Strut-and-tie model for shear capacity of corroded reinforced concrete columns

Tran, Cao Thanh Ngoc,Nguyen, Xuan Huy,Nguyen, Huy Cuong,Vu, Ngoc Son Techno-Press 2020 Advances in concrete construction Vol.10 No.3

An analytical model is developed in this paper to predict the shear capacity of reinforced concrete (RC) columns with corroded transverse reinforcements. The shear strength model for corroded RC columns is proposed based on modifying the existing strut-and-tie model, which considers the deformational compatibility between truss and arch mechanisms. The contributions to the shear strength from both truss and arch mechanisms are incorporated in the proposed model. The effects of corrosion level of transverse reinforcements are considered in the proposed model through the minimum residual cross-sectional area of transverse reinforcements and the reduction of concrete compressive strength for the cover area. The shear strengths calculated from the developed model are compared with the experimental results from Vu's study (2017), which consisted of RC columns with corroded transverse reinforcements showing shear failure under the cyclic loading. The comparison results indicate satisfactory correlations. Parametric studies are conducted based on the developed shear strength model to explore the effects of column axial loading, aspect ratios, transverse reinforcements and the corrosion levels in transverse reinforcements to the shear strength of RC columns with corroded transverse reinforcements.

CePO4:Tb Nanoparticles: Preparation, Structure and Optical Properties

Nguyen Vu Thanh,Tran Kim Anh,Nguyen Quang Liem,Nguyen Huu Quan,Nguyen The Khoi 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

Nanocrystals of CePO4:Tb were prepared by reacting the corresponding metal chlorides, phos- phoric acid and trioctylamine at 200℃ in tris(2-ethylhexyl) phosphate (TEHP). The samples were characterized by X-ray diffraction and scanning electron microscopy (SEM). The photoluminescence (PL) and the absorption spectra of CePO4:Tb nanoparticles will be presented. The PL spectra are described by using the well-known 5D4 - 7FJ transitions (J = 6, 5, 4, 3 ···) of Tb3+ ions with the strongest emission at 543 nm for J = 5. The dependence of PL intensity on Tb3+ concentration has been investigated. Nanocrystals of CePO4:Tb were prepared by reacting the corresponding metal chlorides, phos- phoric acid and trioctylamine at 200℃ in tris(2-ethylhexyl) phosphate (TEHP). The samples were characterized by X-ray diffraction and scanning electron microscopy (SEM). The photoluminescence (PL) and the absorption spectra of CePO4:Tb nanoparticles will be presented. The PL spectra are described by using the well-known 5D4 - 7FJ transitions (J = 6, 5, 4, 3 ···) of Tb3+ ions with the strongest emission at 543 nm for J = 5. The dependence of PL intensity on Tb3+ concentration has been investigated.

An Empirial Study on Vietnam’s Trade Faclilitation in the Digital Economy

Thanh Huong Vu(Thanh Huong Vu ),Thi Thuy Hanh Lam(Thi Thuy Hanh Lam ),Ha Phuong Nguyen(Ha Phuong Nguyen ) The International Academy of Global Business and T 2023 The International Academy of Global Business and T Vol.19 No.2

Purpose - Vietnam is among the fastest growing digital economies in the Southeast Asian region, and has made enormous efforts to adopt digital measures to facilitate trade. The paper aims to assess Vietnam’s performance of digital trade facilitation and estimate the impact of digital trade facilitation on Vietnam’s exports to the Association of Southeast Asian Nations (ASEAN). Design/Methodology/Approach - Vietnam’s implementation of digital trade facilitation is assessed through a constructed framework based on two groups of indicators, including Information Availability and Formalities Automation extracted from the OECD Trade Facilitation database. Further, a gravity model was adopted to estimate the impact of digital trade facilitation on Vietnam’s exports. Findings - The results show that Vietnam performs a slightly better than the average level of ASEAN countries. However, Vietnam’s implementation of digital trade facilitation tends to be ỉmproving at a slower rate than other ASEAN countries’ implementations, as well as the country’s overall implementation of other trade facilitation. The paper is among leading studies to quantify the impact of digital trade facilitation on Vietnam’s exports to ASEAN countries, and finds that if Vietnam and ASEAN countries increase trade facilitation through Information Availability measures by 1%, Vietnam’s exports will increase more than proportionately by 1.29% and 1.01%, respectively. Meanwhile, the digitalization of trade formalities so far has had no effect on Vietnam’s exports to this region. Research Implications - Vietnam should place priority on enhancing automation in trade-related administrative procedures, especially in customs procedures. Furthermore, it should pay more attention to promote the electronic publication of trade-related information, enhance the transparency of government policymaking, and increase the quality of enquiry points.

Optimization of the eco-friendly synthesis of graphene oxide from graphite using Plackett–Burman and Box–Behnken models for industrial production orientation

Phuc Nguyen Thien,Giang Nguyen Thi Huong,An Vu Nguyen Thien Truong,Nam Nguyen Thanh Hoai,Anh Ly Duc,Nguyen Huynh Cam,An Hoang,Phong Mai Thanh,Hieu Nguyen Huu 한국탄소학회 2023 Carbon Letters Vol.33 No.2

In this study, graphene oxide (GO) was synthesized by the improved Hummers’ method. The degree of oxidation from graphite (Gi) to GO was determined through interlayer spacing calculated from X–ray diffraction. Besides, the effect of KMnO4:Gi ratios (X1), H2SO4 volume (X2), oxidation temperature (X3), oxidation time of stage 1 (X4), and oxidation time of stage 2 (X5) was screened by the Plackett–Burman model. The simultaneous impact of three factors that influenced the degree of oxidation (X1, X2, and X3) was studied by the Box–Behnken experimental model of response surface methodology to achieve suitable conditions for the GO synthesis process. The characterization of GO product was investigated via the modern analytical methods: X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, UV–Vis spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. In addition, the study was also carried out on a pilot scale for orientation in industrial application with the yield of 14 g/batch.

Development of label-free electrochemical lactose biosensor based on graphene/poly(1,5-diaminonaphthalene) film

Binh Hai Nguyen,Binh Thanh Nguyen,Hanh Van Vu,Chuc Van Nguyen,Dzung Tuan Nguyen,Loc Thai Nguyen,Thu Thi Vu,Lam Dai Tran 한국물리학회 2016 Current Applied Physics Vol.16 No.2

In this work, a lactose biosensor was developed by co-immobilizing b-galactosidase (b-Gal) and glucose oxidase (GOx) on microelectrodes pre-modified with Pt/graphene/P(1,5-DAN) for estimation of lactose in dairy products to prevent lactose intolerance. The Pt microelectrode was modified with graphene and 1,5-polydiaminonaphthalene film. Graphene was synthesized by chemical vapor deposition on copper tape and manually transferred to the electrode surface. Polymeric P(1,5-DAN) was grafted on top of the graphene film by electropolymerization. Modified surface of the electrode was characterized by Raman spectra analysis, FE-SEM, AFM and cyclic voltammetry. The results indicated that deposition graphene film on electrode surface induced considerable enhancement in current signal, over 20 times as high as the uncoated electrode surface. The developed sensor was successfully used to determine lactose in model samples with sensitivity, correlation coefficient (R2) and limit of detection (LOD) estimated to be 1.33 mA/(mgml1), 0.995 and 1.3 mg/ml, respectively. The combined graphene and conductive P(1,5-DAN) could serve as a novel sensing platform on electrochemical sensors with superior sensitivity.

Does conventional freezing affect sperm DNA fragmentation?

Le, Minh Tam,Nguyen, Thai Thanh Thi,Nguyen, Tung Thanh,Nguyen, Trung Van,Nguyen, Tam An Thi,Nguyen, Quoc Huy Vu,Cao, Thanh Ngoc The Korean Society for Reproductive Medicine 2019 Clinical and Experimental Reproductive Medicine Vol.46 No.2

Objective: Sperm cryopreservation has been widely used in assisted reproductive technology, as it offers great potential for the treatment of some types of male infertility. However, cryopreservation may result in changes in membrane lipid composition and acrosome status, as well as reductions in sperm motility and viability. This study aimed to evaluate sperm DNA fragmentation damage caused by conventional freezing using the sperm chromatin dispersion test. Methods: In total, 120 fresh human semen samples were frozen by conventional methods, using SpermFreeze Solution as a cryoprotectant. Routine semen analysis and a Halosperm test (using the Halosperm kit) were performed on each sample before freezing and after thawing. Semen parameters and sperm DNA fragmentation were compared between these groups. Results: There was a significant decrease in sperm progressive motility, viability, and normal morphology after conventional freezing (32.78%, 79.58%, and 3.87% vs. 16%, 55.99%, and 2.55%, respectively). The sperm head, midpiece, and tail defect rate increased slightly after freezing. Furthermore, the DNA fragmentation index (DFI) was significantly higher after thawing than before freezing (19.21% prior to freezing vs. 22.23% after thawing). Significant increases in the DFI after cryopreservation were observed in samples with both normal and abnormal motility and morphology, as well as in those with normal viability. Conclusion: Conventional freezing seems to damage some sperm parameters, in particular causing a reduction in sperm DNA integrity.

The Impacts of Oil Price and Exchange Rate on Vietnamese Stock Market

NGUYEN, Tra Ngoc,NGUYEN, Dat Thanh,NGUYEN, Vu Ngoc Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.8

This study aims to investigate the effect of oil price and exchange rate on the two Vietnamese stock market indices: VN index and HXN index. This study uses the daily data from August 1^st 2000 to October 25^th 2019 of the two Vietnamese stock indices: VN index and HNX index, the two oil price indices: BRENT and WTI, and the two exchange rates: US dollar to Vietnamese dong and Euro to Vietnamese dong. Due to the presence of heteroskedasticity in our data, we use GARCH (1,1) regression model to perform our analysis. Our findings show that the oil price has a significant positive effect on the two Vietnamese stock market indices. In terms of the stock index volatility, both the VN index and HNX index volatilities are negatively impacted by the return of oil price. While the conclusion about the impact of oil price remained consistent through all three robustness tests, the effect of exchange rate on Vietnamese stock market indices is not consistent. We find thatchanges of the USD/VND exchange rate significantly impact the return and volatility of HNX index only in GARCH (1,1) setting. Our analysis also survives a number of robustness tests.

Effectiveness Analysis of Spin Motion in Reducing Dispersion of Sounding Rocket Flight due to Thrust Misalignment

Vu Dan Thanh Le,Anh Tuan Nguyen,Lac Hong Nguyen,Ngoc Thanh Dang,Ngoc Doan Tran,한재흥 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.5

This paper explores the effectiveness of spin motion in mitigating the flight dispersion of a two-stage solid-propellant rocket model due to thrust misalignment. The aerodynamic coefficients of the rocket model are obtained by the use of a panel method and semi-empirical equations. A simulation program is developed to solve the equations of motion while considering the variations of the inertial parameters. Monte Carlo simulation techniques are applied to provide statistical data that are used to analyze the relationship between the spin motion and flight dispersion. The spin motion is generated by canting the fins to generate the axial aerodynamic moment. The results show that thrust misalignment at the first stage of the rocket has a great impact on the dispersion of rocket flight. By canting the first-stage fins at a relatively large angle to create the spin motion right after launch, the dispersion area of the payload-release location can be minimized considerably. However, thrust misalignment as well as the fin cant angle at the second stage appear to have insignificant effects on the rocket flight trajectory. On the other hand, canting the fins of the second stage at a large angle may lead to an increase in the spin rate, which may be harmful to the rocket operation. The paper also shows the variation of the dispersion characteristics of rocket flight when the fin size is modified.

Original Article : A Cyan Fluorescent Protein Gene (cfp)-Transgenic Marine Medaka Oryzias dancena with Potential Ornamental Applications

( Nguyen Thanh Vu ),( Young Sun Cho ),( Sang Yoon Lee ),( Dong Soo Kim ),( Yoon Kwon Nam ) 한국수산과학회(구 한국수산학회) 2014 Fisheries and Aquatic Sciences Vol.17 No.4

To evaluate their potential utility as an ornamental organism, novel transgenic marine medaka Oryzias dancena strains with a highly vivid fluorescent phenotype were established through transgenesis of a cyan fluorescent protein gene (cfp) driven by the endogenous fast skeletal myosin light chain 2 gene (mlc2f) promoter. The transgenic marine medaka strains possessed multiple copies of transgene integrants and passed their fluorescent transgenes successfully to subsequent generations. Transgenic expression in skeletal muscles at both the mRNA and phenotypic levels was, overall, dependent upon transgene copy numbers. In the external phenotype, an authentic fluorescent color was dominant in the skeletal muscles of the transgenic fish and clearly visible to the unaided eye. The phenotypic fluorescent color presented differentially in response to different light-irradiation sources; the transgenics displayed a yellow.green color under normal daylight or white room light conditions, a strong green-glowing fluorescenceunder ultraviolet light, and a cyan-like fluorescence under blue light from a light-emitting diode.

Correlations between abnormalities of morphological details and DNA fragmentation in human sperm

Nguyen, Hiep Tuyet Thi,Dang, Hong Nhan Thi,Nguyen, Thai Thanh Thi,Nguyen, Trung Van,Dang, Thuan Cong,Nguyen, Quoc Huy Vu,Le, Minh Tam The Korean Society for Reproductive Medicine 2022 Clinical and Experimental Reproductive Medicine Vol.49 No.1

Objective: As the associations of sperm DNA fragmentation with morphology have not been examined in detail, this study aimed to investigate the relationship between abnormalities of morphological details and DNA integrity in human sperm. Methods: In this cross-sectional study, men from infertile couples were enrolled at Hue Center for Reproductive Endocrinology and Infertility, Vietnam. Conventional semen parameters, including morphological details, were analyzed following the World Health Organization 2010 criteria. Sperm DNA fragmentation was evaluated using a sperm chromatin dispersion assay. The relationships and correlations between semen parameters, sperm morphology, and the type of halosperm and the DNA fragmentation index (DFI) were analyzed. Results: Among 130 men in infertile couples, statistically significant differences were not found in the sperm halo type between the normal and abnormal sperm morphology groups. The percentage of round-head spermatozoa was higher in the DFI >15% group (16.98%±12.50%) than in the DFI ≤15% group (13.13% ±8.82%), higher values for amorphous heads were found in the DFI >15% group, and lower values for tapered heads were observed in the DFI ≤15% group; however, these differences were not statistically significant. Small-halo sperm and the DFI were positively correlated with round-head sperm (r=0.243, p=0.005 and r=0.197, p=0.025, respectively). Conclusion: The rate of general sperm morphological abnormalities in semen analysis was not related to sperm DNA integrity. However, round sperm heads were closely associated with sperm DNA fragmentation.