The Bending Analysis of Three Phase Polymer Composite Plate Reinforced by Glass Fiber and Titanium Oxide Particles Including Creep Effect

Duc, Nguyen Dinh,Minh, Dinh Khac,VanThu, Pham The Korean Society for Aeronautical and Space Scie 2010 International Journal of Aeronautical and Space Sc Vol.11 No.4

Three phase composite materials are widely used in the shipbuilding industry. When reinforced with fiber and particle, the physical and mechanical properties of polymer composite materials are improved. This paper presents the bending analysis of a three phase composite plate with an epoxy matrix, reinforced glass fiber and titanium oxide particles including creep effect when shear stress is taken into account. The obtained results indicate that creep strains lead to compression in the composite material. Introducing reinforced fibers and particles reduces the plate's deflection, when increasing the stretch coefficient allows the calculation of creep deflection during a long loading period.

Nonlinear dynamic response and vibration of nanocomposite multilayer organic solar cell

Duc, Nguyen Dinh,Seung-Eock, Kim,Quan, Tran Quoc,Long, Dang Dinh,Anh, Vu Minh Elsevier 2018 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.184 No.-

<P><B>Abstract</B></P> <P>In the recent years, organic solar cell (OSC) has attracted much interest of the research community due to its great promise as renewable sources. This paper presents the first analytical approach to investigate the nonlinear dynamic response and vibration of imperfect rectangular nanocompsite multilayer organic solar cell subjected to mechanical loads using the classical plate theory. Nanocompsite organic solar cell consists of five layers of Al, P3HT:PCBM, PEDOT:PSS, IOT and glass. Motion and compatibility equations are derived using the classical plate theory and taking into account the effects of initial geometrical imperfection and geometrical nonlinearity in Von Karman – Donnell sense. The Galerkin method and fourth – order Runge – Kutta method are used to give explicit expressions of natural frequencies, nonlinear frequency – amplitude relation and nonlinear dynamic responses of nanocompsite organic solar cell. The numerical results show the influences of geometrical parameters, the thickness of layers, imperfections, and mechanical loads on the nonlinear dynamic response and nonlinear vibration of nanocompsite organic solar cell.</P>

Efficacy of electrochemically activated water solution in gingivitis treatment

Dinh‑Toi Chu,Van‑Huy Pham,Thien Chu‑Dinh,Truong Nhu Ngoc Vo,Duc Long Duong,Van Nhon Bui,Minh Son Tong,Thi Thu Phuong Nguyen,Quynh Anh Le,Khanh‑Hoang Nguyen 한국약제학회 2019 Journal of Pharmaceutical Investigation Vol.49 No.3

Mouthwash is one of the most commonly oral healthcare products for prevention and treatment of gum diseases. Dr. ECA is a disinfectant solution manufactured by a Vietnamese company and has been licensed for oral healthcare, but its effect on gingivitis is still unclear. To evaluate the effectiveness of this product in the treatment of gingivitis, we conducted a clinical study in 60 students diagnosed with gingivitis to compare the results of gingivitis treatment using Dr. ECA and a control mouthwash (a demonstrated anti-gingivitis product). The data showed that in the treated group, the rate of good Gingivitis Index (GI) before treatment was 46.67%, but after 2 and 4 weeks of using Dr. ECA that rate was increased to 96.67% and 100%, respectively. The percentage of patients with bleeding on probing was 63.33% but declined sharply after 2 weeks of treatment to 6.67%, and further reduced to 3.33% after 4 weeks of treatment. The treatment outcomes in were similar in the Dr. ECA treated group and control one with no statistically significant difference. Our results suggest that the electrolyte saline solution Dr. ECA is effective in treating gingivitis. Its effects are similar to other mouthwash products that had been approved and marketed.

Evaluation of Economic Damage Caused by Drought in Central Region Vietnam: A Case Study of Phu Yen Province

Dinh Duc Truong,Doan Quang Tri 대한자원환경지질학회 2021 자원환경지질 Vol.54 No.6

This paper aims to study the impact of natural disasters on per capita income in Vietnam both the short and long-term, specifically impact loss of income caused by the extreme drought 2013 for agriculture, forestry and fishery in Phu Yen Province, Central Vietnam. The study valued economic damage by applying the synthetic control method (SCM), which is a statistical method to evaluate the effect of an intervention (e.g. natural disasters) in different case studies. It estimates what would have happened to the treatment group if it had not received the treatment by constructing a weighted combination of control units (e.g. control provinces). The results showed that the 2013 drought caused a decrease in income per capita, mainly in the agriculture, forestry, and fishery sector in Phu Yen. The reduced income was estimated to be VND 160,000 (1 USD = 23,500 VND (2021)) for one person per month, accounting for 11% of total income per capita and continued to affect the income 6 years later. Therefore, authorities need to invest in preventive solutions such as early and accurate warnings to help people to be more proactive in disaster prevention.

Static response and free vibration of functionally graded carbon nanotube-reinforced composite rectangular plates resting on Winkler–Pasternak elastic foundations

Duc, Nguyen Dinh,Lee, Jaehong,Nguyen-Thoi, T.,Thang, Pham Toan Elsevier 2017 AEROSPACE SCIENCE AND TECHNOLOGY Vol.68 No.-

<P><B>Abstract</B></P> <P>In the present article, static response and free vibration of functionally graded carbon nanotube reinforced composite (FG-CNTRC) rectangular plate resting on Winkler–Pasternak elastic foundations using an analytical approach are studied. The rectangular plates are reinforced by single-walled carbon nanotubes (SWCNTs) which are assumed to be graded through the thickness direction with four types of distributions. The mathematical model of the FG-CNTRC plate is developed based on the first-order shear deformation plate theory (FSDT) and Hamilton principle. By using Navier solution, the governing equations are solved to obtain the central deflection and the natural frequency parameters. Several examples are verified to have higher accuracy than those from the previous method in the literature. Also, the effects of different parameters on static response and natural frequency of FG-CNTRC plate are highlighted by solving numerous examples. Finally, these new results may serve as benchmarks for future investigations.</P>

Dynamic response and vibration of composite double curved shallow shells with negative Poisson's ratio in auxetic honeycombs core layer on elastic foundations subjected to blast and damping loads

Duc, Nguyen Dinh,Seung-Eock, Kim,Cong, Pham Hong,Anh, Nguyen Tuan,Khoa, Nguyen Dinh Elsevier 2017 International journal of mechanical sciences Vol.133 No.-

<P><B>Abstract</B></P> <P>The purpose of the present study is to investigate dynamic response and vibration of composite double curved shallow shells with negative Poisson's ratios in auxetic honeycombs core layer on elastic foundations subjected to blast and damping loads using analytical solution. This study considers composite double curved shallow shells with auxetic core which have three layers in which the top and bottom outer skins are isotropic aluminum materials; the central layer has honeycomb structure using the same aluminum material. Based on the first order shear deformation theory (FSDT) with the geometrical nonlinear in von Karman and using Airy stress functions method, Galerkin method and the fourth-order Runge–Kutta method, the resulting equations are solved to obtain expressions for nonlinear motion equations. The effects of geometrical parameters, material properties, elastic foundations Winkler and Pasternak, the nonlinear dynamic analysis and vibration of double curved shallow shells with negative Poisson's ratios in auxetic honeycombs core layer are studied.</P> <P><B>Highlights</B></P> <P> <UL> <LI> To investigate dynamic response and vibration of composite double curved shallow shells by using analytical solution. </LI> <LI> The composite shells have the central auxetic core layer—honeycomb structures with negative Poisson's ratio. </LI> <LI> Based on the first order shear deformation theory (FSDT). </LI> <LI> Used airy stress functions, Galerkin method and fourth-order Runge–Kutta method. </LI> <LI> The effects of geometrical parameters, material properties, elastic Winkler and Pasternak foundations, mechanical and blast loads are studied. </LI> </UL> </P>

ORiginal Article : The Performance of a Modified Glasgow Blatchford Score in Predicting Clinical Interventions in Patients with Acute Nonvariceal Upper Gastrointestinal Bleeding: A Vietnamese Prospective Multicenter Cohort Study

( Duc Trong Quach ),( Ngoi Huu Dao ),( Minh Cao Dinh ),( Chung Huu Nguyen ),( Linh Xuan Ho ),( Nha Doan Thi Nguyen ),( Quang Dinh Le ),( Cong Minh Hong Vo ),( Sang Kim Le ),( Toru Hiyama ) 대한간학회 2016 Gut and Liver Vol.10 No.3

Background/Aims: To compare the performance of a modified Glasgow Blatchford score (mGBS) to the Glasgow Blatchford score (GBS) and the pre-endoscopic Rockall score (RS) in predicting clinical interventions in Vietnamese patients with acute nonvariceal upper gastrointestinal bleeding (ANVUGIB). Methods: A prospective multicenter cohort study was conducted in five tertiary hospitals from May 2013 to February 2014. The mGBS, GBS, and pre-endoscopic RS scores were prospectively calculated for all patients. The accuracy of mGBS was compared with that of GBS and preendoscopic RS using area under the receiver operating characteristic curve (AUC). Clinical interventions were defined as blood transfusions, endoscopic or radiological intervention, or surgery. Results: There were 395 patients including 128 (32.4%) needing endoscopic treatment, 117 (29.6%) requiring blood transfusion and two (0.5%) needing surgery. In predicting the need for clinical intervention, the mGBS (AUC, 0.707) performed as well as the GBS (AUC, 0.708; p=0.87) and outperformed the pre-endoscopic RS (AUC, 0.594; p<0.001). However, none of these scores effectively excluded the need for endoscopic intervention at a threshold of 0. Conclusions: mGBS performed as well as GBS and better than pre-endoscopic RS for predicting clinical interventions in Vietnamese patients with ANVUGIB. (Gut Liver 2016;10:375- 381)

Size-dependent Field-emission Properties from Triangular-shaped GaN Nanostructures

Duc V. Dinh,J. H. Yang,S. M. Kang,S. W. Kim,윤대호 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1

Gallium nitride (GaN) nanostructures were synthesized on Si substrates by using the vapor-phase epitaxy (VPE) method. The as-synthesized GaN nanostructures with a hexagonal, single-crystalline structure possessed a triangular cross-section with nanorod and nanowire diameters ranging from about 100 to 280 nm and from about 20 to 60 nm, respectively. The field-emission (FE) properties of the GaN nanostructures were investigated in terms of their size dependence. Turn-on fields of about 4.85 V/ and 4.10 V/, respectively, for the GaN nanorods and nanowires were obtained, corresponding to field-enhancement factors of about 373 and 1427. The higher aspect ratio of the GaN nanowires compared to that of the GaN nanorods caused the differences in FE properties.

The Bending Analysis of Three Phase Polymer Composite Plate Reinforced by Glass Fiber and Titanium Oxide Particles Including Creep Effect

Nguyen Dinh Duc,Dinh Khac Minh,Pham VanThu 한국항공우주학회 2010 International Journal of Aeronautical and Space Sc Vol.11 No.4

Three phase composite materials are widely used in the shipbuilding industry. When reinforced with fiber and particle, the physical and mechanical properties of polymer composite materials are improved. This paper presents the bending analysis of a three phase composite plate with an epoxy matrix, reinforced glass fiber and titanium oxide particles including creep effect when shear stress is taken into account. The obtained results indicate that creep strains lead to compression in the composite material. Introducing reinforced fibers and particles reduces the plate’s deflection, when increasing the stretch coefficient allows the calculation of creep deflection during a long loading period.

Dry semi-continuous anaerobic digestion of food waste in the mesophilic and thermophilic modes: New aspects of sustainable management and energy recovery in South Korea

Nguyen, Dinh Duc,Chang, Soon Woong,Cha, Jae Hun,Jeong, Seong Yeob,Yoon, Yong Soo,Lee, Sin Jin,Tran, Minh Chi,Ngo, Huu Hao Elsevier 2017 Energy conversion and management Vol.135 No.-

<P><B>Abstract</B></P> <P>In this study, parallel, bench-scale, mesophilic and thermophilic, dry, semi-continuous anaerobic digestion (DScAD) of Korea food waste (FW, containing 22% total solids (TS) and 20% volatile solids (VS)) was investigated thoroughly under varying operational conditions, including hydraulic retention times (HRTs) and organic loading rates (OLRs). The aim was to evaluate the start-up, stability, overall removal efficiency, and inhibitory effects of toxic compounds on process performance over a long-term operation lasting 100days. The results from both digesters indicate that the simultaneous reduction of VS and the production of gas improved as the HRT decreased or the OLR increased. The highest average rates of VS reduction (79.67%) and biogas production (162.14m<SUP>3</SUP> biogas/ton of FW, 61.89% CH<SUB>4</SUB>), at an OLR of 8.62±0.34kgVS/m<SUP>3</SUP> day (25days of HRT), were achieved under thermophilic DScAD. In addition, the average rates of reduction of VS and the production of biogas in thermophilic DScAD were higher by 6.88% and 16.4%, respectively, than were those in mesophilic DScAD. The inhibitory effects of ammonia, H<SUB>2</SUB>S, and volatile fatty acids (VFAs) on methane production was not clear from either of the digesters, although, apparently, their concentrations did fluctuate. This fluctuation could be attributed to the self-adaptation of the microbial well. However, digestion that was more stable and faster was observed under thermophilic conditions compared with that under mesophilic conditions. Based on our results, the optimum operational parameters to improve FW treatment and achieve higher energy yields could be determined, expanding the application of DScAD in treating organic wastes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> DScAD remained stable even at a high rate of organic loading. </LI> <LI> Higher OLR led to the more reduction of VS and the production of biogas. </LI> <LI> Thermophilic digesters had higher reduction of VS and the generation of biogas. </LI> <LI> Stable with faster digestion and higher OLR was achieved in the thermophilic operation. </LI> <LI> Acetic and propionic acids were the most prominent in the TVFA. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>