domains (e.g., WordNet) and text corpus are defined in the proposed approach. An enriched ontology model (EOM) has been proposed to reduce the initial complexity of the process of ontology integration. Subsequently, the semantic network called OnConceptSNet is provided. The relations between the concepts in the OnConceptSNet are derived from the SSE. An enhanced algorithm (EA) has been proposed to enhance OnConceptSNet.</P>

Domain structure and finite-size effects in Sr2-La FeMoO6 nanoparticles: A study by magnetic measurements

Duong Nguyen Phuc,Nguyet Dao Thi Thuy,Loan To Thanh,Man Nguyen Khac,Anh Luong Ngoc 한국물리학회 2023 Current Applied Physics Vol.49 No.-

In this work, a model for the microstructure of Sr2-xLaxFeMoO6 nanoparticles samples (0 ≤ x ≤ 0.4) was established based on scanning electron microscopy and magnetic studies. The analysis reveals antiphase crystalline domains in the particles with the size distribution centered around mean values below ~12 nm for all the samples. Such small-size domains are responsible for the superparamagnetic properties observed for temperatures below room temperature, which are dependent on their dipole interactions. According to the fraction of Fe atoms at the antiphase boundaries calculated under the spherical domain assumption, these domains have lower degrees of atomic disorder than those estimated from the saturation magnetization values at 5 K, which are consistent with the high spin polarization values previously reported. The Curie temperature values, and the broadening of the magnetic phase transition can be satisfactorily explained based on the domain size distribution.

Identification of aquifer system in the whole Red River Delta, Vietnam

Duong Du Bui,Akira Kawamura,Thanh Ngoc Tong,Hideo Amaguchi,Naoko Nakagawa,Yoshihiko Iseri 한국지질과학협의회 2011 Geosciences Journal Vol.15 No.3

The Red River Delta is one of two biggest deltas in Vietnam. People living in the delta depend entirely on groundwater for their domestic water. However, the aquifer system in the whole Red River Delta remains poorly understood due to the lack of available data. Recently, we were nominated to construct a hydrogeological database. Using these valuable data contained in this database, this paper comprehensively analyzed the best number of 778 boreholes including well logs and their hydrogeological parameters obtained from pumping tests for the first time in order to identify the entire aquifer system and characterize hydrogeological conditions in the whole delta for potential groundwater resources. Great efforts have been made to establish and analyze hydrogeological maps, cross sections, and contour maps of main aquifers’ thickness and transmissivity. As for the results, we found that groundwater mainly exists in Quaternary unconsolidated sediments as porous water forming the topmost Holocene unconfined aquifer (HUA) and the shallow Pleistocene confined aquifer (PCA) sandwiching the Holocene-Pleistocene aquitard (HPA), while cleft and karst water exist in consolidated Neogene formations and Mesozoic rocks constituting the Neogene water bearing layer (NWL) and Mesozoic fractured zones (MFZ), respectively. PCA is almost entirely distributed over the delta. It serves as the highest groundwater potential and the most important aquifer for water supply. HUA is also widely distributed about 88% over the delta and has a high groundwater potential. NWL and MFZ, placed below PCA but exposed on the surface outside the delta, are minor sources for local domestic water supply only. These findings are indispensable for further groundwater analyses needed to ensure the sustainable groundwater development for the high-security water requirements in the delta, but have never been completed sufficiently before due to the unavailability of large-scale basic data sets

The Effect of Social Capital on Social Entrepreneurial Intention among Vietnamese Students

HA, Ngoc Thang,DOAN, Xuan Hau,VU, Trong Nghia,NGUYEN, Thi Phuong Linh,PHAN, Thanh Hoa,DUONG, Cong Doanh Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.8

This study develops the model to estimate the links between social capital, social entrepreneurial self-efficacy, perceived desirability and social entrepreneurial intention. Besides exploring the direct impacts of social capital, social entrepreneurial self-efficacy, and perceived desirability on social entrepreneurial intention, this study also focus on discovering the mediating roles of perceived desirability and social entrepreneurial self-efficacy on this relationship. Throughout adopting measures from some previous studies, the authors design the questionnaires and distribute to students in Vietnam. The study presents some demographic information of 289 students, who are studying at university and colleges in Vietnam. Then, the validity and reliability of scales are assessed using the value of Cronbach's alpha, Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA). In addition, by utilizing the structural modeling structure (SEM), the authors show that social capital plays the important role in shaping social entrepreneurial self-efficacy, perceived desirability, and social entrepreneurial intention. Interestingly, besides the direct effects on social entrepreneurial intention, perceived desirability and social entrepreneurial self-efficacy also mediate the correlation between social capital and social entrepreneurial intention. Also, with the interesting findings of the study, the authors propose several recommendations for policy-makers, educators and academics to promote the social entrepreneurship and innovation among Vietnamese students.

Determinants of Operational Self-Sustainability of Microfinance Institutions in Vietnam

LE, Thanh Tam,DAO, Lan Phuong,DO, Ngoc Mai,TRUONG, Thi Hoai Linh,NGUYEN, Thi Thuy Duong,TRAN, Chung Thuy Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.10

The purpose of this paper is to investigate the determinants of the Operational Self-Sustainability (OSS) of Vietnamese microfinance institutions (MFIs). This research uses both qualitative and quantitative research methods: (i) qualitative research was via in-depth interviews with ten microfinance practitioners, policymakers and researchers; (ii) quantitative research was conducted by using panel data of 34 MFIs in the period 2011-2015 with binary logistics and OLS regressions. Results are as follows: (i) MFIs' OSS in Vietnam are mainly determined by five key factors: portfolio at risk (PAR>30), capital structure, gross loan portfolio, scope of activities and legal form; (ii) OSS are most affected by legal status (social organizations have better OSS than formal MFIs or programs/projects), location (MFIs focus in one province have higher OSS than working nationwide or just in one district), capital structure (MFIs with more equity proportion have higher OSS); (iii) surprisingly, average loan size per borrower and age of MFIs do not have statistically significant correlation with OSS. The key recommendations are: (i) MFIs should focus on its professionality and increase its equity; (ii) related stakeholders such as State Bank of Vietnam should promote the enabling ecosystem for microfinance development to enhance poverty reduction and economic development.

The Impact of Foreign Ownership on Firm Performance

Quynh Nga DUONG,Thanh Binh VU,Thi-Phuong VO,Ngoc Hoan NGUYEN-LE,Van Diep NGUYEN 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.6

The purpose of the research examines the relationship between foreign ownership and listed firms’ performance in Vietnam. This study employs an extensive set of panel data comprising 288 non-financial listed Vietnamese firms, over a period from 2015 to 2019 taken for analysis. The results show that the higher the foreign ownership ratio, the higher the performance, however, the relationship between foreign ownership and firm’s performance is U-shaped. In contrast, when the foreign ownership ratio is becoming too high, it will reduce the firm’s performance and firm size, liquidity, financial leverage, capital intensity, and growth opportunities. Furthermore, we find that foreign ownership and performance are linked by an inverted U-shaped relationship. A firm’s performance increases with greater foreign ownership up to the range of 36.26%, and declines thereafter. The paper also found positive effects of firm size and growth opportunities, and an inverse relationship between liquidity, financial leverage and capital intensity, and firm’s performance. This study has several implications for the enhancement of information and understanding of the foreign ownership as it sheds light on the foreign ownershipfirm’s performance relationship. Moreover, the study findings contribute to the literature concerning the ownership structure in the context of developing countries.