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Fabrication of Polymer Inkjet Head for Electrohydrodynamic(EHD) Printing
Vu Dat Nguyen,Doyoung Byun(변도영),Si Bui Quang Tran 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
A polymer ink jet nozzle is designed and fabricated with 370 ㎛ outer diameter. Polymethyl-methacrylate (PMMA) is used for the nozzle, which can offer better wetting properties and low cost features Due to dynamic behavior of meniscus on the nozzle, it requires duration time for the meniscus to move from the initial position to the jet state. To improve drop-on-demand jetting speed, the effect of frequency of applied voltage is investigated.
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<sup>st</sup> 2000 to October 25<sup>th</sup> 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.
Nguyen Thi Mai Tho,Bui The Huy,Dang Nguyen Nha Khanh,Ho Nguyen Nhat Ha,Vu Quang Huy,Ngo Thi Tuong Vy,Do Manh Huy,Duong Phuoc Dat,Nguyen Thi Kim Phuong 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.12
Novel highly active visible-light photocatalysts in the form of zinc bismuth oxide (ZnBi2O4) and graphite hybrid composites were prepared by coupling via a co-precipitation method followed by calcination at 450 oC. The asprepared ZnBi2O4-graphite hybrid composites were tested for the degradation of rhodamine B (RhB) solutions under visible-light irradiation. The existence of strong electronic coupling between the two components within the ZnBi2O4- graphite heterostructure suppressed the photogenerated recombination of electrons and holes to a remarkable extent. The prepared composite exhibited excellent photocatalytic activity, leading to more than 93% of RhB degradation at an initial concentration of 50mg·L1 with 1.0 g catalyst per liter in 150min. The excellent visible-light photocatalytic mineralization of ZnBi2O4-1.0graphite in comparison with pristine ZnBi2O4 could be attributed to synergetic effects, charge transfer between ZnBi2O4 and graphite, and the separation efficiency of the photogenerated electrons and holes. The photo-induced h+ and the superoxide anion were the major active species responsible for the photodegradation process. The results demonstrate the feasibility of ZnBi2O4-1.0graphite as a potential heterogeneous photocatalyst for environmental remediation.
A hybrid piezo-electrohydrodynamic inkjet system
구엔부닷(Vu Dat Nguyen),변도영(Doyoung Byun) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The paper reports a new, hybrid ElectroHydroDynamic (EHD) printing technique that offers better the uniformity of Drop-On-Demand (DOD) patterns compared to conventional method. The technique is hybrid between EHD and piezoelectric inkjet printing.
Nguyen Dinh HOA,Vu Duc-Dat,Doan Thi-Ngoc-Ha,Vo Hoang-Long 대한정형외과학회 2020 Clinics in Orthopedic Surgery Vol.12 No.2
Background: The evidence for the efficacy and safety of balloon kyphoplasty (BKP) in treating the Vietnamese patients is sparse. There is no convincing evidence regarding BKP’s efficacy in Vietnamese patients, especially in the patients with thoracic osteoporotic vertebral compression fractures (VCFs). This article aims to evaluate the outcomes of restoring the body height of the compressed thoracic vertebrae in patients undergoing BKP. Methods: We prospectively enrolled 65 consecutive patients with thoracic VCFs (73 vertebrae) due to osteoporosis who were treated with BKP between June 2018 and May 2019. Results: A trocar was inserted through the pedicle in 84.9% (62/73) and beside the pedicle in 15.1% (11/73). The mean amount of mixed cement injected was 4.1 ± 1.1 mL (range, 1.5–7 mL). Cement leakage was radiographically confirmed in 30.8% of 65 patients. Among patients with complications caused by cement extravasation, the leakage was through the anterior margin of the vertebrae in 15.4%, through the vertebral disc in 12.3%, and through the posterior margin of the vertebrae in 3.1%. In the last 3.1% of patients, there was no clinically notable lesions of the nerve roots or spinal cord. The mean visual analog scale score decreased significantly from 7.3 ± 1.1 preoperatively to 3.3 ± 0.6 at 24 hours after surgery, and then to 1.2 ± 1.1 at 3 months after surgery (p < 0.01). The mean reduction in Cobb angle measured on standing radiographs after treatment was 3.7°, showing statistical significance (p < 0.01). Conclusions: BKP is a minimally invasive treatment effective for immediate pain relief, early motor rehabilitation, and humpback correction. The present study provided convincing evidence to support the use of BKP by spine surgeons and clinical specialists in treating osteoporotic thoracic VCFs in Vietnamese patients.
Relaxor characteristics of PSLZT-BMT-based ferroelectric material ceramics
Nguyen Van Thinh,Le Dai Vuong,Do Viet On,Truong Van Chuong,Le Vu Truong Son,Trinh Ngoc Dat,Le Van Thanh Son,Vo Thanh Tung 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.3
(1-x)[(Pb0.94Sr0.05La0.01)(Zr0.54Ti0.46)0.9975O3]-x[Bi(Mn1/2Ti1/2)O3] (PSLZT-BMT) ferroelectric material ceramics with x in therange of 0-0.05 mol were successfully synthesized following the conventional solid-phase route. The materials were thoroughlyinvestigated to study their structural phase, microstructure, ferro-piezoelectric characteristics, and dielectric behavior. Theexperimental results show that the density of the samples decreased from 7.75 to 7.58 g/cm3, and the relative density decreasedin the range of 98.48%-96.28%. However, with increasing contents of BMT, the dielectric and ferroelectric properties ofPSLZT-BMT ceramics tend to decrease, specifically the maximum dielectric constant (εmax) of PSLZT-BMT decreased in therange of 23579-9991 and the residual polarization (Pr) decreases in the range of 22.54-7.87 μC/cm2 when the doping contentincreased in the range of 0.0-0.05 mol. The diffusivity values (γ) of the PSLZT-BMT material are 1.74, 1.78, 1.82, 1.84, 1.79,and 1.77 when the doping content x varies as 0.0, 0.01, 0.02, 0.03, 0.04, and 0.05 mol, respectively, which is characteristic ofrelaxor ferroelectric materials. Besides, the Tm, TB, TC-W, and C values depend on BMT concentration, and the trend decreases.
Inhibitory Effects of Vietnamese Medicinal Plants on Monoamine Oxidase Activity
Hung, Vu Manh,Minh, Chau Van,Kiem, Phan Van,Dang Thi Lan Huong,Nguyen Tien Dat,Kim, Young Ho 충남대학교 약학대학 의약품개발연구소 2002 藥學論文集 Vol.17 No.-
In vitro in screening test aiming to find monoamine oxidase (MAO) inhibitors from Vietnamese medicinal plants, the MeOH extracts of seventeen medicinal plants were tested for the inhibitory effects on monoamine oxidase activity. MAO was purified from mouse brain and its activity was determined by fluorospectrophotometer using kynuramine as a substrate. Five MeOH extracts of medicinal plants including Cnidium monnineri showed quite strong inhibitory effects at the concentration of 250 ㎍/㎖. Six MeOH extracts of herbs including Astragalus membranaceus showed moderate inhibitory effects on this enzyme. Seven medicinal plants which showed good inhibitory effects on MAO were fractionated with CH_2Cl_2, EtOAc, BuOH and H_2O, successively. They were investigated for the inhibitory effects on MAO.