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Nguyen Huu Nghia,Nguyen Thi Nguyen,Phan Trong Binh,Le Thi May,Tong Tran Huy,Pham Thai Giang,Sophie St-Hilaire,Phan Thi Van 한국수산과학회 2022 Fisheries and Aquatic Sciences Vol.25 No.8
This study assessed the effects of oxygen and ozone nanobubbles on gill morphology, weight gain, and mortality of Pacific white shrimp (Penaeus vannamei), as well as the level of Vibrio parahaemolyticus and water quality of shrimp culture tanks under lab conditions. Two experiments were carried out with oxygen macrobubble, ozone macrobubble, oxygen nanobubble, ozone nanobubble, and control treatments (air-stone macrobubble). Experiments were done in triplicate in 100 L tanks with 15‰ saline water, and 20 shrimp per tank. Tanks in Experiment 1 were not inoculated with bacteria; tanks in Experiment 2 were inoculated with V. parahaemolyticus at a concentration of 106 CFU/mL. The results revealed that short treatments with ozone nanobubbles had minimal impact on shrimp gills, mortality, and growth rates, reduced V. parahaemolyticus concentration in water compared to the other groups, and improve water quality. These laboratory results indicate that ozone nanobubble treatment may be useful for controlling V. parahaemolyticus. More work is needed to find the best protocol to apply the technology on a commercial scale.
Applications of Magnetite Nanoparticles for Water Treatment and for DNA and Cell Separation
Nguyen Hoang Hai,Nguyen Chau,Nguyen Hoang Luong,Nguyen Thi Van Anh,Phan Tuan Nghia 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3
Magnetic nanoparticles with a diameter of 15 nm prepared by using the coprecipitation method have been applied to enforce the sedimentation of the solid waste, to adsorb the arsenic ions in water, to increase the DNA concentration by using a magnetic eld for the electrochemical DNA sensor and to separate the helper CD4+ T cells to determine the number of the cells in blood. A combination of magnetic nanoparticles and alum makes the solid waste in water under a magnetic field aggregate a dozen times faster than under the gravity alone. A concentration of 0.1 mg/l of arsenic in water was reduced to a value lower than the permissible concentration of 0.01 mg/l after few minutes of stirring. The particles functionalized with 3-aminopropyl triethoxysilane were used to enrich the DNA of the Herpes virus, which extended the sensitivity of an electrochemical sensor down to a concentration lower than nM/l. The particles coated with fluorescent-labeled antiCD4 antibody were used to count the helper CD4+ T cells. The fluorescence signals of the particle/cell system were two times stronger than those of the uorescence antiCD4 cell system. This can be used for the treatment of an HIV-infected patient with a simple fluorescent microscope. Magnetic nanoparticles with a diameter of 15 nm prepared by using the coprecipitation method have been applied to enforce the sedimentation of the solid waste, to adsorb the arsenic ions in water, to increase the DNA concentration by using a magnetic eld for the electrochemical DNA sensor and to separate the helper CD4+ T cells to determine the number of the cells in blood. A combination of magnetic nanoparticles and alum makes the solid waste in water under a magnetic field aggregate a dozen times faster than under the gravity alone. A concentration of 0.1 mg/l of arsenic in water was reduced to a value lower than the permissible concentration of 0.01 mg/l after few minutes of stirring. The particles functionalized with 3-aminopropyl triethoxysilane were used to enrich the DNA of the Herpes virus, which extended the sensitivity of an electrochemical sensor down to a concentration lower than nM/l. The particles coated with fluorescent-labeled antiCD4 antibody were used to count the helper CD4+ T cells. The fluorescence signals of the particle/cell system were two times stronger than those of the uorescence antiCD4 cell system. This can be used for the treatment of an HIV-infected patient with a simple fluorescent microscope.
Preparing cuprous oxide nanomaterials by electrochemical method for non-enzymatic glucose biosensor
Nguyen, Thu-Thuy,Huy, Bui The,Hwang, Seo-Young,Vuong, Nguyen Minh,Pham, Quoc-Thai,Nghia, Nguyen Ngoc,Kirtland, Aaron,Lee, Yong-Ill IOP 2018 Nanotechnology Vol.29 No.20
<P>Cuprous oxide (Cu<SUB>2</SUB>O) nanostructure has been synthesized using an electrochemical method with a two-electrode system. Cu foils were used as electrodes and NH<SUB>2</SUB>(OH) was utilized as the reducing agent. The effects of pH and applied voltages on the morphology of the product were investigated. The morphology and optical properties of Cu<SUB>2</SUB>O particles were characterized using scanning electron microscopy, x-ray diffraction, and diffuse reflectance spectra. The synthesized Cu<SUB>2</SUB>O nanostructures that formed in the vicinity of the anode at 2 V and pH?=?11 showed high uniform distribution, small size, and good electrochemical sensing. These Cu<SUB>2</SUB>O nanoparticles were coated on an Indium tin oxide substrate and applied to detect non-enzyme glucose as excellent biosensors. The non-enzyme glucose biosensors exhibited good performance with high response, good selectivity, wide linear detection range, and a low detection limit at 0.4 <I>μ</I>M. Synthesized Cu<SUB>2</SUB>O nanostructures are potential materials for a non-enzyme glucose biosensor.</P>
Warping stresses of a rectangular single leaf flexure under torsion
Nghia Huu Nguyen,Ji-Soo Kim,이동연 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.59 No.3
We describe a stress analysis of a single leaf flexure under torsion in which the warping effect is considered. The theoretical equations for the warping normal stress (xx) and shear stresses (xz and xy) are derived by applying the warping function of a rectangular cross-sectional beam and the twist angle equation that includes the warping torsion. The results are compared with those of the non-warping case and are verified using finite element analysis (FEA). A sensitivity analysis over the length, width, and thickness is performed and verified via FEA. The results show that the errors between the theory of warping stress results and the FEA results are lower than 4%. This indicates that the proposed theoretical stress analysis with warping is accurate in the torsion analysis of a single leaf flexure.
Nguyen, Tai Nghia,Lee, Jong-Wook Wiley Subscription Services, Inc., A Wiley Company 2010 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.52 No.8
<P>A low phase noise tuned-input tuned-output (TITO) voltage-controlled oscillator (VCO) using PMOS transistors is presented in this article.The TITO-VCO, implemented using a 0.18 μm RF CMOS process, resulted in a phase noise performance of −118 dBc/Hz at 1 MHz offset from the center frequency of 4.7 GHz. The figure-of-merit of the TITO-VCO was 188 dB. To the author's knowledge, this is the first report on the measured performance of differential TITO-VCO implemented using PMOS transistors. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1852–1855, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25341</P>
Torsional analysis of a single-bent leaf flexure
Nguyen, Nghia Huu,Lim, Byoung-Duk,Lee, Dong-Yeon Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.1
We present a torsion analysis of single-bent leaf flexure that is partially restrained, subject to a torsional load. The theoretical equations for the torsional angle are derived using Castigliano's theorem. These equations consider the partially restrained warping, and are verified using finite element analysis (FEA). A sensitivity analysis over the length, width, and thickness is performed and verified via FEA. The results show that the errors between the theory result and the FEA result are lower than 6%. This indicates that the proposed theoretical torsional analysis with partially restrained warping is sufficiently accurate.
Real Time Control of an Induction Motor Using IMC Approach
Nghia, Duong Hoai,Nho, Nguyen Van,Bac, Nguyen Xuan,Lee, Hong-Hee The Korean Institute of Power Electronics 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.3
The paper presents a method for controlling induction motors using a nonlinear internal model control (IMC) approach. The process model and the inverse model are developed in the rotor flux coordinate. The main advantage of the proposed method is that it easily specifies the performance (steady state error, transient response, etc.) and the robustness of the controller by means of the IMC filters. Simulation results illustrate the effectiveness of the proposed method. Results on a real time system show that the control system has good performance and robustness against changes in motor parameters (rotor and stator resistances, rotor and stator inductances, rotor inertia).
Peer Effects on Corporate Cash Holdings: Evidence from Vietnam
Nghia Huu Nguyen,Wei-Hsien Li 한국재무학회 2022 財務硏究 Vol.35 No.2
This research examines corporate cash holdings in Vietnam, an emerging market, and finds reverse peer effects on them - that is, a firm’s level of cash holdings negatively relates to those of its peers. We also note the reverse peer effects are stronger for firms facing less competition and with low intangibility. Because the Vietnam market has noticeably lower competition and investment in innovation than in developed economics like the U.S., our evidence supports the role of competition and innovation investment in driving cash holdings’ peer effects and complements the literature that mostly focuses on developed economies. Our findings are consistent with the notion that some firms strategically accumulate cash to drive their competitors’ cash level lower when they are in less competitive industries or when they have lower innovation investments. Thus, the existing competition or innovation environment is crucial when modeling the cash holding behavior among industry peers. However, our tests on the preemptive motive for peer effects on cash holdings are inconclusive. Lastly, our results also support heterogeneity across countries in peer mimicking behavior and contributes to the cash holdings literature for the Vietnam market.