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Dao,Duy Thang,Hyun,In-Gyou 한국유통과학회 2019 KODISA ICBE (International Conference on Business Vol.2019 No.-
Vietnam E-commerce has been used and developed 10 years ago but recently, with removing tariff barriers, Vietnam’s customer can easily buy almost thing in the foreign web-site. However, little research has been done to study how to customer’s using intention on across national borders. This study aims to find the factors that effect to customer’s using intention on foreign direct online shopping. A conceptual model is developed from the perspectives of customer’s trust and value. We also examine the impact of information’s signal, security and safe, country image on customer’s trust, as well as the impact of benefits, innovation, cost on customer’s perceived value. This study use an online survey to make questionnaire about the factor and use the answer to test the research model. Our findings can help researchers and practitioners understand the barriers and behaviour of Ho Chi Minh City’s customers to cross-border e-commerce and devise strategies to make profit.
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Dao,Duc Anh,Kim,Soohyun,Kim,Tae-Woong,Kim,Dongkyun 한국방재학회 2019 한국방재학회논문집 Vol.19 No.6
본 연구는 in-situ 강우자료와 레이더자료를 병합하는 조건부 합성(CM)기법의 성능 평가를 목표로 한다. 합성방법은 다음 단계를 통해 처리된다. (1) 정규 크리깅(OK) 기법은 관측소와 레이더 기반 크리깅 강우장을 얻기 위해 적용한다. (2) 보정 강우장은 원래 레이더 강우장에서 레이더기반 크리깅 강우장의 차로 계산한다. (3) 합성강우량은 관측소기반 크리깅 강우장에 보정 강우장을 더하여 도출한다. 분석결과는 CM기반 강우장이 조사된 모든 33개의 10분 강우장 중 22개 사례에 대해 관측소기반 강우장보다 더 정확한 것으로 나타났다. CM 방법과 관측소기반 OK기법의 상관계수는 각각 0.63과 0.83 그리고 0.01과 0.74 사이 값을 보인다. 두 방법의 성능은 관측소 밀도가 높고 시간해상도가 낮을수록 향상되었다. OK기법의 성능은 관측소 밀도에 더 민감하고, CM 기법의 성능은 시간해상도에 더 민감한 것으로 나타났다. 또한, 기존 관측소 밀도가 100 km2 당 1개 일 때, 관측소를 추가하면 두 방법의 성능이 크게 향상되었다. 관측소 증가에 의한 강우량 측정 개선 정도는 관측소 개수가 100 km2 당 4개 이상에 도달할 시 효과가 미미한 것으로 나타났다. This study aims to evaluate the performance of conditional merging (CM) technique to merge radar and in-situ rain gauge data. The merging method contains the following steps: (1) the ordinary kriging(OK) technique is applied to obtain the gauge-only and radar-only kriged rainfall fields; (2) the correction field is calculated by subtracting the radar-only kriged rainfall field from the original radar field; (3) the composite rainfall is derived by adding the correction field to the gauge-only kriged field. We investigated 33 10-min rainfall fields; there were 22 instances where the CM-based rainfall fields were more accurate than the gauge-only fields. The correlation coefficients of the CM and the gauge-only OK methods varied between 0.63 and 0.83, and 0.01 and 0.74 respectively. The performance of both methods improved with greater gauge density and coarser temporal resolution. Furthermore, the OK and CM techniques’performances were more sensitive to gauge density and temporal resolution respectively. We also found that the addition of gauge significantly improved the performance of both methods when the existing gauge density is approximately 1 gauge/100 km2. However, this effect is absent when the density reaches 4 gauges/100 km2.
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Ultrasonic Vibration Assisted Cutting of Nomex Honeycomb Core Materials
Dao‑Hui Xiang,Bang‑Fu Wu,Yun‑Long Yao,Bo Zhao,Jin‑Yuan Tang 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.1
Nomex honeycomb core materials have been widely used in the aviation industry due to their special structure and performance. Conventional high-speed machining have resulted in the poor machinability of the honeycomb core so that the ultrasonic machining technology was applied. The kinematic characteristics in the ultrasonic vibration assisted cutting process were analyzed according to the movement of the sharp tool. Based on slide effect, a cutting force model was proposed to study the relationship between cutting parameters and cutting force. Ultrasonic vibration assisted cutting and ordinary cutting tests of Nomex honeycomb core material were conducted by considering feed rate, the inclined angle and the deflected angle. Besides, the effects of cutting parameters on machined surface quality of honeycomb core wall were studied. The test results show that slide effect caused by ultrasonic vibrations can reduce cutting resistance compared with ordinary cutting. The developed cutting force model can be applied to evaluated the cutting force in the ultrasonic vibration assisted cutting of Nomex honeycomb core material. The inclined angle has a great influence on the cutting force during ultrasonic vibration assisted cutting. High-speed reciprocating sliding action can effectively cut aramid fibers so that burrs and tearing defects of the incision have been greatly improved under condition of ultrasonic vibration assisted cutting.
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Stewardship Theory and Information on Family Firm Performance in Vietnam
Thi Thanh Binh DAO(Thi Thanh Binh DAO ),Linh Chi HOANG(Linh Chi HOANG ) 한국유통과학회 2022 유통과학연구 Vol.20 No.12
Purpose: The paper contributes to the existing literature on Vietnamese corporate governance and firm performance with a focus on listed family firms and the use of a more suitable econometric framework to analyze firm performance. The study investigates how family firm performance is affected by corporate governance under the standpoint of stewardship theory in Vietnam. Research design, data and methodology: With the use of different measures for firm performance (Tobin’s Q, ROA, and ROE), regression models were estimated using Generalized Least Square (GLS) method on a panel data of a total of 113 listed companies during the five-year period from 2015 to 2019. Results: We found that family ownership as the main characteristic of the stewardship theory affects family firms positively. In addition, several other characteristics in corporate governance as board composition (board independence, board audits, and board committees), CEO (age and tenure) and firm characteristics (size, age, expansion, and annual sales) showed significant impacts on firm performance. Our findings also suggest that family firm performance can be either positively or negatively affected based on the characteristics of corporate governance. The findings can help companies evaluate the significance of corporate governance through deciding board structure and the selection of CEOs to match family firm characteristics. It also gives insights for investors, rating agencies, and policymakers for relevant purposes.
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Dao Huy Cuong,Mai Duc Thanh 대한수학회 2017 대한수학회지 Vol.54 No.1
We present a high-resolution van Leer-type numerical scheme for the isentropic model of fluid flows in a nozzle with variable cross-section. Basically, the scheme is an improvement of the Godunov-type scheme. The scheme is shown to be well-balanced, as it can capture exactly equilibrium states. Numerical tests are conducted which include comparisons between the van Leer-type scheme and the Godunov-type scheme. It is shown that the van Leer-type scheme achieves a very good accuracy for initial data belong to both supersonic and supersonic regions, and the exact solution eventually possesses a resonant phenomenon.
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The effect of oxidation on properties of graphene and its polycaprolactone nanocomposites.
Dao, Trung Dung,Oh, Kyung Min,Choi, Jin Taek,Lee, Hyung-Il,Jeong, Han Mo,Kim, Yong Sung,Park, Sung-Jin,Kim, Byung Kyu American Scientific Publishers 2012 Journal of nanoscience and nanotechnology Vol.12 No.11
<P>A functionalized graphene sheet (FGS), which was prepared by the thermal reduction of graphite oxide, was modified by oxidation with H2O2. Elemental analysis, X-ray photoelectron spectroscopy, and Fourier transform infrared (FTIR) spectroscopy showed that additional oxygen functional groups, either doubly or singly bound to carbon, were created by the oxidation. The size and electrical conductivity of the FGS were reduced by the oxidation. During FGS/Polycaprolactone (PCL) nanocomposite preparation by an in situ polymerization method, PCL was grafted onto a FGS by chain growth from a functional group on FGS such as hydroxyl. Thermogravimetry and FTIR spectra demonstrated that the amount of grafted polycaprolactone (PCL) was decreased by the oxidation of FGS, suggesting that PCL chain growth from the FGS surface was inhibited by the neighboring carboxylic acid group on the FGS. Enhanced compatibility between the oxidized FGS and the PCL matrix was observed by optical microscopy and scanning electron microscopy. The reinforcing effect on tensile properties was also enhanced by the oxidized FGS in the FGS/PCL nanocomposites. This suggests that the surface coverage by the grafted PCL chains on the oxidized FGS is higher than that on a pristine FGS, although the grafted PCL chain length is shorter and the amount grafted is smaller.</P>
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Dao, Van-Duong,Larina, Liudmila L.,Choi, Ho-Suk The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.12
<P>This study presents a novel strategy for increasing the efficiency of dye-sensitized solar cells (DSCs) through modifying the surface of the fluorine-doped tin oxide (FTO) substrates using an atmospheric pressure plasma treatment. This strategy allows the suppression of charge recombination at the interface between the FTO substrate and electrolyte due to the formation of a thin, compact TiO<SUB>2</SUB> blocking layer (BL) on the FTO surface without cracks and holes. Furthermore, the transmittance of the plasma-treated FTO/BL interface is higher than that of the pristine structure due to the compact morphology of the BL on the plasma-treated FTO. Thus, this strategy enables simultaneous improvement in light harvesting and photo-generated carrier collection. DSCs that use plasma-treated FTO substrates achieve higher efficiencies of 8.86% compared with the 8.04% of the reference device.</P>
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Role of Atomic and Molecular Nitrogen in Carbon Nanotube Formation
Dao Quang Duy,김현석,Dang Mo Yoon,Jung Woong Ha,Kang Jea Lee,황용규,Bach Thanh Cong,이충훈 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.4
We have investigated the pretreatment effects of nitrogen on the length and the alignment of carbon nanotubes (CNTs) grown on a Ni catalyst by using dc-plasma enhanced chemical vapor deposition system. The surface of the Ni catalyst was pretreated with a mixture of NH3 and N2, instead of pure NH3 and the length of the CNTs has changed from 1.6 um to 400 nm as the NH3/N2 flow rate ratio was decreased. We showed that the length and the alignment of the CNTs could be controlled by changing the NH3/N2 flow rate ratio. The fabricated CNTs were further evaluated by using their Raman spectra. The nitrogen concentration on the surface of the Ni catalyst after the pre-treatment was analyzed by using X-ray photoelectron spectroscopy and the physical structure of CNTs was analyzed using scanning electron microscopy and high resolution transmission electron microscope. We suggest that the N2 adsorption on the surface of Ni changes the carbon atom diffusion during the CNT growth and that the physical structures of CNTs are drastically changed We have investigated the pretreatment effects of nitrogen on the length and the alignment of carbon nanotubes (CNTs) grown on a Ni catalyst by using dc-plasma enhanced chemical vapor deposition system. The surface of the Ni catalyst was pretreated with a mixture of NH3 and N2, instead of pure NH3 and the length of the CNTs has changed from 1.6 um to 400 nm as the NH3/N2 flow rate ratio was decreased. We showed that the length and the alignment of the CNTs could be controlled by changing the NH3/N2 flow rate ratio. The fabricated CNTs were further evaluated by using their Raman spectra. The nitrogen concentration on the surface of the Ni catalyst after the pre-treatment was analyzed by using X-ray photoelectron spectroscopy and the physical structure of CNTs was analyzed using scanning electron microscopy and high resolution transmission electron microscope. We suggest that the N2 adsorption on the surface of Ni changes the carbon atom diffusion during the CNT growth and that the physical structures of CNTs are drastically changed
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