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Two new species of Camellia (Theaceae) from Vietnam
Lieu Thi Nguyen,Ninh Tran,Uematsu CHIYOMI,Katayama HIRONORI,Dung Van Luong,Son Thanh Hoang,Ky Danh NGUYEN,Hung Viet NGUYEN,Toan Canh THAI 한국식물분류학회 2018 식물 분류학회지 Vol.48 No.2
Two new species of Camellia (Theaceae) are described from Vietnam: Camellia vuquangensis Luong, Tran & L. T. Nguyen and Camellia hatinhensis Luong, Tran & L. T. Nguyen. The new taxa were col- lected from Vu Quang National Park in the center of Vietnam. The new finds are morphologically dissimilar to all known Camellia species. Recent Camellia discoveries have increased the number of species recorded in Viet- nam from 50 to 75, making Vietnam a center of diversity and a crucial area for more research into the diversity and distributions of Camellia.
Treatment of surface water using cold plasma for domestic water supply
Dung Van Nguyen,Phong Quoc Ho,Toan Van Pham,Tuyen Van Nguyen,Lavane Kim 대한환경공학회 2019 Environmental Engineering Research Vol.24 No.3
This paper presents the results of using cold plasma to treat surface water for domestic use purpose. Experimental results showed that cold plasma was an effective method for destroying bacteria in water. After treatment with cold plasma, concentration of coliform and Escherichia coli dramatically reduced. Besides, cold plasma significantly removed water odor, increased dissolved oxygen and decreased the concentration of chemical oxygen demand. However, cold plasma significantly raised the concentration of nitrite and nitrate. Other disadvantages of treating with cold plasma were conductivity increase and pH reduction. Pretreatment steps of coagulation, flocculation, sedimentation and sand filtration followed by disinfection with cold plasma exhibited a high efficiency in surface water treatment. All parameters of surface water after treatment by using the prototype satisfied with the allowance standard of domestic water quality.
Determinants Influencing Housing-Option Decision of Gen Y: The Case of Vietnam
Ha Thu LUONG(Ha Thu LUONG ),Dung Manh TRAN(Dung Manh TRAN ),Dan Linh Ngoc NGUYEN(Dan Linh Ngoc NGUYEN ),Van Bao NGUYEN(Van Bao NGUYEN ),Anh Thuc LE(Anh Thuc LE ),Hieu Van PHAM(Hieu Van PHAM ) 한국유통과학회 2023 유통과학연구 Vol.21 No.7
Metamaterial Perfect Absorber Using the Magnetic Resonance of Dielectric Inclusions
Nguyen Van Dung,Bui Son Tung,Bui Xuan Khuyen,Young Joon Yoo,YoungPak Lee,Joo Yull Rhee,Vu Dinh Lam 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.8
In this report, we introduce a stable metamaterial perfect absorber at GHz frequency based on a novel design of a Mie-type resonance. A single perfect absorption peak is achieved at 9.54 GHz, and the influence of the structural parameters on the absorption behavior is studied; the results were consistent with dielectric-resonator theory. The absorption is demonstrated to be polarizationinsensitive; furthermore, the absorber structure can work for a wide incident angle without any change in the resonance peak. Our absorber structure can also control 47% of the resonance peak’s position by changing the temperature of the dielectric layer. Our absorber structure can also be applied as an electromagnetic-wave absorber for wide-incident-angle, thermally-controllable devices.
Nguyen Van Dung,유영준,이영백,Nguyen Thanh Tung,Bui Son Tung,Vu Dinh Lam 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.1
The influence of lattice constants on the electromagnetic behavior of a cut-wire-pair (CWP)structure has been elucidated. In this report, we performed both simulations and experiments todetermine the influence of polarization on the metamagnetic resonance of the CWP structure. Thekey finding is the result of an investigation on the plasmon hybridization between the two CWs,which showed that the polarization of the incident wave was affected. Good agreement betweennumerical simulation and measurement is achieved.
NGUYEN, Dung Duc,NGUYEN, Cong Van Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.5
The paper examines the impact of information about cash flow from operating activities of firms listed on Vietnam's stock market to the decision making of individual investors. Data were collected from interviews with 160 individual investors about their investment decisions based on information on profit growth and cash flow growth from operating activities. T-test was conducted to research on Vietnam's stock market - a market considered as information that is not really public, transparent and ineffective. The research results show that: (1) investors do not care about cash flow from operating activities when making investment decisions if the company's profits grow positively, (2) information about cash flow from operating activities only affects the decisions of individual investors once profit growth is negative, and (3) conflicting information between profit growth and cash flow growth from business activities significantly affects the confidence and comfort of investors in Vietnam's stock market when they make investment decisions. Then, the study points out the mistake of investors when making investment decisions, and offers recommendations to investors when making investment decisions, not only concerned with profit growth, but also paying special attention to cash flow growth, especially cash flow from the company's business operations.
Breakdown, V-t and Degradation Characteristics of Insulation in Liquid Nitrogen for HTS Transformer
Nguyen, Van-Dung,Joung, Jong-Man,Baek, Seung-Myeong,Lee, Chang-Hwa,Suck, Song-Hee,Kim, Sang-Hyun The Korean Institute of Electrical Engineers 2004 전기학회논문지C Vol.53 No.6
HTS transformer is one of the most promising devices to supply enough electric energy for quick increase consumption. However, for practical design of the HTS transformer, it is necessary to establish the research on breakdown, V-t characteristics, degradation, and so on. In this paper, we discussed breakdown characteristics and V-t characteristics of polyimide/L$N_2$ and glass fiber reinforced plastic/$LN_2$ composite insulations. These composite insulations have been used as turn-to-turn and layer-to-layer insulations for HTS transformer respectively, Moreover, we investigated the degradation of these insulation samples after breakdown using microscope and SEM photograph.
Carbon-Nanotube Growth over Iron Nanoparticles Formed on CaCO3 Support by Using Hydrogen Reduction
Nguyen Duc Dung,Nguyen Van Chuc,Ngo Thi Thanh Tam,Nguyen Hong Quang,Phan Hong Khoi,Phan Ngoc Minh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Carbon nanotubes (CNTs) were grown by chemical vapor deposition on a mixture of iron salt and CaCO3. Salt mixtures of Fe(NO₃)₃9H₂O/CaCO₃ and FeCl₃6H₂O/CaCO₃ with various Fe weight contents were used as catalysts for growing the CNTs. A scanning electron microscope study revealed that the CNTs were densely grown on the Fe(NO₃)₃9H₂O/CaCO₃ catalyst containing 5 wt.% Fe. The effect of growth temperature on the segregation of Fe nanoparticles formed by hydrogen reduction is discussed. The result shows that 800 ℃ is the optimal temperature for the formation of Fe nanoparticles over which CNTs grow with the highest yield of 78.61 %. A raman spectroscope and a scanning transmission electron microscope were utilized to characterize the multiwall structure of the CNTs. The 92.16 % purity of the CNTs was determined by using thermal gravimetric analysis. Carbon nanotubes (CNTs) were grown by chemical vapor deposition on a mixture of iron salt and CaCO3. Salt mixtures of Fe(NO₃)₃9H₂O/CaCO₃ and FeCl₃6H₂O/CaCO₃ with various Fe weight contents were used as catalysts for growing the CNTs. A scanning electron microscope study revealed that the CNTs were densely grown on the Fe(NO₃)₃9H₂O/CaCO₃ catalyst containing 5 wt.% Fe. The effect of growth temperature on the segregation of Fe nanoparticles formed by hydrogen reduction is discussed. The result shows that 800 ℃ is the optimal temperature for the formation of Fe nanoparticles over which CNTs grow with the highest yield of 78.61 %. A raman spectroscope and a scanning transmission electron microscope were utilized to characterize the multiwall structure of the CNTs. The 92.16 % purity of the CNTs was determined by using thermal gravimetric analysis.
Synthesis of Carbon Nanotubes on Steel Foils
Nguyen Van Chuc,Nguyen Duc Dung,Phan Ngoc Hong,Le Dinh Quang,Phan Hong Khoi,Phan Ngoc Minh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Carbon nanotubes (CNTs) were synthesized by using a thermal chemical vapor deposition (CVD) at 800 ℃ in a mixture of C₂H₂, H₂ and N₂ gases with steel foils as both catalysts and substrates. More than 2 grams of CNTs were grown on approximately 7 grams of steel foil with a 0.5 cm² surface area after 30 minutes of growth. The effects of CVD parameters, such as the growth temperature and the deposition time, on the size and the morphology of the CNTs were studied using scanning electron microscopy (SEM). We found that the optimized temperature and growth time for having high quality CNTs were 800 ℃ and 30 minutes, respectively. The purity of the CNTs was evaluated by using thermogravimetric analysis (TGA) and the result showed that the carbon content was approximately 93 wt.%. The graphite crystallinity of the CNTs was analyzed by using Raman spectroscopy. The steel foil was found to maintain its catalytic behavior after several growths. The technique holds great promise for use in mass production (approximately 120 grams CNTs per day) with signicantly reduced cost. Carbon nanotubes (CNTs) were synthesized by using a thermal chemical vapor deposition (CVD) at 800 ℃ in a mixture of C₂H₂, H₂ and N₂ gases with steel foils as both catalysts and substrates. More than 2 grams of CNTs were grown on approximately 7 grams of steel foil with a 0.5 cm² surface area after 30 minutes of growth. The effects of CVD parameters, such as the growth temperature and the deposition time, on the size and the morphology of the CNTs were studied using scanning electron microscopy (SEM). We found that the optimized temperature and growth time for having high quality CNTs were 800 ℃ and 30 minutes, respectively. The purity of the CNTs was evaluated by using thermogravimetric analysis (TGA) and the result showed that the carbon content was approximately 93 wt.%. The graphite crystallinity of the CNTs was analyzed by using Raman spectroscopy. The steel foil was found to maintain its catalytic behavior after several growths. The technique holds great promise for use in mass production (approximately 120 grams CNTs per day) with signicantly reduced cost.