Optical Spectra of the Colloidal Fe-doped Manganate CaMn1−xFexO3 (x = 0, 0.01, 0.03, 0.05)

Duc Huyen Yen Pham,Duc Tho Nguyen,Duc Thang Pham,Nam Nhat Hoang,The Tan Pham 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12

We report the optical behaviors of the Fe-doped CaMnO3 family of compounds at low dopingconcentrations x 5%. The study aims at assisting the evaluation of the competition between ferroandantiferromagnetic orderings, which is believed to be a cause of many interesting properties of thisclass of compounds, including the magnetization reversal effect recently discovered. The structuralcharacterization showed a predominant orthorhombic phase with slightly increased cell constantsdue to doping. The Raman spectra revealed changes associated with the Mn sites, and the IRabsorption spectrum showed a characteristic Fe band at 1.2 eV, which should be accompanied bya change of spin. The analysis of the magnetization data allowed us to predict that while thedoping reduced the ferromagnetic coupling strength, and therefore the TC, the maximal dopingconcentration for the effective exchange to be zero was around 14%.

Numerical Simulation of Air Flow and Gas Dispersion around Obstacles

The-Duc Nguyen,Ngoc-Hai Duong,Warn-Gyu Park 한국전산유체공학회 2003 한국전산유체공학회 학술대회논문집 Vol.2003 No.-

Computations of the mean and turbulence flows over three-dimensional hill of conical shape have implemented. Beside the standard k-ε, two other modifications proposed by Detering & Etling and Duynkerke for atmospheric applications were also considered. These predictions were compared with the data of a wind tunnel experiment. From the comparison, it was concluded that all three models predict<br/> the mean flow velocities equally well while only the Duynkerke's model accurately predicts the turbulence data statistics. It also concluded that there are large discrepancies between model predictions and the measurements near the ground surface.<br/> The flow field, which was obtained by using the Duynkerke's modification, was used to simulate gas dispersion from an upwind source. The calculation results are verified based on the measurement data. Modifications of the turbulent Schmidt number were carried out in order to match the measured results. The code was used to investigate the influence of the recirculation zone behind a building of cubical shape on the transport and dispersion of pollutant. For a stack behind and near the obstacle, some conclusions about the effect of the stack height and stack location were derive

The potential efficacy of the E2-subunit vaccine to protect pigs against different genotypes of classical swine fever virus circulating in Vietnam

Ha Thi Thanh Tran,Duc Anh Truong,Viet Duc Ly,Hao Thi Vu,Tuan Van Hoang,Chinh Thi Nguyen,Nhu Thi Chu,Vinh The Nguyen,Duyen Thuy Nguyen,Kohtaroh Miyazawa,Takehiro Kokuho,Hoang Vu Dang 대한백신학회 2020 Clinical and Experimental Vaccine Research Vol.9 No.1

Purpose: To date, many kinds of classical swine fever (CSF) vaccines have been developed to protect against this disease. However, the efficacy of these vaccines to protect the pig against field CSF strains needs to be considered, based on circulating strains of classical swine fever virus (CSFV). Materials and Methods: Recombinant E2-CSFV protein produced by baculovirus/insect cell system was analyzed by western blots and immunoperoxidase monolayer assay. The effect of CSFV-E2 subunit vaccines was evaluated in experimental pigs with three genotypes of CSFV challenge. Anti-E2 specific and neutralizing antibodies in experimental pigs were analyzed by blocking enzyme-linked immunosorbent assay and neutralization peroxidize-linked assay. Results: The data showed that CSFV VN91-E2 subunit vaccine provided clinical protection in pigs against three different genotypes of CSFV without noticeable clinical signs, symptoms, and mortality. In addition, no CSFV was isolated from the spleen of the vaccinated pigs. However, the unvaccinated pigs exhibited high clinical scores and the successful virus isolation from spleen. These results showed that the E2-specific and neutralizing antibodies induced by VN91-E2 antigen appeared at day 24 after first boost and a significant increase was observed at day 28 (p<0.01). This response reached a peak at day 35 and continued until day 63 when compared to controls. Importantly, VN91-E2 induced E2-specific and neutralizing antibodies protected experimental pigs against high virulence of CSFVs circulating in Vietnam, including genotype 1.1, 2.1, and 2.2. Conclusion: These findings also suggested that CSFV VN91-E2 subunit vaccine could be a promising vaccine candidate for the control and prevention of CSFV in Vietnam.

Impact of Motivational Factors on the Work Results of Lecturers at Vietnam National University, Hanoi

DO, Anh Duc,PHAM, Ngoc Thach,BUI, Hong Phuong,VU, Duc Thanh,NGUYEN, The Kien,NGUYEN, Thi Huyen Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.8

This paper aims to develop a conceptual framework for evaluating the impact of motivational factors on the work results of lecturers at Vietnam National University, Hanoi (VNU), one of two leading multidisciplinary and multi-sectoral national universities in Vietnam. This study has considered wages and other benefits (WB), training and development (TD), working environment (WE) and working motivation (WM) as motivational factors, and proposed a structural model of the impact of motivational factors on the work results of lecturers at VNU. The empirical analysis used data from the survey data of 321 university lecturers. Comprehensive, valid, and reliable tools (SPSS 26 and SmartPLS 3.0 software) are used to evaluate rigorous statistical tests including convergence validity, discriminatory validity, reliability, and average variance extracted to analyze and verify the gathered data, and the hypotheses developed. The result of path analysis shows that four motivational factors constitute a structured system with different degrees of influence on the work results of lecturers. There is also a positive relationship between the motivational factors and the work results of lecturers. As a result, it can be concluded that all hypotheses developed are supported. Several recommendations are further suggested to improve the performance of lecturers at VNU.

Impact of Corporate Social Responsibility Disclosures on Bankruptcy Risk of Vietnamese Firms

NGUYEN, Soa La,PHAM, Cuong Duc,NGUYEN, Anh Huu,DINH, Hung The Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.5

This study investigates the nexus between the level of Corporate Social Responsibility Disclosures (CSRD) and Risk of Bankruptcy of companies that are listing in the Stock Exchanges of Vietnam. To investigate that relationship, this study collected secondary data from annual audited financial statements from 2014 to 2018 of listing companies. Applying two different regression models with two dependent variables and six independent and control variables, we find out that Vietnamese firms with higher level of CSRD performance can rapidly reduce their risk of bankruptcy. This phenomenon happens in the current year and in the coming years in all firms in the research sample. This result may be that the disclosures of social responsibility information can bring financial and non-financial benefits to the firms. In addition, the results also point out that there is a difference in risk of bankruptcy between the group of companies, which discloses and the one which does not disclose corporate social responsibility on their annual reports. This might be from the effects of various factors such as business size, financial leverage, market to book ratio, return on assets, cash flow from operations, etc. Our research results can be applied to other firms in Vietnam and in other similar jurisdictions.

AFM Study and Magnetic Properties of Nanocrystalline Fe<SUB>73.5</SUB>-xCrxSi<SUB>13.5</SUB>B<SUB>9</SUB>Nb₃Au₁ (x = 1~5) Alloys

Anh-Tuan Le,Nguyen Chau,Nguyen Duy Cuong,Ngo Duc The,Chong-Oh Kim,Jang-Roh Rhee,Heebok Lee 한국자기학회 2006 Journal of Magnetics Vol.11 No.1

In this paper, the influences of microstructural and surface morphological developments on the soft magnetic properties and giant magneto-impedance (GMI) effect of the Fe73.5-xCrxSi13.5B9Nb₃Au₁ (x = 1, 2, 3, 4, 5) alloys have been presented. It was found that the Cr addition slightly decreased the mean grain size of α-Fe(Si) grains. AFM results indicate a large variation of surface morphology of density and size of protrusions along the ribbon plane due to microstructural changes caused by thermal annealing with increasing Cr content. Ultrasoft magnetic properties of the nanocrystallized samples were noticeably enhanced by properly heat treatments at Ta=540℃ such as an increase of the magnetic permeability and the decrease of coercivity, which is likely due to the formation of nanoscale α-Fe(Si) phase which reduced the magnetoelastic anisotropy of samples. Accordingly, the GMI effect was observed in the annealed samples. The correlation between the microstructure, surface morphology, and soft magnetic properties were explained by nucleation and growth model.

Application/Comparison Study of a Graphical Method of Forming Limit Curve Estimation for DP590 Steel Sheets

The-Thanh Luyen,Quoc-Tuan Pham,Young-Suk Kim,Duc-Toan Nguyen Korean Society for Precision Engineering 2019 한국정밀공학회지 Vol.36 No.9

Since its introduction, the Modified Maximum Force Criterion proposed by Hora et al., has been widely used to theoretically estimate the forming limit curve of metal sheets. On the basis of this criterion, a graphical method was presented in our previous study to simplify the evaluation of the forming limit curve (FLC) of metal sheets. This paper presents an application of the graphical method to estimate the FLCs of an advanced high-strength steel sheet material, DP590. The material is frequently used in the automotive industry. To verify the ability of the graphical method, various hardening laws and yield functions were used to estimate the forming limiting curves for the examined material. The calculated forming limiting curves are then adopted for the finite element method (FEM) to predict the fracture heights of different notch specimens desired by the Hecker’s punch stretching tests. The results of the finite element method simulations agree well with the values of the fracture heights, in comparison to the experimental data. This verifies the ability and potential of the graphical method in industrial engineering.

Optimal control of vibration by multiple tuned liquid dampers using Taguchi method

Nguyen Van Khang,Do The Duong,Nguyen Thi Van Huong,Nguyen Duc Thi Thu Dinh,Vu Duc Phuc 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.4

This paper investigates the multiple tuned liquid dampers (MTLD), which consist of a number of MTLD whose first natural frequencies of sloshing are distributed over a certain range around the natural frequency of a structure. The liquid motion in the MTLD as well as the MTLD-structure interaction are numerically simulated using a shallow water-wave theory. An optimal procedure based on Taguchi method is proposed to determine the optimum parameters of MTLD to suppress the vibration amplitude of the considered structure. A number of numerical tests are included to demonstrate and verify the effectiveness of the proposed procedure.

Factors Affecting the Internal Audit Effectiveness of Steel Enterprises in Vietnam

The Hung DINH,Duc Cuong PHAM,Tuan Thi NGUYEN 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.1

This article provides empirical evidence on factors of internal audit (IA) characteristics affecting the internal audit effectiveness in steel enterprises in Vietnam. The study uses data from survey obtained from 114 responses representing owners, managers, and internal auditors from 38 steel enterprises in Vietnam for period from 2018 to 2019. Data collected is firstly checked with Cronbach’s Alpha, then the EFA test, and the model linear regression is used to test the relationship between internal audit characteristics and internal audit effectiveness. Results reveal that internal audit effectiveness in steel enterprises in Vietnam is influenced by various internal factors, including the size of internal audit, the scope of internal audit, the capacity of internal auditors, the independence of internal auditor, and the operational bases and methods of internal audit. Based on the research results, the paper makes six recommendations: strengthening operational basis of IA; increasing the independence of IA; increasing the size and capacity of IA staff; expanding and not underestimate the scope of IA; and reforming the internal governance structure. These proposed recommendations could be applied, not only for steel companies in Vietnam, but also for other companies in Vietnam or other companies in jurisdictions that have similar conditions.

Argyreia gyrobracteata Traiperm & Chitchak (Convolvulaceae): A new record to the flora of Vietnam

Binh Duc TRAN,Bach The TRAN,Do Van Hai,Quang Hong BUI,Son Hoang DOAN,Han Ngoc LE,Thuy Thu NGUYEN,엄상미 한국식물분류학회 2020 식물 분류학회지 Vol.50 No.3

Argyreia gyrobracteata Traiperm & Chitchak (Convolvulaceae) is newly recorded in Vietnam. It is similar to A. mekongensis Gagnep & Courch in having a white campanulate corolla but differs from that species by having whitish surface of the abaxial leaf, narrowly lanceolate or linear-oblong, curly, rolled up the bract with a longer length of the petiole and a shorter pedicel. It was previously known only in Thailand, but was recently found in Lam Dong Province, Vietnam, for the first time. The present study provides a detailed description, colorful photos and the distribution of the species. Furthermore, a comparison of the diagnostic characters between this species and a related species in Vietnam, A. mekongensis Gagnep & Courch, is provided.